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STANDARD MEDICAL WORKS.

By T. M‘CALL ANDERSON, M.D.,

Professor of Clinical Medicine, University of Glasgow.
Royal 8y 0, With Two Chromo-Lithographs, Steel-Plate, and Numerous Illustrations,
Handsome Cloth. 25s.

SKIN DISEASES (A Treatise on). With Special Reference to Diagnosis and Treat-
ment, including an Analysis of 11,000 Consecutive Cases.

By Dr EDOUARD MEYER,

Prof. a U Ecole Pratique de la Faculté de Médecine de Paris, Chev. of the Legion of Honour, ke.
Royal 8vo, with Three Chromo-Lithographs and Numerous Illustrations. 25s.
DISEASES OF THE EYE (A Practical Treatise on). Translated, with the

assistance of the Author, from the Third. French Edition, with additions as contained
in the Fourth German Edition, by A. FREELAND Fercus, M.B.

By JOHN THORBURN, M.D., E.B.C.P.,
Late Professor of Obstetric Medicine, Victoria University, Manchester.
Royal 8vo, Illustrated, Handsome Cloth. 21s.
THE DISEASES OF WOMEN (A Practical Treatise on). Prepared with Special

Reference to the Wants of the General Practitioner and Advanced Student.

By A.C; HADDON;.M.A.,

Professor of Zoology, Royal College of Science, Dublin.
Royal 8vo, Illustrated, Handsome Cloth. 18s.

EMBRYOLOGY (An Introduction to the oma of). For the use of Students.

By Sir DYCE DUCKWORTH, M.D. (Edin.), F.R.C. P.
Royal 8vo, Illustrated.
GOUT (A Treatise on). For the use of Practitioners and Students.

By ALEXANDER MACALISTER, M.D., F.R.S.,

Professor of Anatomy in the University of Cambridge.
Royal 8vo, with Numerous Illustrations.

HUMAN ANATOMY (A Text-Book on). For the use of Students and Practitioners.

By W. BEVAN LEWIS, L.R.C.P., M. R. C.Bi;

Medical Director of the West Riding Asylum, Wakefield.
Royal 8vo, Illustrated.

MENTAL DISEASES (A Text-Book of). With Special Reference to the Pathological
Aspects of Insanity.

By Dr RUDOLPH vy. JAKSCH,

University of Prague.
Royal 8vo, with Numerous Illustrations.
L DIAGNOSIS: A Text-Book of the Chemical, Microscopical, and Bacteriological
cg tle of Disease. ‘Franslated from the German by James Cacney, M.A., M.D.,
St Mary’s Hospital. é

¥ 7

ee GRIFFIN & COMPANY, LONDON.

PeX
ov

ALP Te BO OK 708

HUMAN PHYSIOLOGY,

INCLUDING

HISTOLOGY AND MICROSCOPICAL ANATOMY:

WITH SPECIAL REFERENCE TO THE REQUIREMENTS OF
Pew dC ok. oP ie © kN Be

BY

Dre Wok Ne Oreo

PROFESSOR OF PHYSIOLOGY AND DIRECTOR OF THE PHYSIOLOGICAL INSTITUTE,
UNIVERSITY OF GREIFSWALD.

TRANSLATED FROM THE SIXTH GERMAN EDITION.

WITH ADDITIONS BY

Waid FAN. OS Tal tN GG. MD se,

BRACKENBURY PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN THE OWENS COLLEGE
AND PROFESSOR IN THE VICTORIA UNIVERSITY, MANCHESTER ;
EXAMINER IN PHYSIOLOGY, UNIVERSITY OF OXFORD.

Witt VERY NUMEROUS: TLLUSTRATIONS.

TER: De EDs FON:

LONDON:
GHARLES GRIFFIN-AND COMPANY,
EXETER STREET, STRAND.

1888.
[Al Rights Reserved. |

‘FO

SK. JOSEPH LIsTER, Baronet,

M.D., D.C.L., LL.D., F.R.SS. (LOND. AND EDIN.),

PROFESSOR OF CLINICAL SURGERY IN KING'S sarees LONDON, SURGEON-EXTRAORDINARY TO THE QUEEN j

FORMERLY REGIUS PROFESSOR OF CLINICAL SURGERY IN THE UNIVERSITY OF EDINBURGH.

IN ADMIRATION OF
Che flan of Science,

WHOSE BRILLIANT DISCOVERIES HAVE REVOLUTIONISED
MEDICAL PRACTICE, AND CONTRIBUTED INCALCULABLY TO THE
WELL-BEING OF MANKIND 5
ACN JD EN GaneACT EA Dale “EO
Che Ceacher,

WHOSE NOBLE EARNESTNESS IN INCULCATING
THE SACREDNESS OF HUMAN LIFE
STIRRED THE HEARTS OF ALL WHO HEARD HIM:
This Work is respectinlly Dedicated

BY HIS FORMER PUPIL,

; THE TRANSLATOR.

PREFATORY NOTE TO THE THIRD ENGLISH EDITION.

In offering to the Profession this THirD English Edition, I would
only say that the whole work has again been thoroughly revised and
in many parts extended. In all oe a I have endeavoured to keep
it abreast of the latest investigations in Physiology and their bearing
on Practical Medicine and Surgery.

I have again to thank my publishers for enabling me to enhance
the usefulness of the work by very numerous additions to the Tllustra-
tions, which now number 692 as compared with the 494 of the First
Edition. Many of these new engravings are original; others are
derived from the 6th German edition of the work, from Stohr’s Lehrbuch
der Histologie, Quain’s Anatomy, Ferrier’s Functions of the Brain (2nd
dition), H. Obersteiner’s Anleitung beim Studium des Baues der nervosen
Centralorgane, Rollett’s Article on “Muscle” in the Real-Encyclopadie,
Gowers’ Diseases of the Nervous System, and most of those for the
chapter on Reproduction from Haddon’s Jntroduction to Embryology.

In addition, I have to tender special acknowledgments to my
colleagues and friends, Professors A. H. Young, James Ross, A. W. Hare,
and Dr Aug. D. Waller; as well as to Messrs Carl Reichert of Vienna,
W. Petzold of Leipzic, Rothe of Prague, Maw, Cassella, Krohne and
Sesemann, Evans & Wormall of London, and Ferries & Co. of Bristol.

For the first time the work appears here in one volume—an arrange-
ment adopted both to meet the wishes of Students and to facilitate
easy reference. I can but express a hope that the present Edition, in
its new form, will meet with the same very kind reception accorded to
its predecessors,
WILLIAM STIRLING.

THE OWENS CoLLEcE,
MANCHESTER, September 1888.

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THE fact that Professor Lanpois’ “Lehrbuch der Physiologie des Menschen”
has already passed through Four large Editions since its first appearance
in 1880, shows that in some special way it has met the wants of Students
and Practitioners in Germany. The characteristic which has thus com-
mended the work will be found mainly to lie in its eminent practicality ;
and it is this consideration which has induced me to undertake the task
of putting it into an English dress for English readers,

Landois’ work, in fact, forms a Bridge between Physiology and the
Practice of Medicine. It never loses sight of the fact that the Student
of to-day is the practising Physician of to-morrow. Thus, to every
Section is appended—after a full description of the normal processes—
a short réswmé of the pathological variations, the object of this being to
direct the attention of the Student, from the outset, to the field of his
future practice, and to show him to what extent pathological processes
are a disturbance of the normal activities.

In the same way, the work offers to the busy physician in practice a
ready means of refreshing his memory on the theoretical aspects of
Medicine. He can pass backwards from the examination of pathological
phenomena. to the normal processes, and, in the study of these, find new
indications and new lights for the appreciation and treatment of the cases
under consideration,

With this object in view, all the methods of investigation which may
with advantage be used by the Practitioner, are carefully and fully
described ; and Histology, also, occupies a larger place than is usually
assigned o it in Text-books of Phy siology.

A word as to my own share in the present version :— !

(1.) In the task of translating, I have endeavoured throughout to
convey the author’s meaning accurately, without a too rigid adherence
to the original. Those who from experience know something of the
difficulties of such an undertaking will he most ready to Se any
shortcomings they may detect. |

(2.) Vow considerable additions have been made to the Histological,
and also (where it has seemed necessary) to the Physiological sections.
All such additions are enclosed within square brackets [ ]. I have to

Xx PREFACE.

acknowledge my indebtedness to many valuable Papers in the various
Medical Journals—British and Foreign—and also to the Histological
Treatises of Cadiat, Ranvier, and Klein; Quain’s Anatomy, vol. IL, ninth
edition; Hermann’s Handbuch der Physiologie; and the Text-books on
Physiology by Rutherford, Foster, and Kirkes; Gamgee’s Physiological
Chemistry ; Ewald’s Digestion ; and Roberts’s Digestive Ferments,

(3.) The Illustrations have been greatly increased in number, viz.,
from 275 in the Fourth German Edition to 494 in the English version.
These additional Diagrams, with the sources whence derived, are dis-
tinguished in the List of Woodcuts by an asterisk.

There only remains for me now to express my thanks to all who
have kindly helped in the progress of the work, either by furnishing
‘Illustrations or otherwise—especially to Drs Byrom Bramwell, Dudgeon,
Lauder Brunton, and Knott; Mr Hawksley; Professors Hamilton and
M‘Kendrick ; to my esteemed teacher and friend, Professor Ludwig, of
Leipzic ; and, finally, to my friend, Mr A. W. Robertson, M.A., formerly
Assistant Librarian in the University, and now Librarian of the Aberdeen
Pubhe Library, for much valuable assistance while the work was passing
through the press.

In conclusion—and forgetting for the moment my own connection
with it—I heartily commend the work per se to the attention of Medical
Men, and can wish for it no better fate than that it may speedily become
as popular in this country as it is in its Fatherland.

WILLIAM STIRLING.

ABERDEEN UNIVERSITY,
November 1884.

-
.

y,

GHNERAL CONTENTS.

INTRODUCTION.

PAGE
The Scope of Physiology and its Relation to the other Branches of Natural Science, 5, eK
Matter, : ‘ : ; : ; : ; : : ¢ REVI
orcas, ; ; : : - ; : Pe 26.4700
Law of the Conserv ce of Ener = ; : d : ; : xli
Animals and Plants, ; ; : : : : : . welit
Vital Energy and Life, ; E ; : : ; : =. hiv

I. PHYSIOLOGY OF THE BLOOD.
SECTION
1. Physical Properties of the Blood, 1
2. Microscopic Examination of the Blood, : : : : : 3
3. Histology of the Human Red Blood-Corpuscles, ? : : ; 6
4, Effects of Reagents on the Blood-Corpuscles, . ; ; , 6
5. Preparation of the Stroma—Making Blood ‘‘ Lake Colsaned a 8
6
7
8

. Form and Size of the Blood- Gace of Different Animals, : d 9

. Origin of the Red Blood-Corpuscles, . ; . , : : ; 10

. Decay of the Red Blood-Corpuscles, . : j ‘ : 12
9. The Colourless Corpuscles—Leucocytes—Blood Pine Creston ' : ; 13
10. Abnormal Changes of the Blood-Corpuscles, . 8 8g os : : 17
11. Chemical Constituents of the Red Blood-Corpuscles, . : = : 18
12. Preparation of Hemoglobin Crystals, . ; E i ; : 19
13. Quantitative Estimation of Hemoglobin, 5 ‘ 3 ; : : 19
14, Use of Spectroscope, . ‘ ‘ : : ; 21
15. Compounds of Heemoglobin—Metheemoglobin, : ‘ ‘ : 22
16. Carbonic Oxide-Hemoglobin—Poisoning with Carbonic pone ; : : 24
17. Other Compounds of Hemoglobin, . : : , : : 25
18. Decomposition of Hemoglobin, . : ; ee : ; : 25
19. Hemin and Blood Tests, ‘ ; : ; : care : : 26
20. Hematoidin, . ee as
21. The Colourless Proteid of Hemoglobin, : 3 ‘ : : : 28
22. Proteids of the Stroma, : : 2 ; : 28
23. The other Constituents of Red Blood- -Corpuscles, : ; ‘ ‘ , 28
24. Chemical Composition of the Colourless Corpuscles, . Ey ens 29
25. Blood-Plasma, and its Relation to Serum, : : : ‘ : 29
26. Preparation of Plasma, oe ATG EP, ee : : ; , 29
27. Fibrin—Coagulation of the Blood, gi 3 : ‘ ; 2 efit OO)
28. General Phenomena of Coagulation, . J ; fF eat eT: , . 31
29. Cause of Coagulation of the Blood, 7 : : . ; : 33

30. Source of the Fibrin-Factors, . , : ; ; : ‘ 36

(

a See

xii CONTENTS.

SECTION ‘
81. Relation of the Red Blood-Corpuscles to the Formation of Fibrin, . : : 37 ‘a
32. Chemical Composition of the Plasma and Serum, : ; , : a | a
33. The Gases of the Blood, . ; : ; . , : : 39 '
34. Extraction of the Blood Gases, : : : : : ’ 40.

35. Quantitative Estimation of the Blood Gace, : : ; . ; : 42

36. The Blood Gases, - i . : ; : : : 42

37. Is Ozone (Og) present’ in Blood ! : : ; : ‘ 3 43

38. Carbon dioxide and Nitrogen in Blood, ; : ; : : ; 44

39. Arterial and Venous Blood, . . : , . : ; : 45

40. Quantity of Blood, ‘ ; : 2 45

41. Variations from fhe Normal Conditions of fhe Blood, : : : ; 46

II. PHYSIOLOGY OF THE CIRCULATION.

42, General View of the Circulation, ; ‘ : ; ; ‘ : 50
43. The Heart, 2 : : . ; ; ; 51
44. Arrangement of the C ardine Muscular Bibecs, ‘ : ; : ; 51
45. Arrangement of the Ventricular Fibres, ; : ; ; : : 53
46. Pericardium, Endocardium, Valves, . ; : : ; F : 54
47. Automatic Regulation of the Heart, . : ; ; ; : ‘ 55
48. The Movements of the Heart, ; : : , : ‘ 57
49. Pathological Disturbances of Gardixe Acti ae : ; : ; 60
50. The Apex-Beat--The Cardiogram, ; : : 2
51, The Time occupied by the Cardiac Mov einehts, : : P : 66
52. Pathological Disturbance of the Cardiac Impulse, : : . ; : 69
58. The Heart-Sounds, : : : : : : : ‘ 71
54. Variations of the Heart- Soenia: ; : : ‘ , 73
55. The Duration of the Movements of the Heart: : : : ; : 74
56. Physical Examination of the Heart, . : , ; ‘ 75
57. Innervation of Heart—Cardiac Nerves, ; : ; ; ; ; 76
58. The Automatic Motor-Centres of the Heart, . . : ; ‘ 78
59. The Cardio-Pneumatic Movements, . ‘ 5 : . : 86
60. Influence of the Respiratory Pressure of the Henri, : : 2 : ; 87

THE CIRCULATION.

61. The Flow of Fluids through Tubes, . : “ ; ; ; 89
62. Propelling Force, Velocity of Current, Lateral Panu F : ; F 90 }
63. Currents through Capillary Tubes, ; ; ; : 91
64. Movements of Fluids and Wave-Motion in Elastic Tarbes, ; : ; : 92
65. Structure and Properties of the Blood- Vessels, ; ; ‘ ; : 92
66. Investigation of the Pulse, . ; : : , ; ; : 97
67. Pulse Tracing or Sphygmogram, ; ; : : : ; . 163
68. Origin of the Dicrotic Wave, . : ; ; : : F . 108
69. Dicrotic Pulse, . . : , ; i ; : : . 106
70. Characters of the Pulse, ~ ; : : . 106
71. Variations in the Strength, Tension, aud Volume of the Pulee, : , . 108
72. The Pulse-Curves of various Atoring: ; ; : j : , . 108
73. Anacrotism, . ' : . 109
74. Influence of the Respiratory Movements on the Pulse-Curve, , : . 110
75. Influence of Pressure upon the Form of the Pulse-Wave, ‘ . ‘ ae
76. Rapidity of Transmission of Pulse- Waves, ; ; | 3

77. Propagation of the Pulse-Wave in Elastic Tubes, ‘ Fut f M
78. Velocity of the Pulse-Wave in Man, . ; ; 7 ' ;
79. Other Pulsatile Phenomena, $ .

CONTENTS.

SECTION

104.
. Historical Retr et

106.
107.
108.
109.
110.
iii.
112.
113.
114.
115.
116.
117.
118.
119.
120.
121.
122.
123.
124,
125.
126.
“RBZ,

. Vibrations communicated to the se by the Action of the Heart,
. The Blood-Current, F

. Schemata of the Circulation, .

. Capacity of the Ventricles,

. Estimation of the BJood-Pressure,

. Blood-Pressure in the Arteries,

. Blood-Pressure in the Capillaries,

. Blood-Pressure in the Veins,

. Blood-Pressure in the Pulmonary Ar ee

. Measurement of the Velocity of the Blood-Streaim,

. Velocity of the Blood in Arteries, Capillaries, and Veins,
. Estimation of the Capacity of the Ventricles,

. The Duration of the Circulation,

. Work of the Heart,

. Blood-Current in the Sihallest Wessel: ,

. Passage of the Blood-Corpuscles out of the Vessels—(Diapedess
. Movement of the Blood in the Veins,

. Sonnds or Bruits within Arteries,

. Venous Murmurs,

. The Venous Pulse Phtshosen,

. Distribution of the Blood,

. Plethysmography,

. Transfusion of Blood,

THE BLOOD-GLANDS.

: The Spleen—Thymus—Thyroid—Supra-Renal Raed ae

Coccygeal and Carotid Glands,
Comparative, .

III. PHYSIOLOGY OF RESPIRATION.

Structure of the Air-Passages and Lungs,

Mechanism of Respiration,

Quantity of Gases Respired,

Number of Respirations,

Time occupied by the Respiratory Monet
Pathological Variations of the Respiratory Movements,
General View of the Respiratory Muscles,

Action of the Individual Respiratory M useles,
Relative Size of the Chest, .

Pathological Variations of the Percussion Senne
The Normal Respiratory Sounds,

Pathological Respiratory Sounds,

Pacurs | in the Air,Passages during Te
Appendix to Respiration, .

Peculiarly Modified Respiratory Sounds,

Quantitative Estimation of CO,, O, and Watery Vapour,
Methods of Investigation,

Composition and Pioper ties of Atmospheric Air,
Composition of Expired Air, :

Daily Quantity of Gases Exchanged, . ‘

Review of the Daily Gaseous Income and Expenditure,
Conditions influencing the Gaseotis Exchanges,

xiv CONTENTS. ‘

SECTION

128. Diffusion of Gases within the Lungs,

129. Exchange of Gases between the Blood and Air,
130. Dissociation of Gases, ‘
131. Cutaneous Respiration,

132. Internal Respiration, :

133. Respiration in a Closed Space,

134. Dyspnea and Asphyxia,

135. Respiration of Foreign Gases,

136. Accidental Impurities of the Air,

137. Ventilation of Rooms, :

138. Formation of Mucus, .

139. Action of the Atmospheric Pressure,

140. Comparative and Historical,

IV. PHYSIOLOGY OF DIGESTION.

141. The Mouth and its Glands,
142. The Salivary Glands, .
143. Histological Changes in Saliv: ary @iande:
144. The Nerves of the Sali ary Glands,
145. Action of Nerves on the Salivary Secretion,
146. The Saliva of the Individual Glands,
147. The Mixed Saliva in the Mouth,
148. Physiological Action of Saliva,
149. Tests for Sugar,
150. Quantitative Estimation of see
151. Mechanism of the Digestive Apparatus,
152. Introduction of the Food, :
153. The Movements of Mastication,
154. Structure and Development of the Teeth,
155. Movements of the Tongue, ,
156. Deglutition,
157. Movements of the Seoul:
158. Vomiting,
159. Movements of thie faeaune,
160. Excretion of Fecal Matter,
161. Conditions influencing the Moy cae of his Preesine:
162. Structure of the Siomach.
163. The Gastric Juice,
164. Secretion of Gastric Juice,
165. Methods of obtaining Gastric Juice,
166. Process of Gastric Digestion, .
167. Gases in the Stomach,
168. Structure of the Pancreas,
169. The Pancreatic Juice,
170. Digestive Action of the Pancreatic Ju uice,
171. The Secretion of the Pancreatic Juice,
172. Preparation of Peptonised Food, .
173. Structure of the Liver,
174. Chemical Composition of the Liver-Cells,
175. Diabetes Mellitus,’ or Glycosuria,
176. The Functions of the Liver,
177. Constituents of the Bile,
178. Secretion of Bile,
179. Excretion of Bile,

CONTENTS. XV

SECTION PAGE
180. Reabsorption of Bile—Jaundice, ; : : -* 2272
181. Functions of the Bile, : ; : , ; ; : a” - RS
182. Fate of the Bile in the Intestine, : ; 7. Gay: +. 275
183. The Intestinal Juice, : ; ; : .- 276
184. Fermentation Processes in fhe Tatecnne: : : ; d ; so 29
185. Processes in the Large Intestine, : : ; : ; ey A235)
186. Pathological Variations, : : ’ , : af 2 285
187. Comparative Physiology, : : : : : : 7° 288
188. Historical Retrospect, , : : : . 5/2, 200

189.
190.
Tor,
192.
193.
194.
195.
196.
197.
198.
199.
200.
201.
202.
203.
204.
205.

206.
207.
208.
209.
210.
211.
212.
213.
214,
215.
216.
4217.
218.
219.
220.
221.
222.
223.
224,
2957
226.
227.
228.

V. PHYSIOLOGY OF ABSORPTION.

The Organs of Absorption, . : : ; p= 290
Structure of the Small and Large idee : a tee ks n> 200
Absorption of the Digested Food, . : é ; e295
Absorptive Activity of the Wall a the fatesane. : : oor
Influence of the Nervous System, . , ; ; . 801
Feeding with ‘‘ Nutrient Enemata,” : : ; . 601
Chyle- Vessels and Lymphatics, : ; ; s : : 4. ASO
Origin of the Lymphatics, . ; ; : ’ . 3802
The Lymph-Glands, . , : : a . 804
Properties of Chyle and leviaih : ; : : ; . 3806
Quantity of Lymph and Chyle, : . : #) OOS
Origin of Lymph, ; ’ . 809
Movement of Chyle and rae , : : : : ; > ed
Absorption of Parenchymatous Effusions, . . om, : é . 812
Dropsy, Gidema, Serous Effusions, . : : : : = 12
Comparative Physiology, : : : : : : 3 olf
Historical Retrospect, , , ‘ . : : ; . 3814

VI. PHYSIOLOGY OF ANIMAL HEAT.

Sources of Heat, ; : : : o) ols
Homoiothermal and Poileieticrmal aanale : ; , ; a eee
Methods of Estimating Temperature—Thermometry, ; s 819
Temperature Topography, . : : : = 8oh
Conditions Influencing the iemnenince of Creare : : : . 822
Estimation of the Amount of Heat—Calorimetry, . ; d : ee Uae
Thermal Conductivity of Animal Tissues, . : : ; : : «820
Variations of the Mean Temperature, . : : ' ‘ : © 825
Regulations of the Temperature, ; : , ‘ . . . $828
Income and Expenditure of Heat, . a : : ‘ . 831
Variations in Heat Production, ; : ; : : . 33d
Relation of Heat Production to Bodily Work, : ; is : . 833
Accommodation for Different Temperatures, : : : ; . 334
Storage of Heat in the Body, ; 5 : ; ; . 3834
Raver. : : : i : F iu Goo
Artificial Increase of the Temperature, , ; : : . 336
Employment of Heat, ; : : ; : : : x OOK
Increase of Temperature post mortem, é : : ‘ ol SOS7
Action of Cold on the Body, . a ioe ; : ; a aed:
Artificial Lowering of Temperature, .~ ; feats OG ; .| -, 888
Employment of Cold, sz ; ; , : ; : . .839
Heat of Inflamed Parts, ; Be ‘. : : } .' , 839

Historical and Comparative, iy : : j ; , . 340

xvi CONTENTS.

VII. PHYSIOLOGY OF THE METABOLIC PHENOMENA |
OF THE BODY.

SECTION PAGE

229. General View of Food-Stuffs, ; ; : a : . d4l1

230. Structure and Secretion of the Mammary Glande; ; d ; ; . 843

231. Milk and its Preparations, . ; ‘ : ; : ; . 845

232. Eggs, ‘ : : ; : : : ; ; . 849 -
233. Flesh and its Preparations, . ; : : : . ‘ . 849

234. Vegetable Foods, é ; ; : e ; . oe

235. Condiments—Coffee, Tea, aud ieohel : : : ; : . 852

236. Equilibrium of the Metabolism, ; : , : : . 355

237. Metabolism during Hunger and Starvation, . : ‘ ‘ : . . 360

238. Metabolism during a purely Flesh Diet, ; . ; ' . Soa—
239. A Diet of Fat or of Carbohydrates, . . : ‘ : ; . 363 |
240. Mixture of Flesh and Fat, . : : : : . : “St - :
241, Origin of Fat in the Body, . : ; . 864 |
242. Corpulence, . ; : ‘ ; : : . 366

243. The Metabolism of the Tesiies: ; : : : : ; . 867

244. Regeneration of Organs and Tissues, ; ' ; : . 869

245. Transplantation of the Tissues, : : : : : . sf

246. Increase in Size and Weight during Growth, é , : ; . 872 ‘Zi

GENERAL VIEW OF THE CHEMICAL CONSTITUENTS OF
THE ORGANISM.

247. Inorganic Constituents, ; ; ‘ F : : ' . 878
248. Organic Compounds—Proteids, : . : : . 874
249. The Animal and Vegetable Proteids and their Post ties, . : : . 3876
250. The Albuminoids, . j ; ; ; ; : ; . 878
251. The Fats, : , ; ; : : : : : . 881
252. The Carbohydrates, . , ; ; : : : , . 882
253. Historical Retrospect, ; : ; ; ' ; ‘ . 385

VIII. THE SECRETION OF URINE.

254. Structure of the Kidney,
255. The Urine,
256. Organic Constituents ee ene rea,
257. Qualitative and Quantitative Estimation of Urea,
258. Uric Acid, ;
259. Guahiatve and Quantitative ehmaten of cia cid.
260. Kreatinin and other Substances,
261. Colouring Matters of the Urine, , ; , : : .
262. Indigo, Phenol, Kresol, Pyrokatechin, ; . : 5 ve
263. Spontaneous Changes in Urine, Fermentations,
264. Albumin in Urine,
265. Blood in Urine,
266. Bile in Urine,
- 267. Sugar in Urine,
268. Cystin,
i 269. Leucin, Tyrosin,
270. Depositsin Urine, .
271. General Scheme for Detecting Urinary Deposits
272. Urinary Calculi,
273. The Secretion of Urine, ; .

CONTENTS. Xvil

SECTION PAGE
274. The Formation of Urinary Constituents, : : a : ; . 425
275. Passage of Various Substances into the Urine, : E , ; . 426
276. Influence of Nerves on the Renal Secretion, — ; : : : a: aoe
277. Uremia, Ammoniemia, F ‘ ; : ae ; . 430
278. Structure and Functions of the tester : ; P | ? ee
. 279. Urinary Bladder and Urethra, 5 : ' ; : ; . 438
280. Accumulation and Retention of Urine, ; : : : : . 434
281. Retention and Incontinence of Urine, . au : ’ : . 436
282. Comparative and Historical, : : : . ; F . 487

IX. FUNCTIONS OF THE SKIN.

283. Structure of the Skin, Nails, and Hair, ; : : : : ~ 487
284. The Glands of the Skin, : : ; ; , : : . 442
285. The Skin as a Bioescuive Covering, ; ; : : . 443
286. Cutaneous Respiration and Section Sweat. : : ; ; . 444
287. Conditions Influencing the Secretion of Sweat, : : : : . 446
288. Pathological Variations, . , ‘ ; : . 448
289. Cutaneous Absorption—Galvanic Conduction, ; : ; : . 449
290. Comparative—Historical, . : ‘ ; ‘ : ; . 449

X. PHYSIOLOGY OF THE MOTOR APPARATUS.

291. Ciliary Motion, Pigment Cells, 3 é ; ; ; : se. 2 AS
292. Structure and Arrangement of the Muscles, : é , . 453
293. Physical and Chemical Properties of eee ; . : ; . 462
294. Metabolism in Muscle, ’ : ; : : : : . 464
295. Rigor mortis, z ; ‘ stb : : ‘ . 466
296. Muscular eee : 3 : ee ts ' 2.2 £00
297. Changes in a Muscle during Caueeuon : : : ea A 41D
298. Muscular Contraction, ; : iy : ee ys
299. Rapidity of Transmission of a Muscular Coherent, : : : ASF
300. Muscular Work, ; : ; ; ; ; : : . ~ 489
301. The Elasticity of Muscle, 2 ; : ; ; « 49]
302. Formation of Heat in an Active Diasdle: ; ; : ; ; . 498
303. The Muscle-Sound, . ‘ ; ae : ; , : . 495
304. Fatigue and Recovery of Muscle, : : ; . : . . 495
305. The Mechanism of the Joints, : : : P : . 498
306. Arrangement and Uses of the Muscles of the Hoa hee : ; : . 500
307. Gymnastics—Pathological Motor Variations, : : ; : . 508
308. Standing, . : : ; ; ; ‘ : : . 504
309. Sitting, 5 eens : : ; : - ; ‘ . 505
310. Walking, Running, and Leaping, . ; ; ; ; . 505

311. Comparative, , : ; : , Wee ge She : . 508

VOICE AND SPEECH.

312. Voice and Speech, . ; ; ‘ ; : » 509

313. Arrangements of the Larynx, ; ; : : 3 : . 510

314. Organs of Voice—Laryngoscopy, ‘ ; : : . 515

815. Conditions Modifying the Laryngeal Sounds, —_.. : : : . §18

316. Range of the Voice, . , ‘ BP ieee att , ; : . 519

317. Speech—The Vowels, ‘ on ‘ ‘ ; Saints eo
2 318. The Consonants, . : : ; : > $21
319. Pathological Variations of Veicw and’ Speech’; os ‘ ‘ -.» Pee
r: 820. Comparative—Historical, . : “| em “4 . be gut 523
%

XViil CONTENTS.
XI. GENERAL PHYSIOLOGY OF THE NERVES AND
ELECTRO-PHYSIOLOGY.

SECTION . PAGE
321. Structure and Arrangement of the Nerve-Elements, . : wg . , 625
322. Chemical and Mechanical Properties of Nerve-Substance, . : 5 . 531
323. Metabolism of Nerves, j , ; : ; : . 582
324. Excitability of Nerves—Stimuli, ; : . 533
325. Diminution of Excitability—Degeneration aud Regeneration of Ner ves, . | , SRF
326. The Galvanic Current, : : ‘ : : . a2
327. Action of the Galvanic Ciment Gale PE ory : : : : . 548
328. Electrolysis, ; : . 545
329. Induction--Extra- CRY CES Indue ain, Os : . : . 549
330. Du Bois-Reymond’s Inductorium, . : ; : .,
331. Electrical Currents in Passive veer le and Not Bin ge : . 654;
332. Currents of Stimulated Muscle and Nerve, : . 2 ; . 857
333. Currents in Nerve and Muscle during Electrotonus, ; ; ; . 561
334. Theories of Muscle and Nerve Currents, : : — , : . 662
335. Electrotonic Alteration of the Excitability, "ae , : ‘ . 665
336. Electrotonus—Law of Contraction, . ; : : . 567
337.. Rapidity of Transmission of Nervous Ihpulses, eo . ; : : . 570
338. Double Conduction in Nerves, ; : : . 878
339. Therapeatical Uses of Electricity —Reaction ot Degeneration : . 574
340. Electrical Charging of the Body, : ‘ ; , : . 579
341. Comparative—Historical, . . or: ay 3: Mas : : : . 579

XII. PHYSIOLOGY OF THE PERIPHERAL NERVES.

342. Classification of Nerve-Fibres, , : Nae ‘ , ‘ « $81
343. Nervus Olfactorius, . ‘ : ‘ae , ; : : . 584
344. Nervus Opticus, : ; Are : ; ' ; . 884
345. Nervus Oculomotorius, . : ‘ : ; : : . 587
346. Nervus Trochlearis, . - : : : if —_ : . 589
347. Nervus Trigeminus, . : a eae Se é . 590
348. Nervus Abducens, . | : Ky ga eas ans : : , . 599
349. Nervus Facialis, : : . ; : : ; . 599
350. Nervus Acusticus, . aa ; ~ oa bay “Ry : . 603
351. Nervus Glosso-pharyngeus, . - ; : i. , : . 606
352. Nervus Vagus, : ; ‘ Se P <s : ; . 606
353. Nervus Accessorius, . . -: .., : : : : ir cree. ae
354. Nervus Hypoglossus, : ee : : . °615
355. The Spinal Nerves, . pe FY = 2 ete’ oer : . 615
356. The Sympathetic Nerve, : 3 a : ao : ; . +620

357. Comparative—Historical, . arc re : ; . VV Se

XIII. PHYSIOLOGY OF THE NERVE-CENTRES.

358. General, : ys A a a : . “a

359. Structure of the Spiisl Gard: ; ; eke Se , ; . "626

360. Spinal reflexes, ; , , ; CES as
361. Inhibition of the reflexes, . . ; : : , : . 639 » ol
362. Centres in the Spinal Cord, . ; pO ee gp FOES Ct ae ; . 643 2
363. Excitability of the Spinal Cord, . ° A \* 6th a
364. The Conducting Paths in the Bee Gord, ; Rea ibe Ne tea ; . 646

865. General Schema of the Brain, fot Je estou . 649

366. The Medulla Oblongata, .-° ~ . bits —< ees ; : 655

CONTENTS. . X1X

SECTION PAGE

367. Reflex Centres of the Medulla Oblongata, . : : : ‘ . 659
368. The Respiratory Ceutre, : 7 : : ; : ; =, OGL
369. The Cardio-Inhibitory Centre, ; : ; : : ‘= G67
370. The Accelerans Cordis Centre, é ; F . oe aes . 669
371. Vaso-motor Centre and Vaso-motor Nerves, , , : : =» 672
372. Vaso-dilator Centre and Vaso-dilator Nerves, : ; : ‘ eo OLS
373. The Spasm Centre—The Sweat Centre, : : : ; : . 680
374. Psychical Functions of the Cerebrum, ; : : ; ‘ =~ 681
375. Structure of the Cerebrum—Motor Cortical Centres, ; , ‘ . 686
376. The Sensory Cortical Centres, , : , ; . : > OL
377. The Thermal Cortical Centres, , ; ; ; ; : s 1408
378. Topography of the Cortex Cerebri, . : ‘ : : ; . 706
379. The Basal Ganglia—The Mid- ieuin, ' © os : : ; Pa ENO
380. The Structure and Functions of fie Cer oncliun, : : : : “hee
281. The Protective Apparatus of the Brain, : : ; : - ¢26
382. Comparative—Historical, , ; : : : : : oho

XIV. PHYSIOLOGY OF THE SENSE ORGANS.
1. SIGHT.

383. Introductory Observations,

384. Histology of the Eye,

385. Dioptric Observations, ;

386. Formation of a Retinal Image,

387. Accommodation of the Eye,

388. Normal and Abnormal Refraction,

389. The Power of Accommodation,

390. Spectacles,

391. Chromatic Aberation and auinons.

392. The Iris, ;

393. Entoptical Phenomena,

394. Illumination of the Eye Phi Opthalmossope
395. Aetivity of the Retina in Vision,

SST SST
He He OD OO
ND WwW eS

COND Or W —

STS ST a ST SS STO SST SST
MIO OS Sd OV OV Or OW Or He
CO Fm Ww

396. Perception of Colours, : : ; : , 3
397. Colour-blindness, ; F : ; : : ; ; ae RES
398. Stimulation of the Retina, . , : , : : ek.
399. Movements of the Eyeballs, ° : : : ; ; ‘ oo EBS
400. Binocular Vision, . ; : : ; : : fh OL
401. Single Vision tdentieal Pointe : : : , ote Oe
402. Stereoscopic Vision, , : : : , : ~ 789
403. Estimation of Size and Distance, : . . ; : a OR
404, Protective Organs of the Eye, ; ; : : = : . £93
405. Comparative-—Historical, . : ; : : . . » 795

2. HEARING.

406. Structure of the Organ of Hearing, : ‘ ; . : - 797
407. Physical Introduction, ; : ; : ; ; : - 498
408. Ear Muscles, | ‘ , . ae <7 ; ea i. 3898
409. Tympanic Membrane, Sa Pas MD AT : : so 499
410. The Auditory Ossicles and their Muscles; . : . . - 801
411. Eustachian Tube—Tympanum, ; , i : i ‘ - - 805
412. Conduction of Sound inthe Labyrinth,; . ° . ° . °: . . 806

413. Structure of the Labyrinth, . : _ , : ‘ - 808

Xx | | CONTENTS.

SECTION

414. Auditory Perceptions of Pitch,
415. Perception of Quality—Vowels,
416. Action of the Labyrinth,

417. Harmony—Discords—Beats,
418. Perception of Sound,

419. Comparative—Historical,

3. SMELL.
420. Structure of the Organ of Smell,
421. Olfactory Sensations,
4, TASTE.
422. Position and Structure of the Organs of Taste, 3 : : ; . 823
423. Gustatory Sensations, : ; ‘ ; : : : . 825
5. TOUCH.
424. Terminations of Sensory Nerves, ? : . ; : F - 827
425. Sensory and Tactile Sensations, : ; i : . . 830
426. The Sense of Locality, : : ; : : ‘ . 831
427. The Pressure Sense, . , : . : ; F : . 833
428. The Temperature Sense, , : ‘ ; ‘ : . . 836
429. Common Sensation—Pain, . : : : : : 5 . 838
430. The Muscular Sense, : : F ; : : : . 839 | B

XV. PHYSIOLOGY OF REPRODUCTION AND DEVELOPMENT. |

431. Forms of Reproduction, : - ; , ; . . . 841
432. ‘lestis—Seminal Fluid, é , , : : : . . 844 |
433. The eh a mea ; : ee ‘ ; > 2a
434. Puberty, : ; ‘ , ; : : : . 858
435. Menstruation, ; ‘ . ‘ : : : . . 854
436. Penis—Erection, ; ; ; : : : . 857 |
437. Bjaculation—Reception of the Sante. : : : - . . 859
438. Fertilisation of the Ovum, . : : nA ; ; . 860 .
439. Impregnation and Cleavage of the Crate ‘ : y : ae . 861
440. Structures formed from the Epiblast, : : : ; . 865
441. Structures formed from the Mesoblast and Hypoblas ; ; - . 867.
442. Formation of tlhe Heart and Embryo, : ; ; : . 869
443. Further formation of the Body, j : ; : : ‘ - &70
444. Formation of the Amnion and Allantois, . F oat ; ; . 871
445. Human Fetal Membranes—Placenta, : ; ; ; ; - , ae
446. Chronology of Human Development, : : : ; : : ee
447. Formation of the Osseous System, . : ; ; : a . 878
448. Development of the Vascular System, ; ; ‘ . ; . 882
449. Formation of the Intestinal Canal, . ; ‘ : . ; . 886
450. Development of Genito-Urinary Organs, ; : ; ‘ : . 888
451. Formation of the Central Nervous System, . - ‘ , oy) oo
452. Development of the Sense a : ; a > ; P . 892
453. Birth, ‘ ; ‘ ‘ ‘ , , - 894
454. Comparative—Historical, ‘ ; : ; i oe ee . ° 895
Appendiz A.; Bibliography, . . 898

Appendiz B.; Tables of Measure (Metric and Ordinary) sad of Temperature, - 902
Index, . ; : . - 903

7 $
~

Jolson Laie Pra LLONS.

FIGURE

. Human coloured blood-corpuscles, :
. Apparatus of Abbé and Zeiss for estimating the iibod: sormucees :
. Mixer, : ; ;
. Gower’s hemacy beitrote (Hamisele 4),

. Crenation of human blood- corpuscles,

. Red blood-corpuscles showing various changes of shane:

. Effect of reagents on blood-corpuscles (Stirling),

. Vaso-formative cells, :

. White blood-corpuscles and fibrin,

. White blood-corpuscles (A7ein), :

. Amceboid movements of colourless corpuscles,

. Blood-plates and their derivatives,

. Hemoglobin crystals,

. Gower’s ie noloninomeer aibkate Y)s

. Fleischl’s hemometer (Reichert),

. Scheme of a spectroscope, :

. Various spectra of hemoglobin and its Enieaune

. Heemin crystals,

. Hemin crystals prepared fr om fates of bloaa:

. Hematoidin crystals,

. Hewson’s experiment,

. Scheme of Pfliiger’s gas-pump,

. Micrococcus, bacterium, vibrio,

. Bacillus anthracis,

. Scheme of the circulation,

. Muscular fibres from the heart,

. Muscular fibres in the left auricle,

. Muscular fibres in the ventricles,

. Lymphatic from the pericardium (Cadiat),

. Section of the endocardium (Cadiat),

. Purkinje’s fibres (Ranvier), .

. Cast of the ventricles of the human Heart,

. The closed semilunar valves, : :
. Gaule’s maximum and minimum maoniere: (Omhetdien). :
. Manometer of Gaule (Gscheidlen),

. Various cardiographs (Hermann),

. Cardiogram, .

. Arteriogram and Gordiogram,

. Curves of the apex-beat, . °

. Changes of the heart during systole, and sections of thorax,
. Dog’s heart, posterior surface (Ludwig-and Hesse),

2. Left lateral surface (Ludwig and Hesse),

. Anterior surface (Ludwig and Hesse),

. Base of heart (Ludwig and Hesse), .

PAGE

XXii LIST OF ILLUSTRATIONS.

FIGURE

*45. Base of heart in systole and diastole aac and cru ;

46. Curves from a rabbit’s ventricle,

*47. Marey’s registering tambour (Hermann),
48. Curves obtained with a cardiac sound,
49. Curves from the cardiac impulse,

*50. Scheme of cardiac cycle,

*51. Position of the heart in the chest Uinidenkn ana Gen dner ),

*52. Curves of excised rabbits’ hearts (Stirling, after Waller),
*53. Heart of frog from the front (Ecker), ;
*54. Heart of frog from behind (Zcker),

*55. Auricular septum (Ecker),

*56. Bipolar nerve-cells from a frog's eee

*57. Scheme of frog’s heart (Brunton),

*58. Stannius’s experiment (Brunton),

*59. Luciani’s groups of cardiac pulsations (Hermann),
*60. Scheme of a frog-manometer (Stirling),

*61. Perfusion cannula (Aronecker and Stirling),

*62. Roy’s tonometer (Stirling), .

*63. Curves of a frog’s heart at different Sumgersuices (enna

64. Cardio-pneumograph of Landois,

65. Apparatus for showing the effect of icon

66. Cylindrical vessel filled with water,

67. Cylindrical vessel with manometers,

68. Small artery with its various coats,

69. Capillaries injected with silver nitrate, :
*70. Longitudinal section of a vein at a valve (Cadiat),

71. Sphygmometer of Herisson,

72. Scheme of Marey’s sphygmograph, . :
*73. Marey’s improved sphygmograph (2B. Braimzell),
*74. Ludwig’s sphygmograph, : :
*75. Dudgeon’s sphygmograph (Dudgeon),

76. Scheme of Brondgeest’s pansphygmograph,

77. Scheme of Landois’ angiograph,

78. Pulse-curves of the carotid, radial, and posterior ae arenes

*79. S. Mayer’s gas- aaiiiy ornoscope:

80. Hemautographic curve,
*81. Sphygmogram of radial artery (Duds geon),
*82. Irregular pulse, mitral regurgitation,

83. Sphygmograms of various arteries,

*84. Pulse tracings after amyl] nitrite (Stirling, afer feb. :

*85. Aortic regurgitation,
86. Pulsus dicrotus, P. caprizans, P. monocrotua,
*87. Hyperdicrotic pulse,
88. Pulsus alternans,
89. Curves of the posterior tibial artery,
90. Anacrotic pulse-curves,
91. Anacrotic pulse-curves,
92. Influence of the respiration on the sphygmogr am,
93. Pulse-curves during Miiller’s and Valsalva’s experiments,
94, Pulsus paradoxus, . ;
95. Various radial curves altered by pressure,
96. Pulse tracings of the radial artery, . ‘
97. Tracings from the posterior tibial, and carotid arteries,

98. Apparatus for registering the molar motions of the body, .

99. Vibration and heart curves,

112
112
113

116

LIST OF ILLUSTRATIONS.

FIGURE

100.
*101.
*102,
*103.

104,
*105.
*106.
*107.
*108.
*109.
“110,

a1,

112,

113.

114.
*UTG,

116.

bye

118.
*T19.
*120.
*t21,
*122.
ba B42
*124,
*125.
*126.
a 8
*128.

129.
*130.
“133;

132.
*133.

134.

135.

136.
. Pneumatograms,

. Section through ecolraghe (Her aes
2 Action of intercostal muscles,

. Crytometer curve, .

. Sibson’s thoracometer,

. Topography of the lungs and heath

. Andral and Gavarret’s respiration apparatus,
. Scharling’s apparatus,

. Regnault and Reiset’s apparatus,

. v. Pettenkofer’s apparatus,

. Valentin and Brunner’s apparatus,

. Ciliated epithelium,

. Objects found in sputum,

Ludwig and Fick’s kymographs, 23
Ludwig’s improved revolving cylinder (Hernan
Blood-pressure tracing of the carotid of a dog (Hermann),
Fick’s spring manometer, by Hering (Hermann:

Fick’s flat spring kymograph, :

Scheme of height of blood-pressure,

Depressor curve (Stirling), .

Blood-pressure and respiration tracings fier sanultesemaly (Stir ling), .

Blood-pressure tracing during stimulation of the vagus (Stirling),
Apparatus of v. Kries for capillary pressure (C. Ludwig), .
Scheme of the blood-pressure, ‘ : :
Volkmann’s hemadromometer,

Ludwig and Dogiel’s rheometer,

Vierordt’s heneuchonc ree omogra pie
Photohematachometer,

Scheme of sectional area (after ee.

Diapedesis,

Various forms of venous nites

Mosso’s plethysmograph,

Section of spleen (Stéh7), ;

Trabecule of the spleen (Cadiat), .

Adenoid tissue of spleen (Cadiat), .

Malpighian corpuscle of the spleen (Cadiat),

Elements of splenic pulp (S¢éh7),

Tracing of the splenic curve (Roy),

Tye gland (Cadiat),

Elements of the thymus gland (Cadiat),

Thyroid gland (Cadiat), :

Supra-renal capsule (Cadiat),

Schemata of the circulation,

Human bronchus (Hamilton),

Air-vesicles injected with silver nitrate iHome.
Scheme of the air-vesicles of lung, .

Interlobular septa of lung (Hamiltoi),

Scheme of Hutchinson’s spirometer,

Brondgeest’s tambour and curve,

Marey’s stethograph (I‘Kendrick),

. Squamous epithelium from the month (Stir ling), . :
. Mucous follicle and salivary corpuseles (Schenk),

. Section of tonsil (Stéhr),

. Scheme of glands, .

. Rodded epithelium of a salivar y duct;

x 'y * me: » , ee — = 7 —— . ’ eel Li aa Z

XXivV LIST OF ILLUSTRATIONS.

FIGURE

155. Histology of the salivary glands, .
*156. Human sub-maxillary gland (Heidenhain),
*157. Parotid gland of rabbit at rest (Heidenhain),
*158. Parotid gland of rabbit, active phase (Heidenhain),
*159. Scheme of the nerves of the salivary glands (Stirling),
*160. Diagram of a salivary gland (Stirling),

161. Apparatus for estimation of sugar, .

162. Polarisation apparatus,

163. Vertical section of a tooth,

164. Dentine,

165. Interglobular sone

166. Dentine and enamel,

167. Dentine and crusta petrosa,

168.
169. ¢ Development of a tooth, . : ‘ ; ; ; : . ° 226
170.
171. Section of esophagus (Schenk), . : ; ; : : ‘ 230
172. Perineum and its muscles, ; : : F : : : 234
173. Levator ani externus and latcenas. ; : : ; ‘ 235
*174. Vertical section of Auerbach’s plexus (Geduny, , , 4 ; ; 236
*175. Auerbach’s plexus (Cadiat), ‘ : : . ‘ : : 236
*176. Meissner’s plexus (Cadiat), . : : : ‘ acialy : 237
*177. Vertical section of stomach as, P F ‘ P ; 240
178. Goblet cells, : : — 5 : ; 240
179. Surface section of gastric mucous omnes , ; : ‘ : 240
180. Fundus gland of the ee ‘ ‘ ‘ . : . 240
181. Pyloric gland, 5 ; F : : ; ; 241
182. Scheme of the gastric mucous sivsvieatie, : ; : : ; : 242 -
*183. Pyloric mucous membrane (Hermann), . ; , : : ' 243
*184. Pyloric glands during digestion (Hermann), : ; ‘ , ‘ 243
*185. Scheme of pyloric fistula (Stirling), ‘ ; ' . ; : 245
*186. Section of the acini of the pancreas (Hermann), . : ‘ : : 252
187. Changes of the pancreatic cells during activity, . ‘ ‘ ; ; 253
*188. Section of human liver (Stéhr), . : ‘ : , ‘ ‘ 258
189. Scheme of a liver lobule, . ‘ P ; : : ‘ : 259
*190. Human liver-cells (Cadia‘), ‘ ‘ ‘ ‘ ‘ , ‘ 260
*191. Liver-cells during fasting (Hermann), : ' é j : ; 260
192. Bile ducts, . : , : , : ‘ 260
*193. Liver-cells (Stirling, after Stolnikoff), : : : in , ‘ 261
194. Various appearances of the liver-cells, ; : . ‘ : : 261
195. Interlobular bile duct, ; : : ; : : ; ‘ 262
*196. Cholesterin (Stirling), : é ; . ; , : 4 269
*197. Biliary fistule (Stirling), . : : ‘ ; ‘ : : 271
*198, Section of duodenum (Stéhr), . : ’ ‘ F : I 276
*199, Lieberkiihn’s gland (Hermann), . : ; : ; 277 ©
200. Trausverse section of Lieberkiihn’s follicles heheh: : : A ; 277
*201. Schemata of intestinal fistule (Stirling), . ; ; : f ; 277
*202. Moreau’s fistula (after Brunton), . : , ; : : ; 279
203. Bacterium aceti and B. butyricus, ‘ ; ‘ : i .~ Sage a
204. Bacillus subtilis, . ; : ; ; ; : . » 961 .
205. Bacteria of feces, . . : : f i 285. ,
*206. Scheme of intestinal absorption (Beaunis), A ; : : . + 290
*207. Longitudinal section of small intestine Neg ; d ‘ | a » ;
208. Scheme of an intestinal villus ‘ . ; ‘ ; oo ye

209, Injected villus (Schenk), . > : é 3 Habeas. Sots 3

LIST OF ILLUSTRATIONS.

FIGURE

*210.

*211,

*212.
*213.
214.
215.
216.
S217,
218.
219.
220.
*921.
222.
*223.
*224,
"220;
226.
F227,
*228,
229.
230.
231.
232.
*233.
234,
*235.
*236.
237.
238.
*239,
*240.
*241,
#242.
243.
244,
*245.
*246,
*247,
*248,
249,
250.
251.
252.
*253.
*254.
' 255.
256.
257.
*258.
259.
260.
261.
262.
. Esbach’s albumimeter,
. Blood-corpuscles in urine, .

Villi of small intestine injected (Cadiat), .
Duodenum injected (Stéhr),

Section of a solitary follicle (Cadiat),

Section of a Peyer’s patch (Cadiat),

Section of large intestine (Schenk),
Endosmometer,

Origin of lymphatics in ae tendon of aphweam.
Eyinpeeecs of diaphragm silvered (Ranvier),
Perivascular lymphatics,

Stomata from lymph-sac of frog,

Section of two lymph-follicles,

Scheme of a lymphatic gland (Sikes Y)s
Part of a lymphatic gland, .

Section of the central tendon of dapiraens (Brunton),

Section of fascia lata of a dog (Brunton),

Lymph hearts (Zcker),

Water-calorimeter of Favre and Siberueen,
Water-calorimeter of Dulong (Rosenthal),

Clinical Thermometers,

Walferdin’s metastatic picumonicier

Scheme of thermo-electric arrangements,

Kopp’s apparatus for specific heat,

Daily variations of temperature, . : ,
Acini of the mammary gland of a sheep (Cadiat), .
Milk-glands during inaction and secretion,

‘Milk and colostrum (Stirling),

Section of a grain of wheat (Blyth),
Yeast-cells growing,

Composition of animal and oul foods,
Starch grains,

Longitudinal eeceion of fie: kidney, (Henle),
Malpighian pyramid (7'yson, after Ludwig),

Scheme of the uriniferous tubules (Klein and Noble Sinith),

Scheme of the structure of the kidney,
Glomerulus and renal tubules,
Convoluted renal tubule (Heidenhain),
Irregular tubule ( Tyson, after Klein),

Transverse section of the apex of a Malpighian See (Ca adiat),

Development of a glomerulus (Cadiat),
Graduated urinary flask,

Urinometer, ‘

Graduated burette, .

Urea and urea nitrate,

Oxalate of urea (after Beale),
Ureameter (Charteris),

Graduated pipette, .

Uric acid, ;
Kreatinin-zine-chloride,

Oxalate of lime,

Hippuric acid,

Deposit in urine during ‘he ** acid fermentation,
Deposit in agsmoniacal urine, eS
Micrococcus urex,

”?

XXV

PAGE
293
293
294
294
295
296
302
303
304
304
504
305
306
310
310
311
315
316
320
320
320
324
327
343
344
345
351
354
358
384
3856
387
388

389

390
390
390
391
392
392
392
395
396
397
398
— 898
399
401
402
402
407
408
408
410
411

by abe Spe

XXVI LIST OF ILLUSTRATIONS.
FIGURE
265. Peculiar forms of blood-corpuscles, ; ‘

266. Coloured and colourless corpuscles in urine,
267. Blood-corpuscles and triple phosphate,
268. Spectroscopic examination of urine,

*269. Picio-saccharimeter (G. Johnson), .

*270. Inosit (Beale, after Funke),

271. Cystin and oxalate of lime,

272. Leucin, tyrosin, and ammonium urate,

273. Fungi in urine,

274. Epithelial casts,

275. Blood casts,

276. Leucocyte cast,

277. Cast of urate of soda,

278. Finely granular casts,

279. Coarsely granular casts,

280. Hyaline casts,

281. Calcic carbonate and phosphate,

282. Triple phosphate, :

283. Imperfect forms of triple pioschnte,

284. Acid ammonium urate, ;

285. Basic magnesic phosphate,

*286. Oncometer (Stirling, after Koy),

*287. Oncograph (Stirling, after Roy),

*288. Renal oncograph curve (Stirling, after Ray
*289. Section of ureter (Stohr), ;
*290. Transitional epithelium (Beale),

291. View of the trigone of the bladder,
*292. Nervous Pelisvisi of micturition (Stirling, after cre wey
*293. Section of epidermis and its nerves (Ranvier),

294. Scheme of the structure of the skin,

*295. Papille of the skin injected,

296. Transverse section of a nail, ;

297. Transverse section of a hair-follicle,

298. Longitudinal section of a hair-follicle,

299. Sebaceous gland,

300. Ciliated epithelium,

*301. Pigment and guanin cells BE frog (Stir ting,

302. Histology of muscular tissue,

*303. Muscular fibre (Quain),

*304. Insect’s muscle (Lol/ett),

*305. Insect’s muscle (Rollett),

#306. Network in muscle (Melland),
307. Tendon attached to a muscle,

- *308. Injected blood-vessels of muscle (Kélliker ),

309. Motorial end-plates, . °
*310. Termination of a nerve in a frog’s muscle (Kuhne),
*311. Scheme of nerve-ending in muscle ara after Kiihne), .
*312. Smooth muscle, . : :
*313. Non-striped muscle-cell (Stirling), ‘
*314. Nerve-ending in smooth muscle (Cadiat), .
*315. Frog with its sciatic artery ligatured (Stirling),
*316. Scheme of the curara experiment (after Rutherford),
*317. Excitability in a frog’s sartorius (Stirling, after Pollitzer),
*318. Excitability in a curarised sartorius (Stirling, after rey
319. Microscopic appearances in contracting muscle, .

455
456

‘ z ¥
so =

Pere te

LIST OF ILLUSTRATIONS.

FIGURE P
320. Helmholtz’s myograph, .
*321. Pendulum myograph,
*322. Scheme of the pendulum ae ool (Stir tina),
*323. Du Bois-Reymond’s spring myograph,
324. Muscle-curve,
*325. Muscle-curve of pendulum See (Stir ieee ;
*326. Method of studying a muscular contraction (after Rutherford),
*327. Effect of make and break induction shocks (Stirling),
328. Muscle-curves, : :
329. Muscle-curve, opening and Sosine hecks,
*330. Veratrin-curve (Stirling),
331. Muscle-curves, tetanus, :
*332. Staircase contractions (Buckmaster),
333. Curves of voluntary impulses,
*334. Curves of a red and pale muscle (A7 oe and Sela
*335. Muscle-curves (Kronecker and Stirling),
*336. Tone-inductorium (Kronecker and Stirling),
*337. Muscle-curves (J/arey),
*338. Height of the lift by a muscle,
*339. Dynamometer,
*340. Curve of elasticity (after ie ey),
*341. Curve of elasticity of a muscle (after Marea a
*342. Curve of elasticity (Marey), :
*343. Fatigue curve (Stirling),
*344, Fatigue curve (Wailer),
*345. Vertical section of articular car ieee (Stir fan q),
*346. Orders of levers, ‘
*347. Scheme of the action of nee on bodes
348. Phases of walking, .
349. Instantaneous photograph of a neree w aii,
350. Instantaneous photograph of a runner,
351. Instantaneous photograph of a person jumping,
352. Larynx from the front,
353. Larynx from behind,
354, Larynx from behind,
355. Nerves of the larynx,
356. Action of the posterior crico- apt arctan
357. Action of the arytenoid muscles,
358. Action of the lateral crico-arytenoid cele
359. Vertical section of the head and neck,
360. Examination of the larynx,
361. Laryngoscopic view of the larynx,
362. View of the larynx during a high note,
363. View of the larynx during a deep inspiration,
364. Rhinoscopy, . ;
365. View of the posterior nares,
366. Parts concerned in phonation,
367. Tumours on the vocal cords,
368. Histology of nervous tissues, é
*369. Transverse section of nerve-fibres (Cadiat),

.*370. Sympathetic nerve-fibre (Ranvier),

*371. Medullated nerve-fibre (Stirling), ~.
372. Medullated nerve-fibre, .

*373. Medullated nerve-fibres (Schwalbe),

*374. Ranvier’s crosses (Ranvier),

XXViii LIST OF ILLUSTRATIONS,
FIGURE
375. Transverse section of a nerve, .

*376. Cell from the Gasserian ganglion (Schwalbe),
377. Degeneration and regeneration of nerve-fibres,
*378. Waller’s experiments (after Dalton),
379. Rheocord of du Bois-Reymond,
380. Scheme of a galvanometer, :
*381. Large Grove’s battery (@scheidlen),
*382. Daniell’s cell (Stirling),
*383. Grennet’s battery ((scheidlen),
*284. Leclanché’s element (Gscheidlen), .
*385. Non-polarisable electrodes (Eiliott Br Pr
*386. Fleischl’s non-polarisable electrodes (Petzoldt),
*387. Thomson’s galvanometer (Elliott Brothers),
*388. Lamp and scale (£iliott Brothers), .
*389. Galvanometer shunt (Elliott Brothers),
*390. Scheme of the induced currents (Hermann),
*391. Helmholtz’s modification (Hermann),
392. Scheme of an induction machine,
*393. Inductorium (Elliott Brothers),
*394. Inductorium (Petzoldt),
; 395. Stohrer’s apparatus,
, *396. Friction key (£ilivtt Bie s),
*397. Plug key (Eliott Brothers),
*398. Capillary contact (Kronecker and Stirting,
399. Scheme of the muscle-current,
400. Capillary electrometer,
*401. Nerve-muscle preparation, .
*402. Kiihne’s experiment (Stirling), :
*403. Electrometer curve, frog’s muscle ( Waller),
*404. Electrometer curve, frog’s heart (Wailer),
*405. Secondary contraction, ‘ ;
406. Bernstein’s differential rheotome,
407. Nerve-current in electrotonus,
408. Scheme of electrotonic excitability,
409. Method of testing electrotonic excitability,
410. Distribution of an electrical current,
411. Velocity of nerve-energy,
*412. Scheme for testing velocity of a nerve- fae
*413. Curves of a nerve-impulse (Marcy),
*414. Kiihne’s gracilis experiment,
*415. Sponge rheophores ( Weiss),
*416. Disk rheophore (Weiss), .
*417. Metallic brush ( Weiss),
_418. Motor points of the arm,
419. Motor points of the arm,
420. Motor points of the leg, ..
421. Motor points of the leg, . °
*422. Scheme of a reflex act (Stirling), .
423, Optic chiasma,
*424. Relation of field of vision, votive: ond optie tracts (Gowers,
*425. Decussation of the optic tracts (Charcot), . ’
*426. Scheme of images in squinting (Bristowe),
427. Medulla oblongata, : ; °
*428, Under surface of the brain, ; 4
429. Connections of the cranial nerves, .

‘LIST OF ILLUSTRATIONS. XXiX

FIGURE PAGE
430. Sensory nerves of the face, , : i : , ; 597
431. Motor points of the face and neck, ; ; : : : : 601

*432. Disposition of the semicircular canals (Stirling), . : ; : : 605
433. Scheme of the branches of vagus and accessorius, . : ; : 608

*434, Cardiac nerves of the rabbit (Stirling), . : ‘ a : ; 610

*435, Diagram of a spinal nerve (Loss), . : : ; : : : 616

*436. Spinal ganglion (Cadiat), . : = ; ‘ : ; ; 617
437. Cutaneous nerves of the arm, : : : : ; : 3 618

- 438. Cutaneous nerves of the leg (Henle), ; : . : ; ; 619

*439. Visceral nerves of the dog (Gaskel/), ; ; : : i : 622
440. Transverse section of the spinal cord, ; . , : : 626

*441, Transverse section of the white matter tonercieties . : , ; : 627

*442. Multipolar nerve-cells of the cord (Cadiat), ; : : : : 627

*443. Relation of white and grey matter of the cord (Schafer), . : : ‘ 627

*444, Transverse sections of the spinal cord, . - : : ‘ ‘ 628

*445, Cell from Clarke’s column (Oversteiner), . : ; : , : 629

*446, Transverse section of the cord (Cadiat), . : : : : ‘ 629

*447, Longitudinal section of the cord (Cadiat), . : : : : ‘ 630

*448. Multipolar nerve-cell, . ; ; : : , 630

*449,. Scheme of fibres in cord (Oberdiner. : : : : ; ; 630

*450. Glia cell (Obersteiner), ; } : ; ; ; : : 631

*451. Glia cells of cord (Obersteiner), : : ; : , a 3 631

*452. Spinal cord injected (Obersteiner), . : : : : : 632

*453. Injected blood-vessels of the cord (KX ‘lliker), : : ; , : 632
454. Conducting paths in the cord, : ‘ 5 ; ; , 633

*455. Degeneration paths in the soca (ees, : ae : : : 635

*456. Scheme of a reflex act (Stirling), : : : ; 636

*457. Section of a spinal segment (Stirling), , : ‘ : : . 636

*458. Propagation of reflex movements (Beawnis), : a ice ae 637

*459. Effect of section of half of the cord (£rb), ; : : : ; 649

*460. Brain, ventricles, and basal ganglia, ; : , : ; ; 650
461. Scheme of the brain, : : ; : 651

*462. Connections of the cerebellum, , j é : A : : 652

*463. Diagram of a spinal segment (Bramwell), . a ; ‘ , 655

*464. Section across the pyramids (Schwalbe), . . ; ; : ; 656

*465. Section of the medulla oblongata (Schwalbe), ; al : yy : 657

*466. Section of the olivary body (Schwalbe), . : a : : : 657

*467. Scheme of the respiratory centres (Rutherford), . , ; : 662

*468. Action of vagus on frog’s heart (Stirling), ; “* : ‘ : 668

*469. Scheme of the accelerans fibres (Stirling), . ‘ ; ; 670

*470. Cardiac plexus of a cat (Béhm), . : : : ; c 670

*471. Frog without its cerebrum (Stirling, after Ca : : a : : 683

*472. Frog without its cerebrum (Stirling, after Goltz), . oe ; : : 683

*473. Pigeon with its cerebrum removed (after Dalton), : ; : 683

*474, Motor area of cerebral convolution (Ferrier and B. Taees : ‘ oe 687

*475. Cerebral convolution ; sensory area (Ferrier and B. Lewis), : : mae 688

*476. Perivascular lymph-spaces (Ober'steiner), . : ; : ‘ 688

*477. Frontal convolution by Weigert’s method (oberseineny: : ‘ aes 688

‘ *478. Cerebral convolution injected, . ; : ‘ : : 689
i *479, Left side of the human brain (Ecker), : . 690
\ *480. Inner aspect of right hemisphere (Zcker),. : : , 691

*481. Left frontal lobe and island of Reit be wENer), “4% : : : : 692

*482. Brain from above (Ecker), . : ae é ; : 693
483. Cerebrum of dog, carp, frog, pigéon; and rabbit, . . . 694

484. Relation of the cerebral convolutions to the skull, ’ ne ' ; 697

XXX

LIST OF ILLUSTRATIONS.

FIGURE

*485.

*487.
*488.
*489.
*490.
*491.
*492.
*493.
*494.
*495,
*496.
*497.
*498.
*499.
*500.
*501.
*502.
*503.
*504.
*505.
*506.
*507.
*508.
*509.
*510.
*511.
“biz;
*513.
514.
"515.
*516.
TOL.
518.
*519.
520.
*521.
*522.
523.
524.
525.
526.
527.
-§28.
529.
530.
531.
532.
533.
534.
535.
*536.
537.
538.
539.

Motor areas of a monkey’s brain (Horsley and Schéfer),

*486. Motor areas of the marginal convolution iit and aie Aare

Pyscho-optic fibres (Munk),

Motor areas (after Gowers),

Motor centres (after Schafer and Nona

Section of a cerebral hemisphere (Hors/ey),
Innervation of associated muscles (Ross), .

Secondary degeneration in a crus (Charcot),

Transverse section of the crus cerebri (Charcot),
Scheme of aphasia (Lichtheim),

Scheme of aphasia (Lichtheim),

Scheme of aphasia (Ross), . :
Relation of the convolutions to itis skull (R. W. Reid),
Relation of motor centres to skull (Hare), ,
Outline markings on skull (Hare),

Basal ganglia and the ventricles,

Transverse section of the right Rome iers (Ge eon
Transverse section of the crura (Wernicke and Gowers),
Transverse section of the pons ( Wernicke),

Course of the fibres in pons (£7b),

Longitudinal section of a human brain CV, a se
Section of the cerebellum (Sankey),

Purkinje’s cell (Obersteiner),

Pigeon with its cerebellum mores alten

Cortex cerebri and its membranes (Schzalbe),

Circle of Willis (Charcot), .

Ganglionic arteries (Charcot),

Corneal corpuscles (Ranvier),

Corneal spaces (Ranvier),

Junction of the cornea and sieve

Vertical section of cornea with nerve fibuli Chanvier).

Horizontal section of cornea with nerve fibuli (Ranvier), .

Vertical section of choroid and sclerotic (Stéhr),
Blood-vessels of the eyeball, ; .
Vertical section human retina (Cadiat),. .

Layers of the retina,

Vertical section of the fovea centr. ale (Cadiat),
Fibres of the lens (Kélliker),

Section of the optic nerve,

Action of lenses on light,

Refraction of light, ,

Construction of the refracted ray, :

Optical cardinal points, ,

Construction of the refracted ray, .

Construction of the image,

Refracted ray in several media,

Visual angle and retinal image, .

Scheme of the ophthalmometer,

Horizontal section of the eyeball, .

Scheme of accommodation,

Sanson-Purkinje’s images, .

Phakoscope (M‘Kendrick),

Scheiner’s experiment, . oe, ws
Refraction of the eye, 3 a é ,
Myopic eye, <= ‘ YF: is wt

P ;
Ee ee

; \
a ee ae a Pe)

586
. 587
. *588
*589

590

LIST OF ILLUSTRATIONS.

‘FIGURE
540.
541.

*5 42.

«43.

*544,

*545,

_ *546.

=. ' 547.

om - | 648.

549.

550.
551.
552.
*553.
*h54,
*555.
*556.
*557.
*558.
*559.
560.

. Geometrical colour cone, :

. Action of light rays on the retina,

. Cones of the retina (Stirling after En a ae

. Irradiation, ‘ : , :

. Irradiation, :

. Scheme of the action of fie ocular paulo

. Identical points of the retina,

. The horopter, :

. Two stereoscopic drawings,

. Wheatstone’s stereoscope,

. Brewster’s stereoscope,

. Telestereoscope, ce

. Wheatstone’s pseudoscope,

. Rollett’s apparatus,

. Zollner’s lines,

. Section of an eyelid,

. Scheme of the organ of hearing,

. External auditory meatus,

. Left tympanic membrane and ossicles,

. Membrana tympani and ossicles,

. Tympanic membrane from within,

. Ear specula (Krohne and Sesemann),

. Toynbee’s artificial membrana tympani ie ohne and Sesemann),

. Right auditory ossicles, :

. Tympanum and auditory ossicles,

. Tensor tympani and Eustachian tube,

. Right stapedius muscle,

. Eustachian catheter, , ‘

. Politzer’s ear bag (Krohne and Sesemani),

. Right labyrinth,

. Scheme of the cochlea,

2. Interior of the right labyrinth,

. Semicircular canals, "

. Section of the macula acustica LRansior),

Mecerntotronic ¢ eye,

Power of accommodation,
Diagram of astigmatism (Fost),
Cylindrical glasses,

_Scheme of the nerves of fie’ iris (Erb),

Pupilometer (Gorham),

Pupilometer (Gorham),

Entoptical shadows,

Scheme of the original Solile Iuoscaye,
Scheme of the indirect method,

Action of a divergent lens,

Action of a divergent lens,

View of the fundus oculi,

Morton’s aphithalmoscope (Pievard and Can
Frost’s artificial eye (Frost),

Action of the orthoscope,

Mariotte’s experiment,

Horizontal section of the right eye,

M‘Hardy’s perimeter (Pickard and Curry),
Priestley Smith’s perimeter (Pickard and Curry), -
Perimetric chart, :

801
802
802
803
804
806
806
807
- 808
809
809
809

— = 2

XXXii LIST OF ILLUSTRATIONS.

FIGURE

595.
*596.
597.
*598.
*599.
*300.
601.

*602.

603.
*604.
*605.

606.
*607.

608.

609.

610.
*611,
*612.
*613.
*614.

615.
*616.
"Glin

618.

619.

620.

621.

622.
*623.
*624.
*625.

626,

627.

628.

629.

630.

631.
*632.
*633.
*634.

635.

636.

637.
*638.
*639.

640.

641,

642.

643.

*644.

*645.
*646.
*647.
*648.
*649.

Tenia solium,

Scheme of the canalis cochlearis, ¢
Galton’s whistle (Krohne and Sesemann),
Curve of a musical note and its overtones,
Keenig’s manometric capsule (Kanigq),
Flame-pictures of vowels (Kwnig),
Keenig’s analysing apparatus (Kenig),
Nasal and pharyngo-nasal cavities, {
Section of the olfactory region ail
Olfactory cells, ;

Filiform papille (Stéhr),

Fungiform papille (Stéhr),
Circumvallate papilla and taste- bulbs,
Papille foliate (Stéhr),

Vertical section of skin,

Wagner's touch corpuscle (Raneier }
Pacini’s corpuscle,

End-bulb from conjunctiva (Onan)
Tactile corpuscle from clitoris (Quain),
Tactile corpuscles from a duck’s bill (Quazn),
Bouchon epidermique (Ranvier),
Asthesiometer,

sthesiometer of Siev dae

Aristotle’s experiment,

Pressure-spots,

Landois’ pressure mercur ial alae:
Cold- and hot-spots,

Cold- and hot-spots, :
Topography of temperature-spots,
Karyokinesis (Gegenbaur),

Typical nucleated cell (Carnoy),

Mitosis or nuclear division (Flemming),
Ovum of Tenia solium,

Cysticercus,

Cysticerci of Tenia Sine

Scolex,

Echinococcus,

Section of testis (Schenk);

Tubule of testis (Schenk),

Section of epididymis (Schenk),

Spermatic crystals, ,

Spermatozoa,

Spermatogenesis,

A cat’s ovary (Hart and Barbour, after Schrin),
Section of an ovary (7'urner), ;

Ripe ovum of rabbit,

Ovary and polar globules,

Scheme of a meroblastic ovum,

White and yellow yolk,

Hen’s egg (Kélliker),

Mucous membrane of the uterus (Hart ond Sarbous; after Turser,
Fallopian tube and its annexes (Henle), ‘

Section of Fallopian tube (Schenk),

Uterus before menstruation (J. Williams),

Uterus after menstruation (J. Williams),

as . LIST OF ILLUSTRATIONS. XXXill

FIGURE PAGE

650. Fresh corpus luteum, ; ‘ . : : : ; 856
651. Corpus luteum of a cow, . 3 ; : 856
652. Lutein cells, ‘ : ; “ ; s Bol hae o Sk 856
*653. Erectile tissue (Cadiat), . ; : , ; 857
- 654. The urethra and adjoining muscles, : , 858
*655. Formation of polar globules, ° : : ; ; : 861
656. Extrusion of a polar globule, : é ‘ ; : 861
657. Polar globules, male and female pronueleus, : , : , 862
*658. Segmentation of a rabbit’s ovum (Quain, after v. Boneien , ; : 862
659. Cleavage of the yelk, : : . ‘ 862
*660. Blastodermic vesicle of rabbit (Guain, ae V. Beaten, : : : 863
661. The blastoderm, . : : : ; ; 863
*662. Primitive speak (Balfour), : : 864
*663. Transverse section of an embryo neve GO : ; : 864
*664. Vertical section of a blastoderm (Klein), . ; : A 865
665. Schemata of development, : : : : , : 866
*666. Embryo fowl, 2nd day (Kélliker), : d ; ; ; , 867
*667. Transverse section of an embryo duck (Balfour), : . ; ; 868
*668. Uterine mucous membrane (Coste), ’ : ; ‘ , : 873
*669. Placental villi (Cadiat), . : d : : é : 874
*670. Foetal circulation (Cleland), : : : ‘ 876
*671. Head of embryo rabbit (Kolliker), : ; : . : 879
672. Hare lip, . ; : : : : : 879
*673. Meckel’s cartilage UW. K; Pier \, : : : : ‘ ” 879
674. Centres of ossification in the innominate bone, : . i : 881
675. Development of the heart, _ : ; : ; : ; : 883
676. The aortic arches, ; ; : : : ; : : 884
677. Veins of the embryo, : : ; ; : 885
678. Development of the veins and por tal syatem, : ; ; : : 885
679. Development of the intestine, -. : ; : 886
680. Development of the lungs, ‘ : : é : : 886
681. Formation of the omentum, : ; , : ; 887
682. Development of the internal generative organs, : ; 887
*683. Development of ova (Wiedersheim), : ; 888
684. Development of the external genitals, . ; ; ; 890
*685. 890
*686. i ae he 890
#687. Changes in the external organs of generation in the female (after Schroeder), . 890
*688. 890
*689. Transverse section of an embryo brain (Kélliker), : : 3 ; 891
*690. Embryo brain of fowl (Quain, after Mihalkowics), : : : ‘ 892
691. Development of the eye, . - : ; ; ; 893
*692. Development of the vertebrate ear (Haddon’, ; : : : ; 893

[The illustrations indicated by the word Hermann, are from Hermann’s Handbuch der
Physiologie ; by Cadiat, from Cadiat’s Traité @ Anatomie Générale ; by Ranvier, from Ranvier’s
Traité Technique d’Histologie; by Brunton, from Brunton’s Text-book of Pharmacology,
Therapeutics, and Materia Medica; by Schenk, from Schenk’s Grundriss der normalen Histo-
logie ; by Ecker, from Ecker’s Anatomie des Frosches, 2nd ed.; by Quain, from Quain’s
Anatomy; by Stohr, from Stohr’s Lehrbuch der Histologic, Jena, 1887; by Obersteiner,
from H. Obersteiner’s Anleitung beim Studiwm des Baues der nervosen Gongs Wien,
1888. ] =

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7
:

Introduction.

The Scope of Physiology and its Relations to other Branches
of Natural Science.

PHysIoLoGcy is the science of the vital phenomena of organisms, or, broadly, it is
the Doctrine of Life. Correspondingly to the divisions of organisms, we distinguish
—(1) Animal Physiology; (2) Vegetable Physiology; and (3) the Physiology of
the Lowest Living Organisms, which stand on the border line of animals and
plants, 7.¢., the so-called Protistz of Haeckel, micro-organisms, and those elementary
organisms or ced/s which exist on the same level.

The object of Physiology is to establish these phenomena, to determine their

regularity and causes, and to refer them to the general fundamental laws of

Natural Science, viz., the Laws of Physics and of Chemistry.
The following Scheme shows the relation of Physiology to the allied branches of
Natural Science :—
BIOLOGY.
The science of organised beings or organisms (animals, plants, protiste, and
elementary organisms).

I. Morphology. II. Physiology.
The doctrine of the form of organisms. The doctrine of the vital phenomena
General Special of organisms.
Morphology. Morphology. |
The doctrine of the The doctrine of the General Special
- formed elementary parts and organs of Physiology. . Pa TSOOEy,
- constituents of or- organisms. The doctrine of vital The doctrine of the
ganisms. (Organology — phenomena in gene- activities of the in-
(Histology )— Anatomy)— ral— dividual organs—
(a) Histology of Plants. (a) Phytotomy. (a) Of Plants. (a) Of Piants.
(b) Histology of Animals. (b) Zootomy. (b) Of Animals. (b) Of Animals.

III. Embryology.

The doctrine of the generation and development of organisms.
(1, History of the development of )
single beings, of the individual
(e.g., of man) from the ovum

Morphological part of the onwards (Ontogeny)— Physiological part of the
doctrine of development, (a) In Plants. doctrine of development,
i.¢., the doctrine of form (b) In Animals. | i.é., the doctrine of the
a ke om f oy, ; ;
in its stages of develop 2, History of the development of oe during develop
paeintier a whole stock of organisms from on: Se

(a) General. ‘ (a) General.
. the lowest forms of the series :
(b) Special. (b) Special.

upwards (Phylogeny)—
(a) In Plants. .
L (6) In, Animals. 7

XXXVi INTRODUCTION.

Morphology and Physiology are of equal rank in biological science, and a previous
acquaintance with Morphology is assumed asa basis for the comprehension of
Physiology, since the work of an organ can only be properly understood when its ~
external form and its internal arrangements are known. Development occupies a
middle place between Morphology and Physiology ; it is a morphological discipline
in so far as it is concerned with the description of the parts of the developing
organism ; it is a physiological doctrine in so far as it studies the activities and
vital phenomena during the course of development.

MATTER,—The entire visible world, including all organisms, consists of matter,
z.e., Of substance which occupies space.

We distinguish ponderable matter which has weight, and zmponderable matter
which cannot be weighed in a balance. The latter is generally termed ether.

In ponderable materials, again, we distinguish their form, z.e., the nature of their
limiting surfaces; further, their volume, 2.e., the amount of space which they
occupy ; and lastly, their aggregate condition, v.e., whether they are solid, fluid, or
gaseous bodies.

Ether.—The ether fills the space of the universe, certainly as far as the most
distant visible stars. This ether, notwithstanding its imponderability, possesses
distinct mechanical properties ; it is infinitely more attenuated than any known
kind of gas, and behaves more like a solid body than a gas, resembling a gelatinous
mass rather than the air. It participates in the luminous phenomena due to the
vibrations of the atoms of the fixed stars, and hence it is the transmitter of light,
which is conducted by means of its vibrations, with inconceivable rapidity (42,220
geographical: miles per second) to our visual organs (7'yndall).

Imponderable matter (ether) and ponderable matter are not separated sharply
from each other ; rather does the ether penetrate into all the —— existing
between the aatieet particles of ponderable matter.

Particles.—Supposing that ponderable matter were to ‘be subdivided con-
tinuously into smaller and smaller portions, until we reach the last stage of
division in which it is possible to recognise the aggregate condition of the matter
operated upon, we should call the finely-divided portions of matter in this state
particles, Particles of iron would still be recognised as solid, particles of water as
Jluid, particles of oxygen as gaseous.

Molecules.—Supposing, however, the process of division of the particles to
be carried further still, we should at last reach a limit, beyond which, neither by
mechanical nor by physical means, could any further division be effected. We
should have arrived at the molecules. A molecule, therefore, is the smallest amount’
of matter which can still exist in a free condition, and which as a unit no longer
exhibits the aggregate condition.

Atoms.—But even molecules are not the final units of matter, since every
molecule consists of a group of smaller units, called atoms. An atom cannot exist
by itself in a free condition, but the atoms unite with other similar or dissimilar
atoms to form groups, which are called molecules. Atoms are incapable of further
subdivision, hence their name. We assume that the atoms are invariably of the
same size, and that they are solid. From a chemical point of view, the atom of

,

INTRODUCTION, XXXVIli

an elementary body (element) is the smallest amount of the element which can enter
into a chemical combination. Just as ponderable matter consists in its ultimate
parts of ponderable atoms, so does the ether consist of analogous small ether-atoms.

Ponderable and Imponderable Atoms.—The . ponderable atoms within
ponderable matter are arranged in a definite relation to the ether-atoms. The
ponderable atoms mutually attract each other, and similarly they attract .the
imponderable ether-atoms; but the ether-atoms repel each other. Hence, in
ponderable masses, ether-atoms surround every ponderable atom. These masses,
in virtue of the attraction of the ponderable atoms, ‘tend to come together, but only
to the extent permitted by the surrounding ether-atoms. Thus the ponderable
atoms can never come so close as not to leave interspaces. All matter must,
therefore, be regarded as more or less loose and open in texture, a condition due to the
interpenetrating ether-atoms, which resist the direct contact of the ponderable atoms.

Aggregate Condition of Atoms.—The relative arrangement of the molecules,
2.¢., the smallest particles of matter which can be isolated in a free condition,
determines the aggregate condition of the body.

Within a solid body, characterised by the permanence of its volume as well as
by the independence of its form, the molecules are so arranged that they cannot
readily be displaced from their relative positions. |

Fluid bodies, although their volume is permanent, readily change their shape,
and their molecules are in a condition of continual movement.

When this movement of the molecules takes so wide a range that the individual
molecules fly apart, the body becomes gaseous, and as such is characterised by
the instability of its form as well as by the changeableness of its volume.

Physics is the study of these molecules and their motions.

Forces.

1. Gravitation—Work done.—All phenomena appertain to matter. These
phenomena are the appreciable expression of the forces inherent in matter.
The forces themselves are not appreciable, they are the causes of the phenomena.

Gravitation.—The law of gravitation postulates that every particle of
ponderable matter in the universe attracts every other particle with a certain
force. This force is inversely as the square of the distance. Further, the
attractive force is directly proportional to the amount of the attracting matter,

_ without any reference to the quality of the body. We may estimate the intensity

of gravitation by the extent of the movement which it communicates to’ a body
allowed to fall, for one second, through a given distance, in a space free from air.
Such a body will fall in vacuo 9809 metres per second. This fact has been arrived
at experimentally.

Let us represent g=9°809 metres, the final velocity of the freely falling body at the end of
one second, The velocity, V, of the freely falling body is ie ee to the time, ¢, so that

V= = gt 6 . ° . . . . ° ue? (1); ’
, at the end of the 1st sec., and V=g, 1=g=9°809 M—the distance traversed —
3= se ET a ERE Pa (2) ;

XXXViii INTRODUCTION.

i.e., the distances are as the square of the times. Hence, from (1) and (2) it follows (by
eliminating ¢t) that—

VaV99s - 2 2 6 ee ee ee 8)
The velocities are as the square roots of the distances traversed—
. y2
Therefore ak Ae I ee i Me (4).

The freely falling body, and in fact every freely moving body, possesses kinetic
energy, and is in a certain sense a magazine of energy. The kinetic energy of any
moving body is always equal to the product of its weight (estimated by the balance),
and the height to which it would rise from the earth, if it were thrown from the
earth with its own velocity.

Let W represent the kinetic energy of the moving body, and P its weight, then W=P.s, so
that from (4) it follows that—

W=P>. Stas che ees ay ae ee tO
Bg (5)

Hence, the kinetic energy of a body is proportional to the square of its velocity.

Work.—If a force (pressure, strain, tension) be so applied to a body as to move
it, a certain amount of work is performed. The amount of work is equal to the
product of the amount of the pressure or strain which moves the body, and of the
distance through which it is moved.

Let K represent the force acting on the body, and S the distance, then the work W=KS.
The attraction between the earth and any body raised above it is a source of work.

It is usual to express the value of K in kilogrammes, and S in metres, so that
the “unit of work ” is the kilogramme-metre, 7.¢., the force which is required to
raise 1 kilo. to the height of 1 metre.

2. Potential Energy.— The transformation of Potential into Kinetic Energy, and
conversely: Besides kinetic energy, there is also “ potential energy,” or energy of
position. By this term are meant various forms of energy, which are suspended in
their action, and which, although they may cause motion, are not in themselves
motion. A coiled watch-spring kept in this position, a stone resting upon a tower,
are instances of bodies possessing potential energy, or the energy of position. It
requires merely a push to develop kinetic from the potential energy, or to transform
potential into kinetic energy.

Work, w, was performed in raising the stone to rest upon the tower.

w=p, s, where p=the weight and s=the height,

p=m.g, is=the product of the mass (m), and the force of gravity (g), so that w=m qs.

This is at the same time the expression for the potential energy of the stone.
This potential energy may readily be transformed into kinetic energy by merely
pushing the stone so that it falls from the tower. The kinetic energy of the stone
is equal to the final velocity with which it impinges upon the earth.

=/2g s (see above (3) ).

iin 29 8.
mY*= IWwmygs.

sv Mg 8.

m gy 8 was the expression for the potential energy of the stone while it was still

yang =f

,
‘
- .
-

:
,
i
4
:

INTRODUCTION. XXX1X

resting on the height ; =v, is the kinetic energy corresponding to this potential

energy (Briicke).

Potential energy may be transformed into mechanical energy under the most
varied conditions ; it may also be transferred from one body to another.

The movement of a pendulum is a striking example of the former. When the pendulum is
at the highest point of its excursion, it must be regarded as absolutely at rest for an instant,
and as endowed with potential energy, thus corresponding with the raised stone in the previous
instance. During the swing of the pendulum this potential energy is changed into kinetic
energy, which is greatest when the pendulum is moving most rapidly towards the vertical. As
it rises again from the vertical position, it moves more slowly, and the kinetic energy is
changed into potential energy, which once more reaches its maximum when the pendulum
comes to rest at the utmost limit of its excursion. Were it not for the resistances continually
opposed to its movements, such as the resistance of the air and friction, the movement of the
pendulum, due to the alternating change of kinetic into potential energy and vice versd, would
continue uninterruptedly, as with a mathematical pendulum. Suppose the swinging ball of the
pendulum, when exactly in a vertical position, impinged upon a resting but movable sphere,
the potential energy of the ball of the pendulum would be transferred directly to the sphere,
provided that the elasticity of the ball of the pendulum and the sphere were complete ; the
pendulum would come to rest, while the sphere would move onward with an equal amount of
kinetic energy, provided there were no resistance to its movement. This is an example of the
transference of kinetic energy from one body to another. Lastly, suppose that a stretched
watch-spring on uncoiling causes another spring to become coiled ; and we have another example
of the transference of kinetic energy from one body to another.

The following general statement is deducible from the foregoing examples :—
If, in a system, the individual moving masses approach the final position of equi-
librium, then in this system the sum of the kznetic energies increases ; if, on the
other hand, the particles move away from the final position of equilibrium, then
the sum of the potential energies is increased at the expense of the kinetic energies,
i.¢., the kinetic energies diminish (Briicke).

The pendulum, which, after swinging from the highest point of its excursion, approaches the
vertical position, 7.e., the position of equilibrium of a passive pendulum, has in this position
the largest amount of potential energy; as it again ascends to the highest point of its excursion
on the other side, it again gradually receives the maximum of potential energy at the expense
of the gradually diminishing movement, and therefore of the kinetic energy.

3. Heat.—Jts Relation to Potential and Kinetic Energy.—If a lead weight be
thrown from a high tower to the earth, and if it strike an unyielding substance, the
movement of the mass of lead is not only arrested, but the kinetic energy (which
to the eye appears to be lost) is transformed into a lively vibratory movement of
the atoms. When the lead meets the earth, heat is produced. The amount of
heat produced is proportional to the kinetic energy, which is transformed through
the concussion, At the moment when the lead weight reaches the earth, the atoms
are thrown into vibrations ; they impinge upon each other; then rebound again
from each other in consequence of their elasticity, which opposes their direct juxta-
position; they fly asunder to the maximum extent permitted by the attractive force
of the ponderable atoms, and thus oscillate to and fro. All the atoms vibrate like
a pendulum, until their movement is communicated to the ethereal atoms sur-
rounding them on every side, 7.¢., until the heat of the heated mass is “ radiated.”
Heat is thus a vibratory movement of the atoms.

et: INTRODUCTION.

As the amount of heat produced is proportional to-the kinetic energy, which is
transformed through the concussion, we must find an adequate measure for both
forces.

Heat-Unit.—As a standard of measure of heat, we have the “ heat-unit” or
calorie. The “‘heat-unit ” or calorie is the amonnt of energy required to raise the
temperature of 1 gramme of water 1° centigrade. The “ heat-unit ” corresponds to
425°5 gramme-metres, i.e., the same energy required to heat 1 gramme of water
1° C. would raise a weight of 425-5 grammes to the height of 1 metre; or, a weight
of 425-5 grammes, if allowed to fall from the height of 1 metre, would by its concus-
sion produce as much heat as would raise the temperature of 1 gramme of water 1° C.
The ‘mechanical equivalent ” of the heat-unit is, therefore, 425-5 gramme-metres.

It is evident that from the collision of moving masses an immeasurable amount of heat can
be produced. Let us apply what has already been said to the earth. Suppose the earth to be
disturbed in its orbit, and suppose further that, owing to the attraction of the sun, it were to
impinge on the latter (whereby, according to J. R. Mayer, its final velocity would be 85
geographical miles per second), the amount of heat produced by the collision would be equal to
that produced by the combustion of a mass of pure charcoal more than. 5000 times as heavy
(Julius Robert Mayer, Helmholtz).

Thus, the heat of the sun itself can be produced by the collision of masses of cold matter.
If the cold matter of the universe were thrown into space, and there left to the attraction of its
particles, the collision of these particles would ultimately produce the light of the stars. At
the present time, numerous cosmic bodies collide in space, while innumerable small meteors
(94,000 to 188,000 billions of kilos. per minute) fall into the sun. The force of gravity is
perhaps, in fact, the only source of all heat (J. R. Mayer, Tyndall).

We have a homely example of the transformation of kinetic energy into heat in the fact that
a blacksmith may make a piece of iron red-hot by hammering it. Of the conversion of heat
into kinetic energy we have an example in the hot watery vapour (steam) of the steam-engine
raising the piston. An example of the conversion of potential energy into heat occurs ina
metallic spring, when it uncoils and is so placed as to rub against a rough surface, producing
heat by friction. | |

4. Chemical Affinity: Relation to heat.— Whilst gravity acts upon the particles
of matter without reference to the composition of the body, there is another atomic
force which acts between atoms of a chemically different nature ; this 1s chemical
affinity. This is the force in virtue of which the atoms of chemically different
bodies unite to form a chemical compound. ‘The force itself varies greatly between
the atoms of different'chemical bodies; thus we speak of strong chemical affinities
and weak affinities. Just as we were able to estimate the potential energy of a
body in motion from the amount of heat which was produced when it collided with
an unyielding body, so we can measure the amount of heat which is formed when
the atoms of chemically different bodies unite to form a chemical compound. As
a rule, heat is formed when separate chemically-different atoms form a compound
body. When, in virtue of chemical affinity, the atoms of 1 kilo. of hydrogen and
8 kilos. of oxygen unite to form the chemical compound water, an amount of heat is
thereby evolved which is equal to that produced by a weight of 47,000 kilos. falling
and colliding with the earth from a height of 1000 feet above the surface of the
earth. If 1 gramme of H be burned along with the requisite amount of O to form
water, it yields 34,460 heat-units or calories ;: and 1 gramme carbon burned to car-
bonie acid: (carbon dioxide) yields 8080 heat-units. Wherever, in chemical processes,
strong chemical affinities are satisfied, heat 1s set free, t.e., chemical affinity ae

INTRODUCTION. xli

changed into heat. Chemical affinity is a form of potential energy obtaining
between the most different atoms, which during chemical processes is changed into
heat. Conversely, in those chemical processes where strong affinities are dissolved,
and chemically-united atoms thereby pulled asunder, there must be a diminution of
temperature, or, as it is said, heat becomes latent—that is, the energy of the heat
which has become latent is changed into chemical energy, and this, after decom-
position of the compound chemical body, is again =eprese iter by the chemical
affinity between its isolated different atoms.

LAW OF THE CONSERVATION OF ENERGY.—Julius Robert Mayer and
Helmholtz have established the important law that, in a system which does not
- receive any influence and impression from without, the sum of all the forces acting
within it is always the same. The various forms of energy can be transformed one
into the other, so that kinetic energy may be transformed into potential energy and vice
versi, but there is never any part of the energy lost. The transformation takes place
in such measure that, from a certain definite amount of one form of energy, a
definite amount of another can be obtained.

The various forms of energy acting in organisms occur in the following modi-
fications :—

1. Molar motion (ordinary movements), as in the movements of the whole body
of the limbs, or of the intestines, and even those observable microscopically in
connection with cells.

2. Movements of Atoms as Heat.-—We know, in connection with the vibration
of atoms, that the number of vibrations in the unit of time determines whether the
oscillations appear as heat, light, or chemically-active vibrations. Heat-vibrations
have the smallest number, while chemically-active vibrations have the largest
number, light-vibrations standing between the two. In the human body we only
observe heat-vibrations, but some of the lower animals are capable of exhibiting
the phenomena of light. -

In the human organism the molar movements in the individual organs are con-
stantly being transformed into heat, e.g., the kinetic energy in the organs of the
circulation is transformed by friction into heat. The measure of this is the ‘“ unit
of work ”=1 gramme-metre, and the “ unit of heat ” = 425-5 gramme-metres.

3. Potential Energy.—The organism contains many chemical compounds which
are characterised by the great complexity of their constitution, by the imperfect
saturation of their affinities, and hence by their great ponent’ to split up into
simpler bodies.

The body can transform the potential energy into heat as well as into kinetic
energy, the latter always in conjunction with the former, but the former always by
itself alone. The simplest measure of the potential energy is the amount of heat
which can be obtained by complete combustion of the chemical compounds re-
presenting the potential energy. The number of work-units can then be calculated
- from the amount of heat produced. |

4. The phenomena of electricity, magnetism, and diamagnetism may be
recognised in two directions, as movements of the smallest particles, which are
recognised in the glowing of a thin wire when it is traversed by strong electrical

(

xlii INTRODUCTION.

currents (against considerable resistance), and also as molar movement, as in the
attraction or repulsion of the magnetic needle. Electrical phenomena are manifested
in our bodies by muscle, nerve, and glands, but these phenomena are relatively small
in amount when compared with the other forms of energy. It is not improbable

that the electrical phenomena of our bodies become almost completely transformed

into heat. As yet experiment has not determined with accuracy a “unit of
electricity ” directly comparable with the “ heat-unit ” and the “ work-unit. ”

It is quite certain that within the organism one form of energy can be trans-
formed into another form, and that a certain amount of one form will yield a
definite amount of another form; further, that new energy never arises spontane-
ously, nor is energy already present ever destroyed, so that in the organism the
law of the conservation of energy is continually in action.

ANIMALS AND PLANTS.—The animal body contains a quantity of chemically-
potential energy stored up in its constituents. The total amount of the energy
present in the human body might be measured by burning completely an entire
human body in a calorimeter, and thereby determining how many heat-units are
produced when it is reduced to ashes (see Animal Heat).

The chemical compounds containing the potential energy are characterised by the
complicated relative position of their atoms, by a comparatively imperfect saturation
of the affinities of their atoms, by the relatively small amount of oxygen which
they contain, by their great tendency to decomposition, and the facility with which
they undergo decomposition.

If a man were not supplied with food he would lose 50 grammes of his body-
weight every hour; the material part of his body, which contains the potential
energy, is used up, oxygen is absorbed, and a continual process of combustion takes
place ; by the process of combustion simpler substances are formed from the more
complex compounds, whereby potential is converted into kinetic energy. Itis im-
material whether the combustion is rapid or slow; the same amount of the same
chemical substances always produces the same amount of kinetic energy, 7.e., of
heat.

A person, when fasting, experiences after a certain time the disagreeable feeling

of exhaustion of his reserve of potential energy, hunger sets in, and he takes food.
All food for the animal kingdom is obtained, either directly or indirectly, from the
vegetable kingdom. Even carnivora, which eat the flesh of other animals, only eat
organised matter which has been formed from vegetable food. ‘The existence of
the animal kingdom presupposes the existence of the vegetable kingdom.

All substances, therefore, necessary for the food of animals occur in vegetables.
Besides water and the inorganic constituents, plants contain,. amongst other
organic compounds, the following three chief representatives of food-stufis—fats,
carbohydrates, and proteids.

All these contain stores of potential energy, in virtue of their complex chemical
constitution.

CnH,,,_;O(OH) = fatty acids
Th f. t ta oer : 2 °
e fats contain +C,H,(OH), = glycerin } ($251)

The carbohydrates contain:—C,H,,O, . . ($252).

i a!

—————oo te

INTRODUCTION. xliii

( C. 515-545
H. 6°9- 7:3
The proteids contain per cent.:— J N. 15:2-17:0
O. 20°9-23°5
(Be. WOS= 20 |

A man who takes a certain amount of this food adds thereto oxygen from the
air in the process of respiration. Combustion or oxidation then takes place, where-
by chemically-potential energy is transformed into heat.

It is evident that the products of this combustion must be bodies of simpler con-
stitution—bodies with less complex arrangement of their atoms, with the greatest
possible saturation of the affinities of their atoms, of greater stability, partly rich in
O, and possessing either no potential energy, or only very little. These bodies are
carbon dioxide, CO, ; water, H,O ; and as the chief representative of the nitro-
genous excreta, urea (CO(NH,),), which has still a small amount of potential
energy, but which outside the body readily splits into CO, and ammonia (NH.,).

The human body is an organism in which, by the phenomena of oxidation, the
complex nutritive materials of the vegetable kingdom, which are highly charged
with potential energy, are transformed into simple chemical bodies, whereby the
potential energy is transformed into the equivalent amount of kinetic energy (heat,
work, electrical phenomena).

But how do plants form these complex food-stuffs so rich in potential energy ?
It is plain that the potential energy of plants must be obtained from some other
form of energy. This potential energy is supplied to plants by the rays of the
sun, whose chemical light-rays are absorbed by plants. Without the rays of the
sun there could be no plants. _ Plants absorb from the air and the soil CO,, H,O,
NH,, and N, of which carbon dioxide, water, and ammonia (from urea) are also
produced by the excreta of animals. Plants absorb the kinetic energy of light from
the sun’s rays and transform it into potential energy, which is accumulated during
the growth of the plant in its tissues, and in the food-stuffs produced in them
during their growth. This formation of complex chemical compounds is accom-
panied by the simultaneous excretion of O.

Occasionally, kinetic energy, such as we universally meet with in animals, is liberated in
plants. Many plants develop considerable quantities of heat in their flowers, ¢.g., the arum
tribe. _We must also remember that during the formation of the solid parts of plants, when
fluid juices are changed into solid masses, heat is set free. In plants, under certain circum-
stances, O is absorbed, and CO, is excreted, but these processes are so trivial as compared with
the typical condition in the vegetable kingdom, that they may be regarded as of small
moment.

Plants, therefore, are organisms which, by a reduction process, transform simple
stable combinations into complex compounds, whereby potential solar energy is
transformed into the chemically-potential energy of vegetable tissues. Animals
are living beings, which by oxidation decompose or break up the complex grouping
of atoms manufactured by plants, whereby potential is transformed into kinetic
energy. Thus, there is a constant circulation of matter and a constant exchange of
energy between plants and animals. All the energy of animals is derived from
plants. All the energy of plants arises from the sun. Thus the sun is the cause,
the original source of all energy in the organism, 7.¢., of the whole of life.

(S$ 248 and 249).

ee ee,

xliv INTRODUCTION.

- As the formation of solar heat and solar light is explicable by the gravitation of
masses, gravity is perhaps the original form of energy of all life.

We may thus represent the formation of kinetic energy in the animal body from
the potential energy of plants. Let us suppose the atoms of the substances formed
in organisms, as simple small bodies, balls, or blocks. As long as these lie ina
single layer, or in a few layers, upon the surface, there is a stable arrangement,
and they continue to remain at rest. If, however, an artificial tower be built of
these blocks, so that an unstable erection is produced, and the same tower be after-
wards knocked down, then for this purpose we require—(1) the motor power of the
workman who lifts and carries the blocks ; (2) a blow or other impulse from with-
out applied to the unstable structure—when the atoms will fall together, and as
they fall collide with each other and produce heat. Thus, the energy employed by
the workman is again transformed into the last-named form of energy.

In plants the complex unstable building of the groups of atoms is carried on,
the constructer being the sun. In animals, which eat plants, the complex groups
of the atoms are tumbled down, with the liberation of kinetic energy.

Vital Energy and Life.—The forces which act in organisms, in plants, and
animals are exactly the same as are recognisable as acting in dead matter. A so-
called “ vital force,” as a special force of a peculiar kind, causing and governing the
vital phenomena of living beings, does not exist. The forces of all matter, of
organised as well as unorganised, exist in connection with their smallest particles
or atoms. As, however, the smallest particles of organised matter are, for the
most part, arranged in a very complicated way, compared with the much simpler
composition of inorganic bodies, so the forces of the organism connected with the
smallest particles yield more complicated phenomena and combinations, whereby it
is excessively difficult to ascribe the vital phenomena in organisms to the simple
fundamental laws of physics and chemistry.

The Exchange of Material, or Metabolism (“ Stof‘wechsel”) as a Sign of Life.
—Nevertheless, there appears to be a special exchange of matter and energy
peculiar to living beings. This consists in the capacity of organisms to assimilate
the matter of their surroundings, and to work it up into their own constitution, so
that it forms for a time an integral part of the living being, to be given off again.
The whole series of phenomena is called metabolism or ‘“ Stoffwechsel,” which
consists in the introduction, assimilation, integration, and excretion of matter.

We have already shown that the metabolism of plants and that of animals are
quite different. The processes, as already described, actually occur in the typical
higher plants and animals.

But there is a large group of organisms which, throughout their entire organisa-
tion, exhibit so low a degree of development, that by some observers they are con-
sidered as undifferentiated “ ground-forms.” They are regarded as neither plants
nor animals, and are the most simple forms of animated matter. Haeckel has
called these organisms Protiste, as being the original and primitive forms.

We must assume that, corresponding with their simpler vital conditions, their
metabolism is also simpler, but on this point we still require further ther atiaae |
and pee Y

Physiology of the Blood.

—— ef a

{THE blood is aptly described by Claude Bernard as an internal medium which
acts as a “‘ go-between ” or medium of exchange for the outer world and the tissues.
Into it are poured those substances which have been subjected to the action of the
digestive fluids, and in the lungs or other respiratory organs it receives oxygen.
It thus contains xew substances, but in its passage through the tissues it gives up
some of these new substances, and receives in exchange certain waste products
which have to be got rid of. Its composition is thus highly complex. Besides
carrying the new nutrient fluids to the tissues, it is also the great oxygen-carrier,
as well as the medium by which some of the waste products, ¢.g., CO, urea, are
removed from the tissues, and brought to the organs, ¢.y., the lungs, kidneys, skin,
which eliminate them from the body. It. is at once a great pabulum-supplying
medium and a channel for getting rid of useless materials. As the composition of
the organs through which the blood: flows varies, it is evident that its composition
must vary in different parts of the circulatory system ; and it also varies in the
same individual under different conditions. Still, with slight variations, there are
‘certain general physical, histological, and chemical properties which characterise
blood as a whole. |

1. PHYSICAL PROPERTIES.—(1) Colour.—The colour of blood varies froma
bright scarlet-red in the arteries to a deep, dark, bluish-red in the veins. Oxygen
(and, therefore, the air) makes the blood bright red; want of oxygen makes it
dark. Blood free from oxygen (and also venous blood) is dichroic—i.e., by reflected
light it appears dark red, while by transmitted light it is green. [Arterial blood is
monochroic. |

In thin layers blood is opaque, as is easily shown by shaking blood so as to form
bubbles, or by allowing blood to fall upon a plate with a pattern on it, and pouring
it off again. [Printed matter cannot be read through a thin layer of blood spread on
-a glass slide.] Blood behaves, therefore, like an “ opaque colour,” as its colouring-
matter is suspended in the form of fine particles—the blood-corpuscles.

Hence, it is possible to separate the colouring-matter from the fluid part of the blood by
‘filtration, This is accomplished. by mixing the blood with fluids which render the blood-
corpuscles sticky or rough. If mammalian blood be treated with one-seventh of its volume of
solution of sodic sulphate, or if frog’s blood be mixed with a 2 per cent. solution of sugar (Joh,
rohagie and filtered, the shrivelled corpuscles, now robbed of part of their water, remain upon
the filter.

(2) Reaction.—The reaction is alkaline, owing to the presence of disodic
phosphate, Na,HPO,, and bicarbonate of soda. After blood is shed, its alkalinity
rapidly diminishes, and this occurs more rapidly the greater the alkalinity of the
blood. This is due to the formation of an acid, in which, perhaps, the coloured
corpuscles take part, owing to the decomposition of their colouring-matter. A high

' A

{

2 PHYSICAL PROPERTIES OF THE BLOOD.

temperature and the addition of an alkali favour the formation of the acid (4.
Zuniz). B
The alkaline reaction of blood is diminished : (a) by great muscular exertion, owing to the

formation of a large amount of acid in the muscles ; (8) during coagulation ; () in old blood, .

or blood dissolved by water from old blood-stains, such blood being usually acid ; fresh eruor
has a stronger alkaline reaction than serum ; (8) after the prolonged use of soda the alkalinity
is increased, after the use of acids it is decreased. ;

Methods. —Owing to the colour of the blood we cannot employ ordinary litmus paper to test

its reaction. One of the following methods may be used :—(1) Moisten a strip of glazed red .

litmus paper with solution of common salt, and allow a drop of blood to fall on the paper ;
then rapidly wipe it off before its colouring matter has time to penetrate and tinge the paper
(Zuntz). (2) Liebreich used thin plates of plaster-of-Paris of a perfectly neutral reaction.
These are dried, and afterwards moistened ith a neutral solution of litmus. When a drop of
blood is placed upon the porous plate, the fluid part of the blood passes into it, while the
corpuscles are washed off with water, and the altered colour of the litmus-stained slab is
apparent. [(3) Schiifer uses dry faintly-reddened glazed litmus paper, and on it is placed a
drop of blood, which is wiped off after a few seconds. The place where the blood rested is
indicated by a blue patch upon a red or violet ground. ]

Estimation of the Alkalinity.—_A very dilute solution of tartaric acid (1 cubic centimetre
combines with 3°1 milligrams of soda, é.e., 1 litre of water contains 7°5 grams of crystallised
tartaric acid) is added to blood until a blue litmus paper is turned red (by Zuntz’s method).
100 grams of rabbit’s blood have an alkalinity corresponding to 150 milligrams of soda; the
blood of carnivora to about 180 milligrams (Zassav), while 100 ¢.c. of normal human blood have
an alkalinity equal to 260-300 milligrams of soda (v. Jaksch).

The following method can be used with a few drops of blood :—To neutralise the blood, tar-
taric acid in the above concentration is used. Prepare the following mixture by mixing it with
a concentrated neutral solution of sodic sulphate, and then adding sodic sulphate until the
mixture is completely saturated. I., 10 parts of solution of tartaric acid to 100 parts of con-
centrated sodic sulphate solution ; II., 20 parts tartaric acid solution to 90 sodic sulphate solu-
tion ; III. contains these substances in the proportion of 30 to 80; IV., 40 to 70; V., 50 to
60; VI., 60 to50; VII., 70 to 40; VIII., 80 to 30; IX., 90 to 20; and X., 100 to10. Excess
of sodic sulphate is present in all the flasks.

A known volume of the blood to be investigated is mixed with an equal volume of each of
the mixtures, in a small tube, which is made by drawing out a glass tube 1 millimetre in
diameter to a fine point. To calibrate this tube, suck up water, say, to the height of 8 mm.,
make a mark on the tube with a fine file, then suck up the water until its lower level corre-
sponds with the mark. Again mark the upper limit of the water. To test the blood, suck a
lrop of the mixture I. up to the level of the first mark on the glass pipette, and, after wiping
its point, suck up an equal quantity of blood. Again clean the point of the pipette, and blow
its contents into a watch-glass ; then inix, and test the reaction with sensitive violet-coloured
litmus paper. Proceed in the saine way with the several mixtures, II., to X., until the
alkaline reaction disappears or the acid appears. The narrow strips of litmus paper are dipped
into each of the mixtures, the corpuscles remain in the wetted part of the paper, while the
fluid permeates further and shows the reaction. As a rule, the degree of alkalinity in human
blood corresponds to VI. Human blood can be sucked directly from a small wound made
by a needle, either by attaching an elastic tube or a small hypodermic syringe to the pipette
(Landois).

Pathological.—The alkalinity is increased during persistent vomiting, and decreased in
pronounced anemia, cachexia, uremia, rheumatism, high fever, diabetes, aud cholera. [Imme-
diately before death by cholera it may be acid (Cantani). ]

(3) Odour..—Blood emits a peculiar odour, the halitus sanguinis, which differs
in animals and man,

It depends upon the presence of volatile fatty acids. If concentrated sulphuric acid be added
to blood, whereby the volatile fatty acids are set free from their combinations with alkalies, the
characteristic odour, somewhat similar to that of butyric acid, becomes much more perceptible.

(4) Taste.—Blood has a saline taste, depending upon the salts dissolved in the
fluid of the blood.

(5) Specific Gravity.—The specific gravity is 1056-1059 in man, 1051-1055
in woman ; in children less. The specific gravity of the blood-corpuscles.is 1105,
that of the plasma 1027. Hence the corpuscles tend to sink,

Clinical Method.—A thin glass tube is drawn out till it is of small calibre, and then bent at

aright angle, and closed above with a caoutchoue cap. Press slightly on the caoutchoue cap,
aud suck up a drop of the freshly-drawn blood obtained by pricking the finger. The fine capil-

—_

MICROSCOPIC EXAMINATION OF THE BLOOD. 3

lary-tube is at once immersed in a solution of sodic sulphate, and a drop of the blood expressed
into the saline solution, It is necessary to prepare several solutions of sodic sulphate with
specific gravities varying from 1050-1070. The solution in which the corpuscles remain
* suspended indicates the specific gravity of the blood (Roy, Landois).

_. The drinking of water and hunger diminish the specific gravity temporarily, while thirst and
the digestion of dry food raise it. If blood be passed through an organ artificially, its specific
gravity rises in consequence of the absorption of dissolved matters and the giving off of water.
It falls after hemorrhage, and is diminished in badly-nourished individuals. [By working
with solutions of glycerine, Jones finds that it is highest at birth, is at a minimum between the
second week and the second year; it rises gradually until the 35th-45th year. It is usually
higher in the male than the female, is diminished by pregnancy, the ingestion of solid or liquid
food, and gentle exercise. |

((6) Temperature.—Blood is viscid, and its temperature varies from 36°5° C.
(97:7° F.) to 378° (100° F.). The warmest blood in the body is that of the
hepatic vein (§ 210). |

2,. MICROSCOPIC EXAMINATION .--| Blood, when examined by the microscope,
is seen to consist of an enormous number of corpuscles—-coloured and colourless—-
floating in a transparent fluid, the plasma, or liquor sanguinis.

Wig, 1;

A, human coloured blood-corpuscles—-1, on the flat; 2, on edge ; 3, rouleau of coloured cor-
puscles. .B, amphibian coloured blood-corpuscles—1, on the flat; 2, on edge. C, ideal
transverse section of a human coloured blood-corpuscle magnified 5000 times linear—ab,
diameter ; cd, thickness.

Human Red Blood-Corpuscles.—-(~) Form.—They are circular, coin-shaped,
homogeneous discs, with saucer-like depressions on both surfaces, and with rounded
margins ; in other words, they are bi-concave, circular non-nucleated discs.

(6) Size.—The diameter (ab) is 7‘7y,! (6°7-9°3n) the greatest thickness (c#) 1°9p
(fig. 1, C), [ze it is 459 to xayq Of an inch in diameter, and about one-fourth of
that in thickness].

They are slightly diminished in size by septic fever, inanition, morphia, increased bodily
i, ae and CO,; and increased by O, watery condition of the blood, cold, consumption
of alcohol, quinine, and hydrocyanic acid. Compare § 10, 3.

If the total amount of blood in a man be taken at 4400 cubic centimetres, the corpuscles.
therein contained have a surface of 2816 square metres, which is equal to a square surface with
a side of 80 paces ; 176 cubic centimetres of blood pass through the lungs in a second, and the
blood-corpuscles in this amount of blood havea superficies of 81 square metres, equal to a square
surface with a side of 13 paces (Welcker). ~

- (ce) The weight of a blood-corpuscle is 0:00008 milligramme. —

1 The Greek letter « represents one-thousandth of a millimetre (u=0'001 mm.), and is the
sign of a micro-millimetre, or a micron.

ae: MICROSCOPIC EXAMINATION OF THE BLOOD,

(¢) The number exceeds 5,000,000 per cubic millimetre in the male, and
4,500,000 in the female ; so that, in 10 lbs. of blood, there are 25 billions of
corpuscles. The number is in inverse ratio to the amount of plasma; hence, the
number must vary with the state of contraction of the blood-vessels, the pressure,
diffusion currents, and other conditions.

The number of red corpuscles is increased ; in venous blood (especially in the small cutane-_
ous veins), after the use of solid food, after much sweating, and the excretion of much water by
the bowel and kidneys ; during inanition, because the blood-plasma undergoes decomposition
sooner than the blood-corpuscles themselves ; in the blood of the newly-born child, especially
when the umbilical cord is long in being tied (§ 40), from the 4th day onward the number is
diminished ; in persons of robust constitution, and in those who live in the country. The
number is diminished, during pregnancy, after copious draughts of water.. In the earlier
period of fetal life the number is only $--1 million in 1 cubic millimetre. (For the pathological
conditions see § 10.)

Methods of Counting the Blood-Corpuscles.—The pointed end of a glass pipette (fig. 3), the
mixer, is dipped into the blood, and by sucking the elastic tube /, blood is drawn into the tube

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Fig, 2. Fig. 3. .
Apparatus of Abbé and Zeiss for counting the The Melangéur, pipette
corpuscles. A,.in section ; C, surface view or mixer, 4

without cover-glass; B, microscopic appear-
ance with the blood-corpuscles.

until it reaches the mark 4, on the stem of the pipette, or until the mark 1 is reached. The
carefully-cleaned point of the pipette is dipped into the artificial serum, and this is sucked into
the pipette until it reaches the mark, 101. The artificial serum consists of 1 vol. of solution of ;
gum arabic (sp. gr. 1020) and 3 vols. of a solution of equal parts of sodic sulphate and sodie
chloride (sp. gr. 1020), The rocess of mixing the two fluids is aided by the presence of a little
glass ball (a) in the bulb of the pipette. If blood is sueked up to the mark 4, the strength of
the mixture is 1: 200 ; if to the mark 1, itis 1: 100; a small drop of the mixture is ee to.

—,

—_

run into the counting chamber of Abbé and Zeiss (fig. 2). The first portions are not.
order to obtain a uniform sample from the bulb of the" pipettes This ohainiite coneeonee I

MICROSCOPIC EXAMINATION OF THE BLOOD. 5

receptacle 0°1 mm. deep, with its base divided into squares, and cemented to a glass slide, the
whole being covered with a thin covering-glass. ‘The space over each square= gp cubic
millimetre. Count, with the aid of a microscope, the number of blood-corpuscles in each
square, and the number found, multiplied by 4000, will give the number of blood-corpuscles in
le.mm. This number, again, must be multiplied by 100 or 200, according as the blood was
diluted 100 or 200 times. To ensure greater accuracy, it is well to count the number in severa/
squares, and to take the inean of these.

[Gowers’ Method. —‘‘ The Hemacytometer (fig. 4) consists of—(1) a small pipette, which, when
filled to the mark on its stem, holds exactly 995 cubic millimetres. It is furnished with an
india-rubber tube and mouthpiece to facilitate filling and emptying. (2) A capillary tube
marked to contain exactly 5 cubic miilimetres, with india-rubber tube for filling, &. (3) A
small glass jar in which the dilution is made. (4) A glass stirrer for mixing the blood and
solution in the glass jar. (5) A brass stage plate, carrying a glass slip, on which is a cell, 4 of a
millimetre deep. The bottom of this is divided into ;45 millimetre squares. Upon the top of
the cell rests the cover-glass, which is kept in its place by the pressure of two springs proceeding
from the ends of the stage plate.” The diluting solution used is a solution of sodic sulphate in
distilled water, sp. gr. 1025, or the following—sodic sulphate, 104 grains ; acetic acid, 1 drachm ;
distilled water, 4 oz. .

“995 cubic millimetres of the solution are placed in the mixing jar ; 5-cubic millimetres of
blood are drawn into the capillary tube from the puncture in the finger, and then blown into
the solution. The two fluids are well mixed by rotating the stirrer between the thumb and
finger, and a small drop of this dilution is placed in the centre of the cell, the covering-

Fig. 4,

Gowers’ apparatus. A, pipette for measuring the diluting solution; B, capillary tube for
measuring the blood ; C, cell with divisions on the floor, mounted on a slide ; D, vessel in
which the dilution is made ; E, glass stirrer ; F, guarded spear-pointed needle,

glass gently put upon the cell, and secured by the two springs, and the plate placed upon the
stage of the microscope. The lens is then focussed for the squares. In a few minutes the
corpuscles have sunk to the bottom of the cell, and are seen at rest on the squares. The
number in ten squares is then counted, and this, multiplied by 10,000, gives the number in
a cubic millimetre of blood.”

To estimate the colourless corpuscles only, mix the blood with 10 parts of 0°5 per cent. solu-
tion of acetic acid, which destroys all the red corpuscles ( Zhoma).

(e) Red blood-corpuscles are characterised by their great elasticity, flexibility,
and softness. [The elastic property is shown by the extent to which red corpuscles
while circulating may be distorted, and yet resume their original form as soon as -
the pressure is removed. | 3

6 HISTOLOGY OF THE HUMAN RED BLOOD-CORPUSCLES.

3. HISTOLOGY OF THE HUMAN RED BLOOD-CORPUSCLES.— When
observed singly, human red blood-corpuscles are bi-concave circular discs of a
yellow colour with a slight tinge of green ; they seem to be devoid of an envelope,
are certainly non-nucleated, and appear to be homogeneous throughout. Each
corpuscle consists (1) of a framework, an .exceedingly pale, transparent, soft
protoplasm—the stroma ; and (2) of the red pigment, or hemoglobin, which
impregnates the stroma, much as fluid passes into and is retained in the interstices
of a bath-sponge,

4, EFFECT OF REAGENTS.-~(A) On their Vital Phenomena,—The blood-
corpuscles present in shed blood—or even in defibrinated blood, when it is
reintroduced into the circulation—retain their vitality and functions undiminished.
Heat acts powerfully on their vitality, for if blood be heated to 52° C., the vitality
of the red corpuscles is destroyed. Mammalian blood may be kept for four or
tive days in a vessel under iced water, and still retain its functions; but if it be
kept longer, and reintroduced into the circulation, the corpuscles rapidly break up
——a proof that they have lost
their vitality. The red corpuscles
in freshly shed blood sometimes
exhibit a peculiar melberry-like
appearance (figs. 5, 6, g, 2). [This
is called crenation of the coloured
corpuscles. It occurs in cases
of poisoning with Calabar bean ;
and also by the addition of a 2 per
cent. solution of common salt. ]
The blood of many persons crenates
spontaneously —a condition as-
cribed to an active contraction of
the stroma, but it is doubtful if
this is the cause. The red cor-
puscles of the embryo-chick undergo
active contraction.

(B) On their External Charac-
ters.—(«) The colour is changed
by many gases. O makes blood
scarlet, want of O renders it dark
bluish-red, CO makes it cherry-red,
NO violet-red. There is no difference between the shape of the corpuscles in arterial
and venous blood. All reagents (¢.g., a concentrated solution of sodic sulphate),
which cause great shrinking of the coloured corpuscles, produce a very bright scarlet
or brick-red colour. The red colour so’produced is quite different from the scarlet-
red of arterial blood. Reagents which render blood-corpuscles globular darken the
blood, ¢.7., water.

(The contrast is very striking, if we compare blood to which a 10 per cent. solution of common
salt has been added with blood to which water has been added. With reflected light the one
is bright red, and the other a very dark deep crimson, almost black. ]

(}) Formation of Rouleaux.—A very common phenomenon in shed blood is the
tendency of the corpuscles to run into rouleaux (fig. 1, A, 3).

Conditions that increase the coagulability of the blood favour this phenomenon, which is
ascribed by Dogiel to the attraction of the dises and the formation of a sticky substance. [The
cause of the formation of rouleaux is by no means clear. The corpuscles may be detached from
each other by gently touching the cover-glass, but the rouleaux may re-form. . Lister su

that the surfaces of the corpuscles were so altered that they became adhesive. Norris made ex-
periments with corks weighted with tacks or pins, so as to produce partial submersion of the cork

Fig. §,

Crenation of human red blood-corpuscles.

CHANGES OF FORM OF THE CORPUSCLES. Ze

dises. These discs rapidly cohere, owing to capillarity, and form rouleaux. If the dises be
completely submerged they remain apart, as occurs with unaltered blood-corpuscles within the
blood-vessels. If, however, the corpuscles be dipped in petroleum, and then placed in water,
rouleaux are formed.] If reagents which cause the corpuscles to swell up be added to the blood,
the corpuscles become globular and the rouleaux break up. According to E. Weber and Suchard,
the uniting medium is not fibrin (although it may sometimes assume a fibrous form), but belongs
to the peripheral layer of the corpuscles.

(c) Changes of Form.—The discharge of a Leyden jar causes the corpuscles to
crenate, so that their surfaces are beset with coarse or fine projections (fig. 6, ¢, d,
¢, g, h) ; it also causes the corpuscles to assume a spherical form (7, 7), and they

Red blood-corpuscles. «, b, normal human red corpuscles, the central depression more or less
in focus; c, d, e¢, mulberry, and g, h, crenated forms; %, pale corpuscles decolorised by
water ; 7, stroma ; f, frog’s blood-corpuscle acted on by a strong saline solution.

become smaller than normal. The corpuscles so altered are sticky, and run together
like drops of oil, forming larger spheres. The prolonged action of the electrical
spark causes the hemoglobin to separate from the stroma (4), whereby the fluid
part of the blood is reddened, while the stroma is recognisable only as a faint
shadow (/). Similar forms are to be found in decomposing blood, as well as after
the action of many other reagents. Heat.—When blood is heated, on a warm
stage, to 52° C. the corpuscles exhibit remarkable changes. Some of them become
spherical, others biscuit-shaped ; some are perforated, while in others small portions
become detached and swim about in the surrounding fluid, a proof that heat
destroys the histological individuality of the corpuscles. If the heat be continued,
the corpuscles are ultimately dissolved (§ 10, 3).

‘Heat acts like the addition of a concentrated solution of urea to blood. If strong pressure
he exerted upon a microscopic preparation, the blood-corpuscles may break in pieces. The
latter process is called hemocytotrypsis, in contradistinction to that of solution of the cor-
puscles or heemocytolysis.

If a finger moistened with blood be rapidly drawn across a warm slip of glass, so that the
fluid dries rapidly, the corpuscles exhibit very remarkable shapes, showing their great ductility
and softness.

Cytozoon—Gaule’s Experiment.—A few drops of freshly-shed frog’s blood are mixed with 5
c.c. of 0°6 per cent. solution of common salt, and the mixture defibrinated by shaking it along
with a few ¢.c. of mercury. A drop of the defibrinated blood is examined on a hot stage
(30°-32° C.) under a microscope, when a protoplasmic mass, the. so-called ‘‘ Wiirmchen,”
escapes with a lively movement from many corpuscles, and ultimately dissolves. Similar
“feytozoa”” were discovered by Gaule in the epithelium of the cornea, of the stomach and
intestine, in connective-tissue, in most of the large glands, and in the retina (frog, triton). In
mammals: also he found similar but smaller structures. Most probably these structures are
parasitic in their nature, as suggested by Ray Lankester, who called the parasite Drepanidium
ranarum,

[Staining Reagents.—Such reagents as magenta, picro-carmine, carmine, and
many of the aniline dyes, stain the nucleus deeply when such is present, and
although they must traverse the hemoglobin to reach the nucleus, the hemoglobin
itself is not stained. When no nucleus is present, therefore, the corpuscles are not

+"

. /
8 STROMA—-LAKE-COLOURED BLOOD.

stained. Magenta causes one or more small spots or maculz to appear on the edge
of the corpuscles (fig. 7,@). What its significance is, is entirely unknown, Normal
saline solution (0°6 per cent. NaCl), tinged with methyl violet, is a good staining
and preservative agent. | "

[Agitation with Mercury.—If ox blood be shaken up with mercury for 7 or 8 hours, the cor-
puscles completely disappear, no trace of stroma or corpuscles being found in the fluid (Meltzer
and Welch). The addition of pyrogallic acid (20 per cent.), potassic chlorate (6 per cent. ),
and silver nitrate (3 per cent.), completely prevents dissolution of the corpuscles, even though
the shaking be kept up for fourteen days. ] ,

If blood be mixed with concentrated gum solution, and if concentrated salt solution be added
to it under the microscope, the corpuscles assume elongated forms. Similar forms are obtained
by mixing blood with an equal volume of gelatine at 36° C., allowing it to cool, and then
making sections of the coagulated mass. The corpuscles may be broken up by pressing
firmly on the cover-glass, In all these experiments no trace of an envelope around the cor-
puscles is observed. [An excellent reagent for ‘‘ fixing” the blood-corpuscles is either a dilute
solution or the vapour of osmic acid. ] ;

Conservation of the Corpuscles.—In investigating blood with the microscope for forensic
purposes, it is necessary to have a solvent for the blood when it occurs as stains on a garment
or instrument. Dried stains are dissolved by a concentrated, or a 30 per cent., solution of

«C) f e bia a
“S jogs q
a i ie
ee oes A

Rigg.

a, b, human red blood-corpuscles ; a, acted on by magenta; 0, by tannic acid. The others are
amphibian red blood-corpuseles ; c, d, ¢, effect of tannic acid ; /, of dilute acetic acid ; g, of
dilute aleohol ; d, by boracic acid (Stirling). ; |

caustic potash, or with one of the preserving fluids. If the stain be softened with con- |

centrated tartaric acid, colourless corpuscles are specially distinct (Strwwe). Nevertheless,
corpuscles are often not found in such stains. If the corpuscles have become very pale,

their colour may be improved by adding a solution of iodide of potassium, a saturated solution

of picric acid, 20 per cent. pyrogallic acid, or 3 per cent. solution of silver nitrate.

5. STROMA—LAKE-COLOURED BLOOD.—Many reagents cause the hemo-
globin to separate from the stroma. The hemoglobin dissolves in the serum ; the
blood becomes dark red and transparent, as it contains its colouring matter in
solution, and hence it is called ‘ lake-coloured”’ (/o//ett). The aggregate condition
of the haemoglobin is not altered when the corpuscles are dissolved—it only
changes its place, leaving the stroma and passing into the serum. Hence, the
temperature of the blood is not lowered thereby.

Methods. —To obtain a large quantity of the stroma for chemical purposes, add 10 vols, of

‘a solution of common salt (1 vol. concentrated solution, and 15 to 20 vols. of water) to 1 vol.

of defibrinated blood, when the stromata are thrown down as a whitish precipitate.

For microscopical purposes, mix blood with an equal volume of a concentrated solution of
sodic yr comin and cautiously add a 1 per cent. solution of tartaric acid.

The following reagents cause a separation of the stroma from the hemoglobin, and thus make
blood transparent :—

(a) Physical Agents.—1. Heating the blood to 60° C. (Schultze) ; the temperature, however,
varies for the blood of different animals. 2. Repeated freezing and thawing of the blood —
(Rollett), 3. Sparks from an electrical machine (but not after the addition of salts to the
blood) (Rollett) ; the constant and induced currents (Newmann). phe

(b) Chemically active Substances produced within the Body.—-4, Bile (Hiinefeld), or bile salts

(Plattner, v. Dusch). 5, Serum of other species of animals (Landois) ; thus dog’s serum and
frog’s serum dissolve the blood-corpuscles of the rabbit in a few minutes. 6. The addition of
lake-coloured blood of many species of animals (Landois). ae

(c) Other Chemical Reagents.—7. Water. 8. The vapour of chloroform (Béttcher); ether (v.
Wittich); amyls, small quantities of alcohol (Rollett) ; thymol (Marchand) ; nitrobenzol, —
ethylic ether, aceton, petroleum ether, &ec. (LZ, Lewin), 9. Antimoniuretted hydrogen, arseni-
uretted hydrogen ; carbon bisulphide ; boracic acid (2 per cent.), added to amphibian bloo
causes the red mass (which also encloses the nucleus when such is present), the so-called __

FORM AND SIZE OF THE BLOOD-CORPUSCLES, 9

zooid, to separate from the cecoid (fig. 7, d@). The zooid may shrink from the periphery of the
corpuscle, or it may pass out of the corpuscle altogether (Briicke) ; Briicke regards the stroma in
a certain sense as a house, in which the remainder of the substance of the corpuscle, the chief
part endowed with vital phenomena, lives. 11. Strong solutions of acids dissolve the cor-
puscles ; more dilute solutions cause precipitates in the hemoglobin. This is easily seen with
earbolic acid (Hiils and Landois, Stirling and Rannie). 12, Alkalies of moderate strength
cause sudden solution. A 10 per cent. solution of potash, placed at the edge of a cover-
glass, shows the process. of solution going on under the microscope. At first the corpuscles
become globular, and so appear smaller, but afterwards they burst like soap-bubbles. [13.
NH,Cl injected into the blood causes vacuolation of the red corpuscles (Bobritzky). 14. Sodic

_ salicylate, benzoate, and colchicin, dissolve the red corpuscles (N. Paton). ]

[Tannic Acid.—A freshly prepared solution of tannic acid has a remarkable effect on the col-
oured blood-corpuscles of man and animals—causing a separation of the hemoglobin from the
stroma (W. Roberts). The usual effect is to produce one or more granular buds of hemo-
globin on the side of the corpuscles (fig. 7, 6, c); more rarely the hemoglobin collects around
the nucleus, if such be present (fig. 7, @), or is extruded, as shown in fig. 7, e.]

[Ammonium or Potassium Sulpho-cyanide removes the hemoglobin, and reveals a reticular
structure—intra-nuclear plexus of fibrils (Stirling and Raniice). |
The Amount of Gases in the blood exercises an important influence on their solubility. The

corpuscles of venous blood, which contains much CO,, are more easily dissolved than those of

arterial blood ; while between both stands blood containing CO. When the gases are com-
pletely removed from the blood, it becomes lake-coloured.

Salts increase the resistance of the corpuscles to physical means of solution, while
they facilitate the action of chemical solvents.

If certain salts be added in substance to blood, they make blood lake-coloured ; potassic
sulphocyanide, sodic chloride, &c. (Kowalewsky).

Resistance to Solvents.—The red blood-corpuscles offer a certain degree of
resistance to the action of solvents,

Method.—Mix a small drop of blood with an equal volume of a 3 per cent. solution of sodic
chloride, and then add distilled water until all the coloured corpuscles are dissolved. Fill the
mixer (fig. 3) up to the mark 1 with blood obtained by pricking the finger, and blow this blood
into an equal volume of a 3 per cent. solution of NaCl previously placed in a hollow in a glass
slide. Mix the fluids, and the corpuscles will remain undissolved. By means of the pipette
add distilled water, and go on doing so until all the corpuscles are dissolved ; which is ascertained
with the microscope. In normal blood, solution of the corpuscles occurs after 30 volumes of
distilled water have been added to the blood (Landois).

There are some individuals whose blood is more soluble than that of others ; their corpuscles
are soft, and readily undergo changes. Many conditions, such as cholemia, poisoning with
substances which dissolve the corpuscles, and a markedly venous condition of the blood, affect
the corpuscles. Interesting observations may be made on the blood in infectious diseases,
hemoglobinuria, and in cases of burning. In anemia and fever, the capacity for resistance
seems to be diminished.

6. FORM AND SIZE OF THE BLOOD-CORPUSCLES OF ANIMALS.—All
mammals (with the exception of the camel, llama, alpaca, and their allies), and the
cyclostomata amongst fishes, ¢.g., Petromyzon, possess circular bi-concave non-
nucleated disc-shaped corpuscles. Elliptical corpuscles without a nucleus are found
in the above-named mammals, while all birds, reptiles, amphibians (fig. 1, B, 1, 2),
and fishes (except cyclostomata) have nucleated elliptical bi-convex corpuscles.

Size (u4=0-°001 Millimetre)
Of the Elliptical Corpuscles,
Of the Disc-shaped ES
Coxpusnies. Short: Diameter. | Long Diameter.
Elephant, 9-4 Llama, . .. 40m | 8:0 u
Man, . yer Dove, d i CED it 14°63;
Dog, . 7°3 Frog, ‘ sre LUTE ie 7 Aa ia
Rabbit, 6°9 Triton, — soe ety | 29°3 ,,
Cat, 6°5 Proteus,~ . 35°0,, | 58°0 ,,
Sheep, . 5:0
Goat, . : 4'1,, The corpuscles of Amphiuma are nearly one-third larger
Musk-deer, . Pg than those of Proteus (Ridde/).

10 ORIGIN OF THE RED BLOOD-CORPUSCLES.

Amongst vertebrates, amphioxus has colourless blood. The anes blood-corpuscles of many
amphibia, ¢.g., amphiuma, are visible to the naked eye. The blood-corpuscles of the frog
contain, in addition toa nucleus, a nucleolus (Auerbach, Ranvier), [and the same is true of the
coloured corpuscles of the newt (Stirling), The nucleolus is revealed by acting on the
corpuscles with dilute alcohol (1, aleohol ; 2, water ; Ranvier's “ alcool au tiers” (fig. 7, g).] It
is evident that the larger the blood-corpuscles are, the smaller must be the number and total
superficies of the corpuscles in a given volume of blood. In birds, however, the number is
relatively larger than in other classes of vertebrates, notwithstanding the larger size of their
corpuscles ; this, doubtless, has a relation to the very energetic metabolism that takes place in
birds (Malassez). Amongst mammals, carnivora have more blood-corpuscles than herbivora.
Goat’s blood contains 9,720,000 corpuscles per cubic millimetre ; llama’s, 13,000,000 ; bull-
tinch’s, 3,600,000 ; lizard’s, 1,420,000 ; frog’s, 404,000 ; and that of proteus, 36,000 ( Welcker).
In hybernating animals, the number diminishes from 7,000,000 to 2,000,000 per cubic -
millimetre. No relation exists between the size of the animal and that of its blood-
corpuscles.

The invertebrata generally have colourless blood, with colourless corpuscles ; but the earth-
worm, and the larva of the large gnats, &c., have red blood whose plasma contains hemoglobin,
while the blood-corpuscles themselves are colourless. Many invertebrates possess red, violet,
brown, or green onalescent blood with colourless corpuscles (amceboid cells). In cephalopods,
and some crabs, the blood is blue, owing to the presence of a colouring matter (hemocyanin),
which contains copper, and combines with O.

7. ORIGIN OF THE RED BLOOD-CORPUSCLES.—(A) During Embryonic
Life.—Blood-corpuscles are developed in the fowl during the first days of embryonic
life. [They appear in groups within the large branched cells of the mesoblast, in the
vascular area of the blastoderm outside the developing body of the chick, where
they form the ‘ blood-islands ” of Pander. The mother-cells form an irregular
network by the union of the processes of adjoining cells, and meantime the central
masses split up, and the nuclei multiply. The small nucleated masses of proto-
plasm, which represent the blood-corpuscles, acquire a reddish hue, while the sur-
rounding protoplasm, and also that of the processes, becomes vacuolated or hollowed
out, constituting a branching system of canals ; the outer part of the cells remaining
with their nuclei to form the walls of the future blood-vessels. A fluid appears
within this system of branched canals in which the corpuscles lie, and gradually a
communication is established with the blood-vessels developed in connection with
the heart. According to Klein, the nuclei of the protoplasmic wall also proliferate,
and give rise to new cells, which are washed away to form blood-corpuscles.| At
first the corpuscles exhibit amceboid movements, are devoid of pigment, nucleated,
globular, larger, and more irregular than the permanent corpuscles. They become
coloured, retain their nucleus, and are capable of undergoing multiplication by
division ; Remak observed all the stages of the process of division, which is best
seen from the 3rd to the 5th day of incubation. Increase by division also takes place
in the larvee of the salamander, triton, and toad (lemming); and during the intra-
uterine life of a mammal, in the spleen, bone-marrow, the liver, and the circulating
blood (Bizzozero).

Neumann found in the liver of the embryo protoplasmic cells containing red blood-
corpuscles. Cells, some with, others without, hemoglobin, but with large nuclei,
have been found. These cells increase by division, their nucleus shrivels, and they
ultimately form blood-corpuscles (Zéwit). The spleen is also regarded as a centre
of their formation, but this seems to be the case only during embryonic life
(Neumann). Here the red corpuscles are said to arise from yellow, round, nucleated
cells, which represent transition forms. .Foa and Salvioli found red corpuscles
forming endogenously within large protoplasmic cells in lymphatic glands. In the
later period of embryonic life, the characteristic non-nucleated corpuscles seem to
be developed from the nucleated corpuscles. The nucleus becomes smaller and
smaller, breaks up, and gradually disappears. In the human embryo at the fourth
week, only nucleated corpuscles are found ; at the third month their number is still
}- of the total corpuscles, while at the end of foetal life nucleated blood-corpuscles

ae

—

ORIGIN OF THE RED BLOOD-CORPUSCLES. II

are very rarely found. Of course, in animals with nucleated’ blood-corpuscles, the
nucleus of the embryonic blood-corpuscles remains.

(B) During Post-Embryonic Life.— K6lliker assumed that in the tail of the tadpole
capillaries are formed by the anastomoses of the processes of branched and radiating
connective-tissue corpuscles. These corpuscles lose their nuclei and protoplasm,
become hollowed out, join with neighbouring capillaries, and thus form new blood-
channels. J. Arnold and Golubew oppose this view, asserting that the blood-
capillaries in the tail of the tadpole give off solid buds at different places, which
grow more and more into the surrounding tissues, and anastomose with each other ;
after their protoplasm and contents disappear they become hollow, and a branched
system of capillaries is formed in the tissues. Ranvier noticed the same mode of
growth in the omentum of newly-born kittens.

Young rabbits, a week old, have, in their omentum, small white or milk spots
(Ranvier), in which lie “ vaso-formative cells,” ¢.¢., highly refractive cells of
variable shape, with long cylindrical protoplasmic processes (fig. 8). In its refractive
power the protoplasm of these
cells resembles that of lymph-
corpuscles. Long rod-like nuclei
lie within these cells (K, K), and
also red blood-corpuscles (r, r), ‘
and both are surrounded with <@=
protoplasm. These vaso-forma-
tive cells give off protoplasmic
processes (a, a), some of which
end free, while others form a
network. Here and there elon-
gated connective-tissue corpuscles
lie on the branches, and ulti-

mately form the adventitia of the 7 Fig. 8.

blood-vessel. The vaso-formative formation of red blood-corpuscles within ‘‘ vaso-forma-
cells have many forms: they may tive cells,” from the omentum of a rabbit seven
be elongated cylinders ending in days old. 7, 7, the formed corpuscles ; Kk, K, nuclei

of the vaso-formative cell; a, a, processes which

points, or more round and oval “ Re
I ‘ : ultimately unite to form capillaries.

resembling lymph cells, or modi-
fied connective-tissue corpuscles. These cells are always the seat of origin of non-
nucleated red blood-corpuscles, which arise in the protoplasm of vaso-formative cells,

‘as chlorophyll grains or starch granules arise within the cells of plants. The

corpuscles escape, and are washed into the circulation when the cells, by means of
their processes, form connections with the circulatory system. Probably the vessels
so formed in the omentum are only temporary. May it not be that there are many
other situations in the body where blood is regenerated ?

[The observations of Schafer also prove the intra-cellular origin of red blood-
corpuscles, and although this mode usually ceases before birth, still it is found in
the rat at birth. The protoplasm of the subcutaneous connective-tissue corpuscles,

which are derived from the mesoblast, has in it small coloured globules about the
‘size of a coloured corpuscle. ‘The mother-cells elongate, become pointed at their
ends, and unite with processes from adjoining cells. The cells become vacuolated ;

fluid or plasma, in which the liberated corpuscles float, appears in their interior, and
ultimately a communication is established with the general circulation. |

Neumann obseryed similar formations-in the embryonic liver ; Wissotzky in the rabbit's
amnion ; Klein in the embryo chick ; and Bayerl in ossifying cartilage. All these observations

_ go to show that at a certain early period of development. blood-corpuscles are formed within
other large cells of the mesoblast, and that part of the protoplasm of these blood-forming cells

remains to form the wall of the future blood-vessel. ..

12 DECAY OF THE RED BLOOD-CORPUSCLES.

(C) Later Formation.—Most observers agree that the red blood-corpuscles are
formed from special nucleated cells, which gradually assume the form and colour of
the perfect red corpuscle. According to Neumann, however, these corpuscles are
pigmented from the first. In the tailed amphibians and fishes, the spleen, in all
other vertebrates the red marrow of bone, are the seats of formation of these
corpuscles, which subsequently increase by division (Neumann, Rindfleisch,
Bizzozero). In the red marrow of bone we can study all the stages of the transforma-
tion ; especially pale contractile cells similar to colourless corpuscles, and also red
nucleated corpuscles, which are similar to the nucleated corpuscles of the embryo,
and the progenitors of the red corpuscles. These transition cells are said by Erb to
be more numerous after severe hemorrhage, the number of them occurring in the
blood corresponding with the energy of the formative process. After copious.
hemorrhage, these transition forms appear in numbers in the blood-stream. The
small veins, and, perhaps, the capillaries of the red marrow of bone and the spleen
have no proper walls, so that the red corpuscles when formed can pass into the
circulation.

Red or blood-forming marrow occurs in the bones of the skull, and in most of the bones of
the trunk, while the bones of the extremities either contain yellow marrow (which is essentially
fatty in its nature), or, at most, it is only the heads of the long bones that contain red marrow.

Where the blood-regeneration process is very active, however, the yellow marrow may be
changed into red, even throughout all the bones of the extremities (Vewmann).

8. DECAY OF THE RED BLOOD-CORPUSCLES.—The blood-corpuscles
undergo decay within a limited time, and the liver is regarded as one of the chief
places in which their disintegration occurs, because bile-pigments are formed from
hemoglobin, and the blood of the hepatic vein contains fewer red corpuscles than
the portal vein.

The splenic pulp contains cells which indicate that coloured corpuscles are
broken up within it. hese are the so-called “ blood-corpuscle-containing cells ”
(§ 102). Quincke’s observations go to show that the red corpuscles—which may
live from three to four weeks—when about to disintegrate, are taken up by the white
blood-corpuscles in the hepatic capillaries, by the cells of the spleen and the bone-
marrow, and are stored up chiefly in the capillaries of the liver, in the spleen,
and in the marrow of bone. They are transformed, partly into coloured, and
partly into colourless proteids which contain iron, and are either deposited in a
granular form, or are dissolved. Part of the products of decomposition is used for
the formation of new blood-corpuscles in the marrow and in the spleen, and also
perhaps in the liver, while a portion of the iron is excreted by the liver in the bile.

That the normal red blood-corpuscles and other particles suspended in the blood-stream are
not taken up in this way, may be due to their being smooth and polished. As the corpuscles
grow older and become more rigid, they, as it were, are caught by the ameeboid cells. As cells.
containing blood-corpuscles are very rarely found in the general circulation, one may assume ~

that the occurrence of these cells within the spleen, liver, and marrow of bone is favoured by
the slowness of the circulation in these organs (Quincke).
Pathological.—In certain pone oe conditions, ferruginous substances derived from the-
red blood-corpuscles are found in masses in the spleen, the marrow of bone, and the capillaries
of the liver:—(1) When the disintegration of: blood-corpuscles is increased, as in anemia
(Stahel). (2) When the formation of red blood-corpuscles from the old material is diminished.
If the excretion from the liver cells be prevented, iron accumulates within them ; it is also more-
abundant in the blood-serum, and it may even accumulate in the secretory cells of the cortex
_of the kidney and pancreas, in gland cells, andin the tissue elements of other organs. When
the amount of blood in dogs is greatly increased, after four weeks an enormous number of
granules containing iron occur in the leucocytes of the liver capillaries, the cells of the spleen,
bone-marrow, lymph-glands, liver cells, and the epithelium of the cortex of the kidney. “The
iron reaction in the last two situations occurs after the introduction of hemoglobin, or of salts.
of iron into the blood (Glaeveck, v. Stark.) aiak

When we reflect how rapidly large quantities of blood are replaced after
_ hemorrhage and after menstruation, it is evident that there must be a brisk manu-_

THE COLOURLESS BLOOD-CORPUSCLES. 13
factory somewhere. As to the number of corpuscles which daily decay, we have in
some measure an index in the amount of bile-pigment and urine-pigment resulting
from the transformation of the liberated hemoglobin (§ 20).

9. COLOURLESS CORPUSCLES, BLOOD-PLATES, AND GRANULES.—
White Blood-Corpuscles.— Blood, like many other tissues, contains a number of
cells or corpuscles which reach it from without ; the corpuscles vary somewhat in
form, and are called colourless or white biood-corpuscles, or ‘leucocytes ”
(Hewson, 1770). Similar corpuscles are found in lymph, adenoid tissue, marrow
of bone, and as wandering cells or leucocytes in connective-tissue, and also between
glandular and epithelial cells. So that these corpuscles are by no means peculiar
to blood alone. They all consist of more or less spherical masses of protoplasm,
which is sticky, highly refractile, soft, capable of movement, and devoid of an
envelope (fig. 9). When they are quite fresh (A) it is difticult to detect the
nucleus, but after they have been
shed for some time, or after the
addition of water (B), or acetic
acid, the nucleus (which is usually
a compound one) appears ; acetic
acid clears up the perinuclear
protoplasm, and reveals the pres-
ence of the nuclei, of which the

. : D
number varies from one to four, a ,
although generally three are found. ae ae Soo) en
The subsequent addition of ma- cw vs sae ae
genta solution causes the nuclei to ee wre Br ait
stain deeply. Water makes the 4
contents more turbid, and causes E
the corpuscles to swell up. One eee nee : 2
or more nucleoli may be present \| y Re
in the nucleus. The size of the \+-/—=>4— _ een
l : 2 fr oe < aes « Uae se = *) 5
corpuscles varies from 13 pw, | - Lf : ee
and as a rule they are about Lo a go Sg
xsoo Of an inch in diameter ; in Poe \
the smallest forms the layer of Fis, 9
g.
the p rotoplasm of extremely thin. A, human white blood-corpuscles, without any reagent ;
They all exhibit amoeboid move- B, after the action of water; C, after acetic acid ;
ments which are very apparent D, frog’s corpuscles, changes of shape due to ame-
i no poid movement ; E, fibr ils of fibrin from coagulated
in the larger corpuscles, and were

discovered by Wharton Jones in pleats: Ei elementary ec

the skate (1846), and by Davine in the corpuscles of man (1850). Max Schultze
describes three different forms in human blood :—

(1) The smallest, spherical forms, less than the red corpuscles, with one or two
nuclei, and a very small amount of protoplasm.

(2) ‘Spherical forms, the same size as the coloured blood-corpuscles.

(3) The large amceboid corpuscles, with much protoplasm and distinctly evident
movements.

[On examining human blood microscopically, more especially after the coloured blood-cor-
puscles have run into rouleaux, the colourless corpuscles may readily be detected, there being
usually three or four of them visible in the field at once. They adhere to the glass slide, for if
the cover-glass be moved, the coloured tie readily glide over each other, while the
colourless can be seen still adhering to the’slide. ]

[White Corpuscles of Newt’s Blood.—The characters of the colourless corpuscles are best
studied in a drop of newt’s blood, which contains the following varieties :—

(1) The large finely granular corpuscle, which is about +4, of an inch in diameter, irregular
in outline, with fine processes or pseudopodia, projecting from its surface, It rapidly changes

(

14 THE COLOURLESS BLOOD-CORPUSCLES.

its shape at the ordinary temperature, and in its interior a bi- or tri-partite nucleus may be seen,
surrounded with fine granular protoplasm, whose outline is continually changing. Sometimes.
vacuoles are seen in the protoplasm.

(2) The coarsely granular variety is less common than the first-mentioned, but when de-
tected its characters are distinct. The protoplasm contains, besides a nucleus, a large number
of highly refractive granules, and the eocpasee® usually exhibits active amceboid movements ;.
suddenly the granules may be seen to rush from one side of the corpuscle to the other. The
processes are usually more blunt than those emitted by (1). The relation between these two.
kinds of corpuscles has not been ascertained.

(3) The small colourless corpuscles are more like the ordinary human colourless corpuscle,
and they, too, exhibit amceboid movements. }

Two kinds of colourless corpuscles like (1) and (2) exist in frog’s blood. In the coarsely
granular corpuscles the glancing granules may be of a fatty nature, since they dissolve in
alcohol and ether, but other granules exist which are insoluble in these fluids. The nature
of the latter is unknown. Very large colourless corpuscles exist in the axolotl’s blood.

[Action of Reagents.—(«) Water, when added slowly, causes the colourless.
corpuscles to become globular, and the granules within them to exhibit Brownian
movements. (+) Pigments, such as magenta or carmine, stain the nuclei very
deeply, and the protoplasm to a less extent. (c) Dilute Acetic Acid clears up the
surrounding protoplasm and brings clearly into view the composite nucleus, which
may be stained thereafter with magenta. (d) Iodine gives a faint port-wine colour,
especially in horse’s blood, indicating the presence of glycogen. (e) Dilute Alcohol
causes the formation of clear blebs on the surface of the cor-
puscles, and brings the nuclei into view (Ranvier, Stirling). |

[A delicate plexus of fibrils—intra-nuclear plexus—
exists within the nucleus just as in other cells. It is very
probable that the protoplasm itself is pervaded by a similar
plexus of fibrils, and that it is continuous with the intra-
nuclear plexus (fig. 10).] The colourless corpuscles divide,
and in this way reproduce themselves.

Fig. 10. than that of the red corpuscles, and is subject to consider-

Plexus of fibrils in a able variations. It is certain that the colourless corpuscles.

colourless blood-cor- are very much fewer in shed blood than in blood still within

pustie: the circulation. Immediately after blood is shed, an enor-
mous number of white corpuscles disappear (§ 31).

_Al. Schmidt estimates the number that remain at #5 of the whole originally present in the
circulating blood. The proportion is greater in children than in adults. The following table

gives the number in shed blood :—

NUMBER OF WHITE IN PRopoRTION TO RED BLOop-CoRPusCLES—

In Normal Cunditions. — In Different Places. In Different Conditions.

| Portal Vein, 1: 740 emia, Quinine, Bitters.
. | Generally more numerous | Dinvinished by Hunger, Bad
| ; in Veins than Arteries. Nourishment.

|

|

(erreen ee ge ed oe ay |
| 1: 335 ( Welcker). | Splenic Vein, 1: 60 | Increased by Digestion, Loss
1 : 357 (Moleschott). _ Splenic Artery, 1: 2,260 | of Blood, Prolonged Sup-
| Hepatic Vein, 1:170 | puration, Parturition, Leuk-

|

The Number of Colourless Corpuscles is very much less

[The number also varies with the Age and Sex :—

| Age. Sex. | White. Red. || General Conditions. White. Red.

i eee 1 : 405 | While fasting, 1: 716

| Boys, , ‘ 1 : 226 _ After a meal, f ; 1: 347

_ Adults, : et 1 : 334 '| During pregnancy, . 1: 281)

| Old Age, . Te et 3 1: 881 } :

—

de |
’ 2

their interior (fat, pigment, foreign bodies).

AMCEBOID MOVEMENTS OF THE COLGURLESS CORPUSCLES. 15

The ameboid movements of the white corpuscles (so called because they
resemble the movements of amceba) consist in an alternate contraction and relaxation
of the protoplasm surrounding the nucleus. Processes are given off from the
surface, and are retracted again. There is an ternal current in the protoplasm,
and the nucleus has also been observed to change its form [and exhibit contractions
without the corpuscle dividing. The .
karyokinetic aster, and convolution of the
intranuclear plexus have been séen|. Two
series of phenomena result from these
movements :—(1) The “ wandering” or
locomotion of the corpuscles due to the
extension and retraction of their processes ;
(2) the absorption of small particles into

The particles adhere to the sticky exter-
nal surface, are carried into the interior
by the internal currents, and may eventu-
ally be excreted, just as particles are taken
up by amceba and the effete particles Sop
excreted. [Max Schultze observed that Fig. 11.

coloured particles were readily taken up by Human leucocytes showing amceboid
these corpuscles. Conditions for move- movements.

ment.—In order that the amceboid movements of the leucocytes may take place,
it is necessary that there be—(1) a certain temperature and normal atmospheric
pressure ; (2) the surrounding medium, within certain limits, must be ‘ indifferent,”
and contain a sufficient amount of water and oxygen ; (3) there must be a basis or
support to move on. |

Struggle between Microbes and the Organism. —Metschnikoff emphasises the activity of the
leucocytes in retrogressive processes, whereby the parts to be removed are taken up by them in
fine granules, and, as it were, are ‘‘eaten.”” Hence, he calls such cells ‘‘ phagocytes.” They
may be found in the atrophied tails of batrachians, the cells containing in their interior whole
pieces of nerve-fibre and primitive muscular bundles. Schizomyecetes which have found their
way into the blood (§ 183) have been found to be partly taken up by the colourless corpuscles.
[The spores of a kind of yeast are similarly attacked in the transparent tissues of the water-
flea by the leucocytes, and the connective-tissue cells also destroy microbes. ]

Effect of Reagents.—On a hot stage (35°-40° C.) the colourless corpuscles of
warm-blooded animals retain their movements for a long time ; at 40° C. for two
to three hours ; at 50° C. the proteids are coagulated and cause “heat rigor”
and death, [when their movements no longer recur on lowering the temperature].
In cold-blooded animals (frogs), colourless corpuscles may be seen to crawl out of
small coagula, in a moist chamber, and move about in the serum. [Draw a drop
of newt’s blood into a capillary tube, seal up the ends of the latter and allow the

_ blood to coagulate. After a time, examine the tube in clove oil, when some of the

colourless corpuscles will be found to have made their way out of the clot.|
Induction shocks cause them to withdraw their processes and become spherical,
and, if the shocks be not too strong, their movements recommence. Strong and
continued shocks kill them, causing them to swell up, and completely disintegrating
them.

Diapedesis.— These amoeboid movements are of special interest on account of the
‘wandering out ” (diapedesis) of colourless blood-corpuscles through the walls of
the blood-vessels (§ 95). |

[Effect of Drugs.—Acids and alkalies, if very dilute, at first increase, but afterwards arrest
their movements. Sodic chloride in a 1 per cent. solution at first accelerates their movements,

but afterwards produces a tetanic contraction, and, it may be, expulsion of any food particles
they contain. ‘The Cinchona alkaloids—quinine, quinidine, cinchonidine (1 : 1500)—quickly

-

_osmic acid. They rapidly change in shed blood (fig. 12, 5), disintegrating, forming

_ These masses may be associated in coagulated blood with fibrils of fibrin (fig. 12),

16 THE BLOOD-PLATES.

arrest the locomotive movements, as well as the protrusion of pseudopodia, although the
leucocytes of different animals vary somewhat in their resistance to the action of drugs.
Quinine not only arrests the movements of the leucocytes when applied to them directly, but
when injected into the circulation of a frog the leucocytes no longer pass through the walls of
the capillaries (Binz).

The chyle contains leucocytes, which are more resistant than those of the blood, but less so
than those of the coagulable transudations. The leucocytes of the lymphatic glands may also
be dissolved (Rauschenbach).

Relation to Aniline Pigments.—Ehrlich has observed a remarkable relation of the white
corpuscles to acid (eosin, picric acid, aurantia), basic (dahlia, acetate of rosanilin), or neutral
(picrate of rosanilin) reactions. The smallest protoplasmic granules of the cells have different
chemical affinities for these pigments. Thus Ehrlich distinguishes ‘‘ eosinophile,”’ ‘‘ basophile,”
and ‘‘neutrophile” granules within the cells Eosinophile granules occur in the leucocytes
which come from bone-1arrow, the myelogenic leucocytes. The small leucocytes, ¢.e., those
about the size of a coloured blood-corpuscle or slightly larger, are formed in the lymphatic
glands, the lymphogenic. The large amwboid multi-nucleated cells, which are found outside
the vessels in inflammations, exhibit « neutrophile reaction. Their origin is unknown, and
so is that of the large uni-nucleated cells, and the large cells with constricted nuclei. The’
eosinophile corpuscles are considerably increased in leukemia. The basophile granules oceur
also in connective-tissue corpuscles, especially in the neighbourhood of epithelium ; they
are always greatly increased where chronic inflammation occurs.

III. Blood-Plates.—Special attention las recently been directed to a third
element of the blood, the “ blood-plates ” or ‘‘ blood-tablets ’’ of Bizzozero ; pale,
colourless, oval, round, or lenticular discs of variable size (mean, 3m). Ina
healthy man Fusari found 18,000 to 250,000 in 1 cubic millimetre of blood. These
blood-plates may be recognised in the circulating blood of the mesentery of a

OQ
g 3 \ : ,
5 a :
é ! |
oe
) "|

Fig. 12.

‘+ Blood-plates ” and their derivatives. 1, a red blood-corpuscle on the flat ; 2, on the side; 3,
unchanged blood-plates ; 4, lymph-corpuscle, surrounded by blood-plates ; 5, altered blood- *
plates ; 6, pects ‘le with two heaps of fused blood-plates and threads of fibrin se:
group of fused blood-platss ; 8, small group of partially dissolved blood-plates with fibrils -

of fibrin,
chloralised guinea-pig and the wing of the bat. They are precipitated in enormous
numbers upon threads sus} en led in fresh shed blood. They may be obtained-from
blood flowing directly from a blood-vessel, on mixing it with 1 per cent. solution of

small particles, and ultimately dissolving. When several occur together they
rapidly unite, form small groups (7), and collect into finely granular mass se
[These blood-plates are best seen in the shed blood of t inea-pi salle if te
mixed with a solution of sodic sulphate (sp. gr, 1022) or 2 bat tae Ne T sineel with ihe oa
violet. Bizzozero regards them as the agents which immediately induce coagulation and take _

-

=—o =e wy

——

——

CHANGES OF THE BLOOD CORPUSCLES. I7

part in the formation of fibrin during coagulation of the blood ; Eberth and Schimmelbusch
ascribe the initial formation of white thrombi to them. According to Lowit they are formed
from partially disintegrated leucocytes, as a consequence of alteration of the blood. Along with
the leucocytes they are concerned in the formation of fibrin (H/ava). These structures were
known to earlier observers ; but their significance has been variously interpreted. Hayem called
them hematoblasts. Halla found that they increased in pregnancy, Afanassiew in conditions
of regeneration of the blood, and Fusari in febrile anemia ; they are diminished in fever.

[As to the hematoblasts, or, as they have also been called, the ‘‘ globules of Donné” by
Pouchet, there scems to be some confusion, for both coloured and colourless granules are
described under these names. As Gibson suggests, the former are, perhaps, parts of disintegrated
coloured corpuscles, whilst the latter are the blood-plates. The ‘‘invisible blood-corpuscles ”
described by Norris seem to be simply decolorised red corpuscles (Hart, Gibson). ]

IV. Elementary Granules.--Blood contains elementary granules (fig. 9, F),
[ae the elementary particles of Zimmermann and Beale. They are irregular
bodies, much smaller than the ordinary corpuscles, and appear to consist of masses
of protoplasm detached from the surface of leucocytes, or derived from the dis-
integration of these corpuscles, or of the blood-plates. Others, again, are com-
pletely spherical granules, either consisting of some proteid substance or fatty in
their nature. The protoplasmic and the proteid granules disappear on the addition
of acetic acid, while the fatty granules (which are most numerous after a diet rich
in fats) dissolve in ether].

V. In coagulated blood, delicate threads of fibrin (figs. 9, E, and 12, 6, 7, 8
are seen, more especially after the corpuscles have run into rouleaux. At the
nodes of these fibres are found granules which closely resemble those described
under III.

[When the blood-forming process is particularly active, ‘‘nucleated coloured corpuscles’
or the ‘‘ corpuscles of Neumann,” are sometimes found in the blood. They are identical with

the nucleated coloured blood-corpuscles of the foetus, being somewhat larger than the non-
nucleated coloured corpuscle (§ 7). ] < desinee

10. ABNORMAL CHANGES OF THE BLOOD-CORPUSCLES.—(1) Hemorrhages diminish
the number of red corpuscles (at most one-half), and so does menstruation, The loss is partly
covered by the absorption of fluid from the tissues. Menstruation shows us that a moderate
Joss of red corpuscles is replaced within twenty-eight days. When a large amount of blood is
Jost, so that all the vital processes are lowered, the time may be extended to five weeks. In

acute fevers, as the temperature increases, the number of ved corpuscles diminishes, while the

white corpuscles increase in number. By greatly cooling peripheral parts of the body, as by
keeping the hands in iced water, in some individuals possessing red blood-corpuscles of low
resisting power, these corpuscles are dissolved, the blood-plasma is reddened, and even hemo-
globinuria may occur (§ 265).

Diminished production of new red corpuscles causes a decrease, since blood-corpuscles are
continually being used up. In chlorotic females there seems to be a congenital weakness in the
blood-forming and blood-propelling apparatus, the cause of which is to be sought for in some
faulty condition of the mesoblast. In them the heart and the blood-vessels are small, and the

absolute number of corpuscles may be diminished one-half, although the sedative number may

be retained, while in the corpuscles themselves the hemoglobin is diminished almost one-
third ; but it rises again after the administration of iron (Hayem). The administration of iron
increases the amount of hemoglobin in the blood. [The action of iron in anemic persons has
been known since the time of Sydenham. MHayem also finds in certain forms of anemia that
there is considerable variation in the size of the red corpuscles, and that in chronic anemia the
mean diameter of the corpuscles is always less than normal (7 w to 6 uw). There is, moreover,
a persistent alteration in the volume, colouring power, and consistence of the corpuscles, con-

sequently a want of accord between the nwmber of the corpuscles and their colouring power,

z.¢., the amount of hemoglobin which they contain. In pernicious anemia, in which the con-
tinued decrease in the red corpuscles. may ultimately produce death, there is undoubtedly a
Severe affection of the blood-forming apparatus. The corpuscles assume many abnormal and
bizarre forms, often being oval or tailed, irregularly shaped, and sometimes very pale ; while
numerous cells containing blood-corpuscles are found inthe marrow of bone. In this disease,
although the red blood-corpuscles are diminished in number, some may be larger and con-

tain more hemoglobin than normal corpuscles. The number of coloured corpuscles is also

diminished in chronic poisoning by lead or miasmata, and also by the poison of syphilis.
(2) The size of the corpuscles varies in disease from 2°9-12°9 uw (mean 6-8 4) ; ‘‘ dwarf cor-
puscles” or microcytes (6 4 and less) are regarded as young forms, and occur plentifully in
; B

{

18. CONSTITUENTS OF THE RED BLOOD-CORPUSCLES.

nearly all cases of anemia. ‘‘ Giant blood-corpuscles” or macrocytes (10 « and more) are con-
stant in pernicious anemia, and sometimes in leukemia, chlorosis, and liver cirrhosis (Gram).

(3) Abnormal forms of the red corpuscles have been observed after severe burns (Lesser) ; the cor-
puscles are much smaller, and under the influence of the heat, particles seem to be detached from
them just as can be seen happening under the microscope as the effect of heat. Disintegration
of the corpuscles into fine droplets has been observed in various diseases, as in severe malarial |
fevers. The dark granules of a pigment closely related to hematin are derived from the,
granules arising from the disintegration of the blood-corpuscles, and these particles float in the
blood (melanemia). This condition can be produced artificially by injecting bisulphide of
carbon (7 to 70 of oil) subcutaneously into rabbits (Schwalbe). They are partly absorbed by the
colourless corpuscles, but they are also deposited in the spleen, liver, brain, and bone-marrow,

(4) Sometimes the red corpuscles are abnormally soft, and readily yield to pressure.

Parasites of Blood-Corpuscles.— Within the red blood-corpuscles of birds, fishes, and tortoises,
parasites are occasionally developed in the form of round ‘‘ pseudo-vacuoles ” from which free
varasites are subsequently discharged (Danilewsky). In malarial conditions in man, protozoon-
like organisms have been seen within the red corpuscles, the plasmodium malarie (JMar-
chiafava).

The white corpuscles are enormously increased in number in leukemia (J. H. Bennett,
Virchow). In some cases the blood a8 as if it were mixed with milk. The colourless cor-
boats seem to be formed chiefly in bone-marrow (#. Newmann), and also in the spleen and
ymphatic glands (myelogenic, splenic, and lymphatic leukemia).

11. CHEMICAL CONSTITUENTS OF THE RED BLOOD-CORPUSCLES.—
(1) The colouring matter or hemoglobin (Hb) is the cause of the red colour of
blood ; it also occurs in muscle, and in traces in the fluid part of blood, but in the
last case only as the result of the solution of some red corpuscles. Its percentage
composition is :—C 53°85, H 7°32, N 16°17, Fe 0°42, S 0°39, O 21°84 (dog). Its
rational formula is unknown, but Preyer gives the empirical formula Coo, Hogo;
Nisy Fe, S,, O,-.. Although it is a colloid substance it crystallises in all classes

» of vertebrates, according to the rhombic system,

. E 40 and chiefly in rhombic plates or prisms; in the

> & A guinea-pig in rhombic tetrahedra ; in the squirrel,
VW however, it yields hexagonal plates. The varying
& forms, perhaps, correspond to slight differences

in the chemical composition in different cases.
Crystals separate from the blood of all classes of
vertebrata during the slow evaporation of lake-
coloured blood, but with varying facility (fig. 13).

The colouring matter crystallises very readily from the
blood of man, dog, mouse, guinea-pig, rat, cat, hedgehog,
horse, rabbit, birds, fishes ; with difficulty from that of
the sheep, ox, and pig. Coloured crystals are not obtained
from the blood of the frog. More rarely a crystal is formed
from a single corpuscle enclosing the stroma. Crystals
have been found near the nucleus of the large corpuscles
of fishes, and in this class of vertebrates colourless crystals

f
Ge i have been observed.
Wy S Dichroism.—Hmoglobin crystals are doubly

Fig. 13. refractive and pleo-chromatic ; they are bluish-

Hemoglobin crystals from blood. a, red with transmitted light, scarlet-red by reflected
b, human ; ¢, cat ; d, guinea-pig; light. They contain from 3 to 9 per cent. water

¢, hamster ; f, squirrel. of crystallisation, and are soluble in water, but
more so in dilute alkalies. They are insoluble in alcohol, ether, chloroform, and ,

are The solutions are dichroic: red in reflected light, and green in transmitted
ight.

_ In the act of crystallisation the hemoglobin seems to undergo some internal change. Before
it erystallises it does not diffuse like a true colloid, and rate rapidly decesnaieala hydric
xide. If it be redissolved after crystallisation, it diffuses, although only to a small extent,

nl )
tit no longer decomposes hydric peroxide, and is d . it.
favours crystallisation. { 4 Fn apsan aC aie (The ta a .0 1 y.

ESTIMATION. OF HASMOGLOBIN, Ig

12. PREPARATION OF HAMOGLOBIN CRYSTALS.—Method of Rollett.—Put defibrinated
blood in a platinum capsule placed on a freezing mixture, freeze the blood, and then thaw it ;
pour the lake-coloured blood into a plate, until it forms a stratum not more than 14 mm, in
thickness, and allow it to evaporate slowly in a cool place, when crystals will separate.

Method of Hoppe-Seyler.—Mix defibrinated blood with 10 volumes of a 20 per cent. salt
solution, and allow it to stand for two days. Remove the clear upper fluid with a pipette,
wash the thick deposit of blood-corpuscles with water, and afterwards shake it for a long time
with an equal volume of ether, which dissolves the blood-corpuscles. Remove the ether, filter
the lake-coloured blood, add to it $ of its volume of cold alcohol (0°), and allow the mixture to
stand in the cold for severaldays, The numerous crystals can be collected on a filter and pressed
between folds of blotting-paper.

Method of Gscheidlen.—Take defibrinated blood, which has been exposed for twenty-four
hours to the air, and keep it in a closed tube of narrow calibre for several days at 37°C. When
the blood is spread on glass, the crystals form rapidly, [Vaccine tubes answer very well. ]

[Method of Stirling and Brito.—It is in many cases sufficient to mix a drop of blood with a
few drops of water on a glass slide, and to seal up the preparation. After a few days beautiful
crystals are developed. The addition of water to the blood of some animals, such as the rat
and the guinea-pig, is rapidly followed by the formation of crystals of hemoglobin, Very
large crystals may be obtained from the stomach of the leech several days after it has sucked ~
blood. ]

13. QUANTITATIVE ESTIMATION OF HA MOGLOBIN,—(a) From the Amount of Iron. —
As dry (100° C.) hemoglobin contains 0°42 per cent. of iron, the amount of hemoglobin may be
calculated from the amount of iron. If mm represents the percentage amount of metallic iron,

then the percentage of hemoglobin in blood is =" —, The procedure is the following :—

Calcine a weighed quantity of blood, and exhaust the ash with HCl to obtain ferric chloride,
which is transformed into ferrous chloride, The solution is then titrated with potassic
permanganate.

(b) Colorimetric Method.-—Prepare a dilute watery solution of hemoglobin crystals of a
known strength. With this compare an aqueous dilution of the blood to be investigated, by
adding water to it until the colour of the test solution is obtained. Of course, the solutions
must be compared in vessels with parallel sides and of exactly the same width, so as to give the
same thickness of fluid (Hoppe-Seyler). [In the vessel with parallel sides, or hematinometer,
the sides are exactly 1 centimetre apart. Instead of using a standard solution of oxyhemoglobin,
a solution of picro-carminate of ammonia may be used (Rajewsky, Malassez). ]

(c) By the Spectroscope.—Preyer found that a 0°8 per cent. watery solution (1 cm. thick),
allowed the red, the yellow, and the first strip of green to be seen (fig. 17, 1), Take the blood
to be investigated (about 0°5 c.cm.), and dilute it with water until it shows exactly the same
optical effects in the spectroscope. If & is the percentage of Hb, which allows green to pass
through (0°8 per cent.), 0, the volume of blood investigated (about 0°5 c.cm.), w, the necessary
amount of water added to dilute it, then «=the percentage of Hb in the blood to be investi-
gated— ;

k(w + b)
huey ae

It is very convenient to add a drop of caustic potash to blood and then to saturate it with

[(z2) The Hemoglobinometer of Gowers is used for the clinical estimation of hemoglobin
(fig. 14). ‘* The tint of the dilution of a given volume of blood with distilled water is taken
as the index of the amount of hemoglobin. The distilled water rapidly dissolves out all the
hemoglobin, as is shown by the fact that the tint of the dilution undergoes no change on
standing, The colour of a dilution of average normal blood one hundred times is taken as the
standard. The quantity of hemoglobin is indicated by the amount of distilled water needed
to obtain the tint with the same volume of blood under examination as was taken of the
standard. On account of the instability of a standard dilution of blood, tinted glycerine-jelly
is employed instead. This is perfectly stable, and by means of carmine and picro-carmine the
exact tint of diluted blood can be obtained. The apparatus consists of two glass tubes of
exactly the same size. One contains (D) a standard of the tint of a dilution of 20 cubic mm.
of blood, in 2 cubic centimetres of water (1 in 100). The second tube (C) is graduated, 100
degrees = 2 centimetres (100 times 20 cubic millimetres), The 20 cubic millimetres of blood
are measured by a capillary pipette (B). This quantity of the blood to be tested is ejected
into the bottom of the tube, a few drops of distilled water being first placed in the latter. The
mixture is rapidly agitated to prevent the coagulation of the blood. The distilled water is
then added drop by fron (from the pipette stopper of a bottle (A) supplied for that purpose),
until the tint of the dilution is the same as that of the standard, pet the amount of water
which has been added (i.¢., the degree of dilution) indicates the amount of hemoglobin.”

20 QUANTITATIVE ESTIMATION OF H-EMOGLOBIN,

“ Since average normal blood yields the tint of the standard at 100 degrees of dilution, the
number of degrees of dilution necessary to obtain the same tint with a given specimen of blood
is the percentage proportion of the hemoglobin contained in it, compared to t e normal. For
instance, the 20 cubic millimetres
of blood from a patient with anz-
mia gave the standard tint of 30
degrees of dilution. Hence it
contained only 30 per cent. of the
normal quantity of hemoglobin.
By ascertaining with the hema-
cytometer the corpuscular richness
of the blood, we are able to compare
the two. <A fraction, of which the
numerator is the percentage of
hemoglobin, and the denominator
the percentage of corpuscles, gives
at once the average value per cor-
puscle. Thus the blood mentioned
above containing 30 per cent. of
hemoglobin, contained 60 per cent.
of corpuscles; hence the average
value of each corpuscle was }$ or 4
of the normal. Variations in the
amount of hemoglobin may be re-
corded on the same chart as that
employed for the corpuscles. The
Fig. 14 instrument is only expected to

Gowers’ hemoylobinometer. A, pipette bottle for distilled yield approximate results, accurate
water ; B, capillary pipette ; C, graduated tube ; D, tube Within 2 or 3 per cent. It has,
with standard dilution ; F, lancet for pricking the finger. however, been found of much

utility in clinical observation.”’]
(ce) Fleischl’s Hemometer.—For clinical purposes this instrument (fig. 15) is useful. <A
cylinder G, of two compartments @ and a’, rests on a metallic table. Both compartments are
filled with water, but in one (@) is placed

a known quantity of blood measured in

a measuring-tube of known capacity.

The red colour of the solution of hzemo-

globin thus obtained is compared with

ared wedge of glass (K), which is moved
by means of a wheel (R and T) under
the other compartment (a’) until the
two colours are identical. The illumina-
ation of the dilute blood solution and
the red glass wedge is done from below
by lamp light reflected from the white
reflecting surface (S). The frame in
which the red glass wedge is fixed bears
numbers, and when the colour is iden-
tical in the two compartments a and a’,
the percentage of hemoglobin as com-
= pared with normal blood can be read off
= directly. Suppose it to be 800n the scale,
then the blood examined contains 80 per
cent. of the hemoglobin of normal blood.

The amount of hemoglobin in
man is 13°77 per cent. in the
woman 12°59 per cent., during
V. Fleischl’s hemometer. K, red coloured wedge of Pregnancy 9 to 12 per cent (Preyer).

glass moved by R; G, mixing vessel with two According to Leichtenstern, Hb is

ot te pero of hasan ia oe ae en en muon in thea

T, to Ase K ; 8, mirror of ar Paris, pee newly -born infant, but after ten

weeks the excess disappears. Be-
tween six months and five years it is smallest in amount; it reaches its second
highest maximum between twenty-one and forty-five, and then sinks again. From

USE OF THE SPECTROSCOPE. 2t

the tenth year onwards, the blood of the female is poorer in Hb. The taking of
food causes a temporary decrease of the Hb, owing to the dilution of the blood.
~ In Animals.—In the dog, 9°7 ; ox, 9°9 ; sheep, 10°3 ; pig, 12°7; horse, 13'1; birds, 16-17
per cent.

Pathological.—A decrease is observable during recovery from febrile conditions, and also
during phthisis, cancer, ulcer of the stomach, cardiac disease, chronic diseases, chlorosis,
leukemia, pernicious anemia, and during the rapid mercurial treatment of syphilitic persons.

14, THE SPECTROSCOPE.—As the spectroscope is frequently used in the investigation of
blood and other substances, a short description of the instrument is given here (fig. 16). It

Fig. 16.
Scheme of a spectroscope for observing the spectrum of blood. A, tube; S, slit; am, m,
layer of blood with flame in front of it; P, prism ; M, scale ; B, eye of observer looking
through a telescope ; 7, v, spectrum.

consists of—(1) a tube, A, which has at its peripheral end a slit, S (that can be narrowed or
widened). At the other end a collecting lens, C (called a collimator), is placed, so that its
focus is in exact line with the slit. Light (from the sun or a lamp) passes through the slit, and
thus goes parallel through C to—(2) the prism, P, which decomposes the parallel rays into a
coloured spectrum, 7, v. (3) An astronomical telescope is directed to the spectrum 7, 7,
and the observer, B, with the aid of the telescope, sees the spectrum magnified from six to
eight times. (4) A third tube, D, contains a delicate scale, M, on glass, whose image, when
illuminated, is reflected from the prism to the eye of the observer, so that he sees the
spectrum, and over or above it the scale. To keep out other rays of light the inner ends of
the three tubes are covered by metal or by a dark cloth (see also § 265).

[The micro-spectroscope, ¢.y., as made by Browning or Zeiss, may be used when small quan-
tities of a solution are to be examined. Every spectroscope ought to give two spectra, so that the
position of any absorption-band may be definitely ascertained. The spectroscope is fitted into
the ocular end of the tube of a microscope instead of the eye-piece. Small cells for containing
or fluid to be examined are made from short pieces of barometer-tubes cemented to a plate of
glass. | oe

Absorption Spectra.—If a coloured medium (e¢.g., a solution of blood) be placed between the
slit and a source of light, all the rays of coloured light do not pass through it—some are
absorbed ; many yellow rays are absorbed by blood, hence that part of the spectrum appears
dark to the observer, On account of this absorption, such a spectrum is called an “ absorption
spectrum.” Se - =

Flame Spectra.—If mineral substances-be burned on a platinum-wire in a non-lwminous
flame or Bunsen’s burner in front of the slit, the elements present in the mineral or ash give
special coloured band or bands, which have a definite position. Sodium gives a yellow,
mafassints ared and violet line. These substances are found on burning the ashes of almost
all organs. :

If sunlight be allowed to fall upon the slit, the spectrum shows a large number of lines

22 COMPOUNDS OF HAMOGLOBIN.

(Fraunhofer’s lines) which occupy definite positions in the coloured spectrum. These lines are
indicated by the letters A, B, C, D, &e., a, b, ¢, &e. (fig. 17).

15. COMPOUNDS OF HB WITH 0; OXYHAZMOGLOBIN AND METHZE-
MOGLOBIN.—1. Oxyhemoglobin (O0,Hb) behaves as a weak acid, and oceurs to
the extent of 86°78 to 94°30 per cent. in dry human red corpuscles (Jiédell). It is
formed very readily whenever Hb comes into contact with O or atmospheric air.
According to Bohr, 1 gramme Hb unites with 1°56 cubic centimetre of O at 0° and
760 mm. Hg pressure, the union being stronger 1n weak than in concentrated
solutions. Oxyhmoglobin is a very loose chemical compound, and is slightly
less soluble than Hb; its spectrum shows in the yellow and the green two dark

Red. Orange. Yellow. Green. Cyan blue.

D E b r
te i : 60 bo 70 80 00 100 110

ruil ! lagu ciaadianieanaen ely } rie betel ul |

Oxy.=
| Himoglobin

08 %

Oxy. =
Himoglobin
0-18 %

o4

Carbonic
Oxide
Hiimogiobin.

Reduced
Himoglobin.

‘Methe-
moglobin.
Hiimatin in
Acid
Solution.

|

Mil
Hi

a

WN Hiimatin in
| H an Alkaline
Solution.

f

Hemo-
i chromogen

in Alkaline
Solution.

| | ligt

|_| Yi: | Reduced
a Ady ULL. POTty Ue Wi [itt A) LS neg pe

40 ! 50 | bo | 70 ts | Ah | a | vo
Aa BC _ oO E F
Fig. 17.
Spectra of hemoglobin and its compounds.

ae whose length and breadth in a 0°18 per cent. solution are given
in fig. 17 (2). *

It occurs in the blood-corpuscles circulating in arteries and capillaries, as can be
shown by the spectroscopic examination of the ear of a rabbit, of the prepuce, and
the web of the fingers (Vierordt). 7

[Spectrum of Oxyhemoglobin.—In the spectrum of a dilute solution of hem

globin crystals or arterial blood, part of the red and violet rays are absorbed,

METHAMOGLOBIN. 23

but two well-marked absorption-bands exist between D and E. The line nearest
D, 1.e., next the red end of the spectrum, sometimes designated by the letter (a)
is narrow, sharply defined, and black at its centre, and its position corresponds to
the wave-length 579. The other absorption-band near E, conveniently designated
by (8), is broader, not so dark, and its edges are less sharply defined. Its centre
corresponds to the wave-length 553°8. In very dilute solutions the a band is the
only one visible. In a strong solution, as shown in fig. 17, the two bands fuse, but
are again made visible as two on dilution of the blood.] . so

Reduction of Oxyhemoglobin.—It gives up its O very readily, however, even
when means which set free absorbed gases are used. It is reduced by the removal
of the gases by the az-pump, by the conduction through its solution of other gases
(CO), and by heating to the boiling-point. In the circulating blood its O is very
rapidly given up to the tissues, so that in suffocated animals only reduced hemo-
globin is found in the arteries. Some constituents of the serum and sugar remove
its O. By adding to a solution of oxyhemoglobin reducing substances—e.v.,
ammonium sulphide, iron filings, or Stokes’s fluid [tartaric acid, iron proto-sulphate,
and excess of ammonia |—the two absorption-bands of the spectrum disappear, and
reduced hemoglobin (gas-free), with one absorption-band, is formed. The colour
changes from a bright red to a purplish or claret tint. The two bands are
reproduced by shaking the reduced hemoglobin with air, whereby O,Hb is again
formed. Solutions of oxyhzmoglobin are readily distinguished by their scarlet
colour from the purplish tint of reduced hemoglobin.

[The single absorption-band (fig. 17, 4) designated by the letter (y), lying about
midway between the position of the two previous bands, is broader, fainter, less
deeply shaded, and its centre is about, but not quite, intermediate between D and
E. It extends between the wave-lengths 595 and 538, and is blackest opposite the
wave-length 550, so that it lies nearer D than E. At the same time more of the
blue rays are transmitted. On dilution the band is not resolved into two, but
simply becomes fainter and disappears. |

[ Hemoglobin has certain remarkable characters :—(1) Although it is a crystalloid
body it diffuses with difficulty through an animal membrane, owing to the large
size of its molecule. (2) It readily combines with O to form an unstable and oose
chemical compound, oxyhemoglobin. (3) This O it gives up readily to the tissues
or other deoxidising reagents. (4) Its composition is very complex, for, in addition
to the ordinary elements present in proteids, it contains a remarkable amount of
iron (0°4 per cent.). | ;

If a string be tied round the base of two fingers so as to interrupt the circulation, spectro-
scopic examination shows that the oxyhemoglobin rapidly passes into reduced Hb (Vierordt).
Cold delays this reduction ; it is accelerated in youth, during muscular activity, or by suppressed
respiration, and usually also during fever.

The spectroscopic examination of small blood-stains is often of the utmost forensic import-
ance. A minimal drop is sufficient. Dissolve the stain in a few drops of distilled water, and

place the solution in a thin glass tube in front of the slit of the spectroscope.
Para-hemoglobin.—If O,Hb be preserved under alcohol it passes into a modified form,

which is insoluble in water (Nencki and Sieber).

2. Methemoglobin is a more stable, crystalline compound (Hoppe-Seyler). It
contains the same amount of O as O,Hb, but in a different chemical union, while
the O is also more firmly united with it. It shows four absorption-bands like
hematin in acid solution (fig. 17, 5), of which that between C and D is distinct ;
the second is very indistinct, while the third and fourth readily fuse, so that these
last two bands are only well seen with good apparatus. |
- It is produced spontaneously in old brown blood-stains, in the crusts of bloody wounds, in blood
eysts, and in bloody urine. Chemically, it can be prepared from a solution of Hb, by the action of

potassic ferri-cyanide (Jéderholm) or potassic chlorate (Marchand), [or by adding to a solution
of Hb a freshly prepared solution of potassic permanganate], and in non-laky blood by alloxantin

24 CARBONIC OXIDE-HASMOGLOBIN.

(Kowalewsky). It crystallises if defibrinated blood is shaken with amyl nitrite and the
mahogany-brown laky fluid be allowed to evaporate slowly (Halliburton). : ‘

If a trace of ammonia be added to a solution of methemoglobin, it gives an alkaline solution
of methemoglobin, which shows two bands like oxyhemoglobin, of which the first one is the
broader, and extends more towards the red. If ammonium sulphide be added to the methemo-

globin solution, reduced Hb is formed.

[Action of Nitrites.—The addition of amy] nitrite dissolved in alcohol, or sodic
or potassic nitrite to defibrinated blood causes the latter to assume a chocolate
colour, which, on the addition of ammonia, changes to red. The chocolate-coloured
fluid shows one well-defined band in the red, and less distinctly other three bands like
methemoglobin (Gamgee). |

[The nitrites therefore form a compound with its oxygen more firmly fixed than the O in
HbO,, so that large doses of nitrites arrest the internal respiration and are poisonous. It is,
however, affected by the products formed in the blood during asphyxia, while CO-Hb is not,
the methemoglobin formed by the nitrites is reduced by these products to Hb, which as it
passes through the lungs takes up O.]

16. CARBONIC OXIDE-HZMOGLOBIN, POISONING WITH C0.—-3. CO-
Hemoglobin is a more stable chemical compound than the foregoing, and is pro-
duced at once when carbonic oxide is brought into contact with pure Hb or O,Hb
(Cl. Bernard, 1857). Ithas an intensely florid or cherry red colour, is not dichroic,
and its spectrum shows two absorption-bands, very like those of O,Hb, but they
are slightly closer together and lie more towards the violet (fig. 17, 3). Reducing
substances which act upon HbO,, e.g., ammonium sulphide or Stokes’s fluid, do not
affect these bands, 7.e., they cannot convert the CO-Hb into reduced Hb. Ifa 10
per cent. solution of caustic soda be added to a solution of CO-Hb, and heated, it
gives a cinnabar red colour ; while, with an HbO, solution, it gives a dark brown,
greenish, greasy mass. Oxidising substances [solutions of potassic permanganate
(0025 per cent.), potassic chlorate (5 per cent.), and dilute chlorine solution] make
solutions of CO-Hb cherry red in colour, while they turn solutions of O,Hb pale
yellow. After this treatment both solutions show the absorption-bands of methz-
mogoblin, but those of the CO-Hb appear considerably later. If ammonium
sulphide be added, O,Hb and CO-Hb are re-formed.

On account of its stability, CO-Hb resists external influences and even putrefaction for a long
time, and the two bands of the spectrum may be visible after many months. Landois obtained
the soda test and spectroscopic bands in the blood of a woman poisoned eighteen months pre-
viously by CO, ana after great putrefaction of the body had ne place. [Stirling has kept
CO-Hb in a stoppered bottle for five years without putrefaction taking place. ]

If CO or air containing it be inspired, it gradually displaces the O, volume for

volume, out of the red blood-corpuscles, and death soon occurs ; 1000 c.cm. inspired

at once will killa man. A very small quantity in the air (;4y9- zp) suffices, in
a relatively short time, to form a large quantity of CO-Hb. As continued contact
with other gases (such as the passing of O through it for a very long time)
gradually separates the CO from the Hb, with the formation of O,Hb, it happens
that, in very partial poisoning with CO, the blood gradually gets rid of the CO by
the respiratory organs. It is uncertain if any part is excreted as CO,. ae
Hemoglobin, being a stable compound when once formed, circulates in the blood-
vessels ; but it neither gives up oxygen to the tissues, nor takes up oxygen in the
lungs, hence its very poisonous properties. The real cause of death in animals
poisoned with it is, that the internal respiration is arrested. | ;
Poisoning with Carbonic Oxide.—Carbonic oxide is formed during the incomplete combustio
of coal or coke, and passes into the air of the room, provided there is not a free outlet for the
roducts of combustion. It occurs to the extent of 12-28 per cent. in ordinary gas, which
argely owes its poisonous properties to the presence of CO. If the O be gradually displaced from
the blood by the respiration of air containing CO, life can only be maintained as long as suffi-
cient O can be obtained from the blood to support the oxidations necessary for life. Death
occurs before all the O is displaced from the blood. CO has no effect when directly applied to
muscle and nerve. When it is mixed with air, as in coal-gas poisoning, and inhaled, there is first

OTHER COMPOUNDS OF HAIMOGLOBIN, 25

stimulation and afterwards paralysis of the nervous system, as shown by the symptoms induced,
e.g., Violent headache, great restlessness, excitement, increased activity of the heart and respira-
tion, salivation, tremors, and spasms. Later, unconsciousness, weakness, and paralysis occur,
laboured respiration, diminished heart-beat, and lastly, complete loss of sensibility, cessation
of the respiration and heart-beat, and death. At first the temperature rises several tenths of a
degree, but it soon falls 1° or more. The pulse is also increased at first, but afterwards it
becomes very small and frequent. In poisoning with pure CO there is no dyspncea, but some-
times muscular spasms occur, the coma not being very marked. There is also temporary but
pronounced paralysis of the limbs, followed by violent spasms. After death the heart and brain
are congested with intensely florid blood. In poisoning with the vapour of charcoal, where
CO and CO, both occur, there is a varying degree of coma; pronounced dyspnoea, muscular
spasms which may last several minutes, gradual paralysis and asphyxia, moniliform contrac-
tions and subsequent dilatation of the blood-vessels, with congestion of various organs, occur,
accompanied by a fall of the blood-pressure (A7eds), indicating initial stimulation and subsequent
paralysis of the vaso-motor centre. This also explains the variations in the temperature and
the occasional occurrence of sugar in the urine after poisoning with CO. After death, the
blood-vessels are found to be filled with fluid blood of an exquisitely bright cherry red colour,
while all the muscles and viscera and exposed parts of the body (such as the lips) have the same
colour. The brain is soft and friable; there is catarrh of the respiratory organs and degenera-
tion of the muscles, and great congestion and degeneration of the liver, kidneys, and spleen.
The spots of lividity, post-mortem, are bright red. After recovery from poisoning with CO
there may be paraplegia and (although more rarely) disturbances of the cerebral activity.

17. OTHER COMPOUNDS OF HAMOGLOBIN.—4. Nitric Oxide-Hzemo-
globin (NO-Hb) is formed when NO is brought into contact with Hb (JZ.
Hermann).

As NO has a great affinity for O, red fumes of nitrogen peroxide (NO.) being formed when-
ever the two gases meet, it is clear that, in order to prepare NO-Hb, the O must first be
removed, This may be done by passing H through it, [or ammonia may be added to the blood, and
a stream of NO passed through it ; the ammonia combines with all the acid formed by the union
of the NO with the O of the blood]. . NO-Hb is a more stable chemical compound than CO-Hb,
which, as we have seen, is again more stable than O,Hb. It has a blwish-violet tint, and also
gives two absorption-bands in the spectrum similar to those of the other two compounds, but
not so intense. These bands are noé abolished by the action of reducing agents. As NO-Hb
cannot be formed in the body, it has no practical significance.

The three compounds of Hb, with O, CO, and NO are crystalline, like reduced
Hb ; they are isomorphous, and their solutions are not dichroic. All three gases
unite in equal volumes with Hb. If O be conducted through a concentrated
solution of Hb devoid of gases, a crystalline mass of O,Hb is thereby readily
formed.

5, Cyanogen, CNH (Hoppe-Seyler), and acetylene, C,H, (Bistrow and Licbreich), form easily
decomposable compounds with Hb. The former occurs in poisoning with hydrocyanic acid, and
has a spectrum nearly identical with that of O,Hb, and, like O,Hb, it is reduced, but very
slowly, by special reagents. [The existence of these compounds is, however, highly doubtful
(Gamgee). |

18. DECOMPOSITION OF HAMOGLOBIN.—In solution and in the dry
state Hb gradually becomes decomposed, whereby the iron-containing pigment
hematin (along with certain bye-products, formic, lactic, and butyric acids), is
formed. Hemoglobin, however, may be decomposed at once into-——(1) Heematin,
a body containing iron, and (2) a colourless proteid closely related to globulin ; by
(a) the addition of all acids, even by CO, in the presence of plenty of water ; (b)
strong alkalies ; (c) all reagents which coagulate albumin, and by heat at 70°-80°
C.; (d) by ozone. : ,

(A) Hematin, C,,H,.N,FeO, (Nencki and Stieber), is a bluish-black amorphous
body, which forms about 4 per cent. of haemoglobin (dog). It is insoluble in water,
alcohol, and ether ; so/wb/e in dilute alkalies and acids, and in acidulated ether and
alcohol. ; |

(1) Acid Heematin.—Lecanu extracted it from dry blood-corpuscles by using
alcohol containing sulphuric and tartaric acids. [If acetic acid be added to a
solution of Hb and slightly heated, a mahogany-brown fluid is obtained, containing

26 H-EMIN AND BLOOD TESTS.

hematin in acid solution, which gives a spectrum with one absorption-band to the
red side of D near C (fig. 17, 5). There is at the same time a considerable
absorption of the blue end of the spectrum. If an ethereal extract of the acid-—
heematin be made, the ether is coloured brown and shows four absorption-bands,
as in fig. 17, 5. ; } |

(2) Alkali-hematin.—[If to the above solution ammonia or caustic soda be
added, on heating gently, the colcur changes, and the fluid becomes dichroic, showing
a greenish tinge. On mixing the solution thoroughly with air the spectrum of
oxy-alkali-hematin is obtained, i.c., one absorption-band just to the red side of D
(fig. 17, 6), so that it is much nearer D than the corresponding band of acid-
hematin. Much of the blue end of the spectrum is absorbed as well. ] |

[(3) Reduced Alkali-hematin or Hemochromogen.—If the solution of alkali-
hematin be reduced by ammonium sulphide, the spectrum of hemochromogen is
obtained, viz., two absorption-bands between D and E, but they are nearer the
violet end than in the case of HbO, and Hb-CO (fig. 17, 7).] :

[((4) Hematoporphyrin or Iron-free Hematin.—On adding blood to con-
centrated sulphuric acid a clear purplish-red solution is obtained, which shows two
absorption-bands, one close to and on the red side of D, and a second half-way
between D and E. If water be added a brown precipitate is thrown down. When
this precipitate is dissolved in caustic soda, it gives a fluid which shows four
absorption-bands. |

Action of CO,.—-If CO, be passed through a solution of oxyhemoglobin for a considerable
time, reduced Hb is first formed ; but if the process be prolonged the Hb is decomposed, a
heey aoe of globulin is thrown down, and an absorption-band, similar to that obtained when |
{b is decomposed with acids, is observed (p. 25). ‘

An alkaline solution of hematin, when reduced by tin and hydrochloric acid,
yields urobilin (compare § 261).

When hemoglobin is extravasated into the subcutaneous tissue, it becomes so altered that
at first hematoidin (§ 20), and ultimately hydrated oxide of iron, appear in its place.

19. HAMIN AND BLOOD TESTS.—In 1853 Teichmann prepared crystals of
hemin from blood, which Hoppe-Seyler showed to be chloride of hematin

Dae Tr , ae
§ 2 yf! 9° ae are)
4 => \
1 ™ ps > = j 4 = -<™% \
= ; Wo” ae Aq
=“ ie Pace +k re ba E
Wy, 4 $ ow = a <—" = _
y = xt yy — a Uy Be
® ees eo \ 4S. ee
\ v Be, 5 |
_ 4 Yn
" Fig. 18. Fig. 19.
emin crystals. 1, human ; 2, seal; 3, calf; Hemin crystals prepared —
4, pig; 5, lamb; 6, pike; 7, rabbit. froth pes lood.

‘

" ~

7 es

‘characteristic spectrum (Axenfeld).

‘and becomes decomposed—as when blood is extravasated

HAMATOIDIN. | oy

plates, or rods ; sometimes they are single—at other times they are aggregated in
groups, often crossing each other. Some kinds of blood (ox and pig) yield very
irregular, scarcely crystalline, masses. The crystalline forms of hemin are identical
in all the different kinds of blood that have been examined. They are doubly
refractive ; under the polarization microscope they are a glancing yellow, appear-
ing raised on the dark field, with a strong absorption of the light parallel to the
long axis of the crystals (Walk and Morache). They are pleochromatic: by
transmitted light they are mahogany-brown, and by reflected light bluish-black,
glancing like steel.

(1) Preparation from Dry Blood-Stains.—Place a few particles of the blood-stain on a glass

slide, add 2 to 3 drops of glacial acetic acid and a small crystal of common salt ; cover with a
‘cover-glass, and heat gently over the flame of a spirit lamp until bubbles of gas are given off.

On cooling, the crystals appear in the preparation (fig. 19). :

(2) From Stains on Porous Bodies. —The stained object (cloth, wood, blotting paper, earth)
is extracted with a small quantity of dilute caustic potash, and afterwards with water in a
watch-glass. Both solutions are carefully filtered, and tannic acid and glacial acetic acid are
added until an acid reaction is obtained. The dark precipitate which is formed is collected on
a filter and washed. A small part of it is placed on a microscope slide, a granule of common

-salt is added, and the whole dried ; the dry stain is treated as in (1) (Struae).

(3) From Fluid Blood.—Dry the blood slowly at a low temperature, and proceed as in (1).

(4) From Dilute Solutions of Hemoglobin.—(a) Struwe's Method.—Add to the fluid, am-
monia, tannic acid, and afterwards glacial acetic acid, until it is acid; a black precipitate of
tannate of hematin is thrown down. This is isolated, washed, dried, and treated as in (1), but
instead of NaCl a granule of ammonium chloride is added.

Hemin crystals may sometimes be prepared from putrefying or lake-coloured
blood, but they are very small, and the test often fails. When mixed with iron-
rust, as on iron weapons, the blood-crystals are generally not formed. In such cases,
scrape off the stains and boil them with dilute caustic potash. If blood be present,
the dissolved hematin forms a fluid, which in a thin layer is green, in a thick
layer red (ZH. Rose).

Hemin crystals have been prepared from all classes of vertebrates and from the blood of

the earth-worm. From the blood of the ox and pig they may be almost amorphous.
Chemical Characters.—They are insoluble in water, alcohol, ether, chloroform ; but con-

-centrated H,SO, dissolves them, expelling the HCl, and giving a violet-red colour. Ammonia

also dissolves them, and if the resulting solution be evaporated, heated to 130° C., and treated
with boiling water (which extracts the ammonium chloride), hematoporphyrin—identical with
Mulder’s iron-free hematoin, and with Preyer’s hematoin, is obtained (Hoppe-Seyler).
It is a bluish-black substance, which on being pounded forms a brown and amorphous powder.
Its solutions in caustic alkalies are dichroic : in reflected light brownish-red ; in transmitted
light, in a thick stratum, red—in a thin one, olive-green. The acid solutions are monochro-
matic and brown.

Preparation in Bulk.—To obtain it in quantity, heat dried horse’s blood with 10 parts of
formic acid. If the crystals be suspended in methyl alcohol, on adding iodine and heating
them they dissolve with:a purple colour; after adding bromine,
brown ; and after passing chlorine gas, green ; all these give a

The glacial acetic acid may be replaced by oxalic or tartaric -
acid, the common salt by salts of iodine or bromine; in the latter
‘case similar bromine- or iodine-hematin is formed (Bikfalvi).

20. HAMATOIDIN.—Virchow discovered this im-
portant derivative of hzemoglobin. It occurs in the
body wherever blood stagnates outside the circulation,

Fig. 20.
Hematoidin crystals.

into the tissues—eg., the brain—in solidified blood-
plugs or thrombi; especially in veins; invariably in the Graafian follicles. It con-

_ tains no iron (C,,H,,N,O,), and crystallises in clino-rhombic prisms (fig. 20) of a

yellowish-brown colour. It is soluble in warm alkalies and chloroform. Very
probably it is identical with the bile-pigment—bilirubin. [When acted upon

{

28 THE COLOURLESS PROTEID OF HAMOGLOBIN.

by impure nitric acid (Gmelin’s reaction), it gives the same play of colours as:
bile. }
Pathological.—In cases where a large amount of blood has undergone solution within the-

blood-vessels (as by injecting foreign blood) hematoidin crystals have been found in the urine..
For their occurrence in the urine in jaundice (§ 180), and in the sputum (§ 188).

21. (B.) THE COLOURLESS PROTEID OF HAMOGLOBIN.—It is closely
related to globulin; but, while the latter is precipitated by all acids, even by CO,,
and re-dissolved on passing O through it, the proteid of hemoglobin, on the other:
hand, is not dissolved after precipitation on passing through it a stream of O.

As crystals of hemoglobin can be decolorised under special circumstances, it is probable that
there owe their crystalline form to the proteid which they contain. Landois laced crystals’ of
hemoglobin along with alcohol in a dialyser, putting ether acidulated with sulphuric acid out- dj
side, and thereby obtained colourless crystals. [If frogs’ blood be sealed up on a microscopic:
slide along with a few drops of water for several days, long colourless acicular crystals are
developed in it (Stirling and Brito).]

22. Il. PROTEIDS OF THE STROMA.—Dry red human blood-corpuscles con-.
tain from 5°10-12°24 per cent. of these proteids, but little is known about them:
(Jiidell), One of them is globulin, which is combined with a body resembling
nuclein (Wooldridge), and traces of a diastatic ferment (v. Wettich). The stroma
tends to form masses which resemble fibrin.

L. Brunton found a body resembling mucin in the nuclei of red blood-corpuscles, andi
Miescher detected nuclein (§ 250, 2).

23. OTHER CONSTITUENTS OF RED BLOOD-CORPUSCLES.—III. Lecithin
(0°35-0°72 per cent.) in dry blood-corpuscles (§ 250, 2). Cholesterin (0°25 per-
cent.) (§ 250, III.), no Fats.

Lecithin is regarded as a glycero-phosphate of neurin, in which, in the radical of glycero-
yhosphoric acid, two atoms of H are replaced by two of the radical of stearic acid. By gentle.
best glycero-phosphoric acid is split up into glycerine and phosphoric acid (§ 250).

These substances are obtained by extracting old stromata or isolated blood-corpuscles with
ether. When the ether evaporates, the characteristic globular forms (‘‘ myelin-forms”) of
lecithin, and crystals of cholesterin are recognised. The amount of lecithin may be determined:
from the amount of phosphorus in the ethereal extract.

IV. Water (681-63 per 1000—C. Schmidt).

V. Salts (7°28 per 1000), chiefly compounds of potash and phosphoric acid ; the:
phosphoric acid is derived only from the burned lecithin ; while the greater part of.
the sulphuric acid is derived from the burning of the hemoglobin in the analysis.

Analysis of Blood.—1000 parts, by weight, of horse’s blood contain :—

344°18 blood-corpuscles (containing about 128 per cent. of solids).
655°82 plasma (containing about 10 per cent. of solids).

1000 parts, by weight, of moist blood-corpuscles contain :—

Solids, , : 367°9 (pig); 400°1 (ox).
Water, . ; . § 632". -,, ~599°9 ...
The solids are :—
Pig. Ox.
Hemoglobin, . -. : : ; ‘ . 261 280°5 , !
Soy «ng ee ae a ee ee Se, 107 ,
Lecithin, Cholesterin, and other Organic Bodies, 12°0 75 |
Inorganic salts, . : : ‘ , : : 8°9 4°8
Pom, 0 Pt Fyn emogagas 0°747
Magnesia, , : , ‘ : 0°158 0°017
Including + Chlorine, ‘ . : ‘ ‘ 1°504 1°635
| Phosphoric 1 | Ea aerE nT ea plete 0-703
Soda, . > ; 4 ; ? 0 2°093 (Buige)..

An approximate estimate of the composition of human blood is given inthe
following table :— | (omy gt

——e eC

COMPOSITION OF THE WHITE CORPUSCLES. 29
Composition of Human Blood as a Whole.
Water, La ‘ ‘ R : . _ : ; ; . 780
Solids—of these—

Corpuscles, ; : : ; : : 134
Serum-albumin, 70
Serum-globulin,

Fibrin of Clot (? Fibrinogen), : ; : 2°2 + 220
Inorganic Salts (of serum), : ‘ ; ; 6:0
Extractives, : : : ‘ ; 62

Fatty matters, 14 J

Gases, O, CO,, N.] |
24. CHEMICAL COMFOSITION OF THE WHITE CORPUSCLES.—Investi-

‘-gations have been made on pus cells, which closely resemble colourless blood-

corpuscles. They contain several proteids ; alkali-albuminate, a proteid which
coagulates at 48° C., an albuminate resembling myosin, paraglobulin, peptone, and a
coagulating ferment ; nuclein in the nuclei (§ 250, 2), glycogen (§ 252), lecithin,

-cerebrin, cholesterin, and fat.

100 parts, by weight, of dry pus contain the following Salts :—

Earthy Phosphates, : ; 0°416 Potash, . : : ‘ ‘ 0°201
Sodic Phosphate, . : ‘ 0°606 Sodic Chloride, : ‘ ‘ 0°143

25. BLOOD-PLASMA AND ITS RELATION TO SERUM.—The unaltered

fluid in which the blood-corpuscles float is called blood-plasma, or liquor sanguinis.

This fluid, however, after blood is withdrawn from the vessels, rapidly undergoes a
change, owing to the formation of a solid fibrous substance—fibrin. After this
occurs, the new fluid which remains, no longer coagulates spontaneously (it is
plasma, minus the fibrin-factors), and is called serum. Apart from the presence of
the fibrin-factors, the chemical composition of plasma and serum is the same.

[When blood coagulates, Table I. shows what takes place, while Table II. shows what occurs
when it is beaten :—

I. Dud:
Coagulation. When beaten,
BLoop. BLoop.
|
| ee eee
Bete Corpuscles. Plasma. Corpuscles.
| pa es
| | | | |
‘Serum. Fibrin-factors. Fibrin-factors. Serum. |
| |
| |
Blood-Clot. Fibrin. Defibrinated Blood.

Plasma is a clear, transparent, slightly thickish fluid, which, in most animals

(rab bit, ox, cat, dog), is almost colourless ; in man it is yellow, and in the horse

citron yellow.

26. PREPARATION OF PLASMA.—(A) Without Admixture.—Taking
advantage of the fact that plasma, when cooled to 0° outside the body, does not
coagulate for a considerable time, Briicke prepares the plasma thus :—The blood of
the horse (because it coagulates slowly, and its corpuscles sink rapidly to the bottom)
is received, as it flows from an artery, into a tall narrow glass, placed in a freezing-
mixture, and cooled to 0°. The blood remains fluid, the coloured corpuscles
‘subside in a few hours, while the plasma remains above as a clear layer, which can
be removed with a cooled pipette. If this plasma be then passed through a cooled
filter, it is robbed of all its colourless corpuscles. [Burdon-Sanderson uses a vessel
consisting of three compartments—the outer and inner contain ice, while the blood
is caught in the central compartment, which does not exceed half an inch in
diameter.| The quantity of plasma may be roughly (but only roughly) estimated
by using a tall, graduated measuring-glass. If the plasma be warmed, it soon

30 COAGULATION OF THE BLOOD.

coagulates (owing to the formation of the fibrin), and passes into a trembling jelly.
If, however, it be beaten with a glass-rod, the fibrin 1s obtained as a white stringy
mass, adhering to the rod. The quantity of fibrin in a given volume of plasma is.
very small (p. 31), although it varies much in different cases.

(B) With Admixture.—Blood flowing from an artery is caught in a tall vessel
containing }th of its volume of a concentrated solution of sodic sulphate (Hewson)
—or ina 25 per cent. solution of magnesic sulphate (1 vol. to 4 vols. blood—
Simmer)—or 1 vol. blood with 2 vols. of a 4 per cent. solution of monophosphate:
of potash (asia). When the blood is mixed with these fluids and put in a cool
place, the corpuscles subside, and the clear stratum of plasma mixed with the salts
may be removed with a pipette. [The plasma so obtained is called “salted
plasma.”] If the salts be removed by dialysis, coagulation occurs ; or it may be:
caused by the addition of water (Joh. Miller). Blood which is mixed with a 4 per
cent. solution of common salt does not coagulate, so that it also may be used for:
the preparation of plasma. [For frogs’ blood Johannes Miiller used a 3 per cent.
solution of cane-sugar, which permits the corpuscles to be separated from the
plasma by filtration. The plasma mixed with the sugar coagulates in a short
time. | aps

2.7. FIBRIN—COAGULATION OF THE BLOOD.—General Characters.—
Fibrin is that substance which, becoming solid in shed blood, in plasma and im
lymph causes coagulation of these fluids. In these fluids, when left to themselves,
fibrin is formed, consisting of innumerable, excessively delicate, closely-packed,
microscopic, doubly refractive fibrils (fig. 7, E). These fibrils entangle the blood-
corpuscles as in a spider’s web, and form with them a jelly-like solid mass called
the blood-clot or placenta sanguinis. At first the clot is very soft, and after the:
first 2 to 15 minutes a few fibres may be found on its surface ; these may be
removed with a needle, while the interior of the clot is still fluid. The fibres
ultimately extend throughout the entire mass, which, in this stage, has been called
cruor. After from 12 to 15 hours the fibrin contracts, or, at least, shrinks more
and more closely round the corpuscles, and a fairly solid, trembling, jelly-like clot,
which can be cut with a knife, is formed. During this time the clot takes the
shape of the vessel in which the blood coagulates, and expresses from its substance
a fluid—the blood-serum. Fibrin may be obtained by washing away the corpuscles
from the clot with a stream of water. ?

Crusta Phlogistica.—If the corpuscles subside very rapidly, and if the blood
coagulates slowly, the upper stratum of the clot is not red, but only yellowish, on
account of the absence of coloured corpuscles. This is regularly the case in horse’s_
blood, and in human blood it is observed especially in inflammations ; hence this
layer has been called crusta phlogistica. Such blood contains more fibrin, and so
coagulates more slowly.

The crusta is formed under other circumstances, ¢.g., with increased sp. gr. of the corpuseles,
or diminished sp. gr. of the plasma (as in hydremia and chlorosis), whereby the corpuscles sink
more rapidly, and also during pregnancy. The taller and narrower the glass, the thicker is
the crusta (compare § 41). The upper end of the clot, where there are few corpuscles, shrinks
more, and is therefore smaller than the rest of the clot. This upper, lighter-coloured layer is.
called the ‘‘ buffy coat” ; but it gradually passes both in size and colour into the normal dark-
coloured clot. [Sometimes the upper surface of the clot is concave or ‘‘cupped.” The older |
ae attached great importance to this condition, and also to the occurrence of the buffy _
coat. ;
Defibrinated Blood.—If freshly-shed blood be beaten or whipped with a glass.
rod, or with a bundle of twigs, fibrin is deposited on the rod or twigs in the form
of a solid, fibrous, yellowish-white, elastic mass, and the blood which remains is
called “defibrinated blood” (p. 29). [The twigs and fibrin must be washed in a
stream of water to remove adhering corpuscles. ] ei

GENERAL PHENOMENA OF COAGULATION. 31

Coagulation of Plasma.—Plasma shows phenomena exactly analogous, save that
the clot is not so well marked, owing to the absence of the resisting corpuscles ;
there is, however, always a soft trembling jelly formed when plasma coagulates.
[In Hewson’s experiment on the blood of a horse tied in a vein, he found that the
plasma coagulated—fibrin being formed, so that he showed coagulation to be due to
changes in the plasma itself (§ 29). ]

Properties of Fibrin.—Although the fibrin appears voluminous, it only occurs
to the extent of 0-2 per cent. (0°1 to 0°3 per cent.) in the blood. The amount
varies considerably in two samples of the same blood. It is insoluble in water and
ether ; alcohol shrivels it by extracting water; dilute hydrochloric acid (0:1 per
cent.) causes it to swell up_and_become clear, and changes it into syntonin or acid-
albumin (§ 249, III.). When fresh, it has a greyish-yellow fibrous appearance,
and is elastic ; when dried, it is horny, transparent, brittle, and friable.

When fresh it dissolves in 6-8 per cent. solutions of sodium nitrate or sulphate, in dilute
alkalies, and in ammonia, thus forming alkali-albuminate. Heat does not coagulate these
solutions. [It is also soluble in, or rather decomposed by, 5-10 per cent. solutions of neutral
salts, ¢.g., NaCl, yielding two fibro-globulins (Green).] Hydric peroxide is rapidly decomposed
by fibrin into water and O (7hénard). Fibrin which has been exposed to the air for a long time
is no longer soluble in solution of potassic nitrate, but in neurin (Jauthner). During putre-
faction it passes into solution, albumin being formed. Fibrin contains, entangled in it, ferric,
calcic, and magnesic phosphates, and calcium sulphate whose origin is unknown.

Time for Coagulation.—The first appearance of a coagulum occurs in man’s blood after 3

minutes 45 seconds, in woman’s blood after 2 min. 20 sec. (H. Nasse). Age has no effect; with-
drawal of food accelerates coagulation (H. Vierordt).

28, GENERAL PHENOMENA OF COAGULATION.—TI. Blood in direct
contact with living unaltered blood-vessels does not coagulate. [Hewson
(1772) found that when he tied the jugular vein of a horse in two places, and
excised it, the blood did not coagulate for a long time.| Briicke filled the heart
of a tortoise with blood which had stood 15 minutes exposed to the air at 0°,
and kept it in a moist chamber ; at 0° C. the blood was still uncoagulated in the
contracting heart after eight days. Blood in a contracting frog’s heart preserved
under mercury does not coagulate. If the wall of the vessel be altered by
pathological processes (¢.7., if the intima becomes rough and uneven, or under-
goes inflammatory change), coagulation is apt to occur at these places. Blood
rapidly coagulates in a dead heart, or in blood-vessels (but not in capillaries) or
other canals (e.g., the ureter), If blood stagnates in a living vessel, coagulation
begins in the central axis, because here there is no contact with the wall of the
living blood-vessel.

IT. Conditions which Hinder or Delay Coagulation.—(a) The addition of
small quantities of alkalies, ammonia, or concentrated solutions of neutral salts
of the alkalies and earths (alkaline chlorides, sulphates, phosphates, nitrates,
carbonates). Magnesic sulphate acts most favourably in delaying coagulation
(1 vol. solution of 28 per cent. to 34 vols. blood of the horse).

(0) Precipitation of the fibrino-plastin by adding weak acids, or CO,,.

By the addition of acetic acid until the reaction is acid, coagulation is completely arrested.
A large amount of CO, delays it, hence venous blood coagulates more slowly than arterial, and
the blood of suffocated persons remains fluid for the same reason.

(c) The addition of egg-albumin, syrup, glycerine, and much water. If un-
coagulated blood be brought into contact with a layer of already-formed fibrin,
coagulation occurs later.

_ (d) By cold (0° C.) coagulation may be delayed for one hour. If blood is frozen
at once, after thawing it is still fluid; and then coagulates (Hewson). When shed
blood is under high pressure it coagulates slowly. ses,

(¢) Blood of embryo-fowls does not coagulate before the twelfth or fourteenth day
of incubation (Boll) ; that of the hepatic vein very slightly ; menstrual blood shows

¢

32 GENERAL PHENOMENA OF COAGULATION.

little tendency to coagulate when alkaline mucus from the vagina is mixed with it,
If it be rapidly discharged, it coagulates in masses. Fetal blood at the moment of

birth coagulates soon. : |
(f) Blood rich in yibrin from inflamed parts cvagulates slowly, but the clot so

formed is firm. >

(7) [Blood coagulates more slowly in a smooth than a rough vessel, and also in
a shallow vessel than in a deep one. |

Hemophilia. —A very slight scratch in some persons may cause very free bleeding. These
persons are called collo ally ‘‘bleeders,” and are said to have hemophilia or the hemorrhagic
diathesis. In di leeds ” coagulation seems not to take place, owing to a want of the
substances producing fibrin ; hence, in these cases, wounds of vessels are not plugged with
fibrin. [A tendency to hemorrhage occurs in scurvy, purpura, in some infectious diseases,
such as typhus, plague, yellow fever, and in poisoning with phosphorus. ] :

Injection of Peptones.—Albertoni observed that if tryptic pancreas ferment (dissolved in
glycerine) be injected into the blood of an animal, the blood does not coagulate. Schmidt-
Miilheim found that after the injection of pure peptone into the blood (0°5 gram per kilo.) of a
dog, the blood lost its power of coagulating. [This occurs in the dog, but not in the rabbit.
Peptonised blood coagulates when it is treated with CO, or water. It appears, however, that
it is not the peptone which prevents the coagulation, but the albumoses adhering to it which
do so.] A substance is formed in the plasma, which prevents coagulation, but which is pre-
cipitated by CO,. Lymph behaves similarly (Fano). After peptones are injected, there is a
great solution of leucocytes in the blood (v. Samson-Himmelstjerna). The secretion of. the
mouth of the medicinal leech, [although its action is not due toa ferment (Haycraft)], and
snake poison also prevent coagulation (JVal/). [Diastatic ferment also prevents coagulation
(Salvioli).]

III. Coagulation is accelerated—(~) By contact with foreign Substances
of all kinds, but only wheu the blood adheres to them, hence, threads or needles
introduced into arteries are rapidly covered with fibrin. Blood does not coagulate
in contact with bodies covered with fat or vaseline (/’rewnd). Even the introduction
of air-bubbles into the circulation or the passage of indifferent gases, N or H,
through blood, accelerates it. The pathologically altered wall of a vessel acts like
a foreign body. Blood shed from an artery rapidly coagulates on the walls of
vessels, on the surfaces exposed freely to air, and on the rods or twigs used to beat it.

(4) The products of the retrogressive metabolism of proteids (uric acid, glycin,
leucin, taurin, kreatin, sarkin, but not urea) favour coagulation by increased
ferment formation ; but if they are added in excess, they retard the process.

From a watery extract of the testis or thymus, on the addition of acetic acid, is precipitated a
substance which is soluble in sodic carbonate. It is a mixture of lecithin and albumin, and
when it is injected into the blood-stream it causes almost instantaneous death by intravascular
coagulation ( Wooldridge). |

(c) During rapid hemorrhage, the last portions of blood coagulate most rapidly
(Holzmann).

(2) Heating the blood from 39° to 55° C. (Hewson).

(e) Agitation of the blood (/ewson and Hunter).

[(7) The addition of a small quantity of water.

(7) A watery condition of the blood. The clot is small and soft.

(i) Contact with oxygen. |

IY. Rapidity of Coagulation.—Amongst vertebrates, the blood of birds
(especially of the pigeon) coagulates almost momentarily ; in cold-blooded animals
coagulation occurs much more slowly, while mammals stand midway between the

two.
{The blood of a fowl begins to coagulate in 4 to 14 minute; pig, sheep, rabbit, in } to 14
minute ; dog, 1 to 3 minutes ; horse and ox, 5 to 13 minutes ; man, 3 to 4 minutes ; solidifica-
tion is completed in 9 to 11 minutes (Nasse).] The blood of invertebrates, which is usually
colourless when it is oxidised (§ 32), forms a soft whitish clot of fibrin. Even in lymph and
chyle, a small soft clot is formed. . booted

V. When coagulation occurs, the aggregate condition of the fibrin-factors is
altered, so that heat must be set free (Valentin, 1844). ) nol edi

,
a
:

-and a soluble proteid. ]

COAGULATION OF THE BLOOD. 33

VI. In blood shed from an artery, the degree of alkalinity diminishes from the
time of its being shed until coagulation is completed (Pfliiger and Zuntz). This is
probably due to a decomposition in the blood, whereby an acid is developed, which

‘diminishes the alkalinity (p. 1).

VII. During coagulation there is a diminution of the 0 in the blood, although
a similar decrease also occurs in non-coagulated blood. Traces of ammonza are also
given off, which Richardson erroneously supposed to be the cause of the coagulation

of the blood.

[This is refuted—(1) by the fact that blood, when collected under mercury (whereby no escape
of ammonia is possible), also coagulates ; and (2) by the following experiment of Lister :—He
placed two ligatures on a vein containing blood, moistening one-half of the outer surface of the
vein with ammonia, leaving the other half intact. The blood coagulated in the first half, and
not in the other, owing to the properties of the wall of the vein of the former being altered.
Neither the decrease of O nor the evolution of ammonia seems to have any causal connection
with the formation of fibrin. ]

Pathological.— When the blood coagulates within the vessels during life, the process is called
thrombosis, and the coagulum or plug so formed is termed a thrombus. When a clot of blood
or other body is carried by the blood-stream to another part of the vascular system where it
blocks up a vessel, the plug is called an embolus, and the result embolism.

29. CAUSE OF THE COAGULATION OF BLOOD.—[{Hewson’s Experiments (1772.)—Hew-
son tied the jugular vein of a horse between two ligatures, removed it, and then suspended it by
one end (fig. 21). He found that the blood remained fluid for a long time
(48 hours), the red corpuscles sank (RC) and left a clear layer of plasma
on the surface (P). On drawing off some of this clear plasma it coagulated,
thus proving coagulation to be due to changes in the plasma. Lister
repeated this experiment, and found that, even if the upper end of the
tube be opened and the blood freely exposed to the air, coagulation is but.
slightly hastened. He showed that the blood might be poured from one
vein into another, just as one might pour fluid from one test-tube into
another. In this case there were two test-tubes, z.e., the veins—and
although the blood, on being poured from the one to the other, came into
contact with the air, it did not coagulate. Hewson, however, found that
blood poured from the vein into a glass vessel coagulated, so that, in his
opinion, the blood-vessels exerted a restraining influence on coagulation.
By cooling the blood and preventing it from coagulating, he proved that
coagulation was not due to the loss of heat. Nor could it be a vital act,
as sodic sulphate or other neutral salt prevented coagulation indefinitely,
but coagulation took place when the blood was diluted with water. | Rig <2.

[Buchanan’s Researches.—The serous sacs of the body contain a fluid Vein of horse tied
which in some respects closely resembles lymph. The pericardial fluid of between two liga-
some animals coagulates spontaneously (¢.g., in the rabbit, ox, horse, and tures, P, plasma ;
sheep) if the fluid be removed immediately after death. If this be not WC. white, and
done till several hours after death, the fluid does not coagulate spontane- RG, a aaa es

-ously, The fluid of the tunica vaginalis of the testis sometimes accumu- _ puscles.

lates to a great extent, and constitutes hydrocele, but this fluid shows no

tendency to coagulate spontaneously. Andrew Buchanan found, however, that if to the fluid of
ascites, pleuritic fluid, or hydrocele fluid, there be added clear blood-serum, then coagulation
takes place, z.¢., two fluids—neither of which shows any tendency by ttse/f to coagulate—form a
clot when they are mixed (1831). He also found, that if ‘‘ washed blood-clot” (which consists

-of a mixture of fibrin and colourless corpuscles) be added to hydrocele fluid, coagulation occurred.

He compared the action of washed blood-clot to the action of rennet in coagulating milk, and:
he imagined the agents which determined the coagulation to be colowrless corpuscles. 'Thus, the
buffy coat of horses’ blood is a powerful agent, and it contains numerous colourless corpuscles.
He finally concluded that some constituent in the plasma, to which he gave the name of a
‘soluble fibrin,” is acted upon by the colourless corpuscles and converted into fibrin. The
soluble fibrin of Buchanan is comparable to the fibrinogen in Hammarsten’s theory. Buchanan,
however, did not separate the substance. ]

[Denis’s Plasmine (1859).—Denis mixed uncoagulated blood with a saturated solution of
sodic sulphate, and allowed the corpuscles to subside. The salted plasma thus obtained he pre-

-cipitated with sodic chloride. The precipitate, when washed with a saturated solution of sodic
-chloride, he called plasmine, If plasmine be, mixed with water, it coagulates spontaneously,

resulting in the formation of fibrin, while another proteid remains in solution. According to
the view of Denis, fibrin is produced by the splitting: up of plasmine into two bodies—fibrin

C

34 THE FIBRIN-FACTORS.

[A. Schmidt’s Researches (1861).—This observer rediscovered the chief facts already knowr
to Buchanan, viz., that some fluids which do not coagulate spontaneously, clot when mixed
with other Auids which show no tendency to coagulate spontaneously, ¢.g., hydrocele fluid and
blood-serum. He isolated from these fluids the bodies described us fibrinogen and fibrino-

lastin. ‘The bodies so obtained were not pure, but Schmidt supposed that the formation of
tbrin was due to the interaction of these two proteids. The reason hydrocele fluid does not.
coagulate, he says, is that it contains fibrinogen and no fibrino-plastin, while blood-serum con-
tains the latter, but not the former. Schmidt afterwards discovered that these two substances
may be present ina fluid, and yet coagulation may not occur (¢.g., ocvasionally in hydrocele
fluid). He supposed, therefore, that blood or blood-serum contained some other constituent
necessary for coagulation. This he afterwards isolated in an impure condition and called

Sibrin-ferment. |

A. Schmidt’s theory is that fibrin is formed by the coming together of two
proteid substances which occur dissolved in the plasma, viz.:—(1) fibrinogen,
i.c., the substance which yields the chief mass of the fibrin, and (2) fibrino-plastic
substance or fibrino-plastin (serum-globulin or paraglobulin, § 32). In order to
determine the coagulation a ferment seems to be necessary, and this is supplied by
(3) the fibrin-ferment.

1. Properties.—Fibrinogen and fibrino-plastin belong to the group of proteids.
called globulins, ¢.c., they are insoluble in pure water, but are soluble in dilute
solutions of common salt (§ 249), and are not distinguished from each other by well-
marked chemical characters. Still they differ as follows :—

Fibrino-plastin is more easily precipitated from its solutions than fibrinogen..
It is more readily redissolved when once it is precipitated. It forms when pre-
cipitated a very light granular powder.

Fibrinogen adleres as a sticky deposit to the side of the vessel. It coagulates
at 56° C.

On account of their great similarity, both substances are not usually prepared
from blood-plasma. J/ibrinogen is prepared from serous transudations (pericardial,.
abdominal, or pleuritic fluid, or the fluid of hydrocele), which contain no fibrino-
plastin. /%brino-plastin is most readily prepared from serum, in which there is still
plenty of fibrino-plastin, but no fibrinogen.

2. Preparation of Fibrino-plastin, Serum-globulin, or Paraglobulin.—(a)
Dilute blood-serum with twelve times its volume of ice-cold water, and almost
neutralise it with acetic acid [add 4 drops of a 25 per cent. solution of acetic acid
to every 120 c.c. of diluted serum]; or (4) pass a stream of carbon dioxide through
the diluted serum, which soon becomes turbid ; after a time a fine white powder,
copious and granular, is precipitated.

((c) Method of Hammarsten.— All the fibrino-plastin in serum is not precipitated
either by adding acetic acid or by CO, Hammarsten found, however, that if
crystals of magnesium sulphate be added to complete saturation, it precipitates the
whole of the serum-globulin, but does not precipitate serum-albumin; serum-globulin.
is more abundant than serum-albumin in the serum of the ox and horse, while:
in man and the rabbit the reverse obtains ; (compare § 32).]

_ Schmidt found that 100 c.c. of the serum of ox blood yielded 0°7 to 0°8 grm. 5 horse’s:
serum, 0°3 to 0°56 grm. of dry fibrino-plastin. Fibrino-plastin’ occurs not only in serum, but
also in red blood-corpuscles, in the fluids of connective-tissue, and in the juices of the cornea.

3. Preparation of Fibrinogen.—This is best prepared from hydrocele fluid,
although it may also be obtained from the’ fluids of serous cavities, ¢.g., the pleura,.
pericardium, or peritoneum. It does not exist in blood-serum, although it does.
exist in blood-plasma, lymph, and chyle, from which it may be obtained by a
stream of CO,, after the paraglobulin is precipitated. (a) Dilute hydrocele fluid
with ten to fifteen times its volume of water, and pass a.stream of CO, through it
for a long time. (+) Add powdered common salt to saturation to a serous trans-
rented when a sticky glutinous (not very abundant) precipitate of fibrinogen is
obtained. ie

“
if
4

THE FIBRIN-FACTORS. 35

[Hammarsten and Eichwald find that, although paraglobulin and fibrinogen are soluble in
solutions of common salt (containing 5 to 8 per cent. of the salt), a saline solution of 12 to 16
per cent. is required to precipitate the fibrinogen, leaving still in solution paraglobulin,
which is not precipitated until the amount of salt exceeds 20 per cent. ]

Properties of the Fibrin-Factors.—They are insoluble in pure water, but
dissolve in water containing O in solution. Both are soluble in very dilute alkalies,
é.g., caustic soda, and are precipitated from this solution by CO,. They are soluble
in dilute common salt—like all globulins—but if a certain amount of common
salt be added in excess, they are precipitated. Very dilute hydrochloric acid
dissolves them, but after several hours they become changed into a body resembling
syntonin or acid-albumin (§ 249, IIT.). Fibrinogen held in solution by common
salt coagulates at 52° to 55° C. [Frédéricq finds that fibrinogen exists as such in
the plasma ; it coagulates at 56° C., and the plasma thereafter is uncoagulable. |

4, Preparation of the Fibrin-Ferment.—(a) Mix blood-serum (ox) with twenty
times its volume of strong alcohol, and after one month filter off the deposit
thereby produced. The deposit on the filter consists of coagulated insoluble
albumin and the ferment; dry it carefully over sulphuric acid, and reduce to a
powder. Triturate 1 gram of the powder with 65 c.c. of water for ten
minutes, and filter. The ferment is dissolved by the water, and passes through
the filter, while the coagulated albumin remains behind (Schmidt).

[(b) Gamgee’s Method. —Buchanan’s ‘‘ washed blood-clot”’ (p. 33) is digested in an 8 per cent.
solution of common salt. The solution so obtained possesses in an intense degree the properties
of Schmidt’s fibrin-ferment. ]

In the preparation of fibrino-plastin, the ferment is carried down withit mechanically. The
ferment seems to be formed first in fluids outside the body, very probably by the solution of
the colourless corpuscles. More ferment is formed in the blood the longer the interval between
its being shed and its coagulation. It is destroyed at 70° C. Blood flowing directly from an
artery into alcohol contains no ferment. It is also formed in other protoplasmic parts
(Rauschenbach), e.g., in dead muscle, brain, suprarenal capsule, spermatozoa, testicle (Foa and
Pellacani), and in vegetable micro-organisms [¢.g., yeast] and protozoa (Grohmann), [so that it
would seem to be a general product of protoplasm. As the ferment does not pre-exist in
colourless blood-corpuscles, it seems to be formed from some mother-substance in them, the
blood-plasma itself decomposing this substance].

Coagulation Experiments.—According to A. Schmidt, if pure solutions of (1)
fibrinogen, (2) fibrino-plastin, and (3) fibrin-ferment be mixed, fibrin is formed.
The process goes on best at the temperature of the body ; it is delayed at 0° ; and
the ferment is destroyed at the boiling-point. The presence of O seems necessary
for coagulation. The amount of the ferment appears to be immaterial ; large
quantities produce more rapid coagulation, but the amount of fibrin formed is not
greater.

[Fou and Pellacani find. that a filtered watery extract of fresh brain, capsule of the kidneys,
testes, and some other tissues, when injected into the blood-vessels of a rabbit, causes
coagulation of the blood in the pulmonary circulation and the heart, death being caused by the
action of a substance identical with the fibrin-ferment. ] ;

The amount of salts present has a remarkable relation to coagulation. Solutions
of the fibrin-factors deprived of salts, and redissolved in very dilute caustic soda,
when mixed, do not coagulate until sufficient NaCl be added to make a 1 per cent.
solution of this salt (Schmidt), [Green finds that calcium sulphate brings about
coagulation in plasma which shows little or no tendency to clot, while coagulation
in its absence is almost or quite prevented. ] ;

When blood or blood-plasma coagulates, all the fibrinogen is used up, so that the
serum contains only fibrino-plastin and fibrin-ferment ; hence, the addition of
hydrocele fluid (which contains fibrinogen) to serum causes coagulation.

{Hammarsten’s Theory.—Hammarsten’s researches led him to believe that
fibrino-plastin is quite unnecessary for coagulation... According to him, fibrin is
formed from one body, viz., fibrinogen, which is present in plasma when it is acted
upon by the jibrin-ferment ; the latter, however, has not been obtained in a pure

36 SOURCE OF THE FIBRIN-FACTORS,

state. Neither he nor Schmidt asserts that this body is of the nature of a ferment,
although they use the term for convenience. It is quite certain that fibrin may be
formed when no fibrino-plastin is present, coagulation being caused by the addition
of calcic chloride or casein prepared in a special way. But, whether one or two
proteids -be required, in all cases it is clear that a certain quantity of salts,
especially of NaCl, is necessary. |

[The main drift of the foregoing evidence points to the presence of one proteid
—fibrinogen—in the plasma, which under certain circumstances yields fibrin. In
shed blood this act seems to be determined by a ferment, perhaps derived from the
disintegration of colourless corpuscles. |

[Theory of Wooldridge.—Wooldridge attributes great importance to lecithin, In shed
blood the coagulation is brought about by the interaction of the plasma and the colourless
corpuscles. If lecithin (which is present in considerable amount in the colourless a ae
(liffuses into the blood, coagulation takes place. When peptone is injected into the blood of
the dog, the blood does not clot; this is due, according to Wooldridge, to the ae
‘“ preventing the interaction of leucocytes and plasma.” If, however, the corpuscular elements
are removed by the centrifugal machine, the peptone-plasma can be. made to clot. He also
believes that fibrin-ferment does not pre-exist in normal plasma, but that ‘‘it may make its
appearance in that plasma in the absence of all cellular elements, and must therefore come
from some constituent or constituents of the plasma itself.”’]

30. SOURCE OF THE FIBRIN-FACTORS.—AI. Schmidt maintains that all
the three substances out of which fibrin is said to be formed, arise from the break-
ing up of colourless blood-corpuscles. In the blood of man and mammals, fibrinogen
' exists dissolved in the circulating blood as a dissolution-product of the retrogressive
changes of the white corpuscles. Plasma contains dissolved fibrinogen and serum-
albumin. ‘The circulating blood is very rich in colourless blood-corpuscles, much
richer, indeed, than was formerly supposed. As soon as blood is shed from an
artery, enormous numbers of the colourless corpuscles are dissolved—according to
Al. Schmidt 71:7 per cent. (horse). First the body of the cell disappears, and
then the nucleus. The products of their dissolution are dissolved in the plasma,
and one of these products is jibrino-plastin. At the same time the fibrin-ferment
is also produced, so that it would seem not to exist in the intact blood-corpuscles.
Fibrino-plastin and fibrin-ferment are also produced by the “ transition forms” of
blood-corpuscles, z.¢., those forms which are intermediate between the red and the
white corpuscles. They seem to break up immediately after blood is shed, The
hlood-plates (p. 16) are also probably sources of these substances.

In pb paper and birds the ved nucleated corpuscles rapidly break up after blood is shed,
and yield the substance or substances which form fibrin. Al. Schmidt convinced himself that
in these animals fibrinogen is originally a constituent of tne blood-corpuscles.

It is clear, therefore, according to Schmidt’s view, that as soon as the blood-
corpuscles, white or red, are dissolved, the fibrin-factors pass into solution, and the
formation of fibrin by the interaction of the three substances will ensue.

If a large number of leucocytes be introduced into the circulation of an animal,
the leucocytes are dissolved in great numbers in the blood, so that death takes
place by diffuse coagulation. Should the animal survive the immediate danger of

death, the blood, owing to the want of leucocytes, is completely incapable of

coagulating (Groth).

[And. Buchanan thought that the potential element of his ‘‘ washed blood-clot” resided. in

_the colourless corpuscles, ‘primary cells or vesicles.” He, like Schmidt, found that the

buffy coat of horses’ blood, which is very rich in white corpuscles, produced coagulation rapidly.
Buchanan compared the action of his washed clot to that of rennet in coagulating milk.] ~

Pathological. —Al. Schmidt and his pupils have shown that some ferment, probably derived _

from the dissolution of colourless corpuscles, is found in circulating blood, and that it is more
abundant in venous than in arterial blood, while it is most abundant in shed blood, It
specially remarkable that in septic fever the amount of ferment in blood may increase to sich
an extent as to permit the occurrence of spontancous coagulation (thrombosis), which may evel

produce death (Arn. Kohler). In febrile cases generally, the amount of. ferment is: somewhat

COMPOSITION OF PLASMA AND SERUM. . a7

more abundant (Zdelberg and Birk). After the injection of ichor into the blood an enormous
number of colourless corpuscles are dissolved (#. Hoffmann). The injection of peptone, Hb,
and to a less degree of distilled water, is followed by dissolution of numerous leucocytes.

There ate changes in the blood, constituting true blood diseases, in which the physiological
metabolism of the colourless corpuscles is enormously increased, so that the metabolic products
accumulate in the blood (Alex. Schmidt). ‘The result of this is spontaneous coagulation within
the circulatory system, and death even may occur; there is always an increase of tempera-
ture. After such a condition, the coagulability of the blood is diminished.

31, Formation of Fibrin.—After several observers had shown that the red blood-corpuscles
(bird, horse, frog) participate in the production of fibrin, Landois observed, in 1874, under the
microscope that the stromata of the red blood-corpuscles of mammals passed into fibrin. Ifa
drop of defibrinated rabbit’s blood be placed in serum of frog’s blood, without mixing them, the -
red corpuscles. can be seen collecting together ; their surfaces are sticky, and they can only be
separated by a certain pressure on the cover-glass, whereby some of the now spherical corpuscles
are drawn out into threads. The corpuscles soon become spherical, and those at the margin
allow the hemoglobin to escape, the decolorisation progresses, from the margin inwards, until
at last there remain masses of stroma adhering together. The stroma-substance is very sticky,
but soon the cell-contours disappear, and the stromata adhere and form fine fibres. Thus
(according to Landois) the formation of fibrin froin red blood-corpuscles can be traced step
by step. The red corpuscles of man and animals, when dissolved in the serum of other
animals, show much the same phenomena.

Stroma-Fibrin and Plasma-Fibrin.—Landois calls fibrin formed direct from stroma, stroma-
Jibrin; fibrin formed in the usual way plasma-fibrin. The stroma-fibrin is closely related
chemically to stroma itself ; as yet, however, the two kinds of fibrin have not been sharply dis-
tinguished chemically. Substances which rapidly dissolve red corpuscles cause extensive coagul-
ation, ¢.g., injection of bile or bile salts, or lake-coloured blood, into ‘arteries. After the
injection of foreign blood the newly-injected blood often breaks up in the blood-vessels of the
recipient, while the finer vessels are frequently found plugged with small thrombi (§ 102).

Coagulable Fluids.—With regard to coagulability, fluids containing proteids
may be classified thus :—

(1) Those that coagulate spontaneously, i.e., blood, lymph, chyle.

(2) Those capable of coagulating, ¢.g., fluids secreted pathologically in serous cavities ; for
example, hydrocele fluid, which, as usually containing fibrinogen only, does not coagulate
spontaneously, but it coagulates on the addition of fibrino-plastin and ferment (or of blood-
serum in which both occur). .

(3) Those which do not coagulate, e.g., milk or seminal fluid, which do not seem to contain
fibrinogen.

32. CHEMICAL COMPOSITION OF PLASMA AND SERUM.—I. Proteids
occur to the amount of 8 to 10 per cent. in the plasma. Only 0:2 per cent. of
these go to form fibrin. After the formation of the fibrin the plasma is converted
into serum. The sp. gr. of human serum is 1027 to 1029. It contains several
proteids. [According to Hammarsten, human serum contains 9°207 per cent. of
solids,—of these, 3:103 = serum-globulin, and 4°516 = serum-albumin, 7.¢., in the ratio
of 1: 1°511. In horse-serum the proportion is 4°5 ; 2°6, in ox-serum 4°16 : 3°29,
and rabbit-serum 6°22: 1°78. The total amount of proteids in blood seems to be
much more constant than are the relative proportions of serum-albumin and serum-
globulin (Salviolz). |.

(a) Serum-globulin or Paraglobulin (2 to 4 per cent.). If crystals of
magnesium sulphate be added to saturation to serum at 35° C., serum-globulin is
precipitated, but not serum-albumin. It is soluble in 10 per cent. solution of
common salt, and coagulates at 69-75° C, Its specific rotatory power is — 47°8°
(Frédéricq). | Pe

[Serum-globulin was described by Panum under the name of “serum-casein”; by Al.
Schmidt, as “‘fibrino-plastic substance”; and by Kiihne, as “ paraglobulin.”] During hunger
the globulin increases and the albumin diminishes. |

(6) Serum-albumin (3-4 per cent). Its solutions begin to be turbid at 60° C.,
and coagulation occurs at 73° C., the fluid becoming slightly more alkaline at the
same time. If sodium chloride be cautiously added to serum, the coagulating
temperature may be lowered to 50°C. Its specific rotatory power is from — 62°6

t

38 : PROTEIDS OF THE SERUM.

to 64:5° (Starke). It is changed into syntonin or acid-albumin by the action of
dilute HCl, and by dilute alkalies into alkali-albuminate.

Serum-albumin is absent from the blood of starving snakes; and reappears after they are
fed ( Tiegel). a.

(Serum-Albumin v. Egg-Albumin.—Although serum-albumin is closely related to egg-
albumin they differ—(a) as regards their action upon polarised light ; (6) the precipitate pro-
dueed by adding HCl or HNO, is readily soluble in 4 c.c. of the reagent in the case of serum-
albumin, while the precipitate in egg-albumin is dissolved with very great difficulty ; (c) egg-
albumin, injected into the veins, is excreted in the urine as a foreign body, while serum-albumin
is not ; (d) serum-albumin is not coagulated by ether, while egg-albumin is, if the solution is
not alkaline (¢ 249). Serum-albumin has never been obtained free from salts, even when it is
dialysed for a very long time. ] J

After all the serum-globulin in serum is precipitated by magnesium sulphate, serum-albumin
still remains in solution. If this solution be heated to 40 or 50° C. a copious precipitate of
non-coagulated serum-albumin is obtained, which is soluble in water. If the serum-albuimin be
tiltered trom the fluid, and if the clear fluid be heated to over 60° C., Frédéricq found that it
becomes turbid from the precipitation of other proteids; the amount of these other bodies,
however, is small.

[Proteids of the Serum.—Halliburton has shown by the method of “ fractional
heat-coagulation” (7.., ascertaining the temperature at which a proteid is
coagulated, filtering the fluid and again heating the filtrate to a higher temperature),
that from the same fluid perhaps two or more proteids, all with different tempera-
tures of coagulation, may be obtained. Care must be taken to keep the reaction
constant. He finds that serum-globulin coagulates at 75° C., while serum-albumin
in reality consists of three proteids, which coagulate at different temperatures ; (a)
at.73°, (8) at 77°, and (y) at 84° C.]

[Precipitation by Salts.—Sulphate of magnesia not only precipitates serum-globulin but also
fibrinogen. The fluid must be shaken for several hours to get complete saturation. Sodic
sulphate, when added to serum deprived of its globulin by MgSO,, precipitates serum-albumin,
but it produces no precipitate with ey serum. In this way serum-albumin.may be obtained
in a pure, uncoagulated, and still soluble condition. Serum-globulin is thrown down by sodie
nitrate, acetate, or carbonate ; while a// the proteids of the serum are precipitated by potassic
acetate or phosphate, and the same result is brought about by adding two salts, e.g., MgSO,
and Na,SO, (in this case sodio-magnesic sulphate is formed); MgSO, and NaNO, ; MgSO, and
KI; NaCl and Na,SO,. After serum-globulin is thrown down by MgSO,, the addition of
MgSO, and Na,SO, or the double-salt, precipitates the serum-albumin, which is still soluble in
water. As sulphate of ammonia precipitates all the proteids except peptones, it may be used
(Halliburton). }

[The plasma of Invertebrata ((lecapod crustaceans, some gasteropods, cephalopods, &c.) clots
like vertebrate blood, and contains fibrinogen, but, in addition, there is found in it a substance
corresponding to hemoglobin, and called by Frédéricq, heemocyanin. It exists like Hb in two-
conditions, one reduced and the other oxy-hemocyanin, the former being colourless, the latter
blue. In its general characters it resembles Hb, although it contains copper instead of iron,
and gives no absorption-bands (Halliburton). In the blood of some decapod crustaceans there
is a reddish pigment, tetronerythrin, which is identical with that in the exoskeleton and
hypoderm. It belongs to the group of lipochromes, like some of the pigments of the retina.
The hemocyanin is respiratory in function, and it is remarkable that it is contained in the
plasma, and not in the formed elements like the Hb of vertebrates. So that, stated broadly,
in these invertebrates the plasma is both nutritive and respiratory in its functions, while in
vertebrates the red corpuscles chiefly are respiratory and the plasma nutritive. ]

II. Fats (O°l to 0-2 per cent.).—Neutral fats (tristearin, tripalmitin, triolein)
occur in the blood in the form of small microscopic granules, which, after a meal
rich in fat (or milk) render the serum quite milky.

[The amount of fat in the serum of fasting animals is about 0°2 per cent.; during digestion
0°4 to 0°6 per cent. ; and in dogs fed on a diet rich in fat it may be 1°25 per cent. There are
also minute traces of fatty acids (succinic). Réhrig showed that soluble soaps, i.e, alkaline
salts of the fatty acids, cannot exist in the blood. Cholesterin may be considered along with
the fats. It occurs in considerable amount in nerve-tissues, and, like fats, is extracted by ether
from ‘the ory residue of blood-serum. Hoppe-Seyler found 0°019 to 0°314 per cent. in the serum
of the blood of fattened geese. There is no fat in the red blood-corpuscles. Lecithin (its de-
tai ee glycerin-phosphoric acid and protagon) occur in serum and also in the
blood-corpuscles. } | pia 1

e-—=””-
fy

GASES OF THE BLOOD. | , 39

. ITI. Traces of Grape-Sugar [0:1 to 0:15 per cent. (more in the hepatic vein,
0:23 per cent.)| derived from the liver and muscles, and increased after hemorrhage
(§ 175); some glycogen, and another reducing fermentative substance also
increased by hemorrhage. .

The amount of grape-sugar in the blood increases with the absorption of sugar from the
intestine, and this increase is most obvious in the blood of the portal and hepatic veins ; there
is also a slight increase in the arterial blood, but there it is rapidly changed. The presence of
sugar is ascertained by coagulating blood by boiling it with sodium sulphate, pressing out the
fluid and testing it for sugar with Fehling’s solution (Cl. Bernard). Pavy coagulates the blood
with alcohol.

IV. Extractives.—Kreatin, urea (0°016 per cent., increased after nitrogenous
food), succinic acid, and uric acid (more abundant in gouty conditions), guanin (1),
carbamic acid, sarcolactic acid ; all occur in very small amounts.

V. Salts (0°85 per cent.), especially sodic chloride (0°5 per cent.) and sodic
carbonate. [It is most important to note that the soda salts are far more abundant
in the serum than the potassium salts. The ratio may be as high as 10: 1.]
Animal diet increases the amount of salts, vegetable food diminishes it tempo-

-rarily.

Salts in human blood-serum (Hoppe-Seyler).

Sodic Chloride, . : 4°92 per 1000 Sodic Phosphate, . 0°15 per 1000
», Sulphate, ‘ 0°44 3 Calcic Phosphate, 0°73
», Carbonate, . OFZl ne Magnesic_,, : ss

If large quantities of salts are introduced into the blood, they almost entirely disappear from
the blood-stream within a few minutes, chiefly by diffusion into the tissues. They are gradually
eliminated by the kidneys. The same is true of sugar and peptones (Ludwig and Klicowicz).

VI. Water about 90 per cent.
VII. A yellow pigment.

The pigment may be extracted with methylic alcohol. It shows two absorption-bands of a
lipochrome like lutein (AKvwkenberg). Thudichum regards the pigment of the serum as lutein ;
Maly, as hydrobilirubin; and MacMunn as choletelin.

33. THE GASES OF THE BLOOD. —Absorption by Solid Bodies.—<A considerable attraction
exists between the particles of solid porous bodies and gases, whereby the latter are attracted and
condensed within the pores of solid bodies, ¢.e., the gases are absorbed. Thus, 1 volume of
boxwood charcoal (at 12° C. and ordinary barometric pressure) absorbs 35 volumes CO,, 9°4
vol. O, 7°5 vol. N, 1°75 vol. H. Heat is always formed when gases are absorbed, and the
amount of heat evolved bears a relation to the energy with which the absorption takes place.
Non-porous bodies are similarly invested by a layer of condensed gases on their surface.

By Fluids.—Fluids can also absorb gases. A known quantity of fluid at different pressures
always absorbs the same volwme of gas. Whether the pressure be great or small, the volume of
the gas absorbed is equally great (W. Henry). But according to Boyle (1662) and Mariotte’s
law (1679) on the compression of gases, when the pressure within the same volume of gas is
increased, the volume varies inversely as the pressure. Hence it follows that, with varying
pressure, the volume of gas absorbed remains the same, but the quantity of gas (weight) is
directly proportional to the pressure. If the pressure = 0, the weight of the gas absorbed must
also = 0. As a necessary result of this, we see that (1) fluids can be freed of their absorbed
gases in a vacuum under an air-pump.

Coefficient of Absorption means the volume of a gas (0° C.) which is absorbed by a unit of
volume of a liquid (at 760 mm. Hg) at a given temperature. The volwme of a gas absorbed,
and therefore the coefficient of absorption, is quite independent of the pressure, while the weight
of the gas is proportional to it. Temperature has an important influence on the coefficient of
absorption. With a low temperature it is greatest ; it diminishes as the temperature increases ;
and at the boiling-point it = 0. Hence, it follows that—(2) absorbed gases may be expelled

Srom fluids simply by causing,the fluids to boil. The coefficient of absorption diminishes for

different fluids and gases, with increasing temperature, in a special, and by no means uniform,
manner, which must be determined empirically for each liquid and gas. Thus the coefficient
of absorption’for CO, in water diminishes with an increasing temperature, while that for H in
water remains unchanged between 0° and 20° C.
Diffusion of Gases.—Gases which do not enter into chemical combinations with each other
mix with each other in definite proportions. If the necks of two flasks be placed in communi-
cation by means of a glass or other tube, and if the lower flask contain CO,, and the upper one
H, the gases mix quite independently of their different specific gravities, both gases forming in

40 EXTRACTION OF THE BLOOD GASES.

each flask a perfectly uniform mixture. The phenomenon is called the diffusion of gases. EE
a porous membrane be previously inserted between the gases, the exchange of gases still goes on
through the membrane. But (as with endosmosis in fluids) the gases pass with unequal rapidi

through the pores, so that at the beginning of the experiment a larger amount of gas is foun

on one side of the membrane than on the other. According to Graham, the rapidity of the
diffusion of the gases through the pores is inversely proportional to the square root of their
specific gravities. (According to Bunsen, however, this is not quite correct. ) :

Different Gases in a Gaseous Mixture do not Exert Pressure upon one another.—Gases,
therefore, pass into a space filled with another gas, as they would pass into a vacuum. If the
surface of a fluid containing absorbed gases be placed in contact with a very large quantity of
another gas, the absorbed gases diffuse into the latter. Hence, absorbed gases can be removed
by (3) passing a stream of another gas through the fluid, or by merely shaking up the fluid with
another qas. ;

artial Pressure.—If two or more gases are mixed in a closed space over a fluid, as the
different gases existing in a gaseous mixture exert no pressure upon each other, the several gases
are absorbed. The weight of each absorbed is proportional to the oe under which each
gas would be, were it the only gas in the 5 sea This pressure is called the partial pressure of
a gas (Bunsen). The absorption of gases from their mixtures, therefore, is proportional to the
partial pressure. The partial pressure of a gas in a space is at the same time the expression for
the tension of the gas absorbed by a fluid. ;

The air contains 0°2096 volume of O, and 0°7904 volume N. If 1 volume of the air be placed
under a pressure, P, over water, the partial pressure under which O is absorbed =0°2096 P ;
that for N=0°7904 P. At 0° C., and 760 mm. pressure, 1 volume of water absorbs 0°02477
volume of air, consisting of 0°00862 volume O, and 0°01615 volume N. It contains, therefore,
34 per cent. O and 66 per cent. N. Therefore, water absorbs from the air a mixture of gases
containing a larger percentage of O than the air itself.

34, EXTRACTION OF THE BLOOD GASES.—{The blood to be analysed must be collected
over mercury so as to avoid contact with air. This is done by means of a special apparatus,
consisting of a graduated tube filled with mercury and communicating with a glass globe also
filled with mercury, which can be lowered as the blood flows into the graduated tube.] The
extraction of the gases from the blood, and their collection for chemical analysis, are carried out
by means of the mercurial pump (C. Ludirig). Fig. 22 shows in a diagrammatic form the
arrangement of Pfliiger’s gas-pump.

It consists of a receptacle for the blood, or ‘‘ blood-bulb’”’ (A), a glass globe capable of con-
‘aining 250 to 300 c.c., connected above and below with tubes, each of which is provided with
a stop-cock, « and 6; 6 is an ordinary stop-cock, while a has through its long axis a perforation
which opens at x, and is so arranged that, according to the position of the handle, it leads up.
into the blood-bulb (position ~, @), or downwards through the lower tube (position 2’, a’), This
blood-bulb is first completely emptied of air (by means of a mercurial air-pump), and then care-
fully weighed. One end (z’) of it is tied into an artery or a vein of an animal, and when the
lower stop-cock is placed in the position x, a blood flows into the receptacle. When the
necessary amount of blood is collected, the lower stop-cock is put into the position 2’, a’, and the
blood-bulb, after being cleaned most carefully, is weighed to ascertain the weight of the amount
of blood collected. The second part of the apparatus consists of the froth-chamber, B, leading
upwards and downwards into tubes, each of which is provided with an ordinary stop-cock, ¢ and
d. The froth-chamber, a8 its name denotes, is to catch the froth which is formed during the
energetic evolution of the gases from the blood. The lower aperture of the froth-chamber is.
connected by means of a well-ground tube with the blood-bulb, while above it communicates
with the third part of the apparatus, the drying-chamber, G. This consists of a U-shaped tube,

rovided below with a small glass bulb, which is half filled with sulphuric acid, while in its.
imbs are placed pieces of pumice-stone also moistened with sulphuric acid. As the blood
es through this apparatus (which may be shut off by the stop-cocks ¢ and f), they are
reed from their watery vapour by the sulphuric acid, so that they pass quite dry through the
stop-cock, f. The short well-ground tube, D, is fixed to 7, and to the former is attached the
small barometric twhe or manometer, y, which indicates the extent of the vacuum. From D we
pass to the pump proper. This consists of two large glass bulbs, which are continued above
and below into open tubes; the lower tubes, Z and w, being united by a caoutchouc tube, G.
Both the bulbs and the caoutchouc tube contain mercury—the bulbs being about half full, and
F being larger than E. The bulb, E, is fixed; but F can be raised or lowered by means of a ~
ulley with a rack and pinion motion. If F be raised, E is filled ; if F be lowered, E is emptied,
he ape end of E divides into two tubes, g and h, of which g is united to D. The spinon,
tube, / (gas-delivery tube), is very narrow, and is bent so that its free end dips into a vesse
containing mercury, v (a pneumatic trough), and the opening is placed exactly under the tube
for collecting the gases, the eudiometer, J, which is also filled with mercury, Where g and H
unite, there is a two-way stop-cock, which in one position, H, places E in communication with —
A, B, G, D, the chambers to be exhausted, and in the position K shuts off A, B, G, D, and

EXTRACTION OF THE BLOOD GASES. 41

places the bulb, E, in communication with the gas-delivery tube, , and the eudiometer, J.
B, G, D are completely emptied of air, thus :—The stop-cock is placed in the position, K ; raise
F until drops of mercury issue from the fine tube, 7 (not yet placed under J); place the stop-
cock in the position H, lower F ; stop-cock in position, K, and so on until the barometer, y,
indicates a complete vacuum, J is now placed over 7% Open the cocks, ¢ and J, so that the
blood-bulb, A, communicates with the rest of the apparatus, and the blood gases froth up in B,

FPAMwIDo

Gq)

ero

=
i
PDADS DIC IAVDRAD

ut if \SERus

| co
4f=-K Xe

Load
Fig. 22.
Scheme of Pfliiger’s gas-pump. A, blood-bulb; a, stop-cock, with a longitudinal perforation
opening upwards; a’, the same opening downwards; bd andc, stop-cocks ; B, froth-chamber ;
d, e, f, stop-cocks; G, drying-chambers, containing sulphuric acid and pumice-stone ; D,
tube, with manometer, y. :

and after being dried in G pass towards E. Lower F, and they pass into E; stop-cock in
position, K, raise F, and the gases are collected in J under mercury. The repeated lowering
and raising of F with the corresponding position of the stop-cocks ultimately drives all the
gases into J. The removal of the gases is greatly facilitated by placing the blood-bulb, A, in a
vessel containing water at 60° C. | ,
It is well to remove the gases from the blood immediately after it is collected from a blood-
vessel, because the O undergoes a diminution if the blood be kept. Of course, in making several

42 ESTIMATION OF THE BLOOD GASES,

analyses it is difficult to do this, and the best plan to pursue in that case is to keep the recep-
tacles containing the blood on ice. { ;

Mayow (1670) observed that gases were given off from blood in vacuo. Magnus (1837) in-
vestigated the percentage ee of the blood gases. The more important recent investi-
gations have been made by Lothar Meyer (1857), and by the pupils of C. Ludwig and E.
Pfliiger. -

35. QUANTITATIVE ESTIMATION OF THE BLOOD GASES.—The gases
obtained from blood consist of O, CO,, and N. Pfliiger obtained (at 0° C. and 1
metre Hg pressure) 47°3 volumes per cent., consisting of—

0, 16-9 per cent. ; CO,, 29 per cent.; N, 1°4 per cent.

As is shown in fig. 22, J, the gases are obtained in an eudiometer, 7.¢., in a narrow
tube, closed at one end, and with a very exact scale marked on it, and having two
fine platinum wires melted into its upper end, with their free ends projecting into
the tube (p and n). .

(1) Estimation of the CO,.—A small ball of fused caustic potash, fixed on a platinum wire, is
introduced into the mixture of gases through the lower end of the eudiometer under cover of
the mercury. The surface of the potash ball is moistened before it is introduced. The CO,
unites with the potash to form potassium carbonate. The potash bulb is withdrawn after 24
hours. The diminution in volume indicates the amount of CO, absorbed.

(2) Estimation of the 0.—(«) Just as in estimating the CO,, a ball of phosphorus on a
platinum wire is introduced into the eudiometer ; it absorbs the O and forms phosphoric acid.
Another plan is to employ a small papier-maché ball saturated with pyrogallic acid in caustic
potash, which rapidly absorbs O. After the ball is removed, the diminution in volume indicates
the quantity of O.

(4) The O is most easily and accurately estimated by exploding it in the eudiometer. Intro-
duce a sufficient quantity of H into the eudiometer, and accurately ascertain its volume ; an
electrical spark is now passed between the wires, p and 2, through the mixture of gases ; the O
and H unite to form water, which causes a diminution in the volume of the gases in the eudio-
meter, of which 4 is due to the O used to form water (H,O).

(c) Estimation of the N.—When the CO, and O are estimated by the above method, the
remainder is pure N,

36. THE BLOOD GASES.—{In human blood the average total gases are
estimated to be, at 0° C. and 1 metre pressure,

0 CO, N
Arterial blood, 17 30 1 to 2 per cent.
Venous blood, 6 to 10 35 1 to 2

9
or, calculated at 0° C. and 760 mm. pressure,
Arterial blood, 20 39 1:4 per cent. :
Venous blood, 8 to 12 46 i ar

I. Oxygen exists in arterial blood (dog) on an average to the extent of 17
volumes per cent. (at 0° C. and 1 metre Hg pressure) (Pfliiger). According to
Pfliiger, arterial blood (dog) is saturated to ,%, with O, while, according to Hiifner,
it is saturated to the extent of 14. In venous blood the quantity varies very
greatly ; in the blood of a passive muscle 6 volumes per cent. have been found ;
while in the blood after asphyxia it is absent, or occurs only in traces. It is
certainly more abundant in the comparatively red blood of active glands (salivary
glands, kidney), than in ordinary dark venous blood.

Conditions.—The amount of 0 obtainable from the blood depends upon the organ

Sed which the blood comes, or whether the organ be active or at rest. Thus the O present
in the

Carotid artery is , : 21 per cent. Renal vein (kidney active), 17 per cent. _
Renal artery, é : 20 th Renal vein (kidney at rest), 6 ,,
Bert finds that increase of the atmospheric pressure from 1 to 10 atmospheres raises the

amount of O in arterial blood from 20 to over 24 per cent., and the N from 1° ie
per cent,, while the CO, is but slightly affected, ]. - tg e N from 1°8 to over 9

The O in Blood oceurs—(a) simply absorbed in the plasma. This is ontyiae :@

——- =

THE BLOOD GASES. 43

‘minimal amount, and does not exceed what distilled water at the temperature of

the body would take up at the partial pressure of the O in the air of the lungs
(Lothar Meyer).

(b) Almost the total O- of the blood is chemically united, and therefore not subject
to the law of absorption. It is loosely united to. the hemoglobin of the red
corpuscles, with which it forms oryhxmoglobin (§ 15). With regard to the taking
up of O, the total quantity of blood behaves exactly like a solution of hemoglobin
free from O (Preyer). The absorption of O is more rapid in blood than in a
solution of Hb.

The absorption of this quantity of O is completely independent of pressure; hence, animals
confined in a closed space, until they are nearly asphyxiated, can use up almost all the O from
the surrounding atmosphere. The fact of the union being independent of pressure is proved by
the following ;—The blood only gives off copiously its chemically united O when the atmo-
spheric pressure is lowered to 20 millimetres, Hg (Worm Miller); and, conversely, blood only
takes up a little more O when the pressure is increased to 6 atmospheres (Bert).

Physical Methods of obtaining 0 from Blood.—Notwithstanding the chemical
union between the Hb and O, all the O of the blood can be expelled from its state
of combination by those means which set free absorbed gases—(a) by introducing
blood into a Torricellian vacuum ; (d) by boiling ; (c) by the conduction of other
gases [H, N, CO, or NO] through the blood, because the oxyhemoglobin compound
is so loose that it is decomposed even by these physical means.

Reducing Reagents.—Amongst chemical reagents the following reducing
substances—ammonium sulphide, sulphuretted hydrogen, alkaline solutions of sub-
salts or Stokes’s fluid, iron filings, &c., rob blood of its O (§ 15).

Relation to Fe.—The amount of iron in the blood (0°55 in 1000 parts) stands in direct relation
to the amount of Hb; this to the quantity of blood-corpuscles ; and this, in turn, to the specific
gravity of the blood. The amount-of O in the blood, therefore, is nearly proportional to the.
specific gravity of the blood, and it is also in proportion to the amount of iron in the blood.
Picard affirms that 2°36 grams of iron in the blood can fix chemically 1 gram O; while,
-according to Hoppe-Seyler, the proportion is 1 atom iron to 2 atoms O.

During morphia narcosis the amount of O in the blood is diminished (Zwald); after hemor-
rhage the arterial blood is saturated with O (J. G. Ot).

Disappearance of O in Shed Blood.—Even immediately after blood is shed, thcre is a slight
(lisappearance of O, as a physiological index of respiration of the tissues within the living blood
itself (§ 182). When blood is kept long outside of the blood-vessels, the quantity of O gradually
diminishes, and if it be kept for a length of time at a high temperature it may disappear
altogether: This depends upon decomposition occurring in the blood, whereby reducing sub-
stances are formed which consume the O. All kinds of blood, however, do not act with equal

‘energy in consuming O, e.g., venous blood from active muscles acts most energetically, while

that from the hepatic vein has very little effect. CO, appears in the blood in place of the O,
and the colour darkens. The amount of CO, produced is sometimes greater than that of the O

-consumed.

Relation to Acids.—If blood (or a solution of oxyhemoglobin) be acted upon by acids (e.g.,
tartaric acid) until it is strongly acid, O can be pumped out in considerably less amount, while
the formation of CO, is not increased. We must, therefore, assume that, during the decomposi-
tion of the Hb caused by the acids (§ 18), a decomposition product becomes more highly oxidised
by the intense chemical union of the O at the moment of its origin (Lothar Meyer, Zuwntz,

Strassburg). The same phenomenon occurs when oxyhemoglobin is decomposed by boiling.

87. IS OZONE PRESENT IN BLOOD ?—On account of the numerous and

energetic oxidations which occur in connection with the blood, the question has

often been raised as to whether the O of the blood exists in the form of ozone (O,).
Ozone, however, is contained neither in the blood itself (Schénbein) nor in the

blood-gases obtained from it. Nevertheless, the red corpuscles (and Hb) have a
‘distinct relation to ozone. :

(1) Tests for Ozone.—Hemoglobin acts as a conveyer of ozone, t.¢., it is able to remove the

active O of other bodies and to convey or transfer it at once to other easily oxidisable substances.
(a) Turpentine which has been exposed to the air for a long time always contains ozone. The

tests for the latter are starch and potassium iodide, the ozone decomposing the iodide, when the

iodine strikes a blue with the starch. (b) Freshly-prepared tincture of guaiacum is also rendered —

44 CARBON DIOXIDE AND NITROGEN IN BLOOD.

blue by ozone. If some tincture of guaiacum be added to tu ntine there is no reaction, but on
sade: a drop of blood a deep blue selina is immediately produced, ¢.¢., blood takes the ozone
from the turpentine and conveys it at once to the dissolved guaiacum, which becomes blue, - It
is immaterial whether the Hb contains O or not. ; Yea

(2) It is also asserted that hemoglobin acts as an ozone-producer, 7.¢., that it can convert the
ordinary .0 of the air into ozone. Hence the reason why red blood-corpuscles alone render

aiacum blue, This reaction succeeds best when the guaiacum solution is allowed to dry on

lotting-paper, and a few drops of blood (diluted 5 to 10 times) are poured on it. That the Hb-

forms ozone from the surrounding O, is shown by the fact that red blood-corpuscles containing
carbonic oxide cause the blue colour (Kiihne and Scholz). According to Pfliiger, however, these-
reactions only occur from decomposition of the Hb, so that on this view the blood-corpuscles
cannot be regarded as producers of ozone. ; be

Sulphuretted hydrogen is decomposed by blood (as by ozone itself) into sulphur and water,
Hydric peroxide is decomposed by blood into O and water [but this reaction is prevented by the-
addition of a small amount of hydrocyanic acid (Schinbein)]. Crystallised Hb does not do this,
and H,O, may be cautiously injected into tle blood-vessels of animals, This would show that
unchanged Hb does not produce ozone.

Various Forms of Oxygen. —There are three forms of oxygen:—(1) The ordinary oxygen (0,):
in the air. (2) Active or nascent oxygen (O), which never can occur in the free state, but the
moment it is formed acts as a powerful oxidising agent and produces chemical compounds, It
converts water into hydric peroxide—the N of the air into nitrous and nitric acids, and even
CO into CO,, which ozone does not. It certainly plays an important part in the organism.
(3) Ozone (O,), which is formed by the decomposition of several molecules of ordinary. oxygen
(O,) into two atoms of O, and the appropriation of each of these atoms by a molecule of unde-
composed oxygen. It is oxygen condensed to 3 of its volume.

38. CO, AND N IN BLOOD.—II. Carbon Dioxide.—In arterial blood there.
are about 30 volumes per cent. of CO, at 0° C. and 1 metre pressure (Setschenow) ;
but in venous blood the amount is very variable, ¢.g., in the venous blood of passive:
muscles there are 35 volumes per cent. (Sczelkow), while in the blood of asphyxia
there may be 52°6 volumes per cent. The CO, in the lymph of asphyxia is less.
than that in the blood (Buchner, Gaule), The CO, of the blood may be extracted' .
from it or completely pumped out, but during the process of evacuation, or removal |
of the gas, a new property of the red blood-corpuscles is produced, whereby they
assume the function of an acid, and thus aid in the chemical expulsion of the CO,..

This acid-like property of the red corpuscles occurs especially in the presence of O: |
and heat.

(A) The CO, in the Plasma.— 7'he largest portion of the CO, belongs to the plasma 4
(or serum), and it all appears to be in a state of chemical combination. Serum |
takes up CO, quite independently of pressure, hence it cannot be merely absorbed.

A certain part of the CO, can be removed from the serum (plasma) by the-
Torricellian vacuum, while another part is obtained only after the addition of an :
acid. [The latter is called the “fixed” CO,, while the former is known as the- .
“loose” CO,.] The CO, in the serum exists in the following conditions :—

(1) CO, is united to the soda of the plasma in the form of “neutral sodic:
carbonate.” This portion of the CO, can only be displaced from its combination:
_ by the addition of an acid. (In depriving blood of its gases the red corpuscles play

the réle of an acid.) . A

(2) A portion of the CO, is loosely united to sodic carbonate in the form of sodic:
bicarbonate ; the carbonate takes up 1 equivalent of CO, ; N a,CO, + CO, + H,O =
2NaHCO,. This CO, may be pumped out, as in the process the bicarbonate splits:
up again into the neutral carbonate and CO,,. |

Preyer has objected to this view on the ground that blood is alkaline in reaction, whilst all
solutions that contain CO, in a state of absorption, or loose chemical combination, are always
acid. Pfliiger and Zuntz showed that blood, after being completely saturated with CO,, still.
remains alkaline. ‘25

As the bicarbonate only gives up its CO, very slowly in vacuo, while blood gives off its CO,.
“7 energetically, perhaps the , united with an albuminous body, combines with the CO, —
and forms a complex compound, from which the CO, is rapidly given off in vacuo. .

(3) A minimal portion of the CO, may be chemically united with neutral sodic- o)

le

ARTERIAL AND VENOUS BLOOD. . 45

phosphate in the plasma (Fernet). One equivalent of this salt can fix one
-. equivalent of CO,, so acid sodium phosphate and acid sodium carbonate are formed,

Na,HPO, + CO, + H,O = NaH,PO,+ NaH,CO, (Hermann). When the gases are
removed the CO, escapes, and neutral sodic phosphate remains.

It is probable, however, that almost ail the sodic phosphate found in the blood-ash arises
from the burning of lecithin ; we have, therefore, to consider only the very small amount of
this salt which occurs in the plasma (Hoppe-Seyler and Sertolt).

_ (B) The CO, in the Blood-Corpuscles.—The red corpuscles contain CO, in loose
chemical combination ; for (1) a volume of blood can fix nearly as much CO, as an

-equal volume of serum (Ludwig, Al. Schmidt); and (2) with increasing pressure

the absorption of CO, by blood takes place in a different ratio from what occurs
‘with serum (Pfltiger, Zuntz). The red corpuscles can fix more CO, than their own
volume, and the union of the CO, seems to depend upon the Hb, for Setschenow

found that, when Hb was acted on by CO,, its power of fixing the latter was

increased, which is perhaps due to the formation of some substance more suited for
fixing CO,. The colourless corpuscles, after the manner of the serum-constituents,
also fix CO, to the extent of 4 to ;4, of the absorbing power of serum.

After the use of I, Hg, sodic oxalate, and nitrite, there is a diminution of CO, in arterial
blood (Feitelberg), and also in fever (Geppert, Minkowski). [In the last case it is perhaps due

to the diminished akalinity, and this is in part owing to the acid products formed during

the decomposition of the tissues. ]
III. Nitrogen exists in the blood to the extent of 1:4 to 1°6 vol. per cent., and

it appears to be simply absorbed.

. It is doubtful if any part of the N exists chemically united in the red corpuscles. Blood
warmed outside the body, and with a free supply of oxygen, gives off a minute quantity of

-ammonia, which is perhaps derived from the decomposition of some salt of ammonia as yet

unknown (Kiihne and Strauch),

389. ARTERIAL AND VENOUS BLOOD. —Arterial blood contains in solution

all those substances which are necessary for the nutrition of the tissues, those which

are employed in secretion, and it also contains a rich supply of O. Venous blood

must contain less of all these, but in addition it holds the used-up or effete
substances derived from the tissues, and the products of their retrogressive
metabolism are more numerous ; there is in venous blood a larger amount of CO,.
It is evident also that the blood of certain veins, the portal and hepatic, must have

special characters.

The following are the most important points of difference between arterial blood

-and venous blood :—

Arterial Blood contains—

more O, more extractives, less urea.

less CO,, more salts, It is bright red and not
more water, more sugar, dichroic.

more fibrin, fewer blood-corpuscles, As a rule it is 1° C. warmer.

The bright red colour of arterial blood depends on the presence of oxyhzmo-
globin, whilst the dark colour of venous blood is due to its smaller proportion of

-oxyhzemoglobin, and the quantity of reduced hemoglobin which it contains. The
-dark change of colour is not to be attributed to the larger quantity of CO, in

venous blood (Marchand); for if equal quantities of O be added to two portions of
blood, and if CO, be added to one of them, the colour is not changed (Pjliger).
[According to C, Schmidt, the blood of the portal vein contains more water, plasma, salts,

-and fats, but less extractives and corpuscles than the blood of the hepatic vein ; while (when

an animal is not digesting) sugar is absent or at least only in traces in the portal vein, and in

-considerable amount in the hepatic vein (§ 175).]

' 40. QUANTITY OF BLOOD, —In the adult the quantity of blood is equal to
gy part of the body-weight (Bischof), in newly-born children 31, ( Welcker).

_ According to Schiicking, the amount of blood in a newly-born child depends to some extent

pon the time at which the umbilical cord is ligatured. The amount =; of the body-weight

46 ABNORMAL CONDITIONS OF THE BLOOD.

when the cord is tied at once, while if it is tied somewhat later it may be }. Immediate
ligature of the cord may, therefore, deprive a newly-born child of 100 grams of blood.
Further, the number of corpuscles is less in a child after immediate ligature of the umbilical
cord than when it is tied somewhat later (Helot).

The methods of Valentin (1838), and Ed. Weber (1850), are not now used, as the results:

ined are not sufficiently accurate. ; ;

oO tethod of Welcker (1854).—Begin by taking the weight of the animal to be experimented
on ; place a cannula in the carotid, and allow the blood to run into a flask previously weighed,
aud in which small pebbles (or Hg) have been placed in order to defibrinate the blood by
shaking. Take a part of this defibrinated blood, and make it cherry-red in colour by passing:
through it a stream of CO (because ordinary blood varies In colour according to the amount of
O contained in it—G@scheidlen, Heidenhain). Tie a} shaped cannula in the two cut ends of the
carotid, and allow a 0°6 per cent. solution of common salt to flow into the vessel from a
pressure bottle ; collect the coloured fluid issuing from the jugular veins and inferior vena cava
util the fluid is quite clear. The entire body is then chopped up (with the exception of the
contents of the stomach and intestines, which are weighed, and their weight deducted from the
body-weight), and extracted with water, and after twenty-four hours the fluid is expressed,
This water, as well as the washings with salt solution, are collected and weighed, and rt of
the mixture is saturated with CO. A sample of this dilute blood is placed in a vessel with
parallel sides (1 cm. apart) opposite the light (the so-called hematinometer), and in a second
vessel of the same dimensions a sample of the undiluted CO blood is diluted with water from a
burette, until both fluids give the same intensity of colour. From the quantity of water required
to dilute the blood to the tint of the washings of the blood-vessels, the quantity of blood in the
washings is calculated. On chopping up the muscles alone, we obtain the amount of Hb
present in them, which is not taken into calculation. .

Quantity of Blood in Various Animals.—The quantity of blood in the mouse
=z; to yy; guinea-pig ~}-7 (py to gy); rabbit = 34.7 (q's to gy); dog= yy (7 to
js); cat=5}.; birds= 44 to py; frog=7; to 5; fishes= yy to yy of the body-
weight (without the contents of the stomach and intestines).

The specific gravity of tle blood ought always to be taken when estimating the amount of
blood. The amount of blood is diminished during inanition ; fat persons have relatively less

blood ; after hemorrhage the loss is at first replaced by a watery fluid, while the blood-cor-
puscles are gradually regenerated.

Blood in Organs.—The estimation of the quantity of blood in different organs is. :

done by suddenly ligaturing their blood-vessels intra vitam. A watery extract of
the chopped-up organ is prepared, and the quantity of blood estimated as described
above. {Roughly it may be said that the lungs, heart, large arteries, and veins.
contain +; the muscles of the skeleton, 4; the liver, 4; and other organs, 4
(Ranke).

41, ABNORMAL CONDITIONS OF THE BLOOD. —(A) 1 Polywmia.—(1) An increase in the:
entire mass of the blood, uniformly in all organs, constitutes polyemia or plethora, and in over-
nourished individuals it may approach a perelones. condition. A bluish-red colour of the
skin, swollen veins, large arteries, hard full pulse, injection of the capillaries and smaller
vessels of the visible mucous membranes are signs of this state, and, when accompanied by
congestion of the brain, there is vertigo, congestion of the lungs, and breathlessness. After
major amputations with little loss of blood a relative but transient increase of blood has been
found (?) (plethora apocoptica). '

Transfusion.—Polyzemia tmay be produced artificially by the injection of blood of the same
species. If the normal quantity of blood be increased 83 per cent. no abnormal condition
occurs, because the blood-pressure is not permanently raised. The excess of blood is accommo-
dated in the greatly distended capillaries, which may be stretched beyond their normal elasticity.
If it be increased to 150 per cent. there are variations in the blood-pressure, life is endangered,
and there may be sudden rupture of blood-vessels (Worm Miiller).

Fate of Transfused Blood.—After the transfusion of blood the formation of lymph is greatly
increased ; but in one or two days the serum is used up, the water is excreted chiefly by the
urine, and the albumin is partly changed into urea. Hence, the blood at this time appears to:
be relatively richer in blood-corpuscles (Panum, Lesser, Worm Miiller). The red corpuscles.
break up much more slowly, and the products thereof are partly excreted as urea and ly
(but not constantly) as bil -pigments. Even after a month an increase of coloured Flood.
corpuscles has been observed (7'schirjew). That the blood-corpuscles are broken up slowly in
the economy is proved by the fact, that the amount of urea is much larger when the same quan+
tity of blood is swallowed by the animal than when an equal amount is transfused (7'sch:

Landois). In the latter case there is a moderate increase of the urea, lasting for days, a proof

ABNORMAL CONDITIONS OF THE BLOOD. 47

of the slow decomposition of the red corpuscles. Pronounced over-filling of the vessels causes
loss of appetite and a tendency to hemorrhage of the mucous membranes.

(2) Polyemia serosa is that condition in which the amount of serum, 7.¢., the amount of
water in the blood, is increased. This may be produced artificially by the transfusion of blood-
serum from the same species. The water is soon given off in the urine, and the albumin is
decomposed into urea, without, however, passing into the urine. An animal forms more urea
in a short time from a quantity of transfused serum than from the same quantity of blood, a
proof that the blood-corpuscles remain longer undecomposed than the serum (Forster, Landois).
If serum from another species of animal be used (e.g., dog’s serum transfused into a rabbit), the
blood-corpuscles of the recipient are dissolved ; hemoglobinuria is produced (Ponjick) ; and if
there be general dissolution of the corpuscles, death may occur (Landois).

(8) Polyseemia aquosa is a simple increase of the water of the blood, and occurs temporarily
after copious drinking, but increased diuresis soon restores the normal condition. Diseases of
the kidneys, which destroy their secreting parenchyma, produce this condition, and often
general dropsy, owing to the passage of water into the tissues. Ligature of the ureter produces
a watery condition of the blood.

(4) Plethora polycythemica, Hyperglobulie.—An increase of the red corpuscles has been
assumed to occur when periodically recurring heemorrhages are interrupted, ¢.g., menstruation,
bleeding from the nose, &c.; but the increase of corpuscles has not been definitely proved.
There is a proved case of temporary polycythemia, viz., when similar blood is transfused, a
part of the fluid being used up, while the corpuscles remain unchanged for a considerable time.
There is a remarkable increase in the number of blood-corpuscles (to 8°82 millions per cubic
millimetre) in certain severe cardiac affections where there is great congestion, and much water
transudes through the vessels. In cases of hemiplegia, for the same reason, the number cf
corpuscles is greater on the paralysed congested side (Pensoldt). After diarrhcea, which dimin-
ishes the water of the blood, there is also an increase (Brouardel), and the same is the case after
profuse sweating and polyuria. Drugs (alcohol, chloral, amyl nitrite) which act on the blood-
vessels affect the number of corpuscles ; during contraction of the blood-vessels their number
increases, during dilatation they diminish in number (Andreesen). There is a temporary increase
in the hematoblasts as a reparative process after severe hemorrhage (§ 7), or after acute diseases.
In cachectic conditions this increase continues, owing to the diminished non-conversion of these
corpuscles into red corpuscles. In the last stages of cachexia the number diminishes more and
more until the formation of hematoblasts ceases (Hayei).

(5) Plethora hyperalbuminosa is a term applied to the increase of albumins in the plasma,
such as occurs after taking a large amount of food. A similar condition is produced by trans-
fusing the serum of the same species, whereby, at the same time, the urea is increased. Injec-
tion of egg-albumin produces albuminuria (Stokvis, Lehmann).

[The subcutaneous injection of human blood has been practised with good results in anemia
(v. Ziemssen). When defibrinated human blood is injected subcutaneously, while its passage
into the circulation is aided by massage, it causes neither pain nor inflammation, but tlhe blood
of animals, and a solution of hemoglobin, always induce abscess (Benczur). Blood is also
rapidly absorbed when injected in small amount into the respiratory passages. ]

ellitemia.—The sugar in the blood is partly given off by the urine, and in ‘ diabetes
mellitus ” 1 kilo. (2°2 lbs.) may be given off daily, when the quantity of urine may rise to 25
kilos. To replace this loss of grape-sugar a large amount of food and drink is required, whereby
the urea may be increased threefold. The increased production of sugar causes an increased
decomposition of albuininous tissues ; hence the urea is always increased, even though the supply
of albumin be insufficient. The patient loses flesh ; all the glands, and even the testicles, atrophy
or degenerate (pulmonary phthisis is common); the skin and bones become thinner; the
nervous system holds out longest. The teeth become carious on account of the acid saliva, the
crystalline lens becomes turbid from the amount of sugar in the fluid of the eye which extracts
water from the lens, and wounds heal badly because of the abnormal condition of the blood.
Absence of all carbohydrates in the food causes a diminution of the sugar in the blood, but
does not cause it to disappear entirely. [The sugar in the blood is also increased after the
inhalation of chloroform or amyl nitrite, and after the use of curara, nitro-benzole, and chloral
(§ 175).] An excessive amount of inosite has been found in the blood and urine (§ 267, con-
stituting mellituria inosita (Voh/).

Lipsmia, or an increase of the Fat in the Blood, occurs after every meal rich in fat (¢.g., in
sucking kittens), so that the serum may become turbid like milk. Pathologically, this occurs
in a high degree in drunkards and in corpulent individuals. When there is great decomposi-
tion of albumin in the body (and therefore in very severe diseases), the fat in the blood increases,
op this also takes place after a liberal supply of easily decomposable carbohydrates and much
fat. « |

After injuries to bones affecting the marrow, not unfrequently fatty granules pass from the
marrow through the imperfect walls of the blood-vessels into the blood-stream. These fatty.
particles may form fat emboli, ¢.g., in the liver or lungs, or they may appear in the urine.

_ If granules of cinnabar or indigo are injected into the blood, they are taken up by the

é

48 ABNORMAL CONDITIONS OF THE BLOOD.

leucocytes, and by them are carried outside the blood-stream. The cells of the splenic pulp,
marrow of bone, and the liver also take up these cles (Stebel).

The salts remain very persistently in the blood. The withdrawal of common salt produces
albuminuria, and, if all alte be withheld, paralytic phenomena occur (Forster). Over-feeding
with salted food, such as salt meat, has caused death through fatty degeneration of the tissues,
especially of the glands. Withdrawal of lime and phosphoric acid produces atrophy and soften-
ing of the bones. In infectious diseases and dropsies the salts of the blood are often increased,
and diminished in inflammation and cholera. [NaCl is absent from the urine in certain stages
of pneumonia, and it is a yood sign when the chlorides begin to return to the urine.] {In
scurvy the corpuscular elements are diminished in amount, but we have not precise information
as to the salts, although this disease is prevented, in persons forced to live upon preserved and
salted food, by a liberal use of the salts—especially potash salts—of the organic acids, as con-
tained in lime-juice. In gout the blood, during an acute attack, and also in chronic gout,
contains an excess of uric acid (Garrod). ]

The amount of fibrin is increased in inflammations of the lung and pleura [croupous
pneumonia, erysipelas], hence such blood forms a crusta phlogistica (§ 27). In other diseases,
where decomposition of the blood-corpuscles occurs, the fibrin is increased, perhaps because the
dissolved red corpuscles yield material for the formation of fibrin. After repeated hemorrhages,
Sigm. Mayer found an increase of fibrin. Blood rich in fibrin is said to coagulate more slowly
than when less fibrin is present—still there are many exceptions. ; ;

(B) I.) Diminution of the Quantity of Blood, or its Individual Constituents, —(1) Oligeemia
vera, Anemia, or diminution of the quantity of blood as a whole, occurs whenever there is
hemorrhage. Life is endangered in newly-born children when they lose a few ounces.of blood ;
in children a year old, on losing half a pound ; and in adults, when one-half of the total blood
is lost. Women bear loss of blood much better than men. The periodical formation of blood
after each menstruation seems to enable blood to be renewed more rapidly in their case. Stout

rsons, old people, and children do not bear the loss of blood well. ‘The more rapidly blood
1s lost, the more dangerous it is. [A moderate loss of blood is soon made up, but the fluid part
is more quickly restored than are the corpuscles. ] ;

Symptoms of Loss of Blood.—Great loss of blood is accompanied by general paleness and
coldness of the cutaneous surface, increased oppression, twitching of the eyeballs, noises in the
ears and vertigo, loss of voice, great breathlessness, stoppage of secretions, coma ; dilatation of
the pupils, involuntary evacuations of urine and feces, and lastly, general convulsions, are sure
signs of death by hemorrhage. In the gravest cases recovery is only possible by means of
transfusion, Animals can bear the loss of one-fourth of their entire blood without the blood-
pressure in the arteries permanently falling, because the blood-vessels contract and accommodate
themselves to the smaller quantity of blood (in consequence of the stimulation of the vasomotor
centre in the medulla). The loss of one-third of the total blood diminishes the blood-pressure
considerably (one-fourth in the carotid of the dog). If the hemorrhage is not such as to cause
death, the fluid part of the blood and the dissolved salts are restored by absorption from the
tissues, the blood-pressure gradually rises, and then the albumin is restored, though a longer
time is required for the formation of red corpuscles. At first, therefore, the blood is abnormally
rich in water (hydremia), and at last abnormally poor in corpuscles (oligocythemia, hypoglo-
bulie). With the increased lymph-stream which pours into the blood, the colourless corpuscles
are considerably increased above normal, and during the period of restitution fewer red corpuscles
seem to be used up (¢.g., for bile).

After moderate bleeding from an artery in animals, Buntzen observed that the volwme of the
blood was restored in several hours ; after more severe hemorrhage in 24 to 48 hours. The red
blood-corpuscles, after a loss of blood equal to 1°1 to 4°4 per cent. of the body-weight, are
restored only after 7 to 34 days. The regeneration begins atter 24 hours. During the period
of regeneration the number of the blood-corpuscles in an early stage of development is increased.
The newly-formed corpuscles contain less Hb than normal (Jac. G. Ott). Even in man the
duration of the period of regeneration depends upon the amount of blood lost (Lyon). The
amount of hemoglobin is diminished nearly in proportion to the amount of the hemorrhage
(Bizzozero and Salvioli).

Metabolism in Anwmia.—The condition of the metabolism within the bodies of anemic
eaegan is important. The decomposition of proteids is increased (the same is the case in

unger), hence the excretion of urea is increased (Bauer). The decomposition of fats, on the
contrary, is diminished, which stands in relation with the diminution of CO, given off.
Anzmic and chlorotic persons put on fat easily. The fattening of cattle is aided by occasional
bleedings and by intercurrent periods of hunger (Aristotle),

(2) An excessive thickening of the blood through loss of water is called Oligeemia sicca,
This occurs in man after oC pa watery evacuations, as in cholera, so that the thick tarry
blood stagnates in the vessels, Perhaps a similar condition—though to a less degree—may
exist after very copious perspiration. ev

(3) If the proteids in blood be abnormally diminished the condition is called Oligemia
hypal osa; they may be diminished about one-half. They are usually replaced by an

ORGANISMS IN THE BLOOD. 49

excess of water in the blood [so that the blood is watery, constituting hydremia]. Loss
of albumin from the blood is caused directly by albuminuria (25 grams of albumin may be
given off by the urine daily), persistent suppuration, great loss of milk, extensive cutaneous
ulceration, albuminous diarrhcea (dysentery). Frequent and copious hemorrhages, however,
by increasing the absorption of water into the vessels, at first produce oligeemia hypalbuminosa.

For the abnormal changes of the red and white blood-corpuscles, see § 10 ; for Hemophilia,
§ 28.

[Organisms in the Blood.—The presence of animal and vegetable parasites in the blood gives
rise to certain diseases. Some of these, and especially the vegetable organisms, have the power
of multiplying in the blood. The vegetable forms belonging to the schizomycetes are frequently
spoken of collectively under the title bacteria. They are classified by Cohn into

I. Spheerobacteria. III. Desmobacteria

II. Microbacteria, exhibit movements. IV. Spirobacteria
These forms are shown in fig. 23. The micrococci (A) are examples of I. ; while Bacterium
termo (B) is an example of II. In III. the members are short cylindrical rods, straight
(Bacillus, D) or wavy (Vibrio, C). Splenic fever of cattle is due to the presence of Bacillus
anthracis (fig. 24). These rod-shaped bodies under proper conditions divide transversely and

exhibit movements.

Fig, 23. Fig. 24.
A, micrococcus ; B, bacterium ; C, vibrios ; Bacillus anthracis from the blood (ox) in
D, bacilli; E, spirillum. splenic fever.

elongate, but they also form spores in their interior, which in turn under appropriate‘ conditions
may germinate (fig. 24). Class IV. is represented by two genera, Spirocheta and Spirillum
(fig. 23), the former with close, and the latter with open spirals. The Spirocheta Obermeieri
(often spoken of as ‘‘Spirillum”) is present in the blood during the paroxysms in persons
suffering from relapsing tever. Amongst animal parasites are Filaria sanguinis, and Bilharzia
Hematobia, which occurs in the portal vein and in the veins of the urinary apparatus. ]

Physiology of the Circulation.

42. GENERAL VIEW.—The blood within the vessels is in a state of continual
motion, being carried from the ventricles by the large arteries (aorta and pulmonary)

Fig. 25.

Scheme of the circulation.—a, right,
b, left auricle ; A, right,-B, left
ventricle ; 1, pulmouary artery ;
2, aorta ; J, area of pulmonary, K,
area of systemic circulation ; 0, the
superior vena cava; G, area sup-
plying the inferior vena cava, ¥ ;
d, d, intestine; m, mesenteric
artery ; g, portal vein; L, liver ;
h, hepatic vein.

and their branches to the system of capillary
vessels, from which again it passes into the vewns
that end in the atria of the auricles (W. Harvey,
1628).

The cause of the circulation is the difference of
pressure Which exists between the blood in the
aorta and pulmonary artery on the one hand, and
the two ven cave and the four pulmonary veins
on the other. The blood, of course, moves con-
tinually in its closed tubular system in the direction
of least resistance. The greater the difference of
pressure, the more rapid the movement will be.
The cessation of the difference of pressure (as after
death) naturally brings the movement to a stand-
still (§ 81). ‘The circulation is usually divided
into—

(1) The greater, or systemic circulation,
which includes the course of the blood from the
left auricle and left ventricle, through the aorta and
all its branches, the capillaries of the body and the
veins, until the two ven cave terminate in the
right auricle.

(2) The lesser, or pulmonic circulation, which
includes the course from the right auricle and right
ventricle, the pulmonary artery, the pulmonary
capillaries, and the four pulmonary veins springing
from them, until these open into the left auricle.

(3) The portal circulation is sometimes spoken
of as a special circulatory system, although it repre-
sents only a second set of capillaries (within the
liver) introduced into the course of a venous trunk.
It consists of the vena portarum—formed by the
union of the intestinal or mesenteric and splenic
veins, and it passes into the liver, where it divides
into capillaries, from which the hepatic veins arise.
The hepatic vein joins the inferior vena cava.

Strictly speaking, however, there is no special portal circulation. Similar arrangements

occur in other animals in different organs, e.g., snakes have such a system in their supra-renal —

STRUCTURE AND MUSCULAR FIBRES OF THE HEART. 51

_ capsules, and the frog in its kidneys. When an artery splits up into fine branches during its
course, and these branches do not form capillaries, but.reunite into an arterial trunk, a rete
mirabile is formed, such as occurs in apes and the edentata. Microscopic retia mirabilia exist
in the human mesentery (Schéb/). Similar arrangements may exist in connection with veins,
giving rise to venous retia mirabilia.

43, THE HEART.—The muscular fibres of the mammalian heart consist of short (50 to
70 in man), very fine, transversely striated fibres, which are actual unicellular elements, devoid
of a sarcolemma (15 to 25 u broad), and usually divided at their blunt ends, by which means they
anastomose and form a network (fig. 26, A,B). The individual muscle-cells contain in their

Fig. 26.

A, muscular fibres from the heart of a mammal, and C from a frog ; B, transverse section of the
cardiac fibres ; b, connective-tissue corpuscles ; c, capillaries.

centre an-oval nucleus, and are held together by a cement which is blackened by silver nitrate,
and dissolved by a 33 per cent. solution of caustic potash. This cement is also dissolved
by a 40 per cent. solution of nitric acid. The transverse strie are not very distinct,
and not unfrequently there is an appearance of longitudinal striation, produced by a
number of very small granules arranged in rows within the fibres. The fibres are gathered
lengthwise in bundles, or fasciculi, surrounded and separated from each other by delicate
processes of the perimysium. When the connective-tissue is dissolved by prolonged boiling,
these bundles can be isolated, and constitute the so-called ‘‘fibres” of the heart. The
transverse sections of the bundles in the auricles are polygonal or rounded, while in the
ventricles they are somewhat flattened. [The muscular mass of the heart is called the
myocardium, and is invested by fibrous tissue. It is important to notice that the connective-
tissue of the visceral pericardium (epicardium) is continuous with that of the endocardium by
means of the perimysium surrounding the bundles of muscular fibres.] The fine spaces which
exist: between these bundles form narrow lacun, lined with epithelium, and constituting part
of the lymphatic system of the heart.

[The cardiac muscular fibres occupy an intermediate position between striped and plain
muscular fibres. Although they are striped, they are involuntary, not being directly under the
influence of the will, while they contract more slowly than a voluntary muscle of the skeleton. ]
In the frog’s heart the muscular fibres are in shape elongated spindles, or fusiform, in this
respect resembling the plain muscle-cells, but they are transversely striped (fig. 26, C). They
are easily isolated by means of a 33 per cent. solution of potash or dilute alcohol.

44. ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES.—The
study of the embryonic heart is the key to a proper understanding of the complicated
arrangement of the fibres in the adult heart. The simple tubular heart of the
embryo has an owter circular and an inner longitudinal layer of fibres. The septum
is formed later; hence, it is clear that a part, at least, of the fibres must be
common to the ‘two auricles, and a part also to the two ventricles, since there is,
originally, but one chamber in the heart. The muscular fibres of the auricles are,
however, completely separated from those of the ventricles by the fibro-cartilaginous
rings. In the auricles the fundamental arrangement of the embryonic fibres partly
remains, while in the ventricles it becomes obscured as the cavities undergo a sac-
like dilatation, and also become twisted in a spiral manner.

52 ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES, ; i

(1) The muscular fibres in the auricles are completely separated from the fibres
of the ventricles by the fibrous rings which surround the auriculo-ventricular orifices,
and which serve as an attachment for the auriculo-ventricular valves (fig. 27, I).
The auricles are much thinner than the ventricles, and their fibres are generally
arranged in two layers ; the outer transverse layer is continuous over both auricles,
whilst the inner one is directed longitudinally. The outer transverse fibres may be
traced from the openings of the venous trunks anteriorly and posteriorly over the
auricular walls. The longitudinal fibres are specially well marked where they are
inserted into the fibro-cartilaginous rings, while in some parts of the anterior
auricular wall they are not continuous. In the auricular septum, some fibres,
circularly disposed around the fossa ovalis (formerly the embryonic opening of the
foramen ovale), are well marked. Circular bands of striped muscle exist around
the veins where they open into the heart ; these are least marked on the inferior
vena cava, and are stronger and reach higher (2°5 cm.) on the superior vena cava
(fig. 27, I). Similar fibres exist around the pulmonary veins, where they join the
left auricle, and these fibres (which are arranged as an inner circular and an outer
longitudinal layer) can be traced to the hilus of the lung in man and some

V.p.

Fig. 27.

1. Course of the muscular fibres on the left auricle with the outer transverse and inner longi-
tudinal fibres, the circular fibres on the pulmonary veins (v. p.); V, the left ventricle (John
Reid). 11. Arrangement of the striped muscular fibres on the superior vena cava (Zischer)
—a, opening of vena azygos ; v, auricle. .

mammals ; in the ape and rat they extend on the pulmonary veins right into the
lung. In the mouse and bat, again, the striped muscular fibres pass so far into
(Se lungs that the walls of the smaller veins are largely composed of striped muscle
tveda).
- Circular muscular fibres are found where the vena magna cordis enters the heart,
and in the Valvula Thebesii which guards it.
.. Physiological Significance—(1) The auricles contract independently of the
ventricles. This is seen when the heart is about to die; when there may be several
auricular contractions for one ventricular, and at last only the auricles pulsate.
The auricular portion of the right auricle beats longest ; hence it is called the
“‘ultimum moriens.” Independent rhythmical contractions of the ven cave and
pulmonary veins are often noticed after the heart has ceased to beat. . | This beating
sr _° be observed in those veins in a rabbit after the heart is cut out of the
y- . - : )
(2) The double arrangement of the fibres (transverse and longitudinal) produces
a simultaneous and uniform diminution of the auricular cavity (such as occurs ii
most of the hollow viscera). J, i. evil
(3) The contraction of the circular muscular fibres around the venous orifices;

and the subsequent contraction of the auricle, cause these veins to empty themselves

ARRANGEMENT OF THE VENTRICULAR FIBRES. 53

into the auricle ; and by their presence and action they prevent any large quantity
of blood from passing backward into the veins when the auricle contracts. [No
valves are present in the superior and inferior vena cava in the adult heart, or in
the pulmonary veins, hence the contraction of these circular muscular fibres plays

an important part in preventing any reflux of blood during the contraction of the
auricles. | ;

45. ARRANGEMENT OF THE VENTRICULAR FIBRES.—(2) The
muscular fibres in the thick wall of the ventricles are arranged in several layers
(fig. 28, A) under the pericardium. First, there is an ower longitudinal layer (A)
which is in the form of single bundles on the right ventricle, but forms a complete
layer on the left ventricle, where it measures about one-eighth of the thickness of
the ventricular wall. A second longitudinal layer of fibres lies on the inner surface
of the ventricles, distinctly visible at the orifices, and within the vertically placed
papillary muscles, whilst elsewhere it is replaced by the irregularly arranged
trabeculz carne, Between these two layers there lies the thickest layer, consisting
of more or less transversely arranged bundles, which may be broken up into single
layers more or less circularly disposed. The deep lymphatic vessels run between the
layers, whilst the blood-vessels lie within the substance of the layers, and are sur-
rounded by the primitive bundles of muscular fibres. All three layers are not
completely independent of each other; on the contrary, the fibres which run
obliquely form a gradual transition between the transverse layers and the inner and
outer longitudinal layers. It is not, however, quite correct to assume that the

Fig, 28.
Course of the ventricular muscular fibres. A, on the anterior surface ; B, view of the apex with

the vortex ; C, course of the fibres within the ventricular wall ; D, fibres passing into a
papillary muscle. : :

outer longitudinal layer gradually passes into the transverse, and this again into
the inner longitudinal layer (as is shown schematically in C) ; because, as Henle
pointed out, the transverse fibres are relatively far greater in amount. In general,
the outer longitudinal fibres are so arranged as to cross the inner longitudinal layer
at an acute angle. The transverse layers lying between these two form, gradual
transitions between these directions. At the apex of the left ventricle, the outer
longitudinal fibres bend or curve so as to meet atthe so-called vortex B, where they
enter the muscular substance, and, taking an upward and inward direction, reach
the papillary muscles, P, D ; although it is a mistake to say that all the bundles
which ascend to the papillary muscles arise from the vertical fibres of the outer
surface : many seem to arise independently within the ventricular wall. According
to Henle, all the external longitudinal fibres do not arise from the fibrous rings or
the roots of the arteries. The mitral orifice is surrounded by circular fibres which
act like a sphincter (Henle). 3

54 . PERICARDIUM, ENDOCARDIUM, VALVES.

[The assumption that the muscles of the ventricle are arranged so as to form a figure of 8, or
in loops, seems to be incorrect ; thus, fibres are said to arise at the base of the ventricle, to pass.
over it, and to reach the vortex, where they pass into the interior of the muscular substance, to
end either in the papillary muscles or high up on the inner surface of the heart at its base.
Figs. C and D give a schematic st peepaielpaes of this view. ] xan
- Only the general arrangement of the ventricular muscular fibres has been indicated. Accord-
ing to Pettigrew, there are seven layers in the ventricle, viz., three external, a fourth or
central layer, and three internal. These internal layers are continuous with the corresponding
external layers at the apex, thus—one and seven, two and six.

46. PERICARDIUM, ENDOCARDIUM, VALVES. —The pericardium encloses within its two |

layers [visceral and parietal] a lymph space—the pericardial space—which contains a small |
quantity of lymph—the pericardial fluid, It
has the structure of a serous membrane, 7.¢.,
it consists of connective-tissue mixed with fine
elastic fibres arranged in the form of a thin
delicate membrane, and covered on its free
surfaces with a single layer of epithelium or
endothelium, composed of irregular, polygonal,
flat cells. A rich lymphatic network lies under
the pericardium (fig. 29) and endocardium ;
also in the deeper layers of the visceral peri-
cardium next the heart and between muscular
bundles (Salvioli). No stomata exist either
on its visceral or parietal layers. Around the
coronary arteries of the heart exist lymph-
vessels and deposits of fat, which lie in the
furrows and grooves in the subserosa of the

epicardium (visceral layer).

The endocardium, next the cavity of the
ms heart, consists of a single layer of polygonal,
Fig. 29. . flat, nucleated endothelial cells. [Under this
Lymphatic of the pericardium, epithelium stained there is a nearly homogeneous hyaline layer
with nitrate of silver. (fig. 30, a), slightly thicker on the left side,.
which gives the endocardium its polished
appearance.| Then follows, as the basis of the membrane, a layer of fine elastic fibres—stronger
in the auricles, and in some places thereof assuming the characters of a fenestrated membrane..
Between these fibres a small quantity of
connective-tissue exists, which is in larger
amount and more areolar in its characters
next the myocardium. Bundles of non-
striped muscular fibres (few in the auricles)
are scattered and arranged for the most
part longitudinally between the elastic
fibres, These seem evidently meant to
* resist the distention which is apt to occur
when the heart contracts and great pres-
sure is ee upon the endocardium. In all
cases where high pressure is put upon walls
composed of soft parts, we always find
Fig. 30. muscular fibres present, and never elastic

Section of the endocardium, a, hyaline layer; b, fibres alone, No blood-vessels occur in the
network of fine elastic fibres; c, network of endocardium (Langer). ) BOF
stronger elastic fibres; d, myocardium with The valves also belong to the
Mectrvemels, which do not pass into the endo- endocardium—both the semi-lunar

’ valves of the aorta and pulmonary
artery, which prevent the blood from passing back into the ventricles, and the
tricuspid (right auriculo-ventricular) and mitral (/ef¢ auriculo-ventricular), which
protect the auricles from the same result. The lower vertebrata have valves in the
orifices of the ven cave, which prevent regurgitation into them; while in birds
and some mammals these valves exist in a rudimentary condition. The valves are
fixed by their base to resistant fibrous rings, consisting of elastic and fibrous tissue.

They are formed of two layers—(1) the jibrous, which is a direet continuation of

the fibrous rings, and (2) a layer of elastic elements, , The elastic layer of the

\ “{

ee

ier

aa Lt Tas

AUTOMATIC REGULATION OF THE HEART. 55

auriculo-ventricular valves is an immediate prolongation of the endocardium of the

auricles, and is directed towards the auricles. The semi-lunar valves have a thin
elastic layer directed towards the arteries, which is thickest at their base. The
connective-tissue layer directed towards the ventricle is about half the thickness
of the valve itself. .

The auriculo-ventricular valves also contain striped muscular fibres. Radiating
fibres proceed from the auricles and pass into the valves, which, when the atria
contract, retract the valves towards their base, and thus make a larger opening for
the passage of the blood into the ventricles ; according to Paladino, they raise the
valves after they have been pressed down by the blood-current. This observer also
described some longitudinal fibres which proceed from the ventricles to enter these
valves. There is also a concentric layer of fibres arranged near their point of
attachment, and directed more towards their ventricular surface. These fibres
seem to contract sphincter-like when the ventricle contracts, and thus approximate
the base of the valves, and so prevent too great tension being put upon them. The
larger chorde tendineew also contain striped muscle, while a delicate muscular
network exists in the valvula Thebesii and valvula Eustachii,

Purkinje’s Fibres consist of an anastomosing system of greyish fibres which exist in the sub-
endocardial tissue of the ventricles, especially in the heart of the sheep and ox. The fibres are
made up of polyhedral clear cells, containing some granular protoplasm, and usually two nuclei
(fig. 81). The margins of the cells are striated. Transition-forms are found between these cells
and the ordinary cardiac fibres; in
fact, these cells become continuous
with the true fully developed cardiac
fibres. They represent cells which
have been arrested in their develop-
ment. They are absent in man and
the lower vertebrates, but in birds and
some mammals they are well marked
(Schweigger-Seidel, Ranvier).

Blood-Vessels occur in the auriculo-
ventricular valves only where muscular
fibres are present, while the semi-lunar
valves are usually devoid of vessels
except at their base. The best figures
of the blood-vessels of the valves are
given by Langer. The network of
pine ncnpre in ae teagan reaches Fig. 31.

Weight ae the ele tenere ¢ Purkinje’s fibres isolated with dilute alcohol. ¢, cell ; /,
ioW. Miller the proportion Lericen striated substance ; 2, nucleus. x 300.

the weight of the body and the heart in the child, and until the body reaches 40 kilos., is 5
grms. of heart-substance to 1 kilo. of body-weight; when the body-weight is from 50 to 90
kilos, the ratio is 1 kilo. to 4 grms. of heart-substance ; at 100 kilos. 3°5 grms. As age advances,
the auricles become stronger. The right ventricle is half the weight of the left. The weight
of the heart of an adult man is about 309 grms.; female, 274 grms. [According to Laennec the
heart is about the size of the closed fist of the individual.] Blosfeld and Dieberg give 346 grms.
for the male, and 310 to 340 grms, for the female heart. The specific gravity of the heart-
muscle is 1069. The thickness-of the left ventricle in the middle in man is 11°4 mm., and in
woman 11°15; that of the right is 4°1 and 3°6 mm. respectively. |

4'7. AUTOMATIC REGULATION OF THE HEART.—Anatomical Investigations. —The two
coronary arteries arise from the first part of the aorta in the region of the sinus of Valsalya. The
position of origin varies—(1) either the orifices lie within the sinus, or (2) their openings are
only partially reached by the margins of the semi-lunar valves (which is wswally the case in the
left coronary artery of man and the ox), or (3) their orifices lie ‘clear above the margins of the
valves. Post-mortem observations seem to show that during contraction of the ventricle it is
very improbable that the semi-lunar valves constantly cover the origin of the coronary arteries.

Automatic Regulation of the Heart.—Briicke attempted to show that during
the systole, or contraction of the ventricle, the semi-lunar valves covered the
openings of the coronary arteries, so that these vessels could be filled with blood

t

56 LIGATURE OF THE CORONARY ARTERIES.

only during the diastole or relaxation of the ventricle. To him it seemed that (a)
the diastolic filling of the coronary arteries would help to dilate the ventricles ;.
(6) on the contrary, a systolic filling of these arteries would oppose the contraction,
because the systolic filling and expulsion of the blood from the coronary arteries
would -diminish the force of the ventricular contraction. [To this supposed
arrangement Briicke gave the name “ Selbststeuerung,” which may be rendered as
above, or as “ self-controlling ” action of the heart by the aortic valves. |

ents against Briicke’s View.—The following considerations militate against this
theory :—(1) Filling the coronary vessels under a high pressure in a dead heart causes a
diminution of the ventricular cavity (v. Wittich). (2) The chief trunks of the coronary arteries
lie in loose sub-pericardial fatty tissue in the cardiac sulci, hence a dilatation of the ventricle
through this agency is most unlikely (Zandois). (3) Experiments on animals have shown that _
a coronary artery spouts, like all arteries, during the systole of the ventricle. Von Ziemssen
found that in the case of a woman who had a large part of the anterior wall of the thorax
removed by an operation, the heart being covered only by a thin membrane, the pulse in the
coronary arteries was synchronous with the pulse in the pulmonary artery. H. N. Martin and
Sedgwick placed a manometer in connection with the coronary artery, and another with the
carotid in a large dog, and they found that the pulsations occurred simultaneously. When
a coronary artery is divided, the blood flows out continuously, but undergoes acceleration during
the systole of the ventricles (Endemann, Perils). (4) If a strong intermittent current of water
be allowed to flow through a sufficiently wide tube into the left auricle of a fresh pig’s heart,
so that the water passes into the aorta, and if the aorta be provided with a vertical tube, the
water flows continuously from the coronary arteries, and is accelerated during the systole.
(5) It is exceedingly improbable that the coronary arteries should be filled during the diastole,
while all the other arteries are filled during systole of the ventricle. (6) There is always a
sufficient quantity of blood in the sinus of Valsalva to fill the arteries during the first part of
the systole. (7) The valves, when raised, are not applied directly to the aortic wall (Hamberger,
Riidinger) even by the most energetic pressure from the ventricle (Sandborg and Worm Miiller).
(8) Observations on voluntary muscles have shown that the small arteries dilate during con-
traction of the muscle, and the blood-stream is accelerated. (9) By the systolic filling of the
aorta the arterial path is elongated—this elastic distention is compensated before the diastole
occurs. By the recoil of the aortic walls the layer of blood in them is driven backwards and
closes the valves (Ceradini). According to Sandborg and Worm Miiller, the semilunar valves
close just after the ventricles have begun to relax, which agrees with the curve obtained from
the cardiac impulse (fig. 39, A).

During the systole, the small arterial trunks lying next the ventricular cavities
have to bear a higher pressure than that borne by the aorta, and their lumen must
be compressed during the systole so that their contents are propelled towards the
veins,

Peculiarities of the Cardiac Blood-Vessels, —The capillary vessels of the myocardium are
very numerous, corresponding to the energetic activity of the heart. Where they pass into
veins, several unite at once to form a wide venous trunk, whereby an easy passage is offered to
the blood. The veins are provided with valves so that (1) during systole of the right auricle
the venous stream is interrupted ; (2) during contraction of the ventricles, the blood in the
coronary veins is similarly accelerated as in the veins of muscles. The coronary arteries are
characterised by their very thick connective-tissue and elastic intima, which perhaps accounts
for the frequent occurrence of atheroma of these vessels (Henle). Some observers maintain that
the coronary arteries do not anastomose, but this is denied by Langer and Krause. [West has
injected the one artery from the other.] Many of the smal] lower vertebrates have no blood-
vessels in their heart-muscle, ¢.g., frog (Hyrtl).

__ Ligature of the Coronary Arteries—The phenomena produced by partial
obliteration or ligature of the coronary arteries are most important. In man
analogous conditions occur, as in atheroma or calcification of these arteries. Sée
and others have ligatured the coronary arteries in dogs, and found that after two
minutes the cardiac contractions gave place to twitchings of the muscular fibres,
and ultimately the heart ceased to beat. Ligature of the anterior coronary artery
alone, or of both its branches, is sufficient to produce this result. If the coronary
arteries be compressed or tied in a rabbit in the angle between the bulbus aorte
and the ventricle, the heart’s action is soon weakened, owing to the sudden anemia
and to the retention of the decomposition-products of the metabolism in the heart-

|

THE MOVEMENTS OF THE HEART. ce

muscle. Ligature of one artery first affects the corresponding ventricle, then the
other ventricle, and, last of all, the auricles. Hence, compression of the left
coronary artery, (with simultaneous artificial respiration in a curarised animal),
causes slowing of the contractions, especially of the left ventricle, whilst the right
one at first contracts more quickly, and then, gradually its rhythm is slowed.
The contractions of the left ventricle are not only slowed but also weakened, whilst
the right pulsates with undiminished force. Hence it follows that, as the left half
of the heart cannot expel the blood in sufficient quantity, the left auricle becomes
filled, whilst the right ventricle, not being affected, pumps blood into the lungs.
Qidema of the lungs is produced by thé high pressure in the pulmonary circulation,
which is propagated from the right heart through the pulmonary vessels into the
left auricle (Samuelson and Griinhagen). According to Sig. Mayer, protracted
dyspncea causes the left ventricle to beat more feebly sooner than the right, so that
the left side of the heart becomes congested. Perhaps this may explain the
occurrence of pulmonary cedema during the death-agony.

Cohnheim and v. Schulthess-Rechberg found, after ligature of one of the large branches of a
coronary artery in a dog, that at the end of a minute the pulsations become intermittent.
This intermittence becomes more pronounced, the two sides of the heart do not contract
simultaneously (arhythmia), the heart beats more slowly, and the blood-pressure falls.
Suddenly, about 105 seconds after the ligature is applied, both ventricles cease to beat, and
there is a great fall of the blood-pressure. After an arrest lasting for 10 to 20 seconds,
twitching movements occur in the ventricles, while the auricles pulsate regularly, and may
continue to do so for many minutes, but the ventricles cease to beat altogether after 50 seconds.
According to Lukjanow, there is a peristaltic condition which operates upwards and downwards,
and occurs in the period between the regular contraction and the twitching vibratory move-
ment, Stimulation of the vagus does not arrest these peristaltic movements.

Pathological.—In so-called sclerosis of the coronary arteries in old age, there are attacks of
diminished cardiac activity, weakness of the heart, an altered rhythm and frequency, with
consequent breathlessness ; there may also be loss “of consciousness, congestions, and attacks
of pulmonary cedema. Death may take place unexpectedly from sudden arrest of the heart’s
action.

48. MOVEMENTS OF THE HEART.—Cardiac Revolution.—The movement
of the heart is characterised by an alternate contraction and relaxation of its walls.
The total cardiac movement is called a ‘‘ cardiac revolution,” or a ‘cardiac
cycle,’ and consists of three acts—the contraction or systole of the aurvcles, the
contraction or systole of the ventricles, and the pause (fig. 50). During the pause,
the auricles and ventricles are relaxed ; during the contraction of the auricles the
ventricles are at rest ; whilst during the contraction of the ventricles the auricles
are relaxed. The rest during the phase of relaxation is called the diastole. The
following is the sequence of events in the heart during a cardiac revolution :—

(A) The blood flows into the auricles. and thus distends them and the auricular
appendices. This is caused by—

(1) The pressure of the blood in the vene cave (right side) and the pulmonary
veins (left side) being greater than the pressure in the auricles. (2) The elastic
traction of the lungs (§ 68), which, after complete systole of the auricles, pulls
asunder the now relaxed and yielding auricular walls. The auricular appendages
are also filled at the same time, and they act to a certain extent as accessory
reservoirs for the large supply of blood streaming into the auricles.

(B) The auricles contract, and we observe in rapid succession—

(1) The contraction and emptying of the auricular appendix towards the atrium.
Simultaneously the mouths of the veins become narrowed, owing to the contraction

of their circular muscular fibres (more especially the superior vena cava and the

pulmonary veins); (2) the auricular walls contract simultaneously towards the
auriculo-ventricular valves and the venous orifices, whereby (3) the blood is
driven into the relaxed ventricles, which are considerably distended thereby.

The contraction of the auricles i is followed by

f

58 EVENTS DURING A CARDIAC CYCLE.

(a) A slight stagnation of the blood in the large venous trunks, as can be
observed in a rabbit after division of the pectoral muscles so as to expose the
junction of the jugular with the subclavian vein. There is no actual regurgitation
of the blood, but only a partial interruption of the inflow into the auricles, because
the mouths of the veins are contracted, and the pressure in the superior vena cava
and pulmonary veins soon holds in equilibrium any reflux of blood ; and lastly,
because any reflux into the cardiac veins is prevented by valves. The movement

ta
Y My 4

ty

UT

Fig. 32.

Cast of the ventricles of the human heart viewed from behind and above ; the walls have been
removed, and only the fibrous rings and the auriculo-ventricular valves are retained. L,
left, R, right ventricle ; S, septum; F, left fibrous ring, with mitral valve closed; D,
right fibrous ring, with tricuspid closed ; A, aorta, with the left (C,) and right (C) coronary
arteries; S, sinus of Valsalva; P, pulmonary artery.

of the heart causes a regular pulsatile phenomenon in the blood of the vene cave,
which under abnormal circumstances may produce a venous pulse (see § 99).

(6) The chief motor effect of the contraction of the auricles is the dilatation of
the relaxed ventricle, which has already been dilated to a slight extent by the
elastic traction of the lungs.

Aspiration of the Ventricles.—The dilatation of the ventricles has been ascribed to the
seep spent of the muscular walls—the strongly contracted ventricular walls (like a compressed
india-rubber bag), in virtue of their elasticity, are supposed, in returning to their normal resting

form, to suck in or aspirate the blood under a negative pressure ; this power on the part of the
ventricle is not great (p. 59). - UF

—

diastole of the ventricles is followed by the pause.

action, This they determined by a maximal and minimal

‘within the ventricle obtains shortly before the systole has reached

EVENTS DURING A CARDIAC CYCLE. 59

(c)’When the ventricles are distended by the inflowing blood, the auriculo-
ventricular valves are floated up, partly by the recoil or reflexion of the blood from
the ventricular wall, and partly owing to their lighter specific gravity, whereby
they easily float into a more or less horizontal position. The valves are also raised
to a slight extent by the longitudinal muscular fibres, which pass from the auricles
into the cusps of the valve.

(C) The ventricles now contract, and simultaneously the auricles relax,
whereby— ,

(1) The muscular walls contract forcibly from all sides, and thus diminish the
ventricular cavity. (2) The blood is at once pressed against the under surface of
the auriculo-ventricular valves, whose curved margins are opposed to each other like
teeth, and are pressed hermetically against each other (fig. 32). It is impossible
for the blood to push the cusps backwards into the auricle, as the chorde tendines
hold fast their margins and surfaces like a taut sail. The margins of the neigh-
bouring cusps are also kept in apposition, as the chordee tendinez from one papillary
muscle always pass to the adjoining edges of two cusps. The extent to which the
ventricular wall is shortened is compensated by the contraction of the papillary
muscle, and also of the large muscular chordz, so that the cusps cannot be pushed
into the auricle. When the valves are closed, their surfaces are horizontal, so that,
even when the ventricles are contracted to their greatest extent, there remains in
the supra-papillary space a small amount of blood which is not expelled (Sandborg
and Worm Miiller). (3) When the pressure within the ventricles exceeds that in
the arteries, the semi-lunar valves are forced open and stretched like a sail across

the pocket-like sinus, without, however, being directly applied to the wall of the

arteries (pulmonary and aorta), and thus the blood enters the arteries.
(D) Pause.—As soon as the ventricular contraction ends, and the ventricles
begin to relax, the semi-lunar valves close (fig. 33). The

Under normal circumstances, the right and left halves
of the heart always contract or relax uniformly and
simultaneously.

Negative Pressure in the Ventricle.—Goltz and Gaule found
that there was a negative pressure of 23°5 mm. Hg. (dog) in the
interior of the ventricle during a certain phase of the heart’s

manometer. They surmised that this phase coincided with the
diastolic dilatation, for which they assumed a considerable power
of aspiration. Moens is of opinion that this negative pressure

its height, t.e., just before the inner surface of the ventricles and
the valves, after the blood is expelled, are nearly in apposition. The closed semi-lunar valve of
He explains this aspiration as being due to the formation of an the pulmonary artery seen
empty space in the ventricle caused by the energetic expulsion _fy9m below.
of the blood through the aorta and pulmonary artery.

[Maximum and Minimum Manometer.—Into the tube connecting the interior of the ventricle
of the heart with the ordinary U-shaped mercury manometer, is introduced the maximum

Fig. 34. Fig. 35.
. Gaule’s maximum and minimum manometer.
manometer, which is constructed on the principle of a ball and cup valve (fig. 34), the ball A

being kept closed in B by a spring C. To make it a maximum manometer the end A is con-
nected with the heart, and B with the mercurial manometer (fig. 35). When a clamp is placed

60 PATHOLOGICAL CARDIAC ACTION.

on the upper limb the valve is acted on only at each systole of the heart, blood is driven beyond
it, bat during diastole it closes and no blood can return. This goes on until the pressure beyond
the valve in the mercury manometer is the same as in the heart. If the valve be reversed, it is
converted into a minimum manometer. ]

49. PATHOLOGICAL CARDIAC ACTION.—Cardiac Hypertrophy.—All resistances to the
movement of the blood through the various chambers of the heart, and through the vessels com-
municating with it, cause a greater amount of work to be thrown upon the portion of the heart
specially related to this part of the circulatory system ; consequently, there is produced an
increase in the thickness of the muscular walls and dilatation of the heart. If the resistance or
obstacle does not act upon one part of the heart alone, but on parts lying in the onward direc-
tion of the blood-stream, these parts also subsequently undergo hypertrophy. If in addition
to the muscular thickening of a part of the heart, the cavity is simultaneously dilated, it is
spoken of as eccentric hypertrophy or hypertrophy with dilatation. The obstacles most
likely to occur in the blood-vessels, are narrowing of the lumen or want of elasticity in their
walls; in the heart, narrowing of the arterial or venous orifices or insufficiency or incompetency
of the valves. Incompetency of the valves forms an obstruction to the movement of the blood,
by allowing part of the blood to flow back or regurgitate, thus throwing extra work upon the
heart.

Thus arise—(1) Hypertrophy of the left ventricle, owing to resistance in the area of the
systemic circulation, especially in the arteries and capillaries—not in the veins. Amongst
the causes are—constriction of the orifice or other parts of the aorta, calcification, atheroma, and
want of elasticity of the large arteries and irregular dilatations or aneurisms in their course ;
insufficiency of the aortic valves, in which case the same pressure always obtains within the
ventricle and in the aorta ; and, lastly, cirrhosis of the kidneys, whereby the excretion of water
by these organs is diminished. Even in mitral insufficiency, compensatory hypertrophy of the
left ventricle must occur, owing to the hypertrophy of the left atrium in consequence of the
increased blood-pressure in the pulmonary circuit.

(2) Hypertrophy of the left auricle occurs in stenosis or constriction of the left auriculo-ven-
tricular orifice, or in insufficiency of the mitral valve, and it occurs also as a result of aortic |
insufficiency, because the auricle has to overcome the continual aortic pressure within the
ventricle.

(3) Hypertrophy of the right ventricle occurs (a) when there is resistance to the blood-
stream through the pulmonary circuit. The resistance may be due to (a) obliteration of large
vascular areas in consequence of destruction, shrinking or compression of the lungs, and the
disappearance of numerous capillaries in emphysematous lungs; (§) overfilling of the
pulmonary circuit with blood in consequence of stenosis of the left auriculo-ventricular orifice, or
mitral insufficiency—consequent upon hypertrophy of ‘the left auricle resulting from aortic
insufficiency. (b) When the valves of the pulmonary artery are insufficient, thus permitting
the blood to flow back into the ventricle, so that the pressure within the pulmonary artery
prevails within the right ventricle (very rare).

(4) Hypertrophy of the right auricle occurs in consequence of the last-named condition, and
also from stenosis of the tricuspid orifice, or insufficiency of the tricuspid valve (rare).

Artificial Injury to the Valves.—If the aortic valves are perforated, with or without
simultaneous injury to the mitral or tricuspid valves, the heart does more work; thus the
physical defect is overcome fora time, so that the blood-pressure does not fall. The heart seems
to have a store of reserve energy which is called into play. Soon, however, dilatation takes
place: on account of the regurgitation of the blood into the heart. Hypertrophy then occurs,

ut the compensation meanwhile must be obtained through the reserve energy of the heart
(O. Rosenbach). :

Impeded Diastole. —Among causes which hinder the diastole of the heart are—copious effusion
into the pericardium, or the pressure of tumours upon the heart. The systole is greatly inter-
fered with when the heart is united to the pericardium and to the connective-tissue in the
mediastinum. Asa consequence the connective-tissue, and even the thoracic wall, are drawn
in during contraction of the heart, so that there is a retraction of the region of the apex-beat
during systole, and a protrusion of this part during the diastole.

[Palpitation is a symptom indicating generally very rapid and quick action of the heart, the
pulsations often being unequal in time and intensity, while the person is generally conscious of
the irregularity of the cardiac action. It may be due to some organic condition of the heart
itself, especially where the cardiac muscles are weak, in cases of dilatation and hypertrophy of
the left ventricle, where the heart is gradually becoming unable to overcome the resistances offered
to its work, and especially during exertion when the heart is taxed above its strength. It may
also occur where the blood-pressure is low, as in anemia, so that the heart contracts quickly,
there being little resistance opposed to its action, The excitability of the cardiac muscle may
be increased as in fatty heart, when very slight exertion may excite it often in a paro
way. In other cases, it is nervous in its origin, being either direct or reflex. In very emotional
and excitable people (especially in women) it is easily set up, and in some people it may be —

- THE CARDIOGRAM. . 61

produced reflexly by gastric or intestinal irritation or dyspepsia. It also frequently results

- from excesses of all kinds and the over-use of tobacco. The remedies to be used obviously

depend on the cause. Where the blood-pressure is low, as in anemia, digitalis and iron will
do good ; the former by increasing the blood-pressure, .and the latter by improving the general
nutrition of the body and the blood in particular. In neurotic cases cardiac sedatives are indi-
cated, while in cases due to indigestion hydrocyanic acid is useful (Brunton)].

[Fainting or Syncope.—JIn fainting the person loses consciousness, owing to a sudden arrest
of the blood-supply to the brain, the face is pallid, the respiration is feeble or ceases, while the
heart beats but feebly or not at all. The defective supply of blood to the brain may depend
upon sudden arrest of the heart’s action, caused, it may be, by a fright, or the heart’s action
may be arrested reflexly. Any cause which suddenly diminishes the blood-pressure may pro-
duce it, or when pressure is suddenly removed from the large vessels, as in tapping the abdomen
in ascites, without at the same time giving sufficient support to the abdominal viscera. When
a person has been long in the recumbent position, on being rapidly set up in bed he may faint. ~
In some forms of heart disease, sudden exertion or change of posture may produce it.

[Treatment.—The object is to restore consciousness and the action of the heart. Place the
person in the horizontal position, keep the head low, even lower than the body, and do not
support it with pillows. Dashing cold water on the face, so as to stimulate the fifth nerve,
usually succeeds in causing the person to take a deep inspiration. In other cases a sniff of
smelling salts or ammonia, acting through the nasal branch of the fifth nerve, will excite the
cardiac and respiratory functions (§ 368). ]

50. THE APEX-BEAT, CARDIOGRAM.—Cardiac Impulse.—By the term
‘‘apex-beat”’ or ‘cardiac impulse”’ is understood under normal circumstances an
elevation (perceptible to touch and sight), in a circumscribed area of the jifth le/t
intercostal space, and caused by the movement of the heart. [The apex-beat is felt
in the fifth left intercostal space, 2 inches below the nipple, and 1 inch to its sternal
side, or at a point 2 inches to the left of the sternum.] The impulse is more rarely
felt in the fourth intercostal space, and it is much less distinct when the heart beats
against the fifth rib itself. The position and force of the cardiac impulse vary
with changes in the position of the body.

[The cardiac impulse is synchronous with the systole of the heart, but although this name
and apex-beat' are frequently used as synonymous terms, it is to be remembered that the
impulse may be caused by different parts of the heart being in contact with the chest-wall.
The cardiac impulse is usually higher than normal in children, while it is lower during inspira-
tion than expiration. ]

[Methods.—To obtain a curve of the apex-beat or a cardiogram, we may use one or other of
the following cardiographs (fig. 35). Fig. 36, A, is the first form used by Marey, and it consists
of an oval wooden capsule applied in an air-tight manner over the apex-beat. The disc, p,
capable of being regulated by the screw, s, presses upon the region of the apex-beat, while ¢ is a
tube which may be connected with a recording tambour (fig. 47). B is an improved form of
the instrument, consisting essentially of a tambour, while attached to the membrane is a button,
p, to be applied over the apex-beat. The movements of the air within the capsule are com-
municated by the tube, ¢, to a recording tambour. Fig. 36, C, is the pansphygmograph of -
Brondgeest, which consists of a Marey’s tambour, in an iron horse-shoe frame, and adjustable
by means of ascrew, s. Burdon-Sanderson’s cardiograph is shown in D, The button, p, carried
by the spring, ¢, does not rest upon the caoutchouc membrane, but on an aluminium plate
attached to it. The apparatus is adjusted to the chest by three supports. Fig. 36, E, shows
a modified instrument on the same principle by Grummach and v. Knoll. In all these
figures the ¢ indicates the exit-tube communicating with a recording tambour (fig. 47), D and
E may be used for other purposes, ¢.g., for the pulse, so that they are polygraphs. See also
fig. 76. ]

Fig. 39, A, shows the cardiogram or the impulse-curve of the heart of a healthy
man; B, that of a dog, obtained by means of a sphygmograph. In both the follow-
ing points are to be noticed, :—ab, corresponds to the time of the pause and the
contraction of the auricles. As the atria contract in the direction of the axis of the
heart from the right and above towards the left and below, the apex of the heart
moves towards the intercostal space. The two or three smaller elevations are
perhaps caused by the contractions of the ends of the veins, the auricular appendices,

’ and the atria themselves.

The portion bc, which communicates the greatest impulse to the instrument, and
also to one’s hand when it is placed on the apex-beat, is caused by the contraction

62 THE CARDIOGRAM.

of the ventricles, and during it the first sound of the heart occurs. Frequently,

Cardiographs. A, Marey’s original form ; B, Marey’s improved form ; C, pansphy gine
(Brondgeest) ; D, cardiograph (Burdon-Sanderson) ; E, that of v. Knoll.
but erroneously, the cardiac impulse has been ascribed to the contraction of the
ventricles alone. It,
however, is due to
all those conditions
which cause an eleva-
tion in the region of
the cardiac impulse.
[Edgren recorded a
human cardiogram, and
listened at the same time
to the heart sounds, re-
cording the latter by
Fig. 37. means of an electric sig-

as cil Lo ‘ises a
Cardiogram. a-f; 1, beginning of 1st, and 2, 2nd sound. % with the beglaeal -

the first sound, 7.e., with the contraction of the ventricles, and reaches the abscissa at f with the
beginning of the second sound, 7.e., when
the semi-lunar valves are closed. The
relation between a and the points inter-
mediate between it and /, and to the pulse-
curve of the carotid, is shown in fig, 38.
The letters with the dash ‘correspond to
the unmarked letters in the cardiogram. ]
The cause of the ventricular
impulse has been much discussed.
It depends upon the following :—
(1) The base of the heart (auriculo-
ventricular groove) represents during
Fig. 38. diastole a transversely-placed ellipse
The upper curve from the human carotid; the lower (fig. 40, I., FG), while during con-
a cardiogram taken simultaneously. traction it has a more circular figure,

CAUSE OF THE CARDIAC IMPULSE, 63

ab, Thus, the long diameter of the ellipse (FG) is diminished, the small diameter
de is increased, while the base is brought nearer to the chest-wall e. This alone

Fig. 39.

Curves from the apex-beat. A, normal curve (man); B, from a dog; C, very rapid curve
(dog) ; D and E, normal curves (man) registered on a vibrating glass plate where each
indentation = 0°01613 sec. In all the curves a) means contraction of the auricles, and
be of the ventricles ; d, closure of the aortic, and e, of the pulmonary valves ; ¢/, diastole
of the ventricle.

does not cause the impulse, but the basis of the heart, being hardened during the
systole and brought nearer to the chest-wall, allows the apex to execute the move-
ment which causes the.impulse (p. 61).

(2) During relaxation, the ventricle lies with its apex (fig. 40, II., 7) obliquely
downwards, and with its long axis in an oblique direction—so that the angles (dcz,
act) formed by the axis of the ventricles with the diameter of the base are unequal
—during systole it represents a regular cone, with its axis at right angles to its
base. Hence, the apex (7) must be erected from below and behind (p), forwards
and upwards (Harvey—“ cor sese erigere”), and when hardened during systole
presses itself into the intercostal space (fig. 40, II.).

(3) The ventricles undergo during systole a slight spiral twisting on their long
axis (‘‘lateralem inclinationem ”—Harvey), so that the apex is brought from
behind more forward, and thus a greater portion of the left ventricle is turned to
the front. This rotation is caused by the muscular fibres of the ventricles, which
proceed from that part of the fibrous rings between the auricles and ventricles
which lies next the anterior thoracic wall. The fibres pass from above obliquely
downwards, and to the left, and also run in part upon the posterior surface of the
ventricles. When they contract in the axis of their direction, they tend to raise
the apex, and also to bring more of the posterior surface of the heart in relation
with the anterior thoracic wall. It is favoured by the slightly spiral arrangement
of the aorta and pulmonary artery.

These are the most important causes, but the minor causes are,

(4) The “reaction impulse” or “recoil,” or that movement which the ventricles
are said to undergo, (like.an exploded gun or rocket), at the moment when the

64 CAUSE OF THE CARDIAC IMPULSE.

blood is discharged into the aorta and pulmonary artery, whereby the apex goes in
the opposite direction, i.e, downwards and slightly outwards. Landois, however,
has shown that the mass of blood is discharged into the vessels 0°08 of a second
after the beginning of the systole, while the cardiac impulse occurs with the first
sound. .

(5) When the blood is discharged into. the aorta and pulmonary artery, these
vessels are slightly elongated, owing to the increased blood-pressure. As the heart
js suspended from above by these vessels,
the apex is pressed slightly downwards and
forwards towards the intercostal space (‘).

As the cardiac impulse is observed in the empty
hearts of dead animals, (4) and (5) are certainly
of only second-rate importance. Filehne and

Pentzoldt maintain that the apex during systole
does not move to the left and downwards, as must ©

Fig. 40.

I. Schematic horizontal section through the heart, lungs, and thorax, to show the change of
shape which the base of the heart undergoes during contraction of the ventricle—F, G
transverse diameter of the ventricle during diastole ; ¢, position of the thoracic wall ; a, b,
transverse diameter of the heart during systole, with ¢, position of the anterior thoracic
yea systole. II. Side-view of the heart—i, apex during diastole; p, during

. e, :

be me case in (4) and (5), but that it moves upward and to the right—a result corroborated by
v. Ziemssen. [Barr attributes the cause of the impulse to the rigidity or hardening of the ven-
raed Loe a cig ie Sa rotatory movement and lengthening downwards of the blood-
c 1 in the aorta and pulmonary artery, while towards the end of the systole th i

of recoil takes place and aie contributes to cause it. ] Te) a

It is to be remembered that as the apex is alwa : i
, t ys applied to the chest-wall, separated from it
merely by the thin margin of the lung, it only presses against the intercosta space during

systole (Xiwisch).

After the apex of the curve, c, has been reached at the end of the systole, the
curve falls rapidly, as the ventricles quickly become relaxed. In the descending
part of the curve, at d and e, are two elevations, which occur simultaneously
with the second sound. These are caused by the sudden closure of the semi-lunar
valves, whereby an impulse is propagated through the axis of the ventricle to its
apex, and thus causes a vibration of the intercostal space ; d corresponds to the
closure of the aortic valves, and e to the closure of the pulmonary valves. The
closure of the valves in these two vessels is not simultaneous, but is separated by
an interval of 0°05 to 0°09 sec. The aortic valves close sooner on account of the ‘

- > ’
\ BF

:

CHANGE IN SHAPE OF HEART, 6 5

greater blood-pressure there. Complete diastolic relaxation of the ventricle occurs
from e to f in the curve.

It is clear, then, that the cardiac impulse is caused chiefly by the contraction of
the ventricles, while the auricular systole and the vibration caused by the closure
of the semi-lunar valves are also concerned in its production.

[Change in Shape of Heart.—The experiments of Ludwig and Hesse on the heart
of the dog show that the shape of the ventricles varies remarkably in systole and
diastole, and that the shape of the heart as found post-mortem is not its natural shape. |

[Method.—Bleed a dog rapidly from the carotids, defibrinate the blood, expose the heart, tie
graduated straight tubes into the pulmonary artery and aorta, and ligature the auricular vessels.
Pour the blood into the heart until it is dilated under a pressure equal to the mean arterial pres-
sure (150 mm.). The ventricles are in the diastolic phase, the auricles still pulsate. A plaster
cast is now rapidly made of the ventricles. This represents the diastolic phase. To obtain what
may be regarded as the systolic phase, a heart, similarly prepared but emptied of blood, is
suddenly plunged into a hot (50° C.) saturated solution of potassic bichromate, when the heart
gives one rapid and final contraction and remains permanently contracted owing to the heat-
rigor, its proteids being coagulated (§ 295). Thisis thesystolic phase. Little pins with twisted
points are previously inserted in the organ to mark certain parts of both hearts for comparison. ]

[In diastole, the shape of the ventricle is hemispheroidal, the apex being rounded,
while the posterior surface is flatter than the anterior (fig. 41). In the plane of
the ventricular base, the greatest diameter is from right to left, and the shortest
froin base to apex. The conus arteriosus is above the plane of the base. During

Fig. 42.
Projection of a dog’s heart. Anterior surface. Left lateral surface.
Posterior surface.

systole, the apex is more pointed, the ventricle more conical, while all the diameters
in the plane of the base are equally diminished, hence’ the vertical measurement
from base to apex is longer now than either of the diameters at the base (fig. 43).
The conus arteriosus sinks towards the plane of the base, while the base of the
ventricle becomes more circular, so that the difference of the curvatures of the
anterior and posterior surfaces van- :

ishes (fig. 42). In all these figs. the
shaded part represents diastole and
the clear part systole. The most re-
markable point is that the vertical B=
measurement remains unchanged. ¥
This refers to the left ventricle, which
of course forms the apex; the right is
shortened. The plane of the ven- —
tricular base in systole is about one- Fig. 44.
half of what it is in diastole, as is Projection of the base in A, aorta; PA, pulmon-
shown in fig. 44. Thus the heart is systole and diastole, RV, ,,, ary artery; M, mitral,
diminished in all its diameters except right, and LV, left ven- and qT, tricuspid ori-
one, the arterial orifices are scarcely Bele, | fs

affected, while the area of the auriculo-ventricular orifices (M, T) is diminished
about one-half (fig. 45). This is most important in connection with the closure of

<=

fs —

66 THE TIME OF THE CARDIAC MOVEMENTS.

the auriculo-ventricular valves ; as it shows that the muscular fibres of the heart,
by diminishing these orifices during systole, greatly aid in the perfect closure of
these valves. Thus we explain why defective nutrition of the cardiac muscle may
give rise to incompetency of these valves, without the valves themselves being
diseased (Macalister). | . i

{In order to account for the vertical diameter remaining unchanged, we may
represent the ventricular fibres as consisting of three layers, viz., an inner and outer
set, more or less longitudinal, and a middle set, circular. Both sets will tend, when
they contract, to diminish the cavity, but the shortening of the longitudinal layers
is compensated for by the contraction, ze. the elongation produced by the circular
set. |

[In order to obtain the shape of the cavities, dogs were taken of the same litter and as nearly
alike as possible. One heart was filled with blood, as already described, and placed in a cool

solution of potassic bichromate, whereby it was slowly hardened in the diastolic form, while the
other was plunged as before into a hot solution. Casts were then made of the cavities. ]

5]. THE TIME OF THE CARDIAC MOVEMENTS. —Methods.—The time occupied by the
various phases of the movements of the heart may be determined by studying the apex-beat
curve.

(1) If we know at what rate the plate on which the curve was obtained moved during the ex-
periment, of course all that is necessary is to measure the distance, and so calculate the time
occupied by any event (see Pulse, § 67).

(2) It is preferable, however, to cause a tuning-fork, whose rate of vibration is known, to
write its vibrations under the curve of the apex-beat, or the curve may be written upon a plate
attached to a vibrating tuning-fork (fig. 39, D, E). Such a curve contains fine teeth caused by
the vibrations of the tuning-fork. D and E are curves obtained from the cardiac impulse in
this way from healtliy students. In D the notch d is not indicated. Each complete vibration
of the tuning-fork, reckoned from apex to apex of the teeth =0°01613 second, so that it is simply
necessary to count the number of teeth and multiply to obtain the time. The values obtained
vary within certain limits even in health.

The value of « ) = pause + contraction of the auricles, is subject to the
greatest variation, and depends chiefly upon the number of heart-beats per minute.
The more quickly the heart beats, the shorter is the pause, and conversely. In
some curves, even when the heart beats slowly, it is scarcely possible to distinguish
the auricular contraction (indicated by a rise) from the part of the curve correspond-
ing to the pause (indicated by a horizontal line). In one case (heart-beats 55 per
minute) the pause = 0°4 second, the auricular contraction=0°177 second. In fig.
39, A, the time occupied by the pause + the auricular contraction (74 beats per
minute)=0°5 second. In D,ab = 19 to 20 vibrations = 0°32 second ; in E=
26 vibrations = 0°42 second.

The ventricular systole is calculated from the beginning of the contraction 4, to ¢
when the semi-lunar valves are closed ; it lasts from the first to the second sound,
It also. varies somewhat, but is more constant. When the heart beats rapidly, it
is somewhat shorter—during slow action longer. In E=0°32 second ; inD= 0°29
second ; with 55 beats per minute Landois found it = 0°34, with a very high rate
of beating = 0°199 second. , ) )

When the ventricles beat feebly, they contract more slowly, as can be shown by applying the *
epetering apparatus to the heart of an animal just killed. In fig. 46, from the ventricle of a ;

just killed, the slow heart-beats, B, are seen to last longest. In cases of enormous
hypertrophy and dilatation of the left ventricle, the duration of the ventricular systole is not
longer than normal (Landois).

In calculating the time occupied by the ventricular systole we must remember—(1) The time
between the two sownds of the heart, z.c., from the beginning of the first to the end of the second
sound (6 toe). (2) The time the blood flows into the aorta, which comes to an end at the de- .
ome between cand d (in fig. 39, E). Its commencement, however, does not coincide with '

, a8 the aortic valves open 0°085 to 0-073 second after the beginning of the ventricular systole.
Hence the aortic current lasts 0°08 to 0°09 second. This is calculated in the following way :-—
The time between the first sound of the heart and the pulse in the axillary artery is 0°137
second, and of this time 0°052 second is occupied in the propagation of the pulse-wave along aa
80 cm. of artery lying between the root of the aorta and the axilla. ‘Thus the pulse-wave

ENDOCARDIAL PRESSURE. | - 67

the aorta occurs 0°137 minus 0°052=0°085 second after the beginning of the first sound. The
current in the pulmonary artery is interrupted in the depression between d and e. (3) Lastly,
the time occupied by the muscular contraction of the ventricle, which begins at 6, reaches its

A B

Sa eey aa UR CS
jer oie
aaa n'a'oatea naan conse aaa aainmmete

Fig. 46.
Curves recorded by the ventricle of a rabbit, upon a vibrating plate attached to a tuning-fork
(vibration =0°016138 sec.). A, soon after death ; B, from the dying ventricle.

greatest extent at c, and is completely relaxed at 7. The apex of the curve, c, may be higher or
lower according to the flexibility of the intercostal space, hence the position of ¢ varies. In
hypertrophy with dilatation of the left ventricle, the duration of the ventricular contraction
does not greatly exceed the normal.

The time which elapses between d and ¢, 7.¢., between the complete closure of
the aortic and pulmonary valves, is greater the more the pressure in the aorta
exceeds that in the pulmonary artery, as the valves are closed by the pressure
from above, and the difference in time may be 0°05 second, or even double that
time, in which case the second sound appears double (compare § 54). If the aortic
pressure diminishes while that in the pulmonary artery rises, d and e may be so
near each other that they are no longer marked as distinct elements in the curve.

The time, ef, during which the ventricles relax varies somewhat: 0:1 second
may be taken as a mean.

Accelerated Cardiac Action, —When the action of the heart is greatly accelerated, the’ pause
is considerably shortened in the first instance (Donders), and to a less extent the time of con-
traction of the auricles and ventricles. When the pulse-rate is very rapid, the systole of the
atria coincides with the closure of the arterial valves of the preceding contraction, as is shown
in fig. 39, C (dog).

In registering the cardiac impulse, the appara-
tus is separated by a greater or less depth of
soft parts from the heart itself, so that in all cases
the intercostal tissues do not follow exactly the
movements of the heart, and thus the curve ob-
tained may not coincide mathematically with the
movements of the heart. It is desirable that
curves be obtained from persons whose hearts are
exposed, 7.¢., in cases of ectopia cordis.

Cleft Sternum.—Gibson inscribed cardiograms
from the heart of a man with cleft sternum. The
following were the results obtained :—Auricular
contraction =0°115; ventricular contraction (d, d)
=('28 ; ditterence between closure of valves (d, ¢)
=0°09; ventricular diastole (¢, 7) =0°11; pause :
= 0°45 second. ; Fig, 47

2 g. 47.

Endocardial Pressure.—In large mam-- Marey’s registering tambour. T, metallic
mals, such as the horse, Chauveau and capsule, with thin india-rubber stretched
Marey (1861) determined the duration of over it, and bearing an aluminium disc,
th bs Bint itn ehe hacia a which acts upon the writing lever, H.

e events that occur within the neart, an By means of a thick-walled caoutchouc
also the endocardial pressure by means of tube, it may be connected with any system
a cardiac sound. Small elastic bags at- containing ail, so as to record variations of
tached to tubes were introduced through Pressure. |
the jugular vein into the right auricle and ventricle. Each of these tubes was
connected with a registering tambour (fig. 47), and simultaneous tracings of the
variations of pressure within the cavities of the heart were obtained by causing the
writing-points of the levers of the tambours to write upon a revolving cylinder.

68 ENDOCARDIAL PRESSURE.

Fig. 48, A, gives the result obtained when one elastic bag was placed in the right auricle,
‘being introduced through the jugular vein and superior vena cava ; B, when the other
sushed through the tricuspid orifice was in the right ventricle; D, in the root of the aorta, ushe
in through the carotid ; C, pushed past the semi-lunar valves into the left ventricle; while at
E a similar bag has been placed externally between the heart's apex and the inner wall of the
chest. In all cases v=auricular contraction; V, that of the ventricle ; s, closure of semi-lunar
valves, sooner in C than B; P=pause. ie :

Methods.—(1) The cardiac sound consists of a tube containing two separate alr-passages, and
in connection with each of these there is a small elastic bag or ampulla, One of the bags is
fixed to the free end of the sound, and communicates with one of the air-passages, The other

+: Right Auricle.

‘#\- Right Ventricle.

-|-- Left Ventricle.

- Aorta,

‘+ Cardiac Impulse.

Fig. 48,
Curves obtained from the heart of a horse by the cardiac sound,

bag is placed in connection with the second air-passage in the sound, and at such a distance
that, when the former bag lies within the ventricle, the latter is in the auricle. Each bag and
air-tube communicating with it is connected with a Marey’s tambour (fig. 47), provided with
a lever which inscribes its movements upon a revolving cylinder. Any variation of pressure
within the auricle or ventricle will affect the elastic ampulle, and thus raise or depress the
lever. Care must be taken that the writing-points of the levers are placed exactly above each
other. A tracing of the cardiac impulse is taken simultaneously by means of a cardiograph
attached to a separate tambour, ' vs

It has still to be determined whether the auricles and ventricles act alternately,
so that at the moment of the beginning of the ventricular contraction the auricles
relax, or whether the ventricles are contracted while the auricles still remain slightly
contracted, so that the whole heart is contracted for a short time at least. The
latter view was supported by Harvey, Donders, and others, while Haller and many

;

PATHOLOGICAL CARDIAC IMPULSES. 69

of the more recent observers support the view that the action of the auricles and
ventricles alternates. In the case of Frau Serafin, whose heart was exposed,
v. Ziemssen obtained curves from the auricles, which showed that the contraction
of the auricles continued even after the commencement of the ventricular systole.
In Marey’s curve the contraction of the ventricle is represented as following that
of the auricle (fig, 48).

[(2) Rolleston used a special apparatus which was connected with the interior of the heart,
and he finds that there is no distinct rise of pressure in the dog within the ventricles corre-
sponding to the auricular systole such as was obtained by Marey in the horse. During the
ventricular diastole in certain cases the pressure falls below the atmospheric pressure, and may be
equal to -20 mm. mercury or more in the left ventricle (§ 48). It is probably caused by
the elastic expansion of the ventricle continuing after the blood in the auricle at the moment
of the cessation of the ventricular systole has entered the ventricle, ¢.e., the quantity of
blood in the auricle is not sufficient in all cases to distend the left ventricle tv the point at
which its suction action ceases. Magini, operating on dogs with a trocar which perforated
the cavities of the heart, found none of the secondary elevations obtained by Marey with his
sound. |

A. Fick regards the alternating contraction as a means whereby the pressure in the large
venous trunks is kept nearly constant. At the moment of ventricular systole the auricles
relax, and the venous blood flows freely into the latter, while if the auricles remained contracted,
the blood in the veins would be kept back. Further, at the moment of ventricular diastole
the auricles contract, so that there is not an abnormal diminution of the pressure in the veins.
Thus the pressure in the auricle is more equable, while the current in the terminal parts of the
veins is kept more constant.

52, PATHOLOGICAL CARDIAC IMPULSES.—Change in the Position of the Apex-Beat. —
The position of the cardiac impulse is changed—(1) by the accumulation of fluids (serum, pus,
blood) or gas in one pleural cavity. A copious effusion into the left pleural cavity compresses
the lung, and may displace the heart towards the right side, while effusion on the right side
may push the heart more to the left. As the right heart must make a greater effort to propel
the blood through the compressed. lung, the cardiac impulse is usually increased. Advanced
emphysema of the lung, causing the diaphragm to be pressed downwards, displaces the heart
downwards and inwards, while pushing or pulling up of the diaphragm (by contraction of
the lung, or through pressure from below) causes the apex-beat to be displaced upwards,
and also slightly to the left. Thickening of the muscular walls with dilatation of the cavities
of the left ventricle makes that ventricle longer and broader, while the increased cardiac
impulse may be felt in the axillary line in the sixth, seventh, or even eighth intercostal
space to the left of the mammary line. Hypertrophy, with dilatation of the right side,
increases the breadth of the heart, so that the cardiac impulse is felt more to the right, even
to the right of the sternum. In the rare cases where the heart is transposed, the apex-
beat is felt on the right side. When the cardiac impulse goes to the left of the left mammary
line, or to the right of the parasternal line, the heart is increased in breadth, and there is
hypertrophy of the heart. A greatly increased cardiac impulse may extend to several inter-
costal spaces.

The cardiac impulse is abnormally weakened in cases of atrophy and degeneration of the
cardiac muscle, or by weakening of the innervation of the cardiac ganglia. It is also weakened
when the heart is separated from the chest-wall owing to the collection of fluids or air in
the pericardium, or by a greatly distended left lung ; and, indeed, when the left side of the
chest is filled with fluid, the cardiac impulse may be extinguished. The same occurs when the
left ventricle is very imperfectly filled during its contraction (in consequence of marked
narrowing of the mitral orifice), or when it can only empty itself very slowly and gradually,
as during marked narrowing of the aortic orifice. ;

An increase of the cardiac impulse occurs during hypertrophy of the walls, as well as under
the influence of various stimuli (psychical, inflammatory, febrile, toxic) which affect the cardiac

anglia. Great hypertrophy of the left ventricle causes the heart to heave, so that a part of the
eft chest-wall may be raised and also vibrate during systole.

A pulling in of the anterior wall of the chest during the cardiac systole occurs in the third
and fourth interspaces, not unfrequently under normal circumstances, sometimes during in-
creased cardiac action, and in eccentric hypertrophy of the ventricles. As the heart’s apex is
slightly displaced, and: the ventricle becomes slightly smaller during its systole, the empty
space is filled by the yielding soft parts of the intercostal space. When the heart is united
with the pericardium and the surrounding connective-tissue, which renders systolic locomotion
of the heart impossible, retraction of the. chest-wall during systole takes the place of the
cardiac impulse (Skoda). During the diastole, a diastolic cardiac impulse of the corresponding _
part of the chest-wall may be said to occur, ,

JO VARIATIONS OF THE CARDIAC IMPULSE,

Clinically, changes in the cardiac impulse are best ascertained by taking graphic representa-
tions of the cardiac impulse, and studying the curves so obtained (fig. 49). ;

In curve P (much reduced), from a case of marked hypertrophy with dilatation, the ven-
tricular contraction, bc, is usually very great, while the time occupied by the contraction is not
much increased. P and Q were obtained from a case of marked eccentric hypertrophy of the
left ventricle, due to insufficiency of the aortic valves. Curve Q was taken intentionally over
the auriculo-ventricular groove, where retraction of the chest-wall occurred during systole ;
nevertheless the individual events occurring in the heart are indicated.

Fig. E is from a case of aortic stenosis, The auricular contraction (ab) lasts only a short
time : the ventricular systole is obviously lengthened, and after a short elevation (bc) shows a

Fig. 49.
Curves of the cardiac impulses. «ab, contraction of auricles ; bc, ventricular systole ; d, closure
of aortic, and e, of pulmonary valves ; ef, diastole of ventricle; P, Q, hypertrophy and
dilatation of the left ventricle ; E, stenosis of the aortic orifice ; F, mitral insufficiency ;
G, mitral stenosis ; L, nervous palpitation in Basedow’s disease ; M, so-called hemisystole.

series of fine indentations (c, ¢) caused by the blood being pressed through the narrowed:.and
roughened aorta.

Fig. F, from a case of insufficiency of the mitral valve, shows (ab) well marked on account
of the increased activity of the left auricle, while the shock (d) from the closure of the aortic
valves is small, on account of the diminished arterial tension. On the other hand, the shock
from the accentuated pulmonary sound (e) is very great, and is in the apex of the curve. On
account of the great tension in the pulmonary artery, the second pulmonary tone may be so
strong, and succeed the second aortic sound (d) so rapidly, that both almost merge completely
into each other (H and K).

The curve of stenosis of the mitra] orifice (G) shows a long, irregular, notched, auricular
contraction (ab), caused by the blood being forced through an irregular narrow orifice. The ven-
tricular contraction (bc) is feeble because the ventricle is imperfectly filled. The closures of the
two valves, d and ¢, are relatively far apart, and one:can hear distinctly a reduplicated second
sound. The aortic valves close rapidly, because the aorta is imperfectly supplied with blood,
while the more copious inflow of blood into the pulmonary artery causes its valves to-close later.

le Se be ,

. defined at first, and is synchronous with the systole of

THE HEART-SOUNDS., 7%

If the heart beats rapidly and feebly—if the blood-pressure in the aorta and pulmonary
artery be low, the signs of closure of the pulmonary valves may be absent—as in curve L—
taken from a girl suffering from nervous palpitation and morbus Basedowii.

In very rare cases of insufficiency of the mitral valve, it has been observed that at certain
times both ventricles contract simultaneously, as in a normal heart, but that this alternates
with a condition where the right ventricle alone seems to contract. Curve M is such a curve
obtained by Malbranc, who called this condition intermittent hemisystole. The first curve
(I.) is like a normal curve, during which the whole heart acted as usual. The curve II., how-
ever, is caused by the right side of the heart alone ; it wants the closure of the aortic valves, d,
and there was no pulse in the arteries. Owing to insufficiency of the tricuspid valve, the same
person had a venous pulse with every cardiac impulse, so that the arterial and venous pulses
first occurred together, and then the venous pulse alone occurred. In these cases the mitral
insufficiency leads to the right ventricle being overdistended, while the left is nearly empty, so
that the right side requires to contract more energetically than the left, It does not seem that
the right ventricle alone contracts in these cases, but rather that the action of the left side is
very feeble.

53. THE HEART-SOUNDS.—On listening over the region of. the heart in a
healthy man, either with the ear applied directly to the chest-wall (Harvey), or by
means of a stethoscope (Laennec, 1819), we hear two characteristic sounds, the so-
called ‘“‘ heart-sdunds.’’ The two sounds are called first and second, and together
they correspond to a single cardiac cycle. These sounds are separated by silences.
[Fig. 50 shows the relation of the events occurring in the heart during a cardiac
cycle to the sounds and silences. |

1. The first sound.

2. The first or short silence.

3. The second sound.

4. The second or long silence.

[Relative Duration.-—There is no absolute duration of each phase of a cardiac
cycle, but we may take the average duration calculated from the measurements of
Gibson, in a case of fissure of the sternum, to be as
follows :—

Auricular systole, : "112 sec.

Ventricular systole, : : "368 ,,

Ventricular diastole, . : yee
Cardiac cycle, 1°058 sec.

Suppose we divide the cycle into tenths ( Walshe),
then the first sound will last 545, the first silence 54,
the second sound ;%, and the long silence ;%, of the
entire period. | Fig. 50.

The first sound [long or systolic] is twice as long gcheme of a cardiac cycle. The
as, somewhat duller, and one-third or one-fourth inner circle shows what events

deeper, than the second sound; it is less sharply occur in the heart, and the
outer, the relation of the sounds

and silences to these events, —

the ventricles.

The second sound [short or diastolic] is clearer, sharper, shorter, more sudden,
and is one-third to one-fourth higher ; it is sharply defined and synchronous with
the closure of the semi-lunar valves, ‘The sounds emitted during each cardiac cycle
have been compared to the pronunciation of the syllables Jubb, ditp, Or the result
may be expressed thus— fa Fuay

V V
ssi? T ener TEs Tht ae T SEE Sw
[= = t = to F =s 15 =

ry 5 . S obi 7 Ue ;
Bu - tip. br Bul e - tip.

72 CAUSES OF THE HEART-SOUNDS.

[It is to be remembered that in reality fowr sounds are produced in the heart,
but the two first sounds occur together and the two second, so that only a single
first and a single second sound are heard. |

The causes of the first sound are due to two conditions. As the sound is heard,
although enfeebled, in an excised heart in which the movements of the valves are
arrested, and also when the finger is introduced into the auriculo-ventricular orifices
so as to prevent the closure of the valves (C. Ludwig and Dogiel), one of. the chief
factors lies in the “ muscle sound” produced by the contracting muscular fibres of
the ventricles. This sound is supported and increased by the sound produced by
the tension and vibration of the auriculo-ventricular valves and their chorde
tendinez, at the moment of the ventricular systole. Wintrich, by means of proper
resonators, has analysed the first sound and distinguished the clear, short, valvular
part from the deep, long, muscular sound.

The miusele-sound produced by transversely-striped muscle does not occur with a simple con-
traction (p. 86), but only when several contractions are superposed to produce tetanus (§ 303).
The ventricular contraction is only a simple contraction, but it lasts considerably longer than
the contraction of other muscles, and herein lies the cause of the occurrence of the muscle-sound
during the ventricular contraction.

Defective Heart-Sounds.—In certain conditions (typhus, fatty degeneration of the heart),
where the muscular substance of the heart is much weakened, the first sound may be completely
inaudible. In aortic insufficiency, in consequence of the reflux of blood from the aorta: into
the ventricle, the mitral valveis gradually stretched, and sometimes even before the beginning
of the ventricular systole, the first sound may be absent. Such pathological conditions seem to
show that, for the production of the first sound, muscle-sound and valve-sound must eventually
work together, and that the tone is altered, or may even disappear, when one of these causes is
absent. [Yeo and Barrett state that the sound is purely muscular (?).]

The cause of the second sound is undoubtedly due to the prompt closure, and
therefore sudden stretching or tension, of the semi-lunar valves of the aorta and
pulmonary artery, so that it is purely a valvular sound. Perhaps it is augmented
by the sudden vibration of the fluid-particles in the large arterial trunks. [The
second sound has all the characters of a valvular sound. That the aortic valves
are concerned in its production, is proved by introducing a curved wire through the
left carotid artery and hooking up one or more segments of the valve, when the
sound is modified, and it may disappear or be replaced by an abnormal sound or
“murmur.” Again, when these valves are diseased, the sound is altered, and it
may be accompanied or even displaced by murmurs.] Although the aortic and
pulmonary valves do not close simultaneously, usually the difference in time is
so small that both valves make one sound, but the second sound may be double
or divided when, through increase of the difference of pressure in the aorta
and pulmonary artery, the interval becomes longer. Even in health this may be
a rot as occurs at the end of inspiration or the beginning of expiration (v,

ch). :

Where the Sounds are Heard Loudest.—The sound produced by the tricuspid
valve is heard loudest at the junction of the lower right costal cartilages with the
sternum ; as the mitral valve lies more to the left and deeper in the chest, and is
covered in front by the arterial orifice, the mitral sound is best heard at the apex-
beat, or immediately above it, where a strip of the left ventricle lies next the chest-
wall. (The sound is conducted to the part nearest the ear of the listener by the
muscular substance of the heart.] The aortic and pulmonary orifices lie so close
together that it is convenient to listen for the second (aortic) sound in the direction
of the aorta, where it comes nearest to the surface, ¢.¢., over the second right costal —
cartilage or aortic cartilage close to its junction with the sternum. The sound,
although produced at the semi-lunar valves, is carried upwards by the column of
blood, and by the walls of the aorta. The sound produced by the pulmonary artery
is heard most distinctly over the third left costal cartilage, somewhat to the left
and external to the margin of the sternum (fig. 51). © .

VARIATIONS OF THE HEART-SOUNDS. 73

54. VARIATIONS OF THE HEART-SOUNDS. —Increase of the first sound of both ventricles
indicates a more energetic contraction of the ventricles and a simultaneously greater and more
sudden tension of the auriculo-ventricular valves. Increase of the second sound is a sign of
increased tension in the interior of the corresponding large arteries. Hence increase of the

Tip MMA TT ft
tN tbene

ue

t

EN
typi

‘if

\ .

Ne,
\ Aw

7 |
Fig. 51.

The heart—its several parts and great vessels in relation to the front of the thorax. The lungs
are collapsed to their normal extent, as after death, exposing the heart. The outlines of
the several parts of the heart are indicated by very fine dotted lines. The area of pro-
pagation of valvular murmurs is marked out by more visible dotted lines. A, the circle
of mitral murmur, corresponds to the left apex. The broad and somewhat diffused area,
roughly triangular, is the region of tricuspid murmurs, and corresponds generally with
the right ventricle, where it is least covered by lung. The letter C is in its centre. The
circumscribed circular area, D, is the part over which the pulmonic arterial murmurs
are commonly heard loudest. In many cases it is an inch, or even more, lower down,
corresponding to the conus arteriosus of the right véntricle, where it touches the wall of
the thorax. The internal organs and parts of organs are indicated by letters as follows :—
r.au, right auricle, traced in fine dotting; ao, arch of aorta, seen in the first intercostal

_ Space, Andettaged in fine dotting on the sternum ;.v.7., the two innominate veins; 7.%,
right ventricle ; .v., left ventricle. “4

second (pulmonary) sound indicates overfilling and excessive tension in the pulmonary circuit.
A feeble action of the heart, as well as abnormal want. of blood in the heart, causes weak
heart-sounds, which is the case in degenerations of the heart-muscle. -

Irregularities in structure of the individual valves may cause the heart-sounds {to become

é

74 DURATION OF THE MOVEMENTS OF THE HEART.

‘‘impure.” Ifa pathological cavity, filled with air, be so placed, and of such a form as to act
as a resonator to the heart-sounds, they may assume a ‘‘metallic’”’ character. The first and
second sounds may be ‘‘reduplicated” or [although ‘‘ duplication” is a more accurate term
(Barr)] doubled. “The reduplication of the first sound is explained by the tension of the
tricuspid and that of the mitral valves not occurring simultaneously. Sometimes in disease a
sound is produced by a hypertrophied auricle producing an audible presystolic sound, 7.¢., a
sound or ‘‘murmur,” preceding the first sound. [This has been questioned quite recently. ]
As the aortic and pulmonary valves do not close quite simultaneously, a reduplicated second sound
is only an increase of a physiological condition. All conditions which cause the aortic valves
to close rapidly (diminished amount of blood in the left ventricle) and the pulmonary valves to
close later (congestion of the right ventricle—both conditions together in mitral stenosis),
favour the production of a reduplicated second sound. :

Cardiac Murmurs.—If irregularities occur in the valves, either in cases of stenosis or in
insufficiency, so that the blood is subjected to vibratory oscillations and friction, then, instead
of the heart-sounds, other sounds—murmurs or bruits—arise or accompany these. A combina-
tion of these sounds is always accompanied by disturbances of the circulation. [These murmurs
may be produced within the heart, when they are termed endocardial ; or outside it, when they
are called exocardial murmurs. But other murmurs are due to changes in the quality or
amount of the blood, when they are spoken of as hemic murmurs. In the study of all murmurs,
note their rhythm or exact relation to the normal sounds, their point of maximum intensity, and
the direction in which the murmur is propagated.] It is rare that tumours or other deposits
projecting into the ventricles cause murmurs, unless there be present at the same time lesions
of the valves and disturbances of the circulation. The cardiac murmurs are always related to
the systole or diastole, and usually the systolic are more accentuated and louder. Sometimes
they are so loud that the thorax trembles under their irregular oscillations (fremitus, frémisse-
ment cataire),

In cases where diastolic murmurs are heard, there are always anatomical changes in the cardiac
mechanism. These are insufficiency of the arterial valves, or stenosis of the auriculo-ventricular
orifice (usually the left). Systolic murmurs do not always necessitate a disturbance in the
cardiac mechanism. They may occur on the left side, owing to insufficiency of the mitral
valve, stenosis of the aorta, and in the calcification and dilatation of the ascending part of the
aorta. These murmurs occur very much less frequently on the right side, and are due to
insufficiency of the tricuspid and stenosis of the pulmonary orifice.

Functional Murmurs.-—Systolic murmurs often occur without any valvular lesion, although
they are always less loud, and are caused by abnormal vibrations of the valves or arterial walls,
They occur most frequently at the orifice of the pulmonary artery [and are generally heard at
the base], less frequently at the mitral, and still less frequently at the aortic or the tricuspid
orifice. Anmia, general malnutrition, acute febrile affections, are the causes of these murmurs.
[Some of these are due to an altered condition of the blood, and are called hemic, and others
to defective cardiac muscular nutrition, and are called dynamic ( Walshe). |

Sounds may also occur during a certain stage of inflammation of the pericardium (pericarditis)
from the roughened surfaces of this membrane rubbing upon each other. Audible friction
sounds are thus produced, and the vibration may even be perceptible to touch. [These are
‘* friction sounds,” and quite distinct from sounds produced within the heart itself. ]

55. DURATION OF THE MOVEMENTS OF THE HEART.—The heart con-
tinues to beat for some time after it is
cut out of the body. The movement
lasts longer in cold-blooded animals (frog,
turtle)—extending even to days—than in
mammals. <A rabbit’s heart beats from
3 minutes up to 36 minutes after it is cut
out of the body. The average of many
experiments is about 11 minutes. [Waller
and Reid recorded the ventricular contrac-
tions of a rabbit’s heart 72 minutes after
its excision. Fig, 52 shows the prolonga-
Fig. 52. tion of the ventricular systole in an ex-

Curves of excised rabbit’s heart, 1, 6 mins. after cised rabbit’s heart, the movements bein

excision ; 2, 10 mins.; 3, 20 mins.; 4, 70 recorded by a lever resting on the heart.
- mins. (after Waller and Reid). Panum found the last trace of contraction
to occur in the right auricle (rabbit) 15 hours after death ; in a mouse’s' heart, 46
hours; in a dog’s, 96 hours. An excised frog’s heart beats, at the longest, 24 days

"
:

PHYSICAL EXAMINATION OF THE HEART. 75

(Valentin). In a human embryo (third month) the heart was found beating after
4 hours. In this condition stimulation causes an increase and acceleration of the
action. The ventricular contraction weakens, and soon each auricular contraction is
not followed by a ventricular contraction, two or more of the former being suc-
ceeded by only one of the latter. At the same time the ventricles contract more
slowly (fig. 46), and soon stop altogether, while the auricles continue to beat. If
the ventricles -be stimulated directly, as by pricking them with a pin, they may
execute a contraction. The left auricle soon ceases to beat, while the right auricle
still continues to contract. The right auricular appendix continues to beat longest,
as was observed by Galen and Cardanus (1550), and it is termed “ultimum
moriens.” Similar observations have been made upon the hearts of persons who
have been executed.
If the heart has ceased to beat, it may be excited to contract for a short time by
direct stimulation, more especially by heat (/arvey); even under these circum-
stances the auricles and their appendices are the last parts to cease contracting.
As a general rule, direct stimulation, although it may cause the heart to act more
vigorously for a short time, brings it to rest sooner. In such cases, therefore, the
regular sequence of events ceases, and there is usually a twitching movement of the
muscular fibres of the heart. C. Ludwig found that, even after the excitability is
extinguished in the mammalian heart, it may be restored by injecting arterial blood
into the coronary arteries: conversely lesion of these vessels is followed by
enfeebled action of the heart (§ 47). Hammer found that in a man, whose left
coronary artery was plugged, the pulse fell from 80 to 8 beats per minute.

[The beats of the excised heart of a rabbit gradually decline in force and frequency, the latent
period and contraction become longer and the excitability more obtuse. The duration of a con-
traction may be 6 sec., the normal being °3 sec. The beats have often a bigeminal character. An
excised heart may be frozen quite hard, yet on being thawed it contracts spontaneously. The
contraction proceeds in a wave from the spot stimulated in the frog’s heart at 8° to 12° C. at 30
to 90 mm. per sec.; in the mammalian excised heart about 8 metres per sec. (Waller and Reid). |

Action of Gases on the Heart.—Dnuring its activity the heart uses O, and produces CO,, so
that it beats longest in pure O (12 hours), and not so long in N,—H (1 hour)—CO, (10 minutes)
—CO (42 minutes)—Cl (2 minutes), or in a vacuum (20 to 30 minutes), even when there is watery
vapour present to prevent evaporation. If the heart be reintroduced into O it begins to beat
again. [A frog’s heart ceases to beat in compressed O (10 to 12 atmospheres) in about one-third
-of the time it would do were it simply excised and left to itself. An excised heart suspended
in ordinary air beats three to four times as long as a heart which is placed upon a glass-plate. |

[56. PHYSICAL EXAMINATION OF THE HEART.—The physical
methods of diagnosis enable us to obtain precise knowledge regarding the actual

state of the heart. The methods available are :-—

1. Inspection, 3. Percussion.

2. Palpation. 4, Auscultation.
_To arrive at a correct’diagnosis all the methods must be employed. |
[Inspection.—The person is supposed to have his chest exposed and to be in the recumbent

_ position. It is important to remember the limits of the heart. The dase corresponds to a line
Joining the upper margins of the third costal cartilages, the apex to the fifth interspace, while trans-

versely it extends from a little to the right of the sternum to within a little of the left nipple ;
this area occupied by the heart being called the deep cardiac region. By the eye we can detect
any alteration in the configuration of the precordia, bulging or retraction of the region as a
whole or of the intercostal spaces, and we may detect.variations in the position, character,
extent of the cardiac impulse, or the presence of other visible pulsations. ] . )
[Palpation.—By placing the whole hand flat upon the precordia, we can ascertain the
presence or absence, the situation and extent, and any alterations in the characters of the apex-
eat; or we niay detect the existence of abnormal pulsations, vibrations, thrills, or friction in
this region. In feeling for the apex-beat; if it be at all feeble, it is well to make the patient
lean forward. Of course, it must be remembered that the whole heart may be displaced by
tumours or accumulations of fluids. pressing upon it, ¢.¢., conditions external to itself, or the
apex-beat may be displaced from causes avithin the heart itself, as in hypertrophy of the left
ventricle} - — : S-YSLS fool’ OW “Ong :

76 THE CARDIAC NERVES.

[Percussion.—As the heart is a solid organ, and is surrounded by the lungs, which contain
air, it is evident that the sound emitted by striking the chest over the region of the former
must be different from that produced over the latter. Not only is there a difference in the
sound or note emitted, but the ‘‘ sensation of resistance” which one feels on percussing the two
organs is different. We may ascertain—

1. The superficial or absolute cardiac dulness.
2. The deep or relative dulness. ]

[Superficial Cardiac Dulness.—This theoretically is the part of the heart in direct contact
with the chest-wall and uncovered by lung, but obviously as the lungs vary in size during
respiration, it must be smaller during inspiration and larger during expiration. It forms a
roughly triangular space, whose base cannot be accurately determined, as the heart-dulness
merges into that of the liver, situate below it, but it corresponds to a horizontal line 24 inches
long, extending from the apex-beat to the middle of the sternum. The internal side corre-
sponding to the left edge of the sternum is 2 inches long, and reaches from the junction of the
fourth costal cartilage with the sternum—apex of the triangle—to the sternal end of the base
line. The superior, outer, or oblique line, 3 inches in length, is somewhat curved, and passes
downwards and outwards from the apex of the triangle to the apex of the heart. ]

[Deep Cardiac Dulness.—By this method theoretically we seek to define the exact limits of
the heart as a whole, and thus to ascertain its absolute size, and of course percussion has to be
done through a certain thickness of lung tissue, and hence one must strike the pleximeter
forcibly. It extends vertically from the third rib and ends at the sixth, but owing to the
cardiac merging in the hepatic dulness, this lower limit cannot be accurately ascertained ; while
transversely at the fourth rib it extends from just within the nipple line to slightly beyond the
right of the sternum. By these means we may detect increase in the size of the heart or altera-
tions in the relation of the lungs to the heart, fluid in pericardium, &c. ]

[Auscultation.—This is one of the most valuable methods, for by it we can detect variations.
and modifications in the healthy sounds of the heart, the rhythm and frequency of the heart-
beat, the existence of abnormal sounds, and their exact relation to the normal sounds, also
their characters and relation to the cardiac cycle, and. the direction in which these sounds are
propagated (§ 54).]

5'7. INNERVATION OF THE HEART. —[Intra- and Extra-Cardiac Nervous
Mechanism.—When the heart is removed from the body, or when all the nerves
which pass to it are divided, it still beats for some time, so that its movements
must depend upon some mechanism situated within itself. The ordinary rhythmical
movements of the heart are undoubtedly associated with the presence of nerve
ganglia, which exist in the substance of the heart—the intra-cardiac ganglia. But
the movements of the heart are influenced by nervous impulses which reach it from
without, so that there falls to be studied an intra-cardiac and an extra-cardiac
nervous mechanism. | :

The cardiac plexus is composed of the following nerves:—(1) The cardiac
branches of the vagus, the branch of the same name from the external branch of
the superior laryngeal, a branch from the inferior laryngeal, and sometimes branches
from the pulmonary plexus of the vagus (more numerous on the right side); (2)
- the superior, middle, inferior, and lowest cardiac branches of the three cervical
ganglia and the first thoracic ganglia of the sympathetic ; (3) the inconstant twig
of the descending branch of the hypoglossal nerve, which, according to Luschka,
arises from the upper cervical ganglion. From the plexus there proceed—the deep
and the superficial nerves (the latter usually at the division of the pulmonary |
artery under the arch of the aorta, and containing the ganglion of Wrisberg)
(§ 370). The following nerves may be separately traced from the plexus :—

(a) The plexus coronarius dexter and sinister, which contains the vaso-motor
nerves for the coronary vessels (physiological proof still wanting) as well as the’

nerves (sensory ?) proceeding from them (to the pericardium ). ry

(6) Intra-cardiac nerves and ganglia.—The nerves lying in the grooves of the
heart and in its substance contain numerous ganglia (Remak), and are regarded as
the automatic motor centres of the heart. “A nervous ring containing numerous
ganglia corresponds to the margin of the septum atriorum ; there is another in the

}

auriculo-ventricular groove. Where the two meet, they exchange ‘fibres, The

o

{

{
A
t
-

THE FROG’S HEART. a

ganglia usually lie near the pericardium. In mammals, the two largest ganglia lie
near the orifice of the superior vena cava—in birds, the largest ganglion (containing
thousands of ganglionic cells) lies posteriorly where the longitudinal and transverse
sulci cross each other. Fine branches, also provided with small ganglia, proceed
from these ganglia, and penetrate the muscular walls of the auricles and ventricles.

[Frog’s Heart.—The frog’s heart consists of the sinus venosus, into which open the single
inferior and the two superior vene cave (fig. 54). There are two auricles ; the right one com-
municates with the sinus venosus, and opens into the single ventricle ; the left auricle also

Fig. 53.
Heart of frog from the front. V, single ven- Heart of frog from behind. s.v., sinus ve-
tricle ; Ad, As, right and left auricles ; nosus opened ; cz, inferior ; csd, css, right
B, bulbus arteriosus ; 1, carotid, 2, aorta, and left superior vene cave; vp., pul-
and 3, pulmo-cutaneous arteries; C, ca- monary vein; Ad, and As, right and
rotid gland, left auricles ; Ap, communication between

the right and left auricle,

opens into the single ventricle (fig. 538, v), and in the latter are mixed the venous blood returned
by the right auricle and the arterial blood from the left auricle. The aorta with its bulbus
arteriosus conducts the blood from the ventricle. The various orifices are guarded by projec-

Fig. 56.
Auricular septum of a frog’s heart. a, an- Pyriform ganglionic bi-polar nerve-cell from
terior, and y, posterior branch of the car- the heart of a frog. m, sheath; n, straight
diac vagus ; B, Bidder’s ganglion. process ; 0, spiral process,

tions of tissue, which act like valves, The two auricles are completely separated by a septum.
This septum, ends posteriorly in a free concave margin so as to divide the auriculo-ventricular
orifice into a right and a left orifice. Each orifice is guarded by two thick fleshy valves, which
close it.] "

_ [Nerves.—The two cardiac branches of the vagi—the nervi cardiaci-—proceed to the posterior
_ surface of the sinus venosus, and where the latter joins the auricle they interlace, and are mixed

with a number of ganglion cells (fig. 57). This spot is called Remak’s ganglion, is sometimes

78 MOTOR CENTRES OF THE HEART.

single, at others double, and it can be seen as a white ‘‘ crescent ” when the heart is lifted up -
and looked at from behind (fig. 54). The cardiac nerves proceed downwards on the auricular
septum, exchanging fibres in their course to join two ganglia at the auriculo-ventricular groove,
and known as Bidder’s ganglia (fig. 57). It has been stated by one observer that the bulbus
arteriosus contains ganglionic cells, but this is denied by others. ] a
According to Openchowsky, every part of the heart (frog, triton, tortoise) contains. nerve-
fibres which are connected with every muscular fibre. In the auricles, at the end of the non-

ys (J ce
2

a

1

Fig. 57. Fig. 58.

Scheme of nerves of frog’s heart. Stannius’s experiment. A, auricle ;
R. Remak’s, and B, Bidder’s gan- V, ventricle ; 8. ¥. , Sinus venosus.
glia; S.V., sinus venosus; A, The zig-zag lines indicate which
auricles; V, ventricle; B.A., parts continue to beat; in 2 the
bulbus arteriosus ; vag, vagi. ventricle beats at a different rate.

medullated fibre, a tri-radiate nucleus exists which gives off fibrils to the muscular bundles.
There is a network of fine nerve-fibres distributed immediately under the endocardium—these-
fibres act partly in a centripetal direction on the cardiac ganglia, and are partly motor for the
endocardial muscles. The parietal layer of the pericardium contains (sensory) nerve-fibres,
The following kinds of nerve-cells are found—wunipolar cells, the single processes of which after-
wards divide ; bipolar pyriform cells (fig. 56), which in the frog possess a-straight (7) and
usually also a spiral process (0).

58. THE AUTOMATIC MOTOR CENTRES OF THE HEART.—(1) It is.
generally assumed that the nervous centres which excite the cardiac movements,.
and maintain the rhythm of these movements, lie within the heart, and that they
are probably represented by the ganglia.

(2) There are—not one, but several of these centres in the heart, which are:
connected with each other by conducting paths. As long as the heart is intact, all
its parts move in rhythmical sequence from a principal central point, an impulse.
being conducted from this centre through the conducting paths. What the
‘discharging forces” of these regular progressive movements are, is unknown.
If, however, the heart be subjected to the action of diffuse stimuli (e¢.g., strong
electrical currents), all the centres are thrown into action, and a spasm-like action
of the heart occurs. The dominating centre lies in the auricles, hence the regular:
progressive movement usually starts from them. If the excitability is diminished,
as by touching the septum with opium, other centres seem to undertake this.
function, in which case the movement may extend from the ventricles to the:
auricles. According to Kronecker and Schmey, in the dog’s heart there is a spot.
above the lower limit of the upper third of the ventricular septum, which, when it. |
is injured, e.y., by destroying it with a stout needle, brings the heart to a stand-
still ; this has been called a co-ordinating centre.

(3) All stimuli of moderate strength applied directly to. the heart cause at first.
an increase of the rhythmical heart-beats ; stronger stimuli cause a diminution, and
it may be paralysis, which is often preceded by a convulsive movement. Increased.
activity exhausts the energy of the heart sooner. —

» (4) Single very weak stimuli, which have no effect on the heart when applied
singly, if repeated sufficiently often, may become active owing to “summation of
the stimuli” (v. Basch). gen 4

(5) Even the weakest stimulus which can excite a contraction always causes an
energetic contraction, z¢., “the minimal stimulus causes a maximal effect”
(Bowditch, Kronecker and Stirling). 3 1 Aa

EXPERIMENTS ON THE HEART. 79

(6) After every contraction of the heart there is a short period of ‘“ diminished
excitability ” or Marey’s “refractory period,” during which the heart is less
susceptible to further stimulation.

(7) The non-ganglionic apex of the heart, when it is not ermal no longer
beats spontaneously, but it responds each time by a single contraction to a single
direct. stimulus. If, however, a continuous stimulus, ¢.g., a continuous current of
electricity, be applied to it, it executes a series of beats. Such continuous stimuli
are obtained through a continuous pressure of fluid, exerted on the interior of the
heart or by moistening the heart with chemical substances. :

(8) The auricular centres seem to be more excitable than those of the ventricle ;
hence, in a heart left to itself the auricles pulsate longest.

(9) The heart may be excited (reflexly) from its inner surface. Weak stimuli
applied to the inner surface of the heart greatly accelerate the heart’s action, the
stimulus required being much feebler than that applied to the external surface of
the heart. Strong stimuli, which bring the heart to rest, also act more easily when
applied to the inner surface than when they are applied to its outer surface. The
ventricle is always the first part to be paralysed.

(10) In order that the heart may continue to contract, it is necessary that it be
supplied with a fluid which, in addition to O, must contain the necessary nutritive
materials. The most perfect fluid, of course, is blood. Hence the heart after a
time ceases to beat in an indifferent fluid (0°6 per cent. sodium chloride), but its
activity may be revived by supplying it with a proper nutritive fluid.

Cardiac Nutritive Fluids.—These nutritive fluids are such as contain serum-albumin, ¢.g.,
blood, serum, or lymph. Serum retains its nutritive properties even after it has been subjected
to diffusion (Martius and Kronecker). Milk and whey (v. Oft), normal saline solution mixed with
blood, albumin, or peptone, and 0°3 per cent. sodium carbonate (Kronecker, Merunowicz and
Stiénon), a trace of caustic soda (Gaule), or a solution of the salts of serum, are suitable. Alka-

line solution of soda revives a feebly beating heart by neutralising the acid formed in the cardiac
muscle, or normal saline containing calcic phosphate and potassic chloride (S. Ringer).

(11) The independent pulsations of parts of the heart which are devoid of
ganglia, show that the presence of ganglia is not absolutely necessary in order to
have rhythmical pulsation. Direct stimulation of the heart may cause these move-
ments. But the ganglia are more excitable than the heart muscle itself, and they
conduct the impulses which lead to the regular alternating action of the various
parts of the heart, so that, under normal circumstances, we must assume that the
action of the heart is governed by the ganglia.

(12) If a heart be cut into pieces, so that the individual pieces still remain
connected with each other, the regular peristaltic or wave-like movements proceeding
from the auricles to the ventricle may continue for a long time (Donders,
Engelmann). If the heart, however, be completely divided into two distinct pieces
(auricle and ventricle), the movements of both parts continue, but not in the same
sequence—they beat at different rates.

The chief experiments upon which the above statements are based are as
follows :— !

I. Experiments by cutting and ligaturing the heart. These experiments have
been made chiefly upon the heart of the frog. The ligature experiments are per-
formed by tightening and then relaxing a ligature placed around the heart, so that
the physiological connection is destroyed, while the anatomical or mechanical con-
nections (continuity of the cardiac wall, intact condition of its cavities) still exist.
The most important of these experiments are—

(1) Stannius’s Experiment.—If the sinus venosus of a frog’ s heart be separated
from the auricles, either by an incision or by a ligature, the auricles and ventricle
stand still in diastole, whilst the veins and the’ remainder of the sinus continue to
beat (fig. 58, 1), If a second incision be made at the auriculo-ventricular groove,

80 STANNIUS’'S EXPERIMENT,

as a rule the ventricle begins at once to beat again, whilst the auricles remain in

the condition of diastolic rest. [Thus the sinus venosus and ventricle continue to
beat, while the auricle stands still, but the two former no longer beat with the same
rhythm, the ventricle usually beats more slowly, as is shown in fig. 58, 2, by the
large zig-zags.] According to the position of the second ligature or incision, the
auricles may also beat along with the ventricles, or the auricles alone may. beat,

while the ventricles remain at rest.
Theoretical.—Various explanations of these experiments have been given :—(a) Remak’s
ganglion in the sinus venosus is distinguished by its great excitability, while Bidder’s ganglion
in the auriculo-ventricular groove is less excitable ; in the normal condition of the heart the
motor impulse is carried from the former to the latter. If the sinus venosus be separated from
the heart, Remak’s ganglion has no action on the heart. The heart stops for two reasons—
first, because Bidder’s ganglion alone has not sufficient energy to excite it to action, and because
the inhibitory fibres of the vagus going to the heart have been stimulated by being divided at
this point (Heidenhain). [That stimulation of the inhibitory fibres of the vagus is not the
cause of the standstill, is proved by the fact that the standstill occurs even after the adminis-
tration of atropine, which paralyses the cardiac inhibitory mechanism.] The passive heart,
however, may be made to contract by mechanically stimulating Bidder's ganglion, e.g., by a
slight prick with a needle in the auriculo-ventricular groove, or by the action of a constant :
current of moderate strength (Zckhard), the ventricular pulsation at the same time preceding
the auricular (v. Bezold, Bernstein), If the auriculo-ventricular groove be divided, the ventricle
pulsates again, because Bidder’s ganglion has been stimulated by the act of dividing it ; while,
at the same time, the ventricle is withdrawn from the inhibitory influence of the vagus pro-
duced by the first division at the sinus venosus. If the line of separation is so made that
Bidder’s ganglion remains attached to the auricles, these pulsate, and the ventricle rests ; if it
be divided into halves, the auricles and ventricles pulsate, each half being excited by the portion
of the ganglion in relation with it. (0) hewhung to another view, both Remak’s (a) and
Bidder’s ganglia () are motor centres, but in the auricles there is in addition an inhibitory
ganglionic system (c) (Bezold, Traube). Under normal circumstances a+0 is stronger than e,
while c is stronger than a or b separately, If the sinus venosus be separated it beats in virtue
of a ; on the other hand, the heart rests because c is stronger than b. If the section be made
at the level of the auriculo-ventricular groove, the auricles stand still owing to c, while the
ventricle beats owing to 0,
(2) If the ventricle of a frog’s heart be separated from the rest of the heart by
means of a ligature, or by an incision carried through it at the level of the
auriculo-ventricular groove, the sinus and atria pulsate undisturbed as before
(Descartes, 1644), but the ventricle stands still in diastole. A single local stimulus
applied to the ventricle is responded to by a single contraction. If the incision be
so made that the lower margin of the auricular septum remains attached to the
ventricle, the latter pulsates. Even the ventricles of a rabbit’s heart, when separated

with a part of the auricles in connection with them, pulsate (Zigerstedt),

[Gaskell’s Clamp.—Gaskell uses a clamp, regulated by a millimetre screw, to compress the
heart, and thus to obstruct the passage of impulses from one part of the heart to the other, or
to “‘block” the way, the pulsations of the auricles and ventricles being separately registered.
By compyessing the heart at the auriculo-ventricular groove, the ratio of auricular and ventri- Z
cular beats alters, and instead of being 1 : 1, there may be 2, 8, or more auricular beats for each |
beat of the ventricle, expressed thus— + ’ v ; at ; a . After the heart is fixed by the
clamp, levers are placed horizontally above and below the heart. These levers are fixed to part
of the auricles and to the apex by means of threads, Each part. of the heart attached to a
lever, as it contracts, pulls upon its own lever, so that the extent and duration of each con-
traction may be registered. This method is applicable for studying the effect of the vagus
and other nerves upon the heart. ]

_ (8) Section.—A. Fick showed that the process of excitement in the contractile
tissue of the frog’s heart is propagated in all directions (1874), so that to a certain
extent the whole frog’s heart behaves like one continuous muscular fibre, thus one
transverse cut into the ventricle does not prevent contraction: from taking place in
the separated parts. Engelmann’s experiments also show that if the ventricle of a
frog’s heart be cut up into two or more strips in a zig-zag way, so that the
individual parts still remain connected with each other by muscular tissue, the

ACTION OF FLUIDS ON THE HEART. 81

strips still beat in a regularly progressive rhythmical manner, provided one strip
is caused to contract. The rapidity of the transmission is about 10 to 15 mm. per
sec. Hence, it appears that the conducting paths for the impulse causing the con-
traction are not nervous, but must be the contractile mass itself. It has not been
proved that nerve-fibres proceed from the ganglia to all the muscles.

[According to Marchand’s experiments, it takes a very long time for the excitement to pass
from the auricles to the ventricle—a much longer time, in fact, than it would require to conduct
the excitement through muscle—so that it is probable that the propagation of the impulse from
the auricles to the ventricle is conducted by nervous channels to the auricnlo-ventricular
nervous apparatus. In fact, in the mammalian heart the muscular fibres of the auricles are
quite distinct from those of the ventricles. ]

(4) When the apex of a frog’s heart is ligatured off from the rest of the heart, it
no longer pulsates (Hezdenhain, Goltz), but such an apex, if stimulated directly,
e.g., by a prick of a pin, responds with a single coutraction. If the “ heart-apex ”
be filled with normal saline solution under pressure, which acts as a stimulus, the
heart begins to pulsate, and the same is the case with a solution of delphinin or
quinine. If a cannula be tied into the heart over the auriculo-ventricular groove,
the ventricle does not beat, but if the ventricle be filled through the cannula with
blood containing oxygen, under a constant and sufficient pressure, it also pulsates
(Ludwig and Merunowiz).

[(5) Luciani found that a heart ligatured above the auriculo-ventricular groove,
when filled with pure serum, produced groups of pulsations with a long diastolic
pause between every two groups (fig. 59). The successive beats in each group

i! 7
|
_—a |

+ ae

———2
rT

Tr Le Ma pasa Samet Tome) T T T 7 T ae

Fig. 59.
Four groups of pulsations with intervening pauses, with their ‘‘ staircase” character. The
points on the abscissa were marked every 10 seconds.

assume a ‘‘staircase” character (p. 84). These periodic groups undergo many
changes ; they occur when the heart is filled with pure serum free from blood-
corpuscles, and they disappear and give place to regular pulsations when defibrinated
blood or serum containing hemoglobin or normal saline solution is used (Rossbach).
They also occur when the blood within the heart has become dark-coloured, 2.e.,
when it has been deprived of certain of its constituents, and if a trace of veratrin
be added to bright red blood they occur. |

(6) An apex.preparation, when stimulated with even a weak induction shock,
always gives its maximal contraction, and when a tetanising current is applied,
tetanus does not occur (Kronecker and Stirling). When the opening and closing
shocks of a sufficiently strong constant current are applied to the heart-apex, it
contracts with each closing or opening shock. [When a constant current is applied

- to the lower two-thirds of the ventricle (heart-apex), under certain conditions the

apex contracts rhythmically. This is an important fact in connection with any

theory of the cardiac beat. |

_ (7) If the bulbus aorte (frog) be ligatured, it still pulsates, provided the internal

pressure be moderate.. Should it cease to beat, a single stimulus makes it respond

by a series of contractions. Increase of temperature to 35° C., and raising the

pressure within it, increase the number of pulsations (Zngelmann). :
Action of Fluids.—Haller was of opinion that the venous blood was the natural

stimulus which caused the heart to contract. That this is not so, is proved at once
| wok

82 ACTION OF FLUIDS ON THE HEART.

by the fact that the heart beats rhythmically when it contains no blood. Blood
and other fluids which are supplied to an excised heart are not the cause of its
rhythmical movements, but only the conditions on which these movements depend.

(Methods.—The study of the action of fluids upon the excised frog’s heart has been rendered
possible by the invention of Ludwig's ‘‘frog-manometer.’’ The apparatus (fig. 60) consists
; of (1) a double-way cannula, c, which is tied into the
heart, A; (2) a manometer, m, connected with ¢c, and
registering the movements of its mercury on a bidity.
cylinder, cyl ; (3) two Mariotte’s flasks, a and b, whic
are connected with the other limb of the cannula.
Either a or } can be placed in communication with the
interior of the heart by means of the stop-vock, s. The
fluid in one graduated tube may be poisoned, and the
other not; d@ is a glass vessel for fluid, in which the
heart pulsates, ¢’ and ¢ are electrodes, ¢ is inserted into
the fluid in d, e’ is attached to the German silver cannula
which is shown in fig. 61.]

[In the tonometer of Roy (fig. 62) the ventricle, A,
or the whole heart, is placed in an air-tight chamber, 9,
filled with oil. As before, a ‘‘ perfusion” cannula is
tied into the heart. A piston, y, works up and down in
a cylinder, and is adjusted by means of a thin flexible
animal membrane, such as is used by perfumers,
Attached to the piston by means of a thread is a

) writing-lever, 2, which records the variations of pres-

a sure within the chamber, 0. When the ventricle con- |

ay tracts, it becomes smaller, diminishes the pressure within |

Fig. 60 o, and hence the piston and lever rise ; conversely, when |
sn the heart dilates, the lever and piston descend. Varia-

Scheme of a frog-manometer. @, %, tions in the volume of the ventricle may be registered
} ’ ha + . ’
Mariotte’s flasks for the nutrient without in any way interfering with the flow, at fluids =
fluids ; s, stop-cock; c, cannula; m, thronch it ] )
: 5 5 5 :

Pa aes pp isenepae eo ee [Two preparations of the frog’s heart have been used
a a 9 CY", ms —(1) The “heart,” in which case the cannula is intro-

: f duced into the heart through the sinus venosus, and

a ligature is tied over it around the auricle, i.e., above the auriculo-ventricular groove, Thus
the auriculo-ventricular ganglia and other nervous structures remain in the preparation. This
was the heart preparation em-
ployed by Luciani and Rossbach.
(2) In the ‘‘heart-apex” or
apex preparation, the cannula
is introduced as before, but the
ligature is tied on it over the
ventricle, several millimetres
below the auriculo-ventricular
groove, so that this preparation
contains none of the auriculo-
ventricular ganglia, and, accord-
ing to the usual statement, this
part of the heart is devoid of
nerve ganglia. This is the pre-
aration which was used by
owditch, Kronecker and Stir-
ling, Merunowicz, and others.

Es

Fig. 61.
Perfusion cannula for a frog’s l all
heart. c, for fixing an electrode;
d, the heart is tied over the Fig. 62.
flanges, preventing it from Roy’s heart tonometer. h, heart ; 0, air-tight chamber ;
slipping out ; ¢, section of d. p, piston ; 1, writing-lever ; e, outflow tube.

The first effect of the application of the ligature in both cases is, that both preparations cease to

beat, but the ‘‘ heart” usually resumes its rhythmical contractions within wconslthaubel i

the “ heart-apex ” does not contract spontaneously until after a much longer time (10 to 90 )
{If the ‘‘ heart-apex ” be filled with a 0°6 per cent. solution of common salt, the contrac

are at first of greater extent, but they afterwards cease, and the preparation passes intoacon-

ACTION OF HEAT AND DRUGS ON THE HEART. 83

dition of “‘apparent death,” lasting 30-90 mins. ; while, if the action of the fluid be prolonged,
the heart may not contract at all, even when it is stimulated electrically or mechanically. It
may be made, however, to pulsate again, if it be supplied. with saline solution containing blood
(1 to 10 per cent.). Ifthe ventricle be nipped with wire forceps at the junction of the upper
with its middle third, so as to separate the lower two-thirds of the ventricle, physiologically but
not anatomically, from the rest of the heart, then the apex will cease to contract, although it is
still supplied with the frog’s own blood (Bernstein, Bowditch). The physiologically isolated
apex may be made to beat by clamping the aortic branches so as to prevent blood passing out
of the heart, and thus raising the intracardiac pressure. The rate of the beat of the apex is
independent of and slower than that of the rest of the heart. This experiment proves that the
amount of pressure within the apex-cavity is an important factor in the causation of the spon-
taneous beats of the apex. If blood-serum, to which a trace of delphinin is added, be trans-
fused or ‘‘ perfused” through the heart, it begins to beat within a minute, continues to beat for
several seconds, and then stands still in diastole (Bowditch). Quinine and a mixture of atropine
and muscarin have a similar action. These experiments show that, provided no nervous appar-
atus exists within the heart-apex, the cause of the varying contraction is to be sought for in the
musculature of the heart, and that the stimulus necessary for the systole of the heart’s apex
may arise within itself. If there is no nervous apparatus of any kind present, then we must
assume that the heart-muscle may execute rhythmical movements independently of the presence
of any nervous mechanism, although it is usually assumed that the ganglia excite the heart-
muscle to pulsate rhythmically. It is by no means definitely proved that the heart-apex is
devoid of all nervous structures, which may act as originators of these rhythmical impulses. ]

[Action of Drugs.—If the heart-apex contains no nervous structures, it must form a good
object for the study of the action of drugs on the cardiac muscle. Some of these have been
mentioned already. Ringer finds that a calcium salt makes the contractions higher and longer.
Dilute acids added to saline solution, ¢.g., lactic, cause complete relaxation of the cardiac
musculature, while dilute alkalies produce an opposite effect or tonic contraction, even though
the apex be not pulsating. The action of a dilute acid may be set aside by a dilute alkali and
vice versd. LDigitalin, antiarin, barium, and veratria act like alkalies, while saponin, muscarin,
and pilocarpin have the effect of acids (§ 65). An isolated frog’s heart, fatigued after being

supplied with a solution of blood, is caused to beat more vigor-
ously by a solution of kreatinin, or extract of meat (Jays). ]

[The ‘‘ heart” preparation in many respects behaves like the
foregoing, ¢.¢., it is exhausted after a time by the continued appli-
cation of normal saline solution (0°6 per cent. NaCl), while its
activity may be restored by supplying it with albuminous and
other fluids (p. 79).]

If. Direct Stimulation of the Heart.—All direct
cardiac stimuli act more energetically on the inner than
on the outer surface of the heart. If strong stimuli are
applied for too long a time, the ventricle is the part first
paralysed.

(a) Thermal Stimuli.—[Heat affects the number or frequency

C

Fig. 63.
A, contractions of a frog’s heart at 19° C.; B, at 34°C. ; C, at 3° C.

and the amplitude of the pulsations, as well as the dwration of the systole and diastole and
the excitability of the heart.] Descartes (1644) observed that heat increases the number of
pulsations of an eel’s heart. As the temperature increases, the number of beats is at first con-
siderably increased, but afterwards the beats again. become fewer, and if the temperature Is
raised above a certain limit the heart stands still, the myosin of which its fibres consist is
coagulated, and ‘‘heat-rigor” occurs. Even before this stage is reached, however, the heart
may stand still, the muscular fibres appearing to remain contracted. The ventricles usually
cease to beat before the auricles (Schelske). The size and extent of the contractions increase up
to about 20°-C., but above this point they diminish (fig. 63). The time occupied by any single

ae ACTION OF MECHANICAL AND ELECTRICAL STIMULI.

contraction at 20° C. is only about 44, of the time occupied by a contraction occurring at 5° C.
A heart which has been warmed is capable of reacting I rps rapidly to intermittent stimuli,
while a heart at a low temperature reacts only to stimuli occurring at a considerable interval
(Gold. —When the temperature of the blood is diminished, the heart beats more ey: A
frog’s heart, placed between two watch-glasses and laid on ice, beats very much more slowly.
The pulsations of a frog's heart stop when the heart is exposed to a temperature of 4° C. to 0°.
If a frog’s heart be taken out of warm water, and suddenly placed upon ice, it beats more
rapidly, and conversely, if it be taken from ice and placed over warm water, it beats more
slowly at first and more rapidly afterwards (Aristow). _ ;
[Methods.—The effect of heat on a heart may be studied by the aid of the frog-manometer, the
fluid in which the heart is placed being raised to any temperature required. For demonstra-
tion purposes, the heart of a pithed frog is excised and placed on a glass slide under a light
lever, such as a straw. The slide is warmed by means of a spirit-lamp. In this way the
frequency and amplitude of the contractions are readily made visible at a distance. ]
(6) Mechanical Stimuli.—Pressure applied to the heart from without accelerates its action.
In the case of Frau Serafin, v. Ziemssen found that slight pressure on the auriculo-ventricular
groove caused a second short contraction of both ventricles after the heart-beat. Strong pres-

sure causes a very irregular action of the cardiac muscle. This may readily be produced by ‘
compressing the freshly excised heart of a dog between the fingers. The intra-cardiac pressure
also affects the heart-beat (p. 83). If the pressure within the heart be increased, the heart- q

beats are gradually increased, if it be diminished the number of beats diminishes (Ludwig and
Thiry). If the intra-cardiac pressure be very greatly increased, the heart’s action becomes very
irregular and slower. A heart which has ceased to beat may, under certain circumstances, be
caused to execute a single contraction if it be stimulated mechanically. :

(c) Electrical Stimuli.—A constant electrical current ,of moderate strength increases the
number of heart-beats. V. Ziemssen found, in the case of Frau Serafin (§ 47, 3), that the
number of beats was doubled when a constant uninterrupted strong current was passed through
the ventricles. If the constant current be very strong, or if tetanising induction currents be
used, the cardiac muscle assumes a condition resembling, but not identical with, tetanus.
(Ludwig and Hoffa), and of course this results in a fall of the blood-pressure. If the auriculo-
ventricular groove be compressed so as to cause the ventricle of a frog’s heart to cease to beat,
on placing one electrode of a constant current on the ventricular wall and the other electrode
on an indifferent part of the body, we obtain on making the current, a systolic contraction of
the ventricle only when the cathode touches the ventricle; and conversely on breaking, only
when the anode is on the heart (Biedermann).

When a single induction shock is applied to the ventricle of a frog’s heart during systole, it
has no apparent effect ; but if it is applied during diastole, the succeeding contraction takes
place sooner. The auricles and also the apex behave in a similar manner. ° Whilst they are
contracted, an induction shock has no effect; if, however, the stimulus is applied during
diastole, it causes a contraction, which is followed by systole’of the ventricle. Even when
strong tetanising induction shocks are applied to the heart, they do not produce tetanus of the
entire cardiac musculature, or as it is said, ‘‘the heart knows no tetanus” (Kronecker and
Stirling). Small white local weal-like elevations—such as occur when the intestinal muscula-
ture is stimulated—appear between the electrodes. They may last several minutes. A frog’s
heart, which yields weak and irregular contractions, may be made to execute regular rhythmical
contractions synchronous with the stimuli, if electrical stimuli are used (Bowditch).

{Break induction shocks, if of sufficient strength, cause the heart to contract, while weak :
stimuli have no effect ; on the other hand, moderate stimuli, when they do cause the heart to an
contract, always cause a maximal contraction, so that a minimal stimulus acts at the same time
like a maximal stimulus. The heart either contracts or it does not contract, and when it con-
tracts the result is always a ‘‘ maximal” contraction (Kronecker and Stirling). Bowditch found
that the excitability of the heart was increased by its own movements, so that after a heart had
once contracted, the strength of the stimulus required to excite the next contraction may be
greatly diminished, and yet the stimulus be effectual. Usually the amplitude of the first beat
so produced is not so great as-the second beat, and the second is less than the third, so that a -
*‘ staircase” (‘‘Treppe”) of beats of successively greater extent was produced (fig. 59). Under -
certain circumstances, however, a skeletal muscle gives contractions of a “ staircase” character.
This staircase arrangement occurs even when the strength of the stimulus is kept constant, so that
the production of one contraction facilitates the occurrence of the succeeding one. A staircase
arrangement of the pulsations is also seen in Luciani’s groups (p. 81). The question, whether
a stimulus will cause a contraction, depends upon whe partioulas phase the heart is in when
the shock is applied. Even comparatively weak stimuli will cause a heart to contract, provided
the stimuli are applied at the proper moment and in the.proper tempo, i.¢, to say, they become
what are called “infallible.” If stimuli are applied to the eart, at intervals which are 1
than the time the heart takes to execute its contraction, they are effectual or “ adequate,” b
if they are applied before the period of pulsation comes to an end, then they are ineffectual _ ~'

:
i
, *
rt
¥,

————e ee or,

ACTION OF CHEMICAL STIMULI AND GASES ON THE HEART. 85

(Kronecker). It is quite clear, therefore, that the relation of the strength of the stimulus to
the extent of the contraction of the cardiac muscle, is quite different from what occurs ina
muscle of the skeleton, where within certain limits the amplitude of the contraction bears a
relation to the stimulus, while in the heart the contraction is always maximal. |

Human Heart.—V. Ziemssen found that he could not alter the heart-beats of the human
heart (Frau Serafin, § 47, 3), even with strong induction-currents. The ventricular diastole
seemed to be less complete, and there were irregularities in its contraction. By opening and
closing, or by reversing a strong constant current applied to the heart, the. number of beats
was increased, and the increase corresponded with the number of electrical stimuli ; thus, when
the electrical stimuli were 120, 140, 180, the number of heart-beats was the same, the pulse
beforehand being 80. The normal pulse-rate of 80 was reduced to 60 and 50 when the number
of shocks was reduced in the same ratio. [In Frau Serafin’s case the electrodes were applied to
the heart, separated from it merely by the pericardium. Ziemssen found that: the Faradic
current did not modify the heart’s action when the thorax was intact, but that the constant
current did; if of sufficient strength. Herbst and Dixon Mann obtained negative results with
both kinds of electricity in the normal thorax. ]

(d@) Chemical Stimuli.—Many chemical substances, when applied in a dilute solution to the
inner surface of the heart, increase the heart-beats, while if they are concentrated, or allowed to
act too long, they diminish the heart-beats, and paralyse it. Bile, and bile salts, diminish the
hheart-beats (also when they are absorbed into the blood as in jaundice) ; in very dilute solu-
tions both increase the heart-beats. A similar result is produced by acetic, tartaric, citric, and
phosphoric acids. Chloroform and ether, applied to the inner surface, rapidly diminish the
heart-beats, and then paralyse it; but very small quantities of ether (1 per cent.) accelerate
the heart-beat of the frog (Kronecker and M‘Gregor-Robertson), while a solution of 14 to
‘2 per cent. passed through the heart arrests it temporarily or completely. Dilute solutions of
‘opium, strychnia, or alcohol applied to the endocardium, increase the heart-beats ; if concen-
‘trated they rapidly arrest its action. Chloral-hydrate paralyses the heart.

Action of Gases.—When blood containing different gases was passed through a frog’s heart,
Klug found that blood containing sulphurous acid rapidly and completely killed the heart ;
chlorine stimulated the heart at first, and ultimately killed it ; and laughing-gas rapidly killed
it also. Blood containing sulphuretted hydrogen paralysed the heart without stimulating it.
Carbonic oxide also paralysed it, but if fresh blood was transfused the heart recovered. [Blood
containing O excites the heart (Castel/), while the presence of much CO, paralyses it, and the
presence of CO, is more injurious than the want of O. Blood or serum completely saturated
with CO, exhausts the heart (Saltet and Kronecker), but it recovers itself when the CO, is
removed. H and N have no effect. ]

Cardiac Poisons are those substances whose action is characterised by special effects upon the
movements of the heart. Amongst these are neutral potash salts, which cause the heart to
stand still in diastole. An excised frog’s heart ceases to beat after one-half to one minute when
it is placed in a 2 per cent. solution of potassic chloride.] Even a very dilute solution of yellow
prussiate of potash injected into the heart of a frog causes the ventricle to stand still in systole.
Antiar (Java arrow-poison) causes the ventricle to stand still in systole and the auricles in
diastole. Some heart-poisons, in small doses, diminish the heart’s action, and in large doses
not unfrequently accelerate it, ¢.g., digitalis, morphia, nicotin. Others, when given in small

‘doses, accelerate its action, and in large doses slow it—veratria, aconitin, camphor.

Special Actions of Cardiac Poisons.—The complicated actions of various poisons upon the
heart have led observers to suppose that there are various intra-cardiac mechanisms on which
these substances may act. Besides the muscular fibres of the heart and its automatic ganglia,
some toxicologists assume that there are inhibitory ganglia into which the inhibitory fibres of
the vagus pass, and accélerator ganglia, which are connected with the accelerating nerve-fibres
of the heart. Both the inhibitory and accelerator ganglia are connected with; the automatic ganglia
‘by conducting channels. :

Muscarin and all other trimethylammonium bases stimulate permanently the inhibitory
ganglia, so that the heart stands still (Schmiedeberg and Koppe). [According to Gaskell, how-
ever, when the action of the sinus is arrested by muscarin, there is no deflection of the galvano-
meter similar to that produced by the excitation of the vagus: He infers that muscarin does not
-cause arrest of the beat by acting as an excitant of inhibitory mechanisms, but as a depressant
to motor activity.] As atropin and daturin paralyse thése ganglia, the standstill of the heart
brought about, by muscarin may be set aside by atropin. [If a frog’s heart be excised and placed
in a watch-glass, and a few drops of a very dilute solution of muscarin be placed on it with a
pipette, it ceases to beat within a few minutes, and will not beat again. If, however, the
tmuscarin be removed, and a solution of atropine applied to the heart, it will resume its con-
tractions after a short time.]. Physostigmin or Calabar bean excites the energy of the cardiac
muscle to stich an extent, that stimulation of the vagus no longer causes the heart to stand still.
Iodine-aldehyd, chloroform, and chloral-hydrate paralyse the automatic ganglia. The heart
stands still, and it cannot be made to contract again by atropine. The cardiac muscle itself
‘remains excitable after. the action of muscarin and iodine-aldehyd, so that if it be stimulated

t

86 THE CARDIO-PNEUMATIC MOVEMENT.

it contracts. [According to Gaskell, antiarin and digitalin solutions produce an alteration in
the condition of the muscular tissue of the apex of the heart of the same nature as that pro-
duced by the action of a very dilute alkali solution, while the action of a blood-solution contain-
ing muscarin closely resembles that of a dilute acid solution (p. 95, § 65).]

[Nature of a Cardiac Contraction.—The question as to whether this is a simple
contraction or a compound tetanic contraction has been much discussed. So
much is certain, that the systolic contraction of the heart is of very much longer
duration (8 to 10 times) than the contraction of a skeletal muscle produced by
stimulation of its motor nerve. When the sciatic nerve of a nerve-muscle pre-
paration is adjusted upon a contracting heart, a simple secondary twitch of the
limb, and not a tetanic spasm, is produced when the heart (auricle or ventricle)
contracts This of itself is not sufficient proof that the systole is a simple spasm,
for tetanus of a muscle does not in all cases give rise to secondary tetanus in the
leg of a rheoscopic limb. Thus, a simple “initial” contraction occurs when the
nerve is applied to a muscle tetanised by the action of strychnia, and the contracted
diaphragm gives a similar result. The question whether the heart can be tetanised

has been answered in the negative, and as yet it has not been shown that the

heart can be tetanised in the same way that a skeletal muscle is tetanised. |

[MacWilliam finds, when the quadriceps extensor cruris contracts to cause the knee-jerk, that
a sound similar to the first sound of the heart is heard. As the former is regarded as a simple
contraction, it is argued that a simple contraction can produce a muscle-sound. Frédéricq
regards the ventricular systole not as a simple contraction, but as composed of three or more
fused contractions corresponding to tetanus. This he concludes from a study of cardiograms as
well as from the electro-motive phenomena of the heart. ]

The peripheral or extra-cardiac nerves (S§ 369 and 370).

59. CARDIO-PNEUMATIC MOVEMENT.—As the heart within the thorax
occupies a smaller space during the systole than during the diastole, it follows that,
when the glottis is open, air must be drawn into the chest when the heart contracts ;
whenever the heart relaxes, z.e., during diastole, air must be expelled through the
open glottis. But we must also take into account the degree to which the larger
intra-thoracic vessels are filled with blood. These movements of the air within the
lungs, although slight, seem to be of importance in hybernating animals. In
animals in this condition, the agitation of the gases in the lungs favours the
exchange of CO, and O in the lungs, and this slow current of air is sufficient to
aerate the blood passing through the lungs. [Ceradini called the diminution of the
volume of the entire heart which occurs during systole meiocardia, and the
subsequent increase of volume, when the heart is distended to its maximum,
auxocardia. |

Method.—A manometric flame may be used. Insert one limb of a Y-tube into the opened
trachea of an animal, while the other limb passes to a small gas-jet, and connect the other tube with
the gas supply. The movements of the heart affect the column of gas, and thus affect the flame,
It may also be done in man by inserting the tube into one nostril, while the other nostril and
the mouth are closed. [A simpler and less irritating plan is to fill a wide curved .glass-tube
with tobacco smoke, and insert one end of the tube into one. nostril while the other nostril and
the mouth are closed. If the glottis be kept open, and respiration be stopped, then the move-
ments of the column of smoke within the tube are obvious. Ora manometer containing a drop
of a coloured fluid may be used under the same conditions. ]

cardiac pneumograph (fig. 64) consists of a tube (D), about 1. inch in diameter and |

6 to 8 inches in length ; the tube is bent at a right angle, and communicates with a small metal
capsule about the size of a saucer (T), over whiel :

oil is loosely stretched. To this membrane is attached a glass rod. (H) used as a writing-style,
which records its movements on a glass-plate (S) moved by clock-work. A small valve aa is

pied on the side of the tube (D), which enables the experimenter to breathe when n a,

he tube (D) is held in an air-tight manner between the lips, the nostrils being closed, the
glottis open, and respiration stopped. In the curves (fig. 64, A,B) we observe that— —
(1) At the moment of the first sound (1) the respiratory gases undergo a sharp &
movement, because at the moment of the first part of the ventricular systole the
ventricle has not left the thorax, while venous blood is streaming into the right auricle thro:
the ven cave, and because the dilating branches of. the pulmonary artery compress the

1 a membrane composed of collodion and castor —

INFLUENCE OF RESPIRATORY PRESSURE ON THE HEART. 87

accompanying bronchi. ©The blood of the right ventricle has not yet left the thorax, it passes
merely into the pulmonary circuit. The expiratory movement is diminished somewhat (a) by
the muscular mass of the ventricle occupying slightly less bulk during the contraction, and (8)
owing to the thoracic cavity being slightly increased by the fifth intercostal space being pushed
forward by the cardiac impulse.

(2) Immediately after (1) there follows a strong inspiratory current of the respiratory gases.
As soon as the blood from the root of the aorta reaches that part of the aorta lying outside the
thorax, more blood leaves the chest than passes into it simultaneously through the vene cave.

(3) After the second sound (at 2), indicated sometimes by a slight depression in the apex of

; Fig. 64.
Landois’ cardio-pneumograph, and the curves obtained therewith. A and B, from man, 1 and
2 correspond to the periods of the first and second heart-sounds; C, from dog; D, method
of using the apparatus.

the curve, the arterial blood accumulates, and hence there is another expiratory movement in
the curve.

(4) The peripheral wave-movements of the blood from the thorax cause another inspiratory
movement of the gases.

(5) More blood flows into the chest through the veins, and the next heart-beat occurs.

60. INFLUENCE OF THE RESPIRATORY PRESSURE ON THE HEART.
—The variation in pressure to which all the intra-thoracic organs are subjected,
owing to the increase and decrease in the size of the chest caused by the respiratory
movements, exerts an influence on the movements of the heart. Examine first the
relations in different passive conditions of the thorax, when the glottis 1s open.

The diastolic dilatation of the cavities of the heart, besides the pressure of the
venous blood and the elastic stretching of the relaxed muscle-wall, is fundamentally
due to the elastic traction of the lungs. This is stronger the more the lungs are
distended (inspiration), and is less active the more the lungs are contracted
(expiration). Hence it follows :— :

(1) When the greatest possible expiratory effort is made, (of course, with the
glottis open), only a small amount of blood flows into the heart ; the heart in
diastole is small and contains a'small amount of blood. Hence the systole must
also be small, thus causing a small pulse-beat.

(2) On taking the greatest possible inspiration (with the glottis open), and
therefore causing the greatest stretching of the-elastic tissue of the lungs, the elastic
traction of the lungs is, of course, greatest =30 mm. Hg (Donders), and may
interfere with the contraction of the thin-walled atria and appendices, in con-
sequence of which these cavities do not completely empty themselves into the
ventricles. The heart is in a state of great diastolic distension, and filled with

88 VALSALVA’S EXPERIMENT.

blood ; nevertheless, in consequence of the limited action of the auricles, only small
pulse-beats are observed. In several individuals Donders found the pulse to be
smaller and slower ; afterwards it became larger and faster.

(3) When the chest is in a position of moderate rest, whereby the elastic traction
is moderate = 7°5 mm. Hg, we have the condition most favourable to the action of the
heart—sufficient diastolic dilatation of the cavities of the heart, as well as un-
hindered emptying of them during systole.

Voluntary increase or diminution of the intra-thoracic pressure affects th
action of the heart. :

(1) Valsalva’s Experiment (1740).—If the thorax is fixed in the position of
deepest inspiration, and the glottis be then closed, and if a powerful expiratory
effort be made by bringing into action all the expiratory muscles, so as to contract

Fig. 65.
Apparatus for demonstrating the action of inspiration, II., and expiration, I., on the heart and
blood-stream. P, 2, lungs ; H, h, heart ; L, 7, closed glottis; M, m, manometers ; E, e,
ingoing blood-stream, vein ; A, a, outgoing blood-stream, artery ; D, diaphragm during
expiration ; d, during inspiration.

the chest, the cavities of the heart are so compressed that the circulation of the
blood is temporarily interrupted. In this expiratory phase the elastic traction is
very limited, and the air in the lungs being under a high pressure also acts upon
the heart and the intra-thoracic great vessels. .No blood can pass into the thorax
from without ; hence the visible veins swell up and become congested, the blood in
the lungs is rapidly forced into the left ventricle by the compressed air in the
lungs, and the blood soon passes out of the chest, so that the heart and lungs contain
eo blood, palestine , etanten supply of blood in the systemic than in the
pulmonary circulation and the heart, e heart-sounds di ls ‘
is absent (2. H. Weber, Donders), nie, Gasppest ee aaa

FLOW OF FLUIDS THROUGH TUBES. | 89

(2) J. Miiller’s Experiment (1838).—Conversely, if after the deepest possible
expiration the glottis be closed, and the chest be now dilated with a great
inspiratory effort, the heart is powerfully dilated, the elastic traction of the lungs,
and the very attenuated air in these organs, act so as to dilate the cavities of the
heart. More blood flows into the right Heart, and, in proportion as the right
auricle and ventricle can overcome the traction outwards, the blood-vessels of the
lungs become filled with blood, and thus partly occupy the lung space. Much less
blood is driven out of the left heart, so that the pulse may disappear. Hence, the
heart is distended with blood and the lungs are congested, while the aortic system
contains a small amount of blood, 2.e, the systemic circulation is comparatively
empty, while the heart and the pulmonary vessels are engorged with blood.

In normal respiration, the air in the lungs during inspiration is under slight
pressure, while during expiration the pressure is higher, so that these conditions
favour the circulation ; inspiration favours the occurrence of diastole, the supply of
blood (and lymph) through the vene cave. In operations where the axillary or
jugular vein is cut, air may be sucked into the circulation during inspiration, and
cause death. Expiration favours the flow of blood in the aorta and its branches,
and aids the systolic emptying of the heart.

The elastic traction of the lungs aids the lesser-circulation through the lungs;
the blood of the pulmonary capillaries is exposed to the pressure of the air in the
lungs, while the blood in the pulmonary veins is exposed to a less pressure, as the
elastic traction of the lungs, by dilating the left auricle, favours the outflow from
the capillaries into the left auricle. The elastic traction of the lungs acts slightly
as a disturbing agent on the right ventricle, and, therefore, on the movement of
blood through the pulmonary artery, owing to the overpowering force of the blood-
stream through the pulmonary artery, as against the elastic traction of the lungs
(Donders).

The above apparatus (fig. 65) shows the effect of the inspiratory and expiratory movements
on the dilatation of the heart, and on the blood-stream in the large blood-vessels. The large
glass vessel represents the thorax ; the elastic membrane, D, the diaphragm ; P, p, the lungs ;
L, the trachea supplied with a stop-cock to represent the glottis ; H, the heart; E, the vene
cave ; A, the aorta. If the glottis be closed, and the expiratory phase imitated by pushing up
D as in I., the air in P, P and the heart H are compressed, the venous valve closes, the arterial
is opened, and the fluid is driven out through A. The manometer, M, indicates the intra-
thoracic pressure. If the glottis be closed, and the inspiratory phase imitated, as in II., p, p
and # are dilated, the venous valve opens, the arterial valve closes ; hence, venous blood flows
from ¢ into the heart. Thus, inspiration always favours the venous stream, and hinders the
arterial ; while expiration hinders the venous, and favours the arterial stream. If the glottis
Land Z be open, the air in P, P, p, » will be changed during the respiratory movements D and
-d, so that the action on the heart and blood-vessels will be diminished, but it will still persist,
although to a much less extent. . .

The Circulation of the Blood.

6]. FLOW OF FLUIDS THROUGH TUBES. —Toricelli’s Theorem states that the velocity of
efflux (v) of a fluid—through an opening at the bottom of a cylindrical vessel—is exactly the
same as the velocity which a body falling freely would acquire, were it to fall from the surface
of the fluid to the base of the orifice of the outflow. If-h be the height of the propelling force,
the velocity of efflux is given by the formula—

v=A/2gh (where g=9°8 metres).
The rapidity of outflow increases with inerease in the height of the propelling force, 2. The
former occurs in the ratio 1, 2, 3, whem % increases in the ratio 1, 4, 9, 2.¢., the velocity of
efflux is as the square root of the height of the propelling force. Hence, it follows that the velocity
of efflux ebeteg upon the height of the liquid above the orifice of outflow, and ot upon the
nature of the fluid. calf .
Resistance.—Toricelli’s theorem, however, is only valid when all resistance to the outflow is

gO VELOCITY OF THE ‘CURRENT.—RESISTANCE.

absent ; but in every physical experiment such resistance exists. Hence, the propelling force,.
h, has not only to cause the efflux of the fluid, but has also to overcome resistance. These two:
forces may be expressed by the heights of two columns of water placed over each other, viz., by
the height of the column of water causing the outflow, F, and the height of the column, D,
which overcomes the resistance opposed to the outflow of the fluid. So that

h=F+D.

62. VELOCITY OF THE CURRENT. RESISTANCE. —In the case of a fluid flowing through
a tube, which it fills completely, we have to consider the propelling force, 2, causing the fluid
to flow through the various sections of the tube. The amount of the propelling force depends.
upon two factors :—

(1) On the velocity of the current, v; (2) on the pressure (amount of resistance) to which the
fluid is subjected at the various parts of the tube, D.

(1) The velocity of the current, v, is estimated—(a) from the lumen, 7, of the tube ; and (b).
from the quantity of fluid, g, which flows through the tube in the unit of time. .So that v=q: /.
Both values, q as well as 7, can be accurately measured. (The circumference of a circular tube,

whose diameter =d is 3'14.d. The sectional area (lumen of the tube) is 7 —=s 2) Having in

this way determined v, from it we may calculate the height of the column of fluid, F, which
will give this velocity, i.c., the height from which a body must fall in vacuo, in order to attain

the velocity v. In this case Saye (where y=the distance traversed by a falling body in 1 sec.
=4°9 metre).

(2) The pressure, D (amount of resistance), is measured directly by placing manometers at
different parts of the tube (fig. 67).

The propelling force at any part of the tube is h=F+D; or, h=7+D (Donders). This
is proved experimentally by taking a tall cylindrical vessel, A, of sufficient size, which is.
kept filled with water at a constant level, 2. The rigid outflow tube, ab, has in connection with

it a number of tubes placed vertically, 1, 2, 8, constituting a piezometer. At the end of the.

7 a . , 4. Z. 3.

———!
1
al

—_-

Tha
/ 7
¢
‘
ao ‘
ee :
/

| TTR

OTR "4

|
|!
:

ie eae ios ae by E I
a Fig. 66. Fig. 67.

Cylindrical vessel filled with water. h, A cylindrical vessel filled with water. ab,
height of the column of fluid; D, height outflow tube, along which are placed at
required to overcome the resistance ; intervals vertical tubes, 1, 2, 3, to estimate
F, height causing the efflux. the pressure.

tube, 4, there is an opening with a short tube fixed in it, from which the water issues to a con--
stant height, provided the level of 4 is kept constant. The height to which it rises depends on
ed hei ht - cd on of ripe ae ee velocity, F. As the pressure in the manometric
ubes, D!, D?, D*, can be read off directly, t opelli i
the mbes’ Eile tlt y, the propelling force of the water at the sections of
h=F+D!; F+D?; F+D*.
At the end of the tube, 6, where D‘=O, A=F +0, i.c., A=F. In the cylinder itself it is the
constant pressure, h, which causes the movement of the fluid. It is clear that the propelling’
force of the water gradually diminishes as we pass from the inflow towards the outflow of the
tube, ’. The water in the pressure-cylinder, falling from the height, A, only rises as high as F
at b, This diminution of the propelling power is due to the presence of resistances, which oppo
the current in the tube, i.¢., part of the energy is transformed into heat. As the propelling
force at b is represented onl F, while in the vessel it is h, the difference must be hee to the-
sum of the resistances, D=h-F; hence it follows that h=F+D. felon e ae

oh

-.

ESTIMATION OF RESISTANCE. gl

Estimation of the Resistance.—-When a fluid flows through a tube of uniforin calibre, the
propelling force, h, diminishes from point to point on account of the uniformly acting resist-

-ance, hence the sum of the resistance in the whole tube is directly proportional to its length.

In a uniformly wide tube, fluid flows through each sectional area with equal velocity, hence v
and also F are equal in all parts of the tube. The diminution which h (propelling force)

- undergoes can only occur from a diminution of pressure D, as F remains the same throughout

(and A=F+D). Experiment with the pressure-cylinder shows that the pressure towards
the outflow end of the tube gradually diminishes. Jn a uniformly wide tube, the height of the
pressure in the manometers expresses the resistances opposed to the current of fluid, which it has to
overcome in its course from the point investigated to the free orifice of efflux.

Nature of the Resistance.—The resistance opposed to the flow of a fluid depends upon the
cohesion of the particles of the fluid amongst themselves. During the current, the outer layer
of fluid which is next the wall of the tube, and which moistens it, is at rest. All the other
layers of fluid, which may be represented as so many cylindrical layers, one inside the other,
move more rapidly as we proceed towards the axis of the tube, the axial thread or stream
being the most rapidly moving part of the liquid. On account of the movement of the
cylindrical layers, one within the other, a part of the propelling energy must be used up. The
amount of the resistance greatly depends upon the amount of the cohesive force which the
particles of the fluid have for each other ; the more firmly the particles cohere the greater will
be the resistance, and vice versd. Hence, the sticky blood-current experiences greater resist-
ance than water or ether.

Heat diminishes the cohesion of the particles, hence it also diminishes the resistance to the
onflow. These resistances are first developed by, and result from, the movement of the particles
of the fluid, they being, as it were, torn from each other. The more rapid the current, there-
fore, i.e., the larger the number of particles of fluid which are pulled asunder in the unit of
time, the greater will be the sun of the resistance. As the layer of fluid lying next the tube,
and moistening it, is at rest, the material which composes the tube exerts no influence on the
resistance.

Tubes of Unequal Diameter.—When the velocity of the current is uniform, the resistance
depends upon the diameter of the tube—the smaller the diameter the greater the resistance ;
the greater the diameter the less the resistance. The resistance in narrow tubes, however,
increases more rapidly than the diameter of the tube decreases, as has been proved experi-
mentally. In tubes of unequal calibre, at different parts of their course, the velocity of the
current varies—it is slowerin the wide part of the tube and more rapid in the narrow parts.
As a general rule, in tubes of unequal diameter the velocity of the current is inversely pro-
portional to the diameter of the corresponding section of the tube; z.¢., if the tube be
cylindrical, it is inversely proportional to the square of the diameter of the circular transverse
section. In tubes of uniform diameter, the propelling force of the moving fluid diminishes
uniformly from point to point, but in tubes of wnequal calibre it does not diminish uniformly.
As the resistance is greater in narrow tubes, of course the propelling force must diminish more
rapidly in them than in wide tubes. Hence, within the wide parts of the tube the pressure is
greater than the sum of the resistances still to be overcome, while in the narrow portions it is
less than these.

Tortuosities and bending of the vessels add new resistance, and the fluid presses more
strongly on the convex side than on the concave side of the bend, and there the resistance to
the flow is greater than on the concave side.

Division of a tube into two or more branches is a source of resistance, and diminishes the
propelling power. When a tube divides into two smaller tubes, of course some of the particles
of the fluid are retarded, while others are accelerated on account of the unequal velocities of
the different layers of the fluid. Many particles which had the greatest velocity in the axial
layer come to lie more towards the side of the tube where they move more slowly ; and con-
versely many of those lying in the outer layers reach the centre, where they move more
rapidly. Hence,-some of the propelling force is used up in this process, and the pulling
asunder of the particles where the tube divides acts in a similar manner. If two tubes join
to form one tube, new resistance is thereby caused, which must diminish the propelling force.
The sum of the mean velocities in both branches is independent of the angle at which the
division takes place (Jacobson). Ifa branch be opened from a tube, the principal current is
accelerated to a considerable extent, no matter at what amgle the branch may be given off.

63. FLOW IN CAPILLARY TUBES.—Poiseuille proved experimentally that the flow in
the capillaries is subject to special conditions— . :

(1) The quantity of fluid which flows out.of the same capillary tube is proportional to the
pressure,”

(2) The time necessary for a given quantity of fluid to flow out (with the like pressure,
diameter of tube and temperature), is proportional to the length of the tubes.
* (8) ha product of the outfiow (other things being equal) is as the fourth power of the
iameter. BN A

92 FLOW IN ELASTIC TUBES.

(4) The velocity of the current is proportional to the pressure and to the square of the
diameter, and inversely proportional to the length of the tube. _
(5) The resistance in the capillaries is proportional to the velocity of the current.

64, FLOW IN ELASTIC TUBES.—(1) When an uninterrupted wni/orm current flows through
an elastic tube, it follows exactly the same laws as if the tube had rigid walls. If the propel-
ling power increases or diminishes, the elastic tubes become wider or narrower, and they behave,
as A as the movement of the fluid is concerned, as wider or narrower rigid tubes,

(2) Wave-Motion.—If, however, more fluid be forced in jerks into an elastic tube, 7.¢., in-
terruptedly, the first part of the tube dilates suddenly, corresponding to the quantity of fluid
propelled into it. The jerk communicates an oscillatory movement to the particles of the fluid,
which is communicated to all the fluid particles from the beginning to the end of the tube; a
positive wave is thus rapidly propagated throughout the whole length of the tube. If we imagine
the elastic tube to be closed at its peripheral end, the positive wave will be reflected from the
point of occlusion, and it may be propagated to and fro through the tube until it finally dis-
appears. In such a closed tube a sudden jet of fluid produces only a wave-movement, i.e., only
a vibratory movement, or an alteration in the shape of the liquid, there being no actual trans-
lation of the particles along the tube.

(3) If, however, fluid be pumped interruptedly or by jerks into an elastic tube filled with
fluid, in which there is already a continuous current, the movement of the current is combined
with the wave movement. We must carefully distinguish the movement of the current of the
Jluid, i.e., the translation of a mass of fluid through the tube, from the wave-movement, the
oscillatory movement, or movement of change of form in the column of fluid. In the former,
the particles are actually translated, while in the latter they merely vibrate. The current in
elastic tubes is slower than the wave-movement, which is propagated with great rapidity. This
last case obtains in the arterial system. The blood in the arteries is already in a state of con-
tinual movement, directed from the aorta to the capillaries ; by means of the systole of the left
ventricle a quantity of fluid is suddenly pumped into the aorta, and causes a positive wave, the
pulse-wave which is propagated with great rapidity to the
terminations of the arteries, while the current of the blood
itself moves much more slowly.

Rigid and Elastic Tubes.—If a quantity of fluid be
forced into a rigid tube under a certain pressure, the same
quantity of fluid will flow out at once at the other end of
the tube, provided there be no special resistance. In an
elastic tube, immediately after the forcing in of a quantity
of fluid, at first only a small quantity flows out, and the
remainder flows out only after the propelling force has
ceased to act. If an equal quantity of fluid be periodically
injected into a rigid tube, with each jerk an equal quantity
is forced out at the other end of the tube, and the outflow
lasts exactly as long as the jerk or the contraction, and
the pause between two periods of outflow is exactly the
same as between the two jerks or contractions. In an
elastic tube it is different, as the outflow continues for a
time after the jerk ; hence, it follows that a continuous
outflow current will be produced in elastic tubes, when
the time between two jerks is made shorter than the dura-
tion of the outflow after the jerk has been completed.
When fluid is pumped periodically into rigid tubes, it
causes a sharp abrupt outflow synchronous with the in-
flow, and the outflow becomes continuous only when the
inflow is continuous and uninterrupted. In elastic tubes,
an intermittent current under the above conditions causes
, acontinuous outflow, which is increased with the systole
AA Or contraction.

Fig. 68. 65. STRUCTURE AND PROPERTIES OF
Coats of a small artery. a, endo- THE BLOOD-VESSELS.—In the body the large
thelium ; }, internal elastic lamina ; vessels carry the blood to and from the various
¢, circular muscular fibres of the tissues and organs, while the thin-walled capillaries
middle coat ; d, the outer coat. bring the blood into intimate relation with the
tissues. Through the excessively thin walls of the capillaries the fluid part of the —

blood transudes, to nourish the tissues outside the capillaries. [At the same time
fluids pass from the tissues into the blood. Thus, there is ari exchange between the —

STRUCTURE OF ARTERIES. 93

blood and the fluids of the tissues. The fluid after it passes into the tissues consti-
tutes the /ymph, and acts like a stream «rigating the tissue elements. |

I. The arteries are distinguished from veins by their thicker walls, due to the
greater development of smooth muscular and elastic tissues—the middle coat
(tunica media) of the arteries is specially thick, while the outer coat (t. adventitia)
is relatively thin. [The absence of valves is by no means a characteristic feature. |

A typical artery consists of three coats (fig. 68). (1) The tunica intima, or inner coat,
consists of a layer of (a) irregular, long, fusiform nucleated squamous cells forming the
excessively thin transparent endothelium, immediately in contact with the blood-stream.
[Like other endothelial cells, these cells are held together by a cement substance, which is
blackened by the action of silver nitrate.] Outside this lies a very thin, more or less fibrous,
layer—sub-epithelial layer—in which numerous spindle or branched protoplasmic cells lie em-
bedded within a corresponding system of plasma canals. Outside this is an elastic lamina (b),
which in the smallest arteries is a structureless or fibrous elastic membrane—in arteries of
medium size it is a fenestrated membrane (Henle), while in the largest arteries there may be
several layers of elastic lamine or fenestrated elastic membrane mixed with connective-tissue.
[In some arteries the elastic membrane is distinctly fibrous, the fibres being chiefly arranged
longitudinally. It can be stripped off, when it forms a brittle elastic membrane, which has a
great tendency to curl up at its margins. In a transverse section of a middle-sized artery it
appears as a bright wavy line, but the curvesare probably produced by the partial collapse of the
vessel. It forms an important guide to the pathologist, in enabling him to determine which
coat of the artery is diseased.] In middle-sized and large arteries a few non-striped muscular
fibres are disposed longitudinally between the elastic plates or lamin. Along with the circular
muscular fibres of the middle coat, they may act so as to narrow the artery, and they may also
aid in keeping the lumen of the vessel open and of uniform calibre.

(2) The tunica media, or middle coat, contains much non-striped muscle (c), which in the
smallest arteries consists of transversely disposed non-striped muscular fibres lying between the
endothelium and the T. adventitia, while a finely granular tissue with few elastic fibres forms
the bond of union between them. As we proceed from the very smallest to the small arteries,
the number of muscular fibres becomes so great as to form a well-marked fibrous ring of non-
striped muscle, in which there is comparatively little connective-tissue. In the large arteries the
amount of connective-tissue is considerably increased, and between the layers of fine connective-
tissue numerous (as many as 50) thick, elastic fibrous or fenestrated lamine are concentrically
arranged. A few non-striped fibres lie \ YL OAS
scattered amongst these, and some of them 8 SEIS
are arranged transversely, while a few ~
have an oblique or longitudinal direction.

The first part of the aorta and pulmonary
artery, and the retinal arteries, are devoid
of muscle. The descending aorta, common
iliac, and popliteal have longitudinal fibres
between the transverse ones. Longitudinal
bundles lying inside the media occur in
the renal, splenic, and internal spermatic
arteries. Longitudinal bundles occur both
on the outer and inner surfaces of the um-
bilical arteries, which are very muscular.

(3) The tunica adventitia, or outer coat,
in the smallest arteries consists of a struc-
tureless membrane with a few connective-
tissue corpuscles attached to it ; in somewhat
larger arteries there is a layer of fine fibrous
elastic tissue mixed with bundles of fibrillar
connective-tissue (d). In arteries of middle
size, and in the largest arteries, the chief

- mnass consists of bundles of fibrillar con- Fig. 69.

Edy, * st. ge Capillaries. ‘The outlines of the nucleated endo-
nective-tissue containing connective-tissue V“PUatles, ine
corpuscles. The bundles cross each other . thelial cells with the cement blackened by “the
in a variety of directions, and fat cells often | 2°tion of silver nitrate. |
lie between them., Next the media there are numerous fibrous or fenestrated elastic lamelle.
In medium sized and small arteries the elastic tissue next the media takes the form of an inde-
pendent elastic membrane (Henle’s external clastic membrane)... Bundles of non-striped muscle,
arranged longitudinally, occur in the adventitia of the arteries of the penis, and in the renal,
splenic, spermatic, iliac, hypogastric, and superior mesenteric arteries.
Il. The capillaries, while retaining their diameter, divide and reunite so as to form net-

idl

94 THE STRUCTURE OF VEINS.

works, whose shape and arrangement differ considerably in different tissues. The diameter of
the capillaries varies considerably, but asa general rule it is such as to admit freely a single row
of blood-corpuscles. In the retina and the muscles the diameter is 5-6 «, and in bone-marrow,
liver, and choroid 10-20 u. The tubes consist of a single layer of transparent, excessively thin,
nucleated, endothelial cells joined to each other by their margins. [The nuclei contain a awell-
marked intra-nuclear plexus of fibrils, like other nuclei.] The cells are more fusiform in the
smaller capillaries and more polygonal in the larger. The body of the cells presents the
characters of very faintly refractive protoplasm, but it is doubtful whether the body of the
cell is endowed with the property of contractility (p. 96). ;

If a dilute solution (} per cent.) of silver nitrate be injected into the blood-vessels, the
cement substance of the endothelium, [and of the muscular fibres as well], is revealed by the
yresence of the black ‘‘silver lines.” The blackened cement substance shows little specks and .
ieee black slits at different points. It is not certain whether these are actual holes through |
which colourless corpuscles may pass out of the vessels, or are merely larger accumulations of |
the cement substance. [Ifa capillary is examined ina pastes eed fresh condition (while living)
and without the addition of any reagent, it is impossible to make out any line of demarcation
between adjacent cells owing to the uniform refractive index of the entire wall of the tube. ]

[Arnold called these small areas in the black silver lines when they are large stomata, and
when small stigmata. They are most numerous after venous congestion, and after the dis-
turbances which follow inflammation of a part. They
are not always present. The existence of cement sub-
stance between the cells may also be inferred from the
fact that indigo-sulphate of soda is deposited in it
(Thoma), and particles of cinnabar and China ink are
fixed in it, when these substances are injected into the
blood (Foa).]

Fine anastomosing fibrils derived from non-medul-
lated nerves terminate in small end-buds in relation
with the capillary wall; ganglia in connection with
the nerves of capillaries occur only in the region of the
sympathetic. .

The small vessels next in size to the capillaries, and
continuous with them, have a completely structureless
covering in addition to the endothelium.

Ill. The veins are generally distinguished
from the arteries by their lumen being wider
than the lumen of the corresponding arteries ;
their walls are thinner on account of the smaller
amount of non-striped muscle and elastic tissue
(the non-striped muscle is not unfrequently
arranged longitudinally in veins). They are
also more extensile (with the same strain). The
adventitia is usually the thickest coat. The
occurrence of valves is limited to the veins of
certain areas.

Structure.—(1) The tunica intima consists of a layer
of shorter and broader endothelial cells, under which in
the smallest veins there is a structureless elastic mem-
brane, swb-epithelial layer, which is fibrous in veins
somewhat larger in size, but in all casesisthinnerthan =
eee in the arteries. In large veins. it may assume the |

Fig, 70,.. 0. characters of a fenestrated membrane, which is double

Longitudinal section of a vein at the in some parts of the crural and iliac veins. Isolated

level of a valve. a, hyaline layer of muscular fibres exist in the intima of the femoral and
the internal coat ; 6, elastic lamina; popliteal veins.

c, groups of smooth muscular fibres 2) The t. media of the larger veins consists of

divided transversely ; d, longitudinal alternate layers of elastic and muscular tissue united

muscular fibres in the adventitia. to each other by a considerable amount of connective-

} : tissue, but this coat is always thinner than in the
corresponding arteries. This coat diminishes in the following order in the following vessels :—
ener veins of the lower extremity, veins of the upper extremity, superior mesenteric, other
abdominal veins, hepatic, pulmonary, and coceneey veins. The following veins contain no
muscle :—veins of bone, central nervous system and its membranes, retina, the superior cava,

Ay

PROPERTIES OF THE BLOOD-VESSELS. 95

- with the large trunks that open into it, the upper part of the inferior cava. Of course, in these

eases the media is very thin. In the smallest veins the media is formed of fine connective-
tissue, with very few muscular fibres scattered in the inner part.

(3) The t. adventitia is thicker than that of the corresponding arteries ; it contains much
connective-tissue, usually arranged longitudinally, and not much elastic tissue. Longitudinally
arranged muscular fibres occur in some veins (renal, portal, inferior cava near the liver, veins
of the lower extremities). The valves consist of fine fibrillar connective-tissue with branched
cells. An elastic network exists on their convex surface, and both surfaces are covered by
endothelium. The valves contain many muscular fibres (fig. 70). [Ranvier has shown that
the shape of the epithelial cells on the side over which the blood passes, are more elongated
than on the cardiac side of the valve, where the long axes of the cells are placed transversely. ]

The sinuses of the dura mater are spaces covered with endothelium. ‘The spaces are either
‘duplicatures of the membrane, or channels in the substance of the tissue itself. ;

Cavernous spaces we may imagine to arise by numerous divisions and anastomoses of tolerably
large veins of unequal calibre. The vascular wall appears to be much perforated and like a
sponge, the internal space being traversed by threads and strands of tissue, which are covered
with endothelium on their surfaces, that are in contact with the blood. The surrounding wall
consists of connective-tissue, which is often very tough, as in the corpus cavernosum, and it
not unfrequently contains non-striped muscle.

Cavernous formations of an analogous nature on arteries are the carotid gland of the frog,

and a similar structure on the pulmonary arteries and aorta of the turtle, and the coccygeal gland

of man. The last structure is richly supplied with sympathetic nerve-fibres, and is a convoluted
mass of ampullated or fusiform dilatations of the middle sacral artery, surrounded and per-
meated by non-striped muscle.

Vasa Vasorum,—[These are sinall vessels which nourish the coats of the arteries and veins.

They arise from one part of a vessel and enter the walls of the same, or another vessel at a

lower level. They break up chiefly in the outer coat, and none enter the inner coat.] In
structure they resemble other small blood-vessels. The blood circulating in the arterial or
venous wall is returned by small veins.

[Lymphatics.—There are no lymphatics on the inner surface of the muscular coat, or under
the intima in large arteries. They are numerous in a gelatinous layer immediately outside the
muscular coat, and the same relation obtains in large muscular veins and lymphatic trunks
(Hoggan). ]

Intercellular Blood-Channels,—Intercellular blood-channels of narrow calibre, and without
walls, occur in the granulation tissue of healing wounds. At first blood-plasma alone is found
between the formative cells, but afterwards the blood-current forces blood-corpuscles through
the channels. The first blood-vessels in the developing chick are formed in a similar way from
the formative cells of the mesoblast.

Properties of the Blood-Vessels.—The larger blood-vessels are cylindrical tubes
composed of several layers of various tissues, more especially elastic tissue and smooth
muscular fibres,and the whole is lined by a smooth polished layer of endothelium. One
of the most important properties is the contractility of the vascular wall, in virtue of
which the calibre of the vessel can be varied, and therefore the supply of blood to
a part is altered. The contractility is due to the plain muscular fibres, which are,
for the most part, arranged circularly. It is most marked in the small arteries, and
of course is absent where no muscular tissue occurs. The amount and intensity of.
the contraction depend upon the development of the muscular tissue ; in fact, the
two go hand in hand. [If an artery be exposed in the living body it soon contracts
under the stimulus of the atmosphere acting upon the muscular fibres. |

[Action of Drugs on the Vascular System.—Gaskell finds that a very dilute solution of lactic
acid (1: 10,000 parts of saline solution), passed through the blood-vessels of a frog, always
enlarges the calibre of the blood-vessels, while an alkaline solution (1 part sodium hydrate to
10,000 saline solution) always diminishes their size, usually to absolute closure, and indeed the
artificial constriction of the blood-vessels may be almost complete. These fluids are antagonistic
to each other as far as regards their action on the calibre of the arteries. Dilute alkaline
solutions act on the heart in the same way. After a series of beats the ventricle stops beating,
the standstill being in a state of contraction. Very dilute lactic acid causes the ventricle to
stand still in the phase of complete relaxation. The acid and alkaline saline solutions are
antagonistic in their action on the ventricle. Cash and Brunton find that dilute acids have
a tendency to increase the transudation through the vessels and produce edema of the surround-
ing tissues. They also observed that barium, calcium, strontium, copper, iron, and tin produce
contraction of the blood-vessels when solutions of their salts are driven through them, while
the same effect is produced by very dilute solutions of potassium. Nicotin, atropin, and

96 PHYSICAL PROPERTIES OF THE BLOOD-VESSELS,.

chloral differ in their action according to the dose. In these experiments the effect was ascer-
tained by the amount of fluid which flowed out of the vessels in a given time.] ‘If blood
containing certain drugs be perfused through the blood-vessels of a freshly excised organ, the
blood-vessels are dilated; e¢.g., by amyl] nitrite, chloral hydrate, morphia, CO, paraldehyde,
kairin, quinine, atropin, ferricyanide of potassium, (urea and sodic chloride in the renal vessels),
—they are contracted by digitalin, veratria, helleborin (Kobert). Heat causes contraction of the
blood-vessels of the frog's mesentery (Gartner). According to Roy the blood-vessels shorten
when heated. :

That the capillaries undergo dilatation and contraction, owing to variations in
the size of the protoplasmic elements of their walls, must be admitted.

Stricker has described capillaries as ‘“ erotepiann in tubes,” and observed that in the tad-
pole they exhibited movements when stimulated. Golubew described an active state of contrac-
tion of the capillary wall, but he regarded the nuclei as the parts which underwent change.
Rouget observed the same result in the capillaries of new-born mammals. Tarchanoff found that
mechanical or electrical stimulation caused a change in the shape and size of the nuclei, so that
he regards these as the actively contractile parts. [Severini also attaches great importance to
the contractility of the capillaries and especially of their nuclei as influencing the blood-stream-
Oxygen acts on the nuclei of the capillary wall (membrana nictitans of frog) and causes them
to swell, while CO, has an opposite effect. The circulation through a lung suddenly filled with
O or atmospheric air is at first very rapid, but it soon diminishes, while with CO, the circula-
tion remains constant.] As the capillaries are excessively thin, soft, and delicate, it is obvious
that the form of the individual cells must depend to a considerable extent upon the degree to
which the vessels are filled with blood. In vessels which are distended with blood the en-
dothelial cells are flattened, but when the capillaries are collapsed they project more or less
into the lumen of the vessel (Renaut).

[It is well known that the capillaries present great variations in their diameter at different
times. As these variations are usually accompanied by a corresponding contraction or dilatation
of the arterioles, it is usually assumed that the variations in the diameter of the capillaries are
due to differences of the pressure within the capillaries themselves, viz., to the elasticity of their
walls. Every one is agreed that the capillaries are very elastic, but the experiments of Roy and
Graham Brown show that they are contractile as well as elastic, and these observers conclude
that, under normal conditions, it is by the contractility of the capillary wall as a whole that
the diameter of these vessels is changed, and to all appearance their contractility is constantly
in action. ‘The individual capillaries (in all probability) contract or expand-in accordance
with the requirements of the tissues through which they pass. The regulation of the vascular
blood-flow is thus more complete than is usually imagined.”

Physical Properties—Amongst the physical properties of the blood-vessels,
elasticity is the most important ; their elasticity is small in amount, 1.e., they offer
little resistance to any force applied to them so as to distend or elongate them but
it is perfect in quality, i.e., the blood-vessels rapidly regain their original size and
form after the force distending them is removed.

[Uses of Elasticity.—The elasticity of the arteries is of the utmost importance in aiding the
conversion of the unequal movement of the blood in the large arteries into a uniform flow in the
capillaries. E. H. Weber compared the elastic wall of the ‘arteries with the air in the air-
chamber of a fire-engine. In both cases an elastic medium is acted upon—the air in the one
case and the elastic tissue in the other—which in turn presses upon the fluid, propelling it
onwards continually, while the action of the pump or the heart, as the case may be, is inter-
mittent. The ordinary spray-producer acts on this principle. A uniform spray or jet is
obtained by pumping intermittently, but only when the resistance is such as to bring into action
the elasticity of the bag between the pump and the spray-orifice. ]

According to E. H. Weber, Volkmann, and Wertheim, the elongation of a blood-vessel and
moist tissues generally is not proportional to the weight used to extend it, the elongation being
relatively less with a large weight than with a small one, so that the curve of extension is nearly
[or, at least, bears a certain relation to] a hyperbola. According to Wundt, we have not only to
consider the extension produced at first by the weight, but also the subsequent ‘elastic
after-effect,” which occurs gradually. The elongation which takes place during the last few
moments occurs so slowly and so gradually that it is well to observe the effect by means of a
magnifying lens. Variations from the general law occur to this extent, that if a certain weight
is exceeded, less extension, and, it mer e, permanent.elongation of the artery not unfrequently
occur. K. Bardeleben found, especially in veins elongated to 40 or 50 per cent. of their original
length, that when the weight employed increased by an equal amount each time, the elongation
was proportional to the square-root of the weight. ‘This is apart from any elastic after-effect.

Veins may be extended to at least 50 per cent. of their length without passing the limit of their

elasticity.

¢

THE PULSE. | 97

.. [Roy experimented upon the elastic properties of the arterial wall. A portion of an artery,
so that it could be distended by any desired internal pressure, was enclosed in a small vessel
containing olive oil arranged in the same way as in fig. 62 for the heart. ‘The variations of the
contents were recorded by means of a lever writing on a revolving cylinder. The instrument is
termed a sphygmotonometer. The aorta and other large arteries are most elastic and most dis-

’ tensible at pressures corresponding more or less exactly to their normal blood-pressure, while in

veins the relation between internal pressure and the cubic capacity is very different. In them the
maximum of distensibility occurs with pressures immediately above zero. Speaking generally,
the cubic capacity of an artery is greatly increased by raising the intra-arterial tension, say from
zero to about the normal internal pressure which the artery sustains during life. Thus in the
rabbit, the capacity of the aorta was quadrupled by raising the intra-arterial pressure from zero
to 200 mm. Hg., while that of the carotid was more than six tines greater at that pressure than
it was in the undistended condition. The pulmonary artery is distinguished by its excessive
elastic distensibility. Its capacity (rabbit) was increased more than twelve times on raising the
internal pressure from zero to about 36 mm. Hg. Veins, on the other hand, are distinguished
by the relatively small increase in their cubic capacity produced by greatly raising the internal
pressure, so that the enormous changes in the capacity of the veins during life are due less to

differences in the pressure than to the great differences in the quantity of blood which they

contain.

Darien Tateeeiues with the nutrition of an artery alters its ‘elasticity, [and that in
cases where no structural changes can be found]. Marasmus preceding death causes the arteries
to become wider than normal. In some old people they become atheromatous and even calcified.

Cohesion.—The cohesion of blood-vessels is very great, and in virtue of this
they are able to resist even considerable internal pressure without giving way. The
carotid of a sheep is ruptured only when fourteen times the usual pressure it is called
upon to bear is put upon it (Volkmann). Given a vein and an artery of the same
thickness, a greater pressure is required to rupture the former than the latter. The
human carotid or iliac artery resists a pressure of 8 atmospheres, the
veins about the half of this.

66. INVESTIGATION OF THE PULSE.—(The characters of
the pulse may be investigated by—(1) the eye (inspection) ; (2) the
finger (palpation) ; (3) instruments.

Two or three fingers are placed over the course of the radial
artery, and the various phenomena in connection with the pulse are st is
noted. It takes much practice for the physician to acquire the [| —|||-
tactus eruditus, and notwithstanding the value of instruments, every
physician, should make a careful study of the pulse-beat with his
finger. In order to feel the pulse-beat or to take a pulse-tracing, |—||||-+
there must be some resistant body, e.g., a bone behind the artery,
and a certain degree of pressure must be exerted on the artery. |

The individual phases of the movement of the pulse can only
be accurately investigated by the application of instruments to the
arteries.

(1) Poiseuille’s Box Pulse-Measurer (1829).—An artery is exposed and
placed in an oblong box filled with an indifferent fluid. A vertical tube with
a scale attached communicates with the interior of the box. The column of
fluid undergoes a variation with every pulse-beat.

(2) Hérisson’s Tubular Sphygmometer consists of a glass tube whose lower
end is covered with an elastic membrane (fig. 71). The tube is partly filled
with Hg. The membrane is placed over the position of a pulsating artery, Fig. 71.
so that its beat causes a movement in the Hg. Chelius used a similar instru- Sphygmometer of
ment, and he succeeded with this instrument in showing the existence of the érisson and
double beat (dicrotism) in the normal pulse (1850). Chelius.

(3) Vierordt’s Sphygmograph (1855).—In this, one of the earliest sphygmo-
graphs, Vierordt departed from the principle of a fluctuating fluid column, and adopted the
principle of the /ever. Upon the artery rested a small pad, which moved a complicated system
of levers. At first he used a straw 6 inches long, which rested on the artery. The point of
one of the levers inscribed its movements upon a revolving cylinder. This instrument was
soon discarded.

(4) Marey’s Sphygmograph consists of a combination of a lever with an elastic spring. The

‘ G

098 INSTRUMENTS FOR INVESTIGATING THE PULSE.

elastic spring (fig. 72, A) is fixed at one end, , free at the other end, and provided with an
ivory pad, y, which is pressed by the spring upon the radial artery. On the upper surface of
the pad there is a vertically-placed fine toothed rod, &, which is pressed upon by a weak spring, ¢,

me é. <~<—— p
Vv
me
t S
j -H Ae
Ne, ; ame |57 ; |
\a ; = |

J |
Ca EY a aD
Fig. 72.

Scheme of Marey’s sphygmograph. A, spring with ivory pad, y, which rests on the artery ; ¢,
weak spring pressing k into ¢; v, writing lever; P, piece of smoked glass or paper moved
by clock-work, U ; H, screw to limit excursion of A; 8, arrangement for fixing the instru-
ment to the arm of the patient.

so that its teeth dovetail with similar teeth in the small wheel, ¢, from whose axis there pro- ,
jects a long, light, wooden lever, v, running nearly parallel with the elastic spring, This lever

as a fine style at its free end, s, which writes upon a smoked plate, P, moved by clock-work,
U, in front of the style. Marey’s instrument, as improved by Mahomed and others, has been
very largely used.

[Its more complete form, as in fig. 73, where it is shown applied to the arm, consists of—(1)
a steel spring, A, which is provided with a pad resting on the artery, and moves with each
movement of the artery ; (2) the lever, C, which records the movement of the artery and spring
in a magnified form on the smoked paper, G ; (3) an arrangement, L, whereby the exaet pressure
exerted upon the artery is indicated on the dial, M ; (4) the clock-work, H, which moves the
smoked paper, G, at a uniform rate; (5) a framework to which the various parts of the
instrument are attached, and by means of which the instrument is fastened to the arm by straps,
K, K (Byrom Bramiecell). }

[Application.-—In applying the sphygmograph, cause the patient to seat himself beside a low
table, and place his arm on the double-inclined plane (fig. 73). In the newer. form of instru-

C'

|
wee EEUU

Fig. 73.

Marey’s improved sphygmograph. A, steel spring ; B, first lever; C, writing lever; C’, its free
writing end ; D, screw for bringing B in contact with C; G, slide with smoked paper ; H,
clock-work ; L, serew for increasing the pressure ; M, dial indicating the pressure; K, K,
straps er fixing the instrument to the arm, and the arm to the double-inclined plane or
support,

ment, the lid of the box is so arranged as to unfold to make this support. The fingers ought to
be semi-flexed. Mark the position of the radial artery with ink, Bee that the clock, work is
wound up, and apply the ivory pad exactly over the radial artery where it lies upon the radius,
fixing it to the arm by the non-elastic straps, K, K. Fix the slide holding the smoked paper
in position. The best paper to use is that with a very smooth surface, or an enamelled card
smoked over the flame of a turpentine lamp, over a piece of burning camphor, or over a fan-
tailed gas-burner, The writing-style is so arranged as to write upon the smoked paper with
the least possible friction. It is most important to regulate the pressure exerted upon the —

DUDGEON'S AND LUDWIG’S SPHYGMOGRAPHS. 99

artery by means of the milled head, L. This must be determined for each pulse, but the rule is
to graduate the pressure until the greatest amplitude of movement of the lever is obtained.
Set the clock-work going, and a tracing is obtained, which must be “fixed” by dipping it in
a rapidly drying varnish, ¢.g., photographic. In every case scratch on the tracing with a needle
the name, date, and amount of pressure employed.} —

[(5) Dudgeon’s Sphygmograph.—This is a convenient form of sphygmograph, although
Broadbent regards its results as untrustworthy. The instrument after being carefully adjusted

Gs
{is

~

ie

Fig. 74.
Ludwig’s sphygmograph.

upon the radial artery is kept in position by an inelastic strap. The pressure of the spring is
regulated by the eccentric wheel to any amount from 1 to 5 ounces. As in other instruments

=O

iy
4

Fig. 75.
Dudgeon’s sphygmograph.
the tracing paper is moved in front of the writing-needle by means of clock-work.. The writing-
levers are so adjusted that the movements of the artery are magnified fifty times (fig. 75). ]
(6) [Ludwig’s improved form is a very serviceable instrument (fig. 74). ]
{7) Marey’s tambours are also employed for registering the movements of the pulse. They
are used in the same way as the pansphygmograph.. Two pairs of metallic cups (fig. 76, S, S,

é

100 BRONDGEEST’S SPHYGMOGRAPH.

and S’, 8S’, Upham’s capsules) are pierced in the middle by thin metal tubes, whose free ends
are seudhoeded. with caoutchouc tubes, K and K’. All the four metallic vessels are covered with
an elastic membrane. On S and S’ are fixed two knob-like pads, p and yp’, which are applied to
the pulsating arteries, and the metal ares, B and B’, retain them in position. On the other
tambours are arranged the writing-levers, Z and Z’. Pressure on the one tambour necessarily
compresses the air, and makes the other, with which it is connected, expand, so as to move the
writing-lever. This arrangement does not give absolutely exact results ; still, it is very easily

Scheme of Brondgeest’s sphygmograph. S, S’, receiving and recording (S, S’) tambours with
writing levers, Z and Z’; K, K’, conducting tubes: p, over heart, p’, over a distant artery.

used, and is convenient. In fig. 76 a double arrangement is shown, whereby one instrument, B,.
may be placed over the heart, and the other, B’, on a distant artery.

(8) Landois’ Angiograph.—To a basal plate, G, G, are fixed two upright supports, p, which
carry between them at their upper part the movable lever, d, 7, carrying a rod bearing a pad,
e, directed downwards, which rests on the pulse. The short arm carries a counterpoise, d, so-

Fig. 77.
Scheme of Landois’ angiograph.
as exactly to balance the long arm. The long arm has fixed to it at r a vertical
rod provided with teeth, h, which is pressed against a toothed wheel firmly fixed
on the axis of the very light writing-lever, e, 7, which is supported between two up-
rights, q, fixed to the opposite end of the basal plate, G, G. ‘The writing-lever is equilibrated
by means of a light weight. The writing-needle, x, is fixed by a joint to ¢, and it writes on the
plate, ¢. The first-mentioned lever, d, 7, carries a shallow cup, Q, just above the pad, into
which weights may be put to press on the pulse. In this instrument the weight can be measured.

\

MAYER’S GAS-SPHYGMOSCOPE. IOI

and varied ; the writing-lever moves vertically, and not in a curve as in Marey’s apparatus,
which greatly facilitates the measuring of the curves (fig. 77).

Other sphygmographs are used, both in this country and abroad, including that of Sommer-
brodt, which is a complicated form of Marey’s sphygmograph, and those of Pond and Mach.

In every pulse-curve—sphygmogram or arteriogram—we can distinguish the
ascending part (ascent) of the curve, the apex, and the descending part (descent).
Secondary elevations scarcely ever occur in
the ascent, which is usually represented by a
straight line, while they are always present
in the descent. Such elevations occurring in
the descent are called catacrotic, and those
in the ascent, anacrotic. When the recoil
elevation or dicrotic wave occurs in a well-
marked form in the descent, the pulse is said
to be dicrotic, and when it occurs twice,
tricrotic.

Measuring Pulse-Curves.—If the smoked surface Big. 78. |
on which the tracing is inscribed is moved at a uni- Normal pulse-curve of the radial artery,
form rate by means of the clock-work, then the obtained by the angiograph writing upon
height and length of the curve are measured by a plate attached to a vibrating tuning-
means of an ordinary rule. If we know the rate at fork. Each double vibration =0°01613
which the paper was moved, then it is easy to calcu- gee,
late the duration of any event in the curve.

The curve may be recorded on a plate of glass fixed to a tuning-fork kept in vibration. Every
part of the curve shows little elevations (whose rate of vibration is known beforehand). All
that is required is to count the number of vibrations in order
to ascertain the duration of any part of the curve (fig. 78).

Gas-Sphygmoscope.—A small metallic or glass capsule (fig.
79), provided with an inlet and an outlet tube, and closed
below by a fine membrane, is placed over an artery. The §&
inlet tube is connected to a gas supply, and the outlet to a | #
rat-tailed gas-burner(b). The gas-jet responds to every pulse- ;
beat. Czermak photographed a beam of light set in motion §
by the movements of the pulse.

Hemautography.— Expose a large artery of an animal, and
divide it so that the stream of blood issuing from it strikes
against a piece of paper drawn in front of the blood-stream.

ee - =>

{

Fig. 80.
Hemautographic curve of the poste-
: rior tibial artery of adog. P, prim-
Fig. 79. ary pulse-wave ; R, dicrotic wave ;
Gas-sphygmoscope of 8, Mayer. -“ ¢, e, elevations due to elasticity.

The curve so obtained (fig. 80) shows, in addition to the primary wave, P, a distinct dicrotic
wave, R, and slight vibrations, ¢, c, due to the variations in the elasticity of the arterial wall,
which shows that the movements occur in the blood itself, and are communicated as waves to’
the arterial wall. By estimating the amount’of blood in the various parts of the curve, we obtain
a knowledge of the amount of blood discharged by the divided artery during the systole and
diastole (7.c., the narrowing and dilatation) of the artery—the ratio is 7: 10. Thus in the
unit of time, during arterial dilatation, rather more than fwice as much blood flows out as
compared with what occurs during arterial contraction.

102 THE PULSE-CURVE.

67. PULSE-TRACING OR SPHYGMOGRAM.—(The Pulse.—With each

systole of the heart, a certain quantity of blood is forced into the already filled and

partially distended arteries, the resistance in the vessels is lowest between the
pulsations, and at this. time the arterial tubes are somewhat flattened, but with
each systole of the left ventricle the pulse-wave, or rather the liquid pressure within
the vessel, is increased, thus forcing the artery back into the circular form. “The
change of shape, from the flattened
condition impressed upon the vessel
by the finger or the sphygmograph
lever, to the round cylindrical shape
which it assumes under the distend-
ing force of the blood within it, con-
stitutes the pulse,” and it indicates
Fig. 81. the degree and duration of the in-
Sphygmogram of radial artery : pressure 20z. Each creased pressure in the arterial 8Y5-
part of the curve between the base of one up-stroke tem caused by the ventricular systole
atid the base of the next up-stroke corresponds to (Broadbent). |

a beat of the heart, so that this figure shows five Analysis.—A sphygmogram or

heart-beats and part of a sixth. pulse-tracing consists of a series of
curves (fig. 81) each of which corresponds with one beat of the heart. Each pulse-
curve consists of —

1. The line of ascent (a to 6 in fig. 81).
2. The apex (P in fig. 83, and 0 in fig. 81).
3. The line of descent (0 to h).

(1) The line of ascent, up-stroke, or percussion stroke, is nearly vertical, and
occurs during the dilatation of the artery produced by the systole of the left ven-
tricle, when the aortic valves are forced open and the ventricular contents are pro-
jected into the arterial system. [The ascent is nearly vertical, but in some cases,
where the ventricle contracts very suddenly, as occasionally happens in aortic
regurgitation, it is quite vertical (fig. 85). |

(2) The apex or percussion wave in a normal pulse is pointed.

(3) The line of descent is gradual, and corresponds to the diminution of diameter
or contraction of the artery. It is interrupted by two completely distinct elevations
or secondary waves. Such elevations are called “catacrotic.” The more distinct
of the two occurs as a well-marked elevation about the middle of the descent (R in
fig. 83 and f in fig. 81); it is called the dicrotic wave, or, with reference to its
mode of origin, the “recoi/ wave.” [As the descent corresponds to the time when
blood is flowing out of the arteries at the periphery into the capillaries, its direction
will depend on the rapidity of the outflow. Thus it will be more rapid in paralysis
of the arterioles and very rapid in aortic regurgitation, where, of course, much of
the blood flows backward into the left ventricle (fig. 85). In this case, the artery
will recoil suddenly from under the finger or pad of the instrument, and this consti-
tutes the “pulse of empty arteries.”|

The dicrotic wave, or recoil wave, corresponds to the time following the closure:
of the aortic valves, and is preceded in the descent by a slight depression, the aortic
notch.

[The tidal wave, or pre-dicrotic, occurs between the apex and the dicrotic wave
(fig. 81, d). It occurs on the descent, and during the contraction of the ventricle.
The tidal wave is best marked in a hard pulse, ze, where the blood-pressure is
high, so that it is usually well marked in cirrhotic disease of the kidney, ac-
companied by hypertrophy of the left ventricle. |

{In some cases, ¢.g., mitral regurgitation, the pre-dicrotic wave may be present in some

pulse-beats and absent in others (fig. 82), where the tidal wave is present in the largest pulse,

———

ORIGIN OF THE DICROTIC WAVE. 103

and absent in the others, while the base line is uneven. In mitral stenosis the amount of blood
discharged into the left ventricle frequently varies, hence the variations in the characters of
the arterial pulse. ]
There may be other secondary waves in the lower part of the descent.
[Respiratory or Base Line.—If a line be drawn so as to touch the bases of all

Fig. 82.
Irregular pulse of mitral regurgitation.

the up-strokes, we obtain a. straight line, hence called by this name. ‘The base line
is altered in disease and during forced respiration (§ 74). |

The pulse-curve indicates the variations of pressure which the blood exerts on the arterial
walls, for the lever rises and falls with the pressure, hence v. Kries calls it the ‘‘ pressure-pulse.”’

68. ORIGIN OF THE DICROTIC WAVE.—The dicrotic or recoil wave,
which is always present in a normal pulse, is caused thus :—During the ventricular
systole a mass of blood is propelled into the already full aorta, whereby a positive
wave is rapidly transmitted from the aorta throughout the arterial system, even to
the smallest arterioles, 7n which this primary wave is extinguished. As soon as the
semi-lunar valves are closed, and no more blood flows into the arterial system, the
arteries, which were previously distended by the mass of blood suddenly thrown
into them, recoil or contract, so that in virtue of the elasticity (and contractility) of
their walls, they exert a counter-pressure upon the column of blood, and thus the
blood is forced onwards. There is a free passage for it towards the periphery, but
towards the centre (heart) it impinges upon the already closed semi-lunar valves.
This develops a new positive wave, which is propagated peripherally through the
arteries, where it disappears in their finest branches. In those cases where there is
sufficient time for the complete development of the pulse-curve, (as in the short
course of the carotids, and in the arteries of the upper arm, but not in those of the
lower extremity, on account of their length), a second reflected wave may be caused
in exactly the same way as the first. Just as the pulse occurs later in the more
peripherally placed arteries than in those near the heart, so the secondary wave
reflected from the closed aortic valves must appear later in the peripheral arteries.
Both kinds of waves, the primary pulse-wave, the secondary, and eventually even
the tertiary reflected wave—arise in the same place, and take the same course, and
the longer the course they have to travel to any part of the arterial system, the
later they arrive at their destination.

[The conditions which favour dicrotism are low blood-pressure and a rapid sharp cardiac con-
traction. When the blood-pressure is low, there is less resistance to the inflow of blood at the
aorta from the left ventricle, so that its systole occurs sharply, forcing on the blood and distending
the arterial walls. The elastic-coats rebound on the contained blood, and thus start a wave from
the closed semi-lunar valves.] .

The following points regarding the dicrotic wave have been ascertained experi-
mentally, chiefly by Landois :— -

1. The dicrotic wave occurs later in the déacendiny part of the curve, the further
the artery experimented upon is distant front the heart. Compare the curves,
fig. 83.

The shortest accessible course is*that™of the carotid ; where the dicrotic wave reaches its
maximum 0°35 to 0°37 sec. after the beginning of the pulse. In the upper extremity the apex

of the dicrotic wave is 0°36 to 0°38 to 0°40 sec. after the beginning of the pulse-beat. The
longest course is that of the arteries of the lower extremity. The apex of the dicrotic wave

104 CHARACTERS OF THE DICROTIC WAVE,
oceurs 0°45 to 0°52 to 0°59 sec. after the beginning of the curve. It varies with the height of
the individual.

2. The dicrotic elevation in the descent is lower, and is less distinct, the further
the artery is situated from the heart, so that the longer the distance which the
wave has to travel the less distinct it becomes.

3. It is best marked in a pulse where the primary pulse-wave is short and

Vi VII VIII

X1if

Fig. 83.
I, foe RS Ga pen of carotid artery ; IV, axillary ; V to IX, radial ; X, dicrotic radial
polae s gad gaentel ; XIII, posterior tibial ; XIV, XV, pedal. In all the curves P
“aves {f iy * , , Tave + fp A i ici a
Hate Pex ; v, dicrotic wave ; ¢, ¢, elevations due to elasticity ; K, elevation caused
y the closure of the semi-lunar valves of the aorta.

energetic. It is greatest relatively when the systole of the heart is short and
energetic, ; ’
4, It is better marked the lower the tension of the blood within the arteries, {and

ELASTIC ELEVATIONS. 105

is best developed in a soft pulse]. In fig. 83, IX and X were obtained when the
tension of the arterial was Jow; V and VI, medium; and VII with high tension.

Conditions influencing Arterial Tension.—It is diminished at the beginning of inspiration
(§ 74), by hemorrhage, stoppage of the heart, heat, an elevated position of parts of the body,
amyl nitrite, nitro-glycerine, and the nitrites generally. [Both drugs accelerate the pulse-beats
and produce marked dicrotism; with amyl nitrite the full effect is obtained in from 15 to 20
sec. after the inhalation of the dose (fig. 84, A, A’), but with nitro-glycerine not until 6 or 7
min. (fig. 84, B, B’) and in the latter case the effects last longer.] It is increased at the

Fig. 84.
Pulse-tracings. A, normal ; A’, one minute after inhalation of amyl nitrite ; B, normal; B,
after a dose of nitro-glycerine (Stirling after Murrell).

beginning of expiration, by accelerated action of the heart, stimulation of vaso-motor nerves,
diminished outflow of blood at the periphery, and by inflammatory congestion by certain
poisons, as lead ; compression of other large arterial trunks, action of cold and electricity on
the small cutaneous vessels, andl by impeded outflow of
venous blood. When a large arterial trunk is exposed, the
stimulation of the air causes it to contract, resulting in an
increased tension within the vessel. In many diseased con-
ditions the arterial tension is greatly increased—{e.g., in
Bright’s disease, where the kidney is contracted (‘‘ granu-
lar’’), and where the left ventricle is hypertrophied].

In all these conditions increased arteriai tension is indi-
cated by the dicrotic wave being less high and less distinct,
while with diminished arterial tension it is a larger and
apparently more independent elevation. Moens has shown
that the time between the primary elevation and the dicrotic
wave increases with increase in the diameter of the tube, Fig. 85,
with diminution of its thickness, and when its coefficient of Aortic regurgitation.
elasticity diminishes.

[The dicrotic wave is absent or but slightly marked in cases of atheroma and in aortic
regurgitation (fig. 85). In this fig. observe also the vertical character of the up-stroke. |

Elastic Elevations.— Besides the dicrotic wave, a number of small less-marked
elevations occur in the course of the descent in a sphygmogram (fig. 83, e, ¢).
These elevations are caused by the elastic tube being thrown into vibrations by the
rapid energetic pulse-wave, just as an elastic membrane vibrates when it is suddenly
stretched. The artery also executes vibratory movements when it passes suddenly
from the distended to the relaxed condition. These small elevations in the pulse-
curve, caused by the elastic vibrations of the arterial wall, are called “elastic
elevations” by Landois.

(1) The elastic vibrations increase in number in one and the same artery with
the degree of tension of the elastic arterial wall. A very high tension occurs in
the cold stage of intermittent fever, in which case these elevations are well marked.

(2) If the tension of the arterial wall be greatly diminished, these elevations may
disappear, so that, while diminished tension favours the production of the dicrotic
wave, it acts in the opposite way with reference to the “elastic elevations.” (3)
In diseases of the arterial walls affecting their elasticity, these elevations are either
greatly diminished or entirely abolished. (4) The farther the arteries are distant
from the heart, the higher are the elastic elevations. (5) When the mean pressure
within the arteries is increased by preventing the outflow of blood from them, the
elastic vibrations are higher and nearer the apex of the curve. .(6) They vary

106 DICROTIC PULSE.

_in number and length in the pulse-curves obtained from different arteries of the
body.

When the arm is held in an upright position, after five minutes the blood-vessels empty
themselves, and collapse, while the elasticity of the arteries is diminished.

69. Dicrotic Pulse.—Sometimes during fever, especially when the temperature is high, 2
dicrotic pulse may be felt, each pulse-beat, as it were, being composed of two beats (fig. 83, X),
one beat being large and the other small, and more like an after-beat. Both beats correspond
to one beat of the heart. The two beats are quite distinguishable by the touch. The
phenomenon is only an exaggerated condition of what occurs in a normal pulse. The sensible

Fig. 86.
Development of the Pulsus dicrotus—-P. caprizans ; P. monocrotus.
I }

second beat is nothing more than the greatly increased dicrotic elevation, which, under ordinary
conditions, is not felt by the finger.

Conditions.—The occurrence of a dicrotic pulse is favoured (1) by a short primary pulse-
wave, as in fevers, where the heart beats rapidly.

(2) By diminished arterial tension. A short systole and diminished arterial blood-pressure are
the most favourable conditions for causing a dicrotic pulse. [So that dicrotism is best marked
in a soft pulse.] The double beat may be felt only at certain parts of the arterial system,
whilst at other parts only a single beat is felt. A favourite site is the radial artery of one or
other side, where conditions favourable to its occurrence appear to exist. This seems to be due
to a local diminution of the blood-pressure in this area, owing to the paralysis of its vaso-
motor nerves (Landois). If the tension be increased by compresisng other large arterial trunks
or the veins of the part, the double beat becomes a simple pulse-beat. The dicrotic pulse in
fever seems to be due to the increased temperature (39° to 40° C.), whereby the artery is more
distended, and the heart-beat is shorter and more prompt.

(3) It is absolutely necessary that the elasticity of the arterial wall be normal. The dicrotic
pulse does not occur in old persons with atheromatous arteries.

Monocrotic Pulse. —In fig. 86, A, B, C, we observe a gradual passage of the normal radial
curve, A, into the dicrotic beat, B, and C, where the dicrotic wave, 7, appears as an indepen-
dent elevation. If the frequency of the pulse increases more and more in fever, the next
following pulse-beat may occur in the ascending part of the dicrotic wave, D, E, F, and it may
even occur close to the apex, G (P. caprizans). If the next following beat occurs in the

depression, 7, between the primary
elevation, p, and the dicrotic eleva-

\ \ \ A n / \
\ | ee Ay eae | pea '\ '\ tion, 7, the latter entirely disappears,
\A A \~ we Va Fe \ i\/ \v | and the curve, H, assumes what Lan-

dois calls the ‘‘ monocrotic”’ type.
Ay ds ae [Degrees of Dicrotism.—W hen the
Fig. 87. aortic notch reaches the respiratory or
Hyperdicrotic pulse. base line, the tidal wave having dis-
appeared, the pulse is said to be fully
dicrotic. When the aortic notch falls below the base line, z.e., below where the up-stroke
begins, the pulse is said to be hyperdicrotic (fig. 87). This form occurs during high fever (104°

F.), and is usually a grave sign, indicating exhaustion and the need for stimulants. ]

70. CHARACTERS OF THE PULSE.—[The three factors concerned in the production of
the pulse are, (1) the action of the heart, (2) the elasticity of the large vessels, (3) the resistance
in the small arteries and capillaries. Any or all or several of these factors may be modified.]}
(1) Frequency.—According as a greater or less number of beats occurs in a given time, ¢.g.,
per minute, the pulse is said to be frequent or infrequent. The normal rate, in man=71
per minute, and somewhat more in the female; in fever it may exceed 120 (250 have been
counted by Bowles), while in other diseases it may fall to 40, and even 10 to 15; but such
cases are rare, and are probably due to an affection of the cardiac nerves (§ 41). The frequency

r
‘

“<— SO
. =)

CONDITIONS AFFECTING THE PULSE-RATE. 107

of the pulse is usually increased when the respirations are deeper, but not more numerous, /.¢.,
rapid shallow respirations do not affect the frequency of the pulse, but deep respirations do.
[The frequency. may be regular or irregular with regard to time. ]

(2) Celerity or Rapidity.—If the pulse-wave is developed, so that the distension of the artery
slowly reaches its height, and the relaxation also takes place gradually, we have the p. tardus
or slow or long pulse ; the opposite condition gives rise to the p. celer or gwick or short pulse.
The rapidity of the pulse is increased by quick action of the heart, power of expansion of the
arterial walls, easy efflux of blood owing to the dilatation of the small arteries, and by nearness
to the heart. [The quickness has reference to a single pulse-beat, the frequency to a number of
beats.] In a quick pulse, the curve is high and the angle at the apex is acute, while in a slow
pulse the ascent is low and the angle at the apex is large.

(3) Conditions affecting the Pulse-Rate.—Frequency in Health.—In man the normal pulse-
rate=71 to 72 beats per minute, in the female about 80. In some individuals the pulse-rate
may is higher (90 to 100), in others lower (50), and such a fact must be borne in mind.

(a) Age :—

Beats per Beats per | : Beats per
Minute. ; Minute. | Minute, ;
Newly born, - 180t0 140 | Syears, . » 94 to 90 | 25 to 50 years, d 70
1 year, ; « 120'to 190) 10°. ; ° . about 90 | 60 years, . : ‘ 74
2 years, ; set 105 10°te 15 years, Pe. a eo.) ee . : 79
2 ae ; « * 100 15-to 20° 5, : . 40 | 80 to 90 years, over 80
aay : oe: 20 to 25: ,, ‘ 2 40

_(b) The length of the body has a certain relation to the frequency of the pulse. The following
results have been obtained by Czarnecki from the formule of Volkmann and Rameaux :—

Length of Body Pulse. Length of Body Pulse.
in 10 cm. Calculated. Observed. in 10 cm. Calculated. Observed.
80 to 90, , Z : 90 103 140 to150,. .. : F 69 74
90 to 100, F ‘. e, 86 91- FOO tO: LOO). ag AK : 67 68
100 to 110, , , : 81 87 160:to-17 0: ) : , 65 65
110 to 120, ; 5 F 78 84 £70. to. 180, , : : 63 64
120 to 130, et es 78 Above 180, . . . 60 60
130 to 140, ee ee Diese 76

(c) The pulse-rate is increased by muscular activity, by every increase of the arterial blood-
pressure, by taking of food, increased temperature, painful sensations, by psychical disturbances,
and [in extreme debility]. Increased heat, fever, or pyrexia increases the frequency, and as a
rule the increase varies with the height of the temperature. [Dr Aitken states that an increase
of the temperature of 1° F. above 98° F. corresponds with an increase of ten pulse-beats per
minute ; thus—

Temp. F. Pulse-Rate. | Temp. F. Pulse-Rate. | Temp. F. Pulse-Rate,
i aw . ; 60 100 ; : 90 10e ; ; 120
hee “ ; 70 102" 3 ; <) 100 105° ‘ : 130

100". «3 : : 80 103°. ‘ Pe EE) 106°. 2 ° 140

This is merely an approximate estimate.] It is more frequent when a person is standing than
when he lies down. Music accelerates the pulse and increases the blood-pressure in dogs and
men. Increased barometric pressure diminishes the frequency.

The Variation of the Pulse-Rate during the Day.—3 to 6 A.M. =61 beats; 8 to114 A.M. =74.
It then falls towards 2 p.m. ; towards 3 (at dinner-time) another increase takes place and goes
on until 6 to 8 p.M.=70; and it falls until midnight=54. It then rises again towards
2 A.M., when it soon falls again, and afterwards rises as before towards 3 to 6 A.M.

[Pulse-Rate in Animals, —(Colin). |

Per Min. Per Min. Per Min.
Elephant, . ; 25-28 Lioness, . ; 68 Rabbit, : . 120-150
Camel, . me as 28-32 Tiger, ‘ : 74 Mouse, . : 120
Giraffe, ; r 66 Sheep, : : 70-80 Goose, . ; ae 110
. Horse, . ; ; 36-40 Goat, : ‘ 70-80 Pigeon, : 136
OST pt oi : 45-50 Leopard, . : 60 dten), : : 140
Tapir, . : ; 44 Wolf (female), . 96 Snake, . : : 24
Bis) x + ; : 46-50 | Hyena, . : ~~ 55 Carp, . : — 20
Fig; : . 70-80 Dog, ‘ . 90-100 Frog, . : : 80
bion,) 2.055% i 40 Cat, ‘ . 120-140 Salamander, . : 77

(4) Variations in the Pulse-Rhythm (Allorhythmia).—On applying the fingers to the normal
pulse, we feel beat after beat occurring at-apparently equal intervals. Sometimes in a normal
series a beat is omitted—=pulsus intermittens, or intermittent pulse. [In feeling an inter-
mittent pulse, we imagine or have the impression that a beat is omitted. This may be due to a
reflex arrest of the ventricular contraction, caused by digestive derangement, in which case it
has no great significance ; but if it be due to failure of the ventricular action, intermittent pulse

108 VARIATIONS IN THE CHARACTERS OF THE PULSE.

is a serious symptom, being frequently present when the muscular walls are degenerated.] At
other times the beats become smaller and smaller, and after a certain time begin as large as
before=p. myurus. When an extra beat is intercalated in a normal series=p. intercurrens,

; The regular alternation of a high and
a low beat=p. alternans (fig. 88). In
the p. bigeminus of Traube the beats
occur in pairs, so that there is a longer
pause after every two beats. Traube
found that he could produce this form
of pulse in curarised dogs by stopping
the artificial respiration for a long
time. The p. trigeminus and quadrigeminus occur in the same way, but the irregularities
occur after every third and fourth beat. Knoll found that in animals such irregularities of the
pulse were apt to occur, as well as great irregularity in the rhythm generally, when there is
much resistance to the circulation, and consequently the heart has great demands upon its
energy. The same occurs in man when an improper relation exists between the force of the
cardiac muscle and the work it has to do (Riegel). Complete irregularity of the heart’s action
is called arhythmia cordis.

71. VARIATIONS IN THE CHARACTERS OF THE PULSE.—Compressibility.—The rela-
tive strength or compressibility of the pulse (p. fortis and debilis), 7.c., whether the pulse is
strong or weak, is estimated by the weight which the pulse is able to raise. A sphygmograph,
provided with an index indicating the amount of pressure exerted upon the spring pressing upon
the artery, may be used (fig. 73). In this case, as soon as the pressure exerted upon the artery
overcomes the pulse-beat, the lever ceases to move. The weight employed indicates the strength
of the pulse. [The finger may be, and generally is used. The finger is pressed upon the artery
until the pulse-beat in the artery beyond the point of pressure is obliterated. In health it re-
quires a pressure of several ounces to do this. Handfield Jones uses a sphygmometer for this
purpose. It is constructed like a cylindrical letter-weight, and the pressure is exerted by means
of a spiral spring which has been carefully graduated.] The pulse is hard or soft when the
artery, according to the mean blood-pressure, gives a feeling of greater or less resistance to the
finger, and this quite independent of the energy of the individual pulse-beats (p. durus and
mollis). In estimating the tension of the artery and the pulse, 7.¢.; whether it is hard or soft,
it is important to observe whether the artery has this quality only during the pulse-wave, 7.¢.,
if it is hard during diastole, or whether it is hard or soft during the period of rest of the arterial
wall. All arteries are harder and less compressible during the pulse-beat than during the period
of rest, but an artery which is very hard during the pulse-beat may be hard also during the
pause between the pulse-beats, or it may be very soft, as in insufficiency of the aortic valves.
In this case, after the systole of the left ventricle, owing to the incompetency of the aortic semi-
lunar valves, a large amount of blood flows back into the ventricle, so that the arteries are
thereby suddenly rendered partially empty. [The sudden collapse of the artery. gives rise to
the characteristic ‘‘ pulse of unfilled arteries” (fig. 85).]

Under similar conditions, the volume of the pulse is obvious from the size of the sphygmo-
gram, so that we speak of a large and a small pulse (p. magnus and parvus). Sometimes the
pulse is so thready and of such diminished volume that it can scarcely be felt. A large pulse
occurs in disease when, owing to hypertrophy of the left ventricle, a large amount of blood is
forced into the aorta. A sma// pulse occurs under the opposite condition, when a small amount
of blood is forced into the aorta, either from a diminution of the total amount of the blood, or
from the aortic orifice being narrowed [aortic stenosis], or from disease of the mitral valve ;
again, where the ventricle contracts feebly, the pulse becomes small and thready.

Compare the two radials. Sometimes the pulse differs on the two sides, or it may be absent
on one side. [The pulse-wave in the two radials is often different when an aneurism is present
on one side, |

Angiometer.—Waldenburg constructed a ‘‘ pulse-clock” to register the tension, the diameter
of the artery, and the volume of the pulse upon adial. It does not give a graphic tracing, the
results being marked by the position of an indicator.

Fig. 88.
Pulsus alternans.

72, THE PULSE.CURVES OF VARIOUS ARTERIES.—1. Carotid (fig. 83, I, II, Ill;

fig. 93, Cand C,). The ascending part is very steep—the apex of the curve (fig. 83, P) is sharp
and high. Below the apex there is a small notch—the “aortic notch” (fig. 83, K)—which
ape $ on a positive wave formed in the root of the aorta, owing to the closure of the aortic
valves, and propagated with almost wholly undiminished energy into the carotid artery.- Quite
close to this notch, if the curve be obtained with minimal friction, the first elastic vibration
occurs (fiy. 83, II, ¢). Above the middle of the descending part of the curve is the dicrotic
elevation, R, produced by the reflection of a positive wave from the already closed semi-lunar
valves. The dicrotic wave is relatively small on account of the high tension in the carotid
artery. After this the curve falls rapidly, but in its lowest third two small elevations may be
seen. Of these the former is due to elastic vibration. The latter represents a second dicrotic

y
¢——,.

ANACROTISM. 109

wave fig. 83, III, R). Here there is a true tricrotism, which is more easily obtained from the
carotid on account of the shortness of the arterial channel.

2. Axillary Artery (fig. 83, IV). In this curve the ascent is very steep, while in the descent
near the apex there is a small.(aortic) elevation, K, caused by a positive wave, produced by the
closure of the aortic valves. Below the middle there is a tolerably high dicrotic elevation, R,
higher than in the carotid curve ; because in the axillary artery the arterial tension is less, and
permits a greater development of the dicrotic wave. Further on, two or three small elastic
vibrations occur, @, é.

8. Radial Artery (fig. 78; fig. 83, V to X; fig. 93, Rand R,). The line of ascent (fig. 83)
is tolerably high and sudden—somewhat in the form of a long f. The apex, P, is well marked.
Below this, if the tension be high, two elastic vibrations may occur (V, ¢, e), but if it be low
only one (VI to IX, ¢). About the middle of the curve is the well-marked dicrotic elevation,
R. This wave is least pronounced in a small hard pulse, and when the artery is much dis-
tended (fig. 83, VII, R,); it is larger when the tension is low (fig.
83, IX, R), and is greatest of all when the pulse is dlicrotic (X, R).
Two or three small elastic elevations occur in the lowest part of
the curve.

4, Femoral Artery (fig. 83, XI, XII). The ascent is steep and
high—the apex of the curve is not unfrequently broad, and in [img
it the closure of the aortic valves (K) is indicated. The curve
falls rapidly towards its lowest third. The dicrotic elevation, R,
occurs late after the beginning of the curve, and there are also small
elastic elevations (eé, e). Fie. 89.

5. Pedal Artery (fig. 83, XIV, XV), and Posterior Tibial (fig. 89 =
and fig. 83, XIII). In pulse-curves obtained fiom these arteries,
there are well-marked indications that the apparatus (heart) pro-
ducing the waves is placed at a considerable distance. The ascent
is oblique and low—the dicrotic elevation occurs late. Two elastic
vibrations (fig. 88, XIV, e, ¢) occur in the descent, but they are very close to the apex, while
the elastic vibrations at the lower part of the curve are feebly marked. Fig. 89 is from the
posterior tibial, When measured, it gives the following result :—

1 to 2 , : 9°5
ek, oe Se 203 1 vibration is=0°01613 sec.
1 to 6 : : 61

73. ANACROTISM. —As a general rule, the line of ascent of a pulse-curve has the forni of an
J, and is nearly vertical. The arterial walls are thrown into elastic vibration by the pulse-beat,
and the number of vibrations depends greatly upon the tension of the arterial walls. The
distension of the artery, or what is the same thing, the ascent of the sphygmogram, usually
occurs so rapidly that it is equal to one elastic vibration. The elongated /f-shape of the ascent
is fundamentally just a prolonged elastic vibration. When the number of-vibrations causing
the elastic variation is small, and when the line of ascent is prolonged, two elevations occasion-
ally occur in the line of ascent. Such a condition may occur normally (fig. 83, VIII, at
land.2; X, at land 2). When a series of closely-placed elastic vibrations occur in the upper

B C 0
i

Fig. 90.
Anacrotic radial curves. a, a, the anacrotic parts.

part of the line of ascent, so that the apex appears dentate and forms an angle with the line
of ascent, then the condition becomes one of anacrotism (fig. 90, a, w), which, when it is so
marked, may be characterised as pathological. Anacrotism of the pulse occurs when the time
of the influx of the blood is longer than the time occupied by an elastic vibration. Hence it
takes place :—

(1) In dilatation and hypertrophy of the left ventricle, ¢.g., fig. 90, A, a tracing from the
radial artery of a man suffering from contracted kidney. The large volume of blood expelled
with each systole requires a long time to dilute the tense arteries. .

(2) When the extensibility of the arterial wall is diminished, even the normal amount of
blood expelled from the heart at every systole requires a long time to dilate the artery. This
oceurs.in old people where the arteries tend to become rigid, ¢.g., in atheroma. Cold also

Curve of posterior tibial.
Written by the angio-
graph upon a vibrating
plate.

110 INFLUENCE OF RESPIRATION ON PULSE-CURVE,

stimulates the arteries, so that they become less extensile. Within one hour after a tepid bath,
the pulse assumes the anacrotic form (fig, 90, D) (@. v. Liebig).

(3) When the blood stagnates in consequence of great diminution in the velocity of the
blood-stream, as occurs in paralysed limbs, the volume of blood propelled into the artery at
every systole no longer produces the normal distension of the arterial coats, and anacrotic
notches occur (fig. 90, B).

(4) After ligature of an artery, when blood slowly reaches the peripheral part of the vessel
through a relatively small collateral circulation, it also occurs. If the brachial artery be com-
pressed so that the blood slowly reaches the radial, the radial pulse may become anacrotic.
It often occurs in stenosis of the aorta, as the blood has difficulty in getting into the aorta (fig.
90, C).

Recurrent Pulse.—If the radial artery be compressed at the wrist, the pulse-
beat reappears on the distal side of the point of pressure through the arteries of
the palm of the hand (Janaud, Neidert), The curve is anacrotic, and the dicrotic
wave is diminished, while the elastic elevations are increased.

(5) A special form of anacrotism occurs in cases of well-marked insufficiency of the aortic
valves. Practically, in these cases, the aorta remains permanently open. The contraction of
the left auricle causes in the blood a wave-motion, which is at once propagated through the
open mouth of the aorta into the large blood-vessels. This wave is followed by the wave caused
by the contraction of the hypertrophied left ventricle, but of course the former wave is not so
large as the latter. In insufficiency of the aortic valves, the auricular wave occurs before the
ventricular wave in the ascending part of the curve, The auricular is well marked only in the
large vessels, for it soon becomes lost in the peripheral vessels. Fig. 91, I, was obtained from

‘ Il,
| Fig. 91,
I., II., I11., curves with anacrotic elevations a, in insufficiency o1 the aortic valves,

the carotid of a man suffering from well-marked insufficiency of the aortic valves, with con
siderable hypertrophy of the left ventricle and left auricle. The ascent is steep, caused by the
force of the contracting heart, In the apex of the curve are two projections ; A is the anacrotic
auricular wave, and V is the ventricular wave, Fig, 91, II, is a curve obtained from the sub-
clavian artery of the same individual. In the femoral artery the auricular projection is only
obtained when the friction of the writing-style is reduced to the minimum, and when it occurs
it immediately precedes the beginning of the ascent (fig. 86, III, a). The pulse-curve, in cases
of aortic insufficiency, is also characterised by-—-(1) its considerable height ; (2) the rapid fall
of the lever from the apex of the curve, because a large part of the blood which is forced into
the aorta regurgitates into the left ventricle when the ventricle relaxes ; (3) not unfrequently a
projection occurs at the apex, due to the elastic vibration of the tense arterial wall ; (4) the
dicrotic wave (R) is small compared with the size of the curve itself, because the pulse-wave,
owing to the lesion of the aortic valves, has not a sufficiently large surface to be reflected from
(fig. 85). The great height of the curve is explained by the large amount of blood projected
into the aortic system by the greatly hypertrophied and dilated ventricle.

74. INFLUENCE OF RESPIRATION ON THE PULSE-CURVE.—The
respiratory movements influence the pulse (1) in a purely physical way. Stated
broadly, the blood-pressure rises during inspiration and falls during expiration,
but when we consider the effect on the pulse-curve, it is found that it varies with
the depth, rapidity, and ease of respiration : (2) the respiratory movements are

NORMAL RESPIRATION. | GB

accompanied by stimulation of the vasomotor centre, which produces variations of
the blood-pressure.

1. Normal Respiration.—Fig. 92 shows what sometimes, but by no means
always, happens. During inspiration, owing to the dilatation of the thorax, more
arterial blood is retained within the chest, while at the same time venous blood is

Fig. ‘92,
Influence of the respiration upon the pulse. J, inspiration ; E, expiration,

sucked into the right auricle by the aspiration of the thorax ; as a consequence of
this, the tension in the arteries during inspiration must be less. The diminution
of the chest during expiration favours the flow in the arteries, while it retards, the
flow of the venous blood in the vene cave, two factors which raise the tension in
the arterial system. The difference of pressure explains the difference in the form
of the pulse-curve obtained during inspiration and expiration, as in fig. 92 and fig.
83, I, III, IV, in which J indicates the part of the curve which occurred during
inspiration, and E the expiratory portion. The following are the points of
difference :—(1) The greater distension of the arteries during expiration causes all
the parts of the curve occurring during this phase to be higher; (2) the line of
ascent is lengthened during expiration, because the expiratory thoracic movement
helps to increase the force of the expiratory wave; (3) owing to the increase of
the pressure, the dicrotic wave must be less during expiration; (4) for the same
reason the elastic elevations are more distinct and occur higher in the curve near
its apex. The frequency of the pulse is slightly greater during expiration than
during inspiration.

2. This purely mechanical effect of the respiratory movements is modified by the
simultaneous stimulation of the vasomotor centre which accompanies these move-
ments. At the beginning of inspiration the blood-pressure in the arteries is lowest,
but it begins to rise during inspiration, and increases until the end of the inspiratory
act, reaching its maximum at the beginning of expiration ; during the remainder
of the expiration the blood-pressure falls until it reaches its lowest level again at
the beginning of inspiration (compare § 85, /); the pulse-curves are similarly
modified, and exhibit the signs of greater or less tension of the arteries correspond-
ing to the phases of the respiratory movements. [There is, as it were, a displace-
ment of the blood-pressure curve relative to the respiratory curve. |

Forced Respiration.—With regard to the effect produced on the pulse-curve
by a powerful expiration and a forced inspiration, observers are by no ieans
agreed. :

Valsalva’s Experiment.—Strong expiratory pressure is best produced by closing
the mouth and nose, and then making a great expiratory effort (§ 60); at jirst
there is increase of the blood-pressure, while the form of the pulse-waves resembles
that which occurs in ordinary expiration, the dicrotic wave being less developed ;
but, when the forced pressure is long continued, the pulse-curves have all the signs
of diminished tension. This effect is due to the action of the vasomotor centre,
which is affected reflexly from the pulmonary nerves. We must assume that forced
expiration, such as occurs in Valsalva’s experiment, acts by depressing the activity
of the vasomotor centre (§ 371, II.), Coughing, singing, and declaiming act like
Valsalva’s experiment, while the frequency of the pulse is increased at the same
time. A/fter the cessation of Valsalva’s experiment, the blood-pressure rises above
the normal state (Sommerbrodt), almost as much as it fell below it; the normal
condition being restored within a few minutes (Lenzmann).

112 INFLUENCE OF PRESSURE ON THE PULSE-CURVE.

Miuller’s Experiment.—When the thorax is in the expiratory phase, close the
mouth and nose, and take a deep inspiration so as forcibly to expand the chest
(§ 60). At first the pulse-curves have the characteristic signs of diminished tension,
viz., a higher and more distinct dicrotic wave; then the tension can, by nervous.
influences, be increased, just as in fig. 93, where C and R are tracings taken from

Fig. 93.
C, curve from the carotid, and R, radial, during Miiller’s experiment ; C, and R,, during
Valsalva’s experiment. Curves written on a vibrating surface.

the carotid and radial arteries respectively, during Miiller’s experiment, in which
the dicrotic waves, 7, 7, indicate the diminished tension in the vessels. In C, and
R,, taken from the same person during Valsalva’s experiment, the opposite con-
dition occurs.

Compressed Air.—On capiring into a vessel resembling a spirometer (see Respiration),
(Waldenburg’s respiration apparatus), and filled with compressed air, the same result is obtained
as in Valsalva’s experiment—the blood-pressure falls and the pulse-beats increase ; conversely,
the inspiration trom this apparatus of air under less pressure acts like Miiller’s experiment, 7.¢.,
it increases the effect of the inspiration, and afterwards increases the blood-pressure, which may
either remain increased on continuing the experiment, or may fall (Lenzmann).

The inspiration of compressed air diminishes the mean blood-pressure (Zwntz), and the after-
effect continues for some time. The pulse is more frequent both during and after the experi-
ment. Lxpiration in rarefied air increases the blood-pressure. The effects which depend upon
the action of the nervous system do not occur to the same extent in all cases. Exposure to
compressed air in a pneumatic cabinet lowers the pulse-curve, the elastic vibrations become
indistinct, and the dicrotic wave diminishes and may disappear (v. Vivenot). The heart’s beat
is slowed and the blood-pressure raised (Bert). Exposure to rarefied air causes the opposite
result, which is a sign of diminished arterial tension.

Pulsus Paradoxus.—Under pathological conditions, especially when there is union of the
heart or its large vessels with the surrounding parts, the pulse during inspiration may be

Fig. 94.
Pulsus paradoxus (after Kussmaul). E, expiration ; J, inspiration.
extremely small and changed, or may even be absent (fig. 94). This condition has been called
pulsus paradoxus (Griesinger, Kussmaul). It depends upon a diminution of the arterial lumen
during the inspiratory movement. Even in health, it is possible by a change of the inspiratory
movement to produce the p. paradoxus (Riegel, Sommerbrodt).

75. INFLUENCE OF PRESSURE ON THE PULSE-CURVE.—It is most important to know
the actual pressure which is applied to an artery while a sphygmogram is being taken. The
changes affect the form of the curve as well as the relation of individual parts thereof. In fig.
95, a, 6, c, d, e are radial curves ; a was taken with minimal pressure, b with 100, ¢ 200, d 250,
and ¢ 450 grams pressure, while A, B, C, D show the relations as to the time of occurrence
of the individual phenomena where the weight was successively increased. The study of these:
eurves yields the following results :—(1) When the weight is small, the dicrotic wave is
relatively less ; the whole curve is high ; (2) with a moderate weight (100 to 200 grams) the
dicrotic wave is best marked, the whole curve is somewhat lower ; (3) on increasing the weight
the size of the dicrotic wave again diminishes ; (4) the fine elastic vibrations preceding the
dicrotic wave appear first when a weight of 220 to 300 grams is used ; (5) the rapidity of the

TRANSMISSION OF PULSE-WAVE. 1 ee

pulse changes with increasing weight, the time occupied by the ascent becoming shorter, the
descent becoming longer ; (6) the height of the entire curve decreases as the weight increases.
In every sphygmogram the pressure under which it was obtained ought always to be stated.
In fig. 95, A, Bare curves obtained from the radial artery of a healthy student. The pressure
exerted upon the artery for A was 100 ; B, 220 grms. (1 vibration =0°01613 sec. ).

Lf pressure be exerted upon an artery for a long time, the strength of the pulse is gradually
increased. If, after subjecting an artery to considerable pressure, a lighter weight be used, not

Fig. 95.
Various forms of curves (radial) obtained by gradually increasing the pressure.

unfrequently the pulse-curve assumes the form of a dicrotic pulse, owing to the greater develop-
ment of the dicrotic elevation. When strong pressure is applied, the blood is forced to find its
way through collateral channels. When the chief artery ceases to be compressed, the total
area is, of course, considerably and suddenly enlarged, which results in the production of a
dicrotic elevation. Fig. 83, X, is such a dicrotic curve obtained after considerable pressure had
been applied to the artery.

76. TRANSMISSION OF PULSE-WAVES.—The pulse-wave proceeds through-
out the arterial system from the root of the aorta, so that the pulse is felt sooner
in parts lying near the heart than in the peripheral arteries. E. H. Weber calcul-
ated the velocity of the pulse-wave as 9:240 metres [284 feet] per second, from
the difference in time between the pulse in the external maxillary artery and the
dorsal artery of the foot. Czermak showed that the elasticity was not equal in all
the arteries, so that the velocity of the pulse-wave cannot be the same in all. The
pulse-wave is propagated more slowly in the arteries with soft extensile walls than
in arteries with resistent and thick walls, so that it is transmitted more rapidly in
the arteries of the lower extremities than in those of the upper. It is still slower
in children, ome

7'7. PULSE-WAVE IN ELASTIC TUBES. -—Waves similar to the pulse may be produced in
elastic tubes. (1) According to E. H. Weber the velocity of propagation of the waves is 11:205
metres per sec.; according to Donders, 11-13 metres (34-42 feet). (2) According to E. H.
Weber increased internal tension causes only an inconsiderable decrease ; Rive found a great
decrease ; Donders found no obvious difference ; while Marey found an increased velocity. (3)
Donders found the velocity to be the same in tubes 2 mm. in diameter as in wider tubes, but
Marey believes that the velocity varies when the diameter of the tube changes. (4) The
velocity is less, the smaller the elastic coefficient. (4) The velocity increases with increased
thickness of the wall, while it diminishes when the specific-gravity of the fluid increases.

Moens has recently formulated the following laws as to the velocity of propagation of waves in
elastic tubes :—(1) It is inversely proportional to the square root of the specific gravity of the
fluid ; (2) it is as the square root of the thickness of the wall, the lateral pressure being the
same ; (3) it is inversely as the square root of the diameter of the tube, the lateral pressure being
the same ; (4) it is as the square root of the elastic coefficient of the wall of the tube, the lateral
pressure being the same (Valentin).

(A) The velocity of the wave is 11°809 metres per second.

(B) The intra-vascular pressure has a. decided influence on the velocity: thus, in the tube,

H

II4 VELOCITY OF THE PULSE-WAVE IN MAN.

A, with 18 cm. (Hg.) pressure, the velocity per metre=0°093 second, while with 21 cm. pres-
sure (Hg.)=0°095 second per metre.

(C) The specific gravity of the liquid influences the velocity of the pulse-wave. In mercury
the wave is propagated four times more slowly than in water.

(D) The velocity in a tube which is more rigid and not so extensile is greater than in a tube
which is easily distended.

78. VELOCITY OF THE PULSE-WAVE IN MAN.—Landois obtained the following results
in a student :—Difference between carotid and radial=0°074 second (the distance being taken
as 62 centimetres) ; carotid and femoral =0°068 second ; femoral (inguinal region) and posterior
tibial=0°097 second (distance estimated at 91 centimetres). [Waller obtained between the
heart and carotid 0°10 second ; heart and femoral, 0°18 sec. ; heart and dorsalis pedis, 0°22. ]

The velocity of the pulse-wave in the arteries of the upper extremities = 8°43
metres per second, and in those of the lower extremity 9°40 metres per second, [7.¢.,
about 30 feet per second]. The velocity is greater in the less extensile arteries of
the lower extremities than in those of the upper limb. For the same reason it is
less in the peripheral arteries and in the yielding arteries of children (Czermah).

Kk. H. Weber estimated the velocity at 9°24 metres per second; Garrod, 9-10°8 metres ;
Grashey, 8°5 metres ; Moens, 8°3 metres, and with diminished pressure during Valsalva’s experi-
ment 7°3 metres (§ 60, § 74).

Influencing Conditions. —In animals, hemorrhage, slowing of the heart produced by stimula-
tion of the vagus (Moens), section of the spinal cord, deep morphia-narcosis, and dilatation of
the blood-vessels by heat, produce slowing of the velocity, while stimulation of the spinal cord
accelerates it (Grunmach).

The wave-length of the pulse-wave is obtained by multiplying the duration of
the inflow of blood into the aorta=0-08 to 0:09 second (§ 51), by the velocity of
the pulse-wave.

Method. —Place the knobs of two tambours (fig. 76) upon the two arteries to be investigated,
or place one over the apex-beat and the other upon an artery. These receiving tambours are
connected with two registering tambours, as in Brondgeest’s pansphygmograph (§ 67, fig. 76);
so that their writing-levers are directly over each other, and so arranged as to write simultane-
ously on one vibrating plate attached to a tuning-fork. [Or they may be made to write upon a
revolving cylinder, whose rate of movement is ascertained by causing a tuning-fork of a known
rate of vibration to write under them.] The apparatus is
improved by using rigid tubes and filling them with water,
in which all impulses are rapidly communicated. In arteries
which are distant from each other, or in the case of the heart
and an artery, the two knobs of the receiving tambours may

reer

Fig, 96.
A, curve of radial artery on a vibrating surface (1 vib, =0°01613 sec.) ; P, apex of curve; e¢, ¢,
elastic vibrations ; R, dicrotic wave. B, curve of same radial taken along with the heart-
beat ; v, H, P, contraction of the ventricle.

be connected by means of a Y-tube with one writing-lever. In fig. 96, B is a curve from the
radial artery taken in this way. In it v H P indicates contraction of the ventricle ; H, the
apex of the ventricular contraction; P, the primary apex of the radial curve; v, the beginning
of the ventricular contraction ; p, of the radial pulse. A is the curve of the radial artery alone.
From these curves it is evident that in this instance nine vibrations occur between the begin-
ning of the ventricular contraction and the beginning of the pulse in the radial artery=
0°15 sec.

In fig. 97 the difference between the carotid and the posterior tibial pulse=0°137 sec.

Pathological. —In cases ot diminished extensibility of the arteries, ¢.g., in atheroma (§ 77, D),.
the pulse-wave is propagated more rapidly. Local dilatations of the arteries, as in.aneurisms,
cause a retardation of the wave, and a similar result arises from local constrictions. Relaxation
of the walls of the vessels in high fever retards the movement (Hamernjh).

79. OTHER PULSATILE PHENOMENA.—1. In the mouth and nose, when they are filled

with air, and the glottis closed, pulsatile phenomena (due to the arteries in their soft parts),

i

OTHER PULSATILE PHENOMENA. ELS

may be found communicating a movement to the contained air. The curves obtained are
relatively small, and closely resemble the curve of the carotid. A similar pulse is obtained in
the tympanum with intact membrana tympani, and when the soft parts of the tympanum are
congested (Schwartze, Tréltsch).
2. Entoptical Pulse.—After violent exercise, an illumination, corresponding to each pulse-
. ry ° . . 5 .
beat, occurs on a dark optical field. When the optical field is bright, an analogous darkening

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Fig. 97.

Curves of the carotid and posterior tibial taken simultaneously with Brondgeest’s pansphygmo-
graph writing upon a vibrating-plate attached toa tuning-fork. The arrows indicate the
identical moment of time in each curve.

occurs. The ophthalmoscope occasionally reveals pulsation of the retinal arteries (Jége7),
which becomes marked in insufficiency of the aortic valves.

3. Pulsatile Muscular Contraction.—The orbicularis palpebrarwin niuscle contracts under
similar conditions synchronously with the pulse; and it is perhaps due to the pulse-beat
exciting the sensory nerves reflexly. The Brothers Weber found that not unfrequently, while
walking, the step and pulse gradually and involuntarily coincide.

4. When the legs are crossed as one sits in a chair, the leg which is supported is raised with
each pulse-beat, and it gives also a second or dicrotic elevation.

5. If, while a person is quite quiet, the incisor teeth of the lower jaw be made just to touch
the upper incisors very lightly, we detect a double beat of the lower against the upper teeth,
owing to the pulse-beat in the external maxillary artery raising the lower jaw. The second
elevation is due to the closure of the semi-lunar valves, and not to a dicrotic wave.

6. Brain and Fontanelles.—The large arteries at the base of the vain communicate a
movement to it, while similar movements occur with respiration—rising during expiration and
falling during inspiration. These movements are visible in the fontanelles of infants. The
respiratory movements depend upon variations in the amount of blood in the veins of the
cranial cavity, and also upon the respiratory variations of the blood-pressure.

7. Amongst pathological phenomena are (a) the beating in the epigastrium, ¢.g., in hyper-
trophy of the right or left ventricle, caused, it may be, by deep insertion of the diaphragm, and
it may be, partly, by the beating of a dilated abdominal aorta or cceliac axis.

(b) Aneurisms or abnormal dilatations of the arteries cause an abnormal pulsation, while they

Fig. 98.

I. Elastic support for registering the molar motions of the body—K, wooden box ; B, feet of
patient ; p, cardiograph ; a, b, elastic tubing. II. Vibration curves of a healthy person.
III. Curve obtained from a patient with insufficiency of the aortic valves and great
hypertrophy of the heart.

produce a slowing in the velocity of the pulse-wave in the corresponding artery. Hence the
pulse appears later in such an artery than in the artery on the healthy side. Hypertrophy and

116 VIBRATIONS OF THE BODY DUE TO THE HEART,

dilatation of the left ventricle cause the arteries near the heart to pulsate strongly. In the
analogous condition of the right ventricle, the beat of the pulmonary artery may be seen and felt
in the second left intercostal space.

80. VIBRATIONS OF THE BODY DUE TO THE HEART,—The beating of the heart and
large arteries communicates vibrations to the body as a whole ; the vibration being not simple
but compound. Gordon was the first to represent this pulsatory vibration graphically. Ifa
person be placed in an erect attitude in the scale-pan of a large balance, the index oscillates,
and its movements coincide with the heart’s movements.

Method. —Take a long four-sided box, K, open at the top, and arrange several coils, a, 6, of
stout caoutchouc tubing round one end (fig. 98). A wooden board, B, is so placed that it rests
with one end on the caoutchouc tubing, and with the other on the narrow end of the box. The
person to be experimented upon, A, stands vertically and firmly on this board, A receiving
tambour, p, is placed against the surface of the board next the elastic tube, which registers the
vibrations of the foot-support. Fig. III. is a curve showing such vibrations, each heart-beat
being followed in this case by four oscillations. To ascertain the relations and causes of these
vibrations, it is necessary to obtain, simultaneously, a tracing of the heart and the vibratory
curve, For this purpose use the two tambours of Brondgeest’s pansphygmograph (§ 67, 76),
placing one knob or pad over the heart and the other on the foot-support, and allow the writing-
tambours to inscribe their vibrations on a glass plate attached to a tuning-fork.

In the lower or cardiac impulse curve (fig. 99), the rapidly-rising part is due to the ventricular

Fig. 99.
The upper curve is the vibration-curve of a healthy person, and the lower one a tracing of the
apex-beat.

systole. It contains eight vibrations (1 vib. =0°01613 sec.). The beginning of the ventricular
systole is indicated in the fig. by -36, -3, -17.

If the corresponding numbers in the upper or vibratory curve are studied, it is obvious that
at the moment of ventricular systole the body makes a downward vibration, i.é., it exercises greater
pressure upon the foot-support. Gordon interprets his curve as giving exactly the opposite
result. This downward motion, however, lasted only during five vibrations of the tuning-fork :
during the last three vibrations, corresponding to the systole,,there is an ascent of the body
corresponding to a less pressure upon the foot-plate. When the ventricle empties itself, it
undergoes a movement in a downward and outward direction—Gutbrodt’s “ reaction impulse.”

_In the upper curve analogous numbers are employed.to indicate the vibrations occurring
simultaneously, viz.,-28,-11,-10. The closure of the semi-lunar valves is well marked in the
three heart-beats at 20,-20. This closure is indicated in analogous points in both curves, after
which there is a descent of the foot-support, and this corresponds to the downward propagation
of the pulse-wave through the aorta to the vessels of the feet.

Pathological.—TIn insufficiency of the aortic valves, as shown in fig. 98, III., the vibration
communicated to the body is very considerable.

81, THE BLOOD-CURRENT.—Cause.—The closed and much-branched vas-
cular system, whose walls are endowed with elasticity and contractility, is not only
completely filled with blood, but it is over-filled. The total volume of the blood
is somewhat greater than the capacity of the entire vascular system. Hence it
follows that the mass of blood must exert pressure on the walls of the entire
system, thus causing a corresponding dilatation of the elastic vascular walls
(Brunner). This occurs only during life; after death the muscles of the vessels

relax, and fluid passes into the tissues, so that the blood-vessels come to contain
less fluid, and some of them may be empty.

ai.

i,

a aE

THE BLOOD-CURRENT. 117

If the blood were uniformly distributed throughout the vascular system and under
the same pressure, it would remain in a position of equilibrium (as after death).
lf, however, the pressure be raised in one section of the tube, the blood will move
from the part where the pressure is higher to where it is lower ; so that the blood-
current is a result of the difference of pressure within the vascular system. If
either the aorta or the venze cave be suddenly ligatured in a living animal, the
blood continues to flow, but gradually more slowly, until the difference of pressure
is equalised throughout the entire vascular system.

The velocity of the current will be greater the greater the difference of pressure,
and the less the resistance opposed to the blood-stream.

The difference of pressure which causes the current is produced by the
heart. Both in the systemic and pulmonary circulation the point of greatest
pressure is in the root or beginning of the arterial system, while the point of lowest
pressure is in the terminal portion of the venous orifices at the heart. Hence the
blood flows continually from the arteries through the capillaries into the venous
trunks. The heart keeps up the difference of pressure required to produce this
result ; with each systole of the ventricles a certain quantity of blood is forced into
the beginning of the arteries, while at the same time an equal amount flows from
the venous orifices into the auricles during their diastole (#. H. Weber).

Donders showed that the action of the heart not only causes the difference of
pressure necessary to establish a blood-current, but also raises the mean pressure
within the vascular system. The terminations of the veins at the heart are wider
and more extensible than the arteries where they arise from the heart (fig. 133),
As the heart propels a volume of blood into the arteries equal to that which it
receives from the veins, it follows that the arterial pressure must rise more rapidly
than the venous pressure diminishes, since the arteries are not so wide nor so ex-
tensible as the veins. Thus the total pressure must also increase. 2

Cause of Continuous Flow.—The volume of blood expelled from the ventricles
at every systole would give rise to a jerky or intermittent movement of the blood-
stream—(1) if the tubes had rigid walls, as in such tubes any pressure exerted upon
their contents is propagated momentarily throughout the length of the tube, and
the motion of the fluid ceases when the propelling force ceases ; (2) the flow would
also be intermittent in character in elastic tubes if the time between two successive
systoles were longer than the duration of the current necessary for the compensa-
tion of the difference of pressure caused by the systole. If the time between two
successive systoles be shorter than the time necessary to equilibrate the pressure,
the current will become continuous, provided the resistance at the periphery of the
tube be sufficiently great to bring the elasticity of the tube into action. The more
rapidly systole follows systole, the greater the difference of pressure becomes, and
the more distended the elastic walls. Although the current thus produced is con-
tinuous, a sudden rise of pressure is caused by the forcing in of a mass of blood at
every systole, so that with every systole there is a sudden jerk and acceleration of
the blood-stream corresponding to the pulse (compare § 64). _

This sudden jerk-like acceleration of the blood-current is propagated throughout
the arterial system with the velocity of the pulse-wave : both phenonema are due
to the same fundamental cause. Every pulse-beat causes a temporary rapid pro-
gressive acceleration of the particles of the fluid. . But just as the form-movement
of the pulse is not a simple movement, neither is the pulsatile acceleration a simple
acceleration. It follows the course of the development of the pulse-wave. The
pulse-curve is the graphic representation of the pulsatory acceleration of the blood-
stream. Every rise in the curve corresponds to an acceleration, every depression
to a retardation of the current.

{Method: Rigid and Elastic Tubes.—These facts are easily demonstrated. Tie a Higginson’s
syringe to a piece of an ordinary gas-pipe. On forcing water through the tube, by compressing

118 CURRENT IN THE CAPILLARIES.

the elastic pump, the water will flow out at the other end of the tube in jets, while during the
intervals of pulsation no water will flow out. As the walls of the tube are rigid, just as much
fluid flows out as is forced into the tube. Ifa similar arrangement be made, and a long elastic
tube be used, a continuous outflow is obtained, provided the pulsations occur with sufficient
rapidity and the length of the tube, or the resistance at its periphery, be sufficient to bring the
elasticity of the tube into action. This can be done by putting a narrow cannula in the outflow
end of the tube, or by placing a clamp on it so as to diminish the exit aperture. This apparatus
converts the intermittent flow into a continuous current.] The fire-engine is a good example
of the conversion of an intermittent inflow into a uniform outflow. The air in the reservoir is
in a state of elastic tension, and it represents the elasticity of the vascular walls. When the
pump is worked slowly, the outflow of the water occurs in jets, and is interrupted. If the
pumping movement be sufficiently rapid, the compressed air in the reservoir causes a continuous
outflow, which is distinctly accelerated at every movement of the pump. [The ordinary spray-
producer is another good example. ]

[Thus, there are two factors—a central one, the heart,—and a peripheral one,
the amount of resistance in the arterioles. Either or both may be varied, and as
this is done, so will the pressure and velocity vary. |

Current in the Capillaries.—In the capillaries the pulsatile acceleration of the
current ceases with the extinction of the pulse-wave. The great resistance which is
offered to the current towards the capillary area causes both to disappear. It is
only when the capillaries are greatly dilated, and when the arterial blood-pressure
is high, that the pulse is propagated through the capillaries into the beginning of
the veins. A venous pulse is observed in the veins of the sub-maxillary gland
after stimulation of the chorda tympani nerve, which contains the vaso-dilator
nerves for the blood-vessels of this gland. If the finger be constricted with an
elastic band, so as to hinder the return of the venous blood, and to increase the
arterial blood-pressure, while at the same time dilating the capillaries, an inter-
mittent increased redness occurs, which corresponds with the well-known throbbing
sensation in the swollen finger. This is due to the capillary pulse. [Roy and
Graham Brown found that pulsatile phenomena were produced in the capillaries by
increasing the extra-vascular pressure (§ 86). Quincke called attention to the
capillary pulse, which can often be seen under the finger-nails. Extend the fingers
completely, when a whitish area appears under the nails. <A red area near the free
margin of the nail advances and retires with each pulse-beat. It is well marked in
some diseased conditions of the heart, especially in incompetence of the aortic
valves, and is probably produced by increased extra-vascular pressure, |

82. SCHEMATA OF THE CIRCULATION.—E. H. Weber constructed a scheme of the cir-
culation. It consisted of a force-pump with properly arranged valves to represent the heart,
portions of gut for the arteries and veins, and a piece of glass tubing containing a piece of
sponge to represent the capillaries. Various schemes have been invented, including the very
complicated one of Marey, [the extremely ingenious one of v. Thanhoffer, and the thoroughly
practical one of Rutherford].

83. CAPACITY OF THE VENTRICLES.—Since the right and left ventricles
contract simultaneously, and just the same volume of blood passes through the
pulmonary as through the systemic circulation, it follows that the right ventricle
must be just as capacious as the left. The capacity of the ventricles has been esti-
mated in the following ways :—

Methods. —(1) Directly, by filling the dead relaxed ventricle with blood or an injection mass.
This method is unsatisfactory and inaccurate.

(2) Indirectly. Volkmann (1850) estimated it thus :—Estimate the sectional area of the aorta,
and the velocity of the blood-stream in it (§1). From this calculate the amount of blood passing
through the aorta in the unit of time. As the total quantity of blood in the body is known
(=7s of the body-weight), we can easily calculate how long this takes to flow through the aorta.
We must also know the number of beats during the time of the circulation. From these data,
and from experiments on animals, Volkmann estimated the volume of blood discharged at each

systole by the ventricle to be 445 of the body-weight. For a man weighing 75 kilos. this is
187°5 grams. This estimate still leaves much to be desired. .

Place calculates it in the following manner :—A man uses about 500 litres of O in 24 hours.
To absorb this into the venous blood (which contains about 7 vols per cent. less O than arterial),

bs a

—

Cc —- —_ - ~~

ESTIMATION OF THE BLOOD-PRESSURE, I19g

about 7000 litres of blood must pass through the lungs in 24 hours.

If one calculates 100,000

heart-beats in 24 hours, then at each systole only 70 cubic centimetres are discharged.

Fig. 100.

84. ESTIMATION OF THE BLOOD-PRESSURE.—(A) In Animals: (1) Methods of Hales.

—The Rev. Stephen Hales (1727) was
the first to introduce a long glass tube
into a blood-vessel in order to estimate
the blood-pressure by measuring the
height of the column of blood.

The tube was provided at its lower
end with a copper tube bent at a right
angle (Pitot’s tube). [The tube he used
was one-sixth of an inch bore and about
9 feet long, and was inserted into the
femoral artery of a horse. The height
to which the blood rose in the tube
was noted, as well as the oscillations
that occurred with every pulsation.
From the height of the column of fluid
he calculated the force of the heart. ]

(2) The Hemadynamometer of Poi-
seuille (1828).—This observer used a
U-shaped tube partially filled with
mercury—a manometer—which was
brought into connection with a blood-
vessel by means of a rigid tube, [The
mercury oscillated with every pulsa-
tion, and the extent of the oscillations
was read off by means of a scale attached
to the bent tube. He called the instru-
ment a hemadynamometer. |

[(3) Vierordt used a tube 5 or 6 feet
long, and filled it with a solution of
sodium carbonate, thus preventing
much blood from entering the tube,
while at the same time the soda solu-
tion prevented the coagulation of the
blood.]

(4) C. Ludwig’s Kymograph.
—C. Ludwig employed a U-shaped

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= = — a WY

De SL
Fig. 101.

LL aR

Ludwig’s improved revolving cylinder, 2, moved by the

clock-work in the box 4, and regulated by a Foucault’s
regulator placed-‘on the top of the box. The disc, D,
moved by the clock-work, presses upon the wheel, ,
which can be raised or lowered by the screw, Z, thus
altering the position of 2 on D, so as to cause the cylin-
der-to rotate at different rates. The cylinder itself can
be raised by the handle, VU. On the left side of the
figure is a mercurial manometer. When the cylinder
is used, it is covered with smoked smooth paper.

manometer, but he placed a light float (fig. 100, @, s) upon the surface of the mer-

120 METHOD OF ESTIMATING BLOOD-PRESSURE.

cury in the open limb of the tube. A writing-style, 7, placed transversely on the free
end of the float, inscribed the movements of the float—and, therefore, of the mercury
—upon a cylinder, c, caused to revolve at a uniform rate. This apparatus registered
the height of the blood-pressure, as well as the pulsatile and other oscillations
occurring in the mercury. Volkmann called this instrument a kymograph or
‘““wave-writer.” The difference of the height of the column of mercury, ¢c, d, in
both limbs of the tube indicates the pressure within the vessel. If the height of
the column of mercury be multiplied by 13-5, this gives the height of the corre-
sponding column of blood. Setschenow placed a stop-cock in the lower bend, A,
of the tube. If this be closed so as just to permit a small aperture of communica-
tion to remain, the pulsatile vibrations no longer appear, and the apparatus indicates
the mean pressure. By the term mean pressure is meant the limit of pressure, above
and below which the oscillations occurring in an ordinary blood-pressure-tracing
range. [Briefly, it is the averaye elevation of the mercurial column. |

In a blood-pressure-tracing, such as fig. 102, each of the smaller waves ‘corresponds to a
heart-beat, the ascent corresponds to the systole and the descent to the diastole. The large

Fig. 102.
Blood-pressure curve of the carotid of a dog obtained with a mercurial manometer. .O-2#=line
"ec "oO Ver "O aa Neen tTEENn « ys ; }
of no pressure, zero line, or abscissa; y—y’ is the blood-pressure-tracing with small waves,
each one caused by a heart-beat, and the large waves due to the respiration. A millimetre
scale shows the height of the pressure in millimetres of mercury,

undulations are due to the respiratory movements. It is clear that the heart-beat is expressed
as a simple rise and fall (fig. 102), so that the curve of the heart-beat obtained with a mercurial
kymograph differs from a sphygmographic curve.

Faults of a Mercurial Manometer,—A perfect recording instrument ought to indicate the
height of the blood-pressure, and also the size, form, and duration of any wave-motion com-
municated to it. The mercurial manometer does not give the true form of the pulse-wave, as
the mercury, when once set In motion, executes vibrations of its own. owing to its great inertia,
and thus the finer movements of the pulse-wave are lost. Hence a mercurial kymograph is used
for registering the blood-pressure, and not for obtaining the exact form of the pulse-wave.
Instruments with less inertia, and with no vibrations peculiar to themselves, are required for this
purpose.

[Method.—Expose the carotid of a chloralised rabbit, and isolate a portion of the vessel

SPRING-KYMOGRAPH. I2]I

between two ligatures, or two spring clamps. With a pair of scissors make an oblique slit in
the artery, and into it tie a straight glass cannula, directing the pointed end of the cannula .
towards the heart. Fill the cannula with a saturated solution of sodium carbonate, taking care
that no air-bubbles enter, and connect it with the lead tube which goes to the ascending limb
of the manometer. The tube which connects the artery with the manometer must be flexible
and yet inelastic, and a lead tube is best. It is usual to connect a pressure-bottle, containing
a saturated solution of sodium carbonate, by means of an elastic tube, with the tube attached to
the manometer. This bottle can be raised or lowered. Before beginning the experiment, raise
the pressure-bottle until there is a positive pressure of mercury in the manometer about equal to
the estimated blood-pressure, and then clamp the tube of the pressure-bottle where it joins the
lead tube. This positive pressure prevents the escape of blood from the artery into the solution
of sodium carbonate. When all is ready, the ligature on the cardiac side of the cannula is
removed, and immediately the float begins to oscillate and inscribe its movements upon the
recording surface. The fluid within the artery exerts pressure latterly upon the sodium
carbonate solution, and this in turn transmits it to the mercury. Peptones, or rather the
albumoses, when injected into the blood keep it from coagulating (p. 32). Roy finds that oil may
take the place of sodic carbonate. ]

[Precautions.—In taking a blood-pressure tracing, after seeing that the apparatus is perfect,
care must be taken that the animal is perfectly quiescent, as every movement causes a rise of
blood-pressure. This may be secured by giving curara and keeping up artificial respiration,
or by the carefully regulated inhalation of ether. When a drug is to be injected to test its
action, if it be introduced into the jugular vein it is apt to affect the heart directly. This may
be avoided by injecting it into a vein of the leg, or under the skin. ‘The solution of the drug
must not contain particles which will block up the capillaries. Care should also be taken that
the carbonate of soda does not flow back into the artery. ]

[Continuous Tracing.—When we have occasion to take a tracing for any length of time, it
must be written upon a strip of paper which is moved at a uniform rate in front of the writing-
style on the float (fig. 100). Various arrangements are employed for this purpose, but it is
usual to cause a cylinder to revolve, so as to unfold a roll or riband of paper placed on a
movable bobbin. As the cylinder revolves, it gradually winds off the strip of paper, which is

- kept applied to the revolving surface by ivory friction-wheels. In Hering’s complicated kymo-

graph a long strip of smoked paper is used. The writing-style may consist of a sable brush, or
a fine glass pen filled with aniline blue dissolved in water, to which a little alcohol and
glycerine are added. ] é

[In order to measure the height of the pressure, we must know the position of the abscissa
or line of no pressure, and it may be recorded at the same time as the blood-pressure, or after-
wards. In fig. 102 O ~~ is the zero-line or the abscissa, and the height of the vertical lines or
ordinates may be measured by the millimetre scale on the left of the figure. The height of the
blood-pressure is obtained by drawing ordinates from the curve to the abscissa, measuring their
length, and multiplying by two. |

(5) Spring-Kymograph.—A. Fick (1864) uses a “hollow spring-kymograph ”
on the principle of Bourdon’s manometer (fig. 100, II).

A hollow ©-shaped metallic spring, F, is filled with alcohol. One end of the hollow spring
is closed, and the other end, covered by a membrane, is brought into connection with a blood-
vessel by a junction-piece filled with a solution of sodium carbonate. As soon as the com-
munication with the artery is opened, the pressure rises, and the spring, of course, tends to
straighten itself. To the closed end, 0, there is fixed a vertical rod attached to a series of levers,
h, i, k, e, one of which writes its movements upon a surface moving at a uniform rate. The
blood-pressure and the periodic variations of the pulse are both recorded, although the latter is
not done with absolute accuracy.

[Hering improved Fick’s instrument (fig. 103). a, b, ¢c, is the hollow spring filled with
alcohol, and communicating at a with the lead tube, d, passing to the cannula inthe artery.
To ¢ is attached a series of light wooden levers with a writing-style, s. The lower part of 4
dips.into a vessel, ¢, filled with oil or glycerine, which serves to damp the vibrations of the
levers. At f is a syringe communicating with the tube, d, filled with solution of sodic
carbonate, and used for regulating the amount of fluid in the tube connecting the
manometer with the blood-vessel. The whole apparatus can be raised or lowered on the toothed
rod, A, by means of the millhead opposite, g, to which all the parts of the apparatus are
attached. |

(6) Fick’s Flat Spring-Kymograph.—The narrow tube a, a (1 mm. diam.) is placed in con-
nection with a blood-vessel by means of the cannula, c, and over its vertical expanded end, A,
is fixed a caoutchoue membrane, with a projecting point, s, which presses against a horizontal
spring, F, joined to a writing-lever, H, by an intermediate piece, b. The whole is held in the
metallic frame, R R (fig. 104). In order to estimate the absolute pressure, the instrument must
be compared previously with a mercurial manometer.

IZ22 . FICK’S FLAT SPRING-KYMOGRAPH.

aph ($67). The pressure required to abolish the movement
ir a ak Sra cat ; : of the lever indicates approxi-
, mately the vascular tension. The
mean blood-pressure in the radial
artery is equal to 550 grams.

(2) Sphygmomanometer of
v. Basch.—A capsule containing
fluid was placed upon a pulsating
artery, while the capsule itself
communicated with a mercurial
manometer. As soon as the pres-
sure within the manometer slightly
exceeded that within the artery,
the artery was compressed so that
a sphygmograph placed on a
peripheral portion of the vessel
ceased to beat. Both arrange-
ments do not give the exact
pressure within the artery ; they
only indicate the pressure which
is required to compress the
artery and the overlying soft
parts. The pressure required to
compress the arterial walls, how-
ever, is very small compared with the blood-pressure. It is only 4 mm. Hg.
V. Basch estimated the pressure in the radial artery of a healthy man to be 135
to 165 millimetres of mercury.

Variations.—In children the blood-pressure increases with age, height, and weight. In the
superficial temporal artery, at 2 to 3
years, it is = 97 mm.: 12 to 13 years,
113 mm. Hg. (Ad. Eckert, c. § 100).
The blood-pressure is raised imme-
diately after bodily movements ; it is
higher when a person is in the hori-
zontal position than when sitting, and
in sitting than in standing. After a

H

Fig. 103.
Fick’s spring-manometer, as improved by Hering.

Fick’s flat spring-k ymograph.

cold as well as after a warm bath, the first effect is an increase of blood-pressure and of the
quantity of urine.

85. BLOOD-PRESSURE IN THE ARTERIES.—The following results have
been obtained by experiment on systemic arteries :—

(2) Mean Blood-Pressure.—The blood-pressure is very considerable, varying
within pretty wide limits ; in the large arteries of large mammals, and perhaps in
man, it = 140 to 160 millimetres [5-4 to 6-4 inches] of a mercurial column. —

The following results have been obtained, those marked thus * by Poiseuille, and those + by
Volkmann :—

* Carotid, Horse, 161 mm. _ + Carotid, Fowl, 88 to 171 mm.
va s» 122 to 214 mm. + Aorta of Frog, 22 to 29 mm.
st s, Dog, 151 mm. + Gill artery of Pike, 35 to 84 mm.
i », 130 to 190 mm. (Ludwig). Brachial artery of Man during an opera- —
¥ », Goat, 118 to 135 mm. tion, 110 to 120 mm. (Faivre), Per-

:> Rabbit, 90 mm. haps too low owing to the injury,

BRANCHING OF THE BLOOD-VESSELS. 123

E, Albert estimated the blood-pressure by means of a manometer, placed in connection with
the anterior tibial artery of a boy whose leg was to be amputated, to be 100 to 160 mm. Hg.
‘The elevation with each pulse-beat was 17 to 20 mm.; coughing raised it to 20 or 30 mm. ;
tight bandaging of the healthy leg, 15 mm. ; while passive elevation of the body, whereby the
hydrostatic action of the column of blood was brought into play, raised it 40 mm.

The pressure in the aorta of mammals varies from 200 to 250 mm. Hg. As a general rule,
the blood-pressure in large animals is higher than in small animals, because in the former the
blood-channel is considerably longer, and there is greater resistance to be overcome. In very
young and in very old animals the pressure is lower than in individuals in the prime of life.

The arterial pressure in the foetus is scarcely half that of the newly-born, while the venous
pressure is higher, the difference of pressure between arterial and venous blood being scarcely
half so great as in adult animals (Cohnstein and Zuntz).

The arterial blood-pressure is highest in the aorta, and falls towards the
smaller vessels, but the fall is very gradual, as shown in fig. 105. <A great fall
takes place on passing from thearea ,
of the arterioles into the capillary ““[ oa
area (C), while it is less in the ven-
ous area, and negative near the heart,
as indicated in the dotted line pass- x
ing below the abscissa, so that the eae
pressure is lowest in the cardiac , ] (Sige : 5
ends of the venz cave (compare fig. 4 A Cc ew errs

Ly. R.A.
111). Fig. 105.

(0) Branching of the Blood- scheme of the blood-pressure, in A, the arteries; C,
Vessels.—Within the large arteries capillaries, and V, veins; O-O, is the abscissa or
the blood-pressure diminishes rela- line of no pressure ; L.V., left ventricle, and R.A.,
tively little as we pass towards the right auricle; B.P., the height of the blood-

A : pressure.
periphery, because the difference of
the resistance in the different sections of large tubes is very small. As soon, how-
ever, as the arteries begin to divide frequently, and undergo a considerable diminu-
tion in their lumen, the blood-pressure in them rapidly diminishes, because the pro-
pelling energy of the blood is much weakened, owing to the resistance which it has
to overcome (§ 99).

(c) Amount of Blood.—The blood-pressure is increased with greater filling of the
arteries, and vice versd; hence it

Increases. | Decreases.
1. With increased and accelerated action of 1. During diminished and enfeebled action
the heart; of the heart ;
2. In plethoric persons ; 2. In anemic persons ; ,
'3. After considerable increase of the quantity 3. After hemorrhage or considerable excre-

of blood by direct transfusion, or after

tions from the blood by sweating, the
a copious meal.

| urine, severe diarrheea,

The blood-pressure does not vary in the same proportion as the variations in the amount of
blood. The vascular system, in virtue of its muscular tissue, has the property, within liberally
wide limits, of accommodating itself to larger or smaller quantities of blood (C. Ludwig and
Worm Miiller, § 102, d). [In fact, a large amount of blood may be transfused without materi-
ally raising the blood-pressure.] Small and moderate hemorrhages (in the dog to 2°8 per cent.
of the body-weight) have no obvious effect on the blood-pressure. After a slight loss of blood
the pressure may even rise (Worm Miller). fa large amount of blood be withdrawn, it causes
a great fall of the blood-pressure, and when hemorrhage occurs to 4-6 per cent. of the body-
weight, the blood-pressure=0. The transfusion of a moderate amount of blood does not raise
the mean arterial blood-pressure. There are important practical deductions from these experi-
ments, viz., that the arterial blood-pressure cannot be diminished directly by moderate blood-
letting, and that the blood-pressure is not necessarily high in plethoric persons. ]

(d) Capacity of the Vessels.—The arterial pressure rises when the capacity of
the arterial system is diminished, and conversely. The circularly-disposed smooth
muscular fibres of the arteries are the chief agents concerned in this process. When
they relax, the arterial blood-pressure falls, and when they contract, it rises. These

124 COLLATERAL VESSELS.

actions of muscular fibres are controlled and regulated by the action of the vaso-
motor nerves (§ 371).

(e) Collateral Vessels.—The arterial pressure within a given area of the vascular
system must rise or fall according as the neighbouring areas are diminished, whether
by the application of pressure, or a ligature, or are rendered impervious, or as these
areas dilate. The application of cold or warmth to limited areas of the body—in-
creasing or diminishing the atmospheric pressure on a part—the paralysis or stimu-
lation of certain vaso-motor areas (§ 371), all produce remarkable variations in the
blood-pressure. [The effect of dilatation of a large vascular area on the arterial
pressure is well shown by what happens when the blood-vessels of the abdomen are
dilated. Divide both vagi in the neck of a rabbit and stimulate the central end of
the superior cardiac or depressor nerve; after a few seconds, the blood-vessels of
the abdomen dilate, and gradually there is a steady fall of the blood-pressure in the
systemic arteries. Fig. 106 is a blood-pressure tracing showing the height of the
blood-pressure before stimulation, a. The stimulation was continued from a to b,
and after a certain /atent period there is a steady fall of the blood-pressure. |

(f) Respiratory Unduiations.—The arterial pressure also undergoes regular
variations or undulations owing to the respiratory movements. These undulations

Uv

Fig. 106.
Kymographic tracing showing the effect on the blood-pressure of stimulation of the central end
of the depressor nerve in the rabbit after section of both vagi in the neck, Stimulation
began at @ and ended at b; o-x, the abscissa.

are called respiratory undulations (figs. 102 and 107.) Stated broadly, during
every strong inspiration the blood-pressure rises, and during expiration it falls
(§ 74). This is not quite correct. These undulations may be explained by the
fact that, with every expiration, the blood in the aorta is subjected to an increase
of pressure through the compressed air in the chest ; with every inspiration, on the
other hand, it is diminished owing to the rarefaction of the air in the lungs acting
upon the aorta. Besides, the inspiratory movements of the chest aspirate blood
from the vene cave towards the heart, while expiration retards it, and thus
influences the blood-pressure. The undulations are most marked in the arteries
lying nearest to the heart. The respiratory undulations are due in part to a
stimulation or condition of excitement of the vaso-motor centre, which runs parallel
with the respiratory movements. This stimulation of the vaso-motor centre causes

RESPIRATORY UNDULATIONS. 125

the arteries to contract, and thus the blood-pressure is raised. The variations in
the pressure which depend upon a varying activity of the vaso-motor centre are
known as the “curves of Traube and Hering.” Fig. 107 shows the carotid blood-
pressure tracing of a dog. In this curve, when inspiration begins (I) the blood-
pressure is still falling slightly, but gradually rises until it reaches its maximum
shortly after the beginning of expiration (E). [The maxima and minima of the
respiratory and blood-pressure curves do not coincide exactly, but in addition the
number of pulse-beats is greater in the ascent than in the descent. This is well
marked in a blood-pressure tracing from a dog’s carotid (fig. 107), while in a rabbit
this difference of the pulse-rate is but slightly marked (fig. 106). The smaller
number of pulse-beats during the descent, z.e., during the greater part of expiration

Fig. 107.
Carotid blood-pressure tracing of dog ; vagi not divided ; I=inspiration, E=expiration.

(Stirling). ©

—is due to the activity of the cardio-inhibitory centre in the medulla oblongata.
This is proved by the fact that section of both vagi in the dog causes the difference
of pulse-rate to disappear, while other conditions remain the same as before, except
that the heart beats more rapidly. It would seem that, during the ascent, the
cardio-inhibitory centre is comparatively inactive. It is clear, therefore, that the
respiratory and cardio-inhibitory centres in the medulla oblongata act to a
certain extent in unison, so that it is reasonable to suppose that other centres
situated in close proximity to these may also act in unison with them, or, as it were,
‘‘in sympathy.” As already stated, the vaso-motor centre is also in action during
a particular part of the time. |

[If a dog be curarised and artificial respiration established, the respiratory
undulations still occur, although in a modified form. In artificial respiration,
the mechanical conditions, as regards the intra-thoracic pressure, are exactly the
reverse of those which obtain during ordinary respiration. Air is forced into the
chest during artificial respiration, so that the pressure within the chest is increased
during inspiration, while in ordinary inspiration the pressure is diminished, Thus,
the same mechanical explanation will not suffice for both cases. |

If the artificial respiration be suddenly interrupted in a curarised animal, the blood-
pressure rises steadily and rapidly. This rise is due to the stimulation of the
vaso-motor centre in the medulla oblongata by the impure blood. This causes
contraction of the small arteries throughout the body, which retards the outflow
from the large arteries, and thus the pressure within them is raised. [Stated
broadly, the arterial pressure depends on the central organ—the heart, and on the
condition of the peripheral organs—the small arteries. Both are influenced by
the nervous system. If the action of the vaso-motor centre be eliminated by
dividing the spinal cord in the cervical region, arrest of the respiration causes a
very slight rise of the blood-pressure ; hence, it is evident that venous blood acts
but slightly on the heart, or on any local peripheral nervous mechanism, or on the

126 TRAUBE-HERING CURVES.

muscular fibres of the arteries. This experiment shows that it is the ‘vaso-motor
centre which is specially acted upon by the venous blood. |

[Traube-Hering Curves.—The following experiment proves that the varying
activity of the vaso-motor centre suffices to produce undulations in the blood-
pressure tracing. Take a dog, curarise it, expose both vagi and establish artificial
respiration ; then estimate the blood-pressure in the carotid. After section of the

vagi, the heart will continue to beat more rapidly, but it will be undisturbed by.

the cardio-inhibitory centre. Thus the central factor in the causation of the blood-
pressure remains constant. Suddenly interrupt the respiration, and, as already
stated, the blood-pressure will rise steadily and uniformly, owing to the stimulation
of the vaso-motor centre by the venous blood. In this case the peripheral factor,
or state of tension of the small arteries throughout the body, is influenced by the
condition of the nerve-centre, which controls their action. After a time, the blood-
pressure tracing shows a series of bold curves higher than the original tracing.
These can only be due to an alteration in the state of the small arteries, brought
about by a condition of rhythmical activity of the vaso-motor centre. These
curves were described and figured by Traube, and are called the Traube or Traube-
Hering curves. As in other conditions, stimulation causes exhaustion, and soon the
venous blood paralyses the vaso-motor centre and the small arteries relax, blood
flows freely out of the larger arteries, and the blood-pressure rapidly sinks.
Variations in the blood-pressure have been observed after a mechanical pump has
been substituted for the heart, z.¢., after all respiratory movements have been set
aside, so that the only factor which would account for the phenomena of the Traube-
Hering curves is the variation in the peripheral resistance in the small arteries,
determined by the condition of the vaso-motor centre. |

Variations.—The respiratory undulations of the blood-pressure become more pronounced the
greater the force of the respirations, which produce greater variations of the intra-thoracic
pressure. In man, the diminution of the pressure within the trachea is 1 mm. Hg. during
tranquil inspiration ; while during forced respiration, when the respiratory passage is closed, it
may be 57 mm. Conversely, during ordinary expiration, the pressure is increased within the
trachea 2-3 mm. Hg., while during forced expiration, owing to the compression of the abdominal
muscles, it may reach 87 mm. Hg.

Other Factors.—The increase of the blood-pressure during inspiration, as well as the fall
during expiration, must in part depend upon the pressure within the abdomen. As the dia-
phragm descends during inspiration, it presses upon the abdominal contents, including the
abdominal vessels, whereby the blood-pressure must be increased. The reverse effect occurs
during expiration (Schweinburg). [Section of both phrenic nerves and opening of the abdominal
cavity cause the respiratory undulations almost entirely to disappear. The respiratory undula-
tions, therefore, depend in great part upon the changes of the abdominal pressure and the effect
of these changes on the amount of blood in the abdominal vessels. When making a blood-
pressure experiment, pressure upon the abdomen of the animal with the hand causes the blood-
pressure to rise rapidly. ]

(7) Variations with each Pulse-Beat.—The mean arterial pressure undergoes
a variation with each heart-beat or pulse-beat, causing the so-called pulsatory
undulations (fig. 107). The mass of blood forced into the arteries with each
ventricular systole causes a positive wave and an increase of the pressure corre-
sponding with it, which of course corresponds in its development and in its form
with the pulse-curve.

In the large arteries Volkmann found the increase during the heart-beat to be =; (horse)
and +, (dog) of the total pressure.

None of the apparatus described in § 84 gives an exact representation of the pulse-curve.
They all show simply a rise and fall, a simple curve. The sphygmograph alone gives a true
expression of the undulations in the blood-pressure which are due to the heart-beat.

(2) Arrest of the Heart’s Action.—If the heart’s action be arrested or interrupted
by continued stimulation of the vagus, or by high positive respiratory pressure, the
arterial blood-pressure falls enormously, while it rises in the veins as the blood
flows into them from the arteries to equilibrate the difference of pressure in the two:

RELATION OF BLOOD-PRESSURE TO PULSE-RATE. 127

sets of vessels. This experiment shows that, even when the difference of pressure
is almost entirely set aside, the passive blood presses upon the arterial walls, 2e.,
on account of the overfilling of the blood-vessels a slight pressure is exerted upon
the walls, even when there is no circulation. [As already stated, the arterial
pressure depends on the condition of the central organ—the heart—and on the
peripheral organs—the small arteries. If the action of the heart be arrested, then
the blood-pressure rapidly falls. Fig. 108 shows the effect on the blood-pressure

Fig. 108,

Blood-pressure tracing taken with a mercurial kymograph from the carotid of a rabbit.
o—a, abscissa ; stimulation of vagus begun at a and stopped at b.

of arresting the action of the heart by stimulation of the peripheral end of the
vagus. There is a sudden fall of the arterial pressure, as showniby the rapid fall
of the curve from a. |

[Variations in Animals.—The pressure in the arterial system depends upon the balance
between the inflow and outflow, ¢.¢., upon the heart and the state of the arterioles. But it is
to be noted that the central factor, the heart, varies in different animals. In the rabbit the
heart normally beats rapidly, so that section of the vagi does not cause any great increase in
the number of beats, nor is the blood-pressure much raised thereby. In the dog, on the other
hand, the beats are considerably increased by section of the vagi, while the blood-pressure
rises considerably. Atropin paralyses the cardiac terminations of the vagus, and thereby trebles
the number of heart-beats in the dog, while it only raises it 25 per cent. in the rabbit ; in man,
again, the number may be doubled. As Brunton has. shown, this difference of the initial
number of heart-beats and the action of the vagus have important relations to the action of
drugs on the blood-pressure. For example, if an intact rabbit be caused to inhale amyl nitrite,
the blood-pressure falls at once and rapidly, while in the dog the fall may be slight. The pulse
of the dog, however, is greatly accelerated, so much so as to be nearly as rapid as that of the
rabbit. In both, the vessels are dilated, but in the dog, notwithstanding this dilatation, which
per se would cause the pressure to fall, the heart of the dog beats now so rapidly as to com-
pensate for this, and thus keeps the blood-pressure nearly normal ; while the increased rate of
beating in the rabbit is not sufficient for this purposer” If the vagi in the dog be divided, the
subsequent inhalation of amyl nitrite causes a fall of blood-pressure like that in the rabbit
(Brunton).]

[Relation of Blood-Pressure to Pulse-Rate.— When the blood-pressure rises in
an intact animal, as a rule the pulse-rate falls, owing to stimulation of the vagus
centre increasing the cardio-inhibitory action, while a fall of blood-pressure is
accompanied by an increase of the number of pulse-beats for the opposite reason,
the action of the medullary cardio-inhibitory centre being increased. But the

128 BLOOD-PRESSURE IN THE CAPILLARIES.

blood-pressure may be increased either by the action of the heart or the arterioles.
If we divide the vagi the pulse beats more quickly, and in some animals the
blood-pressure rises ; in this case, the rise in the two curves occurs together, and if
the vagi. be stimulated there is a sudden fall of the blood-pressure, due to arrest
of the heart’s action, so that again the two curves are parallel. If the arterioles
contract the blood-pressure rises, but by and by the pulse-rate falls, owing to the
cardio-inhibitory action of the vagus ; while, on the other hand, if the arterioles
are dilated, the blood-pressure falls, and the heart beats faster. Thus, in both of
these cases the pulse-curve and blood-pressure curve run in opposite directions.
These results only obtain when the vagi are intact (Brunton). |

(The increase in the pulse-rate and blood-pressure following section of the vagi do not run
parallel. Both sooner or later reach a maximum, but the blood-pressure gradually falls to or
below the normal, while the pulse-rate remains above the normal (itianzel).}

For the effects of the nervous system upon the blood-pressure see § 371.
Pathological.—In persons suffering from granular or contracted kidney and sclerosis of the
arteries, in lead poisoning, and after the injection of ergotin, which causes contraction of the
small arteries, it is found, on employing the method of v. Basch, that the blood-pressure is
raised. It is also increased in cases of cardiac hypertrophy with dilatation, and by digitalis in
cardiac affections, while it falls after the injection of morphia. The blood-pressure falls in

fever, a fact also indicated in the sphygmogram (§ 69), and it is low in chlorosis and phthisis.

86. BLOOD-PRESSURE IN THE CAPILLARIES, —Methods. —Direct estimation of the capil-
lary pressure is not possible on account of the smallness of the capillary tubes. Ifa glass plate of
known dimensions be placed on a portion of the skin rich in blood-vessels, and if it be weighted
until the capillaries become pale, we obtain approximately the pressure neces-
sary to overcome the capillary pressure. N. v. Kries placed a small glass
plate (fig. 109) 2°5-5 sq. mm., on a suitable part of the skin, e.g., the skin
at the root of the nail on the terminal phalanx, or on the ear in man, and
on the gum in rabbits. Into a scale-pan attached to this, weights were
placed until the skin became pale. The pressure in the capillaries of the
hand, when the hand is raised, Kries found to be 24 mm. Hg. ; when the
hand hangs down, 54 mm. Hg.: in the ear, 20 mm., and in the gum of a
rabbit, 32 mm.

Roy and Graham Brown compressed from below transparent vascular mem-
branes against a glass plate by means of an elastic bag connected with a
manometer, while the variations in the capillaries were observed from above
by a microscope,

Conditions influencing Capillary Pressure.—The capillary
blood-pressure in a given area increases—(1) When the afferent
small arteries dilate, so that the blood-pressure within the large
arteries is propagated more easily into them. (2) By increasing
the pressure in the small afferent arteries. (3) By narrowing the
diameter of the veins leading from the capillary area. Closure of
= Fig. 109. the veins may quadruple the pressure. (4) By increasing the

- Kries’s appara- pressure in the veins (e.g., by altering the position of a limb). A

t . j ai ea . : s j
shah asd diminution of the capillary pressure is caused by the opposite con-

square of glass, ditions.

; Changes in the diameter of the capillaries influence the internal pres-
sure. We have to consider the movements of the capillary wall itself as well as the pressure,
swelling, and consistence of the surrounding tissues. The resistance to the blood-stream is
greatest in the capillary area, and it is evident that the blood in a long capillary must exert
more pressure at the commencement than at the end of the capillary ; in the middle of the
capillary area the blood-pressure is just about one-half of the pressure within the large arteries
(Donders). The capillary pressure must also vary in different regions of the body. Thus, the
pressure within the intestinal capillaries, in those constituting the glomeruli of the kidney,
and in those of lower limbs when the person is in the erect posture, must be greater than in
other regions, depending in the former cases partly upon the double resistance caused by two
sets of capillaries, and in the latter case partly on purely hydrostatic causes.

87. Blood-Pressure in the Veins.—In the large venous trunks near the
heart (innominate, subclavian, jugular) a mean negative pressure of about —0°1

ASPIRATION OF THE HEART. 129

min. Hg. prevails (#/. Jacobson). Hence, the lymph-stream can flow unhindered.
As the distance of the veins from the heart increases, there is a gradual increase
of the lateral pressure; in the external facial vein (sheep) = +3 mm. ; brachial,
4‘1 mm., and in its branches 9 mm. ; crural, 11‘4 mm. [The pressure is said to
be negative when it is less than that of the atmosphere. The gradual fall of the
blood-pressure from the capillary area (C) to the venous area (V) is shown in fig.
108, while within the thorax, where the veins terminate in the right auricle, the
pressure is negative. | !

Modifying Conditions.—(1) All conditions which diminish the difference of
pressure between the arterial and venous systems tncrease the venous pressure, and
vice versa.

(2) General plethora of blood increases it ; anzemia diminishes it.

(3) Respiration, or the aspiration of the thorax, affects specially the pressure
in the veins near the heart ; during inspiration, owing to the diminished tension,
blood flows towards the chest, while during expiration it is retarded. The
effects are greater, the deeper the respiratory movement, and these may be very
great when the respiratory passages are closed (§ 60).

[When a vein is exposed at the root of the neck, it collapses during inspiration, and fills
during expiration. The respiratory movements do not affect the venous stream in peripheral
veins. The veins of the neck and face become distended with blood during crying, and on
making violent expiratory efforts, as in blowing upon a wind instrument. Every surgeon is
acquainted with the fact that air is particularly liable to be sucked into the veins, especially in
operations near the root of the neck. This is due to the negative intra-thoracic pressure occur-
ring during inspiration. ]

(4) Aspiration of the Heart.—Blood is sucked or aspirated into the auricles
when they dilate (p. 59), so that there is a double aspiration—one synchronous
with inspiration, and the other, which is but slight, Bip Ssesu)
synchronous with the heart-beat. There is a cor- “i
responding retardation of the blood-stream in the
vene cave, caused by the contraction of the auricle
(p. 58, a). The respiratory and cardiac undula-
tions are occasionally observable in the jugular
vein of a healthy person (§ 99).

(5) Change in the position of the limbs or of
the body, for hydrostatic reasons, greatly alters the
venous pressure. The veins of the lower extrem-
ity bear the greatest pressure, while at the same
time they contain most muscle (A. Bardeleben, \
§ 65). Hence, when these muscles from any cause
become insufficient, dilatations occur in the veins, _ ¥
giving rise to the production of varicose veins. fg as

. : y ris Fig. 110.

[Braune showed that the femoral vein under Poupart’s
ligament collapsed when the lower limb was rotated out- Scheme of the blood-pressure. H,
wards and backwards, but filled again when the limb was heart; a, auricle ; v, ventricle ; —
restored to its former position. All the veins which open "terial ; C, capillary; and V, ven-
into the femoral vein have valves, which permit blood to OWS @teas. _The circle indicates the
pass into the femoral vein, but prevent its reflux. This parts within the thorax; B.P.,
mechanism acts to a slight degree as a kind of suction and _ Pressure in the aorta.
pressure apparatus when a person walks, and thus favours the onward movement of the blood. ]
_ [(6) Muscular Movements.—Veins which lie between muscles are compressed
when these muscles contract, and as valves exist in the veins, the flow of blood is
accelerated towards the heart; if the outflow-of the blood be obstructed in any
way, then the venous pressure on the distal side of the obstruction may be greatly
increased. When a fillet is tied on the upper-arm, and the person moves the
muscles of the fore-arm, the superficial veins become turgid, and can be distinctly
traced on the surface of the limb. }

THORAX

I

130 BLOOD-PRESSURE IN THE PULMONARY ARTERY.

(7) Gravity exercises a greater effect upon the blood-stream in the extensile
veins than upon the stream in the arteries. It acts on the distribution of the
blood, and thus indirectly on the motion of the blood-stream, It favours the
emptying of descending veins, and retards the emptying of ascending veins,
so that the pressure becomes less in the former and greater in the latter. If
the position of the limb be changed, the conditions of pressure are also altered.
If a person be suspended with the head hanging downwards, the face soon
becomes turgid, the position of the body favouring the inflow of blood through
the arteries and retarding the outflow through the veins. If the hand hangs
down it contains more blood in the veins than if it is held for a short time over
the head, when it becomes pale and bloodless. [As Lister has shown, the condition
of the vessels in the limb is influenced not only by the position of the limb, but
also by the fact that a nervous mechanism is called into play. |

[Ligature of the portal vein causes congestion of the rootlets and dilatation of all the blood-
vessels in the abdomen ; gradually nearly all the blood of the animal accumulates within its
belly, so that, paradoxical as it may seem, an animal may be bled into its own belly. Asa
consequence of sudden and complete ligature of this vein, the arterial blood-pressure gradually
and rapidly falls, and the animal dies very quickly. Ifthe ligature be removed before the
blood-pressure falls too much, the animal may recover. Schiff and Lautenbach regard the
symptoms as due chiefly to the action of a poison, for when the blood of the portal vein in an
animal treated in this way is injected into a frog, it causes death within a few hours, while the
ordinary blood of the portal vein has no effect. |

{Ligature of the Veins of a Limb. —The effect of ligaturing or compressing q// the veins of a
limb is well seen in cases where a bandage has been applied too tightly. It leads to congestion
and increase of pressure within the veins and capillaries, increased transudation of fluid through
the capillaries, and consequent wdema of the parts beyond the obstruction. Ligature of one
vein does not always produce cadema, but if several veins of a limb be ligatured, and the vaso-
motor nerves be divided at the same time, the rapid production of cedema is ensured. In
pathological cases the pressure of a tumour upon a large vein may produce similar results
(§ 203). ]

88. BLOOD-PRESSURE IN THE PULMONARY ARTERY.—Methods.—(1) Direct estima-
tion of the blood-pressure in the pulmonary artery by opening the chest was made by C. Ludwig
and Beutner (1850). Artificial respiration was kept up, and the manometer was placed in con-
nection with the left branch of the pulmonary artery. The circulation through the left lung
of cats and rabbits was thereby completely cut off, and in dogs to a great extent interrupted.
There was an additional disturbing element, viz., the removal of the elastic force of the lungs,
owing to the opening of the chest, whereby the venous blood no longer flowed normally into the
right heart, while the heart itself was under the full pressure of the atmosphere. The estimated
pressure in the dog=29°6 ; in the cat=17°7; in the rabbit, 12 mm. Hg., @.e., in the dog 3
times, the rabbit 4 times, and the cat 5 times less than the carotid pressure.

(2) Hering (1850) experimented upon a calf with ectopia cordis. He introduced glass tubes
directly into the heart, by pushing them through the muscular walls of the ventricles. The |
blood rose to the height of 21 inches in the right tube, and 33°4 inches in the left.

(3) Faivre (1856) introduced a catheter through the jugular vein into the right ventricle,
and placed it in connection with a recording tambour. :

Indirect measurements have been made by comparing the relative thickness of the walls of :
the right and left ventricles, or the walls of the pulmonary artery and aorta.

Beutner and Marey estimated the relation of the pulmonary artery to the aortic
pressure as 1 to 3; Goltz and Gaule as 2 to 5; Fick and Badoud found a pressure
of 60 mm. in the pulmonary artery of the dog, and in the carotid 111 mm. Hg,
‘The blood-pressure within the pulmonary artery of a child is relatively higher than
in the adult. |

Elastic Tension of Lungs.—The lungs within the chest are kept in a state of
distension, owing to the fact that a negative pressure exists on their outer pleural
surface. When the glottis is open, the inner surface of the lung and the walls: of
the capillaries in the pulmonary air-vesicles are exposed to the full pressure of the
air. The heart and large blood-vessels within the chest are not exposed to the full
pressure of the atmosphere, but only to the pressure which corresponds to the
atmospheric pressure minus the pressure exerted by the elastic traction of the lungs

twin > ai,

<
a -
¥
—
i
t

BLOOD-PRESSURE IN THE PULMONARY ARTERY. I31

(§ 60). The trunks of the pulmonary artery and veins are subjected to the same
conditions of pressure. The elastic traction of the lungs is greater the more they are
distended. The blood of the pulmonary capillaries will, therefore, tend to flow
towards the large blood-vessels. As the elastic traction of the lungs acts chiefly
on the thin-walled pulmonary veins, while the semi-lunar valves of the pulmonary
artery, as well as the systole of the right ventricle, prevent the blood from flowing
backwards, it follows that the blood in the capillaries of the lesser circulation must
flow towards the pulmonary veins.

If tubes with thin walls be placed in the walls of an elastic distensible bag, the
lumen of these tubes changes according to the manner in which the bag enclosing
them is distended. If the bag be directly inflated so as to increase the pressure
within it, the lumen of the tubes is diminished (/unke and Latscheuberger). If the
bag be placed within a closed space, and the tension within this space be diminished
so that the bag thereby becomes distended, the tubes in its wall dilate. In the
latter case—viz., by negative aspiration—the lungs are kept distended within the
thorax, hence the blood-vessels of the lungs containing air are wider than those of
collapsed lungs (Quincke and Pfeiffer, Bowditch and Garland, De Jiger). Hence
also, more blood flows through the lungs distended within the thorax than through
collapsed lungs. The d/atation which takes place during inspiration acts in a
similar manner. The negative pressure that obtains within the lungs during
inspiration causes a considerable dilatation of the pulmonary veins, into which
the blood of the lungs flows readily, whilst the blood under high pressure in the
thick-walled pulmonary artery scarcely undergoes any alteration. The velocity of
the blood-stream in the pulmonary vessels is accelerated during inspiration (De
Jager, Lalesque). ‘The blood-pressure in the pulmonary circuit is raised when the
lungs are inflated. Contraction of small arteries, which causes an increase of the
blood-pressure in the systemic circulation, also raises the pressure in the pulmonary
circuit, because more blood flows to the right side of the heart.

The vessels of the pulmonary circulation are very distensible and their tonus is
slight. [Occlusion of one branch of the pulmonary artery does not raise the
pressure within the aorta. Even when one pulmonary artery is plugged with an
embolon of paraffin, the pressure within the aortic system is not raised (Lichtheim).
When a large branch of the pulmonary artery becomes impervious, the obstruction

_is rapidly compensated for, and this is not due to the action of the nervous system.

The vaso-motor system has much less effect upon the pulmonary blood-vessels than
upon those of the systemic circulation. The compensation seems to be due chiefly
to the great distensibility and dilatation of the pulmonary vessels (Lichtheim). |
We know little of the effect of physiological conditions upon the pulmonary artery.
According to Lichtheim suspension of the respiration causes an increase of the
pressure. [In one experiment he found that the pressure within the pulmonary

_artery was increased, while it was not increased in the carotid, and he regards this

experiment as proving the existence of vaso-motor nerves in the lung. |

During the act of great straining, the blood at first flows rapidly out of the pulmonary veins,
and afterwards ceases to flow, because the inflow of blood into the pulmonary vessels is inter-
fered with. As soon as the straining ceases, blood flows rapidly into the pulmonary vessels
(Lalesque).

Severini found that the blood-stream through the lungs is greater and more rapid when the
lungs are filled with air rich in CO, than when the air within them is rich in O. He supposes
ha ae gases act upon the vascular ganglia within the lung, and thus affect the diameter of
the vessels, :

_Pathological.—Increase of the pressure within the area of the pulmonary artery occurs fre-
quently in man, in certain cases of heart disease. In these cases the’ second pulmonary sound
is always accentuated, while the elevation caused thereby in the cardiogram is always more
marked and occurs earlier (§ 52). Electrical and mechanical stimulation of abdominal organs

_ raises the blood-pressure in the pulmonary artery (Morel).

[The action of drugs on the pulmonary circulation may be tested by Holmgren’s apparatus

I 32, VELOCITY OF THE BLOOD-STREAM.

($ 94), which permits of distension of the lung and retention of the normal circulation in the- |
frog. Cold contracts the pulmonary capillaries to one-third of their diameter, and anesthetics ;
arrest the pulmonary circulation, chloroform being most and ether least active, while ethidene is

intermediate in its effect. ]

{Influence of the Nervous System.—The pulmonary circulation is much less.
dependent on the nervous system than the systemic circulation.
Very considerable variations of the blood-pressure within the
other parts of the body may occur, while the pressure within
the right heart and pulmonary artery is but slightly affected
thereby. The pressure is increased by electrical stimulation
of the medulla oblongata, and it falls when the medulla is
destroyed. Section and stimulation of the central or peri-
pheral ends of the vagi, stimulation of the splanchnics, and
of the central end of the sciatic, have but a minimal influence
on the pressure of the pulmonary artery (Aubert). |

—$—— . 89. VELOCITY OF THE BLOODSTREAM. —
fate Methods: (1) A. W. Volkmann’s Hemadromometer
(1850).—A glass tube of the shape of a hair-pin,
60-130 cm. long and 2 or 3 mm. broad, with a scale
etched on it, or attached to it, is fixed toa metallic
basal plate, B, so that each limb passes to a stop-
cock with three channels. The basal plate is per-
forated along its length, and carries at each end
short cannule, c, ¢, which are tied into the ends of
a divided artery. The whole apparatus is first filled
with water, [or, better, with salt solution]. The }
stop-cocks are moved simultaneously, as they are WV
attached to a toothed wheel, and have at first the
position given in fig. 111, I, so that the blood
simply flows through the hole in the basal piece,
i.e., directly from one end of the artery to the
other. Ifata given moment the stop-cock is turned
| in the direction indicated in fig. 111, II, the blood
_ has to pass through the glass tube, and the time it
| takes to make the circuit is noted; and as the length

of the tube is known, we can easily calculate the
velocity of the blood. The method has very obvious
| defects arising from the narrowness of the tube ; the
| introduction of such a tube offers new resistance,

while there are no respiratory or pulse-variations
observable in the stream in the glass tube.

Fig. 112.
Ludwig and Dogiel’s rheo-
ineter. X, Y, axis of
, rotation; A, B, glass
Fig. 111. bulbs; 2, %, cannule
Volkmann's hemadromometer (B). I, blood flows from artery to artery ; inserted in the divided
II, blood must pass through the glass tube of B; c, c, cannul for the artery; ¢, €, rotates.

divided artery. on g, J; ¢, d, tubes.

Volkmann found the velocity to be in the carotid (dog) -=205 to 357 mm.;
carotid (horse) = 306 ; maxillary (horse) = 232 ; metatarsal=56 mm. per second.
_ (2) C. Ludwig and Dogiel (1867) devised a “stromuhr” or rheometer for measur~.
ing the amount of blood which passed through an artery in a given time (fig. 112).

It consists of two glass bulbs, A and B, of exactly the same capacity. These bulbs com-
municate with each other above, their lower ends being fixed by means of the tubes, ¢ and d,
to the metal disc, ¢, ¢,. This disc rotates round the axis, X, Y, so that, after a complete revolu-
tion, the tube ccommunicates with /, and d with g ; f and g are provided with horizontally placed

‘
.

MEASUREMENT OF THE VELOCITY OF THE BLOOD-STREAM. 133

¢cannule, h and &, which are tied into the ends of the divided artery. The cannula h is fixed
in the central end, and & in the peripheral end of the artery (¢.g., carotid) ; the bulb, A, is
filled with oil, and B with defibrinated blood ; at a certain moment the communication through
h is opened, the blood flows in, driving the oil before it, and passes into B, while the defibrinated
blood flows through & intu the peripheral part of the artery. As soon as the oil reaches m—a
moment which is instantly noted, or, what is better, inscribed upon a revolving cylinder—the
bulbs, A, B, are rotated upon the axis X, Y, so that B comes to occupy the position of A. The
same experiment is repeated, and can be continued for a long time. The quantity of -blood
which passes in the unit of time (1 sec.) is calculated from the time necessary to fill the bulb
with blood. Important results are obtained by means of this instrument.
[Suppose 50 c.cm. of blood are delivered in 100 secs., then 1 c.cm. flows through in 2 secs.

_ Suppose the sectional area of the artery to be 3} mm. As the velocity is measured by the ratio

5000
of the quantity to the sectional area, then 354 =159 mm. per second. ]

[As peptone injectel into the blood prevents it from coagulating (dog), this fact has been
turned to account in using the rheometer. ]

(3) Vierordt’s Hematachometer (1858) consists of a small metal box (fig. 113, I) with parallel
glass sides. To the narrow sides of the box are fitted an inlet ¢, and an exit cannula, a. In.
its interior is suspended, against the entrance opening, a pendulum, p, whose vibrations may be
read off on a curved scale. [This instrument, as well as Volkmann’s apparatus, has only an
historical interest. ]

(4) Chauveau and Lortet’s Dromograph (1860) is constructed on the same principle. A tube
A, B (fig. 113), of sufficient diameter, with a side tube fixed to it, C, which can be placed in con-
nection with a manometer, is introduced into the carotid artery of a horse. At a@ a small piece
is cut out and provided with a covering of gutta-percha which has a small hole in it ; through
this a light pendulum, a, b, with a long index, 4, projects into the tube, z.e., into the blood-

/
/
|

be

J NAS hie
Hl

Fig. 113.
I. Vierordt’s hematachometer. A, glass; ¢, entrance; «a, exit cannula; p, pendulum. IL.
Dromograph. A, B, tube inserted in artery ; C, lateral tube connected with a manometer ;

b, index moving in a caoutchouc membrane, @; G, handle. III. Curve obtained by
dromograph.

current, which causes the pendulum to vibrate, and the extent of the vibrations can be read off
on a scale, S,S. G is an arrangement to permit the instrument to be held. Both this and
the former instrument are tested beforehand with a stream of water sent through them with
varying velocities. .

(5) Cybulski’s Photohematachometer.— When fluid flows into a tube (fig. 114, II, de) in the
direction of the arrow, the fluid stands higher in the manometer p than in m. ‘The tube my
indicates the lateral pressure, but pa gives this plus the velocity of the fluid (p. 89). The
velocity of the current may be estimated from the difference in the level in the two tubes.

Pitot’s tube as used by Cybulski is bent at a right angle (I, cp), the end ¢ being inserted and

134 VELOCITY OF THE BLOOD.

tied into the central, and p into the peripheral, part of a divided artery. As the blood flows
through the tube, the blood rises ors in @ than b.

To avoid having the manometers a and b too long, they are connected with each other by a

capillary tube filled with air and provided above with a stop-cock 7. The blood is allowed to

rise to the height of 1 and 2, the stop-cock 7

Z. is closed, and practically an air-manometer is

made, which shows a marked difference in the

level of the blood of the two tubes. The level

of the blood in 1 and 2 is continually changed

by the movements of the heart and those of

respiration, and these variations are photo-

graphed by means of a camera 7” with a rapidly
moving plate &.

Fig. C shows a curve obtained from
the carotid of a dog. The velocity of
the current at 1,-1=238 mm., in the
phase 2,-2 = 225 mm., and at 3,-3 = 177
mm. ‘The velocity is greatest at the end
of inspiration and the beginning of ex-
piration. Asphyxia increases it at first.
Paralysis of the sympathetic increases
it, while stimulation of this nerve
diminishes it. Section of the vagi in-
creases the velocity, while stimulation
diminishes it.

The curve of the velocity may be written
off on a smoked glass plate, moving parallel
with the index b. The dromograph curve, III,
shows the primary elevation, P, and the di-
crotic elevation R.

90. VELOCITY OF THE BLOOD.
—(1) Division of Vessels—Arteries.—
In estimating the velocity of the blood,
it is important to remember that the
sectional area of all the branches of the
aorta becomes greater as we proceed

I.’ Scheme of the photohematachometer ; from the aorta towards the capillaries,
! II. Pitot's tube. so that the capillary area is 700 times
greater than the sectional area of the aorta. As the veins join and form larger
trunks, the venous area gradually becomes smaller, but the sectional area of the
venous orifices at the heart is greater than that
of the corresponding arterial orifices. [We may
represent the result as two cones placed base
to base (fig. 115), the bases meeting in the
capillary area. The sectional area of the ven-
ous orifice (V) is represented larger than that
of the arterial (A). The increased sectional
area influences the velocity of the blood-
current, while the resistance affects the pres-
sure. |

The common iliacs are an exception; the sum of
their sectional areas is less than that of the aorta;
the sections of the four pulmonary veins are together
less than that of the pulmonary artery.

(2) Sectional Area.—An equal quantity of blood must pass through every section
of the circulatory system, through the pulmonic as well as through the systemic
circulation, so that the same amount of blood must pass through the pulmonary

Fig. 115.
Scheme of the sectional area. A, arterial,
and V, venous orifice.

VELOCITY OF THE BLOOD. : 135

artery and aorta, notwithstanding the very unequal blood-pressure in these two
vessels.

(3) Lumen.—-The velocity of the current, therefore, in various sections of the
vessels, must be inversely as their lumen.

(4) Capillaries.—Hence, the velocity must diminish very considerably as we
pass from the root of the aorta and the pulmonary artery towards the capillaries,
so that the velocity in the capillaries of mammals=0°8 millimetre per sec.;
frog=0°53 mm. (Z. H. Weber); man=0°6 to 0°9 (C. Vierordt). According to
A. W. Volkmann, the blood in mammalian capillaries flows 500 times slower than
the blood in the aorta, so that the total sectional area of all the capillaries must be
500 times greater than that of the aorta. Donders found the velocity of the stream
in the small afferent arteries to be 10 times faster than in the capillaries.

Veins.—The current becomes accelerated in the veins, but in the larger trunks it
is 0°5 to 0°75 times less than in the corresponding arteries.

(5) Mean Blood-Pressure.-—The velocity of the blood does not depend upon the
mean blood-pressure, so that it may be the same in congested and in anzemic parts
(Volkmann, Hering).

(6) Difference of Pressure.—On the other hand, the velocity in any section of
a vessel is dependent on the difference of the pressure which exists at the com-
mencement and at the end of that particular section of a blood-vessel’; it depends,
therefore, on (1) the wis a tergo (2.e., the action of the heart), and (2) on the amount
of the resistance at the periphery (dilatation or contraction of the small vessels).

Corresponding to the smaller difference in the arterial and venous pressure in the foetus ($ 85),
the velocity of the blood is less in this case (Cohnstein and Zuntz).

(7) Pulsatory Acceleration.—With every pulse-beat a corresponding acceleration
of the blood-current (as well as of the blood-pressure) takes place in the arteries
(pp. 126, 133). In large vessels, Vierordt found the increase of the velocity during
the systole to be greater by } to $ than the velocity during the diastole. The
variations in the velocity caused by the heart-beat are recorded in fig. 113, obtained
by Chauveau’s dromograph from the carotid of a horse. The velocity curve corre-
sponds with a sphygmogram—P represents the primary elevation and R the
dicrotic wave. This acceleration, as well as the pulse, disappears in the capillaries.
A pulsatory acceleration, more rapid during its first phase, is observable in the
small arteries, although the arteries themselves are not distended thereby.

(8) Respiratory Effect.—Every inspiration retards the velocity in the arteries,
every expiration aids it somewhat ; but the value of these agencies is very small.

If we compare what has already been said regarding the effect of the respiration on the con-

_ traction and dilatation of the heart and on the blood-stream (§ 60), it is clear that respiration

favours the blood-stream, and so does artificial respiration. When artificial respiration is inter-
rupted, the blood-stream becomes slower (Dogiel). If the suspension of respiration lasts some-
what longer, the current is again accelerated on account of the dyspneeic stimulation of the
vaso-motor centre (Heidenhain) (§ 371, I.).

(9) Modifying Conditions.—Many circumstances affect the velocity of the blood
in the veins. (1) There are regular variations in the large veins near the heart
due to the respiration and the movements of the heart (S§ 50 and 60). (2) Irregular
variations due to pressure, e.g., from contracting muscles (§ 87), friction on the
skin in the direction or against the direction of the venous current ; the posation
of a limb or of the body. The pump-like action of the veins of the groin on
moving the leg has been referred to (§ 87). When the lower limb is extended and
rotated outwards, the femoral vein in the iliac fossa collapses, owing to an internal
negative pressure; when the thigh is flexed and raised, it fills under a positive
pressure (Braune). A similar condition obtains in walking.

91. CAPACITY OF THE VENTRICLES.—Vierordt calculated the capacity of the left
ventricle from the velocity of the blood-stream, and the amount of blood discharged per second

136 THE DURATION OF THE CIRCULATION.

by the right carotid, right subclavian, the two coronary arteries, and the aorta below the origin
of the innominate artery. He estimated that with every systole of the heart, 172 cubic centi-
metres (equal to 180 grammes) of blood were discharged into the aorta; this, therefore, must be
the capacity of the left ventricle (compare § 83).

92. THE DURATION OF THE CIRCULATION.—The time required by the
blood to make a complete circuit through the course of the circulation was first de-
termined by Hering (1829) in the horse. He injected a 2 per cent. solution of potas-
sium ferrocyanide into a special vein, and ascertained (by means of ferric chloride)
when this substance appeared in the blood taken from the corresponding vein on the
opposite side of the body. The ferrocyanide may also be injected into the central
or cardiac end of the jugular vein, and the time noted at which its presence is
detected in the blood of the peripheral end of the same vein. Vierordt (1858)
improved this method by placing under the corresponding vein of the opposite side
a rotating disc, on which was fixed a number of cups at regular intervals. The
first appearance of the potassium ferrocyanide is detected by adding ferric chloride
to the serum which separates from the samples of blood after they have stood for
a time. The duration of the circulation is as follows :—

Horse, . . 31°5 seconds. | Hedgehog, . 7°61 seconds. | Duck, . . 10°64 seconds,
Dog, : pO» ae ate 5 ee OS Oe an sae | Buzzard, , Ca 5,
Rabbit, . ey ys: eee Goose, FOr Cig. ae | Fowl, . oe =

Results.—When these numbers are compared with the frequency of the normal
pulse-beat in the corresponding animals, the following deductions are obtained :—

(1) The mean time required for the circulation is accomplished during 27 heart-
beats, @.¢., for man=32°2 seconds, supposing the heart to beat 72 times per
minute.

(2) Generally, the mean time for the circulation in two warm-blooded animals
is inversely as the frequency of the pulse-beats.

Modifying Conditions.__The time is influenced by the following factors :—

1. Long vascular channels (¢.¢., from the metatarsal vein of one foot to the other foot) re-
quire a Jonger time than short channels (as between the jugulars). The difference may be equal
to 10 per cent. of the time required to complete the entire circuit.

2. In young animals (with shorter vascular channels and higher pulse-rate) the time is
shorter than in old animals.

3. Rapid and energetic cardiac contractions (as during muscular exercise) diminish the time.
Hence rapid and at the same time less energetic contractions (as after section of both vagi), and
slow but vigorous systoles (¢.g., after slight stimulation of the vagus), have no effect.

C. Vierordt estimated the quantity of blood in a man, in the following manner :—In all
warm-blooded animals, 27 systoles correspond to the time for completing the circulation.
Hence, the total mass of the blood must be equal to 27 times the capacity of the ventricle, 7.e.,
in man, 187°5 grms. x 27 = 5062°5 grms. This is equal to ;; of the body-weight in a person
weighing 65°8 kilos. (compare § 49).

Itis not to be forgotten that the salt used is to some extent poisonous, but Hermann uses the
corresponding innocuous soda salt (25 per cent. ). .

Pathological.—The duration of the circulation seems to be increased during septic fever
(E. Wolff).

93. WORK OF THE HEART.—The left ventricle expels 0:188 kilo. of blood
with each systole, and in doing so it overcomes the pressure in the aorta, which is
equal to a column of blood 3°21 metres in height. [The amount of blood expelled
from each ventricle during the systole is about 180 grms. (6 oz.). It is forced out
against a pressure of 250 mm. Hg. = 3-21 metres of blood.| The work of the heart
at each systole is 0°188 x 3:21 =0'604 kilogramme-metre. If the number of beats
=75 per minute, then the work of the left ventricle in 24 hours =(0°604 x
75 x 60 x 24) = 65,230 kilogramme-metres ; while the “work” done by the right
ventricle is about one-third that of the left, and therefore = 21,740 kilogramme-
metres. Both ventricles do work equal to 86,970 kilogramme-metres. A workman
during eight hours produces 300,000 kilogramme-metres, 7.¢., about four times as

Lk
=
ra

oe

we, 1 —

BLOOD-CURRENT IN THE SMALLER VESSELS. £37

much as the heart. As the whole of the work of the heart is consumed in over-
coming the resistance within the circulation, or rather is converted into heat,
the body must be partly warmed thereby—(425°5 gramme-metres are equal to 1
heat-unit, 2.¢c., the force required to raise 425°5 grammes to the height of 1 metre
may be made to raise the temperature of 1 cubic centimetre of water 1° C.). So
that 204,000 ‘“heat-units” are obtained from the transformation of the kinetic
energy of the heart. ; :

One gramme of coal when burned yields 8080 heat-units, so that the heart yields
as much energy for heating the body as if about 25 grammes of coal were burned
within it to produce heat.

94. BLOOD-CURRENT IN THE SMALLER VESSELS.— Methods. — The
‘most important observations for this purpose are made by means of the microscope
on transparent parts of living animals. Malpighi was the first to observe the cir-
culation in this way in the lung of a frog (1661).

The following parts have been employed :—The tails of tadpoles and small tishes; the web,
tongue, mesentery, and lungs of curarised frogs ; the wing of the bat ; the third eyelid of the
pigeon or fowl ; the mesentery ; the vessels of the liver of frogs and newts, pia mater of rabbits,
the skin on the belly of the frog, the mucous membrane of the inner surface of the human lip
{ Hiiter’s Cheilangioscope, 1879); the conjunctiva of the eyeball and eyelids. All these may be
examined by reflected light.

[Holmgren’s Method.—In studying the circulation in the frog’s lung, it must be inflated.
A cannula with a bulge on its free end is placed in the larynx, while to the other end is fixed a
piece of caoutchouc tubing. The lung is inflated and then the caoutchouc tube is closed, after
which the lung is placed in a chamber with glass above and below, and examined microscopic-
ally. ] .

[Entoptical appearances of the circulation (Purkinje, 1815). Under certain conditions a
person may detect the movement of the blood-corpuscles within the blood-vessels of his own
eye. The best method is that of Rood, viz., to look at the sky through a dark blue glass, or
through several pieces of cobalt glass placed over each other (Helmholtz). |

Form and Arrangement of Capillaries.—Regarding the form and arrangement of the capil-
laries, we find that

1. The diameter which, in the finest, permits only the passage of single corpuscles in a row—
one behind the other—may vary from 5 uw to 2 w, so that 2 or more corpuscles may move abreast
when the capillary is at its widest.

2. The length is about 0°5 mm. They terminate in small veins.

3. The number is very variable, and the capillaries are most numerous in those tissues where
the metabolism is most active, as in lungs, liver, muscles—less numerous in the sclerotic and in
the nerve-trunks.

4. They form numerous anastomoses, and give rise to networks, whose form and arrangement
are largely determined by the arrangement of the tissue elements themselves. They form
simple loops in the skin, and polygonal networks in the serous membranes, and on the surface
of many gland tubes; they occur in the form of elongated networks, with short connecting
branches in muscle and nerve, as well as between the straight tubules of the kidney ; they con-
verge radially towards a central point in the lobules of the liver, and form arches in the free
margins of the iris, and on the limit of the sclerotic and cornea.

[Direct Termination of Arteries in Veins.—Arteries sometimes terminate clirectly in veins,
without the intervention of capillaries, ¢.g., in the ear of the rabbit, in the terminal phalanges
of the fingers and toes in man and some animals, in the cavernous tissue of the penis. They
may be regarded as secondary channels which protect the circulation of adjacent parts, and they
may also be related to the heat-regulating mechanisms of peripheral parts (Hoyer).]

In connection with the termination of arteries in capillaries, it is important to ascertain if the
arterioles are terminal arteries, ¢.c., if they do not form any further anastomoses with other
similar arterioles, but terminate directly in capillaries, and thus only communicate by capillaries
with neighbouring arterioles—or the arteries may anastomose with other arteries just before
they break up into capillaries. This distinction is important in connection with the nutrition
of parts supplied by such arteries (Cohnheim).

Capillary Circulation.—On observing the capillary circulation, we notice that
the red corpuscles move only in the axis of the current (axial current), while the
lateral transparent plasma-current flowing on each side of this central thread is
free from these corpuscles. [The axial current is the more rapid.| This plasma
layer or “ Poiseuille’s space” is seen in the smallest arteries and veins, where 3 are

t

138 CAPILLARY CIRCULATION.

taken up with the axial current, and the plasma layer occupies } on each side of it.
(fig. 116). A great many, but not all, of the colourless corpuscles move in this
layer. It is much less distinct in the capillaries. Rud. Wagner stated that it is
absent in the finest vessels of the Jung and gills, [although Gunning was unable to.
confirm this statement]. The coloured corpuscles move in the smallest capillaries
in single ji/e one after the other; in the larger vessels, several corpuscles may
move abreast, with a gliding motion, and in their course they may turn over and
even be twisted if any obstruction is offered to the blood-stream. As a general
rule, in these vessels the movement is uniform, but at a sharp bend of the vessel it
may partly be retarded and partly accelerated. Where a vessel divides, not
unfrequently a corpuscle remains upon the projecting angle of the division, and is
doubled over it so that its ends project into the two branches of the tube. There it
may remain for a time, until it is dislodged, when it soon regains its original form on
account of its elasticity. Not unfrequently we see a red corpuscle becoming bent
where two vessels meet, but on all occasions it rapidly regains its original form.
This is a good proof of the elasticity of the coloured corpuscles. The motion
of the colourless corpuscles is quite different in character; they rol/ directly
on the vascu/ay wall, moistened on their peripheral zone by the plasma in
Poiseuille’s space, their other surface being in contact with the thread of coloured
corpuscles in the centre of the stream. Schklarewsky (1868) has shown by
physical experiments, that the particles of least specific gravity in all capillaries
(e.g., of glass) are pressed toward the wall, while those of greater specific gravity
remain in the middle of the stream. [Graphite and particles of carmine were sus-
pended in water, and caused to circulate through capillary tubes placed under a
microscope, when the graphite kept the centre of the stream, and the carmine
moved in the layer next the wall of the tube. ] |

When the colourless corpuscles reach the wall of the vessel, they must roll along,
partly on account of their surface being sticky, whereby they readily adhere to the
vessel, and partly because one surface is directed towards the axis of the vessel
where the movement is most rapid, and where they receive impulses directly from
the rapidly moving coloured blood-corpuscles (Donders). The rolling motion is not
always uniform, not unfrequently it is retrograde in direction, which seems to be
due to an irregular adhesion to the vascular wall. Their s/ower movement (10 to
12 times slower than the red corpuscles) is partly due to their stickiness, and partly
to the fact that, as they are placed near the wall, a large part of their surface lies in
the peripheral threads of the fluid, which of course move more slowly (in fact the
layer of fluid next the wall is passive—p. 91).

[D. J. Hamilton finds that, when a frog’s web is examined in a vertical position, by far the
greater proportion of leucocytes float on the wpper surface, and only a few on the lower surface,
of a small blood-vessel. In experiments to determine why the coloured corpuscles float or glide
exclusively in the axial stream, while a great many, but not all, of the leucocytes roll in the
peripheral layers, Hamilton ascertained that the nearer the suspended body approaches to the
specific gravity of the liquid in which it is immersed, the more it tends to occupy the centre of
the stream. He is of opinion that the phenomenon of the separation of the blood-corpuscles in
the circulating fluid is due to the colourless corpuscles being specifically lighter, and the coloured
either of the same or of very paca greater specific gravity, than the blood-plasma. Hamilton
coutroverts the statement of Schklarewsky, and he finds that it is the relative specific gravity
of a body which ultimately determines its position in a tube. These experiments point to the

immense importance of a due relation subsisting between the specific gravity of the blood-plasma
and that of the corpuscles. ]

In the vessels first formed in the incubated egg, as well as in young tadpoles, the movement
of the blood from the heart occurs in jerks (Spallanzani, 1768).

The velocity of the blood-stream is influenced by the diameter of the vessels, which
undergo periodic changes of calibre. This change occurs not only in vessels pro-
vided with muscular fibres, but also in the capillaries, which vary in. diameter,
owing to the contraction of the cells composing their walls (p. 96). Fs da gg

~whereby the corpuscle appears constricted in

DIAPEDESIS. 139

The amount of water in the blood is of importance ; when it is increased, the
circulation is facilitated and accelerated (§ 62).

The velocity of the blood is greater in the pulmonary than in the systemic
capillaries ; so that the total sectional area of the pulmonary capillaries is less than
that of all the systemic capillaries.

95. DIAPEDESIS.-—If the circulation be studied in the vessels of the mesentery, we may
observe colourless corpuscles passing out of the vessels in greater or less numbers (fig. 116).
The mere contact with the air suffices to excite slight inflammation. At first, the colourless
corpuscles in the plasma-space move more slowly ; several accumulate near each other, and
adhere to the walls—soon they bore into the wall, ultimately they pass quite through it, and may
wander for a distance into the perivascular
tissues. It is doubtful whether they pass
through the so-called ‘‘stomata ’’ which exist
between the endothelial cells, or whether they
simply pass through the cement substance be-
tween the endothelial cells (p. 94). This pro-
cess is called diapedesis, and consists of several
acts:—(a@) The adhesion of lymph-cells or
colourless corpuscles to the inner surface of the
vessel (after moving more slowly along the wall
up to this point). (b) They send processes into
and through the vascular wall. (c) The body .-~
of the cell is drawn after or follows the processes, ~

the centre (fig. 116, c). (d) The complete
passage of the corpuscle through the wall, and
its farther motion in virtue of its own ameeboid Fie. 11¢
movements. Hering observed that in large ie :
vessels with perivascular lymph-spaces, the

Small vessel of a frog’s mesentery showing dia-

corpuscles passed into the spaces, hence cells
are found in lymph before it has passed through
lymphatic glands. The cause of the diapedesis
is partly due to the independent locomotion of
the corpuscles, and it is partly a physical act,

pedesis. w,w,vascular walls ; a, a, Poiseuille’s
space ; 7, 7, red corpuscles ; 7, 7, colourless
corpuscles adhering to the wall, and ¢, ¢, in
various stages of extrusion ; /, 7, extruded
corpuscles.

viz., a filtration of the colloid mass of the cell under the force of the blood-pressure (Hering)—
in the latter respect depending upon the intravascular pressure and the velocity of the blood-
stream. Hering regards this process, and even the passage of the coloured corpuscles through
the vascular wall, as a normal process. The red corpuscles pass out of the vessels when the
venous outflow is obstructed, which also causes the transudation of plasma through the vascular
wall. The plasma carries the coloured corpuscles along with it, and at the moment of their
passage through the wall they assume extraordinary shapes, owing to the tension put upon
them, regaining their shape as soon as they pass out (Cohnheim). This remarkable phenomenon
was described by Waller in 1846. It was re-described by Cohnheim, and according to him the
out-wandering is a sign of inflammation, and the colourless corpuscles which accumulate in the
tissues are to be regarded as true pus-corpuscles, which may undergo further increase by division.

Stasis.—When a strong stimulus acts on a vascular part, hyperemic redness and swelling
occur. Microscopic observation shows, that the capillaries and the small vessels are dilated and
over filled with blood-corpuscles ; in some cases, a temporary narrowing precedes the «dilatation ;
simultaneously the velocity of the stream changes, rarely there is a temporary acceleration,

more frequently it becomes slower. If the action of the stimulus or irritant be continued, the

retardation becomes considerable, the stream moves in jerks, then follows a to-and-fro move-
ment of the blood-column—a sign that stagnation has taken place in other vascular areas. At
last the blood-stream comes completely to a standstill—stasis—and the blood-vessels are plugged

with blood-corpuscles. Numerous colourless blood-corpuscles are found in the stationary blood.

Whilst these various processes are taking place, the colourless corpuscles-—more rarely the red
—pass out of the vessels. Under favourable circumstances the stasis may disappear. The
swelling which occurs in the neighbourhood of inflamed parts is chiefly due to the exudation

of plasma into the surrounding tissues,

96. MOVEMENT OF THE BLOOD IN THE VEINS.—In the smallest
veins coming from the capillaries, the blood-stream is more rapid than in the
capillaries themselves, but less so than in the corresponding arteries. The stream
is uniform, and if no other conditions interfered with it, the venous stream
towards the heart ought to be uniform, but many circumstances affect the stream

140 ' MOVEMENT OF THE BLOOD IN THE VEINS.

in different parts of its course. Amongst these are :—(1) The relative Jawness,
great distensibility, and the ready compressibility of the walls, even of the thickest
veins. (2) The incomplete jilling of the veins, which does not amount to any con-
siderable distension of their walls. (3) The numerous and free anastomoses between
adjoining veins, not only between veins lying in{the same plane, but also between
superficial and deep veins. Hence, if the course of the blood be obstructed in one
direction, it readily finds another outlet. (4) The presence of numerous valves
which permit the blood-stream to move only in a centripetal direction. They are
absent from the smallest veins, and are most numerous in those of middle size.

Position of Valves.—The venous valves always have two pouches, and are placed at definite
intervals, which correspond to the 1, 2, 3, or n power of a certain ‘‘ fundamental distance,”
which is=7 mm. for the lower extremity and 5*5 mm. for the upper. Many of the original
valves disappear. On the proximal side of every valve a lateral branch opens into the vein,
while on the distal side of each branch lies a valve. The same is true for the lymphatics
(K. Bardeleben).

Effect of Pressure.—<As soon as pressure is applied to the veins, the next lowest
valves close, and those immediately above the seat of pressure open and allow the
blood to move freely toward the heart. The pressure may be exerted from without,
as by anything placed against the body ; the thickened contracted muscles, especially
the muscles of the limbs, compress the veins. That the blood flows out of a
divided vein more rapidly when the muscles contract, is shown during venesection.
If the muscles are kept contracted, the venous blood passing out of the muscles
collects in the passive parts, ¢.g., in the cutaneous veins. The pulsatile pressure of
the arteries accompanying the veins favours the venous current. From a hydro-
static point of view the valves are of considerable importance, as they serve to
divide the column of blood into segments (e.g., in the crural vein in the erect
attitude), so that the fine blood-vessels in the foot are not subjected to the whole
amount of the hydrostatic pressure in the veins.

The velocity of the venous blood has been measured directly (with the hemadromometer and
the rheometer—§ 89). Volkmann found it to be 225 mm. per sec. in the jugular vein. Reil
observed that 24 times more blood flowed from an arterial orifice than from a venous orifice of
the same size. The velocity of the venous current obviously depends upon the sectional area of
the vessel. Borelli estimated the capacity of the venous system to be 4 times greater than that
of the arterial; while, according to Haller, the ratio is 9 to 4.

Large Veins.—<As we proceed from the small veins towards the vene cave, the
sectional area of the veins, taken as a whole, becomes less, so that the velocity of the —
current increases in the same ratio. The velocity of the current in the venz cave
may be about half of that in the aorta (Haller). As the pulmonary veins are
narrower than the pulmonary artery, the blood moves more rapidly in the former.

97. SOUNDS WITHIN ARTERIES.—The sounds produced within arteries are, speaking
strictly from a physical point of view, only noises or bruits. Still, following Skoda’s lead, they
are spoken of by physicians as ‘‘ tones.” Clinically, there is no sharp distinction between |
‘‘tones,” sounds, noises, or bruits. In four-fifths of all healthy men two sounds—correspond- |
ing in duration and other characters to the two heart-sounds—are heard in the carotid (Conrad,
Weil). Sometimes only the second heart-sound is distinguishable, as its place of origin is near
to the carotid. They are not true arterial sounds, but are simply ‘‘ propagated heart-sounds.”’
Sometimes the sound of the pulmonary artery can be heard in this way (Weil, Bettelheim).
These murmurs, sounds, or bruits occur either spontaneously, or are produced by the application

of external pressure, whereby the lumen of the vessel is diminished. Hence one distinguishes :
(1) Spontaneous Murmurs, and (2) Pressure Murmurs. +

Arterial Sounds or murmurs are readily produced by pressing upon a strong
artery, ¢.g., the crural in the inguinal region, so as to leave only a narrow passage
for the blood (“stenosal murmur”). A fine blood-stream passes with great
rapidity and force through this narrow part, into a wider portion of the artery
lying. behind the point of compression. Thus arises the “ pressure-stream ”
(P. Niemeyer), or the * fluid vein ” (‘ veine fluide ” of Chauveau). The particles

.
4
4
)

SPONTANEOUS MURMURS. I4I

of the fluid are thrown into rapid oscillation, and undergo vibratory movements, and
by their movements produce the sound within the peripheral dilated portion of the
tube. A sound is produced in the fluid by pressure (Corrigan), The sounds are
not caused by vibrations of the vascular wall, as supposed by Bouillaud.

A murmur of this sort is the ‘‘sub-clavicular murmur ’’ (Roser), occasionally heard during
systole in the subclavian artery; it occurs when the two layers of the pleura adhere to the apex
of the lung (especially in tubercular diseases of the lungs), whereby the subclavian artery
undergoes a local constriction due to its being made tense and slightly curved (Fricdreich).
This result is indicated in a diminution or absence of the pulse-wave in the radial artery (Wei).

It is obvious that arterial murmurs will occur in the human body :—(a) When, owing to
pathological conditions, the arterial tube is dilated at one part, into which the blood-current is
forcibly poured from the normal narrow tube. Dilatations of this sort are called aneurisms,
in which murmurs are generally audible. (+) When pressure is exerted upon an artery,
e.g., by the pressure of the greatly enlarged arteries during pregnancy, or by a large tumour
pressing upon a large artery.

Spontaneous Murmurs. —In cases where no source of external pressure is discoverable, and
when no aneurism is present, the spontaneously occurring sounds are favoured, when at the
moment of arterial rest (cardiac systole) the arterial walls are distended to the slightest extent,
and when during the movement of the pulse (cardiac diastole) the tension is most rapid (7’raube,
Weil), 7.e., when the low systolic minimum tension of the arterial wall passes rapidly into the
high maximum tension. This is especially the case in insufficiency of the aortic valves, in
which case the sounds in the arteries are audible over a wide area. If the minimum tension of
the arterial wall is relatively great, even during diastole, the sounds in the arteries are greatly
diminished.

Arterial murmurs are favoured by—(1) Sufficient delicacy and elasticity of the
arterial walls. (2) Diminished peripheral resistance, e.g., an easy outflow of the
fluid at the end of the stream. (3) Accelerated current in the vascular system
generally. (4) A considerable difference of the pressure in the narrow and wide
portions of the tube. (5) Large calibre of the arteries.

In normal pulsating arteries, sounds may be heard especially at an acute bend of the artery.
Murmurs of this sort are loudest where several large arteries lie together; hence, during
pregnancy, we hear the uterine murmur, or placental bruit, or sowfle in the greatly dilated
uterine arteries. It is much less distinct in the umbilical arteries of the cord (umbilical
murmurs). Similar sounds are heard through the thin walls of the head of infants, and a
murmur is sometimes heard in the enlarged spleen in ague (Maissurianz).

Auscultation of the Normal Pulse.—On auscultating the radial artery under favourable cir-
cumstances, and especially in old thin persons with wide arteries and dicrotic pulse, one may
hear two sounds corresponding to the primary and dicrotic waves.

In insufficiency of the aortic valves, characteristic sounds may be heard in the crural artery.
If pressure be exerted upon the artery, a double blowing murmur is heard ; the tirst one is due
to a large mass of blood being propelled into the artery synchronously with the heart-beat, the
second to the fact that a large quantity of blood flows back into the heart during diastole. If
no pressure be exercised two sounds are heard, and these seem to be due to a wave propagated
into the arteries by the auricles and ventricles respectively—compare § 73, fig. 86, IfI. In
atheroma a double sound may sometimes be heard (§ 73, 2).

98. VENOUS MURMURS.—I. Bruit de Diable.—This sound is heard above
the clavicles in the furrow between the two heads of the sterno-mastoid, most
frequently on the right side, and in 40 per cent. of all persons examined. It is
either a continuous or a rhythmical murmur, occurring during the diastole of the
heart or during inspiration ; it has a whistling or rushing character, or even a
musical quality, and arises within the bulb of the common jugular vein. When
this sound is heard without pressure being exerted by the stethoscope, it is a
pathological phenomenon. If, however, pressure be exerted, and if, at the same
time, the person examined turn his head to the opposite side, a similar sound is
heard in nearly all cases. The pathological bruit de diable occurs especially in
anzemic persons, in lead poisoning, in syphilitic and scrofulous persons, sometimes
in young persons, and less frequently in elderly people. Sometimes a thril/ of the
vascular wall may be felt.

Causes.—It is due to the vibration of the blood flowing in from the relatively
narrow part of the common jugular vein into the wide bulbous portion of the

142 VENOUS MURMURS.

vessel, and seems to occur chiefly when the walls of a thin part of the vein lie close
to each other, so that the current must purl through it. It is clear that pressure
from without, or lateral pressure, as by turning the head to the opposite side, must
favour its occurrence. Its intensity will be increased when the velocity of the
stream is increased, hence inspiration and the diastolic action of the heart (both of
which assist the venous current) increase it. The erect attitude acts in a similar
manner. A similar bruit is sometimes, though rarely, heard in the subclavian,
axillary, thyroid, facial, innominate and crural veins, and superior cava.

Il. Regurgitant Murmurs.—On making a sudden effort, a murmur may be heard in the
erural vein during expiration, which is caused by a centrifugal current of blood, owing to the
incompetence or absence of the valves in this region. If the valves at the jugular bulb are not
tight, there may be a bruit with expiration (expiratory jugular vein bruit—Hamernjk), or
during the cardiac systole (systolic jugular vein bruit—v. Bamberger).

III. Valvular Sounds in Veins.— When the tricuspid valve is incompetent, during the ven-
tricular systole, a large volume of blood is propelled backwards into the vene cave. The
venous valves are closed suddenly thereby and a sound produced. This occurs at the bulb or
dilatation on the jugular vein (v. Bamberger), and in the crural vein at the groin (NV. Friedreich),
i.e., only as long as the valves are competent. Forced expiration may cause a valvular sound
in the crural vein. No sound is heard in the veins under perfectly normal circumstances.

99. THE VENOUS PULSE—PHLEBOGRAM.—Methods.—A tracing of the movements of
a vein, taken with a lightly weighted sphygmograph, has a characteristic form, and is called a
phlebogram (fig. 117). In order to interpret the various events of the phlebogram it is most
important to record simultaneously the events that take place in the heart. The auricular con-
traction (compare fig. 39) is synchronous with ad ; be, with the ventricular systole, during which
time the first sound occurs, whilst a } is a presystolic movement. The carotid pulse coincides
nearly with the apex of the cardiogram, /.c., almost simultaneously with the descending limb
of the phlebogram (Riege/).

Occasionally in healthy individuals a pulsatile movement, synchronous with the
action of the heart, may be observed in the common jugular vein. It is either
confined to the lower part of the vein, the so-called bulb, or extends farther up
along the trunk of the vein. In the latter case, the valves above the bulb are
insufficient, which is by no means rare, even in health. The wave-motion passes
from below upwards, and is most obvious when the person is in the passive
horizontal position, and it is more frequent on the right side, because the right vein
lies nearer the heart than the left. It is propagated more slowly than the arterial
pulse-wave. The venous pulse resembles very closely the tracing of the cardiac
impulse. Compare fig. 117, 1, with fig. 39.

It is obvious that, as the jugular vein is in direct communication with the right
auricle, and as the pressure within it is low, the systole of the right auricle must
cause a positive wave to be propagated towards the peripheral end of the jugular
vein. Fig. 117, 9 and 10, are venous pulse-tracings of a healthy person with
insufficiency of the valves of the jugular vein. In these curves, the part a } 4
corresponds to the contraction of the auricle. Occasionally this part consists of two
elevations, corresponding to the contraction of the atrium and auricle respectively.
As the blood in the right auricle receives an impulse from the sudden tension of
the tricuspid valve, synchronous with the systole of the right ventricle, there is a
positive wave in the jugular vein in fig. 117, 9 and 10, indicated by }, c. Lastly,
the sudden closure of the pulmonary valves may even be indicated (e). As the
aorta lies in direct relation with the pulmonary artery, the sudden closure of its
valves may also be indicated (fig. 91, 9, at d). During the diastole of the auricle
and ventricle, blood flows into the heart, so that the vein partly collapses and the
lever of the recording instrument descends.

Sinus and Retinal Pulse.—The blood in the sinuses of the brain also undergoes a pulsatile
movement, owing to the fact that during cardiac diastole much blood flows into the veins.
(Mosso). Under favourable circumstances, this movement may be propagated-into the veins of

the retina, constituting the venous retinal pulse of the older observers (Helfreich). .
Pathological Jugular Vein Pulse. —The venous pulse in the jugular vein is far better marked

————o

LIVER PULSE, 143

in insufficiency of the tricuspid valve, and the vein may pulsate violently, but if its valves be
perfect, the pulse is not propagated along the vein, so that a pulse in the jugular vein is not
necessarily a sign of insufficiency of the tricuspid valve, but only of insufficiency of the valve of
the jugular vein (Priedreich).

Liver Pulse.—The ventricular systole is propagated into the valveless inferior vena cava, and
causes the liver pulse. With.each systole blood passes into the hepatic veins, so that the liver
undergoes a systolic swelling and injection.

Fig. 117, 2-8, are curves of the pulse in the common jugular vein. Although at first sight
the curves appear to be very different, they all agree in this, that the various events occurring
in the heart during a cardiac revolution are indicated more or less completely. In all the
curves, @ b=auricular contraction. The auricle, when it contracts, excites a positive wave in
the veins. The elevation, } c, is caused by the large blood-wave produced in. the veins, owing
to the emptying of the ventricle. It.is always greater, of course, in insufficiency of the tricuspid
valves than under normal circumstances (fig. 117, 9and 10). In the latter case, the closure of the
tricuspid valve causes only a slight wave-motion in the auricle. The apex, c, of this wave may
be higher or lower, according to the tension in the vein and the pressure exerted by the sphyg-
mograph. As a general rule, at least one notch (4, 5, 6, ¢) tollows the apex, due to the

Hig. 117:

Venous pulses (Friedreich). 1-8, from insufficiency of the tricuspid ; 9, 10, pulse of the jugular
vein of a healthy person. In all the curves, « b=contraction of the right auricle; Uc, of
the right ventricle ; d, closure of the aortic valves; ¢, closure of the pulmonary valves ;
e, f, diastole of the right ventricle.

prompt closure of the valves of the pulmonary artery. ‘he closure of the closely adjacent
aortic valves may cause a small secondary wave near to ¢ (asin 1 and 2, d). The curve falls
towards f, corresponding to the diastole of the heart.

A well-marked venous pulse occurs when the right auricle is greatly congested, as in cases of
insufficiency of the mitral valve or stenosis of the same orifice. In rare cases, in addition to
the pulse in the common jugular vein, the external jugular, the facial, thyroid, external
thoracic veins, or even the veins of the upper and lower, extremities may pulsate. <A similar
pulsation must occur in the pulmonary veins in mitral insufficiency, but of course the result is
not visible..

On rare occasions, a pulse occurs in the veins on the back of the hand and foot owing to the
arterial pulse being propagated through the capillaries into the veins. This may occur under
normal circumstances, when the peripheral ends of the arteries become dilated and relaxed
(Quincke), or when the blood-pressure within these vessels rises rapidly and falls as suddenly,
as in insufficiency of the aortic valves.

In progressive effusion into the pericardium, the carotid pulse at first becomes smaller and the
venous pulse larger; beyond a certain stage of pressure the latter ceases (Riegel).

144 DISTRIBUTION OF THE BLOOD.

100. DISTRIBUTION OF THE BLOOD.—In the rabbit, one-fourth of the-
total amount of the blood is found in each of the following :—-a, in the passive.
muscles ; 4, in the liver; c, in the organs of the circulation (heart and great
vessels) ; d, in all other parts together,

Methods,—The methods adopted do not give exact results. J. Ranke ligatured the parts.
during life, removed them, and investigated the amount of blood while the tissues were still
Eaauaneiid Conditions.—The amount of blood is influenced by—(1) the anatomical dis-
tribution of the vessels (vascularity or the reverse) as a whole ; (2) the diameter of the vessels,
which depends upon physiological causes—(a) on the blood-pressure within the vessels ; (b) on
the condition of the vaso-motor or vaso-dilator nerves ; (c) on the condition of the tissues them-
selves, ¢.g., the vessels of the intestine during absorption ; by the vessels of muscle during
muscular contraction ; of vessels in inflamed parts.

The most important factor, however, is the state of activity of the organ itself ;.
hence, the saying, “‘ubi irritatio, ibi affluxus.” We may instance the congestion
of the salivary glands and the gastric mucous membrane during digestion, and the
increased vascularity of muscles during contraction, As the activity of organs
varies at different times, the amount of blood in the part or organ goes hand in hand
with the variations in its states of activity. When some organs are congested, others.
are at rest; during digestion, there is muscular relaxation and less mental activity :
violent muscular exertion retards digestion—during great congestion of the
cutaneous vessels the activity of the kidneys diminishes. Many organs (heart,
muscles of respiration, certain nerve-centres) seem always to be in a nearly uniform
state of activity and vascularity. During the activity of an organ, the amount of
blood in it may be increased 30 per cent., nay, even 47 per cent. The motor
organs of young muscular persons are relatively more vascular than those of old
and feeble persons (J. Ranke). In the condition of increased activity, a more
rapid renewal of the blood seems to occur ; after muscular exertion the duration of
the circulation diminishes (Vierordt).

During a condition of mental activity, the carotid is dilated, the dicrotic wave in the carotid
curve is increased (the radial shows the opposite condition), and the pulse is increased in
frequency (Gley). '

Age.—The development of the heart and large vessels determines a different distribution of
the blood in the child from that which obtains in the adult. The heart is relatively small from
infancy up to puberty, the vessels are relatively large ; while after puberty the heart is large,.

Fig. 118,

Mosso’s plethysmograph. GG, ‘glass-vessel for holding a limb ; F, flask for varying the waters

pressure in G ; T, recording apparatus. ‘
and the vessels are relatively smaller. Hence it follows that the blood-pressure in the arteries:
of the systemic circulation must be lower in the child than inthe adult. The pulmonary artery
is relatively wide in the child, while the aorta is relatively small ; after puberty both vessels:
have nearly the same size. Hence, it follows that the blood-pressure in the pulmonary vessels.
of the child is relatively higher than that in the adult (Beneke), )

101. PLETHYSMOGRAPHY.—In order to estimate and register the amount
of blood in a limb Mosso devised an instrument (fig, 118), which he termed a
plethysmograph. .

TRANSFUSION OF BLOOD. T45

It consists of a long cylindrical glass-vessel, G, suited to accommodate a limb. The opening
through which the limb is introduced is closed with caoutchouc, and the vessel is filled with
water. There is an opening in the side of the vessel in which a manometer tube, filled to a
certain height with water, is fixed. As the arm is enlarged owing to the increased supply of
arterial blood passing into it at each pulse-beat, of course the water column in the manometer
is raised, Fick placed a float upon the surface of the water, and thus enabled the variations in
the volume of the fluid to be inscribed on a revolving cylinder. The curve obtained resembled
the pulse-curve ; it was even dicrotic. In fig. 118 the movement of the fluid is represented as
conveyed to a Marey’s tambour, T, similar to the recording apparatus employed in Brondgeest’s

pansphygmograph (fig. 76).

The cylinder C may be filled with air. Kries fills it with gas and connects the tube leading
to T to a gas-burner. The variations in the gas-flame are then photographed.

Results.—(1) Pulsatile Variations in the Volume.—aAs the venous current is
regarded as uniform in the passive limb, every increase of the volume-curve
indicates a greater velocity of the arterial current towards the periphery, and vice
versa (Fick). The curves registered by the apparatus are volume-pulses, and they
resemble the curve of the dromograph (fig. 113, III). The ascent of the curve
indicates a greater, the descent a diminished inflow of arterial blood.

At first sight the plethysmograph curve (volume-pulse, § 90, 7) is very like the pulse-curve
(pressure pulse); both are dicrotic. But there are differences ; the volume pulse-curve beyond
the apex falls more rapidly. This rapid fall, which is not accompanied by a corresponding fall
of the pressure, is attributed by v. Kries to peripheral reflexion. The dicrotic wave occurs
sooner in the volume-pulse than in the pulse-curve.

(2) The respiratory undulations correspond to similar variations in the blood-
pressure tracing (§ 85, f). Vigorous respiration and cessation of the respiration
cause a diminution of the volume. The limb swells during straining and coughing,
but diminishes during sighing. (3) Certain periodic undulations occur, due to
the regular periodic contractions of the small arteries. (4) Other undulations, due
to various accidental causes, affect the blood-pressure: changes of the position of
a limb acting hydrostatically, and dilatation or contraction of the vessels in other
vascular regions. (5) Movement of the muscles of the limb under observation
causes diminution of volume, as the venous current is accelerated, the musculature
is also very slightly diminished in volume, even when the intra-muscular vessels are
dilated. (6) Mental exercise causes a diminution in the volume of the limb, and
so does sleep (Vosso). Music influences the blood-pressure in dogs, the pressure
rising or falling under different conditions. The stimulation of the auditory nerve
is transmitted to the medulla oblongata, where it acts so as to cause acceleration of
the action of the heart (Dogiel). (7) Compression of the afferent artery causes a
decrease, and compression of the vein an increase in the volume of the limb (JJosso).
(8) Stimulation of the vaso-motor nerves causes a decrease, that of the vaso-
dilators an increase in the volume (Bowditch and Warren).

102. TRANSFUSION OF BLOOD.—-Transfusion is the introduction of blood
from one animal into the vascular system of another animal.

(a) The red corpuscles are the most important elements in connection with the
restorative powers of the blood. They seem to preserve their functions even in
blood which has been defibrinated outside the body (§ 4, A).

(6) With regard to the gases present in the blood, arterial blood never acts
injuriously ; but venous blood overcharged with carbonic acid ought only to be
transfused when the respiration is sufficient to oxygenate the blood as it passes
through the pulmonary capillaries, whereby venous is’ transformed into arterial
blood. If the respiratory movements have ceased, or are imperfectly performed,
the blood becomes rapidly richer in carbonic acid, and in this condition reaches the
heart ; thence it is propelled into the blood-vessels of the medulla oblongata, where
it acts as a powerful stimulus of the respiratory centre, causing dyspnoea, con-
vulsions, and death.

_ (c) The fibrin, and the substances from which it is formed, do not seem to play

K

146 TRANSFUSION OF BLOOD,

any part in connection with the restorative powers of the blood ; hence, defibrinated
blood performs all the functions of non-defibrinated blood within the body (Panum,
Landois). Mea

(d) The investigations of Worm Miiller showed that an excess of 83 per cent. of
blood may be transfused into the vascular system of an animal (dog) without pro-
ducing any injurious effects. Hence it follows that the vascular system has the
power of accommodating large quantities of blood within it. That the vascular
system can accommodate itself to a diminished amount of blood has been known
for a long time (§ 85, c). [It is very important to observe that the transfusion of
a large quantity of blood does not materially or permanently raise the blood-
pressure. |

When Employed.—The transfusion of blood is used—(1) in acute anemia
(§ 41, 1), e.g., after copious hemorrhage. New blood (150 to 500 c.c.), from the
same species of animal, is introduced directly into the vessels, to supply the place of
the blood lost by the hemorrhage.

(2) In cases of poisoning, where the blood has been rendered useless by being
mixed with a poisonous substance, and hence is unable to support life. In such
cases remove a considerable quantity of the blood, and replace it by fresh blood.
Carbonic oxide is a poison of this kind, and its effects on the body have already
been described ($ 16). A similar practice is indicated in poisoning with ether,
chloral, chloroform, opium, morphia, strychnine, cobra poison, and such substances
as dissolve the blood-corpuscles, ¢.g., potassic chlorate.

(3) Under certain pathological conditions, the blood may become so altered in
quality as to be unable to support life. The morphological elements of the blood
may be altered, and so may the relative proportion of its other constituents.
Amongst these conditions may be cited the pathological condition of ureemia, due,
it may be, to the accumulation of urea or the products of its decomposition within
the blood ; accumulation of the biliary constituents in the blood, and great increase
of the carbonic acid. All these three conditions, when very pronounced, may cause
death. In these cases, part of the impure blood may be replaced by normal human
blood.

Amongst conditions where the morphological constituents of the blood are altered
qualitatively or quantitatively are : hydremia (excessive amount of water in the
blood, § 41, 1) ; oligocytheemia (abnormal diminution of red blood-corpuscles).
When these conditions are highly developed, more especially in pernicious anemia
(§ 10, 2), healthy blood may be substituted. Transfusion is not suited for persons
suffering from leukemia (compare p. 18).

After-Effects.—A quarter or half an hour after normal blood has been injected
into the blood-vessels of a man, there is a greater or less febrile reaction, according
to the amount of blood transfused (Fever, § 220.)

Operation.—The operative procedure to be adopted in the process of transfusion varies accord-
ing as defibrinated or non-defibrinated blood is used. In order to defibrinate blood, some blood
is withdrawn from a vein of a healthy man in the ordinary way, collected in an open vessel, and
whipped or beaten with a glass rod until ali the fibrin is completely removed from it. It is
then filtered through an atlas filter, heated to the temperature of the body (by placing it in
a vessel in warm water), and injected by means of a syringe into an artery opened for the
purpose. A vein (e.g., basilic or great saphenous) may be selected for the transfusion, in which
ease the blood is driven inward in the direction of the heart ; if an artery is selected (radial
or posterior tibial) the blood is injected towards the periphery (Hiiter), or towards the heart.
(Landois, Schafer).

If non-defibrinated human blood is used, the blood may be passed directly from the arm of
the giver to the arm of the receiver by means of a flexible tube. The tube used must be filled
with normal saline solution to prevent the entrance of air. [J. Duncan collects the blood shed

during an operation in a 5 per cent. solution of sodic phosphate (Pavy), and injects the mixture
especially where much blood has been lost previously. ]

_ Dangers. —It is most important that no air be allowed to puss into the circulation, for if it be
introduced in sufficient quantity it may cause death. When air enters the circulation it reaches

TRANSFUSION OF BLOOD. 147

the right side of the heart, where, owing to the movement of the blood, it forms air-bubbles and
makes a froth. The air-bubbles are pumped into the branches of the pulmonary artery, in
which they become impacted, arrest the pulmonary circulation, and rapidly cause death.

Peritoneal Transfusion.—Recently, the injection of defibrinated blood into the peritoneal
cavity has been recommended. The blood so injected is absorbed (Ponfick). Even after twenty
minutes the number of blood-corpuscies in the blood of the recipient (rabbit) is increased, and
the number is greatest on the first or second day. The operation, however, may cause death,
and one fatal case, owing to peritonitis, is recorded (Mosle7). It is evident that this method
of transfusion is not applicable in cases where blood must be introduced into the circulation as
rapidly as possible (¢.g., after severe hemorrhage or in certain cases of poisoning. [Blood has
been injected into the subcutaneous cellular tissue of the abdomen in cases of great debility. ]

Heterogeneous Blood. — The blood of animals ought never to be transfused into the blood-vessels
of man. Itis to be remembered, however, that the blood-corpuscles of the sheep are rapidly
dissolved by human blood, so that the active constituents of the blood are rendered useless
(Landois). Asa general rule, the blood-serum of some mammals dissolves the blood-corpuscles
of other mammals (§ 5, 5).

Solution of the Blood-Corpuscles.—The serum of dog’s blood is a powerful solvent, while
that of the blood of the horse and rabbit dissolves corpuscles relatively slowly. The blood-
corpuscles of mammals vary very greatly with reference to their power to resist the solvent
action of the serum of other animals. The red blood-corpuscles of rabbits’ blood are rapidly
dissolved by the blood-serum of other animals, whilst those of the cat and dog resist the
solvent action much longer. Solution of the corpuscles occurs in defibrinated as well as in
ordinary blood. When the blood of a rabbit or lamb is injected into the blood-vessels of a dog,
the red blood-corpuscles are dissolved in a few minutes. If blood be withdrawn by pricking the
skin with a needle, the partially dissolved corpuscles may be detected.

Liberation of Hemoglobin and Hemoglobinuria. —As a result of the solution of the coloured
corpuscles, the blood-plasma is reddened by the liberated hemoglobin. Part of the dissolved
material may be used up in the body of the recipient, some of it for the formation of bile, but
if the solution of the corpuscles has been extensive, the hemoglobin is excreted in the urine
(heemoglobinuria), in less amount in the intestine, the bronchi, and the serous cavities. Bloody
urine has been observed in man after the injection of 100 grammes of lamb’s blood. Even some
of the recipient’s blood-corpuscles are dissolved by the serum of the transfused blood, ¢.9., on
transfusing dog’s blood into man. In the rabbit, whose corpuscles are readily dissolved, the
transfusion of the blood-serwm of the dog, man, pig, sheep, or cat produces serious symptoms,
and even death. The dog, whose corpuscles are more resistant, bears transfusion of other
kinds of blood well. ;

Dangers.-—When foreign or heterogeneous blood (7.e., blood from a different species) is trans-
fused, two phenomena, which may be dangerous to life, occur :—

(1) Before the corpuscles are dissolved, they usually run together and form sticky masses,
consisting of 10 or 12 corpuscles, which are apt to occlude the capillaries. After a time they give
up their hemoglobin, leaving the stroma, which yields a sticky fibrin-like mass that may
occlude fine vessels (§ 31).

(2) The presence of a large quantity of dissolved heemoglobin may cause extensive coagulation
within the blood-vessels. The injection of dissolved hemoglobin causes extensive coagulations
(Naunyn and Francken).

The coagulation occurs usually in the venous system and in the larger vessels, and may cause
death either suddenly or after a considerable time.

Dissolved hemoglobin seems greatly to increase the activity of the fibrin-ferment (§ 30),
perhaps by accelerating the disintegration of the colourless corpuscles. Hemoglobin exposed
to the air gradually loses this property; and the fibrin-ferment, when in contact with hemo-
globin, is either destroyed or rendered less active (Sachssendah/).

Vascular Symptoms.—As a result of the above-named causes of occlusion of the vessels, there
are often signs of the circulation being impeded in various organs. In man, after transfusion
of lamb’s blood, the skin is bluish-red, in consequence of the stagnation of blood in the
cutaneous vessels. Difficulty of breathing occurs from obstruction in the capillaries of the
lung; while there may be rupture of small bronchial vessels, causing sanguineous expectora-
tion. The dyspnoea may increase, especially when the circulation through the medulla
oblongata—the seat of the respiratory centre—is interfered with. In the digestive tract, for
the same reason, increased peristalsis, evacuation of the contents of the rectum, vomiting, and
abdominal pain may occur. These phenomena are explained by the fact that disturbances of
the circulation in the intestinal vessels cause increased peristaltic movements. Degeneration
of the parenchyma of the kidney occurs as a result of the occlusion of some of the renal vessels.
The uriniferous tubules become plugged with cylinders of coagulated albumin (Ponjick). Owing
to the occlusion of numerous small muscular branches, the muscles may become stiff, or coagula-
tion of their myosin may occur. Other symptoms, referable to the nervous system, sense-organs,
and heart, are all due to the interference with the circulation through them. An important
symptom is the occurrence of a considerable amount of fever half an hour or so after the trans-

148 | THE BLOOD-GLANDS.

fusion of heterogeneous blood (§ 200). When many vessels are occluded, rupture of some small
blood-vessels may take place. This explains the occurrence of slight, yet persistent hemorrhages,
which occur on the free surfaces of the mucous and serous membranes, and in the parenchyma
of organs, as well as in wounds. The blood coagulates with difficulty, and imperfectly.

Transfusion of other Fluids. —Other substances have been transfused. Normal saline solu-
tion (0°6 per cent. NaCl), or serum from the same species, aids the circulation in a purely
mechanical way (Goltz), and it even excites the circulation (Kronecker). In severe anemia this
fluid cannot maintain life (Hulenburg and Landois). The injection of peptone, even in moderate
amount, is dangerous to life, as it causes paralysis of the vessels (p. 32).

The Blood-Glands.

103.—I. THE SPLEEN.—Structure.—The spleen is covered by the peritoneum, except at
the hilum. Under this serous covering there is a tough, thick, elastic, fibrous capsule, which
mma losely invests the organ and gives a covering to
Capsule, I ed Sa the vessels which enter or leave it at the hilum, so
Bog Uae that fibrous tissue is carried into the organ along
the course of the vessels (fig. 119). [The capsule
3 cannot be separated without tearing the splenic
Tahocules. <2 as te ‘i > pulp.] Numerous trabecule pass into the spleen

; eeaa: : from the deep surface of the capsule, where the

branch and anastomose so as to produce a networ
of sustentacular tissue, which is continuous with
the connective-tissue, prolonged inwards and sur-
rounding the blood-vessels (fig. 120). Thus, the
connective-tissue in the spleen, as in other viscera,
is continuous throughout the organ. In this way
an irregular dense network is formed, comparable
to the meshes of a bath sponge. [This network
is easily demonstrated by washing out the pulp
lying in its meshes by means of a stream of water,
when a beautiful soft semi-elastic network or

Malpighian
corpuscles,

Splenic pUlp. wre framework of rounded and flattened threads is
obtained.] The capsule (fig. 119) is composed of
interlacing bundles of connective-tissue mixed

a with numerous fine fibres of elastic tissue and

Ter ae some non-striped muscular fibres.

Reticulum. —Within the meshes of the trabecu-
lar framework there is disposed a very delicate
network or reticulum of adenoid tissue, which,
with the other coloured elements that fill up the
Bere meshes, constitutes the splenic pulp (fig. 121). The

gods ‘ reticulum is continuous with the fibres of the

: Fig. 119. trabecule. [If a fine section of the spleen be

Section of human spleen x 10 «+ pencilled ” in water, so as to remove the cellular

times. elements, the preparation presents much the same

characters as a section of a lymph-gland similarly treated, viz., a very fine network of adenoid

Blood-vessel in
a trabecula,

tissue, continuous with, and surrounding the walls of, the blood-vessels. The spaces of this.

tissue are filled with lymph-and blood-corpuscles. ]
The pulp is a dark reddish-coloured, semi-fluid material, which may be squeezed or washed

out of the meshes in which it lies. It contains a large number of coloured blood-corpuscles,

and becomes brighter when it is exposed to the action of the oxygen of the air.

Blood-Vessels and Malpighian Corpuscles.—The large splenic artery, accompanied by a vein,

splits up into several branches before it enters the spleen. Both vessels and their branches.
are enclosed in a fibrous sheath, which becomes continuous with the trabecule. The smaller
branches of the artery gradually lose this fibrous investment, and each one ultimately divides
into a group or pencil of arterioles or penicilli, which do not anastomose with each other. [Thus
each branch is terminal—a condition which is of great importance in connection with the patho-
logy of embolism or infarction of the vessels of the spleen.] At the points of division of the
branches of the artery, or scattered along their course, are small oval or globular masses of
adenoid tissue (4; to » inch in diameter), the Malpighian corpuscles. [These bodies are

visible to the naked eye as small, round, or oval white structures, about the size of millet seed,

in a section of a fresh spleen. They are very numerous—[70,000 in man]—and are readily
detected in the dark reddish pulp. One pias C

careful not to mistake sections of the trabecule.

BLOOD-VESSELS OF THE SPLEEN. 149

for them. These corpuscles consist of adenoid tissue, whose meshes are filled with lymph-
corpuscles, and they present exactly the same structure as the solitary follicles of the intestine
(§ 197). They are small lym-
phatic. accumulations around
the arteries — peri-arterial
masses of adenoid tissue similar
to those masses that occur in a

Fig. 120. Fig. 121.
‘Trabecule of the spleen of a cat with the splenic pulp washed Adenoid reticulum of
out. a, trabecula; 5, vein. spleen of cat.

‘slightly different form in other organs, ¢.g., the lungs. In a section of the spleen the artery
may pass through the centre of the mass or through one side of it, and in some cases the tissue
is collected unequally on opposite sides of the vessel, so that it is lob-sided. They are not
surrounded by any special envelope. Insome animals the lymphatic tissue is continued for some
distance along the small arteries, so that to some extent it resembles a peri-vascular sheath of
adenoid tissue. In a well-injected spleen, a few fine capillaries are to be found within these
corpuscles. The capillaries distributed in the substance of the Malpighian corpuscle (fig. 122)
form a network, and ultimately pour their blood into the spaces in the pulp. According to
Cadiat, the corpuscles are separated from the
splenic pulp by a lymphatic sinus, which is
traversed by efferent capillaries passing to the
pulp (fig. 122).]

Connection of Arteries and Veins.—It is
very difficult to determine what is the exact
mode of termination of the arteries within the
spleen, more especially as it is extremely diffi-
cult to inject the blood-vessels of the spleen.
According to Stieda, and others, the fine
‘‘capillary arteries” formed by the division

of the small arteries do not open directly
into the capillary veins, but the connection
between the arteries and veins is by means of
the ‘‘ intermediary intercellular spaces” of
the reticulum of the spleen, so that, according
to this view, there is no continuous channel
lined throughout by epithelium connecting
these vessels one with another. Thus the
blood of the spleen flows into the spaces of the
adenoid reticulum just as the lymph-stream ;
flows through the spaces in a lymph-gland. Fig. 122.
According to Billroth and Kolliker, a closed Malpighian corpuscle of a cat’s spleen injected.
blood-channel actually does exist between the a, artery; b, meshes of the pulp injected ;
capillary arteries and the veins, consisting c, the artery of the corpuscle ramifying in the
of dilated spaces (similar to those of erectile lymphatic tissue composing it.
tissue). These intermediary spaces are said to
be completely lined by spindle-shaped epithelium, which abuts externally on the reticulum of
the pulp. [According to Frey, owing to the walls of the terminal vessels being incomplete,
there being clefts or spaces between the cells composing them, the blood passes freely into
Spaces of the adenoid tissue of the pulp ‘‘ in the same way as the water of a river finds its way

: amongst the pebbles of its bed,” these ‘‘ intermediary passages’’ being bounded directly by

" the cells and fibres of the network of the-pulp. From these passages the venous radicles arise.
At first, their walls are imperfect and cribriform, and they often present peculiar transverse
markings, due to the circular disposition of the elastic fibres of the reticulum. The small veins
have at first a different course from the arteries. They anastomose freely, but they soon become

‘ ensheathed, and accompany the arteries in their course. |

150 FUNCTIONS OF THE SPLEEN.

Elements of the Pulp (fig. 123).—The ee elements are very various—(1)
Lymph-corpuscles of various sizes, sometimes partly swollen, and at other times with granular
contents. (2) Red blood-corpuscles. (3) Transition forms between 1 and 2 [although this is
denied by some observers (§ 7, C)]. (4) Cells containing red blood-
corpuscles and pigment granules. [These cells exhibit amceboid
movements.] (Compare § 8.)

[Lymphatics undoubtedly arise within the spleen, but they are
not numerous. There are two systems—a superficial or capsular,
_S @ _-— and trabecular system ; and a peri-vascular set. The superficial

we | Sep lymphatics in the capsule are rather more numerous. Some of them

5 a ‘ 3 eet seem to communicate with the lymphatics within the organ (7omsa,
© i op Kolliker). In the horse’s spleen they communicate with the lym-
BY 4 phatics in the trabecule, and with the peri-vascular lymphatics.

fe 3 The exact mode of origin of the peri-vascular system is unknown,
Y but in part at least it begins in the spaces of the adenoid tissue of

the Malpighian corpuscles and peri-vascular adenoid tissue, and

2 runs along the arteries towards the hilum. There seem to be no

Fig. 123. afferent lymphatics in the spleen such as exist in a lymphatic

gland. }

The nerves of the spleen are composed for the most part of non-
medullated nerve-fibres, and run along with the artery. Their exact
mode of termination is unknown, but they probably go to the
blood-vessels and to the muscular tissue in the capsule and trabecule.
[They are well seen in the spleen of the ox, and in their course very
small ganglia, placed wide apart, have been found by Remak and
W. Stirling. ]

Chemical Composition.—-Several of the more highly oxidised stages
of albuminous bodies exist in the spleen. Besides the ordinary constituents of the blood,
there exist :—leucin, tyrosin, xanthin, hypoxanthin ; lactic, butyric, acetic, formic, succinic,
and uric acids, and perhaps glycero-phosphoric acid (Salkowski); cholesterin, a glutin-like body,
inosit, a pigment containing iron, and even free iron oxide (Nasse), The ash is rich in phos-
phoric acid and iron (p. 151)—poor in chlorine compounds. The splenic juice is alkaline in
reaction ; the specific gravity of the spleen = 1059-1066.

The functions of the spleen are obscure, but we know some facts on which to
form a theory. [The spleen differs from other organs in that no very apparent
effect is produced by it, so that we must determine its uses in the economy from a
consideration of such facts as the following :—(1) The effects of its removal or
extirpation. (2) The changes which the blood undergoes as it passes through it.
(3) Its chemical composition. (4) The results of experiments upon it. (5) The
effects of diseases. |

(1) Extirpation.—The spleen may be removed from an animal—old or young—
without the organism suffering any very obvious change (Galen). The human
spleen has been successfully removed by Kéberle, Péan, and others. As a result
(compensatory ?) the lymphatic glands enlarge, but not constantly, while the blood-
forming activity of the red marrow of bone is increased. Small brownish-red
patches were observed in the intestines of frogs after extirpation of the spleen.
These new formations are regarded by some observers as compensatory organs.
Tizzoni asserts that new splenic structures are formed in the omentum (horse, dog)
after the destruction of the parenchyma and blood-vessels of the spleen. The spleen
is absent extremely seldom.

Elements of human splenic
pulp. 1, colourless cells;
2, endothelium ; 3, col-
oured blood-corpuscles ;
4, cells containing gran-
ules, the upper one with
a colourless blood-cor-
puscle, b, enclosed.

[The weight of the animal (dog) diminishes after the operation, but afterwards increases.
The number of red blood-corpuscles is lessened, reaching its minimum about the 150th to the
200th day, while the colourless corpuscles are ‘ndecaabe in number. The lymphatic glands
(especially the internal, and those in the neck, mesentery, and groin) enlarge, while on section
the cortical substance of these structures is redder, owing to the great number of red corpuscles,
many of them are nucleated in the lymph spaces (Gibson). The marrow of all the long bones
(those of the foot excepted), becomes very red and soft, with the characters of embryonic bone-
marrow. Such animals withstand hemorrhage (to 4 of the total amount of blood) without any
specially bad results (Tizzoni, Winogradow). Schindeler observed that animals after extirpa-
tion of the spleen became very ravenous. }

(Regeneration. —After entire removal of the spleen, nodules of splenic tissue are reproduced:

CONTRACTION OF THE SPLEEN. 151

(fox) ; while new adenoid tissue is formed in the lymphatic glands, and in Peyer’s patches,
the parenchyma of the former coming to resemble splenic tissue ( Z'izzoni, Eternod). ]

(2) According to Gerlach and Funke the spleen is a blood-forming gland. The
blood of the splenic vein contains far more colourless corpuscles than the blood of the
splenic artery (p. 14). Many of these corpuscles undergo fatty degeneration, and
disappear in the blood-stream. That colourless blood-corpuscles are formed within
the spleen seems to be proved: by the enormous number of these corpuscles which
are found in the blood in cases of leukeemia (Bennett (1852), Virchow). Bizzozero and
Salvioli found that, several days after severe hemorrhage, the spleen became CE SATEOUs
-and its parenchyma contained numerous red nucleated hzmatoblasts.

(3) Other observers (Kélliker and Ecker) regard the spleen as an organ in which
coloured blood-corpuscles are destroyed, and they consider the large protoplasmic
cells containing pigment granules as a proof of this (p. 12). According to the
observations of Kusnetzow, these structures are merely lymph-corpuscles, which, in
virtue of their amceboid movements, have entangled coloured blood-corpuscles.
[Such corpuscles exhibit similar properties when placed upon a warm stage. |
Similar cells occur in extravasations of blood. The coloured blood-corpuscles within
the lymph-cells gradually become disintegrated, and give rise to the production of
granules of hematin and other derivatives of hemoglobin. [The spleen contains
so much free iron that a section of this organ, especially from a young animal,
when treated with Tizzoni’s fluid, 2.e., with potassic ferrocyanide and hydrochloric
acid, gives a distinct blue colour (§ 174, 4).] Hence, the spleen contains more
iron than corresponds to the amount of- blood present in it. When we consider
that the spleen contains a large number of extractives derived from the decomposi-
tion of proteids, it is very probable that coloured blood-corpuscles are destroyed
‘in the spleen. Further, the juice of the spleen contains salts similar to those that
occur in the red blood-corpuscles.

The blood from the spleen is said to have undergone other changes, but the following state-
ment must be accepted with caution :—The blood ‘of the splenic vein contains more water and
fibrin, its red blood-corpuscles are smaller, brighter, less flattened, more resistant, and do not
form rouleaux ; its hemoglobin crystallises more easily, and there is a large proportion of O
during digestion.

[The spleen has therefore very direct relations to the blood ; in it coloured blood-
corpuscles undergo disintegration, it produces colourless corpuscles, and it is said to
transform white corpuscles into red. |

(4) Contraction.—In virtue of the plain muscular fibres in its capsule and
trabeculze, the spleen undergoes variations in its volume. Stimulation of the spleen
or its nerves, by cold, electricity, quinine, eucalyptus, ergot of rye, and other “ splenic
reagents” causes it to contract, whereby it becomes paler, and its surface may even
appear granular. After a meal, the spleen increases in size, and it is usually largest
about five hours after digestion has begun, 7.¢., at a time when the digestive crgans
have almost finished their work, and have again become less vascular. After a time
it regains its original volume. For this reason the spleen was formerly regarded
as an apparatus for regulating the amount of blood in the digestive organs. [The
congestion of the spleen after a meal is more probably related to the formation of
new colourless corpuscles than to the destruction of red corpuscles. It may be,
however, that some of the products of digestion are partially acted upon in the
spleen, and undergo further change in the liver. ] There is a relation between the
size of the spleen and that of the liver, for it is found that when the spleen
contracts—e,g., by stimulation of its nerves—the liver becomes enlarged, as if it
were injected with more blood than usual (Drosdow and Botschetschkarow).

[Oncograph. —Botkin, and more recently Roy, have studied various conditions
which affect the size of the spleen. Roy enclosed the spleen of a dog in a box
with rigid walls, the oncograph en volume) and filled with oil after the manner

152 INFLUENCE OF NERVES ON THE SPLEEN,

of the plethysmograph (§§ 101, 276).. Any variations in the size of the organ
caused a variation in the amount of oil within the box, and these variations were
recorded. The blood-pressure was recorded at the same time. The circulation
through the spleen is peculiar, and is not due to the blood-pressure within the
arteries, but is carried on chiefly by a rhythmical contraction of the muscular
fibres of the capsule and trabecule. The spleen undergoes very regular rhyth-
mical contractions (systole) and dilatations (diastole). This alternation of systole
and diastole may last for hours, and the two events together occupy about one minute
(fig. 124). Changes in the arterial blood-pressure have comparatively little in-

}

\,---Spleen
/ \
|
j
Blood pressure

f\

afi | Wal
Al WIV Th
} ; vy

n
ry
|

}
\ 1 ll WY Wd !
anh INN! im on \ on hate Hl
| Athy ‘yA! iy M Nl / ha Ww oathd yey Myth

n \ rf
f}, wy Ah MI
Mat hd bt TY
ny

Abscissa of Blood-pressure-curve 2 sec® intervals
FRI VTCCMsreP Vary Veare rey errvreut.© CLPTerrTia er tt rrvetuy t PP? ? tT tl tt? Tt Pa TT Til th? ah tl” TT TUT +

Fig. 124.

Tracing of a splenic curve, reduced one-half, taken with the oncograph. The upper line with
large waves is the splenic curve, each ascent corresponds to an increase, and each descent
to a diminution in the volume of the spleen. The curve beneath is a blood-pressure
tracing from the carotid artery. The lowest line indicates the time, the interruptions of
the marker occurring every two seconds. ‘The vertical lines, a and 8, give the relative
positions of the lever-point of the oncograph, and of the point of the recording style of the
kymograph respectively (2oy).

fluence on the volume of the spleen. The rhythmical contractions, although
modified, still go on after section of the splenic nerves. This would seem to
indicate that the spleen has an independent (nervous) mechanism within itself,
causing its movements. |

[Influence of Nerves.—Section of the splenic nerves is followed by an increase
in the size of the spleen. The nerves have their centre in the medulla oblongata.
Stimulation of the medulla oblongata, either directly or by means of asphyxiated
blood, causes contraction of the spleen, hence the spleen is “ small and contracted ”
in death from asphyxia. The fibres proceed down the cord, and leaving it in the
dorsal region, enter the left splanchnic, pass through the semi-lunar ganglion, and
thus reach the splenic plexus, Stimulation of the peripheral ends of these nerves
causes contraction of the spleen, and so does cold applied to the spleen directly or
over the region of the organ. In the last case the result is brought about reflexly.
Botkin found that the application of the induced current to the skin over the
spleen, in a case of leukemia, caused well-marked contraction of the spleen in all
its dimensions, and the result lasted some time. After every stimulation the
number of colourless corpuscles in the blood increased, and the condition of the
patient improved. |

[There is a popular notion that the spleen is influenced by the condition of the
nervous system. Botkin found that depressing emotions increased its size, while

THE THYMUS. . 153

exhilarating ideas diminished it. The causes of these changes are referable not
only to changes in the amount of blood in the spleen, but also to the greater or less
degree of contraction of its muscular tissue. And it would appear that, like the
small arteries, the muscular tissue of the spleen is in a state of tonic contraction.
The size of the spleen may be influenced reflexly. Thus, Tarchanoff found that
stimulation of the central end of the vagus, when the splanchnics were intact,
caused contraction of the spleen, while stimulation of the central end of the
“sciatic also caused contraction, but toa less degree. It is quite certain that all the
phenomena are not due to the action of vaso-motor nerves on the splenic blood-
vessels. There is a certain amount of independent action of the muscular fibres of
the organ, and it is not improbable that the innervation of the spleen is similar to
the innervation of arteries, and that it has a motor centre in the cord capable of
being influenced reflexly by afferent nerves, while it also sends out efferent im-
pulses. |

[Stimulation of (1) the central end of asensory nerve ; (2) of the peripheral ends
of both splanchnics ; (3) of the peripheral ends of both vagi, causes contraction of
the spleen. But even after section of the splanchnics and vagi, stimulation of a
sensory nerve still causes contraction, so that there must be some other channel as
yet unknown (oy). Bochefontaine found that electrical stimulation of certain
parts of the cortex cerebri produced contraction of the spleen.] Sensory nerves”
seem to occur only in the peritoneum covering the spleen.

Pressure on the splenic vein causes enlargement of the spleen, hence, increased pressure in
this vein (congestion of the portal vein, cessation of hemorrhoidal and menstrual discharges)
also causes its enlargement. With regard to the action of ‘‘splenic reagents,’’ such as quinine,
on the contraction of the spleen, Binz is of opinion that this drug retards the formation of the
colourless blood-corpuscles, so that its chief function is interfered with and the organ becomes
less vascular. It is not definitely decided, however, whether it is contraction or dilatation of
the spleen that alters the proportion of red and white corpuscles in the blood.

Splenic Tumours.—The increase in size of the spleen in various diseases early attracted the
attention of physicians. The healthy spleen undergoes several variations in volume during
the course of a day, corresponding with the varying activity of the digestive organs. In this
respect the spleen resembles the arteries. In many fevers the spleen becomes greatly enlarged,
i probably due to paralysis of its nerves. It is greatly
Wy . increased in intermittent fever or ague, and often
IS AA during the course of typhus. When it becomes ab-
a Ee " normally enlarged, and remains so after repeated
attacks of the ague, it is greatly hypertrophied, and
constitutes ‘‘ague cake.”
In cases of splenic leuksemia
‘it is greatly enlarged, and
at the same time there is a
great increase in the number
of colourless corpuscles in
the blood and also a decrease
of the coloured ones (§ 10).

II. The Thymus. — During
foetal life this gland is largely
developed, and it increases
during the first two or three

years of life, remaining sta- :

. tionary until the tenth or io, 126.
ee Pease fourteenth year, when it be- oe
gins to atrophy and undergo
fatty degeneration. [The de-
generation begins at the

Section of the thymus gland of a cat, with
one complete lobule with a cortical
part a, and a centre, db. a, lymphoid
tissue ; ¢, blood-vessels injected ; d, con- Suter part of each lobule and centric .corpuscle of

nective-tissue. progresses inwards (His). ] Hassall.

Structure.—‘‘It consists of an aggregation of lymph-follicles (resembling the glands of
Peyer) or masses of adenoid tissue held together by a framework of connective-tissue which
contains blood-vessels, lymphatics, and a few nerves (fig. 125). The framework of connective-
tissue gives off septa which divide the gland into lobes, these being further subdivided by finer |

Elements of the thymus
(x 300). a, lymph-
corpuscles ; 0, con-

154 THE THYROID.

septa into lobules, the lobules being separated by fine intra-lobular lamelle of connective-tissue
into follicles (0°5-1°5 mm.). These follicles make up the gland-substance, and they are usually
polygonal when seen ina section. Each follicle consists of a cortical and a medullary part,
Hg the matrix or framework of both consists of a fine adenoid reticulum whose meshes are
filled with lymph-corpuscles” (fig. 126, @).] Many of these corpuscles exhibit various stages.
of disintegration. In the medulla are found the concentric corpuscles of Hassall, [‘‘ They
consist of a central granular part, around which are disposed layers of flattened nucleated
endothelial cells arranged concentrically. When seen in a section they resemble the ‘cell-
nests’ of epithelioma (fig. 126, 0). They have also been compared to similar bodies which
occur in the prostate. They are most numerous when the gland undergoes its retrograde
metamorphosis.” Sig. Mayer finds that the thymus of the frog contains structures, with
transverse markings, identical with the stripes of striped muscular fibres, The structures are-
identical with those called “sarcoplasts” by Margo and Paneth, and “sarcolytes” by Sig.
Mayer. They also occur in large numbers in the tail of the larve of batrachians, when the tail |
is undergoing a retrograde metamorphosis. ]

Simon, His, and others described a convoluted blind canal, the ‘‘ central canal,” as occur-
ring within the gland, and on it the follicles were said to be placed. Other observers, -
Jendrassik and Klein, either deny its existence or regard it merely as a lymphatic or an
artificial product. Numerous fine lymphatics penetrate into the interior of the organ, and -
many are distributed over its surface, but their mode of origin is unknown. [They seem to be.
channels through which the lymph-corpuscles are conveyed away from the gland.] . Numerous
blood -vessels are also distributed to the septa and follicles (fig. 125, c).

Chemical Composition.—Besides gelatin, albumin, soda-albumin, there are sugar and fat,
leucin, xanthin, hypoxanthin, formic, acetic, butyric, and succinic acids. Potash and
phosphoric acid are more abundant in the ash than soda, calcium, magnesium (?ammonium), .
chlorine, and sulphuric acid.

Function.—<As long as it exists, it seems to perform the functions of a true lymph-gland.
This view is supported by the fact that in reptiles and amphibians, which do not possess
lymph-glands, the thymus remains as a permanently active organ. [Extirpation gave few positive
results, but chemical investigation shows that the parenchyma contains a large number of
products indicating considerable metabolic activity (Hriedleben). ]

III. The Thyroid.—Structure.—The gland consists of lobes and lobules held together by
connective-tissue rich in cells. Each lobule is made up of numerous completely closed sacs.
(0°04 to 0°1 mm. in diameter), which
in the embryo and the newly-born
animal are composed of a membrana
propria lined by a single layer of
nucleated cubical cells (fig. 127).
The sacs contain a transparent, viscid,
albuminous fluid. [Not unfrequently
the sacs contain many coloured blood-
corpuscles (Baber).] Each sac is sur-
rounded by a plexus of capillaries.

Eee which do not penetrate the mem-
IY once? brana propria. There are also numer-
ee ous ferpbratics At an early period
the sacs dilate, their cellular lining:
atrophies, and their contents undergo- .
se ro. amit Pe a 4
y 2 and-vesicles are atly enlarge a
yy, {Ps Pears GX 8 rol is reduce. "a ? , |

i Quay —— The chemical com on of this.

= SS gland has not been much investigated. ~
In addition to the ordinary constitu-.
Fig. 127. ents, leucin, xanthin, sarkin, lactic,

Section of the thyroid gland. a, closed vesicles; 0, dis- ee ae cha tatty acids Rata

tended by colloid masses and lined by low columnar [Excision.—The effects differ ac-
_ epithelium ; ¢, inter-vesicular connective-tissue. cording to the animal operated on.

This gland has been excised in the human subject in cases of goitre. Reverdin pointed out that
a peculiar condition results, called cachexia stumipriva, and paclonlly the human being:
becomes a cretin. This operation therefore is highly questionable when performed on man.
Rabbits endure the operation well, and so do the sheep, calf, and horse. Of dogs, cats, and
foxes, only a very small number survive, nearly all die. It appears therefore that herbivora bear
the operation and suffer fewer after-effects than carnivora (Sanquirico and Orecchia). The Z
immediate effects are fibrillar contractions, which ultimately influence the gait of the pomp “a
convulsions, anesthesia, great diminution of sensibility, loss of flesh, redness of the ears and

~ : \ MAL,
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Mil 2)
HY A =x
\ Cee (5) / eo
< AN
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4
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:.
jb

LOSS OF THE FUNCTION OF THE THYROID GLAND, 155

intense heat of the skin (which disappear after several days), difficulty in seizing and eating food,
kerato-conjunctivitis, and frequently disturbance of the rhythm of respiration with dyspncea and
spasms of the abdominal muscles (Schif). The arterial blood contains about the same amount of
O as venous blood. Certain parts of the peripheral nerves undergo a kind of degeneration similar
to that found after nerve-stretching. There is albuminuria and fall of the blood-pressure. Death
usually occurs between the third and fourth day, the animals being comatose (Wagner). Schiff
found that if one-half of the gland was excised at once, and the other half a month afterwards,
death did not occur ; but Wagner denies this, for he asserts that the remaining half hypertrophies,
and if it be excised, death occurs with the usual symptoms. In monkeys, five days after the
operation, there are symptoms of nervous disturbance. The animals have lost their appetite, there
are fibrillar contractions of the muscles of the face, hands, and feet, but the tremors disappear on
voluntary effort. The appetite returns and is increased, but notwithstanding, the animal grows
thin and pale ; while the tremors increase and affect all the muscles of the body. These tremors
are of central origin, because they disappear on dividing the nerve. Thus there is profound
alteration of the motor powers. Amongst the outward symptoms are puffiness of the eyelids,
swelling of the abdomen, increased hebetude, and dyspnea, while afterwards there is a fall of
the temperature and imbecility ; the tremors disappear, there isa palor of the skin, and ulti-
mately after five to seven weeks the animals die comatose. Thus there isa slow onset of hebetude,
terminating in imbecility. Very remarkable changes occur in the blood. There is a steady fall
of the blood-pressure; a diminution of the red blood-corpuscles, or rather profound anemia ;
leucocythemia, the colourless corpuscles being increased to the ratio of four to fourteen; and
lastly mucin is present in the blood, although normally it is not so. The salivary glands are
hypertrophied, owing to the presence of mucin, which is found even in the parotid, although
this is normally a serous gland (§ 141). The swelling of the abdomen is due to hypertrophy of
the great omentum. Mucin is found in the peritoneal fluid, and the spleen is also enlarged.
Thus these symptoms present many features in common with those of myxcedema as described
by Ord (v. Horsley). ]

[Stages.—Horsley distinguishes three stages. In the first or neurotic stage, the animals
exhibit constant tremors, 8 per second, and young animals do not appear to survive this stage.
In the second or mucinoid stage, mucin is deposited in the tissues and blood ; this change,
however, is only seen to perfection in monkeys. If these animals be kept at a high artificial
temperature, their life is considerably prolonged. In the third, atrophic, or marasmic period,
the animals die of marasmus, while they lose their excess of mucin, Age seems to exert an
important influence in thyroidectomy ; young dogs survive but a short time, while old dogs
merely exhibit symptoms of indolence and incapacity ; and, as a matter of fact, the activity of
the gland seems to be most active when tissue-metabolism is most active. ]

[The following table, after Horsley, indicates the symptoms that follow loss of the function
of the thyroid gland.

Stages. Duration. Symptoms. Remarks.

I. Neurotic. | 1 to 2 weeks in dogs; | Tremors, rigidity, dys-| Young dogs and monkeys
1 to 3 weeks in| pnea, alike die in this stage.
monkeys.

II. Mucinoid. | 4 to 1 week in dogs; | Commencing. hebetude | Dogs survive only to the
3 to 7 weeks in| and mucinoid degen- beginning of this stage ;
monkeys. eration of the connec- monkeys die at the end,

; tive-tissues. if not treated.
III. Atrophic. | 5 to 8 weeks in mon- | Complete imbecility and| Monkeys survive accord-
keys. atrophy of all tissues,| ing to the temperature
especially muscles. of the air-bath. ]

Functions.—The functions of the thyroid gland are very obscure. Perhaps it may be an

apparatus for regulating the blood-supply to the head (?). It becomes enlarged in Basedow’s

disease, in which there is great palpitation, as well as protrusion of the eyeball or exophthalmos,
which seem to depend upon a simultaneous stimulation of the accelerating nerve of the heart,
and the sympathetic fibres of the smooth muscles in the orbital cavity and the eyelids, as well
as of the inhibitory fibres of the vessels of the thyroid. In many localities it is common to find
swelling of the thyroid constituting goitre, which is sometimes, but far from invariably, associ-
ated with idiocy and cretinism. [Horsley finds that its removal is the essential cause of
myxcedema and.cretinism. He regards it (1) as a blood-forming gland, so that it has a hema-
poietic function, but Gibson finds no grounds for supporting this view. During the anemia
resulting from its removal, the blood of the thyroid vein contains 7 per cent. more red blood-
corpuscles than the corresponding artery (Horsley). (2) It seems to regulate the formation of
mucin in the body. After its removal the normal metabolism is no longer maintained, and
there is a corresponding increasingly defective condition of nutrition. ]

>

156 THE SUPRARENAL CAPSULES.

In the Tunicata, this gland, represented by a groove, secretes a digestive fluid. In verte-
brates, it is an organ which has undergone a retrograde change (Gegenbaur).

IV. The Suprarenal Capsules.—Structure.—These organs are invested by a thin capsule
which sends processes into the substance of the organ. They consist of an outer (broad) or
cortical layer and an inner (narrow) or medullary layer. The former is yellowish in colour, .
firm and striated, while the latter is softer and deeper in tint. In the outermost zone of the |
cortex (fig. 128, b), the trabecule form polygonal meshes, which contain the cells of the gland- |
substance ; in the broader middle zone the meshes are elongated, and the cells filling them are
arranged in columns radiating outwards. Here the cells are transparent and nucleated, often
containing oil-globules ; in the innermost narrow zone
the polygonal arrangement prevails, and the cells often
contain yellowish-brown pigment. In the medulla
(c), the stroma forms a reticulum containing groups of
cells of very irregular shape. Numerous bisod yeaa
occur in the gland, especially in the cortex. [The
nerves are extremely numerous, and are derived from
the renal and solar plexuses. Many of the fibres are
medullated. After they enter the gland, numerous
ganglionic cells occur in the plexuses which they form.
Indeed, some observers regard the cells of the medulla
as nervous. Undoubtedly, numerous multipolar nerve-
cells exist within the gland. ]

Chemical Composition.—The suprarenals contain
the constituents of connective- and nerve-tissue ; also
leucin, hypoxanthin, benzoic, hippuric, and tauro-
cholic acids, taurin, inosit, fats, and a body which
becomes pigmented by oxidation. Amongst inorganic
substances potash and phosphoric acid are most abun-
dant. .

The function of the suprarenal bodies is very ob-
scure. It is noticeable, however, that in Addison’s
disease (‘‘ bronzed skin”), which is perhaps primarily
a nervous affection, these glands have frequently, but
not invariably, been found to be diseased. Owing to
the injury to adjacent abdominal organs, extirpation
of these organs is often, although not always, fatal ;
in dogs pigmented patches have been found in the skin
near the mouth. Brown Séquard thinks they may be
concerned in preventing the over-production of pig-
ment in the blood.

[Spectrum.—MacMunn finds that the medulla of

Fig. 128. the suprarenal bodies (in man, cat, dog, guinea-pig,
Section of a human suprarenal capsule. "at, &c.) gives the spectrum of heemochromogen (§ 18),
a, capsule ; 6, gland-cells of the cortex while the cortex shows that of what he calls histo-
arranged in columns ; ¢, glandular net- hematin, the latter being a group of respiratory pig-
work of the medulla: d, blood-vessels, ents. He finds that hemochromogen is only found
ok: in excretory organs (the bile, the liver), hence he re-
gards the medulla as excretory, so that part of the function of the adrenals may be “‘ to meta-
morphose effete hemoglobin or hematin into hemochromogen,” and when they are diseased,
the effete pigment is not removed, hence the pigmentation of the skin and mucous membranes.
Taurocholic acid has been found in the medulla by Vulpian, and pyro-catechin by Krukenberg.
MacMunn believes that ‘‘ they have a large share in the downward metamorphosis of colouring
matter. ’’]

V. Hypophysis Cerebri—Coccygeal and Carotid Glands.—The hypophysis cerebri, or
pituitary body, consists of an anterior lower or larger lobe, partly embracing the posterior lower
or smaller lobe. These two lobes are distinct in their structure and development. The posterior
lobe is a part of the brain, and belongs to the infundibulum. The nervous elements are dis-
placed by the ingrowth of connective-tissue and blood-vessels. The anterior portion represents
an inflected and much altered portion of ectoderm, from which it is developed. It contains
gland-like structures, with connective-tissue, lymphatics, and blood-vessels, the whole being
surrounded by a capsule. According to Ecker and Mihalkowicz, it resembles the su
capsule in its structure, while, according to other observers, in some animals it is more like the
thyroid. Its functions are entirely nown. [Excision.—Horsley has removed this gland
twice successfully in dogs, which lived from five to six months. No nervous or other symptoms
were noticed, but when the cortex of the brain was exposed and stimulated, a great rae in
the excitability of the motor regions was induced, even slight stimulation being followed by
violent tetanus and prolonged epilepsy. } da

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HYPOPHYSIS CEREBRI. E67

Coccygeal and Carotid Glands.—The former, which lies on the tip of the coccyx, is composed
to a large extent of plexuses of small, more or less cavernous, arteries, supported and enclosed
by septa and a capsule of connective-tissue (Lwschka). Between these lie polyhedral granular
cells arranged in networks. The carotid gland has a similar,structure (p. 77). Their functions
are quite unknown. Perhaps both organs may be regarded as the remains of embryonal blood-
vessels (Arnold).

104. COMPARATIVE. —The heart in fishes (fig. 129, I.), as well as in the larve of amphi-
bians with gills, is a simple venous heart, consisting of an auricle and a ventricle. The
ventricle propels the blood to the gills, where it is oxygenated (arterialised) ;
thence it passes into the aorta to be distributed to all parts of the body, and
returns through the capillaries of the body and the veins to the heart. The
amphibians (frogs) have two auricles and one ventricle (Frog, II.). From
the latter there proceeds one vessel which gives off the pulmonary arteries,
and as the aorta supplies the rest of the body with blood, the veins of the
systemic circulation carry their blood to the right auricle, those of the lung
into the left auricle. In fishes and amphibians there is a dilatation at the

Fig. 129.

Schemata of the circulation. I. Fish.—A, auricle ; S, sinus venosus ; V, ventricle ; B, bulbus
aorte ; c, branchial arteries ; 7, branchial vessels ; Vv, branchial veins ; Z, circulus cephali-
cus aorte ; /, common aorta; G, caudal artery ; H, duct of Cuvier ; J, anterior, and K,
posterior cardinal veins ; Z, caudal vein ; M, WM, kidneys. II. Frog.—I, sinus venosus ; II,
and III, right and left auricles; IV, ventricle ; V, aorta with the bulb; 1, pulmonary
arteries ; 2, arch of the aorta ; 3, carotid; 4, lingual; 5, carotid gland, and 6, axillary
arteries ; 7, common aorta ; 8, cceliac artery ; 9, cutaneous artery ; Vv, pulmonary veins ;
Pp, p, lungs. III. Sawrians.—l, right auricle, with the vens cave ; II,‘right ventricle ;
III, left auricle; IV, left ventricle ; V, anterior common aorta; 1, pulmonary artery ;
2, arch of the aorta; 3, carotid artery ; 4, posterior common aorta; 5, cceliac; and 6,
subclavian, arteries ; 7, pulmonary veins ; 8, lungs. IV. Tortoise.—I, right auricle with
the vene cave; II, right, and IV, left ventricles ; III, left auricle; 1 and 2, right
and left aorte ; 3, posterior common aorta ; 4, cceliac, 5, subclavian, 6, carotid, and 7,
pulmonary arteries ; 8, pulmonary veins. =

commencement of the aorta, the bulbus arteriosus, which is partly provided with strong muscles.
The reptiles (III.) possess two separate auricles, and two imperfectly separated ventricles.
The aorta and pulmonary artery arise separately from the two latter chambers. The venous
blood of the systemic and pulmonary circulations flows separately into the right and left auricles,
and the two streams are mixed in the ventricle. In some reptiles the opening in the ventricular
x septum seems capable of being closed. The complete separation of the ventricle into two is
* seen in fig. IV., in the tortoise. The lower vertebrates have valves at the orifices of the vene
cave, which are rudimentary in birds and some mammals. All birds and mammals have two.

158 HISTORICAL RETROSPECT OF THE CIRCULATION,

completely separate auricles and two 2 ose ventricles. In the halicore the apex of the ven-
tricles is deeply cleft. Some animals have accessory hearts, ¢.g., the eel in its caudal vein.
They are very probably lymph-hearts (Robin), The veins of the wing of the bat pulsate (Schif).
The lowest vertebrate, amphioxus, has no heart, but only a rhythmiecally-pulsating vessel.
Amongst blood-glands, the thymus and spleen occur throughout the vertebrata, the latter
being absent only in amphioxus and a few fishes. y :
Amongst invertebrata a closed vascular system, with pulsatile movement, occurs here and
there, e.g., amongst echinodermata (star-fishes, sea-urchins, holothurians) and the higher worms,
The insects have a pulsating ‘“‘ dorsal vessel” as the central organ of the circulation, which
is a contractile tube provided with valves and dilated by muscular action ; the blood being
propelled rhythmically in one direction into the spaces which lie amongst the tissues and organs, |
so that these animals do not possess a closed vascular system. The mollusca have a heart with |
a lacunar vascular system. The cephalopods (cuttle-fish) have three hearts—a simple arterial |
heart, and two venous simple gill-hearts, each placed at the base of the gills. The vessels form
a completely closed circuit. ‘The lowest animals have either a pulsatile vesicle, which propels
the colourless juice into the tissues (infusoria), or the vascular apparatus may be entirely

absent.

105. HISTORICAL RETROSPECT.—The ancients held various theories regarding the
movement of the blood, but they knew nothing of its circulation. According to Aristotle
(384 n.c.), the heart, the acropolis of the body, prepared in its cavities the blood, which
streamed through the arteries as a nutrient fluid to all parts of the body, but never returned
to the heart. With Herophilus and Erasistratus (300 B.c.), the celebrated physicians of the
Alexandrian school, originated the erroneous view that the arteries contain air, which was
supplied to them by the respiration (hence the name artery). They were led to adopt this
view from the empty condition of the arteries after death. By experiments upon animals,
Galen disproved this view (131-201 a.p.)—‘‘ Whenever I injured an artery,” he says, ‘‘ blood
always flowed from the wounded vessel. On tying part of an artery between two ligatures, the
part of the artery so included is always filled with blood.”

Still, the idea of a single centrifugal movement of the blood was retained, and it was assumed
that the right and left sides of the heart communicated directly by means of openings in
the septum of the heart, until Vesalius showed that there are no openings in the septum. Michael
Servetus (a Spanish monk, burned at Geneva, at Calvin’s instigation, in 1553) discovered
the pulmonary circulation. Cesalpinus confirmed this observation, and named it ‘‘ Circulatio.”
Fabricius ab Aquapendente (Padua, 1574) investigated the valves in the veins more carefully
(although they were known in the 5th century to Theodoretus, Bishop in Syria), and he was
acquainted with the centripetal movement of the blood in the veins. Up to this time it was
imagined that the veins carried blood from the centre to the periphery, although Vesalius
_ was acquainted with the centripetal direction of the blood-stream in the large venous trunks.
At length William Harvey, who was a pupil of Fabricius (1604), demonstrated the complete
circulation (1616-1619), and published his great discovery in 1628. [For the history of the
discovery of the circulation of the blood, see the works of Willis on ‘‘ W. Harvey,” ‘‘ Servetus
and Calvin,” those of Kirchner, and the various Harveian orations. ]

According to Hippocrates, the heart is the origin of all the vessels ; he was acquainted with
the large vessels arising from the heart, the valves, the chorde tendinez, the auricles, and the
closure of the semi-lunar valves. Aristotle was the first to apply the terms aorta and vene
cave ; the school of Erasistratus used the term carotid, and indicated the functions of the
yenous valves. In Cicero a distinction is drawn between arteries and veins. Celsus mentions
that if a vein be struck below the spot where a ligature has been applied to a limb, it’ bleeds,
while Aretaeus (50 A.D.) knew that arterial blood was bright and venous dark. Pliny (+ 79
A.D.) described the pulsating fontanelle in the child. Galen (131-203.4.p.) was acquainted
with the existence of a bone in the septum of the heart of large animals (ox, deer, elephant).
He also surmised that the veins communicated with the arteries by fine tubes. The demon-
stration of the capillaries, however, was only possible by the use of the microscope, and
employing this instrument, Malpighi (1661) was the first to demonstrate the capillary cireula-
tion. Leuwenhoek (1674) described the capillary circulation more carefully, as it may be seen
in the web of the frog’s foot and other transparent membranes, Bigaoant (1676) proved the
existence of capillary passages by means of injections. William Cooper (1697) proved that the
‘same condition exists in warm-blooded auitia’b, and Ruysch made similar injections. Stenson
(born 1638) established the muscular nature of the heart, although the Hippocratic and
Alexandrian schools had already surmised the fact. Cole proved that the sectional area of the
blood-stream became wider towards the capillaries (1681). Joh. Alfons Borelli (1608-1679) was
the first to estimate the amount of work done by the heart.

;
a
!

Physiology of Respiration.

THE object of respiration is to supply the oxygen necessary for the oxidation-
processes that go on in the body, as well as to remove the carbon dioxide formed
within the body. The most important organs for this purpose are the lungs.
There is an outer and an inner respiration—the former embraces the exchange of
gases between the external air and the blood-gases of the respiratory organs (lungs
and skin)—the latter, the exchange of gases between the blood in the capillaries of
the systemic circulation and the tissues of the body.

(The pulmonary apparatus consists of (1) an immense number of small sacs—
the air-vesicles—filled with air, and covered externally by a very dense plexus of
capillaries; (2) air-passages—the nose, pharynx, larynx, trachea, and bronchi
communicating with (1); (3). the thorax with its muscles, acting like a pair of
bellows, and moving the air within the lungs. |

106. STRUCTURE OF THE AIR-PASSAGES AND LUNGS.—The lungs are compound
tubular glands, which separate CO, from the blood. Each lung is provided with an excretory
duct (bronchus) which joins the common respiratory passage of both lungs—the trachea.

Trachea.—The trachea and extra-pulmonary bronchi are similar in structure. The basis of
the trachea consists of 16-20 C-shaped incomplete cartilaginous hoops placed over each other.
These rings consist of hyaline cartilage, and are united to each other by means of tough fibrous
tissue containing much elastic tissue, the latter being arranged chiefly in a longitudinal
direction. The function of the cartilages is to keep the tube open under varying conditions
of pressure. Pieces of cartilage having a similar function occur in the bronchi and their
branches, but they are absent from the bronchioles, which are less than 1 mm. in diameter.
In the smaller bronchi, the cartilages are fewer and scattered more irregularly. [Ina transverse
section of a large intra-pulmonary bronchus, two, three, or more pieces of cartilage, each
invested by its perichondrium, may be found.] At the points where the bronchi subdivide,
the cartilages assume the form of irregular plates embedded in the bronchial wall.

An external fibrous layer of connective-tissue and elastic fibres covers the trachea and the
-extra-pulmonary bronchi externally. Towards the cesophagus, the elastic elements are more
numerous, and there are also a few bundles of plain muscular fibres arranged longitudinally.
Within this layer there are bundles of non-striped muscular fibres which pass transversely
between the cartilages behind, and also in the intervals between the cartilages. [These pale
reddish fibres constitute the trachealis muscle, and are attached to the inner surfaces of the
cartilages at a little distance from their free ends, The arrangement varies in different animals
~—thus, in the cat, dog, rabbit, and rat the muscular fibres are attached to the external surfaces
of the cartilages, while in the pig, sheep, and ox they are attached-to their internal surfaces
(Stirling).] Some muscular fibres are arranged longitudinally external to the transverse fibres.
The function of these muscular fibres is to prevent too great distension when there is great
pressure within the air-passages. :

The mucous membrane consists of a basis of very fine connective-tissue, containing much
adenoid tissue, with numerous lymph-corpuscles. Numerous elastic fibres are arranged chiefly
‘in.a longitudinal direction under the basement membrane. They are also abundant in the
deep layers of the posterior part of the membrane opposite the intervals between the cartilages.
‘A small quantity of loose sub-mucous connective-tissue containing the large blood-vessels,
Hands, and lymphatics unites the mucous membrane to the perichondrium of the cartilages.
‘The epithelium consists of a layer of columnar ciliated cells with several layers of immature

160 STRUCTURE OF THE

cells under them.
tened

membrane,

——S Se avBZ
Saaz
6 ar Sa COALS OF hel
I {O5; Boel Ms

C3 IE g

a lose

oa

S25

Transverse section of part of a human bronchus ( x 450).
a, precipitated mucus; b, ciliated columnar epithe-
lium ; ¢, deep germinal layer of cells (Débove’s mem-

TRACHEA.

[The superficial layer of cells is columnar and ciliated (fig. 130, b), while-
those lying under them present a variety of forms, and below all is a layer of sot

squames, c, resting on the basement membrane, d. These squames constitute a layer
quite distinct from the basement membrane, and they form the layer described as Débove’s.
They are active germinating cells, and play a most important part in connection

omewhat flat-

with the regeneration of the epithelium,
after the superficial layers have been
shed, in such conditions as bronchitis.

Not. unfrequently a little viscid mucus.

(a) lies on the free ends of the cilia. In
the intermediate layer, the cells are more
or less pyriform or battledore-shaped,

- with their long tapering process inserted

amongst the deepest layer of squames.

According to Drasch, this long process is.

attached to one of these cells and is an
outgrowth from it, the whole constituting
a ‘‘ foot-cell.”’]

Under the epithelium is the homo-.

geneous basement membrane, through

which fine canals pass, connecting the:

cement of the epithelium with spaces in
the mucosa. [This membrane is well
marked in the human trachea, where it
plays an important part in many patho-
logical conditions, ¢.g., bronchitis. It

is stained bright red with picrocarmine. }’

The cilia act so as to carry any secretion
towards the larynx. Goblet cells exist
between the ciliated columnar cells.
Numerous small compound tubular
mucous glands occur in the mucous
membrane, chiefly between the cartilages.

Their ducts open on the surface by means .

of a slightly funnel-shaped aperture, into
which the ciliated epithelium is prolonged
for a short distance.
of these glands lie outside the trachealis
muscle.
or columnar secretory epithelium. In
some animals (dog) these cells are clear,
and present the usual characters of a

mucus-secreting gland; in man, some of

[The acini of some -

The acini are lined by cubical.

brane) ; d, elastic basement membrane; e, elastic

ee the cells may be clear, and others ‘‘ gran-
fibres divided transversely (inner fibrous layer); /, ular,” but the appearance of the eellb.

bronchial muscle ; g, outer fibrous layer with leuco- depends upon the physiological state
cytes and pigment granules (black) ; below a mass of activity.] These glands secrete the
of adenoid tissue. mucus, which entangles eke: inspired’
with the air, and is carried towards the larynx by ciliary action. [Numerous lymphatics exist
in the mucous and sub-mucous coat, and not unfrequently small speregetions of adenoid tissue
occur (especially in the cat) in the mucous coat, usually around the ducts of the glands. They
are comparable to the solitary follicles of the alimentary tract. The blood-vessels are not so
numerous as in some other mucous membranes. [A plexus of nerves containing numerous.
ganglionic cells at the nodes exists on the posterior surface of the trachealis muscle. The
fibres are derived from the vagus, recurrent laryngeal, and sympathetic (C. Frankenhauser, W.
Stirling, Kandarazi).] ,
[The mucous membrane of the trachea and extra-pulmonary bronchi, therefore, consists of
the following layers from within outwards :—
(1) Stratified columnar ciliated epithelium.
(2) A layer of flattened cells (Débove’s membrane).
(3) A clear homogeneous basement membrane.
(4) A basis of areolar tissue, with adenoid tissue and blood-vessels, and outside this a layer
of longitudinal elastic fibres.

Outside this, again, is the sub-mucous coat, consisting of loose areolar tissue, with the larger:
vessels, lymphatics, nerves, and mucous glands, ] ae
[The chi.—In structure the extra-pulmonary bronchi resemble the trachea. As they

STRUCTURE OF THE BRONCHI AND BRONCHIOLES. 161

ass into the lung they divide very frequently, and the branches do not anastomose. In the

tra-pulmonary bronchi the subdivisions become finer and finer, the finest branches being
called terminal bronchi, or bronchioles, which open separately into clusters of air-vesicles. ]

[Bparterial and Hyparterial Bronchi.—As the bronchi proceed, one main trunk passes into
the lung, running towards its base, and from it are given off branches dorsally and ventrally,
and these branches again subdivide. In man one main branch comes off from the right
bronchus and proceeds to the upper right lobe, above the place where the pulmonary artery
crosses the bronchus. Such branches are called eparterial, and they are more numerous in
birds. In man, all the branches, both on the right and left side, come off below the point
where the pulmonary artery crosses the bronchus, and are called hyparterial bronchi (C. Aeby).]

{In the middle-sized intra-pulmonary bronchi, the usual characters of the mucous membrane
are retained, only it is thinner; the cartilages assume the form of irregular plates situated in
the outer wall of the bronchus; while the muscular fibres are disposed in a complete circle,
constituting the bronchial muscle (fig. 130, 7). When this muscle is contracted, or when the
bronchus as a whole is contracted, the mucous membrane is thrown into longitudinal folds, and
opposite these folds the elastic fibres form large elevations. This muscle is particularly well
developed in the smaller microscopic bronchi. Numerous elastic fibres, ¢, disposed longi-
tudinally, exist under the basement membrane, d. They are continuous with those of the
trachea, and are prolonged onwards into the lung. The mucous membrane of the larger intra-
pulmonary bronchi consists of the following layers from within outwards :—

(1) Stratified columnar ciliated epithelium (fig. 130, 0).

(2) Débove’s membrane (fig. 130, c).

(3) Transparent homogeneous basement membrane (fig. 130, ¢@).

(4) Areolar tissue with longitudinal elastic fibres (fig. 130, e).

(5) A continuous layer of non-striped muscular fibres disposed circularly (bronchial muscle,

fig. 130, f).

Outside this is the sub-mucous coat, consisting of areolar tissue mixed with much adenoid tissue
(fig. 130, g), sometimes arranged in the form of cords, the lymph-follicular cords. It also
contains the acini of the numerous mucous glands, blood-vessels, and lymphatics. The ducts
of the glands perforate the muscular layer, and open on the free surface of the mucous
membrane. The sub-mucous coat is connected by areolar tissue with the perichondrium of the
cartilages. Outside the cartilages are the nerves and nerve-ganglia accompanying the
bronchial vessels. The branches of the pulinonary artery and of the pulmonary vein usually
lie on opposite sides of the bronchus, while there are several branches of the bronchial arteries
and veins. Fat cells also occur in the peri-bronchial tissue. ]

In the small bronchi the cartilages and glands disappear, but the circular muscular fibres
are well developed. They are lined by lower columnar ciliated epithelium, containing goblet
cells.

Bronchioles.—After repeated subdivision, the bronchi form the ‘‘ smallest bronchi” (about
0°5 to 1 mm.) or lobular bronchial tubes. Each tube is lined by a layer of ciliated epithelium,
but the glands and cartilages have disappeared. These tubes have a few lateral alveoli or air-
cells communicating with them. Each smallest bronchus ends in a ‘‘respiratory bronchiole ”
(Kolliker), which gradually becomes beset with more air-cells, and in which squamous epithelium
begins to appear between the ciliated epithelial cells. [Each bronchiole opens into several
wider alveolar or lobular passages. Each passage is completely surrounded with air-cells, and
from it are given off several similar but wider blind branches, the infundibula, which, in their
turn, are beset on all sides with alveoli or air-cells. Several infundibula are connected with
each bronchiole, and the former are wider than the latter. Each bronchiole, with its alveolar
passages, infundibula, and air-vesicles, is termed a lobule, whose base is directed outwards, and
whose apex may be regarded as a terminal bronchus. The lung is made up of an immense
number of these lobules, separated from each other by septa of connective-tissue, the inter-
lobular septa (fig. 133, ¢) which are continuous on the one hand with the sub-plural connective-
tissue, and on the other with the peri-bronchial connective-tissue. ]

[There is an alteration in the structure of the bronchi, as we proceed from the larger to
the smaller tubes. The cartilages and glands are the first structures to disappear. The circular
bronchial muscle is well developed in the smaller bronchi and bronchioles, and exists as a
continuous thin layer over the alveolar passages, but it is not continued over and. between the
air-cells. Elastic fibres, continuous, on the one hand, with those in the smaller bronchi, and
on the other with those in the walls of the air-cells, lie outside the muscular fibres in the bron-
chioles and infundibula. In the respiratory bronchioles, the ciliated epithelium is reduced
to a single layer, and is mixed with the stratified form of epithelium, while, where the alveolar
passages open into the air-cells or alveoli, the’epithelium is non-ciliated, low, and polyhedral. ]

Alveoli or Air-Cells.—The form of the cells, which are 250 wu (z+5 inch) in diameter, may be
more or less spherical, polygonal, or cup-shaped. They are disposed around and in communi-
cation with the alveolar passages. Their form is determined by the existence of a nearly
structureless membrane, composed of slightly fibrillated connective-tissue containing a few

, L

162 STRUCTURE OF THE AIR-CELLS.

corpuscles. This is surrounded by numerous fine elastic fibres, which give to the pulmon
parenchyma its well-marked elastic characters (fig. 132, e, ¢). These fibres often bifurcate, and
are arranged with reference to the alveolar wall. They are very resistant, and in some cases of
lung disease may be recognised in the sputum. A few. non-striped muscular fibres exist in the
delicate connective-tissue between adjoining air-vesicles. These muscular fibres sometimes
become greatly developed in certain diseases (Arnold, W. Stirling). The air-cells are lined by ©
two kinds of cells—(1) large, transparent, clear polygonal (nucleated ?) squames or pee
(22-45 «) lying over and between the capillaries in the alveolar wall (fig. 131, a); (2) sma
irregular ‘‘ granular ” nucleated cells (7-15 u) arranged singly or in groups (two or three) in the
interstices between the capillaries. They are well seen in a cat’s lung (fig. 181, d). [When acted
on with nitrate of silver the cement-
substance bounding the clear cells is
stained, but the small cells become of a
uniform brown granular appearance, so
that they are readily recognised. Small
holes or ‘* pseudo-stomata’’ seem to.
exist in the cement-substance, and are
most obvious in distended alveoli. They
open into the lymph-canalicular system
ot the alveolar wall (Kein), and through
them the lymph-corpuscles, which are
always to be found on the surface of
the air-vesicles, migrate, and carry with
them into the lymphatics particles of
carbon derived from the air.] In the
alveolar walls is a very dense plexus of
fine capillaries (fig. 132, c), which lie
more towards the cavity of the air-ves-
icle, being covered only by the epithelial
lining of the air-cells. Between two
adjacent alveoli there is only a single
layer of capillaries (man), and on the
boundary-line between two air-cells the
course of the capillaries is twisted, thus
proce sometimes into the one alveo-
us, sometimes into the other.
Fig. 131. [The number of alveoli is stated to
Air-vesicles injected with silver nitrate. a, outlines be about 725 millions, a result obtained
of squamous epithelium ; b, alveolar wall ; c, young by measuring the size of the air-vesicles
epithelium cell ; d, aggregation of young epithelia and ascertaining the amount of air in
cells germinating. the lung after an ordinary inspiration,
determining how much of this air is in
the air-vesicles and bronchi respectively. The superficial area of the air-vesicles is about 90
square metres, or 100 times greater than the surface of the body (°8 to ‘9 sq. metre). ]

The Blood-vessels of the lung belong to two different systems:—(A) Pulmonary vessels
(lesser circulation). The branches of the pulmonary artery accompany the bronchi and are
closely applied to them. [As they proceed they branch, but the branches do not anastomose,
and ultimately they terminate in small arterioles, which supply several adjacent alveoli, each
arteriole splitting up into capillaries for several air-cells (fig. 182, v, c). An efferent vein usually
arises at the opposite side of the air-cells, and carries away the purified blood from the capillaries,
In their course these veins unite to form the pulmonary veins, which, again, are joined in their
course by a few small bronchial veins. The veins usually anastomose in the earlier part of their
course, whilst the corresponding arteries do not.] Although the capillary plexus is very fine and
dense, its sectional area is less than the sectional area of the systemic capillaries, so that the
blood-stream in the pulmonary capillaries must be more rapid than that in the capillaries of the
body generally. The pulmonary veins, unlike veins generally, are collectively narrower than
the pulmonary artery (water is given off in the lung), and they have no valves. [The pulmonary
artery contains venous blood, and the pulmonary veins pure or arterial blood]. ;

(B) The bronchial vessels represent the nutrient system of the lungs. They (1-3) arise from
the aorta (or intercostal arteries) and accompany the bronchi without anastomosing with the
branches of the pulmonary artery. In their course they give branches to the lymphatic glands
at the hilum of the lung, to the walls of the large blood-vessels (vasa vasorum), the pee
pleura, the bronchial walls, and the inteHobalae septa, The blood which issues from their
capillaries is returned—partly by the pulmonary veins—hence, any considerable interference
with the pulmonary circulation causes congestion of the bronchial mucous membrane, resulting
in a catarrhal condition of that membrane. The greater part of the blood is returned by the

bronchial veins, which open into the vena azygos, intercostal vein, or superior vena cava. The re

*

.THE BLOOD-VESSELS OF THE LUNGS. 163

veins of the smaller bronchi (fourth order onwards) open into the pulmonary veins, and the
anterior bronchial also communicate with the pulmonary vein (Zuckerkand?).

[The Pleura.—Each pleural cavity is distinct, and is a large serous sac, which really belongs
to the lymphatic system of the lung. The pleura. consists of two layers, visceral and parietal.
The visceral pleura covers the lung ; the parietal portion lines the wall of the chest, and the
two layers of the corresponding pleura are continuous with one another at the root of the lung.
The visceral pleura is the thicker, and may readily be separated from the inner surface of the
chest. Structurally, the pleura resembles a serous membrane, and consists of a thin layer of
fibrous tissue covered by a layer of endothelium. Under this layer, or the pleura proper, is a
deep or sub-serous layer of looser areolar tissue, containing many elastic fibres. The layer of
the pleura pulmonalis of some animals, as the guinea-pig, contains a network’ of non-striped
muscular fibres (Klein). Over the lung it is also continuous with the interlobular septa. The
interlobular septa (fig. 133, ¢) consist of bands of fibrous tissue separating adjoining lobules,

Fig. 182.
Semi-diagrammatic representation of the air-vesicles of the lung. v, v, blood-vessels at the
margins of an alveolus; ¢, c, its blood-capillaries ; E, relation of the squamous epithelium

of an alveolus to the capillaries in its wall ; f, alveolar epithelium shown alone ; ¢, ¢, elastic
tissue of the lung.

and they become’continuous with the peri-bronchial connective-tissue entering the lung at its
hilum. Thus the fibrous framework of the lung is continuous throughout the lung, just ‘as in
other organs. The connection of the sub-pleural fibrous tissue with the connective-tissue
within the substance of the lung has most important pathological bearings. The interlobular
septa contain lymphatics and blood-vessels. The endothelium covering the parietal layer is of
the ordinary squamous type, but on the pleura pulmonalis-the cells are less flattened, more
polyhedral, and granular. They must necessarily vary in shape with changes in the volume
of the lung, so that they are more flattened when the lung is distended, as during inspiration.
The pleura contains many lymphatics, which communicate by means of stomata with the
pleural cavity. ] a“
[The Lymphatics of the lung are numerous, and are arranged in several systems. The various
air-cells are connected with each other by very delicate connective-tissue, and, according to J.
Arnold, in some parts this interstitial tissue presents characters like those of adenoid tissue ; so
that the lung is traversed by a system of juice-canals or ‘‘Saft-canilchen.”] [In the deep
layer of the pleura there is a (a) sub-pleural plexus of lymphatics partly derived from the pleura,

164 THE LYMPHATICS OF THE LUNG.

but chiefly from the lymph-canalicular system of the pleural alveoli. Some of these branches
proceed to the bronchial glands, but others pass into the interlobular septa, where they join (b)
the peri-vascular lymphatics which arise in the lymph-canalicular system of the alveoli. These
trunks, provided with valves, run alongside the pulmonary artery and vein, and in their course
they form frequent anastomoses. Special vessels arise within the walls of the bronchi, and occur
chiefly in the outer coat of the latter, constituting (c) the peri-bronchial lymphatics, which
anastomose with b. The branches of these two sets run towards the bronchial glands. - Not
unfrequently (cat) masses of adenoid tissue are found in the course of these lymphaties.] The
lymph-canalicular system and the lymphatics become injected when fine-coloured particles are
inspired, or are introduced into the air-cells artificially. The pigment particles pass through
the semi-fluid cement-substance into the lymph-canalicular system and thence into the lym-
_. phatics; or, according to Klein, they
SEF =| pass through actual holes or pores in
— = BAX VN the cement (p. 162).] [This pigmenta-
Fay expe maid tS tion is well seen in coal-miner’s lung or
) N\A NNT ERIC ET anthracosis, where the particles of car-
. “2 hk a bon pass into and are found in the .
lymphatics. Sikorski and Kiittner
showed that pigment reached the lym-
phatics in this way during life. If
pigment, China ink, or indigo-carmine
¥ be introduced into a frog’s lung, it is
Ave found in the lymphatic system of the
ane Qurg lung. Ruppert, and also Schotielius,
Fhe showed that the same result occurred
in dogs after the inhalation of charcoal,
cinnabar, or precipitated Berlin blue,
and von Ins after the inhalation of
silica. Schestopal used China ink and
cinnabar suspended in #? per cent. salt
solution.] Excessively fine lymph-
canals lie in the wall of the alveoli in
the interspaces of the capillaries, and
there are slight dilatations at the points
of crossing. According te Pierret and
Renaut every air-cell of the lung of the
ox is surrounded by a large lymph-
space, such as occurs in the salivary
glands. When a large quantity of fluid
is injected into the lung, it is absorbed
with great rapidity ; even blood-cor-
puscles rapidly pass into the lym-
phaties.

The superficial lymphatics of the
pulmonary pleura communicate with

Fig. 133. the pleural cavity by means of free
Human lung (x 50 and reduced }). a, small bronchus ; 0penings or stomata, and the same is
b, b, pulmonary artery ; ¢, pulmonary vein; e, inter- true of the lymphatics of the parietal
lobular septa, continuous with the deep layer of the pleura, but these stomata are confined
pleura, p. to limited areas over the diaphragmatic
pleura. [The lymphatics in the costal
pleura occur over the intercostal spaces and not over the ribs (Dybkowski).] The large arteries
of the lung are provided with lymphatics which lie between the middle and outer coats, [The ;
movements of the lung during respiration are most important factors in moving the lymph
abe in the pulmonary lymphatics. The reflux of the lymph is prevented by the presence
of valves. ]

(The nerves of the lung are derived from the anterior and posterior pulmonary plexuses, and
consist of branches from the vagus and sympathetic. They enter the lungs and follow the dis-
tribution of the brunchi, several sections of nerve-trunks being usually found in a transverse
section of a large bronchial tube. The nerves lie outside the cartilages, and are in close relation
with the branches of the bronchial arteries. Medullated and non-medullated nerve-fibres occur
in the nerves, which also contain numerous small ganglia (Remak, Klein, Stirling). In the
lung of the calf the ganglia are large. The exact mode of termination of the nerve-fibres
within the lung has yet to be ascertained in mammals, but some fibres pass to the bronchial
muscle, others to the large blood-vessels of the lung, and it is highly probable that the mucous —
glands are also supplied with nerve-filaments. In the comparatively simple lungs of the frog, —
nerves with numerous nerve-cells in their course are found (Arnold, Stirling), and in the very —

,3
a

Ss

ar = Te =

PHYSICAL PROPERTIES OF THE LUNGS. | 165

simple lung of the newt, there are also numerous nerve-cells disposed along the course of the
intra-pulmonary nerves. Some of these fibres terminate in the uniform layer of non-striped
muscle which forms part of the pulmonary wall in the frog and newt, and others end in the mus-
cular coat of the pulmonary blood-vessels (Stirling). The functions of these ganglia are unknown,
but they may be compared to the nerve-plexuses existing in the walls of the digestive tract. ]

The Function of the non-striped muscle of the entire bronchial system seems to
be to offer a sufficient amount of resistance to increased pressure within the air-
passages ; as in forced expiration, speaking, singing, blowing, &c. The vagus is the
motor nerve for these fibres, and according to Longet, the “lung-tonus” during
increased tension depends upon these muscles.

[Effect of Nerves. —By connecting the interior of a small bronchus with an oncograph (§ 103)
in curarised dogs (the thorax being opened), Graham Brown and Roy found that section of one
vagus causes a marked expansion of the bronchi of the corresponding lung, while stimulation
of the peripheral end of a divided vagus causes a powerfui contraction of the bronchi of both
lungs. Stimulation of the central end of one vagus, the other being intact, also causes a con-
traction (feebler) under the same circumstances. Especially in etherised dogs, expansion and
not contraction results. If both vagi be divided, no effect is produced by stimulation of the
central end of either vagus. It seems plain that the vagi contain centripetal or afferent fibres,
which can cause both expansion and contraction of the bronchi. Asphyxia causes contraction
provided the vagi are intact, but none if they are divided, although in etherised dogs expansion
frequently occurs, while stimulation of the central end of other sensory nerves has very rarely
any, or, if any, but a slight, effect on the calibre of the bronchi, so that in the dog the only
connection between the cerebro-spinal centres and the bronchi is through the vagi. ]

Pathological.—Stimulation of the smooth muscles, whereby a spasmodic narrowing of the
smaller bronchi is produced, may excite asthmatic attacks. Ifthe expiratory blast be interfered
with, acute emphysema may take place (biernier).

Chemistry. —In addition to connective, elastic, and muscular tissue, the lungs contain lecithin,
inosit, uric acid (taurin and leucin in the ox), guanin, xanthin (?), hypoxanthin (dog)—soda,
potash, magnesium, oxide of iron, much phosphoric acid, also chlorine, sulphuric, and silicic
acids—in diabetes sugar occurs—-in purulent infiltration glycogen and sugar—in renal degenera-
tion urea, oxalic acid, and ammonia salts; and in diseases where decomposition takes place,
leucin and tyrosin.

[Physical Properties of the Lungs.—The Jungs, in virtue of the large amount
of elastic tissue which they contain, are endowed with elasticity ; and when the
chest is opened they collapse. Ifa cannula with a small lateral opening be tied
into the trachea of a rabbit’s or sheep’s lungs, the lungs may be inflated with a
pair of bellows, or elastic pump. After the artificial inflation, the lungs, owing
to their elasticity, collapse and expel the greater part of the air. As much air
remains within the light spongy tissue of the lungs, even after they are removed
from the body, a healthy lung floats in water. If the air-cells are filled with
pathological fluids or blood, as in certain diseased conditions of the lung
(pneumonia), then the lungs or parts thereof may sink in water. The lungs of the
foetus, before respiration has taken place, sink in water, but after respiration has
been thoroughly established in the child, the lungs float. Hence, this hydrostatic
test is largely used in medico-legal cases, as a test of the child’s having breathed.
If a healthy lung be squeezed between the fingers, it emits a peculiar and character-
istic fine crackling sound, owing to the air within the air-cells. A similar sound is
heard on cutting the vesicular tissue of the lung. The colour of the lungs varies
much ; in a young child it is rose-pink, but afterwards it becomes darker, especially
in persons living in towns or a smoky atmosphere, owing to the deposition of
granules of carbon. In coal-miners the lungs may become quite black: |

{Excision of the Lung.—Dogs recover after the excision of one entire lung, and they even sur-
vive the removal of portions of lung infected with tubercle (Biondz). ]

10'7. MECHANISM OF RESPIRATION:—The mechanism of respiration
consists in an alternate dilatation and contraction of the chest. The dilatation
is called inspiration, the contraction expiration. As the whole external surfaces
of both elastic lungs are applied directly, and in an air-tight manner, by their
smooth moist pleural investment to the inner wall of the chest, which is covered by

166 MECHANISM OF RESPIRATION.

the parietal pleura, it is clear that the lungs must be distended with every dilatation
of the chest, and diminished by every contraction thereof. The movements of the
lungs, therefore, are entirely passive, and are dependent on the thoracic movements.

On account of their complete elasticity and their great extensibility, the lungs
are able to accommodate themselves to any variation in the size of the thoracic —
cavity, without the two layers of the pleura becoming separated from each other.
As the capacity of the non-distended chest is greater than the volume of the
collapsed lungs after their removal from the body, it is clear that the lungs, even
in their natural position within the chest, are distended, 7.e., they are in a certain
state of elastic tension (§ 60). The tension is greater the more distended the
thoracic cavity, and vice versa. As soon as the pleural cavity is opened by perfora-
tion from without, the lungs, in virtue of their elasticity, collapse, and a space filled
with air is formed between the surface of the lungs and the inner surface of the
thoracic wall (pneumo-thorax). The lungs so affected are rendered useless for
respiration ; hence a double pneumo-thorax causes death.

Pneumo-thorax.—It is also clear that, if the pulmonary pleura be perforated from within the
lung, air will pass from the respiratory passages into the pleural sac, and also give rise to
pneumo-thorax. [Not unfrequently the surgeon is called on to open the chest, say by removing
a portion of a rib to allow of the free exit of pus from the pleural cavity. If this be done with
proper precautions, and if the external wound be allowed to heal, after a time the air in the
pleural cavity becomes absorbed, the collapsed lung tends to regain its original form, and again
becomes functionally active. ]

Estimation of Elastic Tension.—If a manometer be introduced through an intercostal space
into the pleural cavity, ina dead subject, we can measure, by means of a column of mercury,
the amount of the elastic tension required to keep the lung in its position. This is equal to
6 mm. in the dead subject, as well as in the condition of expiration. If, however, the thorax
be brought into the position of inspiration by the application of traction from without, the
elastic tension may be increased to 30 mm. Hg. (Donders).

If the glottis be closed and a deep inspiration taken, the air within the lungs must
become rarefied, because it has to fill a greater space. If the glottis be suddenly
opened, the atmospheric air passes into the lungs until the air within the lungs has
the same density as the atmosphere. Conversely, if the glottis be closed, and if an
expiratory effort be made, the air within the chest must be compressed. If the
glottis be suddenly opened, air passes out of the lungs until the pressure outside and
inside the lung is equal. As the glottis remains open during ordinary respiration,
the equilibration of the pressure within and without the lungs will take place gradu-
ally. During tranquil inspiration there is a slight negative pressure; during ex-
piration a slight positive pressure, in the lungs; the former=1 mm., the latter 2-3
mm. Hg. in the human trachea (measured in cases of wounds of the trachea).

108. QUANTITY OF GASES RESPIRED.—As the lungs within the chest
never give out all the air they contain, it follows that only a part of the air of the
lungs is changed during inspiration and expiration. The volume of this air will |
depend upon the depth of the respirations.

; eS Hutchinson defined the following :—
COMPLEMENTAL ro (1) Residual air is the volWiiin oP air which remains in the
410 Ss chest after the most complete expiration. It is =1230-1640 c.c.
2 [100-130 cubic inches].
| TIDAL AIR ee (2) Reserve or supplemental air is the volume of air which
20 =. can be expelled from the chest after a normal quiet expiration.
5 ¢ Itis =1240-1800 c.c. [100 eubic inches].
RESERVE AIR = S (3) Tidal air is the volume of air which is taken in and given
100 # a caer respiration. It is =500 eubie centimetres [20 cubic ©
inches].
RESIDUAL AIR r (4) Complemental air is the volume of air that can be forcibly
100 inspired over and above what is taken in at a normal respiration.

It amounts to about 1500 c.c. [100-180 cubic inches].
(5) Vital Capacity is the term applied to the volume of air which can be —

NUMBER OF RESPIRATIONS. 167

forcibly expelled from the chest after the deepest possible inspiration. It is equal
to 3772 ¢.c. (or 230 cubic inches) for an Englishman (Hutchinson), and 3222 for a
German (Haeser).

Hence, after every quiet inspiration, both lungs contain (1+2+3)=3000 to
3900 c.cm. [220 cubic inches]; after a a expiration (1 +2)=2500 to 3400
c.cm. [200 cubic inches]. So that about 4 to + of the air in the lungs is subject to
renewal at each ordinary respiration.

_Donders calculated that the entire bronchial system and the trachea contain about 500 c.c. of
alr.

Estimation of Vital Capacity.—This was formerly thought to be of great
utility, but at the present time not much importance is attached to it, nor is it
frequently measured in cases of disease. It is estimated by means of the spiro-
meter of Hutchinson (fig. 134), which consists of a J uauks cylinder filled with
water and inverted like a gasometer over water,
and balanced by means of a counterpoise. Into > Qo Oo =
the cylinder a tube projects, and this tube is
connected with a mouthpiece. The person to be |
experimented upon takes the deepest possible in- |
spiration, closes his nostrils, and breathes forcibly
into the mouthpiece of the tube. After doing so |
the tube is closed. The cylinder is raised by the ial
air forced into it, and after the water inside and an: -
outside the cylinder is equalised, the height to ees
which the cylinder is raised indicates the amount , f =
of ar expired, or the vital or respiratory capacity.
In a man of average height, 5 feet 8 inches, it
is equal to 230 cubic inches.

The following circumstances affect the vital capa-
city

(1) ‘The Height.—Every inch added to the height of
persons between 5 and 6 feet gives an increase ot the
vital capacity = 130 c.c. [8 cubic inches. |

(2) The Body-weight.— When the body-weight exceeds See eee
the normal by 7 per cent. there is a diminution of 37
c.c. of the vital capacity for every kilo. of increase. :

(3) Age.—The vital capacity is at its maximum at 35 ; Fig. 134.
there is an annual decrease of 23°4 c.c., from this age Scheme of Hutchinson’s spirometer.
onwards to 65, and backwards to 15 years of age.

(4) Sex. —It is less in women than men, and even where there is the same circumference of
chest, and the same height in a man and a woman, the ratio is 10: 7.

(5) Position and Occupation.—More air is respired in the erect than in the recumbent

osition.
: (6) Disease. —Abdominal and thoracic diseases diminish it.

109. NUMBER OF RESPIRATIONS.—In the adult, the number of respira-
tions varies from 16 to 24 per minute, so that about 4 pulse-beats occur during each
respiration. The number of respirations is influenced by many conditions :—

(1) The Position of the Body.—In the adult, in the horizontal position, Guy counted 13,
while sitting 19, while standing 22, respirations per minute.
(2) Age — Quetelet found the mean number of respiratigqns in 300 individuals to be :—

ff

Year. Respirations. Year, Respirations.
0to 1, dt Average 20 to 25, 18°7 Average
5, 26° - Number per 25 to 30, 16 Number per
15 to 20, © 20 Minute. 30 to 50, 18:1 Minute.

(3) The State of Activity. —Gorham coutited in children of 2 to 4 years of age during standing
32, in sleep 24, respirations per minute. During bodily exertion the number of respirations
increases before the heart-beats. [Very slight muscular exertion suffices to increase the frequency
of the respirations. ]

[(4) The Temperature of the surrounding medium.—The respirations become more numerous

168 NUMBER OF RESPIRATIONS.

the higher the surrounding temperature, but this result only occurs when the actual tempera-

ture of the blood is increased, as in fever.

(5) Digestion.—There is a slight variation during the course of the day, the increase being
most marked after mid-day dinner (Vierordt).

(6) The Will can to a certain extent modify the number and also the depth of the respira-
tions, but after a short time the impulse to respire overcomes the voluntary impulse.

(7) The Gases of the Blood have a marked etfect, and so has the heat of the blood in fever.]

[(8) In Animals—

Mammals. Per Min. Per Min.| Per Min.
Per Min.| Rabbit, . . 55 | Pigeon, . . 30 | Perch, ; . 380

Tiger, : . 6 | Rat (waking), . 210 | Siskin, . . 100 | Mullet, ‘ . 60
Lion, . ; . 10] Rat (asleep), . 100] Canary, . . 18:) Mel. . : - 50
Jaguar, . . 11 | Rhinoceros, 6-10 | | Hippocampus, . 33
Panther, . . 18 | Hippopotamus, . by Reptiles. |
Cat, . ; . 24 Horse, : 10-12 | Snake, : 5 Invertebrata,
Dog, . : ; LG) ABS, , . 7 | Tortoise, . . 22.) Gek. ; ; 38
Dromedary, mee Mollusea, . 14-65
Giraffe, 8-10 Birds. Fish. | (P. Bert.)
Ox, . 15-18 | Condor, . . 6 | Raja, ‘ . 50]
Squirrel, . . 70 | Sparrow, . . 90 Torpedo, . » OL |

[(9) In Disease.—The number may be greatly increased from many causes, ¢.g., in fever,
pleurisy and pneumonia, some heart diseases, or in certain cases of alteration of the blood, as

Fig. 135.

A, Brondgeest’s tambour for registering the respiratory movements. 0, c, inner and outer
caoutchoue membranes ; a, the capsule; d, d, cords for fastening the instrument to the
chest ; S, tube to the recording tambour. B, normal respiratory curve obtained ona
vibrating plate (each vibration =0°01613 sec. ),

in anemia ; and diminished where there is pressure on the respiratory centre in the medulla,
incoma. It is important to note the ratio of pulse-beats to respirations. ]

110, TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS.—The
time occupied in the various phases of a respiration can only be accurately ascer-
tained by obtaining a curve or pneumatogram of the respiratory movements by
means of recording apparatus.

Methods.—The graphic method can be employed in three directions :—(1) To
record the movements of individual parts of the chest-wall.

(1) Vierordt and C, Ludwig transferred the movements of a part of the chest-wall to a lever
which inscribed its movements upon a revolving cylinder. Riegel (1873) constructed a
‘* double stethograph ” on the same principle. This instrument is so arranged that one arm
of the lever may be applied in connection with the healthy side of a person’s chest, and the

TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. 169

other.on the diseased side. In the case of animals placed on their backs, Snellon introduced
a long needle vertically through the abdominal walls into the liver. Rosenthal opened the
abdomen and applied a lever to the under surface of the diaphragm, and thus registered its
movements (Phrenograph),

(2) An air-tambour, such as is used in Brondgeest’s pansphygmograph (fig. 135, A), may be
employed. Itconsists of a brass vessel, a, shaped like a small saucer. The mouth of the brass
vessel is covered with a double layer of caoutchoue membrane, J, c, and air is forced in between
the two layers until the external membrane bulges outwards. This is placed on the chest, and
the apparatus is fixed in position by means of the bands, d, d. The cavity of the tambour
communicates by means of a caoutchouc tube, s, with a recording tambour, which inscribes its
movements upon a revolving cylinder. Every dilatation of the chest compresses the membrane,
and thus the air within the tambour is also compressed. [A somewhat similar apparatus is
used by Burdon-Sanderson, and called a ‘‘recording-stethograph.” By it movements of the
corresponding points on opposite sides of the chest can be investigated.] A cannula or
cesophageal sound may be introduced into that portion of the cesophagus which lies in the
chest, and a connection established with’ Marey’s tambour (Rosenthal). [This method also
enables one to measure the intrathoracic pressure. |

Marey’s Stethograph or Pheumograph.—[There are two forms of this instrument, one modi-
fied by P. Bert and the more modern form (fig. 186). A tambour (/) is fixed at right angles to a
thin elastic plate of steel (f). The
aluminium dise on the caoutchouc
of the tambour is attached to an
upright (>), whose end lies in con-
tact with a horizontal screw (gq).
Two arms (d, c) are attached to
opposite sides of the steel plate,
and to them the belt (e) which
fastens the instrument to the
chest is attached. When the
chest expands, these two arms are |
pulled asunder, the steel plate is oF) uy — a
bent, and the tambour is affected, — |{
and any movement of the tam-
bour is transmitted to a register-
ing tambour by the air in the
tube (a)].

(2) Lo record variation in
volume of the thorax or of the
respired gases.

For this purpose E. Hering
secures the animal, and places it
in a tight box provided with two openings in its side; one hole contains a tube, which is
connected to a cannula tied into the transversely divided trachea of the animal, so that
respiration can go on undisturbed. In the other orifice is fixed a water-manometer provided
with a swimmer arranged to write on a-recording surface. Gad registered graphically the
respired air by means of a special apparatus ; the expired air raised a very light and carefully
equipoised box placed over water. As it was raised, it moved a writing-style. During inspira-
tion the box sank.

aM
Fig. 136.
Marey’s stethograph.

(3) Zo record the rate at which the respiratory gases are exchanged.

If the trachea of an animal, or the mouth of a man (the nostrils being closed), be connected
with a tube like that of the dromograph (fig. 113), then during inspiration and expiration the
pendulum will be moved to and fro by the air, and the movements of the pendulum can be
registered. [Some years ago, an instrument, called the ‘‘ Anapnograph,” was constructed on
this principle. ]

The curve (fig. 135, B) was obtained by placing the tambour of a Brondgeest’s
pansphygmograph upon the xiphoid process, and recording the movement upon a
plate attached to a vibrating tuning-fork. The inspiration (ascending limb) begins
with moderate rapidity, is accelerated in the middle, and towards the end again
becomes slower. The expiration also begins with moderate rapidity, is then
accelerated, and becomes much slower at the latter part, so that the curve falls
very gradually.

Inspiration is slightly shorter than Expiration.— According to Sibson, the

170 TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS.

ratio for an adult is as 6 to 7; in women, children, and old people, 6 to 8 or 6 to
9. Vierordt found the ratio to be 10 to 14:1 (to 24:1); J. R. Ewald, 11 to 12.
It is only occasionally that cases occur where inspiration and expiration are equally
long, or where expiration is shorter than inspiration. When respiration proceeds
quietly and regularly, there is usually no pause (complete rest of the chest-walls)
between the inspiration and expiration. The very flat part of the expiratory curve
has been wrongly regarded as due to a pause. Of course, we may make a volun-
tary pause between two respirations, or at any part of a respiratory act.

Some observers, however, have described a pause as occurring between the end of expiration
and the beginning of the next inspiration (expiration pause), and also another pause at the end
of inspiration (inspiration pause). The latter is always of very short duration, and consider-
ably shorter than the former. During very deep and slow respiration, there is usually an

T
b b

Fig. 137.
Pneumatograms obtained by means of Riegel’s stethograph. I, normal curves; II, curve from
a case of emphysema ; a, ascending limb ; b, apex ; c, descending limb of the curve. The
small elevations are due to the cardiac impulse.

expiration pause, while it is almost invariably absent during rapid breathing. An inspiration
pause is always absent under normal circumstances, but it may occur under pathological
conditions.

In certain parts of the respiratory curve slight irregularities may appear, which are sometimes
due to vibrations communicated to the thoracic walls by vigorous heart-beats (fig. 187).

The ‘‘ type’ of respiration may be ascertained by taking curves from various
parts during the respiratory movements. Hutchinson showed that, in the female,
the thorax is dilated chiefly by raising the sternum and the ribs (Respiratio costalis),
while in man it is caused chiefly by a descent of the diaphragm (Respiratio
diaphragmatica or abdominalis). In the former, there is the so-called ‘“‘ costal type,”
in the latter the ‘‘ abdominal or diaphragmatic type.”’

This difference in the type of respiration in the sexes occurs only during normal quiet
respiration. During deep and forced respiration, in both sexes the dilatation of the chest is
caused chiefly by raising the chest and the ribs. In man, the epigastrium may be pulled in
sooner than it is protruded. During sleep, the type of respiration in both sexes is thoracic,

1
a
ST]

PATHOLOGICAL VARIATIONS OF RESPIRATORY MOVEMENTS. 171

while at the same time the inspiratory dilatation of the chest precedes the elevation of the
abdominal wall (Mosso). It is not determined whether the costal type of respiration in the
female depends upon the constriction of the chest by corsets or other causes (Sibson), or whether
it is a natural adaptation to the child-bearing function in women (Hutchinson). Some observers
maintain that the difference of type is quite distinct, even in sleep, when all constrictions are
removed, and that similar differences are noticeable in young children. This is denied by
others, while a third class of observers hold that the costal type occurs in children of both
sexes, and they ascribe asa cause the greater flexibility of the ribs of children and women,
which permits the muscles of the chest to act more efficiently upon the ribs.

111, PATHOLOGICAL. —Examination of the Lungs. —'l'he same methods that are applicable
to the heart, viz., I., Inspection ; II., Palpation ; III., Percussion ; and IV., Auscultation,
apply here also. ]

[By inspection we may determine the presence of symmetrical or unilateral alterations in the
shape of the chest, the presence of bulging or flattening at one part, and variations in the
movement of the chest-walls. By palpation, the presence or absence, character, seat, and
extent of any movements are more carefully examined. But we may also study what is called
vocal fremitus (§ 117). Percussion (§ 114), Auscultation ($ 116). ]

[In investigating the respiratory movements, we should observe (1), the frequency (§ 109) ;
(2), the type (§ 110); (3), the nature, character, and extent of the movements, noting also
whether they are accompanied by pain or not (§ 110) ; (4), the rhythm. ]

I. Changes in the mode of Movement.—lIn persons suffering from disease of the respiratory
organs, the dilatation of the chest may be diminished (to the extent of 5 or 6 cm.) on both sides
or only on one side. In affections of the apex of the lung (in phthisis), the sub-normal
expansion of the upper part of the wall of the chest may be considerable. Retraction of the
soft parts of the thoracic wall, the xiphoid process, and the parts where the lower ribs are
inserted, occurs in cases where air cannot freely enter the chest during inspiration, ¢.g., in
narrowing of the larynx; when this retraction is confined to the upper part of the thoracic
wall, it indicates that the portion of the lung lying under the part so affected is less extensile
and diseased.

Harrison’s Groove.—In persons suffering from chronic difficulty of breathing, and in whom,
at the same time, the diaphragm acts energetically, there is a slight groove, which passes hori-
zontally outwards trom the xiphoid cartilage, caused by the pulling in of the soft parts and
corresponding to the insertion of the diaphragm.

The duration of inspiration is lengthened in persons suffering from narrowing of the trachea
or larynx ; expiration is lengthened in cases of dilatation of the lung, as in emphysema, where
all the expiratory muscles must be brought into action (fig. 137, I1).

II. Variations in the Rhythm.—When the respiratory apparatus is much affected, there is
either an increase or a deepening of the respirations, or both. When there is great difficulty of
breathing, this is called dyspnoea.

Causes of Dyspnoea.—(1) Limitation of the exchange of the respiratory gases in the blood due
to—(a) diminution of the respiratory surface (as in some diseases of the lungs) ; (0) narrowing
of the respiratory passages ; (c) diminution of the red blood-corpuscles ; (d) disturbances of the
respiratory mechanism (¢.g., due to affections of the respiratory muscles or nerves, or painful
affections of the chest-wall) ; (¢) impeded circulation through the lungs due to various forms of
heart-disease. (2) Heat-dyspnoea.—The frequency of the respirations is increased in febrile
conditions. The warm blood acts as a direct irritant of the respiratory centre in the medulla
oblongata, and raises the number of respirations to 30-60 per minute (‘‘ Heat-dyspnea’’). If
the carotids be placed in warm tubes, so as to heat the blood going to the medulla oblongata,
the same phenomena are produced (§ 368). [When a child sucks, it breathes exclusively
through the nose, hence catarrhal conditions of the nasal mucous membrane are fraught with
danger to the child.]

[Orthopneea.—Sometimes the difficulty of breathing is so great that the person can only
respire in the erect position, 7.e., when he sits or is propped up in bed. This occurs frequently
towards the close of some heart affections, notably in mitral lesions ; dropsical conditions,
especially of the cavities, may be present. ]

Cheyne-Stokes’ Phenomenon.—This remarkable phenomenon occurs in certain diseases,
where the normal supply of blood to the brain is altered, or where the quality of the blood itself
is altered, ¢.g., in certain affections of the brain and heart, and in uremic poisoning. Respir-
atory pauses of one-half to three-quarters of a minute alternate with a short period (4—# min.) of
increased respiratory activity, and during this time 20-30 respirations occur. The respirations
constituting this ‘‘ series” are shallow at first ; gradually they become deeper and more dyspneeic,
and finally become shallow or superficial again. Then follows the pause, and thus there is an
alternation of pauses and series (or groups) of modified respirations. During the pause, the
pupils are contracted and inactive ; and when the respirations begin, they dilate and become
sensible to light ; the eyeball is moved as a whole at the same time. Hein observed that con-
sciousness was abolished during the pause, and that it returned when respiration commenced.

172 THE MUSCLES OF FORCED RESPIRATION.

Causes. —Luciani and Rosenbach regard variations in the excitability of the respiratory centre
as the cause of the phenomenon, which they compare with the periodic contraction of the heart
(§ 58). The excitability of the respiratory centre is lowest during the pause. They observed this
phenomenon after injury to the medulla oblongata above the respiratory centre, and after apnoea
produced in animals deeply narcotised with opium, and in the last stages of asphyxia, during
respiration in a closed space. During hybernation, this mode of respiration is normal in Myoxus,
the hedgehog, and the caiman.

Periodic Respiration.—If frogs be kept under water, or if the aorta be clamped, after several
hours, they become passive. If they be taken out of the water, or if the clamp be removed from
the aorta, they gradually recover and always exhibit the pias hegtaka id phenomenon. Insuch
frogs the blood-current may be arrested temporarily, while the phenomenon itself remains
(Sokolow and Luchsinger). If the blood-current be arrested by ligature of the aorta, or if the
frogs be bled, the respirations occur in groups. This is followed by a few single respirations,
and then the respiration ceases completely. During the pause between the periods, mechanical
stimulation of the skin causes the discharge of a group of respirations (Siebert and Langendorff).

Action of Drugs.—Muscarin, digitalin, curara, chloral, sulphuretted hydrogen, and the poison
of many infectious diseases (typhus, diphtheria, scarlet fever) may also cause periodic respiration
in frogs [which is not due to the action of these drugs on the heart].

Periodic respiration without any variation in the size of the individual respirations—the so-
called ‘‘ Biot’s respiration ”—occurs normally during sleep. While the nervous system as it
were strives to rest, and thus forgets the respiration, the organism does not observe the short
pauses (Mosso). [There is a periodic increase or decrease in the depth of the respiration,
especially in old people and children, even to the extent of the de aes becoming ‘‘ remit-
tent,” or even ‘‘intermittent,” for a period of 30 sec. during sleep. During periodic-respiration
the action of the several respiratory muscles does not coincide. As a rule, one respires more than
is required by the organism. Mosso calls this ‘‘luxus-respiration.”’] Periodic irregularities
in the respiration are often of reflex origin (Knoll).

112. GENERAL VIEW OF THE RESPIRATORY MUSCLES.
(A) Inspiration.

I. During Ordinary Inspiration.
The diaphragm (Nervus phrenicus).
The Mm. levatores costarum longi et breves (Rami posteriores Nn. dorsalium).
The Mm. intercostales externi et intercartilaginei (Vn. intercostales).

II. During Forced Respiration.
(a) Muscles of the Trunk.
The three Mm. scaleni (Rami musculares of the plexus cervicalis et brachialis),
M. sternocleidomastoideus (Ram. externus N. accessorii).
M. trapezius (2. externus N. accessor et Ram. musculares plexus cervicalis).
M. pectoralis minor (Vn. thoracict anteriores).
M. serratus posticus superior (V. dorsalis scapulz).
Mm. rhomboidei (VV. dorsalis scapule).
Mm. extensores columne vertebralis (am. posteriores nervorum dorsalium)
. Mm. serratus anticus major (1. thoracicus longus). ? ?]
(b) Muscles of the Larynex.

M. sternohyoideus (Ram. descendens hypoglossi).
M. sternothyreoideus (Ram. descendens hypoglosst).
M
M

bo

"GO SVS? OU G9 LD

. crico-arytaenoideus posticus (VV. laryngeus inferior vag).
. thyrec-arytaenoideus (1. laryngeus inferior vagt).
(c) Muscles of the Face.
1, M. dilatator narium anterior et posterior (WV. facialis).
2. M. levator ale nasi (V. facialis).
3. The dilators of the mouth and nares, during forced respiration, [ “ gasping
for breath ”] (VV. facialis).

ga ed

(d) Muscles of the Pharyna.
1, M. levator veli palatini (NV. facialis). |
2. M. azygos uvule (NV. facialis),
3. According to Garland, the pharynx is always narrowed.

4
:

i?

ACTION OF THE DIAPHRAGM. $73

(B) Expiration.
| I. During Ordinary Respiration.
The thoracic cavity is diminished by the weight of the chest, the elasticity of the
lungs, costal cartilages, and abdominal muscles.

II. During Forced Expiration.
The Abdominal Muscles.

1. The abdominal muscles [including the obliquus externus and internus, and
transversalis abdominis] (Wn. abdominis internis anteriores e nervis intercostalibus,
8-12).

2. Mm. intercostales interni, so far as they lie between the osseous parts of the
ribs, and the Mm. infracostales (Wn. intercosiales).

3. M. triangularis sterni (Wn. intercostales).

4, M. serratus posticus inferior (Ram. externi nerv. dorsalium).

5, M. quadratus lumborum (Ram. muscular e plexu lumbali).

113. ACTION OF THE INDIVIDUAL RESPIRATORY MUSCLES.—(A) Inspiration. —(1)
The Diaphragm arises from the cartilages and the adjoining osseous parts of the lower six ribs
(costal portion), by two thick processes or crura, from the upper three or four lumbar vertebre,
and a sternal portion from the back of the ensiform process. It represents an arched double
cupola or dome-shaped partition, directed towards the chest ; in the larger concavity on the
right side lies the liver, while the smaller arch on the left side is occupied by the spleen and
stomach. During the passive condition, these viscera are pressed against the under surface of
the diaphragm, by the elasticity of the abdominal
walls, and by the intra-abdominal pressure, so that
the arch of the diaphragm is pressed upwards into the
chest. The elastic traction of the lungs also aids in
producing this result. The greater part of the upper
surface of the central tendon of the diaphragm is
united to the pericardium. The part on which the
heart rests, and which is perforated by the inferior
vena cava (foramen quadrilaterum) is the deepest part
of the middle portion of the diaphragm during the
passive condition.

Action of the Diaphragm.— When the dia-
phragm contracts, both arched portions become
flatter, and the chest is thereby elongated from
above downwards. In this act, the lateral
muscular parts of the diaphragm pass from an
arched condition into a flatter form (fig. 138),
and during a forced inspiration the lowest
lateral portions, which during rest are in con-
tact with the chest-wall, become separated
from it. The middle of the central tendon
where the heart rests (fixed by means of the
pericardium and inferior vena cava) takes no

share in this movement, especially in ordinary Fig. 138.
quict breathing, but during the deepest in- Sagittal section through the second rib on
spiration it sinks somewhat. the right side. When the arched mus-

cular part of the diaphragm contracts, a
“wedge-shaped space, with its apex down-
wards, is formed around the circumfer-
ence of the lower part of the chest.

Undoubtedly, the diaphragm is the most powerful
agent in increasing the cavity of the chest. Briicke
believes that in addition to increasing the length of
the thoracic cavity from above downwards, it also
increases the transverse diameter of the lower part of the chest. It presses upon the abdominal
viscera from above, and strives to press these outwards, thus tending to push out the adjoining
thoracic wall. If the contents of the abdomen are removed from a living animal, every time the
diaphragm contracts the ribs are drawn inwards. This, of course, hinders the chest from
becoming wider below, hence the presence of the abdominal viscera seems to be necessary for the
normal activity of the diaphragm. Every contraction of the diaphragm, by increasing the

174 CHANGES IN THE CHEST.

intra-abdominal pressure, favours the venous blood-current in the abdomen towards the vena
cava inferior.

Phrenic Nerve.—The immense importance of the diaphragm as the great inspiratory muscle is
pace by the fact that, after both phrenic nerves (third and fourth cervical nerves) are divided,

eath occurs. The phrenic nerve contains some sensory fibres for the pleura, pericardium, and
a portion of the diaphragm. The contraction of the diaphragm is not to be regarded as a
‘*simple muscular contraction,” since it lasts 4 to 8 times longer than a simple contraction ; it
is rather a short tetanic contraction, which we may arrest in any stage of its activity, without
bringing into action any antagonistic muscles (Kronecker and Marckwald).

(2) The Elevators of the Ribs.—The ribs at their vertebral ends (which lie much higher than
their sternal ends) are united by means of joints by their heads and tubercles to the bodies and
transverse processes of the vertebra. A horizontal axis can be drawn through both joints,
around which the ribs can rotate upwards and downwards. If the axis of rotation of each pair
of ribs be prolonged on both sides until they meet in the middle line, the angles so formed are
greatest above (125°), and smallest below (88°). Owing to the ribs being curved, we can imagine
a plane which, in the passive (expiratory) condition of the chest, has a slope from behind and
inwards to the front and outwards. If the ribs move on their axis of rotation, this plane
becomes more horizontal, and the thoracic cavity is increased in its transverse diameter. As
the axis of rotation of the upper ribs runs in a more frontal, and that of the lower ribs in a more
sagittal direction, the elevation of the upper ribs causes a greater increase from before back-
wards, and the lower ribs from within outwards (as the movements of ribs which are directed
downwards are vertical to the axis). The costal cartilages undergo a slight tension at the same
time, which brings their elasticity into play.

Changes in the Chest.— All “inspiratory muscles” which act directly upon the
chest-wall do so by raising the ribs :—(a) When the ribs are raised, the intercostal
spaces are widened. (+) When the upper ribs are raised, all the lower ribs and the
sternum must be elevated at the same time, because all the ribs are connected with
each other by means of the soft parts of the intercostal spaces. (c) During inspira-
tion, there is an elevation of the ribs and a dilatation of the intercostal spaces.
(The lowest rib is an exception: during forced respiration, at least, it is drawn
downwards.) (d) If, on a preparation of the chest, the ribs be raised as in inspira-
tion, we may regard all those muscles as elevators of the ribs, whose origin and
insertion become approximated. Every one is agreed that the scaleni and levatores
costarum longi et breves, the serratus posticus superior, are inspiratory muscles.
These are the most important inspiratory muscles which act upon the ribs.

Intercostal Muscles.— With regard to the action of the intercostal muscles, there
is a great difference of opinion. According to the above experiment, the external
intercostals and the intercartilaginous parts of the internal intercostals act as in-
spiratory muscles, whilst the remaining portions of the internal intercostals (as far as
they are covered by the external) are elongated when the ribs are raised, while they
shorten when the chest-wall descends. A muscle shortens only during its activity.
The internal intercostals were regarded by Hamberger as depressors of the ribs or
expiratory muscles.

In fig. 139, I, when the rods, a and b (which represent the ribs), are raised, the intercostal
epee must be widened (e f>cd). On the opposite side of the figure, it is evident that when
the rods are raised, the line, g h, is shortened (i k<g h, direction of the external intercostals)
Z m is lengthened (J m<o n, direction of internal intercostals). Fig. 139, II, shows, that when
the ribs are raised, the inter-cartilaginei, indicated by g h, and the external intercostals in-
dicated by 7 k, are shortened. When the ribs are raised, the position of the muscular fibres is
indicated by the diagonal of the rhomb becoming shorter.

The mode of action of the intercostal muscles is an old story, Galen (131-203 A.p.) regarding
the externals as inspiratory, the internals as expiratory. ernest, (1727) accepted this
proposition, and considered the intercartilaginei also as inspiratory. Haller looked upon both
the external and internal intercostals as inspiratory, while Vesalius (1540) regarded both as
expiratory. Landerer, observing that the apes two or three intercostal spaces became narrower
duriug inspiration, regarded both as active during inspiration and expiration. They keep one
rib attached to the other, so that their action is to transmit any strain put upon them to the
wall of the chest. On this view they will be in action, even when the distance between their
points of attachment becomes greater. Landois regards the external intercostals and inter-
cartilaginei as active only during inspiration, the internal intercostals only during expiration.

Martin and Hartwell exposed the internal intercostals, and.observed whether they contracted

MECHANISM OF ORDINARY EXPIRATION. 175

along with the diaphragm, or whether the contractions of these two muscles alternate. As the
result of their experiments, they conclude that ‘‘ the internal intercostal muscles are expiratory
throughout their whole extent, at least in the dog and cat ; and that in the former animal they
are almost ‘ordinary’ muscles of respiration, while in the latter they are ‘extraordinary ’
respiratory muscles.”] Landois is of —

opinion that the chief action of these f

k
muscles is not to raise or depress the =
ribs, but rather that the external inter-
costals and the intercartilaginei offer << j h
resistance to the inspiratory dilatation +
m

of the intercostal spaces, and to the
simultaneously increased elastic tension

ye
of the lungs. The internal intercostals C a

act during powerful expiratory efforts, g a
Pie i

(é.g., coughing), and oppose the disten-
sion of the lungs and chest caused by
this act. Unless muscles were present
to resist the uninterrupted tension and
pressure, the intercostal substance would
become so distended that respiration
would be impossible. [According to
Rutherford, the internal intercostals are
probably muscles of inspiration. ]

The Pectoralis minor and
(tSerratus anticus major) can
only act as elevators of the ribs
when the shoulders are fixed, partly
by the rhomboidei, and partly by
fixing the shoulder-joint and sup- II
porting the arms, as is done instinc-
tively by persons suffering from
breathlessness.

(3) Muscles acting on the Ster-
num, Clavicle, and Vertebral
Column.—When the head is fixed by the muscles of the neck, the sternocleidomastoid
raises the manubrium sterni and the sternal end of the clavicle, so that the thorax is
raised and thereby dilated. The scaleni also aid inthis act. The clavicular portion
of the trapezius may act in a similar although less energetic manner. When the
vertebral column is straightened, it causes an elevation of the upper ribs, and a dila-
tation of the intercostal spaces which aid inspiration. During deep respiration, the
straightening of the vertebral column takes place involuntarily.

(4) Laryngeal Movements.—During laboured respiration, with every inspiration,
the larynx descends and the glottis is opened. At the same time the palate is raised,
so as to permit a free passage to the air entering through the mouth.

(5) Facial Movements.—During laboured respiration, the facial muscles are
involved ; there is an inspiratory dilatation of the nostrils (well marked in the horse
and rabbit). When the need for respiration is very great, the mouth is gradually
widened, and the person as it were gasps for breath. During expiration, the
muscles that are active during (4) and (5) relax, so that a position of equilibrium
is established without there being any active expiratory movement to counteract the
inspiratory movement. During inspiration the pharynx becomes narrow (Garland).

(B) Expiration.—Ordinary expiration occurs without the aid of muscles, owing to
the weight of the chest, which tends to fall into its normal position from the
position to which it was raised during inspiration. This is aided by the elasticity
of the various parts of the chest. When the costal cartilages are raised, which is
accompanied by a slight rotation of their lower margins from below forwards and
upwards, their elasticity is called into play. As soon, therefore, as the inspiratory
forces cease, the costal cartilages return to their normal position, 7.¢., the position

Fig. 139.
Scheme of the action of the intercostal muscles,

176 RELATIVE DIMENSIONS OF THE CHEST.

of expiration, and tend to untwist themselves ; at the same time, the elasticity of
the distended lungs draws upon the thoracic walls and the diaphragm. Lastly,
the tense and elastic abdominal walls, which, in man chiefly, are stretched and
pushed forward, tend to return to their non-distended passive condition when the
abdominal viscera are relieved from the pressure of the contracted diaphragm.
(When the position of the body is reversed, the action of the weight of the chest is
removed, but in place of it there is the weight of the viscera, which press upon the
diaphragm. )

The abdominal muscles [obliquus internus and externus, transversalis abdominis
and levator ani] are always active during laboured respiration. They act by diminish-
ing the abdominal cavity, and they press the abdominal contents upwards against the
diaphragm. When they act simultaneously, the abdominal cavity is diminished
throughout its whole extent. The triangularis sterni depresses the sternal ends
of the united cartilages and bones, from the third to sixth ribs downwards ; and the
serratus posticus inferior depresses the lowest four ribs, causing the others to
follow. It is aided by the quadratus lumborum, which depresses the last rib.
According to Henle, the serratus posticus inferior fixes the lower ribs for the action
of the slips of the diaphragm inserted into them, so that it acts during inspiration.
According to Landerer, the downward movement of the ribs in the lower part of
the thorax dilates the chest.

In the erect position, when the vertebral column is fixed, deep inspiration and expiration
naturally alter the position of the centre of gravity, so that during inspiration, owing to the
protrusion of the thoracic and abdominal walls, the centre of gravity lies somewhat more to the
front. Hence, with each respiration there is an involuntary balancing of the body. During
very deep inspiration, the accompanying straightening of the vertebral column and the throw-
ing backwards of the head compensate for the protrusion of the anterior walls of the trunk.

114, RELATIVE DIMENSIONS OF THE CHEST.—The diameter of the chest is ascertained
by means of callipers ; the circumference with a flexible centimetre or other measure.

In strong men, the circumference
of the upper part of the chest (imme-
diately under the arms) is 88 centi-

R L

HEALTHY * RETRACTED
4000 .
—_—_—_ ——_

105Cm.

Fig. 140. | :
Cyrtometer curve. Left side of the chest re- Fig. 141.
tracted in a girl aged twelve. Sibson’s thoracometer.

metres (34°3 inches), in females 82 centimetres (32 inches); at the level of the ensi-
form process 82 centimetres (32 inches) and 78 centimetres (30°4 inches) respec-
tively. When the arms are placed horizontally, during moderate expiration, the
circumference immediately under the nipple and the angles of the scapulz is equal
to half the length of the body; in man 82, and during deep inspiration 89 centi-
metres. The circumference at the level of the ensiform cartilage is 6 centimetres
less. In old people, the circumference of the upper part of the chest is diminished,

—

2

LIMITS OF THE LUNGS. . 177

so that the lower part becomes the wider of the two. The right half of the chest is
usually slightly larger than the left half, owing to the greater development of the
muscles on that side. The long diameter of the chest—from the clavicle to the
margin of the lowest rib—varies very much.

The transverse diameter in man, above and Ceiee is 25 to 26 centimetres (9°7
to 10°1 inches), in females 23 to 24 centimetres (8°9 to 9:2 inches) ; above the
nipple it is 1 centimetre more. The antero-posterior diameter (distance of
anterior chest-wall from the tip of a spinous process) in the upper part of the chest
is = 17 (6°6 inches), in the lower 19 centimetres (7°4 inches). ‘Valentin found
that in a man, during the deepest sail deesaae the chest on a level with the
groove in the heart was increased about 54, to +; while Sibson estimates the increase

at the level of the nipple to be 54.

_ Thoracometer.—In order to obtain a knowledge e the degree of movement—rising or fall-
ing—of the chest-wall during respiration, various instruments have been invented. The
thoracometer (fig. 141) measures the elevation in different parts of the sternum. It consists of
two metallic bars placed at right angles to each other; one of them, A, is placed on the
vertebral column. On B there is placed a movable transverse bar, C, which carries on its
free end a toothed rod, Z, directed downwards. The lower end of this rod is provided with
a pad which rests on the ’ sternum, while its toothed edge drives a small wheel, which moves
an index, whose excursions are indicated on a circle with a scale attached to it.

The Cyrtometer of Woillez consists of a brass chain of movable links, to be applied in a definite
direction to part of the chest-wall, ¢.g., transversely on a level with the nipple, or vertically
upon the mammillary or axillary lines anteriorly. There are freely movable links at two parts,
which permit the chain to be easily removed, so that as a whole it still retains its form. The
chain is laid upon a sheet of paper, and a line drawn with a pencil around its inner margin
gives the form of the thorax (fig. 140). [A lead wire answers the same purpose. |

Limits of the Lungs.—The extent and boundaries of the lungs are ascertained
in the living subject by means of percussion, which consists in lightly tapping the
chest-wall by means of a hammer (percussion-hammer). A small ivory or bone
plate or pleximeter, held in the left hand, is laid on the chest, and the hammer is
made to strike this plate, whereby a sound is emitted, which sound varies with the
condition of the subjacent lung-tissue. Whenever the lung-substance in contact
with the chest-wall contains air, a clear resonant tone or sound—such as is obtained
by striking a vessel containing air, a clear percussion-sound—is obtained. Where
the lung does not contain air, a dull sound—like striking a limb—is obtained.
If the parts containing air be very thin, or only partially filled with air, the
sound is ‘* muffled.”

Fig. 142 indicates the relation of the lungs to the anterior surface of the chest.
The apices of the lungs reach 3 to 7 centimetres (1*1 to 27 inches) above the
clavicles anteriorly, while posteriorly they extend from the spines of the scapule
as high as the seventh spinous process. The lower margin of the right lung in the
passive position (moderate expiration) of the chest, commences at the right margin
of the sternum at the insertion of the sixth rib, runs under the right nipple, nearly
parallel to the upper border of the sixth rib, and descends a little in the axillary
line, to the upper margin of the seventh rib. On the /efé side (apart from the
position of the heart), the lower limit reaches as far down anteriorly as the right.
In fig.-142-the.line a, ¢t, b.shows the lowest limit of the passive lungs. Posteriorly
both lungs reach as far down as the tenth rib. During the deepest inspiration, the
lungs descend anteriorly as far as between the sixth-and seventh ribs, and posteriorly
tothe eleventh rib—whereby the diaphragm is separated from the thoracic wall
(fig. 143). During the deepest expiration, the lower margins of the lungs are
elevated almost as much as they descend during inspiration. In fig. 142, m, 2
indicates the margin of the right lung during deep inspiration ; /, J, during deep
expiration. [The part of the chest-wall covered by the costal pleura i is considerably
larger than the circumference of the lung. This is specially marked:at the lower
margin of the lung, and where the left lung is incised over the heart. In- these

M

178 LIMITS OF THE LUNGS.

regions, during expiration, the surfaces of the visceral and parietal pleure are in
contact, but during inspiration they are separated, and allow the thin margitis of
the lung to be insinuated between them. ‘This available space is called comple-
mental space (Gerhardt), or ‘‘ disposable” or reserve-pleural space by Luschka
(Eichhorst). |

It is important to observe the relation of the margin of the left lung to the heart.
In fig. 142 a somewhat triangular space, reaching from the middle of the point of
insertion of the fourth rib to the sixth rib on the left side of the sternum, is
indicated. In the passive chest, the heart lies in contact with the thoracic wall in
this triangular area (§ 56). This area is represented by the triangle ¢, ¢’, ¢’, and
percussion over it gives a dull sound (superficial dulness).

In the area of the larger triangle, d, d’, d’, where the heart is separated from the
chest-wall by the thin anterior margins of the lung, percussion gives a muffled sound,
while further outwards a clear lung percussion-sound is obtained. During deep
inspiration, the inner margin of the left lung reaches over the heart as far as the

Topography of the lungs and heart. h, 7, upward limit of margin of lung during deepest expira-
tion; m, ”, lower limit during deepest inspiration ; ¢, ¢’, ¢’, triangular area where the
heart is uncovered by lung, dull percussion-sound ; d, d’, d@”, muffled percussion-sound ; 4,

“, anterior margin of left lung reaches this line during deep inspiration, and during deep
expiration it recedes as far as e, ¢’.

insertion of the mediastinum, whereby the dull sound is limited to the smallest
triangle, ¢, 2,7’. Conversely, during very complete expiration, the margin of the
lung recedes so far that the cardiac dulness embraces the space, ¢, ¢, ¢’. ’

115. PATHOLOGICAL PERCUSSION-SOUNDS.—Abnormal Dulness.—The normal clear re-
sonant percussion-sound of the lungs becomes muffled when infiltration takes place into the
lungs, so as to diminish the normal amount of air within them, or when the lungs are com-
pressed from without, ¢.g., by effusion of fluid into the pleura. The percussion-sound becomes
clearer when the chest-wall is very thin, as in spare individuals, during very deep inspiration,

NORMAL RESPIRATORY SOUNDS. 179

and especially in emphysema, where the air-vesicles of certain parts of the lung (apices and
margins) become greatly dilated.

The pitch of the percussion-sound ought also to be noted. It depends upon the greater or
less tension of the elastic pulmonary tissue, and on the elasticity of the thoracic wall. The
tension of the elastic tissue is increased during inspiration and diminished during expiration, so
that even under physiological conditions, the pitch of the sound varies.

The sound is said to be tympanitic when it has a musical quality resembling in its timbre
the sound produced on drums, and when it has a slight variation in pitch. If a caoutchouc
ball be placed near the ear, on tapping it gently; a well-marked tympanitic sound is heard, and
the sound is of higher pitch the smaller the diameter of the ball. A tympanitic sound is
always produced on tapping the trachea in the neck. A tympanitic sound produced over the
chest is always indicative of a diseased condition. It occurs in cases of cavities or vomice within
the substance of the lung, (the sound becomes deeper when the mouth, or better, the mouth
and nese, are closed), when air is present in one pleural cavity, as well as in conditions where
the tension of the pulmonary tissues is diminished. The tympanitic sound resembies the
metallic tinkling which is heard in large pathological cavities in the lungs, or which occurs
when the pleural cavity contains air, and when the conditions which permit a more uniform
reflection of the sound-waves within the cavity are present.

[When a cavity, freely communicating with a large bronchus, exists in the upper and
anterior part of the lung, a peculiar ‘‘cracked-pot sound” is heard on percussing over the
part. Some notion of this sound may be obtained by clasping the two hands so as to bring the
palms nearly together, leaving an air-space between, and then striking them on the knee.
When percussion is made over a large cavity communicating with a bronchus, some of the air is
expelled, and the sound thereby emitted is blended with the fundamental note of the air in the
cavity itself, the combination of these two sounds thus producing the ‘‘ cracked-pot” sound. ]

Resistance.—-When percussing a chest, we may determine whether the substance lying under
the portion of the chest under examination presents great or small resistance to the blow, either
of the percussion-hammer or of the tips of the fingers, as the case may be, [e.g., in great
pleuritic effusion exerting much pressure on, and so distending, the thoracic walls].

Phonometry.—If the stem of a vibrating tuning-fork be placed on the chest-wall over a part
containing air, its sound is intensified ; but if it be placed over a portion of the lung which con-
tains little or no air, its sound is enfeebled (von Baas).

116. THE NORMAL RESPIRATORY SOUNDS.—If the ear directly, or
through the medium of a stethoscope, be placed in connection with the chest-wall, we
hear over the entire area, where the lung is in contact with the chest, the so-called
‘normal vesicular sound,” which is audible during inspiration, and its typical
characters may be studied by listening in the infra-scapular region in an adult. It
is a fine sighing or breezy sound, [which gradually increases in intensity until it
reaches a maximum, and falls away before expiration begins]. It is said to be
caused by the sudden dilatation of the air-vesicles (hence ‘ vesicular”) during inspira-
tion, and it is also ascribed to the friction of the current of air entering the alveoli.
The sound has, at one time, a soft, at another, a sharper character ; the latter occurs
constantly in children up to 12 years of age. In their case, the sound is sharper,
because the air, in entering vesicles one-third narrower, is subjected to greater fric-
tion. This is followed by an expiratory sound, which may be absent during quiet
breathing. It is a feeble sighing sound, of an indistinct soft character, caused by
the air passing out of the air-vesicles, is three or four times shorter than the
— inspiratory, is loudest at first, and soon disappears, the latter part of the expiratory
act giving rise to no audible sound. Its absence is not a sign of disease, but when
it is prolonged and loud, suspicion is aroused. |

Bronchial Respiration.—Within the larger air-passages—larynx, trachea, bronchi
—during inspiration and expiration, there are loud, rough, harsh sounds like a
sharp h or ch—the “ bronchial”—the laryngeal, tracheal, or “tubular” sound, or
breathing. [In normal bronchial breathing, as heard over the trachea, there is a
_ pause between, the inspiratory and expiratory sounds, which are of nearly equal
duration and of about the same intensity throughout. These sounds are also heard
between the scapulz, at the level of the fourth dorsal vertebra (bifurcation of |
trachea), and they occur also during expiration, being slightly louder on the right
side, owing to the slightly greater calibre of the right bronchus. At all other parts

180 PATHOLOGICAL RESPIRATORY SOUNDS,

of the chest, the vesicular sound obscures the tubular or bronchial sound. If the
air-vesicles are deprived of their air, the tubular breathing becomes distinct. _
Bronchial respiration is produced chiefly in the larynx, owing to the formation of
air-eddies in consequence of the narrowing of the respiratory part of the glottis.
This “laryngeal stenosis sound ” excites resonance of the tracheo-bronchial column of —
air, and communicates to it the specific character of bronchial breathing which is
heard over the large tubes of the bronchial system (Dehio). Fel

It is asserted that, when lungs containing air are placed over the trachea, the tubular soun
there produced becomes vesicular. In this case, we must suppose that the vesicular sound
arises from the tubular breathing becoming weakened, and acoustically altered by being
conducted through the lung alveoli. A sighing sound is often produced at the apertures of
the nose and mouth during forced inspiration.

11'7. PATHOLOGICAL RESPIRATORY SOUNDS.—[The breath-sounds heard in disease may
be merely modifications of the normal vesicular or bronchial sounds, or new sounds, such: as
friction sounds, rales, or rhonchi. ] ;

[Puerile Breathing is merely an exaggerated vesicular sound, so called because it resembles
the louder vesicular sound heard in children. It occurs when some part of the lung is unable to
act, and there is, as it were, extra work of the other parts to compensate, and thus the sound is
exaggerated. | ga i, iat

(1) Bronchial or Tubular Breathing occurs over the entire area of the lung, either when the
air- vesicles are devoid of air, which may be caused by the exudation of fluid or solid constituents,
or when the lungs are compressed from without. In both cases vesicular sounds disappear, and
the condensed or solidified lung-tissue conducts the tubular sound of the large bronchi to the
surface of the chest. [The sound heard over a hepatised lobe of the lung in pneumonia is a
typical example.] It also occurs in large cavities, with resistent walls near the surface of the
lung, provided these cavities communicate with a large bronchus. [In this case it is. termed
cavernous breathing. |

(2) The amphoric sound is compared to that produced by blowing over the mouth of an
empty bottle. It occurs either when a cavity—at least the size of the fist—exists in the lung,
which is so blown into during respiration that a peculiar amphoric-like sound, with a metallic
timbre, called metallic tinkling, is produced ; or when the lungstill contains air, and is capable
of expansion ; as there is still air in the pleural cavity, it acts as a resonator, and causes an
amphoric sound, simultaneous with the change of air in the lungs. [The amphoric sound or
echo and metallic tinkling are the only certain signs of the existence of a cavity in the lung.]

(3) If obstruction occurs in the course of the air-passages of the lungs, various results may
accrue, according to the nature of the resistance :—(a) owing to various causes, ¢.g., in, the
apices of the lungs, there may be partial swelling of the walls of the air-tubes, or infiltration
into the air-cells which hinders the regular supply of air. In these cases, parts of the lun
are not supplied with air continuously ; it only reaches them periodically, when a cogwhee
sound occurs. A similar sound may be heard occasionally in a normal lung, when the
muscles of the chest contract in a periodic spasmodic manner. (+) When the air entering large
bronchi causes the formation of bubbles in the mucus which may have accumulated there,
‘‘ mucous rales” are produced. They also occur in small spaces when the walls are separated
from their fluid eontents by the air entering during inspiration, or when the walls, being adherent
to each other, are suddenly pulled asunder. The rales are distinguished as moist, (when the
contents are fluid), or as dry (when the contents are sticky) ; they may be inspiratory, expiratory,
or continuous, or they may be coarse or fine ; further, there is the very fine crepitation, or
crackling sound, and, lastly, the metallic tinkling caused in large cavities through resonance.
[Crepitation or vesicular rales are fine crepitating sounds like those produced by rubbing a lock —
of hair between the fingers near one’s ear ; they occur only during inspiration, and area proof that
some air is entering the air-vesicles. It is heard in its typical form during the first stage of

neumonia, and seems to be produced by the bursting of minute bubbles of air in a fluid.] (¢)
hen the mucous membrane of the bronchi is greatly swollen, or is so covered with viscid
mucus that the air must force its way through, deep sonorous rhonchi (rhonchi sonori) may
occur in the large air-passages, and clear shrill sibilant sounds (rhonchi sibilantes) in the smaller
ones, [Rhonchi are usually due to catarrh or to affections of the bronchial mucous membrane
or bronchitis.] When there is extensive bronchial catarrh, not unfrequently we feel the chest-
wall vibrating with the rale sounds (bronchial fremitus), ; | othe

(4) If fluid and air occur together in one pleural: cavity in which the lung is collapsed, on
shaking the person’s thorax vigorously we hear a sound such as is produced when air and
water are shaken together in a bottle. This is the succussion sound of Hippocrates, Much
more rarely this sound is heard under similar conditions in large pulmonary cavities. |

(5) Pleural Friction._When the two opposed surfaces of the pleura are inflamed, have
become soft, and are covered with exudation; they move over-each other during respitation, and

PRESSURE IN THE AIR-PASSAGES DURING RESPIRATION, _ I8t

in doing so give rise to friction-sounds, which can be felt (often by the patient himself), and
can also be heard. The sound is comparable to the sound produced by bending new leather.

(6) Pectoral Fremitus.—When we speak or sing in a loud tone, the walls of the chest vibrate,
because the vibration of the vocal cords is propagated throughout the entire bronchial ramifica-
tions. The vibration is, of course, greatest near the trachea and large bronchi. The ear cannot
detect the sounds distinctly. If there be much exudation or air in the pleura, or great aceumula-
tion of mucus in the bronchi, the pectoral fremitus is diminished or altogether absent. [In
health, when a person speaks, the vocal resonance over the trachea, although loud, may be
inarticulate ; and on listening over the sternum the sound is diminished and quite inarticulate ;
while over the chest-wall generally the sound, though distinct, is feeble.

All conditions which cause bronchial breathing increase the pectoral fremitus. Under
normal ‘circumstances, therefore, it is louder where bronchial breathing is heard normally. The
ear hears an intensified sound, called bronchophony, [which is a sound like that heard normally
over the trachea or bronchi, but audible over the vesicular lung-tissue. The conditions that
cause it are the same as those on which bronchial breathing depends, so that it is heard in
pneumonia and phthisis. If, through effusion into the pleura or inflammatory processes in the
lung-tissue, the bronchi are pressed flat, a peculiar bleating sound (#gophony) may be heard. ]

118. PRESSURE IN THE AIR-PASSAGES DURING RESPIRATION.—
‘Respiratory Pressure.-—_If a manometer be tied into the trachea of an animal,
so that the respiration goes on completely undisturbed, ¢.c., normal respiration,
during every inspiration there is a negative pressure (-3 mm. Hg) and during
expiration a positive pressure. Donders placed the (J-shaped manometer tube in
one nostril, closed his mouth, leaving the other nostril open, and respired quietly.
During every quiet inspiration the mercury showed a negative pressure of - 1 mm.,
and during expiration a positive pressure of 2-3 mm. (Hg).

Forced. Respiration.—As soon as the air was inspired or expired with greater
force, the variations in pressure became very much greater, e.g., during speaking,
singing, and coughing. The inspiratory pressure was = — 57 mm. (36-74), the
greatest expiratory pressure + 87 (82-100) mm. Hg. The pressure of forced expira-
tion, therefore, is 30 mm. greater than the inspiratory pressure (Donders).

Resistance to Inspiration. —Notwithstanding this, we must not conclude that the
expiratory muscles act more powerfully than the inspiratory ; for during inspiration
a variety of resistances have to be overcome, so that after these have been met, there
is only a residue of the force for the aspiration of the mercury. The resistances to
be overcome by the inspiratory muscles are :—(1) The elastic tension of the lungs,
which during the deepest expirations = 6 mm. ; during the deepest inspirations = 30
mm. Hg (§ 107). (2) The raising of the weight of the chest. (3) The elastic
torsion of the costal cartilages. (4) The depression of the abdominal contents, and
the elastic distension of the abdominal walls. All these not inconsiderable resist-
ances, which the inspiratory muscles have to overcome, act during expiration, and
aid the expiratory muscles. The forces concerned in inspiration are decidedly much
greater than those of expiration.

Intra-thoracic Pressure.—As the lungs within the chest, in virtue of their elas-
ticity, continually strive to collapse, necessarily they must cause a negative pressure
within the chest. This amounts in dogs, during inspiration, to — 7°1 to — 7°5 mm. Hg,
and during expiration to—4 mm. Hg. The corresponding values for man have
been estimated at —4°5 mm. Hg and —3 mm. Hg, by Hutchinson.

{We must distinguish between the respiratory pressure of the air within the respiratory passages, —
and the intra-thoracic pressure. The former is the same asthe atmospheric pressure when the
chest is passive, but less than it as the chest is being enlarged, and greater than it when it is
being diminished in size. The intra-thoracic pressure is the pressure within the chest, but
outside the lungs, %.e., in the pleura, mediastinum, &c. It is negative, ¢.e., less than the
atmospheric pressure, and must vary with the.degree of distension of the lungs. ]

[Methods.—A direct estimation was made by Adamkiewicz and Jacobson. A trocar with its
stylette was forced into the fourth left intercostal space near the sternum and pushed into the
pericardium seaeep The stylette was then withdrawn, and the trocar connected with a

manometer,. and the negative pressure of —3 to -5 mm. Hg was obtained. During severe
dyspnea it was -9 mm. Hg. Rosenthal introduced an cesophageal sound with an elastic

= > 8
cs C y

182 NASAL BREATHING.

ampulla on its lower end into the cesophagus, so that the ampulla came to lie opposite’ the
sterior mediastinum. The sound was connected with a registering tambour or manometer,
uring inspiration the manometer fell, and during inspiration it rose. ]

Even the greatest inspiratory or expiratory pressure is always much less than the blood-
pressure in the large arteries; but if the pressure be calculated upon the entire respiratory
surface of.the thorax, very considerable results are obtained. .

Pneumatometer,—This instrument of Waldenburg is merely a mercurial manometer fixed toa
stand, and connected to an elastic tube with a suitable mouthpiece, which is fitted over the
mouth and nose, while the variations of the Hg can be read off ona scale. [In the male, the
expiratory pressure is 90-120 mm. Hg, and the respiratory 70-100. The relation of the
pressures during expiration and inspiration is more important than the absolute pressure. ]
‘The inspiratory pressure is diminished in nearly all diseases where the expansion of the lung is
impaired [phthisis], or the expiratory pressure is diminished, as in emphysema and asthma,

ffects of the first Respiration on the Thorax.—Until birth, the airless lungs are completely
collapsed (atelectic) within the chest, and fill it, so that on opening the chest in a dead feetus,
pneumo-thorax does not occur (Bernstein). Supposing, however, respiration to have been fully
established after birth, and air to have freely entered the lungs, if a manometer be placed in
connection with the trachea, and the chest be opened, the manometer will register a pressure of
6 mm. Hg, due to the collapse of the elastic lungs. Bernstein supposes that the thorax assumes
a new permanent form, due to the first respiratory distension ; it is as if, owing to the
respiratory elevation of the ribs, the thorax had become permanently too large for the lungs,
which are, therefore, kept permanently distended, but collapse as soon as air passes into the
pleura. When a lung has once been filled with air, it cannot be emptied by pressure from
without, as the small bronchi are compressed before the air can pass out of the alveoli. The
expiratory muscles cannot possibly expel all the air from the lungs, while the inspiratory
muscular force is sufficient to distend the lungs beyond their elastic equilibrium. Inspiration
distends the lungs, increasing their elastic tension, while expiration diminishes the tension
without abolishing it.

119. APPENDIX TO RESPIRATION.—Nasal Breathing.—During quiet
respiration we usually- breathe—or ought to breathe—through the nostrils, the
mouth being closed. The current of air passes through the pharyngo-nasal cavity
—so that, in its course during inspiration, it is (1) warmed and rendered mozst, and
thus irritation of the mucous membrane of the air-passages by the cold air is pre-
vented ; (2) small particles of soot, or other foreign substances in the air, adhere to,
and become embedded in the mucus covering the somewhat tortuous walls of the
respiratory passages, and are carried outwards by the agency of the ciliated epi-
thelium of the respiratory passages ; (3) disagreeable odours and certain impurities
are detected by the sense of smell.

If a lung be inflated, air constantly passes through the walls of the alveoli and trachea. This
also occurs during violent expiratory efforts (cutaneous emphysema in whooping-cough), so that
pneumo-thorax may occur (J. R. Hwald and Kobert).

Pulmonary (Edema, or the exudation of lymph into the pulmonary alveoli, occurs—(1)
When there is very great resistance to the blood-stream in the aorta or its branches, ¢.g., by
ligaturing all the arteries going to the head or the arch of the aorta, so that only one carotid
remains pervious. (2) When the pulmonary veins are occluded. (3) When the left ventricle,
owing to mechanical injury, ceases to beat, while the right ventricle goes on contracting (§ 47).
These conditions produce at the same time anemia of the vaso-motor centre, which results in
stimulation of that centre, and consequent contraction of all the small arteries. Thus the
blood-stream through the veins to the right heart is favoured, and this in its turn favours the
production of cedema of the lungs.’ [The injection of muscarin rapidly causes pulmonary |
cedema, due to the increase of pressure and slowing of the blood-stream in the pulmonary capillaries.

It is set aside by atropin (Weinzweig, Grossmann). ] |

120. MODIFIED RESPIRATORY MOVEMENTS.—(1) Coughing consists in a sudden
violent expiratory explosion after a previous deep inspiration and closure of the glottis, whereby
the glottis is forced open, and any substance, fluid, gaseous, or solid, in contact with the res-
piratory mucous membrane is violently ejected through the open mouth, It is produced volun-
tarily or reflexly ; in the latter case, it can be controlled by the will only to a limited extent.

[Causes.—A cough may be discharged reflexly from a large number of surfaces:—({1) A
draught of cold air striking the skin, especially of the upper part of the body. This may cause
congestion of blood in the air-passages, this in turn exciting the cough. (2) More frequently
it is discharged from the respiratory mucous membrane, especially of the larynx, the
branches of the vagus and the superior laryngeal nerve being the afferent nerves. A co
cannot be discharged from every part of the larynx: thus there is none from the true vocal cords, _

le

P
4
3
“4
,

CHEMISTRY OF RESPIRATION. 183

but only from the glottis respiratoria. All other parts of the larynx are inactive, and so is the
trachea as far as the bifurcation, where stimulation excites cough (Kohts). (3) Sometimes an
offending body, such as a pea or inspissated cerumen in the external auditory meatus, gives rise
to coughing, the afferent nerve being the auricular branch of the vagus. (4) There seems to be
no doubt that there may be a “‘ gastric or stomach cough,” produced by stimulation of the gastric
branches of the vagus, especially in cases of indigestion, accompanied by irritation of the larynx
and trachea. (5) Irritation of the costal pleura and even of the cesophagus (KoAts). (6) Irrita-
tion of some parts of the nose. (7) Sometimes also from irritation of the pharynx, as by an
elongated uvula. (8) In some diseases of the liver, spleen, and generative organs, when pressure
is exerted on these parts. ]

(2) Hawking, or clearing the throat.—An expiratory current is forced in a continuous stream
through the narrow space between the root of the tongue and the depressed soft palate, in order
to assist in the removal of foreign bodies. When the act is carried out periodically, the closed
glottis is suddenly forced open, and it is comparable to a voluntary gentle cough. This act can
only be produced voluntarily.

(3) Sneezing consists in a sudden violent expiratory blast through the nose, for the removal
of mucus or foreign bodies (the mouth being rarely open) after a simple or repeated spasm-like
inspiration—the glottis remaining open. It is usually caused reflexly by stimulation of sensory
nerve-fibres of the nose [nasal branch of the fifth nerve], or by sudden exposure to a bright light
[the afferent nerve is the optic]. This reflex act may be interfered with to a certain extent, or
even prevented, by stimulation of sensory nerves, or firmly compressing the nose where the
nasal nerve issues. The continued use of sternutatories, as in persons who take snuff, dulls the
sensory nerves, so that they no longer act when stimulated reflexly.

[Sternutatories or Errhines, such as powered ipecacuanha, snuff, and euphorbium, also in-
crease the secretion from the nasal glands. The afferent impulses sent to the respiratory centre
also affect the vaso-motor centre, so that, even when sneezing does not occur, the blood-pressure
throughout the body is raised. ]

(4) Snoring occurs during respiration through the open mouth, whereby the inspiratory and
expiratory stream of air throws the uvula and soft palate into vibration. Itis involuntary, and
usually occurs during sleep, but it may be produced voluntarily.

(5) Gargling consists in the slow passage of the expiratory air-current in the form of bubbles
through a fluid lying between the tongue and the soft palate, when the head is held backwards.
It is a voluntary act.

(6) Crying, caused by emotional conditions, consists in short, deep inspirations, long expira-
tions with the glottis narrowed, relaxed facial and jaw muscles, secretion of tears, often com-
bined with plaintive inarticulate expressions, When crying is long continued, sudden and
spasmodic involuntary contractions of the diaphragm occur, which cause the inspiratory sounds
in the pharynx and larynx known as sobbing. This is an involuntary act.

(7) Sighing is a prolonged inspiration, usually combined with a plaintive sound, often caused
involuntarily, owing to painful or unpleasant recollections.

(8) Laughing is due to short rapid expiratory blasts through the tense vocal cords, which
cause a clear tone, and there are characteristic inarticulate sounds in the larynx, with vibra-
tions of the soft palate. The mouth is usually open, and the countenance has a characteristic
expression, owing to the action of the M. zygomaticus major. It is usually involuntary, and
can only be suppressed, to a certain degree, by the will (by forcibly closing the mouth and
see respiration).

(9) Yawning is a prolonged deep inspiration occurring after successive attempts at numerous
inspirations —the mouth, fauces, and glottis being wide open; expiration shorter—both acts
often accompanied by prolonged characteristic sounds. It is quite involuntary, and is usually
excited by drowsiness or ennui.

[(10) Hiccough is due to a spasmodic involuntary contraction of the diaphragm, causing an
inspiration, which is arrested by the sudden closure of the glottis, so that a characteristic sound
is emitted. Not unfrequently it is due to irritation of the gastric mucous membrane, and some-
times it is a very troublesome symptom in uremic poisoning. ]

121, CHEMISTRY OF RESPIRATION—CARBON DIOXIDE, OXYGEN, and WATERY
VAPOUR GIVEN OFF.—I. Estimation of CO,.—1. The volume of CO, is estimated by means
of the anthracometer (fig. 143, II). The volume of gas.is collected in a graduated tube, 77,
provided with a bulb at one end (previously filled with water and carefully calibrated, 7.¢., the
exact amount which each part of the tube contains is accurately measured), and the tube is closed.
The lower end has a stop-cock, h, and to this is screwed a flask, , completely filled with a solu-
tion of caustie potash ; the stop-cock is then opened, the potash solution is allowed to ascend
into the tube, which is moved about until-all the CO, unites with the potash to form potassium
carbonate. Hold the tube vertically and allow the potash to run back into the flask, close the
stop-cock, and remove the bottle with the potash. Place the stop-cock under water, open it, and
allow the water to ascend in the tube, when the space in the tube occupied by the fluid indicates
the volume of CO, which is combined with the potash.

184 ANDRAL AND GAVARRET’S APPARATUS.

2. By Weight.—A large quantity of the mixture of gases which has to be investigated is made
to pass through a Liebig’s bulb filled with caustic potash. The pease apparatus er
carefully weighed beforehand, the increase of weight indicates the amount of CO, which has
been taken up by the potash from the air passed through it. f .

3. By Titration.—A large volume of the air to be investigated is conducted through a known
volume of a solution of barium hydrate. The CO, unites with the barium and forms barium
carbonate. The fluid is neutralised with a standard solution of oxalic acid, and the more barium
that has united with the CO, the smaller will be the amount of oxalic acid used, and vice versd.

II. Estimation of Oxygen. —According to volume—(a) By the union of the O with potassium

pyrogallate.. The same

© © procedure is adopted

K as for the estimation

of CO,, only the flask,

nm, is filled with the

| pyrogallate solution in-

aT stead of potash. (6)
By explosion in an

eudiometer (see Blood-

Gases, § 35).

III. Estimation of
Watery Vapour.—The
air to be investigated is
passed through a bulb
containing concentrated
sulphuric acid, or
through a tube filled
with pieces of calcium
chloride. The amount

Fa ee ea a

of water is directly in-
dicated by the increase

: of weight.
: 22. METHODS OF
oe INVESTIGATION.—I.

Collecting the Expired
Air.—(1) The ~ ex-
zi vired may be collected
Fig. 143. A the cylinder of the

I. Apparatus of Andral and Gavarret for collecting the expired air. C, spirometer, which is
large cylinder to collect the air expired ; P, weight to balance cylin- suspended in concen-
der ; a, b, two Miiller’s valves; M, mouthpiece. II. Anthracometer trated salt solution to
of Vierordt. avoid the absorption

of CO, (§ 108).

Andral and Gavarret’s Apparatus.—The operator breathed several times into a capacious
cylinder (fig. 143). A mouthpiece (M) was placed air-tight over the mouth while the nostrils
were closed. The direction of the respiratory current was regulated by two so-called ‘‘ Miiller’s
Valves” (mercurial), (a and 6). With every inspiration the bottle or valve, a (filled below with
Hg and hermetically closed above), permits the air inspired to pass to the lungs—during every
expiration the expired air can pass only through b to the collecting-cylinder C.

(2) If the gases given off by the skin are to be collected, a limb, or whatever part is to be
investigated, is secured in a closed vessel, and the gases so obtained are analysed.

II. The most important apparatus for this purpose are those of—(a) Scharling (fig. 144),
which consists of a closed box, A, of sufficient size to contain a man. It is provided with an
inlet z and outlet b. The latter is connected with an aspirator, C, a large barrel filled with
water. When the stop-cock, h, is opened and the water hows out of the barrel, fresh air will
rush in continuously into the box, A, and the air mixed with the expired gases will be drawn
towards C. A Liebig’s bulb, d, filled with caustic potash, is connected with the entrance tube,
z, through which the in-going air must pass, whereby it is completely deprived of CO,, so that
the person experimented on is supplied with air free from CO, The air passing out by the
exit tube, 6, has to pass first through ¢, where it gives up its watery vapour to s phurie acid,
whereby the amount of watery vapour is estimated by the increase of the weight of the
apparatus, ¢. Afterwards the air passes through a bulb, /, containing caustic potash, which
absorbs all the CO,, while the tube, g, filled with sulphuric acid, absorbs any watery Wea x
that may come from f. The increase in weight of f and g indicates the amount of CO,.
total volume of air used is known from the capacity of ©. At

(5) Regnault and Reiset’s Apparatus is more complicated, and is used when it is necessary
to keep animals for some time under observation in a bell-jar. It consists of a globe, R, in

SCHARLING, REGNAULT, AND REISET’S APPARATUS. 185

hich is placed the dog to be experimented on (fig. 145). Around this is placed a cylinder,
9, 9, (provided with a thermometer, ¢), which may be used for calorimetric experiments. A
tube, c, leads into the globe, R; through this tube passes a known quantity of pure oxygen
(fig. 145, O). To absorb any trace of CO,, a vessel containing potash (fig. 145, CO,) is placed

!
T

:
]

Fig. 144.

Scharling’s apparatus. d, bulb containing caustic potash to absorb CO, trom in-going air; A,
box for animal experimented on; ¢ and g, tubes containing sulphuric acid to absorb
watery vapour; 7, potash bulb to absorb CO, given off; C, vessel filled with water to
aspirate air ; h, stop-cock.

in the course of the tube. The vessel for measuring the O is emptied towards R, through a
solution of calcium chloride from a large pan (CaCl,) provided with large flasks. Two tubes,
d and e, lead from R, and are united by caoutchouc tubes with the potash bulbs (KOH, Koh),
which can be raised or depressed alternately by means of the beam, W. In this way they

Fig. 145.

Scheme of the respiration apparatus of Regnault and Reiset. R, globe for animal; g, g, outer
casing for R, provided with a thermometer, ¢; @ and.é, exit tubes to movable potash bulbs,
KOH and Koh; O, in-going oxygen; CO,, vessel to absorb any carbonic acid ; CaCl,,
apparatus for estimating the amount of O supplied ; /, manometer.

aspirate alternately the air from R, and the caustic potash absorbs the CO,._ The increase in
weight of these flasks after the experiment-indicates the amount of CO, expired. The mano-
meter, f, shows whether there is a difference of the pressure outside and inside the globe, R.

(c) V. Pettenkofer has invented the most complete apparatus (fig. 146). It consists of a
chamber, Z, with metallic walls, and provided with a door and a window. At ais an opening
for the admission of air, while a large double suction-pump, PP, (driven by means of a steam-

186 COMPOSITION OF ATMOSPHERIC AIR.

engine) continually renews the air within the chamber. The air passes into a vessel, B, filled
with pumice-stone saturated with sulphuric acid, in which it is dried ; it then passes through a
large gas-meter, c, which measures the total amount of the air pening through it. After the air —
is measured, it is emptied outwards by means of the pump, PP). From the chief exit tube, 2,

of the chamber provided with a small manometer, g, a narrow laterally placed tube, , passes
conducting a small secondary stream, which is chemically investigated. This current passes
through the suction-apparatus, MM, (constructed on the principle of Miiller’s mercurial valve,
and driven by a steam-engine). Before reaching this apparatus, the air passes through the
bulb, K, filled with sulphuric acid, whose increase in weight indicates the amount of watery
vapour. After passing through MM,, it goes through the tube, R, filled with baryta solution,
which takes up CO,. The quantity of air which passes through the accessory current, 2, is

Fig. 146.

Respiration apparatus of v. Pettenkofer. Z, chamber for person experimented on; 2, exit

tube with manometer, g; 0, vessel with sulphuric acid; C, gas-meter; PP,, pump; 2

secondary current, with, &, bulb; MM,, suction apparatus ; ~, gas-meter ; N, stream for
investigating air before it enters Z.

measured by the small gas-meter, wu, from which it passes outwards. The second accessory
stream, N, enables us to investigate the air before it enters the chamber, and it is arranged in
exactly the same way as”. The increase of CO, and H,O in the accessory stream, n (i.e., more
than in N), indicates the amount of CO, given off by the person in the chamber, Z.

123. COMPOSITION OF ATMOSPHERIC AIR.—1. Dry Air contains :—

Gas, By Weight. By Volume,
O, : : ; P : ; 23°015 - 20°96
eee nae p ; ; 76°985 79°02
BOE sins at fe 0:03-0°034

2. Aqueous vapour is always present in the air, but it varies greatly in amount,
and generally increases with the increase of the temperature of the air. We
distinguish (a) the absolute moisture, i.e., the quantity of watery vapour which a
volume of air contains in the form of vapour; and (6) the relative moisture, i.¢.,
the amount of watery vapour which a volume of air contains with respect to its
temperature,

Experience shows that people genitals can breathe most comfortably in an atenapnets which
not completely saturated with aqueous vapour according to its temperature, but. is. only

.

COMPOSITION OF EXPIRED AIR. . 187

saturated to the extent of 70 per cent. If the air be too dry, it irritates the respiratory mucous
membrane ; if too moist, there is a disagreeable sensation, and if it be too warm, a feeling of
closeness. Hence, it is important to see that the proper amount of watery vapour is present in
the air of our sitting-rooms, bedrooms, and hospital wards.

The absolute amount of moisture varies:—In towns during the day it increases with
increase of temperature, and diminishes when the temperature falls ; it also varies with the
-direction of the wind, season of the year, and the height above sea-level.

The relative amount of moisture is greatest at sunrise, least at midday; small on high
mountains ; greater in winter than in summer ; larger with a south or a west wind than with a
north or an east wind.

The air in midsummer contains absolutely three times as much watery vapour as in mid-
winter, nevertheless the air in summer is relatively drier than the air in winter.

3. The air expands by heat. Rudberg found that 1000 volumes
of air, at 0°, expanded to 1365 when heated to 100° C.

4. The density of the air diminishes with increase of the height
-above the sea-level.

124. COMPOSITION OF EXPIRED AIR.—1. The expired air
contains more CO,—in normal respiration = 4°38 vols. per cent. (3°3
to 5°5 per cent.), so that it contains nearly 100 times more CO,
than the atmospheric air.

2. It contains less 0 (4°782 vols. per cent. less) than the atmo-
spheric air, 7.¢e., it contains only 16°033 vols. per cent. of O.

3. Respiratory Quotient.— Hence, during respiration, more O is
taken into the body from the air than CO, is given off; so that the
volume of the expired air is (4, to3,) smaller than the volume of
the air inspired, both being calculated as dry, at the same tempera-
ture, and at the same barometric pressure. The relation of the O
absorbed to the CO, given off is 4°38 : 4°782. This is expressed
by the “respiratory quotient ”—

CO,/ 4°38
O (= S759) =° oe

4. An excessively small quantity of N is added to the expired air
(Regnault and Reiset). Segen found that all the N taken in with
the food did not reappear in the excreta (urine and feeces), and he
assumed that a small part of it was given off by the lungs.

5. During ordinary respiration the expired air is saturated with
watery vapour. It is evident, therefore, that when the watery
vapour in the air varies, the lungs give off different quantities of /7
water from the body. The percentage of watery vapour falls during (Z//
rapid respiration (Joleschott).

6. The expired air is warmer (36°3° C.). It is very near the
temperature of the body, and although the temperature of the sur-
rounding atmosphere be very variable, the temperature of the expired air still
remains nearly the same.

Fig. 147.

Fig. 147 shows the instrument used by Valentin and Brunner to determine the temperature
of the expired air. It consists of a glass tube, A, A, with a mouthpiece, B, and in it is a fine
thermometer, C. The operator breathes through the nose and expires slowly through the
mouthpiece into the tube.

Temperature of Temperature of the
the Air. Expired Air,
OE ln a hme Oe REST a, oe. So. Egger Ey,

+17-19°C., . L pr 2, : ; . : + 86°2-37° C.
HME Ootow-xhvd.cs « altiots + 38°5° C.

7. The diminution of the volume of the expired air mentioned under (3) is far
more than compensated by the warming which the inspired air undergoes in the

188 QUANTITY OF GASES’ EXCHANGED.

respiratory passages, so that the volume of the expired air is one- ninth greater
than the air inspired.

8. A very small quantity of ammonia is found in the expired air=0°0204
grammes in 24 hours ; it is probably derived from the blood.

9. Small quantities of H and CH, are expired, both being absorbed from the in:
testine. In herbivora, Reiset found that 30 litres of CH, were expired in 24 hours:

125. QUANTITY OF GASES EXCHANGED.—As under normal circum-
stances more O is absorbed than there is CO, given off (equal volumes of O and
CO, contain equal quantities of O), a part of the O must be used for other oxida-
tion-processes in the body. According to the extent of these latter processes, the
ratio of the O taken in to the CO, given out— |

(= = 0°906 normally ) must vary.

The amount of CO, given off may be less than the “mean” above stated. The
quantity of CO, alone is not a reliable indication of the entire exchange of gases
during respiration ; we must estimate simultaneously the amount of O absorbed
and the CO, given off.

126. DAILY GASEOUS INCOME AND EXPENDITURE :—

Income in 24 hours. Expenditure in 24 hours.
Oxygen— Carbonic Acid—

744 grms. = 516°500 c.cmtr. (Vierordt). 900 grms. = 455500 c.cmtr. ( Vierordt).
36 grms. per hour (Scharling).
32°8 to 33°4 grms. * (Liebermeister).
34 grms._. : a ‘ (Panwmn).
31°5 to 33 grms. . a ; (Ranke).
Water—640 grms. . ; . (Valentin).
(At 0° C. and mean barometric pressure.) Sou ge 7 , . (Vierordt).

12'7. CONDITIONS INFLUENCING THE GASEOUS EXCHANGES.—The
formation of CO,, in all probability, consists of two distinct processes. First, com-
pounds containing CO,, which are o«idation-products of substances containing
carbon, seem to be formed in the tissues. The second process consists in the separa-
tion of this CO,, which, however, takes place without the absorption of O. Both
processes do not always occur simultaneously, and the one process may exceed =
other in extent. The formation of CO, is affected by :—

1. Age.—Until the body is fully developed, the CO, given off increases, but it
diminishes as the bodily energies decay. Hence, in young persons the O absorbed
is relatively greater than the CO, given off ; at other periods both values are pretty
constant. Example :—

In 24 Hours.
Age—Years.
CO, Gram. Excreted. = Carbon. O Absorbed Gram.
8 443 gram. = 121 Carbon. 375 grammes.
15 By fs Sar = 209 ¥ 652 ra
16 950 ,, = 259 = 809 a
18-20 1003 ,, = 274 ,, 854,
20-24 1074 _ ,, = 293 ‘9 914 <
40-60 889 __s,, = 242 7) 757 55
60-80 S10: «, = 221 ys 689 .%

The absolute amount of CO, given off is less in children than in adults; but if
the CO, given off be calculated with reference to body-weight, then, weight for
weight, a child gives off twice as much CO, as an adult.

2. Sex.—Males, from the eighth year onward to old age, give off about one-

—_—

CONDITIONS INFLUENCING THE GASEOUS EXCHANGES, 189

third more CO, than females. This difference is more marked at puberty, when the
difference may rise to one-half. After cessation of the menses, there is an increase,
and in -old age the:amount of CO, given off diminishes. Pregnancy increases
the amount, owing to causes which are easily understood (Andral and Gavarret).

-3. Constitution.—In general, muscular energetic persons use more O and excrete
more CO, than: less active persons of the same weight.

4. Alternation of Day and Night.—The CO, given off is diminished about one-
fourth during sleep, due to the constant heat of the surroundings (bed), darkness,
absence of muscular activity, and the non-taking of food (see 5, 6, 7, 9). Ov is not
stored up during sleep (S. Zewin).. After awaking in the morning, the respirations
are deeper and more rapid, while the amount of CO, given off is increased. It
decreases during the forenoon, until dinner at mid-day causes another increase. It
falls during the afternoon, and increases again after supper.

During hybernation, when no food is taken, and when the respirations cease, or are greatly
diminished, the respiratory exchange of gases is carried out by diffusion and the cardio-
pneumatic movements (§ 59), The COs given off falls to 7;, the O taken in to 4, of what they
are in the waking condition. Much less CO, is given off than O taken in, so that the body-
weight may increase through the excess of O.

5. Temperature of the Surroundings.—Cold-blooded animals become warmer
when the temperature of their environment is raised, and they give off more CO,
in this condition than when they are cooler ; ¢.g., a frog with the temperature of the
surroundings at 39° C. excreted three times as much CO, as when the temperature
was-6° C. Warm-blooded animals behave quite differently when the tempera-
ture of the surrounding medium is changed. When the temperature of the animal
is lowered thereby, there is a considerable decrease in the amount of CO, given off, as
in cold-blooded animals, but if the temperature of the animal be increased (and also
in fever), the CO, is increased (C. Ludwig and Sanders-Ezn). Exactly the reverse
obtains when the temperature of the surroundings varies, and the bodily tempera-
ture remains constant. As the cold of the surrounding medium increases, the pro-
cesses of oxidation within the body are increased through some as yet unknown
reflex mechanism ; the number and depth of the respirations increase, whereby
more O is taken in and more CO, is given out. A man in January uses 32:2
grammes O per hour; in July only 31:7 grammes. In animals, with the tempera-
ture of the surroundings at 8° C., the CO, given off was one-third greater than
with a temperature of 38° C. When the temperature of the air increases—the
body temperature remaining the same—the respiratory activity and the CO, given
off diminish, while the pulse remains nearly constant. On passing suddenly from
a cold to a warm medium the amount of CO, is considerably diminished ; and con-
versely, on passing from a warm to a cold medium, the amount is considerably in-
creased (§ 214). | | 7

6.. Muscular exercise causes a considerable increase in the CO, given out, which
may be three times greater during walking than during rest (Hd. Smith). Ludwig
and Sezelkow estimated the O taken in and the CO, given off by a rabbit during rest,
and when the muscles of the hind limbs were tetanised. During tetanus the O and
CO, were increased considerably, but in tetanised animals more O was given off in
the CO, expired than was taken up simultaneously during respiration. The passive
animal absorbed nearly twice as much O as the amount of CO, given off (§ 294).

7. Taking of food causes a not inconsiderable increase in the CO, given off,
which depends upon the quantity taken; the increase generally occurs about an hour
after the chief meal—dinner. During inanition, the exchange of gases diminishes
considerably until death occurs. At first the CO, given off diminishes more |
quickly than the O is taken up. The quality of the food influences the CO, given
off to this extent, that substances rich in carbon (carbohydrates and fats) cause
a greater excretion of CO, than: substances which contain less C (albumins).

190 CONDITIONS INFLUENCING THE GASEOUS EXCHANGES.

Regnault and Reiset found that a dog gave off 79 per cent. of the O inspired after
a flesh diet, and 91 per cent. after a diet of starch. If easily oxidisable substances.
(glycerin or lactate of soda) are injected into the blood, the O taken in, and the
CO, given off, undergo a considerable increase (Ludwig and Scheremetjewsky).
Alcohols, tea, and ethereal oils diminish the CO, (Prout, Vierordt). [Ed. Smith
divided foods, with reference to the excretion of CO,, into two classes. The respira-
tory excitants include nitrogenous foods, rum, beer, sugar, stout, &c.; the non-
exciters starch, fat, some alcoholic mixtures. The most powerful respiratory
excitants, however, are tea, sugar, coffee, and rum, and the maximum effect is.
usually experienced within an hour. He also found that the effects produced by —
alcoholic drinks varied with the nature of the spirituous liquor. Thus brandy,
whisky, and gin diminish the amount ; while pure alcohol, rum, ale, and porter
tend to increase it. |

8. The number and depth of the respirations have practically no influence on the
formation of CO, or the oxidation-processes within the body, these being regulated
by the tissues themselves, by some mechanism as yet unknown (Pfliger). They
have a marked effect, however, upon the removal of the already formed CO, from
the body. An increase in the number of respirations (their depth remaining the
same), as well as an increase of their depth (the number remaining the same), causes
an absolute increase in the amount of CO, given off, which, with reference to the
total amount of gases exchanged, is relatively diminished. The following example
from Vierordt illustrates this:—

No. of Resps. Volume of | Amount of _ per cent. Depth of | Amount of _ per cent.
per Minute. | Air. | CO,. ~ COg. Resps. COs.» = COs.
| 12 | 6000 | 258 c.cmtr. =4°3 °/, 500 21 c.cmtr. =4°3 °/,
24 | 12000 | 420 Pe =3°5,, 1000 36 i =3°6 ,,
| 48 | 24000 744 es =3°'l ,, 1500 51 rr =3°4 ,,
96 | 48000 | 1392 ,, =29,, 2000 CL. ay oS 2.
| | 3000 7 5, =i.

9. Exposure to a bright light causes an increase in the CO, given off in frogs,
in mammals and birds, even in frogs deprived of their lungs, or in those whose
spinal cord has been divided high up. The consumption of O is increased at the
same time. The same results occur in blind persons, although to a less degree.
Bluish-violet light is almost as active as white light, while red light is less active.

10. The experiments of Gréhant, on dogs, seem to show that intense inflammation of the
bronchial mucous membrane influences the CO, given off.

11, Amongst poisons, thebaia increases the CO, given off, while morphia, codeia, narcein,
narcotin, papaverin, diminish it (Fiubini).

128. DIFFUSION OF GASES WITHIN THE LUNGS. The air within the air-.
vesicles contains most CO, and least O, and as we pass from the small to the large
bronchi and onwards to the trachea, the composition of the air gradually approaches.
more closely to that of the atmosphere. Hence, if the air expired be collected in two
portions, the first half (¢.e., the air from the larger air-passages) contains less CO, (3°7
vols. per cent.) than the second half (5-4 vols. per ceut.). The difference in the per-
centage of gases gives rise to a diffusion of the gases within the air-passages ; the.
CO, must dif‘use from the air-vesicles outwards, and the O from the atmosphere
and nostrils inwards (§ 33). This movement is aided by the cardio-pneumatic:
movement (§ 59), In hybernating animals and in persons apparently but not
actually dead, the exchange of gases within the lungs can only occur in the above-
mentioned ways. For ordinary purposes this mechanism is insufficient, and there.
are added the respiratory movements whereby atmospheric air is introduced into.
the larger air-passages, from which and into which the diffusion currents of O and.
CO, pass, on account of the difference of tension of the gases. — fyyh -

‘Pp Maat

F
>»
.

EXCHANGE OF GASES IN THE AIR-VESICLES. IQI

129. EXCHANGE OF GASES IN THE AIR-VESICLES.—The exchange of
gases between the gases of the blood and those in the air-vesicles occurs almost
exclusively through the agency of chemical processes, and therefore independently
of the diffusion of gases.

Method.—It is important to ascertain the tension of the O and CO, in the venous blood of
the pulmonary capillaries. Pfliiger and Wolfberg estimated the tension by ‘‘ catheterising the
lungs.’”’ An elastic catheter was introduced through an opening in the trachea of a dog into
the bronchus leading to the lowest lobe of the left lung. An elastic sac was placed round the
catheter, and when the latter was introduced into the bronchus, the sac around the catheter was
distended so as to plug the bronchus. No air could escape between the catheter and the wall of
the bronchus. The outer end of the catheter was closed at first, and the dog was allowed to
respire quietly. After four minutes the air in the air-vesicles was completely in equilibrium
with the blood-gases. The air of the lung was sucked out of the catheter by means of an air-
pump, and afterwards analysed.

Thus we may measure indirectly the tension of the O and CO, in the venous
blood of the pulmonary capillaries. The direct estimation of the gases in different
kinds of blood is made by shaking up the blood with another gas. The gases so
removed indicate directly the proportion of blood-gases.

The following statement shows the tension and percentage of O and CO, in
arterial and venous blood, in the atmosphere, and in the air of the alveoli :—

O-Tension in the air of the alveoli of the
catheterised lung=27°44 mm. Hg (cor-

O-Tension in arterial blood=29°6 mm. Hg
(corresponding to a mixture containing 3°9

vol. per cent. of O).

if
CO,-Tension in arterial blood=21 mm. Hg
(corresponding to 2°8 vol. per cent. ).

O-Tension in venous blood=22 mm. Hg
(corresponding to 2°9 vol. per eent.).

LV.
CO,-Tension in venous blood=41 mm. Hg
(corresponding to 5°4 vol. per cent. ).

responding to 3°6 vol. per cent. ).
bgt

CO,-Tension in the air of the alveoli of the
catheterised lung=- 27 mm. Hg (correspond-
ing to 3°56 vol. per cent.).

NAL

O-Tension in the atmosphere = 158 mm. Hg
(corresponding to 20°8 vol. per cent.).
Vi

CO,-Tension in the atmosphere=0°38 mm.
Hg (corresponding to 0°03-0°05 vol. per
cent. ).

When we compare the tension of the O in the air (VII. = 158 mm. Hg) with
the tension of the O in venous blood (III. =22 mm. Hg, or V. = 27°44 mm. Hg),
we might be inclined to assume that the passage of the O from the air of the air-
vesicles into the blood was due solely to diffusion of the gases ; and similarly, we
might assume that the CO, of the venous blood (IV. or VI.) diffused into the air-
vesicles, because the tension of the CO, in the air is much less (VIII.). There are
a number of facts, however, which prove that the exchange of the gases in the lungs
is chiefly due to chemical forces.

[V. Fleischl finds that fluids yield up their gases very much more easily when they receive a
shock, and he regards the shock communicated to the blood, by the contraction of the heart, as

an important factor in preparing the blood for the diffusion of CO, from the blood-plasma
into the lungs. ] |

[Changes produced in the Blood by Respiration.—The blood of the pul-
monary artery is changed from venous into arterial blood (§ 39), the most obvious
alterations being (1) the change in colour from dark crimson to bright scarlet. (2)
It loses CO,. (3) It gains O. (4) The reduced Hb of the venous blood is con-
verted into HbO,. (5) As to a supposed difference of temperature, see § 209, 3.
(6) Pawlow finds that blood which passes several times through the lungs loses its
power of coagulation. Are we to assume that the pulmonary tissues have the
property of destroying the fibrin-ferment ?]

1. Absorption of 0.—Concerning the absorption of O from the air in the alveoli
into the venous blood of the lung-capillaries, whereby the blood is arterialised, it is

192 ABSORPTION OF OXYGEN IN THE LUNGS,

proved that this is a chemical process. The gas-free (reduced) hemoglobin takes
up O to form oxyhemoglobin (§ 15, 1). That this absorption has nothing to do
directly with the diffusion of gases, but is due to a chemical combination of the
atomic compounds, is shown by the fact that, when pure O is respired, the blood does
not take up more O than when atmospheric air is respired ; further, that animals
made to breathe in a limited closed space can absorb almost. all the O—even to
traces—into their blood before suffocation occurs. Of course, if the absorption of
O were due to diffusion, in the former case more O would be absorbed, while in the
latter case the absorption of O could not possibly occur to such an extent as it does.
The law of diffusion comes into play in connection with the absorption of O to this
extent, viz., that the O diffuses from the air-cells of the lung into the blood-plasma,
where it reaches the blood-corpuscles floating in the plasma. The hemoglobin of the
blood-corpuscles forms at once a chemical compound (oxyhzemoglobin) with the O,

Even in very rarefied air, such as is met with in the upper regions of the atmosphere during
a balloon ascent, the absorption of O still remains independent of the partial pressure. But.a
much longer ¢ime is required for this process at the ordinary temperature of the body, so that
in rarefied air, the absorption of O is greatly delayed, but it is not diminished. This is the
cause of death in aeronauts who have ascended so high that the atmospheric pressure is dimin-
ished to one-third (Setschenow).

2. Excretion of CO,.—With regard to the excretion of CO, from the blood, we
must remember that the CO, in the blood exists in two conditions. Part of the
CO, forms a loose or feeble chemical compound, while another portion is more
firmly combined. The former is obtained by those means which remove gases from
fluids containing them in a state of absorption, so that in removing the CO, from
the blood it is difficult to determine whether the CO,, so removed, obeyed the law
of diffusion, or if it was expelled by chemical means.

Although it is convenient to represent the excretion of CO, from the blood into
the air-vesicles of the lung, as due to equilibration of the tension of the CO, on
opposite sides of the alveolar membrane, 7.¢., to diffusion—nevertheless, chemical
processes play an important part in this act. The absorption of O by the coloured
corpuscles acts, at the same time, in expelling CO,. This is proved by the fact
that the expulsion of CO, from ‘the blood takes place more readily when O is
simultaneously admitted. The free supply of O not only favours the removal of
the CO,, which is loosely combined, but it also favours the expulsion of that portion
of the CO, which is more firmly combined, and which can only be expelled by the
addition of acids to the blood: That the oxygenated blood-corpuscles (2.e., their
oxyhzemoglobin) are concerned in the removal of CO, is proved by the fact that
CO, is more easily removed from serum ‘which contains eer blood-corpuscles
than from serum charged with O. ;

[The following scheme may serve to illustrate the extent to which diffusion comes
into play. The O must pass through the alveolar membrane, AB—including the
alveolar epithelium and the wall of the capillaries—as well as the blood-plasma, to.
reach the hemoglobin of the blood-corpuscles. Similarly, the CO, must leave the
salts of the plasma with which it is in combination, and diffuse in the opposite
direction, through the wall of the capillaries, the alveolar membrane, and epithelium,
to reach the air-vesicles. Let AB represent the alveolar membrane ; on the one
side of it is represented the partial pressure of the CO, and O in the air-vesicles ;
and on the other, the partial pressure of the CO, and O in the venous blood Poses
the lung. The arrows indicate the direction of diffusion. |

Partial pressure of air in CO, . woul ye emer uit WO (ct)
alveoli of lung. 922 6; geen OF be 51 hs gla co STE sere
A 0, iaiar

Tension of gases in venous fh off dtaeial) 0 to Men Se
blood of lung. COS: 7215 pha pips e 04 ove Late Barus Ov - old

|

DISSOCIATION OF GASES. 193

Nature of the Process.—The exchange of gases between the blood and. the air
in the lungs has been represented by Donders as due to the process of dis-
sociation.

[Bohr used a modified rheometer of Ludwig’s, whereby living arterial blood was brought into
direct contact with a volume of air containing a greater or less percentage of CO,. Even when
the amount of CO, in the air in direct contact with the blood was very small, it was found that
very little CO, diffused from the blood into the air-space. Bohr therefore concludes that the
separation of CO, from the venous blood in the lungs, and its passage into the air-vesicles, are
not explicable on the hypothesis of diffusion, but we must rather regard the CO, as removed
from the blood by the pulmonary tissue by means of a kind of secretory process, analogous to
the excretion-processes in glands. ].

130. DISSOCIATION OF GASES.—Many gases form true chemical compounds
with other bodies (7.¢., they combine according to their equivalents), when the con-
tact of these bodies is effected under conditions such that the partial pressure of
the gases is high. The chemical compound formed under these conditions is broken
up, whenever the partial pressure is diminished, or when it reaches a certain mini-
mum level, which varies with the nature of the bodies forming the compound.
Thus, by increasing and diminishing the partial pressure alternately, a chemical
compound of the gas may be formed and again broken up. ‘This process is called
dissociation of the gases. The minimal partial pressure is constant for each of
the different substances and gases, but temperature, as in the case of the absorption
of gases, has a great effect on the partial pressure ; with increase of temperature
the partial pressure, under which dissociation occurs, diminishes.

As an example of the dissociation of a gas, take the case of calcium carbonate. When it is
heated in the air to 440° C., CO, is given off from its state of chemical combination, but is
taken up again and a chemical compound formed, which is changed into chalk when it cools,

Dissociation in the Blood.—The chemical combinations containing CO, and
those containing O within the blood-stream, viz., the salts of the plasma, which
are combined with CO,, and the oxyhzemoglobin, behave in a similar manner. If
these compounds of O and CO, are placed under conditions where the partial
pressure of these gases is very low—z.e., in a medium containing a very small
amount of these gases, the compounds are dissociated, 7.e., they give off CO, or O.
If after being dissociated they are placed under conditions where, owing to the
large amount of these gases, the partial pressure of O or of CO, is high, these gases
are taken up again, and enter into a condition of chemical combination.

The hemoglobin of the blood in the pulmonary capillaries finds plenty of O in
the alveoli; hence, it unites with the O owing to the high partial pressure of the O
in the lung, and so forms the compound oxyhemoglobin. On its course through
the capillaries of the systemic circulation, the oxyhemoglobin of the blood comes
into relation with tissues poor in O; the oxyhzmoglobin is dissociated, the O is
supplied to the tissues, and the blood freed from this O returns to the right heart,
and passes to the lungs, where it takes up the new O.

The blood whilst circulating meets with most CO, in the tissues; the high
partial pressure of the CO, in the tissues causes the CO, to unite with certain con-
stituents in the blood so as to form chemical compounds, which carry the CO, from
the tissues to the lungs. In the air of the lungs, however, the partial pressure of
the CO, is very low, dissociation of these chemica] compounds occurs under the
low partial pressure, and the CO, passes into the air-cells of the lung, from which
it is expelled during expiration, It is evident that the giving up of O from the
blood to the tissues, and the absorption of CO, from the tissues, go on side by side
and take place simultaneously, while in the lungs the reverse processes occur almost
simultaneously. - , :

131, CUTANEOUS RESPIRATION.—Methods.—If a man or an animal be placed in the
chamber of the respiratory apparatus (§ 122), and if tubes be so arranged that the respiratory gases
do not enter the chamber, of course we obtain only the ‘‘perspiration” of the skin in the

N

~~
|
i.

chamber. It is less satisfactory to leave the head of the person outside the chamber, while the
neck is fixed air-tight in the wall of the chamber. The extent of the cutaneous respiration of a
limb may be ascertained by enclosing it in an air-tight vessel (Réhrig) similar to t at used for
the arm in the plethysmograph (§ 101).

Loss by Skin.—A healthy man loses by the skin, in 24 hours, =, of his body-
weight, which is greater than the loss by the lungs, in the ratio of 3:2. Only 10
grammes—150 grains,—or it may be 3‘9 grammes 60 grains,—of the entire loss are
due to the CO, given off by. the skin. The remainder of the excretion from the
skin is due to water [14-2 Ib daily] containing a few salts in solution. When the
surrounding temperature is raised, the CO, is increased, in fact it may be doubled ;
violent muscular exercise has the same effect. :

O Absorbed.—The O taken up by the skin is either equal to, or slightly less
than, the CO, given off. As the CO, excreted a the skin is only zy}, of that ex-
creted by the lungs, while the O taken in = +}, of that taken in by the lungs, it
is evident that the respiratory activity of the skin is very slight. Animals whose
skin has been covered by an impermeable varnish die, not from suffocation, but
from other causes (§ 225).

In animals with a thin moist epidermis (frog) the exchange of gases is much greater, and in
them the skin so far supports the lungs in their function, and may even partly replace them

functionally. In mammals with thick dry cutaneous appendages, the exchange of gases is,
again, much less than in man.

1382. INTERNAL RESPIRATION. —Where CO, is formed.—By the term
“internal respiration ” is understood the exchange of gases between the capillaries
of the systemic circulation and the tissues of the organs of the body. As organic
constituents of the tissues, during their activity, undergo gradual oxidation, and
form, amongst other products, CO,; we may assume—(1) that the chief focus for
the absorption of O and the formation of CO, is to be sought for within the
tissues themselves. That the O from the blood in the capillaries rapidly penetrates
or diffuses into the tissues, is shown by the fact that the blood in the capillaries
rapidly loses O and gains CO,, while blood containing O, and kept warm out-
side the body, changes very slowly and incompletely. If portions of fresh tissues
be placed in defibrinated blood containing O, then the O rapidly disappears.
Frogs deprived of their blood exhibit an exchange of gases almost as great as
normal. This shows that the exchange of gases must take place in the tissues
themselves. If the chief oxidations took place in the blood and not in the tissues,
then, during suffocation, when O is excluded, the substances which use up O, @.¢.,
those substances which act as reducing agents, ought to accumulate in the blood.
But this is not the case, for the blood of asphyxiated animals contains mere traces
of reducing materials (Pjliiger). It is difficult to say how the O is absorbed by the
tissues, and what. becomes of it immediately it comes in contact with: the. living
elements of the tissues. Perhaps it is temporarily stored up, or it may form certain
intermediate less oxidised compounds. This may be followed by a period of rapid
formation and excretion of CO,. On this supposition, it is evident that the absorp:
tion of O and the excretion of CO, need not occur to the same extent, so that the
amount of CO, given off at any period is not necessarily an index of the amount of
O absorbed during the same period (§ 127).

[There are two views as to where the CO, is formed as the blood passes through!
the tissues. One view is that the seat of oxidation is in the blood itself, and the
other is that it is formed in the tissues. If we knew the tension of the gases in
the tissues, the problem would. be easily solved, but we can only. arrive ata knows
ledge of this subject indirectly, in the following ways]: — ‘i

- CO, in Cavities.—-That the CO, is formed in the tissues, is supported by the fact that Ere

amount of CO, in the fluids of the cavities of ae body-4 is greater than the GO; iy ue bless of
the ae The tension of CO, in— . nO

194 INTERNAL RESPIRATION.

TENSION OF THE GASES IN CAVITIES AND LYMPH. 195

: uo Pe - Mm. Mm.
Arterial blood, . : 12°28 Hgtension. | Bile, . . . . 50°0 Hg tension.
Peritoneal cavity, ‘ S855: 45 : Hydrocele fluid, ; 46°5 ,, os
Acid urine, ; GEO. =. 5 (Pfliiger and Strassburg).

The large amount of CO, in these fluids can only arise from the CO, of the tissues passing into
70, : .

Gases of Lymph.—In the lymph of the ductus thoracicus the tension of CO,=38°4 to 37°2
mm. Hg, which is greater than in arterial blood, but considerably less than in venous blood
(41°0 mm. Hg). [Ludwig and Hammarsten, Tschirjew.] This does not entitle us to conclude
that in the tissues from which the lymph comes only a small quantity of CO, is formed, but
rather that in the lymph there is less attraction for the CO, formed in the tissues than in the
blood of the capillaries, where chemical forces are active in causing it to combine, or that in the
course of the long lymph-current, the CO, is partly given back to the tissues, or that CO, is
formed in the blood itself. Further, the muscles, which are by far the largest producers of CO,,
contain few lymphatics, nevertheless they supply much CO, to the blood. The amount of free
“‘non-fixed” CO, contained in the juices and tissues indicates that the CO, passes from the
tissues into the blood ; still, Preyer. believes that in venous blood CO, undergoes chemical com-
bination. The exchange of O and CO, varies much in the different tissues. The muscles are
the most important organs, for in their active condition they excrete a large amount of CO,,

and use up much O. The O is so rapidly used up by them that no free O can be pumped out

of muscular tissue (Z. Hermann). The exchange of gases is more vigorous during the activity
of the tissues. Nor are the salivary glands, kidneys, and pancreas any exception, for although,
when these organs are actively secreting, the blood flows out of the dilated veins in a bright red
stream, still the relative diminution of CO, is more than compensated by the increased volume

of blood which passes through these organs.

Reductions by the Tissues.—The researches of Ehrlich have shown that in most tissues very
energetic reductions take place. If colouring-matters, such as alizarin blue, indophenol blue,
or methyl blue, be introduced into the blood-stream, the tissues are coloured by them. Those
tissues or organs which have a particular affinity for O (e.g., liver, cortex of the kidney, and
lungs), absorb O from these pigments, and render them colourless. The pancreas and sub-
maxillary gland scarcely reduce them at all.

(2) In the blood itself, as in all tissues, O is used up and CO, is formed.
This is proved by the following facts:—That blood withdrawn from the body
becomes poorer in O and richer in CO,; that in the blood of asphyxia, free from
O, and in the blood-corpuscles, there are slight traces of reducing agents, which
become oxidised on the addition of O. Still, this process is comparatively insigni-
ficant as against that which occurs in all the other tissues. That the walls of the
vessels—more especially the muscular fibres in the walls of the small arteries—use
O and produce CO, is unquestionable, although the exchange is so slight that the
blood in its whole arterial course undergoes no visible change. |

Ludwig and his pupils have proved that CO, is. actually formed in the blood. If the easily

-oxidisable lactate of soda be mixed with blood, and this blood be caused to circulate in an

excised but still living organ, such as a lung or kidney, more O is used up and more CO, is
formed than in unmixed blood similarly transfused.

(3) That the tissues of the living lungs use O and give off CO, is probable.
When C. Ludwig and Miiller passed arterial blood through the blood-vessels of a
lung deprived of air, the O was diminished and the CO, increased. As the total
amount of CO, and O found in the entire blood, at any one time, is only 4
grammes, and as the daily excretion of CO,=900 grammes, and the O absorbed
daily =744 grammes, it is clear that exchange of gases must go on with great
rapidity, that the O absorbed must be used quickly, and the CO, must be rapidly
excreted. : .

Still, it is a striking fact that oxidation-processes of such magnitude, as ¢.g., the union of C
to form CO,, occur at the relatively low temperature of the blood and the tissues. It has been
surmised that the blood acts as an ozone-producer, and transfers this active form of O to the

tissues. Liebig showed that the alkaline reaction of most of the juices and tissues favours the

Sg of oxidation. Numerous organic substances, which are not altered by O alone,
come rapidly oxidised in the presence of free alkalies, ¢.g., gallic acid, pyrogallic acid, and
sugar; while many organic acids, which are unaffected by ozone alone, are changed into
carbonates when in the form of alkaline salts (Gorwp-Besanez); and, in the same way, when
they are introduced into the body in the form of acids, they are partly-or wholly excreted in

196 RESPIRATION IN A LIMITED SPACE.

_earbonates. ‘ ‘

1383. RESPIRATION IN A LIMITED SPACE.—Respiration in a limited
space causes—(1) a gradual diminution of O; (2) a simultaneous increase of CO, ;
(3) a diminution in the volume of the gases. If the space be of moderate dimen-
sions, tlie animal uses up almost all the O contained therein, and dies ultimately
from spasms caused by the asphyxia. The O is absorbed, therefore—independently
of the laws of absorption—by chemical means. The O in the blood is almost com-
pletely used up (§ 129). Ina larger space, the CO, accumulates rapidly, before
the diminution of O is such as to affect the life of the animal. As CO, can only
be excreted from the blood when the tension of the CO, in the blood is greater
than the tension of CO, in the air, as soon as the CO, in the surrounding air in
the closed space becomes the same as in the blood, the CO, will be retained in the
blood, and finally CO, may pass back into the body. This occurs in a large closed
space, when the amount of O is still sufficient to support life, so that death occurs
under these circumstances (in rabbits) through poisoning with CO, causing
diminished excitability, loss of consciousness, and lowering of temperature, but no
spasms (Worm Miller). In pure O animals breathe in a normal way ; the quantity
of O absorbed and the CO, excreted is quite independent of the percentage of O,
so that the former occurs through chemical agency independent of pressure. In
limited spaces filled with O, animals died by absorption of the CO, excreted.
Worm Miiller found that rabbits died after absorbing CO, equal to half the volume
of their body, although the air still contained 50 per cent. O. Animals can
breathe quite quietly a mixture of air containing 14°8 per cent. (20°9 per cent.
normal) ; with 7 per cent. they breathe with difficulty ; with 4°5 per cent. there is
marked dyspnoea ; with 3 per cent. O there is tolerably rapid asphyxia. The air
expired by man normally contains 14 to 18 per cent. O. According to Hempner,
mammals placed in a mixture of gases poor in O use slightly less O.

Dyspncea occurs when the respired air is deficient in O, as well as when it is overcharged
with CO,, but the dyspnoea in the former case is prolonged and severe ; in the latter, the
respiratory activity soon ceases. The want of O causes a greater and more prolonged increase
of the blood-pressure than is caused by excess of CO,. Lastly, the consumption of O in the
body is less affected when the O in the air is diminished than when there is excess of CO. If
air containing a diminished amount of O be respired, death is preceded by violent phenomena
of excitement and spasms, which are absent in cases of death caused by breathing air over-
charged with CO,. In poisoning with CO,, the excretion of CO, is greatly diminished, while
with diminution of O it is almost unchanged.

If animals be supplied with a mixture of gases similar to the atmosphere, in
which N is replaced by H, they breathe quite normally (Lavoisier and Seguin) ;
the H undergoes no great change.

Cl. Bernard found that, when an animal breathed in a limited space, it became partially
accustomed to the condition. On placing a bird under a bell-jar, it lived several hours ; but
if several hours beforé its death, another bird fresh from the outer air were placed under the
same bell-jar, the second bird died at once, with convulsions.

Frogs, when placed for several hours in air devoid of O, give off just as much CO, as in air
containing O, and they do this without any obvious disturbance. Hence, it appears that the
formation of CO, is independent of the absorption of O, and the CO, must be formed from the
decomposition of other compounds. Ultimately, however, complete motor paralysis occurs,
whilst the circulation remains undisturbed (Aubert).

[1384. DYSPNEA AND ASPHYXIA.—For the causes of dyspnoea see § 111,
and those of asphyxia see § 368. If from any cause an animal be not supplied with
a due amount of air, normal respiration becomes greatly altered, passing through the
phases of hyperpneea, or increased respiration, dyspnoea, or difficulty of breathing,

the urine, but when they are administered as alkaline compounds they are changed into:

to the final condition of suffocation or asphyxia. The phenomena of asphyxia

may be developed by closing the trachea of an animal with a clamp, or by any
means which prevents the entrance of air or blood into the lungs. ~ eee

PHENOMENA OF ASPHYXIA. 197

The phenomena of asphyxia are usually divided into several stages :—1. During
the first stage there is hyperpncea, the respirations being deeper, more frequent,
and laboured. The extraordinary muscles of respiration—both those of inspiration
and expiration (§ 118)—are called into action, dyspncea is rapidly produced, and the
struggle for air becomes more and more severe. At the same time the oxygen of
the blood is being used up, while the blood itself becomes more and more venous.
The venous blood circulating in the medulla oblongata and spinal cord stimulates
the respiratory centres, and causes the violent respirations. This stage usually lasts
about a minute, and gradually gives places to—

2. The second stage, when the inspiratory muscles become less active, while
those concerned in laboured expiration contract energetically, and indeed almost
every muscle in the body may contract ; so that this stage of violent expiratory
efforts ends in general convulsions. The convulsions are due to stimulation of the
respiratory centres by the venous blood. The convulsive stage is short, and is
usually reached in a little over one minute. This storm is succeeded by—

3. The third stage, or stage of exhaustion, the transition being usually some-
what sudden. Itis brought about by the venous blood acting on and paralysing
the respiratory centres. The pupils are widely dilated, consciousness is abolished,
and the activity of the reflex centres is so depressed that it is impossible to discharge
a reflex act, even from the cornea. The animal lies almost motionless, with flaccid
muscles, and to all appearance dead, but every now and again, at long intervals, it
makes a few deep inspiratory efforts, showing that the respiratory centres are not
quite, but almost paralysed. Gradually the pauses become longer and the inspira-
tions feebler and of a gasping character. As the venous blood circulates in the spinal
cord, it causes a large number of muscles to contract, so that the animal extends its
trunk and limbs. It makes one great inspiratory spasm, the mouth being widely
opened and the nostrils dilated, and ceases to breathe. After this stage, which is
the longest and most variable, the heart becomes paralysed, partly from being over-
distended with venous blood, and partly, perhaps, from the action of the venous
blood on the cardiac tissues, so that the pulse can hardly be felt. To this pulseless .
condition the term “asphyxia” ought properly to be applied. In connection with
the resuscitation of asphyxiated persons, it is important to note that the heart con-
tinues to beat for a few seconds after the respiratory movements have ceased.

The whole series of phenomena occupies from 3 to 5 minutes, according to the
animal operated on, and depending also upon the suddenness with which the trachea
was closed. If the causes of suffocation act more slowly, the phenomena are the
same, only they are developed more slowly.

The Circulation.—The post-mortem appearances in man or in an animal are
generally well marked. The right side of the heart, the pulmonary artery, the
venze cave, and the veins of the neck are engorged with dark venous blood. The
left side is comparatively empty, because the rigor mortis of the left side of the
heart, and the elastic recoil of the systemic arteries, force the blood towards
the systemic veins. The blood itself is almost black, and is deprived of almost all
its oxygen, its hemoglobin being nearly all in the condition of reduced hemoglobin,
while ordinary venous blood contains a considerable amount of oxyhzmoglobin as
well as reduced Hb. The blood of an asphyxiated animal practically contains none
of the former and much of the latter. It is important to study the changes in the
circulation in relation to phenomena exhibited by an animal during suffocation.

We may measure the blood-pressure in any artery of an animal while it is being
asphyxiated, or we may open its chest, maintain artificial respiration, and place a
‘manometer in a systemic artery, ¢.7., the carotid, and another in a branch of the
pulmonary artery. In the latter case, we can watch the order of events in the
heart itself, when the artificial ‘respiration is interrupted, It is well to study
the events in both cases. !

198 THE CHANGES OF THE CIRCULATION DURING ASPHYXIA.

If'the blood-pressure be measured in a systemic artery, ¢.g., the carotid, it is.
found that the blood-pressure rises very rapidly, and to a great extent during the
first and second stages ; the pulse-beats at first are quicker, but soon become slower
and more vigorous. During the third stage it falls rapidly to zero. The great,
rise of the blood-pressure, during the first and second stages, is chiefly due to the
action of the venous blood on the general vaso-motor centre, causing constriction of
the small systemic arteries. The peripheral resistance is thus greatly increased,
and it tends to cause the heart to contract more vigorously, but the slower -and
more vigorous beats of the heart are also partly due to the action of the venous.
blood on the cardio-inhibitory centre in the medulla.

If the second method be adopted, viz., to open the chest, keep up artificial
respiration, and measure the blood-pressure in a branch of the pulmonary artery,
as well as in a systemic artery,—e.g., the carotid,—we find that when the artificial
respiration is stopped, in addition to the rise of the blood-pressure indicated in the
carotid manometer, the cavities of the heart and the large veins near it are engorged
with venous blood. There is, however, but a slight comparative rise in the blood-
pressure in the pulmonary artery. This may be accounted for, either by the pul-
monary artery not being influenced to the same extent as other arteries by the
vaso-motor centre, or by its greater distensibility (§88). But, as the heart itself is
supplied through the coronary arteries with venous blood, its action soon becomes
weakened, each beat becomes feebler, so that soon the left ventricle ceases to con-
tract, and is unable to overcome the great peripheral resistance in the systemic
arteries, although the right ventricle may still be contracting. As the blood
becomes more venous, the vaso-motor centre becomes paralysed, the small systemic
arteries relax, and the blood flows from them into the veins, while the blood-pressure
in the carotid manometer rapidly falls. The left ventricle, now relieved from the
great internal pressure, may execute a few feeble beats, but they can only be feeble,
as its tissues have been subjected to the action of the very impure blood. More
and more blood accumulates in the right side from the causes already mentioned.
The violent inspiratory efforts in the early stages aspirate blood from the veins
towards the right side of the heart, but of course this factor is absent when the
chest is opened. |

[Convulsions during asphyxia occur only in warm-blooded animals, and not in
frogs. If a drug when injected into a mammal excites convulsions, but does not
do so in the frog, then it is usually concluded that the convulsions are due to its
action on the circulation and respiration, and not to any direct stimulating effect
upon the motor centres. But if the drug excites convulsions both in the mammal
and frog, then it probably acts directly on the motor centres (Brunton). |

[Recovery from the condition of Asphyxia.—If the trachea of a dog be closed suddenly and
completely, the average duration of the respiratory movements is 4 minutes 5 seconds, while
the heart continues to beat for about 7 minutes. Recovery may be obtained if proper means be
adopted before the heart ceases to beat ; but after this, never. Ifa dog be drowned, the result
is different. After complete submersion for 14 minute, recovery did not take place. In
drowning, air passes out of the chest, and water is inspired into and fills the air-vesicles.- It
is rare for recovery to take place in a person deprived of air for more than five minutes. If the
statements of sponge-divers are to be trusted, a person may become accustomed to the deprival
of air for a longer time than usual. In cases where recovery takes place after a much longer
period of submersion, it has been suggested that, in these cases, syncope occurs, the heart beats.
‘but feebly or not at all, so that the oxygen in the blood is not used up with the same rapidity.
It is a well-known fact that newly-born and young puppies can be submerged for a long time
before they are suffocated. }
Artificial iration in Asphyxia.—In cases of suspended animation, artificial respiration
must be performed. The first thing to be done is to remove any foreign substance from the
respiratory age oy (mucus or cedematous fluids) in the newly-born or asphyxiated. In doubt-
‘ful cases, open the trachea and suck out any fluid by means of.an elastic catheter (v. Hiiter).
Recourse must in all cases be had to artificial respiration. There are several methods of dilating
and compressing the chest so as to cause an exchange of gases, One method is to compress the
chest rhythmically with the hands. iy

ARTIFICIAL’ RESPIRATION :IN ASPHYXIA. 199

\[Marshall Hall’s Method. —‘‘ After clearing the mouth and throat, place the patient on the
face, raising and supporting the chest well on a folded coat or other article of dress. Turn the
body very gently on the side and a little beyond, and then briskly on the face, back again,
repeating these measures cautiously, efficiently, and perseveringly, about fifteen times in the
minute, or once évery four or-five seconds, occasionally varying the side. By placing the
patient on the chest, the weight of the body forces the air out ; when turned on the side,. this
pressure is removed, and air enters the chest.; On each occasion that the body is replaced on
the face, make uniform but efficient pressure with brisk movement.on the back between and
below the shoulder-blades or bones on each side, removing the pressure immediately before
turning the body on the side. During the whole of the operations let one person attend solely
to. the movements of the head and of the arm placed under it.’’] pe - OU NC a

[Sylvester’s Method.—‘‘ Place the patient on the back on the flat surface, inclined a little
upwards from the feet ; raise and support the head and shoulders on a small firm cushion or
folded article of dress.placed under the shoulder-blades. Draw forward the patient's tongue,
and keep it projecting beyond the lips ; an elastic band over the tongue and under the chin
will answer this purpose, or a piece of string or tape may be tied round them, or by raising the
lower jaw the teeth may be made to retain the tongue in that position. Remove all. tight
clothing from about the neck and chest, especially the braces.” ‘‘Z’o Imitate the Movements of
Breathing. —Standing at the patient’s head grasp the arms just above the elbows, and draw the
arms gently and steadily upwards. above the head, and keep them stretched upwards for two
seconds. ; By this means air is drawn into the lungs. Then turn down the patient’s arms, and
press. them gently and firmly for two seconds against the sides of the chest. By this means air
is pressed ont of thé lungs. Repeat these measures alternately, deliberately, and perseveringly
about fifteen times in a minute, until a spontaneous effort to respire is perceived, immediately
upon which cease to imitate the movements of breathing, and proceed to induce circulation and
warmth.” | ° RCS aie ot Sarees Yo | ids

_ Howard advises rhythmical compression of the chest and abdomen by sitting like a rider
astride of the body, while Schiiller advises that the lower ribs be seized from above with both
hands and raised, whereby. the chest is dilated, especially when the thigh is pressed against the
abdomen to compress the abdominal walls. The chest is compressed by laying the hands flat
upon the hypochondria. Artificial respiration acts favourably by supplying O to, as well as
removing CO, from, the blood ; further, it aids the movement of the blood within the heart
and in the large vessels of the thorax. If the action of the heart has ceased, recovery is impos-
sible. In asphyxiated newly-born children, we must not cease too soon to perform artificial
respiration. Even when the result appears hopeless, we ought to persevere. Pfliiger and Zuntz
observed that the reflex excitability of the foetal heart continued for several hours after the
death of the mother. ; .

Resuscitation by compressing the heart.—Bthm found that in the case of cats poisoned with
potash salts or chloroform, or asphyxiated, so as to arrest respiration and the action of the
heart, —even for a period of forty minutes,—and even when the pressure within the carotid had
fallen to zero, he could restore animation by rhythmical compression of the heart, combined with
artificial respiration, The compression of the heart causes a slight movement of the blood,
while it acts at the same time as a rhythmical cardiacstimulus. After recovery of the respiration,
the reflex excitability and gradually also voluntary movements are restored. The animals are
blind for several days, the brain acts slowly, and the urine contains sugar. These experiments
show how important it is in cases of asphyxia to act at the same time upon the heart.

For physiological purposes, artificial respiration is often made use of, especially after
poisoning with curara. Air is forced into the lungs by means of an elastic bag or bellows,
attached to a cannula tied in the trachea. The cannula has a small opening in the side of it
to allow the expired air to escape.

Pathological.—After the lungs have once been properly distended with air, it is impossible
by any amount of direct compression of them to get rid of all the air. This is probably due to
the pressure acting on the small bronchi, so as to squeeze them, before the air can be forced out
of the air-vesicles. If, however, a lung be filled with CO,, and be suspended in water, the CO,
is absorbed by the water, and the lungs become quite free from air and are atelectic (Hermann
and Keller). The atelectasis, which sometimes occurs in the lung, may thus be explained :—If
a bronchus is stopped with mucus or exudation, CO, accumulates in the air-vesicles belonging
to this bronchus. If the CO, is absorbed by the blood or lymph, the corresponding area
of the lung will become atelectic. Sometimes there is spasm of the respiratory muscles, brought
about by direct or reflex stimulation of the respiratory centre.

135. RESPIRATION OF FOREIGN GASES.—No gas without a sufficient admixture of O.
can support life. Even with completely innocuous and indifferent gases, if no O be mixed
with ‘them, they cause suffocation in 2 to 3 minutes. ee iT! PANES
I. Completely indifferent Gases are N, H, CH, The living blood of an animal breathing
these gases yields no O to them (Pfliiger). . :

. II. Poisonous Gases, —0-displacing Gases.—(w) Those that displace O, and form a stable com: .

,

200 ACCIDENTAL IMPURITIES OF. THE AIR,
apes with the hemoglobin—(1) CO (§§ 16 and 17). (2) CNH (hydrocyanic acid) displaces '(?)

from hemoglobin, forming a more stable compound, and kills caste: rapidly, Blood-
corpuscles charged with hydrocyanic acid lose the property of decomposing hydric peroxide into
water and O (§ 17, 5).

(6) Narcotic Gases.—(1) CO,.—V. Pettenkofer characterises atmospheric air containing ‘1
cent. CO, as ‘‘ bad air” ; still, air ina room containing this amount of CO, produces a disagreeable
feeling, rather from the impurities mixed with it than from the actual amount of CO, itself.
Air containing 1 per cent. CO, produces decided discomfort, and with 10 per cent. it endangers
life, while larger amounts cause death, with symptoms of coma. (2) N,O (nitrous oxide), respired,
mixed with 4 volume O, causes, after 1 to 2 minutes, a short temporary stage of excitement
(‘* Laughing gas” of H. Davy), which is succeeded by unconsciousness, and afterwards by an
increased excretion of CO,. (8) Ozonised air causes similar effects (Binz).

(c) Reducing Gases.—(1) H.S (sulphuretted hydrogen) rapidly robs blood-corpuscles of O,
S and H,0 being formed, and death occurs rapidly before the gas can decompose the hemoglobin
to form a sulphur-methemoglobin compound.

(2) PH, (phosphuretted hydrogen) is oxidised in the blood to form phosphoric acid and
water, with decomposition of the hemoglobin.

(3) AsH, (arseniuretted hydrogen) and SbH, (antimoniuretted hydrogen) act like PHg, but
the hemoglobin passes out of the stroma and appears in the urine.

(4) C,N, (cyanogen) absorbs O, and decomposes the blood.

Ill. trrespirable gases, i.¢., gases which, on entering the larynx, cause reflex spasm of the
glottis. When introduced into the trachea, they cause inflammation and death. Under this
category come hydrochloric, hydrofluoric, sulphurous, nitrous, and nitric acids, ammonia,
chlorine, fluorine, and ozone.

136. ACCIDENTAL IMPURITIES OF THE AIR.— Amongst these are dust-particles, which
occur in enormous amount suspended in the air, and thereby act injuriously upon the respiratory
organs. The ciliated epithelium of the respiratory passages eliminates a large number of them
(fig. 148). Some of them, however, reach the air-vesicles of the lung, where they penetrate the

epithelium, reach the interstitial lung-tissue

and lymphatics, andso pass with the laa
stream into the bronchial glands, Particles
of coal or charcoal are found in the lungs
of all elderly individuals, and blacken the
alveoli. In moderate amount, these black
particles do not seem to do any harm in the
ee Intermediate tissues, but when there are large accumu-
‘ lations they give rise to lung-affections,

Strait
Ciiatea Yoo
Epithelium. \@y" on

Clear disc.

ek Beet YM) nner layer, Which lead to disintegration of these organs.
Dévove's OOo: eS sa da [In coal-miners, for example, the lung-
eee Pre rn an tissues along the track of the lymphatics
Fig. 148. and in the bronchial glands are quite black,

constituting ‘‘coal-miners’ lung.”] In
many trades various particles occur in the
air; miners, grinders, stone-masons, file-makers, weavers, spinners, tobacco manufacturers,
millers, and bakers suffer from lung affections caused by the introduction of particles of various
kinds inhaled during the time they are at work. .
Germs.—There seems no doubt that the seeds of some contagious diseases may be inhaled.
Diphtheritic bacteria (Bacillus diphtheris) become localised in the pharynx and in the larynx—
glanders in the nose—measles in the bronchi—whooping-cough in the bronchi—hay-monads
in the nose—the Bacillus pneumonie of pneumonia. in the pulmonary alveoli. ‘Tuberculosis,
according to R. Koch, is due to the introduction and development of the Bacillus tuberculosis
in the lungs, the bacillus being derived from the dust of tuberculous sputa. The same seems to be
the case with the Bacillus of leprosy and with Bacillus malarie, which is the cause of malaria,
The latter organism thus reaches the blood ; it changes the Hb within the red blood-corpuscles
into melanin (§ 10, 8), and causes them to break up. The Micrococcus vaccine of smallpox
gains access to the blood in the same way, also the Spirillum of remittent fever (fig. 23), the
microbe of scarlet fever, &c. ;
Seeds of disease passing into the mouth along with air, and also with the food, are swallowed,
and Seg development in the intestinal tract, as is probably the case in cholera (Comma-
eer of R. Koch), dysentery, typhoid, and anthrax which is due to Bacterium anthracis
g. 24). j .

13'7. VENTILATION OF ROOMS, —Fresh air is as necessary for the healthy as for the sick.
Every healthy person ought to have a cubic space of at the very least 800 cubic feet, and rd
sick person at the very least 1000 cubic feet of space. [The cubic space allowed per individ
varies greatly, but 1000 cubic feet is a fair average. If the air in this space is to be kept sweet,

Ciliated epithelium.

VENTILATION OF ROOMS. 201

so that the CO, does not exceed ‘06 per cent., 3000 cubic feet of air per hour must be supplied,
4.¢., the air in the space must be renewed three times per hour. ]

[Floor-Space. — It is equally important to secure sufficient floor-space, and this is especially
the case in hospitals. If possible, 100-120 square feet of floor-space ought to be provided for
each patient in a hospital-ward, and if it is obtainable a cubic space of 1500 cubic feet (Parkes),
In all cases the minimum floor-space should not be less than 5 of the cubic space. ]

Overcrowding.—When there is overcrowding in a room, the amount of CO, increases. V.
Pettenkofer found the normal amount of CO, (‘04 to ‘05 per 1000) increased in comfortable
rooms to 0°54-0°7 per 1000; in badly ventilated sick chambers=2°4 ; in overcrowded audi-
toriums, 3°2 ; in pits=4°9; in schoolrooms, 7°2 per 1000. Although it is not the quantity of
CO, which makes the air of an overcrowded room injurious, but the excretions from the outer
and inner surfaces of the body, which give a distinct odour to the air, quite recognisable by the
sense of smell, still the amount of CO, is taken as an index of the presence and amount of these
other deleterious substances. Whether or not the ventilation of a room or ward occupied by
persons is sufficient, is ascertained by estimating the amount of CO,. A room which does not
give a disagreeable, somewhat stuffy, odour has less than 0°7 per 1000 of CO,, while the ventila-
tion is certainly insufficient if the CO,=1 per 1000. As the air contains only 0°0005 cubic
metre CO, in 1 cubic metre of air, and as an adult produces hourly 0°0226 cubic metres CO,,
calculation shows that every person requires 113 cubic metres of fresh air per hour, if the CO, —
is not to exceed 0°7 per 1000: for 0°7 : 1000=(0°0226 +2 x 0°0005): x, t.e., 2=113.

[Vitiating Products.—In a state of repose, an adult man gives off from 12 to 16 cubic feet of
CO, in twenty-four hours, or on an average ‘6 cubic feet per hour. To this must be added a
certain quantity of organic matter, which is extremely deleterious to health. While the CO,
diffuses readily and is easily disposed of by opening the windows, this is not the case with the
organic matter, which adheres to clothing, curtains, and furniture ; hence to get rid of it, a
room, and especially a sleeping apartment, requires to be well aired for a long time, together
with the free admission of sunlight. We must also remember that an adult gives off from 25 to
40 oz. of water by the skin and lungs. The nature of the organic matters is not precisely
known, but some of it is particulate, consisting of epithelium, fatty matters, and organic
vapours from the lungs and mouth. It blackens sulphuric acid, and decolourises a weak solu-
tion of potassic permanganate. As a test, if we expire through distilled water, and this water
be set. aside for some time in a warm place, it will soon become fcetid. We must also take into
consideration the products of combustion ; thus 1 cubic foot of coal-gas, when burned, destroys
all the O in 8 cubic feet of air (Parkes). ]

Methods.—In ordinary rooms, where every person is allowed the necessary cubic space (1000
cubic feet), the air is sufficiently renewed by means of the pores in the walls of the room, by the
opening and shutting of doors, and by the fireplace, provided the damper is kept open. It is
most important to notice that the natural ventilation be not interfered with by dampness of the
walls, for this influences the pores very greatly. At the same time, damp walls are injurious to
health by conducting away heat, and in them the germs of infectious diseases may develop.

[Natural Ventilation.—By this term is meant the ventilation brought about by the ordinary
forces acting in nature ; such as diffusion of gases, the action of winds, and the movements
excited owing to the different densities of air at unequal temperatures. ]

[Artificial Ventilation.—Various methods are in use for ventilating public buildings and
-dwelling-houses. Two principles are adopted for the former, viz., extraction and propulsion of
air, In the former method, the air is sucked out of the rooms by a fan or other apparatus, while
in the latter, air is forced into the rooms, the air being previously heated to the necessary
temperature. |

[A very convenient method of introducing air into a room is by means of Tobin’s tubes,
placed in the walls. The air enters through these tubes from the outside near the floor, and is
carried up six or more feet, to an opening in the wall ; the cool air thus descends slowly. For
a sitting-room, a convenient plan of window ventilation is H. Bird’s Method :—Raise the
lower sash and place under it, so as to fill up the opening, a piece of. wood 3 or 4 inches high.
Air will then pass in, in an upward direction, between the upper part of the lower sash-frame
and the lower part of the upper one. ]

138. FORMATION OF MUCUS, SPUTUM.—The respiratory mucous mem-
brane is covered normally with a thin layer of mucus (fig. 130, a). It so far inhibits
the formation of new mucus by protecting the mucous glands from the action of
cold or other irritative agents. New mucus is secreted as that already formed is
removed. An increased secretion accompanies congestion of the respiratory mucous
membrane [or any local irritation]. ~ Division of the nerves on one side of the
trachea (cat) causes redness of the tracheal mucous membrane and increased secre-
tion (Rossbach), [but the two processes do not stand in the relation of cause and
effect]. The secretion cannot be excited by stimulating the nerves going to the

202 -o+ THE SPUTUM.

mucous membrane. This merely causes anemia of the mucous membrane, while
the secretion continues. | . eit

Modifying Conditions.—If ice be placed on the belly of an animal so as to cause the animal
‘* to take a cold,” the respiratory mucous membrane first becomes pale, and afterwards there is.
a copious mucous secretion, the membrane becoming deeply congested. The injection of sodium
carbonate and ammonium chloride into the blood limits the secretion, The local application of
alum, silver nitrate, or tannic acid, makes the mucous membrane turbid, and the epithelium is
shed, The secretion is excited by apomorphin,{emetin, pilocarpin, and ipecacuanha when given
internally, while it is limited by atropin and morphia (Rosshach). :

[Expectorants favour the removal of the secretions from the air-passages. This they may do.
either by (a) altering the character and qualities of the secretion itself, or (b) by affecting ‘the
expulsive mechanism. Some of the drugs already mentioned are examples of the first class.
The second class act chiefly by influencing the respiratory centre, e.g., ipecacuanha, strychnia,
ammonia, senega ; emetics also act energetically as expectorants, as in some cases of chronic
bronchitis ; warmth and moisture in the air are also powerful adjuncts. ]

Sputum.— Under normal circumstances, some mucus—mixed with a little saliva—
may be coughed up from the back of the throat. In catarrhal conditions of the

Fig. 149.
Various objects found in sputum. 1, detritus and particles of dust; 2, alveolar epithelium
with pigment ; 3, fatty and pigmented alveolar epithelium ; 4, alveolar epithelium with
myelin-forms ; 5, free myelin-forms ; 6, 7, ciliated epithelium, some without cilia; 8,
squamous epithelium from the mouth ; 9, leucocytes ; 10, elastic fibres ; 11, fibrin-cast of a
small bronchus ; 12, leptothrix buccalis with cocci, bacteria, and spirochaetae ; a, fatty acid
crystals and free fatty granules ; b, hematoidin ; c, Charcot’s crystals ; d, cholesterin.
respiratory mucous membrane, the sputum is greatly increased in amount, and is.
often mixed with other characteristic products. Microscopically, sputum con-
tains— 7
1. Epithelial Cells, chiefly squames from the mouth and pharynx (fig. 149),
more rarely alveolar epithelium and ciliated epithelium (7) from the respiratory
passages. They are often altered owing to maceration or other changes, Thus.
some cells may have lost their cilia (6). rides on tee ted fear i 7
The epithelium of the alveoli (2) is squamous epithelium, the cells being two to four times.
the breadth of a colourless blood-corpuscle. These cells oceur chiefly in the morning sputum in
individuals over 30 years of age. In younger persons their presence indicates a pathological
condition of the pulmonary, parenchyma, | z / y hots ) oa

’
:

~ - ACTION OF THE ATMOSPHERIC PRESSURE, 203

. They often undergo fatty degeneration, ana they may contain pigment-granules (3); or they
may present the appearance of what Buhl has called ‘‘ myelin degenerated cells,” i.e., cells filled
with clear refractive drops of various sizes, some colourless, others with coloured particles, the latter
having been absorbed (4). Mucin in the form of myelin drops (5) is always present in sputum.

2. Lymphoid cells (9) are colourless blood-corpuscles which have wandered out
of the blood-vessels ; they are most numerous in yellow sputum, and less numerous
in the clear mucus-like excretion. The lymph-cells often present alterations in their
characters ; they may be shrivelled up, fatty, or present a granular appearance.

The fluid substance of the sputum contains much mucus, arising from the
mucous glands and goblet cells, together with nuclein, and lecithin, and the con-
stituents of saliva, according to the amount of the latter mixed with the secretion.
Albumin occurs only during the inflammation of the respiratory passages, and its
amount increases with the degree of inflammation, Urea has been found in cases
of nephritis,
~ In cases of catarrh, the sputum is at first usually sticky and clear (sputa cruda), but later it
becomes more firm and yellow (sputa cocta). Under pathological conditions, there may be found
in the sputum—(qa) red blood-corpuscles from rupture of a blood-vessel. () Elastic-fibres (10)
from disintegration of the alveoli of the lung; usually the bundles are fine, curved, and the
fibres branched. [In certain cases it is well to add a solution of caustic potash, which dissolves
most of the other elements, leaving the elastic fibres untouched.] Their presence always
indicates destruction of the lung-tissue. (c) Colourless plugs of fibrin (11), casts of the smaller
or larger bronchi, occur in some cases of fibrinous exudation into the finer air-passages. _ (d)
Crystals of various kinds—crystals of fatty acids in bundles of fine needles (fig. 149, 7). They
indicate great decomposition of the stagnant secretion. Leucin and tyrosin crystals are rare
(§ 269). Tyrosin occurs in considerable amount when an old abscess breaks into the lungs.
Colourless, sharp-pointed, octagonal or rhombic plates—Charcot’s crystals (c)—have been found
in the expectoration in asthma, and exudative affections of the bronchi. Hematoidin ()) and
cholesterin crystals (@) occur much more rarely. ,

Fungi and other lowly organisms are taken in during inspiration (§ 136). The threads of
Leptothrix buccalis (12), detached from the teeth, are frequently found.(§ 147). Mycelium and
spores are found in thrush (Oidium albicans), especially in the mouths of sucking infants. In
malodorous’ expectoration rod-shaped bacteria are present. In pulmonary gangrene are found
monads, and cercomonads ; in pulmonary phthisis the tubercle bacillus ; very rarely sarcina,
which, however, is often found in gastric catarrh in the stomach and also in the urine (§ 270).

Physical Characters,—Sputum, with reference to its physical characters, is described as
mucous, nvuco-purulent, or purulent.

Abnormal coloration of the sputum—red from blood ; when the blood remains long in the
lung it undergoes a regular series of changes, and tinges the sputum dark-red, bluish-brown,
brownish-yellow, deep yellow, yellowish-green, or grass-green. The sputum is sometimes
yellow in jaundice. The sputum may be tinged by what is inspired [as in the case of the
**black-spit ” of miners].

The odour of the sputum is more or less unpleasant. It becomes very disagreeable when it
has remained long in pathological lung-cavities, and it is stinking in gangrene of the lung.

139. ACTION OF THE ATMOSPHERIC PRESSURE.—At the normal
pressure of the atmosphere (height of the barometer, 760 millimetres Hg), pressure is
exerted upon the entire surface of the body = 15,000 to 20,000 kilos., according to
the extent of the superficial area. This pressure acts equally on all sides upon the
body, and also occurs in all internal cavities containing air, both those that are con-
stantly filled with air (the respiratory passages and the spaces in the superior maxil-
lary, frontal, and ethmoid bones), and those that are temporarily in direct communi-
cation with the outer air (the digestive tract and tympanum). As the fluids of the
body (blood, lymph, secretions, parenchymatous juices) are practically incompres-
sible, their volume remains unchanged under the pressure ; but they absorb gases
from the air corresponding to the prevailing pressure (7.¢., the partial pressure of
the individual gases), and according to their temperature (§ 33). The solids
consist of elementary parts (cells and fibres), each of which presents only a micro-
scopic surface to the pressure, so that for each cell the prevailing pressure
of the air can only be calculated at a few millimetres—a pressure under
which the most delicate histological tissues undergo development. As an example

204 ACTION OF DIMINISHED ATMOSPHERIC PRESSURE.

of the action of the pressure of the atmospheric pressure upon large masses, take
that brought about by the adhesion of the smooth, sticky, moist, articular surfaces
of the shoulder and hip joints ; the arm and the leg are supported without the
action of muscles. The thigh-bone remains in its socket after section of all the
muscles and its capsule. Even when the cotyloid cavity is perforated, the head of
the femur does not fall out of its socket. The ordinary barometric variations affect
the respiration—a rise of the barometric pressure excites, while a fall diminishes,
the respirations. The absolute amount of CO, remains the same (§ 127, 8).

Great diminution of the atmospheric pressure, such as occurs in ballooning (highest ascent,
8600 metres), or in ascending mountains, causes a series of characteristic phenomena :—(1) In
consequence of the diminution of the pressure upon the gas directly in contact with the air,
they become greatly congested, hence there is redness and swelling of the skin and free mucous
membranes ; there may be hemorrhage from the nose, lungs, gums ; turgidity of the cutaneous
veins ; copious secretion of sweat; great secretion of mucus. (2) A feeling of weight in the
limbs, a pressing outwards of the tympanic membrane (until the tension is equilibrated by
opening the Eustachian tube), and as a consequence noises in the ears and difficulty of hearing.
(3) In consequence of the diminished tension of the O in the air (§ 129), there is difficulty of
breathing, pain in the chest, whereby the respirations (and pulse) become more rapid, ph
and irregular. When the atmospheric pressure is diminished 4-4, the amount of O in the blood
is diminished, the CO, is imperfectly removed from the blood, and in consequence there is
diminished oxidation within the body. When the atmospheric pressure is diminished to one-
half, the amount of CO, in arterial blood is lessened ; and the amount of N diminishes pro-
portionally with the decrease of the atmospheric pressure. The diminished tension of the air
prevents the vibrations of the vocal cords from occurring so forcibly, and hence the voice is feeble.
(5) In consequence of the amount of blood in the skin, the internal organs are relatively anemic ;
hence, there is diminished secretion of urine, muscular weakness, disturbances of digestion,
dulness of the senses, and it may be unconsciousness, and all these phenomena are intensified by
the conditions mentioned under (3). Some of these phenomena are modified by usage. The
highest limit at which a man may still retain his senses is placed by Tissandier at an elevation
of 8000 metres (280 mm. Hg). In dogs the blood-pressure falls, and the pulse becomes small
and diminished in frequency, when the atmospheric pressure falls to 200 mm. Hg.

Those who live upon high mountains suffer from a disease ‘‘ mal de montagne,” which consists
essentially in the above symptoms, although it is sometimes complicated with anemia of the
internal organs. Al. v. Humboldt found that in those who lived on the Andes the thorax was
capacious. At 6000 to 8000 feet above sea-level, water contains only one-third of the absorbed
gases, so that fishes cannot live in it. Animals may be subjected to a further diminution of the
atmospheric pressure by being placed under the receiver of an air-pump. Birds die when the
pressure is reduced to 120 mm. Hg; mammals at 40 mm. Hg; frogs endure repeated evacua-
tions of the receiver, whereby they are much distended, owing to the escape of gases and water,
but after the entrance of air they become greatly compressed. The cause of death in mammals
is ascribed hy Hoppe-Seyler to the evolution of bubbles of gas in the blood ; these bubbles stop
up the capillaries, and the circulation is arrested. Local diminution of the atmospheric presswre
causes marked congestion and swelling of the part, as occurs when a cupping-glass is used,

Great increase of the atmospheric pressure causes phenomena, for the most part, the reverse
of the foregoing, as in pneumatic cabinets and in diving-bells, where men may work even under
44 atmospheres pressure. (1) Paleness and dryness of the external surfaces, collapse of the
cutaneous veins, diminution of perspiration, and mucous secretions. (2) The tympanic mem-
brane is pressed inwards (until the air escapes through the Eustachian tube, after causing a
sharp sound), acute sounds are heard, pain in the ears, and difficulty of hearing. (3) ‘A feeling
of lightness and freshness during respiration, the respiration becomes slower (by 2-4 per minute),
inspiration easier and shorter, expiration lengthened, the pause distinct. The capacity of the
lungs increases, owing to the freer movement of the diaphragm, in consequence of the diminu-
tion of the intestinal gases. Owing to the more rapid oxidations in the body, muscular move-
ment is easier and more active. The O absorbed and the CO, excreted are increased. The
venous blood is reddened. (4) Difficulty of speaking, alteration of the tone of the voice,
inability to whistle. (5) Increase of the urinary secretion, more muscular energy, more rapid
metabolism, increased appetite, subjective feeling of warmth, pulse beats slower, and pulse-curve
is lower (compare § 74). In animals subjected to excessively i h atmospheric pressure, P, Bert
found that the arterial blood contained 30 vols. per cent. O (at 760 mm. Hg); when the
amount rose to 35 vol. per cent., death occurred with convulsions. Compressed air has been
used for therapeutical purposes, but in doing so a too rapid increase of the pressure is to be —
avoided. Waldenburg has constructed such an apparatus, which may be used for the respira-
tion of air under a greater or less pressure. ;

Frogs, when placed in compressed O (at 14 atmospheres), exhibit the same phenomena as if

COMPARATIVE AND HISTORICAL. 205

they were in a vacuum, or pure N. There is paralysis of the central nervous system, sometimes
preceded by convulsions, The heart ceases to beat (not the lymph hearts), while the excitability
of the motor nerves is lost at the same time, and lastly the direct muscular excitability disappears.
An excised frog’s heart placed in O under a very high pressure (18 atmospheres), scarcely beats
one-fourth of the time during which it pulsates in air, If the heart be exposed to the air
again, it begins to beat, so that compressed O renders the vitality of the heart latent before
abolishing it.

_ Phosphorus retains its luminosity under a high pressure in O, but this is not the case with

_ the luminous organisms, ¢.g., Lampyris, and luminous bacteria. High atmospheric pressure is

also injurious to plants.

140. COMPARATIVE AND HISTORICAL. —Mammals have lungs similar to those of man.
The lungs of birds are spongy, and united to the chest-wall, while there are openings on their
surface communicating with thin-walled ‘‘ air-sacs,” which are placed amongst the viscera.
The air-sacs communicate with cavities in the bones, which give the latter great lightness. The
diaphragm is absent. In reptiles the lungs are divided into greater and smaller compartments ;
in snakes one lung is abortive, while the other has the elongated form of the body. The amphi-
bians (frog) possess two simple lungs, each of which represents an enormous infundibulum with
its alveoli. The frog pumps air into its lungs by the contraction of its throat, the nostrils
being closed and the glottis opened. When young—until their metamorphosis—frogs breathe
like fishes by means of gills. The perennibranchiate amphibians (Proteus) retain their gills
throughout life. Amongst fishes, which breathe by gills and use the O absorbed by the water,
the Dipnoi have in addition to gills a swim-bladder provided with afferent and efferent vessels,
which is comparable to the lung. The Cobitis respires also with its intestine. Insects and
centipedes respire by ‘‘ trachee,” which are branched canals distributed throughout the body ;
they open on the surface of the body by openings (stigmata) which can be closed. Spiders
respire by means of traches and tracheal sacs, crabs by gills. The molluscs and cephalopods
have gills ; some gasteropods have gills and others lungs. Amongst the lower invertebrata some
breathe by gills, others by meaus of a special ‘‘ water-vascular system,” and others again by no
special organs.

Historical. —Aristotle (384 B.c.) regarded the object of respiration to be the cooling of the
body, so as to moderate the internal warmth. He observed correctly that the warmest animals
breathe most actively, but in interpreting the fact he reversed the cause and effect. Galen
(131-203 a.p.) thought that the ‘‘soot” was removed from the body along with the expired
water. The most important experiments on the mechanics of respiration date from Galen ; he
observed that the lungs passively follow the movements of the chest ; that the diaphragm is the
most important muscle of inspiration ; that the external intercostals are inspiratory ; and the
internal, expiratory. He divided the intercostal nerves and muscles, and observed that loss of
voice occurred. On dividing the spinal cord higher and higher, he found that as he did so the
muscles of the thorax lying higher up became paralysed. Oribasius (360 a.D.) observed that in
double pneumothorax both lungs collapsed. Vesalius (1540) first described artificial respiration
as a means of restoring the beat of the heart. Malpighi (1661) described the structure of the
lungs. J. A. Borelli (+ 1679) gave the first fundamental description of the mechanism of .the
respiratory movements. The chemical processes of respiration could only be known after the
discovery of the individual gases therein concerned. Van Helmont (+ 1644) detected CO,.
[Joseph Black (1757) discovered that CO,, or ‘‘ fixed air,” is given out during expiration.] In
1774 Priestley discovered O. Lavoisier detected N (1775), and ascertained the composition of
atmospheric air, and he regarded the formation of CO, and H,0O of the breath as a result of a
combustion within the lungs themselves. J. Ingen-Houss (1730-1799) discovered the respira-
tion of plants. Vogel.and others proved the existence of CO, in venous blood, and Hotimann
and others that of O in arterial blood. The more complete conception of the exchange of
gases was, however, only possible after Magnus had extracted and analysed the gases of arterial
and venous blood (§ 36).

Physiology of Digestion.

14]. THE MOUTH AND ITS GLANDS.—The mucous membrane of the cavity of the mouth,
which becomes continuous with the skin at the red margin of the lips, has a number of seba-
ceous glands in the region of the red part of the lip. The buccal mucous membrane consists
of bundles of fine fibrous tissue mixed with elastic fibres, which traverse it in every direction.
Papille—simple or compound—occur near the free surfaces) The sub-mucous tissue, which
is directly continuous with the fibrous tissue of the mucous membrane itself, is thickest where
the mucous membrane is thickest, and densest where it is firmly fixed to the periosteum of the
bone and to the gum ; it is thinnest where the mucous membrane is
most movable, and where there are most folds. The cavity of the
mouth is lined by stratified squamous epithelium (fig. 150), which
is thickest, as a rule, where the longest papille occur. :

All the glands of the mouth, including the salivary glands,

Os may be divided into different classes according to the nature
‘ | , of their secretions. bie

J 1. The serous or albuminous glands [true salivary],

/) whose secretion contains a. certain amount of albumin, e..,

the human parotid. . /

2. The mucous glands, whose secretion, in. addition to

. “st some albumin contains the characteristic constituent mucin.

Fig. 150. 3. The mixed [or muco-salivary] glands, some of the

Cells of stratified squamous acini secreting an albuminous fluid and others mucin, ¢.g., the

agar gsm Tale human maxillary gland.

kes ue s,. salivary Numerous mucous glands (labial, buccal, palatine, lingual, molar)
3 ; have the appearance of small macroscopic bodies lying in the sub-
mucosa. They are branched tubular glands, and the contents of: their secretory cells consist
partly of mucin, which is expelled from them during secretion. The excretory ducts of these
glands, which are lined by cylindrical epithelium, are constricted where they enter the mouth.
Not unfrequently one duct receives the secretion of a neighbouring gland.

The glands of the tongue form two groups, which differ morphologically and physiologically.
(1) The mucous glands (Weber's glands), occurring chiefly near the root of the tongue, are
branched tubular glands lined with clear transparent secretory cells whose nuclei are placed
near the attached end of the cells. The acini have a distinct membrana propria. (2) The
serous glands (Hbner’s) are acinous glands occurring in the region of the circumvallate papille
(and in animals near the papillée foliate). They are lined with turbid granular epithelium with
a central nucleus, and secrete saliva. (3) The glands of Blandin and Nuhn are placed near the
tip of the tongue, and consist of mucous and serous acini, so that they are mixed glands
(Podwisotzky).

The blood-vessels are moderately abundant, and the larger trunks lie in the sub-mucosa,
Mace a8 finer twigs penetrate into the papille, where they form either a capillary network or
simple loops.

The tate lymphatics lie in the sub-mucosa, whilst the finer branches form a fine network
placed in the mucosa. The lymph-follicles also belong to the lymphatic system (§ 197). On
the dorsum of the posterior part of the tongue they form an almost continuous layer. They are
round or oval (1-1°5 mm. in diameter), lying in the sub-mucosa, and consist of adenoid tissue
loaded with lymph-corpuscles, The outer part of the adenoid reticulum is compressed so as to

1

7
;
1a

THE MOUTH AND ITS GLANDS. . 207.

form a kind of capsule for each follicle. Similar follicles occur in the intestine as solitary
follicles ; in the small intestine they are collected together into Peyer’s patches, and in the
spleen they occur as Malpighian corpuscles. On the dorsum of the tongue several of these
follicles form a slightly oval elevation, which is surrounded by connective-tissue. In the
centre of this elevation there is a depression,
into which a mucous gland opens, which fills .
the small crater with mucus (fig. 151). Closed
The tonsils have fundamentally the same ¢ohiiele.
structure. On their surface are a number of
depressions into which the ducts of small
mucous glands open. These depressions are
surrounded by groups (10-20) of lymph- B
follicles, and the whole is environed -by a Depression.
capsule of connective-tissue (fig. 152). Large Adenoid —
lymph-spaces, communicating with lym- "sUe-
phatics, occur in the neighbourhood of the
tonsils, but as yet a direct connection between
the spaces in the follicles and the lymph-
vessels has not been proved to exist. Similar
structures occur in the tubal and pharyngeal
tonsils. [Stohr asserts that an enormous num-
ber of leucocytes wander out of the tonsils, Mucous
solitary and Peyer’s glands, and the adenoid
tissue of the bronchial mucous membrane.
‘The cells pass out between the epithelial cells,
but do not pass into the interior of the latter. ]

Epithelium.

Closed
follicles.

~

—s

7

Fig. 151.
Section of a mucous follicle from the tongue.
Nerves.—Numerous medullated nerve-fibres occur in the sub-mucosa, pass into the mucosa,
and terminate partly in the individual papille in Krause’s end-bulbs, which are most abundant
in.the lips and. soft palate, and not so numerous in the cheeks and floor of the mouth. The
| nerves administer not only to common sensation, but they are also the organs of transmissions

for tactile (heat and pressure)
impressions. It is highly
probable, however, that some
nerve-fibres end in fine ter-
minal fibrils, between the
‘epithelial cells, as in the

‘cornea and elsewhere.
[Secretory glands may be
simple (fig. 153, B, C, D) or
compound (E). In the latter
case the duct is branched.
In the process of develop-
ment, a solid process of the
. epithelium sinks into the
| subjacent fibrous tissue, and, ie i We?
to form a simple gland, a Mes sess a Eee \ Tunica:
y cavity appears in this bud, AN ee
but for a compound gland,
other epithelial buds sprout
from its blind end. © Each
bud acquires a central cavity,
these elongate and increase
in number, thus forming a
much branched system, the

terminal blind ends formi , eee ‘ : Se sa
thefeini, alveoli ae eae Vertical section of a human tonsil, x 20. 1, cavity ; 2, epithelium

_ Ifthealveoli infiltrated with leucocytes below and on the left, but free on the
seghertal sais onbongr right ; 3, adenoid tissue with sections a, J, ¢, of masses of it ;
gland is called a compound 4, fibrous sheath ; 5, séction of a gland-duct ; d, blood-vessel.

tubular gland. Thus in the compound glands some parts are ‘secretory, and others act as ducts,
while in the simple glands, all the parts may be secretory. All the glands opening on thé surface
‘of the body are of epiblastic origin. The secretory cells lining the acini rest on a basement
membrane, and outside this are the lymph-spaces and capillary blood-vessels. ] mr .

| 1142. THE SALIVARY GLANDS,—The three pairs of salivary glands, sub-maxillary, sub-
lingual, and parotid, are compound tubular glands. Fig. 155, A, shows .a fine duct, terminating
in. the more or less. flask-shaped alveoli or-acini,.. [Each gland consists ofa: numberof lobes, and

Epithelium.

“OC

208 _ THE SALIVARY GLANDS,

each lobe in turn of a number of lobules, which, again, are composed of acini, Al]l these are held
together by a framework of connective-tissue, The larger branches of the duct lie between the
lobules, and constitute the interlobular ducts, giving branches to each lobule which they enter,
: —_ constituting the intralobular ducts,

_| ;

which branch and finally terminate’ in.
connection with the alveoli, by means
of an intermediary or intercalary part.
The larger interlobar and interlobular
ducts consist of a membrana. propria,
strengthened outside with fibrous and
elastic tissue, and in some places also by
non-striped muscle, while the ducts are
lined by columnar epithelial cells, In
the largest branches, there is a second
row of smaller cells, lying between the
large cells and the membrana propria,

Fig. 153.

Fig. 153.—Evolution of glands. <A, schema of skin; ep, epidermis; d, cutis with a capillary c;
B, simple gland with its blood-vessels ; C, D, more complex glands ; E, compound gland,
blood-vessels omitted.

Fig. 154.—Rodded epithelium lining the duct of a salivary gland,

Fig. 155,

A, duct and acini of the parotid gland of a dog ; B, acini of the sub-maxillary gland of a dog ;
c, refractive mucous cells ; d, granular half-moons of Gianuzzi ; C, similar alveoli after
prolonged secretion ; D, basket-shaped tissue-investment of an acinus; F, entrance of a
non-medullated nerve-fibre into a secretory cell, ( ;

The intralobular ducts are lined by a single layer of Large cylindrical epithelium with the:

nucleus about the middle of the cell, while the outer half of the cell is finely striated longitud-

inally, or ‘‘rodded,” which is due to fibrille (fig. 154); the inner half next the lumen igs

granular. The intermediary part is narrow, and is lined by a single layer of flattened cells,
each with an elongated oval nucleus, There is usually-a narrow neck,” where the intra-
lobular duct becomes continuous with the intermediary part, and here the cells are polyhedral. ]
The acini, or alveoli, are the parts where the sina process of secretion takes )
vary somewhat in shape—some are tubular, others branched, some are dilated and resemble a

Wyre
oe

THE STRUCTURE OF THE SALIVARY GLANDS. 209

Florence flask, and several of them usually open into one intermediary part of a duct. Each
alveolus is bounded by a basement membrane, with a reticulate structure made up of nucleated,
- branched, and anastomosing cells so as to resemble a basket (D). There is a homogeneous
membrane bounding the alveoli in addition to this basket-shaped structure, Immediately out-
side this membrane is a lymph-space, and outside this again the network of capillaries is
distributed, [The extent to which this lymph-space is filled with lymph determines the
distance of the capillaries from the membrana propria. The interalveolar lymph-spaces com-
municate with large lymph-spaces between the lobules, which in turn communicate with
perivascular lymphatics around the arteries and veins.] The lymphatics emerge from the gland
at the hilum,

The secretory cells vary in structure, according as the salivary gland is a mucous
[sub-maxillary and sub-lingual of the dog and cat], a serous [parotid of man and
mammals, and sub-maxillary of rabbit], or a mixed gland [human sub-maxillary
~ and sub-lingual]. |

Mucous Acini,—The secretory cells of mucous glands, and the mucous acini of mixed glands
(fig. 156), are lined by a single layer of ‘‘ mucin cells” (fig. 155, B, ce), which are large cells dis-
tended with mucin, or with a hypothetical
substance, mucigen, which yields mucin. The
mucin cells are more or less spheroidal in
shape, clear, shining, highly refractive, and
nearly fill the acinus, The flattened nucleus
is near the wall of the acinus. Each cell has a
fine process which overlaps the fixed parts of
the cells next to it. Owing to the body of
each cell being infiltrated. with mucin, these x
cells do not stain with carmine, although the
nucleus and its immediately investing proto- «:8%
plasm do. Another kind of cell occurs in the {/55758
sub-maxillary gland of the dog, It forms a
half-moon-shaped structwre lying in direct RAV
contact with the wall of the acinus (Gvanwzzz).
Each ‘‘half-moon’”’ or ‘‘ crescent ’’ consists
of a number of small, closely packed, angu-
lar, highly albuminous cells with small oval
nuclei, which, however, are separated only
with difficulty. Hence, Heidenhain has called
them ‘‘composite marginal cells” (B, d),
They are granular, darker, devoid of mucin,
and stain readily with pigments. [In the
sub-maxillary gland of the cat, there is a
complete layer of these ‘‘ marginal” carmine-
staining cells lying between the mucous cells
and the membrana propria. ]

[Serous Acini.—In true serous glands
(parotid of man and mammals) and in the
serous acini of mixed glands, the acini are lined by a single layer of secretory columnar finely-
granular cells, which in the quiescent condition completely fill the acinus, so that scarcely any
lumen is left. Just before secretion, or when these cells are quiescent, Langley has shown that
they are large and filled: with numerous granules, which obscure the presence of the nucleus.
As secretion takes place, these granules seem to be used up or discharged into the lumen ; at
least, the outer part-of each cell gradually becomes clear and more transparent, and this con-
dition spreads towards the inner part of the cell. ]

[In the mixed or muco-salivary glands (¢.g., human sub-maxillary) some of the alveoli are
mucous and others serous in their characters, but the latter are always far more numerous, and
the one kind of acinus is directly continuous with the others (fig. 156). ]

143. HISTOLOGICAL CHANGES DURING THE ACTIVITY OF THE
SALIVARY GLANDS.—[The condition of physiological activity of the gland-cells
is accompanied by changes in the histological characters of the secretory cells,
Changes in serous glands have been carefully studied in the parotid of the rabbit,
but the appearances vary somewhat, according as the glands. are examined in the
fresh condition or after hardening in various reagents, such as absolute alcohol.
When the gland is at rest, in a preparation hardened in alcohol, and stained with
carmine, the cells consist of a pale, almost uncoloured substance, with a few fine

O

Section of a human sub-maxillary gland. On
the left is a group of serous alveoli, and on the
right a group of mucous alveoli.

210 HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS.

granules, and a small, irregular, red-stained, shrivelled nucleus devoid of a nucleolus.
The appearance of the nucleus suggests the idea of its being shrivelled by the
action of the hardening reagent (fig. 157.] |

[During activity, if the gland be caused to secrete by stimulating the sympa-
thetic, all parts of the cells undergo a change (figs. 157, 158). In preparations
hardened in alcohol—(1) the cells diminish somewhat in size; (2) the nuclei
are no longer irregular, but round, with a sharp contour and nucleoli; (3) the sub-
stance of the cell itself is turbid owing to the diminution of the clear substance,
and the increase of the granules, especially near the nuclei; (4) at the same time,
the whole cell stains more deeply with carmine (Heidenhain). |

[On studying the changes which occur in a living serous gland, Langley found
that the substance of the cells of the parotid is pervaded by fine granules, which

Fig. 157. : Fig. 158.

Sections of a “‘serous” gland. The parotid of a rabbit, fig. 157, at rest; fig. 158, after

stimulation of the cervical sympathetic.

are so numerous as to obscure the nucleus, while the outlines of the cells are indis-
tinct. No lumen is visible in the acini during activity, the granules disappear
from the outer zone of the cells, the cells themselves becoming smaller and more
distinct, After prolonged secretion, the granules largely disappear from the cell-
substance except quite near the inner margin. The cells are smaller, their outlines
more distinct, their spherical nuclei apparent, and the lumen of .the acini is wide
and distinct. Thus, it is evident that, during rest, granules are manufactured,
which ‘disappear during the activity of the cells, the disappearance taking place
from without inwards. Similar changes occur in the cells of the pancreas. |

[More complex changes occur in the mucous glands, such as the sub-maxillary

or orbital glands of the dog (Lavdovsky). The appearances vary according to the
intensity and duration of the secretory activity. The mucous cells at rest are large,
clear, and refractive, containing a flattened nucleus (fig. 155, C), surrounded with a
small amount of protoplasm, and placed near the basement membrane. \ The clear
substance does not stain with carmine, and consists of mucigen lying in the wide
spaces of an intracellular plexus of fibrils. After prolonged secretion, produced,
it may be, by strong and continued stimulation of the chorda, the mucous cells of
the sub-maxillary gland of the dog undergo a great change.| - The distended, re-
fractive, and ‘‘ mucous cells,” which occur in the quiescent gland, and which donot
stain with carmine, do not appear after the gland has been in a state of activity.
Their place is taken by small dark protoplasmic cells devoid of mucin (fig. 155, C).
These cells readily stain with carmine, whilst their nucleus is scarcely, if at all,
coloured by the dye. The researches of R. Heidenhain (1868) have shed much
light on the secretory activity of the salivary glands. we:
The change may be produced in two ways. Either it is due to the ‘‘ mucous cells” rs

secretion becoming broken up, so that they yield their mucin directly to the saliva; in salivariech }
> a

—_—
OO

- THE NERVES OF THE SALIVARY GLANDS. 2If

in mucin, small microscopic pieces of mucin are found, and sometimes mucous cells themselves
are present. Or, we must assume that the mucous cells simply eliminate the mucin from their
bodies (Ewald, Stéhr); while, after a period of rest, new mucin is formed. According to this
view, the dark granular cells of the glands, after active secretion, are simply mucous cells, which
have given out theirmucin. Ifweassume, with Heidenhain, that the mucous cells break up, then
these granular non-mucous cells must be regarded as new formations produced by the prolifera-
tion and growth of the composite marginal cells, 7.¢., the crescents, or half-moons of Gianuzzi.
[During rest, the protoplasm seems to manufacture mucigen, which is changed
into and discharged as mucin in the secretion, when the gland is actively secreting.
Thus, the cells become smaller, but the protoplasm of the cell seems to increase,

new mucigen is manufactured during rest, and the cycle is repeated. |

144, THE NERVES OF THE SALIVARY GLANDS.—The nerves are for the
most part medullated, and enter at the hilum of the gland, where they form a
rich plexus provided with ganglia between the lobules. [There are no ganglia in
the parotid gland (Ken). |

All the salivary glands are supplied by branches from two different nerves—from
the sympathetic and from a cranial nerve.

1. The sympathetic nerve gives branches (a) to the sub-maxillary and the sub-
lingual glands, derived from the plexus on the external maxillary artery ; (0) to the
parotid gland from the carotid plexus (fig. 159).

Lingual,

Scheme of the nerves of the salivary glands. P., pons; M.O., medulla oblongata; J.N., nerve of
Jacobson ; O., S.M., I.M., ophthalmic, superior, and inferior maxillary divisions of fifth
nerve, V.; VII., seventh nerve; S.s.p., small superficial petrosal nerve ; Vag., vagus ;
Sym., sympathetic ; O.G., otic, and 8.G., submaxillary ganglia ; P., S., and 8.L., parotid,
submaxillary, and sublingual glands ; T., tongue,

2. The facial nerve gives branches to the sub-maxillary and sub-lingual glands from
the chorda tympani, which accompanies the lingual branch of the fifth nerve (fig. 159).
The branches to the parotid arise from the tympanic branch of the glosso-pharyngeal
nerve (dog). The tympanic plexus sends fibres to the small superficial petrosal
nerve, and with it these fibres run to the anterior surface of the pyramid in the
temporal bone, emerging from the skull through a fissure between the petrous and
great wing of the sphenoid, and then joining the otic ganglion. This ganglion
sends branches to the auriculo-temporal nerve (itself derived from the third branch
of the trigeminus), which, as it passes upwards to the temporal region under cover
of the parotid, gives branches to this gland. .

_ The sub-maxillary ganglion, which gives branches to the sub-maxillary and sub-

lingual glands, receives fibres from the tympanico-lingual nerve (chorda tympani)

as well as sympathetic fibres from the-plexus on the external maxillary artery.

Termination of the Nerve-Fibres.—With regard to the ultimate distribution of
these nerves we can distinguish (1) the vaso-motor nerves, which give branches to
the walls of the blood-vessels, and (2) the secretory nerves proper. “ptsld

212 ACTION OF NERVES ON THE SECRETION OF SALIVA.

Pfliiger states, with regard to the latter, that (a) medullated nerve-fibres penetrate the acini;
the Sheath of Schwann unites with the membrana propria of the acinus ; the medullated fibre
—still medullated—passes between the secretory cells, where it divides and becomes non-
medullated, and its axial cylinder terminates in connection with the nucleus of a secretory cell.
[This, however, is not proved] (fig. 155, F). (b) According to Pfliiger, some of the nerve-fibres end
in multipolar ganglion cells, which lie outside the wall of the acinus, and these cells send
branches to the secretory cells of the acini, [These cells probably correspond to the branched
cells of the basket-shaped structure.] (c) Again, he Acoreibes medullated fibres which enter the
attached end of the cylindrical epithelium lining the excretory ducts of the glands (E). Pfliiger
thinks that those fibres entering the acini directly are cerebral, while those with ganglia in their
course are derived from the sympathetic system. [(@) The direct termination of nerve-fibres has
been observed in the salivary glands of the cockroach by Kupffer. ]

145. ACTION OF THE NERVOUS SYSTEM ON THE SECRETION OF
SALIVA.—A. Sub-maxillary Gland.—Stimulation of the facial nerve at its
origin causes a profuse secretion of a thin watery saliva, which contains a very
small amount of specific constituents. Simultaneously with the act of secretion, the
blood-vessels of the glands dilate, and the capillaries are so distended that the pulsatile
movement in the arteries is propagated into the veins. Nearly four times as much
blood flows out of the veins (Cl. Bernard), the blood being of a bright red colour,
and containing one-third more O than the venous blood of the non-stimulated gland.
Notwithstanding this relatively high percentage of O, the secreting gland uses more
O than the passive gland (§ 131, 1).

(I. Stimulation of Chorda.—If a cannula be placed in Wharton’s duct, e.g., in
a dog, and the chorda tympani be divided, no secretion flows from the cannula.
On stimulating the peripheral end of the chorda tympani with an interrupted
current of electricity, the same results—copious secretion of saliva and vascular
dilatation, with increased flow of blood through the gland—occur as when the
origin of the seventh nerve itself is stimulated. —The watery saliva is called chorda
saliva. |

Two functionally different kinds of nerve-fibres occur in the facial nerve—(1)
true secretory fibres, (2) vaso-dilator fibres.

II. Stimulation of the sympathetic nerve causes a scanty amount of a very
thick, sticky, mucous secretion, in which the specific salivary constituents, mucin,
and the salivary corpuscles are very abundant. The specific gravity of the saliva
is raised from 1007 to 1010. Simultaneously the blood-vessels become contracted,
so that the blood flows more slowly from the veins, and has a dark bluish colour.

The sympathetic also contains two kinds of nerve-fibres—(1) true secretory
fibres, and (2) vaso-constrictor fibres. :

[Electrical Variations during Secretion.—That changes in the electromotive properties of
glands occur during secretion was shown in the frog’s skin. Bayliss and Bradford find that the
same is true of the sub-maxillary gland (dog). uring secretion, the excitatory change on
stimulating the chorda is a positive variation of the current of rest (the hilum of the gland
_ becoming more positive), but it is frequently followed by a second phase of opposite sign, The
latent period is always very short, about 0°37”, Atropin abolishes the chorda variation. On
stimulating the sympathetic, the excitatory change is of an opposite sign to that of the chorda,
_and the hilum becomes less positive, so that there is a negative variation. It requires a more

werful stimulus, is less in amount, and its latent period is longer (2’’-4”), while atropin lessens

ut does not abolish it.]

Relation to Stimulus.—On stimulating the cerebral nerves, at first with a weak and gradually
with a stronger stimulus, there is a gradual development of the secretion in which the solid
constituents—occasionally the organic—are increased (Heidenhain). If a strong stimulus be
applied for a long time, the secretion diminishes, becomes watery, and is poor in specific con-
stituents, especially in the organic elements, which are more affected than the inorganic (C,
Ludwig and Becher). After bole stimulation of the sympathetic, the secretion resembles
the chorda saliva. It would seem, therefore, that the chorda and sympathetic saliva are not
specifically distinct, but vary only in degree, On continuing the stimulation of the nerves up to
a certain maximal limit, the rapidity of secretion becomes greater, and the percentage of salts
also increases to a certain maximum, and this independently of the former condition of the
glands. The percentage of organic constituents also depends on the strength of the nervous
stimulation, but not on this alone, as it is essentially contingent upon the condition of the gland

ACTION OF NERVES ON THE SECRETION OF SALIVA. 213

before the secretion took place, and it also depends upon the duration and intensity of the
previous secretory activity. Very strong stimulation of the gland leaves an ‘‘ after-effect,”
which predisposes it to give off organic constituents into the secretion (Heidenhain). <A latent
period of 1°2 sec. to 24 sec. may elapse between the nerve-stimulation and the beginning of the
secretion.

[Langley has shown that in the cat the sympathetic saliva of the sub-maxillary gland is less
viscid than the chorda saliva. ]

Relation to Blood-Supply.— The secretion of saliva is not simply the result of the
amount of blood in the glands ; that there isa factor independent of the changes in
the state of the vessels is shown by the following facts :—

(1) The secretory activity of the glands when their nerves are stimulated continues for some
time after the blood-vessels of the gland have been ligatured. [If the head of a rabbit be cut
off, stimulation of the seventh nerve, above where the chorda leaves it, causes a flow of saliva,
which cannot be accounted for on the supposition that the saliva already present in the salivary

- glands is forced out of them. Thus we may have secretion without a blood-stream. The
saliva is really secreted from the lymph present in the lymph-spaces of the gland (Ludwig). ]

(2) Atropin and daturin abolish the activity of the secretory fibres in the chorda
tympani, but do not affect’the vaso-dilator fibres (/Zeidenhain). The same results
occur after the injection of acids and alkalies into the excretory duct (Gianuzz0).

[Action of Atropin.—The vascular dilatation and the increased flow of saliva,
due to the activity of the secretory cells, produced by stimulation of the chorda
tympani, although they occur simultaneously, do not stand in the relation of cause
and effect. We may cause vascular dilatation without an increased flow of saliva,
as already stated (2). If atropin be given to an animal, stimulation of the chorda
produces dilatation of the blood-vessels, but no secretion of saliva. Atropin
paralyses the secretory fibres, but not the vaso-dilator fibres (fig. 160). The
increased supply of blood, while not causing, yet favours the act of secretion, by
placing a larger amount of pabulum at the disposal of the secretory elements, the
cells. |
Gh The pressure in the excretory duct of the salivary gland—measured by
means of a manometer tied into it—may be nearly twice as great as the pressure
within the arteries of the glands, or even in the carotid itself (Ludwig). The
pressure in Wharton’s duct may reach 200 mm. Hg.

[Secretory Pressure.—The experiment described under (3) proves, in a definite
manner, that the passage of the water from the blood-vessels, or at least from the
lymph into the acini of the gland, cannot be due to the blood-pressure ; that, in
fact, it is not a mere process of filtration, such as occurs in the glomeruli of the
kidney. In the case of the salivary gland, where the pressure within the gland
may be double that of the arterial pressure, the water actually moves from the
lymph-spaces against very great resistance. We can only account for this result
by ascribing it to the secretory activity of the gland-cells themselves. Whether
the activities of the gland-cells, as suggested by Heidenhain, are governed directly
by two distinct kinds of nerve-fibres, a set of solid-secreting fibres, and a set of
water-secreting fibres, remains to be proved. | .

(4) Just as in the case of muscles and nerves, the salivary glands become fatigued or
exhausted after prolonged action. This result may also be brought about by injecting acids or
alkalies into the duct, which shows that the secretory activity of the gland is independent of
the circulation (Gianuzzi).

All these facts lead us to conclude that the nerves exercise a direct effect upon the secretory
cells, apart from their action on the blood-vessels.

Extirpation of Salivary Glands.—When the chorda tympani is extirpated on one side in
young dogs, the sub-maxillary gland on that side does not develop so much—its weight is 50
per cent. less—while the mucous cells and.the “crescents” are smaller than on the sound side

(Bufalint).

During secretion, the temperature of the gland rises 1°5° C. (Ludwig), and the
blood flowing from the veins is often warmer than the arterial blood. [The electro-
motive changes are referred to at p. 212.] .

i) ie REFLEX SECRETION OF SALIVA,

‘“‘Paralytic Secretion ” of Saliva.—By this term is meant the continued secre-
tion of a thin watery saliva from the sub-maxillary gland, which occurs twenty-
four hours after the section of the cerebral nerves (chorda of the seventh), 7.¢., those
branches of them that go to this gland, whether the sympathetic be divided or not
(Cl. Bernard). It increases until the eighth day, after which it gradually diminishes,
while the gland-tissue degenerates. The injection of a small quantity of curara
into the artery of the gland also causes it. |

[Heidenhain showed that section of one chorda is followed by a continuous secretion of saliva
from both sub-maxillary glands. The term ‘‘ paralytic” secretion is applied to that which
takes place on the side on which the nerve is cut, and Langley proposes to call the secretion on
the opposite side the antilytic. Apnoea (§ 368) stops both the paralytic and antilytic secretion,
while dyspnoea increases the flow in both cases ; and as section of the sympathetic fibres to the
gland (where the chorda is cut) arrests the paralytic secretion excited by dyspnea, it is evident
that both the paralytic secretion and the secretion following dyspnoea are caused by stimuli
travelling down the sympathetic fibres. In the later stages of the paralytic secretion, the cause
is in the gland itself, for it goes on even if all the nerves passing to the gland be divided, and
is probably due to a local nerve-centre. In this stage the secretion is arrested by a large dose of
chloroform. The paralytic secretion, in the first stage, may be owing to a venous condition of
the blood acting on a central secretory centre whose excitability is increased ; and in the latter
stages probably on local nerve-centres within the gland. The fibres of the chorda in the cat are

sg ead at degenerated thirteen days after section (Langley). ]
[Histological Changes.—In the gland during paralytic secretion, the gland-cells of the alveoli

(serous, mucous, and demilunes) diminish in size and show the typical “ resting ” appearance,
even to a greater extent than the normal resting gland (Langley). ]

B. Sub-lingual Gland.—Very probably the same relations obtain as in the sub-
maxillary gland. |

C. Parotid Gland.—In the dog, stimulation of the sympathetic alone causes no
secretion ; it occurs when the glosso-pharyngeal branch to the parotid is simul-
taneously excited. This branch may be reached within the tympanum in the
tympanic plexus. A thick secretion containing much organic matter is thereby ob-
tained. Stimulation of the cerebral branch alone yields a clear thin watery secretion,
containing a very small amount of organic substances, but a considerable amount
of the salts of the saliva.

[Stimulation of Jacobson’s Nerve (Parotid of Dog)—
Total Solids. Salts. Organic Matter.
0°56 ° 0°24

Without sympathetic, : , : 56 °/, 0°31

With sympathetic, . ; ; : ; 2°42 °/, 0°36 2°06]
[Reflex Secretion of Saliva.—If a cannula be placed in Wharton’s duct, ¢.g., in a
dog, during fasting, no saliva will flow out, but on applying a sapid substance to the
mucous membrane of the mouth or
the tongue, there is a copious flow
of saliva. If the sympathetic nerve
Duct of Gland. be divided, secretion still takes place
when the mouth is stimulated, but if
the chorda tympani be cut, secretion
no longer takes place. Hence, the
Secreting Secretion is due toa reflex act; in
cells. this case, the lingual is the afferent,
and the chorda the efferent nerve
carrying impulses from a centre
situated in the medulla oblongata
(fig. 160).] In the intact body, the
secretion of saliva occurs through a

Mucous Membrane

Bloodvessels

of Gland.
Fig. 160. reflex stimulation of the nerves con-
Diagram of a salivary gland. cerned, whereby, under normal cir-

cumstances, the secretion is always watery (chorda or facial saliva). The centripetal
or afferent nerve-fibres concerned are :—(1) The nerves of taste. (2) The sensory -

REFLEX SECRETION OF SALIVA. . 215

branches of the trigeminus of the entire cavity of the mouth and the glosso-
pharyngeal (which appear to be capable of being stimulated by mechanical stimuli,
pressure, tension, displacement). The movements of mastication also cause a
secretion of saliva. Pfliiger found that one-third more saliva was secreted on the
side where mastication took place; and Cl. Bernard observed that the secretion
ceased in horses during the act of drinking. (3) The nerves of smell, excited by
certain odours. (4) The gastric branches of the vagus. A rush of saliva into the
mouth usually precedes the act of vomiting (§ 158).

(5) The stimulation of distant sensory nerves, ¢.g., the central end of the sciatic—certainly
through a complicated reflex mechanism—causes a secretion of saliva (Owsjannikow and
Tschierjew). Stimulation of the conjunctiva, ¢e.g., by applying an irritating fluid to the eye of
carnivorous animals, causes a reflex secretion of saliva (Aschenbrandt). Perhaps the secretion
of saliva which sometimes occurs during pregnancy is caused in a similar reflex manner.

(6) The movements of mastication excite secretion, but although, during the act of rumination;
this is the case in ruminants, in whom the process of mastication is very thorough, there is no
secretion from the sub-maxillary gland, although the parotid secretes (Colin, Ellenberger and
Hofmeister). .

The reflex centre for the secretion of saliva lies in the medulla oblongata, at
the origin of the seventh and ninth cranial nerves, The centre for the sympa-
thetic fibres is also placed here. ‘This region is connected by nerve-fibres
with the cerebrum; hence, the thought of a savoury morsel, sometimes,
when one is hungry, causes a rapid secretion of a thin watery fluid—[or, as we
say, ‘makes the mouth water”]. If the centre be stimulated directly by a
mechanical stimulus (puncture), salivation occurs, while asphyxia has the saine
effect. The reflex secretion of saliva may be inhibited by stimulation of certain
sensory nerves, ¢.g., by pulling out a loop of the intestine. Stimulation of the cortex
cerebri of a dog, near the sulcus cruciatus, is often followed by secretion of saliva.
. Disease of the brain in man sometimes causes a secretion of saliva, owing to the

effects produced on the intracranial centre. ;

So long as there is no stimulation of the nerves, there is no secretion of saliva, as
in sleep. Immediately after the section of all nerves, secretion stops, for a time
at least. .

Pathological Conditions and Poisons.—Certain affections, as inflammation of tae mouth,
neuralgia ; ulcers of the mucous membrane, and affections of the gums, due to teething or the
prolonged administration of mercury, often produce a copious secretion of saliva or ptyalism.
- Certain poisons cause the same effect by direct stimulation of the nerves, as Calabar bean
(physostigmin), digitalin, and especially pilocarpin. Many poisons, especially the narcotics—
above all, atropin—paralyse the secretory nerves, so that there is a cessation of the secretion and
the mouth becomes dry ; while the administration of muscarin in this condition causes secretion.
Pilocarpin acts on the chorda tympani, causing a profuse secretion, and if atropin be given, the
secretion is again arrested. Conversely, if the secretion be arrested by atropin, it may be
restored by the action of pilocarpin or physostigmin. Nicotin, in small. doses,. excites the
secretory nerves, but in large doses paralyses them. Daturin, cicutin, and iodide of ethylstrych-
nin, paralyse the chorda. The saliva is diminished in amount in man, in cases of paralysis of
the facial or sympathetic nerves, as is observed in unilateral paralysis of these nerves. a

[Sialogogues are those drugs which increase the secretion of saliva. Some are topical, and
take effect when applied to the mouth. They excite secretion reflexly by acting on the sensory
nerves of the mouth. They include acids, and various pungent bodies, such as mustard, ginger,
pyrethrum, tobacco, ether, and chloroform ; but they do not all produce the same effect on the
amount or quality of the saliva; others, the general sialogogues, cause salivation when intro-
duced into the blood; physostigmin, nicotin, pilocarpin, muscarin. The drugs named act after
all the nerves going to the gland are divided, so that they stimulate the peripheral ends of the
nerves in the glands. The two former also excite the central ends of the secretory nerves. ]

[Anti-sialics are those substances which diminish the secretion of saliva, and they may take
effect upon any part of the reflex arc, z.¢., on the mouth, the afferent nerves, the nerve-centre
and afferent nerves, or upon the blood-stream through the glands, or on the glands themselves.
Opium and morphia affect the centre, large doses of physostigmin affect the blood-supply, but
atropin is the most powerful of all, as it paralyses the terminations of the secretory nerves in
the th é.g., the chorda tympani, and even the sympathetic in the cat (but not in the

dog)

216 - THE PAROTID SALIVA,

_ [Excretion by the Saliva,—Some drugs are excreted by the saliva, Iodide of potassium is
me eliminated by the kidneys, and by the salivary glands, and so also is iodide of
Iron. ,

Theory of Salivary Secretion.—Heidenhain has recently formulated the following theory
regarding the secretion of saliva :—‘‘ During the passive or quiescent condition of the gland,
the organic materials of the secretion are formed from and by the activity of the protoplasm of
the secretory cells. A quiescent cell, which has been inactive for some time, therefore contains
little protoplasm, and a large amount of these secretory substances. In an actively mete
gland, there are two processes occurring together, but independent of each other, and regulate
by two different classes of nerve-fibres ; secretory fibres cause the act of secretion, while trophic
Jibres cause chemical processes within the cells, partly resulting in the formation of the soluble
constituents of the secretion, and partly in the growth of the protoplasm. According to the
number of both kinds of fibres present in a nerve passing to a gland, such nerve being stimu-
lated, the secretion takes place more rapidly (cerebral nerve) or more slowly (sympathetic),
while the secretion contains less or more solid constituents. The cercbral nerves contain many
secretory fibres and few trophic fibres, while the sympathetic contain more trophic but few
secretory fibres. The rapidity and chemical composition of the secretion vary according to the
strength of the stimulus. During continued secretion, the supply of secretory materials in the
gland-cells is used up more rapidly than it is replaced by the activity of the protoplasm ; hence,
the amount of organic constituents diminishes, and the microscopic characters of the cells are
altered. The microscopic characters of the cells are altered also by the increase of the pro-
toplasm, which takes place in an active gland. The mucous cells disappear, and seem to be
dissolved after prolonged secretion, and their place is taken by other cells derived from the pro-
liferation of the marginal cells. The energy which causes the current of fluid depends upon the
protoplasm of the gland-cells.”

146. THE SALIVA OF THE INDIVIDUAL GLANDS.—(c) Parotid saliva
is obtained by placing a fine cannula in Steno’s duct; it has an alkaline reaction, but
during fasting, the first few drops may be neutral or even acid on account of free
CO, ; its specific gravity is 1003 to 1004. After standing it becomes turbid,
and deposits, in addition to albuminous matter, calcium carbonate, which is present

in the fresh saliva in the form of bicarbonate. It contains small quantities (more |

abundant in the horse) of a globulin-like body, and never seems to be without
CNKS, ze., sulphocyanide of potassium (or sodium),—which, however, is absent in
the sheep and dog.

[The sulphocyanide gives a dark red colour (ferric sulphocyanide) with ferric chloride, and the
colour is discharged by mercuric chloride, but this is not the case with meconic acid, which
gives a similar colour-reaction.] It also reduces iodic acid when added to saliva, causing a
yellow colour from the liberation of iodine, which may be detected at once by starch (Solera).

Amongst the organic substances the most important are ptyalin, a small amount -

of wrea, and traces of a volatile acid. Mucin is absent, hence the parotid saliva is
not sticky, and can readily be poured from one vessel into another. It contains 1°5
to 1°6 per cent. of solids in man, of which 0°3 to 1-0 per cent. is inorganic.

Of the inorganic constituents—the most abundant are potassium and sodium chlorides ; then
lar sodium, and calcium carbonates, some phosphates, and a trace of an alkaline
sulphate.
Salivary calculi are formed in the ducts of the salivary glands owing to the deposition of
lime-salts, and they contain only traces of the other salivary constituents ; in the same way is
formed the tartar of the teeth, which contains many threads of leptothrix, and the remains of
low organisms which live in decomposing saliva in carious cavities between the teeth.
__ (6) Sub-maxillary saliva is obtained by placing a cannula in Wharton’s duct ;
it is alkaline, and may be strongly so. After standing for a time, fine crystals of
calcium carbonate are deposited, together with an amorphous albuminous body.

It always contains mucin (which is precipitated by acetic acid) ; hence, it is usually

somewhat tenacious. It contains ptyalin, but in less amount than in parotid
saliva ; and, according to Oehl, only 0:0036 per cent. of potassium sulphocyanide.
Chemical Composition, —Sub-maxillary saliva (dog) :
Water, . 991°45 per 1000,
Organic Matter, 2°89 ,,

vee) 4°50 NaCl and CaCl,. eb lake ea?
Inorganic Matter, 5°66 1:16 CaCO,, Calcium and Magnesium phosphates.

“vey

THE MIXED SALIVA IN THE MOUTH. 217

Mixed Saliva Parotid Submaxillary
(Human) (Human) (Dog)
(Jacubowitsch). (Hoppe-Seyler), (Herter).
[Water, . : ; : i ; 99°51 99°32 99°44
Solids, . ; ‘ : , ; 0°49 0°68 0°56
Soluble organic bodies (ptyalin), : 0°13 0°34 0°066
Epithelium, mucin, , ; ‘ ‘ 0°16 0°17
Inorganic salts, ; : : : 0°102 0°34 0°43
Potassic sulphocyanide, . . : 0°006 0°03 se
Potassic and sodic chlorides, . ‘ 0°084 e ]

Gases. —Pfliiger found that 100 cubic centimetres of the saliva contained 0°6 O; 64°7 CO,
(part could be pumped out, and part required the addition. of phosphoric acid) ; 0°8 N. ; or, in
100 vol. gas, 0°91 O ; 97°88 CO, ; 1°21 N. [It therefore contains much more CO, than venous
blood. Kiilz obtained from 100 c.c. of human saliva 7 c.c. of gaa—O=1c¢.c., N=2'5 ce. and
CO,=3'5 c.c. Besides this there is 40-60 c.c. of fixed CO, in the form of carbonates. ]

(c) Sub-lingual saliva is obtained by placing a very fine cannula in the
ductus Rivinianus; it is strongly alkaline in reaction, very sticky and cohesive,
contains much mucin, numerous salivary corpuscles, and some potassium sulpho-
cyanide.

147. THE MIXED SALIVA IN THE MOUTH.—The mixed saliva in the
mouth is a mixture of the secretions from the salivary, mucous, and other glands of
the mouth.

(1) Physical Characters.—It is an opalescent, tasteless, odourless, slightly
glairy fluid, with a specific gravity of 1004 to 1009, and an alkaline reaction. The
amount secreted in twenty-four hours=200 to 1500 grammes (7 to 50 oz.) ;
according to Bidder and Schmidt, however, =1000 to 2000 grammes. ‘The solid
constituents = 5°8 per 1000.

Composition. —The solids are :—Epithelium and mucus, 2°2; ptyalin and albumin, 1°4 ; salts,
2°2; potassium sulphocyanide, 0°04 per 1000. The ash contains chiefly potash, phosphoric
acid, and chlorine (Hammerbacher).

Decomposition-products of epithelium, salivary corpuscles, or the remains of food, may render
it acid temporarily, as after long fasting, and after much speaking; the reaction is acid in some
cases of dyspepsia and in fever, owing to the stagnation and insufficient secretion.

(2) Microscopic Constituents.—(a) The salivary corpuscles are slightly larger
than the white blood-corpuscles (8 to 11 ), and are nucleated protoplasmic globular
cells without an envelope (fig. 150, s). During their living condition, the particles
in their interior exhibit molecular or Brownian movement. The dark granules
lying in the protoplasm are thrown into a trembling movement, from the motion of
the fluid in which they are suspended. This dancing motion stops when the cell
dies,

[The Brownian movements of these suspended granules are purely physical, and are exhibited
by all fine microscopic particles suspended in a limpid fluid, ¢.g., gamboge rubbed up in water,
particles of carmine, charcoal, &c. ]

(6) Pavement epithelial cells from the mucous membrane of the mouth and tongue ; they
are very abundant in catarrh of the mouth (fig. 150).

(c) Living organisms, which live and thrive in the cavities of teeth, nourished by the remains
of food. Amongst these are Leptothrix buccalis (fig. 149, 12) and small bacteria-like organisms.
The threads of the leptothrix penetrate into the canals of the dentine, and produce dental caries.
{Miller has found twenty-five varieties of micro-organisms, including cocci, bacteria, vibrios,
spirilla, and spirochete, eight of them present in the stomach and twelve in the intestines. ]

_ (3) Chemical Properties.—(a) Organic Constituents.—Serwm-albumin is preci-
pitated by heat and by the addition of alcohol. In saliva, mixed with much water
and shaken up with CO,, a globulin-like body is precipitated ; mucin occurs in small
amount. Amongst the extractives, the most important is ptyalin ; fats and urea
occur only in traces. In twenty-four hours 130 milligrammes of potassium or
sodium sulphocyanide are secreted. |

_ (6) Inorganic Constituents.—Sodium and potassium chlorides, potassium
sulphate, alkaline and earthy phosphates, ferric phosphate. |

218 PHYSIOLOGICAL ACTION OF SALIVA.

According to Schénbein, the saliva contains traces of nitrites, (detected by adding dilute
sulphuric acid and diamido-benzol to dilute saliva), which give a yellow colour (Gries). There
are also traces of ammonia (Briicke). FY

Abnormal Constituents.—In diabetes mellitus, lactic acid, derived from a further decomposi-
tion of grape-sugar, is found, It dissolves the lime in the teeth, giving rise to diabetic dental
caries. Frerichs found lewcin, and Vulpian increase of albumin in albuminuria. Of foreign
substances taken into the body, the following appear in the saliva :—Mercury, potassium, |
iodine, and bromine.

Saliva of New-Born Children.—In new-born children, the parotid alone contains
ptyalin. The diastatic ferment seems to be developed in the sub-maxillary gland
and pancreas, at the earliest after two months. Hence, it is not advisable to give
starchy food to infants. No ptyalin has been found in the saliva of infants suffer-
ing from thrush (Oidium albicans—Zweifel). The diastatic action of saliva is not
absolutely necessary for the suckling, feeding as it does upon milk. The mouth
during the first two months is not moist, but at a later period saliva is copiously
secreted (Korowin) ; after the first six months, the salivary glands increase con-
siderably. The eruption of the teeth—owing to the irritation of the mucous
membrane—produces a copious secretion of saliva.

148. PHYSIOLOGICAL ACTION OF SALIVA.—I. Diastatic Action.—The
Prost important chemical action exerted by saliva in digestion is its diastatic or

amylolytic action (Leuchs, 1831), 2.e., the transformation of starch into dextrin and
some form of sugar. This is due to the ptyalin—a hydrolytic ferment or enzym
—which, even when it is present in very minute quantity, causes starch totake up
water and become soluble, the ferment itself undergoing no essential change in the
process. [Ptyalin belongs to the group of unorganised ferments (§ 250, 9). Like
all other ferments it acts only within a certain range of temperature, being most
active about 40° C. Its energy is permanently destroyed by boiling. Its acts best
in a slightly alkaline or neutral medium. ]_ !

{Action on Starch.—Starch-grains consist of granulose or starch enclosed by
coats of cellulose. Cellulose does not appear to be affected by saliva, so that saliva
acts but slowly on raw unboiled starch. If the starch be boiled, so as to swell up
the starch-grains, and rupture the cellulose envelopes, the amylolytic action takes
place rapidly. If starch-paste or starch-mucilage, made by boiling starch in water,
be acted upon by saliva, especially at the temperature of the body, the first physical
change observable is the liquefaction of the paste, the mixture becoming more fluid
and transparent. The change takes place in a few minutes. When the action is
continued, important chemical changes occur. |

According to O’Sullivan, Musculus, and v. Mering, the diastatic ferment of saliva
(and of the pancreas), by acting upon starch or glycogen, forms dextrin and maltose
(both soluble in water). Several closely allied varieties of dextrin, distinguishable
by their colour-reactions, seem to be produced (Briicke). Erythrodextrin is
formed first, it gives a red colour with iodine ; then a reducing dextrin—achroo-
dextrin, which gives no colour-reaction with iodine. The sugar formed by the
action of ptyalin upon starch is maltose (C,,H..0,, + H,O), which is distinguished
from grape-sugar (C,,H,,0,,) by containing one molecule less of water, which, how-
ever, it holds as a molecule of water of hydration. [Maltose also differs from grape-
sugar in its greater rotatory power on polarised light, the former = + 150”, the;latter
+ 56°, the ratio being 61: 100; and in its smaller power of reducing cupric oxide.
Thus, between the original starch and the final product, maltose, several interme-
diate bodies are formed. ‘The starch gives a blue with iodine, but after it has been
acted on for a time it gives a red or violet colour, indicating the presence of ery-
throdextrin, there being a simultaneous production of sugar; but ultimately no
colour is obtained on adding iodine—achroodextrin, which gives no colour with
iodine, maltose being formed. ‘The presence of the maltose is easily determined
by testing with Fehling’s solution. ] ° Deas |

4, ee a tek

FUNCTIONS OF SALIVA. 219

{Brown and Heron suggest that the final result of the transformation may be re-
presented by the equation—

10(C,H 9019) + 8H,0 = 8(C1H,.041) + 2(Cy9H 59040)
Soluble starch. Water. Maltose. Achroodextrin.

The ferment slowly changes maltose into grape-sugar or dextrose. This result
may be brought about much more rapidly by boiling maltose with dilute sulphuric
or hydrochloric acid.] Achroodextrin ultimately passes into maltose, and this
again into dextrose ; the other form of dextrin does not seem to undergo this change
(Seegen’s Dystropodextrin). For the further changes that maltose undergoes in

_ the intestine, see § 183, II. 2.

[The formula of starch is usually expressed as C,H,,)O;, but the researches already men-
tioned, and those of Brown and Heron, make it probable that it is more complex, which we
may provisionally represent by n(C,,H. 019). According to Musculus and Meyer, erythrodextrin
is a mixture of dextrin and soluble starch. }

Preparation of Ptyalin.—(1) Like all other hydrolytic ferments, it is carried down with any
copious precipitate that is produced in the fluid which contains it, and it can be isolated from
the precipitate. The saliva is acidulated with phosphoric acid, lime-water is added until the
reaction becomes alkaline, when a precipitate of the basic calcium phosphate occurs, which
carries the ptyalin along with it. This precipitate is collected on a filter, washed with water,
which dissolves the ptyalin, and from its watery solution it is precipitated by alcohol as a white
powder. It is redissolved in water and reprecipitated, and is obtained pure (Cohnheim).

(2) Glycerine or v. Wittich’s Method.—The salivary glands [rat] are chopped up, placed in
absolute alcohol for twenty-four hours, taken out and dried, and afterwards placed in glycerine
for several days, which extracts the ptyalin. Itis precipitated by alcohol from the glycerine
extract. :

(3) William Roberts recommends the following solutions for extracting ferments from organs
which contain them :—(1) A 3 to 4 per cent. solution of a mixture of 2 parts of boracic acid and 1
part borax. (2) Water, with 12 to 15 percent. of alcohol. (3) 1 part chloroform to 200 of water.

Diastatic Action of Saliva.—(a) The diastatic or sugar-forming action is known by—(1)
The disappearance of the starch. When a small quantity of starch is boiled with several
hundred times its volume of water, starch-mucilage-is obtained, which strikes a blue colour
with iodine. If to a small quantity of this starch a sufficient amount of saliva be added, and
the mixture kept for some time at the temperature of the body, the blue colour disappears. (2)
The presence of sugar is proved directly by using the tests for sugar (§ 149).

(b) The action takes place more slowly in the cold than at the temperature of the body—its
action is enfeebled at 55° C., and destroyed at 75°C. (Paschutin). The most favourable
temperature is 35° to 39° C, , :

(c) The ptyalin itself does not seem to be changed during its action, but ptyalin which has
been used for one experiment is less active when used the second time (Paschutin).

Ptyalin differs from diastase—the ferment in germinating grains—in so far that the latter
first begins to act at +66° C. Ptyalin decomposes salicin into saligenin and grape-sugar
(Frerichs and Stadler).

(d) Saliva acts best in an exactly neutral medium, but it also acts in an alkaline and even in a
slightly acid fluid; strong acidity prevents its action. The ptyalin is only active in the stomach
when the acidity is due to organic acids (lactic or butyric), and not when free hydrochloric acid
is present (van de Velde). In both cases, however, dextrin isformed. Ptyalin is destroyed by
hydrochloric acid or digestion by pepsin (Chittenden and Griswold, Langley). Even butyric
and lactic acids formed from grape-sugar in the stomach may prevent its action ; but if the
acidity be neutralised, the action is resumed (Cl. Bernard). ;

(e) The addition of common salt, ammonium chloride, or sodium sulphate (4 per cent. solu-
tion), increases the activity of the ptyalin, and CO,, acetate of quinine, strychnia, morphia,
curara, 0°025 per cent. sulphuric acid, have the same effect. :

(f) Much alcohol and caustic potash destroy the ptyalin ; long exposure to the air weakens
its action, sodium carbonate and magnesium sulphate delay the action (Pfeiffer). Salicylic
acid and much atropin arrest the formation of sugar. >

(g) Ptyalin acts very feebly and very gradually upon raw starch, only after 2 to 3 hours
(Schiff) ; while upon boiled starch it acts rapidly. [Hence the necessity for boiling thoroughly
all starchy foods. |

(h) The various kinds of starch are changed more or less rapidly according to the amount of
cellulose which they contain,; raw potato starch after 2 to 3 hours, raw maize starch after 2 to
3 minutes (Hammarsten) ; wheat starch more quickly than that of rice. When the starches
are powdered and boiled, they are changed with equal rapidity.

_ (i) A mizture of the saliva from all the glands is more active than the saliva from any single
gland (Jakubowitsch), while mucin is inactive. .

220. TESTS FOR SUGAR.

[Effect of Tea.—Tea has an intensely inhibitory effect on salivary digestion, which is due to
the large quantity of tannin contained in the tea-leaf. Coffee and cocoa have only a slight
effect on salivary digestion. The only way to mitigate the inhibitory effect of tea on salivary
digestion is ‘‘not to sip the beverage with the meal, but to eat first and drink afterwards ”
(Roberts).]

II. Saliva dissolves those substances which are soluble in water ; while the alka-
line reaction enables it to dissolve some substances which are not soluble in water
alone, but require the presence of an alkali.

III. Saliva moistens dry food and aids the formation of the “bolus,” while by
its mucin it helps the act of swallowing, the mucin being given off unchanged in the
feces. The ultimate fate of ptyalin is unknown. |

[IV. Saliva also aids articulation, while according to Liebig it carries down into
the stomach small quantities of O. ] ,

[V. It is necessary to the sense of taste to dissolve sapid substances, and bring
them into relation with the end-organs of the nerves of taste. |

Saliva has no action on proteids or on fats.

The presence of a peptone-forming ferment has recently been detected in saliva (Hiifner,
Munk, Kiihne), [Pertectly healthy human saliva has no poisonous properties. ]

149. TESTS FOR SUGAR.—1. Trommer’s test depends upon the fact that, in
alkaline solutions, sugar acts as a reducing agent; in this case a metallic oxide is
changed into a suboxide. To the fluid to be investigated, add } of its volume of
a solution of caustic potash (soda), specific gravity 1:25, and a few drops of a weak
solution of cupric sulphate, which causes at first a bluish precipitate, consisting of
hydrated cupric oxide, but it is redissolved, giving a clear blue fluid, if sugar be
present. Heat the upper stratum of the fluid, and a yellow or red ring of cuprous
oxide is obtained, which indicates the presence of sugar ; 2CuO -O=€u,0.

The solution of hydrated cupric oxide is caused by other organic substances ; but the final
stage, or the production of cuprous oxide, is obtained only with certain sugars—grape-, fruit-,
and milk- (but not cane-) sugar. Fluids which are turbid must be previously filtered, and if
they are highly coloured, they must be treated with basic lead acetate ; the lead acetate is after-
wards removed by the addition of sodium phosphate and subsequent filtration. If very small
quantities of sugar are present along with compounds of ammonia, a yellow colour instead of a
yellow precipitate may be obtained. In doing the test, care must be taken not to add too much
cupric sulphate.

(2, Fehling’s Solution is an alkaline solution of potassio-tartarate of copper.
Boil a small quantity of the deep-blue-coloured Fehling’s solution in a test-tube,
and add to the boiling test a few drops of the fluid supposed to contain the sugar.
If sugar be present, the copper solution is reduced, giving a yellow or reddish pre-
cipitate. The reason for boiling the test itself is, that the solution is apt to
decompose when kept for some time, when it is precipitated by heat alone. This
is one of the best and most reliable tests for the presence of sugar. In Pavy’s
modification of this test, ammonia is used instead of a caustic alkali (§ 267). |

(3) Bottger’s Test. —Alkaline bismuth oxide solution is best prepared, according to Nylander,
as follows :—2 grms. bismuth subnitrate, 4 grms. potassic snd sodic tartarate, 100 grms.
caustic soda of 8 percent. Add 1c.c. to every 10 c.c. of the fluid to be investigated. hen
boiled for several minutes, the sugar causes the reduction and deposits a black precipitate of

metallic bismuth. [According to Salkowski the urine of a person taking rhubarb gives the
same reaction with this test. ]

(4) Moore and Heller’s Test.—Caustic potash or soda is added until the mixture is strongly
alkaline ; it is afterwards boiled. If sugar be present, a yellow, brown, or brownish-black colora-
“pee anaes If nitric acid be added, the odour of burned sugar (caramel) and formic acid
is obtained.

(5) Mulder and Neubauer’s Test.—A solution of indigo-carmine, rendered alkaline with sodic
carbonate, is added to the sugar solution until a slight bluish colour is obtained. When the
mixture is heated, the colour passes into purple, red, and yellow. When shaken with atmo-
spheric air, the fluid again becomes blue.

Molisch’s Test.—To 5 c.cm. of the fluid add 2 drops of a 17 per cent. alcoholic solution
of a—naphthol, or a solution of thymol. Add 1 to 2 c.cm. of concentrated sulphuric acid,
and shake the mixture, The presence of sugar colours the a-naphthol mixture deep violet,

QUANTITATIVE ESTIMATION OF SUGAR. 2oF

the thymol deep red, The subsequent addition of water causes a precipitate of similar colour,
which is insoluble in concentrated hydrochloric acid, Albumin, casein, and peptone give the
same reaction (Seegen), but the deposit on the addition of water is soluble in concentrated
hydrochloric acid,

Other tests are described in § 266, ah :

In all cases where albumin is present it must be removed—in urine by acidulating with aceti
acid and boiling ; in blood, by adding four times its yolume of alcohol and afterwards filtering,
while the alcohol is expelled by heat, :

150. QUANTITATIVE ESTIMATION OF SUGAR.—I. By Fermentation,—In the glass
vessel (fig. 161, a) a measured quantity (20 c.cm.) of the fluid (sugar) is placed along with some
yeast, while } contains concentrated sulphuric acid, The
whole apparatus is then weighed. When exposed to a suffi-
cient temperature (10° to 40° C.), the sugar splits into 2
molecules of alcohol and 2 of carbon dioxide,

CgH},0g = 2(C,H,O) + 2(COs),

Grape-sugar =. 2 alcohol -+ 2 carbon dioxide;
and in addition there are formed traces of glycerine and suc-
cinic acid. The CO, escapes from 3, and as it passes through
the H,SO,, the CO, yields to the latter its water. The —
apparatus is weighed after two days, when the reaction is : Fig, 161.
ended, and the amount of sugar is calculated from the loss of Apparatus for the quantitative
weight in the 20 c.cm. of fluid. 100 parts of water-free sugar ‘estimation of sugar by fer-
= 48°89 parts CO,, or 100 parts CO, correspond to 204°54 ~— mentation. cs
parts of sugar,

II, Titration.—By means of Fehling’s solution, which is made of such a strength that all the
copper in 10 cubic centimetres of the solution is reduced by 0°05 grammes of grape-sugar
(§ 267). . .

III. Circumpolarisation,—The saccharimeter of Soleil-Ventzke may be used to determine the
amount of sugar present, It may also be used for the quantitative estimation of albumin.
Sugar rotates the ray of polarised light to the right and albumin to the left. The amount of
rotation, or ‘‘ specific rotatory power,” is directly proportional to the amount of the rotating
substance present in the solution, so that the amount of rotation of the ray indicates the amount
of the substance present, By the term ‘‘specific rotatory power” is meant the degree of
rotation which is produced by 1 grm, of the substance dissolved in 1 c,cm. of water, when
examined in a layer 1 decimeter thick. For yellow light the specific rotation of grape-sugar is
+ 56°.

In fig. 162 the light from the lamp falls upon a crystal of cale-spar. Two Nicol’s prisms are
placed at v and s, v is movable round the axis of vision, while s is fixed. In m Soleil’s double
plate of quartz is placed, so that one-half of it rotates the ray of polarised light as much to the
right as the other rotates it to the left. In 7 the field of vision is covered by a plate of left-
rotatory quartz. Atb c¢ is the compensator, composed of two right-rotatory prisms of quartz,
which can be displaced laterally by the milled head, g, so that the polarised light passing
through the apparatus can be made to pass through a thicker or thinner layer of quartz. When
these right-rotatory prisms are placed in a certain position, the rotation of the left-rotatory
quartz at 7 is exactly neutralised. In this position the scale on the compensator has its nonius
exactly at 0, and both halves of the double plate at m appear to have the same colour to the
observer, who from v looks through the telescope placed at ¢. Rotate the Nicol’s prism at v
until a bright rose-coloured field is obtained. In this position the telescope must be so adjusted
that the vertical line bounding the two halves shall be distinctly visible, The apparatus is now
ready for use,

Fill a tube, 1 decimetre in length, with urine containing sugar or albumin, the urine being
perfectly clear. The tube is placed between mand xn. By rotating the Nicol’s prisms, v, the
rose-colour is again obtained. The compensator at g is then rotated until both halves of the
field of vision have exactly the same colour, When this is obtained, read off on the scale the
number of degrees the nonius is displaced to the right (sugar) or to the left (albumin) from zero.
The number of degrees indicates directly the number of grammes of the rotating substance
present in 100 c.c. of the fluid. Ifthe fluid is very dark coloured, it must be decolourised by
filtering it through animal charcoal (Scegen), [or the colouring matter may be preciptated by the
addition of lead acetate.] If the sugary urine contains albumin, the latter must be removed by
boiling and filtration, A turbidity not removed by-filtration may be got rid of by adding a drop
of acetic acid or several drops of sodic carbonate or milk of lime, and afterwards filtering. [One
may also employ the apparatus of Mitscherlich, or the “‘ half-shadow apparatus ” of Laurent. ]

151. MECHANISM OF THE DIGESTIVE APPARATUS.—This embraces
the following acts :— tal tog | ;

222 INTRODUCTION OF THE FOOD,

—_

The introduction and mastication of the food; the movements of the tongue ; .
insalivation ; formation of the bolus of food. |
2. Deglutition. , :
_ 3. The movements of the stomach, small and large intestine.
4. The excretion of feecal matters.

152. INTRODUCTION OF THE FOOD.—Fluids are taken into the mouth in
three ways :—(1) By suction, the lips are applied air-tight to the vessel containing
the fluid, while the tongue is retracted (the lower jaw being often depressed) and

Fig. 162.
Soleil-Ventzke’s polarisation apparatus.

acts like the piston in a suction-pump, thus causing the fluid to enter the mouth.
Herz found that the negative pressure caused by an infant while sucking =3 to 10
mm. Hg. (2) The fluid is lapped when it is brought into direct contact with the
lips, and is raised by aspiration and mixed with air so as to produce a characteristic
sound in the mouth. (3) Fluid may be poured into the mouth, and as a general
rule the lips are applied closely to the vessel containing the fluid.
Solids, when they consist of small particles, are licked up with the lips, aided b

the movements of the tongue. In the case of large masses, a part is bitten off with

MASTICATION. 223

the incisor teeth, and is afterwards brought under the action of the molar teeth by
means of the lips, cheeks, and tongue.

153. MASTICATION. —The articulation of the jaw is provided with an interarticular cartilage
—the meniscus—which prevents direct pressure being made upon the articular surface when the
jaws are energetically closed, and which also divides the joint into two cavities, one lying over
the other. The capsule is so lax that, in addition to the raising and depressing of the lower
jaw, it permits of the lower jaw being displaced forwards, whereby the meniscus moves with it,
and covers the articular surface.

The process of mastication embraces :—(a) The elevation of the jaw, accom-
plished by the combined action of the Temporal, Masseter, and Internal Pterygoid
Muscles, If the lower jaw was previously so far depressed that its articular surface
rested upon the tubercle, it now passes backwards upon the articular surface.

(6) The depression of the lower jaw is caused by its own weight, aided by the
action of the anterior bellies of the Digastrics, the Mylo- and Genio-hyoid and
Platysma. The muscles act especially during forcible opening of the mouth. The
necessary fixation of the hyoid bone is obtained through the action of the Omo- and
Sterno-hyoid, and by the Sterno-thyroid and Thyro-hyoid.

When the articular surface of the lower jaw passes forwards on to the tubercle, the External
Pterygoids actively aid in producing this (Bérard).

(c) Displacement of the Articular Surfaces.—During rest, when the mouth is
closed, the incisor teeth of the lower jaw are within the arch of the upper incisors.
When in this position the jaw is protruded by the External Pterygoids, whereby the
articular surface passes on to the tubercle (and, therefore, downwards), while the lateral _
teeth are thereby separated from each other. The jaw is retracted by the Internal
Pterygoids without any aid from the posterior fibres of the Temporals. When one
articular surface is carried forwards, the jaw is protruded and retracted by the Exter-
nal and Internal Pterygoid of the same side. At the same time, there is a transverse
movement, whereby the back teeth of the protruded side are separated from each other.

During mastication, the individual movements of the lower jaw are variously com-
bined, and especially with lateral grinding movements, while the food to be masticated
is kept from passing outwards by the action of the muscles of the lips (Orbicularis
oris) and the Buccinators, while the tongue continually pushes the particles between
the molar teeth. The energy of the muscles of mastication is regulated by the
sensibility of the teeth, and the muscular sensibility of the muscles of mastication,
as well as by the general sensibility of the mucous membrane of the mouth and
lips. Atthesame time, the mass is mixed with saliva, the divided particles cohere,
and are formed into a mass or bolus, of a long, oval shape, by the muscles of the
tongue. The bolus then rests on the back of the tongue, ready to be swallowed.

Nerves of Mastication.—The muscles of mastication receive their motor nerves from the third
branch of the trigeminus, the mylo-hyoid and the anterior belly of the digastric being supplied
from the same source. The genio-, omo-, and sterno-hyoid, sterno-thyroid, and thyro-hyoid
are supplied by the hypoglossal, while the facial supplies the posterior belly of the digastric, the
stylo-hyoid, the platysma, the buccinator, and the muscles of the lips. The general centre for
the muscles of mastication lies in the medulla oblongata (§ 367).

When the mouth is closed, the jaws are kept in contact by the pressure of the air, as the
cavity of the mouth is rendered free from air, and the entrance of air is prevented anteriorly
by the lips, and posteriorly by the soft palate. The pressure exerted by the air is from 2 to 4
mm. Hg. (Metzger and Donders).

[Effect on the Circulation.—Marey found that mastication trebled the velocity of the blood-
current in the carotid (horse), while Francois Frank observed that the circulation of the brain
{in man) is increased ; hence it is evident that mastication implies an increased supply of blood
to the nerve-centres. |

- 154, STRUCTURE AND DEVELOPMENT OF THE TEETH. —-A tooth is just a papilla of the
mucous membrane of the gum, which has undergone a characteristic development. In its simplest
form, as in the teeth of the lamprey, the connective-tissue basis of the papilla is covered with
many layers of corneous epithelium. In human teeth, part of the papilla is transformed into a
layer of calcified dentine, while the epithelium of the papilla produces the enamel, the fang of
the tooth being covered by a thin accessory layer of bone, the crusta petrosa or cement.

224. STRUCTURE OF DENTINE,

The dentine or ivory which surrounds the pulp-cavity and the canal of the fang (fig, 163) is .
very firm, elastic, and brittle, Dentine, like the matrix
of bone, when treated in a certain way, at a fibrillar
structure; It is permeated by innumerable long, tortuous,

Ename!,

Fig, 163, Ae
Fig. 163.— Longitudinal section of an incisor tooth. Fig. 164.—Transverse section of dentine.
The light rings are the walls of the dentinal tubules; the dark centres with the light points
are the fibres of Tomes lying in the tubules, Fig. 165.—Interglobular spaces in dentine,

wavy tubes—the dentinal tubules—each of which communicates with the pulp-cavity by means
of a fine opening, and passes more or less horizontally outwards as far as the outer layers of the
dentine, The tubules are bounded by
an extremely resistant, thin, cuticular
membrane, which strongly resists the
action of chemical reagents. These

ei
ri
re

Wey

’ U/.

Fig, 166. Fig. 167,
Fig, 166.—Section of a tooth between the dentine and enamel, a, enamel; c, dentinal tubules ;
B, enamel prisms highly magnified ; C, transverse sections of enamel prisms. Fig, 167,—
Transverse section of the fang. a, cement with bone-corpuscles ; b, dentine with tubules ;
c, boundary between both, _ : sted

tubules are filled completely by soft fibres, the ‘‘ fibres of Tomes,” which are merely greatly
elongated and branched processes of the odontoblasts of the pulp. 8,

CHEMISTRY AND DEVELOPMENT OF A TOOTH. 225

The dentinal tubules, as well as the fibres of Tomes, anastomose throughout their entire extent
by means of fine processes. As the fibres approach the enamel, which they do not penetrate,
some of them bend on themselves, and form a loop (fig. 166, c), whilst others pass into the -
‘*interglobular spaces ’”’ (fig. 165) which are so abundant in the outer part of the dentine. The
interglobular spaces are small spaces bounded by curved surfaces. Certain curved lines,
‘* Schreger’s lines,’’ may be detected with the naked eye in the dentine (e.g., of the elephant’s
tusk) running parallel with the contour of the tooth. They are caused by the fact that at these
parts all the chief curves in the dentinal tubules follow a similar course.

The enamel, the hardest substance in the body (resembling apatite), covers the crown of the
teeth. It consists of hexagonal flattened prisms arranged side by side like a palisade (fig. 166,
Band C). They are 3 to 5 mw (sy5y inch) broad, not quite uniform in thickness, curved
slightly in different directions, and, owing to inequalities of thickness, they exhibit transverse
markings. They are elongated, calcified, cylindrical, epithelial cells. Retzius described dark
brown lines running parallel with the outer boundary of the enamel, due to the presence of
pigment (fig. 163). The fully formed enamel is negatively doubly refractive and uniaxial, while
the developing enamel is positively doubly refractive (Hoppe-Seyler).

The cuticula or Nasmyth’s membrane covers the free surface of the enamel as a completely
structureless membrane 1 to 2 uw thick, but in quite young teeth it exhibits an epithelial struc-
ture, and is derived from the outer epithelial layer of the enamel organ.

The cement or crusta petrosa is a thin layer of bone covering the fang (fig. 167, a). The
bone lacune communicate directly with the dental tubules of the fang. Haversian canals and
lamelle are only found where the layer of cement is thick, and the former may communicate
with the pulp-cavity. Very thin layers of cement may be devoid of bone-corpuscles. Sharpey’s
fibres occur in the cement of the dog’s tooth ; while in the horse’s tooth single bone-corpuscles
are developed by a capsule. In the periodontal membrane, which is just the periosteum of the
alveolus, coils of blood-vessels similar to the renal glomeruli occur. They anastomose with each
other, and are surrounded by a delicate capsule of connective-tissue.

Chemistry of a Tooth.—The teeth consist of a gelatine-yielding matrix infiltrated with cal-
cium phosphate and carbonate (like bone). (1) The dentine contains—organic matter, 27°70 ;
calcium phosphate and carbonate, 72°06 ; magnesium phosphate, 0°75; with traces of iron,
fluorine, and sulphuric acid.

(2) The enamel contains an organic proteid matrix allied to the substance of epithelium. It
consists of 3°60 organic matter and 96°00 of calcium phosphate and carbonate, 1°05 magnesium
phosphate, with traces of calcium fluoride and an insoluble chlorine compound.

(3) The cement is identical with bone.

The pulp in a fully-grown tooth represents the remainder of the dental papilla around which
the dentine was deposited. It consists of a very vascular indistinctly fibrillar connective-tissue,
laden with cells. The layers of cells, resembling epithelium, which lie in direct contact with
the dentine, are called odontoblasts, 7.c., those cells which build up the dentine. These cells
send off long branched processes into the dentinal tubules, whilst their nucleated bodies lie
on the surface of the pulp, and form connections by processes with other cells of the pulp and
with neighbouring odontoblasts. Numerous non-medullated nerve-fibres (sensory from the
trigeminus), whose mode of termination is unknown, occur in the pulp.

The periosteum or periodontal membrane of the fang is, at the same time, the alveolar peri-
osteum, and consists of connective-tissue with elastic fibres and many nerves.

The gums are devoid of mucous glands, very vascular, and often provided with long vascular
papille, which are sometimes compound.

Development of a Tooth.—It begins at the end of the second month of foetal life. Along the
whole length of the foetal gum is a thick projecting bridge (fig. 168, a) composed of many layers
of epithelium, A depression, the dental groove, also filled with epithelium, occurs in the gum,
and runs along under the ridge. The dental groove becomes deeper throughout its entire length,
and on transverse section presents the appearance of a dilated flask (0), while at the same time
it is filled with elongated epithelial cells, which form the ‘‘enamel organ.” A conical papilla,
the ‘‘dentine germ,” grows up from the mucous tissue, of which the gum consists, towards the
enamel organ (fig. 169, c), so that the apex of the papilla comes to have the enamel organ resting
upon it likea double cap. Afterwards, owing to the development of connective-tissue, the parts
of the enamel organ lying between and uniting the individual dentine germs, disappear, and
gradually the connective-tissue forms a tooth-sac enclosing the papilla and its enamel organ (d).

Those epithelial cells (fig. 169, 3) of the enamel organ, which lie next the top of the papilla,
are cylindrical, and become calcified to form enamel prisms. The layer of cells of the
double cap, which is directed towards the tooth-sac (1), becomes flattened, fuses, undergoes a
horny transformation, and becomes the cuticula, whilst the cells which lie between both layers
undergo an intermediate metamorphosis, so that they come to resemble the branched stellate
cells of the mucous tissue (2), and gradually disappear altogether.

The dentine is formed in the most superficial layer of the projecting connective-tissue of the
dental papilla, owing to the calcification of the continuous layer of odontoblasts which occur
there (figs. 169 and 170, %). During the process, fibres or branches of these cells are left

: P

> °° ae

226 | a9 _ ERUPTION OF THE TEETH...

unaffected, and remain as the fibres of Tomes. Exactly the same process occurs as in the-

formation of bone, the odontoblasts forming around themselves a calcified matrix. The cement |

’ is formed from the soft connective-tissue of the dental alveolus. 4
Dentition.—During the development of the first temporary or milk-teeth a special enamel
organ (fig. 169, c) is formed near these, but it does not undergo development until the milk-
teeth are shed ; even the papilla is wanting at first. When the permanent tooth begins to

J
LS XBR 3 DANY SS-- i y tS \
\\ EE ont fy = : S ¥ ne BA 3 A ANI MW PR Se ----- f°
2 Ne RACK ny ‘ 4 hu My + ANG ae
\\\ GR BROS VER hii ARO J
\ ASS 1 ERR AER BH). aR AANA ok
OGRE 6» AR Oi eA ET ----
( CR eee VAAN Bo | Ud y, re
SNS G BONN OG a
pied oo Ui Et ----4 hee)
SSE?
Fig. 168. Fig. 169. Fig. 170.

Fig. 168.—a, Dental ridge ; 6, enamel organ ; ¢, beginning of the dentine germ; d, first indication
of the tooth-sac. Fig. 169.—a, Dental ridge ; 6, enamel organ with (1) outer epithelium,
(2) middle stellate layer, (3) enamel prism-cell layer; c, dentine germ with blood-vessels
and the long osteoblasts on the surface ; d, tooth-sac ; ¢, secondary enamel germ. Fig.
170.—a, Dental ridge ; 6, enamel organ; c, dentine germ ; /, enamel ; g, dentine; h, inter-
val between enamel organ and the position of the tooth ; %, layer of odontoblasts.

develop, it opens into the alveolar wall of the milk-teeth from below. The tissue of this dental

sac causes erosion, or eating away of the fang and even of the body of the milk-teeth, without

its blood-vessels undergoing atrophy. The chief agents in the absorption are the ameeboid cells

of the granulation tissue. [Multinuclear giant-cells also erode the fangs of the teeth. ]
Eruption of the Milk-Teeth. —The following is the order in which the twenty milk-teeth cut the

gum, 7z.¢., from the seventh month to the second year :—Lower central incisors, upper central

incisors, upper lateral incisors, lower lateral incisors, first molar, canine, the second molars.
[The figures indicate in months the period of eruption of each tooth. ]

“

Molars. Canines. Incisors. Canines. Molars.

“24 12 18 9779 18 24 12

[The permanent teeth succeed the milk-teeth, the process beginning about the seventh year.
Ten teeth in each jaw take the place of the milk-teeth, while six teeth appear further back in
each jaw. Thus the total number of permanent teeth is thirty-two. As the sacs, from which
the permanent teeth are developed, are formed before birth, they merely undergo the same
process of development as the temporary teeth, only at a much later period. The last of the |
permanent molars—the wisdom-tooth—may not cut the jaw until the seventeenth to the twenty- j
Jifth year. At the sixth year the jaw contains the largest number of teeth, as all the temporary
teeth are present, and, in addition, the crowns of all the permanent teeth, except the wisdom-
teeth, making forty-eight in all.] |

[Eruption of Permanent Teeth.—The age at which each tooth cuts the gum is given in years
in the following table :—

Molars. Bicuspid. | Canines. Incisors. Canines. Bicuspid. Molars. —
17 12 12 17
to to 6 10 9 11 to 12 8778 11 to 12 9 10 6 to to
25 13 | 13 25

[Action of Drugs on the Teeth.—All the conditions for putrefaction are present in the mouth;
and when putrefaction occurs, the products (often acid) attack the dentine and hasten its decay.
Hence, the necessity for thorough daily cleansing of the teeth and mouth. The teeth may be
cleaned by means of a soft tooth-brush and water, with or without the use of any of the

MOVEMENTS OF THE TONGUE. 227

numerous dentifrices, such as powdered chalk or charcoal. Astringents such as catechu and
areca-nut are sometimes used. Mineral acids attack the teeth, and ought, when taken, to be
sucked through a tube. ]

155. MOVEMENTS OF THE TONGUE.—The tongue, being a muscular
organ, and extremely mobile, plays an important part in the process of mastica-
tion (1) It keeps the food from passing from between the molar teeth. (2) It
forms into a bolus the finely-divided food after it is mixed with saliva. (3) When
the tongue is raised, the bolus lying on its dorsum is pushed backwards into the
pharynx and cesophagus.

The course of the fibres is threefold—longitudinally, from base to tip;
transversely, the fibres for the most part proceeding outwards from the vertically-
placed septum linguz ; vertically, from below upwards. Some of the muscles are
confined to the tongue (intrinsic), while others (extrinsic) are attached beyond it
to the hyoid bone, lower jaw, the styloid process, and the palate.

Microscopically, the fibres are transversely striated, with a delicate sarcolemma, and very
often they are branched where they are inserted intot he mucous membrane. The muscular
bundles cross each other in various directions, and in the interspaces fat-cells and glands occur.

Changes in form and position :—

(1) Shortening and broadening by the longitudinal muscle, aided by the hyo-
glossus.

(2) Elongation and narrowing, by the transversus lingue.

(3) The dorsum is rendered concave by the transversus and the simultaneous action
of the median vertical fibres.

(4) Arching of the dorsum :—(a) Transversely, by the lowest transverse bundles ;
(6) longitudinally, by the lowest longitudinal muscles.

(5) Protrusion, by the genio-glossus, while at the same time the tongue usually
becomes narrower and longer (2).

(6) Retraction, by the hyo-glossus and stylo-glossus, and (1) usually occurring at
the same time.

(7) Depression into the floor of the mouth, by the hyo-glossus. The floor of the
mouth may be made deeper by depressing the hyoid bone.

(8) Elevation of the tongue towards the palate :—(a) At the tip by the anterior
part of the longitudinal fibres ; (6) in the middle by elevating the entire hyoid bone
by the mylo-hyoid (WV. trigeminus) ; (c) at the root by the stylo-glossus and palato-
glossus, as well as indirectly by the stylo-hyoid (WV. faczalis).

(9) Lateral movements, the tip of the tongue passing to the right or left ; these
are caused by the longitudinal fibres of one side.

Motor Nerves.—The motor nerve of the tongue is the hypoglossal. When this nerve is
divided or paralysed on one side, the tip of the tongue lying in the floor of the mouth is directed
towards the sound side, because the tonus of the non- paralysed longitudinal fibres shortens the
sound side slightly. If the tongue be protruded, however, the tip passes towards the paralysed
side. This arises from the direction of the genio-glossus (from the middle downwards and out-
wards), and the tongue follows the direction of its action. The tongues of animals which have
been killed exhibit fibrillar contractions of the muscles, sometimes lasting for a whole day.
[Stirling has frequently found nerve-ganglia in the nerves of the tongue].

156. DEGLUTITION.—The onward movements of the contents of the denies
eanal are effected by a special kind of action whereby the tube or canal contracts
upon its contents, and as this contraction proceeds along the tube, the contents are
thereby carried along. This is the “‘ peristaltic movement,”’ or peristalsis.

In the first and most complicated part of the act of deglutition, we nee
in order the following individual movements :—

o) The aperture of the mouth is closed by the orbicularis oris (WV. facralis).

2) The jaws are pressed against each other by the muscles of mastication
(NV. trigeminus), while at the same time the lower jaw affords a fixed point for the
action of the muscles attached to it and the hyoid bone.

228 p DEGLUTITION.

(3) The tip, middle, and root of the tongue, one after the other, are pressed -
against the hard palate, whereby the contents of the mouth are propelled towards
the pharynx.

(4) When the bolus has passed the anterior palatine arch (the mucus of the
tonsillar glands making it slippery again), it is prevented from returning to the
mouth by the palato-glossi muscles which lie in the anterior pillars of the fauces,
coming together like two side-screens or curtains, meeting the raised dorsum of the
tongue (Stylo-glossus).

(5) The morsel is now behind the anterior palatine arch and the root of the
tongue, and has reached the pharynx, where it is subjected to the successive action
of the three pharyngeal constrictor muscles which propel it onwards. The action
of the superior constrictor of the pharynx is always combined with a horizontal
elevation (Levator veli palatini; MW. facialis) and tension (Tensor veli palatini ;
NV. trigeminus, otie ganglion) of the soft palate. The upper constrictor presses
(through the pterygo-pharyngeus) the posterior and lateral walls of the pharynx
tightly against the posterior margin of the horizontal, tense, soft palate, whereby the
margins of the posterior palatine arches (palato- pharyngeus) are approximated.
The pharyngo-nasal cavity is thus completely shut off, so that the bolus cannot be
pressed backwards into the nasal cavity.

In persons with congenital or acquired defects of the soft palate, or cleft-palate, during
swallowing, food passes “into the nose. ;

(6) Falk and Kronecker assert, that by the energetic contraction of the muscles
which diminish the cavity of the mouth, especially the mylo-hyoid, the bolus is
“projected” through the pharynx and cesophagus. [They even assert that the
bolus reaches the cardia before even the musculature of the pharynx or cesophagus
can contract, and further that the pharyngeal muscles of a dog may be divided
without making swallowing impossible.| If we make a series of efforts to swallow,
one after the other, as in drinking, contraction of the pharynx and cesophagus takes
place only after the Jast effort. Thus each new act of deglutition in the mouth
inhibits (by stimulation of the glosso-pharyngeal nerve) the movements in the parts
of the cesophageal tube situated below it.

(7) The bolus is propelled onwards by the successive contraction of the upper,
middle, and lower constrictors of the pharynx until it passes into the cesophagus,.
At the same time the entrance to the glottis is closed, else the morsel would pass
into the larynx, or, as is generally said, would “ pass the wrong way.” |

Duration. —According to Meltzer and Kronecker, the duration of deglutition in the mouth
is 0°3 sec.; then the constrictors of the pharynx contract 0°9 sec. ; afterwards, the upper part
of the esophagus ; then after 1°8 sec. the middle; and after another 3 sec. the lower constrictor.
The closure of the cardia, after the entrance of the bolus into the stomach, is the final act in the
total series of movements.

Sounds during Deglutition.—If the region of the stomach be auscultated during the act of
swallowing, two sounds may be heard; the first one is produced when the bolus is projected into
the stomach ; the second occurs when ‘the peristalsis, which takes place at the end of swallow-
ing, squeezes "the contents of the esophagus through the cardia (Meltzer, Zenker, Ewald). [The
latter occurs 4-5 mins. afterwards. In man, when water alone is swallowed, there is no sound,
but when it is mixed with air there is, and it is generally heard because air is usually swallowed
with the food or drink (Quincke). ]

The closure of the glottis is effected in the following manner :—(a) The whole
larynx—the lower jaw being fixed—is raised upwards and forwards, while at the
same time the root of the tongue hangs over it. The hyoid bone is raised forwards
and upwards by the genio-hyoid, anterior belly of the digastric, and mylo-hyoid ;
the larynx is approximated close to the hyoid bone by the thyro-hyoid. (6) When
the larynx is raised, so that it comes to lie below the overhanging root of the
tongue, the epiglottis is pressed downwards over the entrance to the glottis, and
the bolus passes over it. The epiglottisis also pulled down by the special muscular

P oy,

NERVOUS MECHANISM. ) 220

fibres of the reflector epiglottidis and aryepiglotticus. (c) The closure of the glottis
by the constrictors of the larynx also prevents the entrance of substances into the
larynx (§ 313, IT. 2).

Injury to the Epiglottis.—Intentional injury of the epiglottis in animals, or its destruction
in man, may cause fluids to ‘‘ go the wrong way,” 7.¢., into the glottis, whilst solid food can be
swallowed without disturbance. In dogs, coloured fluids placed on the root of the tongue have
been observed to pass directly into the pharynx without coming into contact with it, so as to
tinge the upper surface of the epiglottis (Magendie). [The basis of the epiglottis is yellow
elastic cartilage, so that it shows no tendency to ossify, and always retains its elasticity (§ 313).]

‘In order that the descending bolus may be prevented from carrying the pharynx
with it, the stylo-pharyngeus, salpingo-pharyngeus, and baseo-pharyngeus contract
upwards when the constrictors act. |

Nervous Mechanism.—Deglutition is voluntary only during the time the bolus
is in the mouth. When the food passes through the palatine arch into the gullet
the act becomes involuntary, and is, in fact, a well-regulated reflex action. When
there is no bolus to be swallowed, voluntary movements of deglutition can be
accomplished only within the mouth; the pharynx only takes up the movement,
provided a bolus (food or saliva) mechanically excites the reflex act. The afferent
nerves, which, when mechanically stimulated, excite the involuntary act of degluti-
tion, are, the palatine branches of the trigeminus (from the spheno-palatine gang-
lion) and the pharyngeal branches of the vagus. The centre for the nerves con-
cerned (for the striped muscles) lies in the superior olives of the medulla oblongata.
Swallowing can be carried out when a person is unconscious, or after destruction
of the cerebrum, cerebellum, and pons (§ 367, 6). [Even in the deep coma of alco-
holism, the tube of a stomach-pump is carried into the stomach reflexly, provided
the surgeon passes it back into the pharynx.| The nerves of the pharynx are de-
rived from the pharyngeal plexus, which receives branches from the vagus, glosso-
pharyngeal, and sympathetic (§ 352, 4).

Within the esophagus, whose stratified epithelium is moistened with the mucus
derived from the mucous glands in its walls, the downward movement is involun-
tary, and depends upon a complicated reflex movement discharged from the centre
for deglutition. There is a peristaltic movement of the outer longitudinal and
inner circular non-striped muscular fibres.

In the upper part of the cesophagus, which contains striped muscular fibres, the peristalsis
takes place more quickly than in the lower part. The movements of the cwsophagus never
occur independently, but are always the continuation of a foregoing act of deglutition. If food
be introduced into the cesophagus through a hole in its wall, there it lies ; and it is only carried
downwards when a movement to swallow is made. The peristalsis extends along the whole
length of the cesophagus, even when it is ligatured or when a part of it is removed (Mosso). If
a dog be allowed to swallow a piece of flesh tied to a string, so that the flesh goes halfway
down the cesophagus, and if the flesh be withdrawn, the peristalsis still passes downwards
(C. Ludwig and Wild). -

The motor nerve of the cesophagus is the vagus (not the accessory fibres) [cesophageal, whose
branches have numerous small ganglia in their course]. After it is divided, the food lodges in
.the lower part of the esophagus. ' Very large and very small masses. are swallowed with more
difficulty than those of moderate size. Dogs can swallow an olive-shaped body weighted with a
counterpoise of 450 grammes (Mosso). When the thorax is greatly distended, as in Miiller’s
experiment, or greatly diminished, as in Valsalva’s experiment (§ 60), deglutition is rendered
more difficult. .

Goltz’s Experiments, —The cesophagus and stomach of-the frog become more excitable, 7.e.,
the excitability of the ganglionic plexuses in their walls is increased, when the brain and
spinal cord or both vagi are destroyed. These organs contract energetically after slight
stimulation, while frogs, whose central nervous system is intact, swallow fluids simply by
peristalsis. Females, and sometimes men also, suffering from hysteria, not unfrequently have
similar spasmodic contractions of the cesophageal region (globus hystericus). After section of
both vagi in the dog, Schiff observed spasmodic contraction of the cesophagus.

Effect on Circulation.—Every time one swallows, the heart’s action is accelerated, the blood-
pressure falls, the necessity for respiration diminishes, while many movements (labour pains,
erection) are inhibited, These effects are brought about reflexly (Kronecker and Meltzer, § 369).

230 | STRUCTURE OF THE SOPHAGUS.

[Structure of the @sophagus.—The walls of the cesophagus are composed of four coats—
mucous, sub-mucous, muscular, and fibrous (fig, 171).

(1) The mucous coat is firm, and is thrown into longitudinal folds, which disappear when the
tube is distended. It is lined by several layers of stratified squamous epithelium. The
membrane itself is composed, especially at itsinner part, of dense fibrous tissue, which projects,
in the form of papille, into the stratified epithelium. The papille are present in the child, but
are largest in old people. At its outer part is a continuous longitudinal layer of non-striped
muscle, the muscularis mucose, The layer consists of small bundles of non-striped muscle
separate from each other.

(2) The sub-mucous coat is thicker than the foregoing, and consists of loose connective-
tissue, with the acini of small mucous glands imbedded in it. The ducts pierce the muscularis
mucose to open on the inner surface of the tube.

_ (8) The muscular coat consists of an inner, thicker, circular, and an outer, thinner, longi-
tudinal layer of non-striped muscle, commencing on a level with the cricoid cartilage. In man
the upper third of the gullet consists of striped muscular fibres. (4) Outside the muscular coat

Excretory duct.

Stratified

ig Injected
epithelium. 1% :

capillaries,

Mucous mem-
brane with

Connective- muscularis
tissue with —¢ mucose,
papille,

Mucous
gland. =i

Circular mus-—

+

a

=) cular fibres.
.S)

bol

=

5 | Longitudinal
= muscular

= fibres.

Figs 171,
Transverse section of part of the cesophagus.

is a layer of fibrous tissue with elastic fibres. The structure of the muscular coat of the
cesophagus varies much in different animals. In the rabbit, in the first quarter of its length,
it has two layers, but below this there are three layers, 7.¢., a circular between an outer and an
aati longitudinal layer, while the non-striped fibres are confined to the lowest quarter of the
tube. ]

[Nerve-Plexuses,—As in the intestine, there are two plexuses of nerves with ganglia; one in
the sub-mucous coat (Meissner’s) and the other between the two muscular coats (Awerbach’s);
which are continuous with those in the stomach and intestine. Blood-vessels and numerous
lymphatics lie in the mucous and sub-mucous coats. ] .

157. MOVEMENTS OF THE STOMACH.—Position.—When the stomach
is empty, the great curvature is directed downwards and the lesser upwards ; but
when the organ is full, it rotates on an axis running horizontally through the
pylorus and cardia, so that the great curvature appears to be directed to the front
and the lesser backwards. |
_ Arrangement of the Muscular Fibres.—The non-striped muscular fibres of the stomach are
arranged in three directions or layers, an outer longitudinal continuous with those of the
cesophagus. This layer is best developed along the curvatures, especially the lesser. At the
pylorus the fibres form a thick layer, and become continuous with the longitudinal fibres of the
duodenum. The circular fibres form a complete layer; at the pylorus they are more numerous,
and constitute the sphincter-muscle or pyloric valve ; whilst at the cardia (inlet), such a
muscular ring is absent. The innermost oblique or diagonal layer is complete.

The Movements of the Stomach are of two kinds :—(1) The rotatory or churn-

ing movements, whereby the parts of the wall of the stomach in contact with the __

cv” =~

MOVEMENTS OF THE STOMACH, 231

contents glide to and fro witha slow rubbing movement. Such movements seem
to occur periodically, every period lasting several minutes (Beaumont). By these
movements the contents are moistened with the gastric juice, while the masses of
food are partly broken down. The formation of hair-balls in the stomach of dogs
and oxen indicates that such rotatory movements of the contents of the stomach
take place. (2) The other kind of movement consists in a periodically occurring
peristalsis, whereby, as with a push, the first dissolved portions of the contents of
the stomach are forced into the duodenum. ‘They begin after a quarter of an hour,
and recur until about five hours after a meal. This peristalsis is most pronounced
towards the pyloric end, and the muscles of the pyloric sphincter relax to allow the
contents to pass into the duodenum. According to Riidinger, the longitudinal
muscular fibres, when they contract, especially when the pyloric end is filled, may
act so as to dilate the pylorus.

Gizzard.—The strongly muscular walls of the stomach of grain-eating birds effect a tritura-

tion of the food. The older physiologists found that glass balls and lead tubes, which could
be re only by a weight of 40 kilos., were broken or compressed in the stomach of
a turkey.

Influence of Nerves.—|The stomach is supplied by the vagi and by the sympa-
thetic, the right vagus being distributed to the posterior surface, and the left to the
anterior surface, of the organ.] Auerbach’s ganglionic plexus of nerve-fibres and
nerve-cells, which lies between the muscular coats of the stomach, must be regarded
as its proper motor centre, and to it motor impulses are conducted by the vagi.
Section of both vagi does not abolish, but it diminishes the movements of the
stomach. The muscular fibres of the cardia may be excited to action, or their
action inhibited by fibres which run in the vagus (Nn. constrictores, et dilatator
cardie). [If the vagi be divided in the neck, there is a short temporary spasmodic
contraction of the cardiac aperture. On stimulating the peripheral end of the vagus
with electricity, after a latent period of a few seconds, the cardiac end contracts,
more especially if the stomach be distended, but the movements are slight if the
stomach be empty. In curarised dogs, the pylorus contracts with varying inten-
sity, and irregularly whether the vagi and splanchnics be intact or divided.
Stimulation of the vagi in the neck causes contraction of the pylorus, when the
latent period may be seven seconds. Stimulation of the splanchnics in the thorax
arrests the spontaneous pyloric contractions, the left splanchnic being more active
than the right (Oser). |

Local electrical stimulation of the surface of the stomach causes circular constrictions
of the organ, which disappear very gradually, while the movement is often propagated to
other parts of the gastric wall. When heated to 25° C., the excised empty stomach exhibits
movements. Injury to the pedunculi cerebri, optic thalamus, medulla oblongata, and even to
the cervical part_of the spinal cord, according to Schiff, causes paralysis of the vessels of certain
areas of the stomach, resulting in congestion and subsequent hemorrhage into the mucous
membrane. [It is no uncommon occurrence to find hemorrhage into the gastric mucous mem-
brane of rabbits, after they have been killed by a violent blow on the head. ]

[Action of Drugs.—The automatic centres are excited by emetin, apomorphin, tartar emetic,
while.muscarin causes general contraction of the stomach. The activity of the automatic centres
is diminished by chloral, urethan, morphin, and nicotin, while atropin causes paralysis of the
nerve-endings (LZ. Schiitz).] |

158. VOMITING.—Mechanism.— Vomiting is caused by contraction of the
walls of the stomach, the pyloric sphincter being-closed. It occurs most readily
when the stomach is distended—(dogs usually greatly distend the stomach by
swallowing air before they vomit); it readily occurs in infants, in whom the
cul-de-sac at) the cardia is not developed. It is quite certain that in children
vomiting oceurs through contraction of the walls of the stomach, without the
spasmodic action of .the abdominal walls. When vomiting is violent, the
abdominal muscles act energetically. [The act of vomiting is generally preceded
by a feeling of nausea, and usually there is a rush of saliva into the mouth,

232 | _ VOMITING.

caused by a reflex stimulation of afferent fibres in the gastric branches of the
vagus, the efferent nerve for the secretion of saliva being the chorda tympani.
After this a deep inspiration is taken, and the glottis closed, so that the diaphragm

is firmly pressed downwards against the abdominal contents, and it is kept con-
tracted ;.the lower ribs are pulled in. The diaphragm being kept contracted and

the glottis closed, a violent expiratory effort is made, so that the contraction of the
abdominal muscles acts upon the abdominal contents, the stomach being forcibly
compressed. The cardiac orifice is opened at the same time, and the contents of

the stomach are ejected. The chief agent seems to be the abdominal compression,

but the walls of the stomach also help, though only to a slight extent. |

The contraction of the walls of the stomach, which causes a general diminution of the gastric
cavity, is not a true anti-peristalsis, as can be seen in the stomach when it is exposed. The
cardia is opened by the longitudinal muscular fibres, which pull towards the lower orifice of the
cesophagus, so that when the stomach is full they must act as dilators. The act of vomiting is
preceded by a ructus-like dilating movement of the intra-thoracic part of the cesophagus, which
is caused thus :—The glottis is closed, inspiration occurs suddenly and violently, whereby the
cesophagus is distended by gases proceeding from the stomach. The larynx and hyoid bone, by
the combined action of the genio-hyoid, sterno-hyoid, sterno-thyroid, and thyro-hyoid muscles, are
forcibly pulled forwards, so that the air passes from the pharynx downwards into the upper
section of the cesophagus. If the abdominal walls contract suddenly, and if this sudden impulse
be aided by the movements of the stomach itself, the contents of the stomach are forced out-
wards. During continued vomiting, antiperistalsis of the duodenum may occur, whereby bile
passes into the stomach, and becomes mixed with its contents,

Children, in whom the fundus is absent, vomit more easily than adults. [In them also the
nervous system is more excitable. ] :

Influence of Nerves.—The centre for the movements concerned in vomiting
lies in the medulla oblongata, and is in relation with the respiratory centre, as
is shown by the fact that nausea may be overcome by rapid and deep respirations.
In animals, vomiting may be inhibited by vigorous artificial respiration. On
the other hand, the administration of certain emetics prevents the occurrence of
apnoea.

In vomiting, the afferent impulses may be discharged from (1) the mucous
membrane of the soft palate, pharynx, root of the tongue (glosso-pharyngeal nerve),
as in tickling the fauces with the finger; (2) the nerves of the stomach (vagus and
sympathetic) ; (3) stimulation of the uterine nerves (pregnancy); (4) the mesenteric
nerves (inflammation of the abdomen and hernia); (5) nerves of the urinary
apparatus (passing a renal calculus) ; (6) nerves to the liver and gall-duct (vagus) ;
(7) nerves to the lungs in phthisis (vagus). Vomiting is also produced by direct
stimulation of the vomiting centre. [The efferent impulses are carried by the
phrenics (diaphragm), vagus (cesophagus and stomach), and intercostals (abdominal
muscles). |

Vomiting, produced by the thought of something disagreeable, appears to be caused by the |
conduction of the excitement from the cerebrum to the vomiting centre. [It may also be excited
through the brain by a disagreeable smell, shocking sight, or by other impressions on the nerves
of special sense.] Vomiting is very common in diseases of the brain [tubercle, inflammation,

. hemorrhage]. Section of both vagi generally, but not always, prevents vomiting.

Emetics act (1) partly by mechanically or chemically stimulating the ends of the centripeta
(afferent) nerves of the mucous membrane. [These are local emetics.] Tickling the fauces, touch-
ing the surface of the exposed ‘stomach (dog) ; and many chemical emetics, ¢.g., mustard, cupric
and zine sulphate, and other metallic salts, act in this way. (2) Other substances cause vomitin
when they are introduced into the blood (without being first introduced into the stomach), an
act directly upon the vomiting centre, ¢.g., apomorphin. [These are general emetics.] (3) |
Lastly, there are some substances which act in both ways, ¢.g., tartar emetic. Emetics may also
remove mucus from the lungs, and in this case it is probable that the emetic acts upon the
respiratory centre, and so favours the respirations. The general emetics usually create con-
siderable depression, while the vomiting lasts longer than with local emetics. The former
increase the salivary, gastric, and Bespientony secretions. )

[Uses of Emetics,—Emetics are useful not only for pensive, from the stomach any offendin
body, be it a poison or the products of imperfect or perverted gastric digestion, or bile which
has passed-back into the stomach, but foreign bodies impacted in the cesophagus may be got

MOVEMENTS OF THE INTESTINE. 233

rid of on exciting vomiting by the subcutaneous injection of apomorphin. As the diaphragm
contracts vigorously during vomiting, it compresses the liver, and thus bile is.expelled into the
duodenum, or the passage of a small calculus along the bile-duct may be aided. They also are
useful in removing mucus or false membranes from the respiratory passages. ]

[Anti-Emetics,— Vomiting may be allayed by docal anti-emetics such as ice, and many chemical
substances such as bismuth, hydrocyanic acid, opium, and morphia, as well as by general
remedies which act on the vomiting centre. Some of the foregoing drugs perhaps act. both
locally and generally. ]

Vomiting is analogous to the process of rumination in animals that chew the cud (§ 187).
Some persons can empty their stomach in this way.

159. MOVEMENTS OF THE INTESTINE.—Peristalsis.—The best example
of peristaltic movements is afforded by the small intestine; the progressive
narrowing of the tube proceeds from above downwards, thus propelling the
contents before it. Frequently after death, or when air acts freely upon the gut,
the peristalsis develops at various parts of the intestine simultaneously, whereby
the loops of intestine present the appearance of a heap of worms creeping amongst
each other. The advance of new intestinal contents again increases the movement.
In the large intestine, the movements are more sluggish and less extensive. The
peristaltic movements may be seen and felt when the abdominal walls are very
thin, and also in hernial sacs. They are more lively in vegetable feeders than in
carnivora. The peristalsis is perhaps conducted directly through the muscular
substance itself, as in the heart and ureter. The movements of the stomach and
intestine cease during sleep (Busch).

[Rate of Motion.—In a Thiry-Velly fistula (§ 183, II.) Fubini estimated the rate of motion of
a smooth sphere of sealing-wax. It took 55 sec. to travel 1 ctm. [4 in.]; an induction-current
greatly increases the motion, to 1 ctm. in 10 seconds; NaCl does not affect it, but excites
secretion ; laudanum paralyses it. ]

Method of Observation. —Open the abdomen of an animal under a ‘6 per cent. saline solution
to prevent the exposure of the gut to air (Sanders and Braam-Houckgeest).

The ileo-colic valve, as a rule, prevents the contents of the large intestine from
passing backwards into the small intestine.

When fluid is slowly introduced into the rectum through a tube, it passes upwards into the
intestine, and even goes through the ileo-colic valve into the small intestine. Muscarin excites
very lively peristalsis of the intestines, which may be set aside by atropin (Schmiedeberg and
Koppe).

Pathological.— When any condition excites an acute inflammation of the intestinal mucous
membrane, catarrh is rapidly produced, and very strong contractions of the inflamed parts filled
with food take place. When these parts of the gut become empty, the movements are not
stronger than normal. If new material passes into the inflamed part, the peristalsis recurs,
becomes more lively than normal, and the result is diarrhoea (Nothnagel). Sometimes a greatly
contracted part of the small intestine is pushed into the piece of gut directly continuous with it,
giving rise to invagination or intussusception.

Anti-peristalsis, 7.¢., a movement which travels in an upward direction towards the stomach,
does not occur normally. This has been inferred from the fact, that in cases where the intestine
is occluded, called ileus, feecal matter is vomited. Nothnagel’s experiments throw doubts upon
this view, as he failed to observe anti-peristalsis in cases where the intestine was occluded
artificially. The fecal odour of the ejecta may result from the prolonged retention of the
material within the small intestine.

160. EXCRETION OF FHCAL MATTER.—The contents of the small
intestine remain in it about three hours, and about twelve hours in the large
intestine, where they become less watery, and they assume the characters of
feces, become “formed” in the lower part of the great intestine. The feces are
gradually carried along by the peristaltic movement, until they reach a point a
little above that part of the rectum which is surrounded by both sphincters, the
internal sphincter consisting of non-striped, and the external of striped muscle.

Immediately after the expulsion of the feces the external sphincter (fig. 172, S,
and fig. .173) usually contracts vigorously, and remains so for some time. After-
wards it relaxes, when the elasticity of the parts surrounding the anal opening,

234 EXCRETION OF FACAL MATTER.

particularly of the two sphincters, suffices to keep the anus closed. In the interval
between two evacuations, there does not seem to be a continued tonic contraction
of the sphincters. As long as the feces lie above the rectum, they do not excite
any conscious sensations, but the sensation of requiring to go to stool occurs when
the feces —pass into the rectum. At the same time, the stimulation of the sensory
nerves of the rectum causes a reflex excitement of the sphincters. The centre for
these movements (Budge’s centrum anospinale) lies in the lumbar region of the
spinal cord (§ 362); in the rabbit between the sixth and seventh, and in the dog
at the fifth lumbar vertebra (Maszus).

In animals whose spinal cord is divided above the centre, a slight touch in the region of the
anus causes this orifice to contract, but after this lively reflex contraction, the sphincters relax

again, and the anus may remain open fora time. This occurs because the voluntary impulses
which proceed from the brain to*cause the contraction of the external sphincter are absent,

Fig. 172.
The perineum and its muscles. 1, anus; 2, coceyx; 3, tuberosity ; 4, sciatic ligament; 5,
cotyloid cavity ; B, bulbo-cavernosus muscle ; T's, superficial transverse ae muscle ;
e

F, fascia of the deep transverse perineal muscle ; J, ischio-cavernosus musc
internus ; 8S, external anal sphincter ; L, levator ani; P, pyriformis.

Landois observed that in dogs with the posterior roots of their lower lumbar and sacral nerves
divided, the anus remained open, and not unfrequently a mass of faces remained half ejected.
As the sensibility of the rectum and anus was abolished in these animals, the sphincters could
not contract reflexly, nor could there be any voluntary contraction of the sphincters, the result
of sensory impulses from the rectum,

; M, obturator

The external sphincter can be contracted voluntarily, like any voluntary muscle,
but the closure of the anus can only be effected up toa certain degree. When
the pressure from above is very great, the energetic peristalsis at last overcomes

—$, —_ ———-

wee 4! Oe eae

“"DEFACATION, — 235

the strongest voluntary impulses. Stimulation ofthe peduncles of the cerebrum and
of the spinal cord below this point causes contraction of the external sphincter.
Defecation.—The evacuation of the feces, which in man usually occurs at
certain times, begins with a lively peristalsis of the large intestine, which passes
downwards to the rectum. In order that the mass of feces may not excite reflexly
the sphincter-muscles, in consequence of mechanical stimulation of the sensory
nerves of the rectum, there seems to be a centre which inhibits the reflex action
of the sphincters, which is called into play, owing, as it appears, to voluntary
impulses. Its seat is in the brain, perhaps in the optic thalami. When this

Fig, 173,
Levator ani and sphincter ani externus.

inhibitory apparatus is in action, the fecal mass passes through the anus,’ without
causing it to close reflexly. The strong peristalsis which precedes defeecation can
be aided, and to a certain degree excited, by rapid voluntary movements of the
external sphincter and levator ani, whereby the plexus myentericus of the large
intestine is stimulated mechanically, thus causing lively peristaltic movements in
the large intestine. The expulsion of the faces is also aided by the pressure of
the abdominal muscles, and most efficiently when a deep respiration is taken, so
as to fix the diaphragm, whereby the abdominal cavity is diminished to the
greatest extent. The soft parts of the floor of the pelvis, during a strong effort at
stool, are driven downwards in the form of a cone, causing the mucous membrane
of the anus, which contains much venous blood, to be everted. The function of

the levator ani (figs. 172, 173) is to raise voluntarily the soft parts of the floor of

the pelvis, and to pull the anus to a certain extent upwards over the descending
fecal mass. At the same time, it prevents the distension of the pelvic fascia. As

236 CONDITIONS INFLUENCING THE INTESTINAL MOVEMENTS.

the fibres of both levatores converge below, and become united with the fibres of
the external sphincter, they aid the latter, during energetic contraction of the
sphincter ; or, as Hyrtl put it, the levatores are related to the anus, like the two
cords of a tobacco pouch. During the periods between the evacuation of the gut,
the feeces appear only to reach the lower end of the sigmoid flexure. As a rule,
from thence downwards, the rectum is normally devoid of feces. It seems that
the strong circular fibres of the muscular coat, which Nélaton has ealled sphincter
ani tertius, when they are well developed, contract and prevent the entrance of
the feces. When the tendency to the evacuation of the rectum is very pressing,

Fig. 174.
Auerbach’s plexus shown in section (human). a, ganglionic cells; 0, nerve fibres ;
c, section of the circular muscular fibres ; d, longitudinal muscular fibres.

the anus may be closed more firmly from without, by energetically rotating the
thigh outwards, and contracting the muscles of the gluteal region. :

161. CONDITIONS INFLUENCING THE INTESTINAL MOVEMENTS.—

The intestinal canal contains an automatic motor centre within its walls,—the

Fig. 175.
Plexus of Auerbach, prepared from the small intestine of a dog, by the action of gold chloride.
The nerve-cells are shown at the nodes, while the fibrils proceeding from the ganglia, and
the anastomosing fibres, lie between the muscular bundles.

plexus myentericus of Auerbach—which lies between the longitudinal and circular
muscular fibres of the gut. It is this plexus which enables the intestine, when cut
out of the body, to execute, apparently spontaneously, movements for some time.

AUERBACH AND MEISSNER’S PLEXUSES. 237

- [Structure,—Auerbach’s Plexus consists of non-medullated nerve-fibres which form a dense
network, groups of ganglion cells occurring at the nodes (fig. 175, and when seen in vertical
sections between the muscular coats it is like fig. 174). A similar plexus extends throughout
the whole intestine between the longitudinal and circular muscular coats from the cesophagus
to the rectum. Branches are given off to the muscular bundles. A similar, but not so rich a
ee lies in the submucous coat,

eissner’s plexus, which gives branches rf
to supply the muscularis mucose, the |
smooth muscular fibres of the villi, and
the glands of the intestine (fig. 176).

1. If this centre is not affected
by any stimulus, the movements of
the intestine cease—comparable to
the condition of the medulla ob-
longata in apnoea. The same is
true—just as in the case of the
respiration—during intra-uterine
life, in consequence of the fcetal
blood being well supplied with O.
This condition may be termed
aperistalsis. It also occurs during
sleep, perhaps on account of the
greater amount of O in the blood
during that state.

2. When blood containing the
normal amount of blood-gases
passes through the intestinal blood-
vessels, the quiet peristaltic move-
ments of health occur (euperistal-
sis) provided no other stimulus be
applied to the intestine. Te

3. All stimuli applied to the i? Wee
plexus myentericus increase the
peristalsis, which may become so Fig. 176.
very violent as to cause evacuation Plexus of Meissner. a, ganglia; 0, anastomosing
of the contents of the large gut, fibres; c, artery; d, vaso-motor nerve-fibres accom-
and may even produce spasmodic Panying ¢. |
contraction of the musculature of the intestine. This condition may be termed
dysperistalsis, corresponding to dyspneea. The condition of the blood flowing
through the intestinal vessels affects the peristalsis.

Condition of the Blood.—Dysperistalsis may be produced by (a) interrupting the circulation
of the blood in the intestines, no matter whether anemia (as after compressing the aorta—
Schiff) or venous hyperemia be produced. The stimulating condition is the want of O, z.e.,
the increase of CO,. Very slight disturbance in the intestinal blood-vessels, ¢.g., venous con-
gestion after copious transfusion into the veins, whereby the abdominal and portal veins become
congested, causes increased peristalsis. The intestines become nodulated at one part and narrow
at another, and involuntary evacuation of the feces takes place when there is congestion, owin
to the plugging of the intestinal blood-vessels when blood from another species of animal is use
for transfusion (§ 102). The marked peristalsis which occurs on the approach of death is
undoubtedly due to the derangements of the circulation, and the consequent alteration of the
amount of gases in the blood of the intestine. The sanfe is true of the increased movements of
the intestines which occur as a result of psychical excitement, ¢.g., grief. The stimulus, in this
case, passes from the cerebrum through the medulla oblongata (vaso-motor centre) to the intes-
tinal nerves, and causes anemia of the intestine (corresponding to the palor occurring elsewhere).
When the normal condition of the circulation is restored, the peristalsis diminishes. (6) Direct
stimulation of the intestine, conducted to the plexus myentericus, causes dysperistalsis; direct
exposure of the intestines to the air (stronger when CO, or Cl is present)—introduction of
various irritating substances into the intestine—increased filling of the intestine when there is
any difficulty in emptying the gut (often in man)—direct stimulation of various kinds (also

238 INFLUENCE OF NERVES ON THE INTESTINE,

inflammation),—all act upon the intestine, either from without or from within. Induction-
shocks applied to a loop of intestine in a hernial sac cause lively peristalsis in the hernia. The
intestinal movements are favoured by heat.

4. The continued application of strong stimuli causes the dysperistalsis to give
place to rest, owing to over-stimulation, which may be called “ intestinal paresis,”
or exhaustion.

This condition is absolutely different from the passive condition of the intestine in aperistalsis,
Continued congestion of the intestinal blood-vessels ultimately causes intestinal paralysis, e.g.,
when transfusion of foreign blood causes coagulation within these vessels. Filling the blood-
vessels with ‘‘ indifferent” fluids, after the peristalsis has been previously brought about by
compressing the aorta, also causes cessation of the movements (0. Nasse). The movements
cease when the intestines are cooled to 19° C. (Horwath), while severe inflammation of the
intestine has a similar effect. Under favourable circumstances, the intestine may recover from
this condition. Arterial blood admitted into the vessels of the exhausted intestine causes
peristalsis, which at first is more vigorous than normal.

5. The continued application of strong stimuli causes complete paralysis of the
intestine, such as occurs after violent peritonitis, or inflammation of the muscu-
lature or mucous coat in man. In this condition, the intestine is greatly distended, ~
as the paralysed musculature does not offer sufficient resistance to the intestinal
gases which are expanded by the heat. This constitutes the condition of
meteorism.

Influence of Nerves.—With regard to the nerves of the intestine, stimulation of
the vagus increases the movements (of the small intestine), either by conducting
impressions to the plexus myentericus, or by causing contraction of the stomach,
which stimulates the intestine in a purely mechanical manner (Braam-Houckgeest).
The splanchnic is (1) the inhibitory nerve of the small intestine (Pfliiger), but
only as long as the circulation in the intestinal blood-vessels is undisturbed, and
the blood in the capillaries does not become venous ; when the latter condition
occurs, stimulation of the splanchnic increases the peristalsis. If arterial blood be
freely supplied, the inhibitory action continues for some time. Stimulation of the
origin of the splanchnics, of the spinal cord in the dorsal region (under the same
conditions), and even when general tetanus has been produced by the administration
of strychnia, causes an inhibitory effect. It is inferred that the splanchnic contains
—(2) inhibitory fibres, which are easily exhausted by a venous condition of the
blood, and also motor jibres, which remain excitable for a longer time, because after
death, stimulation of the splanchnics always causes peristalsis, just like stimulation
of the vagus. (3) It is the vaso-motor nerve of the intestinal blood-vessels, so that
it governs the largest vascular area in the body. When it is stimulated, all the
vessels of the intestine which contain muscular fibres in their walls contract ; when
it is divided, they dilate. In the latter case, a large amount of blood accumulates
within the blood-vessels of the abdomen, so that there is anemia of the other parts
of the body, which may be so great as to cause death—owing to the deficient supply
of blood to the medulla oblongata. (4) It is the sensory nerve of the intestine,
and, under certain circumstances, it may give rise to very painful sensations.

As stimulation of the splanchnic contracts the blood-vessels, von Basch has raised the ques-
tion whether the intestine does not come to rest, owing to the want of the blood, which acts as
a stimulus. But, when a weak stimulus is applied to the splanchnic, the intestine ceases to
move before the blood-vessels contract (van Braam-Houckgeest) ; it would therefore seem that
the stimulation diminishes the excitability of the plexus myentericus. According to Engel-
mann and v. Brakel, the peristaltic movement is chiefly propagated by direct muscular con-
duction, as in the heart and ureter, without the intervention of any nerve-fibres.

[Effect of Nerves on the Rectum.—The nervi erigentes, when stimulated, cause the longi-
tudinal muscular fibres of the rectum to contract, while the circular muscular fibres are pe League
by the hypogastric nerves. Stimulation of the latter nerves also exerts an inhibitory effect on
the longitudinal muscles. Stimulation of the nervi erigentes inhibits not only the spontaneous
movements of the circular fibres of the rectum, but also those movements excited by stimulation
of the hypogastric nerves (Fellner).}

_ [Artificial Circulation in the Intestine.—Ludwig and Salvioli excised a loop of intestine

EFFECTS OF DRUGS ON THE INTESTINE. 239

from an animal, tied a cannula into an artery and another into a vein, and kept it in a warm moist
atmosphere. The arterial cannula was connected with a vessel containing defibrinated blood,
to which different drugs could be added. A lever rested on the intestine, and registered its
movements on a recording surface. As long as arterial blood was tranfused, the intestine was
nearly quiescent, but when it was arrested, so that the blood became venous, a series of con-
tractions occurred. Nicotin diminished the flow of blood and quickened the intestinal move-
ments, while at the same time the circular muscular fibres remained contracted or tetanic.
Tincture of opium, in the proportion of ‘01 to ‘04 in the blood, causes at first contraction of the
vessels, and lessens the amount of blood circulating in the intestine ; but it very rapidly increases
—even to six times—the amount of blood which transfuses, while at the same time the move-
ments of the intestine cease, the walls of the intestine being contracted. Peptone caused first
strong and then irregular contractions. ]

Effect of Drugs.—Amongst the reagents which act upon the intestinal movements are :—(1)
Such as diminish the excitability of the plexus myentericus, 7.e., which lessen or even abolish
intestinal peristalsis, ¢.g., belladonna. (2) Such as stimulate the inhibitory fibres of the
splanchnic, and in large doses paralyse them—opium, morphia ; 1 and 2 produce constipation.
(3) Other agents excite the motor apparatus—nicotin (even causing spasm of the intestine),
muscarin, caffein, and many laxatives, which act as purgatives. The movements produced by
muscarin are abolished by atropin. These substances accelerate the evacuation of the intestine,
and, owing to the rapid movement of the intestinal contents, only a small amount of water is
absorbed ; so that the evacuations are frequently fluid. (4) Amongst purgatives, colocynth and
croton oil act as direct irritants. With regard to drugs of this sort, they seem to cause a watery
transudation into the intestine, just as croton oil causes vesicles when applied to the skin. (5)
Calomel is said to limit the absorptive activity of the intestinal wall, and to control the decom-
positions in the intestine. The stools are thin and greenish, from the admixture of biliverdin.
(6) Certain saline purgatives—sodium sulphate, magnesium sulphate—cause fluid evacuations
by retaining the water in the intestine ; and it is said that if they be injected into the blood-
vessels of animals, they cause constipation. [When acrystal of a potash salt is applied to the
peritoneal surface of the intestine of an animal, it causes merely a‘local constriction of the mus-
cular fibres of the gut, while a sodiwm salt excites a contraction which passes tpwards towards
the stomach, and never towards the rectum. In any case it may serve as a useful guide to the
surgeon, in determining which is the upper end of a piece of intestine during an operation on
the intestines (Vothnagel). ]

[Saline Cathartics.—A salt exerts a genuine excito-secretory action on the glands of the
intestines, whilst at the same time, ‘in virtue of its low diffusibility, it impedes absorption.
Thus, between stimulated secretion and impeded absorption there is an accumulation of fluid
within the canal, which reaches the rectum and results in purgation. Purgation does not ensue
when water is withheld from the diet for one or two days previous to the administration of the
salt in a concentrated form. When a concentrated solution of a salt is administered to an
animal whose alimentary canal is empty, but whose blood is in a natural state of dilution, the
blood becomes rapidly very concentrated, and reaches the maximum of its concentration in from
half an hour to an hour and a half ; within four hours the blood has gradually returned to its
normal state of concentration, without having reabsorbed fiuid from the intestine. It appar-
ently recoups itself from the tissue-fluids. The salt—sulphate of magnesia or sulphate of soda
—becomes split up in the small intestine, and the acid is more rapidly absorbed than the base.
A portion of the absorbed acid shortly afterwards returns to the intestines, evidently through
the intestinal glands. The salt does not purge when injected into the blood, and excites no
intestinal secretion ; nor does it purge when injected subcutaneously, unless on account of its
causing local irritation of the abdominal subcutaneous tissue, which acts reflexly on the intestines,
dilating their blood-vessels, and perhaps stimulating their muscular movements (M. Hay).

162. STRUCTURE OF THE STOMACH.—{The stomach receives the bolus,
and secretes a juice which acts on certain constituents of the food, while by its
muscular walls it moves the latter within its own cavity, and after a time expels
the partially digested products towards the aencenere

Structure.—|The walls of the stomach consist of four coats, which are from
without inwards (fig. 177)—

(1) The serous layer, from the peritoneum.

(2) The muscular layer, composed of three layers of non-striped muscular fibres—(a)

longitudinal, (0) circular, (c) oblique (§ 15).

(3) The sub-mucous layer of loose connective-tissue, with the larger blood-vessels, lym-

phatics, and nerves.

(4) The mucous layer. }

_ The well-developed mucous membrane of the stomach is thrown into a series of folds or
rugs, in a contracted condition of the organ. With the aid of a hand-lens, it is seen to be

-

240 . §$TRUCTURE OF THE STOMACH,

beset with small irregular depressions or pits (fig. 179). Throughout its entire extent it is
covered by a single layer of moderately tall, narrow, cylindrical epithelium, which seems to
consist of mucus-secreting goblet-cells (fig. 178). The
epithelium is sharply defined at the cardia from the
stratified epithelium of the cesophagus, and also at the
pylorus, from the true cylindrical epithelium with the
striated disc in the duodenum. [The cells contain a
plexus of fibrils, and in the passive condition seem to

Mucous coat.

Sub-mucous
coat.

,
{
a
,
:

Muscular °
coat.

Serosa. — *
Fig. 177. >» Big, 1793
Fig. 177.—Vertical section of the wall of the human stomach, x15. £., epithelium; G7, glands;

Mm., muscularis mucose. Fig. 178.—Goblet-cells of the stomach, Fig. 179.—Surface sec-
tion of the dog’s gastric mucous membrane, showing pits, 7, 7 ; a, the elevations round 4, @,

consist of two zones, an outer clear part, next the lumen of the organ, consisting of a sub-
stance (mucigen) which yields mucus, the attached end of the cell being granular.] The oval
nucleus lies about the centre of the cells. Spindle-shaped, nucleated cells, probably for re-

Fig. 180.

I, Transverse section of a duct of a fundus-gland—a, membrana propria ; 6, mucus-secreting
goblet-cells ; c, adenoid interstitial substance. II, Transverse section of a fundus-gland—
a, chief, h, parietal-cells ; 7, adenoid tissue ; c, capillaries,

placing the others, are said by Ebstein to occur at their bases.- All the cells are open at
their free ends, so that the mucus is readily discharged, leaving the cells empty. Numerous —
taleiae glands of ¢wo distinct kinds are placed vertically, like rows of test-tubes, in the mucous
membrane, . ys ; ST

PYLORIC GLANDS OF THE STOMACH. 241

*

_ The cardiac portion of the gastric mucous membrane consists of a number of microscopic
tubular glands placed side by side, the fundus-glands of Heidenhain, otherwise called peptic,
or cardiac. Several gland-tubes, which are wider below, usually open into the duct (fig. 182),
Each gland consists of a structureless membrana propria with anastomosing branched cells in
relation with it. The duct is short, about one-fifth of the whole tube, and is lined by a layer
of cells like those lining the stomach, while the secretory part of the tubes is lined through-
out by a layer of granular, short, small, polyhedral, or columnar
nucleated cells. ‘hese cells border the very narrow lumen,
and are called principal (Heidenhain), central (fig. 180, II,
a), or adelomorphous cells (a5nAos, hidden). At various places,
between these cells and the membrana propria, are large, oval,
or angular, well-defined, granular, densely reticulated, nucleated
cells, the parietal cells of Heidenhain, the delomorphous cells of
Rollett, or the oxyntic (acid-forming) cells of Langley (fig. 180,
II, 2). They are most numerous in the neck of the glands, and
least so in the deep blind end of the tubes. These cells are stained
deeply by osmic acid and aniline blue, so that they are readily dis-
tinguished from the other cells. They bulge out the membrana
propria of the gland opposite where they are placed. The parietal
cells in man are said to reach to the lumen of the gland-tubes
(Stéhr). Isolated cells are sometimes found under the epithelium
of the surface of the stomach, and occasionally in individual pyloric
glands. The fundus-glands are most numerous (about five millions),
and are of considerable size in the fundus.

2. The pyloric glands occur only in the region of the pylorus,
where the mucous membrane is more yellowish-white in colour (fig.
181, A). These glands are generally branched at their lower ends,
so that several tubes open into a single duct [which, in contra-
distinction to the duct of the other glands, is wide and long, extend-
ing often to half the depth of the mucous membrane. The duct is
lined by epithelium like that lining the stomach, while the secretory
part is lined by a single layer of short, finely granular, columnar
cells, whose secretion is quite different from that of the cells lining
the duct. The lumen is well defined. Nussbaum has occasionally
found other cells, which stain deeply with osmic acid, between the
bases of these. The appearance of the cells differs according to
their state of physiological activity (figs. 183, 184). When they are
exhausted they are smaller and more granular, owing to the denser
reticulation of their network; at any rate they are granular in pre-
parations hardened in alcohol (fig. 184). There are no parietal
cells, ]

The glands are supported by very delicate connective-tissue : a
mixed with adenoid sce (fig. 180). Below this are two layers, A, Isolated pyloric gland.
circular and longitudinal, of non-striped muscle, the muscularis mucose (fig. 177, Mm.),
and from it fine processes of smooth muscular fibres pass up between groups of the glands
towards the free epithelial surface of the mucous membrane. Perhaps these processes are con-
cerned in emptying the glands. [In the gastric mucous membrane of the cat, there is a clear
homogeneous layer, which is stained red by picro-carmine, and placed immediately internal
to the muscularis mucose. It is pierced by the processes passing from the muscularis mucose. ]

Masses of adenoid tissue occur in the mucous membrane, especially near the pylorus, con-
stituting lymph-follicles, which are comparable to the solitary glands of the small intestine.
The lymphatics are numerous, and begin close under the epithelium by dilated extremities or
loops (fig. 182, d) ; they run vertically, and anastomose in the mucosa between the gland-tubes,
which they envelop in sinus-like spaces. They join large trunks in the mucosa ; another plexus
of large vessels exists in the sub-mucosa (Lovéi). .

[The Nerves,—A plexus of non-medullated nerve-fibres and a few ganglion cells exist in the
muscular coat [Auerbach’s], and another [Meissner’s] in the sub-mucosa. ] .

The blood-vessels are very numerous. Small arterial.branches, a, run in the sub-mucosa,
and ascend between the glands to form a longitudinal capillary network, c,c, under the epithe-
lium, and between its meshes the gland-ducts open, g. The veins gradually collect from this
horizontal capillary network, and run towards the large veins of the sub-mucosa, v.

- 163, THE GASTRIC JUICE.—Properties.—The gastric juice is a tolerably

clear colourless fluid, with a strong acid reaction, sour taste, and peculiar character-

istie odour; it rotates the plane of polarised light to the left. It is not rendered

turbid: by boiling, and resists putrefaction for a long time. Its specific gravity =
é; | Q

AN
AY}!
\S

Se ot
fo,
Uyy,O

//
L/ole/e/y Q
IN MALY

/ y
[Df o/-f, Je
MPM

6! alo
Li)

242 , THE GASTRIC. JUICE.

1002°5 (dog, 1005), and it contains only $ per cent. of solid constituents. The
quantity secreted in 24 hours was estimated by Beaumont, from observations upon
Alexis St Martin, who had a gastric fistula (1834)—at only 180 grms. daily (!); by
Grunewald (1853), in a similar case, as equal to 26-4 per cent. of the body-weight;
while Bidder and Schmidt (from corresponding observations on dogs) estimated it as
equal to 64 kilos. daily, corresponding to +4, of the body-weight. It contains:—
(1) Pepsin, the characteristic hydrolytic ferment or enzym, which dissolves

Teese

“

Fig. 182.

Vertical section of the gastric mucous membrane, ,g, pits on the surface ; p, neck of a fundus-
gland opening into a duct, g; 2, parietal, and y, chief cells; a, v, c, artery, vein, capil-
laries ; d, d, lymphatics, emptying into a large trunk, e.

proteids. E. Schiitz obtained 0°41 to 1:17 per cent. from a fasting person by
means of the cesophageal sound.

(2) Free hydrochloric acid (Prout, 1824), 0:2 to 0:3 (Richet, 0°8 to 2:1) per
1000; (in the dog, 0°52 per cent.). It occurs free, as the gastric juice always con-
tains more free chlorine than bases, to which it can be united (C. Schmidt). Lactic
eee prvally met with, but it arises from the fermentation of the carbohydrates.
of the food.

_ Tests.—Free hydrochloric acid is detected by the following reactions :—-0°025 per cent. solu-
tion of mythyl-violet becomes blue ; or alkaline solution of 00-tropseolin becomes lilac ; or, red

243:

ppears, becomes rose-

[Giinzburg recommends an alcoholic solution of phloroglucin-vanillin, 2 grammes of

ca]
oO
—
>
>
oO
rea
(=)
aH
M
<
es)
&
en
al

Bordeaux wine, treated with amylic alcohol until its colour almost disa

coloured,

grammes of absolute alcohol, which gives a
y weak mineral acids cause, with this solution,

ght red colour with the formation of bright red cryst

phloroglucin are mixed with 1 gramme of vanillin in 30
o not affect. it.

yellowish-red solution. Concentrated and even ver

a bri
d

als, while concentrated organic acids
of the filtered gastric juice and the

and evaporate carefully, not allowing it to boil; a red pellicle

qual quantities
presence of minute traces of hydrochloric acid. Congo-red,

go-red papers, becomes blue, but the reaction is interfered with by

For gastric juice mix e

either in solution or as con

with red erystals indicates the
the presence of ammonia

above solution in a watch-glass,

, or ammoniacal salts. ]

Lactic Acid.
carbolic acid

is changed to

TS
=S
= Se

NESS
5

Se fie
Rapesy

as,

SSE
SS

and 1 drop of liquor ferri perchloride,

oC

{<3

x)
7 2, A ra
f ij PGF LUUl, y i

—The freshly-prepared blue solution of 10 c.c. of a 4 per cent. solution of

, with 20 c.c. of distilled water,

yellow by lactic acid (Ufelmann).

Titteangel

Degas O

STI \\
5

Pyloric glands showing changes of the
cells during digestion.

Fig. 183.
Section of the pyloric mucous membrane.

(3) The large amount of mucus covering the surface of the mucous membrane is

(§ 162), (§ 136, II.).

-curdling ferment,

and a milk

-cells of the mucous membrane

2
(ep
>
S
ro
om
oO
a,
NI
a
[e?)
3s
mo S
ore
a
b
2.8
3
p ees
o
aS
eo ~*~
RQ

y are chiefly sodium and

also in animals),

and iron.
following appear:
yanide, ferric

iodide—potassium sulphoc

horic acid with lime, magnesium,
—HI, after the use of potassium io
and ammonium carbonate in uremia,

chlorides, less calcic chloride (ammonium chloride,
be introduced into the body, the

unds of phosp

potassium
which may

and the compo

sugar ;

gst foreign substances,

gastric juice—

~ The
Amon

in the

lactate, and

244 SECRETION OF GASTRIC JUICE.
_ {Composition of Gastric Juice (Hoppe-Seyler after C. Schmidt).
a ,

Constituents. | Hama: Il MA ul Sheep.

: | With saliva. No saliva.
Water, . . . .| 994404 971°171 973°062 * 986143
Organic matter, . . | 3°195 17°336 17°127 4°055
Free HCl _ 0:200 2°337 3°050 1°284
CaCl,, | 0-061 1°661 0-624 0-114
NaCl, | 1°465 3147 2507 4369
KCl, | 0°550 1:073 1°125 —-1°518
NH,Cl, ane 0°537 0468 0°473
Ca,2(PO,), |) \ 2°294 1°729 1°182
Mg,2(PO,), . ; fl 0°125 0323 0226 0°577
FePO,, ire \f ( 0-121 0-082 0'331

Good human saliva is not so dilute or so poor in HClas I. Szabo has found even 3 of HCl
per 1000 in man. ]

164. SECRETION OF GASTRIC JUICE.—After the discovery of the two
kinds of glands in the stomach and the two kinds of cells in the fundus-glands,
the question arose as to whether the different constituents of gastric juice were
formed by different histological elements.

Changes of the Cells during Digestion.—During the course of digestion, the cells of the
fundus (and pyloric glands, dog) undergo important changes (Heidenhain). During hunger, the
chief cells are clear and large, the parietal investing-cells are small, the pyloric cells clear and
of moderate size. During the first six hours of digestion, the chief cells become enlarged and
moderately turbid or granular, the parietal cells also enlarge, while the pyloric cells remain
unchanged. The chief cells become diminished and more turbid or granular until the ninth
hour, the parietal cells are still swollen, and the pyloric cells enlarge. During the last hours
of digestion, the chief cells again become larger and clearer, the parietal cells diminish, the
pyloric cells decrease in size and become turbid (figs. 183 and 184).

[Langley gives a different description of the appearances presented by these cells. The
results may be reconciled by remembering that the gland-cells were examined under different
conditions, The secretory cells consist of a cell-substance composed of (a) a framework of living
protoplasm, either in the form of an intracellular fibrillar network, or in flattened bands. The
meshes of this framework enclose at least two chemical substances, viz., (b) a hyaline substance
in contact with the framework, and (c) spherical granules which are embedded in the hyaline
substance. During active secretion, the granules decrease in number and size, the hyaline sub-
stance increases in amount, the network grows. This is the reverse of what is stated above as the
observation of Heidenhain, but the granular appearance described by Heidenhain after secretion
is very probably due to the action of the hardening agent, alcohol. Langley found that in the
living condition, or after the use of osmic acid, in some animals at least, the chief cells are
granular during rest, but during a state of activity two zones are differentiated, an outer one,
which is clear, owing to the disappearance of the granules, and an inner more or less granular
one. Granules reappear in the outer part after rest. During digestion, the parietal cells
increase in size, but do not become granular. In all cells containing much pepsinogen, distinct
granules are present, and the quantity of pepsinogen varies directly with the number and size
of the granules. In the glands of some animals there is little difference between the resting
and active phases. Compare Serows Glands, § 143, and Pancreas, § 168.]

The pepsin is formed in the chief cells (Heidenhain). When these are clear and
large, they contain much pepsin ; when they are contracted and turbid, the amount is
small. The pyloric glands are also said to secrete pepsin, but only to a small extent.
Pepsin accumulates during the first stage of hunger, and it is eliminated during
digestion and also during prolonged hunger. © Pepsin as such; is not present within
the cells, but only as a “ mother-substance,” a pepsinogen-substance (zymogen), or:
propepsin, which occurs in the granules of the chief cells. - This zymogen, or mother-
substance, by itself, has no effect upon proteids; but if it be treated with hydrochloric
acid or sodium chloride, it is changed into pepsin. Pepsin and pepsinogen may be.
extracted from the gastric mucous membrane by means of water free from acids,

[Pepsinogen and Pepsin.—Glycerine extracts very little pepsin from the. perfectly resh
gastric mucous membrane, but a large amount is afterwards obtained by extracting it with

FORMATION OF HYDROCHLORIC ACID. 2 45

dilute hydrochloric acid, or with ‘this acid and glycerine. The relative amount of pepsinogen
and pepsin in a fluid may be determined approximately by the method of Langley and Edkins.
A 1 per cent. solution of sodic carbonate exerts a greater destructive action on pepsin than on

pepsinogen, while a current of CO, destroys pepsinogen to a greater extent than pepsin. Both
substances are unaffected by CO, but are destroved at 54° to 57° C.] '

- The pyloric glands secrete pepsin, but no acid. Klemensiewicz excised in a
living dog the pyloric portion of the stomach, and afterwards stitched together the
duodenum and the remaining part of the stomach. The excised pyloric part, with
its vessels intact, he stitched to the abdominal wall, after sewing its lower end.
The animals experimented on died, at the latest, after six days. The secretion of
this part was thin, alkaline, and contained 2 per cent. of solids, including pepsin.

[Pyloric Fistula.—In fig. 185 P represents the excised pyloric portion, C the cardiac. The
parts a, a, and a’ a’ were then stitched together, and the con-

tinuity of the organ established. The lower end (d) of P was

closed by sutures, while the edges of P at O were stitched to

the abdominal walls, thus making a pyloric fistula. ] * eso “
In the frog the alkaline glands of the cesophagus ,/

contain only chief cells which produce pepsin; while f{;

the stomach has glands which secrete acid (and per-

haps some pepsin), and are lined by parietal cells.

Amongst fishes the carps have no fundus-glands in the
stomach (Luchaw). [The secreting portions of glands of the
eardiac sac (crop) of the herring are lined by a single layer of
polygonal cells (W. Stirling).]

The hydrochloric acid is formed, according to Diagram of pees
Heidenhain, by the parietal cells. It occurs on the Sap eA
free surface of the gastric mucous membrane as well as in the ducts of the fundus-
glands. The deep parts of the glands are usually alkaline. Free HCl is detected
in human gastric juice, within 45 minutes to 1 to 2 hours after a moderate meal,
but in 10 to 15 minutes in a fasting condition after drinking water; the amount
gradually increases during the process of digestion. Lactic acid, perhaps derived
from the food, is found in the stomach immediately after taking food, after half an
hour along with HCI, while after an hour only HCl is found (Hwald and Boas),

Cl. Bernard injected potassium ferrocyanide and afterwards lactate of iron into the veins of
a dog. After death, blue coloration occurred only in the upper acid layers of the mucous
membrane. Nevertheless, we must assume that the hydrochloric acid is secreted in the parietal
cells of the fundus of the glands, and that it is rapidly carried to the surface along with the
pepsin. Briicke neutralised the surface of the gastric mucous membrane with magnesia usta,
chopped up the mucous membrane with water, and left it for some time, when the fluid had
again an acid reaction. :

As to the formation of a free acid, the following statements may be noted :—
The parietal cells form the hydrochloric acid from the chlorides which the mucous
membrane takes up from the blood. According to Voit, the formation of acid
ceases, if chlorides be withheld from the food. Maly suggests that the active
agent is lactic acid, which splits up sodium chloride and forms free HCl. The
base set free is excreted by the urine, rendering it at the same time less. acid.
The formation of acid is arrested during hunger. According to H. Schultz, watery
solutions of alkaline and earthy. chlorides are decomposed, even at a low tempera-
ture, by CO,, free hydrochloric acid being formed. |

[The source of the HCl is undoubtedly the sodic chloride in the blood and lymph, but what
other acid displaces the HCl is a matter of conjecture. In this connection, it is important to
remember that Jul. Thomsen has shown that every acid can displace a part of another acid from
its combination with its base, and. the weaker acid may even combine with the greater part of
the base. Thomsen calls this ‘‘ avidity.” Even strong mineral acids may be displaced by weak
organicones. Thus the free CO, in the alkaline blood may set free a small quantity of HCl from
the sodic chloride. What is still more remarkable is, that the free HCl should be transferred by
the cells towards the gland-duct, while the sodic carbonate diffuses towards the blood and lymph. J

- Secretion.— When the stomach is empty, there is usually no secretion of gastric

246 INFLUENCE OF NERVES ON THE SECRETION.

juice ; this takes place only after appropriate (mechanical, thermal, or chemical)
‘stimulation. In the normal condition, it takes place immediately on the introduc-
tion of food, but also of indigestible substances, such as pebbles. The mucous
membrane becomes red, and the circulation more active, so that the venous blood
becomeg brighter. [That the vagi are concerned in this vascular dilatation, is
proved by the fact, that if both nerves be divided during digestion, the gastric
mucous membrane becomes pale (futherford).| The secretion is probably caused
reflexly, and the centre perhaps lies in the wall of the stomach itself (Meissner’s
plexus in the sub-mucous coat). It is asserted that the idea of food, especially
during hunger, excites secretion, As yet we do not know the effect produced upon
the secretion by stimulation or destruction of other nerves, e.g., vagus, sympathetic.
[There is no nerve passing to the stomach, whose stimulation causes a secretion of
gastric juice, as the chorda tympani does in the submaxillary gland. If the vagi be
divided sufficiently low down not to interfere with respiration, the introduction of
food still causes a secretion of gastric juice ; even if the sympathetic branches be
divided at the same time, secretion still goes on (Heidenhain). This experiment
points to the existence of local secretory centres in the stomach. But there is
evidence to show that there is some connection, perhaps indirect, between the central
nervous system and the gastric glands. Richet observed a case of complete occlusion
of the cesophagus in a woman, produced by swallowing a caustie alkali. A gastric
fistula was made, through which the person could be nourished. On placing sugar
or lemon juice in the person’s mouth, Richet observed a secretion of gastric juice.
In this case no saliva could be swallowed to excite secretion, so that it must have
taken place through some nervous channels. Even the sight or smell of food caused
secretion, Emotional states also are known to interfere with gastric digestion. |

Effect of Absorption. —Heidenhain isolated a part of the mucous membrane of
the fundus so as to forma blind sac of it, and he found that mechanical stimulation
caused merely a scanty Jocal secretion at the spots irritated. If, however, at the
same time, absorption of digested matter also occurred, secretion took place over
larger surfaces. [He distinguishes a primary and merely local secretion excited by
the mechanical stimulus of the ingesta, and a secondary depending on absorption,
and extending to the whole of the mucous membrane. |

The statement of Schiff, that active gastric juice is secreted only after absorption of the so-
called peptogenic substances (especially dextrin), is denied.

The acid contents of the stomach called chyme, which pass into the duodenum
after gastric digestion is completed, are neutralised by the alkali of the intestinal
mucous membrane and the pancreatic juice, [at the same time, a precipitate is
formed and deposited on the walls of the duodenum, and it carries the pepsin down
with it]. Part of the pepsin is reabsorbed as such, and is found in traces in the
urine and muscle juice (Briicke). If the gastric juice be completely discharged ex-
ternally through a gastric fistula, the alkalinity of the intestine is so strong that
the urine becomes alkaline (Maly).

The acid gastric juice of the new-born child is already fairly active ; casein is most easily
digested by it, then fibrin and the other proteids (Zweifel). When the amount of acid is too
great in the stomach of sucklings, large firm indigestible masses of casein are apt to be formed,
especially after the use of cow’s milk (§ 230).

_ [Action of Drugs on Gastric Secretion. —Dilute alkalies, if given before food ; saliva ; some
substances called peptogens by Schiff, such as dextrin and peptones, alcohol and ether, all
excite secretion, the last being very powerful. When the secretion is excessively acid, antacids
are given, some diminishing the acidity in the stomach, as the carbonates and bicarbonates of
the alkalies, liquor potasse, and the carbonate of magnesia; while the citrates and tartrates of
the alkalies, becoming converted into carbonates in their passage peed, the organism, diminish
the acidity of the urine.] Small doses of alcohol, introduced into the stomach, increase the
secretion of gastric juice ; large doses arrest it. Artificial digestion is affected by 10 per cent.

of alcohol, is retarded by 20 per cent., and is arrested by stronger doses. Beer and wine hinder
digestion, and in an undiluted form interfere with artificial digestion.

METHODS OF OBTAINING GASTRIC JUICE. 247

165. METHODS OF OBTAINING GASTRIC JUICE.—Historical—Spallanzani caused
starving animals to swallow small pieces of sponge enclosed in perforated lead capsules, and
after a time, when the sponges had become saturated with gastric juice, he removed them from
the stomach. ' To avoid the admixture of saliva, the sponges are best introduced through an
opening in the. esophagus. Dr Beaumont (1825), an American physician, was the first to
obtain human gastric juice, from a Canadian named Alexis St Martin, who was injured by a
gun-shot wound, whereby a permanent gastric fistula was established. Various substances
were introduced through the external opening, which was partially covered with a fold of skin,
and the time required for their solution was noted. Bassow (1842), Blondlot (1848), and Bar-
deleben (1849) were thereby led to make artificial gastric fistule.

Gastric Fistula.—The anterior abdominal wall is opened by a median incision just below the
ensiform cartilage, the stomach is exposed, and its anterior wall opened and afterwards stitched
to the margins of the abdominal walls. A strong cannula is placed in the fistula thus formed.
The tube is kept corked. If the ducts of the salivary glands be tied, a perfectly uncomplicated
object for investigation is obtained.

According to Leube, dilute human gastric juice may be obtained by means of a syphon-like
tube introduced into the stomach. Water is introduced first, and after a time it is withdrawn.

An important advance was made when Eberle (1834) prepared artificial gastric juice, by
extracting the pepsin from the gastric mucous membrane with dilute hydrochloric acid. Four
litres of solution of hydrochloric acid, containing 4 to 8 c.c. HCl per 1000, are sufficient to extract
the chopped-up mucous membrane of a pig’s stomach. Halfa litre is infused with the stomach and
renewed every six hours. The collected fluid is afterwards filtered. The substance to be digested
is placed in this fluid, and the whole is kept at the temperature of the body, but it is necessary
to add a little HCl from time to time (Schwann). The HCl may be replaced by ten times its
volume of lactic acid and also by nitric acid ; while oxalic, sulphuric, phosphoric, acetic, formic,
succinic, tartaric, and citric acids are much less active ; butyric and salicyclic acids are inactive.

Von Wittich’s Method.—(a) Glycerine extracts pepsin in a very pure form. The mucous
membrane is rubbed up with powdered glass until it forms a pulp, mixed with glycerine, and
allowed to stand for eight days. The fluid is pressed through cloth, and the filtrate mixed with
alcohol, thus precipitating the pepsin, which is washed with alcohol and afterwards dissolved in

- the dilute HCl, to form an artificial digestive fluid. (0) Or the mucous membrane may be

placed for twenty-four hours in alcohol, and afterwards dried and extracted for eight days with
glycerine. (c) Wm. Roberts has used other agents for extracting enzymes (§ 148).

Preparation of Pure Pepsin.—Briicke pours on the pounded mucous membrane of the pig’s
stomach a 5 per cent. solution of phosphoric acid, and afterwards adds lime-water until the
acid reaction is scarcely distinguishable. A copious precipitate, which carries the pepsin with
it, is produced. This precipitate is collected on cloth, repeatedly washed with water, and
afterwards dissolved in very dilute HCl. A copious precipitation is caused in this fluid, by
gradually adding to it a mixture of cholesterin in four parts of alcohol and one of ether. The

_ cholesterin pulp is collected on a filter, washed with water containing acetic acid, and after-

wards with pure water. The cholesterin pulp is placed in ether to dissolve the cholesterin, and
the ether is then removed. The small watery deposit contains the pepsin in solution.

Pepsin so prepared is a colloid substance ; it does not react like albumin with
the following tests, viz.:—It does not give the xanthroprotein reaction (§ 248), is
not precipitated by acetic acid and potassium ferrocyanide, nor by tannic. acid,
mercuric chloride, silver nitrate, or iodine. In other respects it belongs to the
group of albuminoids. It is rendered inactive in an acid fluid by heating it to
55° to 60° C.

166. PROCESS OF GASTRIC DIGESTION.—[In the process of gastric
digestion we have to consider—
1. The secretion of gastric juite and its action on food.
2. The absorption of the products of this digestion.
3. The movements of the stomach itself. |

Chyme.—The finely divided mixture of food and gastric juice is called chyme
The gastric juice acts upon certain constituents of chyme. .

I. Action on Proteids.—Pepsin and the dilute hydrochloric acid, at the
temperature of the body, transform proteids into a soluble form, to which Lehmann
(1850) gave the name of “peptone” (§ 249, III.). Fibrin (or coagulated pro-
teids) first becomes clear and swollen up.

[It is commonly stated that the first product formed during the gastric digestion
of proteids is syntonin or para-peptone, then hemi-albumose or pro-peptone, and

248 ~ PROCESS OF GASTRIC DIGESTION.”

finally peptone. The products vary, however, with the proteid digested. Kiihne
has shown that the proteid molecule is split up, and yields two groups, which‘he
ealls anti-peptone and hemi-peptone ; the former can be split up into leucin and
tyrosin by trypsin, while the latter does not)undergo this change. A mixture of the
two he calls ampho-peptone.—The intermediate body or pro-peptone, is really a
mixture of several bodies. Kiihne called it hemi-albumose. These intermediate
bodies from albumin are called albumoses, from globulins globuloses, from casein
caseoses. Halliburton calls all these intermediate bodies ‘ proteoses. ” |

Properties. —Hemi-albumose, although a composite body, gives the following reactions :—It is
highly soluble in water ; when heated to 50° to 60° it becomes somewhat turbid, but when boiled
it becomes clear, and gets turbid again on cooling. This effect is most marked when it is treated
with acetic acid and sodic chloride, or the latter alone. It is precipitated by acetic acid and
potassic ferrocyanide, but the precipitate disappears on heating and reappears on cooling. It
gives the biuret rosy tint reaction like peptones. . It is precipitated by nitric acid, and the pre-
cipitate adheres to the glass, but is soluble in the acid with the aid of heat, yielding ‘a yellow
fluid, but is precipitated on cooling. It is precipitated by boiling with acetic acid and a strong
solution of sodic sulphate, metaphosphoric acid, and pyrogallic acid (Kiihne). It is said to be
present in all animal tissues except muscle and nerve (§ 293).

{Albumoses are the first products of the splitting up of proteids by enzymes, and
from them peptones are ultimately formed. They may be made from Witte’s
peptone, or by the peptic digestion of fibrin. Such a mixture, on being neutralised ~
with sodic carbonate, gives a copious precipitate of para-peptones, which can be
filtered off, leaving a clear solution of albumoses. On saturating the clear fluid
with NaCl, a dense white precipitate, consisting of three albumoses, called proto-,
dys-, and hetero-albumose is obtained; a fourth, deutero-albumose, remains in
solution, but can be precipitated by adding acetic acid. If the albumose precipitate
be treated with 10 per cent. NaCl solution, proto- and hetero-albumose are dissolved,
leaving dys-albumose undissolved. Dialysis of the saline solution precipitates
hetero-albumose, leaving proto-albumose in solution. It is probable, however, that
hetero- and dys-albumose are identical, or that the former is merely an insoluble
form of the latter. The albumoses are bodies intermediate between albumins and
-peptones, and of the three, deutero-albumose is nearest to peptones. |

[ Properties. —Proto-albumose is soluble in distilled water, is not changed by heat, but is pre-
cipitated by saturation of the solution with sodic chloride, by HNOs, acetic acid and potassic
ferrocyanide, copper sulphate, mercuric chloride. Deutero-albumose is very like the foregoing,
but it is not precipitated by HNO, or on adding sodic chloride to saturation, but precipitation
occurs when 20 to 30 per cent. of acetic acid is added. Hetero-albumose resembles a globulin in
its properties ; it is insoluble in distilled water, but is soluble in saline solutions (10 to 15 per
cent.), and is partly precipitated from its solution by saturation with NaCl or dialysis. It is
coagulated by heat. All give the rosy-pink colour with the biuret-reaction, and they are all pre-
cipitated by saturation with neutral ammonia sulphate, which peptones are not (Kihne and
Chittenden). |

[Globuloses from the globulin of ox-serum are obtained in the same way, although the ferment
has much less action on globulin than on albumin. Speaking generally, they resemble the
-albumoses]. c

By the continued action of the gastric juice, the pro-peptone passes into a true
soluble peptone. ‘The unchanged albumin behaves like an anhydride with respect
to the peptone. The formation of peptone is due to the taking up of a molecule
of water, under the influence of the hydrolytic ferment pepsin, and the action ©
takes place most readily at the temperature of the body.. Gelatin is changed into
a gelatin-peptone. ae aree a3

According to Kiihne, the proteid molecule contains two substances preformed : anti-albumin
and hemi-albumin. Gastric juice atlfirst converts them into anti-albumose and hemi-albumose,
and both ultimately into anti-peptone and hemi-peptone (§ 170, II.). Only the latter is split up
by trypsin into leucin and tyrosin.

The greater the amount of pepsin (within certain limits), the more rapidly does
the solution take place. The pepsin suffers scarcely any change, and if care be
taken to renew the hydrochloric acid, so.as to keep it at a uniform amount, the

' OPROPERTIES OF PEPTONES. 249

pepsin can dissolve new quantities of albumin. Still, it seems that some pepsin is
used up in the process of digestion (G'riitzner), Proteids are introduced into the
stomach either-in a solid (coagulated) or. fluid condition. . Casein alone of the
fluid forms is precipitated or coagulated, and afterwards dissolved. The non-
coagulated proteids are transformed. into syntonin, without being -previously
coagulated, and are then changed into pro-peptone and directly peptonised, 7.e.,
actually dissolved. | oe mA ;

When albumin is digested by pepsin at the temperature of the body, a not inconsiderable
amount of heat disappears, as can be proved by calorimetric experiment (Maly). Hence, the
temperature of the chyme in the stomach falls 0°°2 to 0°’6 C. in two to three hours (v. Vintschgaw
and Dietl). Die ie Reine sae .

Coagulated albumin may be regarded as the anhydride of the fluid form, and the
latter again as the anhydride of peptone. The peptones, therefore, represent the
highest degree of hydration of the proteids. |

Hence, peptones may be formed from proteids by those reagents which usually cause hydra-
tion, viz., treatment with strong acids (from fibrin, with 0°2 HCl), caustic alkalies, putrefactive
and various other ferments, and ozone.

The anhydride proteid has been prepared from the hydrated form. Henniger
and Hofmeister, by boiling pure peptone with dehydrating substances (anhydrous
acetic acid at 80° C.), have succeeded in decomposing it into a body resembling
syntonin. ; : |

Peptones.—(1) They are completely soluble in water. (2) They diffuse very
easily through membranes. (3) They filter quite easily through the pores of animal
membranes. (4) They are not precipitated by boiling, nitric acid, acetic acid and
potassium ferrocyanide, acetic acid and saturation with common salt. (5) They
are precipitated from neutral or feebly acid solutions by mercuric chloride, tannic
acid, bile acids, and phosphoro-molybdic acid. (6) With Millon’s reagent they react
like proteids, and give a red colour, and with nitric acid give the yellow xantho-
protein reaction. (7) With caustic potash or soda and a small quantity of cupric
sulphate, [or Fehling’s solution], they give a beautiful rosy-red colour, the biuret-
reaction. (8) They rotate the plane of polarised light to the left.

[Kiihne and Chittenden, making use of the fact that ammonium sulphate to
saturation precipitates all proteids from solution except peptone, have reinvestigated
the subject, and they find that many of the peptones of commerce contain albumoses.
Pure peptone has remarkable properties. When dissolved in water, it hisses and
froths like phosphoric anhydride, heat is evolved, and a brown solution is formed.
It is difficult to preserve it. It is not precipitated by NaCl, or NaCl and acetic
acid, but is completely precipitated by phospho-tungstic and phospho-molybdic
acids, tannin, iodo-mercuric iodide, picric acid. Peptones have a cheesy taste, while
albumin and albumoses are tasteless. |

The biuret-reaction is obtained with pro-peptone, as well as with a form of albumin, which is
formed during artificial digestion and is soluble in alcohol. It is called ‘‘alkophyr” by Briicke.
[Darby’s fluid-meat gives all the above reactions, and is very useful for studying the tests for

eptones. !

— e rapidity of solution of fibrin is tested by placing fibrin, which is swollen up by the
action of 0°2 per cent. HCl in a glass funnel, and adding the digestive fluid, observing the
rapidity with which the fluid, the altered fibrin, drops from}the funnel, and the fibrin disappears
(Griinhagen). Or the fibrin may be coloured with carming, swollen up in 0°1 per cent. HCl,
and placed in the digestive fluid. The more rapidly the fluid is coloured red, the more energetic
is the digestion. .

Preparation.—Pure peptones are prepared by taking fluid which contains them and neutralis-
ing it with barium carbonate, evaporating upon a water-bath, and filtering. The barium is
removed from the filtrate by the careful addition of sulphuric acid, and subsequent filtration.

. ines,—Brieger extracted from gastric peptones by amylic alcohol a peptone-free poison,
with actions like those of curara. It belongs to the group of ptomaines, i.¢., alkaloids obtained
from dead bodies or decomposing proteids. [Ptomaines are identical with the alkaloids in
plants, and many have been isolated. The term leucomaine has been applied by Gautier to

250: ARTIFICIAL DIGESTION OF THE PROTEIDS.

alkaloids formed by the decomposition of albuminous bodies during the normal metabolic
scorers taking place in the tissues. They are not formed by the activity of micro-organisms.
ome seem to be formed in muscle, and are closely allied to creatin and xanthin. ]

Peptones are undoubtedly those modifications of albumin or proteids which, after
their absorption from the intestinal canal into the blood, are destined to make good
the proteids used up in the human organism. By giving peptones (instead of
albumin) as food, life can not only be maintained, but there may even be an increase
of the body-weight (Plész and Maly, Adamkiewicz). Very probably, before being
absorbed into the blood-stream, peptones are retransformed into serum-albumin
(§ 192).

Conditions affecting Gastric Digestion. —The seins of already-formed peptones interferes
with the action of the gastric juice, in so far as the greater concentration of the fluid interferes
with and limits the mobility of the fluid-particles. Boiling, concentrated acids, alum, and
tannic acid, alkalinity of the gastric juice (¢.g., by the admixture of much saliva), abolish the
action ; also sulphurous and arsenious acids and potassiciodide. The salts of the heavy metals,
which cause precipitates with ae peptone, and mucin, interfere with gastric digestion, and
so do concentrated solutions of alkaline salts, common salt, magnesium and sodium sulphates.
A small quanity of NaCl increases the secretion (@riitzner) and favours the action of pepsin.
Alkalies rapidly destroy pepsin, but less rapidly pro-pepsin (Langley). Alcohol precipitates the
pepsin, but by the subsequent addition of water it is redissolved, so that digestion goes on as
before. Any means that prevent the proteid bodies from swelling up, as by binding them
firmly, impede digestion. Slightly over half a pint of cold water does not seem to disturb
healthy digestion, but it does so in cases of disease of the stomach. Copious draughts of water,
and violent muscular exercise, disturb digestion ; while warm clothing, especially over the pit
of the stomach, aids it. Menstruation retards gastric digestion. [Oddi finds that the presence
of large quantities of ox bile, or even of its own bile in the stomach of a dog, does not affect the
activity of the gastric juice, does not precipitate peptones, and does not excite vomiting. ]

[Artificial Digestion.—The action of gastric juice on proteids may be observed
outside the body, and we can prove, as is shown in the following table, after
Rutherford, that pepsin and an acid—e.g., hydrochloric, along with water—are
essential to the formation of gastric peptones:— |

Beaker A. Beaker B, Beaker C,
Water. Water. Water.
Pepsin, 0°3 per cent. | HCl, 0°2 per cent. Pepsin, 0°3 per cent.
Fibrin. Fibrin. HCl, . 02 Pe
Fibrin.

Keep all in water-bath at 38° C,

Unchanged. Fibrin swells up, becomes clear, and is | Fibrin ultimately changed
changed into acid-albumin or syntonin. into peptone.

[In‘all animals, gastric digestion is essentially an acid digestion, and between the
native proteid, fibrin, albumin, or any other form of proteid, and the end-product
peptone, there are numerous intermediate substances, many of whose properties and
characters have still to be investigated.

[Exclusion of the Stomach.—Ogata finds that if the stomach be divided at the pyloric end so
as to exclude the stomach from the digestive apparatus, a dog can be nourished for a long time
by introducing food through the pylorus into the duodenum. A dog has lived several years
after excision of its stomach (Czerny). Raw flesh so introduced is digested more rapidly in the
small intestine than in the stomach. The stomach not only digests, but it acts on the connective-
tissue of flesh so as to prepare the latter for intestinal digestion. ]

II. Action on other Constituents of Food.—Milk coagulates when it enters the
stomach, owing to the precipitation of the casein, and in doing so it entangles
some of the milk-globules. During the process of coagulation, heat is given
off. The free hydrochloric acid of the gastric juice is itself sufficient to
cipitate it; the acid removes from the alkali-albuminate or casein the alkali which

keeps it in solution. Hammarsten separated a special ferment from the gastric :

ACTION OF GASTRIC JUICE ON THE VARIOUS TISSUES. 251

juice—quite distinct from pepsin—the milk-curdling ferment which, quite inde-
pendently of the acid, precipitates the casein either in neutral or alkaline solutions.
It is this ferment or rennet which is used to coagulate case in the making of
cheese. [Rennet is an infusion of the fourth stomach of the calf in brine (§ 231).
The ferment which coagulates milk is quite distinct from pepsin. If magnesic car-
bonate be added to an infusion of calf’s stomach, a precipitate is obtained. The

clear fluid has strongly coagulating properties, while the precipitate is strongly
peptic. |

The action of the milk-curdling ferment is perhaps, like the action of all ferments, a hydration
of casein ; it is greater in the presence of 0°2 HCl.

One part of the rennet-ferment can precipitate 800,000 parts of casein. When casein
coagulates, two new proteids seem to be formed—the coagulated proteid which constitutes
cheese, and a body resembling peptone dissolved in the whey. The addition of calcium chloride
accelerates, while water retards the coagulation (§ 231) (Hammar'sten). [A ferment similar to
rennet is contained in the seeds of Withania coagulans (S. Lea). ]

Casein is first precipitated in the stomach, then a body like syntonin is formed, and finally
peptone. During the process, a substance containing phosphorus and resembling nuclein
appears (Lubavin).

There is a ‘“‘lactic acid ferment” also present, which changes milk-sugar into
lactic acid (Hammarsten). Part of the milk-sugar is changed in the stomach and
intestine into grape-sugar.

Action on Carbohydrates.—Gastric juice does not act as a solvent of starch,
inulin, or gums. Cane-sugar is slowly changed into grape-sugar. According to
Uffelmann, the gastric mucus, and according to Leube, the gastric acid, are the
chief agents in this process. On albumenoids.—During the digestion of true
cartilage, there is formed a chondrin-peptone, and a body which gives the sugar-
reaction with Trommer’s test. Perfectly pure elastin yields an elastin-peptone,
similar to albumin-peptone, and hemi-elastin similar to hemi-albumose. <A very
minute quantity of fat is broken up into glycerine and fatty acids. [On neutral
olive-oil being injected into the stomach of a dog, after several hours—the pylorus
being plugged with an elastic bag—it partly splits up and yields oleic acid (Cash
and Ogata). |

[We still require further observations on the gastric digestion of fats. Richet observed in
his case of fistula, that fatty matters remained a long time in the stomach, and Ludwig found
the same result in the dog. In some dyspeptics, rancid eructations often take place towards
the end of gastric digestion. ] .

III. Action on the various Tissues,—(1) The gelatin-yielding substance (collagen) of all the
connective-tissues (connective-tissue, white fibro-cartilage, and. the matrix of bone), as well as
glutin, is dissolved and peptonised by the gastric juice. [Gelatin, when acted on by gastric juice,
no longer solidifies in the cold, but a gelatin-peptone is formed, which is soluble and diffusible,
although it differs from true peptone. In the dog, connective-tissues are specially acted on in
the stomach, while the other parts of organs used as food are prepared for digestion in the small
intestine, where the cellular and nuclear elements are digested by the pancreatic juice
(Bikfalvi).] (2) The structureless membranes (membrane proprie) of glands, sarcolemma,
Schwann’s sheath of nerve-fibres, capsule of the lens, the elastic lamine of the cornea, the
membranes of fat-cells are dissolved, but the true elastic (fenestrated) membranes and fibres are
not affected. (3) Striped muscle, after solution of the sarcolemma, breaks up transversely into
discs, and, like non-striped muscle, is dissolved, and forms a true soluble peptone, but parts of
the muscle always pass into the intestine. (4) The albuminous constituents of the soft cellular
elements of glands, stratified epithelium, endothelium, and lymph-cells, form peptones, but the
nuclein of the nuclei does not seem to be dissolved. (5) The horny parts of the epidermis,
nails, hair, as well as chitin, silk, conchiolin, and spongin of the lower animals are indigestible,
and so are amyloid-substance and wax. (6) The red blood-corpuscles are dissolved, the hemo-
globin decomposed into hematin and a globulin-like substance ; the latter is peptonised, while
the former remains unchanged, and is partly absorbed and transformed into bile-pigment.
Fibrin is easily dissolved to form hemi- and anti-peptone. (7) Mucin, which is also secreted
by the goblet-cells of the stomach, passes through the intestines unchanged. (8) Vegetable fats
are not affected by the gastric juice ; these cells yield their protoplasmic contents to form pep-
tones, while the cellulose of the cell-wall, in the case of man at least, remains undigested (§ 184).

Why the Stomach does not digest itself.—That the stomach can digest living things is
shown by the following facts :—Bernard introduced the leg of .a living frog through a gastrie

252 J JECTT GJ) (GASES IN“ THE STOMACH, 9 >) (Olivos

fistula into the stomach of a dog. Pavy did the same with the ear of a rabbit, and in both the
objects introduced were digested. [Frenzel has modified this experiment, and shown that the
legs of a living frog are digested by artificial gastric juice, the tissues being first-killed-and then
digested, His experiments go to show that the alkalinity of the blood is not* the protective
medium.] The margins of a gastric ulcer and of gastric fistule in man are attacked. by the
gastric juice. John Hunter (1772) discussed the question why the stomach does not digest
itself. Not unfreqtently after death the posterior wall of the stomach is found digested, [more
especially if the person die after a full meal and the body be kept in a warm place, whereby the
contents of the stomach may escape into‘the peritoneum. Cl. Bernard showed, that if a rabbit
be killed and placed in an oven at the temperature of the body, the walls of the stomach are
attacked by its own gastric juice. . Fishes also are frequently found with their stomach par-
tially digested after death]. It would seem, therefore, that, so long as the circulation continues,
the tissues are protected from the action of the acid by the alkaline blood ; this action cannot.
take place if the reaction be alkaline (Pavy). [This, however, does not explain why the pan-
creatic juice does not digest the pancreas.] Ligature of the arteries of the stomach, causes
digestive softening of the gastric mucous membrane. The thick layer of mucus may also aid in
protecting the stomach from the action of its own gastric juice (Cl. Bernard). t

1677. GASES IN THE STOMACH.—The stomach always contains a certain
quantity of gas, derived partly from the gases swallowed with the saliva, partly from
gases which pass backwards from the duodenum.

_ The air in the stomach is constantly undergoing changes, whereby its O is
absorbed by the blood, and for 1 vol. of O absorbed 2 vols. of CO, are returned to
the stomach from the blood. Hence, the amount of O in the stomach ‘is very
small, the CO, very considerable (Planer). : | | as

Gases in the Stomach, —Vol. per cent. (Planer).

Human Subject after Vegetable Diet. | Dog.
= 1 boise opts IL,
; | After Animal Diet. After Legumes.
CO,, 20°79 33°83 | 25:2, 32°9
H, 6°71 27°58 | vas ‘ee
| NN, 72°50 38°22 i} a a 66°3
O, sits 0°37 | 6°1 0°8

By the acid of the stomach a part of the CO, is set free from the saliva, which
contains much CO, (§ 146). The N acts as an indifferent substance.

Abnormal development of gases in persons suffering from gastric catarrh, occurs when the

gastric-contents are neutral in reaction ; during the butyric acid fermentation H and CO, are

JEP ee formed ; the acetic acid and lactic acid fermentations do not cause the

dees Sea formation of gases. Marsh-gas (CH,) has been found, but it comes from

iF. =<") the intestine, as it can only be formed when no O is present (§ 184).

yaa / 168. STRUCTURE OF THE PANCREAS.—The pancreas is a coms

’ pound tubular gland, and in its general arrangement into lobes, lobules,

-\ and system of ducts and acini, it corresponds exactly to the true

?\ salivary glands. The epithelium lining the ducts is not at all, or only

/ faintly, striated. The acini are tubular or flasked-shaped, and often

. convoluted. They consist of a membrana propria, resembling that of

*| the salivary glands, lined by a single layer of somewhat cylindrical

=| cells, with a more or less conical apex, directed towards the very narrow

%{/ lumen of the acini. [As in the salivary glands, there is a narrow

a intermediary part of the ducts opening into the acini, and lined by

Fig. 186. flattened epithelium.] The cells lining the acini consist of two zones

“Bae of thie frooh ‘(lige 186) keel) cn cai

cao octhe) Sorgen ie tg (1) The smaller outer or parietal layer is transparent, homogeneous,
Syasyee ee sometimes faintly striated, and’ readily stained with carmine and log:
wood ; and (2) the inner layer (Bernard’s granular layer) is granular, and stains but slightly

with carmine (fig. 186). It undoubtedly contributes to the secretion by giving off material,
the granules being dissolved, while the zone itself becomes:smaller. The spherical nucleus lies
between the two zones. [The lumen of the acini is very small, and spindle-shaped or branched —
cells (centro-acinar cells) lie in it, and send their processes between the secretory cells, thus
acting as supporting cells for the elements of the wall of the acini, During secretion, there is’a

THE PANCREATIC JUICE. . 253

eontinuous change in the appearance of the cell-substance ; the granules of the inner zone dis-
solve to form part of the secretion ; new granules are formed in the homogeneous substance of
the outer zone, and pass towards the inner zone (Heidenhain, Kiihne and Lea).

’ Changes in the Cells during Digestion.—During the jirst stage (6 to.10 hours) the granular
inner zone diminishes in size, the granules disappear, while the striated outer zone increases in
size (fig. 187, 2). In the second stage (10 to 20 hours) the inner zone is greatly enlarged and
granular, while the outer zone is small (fig. 187, 3). During hunger the outer zone again
enlarges (fig. 187, 1). In a gland where paralytic secretion takes place, the gland is much
diminished in size, the cells are shrivelled (fig. 187, 4) and greatly changed. According to
Ogata, some cells actually disappear during secretion. ~ —— *

The axially-placed excretory duct consists of an inner thick and an outer loose wall of con-
nective and elastic tissues, lined by a single layer of columnar epithelium. Small mucous
glands lie in the largest trunks. Non-medullated nerves, with ganglia in their course, pass to
the acini, but their mode of termination is unknown. The blood-vessels form a rich capillary
plexus round some acini, while round others there are very few. Kiihne and Lea found peculiar
small cells in groups between the alveoli, and supplied with convoluted capillaries like glomeruli.
Their significance is entirely '
unknown. [They are probably
lymphatic in their nature.]
The lymphatics resemble those
of the salivary glands. When
a coloured injection is forced
into the ducts under a high
pressure, fine intercellular. pas-
sages between - the secreting

cells are formed (Saviotti’s Fig. 187. '
canals), but they are artificial Changes of the pancreatic cells in various stages of activity. 1,
products. ] During hunger ; 2, in the first stage of digestion ; 3, in the

[Number of Ducts.—In second stage ; 4, during paralytic secretion.
making experiments upon the
pancreatic secretion, it is important to remember that the number of pancreatic ducts varies in
different animals. In man there is one duct opening along with the common bile-duct at Vater’s
ampulla, at the junction of the middle and lower third of the duodenum. The rabbit has two
ducts, the larger opening separately about 14 inches (30 to 35 cm.) below the entrance of the
bile-duct. The dog and cat have each two ducts opening separately. ]

Chemistry.—The fresh pancreas contains : water, proteids, ferments, fats, and salts. In a
gland which has been exposed for some time, much leucin, isoleucin, butalin, tyrosin, often
xanthin and guanin, are found: lactic and fatty acids seem to be formed from chemical decom-
positions taking place.

169, THE PANCREATIC JUICE. —Method.—Regner de Graaf (1664) tied a cannula in the
pancreatic duct of a dog, and collected the juice inja small bag. Other experimenters made a
temporary fistula, To make a permanent fistula, the abdomen is opened (dog), the pancreatic
duct pulled forward, and stitched to the abdominal wall, with which it unites. Heidenhain
cuts out the part of the duodenum where the duct opens into it, from its continuity with the
intestine, and fixes it outside the abdominal wound. ;

The secretion obtained from a permanent fistula is a copious, slightly active,
watery secretion, containing much sodium carbonate ; while the thick fluid obtained
from the fistula before inflammation sets in, or that from a temporary fistula, acts
far more energetically. This thick secretion, which is small in amount, is the
normal secretion. The copious watery secretion is perhaps caused by the increased:
transudation from the dilated blood-vessels (possibly in consequence of the paralysis
of the vaso-motor nerves). It is, therefore, in a certain sense, a “ paralytic secre-
tion” (§ 145). The quantity varies :much, according as the fluid is thick or thin.
During digestion, a large dog secretes 1 to 1°5 gramme of a thick secretion (Cl.
Bernard). Bidder and Schmidt obtained in twenty-four hours 35 to 117 grammes
of a watery secretion per kilo. of a dog. When the gland is not secreting, and is
at rest, it is soft, and of a pale yellowish-red colour, but during secretion it is red
and turgid with blood, owing to the dilatation of the blood-vessels.

The normal secretion is transparent, colourless, odourless, saltish to the taste,
and has a strong alkaline reaction, owing to the presence of sodium carbonate, so
that when an acid is added, CO, is given off. It contains albumin and alkali-

albuminate ; it is sticky, somewhat viscid, flows with difficulty, and is coagulated

254 ACTION OF THE PANCREATIC JUICE,
by heat into a white mass. In the cold, there separates a jelly-like albuminous
coagulum. Nitric, hydrochloric, and sulphuric acids cause a precipitate; while the
precipitate caused by alcohol is redissolved by water, Cl Bernard found in the
pancreatic juice of a dog 82 per cent. of organic substances, and 0°8 per cent, of
ash, The juice (dog) analysed by Carl Schmidt contained in 1000 parts :—

Sodic chloride, , 7°36 —C«
: 5, phosphate, : ; 0°45
Organic, , : 81°84 », sulphate, . é , 0°10.
Solids, 90°38 in ) Inorganic, , : 8°54 j Soda, , : ‘ ; i 0°32
1000 parts. (like those of Lime, . : : : ; 0°22
blood-serum), Magnesia, , ‘ ‘ ! 0°05
Potassic sulphate, j eo aes.
Ferric oxide, ‘ ‘ ; 0:02

The more rapid and more profuse the secretion, the poorer it is in organic substances, while
the inorganic remain almost the same ; nevertheless, the total quantity of solids is greater than
when the quantity secreted is small (Bernstein). Traces of leucin and soaps are present in the
fresh juice. [It usually contains few or no structural elements. Any structural elements
present in the fresh juice, as well as its proteids, are digested by the peptone-forming ferment
of the juice, especially if the latter be kept for some time. If the fresh juice is allowed to stand
for some time, and then mixed with chlorine water, a red colour is obtained. ]

Concretions are rarely formed in the pancreatic ducts; they usually consist of calcic carbonate.
Dextrose has been found in the juice in diabetes, and urea in jaundice. Schiff’s statement that
the pancreas secretes only after the absorption of dextrin, has not been confirmed, , The secretory
activity of the pancreas is not dependent on the presence of the spleen,

170. ACTION OF THE PANCREATIC JUICE.—The presence of at least
four enzymes, or hydrolytic ferments, makes the pancreatic juice one of the most
important digestive fluids in the body.

I. Diastatic action is due to the diastatic ferment, amylopsin, a substance
which seems to be identical with the saliva ferment ; but it acts much more
energetically than the ptyalin on saliva, on raw starch as well as upon boiled
starch ; at the temperature of the body the change is effected almost at once,
while it takes place more slowly at a low temperature. Glycogen is changed into
dextrin and grape-sugar ; and achroodextrin into sugar. Even cellulose is said to be
dissolved, and gum changed into sugar by it, but inulin remains unchanged,

According to v. Mering and Musculus, the starch (as in the case of the saliva, § 148) is
changed into maltose, and a reducing-dextrin ; so also is glycogen. Amylopsin changes
achroodextrin into maltose ; at 40° C. maltose is slowly changed into dextrose, but cane-sugar
is not changed into invert-sugar. The ferment is precipitated by alcohol, while it is extracted by
_ glycerine without undergoing any essential change. All conditions which destroy the diastatic
action of saliva (§ 148) similarly affect its action, but the admixture with acid gastric juice (its
acid being neutralised) or bile does not seem to have any injurious influence, This ferment is
absent from the pancreas of new-born children (Korowin).

Preparation.—The ferment is isolated by the same methods as obtain for ptyalin ($ 148) ; but
the tryptic ferment is precipitated at the same time. The addition of neutral salts (4 per cent. .
solution), ¢.g., potassium nitrate, common salt, ammonium chloride, increases the diastatic
action,

II, Tryptic action, or the action on proteids, depends upon the presence of a
hydrolytic ferment which is now termed trypsin (Kiihne). Trypsin acts upon
proteids at the temperature-of the body, when the reaction is alkaline, and changes
them first into a globulin-like substance, then into pro-peptone or albumose, and —
lastly into a true peptone, sometimes called tryptone. The albumoses are not so
abundant or so easily separated as in gastric digestion (see also p. 248). The pro-
teids do not swell up before they are changed into peptone, [but they are eroded
or eaten away by the action of the juice]. When the proteid has been previously
swollen up by the action of an acid, or when the reaction of the medium is acid,
the transformation is interfered with. 3

Substances yielding gelatin, nuclein, and Hb, resist trypsin ; glutin and swollen-up gelatin-
yielding substances are changed into gelatin-peptone, but the latter undergoes no further

ACTION. OF THE PANCREATIC JUICE. 255

change, Hb-0, is split up into albumin and hemochromogen. In other respects, trypsin acts
on tissues containing albumins just like pepsin (§ 166, ITI.).

Trypsin is never absent from the pancreas of new-born children (Zweifel), and it may be
extracted by water, which, however, also dissolves the albumin. Kiihne has carefully separated
the albumin and obtained the ferment in a pure state. It is soluble in water, insoluble in
alcohol. Pepsin and hydrochloric acid together act upon trypsin and destroy it; hence it is
not advisable to administer trypsin by the mouth, as it would be destroyed in the stomach,
When dried it may be heated to 160° without injury,

Trypsin is formed within the pancreas by a “‘ mother-substance,” or zymogen,
taking up oxygen. The zymogen is found in small amount, 6 to 10 hours after
a meal, in the inner zone of the secretory cells, but after 16 hours it is very abund-
ant in the inner zone of the cells. It is soluble in water and glycerine. Trypsin
is formed in the watery solution from the zymogen, and the same result occurs when
the pancreas is chopped up and treated with strong alcohol (Atihne), The addition
of sodium chloride, carbonate, and glycocholate, favours the activity of the tryptic
ferment (Heidenhain). [The following facts show that zymogen (Cvuy, ferment), or,
as it has been called, trypsinogen, is the precursor of trypsin, that it exists in the
gland-cells, and requires to be acted upon before trypsin is formed. If a glycerine
extract be made of a pancreas taken from an animal just killed, and if another
extract be made from a similar pancreas which has been kept for 24 hours, it will
be found that an alkaline solution of the former has practically no effect on fibrin,
while the latter is powerfully proteolytic. If a fresh, and still warm, pancreas be
rubbed up with an equal volume of a 1 per cent. solution of acetic acid, and then
extracted with glycerine, a powerfully proteolytic extract is at once obtained.
Trypsin is formed from zymogen by the action of acetic acid. There is reason to
believe that trypsin is formed from zymogen by oxidation, and that the former
loses its proteolytic power after removal of its oxygen. The amount of zymogen
present in the gland-cells seems to depend upon the number and size of the
granules present in the inner granular zone of the secretory cells. |

Further Effects.—When trypsin is allowed to act upon the hemi-peptone
formed by its own action, the latter is partly changed into the amido-acid, leucin,
or amido-caproic acid (C,H,,NO,), and tyrosin (C,H,,NO,), which belongs to the
aromatic series (§ 252, IV. 3). Hypoxanthin, xanthin, and aspartic or amido-succinic
acid (C,H,NO,), are also formed during the digestion of fibrin and gluten, and so
are glutamic (C;H,NO,) and amido-valerianic acid (C,H,,NO,). Gelatin is first
changed into a geletin-peptone, and afterwards is decomposed into glycin and
ammonia.

Putrefactive Phenomena.—lIf the action of the pancreatic juice be still further
prolonged, especially if the reaction be alkaline, a body with a strong, stinking,
disagreeable feecal odour, indol (C,H,N), skatol (C,H,N), and phenol (C,H,O), and
a substance which becomes red on the addition of chlorine-water (Bernard), [or it
gives with bromine-water first a pale red and then a violet tint (Aiihne)], volatile
fatty acids are formed, while, at the same time, H, CO,, HS, CH,, and N are given
off. The formation of indol and the other substances just mentioned depends upon
putrefaction (§ 184, III.). Their formation is prevented by the addition of salicylic
acid, or thymol, which kills the organisms upon which putrefaction depends
(Kiihne).

[Artificial Digestion.—From fibrin placed in pancreatic juice, or in a 1 per cent.
solution of sodium carbonate containing the ferment trypsin, peptones are rapidly
formed at 40° C. When we compare gastric with pancreatic digestion, we find
that the fibrin in pancreatic digestion is eroded, or eaten away, and never swells up.
The process takes place in an alkaline medium, and never in an acid one. In fact,
al per cent. solution of sodic carbonate seems to play the same part in assisting
trypsin, that a ‘2 per cent. solution of HCl does for pepsin, in gastric digestion, In
gastric digestion acid-albumin or syntonin is formed in addition to the true peptones.

256 ACTION OF THE PANCREATIC JUICE.

In pancreatic digestion a body resembling alkali-albumin, which passes into a
globulin-like body, and ultimately into a peptone, is formed. Of the peptones so
produced, one is called anti-peptone, and it is not further changed, but part of the
proteid is changed into hemi-peptone. This body, when acted upon, yields leucin
and tyrosin. When putrefaction takes place, the bodies above-mentioned are also
formed. We might represent the action of trypsin thus :—Proteid + trypsin + 1
per cent. sodium carbonate, kept at 38° C. =formation of a globulin-like body, and
then anti-peptone and hemi-peptone are formed,

i

ey
ANTI-PEPTONE HEMI-PEPTONE
yields yields
Normal Digestive Products. Putrefactive Products,

undergoes no Leucin, Indol, Volatile Fatty Acids,
further change. Tyrosin, Skatol, H, CO,, HS,

Hypoxanthin, Phenol. CH,, N

Aspartic Acid.

It seems that trypsin in pure water can act slowly upon fibrin to produce
peptone. Pepsin cannot do this without the aid of an acid. |

[Kiihne’s Pancreas Powder.—This is prepared by the prolonged extraction of
fresh pancreas of ox with alcohol and then with ether. If the dry powder be
extracted for several hours with a 1 per cent. solution of salicylic acid, and filtered,
a fluid with powerful proteolytic, but no diastatic, properties is obtained. Several
hours afterwards much tyrosin may separate out, which, of course, must be removed
by filtration. The clear fluid, when mixed with fibrin anda 1 per cent. solution of
sodic carbonate, rapidly digests fibrin. If it be desired to obtain a true pancreatic
digestion, with none of the products of putrefaction, the mixture must be strongly
“thymolised ” with a 25 per cent. alcoholic solution of thymol (Avhne). |

[Setschenow finds that egg-albumin, boiled in a vacuum at 35°-40° C., is more rapidly digested
than fibrin by a specially prepared trypsin.] When proteids are boiled for a long time with
dilute H,SO,, we obtain peptone, then dewcin and tyrosin ; gelatin yields glycin. Hypoxanthin
and xanthin are obtained in the same way by similarly boiling fibrin, and the former may even
be obtained by boiling fibrin with water (Chittenden).

It is very remarkable that the juice of the green fruit of the papaya tree, or Carica papaya,
possesses digestive properties (Roy, Wittmack), and that the action is due to peptonising ferment,
closely related to trypsin, and called caricin or papain. [It forms a true peptone, an inter-
mediate body, and leucin and tyrosin. It also contains a milk-coagulating ferment (Jartin).]
The milky juice of the fig-tree has a similar action. Sprouting malt, vetch, hop, hemp during
sprouting, and the receptacle of the artichoke contain a peptonising ferment. Leucin, tyrosin,
glutamic and aspartic acids, and xanthin are formed in the seeds of some plants ; hence we
may assume that the processes of decomposition in some seeds are closely allied to the fermenta-
tive actions that occur in the intestine.

III. The action on neutral fats is twofold :—(1) It acts upon fats so as to
form a fine permanent emulsion. (2) It causes neutral fats to take up a
molecule of water and split into glycerine and their corresponding fatty acids :—

(C;7Hy190¢) + 3(H,O) =(C,H,O03) + 3(CgH3,0.).
Tristearin. Water. Glycerine, Stearic Acid.
The latter result is due to the action of an easily-decomposable fat-splitting
ferment (Cl. Bernard), also called steapsin. Lecithin is decomposed by it into
glycero-phosporic acid, neurin and fatty acids. The fatty acids thus liberated are
partly saponified by the alkali of the pancreatic and intestinal juices, and partly
emulsionised by the alkaline intestinal juice. Both the soaps and emulsions are
capable of being absorbed (§ 191), , |

Emulsification.—The most important change effected on fats in the small intestine is the
production of an emulsion, or their subdivision into exceedingly minute particles (§ 191). Thi
is necessary in order that the fats may be taken up by the lacteals. If the fat to be emulsifie
contain a free fatty acid, i.¢., if it be slightly rancid, and if the fluid with which it is mixed

st # )
. SECRETION OF PANCREATIC JUICE. 257

be alkaline, emulsification takes place extremely rapidly (Briicke). A drop of cod-liver oil,
which in its unpurified condition always contains fatty acids, on being placed in a drop of 0°3
per cent. solution of soda, instantly gives rise to an emulsion (Gad). The excessively minute
oil-globules that compose the emulsion are first covered with a layer of soap, which soon
dissolves, and in the process small globules are detached from the original oil-globules. The
fresh surface is again covered by a soap film, and the process is repeated over and over again
until an excessively fine emulsion is obtained. If ‘the fat contain much fatty acid, and the
solution of soda be more concentrated, ‘‘ myelin forms” are obtained similar to those which
are formed when fresh nerve-fibres are teased in water. Animal oils emulsionise more readily
than vegetable oils ; castor oil does not emulsionise (Gad). [It is extremely difficult to obtain
a perfectly neutral oil, as most oils contain a trace of a fatty acid. In fact, if on adding a weak
solution of sodic carbonate to oil.or fatty matters, fluid at the temperature of the body, an
emulsion is obtained, one may be sure that the oil contained a fatty acid, so that Bernard’s
view about an ‘‘ emulsive ferment” being necessary is not endorsed. The fatty acid set free by
the fat-splitting ferment enables the alkaline pancreatic juice at once to produce an emulsion. ]

Fat-Splitting Ferment.—This is a very unstable body, and must be prepared from the

perfectly fresh gland by rubbing it up with powdered glass, glycerine, and a 1 per cent. solution
of sodic carbonate, and allowing it to stand for a day or two (@riitzner). [This ferment is said
to cause an emulsion of oil and mucilage tinged blue with litmus at 40°C. to become red
(Gamgee). In performing this experiment notice that the mucilage is perfectly neutral, as
gum-arabic is frequently acid. ]
_ [Pancreatic Extracts,—The action of the pancreas may be tested by making a watery extract
of a perfectly fresh gland. Such an extract always acts upon starch and generally upon fats,
but this extract and also the glycerine extract vary in their action upon proteids at different
times. If the extract—watery or glycerine—be made from the pancreas of a fasting animal,
the tryptic action is slight or absent, but is active if it be prepared from a gland 4 to 10 hours
after a meal. The pancreatic preparations of Benger of Manchester, Savory and Moore, or
Burroughs and Welcome, all possess active diastatic and proteolytic properties. ]

[Pancreas Salt.—Prosser-James proposes to employ common salt mixed with pepsin, which
he calls peptic salt ; and he advocates the use of another preparation composed of the pancreatic
ferments and common salt, pancreatic salt.]

The pancreas of new-born children contains trypsin and the fat-decomposing ferment, but
not the diastatic one (Zweifel). Aslight diastatic action is obtained after two months, but the
full effect is not obtained until after the first year (Korowin).

IV. The pancreas contains a milk-curdling ferment, which may be extracted
by means of a concentrated solution of common salt.

171. THE SECRETION OF THE PANCREATIC JUICE.—Rest and
Activity.—As in other glands, we distinguish a quiescent state, during which
the gland is soft and pale, and a state of secretory activity, during which the
organ swells up and appears pale red. The latter condition only occurs after a
meal, and is caused probably reflexly owing to stimulation of the nerves of
the stomach and duodenum. - Kiihne and Lea found that all the lobules of the
gland were not active at the same time. The pancreas of the herbivora secretes
uninterruptedly, [but in the dog secretion is not constant].

Time of Secretion.—According to Bernstein and Heidenhain the secretion
begins to flow when food is introduced into the stomach, and reaches its maximum
2 to 3 hours thereafter. The amount falls towards the 5th or 7th hour, and rises
ragain (owing to the entrance of the chyme into the duodenum) towards the 9th
and 11th hour, gradually falling towards the 17th to 24th hour until it ceases
completely. When more food is taken, the same process is repeated. ‘As a general
rule, a rapidly-formed secretion contains less solids than one formed slowly.

Condition of Blood-Vessels.—During secretion, the blood-vessels behave like
the blood-vessels of the salivary glands after stimulation of the chorda—they
dilate, and the venous blood is bright red—thus, it is probable that a similar
nervous mechanism exists, [but as yet no such mechanism has been discovered].
The secretion is excreted at a pressure of more than 17 mm. Hg. (rabbit).

Effect of Nerves.—The nerves arise from the hepatic, splenic, and superior
mesenteric plexuses, together with branches from the vagus and sympathetic.
‘The secretion is excited by stimulation of the medulla oblongata, as well as by
direct stimulation of the gland itself by induction-shocks. [It is not arrested by

‘ R

258 PREPARATION OF PEPTONISED FOOD.

section of the cervical spinal cord.] The secretion is suppressed by atropin [in the
dog, but not the rabbit], by producing vomiting, by stimulation of the central end of
the vagus, as well as by stimulation of other sensory nerves, ¢.g., the crural and
sciatic. Extirpation of the nerves accompanying the blood-vessels prevents the
above-named stimuli from acting. Under these circumstances, a thin “paralytic se-
cretion,’’ with feeble digestive powers, is formed, but its amount is not influenced by
the taking of food. [Secretion is excited by the injection of ether into the stomach, |

Extirpation of the gland may be performed, or the duct ligatured in animals, without causing
any very great change in their nutrition; the absorption of fat from the intestine does not
cease. After the duct is ligatured it may be again restored. Ligature of the duct may cause
the formation of cysts in the duct and atrophy of the gland-substance, Pigeons soon die after
this operation, :

[172. PREPARATION OF PEPTONISED FOOD.—Peptonised food may
be given to patients whose digestion is feeble (Roberts). Food may be pep-
tonised either by peptic or tryptic digestion, but the former is not so suitable
as the latter, because in peptic digestion the grateful odour and taste of the
food are destroyed, while bitter bye-products are formed, so that pancreatic
digestion yields a more palatable and agreeable product. As trypsin is destroyed
by gastric digestion, obviously it is useless to give extract of the pancreas to a
patient along with his food.]

[Peptonised Milk. —‘‘ A pint of milk is diluted with a quarter of a pint of water and heated
to 60°C. Two or three tea-spoonfuls of Benger’s liquor pancreaticus, together with 10 or 20
grains of bicarbonate of soda, are then mixed therewith.” Keep the mixture at 38° C. for
about two hours, and then boil it for two or three minutes, which arrests the ferment action. ]

[Peptonised Gruel, prepared from oatmeal, or any farinaceous food, is more agreeable than

peptonised milk, as the bitter

Sublobular Vein, Intralobular Vein. flavour does not appear to be

developed in the pancreatic
digestion of vegetable proteids, ]

[Peptonised Milk-Gruel yielded
Roberts the most satisfactory re-
sults,as a complete and highly nu-
tritious food for weak digestions.
Make a thick gruel from an
farinaceous food, e.g., oatmeal,
and while still hot add to it an
equal volume of cold milk, when
the mixture will have a tempera-
Ducts, ture of 52°C. (125° F.). To each

pint of this mixture add two or
petty three tea-spoonfuls of liquor pan-
Sins Nena creaticus and 20 grains of bicar-

Ea ea tNy 2 bonate of soda. It is kept warm

poi Eeaite tweed MoAEy for two hours under a ‘* cosey.”
tue Pree acer) pee Inter- It is then boiled for a few minutes

Cctesy fing lobular and strained. The bitterness of
Std Bat

Ms °
OO ke Ol

— ine ay ey
» SOF es 34 35 Dy
<3 ew eaehe “t

peated was te Bas Vein, the digested milk is almost com-
hae tatias Fees aS MaMa Rta pletely covered by the sugar pro-
NS 7 duced during the process. ]
Fig. 188. [Peptonised soups and beef-tea

Section of human liver, x 20, showing the liver-lobules and have also been made and used
the radiate arrangement of their cells from the central or with success, and have been ad-
intralobular vein. ministered both by the mouth

and rectum. }
[Peptonising powders containing the proper proportions of ferment and sodic bicarbonate are
prepared by Benger, and Burroughs and Welcome. ]

173. STRUCTURE OF THE LIVER.—The liver, the largest gland in the
body, consists of innumerable small lobules or acini, 1 to 2 millimetres (4 to
sk; inch) in diameter. These lobules are visible to the naked eye. All the lobules
have the same structure,. , aay

‘STRUCTURE OF THE LIVER. 250.

1, The Capsule.—The liver is covered by a thin, fibrous, firmly-adherent capsule, which has
on its free surface a layer of endothelium derived from the peritoneum. The capsule sends fine
septa into the organ between the lobules, but it is also continued into the interior at the trans-
verse fissure, where it surrounds the ee vein, hepatic artery, and bile-duct, and accompanies
these structures as the capsule of Glisson, or interlobular connective-tissue. The spaces in
which these three structures lie are known as portal canals, In some animals (pig, camel, polar
bear) the lobules are separated from each other by the somewhat lamellated connective-tissue
of Glisson’s capsule, but in man this is but slightly developed, so that adjoining lobules are
more or less fused. Very delicate connective-tissue, but small in amount, is also found within
‘the lobules, Leucocytes are sometimes found in the tissue of Glisson’s capsule,

_ 2, Blood-Vessels.—(«) Branches of the Venous System.—The portal vein, after its entrance
into the liver at the portal fissure, gives off numerous branches lying between the lobules, and
ultimately forming small trunks which reach the periphery of the lobules, where they form a
rich plexus, These are the interlobular veins (figs. 188, 189, V,z), From these veins numerous

Fig, 189,

I, Scheme of a liver-lobule—V.7, V.i, interlobular veins (portal); V.c, central or intralobular
vein (hepatic); c¢,c, capillaries between both; V.s, sublobular vein; V.v, vena vascu-
laris; A, A, hepatic artery, giving branches, 7, 7, to Glisson’s capsule and the larger vessels,
and ultimately forming the vene vasculares at 7, 7, opening into the intralobular capil-
laries; g, bile-ducts; x, x, intralobular biliary channels between the liver-cells; d, d,
position of the liver-cells between the meshes of the blood-capillaries. II, Isolated liver-
cells—e, a blood-capillary ; a, fine bile-capillary channel. .

capillaries (c, c) are given off to the entire periphery of the lobule. The capillaries converge
towards the centre of the lobule. As they proceed inwards, they form elongated meshes, and
between the capillaries lie rows or columns of liver-cells (d, d). The capillaries are relatively
wide, and are so disposed as to lie between the edges of- the columns of cells, and never between
the surfaces of two neighbouring cells. Thé capillaries converge towards the centre of each
lobule, where they join to form one large vein, the intralobular, hepatic, or central vein (V.c),
which traverses each lobule, reaches its surface at one point, passes out, and joins similar veins
from other lobules to form the sublobular veins (/”.s), These in turn unite to form wide veins,
_ the origins of the hepatic vein, which opens into the vena cava inferior.

(b) The branches of the hepatic artery accompany the branches of the portal vein and bile-

.200 STRUCTURE OF THE LIVER.

duct in the portal canals between the lobules, and in their course give off capillaries to supply
the walls of the portal vein and larger bile-ducts. The branches of the pepree artery anasto-
mose frequently where they lie between the lobules. On reaching the periphery of the lobules,
a certain number of capillaries are given off, which penetrate the lobule and terminate in the
capillaries of the portal vein (7, 7). These capillaries, however, which supply the walls of the
peel vein and large bile-ducts (7, 7), terminate in veins which end in the portal vein (V.v).
everal branches—capsular—pass to the surface of the liver, where they form a wide-meshed
Seite under the peritoneum. The blood is returned by veins, which open into branches of the
portal vein,
[Hepatic Zones.—Pathologists draw a sharp distinction between different zones within a
hepatic lobule. Thus the central area, capillaries, and cells form the hepatic vein zone, which
is specially liable to cyanotic changes ; aus area next the periphery of the lobule is the portal

q BN ad
sae 2s ae
a

va

Human liver-cells containing oil-globules, 0 ; Liver-cells after withholding food for
d, has two nuclei. 36 hours.

vein zone, whose cells under certain circumstances are particularly apt to undergo fatty de-
generation ; while there is an area lying midway between the two foregoing—the hepatic

artery zone—which is specially liable to amyloid or waxy degeneration. ]
3. The hepatic cells (fig. 189, II, a) are irregular polygonal cells of about yo'yth of an inch
(34 to 45 w) in diameter (fig. 190). The arrangement of the capillaries within a lobule deter-
mines the arrangement of the

Finest bile-duct. Finest bile-duct divided. liver-cells. The liver-cells
; form anastomosing columns
MTT ATT (I | UICUUTU ATUL - which radiate from the centre
Ji lala Wee F to the periphery of each lobule
Goat Blood- (fig. 191). [The liver-cells
PEN ee \y yas mt pe noses paseo

Reps. Captaaencn ne 3 oe i HARE \\\ or an relope,
a? Pers (is ion EP eas x Haycraft states that they
oi ee Paait\y st possess one. They usually
See \\\ aa: contain a single nucleus, with
al gyro K\\ one or more nucleoli, but
a amare ae sometimes two nuclei occur.

The protoplasm and nucleus
of each cell contain a plexus
of fibrils just like other epi- |
thelialcells, Insomeanimals,
globules of oil and pigment-
granules are found in the
cell-protoplasm (fig, 190).
Each cell is in relation with
the wide-meshed blood-capil-

(eel

Nucleus ofa _ Finest. laries (d, d), and also with

RFOE SEDs, DBS Cae the much narrower meshwork
Fig. 192. _of bile-ducts (I, a).

Blood-capillaries ; finest bile-ducts in their relative position ina | Changes in Liver-Cells.—

rabbit’s liver. The appearance of the cells

_ varies with the period of di-
gestion. During hunger, the liver-cells are finely granular and very cloudy (fig. 191), [and
contain little glycogen, but many pigment-granules, and the nucleus is more frequently absent.
Often free salad and pale nuclei are found (Ellenberger and Baum). _ During activity, ée.,
after a full meal, especially of starchy food, the cells are larger and more distinct, stain more deeply
with eosin, and contain fewer granules]. The protoplasm contains coarse, glancing masses of
glycogen (fig. 194, 2), and near the surface of the cell it is condensed, and a fine networ 6 sis is

STRUCTURE OF THE LIVER. 261

toward the centre of the cell, and in it is suspended the nucleus. All the hepatic cells are
not in the same phase of activity at the same time. Afanassiew finds that if the formation of
bile in the liver be increased (¢.g., by section of the hepatic nerves, or feeding with proteids),
the cells are moderately enlarged in size, and contain numerous granules, which are proteid in
their nature ; such cells resist the action of caustic potash. When there is a great formation
of glycogen (as after feeding with potatoes and sugar), all the cells are very large and sharply
defined, and contain many granules of glycogen, the cells being so large as to compress the
capillaries. These cells dissolve quickly in caustic potash.

Action of Drugs.—Some substances excite the cells to activity, and cause them to present the
appearance of cells in activity, e.g., pilocarpin, muscarin, aloes, less so salicylate and benzoate
of soda and rhubarb, while atropin and lead acetate inhibit the signs of activity. These results
were obtained in the horse by Ellenberger and Baum. [Stolnikow, by using the quadruple-
staining method of Gaule, finds that the hepatic cells of the frog undergo remarkable changes
in poisoning by phosphorus, It is well known that this drug produces fatty degeneration of
the liver-cells, but a deeper study shows that the changes are both histological and chemical.
Besides producing remarkable changes in the protoplasm of the cell, the protoplasm of the

Fig. 193,

Liver-cells of frog. a, early, and 6, late stage in poisoning by phosphorus; c, liver-cell of
frog getting water only, d, getting sugar, and ¢, peptone (Stirling after Stolnikow).

nucleus, in the form of small masses called plasmosoma, passes out into the cell-body, perhaps
to renew the latter. The cells are increased in size, both after poisoning with phosphorus and
after excision of the fat bodies in the frog (fig. 193). The fat present in the liver in phosphorus-
poisoning is not present as droplets of oil, but probably in a loose combination, e.g., lecithin,
and as a matter of fact the amount of liver-lecithin is extracrdinarily increased. There is also an
increase of the nuclein ; while glycogen is absent. The season of the year also affects them.
There is a period of growth from July to November, and one of decay from December to May
(A. Leonard). Antipyrin also produces profound changes, especially in the nuclei. ] :

4, The Bile-Ducts.—The finest bile-capillaries, channels, or canaliculi arise from the centre of
the lobule, and indeed throughout the whole lobule they form a regular anastomosing network
of very fine tubes or channels. Each cell is surrounded by a polygonal—usually hexagonal—
mesh (fig. 194, 3). The bile-capillaries always lie in the middle of the surface between two
adjoining cells (II, a), where they form actual intercellular passages (fig. 192). [According
to some observers, they are merely excessively narrow channels (1 to 2 w wide) in the cement
substance between the cells, while according to others they have a distinct delicate wall. The
bile-capillary network is much closer than the blood-capillary
network. [Thus, there are three networks within each lobule—

Sis
(1) A network of blood-capillaries ; 1: ae
(2) - ~ hepatic cells ; Ce §
(3) . bile-capillaries; (fig, 192).] A r =

_ Excessively minute intracellular passages are said to pass from Fic. 194

the bile-capillaries into the interior of the liver-cells, where they ; ay ae
communicate with certain small cavities or vacuoles (Asp, Kupffer) 1s Liver-cell during fasting ;
(fig. 194, 3). As the blood-capillaries run along the edge of the 2, containing masses of gly-
liver-cells, and the bile-capillaries between the opposed surfaces C0S¢M; 3, a liver-cell sur-
of adjacent cells, the two systems of canals within the lobule are Tounded with bile-channels,
kept separate. Some bile-capillaries run along the edges of the tom which fine twigs pro-
liver-cells in the human liver, especially during. embryonic life. ©&¢4 into the cell-substance
Towards the peripheral part of the lobule, the bile-capillaries are © end in vacuoles.

larger, while adjoining channels anastomose, and leave the lobule, where they become inter-
lobular ducts (7), which join with other similar ducts to form larger interlobular bile-ducts.
These accompany the hepatic artery and portal vein, and leave the liver at the transverse
fissure. The finer interlobular ducts frequently anastomose in Glisson’s capsule, possess a struc-
tureless basement membrane, and are lined by a single layer of low polyhedral epithelial cells.
The larger interlobular ducts have a distinct wall, consisting of connective and elastic tissue,’

262 STRUCTURE OF THE LIVER,

mixed with circnlarly-disposed smooth muscular fibres (fig. 195). Capillaries are supplied to
the wall, which is lined by a single layer of columnar epithelium. A sub-mucosa occurs only
in the largest bile-ducts, and in the gall-bladder. Smooth muscular fibres, arranged in single
* bundles, occur in the largest ducts, and as longitudinal and
circular layers in the gall-bladder, whose mucous membrane
is provided with numerous folds and depressions. The

Circular * epithelium lining the gall-bladder is cylindrical, with a dis-
fibres. tinct clear disc, and between these cells are goblet-cells.
; Small branched tubular mucous glands occur in the larger
fs bile-ducts and in the gall-bladder.
<. Vasa aberrantia are isolated bile-ducts which occur on
Cylindrical ys the surface of the liver, but have no relation to any system
epithelium. * of liver-lobules. They occur at the sharp margin of the

- liver, in the region of the inferior vena cava, of the gall-
bladder, and of the parts near the portal fissure. It seems
that the liver-lobules to which they originally belonged
en ee have atrophied and disappeared (Zuckerkandl and Told.
Fig. 195. 5. The lymphatics begin as pericapillary tubes around
Interlobular bile-duct (human), the capillaries within the lobules, emerge from the lobule,
and run within the wall of the branches of the hepatic and
portal veins, and afterwards surround the venous trunks, thus forming the interlobulay lym-
phatics. These unite to form larger trunks, which leave the liver partly at the portal fissure,
artly along with the hepatic veins, and partly at different points on the surface of the organ.
here is a narrow superficial meshwork of lymphatics under the peritoneum—swb-peritoneal—
which communicate with the thoracic lymphatics through the triangular ligament and suspen-
sorium, while on the under surface they communicate with the lymphatics of the interlobular
connective-tissue. :

6. The nerves consist partly of medullated and partly of non-medullated fibres from branches
of the sympathetic and left vagus to the hepatic plexus. They accompany the branches of the
hepatic artery, and ganglia occur on their branches within the liver. Some of the nerve-fibres
are vaso-motor in function, and, according to Pfliiger, other nerve-fibres terminate directly in
connection with liver-cells. [MacCallum describes an interlobular plexus of non-medullated
fibres in man and menobranchus, from which a peri-vascular and intercellular plexus proceeds.
From the latter fibrils pass to terminate within the cells near the nucleus. ]

Pathological.—The connective-tissue between the lobules may undergo great increase in
amount, especially in alcohol- and gin-drinkers, and thus the substance of the lobules may be
greatly compressed, owing to the cicatricial contraction of the newly-formed connective-tissue
(cirrhosis of the liver). In such interlobular connective-tissue, newly-formed bile-ducts are
found.

Ligature of the ductus choledochus [causes enlargement of the spleen (rabbit), and a
diminution in the number of the blood-corpuscles], and, after a time, interstitial inflammation
of the liver. In rabbits and guinea-pigs the liver-parenchyma disappears, and its place is
taken by newly-formed connective-tissue and bile-ducts (Charcot and Gombauilt). In all these
cases of interstitial inflammation, there is proliferation of the epithelium of the bile-ducts.

[Regeneration of the Liver.—Tizzoni finds that there may be partial regeneration and new
formation of liver-lobules in the dog, the process being the same as that which occurs in the
embryonic development of the organ, z.e., the growth of solid cylinders of liver-cells, formed by
the pre-existing liver-cells, which penetrate into the connective-tissue uniting the edges of the
wound. These cells ultimately differentiate into hepatic cells and bile-ducts. Other observers
attribute the new formation to outgrowths of the epithelial cells of the bile-cells. ]

174. CHEMICAL COMPOSITION OF THE LIVER-CELLS.—(1) Proteids,
—The fresh, soft, parenchyma of the liver is alkaline in reaction; after death,
coagulation occurs, the cell-contents appear turbid, the tissue becomes friable, and
gradually an acid reaction is developed. This process closely resembles what occurs
in muscle, and is due to the coagulation of a myosin-like body, which is soluble
during life, but after death undergoes spontaneous coagulation (Plész). The liver

contains other proteids; one coagulating at 45° C., another at 70° C., and one
which is slightly soluble in dilute acids and alkalies. The nuclei contain nuclein.
The connective-tissue yields gelatin.

(2) Glycogen or Animal Starch—1:2 to 2°6 per cent.—is a true carbohydrate
most closely related to inulin, soluble in water, but diffuses with difficulty, and has
the formula 6(C,H,,O;)+H,O. It is stored up in the liver-cells in amorphous
granules around the nuclei (fig. 194, 2), but is not uniformly distributed in all

kal

CHEMICAL COMPOSITION OF THE LIVER-CELLS. 263

parts of the liver. Like inulin, it gives a. deep red colour with solution of iodine
in iodide of potassium. It is changed into dextrin and sugar by diastatic ferments,
and when boiled with dilute mineral acids, it yields grape-sugar (§ 148, I.; § 170,
I.; § 252, IIL).

Preparation of Glycogen.—[Feed a rabbit on carrots or boiled rice, and kill it three or four
hours thereafter. Remove the liver immediately after death, cut it into fine pieces, and place
these in boiling water, and boil it for some time in order to obtain a watery extract of the liver.
The boiling water destroys the ferment supposed to be present in the liver, which would transform
the glycogen into grape-sugar. To the cold filtrate are added alternately dilute hydrochloric acid
and potassio-mercuric iodide, which precipitates the proteids. Filter, when a clear opalescent
fluid, containing the glycogen in solution, is obtained. The glycogen is precipitated from the
filtrate, as a white amorphous powder, on adding an excess of 70 to 80 per cent. alcohol. The
precipitate is washed with 60 per cent. and afterwards with 95 per cent. alcohol, then with ether,
and lastly, with absolute alcohol ; it is dried over sulphuric acid and weighed (Briicke). Kiilz
modifies the method somewhat. After boiling the liver for half an hour, it is rubbed up with
liquor potassz (100 grm. liver, 4 grm. KHO). Evaporate in the water-bath until all is dissolved,
which occurs in about 3 hours. After cooling, neutralise with HCl and precipitate the proteids
as above. F. Eves asserts that the post-mortem conversion of sugar in the liver is not attribut-
able to a ferment action, and the rapid appearance of sugar in the liver after death is due to the
specific metabolic activity of the dying cells. ]

Sources.—The ‘‘mother-substance’”’ of the glycogen of the liver has been
variously stated to be the carbohydrates of the food (Pavy) ; fats (olive oil,
Salomon); glycerine, taurin, and glycin (the latter splitting into glycogen and urea),
the proteids (Cl. Bernard); and gelatin (Salomon). If it is derived from the
albumins, it must be formed from a non-nitrogenous derivative thereof.

Rohmann found that the use of ammonia carbonate and asparagin or glycin, along with a
carbohydrate diet, in rabbits considerably increased the formation of glycogen. The excessive
formation of acid observed by Stadelmann in diabetes unites with the ammonia and diminishes
considerably the formation of glycogen.

Effects of Food.—Rabbits, whose livers have been rendered free from glycogen
by starvation, yield new glycogen from their livers when they are fed with cane-
sugar, grape-sugar, maltose, or starch. Forced muscular movements soon make
the liver of dogs free from glycogen, exposure to cold diminishes its amount.
Dextrin and grape-sugar occur in the dead liver, but, in addition, some glycogen is
found for a considerable time after death in the liver and in the muscles.

If glycogen is injected into the blood, achroodextrin appears in the urine, and also
hemoglobin, as glycogen dissolves red blood-corpuscles. Ligature of the bile-duct causes
decrease of the glycogen in the liver.

Other Situations.—Glycogen is not confined to the liver-cells; it occurs during fcctal life
in all the tissues of the body of the embyro [including the embryonic skeleton], in young
animals (Kiihne), the placenta (Bernard). [It occurs in large amount in the liver during intra-
uterine life.] In the adult it occurs in the testicle, in the muscles (MacDonnell, O. Nasse), in
numerous pathological products, in inflamed lungs (Xiihne), and also in the corresponding
tissues of the lower animals. [It also occurs in the chorionic villi, in colourless blood-
corpuscles, in fresh pus cells which still exhibit amceboid movements, and in fact in all
developing animal cells, with amceboid movement ; it is a never-failing constituent in cartilage,
and in the muscles and liver of invertebrata, such as the oyster. There is none in the fresh
brain of the dog or rabbit, but it is found in the brain in diabetic coma (Abeles). |

Modifying Conditions.—If large quantities of starch, milk-, fruit-, or cane-sugar,
or glycerine, but not mannite, or glycol, or inosite, be added to the proteids of the
food, the amount of glycogen in the liver is very greatly increased (to 12 per cent.
in the fowl), while a purely albuminous or purely fatty diet diminishes it enor-
mously. During hunger it almost disappears. The injection of dissolved carbo-
hydrates into a mesenteric vein of a starving rabbit causes the liver, previously free
from glycogen, to contain glycogen. ;

[Effect of Drugs.—Arsenic, phosphorus; and antimony destroy the glycogenic function of the
liver, no glycogen being present in the liver in animals poisoned with these drugs, so that
puncture of the floor of the fourth ventricle no longer causes glycosuria in them. In animals ~

es ete by strychnia or curara, it is greatly diminished, both in the liver and in the muscles,
ugar is always present in the urine in the latter case but not in the former. ]

264 CHEMICAL COMPOSITION OF THE LIVER-CELLS.

During life, under normal conditions, the glycogen in the liver is either not
transformed into grape-sugar (Pavy), or, what is more probable, only a very small 4
amount of it is so changed. The normal amount of sugar in blood is 0°5 to 1 per
1000, although the blood of the hepatic vein contains somewhat more. A consider-
able amount is transformed into sugar only when there is a decided derangement of
the hepatic circulation, and in these circumstances the blood of the hepatic vein
contains more sugar. The glycogen undergoes this change very rapidly after death,
so that a liver which has been dead for some time always contains more sugar and
less glycogen. ; |

The diastatic ferment in the liver is small in amount, and can be obtained’ from
the extract of the liver-cells by the same means as are applicable for obtaining
other similar ferments, such as ptyalin ; but it does not seem to be formed within.
the liver-cells, but only passes very rapidly from the blood into them. The ferment
seems to be rapidly formed when the blood-stream undergoes considerable derange-
ment. Asimilar ferment is formed when red blood-corpuscles are dissolved (7%egel),
and, as red blood-corpuscles are continually destroyed within the liver, there is one
source from which the ferment may be formed, whereby minute quantities of sugar
would be continually formed in the liver.

According to Seegen, the blood of the hepatic vein contains twice as much sugar (0°23 per
cent.) as that in the portal vein (0°119 per cent.) ; observations on dogs showed that the blood
flowing through the liver gives up over 400 grms. sugar in 24 hrs. Hence, in carnivora, the
greatest part of the C of the animal food must pass into sugar, so that the formation of sugar
in the liver, and its decomposition in the blood, or in the organs traversed by the blood, must
be a very important function of the metabolism. Seegen is also of opinion that the liver-

glycogen takes no part in the formation of sugar in the liver.
[Blood when perfused through a freshly excised liver, (or through the kidneys, lungs, or

muscles), gains lactic acid (G. Aglioand Wissokowitsch). ]

(3) Fats, in the form of highly refractive granules, occur in the liver-cells, as
well as free in the bile-ducts ; sometimes, when the food contains much fat (more
abundant in drunkards and the phthisical), olein, palmatin, stearin, volatile fatty

acids, and sarcolactic acid are found. ?

There are also found traces of cholesterin, minute quantities of urea, uric acid, and the little-
known body. jecorin. [Jecorin, discovered by Drechsel, contains S and P, and reduces alkaline
solutions.of copper like grape-sugar. It is also found in the spleen, muscles, and blood
(Baldi). The liver of birds contains a relatively large amount of uric acid, even 6 to 14 times
as much as the bood (v. Schreder).] [Leucin (? guanin), sarkin, xanthin, cystin, and tyrosin
occur pathologically in certain diseases where marked chemical decompositions occur. ]

[Fatty Dengeneration and Infiltration..—Fatty granules are of common occurrence within
the cells of the liver, constituting fatty infiltration, and when not too numerous do not seem
to interfere greatly with the functions of the liver-cells. Fatty particles occur if too much
fatty food be taken, and they are commonly found in the livers of stall-fed animals; the
well-known pdté-de-foie gras is largely composed of the livers of geese, which have been fed
on large amounts of farinaceous food, and which have been subjected to other unfavourable
hygienic conditions. Fatty granules are recognised by their highly refractive appearance, by
their solubility in ether, and by being blackened by osmic acid. ] |

(4) The inorganic substances in the human liver are—potassium, sodium,
calcium, magnesium, iron, manganese, chlorine, and phosphoric, sulphuric, car-
bonic, and silicic acids; while copper, zinc, lead, mercury, and arsenic may be
accidentally deposited in the hepatic tissue.

[Tizzoni’s Reaction, —If a section of a liver (especially of a young animal) hardened in alcohol
be treated with a solution of potassic ferrocyanide, and then with dilute hydroehloric acid, as a
general rule the preperation becomes blue, even to the naked eye; but failing that, one can
usually see with the microscope granules of Prussian blue in the protoplasm of the cells, indi-
cating the presence of free iron oxide. ] :

175. DIABETES MELLITUS AND GLYCOSURIA.—{Glycosuria is char-~
acterised by the presence of grape-sugar in the urine. According to Briicke a
trace of sugar exists normally in urine, and when this amount is increased we
have glycosuria. When the normal amount of grape-sugar in the blood is —

DIABETES MELLITUS AND GLYCOSURIA. 265

inéreased, grape-sugar appears in the urine. In diabetes mellitus, srape-sugar
also appears in the urine, but this is really a serious disease, involving the
alteration of many tissues, and distinguished by profound disturbance of the whole
metabolic activity, which leads to numerous pathological, changes and often to
death. The appearance of grape-sugar in urine does not necessarily mean that a
person is suffering from this disease. |

The formation of large quantities of grape-sugar by the liver, and its passage
into the blood, and from the blood into the urine, constitute glycosuria. Extirpa-
tion of the liver in frogs, or destruction of the hepatic cells, as by fatty degeneration
from poisoning with phosphorus or arsenic, does not cause this condition. It occurs
for several hours, after the injury of a certain part—the centre for the hepatic
vaso-motor nerves—of the jloor of the lower part of the fourth ventricle (Cl.
Bernard’s “piqtre”); also after section of. the vaso-motor channels in the spinal
cord, from above down as far as the exit of the nerves for the liver, viz., to the
lumbar region, and in the frog to the fourth vertebra (Schiff). When the vaso-
motor nerves, which proceed from this centre-to the liver, are cut or paralysed in any
part of their course, mellituria or glycosuria is produced. All the nerve channels
do not run through the spinal cord alone. A number of vaso-motor nerves leave
the spinal cord higher up, pass into the sympathetic, and thus reach the liver ; so
that destruction of the superior (Pavy), as well as of the inferior cervical
sympathetic ganglion, and the first thoracic ganglion (Zckhard) of the abdominal
sympathetic, and often of the splanchnic itself produces it. The paralysis of the
blood-vessels causes the liver to contain much blood, and the intrahepatic blood-
stream is slowed. The disturbance of the circulation causes a great accumulation
of sugar in the liver, as the blood-ferment has time to act upon the glycogen and
transform it into sugar. By stimulation of the sympathetic at the lowest cervical
and first thoracic ganglion, the hepatic vessels at the periphery of the liver-lobules
become contracted and pale (Cyon). It is remarkable that glycosuria when
present may be set aside by section of the splanchnic nerves. This is explained
by supposing that the enormous dilatation and congestion, or the hyperzemia of
the abdominal blood-vessels thereby produced, renders the liver anzemic,

Continued stimulation of peripheral nerves may act reflexly upon the centre for the vaso-
motor nerves of the liver. Diabetes has been observed to occur after stimulation of the central
end of the vagus (Cl. Bernard), and also after stimulation of the central end of the depressor
nerve (Filehne). Even section and subsequent stimulation of the central end of the sciatic
nerve causes diabetes. This may explain the occurrence of diabetes in people who suffer from
sciatica. [It may occur also after perverted nervous activity, as psychical excitement, neuralgias
(sciatica, trigeminal or occipital), concussion of the brain, as well as after certain injuries to the
skull and vertebral column and some cerebral diseases. ]

According to Schiff, the stagnation of blood in other vascular regions of the body may
cause the ferment to accumulate in the blood to such an extent that diabetes occurs. The
glycosuria that occurs after compression of the aorta or portal vein may perhaps be ascribed to
this cause, but perhaps the pressure caused by these procedures may paralyse certain nerves.
According to Eckhard, injury to the vermiform process of the cerebellum of the rabbit causes
diabetes. In man, affections of the above-named nervous regions cause diabetes.

[In most individuals the use of a large quantity of sugar in the food is not followed by the
appearance of sugar in the urine ; but in some exceptional cases it is often present, ¢.g., in
persons suffering from gastric catarrh, especially if they are gouty.]

A number of poisons which paralyse the hepatic vaso-motor nerves produce diabetes ; curara
(when artificial respiration is not maintained), CO, amyl nitrite, ortho-nitro-propionic acid, and
methyl-delphinin ; less certainly morphia, chloral hydrate, HCN, and some other drugs ;
[phlorizin (v. Mering)] ; and some infectious diseases. But congestion of the liver produced in
other ways appears to cause diabetes, ¢.g., after mechanical stimulation of the liver. To this
class belongs the injection of dilute saline solutions into the blood (Bock, Hoffmann), whereby
either the change in form or the solution of the coloured blood-corpuscles causes the congestion.
The circumstance, that repeated blood-letting makes the blood richer in sugar, may perhaps be
explained by the slowing of the circulation. )

_ [Most of the means which produce glycosuria in other animals fail to do so in birds; even
the piqfire rarely produces it. This Thiel and Minkowski attribute to the intensely active

266 _ THE FUNCTIONS OF THE LIVER.

oxidation-processes in birds. Phlorizin causes glycosuria, even after extirpation of the liver,
which shows that in these cases there are other causes at work that obtain in the forms of
glycosuria.] Phlorizin makes animals, which are free from carbohydrates, diabetic. In this
case the sugar must be derived from proteids (v. Mering).

Theoretical.—In order to explain the more immediate cause of these phenomena several
~ hypotheses have been advanced :—

(a) The'liver-glycogen may be transformed unhindered into sugar, as the blood in its passage
through the liver deposits or gives up the ferment to the liver-cells. So that the normal
function of the vaso-motor system of the liver, and its centre in the floor of the fourth
ventricle, may be regarded as, in a certain sense, an ‘‘ inhibitory system” for the formation
of sugar.

(i) If we assume that, normally there is continually a small quantity of sugar passing from
the liver into the hepatic vein, we might explain the diabetes as due to the disappearance of
these decompositions—diminished burning-up of the sugar in the blood, which are constantly
removing the sugar from the blood. In fact, diabetic persons have been found to consume less
O and to have an increased formation of urea.

[Injection of Grape-Sugar into the Blood.—When grape-sugar is injected into the jugular
vein of a dog, only 33 per cent. at most is given off in the urine; within 2 to 5 hours the
urine is free from sugar. Even within a few minutes after the injection, only a certain propor-
tion (4-4) of the sugar is found in the blood ; part of the sugar has been detected in the muscles,
liver, and kidneys, but the fate of the remainder is not known. Immediately after the injec-
tion, the amount of hemoglobin and also of serum-albumin is diminished (50 per cent.), which
is due to increase of the quantity of water within the vessels ; but within two hours the normal
state is restored (Brasol). In a curarised dog the injection of grape-sugar into a vein increases
the blood-pressure, but this effect is not observed after the injection of morphia and chloral. ]

Persons suffering from diabetes require a large amount of .food; they suffer greatly from
thirst, and drink much fluid. They exhibit signs of marked emaciation, when the loss of the
body is greater than the supply. [In advanced diabetes the glycogenic function of the liver is
almost abolished, as was proved by removing with a trocar a small part of the liver from man,
when almost no glycogen was found (Ehrlich). The absorbed sugar in the portal vein passes
directly into the general circulation without being submitted to the action of the liver (v.
Frerichs).] In severe cases, towards death, not unfrequently a peculiar comatose condition—
diabetic coma—occurs, when the breath often has the odour of aceton, which is also found in
the urine. But neither aceton nor its precursor, aceto-acetic acid, nor sthyl-diacetic acid, nor
the unknown substance, in diabetic urine, which gives the red colour with ferric chloride (v.
Jaksch), is the cause of the coma (Frerichs and Brieger).

176, THE FUNCTIONS OF THE LIVER.—[To understand the functions
of the liver, we must remember its unique relation to the vascular and digestive
systems, whereby many of the products of gastric and intestinal digestion have to
traverse it before they reach the blood, and some of them as they traverse the
liver are altered. We have still much to learn regarding the liver. It has several
distinct functions—some obvious, others not. (1) The liver secretes bile, which is
formed by the hepatic cells, and leaves the organ by the bile-ducts, to pass into
the duodenum. (2) The liver-cells also form glycogen, which does not pass into
the ducts, but in some altered and diffusible form passes into the blood-stream,
and leaves the liver by the hepatic veins. Hence, the study of the liver materially
influences our conception of a secreting organ. In this case, we have the products
of its secretory activity leaving it by two different channels—the one by the ducts, |
and the other by the blood-stream. The liver, therefore, is a great storehouse of
carbohydrates, and it serves them out to the economy as they are required. All
this points to the liver as being an organ intimately related to the general
metabolism of the body. (3) In a certain period of development it is concerned
in the formation of blood-corpuscles (§ 7). (4) It has some relation to the
breaking up of blood-corpuscles and the formation of urea and other metabolic
products (§ 20, § 177, 3). (5) Brunton attributes some importance to the liver in
connection with the arrest of certain substances absorbed from the alimentary
canal, whereby they are either destroyed, stored up in the liver, or, it may be,
prevented from entering the general circulation in too large amount. It is possible
that ptomaines may be arrested in this way (§ 166).] .

[The liver has no special action on certain mineral substances which traverse it in the blood,

CONSTITUENTS OF THE BILE. 267

e.g., potassic chloride, but it retains the vegetable alkaloids, provided they are not present in
too large an amount in the blood. The ptomaines are similarly retained in the liver. The
liver possesses this property only as long as it contains glycogen (H. Rogers).]

177. CONSTITUENTS OF THE BILE.—Bile is a yellowish-brown or dark
green coloured transparent fluid, with a sweetish, strongly bitter taste, feeble musk-
like odour, and neutral reaction. The specific gravity of human bile from the gall
bladder = 1026 to 1032, while that from a fistula=1020 to 1011. It contains :—

(1) Mucus, which gives bile its sticky character, and not unfrequently makes it
alkaline ; it is the product of the mucous glands and the goblet-cells of the mucous
membrane of the larger bile-ducts. When bile is exposed to the air, the mucus
causes it to putrefy rapidly. It is precipitated by acetic acid, or alcohol.

[The bile formed in the ultimate bile-ducts does not seem to contain mucin or mucus, but
bile from the gall-bladder always does. It is formed by the mucous glands in the larger bile-
ducts (§ 173). ]

(2) The Bile-Acids.—Glycocholic and taurocholic acids, so-called conjugate acids,
are united with soda (in traces with potash) to form glycocholate and taurochol-
ate of soda, which have a bitter taste, and rotate the plane of polarised light to the
right. In human bile (as well as in that of birds, many mammals, and amphi-
bians) taurocholic acid is most abundant; in other animals (pig, ox) glycocholic acid
is most abundant but is absent in sucklings.

(a) Glycocholie acid, C,,H,,NO,;; when boiled with caustic potash, or baryta
water, or with dilute mineral acids, it takes up H,O and splits into—

Glycin (= Glycocoll = Gelatin Sugar = Amido-acetic acid) =C,H,NO,,.
+ Cholalic acid (also called Cholic acid) s : = C,,H49;.
=Glycocholic acid+ Water . A = C,,H4,NO,+ H,0.

(b) Taurocholic acid, C,,H,,NSO., when similarly treated, takes up water and
splits into— ’
Taurin (= Amidozthyl-Sulphuric acid) =C,H,NSO3.
+Cholalic acid . , : ; = C,,H 405.
=Taurocholic acid + Water. . = C.gH,;NSO,+ H,O (Strecker).

[Solutions of taurocholic acid are antiseptic, and if sufficiently strong interfere with the de-
velopment of bacteria, and prevent the alcoholic and lactic fermentations, as well as the tryptic
and diastatic action of the pancreas (Hmich).]

Preparation of the Bile-Acids.—Evaporate bile to } of its volume, rub it up into a paste with
excess of animal charcoal, and dry at 100°C. Extract the black mass with absolute alcohol,
and filter. After a part of the alcohol has been removed by distillation, the bile-salts are pre-
cipitated in a resinous form, and on the addition of excess of ether, there is formed immediately
a crystalline mass of glancing needles (Platner’s ‘‘ crystallised bile’’). The alkaline salts of
the bile-acids are freely soluble in water or alcohol, and insoluble in ether. Newtral lead acetate
precipitates the glycocholic acid—as lead glycocholate—from the solution of both salts; the
precipitate is collected on a filter, dissolved in hot alcohol, and the lead is precipitated as lead
sulphide by H.S; after removal of the lead sulphide, the addition of water precipitates the
isolated glycocholic acid. If, after precipitating the lead glycocholate, the filtrate be treated
with basic lead acetate, a precipitate of lead taurocholate is formed, from which the acid may
be obtained in the same way as described above (Strecker).

With regard to the decomposition products of the bile-acids, glycin, as such,
does not occur in the body, but only in the bile in combination with cholic acid, in
urine in combination with benzoic acid, as hippuric acid, and lastly, in gelatin in
complex combination.

Cholalic acid rotates the ray of polarised light to the right, and its chemical
composition is unknown. It is insoluble in water, soluble in alcohol, but soluble
with difficulty in ether, from which it separates in prisms. Its crystalline alkaline
salts are readily soluble in water. It is coloured blue by iodine, and occurs free
only in the intestine. ’ 7

Cholalic acid is replaced in the bile of many animals by a nearly related acid, ¢.g., in pig’s
bile, by hyo-cholalic acid (Strecker); in the bile of the goose, cheno-cholalic acid is present
(Marsson, Otto), :

268 ”) “THE BILE-ACIDS) >

- When cholalic acid is boiled with concentrated HCl, or heated dry at 200° C.; it
becomes an anhydride, thus :— -

Cholalic acid. . =C.,H,,0;, produces.
Choloidinic acid . =C,,H;,0,+H,0, and this again yields
Dyslysin . ‘ = C,,H,,0,;= HO:

Choloidinic acid is, however, not improbably a mixture.of cholalic acid and dyslysin ; dys-
lysin, when fused with caustic potash, is changed into cholalate of potash. By oxidation
cholalic acid yields a tribasic acid, as yet uninvestigated, and a fair amount of oxalic acid, but
no fatty acids (CZéve).

Pettenkoffer’s Test.—The bile-acids, cholic acid, and their anhydrides, when
dissolved in water, yield on the addition of 2 concentrated sulphuric acid (added in
drops so as not to heat the fluid above 70° C.), and several drops of a 10 per cent.
solution of cane-sugar, a reddish-purple transparent fluid, which shows two absorp-
tion-bands at E and F (Schenk). [A very good’ method is to mix a few drops of
the cane-sugar solution with the bile, and to shake the mixture until a copious
froth is obtained. Pour the sulphuric acid down the side of the test-tube, and then
the characteristic colour is seen in the froth. Any albumin present must be re-
moved before applying the test. | |

According to Drechsel, it is better to add phosphoric acid, instead of sulphuric acid, until
the fluid is syrupy, then add the cane-sugar, and afterwards place the whole in boiling water.
When investigating the amount of bile-acids in a liquid, the albumin must be removed before-
hand, as it gives a reaction similar to the bile-acids, but in that case the red fluid has only one
absorption-band. If only small quantities of bile-acids are present, the fluid must in the first
place be concentrated by evaporation.

[Hay’s Test.—The bile-acids or their soluble salts lower the surface-tension of fluids in which
they are dissolved. Throw a small quantity of sulphur (sublimed or precipitated) on the surface
of the fluid containing bile-acids, and if the bile-acids be present, the sulphur will at once begin
to sink, and will be wholly precipitated within a few minutes. (Privately comnvunicated.)]

The bile-acids are formed in the liver. After its extirpation, there is no ac-
cumulation of biliary matters in the blood. _ | .

How the formation of the nitrogenous bile-acids is effécted, is quite unknown. They must
be obtained from the decomposition of albuminous materials, and it is important to note that
the amount of bile-acids is increased by albuminous food. Taurin contains part of the sulphur
of albumin ; bile-salts contain 4 to 4°6 per cent., which may perhaps be derived from dissolved
red blood-corpuscles.

(3) The Bile-Pigments.—The freshly secreted bile of man and many animals
has a yellowish-brown colour, due to the presence of bilirubin. When it remains
for a considerable time in the gall-bladder, or when alkaline bile is exposed to the
air, the bilirubin absorbs O and becomes changed into a green pigment, biliverdin.
This substance is present naturally, and is the chief pigment in the bile of herbivora
and cold-blooded animals. . :

(a) Bilirubin (C,,H,,N,O,) is perhaps united with an alkali; it crystallises in
transparent fox-red clinorhombic prisms. It is insoluble in water, soluble in chloro-
form, by which substance it may be separated from biliverdin, which is insoluble
in chloroform. It unites.as a monobasic acid with alkalies, and as such is soluble.
It is identical with Virchow’s hematoidin (§ 20). , | ,

Preparation.—It is most easily prepared from the red (bilirubin-chalk) gall-stones of man or
the ox. The stones are pounded, and their chalk dissolved by hydrochloric acid ; the pigment
is then extracted with chloroform. That bilirubin is derived from pera we is very prob-
able, considering its identity with’ hematoidin. - Very probably red blood-corpuscles are
dissolved in the liver, and their hemoglobin changed into bilirubin. )

(6) Biliverdin, C,,H,,N,O,, is an oxidised derivative of the former, fram which
it can be obtained by various oxidation-processes, It is readily soluble in alcohol,
very slightly so in ether, and not at all soluble in chloroform. It occurs in the
placenta of the bitch. As yet it has not been retransformed by reducing agents
inte Dalirabia.yielod-cusds woos ult to ohh see aes Gk bisa BAP

Tests for Bile-Pigments,—Bilirubin and biliverdin may occur in other fluids,

CHOLESTERIN. 269

e.g., the urine, and are detected by the Gmelin-Heintz’ reaction. When nitric
acid containing some nitrous acid is added to a liquid containing these pigments, a
play of colours is obtained beginning with green (biliverdin), blue, violet, red, end-
ing with yellow. {This reaetion-is best done by placing a.drop of the liquid on a
white porcelain plate, and adding a drop of the impure nitric acid. |

(c) If, when the blue colour is reached, the oxidation process is arrested, bilicyanin (Heynsius,
Campbell), in acid solution blue (in alkaline violet), is obtained, which shows two ill-defined
absorption-bands near D (Jaffé). .

(zd) Bilifuscin occurs in small amount in decomposing bile and in gall-stones=bilirubin
+H,0.

(e) Biliprasin (Stadler) also occurs = Bilirubin + H,O +0.

(f) The yellow pigment, which ultimately results from the prolonged action of the oxidising
reagent, is the choletelin (C,,H,,N,O,) of Maly; it is amorphous, and soluble in water, alcohol,
acids, and alkalies.

[Spectrum of Bile.—The bile of carnivorous animals is generally free from absorption-bands,
except when acids are added to it, in which case the band of bilirubin is revealed. Bilirubin
‘and biliverdin yield characteristic spectra only when they are treated with nitric acid. The
bile of some animals yields bands, but when this is the case they are due to the presence of a
derivative of hematin, and MacMunn calls this body cholohematin, which gives a three- or
four-banded spectrum (ox, sheep).] —

(7) Bilirubin absorbs H+H,O (by putrefaction, or by the treatment of alkaline
watery solutions with the powerfully reducing sodium amalgam), and becomes con-
verted into Maly’s hydrobilirubin (C,,H,,N,O-), which is slightly soluble in water,
and more easily soluble in solutions of salts, or alkalies, alcohol, ether, chloroform,
and shows an absorption-band at 6, F. This substance, which, according to Hammar-
sten, occurs in normal bile, is a constant colouring-matter of feeces, and was called
stercobilin by Vaulair and Masius, but is identical with hydrobilirubin (JMaly).
It is, however, probably identical with the urinary pigment wrobiin of Jafté (Stokvis,
$20).

[The bile of invertebrates contains none of the bile-pigments present in vertebrates, although
hemochromogen is found in the cray-fish and pulmonate molluscs. In some organs, and in bile,
a pigment like vegetable chlorophyll—entero-chlorophyll—is found, but whether it is derived
from without, or formed within the organism, is not certain (J/acMunn). ]

(4) Cholesterin, C,,H,,O(H,O), is a monatomic alcohol which rotates the ray of
polarised light to the left, it occurs also in blood, yelk, nervous matter [and gall-
stones]. It forms transparent rhombic plates, which
usually have a small oblong piece cut out of the corner
(fig. 196). It is insoluble in water, soluble in hot alcohol,
ether, or chloroform. It is kept in solution in the bile
by the bile-salts.

Preparation.—It is most easily prepared from so-called white
gall-stones, which not unfrequently consist entirely of cholesterin,
by extracting them with hot alcohol after they are pulverised.
Crystals are excreted after evaporation of the alcohol. Tests,— Fig. 196
They give a red colour with sulphuric acid (5 vol. to 1 vol. HO), 8: :
while they give a blue—as cellulose does—with sulphuric acid and
iodine. When dissolved in chloroform, one drop of concentrated sulphuric acid causes a deep
red colour (H. Schiff). . | :

(5) Amongst the other organic constituents :—Lecithin (§ 23), or its decomposi-
tion-product, neurin (cholin), and glycero-phosphoric acid (into which lecithin may
be artifically transformed by boiling with baryta) ; palmatin, stearin, olein, as
well as their soda soaps; diastatic ferment; traces of urea; (in ox bile, acetic acid
and propionic acid, united with glycerine and metals, Dogiel).

(6) Inorganic constituents of bile (0°6 to 1 per cent.) :—

They are—sodic and potassic chloride, calcic and magnesic phosphate, and much iron, which
in fresh bile gives the ordinary reactions for iron, so that iron must occur in one of its oxidised
compounds in bile ; manganese and silica. Gases.—Freshly-secreted bile contains in the dog.
‘more than 50 vol., and in; the rabbit 109 vol. per cent. CO,, Bary eee to alkalies, partly
absorbed, the latter, however, being almost completely absorbed within the gall-bladder.

Crystals of cholesterin.

270 SECRETION OF BILE,

The mean composition of human bile is :—

Water, ; . 82 to 90 per cent. Lecithin, . : : 0°5 per cent.
Bile-salts, , : 6 toll ./,, Mucin and pigments, . 1 to 3 ey
Fats and soaps, . ; B her a Ash, , . . b yA dss

Cholesterin, : ‘ 04 ,,

Further, unchanged fat probably’always passes into the bile, but it is again absorbed therefrom
(Virchow). The amount of S in dry dog’s bile=2°8 to 3°1 per cent., the N=7 to 10 per cent,
(Spiro) ; the sulphur of the bile is not oxidised into sulphuric acid, but it appears as a sulphur-
compound in the urine (Kunkel, v. Voit),

178. SECRETION OF BILE—(1) The secretion of bile is not a mere
filtration of substances already existing in the blood of the liver, but it is a
chemical production of the characteristic biliary constituents, accompanied by
oxidation, within the hepatic cells, to which the blood of the gland only supplies
the raw material. The liver-cells themselves undergo histological changes during
the process of digestion, It is secreted continually ; but part is stored up in the
gall-bladder, and is poured out copiously during digestion, The higher temperature
of the blood of the hepatic vein, as well as the large amount of CO, in the bile,
indicates that oxidations occur within the liver. The water of the bile is not
merely filtered through the blood-capillaries, as the pressure within the bile-ducts
may exceed that in the portal vein,

(2) The quantity of bile was estimated by v. Wittich, from a biliary fistula, at
533 cubic centimetres in twenty-four hours (some bile passed into the intestine) ;
by Westphalen, at 453 to 566 grms. [by Murchison, at 40 0z.]; by Joh. Ranke, on
a biliary-pulmonary fistula, at 652 cubic centimetres. The last observation gives
14 grms, (with 0°44 grms. solids) per kilo. of man in twenty-four hours.

Analogous values for animals are—1 kilo. dog, 32 grm. (1°2 solids) ; 1 kilo, rabbit, 137 grm,
(2°5 solids) ; 1 kilo. guinea-pig, 176 grms, (2°5 solids). ;

(3) The excretion of bile into the intestine shows two maxima during one period
of digestion, the first from 3 to 5 hours, and the second from 13 to 15 hours,
after food. The cause is due to simultaneous reflex excitement of the hepatic blood-
vessels, which become greatly dilated.

(4) The influence of food is very marked, The largest amount is secreted
after a flesh diet, with some fat added; less after vegetable food ; a very small
amount with a pure fat diet ; it stops during hunger. Draughts of water increase
the amount, with a corresponding relative diminution of the solid constituents.
[The biliary solids are increased by food, reaching their maximum about one hour
after feeding. |

(5) The influence of blood-supply is variable :—

(a) Secretion is greatly favoured by a copious and rapid blood-supply. The blood-pressure
is not the prime factor, as ligature of the cava above the diaphragm, whereby the greatest
blood-pressure occurs in the liver, arrests the secretion.

(6) Simultaneous ligature of the hepatic artery (diameter 54 mm.) and the portal vein
(diameter, 16 mm.) abolishes the secretion (Rédhrig), These two vessels supply the raw
material for the secretion of bile.

(c) If the hepatic artery be ligatured, the portal vein alone supports the secretion, Ligature
of the artery or one of its branches ultimately causes necrosis of the parts supplied by that
branch, and eventually of the entire liver, as this artery is the nutrient vessel of the liver.

(d) If the branch of the portal vein to one lobe be ligatured, there is only a slight secretion in
that lobe, so that the bile must be formed from the arterial blood, Complete ligature of the portal
vein rapidly causes death (§ 87). Neither ligature of the hepatic artery by itself, nor gradual
obliteration of the portal vein by itself, causes cessation of the secretion, but it is diminished,
That sudden ligature of the portal vein causes cessation is due to the fact that, in addition to
diminution of the secretion, the enormous stagnation of blood in the rootlets of the portal vein
in the abdominal orgatis makes the liver very anemic, and thus prevents it from secreting. _

(e) If the blood of the hepatic artery is allowed to pass into the portal vein (which has been
ligatured on the peripheral side), secretion continues (Schiff). t

(f) Profuse loss of blood arrests the secretion of bile, before the muscular and nervous
apparatus become paralysed. A more copious supply of blood to other organs—e.g., to the

BILIARY FISTULA, 271

muscles of the trunk—during vigorous exercise, diminishes the secretion, while the transfusion
of large quantities of blood increases it, but if too high a pressure is caused in the portal vein,
by introducing blood from the carotid of another animal, it is diminished. .

(g) Influence of Nerves.—A1l conditions which cause contraction of the abdominal blood-
vessels, ¢.g., stimulation of the ansa Vieussenii, of the inferior cervical ganglion, of the hepatic
nerves, of the splanchnics, of the spinal cord (either directly by strychnia, or reflexly through
stimulation of sensory:nerves), affect the secretion ; and so do all conditions which cause stagna-
tion or congestion of the blood in the hepatic vessels (section of the splanchnic nerves, diabetic
puncture, § 175), section of the cervical spinal cord. Paralysis (ligature) of the hepatic nerves
causes at first an increase of the biliary secretion.

(h) Portal and Hepatic Veins,—With regard to the raw material supplied to the liver by its
blood-vessels, it is important to note the difference in the composition of the blood of the
hepatic and portal veins. The blood of the hepatic vein contains more sugar (?), lecithin,
cholesterin (Drosdof), and blood-corpuscles, but ess albumin, fibrin, hemoglobin, fat, water,
and salts,

[(¢) Uffelmann observed that the flow of bile from a person with a biliary fistula was arrested
during fever. ]

(6) The formation of bile is largely dependent upon the decomposition of red
blood-corpuscles, as they supply the material necessary for the formation of some
of its constituents,

Hence, all conditions which cause solution of the coloured blood-corpuscles are accompanied
by an increased formation of bile (§ 180),

(7) Of course a normal condition of the hepatic cells is required for a normal
secretion of bile,

Biliary Fistules.—The mechanism of the biliary secretion is studied in animals by means of
biliary fistule. Schwann opened the belly by a vertical incision a little to the right of the
ensiform process, cut into the fundus of the
gall-bladder, and sewed its margins to the edges AP¢
of the wound in the abdomen, and afterwards
introduced a cannula into the wound (fig. 197).
To secure that all the bile is discharged exter-
nally, tie the common bile-duct in two places and
divideit between thetwoligatures, Aftera fistula
is freshly made the secretion falls, This depends
upon the removal of the bile from the body, If
bile be supplied, the secretion is increased. Re-
generation of the divided bile-duct may occur in
dogs. V. Wittich observed a biliary fistula in
man. [A temporary biliary fistula may also be Y)
made. The abdomen is opened in the same Fie.-197
way as described above. A long bent glass 5 S: : Ar
cannula is introduced and tied into the common S¢hwann’s permanent fistula, and a temporary
bile-duct, and the cystic duct is ligatured or ‘fistula. Abd, abdominal ie Fe fies gall-
clamped (fig. 197). The tube is brought out bladder; INT., Ea ie be a
through the wound in the abdomen. ] rary fistula (Stirling),

[Influence of the Liver on Metabolism,—lIf the liver be excluded from the circulation, im-
portant changes must necessarily occur in the metabolism. In birds (the goose) there is an
anastomosis between the portal system of the liver and that of the kidneys, so that, when the
portal circulation is interrupted in these animals, there is never any great congestion in the
abdominal organs. The goose dies generally eight to ten hours after the operation. The wric
acid in the urine rapidly falls to a minimum (4; to 34 of normal) ; the chief constituent of the
urine is then sarcolactic acid, while in normal urine there is none ; the ammonia is increased
(Minkowski). This experiment goes to indicate that uric acid is formed in the liver, Dog.—
If the liver be excluded from the portal circulation, by connecting the portal vein with the
inferior vena cava, and ligaturing the hepatic artery, a dog will live in the former case three to
six days and in the latter one to two. The liver does notrundergo necrosis, nor does bile cease
to be secreted. The liver is nourished by the blood in the hepatic vein, the reflux in this vein
being probably caused by the respiratory movements (Stolnikow). Noél Paton finds that in dogs,
ina condition of nitrogenous balance, some drugs which increase the flow of bile (¢.g., salicylate
and benzoate of soda, colchicum, perchloride of mercury, and euonymin) also increase the pro-
duction of urea ; hence, he concludes that the formation of urea in the liver bears a very direct
relationship to the secretion of bile (§ 256). ]

179. EXCRETION OF BILE.—[In this connection we must keep in view two
distinct mechanisms. (1) The bile-secreting mechanism dependent upon the

Abd

, ors oe

272 EXCRETION OF BILE,

liver-cells, which are always in a greater or less degree of activity ; (2) the bile-
expelling mechanism, which is specially active at certain periods of digestion
(§ 178)}. +4

Excretion of bile is due to (1) the continual pressure of the newly-formed
bile within the interlobular bile-ducts forcing onward the bile in the excretory
ducts.

(2) The interrupted periodic compression of the liver from above, by the
diaphragm, at every inspiration. Further, every inspiration assists the flow of
blood in the hepatic veins, and every respiratory increase of pressure within the
abdomen favours the current in the portal vein.

It is probable that the diminution of the secretion of bile, which occurs after bilateral division
of the vagi, is to be explained in this way ; still it is to be remembered, that the vagus sends
branches to the hepatic plexus. It is not decided whether the biliary excretion is diminished
after section of the phrenic nerves and paralysis of the abdominal muscles.

(3) The contraction of the smooth muscles of the larger bile-ducts and the gall-
bladder. Stimulation of the spinal cord, from which the motor nerves for these
structures pass, causes acceleration of the outflow, which is afterwards followed by
a diminished outflow. Under normal conditions, this stimulation seems to occur
reflexly, and is caused by the passage of the ingesta into the duodenum, which, at
the same time, excites movement of this part of the intestine. _

(4) Direct stimulation of the liver, and reflex stimulation of the spinal cord,
diminish the excretion ; while extirpation of the hepatic plexus and injury to the
floor of the fourth ventricle do not exert any disturbing influence. |

(5) A relatively small amount of resistance causes bile to stagnate in the bile-
ducts.

Secretion Pressure.—A manometer, tied into the gall-bladder of a guinea-pig, supports a
column of 200 millimetres of water; and secretion can take place under this pressure. If this
pressure be increased, or too long sustained, the watery bile passes from the liver into the
blood, even to the amount of four times the weight of the liver, thus causing solution of the
red blood-corpuscles by the absorbed bile; and very soon thereafter hemoglobin appears in the
urine. [This fact is of practical importance, as duodenitis may give rise to symptoms of
jaundice, the resistance of the inflamed mucous membrane being sufficient to arrest the out-
tlow of bile. ]

Passage of Substances into the Bile.—Some substances which enter the blood pass into the
bile ; especially the metals, copper, arsenic, iron,: &c. ; potassium iodide, bromide, and
sulphocyanide, and turpentine ; to a less degree, cane-sugar and grape-sugar ; sodium salicylate,
and carbolic acid. If a large amount of water be injected into the blood, the bile becomes
albuminous ; mercuric and mercurous chlorides cause an increase of the water of the bile.
Sugar has been found in the bile in diabetes ; leucin and tyrosin in typhus, lactic acid and
albumin in other pathological conditions of this fluid,

_ 180, REABSORPTION OF BILE; JAUNDICE.-—I. Absorption-Jaundice.—When resist-
ance is offered to the outflow of bile into the intestine, ¢.g., by a plug of mucus, or a gall-stone
which occludes the bile-duct, or where a tumour or pressure from without makes it impervious.
—the bile-ducts become filled with bile and cause an enlargement of the liver. The pressure
within the bile-ducts is increased. As soon as the pressure has reached a certain amount,
which it soon does when the bile-duct is occluded (in the dog 275 mm. of a column of bile),
reabsorption of bile from the distended larger bile-ducts takes place into the lymphatics (not
the blood-vessels) of the liver, the bile-acids pass into the lymphatics of the liver. [The
lymphatics can be seen at the portal fissure filled with yellow-coloured lymph.] The lymph
passes into the thoracic duct, and so into the blood (Fleisch/), Even when the pressure is very
low within the portal vein, bile may pass into the blood without any obstruction to the bile-duct

- being present. This is the case in Icterus neonatorum, as after ligature of the umbilical cord
no more blood passes through the umbilical vein ; further, in the icterus of hunger, ‘‘ hunger-
jaundice” as the portal vein is relatively empty, owing to the feeble absorption from the
intestinal canal (Cl. Bernard),

II. Cholemia may also occur, owing to the excessive production of bile (hypercholia), the

bile not being all excreted into the intestine, so that part of it is reabsorbed. This takes
place when there is solution of a great number of blood-corpuscles (§ 178, 6), which yield
material for the formation of bile. Thick inspissated bile accumulates in the bile-ducts, so that
stagnation, with subsequent reabsorption of the bile, takes place, The transfusion of hetero,

“—
A

@g

REABSORPTION OF BILE; JAUNDICE. 2/35

geneous blood obtained by dissolving coloured blood-corpuscles acts in this direction. Icterus is
a common phenomenon after too copious transfusion of the same blood. _ The blood-corpuscles
are dissolved by the injection into the blood of heterogeneous blood-serum, by the injection of
bile-acids into the vessels, and by other salts, by phosphoric acid, water, chloral, inhalation of
chloroform and ether; the injection of dissolved hemoglobin into the arteries or into a loop of
the small intestine acts in the same way.

_ -Icterus Neonatorum.—When, owing to compression of the placenta within the uterus, too
much blood is forced into the blood-vVessels of the newly-born infant, a part of the surplus
blood during the first few days becomes dissolved, part of the hemoglobin is converted into
bilirubin, thus causing jaundice (Virchow, Violet).

Absorption-Jaundice.—When the jaundice is caused by the absorption of bile

already formed in the liver, it is called hepatogenic or absorption-jaundice. The

following are the symptoms :—

(1) Bile-pigments and bile-acids pass into the tissues of the body; hence, the most pro-
nounced external symptom is the yellowish tint or jaundice. The skin and the sclerotic
become deeply coloured yellow. In pregnancy the foetus is also tinged.

(2) Bile-pigments and bile-acids pass into the urine (not into the saliva, tears, or mucus),
($ 177). When there is much bile-pigment, the urine is coloured a deep yellowish-brown, and
its froth is citron-yellow; while strips of gelatin or paper dipped into it also become coloured.
Occasionally bilirubin (= hematoidin) crystals occur in the urine (§ 266). |

(3) The feeces are ‘‘ clay-colowred” (because the hydrobilirubin of the bile is absent from the
fecal matter)—very hard (because the fluid of the bile does not pass into the intestine);
contain. much fat (in globules and crystals), because the fat is not sufficiently digested in the
intestine without bile, so that 78 per cent. of the fat taken with the food reappears in the feces
(v. Voit); they have a very disagreeable odour, because the bile normally greatly limits the
putrefaction in the intestine. [V. Voit finds that putrefaction does not take place if fats be

withheld from the food.] The evacuation of the feces occurs slowly, partly owing to the hardness

of the feces, partly because of the absence of the peristaltic movements of the intestine, owing
to the want of the stimulating action of the bile. ;

(4) The heart-beats are greatly diminished, ¢.g., to 40 per minute. This is due to the
action of the bile-salts, which at first stimulate the cardiac ganglia, and then weaken them.
Bile-salts injected into the heart produce at first a temporary acceleration of the pulse, and after-
wards slowing (Réhrig). The same occurs when they are injected into the blood, but in this
case the stage of excitement is very short. The phenomenon is not affected by section of the
vagi. It is probable, that when the action of the bile-salts is long continued, they act upon the
heart-muscle. In addition to the action on the heart, there is slowing of the respiration and
diminution of temperature.

(5) That the nervous system, and perhaps also the muscles, are affected, either by the bile-
salts or by the accumulation of cholesterin in the blood, is shown by the very general relax-
ation, sensation of fatigue, weakness, drowsiness, and lastly deep coma—sometimes there is
sleeplessness, itchiness of the skin, even mania, and spasms. Lowit, after injecting bile into
animals, observed phenomena referable to stimulation of the respiratory, cardio-inhibitory,
and vasomotor nerve-centres.

(6) In very pronounced jaundice there may be ‘‘ yellow vision,” owing to the impregnation ‘of
the retina and macula lutea with the bile-pigment. :

(7) The bile-acids in the blood dissolve the red blood-corpuscles. The hemoglobin is
changed into new bile-pigment, and the globulin-like body of the hemoglobin may form
ey cylinders or casts in the urinary tubules, which are ultimately washed out of the tubules

y the urine. '

[Influence of Drugs on the Secretion of Bile.—On animals one may make either a permanent
or a temporary fistula. The latter is the more satisfactory method, and the experiments are
usually made on fasting curarised dogs. A suitable cannula is introduced into the common
bile-duct (fig. 197), the animal is curarised, artificial respiration being kept up, while the drug
is injected into the stomach or intestine. Rohrig used this method, which was improved by
Rutherford and Vignal. Rohrig found that some purgatives, croton oil, colocynth, jalap, aloes,
rhubarb, senna, and other substances, increased the secretion of bile. Rutherford and Vignal
investigated the action of a'large number of drugs on the bile-secreting mechanism. They

found that croton oil is a feeble hepatic stimulant, while podophyllin, aloes, colchicum, euony-

min, iridin, sanguinarin, ipecacuan, colocynth, sodium phosphate, phytolaccin, sodium benzoate,
sodium salicylate, dilute nitro-hydrochloric acid, ammonium phosphate, mercuric chloride (cor-
rosive sublimate), are all powerful, or very considerable, hepatic stimulants, Some substances
stimulate the intestinal glands, but not thé liver, ¢.g., magnesium sulphate, castor oil, gam-
boge, ammonium chloride, manganese sulphate, calomel. Other substances stimulate the liver
as well as the intestinal glands, although not to the same extent, ¢.g., scammony (powerful
intestinal, feeble hepatic stimulant); colocynth excites both powerfully; jalap, sodium sulphate,
. )

274 FUNCTIONS OF THE BILE.

and baptisin, act with considerable power both on the liver and the intestinal glands, Cala-
bar bean stimulates the liver, and the increased secretion caused thereby may be reduced by
sulphate of atropin, although the latter drug, when given alone, does not notably affect the
secretion of bile. The injection of water or bile slightly increases the secretion. In all cases
where purgation was produced by purdy intestinal stimulants, such as magnesium sulphate,
gamboge, and castor oil, the secretion of bile was diminished. In all such experiments it is most
important that the temperature of the animal be kept up, else the secretion of bile diminishes.
Paschkis’s results on dogs differ considerably from those of Rutherford. He asserts that only
the bile-acids (salts) of all the substances he investigated excite a prompt and distinct chola-
gogue action. }

[As yet we cannot say definitely whether, or not, these substances stimulate the secretion of bile,
by exciting the mucous membrane of the small intestine, and thereby inducing reflex excitement
of the liver. Their action does not seem to be due to increase of the blood-stream through the
liver. More probably, as Rutherford suggests, these drugs act directly on the hepatic-cells or
their nerves. Acetate of lead directly depresses the biliary secretion, while some substances
affect it indirectly. ]

[Cholestereemia.—F lint ascribes great importance to the excretion of cholesterin by the bile,
with reference to the metabolism of the nervous system. Cholesterin, which is a normal in-
gredient of nervous tissue, is excreted by the bile ; and if it be retained in the blood ‘‘ choles-
teremia,” with grave nervous symptoms, is said to occur. This, however, is problematical,

and the phenomena described are probably referable to the retention of the bile-acids in the
blood. ]

181. FUNCTIONS OF THE BILE.—{[(1) Bile is concerned in the digestion of
certain food-stuffs ; (2) part is absorbed ; (3) part is excreted. |

(A) Bile plays an important part in the absorption of fats :—

(1) It emulsionises neutral fats, whereby the fatty granules pass more readily
through or between the cylindrical epithelium of the small intestine into the lac-

teals. It does not decompose neutral fats into glycerine and a fatty acid, as the
pancreas does (§ 170, III).

When, however, fatty acids are dissolved in the bile, the bile-salts are decomposed, the bile-
acids being set free, while the soda of the decomposed bile-salts readily forms a soluble soa
with the fatty acids. These soaps are soluble in the bile, and increase considerably the emulsi-
fying power of this fluid. Bile can dissolve fatty acids to form an acid fluid, which has high
emulsionising properties (Steiner), Emulsification is influenced by a 1 per cent. solution of

NaCl, or Na,SO,.

(2) As fluid fat flows more easily through capillary tubes moistened with bile, it
is concluded that, when the pores of the wall of the small intestine are moistened
with bile, the fatty particles pass more easily through them.

(3) Filtration of fat takes place through a membrane moistened with bile or bile-
salts under less pressure than when it is moistened with water or salt solutions (v.
Wistinghausen).

(4) As bile, like a solution of soap, has a certain relation to watery solutions, as
well as to fats, it permits diffusion to take place between these two fluids, as the
membrane is moistened by both fluids.

It is clear, therefore, that the bile is of great importance in the absorption of fats. This is
strikingly illustrated by experiments on animals, in which the bile is entirely discharged exter-
nally through a fistula. Dogs under these conditions, absorbed at most 40 per cent. of the fat
taken with the food [60 per cent, being given off by the feces, while a normal dog absorbs 99
per cent. of the fat]. The chyle of such animals is very poor in fat, is not white but trans-
parent ; the feces, however, contain much fat, and are oily; the animals have a ravenous
appetite ; the tissues of the body contain little fat, even when the nutrition of the animals has
not been much interfered with. Persons suffering from disturbances of the biliary secretion, or
from liver affections, ought, therefore, to abstain from fatty food. [The digestion of flesh and
gelatin is not interfered with in dogs by the removal of the bile (v, Voit).]

(B) Fresh bile contains a diastatic ferment, which transforms starch into sugar,
and also glycogen into sugar. .

(C) Bile excites contractions of the muscular coats of the intestine, and con-
tributes thereby to absorption,

(1) The bile-acids act as a stimulus to the muscles of the villi, which contract from time to

time, so that the contents of the origins of the lacteals are emptied towards the larger lym- =

FATE OF THE BILE. 275

phatics, and the villi are thus in a position to absorb more, [The villi act like numerous small
pumps, and expel their contents, which are prevented from returning by the presence of valves
in the larger lymphatics. ]

(2) The musculature of the intestine itself seems to be excited, perhaps through the agency
of the plexus myentericus. In animals with a biliary fistula, and in which the bile-duct is
obstructed, the intestinal peristalsis is greatly diminished, while the salts of the bile-acids
administered by the mouth cause diarrhea and vomiting. As contraction of the intestine aids
absorption, bile is also necessary in this way for the absorption of the dissolved food-stuffs.

(D) The presence of bile seems to be necessary to the vital activity of the intes-
tinal epithelium in its supposed function of being concerned in the absorption of
fatty particles (§ 190).

(E) Bile moistens the wall of the intestines, and gives to the feeces their normal
amount of water, so that they can be readily evacuated, Animals with biliary
fistula, or persons with obstruction of the bile-ducts, are very costive. The mucus
aids the forward movement of the ingesta through the intestinal canal, [Thus, in
a certain sense, bile is a natural purgative. |

(F) The bile diminishes putrefactive decomposition of the intestinal contents,
especially with a fatty diet, § 190, [Thus, it is an antiseptic, although this is
doubted by v. Voit. |

(G) When the strongly acid contents of the stomach pass into the duodenum,
the glycocholic acid is precipitated by the gastric acid, and carries the pepsin with
it (Burkart). Some of the albumin, which has been simply dissolved (but not
peptone or propeptone), is also precipitated, by the taurocholic acid (Maly and
Emich). The bile-salts are decomposed by the acid of the gastric juice. When the
mixture is rendered alkaline by the pancreatic juice and the alkali derived from the
decomposition of the bile-salts, the pancreatic juice acts energetically in this alka-
line medium (Moleschott).

[Taurocholic acid and its soda salts precipitate albumin, but not peptone ; glycocholic acid
does not precipitate albumin, so that in the intestine the peptone is separated from the albumin
(and syntonin), and may therefore be more readily absorbed, while the precipitate adhering to
the intestinal wall can be further digested (Maly and Emich), Taurocholic acid behaves in the
same way towards gelatin peptone. ]

Bilious Vomit.— When bile passes into the stomach, as in vomiting, the acid of the gastric
juice unites with the bases of the bile-salts ; sodium chloride and free bile-acids are formed, and
the acid-reaction is thereby somewhat diminished. The bile-acids cannot carry on gastric
digestion ; the neutralisation also causes a precipitation of the pepsin and mucin. As soon,
however, as the walls of the stomach secrete more acid, the pepsin is redissolved. The bile
which passes into the stomach deranges gastric digestion, by shrivelling the proteids, which can
only be peptonised when they are swollen up (p. 250).

182. FATE OF THE BILE.—Some of the biliary constituents are completely
evacuated with the feces, while others are reabsorbed by the intestinal walls,

(1) Mucin passes unchanged into the feces.

(2) The bile-pigments are reduced, and are partly excreted with the faces as
hydrobilirubin, and partly as the identical end-product urobilin by the urine
(§ 177, 3 9).

From meconium hydrobilirubin is absent, while crystalline bilirubin and biliverdin, and an
unknown red oxidation-product of them, are present [bile-acids, even taurocholic, and small
trace of fatty acids] (Zweifel), so that it gives Gmelin’s reaction. Hence, no reduction—but
rather oxidation—processes occur in the feetal intestine. [Composition.—Dary gives 72°7 per
cent. water, 23°6 mucus and epithelium, 1 per cent. fat and cholesterin, and 3 per cent. bile
Cents Zweifel gives 79°78 per cent. water, and solids 20°22 per cent. It does not contain
ecithin, but so much bilirubin that Hoppe-Seyler uses it as a good source whence to obtain this
pigment. It gives a spectrum of a body related to urobilin, ]

(3) Cholesterin is given off with the feces. -

(4) The bile-salts are for the most part reabsorbed by the walls of the jejunum
and ileum, to be re-employed in the animal’s economy, Tappeiner found them in
the chyle of the thoracic duct—minute quantities pass normally from the blood
into the urine. Only a very small amount of glycocholic acid appears unchanged

——_ —. eo
: ve atk
; . 4

276 THE INTESTINAL JUICE.

in the feces. The taurocholic acid, as far as it is not absorbed, is easily decom-
posed in the intestine,-by the putrefactive processes, into cholalic acid and taurin ;
the former of these is found in the feces, but the taurin at least seems not to be
constantly present. Part of the cholalic acid is absorbed, and may unite in the
liver either with glycin or taurin (Weiss).

(5) The feces contain mere traces of lecithin.

Impaired Nutrition.—The greatest part of the most important biliary constituents, the bile-
acids, re-enter the blood, and thus is explained why animals with a biliary fistula, where all the
bile is removed (without the animal being allowed to lick the bile), rapidly lose weight. This
depends partly upon the digestion of the fats being interfered with, and also upon the direct
loss of the bile-salts, If such dogs are to maintain their weight, they must eat twice as much
food. In such cases, carbohydrates most beneficially replace the fats. If the digestive
apparatus is otherwise intact, the animals, on account of their voracity, may even increase in
weight, but the flesh and not the fat is increased.

Bile partly an Excretion.—The fact that bile is secreted during the feetal
period, whilst none of the other digestive fluids is, proves that it is an excretion.

The cholalic acid which is reabsorbed by the intestinal walls passes into the body, and seems
ultimately to be burned to form CO, and H,O. The-glyein (with hippuric acid) forms urea, as
the urea is increased after the injection of glycin. The fate of taurin isunknown. When large
quantities are introduced into the human stomach, it reappears in the urine as tauro-carbamic

acid, along with a small quantity of unchanged
v taurin. When injected subcutaneously into a
oy 1 rabbit, nearly all of it reappears in the urine.
hil \ [Practical.—In practice it is important to re-
1 | E member that bile, once in the intestine, is liable
to be absorbed unless it be carried down the
‘Mucous § intestine ; hence, it is one thing to give a drug
weet. which will excite the secretion of bile, de, a
hepatic stimulant, and another to have the bile so
secreted expelled. It is wise, therefore, to give a
drug which will do both, or at least to combine a
iy NAN, hepatic stimulant with one which will stimulate
if eae i. the musculature of the intestine as well. Active

exercise, Whereby the diaphragm is vigorously
> | Sub- called into action to compress the liver, will aid in
nate the expulsion of the bile from the liver (Brunton).]

183. THE INTESTINAL JUICE.—Length of

: Intestine.—The human intestine is ten times
longer than the length of the body, as measured

Muscuter 250 the vertex to the anus. It is longer com-

cont. paratively than that of the omnivora. Its mini-

= Be IA GE mum length is 507, its maximum 1194 centimetres

Soe ee, [17 to 35 feet]; its capacity is relatively greater in
——tioen a _. Serouscoat. children (Beneke).

Fig. 198. The succus entericus is the digestive

Vertical section of ‘duodenum (cat), x30, fluid secreted by the numerous glands of the
BZ, epithelium ; cand J, circular and Jongi- intestinal mucous membrane. The largest -
tudinal muscular fibres; Z.g, Lieberkiihn’s amount is produced by Lieberkiihn’s glands,
earn es peas s glands, g, ganglion while in the duodenum there is added the

sagt f ober Om . scanty secretion of Brunner’s glands.

Brunner’s glands are small, branched, tubular glands, lying in the sub-mucosa of the duo-
‘denum. Their fine ducts run inwards, pierce the mucous membrane, and open at the bases of the
villi (fig. 198). The acini are lined by cylindrical cells, like those lining the pyloric glands. In
faet Brunner’s-glands-are structurally and anatomically identical with the pyloric gam of the
stomach. During hunger, the cells are turbid and small, while during digestion they: are large
and clear. The glands receive nerve-fibres from Meissner’s plexus (Drasch),
... L. The Secretion of Brunner’s Glands.—The granular contents of the secretory
cells of these glands, which occur singly in man, but form a continuous layer in
‘the duodenum of the sheep, besides proteids consist of mucin and a ferment-~
_substanceof unknown constitution. The watery extract of the glands causes—(I)

J 707, LEEBERKUHN’S GLANDS, ==> - omy
Solution of proteids at the temperature of the body (Krolow). (2) It also has a
diastatic action. It converts maltose into glucose (Brown and Heron). It does not
appear to act upon fats.

On account of the smallness of the objects, such experiments are only made with great

- difficulty, and, therefore, there is a considerable uncertainty with regard to the action of the

secretion.

Lieberkiihn’s glands are simple tubular glands resembling the finger of a glove [or a test-
tube], which lie closely packed, vertically near each other, in the mucous membrane (fig. 199) ;
they are most numerous in the large intestine, owing to the absence of villi in this region.
They consist of a structureless membrana propria lined by a single layer of low cylindrical
epithelium, between which numerous goblet-cells occur, the goblet-cells being fewer in the
small intestine and much more numerous in the large (fig. 199). The glands of the small
intestine yield a thin secretion, while those of the large intestine yield a large amount of sticky.

mucus from their goblet- >

cells (Klose and Heiden-
hain). [In a vertical
section of the small in-
testine they lie at the
base of the villi (fig.
198). In transverse section they
are shown in fig. 200.]

II. The Secretion of
Lieberkiihn’s Glands, from
the duodenum onwards, is
the chief source of the in-
testinal juice. )

Intestinal Fistula.—The in-
testinal juice is obtained by —
making a Thiry’s Fistula (1864).
A loop of the intestine of a dog
is pulled forward (fig. 201, 1),
and a piece about 4 inches in
length is cut out, so that the
continuity of the intestinal tube
is broken, but the mesentery and
its blood-vessels are not divided. 8
One end of’ this tube is closed, § jg
and the other end is left open
and stitched to the abdominal
wall (fig. 201, 3). The twoends #8
of the intestine, from which this /&
piece was taken, are brought to- ff
gether with. sutures, so as to
establish the continuity of the \@2-2\
intestinal canal (fig.201,2). The Wey
excised piece of intestine yieldsa CQ
secretion whichisuncontaminated pi, 199
with any other digestive secre- ... 8°",
tion. [Thiry’s method is very aemtgr ie 8
unsatisfactory, as judged from $land from
the action of the separated loop the large in-
in relation to medicaments, prob-

hi

va
e

Ze We =

ont ¥
RY

testine (dog).

i} epithelium.

gba

Blood-vessel.

Fig. 200.
Transverse section of Lieberkiihn’s
follicles.

KX?
NS

a :

Fig. 201.

Scheme of Thiry’s fistula 1, 2, 3, 4,
Vella’s Fistula. AA’ are stitched
together; Abd, Abdominal wall
(Stirling).

ably owing to its mucous membrane becoming atrophied from disuse, or injured by inflamma-

tion.] .

[Meade Smith makes a small opening in the intestine, through which he introduces two
small collapsed india-rubber balls, one above and the other below the opening, which are then
distended by inflation until they completely block a certain length of the intestine. The loop
thus blocked off, having been previously well washed out, is allowed to become filled with
succus, which is secreted on the application of various stimuli. By means of Bernard’s_

tric cannula (§ 165) inserted into the fistula in the loop, the secretion can be removed when
lesired.] “ :

- [Vella’s Sebo e the the belly of a dog, and pull out a loop (30 to 50 ctm.) [1 to 14 feet]

of small intestine, and ligature it ; divide it above and below, re-establish the continuity of the

_ rest of the intestine. Stitch both ends of the loop of intestine into the wound in the linea alba.

278 * ACTIONS OF THE INTESTINAL JUICE,

(fig. 201, 4), so that there is a loop of intestine supplied by its blood-vessels and nerves, isolated
and with an upper and lower aperture. |

The intestinal juice of such fistule flows spontaneously in very small amount,
and is increased during digestion; it is increased—especially its mucus—by
mechanical, chemical, and electrical stimuli; at the same time, the mucous
membrane becomes red, so that 100 centimetres yield 13 to 18 grammes of this
juice in an hour (Zhiry). The juice is light yellow, opalescent, thin, strongly
alkaline, specific gravity 1011, evalves CO, when an acid is added; it contains
albumin, ferments, and mucin—especially the juice of the large intestine. Its
composition is—water, 97°59; proteids, 0°80; other organic substances = 0°73; salts,
0°88 per cent. ; amongst these—sodium carbonate, 0°32 to 0°34 per cent.

[The intestinal juice obtained by Meade Smith’s method contained only 0°39 per cent. of
organic matter, and in this respect agreed closely with the juice which A. Moreau procured by
dividing the mesenteric nerves of a ligatured loop of intestine. The secretion of the large
intestine is much more viscid than that of the small intestine. ]

Actions of Succus Entericus.—It is most active in the dog, and in other animals
it is more or less inactive.

(1) It is less diastatic than the saliva and the pancreatic juice, but it does not
form maltose ; while the juice of the large intestine does not possess this property
(Eichhorst). .

(2) It converts maltose into grape-sugar. It seems, therefore, to continue the
diastatic action of saliva (§ 148) and pancreatic juice (§ 170), which usually form only
maltose. |

According to Bourquelot this action is due to the intestinal schizomycetes and not to the
intestinal juice as such, the saliva, gastric juice, or invertin. The greater part of the maltose
appears, however, to be absorbed unchanged.

(3) Fibrin is slowly: (by the trypsin and pepsin—KXvihne) peptonised (Thiry,
Leube); less easily albumin (JJaslof), fresh casein, flesh raw or cooked,
vegetable albumin ; probably gelatin also is changed by a special ferment into a
solution which does not gelatinise (Zichhorst).

(4) Fats are only partly emulsionised (Schif), and afterwards decomposed
( Vella). )

(5) According to Cl. Bernard, invertin occurs in intestinal juice (this ferment
can also be extracted from yeast). It causes cane-sugar (C,,H,.,O,,) to take up
water (+H,O), and converts it into invert-sugar, which is a mixture of left rotating
sugar (levulose, C,H,,0,) and of grape-sugar (dextrose, C,H,.0,). Heat seems to
be absorbed during the process. |

[Hoppe-Seyler has suggested that this ferment is not a natural product of the body, but is
introduced from without with the food. Matthew Hay, however, finds it to be invariably present
in the small intestine of the feetus. ] ~

[Effect of Drugs.—The subcutaneous injection of pilocarpin causes the mucous membrane of
a Vella’s fistula to be congested, when a strongly alkaline, opalescent, watery, and slightly albu-
minous secretion is obtained. This secretion produces a reducing sugar, converts cane-sugar
into SDV ECE ARGAKe emulsifies neutral fats, ultimately splitting them up, peptonises proteids, and
coagulates milk, even although the milk be alkaline. The juice attacks the sarcous substance
of muscle before the connective-tissues—the reverse of the gastric-juice. The mucous mem- |
brane in a Vella’s fistula does. not atrophy. K. B. Lehmann finds that the succus entericus
obtained from the intestine of a goat by a Vella fistula has no digestive action.] ©

The Action of Nerves on the secretion of the intestinal juice is not well determined. Section
or stimulation of the vagi has no apparent effect ; while extirpation of the large sympathetie
abdominal ganglia causes the intestinal canal to be filled with a watery fluid, and gives rise to
diarrhea. This may be explained by the pony of the vaso-motor nerves, and also by the
section of large pane vessels during the operation, whereby absorption is interfered with
and transudation is favoured. Moreau’s Experiment.—Moreau placed four ligatures on a loop
of intestine at equal distances from each other (fig. 202). The ligatures were tied so that three
loops of intestine were shut off. The nerves (N) to the middle loop were divided, and the
intestine was replaced in the abdominal cavity. After a time, a very small amount of secretion, —
or none at all, was found in two of the ligatured compartments of the gut, z.¢., in thosewith
the nerves and blood-vessels intact (1, 3), but the compartment (2) whose nerves had been

FERMENTATION IN THE INTESTINE. 279

divided contained a watery secretion. Perhaps the secretién which occurs after section of the
mesenteric nerves is a paralytic secretion. The secretion of the intestinal and gastric juices is
diminished in man in certain nervous affections (hysteria, hypo-
chondriasis, and various cerebral diseases); while in other condi-
tions these secretions are increased.

Excretion of Drugs.—lIf an isolated intestinal fistula be made,
‘and various drugs administered, the mucous membrane excretes
iodine, bromine, lithium, sulphocyanides, but no¢ potassium ferro-
cyanide, arsenious or boracic acid, or iron salts.

In sucklings, ‘not unfrequently a large amount of acid is formed,
when the fungi in the intestine split up milk-sugar or grape-sugar
into lactic acid (Zeuwbe). Starch changed into grape-sugar may
undergo the same abnormal process; hence, infants ought not to
be fed with starchy food.

Fig. 202.

; ‘
[Fate of the Ferments.—Langley is of opinion that the digestive Scheme of Moreau’s experi-

ferments are destroyed in the intestinal canal; the diastatic fer- ment (Stirling).

ment of saliva is destroyed by the free HCl of the gastric juice ; pepsin and rennet are acted

upon by the alkaline salts of the pancreatic and intestinal juices, and by trypsin ; while the

diastatic and peptic ferments of the pancreas disappear under the influence of the acid fermenta-

tion in the large intestine. ]

184, FERMENTATION IN THE INTESTINE.—Those processes, which
are to be regarded as fermentations or putrefactive processes, are quite different from
those caused by the digestive enzymes or ferments just considered. The putre-
factive changes are connected with the presence of lower organisms, so-called
fermentation- or putrefaction-producers: and they may develop in suitable media
outside the body. The lowly organisms which cause the intestinal fermentation
are swallowed with the food and drink, and also with the saliva. When they
are introduced, fermentation and putrefaction begin, and gases are evolved.

Intestinal Gases.— During the whole of the foetal period, until birth, fermenta-
tion cannot occur ; hence gases are never present in the intestine of the newly-born.
The first air-bubbles pass into the intestine with the saliva which is swallowed, even
before food has been taken. The germs of organisms are thus introduced into the
intestine, and give rise to the formation of gases. The evolution of intestinal
gases goes hand-in-hand with the fermentations. Air is also swallowed, and an
exchange of gases take place in the intestine, so that the composition of the in-
testinal gases depends upon various conditions. Kolbe and Ruge collected the gases
from the anus of a man, and found in 100 vols, :—

Food. COR H. CH,. N. | HS.
Milk - ;: 16°8 43°3 0°9 38°3 °
Flesh, . . 12°4 21 275 57°8 pret ae
Peas, ee e.g 21°9 4°0 55°9 18°9 ;

1. Air-bubbles are swallowed with the food. The O is rapidly absorbed in the
intestinal tract, so that in the lower part of the large intestine, even traces
of O are absent. In exchange, the blood-vessels in the intestinal wall give off CO,
into the intestine, so that part of the CO, in the intestine is derived by diffusion
from the blood.

2. H, CO,,NH,, and CH, are also formed from the intestinal contents by
fermentation, which takes place even in the small intestine.

Fungi.—The chief agents in the production of fermentations, putrefaction, and other similar
decompositions are undoubtedly the group of fungi called schizomycetes. They are small uni-
cellular organisms of various forms—globular, micrococcus ; short rods, bacterium ; long rods,

acillus ; or spiral threads, vibrio, spirillum, spirocheta (fig. 23). The modé of reproduction
is by division, and they may either remain single or unite to form colonies. Each organism is
usually capable of some degree of motion. They produce profound chemical changes in the
fluids or media in which they grow and multiply, and these changes depend upon the vital
activity of their protoplasm. These minute microscopic organisms take certain constituents
from the “nutrient fluids” in which they live, and use them partly for building up their own

286° —. FERMENTATION OF CARBOHYDRATES, |

tissues and partly for their own metabolism, In these processes, some of the substances so
absorbed and assimilated undergo chemical changes, some ferments seem thereby to be produced,
which in their turn may act upon material present in the nutritive fluid, —

These fungi consist of a capsule enclosing protoplasmic contents. Many of them are provided
with excessively delicate cilia, by means of which they move about. The new organisms,
produced by the division of pre-existing ones, sometimes form large colonies visible to the naked
eye, the individual fungi being united by a jelly-like mass, the whole constituting zoogloea.
In some fungi, reproduction takes place by spores ; more especially when the nutrient fluids are
poor in nutritive materials. The bacteria form longer rods or threads, which are jointed, and
in each joint or segment small (1-2 uw) highly refractive globules or spores are developed (fig.
203, 7). In some cases, as in the butyric acid fermentation, the rods become fusiform before
spores are formed. When the envelope of the mother-cell is ruptured or destroyed, the spores
are liberated, and if they fall upon or into a suitable medium, they germinate and reproduce
organisms similar to those from which they sprang. The process of spore-production is
illustrated in fig. 203, 7, 8, 9, and in 1, 2, 8, 4is shown the process of germination in the
butyric acid fungus. The spores are very tenacious of life; they may be dried, when they
resist death for a very long time ; some of them are killed by being boiled. Some fungi exhibit
their vital activities only in the presence of O (srobes), while others require the exclusion of O
(anserobes, Pastewr). According to the products of their action, they are classified as follows :—
Those that produce fermentations (zymogenic schizomycetes) ; those that produce pigments
(chromogenic) ; those that produce disagreeable odowrs, as during putrefaction (bromogenic) ;
and thosethat, when introduced
into the living tissues of other
organisms, produce pathological
conditions, and even death
(pathogenic). All these dif-
ferent kinds occur in the human
body. ;
When we consider that num-

erous fungi are introduced into
the intestinal canal with the
food and drink—that the tem-
perature and other conditions
within this tube are specially
favourable for their develop-
ment; that there also they meet
_with snfficient pabulum for
their development and repro-

| | a A. duction—we cannot wonder

A 1 2 4 that a rich crop of these organ-’

oO O @ isms is met with in the intes-

Fig. 203. tine, and that they produce

A, Bacterium aceti in the form of—cocci (1); diplococci (2); there numerous fermentations.

short rods (3) ; and jointed threads (4, 5). Bacillus butyricus I. Fermentation of Car-

—(1) wires pn : 2, : 4) Sergey ia condition of the bohydrates. —(1) Bacil-
spores ; (5, 6) short and long rods; (7, 8, 9) formation of ‘di ‘ai ‘

spores within a cellular fungus. ; lus wey idi lactici consists of

biscuit-shaped cells, 1°5-3

in length, arranged in groups or isolated. They split up grape-sugar into lactic

acid ;

1 grape-sugar = C,H,,0, = 2(C,H,O3) = 2 lactic acid. :

Milk-sugar (C,,H,.0,,) can be split up by the same ferment causing it to take up
H,O, and forming 2 molecules of grape-sugar, 2(C,;H,,0,), which are again split
into 4 molecules of lactic acid 4(C,H,O,).

__ This fungus and its spores occur everywhere in the atmosphere, and are the cause of the spon-
taneous acidification and subsequent coagulation of milk (§ 230). 1s:

(2) Bacillus butyricus, which in the presence of starch is often coloured blue
by sie changes lactic acid into butyric acid, together with CO, and H (Praz-
mowskt). if

C,H,O,=1 butyric acid.
2(CO,) = 2 carbon dioxide.

2(C,H,O,) lactic acid = 2(C
_ - 4H =4 hydrogen.

FERMENTATION OF PROTEIDS. 281

This fungus (fig. 203, B) is a true anzrobe, and grows only in the absence of O. The lactic acid
fungus uses O very largely, and is, therefore, its natural precursor. The butyric acid fermenta-
tion is the last charige undergone by many carbohydrates, especially by starch and inulin. It
takes place constantly in the feces.

(3) Certain micrococeci cause alcohol to be formed from carbohydrates. The
presence of yeast may cause the formation of alcohol in the intestine, and in both
cases also from milk-sugar, which first becomes changed into dextrose.

(4) Bacterium aceti (fig. 203, A) converts alcohol into acetic acid outside the body. Alcohol
(C,.H,O)+O0=C,H,0 (Aldehyd)+H,O. Acetic acid (C,H,0,) is formed from aldehyd by oxida-
tion. According to Nigeli, the same fungus causes the formationjof a small amount of CO, and
H.O. As the acetic fermentation is arrested at 35° C., this fermentation cannot occur in the
intestine, and the acetic acid, which is constantly found in the feces, must be derived from
another source. During putrefaction of the proteids, with exclusion of air, acetic acid is
produced (Venckt). ;

(5) Starch and cellulose are partly dissolved by the schizomycetes (Bac. butyricus
and Vibrio rugula) of the intestine. If cellulose be mixed with cloacal-mucus,
or with the contents of the intestine, it passes into a saccharine carbohydrate which
decomposes into equal volumes of CO, and CH, (Hoppe-Seyler).

(6) Fungi, whose nature is unknown, can partly transform starch (1 and
cellulose) into sugar.

_ (7) Others produce invertin. Invertin changes cane-sugar into invert-sugar
(§ 183, IL, 5). Cane-sugar, C,,Ho.C,, + H,O=C,H,,0, (Dextrose) +C,H,,0,
(Lzevulose). |

II. Fermentation of Fats (§ 251).—During putrefaction, organisms of an
unknown nature cause neutral fats to take up water and split into glycerine and
their corresponding

fatty acid (§ 170). , \
Glycerine is cap-

able of undergoing Q 0 ?

several fermenta- or "ii

tions, according to 7 > ee ae | 5 6
the fungus which

acts upon it (§ 251).
With a neutral re-
action, in addition
to succinic acid, a | Fig. 204.
number Of fatty prcitiue subtilie, 1, spore ; 2, 8, 4, its germination ; 5, 6, short rods ;
acids, H and CO., 7, jointed thread, with the formation of spores in each segment ; 8,

are formed. short rods, some of them containing spores ; 9, spores in single short
Fitz found that the 1048; 10 fungus with a cilium.

hay-bacillus (Bacillus subtilis, fig. 204) formed alcohol with caproic, butyric, and acetic acids ;
in other cases, especially butylic alcohol, van de Velde found butyric, lactic, and traces of suc-
cinic acid with CO,, H,O, N.

The fatty acids, especially as chalk soaps, form an excellent material for
fermentation. Calcium. formiate mixed with cloacal-mucus ferments and, yields
calcium carbonate, CO, and H; calcium acetate, under the same conditions,
produces calcium carbonate, CO, and CH, Amongst the oxy-acids, we are
acquainted with the fermentations of lactic, glycerinic, malic, tartaric, and citric
acids. |

According to Fitz, lactic acid (in combination with chalk) produces propionic and acetic
acids, CO,, H,O. Other ferments cause the formation of valerianic acid. Glycerinic acid, in
addition to alcohol and succinic acid, yields chiefly acetic acid ; malic acid forms succinic and
acetic acid. The other acids above enumerated yield somewhat similar products.

III. Fermentation of Proteids (§ 249).—The undigested proteids and their
derivatives appear to be acted upon by fungi. Many schizomycetes (hay bacillus
and Bae. subtilis), however, can produce a peptonising ferment. We have already

282 REACTIONS FOR INDOL.

seen that pancreatic digestion acts upon the proteids, forming, among other
products, amido-acids, leucin, tyrosin, and other bodies (§ 170, II.). Under normal
conditions, this is the greatest decomposition produced by the pancreatic juice.
The putrefactive fermentation of the large intestine causes further and more
profound’ decompositions. Leucin (C,H,,NO,) takes up two molecules of water
and yields valerianic acid (C,H,,O,), ammonia, CO, and 2(H,); glycin behaves
in a similar manner. Tyrosin (C,H,,NO,) is decomposed into indol (C,H,N),
which is constantly present in the intestine along with CO,,H,O,H. If O be
present, other decompositions take place. These putrefactive products are absent
from the intestinal canal of the foetus and the newly-born. During the putre-
factive decomposition of proteids, CO,, H,S, H, and CH,, are formed; the same
result is obtained by boiling them with alkalies. Gelatin, under the same con-
ditions, yields much leucin and ammonia, CO,, acetic, butyric, and valerianic
acids, and glycin, Mucin and nuclein undergo no change. Artificial pancreatic
digestion-experiments rapidly tend to undergo putrefaction.

The substance which causes the peculiar feecal odour is produced by putrefaction, but its
nature is not known. It clings so firmly to indol and skatol that these substances were
— regarded as the odorous bodies, but when they are prepared pure they are odourless
bayer).

Amongst the solid substances in the large intestine formed only by putrefaction
is indol (C,H._N), a substance which is also formed when proteids are heated with
alkalies, or by superheating them with water to 200°C. It is the stage preceding
the indican in the urine. If the products of the digestion of the proteids—the
peptones—are rapidly absorbed, there is only a slight formation of indol; but
when absorption is slight, and putrefaction of the products of pancreatic digestion
occurs, much indol is formed, and indican appears in the urine.

Jaffé found much indican in the urine in strangulated hernia, and when the small intestine
was obstructed. |

Reactions for Indol.—Acidulate strongly with HCl, and shake vigorously after adding a few
drops of turpentine. If there be an intense red colour, the pigment is removed by ether.
The substance which is formed after the digestion of fibrin by trypsin, and which gives a violet
colour with bromine water (§ 170, 2), can be removed by chloroform. In addition to the last
pigment, there is asecond one, which passes over during distillation, and which can be extracted
from the distillate by ether. Both substances seem to belong to the indigo group (Krukenberg).

A. Bayer prepared indigo-blue artificially from ortho-phenyl-propionic acid, by boiling it
with dilute caustic soda, after the addition of a little grape-sugar. He obtained indol and
skatol from indigo-blue. Hoppe-Seyler found that on feeding rabbits with ortho-nitrophenyl-
propionic acid, much indican was present in the urine. |

Phenol (C,H,O) is formed during putrefaction in the intestine, and it is also
formed when fibrin and pancreatic juice putrefy outside the body, while Brieger
found it constantly in the feeces. It seems to be increased by the same circum-
stances that increase indol, as an excess of indican in the urine is accompanied by
an increase of phenylsulphonic acid in that fluid (§ 262).

From putrefying flesh and fibrin, amido-phenylpropionic acid is obtained, as a decomposition-
product of tryrosin. A part of this is transformed by putrefactive ferments into hydrocinnamic¢
acid (phenylpropionic acid). The latter is completely oxidised in the body into benzoic acid,
and appears as hippuric acid in the urine. Thus is explained the formation of hippuric acid
from a purely albuminous diet.

Skatol (C,H,N = methylindol) is a constant human fecal substance, and has
been prepared artificially by Nencki and Secretan from egg-albumin, by allowing
it to putrefy for a long time under water. It also appears in the urine as a
sulphur compound. The excretin of human feces, described by Marcet, is
related to cholesterin, but its history and constitution are unknown, |
- According to Salkowski, skatol and indol are both formed from a common substance which
exists preformed in albumin, and which, when it is decomposed, at one time yields more indol,

at another skatol, according as the hypothetical ‘‘ indol-fwngus,” or ‘* skatol-fungus,” is the
more abundant. here

PROCESSES IN THE LARGE INTESTINE. 283

It is of the utmost importance, in connection with the processes of putrefaction,
to determine whether they take place when oxygen is excluded, or not. When O
is absent, reductions take place ; oxy-acids are reduced to fatty acids, and H,CH,
and H,S are formed; while the H may produce further reductions. If O be
present, the nascent H separates the molecule of free ordinary oxygen (=O,) into
two atoms of active oxygen (=O). Water is formed on the one hand, while the
second atom of O is a powerful oxidising agent (Hoppe-Seyler).

It is remarkable that the putrefactive processes, after the development of phenol, indol,
skatol, cresol, phenylpropionic and phenylacetic acids are subsequently limited, and after a
certain concentration is reached, they cease altogether. The putrefactive process produces
antiseptic substances which kill the micro-organisms, so we may assume that these substances
limit to a certain extent the putrefactive processes in the intestine.

The reaction of the intestine immediately below the stomach is acid, but the
pancreatic and intestinal juices cause a neutral and afterwards an alkaline reaction,
which obtains along the whole small intestine. In the large intestine, the reaction
is generally acid, on account of the acid fermentation and the decomposition of

the ingesta and the feeces.
185. PROCESSES IN THE LARGE INTESTINE.—Within the large in-

testine, the fermentative and putrefactive processes are certainly more prominent
than the digestive processes proper, aS only a very small amount of the intestinal
juice is found in it. The absorptive function of the large intestine is greater than
its secretory function, for at the beginning of the colon its contents are thin and
watery, but in the further course of the intestine they become more solid. Water and
the products of digestion in the solution are not the only substances absorbed, but
under certain circumstances, unchanged fluid egg-albumin, milk and its proteids,
flesh-juice, solution of gelatin, myosin with common salt, may also be absorbed.
Experiments with acid-albumin, syntonin, or blood-serum gave no result. Toxic
substances are certainly absorbed more rapidly than from the stomach. [In the
dog the secretion of the large intestine has no digestive properties, but fats are
absorbed init. Klug and Koreck regard its Lieberkiihnian glands not as secreting-
but as absorbing-structures.]| The feecal matters are formed or rather shaped in
the lower part of the gut. The cecum of many animals, e:g., rabbit, is of consider-
able size, and in it fermentation seems to occur with considerable energy, giving
rise to an acid-reaction. In man, the chief function of the cecum is absorption,
as is shown by the great number of lymphatics in its walls. From the lower part
of the small intestine and the cecum onwards, the ingesta assume the feecal odour.

The amount of feces is about [5 oz. or] 170 grms. (60 to 250 grms.) in twenty-
four hours; but if much indigestible food be taken, it may be as much as
500 grms. The amount is less, and the absolute amount of solids is less, after
a diet of flesh and albumin, than after a vegetable diet. The feces are rendered
lighter by the evolution of gases, and hence they float in water.

The consistence depends on the amount of water present—usually about 75 per
cent. The amount of water depends partly on the food—pure flesh diet causes
relatively dry feces, while substances rich in sugar yield feces with a relatively
large amount of water. The quantity of water taken has no effect upon the amount
of water in the feeces. But the energy of the peristalsis has. The more energetic the
peristalsis is, the more watery the feces are, because sufficient time is not allowed
for absorption of the fluid from the ingesta. Paralysis of the blood- and lymph-
vessels, or section of the nerves, leads to a watery condition of the feces (§ 183).

The reaction is often acid, in consequence of lactic acid being developed from the
carbohydrates of the food. Numerous other acids produced by putrefaction are
also present (§ 184), If much ammonia be formed in the lower part of the intestine,
a neutral or even alkaline reaction may obtain. A copious secretion of mucus
favours the occurrence of a neutral reaction.

284 ~ > COMPOSITION. OF THE FACES. .- »

The odour, which is stronger after a, flesh diet than after a. vegetable diet, is
caused by some facal products of putrefaction, which have not yet been isolated ;
also by volatile fatty acids and by sulphuretted hydrogen, when it is present.

The colour of the feces depends upon the amount of altered bile-pigments
mixed with them, whereby a bright yellow to a dark brown colour is obtained.

The colonr of the food is also of importance. If much. blood be present in the food, the
feces are almost brownish-black from hematin ; green vegetables = brownish-green from
chlorophyll ; bones (dog) = white from the amount of lime ; preparations of iron = black from
the formation of sulphide of iron.

The feces contain—

(1) The unchanged residue of ‘animal or vegetable tissues used as food ; hairs,
horny and elastic tissues; most of the cellulose, woody fibres, spiral vessels of
vegetable cells, gums.

(2) Portions of digestible substances, especially when these have been taken in
too large amount, or when they have not been sufficiently broken up by chewing.
Portions of muscular fibres, ham, tendon, cartilage, particles of fat, coagulated
albumin—vegetable cells from potatoes, and other vegetables, raw starch, &c.

All food yields a certain amount of residue—white bread, 3°7 per cent.; rice, 4°1 per cent. ;
flesh, 4°7 per cent.; potatoes, 9°4 per cent.; cabbage, 14°9 per cent. ; black bread, 15 per cent. ;
yellow turnip, 20° 7 per cent. (Rubner).

(3) The decomposition-products of the bile-pigments, which do not now give
Gmelin’s reaction ; as well as the altered bile-acids (§ 177, 2). This reaction,
however, may be obtained in pathological stools, especially in those of a green
colour; unaltered bilirubin, biliverdin, glycocholic and taurocholic acids occur
in meconium (§ 182). |

[MacMunn found no unchanged bile-pigments in the feces. A substance called stercobilin is
obtained from the feces, and it closely resembles what has been called ‘‘ febrile” urobilin, but
it is certainly different from normal urobilin. ]

(4) Unchanged mucin and nuclein—the latter occasionally after a diet of bread,
together with partially disintegrated cylindrical epithelium from the intestinal
canal, and occasionally drops of oil. Cholesterin is very rare. [Ten grains of a
substance, stercorin, said to be a modification of cholesterin, occur in the feces,
(Flint).| The less the mucus is mixed with the feeces, the lower the part of the
intestine from which it was derived (Wothnagel).

(5) After a milk diet, and also after a fatty diet, crystalline needles of lime com-
bined with fatty acids and chalk soaps constantly occur, even in sucklings ( Weg-
scheider). Even unchanged masses of casein and fat occur during the milk cure.
Compounds of ammonia, with the acids mentioned as the result of putrefaction
(§ 184, III.), belong to the fecal matters (Brieger).

(6) ‘Amongst i inorganic residues, soluble salts rarely occur in the feces because
they diffuse readily, e.g., common salt, and the other alkaline chlorides, the compounds
of phosphoric acid, and some of those of sulphuric acid. The insoluble compounds
of which ammoniaco-magnesic or triple phosphate, neutral calcic phosphate, yellow
coloured lime salts, calcium carbonate, and magnesium phosphate are the chief,
form 70 per cent. of the ash. Some of these insoluble substances are derived from
the food, as lime from bones, and in part they are excreted after the food has been
digested, as ashes are eliminated from food which has been burned.

Concretions.—The excretion of inorganic substances is sometimes so great, that they form
incrustations around other fecal matters. Usually ammoniaco-magnesic phosphate occurs in
large crystals by itself, or it may be mixed with magnesium phosphate. .

(7) Micro-organisms.—A considerable portion of normal fzcal matter consists

of micrococci and microbacteria, yeast is seldom absent (Prerichs, Nothnagel).

. To isolate the individual fungi, Escherich has made pure cultivations from the intestinal’
contents of sucklings, and Bienstock from adults. In the intestine of sucklings which
have been nourished entirely on their mother’s milk, the Bacterium lactis aay (fig. 205, 2)

PATHOLOGICAL VARIATIONS, ~ 285

‘causes the lactic acid fermentation with the evolution of CO, and H, in the upper part of
the canal where some milk-sugar is still unabsorbed. In the evacuations is the characteristic
slender Bacterium coli commune (fig. 205, 1). In addition, occasionally there are other bacilli,
‘cocci, spores of yeast, and a mould.

8a 994 &
en SN) MAN

oe ee

son) WW A SSS Ie

a b c d c me J

. | Fig. 205.

1,, Bacterium coli commune; 2, bacterium lactis aérogenes; 3 and 4, the large bacilli of

.ceq Bienstock, with partial endogenous spore-formation ; 5, the various stages in the develop-
ment of the bacillus which causes the fermentation of albumin.

In the feces of an adult, Bienstock detected two large forms of bacilli (fig. 205, 3, 4), closely
resembling Bacillus subtilis in form and size, but distinguished from it only by the form of
its pure cultivation, by the mode of growth of its spores, and by the absence of movements.
These two forms can be distinguished microscopically by the mode of their cultivation, which
is either in the form of a grape or a flat membrane. These two do not excite a fermentative
action. A third micrococcus-like, small, very slowly-developing bacillus occurs in three-fourths
of all stools. A fourth kind (absent in sucklings) is the specific bacillus (§184, III.), causing
the decomposition of albumin, resulting in the products of putrefaction and a fecal odour.
This is the only bacillus that excites these processes in the intestine ; but it does not decompose
casein and alkali-albumin. In fig. 205, 5, a-g, the stages in the development of this bacillus
are represented, but the stages from c and g are absent in the feces, and are found only in
artificial cultivations. .

If the feces are simply investigated microscopically and without special precautions, there
are other fungi, some of which may be introduced through the anus. In stools that contain
much starch, the bacillus butyricus, which is tinged blue with iodine, occurs (§ 184), and other
small globular or rod-like fungi, which give a similar reaction (Nothnagel, Uffelmann).

The changes of the intestinal contents have been studied on persons with an accidental
intestinal fistula, or an artificial anus.

[The following scheme from Krukenberg shows graphically the reaction of the contents of the
various parts of the alimentary canal, and also the distribution of the ferments. ]

“i er \ kerala. ue
of ee on a . eee
O : 4 ‘ ‘ I ¥ Pie a ae ou
ae LL a” be eae i ; gee Coc een — a
be oni PE ghee kot ae ies sane iscsee
ee cin STOMACH | SMALL_ INTESTINE LARGE INTESTINE
ALKALINE ACID ALKALINE ALKALINE |
———————————————————
Aylolds Brtient 186. PATHOLOGICAL VARIATIONS.—A. The
m++--—----- Milk coagulating ferment taking of food may be interfered with by spasm of the
----------- Pepsin muscles of mastication (usually accompanied by general
Saeeneeses Trypsin : spasms), stricture of the cesophagus, by cicatrices after
Paces aii carcass Bacteria swallowing caustic fluids (¢.g., caustic potash, mineral

ss acids), or by the presence of a tumour, such as cancer.
Inflammation of all kinds in the mouth or pharynx interferes with the taking of food. Inability
to swallow occurs as part of the general phenomena in disease of the medulla oblongata, in con-
“sequence of paralysis of the motor centre (superior olives),for the facial, vagus, and hypoglossal
nerves, and also for the afferent or sensory fibres of the glosso-pharyngeal, vagus, and trigeminus.
‘Stimulation or abnormal excitation of these parts causes spasmodic swallowing, and the disagree-
‘able feeling of a constriction in the neck (globus hystericus). geod
- B. The secretion of saliva is diminished during inflammation of the salivary glands; occlu-
‘sion of their ducts by concretions (salivary calculi); also by the use of atropin, daturin, and
‘during fever, whereby the secretory (not the vaso-motor) fibres of the chorda appear to be
“paralysed (§ 145). ‘When the fever is very high, no saliva is secreted. The saliva secreted
during moderate fever is turbid and thick, and usually acid. “As the fever increases, the dia-
static action of the saliva diminishes. . The secretion is increased by- stimulation of the -buccal

286 PATHOLOGICAL VARIATIONS OF DIGESTION,

nerves (inflammation, ulceration, trigeminal neuralgia), so that the saliva is secreted in great
quantity. Mercury and jaborandi cause secretion of saliva, the former causing stomatitis, which
excites the secretion of saliva reflexly. _ Evem diseases of the stomach accompanied by vomiting
cause secretion of saliva, A very thick tenacious sympathetic saliva occurs when there is vio-
lent stimulation of the vascular system during sexual excitement, and also during certain
psychical conditions, The reaction of the saliva is acid in catarrh of the mouth, in fever in
consequenée of decomposition of the buccal epithelium, and in diabetes mellitus in consequence
of acid fermentation of the saliva which contains sugar, Hence, diabetic persons often suffer
from carious teeth, Unless the mouth of an infant be kept scrupulously clean, the saliva is apt
to become acid.

C. Disturbances in the activity of the musculature of the stomach may be due to paralysis of
the muscular layers, whereby the stomach becomes distended, and the ingesta remain a long
time in it. A special form of paralysis of the stomach is due to non-closure of the pylorus
(Ebstein). This may be due to disturbances of innervation of a central or peripheral nature,
or there may be actual paralysis of the pyloric sphincter, or anethesia of the pyloric mucous
membrane, which acts reflexly upon the sphincter muscle; and lastly, it may be due to the
reflex impulse not being transferred to the efferent fibre within the nerve-centre. Abnormal
activity of the gastric musculature hastens the passage of the ingesta into the intestine ; vomit-
ing often occurs.

D. Gastric digestion is delayed by violent bodily or mental exercise, and sometimes it is arrested
altogether. Sudden mental excitement may have the same effect. These efforts are very
probably caused through the vaso-motor nerves of the stomach. Feeble and imperfect digestion
may be of a purely nervous nature (Dyspepsia nervosa—Leube ; Neurasthenia gastrica—
Burkart). An excessive formation of acid may be due to nervous disturbance, and is called
** nervous gastroxynsis,” by Rossbach.

[Action of Alcohol, Tea, &c., in Digestion.—According to J. W. Fraser, all infused
beverages, tea, coffee, cocoa, retard the peptic digestion of proteids, with few exceptions. The
retarding action is less with coffee than with tea. The tannic acid and volatile oil seem to
be the retarding ingredients in teas. Distilled Spirits—brandy, whisky, gin—have but a
trifling retarding effect on the digestive processes ; and when one considers their action on
the secretory glands, it follows that in moderate dietetic doses they promote digestion. Wines
are highly inimical to salivary digestion, but this is due to their acidity ; and this effect can
be removed by the addition of an alkali. Wines retard peptic digestion, the sparkling less
than the still wines. Tea has an intensely inhibitory action on salivary digestion, in fact a
small.quantity paralyses the action of saliva, while coffee has only a slight effect, This
action of tea is due to the tannin. Tea, coffee, and cocoa all retard peptic digestion, when they
form 20 per cent. of the digestive mixture (W, Roberts). ]

Inflammatory or catarrhal affections of the stomach, as well as ulceration and new forma-
tions, interfere with digestion, and the same result is caused by eating too much food which is
difficult of digestion, or taking too much highly spiced sauce or alcohol. In the case of a dog
suffering from chronic gastric catarrh, Griitzner observed that the secretion took place con-
tinuously, and that the gastric-juice contained little pepsin, was turbid, sticky, feebly acid, and
even alkaline. The introduction of food did not alter the secretion, so that in this condition
the stomach really obtains no rest. The chief cells of the gastric-glands were turbid. Hence,
in gastric catarrh, we ought to eat frequently, but take little at a time, while at the same time
dilute hydrochloric acid ought to be administered (0°4 per cent,), Small doses of common salt
seem to aid digestion. we

[Absence of HC].—HC] is almost always absent in carcinoma of the stomach (van de Velde),
amyloid degeneration of the gastric mucous membrane (Hdinger), and sometimes in fever. In
all these cases the acid-reaction is due to lactic or butyric acid, The absence of HCl in
cancer of the stomach is an important diagnostic and prognostic symptom, It is not absent in
simple dilatation of the stomach. ‘Test the contents of the stomach for free HCl with tropolin
(red colour), methylviolet (blue), and with ferric chloride and carbolic acid (Uffelmann). dy
per cent. of free HCl causes the amethyst-blue of the last to become steel-grey, while somewhat
more discharges the colour altogether. [In testing for the presence of free lactic acid in the
gastric contents use Uffelmann’s reaction (§ 163). The lactic acid is easily extracted by ether
from the gastric contents, and the reaction can then be performed with the residue obtained
after evaporating the ether. A solution of 1 drop of the liquor perchloride in 50 c.c, of water is
made yellow by lactic acid, ] :

Feeble digestion may be caused either by imperfect formation of acid or pepsin, so that both
substances may be administered in such a condition. [It may also be due to deficient muscular
power in the wall of the stomach.] In other cases, lactic, butyric, and acetic acids are formed,

owing to the presence of lowly organisms. In such cases, small doses of salicylic acid, together _

with some hydrochloric acid, are useful, Pepsin need not be given often, as it is rarely absent,
even from the diseased gastric mucous membrane, Albumin has been found in the gastric-

juice in cases of gastric catarrh and cholera. . int
E. Digestion during Fever and Anemia.—Beaumont found that in the case of Alexis St

i
b

CONSTIPATION AND DIARRH@A. 287

Martin, when fever occurred, a small amount of. gastric-juice was secreted; the mucous
membrane was dry, red, and irritable, Dogs suffering from septicemic fever, or rendered
anemic by great loss of blood, secrete gastric-juice of feeble digestive power and containing
little acid (Manassein), [In acute diseases accompanied by fever, the inner cells of the fundus-
glands of the human stomach may disappear (C. Kupffer).] Hoppe-Seyler investigated the
tric-juice of a typhus patient in which van de Velde found no free acid. Usually no free
ydrochloric acid is found in cancer of the stomach. The gastric-juice of the typhus patient
did not digest artificially, even after the addition of hydrochloric acid. The diminution of
acid, under these circumstances, favours the occurrence of a neutral reaction, so that, on the
one hand, digestion cannot proceed, and on the other, fermentative processes (lactic and butyric
acid fermentations with the evolution of gases) occur. These results are associated with the
presence of micro-organisms and Sarcina ventriculi (Goodsir). Uffelmann found that the secretion
of a peptone-forming gastric-juice ceased in fever, when the fever is severe at the outset, when
a feeble condition occurs, or when the temperature is very high. The amount of juice secreted
is certainly diminished during fever. The excitability of the mucous membrane is increased,
so that vomiting readily occurs, The increased excitability of the vaso-motor nerves during fever
is disadvantageous for the secretion of the digestive fluids (Heidenhain). Beaumont observed
that fluids are rapidly absorbed from the stomach during fever, but the absorption of peptones
is diminished on account of the accompanying catarrhal condition of the stomach, and the
altered functional activity of the muscularis mucosee (Leube).

Many salts, when given in Jarge amount, disturb gastric digestion, e.g., the sulphates. While
the alkaloids, morphia, strychnia, digitalin, narcotin, veratria have a similar action, quinine
favours it (Wolberg). In some nervous individuals ‘‘ peristaltic unrest of the stomach,” con-
joined with a dyspeptic condition, occurs (Kussmaul), [Prosser James directs attention to the
value of peptic and pancreatic salts, which are preparations of common salt mixed with pepsin
and the ferments of the pancreas respectively. ]

[Artificial Digestion is affected by various salts according to their nature and dilution. The
digestion of fibrin by pepsin goes on best without the addition of salts, being diminished by
magnesic sulphate, sodic carbonate, and sulphate, The digestion of fibrin by pancreatic extract
is accelerated by sodic carbonate (Heidenhain), and retarded by MgSO, and Na,SO, The
diastatic action of the saliva and pancreas on starch is greatly accelerated by NaCl (2 per cent.),
while Na,CO,, Na,SO,, and MgSO, hinder it (Pfeiffer).| According to Schiitz, artificial gastric
digestion is retarded by a 2 per cent. solution of alcohol, and also by a solution of salicylic acid
(06 to ‘1 per cent.). Buchner, however, finds that 10 per cent. of alcohol does not affect artificial
gastric digestion, while above 20 per cent. arrests it. Beer hinders digestion.

F. In acute diseases, the secretion of bile is affected ; it becomes less in amount and more
watery, z.¢,, it contains fewer specific constituents. If the liver undergoes great structural
change, the secretion may be arrested. :

G. Gall-Stones.— When decomposition of the bile occurs, gall-stones are formed in the gall-
bladder or in the bile-ducts. Some are white, and consist almost entirely of stratified layers of
crystals of cholesterin. The drown forms consist of bilirubin-lime, and calcium carbonate, often
mixed with iron, copper, and manganese. The gall-stones in the gall-bladder become facetted
by rubbing against each other. The nucleus of the white stones often consist of chalk and bile-
colouring matters, together with nitrogenous residues, derived from shed epithelium, mucin,
bile-salts, and fats. Gall-stones may occlude the bile-duct and cause cholemia. When a small
stone becomes impacted in a duct, it gives rise to excessive pain, constituting hepatic colic, and
may even cause rupture of the bile-duct with its sharp edges.

H. Nothing certain has been determined regarding the pancreatic secretion in disease, but
in fever it appears to be diminished in amount and digestive activity. The suppression of the
pancreatic secretion, [as by a cancerous tumour of the head of the pancreas], is often accompanied
by the appearance of fat, in the form of globules or groups of crystals in the feeces.

I, Constipation is a most important derangement of the digestive tract. It may be caused
by—(1) Conditions which obstruct the normal channel, e.g., constriction of the gut from stricture
—in the large gut after dysentery, tumours, rotation on its axis of a loop of intestine (volvulus),
or invagination, occlusion of a coil of gut in a hernial sac, or by the pressure of tumours or
exudations from without, or congenital absence of the anus. (2) Too great dryness of the con-
tents, caused by too little water in the articles of diet, diminution of the amount of the digestive
secretions, ¢.g., of bile in icterus; or in consequence of much fluid being given off by other
organs, as after copious secretion of saliva, milk, or in fever. (3) Variations in the functional
activity of the muscles and motor-nervous apparatus of the gut may cause constipation, owing to
imperfect peristalsis. This condition occurs in inflammations, degenerations, chronic catarrh,
and diaphragmatic inflammation. Affections of the spinal cord, and sometimes also of the brain,
are usually accompanied by slow evacuation of the intestine. Whether diminished mental
activity and hypochondriasis are the cause of, or are caused by, constipation is not proved.
Spasmodic contraction of a part of the intestine may cause temporary retention of the intestinal
contents, and, at the same time, give rise to great pain or colic; the same is true of spasm of
the anal sphincter, which may be excited reflexly from the lower part of the gut. The fecal

‘288 COMPARATIVE PHYSIOLOGY OF DIGESTION,

‘masses in constipation are usually hard and dry, owing to the water being absorbed ; hence
they form large masses or scybala within the large intestine, and these again give rise to new
resistance. Amongst the reagents which prevent evacuation of the bowels, some paralyse the
‘motor apparatus temporarily, ¢.g., opium, morphia; some diminish the secretion of the intestinal
mucous membrane, and cause constrictian of the blood-vessels, as tannic acid, vegetables con-
taining tannin, alum, chalk, lead acetate, silver nitrate, bismuth nitrate.

J. Increased evacuation of the intestinal contents is usually accompanied by a watery condition
of the feces, constituting diarrhoea, The causes are :—

1, A too rapid movement of the contents through the intestine, chiefly through the large
intestine, so that there is not time for the normal amount of absorption to take place. The
increased peristalsis depends upon stimulation of the motor-nervous apparatus of the intestine,
usually of a reflex nature. Rapid. transit of the contents through the intestine causes the
evacuation of certain substances, which cannot be digested in so short a time.

2. The stools become thinner from the presence of much water, mucus, and the admixture
with fat, and by eating fruit and vegetables. In rare cases, when the evacuations contain much
mucin, Charcot’s crystals occur (fig. 144, c). In ulceration of the intestine, leucocytes (pus) are
present (Nothnagel).

3. Diarrhoea may occur as a consequence of disturbance of the diffusion-processes through the
intestinal walls, as in affections of the epithelium, when it becomes swollen in inflammatory or
catarrhal conditions of the intestina® mucous membrane. [Irritation over the abdomen, as from
the subcutaneous injection of small quantities of saline solutions, causes diarrhcea. ]

4, It may also be due to increased secretion into the intestine, as in capillary diffusion, when
magnesium sulphate in the intestine attracts water from the blood.

The same occurs in cholera, when the stools are copious and of a rice-water character, and are
loaded with epithelial cells from the villi. The transudation into the intestine is so great that
the blood in the arteries becomes very thick, and may even on this account cease to circulate. -

Transudation into the intestine also takes place as a consequence of paralysis of the vaso-
motor nerves of the intestine. This is perhaps the case in diarrhea following upon a cold:
Certain substances seem directly to excite the secretory organs of the intestines or their nervés,
such as the drastic purgatives (§ 180). Pilocarpin injected into the blood causes great secretion
(Masloff).

During febrile conditions, the secretion of the intestinal glands seems to be altered quanti-
tatively and qualitatively, with simultaneous alteration of the functional activity of the muscul+
ature and the organs of absorption, while the excitability of the mucous membrane is increased
(Uffelmann). Itis important to note that in many acute febrile diseases the amount of common
salt in the urine diminishes, and increases again as the fever subsides,

18'7, COMPARATIVE. —Salivary Glands.—Amongst mammals, the herbivora have larger
salivary glands than the carnivora ; while midway between both are the omnivora. The whale
has no salivary glands. The pinnipedia have asmall parotid, which is absent in echidna. The
dog and many carnivora have a special gland lying in the orbit, the orbital or zygomatic gland,
In birds the salivary glands open at the angle of the mouth, but the parotid is absent.
Amongst reptiles the parotid of some species is so changed as to form poison-glands; the
tortoise has sublingual glands; reptiles have labial glands, The amphibia and fishes have
merely small glands scattered over the mouth. The salivary glands are large in insects ; some
of them secrete formic acid. The salivary glands are well developed in molluscs, and the saliva
of Dolium galea contains more than 3 per cent. of free sulphuric acid (?). The cephalopods
have double glands, .

A crop is not present in any mammal; the stomach is either simple, as in man, or, as in
many rodents, it is divided into two halves, into a cardiac and a pyloric portion. The intestine
is short'in flesh-eating animals and long in herbivora. The stomach of ruminants is compound,
and consists of four cavities. The first and largest is the paunch or rumen, then the reticulum,
In these two cavities, especially the former, the ingesta are softened and undergo fermentation,
They are then returned to the mouth by the action of the voluntary muscular fibres, which
reach to the stomach. This is the process of rumination, The ingesta are chewed again in the
mouth, and are again swallowed, fist this time they enter the third cavity or psalterium—
(which is absent in the camel)—and thence into the fourth stomach or abomasum, in which
the fermentative digestion takes place. The cecum is a very large and important digestive
organ in herbivora and in most rodents; it is small in man, and absent in carnivora. The
cesophagus in grain-eating birds not unfrequently has a blind diverticulum or crop for softening
the food. In the crop of pigeons during the breeding season, there is formed a peculiar secre-
tion—‘‘ pigeon’s milk,” which is used to feed the young (J. Hunter), The stomach consists of
a glandular proventriculus and a strong muscular stomach which is covered with horny epi-
thelium and triturates the food. There are usually two fluid diverticula on the small intestine
near where it joins the large gut. In fishes the intestinal canal is generally simple; the stomach
is merely a dilatation of the tube; and at the pylorus there may be one, but usually many,
blind glandular appendages (the appendices pylorice). They are generally longitudinal folds x

HISTORICAL ACCOUNT OF DIGESTION, 289.

the intestinal mucous membrane, but in some fishes, e.g., the shark, there is a spiral valve. [The
inversive (cane-sugar) ferment is wanting in the herbivora, as the cow, horse, and sheep, but is
present in the dog and cat. It is also met with in birds and reptiles, and in many of the
invertebrates, as the ordinary earth-worm (JZ. Hay). ]

In amphibia and reptiles the stomach is a simple dilatation; the gut is larger in vegetable
feeders than in flesh feeders. The liver is never absent in vertebrates, although the gall-bladder
frequently is, The pancreas is absent in some fishes.

igestion in Plants.—The observations on the albumin-digesting power of some plants
are extremely interesting (Canby, 1869; Ch. Darwin, 1875). The sundew or drosera has a
series of tentacles on the surface of its leaves, and the tentacles are provided with glands. When
an insect alights upon a leaf, it is suddenly seized by the tentacles; the glands pour out an acid
juice over the prey, which is gradually digested, all except the chitinous structures, The secre-
tion, as well as the subsequent absorption of the products of digestion, are accomplished by the
activity of the protoplasm of the cells of the leaves. The digestive juice contains a pepsin-like
ferment and formic acid. Similar phenomena are manifested by the Venus flytrap (Dionea),
by pinguicula, as well as by the cavity of the altered leaves of nepenthes. About fifteen species
of these ‘‘ insectivorous ” or carnivorous plants are known, [Papain, and other ferments analo-
gous in their action to trypsin, are referred to in § 170,]

188, HISTORICAL. —Digestion in the Mouth,—The older observers regarded the saliva as a
solvent, and in addition, many bad qualities, especially in starving animals, were ascribed to it,
This arose from the knowledge of the saliva of mad animals, and the parotid saliva of poisonous
snakes, The salivary glands have been known fora long time. Galen (131-203 A.D.) was ac-
quainted with Wharton’s duct, and Aétius (270 A.D.) with the sub-maxillary and sub-lingual
glands, Hapel de la Chenaye (1780) obtained large quantities of saliva from a horse, in which
he was the first to make a salivary fistula, Spallanzani (1786) asserted that food mixed with saliva
was more easily digested than food moistened with water. Hamberger and Siebold investigated
the reaction, consistence, and specific gravity of saliva, and found in it mucus, albumin, common
salt, calcium and sodium phosphates. Berzelius gave the name ptyalin to the characteristic
organic constituent of saliva, but Leuchs (1831) was the first to detect its diastatic action.

Gastric Digestion,—Digestion was formerly compared to ‘‘ coction,” whereby solution was
effected. According to Galen, only substances that have been dissolved passed through the
pylorus into the intestine. He described the movements of the stomach and the peristalsis of the
intestines. Aelian gave names to the four stomachs of the ruminants. Vidius (+ 1567) noticed
the numerous small apertures of the gastric glands, Van Helmont (+ 1644) expressly notices
the acidity of the stomach. Reaumur (1752) knew that a juice was secreted by the stomach,
which effected solution, and with which he and Spallanzani performed experiments on digestion
outside the body. Carminati (1785) found that the stomachs of carnivora during digestion
secreted a very acid juice. Prout (1824) discovered the hydrochloric acid of the gastric-juice,
Sprott and Boyd (1836) the glands of the gastric mucous membrane, while Wasmann and Bischoff
noted the two kinds of gastric-glands, After Beaumont (1834) had made his observations upon
Alexis St Martin, who had a gastric fistula caused by a gunshot wound, Bassow (1842) and
Blondlot (1843) made the first artificial gastric-fistule upon animals. Eberle (1834) prepared
artificial gastric-juice. Mialhe called albumin, when altered by gastric digestion, albuminose ;
Lehmann, who investigated this substance more carefully, gave it the name peptone. Schwann
isolated pepsin (1836), and established the fact of its activity in the presence of hydrochloric acid.

Pancreas, Bile, Intestinal Digestion.—The pancreas was known to the Hippocratic School ;
Maur, Hoffmann (1642) demonstrated its duct (fowl), and Wirsung described it in man. Regner
de Graaf (1664) collected the pancreatic juice from a fistula, and Tiedemann and Gmelin found
it to be alkaline, while Lauret and Lassaigne found that it resembled saliva. Valentin dis-
covered its diastatic action, Eberle its emulsionising power, and Cl. Bernard (1846) its tryptic
and fat-splitting properties. The last-mentioned function was referred to by Purkinje and
Pappenheim (1836). Aristotle characterised the bile as a useless secretion; according to
Erasistratus (304 B.c.), fine invisible channels conduct the bile from the liver into the gall-
bladder, Arétaeus ascribed icterus to obstruction of the bile-duct. Benedetti (1493) described
gall-stones. According to Jasolinus (1573), the gall-bladder is emptied by its own contractions,
Sylvius noticed the lymphatics. of the liver (1640); Walaeus, the connective-tissue of the so-
called capsule of Glisson (1641). Haller indicated the uses of bile in the digestion of fats. The
‘liver-cells were described by Henle, Purkinje, and Dutrochet (1838). Heynsius discovered the
urea and Cl, Bernard (1853) the sugar in the liver, and he and Hensen (1857) found glycogen
in the liver, Kiernan gave a more exact description of the hepatic blood-vessels (1834), Beale
hie the lymphatics, and Gerlach the finest bile-ducts. Schwann (1844) made the first
biliary fistula ; Demareay particularly referred to the combination of the bile-acids with soda
(1838) ; Strecker discovered the soda compounds of both acids, and isolated them. Celsus
mentions nutrient enemata (8-5 A,D.). - Fallopius (1561) described the valvule conniventes and
villi of the intestinal mucous membrane, and the nervous plexus of the mesentery, ‘The
agminated glands or patches of Peyer were known to Severinus (1645),

. H

290 . THE ORGANS.-OF -ABSORPTION, ©:

Physiology of Absorption.

189. THE ORGANS OF ABSORPTION.—|As most substances in the state
in which they are used for food are either insoluble, or diffuse but -imperfectly
through membranes, the whole drift of the complicated digestive processes is to
render these substances soluble and diffusible, and thus fit them for absorption;
while most of the fats are emulsionised.

The mucous membrane of the whole intestinal tract, as far as it is covered by a
single layer of columnar epithelium, 2.e., from the
cardiac orifice of the stomach to the anus—is
adapted for absorption. The mouth and ceso-
phagus, lined as they are by stratified squamous
epithelium, are much less adapted for this pur-
pose. Still, poisoning is caused by placing potas-
, sium cyanide in the mouth. The channels of
absorption in the intestinal tract are (fig. 206)—
‘ the capillaries [direct], and (2) the lacteals
indirect] of the mucous membrane. Almost the
Scheme of intestinal absorption. LAC., Whole of the substances absorbed by the former

lacteals ; T.D., thoracic duct ; P.V. pass into the rootlets of the portal vein, and tra-

and H.V., portal and hepatic veins ; verse the liver, while those that enter the lacteals

INT., intestine. really pass into lymphatics, so that the chyle
passes through the thoracic duct and is poured by it into the blood, where the
thoracic duct joins the subclavian vein.

Watery solutions of salts, grape-sugar, peptone, poisons, and in a still higher
degree alcoholic solutions of poisons, are absorbed in the stomach. The empty
stomach absorbs more rapidly than one filled with food; gastric catarrh delays
absorption. After a copious diet of milk, fatty granules have been found in the
protoplasm of the goblet-cells ; so that according to this view, the goblet-cells have
a double function, to secrete mucus and to absorb nutriments.

The greatest area of absorption is undoubtedly the small intestine, especially
its upper half, owing to the presence of the valvule conniventes and the villi.

190. STRUCTURE OF THE SMALL AND LARGE INTESTINES.—(The
wall of the small intestine consists of four coats; which, from without inward, are
named serous, muscular, sub-mucous, and mucous (fig. 207).

(1) The serous coat has the same structure as the peritoneum, 7.¢., a thin basis of fibrous
tissue covered on its outer surface by endothelium.

(2) The muscular coat consists of a thin outer longitudinal and an inner thicker circular
layer of non-striped muscular fibres (fig. 207). .

(3) The sub-mucous coat consists of loose connective-tissue containing large blood-vessels
and nerves, and it connects the muscular with the mucous coat.

(4) The mucous coat is the most internal coat, and its absorbing surface is largely increased
by the presence of the valvule conniventes and villi. [The valvule conniventes are permanent
folds of the mucous membrane of the small intestine, arranged across the long axis of the gut.
They pass round a half or more of the inner surface of the gut. They begin a little below the
commencement of the duodenum, and are large and well marked in the duodenum, and remain
so as far as the upper half of the jejunum, where they begin to become smaller, and finally dis-
appear about the lower part of the ileum.] The villi are characteristic of the small intestine,
and are confined to it ; they occur everywhere as closely-set projections over and between the
valvule conniventes (fig. 207). When the inner surface of the mucous membrane is examined
in water, it has a velvety appearance owing to their presence. [They vary in length from yy to
gy of an inch, are largest and most numerous in the nape part of the intestine, duodenum, and

jejunum, where absorption is most active, but they are less abundant in the ileum. Their total
number has been calculated at four millions by Krause.] Each villus is a projection of the
entire mucous membrane, so that it contains within itself representatives of all the tissue-

STRUCTURE OF A_VILLUS. 291

élements of the mucosa. The orifices of. the glands of Lieberkiihn open between the bases of
villi (fig. 207). ; ; -

Each villus, be it cylindrical or conical in shape, is covered by a single layer of columnar
epithelium, whose protoplasm is reticulated, and contains a well-defined nucleus with an intra-
nuclear plexus of fibrils. The ends of the epithelial cells directed towards the gut are polygonal,
and present the appearance of a mosaic (fig. 208, D). When looked at from the side, their free
surface is seen to be covered with a clear, highly refractive disc or ‘‘cuticula,’’ which is marked
with vertical strie. These striz were supposed by Kolliker to represent pores for the absorp-
tion of fatty particles, but this has not been confirmed, while Brettauer and Steinach regarded
them as produced by prisms placed side by side. :

According to v. Thanhoffer, however, this clear disc is comparable to the thickened flange
around the bottom of a vessel, such as is used for collecting gases. On this supposition, the
upper end of each cell is open, and from it
there project pseudopodia-like bundles of
protoplasmic processes (fig. 208, B). These
processes are supposed to be extended beyond
the margin of the cell, and again rapidly re-
tracted, and in so acting they are said to
carry the fatty particles into the interior of
the cells, much as the pseudopodia of an
amoeba entangle its food. [This view has
not been confirmed by a sufficient number of
observers.] Between the epithelial cells are
the so-called goblet-cells (fig, 208, C). [Each
goblet-cell is more or less like a chalice,
narrower above and below, and broad in the
middle, with a tapering fixed extremity. The
outer part of these cells is filled with a clear
substance or mucigen, which, on the addition
of water, yields mucus.. The mucigen lies in
the intervals of a fine network of fibrils,.
which pervades the cell-protoplasm, while [B
the protoplasm, containing a globular or tri- e
angular nucleus, is pushed into the lower
part of the cell. Those goblet-cells are simply
altered columnar epithelial cells, which secrete
mucus in their interior. They are more
numerous under certain conditions. Not un-
frequently in a section of the mucous mem-
brane of the gut, after it is stained with
logwood, we may see a deep blue plug of
mucus partly exuded from these cells. When
looked at from above they give the appearance
seen in fig. 208, D.] The epithelial cells
are shed in enormous numbers in cholera,
and in poisoning with arsenic and muscarin
(Bohm).

[The epithelial cells covering the villus are Longi-
placed upon a layer of squamous epithelium Se — === tudinal
(basement membrane)—the sub-epithelial SSS mutecle.
membrane of Débove. This basement mem- Sass
brane is said to be connected by processes Fig. 207
with the so-called branched cellsof theadenoid Lonatidinnl aint ‘ ; li eer
tissue of the villus, while it also sends up pro- ““4°28!tu ae atc e eee a a
cesses between the epithelial covering. ] og through a Peyer's patch.

The villus itself consists of a basis of adenoid tissue, containing in its centre one or more
lacteals, closely invested with bundles of longitudinal smooth muscular fibres, derived from the
muscularis mucose, and a plexus of blood-vessels. The adenoid tissue of the villus consists of
a reticulum of fibrils with endothelial plates at its nodes. The spaces of the adenoid tissue form
a. spongy network of inter-communicating channels containing stroma-cells or léucocytes (fig.
208, A, ¢,¢) These leucocytes or lymph-corpuscles have been seen to contain fatty granules,
and they are perhaps concerned in the absorption of fatty particles. . :

The lymphatic or lacteal lies in the axis of the villus (fig. 210, d). Some regard the lacteal
merely as a a yee in the centre of the villus, but more probably it has a distinct wall composed
_ of endothelial cells, with apertures or stomata here and there between the cell-plates. These
stomata eae the interior of the lacteal in direct communication with the spaces of the adenoid
tissue. Perhaps, white blood-corpuscles wander out of the blood-vessels of the villi into the

Villi
with epi-
thelium.

LibIZZ>

Ee ELLIe

eee Lee

=oOCoes
= poUGd!

q
po0I8s==s

goo00

== ARO

poddee
Sod = 5 C ph = ———=—
[-T-1-[-] = eee = =

ID OUCOCOSOULe:

rooogonooD

OSS

aay ss
SST

7 <A, [oleleleleL ete lel olela(alefe,
600-00 Gs as Se
KOOs-GOr SS —— SSS SG

Lieber-
-\ Xe kiihn’s
N\5 \

( oN glands.
) AY ae Muscu-

g laris

mucose.

Re Te[ee[PL-T*

Xl
[el

0%
Wi
“iI Z

SS .*
5

Saeon!

SS
(et)

TL)
Is]

Post
<-Ze]

ooo
RES

<li =
es

% Peyet’s
q ~~ patch.

Sub-mucous coat.

Circular
muscle.

292 STRUCTURE OF A VILLUS,

spaces of the adenoid tissue, where they become loaded with fatty granules, and pass into the
be. A |

Fig. 208, S39

A, scheme of a transverse section of part of a villus ; a, columnar epithelium with, }, clear disc ;
c, goblet-cell ; 7, 7, adenoid reticulum ; d, d, spaces containing leucocytes, ¢e, e¢; jf, section
of the central lacteal. B, scheme of a cell with processes projected from its,interior, C,
columnar epithelium after the absorption of fatty granules, D, columnar epithelium of a

villus seen from above with a goblet-cell in the centre.

central lacteal, Zuwarykin and Wiedersheim suppose that the leucocytes pass from the

cal epi-

Disc on
the. epi-
‘ thelium

Capillary,

Artery,

Fig. 209.
Injected blood-vessels of a villus, :
together by oblique strands; while the longitudinal bundles shorten the villus, the oblique

Cylindri-

thelium,

parenchyma of the villus towards
the epithelial layer, and even be-
tween the epithelial cells, from
which they return towards the axis
of the villus, laden with substances -

which they have taken into their

interior (§ 192, II.).
Asmall artery placed eccentrically

* passes into each villus (fig. 209), In
_man it begins to divide about the

middle of the villus, but in animals
it usually runs to the apex before it
divides. The capillaries resulting
from the division of the artery form
a fine dense network placed super-
Jicially, immediately under the epi-
thelium of the surface, The blood
is carried out of a villus by one or
two veins (figs, 207, 209).
Non-striped muscular fibres are
present in villi, They are arranged
ongitudinally in several bun

_ from base to aper, immediately out-

side the central lacteal. When they
contract they tend to empty the
lacteal, A few muscular fibres are
placed more superficially, and run in
a more transverse direction,

_ longitudinal bundles of non-striped _ |

muscle in the villi are connected

-BRUNNER’S GLANDS. 293

fibres’ keep the lacteal open ; thus the parenchyma of the villus is also compressed transversely,
whereby the products of absorption are ’

forced into the lacteal. The muscles
are fixed by cement to the sub-epi-
thelial basal membrane. ‘The muscu-
lar fibres of the villi are direct pro-
longations of the muscularis mucose. ]

. Nerves pass into thevilli from Meiss-
ner’s plexus lying in the sub-mucous
coat. The nerves to the villi are said |
to have small granular ganglionic cells (
in their course, and they terminate \ a\ \ (AEN yy hb Ya}
partlyin the muscular fibres and partly (ae) . a4. \ Ns = we
in the arteries of the villi. \ \ We LAN je

[On making a vertical section of the HL Hi We
mucous membrane of the small in- iA ENyiah) ( j

testine, it is seen to consist of a net- y i)
work of adenoid tissue loaded with
leucocytes. This tissue forms its basis,
and in it are placed vertically side by
side, like test-tubes in a stand, im-
mense numbers of simple tubular
glands—the crypts of Lieberkuhn (fig.
207).] [Kultschitzki finds that the
connective-tissue framework of the
mucous membrane of the small in-
testine is not true adenoid tissue, but
a transition form between the latter j
and loose fibrous tissue.] Lieberkiihn’s Sm | ass
glands open above at the bases of the _ a
villi, while their closed lower extrem- _ a Fig. 210, 4

ity reaches almost to the muscularis Mucous membrane of the small intestine of the dog ;
mucose, Each tube consists of abase- the lacteals are black, and the blood-vessels lighter.
ment membrane lined by asingle layer —&, artery; b, lymphatic; ¢, plexus of capillaries in the

of columnar epithelium, leaving a wide shia F ieberkiihn’s ol
fa ate ele inde then hans villi; d, lacteal; ¢, Lieberktihn’s glands.

continuous with those that cover the mucous membrane. Some goblet-cells are often found
between the columnar epi- Villi with blood-vessels injected. Solitary follicle.

thelium. Immediately below
the bases of the follicles of
Lieberkiihn is the muscu-
laris mucosx, consisting of
two or three narrow layers of
non-striped muscular fibres
arranged circularly and
longitudinally. [It is con-
tinuous with the muscularis
mucose of the stomach, and »
extends throughout the
whole intestine, not as a con-
tinuous layer, but as a close
network of bundlesof smooth
muscle. It sends fibres up-
wards into the villi (fig. 212,
e).]

{[Brunner’s Glands are
compound tubular glands
lying in and confined to the
sub-mucous coat of the duo-
denum (fig. 198). Their
ducts perforate the muscu-
laris mucosee to open on the
surface, They seem to be
the homologues of the py-
loric Cae of the stomach. |

[Solitary Follicles are small round. or oval white masses of adenoid tissue, with their
deeper parts embedded in the sub-mucosa, and their apices projecting into-the mucosa of the

e..

Mucous
membrane
with villi.

Blood-
23 vessels,

2

==2— Muscular
. coat.

Transverse section of duodenum of a rabbit injected, x-50.

204

SOLITARY FOLLICLES,

intestine, - They begin at the pyloric end of the stomach and are found throughout the whole
intestine, They consist of small masses of adenoid tissue loaded with leucocytes (fig. 214).

2 Cai rg at

33%
Se

~

ers
.
i, otha

ory
Sow

Fig, 212,

Section of a solitary follicle of the small intestine (human).
a, lymph-follicle covered with epithelium (b) which has
fallen from the villi, c; d, Lieberkiihn’s follicle ; e, mus-
cularis mucosz ;:/, sub-mucous tissue.

They are. well supplied with
blood-vessels (§ 197), although no
— vessels enter them.
hey are surrounded by lym-
phatics, and, in fact, they may be

said to hang into a lymph-stream.

The distribution of solitary fol-
licles is: fairly uniform in. the
small intestine; their number
generally increases from the
stomach to the large intestine ;
although there are considerable
variations in different individuals,
there seems to be the same num-
ber of solitary follicles and Peyer’s
patches in the infant as in the
adult (Passow). } ;

[Peyer’s glands, or agminated
glands, consist of groups. of
lymph-follicles like the foregoing
(figs. 207, 213). The masses are
often more or less fused together,
their bases lie in the sub-mucosa,
while their summits project into
the mucosa, where they are
covered merely by the columnar
epithelium of the intestine. _The
lymph-corpuscles often pass be-
tween the epithelial cells. The
patches so formed have their long
axis in the axis of the intestine,

and they are always placed opposite the attachment of the mesentery. Like the solitary glands,
they are well supplied with blood-vessels, while around them is a dense plexus of lymphatics

(3

LB
se
=e
EE

ie
BZ

5 Fig. 213.
Diagram of a vertical section

intestine of a dog showing the closed follicles, aa; b, muscularis bein

mucose,

or lacteals. They are
most abundant in the
lower part of the ileum,
These glands are speci-
ally affected in typhoid
fever. ] :

Nerves of the Intes-
tine.—Throughout the
whole intestinal tract
there exists the plexus
of Auerbach, lying be-
tween the longitudinal
and circular muscular
coats (figs. 174, 175).
This plexus consists. of
non-medullated nerves
with groups of ganglio-
nic cells at the nodes,
Fibres are given off by
it tothe muscular coats,
Connected: by branches
with the foregoing, and
lying in the sub-mu-
cosa, is the plexus of
- Meissner, .which is

of the mucous membrane of the smal} much finer, the meshes

wider, the nodes
but also pro-
vided with ganglionic

smaller,

cells, It supplies the muscular fibres and arteries of the mucosa, including those of the villi.

It also sends branches to Lieberkiihn’s glands (fig. 176).

_ [Structure of the Large Intestine. —It has four coats, like those of the small intestine,

STRUCTURE OF THE LARGE INTESTINE, 295

serous coat-has the same structure as-that of the small intestine. The muscular coat has

external longitudinal fibres occurring all round the gut, but they form three flat ribbon-like
longitudinal bands in the cecum. aid colon (fig. 214). Inside this coat are the circular fibres.
The sub-mucosa is practically the same as that of the small intestine. The mucosa is distin-
guished by negative characters. It has no villiand no Peyer’s patches, but otherwise it resembles
structurally the small intestine, consisting of a basis of adenoid tissue with the simple tubular
glands of Lieberkiihn (fig. 199). These glands are very numerous and somewhat longer than
those of, the small intestine, and they always contain far more goblet-cells—about ten times as
many. The cells lining them are devoid of a clear disc. Solitary glands occur throughout
the entire length of the large intestine. At the bases of Lieberkiihn’s glands is the muscularis
mucose#, The blood-vessels and nerves have a similar arrangement to those in the stomach. ]

Epi-
thelium o°
(VD ALD |
OEE Be Ea
ASIC Sneha | Lieber-
, Sse Eee) kth
Ee! SNCS Rae HAI anne
Mucous SE) 2 Q) alehh
membrane. \ Safle) AYA SARS)
cai) Wrens
Shi) SUN
F bet 4 Q
Capillary. ANY )
ey
Yj Muscu-
Yy laris
mucose,
Solitary
follicle.
Sub-
mucous
“coat.
Circular
fibres.
Muscular
coat,
Longitudi-
nal fibres.

Fig. 214.
Longitudinal section of the large intestine,

[Blood-Vessels.—On looking down on an opaque injection ‘of the mucous membrane of the
stomach, one sees a dense meshwork of polygonal areas of unequal size, with depressions here
and there. The orifices are the orifices of the gastric glands, each surrounded by a capillary.
A somewhat similar appearance is seen in an opaque injection of the mucous membrane of the

large intestine, but in the latter the meshwork is wniform, all the orifices (of Lieberkiihn’s
glands) being of the same size.] .

191. ABSORPTION OF THE DIGESTED FOOD.—The physical forces con-
cerned are :—endosmosis, diffusion, and filtration.

All the constituents of the food, with the exception ef the fats, which in part are changed
i into a fine emulsion, are brought into a state of solution by the digestive processes. These
ye substances pass through the walls of the intestinal tract, either into the blood-vessels of the
mucous membrane or into the beginning of the lymphatics. In this passage of the fluids two
physical pens come into play—endosmasis and diffusion as well as filtration. .

I, Endosmosis and diffusion occur between two fluids which are capable of forming an inti-
mate mixture with each other, ¢.g., hydrochloric acid and water, but never between two fluids
which do not form a perfect mixture, such as oil and water. If two fluids capable of mixing with
eaeh other, but of different compositions, be separated from each other by means of a septum
with physical pores (which occur even in a homogeneous membrane), an exchange of the constitu-

296 - FORCES CONCERNED IN ABSORPTION,

ents in the fluids occurs until both fluids have the same composition. This exchange of fluids
is termed endosmosis or diosmosis.

Diffusion.—If the two mixible fluids are placed in a vessel, the one fluid over the other, but |
without being separated by a porous septum, an exchange of the particles of the fluids also
occurs, until the whole mixture is of uniform composition. This process is called diffusion.

Conditions Influencing Diffusion.—Graham’s investigations showed that the ol ant of
diffusion is influenced by—(1) The nature of the fluids themselves ; acids diffuse most rapi y;
the alkaline salts more slowly ; and most slowly, fluid albumin, gelatin, gum, dextrin.. These
Rg last do not crystallise, and perhaps do not form true solutions. (2) The

more concentrated the solutions, the greater the diffusion. (8) Heat accel-
erates, while cold retards, the process. (4) If a solution of a body which
diffuses with difficulty be mixed with an easily diffusible one, the former
diffuses with still greater difficulty. (5) Dilute solutions of several substances
diffuse into each other without any difficulty, but if concentrated solutions
are employed, the process is retarded. (6) Double salts, one constituent of
which nlite aes more readily than the other, may be chemically separated by
. diffusion.
y Endosmometer.—The exchange of the fluid-particles takes place inde-
| pendently of the hydrostatic pressure. An endosmometer (fig. 215) consists of -

a glass cylinder filled with distilled water, and into this is placed a flask, J,

without a bottom, instead of which a membrane, m, is tied on. A glass tube,

R, is fixed firmly by means of a cork into the neck of the flask. The flask

is filled up to the lower end of the tube with a concentrated salt solution,

and is then placed in the cylindrical vessel until both fluids are on the same
level, x. The fluid in the tube, R, soon begins to rise, because water passes
through the membrane into the concentrated solution in the flask, and this
independently of the hydrostatic pressure. Particles of the concentrated
Psat solution pass into the cylinder and mix with the water, F. These out-

going and ingoing currents continue until the fluids without and within J
are of uniform composition, whereby the fluid in R always stands higher (e.g.,
at y), while it is lowered in the cylinder. The circumstance of the level of
the fluid within the tube being so high, and remaining so, is due to the fact
that the pores in the membrane are too fine to allow the hydrostatic pressure
to act through them.

Endosmotic Equivalent.—Experiment has shown that equal weights of
different soluble substances attract different amounts of distilled water
< -through the membrane, 7.¢., a known weight of a soluble substance (in the

Fig. 215. flask) can be exchanged by endosmosis for a definite weight of water. The
term ‘‘endosmotic equivalent” indicates the weight of distilled water that
passes into the flask of the endosmometer, in exchange for a known weight
of the soluble substance (Jolly). For 1 grm. alcohol 42 grms. water were exchanged; while
for 1 grm. NaCl, 4:3 grms. water passed into the endosmometer, The following numbers give
the endosmotic equivalent of

Endosmometer.

Acid potassium sulphate, . = 2°3 Magnesium sulphate,. ° = 11°7
Common salt, : ; : = 43 Potassium sulphate, . ‘ = 12°0
Sugar, . : etn ° = 71 Sulphuric acid, . , : = 0°39
Sodium sulphate, . ‘ ‘ =11°6 Potassium hydrate, . : =215°0

The amount of the substance which passes through the membrane into the water of the cylin-
der is proportional to the concentration of the solution. If the water in the cylinder, there-
fore, be repeatedly renewed, the endosmosis takes place more rapidly and the process of equili-
bration is accelerated. The larger the pores of the membrane, and the smaller the molecules of
the substance in solution, the more rapid is the endosmosis. Hence, the rapidity of endosmosis
of different substances varies, ¢.g., the rapidity of sugar, sodium sulphate, common salt, and
urea is in the ratio of 1: 1°1: 5.: 9°5. .

The endosmotic equivalent is not constant for each substance. It is influenced by—(1) The
temperature, which, as it increases, generally increases the endosmotic equivalent. (2) It also
varies with the degree of concentration of the osmotic solutions, being greater for dilute solu-
tions of the substances. :

If a substance other than water be placed in the cylinder, an endosmotic current occurs on
both sides until complete equality is obtained. In this case, the currents in opposite directions
disturb each other. If two substances be dissolved in the water in the flask at the same time,
they diffuse into water without affecting each other. (3) It also varies with membranes of —
varying porosity, Common salt, which gives an endosmotic equivalent with a pgs bladder
=4°3, gives 6'4 when an ox bladder is used ; 2°9 with a swimming bladder ; and 202 with a
collodion membrane. at vt hide

Colloids.—There are many fluid-substances which, on account of the great size of their

t ‘a
&
¥
Ti

COLLOIDS, | 297

molecules, do not pass, or pass only with difficulty, through the pores of a membrane impreg-
nated with gelatinous bodies, which diffuse slowly. These substances are not actually in a true
state of solution, but exist in a very dilute condition of imbibition. Such substances are the
fluid proteids, starches, dextrin, gum, and gelatin. These diffuse when no septum is present,
but diffuse with difficulty or not at all through a porous septum. Graham called these sub-
stances colloids, because, when concentrated, they present a glue-like or gelatinous appearance ;
further, they do not crystallise, while those substances which diffuse readily are crystalline, and
are called crystalloids. Crystallisable substances may be separated from non-crystallisable by
this process, which Graham called dialysis. Mineral salts favour the passage of colloids through
membranes.

That endosmosis takes place in the intestinal tract, through the mucous
membrane and the delicate membranes of the blood and lymph-capillaries, cannot
be denied. On the one.side of the membrane, within the intestine, are relatively
concentrated solutions of highly diffusible salts, peptones, sugar, and soaps, and
within the blood-vessels are the colloids which are scarcely diffusible, ¢.g., the pro-
teids of blood and lymph.

II, Filtration is the passage of fluids through the coarse intermolecular pores of a membrane
owing to pressure, The greater the pressure, and the larger and more numerous the pores, the
more rapidly does the fluid pass through the membrane ; increase of temperature also accelerates
it. Those substances which are imbibed by the membrane filter most rapidly, so that the same
substance filters through different membranes with varying rapidity. The filtration is usually
slower, the greater the concentration of the fluid. The filter has the property of retaining some
of the substances from the solution passing through it, ¢.g., colloid substances—or water (in
dilute solutions of nitre). In the former case, the filtrate is more dilute, in the latter more
concentrated, than before filtration. Other substances filter without undergoing any change of
concentration. Many membranes behave differently, according to which surface is placed next
the fluid ; thus the shell-membrane of an egg permits filtration only from without inwards ;
[and the same is true to a much less extent with filter-paper ; the smooth side of the filter-
paper ought always to be placed next the fluid to be filtered. The intact skin of the grape pre-
vents the entrance of fungi into the fruit]. There is a similar difference with the gastric and
intestinal mucous membrane.

[By using numerous layers of filter-paper, many colloids and crystalloids are retained in the
filter, e.g., heemoglobin, albumin, and many colouring matters, especially aniline colours, the last
being arrested by glass-wool (Krysinskz). ]

[Filtration of Albumin.—Runeberg finds that the amount of albumin in pathological transu-
dations varies with (1) the capillary area, being least in cedema of the subcutaneous tissue.
(2) The presence or absence of inflammatory processes in the vascular wall, non-inflammatory
pleuritic effusion containing 2 per cent., and inflammatory 6 per cent., of albumin. (3) The con-
dition and amount of albwmin in the bbood. The amount of albumin in the transudate never
reaches, although it sometimes approaches, that in blood. In ascites in general dropsy the
amount is ‘03 to 04 percent. (4) The dwration of the transudation. (5) Perhaps the blood-
pressure and the condition of the circulation. ]

Filtration of the soluble substance may take place from the canal of the
digestive tract when :—(1) The intestine contracts and thus exerts pressure upon its
contents. This is possible when the tube is narrowed at two points, and the mus-
culature between these two points contracts upon the fluid-contents. (2) Filtration,
under negative pressure, may be caused by the villi (Briicke), When the villi con-
tract energetically, they empty their contents towards the blood- and lymph-vessels.
The lacteal remains empty, as the chyle is prevented from passing backwards into the
origin of the lacteal within the villi, owing to the presence of numerous valves in
the lymphatics. When the villi relax, they are refilled with fluids from the intes-

tine.

192. ABSORPTION BY THE INTESTINAL WALL.—I. True solutions
undoubtedly pass by endosmosis into the blood-vessels and lymphatics of the
intestinal walls, but numerous facts indicate that the protoplasm of the cells takes
an active part in the process of absorption. The forces concerned have not as yet
been proved to be purely physical and chemical in their nature. :

(1) Inorganic Substances.—Water and the soluble salts necessary for nutri-
tion are easily absorbed, the latter especially by the blood- and lymph-vessels.

_ When saline solutions pass by endosmosis into the vessels, water must pass from

298 ABSORPTION OF SOLUBLE CARBOHYDRATES.

the intestinal vessels into the intestine. The amount of water, however, is small,
owing to the small endosmotic equivalent of the salts to be absorbed. More salts
are absorbed from concentrated than from dilute solutions. If large quantities of
salt, with a high endosmotic equivalent, e.g., magnesium or sodium sulphate, are
introduced’ into the intestine, these salts retain the water necessary for their solu-
tion, and may thus cause diarrhoea, Conversely, when these substances are injected
into the blood, a large quantity of water passes from the intestine into the blood,
so that constipation occurs, owing to dryness of the intestinal contents (Aubert).

[M. Hay concludes from his experiments (§ 161), that salts, when placed in the intestines,
do not abstract water from the blood, or are themselves absorbed, in virtue of an endosmotic
relation being established between the blood and the saline solution in the intestines. Absorp-
tion is probably due to the filtration and diffusion, or processes of inhibition other than endos-
mosis, as yet little understood. The result obtained by Aubert, which is not constant, is mostly
caused by the great diuresis which the injected salt excites.] The absorption of fluids takes
place best at a medium pressure of 80 to 140 c.cm. of water within the intestine ; higher pressure
compresses the blood-vessels and diminishes the absorption. During digestion, owing to the
dilatation of the vessels, absorption is more rapid. The fact that 0°5 per cent. solution of NaCl
is absorbed better than water, and soda solution than potash solution, seems to show that
physical forces are not the only factors concerned.

Numerous inorganic substances, which do not occur in the body, are absorbed by endosmosis
from the intestine, ¢.g., dilute sulphuric acid, potassium iodide, chlorate, and bromide, and
many other salts.

(2) The soluble carbohydrates, such as the sugars, of which the chief repre-
sentatives are dextrose and maltose, with a relatively high endosmotic equivalent.
Cane-sugar is changed by a special ferment into invert-sugar (§ 183, 5). Absorption
appears to take place somewhat slowly, as only very small quantities of grape-sugar
are found in the chyle vessels, or the portal vein, at any time. According to v.
Mering, the sugar passes from the intestine into the rootlets of the portal vein ;
dextrin also occurs in the portal vein. When the blood of the portal vein is boiled
with dilute sulphuric acid, the amount of sugar is increased. The amount of sugar
absorbed depends upon the concentration of its solution in the intestine ; hence the
amount of sugar in the blood is increased after a diet containing much of this sub-
stance, so that it may appear in the urine ; in which case the blood must contain at
least 0°6 per cent. of sugar. A small amount of cane-sugar has also been
found in the blood (Cl. Bernard). The sugar is used up in the bodily metabolism ;
some of it is perhaps oxidised in the muscles (§ 176).

(3) The peptones have a small endosmotic equivalent, a 2 to 9 per cent. solution
=7 to 10. Owing to their great diffusibility they are readily absorbed, and they
are the chief representatives of the proteids which are absorbed. The amount
absorbed depends upon the concentration of their solution in the intestine. When
animals are fed on peptones (with the necessary fat or sugar), they serve to maintain
the body-weight. [According to Plész and Gyérgyai, Drosdorff and Schmidt-
Mulheim, peptones occur only in traces in the blood of the portal vein. Neumeister,
however, using the best methods, finds that although peptones are abundant in the
intestine, not a trace of peptone or of the albumoses is found either in the blood or
lymph. This coincides with Hofmeister’s researches, and is of course opposed to
the results of the above-named observers: As no peptones or albumoses have been
found in the blood, and as they can compensate for the total metabolism of ‘the
proteids within the body, we must assume that they are rapidly converted into
true albuminous bodies.| Hofmeister supposes that the leucocytes absorb the
peptones and act as their carriers, much as the red corpuscles are oxygen carriers.
They carry the peptones into the mucous membrane of the stomach and small
intestine, which are.very rich in peptone at the fourth hour of digestion. Tie
number of leucocytes is greatly increased in the mucous membrane, especially in
the stomach and upper part of the duodenum, during digestion, and diminished —
during fasting in dogs and cats, The same is the case with the lymph-follicles, the

ABSORPTION OF PEPTONES AND PROTEIDS. 299

eells of which are formed by the division of the pre-existing cells.] It is asserted
by Salvioli that the mucous membrane possesses the property of changing peptone
into albumin. a

[Injection of Peptone into Blood.—When peptone is injected into the blood of an animal,
within twenty minutes thereafter no trace of the peptone is to be found in the blood, although
it has not been excreted by any of the organs. Peptones so:injected prevent the blood of the
dog (not of the rabbit or pig) from coagulating. In large quantity they are fatal. Fano asserts
that the peptone is taken up by the red blood-corpuscles, which thus become of greater specific
gravity, and change it into globulin. - After three or more hours the corpuscles return the
globulin to the blood, so that the corpuscles represent a reserve store of proteid. The peptones
used in these experiments were really a mixture of peptones and albumoses. ‘ Neumeister finds
that in the dog, when albumoses are injected into the blood they reappear in the urine, but
somewhere in the body they undergo hydration in the sense in which peptic digestion causes
hydration. The two primary albumoses reappear almost completely as deutero-albumose, and
deutero-albumose, when introduced, reappears as peptone. Peptone, however, reappears un-
changed. In rabbits, albumose reappears unchanged in the urine. ]

(4) Unchanged true proteids filter with great difficulty, and much albumin
remains upon the filter. On account of their high endosmotic equivalent they pass
with extreme slowness, and only in traces, through membranes. Nevertheless, it
has been conclusively proved that unchanged proteids can be absorbed (Briicke),
€.g., casein, soluble myosin, alkali-albuminate, albumin mixed with common salt,
gelatin (Voit, Bauer, Hichhorst), They are absorbed even from the large intestine
(Czerny and Latschenberger), although the human large intestine cannot absorb
more than 6 grms. daily. But the amount of unchanged proteids absorbed is
always very much less than the amount of peptone. |

Egg-albumin without common salt, syntonin, serum-albumin, and fibrin are not absorbed

{Hichhorst). Landois observed, in the case of a young man who took the whites of 14 to 20
egos along with NaCl, that albumin was given off by the urine for 4 to 10 hours thereafter.
The amount of albumin given off rose until the third .day, and ceased on the fifth day. The
more albumin taken, the sooner the albuminuria appeared, and the longer it lasted. The
unchanged egg-albumin reappeared in the urine. If egg-albumin be injected into the blood,
part of it reappears in the urine (§ 41, 2) (Stokvis, Lehmann).
_ (5) The soluble fat-soaps represent only a fraction of the fats of the food which
are absorbed ; the greater part of the neutral fats being absorbed in the form of
very fine particles—as an emulsion (§ 192, II.). The absorbed soaps have been found
an. the chyle, and as the blood of the portal vein contains more soaps during digestion
than during hunger, it has been assumed that the soaps pass into the intestinal
blood-capillaries. The investigations of Lenz, Bidder, and Schmidt, render it
probable that the organism can absorb only a limited amount of fat within a given
period ; the amount perhaps bears a relation to the amount of bile and pancreatic
juice. The maximum per kilo. (cat) was 0°6 grms. of fat per hour,

Perhaps the soaps reunite with glycerine in the parenchyma of the villi, to form
neutral fats, as Perewoznikoff and Will found neutral fats, after injecting these two
ingredients into the intestinal canal, while Ewald found that fat was formed when
soaps and glycerine were brought into contact with the fresh intestinal mucous
membrane. Perhaps this is the explanation of the observation of Bruch, who
found fatty particles within the blood-vessels of the villi, No fatty-acids are
found in blood, or chyle. | e ;

. Absorption of other Substances. —Of soluble substanées which are introduced into the intes-
tinal canal, some are absorbed and others are not. The following are absorbed :—alcohol, part
of which appears in the urine (not in the expired air), viz., that part which is not changed into
CO, and H,O, within the body ; tartaric, citric, malic, and lactic acids ; glycerine, inulin; gum
and vegetable mucin, which give rise to the formation of glycogen in the liver.

_ Amongst colouring matters, alizarin (from madder), alkannet, indigo-sulphuric acid, and its
soda-salt are absorbed; hematin is partly absorbed, while chlorophyll is not, Metallic salts
seem to be kept in solution by proteids, are perhaps absorbed along with them, and are partly

carried by the blood of the portal vein to the liver (ferric sulphate has been found in chyle).
Numerous poisons are very rapidly absorbed, ¢.g., hydrocyanic acid after a few seconds ; potas-

300 ABSORPTION OF FATTY PARTICLES.

sium cyanide has been found in the chyle. [If salts (KI, sulphocyanide of ammonium) be
injected into a ligatured loop of intestine (dog, cat, rabbit), these substances are absorbed both
by the blood- and lymph-vessels, and in both nearly simultaneously.] Even for the absorption
of completely fluid substances, endosmosis and filtration seem to be scarcely sufficient. An
active participation of the protoplasm of the cells seems here also—in part at least—to be
necessary, else it is difficult to explain how very slight disturbances in the activity of these
cells, ¢.g., from intestinal catarrh, cause sudden variations of absorption, and even the passage
of fluids into the intestine.

If absorption were due to diffusion alone, when alcohol is injected into the intestine, water
ought to pass into the intestine, but this does not occur. Brieger found that the injection of a
0°5 to 1 per cent. solution of salts into a ligatured loop of intestine did not cause water to pass
into the intestine; but it appeared when a 20 per cent. solution was injected.

II. Absorption of the Smallest Particles.—The largest amount of the fats is
absorbed in the form of a milk-like emulsion, formed by the action of the bile and
the pancreatic juice, and consisting of excessively small granules of uniform*size
(§ 170, IIL; § 181). The fats themselves are not chemically changed, but remain
as undecomposed neutral fats. The particles seem to be surrounded by a delicate
albuminous envelope, or haptogen membrane, partly derived from the pancreatic
juice [probably from its alkali-albuminate]. The villi of the small intestine are
the chief organs concerned in the absorption of the fatty emulsion, but the epithe-
lium of the stomach and that of the large intestine also take a part. The fatty
granules are recognised in the villi—(1) Within the delicate canals ? (§ 190) in the
clear band of the epithelium (K6lliker). [It is highly doubtful if the vertical lines
seen in the clear disc of the epithelium of the intestine are due to pores.]| (2) The
protoplasm of the epithelial cells is loaded with fatty granules of various sizes
during the time of absorption, while the nuclei of the cells remain free, although,
from the amount of fat within the cells, it is often difficult to distinguish them.
(3) The granules pass into the spaces of the parenchyma of the villi; these spaces
communicate freely with each other. (4) The origin of the lacteal in the axis of
the villus is found to be filled with fatty granules. The amount of fat in the chyle
of a dog, after a fatty meal, is 8 to 10 per cent., while the fat disappears from the
blood within thirty hours.

With regard to the forces concerned in the absorption of fats, v. Wisting-
hausen proved, that when a porous membrane is moistened with bile, the passage
of fatty particles through it is thereby facilitated, but this fact alone does not ex-
plain the copious and rapid absorption of fats. It is possible that the protoplasm
of the epithelial cells is actively concerned in the process, and that it takes the
particles into its interior, Perhaps a fine protoplasmic process is thrown out by
these cells, just as pseudopodia are thrown out and retracted by lower organisms.
It is possible that absorption may take place through the open mouths of the
goblet-cells, The protoplasm of the epithelial cells is in direct communication with
the numerous protoplasmic lymph-cells within the reticulum of the villi, so that the
particles may pass into these, and from them through the stomata (?) between the
endothelial cells into the central lacteal of the villus. According to this view, the
absorption of fatty particles, and perhaps also the absorption of true proteids, is
due to an active vital process, as indicated by the observations of Briicke and v.
Thanhoffer. This view is supported by the observation of Griinhagen, that the
absorption of fatty particles in the frog is most active at the temperature at which
the motor phenomena of protoplasm are most lively. That it is due to simple
filtration alone is not a satisfactory explanation, for the amount of fatty particles
in the chyle is independent of the amount of water in it.. If absorption were chiefly
due to filtration, we would expect that there would most probably be a direct re-
lation between the amount of water and fat (Ludwig and Zawilsky). [The
observations of Watney have led him to suppose that the fatty particles do not
pass through the cell protoplasm to reach the lacteal, but that they pass through
the cement-substance between the epithelial cells covering a villus. If this view be

INFLUENCE OF THE NERVOUS SYSTEM, 301

correct, the absorbing surface is thereby greatly diminished. Zuwarykin and
Schafer suggest that the leucocytes, which have been observed between the columnar
cells of the villi of the small intestine, are carriers of at least part of the fat from
the lumen of the gut to the lacteal ; they also, perhaps, alter it for further use in the
economy. According to Zuwarykin, Peyer’s patches in the rabbit seem to be
especially active in the absorption of fat, so that he attaches great importance to
the leucocytes of the adenoid tissue in the absorption of fat. |

[According to Griinhagen there are several channels for the absorption of fats, but they are
different in different animals. Some are absorbed by the columnar epithelium cells themselves,
and some passes between them. ]

The activity of the cells of the intestine with pseudopodial processes may be studied in the

intestinal canal of Distomum hepaticum. Sommer has figured these pseudopodial processes
actively engaged in the absorption of particles from the intestine.

193. INFLUENCE OF THE NERVOUS SYSTEM.—With regard to the
influence of the nervous system upon intestinal absorption, we know very little,
After extirpation of the semi-lunar ganglion, as well as after section of the mesen-
teric nerves (Moreau), the intestinal contents become more fluid, and are increased
in amount (§ 183). This may be partly due to diminished absorption. V. Than-
hoffer states that he observed the protrusion of threads from the epithelial cells of
the small intestine only after the spinal cord, or the dorsal nerves, had been divided
for some time.

194. ‘NUTRIENT ENEMATA,’’—In cases where food cannot be taken by the mouth, ¢.g.,
in stricture of the cesophagus, continued vomiting, &c., food is given per rectum. As the diges-
tive activity of the large intestine is very slight, fluid food ought to be given in a condition
ready to be absorbed, and this is best done by introducing it into the rectum through a tube
with a funnel attached, and allowing the food to pass in slowly by its own weight. The patient
must endeavour to retain the enema as long as possible, When the fluid is slowly and gradu-

ally introduced, it may pass above the ileo-cecal valve.

Solutions of grape-sugar, and perhaps a small amount of soap solution, are useful; and

amongst nitrogenous substances the commercial flesh-, bread-, or milk-peptones of Sanders-Ezn,

Adamkiewicz, in Germany, and Darby’s fluid meat, and Carnrick’s beef-peptonoids in this
country, are to be recommended. The amount of peptone required is 1°11 grm. per kilo. of
body-weight (Catillon) ; less useful are butter-milk, egg-albumin with common salt. Leube
uses a mixture of 150 grms. flesh, with 50 grms. pancreas and 100 grms. water, which he

slowly injects into the rectum, where the proteids are peptonised and absorbed, [Peptonised

food prepared after the method of Roberts is very useful (§ 172).] The method of nutrient
enemata only permits imperfect nutrition, and at most only } of the proteids necessary for
maintaining the metabolism of the body is absorbed (v, Voit, Bauer).

195, CHYLE-VESSELS AND LYMPHATICS.—Lymphatics.—Within the tissues of the
body, and even in those tissues which do not contain blood-vessels, ¢.g., the cornea, or in those
which contain few blood-vessels, there exists a system of vessels or channels which contain the
juices of the tissues, and within these vessels the. fluid always moves in a centripetal direction.
These canals arise within the tissues in a variety of ways, and unite in their course to form
delicate and afterwards thicker tubes, which ultimately terminate in two large trunks which
open at the junction of the jugular and subclavian veins ; that on the left side is the thoracic
duct, and that on the right, the right lymphatic trunk.

With regard to the lymph and its movements in different organs, it is to be noticed
that this occurs in different ways in different places. (1) In many tissues, the lymph-
atics represent the nutrient channels, by which the fluid that transudes through the
neighbouring vessels is distributed, as in the cornea and in many connective-tissues.
(2) In many tissues, as in glands, e.g., the salivary glands and the testis, the lymph-
spaces are the chief reservoirs for fluid, from which the cells during the act of
secretion derive the fluid necessary for that process. (3) The lymphatics have the
general function of collecting the fluid which saturates the tissues, and carrying it
back again to the blood. The capillary blood-system may be regarded as an irriga-
tion system, which supplies the tissues with nutrient fluids, while the lymphatic
system may be regarded as a drainage apparatus, which conducts away the fluids
that have transuded through the capillary walls. Some of the decomposition pro-

302 ) . .. ORIGIN OF THE LYMPHATICS," ”

ducts of the tissues, proofs of their retrogressive’ metabolism, become mixed with
the lymph-stream, so that the lymphatics are at the same time absorbing vessels.’
Substances introduced into the parenchyma of the tissues.in other ways, e.g., by
subcutaneous injection, are partly absorbed by the lymphatics. A study of these
conditions shows that the lymphatic system represents an appendix to the blood-
vascular system, and further that there can be no lymph system when the blood-
stream is completely arrested ; it acts only as a part of the whole, and with the whole..

Lacteals.— When we speak of the lymphatics proper as against the chyle-vessels
or lacteals, we do so from anatomical reasons, because the important and consider-
able lymphatic channels coming from the whole of the intestinal tract are, in a
certain sense, a fairly independent province of the lymphatic vascular area, and are
endowed with a high absorptive activity, which, from ancient times, has attracted
the notice of observers. The contents of the chyle-vessels or lacteals are mixed
with a large amount of fatty granules, giving the chyle a white colour, which dis-
tinguishes them at once from the true lymphatics with their clear watery contents.
From a physiological point of view, however, the lacteals must be classified with
the lymphatics, for, as regards their structure and function, they are true lymphatics,
and their contents consist of true lymph mixed with a large amount of absorbed
substances, chiefly fatty granules. [The contents of the lacteals are white only
during digestion, at other times they are clear like lymph. |

_196. ORIGIN OF THE LYMPHATICS.—(1) Origin in Spaces.—Within the connective-
tissues (connective-tissue proper, bone) are numerous stellate, irregular, or branched spaces,
which communicate with each other by
numerous tubular processes (fig. 216, s) ;
in these communicating spaces lie the
cellular elements of these tissues. These
spaces, however, are not completely filled
by the cells, but an interval exists between
the body of the cell and the wall of the
space, which is greater or less according
to the condition of movement of the proto-
plasmic cell. These spaces are the so-
called “juice canals” or “Saft-canalchen,”
and they represent the origin of the lym-
phatic vessels (v. Recklinghausen). As
they communicate with neighbouring
spaces, the movement of the lymph is
provided for. The cells which lie in the
spaces exhibit amceboid movements.
Some of these cells remain permanently
each in its own space, within which,
however, it may change its form—these
are the so-called ‘‘fixed connective-
tissue corpuscles,” and bone corpuscles—
while others merely wander or pass into
these spaces, and are called ‘‘ wandering
Fig, 216 cells,” or ‘‘leucocytes”; but the latter

Te : eR: are merely lymph-corpuscles, or colourless
Origin of lymphatics from the central tendon of the hlood-corpuscles which have passed out of
diaphragm stained with nitrate of silver. s, the the blood-vessels into the origin of the
juice-canals, communicating at « with the lym- lymphatics, These cells exhibit amceboid
phatics ; a, origin of the lymphatics by the conflu- movements. These spaces communicate
ence of several juice-canals. with the small tubular lymphatics—the
so-called 7ymph-capillaries (L). The spaces lie close together, where they pass into a lymph-
eapillary (a). The lymph-capillary, which is usually of greater diameter than ‘the blood-
capillary, generally lies in the middle of the space within the capillary arch (B). The finest
lymphatics are lined by a layer of delicate, nucleated, endothelial cells (¢, ¢), with characteristic
sinuous margins, whose characters are easily revealed by the action of silver nitrate (fig. 217, L).

This substance blackens the cement-substance which holds the endothelial cells together.
Between the endothelial cells are small holes, or stomata, by means of which the lymph-capil-
laries communicate (atx). with the juice-canals, B62 ths b sdye iu 3

ORIGIN OF THE LYMPHATICS. 303

It.is assumed by Arnold that the blood-vessels communicate with the juice-canals, and that
fluid passes out of the thin-walled capillaries through their stomata into these spaces (§ 65).
This fluid nourishes the tissues, the tissues take up the substances appropriate to each, while
the effete materials pass back into the spaces, and from these reach the lymphatics, which
ultimately discharge them into the venous blood.

Whether the cells within these spaces are actively concerned in the pouring out of the blood-
plasma, or take part in its movement, is matter of conjecture. We can imagine that by con-
tracting their body, after it has
been impregnated with fluid, this
fluid may be propelled from space
to space towards the lymphatics.
The leucocytes wander through
these spaces until they pass into
the lymphatics. Fine particles
which are contained in these spaces
—e.g., after tattooing the skin,
and even fatty particles after in-
unction —are absorbed by the «=
leucocytes, and carried by them to |!
other parts of the body. [The
pigment particles used to tattoo the
finger are usually found within the
first lymphatic gland at the elbow. |

The migration of cellular
elements from the blood-vessels
into the origin of the lym-
phatics is to be considered as
a normal process. Granular
colouring-matter passes from
the blood into the protoplasmic
body of the cells within the
lymph-spaces ; and only when
the granular pigment 1s in Pleural surface of the central tendon of the diaphragm of
large amount, does it appear the rabbit stained with silver nitrate. L, lymphatic with
as a granular injection in the its sinuous endothelium 5 ¢, cells of the connective-tissue
branches of the juice-spaces. brought into view by the silver nitrate.

(2) Origin within villi—i.c., of the chyle vessel or lacteal—has been described ($ 190).

(3) Origin in perivascular spaces (fig. 218).—The smallest blood-vessels of bone, the central
nervous system, retina and the liver, are completely surrounded by wide lymphatic tubes, so
that the blood-vessels are completely bathed by a lymph-stream. In the brain these lymphatics
are partly composed of delicate connective-tissue fibres, which traverse the lymph-space and
become attached to the wall of the included blood-vessel. Fig. 218, B, represents a transverse
section of a small blood-vessel, B, from the brain; p is the divided perivascular space. This
space is called the perivascular space of His, but in addition to it the blood-vessels of the brain
have a lymph-space within the adventitia of the blood-vessels (Virchow-Robin’s space). It is
partly lined by well-defined endothelium. Where the blood-vessels begin to increase consider-
ably in diameter, they pass through the wall of the lymphatics, and the two vessels afterwards

. take separate courses. In all cases, where there is a perivascular space, the passage of lymph-

and blood-corpuscles into the lymphatics is greatly facilitated. In the tortoise the large blood-
vessels are often surrounded with perivascular lymphatics. Fig. 218, A, gives a representation
of the aorta surrounded by a perivascular space which is visible to the unaided eye. In mam-
mals the perivascular spaces are microscopic.

(4) Origin in the form of interstitial slits within organs.—Within the testis the lymphatics
begin simply in the form of numerous slits, which occur between the coils and twists of the
seminal tubules. They take the form of elongated spaces bounded by the curved cylindrical
surfaces of the tubules. The surfaces, however, are covered with endothelium. The lymphatics
of the testis get independent walls after they leave the parenchyma of the organ. In many
other gous the gland-substance is similarly surrounded by a lymph-space. The blood-vessels
pour the lymph into these spaces, and from them the secreting cells obtain the materials
necessary for the formation of their secretion.

(5) Origin by means of free stomata on the walls of the larger serous cavities, which (fig.
219, a) communicate freely with the lymphatics. The investigation of the serous surfaces is
most easily accomplished on the septum of the great abdominal lymph-sac of the frog. Silver

304 ’ LYMPH-FOLLICLES,

nitrate reveals the presence of relatively large free openings or stomata lying between the
endothelium. Each stoma is bounded by several germinating cells, which have a granular
appearance, and undergo a change of shape, so that the size of the stoma depends upon the
degree of contraction of these cells ; thus the stoma may be open (a), half-open (6), or com-
letely closed (c). These stomata are the origin of the lymphatics, The serous cavities
long therefore to the lymphatic system, and fluids placed in the serous cavities readily pass

Fig, 218, Fig. 219.
Perivascular lymphatics. A, aorta of tortoise ; Stomata in the great lymph-sac (frog),
B, artery from the brain. a, open ; b, half-closed ; ¢, closed,

into the lymphatics, The cavities of the peritoneum, pleura, pericardium, tunica vaginalis,
testis, arachnoid space, aqueous chambers of the eye, and the labyrinth of the ear, are true lymph-
cavities, and the fluid they contain is to be regarded as lymph. [Hoffmann has found that a
nerve-fibre surrounds the stomata in the frog and sends branches between the germinal epi-
thelium.
(6) aon open pores have been observed on some mucous membranes, which are regarded as
the origin of lymphatics, ¢.g., in the bronchi, nasal mucous membrane, trachea, and larynx.
Structure. —The larger lymphatics resemble in structure the veins of corresponding size, The
valves are particularly numerous in the lymphatics, so that a distended lymphatic resembles a |
chain of pearls. [Lymphatics have dilations here and there in their course (fig. 217).] |

197, THE LYMPH-GLANDS.—The lymphatic glands belong to the lymph -
apparatus, They are incorrectly termed glands, as they are merely much branched
lacunar labyrinthine spaces
composed of adenoid tissue,
and intercalated in the course
of the lymphatic vessels.
There are simple and com-
pound lymph-glands,
(1) The simple lymph-glands,
B or, more correctly, lymph-follicles,
are small rounded bodies, about
the size of a pin-head. They
consist of a mass of adenoid tissue
(fig. 220, A), z.e., of a very delicate
network of fine reticular fibres
with nuclei at their points of
intersection, and in the spaces of

Two lymph-follicles, A, a small follicle highly magnified, #® meshwork lie the lymph and
showing the adenoid reticulum ; B, a follicle lead “hightle the lymph-corpuscles. ‘Near the

magnified, showing injected blood-vessels, caren, sane) pr votes vpeiie
> ?

which is not however a true capsule, as-it is permeated with numerous small sponge-like spaces,
Small lymphatics come directly into contact with these lymph-follicles, and often cover their
surface in the form of a close network. ' The surface of the lymph-follicles is not unfrequently
placed in the wall of a lymph-vessel, so that it is directly bathed by the lymph-stream.
Although no direct canal-like opening leads from the follicle into the lymphatic stream in

LYMPHATIC GLANDS. 305

relation with it, a communication must exist, and this is obtained by the numerous spaces in the
follicle itself, so that a lymph-follicle is a true lymphatic apparatus whose juices and lymph-
corpuscles can pass into the nearest lymphatic, The follicles are surrounded by a network of
blood-vessels which sends loops of capillaries into their interior (fig. 220, B). We may assume
that lymph-corpuscles pass from these capillaries into the follicle.

In connection with these follicles, including those of the back of the tongue, the solitary
glands of the intestine and the adenoid tissue in the bronchial tract, the tonsils, and Peyer’s
patches, it is important to remember that enormous numbers of leucocytes pass out between
the epithelial cells covering these follicles, The extruded leucocytes undergo disintegration
subsequently.

(2) The compound lymph-glands—the lymphatic glands—represent a collection of lymph-
follicles, whose form is somewhat altered. Every lymph-gland is covered externally with a
connective-tissue capsule (fig. 221, c), which contains numerous non-striped muscular fibres.
From its inner surface, numerous
septa and trabecule (t7.) pass into the
interior, so that the gland-substance
is divided into a large number of
compartments. Thesecompartments
in the cortical portion of the gland
have a somewhat rounded form, and
constitute the alveoli, while in the ,
medullary portion they have a more ff§
elongated and irregular form. [On [AX
making a section of a lymph-gland }
we can readily distinguish the cor-
tical from the medullary portion of | SX \ «
the gland.] All the compartments WX AN a Wee AR
are of equal dignity, and they all ot TS SS atte Seaiet \
communicate with each other by = [Zs CON
means of openings, so that the septa RYE
bound a rich network of spaces
within the gland, which communi-
cate on all sides with each other.

These spaces are traversed by the
follicular threads (fig. 222, 7, /).
These represent the contents of the Lay
spaces, but are smaller than the Fig. 221.
spaces in which they lie, and do not Diagrammatic section of alymphatic gland. a.J., afferent,
come into contact anywhere with e./., efferent, lymphatics; C, cortical substance; M,
the walls of the spaces. If we reticular cords of medulla; /.s, lymph-sinus ; ¢, capsule,
imagine the spaces to be injected with trabecule, ¢r,
with a mass, which ultimately
shrinks to one-half of its original volume, we obtain a conception of the relation of these
follicular threads to the spaces of the gland. The blood-vessels of the gland (0) lie within
these follicular threads. They are surrounded by a tolerably thick crust of adenoid tissue,
with very fine meshes (x, x) filled with lymph-corpuscles, and with its surface (0, 0) covered by
the cells of the adenoid reticulum, in such a way as to leave free communications through
the narrow meshes. ;

Between the surface of the follicular threads and the inner wall of all the spaces of the
gland, lies the lymph-channel or lymph-path (B, B), which is traversed by a reticulum of
adenoid tissue, containing relatively few lymph-corpuscles. It is very probable that these
lymph-paths are lined by endothelium,

The vasa afferentia (fig. 221, a./.), of which there are usually several, expand upon the
surface of the gland, perforate the outer capsule, and pour their contents into the lymph-paths
of the gland (C). The vasa efferentia, which are less numerous than the afferentia, and come
out at the hilum, form large, wide, almost cavernous dilatations, and they anastomose near
the gland (e¢./.). Through them the lymph passes out at the opposite surface of the gland.
The lymph percolates through the gland, and passes along the lymph-paths, which represent
a kind of rete mirabile interposed between the afferent and efferent lymph-vessels,

During its passage through this complicated branched system of spaces, the movement of
the lymph through the gland is retarded, and, owing to the numerous resistances which occur
in its path, it has very little propulsive energy. The lymph-corpuscles which lie in ‘the
meshes of the adenoid reticulum are washed out of the gland by the lymph-stream. The
lymph-corpuscles lying within the follicular threads pass through the narrow meshes (0) into
the lymph-paths. The formation of lymph-corpuscles either occurs locally, from division of
the pre-existing cells, or new leucocytes wander out into the follicular threads. The movement
of the lymph through the gland is favoured by the muscular action of the capsule: When the

U

al.

4s

306 PROPERTIES. OF CHYLE AND LYMPH.

capsule contracts energetically, it must compress the gland like a sponge, and the direction in
e valves.

which the fluid moves is regulated by the position and arrangement of t

h
\
4:

Fig. 222.
Part of a lymphatic gland. A, vas afferens; B, B, lymph-paths; a, a, trabecule seen on
edge ; 7, f, follicular strand from the medulla; x, «, its adenoid reticulum; 8, its blood-
vessels ; 0, 0, narrow-meshed part limiting the follicular strands from the lymph-path.

Chemistry.—In addition to the constituents of lymph, the following chemical substances
have been found in lymphatic glands :—leucin and xanthin.

198. PROPERTIES OF CHYLE AND LYMPH.—Chyle and lymph are
albuminous, colourless, clear juices, containing lymph-corpuscles, which are identical
with the colourless blood-corpuscles (§ 9). In some places, e.g., in the lymphatics
of the spleen, especially in starving animals, and in the thoracic duct, a few coloured
blood-corpuscles have been found. The lymph-corpuscles are supplied to the lymph
and chyle from the lymphatic glands and the adenoid tissue. As to their source —
see § 200, 2. They also pass out of the blood-vessels and wander into the
lymphatics. As red blood-corpuscles have also been seen to pass out of the blood-
vessels, this explains the occasional presence of these corpuscles in some lymphatics;
but when the pressure within the veins is high, near the central orifice of the
thoracic duct, red blood-corpuscles may pass into the thoracic duct. But we are
not entitled to conclude from their pressure that lymph-cells form red blood-
corpuscles. In addition, the chyle contains numerous fatty granules, each sur-
rounded with an albuminous envelope. [Thus the chyle, in addition to the con-
stituents of the lymph, contains, especially during digestion, a very large amount
of fat, in the form of the finely-emulsionised fat of the food, which gives it its
characteristic white or milky appearance. During hunger, the fluid in the lae-
teals resembles ordinary lymph. ‘The fine fat-granules constitute the so-called
“‘ molecular basis ”’ of the chyle. | . . Soe

COMPOSITION OF LYMPH AND CHYLE. 307

Composition of Lymph.—The lymph consists of lymph-plasma with lymph-
corpuscles suspended in it. The corpuscles or leucocytes are described in § 24.
The lymph-plasma contains the three so-called fibrin-factors, derived very probably
from the breaking up of lymph-corpuscles (§ 29). When lymph is withdrawn
from the body, these substances cause it to coagulate. Coagulation occurs slowly,
owing to the formation of a soft, jelly-like, small ‘‘lymph-elot,” which contains
most of the lymph-corpuscles. The exuded fluid or lymph-serum contains alkalc-
albuminate (precipitated by acids), serwm-albumin (coagulated by heat), and para-
globulin—the two latter occurring in the same proportion as in blood-serum ; 37
per cent. of the coagulable proteids is paraglobulin.

(1) Chyle, which occurs within the lacteals of the intestinal tract, can only be
obtained in very small amount before it is mixed with lymph, and hence the difti-
culty of investigating it. A few lymph-corpuscles occur even in the origin of lacteals
within the villi, but their number increases in the vessels beyond the intestine,
more especially after the chyle has passed through the mesenteric glands. The
amount of solids, which undergoes a great increase during digestion, on the
contrary, diminishes when chyle mixes with lymph. After a diet rich in fatty
matters, the chyle contains innumerable fatty granules (2-4 win size). [This is the
so-called “molecular basis” of the chyle.] The amount of jibrin-factors increases
with the increase of lymph-corpuscles, as they are formed from the breaking up of
the phn corpuscles ; a diastatic ferment absorbed from the intestine ; occasionally
ee (to 2 per cent. ); ; after much starchy food, lactates ; peptone in the leucocytes
(§ 192, L., 3), and traces of urea and leucin.

The Chyle of a person who was executed contained 90°5 per cent. of water.

( Fibrin, trace
| Albumin, ; igs |
Solids, . : ; Pa hee ue
| Extractives, 1°0
USalts, Z Orn
Schmidt found the following inorganic substances in 1000 pats of dive
Sodic chloride, < -DSt Sulphuric acid, . 0°05 Magnesic phosphate, 0°05
Soda, ; : ae ee Phosphoric acid, = 005 Iron, : ; . trace,
Potash, , mm Os Calcic phosphate, . 0°20 (Horse).

(2) The lymph obtained from the beginning of the lymphatic system contains
very few lymph-corpuscles ; it is clear, transparent, and colourless, and closely
resembles the fluids of serous cavities. That the lymph coming from different
tissues varies somewhat, is highly probable, but this has not been proved. After
lymph has passed through lymphatic glands, it contains more corpuscles, and also
more solids, especially albumin and fat. Ritter counted 8200 lymph-corpuscles in
1 cubic centimetre of the lymph of a dog.

Pure lymph obtained from a lymphatic fistula in the leg of aman has an alkaline
reaction and a saline taste, and the following composition :—.

Pure Lymph : Cerebro-spinal Fluid Pericardial Fluid
(Hensen & Déhnhardt), (Hoppe-Seyler). | (v. Gorup-Besanez).

Water, . ; . » 98°63 98°74 95°51
Boda Cg Sg? 1°25 | 4°48
Fibrin, . : Car O'll ay 0°08
Albumin, : : : 0°14 0°16 2°46
Alkali-albuminate, . : 0 09 a ui
Extractives, . ; ; ae fs reas 1°26
Urea, hencin, ‘ . ‘ 1°05 The-cerebro-spinal fluid and ab-

Salts, : 0°88 dominal lymph contain a kind of

70 vol. °/, of absorbed CO,, 50 °/, sugar (without the property of

could be pumped out, and 20 */, by rotating polarised light—Hoppe-

the ee of an acid, Seyler).

308 QUANTITY OF LYMPH AND CHYLE.

100 parts of the ash of lymph contained the following substances :—

Sodium chloride, . 74°48 Lime, . ’ . 0°98 Sulphuric acid, ~ Tas
Soda, . : . 10°36 Magnesia, . » - O27 Carbonie acid, . < OSE
Potash, . rt ee 26 Phosphoric acid, . 1°09 Iron oxide, ; . 0°06

Just as in blood, potash and phosphoric acid are most abundant in the
corpuscles ; while soda (chiefly sodium chloride) is most abundant in the lymph-
serum. The potash and phosphoric acid compounds are most abundant in cerebro-
spinal fluid, according to C, Schmidt. The amount of water in the lymph rises
and falls with that of the blood. Gases.—Dog’s lymph contains much CO,—more
than 40 vols. per cent., of which 17 per cent. can be pumped out, and 23 per cent.
expelled by acids, while there are only traces of O and 1:2 vols. per cent, N
(Ludwig, Hammersten).

[The cerebro-spinal fluid contains a substance which reduces an alkaline solution of cupric
hydrate. The potassic are in excess of the soda-salts, while the fluid of meningoceles and chronic
hydrocephalus contains proto-albumose, some serum-globulin, no serum-albumin, but the last

is present in acute hydrocephalus fluid. No albumose is found in pericardial or pleuritic fluids
(Halliburton). ]

199. QUANTITY OF LYMPH AND CHYLE.—When it is stated that the
total amount of the lymph and chyle passing through the large vessels in twenty-
four hours is equal to the amount of the blood, it must be remembered that this is
merely a conjecture. Of this amount one-half may be lymph and the other half
chyle. The formation of lymph in the tissues takes place continually, and without
interruption. Nearly 6 kilos. of lymph were collected in twenty-four hours from a
lymphatic fistula in the arm of a woman, by Gubler and Quevenne ; 70 to 100
grms. were collected in 14 to 2 hours from the large lymph-trunk in the neck of a
young horse. The following conditions affect the amount of chyle and lymph :—

(1) The amount of chyle undergoes very considerable increase during digestion,
more especially after a full meal, so that the lacteals of the mesentery and intestine
are distended with white or milky chyle. During hunger the lymph-vessels are
collapsed, so that it is difficult to see the large trunks.

(2) The amount of lymph increases especially with the activity of the organ
from which it proceeds. Active or passive muscular movements greatly increase
its amount. Lesser obtained in this way 300 cubic centimetres of lymph from a
fasting dog, whereby its blood became so inspissated as to cause death.

(3) All conditions which increase the pressure upon the juices of the tissues
increase the amount of lymph, and vice vers, These conditions are :—

(a) An increase of the blood-pressure, not only in the whole vascular system, but also in the
vessels of the corresponding organ, augments the amount of lymph and vice versd (Ludwig,
Tomsa). This however is doubtful, as has been shown by Paschutin and Emminghaus, [In
order to increase the amount of lymph depending upon pressure within the vessels, what
must happen is increased pressure within the capillaries and veins. ]

(b) Ligature or obstruction of the efferent veins greatly increases the amount of lymph which
flows from the corresponding parts (Bidder, Emminghaus). It may be doubled in amount.
Tight bandages cause a swelling of the parts on the peripheral side of the bandage, owing to a
copious effusion of lymph into the tissue (congestive cedema),

(c) An increased supply of arterial blood acts in the same way, but to a less degree,
Paralysis of the vaso-motor nerves, or stimulation of vaso-dilator fibres, by increasing the supply
of blood increases the amount of lymph; while diminution of the blood-supply, owing) to —
stimulation of vaso-motor fibres or other causes, diminishes the amount. Even after ligature
of both carotids, as the head is still supplied with blood by the vertebrals, the lymph-stream in
the large cervical lymphatic does not cease.

(4) When the total amount of the blood is increased, by the injection of blood or serum
into the arteries, much fluid passes into the tissues and increases the formation of lymph.

(5) The formation of lymph still goes on fora short time after death, and after complete
cessation of the action of the heart, but only to a slight extent. If fresh blood be caused to
circulate in the body of an animal, while it is still warm, more lymph flows from the lym-
phatics. It appears as if the tissues obtained plasma from the blood for a time after the
stoppage of the circulation. This perhaps explains the circumstance that some tissues, ¢.g.,

a

ORIGIN OF LYMPH. 309

connective-tissues, contain more fluid after death than during life, while the blood-vessels have
given out a considerable amount of their plasma after death. :

(6) The amount of lymph is increased under the influence of curara, and so is the amount
of solids in the lymph (Lesser). A large amount of lymph collects in the lymph-sacs [especially
the sub-lingual] of trogs poisoned with curara, which is partly explained by the fact that the
lymph-hearts are paralysed by curara. The amount of lymph is also increased in inflamed
parts,

200. ORIGIN OF LYMPH.—(1) Source of the Lymph-Plasma.—The
lymph-plasma may be regarded as fluid which has been pressed through the walls
of the blood-vessels by the blood-pressure, 2.e., by filtration into the tissues. The
salts which pass most readily through membranes, go through nearly in the same
proportion as they exist in blood-plasma—the jibrin-factors to about two-thirds, and
albumin to about one-half of that in the blood. As in the case of other filtration-
processes, the amount of lymph must increase with increasing pressure.

This was proved by Ludwig and Tomsa, who found that when they passed blood-serum under
varying pressures through the blood-vessels of an excised testis, the amount of transnded fluid
which flowed from the lymphatics varied with the pressure. This “ artificial-lymph” had a
composition similar to that of the natural lymph. Even the amount of albumin increased with
increasing pressure. The lymph-plasma is mixed in the different tissues with the decomposition
products, the results of the metabolism of the tissues.

When the muscles act, not only is the lymph. poured out more rapidly, but
more lymph is formed. The tendons and fasciz of the muscles of the skeleton,
which are provided with numerous small stomata, absorb the lymph from the
muscles. By the alternate contraction and relaxation of these fibrous structures,
they act like suction-pumps, whereby the lymphatics are alternately filled and
emptied, while the lymph is propelled onwards. Even passive-movements act in
the same way. If solutions be injected under the fascia lata, they may be propelled
onwards to the thoracic duct by passive movements of the limb (Ludwig, Schweigger-
Seidel).

(2) The source of the lymph-corpuscles varies.—(1) A very considerable
number of lymph-corpuscles are derived from the lymphatic glands ; they are
washed out of these glands into the vas efferens by the lymph-stream, hence, the
lymph always contains more corpuscles after it has passed through a lymph-gland.
Small isolated lymph-follicles permit corpuscles to pass through their limiting layer
into the lymph-stream. (2) Those organs whose basis consists of adenoid tissue,
and in whose meshes numerous lymph-corpuscles occur, e.g., the mucous membrane
of the entire intestinal tract, red marrow of bone, and the spleen (§ 103). The

cells reach the origin of the lymph-stream by their own amceboid movements. (3)

As lymph-corpuscles are returned to the blood-stream, where they appear as colour-
less blood-corpuscles, so they again pass out of the blood-capillaries into the
tissues, partly owing to their amceboid movements, and they are partly expelled
by the blood-pressure. In rare cases lymph-corpuscles wander from lymphatic
spaces back again into the blood-vessels,

Fine particles of cinnabar or milk-globules introduced into the blood soon pass into the lym-
phatics. The extrusion of particles is greater during venous congestion than when the circula-
tion is undisturbed, just as with diapedesis (§ 95); inflammatory affections of the vascular wall
also favour their passage. The vessels of the portal system are especially pervious.

(4) By division of the lymph-corpuscles, and also by proliferation of the fixed
connective-tissue corpuscles. This process certainly occurs during inflammation
of many organs. This has been proved for the excised cornea kept in a moist
chamber ; the nuclei of the cornea-corpuscles also proliferate.

That the connective-tissue corpuscles proliferate is shown by the enormous production of |
lymph-corpuscles in acute inflammations (with the formation of pus), ¢.g., in extensive erysipelas,
and inflammatory purulent effusions into serous cavities, where the number of corpuscles is
too great to be explained by the wandering of blood-corpuscles out of the blood-vessels.

Decay of Lymph-Corpuscles.—The lymph-corpuscles disappear partly where the

330° sC*=«@w MOVEMENT OF CHYLE AND LYMPH.

lymphatics arise. The presence of the fibrin-factors in the lymph—formed as they’
are from the breaking-up of lymph-corpuscles—seems to indicate this. In inflam-
mation of connective-tissue, in addition to the formation of numerous new lymph-
corpuscles, a considerable number seems to be dissolved; hence the lymph, and
also the blood, in this case.contains more fibrin.. Lymph-corpuscles are also dis-
solved within the blood-stream, and help to form the fibrin-factors. |

201. MOVEMENT OF CHYLE AND LYMPH.—The ultimate cause of the
movement of the chyle and lymph depends upon the difference of the pressure at
the origin of the lymphatics, and the pressure where the thoracic duct opens into
the venous system.

(1) The forces which are active at the origin of the lymphatics are concerned
in moving the lymph, but these must vary according to the place of origin—(a)
The lacteals receive the first impulse towards the movements of their contents—.
the chyle—from the contraction of the muscular fibres of the villi (pp. 292, 297).
When these contract and shorten, the axial lacteal is compressed, and its contents
are forced in a centripetal direction towards the large lymphatic trunks. When the
villi relax, the numerous valves prevent the return of the chyle into the villi. (0)
Within those lymphatics which take the form of perivascular spaces, every time the
contained b/ood-vessel is dilated the surrounding lymph will be pressed onwards. (c)
In the case of the pleural lymphatics with open mouths, every inspiratory move-
ment acts like a suction-pump upon the lymph, and the same is the case with
the openings or stomata of the lymphatics on the abdominal side of the diaphragm.
(d) In the case of those vessels which begin by means of fine juice canals, the move-
ment of the lymph must largely depend upon the tension of the juices of
the parenchyma, and
] this again must depend

upon the tension or
pressure in the blood-
= capillaries, so that the
blood-pressure acts like
a vis a tergo in the
Fig. 223. rootlets of the lym-

Section of central tendon of diaphragm. The injected lymph-spaces, phatics.

hand h, are black. At / the walls of the space have collapsed. [In some organs peculiar
yumping arrangements are brought into action. The abdominal surface of the central tendon
of the diaphragm is provided with stomata, or open communications between the peritoneal

cavity and the lym-
z= phatics in the sub-
=¥ stance of the tendon.
Von Recklinghausen
» found that milk put .
upon the peritoneal
i surface of the central
tendon showed little
eddies, caused by the
milk-globules passing
through the stomata
me and entering the lym-

; phatics. The central
: Fig. 224. A tendon consists of
Injected lymph-spaces (black) from the fascia lata of the dog. two layers of fibrous
tissue arranged in different directions (fig. 223, b, c). When the diaphragm moves during
respiration, these layers are alternately pressed together and pulled apart. Thus the spaces
are alternately dilated and contracted, lymph being drawn into the lymphatics through the
stomata (fig. 223, /). The same kind of pumping mechanism exists over the costal pleura.
The fascia covering the muscles is another similar mechanism. The fascia consists of two layers
of fibrous tissue, with intervening lymphatics (fig. 224). When a muscle contracts, lymph is
forced out from between the layers of the fascia, while when it relaxes, the lymph from the

> MY. Y — GY}

Y WU

;

Y “y ex W/, 2a

My

MOVEMENT OF THE LYMPH. Sif

muscle, carrying with it some of the waste products of muscular action, passes out of the
muscle into the fascia, between the now partially separated layers. ]

[Ludwig’s Experiment.—Tie a respiration cannula in the trachea of a dead rabbit ; cut
across the body of the animal immediately below the diaphragm; remove the viscera, and
ligature the vessels passing between the thorax and abdomen; tie the thorax to an iron ring,
and hang it up with the head downwards; pour a solution of Berlin blue upon the peritoneal
surface of the diaphragm; connect the respiration cannula either with a pair of bellows or an
apparatus for artificial respiration, and imitate the respiratory movements. After a few
minutes the lymphatics are filled with a blue injection showing a beautiful plexus. ]

(2) Within the lymph-trunks themselves, the independent contraction of their
muscular fibres partly aids the lymph-stream. Heller observed in the mesentery
of the guinea-pig that the peristaltic movement of the lymphatic wall passed in a
centripetal direction. The numerous valves prevent any reflux. The contraction
of the surrounding muscles, and pressure upon the vessels and the tissues, aid the
current. If the outflow of blood from the veins is interfered with, lymph flows
copiously from the corresponding tissues. [If a cannula be tied in a lymphatic of
a dog, a few drops of lymph flow out at long intervals. But if even passzve move-
ments of the limb be made, e.g., simply flexing and extending the limb} the outflow
becomes very considerable and continuous. |

(3) The lymph-glands, which occur in the course of the lymphatics, offer very
considerable resistance to the lymph-stream, which must pass through the lymph-
paths, whose spaces are traversed by adenoid tissue, and contain a few lymph-
‘corpuscles. But this is, toa certain extent, compensated for by the non-striped muscle
which exists in the capsule and trabecule of the glands. When they contract they
force on the lymph, while the valves prevent its reflux. Enlarged lymphatic
glands have been seen to contract when stimulated electrically. [Botkin has
stimulated enlarged lymphatic glands with electricity in cases of leukeemia. |

(4) The lymph-vessels gradually join to form larger vessels, and finally end in
one trunk. ‘Thus the sectional area diminishes, so that the velocity of the current
and the pressure are increased. Nevertheless, the velocity is always small; it
varied from 230 to 300 millimetres per minute in the large lymphatic in the neck
of a horse, a fact which enables us to conclude that the movement must be very
slow in small vessels. The lateral pressure at the same place was 10 to 20 mm.,
and in the dog 5 to 10 mm. of a weak solution of soda, although it was=12 mm.
Hg in the thoracic duct of a horse.

(5) The respiratory movements exercise a considerable influence upon the lymph-
stream in the thoracic duct, and in the right lymphatic duct ; every inspiration
favours the passage of the venous blood, and | 3
also of the lymph towards the heart, whereby |
the tension in the thoracic duct may even be- |
come negative. [The dvastolic suction of the \
heart, by diminishing the pressure in the sub- 4
clavian vein, also favours the inflow of lymph

‘into the thorax. | a
(6) Lymph-hearts exist in certain cold-blooded —~_
animals. ‘The frog has two axillary hearts (above the
shoulder near the vertebral column), and two sacra/
hearts, one on each side of the coccyx near the anus ©
(fig. 225, L). They beat, but not synchronously, about
sixty rae a ae oe ee ns hate deen
metres 0 mph. ‘They have transversely-striped mus- * ‘
cular ra ia dbeir walls and are also pened with Posterior pair of lymph-hearts (L) of
nerve-ganglia. The posterior pair pump the lymph the frog.
into the branch of the vena iliaca communicans, and the anterior pair into the vena sub-
scapularis. Their pulsation depends partly, but not exclusively, upon the spinal cord, for if
the cord be rapidly destroyed, they may cease to pulsate, but not unfrequently they continue
to pulsate after removal of the cord. [And if the cord be destroyed gradually, they continue to
beat (Kabrhel).| A second source of their pulsatile movements is to be sought for in

312 ABSORPTION OF PARENCHYMATOUS EFFUSIONS.

Waldeyer’s ganglia. Stimulation of the skin, intestine, or blood-heart influences them reflexly “49
—partly accelerating and partly retarding them, [most frequently arresting them in diastole,
so that there seems to be an inhibitory mechanism in the cord, but it is not affected by
atropine (Kabrhel).] If the coccygeal nerve, which connects the sacral hearts to the spinal
cord, be divided, these effects do not occur. Strychnia accelerates their movements, and so
does heating of the spinal cord; but if the cord be cooled, they are retarded, A lymph-heart
arrested by being exposed, or after the action of muscarin, can be caused to beat by filling it
under pressure, but this is not the case when the arrest is caused by destruction of its nerves.
Antiarin paralyses the lymph-heart and the blood-heart at the same time, while cwrara
paralyses the former alone. se other amphibians. there are two lymph-hearts ; in the ostrich
and cassowary and some swimming birds, and in the embryo chick 1 or 2, They occur in some
fishes, ¢.g., near the caudal vein of the eel. .
(7) The nervous system has a direct effect upon the lymph-stream, on account
of its connection with the muscles of the lymphatics and lymph-glands, and with
the lymph-hearts where these exist. Kiihne observed that the cornea corpuscles
contracted when the corneal nerves were stimulated, [and Hoffman has described the
termination of nerves in connective-tissue corpuscles]. Goltz also observed that,
when a dilute solution of common salt was injected under the skin of a frog, it was
rapidly absorbed, but if the central nervous system had been destroyed, it was not

absorbed.

If inflammation be produced in the hind legs of a dog, and if the sciatic nerve be divided on
one side, cedema and a simultaneous increase of the lymph-stream occur on that side. [A
combination of congestion and inflammation greatly increases the lymph-stream, and this is
still more the case when the nerves are divided at the same time. ]

Ligature the leg of a frog, except the nerves, so as to arrest the circulation, and place the
leg in water ; it swells up very rapidly, but a dead limb does not swell up. So that absorption
is independent of the continuance of the circulation, Section of the sciatic nerve, or
destruction of the spinal cord (but not section of the brain), arrests absorption.

202. ABSORPTION OF PARENCHYMATOUS‘EFFUSIONS.—Fluids which pass from the ~
blood-vessels into the spaces in the tissues, or those injected subcutaneously, are absorbed
chiefly by the blood-vessels, but also by the lymphatics. Small particles, as after tattooing
with cinnabar or China ink, may pass from the tissue-spaces into the lymphatics—and so do
blood-corpuscles from extravasations of blood, and fat-granules from the marrow of a broken
bone. If all the lymphatics of a part are ligatured, absorption takes place quite as rapidly as
before; hence, absorbed fluid must pass through the thin membranes of the blood-vessels. The
corresponding experiment of ligaturing all the blood-vessels, when no absorption of the paren-
ehymatous juices takes place, does not prove that the lymphatics are not concerned in absorp-
tion, for, after ligaturing the blood-vessels of a part, of course the formation of lymph,
and also the lymph-stream, must cease. When fluids are injected under the skin, absorption
takes place very rapidly—more rapidly than when the substance is given by the mouth. The
subcutaneous injection of drugs is extensively used, but of course the substances used must
not corrode, irritate, or coagulate the tissues. Some substances do not act when given by
the mouth, as snake poison, poisons from dead bodies, or putrid things, although they act
rapidly when introduced subcutaneously. If emulsin be given by the month, and amygdalin
be injected into the veins of an animal, hydrocyanic acid is not formed, as the emulsin seems
to be destroyed in the alimentary canal. If the emulsin, however, be injected into the blood,
and the amygdalin be given by the mouth, the animal is rapidly poisoned, owing to the forma-
tion of hydrocyanic acid, as the amygdalin is rapidly absorbed from the intestinal canal. The
amygdalin, a eee (CyoH,,NO,,), is acted upon by fresh emulsin like a ferment ; it takes+
up 2(H,O) and yields hydrocyanic acid (CHN), + oil of bitter almonds (C;H,0), + 8
2(C,H,.0,). Serum injected subcutaneously is rapidly absorbed; it is decomposed within the
blood-stream, and increases the amount of urea. Albuminous solutions, oil, peptones, and
sugars are also absorbed. ;

203, EDEMA, DROPSY, AND SEROUS EFFUSIONS,—[Dropsy.—As aptly illustrated —
by Lauder Brunton, the lymph-spaces may be represented by cisterns, each of which is —
provided with supply Pipes te arteries and capillaries; while there are two exit pi r

n the —

ee

veins and lymphatics. health, the balance between the inflow and outflow is such that
jee are merely moistened with fluid. When a cannula is placed in a lymphatic vessel in a

og, only a few drops of lymph flow out at long intervals, but if the veins of the limb be ligatured, —
the lymph flows much more quickly. This is in part due to the increased transudation of flui
from the small blood-vessels, but it may also be due to fluid passing away by the lymph
when it can no longer be carried away by the veins. We cannot say what is the relative sha
of the. veins and the lymphatics, nor in the above experiment do we know how much is due +

‘

(EDEMA AND DROPSY. ar 3

increased transudation or diminished absorption. When there is an undue accumulation of
fluid more or less like serum in the lymph-spaces, we have the condition termed dropsy. When
._ there is general dropsy it is called anasarca. ]

(Edema.—lIf the efferent veins and lymphatics of an organ be ligatured, or if resistance be
offered to the outflow of their contents, congestion and a copious transudation of lymph into
the tissue take place. These are most marked in the skin and subcutaneous cellular tissue.
The soft parts swell up, without pain or redness, and a doughy swelling, which pits on pressure
with the finger, results. These are the signs of lymph-congestion, which is called cedema
when the fluid is watery and localised.

Under similar circumstances lymph is effused in the serous cavities. [In the peritoneum it
is ascites—thorax, hydro-thorax—pericardium, hydro-pericardium—cranium, hydrocephalus
—tunica vaginalis, hydrocele—joints, hydrarthrosis, &c.] If, at the same time, a large
number of colourless blood-corpuscles pass out of the blood-vessels into the cavity, the fluid
becomes more and more like pus. In order that these corpuscles may proliferate, a consider-
able percentage of albumin is necessary. When the pressure within the serous cavity rises
above that in the small blood-vessels, water may pass into the blood. These sero-purulent
effusions not unfrequently undergo changes, and yield decomposition-products, such as
leucin, tyrosin, xanthin, kreatin, kreatinin (?), uric acid (?), urea. Endothelium from the
serous cavity, sugar in pleuritic effusions and in cedemas with little albumin, cholesterin
frequently in hydrocele fluid, and succinic acid in the fluid of echinococci have all been found
in these effusions. The effusion of lymph may arise not only froin pressure upon the lym-
phatics, but also from inflammation and thrombosis of the lymphatics themselves, in which
cases not unfreyuently new lymphatics are formed, so that the communication is re-established.
Sometimes the ductus thoracicus bursts, and lymph is poured directly into the abdomen or
thorax. [Ligature of the thoracic duct results in rupture of the receptaculum chyli and escape
of chyle and lymph into the large serous cavities (Ludwig). ]

When dropsy or effusion of fluids occurs into serous cavities, there is always a greater
transudation of fluid through the blood-vessels. The abdominal blood-vessels, and those which
yield a watery effusion under normal circumstances, are those most liable to be affected.

Transudation is favoured by—(1) Venous congestion, so as to raise the blood-pressure, in
which case the effusion usually contains little albumin and few lymph-corpuscles, while the
coloured corpuscles, on the contrary, are more numerous the greater the venous obstruction.
Ranvier produced cedema artificially by ligaturing the vena cava in a dog, and at the same time
dividing the sciatic nerve. The paralytic dilatation of the blood-vessels thereby produced
caused an increased amount of blood to pass to the limb, while the blood-pressure was raised,
and both factors favoured the transudation of fluid. [Ranvier’s experiment proves that mere
ligature of the venous trunk of a limb by itself is not sufficient to cause oedema. The cedema
is due to the concomitant paralysis of the vaso-motor nerves. If the motor roots of the sciatic
nerve alone be divided along with ligature of the vena cava, no cedema occurs, but if the vaso-
motor fibres are divided at the same time, the limb rapidly becomes cedematous. There is such
an increased transudation through the vascular walls that the veins and lymphatics cannot
remove it with sufficient rapidity, and cedema occurs. If there be weakness of the vaso-motor
nerves, slight obstruction is sufficient to produce cedema.] When the leg-veins are occluded
with an injection of gypsum, cedema occurs. (2) Some unknown physical changes occur in the
protoplasm of the endothelium of the capillaries and blood-vessels, which favour the transudation
of albumin, hemoglobin, and even blood-corpuscles. This occurs when abnormal substances
accumulate in the blood—e.g., dissolved hemoglobin—and when the blood contains little O or
albumin. The same has been observed after exposure to too high temperatures, and the swelling
of soft parts in the neighbourhood of an inflammatory focus seems due to the transudation of fluid
through the altered vascular wall. It is probable that a nervous influence may affect particular
areas through its action on the blood-vessels of the part (it may be upon the protoplasm of the
blood-capillaries). The transudations of this nature usually contain much albumin and many
lymph-corpuscles. (3) When the blood contains a very large amount of water, the tendency to
transudation of fluid is increased. After a time it may produce the changes indicated in (2),
and when long continued may increase the permeability of the vascular wall. Watery lym-
phatic effusions from watery blood—* cachectic oedema ”—occur in feeble and badly-nourished
individuals. [One of the commonest forms of dropsy is the slight cedema of the legs in anemic
persons, in whom the heart and lungs are healthy. Many factors are involved—the blood-
pressure, watery condition of the blood, the condition of nutrition of the capillaries, and
probably a tendency to vaso-motor paresis (Brunton). ]

_ [The fluid poured out varies according to the rapidity with which this occurs. In acute
inflammations éffusion or exudation takes place rapidly, and the fluid contains the fibrin-factors,
so that it tends to coagulate spontaneously. There is every gradation between the non-coagulable
hydrocele fluid and the coagulable exudation in inflammation. The fluids in different dropsies
vary in composition, and some have more cells in them, depending on local causes, as in some
Situations absorption is more active than in others. The pleural fluid contains most solids,
then ascitic, cerebro-spinal, and lastly that in the subcutaneous tissue. Transudation cor-

314 COMPARATIVE AND HISTORICAL.

responds to the process of filtration through animal membranes, 7.e., the transudation contains
only those substances already present in the blood-plasma. The filtrate may even contain
more salts than the original fluid, as is often the case with fluids containing crystalloid and
colloid bodies. Senator finds, in cases of cedema of the leg, that increase of the venous
pressure increases the proteids in the transudation, but causes no essential change in the
amount of the salts. ]

[(4) Ostroumoff found that stimulation of the lingual nerve not only causes the blood-vessels
of the tongue to dilate, but that the corresponding side of the tongue becomes cedematous. Ifa
solution of dilute hydrochloric acid or quinine (§ 145) be injected into the duct of the sub-
maxillary gland, and the chorda tympani stimulated, there is no secretion of saliva, but the
gland becomes cedematous. In an animal poisoned with atropin, stimulation of the chorda
causes dilatation of the blood-vessels, although there is no secretion of saliva, nevertheless the
gland does not become cedematous (Heidenhain). As Brunton suggests, this experiment 7
to some action of atropin on the blood-vessels which has hitherto been entirely overlooked. }

9204. COMPARATIVE PHYSIOLOGY. —In the frog large lymph-sacs, lined with endothe-
lium, exist under the skin, while large lymph-sacs lie in relation with the vertebral column.
—one on each side—separated from the abdominal cavity by a thin membrane, perforated with
stomata. This is the cysterna lymphatica magna of Panizza. Some amphibians and many
reptiles have under the skin large lymph-spaces, which occupy the whole of the dorsal region
of the body. All a eee and the tailed amphibians have large elongated reservoirs for lymph
along the course of the aorta. The lymph-apparatus of the tortoise (fig. 218) is very extensive.
The osseous fishes have in the lateral parts of their backs an elongated lymph-trunk, which
reaches from the tail to the anterior fins, and is connected with the dilated lymphatic rootlets
in the base of the tail and in the fins. The largest internal lymph-sinus is in the region of the
cesophagus. Many birds possess a sinus-like dilatation or lymph-space in the region of the
tail. The lymph-spaces communicate with the venous system—with valves properly arranged—
usually in connection with the upper vena cava. Lymph-hearts have already been referred to
($ 201, 6). In carnivora the lymph-glands of the mesentery are united into one large compact
mass, the so-called ‘‘ pancreas Asellii.”

205. HISTORICAL.—Although the Hippocratic School was acquainted with the lymph-
glands from their becoming swollen from time to time, and although Herophilus and
Erasistratus had seen the mesenteric glands, yet Aselli (1662) was the first who accurately
described the lacteals of the mesentery with their valves. Pecquet (1648) discovered the
receptaculum chyli; Rudbeck and Thom. Bartholinus the lymphatic vessels (1650-52) ;
Eustachius (1563) was acquainted with the thoracic duct, which Gassendus (1654) maintained
that he was the first to see; Lister noticed that the chyle became blue when indigo was injected
into the intestine (1671) ; Sbmmering observed the separation of fibrin when lymph coagulated ;
Reuss and Emmert discovered the lymph-corpuscles. The chemical investigations date from
the first quarter of this century ; they were carried out by Lassaigne, Tiedemann, Gmelin, and
others. The two last-named observers noticed that the white colour of chyle was due to the
presence of fatty granules.

Physiology of Animal Heat.

2.06. SOURCES OF HEAT.—The heat of the body is an uninterrupted
evolution of kinetic energy, which we must represent to ourselves as due to
vibrations of the corporeal atoms. The ultimate source of the heat is contained in
the potential energy taken into the body with the food, and with the O of the air
absorbed during respiration. The
amount of heat formed depends upon LE
the amount of energy liberated. ae

The energy of the food-stufis may
be called “latent heat,” if we
assume that when they are used up
in the body, chiefly by a process of
combustion, kinetic energy is liber-
ated only in the form of heat. Asa
matter of fact, however, mechanical
energy and electrical energy are de-
veloped from the potential energy.
In order to obtain a unit-measure for
the energy liberated, it is advisable
to express all the potential energy
as heat-units.

The Calorimeter.—This instru- N
ment enables us to transform the
potential energy of the food into heat,
and, at the same time, to measure
the number of heat-units produced.

Favre and Silbermann used a water- N
calorimeter (fig. 226). The substance to
be burned is placed in a large cylindrical
combustion-chamber (K), suspended in a ————
large cylindrical vessel (L) filled with 1 :
water (w), so that the combustion-chamber ————
is completely surrounded by the water. =
Three tubes open into the upper part of Hig. 226.
the chamber; one of them (Q) supplies Water-calorimeter of Favre and Silbermann.
the air which is necessary for combustion,
it reaches almost to the bottom of the chamiber ; the second (a) is fixed in the middle of the
lid, and is closed above with a thick glass plate, and on this is placed, at an angle, a small
mirror (s), which enables an observer to look into the chamber, and observe the process of
combustion atc. The third tube (d) is used only when combustible gases are to be burned in
the chamber. It can be closed by means of a stop-cock. A lead tube (¢, ¢), with many
twists, passes from the upper part of the chamber through the water, and finally opens at g.

tii

tA

ll
tl

316 CALORIMETRY.

The gaseous products of combustion pass out through this tube, and in doing so help to heat —
the sp he cylindrical vessel with the water is closed with a lid which transmits the four
tubes. The water-cylinder stands on four feet within a large cylinder (M), which is filled with
some good non-conducter of heat, and this again is placed in a large vessel filled with water
(W). This is to prevent any heat sere the inner cylinder from without. A weighed quan-
tity of thé substance (c) to be investigated is placed in the combustion-chamber. hen com-
bustion is ended, during which the inner water must be repeatedly stirred, the temperature of
the water is ascertained by means of a delicate thermometer. If the increase of the tempera-
ture and the amount of water are known, then it is easy to calculate the number of heat-units
produced by the combustion of a known weight of the substance (see Introduction).
The ice-calorimeter may also be used. ‘The inner cylinder is filled with ice and not with
water, and ice is also placed in the outer cylinder to prevent any heat from without from
; at j acting upon the inner ice. The heat
pT z given off from the combustion-chamber
causes a certain amount of the ice to
melt, and the water thereby produced
is collected and measured. It requires
79 heat-units to melt 1 grm. of ice tol
erm. of water at 0° C.
[The amount of heat produced by a
|

living animal is similarly measured.
The animal (fig. 227), in a cage, is
placed in a large vessel, which is placed
within another vessel, and the inter- A
space filled with water. The whole |
should be enclosed in a large box packed
with fur, shavings, feathers, or other
bad conductor of heat. A tube, D, :
opens into the inner space, and from
yy it there is an exit-tube, D, which winds )
many times in the water-space beneath. |
z N Air passes in through D and out by :
Water-calorimeter of Dulong. D’. The temperature of the water is -
ascertained hy thermometers T and T’, while the water is moved by a stirrer (S) placed between
the two. ] ;

Just as in a calorimeter, although mach more slowly, the food-stuffs within our
body are burned up, oxygen being supplied, and thus potential energy is trans-
formed into kinetic energy, which, in the case of a person at rest, almost completely
appears in the form of heat.

Heat-Units.—Favre, Silbermann, Frankland, Rechenberg, B. Danilewsky, and others have

made calorimetric experiments on the heat produced by food. According to Danilewsky, 1
gramme of the following dry substances yields heat-units :—

Casein, . . 5855 Palmitin, . 8883 Cow’s milk, 5733 | Maize, . . 5188
Fibrin, . - 6772 | Olein, . 8958 Woman’s _ Alcohol, . 6980
Peptone, . 4876 Stearin, . 9036 milk, . 4837 | Urea, . . 25387
Glutin, . . 5493 Ox-fat, . 9686 Egg-yelk, . 4479 Muscle
Ox-blood, . 5900 Glycerine, . 4179 Potatoes, . 4284 Extractives | 4400
Ox-flesh, . 5724 | Starch, . 4479 Rye-bread, 4471 (Liebig’s)
Vegetable Dextrose, . 3939 Wheat-bread, 4351 Flesh extract, 3216
fibrin, . 6231 | Maltose, . 4163 Rice, . . 4806 Acetic acid, . 3318
Glutin, . . 6141 | Milk-sugar, 4162 Peas, . . 4889 | Butyric acid, 5647

Legumin, . 5573 Cane-sugar, 4173 Buck-wheat, 4288 | Palmitic acid, 9316

As albumin is only oxidised to the stage of urea, we must deduct the heat-units obtainable
from urea froin those of albumin, and as 1 part of albumin yields in round numbers about § of
urea, we obtain about 5100 calories [= 2170 kilogram-metres] for 1 grm. of albumin. +

lynamic foods, i.e., those that produce an equal amount of heat; 100 grms. animal
albumin (after deducting the heat-units of urea)=52 fat=114 starch=129 dextrose; 100 —
grms. fat are isodynamic with 243 dry flesh or 225 of dry syntonin (Rubner); 100 grms. of
vegetable albumin=55 fat=121 starch =137 .dextrose (Danilewsky). Rubner calculated that —
in man, with a mixed diet, the available heat-units for 1 grm. of albumin=4100; 1 grin.
fat = 9300 ; and for 1 grm. carbohydrate = 4100 calories. zl

When we know the weight of any of the above-named substances consumed by a
man in twenty-four hours, a simple calculation enables us to determine how

CHEMICAL SOURCES OF HEAT. 317

heat-units are formed in the body by oxidation, 2.e., provided the substance is com-
pletely oxidised.

[Several sources of heat-production or thermogenesis are to be found in all
tissues wherever oxidation is going on. The metabolism of protoplasm is always
associated with the evolution of heat. ]

(1) Ln the transformation of the chemical constituents of the food, endowed with a

large amount of potential energy, into such substances us have little or no energy.
The organic substances used as food consist of C, H, O, N, so that there takes
place—(a) Combustion of C into CO,, of H into H,O, whereby heat is produced ;
1 grm. C burned to produce CO, yields 8080 heat-units, while 1 grm. H oxidised
to H,O yields 34,460 heat-units. The O necessary for these purposes is absorbed
during respiration, so that, to a certain extent at least, the amount of heat produced
may be estimated from the amount of O consumed. The same consumption of O
gives rise to the same amount of heat whether it is used to oxidise H or C
(Pfliiger). There is a relation, amounting to cause and effect, between the amount
of heat produced in the body and the O consumed. The cold-blooded animals,
which consume little O, have .a low temperature ; amongst warm-blooded animals,
1 kilo. of a living rabbit takes up within an hour 0°914 grm. O, and its body is
heated to a mean of 38° C. 1 kilo. of a living fowl uses 1°186 grms. O, and gives a
mean temperature of 43°9° C. The amount of heat produced is the same whether
the combustion occurs slowly or quickly; the rapidity of the metabolism, therefore,
affects the rapidity, but not the absolute amount of heat-production. The com-
bustion of inorganic substances in the body, e.g., of the sulphur into sulphuric acid,
the phosphorus into phosphoric acid, is another, although very small, source of
heat. .
[The muscles form about the half of the whole mass of the body and the bones
nearly the other half. In the latter, oxidation does not go on actively, so that the
muscles must be the great seats of heat-production or thermogenesis in the body.
This view is supported by the fact that the blood leaving a muscle at rest contains
more CO, than the blood in the right ventricle. Muscular exercise greatly
increases the metabolism and the CO, excreted (§ 127), but at the same time, there
is a great increase in heat-production. The muscles, therefore, are the great ther-
mogenic tissues, and they yield {ths of the heat in health. The several secreting
glands, especially the liver and the alimentary canal, during digestion, are also foci
of heat-formation. |

(6) In addition to the processes of combustion or oxidation, all those chemical
processes in our body, by which the amount of the available potential energy
which is present is diminished, in consequence of a greater satisfaction of atomic
affinities, lead to the production of heat. In all cases where the atoms assume more
stable positions with their affinities satisfied, chemical energy passes into kinetic
thermal energy, as in the alcoholic fermentation of grape-sugar, and other similar
processes. :

Heat is also developed during the following chemical processes : —

(a) During the union of bases with acids. The nature of the base determines the amount of
heat produced, while the nature of the acid is without effect, Only in those cases where the
acid, ‘¢.g., CO,, is unable to set aside the alkaline reaction, the amount of heat produced is less,
The formation of compounds of chlorine (¢.g., in the stomach) produces heat.

(8) When a neutral salt is changed into a basic one. In the blood the sulphuric and
poo horic acids derived from the combustion of S and P are united with the alkalies of the

lood to form basic salts, The decomposition of the carbonates of the blood by lactic and
phosphoric acids forms a double source of leat, on the one hand, by the formation of a new

salt, and, on the other, by the liberation of CO,, which is partly absorbed by the blood.
_ (y) The combination of hemoglobin with O (§ 36).

During those chemical processes, whereby the heat of the body is produced,
heat-absorbing intermediate compounds are not unfrequently formed. Thus, in

318 HOMOIOTHERMAL AND POIKILOTHERMAL ANIMALS,

order that the final stage of more complete saturation of the affinities be reached, :
intermediary atomic groups are formed, whereby heat is absorbed. Heat is also
absorbed when the solid aggregate condition is dissolved during retrogressive
processes. But these intermediary processes, whereby heat is lost, are very
small compared with the amount of heat liberated when the end-products are
formed. |

(2) Certain physical processes are a second source of heat.—(a) The trans-
formation of the kinetic mechanical energy of internal organs, when the work
done is not transferred outside the body, produces heat. Thus the whole of the
kinetic energy of the heart is changed into heat, owing to the resistance opposed to
the blood-stream ($93). The same is true of the mechanical energy evolved by
many muscular viscera. The torsion of the costal cartilages, the friction of the
current of air in the respiratory organs, and the ingesta in the digestive tract, all
yield heat. |

An excessively minute amount of the mechanical energy of the heart is transferred to
surrounding bodies by the cardiac impulse and the superficial pulse-beats, but this is infini-
tesimally small. During respiration, when the respiratory gases and other substances are
expired, a very small amount of energy disappears externally, which does not become changed
into heat. If we assume that the daily work of the circulation exceeds 86,000 kilogram-metres, |
the heat evolved is equal to 204,000 calories, in twenty-four hours (§ 93), which is sufficient to |
raise the temperature of a person of medium size 2° C.

(b) When, owing to muscular activity, the body produces work which is trans-
ferred to external objects, e.g., when a man ascends a tower or mountain, or throws ;
a heavy weight, a portion of the kinetic energy passes into heat, owing to friction
of the muscles, tendons, and the articular surfaces, as well as to the shock and
pressure of the ends of the bones against each other. |

(c) The electrical currents which occur in muscles, nerves, and glands very ;
probably are changed into heat. The chemical processes which produce heat evolve
electricity, which is also changed into heat. This source of heat, however, is very
small,

(d) Other processes are the formation of heat from the absorption of CO,, by the concentration
of water as it passes through membranes, in cmbibition, and the formation of the solids, e.g., of
chalk in the bones. After death, aud in some pathological processes during life, the coagula-
tion of blood and the production of rigor mortis are sources of heat. ;

207. HOMOIOTHERMAL AND POIKILOTHERMAL ANIMALS.—In
place of the old classification of animals into “ cold-blooded ” and “‘ warm-blooded,”
another basis of classification seems desirable, viz., the relation of the temperature
of the body to the temperature of the surrounding medium. Bergmann introduced
the word homoiothermal for the warm-blooded animals (mammals and birds),
because these animals can maintain a.very uniform temperature, even although the
surrounding temperature be subject to considerable variations. The so-called cold-
blooded animals are called poikilothermal, because the temperature of their
bodies rises or falls, within wide limits, with the heat of the surrounding medium, —

When homoiothermal animals are kept for a long time ina cold medium, their
heat-production is increased, and when they are kept for a long time in a warm
medium it is diminished. (

Fordyce gave a proof of the nearly uniform temperature in man. A man remained ‘ten
minutes in an oven containing very dry hot air (§ 218), and yet the temperature of the palm
of his hand, mouth, and urine was increased only a few tenths of a degree. Becquerel and
Brechet investigated the temperature of the human biceps (by means of thermo-electrie
needles), when the arm had been one hour in iced water, and yet the temperature of the
muscular tissue was cooled only 0°2° C. The same muscle did not undergo any increase in

temperature, or at most 0°2° C., when the man’s arm was placed for a quarter of an hour in’
water at 42° C, :

If heat be rapidly abstracted (§ 225) or rapidly supplied (§ 221) to the: body, .
so as to produce rapid variation of the temperature, life is endangered. © =

THERMOMETRY. 319

Poikilothermal animals behave very differently; the temperature of their
bodies generally follows, although with considerable variations, the temperature of
the surroundings. When the temperature of the surroundings is increased, the
amount of heat produced is increased, and when the surrounding temperature falls,
the amount of heat evolved within the body also falls.

The following table shows very clearly the characters of poikilothermal animals, ¢.g., frogs, :
which were placed in air and water of varying temperatures. They were immersed up to the
mouth. The temperature was measured by means of a thermometer introduced through the
mouth into the stomach.

In Water. In Air.
Temperature of the Temperature of Frog’s Temperature of the Temperature of Frog’s
Water. Stomach. Air. Stomach,
Wh Uap @- 38°0° C, 40°4° C 0 ay fae
30°0 29°6 27°4 1%
20°6 20°7 16°4 14°6
59 8°0 6°2 76
2°8 5°3 5°9 8°6
[Temperature of Different Animals,
Birds, Temp. Temp.
Temp. Swallow, od 40005 Panther, . : . 38°90
Thalassidroma, . 40°30 Gull, . é s Ors Mouse, . : Bs tl |
Procellaria, : . 40°80 Mammals, Dolphin, . ; a. BOO
Goose, . : Pee lag’ 8) Tiger; ; . 37°20 j 37 °30-40°00
TER enG ( 39°08 Horse, . . 36°80-37 °50 Sheep, ... 39°50-40°00
SPATE OW a8 aaN0. 4 CRat, es, 8e8O | 40-00-40-50
Pigeon, . . 41°80-42°50 Hare, . : . 37°80 Ape, : ; . 85°50
Turkey, . : . 42°70 Cat, . . 38°30-38°90 Guinea-pig, 35°76-38 00
Guinea-fowl, . . 43°90 Guinea-pig, . . 38°80 Rabbit, . . 37°50-38°00
Buck 43°90 37°40 Ox. ; , - 87°50
: * ( 42°50 Dog, . : . § 89°00 Ass, : ‘ - 86°95
Crow, A ; . 41°17 39°60 (Gavarret & Rosenthal). ]

°

Reptiles—Snakes, 10°-12°, but higher when incubating. Amphibians and fishes—0°5°-3
above the temperature of the surroundings. A7thropoda—0°i°-5'8° above the surroundings.
Bees in a hive, 30°-32°, and when swarming, 40°. The following animals have a temperature
higher than the surrounding temperature :—-Cephalopods, 0°57°; molluscs, 0°46°; echinoderms,
0°40°; medusz, 0°27°; polyps, 0°21° C.

208. ESTIMATION OF TEMPERATURE.—By using thermometric apparatus, we are
enabled to obtain information regarding the degree of heat of the body to be investigated. For
this purpose the following methods are employed :—

A. The Thermometer.—Celsius (1701-1744) divided his thermometer into 100 parts, and

each part was again divided into 10 parts, so that 34° C. could be easily read off. All thermo-
meters which have been used for a long time give too high readings, hence they should be com-
pared, from time to time, with a normal thermometer. When taking the temperature, the
bulb ought to be surrounded for fifteen minutes, and during the last five minutes the mercury
column ought not to vary. <A very sensitive thermometer will indicate the temperature after
seven seconds if the urine stream be directed upon its bulb. Minimal and maximal thermo-
meters are often of use to the physician. :
. [Clinically, one of the thermometers shown in fig. 228 may be used. They are self-registering
maximum thermometers, 7.¢., a portion of the mercury is-separated from the mercurial column,
to form the index, the top of which indicates the temperature. Before being used, the index
eet be well below the normal temperature. Various forms of surface thermometers have been
used. ] ‘ ro

Walferdin’s metastatic thermometer (fig. 229) is specially useful for comparative observation.
The tube is very narrow in comparison with the bulb, and in order that the stem be not too
long, it is constructed so that the amount of mercury can be varied: A quantity of mercury is
taken, so that with the temperature expected the thread of mercury will stand about the middle
of the stem. A small bulb at the upper part of the stem receives the excess of Hg. Suppose a
temperature between 37°--40° C, is to be measured, the bulb is first heated a little over 40° C.,

320 THERMO-ELECTRIC MEASUREMENT OF HEAT, s

it i 1 1. and shaken at the same time, so that the thread of mercury is
it is then suddenly cooled, and shake , thereby aaitenl? ae
ll ada i above 40°. The tube is so.
narrow that 1° C, is equal

WON] Lai Male fad ares r AA Bl | pa)
: 5 ooo

C

pail}

Fig. 228.
A, Cassella’s ‘‘infallible,” B, “ Ferris’ perfect,” and C, Evans’ and Wormull’s ‘‘standard”
clinical thermometers.

|

to about 10 centimetres of the length of the tube, so that ;4,° C. is still 1 millimetre in
—_| length, The scale is divided empirically, but the value of the divisions must be com.
pared with a normal ther-
mometer.

Kronecker and Meyer
used very small maximal
‘‘outflow thermometers,”
and caused them to pass
through the intestinal
canal, or through large
blood-vessels. The mer-
cury flows out of the short
open tube, and of course
more flows out the higher
the temperature. After
these small bulbs have
passed through the animal,
a comparison is instituted |
with a normal thermo-
meter, to determine at what -
temperature the mercury
reaches the free. margin of
the tube.

B. Thermo-electric Me-
thod.—This method en-
ables us to determine the
temperature accurately and
rapidly (fig. 230, I). The
thermo-electric galvano-
meter of Meissner and
Meyerstein consists of a
circular magnet (m), sus-
pended by a thread of silk
(c), to which a_ small
mirror (S) is attached. A
large stationary bar mag-
net (M) is placed. near the
magnet (m), so that the
north poles (x and N) of
both magnets point in the
same direction, and it is so
arranged that the sus-
pended magnet is caused
to point to the north by a

Fig, 229, ieee action of a ts

sn? , thick copper wire (6, 5) is
bidwriose ly Fig, 230. coiled ioves times round

gt eran Scheme of thermo-electric arrangements for —_m (although in the fig. it
meter. estimating the temperature, is represented as a single
coil), and the ends of the

wire are soldered to two thermo-elements, each composed of two different metals—iron :

THERMO-ELECTRIC NEEDLES. 321

German silver, the two similar free elements being united by a wire (,), so that the
two thermo-elements form part of a closed circuit. A horizontal scale (K, K) is placed at
a distance of 3 metres from the mirror, so that the divisions of the scale are seen in the
mirror. The scale itself rests upon a telescope (F) directed towards the mirror. The
observer (B), who looks through the telescope, can see the divisions of the scale in the
mirror. When the magnet, and with it the mirror, swing out of the magnetic meridian, the
observer notices other divisions of the scale in the mirror. When one of the thermo-elements
is heated, an electrical current is produced, which passes from the iron to the German silver in
the heated couple, and causes a deviation of the suspended magnet. Suppose a person were
swimming in the direction of the current in the conducting wire, then the north pole of the
magnet goes to the north (Ampére). The tangent of the angle ¢, through which the freely
movable magnet is diverted by a galvanic current, from its position of rest or zero, in the
magnetic meridian, is the same as the galvanic stream; G is proportional to the magnetic

energy D, 7.¢., tang. o=5 . IfG is to remain the same, and the tang. ¢ to be as large as pos-

sible, the magnetic energy must be diminished as much as possible. If the magnetism of the
suspended magnet be indicated by m, and that of the earth by T, the magnetic directing energy
D=Twm, so that D can be distinguished in two ways: (1) by diminishing the magnetic moment
of the suspended magnet, as may be done by using a pair of astatic needles, such as are used in
Nobili’s galvanometer ; (2) and also by weakening the magnetism of the earth, by placing an
accessory stationary magnet (Hauy’s rod) in the same direction, and near the suspended magnet.
An important arrangement for rapidly getting the magnet to zero is the dead-beat arrangement
of Gauss (not figured in the scheme). It consists of a thick copper cylinder, on which the wire
of the coil is wound. This mass of copper may be regarded as a closed multiplicator with a
very large transverse section. The vibrating magnet induces in this closed circuit a current
of electricity, whose intensity is greatest when the velocity of the excursion of the magnet is
greatest, and which takes the opposite direction as soon as the magnet returns towards zero.
These induced currents cause a diminution of the vibrations of the magnet in this way, that the
are of vibration of the magnet diminishes very rapidly, almost in a geometrical progression.
The induced damping-current is stronger, the less the resistance in the closed circuit, and in
the damper or dead-beat arrangement itself, the greater the section of the copper ring. This
damping arrangement limits the oscillations of the magnet, and it comes to rest rapidly and
promptly after 3 or 4 small vibrations, so that much time is saved. The angle of deviation is
so small that the angle itself may be: taken instead of the tangent.

The thermo-electric needles of Dutrochet (II) may be placed in the circuit. They consist
of iron and German silver soldered at their points; or the needles of Becquerel (III) may be
used. They consist of the same metals soldered in a straight line, one behind the other. The
needles must always be covered by a varnish, which will prevent the parenchymatous juices
from acting upon them, and so causing a current. Before the experiment we must determine
what extent of excursion on the scale is obtained with a certain temperature. In order to
determine this, a delicate thermometer is fixed to each of the thermo-couples, and both are
placed in oil baths, which differ in temperature—say by 1° C.—as can be determined by the
thermometer. When the current is closed, the excursion on the scale will indicate 1° C.
Suppose that the excursion was 150 mm., then each mm. of the scale would be equal to 745° C.
When this is determined, the two thermo-needles may be placed in the different tissues or
organs of animals, and, of course, we obtain the difference of temperature in these places.
Or one thermo-couple may be placed in a bath of constant temperature (nearly that of the
body), in which is placed a delicate thermometer, while the other needle is introduced into
the organ to be investigated. In this case, we obtain the difference of temperature between
the tissue and the source of the constant heat. The electric current passes in the warmer
needle from the iron to the German silver, and thus through the wires of the apparatus.
For small differences of temperature, such as occur in the body, the. thermo-electric energy
is always proportional to the difference of temperature of the two needles or couples. In
place of a single pair of needles several may be used, whereby the sensitiveness of the apparatus
is greatly increased. Helmholtz found that by using sixteen antimony-bismuth couples, he
could detect an increase of ga455° C. Schiffer prepared a simple thermopile (IV) by solderin
together alternately four pairs of wires of iron (f) and German silver (a). These are alstad
in the two organs (A and B) which are to be investigated, whereby a very high degree of
exactness is obtained.

209. TEMPERATURE TOPOGRAPHY.—Although the blood, in virtue of
its continual motion (completing, as it does, the circulation in twenty-three seconds),
must exercise a very considerable influence on the equilibration of the temperature
in different organs, nevertheless, a completely uniform temperature does not exist,
and the temperature varies in different parts :—

X

322 TEMPERATURE TOPOGRAPHY.

1. Skin (J. Davy). Bae,
Middle of x sole of the foot, 32°26°C.| Middle of upper arm, . K 35°40° C,

Near tendo Achillis, . . 38°85 . | Inguinalfold, .. +, + \, 35780 i
Anterior surface of leg, . 33°05 Near cardiac impulse, . ‘ 34°40 -
Middle of calf, . : . 83°85 Face, . . é ; ‘: 31°00 @
Bend of knee, . 35°00 Nose and tip of ear, : ‘ 22°24

In the closed axilla, 36°49 (mean, of 505 individuals) ;—36°5 to 37°25 ( Wwnderlich) ;—36°89° C, .

(Liebermeister). The skin over muscles is warmer than that over bone (Kunkel). (

The temperature of the skin of the head is higher in the forehead and parietal region than in

tle occipital region; the skin on the left side of the head is warmer than on the right.
Dyspneea increases the temperature of the skin.

“Method. —Liebermeister determines the temperature of free cutaneous surfaces thus :—The
bulb of the thermometer is heated slightly above the temperature expected ; after the mercury
legins to fall, the bulb is placed on the skin, and if the bulb has the same temperature as the
skin, the mercury remains stationary. This experiment must be repeated several times.

2. Cavities.
Mouth under the tongue, . 37°19°C. | Vagina, . ; ; ; ; 38°30° C,
Rectum, . : : . 88°01 Urine, . ; , ? ‘ 37°03

Uterine cavity somewhat warmer ; cervical canal of the uterus somewhat cooler.

The temperature falls in the stomach during digestion (§ 166, 1). Cold injec-
tions (11° C.) into the rectum rapidly lower the temperature in the stomach 1° C.
( Winternitz). .
3. The temperature of the blood is, as a mean, 39° C. The venous blood in
internal viscera is warmer than the arterial, but it is cooler in peripheral parts :—

Blood of the right heart, ’ : 38°8° Blood of the superior vena cava, . 36°78° .
‘ left heart, . ; ; 38°6 4 inferior vena cava, . 38°11 |

oe aorta, : : : 38°7 a crural vein, . : 37°20 p

J hepatic vein, : : 39°7 (Cl. Bernard, and v. Liebig.)

The lower temperature of the blood in the left heart may be explained by the blood becoming .

cooled in its passage through the lungs during respiration. According to Heidenhain and
Korner, the right heart is slightly warmer because it lies in relation with the warm liver, whilst
the left heart is surrounded by the lung, which contains air. This observation is disputed by
others, who say that the left heart is slightly warmer because the combustion-processes are
more active in arterial blood, and heat is evolved during the formation of oxyhemoglobin. The
blood in the veins is usually cooler than in the corresponding arteries, owing to the superficial
position of the former, whereby they give off heat during their long course ; thus the blood of the
jugular vein is 4 to 2° C. lower than the blood in the carotid ; the crural vein 3 to 1° cooler than
in the crural artery. Superficial veins, more especially those of the skin, give off much heat,
and their blood is, therefore, somewhat cooler. The warmest blood is that of the hepatic vein,
39°7° C., partly owing to the great chemical changes which occur within the liver, from its
secretory activity (§ 210, a), and partly to its protected situation.

4. The individual tissues are warmer: (1) the greater the transformation of
kinetic energy into heat, ¢.¢, the greater the tissue-metabolism ; (2) the more blood
they contain ; (3) and the more protected their situation. According to Heidenhain
and Korner, the cerebrum is the warmest organ in the body.

Subcutaneous tissue (sheep), 37°35° C. Rectum, . : : ‘ 40°67° C.

Brain, . 40-25 | Rightheart, . . . 41°60
Liver, ‘ ; - 41°25 | Left heart, . ; ° 40°90
Lungs, . ; é : 41°40 ( Berger.)

Becquerel and Brechet found the temperature of the human subcutaneous tissue to be 2°1° ©,
lower than that of the neighbouring muscles. The horny tissues do not produce heat, and
their low temperature is due to the conduction of heat from the parts on which they grow. The
gape of the cornea partly depends on that of the iris, and the more contracted the pupil —
is, the more heat it receives from the blood-vessels of the iris. : ac

210, CONDITIONS AFFECTING THE TEMPERATURE OF ORGANS,— —
The temperature of the individual organs is by no means constant ; it is infl de
by many conditions ; amongst these are the following :— | 2% Seat
(1) The more heat produced independently within a part, the higher is its tempera:
ture. As the amount of heat produced within a part depends upon its metabolism,

enc

TEMPERATURE OF ORGANS. 323

therefore, when the metabolism is increased, the amount of heat produced is

similarly increased. ,
(a) Glands produce more heat during the act of secretion, as is proved by the

higher temperature of their secretion, or by the higher temperature of the venous

blood flowing out of their veins,

Ludwig found that when he stimulated the chorda tympani, the saliva of the submaxillary
gland was 1°5° C. warmer than the blood in the carotid, which supplied the gland with blood
(p. 213). The blood in the renal vein in a kidney which is secreting is warmer than the blood
in the renal artery. The secreting liver produces much heat (§ 178). Cl. Bernard investigated
the temperature of the blood of the portal and hepatic veins during hunger, at the beginning
of digestion, and when digestion was most active, and he found :— ,

Temperature of portal vein, : 27°8° C. After 4 days } Blood of right heart,
4 hepatic vein, .. 38°4 starvation. 38°8°
(Hunger period. )
Temperature of portal vein, ‘ 39°9 ) Beginning of
a hepatic vein, 39°5 ( digestion.
Temperature of portal vein, ; 39°7 ) Digestion most Blood of right heart,
5 hepatic vein, ; 41°3 active. during digestion, 39°2°.

In the dog a moderate diet, chemical or mechanical stimulation of the gastric mucous mem-
brane, or even the sight of food, raises the temperature in the stomach and intestine.

(6) When the muscles contract, they evolve heat. Davy. found that an active
muscle became 0°7° C. warmer ; while Becquerel, by means of a thermo-galvano-
meter, found that human muscles, when kept contracted for five minutes, became
1° C. warmer (§ 302). 7

This is one of the reasons why the temperature may rise above 40° during rapid running.
A temperature obtained by energetic muscular action usually does not fall to the normal until
after resting for 14 hour. The low temperature of paralysed limbs depends partly upon the
absence of the muscular contractions.

(c) With regard to the effect of sensory nerves upon the temperature, some of
the chief points to ascertain are—whether the corculation is accelerated or retarded
by their stimulation, or whether the respiration is increased or diminished (§ 214,
II., 3), and whether the muscles of the skeleton are relaxed or contracted reflexly
(§ 214, 1.,3). In the former case the temperature of the interior and rectum is in-
creased ; in the latter, diminished.

(d) The temperature of the body rises during mental exertion. Davy observed
an increase of 0°3° C. after vigorous mental exertion.

(e) The parenchymatous fluids, serous fluids, and lymph produce little heat,
owing to their feeble metabolism, hence they have the same temperature as their
surroundings ; the epidermal and horny tissues do not produce heat, they merely
conduct it from subjacent structures.

(2) The temperature depends, to a large extent, upon the amount of blood in an
organ, and also upon the rapidity with which the blood is renewed by the circula-
tion. This is best observed in the difference of the temperature between a cold,
pale, bloodless hand, and a warm, red, congested one.

Becquerel and Brechet found that the temperature of the human biceps fell several tenths of

_a degree, when the axillary artery was compressed. Ligature of the crural artery and vein in
a dog causes a fall of several degrees. If the extremities be kept suspended in the air, they
become bloodless and cold.

_ Liebermeister has pointed out a difference with regard to the external and internal parts of
the body. The external parts give off more heat than they, produce, so that they become cooler
the more slowly new blood flows into them, and warmer the greater the rapidity of the blood-
stream through them. Acceleration of the blood-stream, therefore, causes the temperature of
peripheral parts to approximate more and more to the temperature of internal organs, while
retardation of the blood-stream causes them to approach the temperature of the surrounding
medium. Exactly the reverse is the case with internal parts, where a large amount of heat is
produced, and heat is given up almost alone to the blood which flows through them. Their
temperature must fall when the blood-stream through them is accelerated, and it is raised when

the blood-stream is retarded. Hence it follows, that the greater the difference of the temperature
between peripheral and internal purts, the slower must be the velocity of the circulation.

324 ESTIMATION OF HEAT.

(3) If the position of an organ be such, or if other conditions cause it to give
off heat by conduction or radiation, then its temperature falls.

A good example of this is the skin, which varies greatly in temperature according to the
temperature of the surrounding medium, whether it is covered or uncovered, whether it is dr.
or moist with sweat (which abstracts heat when it evaporates). When much cold food or drin
is taken, the stomach is cooled, and when ice-cold air is breathed, the respiratory passages
as far as the bronchi are cooled.

211. ESTIMATION OF HEAT.—Calorimetry is the method of determining
the amount of heat possessed by any body, or what amount of heat it is capable of
producing. The unit of measurement is the “ heat-unit,” 2.¢., the amount of heat
(or potential energy) required to raise the temperature of 1 gramme of water 1° C.
(see Jntroduction).

Experiment has shown that equal quantitics of different substances require very unequal
amounts of heat to raise them to the same temperature, e.g., 1 kilo. water requires nine times as
much heat as 1 kilo. iron to raise it to the same temperature. In the human body, therefore,
which is composed of very different substances, unequal amounts of heat will be required to
raise them all to the same Coes. The same amount of heat transferred to two different
substances will raise them to different temperatures. Hence, bodies of different temperatures
may contain equal amounts of heat. The amount of heat required to raise a definite quantity
(e.g., 1 grm.) of a substance to a certain higher degree (e.g., 1° C.) is called ‘‘ specific heat.”
The specific heat of water (which of all bodies has the highest specific heat) is taken as=1.
By ‘‘ heat-capacity”’ is meant, that property of bodies in virtue of which they must absorb a
given amount of heat in order to have a certain temperature.

Calorimetry is employed :—I. To determine the specific heat of the different organs
of the body.—Only a few observations have been made. The mean specific heat
of the following animal parts (water = 1) is :—

Human blood = 1:02 (?) Human muscle = 0°741 | Fat tissue = 0°712
Arterial blood = 1:°031 (7) Ox muscle = 0°787 Striped muscle = 0°825
Venous blood = 0°892 (?) Compact bone = 0°3 Defibrinated blood = 0°927
Cow’s milk = 0°'992 Spongy bone = 071 (J. Rosenthal. )

The specific heat of the human body, as a whole, is about that of an equal volume |
of water (?). .

Kopp’s Method. — The solid to be investigated is broken in pieces about the size of a pea, and r
placed in a test-tube, A, with thin walls, which is closed above with a cork, from which a
copper wire with a hook on it projects (fig.
231). The test-tube contains a certain
quantity of fluid which does not dissolve
the substance, but which lies between its
pieces and covers it. It is weighed three
times to ascertain the weight (1) of the
empty glass, (2) after it is filled with the

"a solid substance, (3) after the fluid is added,
"© = (a) so that we obtain the weight of the solid

substance, m, and that of the fluid, 7.
The test-tube and its contents are placed.
in a mercury bath, BB, and this again in
an oil bath, CC, and the whole is raised
toa high temperature. Into BB there is
introduced a fine thermometer, T. When
the tube, A, has reached the necessary tem-
perature (say 40°) it is rapidly placed in
the water of the accompanying calori-
meter-box, DD. The water in this box,
ae also contains : it las canpeall

Fo nent peere, . ept in motion until it has completely

Kopp’s apparatus for estimating specific heat. sPoxbed all the heat given off by Avuilaenin
T represent the temperature to which A and its contents were raised in the mercury bath, and —
T, the temperature to which it fell in the calorimeter ; let s be the specific heat, and m the
weight of the solid substance in the test-tube, while ¢ and u represent the specific heat of the —
weight of the interstitial fluid in the test-tube ; and lastly, let w equal the amount of water in
contact with A, which absorbs and gives off heat ; then W represents the amount of heat
which the test-tube and its contents give off during cooling. a

CALORIMETRY. 325

W=(s.m + wt+op)(T-T)).
The amount of heat, W,, absorbed by the calorimeter is
W\= M (t; a; t) ’
where M represents the amount of water in the calorimeter, ¢ the original temperature of the
water in the calorimeter, and ¢, the temperature to which it is raised by placing Ain it. If
W and W, are equal, then
| M(t, -t)-(w+o.u)(T—T,)
m(T —T,) ;
If a fluid substance is placed in the test-tube, and its weight = m, and its specific heat =
the formula for the specific heat of the fluid to be investigated is
_ M(¢,-t)-w(T-T,)
ear m (T-T;) j
II. Calorimetry is more important for determining the amount of heat produced
in a given time by the body as a whole, or by its individual parts.

Lavoisier and Laplace made the first calorimetric observations on animals in 1783, by means
of an ice-calorimeter ; a guinea-pig melted 13 oz. of ice in ten hours. Crawford, and afterwards
Dulong and Despretz, used Rumford’s water-calorimeter, which is similar to Favre and
Silbermann’s. Small animals are placed in the inner thin-walled copper chamber (K), which
is placed in a water-bath surrounded on all sides by some non-conducting material. We
require to know the amount of water, and its original temperature. The number of calories
is obtained from the increase of the temperature at the end of the experiment, which lasts
several hours. The air is supplied to the animal through a special apparatus, resembling a
gasometer. The amount of CO, in the gases evolved is estimated.

According to Despretz, a bitch forms 14,610 heat-units per hour—z.e., 393,000
in twenty-four hours. Other things being equal, a man seven times heavier than
this would produce in twenty-four hours about 2,750,000 calories. Senator found
that a dog weighing 6330 grms. produced 15,370 calories, and excreted at the same
time 367 grms. CO,. The first calorimetric experiments on man were made by
Scharling (1849). Liebermeister estimated the amount of heat given off by a man
placed in a cold bath, which was surrounded with a woollen covering. Leyden
_placed a lower limb in the calorimeter, whereby 6000 grms. water were raised 1°
C. in an hour. If we assume that the total superficial area of the body is fifteen
times greater than that of the leg, the human body would produce 2,376,000
calories in twenty-four hours.

212, THERMAL CONDUCTIVITY OF TISSUES.—The thermal conductivity of animal
tissues is of special interest in connection with the skin and subcutaneous fatty tissue. The
fatty layer under the skin, more especially in the whale, walrus, and seal, forms a protective
covering, whereby the conduction of heat from internal organs is rendered almost impossible.
Investigations upon this subject, however, are few. Griess attempted to estimate the thermal
conductivity by heating one part of the tissue, and determining when and in what direction
pieces of wax placed on the tissue to be investigated began to melt. He investigated the
stomach of the sheep, the bladder, skin, hoof, horn, and bones of an ox, deer’s horn, ivory,
mother-of-pearl, shell of haliotis. He found that fibrous tissues conducted heat more readily
in the direction of their fibres than at right angles to the course of the fibres. Hence, the
figures obtained from the melted wax were usually elliptical. Landois has made similar
observations, and he finds that tissues conduct better in the direction of their fibres. After
bones, blood-clot was the best conductor, then followed spleen, liver, cartilage, tendon, muscle,
elastic tissue, nail and hair, bloodless skin, gastric mucous membrane, washed fibrin. It is
specially interesting to note how much better skin containing blood in its blood-vessels
conducts than does bloodless skin. Hence little heat is given off from a bloodless skin, while
congested skin conducts and gives off much more heat.

Like all other substances, the human body i is enlarged by heat. A man weighing 60 kilos.,
and whose temperature is raised from 37° C. to 40° C. , is enlarged about 62 cubic centimetres.
Connective-tissue (tendon) is extended by heat, while elastic tissue and the skin, like caoutchouc,
are contracted.

913. VARIATIONS OF THE MEAN TEMPERATURE.—(1) General
Climatic and Somatic Influences.—In the tropics the mean temperature of the
body is about 4° C. higher than in temperate climates, where again it is several
tenths of a degree warmer than in cold climates; but this has recently been

the specific heat, s=

326 VARIATIONS OF TEMPERATURE.

, :
4

denied. The difference is comparatively trivial, when we remember that a man is
subjected to a variation of over 40° C. in passing from the equator to the poles.
Observations on more than 4000 persons show that when a person goes from a
warm to’a cold climate, his temperature is but slightly diminished, but when he
goes from a cold to a warm climate his temperature rises relatively considerably '
more, In the temperate zone, the temperature of the body during a cold winter is
usually 0°1° to 0°3° C. lower than it is on a warm summer day. The elevation of
a place above sea-level has no obvious effect on the temperature of the body.
There seems to be no difference in different races, nor in the SEXES, other conditions
being the same. Persons of powerful physique and constitution are said to have ©
generally a slightly higher temperature than feeble, weak, anemic persons. ;

(2) Influence of the General Metabolism.—As the formation of heat depends
upon the transformation of chemical compounds, whose chief final products, in —
addition to HO, are CO, and urea, the amount of heat formed must go par? passu
with the amount of these excreta. The more rapid metabolism which sets in after
a full meal causes a rise of temperature to several tenths of a degree (“ Digestion-
fever”). As the metabolism is much diminished during hunger, this explains why
the mean temperature in a fasting man is 36°6°,while it is 37°17° on ordinary days
(§ 237).

Jiirgensen also found that the temperature fell on the first day of inanition (although there
was a temporary rise on the second day). In experiments made upon starving animals, the
temperature at first fell rapidly, then remained constant for a considerable time, while during
the last days it fell considerably. Schmidt starved a cat—on the 15th day the temperature was
38°6°; on the 16th, 38°3°; 17th, 37°64°; 18th, 35°8°; 19th (death) =33°0°. Chossat found that
starving mammals and birds had a temperature 16° C. below normal on the day of their death.

(3) Age has a decided effect upon the temperature of the body. The extent of |
the general metabolism is in part an index of the heat of the body at different ages,
but it is possible that other, as yet unknown, influences are also active.

Age. a OM | Normal Limits. | Where Measured.
| Newly-born, 37°45° C, 37°35-37°56° C. Rectum.
5-9 year, | 37°72 36°87-37 62 Mouth and Rectum.
15-20 ,, | 37°37 36°12-38°1 Axilla.
21-30 ,, 37°22 Py e
25-30 ,, 36°91 es a
31-40 ,, | 37°1 36 '25-37 °5 ‘s
41-50 ,, 36°87 Bre Pe
| 51-60 _,, 36°83 a 54
80 ,, 37°46 te! Mouth.

Newly-born animals exhibit peculiarities owing to the sudden change in their
conditions of existence. Immediately after birth, the infant is 0°3° warmer than
the vagina of the mother, viz., 37°86°. A short time after birth, the temperature
falls 0-9°, while twelve to twenty-four hours afterwards, it has risen to the normal
temperature of an infant, which is 37°45°. Several irregular variations occur
during the first weeks of life. During sleep, the temperature of an infant falls
0°34° to 0°56", while continued crying may raise it several tenths of a degree,
Old people, on account of their feeble metabolism, produce little heat ; they —
become cold sooner, and hence ought to wear warm clothing to keep up their
temperature. vena

(4) Periodical Daily Variations.—In the course of twenty-four hours there are
regular periodic variations in the mean temperature, and these occur at all ages.
As a general rule, the temperature continues to rise during the day (maximum at
5 to § p.M.), while it continues to fall during the night (minimum 2 to 6 A.M.),
The mean temperature occurs at the third hour after breakfast. | 7

———

VARIATIONS OF TEMPERATURE. 327

The mean height of all the temperatures taken during a day in a patient is
called the “daily mean,” and according to Jaeger it is 37°13° in the rectum in

Fig. 232.
Variations of the daily temperature in health during twenty-four hours. L
after Liebermeister ; J——-—,, after Jiirgensen.

>

*)

health. A daily mean of more than 37°8° is a ‘‘ fever temperature,” while a mean

under 37:0° C. is regarded as a “collapse temperature.”

Time. Barensprung. J. Davy. | Hallmann. | Gierse. | Jiirgensen. | Jiigel
Morning, 5 ai | : 36°7 36°6 | 36:9
6] 36°68 ae is 36°7 36-4) 3771

7 a 36°94* 36°63 36°98 36°7* | 36°5* | 37°5*

8 | 937-16" ze 36°80* 87°08" | 36°8 36°7 | 37°4

9 36°89 if | 36°9 36°8 37°5

10| 37°26 i 10$—37°36 | 37°28 | 37°0 | 37-0 | 37°5

ll a 36°89 37 °2 Yi en a
Mid-day,12 | 36°87 ~ a 373" | 89:3") 87-5"
1] 36°83 a S791. |. B78. 4 ars 87°3 | 37-4

2 ’ 37°05 | 37-50" | 37-4 | 37-4 | 37-5

3.4) 37-15" me | 37°48 B74 | S738) a 7ah

4 37°17 | | 37-4 87°3 87-5"

5 | 37°48 37°05" | 54=37°31 37°43 37°5 37°5 37°5

6 wy 64=36°83 | i 37 29 37°5 376 37°4

7 | 87:43 74=36°50* , 87°31" 37°b* | 387°6* | 37:3

8 . > | ort Ba | ya

9| 37-02" | Re 87°4 | 387°5 | 36:9

10 a Zz ie | 87°29 37°3 37:4 36°8

11 | 36°85 36°72 36°70 | 36°81 37°2 37°1 36°8

Night, 12 kes =A | a | 37-1 36°9 36°9
36°65 36°44 | 37-0 36°9 369

2 i a 36°9 36°7 36°8

3 - o | io eT by Win 8088 36°7 36°7

4 |. 86°81 os | ~ | - | 36°7 36°7 36°7

As the variations occur when a person is starved for a day-—although those that occur at
the periods at which food ought to have been taken are less—it is obvious that the variations

are not due entirely to the taking of food. [The * indicatés taking of food. ]

The daily variation in the frequency of the pulse often coincides with variation of the
temperature. Birensprung found that the mid-day temperature maximum slightly preceded
the pulse maximum (§ 70, 3, C).

If we sleep during the day, and do all our daily duties during the night, the
above described typical course of the temperature is reversed. With regard to the
effect of activity or rest, it appears that the activity of the muscles during the day
tends to increase the mean temperature slightly, while at night the mean tempera-
ture is less than in the case of a person at rest.

328 REGULATION OF THE TEMPERATURE.

The peripheral parts of the body exhibit more or less regular variations of their, temperature.
In the palm of the hand, the progress of events is the following :—After a relatively high night
temperature there is a rapid fall at 6 A.M., which reaches its minimum at 9 to10 a.m. This is
followed by a slow rise, which reaches a high maximum after dinner; it falls between 1 to 3)
p.M., and.after two or three hours reaches a minimum. It rises from 6 to 8 P.M., and falls —
again towards morning. rapid fall of the temperature in a peripheral part corresponds to a —
rise of temperature in internal parts. | ;

(5) Many operations upon the body affect the temperature. After hemorrhage —
the temperature falls at first, but it rises again several tenths of a degree, and is —
usually accompanied by a shiver or slight rigor ; several days thereafter it falls to
normal, and may even fall somewhat below it. The sudden loss of a large amount
of blood causes a fall of the temperature of } to 2° C. Very long-continued ~
hemorrhage (dog) causes it to fall to 31° or 29° C.

This is obviously due to the diminution of the processes of oxidation in the anemic bodys
and to the enfeebled circulation. Similar conditions causing diminished metabolism effect the

same result. Continued stimulation of the peripheral end of the vagus, so that the heart's
action is enormously slowed, diminishes the temperature several degrees in rabbits (Landois

and Ammon), ;

The transfusion of a considerable quantity of blood raises the temperature
about half an hour after the operation. This gradually passes into a febrile attack,
which disappears within several hours. When blood is transfused from an artery
to a vein of the same animal, a similar result occurs (§ 102).

(6) Many poisons diminish the temperature, e.g., chloroform and the anzesthetics,
alcohol (§ 235), digitalis, quinine, aconitin, muscarin. These appear to act partly
by rendering the tissues less liable to undergo molecular transformations for the pro-
cluction of heat. In the case of the anesthetics, this effect perhaps occurs, and is
due possibly to a semi-coagulation of the nervous substance (7). They may also
act partly by influencing the giving off of heat (§ 214, II.). Other poisons
increase the temperature for opposite reasons.

The temperature is increased by strychnin, nicotin, pee veratrin, laudanin.

_(7) Various diseases diminish the temperature, which may be due either to lessened’ produe-
tion of heat (diminution of the metabolism), or to increased expenditure of heat. Loewenhardt
found that in paralytics and in insane persons, several weeks before their death, the rectal
temperature was 30° to 31° C., in diabetes 30° C. or less ; the lowest temperature observed and
life retained, in a drunk person was 24° C.

The temperature is increased in fever, and the highest point reached just before death, and
recorded by Wunderlich, was 44°65° C. (compare § 220).

214, REGULATION OF THE TEMPERATURE. —As the bodily temperature
of man and similar animals is nearly constant, notwithstanding great variations in
the temperature of their surroundings, it is clear that some mechanism must exist
in the body, whereby the heat economy is constantly regulated. This may be
brought about in two ways ; either by controlling the transformation of potential —
energy into heat, or by affecting the amount of heat given off according to the |
amount produced, or to the action of external agencies. |

[The constancy or thermostatic condition of the temperature is brought about by
three co-operant factors, the thermogenic or heat-producing, the thermolytic or
heat-discharging, and the thermotaxic or mechanism by which heat-production and
heat-loss are balanced, and it is obvious that the last must be in relation with the ~
other two. The thermotaxic mechanism is developed last, is least pronounced inthe —
ys Taam and is most easily liable to fail under injury or disease (Mac- ,

I. Regulatory Arrangements governing the Production of Heat.—Lieber- —
meister estimated the amount of heat produced by a healthy man at 1°8 calorie per |
minute. It is highly probable that, within the body,. there exist. mechanisms
which determine the molecular transformations, upon which the evolution of heat
depends. This is accomplished chiefly in areflexmanner. The peripheral ends of

REGULATION OF THE TEMPERATURE. 329

cutaneous nerves (by thermal stimulation), or the nerves of the intestine and the
digestive glands (by mechanical or chemical stimulation during digestion or inani-
tion), may be irritated, whereby impressions are conveyed to the heat-centre, which
sends out impulses through efferent fibres to the depdts of potential energy, either .
to increase or diminish the extent of the transformations occurring in them. The
nerve channels herein concerned are entirely unknown. Many considerations,
however, go to support such an hypothesis (§ 377).

[Thermotaxic Mechanism, Thermal Nerves and Centres.—Just as the respiration and the
state of the blood-vessels are regulated from a central focus, so the question arises, does the
same obtain with regard to temperature. Studying this question, however, it must be borne
in mind that thermometric observations alone are not sufficient ; the true test must be calori-
metric. Sir Benjamin Brodie observed that in a case of injury of the spinal cord in the neck
the temperature in the thigh rose very high. In some cases the temperature falls. Wood has
shown that section of cord above the origin of the splanchnics leads to decided increase in the
amount of heat dissipated, but to a decided diminution of heat-production. The vaso-motor
paralysis has much to do in these cases with the loss of heat. In warm-blooded animals,
exposed to a high temperature, the heat-production is diminished, but when they are exposed
to a low temperature it is increased. Ifa warm-blooded animal’s medulla oblongata be divided,
there is a fall of temperature, chiefly due to its vaso-motor paralysis, and such an animal behaves,
as regards the effect of heat and cold, exactly like a poikilothermal animal, 7.e., its metabolism
and heat-production are increased by cold and diminished by heat. If, however, the incision
be made above the pons, so as to leave the vaso-motor centre intact in the dog, there is a rise of
the temperature and increased heat-production for 24 hours afterwards. This suggests the idea
that this region is traversed by inhibitory nerves, so that when they are cut off from their centres
. situate above, the augmentor nerves can act more vigorously. This suggests the existence of
thermo-inhibitory centres situate higher up in the brain. If an animal be curarised, not only
is there paralysis of voluntary motor acts, but on stimulating an ordinary motor nerve, not
only is there no muscular contraction, but there is no rise of temperature of the muscles supplied
by that nerve. In such an animal the temperature rises and falls with the temperature of the
surrounding medium. Even although the respirations be kept constant and the vaso-motor
nerves intact, the thermogenic activity of muscles, therefore, seems to be dependent on their
innervation. ]

[Cerebral Centres.—Apart from the cortical heat centres (§ 377), Ott, Aronsohn, Sachs,
Richet and others have shown that if a needle be thrust through the skull and brain, so as
to injure certain deeper-seated parts, there is a rise of temperature and increased heat-produc-
tion for several hours. The experiment may be repeated several times in the same rabbit. Ott
gives three areas which, when so injured, cause these effects—(1) a part of the brain in the
median side of the corpus striatum, and near the nodus cursorius ; (2) a part between the corpus
striatum and the optic thalamus ; and (8) the anterior end of the optic thalamus itself. From
the effect of atropin, Ott suggests the existence of spinal centres as well. ]

The following phenomena indicate the existence of mechanisms regulating the
production of heat :— | 7

(1) The temporary application of moderate cold raises the bodily temperature,
while heat, similarly applied to the external surface, lowers it (§§ 222 and 224).

(2) Cooling of the surroundings increases the amount of CO, excreted, by in-
creasing the production of heat, while the O consumed is also increased simul-
taneously ; heating the surrounding medium diminishes the CO, (§ 127, 5).

D. Finkler found, from experiments upon guinea-pigs, that the production of heat was more
than doubled when the surrounding temperature was diminished 24° C. The metabolism of the
guinea-pig is increased in winter 23 per cent. as compared with summer, so that the same rela-
tion obtains as in the case of a diminution of the surrounding temperature of short duration.

C. Ludwig and Sanders-Ezn found that in a rabbit there was a rapid increase in the amount
of CO, given off, when the surroundings were cooled from.38° to 6° or 7° C.; while the excre-
tion was diminished when the surrounding temperature was raised from 4°-9° to 35°-37°, so
that the thermal stimulation, due to the temperature of the surrounding medium, acted upon
the combustion within the body. Pfliiger found that a rabbit which was dipped in cold water
used more O and excreted more CO,.

If the cooling action was so great as to reduce the bodily temperature to 30°, the exchange of
gases diminished, and where the temperature fell to 20°, the exchange of gases was diminished
one-half. It is to be remembered, however, that the excretion of CO, does not go hand in
hand with the formation of CO,. If mammals be placed in a warm bath, which is 2° to 3°
higher than their own temperature, the excretion of CO, and the consumption of O are increased,

7.

330 REGULATION OF THE TEMPERATURE.

owing to the stimulation of their metabolism, while the excretion of urea is also increased in—
animals and in man (§ 133, 5).

(3) Cold acting upon the skin causes involuntary muscular movements
(shivering, rigors), and also voluntary movements, both of which produce heat.

The cold excites the action of the muscles, which is connected with processes of oxidation
(Pfliiger). After poisoning with curara, which paralyses voluntary motion, this regulation of
the heat falls to a minimum (Réhrig and Zuntz), [while the bodily temperature rises and falls
with a rise or fall in the temperature of the surrounding medium],

(4) Variations in the temperature of the surroundings affect the appetite
for food : in winter, and in cold regions, the sensation of hunger and the appetite
for the fats, or such substances as yield much heat when they are oxidised, are
increased ; in summer, and in hot climates, they are diminished. Thus the mean
temperature of the surroundings, to a certain extent, determines the amount of the
heat-producing substances to be taken in the food.

II. Regulatory Mechanisms governing the Excretion of Heat or Thermolysis.
—The mean amount of heat given off by the human skin in twenty-four hours, by
a man weighing 82 kilos., is 2092 to 2592 calories, z.¢., 1°36 to 1°60 per minute.

(1) Heat causes dilatation of the cutaneous vessels ; the skin becomes red,
congested, and soft ; it contains more fluids, and becomes a better conductor of
heat ; the epithelium is moistened, and sweat appears upon the surface. Thus
increased excretion of heat is provided for, while the evaporation of the sweat also
abstracts heat.

The amount of heat necessary to convert into vapour 1 grm. of water at 100° C., is equal to
that required to heat 10 grms. from 0° to 53°67° C. The sweat as secreted is at the temperature
of the body; if it were completely changed into vapour, it would require the heat necessary to
raise it to the boiling point, and also that necessary to convert it into vapour.

Cold causes contraction of the cutaneous vessels ; the skin becomes pale, less
soft, poorer in juices, and collapsed; the epithelium becomes dry, and does not
permit fluids to pass through it to be evaporated, so that the excretion of heat is
diminished. The excretion of heat from the periphery, and the transverse thermal
conduction through the skin, are diminished by the contraction of the vessels and
muscles of the skin, and by the expulsion of the well-conducting blood from the
cutaneous and subcutaneous vessels. The cooling of the body is very much affected,
owing to the diminution of the cutaneous blood-stream, just as occurs when the
current through a coil or worm of a distillation apparatus is greatly diminished.
If the blood-vessels dilate, the temperature of the surface of the body rises, the
difference of temperature between it and the surrounding cooler medium is increased,
and thus the excretion of heat is increased. Tomsa has shown that the fibres of
the skin are so arranged anatomically, that the tension of the fibres produced by
the erector pili muscles causes a diminution in the thickness of the skin, this result
being bronght about at the expense of the easily expelled blood.

By the systematic application of stimuli, ¢.g., cold baths, and washing with cold water, the
muscles of the skin and its blood-vessels may be caused to contract, and become so vigorous and
excitable, that when cold is suddenly applied to the body, or toa part of it, the excretion of

heat is energetically prevented, so that cold baths and washing with cold water are, to a certain
extent, ‘‘ gymnastics of the cutaneous muscles,” which, under the above circumstances, protect

the body from cold.

(2) Increased temperature causes increased heart-beats, while diminished
temperature diminishes the number of contractions of the heart (§ 58, IL, a).
The relatively warm blood is pumped by the action of the heart from the internal
organs of the body to the surface of the skin, where it readily gives off heat. The
more frequently the same volume of blood passes through the skin—twenty-seven
heart-beats being necessary for the complete circuit of the blood—the greater will —
be the amount of heat given off, and conversely. Hence, the frequency of the —
heart-beat is in direct relation to the rapidity of cooling. In very hot air (over

>

REGULATION OF THE TEMPERATURE. 331

100° C.) the pulse rises to over 160 per minute. The same is true in fever (§ 70,
3, c). Liebermeister gives the following numbers in an adult :—
Pulse-beats, per min., 78°6 9172 99°8 108°5 =. 110 137°5
Temperature in C°., ye 38°. 39° 40° 41° 42°

(3) Increased Temperature increases the Number of Respirations.— Under
ordinary circumstances, a much larger volume of air passes through the lungs
when it is warmed almost to the temperature of the body. Further, a certain
amount of watery vapour is given off with each expiration, which must be
evaporated, thus abstracting heat. Energetic respiration aids the circulation, so
that respiration acts indirectly in the same way as (2). According to other
observers, the increased consumption of O favours: the combustion in the body,
whereby the increased respiration must act in producing an amount of heat greater
than normal (§ 127, 8). This excess is more than compensated for by the cooling
factors above mentioned. Forced respiration produces cooling, even when the air
breathed is heated to 54° C., and saturated with watery vapour.

(4) Covering of the Body.—Animals become clothed in winter with a winter
fur or covering, while in summer their covering is lighter, so that the excretion of
heat in surroundings of different temperatures is thereby rendered more constant.

Many animals which live in very cold air or water (whale) are protected from
too rapid excretion of heat by a thick layer of fat under the skin. Man provides
for a similar result by adopting summer and winter clothing.

(5) The position of the body is also important ; pulling the parts of the body
together, approximation of the head and limbs, keep in the heat; spreading out
the limbs, erection of the hairs, pluming the feathers, allow more heat to be evolved.
If a rabbit be kept exposed to the air with its legs extended for three hours, the
rectal temperature will fall from 39° C. to 37° C. Man may influence his
temperature by remaining in a warm or a cold room—by taking hot or cold
drinks, hot or cold baths—remaining in air at rest or air in motion, e.g., by using
a fan. 3

CLOTHING.—Warm Clothing is the Equivalent of Food.—<As clothes are intended to keep
in the heat of the body, and heat is produced by the combustion and oxidation of the food, we
may say the body takes in heat directly in the food, while clothing prevents it from giving
off too much heat. Summer clothes weigh 3 to 4 kilos., and winter ones 6 to 7 kilos.

In connection with clothes, the following considerations are of importance :—

(1) Their capacity for conduction.—Those substances which conduct heat badly keep us
warmest. Hare-skin, down, beaver-skin, raw silk, taffeta, sheep's wool, cotton wool, flax,
spun-silk, are given in order, from the worst to the best conductors. (2) The capacity for
radiation.—Coarse materials radiate more heat than smooth, but colour has no effect. (3)
Relation to the sun’s rays.—Dark materials absorb more heat than light-coloured ones. (4)
Their hygroscopic properties are important, whether they can absorb much moisture from the
skin and gradually give it off by evaporation, or the reverse. The same weight of wool takes up
twice as much as linen ; hence, the latter gives it off in evaporation more rapidly. Flannel
next the skin is not so easily moistened, nor does it so rapidly become cold by evaporation ;
hence it protects against the action of cold. (5) The permeability for air is of importance, but
does not stand in relation with the heat-conducting capacity. The following substances are

arranged in order from the most to the least permeable—flannel, buck-skin, linen, silk, leather,
waxcloth. .

215, HEAT-BALANCE.—As the temperature of the body is maintained
within narrow limits, the amount of heat taken in must balance the heat given off,
1.¢., exactly the same amount of potential energy must be transformed in a given
time into heat, as heat is given off from the body. An adult produces as much
heat in half an hour as will raise the-temperature of his body 1° C. If no heat
were given off, the body would become very hot in a short time; it would reach
the boiling point in thirty-six hours, supposing the production of heat continued
ee eroptedly, The following are the most important calculations on the
subject :—

332 HEAT-BALANCE,

4
A. Helmholtz was the first to estimate numerically the amount of heat produced by a ;
man :— 14
(1) Heat-income.—(a) A healthy adult, weighing 82 kilos., expires in
twenty-four hours 878°4 grms. CO, iSehonsing The combustion of
the C therein into CO, produces ; . 1,730,760 cal.
(b) But he takes in more O than reappears in the CO, ; : the excess be
used in oxidation-processes, ¢.g., for the formation of H
union with H, so that 13,615 se H will be oxidised ity a
excess of O, which gives . F ; 318,600 ,,
2,049,360 cal.
(c) About 25 per cent. of the heat must be referred to sources other
than combustion (Dulong), so that the total . d . =2,732,000 ,,
2,732,000 calories are actually sufficient to raise the temperature of an adult, weighing
80 to 90 kilos., from 10° to 38° or 39° C., z.e., to a normal temperature.
(2) Heat-expenditure.—(«) Heating the food and drink, which

have a mean temperature of 12° C. , d 70,157 eal. = 2°6 per cent.
(6) Heating the air respired = 16,400 grms. with an initial
temperature of 20°C. . ; 70,082 ,, = 2°6 J

(When the temperature of the air is 0°, 140, 064 cal. =5°2 per cent. $
(c) Evaporation of 656 grms. water by the lungs, ' ‘ 397,536 cal.
(2) The remainder given off by radiation and “evaporation of
water by the skin, ‘ : : é . (77°5 per cent. to)=80°1 ‘

B. Dulong.—(1) Heat-income. Spathng. and others sought to estimate the amount of heat
from the C and H contained in the food. As we know that the combustion of 1 grm. C=8040
heat-units, and 1 grm. H =34,460 heat-units, it would be easy to determine the amount of heat
were the C simply ¢ converted into CO, and the H into H,O. But Dulong omitted the H in the
carbohydrates (¢.g., grape-sugar=Cg, H,,0 «) as producing heat, because the H is already com-
bined with O, or at least is the proportion in which it exists in water. This assumption is
hypothetical, for the atoms of C in a carbohydrate may be so firmly united to the other atoms,
that before oxidation can take place their relations must be altered, so that potential energy is
used up, i.e., heat must be rendered latent; so that these considerations rendered the following
example of Dulong’ s method given by Vierordt very problematical :—
An adult eats in twenty- -four hours, 120 grms. proteids, 90 grms, fat, and 340 grms. starch |
(carbohydrates). These contain :— |

1c aoe

Proteids, . , ; 120 grms. contain 64°18 C. and 8°60 H. k
Ret. ; 90 ,, ‘ 70°20, :10°26 |
Starch, . : : : 330 ,, 5 146°82 eae a

281°20 and 18°86
The urine and feces contain still unconsumed,_ . eee. “ogy 6°3

Remainder to be burned, : : . 251°4 and = 12°56

- 1 grm. C=8040 heat-units and 1 grm. H=34,460 heat-units, we have the following cal-
culation :—
251°4 x 8,040=2,031,312 (from combustion of C).
12:56 x 34,460= 432,818( ,, se H).

2,464,130 heat-units.

(2) Heat-expenditure :— )
Per cent. of

Heat-units. the excreta.

1. 1900 grms. are excreted daily by the urine and feces, and they

are 25° warmer than the food, 47,500.

2. 13,000 grms. air are heated (from 12° to 87° C. ) (heat-capacity
of the air=0- 26), ; 84,500

3. 330 grms. water are evaporated by the respiration (1 grm. = 582
heat-units), , ; . 192,060
4. 660 grms. water are evaporated from the skin, ; ! . 884,120
Total, . ‘ ; ‘ : ; - 708,180
Remainder radiated and conducted from the skin, : , 1,791,820

Total amount of heat-units given off, . ; . 2,500,000 100-0

C. Heat-income.—Frankland burned the food directly in a calorimeter, and aes t
1 grm. of the following substances yielded :— i

VARIATIONS IN HEAT-PRODUCTION. 533

Albumin, 1 grm.,_. ; : i 4998 heat-units.
Grape-sugar, 1 grm., : : : ‘3217
Ox fat, 1 grm., d ; ; 9069 ‘

The albumin, however, is only oxidised to the stage of urea, hence the heat-units of urea
must’ be deducted from 4998, which gives 4263 heat-units obtainable from 1 grm. albumin.
When we know the number of grammes consumed, a simple multiplication gives the number
of heat-units.

The heat-units will vary, of course, with the nature of the food. J. Ranke gives the fol-
lowing :—

With animal diet, : ; : : 2,779,524 heat-units.
,, food free from N, . 3 . . 2,059,506 5
;, mixed diet, : ; : : 2,200, 000 is
,, during hunger, . : 2,012,816 as

216. VARIATIONS IN HEAT-PRODUCTION —(1) Influence of Bodily Surface.—Rubner
found that the production of heat depended more upon the size of the body and its superficial
area than upon the body-weight. Small or young animals have a relatively larger surface than
large or older ones, and as the removal of heat takes place chiefly from the external surface,
animals with a larger surface must produce more heat. Small animals used relatively more O.
Rubner’s investigations on dogs of different size gave a heat-production of 1,143,000 calories for
every square metre of cutaneous surface. On comparing the body-weight with the cutaneous
surface in different animals, he found that for every 1 kilo. of body-weight there was in the rat
1650, rabbit 946, man 287 square centimetres of surface.

(2) Age and Sex.—The heat-production is less in infancy and in old age, and it is less in
proportion in the female than in the male.

(3) Daily Variation.—The heat-production shows variations in twenty-four hours correspond-
ing with the temperature of the body (§ 213, 4).

(4) The heat-production is greater in the waking condition, during physical and mental
exertion, and during digestion, than in the opposite conditions.

2177. RELATION OF HEAT-PRODUCTION TO WORK.—The potential
energy supplied to the body may be transformed into heat and kinetic energy
(see Introduction). In the resting condition, almost all the potential energy is
changed into heat; the workman, however, transforms potential energy into work
—mechanical work—in addition to heat. These two may be compared by using
an equivalent measurement, thus, 1 heat-unit (energy required to raise 1 gramme
of water 1° C.)=425°5 gramme-metres.

Relation of Heat to Work.—The following example may serve to illustrate the relation
between heat-production and the production of work:—Suppose a small steam-engine to be
placed within a capacious calorimeter, and a certain quantity of coal to be burned, then as long
as the engine does not perform any mechanical work, heat alone is produced by the burning of
the coal. Let this amount of heat be estimated, and a second experiment made by burning the
same amount of coal, but allow the engine to do a certain amount of work—say, raise a weight
—by a suitable arrangement. This work must, of course, be accomplished by the potential
energy of the heating material. At the end of this experiment, the temperature of the water
will be inuch less than in the first experiment, 7.c., fewer heat-units have been transferred to the
calorimeter when the engine was heated than when it did no work. Comparative experiments
of this nature have shown that in the second experiment, the useful work is very nearly pro-
portional to the decrease of the heat (Hirn).

Compare this with what happens within the body:—A man in a passive
condition forms from the potential energy of the food between 24 to 2? million
calories. The work done by a workman is reckoned at 300,000 kilogramme-
metres (§ 300).

If the organism were precisely similar to a machine, a smaller amount of heat,
corresponding to the work done, would be formed”in the body. As a matter of
fact, the organism produces less heat from the same amount of potential energy
when mechanical work is done. There is one point of difference between a
workman and,a working machine. The workman consumes much more potential
energy in the same time than a passivé person; much more is transformed in his
body ; and hence the increased consumption is not only covered, but even over-
compensated. Hence, the workman is warmer than the passive person, owing to
the increased muscular activity ($210, 1, 0). Take an example :—Hirn remained

334 ACCOMMODATION FOR VARYING TEMPERATURES.

passive, and absorbed 30 grm..O per hour in a calorimeter, and produced 155
calories. When in the calorimeter he did work equal to 27,450 kilogramme-
metres, which was transferred beyond it ; he absorbed 132 grm. O, and produced
gs een ori lude only the heat-equivalent of the work transferred

imati we must include only the heat-equivalen
Sestrevag =, ies ‘iting acy Ba pushing anything, iumeine « weight, and lifting the body, .
are examples. In ordinary walking we must take into account that we overcome the resistance
of the air and the activity of the muscles. . ;

The organism is superior to a machine in as far as it can, from the same amount
of potential energy, produce more work in proportion to heat. Whilst the very
best steam-engine gives } of the potential energy in the form of work, and gas
heat, the body produces } as work and 4 as heat. Chemical energy can never do
work alone, in a living or dead motor, without heat being formed at the same
time.

218. ACCOMMODATION FOR VARYING TEMPERATURES.—All sub-

stances which possess high conductivity for heat, when brought into contact with

the skin, appear to be very much colder or hotter than bad conductors of heat.

The reason of this is that these bodies abstract far more heat, or conduct more

heat than other bodies. Thus the water of a cool bath, being a better conductor

of heat, is always thought to be colder than air at the same temperature. In our

climate it appears to us that— |

Air, at 18° C. is moderately warm ; | Water, at 18° C. is cold ;

at 25°-28° C., hot; », from 18°-29° €., cool ;

above 28°, very hot. Re », 29°-35° C., warm ; |
“ | + », 937°5° and above, hot. é

Warm Media.—<As long as the temperature of the body is higher than that of
the surrounding medium, heat is given off, and that the more rapidly the better
the conducting power of the surrounding medium, As soon as the temperature of
the surrounding medium rises higher than the temperature of the body, the latter
absorbs heat, and it does so the more rapidly the better the conducting power of
the medium. Hence, hot water appears to be warmer than air at the same
temperature. A person may remain eight minutes in a bath at 45°5° C.
(dangerous to life!) ; the hands may be plunged into water at 50°5° C., but not at
51°65° C., while at 60° violent pain is produced.

A person may remain for eight minutes in hot air at 127° C., and a temperature
of 132° C. has been borne for ten minutes, and yet the body temperature rises only to
38°6° or 38°9°, This depends upon the air being a bad conducter, and thus it gives
less heat to the body than water would do. Further, and what is more important, the
skin becomes covered with sweat, which evaporates and abstracts heat, while the
lungs also give off more watery vapour. The enormously increased heart-beats—
over 160—and the dilated blood-vessels, enable the skin to obtain an ample supply
of blood for the formation and evaporation of sweat, In proportion as the secretion
of sweat diminishes, the body becomes unable to endure a hot atmosphere ; hence
it is that in air containing much watery vapour a person cannot endure nearly so
high a temperature as in dry air, so that heat must accumulate in the body. Ina
Turkish-vapour bath of 53° to 60° C., the rectal temperature rises to 40°7° or 41°6°
C. A person may work continuously in air at 31° C, which is almost saturated with
moisture. ne

If a person be placed in water at the temperature of the body, the normal —
temperature rises 1° C. in one hour, and in 14 hour about 2° C. A gradual —
increase of the temperature from 38°6° to 40°2° C. causes the axiliary temperature ©
to rise to 39°0° within fifteen minutes, .

219. STORAGE OF HEAT.—As the uniform temperature of the body, und
normal circumstances, is due to the reciprocal relation between the amount of hea

+]

3

ee oad.

OO eee

STORAGE OF HEAT. FEVER. 335

produced and the amount given off, it is clear that heat must be stored up in the
body when the evolution of heat is diminished. The skin is the chief organ
regulating the evolution of heat; when it and its blood-vessels contract, the heat
evolved is diminished, when they dilate, it is increased. Heat may be stored up
when— :

(a) The skin is extensively stimulated, whereby the cutaneous vessels are temporarily con-
tracted. (6) Any other circumstances prevent heat from being given off by the skin. (c)
When the vaso-motor centre is éxcited, causing all the blood-vessels of the body—those of the
skin ineluded—to contract. This seems to be the cause of the rise of temperature after trans-
fusion of blood, and the rise of temperature after the sudden removal of water from the body seems
to admit of a similar explanation, as the inspissated blood occupies less space, and the con-
tracted vessels of the skin admit less blood. (d@) When the circulation in the cutaneous vessels
of a large area is mechanically slowed, or when the smaller vessels are plugged by the injection
of some sticky substance, or by the transfusion of foreign blood, the temperature rises (§ 102).

It is also obvious that when a normal amount of heat is given off, an increased
production of heat must raise the temperature. The rise of the temperature after
muscular or mental exertion, and during digestion, seems to be caused in this way.
The rise which occurs several hours after a cold bath is probably due to the reflex
excitement of the skin causing an increased production (Jiirgensen).

_ When the temperature of the body, as a whole, is raised 6° C., death takes place,
as in sunstroke. It seems as if there was a molecular decomposition of the tissues
at this temperature ; while, if a slightly lower temperature be kept up continuously,
fatty degeneration of many tissues occurs (/itten). If animals, which have been
exposed artificially to a temperature of over 42° to 44° C., be transferred to a
cooler atmosphere, their temperature becomes sub-normal (36° C.), and may remain
so for several days.

220, FEVER.—Fever consists in a ‘‘ disorder of the body heat” and at the same time there
is greatly increased tissue metabolism (especially in the muscles). Of course the mechanism
regulating the balance of formation and expenditure of heat is disturbed. During fever the
body is greatly incapacitated for performing mechanical work. It is evident, therefore, that
the large amount of potential energy transformed is almost all converted into heat, so that the
non-transformation of the energy into mechanical work is another important factor. We may
take intermittent fever or ague as a type of fever, in which violent attacks of fever of several
hours’ duration alternate with periods free from fever. This enables us to analyse the symptoms.
The symptoms of fever are :—

(1) The increased temperature of the body (38° to 39° C., slight; from 39° to 41° C. and up-
wards, severe).—The high temperature occurs not only in cases where the skin is red, and has
a hot burning feeling (calor mordax), but even during the rigor or the shivering stage, the
temperature is raised. The congested red skin is a good conductor of heat, while the pale
bloodless skin conducts badly ; hence, the former feels hot to the touch (§ 212).

[The following table in ° C. and ° F. indicates generally the degree of fever :—-

35°C. = 95° F. . : Collapse 39° C, =102°2° F. 7

Bee OG a ee 39°5 =103'1 } Moderate fever.

SOG, "et O ey oe Lk Sub-normal. 40 =104 Hich f

37 = 986 . . Normal, 40°5 =104'9 \ ciate

37°5 = 99°5 41 = 105°8 _ Hyperpyretic.

38 =100°4;, Sub-febrile. Finlayson. |
38°5 ==101°3

(2) The increased production of heat is proved by calorimetric observations. This is, in
small part, due to the increased activity of the circulation being changed into heat (§ 206, 2, a),
but for the most part it is due to increased combustion within the body.

(3) The increased metabolism gives rise to the ‘‘consuming’’ or ‘‘ wasting” character of
fever, which was known to Hippocrates and Galen. In 1852 v. Birensprung asserted that
*‘all the so-called febrile symptoms show that the metabolism is increased.” The increase of
the metabolism is shown in the increased excretion of ©CO,=70 to 80 per cent., while more O is
consumed, although the respiratory quotient*remains the same. According to D. Finkler, the
CO, excreted shows greater variations than the O consumed. The exeretion of urea is increased
4 to 3. In dogs suffering from septic fever, Naunyn observed that the urea began to increase
before the temperature rose, ‘‘ prefebrile rise.” Part of the urea, however, is sometimes retained
during the fever, and appears after the fever is over, ‘‘ epicritical excretion of urea.” The uric

336 FEVER.

acid is also increased; the urine pigment (§ 19), derived from the hemoglobin, may be increased
twenty times, while the excretion of potash may be seven-fold. It is important to observe that
the oxidation or combustion processes within the body of the fever-patient are greatly increased
when he is placed in a warmer atmosphere. The oxidation processes in fever, however, are also
increased under the influence of cooler surroundings (§ 214, I., 2), but the increase of the oxida-
tion in a warm medium is very much greater than in the cold (D. Finkler). The amount of
CO, in the blood is diminished, but not at once after the onset even of a very severe fever
Geppert).

(4) The diminished excretion of heat varies in different stages of a fever. We distinguish
several stages in a fever—(a) The cold stage, when the loss of heat is greatly diminished, owing
to the pale bloodless skin, but at the same time the heat-production is increased 14 to 24 times.
The sudden and considerable rise of the temperature during this stage shows that the diminished
excretion of heat is not the only cause of the rise of the temperature. (5) During the hot stage
the Aeat given off from the congested red skin is greatly increased, but at the same time more
heat is produced. Liebermeister assumes that a rise of 1, 2, 3, x C. corresponds to an increased
production of heat of 6, 12, 18, 24 per cent. (c) In the sweating stage the excretion of heat
through the red moist skin and evaporation are greatest, more than two or three times the
normal. The heat-production is either increased, normal, or sub-normal, so that under these
conditions the temperature may also be sub-normal (36° C.).

(5) The heat-regulating mechanism is injured.—A warm temperature of the surroundings
raises the temperature of the fever-patient more than it does that of a non-febrile person. The
depression of the heat-production, which enables normal animals to maintain their normal
temperature in a warm medium (§ 214), is much less in fever (D. Finkler).

The accessory phenomena of fever are very important :—Increase in the intensity and
number of the heart-beats (§ 214, II., 2) and respirations (in adults 40, and children 60 per
min.), both being compensatory phenomena of the increased temperature ; further, diminished
digestive activity and intestinal movements (§ 186, D) ; disturbances of the cerebral activities ;
of secretion; of muscular activity; slower excretion, ¢.g., of potassium iodide through the
urine. In severe fever, molecular degenerations of the tissues are very common. For the con-
dition of the blood-corpuscles in fever, see § 10, the vascular tension, § 69, the saliva, § 146,
digestion, § 186.

Quinine, the most important febrifuge, causes a decrease of the temperature by limiting the .
production of heat (§ 213, 6). Toxic doses of the metallic salts act in the same way, while
there is at the same time diminished formation of CO,. [Antipyretics or Febrifuges,—All
methods which diminish abnormal temperature belong to this group. As the constant tempera-
ture of the body depends on (1) the amount of heat-production, and (2) the loss of heat, we
may lower the temperature either in the one way or the other. When cold water is applied to
the body, it abstracts heat, 7.¢., it affects the results of fever, so that Liebermeister calls such
methods antithermic. But those remedies which diminish the actual heat-production are true
antipyretic. In practice, however, both methods are usually employed, and spoken of col-
lectively as antipyretics. ]

[Amongst the methods which are used to abstract heat from the body, are the application
of colder fluids, such as the cold bath, affusion, douche, spray, ice, or cold mixtures, &c. A.
person suffering from high fever requires to be repeatedly placed in a cold bath to produce any
permanent reduction of the temperature. Some remedies act by favouring the radiation
of heat, by dilating the cutaneous vessels (alcohol), while others excite the sweat-glands—#.e.,
are sudorifics—so that the water by its evaporation removes some heat. Amongst the drugs.
which influence tissue changes and oxidation, and thereby lessen heat-production, are quinine,
salicylic acid, some of the salicylates, digitalis, and veratrin. Blood-letting was formerly used
to diminish abnormal temperature. Amongst the newer antipyretic remedies are hydrochlorate
of kairin and antipyrin, both of which belong to the aromatic group (derivatives of benzol),
which includes also many of our best antiseptics. ]

221. ARTIFICIAL INCREASE OF THE BODILY TEMPERATURE.—If
mammals are kept constantly in air at 40° C., the excretion of heat from the body
ceases, so that the heat produced is stored up. At first the temperature falls some-
what for a very short time, but soon a decided increase occurs. The respirations
and pulse are increased, while the latter becomes irregular and weaker. TheOab- —
sorbed and CO, given off are diminished after six to eight hours, and death occurs: f
after great fatigue, feebleness, spasms, secretion of saliva, and loss of consciousness, —
when the bodily temperature has been increased 4° or at most 6° C. Death does
not take place owing to rigidity of the muscles, for the coagulation of the myosin —
of mammals’ muscles occurs at 49° to 50° C., in birds at 53° C., and in fro oa
40° C. If mammals are suddenly placed in air at-100° C., death oceurs (in 15 +t

EMPLOYMENT OF HEAT. | 237

20 min.) very rapidly, and with the same phenomena, while the bodily temperature
rises 4° to 5° C. In rabbits the body-weight diminishes 1 grm. per min. Birds
bear a high temperature somewhat longer; they die when their blood reaches 48°
to 50°C. : |

Even man may remain for some time in air at 100-110-132° C., but in ten to
fifteen minutes there is danger to life. The skin is burning to the touch, and red ;
a copious secretion of sweat bursts forth, and the cutaneous veins are fuller and
redder. The pulse and respirations are greatly accelerated. Violent headache, ver-
tigo, feebleness, and stupefaction, indicate great danger to life. The rectal tempera-
ture is only 1° to 2° C. higher. The high temperature of fever may even be
dangerous to human life. If the temperature remains for any length of time at
42°5° C., death is almost certain to occur. Coagulation of the blood in the arteries
is said to occur at 42°6° C. If the artificial heating does not produce death, fatty
infiltration and degeneration of the liver, heart, kidneys, and muscles begin after

thirty-six to forty-eight hours.

Cold-blooded animals, if placed in hot air or warm water, soon have their temperature raised
6 to 10°C. The highest temperature compatible with life in a frog must be below 40° C., as the
frog’s heart and muscles begin to coagulate at this temperature. Death is preceded by a stage
resembling death, during which life may be saved.

Most of the juicy plants die in half an hour in air at 52° C., or in water at 46° C. (Sachs).
Dried seeds of corn may still germinate after long exposure to air at 120° C. Lowly organised
plants, such as alge, may live in water at 60° C. (Hoppe-Seyler). Several bacteria withstand
a boiling temperature (7'yndall).

222, EMPLOYMENT OF HEAT.—Action of Heat.—The short, but not intense, action of
heat on the surface causes, in the first place, a transient slight decrease of the bodily tempera-
ture, partly because it retards reflexly the production of heat, and partly because, owing to the
dilatation of the cutaneous vessels and the stretching of the skin, more heat is given off. <A
warm bath above the temperature of the blood at once increases the bodily temperature.

Therapeutic Uses.—The application of heat to the entire body is used where the bodily
temperature has fallen, or is likely to fall, very low, as in the algid stage of cholera, and in

infants born prematurely. The general application of heat is obtained by use of warm baths,

packing, vapour baths, and the copious use of hot drinks. The docal application of heat is
obtained by the use of warm wrappings, partial baths, plunging the parts in warm earth or.
sand, or placing wounded parts in chambers filled with heated air. After removal of the
heating agent, care must be taken to prevent the great escape of heat due to the dilatation of
the blood-vessels.

9.23. INCREASE OF TEMPERATURE POST-MORTEM.—Phenomena,.—Heidenhain found
that in a dead dog, before the body cooled, there was a constant temporary rise of the tempera-
ture, which slightly exceeded the normal. The same observation had been occasionally made
on human bodies immediately ‘after death, especially when death was preceded by muscular
spasms [also in yellow fever]. Thus, Wunderlich measured the temperature fifty-seven minutes
after death in a case of tetanus, and found it to be 45°375° C.

Causes.—(1) 4 temporary increascd production of heat after death, due chiefly to the change
of the semi-solid myosin of the muscles into a solid form (rigor mortis). As the muscle
coagulates, heat is produced. All conditions which cause rapid and intense coagulation of the
muscles—e.g., spasms, favour a post-mortem rise of temperature (see § 295); a rapid coagulation
of the blood has a similar result (§ 28, 5).

(2) Immediately after death a series of chemical processes occur within the body, whereby heat
‘is produced. Valentin placed a dead rabbit in a chamber, so that no heat could be given off
from the body, and he found that the internal temperature of the animal’s body was increased.
The processes which cause a rise of temperature post-mortem are more active during the first
than the second hour ; and the higher the temperature at the moment of death, the greater is
the amount of heat evolved after death. :

(3) Another cause is the diminished excretion of heat post-mortem. After the circulation is
abolished, within a few minutes little heat is given off from the surface of the body, as rapid
excretion impliesthat the cutaneous vessels must be continually filled with warm blood.

22.4. ACTION OF COLD ON THE BODY.—Phenomena.—A short temporary
slight cooling of the skin (removing one’s clothes in a cool room, a cool bath for a
short time, or a cool douche) causes either no change or a slight rise in the bodily

temperature. The slight rise, when it occurs, is due to the stimulation of the skin
S, >

338 . ARTIFICIAL LOWERING OF THE TEMPERATURE,

causing reflexly a more rapid molecular transformation, and therefore a greater
production of heat, while the amount of heat given off is diminished owing to con-
traction of the small cutaneous vessels and the skin itself (Liebermeister). The
continuous and Intense application of cold causes a decrease of the temperature,
chiefly by conduction, notwithstanding that at the same time there is a greater
production of heat. After a cold bath the temperature may be 34°, 32°, and even
30° C.

As an after-effect of the great abstraction of heat, the temperature of the body
after a time remains lower than it was before (“primary after-effect”—Lneber-
meister); thus after an hour it was 0°22° C. in the rectum. There is a “ secondary
after-efect”” which occurs after the first after-effect is over, when the temperature
rises (Jiirgensen). This effect begins five to eight hours after a cold bath, and is
equal to +0°2° C. in the rectum. Hoppe-Seyler found that some time after the
application of heat there was a corresponding lowering of the temperature. |

Taking Cold.—If a rabbit be taken from a surrounding temperature of 35° C., and suddenly
cooled, it shivers, and there may be diarrhcea. After two days the temperature rises 1°5° C.,
and albuminuria occurs. There are microscopic traces of interstitial inflammation in the
kidneys, liver, lungs, heart, and nerve-sheaths, the dilated arteries of the liver and lung con-
tain thrombi, and in the neighbourhood of the veins are accumulations of leucocytes. In preg-
nant animals the fetus shows the same conditions, Perhaps the greatly cooled blood acts as an
irritant causing inflammation.

Action of Frost.—The continued application of a high degree of cold causes at first contrac-
tion of the blood-vessels of the skin and its muscles, so that it becomes pale. If continued
paralysis of the cutaneous vessels occurs, the skin becomes red owing to congestion of its
vessels. As the passage of fluids through the capillaries is rendered more difficult by the cold,
the blood stagnates, and the skin assumes a livid appearance, as the O is almost completely
used up. Thus the peripheral circulation is slowed. If the action of the cold be still more
intense, the peripheral circulation stops completely, especially in the thinnest and most exposed
organs—ears, nose, toes, and fingers. The sensory nerves are paralysed, so that there is numb-
ness with loss of sensibility, and the parts may even be frozen through and through. As the
slowing of the circulation in the superficial vessels gradually affects other areas of the circu-
lation, the pulmonary circulation is enfeebled, and diminished oxidation of the blood occurs,
notwithstanding the greater amount of O in the cold air, so that the nerve centres are affected.
‘Hence arise great dislike to making movements or any muscular effort, a painful sensation of
fatigue, a peculiar and almost irresistible desire to sleep, cerebral inactivity, blunting of the
sense-organs, and lastly, coma. The blood freezes at —3°9° C., while the juices of the superficial
pate freeze sooner. Too rapid movements of the frost-bitten parts ought to be avoided. Rub-
bing with snow, and the very gradual application of heat, produce the best results. Partial
death of a part is not unfrequently produced by the prolonged action of cold. |

225, ARTIFICIAL LOWERING OF THE TEMPERATURE.—Phenomena.
—The artificial cooling of warm-blooded animals, by placing them in cold air or
in a freezing mixture, gives rise to a series of characteristic phenomena. If the
animals (rabbits) are cooled so that the temperature (rectum) falls to 18°, they
suffer great depression, without, however, the voluntary or reflex movements being
abolished. The pulse falls from 100 or 150 to 20 beats per minute, and the blood-
pressure falls to several millimetres of Hg, The respirations are few and shallow.
Suffocation does not cause spasms, the secretion of urine stops, and the liver is
congested. The animal may remain for twelve hours in this condition, and when
the muscles and nervés show signs of paralysis, coagulation of the blood occurs
after numerous blood-corpuscles have been destroyed. The retina becomes pale,
and death occurs with spasms and the signs of asphyxia. If the bodily temperature
be reduced to 17° and under, the voluntary movements cease before the reflex acts. —
An animal cooled to 18° C., and left to itself, at the same temperature as the sur- _
roundings, does not recover of itself, but if artificial respiration be employed, the —
temperature rises 10° C, If this be combined with the application of external
warmth, the animals may recover completely, even when they have been apparently
dead for forty minutes. Walther cooled adult animals to 9° C., and recovered them
by artificial respiration and external warmth 3 while Horvath cooled young animals 7

act

HYBERNATION AND USE OF COLD. 339

to 5° C. . Mammals, which are born blind, and birds which come out of the egg
devoid of feathers, cool more rapidly than others. Morphia, and more so, alcohol,
accelerate the cooling of mammals, at the same time the exchange of gases falls
considerably ; hence, drunk men are more liable to die when exposed to cold.
Artificial Cold-Blooded Condition.—Cl. Bernard made the important observa-
tion, that the muscles of animals that had been cooled remained irritable for
a long time, to direct stimuli as well as to stimuli applied to their nerves ;
and the same is the case when the animals are asphyxiated for want of O. An
“ artificial cold-blooded condition,” 2.e., a condition in which warm-blooded animals
have a lower temperature, and retain muscular and nervous excitability, may also
be caused in warm-blooded animals, by dividing the cervical spinal cord and keeping
up artificial respiration ; further, by moistening the peritoneum with a cool solution

of common salt.

Hybernation presents a series of similar phenomena. Valentin found that hybernating
animals become half-awake when their bodily temperature is 28° C.; at 18° C. they are in a
somnolent condition, at 6° they are in a gentle sleep, and at 1°6° C. in a deep sleep. The
heart-beats and the blood-pressure fall, the former to 8 to 10 per minute. The respiratory,
urinary, and intestinal movements cease completely, and the cardio-pneumatic movement alone
sustains the slight exchange of gases in the lungs (§ 59). They cannot endure cooling to 0° C.;
and awake before the temperature falls solow. Hybernating animals may be cooled to a greater
degree than other mammals ; they give off heat rapidly, and they become warm again rapidly,
and even spontaneously. New-born mammals resemble hybernating animals more closely in
this respect than do adults.

Cold-blooded animals may be cooled to 0°. Even when the blood has been frozen and ice
formed in the lymph of the peritoneal cavity, frogs may recover. In this condition they appear
to be dead, but when placed in a warm medium they soon recover. A frog’s muscle so cooled
will contract again. The germs and ova of lower animals, ¢.g., insects’ eggs, survive continued
frost ; and if the cold be moderate, it merely retards development. Bacteria, ¢.g., Bacillus
anthracis, survive a temperature of —- 130° C.; yeast, even — 100° C. .

Varnishing the skin causes a series of similar phenomena. The varnished skin gives off a large
amount of heat by radiation, and sometimes the cutaneous vessels are greatly dilated. Hence
the animals cool rapidly and die, although the consumption of O is not diminished. If cooling
be prevented by warming them and keeping them in warm wool, the animals live for a longer
time. The blood post-mortem does not contain any poisonous substances, nor even are any
materials retained in the blood which can cause death, for if the blood be injected into other
animals, these remain healthy.

226, EMPLOYMENT OF COLD.—Cold may be applied to the whole or part of the surface
of the body in the following conditions :—

(a) By placing the body for a time in a cold bath to abstract as much heat as possible, when
the bodily temperature in fever rises so high as to be dangerous to life. This result is best
accomplished and lasts longest when the bath is gradually cooled from a moderate temperature.
If the body be placed at once in cold water, the cutaneous vessels contract, the skin becomes
bloodless, and thus obstacles are placed in the way of the excretion of heat. A bath gradually
cooled in this way is borne longer. The addition of stimulating substances, ¢g., salts, which
cause dilatation of the cutaneous vessels, facilitates the excretion of heat; even salt water
conducts heat better. If alcohol be given internally at the same time, it lowers the
temperature.

(6) Cold may be applied locally by means of ice in a bag, which causes contraction of the
cutaneous vessels and contraction of the tissues (as in inflammation), while at the same time
heat is abstracted locally.

(c) Heat may be abstracted locally by the rapid evaporation of volatile substances (ether,
carbon disulphide), which causes numbness of the sensory nerves. The introduction of media
of low temperature into the body, respiring cool air, taking cold drinks, and the injection of
cold fluids into the intestine act locally, and also produce a more general action. In applying
cold it is important to notice that the initial contraction of the vessels and the contraction of
the tissues are followed by a greater dilatation and turgescence, ¢.¢., by a healthy reaction.

22.7. HEAT OF INFLAMED PARTS,—“Calor,’’ or heat, is reckoned one of the fundamental
oe aban of inflammation, in addition to rubor (redness), tumor (swelling), and dolor (pain),
ut the apparent increase in the heat of the inflamed parts is not above the temperature of the
blood. Simon, in 1860, asserted that the arterial blood flowing to an inflamed part was cooler
than the part itself, but this has been contradicted. The outer parts of the skin in an inflamed
part are warmer than usual, owing to the dilatation of the vessels (rubor) and the consequent

340 . HISTORICAL AND COMPARATIVE.

acceleration of the blood-stream in the inflamed part, and owing to the swelling (tumor) from
the nce of good heat-conducting fluids; but the heat is not greater than the heat of the
bl It is not proved that an increased amount of heat is produced owing to increased
molecular decompositions within an inflamed part.

228. HISTORICAL AND COMPARATIVE.—<According to Aristotle, the heart pre
the heat within itself, and sends it along with the blood to all parts of the body, This
doctrine prevailed in the time of Hippocrates and Galen, and occurs even in Cartesius and
Bartholinus (1667, ‘‘flammula cordis”), The iatro-mechanical school (Bocrhave, van Stwieten)
ascribed the heat to the friction of the blood on the walls of the vessels. The iatro-chemical
school, on the other hand, sought the source of heat in the fermentations that arose from the
passage of the absorbed substances into the blood (van Helmont, Sylvius, Ettmiiller). Lavoisier
(1777) was the first to ascribe the heat to the combustion of carbon in the lungs. After the
construction of the thermometer by Galileo, Sanctorius (1626) made the first thermometric
observations on sick persons, while the first calorimetric observations were made by Lavoisier

and Laplace. Comparative observations are given at § 207, and also under Hybernation (§

225).

Physiology of the Metabolic Phenomena.

By the term metabolism we mean those phenomena, whereby all—even the
most lowly—living organisms are capable of incorporating the substances obtained
from their food into their tissues, and making them an integral part of their own
bodies. This part of the process is known as assimilation. Further, the organism
in virtue of its metabolism forms a store of potential energy, which it can trans-
form into kinetic energy, and which, in the higher animals at least, appears most
obvious in the form of muscular work and heat. The changes of the constituents
_ of the tissues, by which these transformations of the potential energy are accom-
panied, result in the formation of excretory products, which is another part of the
process of metabolism. The normal metabolism requires the supply of food
quantitatively and qualitatively of the proper kind, the laying up of this food
within the body, a regular chemical transformation of the tissues, and the forma-
tion of the effete products which have to be given out through the excretory
organs. [Synthetic or constructive metabolism is spoken of as anabolic, and de-
structive or analytical metabolism as katabolic, metabolism. |

929, THE MOST IMPORTANT SUBSTANCES USED AS FOOD.— Water.
—When we remember that 58°5 per cent. of the body consists of water, that water
is being continually given off by the urine and feces, as well as through the skin
and lungs, that the processes of digestion and absorption require water for the
solution of most of the substances used as food, and that numerous substances
excreted from the body require water for their solution, especially in the urine, the
great importance of water and its continual renewal within the organism are at
once apparent. As put by Hoppe-Seyler, all organisms live in water, and even in
running water, a saying which ranks with the old saying—‘ Corpora non agunt
nisi fluida.” ) ;

Water—as far as it is not a constituent of all fluid foods—occurs in different. forms as drink :—
(1) Rain water, which most closely resembles distilled or chemically pure water, always
contains minute quantities of CO,, NH, nitrous and nitric acids. (2) Spring water usually
contains much mineral substance. It is formed from the deposition of watery vapour or rain
from the air, which permeates the soil, containing much CO, ; the CO, is dissolved by the
water, and aids in dissolving the alkalies, alkaline earths, and metals, which appear in solution
as bicarbonates, ¢.g., of lime or iron oxide. The water is removed from the spring by proper
mechanical appliances, or it bubbles up on the surface in the form of a ‘‘ spring.” (3) River
_ water usually contains much less mineral matter than spring water. Spring water floating

on the surface pee gives off its CO, whereby many substances—e.g., lime—are thrown out
of solution, and deposited as insoluble precipitates. ;

Gases.—Spring water contains little O, but-much CO,, the latter giving to it its fresh taste.
Hence, vegetable organisms flourish in spring water, while animals requiring, as they do, much
O, are but poorly represented in such water. Water flowing freely gives up CO,, and absorbs
O from the air, and thus affords the necessary conditions for the existence of fishes and other
marine animals. River water contains ;; to =; of its volume of absorbed gases, which may be
expelled by boiling or freezing.

342 WATER.

Drinking water is chiefly obtained from springs. River water, if used for this purpose, must
be filtered to get rid of pppebeniea’y suspended impurities. For household purposes a charcoal
filter may be used, as the charcoal acts as a disinfectant. Alum has a remarkable action.
When added to give a dilution containing 0°0001 per cent., it makes turbid water clear. |

Investigation of Drinking Water.—Drinking water, even in a thick layer, |
ought to be completely colourless, not turbid, and without odour, Any odour is
best recognised by heating it to 50° C., and adding a little caustic soda. It ought
not to be too hard, i.e. it ought not to contain too much lime (and magnesia)

salts.

By the term ‘‘degree of hardness” of a water is meant the unit amount of lime (and

magnesia) in 100,000 parts of water; a water of 20 degrees of hardness contains 20 parts of
lime (calcium oxide) combined with CO., sulphuric, or hydrochloric acids (the small amount of
magnesia may be neglected). A good drinking water ought not to exceed 20 degrees of hardness.
The hardness is determined by titrating the water with a standard soap solution, the result
being the formation of a scum of lime-soap on the surface. The hardness of wnboiled water is
called its total hardness, while that of boiled water is called permanent hardness. Boiling
drives off the CO,, and precipitates the calcium carbonate, so that the water at the same time
becomes softer. ; ; ;

The presence of sulphuric acid, or sulphates, is determined by the water becoming turbid on
adding a solution of barium chloride and hydrochloric acid.

Chlorine occurs in small amount in pure spring water, but when it occurs there in large
amount—apart from its being derived from saline springs, near the sea or manufactories—we
may conclude that the water is contaminated from water-closets or dunghills, so that the
estimation of chlorine is of importance. For this purpose use a solution, A, of 17 grms. of
crystallised silver nitrate in 1 litre of distilled water ; 1 cubic centimetre of this solution pre-
cipitates 3°55 milligrammes of chlorine as silver chloride. Use also B,a cold saturated solution
of neutral potassium chromate. Take 50 cubic centimetres of the water to be investigated, and
place it in a beaker, add to it 2 to 3 drops of B, and allow the fluid A to run into it from a
burette until the white precipitate first formed remains red, even after the fluid has been stirred.
Multiply the number of cubic centimetres of A used by 7°1, and this will give the amount of
chlorine in 100,000 parts of the water. Example—50 c.cmtr. requires 2°9 c.cmtr. of the silver
solution, so that 100,000 parts of the water contain 2°9 x 7°1=20°59 parts chlorine (Kubel
Tiemann). Good water ought not to contain more than 15 milligrammes of chlorine per litre. |

The presence of lime may be ascertained by acidulating 50 cubic centimetres of the water ,
with HCl, adding ammonia in excess, and afterwards adding ammonia oxalate ; the white 7
precipitate is lime oxalate. According to the degree of turbidity, we judge whether the water .
is ‘soft ” (poor in lime), or ‘*‘ hard ” (rich in lime).

Magnesia is determined by taking the clear fluid of the above operation, after removing the
precipitate of lime, and adding to it a solution of sodium phosphate and some ammonia ; the
crystalline precipitate which occurs is magnesia.

~The more feeble all these reactions which indicate the presence of sulphuric acid, chlorine,
lime, and magnesia, are, the better is the water. In addition, good water ought not to contain
more than traces of nitrates, nitrites, or compounds of ammonia, as their presence indicates the
decomposition of nitrogenous organic substances.

For nitric acid, take 100 cubic centimetres of water acidulated with two or three drops of
concentrated sulphuric acid, add several pieces of zine together with a solution of potassium
iodide, and starch solution—a blue colour indicates nitric acid. The following test is very
delicate :—Add to half a drop of water in a capsule two drops of a watery solution of Brucinum
sulphuricum, and afterwards several drops of concentrated sulphuric acid ; a rose-red coloration
indicates the presence of nitric acid.

The presence of nitrous acid is ascertained by the blue coloration which results from the
addition of a solution of potassium iodide, and solution of starch, after the water has been
acidulated with sulphuric acid. ;

Compounds of ammonia are detected by Nessler’s reagent, which gives a yellow or reddish
coloration when a trace of ammonia is present in water; while a large amount of these com-
pounds gives a brown precipitate of the iodide of mercury and ammonia.

The contamination of water by decomposing animal substance is determined by the amount
of N it contains. In most cases it is sufficient to determine the amount of nitric acid present.
For this purpose we require (A) a solution of 1°871 grms. potassium nitrate in 1 litre distilled
water—1 cubic centimetre contains 1 milligramme nitric acid ; (B) a dilute solution of in
which is prepared by rubbing together one part of pulverised indigotin with six parts H,SO
and allowing the deposit to subside, when the blue fluid is poured into forty times its v r

15

of distilled water and filtered. This fluid is diluted with distilled water until a layer, 12 to
mm. in thickness, begins to be transparent. ‘1

To test the activity of B, place 1 cubic centimetre of A in 24 cubic centimetres water,

’

MAMMARY GLANDS. . 343

some common salt and 50 cubic centimetres concentrated sulphuric acid, and allow B to flow
from a burette into this mixture until a faint green colour is obtained. The number of cubic
centimetres of B used correspond to 1 milligramme of nitric acid.

Twenty-five cubic centimetres of the water to be investigated are mixed with 50 cubic centi-
metres of concentrated H,SO,, and titrated with B until a green colour is obtained. This process
must be repeated, and on the second occasion the solution B must be allowed to flow in at once,
when usually somewhat more indigo solution is required to obtain the green solution. The
number of cubic centimetres of B (corresponding to the strength of B, as determined above)
indicates the amount of nitric acid present in 25 c.cmtr. of the water investigated. As much
as 10 milligrammes nitric acid have been found in spring water (Marx, Trommsdorf).

Sulphuretted Hydrogen is recognised by its odowr ; also by a piece of blotting-paper moistened
with alkaline solution of lead becoming brown, when it is held over the boiling water. If it
occurs as a compound in the water, sodium nitro-prusside gives a reddish-violet colour.

It is of the greatest importance that drinking water should be free from the presence of organic
matter in a state of decomposition. Organic matter in a state of decomposition, and the
organisms therewith associated, when introduced into the body, may give rise to fatal maladies,
é.g., cholera and typhoid fever. This is the case when the water supply has been contaminated
from water which has percolated from water-closets, privies, and dung-pits. The presence of
organic matter may be detected thus—(1) A considerable amount of the water is evaporated to
dryness in a porcelain vessel, if the residue be heated again a brown or black colour indicates the
presence of a considerable amount of organic matter; and if it contain N, there is an odour of
ammonia. Good water treated in this way gives only a light brown stain. The presence of
micro-organisms may be determined microscopically after evaporating a small quantity of the
water on a glass slide. (2) The addition of potassio-gold chloride to the water gives a black
frothy precipitate after long standing. (3) A solution of potassium permanganate, added to the

- water in a covered jar, gradually becomes decolorised, and a brownish precipitate is formed.

Water containing much organic matter should never be used as drinking water, and this is
especially the case when there is an epidemic of typhoid fever, cholera, or diarrhcea. In all
such circumstances, the water ought to be boiled for a long time, whereby the organic germs
are killed. The insipid taste of the water after boiling may be corrected by adding a little
sugar or lime juice.

230, THE MAMMARY GLANDS AND MILK.—Milk Duct.—About 20 galactoferous ducts
open singly upon the surface of the nipple. Each of these, just before it opens on the surface,
is provided with an oval dilatation—the sinus lacteus. When
traced into the gland, the galactoferous ducts divide like the
branches of a tree, and a large branch of the duct passes to each
lobe of the gland, all the lobes being held together by loose
connective-tissue. Only during lactation do all the fine ter-
minations of the ducts communicate with the globular glandular
acini. Every gland acinus consists of a membrana propria, sur-
rounded externally with a network of branched connective-tissue
corpuscles, and lined internally with a somewhat flattened poly-
hedral layer of nucleated secretory cells (fig. 233). The size of
the lumen of the acini depends upon the secretory activity of
the glands; when it is large, it is filled with milk containing
numerous refractive fatty granules. The walls of the milk ducts Fig. 233.
consist of fibrillar connective-tissue, some fibres are arranged =
longitudinally, but the chief mass are disposed circularly, and
are permeated externally with elastic fibres, while in the finer
ducts there is a membrana propria continuous with that of the
gland acini. The ducts are lined by cylindrical epithelium. .

During the first few days after delivery, the breasts secrete a small amount of milk of greater
consistence, and of a yellow colour—the colostrum—in which large cells filled with fatty
granules occur—the colostrum-corpuscles (fig. 235).. Sometimes a nucleus is observable within
them, and rarely they exhibit amceboid movements (fig. 234, c,d, e). The regular secretion
of milk begins after three to four days. It was formerly supposed that the cells of the acini
underwent a fatty degeneration, and thus produced the fatty granules of the milk. It is more
probable, from recent observations, that the cells of the acini manufacture the fatty granules,
and their protoplasm eliminates them, at the same time forming the clear fluid part of the milk.

Changes during Secretion.—Pratsch and Heidenhain found that the secretory
cells in the non-secreting gland. (fig. 234, I), were flat, polyhedral, and uni-
nucleated, whilst the secreting cells (fig. 234, IT) often contained several nuclei, were
more albuminous, higher, and cylindrical in form. The edge of the cell directed
towards the lumen of the acinus undergoes characteristic changes during secretion.

Acini of the mammary gland
of a sheep during lactation.
a, membrana propria; 3,
secretory epithelium.

344 STRUCTURE OF THE MAMMA.

Fatty granules are formed in this part of the cell, and are afterwards extruded. .
The decomposed portion of the cell is dissolved in the milk, and the fatty granules
become free as milk-globules (fig. 234, II, a). If nuclei are present in that part of
the cell which is broken up, they also pass into the milk and give rise to the presence

of nuclein in the secretion.

Besides the milk-globules and colostrum corpuscles, Rauber has found leucocytes undergoing
fatty degeneration and single pale cells (/). ecasionally milk-globules are found with traces
of the cell-substance adhering to their surface (bd). A gir ;

Formation of Milk.—Concerning the formation of the individual constituents of milk, H.
Thierfelder, who digested fresh mammary glands directly after death, found that during the
digestion of the glands, at the temperature of the body, a reducing substance, probably lactose,
was formed by a process of fermentation. The mother substance (saccharogen) is soluble in
water, but not in B aes or ether, is not destroyed by boiling, and is not identical with glycogen.
The ferment which forms the lactose is connected with the gland-cells—it does not pass into the
milk, nor into a watery extract of the gland. During the digestion of the mammary glands at
the temperature of the body, casein is formed, probably from serum-albumin, by a process of
fermentation. This ferment occurs in the milk.

The nipple and its areola are characterised by the presence of pigment—more abundant
during pregnancy—in the rete Malpighii of the skin, and by large apille in the cutis vera.
Some of the papille contain touch-corpuscles. Numerous non-striped muscular fibres surround
the milk-ducts in the deep layers of the skin and in the subcutaneous tissue, which contains no
fat. These muscular fibres can be traced, following a longitudinal course, to the termination of
the ducts on the surface. The small glands of Montgomery, which occur on the areola during
lactation, are just small milk-glands, each with a special duct opening on the surface of the
elevation.

Arteries proceed from several sources to supply the mamma, but their branches do not
accompany the milk-ducts ; each gland acinus is surrounded by a network of capillaries, which

I. Inactive acinus of the mamma. II. During the secretion of milk—a, }, milk-globules ;
c, d, e, colostrum corpuscles ; f, pale cells (bitch).

communicate with those of adjoining acini by small arteries and veins. The veins of the areola
are arranged in a circle (circulus Halleri). The nerves are derived from the supraclavicular,
and the Il-IV-VI intercostals ; they proceed to the skin over the gland, to the very sensitive
nipple, to the blood-vessels and non-striped muscle of the nipple, and to the gland acini, where
their mode of termination is still unknown. Lymphatics surround the alveoli, and they are
often full. The milk appears to be prepared from the lymph contained in the lymphatics
snrrounding the acini.

The comparative anatomy of the mamma.—The rodents, insectivora, and carnivora have 10
to 12 teats, while some of them have only 4. The pachydermata and ruminantia have 2 to 4
abdominal teats, the whale has 2 near the vulva. The apes, bats, vegetable-feeding whales,
elephants, and sloths have 2, like man. In the marsupials the tubes are arranged in groups,
bos one en of Hage er ibe of a without any nipple. The young animals remain

er’s pouch, an e milk i i i i

musele—the pao reac ere milk is expelled into their mouths by the action of a
e development of the human mamma begins in both sexes during the third A 2.
fourth and fifth months a few simple tubular gland-ducts are pn d ndially aaa ton
an, of the future nipple, which is devoid of hair. In the new-born child the ducts are
ranched twice or thrice, and are provided with dilated extremities, the future acini. Up t
the twelfth year, in both sexes, the duets continue to divide dendritically, but without any
proper acini being formed. In the girl at puberty, the ducts branch rapidly; but the acin
are formed only at the periphery of the gland; during pregnancy, acini are also formed

MILK AND ITS PREPARATIONS. 345)

centre of the gland, while the connective-tissue at the same time becomes somewhat more
opened out. At the climacteric period, or menopause, all the acini and numerous fine milk-
duets degenerate. In the adult male, the gland remains in the non-developed infantile condition.
Accessory or supernumerary glands upon the breast and abdomen are not uncommon, sometimes
the mamma occurs in the axilla, on the back, over the acromion process, or on the leg. <A
slight secretion of milk in a newly-born infant is normal.

During the evacuation of the milk (500-1500 cubic centimetres daily), there is not only the
mechanical action of sucking, but also the activity of the gland itself (§ 152). This consists in
the erection of the nipple, whereby its non-striped muscular fibres compress the sinuses on the
milk-ducts, and empty them, so that the milk may flow out in streams. The gland acini are
also excited to secretion reflexly by the stimulation of the sensory nerves of the nipple. The
vessels of the gland are dilated, and there is a copious transudation into the gland—the
transuded fluid being manufactured into milk under the influence of the secretory protoplasm.
The amount of secretion depends upon the blood-pressure (Réhrig). During sucking, not only
is the milk in the gland extracted, but new milk is formed, owing to the accelerated secretion.
Emotional disturbances—anger, fear, &c.—arrest the secretion. Laffont found that stimulation
of the mammary nerve (bitch) caused erection of the teat, dilatation of the vessels, and secretion
of milk. After section of the;cerebro-spinal nerves going to the mamma, Eckhard observed that
erection of the teat ceased, although the secretion of milk in a goat was not interrupted. The
rarely observed galactorrheea is perhaps to be regarded as a paralytic secretion analogous to the
paralytic secretion of saliva. Heidenhain and Pratsch found that the secretion (bitch) was
increased by injecting strychnine or curara after section of the nerves of the gland. The
“* milk-fever,” which accompanies the first secretion of milk, probably depends on stimulation of
the vaso-motor nerves, but this condition must be studied in relation with the other changes
which occur within the pelvic cavity after birth. [Some substances, such as atropin, arrest the
secretion of milk. ]

231. MILK AND ITS PREPARATIONS.—Milk represents a complete or
typical food in which are present all the constituents necessary for maintaining
the life and growth of the body of an infant (§ 236). [If an adult were to live on
milk alone, to get the 23 oz. of dry solids necessary, he would have to take 9 pints
of milk daily, which would give far too much water, fat, and proteids.]| To every
10 parts of proteids there are 10 parts fat and 20 parts sugar. Relatively more
of the fat than the albumin of the milk is absorbed (Rubner); while a part of
both is excreted in the feces.

Characters.— Milk is an opaque, bluish-white fluid with a sweetish taste and a
characteristic odour, probably due to the peculiar volatile substances derived from
the -cutaneous secretions of the glands, and
it has a specific gravity of 1026 to 1035.
When it stands for a time, numerous milk
globules, butter globules, or cream, collect
on its surface, under which there is a bluish
watery fluid. Human milk is always alka-
dine, cow’s milk may be alkaline, acid, or f@aro’.
amphoteric ; while the milk of carnivora is [6S@:*::
always acid. 6
_ Milk-Globules.—When milk is examined
microscopically, it is seen to contain numerous
small highly refractive oil-globules, floating
in a clear fluid—the milk plasma (figs. 234,
a, 6, 235); while colostrum corpuscles and
epithelium from the milk-ducts are not so
numerous. The white colour and opacity of
the milk are due to the presence of the milk-

Fig. 235,

globules, which reflect the light ; the globules tee eee a ae

consist of a fat, or butter, and are said by
some to be surrounded with a very thin envelope of casein or haptogen membrane.

' If acetic acid be added to a microscopic preparation of milk, the fatty granules run together
to form irregular masses, If cow’s milk be shaken with caustic potash, the casein envelopes

346 FAT AND PLASMA OF MILK.

are dissolved, and if ether be added, the milk becomes clear and transparent, as the ether dis-
solves out all the fatty particles in the solution, Ether cannot extract the fat from cow's milk
until acetic acid or caustic potash is added to liberate the fats from their envelopes ; but shak-
ing with ether is sufficient to extract the fats from human milk. Some observers deny that an
envelope of casein exists, and according to them milk is a simple emulsion, kept emulsionised
owing to the colloid swollen-up casein in the milk plasma. The treatment of milk with potash
and ether makes the casein unable any longer to preserve the emulsion (Soxhlet).

The fats of the milk-globules are the triglycerides of stearic, palmitic, oleic (very
little), myristic, arachinic (butinic), capric, caprylic, caproic, and butyric acid, with
traces of acetic and formic acids and cholesterin.

Butter.—When milk is beaten or stirred for a long time (i.e., churned), the fat of the milk-
globules is ultimately obtained in the form of butter, owing to the rupture of the envelopes of
casein. Butter is soluble in alcohol and ether, and it is clarified by heat (60° C.), or by washing
in water at 40°C. When allowed to stand exposed to the air, it first becomes sour, owing to
the formation of lactic-acid, and afterwards rancid, owing to the glycerine of the neutral fats
being decomposed by fungi into acrolein and formic acid, while the volatile fatty acids give it
its rancid odour.

The milk plasma, obtained by filtration through a clay filter or membranes, is a
clear, slightly opalescent fluid, and contains casein (§ 249, III, 3), some serum-
albumin (§ 32), peptone (0°13 per cent.), nuclein, and a trace of diastatic ferment
(in human milk).

The presence of other peculiar chemical bodies, ¢.g., lactoprotein, globulin, albumose, galactin,
&e., is disputed by some chemists.

When milk is boiled the albumin coagulates, while the surface also becomes

covered with a thin scum or layer of casein, which has become insoluble [the rest
of the milk remaining fluid].

Casein.—When milk is filtered through fresh animal membranes or through a clay filter, the
casein does not pass through. Precipitation.—It is precipitated by adding crystals of MgSO
to saturation. [If to milk twice its volume of a saturated solution of NaCl and crystals of NaCl
be added, and the whole shaken thoroughly, casein is precipitated, and carries down with it
fat, so that the clear filtrate contains the lactose, salts, and coagulable proteids. ]

The plasma contains milk-sugar (§ 252); a carbohydrate resembling dextrin,
(1 lactic acid), lecithin, urea, extractives, kreatin, sarkin, (potassic sulphocyanide in
cow’s milk), sodic and potassic chlorides, alkaline phosphates, calcium and magnesium
sulphates, alkaline carbonates, traces of iron, fluorine, and silica, CO,, N, and O.

The coagulation of milk depends upon the coagulation of its casein. In milk, casein is com-
bined with calcium phosphate, which keeps it in solution}; acids which act on the calcium
phosphate cause coagulation of the casein (acetic and tartaric acids in excess redissolve it). All
acids do not coagulate human milk. It is coagulated by two or more drops of hydrochloric acid
(0°71 Pan cent.) or acetic acid (0°2 per cent.). The spontaneous coagulation of milk after it has
stood for a time, especially in a warm place, is due to the production of lactic acid, which is
formed from the milk-sugar in the milk by the action of bacillus acidi lactici [which is intro-
duced from without] (§ 184, I.). It changes the neutral alkaline phosphate into the acid

hosphate, takes the casein from the calcium phosphate, and precipitates the casein. The sugar
1s decomposed into lactic acid and CO,. ,

Rennet (§ 250, 9, d, § 166, II.) coagulates milk with an alkaline reaction (sweet whey).
This ferment decomposes the casein into the precipitated cheese and also into the slightly soluble
whey-albumin, so that the coagulation by rennet is a process quite distinct from the coagulation
of milk by the gastric and pancreatic juices, [and also from the precipitation produced by acids.
The presence of calcium phosphate seems to be necessary for the complete action of the rennet
(Hammarsten)}.

[Experiments.—Warm a little milk to 40° C., and add a few drops of commercial rennet,
setting aside the mixture in a warm place; a solid coagulum is soon formed, and by and by the
whey go spots from it. If the milk be previously diluted with water, no coagulum is formed ;
and if the rennet be boiled before, it like other ferments is destroyed. A solution of rennet
may be pried by extracting the fourth stomach of the calf with glycerine. [When the milk
is c ated we obtain the curd, consisting of casein with some milk-globules entangled in it ;
the whey contains some soluble albumin and fat, and the great proportion of the salts and milk-
tal together with lactic acid. ] a

A mille ~coagulating ferment is found in certain plants (artichokes, figs, Carica papaya), and
causes milk to coagulate in neutral or alkaline solutions. It is also found in the stuall (

in

4

¢

COMPOSITION OF MILK. 347

of the calf, while a 5 per cent. NaCl solution of the seeds of Withania coagulans coagulates milk
in an alkaline medium. }

Boiling (by killing all the lower organisms), sodium bicarbonate (7/55), ammonia, salicylic
acid (555), glycerine, and ethereal oil of mustard prevent the spontaneous coagulation. Fresh
milk makes tincture of guaiacum blue, but boiled milk does not do so. When milk is exposed
to the air for a long time, it gives off CO, and absorbs O ; the fats are increased (? owing to the
development of fungi in the milk), and so are the alcoholic and ethereal extracts, from the de-
composition of the casein. According to Schmidt-Miilheim, some of the casein becomes con-
verted into peptone, but this occurs only in unboiled milk.

Composition,—100 parts of milk contain—

Human. Cow. Goat. Ass.
Water, . : ; 87°24 to 90°58 86°23 86°85 89°01
Solids, . ; , 9°42 ,, 12°39 1s a a | 13 52 10°99
Casein, ’ ‘ 2:01 Se Oa ae , 3°23 2°53 ;
Albumin, a 1°00 to 2°86 0°50 1°26 3°57
Butter, , ; 2°67 ,, 4°30 4°50 4°34 1°85
Milk-sugar, . , S15. ,,. 6°09 4°93 3°78 505
Salts, . ; , 0°14 ,, 0°28 0°61 0°65

Human milk contains less albumin, which is more soluble than the albumin in the milk of
animals,

Colostrum contains much serum-albumin, and very little casein, while all the other substances,
and especially the fats, are more abundant.

Gases. —Pfliiger and Setschenow found in 100 vols. of milk 5°01 to 7°60 CO, ; 0°09 to 0°32 O;
0°70 to 1°41 N, according to volume. Only part of the CO, is expelled by phosphoric acid.

Salts. —The potash salts (as in blood and muscle) are more abundant than the soda com-
pounds, while there is a considerable amount of calcium phosphate, which is necessary for form-
ing the bones of the infant. Wildenstein found in 100 parts of the ash of human milk—sodium
chloride, 10°73 ; potassium chloride, 26°33; potash, 21°44; lime, 18°78; magnesia, 0°87;
phosphoric acid, 19; ferric phosphate, 0°21; sulphuric acid, 2°64; silica, traces. The amount
of salts present is affected by the salts of the food.

Conditions Influencing the Composition.—The oftener the breasts are emptied, the richer the
milk becomes in casein. The last milk obtained at any time is always richer in butter, as it
comes from the most distant part of the gland—viz., the acini. Some substances are dimin-
ished and others increased in amount, according to the time after delivery. The following are
increased :—Until the 2nd month after delivery, casein and fat ; until the 5th month, the salts
(which diminish progressively from this time onwards) ; from the 8th to the 10th month, the
sugar. The following are diminished:—From 10th to 24th month, casein; from 5th to 6th
and 10th to 11th month, fat; during 1st month, the sugar; from the 5th month, the salts.

The greater the amount of milk that is secreted (woman), the more casein and sugar, and the
less butter it contains. The milk of a primipara is less watery. Rich feeding, especially pro-
teids (small amount of vegetable food), increases the amount of milk and the casein, sugar, and
fat in it; a large amount of carbohydrates (not fats) increases the amount of sugar.

[Modifying Conditions,—That cow’s milk is influenced by the pasture and food is well known.
Turnip as food gives a peculiar odour, taste, and flavour to milk, and so do the fragrant grasses.
The mental state of the nurse influences the quantity and quality of the milk. Jaborandi is
the nearest approach to a galactagogue, but its action is temporary. Atropin is a true anti-
galactagogue. . The composition of the milk may be affected by using fatty food, by the use of
salts, and above all by the diet (Dolan). ]

[Milk may be a vehicle for communicating disease—by direct contamination, from the
water used for adulterating it or cleansing the vessels in which it is kept; by the milk absorb-
ing deleterious gases ; by the secretion being altered in diseased animals.] Milk ought not to
be kept in zinc vessels, owing to the formation of zinc lactate.

Substitutes. —If other than human milk has to be used, ass’s milk most closely resembles
human milk. Cow’s milk is best when it contains plenty of fatty matters—it must be diluted
with its own volume of water at first, and a little milk-sugar added. The casein of cow’s milk
differs qualitatively from that of human milk; its coagulated flocculi or curd are much coarser
than the fine curd of human milk, and they are only # dissolved by the digestive juices, while
papan milk is completely dissolved. Cow’s milk when boiled is less digestible than un-

oiled.

Tests for Milk.—The amount of cream is estimated by placing the milk for twenty-four
hours in a tall cylindrical glass graduated into a hundred parts or creamometer ; the cream
collects on the surface, and ought to form from 10 to 24 vols. per cent. [The cream is gene-
rally about ;$5.] The specific gravity (fresh cow’s milk, 1029 to 1034; when creamed, 1032
to 1040) is estimated with the lactometer at 15°C. The sugar is estimated by titration with
Fehling’s solution (§ 150, II.), but in this case 1 cubic centimetre of the solution corresponds
to 0:0067 grm. of milk-sugar ; or its amount may be estimated with the polariscopic apparatus

348. TESTS FOR MILK,

($150), The proteids are precipitated and the fats extracted with ether. The fats in fresh
milk form about 3 per cent., and in skimmed milk 14 per cent. — The amount of water in rela- :
tion to the milk-globules is estimated by the lactoscope or the diaphanometer of Donné (modi-
fied by Vogel and Hoppe-Seyler), which consists of a glass vessel with plane parallel sides placed:
l centimetre apart. A measured quantity of milk is taken, and water is added to it from a
burette until the outline of a candle flame placed at a distance of 1 metre can be distinctly seen
through the diluted milk. This is done in a dark room. For 1 cubic centimetre of good cow's
milk, 70 to 85 centimetres water are required. [Other forms of lactoscope are used, all depend-
ing on the same principle of an optical test, viz., that the opacity of milk varies with and is
proportional to the amount of butter-fats great i.e., the oil-globules. Bond .uses a shallow
cylindrical vessel with the bottom covered by black lines on a white surface. A measured
quantity of water is placed in this vessel, and milk is added, drop by drop, until the parallel
lines on the pattern at the bottom of the dish cease to be visible. On counting the number of
drops, a table accompanying the appliance gives the percentage of fats. This method gives
approximate results. In all cases it.is well to use fresh milk. ] .

arious substances pass into the milk when they are administered to the mother—many odori-
ferous vegetable bodies, ¢.g., anise, vermuth, garlic, &c.; chloral, rhubarb, opium, indigo,
salicylic acid, iodine, iron, zine, mercury, lead, bismuth, antimony. In.osteomalacia the amount
of lime in the milk is increased (Gusserow). Potassium iodide diminishes the secretion of milk
by affecting the secretory function. Amongst abnormal constituents are—hemoglobin, bile-
pigments, mucin, blood-corpuscles, pus, fibrin. Numerous fungi and other low organisms
develop in evacuated milk, and the rare blue milk is due to the development of bacillus
eyanogenéum. The milk-serum is blue, not the fungus. Blue milk is unhealthy, and causes
diarrhcea. There are fungi which make milk bluish-black or green. Red and yellow milk are
produced by a similar action of chromogenic fungi (§ 184). The former is produced by Micro-
coccus prodigiosus, which is colourless. The colour seems to be due to fuchsin. The yellow
colour is produced by bacillus synxanthus. Some of the pigments seem to be related to the
aniline-, and others to the phenol-colouring matters (Hiippe).

The rennet-like action of bacteria is a widely diffused property of these organisms ; they
coagulate and peptonise casein and may ultimately produce further decompositions. The
butyric acid bacillus ($ 184) first coagulates casein, then peptonises it, and finally splits it up,
with the evolution of ammonia (Hiippe).

Milk becomes stringy owing to the action of cocci which form a stringy substance [=dextran,
CyoHy Oyo (Scheibler)|, just as beer or wine undergoes a similar or ropy change. [The milk of
diseased animals may contain or transmit directly infectious matter. ]

Preparations of Milk.—(1) Condensed milk—80 grms. cane-sugar are added to 1 litre of
milk ; the whole is evaporated to 4; and while hot sealed up in tin cans. For children one
teaspoonful is dissolved in a pint of cold water, and then boiled.

(2) Koumiss is prepared by the Tartars from mare’s milk. After the addition of koumiss
and sour milk, the whole is violently stirred, and it undergoes the alcoholic fermentation,
whereby the milk-sugar is first changed into galactose, and then into alcohol ; so that koumiss
contains 2 to 8 per cent. of alcohol ; while the casein is at first precipitated, but is afterwards
partly redissolved and changed into acid-albumin and peptone. Tartar koumiss seems to be
produced by the action of a special bacterium (Diaspora caucasia). ’

(3) Cheese is prepared by coagulating milk with rennet, allowing the whey to separate, and
adding salt to the curd. When kept for a long time cheese ‘‘ripens,” the casein again becomes
soluble in water, probably from the formation of soda albuminate ; in many cases it becomes
semi-fluid, when it takes the characters of peptones. When further decomposition occurs, leucin
and tyrosin are formed. The fats increase at the expense of the casein, and they again undergo
further change, the volatile fatty acids giving the characteristic odour. The formation of
peptone, leucin, tyrosin, and the decomposition of fat recall the digestive processes, [Cheese
is coagulated casein entangling more or less fat, so that the richness of the cheese will depend
upon the kind of milk from which it is made. There are, in this sense, three kinds of cheese,
whole milk, skim milk, and cream cheese, the last being represented by Stilton, Roquefort,
Cheshire, &c. The composition is shown in the following table after Bauer :—

| | Water. saps te Aa. Fat. Extractives. Ash,
Cream cheese, ar. 35°75 716: 80°43 2°53 ; 4°13
Whole milk, : A 46°82 27°62 20°54 2°97 3°05 —
Skim milk, 48°02 82°65 8°41 6°80 412

Cream cheese, especially if it be made from goat’s milk, acquires a very high odour and s a
flavour when it is kept and ‘‘ripens”; the casein is partly decomposed to yield ammonia and —

ammonium sulphide, while the fats yield butyric, caproic, and other acids. ] ) wo

=o

FLESH AND ITS PREPARATIONS. 349

232. EGGS must be regarded as a complete food, as the organism of the young

‘chick is developed from them. The yolk contains a characteristic proteid body—

vitellin (§ 249), and an albuminate in the envelopes of the yellow yolk spheres—
nuclein, from the white yolk ; fats in the yellow yolk (palmitin, olein), cholesterin,
much /ecithin ; and as its decomposition-product, glycerin-phosphoric acid—grape-
sugar, pigments (lutein), and a body containing iron and related to hemoglobin ;
lastly, salts qualitatively the same as in blood—quantitatively as in the blood-cor-
puscles—and gases. The chief constituent of the white of egg is egg-albumin
(§ 249), together with a small amount of palmitin and olein partly saponified with
soda; grape-sugar, extractives ; lastly salts, qualitatively resembling those of blood,
but quantitatively like those of serwm, and a trace of fluorine. Relatively more of the
nitrogenous constituents than of the fatty constituents of eggs are absorbed (ubner).

[The shell is composed chiefly of mineral matter (91 per cent. of calcic carbonate, 6 per cent.
of calcie phosphate, and 3 per cent. of organic matter. A hen’s egg weighs about 1# oz., of
which the shell forms about 74. Note the amount of fats in the yolk. |

Composition :—
White of Egg. Yolk. White of Egg. Yolk.
Water, . : ; 84°8 51°5 | Mineral matter, , s T 1°4
Proteids, : : 12°0 15°0 Pigment extractives, He 2°1
Fats, &c., . ; 2°0 30°0

233. FLESH AND ITS PREPARATIONS.—Flesh, in the form in which it
is eaten, contains, in addition to the muscle-substance proper, more or less of the
elements of fat, connective- and elastic-tissue mixed with it (§ 293). The following
results refer to flesh freed as much as possible from those constituents. The chief
proteid constituent of the contractile muscular substance is myosin ; serum-albumin
occurs in the fluid of the fibres, in the lymph and blood of muscle. The fats are
for the most part derived from the interfascicular fat-cells, while lecithin and chole-
sterin come from the nerves of the muscles; the gelatin is derived from the connec-
tive-tissue of the perimysium, perineurium, and the walls of blood-vessels and
tendons. The red colour of the flesh is due to the hemoglobin present in the
sarcous substance, but in some muscles, ¢.g., the heart, there is a special pigment,
myohematin (MacMunn). Hlastin occurs in the sarcolemma, neurilemma, and in
the elastic fibres of the perimysium and walls of the vessels; the small amount of
keratin is derived from the endothelium of the vessels. The chief muscular sub-
stance, the result of the retrogressive metabolism of the sarcous substance, is kreatin
(—0°-05 per cent.) ; kreatinin, the inconstant inosinic acid, then lactic, or rather
sarcolactic acid (§ 293). Further, taurin, sarkin, wanthin, uric acid, carnin, inosit
(most abundant in the muscles of drunkards), wea (0°1 per cent.) dextrin (in horse
and rabbit, not constant) ; grape-sugar, but this is very probably derived post-mortem
from glycogen (0°43 per cent.), which occurs in considerable amount in feetal
muscles ; lastly volatile fatty acids. Amongst the salts, potash and phosphoric
acid compounds are most abundant ; magnesium phosphate exceeds calcium phos-
phate in amount. [The composition varies somewhat even in different muscles of
the same animal. |

In 100 parts Flesh there are, according to Schlossberger and v. Bibra—

Ox: Calf. Deer. Pig. Man. Fowl. Carp. Frog.
Water, E j . | 77°50 | 78°20 | 74°68 | 78°80 | 74°45 | 77°30 | 79°78 | 80°43
Solids, F . | 22°50 | 21°80 | 25°37 | 21°70 | 25°55 | 22°7 | 20°22 | 19°57

Soluble albumin, . 9-20 2°60 1°94 9°40 1°93 30 2°35 1°86
Colouring matter, .

Glutin, . . . | 1°30 | 1-60 | 0-50 | .o-80 | 2-07 | 1-2 | 1°98 -| 2:48
Alcoholic extract, . 1°50 1°40 4°75 1°70 3°71 14 3°47 3°46
Fats 4 ed Ma leiners but Bolade Pods ft 0-20

Insoluble albumin,
Blood-vessels, &c., | 17°50 | 16°2 | 16°81 | 16°81 | 15°54 | 16°5 | 11°31 | 11°67

350 FLESH AND ITS PREPARATIONS.

In 100 parts Ash there are—

Horse. Ox. Calf. Pig.

tash, . : : : : ; 39°40 85°94 84-40 37°79
Sean ae , ‘ : : : 4°86 are 2°35 4°02
Magnesia, . ; : ; : 3°88 3°31 1°45 4°81
Chalk, . : ; : . : — 1°80 1°73 1°99 7°54
Potassium, . , , : ‘a 5°36 fp Ae nay
Sodium, : é : ; : : { . } 10°59 { .
Chlorine, Pr Sey ee \ 1°47 4°86 0°62
Iron oxide, . : : . ‘ 1°0 0°98 0°27 0°35
Phosphoric Acid, . ; : : 46°74 34°36 48°13 44°47
Sulphuric _,, ‘ : : : 0°30 3°37 te us
Silicic . : ; ; , sive 2°07 0°81
Carbonic ,, ; : : : oe 8°02 ree
Ammonia, . : P : : eas 0°15

The amount of fat in flesh varies very much according to the condition of the animal. After
removal of the visible fat, human flesh contains 7°15; ox, 11°12; calf, 10°4; sheep, 3°9; wild
goose, 8°8 ; fowl, 2°5 per cent.

The amount of extractives is most abundant in those animals which exhibit energetic
muscular action ; hence it is largest in wild animals, The extract is increased after vigorous
muscular action, whereby sarcolactic acid is developed, and the flesh becomes more tender and is
more palatable. Some of the extractives excite the nervous system, ¢.g., kreatin and kreatinin ;
and others give to flesh its characteristic agreeable flavour [‘‘ osmasome,”] but this is also partly
due to the different fats of the flesh, and is best developed when the flesh is cooked. The ex-
tractives in 100 parts of flesh are in man and pigeon, 3; deer and duck, 4; swallow, 7 per cent.

Cooking of Flesh.—As a general rule, the flesh of young animals, owing to the sarcolemma,
connective-tissue, and elastic constituents being less tough, is more tender and more easily
digested than the flesh of old animals; after flesh has been kept for a time it is more friable
and tender, as the inosit becomes changed into sarcolactic acid and the glycogen into sugar,
and this again into lactic acid, whereby the elements of the flesh undergo a kind of maceration.
Finely divided flesh is more digestible than when it is eaten in large pieces. In cooking meat,
the heat ought not to be too intense, and ought not to be continued too long, as the muscular
fibres thereby become hard and shrink very much. Those parts are most digestible which are
obtained from the centre of a roast where they have been heated to 60° to 70° C., as this
temperature is sufficient, with the aid of the acids of the flesh, to change the connective-tissue
into gelatin, whereby the fibres are loosened, so that the gastric juice readily attacks them. In
roasting beef, apply heat suddenly at first, to coagulate a layer on the surface, which prevents
the escape of the juice.

Meat Soup is best prepared by cutting the flesh into pieces and placing them for several
hours in cold water, and afterwards boiling. Liebig found that 6 parts per 100 of ox flesh were
dissolved by cold water. When this cold extract was boiled, 2°95 parts were precipitated as
coagulated albumin, which is chiefly removed by ‘‘skimming,” so that only 3°05 parts remain
in solution. From 100 parts of flesh of fowl, 8 parts were extracted, and of these 4‘7 was coagulated
and 3°3 remained dissolved in the soup. By boiling for a very long time, part of the albumin
may be redissolved. The dissolved substances are :—(1) Inorganic salts of the meat, of which
82°27 per cent. pass into the soup; the earthy phosphates chiefly remain in the cooked meat.
(2) Kreatin, kreatinin, the inosinates and lactates which give to broth or beef-tea their stimu-
lating qualities, and a small amount of aromatic extractives. (8) Gelatin, more abundantly
extracted from the flesh of young animals. According to these facts, therefore, flesh broth or
beef-tea is a powerful stimulant, supplying muscle with restoratives, but is not a food in the
ordinary sense of the term, as kreatin in general leaves the body unchanged (v. Voit). The
flesh, especially if it be cooked in a large mass, after the extraction of the broth is-still avail-
able as a food. .

Liebig’s Extract of Meat is an extract of flesh evaporated to a thick syrupy consistence. It
contains no fat or gelatin, and is chiefly a solution of the extractives and salts of flesh.

of Fish.—A similar extract is now prepared from fish, and such extract has no fish
flavour, but presents much the same appearance, odour, and properties as extract of flesh.]

234. VEGETABLE FOODS.—tThe nitrogenous constituents of plants are not

so easily absorbed as animal food (Rubner). Carbohydrates, starch, and sugar are
very completely absorbed, and even a not inconsiderable proportion of cellulose may _
be digested. The more fats that are contained in the vegetable food, the less a “¢ i

the carbohydrates digested and absorbed.

|

VEGETABLE FOODS. 351

1, The cereals are most important vegetable foods ; they contain proteids, starch,
_ salts, and water about [4 per cent. The nitrogenous body glutin is most abundant

under the husk (fig. 236, c). The use of whole meal containing the outer layers
of the grain is highly nutritive, but bread containing much bran is somewhat indi-
gestible (Rubner), Their composition is the following :—

100 Parts of the Dry Meal contain 100 Parts of Ash contain
Of Albumin, Starch. Red Wheat. White Wheat.

Wheat, . 16°52 °/, 56°25 °/., 27°87 Potash, . 33°84

Rye, 1} 92 60°91 15°75 Soda, ae

Barley, 17°70 38°31 1°93 Lime, 3°09

Maize, . 13°65 77°74 9°60 Magnesia, 13°54

Rice, : 7°40 86°21 1°36 Iron oxide, 0°31

Buckwheat, 6°8-10°5| 65°05 49°36 Phosphoric Acid, 59°21
0°15 Silics, ~ s ‘ sae

It is curious to observe that soda is absent from white wheat, its place being taken by other
alkalies. Rye contains more cellulose and dextrin than wheat, but less sugar; rye-bread is
usually less porous.

[Oatmeal contains more nitrogenous substances (gliadin and glutin-casein) than wheaten flour,
but owing to the want of adhesive properties it cannot be made into bread, The amount of fat
and salts is large.]

In the preparation of bread the meal is kneaded with water until dough is formed, and to
it is added salt and yeast (Saccharomycetes cerevisie). When placed in a warm oven, the pro-
teids of the meal begin to decompose and
act as a ferment upon the swollen-up starch,
which becomes in part changed into sugar.
The sugar is further decomposed into CO,
and alcohol, the CO, forms bubbles, which
cause the bread to ‘‘rise”’ and thus become
spongy aad porous. The alcohol is driven
off by the baking (200°), while much soluble
dextrin is formed in the crust of the bread.
[But CO, may be set free within the dough
by chemical means without yeast or leaven,
thus forming unfermented bread, This
is done by mixing with the dough an
alkaline carbonate and then adding an acid.

Fig. 236.
Baking powders consist of carbonate of Microscopic characters of wheat ( x 200). a, cells of

soda and tartaric acid. In Dauglish’s pro- the bran; 8, cells of thin cuticle ; ¢, glutin cells ;
cess for aerated bread, the CO, is forced @Q. starch cells.

into water, and a dough is made with this i

water under pressure, and when the dough is heated, the CO, expands and forms the spongy
bread. Bread as an article of food is deficient in N, while it is poor in fats and some salts.
Hence the necessity for using some form of fat with it (butter or bacon).

_ 2. The pulses contain much albumin, especially legumin: together with starch,
lecithin, cholesterin, and 9 to 19 per cent. water. Peas contain 18°02 proteids, and
34°81 starch: beans 28°54, and 37°50: lentils, 29°31, and 40, and more cellulose.
Owing to the absence of glutin they do not form dough, and bread cannot be pre-
pared from them. On account of the large amount of proteids which they contain,
they are admirably adapted as food for the poorer ¢lasses.

[3. The whole group of farinaceous substances used as ‘‘ pudding stuffs,” such as corn-flour,
arrow-root, rice, hominy, are really very largely composed of starchy, substances. ]

4, Potatoes contain 70 to 81 per cent. water. In the fresh juicy cellular tissue,
which has an acid reaction, from the. presence of phosphoric, malic, and hydro-
chloric-acids, there is 16 to 23 per cent. of starch, 2°5 soluble albumin, globulin,
and a trace of asparagin. The envelopes of the cells swell up by boiling, and are
changed into sugar and gums by dilute acids. The poisonous solanin occurs in the
sprouts. In 100 parts of potato ash, May found 49°96 potash, 2:41 sodium chloride,

352 UTILISATION OF FOOD.

8-11 potassium chloride, 6°50 sulphuric acid derived ‘from burned proteids, 7°17
silica. 5 oi

5. In fruits the chief nutrient ingredients are sugar and salts; the organic acids
give them their characteristic taste, the gelatinising substance is the soluble so-called
pectin (C,,H,,O,.), which can be prepared artificially by boiling the very insoluble
pectose of unripe fruits and mulberries.

6. Green Vegetables are especially rich in salts, which resemble the salts of the
blood ; thus, dry salad contains 23 per cent. of salts, which closely resemble the
salts of the blood. Of much less importance are the starch, cell-substance, dextrin,
sugar, and the small amount of albumin which they contain.

[Vegetables are chiefly useful for the salts they contain, while many of them are antiscor-
butic, Their value is attested by the serious defects of nutrition, such as scurvy, which result
when they are not supplied in the food. In Arctic expeditions and in the navy, hme juice is
served out as an antiscorbutic. ]

[Preserved Vegetables. —The dried and compressed vegetables of Messrs Chollet & Company
are an excellent substitute for fresh vegetables, and are used largely in naval and military ex-
peditions. ]

(Utilisation of Food.-—As regards what percentage of the food swallowed is
actually absorbed, we know that, stated broadly, vegetable food is assimilated to a
much less extent than animal food in man. Fr. Hofmann gives the following table
as showing this:—

Vegetable. Animal.
Weight of Food.
| Digested. Undigested. | Digested. Undigested.

| Of 100 parts of solids, :

; : : 75°5 24°5 89°9 pS eet
| ,, 100 3; albumin,... ; : : 46°6 53°4 81°2 18°8
| ,, 100 ,, fats or carbohydrates, . 90°3 9°7 96°9 31]

|

[The following table, abridged from Parkes, shows the composition of the chief articles of
diet, and is also used for calculating diet tables :—

| Articles. _ Water. Proteids. Fats. Reet aba Salts.
ydrates.

Beef steak, 74°4 20°5 3°5 oe 1°6
Fat pork, . 39°0 9°8 48°9 a 2°3
Smoked ham, 27°8 24°0 36°5 a 10°1
White fish, 738°0 18°1 2°9 ee 1°0

| Poultry, . ¢ : 74°0 21°0 3°8 a 1°2

_ White wheaten bread, 40°0 80 Er) 49°2 13
Wheat flour, : 15°0 11°0 2°0 70°3 17
Biscuit, 8-0 15°6 1°3 73°4 17

| Rice, 10°0 5°0 0°8 83°2 0°5

| Oatmeal, . 150 12°6 5°6 63°0 3°0

| Maize, 13°5 10:0 6°7 64°5 1°4
Macaroni, . 18°1 9°0 0°3 76°8 0°8
Arrow-root, 15°4 0°8 sei 83°3 0°27
Peas (dry), 15°0 22°0 2°0 53°0 2°4
Potatoes, . 74°0 2°0 0°16 21°0 1°0
Carrots, 85°0 1°6 0°25 8°4 LU <a
Cabbage, . 91:0 18 5°0 5°8 0°7
Butter, . ; 6°0 0°3 91°0 dds STUN

(#5 for shell), 73°5 13°5 11°6 . 1°0
Cheese, . ; 36°8 33°5 24°3 re 54 4
Milk (S. G. 1032), 86'8 4°0 3°7 4°8 07
Cream, . : 66-0 2:7 26°7 2°8 1B, tg
Skimmed milk, 88°0 4°0 18 5°4 os |
Sugar, ; 3°0 fy 2 96°5 05)
f 4

235, CONDIMENTS, COFFEE, TEA, ALCOHOL.—Some substances are used along with
food, not so much on account of their nutritive properties as on account of their sti

ACTION OF ALCOHOL, - 353.

effects and agreeable qualities, which are exerted pace upon the organ of taste and partly upon
the nervous system. These are called condiments,

Coffee, Tea, and Chocolate are prepared as infusions of certain vegetables [the first of the roasted
berry, the second of the leaves, and the third of the seeds]. Their ‘chief active ingredients are re-
spectively caffein, thein (C, HN 40.+H,0), and theobromin (C,H,N,0,), which are regarded as.
alkaloids of the vegetable bases, and which have recently been prepared artificially from xanthin
(Z. Fischer), [Guarana, or Brazilian cocoa, is made of the seeds ground into a paste in the
form of a sausage. Maté or Paraguay tea (the leaves of a species of holly) is used in South
America, and so “also is the coca of the Andes (Erythroxylon Coca).] These ‘‘alkaloids” occur
as such in the plants containing them; they behave like ammonia; they have an alkaline
reaction, and form crystalline salts with acids. All these vegetable bases act upon the nervous
system ; some more feebly (as the above), others more powerfully (quinine) ; some stimulate
powerfully, or completely paralyse (morphia, atropin, strychnin, curarin, nicotin),

Effects.—All these substances act on the nervous system; they quicken thought,
accelerate movement, and stir one to greater activity. In these ropes they
resemble the stimulating extractives of beef-tea. Coffee contains about 4 per cent.
of caffein, part of which only is liberated by the act of roasting. Tea “has 6 per
cent. of thein; whilst green tea contains 1 per cent. ethereal oil, and black tea 4
per cent.; in green tea there is 18 per cent., in black 15 per cent. tannin; green
tea yields about 46 per cent., and the black scarcely 30 per cent. of extract. The
inorganic salts present are also of importance; tea contains 3°03 per cent. of
salts, and amongst these are soluble compounds of iron, manganese, and soda-
salts. In coffee, which yields 3:41 per cent. of ash, potash salts are most
abundant ; in all three substances the other salts which occur in the blood are also
present.

Alcoholic drinks owe their action chiefly to the alcohol which they contain.
Alcohol, when taken into the body, undergoes certain changes and produces certain
effects :—(1) About 95 per cent. of it is oxidised chiefly into CO, and H,O, so that
it is so far a source of heat. As it undergoes this change very readily, when taken
to a certain extent, it may act as a substitute for the consumption of the tissues of
the body, especially when the amount of food is insufficient. [Hammond found
that when he lived on an insufficient amount of food, alcohol, if given in a certain
quantity, supplied the place of the deficiency of food, and he even gained in weight.
If, however, sufficient food was taken, alcohol was unnecessary. As it interferes
with oxidation, and where there is a sufficient amount of other food, in health, it is
unnecessary for dietetic reasons.| Small doses diminish the decomposition of the
proteids to the extent of 6 to 7 per cent. Only a very small part of the alcohol is
excreted in the urine ; the odour of the breath is not due to alcohol, but to other
volatile substances mixed with it, ¢.g., fusel oil, &c. (2) In small doses it excites,
while in large doses it paralyses the nervous system. By its stimulating qualities
it excites to greater action, which, however, is followed by depression. (3) It
diminishes the sensation of hunger. (4) It excites the vascular system, accelerates
the circulation, so that the muscles and nerves are more active, owing to the greater
supply of blood. It also gives rise to a subjective feeling of warmth. In large
doses, however, it paralyses the vessels, so that they dilate, and thus much heat is
given off (§ 213, 7; § 227). The action of the heart also becomes affected, the
pulse becomes smaller, feebler, and more rapid. In high altitudes the action of
alcohol is greatly diminished, owing to the diminished atmospheric pressure, whereby
it is rapidly given off from the blood.

Alcohol in small doses is of great use in conditions of temporary want, and
where the food taken is insufficient in quantity. When alcohol is taken regularly,
more especially in large doses, it affects the nervous system, and undermines the
psychical and corporeal faculties, partly from the action of the impurities which it
may contain, such as fusel oil, which has a poisonous effect upon the nervous system,
partly by the direct effects, such as catarrh and inflammation of the digestive
organs, which it produces, and lastly, by its effect upon the normal metabolism.

: vt .

354 PREPARATION OF ALCOHOLIC DRINKS.

e action of alcohol in lowering the temperature, even in moderate doses, is most import-
=" By dilating the cutaneous vessels, it thus permits of the radiating of much heat from :
the blood. When the action of alcohol is pushed too far, and especially when this is combined .
with the action of great cold, its use is to be condemned. Brunton has pointed out that, as
regards its action on the nervous system, it seems to induce progressive paralysis, affecting the
nervous ¢issues ‘‘in the inverse order of their development, the highest centres being affected
first and the lowest last.” The judgment is affected first, although the imagination and
‘‘emotions may be more than unusually active.” The motor centres and speech are affected,
then the cerebellum is influenced, and afterwards the cord, while by and by the centres essential
to life are paralysed, provided the dose be sufficiently large. ] : ee

Preparation.—Alcoholic drinks are prepared by the fermentation of various carbohydrates, J
such as sugar derived from starch. The alcoholic fermentation, such as occurs in the manu- ;
facture of beer, is caused by the development of the yeast plant, Saccharomycetes cerevisi ;
while in the fermentation of the grape (wine), S. Ellipsoideus is the species present (ig. 237).

The yeast takes the substances necessary for the maintenance of its organic processes rectly
from the mixture of the sugar, viz., carbohydrates, proteids, and salts, especially calcium and
potassium phosphates and magnesium sulphate. These substances undergo decomposition

«, Within the cells of the yeast
&» plant, which multiply dur-
7% ing the process, and there
Sz are produced alcohol and
CO, (§ 150), together with
glycerine (3°2 to 3°6 per
cent.) and succinic acid (0°6
to 0°7 per cent.). Yeast is

Fig. 237. : 3 :
1, Isolated yeast cells; 2, 3, yeast cells budding; 4, 5, so-called Sage sone pba

endogenous formation of cells ; 6, sprouting and formation of buds. from the air, which always
;

contains its spores. When yeast is completely excluded, or if it be killed by boiling [or if its
action be prevented by the presence of some germicide], the fermentation does not occur. The
alcoholic fermentation is due to the vital activity of a low organism.

In the preparation of brandy, the starch of the grain or potatoes is first changed into sugar .
by the action of diastase or maltin. Yeast is added, and fermentation thereby produced ; the
mixture is distilled at 78°3°C. The fusel oil is prevented from mixing with the alcohol by pase
ing the vapour through heated charcoal. The distillate contains 50 to 55 per cent. of alcohol.

In the preparation of wine, the saccharine juice of the grape—the must—after being expressed
from the grapes, is exposed to the air at 10° to 15° C., and the yeast cells, which are floating
about, drop into it and excite fermentation, which lasts 10 to 14 days, when the yeast sinks to
the bottom. The clear wine is drawn off into casks, where it becomes turbid by undergoing an
after-fermentation, until the sugar is converted into alcohol and CO,, which is accompanied by
the deposition of some yeast and tartar. If all the sugar is not decomposed—which occurs
when there is not sufficient nitrogenous matter present to nourish the yeast—a sweet wine is
obtained. Wine contains 89 to 90 per cent. water, 7 to 8 per cent. alcohol, together with
wthylic, propylic, and butylic alcohol. The red colour of some wines is due to the colouring
matter of the skin of the grapes, but if the skins be removed before fermentation, red grapes
yield white wine. When wine is stored, it develops a fine flavour or bouquet. The characteristic
eri odour is due to cenanthic ether. The salis of wine closely resemble the salts of the

ood.

In the preparation of beer the grain is moistened, and allowed to germinate, when the
temperature rises, and the starch (68 per cent. in barley) is changed into sugar. Thus ‘‘ malt”
is formed, which is dried, and afterwards pulverised, and extracted with water at 70° to 75°,
the watery extract being the ‘‘ wort.” Hops are added to wort, and the whole is evaporated,
when the phtaocind are coagulated. Hops give beer its bitter taste, and make it keep, while their
tannic acid precipitates any starch that may be present, and clarifies the wort. After bei
boiled, it is cooled rapidly (12° C.); yeast is added, and fermentation goes on rapidly and wi
considerable effervescence at 10° to 14°, Beer contains 75 to 95 per cent. water ; alcohol, 2 to
5 per cent. (porter and ale, to 8 per cent.); CO,, 0°1 to 0°8 per cent.; sugar, 2 to 8 per cent.;
gum, dextrin, 2 to 10 per cent.; the hops yield traces of protein, fat, lactic acid, ammonia
pysprane, the salts of the grain and of the hops. In the ash there is a great preponderance —
of phosphoric acid and potash, both of which are of great importance for the formation of blood,
In 100 parts of ash there are 40°8 potash, 20°0 phosphors, magnesium phosphate 20, calcium
phosphate 2°6, silica 16°6 per cent. The formation of blood, muscle, and other tissues from 4
the consumption of beer is due to the phosphoric acid and potash, while if too much be taken, —
the potash produces fatigue, a

Condiments are taken with food, partly on account of their taste, and partly
because they excite secretion. Common salt, in a certain sense, is a condiment

.
‘
:

EQUILIBRIUM OF THE METABOLISM. 355

We may also include many substances of unknown constitution which act upon the
gustatory organs, ¢.g., dextrin, and substances in the crust of bread and in meat
which has been roasted. -

236. EQUILIBRIUM OF THE METABOLISM.—By this term is meant
that, under normal physiological conditions, just as much material is absorbed and
assimilated from the food as is removed from the body by the excretory organs in
the form of effete or end-products, the result of the retrogressive tissue-changes.
The income must always balance the expenditure ; wherever a tissue is used up, it
must be replaced by the formation of new tissue. During the period of growth,
the increase of the body corresponds to a certain increase of formation, whereby the
metabolism of the growing parts of the body is 2°5 to 6:3 times greater than that
of the parts already formed. Conversely, during senile decay, there is an excess
of expenditure from the body.

Methods. —The normal equilibrium of the metabolism of the body is investigated—(1) By
determining chemically that the sum of all the substances passing into the body is equal to the
sum of all the substances given off from it. Thus the C, N, H, O, salts and water of the food,
and the O inspired, must be equal to the C, N, H, O, salts and water given off in the excreta
(urine, feces, air expired, water excreted). (2) The physiological equilibrium is determined
empirically by observing that the body retains its normal weight with a given diet; so that,
by simply weighing a person, a physician is enabled to determine exactly the state of con-
valescence of his patient. The tedious process of making an elementary analysis of the
metabolic substances was first undertaken in the Munich School by v. Bischoff, v. Voit, v.
Pettenkofer, and others. ;

Circulation of C.—In the circulation of materials the total amount of C taken in
the food, if the metabolism be in a condition of physiological equilibrium, must be
equalled by the C in the CO, given off by the lungs and skin (90 per cent.),
together with the relatively small amount of C in the organic excreta of the urine
and feeces (10 per cent.).

Circulation of N.— Nearly all the N taken in with the food is excreted within
twenty-four hours in the form of urea. A very smail amount of nitrogenous matter
is excreted in the faces, while the other nitrogenous urinary constituents (uric acid,
kreatinin, &c.) represent about 2 per cent. of N. A trace of the N is given off by
the breath (§ 124), and a minute proportion in combination, in the epidermal scales

(50 milligrammes daily in the hair and nails), and in the sweat.

Deficit of N.—That nearly all the N taken in the food reappears in the urine and
feeces, as was stated by v. Voit to be the case in the carnivora and in the herbivora,
and by v. Ranke in man, is contradicted partly by old and partly by new observa-
tions, which go to show that the whole of the N cannot be recovered from these
excretions, but that on the contrary there is a considerable dejicit.

According to Leo, only 0°55 per cent. of the albumin transformed within the body (assuming
15 per cent. N in albumin) gives off its N in the form of gaseous N (according to Seegen and
Nowak 12 times more). In every exact analysis of the metabolism of N this gaseous excretion
of N must be taken into account.

The excretion of N after food does not take place regularly from hour to hour, but it increases
at once and distinctly, reaches its maximum in five to six hours, and then gradually falls. The
‘same is true of the excretion of $8 and P; but in these cases the maximum of excretion is reached
at the fourth hour. When fat is added to a diet of flesh, the excretion of N and S is uniformly
distributed over the individual hours of the day (v. Voit and Feder).

The nitrogenous constituents in the body during metabolism become poorer in C, and richer
in N and O. Thus in albumin to 1 atom of N there are 4 atoms C; in gelatin, 34. C; in
Sia 2 C; in kreatin, 1} C; in uric acid, 1} C; in allantoin, 1 C; in urea, only 4 atom
of C.

The H leaves the body chiefly in the form of water—a part, however, is in
combination in other excreta; the O is chiefly excreted as CO, and water ; a little
is given off in combination in other excreta; water is given off by evaporation
from the lungs and skin, and also in the urine and feces. As H is oxidised to
HO, more water is excreted than is taken in. Most of the readily soluble salts

356 EQUILIBRIUM OF THE METABOLISM.

are given off by the urine ; the less soluble salts, especially those of potash, and
the insoluble salts, in the faeces ; while others are given off in the sweat. Of the
sulphur of albumin, about one-half is excreted in the sulphur compounds in the
urine, and the other half in the faeces (taurin) and in the epidermal tissues.

Every organism has a minimum and a maximum limit of metabolism, according
to the amount of work done by the body, and its weight, If less food be given
than is necessary to maintain the former, the body loses weight ; while, if more be
given after the maximum limit is reached, the food so given is not absorbed, but .
remains as a floating balance, and is given off with the feces. When food is . —
liberally supplied and the weight increases, of course the minimum limit rises ; |
hence, during the process of “feeding” or “‘fattening,” the amount of food necessary
is very much greater than in poorly fed animals, for the same increase of the body- |
weight. By continuing the process, a condition is at last reached, in which the
digestive organs are just sufficient to maintain the existing condition, but cannot
act so as to admit of new additions being made to the body-weight (v. Bischof, v.
Voit, v. Pettenkofer). : a

By the term “ luxus consumption” is meant the direct combustion or oxidation
of the superfluous food-stuffs absorbed into the blood. This, however, does not.
exist; on the contrary, the material in the juices is always being used for building j
up the tissues. The albumin found in the fluids, which everywhere permeate the
tissues, has been called ‘circulating albumin,” and according to v. Voit it
undergoes decomposition sooner than the organised or “organic albumin” which ;
forms an integral part of the tissue. According to v. Voit, in 24 hours 1 per cent.
of the organic and 70 per cent. of the circulating albumin is used up.

[Liebig taught that the nitrogenous metabolism of the body depended on a corresponding
decomposition of the proteids of the organs, so that the proteids in the food supplied the place ¥
of the proteids of the organs thus used up. He called the proteids ‘‘ plastic foods” or ‘‘ tissue
formers,” while he regarded the fats and carbohydrates as ‘‘ respiratory foods,” as he supposed
that they alone were concerned in the evolution of heat. As a matter of fact, experiment
proved that the N metabolism is to a large extent independent of the proteids of thefood. The
luxus-consumption theory was invented to explain this. It simply means, that proteids taken
with the food not only replace the amount of proteids which have been decomposed during the
activity of organs and tissues, but that any excess is immediately consumed without being con-
verted into tissue, and thus this surplus amount giving rise to heat, by being oxidised, to a certain
extent replaces the fats and carbohydrates. But Voit showed that nitrogenous metabolism is .
not influenced by the activity of the organism, and he proved that in ordinary conditions, only
a small amount of the organic albumin, 7.e., that composing tissues and organs, undergoes
(lecomposition, while, owing to the action of the cellular elements of the tissue, a large amount
of the circulating albumin is split up, so that under ordinary conditions, the organic albumin is
comparatively stable. This he demonstrated from a comparison of the urea excreted, for the
urea may be taken as an index of the N metabolism in well-fed, fasting, and starving animals,
But in certain pathological conditions the organic albumin may undergo rapid change, having
become less stable, as in fevers, and poisoning with phosphorus. ]

Quality and Quantity of the Diet.—A<s far as his organisation is concerned, man
belongs to the omnivorous animals, 7.¢., those that can live upon a mixed diet. For
an adequate diet man requires for his existence and to maintain health a mixture
of the following four chief groups of food-stuffs along with the necessary relishes ;—
none of them must be absent from the food for any length of time. They are :—

1. Water—for an adult in his food and drink, 2700 to 2800 grms. [70 to 90
oz.] daily (§ 229 and § 247, 1), ia

irst.—The needs of the economy for water are expressed by the sensation of thirst. The
sensation of heat and dryness may be confined to the tongue, mouth and fauces, and indeed ,
may be excited by inhaling dry air. This local thirst may be allayed by swallowing water or —
by eating substances which excite the secretion of saliva. More frequently, however, the —
sensation is the expression of a general condition indicating the diminution of water in he
tissues ; or it may be due to excess of saline matters in the blood. In some diseases this sensation —
is very intense, ¢.9., diabetes. If water be injected into the blood-vessels, or stomach, both the
general and local thirst are abolished; even although no water enters the mouth. ] o..

COMPOSITION OF FOODS. 357

2. Inorganic substances or Salts are an integral part of all tissues, and without
them the tissues cannot be formed. They occur in ordinary food. The addition
of too much salt increases the consumption of water, and this in turn increases the
transformation of N in the body. Ifan animal be deprived of salts, nutrition is
interfered with ; food deprived of its lime affects the formation of the bones; de-
prival of common salt causes albuminuria (247, A, ITI). The alkaline salts serve
_ to neutralise the sulphuric acid formed by the oxidation of the sulphur of the pro-
teids. Iron, which is so essential for the formation of blood, exists in animals and
plants in combination with complex organic bodies.

Only in times of famine is man driven to eat large quantities of inorganic substances, to
extract the organic matter mixed therewith. A. v. Humboldt states, in regard to the inhabit-
ants of the Orinocco, that they eat a kind of earth which contains innumerable infusoria.

3. At least one animal or vegetable albuminons body or proteid (s§ 248, 250).
The proteids are required to replace the used-up nitrogenous tissues, ¢.g., for
muscles, They contain 15°4 to 16‘5 per cent. N.

The proteids are in blood-=20°56 per cent.; muscles, 19°9 per cent.; liver, 11°74 per cent.;
brain, 8°63 per cent.; blood-plasma, 7°5 per cent.; milk, 3°94 per cent.; lymph, 2°46 per cent.
According to Pfliiger and Bohland, a youth of full stature, and 62 kilos. [136 lbs.] weight, de-
composes 89°9 grms, of albumin daily.

Asparagin, in combination with gelatin, can replace albumin in the food (Weiske), -while

asparagin alone limits the decomposition of albumin in herbivora but not in carnivora (J. Munk).
Ammoniacal salts, glycocoll, sarkosin, and benzamid increase with the amount of albumin in

the body.

4, At least one fat (§ 251), or a digestible picbohmin (s 252). These chiefly
serve to replace the transformed fats and non-nitrogenous constituents. Owing to
the large amount of C which they contain, when they undergo oxidation, they form
the chief source of the heat of the body (§ 206). Fats and carbohydrates may
replace each other in the food, and in inverse proportion too, corresponding to
the amount of C which each contains. As far as the mere evolution of heat is
concerned, 100 parts of fat =256 of grape-sugar = 234 of cane-sugar = 221 of dry
starch (Aubner). A man consumes 210 grms. fat daily.

[5. Every proper diet ought to have’a certain degree of sapidity or flavour. The substances
which give this are not useful in the evolution of energy or building up the tissues, but they
stimulate the nervous system and excite secretion. They are called ‘‘ Genussmittel’’ (means
of enjoying food) by the Germans, but we have no exact equivalent for this word in English,

though the articles themselves are included under our expression ‘‘ condiments.” These sub-
stances are the aromatic matter in roast meat (osmasome), tea, vinegar, salt, mustard, pepper,

&e. ]

[Condition of Diet for Health.—In an adequate diet, not only (1) should the
total quantity be sufficient and not more than sufficient, but (2) the constituents
should exist in proper proportions, (3) be digestible, and (4) the whole should be in
‘good oe wholesome, and not adulterated with any substance prejudicial to
health.

With regard to the relative proportions of the various kinds of food which
ought to be taken, experience has shown that the diet best suited for the body
must contain 1 part of nitrogenous foods to 34 or, at most, 44 of the non-nitro-
genous. Looking at ordinary foods from this point of view, we see how far they
correspond to this requirement, and how several substances may be combined to
produce a satisfactory diet.

Nit. Non-Nit.! - Nit. Non-Nit.| Nit. Non-Nit.
1. Veal, : . 10 1 8. Pork, . . 10. 80 14, Barley-meal, 10 57
2. Hare’s flesh, . 10 2 9. Cow’s milk, 10 30 15. White
3. Beef, ‘ me: Claas Wy 10. Humanmilk, 10 37 potatoes, 10 86
4, Lentils, , . 10 21 |. 11, Wheaten 16. Blue ,,, |. 10 115
5. Beans, . ap pA: ae flour, . 10 46 17. Rice, . 10 123
" Peas, ; o ORO ZG 12, Oat-meal, . 10 50 18. Buckwheat-

. Mutton, . Pory > ) Mima § 13. Rye-meal, . 10 57 meal, . 10 130

358 COMPOSITION OF FOODS.

An examination of this table shows that, in addition to human milk, wheat-flour has the ri ht
proportion of nitrogenous to non-nitrogenous substances. A man who tries to nourish himself on
beef alone, commits as great a mistake as the one who would feed himself on potatoes alone.
Experience has taught people that man may live upon milk and eggs, but that in addition to
flesh we must eat bread or potatoes, while pulses require fat or bacon. .

The diet varies with the climate and with the season of the year. As the organism must
produce more heat in cold latitudes, the inhabitants of northern climates must eat more non-
nitrogenous foods, such as fats and sugars or starches, which, on account of the large amount
of C they contain, are admirably adapted for producing heat (§ 214, I., 4).

Water. Protcids. Albuminoids. N-free org. bodies. Salts.
phe i vl
me E Se ee
PR ]
Pork. ee 55 = pe
Fo | 73
Fish. 76
Eee. | 13.5
Cow’s
milk. | 86
Human
milk. 2 89
Vegetable Foods,

Water. Proteids. Digestible. Non-digestible, Salts.
N-free organic bodies,

et es
a Le

Rice
Potatoes. 95

Whi

Turnip. 90,5

li-
Smo | 90
Beer, | 90
Eee
Fig. 238,

The graphic representation of the composition of foods (fig. 238) shows the re-
lative proportions of the most important food-stuffs, and how they vary from the
standard of 1 nitrogenous to 3} or 44 non-nitrogenous.

The absolute amount of food-stufis required by an adult in twenty-four hours
depends upon a variety of conditions. As the food represents the chemical reser-

DAILY QUANTITY OF FOOD REQUIRED. 359

voir of potential energy, from which the kinetic energy (in its various forms) and
the heat of the body are obtained, the absolute amount of food must be increased
when the body loses more heat, as in winter, and when more muscular activity
(work) is accomplished. Asa general rule an adult requires daily 180 grammes
proteids, 84 grammes fats, 404 grammes carbohydrates, and 30 grammes salts.

A Heauruy ApDULT requires In 24 Hours or water-free solids— _

M Laborious Work.
At Rest soernre
Food in Grammes. eee (Moleschott). (Play fair.) sree oe "i
Proteids, : : , ; ; 70°87 130 15592 137
Fats, . : . : : ‘ " 28°35 84 70°87 ny
Carbohydrates (Sugar, Starch, &c.), 310°20 404 567°50 352
Balten co ae. 4 : : : 2 14°00 30 40°00 40

[When we record these numbers in ounces we get the following results as water-
free solids required by an average man (Parkes) :—

| At Rest. | Ordinary Work. | Laborious Work.
Proteids, | 2°5 | 4°6 LS Gee
Fats, . : : | 10 3°0 3°5.to 4°5
Carbohydrates, . ‘ : Be 12°0 | 14°4- 16 to18
a ee 0°5 | 10 12to 1°5
Total water-free food, | vas 6 | 23-0 | 26°7 to 31°0

During ordinary work the proportion is about :—

Proteids 1: fats 0°6: carbohydrates 3:0,
2.¢., 1 nitrogenous to 3°6 non-nitrogenous. |

[In a diet for ordinary work (23 oz. of dry solids) a man takes about ;3, part
of his own weight daily ; ordinary food, however, as it is consumed, contains be-
tween 50 and 60 per cent. of water; if we add this proportion of water to the
actually dry food, we get 48 to 60 oz. of ordinary food (exclusive of liquids). But
we consume 50 to 80 oz. of water in some liquid form, making the total amount of
water 70 to 90 oz. (Parkes). |

The following tables show the elementary composition of the income and ex-
penditure :—
AN ADULT DoING A MoDERATE AMOUNT OF Work takes in :—

C. H. N. oe.
120 grammes albumin, containing . .| 64°18 g60- | 18:88 | 2934 |
90 «=, . fate, ie 1 0706 10:26 a 9°54 |
330 ,, . starch, . . , | 14632 20°33 af eg aR
7 981-20 | 3919 | 18-88 | 200-73 |
Add 744°11 grm. O from the air by respiration.
A .2818 ,, ;
; “a 32 ‘ Inorganic compounds (salts).

The whole is equal to 34 kilos. [7 lbs.], 2.¢., about 4, of the body-weight ; so
that about 6 per cent. of the water, about 6 per cent. of the fat, about 1 per cent.
albumin, and about 0°4 per cent. of the salts of the body are daily transformed
within the organism. |

360 DAILY QUANTITY OF FOOD REQUIRED.

An ADULT DOING A MopERATE AMOUNT OF Work gives off in grammes :—

| Water. | C. H. N. 0.

| By respiration, . ; : ‘S| 330 248°8 ing ? 651°15
Perspiration, . ; . | 660 2°6 a bay 7°2
Urine, . ; : ; = |). “2%00 9°8 3°3 15°8 5 hs BS

| Feces, . . : ho ee 63) 20°0 3°0 3°0 12°0

| | 2818 281°2 6°3 18°8 681°45

——

Add to this (besides 2818 grammes water as drink) 296 grammes water formed in the body by
the oxidation of H. These 296 granimes of water contain 34°89 grms. H, and 263°41 grms.
O ; 26 grms. of salts are given off in the urine, and 6 by the feces. 96°5 grms. of proteid
(=1°46 grm. a kilo.) are used up by a resting adult in 24 hours; but while working 107°6
grms. are used. Nominally 2°3 times as much fat as albumin are used up.

The investigations of the Munich School have shown that the following numbers represent
the minimum amount of food necessary for different ages :—

| Age. | -Nitrogenous. Fat. Carbohydrates,

| Child until 14 year, ‘ ; : . | 20-86 grms. 30-45 grms. 60-90 grms.
», from 6 to 15 years, . : : : 70-80 ,, 37-50, 250-400 ,,

| Man (moderate work), ; : ; : LIB. Ts 56 SC, 500 ,,

| Woman re ; ; j : a 44 ,, 400 ,,

| Old man, . ‘ : i : : , 100° 53 68 ,, 350 ,,

Old woman, ; : ; ; ‘ 80 ,, st ewes 260° 4

Small animals have a more lively metabolism than large ones. In small animals the decom-
position of albumin per unit weight of body is greater than in large animals (v. Voit). Small
animals as a rule consume more proteid than larger ones, because they generally have less bodily
fat (Rubner).

Relation of N to C.—In most of the ordinary articles of diet, nitrogenous and
non-nitrogenous substances are present, but in very varying proportion, in the
different foods. Man requires that these shall {be in the proportion of 1: 34
to 1:43. If food be taken in which this proportion is not observed, in order
to obtain the necessary amount of that substance which is contained in too small
proportion in his food, he must consume far too much food. In order to obtain the
130 grammes of proteids necessary a person must use

Cheese, . . 888 grms.| Beef, . . 614grms,| Rice, . . 2562 grms, ©

Lentils, : eo VROL 43 Eggs, : ~ 868... Rye-bread, . 2875. -«,
Peas, . ; - 582 ,, | Wheat-bread, . 1444 ,, Potatoes, . 10,000 ,,
provided he were to take only one of these substances as food ; so that if a work-
man were to live on potatoes alone, in order to get the necessary amount of N he
would have to consume an altogether excessive amount of this kind of food.

To obtain the 448 grammes of carbohydrates, or the equivalent amount of fat
necessary to support him, a man must eat |
Rice, . . °. 572grms.| Peas, . . 819 grms.| Cheese, . . 2011 grms,

Wheat-bread, . 625 Eggs, ; . 902 ,, | . Potatoes, . . 2039 ,,
Lentils, ‘ est eee Rye-bread, y 980 bebe ; -' 2261. &y

so that if he were to live upon cheese or flesh alone, he would require to eat an
enormous amount of these substances, | |

In the case of herbivora, the proportion of nitroge -ni i
diettin Sorta 666 c:0 Gate fh oid ot te 2 nitrogenous to non-nitrogenous food necessary 1s
237. HUN GER AN D STARVATION.—If a warm-blooded animal be deprived
of all food, it must, in order to maintain the temperature of its body and to
produce the necessary amount of mechanical work, transform and utilise the

?

potential energy of the constituents of its own body. The result is that its body-

weight diminishes from day to day, until death occurs from starvation.

4

LOSS OF WEIGHT DURING STARVATION. 361

The following table, from Bidder and Schmidt, shows the amounts of the different excreta in
the case of a starved cat :—

‘ | : Inorganic Dr ; Water in
Day. | weight. | taken, | Uvine, | Urea, |Substances | pages, | Expired C.| Urine
1. 2464 oE4 98 79 1°3 12 13°9 91°4
2. 2297 11°5 54 5°3 0°8 se 12°9 50°5
3. 2210 “ai 45 4°9 07 ett 13 42°9
4, 2172 68°2 45 3°8 07 1 Bea 12°3 43
5. 2129 wae 55 4°7 0°7 17 11°9 54°1
6. 2024 Re 44 4°3 0°6 0°6 11°6 41°1
i 1946 ae 40 3°8 0°5 07 i 37°5
8. 1873 eer 42 3°9 SSS ea ce | 10°6 40
9. 1782 15'2 42 4 05 | slag 10°6 41°4
10. LG ee 35 3°3 0°4 13 10°5 34
11. 1695 4 32 2°9 0°5 ta 10°2 30°9
12. 1634 22°5 30 2°7 04 he 10°3 29:6
138. 1570 (ee 40 3°4 0°5 0°4 L101 36°6
14, 1518 3 41 3°4 0°5 0°3 9°7 38
15. 1434 ae 41 2°9 0°4 0°3 9°4 38°4
16. 1389 ses 48 3 0°4 0°2 8°8 45°5
ilyg . 1335 pa 2 1°6 O72 0°3 7°8 26°6
18:7 1267 aes 13 0°7 0'1 0°3 6) 12°9
—1197 12a) | 77s 65'8 9°8 | Lay 190°7 734°4
|

The cat lost 1197 grms. in weight before it died, and this amount is apportioned
in the following way :—204°43 grms. (=17:01 per cent.) loss of albumin ; 132°75
grms. (=11-:05 per cent.) loss of fat; 863-82 grms. loss of water (=7 1-91 per
cent. of the total body-weight).

Methods. —In order to investigate the condition of inanition it is necessary—(1) to weigh the
animal daily; (2) to estimate daily all the C and N given off from the body in the feces, urine,
and expired air. The N and OC, of course, can only be obtained from the decomposition of
tissues containing them.

Amongst the general phenomena of inanition, it is found that strong well-nourished dogs
die after 4 weeks, man after 21 to 24 days—(6 melancholics who took water died after 41 days)
small mammals and birds 9 days, and frogs 9 months. Vigorous adults die when they lose 34;
of their body-weight, but young individuals die much sooner than adults. The symptoms
are obvious :—The mouth is dry, the walls of the alimentary canal become thin, and the diges-
tive secretions cease to be formed ; pulse-beats and respirations are fewer ; urine very acid from
the presence of an increased amount of sulphuric and phosphoric acids, whilst the chlorine
compounds rapidly diminish and almost disappear. The blood contains less water and the
plasma less albumin, the gall-bladder is distended, which indicates a continuous decomposition
of blood-corpuscles within the liver. The liver is small and very dark coloured, the muscles
are very brittle and dry, so that there is great muscular weakness, and death occurs with the
signs of great depression and coma.

The relations of the metabolism are given in the foregoing table, the diminu-
tion in the excretion of urea is: much greater than that of CO,, which is due
to a larger amount of fats than proteids being decomposed. According to
the calculation, there is daily a tolerably constant amount of fat used up,
while, as starvation continues, the proteids are ,decomposed in much smaller
amounts from day to day, although the drinking of water accelerates their de-
composition.

Loss of Weight of Organs.—It is of importance to determine to what ex-
tent the individual organs and tissues lose weight; some undergo simple loss
of weight, ¢.g., the bones, the fat undergoes very considerable and rapid decom-
position, while other organs, as the heart, undergo little change, because they
seem to be able to a mem eg from the peeereaeee products of rae
tissues.

362

METABOLISM ON A FLESH DIET,

A starving cat, according to v. Voit, lost—

Per cent. Per cent. of Per cent. Per cent. of

originally the total loss of originally the total loss of

present. body-weight. present. body-weight.
1. Fat, 97 26 °2 10. Lungs, . , ts y (0°
2. Spleen,” 66°7 0°6 11. Pancreas, 17°0 01
3. Liver, 53°7 4°8 12. Bones, ‘ 13°9 54
4. Testicles, 40°0 0'1 13. Central Nerv-
5. Muscles, 30°5 42°2 ous System, 3°2 01
6. Blood, 27°0 3°7 14. Heart, . ; 2°6 0°02
7. Kidneys, 25°9 0°6 15. Total loss of |
8. Skin, . , 20°6 8°8 the rest of . |
9. Intestine, . : 18°0 2°0 the body, . = 368 5*0

There is a very important difference according as the animals before inanition
have been fed freely on flesh and fat [7.e., if they have a surplus store of food
within themselves], or as they have merely had a subsistence diet. Well-fed
animals lose weight much more rapidly during the first few days than on the later
days. V. Voit thinks that the albumin derived from the excess of food occurs in
a state of loose combination in the body as “ circulating” or “ storage-albumin,” so
that during hunger it must decompose more rapidly and to a greater extent than
the “organic albumin,” which forms an integral part of the tissues (§ 236).
Further, in fat individuals, the decomposition of fat is much greater than in slender
persons.

2.38. METABOLISM ON A PURELY FLESH DIET.—A man is not able to
maintain his metabolism in equilibrium on a purely flesh diet ; if he were compelled
to live on such a diet, he would succumb. The reason is obvious. In beef the
proportion of nitrogenous to non-nitrogenous elementary constituents of food is
1: 1:7 (p. 357). A healthy person excretes 280 grammes [8 to 9 oz.] of carbon in the
form of CO,, in the expired air, and in the urine and feces. If a man is to obtain
280 grammes C from a flesh diet he must consume—digest and assimilate—more
than 2 kilos. [4°4 Ibs.] of beef in twenty-four hours. But our digestive organs are
unequal to this task for any length of time. The person is soon obliged to take
less beef, which would necessitate the using of his own tissues, at first the fatty
parts and afterwards the proteid substances,

A carnivorous animal (dog), whose digestive apparatus, being specially adapted for the
digestion of flesh, has a short intestine and powerfully active digestive fluids, can only main-
tain its metabolism in a state of equilibrium when fed on a flesh diet free from fat, provided its
body is already well supplied with fat, and is muscular. It consumes #5 to 3/5 part of the
weight of its body in flesh, so that the excretion of urea increases enormously. If it eats a
larger amount, it may ‘‘ put on flesh,” when, of course, it requires to eat more to maintain itself
in this condition, until the limit of its digestive activity is reached. If a well-nourished dog is
fed on less than 5 to 315 of its body-weight of flesh, it uses part of its own fat and muscle,
gradually diminishes in weight, and ultimately succumbs. Poorly fed, non-muscular dogs are
unable from the very beginning to maintain their metabolism in equilibrium for any length of
time on a purely flesh diet, as they must eat so large a quantity of flesh that their digestive
organs cannot digest it. The herbivora cannot live upon flesh food, as their digestive appa-
ratus is adapted solely for the digestion of vegetable food.

[The proteid metabolism depends (1) on the amount of proteids ingested, for
the great mass of these becomes changed into circulating albumin ; (2) upon the
previous condition of nutrition of the organism, for we know that a certain amount
of proteid may produce very different results in the same individual when he is in
good health, and when he has suffered from some exhausting disease. (3) The use
of other foods, ¢.g., fats and carbohydrates. If a certain amount of fat be added to
a diet of flesh, much less flesh is required, so that the N metabolism is reduced by
fat. This is spoken of as the “albumin-sparing action” of fats.] ,

Exactly the same result occurs with other forms of proteids, as with flesh.
has been proved that gelatin may to a certain extent replace proteids in the food,
in the proportion of 2 of gelatin to 1 of albumin. The carnivora, which can

A DIET‘OF FAT OR OF CARBOHYDRATES. 363,

maintain their metabolism in equilibrium by eating a large amount of flesh, can
do so with less flesh when gelatin is added to their food. A diet of gelatin alone,
which produces much urea, is not sufficient for this purpose, and animals soon lose
their appetite for this kind of food.

(Gelatin. —Voit has shown that gelatin readily undergoes metabolism in the body and forms
urea, and if a small quantity be taken, it is completely and rapidly metabolised. When ad-~
ministered it acts just like fats and carbohydrates as an ‘‘albumin-sparing”’ substance. It seems

~ that gelatin is not available directly for the growth and repair of tissues.] Owing to the great

solubility of gelatin, its value as a food used to be greatly discussed. The addition of gelatin
in the form of calf’s-foot jelly is reeommended to invalids, [When a large amount of gelatin is
given as food, owing to the large and rapid excretion of urea, the latter excites diuresis.] When
chondrin is given along with flesh for a time, grape-sugar is found in the urine.

[The Metabolism of Peptones.—Most of the proteids absorbed into the blood
are previously converted into peptones by the digestive juices. It has been asserted,
more especially by Briicke, that some albumin is absorbed unchanged (§ 192, 4),
and that only this is capable of forming organic albumin, while the peptones, after
undergoing a reconversion into albumin, undergo decomposition as such. This view
is opposed by many observers, who maintain that peptones perform all the func-
tions of proteids, so that peptones, with the other necessary constituents of an
adequate diet, sutfice to maintain a proper standard of health. |

239. A DIET OF FAT OR OF CARBOHYDRATES.—TIf fat alone be given
as a food, the animal lives but a short time. The animal so fed excretes even less
urea than when it is starving; so that the consumption of fat limits the decom-
position of the animal’s own proteids. As fat is an easily oxidised body, it yields
heat chiefly, and becomes sooner oxidised than the nitrogenous proteids which are
oxidised with more difficulty. If the amount of fat taken be very large, all the C
of the fat does not reappear, ¢.g., in the CO, of the expired air; so that the body
must acquire fat, whilst at the same time it decomposes proteids. The animal thus
becomes poorer in proteids and richer in fats at the same time.

[The metabolism of fats is not dependent on the amount of fats taken with the
food. 1. It is largely influenced by work, 7.e., by the activity of the tissues, and
in fact with muscular work CO, is excreted in greatly increased amount (§ 127, 6).
2. By the temperature of the surroundings, as more CO, is produced in the cold
(§ 214, 2), and far more fatty foods are required in high latitudes. In their action
on the organism, proteids and fats so far oppose each other, as the former increase
the waste, and therefore oxidation, while the latter diminish it, probably by affect-
ing the metabolic activity of the cells themselves (Bauer). As a matter of fact, fat
animals or persons bear starvation better than spare individuals. In the latter, the
small store of fat is soon used up, and then the albumin is rapidly decomposed.
For the same reason corpulent persons are very apt to become still more so, even
on a very moderate diet. |

When carbohydrates alone are given, they must first be converted by digestion
into sugar. The result of such feeding coincides pretty nearly with feeding with
fat alone. But the sugar is more easily burned or oxidised within the body than
the fat, and 17 parts of carbohydrate are equal to 10 parts of fat. Thus the diet
of carbohydrates limits the excretion of urea more readily than a purely fat diet.
The animals lose flesh, and appear even to use up part of their own fat.

[The metabolism of carbohydrates also serves to diminish the proteid meta-
bolism, as they are rapidly burned up and thus “spare” the circulating albumin.
But Pettenkofer and Voit assert that they are rapidly destroyed in the body, even
when given in large amount, so that they differ from fats in this respect. They
are more easily oxidised than fats, so that they are always consumed first in a diet
of carbohydrates and fat. By being consumed they protect the proteids and fats
from consumption. | i

364 DIET OF MIXTURE OF FLESH AND FAT,

The direct introduction of grape- and cane-sugar into the blood does not increase the amount
of O used, but the amount of CO, is increased. [The doctrine of Liebig, that the oxygen taken
in is a measure of the metabolic processes, is refuted by these and other experiments. It
would seem that fat is not directly oxidised by O, but that it is split up into other simpler
compounds which are slowly and gradually oxidised ; in fact, fat may lessen the amount of O
taken in, as it diminishes waste. ]

940. FLESH AND FAT, OR FLESH AND CARBOHYDRATES.—An
amount of flesh equal to sj; to jj of the weight of the body is required to nourish a
dog, which is fed on a purely flesh diet ; if the necessary amount of fat or carbo-
hydrates be added to the diet, a smaller quantity of flesh is required (v. Voit). For
100 parts of fat added to the flesh diet, 245 parts of dry flesh or 227 of syntonin
can be dispensed with. If instead of fats carbohydrates are added, then 100 parts
of fat = 230 to 250 of the latter (Aubnev). When the amount of flesh is insufficient,
the addition of fat or carbohydrates to the food always limits the decomposition of
the animal’s own substance. Lastly, when too much flesh is given along with
these substances, the weight of the body increases more with them than without
them. Under these circumstances, the animal’s body puts on more fat than flesh.
The consumption of 0 in the body is regulated by the mixture of flesh and non-
nitrogenous substances, rising and falling with the amount of flesh consumed. It
is remarkable that more O is consumed when a given amount of flesh is taken, than
when the same amount of flesh is taken with the addition of fat.

It seems that, instead of fat, the corresponding amount of fatty acids has the same effect on
the metabolism. [Ifa dog be fed with fatty acids and a sufficient amount of proteid, no fatty
acids are found in the chyle, while fat is formed synthetically, the glycerin for the latter prob-
ably being produced in the body.] They are absorbed as an emulsion just like the fats,.
When so absorbed, they seem to be reconverted into fats in their passage from the intestine to
the thoracic duct probably by the action of the leucocytes (J. Munk, Wil). [Glycerin in small
doses has no effect on the metabolism of proteid, but in large doses it increases it. It is con-
sumed in the body, as shown by experiments on the respiratory products, and it prevents

a certain amount of fat from being used up. About 20 per cent. is excreted in the urine
(Arnschink). }

241. ORIGIN OF FAT IN THE BODY.—I. Part of the fat of the body is
derived directly from the fat of the food, z.¢., it is absorbed and deposited in the
tissues. ‘This is shown by the fact that, with a diet containing a small amount of
albumin, the addition of more fat causes the deposition of a larger amount of fat
in the body (v. Voit, Hofmann).

[Hofinann starved a fat dog for 30 days until all its fat was used up. He fed it on lard and
a little albumin for 5 days and then killed it. In 5 days it absorbed 1854 grms. of fat and 254
grms. of albumin. It added to its body 1353 grms. of fat; but this amount could not be
formed from the proteids of the food, and therefore the fat must have come from the fat of the
food. Pettenkofer and Voit arrived at the same result in another way. They fed dogs on fish
and much fat, and by their respiration apparatus estimated the gaseous income and expendi-
ture (§ 122). All the N taken in reappeared in the excreta, but not all the C. The amount of C
retained was very large, therefore a non-nitrogenous residue must have been laid up in the body,
and it could only be fat, as this was the only substance found in large amount in. the body.
They estimated the possible amount of fat that could be formed from the proteids, and found that
the amount stored up was far greater than this; so that the fat of the food must have been
_ stored up in the tissues. ]

Lebedeff found that dogs, which were starved for a month, so as to get rid of all their own
fat, on being fed with linseed oil, or mutton suet and flesh, had these fats restored to their
tissues. These fats, therefore, must have been absorbed and deposited. J. Munk found the
same on feeding animals with rape-seed oil. Fatty acids may also contribute to the formation
of fats, as glycerin when formed in the body must be stored up during metabolism (J. Munk).

Fatty acids may contribute to the formation of fats by union with the glycerin of the body
during the metabolism.

II. A second source of the fats is albuminous bodies, In the case of the forma-
tion of fat from proteids, which may yield 11 per cent. of fat (according to Henne-

berg 100 parts of dry albumin can form 51:5 parts of fat), these proteids split up
into a non-nitrogenous and a nitrogenous atomic compound. The former, during —

j
er ed is ar 9 —

ss

.
|

ORIGIN OF FAT IN THE BODY. 365

a diet containing much albumin, when it is not completely oxidised into CO,, and
H,O, is the substance from which the fat is formed—the latter leaves the body
oxidised chiefly to the stage of urea.

Examples,—That fats are formed from proteids is shown by the following :—1. A cow which
produces 1 lb. of butter daily does not take nearly this amount of fatty matter in its food, so that
the fat would appear to be formed from vegetable proteids. 2. Carnivora giving suck, when
fed on plenty of flesh and soie fat, yield milk rich in fat. 3. Dogs fed with plenty of flesh
and some fat, add more fat to their bodies than the fat contained in the food. 4. Fatty de-
generation, ¢.g., of nerve and muscle, is due to a decomposition of proteids, 5. The transfor-
mation of entire bodies, ¢.g., such as have lain for a long time surrounded with water, into a
mass consisting almost entirely of palmitic acid or adipocere is also a proof of the transforma-
tion of part of the proteids into fats, 6. Fungi are also able to form fat from albumin during
their growth, [7. In starving dogs, Bauer estimated the N and CO, given off, and O taken in,
and then slowly poisoned them with phosphorus, and he found that the excretion of N was
increased twofold, while the excretion of CO, and the absorption of O were diminished one-half.
Therefore from a large amount of nitrogenous tissue, a nitrogenous body and a small amount of
a carbonaceous compound were excreted, while a large amount of a non-nitrogenous residue was
retained unconsumed. There was fatty degeneration of all the organs, the fat being derived
from the non-nitrogenous part of the proteid. The same obtains with arsenic and antimony. |

Fats not merely absorbed.—Experiments which go to show that the fat of animals, during the
fattening process, is not absorbed as such, from the food, are :—1. Fattening occurs with flesh
and soaps ; it is most improbable that the soaps are transformed into neutral fats by taking
up glycerin and giving up alkali. 2. Ifa lean dog be fed with flesh and palmitin- and stearin-
soda-soap, the fat of its body contains, in addition to palmitin and stearin, olein fat, so that
the last must be formed by the organism from the proteids of the flesh. Further, Ssubotin
found that, when a lean dog was fed on lean meat and spermaceti-fat, a very small amount of
the latter was found in the fat of the animal. Although these experiments show that the fat
of the body must be formed from the decomposition of proteids, they do not prove that adl the
fat arises in this way, and that none of it is absorbed and redeposited (§ 241, I.).

III. According to v. Voit, no fat is formed in the body directly from carbo-
hydrates, ¢.g., by reduction. As fattening occurs on a diet of pure flesh with the
addition of carbohydrates, it is assumed that the carbohydrates are consumed or
oxidised in the body, and that thereby a non-nitrogenous body derived from the
proteids is prevented from being burned up, and that it is changed into fat, and
@ 240). as such. No doubt fat is formed indirectly in the blood in this way
§ 240).

From experiments upon fattening animals, however, Lawes and Gilbert, Lehmann,
Heiden, v. Wolff, and others, think they are entitled to conclude that the carbo-
hydrates absorbed are directly concerned in the formation of fats, a view which is
supported by Henneberg, B. Schulze, and Soxhlet. According to Pasteur, glycerin
(the basis of neutral fats) may be formed from carbohydrates.

(Tscherwinsky fed two similar pigs from the same litter; No. I. weighed 7300 grms.; No. II.
7290 grms. No. I. was killed and its fat and proteids estimated. No. II. was fed for four
months on grain and then killed, the grain and excreta and the undigested fat and proteids
were analysed, so that the amount of fat and proteid absorbed in four months was estimated.
The pig then weighed 24 kilos., it was killed and its fat and proteids estimated.

No. II. contained 2°50 kilos. albumin and 9°25 kilos, fat.
No. I. he 0°96 69

23 39 ee ”? 9?

Assimilated, 166 ~:.,

"9:3 8°56 39 99
Taken in in food, 7°49 ,, e O06. tye as
Difference, —5'°93—,, Wi e190 | 355. 95

There were therefore 7'90 kilos. of fat in the body which could not be accounted for in the fat
of the food, The 5:93 kilos. of albumin of the food which were not assimilated as albumin
could yield only a small part of the 7°90 kilos. of fat, so that at least 5 kilos. of fat must have
been formed from carbohydrate, Lawes and Gilbert calculated that 40 per cent. of the fat in
pigs was derived from carbohydrates. How the carbohydrates are changed into fat in the
y is entirely unknown. |

Formerly it was believed that bees could prepare wax from honey alone; this isa mistake—
an equivalent of albumin is required in addition—the necessary amount is found in the raw
honey itself.

: 366 CORPULENCE.

242. CORPULENCE.—The addition of too much fat to the body is a pathological phends
menon which is attended with disagreeable consequences. With regard to the causes of obesity,
without doubt there is an inherited tendency (in 33 to gh cent, of the cases) in many
families—and in some breeds of cattle, to lay up fat in the , While other families may be
richly supplied with fat, and yet remain lean. ‘The chief cause, however, is taking too much
food, i.c., more than the amount required for the normal metabolism; corpulent people, in
order to maintain their bodies, must eat absolutely and relatively more than persons of spare
habit, under analogous conditions of nutrition (§ 236). ; ; vf
Conditions favouring Corpulence.—(1) A dict rich in proteids, with a corresponding addition
of fat or carbohydrates. As flesh or muscle is formed from proteids, and part of the fat of the body
is also formed from albumin; the assumption that fats and carbohydrates fatten, or, when taken
alone, act as fattening agents, is completely without foundation. (2) Diminished disintegra-
tion of materials within the body, eg., (a) diminished muscular activity (much sleep and little
exercise) ; (b) abrogation of the sexual functions (as is shown by the rapid fattening of castrated
animals, as well as by the fact that some women, after cessation of the menses, readily become
corpulent) ; (¢) diminished mental activity (the obesity of dementia), phlegmatic temperament.
On the contrary, vigorous mental work, excitable temperament, care and sorrow, counteract
the deposit of fat ; (d) diminished extent of the respiratory activity, as occurs when there is a
great Aeponiion of fat in the abdomen, limiting the action of the diaphragm (breathlessness of !
corpulent people), whereby the combustion of the fatty mattersiwhich become deposited in the |
hod, is limited ; (c) a corpulent person requires to use relatively less heat-giving substances in
his body, partly because he gives off relatively less heat from his compact body, than is done
by a slender long-bodied individual, and partly because the thick layer of fat retards the con-
duction of heat (§ 214, 4). Thus, corresponding to the relatively diminished production of
heat, more fat may be stored up; (f)a diminution of the red blood-corpuscles, which are the _
great exciters of oxidation in the body, is generally followed by an increase of fat—fat people, )
as a rule, are fat because they have relatively less blood (§ 41)—women with fewer red blood- |
corpuscles are usually fatter than men ; (g) the consumption of alcohol favours the conservation |
of fat in the body, the alcohol is easily oxidised, and thus prevents the fat from being burned |
up (§ 235). |
|

Disadvantages.—esides the inconvenience of the great size and weight of the body, corpu-
lent people suffer from breathlessness—they are easily fatigued, are liable to intertrigo between
the folds of the skin, the heart becomes loaded with fat, and they not unfrequently are subject
to apoplexy.

ih aden tp counteract corpulence we ought to—(1) Reduce uniformly all articles of diet.
The diet and body ought to be weighed from week to week, and as long as there is no diminu-
tion in the body-weight the amount of food ought to be gradually and uniformly reduced (not-
withstanding the appetite). This must be done very gradually and not suddenly. A moderate
reduction o, fat and carbohydrates in a normal diet, at the same time leads to a diminution of =
the fat of the body itself. Let a person; who is capable of muscular exertion take 156 grms. 7
eke 43 grms. fat, and 114 grms. carbohydrates ; but in those where congestions, hydreemia,

reathlessness have taken place, take 170 grms. proteid, 25 grms. fat, aud 70 grms. carbo- ;
hydrates (Oertel). It is not advisable to limit the amount of fat and carbohydrates alone, as is
done in the Banting-cure or Bantingism. Apart altogether from the fact that fat is formed
from proteids, if too little non-nitrogenous food be taken, severe disturbance of the bodily
metabolisin is apt to occur. (2) It is advisable during the chief meal to limit the consumption
of fluids of all sorts (even until three-quarters of an hour thereafter), and thus render the ab-
sorption and digestive activity of the intestine less active (Oertel). (3) The muscular activity
ought to be greatly developed by doing plenty of muscular work, or taking plenty of exercise,
both physical and mental. (4) Favour the evolution of heat by taking cold baths of consider-
able duration, and afterwards rubbing the skin strongly so as to cause it to become red ; further,
dress lightly, and at night use light bed-clothing ; tea and coffee are useful, as they excite the
circulation. (5) Use gentle laxatives; acid fruits, cider; alkaline carbonates (of Marienbad,
Carlsbad, Vichy, Neuenahr, Ems, &c.) act by increasing ‘the intestinal evacuations and dimin-
ishing absorption. (6) If from accumulation of fat there is danger of failure of the heart’s
action, Oertel recommends hill-climbing, whereby the cardiac muscle is exercised and strength-
ened. At the same time the circulation becomes more lively and the metabolism is increased.

[Oertel’s Method goes on the idea of strengthening the cardiac musculature, which is sought
to be accomplished by (1) limiting the amount of fluids consumed, and (2) carefully regulat
muscular exertion. The amount of food is first reduced one-half, and the water to a still lower
amount, while the nitrogenous elements in food are increased, the non-nitrogenous are decreased,
The person is then instructed to take exercise under certain medical precautions, first, on level
ground, and then on gradually increasing gradients.] aPY :

Fatty Degeneration.—The process of fattening consists in the deposition of drops of fat
within the fat-cells of the panniculus and around the viscera, as well as in the marrow of bone
(but ict are never deposited in the subcutaneous tissue of the eyelids, of the penis, of the red _
part of the lips, in the ears and nose). This is quite different from the fatty atrophy or fatty

‘
as

ae

‘METABOLISM OF THE TISSUES. 367

degeneration which occurs in the form of fatty globules or granules in albuminous tissues, ¢.9.,
in muscular fibres (heart), gland-cells (liver, kidney), cartilage-cells, lymph- and pus-corpuscles,
as well as in nerve-fibres separated from their nerve centres. The fat in these cases is derived
from albumin, much in the same way as fat is formed in the gland-cells of the mammary and
sebaceous glands. Marked fatty degeneration not unfrequently occurs after severe fevers, and
after artificial heating of the tissues ; when a too small amount of O is supplied to the tissues,
as occurs in cases of phosphorus poisoning (Bauer) ; in drunkards ; after poisoning with arsenic
and other substances, and after some disturbances of the circulation and innervation. Some
organs are especially prone to undergo fatty degeneration during the course of certain diseases.

2.43. METABOLISM OF THE TISSUES.—The blood-stream is the chief
medium whereby new material is supplied to the tissues and the effete products re-
moved from them. The lymph which passes through the thin capillaries comes
into actual contact with the tissue elements. Those tissues which are devoid of
blood-vessels in their own substance, such as the cornea and cartilage, receive
nutrient fluid or lymph from the adjacent capillaries, by means of their cellular
elements, which act as juice-conducting media. Hence, when the normal circulation
is interfered with, by atheroma or calcification of the walls of the blood-vessels,
these tissues are secondarily affected [this, for example, is the case in arcus senilis
of the cornea, due to a fatty degeneration of the corneal tissue, owing to some affec-
tion of the blood-vessels on which the cornea depends for its nutrition]. Total com-
pression or ligature of a// the blood-vessels results in necrosis of the parts supplied
by the ligatured blood-vessels.

Atrophies caused by diminution of the normal supply of blood, gradually, in the course of time
become less and less (Samze/).

Hence, there must be a double current of the tissue juices; the afferent or
supply current, which supplies the new material, and the efferent stream which
removes the effete products. The former brings to the tissues the proteids, fats,
carbohydrates, and salts from which the tissues are formed. It is evident that any
interruption of the arterial supply to the tissues will diminish this supply.

That such a current exists is proved by injecting an indifferent, easily recognisable substance .
into the blood, ¢.g., potassium fterrocyanide, when its presence may be detected in the tissues,
to which it has been carried by the outgoing current.

The efferent stream carries away the decomposition products from the various
tissues, more especially urea, CO,, H,O, and salts, and these are transferred as
quickly as possible to the organs through which they are excreted.

That such a current exists is proved by injecting such a substance as potassium ferrocyanide
into the tissues, ¢.g., subcutaneously, when its presence may be detected in the urine within

two to five minutes.

If the current from the tissues to the blood is so active that the excretory organs
cannot eliminate all the effete products from the blood, then these products are
found in the tissues. When certain poisons are injected subcutaneously, they pass
rapidly into the blood and are carried in great quantity to other tissues, ¢.g., to the
nervous system, on which they act with fatal effect, before they are eliminated to
any great extent from the blood by the action of the excretory organs. The effete
materials are carried away from the tissues by ¢wo channels, viz., by the veins and
by the lymphatics, so that if these be interfered with, the metabolism of the tissues
must also suffer. When a limb is ligatured so as to compress the veins and the
lymphatics, the efferent stream stagnates to such an extent that considerable swell-
ing of the tissues or cedema may occur (§ 203). The action of the muscles and
fascie are very important in removing these effete matters.

H. Nasse found that the-blood of the jugular vein is 0°225 per 1000 specifically heavier than

the blood of the carotid, and contains 0°9 parts per 1000 more solids; 1000 cubic centimetres

of blood circulating through the head yield about 5 cubic centimetres of transudation into the
tissues, .

The extent and intensity of the metabolism of the tissues depend upon a
variety of factors.

368 METABOLISM OF THE TISSUES.

1. Upon their activity.—The increased activity of an organ is indicated by the
increased amount of blood going to it, and by the more active circulation through
it (§ 100). Whenan organ is completely inactive, such as a paralysed muscle, or the
peripheral end of a divided nerve, the amount of blood and the nutritive exchange
of fluids diminish within these parts, The parts thus thrown out of activity be-
come pale, relaxed, and ultimately undergo fatty degeneration. The increased
metabolism of an organ during its activity has been proved experimentally in the
case of muscle, and [(§ 263) also in the brain (Speck)|. Langley and Sewell have
recently observed directly the metabolic changes within sufficiently thin lobules of
glands during life. The cells of serous glands (§ 143), and those of mucous, and
pepsin-forming glands (§ 164), during quiescence, become filled with coarse granules,
which are dark in transmitted light and white in reflected light, which granules are
consumed or disappear during granular activity. During sleep, when most organs
are at rest, the metabolism is limited, darkness also diminishes it ; while light
excites it, obviously owing to nervous influences, The variations in the total meta-
bolism of the body are reflected in the excretion of CO, (§ 127, 9) and urea (§ 257),
which may be expressed graphically in the form of a curve corresponding with the
activity of the organism ; this curve corresponds very closely with the daily varia-
tions in the respirations, pulse, and temperature (p. 327).

2. The composition of the blood has a marked effect upon the current on which
the metabolism of the tissues depends. Very concentrated blood, which contains
a small amount of water, as after profuse sweating, severe diarrhoea, cholera, makes
the tissues dry, while if much water be absorbed into the blood, the tissues become
more succulent and even cedema may occur. When much common salt is present
in the blood, and when the red blood-corpuscles contain a diminished amount of O,
and especially if the latter condition be accompanied by muscular exertion causing
dyspnoea, a large amount of albumin is decomposed, and there is a great formation
ot urea. Hence, exposure to a rarefied atmosphere is accompanied by increased
excretion of urea, Certain abnormal conditions of the blood produce remarkable
results ; blood charged with carbonic oxide cannot absorb O from the air, and does
not remove CO, from the tissues (§ 16). The presence of hydrocyanic acid in the
blood (§ 16) is said to interrupt at once the chemical oxidation processes in the
blood, so that rapid asphyxia, owing to cessation of the internal respiration, occurs.
Fermentation is interrupted by the same substance in a similar way. A diminution
of the total amount of the blood causes more fluid to pass from the tissues into the
blood, but the absorption of substances—such as poisons or pathological effusions,
from the tissues or intestines is delayed. If the substances which pass from the
ann into the blood be rapidly eliminated from it, absorption takes place more
rapidly.

3. The blood-pressure, when it is greatly increased, causes the tissues to contain
more fluid, while the blood itself becomes more concentrated, to the extent of 3 to
5 per 1000. We may convince ourselves that blood-plasma easily passes through
the capillary wall, by pressing upon the efferent vessel coming from the chorium
deprived of its epidermis, e.g., by a burn or a blister, when the surface of the
wound becomes rapidly suffused with plasma. Diminution of the blood-pressure
produces the opposite result. The oxidation processes in the body are diminished
after the use of P, Cu, ether, chloroform, and chloral.

4, Increased temperature of the tissues (several hours daily) does not increase
the breaking up of albumin and fats. (See $§ 221, 220, 225.)

5. The influence of the nervous system on the metabolism is twofold. On the
one hand, it acts indirectly through its effect upon the blood-vessels, by causing
them to contract or dilate through the agency of vaso-motor nerves, whereby it

influences the amount of blood supplied, and also affects the blood-pressure. But

quite independently of the blood-vessels, it is probable that certain special nerves— _

)

REGENERATION OF ORGANS AND TISSUES. 369

the so-called trophic nerves, influence the metabolism or nutrition of the tissues
(§ 342, c). That nerves do influence directly the transformation of matter within
the tissues is shown by the secretion of saliva resulting from the stimulation of
certain nerves, after cessation of the circulation (§ 145), and by the metabolism
during the contraction of -bloodless muscles. Increased respiration and apnoea are

- not followed by increased oxidation (Pfltiger) (§ 127, 8).

[Gaskell has raised the question as to the existence of katabolic and anabolic nerves con-
trolling respectively the analytic and synthetic metabolism of the tissues. ]

9244, REGENERATION.—The extent to which lost parts are replaced varies greatly in
different organs. Amongst the lower animals, the parts of organs are replaced to a far greater
extent than amongst warm-blooded animals. When a hydra is divided into two parts, each
part forms a new individual—nay, if the body of the animal be divided into several parts in a
particular way, then each part gives rise to a new individual (Spallanzant). The Planarians
also show a great capability of reproducing lost parts (Dugés). Spiders and crabs can reproduce
lost feelers, limbs, and claws; snails, part of the head, feelers, and eyes, provided the central
nervous system is not injured. Many fishes reproduce fins, even the tail fin. Salamanders
and lizards can produce an entire tail, including bones, muscles, and even the posterior part of
the spinal cord; while the triton reproduces an amputated limb, the lower jaw, and the eye.
This reproduction necessitates that a small stump be left, while total extirpation of the parts
prevents reproduction. In amphibians and reptiles the regeneration of organs and tissues, as
a whole, takes place after the type of the embryonic development, and the same is true as re-
gards the histological processes which occur in the regenerated tail and other parts of the body
of the earth-worm. .

The extent to which regeneration can take place in mammals and in man is very
slight, and even in these cases it is chiefly confined to young individuals. A true
regeneration occurs in—

1. The blood, including the plasma, the colourless and coloured corpuscles. (§ 7
and § 41.)

2. The epidermal appendages (§ 283) and the epithelium of the mucous mem-
branes are reproduced by a proliferation of the cells of the deeper layers of the
epithelium, with simultaneous division of their nuclei. Epithelial cells are repro-
duced as long as the matrix on which they rest and the lowest layer of cells are
intact. When these are destroyed cell-regeneration from below ceases, and the cells
at the margins are concerned in filling up the deficiency. Regeneration, therefore,
either takes place from below or from the margins of the wound in the epithelial
covering ; leucocytes also wander into the part, while the deepest layer of cells
forms large multi-nucleated cells, which reproduce by division polygonal flat
nucleated cells. [In the process of division of the cells, the nucleus plays an
important part, and in so doing it shows the usual karyokinetic figures (§ 431). ]
The nails grow from the root forwards ; those of the fingers in four to five months,
and that of the great toe in about twelve months, although growth is slower in the
case of fracture of the bones. The matrix is co-extensive with the /unule, and if it
be destroyed the nail is not reproduced (§ 284). The eyelashes are changed in
100 to 150 days, the other hairs of the body somewhat more slowly. If the papilla
of the hair follicle be destroyed, the hair is not reproduced. Cutting the hair
favours its growth, but hair which has been cut does not grow longer than ‘uncut
hair. After hair has grown to a certain length, it falls out. The hair never grows
at its apex. The epithelial cells of mucous membranes and secretory glands seem
to undergo a regular series of changes and renewal. The presence of secretory cells

- in the milk (§ 231) and in the sebaceous secretion (§ 285) proves this; the sperma-

tozoa are replaced by the action of spermatoblasts. In catarrhal conditions of

mucous membranes, there is a great increase in the formation and excretion of new

epithelium, while many cells are but indifferently formed and constitute mucous

corpuscles. The crystalline lens, which is just modified epithelium, is reorganised

like epithelium ; its matrix is the anterior wall of its capsule, with the single

layer of cells covering it. If the lens be removed and this layer of cells retained,
2A

370 REGENERATION OF TISSUES.

these cells proliferate and elongate to form lens fibres, so that the whole cavity of
the empty lens capsule is refilled. If much water be withdrawn from the body,
the lens fibres become turbid. [A turbid or opaque condition of the lens may
occur in diabetes, or after the transfusion of strong common salt or sugar solution
into a soe .

3. The blood-vessels undergo extensive regeneration, and they are regenerated in
the same way as they are formed (§ 7, B). Capillaries are always the first stage,
and around them the characteristic coats are added to form an artery or a vein,
When an artery is injured and permanently occluded, as a general rule the part of
the vessel up to the nearest collateral branch becomes obliterated, whereby the
derivatives of the endothelial lining, the connective-tissue corpuscles of the wall,
and the leucocytes change into spindle-shaped cells, and form a kind of cicatricial
tissue. Blind and solid outshoots are always found on the blood-vessels of young
and adult animals, and are a sign of the continual degeneration and regeneration
of these vessels. Lymphatics behave in the same way as_ blood-vessels ; after
removal of a lymphatic gland, a new one may be formed (Bayer).

4. The contractile substance of muscle may undergo regeneration after it has
become partially degenerated. This takes place after amyloid or wax-like degener-
ation, such as occurs not unfrequently after typhus and other severe fevers. This
is chiefly accomplished by an increase of the muscle corpuscles. After being com-
pressed, the muscular nuclei disappear, and at the same time the contractile contents
degenerate. After several days, the sarcolemma contains numerous nuclei which
reproduce new muscular nuclei and the contractile substance. In fibres injured by
a subcutaneous wound, Neumann found that, after five to seven days, there was a
bud-like elongation of the cut ends of the fibres, at first without transverse striation,
but with striation ultimately. If a large extent of a muscle be removed, it is
replaced by cicatricial connective-tissue. Non-striped muscular fibres are also
reproduced ; the nuclei of the injured fibres divide after becoming enlarged, and
exhibit a well-marked intra-nuclear plexus of fibrils. The nuclei divide into two,
and from each of these a new fibre is formed, probably by the differentiation of the
peri-nuclear protoplasm.

5. After a nerve is divided, the two ends do not join at once so as to permit the
function of the nerve to be established. On the contrary, marked changes occur.
If a piece be cut out of a nerve-trunk, the peripheral end of the divided nerve
degenerates, the axial cylinder and the white substance of Schwann disappear.
The interval is filled up at first with juicy cellular tissue. The subsequent changes
are fully described in § 325, 4. There seems to be in peripheral nerves a continual
disappearance of fibres by fatty degeneration, accompanied by a consecutive forma-
tion of new fibres (Sigm. Mayer). The regeneration of peripheral ganglionic cells
is unknown. YV. Voit, however, observed that a pigeon, part of whose brain was
removed, had within five months reproduced a nervous mass within the skull, con-
sisting of medullated nerve-fibres and nerve-cells. Eichhorst and Naunyn found
that in young dogs, whose spinal cord was divided between the dorsal and lumbar
regions, there was an anatomical and physiological regeneration, to such an extent
that voluntary movements could be executed (§ 338, 3). Vaulair, in the case of
frogs, and Masius in dogs, found that mobility or motion was first restored, and
afterwards sensibility. Regeneration of the spinal ganglia did not occur.

6. In many glands, the regeneration of their cells during normal activity is °
very active—sebaceous, mucous, Lieberkiihnian, uterine, mammary glands during

pregnancy—in others less. If a large portion of a secretory gland be removed,as

a general rule, it is not reproduced. A gland, if injured, and if suppuration follows,
is not regenerated. But the bile ducts (§ 173) and the pancreatic duct may be
reproduced (§ 171). According to Philippeaux and Griffini, if part of the spleen

be removed it is reproduced (§ 103). Tizzoni and Collucci observed the formation — 7

REGENERATION OF BONE, 475

of new liver-cells and bile-ducts after injury to the liver (§ 173), and Pisenti makes
the same statement as regards the kidney. After mechanical injury to the secre-
tory cells of glands (liver, kidney, salivary, Meibomian), neighbouring cells undergo
proliferation and aid in the restoration of the cells.
_ 7. Amongst connective tissues, cartilage, provided its perichondrium be :not
injured, reproduces itself by division of its cartilage cells; but usually when a part
of a cartilage is removed, it is replaced by connective-tissue.

8. When a tendon is divided, proliferation of the tendon cells occurs, and the

cut ends are united by connective-tissue.

9. The reproduction of bone takes place to a great extent under certain conditions.
If the articular end be removed by excision, it may be reproduced, although there
is a considerable degree of shortening. Pieces of bone which have been broken off
or sawn off heal again, and become united with the original bone. <A tooth may be
removed, replanted in the alveolus, and become fixed there. Ifa piece of periosteum
be transplanted to another region of the body, it eventually gives rise to the forma-
tion of new bone in that locality. If part of a bone be removed, provided the
periosteum be left, new bone is rapidly reproduced ; hence, the surgeon takes great
care to preserve the periosteum intact in all operations where he wishes new bone
to be reproduced. Even the marrow of bone, when it is transplanted, gives rise
to the formation of bone. ‘This is due to the osteoblasts adhering to the osseous

tissue.

In fracture of a long bone, the periosteum deposits on the surface of the ends of the broken
bones a ring of substance which forms a temporary support, the external callus. At first this
callus is jelly-like, soft, and contains many corpuscles, but afterwards it becomes more solid
and somewhat like cartilage. A similar condition occurs within the bone, where an internal
callus is formed. The formation of this temporary callus is due to an inflammatory prolifera-
tion of the connective-tissue corpuscles, and partly to the osteoblasts of the periosteum and
marrow. According to Rigal and Vignal, the internal callus is always osseous, and is derived
from the marrow of the bone. The outer and inner callus become calcified and ultimately
ossified, whereby the broken ends are reunited. Towards the fortieth day, a thin layer of bone
is formed (intermediary callus) between the ends of the bone. Where this begins to be
definitely ossified, the outer and inner callus begin to be absorbed, and ultimately the inter-
mediary callus has the same structure as the rest of the bone.

There are many interesting observations connected with the growth and metabolism of bones,
1. The addition of a very small amount of phosphorus or arsenious acid to the food causes con-
siderable thickening of the bones. This seems to be due to the non-absorption of those parts of
the bones which are usually absorbed, while new growth is continually taking place. 2. When
food devoid of lime-salts is given to an animal, the growth of the bones is not arrested, but the
bones become thinner, whereby all parts, even the organic basis of the bone, undergo a uniform
diminution, 3. Feeding with madder makes the boues red, as the colouring matter is deposited
with the bone-salts in the bone, especially in the growing and last formed parts. In birds the
shell of the egg becomes coloured. 4. The continued use of lactic acid dissolves the bones.
The ash of bone is thereby diminished. If lime-salts be withheld at the same time, the effect
is greatly increased, so that the bones come to resemble rachitic bones. (Development of Bone,
§ 447.) :

When a lost tissue is not replaced by the same kind of tissue, its place is always
taken by cicatricial connective-tissue. |

When this is the case, the part becomes inflamed and swollen, owing to an exudation of
plasma. The blood-vessels become dilated and congested, and, notwithstanding the slower
circulation, the amount of blood is greater. The blood-vessels are increased, owing to the
. formation of new ones. Colourless blood-corpuscles pass out of the vessels and reproduce them-
selves, and many of them undergo fatty degeneration, whilst others take up nutriment and
become converted into large uninucleated protoplasma cells, from which giant cells are developed.
The newly formed blood-vessels supply all these elements with blood,

245, TRANSPLANTATION OF TISSUES.—The nose, ear, and even a finger, after having
been severed from the body by a clean cut,*have, under certain circumstances, become united
to the part from which they were removed. The skin is frequently transplanted by surgeons,
as, for example, to form a new nose. The piece of skin is cut from the forehead or arm, to
which it is left attached by a bridge of skin, is then stitched to the part which it is desired to
cover in, and when it has become attached in its new situation, the bridge of skin is severed.

372 INCREASE IN SIZE AND WEIGHT. C

Reverdin cut a piece of skin into pieces about the size of a pea and fixed them on an ulcerated
surface, where they, as it were, took root, grew, and sent off from their margins epithelial out-
growths, so that ultimately the whole surface was covered with epithelium. [White skin

- transplanted to a negro ultimately becomes pigmented, and black skin transplanted to a white .
person becomes white.] The excised spur of a cock was transplanted and fixed in the comb of
the ‘same animal, where it grew (John Hunter). P. Bert cut off the tail and legs of rats and
transplanted them under the skin of the back of other rats, where they united with the adjoin-
ing parts. Ollier found that, when periosteum was transplanted, it grew and reproduced bone
in its new situation. Even blood and lymph may be transfused (Transfusion, § 102). [Small
portions (1°5 mm.) of epiphyses, costal cartilage, of a rabbit or kitten, when transplanted quite
fresh into the anterior chamber of the eye, testis, submaxillary gland, kidney, and under the
skin of a rabbit, attach themselves and grow, and the growth is more rapid the more vascular
the site on which the tissue is transplanted. The cartilage is not essentially different from
hyaline cartilage, but the cells are fewer in the centre, while the matrix tends to become fibrous,
Small pieces of epiphysial cartilage introduced into the jugular vein were found as cartilaginous
foci in the lungs. Tissues transplanted from embryonic structures grow far better than adult
tissues. If a portion of the cornea of a rabbit be transplanted to a human eye, provided
Descemet’s membrane be clear, it will grow and remain clear (v. Hippell). A rabbit’s nerve
has been transplanted to the human subject, but without success. ]

Many of these results seem only to be possible between individuals of the same species,’
although Helferich has recently found that a piece of a dog’s muscle, when substituted for
human muscle, united to the adjoining muscle, and became functionally active. [J. R. Wolfe
has transplanted the conjunctiva of the rabbit to the human eye.] Most tissues, however, do
not admit of transplantation, e.g., glands and the sense-organs. They may be removed to
other parts of the body, or into the peritoneal cavity, without exciting any inflammatory re-
action ; they, in fact, behave like inert foreign matter.

2.46. INCREASE IN SIZE AND WEIGHT. —The length of the body, which at birth is usually
gts of the adult body, undergoes the greatest elongation at an early period :—in the first year,
20; in the second, 10 ; in the third, about 7 centimetres ; whilst from, five to sixteen years the
annual increase is about 54 centimetres. In the twentieth year the increase is very slight.
From fifty onwards the size of the body diminishes, owing to the intervertebral discs becoming
thinner, and the loss may be 6 to 7 centimetres about the eightieth year. The weight of the
body (;), of an adult) sinks during the first five to seven days, owing to the evacuation of the
meconium and the small amount of food which is taken at first. Only on the tenth day is the
weight the same as at birth.

The increase of weight is greater in the same time than the increase in length. Within the
first year a child trebles its weight. The greatest weight is usually reached about forty, while
towards sixty a decrease begins, which at eighty may amount even to 6 kilos. The results of
measurements, chiefly by Quetelet, are given in the following table :—

| Length (Cmtr.). Weight (Kilo.). Length (Cmtr.). Weight (Kilo.).
Age. | | Age.
| Man. Woman. Man. | Woman. | Man. Woman. Man. Woman,
0 49°6 48°3 3°20 2°91 15 1559 | 147°5 | 46:41 | 41°30
1 69°6 | 69°0 | 10:00 9°30 || 16 161°0 | 150°0 | 53°39 | 44-44
2 79°6 | 78-0 | 12:00 | 11-40 ||’ 17 | 167-0 | 154-4 | 57-40 | 49°08
| 8 | 860 | 85-0 | 18-21 | 12°45 || 18 170°0 | 1562 | 61:26 | 53°10
uckor 93°2 | 91:0 | 15:07 | 14°18 || ‘19 Wc rad aaa 63°32 od
5 | 99:0 | 97:0 | 16°70 | 15°50 || 20 171'1 | 157°0 | 65°00 | 54°46
| 6 104°6 | 103°2 | 18:04 | 16°74 | 25 172°2 | 157°7 | 68:29 | 55°08
7 | 1112 | 109° | 2016 | 18°45 || .80 172°2 | 157°9 | 68°90 | 5514:
| 8 | 117-0 | 113-9 | 22-26 19°82 | 40 | 171°3 | 155°5 | 68-81 | 56°65
1 9 | 122-7 | 120°0 | 24°09 | 22-44 | 50 | 167°4 | 153°6 | 67°45 | 58°45
10 | 128-2 | 1248 | 2612 | 2424 | 60 | 1638-9 | 1516 | 65:50 | 56-73,
11 1327 | 127°5 | 27°85 | 26°25 || 70 | 1623 | 151-4 | 68°08'| 53°72
12 135°9 | 132-7 | 31°08 | 30°54 80 161°3 | 150°6 | 61°22 | 51°52 |”
13 140°3 | 138°6 | 35°32 | 34°65 90 < a) phere 57°83. | 49°34
14 148°7 | 144°7 | 40°50 | 38°10 || (Chiefly from Quetelet.)

Between the twelfth and fifteenth years the weight and size of the girl are greater than of the
boy. Growth is most active in the last months of feetal life, and afterwards from the sixth to the
hiuth year until the thirteenth to the sixteenth. The full stature is reached about thirty, but
not the greatest weight. ' ae Dt ae

¢ cit.» \
AoW

INORGANIC CONSTITUENTS. 373

\ ‘

General View of the Chemical Constituents of
the Organism.

- 247, (A) INORGANIC CONSTITUENTS.—I. Water forms 58°5 per cent. of the whole
body, but it occurs in different quantity in the different tissues. The kidneys contain the
most water, 82°7 per cent.; bones, 22 per cent.; teeth, 10 per cent.; while enamel contains
the least, 0°2 per cent. (§ 229). According to some observers, peroxide of hydrogen (H,O,) is
also present in the body.

[Approximately, water forms about two-thirds of the weight of the body, so that a body
weighing ‘75 kilos. (165 lbs.) contains 50 kilos. (110 lbs.) of water. The following table,
modified from Beaunis, shows the percentage of water in several tissues and organs :—

Solids.

Tissue or Organ. Water. Solids. | Tissue or Organ. Water. Solids. | Tissue or Organ. Water. Solids.
Enamel, ? 2 99°8 | Spinal cord,. 69°7 30°3 | Thymus, itt 23.0
Dentine . 10°0 90°0 | White matter ? ‘ Connective- BA eae
Bone, ‘ . 48°6 51°4 of brain, 70°0 oe tissue : 196 ane
Fat, ‘ . 29°9 7017) Skiny. Peay 4.) 28°0 | Kidney, . ao Oa 17°3
Elastic tissue, 49°6 50°4 | Brain, . 70-0 25°0 | Grey matter of 858 142
Cartilage, poo 45°0 | Muscles, oA ek 24°3 brain, . :
Liver, . . 69°3 30°7 | Spleen, 45°8 24°2 | Vitreoushumour, 98°7 1°3

Liquids.
Blood, 79°1 20°9 , Lymph, . 95°8 4*2 | Aqueous humour, 98°6 1-4
Bile, : . 86:4 13°6 | Serum, . et Gorey 41 | Cerebro-spinal 98°8 2
Milk, . neue 10°9 | Gastrie juice, . 97°3 27 fluid, :
Liquorsanguinis, 90°1 9°9 | Intestinal juice, 97°5 2°5 | Saliva, . ee 0°5
Chyle, 92°8 7‘2 | Tears, 98-2 1°8 | Sweat, . 2. .209°5 0°5

II. Gases.—O, — ozone (§ 37) -H, -N-CO, (§ 38). Marsh gas CH, (§ 124), NH, (§ 39,
§ 124, § 184), HS (§ 184).

III. Salts.—Sodium chloride [is one of the most important inorganic substances present in
the body. It occurs in all the tissues and fluids of the body, and plays a most prominent part
in connection with the diffusion of fluids through membranes, and its presence is necessary for
the solution of the globulins (p. 376). Sometimes it exists in a state of combination with.
proteid bodies, as in the blood-plasma. Common salt is absolutely necessary for one’s existence ;
if it be withdrawn entirely, life soon comes to an end. About 15 grammes are given off in
twenty-four hours, chiefly by the urine. Boussingault showed that the addition of common
salt to the food of cattle greatly improved their condition].

[Calcium phosphate (Ca,P,0,) is the most abundant salt in the body, as it forms more than
one-half of our bones, but it also occurs in dentine, enamel, and to a much less extent in the
other solids and fluids of the body. Amongst secretions, milk contains relatively the largest
amount (2°72 percent.). In milk it is necessary for forming the calcareous matter of the bones
of the infant. It gives bones their hardness and rigidity. It is chiefly derived from the
food, and, as only a small quantity is given off in the excretions, it seems not to undergo rapid
removal from the body. ] ; :

[Sodium phosphate (PNa,0,), acid sodiwm phosphate (PNa,HO,), acid potassium phosphate
(PK,HO,). The sodium phosphate and the corresponding potash salt give most of the fluids
of the body their alkaline reaction. The alkaline reaction of the blood-plasma is partly due to
alkaline phosphates, which are chiefly derived from the food. The acid sodium phosphate is the
chief cause of the acid reaction of the urine. A small quantity of phosphoric acid is formed in
the body owing to the oxidation of lecithin, which contains phosphorus. ]

[Sodium carbonate (Na,CO,) and sodium bicarbonate (NaHCO ) exist in small quantities in.
the food, and are formed in the body from the decomposition of the salts of the vegetable acids.
They occur in the blood-plasma, where they play an important part in carrying the CO, from
the tissues to the lungs. } os

[Sodium and potassium sulphates (Na,SO, and K,SO,) exist in very small quantity in the
body, and are introduced with the food, but part is formed in the body from the oxidation of
organic bodies containing sulphur.] .

otassium chloride (KCl) is pretty widely distributed, and occurs specially in muscle,
coloured blood-corpuscles, and milk. Calcium fluoride (CaFl,) occurs in small quantity in

374 CHARACTERS OF THE PROTEIDS.

bones and teeth. Calcium carbonate (CaCO;) i is associated with calcium phosphate in ‘bone,
tooth, and in some fluids, but it occurs in relatively much smaller amount. It is kept in
solution by alkaline chlorides, or by the presence of free carbonic acid. Ammonium chloride
(NH,Cl).—Minute traces occur in the gastric juice and the urine. Magnesium phosphate
(Mg; Po,) occurs along with calcium phosphate, but in very much smaller quantity. ]

Table by Beaunis of the relative proportions of Salts.

Heintz. Staffel. Breed. Oidtmann. | C. Schmidt. | Oidtmann,
Bone. oe of Brain. Liver. Lungs. Spleen.
Sodie chloride, , : os 10°59 4°74 ae 13°0 .
Potassic chloride, . ; a8 ae: ale sats i idee
Bala! ou” a, ee », 2°35 10°69 14°51 19°5 44°33
Potash, . : : ‘ a 34°40 34°42 25°23 i'3 9°60
Lime, . , : . | - 87°58 1°99 0°72 3°61 1°9 7°48
Magnesia, : : 1°22 1°45 1°23 0°20 1°9 0°49
Ferric oxide, . ; . oe Pe me 2°74 3°2 7°28
Chlorine, : ; : rer See ae 2°58 as 0°54
F luorine, ; 1°66 aa or a vei
Phosphoric acid (free), ee ae 9°15 ah ay say,
Phosphoric acid (combined), 53°31 48°13 39°02 -| 50°18 48°5 27°10.
Sulphuric acid, : sa a 0°75 0°92 1°4 2°54
Carbon dioxide, : ; 5°47 Lae Bae oe oe See
Silicic acid, . : i a, 0°81 0°12 0°27 ve 017
Ferric phosphate, ne aie 1°23 oat ae Sips /
Table by Beaunis of the Mineral Matter in Animal Fluids.
| | | Fe | |
| Verdeil, | Weber. | Weber. | beers | Porter. | Wier | Rose. | Porter,
| |
Blood. pate Blood. | Lymph. | Urine. Bulk. Bile. | Feces,
Sodie chloride, 58°81 72°88 17°36 74°48 67°28 10°73 27°70 4°33
Potassic chloride, ees, i 29°87 as oe 26°33 ae sic
Soda, ... 4°15 12°93 3°55 10°35 1°33 pe 36°73 5°07
Potash, Se een Game ted 2°95 22°36 3°25 13°64 21°44 4°80 6°10
Lime, .. . 1°76 2°28 2°58 0°97 1°15 18°78 1°43 26°40
Magnesia, . . 1°12 0°27 0°53 0°26 1°34 0°87 0°53 10°54
Ferric oxide, . 8°37 0°26 10°48 0°50 Sela 0°10 0°33 2°50
Phosphoric acid, | 10°23 | 1°73 10°64 1°09 1121 19°00 10°45 36°03
Sulphuric acid, 1°67 2°10 0°09 |... rie 2°64 6°39 a
Carbon dioxide, 119 | 4°40 C17 8-20 seers es 11°26 ad
Silicic acid, .| ... 0°20 0°42 1°27 | 4°06 5: 036 | 3°18

IV. Free Acids.—Hydrochloric acid (HCl) [occurs free in the astric juice, but in combina-
tion with the alkalies it is widely distributed as chlorides]. Sulphuric acid (H,SO,) [is said to
occur free in the saliva of certain gasteropods, as Dolium mare In the body it forms s nates,
chiefly in combination with soda and potash].
eS. ? ilicon as silicic acid (SiO,); manganese, iron, the last forms. an ‘eee

constituent of hemoglobin ; copper (?), ($ 174).

248. (B) ORGANIC COMPOUNDS.—I. Tur ALpumrnous oR PROTEID Sunsraxons, (2)
True Proteids and their Allies are composed of C, H, 0, N, and 8, and are fae from -
(see pie romnne-nartoan [The formation of albumin "from the elements is accomplished if
plants. What the chemical processes are is quite unknown. We only know that the N is in
first instance obtained from the nitric acid or ammonia of the soil. The former is probably not —
used directly as such, but serves, perhaps, for the formation of amides or amido-ac
which, by the action of races os tad Podies, proteids are formed. ] > bend

CHARACTERS OF THE PROTEIDS. . 375

{According to Hoppe-Seyler their general percentage composition is—

0. H. N. (op S.
From . . 20°9 6°9 15°2 51°5 0°3
To 7 - 23°5 to 7°3 to 17°0 to 54°5 to 2°0.]

They exist in almost all animal fluids and tissues partly in the fluid form, although Briicke
maintains that the molecule of albumin exists in a condition midway between astate of imbibi-
tion and a true solution—and partly in a more concentrated condition. Besides forming the
chief part of muscle, nerve, and gland, they occur in nearly all the fluids of the body, including
the blood, lymph, and serous fluids, but in health mere traces occur in the sweat, while they
are absent from the bile and the urine. Unboiled white of egg is the type. In the ali-
mentary canal they are changed into peptones. The chief products derived from their oxida-
tion within the body are CO,, H.O, and especially urea, which contains nearly all the N of the

roteids.

: Constitution.—Their chemical constitution is quite unknown. The N seems to exist in two
distinct conditions, partly loosely combined, so as to yield ammonia readily when they are de-
composed, and partly in a more fixed condition. According to Pfliiger, part of the N in living
proteid bodies exists in the form of cyanogen. [Loew supports Pfliiger’s view that the molecule
of living (active) albumin differs from that of dead albumin, as he finds that the living proto-
plasm of certain algze can reduce silver in very dilute alkaline solutions, which dead protoplasm
cannot do.] The proteid molecule is very large, and is a very complex one ; a small part of the
molecule is composed of substances from the group of aromatic bodies (which become conspicu-
ous during putrefaction), the larger part of the molecule belongs to the fatty bodies ; during
the oxidation of albumin fatty acids especially are developed. _ Carbohydrates may also appear
as decomposition-products. For the decompositions during digestion see § 170, and during
putrefaction § 184. The proteids form a large group of closely related substances, all of which
are perhaps modifications of the same body. When we remember that the infant manufactures
most of the proteids of its ever-growing body from the casein in milk, this last view seems not
improbable.

Characters. —Proteids, the anhydrides of peptones ($ 166) are colloids (§ 191), and therefore
do not diffuse easily through animal membranes ; they are amorphous and do not crystallise,
and hence are isolated with difficulty ; some are soluble, others are insoluble in water ; insoluble
in alcohol and ether ; rotate the ray of polarised light to the /e/t; when burned they give the
odour of burned horn. Various metallic salts and alcohol precipitate them from their solu-
tion; they are coagulated by heat, mineral acids, and the prolonged action of alcohol.
Caustic alkalies dissolve them (yellow), and from this solution they are precipitated by
acids. By powerful oxidising agents they yield carbamic acid, guanidin, and volatile fatty
acids.

Decomposition.—[The number and varieties of these products are exceedingly great, so
that it is not easy to separate the several products. In the first place, there is great diffi-
culty in getting in sufficient quantity a perfectly pure proteid, wherewith to institute the
necessary experiments. The decomposition-products of albumin when acted on by barium
hydrate have been most fully investigated. The action of concentrated HCl, potassic
permanganate, and bromine has also been studied. The action of the animal or vegetable
digestive ferments is very important (§ 170), and specially that of bacteria causing putre-
faction (§ 184).] When acted upon in a suitable manner by acids and alkalies, they
P give rise to the decomposition-products—leucin (10 to 18 per cent.), tyrosin (0°25 to 2
c per cent.), aspartic acid, glutamic acid, and also volatile fatty acids, benzoic and hydro-
cyanic acids, and aldehydes of benzoic and fatty acids; also indol (Hlasiwetz, Hebermann).
Similar products are formed during pancreatic digestion (§ 170) and during putrefaction
(§ 184). [Although it is assumed that the proteids have the closest relation to urea, no
one, so far, has succeeded in preparing urea by the direct decomposition of albumin.
Both by the action of acids and barium hydrate, the splitting up into simpler compounds
- does not take place at once, but by successive stages, one to the formation of different
; bodies. Proteids, when fully decomposed, either by acids or alkalies, yield as the final pro-
3 ducts ammonia, and amido-acids; by alkalies also carbonic, acetic, and oxalic acids. The
* amido-acids contain several series including leucin, tyrosiaf, and glutamic acid. But all proteids
a. do not yield these three bodies, for tyrosin may be absent, while leucin, so far, has been always
i found. It has therefore been attempted to classify proteids into those that yield tyrosin (¢.e.,
aromatic compounds) and those that do not. Classes I.-VII., p. 376, yield when decomposed
aromatic bodies (tyrosin, indol, phenol), while gelatin-yielding bodies and spongin yield no
aromatic bodies, ]

_ General Reactions,—(1) Xanthoproteic Reaction.—Heated with strong nitric acid they give a
yellow, the addition of ammonia gives a deep orange colour.

(2) With Millon’s reagent they give a precipitate, and when heated with this reagent above
60° C. they give a red one, probably owing to the formation of tyrosin. [If the proteids are

——

376 NATIVE ALBUMINS AND GLOBULINS.

resent in large amount, a red precipitate occurs, but if mere traces are present only the fluid
bossesen red. } : ; ; |
(3) The addition of a few drops of a dilute solution of cupric sulphate, and the subsequent
addition of caustic potash or soda, give a violet colour, which deepens on boiling; [the same
colour is obtained by adding a few drops of Fehling’s solution (biuret-reaction)].
(4) They are precipitated after strong acidulation by acetic acid and by potassium ferrocyanide.
(5) When boiled with concentrated hydrochloric acid, they give a violet-red colour (Lieber-

mann’s reaction). : eo ;
(6) Sulphuric acid containing molybdic acid gives a blue colour (Fréhde). |
(7) Their solution in acetic acid is coloured violet with concentrated sulphuric acid, and shows 7

the absorption-band of hydrobilirubin (Adamkiewicz). .

(8) Iodine is a good microscopic reagent, which strikes a brownish-yellow, while sulphuric
acid and cane-sugar give a purplish-violet (£. Schaltze).

[(9) When rendered strongly acid with acetic acid and boiled with an equal volume of a con-
centrated solution of sodic sulphate, they are precipitated. This method is used for removing
proteids from other liquids, as it does not interfere with the presence of other substances,
Saturation with sodio-magnesic sulphate precipitates the proteids, but not peptones, and the
same is the case with saturation with neutral ammonia sulphate (§ 249).]

[(10) The precipitation of albumin by acids is more delicate when the acid is dissolved in
alcohol containing 10 per cent. of ether; the precipitate is not dissolved by an excess of the
reagent.

(11) cee of them are precipitated by strong mineral acids, and metaphosphoric acid, tannic
acid (in an acid solution), phospho-wolframic and phospho-molybdic acids (in acid solution);
potassio-mercuric iodide (in acid solutions); many metallic salts, ¢.g., of Cu, Pb, Ag, Hg; chloral,
phenol, trichloracetic acid, picric acid, aleohol. Taurocholic acid precipitates albumin and syn-
tonin, but not peptone or hemi-albumose (§ 275).]

2.49, THE ANIMAL PROTEIDS AND THEIR CHARACTERS, —Class I.—Native Albumins
occur in a natural condition in animal solids and fluids. They are soluble in water, and are
not precipitated by alkaline carbonates, NaCl, or by very dilute acids. Their solutions are
coagulated by heating at 65° to 73° C. Dried at 40°C., they yield a clear, yellow, amber-coloured,
friable mass, ‘‘soluble albumin,” which is soluble in water.

(1) Serum-albumin (§ 32 and § 41).—[Its specific rotatory power is—56°.] Almost all its
salts may be removed from it by dialysis, when it is no longer coagulated by heat. It is |
coagulated by strong alcohol; and not very readily precipitated by hydrochloric acid, while the /
precipitate so formed is easily dissolved on adding more acid. When precipitated, it is readily
soluble in strong nitric acid. It is not coagulated when shaken up with ether. The addition
of water to the hydrochloric solution precipitates acid-albumin. For its presence in urine,

§ 264.

(2) Egg-albumin.—When injected into the blood-vessels or under the skin, or even when
introduced in large quantity into the intestine, part of it appears unchanged in the urine (§ 192,
4, and § 264), When shaken with ether it is precipitated. These two reactions serve to dis-
tinguish it from (1). The specific rotation is —35°5°, 7.c., for yellow light. Amount of S, 1°6
per cent.

(Metalbumin and Paralbumin have been found by Scherer in ropy solutions in ovarian cysts ;
they are only partially precipitated by heat. The precipitate thrown down by the action of
strong alcohol is soluble in water. )

Class II.—Globulins are native proteids, insoluble in distilled water, but soluble in dilute
neutral saline solutions, 7.c., neutral solutions of the alkalies and alkaline earths, e.g., NaCl,
KCl, NH,Cl, MgSO,, (but not Na,CO,, Na,HPO,), sodium chloride of 1 per cent., and in
magnesium sulphate. These solutions are coagulated by heat, and are precipitated by the
addition of a large quantity of water. Most of them are precipitated from their sodium chloride .
solution by the addition of crystals of sodium chloride, and also by saturating their neutral
solution at 30° with crystals of magnesium sulphate, When acted upon by dilute acids they
yield acid-albumin, and by dilute alkalies, alkali-albumin.

(1) Globulin (Crystallin) is obtained by passing a stream of CO, through a watery extract of
the crystalline lens, ‘ ;

(2) Vitellin is the chief proteid in the yolk of egg. It is also said to occur in the chyle (?)
and in the amniotic fluid (Weyl). Both the foregoing are not precipitated from their neutral
solutions by saturation with sodium chloride.

(3) Para-globulin or Serum-globulin (§ 29), and in urine (§ 264).

(4) Fibrinogen (§ 29).—In the clear jelly-like secretion of the vesicule seminales of the
guinea-pig, there is a globulin-like body closely resembling fibrinogen. It contains 29 per cent. “
of albumin, with scarcely any ash. If it be touched with a trace of blood-serum, without
mere, ene it gradually and completely forms a solid mass quite like fibrin. “98

(5) Myosin is the chief proteid in dead muscle. Its coagulation in muscle post-mortem eon-
stitutes rigor mortis. If muscle be repeatedly washed} and afterwards treated with a 10 per
. ~

ALBUMINATES AND OTHER PROTEIDS. 377

cent. solution of sodium or ammonium chloride, it yields a viscid fluid which, when dropped
into a large quantity of distilled water, gives a white flocculent precipitate of myosin. It
is also precipitated from its NaCl solution by crystals of NaCl. For Kiihne’s and other methods
see § 293.

(6) Globin (Preyer), the proteid residue of hemoglobin (§ 18).

Class III.—Derived Albumins (Albuminates).—(1) Acid-albumin or Syntonin.— When pro-
teids are dissolved in the stronger acids, e.g., hydrochloric, they become changed into acid-
albumins. They are precipitated from soluticn by the addition of many salts, sodic chloride,
acetate or phosphate, or by neutralisation with an alkali, ¢.g., sodic carbonate, but they are not
precipitated by heat. The concentrated solution gelatinises in the cold, and is redissolved by
heat. Syntonin, which is obtained by the prolonged action of dilute hydrochloric acid (2 per
1000) upon minced muscle, is also an acid-albumin. It is formed also in the stomach during
digestion (§ 166, I.). According to Soyka, the alkali- and acid-albumins differ from each other
only in so far as the proteid in the one case is united with the base (metal) and in the other
with the acid.

(2) Alkali-albumin.—-If egg- or serum-albumin be acted upon for some time by dilute
alkalies, a solution of alkali-albumin is obtained. Strong caustic potash acts upon white of
egg, and yields a thick jelly, Lieberktihn’s jelly. The solution is not precipitated by heat, but
it is precipitated by the addition of an acid. [Although alkali-albumin is. precipitated
on neutralisation, this is not the case in the presence of alkaline phosphates, e.g., sodic
phosphate. ]

(3) Casein is the chief proteid in milk (§ 231). It is precipitated by acids and by rennet at
40° C. In its characters it is closely related to alkali-albuminate, but it contains more N. It
contains a large amount of phosphorus (0°83 per cent.). It may be precipitated from milk by
diluting it with several times its volume of water and adding dilute acetic acid, or by adding
magnesium sulphate crystals to milk and shaking vigorously. Owing to the large amount of
phosphorus which it contains, it is sometimes referred to the nucleo-albumins. When it is
digested with dilute HCl (0°1 per cent.) and pepsin at the temperature of the body, it gradually
yields nuclein.

Class IV.—Fibrin.—(§ 27) and for the fibrin-factors (§ 29).

Class V.—Peptones.—For peptones and propeptone or the albumoses (§ 166, I.) ; in urine
(§ 264).

Class VI.—Lardacein and Other Bodies.—There fall to be mentioned the ‘‘ yelk-plates,”
which occur in the yelk :—Ichthin (cartilaginous fishes, frog) ; Ichthidin (osseous fishes) ;
Ichthulin (salmon) ; Emydin (tortoise) ; also the indigestible amyloid substance or lardacein,
which occurs chiefly as a pathological infiltration into various organs, as the liver, spleen,
kidneys, and blood-vessels. It gives a blue with iodine and sulphuric acid (like cellulose), and
a mahogany-brown with iodine. It is difficult to change it into an albuminate by the action of
acids and alkalies.

Class VII.—Coagulated Proteids.—When any native albumins or globulins are coagulated,
¢.g., at 70° C., they yield bodies with altered characters, insoluble in water and saline solutions,
but soluble in boiling strong acids and alkalies, when they are apt to split up. They are dis-
solved during gastric and pancreatic digestion to produce peptones.

Appendix: Vegetable Proteid Bodies.—Plants, like animals, contain proteid bodies,
although in less amount. They occur either in solution in the juices of living plants or in the
solid form. In composition and reaction they resemble animal proteids.

[The characters of vegetable proteids have a great resemblance to animal proteids. They
have frequently been obtained in a crystalline form, e.g., from the seeds of the gourd and various
oleaginous seeds. They occur in greatest bulk in the seeds of plants, aleurone grains being for
the most part composed of them. In seeds, globulins and ‘‘ vegetable peptone” form the
greater proportion of the proteid constituents. ]

[Globulins,—These varieties have been described as occurring in the seeds of plants :—
vegetable myosin, vitellin, and paraglobulin (Martin). They have practically the same pro-
perties as those found in the animal kingdom: vegetable vitellin has, however, not been suffi-
ciently studied. Paraglobulin has been found in papaw juice (Martin). Myosin occurs in the
seed of leguminosz, in flour, and in the potato. ]

[Albumin.—The existence of a body corresponding to egg- or serum-albumin in the vege-
ee _— is doubtful (Ritthausen). Such a body has been described in papaw juice

artin),

[Vegetable Peptone : Albumoses.—A true peptone has not yet been recognised in plants :
what has been described as such is hemi-albumose (Vines). _Albumoses have been found in the
seeds of leguminose, in flour, and in papaw juice. In the last, two forms occur, called respec-
tively a- and f- phytalbumose. The former, a-phytalbumose, agrees with the hemi-albumose
<dlescribed by Vines, being soluble in cold and boiling water ; giving also a biuret-reaction, and
a precipitate by saturation with sodium chloride only in an acid solution. The latter, B-phytal-
bumose, is soluble in cold, but not in bailing, distilled water ; hence it is precipitated by heat.

378 ALBUMINOIDS.

It is also readily thrown down by saturation with sodium chloride, and gives a faint biuret-
reaction (Martin). ] : . .) cdl

[Vegetable Casein is said to occur in the seeds of leguminose ; and it is slightly soluble in
water, but readily so in weak alkalies and in solutions of basic calcic phosphate. A solution of
this body is precipitated by acids and rennet. Two varieties have been described,—(a) legumin,
in , beans, lentils ; acid in reaction, soluble in weak alkalies and very dilute HCl or acetic
acid ; (8) conglutin, a very similar body occurring in hops and almonds. The existence of
vegetable casein is denied. Vines states that both legumin and conglutin are artificial products,
being formed from the globulins present by the dilute alkali used in extraction of the proteids.
This is denied by Ritthausen. ]

(Gluten and Glutin.—Gluten is readily prepared from flour by washing and kneading it in a
muslin bag under a stream of water. So prepared it is yellowish-brown in colour, very sticky,
and capable of being drawn out into long shreds. It is insoluble in water, soluble (but not
completely) by prolonged action in dilute acids and alkalies (*2 per cent. KHO and HCl). The
prolonged action of alcohol (80 to 85 per cent.) dissolves part of the substance of gluten, leaving
a residue, called by Liebig plant-fibrin and by Ritthausen gluten-casein. The alcohol contains
gliadin (glutin), gluten-fibrin, and mucedin., Gluten-casein is readily soluble in dilute alkalies,
almost insoluble in dilute acetic acid, and quite insoluble in cold and boiling water ; the pro-
ducts of its decomposition, by heating with H,SO,, are leucin, tyrosin, glutamic, and aspara-
ginic acids. The three bodies dissolved from glutin by alcohol differ chiefly in their solubility
in alcohol and water. Gluten-fibrin, the least soluble, is coagulated by the action of absolute
alcohol ; it is readily soluble in dilute acids and alkalies, being precipitated by neutralisation.
Gliadin (glutin, plant-gelatin) may be prepared by boiling gluten with water: it deposits on
cooling the solution. Though soluble in water at 100° C. at first, it becomes insoluble by the
prolonged action of water at that temperature. It is, like gluten-fibrin, soluble in dilute acids
and alkalies. Mucedin differs from gliadin in being less soluble in strong alcohol. The water
used in washing the flour in the preparation of gluten contains hemi-albumose (Vines) and a
globulin (Weyl). Rye-tlour, as well as wheaten, yields gluten under similar treatment with water. }

[Nitrogenous Crystalline Principles.—Leucin, tyrosin, asparagin, and glutamic acid have
been found in the seeds of plants. ] .

250. (2) THE ALBUMINOIDS.-—-These substances closely resemble true proteids in their -
composition and origin, and are amorphous non-crystalline colloids ; some of them do not con-
tain S, but the most of them have not been prepared free from ash. Their reactions and de-
composition-products closely resemble those of the proteids ; some of them produce, in addition
to leucin and tyrosin, glycin and alanin (amido-propionic acid). They occur as organised con-
stituents of the tissues and also in fluid form. It is unknown whether they are formed by
oxidation from proteid bodies or by synthesis.

1, Mucin is the characteristic substance present in mucus, That obtained from the sub-
maxillary gland contains—C 52°31, H 7°22, N 11°84, O 28°63. According to Hammarsten it
contains 8 1°79 and N 13°5 per cent. It dissolves in water, making it sticky or slimy, and can
be filtered. It is precipitated by acetic acid and alcohol ; and the alcohol precipitate is again
soluble in water. It is not precipitated by acetic acid and ferrocyanide of potassium, but HNO ;
and other mineral acids precipitate it. It occurs in saliva (§ 146), in bile, in mucous glands,
secretions of mucous membranes, in mucous tissue, in synovia, and in tendons, — Pathologically
it occurs not unfrequently in cysts; in the animal kingdom, especially in snails and in the
skin of holothurians. It yields leucin and 7 per cent. of tyrosin when it is decomposed by
prolonged boiling with sulphuric acid. [The precipitate called mucin has not always the
same characters, and, in fact, it differs according to the animal from which it is obtained
(Landwehr). ]
_ 2, Nuclein (Aiescher, § 198)—(C 29, H 49, N 9, P 3, O 22)—contains phosphoric acid, and
is slightly soluble in water, easily in ammonia, alkaline carbonates, strong HNOg; it gives the .
biuret-reaction ; no reaction with Millon’s reagent ; when decomposed it yields phosphorus;
It occurs in the nuclei of pus and blood-corpuscles (§ 22), in spermatozoids, yelk-spheres, liver,
brain, and milk, yeast, fungi, and many seeds, It has resemblances to mucin, and is perhaps
an intermediate product between albumin and lecithin (Hoppe-Seyler). It is prepared by the —
artificial digestion of pus, when it remains as an indigestible residue ; acids precipitate it from
an alkaline solution. It gives a feeble xantho-proteic reaction ; after the prolonged action of
alkalies and acid, substances similar to albumin and syntonin are formed. Hypoxanthin and
guanin have been obtained as decomposition-products from it (Kossel). ate,

3. Keratin occcurs in all horny and epidermic tissues (epidermic scales, hairs, nails, feathers)
—C 50°3-52°5, H 6*4-7, N 162-17, O 20°8-25, S 0°7-5 per cent.—is soluble in boiling caustic
alkalies, but swells up in cold concentrated acetic acid. When decomposed by H,SQ, it yields
10 per cent. leuein and 3°6 per cent. tyrosin. Neuro-keratin (§ 321). Lig om hee
4, Fibroin is soluble in strong alkalies and mineral acids, in ammonio-sulphate of co
when boiled with H,SO, it yields 5 per cent. tyrosin, leucin, and glycin. It is the
stituent of the cocoons of insects and threads of spiders,

HYDROLYTIC FERMENTS. 379

5. Spongin, allied to fibroin, occurs in the bath-sponge, and yields, as decomposition pro-

. duets, leucin and glycin (Stadeler).

6. Elastin, the fundamental substance in elastic tissue, is soluble only when boiled in con-
centrated caustic potash—C 55-55°6, H 7°1-7°7, N 16°1-17°7, O 19°2-21°1 per cent. It yields
36 to 45 per cent. of leucin and 4 per cent. of tyrosin.

7. Gelatin (Glutin), obtained from connective-tissues by prolonged boiling with water ; it
gelatinises in the cold—C 52°2-50°7, H 6°6-7°2, N 17°9-18°8, S+O 23°5-25 (S 0°7 per cent.).
[The ordinary connective-tissues are supposed to contain the hypothetical anhydride collagen,
while the organic basis of bone is called ossein.] It rotates the ray of polarised light strongly
to the left= -—130°. By prolonged boiling and digestion, it is converted into a peptone-like
body (gelatin-peptone), which does not gelatinise (§ 161, I.). [It swells up, but does not dis-
solve in cold water ; when dissolved in warm water, and tinged with Berlin blue or carmine, it
forms the usual coloured mass which is employed by histologists for making fine transparent
injections of blood-vessels.] A body resembling gelatin is found in leukemic blood and in
the juice of the spleen (§ 103, I.). When decomposed with sulphuric acid it yields glycin,
ammonia, leucin, but no tyrosin. [It is precipitated from its solution by alcohol, mercuric
chloride, metaphosphoric acid, phospho-wolframic acid, taurocholic acid, tannic acid, but the
precipitate with the last does not occur when salts are absent. It is readily soluble in dilute
acids, even in acetic acid. When boiled with Millon’s reagent, it is not coloured red. With
cupric sulphate and caustic soda it gives a violet colour which, on boiling, becomes light red.
It gives no colour with concentrated H,SO, and acetic acid. ]

8. Chondrin occurs in the matrix of hyaline cartilage and between the fibres in fibro-cartilage.
It is obtained from hyaline cartilage and the cornea by boiling. [Its solutions gelatinise on
cooling.] It occurs also in the mantle of molluscs—C 49°5-50°9, H 6°6-7°1, N 14°4-14°9, S+0O
27°2-29 (S 0°4 per cent.). When boiled with sulphuric acid it yields leucin ; with hydrochloric
acid, and when digested, chondro-glucose (Meissner) ; it belongs to the glucosides, which con-
tain N. When acted upon by oxidising reagents it is converted into gelatin (Brame). The
substance which yields chondrin is called chondrogen, which is perhaps an anhydride of chon-
drin. The following properties of gelatin and chondrin are to be noted :—Gelatin is precipi-
tated by tannic acid, mercuric chloride, chlorine water, platinic chloride, and alcohol, but not
by acids, alum, or salts of silver, iron, copper, or lead ; its specific rotation is = — 130°. [Com-
pare these precipitants with those of albumin.] Chondrin is precipitated by acetic acid and
dilute sulphuric and hydrochlori¢ acids, by alum, and by salts of silver, iron, and lead; its
specific rotation = — 218°.

9. The hydrolytic ferments have recently been called enzymes by W. Kiihne, in order to
distinguish them from organised ferments, such as yeast. The enzymes, hydrolytic or organic
ferments, act only in the presence of water. They act upon certain bodies, causing them to
take up a molecule of water. They all decompose hydric peroxide into water and O. They are
most active between 30° to 35° C., and are destroyed by boiling, but when dry they may be
subjected to a temperature of 100° without being destroyed. Their solutions, if kept for a long
time, gradually lose their properties and undergo more or less decomposition.

(a) Sugar-forming or diastatic-ferment occurs in saliva (§ 148), pancreatic juice ($ 170),
intestinal juice (§ 183), bile (§ 180), blood (§ 22), chyle (§ 189), liver (§ 174), in human milk
($ 231).. Invertin in intestinal juice (§ 183). Almost all dead tissues, organic fluids, and even
proteids, although only toa slight degree, may act diastatically. Diastatic ferments are very
generally distributed in the vegetable kingdom.

(6) Proteolytic, or ferments which act upon proteids.—Pepsin in gastric juice and in muscles .
(§ 166), in vetches, myxomycetes (Krukenberg), trypsin in the pancreatic juice (§ 170), a similar
ferment in the intestinal juice (§ 183), and urine (§ 264).

(c) Fat-decomposing in pancreatic juice (§ 170), in the stomach (§ 166).

(d@) Milk-coagulating in the stomach (§ 166), pancreatic juice (§ 170), and perhaps also in the
intestinal juice (?)—(W. Roberts).

[The importance of fermentative. processes has already been referred to in detail, under
‘* Digestion.” Ferments are bodies which excite chemical changes in other matter with which
they are brought into contact. They are divided into two classes :—

(1) Unorganised ; soluble or non-living.
(2) Organised, or living. ] , tt
[(1) The Unorganised Ferments are those mentioned in the following table. They seem to be
nitrogenous bodies, although their exact composition is unknown, and it is doubtful if they
have ever been obtained perfectly pure. They are present in many secretions, and are produced
within the body by the vital activity of the protoplasm of cells. They are termed soluble
because they are soluble in water, glycerin, and some other substances (§ 148), while they can
be precipitated by alcohol and some other reagents. They do not multiply during their
activity, nor is their activity prevented by a certain proportion of salicylic acid. They are
not affected by oxygen subjected to the compression of many atmospheres (P. Bert). They are
non-living. Their other properties are referred to above. |
7

380 UNORGANISED FERMENTS.

._ [The unorganised ferments present in the body, and their actions (W. Roberts) :— 2 J
Fluid or Tissues. Ferment. Actions, ,
Saliva. 1. Ptyalin (§ 148), . | Converts starch chiefly into maltose.
7 aie Converts proteids into peptones in an acid
1. Pepsin, . : : : medium, certain bye-products being
ace) formed (§ 166).
_ Gastric juice, ) 9 Milk-curdling, . «| Curdles casein of milk. .
| 3. Lactic acid ferment, . | Splits up milk-sugar into lactic acid.
4, Fat-splitting, . : . | Splits up fats into glycerin and fatty acids.
I P P Sly y
1. Diastatic or amylopsin, . | Converts starch chiefly into maltose.
Changes proteids into peptones in an
Danneianie 2. Trypsin, : : A alkaline medium, certain bye-products
Meaksteies 1 | being formed (§ 170).
SURE 8. Emulsive (?), . ; ., | Emulsifies fats.
a Fat-splitting or steapsin, Splits fats:into glycerin and fatty acids.
| | 5. Milk-curdling, . . | Curdles casein of milk.
a 1. Diastatic {| Does not form maltose, but maltose is
Ppncrat IB ecteatecoeaae ; | changed into glucose (§ 183).
tia 4 | 2. Proteolytic, . : . | Fibrin into peptone (?).
ia || 3. Invertin, : ; . | Changes cane- into grape-sugar.
L. 4. Milk-eurdling, : . | (2 in small intestine).
_ Blood, )
| Chyle, |
| Liver (?), . } Diastatic ferments.
| Milk, call]
Most tissues, . )
| ree F7.! Pepsin and other ferments.
Blood, . . Fibrin-forming ferment.

[(2) The Organised or living ferments are represented by yeast (§ 235). Other living
ferments belonging to the schizomycetes, occurring in the intestinal canal, are referred to in
$184. Yeast causes fermentation by splitting up sugar into CO, and alcohol (§ 156), but this
result only occurs so long as the yeast is living. Hence, its activity is coupled with the
vitality of the cells of the yeast. If yeast be boiled, or if it be mixed with carbolic or salicylic
acid, or chloroform, all of which destroy its activity, it cannot produce the alcoholic fermenta-
tion. As yet no one has succeeded in extracting from yeast a substance which will excite the
alcoholic fermentation. All the organised ferments grow and multiply during their activity at
the expense of the substances in which they occur. Thus the alcoholic fermentation depends
upon the ‘‘ life” of the yeast. They are said to be killed by oxygen subjected to the compres-
sion of many atmospheres (P. Bert). But it is important to note that Hoppe-Seyler has
extracted from dead yeast (killed by ether) an unorganised ferment which can change cane-
sugar into grape-sugar. ] ae

10. Hemoglobin, the colouring matter of blood, which, in addition to C, H, O, N, and §,
contains iron, may be taken with the albuminoids (§ 11). [Hamocyanin (§ 32).]

' (8) Glucosides containing Nitrogen. |

In addition to chondrin, the following glucosides containing nitrogen, when subjected to
hydrolytic processes, may combine with water, and form sugar and other substances:— -
Cerebrin (§ 322)=C;,H,9N_0.; (Geoghegan). [Parcus has shown that cerebrin as originally —
Sa by W. Miiller is a mixture of three bodies, viz., cerebrin, homocerebrin, and
nce mi a
Protagon—C 66°29, H 10°69, N 2°39, P 1:068, per cent.—occurs in nerves, and contains —
phosphorus (§ 322). , Lt Stee
Chitin, 2(C,;HgN.0,9), is a glucoside containing nitrogen, and occurs in the cutaneous
coverings of arthropoda, and also in their intestine and trachee ;-it is soluble in concentrated
acids, ¢.g., hydrochloric or nitric acid, but insoluble in other reagents. According to Sandwiek, _
chitin is an amin-derivative of a carbohydrate with the general formula n(C,,H»0,9). The —

ee a ee

ORGANIC ACIDS. 381

-- hyalin of worms is closely related to chitin. (Solanin, amygdalin (§ 202), and salicin, &c., are

glucosides of the vegetable kingdom. )

(4) Colouring Matters containing Nitrogen.

Their constitution is unknown, and they occur only in animals. They are in all probability
derivatives of hemoglobin, They are—(1) hematin (§18, A), myohematin (§ 232, § 292, a),
histo-hematin (§ 103, IV.), and hematoidin (§ 20). (2) Bile-pigments (§ 177, 3). (3) Urine-
pigments (except Indican). (4) Melanin—C,,, 1 Hy, Ny.9, Ogo.g—or the black pigment, which
occurs partly in epithelium (choroid, retina, iris, and in the deep layers of epidermis in
coloured races) and partly in connective-tissue corpuscles (Lamina fusca of the choroid).
[Turacin occurs in the red feathers of Corythaix Buffoni or Plantain-Eater. Its ash contains nearly
6 per cent. of copper (Chwrch). The reddish spots or parts of feathers burn with a green flame. |

II. Organic Acids free from Nitrogen.

(1) The fatty acids, with the formula CpHn-,0(OH), occur in the body partly free and
partly in combination. Free volatile fatty acids occur in decomposing cutaneous secretions
(sweat). In combination, acetic acid and caproic acid occur as amido-compounds in glycin
(=amido-acetic acid) and leucin (=amido-caproic acid). More especially do they occur united
with glycerin to form neutral fats, from which the fatty acid is again set free by pancreatic
digestion (§ 170, III.).

(2) The acids of the acrylic acid series, with the formula CnH,-,0(H9), are represented
me the body by one acid, oleic acid, which in combination with glycerin yields the neutral fat
olein.

251, Fats.—(1) Neutral fats occur very abundantly in animals, but they also occur in all
plants ; in the latter more especially in the seeds (nuts, almonds, cocoa nut, poppy), more
rarely in the pericarp (olive) or in the root. They are obtained by pressure, melting, or by
extracting them with ether or boiling alcohol. They [¢.g., tristearin, C;-H,,;)0,] contain much
less O than the carbohydrates, such as sugar and starch ; they give a greasy spot on paper, and
when shaken with colloid substances, such as albumin, they yield an emulsion. When treated
with superheated steam or with certain ferments (p. 256, ¢), they take up water and yield
glycerin and fatty acids, and if the latter be volatile they have a rancid odour. Treated with
caustic alkalies they also take up water, and are decomposed into glycerin and fatty acids ;
the fatty acid unites with the alkali and forms a soap, while glycerin is set free. The soap-
solution dissolves fats.

Glycerin is a tri-atomic alcohol, C,;H;(OH)s, and unites with (1) the following monobasic
Jatty acids (those occurring in the body are printed in italics) :—

Acids. Acids, Acids.

1s HOPI: oy “CHO, 7. Ginanthylic,. C,H,,0, [Margaric, . C,,H,,0,,
2. Acetic, , . C,H,O, | 8: Caprylic, « C@,H,,0, is a mixture
3. Propionic, . . C,H,O, | 9. Pelargoniec, C,H,,0, of 13 and 14. ]
4. Butyric, . COs: | 10. Capric,-. Ci Hing Os 1 b4: Shears, . OgHs,0,

[Isobutyric, . . C,H,O,]} 11. Laurostearic,. C,,H,,0, | 15. Arachinic, » CypH Oo
5. Valerianic, . O,H,.0. | 12. Myristic, i “CO. 116. Hyanio. -. - Can
6. Caproic, . - CgH),0,| 18. Palmitic, . CygH 3,02 | 17. Cerotinic, é Wapktes Os

The acids form a homologous series with the formula CpnHjn-,O(OH). With every CH, added
their boiling point rises 19°, Those containing most carbon are solid, and non-volatile ; those
containing less C (up to and including 10) are fluid like oil, have a burning acid taste, and a
rancid odour. The earlier members of the series may be obtained by oxidation from the later,
‘by CH, being removed, while CO, and H,O are formed ; thus, butyric acid is obtained from
propionic acid. Nos, 13 and 14 are found in human and animal fat, less abundant and more
inconstant are 12, 11,6, 8, 10, 4. Some occur in sweat ($ 287) and in milk (§ 231). Many of
them are developed during the decomposition of albumin and gelatin. Most of rae above
(except 15 to 17) occur in the contents of the large intestine (§ 185).

(2) Glycerin also unites with the monobasic “oleic acid, which also forms a series, whose
general formula is CpaH n-,0(OH) ; and they all contain 2H less than the corresponding
members of the fatty acid series. The corresponding fatty acids can be obtained from the oleic
acid series and vice versd. Oleic acid (olein-elainic acid),,C;,H3,0., is the only one found in
the organism ; united with glycerin, it forms the fluid fat, olein. The fat of new-born
children contains more glyceride of palmitic and stearic acid than that of adults, which contains
more glyceride of oleic acid. \ Oleic acid also occurs united with alkalies (in soaps) and (like
some fatty acids) in the lecithins (§ 23). If lecithin be acted on with barium hydrate, we
obtain insoluble stearic, or oleic, or palmitie acids and barium oleate, together with dissolved
neurin (§ 322, b) and baric glycerin phosphate. It appears as if there were several lecithins, of
which the most abundant are the one with stearic acid and that with palmitin + oleic acid
radicle (Diakonow). Lecithin occurs in the blood- sly (8 23), semen, and nerves, while
neurin is constantly present in fungi. ;

382 ORGANIC ACIDS AND ALCOHOLS.

The neutral fats [palmitin, stearin (both solid), and olein (fluid)], the glycerides of fatty acids,
and of oleicacid, are triple ethers of triatomic alcohol glycerin, With the neutral fats may
be associated glycerin-phosphoric acid, an acid glycerin ether, formed by the union of glycerin
_and phosphoric acid, with the giving off of a molecule of water (C;HgPOg) ; it is a decomposi-
tion-product of lecithin (§ 23).

(3) The glycolic acids (acids of the lactic acid series) have the formula CyaHyn-,0(OH),.
They are formed by oxidation from the fatty acid series by substituting OH (hydroxyl) for one
atom of H of the fatty acids, Conversely, fatty acids may be obtained from the glycolic acids.
The following acids of this series occur in the body :—

(a) Carbonic Acid (oxy-formic acid), CO(OH), ; in this form, however, it only makes salts.
Free carbonic acid or carbon dioxide is an anhydride of the same =COQ,,.

(b) Glycolic Acid (oxy-acetic acid), C,H,O(OH),, does not occur free in the body. One of its
compounds, glyecin (glycocoll, amido-acetic acid, or gelatin-sugar), occurs as a conjugate
acid, viz., as glycocholic acid in the bile (§ 177, 2), and as hippuric acid in the urine (§ 260).
Glycin exists in complex combination in the gelatin,

(c) Lactic Acid (oxy-propionic acid), C;H,O(OH),, occurs in the body in two isomeric forms
—l. The ethylidene-lactic acid, which occurs in two modifications—as the right rotatory
sarcolactic acid (paralactic), a metabolic product of muscle ; and as the ordinary optically in-
active product of ‘‘ lactic fermentation,” which occurs in gastric juice, in sour milk (sauerkraut,
acid cucumber), and can be obtained by fermentation from sugar (§ 184). 2. The isomer,
ethylenc-lactic acid, occurs in the watery extract of muscles (§ 293).

(d) Leucic Acid (oxy-caproic acid), CgH,,03, does not occur as such, but only in the form of
one of its derivatives, leucin (amido-caproic acid), as a product of the metabolism in many tissues,
and is formed during pancreatic digestion ($170, II.). Leucic acid may be prepared from
leucin, and glycolic acid from glycin, by the action of nitrous acid.

(4) Acids of the Oxalic Acid or Succinic Acid Series, having the formula CyHyn-,0.(0H).,
are bi-basic acids, which are formed as completely oxidised products by the oxidation of fatty
acids and glycolic acid, water being removed. It is important to note their origin from sub-
stances rich in carbon, e.g., fats, carbohydrates, and proteids. :

(a) Oxalic Acid, C,0,(OH)., arises from the oxidation of glycol, glycin, cellulose, sugar,
starch, glycerin, and many vegetable acids—it occurs in the urine as calcium oxalate

§ 260).

: (b) Suecinic Acid, C,H,O,(OH),, has been found in small amount in animal solids and fluids ;
spleen, liver, thymus, thyroid; in the fluids of echinococcus, hydrocephalus, and hydrocele, and
more abundantly in dog’s urine after fatty and flesh food ; in rabbit’s urine after feeding with
yellow turnips. It is also formed in small amount during alcoholic fermentation (§ 150).

(5) Cholalic Acid in the bile ($ 177) and in the intestine (§ 182).

(6) Aromatic Acids contain the radicle of benzol. Benzoic acid (=phenyl-formic acid)
occurs in urine united with glycin, as hippuric acid (§ 260).

III. Alcohols.
Alcohols are bodies which originate from carbohydrates, in which the radical hydroxy] (HO)

is substituted for one or more atoms of H. They may be regarded as water, }, ¢ 0, in which
the half of the H is replaced by a CH compound. Thus, C,Hg (ethyl-hydrogen) passes into
at O (ethylic alcohol).

(a) Cholesterin, Colt O; is a true monatomic alcohol, and occurs in blood, yelk, brain,

bile (§ 177, 4), and generally in vegetable cells, and it is the only solid monatomic alcohol in
the body.
OH

(b) Glycerin, C,H, | a is a triatomic alcohol. It occurs in neutral fats united with

fatty acids and oleic acid; it is formed by the splitting-up of neutral fats during pancreatic
digestion (§ 170, III.), and during the alcoholic fermentation (§ 150). ‘

(c) Phenol (=phenylic acid, carbolic acid, oxybenzol) (§ 184, III.).

(d) Pyrokatechin (=dioxybenzol) (§ 252).

(ec) The Sugars are closely related to the alcohols, and they may be regarded as polyatomic
alcohols, Their constitution is unknown. Together with a series of closely-related i
they form the great group of the carbohydrates, some of which occur in the animal body, while
others are widely distributed in the vegetable kingdom.

252. THE CARBOHYDRATES.—Occur in plants and animals, and received their name,
because in addition to C (at least 6 atoms), they contain H and O, in the proportion in which
these occur in water. They are all solid, chemically indifferent, and without odour. They
have either a sweet taste (sugars), or can be readily changed into sugars by the action of dilute
acids; they rotate the ray of polarised light either to the right or left; as far as their

SS agg eee eee

CARBOHYDRATES, 383

constitution is concerned, they may be regarded as fatty bodies, as hexatomic alcohols, in
which 2H are wanting.

They are divided into the following groups :—

I. Division.—Glucoses (C,H,,0,).—(1) Grape-sugar (glucose, dextrose, or diabetic sugar)
occurs in minute quantities in the blood, chyle, muscle, liver (?), urine, and in large amount in
the urine in diabetes mellitus (§ 175). It is formed by the action of diastatic ferments upon
other carbohydrates, during digestion. In the vegetable kingdom, it is extensively distributed
in the sweet juices of many fruits and flowers (and thus it gets into honey). It is formed from
cane-sugar, maltose, dextrin, glycogen, and starch, by boiling with dilute acids. It crystallises
in warty masses with one molecule of water of crystallisation; unites with bases, salts, acids,
and alcohols, but is easily decomposed by bases ; it reduces many metallic oxides (§ 149).
Fresh solutions have a rotatory power of +106°. By fermentation with yeast it splits up into
alcohol and CO, (§ 150); with decomposing proteids it splits into 2 molecules of lactic acid
(§$ 184, I.); the lactic acid splits up under the same conditions in alkaline solutions, into
butyric acid, CO,, and H. For the qualitative and quantitative estimation of glucose, see § 149
and § 150. In alcoholic solution, it forms very insoluble compounds with chalk, barium, and
potassium, and it also forms a crystalline compound with common salt (Estimation, § 150).

(2) Galactose, obtained by boiling milk-sugar (lactose) with dilute mineral acids; it
crystallises readily, is very fermentable, and gives all the reactions of glucose. When oxidised
with nitric acid it becomes transformed into mucic acid. Its specific rotatory power= + 88°08”.

(3) Laevulose (left-fruit-, invert-, or mucin-sugar) occurs as a colourless syrup in the acid
juices of some fruits and in honey; is non-crystallisable, and insoluble in alcohol ; specific
rotatory power= —106°. It is formed normally in the intestine (§ 183), and occurs rarely as a
pathological product in urine.

II. Division.—This contains carbohydrates with the formula C,,H..0,,, and its members
may be regarded as anhydrides of the first division—l. Milk-sugar or lactose occurs only in
milk, crystallises in cakes (with 1 molecule of water) from the syrupy concentrated whey ; it
rotates polarised light to the right= + 59°3, and is much less soluble in water and alcohol than
grape-sugar. When boiled with dilute mineral acids it passes into galactose, and can be
directly transformed into lactic acid only by fermentation; the galactose, however, is capable of
undergoing the alcoholic fermentation with yeast (Koumiss preparation, § 232), For its
quantitative estimation (§ 231). Rare in urine (§ 267).

2. Maltose (C,,H,.0,,;)+H,O (O'Sullivan) has 1 molecule of water less than grape-sugar
(Cy.H,40,2), is formed during the action of a diastatic ferment, such as saliva upon starch
(§ 148) ; is soluble in alcohol, right-rotatory power = +150°; it is crystalline, while its reducing
power is only two-thirds that of dextrose. [The ratio of the reducing power of maltose to that
of glucose is 100 to 66.]

(3. Saccharose (cane-sugar) occurs in sugar-cane and some plants, it does not reduce a
solution of copper, is insoluble in alcohol, is right-rotatory, and not capable of fermentation.
When boiled with dilute acids, it becomes changed into a mixture of easily fermentable glucose
(right-rotatory) and laevulose (invert sugar, § 183, 5, and § 184, I., 6), which ferments with
difficulty and is left-rotatory (§ 183). When oxidised with nitric acid, it passes into glucic acid
and oxalic acid. )

(4. Melitose, from Eucalyptus-manna ; Meleztose, from Larch-manna; Trehalose (Mycose),
from Ergot : are all right-rotatory, and do not reduce alkaline cupric solutions),

III. Division.—This contains carbohydrates, with the formula, CsH,)0;, which may be
regarded as anhydrides of the second division.

1, Glycogen, with a dextro-rotatory power of 211°, does not reduce cupric oxide. It occurs
in the liver (§ 174), muscles, many embryonic tissues, the embryonic area of the chick (Kii/z),
in normal and pathological epithelium; in diabetic persons it is widely distributed ; brain,
pancreas, and cartilage; and in the spleen, pancreas, kidney, ovum, brain, and blood, together
with a small amount of glucose (Pavy). It also occurs in the oyster and some of the molluscs
(Bizio), and indeed in all tissues and ¢lasses of the animal kingdom.

2. Dextrin was discovered by Limpricht in the muscles of the horse. It is right-rotatory =
+138°, soluble in water, and forms a very sticky solution, from which it is precipitated by
alcohol or acetic acid; it is tinged slightly red with iodine. It is formed in roasted starch.
(hence it occurs in large quantity in the crust of bread—see Bread, § 234), by dilute acids, and
in the body by the action of ferments (§ 148). It is formed from cellulose by the action of
dilute sulphuric acid. It occurs in beer, and is found in the juices of most plants.

3. Amylum or Starch occurs in the ‘‘mealy” parts of many plants, is formed within
vegetable cells, and consists of concentric layers with an excentric nucleus (fig. 239). The
diameter and characters of starch-grains vary greatly with the plant from which they aie
derived. At 72° C. it swells up in water and forms a mucilage; in the cold, iodine colours it
blue. Starch-grains always contain more or less cellulose and a substance, erythrogranulose,
which is coloured red with iodine (§ 148) It and glycogen are transformed into dextrose by
certain digestive ferments in the saliva, pancreatic, and intestinal juices, and artificially by

boiling with dilute sulphuric acid.

384 CARBOHYDRATES.

(4.. Gum, C,,H.0,, occurs in vegetable juices (especially in acacie and mimose), also in the
salivary glands, mucous tissue, lungs, and urine; is partly soluble in- water (arabin),
swells up like mucin (bassorin). Alcohol precipitates it. It is fermentable, and when boiled \
with dilute acids yields a reducing sugar. )

(5. Inulin, a crystalline powder occurring in the root of chicory, dandelion, and specially in
the bulbs‘of the dahlia ; it is not coloured blue by iodine. )

(6. Lichenin occurs in the intercellular substance of Iceland moss (Cetraria islandica) and
algw ; is transformed into glucose by dilute sulphuric acid. )

(7. Paramylum occurs in the form of granules resembling starch, in the infusorian, Euglena
viridis. )

(8. Cellulose occurs in the cell-walls of all plants (in the exo-skeleton of arthropoda, and
the skin of snakes) ; soluble only in ammonio-cupric oxide ; rendered blue by sulphuric acid

Fig. 239.
a, West Indian arrow-root ; c, Tahiti arrow-root ; d, Potato starch.

and iodine. Boiled with dilute sulphuric acid, it yields dextrin and glucose. Concentrated
nitric acid mixed with sulphuric acid changes it (cotton) into nitro-cellulose (gun-cotton)
C,H,(NO,),0;, which dissolves in a mixture of ether and alcohol and forms collodion. )

(9. Tunicin is a substance resembling cellulose, and occurs in the integument of the Tunicata _
or Ascidians. )

IV. Division.—This contains the carbohydrates which do not ferment.

1. Inosit (phaseo-mannit, muscle-sugar) occurs in muscle (Scherer), lung, liver, spleen,
kidney, brain of ox, human kidney; pathologically in urine and the fluid of echinococeus. In
the vegetable kingdom, in beans (leguminose), and the juice of the grape. It is an isomer of
grape-sugar ; optically it is inactive, crystallises in warts with 2 molecules of water, in long |
monoclinic crystals ; it has a sweet taste, is insoluble in water, does not give Trommer’s re- 7
action, is capable of undergoing only the sarcolactic acid fermentation. (Nearly allied are
Sorbin, from sorbic acid—Scyllit, from the intestines of the hag-fish and skate—and Eukalyn,
arising from the fermentation of melitose. )

IV. Derivatives of Ammonia and their Compounds.

The ammonia derivatives are obtained from the proteids, and are decomposition-products of
their metabolism.

(1) Amines, i.¢., compound ammonias which can be obtained from ammonia (NHs), or from
ammonium-hydroxide (NH,—- OH), by replacing one or all the atoms of H by groups of carbo-
hydrates (alcohol radicals). The amine derived from one molecule of ammonia is called mona-
mine, We are only acquainted with

H CH, |
H ; N _ Methylamine and Tri-Methylamine CH, N,
CH, CH;

as decomposition-products of cholin (neurin) and of kreatin. Neurin occurs in lecithin in a
very complex combination (see Lecithin, p. 381, and also § 28).

(2) Amides, i.¢., derivatives of acids, which have exchanged the hydroxyl (HO) of the acids
for NH,. Urea, CO(NH,),, the biamid of CO,, is the chief end-product of the metabolism of
the nitrogenous constituents of our bodies (see Urine, § 256). Carbon dioxide containing water
=CO(OH),, where both OH are replaced by NH,—thus we get CO(NH,)., urea. a

(8) Amido-acids, 7.e., nitrogenous compounds, which show partly the character of an acid
and partly that of a weak base, in which the atoms of H of the acid-radical are replaced by
NH,, or by the substituted ammonia groups. ab ks tal
' (a) Glycin (or amido-acetic acid, glycocoll, gelatin-sugar, § 177, 2) is formed by boi
Sem with dilute sulphuric acid. It has a sweet taste (gelatin-sugar), behaves as a weak acic
but also unites with acids as an amine-base. It occurs as glycin+ benzoic acid ie
in urine (§ 260) ; and also as glycin + cholalie acid =glycocholic acid in bile (§ 177). (6) .

HISTORICAL. 385

—(§ 170)=amido-caproic acid. (c) Serin—(= ? amido-lactic acid) obtained from silk-gelatin. -
(ad) Aspartic acid—(amido-succinic acid) ; and (¢) Glutamic acid, obtained by the splitting up
of proteids (§ 170). Other amido-acids are—(/f) Cystin=amido-lactic acid, in which O is
replaced by S (§ 268). (g) Taurin—(§ 177), amido-ethyl-sulphonic acid occurs (except in certain
glands) chiefly in combination with cholalic acid, as taurocholic acid in bile. Tyrosin (para-
hydro-oxyphenyl-amido-propionic acid), an amido-acid of unknown constitution, occurs along
with leucin during pancreatic digestion (§ 170), is a decomposition-product of proteids, and
occurs plentifully in the urine in acute yellow atrophy of the liver (§ 269).

To the amido-acids are related—(a) Kreatin in muscle, brain, blood, urine, regarded as
methyl-uramido-acetic acid (C,H )N3;0,). It has been prepared artificially. When boiled with
baryta-water, it. takes up H,O, and splits into urea—and (b) Sarkosin (C,H,;NO,), methyl-
amido-acetic acid. When boiled with water, heated with strong acids, in the presence of
putrefying substances, kreatin gives off water, and is changed into kreatinin (C,H,;N,0). This
strong base can be rechanged by alkalies into kreatin.

(4) Ammonia Derivatives of Unknown Constitution.—tUric acid (§ 258) ; allantoin (§ 260),
is formed by the oxidation of uric acid by ineans of potassium permanganate ; cyanuric acid
in dog’s urine; inosinic acid in muscle; guanin in traces in the liver and pancreas, in guano, the
excrements of spiders, in the skin of amphibia and reptiles, in the silver sheen of many fishes
(A. Ewald and Krukenberg); by oxidation it yields urea (p. 439); hypoxanthin or sarkin occurs
along with xanthin in many organs and in urine. Kossel prepared hypoxanthin from nuclein
by prolonged boiling of the latter. It may be obtained from fibrin by putrefaction, by gastric
and pancreatic digestion, and by dilute acids (Salomon, H. Krause, Chittenden) ; xanthin is pre-
he by oxidation from hypoxanthin. It occurs very rarely in the form of a urinary calculus.

araxanthin in urine, and a similar body carnin in flesh (§ 233). [Adenin (C;H,N,), dis-
covered by Kossel in the pancreas, yeast, and tea-leaves, has also been isolated from the spleen,
lymphatic glands, and kidney ; it appears to be present in all highly cellular animal and vege-
table tissues. Like the allied bases—xanthin and guanin, it is a derivative of the nuclein of
the nuclei. ]
Aromatic Substances,

1. Monatomic phenols—(a) Phenol (hydroxyl of benzol) in the intestine (§ 184). Phenyl-
sulphonic acid in urine (§ 262). (b) Kresol, in the form of orthokresol and parakresol, united
with sulphonic acid, occur in urine (§ 262). 2. Diatomic phenols—(a) pyrokatechin united
with sulphonic acid in urine (§ 262). 38. Aromatic oxyacids—(a) Hydroparacumaric acid ; (b)
Paraoxyphenylacetic acid in urine (§ 262). 4. Indol and skatol in the intestine (§ 184), con-
joined with sulphonic acid in urine (§ 262).

253, HISTORICAL.—According to Aristotle, the organism requires food for three purposes
—for growth, for the production of heat, and to compensate for the loss of the bodily excreta.
The formation of heat takes place in the heart by a process of concoction, the heat so formed
being distributed to all parts of the body by means of the blood, while the respiration is re-
garded as an act whereby the body is cooled. Galen accepted this view in a somewhat modified
form ; according to him, the metabolic processes may be compared to the processes going on in
a lamp; the blood represents the oil ; the heart, the wick ; the lungs, the fanning apparatus.
According to the view of the iatrochemical school (van Helmont), the metabolic processes of the
body are fermentations, whereby the food is mixed with the juices of the body. Since the
middle of the seventeenth century (Boyle), the knowledge of the metabolic processes has followed
the development of chemistry. A. v. Haller regarded heat as due to chemical processes—the
food continually supplying the waste which is excreted from the body. After the discovery of
oxygen (1774, by Priestley and Scheele), Lavoisier formulated the theory of combustion in the
lungs, whereby carbonic acid and water were formed. Mitscherlich compared the decomposi-
tion-processes in the living body with putrefactive processes. Magendie was the first to emphasise
the difference between nitrogenous and non-nitrogenous foods, and he showed that the latter
alone were not able to support life. Even gelatin alone is not sufficient for this purpose... The
greatest advance in the theory of nutrition was made by J. v. Liebig, who laid the foundation
of our present knowledge of this subject. According to Liebig, foods may be divided into two
classes, viz., the ‘‘ plastic,” suitable for the construction of the organism, and the ‘‘ respiratory ”
for the maintenance of the temperature ; to the former class he referred the albuminates or
proteids, to the latter, the non-nitrogenous carbohydrates-and fats (p. 356). Amongst recent
observers, the Munich School, as represented by v. Bischoff, v. Pettenkofer, and v. Voit, has
done most to give us an exact knowledge of this department of physiology.

bo
wo

254, STRUCTURE OF THE KIDNEY.—[Capsule.—The kidney is a compound tubular
gland, and is invested by a thin, tough, fibrous capsule, easily stripped off from the substance
of the organ, to which it is attached by fine processes of connective-tissue and blood-vessels. ]

[Naked Eye Appearances. —On dividing the kidney longitudinally from the hilum to its
outer border, and examining the cut surface with the naked eye, we observe the parenchyma

Boundary layer mG ” 1” Labyrinth.
of Medulla. | ~ ; y { Medullary
Papillary por- rays.
tion of me- | 2’
dulla.

Transverse section )
of tubules in +3
boundary layer.

MEDULLA.

Fat of renal sinus. 4. Sah : USS (Be a =
nitads \ C Renal calyx.
MN
sly
Ureter.
Transversely )
coursing medul- - *
lary rays, > wat
ranch 0
renal artery.
Artery, 5.
Artery. 5. M

Fig 240.
Longitudinal section through the kidney (7'yson, after Henle).

of the kidney, consisting of an outer cortical and an inner medullary, or prremitee

the latter composed of about twelve conical papille, or pyramids of Mal with their api 7
directed towards and embraced by the calices of the pelvis of the Dine? (fig. 240). 1 |
medullary portion is further subdivided into the boundary layer of Ludwig and the papilla

STRUCTURE OF THE KIDNEY. 387

portion, According to Klein, the relative proportions of these three parts are—cortex, 3°5 ;
boundary layer, 2°5; and papillary portion, 4. The cortex has a light brown colour, and when
torn presents a slightly granular aspect, with radiating lines running at regular distances. The
granules are due to the presence of the Malpighian corpuscles, and the strie to the medullary
rays. The boundary zone is darker, and often purplish in colour. It is striated with clear and
red lines alternating with opaque ones, the former being blood-vessels and the latter uriniferous
tubules. The papillary zone is nearly white and uniformly striated, the strize converging to
the apex of the pyramid. The medulla is
much denser and less friable than the cortex,
owing to the presence of a large amount of
connective-tissue between the tubules. The
bundles of straight tubes of the medulla may
be traced at regular intervals running out-
wards into the cortex, constituting medullary
rays, which become smaller as they pass out-
wards in the cortical zone, so that they are
conical and form the pyramids of Ferrein
(fig. 241, PF). The portion of the cortex
lying between the medullary rays is known as
the labyrinth, from the complicated arrange-
ment of its tubules. ]

[Size, Weight.—The adult kidney is about
11 centimetres (4°4 inches) in length, 5 centi-
metres (2 inches) wide, and 8 centimetres
(1 inch) in thickness. It weighs in the
male 113°5 to 170 grms. (4 to 6 oz.), in the
female 113°5 to 156 grms. (4 to 54 0z.). The

AY Cortex.

width of the cortex is usually 5 to 6 milli- Boundary
metres (4 to 4 inch).] phan
I, The uriniferous tubules all arise within zone.

the labyrinth of the cortex by means of a

globular enlargement, 200 to 300 uw [735 to

z45 inch] in diameter, called Bowman’s

capsule (figs. 242, 243). After pursuing a :
complicated course, altering their direction, creat

diameter, and structure, and being joined by
other tubules, they ultimately form large
collecting tubes, which terminate by minute
apertures, visible with the aid of a hand-lens, ;
on the apices of the papille projecting into Fig. 241.

- the calices of the kidney. Each urinarytubule Longitudinal section of a Malpighian pyramid.

is composed of a homogeneous membrana PF’, pyramids of Ferrein ; RA, branch of renal
propria, lined by epithelial cells, so as to artery ; RV, lumen of a renal vein receiving an
leave a lumen for the passage of the urine interlobular vein; VR, vasa recta; PA, apex
from the Malpighian corpuscles to the pelvis of a renal papilla: 0, b, embrace the bases of the
of the kidney.. The diameter and direction renal lobules.

of the tubules vary, and the epithelium differs

i its characters at different parts of the tube, while the lumen also undergoes alterations in its
diameter.

Course and Structure of the Tubules.—In the labyrinth of the cortex, tubules arise in the
spherical enlargement known as Bowman’s capsule (fig. 242, 1), which invests (in the manner
presently to be described) the tuft of capillary blood-vessels called a glomerulus or Malpighian
corpuscle. By means ofa short and narrow neck (2) the capsule becomes continuous with a
convoluted tubule, X in fig. 243. This tubule is of considerable length, forming many wind-
ings in the cortex (fig. 242, 3); the first part of it is 45 w wide, constituting the proximal or
first convoluted tubule. It becomes continuous with a spiral tubule of Schachowa (4), which
lies in a medullary ray where it pursues a slightly wavy or spiral course. On the boundary
line between the cortical and boundary zone, the spiral tubule suddenly becomes smaller and
passes into the descending portion of Henle’s loop (5), which is 14 w in breadth, and is con-
tinued downwards through the boundary zone into the medulla, where it forms the narrow
loop of Henle (6), which runs backwards in the medullary part to the boundary zone. Here
it becomes wider (20-26 ), and as it continues its undulating course, it enters a medullary ray,
where it constitutes the ascending looped tube (7), which becomes narrower in the cortex.
Leaving the medullary ray again, it passes into the labyrinth, where it forms a tube with
irregular angular outlines—the irregular tubule (10); which is continuous with (fig. 243, ”, 2)
the second or distal convoluted tubule (11), which resembles the proximal tubule of the same
name, Its diameter is 40 uw. A short, narrow, wavy junctional or curved collecting tubule

388 STRUCTURE OF THE TUBULES.

(12) connects the latter with one of the straight collecting tubes (13) of a medullary ray. As
the collecting tubule proceeds through the boundary zone, it receives numerous junctional
tubes, and when it eaities the boundary zone, it forms one of the collecting tubes (fig. 243, O),

‘lO

pighian corpuscles.

a e Sub-capsular layer without Mal-—

. First part of collecting tube.
. Distal convoluted tubule.

. CORTEX.

. lrregular tubule.

. Proximal convoluted tubule.

4. Spiral tube. 4

13. Straight part of collect-
ing tube.

. Wavy part of ascending limb.
. Constriction or neck.

9, Wavy part of ascending

limb of Henle’s loop. eepital-eabine,

. Malpighian tuft surrounded

Inner stratum of cortex ms ; Pars
without Malphigian _ ia \ Sem Rare ee ja, myo wmen Sense:
corpuscles. =) Fue

8

§. Spiral part of ascending limb
of Henle’s loop. é

B. BOUNDARY ZONE.

5. Descending limb of Henle’s
7 loop-tube.

aid

uw

5

7 & 8. Ascending limb of
Henle’s loop-tube.

—_—’

-_-|

———

a
e_

6. Henle’s loop.

e C, PAPILLARY ZONE.

Fig. 242.
Diagram of the course of two uriniferous tubules (Klein and Noble-Smith).

which unite with one another at acute angles to form the larger straight excretory tubes or
ducts of Bellini (15), which open on the summit of the Malpighian pyramids into a calyx of the.

lvis of the kidney. In the cortex the collecting tubules are 45 » in diameter, but where they

ave formed an excretory tube (O), their diameter is 200 to 300 4; 24 to 80 of these tubes open
on the apex of each of the 12 to15 Malpighian pyramids. In the lowest and broadest part, the
membrana propria is strengthened by the presence of a thick supporting framework of con-
nective-tissue.

Structure of the Tubules.—{Below the neck, the tubules are lined everywhere by a
layer of nucleated epithelium.] Bowman’s capsule, which is about 34, inch in diameter (fig.
244, II), consists of a homogeneous basement membrane lined internally by a single continuous
layer of flattened cells (t). According to Roth, the basement membrane itself is composed of
endothelial cells. [In the foetus the lining cells are more polyhedral.] Within the capsu
lies the glomerulus or tuft of blood-vessels. The cells lining the capsule are reflected over a
between the lobules of which the glomerulus consists, The glomerulus may not completely fill”
the capsule, so that, according to the activity of the kidney, there may be a larger or smaller

STRUCTURE OF THE TUBULES. 389

space between the glomerulus and the capsule into which the filtered urine passes. The neck

is lined by cubical cells. These
are ciliated.

cells, in some animals, ¢.g., the rabbit, sheep, mouse, and frog,

The proximal convoluted tubule is lined by characteristic epithelium. ‘The cells, which are

short or polyhedral, contain a
turbid or cloudy protoplasm (fig.
244, III, 1 and 2), which not un-
frequently contains oil-globules,
and they form a single layer.
Each cell consist of two parts ;
the inner, containing the spheri-
eal nucleus, is next the lumen,
and granular (III, 2, g), while
the outer part, next the mem-
brana propria, appears fibril-
lated, or ‘‘rodded,’’ from the
presence of rods or fibrils placed
vertically to the basement-mem-
brane (fig. 245). These appear
like the hairs of a brush pressed
upon a plate of glass (III, 2).
The cells are not easily separated
from each other, asneighbouring
cells interlock by means of the
branched ridges on their sur-
faces (III, 1)—(Heidenhain,
Schachowa). The lumen is well
defined, but its size seems to
depend upon the state of imbibi-
tion of the cells bounding it.

The spiral tubule has similar
epithelium and a corresponding
lumen, although the epithelium
becomes lower and somewhat
altered in its characters at the
lower part of the tube.

The descending limb of

Henle’s loop, and the loop itself.

with a relatively wide lumen,
are bounded by clear, flattened,
epithelial cells, with a bulging
nucleus (IV,'S); the cells lying
on one side of the tube being so
placed that the bulging part of
the bodies of the cells is oppo-
site the thin part of the cells on
the opposite side of the tube.
[These tubes might be mistaken
for blood-capillaries, but-in ad-
dition to their squamous lining,
they have a basement-membrane,
which capillaries have not.] In
the ascending limb, the lumen
is relatively wide, while its epi-
thelium agrees generally with
that in the convoluted tubule,
excepting that the ‘‘ rods” are
shorter. Sometimes the cells
are arranged in an ‘‘ imbricate ”
manner,

_ In the irregular tubule, which
has a very small lumen, the
pebgpedral cells lining it contain
oval nuclei, and are shorter than

ay
BES ES
LS ADO .
Ce ate f
GERI pee Le REAR
Ors |
se ERAS

Fig. 243.

I, Blood-vessels and uriniferous tubules of the kidney (semi-
diagrammatic); A, capillaries of the cortex, B, of the me-
dulla; a, interlobular artery ; 1, vasafferens; 2, vas efferens;
r, €, vasa recta; c, vene recte; v, v, interlobular vein; S,
origin of-a vena stellata; 7, 7, Bowman’s capsule and glo-
merulus ; X, X, convoluted tubules; ¢, ¢, Henle’s loop; n, 2,
junctional piece; 0, 0, collecting tubes; O, excretory tube.

those of the convoluted tubules. The cells, again, are very irregular in size, while their
““rodded” character is much coarser and more defined (fig. 246).
The distal convoluted tubule closely resembles in its structure the proximal convoluted

390 BLOOD-VESSELS OF THE CORTEX.

tubule, and is lined by similar cells. The curved collecting, or junctional tubule, although
narrow, has a relatively wide lumen, as it is lined by clear, somewhat flattened cells. _

The collecting tubes have a distinct lumen, and are lined by clear, somewhat irregular,
cubical cells (fig. 244, V), which in the larger excretory tubes are distinctly columnar (V1).
The basement-membrane is said to be absent in the larger tubes. [Klein describes a thin,
delicate, nucleated centro-tubular membrane lining the surface of the epithelium next the

en.
i the Blood-Vessels.—The renal artery (fig. 250) divides into four or five branches, which
pass into the kidney at the hilum. These branches, surrounded by connective-tissue
continuous with that of the capsule, continue to divide, and es between the papille, to reach
the bases of the pyramids on the limits between the cortical and boundary zones, where they
form incomplete arches. From these horizontal trunks, the interlobular arteries (fig. 243,
a) run vertically and singly into
the cortex, between each two
medullary rays, and in their
course they give off on all sides
the short undivided vasa affer-
entia (1), each of which enters
a Malpighian capsule at the
opposite pole from which the
urinary tubule is given off.
Within the capsule, each afferent
artery breaks up into capillaries
arranged in lobules and sup-
ported by connective-tissue, the
whole forming a tuft of capillary
blood-vessels, or a glomerulus.
Each glomerulus is covered on
its surtace, directed towards the
wall of the capsule by a layer of
flat, nucleated, epithelial cells
(fig. 229, II), which also dip
down between the capillaries.
A vein, the vas efferens (2),
which is always smaller than the
afferent arteriole, proceeds from
the centre of the glomerulus,

Fig. 244.

II, Bowman’s capsule and glomerulus. a, vas afferens; ¢, vas
efferens; c, capillary network of the cortex; k, endothelium
of the capsule; h, origin of a convoluted tubule. III,
‘“rodded”’ cells from a convoluted tubule—2, ape from
the side, with g, inner granular zone; 1, from the surface.

IV, cell lining Henle’s looped tubule. V, cells of a col- ma Leche ga clone te
lecting tube. VI, section of an excretory tube. vessel enters it (fig. 244, II).

In their structure and distribution all the efferent vessels resemble arteries, as they divide into
branches to form a dense, narrow-meshed, capillary network (fig. 243, A, and fig. 244, II, ¢),
which ramifies over and between the convoluted tubules. The meshes are elongated around

PES a

thy : uh te 2
i ARM espe
Hi Aisi \\ Bs) \\\ . ull ess
SLE OR AU
Fig. 245. Fig. 246.
Convoluted tubule (after ammonium chromate) Epithelium of an irregular tubule
showing ‘‘rodded” epithelium. of the kidney of a dog.

the tubules of the medullary rays, and more polygonal around the convoluted tubules (fig, 243).
Some of the lowest efferent vessels split up into vasa recta, which run towards the medulla

The interlobular arteries become smaller as they pass towards the surface of the kidney, and
some of their terminal capillaries communicate with the capillaries of the external capsule itself.
Venous trunks proceed from the capillary network, to terminate in the interlobular veins (V),
which begin close under the capsule by venous radicles arranged in a stellate manner (consti-
tuting the stellule Verheynii, or vene stellate), and accompany the corresponding artery to

the limit between the cortex and boundary zone, where they communicate with the large venous .

trunks in that situation.

The blood-vessels of the medulla arise from the vasa recta (fig. 243, r), which begin on

the limit of the cortex and medulla, either as single, direct, muscular branches (7) of the lar

’

.
v;

LYMPHATICS, NERVES, CONNECTIVE-TISSUE. 391

arterial trunks, or from those efferent vessels (¢) which lie next to the medulla. The latter are
said to be devoid of muscle. According to Huschke, a few vasa recta are formed by the union
of the capillaries of the medullary rays. All the vasa recta enter the boundary layer, where
they split up into a leash or pencil of small arterioles, which pass between the straight tubules
towards the pelvis, and form in their course a capillary network with elongated meshes. From
these capillaries there arise venous radicles, which, as they proceed towards the limit between
the cortex and medulla, form the ven rectze (c), and open into the concave side of the venous
trunks in this region. At the apex of the papille, the capillaries of the medulla form connec-
tions with the rosette-like capillaries surrounding the excretory ducts (at 1).

(The circulation through the vasa recta is most important. The cortical system of blood-
vessels communicates with the medullary, but as most of the vasa recta are derived from the
same vessel as the interlobular arteries, it is evident that they may forma side stream through
which much of the blood may pass without traversing the vessels of the cortex. Very probably
the ‘‘ short-cut” is useful in congestions of the kidney. The amount of distention of these
vessels also will influence the size of the tubules lying between them. There are two other
channels by which blood can pass through the renal arteries without traversing the glomeruli—
(1) The anastomoses between the terminal twigs of the renal artery and the subcapsular venous
plexus ; (2) small branches given off, either by the interlobular arteries or by the afferent
vessels before entering the glomeruli (Brwnton).]

The blood-vessels of the external capsule are derived partly from the terminal twigs of the
interlobular arteries, partly from branches of the supra-renal, phrenic, and lumbar arteries,
which anastomose with each other. The capillary network has simple meshes. The venous
radicles pass partly into the vene stellate, and partly into the veins of the same name as the
arteries. The connection of the area of the renal artery with the other arteries of the capsule
explains why, after ligature of the renal artery within the kidney, the blood still cir-
culates in the external capsule (C. Ludwig, M. Herrmann); in fact, these blood-vessels still -
supply the kidney with a small amount of blood, which may suffice to permit a slight secretion
of urine to take place (Litten, Pawtynsk?).

III. The lymphatics form a wide-meshed plexus in the capsule of the kidney, while under it
they form large spaces (Heidenhain). In the parenchyma of the kidney, the lymphatics are said
to be represented by large slits devoid of a wall in the tissues, and are more numerous around the
convoluted than the straight tubules. The slits pass to the surface of the kidney, and expand
under the capsule. When the lymphatics are greatly distended, they tend to compress the
uriniferous tubules and the blood-vessels (C. Ludwig and Zawarykin). According to Ryndowsky,
the uriniferous tubules are surrounded by true lymphatics with an endothelial lining, and they
even penetrate into the capsule of Bowman along with the vas afferens. [The large blood-
vessels are also surrounded by —
lymphatics.] Large lymphatics,
provided with valves, pass out of
the kidneys at the hilum, while
others emerge through the cap-
sule; both sets are connected
with the lymph-spaces of the cap-
sule of the kidney (4. Budge).

IV. The nerves form small
trunks provided with ganglia,
and accompany the blood-vessels.
[They are derived from the renal
plexus and the lesser splanchnic
nerve.|] They contain medullated
and non-medullated fibres, and
the latter have been traced by
W. Krause as far as the apices of
the papille. Their mode of ter-
mination is unknown. Physio-
logically, we are certain that they
contain both vaso-motor and sen-
sory fibres; perhaps there may
be also vaso-dilator and secretory
fibres.

V. The connective-tissue, or
interlobular stroma, forms in the
a especially at their apices,

brous, concentric layers of con-
siderable thickness between the
excretory tubules (fig. 247). Farther outwards, the fibrillar character becomes less distinct,
while at the same time branched connective-tissue corpuscles occur in greater numbers, In the

Transverse section of apex of Malpighian pyramid, a, large
collecting tubes; 6, c, d, tubules of Henle ; e, 7, blood-
capillaries,

X

392 THE URINE.

cortex, the interstitial stroma consists almost entirely of branched corpuscles, which anastomose
with each other. [There is also a small quantity of delicate fibrous tissue around Bowman's
capsule, and along the course of the arteries: The connective-tissue often plays an important
réle in pathological conditions of the kidney, as interstitial nephritis.] The outer layers of the
capsule of the kidney are composed of dense bundles of fibrous tissue, while the deeper layers
are more loose, and send processes into the cortical layers. The capsule is easily ong 2 off.
None of the secretory substance is removed with it. . Under the capsule in the human kidney,
there is a thin plexus of non-striped muscular fibres. At the hilum it becomes continuous
with the outer fibrous coat of the dilated upper end of the ureter. Smooth muscular fibres also
occur in a sphincter-like arrangement round the apex of each papilla, while others proceed from
the pelvis between the pyramids along the blood-vessels (Jardet). The fat surrounding the
kidney is united to the latter partly by blood-vessels and partly by bands of connéctive-
tissue. [The subcapsular layer of the cortex,
and a thin layer next the boundary zone (fig.
242, a, a), are devoid of Malpighian corpuscles. }

[Development of a Malpighian Capsule.—The
upper end of the urinary tubule is dilated and
closed, and into it there grows a tuft of blood-
vessels (a) pushing one layer of the tube before
it (b), hence the capillaries become invested by
it, just as an organ is surrounded by a serous sac,
so that one layer—the reflected one (b)—of the

dsr 5 tubule is closely applied to the blood-vessels

\ ia sil og J while the other (c) lies loosely over it: witha
ee space between the two (fig. 248). ] .

Fig. 248 955. THE URINE. — Physical

Characters.—A knowledge of the com-
position of this secretion is of the greatest
value to the physician and surgeon.

1. The quantity of urine passed by an
adult man in twenty-four hours is between
1000 and 1500 cubic centimetres, or about
50 ozs., and in the female 900 to 1200
c.c. The minimum is secreted between
2 to 4 A.M., and the maximum between 2
to 4 p.m. ( Weigelin).

The amount is diminished by profuse sweat-
ing, diarrhea, thirst, non-nitrogenous food,
diminution of the general blood-pressure, after
severe hemorrhage, and in some diseases of the
kidneys. The minimum, which may be normal,
is 400 to 500c.c. It is increased by increase of
the general blood-pressure, or of the pressure
within the area of the renal artery, by copious
drinking, contraction of the cutaneous: vessels
through the action of cold, the passage of a
Fig. 249. Fig. 250. large amount of soluble substances (urea, salts,

Fig. 248.—Development of a glomerulus and #24 sugar) into the urine, a large amount of
Malpighian capsule. a, capillary ; }, vis- nitrogenous food, as well as by various drugs,

ceral ; ¢, parietal layer of capsule. such as digitalis, alcohol, squills. After taking
Fig. 249.—Graduated cylinder and flask for {uids charged with CO,, the amount of urine is

measuring the amount of urine. increased during the following hours (Quincke),
Fig. 250.—Urinometer, The secretion is influenced directly by the
nervous system, as in the sudden pol fol-.

lowing. nervous excitement, such as hysteria, [when the person usually passes a large amount
of very pale-coloured urine]; after an epileptic attack, and also after pleasurable excitement
(Beneke). We may have polyuria unaccompanied by the presence of sugar in the urine, which
follows injury to a certain part of the floor of the fourth ventricle (C7. Bernard). The urine is
measured in tall graduated cylindrical vessels (fig. 249). [In estimating the quantity of urine
vassed, the patient must, of course, be directed always to empty his bladder at a particular

our, and collect the urine passed during the next twenty-four hours. ] syn bie

2, The specific gravity varies, as a mean, between 1015 and 1025; the maa

ESTIMATION OF SOLIDS. 393

mum, after copious draughts of water, may be 1002; while the maximun, after
profuse perspiration and great thirst, may be 1040. The mean specific gravity is
about 1020. In newly-born children, the specific gravity falls very considerably
during the first three days, which is due to the amount of food taken (Martin and
Ruge). [The specific gravity of the urine in infants is about 1003 to 1006.| A
healthy adult excretes about 70 grms. [24 0z.| daily of solids by the urine, or
about 1 grm. of solids per 1 kilo. of body-weight.

The specific gravity is estimated by means of a urinometer (fig. 250), the urine being at the
temperature of 16°C. [The urinometer, when placed in distilled water, ought to float at the
mark 0° or zero, which is conventionally spoken of as 1000. Place the urine to be tested in a
tall cylindrical glass, of such width that the urinometer, when placed in it, may float freely
and not touch the sides. Take care that no air-bubbles adhere to the instrument. When
reading off the mark on the stem, raise the vessel to the eye and bring the eye on a level with
the surface of the water, noting the number which corresponds to this. This rule is adopted,
because the water rises on the stem in virtue of capillarity. It is essential that a sample of the
mixed urine of the twenty-four hours be used for ascertaining the mean specific gravity. ]

Christison’s Formula.—To estimate the amount of solids in the urine. This may be done
approximately by means of the formula of Trapp or Haeser, or, as it is called in this country,
‘* Christison’s formula,” viz., “ Multiply the two last figures of a specific gravity expressed in
four figures by 2°33” (Christison and Haeser), or by 2 (Trapp), or 2°2 (Loebisch). This gives
the amount of solids in every 1000 parts. [Suppose a person passes 1200 c¢.c. urine in twenty-
four hours, and the specific gravity is 1022, then

22 x 2°33 =51°26 grms, in 1000 c.¢.
To ascertain the amount in 1200 c.e.
1000 : 1200 :: 51°26: x atl germs. ]

Direct Estimation of Solids.—Place 15 c.c. of urine in a capsule of known weight, and
evaporate it over a water-bath, afterwards completely dry the residue in an air-bath at 100° C.,
and then cool it over concentrated sulphuric acid. During the process, a small amount of urea
is decomposed, so that the value obtained is slightly too small. Of course the specific gravity
varies with the amount of water in the urine. The most concentrated (highest specific gravity)
urine is the morning urine (Urina noctis), especially after being retained in the bladder, ¢.9.,
in prolonged sleep a certain amount of water is absorbed, so that the urine becomes more con-
centrated. The most dilute urine is secreted after copious drinking (Urina potus). Under
pathological conditions, as in diabetes mellitus (§ 175), the urine is, at the same time, very
copious (as much as 10,000 c.c.), and very concentrated, while the specific gravity varies from
1030 to 1060, [due to the presence of a large amount of grape-sugar]. In fever the urine is
concentrated, and smallin amount. In polyuria, due to certain nervous conditions, the urine
is very dilute and copious, while the specific gravity may be as low as 1001.

3. The colour of the urine depends on the colouring-matters present in it, and
varies greatly, but the differences in colour are due chiefly to variations in the
amount of water. Normally it has a pale straw colour, but if it contains more
water than usual it has a very pale tint, and in certain cases (as in the sudden
polyuria occurring after an attack of hysteria) it may be as clear as water. Con-
centrated urine, as after meals, or the first urine passed in the morning, has a
darker colour; it is a dark yellow or brownish-red ; while it is usually dark
coloured in fever. ay

Foetal urine, and also the urine first passed after birth, are as clear and colourless as water.
The admixture of various substances with the urine alters its colour. When mixed with blood,
according to the degree of decomposition of the hemoglobin, the urine is red or dark brownish-
red [more frequently it is smoky], especially if the blood comes from the kidneys and the urine is
acid. When mixed with bile pigments, it is of a deep yellowish-brown, with an intense yellow
froth ; senna taken internally makes it intensely red, rhubarb brownish-yellow, and carbolic
acid black. Urine undergoing the ammoniacal fermentation may present a dirty bluish appear-
ance owing to the formation of indigo. The colour of urine is estimated by Neubauer and
Vogel by means of an empirical ‘‘ colour-scale.” :

' Urine, but especially ammoniacal urine; exhibits fluorescence, which disappears on the
addition of an acid, and reappears after the addition of an alkali.

Normal urine, after standing for several hours, deposits a fine cloud of vesical mucus [like
delicate cotton wool]. The froth of normal urine is white, and disappears pretty rapidly, while
that on an albuminous urine persists much longer. The urine not unfrequently contains some
epithelial cells from the bladder and urethra.

394 _ REACTION OF URINE.
[AMOUNTS OF THE SEVERAL URINARY [AMOUNTS OF THE SEVERAL URINARY
ConstituENts (Loebisch). ConstITUENTS PassEpD In 24 Hours (Parkes).
Man, 28 years of age, Mean of
weight, 72 kilos., observa-) analyses in Perl
tions over 8 days(Kerner).| different By an aver- kilo. of
CONSTITUENTS. individuals CONSTITUENTS. age man of b ody-
| In 24 hours. . (Vogel). 66 kilos. | weight.
| Min. | Max. | Mean. | In 24 hours.
|
| ee | ce. cc. C.c. | grms. grms.
Quantity . . «| 1099 | 2150 | 1491 1500 Water, . . «| 1500-000 23-000
| Specific gravity,. ./ 1015 | 1027 | 1021 1020 Total solids, ~. .{ 727000 1°100
| Water, . : al ganas os see 1440 Urea; 3, |). : .| 383°180 0°500
Solids, es ‘ << aes a 60 Uric acid, . : ° 0°555 0-0084
Urea, . : ‘ .| 82°00; 43°4 38'1 35 Hippuric acid, . : 0°400 0°0060
Uric acid, . ; .| 0°69 1°37 0°94 0°75 Kreatinin, . . F 0°910 0°0140
Sodium chloride, .| 15°00 19°20 16°8 16°5 Pigment and other ‘
| Phosphoric acid, || 3°00| 4°07] 3-42 3°5 substances, . .| 10°300 0°1510
| Sulphuric acid, . “ll 2°26 2°84 2°48 2°0 Sulphuric acid, . . 2°012 0°0305
| Phosphorus, Calcium, | 0°25; 0°51 0°38 aan Phosphoric acid, z 3°164 0°0486
| Magnesium phosphate,. 0°67! 1-29] 0°97 ef Chlorine, . - ~~. |_~—- 7000 (8*12)|_ 0-1260
Total quantity of ee ; my : Ammonia, . 0-770 edi
| earthy phosphates, ; a. a 130 185 , Potassium, . . ‘ 2-500
Ammonia, . 5 - 0°74 1°01 0°83 0°65 Sodium, . : ° 11-090
'Freeacid, . . 1°74 2-20 1°95 3] ||Calctum, . . .| = 0°260 aie
Magnesium, : = 0°207 as |

4. Consistence.—Normal urine, like water, is a freely mobile fluid.

Large quantities of sugar, albumin, or mucus make it less mobile; while the so-called chylous -
urine of warm climates may be like a white jelly.

5. The taste is a saline bitter, the odour is characteristic and aromatic.

Ammoniacal urine has the odour of ammonia. Turpentine taken internally gives rise to the
odour of violets, copaiba and cubebs a strongly aromatic, and asparagus an unpleasant odour.
Valerian, assafcetida, and castoreum [but not camphor] also produce a characteristic odour.
[The odour of diabetic urine is described as ‘‘ sweet.’’]

6. The reaction of normal urine is acid, owing to the presence of acid salts,
chiefly acid sodic phosphate, which seems to be derived from basic sodic phosphate,
owing to the uric acid, hippuric acid, sulphuric acid, and CO, taking to themselves
part of the soda, so that the phosphoric acid forms an acid salt. After a diet of
flesh, acid potassic phosphate is the cause of the acidity. That the urine contains
no free acid is proved by the fact that it gives no precipitate with sodic hypo-
sulphite (v. Voit, Huppert).

The acid reaction is increased after the use of acids, ¢.g., hydrochloric and phosphoric, also
by ammoniacal salts, which are changed within the body into nitric acid; lastly, after
prolonged muscular exertion. The morning urine is strongly acid.

The urine becomes less acid or alkaline—(1) By the use of caustic alkalies, alkaline
carbonates, or alkaline salts of the vegetable acids, the last being oxidised within the body
into carbonates, (2) By the presence of calcic, or magnesic carbonate. (3) By admixture
with alkaline blood, or pus. (4) By removing the gastric juice through a gastric fistula (p. 246,
Maly); further, from one to three hours after a meal. [The reaction of urine passed
digestion may be neutral, or even alkaline. This is due either to the furmation of acid in the
stomach (Bence Jones), or to a fixed alkali derived from the basic alkaline phosphates taken
with the food (W. Roberts).] (5) The urine is rarely alkaline in anemia, owing to a deficiency
of phosphoric and sulphuric acids. [(6) The natwre of the food—vegetable food makes it
— (7) By profuse sweating. (8) By absorption of alkaline transudations (blood,

m).

[Method.—The reaction of urine is tested by means of litmus paper. Normal urine turns
blue litmus paper red, and does not affect red litmus. An alkaline urine makes red litmus
paper blue, while a neutral urine does not alter either blue or red litmus paper.] Sometimes
violet litmus paper is used, which becomes red in acid, and blue in alkaline urine. we

Estimation of the Acidity.—This is done by determining the amount of caustic soda
necessary to produce a neutral reaction in 100 c.c. of urine. A soda solution, containing 0°0031
grm. of soda in each c.c. is used; 1 ¢,c. of this solution exactly neutralises 0°0063 grm. oxalic
acid. To the 100 c.c. of urine in a beaker, soda solution is added, drop by drop, from_
graduated burette (fig. 251), until violet litmus paper becomes neither red nor blue, _
number of ¢.c, of soda solution is now read off on the burette, and as each c,c. corresponds:

UREA. 395

0°0063 grm. oxalic acid, we can easily calculate the amount of oxalic acid which is equivalent
to the degree of acidity in 100 c.c. of urine. So that the degree of acidity of the urine is
expressed by the equivalent amount of oxalic acid, which is completely neutralised by the
same amount of caustic soda.

Urine of Mammals.—The urine of carnivora is pale, passing into a golden-yellow ; its
specific gravity is high, and its reaction strongly acid. The urine of herbivora is alkaline ; it
shows a precipitate of earthy carbonates (hence, it effervesces on the addition of an acid), and
of basic earthy phosphates. During hunger, the urine presents the character of that of car-
nivora, as the animal in this case practically lives upon its own flesh and tissues,

256.—I. THE ORGANIC CONSTITUENTS OF URINE.—Urea, CO(NH.).,
the diamide of CO,, or carbamid, is the chief end-product of the oxidation of the
nitrogenous constituents of the body. Its composi-
tion is comparatively simple: 1 carbonic acid +2
ammonia—1 water. It crystallises in silky four-
sided prisms with oblique ends (rhombic system),
without water of crystallisation (fig. 252, 1), if it
crystallises rapidly it forms delicate white needles.
It has no action on litmus, is odourless, and has a
weak, bitter, cooling taste, like saltpetre ; is readily
soluble in water and alcohol, but insoluble in ether.
It is an isomer of ammonium cyanate, from which it
may be prepared by evaporation, whereby the atoms
rearrange themselves (WéAler, 1828). It can be |
prepared artificially in many other ways. i |

Decomposition.-—When heated above 120°, it gives off |
ainmmonia vapour, while a glassy mass of biuret and cyanic
acid is left. When urine undergoes the alkaline fermenta-
tion (§ 263), or when urea is treated with strong mineral ;
acids, or boiled with the hydrates of the alkalies, or super- ri

heated with water (240° C.), it takes up two molecules of !
water and produces ammonium carbonate, thus— |

CO(NH,), + 2H,0=CO(NH,0)>.

When brought into relation with nitrous acid, it splits up
into water, CO,, and N. The two last decompositions are
made the basis of methods for the quantitative estimation of
urea (§ 257).

Quantity.—In normal urine, urea occurs to the
extent of 2°5 to 3:2 per cent. An adult man ex-
cretes daily from 30 to 40 grms. [500 grains, or a
little over 1 oz.]; women less, children relatively
more ; owing to the relatively greater metabolism in
children, the unit weight of body produces
more urea than the unit weight of an adult,
in the proportion of 1:7: 1. If the metabol- :
ism of the body is in a condition of equi-
librium (§ 236), the urea excreted contains 3
almost as much N as is taken in with the -
nitrogenous constituents of the food. ‘ Fig. 251.

Variations in the Quantity.—The amount Giaddated wavekks
of urea increases when the amount of pro-
teids in the food is increased ; and also when there is a more rapid breaking up
of the nitrogenous tissues of the body itself. As this breaking up is increased
by diminution of O, and by loss of blood, so these conditions also increase the
urea (§ 41). It is also increased by drinking large draughts of water, by various
salts, by frequent urination, and by exposure to compressed air. In diabetic
persons, who eat very large quantities. of food, it may exceed 100 grms. [over 3

396 QUANTITY OF UREA.

oz.] per day ; during hunger it sinks to 6°] grms. [90 grains] per day. _ During
inanition, the maximum amount is excreted towards mid-day, and the minimum in
the morning. The daily amount of urea varies with the quantity of urine ; three
to five hqurs after a meal, the formation of urea is at a maximum, when it sinks
and reaches its minimum during the night. Muscular exercise, as a rule, does
not increase it (v. Voit, Fick and Wislicenus—§ 295), but only when deficiency of
O, causing dyspnoea, occurs at the
same time (Oppenheim).

Fig. 252.
1, 2, Prisms of pure urea; 3, rhomboidal plates ; 4, hexagonal tablets ; 5, 6, irregular scales
and plates of urea nitrate.

Pathological.—In acute febrile inflammations, and in fevers generally (§ 22, 3), the urea
increases until the crisis is reached, and afterwards it diminishes. After the fever has passed
off, the amount excreted is often under the normal. In some cases of high fever, although the
amount of urea formed is increased, it may not be excreted ; there is a retention of the urea,
which, later on, may lead to an increased excretion (Naunyn). In chronic diseases, the amount
depends largely upon the state of the nutrition, the metabolism, and also upon the degree of
fever present. Degenerative changes in the liver, ¢.g., due to poisoning with phosphorus, may
be accompanied by diminished excretion of urea and increased excretion of ammonia
(Stadelmann). It is increased in man by morphia, narcotin, narcein, papaverin, codein,
thebain (Fubini), arsenic (@dthgens), compounds of antimony, and small doses of phosphorus
(Bauer), which favour the decomposition of proteids, and by substances which increase the
bile formation in the liver (V. Paton). Quinine, which “spares” the proteids, diminishes it.

Occurrence.—Urea occurs in the blood (1: 10,000), lymph, chyle (2: 1000), liver, lymph-
glands, spleen, lungs, brain, eye, bile, saliva, amniotic fluid, and pathologically in sweat, ¢.g.,
in cholera, in the vomit and sweat of uremic patients, and in dropsical fluids.

Formation.—It is certain that it is the chief end-product of the metabolism of
the proteids. Less oxidised products are uric acid, guanin, xanthin, hypoxanthin,
alloxan, allantoin. Uric acid administered internally appears in the urine as urea ;
alloxan and hypoxanthin can be changed directly into urea. The urea excretion is
increased by the administration of leucin, glycin, aspartic acid, or ammonia salts
(Schulzen, Nencki). As yet it has not been definitely determined where urea is
formed, but the liver and, perhaps, the lymph glands, are organs where it is pro-
duced (§ 178). |

In birds, the liver forms uric acid from ammonia. The liver can be readily excluded from
the circulation in birds, and Minkowski found that after this operation the uric acid was dimi-
nished and the ammoniacal salts were increased (§ 178).

Antecedents.—During digestion, the proteids are converted into leucin, tyrosin, glycin, and
aspartic acid. If the amido-acids, glycin, leucin, or aspartic acid, or ammoniacal salts, be given
to an animal, the amount of urea excreted is increased. As the molecule of the amido-acids
contains only one atom of N, and the molecule of urea contains two of N, it is probable that
urea may be formed synthetically from these acids. It is possible that the amido-acids meet

QUANTITATIVE ESTIMATION OF UREA. 397

With nitrogenous residues in the juices of the body, ¢.g., carbamic acid or cyanic acid. The
union of these may produce urea. According to Salkowski, feeding with these substances causes
the breaking up of the proper proteids of the body so as to provide the necessary components.
Schmiedeberg is of opinion that urea is formed in the body from ammonia carbonate by the
removal of water; and v. Schroder found that, when he passed blood containing ammonia car-
_ bonate through a fresh liver, the urea in the blood was greatly increased. Drechsel succeeded
in producing urea at ordinary temperatures by the rapid alternating oxidation and reduction of
a watery solution of ammonia carbonate. [We know that the greater part of the urea exists in
the blood, and that the renal epithelium removes it from the blood. Although it is surmised
that some of the nitrogenous bodies named above, more especially leucin, and perhaps also
kreatin, are the precursors of urea, yet we cannot say definitely how or where the transformation
takes place. Perhaps this is effected in the liver, and, it may be, also in the spleen (§ 193).]

Preparation.—Urea may be prepared from dog’s urine (especially after a diet of flesh) by
evaporating it to a syrupy consistence, extracting it with alcohol, and again evaporating the
filtrate to a syrupy consistence. The crystals which

a
separate are washed with water to remove any extractives a o Q
that may be mixed with them, and dissolved in absolute Oo KF a
alcohol. It is then filtered and allowed to crystallise eX rhe, or

slowly. Or, human urine may be evaporated to one-sixth

of its volume and _ cooled to 0°, and excess of strong nitric 4\ a
acid added, which precipitates urea nitrate mixed with c\ = "
colouring-matter. This precipitate is pressed in blotting- a Cc] Ne ‘O)
paper, then dissolved in boiling water containing animal 9) ee
charcoal, and filtered while hot. When it cools, colourless

crystals of urea nitrate separate (fig. 252). These crystals

are redissolved in warm water, and barium carbonate added <
until effervescence ceases ; urea and barium carbonate are

formed. Evaporate to dryness, extract with absolute

alcohol, filter, and allow evaporation to take place, when Big. 258.
urea separates. Perfect crystals of oxalate of urea.

Compounds of Urea.— Urea combines with acids, bases, and salts. The follow-
ing are the most important combinations :—

1. Urea nitrate (CH,N,O, HNO,) is easily soluble in water, and not so soluble in water con-
taining nitric acid. It forms characteristic rhombic crystals (fig. 252, 3, 4, 5, 6). Sometimes
the formation of these crystals is used to determine microscopically the presence of urea in a fluid.
If a fluid is suspected to contain minute traces of urea, it is concentrated and a drop of the fluid
is put on a microscopic slide. <A thread is placed in the fluid, and the whole is covered with a
cover-glass. A drop of concentrated nitric acid is allowed to flow under the cover-glass, and after
a time crystals of urea nitrate adhering to the thread may be detected with the microscope.

2. Urea oxalate (CH,N,O),, C,H,O,+ H,O, is made by mixing a concentrated solution of
urea with oxalic acid. The crystals form groups of rhombic tables, often of irregular shape.
It is only slightly soluble in cold water, and still less so in alcohol (fig. 253).

3. Urea phosphate (CH,N,O, H,PO,), forms large, glancing, rhombic crystals, very easily
soluble in water. It is obtained by evaporating the urine of pigs fed on dough.

4. Sodic chloride+ urea (CH,N,O, NaCl+H,O) forms rhombic, shining prisms, which are
sometimes deposited in evaporated human urine.

5, Urea+mercuric nitrate is obtained as a white cheesy precipitate, when mercuric nitrate
is ey tL) a solution of urea. Liebig’s titration method for urea depends on this reaction
(§ 257, IT.). :

257. QUALITATIVE AND QUANTITATIVE ESTIMATION OF UREA.—I. The qualita-
tive Estimation of Urea.—(1) Jt may be isolated as such. If albumin be present, add to the
fluid three or four times its volume of alcohol, and, after several hours, filter. Evaporate
the filtrate over a water-bath, and dissolve the residue in a few drops of water.

(2) The crystals of urea nitrate may be detected microscopically (fig. 252).

II. Quantitative Estimation.—(1)Sodic hypobromite decomposes urea into CO,, H,O, and N.
On this reaction depends the Knop-Hiifner method of quantitative estimation. ‘The N rises in
the form of small bubbles in the mixed fluid, while the CO, is absorbed by the caustic soda.
[The reaction is the following :—

N,H,CO + 3NaBrO =3NaBr+CO,+2H,0 +N.
The nitrogen is collected and estimated in a graduated tube, and the amount of urea calculated
from the volume of nitrogen. The uric acid is also decomposed, but that.can be estimated
separately and a correction made. We may use the apparatus of Russell and West, or Dupré, .
or that of Charteris (fig. 254).]

[Ureameter.—Make a solution of hypobromite of soda by mixing 100 grammes NaHO in 250
c.c. of water, and adding 25 c.c. of bromine. It is better to be made fresh, as it decomposes by

398 QUANTITATIVE ESTIMATION OF URBA,

keeping. The graduated tube is placed in a cylindrical vessel, filled with water, and depressed
until the zero on the tubes coincides with the level of the water. Introduce 15 c.c. of the
hypobromite solution into the pyramidal-shaped bottle, while into a short test-tube are placed
5 c.c. of urine. The test-tube with the urine is introduced into the bottle by means of a pair
of forceps in such a way that it does not spill, Close the bottle tightly with the caoutchouc
stopper, through which passes a glass tube to connect it with the graduated burette. Incline
the bottle so as to allow the urine to mix with the hypobromite solution when the gases are
given off, and pass into the collecting tube, which is gradually raised until the surfaces of
the liquids, outside and in, coincide. Time should be allowed to permit the whole apparatus
to have the same temperature. Read off the amount of gas N evolved, for the CO, is absorbed
by the caustic soda. The collecting tube is usually pene beforehand, so that each division
of the tube is—0°1 per cent. of urea, or 0°44 gr. per fluid oz. Thus, suppose that 50 oz. of urine
are passed in twenty-four hours, and that 5 c.c. of urine evolve 18 measures of N, then
0°44. x 18 x 50=396 grs. of urea. If, however, the tube be graduated into
c.c., then 30°3 c.c. of N=0°1 grm. of urea at the ordinary temperature and
pressure. ]

III. Volumetric Method (Zicbiy).—By means of a graduated pipette
(fig. 255), 40 cubic centimetres of the urine are placed in a beaker ; add
20 cubic centimetres of barium mixture to precipitate the sulphuric and
phosphoric acids. The barium mixture consists of 1 vol.
of a cold saturated solution of barium nitrate and 2 vols. of
a cold saturated solution of barium hydrate. Filter through
a dry filter, and take 15 cubic centimetres of the filtrate,
which correspond to 10 ¢.c. of wrine, and place in a beaker.
f Allow a titrated standard solution of mercuric nitrate to
drop from a burette into the urine until a precipitate no
longer occurs. The mercuric nitrate
is made of such a strength that 1
cubic centimetre of it will combine
with 10 milligrammes of urea. Test
a drop of the mixture from time to
time in a watch-glass or piece of
glass blackened on its under sur-
face, with a solution of sodic car-
bonate, which iscalled the indicator,
Whenever the slightest excess of
mercuric nitrate is added, the mix-
ture strikes a yellow colour with the

Fig. 254. eee oe peg a solution yah

‘ a2 ne added drop by drop until this

aM ter result is obtained. Read off the

number of cubic centimetres of the standard solution used ; as each centimetre

corresponds to 10 milligrammes of urea, multiply by ten, and the amount of urea
in 10 cubic centimetres of urine is obtained.

This method does not give quite accurate results even in normal urine. To
urine containing much phosphates is added an equal volume of the barium inix-
ture. Very acid urines may require several volumes to be added. Urine contain-
ing albumin or blood must be boiled, after the addition of a few drops of acetic
acid, to remove the albumin. The sodic chloride in the urine also interferes with
the accuracy of the process, as on adding mercuric nitrate to urine, mercuric
chloride and sodic nitrate are formed, so that the urea does not combine until
the sodic chloride is decomposed. When the urine contains, as is usually the
case, 1 to 14 per cent. NaCl, deduct 2 ¢.c. from the number of c.c. of the 8.8.
added to 10 c.c. of urine. ,

Estimation of the total N in Urine.—Pfliiger and Bohland recommend the Fig. 255
following modification of the method of Kjeldahl. Five c.c. of aurine of medium Gradaatell
concentration are allowed to flow from a burette into Erlenmeyer’s flask, capable inette,
of containing about 300 c.c., and to it are added 20 c.c. of concentrated sulphuric pipe
acid, The whole is boiled until all the water and gases are driven off. The fluid at first
becomes black from the action of the sulphuric acid, but when it has become of brownish tone
lessen the heat of the Bunsen burner. About half an hour suffices to heat it, when the fluid at
last becomes bright yellow. Allow it to cool, dilute it with water to 200 c.c., and place the
whole in a flask, add 80 c.c. of caustic soda (S.9. 1°83), cork the flask as quickly as possible, and
distil its contents. The distillate must pass over into sulphuric acid, which must be titrated
beforehand. The quantity of sulphuric acid not combined with ammonia must be estimated by
titration with caustic soda. . ¥

[a 8 of Pe eee Pees a ere:

(

The N in the Urine may be estimated approximately thus. To 10 c.c. of the urine add from _

URIC ‘ACID, 399

a burette Liebig’s mercuric nitrate solution, and test the mixture in a black glass plate with
dry sodic bicarbonate until a yellow speck remains. Multiply the number of c.c. of the burette
fluid used by 9°04 (Pfliiger and Bohland),

2.58. URIC ACID=C.H,N,0, is the nitrogenous substance which, next to
urea, carries off most of the N from the body ; in twenty-four hours 0°5 grm. (7
to 10 grains); during hunger, 0°24 grm. (4 grains) ; after a strongly animal diet,
2°11 grm. (30 to 35 grains) are excreted. The proportion of urea to uric acid is
45:1. Ifamammal be fed with uric acid, part of it becomes more highly oxidised
into urea, while the oxalic acid in the urine is also increased (§ 260); in fowls,
feeding with leucin, glycin, or aspartic acid (v. Anzertem), or ammonia carbonate
(Schroeder), increases the amount of uric acid. When urea is administered to fowls,
it-is reduced chiefly to uric acid.

It is the chief nitrogenous product in the urine of birds, reptiles, and insects, while it is
absent from herbivorous urine.

Properties. —It is dibasic, colourless, and crystallises in various forms (figs. 256
and 257), belonging to the rhombic system (1). When the angles are rounded, the
whetstone form (2) is produced, and if the long surfaces be flattened, six-sided tables
occur. Not unfrequently diabetic urine deposits spontaneously, large, yellow,
transparent rosettes (6, 8). If 20 ¢.c. of HCl, or acetic acid, be added to 1 litre of
urine, crystals (9) are deposited, like cayenne pepper, on the surface and sides of
the glass, after several hours. [The HCl decomposes the urates, and liberates the
acid, which does not crystallise at once, owing to the presence of the phosphates in
the urine. Crystals of uric acid are usually yellowish in colour from the pigment
of the urine, and
they are soluble
in caustic pot-
ash. |

Solubility. —It is
tasteless and odour-
less; reddens lit-
mus; is soluble in
18,000 parts of cold
and in 15,000 of
boiling water, and
insoluble in alcohol
and ether. Hor-
baczewski prepared
it synthetically by
melting together
glycin, or, as it is
also called, glyco-
cin, and urea. It
is freely soluble in
alkaline carbonates,
borates, phosphates,
lactates, and ace-

tates, these salts at ad ale _ Fig. 256.
the same time re- Forms of uric acid. 1, Rhombic plates ; 2, whetstone forms; 3, quadrate

moving a part of forms ; 4, 5, prolonged into points; 6, 8, rosettes; 7, pointed bundles ;
thebase;thus,there 9, barrel forms precipitated by adding hydrochloric acid to urine.

are formed acid urates and acid salts from the neutral salts. It is soluble in concentrated sul-
phuric acid, from which it may be precipitated by the addition of water.

Decomposition. —Dyring dry distillation it decomposes into urea, cyanuric acid, hydrocyanic
acid, and ammonium carbonate. Superoxide of lead converts it into urea, allantoin, oxalic
acid, and CO, ; while ozone forms the same substances, with the addition of alloxan. When it
is reduced by A in statu nascendi, as by sodium amalgam, it forms xanthin and sarkin. It is
a less oxidised metabolic product than urea, but it is by no means proved that uric acid is a
precursor of urea,

Occurrence.—Uric acid occurs dissolved in the urine in the form of acid urates
of soda and potash. These salts occur also in urinary calculi, gravel, and in gouty

400 ESTIMATION OF URIC ACID.

deposits. Ammonium urate occurs in very small quantity in a deposit of “‘urates,”
but is formed in considerable amount when urine becomes ammoniacal from decom-
position (fig. 261). ’ree uric acid occurs in normal urine only in the very smallest
amount. It is sometimes deposited after a time (fig. 260). It frequently forms

urinary ¢alculi and gravel.

The urine of newly-born children contains much uric acid. Uric acid and its salts are
increased after severe muscular exertion, accompanied by perspiration, in catarrhal and rheu-
matic fevers, and such conditions as are accompanied by disturbance of the respiration; in
leukemia and tumours of the spleen, cirrhotic liver, and generally in cases of catarrh of the
stomach and intestinal tract, following the excessive use of alcohol. [It is also increased
during ague and fevers, and perhaps this has some relation to the congestion of the spleen which
accompanies these conditions.) It is diminished after copious draughts of water, after large
doses of quinine, caffein, potassic iodide, common salt, sodic and lithic carbonates, sodic sul-
phate, inhalation of O, slight muscular exertion. In gout, the amount excreted in the urine
is small. In chronic tumours of the spleen, anemia, and chlorosis, when the respiration is not
at the same time embarrassed, it is also diminished.

Urates.—Uric acid forms salts—chiefly acid urates—with several bases, which
dissolve with difficulty in cold water, but are easily soluble in warm water. Neutral
urates are changed by CO, into acid salts. Hydrochloric and acetic acids break
up the compounds, and crystals of uric acid separate.

(1) Acid sodic urate usually appears as a brick-red deposit in urine; more rarely grey or
white (lateritious deposit), tinged with uroérythrin, in catarrhal conditions of the digestive
organs, and in rheumatic and febrile affections. Microscopically, it is completely amorphous,
consisting of granules, sometimes disposed in groups (fig. 260, 6)—sometimes the granules have
spines on them. The corresponding potash salt occurs not unfrequently under the same con-
ditions, and presents the same characters. |

(2) Acid ammonium urate (fig. 261, a) always occurs as a sediment in ammoniacal urine,
either with (1), or mixed with free uric acid, accompanied by triple phosphate. Microscopically,
it is the same as (1). (1) and (2) are distinguished by the sediment dissolving when the urine is
heated. If a drop of hydrochloric acid be added to a microscopic preparation of the sediment,
crystals of uric acid separate.

(3) Acid calcic urate occurs sometimes in calculi, and is a white, amorphous powder slightly
soluble in water. When heated on platinum it leaves an ash of calcium carbonate. Magnesium
urate rarely occurs in urinary calculi.

2.59. ESTIMATION OF URIC ACID. —I. Qualitative.—1. Microscopic Char-
acters.—The appearances presented by uric acid and its salts under the microscope.
It is deposited from urine after several hours, on adding acetic or hydrochloric acid.

2. Murexide Test.—Gently heat a urate or uric acid in a porcelain vessel along
with nitric acid. Decomposition takes place and the colour changes to yellow. N
and CO, are given off; urea and alloxan (C,H,N,O,) remain. Evaporate slowly
and allow the yellowish-red stain to cool; on adding a drop of dilute ammonia a
purplish-red colour of murexide is obtained, it becomes blue on the addition of caustic
potash. If potash or soda be added instead of ammonia, a violet colour is obtained.

3. Schiff’s Test.—Dissolve uric acid or a urate in a solution of an alkaline carbonate, and
drop it upon blotting-paper saturated with a solution of silver nitrate, reduction of the silver
takes place at once, and a black spot is formed.

4. On boiling a solution of uric acid or a urate in an alkali, with Fehling’s solution (§ 149, 2), at
first white urate of the suboxide of copper is deposited, while later, red copper suboxide is formed.

IT. Quantitative Estimation.—Add 5 cubic centimetres of concentrated HCl to 100 c.c. of
urine, and allow it to stand for forty-eight hours in the dark, when the uric acid is precipitated
like fine cayenne pepper crystals. All the uric acid is not precipitated by the HCl, even after
standing fora time. [E. A. Cook uses sulphate of zinc to precipitate the uric acid as urate of —
zinc. Caustic soda is added to precipitate the phosphates, and then to the clear fluid zine sul-
phate solution, which precipitates urate of zinc as a white gelatinous deposit. ]

Fokker-Salkowski Method.—Make 200 c.c. of urine strongly alkaline with sodic carbonate,
and after an hour add 200 c.c, of a concentrated solution of ammonium chloride, whereby acid
urate of ammonium is precipitated. After forty-eight hours filter, through a small weighed
filter, and wash it several times. Fill the filter with dilute HCl and collect the filtrate. Do this
until all the acid urate is dissolved. From the total filtrate after a time all the uric acid separates,
It is collected in the same filter, washed with water and alcohol until the acid reaction dis-
appears, dried at 100° C. and weighed. To the weight in excess of the filter add 0°030 grm.

KREATININ. AND OTHER SUBSTANCES. : 401

260. KREATININ AND OTHER SUBSTANCES.—Kreatinin C,H,N.0O, is
derived from the kreatin of muscle by the removal of a molecule of water, and partly
from flesh food, The quantity excreted daily is 0°6 to 1:3 gramme (8 to 18
grains).

It is diminished in progressive muscular atrophy, tetanus, anemia, marasmus, chlorosis,
consumption, paralysis ; and is increased in typhus, inflammation of the lung; it is absent
from the urine of sucklings. ;

Properties. —Kreatinin is alkaline, easily soluble in water and hot alcohol. It forms colour-
less oblique rhombic columns ; unites with acids and salts, silver nitrate, mercuric chloride,
and especially with zinc chloride. Kreatinin-zine chloride (fig. 257) is used to detect its pres-
ence. Weyl’s Test.—Add to urine a few drops of a slightly brownish solution of nitro-prusside
of soda, and then weak caustic soda solution, producing a Burgundy-red colour, which soon
disappears. When heated with glacial acetic acid, the colour changes to green, which after a
time changes to blue (Salkowski). [The blue colour—Berlin blue—is due to the formation of an
iron-salt ferro-cyanide of sodium from the decomposition of the nitro-prusside. The reaction
also succeeds with formic acid—instead of glacial acetic acid—if some time be allowed to elapse
after Weyl’s reaction. ] ;

Xanthin =C,H,N,O, occurs only to the amount of 1 gramme in 300 kilos. of urine. It isa
substance intermediate between sarkin
and uric acid. Guanin and hypoxan-
thin may be changed into xanthin ; in
contact with water and ferments it passes at
into uric acid. When evaporated with g _.__ “uy
nitric acid, it gives a yellow stain, which n\
becomes yellowish-red on adding potash,
and violet-red on applying more heat.
It is an amorphous, yellowish-white
powder, fairly soluble in boiling water. .
It has also been found in traces in |

muscles, brain, liver, spleen, pancreas,
and thymus. The crystalline body
paraxanthin (dimethylxanthin) and the
amorphous heteroxanthin (methy]xan-
thin) occur in traces in the urine (Salo-
mon).

Sarkin or Hypoxanthin, C,H,N,0.—
As yet this substance has been found
only in the urine of leukemic patients
(Jakubasch), and it has been prepared
in the form of needles or flattened scales
from muscle, spleen, thymus, brain, Fig. 257. sx
bone, liver, and Kidney. In normal Kreatinin-zine chloride. a, balls‘with radiating marks :

urine a body nearly related to, and pos- tee a :
sibly identical with, hypoxanthin oceurs b, crystallised from water ; ¢, from alcohol.

(E£. Salkowski). Wypoxanthin closely resembles xanthin, and can be changed into it by oxida-
tion. Nascent hydrogen, on the other hand, reduces uric acid to xanthin and hypoxanthin.
When evaporated with nitric acid it gives a light yellow stain, which becomes deeper, vut not
reddish-yellow, on adding caustic soda. It is more easily soluble in water than xanthin, and
by this means the two substances can be separated from each other. Guanin is insoluble in
water.

Oxaluric acid (C,H,N.O,) occursin very sinall quantity combined with ammonia in urine.
Physiologically, it is interesting on account of its relation to uric acid. It is a white powder
slightly soluble in water. Ammonia oxalurate can be prepared from uric acid.

Oxalic Acid (C,H,O,) occurs, but not constantly, to the amount of 20 milli-
grammes daily as oxalate of lime, which is known by the “envelope” shape of
the crystals (fig. 258) ; insoluble in acetic acid, and forming transparent octahedra.
More rarely it assumes a biscuit or sand-glass form, The genetic relation of oxalic
acid to uric acid is shown by the fact, that dogs fed with uric acid excrete much
oxalate of lime. Oxalic acid may also-be produced by the oxidation of products
derived from the fatty acid series (p. 381).

Oxaluria,—The eating of substances containing oxalate of lime (rhubarb) increases the excretion.
Increased excretion is called oxaluria ; it is regarded as a sign of retarded metabolism (Beneke),
and it may give rise to the formation of a calculus. In oxaluria the uric acid is also often in-

' 2 C

bk

402 _* HIPPURIC ACID.

creased in amount. Perhaps, in the first instance, there is an increased formation of uric acid,
from which oxalic acid, urea, and CO, may be formed. The amount of oxalic acid is increased
after the use of wine and sodic bicarbonate.

Hippuric Acid = C,H NO, (Benzoylamidoacetic acid) occurs in large amount in
the urme of herbivora, and in them is the chief end-product of the metabolism of
nitrogenous substances ; in human urine the daily quantity is small, 0°3 to 3°8
i grms. (5 to 50 grains). It is an odourless monobasic

, acid with a bitter taste, crystallising in colourless four-

VAL Wh sided prisms (fig. 259). Readily soluble in alcohol, and
" soluble in 600 parts of water.

[Crystals of hi dante acid when heated in a test-tube are decom-
posed, and a sublimate of benzoic acid and ammonic benzoate
condenses on the upper cool part of the tube, while there is an

odour of new hay, and oily drops remain in the tube. ]
Fic, 258. It is a conjugated acid, and is formed in the body from
Oxalate of lime. a, b, octa- benzoic acid, or some nearly related chemical body, such
hedra; c,compound forms; as the cuticular substance of plants, or from oil of bitter
d, dumb-bells. almonds, cinnamic or chinic acid, which easily pass by
reduction (chinic acid) or by oxidation (cinnamic acid) into benzoic acid; glycin

uniting with it, with the formation of water—
C.H,O, +C,H,NO,= C,H,NO, +H,O
Benzoic acid + Glycin = Hippuric acid + Water.

[Formation.—When benzoic acid is introduced into the alimentary canal of an
animal (rabbit or dog), it appears in the urine as hippuric acid ; while nitro-benzoic
acid appears as nitro-hippuric acid.
As the benzoic acid passes through
the body, it becomes conjugated with
glycin or glycocin, chiefly in the kid-
neys. The hippuric acid in the urine
of herbivora is chiefly derived from
some substance with a benzoic acid
residue present in the cuticular cover-
ings of the food. That hippuric acid,
in part at least, is formed in the
kidneys is shown by the following
considerations :—If arterialised blood,
containing benzoic acid and glycin, or
even benzoic acid alone, be passed
through the blood-vessels of a fresh,
living, excised kidney, hippuric acid
is found in the blood after it is per-
\ fused. Even after forty-eight hours,
Fig. 259. if the kidney be kept cool, the syn-
Hippuric Acid. thesis takes place. If the kidney be
kept too long, the conjugation does
not take place. If the fresh kidney be chopped up, and kept at the temperature of
the body with benzoic acid and glycin, hippuric acid is formed. Oxygen seems to
be necessary for the process, for, if blood or serum containing carbonic oxide be used,

there is no formation of hippuric acid. ]
_ According to this view, it is derived chiefly from the food of herbivorous animals, and hence.
it is absent from the urine of sucking calves, as well as after feeding with grain devoid of husk,
But it is also formed in the body from the proteids. In the dog, the formation of hippuric acid
occurs in the kidney (Schmiedeberg and Bunge); and in the frog also outside the ree Kiihne

and Hallwachs thought it was formed in the liver, and Jaarsveld and Stockvis in * 4
liver, and intestine. The observation of Salomon that, after excision of the kidneysin rabbits,

LP
Yj

/

COLOURING-MATTERS OF URINE. 403

and injection of benzoic acid into the blood, hippuric acid was found in the muscles, blood, and
liver, goes to show that it must be formed in other organs beside the kidneys. The power of
changing benzoic acid introduced into the human body, into hippuric acid, may even be
abolished in disease of the kidney. Under certain circumstances it seems that hippuric acid,
already formed, may be again decomposed in the tissues.

It is greatly increased after eating pears, plums, and cranberries; in icterus, some liver
affections, and in diabetes. When boiled with strong acid or alkalies, or with putrid substances,
it takes up H,O and splits into benzoic acid and glycin.

Preparation.—Add milk of lime to the fresh urine of horses or cows to form calcic hippurate.
Filter, evaporate the filtrate to a small bulk, and precipitate the hippuric acid with excess of
hydrochloric acid. To purify the hippuric acid, crystallise it several times from a hot watery
solution.

Cynuric Acid. —C,,H,,N,0,+H,0 occurs in the urine of dogs (J. v. Liebig).

Allantoin, C,H,N,O., which occurs in the amniotic fluid of the cow, is found in
minute traces in normal urine after flesh food, and is more abundant during the

first weeks of life, and during pregnancy.

After large doses of tannic acid, the amount is increased (Schottin), while in dogs feeding with
uric acid also increases it (Salkowskt),

Properties.—It forms shining, prismatic crystals; from the urine of sucking calves it
erystallises in transparent prisms. It is decomposed by ferments into urea, ammonium oxalate,
and carbonate, and another as yet unknown body. Preparation—(a) the urine is precipitated
with basic lead acetate, the lead in the filtrate is removed by sulphuretted hydrogen, and the
filtrate itself is then evaporated to a syrup, from which the crystals separate, after standing
for several days. They are then washed with water, and recrystallised from the water
(Salkowskt).

261. COLOURING-MATTERS OF THE URINE.—1. Urobilin is most
abundant in the highly coloured urine of fevers, but it also occurs in normal urine
(Jafé). It is identical with the hydrobilirubin of Maly (§ 117, 3, 9). It is a de-
rivative of hematin, which also yields the bele-pugments (§ 177). It gives a red, or
reddish-yellow colour to urine, which becomes yellow on the addition of ammonia.

[MacMunn, chiefly from spectroscopic observations, finds that two entirely different substances
have been included under the name of ‘‘ urobilin,” viz., that of normal and that of pathological
urine, and that hydrobilirubin is not identical with either. The pathological urobilin seems
to be closely connected with stercobilin ($ 185). ]

Preparation.—Prepare a chloroform extract of urine containing urobilin—add iodine to the
extract, and remove the iodine by shaking the mixture with dilute caustic potash, which forms
potassic iodide. This potash solution becomes yellow or brownish-yellow, and exhibits beauti-
ful green fluorescence (Gerhardt).

Urobilin may be extracted from many urines by ether (Salkowski). When subjected to the
action of reducing agents, e.g., sodium amalgam, a colourless product: is obtained, which on
exposure to the air absorbs O, and becomes retransformed into urobilin. This colourless body
is identical with the chromogen which Jaffé found in urine.

If urine is treated with soda or potash, the characteristic absorption-band lying between 0 and
F, passes nearer to b, becomes darker and more sharply defined. According to Hoppe-Seyler,
urobilin is formed in urine after it is voided, from another urobilin-forming body (Jaffé’s
chromogen) absorbing oxygen. If urine containing urobilin be made alkaline with ammonia,
and zinc chloride be added, it exhibits marked fluorescence ; it has a green shimmer by reflected
light. When urobilin is isolated, it fluoresces without the addition of zinc chloride. In cases
of jaundice (§ 180), where Gmelin’s test sometimes fails to reveal the presence of bile-pigments,
urobilin occurs. This ‘‘ urobilin-icterus” (Gerhardt) occurs chiefly after the absorption of large
extravasations of blood. . According to Cazeneuve, the urobilin is increased in all diseases
where there is increased disintegration of coloured blood-corpuscles.

2. Urochrome (7hudichum) is regarded as the chief colouring-matter of urine. It may be
isolated in the form of yellow scales, soluble in water, and in dilute acids and alkalies. The
watery solution oxidises, and when exposed to air becomés red owing to the formation of
uroerythrin. When acted on by acids, new decomposition-products are formed, e.g., urome-
lanin. Uroerythrin gives the red colour to deposits of urates (§ 258).

8. A brown pigment containing iron is carried down. with uric acid, which is precipitated
on the addition of hydrochloric acid (§ 258). By repeatedly adding sodic urate to the urine,
fs meer tating the uric acid by hydrochloric acid, a considerable amount may be obtained

wnkel).

4, Urine boiled with HCl yields a garnet-red crystalline pigment, urorubin, to ether.

In eases of melanotic tumours, there has been occasionally observed urine, which becomes
dark, owing to melanin (§ 250, 4), or to a colouring-matter containing iron (Kunke/). .

404 INDICAN AND ITS TESTS.

2°62. INDIGO, PHENOL, KRESOL, PYROKATECHIN, AND SKATOL-

FORMING SUBSTANCES.—1. Indican [C,H,NSO,], or indigo-forming sub-
stance (Schunck), is derived from indol, C,H,;N, the basis of indigo, which is
formed in the intestine by the pancreatic digestion of proteids (§ 170, I1.), but it
also arises as a putrefactive product (§ 184, 6). Indol, when united with the
radical of sulphuric acid, HSO,, and combined with potassium, forms the so-called
indigogen or indican of urine (Brieger, Baumann). This substance (C,H,NSO,K
= potassium indoxyl-sulphate) forms white glancing tablets and plates ; readily
soluble in water and less so in alcohol. By oxidation it forms indigo-blue ;
2 indican + O, = C,,H,)N.O, (indigo-blue) + 2HKSO, (acid potassic sulphate). | It
is more abundant in the urine in the tropics, and it is absent from the urine of
the newly-born (Senator).

Tests.—(1) Add to 40 drops of urine, 3 to 4 c.c. of strong fuming hydrochloric acid, and 2
to 3 drops of nitric acid. Boil, a violet-red colour (with the deposition of true crystalline
indigo-blue (rhombic) and indigo-red attests its presence. Putrefaction causes a similar decompo-
sition in indican ; hence, we not unfrequently observe a bluish-red pellicle of microscopic crystals
of indigo-blue, or even a precipitate of the same. (2) Mix in a beaker equal quantities of urine
and hydrochloric acid, and add two drops of solution of chlorinated lime ; the mixture at first
becomes clear, then blue (Jagfé). Add chloroform, and shake the mixture vigorously for some
time ; the chloroform dissolves the blue colouring matter, which is obtained as a deposit,
when the chloroform evaporates (Senator, Salkowski). (3) Heat to 70° one part of urine with
two parts of nitric acid, and shake up with chloroform; the chloroform dissolves the indigo
whic is formed, assumes a violet colour, and gives an absorption band between C and D,
slightly nearer D (Hoppe-Seyler). Quantity.—Jatfé found in 1500 c.c. of normal human urine,
4°5 to19°5 milligrammes of indigo; horse’s urine contains 23 times asmuch. The subcutaneous
injection of indol increases the indican in the urine (Jaffé). E. Ludwig obtained indican by
heating hematin or urobilin with a caustic alkali and zine dust. It has also been found in the
sweat (Bizio).

Pathological.—The indican in the urine is increased when much indol is formed in the
intestine (§ 172, II.), ¢.g., in typhus, lead colic, trichinosis, catarrh, and hemorrhage of the
stomach, cholera, carcinoma of the liver and stomach; obstruction of the bowel or ileus,
peritonitis, and diseases of the small intestine.

2. Phenol, C,H,O (carbolic acid, § 252), was discovered by Stiideler in human
urine (more abundant in horse’s urine). It does not occur as carbolic acid, but in
combination with a substance from which it is separated by distillation with dilute
mineral acids. The “ phenol-forming substance” is, according to Baumann,
‘‘ phenolsulphonic acid’ (C,H,O, SO.H), which in urine is united with potash.

Phenol is derived from the decomposition of proteids by pancreatic digestion (§ 172, II.),
and also from putrefaction (§ 184, 6), the mother-substance being tyrosin. Hence, the forma-
tion of phenolsulphonic acid is analogous to the formation of indican.

_ If in the employment of carbolic acid it be absorbed, the phenolsulphonic acid becomes greatly
increased in amount, so that sulphuric acid must be united with it; hence, alkaline sulphates .
are decomposed in the body, so that the latter may be absent from the urine (Baumann),
Living muscle or liver, when digested in a stream of air for several hours with blood to which
phenol and sodic sulphate are added, yields phenolsulphonic acid ; while, under the same cir-
cumstances, pyrokatechin forms ethersulphonic acid,

Carboluria.— When carbolic acid is used externally or internally, and it is absorbed, it causes
a deep dark-coloured urine due to the oxidation of phenol into hydrochinon (orthobioxybenzol
mF Pr which for the most part appears in the urine as ethersulphonic acid (Bawmann and
others).

3. Parakresol (hydroxyltoluol, C;H,O), with its isomers ortho- and meta-kresol
(the latter in traces), is more abundant in urine (Baumann, Preusse). It also
occurs in combination with sulphonic acid.

Test for phenol (and also kresol) :—Distil 150 ¢.c. urine with dilute sulphuric acid. The
‘listillate gives a brown crystalline deposit of tribromophenol with bromine water, as well as a
red colour with Millon’s reagent. .

Hydroxybenzol (pyrokatechin, hydrochinon) is obtained from urine, when it is heated for a —
long time with hydrochloric acid. .
orcin, which is an isomer of hydrochinon, when administered internally, also appears in’

the — as ethersulphonic acid. Toluol and naphthalin behave similarly, ‘Benzol is oxidised

0 phenol, a olf

4
-
a
<

PYROKATECHIN AND SKATOL. 405

4. Pyrokatechin = C,;H,O, (metadihydroxylbenzol), is formed along with hydro-
chinon from phenol, and is an isomer of the former. It behaves like indol and
phenol, for when united with sulphonic acid, it yields the pyrokatechin-forming
substance. Small quantities sometimes occurin human urine; itis more abundant
in the urine of children ; it becomes darker when the urine putrefies,

5. Skatol, which is crystalline, and is formed during putrefaction in the intestine,
also appears in the urine as a compound of sulphonic acid (§ 252). On feeding a
dog with skatol, Brieger found much potassic skatol-oxy-sulphate.

Test.—Skatol compounds are recognised by adding dilute nitric acid, which causes a violet
colour, or fuming nitric acid, which precipitates red flakes (Nencki). Its quantity is regu-
lated by the same conditions as indican.

The aromatic oxyacids, hydroparacumaric acid, and paraoxyphenylacetic acid (the former a
putrefactive product of flesh, the latter obtained by,E. and H. Salkowski from putrid albumin)
occur in the urine (Baumann, § 252). Shake the urine treated with a mineral acid with ether,
evaporate the latter, and dissolve the residue in water. If aromatic oxyacids are present, they
give a red colour with Millon’s reagent.

Baumann gives the following series of bodies, which are formed from tyrosin by decomposi-
tion and oxidation ; most of the substances are formed both during the decomposition of
albumin. and also in the intestine, whence they pass into the urine :—Tyrosin, C,H,;NO,+ H,
= ©,H,)03 (hydroparacumaric acid) + NH,. C,H,)0;=C,H,,0 (paraethylphenol, not yet proved)
+CO,. CgH,,0+0,=C,H,O, (paraoxyphenylacetic acid)+ HO. CgH,03=C,H,O (parakresol)
+CO,. C,;H,0+0;=C,H,0,; (paroxybenzoic acid, not yet proved)+H,O. C,H,O=C,H,O
(phenol) + CO,. .

Potassium sulphocyanide, derived from the saliva, also occurs in urine. After acidulation
with hydrochloric acid, its presence may be detected by the ferric chloride test (§ 146—@scheid-
len and J. Munk). One litre of human urine contains 0°02 to 0°08 gramme combined with an
alkali.

Succinic acid (C,H,O,) occurs chiefly after a diet of flesh and fat, and almost disappears after
a vegetable diet. It is a decomposition-product of asparagin, and occurs in considerable amount
in the urine after eating asparagus. It is also a product of the alcoholic fermentation (§ 150),
and as it passes out of the body unchanged, it occurs in the urine of those who imbibe spirituous
glue: It passes unchanged into the urine (Mawbawer).

actic acid (C,;H,O;) is a constant constituent of urine. Other observers have found ferment-
able lactic acid in diabetic urine; sarcolactic acid after poisoning with phosphorus and in
trichinosis. Occasionally traces of volatile fatty acids are present. Some animal gum occurs
in urine (p. 384), and,Bechamy’s ‘‘ nephrozymose” consists for the most part of gum (Land-
wehr). 'This substance is precipitated from urine by adding to it three times its volume of
90 per cent. alcohol. It is not asimple body, but at 60° to 70° C. it transforms starch into
sugar (v. Vintschgau).

Ferments.—Traces of diastatic, peptic, and rennet ferment have been found, especially in
urine of high specific gravity. Trypsin is said not to occur normally (Leo).

Traces of sugar (Briicke, Bence Jones), to the amount of 0°05 to 0°01 per cent., occur in
normal urine. After the ingestion of milk-, cane-, or grape-sugar (50 grms.) these varieties of
sugar appear in small quantity in the urine ( Worm-Miiller— 267, 7).

Kryptophanic acid (C,H,NO;), according to Thudichum, occurs as a free acid in urine, but
Landwehr regards it as an animal gum.

Aceton (C,H,O) is formed when normal urine is oxidised with potassic bichromate and sul-
phuric acid, and it is formed from a reducing substance present in normal urine (apparently
derived from the grape-sugar of the blood). Aceton occurs in traces as a normal urinary con-
stituent, which is increased during increased decomposition of the tissues, ¢.g., carcinoma, in-
anition. It has also been found in the blood in fever (v. Jacksch). Lieben’s Test.—Acidulate
half a litre of urine with HCl and distil; when treated with tincture of iodine and ammonia
there is a turbidity due to iodoform.

II. THE INORGANIC CONSTITUENTS OF THE URINE.—The inorganic
constituents are either taken into the body as such-with the food and pass off un-
changed in the urine, or they are formed in the body, owing to the sulphur and
phosphorus of the food being oxidised and the products uniting with bases to form
Fon The quantity of salts excreted daily in the urine is 9 to 25 grammes [} to

oz. |. 3

1. Sodic chloride—to the amount of 12 (10 to 13) grammes [180 grains]—is
excreted daily. It is increased, after a meal, by muscular exercise, drinking of
water, and generally, when the quantity of urine is increased, by the free use of

406 PHOSPHORIC AND SULPHURIC ACIDS.

large quantities of common salt, but by potash salts also ; it is diminished under

the opposite conditions.

In disease it is greatly diminished ; in pneumonia and other inflammations accompanied by
effusions, in continued diarrhcea and profuse sweating, constantly in albuminuria and in
dropsies. [In cases of pneumonia, sodic chloride may at a certain ae almost disappear from
the urine, and it is a good sign when the chlorides begin to reappear.] In other chronic diseases,
the amount of NaCl excreted runs nearly parallel with the amount of urine passed. In condi-
tions of excitement the amount of sodic chloride is diminished, and potassic chloride increased ;
in conditions of depression the reverse is the case (Zeulzer).

Test.—Add to the urine nitric acid and then nitrate of silver solution, which gives a white
eurdy precipitate of chloride of silver. In albuminous urine the albumin must first be removed,
Microscopically look for the step-like forms of common salt, and also for the crystals of sodic
chloride and urea (§ 256, 4).

2. Phosphoric acid occurs in urine as acid sodic phosphate and acid calcic and
magnesic phosphates to the amount of about 2 grammes daily [30 grains]; it is
more abundant after an animal than after a vegetable diet. The amount increases
after a mid-day meal until evening, and falls during the night until next day at
noon. It is partly derived from the alkaline and earthy phosphates of the food,
and partly as a decomposition-product of lecithin and nuclein. As phosphorus is
an important constituent of the nervous system, the relative increase of phosphoric
acid is due to increased metabolism of the nervous substance.

Pathological. —In fevers, the increased excretion of potassic phosphate is due to a consump-
tion of blood and muscle (§ 220, 3). It is also increased in inflammation of the brain, soften-
ing of the bones, diabetes, and oxaluria ; after the administration of lactic acid, morphia, chloral,
or chloroform. It is diminished during pregnancy, owing to the formation of the fcetal bones ;
also after the use of ether and alcohol, and in inflammation of the kidney.

{Tests.—To urine add nitric acid and solution of ammonium molybdate and boil, a canary-
yellow precipitate of ammonium phosphomolybdate indicates the presence of phosphoric acid,
Or, add half its volume of caustic potash to urine, and boil. The earthy phosphates are precipi-
tated, but not the alkaline phosphates. ]

Earthy phosphates are precipitated by heat in some pathological urines. This
precipitate is distinguished from albumin, which is also precipitated by heat, by
being soluble in nitric acid, which precipitated albumin is not. [The earthy phos-
phates are not precipitated until near the boiling point. ]

Quantitative.—The amownt of phosphoric acid is estimated by tritation with a standard
solution of uranium acetate ; ferrocyanide of potassium being the indicator. The indicator gives
a brownish-red colour when there is an excess of free uranium acetate.

In addition to phosphoric acid, Peon occurs in an incompletely oxidised form in the
urine, ¢.g., glycerinphosphoric acid (§ 251, 2), which occurs to the amount of 15 milligrammes
in a litre of urine; it is increased in nervous diseases and after chloroform narcosis.

3. Sulphuric acid occurs in the urine, the greater part in combination with the

alkalies, and the remainder united with indol, skatol, and pyrokatechin, in the form —

of aromatic ethersulphonic compounds, the ratio being 1: 0°1045. All conditions
which favour the formation of indol, skatol, or pyrokatechin, increase the amount
of combined sulphuric acid. The total daily amount of sulphuric acid is 2°5 to 3°5
grammes [37 to 52 grains]. It is increased by the administration of sulphur,
(Krause). The sulphuric acid is chiefly derived from the decomposition of proteids,
and hence its amount runs parallel with the amount.of urea excreted. The amount
of alkaline sulphates in the food is, as a rule, very small.

An increased excretion of sulphuric acid in fevers indicates an increased metabolism of the
tissues of the body. In renal inflammation it has been observed to be diminished, and in
eczema it is greatly increased. Feeding with taurin (which contains sulphur), in the case of
rabbits, (but not in carnivora or man), increases the sulphuric acid in the urine (Salkowski).
ee to Ziilzer, a copious secretion of bile lessens the relative amount of sulphuric acid in

e urine.

Test.—Barium chloride gives a copious white heavy precipitate of barium sulphate, insoluble
in nitric acid. 5; .

In addition to sulphuric acid, sulphur (}) occurs in an incompletely oxidised form in the
urine (potassium sulphocyanide, cystin, and sulphur-bearing compounds derived from the bile)

ACID FERMENTATION OF ‘URINE. 407

(Kunkel, v. Voit—§ 177, 6). Hyposulphwrous acid, as an alkaline salt, is an abnormal con-
stituent in typhus ; and so is sulphuretted hydrogen, which is recognised by the blackening of
a piece of paper moistened with lead acetate and ammonia, held over the urine.

4, Excessively minute traces of silicic acid and nitric acid derived from drink-
ing water have been found in urine. Organic acids, ¢.g., citric and tartaric, when
taken internally, increase the amount of carbonates in the urine. The urine may
effervesce on the addition of an acid. |

The sodium in the urine is chiefly combined with chlorine, but a small part of
it is united with phosphoric and uric acids ; potassium (which is about } of the
sodium) is-chiefly combined with chlorine. In fevers, more potash is excreted than
soda, and during convalescence, the reverse is the case ; calcium and magnesium
exist in normal acid urine as chlorides or acid phosphates. If the urine is neutral,
neutral calcium phosphate and magnesium phosphate are precipitated. Ebstein
found the Jatter in alkaline urine, as large clear four-sided prisms, in diseases of the
stomach. If the urine is alkaline, calcium carbonate (fig. 281) and tribasic calcic
phosphate are deposited as such, while the magnesium is precipitated in the form
of ammonio-magnesium phosphate, or triple phosphate. The calcium is derived
from the food, and depends upon the amount of lime salts absorbed from the
intestine. Free ammonia is said to occur (0°72 gramme, or 7 grains daily) in per-
fectly fresh urine (Veubauer, Briicke), and the amount is greater with an animal
than with a vegetable diet (Coranda). The amount of fixed ammonia is increased
by the administration of mineral acids (Walter, Schmiedeberg, Githgens). Iron (1
to 11 milligrammes per litre) is never absent. There isa trace of hydric peroxide
(Schonbein), which is detected by its decolorising indigo-solution on the addition of
iron sulphate. |

Gases. —24'4 c.c. of gas was obtained from one litre of urine—100 volumes of the gases
pumped out consisted of 65°40 vol. CO., 2°74 O, 13°86 N. After severe muscular action, the
amount of CO, may be doubled ; digestion also increases it, copious drinking diminishes it.

263. FERMENTATIONS OF URINE.—Acid Fermentation.—When per-
fectly fresh urine is set aside, it gradually becomes more acid from day to day.
This is called the “acid ferment-
ation.” It seems to be due to
the development of special fungi
(fig. 260, a), and the process is
accompanied by the deposition of
uric acid (c), acid sodium urate, in
amorphous grains (4), and calcium
oxalate (d). According to Scherer,
the fungus and the mucus from
the bladder decompose part of the
urinary pigment into lactic and
acetic acids. ‘The latter sets free
uric acid from neutral sodium
urate, so that free uric acid and
sodium urate must be formed.
Butyrie and formic acids have been
found as abnormal decomposition- ig.
products of other urinary constitu- Deposit in “acid fermentation” of urine, a, fungus ;
ents. When the acid fermentation 2 amorphous sodium urate ; ¢, uricacid; d, calcium
begins, the urine absorbs oxygen eye |
(Pasteur). According to Briicke, itis the lactic acid, formed from the minute
traces of sugar present in urine, which causes the acidity. According to Réhmann,
who recognises the acid fermentation as an exceptional phenomenon, the acids are
formed from the decomposition of sugar, and from alcohol which may be present

408 ALKALINE FERMENTATION OF URINE.

accidentally. While the urine is still acid, it becomes turbid and contains nitrous
acid, whose source is entirely unknown. According to v. Voit and Hofmann, phos-

7 phoric acid and a basic salt are formed
from acid sodium phosphate, whereby
part of the uric acid is displaced from
sodium urate, thus causing the forma-
tion of an acid urate.

Alkaline Fermentation.—When urine
is exposed for a still longer time, more
especially in a warm place, it becomes
neutral and ultimately ammoniacal, 2.e.,
it undergoes the alkaline fermentation
(fig. 261).

This condition is accompanied by the
formation of the micrococcus ures (fig.
262) (Pasteur, Cohn) and Bacterium ureze
(fig. 261), which causes the urea to take
up water, and decompose into CO, and
“ammonia. .

Deposit in ammoniacal urine (alkaline fermenta- Urea [CO(HN,), + 2(H,O) = ammo-
tion). 4Q, acid ammonium urate ;. b, ammonio- nium carbonate [(NH ) CO ].

magnesium phosphate ; c, bacterium ure. sailed

The property of decomposing urea belongs
to many different kinds of bacteria, including even the sarcina of the lungs—whose germs seem
tobe universally diffused in the air. These organisms produce a soluble ferment (Musculus),
which, however, only passes from the body of the cells into the fluid after the cell or organism
has been killed by tel (Lea).

The presence of ammonia causes the urine to become turbid, and those substances
which are insoluble in an alkaline urine are precipitated—earthy phosphates, con-
sisting of the amorphous caleic phosphate, acid ammo-
_ nium urate (fig. 261, a), in the form of small dark granules
., covered with spines ; and, lastly, the large clear knife-rest
* or “coftin-lid” form of ammonio-magnesic phosphate,
or triple phosphate (fig. 282). [The last substance
does not exist as such in normal urine, but it is formed
when ammonia is set free by the decomposition of urea,
the ammonia uniting with the magnesium phosphate.
Its presence therefore always indicates ammoniacal fermentation of the urine.] , In
cases of catarrh or inflammation of the bladder, this decomposition may take
place within the bladder, when the urine always contains pus-cells (fig. 267) and
detached epithelium. When much pus is present, the urine contains albumin.
Ammoniacal urine forms white fumes of ammonium chloride, when a glass rod
dipped in hydrochloric acid is brought near it. [When ammonia is added to normal
urine, triple phosphate is precipitated in a feathery form (fig. 283). :

[Significance of Triple Phosphate. -—If urine be alkaline when it is passed, and the alkalinity

be due to a volatile alkali, i.¢,, to NHg, then decomposition of the urine has taken place, and
this kind of urine is a sure sign that there is disease of the genito-urinary mucous membrane. }

264. ALBUMIN IN URINE OR ALBUMINURIA.—Serum-albumin is the
most important abnormal constituent in urine which engages the attention of the
physician. It occurs in blood (§ 32), and its characters are described in § 249..

Causes of Albuminuria.—1.‘Serum-albumin may appear in urine without any apparent ‘a
anatomical or structural change of the renal Pa J his condition has been called by v.
Bamberger We tages gage albuminuria.” It occurs but rarely, however, and sometimes in
healthy individuals when there is an excess of albumin in the blood-plasma (¢.g., after supy ae, 8
sion of the secretion of milk), and after too free use of albuminous food. 2, As a result of
increased blood-pressure in the renal vessels, ¢.g., after copious drinking. It may be temporary,

Fig. 262.
‘Micrococcus ures.

a we

TESTS FOR ALBUMIN IN URINE. 409

or it may be persistent, as in cases of congestion following heart discasc, emphysema, chronic
pleuritic effusions, infiltrations of the lungs, and after compression of the chest, causing conges-
tion in the pulmonary circuit, which extends even into the renal veins, &c. 3. After section
or paralysis of the vaso-motor nerves of the kidneys, which causes great congestion of these
organs. The albuminuria, which accompanies intense and long-continued abdominal pain, is
brought about owing to a reflex paralysis of the renal vessels. 4. After violent muscular
exercise. [Senator found that forced marches in young recruits were very frequently followed
by the appearance of albumin in the urine, which persisted for several days.] Convulsive dis-
orders, ¢.g., epilepsy, the spasms of dyspnoea after strychnin poisoning, in shock of the brain,
apoplexy, spinal paralysis, and violent emotions ; the excessive use of morphia, which perhaps
acts on the vaso-motor centres. 5. It may accompany many acute febrile diseases, ¢.g., the
exanthemata (scarlet fever), typhus, pneumonia, and pyemia. In these cases, it may be due to
the increase of temperature paralysing the vessels, but more probably the secretory apparatus of
the kidney is so changed (e.g., cloudy swelling of the renal epithelium) that the albumin can
pass through the renal membrane. 6. Certain degenerations and inflammations of the kidneys
at several of their stages. 7. Inflammation or suppuration in the ureter or urinary passages.
8. Certain chemical substances which irritate the renal parenchyma, ¢.g., cantharides, carbolic
acid. 9. The complete withdrawal of common salt from the food. The albumin disappears
when the common salt is given again. 10. The epitheliwm may be in such a condition that it
cannot retain the albumin within the vessels, due to imperfect nourishment and functional weak-
ness of the excretory elements. This includes the albuminuria of ischemia, and that after
hemorrhage, in anemia, scorbutus, icterus, diabetes. [Grainger Stewart finds that albuminuria
is more common among presumably healthy people than was formerly supposed. ]

[Besides being derived from the secreting parenchyma of the kidney, albumin may be
present owing to admixture with the secretions from any part of the urinary tract, including
the vagina and uterus in the female. In some cases the transudation of albumin is favoured by
changes in the capillary walls, the albumin being forced through by the intravascular pressure.
Sometimes albuminuria occurs during the course of severe typhoid fever, and in acute fevers
generally, where the temperature is persistently above 40° C. (104° F.). The high temperature
alters the filtering membrane and permits the filtration of albumin. ]

[Physiological Albuminuria.—This term has been applied to that condition of the urine,
where traces of albumin are found in individuals apparently in perfect health. Johnson and
Pavy cite such cases, while Posner asserts that all urine--even healthy urine—contains traces
of proteids, whose presence is ascertained after concentrating the urine. It is safe to assume
that normal urine should give no reaction with the usual tests for albumin. Posner precipi-
tated the urine with alcohol, washed the precipitate, dissolved it in acetic acid, and tested it
with the ferrocyanide test for albumin. He finds that minute traces of proteid are detected by
the following modification of the biuret test :—Make the urine alkaline, and by the ‘‘ contact
method”’ bring a layer of very dilute cupric sulphate over it; when the two fluids touch, a
reddish-violet ring is obtained. ] .

The tests for albumin in urine depend upon the facts that it is coagulated by
heat in neutral or acid solutions, and it is precipitated by various reagents.

[(1) Heller’s Test.—Place 10 ¢.c. of the urine in a test-glass, and pour in pure colourless
HNO, so as to run down the side of the glass, forming a layer beneath the urine. A white
zone of coagulated albumin indicates the presence of albumin. In this test it is important to
wait a certain time for the development of the reaction. In urines of high specific gravity, a
haziness: due to acid urates may be formed above where the two fluids meet, but its upper edge
is not circumscribed. The acid decomposes the neutral urates and forms a more insoluble acid
salt. This cloud of acid urates is readily dissolved by heat, while the albumin is not; the
latter is always a sharply defined zone between the two fluids. In very concentrated urine
(rare), nitric acid may gradually precipitate crystalline urea nitrate. In patients taking
copaiba, nitric acid, by acting on the resin, causes a slight milkiness. ] .

[(2) Boiling and Nitric Acid.—Place 10 c.c. of urine in a test-tube and boil. If albumin be
present in small quantity, a faint haziness, which may be detected in a proper light, will be
produced. Add 10 to 12 drops of HNO. If the turbidity disappears it is due to phosphates,
while if any remains it is due to albumin. If albumin be present in large quantity, a copious
whitish coagulum is obtained. Precautions.—(qa) In all’cases, if the urine be turbid, filter it
before applying any test. (b) How to boil.—Boil the upper strata of the liquid, and take care,
if any coagulum be formed, that it does not adhere to the side of the tube, else the tube is
liable to break. (c) In performing this test with a neutral solution, note when the precipitate
falls, for albumin is precipitated about 70° C., phosphates not till about the boiling point. (d)
Amount of ‘Acid, It too little (2 or 3 drops) HNO, be added, or too much (30 or 40 drops), we
may fail to detect albumin, although it is present. ] ,

(3) Ferrocyanide Test.—By the addition of acetic acid and potassium ferrocyanide. — [If
albumin be present, a white flocculent precipitate separates in the cold. Dr Pavy has intro-
duced pellets, consisting of a mixture of citric acid and sodic ferrocyanide. All that is required

410 TESTS FOR ALBUMIN IN URINE.

is to add a pellet to the suspected urine. Oliver’s papers.—Dr Oliver uses papers, one saturated
with citric acid and another with ferrocyanide of potassium. The two papers are added to the
clear filtered urine. Other precipitants of albumin, such as small pieces of paper impregnated
with potassio-mercuric iodide, are used by Oliver.] | ; ie.

(4) Boiling Acid Urine.—If the urine be alkaline, although albumin. —_ be present, it is
not precipitated by heat alone. We require to add acetic acid until a slightly acid reaction is
obtained. Boiling may give a precipitate of earthy phosphates in an alkaline urine, owing
perhaps to the CO, being driven off. This precipitate might be mistaken for albumin, but
on adding acetic or nitric acid, the earthy precipitate is dissolved, while the precipitate of
albumin is not dissolved. In testing for albumin, always use clear urine. If it is turbid,
filter it.

[(5) Metaphosphoric acid is dissolved in water just before it is to be used and added to clear
urine (Hindenlang). Graham pointed out that metaphosphoric acid pen erage albumin. <A
20 per cent. solution of the ordinary glacial phosphoric acid is a good test for albumin, but it
also precipitates peptones. It, however, changes into ordinary phosphoric acid by keeping,
and then it no longer precipitates albumin. ]

[(6) Sodic Sulphate and Acetic Acid.—Acidulate 10 c.c. of urine with acetic acid, and add 4 of
its volume of a concentrated solution of sulphate of soda or magnesia. On heating, if albumin
be present, a distinct cloudiness is obtained. ]

[(7) In picric acid, according to Dr Johnson, we have a more delicate test for minute traces
of albumin than either heat or nitric acid, or than both these tests combined. It is used either
in the form of crystals or powder, or as a saturated aqueous solution. Take a four-inch column
of urine in a test-tube, hold the tube in a slanting direction, and pour an inch of
the picric acid solution on the surface of the urine, where in consequence of its low
specific gravity (1005) it mixes only with the upper layer of the urine. It coagu-
lates any albumin present. The pearnee occurs at once, and is increased by
heat, while the urate of soda, which is sometimes precipitated, is soluble on
heating. ]

[Dr Roberts regards any test for albumin which requires strong acidulation with
an organic acid, citric, acetic, or lactic, as unsatisfactory, since it precipitates
mucin. For this reason he rejects the tungstate, mercuric iodide, and potassic
ferrocyanide tests. Dr Roberts regards the heat test, with the addition of a small
definite quantity of acetic acid, as the best test for the detection of small quan-
tities of albumin. ]

1. Quantitative Estimation of albumin.—100 c.c. of unne are boiled in a capsule,
some acetic acid being ultimately added, whereby the albumin is precipitated in
flakes. The precipitate is collected on a weighed, dried (110°), ash-free filter, and
repeatedly washed with hot water, then with alcohol, and dried in an air-bath at
110°. The weight of the filter is deducted, and finally the dried filter with the
albumin is burned in a weighed platinum capsule, and the weight of the ash also
deducted, [This method is not available for the busy practitioner on account of
the time it takes, Practically, it is sufficient to compare from day to day the
proportion that the precipitated albumin bears to the bulk of the urine tested. A
graduated tube may be used, so that after the precipitate has subsided, the physi-
cian ney. see what proportion of the whole the precipitate occupies. ]

Esbach’s Albumimeter (fig. 263).—A glass cylinder is filled with the urine up
to the mark U, and to R with the precipitant (20 citric acid, 10 picrie acid, 970
water). The vessel is corked and then shaken. After twenty-four hours the coagu-
lated albumin subsides, when the graduation on the tube indicates the number of
grms. of albumin per 1000 ¢c.c. of urine, Very albuminous urine must be pre-
ey diluted. |

2. Globulin occurs only in albuminous urine, and is frequently present. Its
_ Presence is ascertained by adding powdered magnesium sulphate in excess to the

urine; when it is bia it is precipitated (§ 32). The more globulin there is in
the presence of albumin, the more difficult it is to precipitate it. [Sometimes,
when an albuminous urine is dropped into a large cylinder of water, each drop as
it sinks is followed by a milky train, and when a sufficient number of dopa hs
been added, the water becomes opalescent, the opalescence disappearing on adding an acid. The.
hn is ope in solution by common salt and other neutral salts, but when these are largely
diluted, the globulin is precipitated (Roberts). ]

3. Peptone occurs in some specimens of albuminous urine, but also in non-albuminous urine.
Maixner found it constantly in the urine in all cases where suppuration is present, and even in
phthisis, constituting pyogenic peptonuria, Peptone occurs in pus, and the peptonuria in these
cases is a sign of the breaking up of the pus-cells (Hofmeister). Also when many leuc
are broken up in the blood (hematogenic), It occurs in cases where there is great disintegration _
of albuminous tissues, ¢.g., in cancer, It is frequently found after child-birth. Ammonium
sulphate precipitates all proteids except peptones (p. 249), 1

HZMATURIA AND HAMOGLOBINURIA. 411

Test.—Separate the albumin by boiling and the addition of ‘acetic acid. ‘Treat the filtrate
with three volumes of alcohol; this precipitates the peptone, which, when dissolved in water,
gives the characteristic reactions for peptone (§ 166, 1.).

4. Propeptone, or Hemialbumose, occurs very rarely, ¢.g., in osteomalacia and intestinal
tuberculosis (Bence Jones). The urine is treated to saturation with NaCl and a large quantity
of acetic acid added, and filtered while hot, to separate the albumin and globulin. In the cold
filtrate propeptone forms a turbidity, which is redissolved by heat. The precipitate thrown
down by HCl and HNO, is soluble by heat (Kine). The precipitate is isolated by filtration,
and dissolved in a little warm water, when it gives with HNO, a yellow reaction; like peptone
the solution gives the biuret-reaction (p. 248).

5. Egg-albumin appears in the urine when much egg-albumin is taken in the food, and also
when it is injected into the blood-vessels (§ 192, 4). According to Semmola, the albumin
present in the urine in Bright’s disease has undergone a molecular change (similar to egg-
albumin), and hence it is excreted.

6. Mucus is present in large amount, especially in catarrh of the bladder. It contains
numerous mucus corpuscles, which are scarcely distinguishable from pus corpuscles. They con-
tain albumin, so that urine containing much mucus is albuminous ; mucin is not precipitated
by heat, but acetic acid gives a flocculent precipitate in clear urine. [Minute traces of mucin
occur normally in urine. If clear normal urine be set aside for a short time, a flocculent hazi-
ness, like a cloud of cotton wool, is seen floating in the urine. This is mucus entangling a few
epithelial cells from the genito-urinary tract. ,Mucin Reaction.—According to W. Roberts,
the addition of a concentrated solution of citric acid to urine, as in Heller’s test (§ 264, a),
where the two fluids meet, causes an opalescent zone gradually to be formed above the layer of
acid. ]

265. BLOOD IN URINE (HHMATURIA)—-HHMOGLOBINURIA.—I. Source of the
Blood.-—(1) In hematuria, the blood may come from any part of the urinary apparatus. 1.
In hemorrhage from the kidney, the amount of blood is usually small and well mixed with the
urine. The presence of ‘‘ blood-cylinders,” long microscopic blood coagula, casts of the urini-
ferous tubules, washed out of them by the urine, is characteristic when they are found in the
urine (fig. 275). The urine usually has a smoky appearance. [The urine slowly dissolves out
the colouring matter, the stroma of the corpuscles after a time being deposited as a brownish
sediment. The smoky hue occurs only in acid urine; if the urine. becomes alkaline, the hue
becomes brighter red.] The blood-corpuscles show peculiar changes of form, [they become
crenated] (fig. 264), and exhibit evidence of division, due to the action of urea on them (§ 5).
Large coagula are never found in urine mixed with blood derived from the kidney. 2. In
hemorrhage from the ureter, we occasionally find worm-like masses of clotted blood, casts of
the canal of the ureter. 38. The relatively largest coagula occur in hemorrhage from the
bladder. In all cases where blood is present, we
ynust examine microscopically for the blood-cor-
puscles, and it may be for coagula of fibrin. In
acid urine, blood-corpuscles, but never arranged in
rouleaux, may be found after two to three days.
The blood-corpuscles settle as a red sediment at . sae
the bottom. Ifthe hemorrhage is copious many See ¥
retain their original shape, but if the urine is
very concentrated, they may become crenated.

When there is a small and slow hemorrhage
from ruptured small capillaries, the red blood-
corpuscles are of unequal size, many 4 to 4 the
size of normal, while the pigment has become
brownish-yellow (fig. 265).

If a hemorrhage of this kind be accompanied
catarrhal inflammation of the bladder, there is
found between the red, numerous shrivelled leuco-
cytes (fig. 265), which in freshly passed urine
often exhibit lively amceboid movements. If the urine be alkaline, as it usually is, crystals
of triple phosphate also occur. .

If the remains of the red blood-corpuscles become very pale, their presence may be frequently
ascertained by adding iodine in a solution of KI (fig. 265). Blood is constantly present in the
urine during menstruation.

II. Hemoglobinuria is quite distinct from hematuria. It depends upon the excretion of
hemoglobin as such through the kidneys, and it is produced when hemoglobin occurs free
within the blood-vessels, as in cases where the coloured blood-corpuscles have been dissolved
inside the blood-vessels (heemocytolysis). It occurs when foreign blood is transfused, ¢.g., when
lamb’s blood is transfused into man. The foreign blood-corpuscles are dissolved in the blood
of the recipient, and the hemoglobin appears in the urine ($102), In addition, microscopic

Fig. 265.

by Fig. .264.—Crenated red blood-corpuseles in
urine, x 350. Fig. 265.—Peculiar changes
of the red blood-corpuscles in renal hema-
turia.

412

TESTS FOR BLOOD IN URINE.

‘‘ cylinders,” or ‘‘ casts,” consisting of a globulin-like body tinged yellow with hemoglobin,
may likewise be found in the urine. It also occurs in cases of severe burns (§ 10, 8) ; after
ee of the blood in pyemia, scorbutus, purpura, severe typhus, after respiring arseni-

urette

hydrogen, and after the passage of azobenzol,

naphtol, pyrogallic acid, potassie chlo-

rate, chloral, phosphorus, or carbolic acid into the circulation. [The injection of laky blood,

water ether; glycerin (

Fig. 266.
Fig. 266.—Coloured an

in urine (catarrh of th

Adams), or toluylendiamin (A/fa7

Fig. 267.
d (a) colourless blood-corpuscles
of various forms. Fig. 267.—Shrivelled blood-corpuscles

e bladder), with numerous lymph-

corpuscles, and crystals of triple phosphate, x 350.

vassiew), also causes it, and in such
cases Afanassiew asserts that the Hb
passes out through the glomeruli,
while brown degeneration-products
of the red blood-corpuscles, which
are dissolved by these agents, were
found in the convoluted tubules. }
These substances dissolve the red
blood-corpuscles. Sometimes it oc-

%5 curs periodically from causes and

conditions as yet but little under-
stood, e.g., the application of cold
to the skin.

Tests for Blood in Urine.—1. The
colour of bloody urine shows every
tint, from a faint red to a dark
blackish-brown, according to the
amount of blood present. The urine
is often turbid.

2. Urine containing blood or blood-
pigment contains albumin.

3. Heller’s Blood Test.—Add to urine half its volume of solution of caustic potash, and heat
gently. The earthy phosphates are precipitated, and they carry the hematin with them, fall-
ing as garnet-red flocculi. [This is not a reliable test. ]

4, min Test.—The coloured earthy phos

hemin may be prepared

as directed in § 19.

phates may be collected on a filter, and from them

5. Almen’s Test.—Add to urine, freshly prepared tincture of guaiacum and ozonised ether ;
a blue colour indicates the presence of blood (§ 37).
6. Spectroscope (see § 14). Fig. 268 shows the arrangement of the apparatus. The urine

the observer through the telescope, A. (a) Fresh

Fig. 268.
Spectroscope for investigating the presence of hemoglobin in urine.

is placed in a glass vessel, D, with parallel sides, 1 centimetre apart (hematinometer). Light
from a lamp, E, passes through the fluid. The lamp, F, illuminates the scale which is seen by

urine containing blood gives the spectrum

_ BILE IN URINE, 413

of oxyhemoglobin (fig. 17). (b) When bloody urine is exposed for some time, especially in
a warm place, it becomes more acid, and assumes a dark brownish-black colour. The hemoglobin
becomes changed into methemoglobin (§ 15). It is precipitated by lead acetate, which does
not precipitate oxyhemoglobin; the spectrum of methemoglobin resembles that of hematin in
an acid solution: (§ 15, fig. 17). The spectra may be combined. (c) The microscopic investiga-
tion must never be omitted. The shape of the corpuscles may vary considerably (figs, 264 to
266).

266. BILE IN URINE (CHOLURIA).—The physiological conditions which cause the bile-
constituents to appear in the urine are mentioned in part at § 180.

Hematogenic, or Anhepatogenic Icterus (Quincke), occurs when bilirubin (§ 20) is formed
from extravasated blood by the action of the connective-tissue corpuscles, so that bile pigments,
in addition to colouring the tissues, pass into the urine.

I. Bile Pigments. —Their presence is ascertained by Gmelin-Heintz’s test. reen (Biliverdin)
is the characteristic hue in the play of colours obtained with this test, which is fully described
in § 177.

Modifications of the Test.—1. If icteric urine be filtered through filtering or blotting paper,
a drop of nitric acid containing nitrous acid, when applied to the inner surface of the spread-
out filter, gives a yellowish coloured ring (Rosenbach). 2. In order that the reaction may not
take place too rapidly, add a concentrated solution of sodic nitrate, and then slowly pour in
sulphuric acid (Fleisch). 3. On shaking 50 ¢.c. of icteric urine with 10 c.c. of chloroform,
the bilirubin is dissolved by the latter. On adding bromide water, a beautiful ring of colours
is obtained (Maly). If the chloroform extract be treated with ozonised turpentine and dilute
caustic potash, a green colour, due to biliverdin, occurs in the watery fluid (Gerhardt).

In slight degrees of jaundice, urobilin alone may be found (§ 261, 1) (Qwincke).

In persistent high fever, the urine contains especially biliprasin (Huppert). If it contains
choletelin alone, add to the urine some hydrochloric acid, and examine it with the spectroscope,
which gives a pale absorption-band between 0 and F (§ 177, 3, /).

Hematoidin.—Sometimes crystals of hamatoidin (§ 20, fig. 14) appear in the urine, especially
when blood-corpuscles are dissolved within the blood-stream ; occasionally in scarlet fever and
typhus, and sometimes in cases of periodic hemoglobinuria. The breaking up of old blood-
clots in the urinary passages, as in pyonephrosis (dstein), or the dissolution of necrotic areas
(Hofmann and Ultzmann) produces them, and similar crystals occur in analogous cases in the
sputum (§ 138). In jaundice due to congestion (§ 180), the identical crystalline substance,
bilirubin, is found.

II. Bile acids occur in largest amount in absorption jaundice, but they are never present to
any extent. The test is described at § 177, 2, the cane-sugar solution consisting of 0°5 grm. to
1 litre of water. If the urine be dilute, it is advisable to concentrate it on a water-bath. [It
is rare to get a satisfactory result with Pettenkoffer’s test in ordinary icteric urine:] V.
Pettenkofer’s test may be used with the alcoholic extract of the nearly dry residue, but no
albumin must be present. Dragendorff found 0°8 grm. in 100 litres of normal urine.

Strassburg’s Modification.—Dip filter paper into the urine, to which a little cane-sugar has
been added; dry the paper and apply to it a drop of sulphuric acid, A violet-red colour is
obtained after a short time. [Hay’s Reaction (§ 177).]

267. SUGAR IN URINE (GLYCOSURIA).—Diabetes Mellitus.—The excessively minute
trace of grape-sugar or dextrose, which is constantly present in normal urine, sometimes
becomes greatly increased and constitutes the conditions of diabetes mellitus and glycosuria.
The physiological conditions which determine this result are given at $175. In this condition,
the quantity of urine is greatly increased, it may reach 10 or more litres. Many pints may be
passed daily, [The usual abnormal amount of sugar is from 1 to 8 per cent., although 15 per
cent. has been found, 7.¢., found from 5 to 50 grs. per fluid oz., or 300 to 4000 grs. in twenty-—
four hours.] . The specific gravity is also increased (1030 to 1040). [In a case where a large
amount of urine is passed of a pale colour and a specific gravity above 1030, always suspect
sugar.] <A diabetic person gives off relatively more water by the kidneys and less by the skin
(and lungs ?) than a healthy person. The colour is very pale yellow, although the amount of
pigment is by no means diminished—it is only diluted [the depth of the colour being inversely
as the quantity passed]. The amount of the nitrogendus urinary excreta is increased. The
sugar is increased by a diet of carbohydrates and diminished by an albuminous diet. The uric
acid and oxalate of lime are often increased at the commencement of the disease, while yeast
cells are constantly present after the urine has been exposed to the air for some time.

Sugar has’ been found occasionally after poisoning with or after the use of morphia, CO,
chloral, chloroform, curara; after the injection of ether and amy] nitrite into the blood; and in
gout, intermittent fever, cholera, cerebro-spinal meningitis, hepatic cirrhosis, and cardiac and
pulmonary affections.

[There is no doubt that normal healthy human. urine contains a reducing agent, which reduces
cupric oxide to the same extent as if the urine on an average contained 6 grains of glucose in

414 SUGAR IN URINE.

every 10 fluid ounces of urine, or 1°34 grms. per litre. As this substance does not cause
alcoholic fermentation in its solutions, its identity with glucose appears to be doubtful. The
most active reducing agent is probably kreatinin (G@. S. Johnson).] ;

Tests.—Any of the tests described at § 149 may be used, but the urine must be free from
albumin. The quantitative estimation by fermentation and the titration methods are described
in § 149, [The tests for grape-sugar described in § 149 are (1) Trommer’s 3 (2) Fehling’s ; (3)
Moore & Heller’s ; (4) Buttger’s ; (5) Mulder & Neubauer’s ; (6) Fermentation test.] .

7. Worm-Miiller recommends the following modification of Fehling’s test. Use a 2°5 per
cent. solution of cupric sulphate solution, and another of 10 parts of sodio-potassic tartarate in
100 parts of 4 per cent. solution of soda. Boil 5 c.cm. of urine in a test-tube, while in a second
test-tube is boiled 1 to 3 c.cm. of the copper solution and 2°5 c.cm. of the potassio-tartarate
solution. The boiling of both fluids is stopped simultaneously, and after 20 to 25 seconds the
contents of one test-tube are added to those of the other, but without shaking the mixture, the
reduction taking place spontaneously.

8. Nylander’s modification of Bittger’s test is also good (§ 148).

[9. Picric Acid and Potash Test.—Braun showed that grape-sugar, when boiled with picric
acid and potash, reduces the yellow picric acid to the deep red picramic acid, the depth of the
colour depending on the amount of sugar present. Dr Johnson uses this test for detecting the
presence of sugar in urine, and also for estimating the amount of sugar present, the depth of the
red colour obtained in boiling being compared with a standard dilution of ferric acetate. In
doing the test, use 1 drachm of urine, 4 a drachm of liquor potasse, and 10 minims of picric
acid solution ; make up to 2 drachms with distilled water, and boil the mixture for one minute.
This test indicates the presence of 0°6 grain of sugar per fluid ounce of normal urine. Dr
Johnson claims for this test that it possesses all the advantages of the other tests, while it is
not affected by uric acid or any other normal ingredient of urine ; neither does the presence of
albumin interfere with the action of the test as it does with all the forms of copper testing. }

[10. Indigo-carmine Test.—A blue solution of this substance, when boiled with diabetic
urine containing sodic carbonate, changes from a blue to a violet, purple, red, yellow, and
finally, straw-yellow colour. After cooling and exposure to the air, the various colours are
obtained in the reverse order until the mixture becomes blue again. Dr Oliver uses this test in
the form of test-papers. One bibulous paper is impregnated with the indigo-carmine and the
other with sodic carbonate. Drop one of the test-papers and a sodic carbonate paper into a
test-tube containing 14 inches of water, heat gently, when a blue solution is obtained. Add
the urine slowly, one drop at a time, and boil the mixture, observing any change of colour by.
holding the tube against a white surface below the level of the eye. Uric acid and urates, which
reduce Fehling’s solution, do not affect the carmine test, nor does kreatinin, although it reacts
with the picric acid test. }

[Quantitative Estimation. —-(~) Fermentation Test ($150). Take 4 oz. (120c.c.) of the urine ;
add a lump of German yeast, about the size of a walnut, lightly cork the bottle, and piace it
aside for twenty-four hours in a moderately warm place, ¢.g., on the mantelpiece. Take the
specific gravity before and after the fermentation. Thus, if the specific gravity be 1038 before
and 1013 afterwards, the difference or “ density lost” is 25, which gives 25 grs. of sugar per
fluid oz. (Roberts). If it be desired to get the percentage, multiply the density lost by 0°23,
thus 25 x 0°23 = 5°69 in 100 parts. ]

[(b) Volumetric Analysis. —10 c.c. of Fehling’s solution = ‘05 gramme of sugar.

1. Ascertain the quantity of urine passed in twenty-four hours. 2. Filter the urine, and
remove any albumin present by boiling and filtration. 8. Dilute 10 ¢.c. of Fehling’s solution
with about twenty times its volume of distilled water, and place it in a white porcelain capsule
on a wire gauze support under a burette. (It is diluted because any change of colour is more
easily observed.) 4. Take 5 c.c. of the urine, and 95 c.c. of distilled water, and place the diluted
urine in a burette. 5. Gradually boil the diluted Fehling’s solution, and whilst it is boiling
gradually add the diluted urine from the burette, until all the cuprous oxide is precipitated as
a reddish powder, and the supernatent fluid has a straw-yellow colour, not a trace of blue re-
maining. Read off the number of ¢.c. of dilute urine employed. Say 36 ¢.c. were used—that,
of course, represents 1°8 c.c. of the original urine. Suppose the patient passes 1550 c.c.,
as 1°8 c.c. of urine reduced all the cupric oxide in the 10 ¢.c. of Tehling's solution, it must
contain ‘05 gramme sugar, hence,

1550 x °
1°8:1550:: 05: ae = 237°5 grammes of sugar passed in 24 hours. ]

[Preparation of Fehling’s Solution.—34°64 grammes of pure crystalline cupric sulphate are
powdered and dissolved in 200 c.c. of distilled water ; in another vessel dissolve 173 grammes
of Rochelle salts in 480 ¢.c. of pure caustic soda, specific gravity 1:14. Mix the two solutions,
and dilute the deep coloured fluid which results to 1 litre. N.B.—Fehling’s ought not to be
kept too long ; it is apt to decompose, and should therefore be preserved from the light, or pro-—
tected with opaque paper pasted on the bottle. Some other substances in urine, ¢.g., urates
and uric acid, reduce cupric oxide. ] Lee aw 3 iit oF thing

Fea

MILK-SUGAR, AND OTHER SUBSTANCES IN URINE, 415

(c) According to Worm-Miiller, the polarization method is almost valueless for diabetic
urine.

[Picro-Saccharimeter.—G. Johnson uses a stoppered bottle 12 inches long and inch wide,
graduated in 7,ths and ;4,ths (fig. 269). To it is fixed a shorter bottle containing the
standard iron-solution for comparison, a standard solution, composed of liquor ferri per-
chloride 3j, liq. ammon. acetatis Jiv, glacial acetic acid Jiv, liq. ammoniz 3i, and water to
make up Ziv. All B. P. preparations give a colour identical with a solution containing 1 gr.
of grape-sugar per oz., reduced by picric acid and afterwards diluted four times, so that this
tint =4 gr. of sugar per oz. After reducing the sugar with the picric acid, pour into the tall
tube the dark saccharine liquid produced by boiling to occupy ten divisions of the tube, and add
distilled water cautiously until the colour approaches that of the standard; read off the level of
the fluid. The amount of sugar present is determined from the amount of water added. In
making the test, the picric acid must be added in proportion to the amount of sugar present. ]

If large quantities of dextrose are taken in the food, a part of it (and more in diabetic persons)
appears in the urine. Lzvulose, when taken internally, does not increase the amount of sugar
in diabetes. The free use of starch does not cause glycosuria in health, but in diabetes it in-
creases the amount of sugar.. A large consumption of cane- or milk-sugar causes the passage
of small quantities of both of these sugars into the urine in health, while in diabetes the amount
of dextrose is increased (Worm-Miiller), According to Kiilz, in diabetic
persons cane-sugar splits up into grape- and fruit-sugar, the latter being
used up in the body, the former partly excreted ; and the same is the case
with milk-sugar.

In severe cases of diabetes mellitus, Kiilz found the left-rotatory B-oxy-
butyric acid (the next highest analogue of lactic acid) in the urine, from
which acetic acid is formed by oxidation (§ 175), which in its turn readily
yields CO, and aceton. a-crotonic acid is formed in urine by the removal
of water from oxybutyric acid in the urine in diabetes (Stadelmanin). The
administration of aceton causes albuminuria, and this may in part explain
in some cases the complication of albuminuria in diabetes (Albertont and
Pisenti).

Aceton, or Aceton-yielding substance, probably aceto-acetic acid, is some-
times found in diabetic urine. It has a peculiar vinous odour, and it has
been detected in the urine during fever. Gerhardt described a peculiar
substance in diabetic urine, which gave a deep red colour with perchloride
of iron. This substance is probably diacetic ether, and he considered it to
be the source of aceton; but it is more probably derived from aceto-acetic
acid. Tests for Aceton.—(1) Perchloride of iron=Burgundy-red colour ;
but this is not reliable. (2) Lieben suggested an iodoform test. Dissolve
20 grains of KI in a fluid drachm of liq. potassxe, and boil the fluid. Pour
the suspected urine on the sur-
face, when a ring of phosphates
is deposited from the urine by
the hot alkaline solution. If
aceton be present, after a time
the deposit becomes yellow, and
yellow granules of iodoform ap-
pear and sink to the bottom of
the test-tube. The only other ’,
substance which may be met
~. with in the urine giving this re-
Sx \ action is lactic acid.

Milk-sugar is sometimes found
Fie, 2 in the urine of women who are
g. 269. ‘ .

; : nursing ; when the secretion of
Picro-saccharimeter mj)k is arrested, absorption tak-

of G. Johnson. ing place from the breasts (Kir-
sten, Spiegelberg). Leevulose is sometimes found in
diabetic urine (§ 252).

Dextrin has also been found in diabetic urine. : Fig. 270.
Inosit, or muscle-sugar (§ 252), is sometimes found [nosit crystallised partly from alcohol and
in diabetes, in polyuria, and albuminuria. It is . partly from water (after Funke).

found in traces, evenin normal urine. Occasionally,

after the piqtire in animals (§ 175), inosit, instead of grape-sugar, appears in the urine (fig. 270).
In testing for inosit, remove the grape-sugar by fermentation, and the albumin by heat after the
addition of a few drops of acetic acid and sodice sulphate. Some of the filtrate is evaporated
nearly to dryness on a capsule, To the residue add two drops of mercuric nitrate (Licbig’s
titration fluid for urea), which gives a yellow precipitate. When this coloured residue is spread

416 CYSTIN, LEUCIN, AND TYROSIN.

out and carefully heated, a dark red colour, which disappears on cooling, is obtained (Galois,
Kiilz), [Inosit gives a green when boiled with Fehling’s solution. ]

268. CYSTIN.—This left-rotatory body CgH,.N.S,0,, occurs very seldom in large amount
in urine, although it seems to be a constituent of normal urine. It may be in solution or in
the form of hexagonal crystals (fig. 271, A). It is insoluble in water, alcohol, and ether, but
easily soluble in ammonia, from which solution it may be crystallised. According to Baumann
and Preusse, there are intermediate products of the metabolism, from which are furnished the
materials necessary for the formation of cystin. During normal metabolism these materials
undergo further changes, and the sulphur appears oxidised in the urine as sulphuric acid. In
rare cases these oxidations do not take place, and then the sulphur appears in the cystin of the
urine (Stadthagen).

269, LEUCIN=C,H,,NO,. TYROSIN=C,H,,NO,.—Both bodies occur in the urine in acute
yellow atrophy of the liver, and in poisoning by phosphorus. (Their formation during
pancreatic digestion has been referred to in § 170, II.) As the urea excreted is usually
diminished at the same time, it is assumed that, in these diseases, the further oxidation of the

Fig. 271. Fig. 272.
A, crystals of cystin ; B, oxalate of lime ; a, a, leucin balls; b, b, tyrosin sheaves ;
' ¢, hour-glass forms of B, c, double balls of ammonium urate.

derivatives of the proteids is interfered with. Leucin, which is either precipitated spontane-
ously or obtained after evaporating an alcoholic extract of the concentrated urine, occurs in
the form of yellowish-brown balls (fig. 272, a, a), often with concentric markings, or with fine
spines on their surface. When heated, it sublimes without fusing.

Tyrosin forms silky colourless sheaves of needles (fig. 272, b, b). When boiled with mercuric
nitrate and nitric acid it gives a red colour, and afterwards a brownish-red precipitate. Piria’s
Test.—When slightly heated with a few drops of concentrated sulphuric acid, it dissolves with
a temporary deep red colour. On diluting with water, adding barium carbonate. until it is
neutralised, boiling, filtering, and adding dilute ferric chloride, a violet colour is obtained
(Piria, Stédeler),

270. DEPOSITS IN URINE.—Deposits may occur in normal and in patho-
logical urine, and they may be either “ organised” or “‘ unorganised.”’

I, Organised Deposits,

A. Blood : red and white blood-corpuscles and sometimes fibrin (figs. 264-266).

B, Pus, in greater or less amount in catarrh or inflammation of the urinary passages. Pus
cells exactly resemble colourless blood-corpuscles (figs. 9, 267). Donné’s Test.—Pour off the
supernatant fluid and add a piece of caustic potash to the deposit; if it be pus it becomes
gelatinous, ropy, and more viscid (alkali-albuminate). Mucus, when so acted. on, becomes
more fluid and mixed with floceuli,

, C. +: Sines of various forms occurs, but it is not always possible to say whence it is
erived, Te

TUBE CASTS IN URINE. 417

D, Spermatozoa may be present. a

E. Lower organisms occur in the urinary passages very seldom, but they may be present,
é.g., in the bladder, when germs are introduced from without by means of a dirty catheter.
[Before introducing a catheter into the bladder one ought always to make sure that the instru-
ment is perfectly aseptic.] Micrococci are found in the urine in certain diseases, ¢.g.,
diphtheria. The following forms are distinguished :—

1. Schizomycetes (§ 184). Normal human urine contains neither schizomycetes nor their
spores. In pathological conditions, however, fungi may pass from the blood into the urinary
tubules and thus reach the urine (Zewbe). During
the alkaline fermentation of urine, micrococci,
rod-shaped bacteria or bacilli (fig. 273) appear.
Sarcine belong to the group (§ 186). Rae

2. Saccharomycetes (fermentation fungi): (a) ?-~.,
The fungus of the acid urine fermentation (S.
urine) consists of small bladder-like cells arranged °
either in chains or in groups (figs. 260, a; 273, f). ~ %
(b) Yeast (S. fermentum) occurs in diabetic urine, =
as oval cells with a dotted eccentrically-placed
nucleus (fig. 237). "Bie, 973

3. Phytomycetes (moulds) occur in putrid urine bees : mas
(fig. 278, ¢). They are without clinical signifi- Fungi in urine. ¢, mould; f, yeast; d, g,
cance. micrococci and bacilli ; a, 0, ¢, uric acid.

F. Tube Casts.—The occurrence of tube casts, é.¢., casts of the uriniferons tubules (Henle,
1837), is of great importance in the diagnosis of renal diseases. If these structures are relatively
thick and straight, they probably come from the collecting tubules, but if they are smaller and
twisted, they probably come from the convoluted tubules. There are various forms of tube
casts :—1. Epithelial casts, consisting of the actual cells of the uriniferous tubules.
we They indicate that there is no very great change going on, but only that, as in
-@}4 catarrhal inflammation of any mucous membrane, the epithelium is in process of

desquamation. 2, Hyaline casts (fig. 280) are quite clear and homogeneous, usu-
ally long and small; sometimes they are ‘‘finely granular,” from the
presence of fat or other particles. They are best seen after the addition

of a solution of iodine. They are probably formed from albumin, which

Fig. 278.

Fig. 275.
Fig. 274.—Epithelial casts. Fig. 275.—Blood cast. Fig. 276.— Leucocyte cast. Fig. 277.—
Acid sodic urate in cylinders. Fig. 278.—Finely granular cast. _

passes into the uriniferous tubules. They are dissolved in alkaline urine, while acid urine
favours their formation, They usually occur in the late stages of renal disease, after the
tubular epithelium has been shed. 3. Coarsely granular casts (fig. 279) are brownish-
yellow, opaque, and granular, usually broader than 2. There are various forms. Not unfre-
quently there are fatty granules, and, it may be, epithelial cells in them. 4. Amyloid casts
occur in amyloid degeneration of the kidneys (fig. 280). They are refractive and completely
homogeneous, and give a blue colour (amyloid reaction) with sulphuric acid and iodine. 5. Blood
casts occur in capillary hemorrhage of the kidney, and consist of coagulated blood entangling
blood-corpuscles (fig. 275). When tube casts are present, the urine is always albuminous.

Leucocyte casts occur in suppurating conditions of the urinary tubules (fig, 280). The urates
in the form of casts (fig. 277) are without significance.

II, Unorganised Deposits,

' Some of these are crystalline and others are amorphous, and they have been referred to in
treating of the urinary constituents.
2D

418 DETECTION OF URINARY DEPOSITS.

2.71. SCHEME FOR DETECTING URINARY DEPOSITS.—I. In acid urine there may
occur—
1. An amorphous granular deposit:
(a) Which is dissolved by heat and reappears in the cold; the deposit is often reddish in
- colour =urates (fig. 260).

(b) Which is not dissolved by heat, but is dissolved by acetic acid, but without efferves-
cence = probably tribasic calcic phosphate.

(c) Small bright refractive granules, soluble in ether = fat or oil granules (§ 41), (Lipsmia),
Fat occurs in the urine, especially when the round worm, Filaria sanguinis hominis,
is present in the blood ; sometimes, along with sugar, in phthisis, poisoning with
phosphorus, yellow fever, pyemia, after long-continued suppuration, and lastly, after
the injection of fat or milk into the blood (§ 102). It occurs also in fatty degenera-
tion of the urinary apparatus, admixture with pus from old abscesses, and after severe
injuries to bones. In these cases attention ought to be directed to the presence of
cholesterin and lecithin. Very rarely is the fat present in such amount in the urine
as to form a cream on the surface (chyluria).

Fig. 280. Fig. 282. Fig. 283.

Fig. 279.—Coarsely granular casts. Fig. 280.—Hyaline casts, a; 6, with leucocytes ; c, with
renal epithelium. Fig 281.—a, Granules of calcic carbonate of lime; 8, ¢, i baa neutral

calcic phosphate. Fig. 282.—Ammonio-magnesic phosphate. Fig, 283.—Imperfect forms

of the same.

2. A crystalline deposit may be— |
(a) Urie acid (fig. 256).
(5) Calcium oxalate (fig. 258)—octahedra insoluble in acetic acid.
(c) Cystin (fig. 271).
(d) Leucin and tyrosin—very rare (tig. 272).
II. In alkaline urine there may occur—
1. A completely amorphous granular deposit, soluble in acids without effervescence=
tribasic calcic phosphate, atF

URINARY CALCULI. . 419

2. Sediment crystalline, or with a characteristic form.
(a) Triple phosphate (figs. 282, .283), soluble at once in acids.
(6): Acid ammonium urate—dark yellowish small balls often beset with spines, also
amorphous (fig. 284).
(c) Calcium carbonate—small whitish balls or biscuit-shaped bodies. Acids dissolve
them with effervescence (fig. 281).
(dZ) Leucin and tyrosin (fig. 272)—-very rare.
(¢) Neutral calcic phosphate and long plates of tribasic magnesic phosphate (fig. 285).
Organised deposits may occur both in alkaline and in acid urine; pus-cells are more abundant
in alkaline urine, and so are the lower vegetable organisms.

2'72. URINARY CALCULI.—tUrinary concretions may occur in granules the size of sand,
or in masses as large as the fist. According to their size they are spoken. of as sand, gravel,
stone, or calculi. They occur in the pelvis of the kidney, ureters,
bladder, and sinus prostaticus.
We may classify them as follows (Ultzmann) :—
1. Calculi, whose nucleus consists of the sedimentary deposits
that occur in acid urine (primary formation of calculi). They are
all formed in the kidney, and pass into the bladder, where they
- enlarge by the deposition of mat-

ter on their surface. &()

2. Caleuli, which are either \
sedimentary forms from alkaline gf )
urine, or whose nucleus consists |
of a foreign body (secondary for-
mation of calculi). They are i
. formed in the bladder. | NS)
an The primary formation of cal- :

., Fig. 284. culi begins with free uric acid in oe h

Acid ammonium urate. the form of sheaves (fiz. 256) Basic magnesic phosphate.
which form a nucleus, with concentric layers of oxalate of lime. The secondary formation
occurs in neutral urine by the deposition of calcic carbonate and crystalline calcic phosphate ;
in alkaline urine, by the deposition of acid ammonium urate, triple phosphate, and amorphous
ealcic phosphate.

Chemical Investigation.—Scrape the calculus, burn the scrapings on platinum foil to ascer-
tain if they are burned or not.

I. Combustible concretions can consist only of organic substances.

(a) Apply the murexide test (§ 259, 2), and, if it succeeds, uric acid is present. Uric acid
ealculi are very common, often of considerable size, smooth, fairly hard, and yellow to reddish-
brown in colour.

(6) If another portion, on being boiled with caustic potash, gives the odour of ammonia (or
when the vapour makes damp turmeric paper brown, or if a glass rod dipped in HCl and held
over it gives white fumes of ammonium chloride), the concretion contains ammonium urate.
If 6 gives no result, pure uric acid is present. Calculi of ammonium urate are rare, usually
small, of an earthy consistence, 7.¢., soft and pale yellow or whitish in colour.

(c) If the xanthin reaction succeeds (§ 260), this substance is present (rare). Indigo has been
found on one occasion in a calculus (Ord).

(d) If, after solution in ammonia, hexagonal plates (fig. 271, A) are found, cystin is present.
(e) Concretions of coagulated blood or fibrin, without any crystals, are rare. When burned
. they give the odour of singed hair. They are insoluble in water, alcohol, and ether; but are
soluble in caustic potash, and are precipitated therefrom by acids.

(f) Urostealith is applied to a caoutchouc-like soft elastic substance, and is very rare. When
dry it is brittle and hard, brown or black. When warm it softens, and if more heat be applied
it melts. It is soluble in ether, and the residue after evaporation becomes violet on being
heated. It is soluble in warm caustic potash, with the formation of a soap.

II, If the concretions are only partly combustible, thus leaving a residue, they contain
organic and inorganic constituents. y :

(a) Pulverise a part of the stone, boil it in water, and filter while hot. The urates are dis-
solved. To test if the uric acid is united with soda, potash, lime, or magnesia, the filtrate is
evaporated and burned. The ash is investigated with the spectroscope (§ 14), when the char-
acteristic bands of sodium or potash are observed. Magnesic urate and calcic urate are changed
into carbonate by burning. To separate them, dissolve the ash in dilute hydrochloric acid, and
filter. The filtrate is neutralised with ammonia, and again redissolved by a few drops of acetic
acid. The addition of ammonium oxalate precipitates calcic oxalate. Filter, and add to the
abe edie phosphate and ammonia, when the magnesia is precipitated as ammonio-magnesic
phosphate. _

(b) Calcic oxalate (especially in children, either as small smooth pale stones, or in: dark,

us.
* Gat

420 THE SECRETION OF URINE.

warty, hard “mulberry calculi”) is not affected by acetic acid, is dissolved by mineral acids
without effervescence, and again precipitated by ammonia. Heated on platinum foil it chars
and blackens, then it becomes white, owing to the formation of calcic carbonate, which

effervesces on the addition of an acid. ;
(c) Calcic carbonate (chiefly in whitish-grey, earthy, chalk-like calculi, somewhat rare)
dissolves with effervescence in hydrochloric acid. When burned it first becomes black, owing

to admixture with mucus, and then white.

(d@) Ammonio-magnesic phosphate and basic calcic phosphate usually occur together in soft,
white, earthy stones, which occasionally are very large. These stones show that the urine has
been ammoniacal for a very long time. The first substance when heated gives the odour of
ammonia, which is more distinct when heated with caustic potash; is soluble in acetic acid
without effervescence, and is again precipitated in a crystalline form from this solution on the
addition of ammonia. When heated it fuses into a white enamel-like mass ; [hence, it is called
‘fusible calculus’’]. Basic calcic phosphate does not effervesce with acids. The solution in
hydrochloric acid is precipitated by ammonia. When ammonium oxalate is added to the acetic
acid solution, it yields calcic oxalate.

(e) Neutral calcic phosphate is rare in calculi, while it is frequent in the form of gravel.
Physically and chemically, these concretions resemble the earthy phosphates, only they do not
contain magnesia.

2:73. THE SECRETION OF URINE.—|The functions of the kidney are—

1. To excrete waste products, chiefly nitrogenous bodies and salts ;

2. To excrete water ;

3. And perhaps also to reabsorb water from the uriniferous tubules, after it has
washed out the waste products from the renal epithelium.

The chief parts of the organs concerned in 1, are the epithelial cells of the con-
voluted tubules ; the glomeruli permit water and some solids to pass through them,
while the constrictions of the tubules may prevent the too rapid outflow of water,
and thus enable part of it to be reabsorbed. | :

Theories.—The two chief older theories regarding the secretion of urine are the
following :—1. According to Bowman (1842), through the glomeruli are filtered
only the water and some of the highly diffusible and soluble salts present in the
blood, while the specific urinary constituents are secreted by the activity of the
epithelium of the urinary tubules, and are extracted or removed from the epithelium
by the water flowing along the tubules. This has been called the “ vital” theory.
2. C. Ludwig (1844) assumes that very dilute urine is secreted or filtered through the
glomerulus. As it passes along the urinary tubules it becomes more concentrated,
owing to endosmosis. It gives back some of its water to the blood and lymph of
the kidney, thus becoming more concentrated, and assuming its normal character.
[This is commonly known as the “ mechanical ” theory. |

The secretion of urine in the kidneys does not depend upon definite physical
forces only. A great number of facts force us to conclude that the vital activity
of certain secretory cells plays a foremost part in the process of secretion (R.
Heidenhain).

The secretion of urine embraces—(1) The water, and (2) the urinary constitu-
ents therein dissolved ; both together form the urinary secretion. The amount of
urine depends chiefly upon the amount of water which is filtered through or
secreted by the glomeruli ; the amount of solids dissolved in the urine determines
its concentration.

(A) The amount of urine, which is secreted chiefly within the Malpighian

capsules, depends primarily upon the blood-pressure in the area of the renal artery, .

and follows, therefore, the laws of filtration (§ 191, II.) (Ludwig and Goll). [In
this respect the secretion of urine differs markedly from that of saliva, gastric juice,
or bile. We may state it more accurately thus, that the amount of urine depends
very closely upon the differences of pressure between the blood in the glomeruli
and the pressure within the renal tubules. If the ureter be ligatured, the secretion
of urine is ultimately arrested, even although the blood-pressure be high. The

secretion may also be arrested by ligature of the renal vein; and in some cases of “i

GLOMERULAR EPITHELIUM. 421

cardiac or pulmonary disease the venous congestion thereby produced may bring
about the same result. |

Glomerular Epithelium.—The amount of urine secreted does not depend upon
the hydrostatic pressure alone, but it seems that the epithelial cells covering the
glomerulus also participate actively in the process of secretion. Besides the water,
a certain amount of the salts present in the urine is excreted through the glomeruli.
The serum-albumin of the bood, however, is prevented from passing through. With
regard to the secretory activity of these cells, the quantity of water must also
depend upon the amount of the urinary constituents and water present in the blood

(RR. Heidenhain).

Only when the vitality of the secretory cells is intact, is there independent activity of these
secretory cells (Heidenhain). When the renal artery is closed temporarily, their activity is
paralysed, so that the kidneys cease to secrete, and even after the compression is removed and
the circulation re-established, secretion does not take place for some time (Overbeck).

That the secretion depends in part upon the blood-pressure is proved by the
following considerations :—

1. Increase of the total contents of the vascular system, so as to increase the blood-
pressure, increases the amount of water which filters through the glomeruli. The
injection of water into the blood-vessels, or drinking copious draughts of water,
acts partly inthis way. If the blood-pressure rises above a certain height, albumin
may pass into the urine. The active participation of the cells of the glomeruli is
rendered probable by the fact that, after very copious drinking, the blood-pressure
is not always raised (Pawlow) ; further, after copious transfusion, the quantity of
urine is not increased. Conversely, the loss of water owing to profuse sweating or
diarrhoea, copious hemorrhage, or prolonged thirst, diminishes the secretion of
urine.

2. Diminution of the capacity of the vascular system, provided the pressure
within the renal area be thereby increased, acts in a similar manner. This may be
produced by contraction of the cutaneous vessels, owing to the action of cold,
stimulation of the vaso-motor centre, or large vaso-motor nerves, ligature, or
compression of large arteries (§ 85, e), or enveloping the extremities in tight
bandages. All these conditions cause an increase in the amount of urine, and of
course the opposite conditions bring about a diminution of urine, e.g., the action
of heat on the skin causing redness and dilatation of the cutaneous vessels,
weakening of the vaso-motor centre, or paralysis of a large number of vaso-motor
nerves.

3. Increased action of the heart, whereby the tension and rapidity of the blood in
the arteries are increased (§ 85, c), augments the amount of urine; conversely, —
feeble action of the heart (paralysis of motor cardiac nerves, disease of the cardiac
musculature, certain valvular lesions) diminishes the amount. Artificial stimulation
of the vagi in animals, so as to slow the action of the heart, and thus diminish the
mean blood-pressure from 130 to 100 mm. Hg, causes a diminution in the amount
of urine to the extent of one-fifth (Goll, Cl. Bernard); when the pressure in the
aorta falls to 40 mm. the secretion of urine ceases. [If the medulla oblongata be
divided (dog), there is an immediate fall of the general blood-pressure, and although,
as a general rule, the secretion of urine is arrested when the pressure falls to 40 to
50 mm. Hg, yet secretion has been observed to take place with a lower pressure
than this. |

4. The amount of urine secreted rises or falls according to the degree of fulness of
the renal artery (Ludwig, Max Hermann) ; even when this artery is moderately
constricted in animals, there is a decided diminution in the amount of urine.

Pathological. —In fever the renal vessels are less full and there is consecutive diminution of

urine (Mendelson). It is most important, in connection with certain renal diseases, to note
that ligature of the renal artery, even when it is obliterated for only two hours, causes necrosis

422 . ACTION OF DIURETICS.

of the epithelium of the uriniferous tubules, When the arterial anemia is kept up: for a long
time, the whole renal tissue dies (Litten). After long-continued ligation of the renal artery,
the epithelium of the glomeruli becomes greatly changed (Ribbert).

5. Most diuretics act in one or other of the above mentioned ways,

[Some diuretics act by increasing the general blood-pressure (digitalis and the action of cold
on the skin), others may increase the blood-pressure docally within the kidney, and this they
may do in several ways. The nitrites are said to paralyse the muscular fibres in the vasa
afferentia, and thus raise the blood-pressure within the glomeruli. But some also act on the
secretory epithelium, such as urea and caffein. Brunton recommends the combination of !
diuretics in appropriate cases, and the diuretics must be chosen according to the end in view— 7
as we wish to remove excess of fluids from the tissues and serous cavities, or as we wish to re-
move injurious waste products, or merely to dilute the urine. ]

[6. The amount of urine also depends upon the composition of the blood. Drink-
ing a large quantity of water, whereby the blood becomes more watery, increases
the amount of urine, but this is true only within certain limits. It is not merely
the increase of volume of the blood acting mechanically which causes this increase,
as we know that large quantities of fluid may be transfused without the general
blood-pressure being materially raised thereby. |

[Heidenhain argues, that it is not so much the pressure of the blood in the
glomeruli as its velocity, which determines the process of the secretion of water in
the kidney. He contends that, while increase of the pressure in the renal artery
causes an increased flow of urine, ligature of the renal vein, whereby the pressure
in the glomeruli is also increased, arrests the secretion altogether. In both cases
the pressure is increased within the glomeruli, and the two cases differ essentially
in the velocity of the blood-current through the glomeruli. |

Pressure in the Vas Afferens.—The pressure in each vas aferens must be
relatively great, because (1) the double set of capillaries in the kidney offers con-
siderable resistance, and (2) the lumen of the vas efferens is narrower than that of
the vas afferens. Hence, owing to the high blood-pressure in the capillaries of the
renal glomeruli, filtration must take place from the blood into the Malpighian
capsules. When the vasa afferentia are dilated, the filtration-pressure is increased,
while, when they are contracted, the secretion is lessened. When the pressure,
becomes so diminished as to retard greatly the blood-stream in the renal vein, the
secretion of urine begins to be arrested. Occlusion of the renal vein completely,
suppresses the secretion (//. Meyer, v. Frerichs). Ludwig concluded from this
observation, that the filtration or excretion of fluid could not take place through the
renal capillaries proper, as, owing to occlusion of the renal vein, the blood-pressure,
in these capillaries must rise, which ought to lead to increased filtration. Such an
experiment points to the conclusion that the filtration must take place through the
capillaries of the glomeruli. The venous stasis distends the vas efferens, which
springs from the centre of the glomerulus, and compresses the capillary loops against
the wall of the Malpighian capsule, so that filtration cannot take place through.
them. It is not decided whether any fluid is given off through the convoluted
urinary tubules. |

Venous congestion in the kidneys diminishes the quantity of urine and the urea. The NaCl
remains constant, but pathological albumin is increased (Senator and Munk).

Pressure in Ureter.—As the blood-pressure in the renal artery is about 120 to 140 mm. Hg,
and the urine in the ureter is moved along by a very slight propelling force, so that a counter-
he of from 10 (Lébell) to 40 mm. of Hg is sufficient to arrest its flow, it is clear that the

lood-pressure can also act as a vis a tergo to propel the urine through the ureter. The
reall in the ureter is measured by dividing the ureter transversely and inserting a manometer
In 16.

(B) Secretory Activity of the Renal Epithelium.—The degree of concentra-
tion of the urine depends upon the quantity of the dissolved constituents which
has passed from the blood into the urine. The secretory cells of the convoluted
tubules, by their own proper vital activity, seem to be able to take up, or secrete,

NUSSBAUM’S EXPERIMENTS. 423

some at least of these substances from the blood (Bowman, Heidenhain). The
watery part of the urine, containing only easily diffusible salts, as it flows along the
tubules from the glomeruli, extracts or washes out these substances from the
secretory epithelium of the convoluted tubules.

Experiments.—1. Sulphindigotate of soda and sodium urate, when injected into
the blood, pass into the urine, and are found within the protoplasm of the ced/s of
the convoluted tubules [only in those parts lined by “‘rodded” epithelium], but not
in the Malpighian capsules (Hezdenhain). A little later these substances are found
in the /umen of the urinary tubules, from which they are washed out by the watery
part of the urine coming from the glomeruli. If, however, two days before the
injection of these substances into the blood, the cortical part of the kidney contain-
ing the Malpighian capsules be cauterised, [¢.g., by nitrate of silver], or sliced off,
the blue pigment remains within the convoluted tubules. It cannot be carried on-
ward, as the water which should carry it along has ceased to be secreted, owing to
the destruction of the glomeruli. This experiment also goes to show that, through
the glomeruli the watery part of the urine is chiefly excreted, while through the con-
voluted tubules the specific urinary constituents are excreted. Uric acid salts, injected
into the blood, were observed by Heidenhain to be excreted by the convoluted
tubules. Von Wittich had previously observed that in dards, crystals of uric acid
were excreted by the epithelium of the convoluted tubules. [The presence of
crystals of uric acid in the renal epithelium was observed by Bowman, and used as an
argument to support his theory.] Nussbaum, in 1878, stated that wre is secreted
by the urinary tubules and not by the glomeruli.

The same is true for the bile-pigments, for the tron salts of the vegetable acids when injected

subcutaneously, and for hemoglobin. After injection of midk into the blood-vessels, numerous
fatty granules occur within the epithelium of the urinary tubules (§ 102).

[Nussbaum’s Experiments.—In the frog and newt, the kidney is supplied with
blood in a manner different from that obtaining in mammals. The glomeruli are
supplied by branches of the renal artery. The tubules are supplied by the renal-
portal vein. The vein coming from the posterior extremities divides at the upper
end of the thigh into two branches, one of which enters the kidney, and breaks up
to form a capillary plexus which surrounds the uriniferous tubules, but this plexus
is also joined by. the efferent vessels of the glomeruli. These two systems are
partly independent of each other. After ligaturing the renal artery, Nussbaum
asserted that the circulation in the glomeruli was cut off, while ligature of the renal-
portal vein excluded the functional activity of the tubules. By injecting a sub-
stance into the blood, after ligaturing either the artery or renal-portal vein, and
observing whether it occurs in the urine, he infers that it is given off either by the
glomeruli or the tubules. Sugar, peptones, and egg-albumin rapidly pass through
an intact kidney, but if the renal artery be tied they are not excreted. Uvea
when injected into the circulation is excreted after the artery is tied, so that it is
excreted through the tubules, but at the same time it takes with it a considerable
quantity of water. Thus, water is excreted in two ways from the kidney, by the
glomeruli and also from the venous plexus around the tubules along with the urea.

-Indigo-carmine merely passes into the tubular epithelium of the convoluted tubules,
but it does not cause a secretion of urine. Albumin passes through the glomeruli,
but only after their membranes have been altered in some way, as by clamping the
renal artery for a time. ]

{[Adami’s Experiments on the kidney of the frog tend to show that Nussbaum’s conclusions
are not justified, for Adami found that if the renal arteries in the frog be ligatured, within a
few hours a collateral circulation is established, and a certain amount of blood flows through
the kidney. He proved this by injecting into the blood, carmine or painter’s vermilion, in a
state of fine suspension, and after ligature of the renal arteries, he found it in many of the

glomeruli, while laky blood similarly injected revealed its presence as menisci of Hb in the
Malpighian corpuscles. Even secretion of some urine may go on after ligature of the renal

424 EXCRETION OF PIGMENTS.

arteries. It is evident, then, that Nussbaum’s method is not a reliable one for locating the
parts of the kidney throu h which certain substances are excreted. 5 Adami’s experiments also
give some support to Heidenhain’s view, that the glomerular epithelium ‘‘ possesses powers of a
selective secretory nature,” for he finds that in frogs, after ligature of the renal arteries, where,
of course, the pressure in the glomeruli is just nearly that in the veins, and in the dog after
section of the spinal cord, so that the blood-pressure has fallen below 40 mm. Hg, whereby the
secretion of urine is arrested, the injection of laky blood causes Hb to appear in the capsules,
although there is no simultaneous excretion of water.] - ; af
Excretion of Pigments.—Only during very copious excretion does the capsule participate.

After the introduction of a large amount of sodic sulphindigotate, and when the experiment -

has lasted for a long time, the Sb of the capsule becomes blue. In albuminuria, the
abnormal excretion of urine takes place first in the urinary tubules, and afterwards in the
eapsules, Hb is partly found in the capsules. According to Nussbaum, egg-albumin passes out
through the capsule.

2. Even when the secretion of the watery part of the urine is completely arrested,
either by ligature of the ureter, or after a very great fall of the blood-pressure in
the renal artery, [as after section of the cervical spinal cord], the before-mentioned
substances, when injected into the blood, are found in the cells of the convoluted
tubules. The injection of urea under these circumstances causes renewed secretion.
These facts show that, independently of the filtration pressure, the secretory activity
of these cells is still maintained.

The independent vital activity of the secretory cells of the urinary tubules, which as yet we
are unable to explain on purely physical grounds, renders it probable that the tubules are not to
be compared to an apparatus provided with physical membranes. This is proved by the follow-
ing experiment :—Abeles caused arterial blood to circulate through freshly excised living
kidneys. A pale urine-like fluid dropped from the ureter. On adding some urea or sugar to
the blood, the secretion became more concentrated. Thus, the excised living kidney also
excretes substances in a more concentrated form than those supplied to it in the diluted blood
streaming through it. J. Munk obtained similar results in excised kidneys with common salt,
nitre, caffein, grape-sugar, glycerin, with increase in the amount of urine secreted. The
addition of caffein or theobromin to the perfused blood increases the secretion, exciting the
secretory cells to greater activity (v. Schroeder).

Salts and Gases.—The vital activity explains why the serum-albumin of the blood does not
pass into the urine, while egg-albumin and dissolved hemoglobin readily do so. . Among the
salts which occur in the blood and blood-corpuscles, of course only those in solution can pass
into the urinc. Those which are united with proteid bodies, or are fixed in the cellular
elements, cannot pass out, or at least only after they been split up. Thus, we may explain the
difference between the salts of the urine and those of the blood. Similarly, the urine can only
contain the absorbed and not the chemically-united gases.

Ligature of the Ureter.—If the secretion be arrested by compression or by ligature of the
ureter, the i fal db ti of the kidney become filled with fluid, which may pass into the blood,
so that the organ becomes cedematous, owing to the passage of fluid into its lymph-spaces.
The secretion undergoes a change, as first water passes back into the blood, then the sodic
chloride, sulphuric, and phosphoric acids diminish, and lastly the urea (C. Ludwig, Max Herr-
mann). Kreatinin is still present in considerable amount. There is no longer secretion of
proper urine (Lébel/).

on-Symmetrical Renal Activity.—It is remarkable that both kidneys do not secrete
symmetrically—there is an alternate condition of hyperemia and secretory activity on opposite
sides (§ 100). One kidney secretes a more watery urine, which at the same time contains more
NaCl and urea. Von Wittich observed that the secretion of uric acid was not uniform in all
the urinary tubules of the same bird. Extirpation of one kidney, or disease of one kidney in
man, does not seem to diminish the secretion (Rosenstein). The remaining kidney becomes
more active and larger.

Reabsorption in the Kidney.—In discussing the secretion of the kidney, we must attach
considerable importance to the variations in the calibre of the renal tubules in their: course.
Perhaps in the narrowing of the descending part of the looped tubule of Henle there may be

either a reabsorption of water, so that the urine becomes more concentrated, or there may be.

absorption even of albumin, which may perhaps pass through the glomeruli in small amount.
[That reabsorption of fluid takes place within the kidney was part of Ludwig’s theory, which
is practically a process of filtration and reabsorption. Hiifner pointed out that the structure of
the kidneys of various classes of vertebrates corresponded closely with the requirements for
reabsorption of water. The experiments of Ribbert show that the urine actually secreted in
the cortex of the kidney is more watery than that secreted normally by the entire organ. He

extirpated the medullary portion in rabbits, leaving the cortical part intact, and in this way

~

~

FORMATION OF THE URINARY CONSTITUENTS. 425

collected the dilute urine from the Malpighian corpuscles before it passed through Henle’s
loops. ]

2°74. FORMATION OF THE URINARY CONSTITUENTS.—The question
has often been discussed, whether all the urinary constituents are merely excreted
through the kidneys, 7.e., that they exist preformed in the blood; or whether some
of them do not exist preformed in the blood, but are formed within the kidneys, as
a result of the activity of the renal epithelium.

Urea is formed Outside the Kidney.— Urea exists preformed in the blood, from
which it is separated by the activity of the kidney. This is proved by the follow-
ing considerations :—

1. The blood contains one part of urea in 3000 to 5000 parts, but the renal vein contains less
urea than the blood of the corresponding artery.

2. After extirpation of the kidneys, or nephrotomy, or after ligature of the renal vessels, the
amount of urea accumulates in the blood, and increases with the duration of the experiment to
sty to giz. At the same time there is vomiting and diarrhcea, and the fluids so voided con-
tain urea (Cl. Bernard). Animals die in from one to three days after the operation.

3. After ligature of the ureters, the secretion of urine is soon arrested. Urea accumulates
in the blood, but not to a greater extent than after nephrotomy. It is possible, however, that
the kidneys, like other organs, may form a small amount of urea, due to the metabolism of their
own tissues.

[Urea exists in the blood, whence does the blood derive it? It can only obtain
it from one or more of several organs—(1) muscle, (2) nervous system, and (3)
glands, of which the liver isthe most prominent. This is best stated by the method
of exclusion. |

[1. That urea is not formed in muscle is shown, among other considerations, by the fact that
only a trace of urea occurs in muscle (§ 293), and that the amount is not increased by exercise.
Blood which has been transfused through a muscle, or the blood after circulating in a muscle
during violent exercise, does not contain an increase of urea, nor does the addition of ammonia
carbonate to blood circulating through muscle show any increase of urea. Again, muscular
exertion does not (as a rule) increase the amount of urea in the urine, as shown by the experi-
ments of Fick and Wislicenus (§ 294), Parkes, and others. The excretion chiefly increased by
muscular exertion is the pulmonary CO, (§ 127).]

[2. From what we know of the nervous system, it is not formed there. We are therefore
forced to consider the evidence as to the liver, as the organ, or, at least, the chief organ in which
it is formed. This evidence is in some respects contradictory, but it is partly experimental
and partly clinical. Although Hoppe-Seyler denies the existence of urea in the liver, its
existence there was proved by Gscheidlen ; and Cyon, on passing blood through an excised liver
by the ‘‘ perfusion” method of Ludwig, found that blood, after being passed several times
through the organ, contained an increased amount of urea. The objection to these experiments
is that Cyon’s method of estimating the urea was unreliable. But von Schroeder, using a simi-
lar method, finds that if blood be perfused through the liver of a dog in full digestion, there is
a great increase in the amount of urea, while there is none in the liver of a fasting dog. If
ammonia carbonate be added to the blood, there is a very much greater amount of urea in the
blood of the hepatic vein. This last fact is confirmed by Salomon. The experiments of
Minkowski on the liver of the goose (§ 386) show that, when the liver is excluded from the
circulation, lactic acid takes the place of uric acid in this bird. Brouardel further states,
that if the region of the liver be so beaten as to cause congestion of that organ, there is an
increase of the urea in the urine. ]

[The clinical evidence points strongly to the formation of urea in the liver. Parkes pointed
out that in hepatic abscess, during the early congestive stage, the urea in the urine is increased,
while it is diminished in the suppurative stage, when the hepatic parenchyma is destroyed. The
urea is also diminished in cancer of the liver, phthisis, and some forms of hepatic cirrhosis,
while it is increased during hepatic congestion, and specially so in some cases of diabetes melli-
tus. The most striking fact of all is that, in acute yellow atrophy of the liver, the urea is
enormously diminished in the urine, and may even disappear from it while its place is taken by
the intermediate products, leucin and tyrosin (v. Frerichs). In poisoning by phosphorus, coin-
cident with the atrophy of the liver, there is a fall in the urea excretion. Noél-Paton finds
that some drugs which inerease the quantity of bile in dogs in a state of N-equilibrium (§ 178),
€.g., sodic salicylate and benzoate, colchicum, mercuric chloride and euonymin also increase the
urea in the urine, he therefore concludes ‘‘that the formation of urea in the liver bears a very
direct relationship to the secretion of bile by that organ.”]

As to the antecedents of urea there is the greatest doubt (§ 256).

426 FORMATION OF URIC ACID.

Uric Acid is formed Outside the Kidneys.—1. Birds’ blood normally contains uric acid
(Meissner). [The liver of the pigeon contains 6 to 14 times as much uric acid as the blood.
Ligature of the ureters or renal blood-vessels (Pawlinof), or gradual destruction of the rena
secretory parenchyma by the subcutaneous injection of neutral potassium chromate (Hbstein), is
followed by the deposition of uric acid in the joints and tissues, and it may even form a white
incrustatién on the serous membranes. The brain remains free (Zalesky, Oppler). Acid urates
of ammonia, soda, and magnesia are also similarly deposited. Extirpation of a snake’s kidneys
gives the same result, but to a less degree. :

[Minkowski found that, after excluding the liver from the circulation, lactic acid took the

lace of uric acid in the urine (p, 425). Some uric acid still appears in the urine, which cannot
ye derived from the small amount in the blood, so that, according to v. Schroeder, there are
perhaps other foci of formation of uric acid. ]

(The latter experiment points to the formation of uric acid in the liver in birds,
and this is supposed to be strengthened by the appearance of the deposition of urates
in the urine in certain disorders of digestion.] Von Schroeder and Colasanti, how-
ever, as the result of their experiments upon snakes, come to the conclusion that
there is no special organ concerned in the formation of uric acid.

Hippuric acid is partly formed in the kidney, for the blood of herbivora does not contain a
trace of it (Meissner and Shepard). In rabbits, perhaps it is formed synthetically, in other
tissues as well as in the kidney. If blood containing sodic benzoate and glycin be passed
through the blood-vessels of a fresh kidney, hippuric acid is formed (§ 260) (Bunge, Schmiedeberg,

‘ochs). [The other evidence is given in § 260.]

Kreatinin has intimate relations to kreatin of muscle, but where it is formed is not known.
If phenol and pyrokatechin are digested along with fresh renal substance, a compound of
sulphuric acid similar to that occurring in urine is formed (§ 262). The latter substance,
however, is also formed by similarly digesting liver, pancreas, and muscle. It is concluded
from these experiments that these substances are formed in the body within the kidneys and
the other organs mentioned (Kochs).

Chemistry of the Kidney.—The kidneys contain a very large amount of water. Besides
serum-albumin, globulin, albumin soluble in sodium carbonate (Gottwalt), gelatin-yielding
substances, fat in the epithelium, elastic substance derived from the membrana propria of the
tubules, the kidneys contain leucin, xanthin, hypoxanthin, kreatin, taurin, inosit, cystin (the
last in no other tissue), but only in very small amount. The occurrence of these substances
points to a lively metabolism in the kidneys, which is also proved by the liberal supply of blood
they receive.

Blood-Vessels.—The kidneys receive a very large supply of blood, and during
secretion the blood of the renal vein is bright red. [In the dog, the diameter of
the renal artery may be diminished to ‘5 mm. without the amount of blood flowing
through the kidney being thereby greatly interfered with. Hence, within wide
limits, the amount of blood is independent of the size of the arterial lumen, and is
therefore dependent on the blood-pressure in the aorta, and the resistance to the

blood-current within and beyond the kidney (Heidenhain). |

The reaction of the kidneys is acid, even in those animals whose urine is alkaline. Perhaps
this fact is connected with the retention of the albumin in the vessels.

275, PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE.—1. The following
substances pass unchanged into the urine :—Sulphate, borate, silicate, nitrate, and carbonate
of the alkalies; alkaline chlorides, bromides, iodides; potassium sulphocyanide and ferro-
cyanide ; bile salts, urea, kreatinin ; cumaric, oxalic, camphoric, pyrogallic, and carbolic acids.
Many alkaloids, e.g., morphia, strychnia, curara, quinine, caffein ; pigments, sulphindigotate
of soda, carmine, madder, logwood, colouring matter of cranberries, cherries, rhabeths santonin ;
Jastly, salts of gold, silver, mercury, antimony, arsenic, bismuth, iron (but not lead), although
the greatest part of these is excreted by the bile and the feces.

2. Inorganic acids oe dere in man and carnivora as neutral salts of ammonia, in herbivora,
as neutral salts of the alkalies, ;

3, Certain substances which, when injected in small amount, seem to be decomposed in the
blood, pass in part into the urine, when they occur in such large amount in the blood that
they cannot be completely decomposed—sugar, hemoglobin, egg-albumin, alkaline salts of the
vegetable acids, alcohol, chloroform. |

4, Meer substances appear in an oxidised form in the urine—moderate quantities of
organic alkaline salts as alkaline carbonates (Wéhler), uric acid in part as allantoin
(Salkowski), sulphides and sulphites of soda, in part as sodium sulphate, potassium sulphide as
potassium sulphate, some oxyduls as oxides, benzol as phenol (Naumyn and Schulzen). ©

INFLUENCE OF NERVES AND OTHER CONDITIONS. 427

5. Those bodies which are completely decomposed, as glycerin, resins, give rise to no special
derivatives in the urine.

6. Many substances combine and appear as conjugated compounds in the urine, ¢.g., the
origin of the hippuric acid by conjugation (§ 260), the conjugation of sulphonic acid (§ 262),
and the formation of urea by synthesis from carbamic acid and ammonia (Drechsel) (§ 256).
After the use of camphor, chloral, or butylchloral, a conjugated compound with glycuronic acid
(an acid nearly related to sugar) appears in the urine. Taurin and sarcosin unite with
sulphaminic acid. When bromophenol is given, it unites with mercapturic acid, a body nearly

related to cystin (§ 268).

Ns acid, C,,H,)0,, takes up H,O, and is decomposed into two molecules of gallic acid
=2 | :
| 3 The oe of potash and soda are reduced to iodides ; malic acid (CyH,O,) partly to
eee ee (C,H,0,) ; indigo-blue (C,g,H,)N,0.) takes up hydrogen and becomes indigo-white
9. Some Faden do not pass into the urine at all, ¢.g., oils, insoluble metallic salts and
metals.

2.76. INFLUENCE OF NERVES AND OTHER CONDITIONS.—At present
we are acquainted merely with the influence of the vaso-motor nerves on the
filtration of the urine through the renal vessels. Hach kidney seems to be supplied
with vaso-motor nerves, which spring from both halves of the spinal cord (Nicolaides).
As a general rule, dilatation of the branches of the renal artery, chiefly the vasa
afferentia, must raise the pressure within the glomeruli, and thus increase the
amount of water filtered through them. The more the dilatation is confined to the
area of the renal artery alone, the greater is the amount of the urine. [As yet we
know the nervous system influences the secretion of urine only in so far as it modi-
fies the pressure and velocity of the blood-current in the kidney. We have no
satisfactory evidence of the existence of direct secretory nerves in the kidney. |

1. Renal Plexus and its Centre.—Section of the nerves of the renal plexus—
the nerves around the renal artery—generally causes a considerable increase in the
secretion of urine, hydruria or polyuria ; sometimes, on account of the great rise
of the pressure within the glomeruli, albumin passes into the urine, and there may
be rupture of the vessels of the glomeruli, leading to the passage of blood into the
urine. The nerve-centre for the renal nerves lies in the floor of the fourth
ventricle, in front of the origin of the vagus. Injury to this part of the floor of the
fourth ventricle, ¢.g., by puncture (piqtire), may increase the amount of urine
(diabetes insipidus), which is sometimes accompanied by the simultaneous appear-
ance of albumin and blood in the urine (Cl. Bernard). Section of the parts which
lie directly in the course of these fibres, as they pass from their centre to the kidney,
produces the same effects. Close to this centre in the medulla, lies the centre for
the vaso-motor nerves of the liver, whose injury causes diabetes mellitus (§ 175).
Eckhard found that stimulation of the vermiform process of the cerebellum produced
hydruria. In man, stimulation of these parts by tumours or inflammation, Wc.,
produces similar results.

2. Paralysis of Limited Vascular Areas.—If, simultaneously with the paralysis
of the nerves of the renal artery, the nerves of a neighbouring large vascular area
be paralysed, necessarily the blood-pressure in the renal artery area will not be so
high, as more blood flows into the other paralysed province. Under these circum-
stances, there may be only a temporary, or, indeed, no increase of urine, provided
the paralysed area be sufficiently large. There isa moderate increase of urine for
several hours after section of the splanchnic nerve, This nerve contains the renal
vaso-motor nerves (which, in part, at least, leave the spinal cord at the first dorsal
nerve and pass into the sympathetic nerve), but it also contains the vaso-motor
nerves for the large area of the intestinal and abdominal viscera. Stimulation of
this nerve has the opposite effect (Cl. Bernard, Eckhard), [The polyuria thus
produced is not so great as after section of the renal nerves, because the splanchnic
supplies such a large vascular area, that much blood accumulates in that area, and
also because all the renal nerves do not run in the splanchnics. |

428 RENAL ONCOGRAPH AND ONCOMETER.

3. Paralysis of Large Areas.—If, simultaneously with paralysis of the renal
nerves, the great majority of the vaso-motor nerves of the body be paralysed [as by
section of the medulla oblongata], then, owing to the great dilatation of all these
vessels, the blood-pressure falls at once throughout the arterial system. The result
of this may be, provided the pressure is sufficiently low, that there is a great decrease,
or, it may be, entire cessation of the secretion of urine. The secretion is arrested when
the cervical cord is completely divided, down even as far as the seventh cervical
vertebra (Eckhard). The polyuria caused by injury to the floor of the fourth
ventricle at once disappears when the spinal cord (even down to the twelfth dorsal
nerve) is divided.

[4. Other Conditions.—As already stated, section of the renal nerves is followed
by polyuria, owing to the increased pressure in the glomeruli, but this polyuria
may be increased by stimulating the spinal cord below the medulla oblongata,
because the contraction of the blood-vessels throughout the body still further raises
the blood-pressure within the glomeruli. If, however, the spinal cord be divided
below the medulla oblongata—the renal nerve being also divided—the polyuria
ceases, because of the fall of the general blood-pressure thereby produced.
Division of the spinal cord in the dorsal region also diminishes or arrests the secretion
of urine, owing to the fall of the blood-pressure ; but animals recover from this
operation, the general blood-pressure rises, and with it the secretion of urine.
Stimulation of the cord below the medulla arrests the secretion, as it causes con-
traction of the renal arteries along with the other arteries of the body.

[Volume of the Kidney—Oncometer.—By means of the plethysmograph (§ 101)
we can measure the variations in the size of a limb, while by the oncograph (dyxos,
volume) similar variations in the volume of the spleen are measured (§ 103). Roy
and Cohnheim have measured the variations in the volume of the kidney by means
of an instrument which consists of two parts, one termed the oncometer or renal
plethysmometer, in which the organ is enclosed, while the other part is the
registering portion or oncograph. The kidney is enclosed in a kidney-shaped
metallic capsule (fig. 286), composed of two halves which move on the hinge, A, to

Fig. 286. Fig. 287,

Fig. 286.—Oncometer. K, kidney ; the thick line is the metallic capsule ; h, hinge ; I, tube
for filling ap aratus ; T, tube to connect with T, ; a, v, wu, artery, vein, ureter (Stirling,
after Roy). Fig. 287.—Oncograph. C’, chamber filled with oil, communicating by T, with
T ; p, piston ; /, writing-lever (Stirling, after Roy).

introduce the organ. The renal vessels pass out at a,v. . The kidney is surrounded

with a thin membrane, and between this membrane and the inner surface of the

capsule is a space filled with warm oi through the tube, I, which is closed by
means of a stop-cock after the space is filled with oil. The tube, T, can be made to
communicate with another tube, T,, leading into a metallic chamber, C’, of the

At

EXPERIMENTS WITH THE ONCOMETER. 429

oncograph (fig. 287), which is provided with a movable piston, », attached by a
thread to the writing-lever, 7. Any increase in the size of the organ expels oil
from the chamber, O, into C’, and thus the piston is raised, while a diminution in
the size of the kidney diminishes the fluid in C’, and the lever falls. The actual
volume of the living kidney depends upon the state of distension of its structural
elements, upon the amount of lymph in its lymph-spaces, but chiefly upon the
amount of blood in its blood-vessels, and this again must depend upon the condi-
tion of the non-striped muscles in the renal arteries. When the vessels dilate, the
kidney increases in size, and when they contract it contracts, so that we can
register on the same revolving cylinder the variations of the volume at the same
time that we record the general arterial blood-pressure. |

[In the normal circulation through the kidney, the kidney curve, 7.¢., the curve
of the volume of the kidney, runs parallel with the blood-pressure curve, and shows
the large respiratory undulations, as well as the smaller elevations due to the systole
of the heart (fig. 288). Usually, when the blood-pressure falls, the kidney curve
sinks, and when the blood-pressure rises the volume of the kidney increases.
When the blood-pressure curve is complicated by Traube-Hering waves (§ 85) the
opposite effect is produced on the kidney curve; the highest blood-pressure corre-
sponds to the smallest size of the kidney, and conversely. This is due to the fact
that, when these curves occur, all the small arterioles, including those in the kidney,
are contracted. A kidney placed in an oncometer secretes urine like a kidney
under natural conditions. |

»~ BLOOD PRESSURE CURVE

KIDNEY CURVE

nV

t

Fig. 288.

B.P., Blood-pressure curve ; K., curve of the volume of the kidney ; T, time curve, intervals
indicate a quarter of a minute; A, abscissa (Stirling, after Roy).

(Arrest of the respiration in a curarised animal produces a rapid and great
diminution of the volume of the kidney, caused by the venous blood stimulating the
vaso-motor centres, and thus contracting the small arterioles, including those of the
kidney. This result occurs whether one or both splanchnics are divided, proving
that all the vaso-motor nerves of the kidney do not reach it through the splanch-
nics. When al/ the renal nerves at the hilum are divided, arrest of the respiration
causes dilatation of the organ, which condition runs parallel with the rise of the
blood-pressure. Stimulation of a sensory nerve, e.g., the central end of the sciatic
nerve, while causing an increase of the blood-pressure, makes the kidney shrink. |

(In poisoning with strychnin, the kidney shrinks while the blood-pressure rises.
Stimulation of the central or peripheral end of the splanchnics, divided at the
diaphragm, causes contraction of the renal vessels of both sides; the former is a re-
flex, the latter a direct effect. Stimulation of the peripheral end of one splanchnic
sometimes affects both kidneys. Stimulation of the peripheral end of the renal
nerves always causes a diminution in. the volume of the kidney, so that Cohnheim
and Roy inferred that, although there was evidence of the existence of vaso-motor
and sensory nerves to the kidney, they found none of vaso-dilators, Each kidney
acts independently of the other. Sudden compression of one rental artery has not
the slightest effect upon the blood-current of the other kidney. If a kidney be

430 URZMIA AND AMMONTAEMIA,

exposed in an animal, by making an incision in the lumbar region, on stimulating
the medulla oblongata directly with electricity, we may observe the kidney itself
becoming paler, the palor appearing in a great many small spots on the surface of
the organ, corresponding to the distribution of the interlobular arteries. |

{Cohnheim showed that the composition of the blood has a remarkable effect
on the renal circulation. Some substances (water and urea), when injected into
the blood, cause the kidney first to shrink and then to expand, while sodic acetate
dilates the kidney, even after all the renal nerves are divided—an operation which
is very difficult indeed. Provided all the renal nerves be divided, these effects
would indicate the existence of some local intra-renal vaso-motor mechanism govern-
ing the renal blood-vessels. The general blood-pressure is not thereby modified ;
nor need we wonder at this, as ligature of one renal artery does not increase the
pressure in the aorta. |

(The reciprocal relation between the sKin and the kidneys is known to every
one. Ona cold day, when the skin is pallid, owing to contraction of the cutaneous
vessels, the amount of urine secreted is great, and conversely, in summer less urine
is passed than in winter. Washing the skin of a dog for two minutes with ice-cold
water causes a great contraction of the kidney. |

The perfusion of blood through a living excised kidney is materially in-
fluenced by the substances mixed with the blood perfused. This effect may in part
be due to the action of these chemical ingredients upon the nuclei of the endo-
thelial lining of the blood-vessels, especially the capillaries, or the effects upon the
muscular fibres of the blood-vessels. — Ea

[Strvchnin seems to cause contraction of the renal vessels, independently of its action on the
general vaso-motor centre. Brunton and Power found that digitalis caused an increase of the
blood-pressure (dog), but the secretion of urine was either at the same time diminished, or it
ceased altogether. The latter result was due to contraction of the renal blood-vessels, but
when the aortic blood-pressure began to fall, the amount of urine secreted rose much above
normal, 7.e., when the arteries had begun to relax. ]

During fever, the renal vessels are probably contracted in consequence of the stimulation of
the renal centre by the abnormally warm blood (Mendelson).

The repeated respiration of CO is said to produce polyuria, perhaps in consequence of
paralysis of the renal vaso-motor centre. —

Action of the Vagus. —According to Cl. Bernard, stimulation of the vagus at the cardia in-
creases the urinary secretion, while at the same time the blood of the renal vein becomes red.
This nerve may contain vaso-dilator nerve-fibres corresponding to the fibres in the facial
nerve for the salivary glands (§ 145).

277. UREMIA—AMMONIEMIA.—Symptoms of Ureemia.—After excision of the kidneys,

nephrotomy, or ligature of the ureter ; in man, also, as a result of certain diseased conditions
of the kidney, leading to the suppression of the secretion of urine, there is developed a series of -

characteristic symptoms which are followed by death. The condition is called uremic intoxi-
cation or wremia. There are marked cerebral phenomena, drowsiness, and deep coma, and
occasionally local or more general spasms. Sometimes there is deliriwm ; Cheyne-Stokes pheno-
menon is often observed (§ 111, II.), and there may be vomiting and diarrhea, while in the
fluids voided, as well as in the expired air, ammonia may sometimes be detected. .

The cause of these phenomena has been ascribed to the retention in the blood of those sub-
stances which normally are excreted by the urine, but as yet it has not been definitely ascer-
tained which of these substances causes the phenomena :— .

1. The first thought is to ascribe them to the retention of the urea, V. Voit found that
dogs exhibited uremic symptoms if they were fed for a long time on food containing urea and
little water. Meissner found that in nephrotomised animals, the uremic symptoms were
hastened by the injection of urea into the ood: The injection of a moderate amount of urea
in perfectly healthy animals is not followed by uremic symptoms, probably because the urea
is rapidly excreted by the kidneys ; 1 to 2 grms. [15 to 30 grains] so injected produce comatose
symptoms in rabbits.

2. The injection of ammonium carbonate produces symptoms resembling those of uremia,
so that v. Frerichs thought that the urea was Acco in the blood, yielding ammonium
carbonate—ammonismia. Demjankow observed uremic phenomena after nephrotomy, if at
the time he injected urea-ferment into the blood (§ 263). - Feltz and Ritter obtained uremic
symptoms in dogs by injecting salts of ammonia. i ae

|
;
|
.

STRUCTURE AND FUNCTIONS OF THE URETER. 431

3. As ligature of the ureters produces a comatose condition in those animals which excrete
chiefly uric acid in the urine—e.g., birds and snakes (Zalesky)—it is possible that other sub-
stances may produce the poisonous symptoms. The injection of kreatinin causes feebleness
and contraction of the muscles in- dogs (Meissner). Bernard, Traube, and more recently Feltz
and Ritter ascribe the symptoms to an accumulation of the neutral potassium salts in the blood
(§ 54). The injection of kreatin, succinic acid (Meissner), uric acid, and sodic urate (Ranke), is
without effect. Schottin and Oppler ascribe the results to an accumulation of normal or
abnormal extractives. It is possible that several substances and their decomposition-products
contribute to produce the result, so that there isa combined action of several factors, but
perhaps the retention of the potash salts plays the most important part.

The direct application of some urinary substances (kreatinin, kreatin, acid potassic phosphate,
urates) to the surface of the cerebrum causes all the symptoms of uremia. Urea is inactive,
and slightly active are ammonium and sodic carbonate, leucin, NaCl, KCl (Landois).

[Alkaloids in Urine.—Human urine, and especially febrile urine, when injected under the
skin of frogs or rabbits, acts as a poison, and even causes death, by arresting the respiration.
‘The alkaloids seem to be formed by the action of vegetable organisms in the intestine, whence they
are absorbed into the blood and pass into the urine ($116). Urine rendered colourless by char-
coal loses half its toxic power, and the poisonous substance is not volatile, and even resists boiling.
These alkaloids are increased in the urine in typhoid fever, pneumonia, but not in diabetes. ]

Ammonisemia.—When urine undergoes the alkaline fermentation within the bladder, and
ammonium carbonate is formed, the ammonia may be absorbed and produce this condition.
The breath and excretions smell strongly of ammonia; the mouth, pharynx, and skin are very
dry ; there is vomiting, with diarrhcea or constipation, while ulcers may form in the intestine.
The patient rapidly loses flesh, and death occurs without any disturbance of the mental
faculties.

Uric Acid Diathesis.—When too much nitrogenous food, too much of any alcoholic fluid is
persistently used, and little muscular exercise taken, especially if the respiratory organs are in-
terfered with, uric acid. may not unfrequently accumulate in the blood (Garrod). It may be
deposited in the joints and their ligaments, especially in the foot and hand, giving rise to pain-
ful inflammation, and forming gout-stones or chalk-stones. The heart, liver, and kidneys are
rarely affected. The tissues near these deposits undergo necrosis.

278. STRUCTURE AND FUNCTIONS OF THE URETER.—Mucous Membrane.—The
pelvis of the kidney and the ureter are lined by a mucous membrane, consisting of connective-
tissue, and covered with several
layers of stratified ‘‘ transitional ”
epithelium (fig. 290). The cells
are of various shapes, those of the
lowest layer being usually more or
less spherical and small, while
many of the cells in the upper
layers are irregular in shape, often
with long processes passing into
the deeper layers.

Sub-mucosa.—Under the epi-
thelium there is a layer of adenoid
tissue (Hamburger, Chiari), which
may contain small lymph-follicles
[embedded in loose connective-
tissue]. In the pelvis of the kidney
and ureter there are a few small
mucous glands lined by a single
layer of columnar epithelium
(Unruh, Egli).

The muscular coat consists of an
inner somewhat stronger layer of
longitudinal non-striped fibres, and site ee
an outer circular layer (fig. 289). - Fig. 289.
In the lowest third of the ureter Transverse section of the lower part of human ureter, x 15.
there are in addition a number of ¢, epithelium ; ¢, tunica propria ; s, sub-mucosa ; 7 and 7,
scattered muscular fibres. All longitudinal and circular fibres. é
these layers are surrounded and ,
supported by connective-tissue. The outer layers of the connective-tissue form an outer coat or

ventitia, which contains the large vessels and nerves. The various coats of the ureter can
be followed up to the pelvis of the kidney, and to its calices. The papille are covered only by
the mucous membrane, while the muscular layer ceases at the apex of the pyramids, where
they are disposed circularly, to form a kind of sphincter muscle for each papilla (Hevn/e).

Adventitia.

432 MOVEMENT OF THE URINE.

The blood-vessels supply the various coats, and form a capillary plexus under the epithelium, ©
The nerves are not very numerous, but they contain medulla (few) and non-medullated
fibres, with numerous ganglia scattered in their course. They are partly motor and supply the
muscular layers, and some pass towards the epithelium, and are sensory and excito-reflex in func-
tion. These nerves are excited when a calculus passes along the ureter, and thus give rise to
severe pain. The ureter perforates the wall of the bladder obliquely. The inner opening is a
narrow slip in the mucous membrane, directed downwards and inwards, and provided with a

pointed valve-like process (fig. 291).

Movement of the Urine.—The urine is propelled along the ureter thus :—(1)
The secretion, which is continually being formed under a high pressure in the
kidney, propels the urine onwards in front of
cit, as the urine is under a low pressure in the
mx. cae ureter. (2) Gravity aids the passage of the
we urine when the person is in the erect posture.

(3) The muscles of the ureter contract rhythmi-

4\\ cally and peristaltically, and so propel it towards
g2\ the bladder. This movement is reflex, and is

due to the presence of the urine in the ureter.
Every three-quarters of a minute several drops
of urine pass into the bladder. But the fibres

J

Fig. 290.

Transitional epithelium from the bladder. : : ,
Many of the large cells lie upon the may also be excited directly. The contraction —

summit of the columnar and caudate passes along the tube at the rate of 20 to 30
cells, and depressions are seen on their nm per second always from above downwards
. > | .

under surface. The greater the tension of the ureter due to

the urine, the more rapid is the peristaltic movement.

Local Stimulation.—On applying a stimulus to the ureter directly, the contraction passes
both upwards and downwards, Engelmann observed that the movements occur in parts of the
ureter where neither nerves nor
ganglia were to be found, and
he concluded that the move-
ment was propagated by ‘‘mus- .
cular conduction.” If this be
so, then an impulse may be pro-
pagated from one non-striped
muscular cell to another without
the intervention of nerves (see
Heart, § 58, I., 3).

Prevention of Reflux.
—The urine is prevented
from exerting a backward
pressure towards the kid-
neys:—(1) The urine which
collects in the pelvis of the
kidney is under a high
pressure, and thus tends
= uniformly to compress the
Fig. 291 pyramids, so that the urine

Lower part of the human bladder laid open, showing clear part, CADAOS petals the nine
or trigone, the slit-like openings of the ureters, the divided Orifices of the urinary tub-
ureters, and vesicule seminales; the sinus prostaticus, and ules. (2) When there is a
a tic _ of it, the openings of the ejaculatory ducts, and egnsiderable accumulation

ow both numerous small apertures of the prostate ducts. of urine in a ureter, eg.,

from the presence of an impacted calculus or other cause, there is also more energetic
peristalsis, and, at the same time, the circular muscular fibres round the apices of ©
pyramids compress the pyramids and prevent the reflux of urine through the —
collecting tubules. The urine is prevented from passing back from the bladder
into the ureter, the wall of the bladder itself, and the part of the ureter which © '

URINARY BLADDER AND URETHRA. 433

passes through it, are compressed, so that the edges of the slit-like opening of the
ureter are rendered more tense, and are thus approximated towards each other
(fig. 291).

279. URINARY BLADDER AND URETHRA.—Structure.—The mucous membrane of the
bladder resembles that of the ureter ; the upper layers of the stratified transitional epithelium
are flattened. It is obvious that the form of the cells must vary with the state of distention or
contraction of the bladder. [The mucous membrane and muscular coats are thicker than in

the ureter. There are mucous glands in the mucous membrane, especially near the neck of the

bladder. ]

Sub-mucous Coat.—There is a layer of delicate fibrillar connective-tissue mixed with elastic
fibres between the mucous and muscular layers.

[The serous coat is continuous with, and has the same structure as the peritoneum, and it
covers only the posterior and upper half of the organ.]

Musculature.—The non-striped muscular fibres are arranged in bundles in several layers, an
external longitudinal layer, best developed on the anterior and posterior surfaces, and an inner
circular layer.. [Between these two is an oblique layer.] There are other bundles of muscular
fibres arranged in different directions. Physiologically, the musculature of the bladder represents
a single or common hollow muscle, whose function when it contracts is to diminish uniformly
the size of the bladder, and thus to expel its contents (§ 306). |

The blood-vessels resemble those of the ureter. The nerves form a plexus, and are placed
partly in the mucous membrane and partly in the muscular coat, and, like all the extra-renal
parts of the urinary apparatus, are provided with ganglia, lying in the mucosa, sub-mucosa,
and connected to each other by fibres (Maier). Ganglia occur in the course of the motor nerve-
fibres in the bladder (W. Wolf). Their functions are motor, sensory, excito-motor, and vaso-
motor. [Sympathetic nerve-ganglia also exist underneath the serous coat (Ff. Darwin). ]

A too minute dissection of the several layers and bundles of the musculature of the bladder
has given rise to erroneous inferences. Thus, we speak of a detrusor urine, which, however,
consists chiefly of fibres running on the anterior and posterior surfaces, from the vertex to the
fundus. There does not seem to be a special sphincter vesicee internus; it is merely a thicker
circular (6 to 12 mm.) layer of non-striped muscle which surrounds the beginning of the
urethra, and which, from its shape, helps to form the funnel-like exit of the bladder. Numerous
muscular bundles, connected partly with the longitudinal and partly with the circular fibres of
the bladder, exist, especially in the trigone, between the orifice of the ureters.

In the female, the urethra serves merely for the passage of urine. The mucous membrane
consists of connective-tissue with many elastic fibres, and provided with papille. It is covered
by stratified epithelium and contains several mucous glands (Littré). Outside this is a layer
of longitudinal, smooth, muscular fibres, and outside this again a layer of circular fibres. Many
elastic fibres exist in all the layers, which are traversed by numerous wide venous channels.

The proper sphincter urethre is a transversely striped muscle subject to the will,
and consists of completely circular fibres which extend downwards as far as the
middle of the urethra, and partly of longitudinal fibres, which extend only on the .
posterior surface towards the base of the bladder, where they become lost between

the fibres of the circular layer.

In the male urethra, the epithelium of the prostatic part is the same as that in the bladder ;
in the membranous portion it is stratified, and in the cavernous part the simple cylindrical form.
The mucous membrane, under the epithelium itself, is beset with papillw, chiefly in the
posterior part of the urethra, and contains the mucous glands of Littre.

Non-striped muscle occurs in the prostatic part arranged longitudinally, chiefly at the
colliculus seminalis ; in the membranous portion the direction of the fibres is chiefly circular,
with a few longitudinal fibres intercalated; the cavernous part has a few circular fibres

' posteriorly, but anteriorly the muscular fibres are single and placed obliquely and longitudi-

nally.

Closure of the Bladder.—The so-called internal vesical sphincter of the
anatomists, which consists of non-striped muscle, is in reality an integral part of
the muscular coat of the bladder and surrounds the orifice of the urethra as far
down as the prostatic portion, just above the colliculus seminalis. It is, however,
not the sphincter muscle. The proper sphincter urethre (sph. vesicee externus)
lies below the latter. It is a completely circular muscle disposed around the
urethra, close above the entrance of the urethra into the septum urogenitale at the
apex of the prostate, where it exchanges fibres with the deep transverse muscle of
the perineum which lies under it.

’ 25

434 ACCUMULATION OF URINE—MICTURITION.

Some longitudinal fibres, which run along the vs margin of the prostate from the bladder,
belong to this sphincter muscle. Single transverse bundles passing forward from the surface of
the neck of the bladder, the transverse bands which lie within the prostate, the apex of the
colliculus seminalis, and a strong transverse bundle passing in front of the origin of the urethra
into the substance of the prostate—all belong to the sphincter muscle (Henle). In the male
urethra, the blood-vessels form a rich capillary plexus under the epithelium, below which is a
wide-meshed lymphatic plexus.

[Tonus of Sphincter Urethre.—Open the abdomen of a rabbit, ligature one ureter, tie a
cannula in the other, and pour water into the bladder until it runs out through the urethra,
which is usually under a pressure of 16 to 20 inches. If the spinal cord be divided between
the fifth and seventh lumbar vertebre, a column of 6 inches is sufficient to overcome the
resistance of the sphincter, while section at the fourth lumbar vertebra has no effect on the
height of the pressure. In such an animal the bladder becomes distended, but in one with its
cord divided between the fifth and seventh lumbar vertebre, there is incontinence of urine—
in the former case because the excito-motor impulses are cut off from the centre (5 to 7
vert. ), and in the latter because the tonus of the sphincter is destroyed (Kupressow). This
tonus is denied by Landois and others. ] .

280.—ACCUMULATION OF URINE—MICTURITION.—After emptying
the bladder, the urine slowly collects again, the bladder being thereby gradually
distended. [A healthy bladder may be said to be full when it contains 20 oz. ]
As long as there is a moderate amount of urine in the bladder, the elasticity of the
elastic fibres surrounding the urethra, and that of the sphincter of the urethra
(and in the male of the prostate), suffice to retain the urine in the bladder. This
is shown by the fact that the urine does not escape from the bladder after death.
If the bladder be greatly distended (1°5 to 1°8 litre), so that its apex projects
above the pubes, the sensory nerves in its walls are stimulated and cause a feeling
of a full bladder, while at the same time the urethral opening is dilated, so that a
few drops of urine pass into the beginning of the urethra. Besides the subjective
feeling of a full bladder, this tension of the walls of the bladder causes a reflex
etfect, so that the urinary bladder contracts periodically upon its fluid contents,
and so do the sphincter of the urethra and the muscular fibres of the urethra, and
thus the urethra is closed against the passage of these drops of urine. As long as
the pressure within the bladder is not very high, the reflex activity of the trans-
versely striped sphincter overcomes the other (as during sleep) ; but, as the pressure
rises and the distension increases, the contraction of the walls of the bladder over-
comes the closure produced by the sphincter, and the bladder is emptied, as occurs
normally in young children.

As age advances, the sphincter urethra comes under the control of the will, so
that it can be contracted voluntarily, as occurs in man when he forcibly contracts
the bulbo-cavernosus muscle to retain urine in the bladder. The sphincter ani
usually contracts at the same time. The reflex activity of the sphincter may also
be inhibited voluntarily, so that it may be completely relaxed. This is the con-
dition when the bladder is emptied voluntarily.

Slight movements, confined to the bladder, occur during psychical or emotional disturbances
(e.g., anger, fear), [the bladder may be emptied involuntarily during a fright], after stimulation
of sensory nerves, auditory impressions, restraining the respiration, and by arrest of the heart’s
action. There are slight periodic variations coincident with variations in the blood-pressure.
The contractions of the bladder cease after deep inspiration, and also during apnoea (Mosso and
Pellacani). The excised bladder of the frog, and even portions free from ganglia, exhibit
rhythmical contractions, which are increased by heat (Pfalz). [Ashdown found in pee that the
bladder exhibits regular rhythmical contractions, which were influenced by the degree of
distension of the bladder, being most marked with moderate dilatation and least when the
bladder was feebly or over-distended. The contractions could be registered by means of a
water-manometer communicating with the interior of the bladder. ] ‘

Nerves.—The terves concerned in the retention and evacuation of the urine are :—
1. The motor nerves of the sphincter urethra, which lie in the pudendal nerve
(anterior roots of the third and fourth sacral nerves). When these nerves are divided, —
as soon as the bladder becomes so distended as to dilate the urethral opening, the

EFFECT OF NERVES ON MICTURITION. 435

urine begins to trickle away (incontinence of urine). 2. The sensory nerves of the
urethra, which excite these reflexes, leave the spinal cord by the posterior roots of
the third, fourth, and fifth sacral nerves. Section of these nerves causes incon-
tinence of urine. The centre in dogs lies opposite the fifth, and in rabbits, oppo-
site the seventh, lumbar vertebra (Budge). 3. Fibres pass from the cerebrum—
those that convey voluntary impulses through the peduncles, and the anterior
columns of the spinal cord (according to Mosso and Pellacani, through the posterior
columns and the posterior part of the lateral columns), to the motor fibres of the
sphincter urethre. 4. The inhibitory fibres concerned in the reflex-inhibition of
the sphincter urethre, take the same course (perhaps from the optic thalamus ?)
downwards through the cord to where the third, fourth, and fifth sacral nerves
leave it. 5. Sensory nerves proceed from the urethra and bladder to the brain,
but their course is not known. Some of the motor and sensory fibres lie fora part
of their course in the sympathetic.

Transverse section of the spinal cord above where the nerves leave it, is
always followed in the first instance by retention of urine, so that the bladder be-
comes distended. This occurs because—(1) the section of the spinal cord increases
the reflex activity of the urethral sphincter ; and (2), because the inhibition of this
reflex can no longer take place. As soon, however, as the bladder becomes so dis-
tended, as in a purely mechanical manner to cause dilatation of the urethral orifice,
then the urine trickles away, but the amount of urine which trickles out in drops
is small. Thus the bladder becomes more and more distended, as the continuously
distended walls of the organ yield to the increased tension, so that the bladder may
become distended to an enormous extent. The urine very frequently becomes
ammoniacal, accompanied by catarrh and inflammation of the bladder (§ 263).

Voluntary Micturition.—Observers are not agreed as to the mechanism con-
cerned in emptying the bladder when it is only partially full. It is stated by some
that a voluntary impulse passes from the brain along a cerebral peduncle, and the
cord, to the anterior roots of the 3rd and 4th sacral nerves, and partly through
motor fibres from the 2nd to the 5th lumbar nerves (especially the 3rd), to act
directly upon the smooth muscular fibres of the bladder. This is assumed, because
electrical stimulation of any part of this nervous channel causes contraction of. the
bladder. This view, however, does not seem to be the true one. It is to be re-
membered that Budge showed that the sensory nerves of the wall of the bladder
are contained in the first, second, third, and fourth sacral nerves, and also in part
in the course of the hypogastric plexus, whence they ultimately pass by the rami
communicantes into the spinal cord. |

According to Landois, the smooth musculature of the bladder cannot be excited
directly by a voluntary impulse, but it is always caused to contract reflexly. If we
wish to micturate when the urinary bladder contains a small quantity of urine,
we first excite the sensory nerves of the opening of the urethra, either by causing
contraction or relaxation of the sphincter urethra, or by means of slight abdominal
pressure, and thus force a little urine into the urethral orifice. This sensory
stimulation causes a reflex contraction of the walls of the urinary bladder. At
the same time, this condition is maintained voluntarily, by the action of the intra-
cranial reflex-inhibitory centre of the sphincter urethre. The centre for the reflex
stimulation of the movements of the walls of the urinary bladder is placed some-
what higher in the spinal cord than that for the sphincter urethre. In dogs, it is
opposite the 4th lumbar vertebra (Gianuz, Budge).

[Two centres are assumed to exist in the cord, fig. 292, one the automatic (A.C.) at the segment
corresponding to the 2nd, 3rd, and 4th sacral nerves, which maintains the tonic action of the
sphincter; the other, a reflex centre (R.C.), is situated higher, and through it the detrusor urine
is excited to contraction. Both centres are connected to and governed or controlled by.a cerebral
centre (C.). The automatic centre is connected with the sphincter, and the other with the urine-
expelling fibres. They are also connected with afferent fibres from the bladder and elsewhere.

436 ABSORPTION.

The afferent or sensory fibres are also connected with the brain. The automatic centre maintains
the closure of the bladder, but if the latter be distended, different impulses proceeding from it
reach the spinal centre, and it may be the cerebrum. The impulses reaching the automatic
centre inhibit its action and those to the reflex centre excite it, so that the detrusor urine con-
tracts. If the afferent impulses be powerful, a desire to urinate is excited, and voluntary

. impulses are excited which act upon the spinal centres as the

afferent impulses do, and thus the act of urination is more easily

accomplished. ]

We may conceive a voluntary impulse to pass down special
fibres to an inhibitory centre, which may either act directly on
the motor centre, or possibly may send branches directly to the
sphincter muscles.

Painful stimulation of sensory nerves causes reflex contraction
of the bladder and evacuation of the urine (in children during
teething). Reflex contraction of the bladder can be brought about
in cats, by stimulation of the inferior mesenteric ganglion. After
section of all the nerves going to the bladder, hemorrhage and
asphyxia cause contraction by a direct effect upon the structures
in the wall of the bladder. As yet no one has succeeded in excit-
ing artificially the inhibitory centre in the brain for the sphincter
muscle (Sokowin and Kowalesky).

It seems probable that, as in the case of the anal sphincter
($ 160), there is not a continuous tonic reflex stimulation of the
sphincter urethre ; the reflex is excited each time by the contents.
‘The sphincter vesicee of the anatomists, which consists of smooth
muscular tissue, does not seem to take part in closing the bladder.
Budge and Landois found that, after removal of the transversely
striped sphincter urethre, stimulation of the smooth sphincter
did not cause occlusion of the bladder, nor could L. Rosenthal
or v. Wittich convince themselves of the presence of tonus
ae in this muscle. Indeed, its very existence is questioned by
Fig. 292. Henle.

Scheme of micturition:—A.C., Changes of the Urine in the Bladder.—When the urine is
R.C., C., automatic, reflex, retained in the bladder for a considerable time, according to
andcerebralcentres;B.,blad- Kaupp, there is an increase in the sodium chloride and a decrease
der; S., sensory centre acted jn the urea and water. Urine which remains for a long time in
on by afferent impulses. —_ the bladder is prone to undergo ammoniacal decomposition.
Absorption.—Many observers have shown that the mucous membrane of the bladder is

capable of absorbing substances—potassium iodide and other soluble salts. [Ashdown has shown
that poisons, such as watery solutions of strychnin, curare, eserin, emulsions of chloroform and
ether, are absorbed when injected into the bladder of rabbits. In rabbits, KI injected into the
bladder through a catheter was found in the urine obtained from the divided ureters. Water
and urea are also absorbed—the latter in larger proportion than the former. ]

As the ureters enter near the base of the bladder, the last secreted urine is always lowest. If
a person remain perfectly quiet, strata of urine are thus formed, and the urine may be voided so
as to prove this (£dlefsen).

The pressure within the bladder, when in the supine position=13 to 15 centimetres of
water. Increase of the intra-abdominal pressure (by inspiration, forced expiration, coughing,
bearing-down) increases the pressure within the bladder. The erect posture also increases it,
owing to the pressure of the viscera from above (Schatz, Dubois). [James obtained 4 to 4°5 inches
Hg as the highest expulsive power of the bladder including the abdominal pressure, voluntary
and involuntary. In paraplegia, where there is merely. the expulsive power of the bladder, he
found 20 to 30 inches of water. ]

[Hydronephrosis occurs when the ureters and pelvis of the kidney become dilated, owing to
partial and gradual obstruction of the outflow of urine from the ureters: if the obstruction
become complete, there is cessation of the urinary secretion. James has shown that the bladder
remains contracted for several seconds after it is emptied, and this is specially the case in
irritable bladder; so that this condition may also give rise to hydronephrosis by damming up
the urine in the ureters. ]

Rapidity of Micturition.—The amount of urine voided at first is small,. but it increases with
the time, and towards the end of the act it again diminishes. In men, the last drops of urine,
are ejected from the urethra by voluntary contractions of the bulbo-cavernosus muscle. Adult
dogs increase the stream rhythmically by the action of this muscle.

281.—RETENTION AND INCONTINENCE OF URINE.—Retention of urine or ischuria
occurs :—1. When there is obstruction of the urethra, from foreign bodies, concretions,
stricture, swelling of the prostate. 2. Paralysis or exhaustion of the musculature of the

COMPARATIVE AND HISTORICAL. . 437

bladder ; the latter sometimes occurs after delivery, in consequence of the pressure of the child
against the bladder. 3. After section of the spinal cord (p. 435). 4. Where the voluntary
impulses are unable to act upon the inhibitory apparatus of the sphincter urethre reflex, as well
as when the sphincter urethre reflex is increased.

Incontinence of urine (stillicidium urine) occurs in consequence of—1l. Paralysis of the

Lape urethre. 2. Loss of sensibility of the urethra, which of course abolishes the reflex of

e sphincter. 3. Trickling of the urine is a secondary consequence of section of the spinal
sie, or of its degeneration.

Strangury i is an excessive reflex contraction of the walls of the bladder and sphincter, due to
stimulation of the bladder and urethra; it is observed in inflammation, neuralgia [and after
the use of some poisons, ¢.9., cantharides].

Enuresis nocturna, or involuntary emptying of the bladder at night, may be due to an
increased reflex excitability of the wall of the bladder, or weakness of the sphincter.

282. COMPARATIVE AND HISTORICAL.—Amongst vertebrates, the urinary and genital
organs are frequently combined, except in the osseous “fishes. The Wolffian bodies which act
as organs of excretion during ‘the embryonic period, remain throughout life in fishes and
amphibians and continue to act as such. Fishes.—The myxinotds ‘(eyclostomata) have the
simplest kidneys; on each side is a long ureter with a series of short-stalked glomeruli with
capsules arranged along it. Both ureters open at the genital pore. In the other fishes, the
kidneys lie often as “elongated compact masses along both sides of the vertebral column.
The two ureters unite to form a urethra, which always opens behind the anus, either
united with the opening of the genital organs, or behind this. In the sturgeon and hag-fish,
the anus and orifice of the urethra together form a cloaca. Bladder-like formations, which,
however, are morphologically homologous with the urinary bladder of mammals, occur in fishes,
either on each ureter (ray, hag-fish), or where both join. In amphibians, the vasa eflerentia of
the testicles are united with the urinary tubules ; the duct in the frog unites with the one on
the other side, and both conjoined opens into the cloaca, whilst the eapacious wrinary bladder
opens through the anterior wall of the cloaca. From reptiles upwards, the kidney is no longer
a persistent “Wolffian body, but a new organ. In reptiles, it is usually flattened and elongated;
the ureters open singly into the cloaca. Saurians and tortoises have a urinary bladder. In
birds, the isolated ureters open into the urogenital sinus, which opens into the cloaca, internal
to the excretory ducts of the genital apparatus. The urinary bladder is always absent. In
mammals, the kidneys often consist of many lobules, e.g., dolphin, ox.

Amongst invertebrates, the mollusca have excretory organs in the form of canals, which are
provided. with an outer and an inner opening. In the mussel, this canal is provided with a
sponge-like organ, often with a central cavity, and consisting of ciliated secretory cells, placed at
the base of the gills (organ of Bojanus). In gasteropods, with analogous organs, uric acid has
been found. Insects, spiders, and centipedes have the so-called Malpighian vessels, which are
excretory organs partly for uric acid and partly for bile. These vessels are long tubes, which
open into the first part of the large intestine. In crabs, blind tubes connected with the
intestinal tube, perhaps have the same functions. The vermes also have renal organs.

Historical.—Aristotle directed attention to the relatively large size of the human bladder—
he named the ureters. Massa (1552) found lymphatics in the kidney. Eustachius (+ 1580)
ligatured the ureters and found the bladder empty. Cusanus (1565) investigated the colour
and weight of the urine. Rousset (1581) described the muscular nature of the walls of the
bladder. Vesling described the trigone (1753). The first important chemical investigations on
the urine date from the time of van Helmont (1644). He isolated the solids of the urine and
found among them common salt ; he ascertained the higher specific gravity of fever-urine, and
ascribed the origin of urinary calculi to the solids of the urine. Scheele (1766) discovered uric
acid and calcium phosphate; Arand and Kunckel, phosphorus; Rouelle (1773), urea; and it got
its name from Fourcroy and Vauquelin (1799). Berzelius found lactic acid; Seguin, albumin in
pathological urine ; Liebig, hippuric acid ; Heintz and v. Pettenkofer, kreatin and kreatinin ; ;
Wollaston (1810), cystin. Marcet found xanthin ; and Lindbergson, magnesic carbonate,

Functions of the Skin.

283. STRUCTURE OF THE SKIN, HAIRS, AND NAIL.—The skin te 3 to
2-7 mm. thiek ; specific gravity, 1057) consists of-—

[1. The epidermis ;

2. The chorium, or cutis vera, with the papille (fig. 294). |

The epidermis (0°08 to 0°12 mm. thick) consists of many layers of stratified epithelial cells
united to each other by cement substance (figs. 293, 294). The superficial layers—stratum

438 STRUCTURE OF THE EPIDERMIS.

corneum—consist of several layers of dry horny non-nucleated squames, which swell up-in solu-
tion of caustic soda (fig. 294, E). [It is always thickest where intermittent pressure is applied,
as on the sole of the foot and palm of the hand.] The next layer is the stratum lucidum, which
is clear and transparent in a section of skin, hence the name, and consists of compact layers of
clear cells with vestiges of nuclei. Under this is the rete mucosum or rete Malpighii (fig. 294, @),
consisting of many layers of nucleated protoplasmic epithelial cells which contain pigment in
the dark races, and in the skin of the scrotum, and around the anus. [The superficial cells are
more fusiform and contain granules which stain deeply with carmine. They constitute, 3,
the stratum granulosum. In these cells the formation of keratin is about to begin, and the
granules have been called eleidin granules by Ranvier. They are chemically on the way to
be transformed into keratin. AJ] corneous structures contain similar granules in the area where
the cells are becoming corneous. Then follow
several layers of more or less polyhedral cells,
softer and more plastic in their nature, and ex-
hibiting the characters of so-called ‘* prickle
cells” (fig. 294, R). [The spaces between the
fibrils connecting adjacent cells are lymph spaces. ]

Ahn t sii

Si as ae ‘he deepest layers of cells are more or less
SS SR —_ Stratum columnar, and the cells are placed vertically upon
eee ee a ene papille. Granular leucocytes or wandering
ee ee cells are sometimes found between these cells.
Se SS oe This, the fourth layer, has been called the stratum

ERE ST wey Stratum

Malpighii. The rete Malpighii dips down between
adjacent papille and forms interpapillary pro-
i Stratum cesses. According to Klein, a delicate basement
=~——Tsam, membrane separates the epidermis from the true
"skin. ] The superficial layers of the epidermis are
continually being thrown off, while new cells are
continually being formed in the deeper layers of
the skin by proliferation of the cells of the rete
Malpighii. There is a gradual change in the
microscopic and chemical characters of the cells

‘ from the deepest to the superficial layers of the
epidermis. [In a vertical section of the skin
stained with picro-carmine, the S. granulosum
is deeply stained red, and is thus readily distin-
guished amongst the other layers of the epidermis.]

[Epider- ( (1) Stratum corneum, ) Cuticle

es SS et lucidum.

@
Sh
Ss. es
s SS ier
{ ete
SB) UBS ete oe

mis (2) Stratwm lucidum, . §
(fig. (3) Stratwm granulosum, Rete

293), {(4) Stratum Malpighii, Mucosum. ]

No pigment is formed within the epidermis
itself; when it is present, it is carried by leucocytes
from the subcutaneous tissue (Riehl, Ehrmann,

Fig. 293. Acby). This explains how it is that a piece of

Vertical section of the human epidermis ; white skin, transplanted to a negro, becomes ¥

the nerve-fibrils, 2, b, stained with black (Karg). |
gold chloride. The chorium (fig. 294, I, C) is beset over its

' entire surface by numerous (0°5 to 0°1 mm. high)
papille (fig. 294), the largest being upon the volar surface of the hand and foot, on the nipple
and glans penis. Most of the papillae contain a looped capillary (g), while in certain regions
some of them contain a touch-corpuscle (fig. 295, a). The papillae are disposed in groups,
whose arrangement varies in different parts of the body. In the palm of the hand and sole of
the foot they occur in rows, which are marked out by the existence of delicate furrows on the
surface visible to the naked eye. The chorium consists of a dense network of bundles of white
fibrous tissue mixed with a network of elastic fibres, which are more delicate in the papilla, In
silversmiths the elastic fibres are blackened by the partial deposition of reduced silver, and the
same obtains in those who take silver nitrate in such quantity as to produce argyria. The con-
nective-tissue contains many connective-tissue corpuscles and numerous leucocytes. The deeper
connective-tissue layers of the chorium gradually pass into the subcutaneous tissue, where they
form a trabecular arrangement of bundles, leaving between them elongated rhomboidal spaces
filled for the most part with groups of fat cells (fig. 294, a, a). [In microscopic sections, after
the action of alcohol, the fat cells not unfrequently contain crystals of margarin.] The long axis
of the rhomb corresponds to the greater tension of the skin at that part (C. Langer). In some
situations the subcutaneous tissue is devoid of fat [penis, eyelids]. In many situations, the
skin is fixed by solid fibrous bands to subjacent structures, as fascie, ligaments or bones

STRUCTURE OF THE EPIDERMIS. 439

(tenacula cutis); in other parts, as over bony prominences, burse partially lined with endo-
thelium and filled with synovia-like fluid, occur.
Smooth muscular fibres occur in the chorium in certain situations on extensor surfaces

LiL if \
\ \\) |

Fig. 294,

I, Vertical section of the skin, with a hair and sebaceous gland, T. Epidermis and chorium
shortened—1, outer ; 2, inner fibrous layer of the hair-follicle ; 3, its hyaline layer; 4,
outer root sheath ; 5, Huxley’s layer of the inner root sheath; 6, Henle’s layer of the
same ; p, root of the hair, with its papilla; A, arrector pili muscle ; C, chorium ; a, sub-
cutaneous fatty tissue ; 0, epidermis (horny layer); d, rete Malpighii; g, blood-vessels of
papille ; v, lymphatics of the same; /, horny or corneous substance; 7, medulla or pith ;
k, epidermis or cuticle of hair ; K, coil of sweet-gland ; E, epidermal scales (seen from above
and en face) from the stratum corneum ; R, prickle cells from the rete Malpighii ; , super-
ficial, and m, deep cells from the nail; H, hair magnified; ¢, cuticle; c, medulla, with cells;
J, f, fusiform fibrous cells of the substance of the hair; x, cells of Huxley’s layer ; 7, those
of Henle’s layer ; S, transverse section of a sweat-gland from the axilla ; a, smooth muscular
fibres surrounding it; ¢, cells from a sebaceous gland, some of them containing granules of oil.

(Neumann); nipple, areola mamme, prepuce, perineum, and in special abundance in the
tunica dartos of the scrotum. : a
‘(Guanin in the Skin.—The skin of many amphibians and reptiles contains brown or black
Pee ntl, and other granules of a white, silvery, or chalky appearance. Ewald and
rukenberg have shown that the latter consists of guanin, and that this substance is very
widely diffused in the skin of fishes, amphibians, and reptiles. Test :—Select a piece of skin

440 DEVELOPMENT OF THE NAILS AND HAIR.

m the belly of a frog; place it in a porcelain capsule as for the murexide test ; add concen-
erated nitric meld: snd eat to aied aha a yellow residue is obtained ; on adding a drop of
caustic soda a red colour is struck. The yellow residue gives no reaction with ammonia. If to
the fluid more water be added, and it be then heated, distributed over the surface of the cap-
sule, and cooled by blowing upon it, various shades of purple and violet are obtained. ]

The nails (specific gravity 1°19) consist of numerous layers of solid, horny, homogeneous,
epidermal, or nail-cells, which may be isolated with a solution of caustic alkali, when they
swell up and exhibit the remains of an elongated nucleus (fig. 294, m, 7). The whole under
surface of the nail rests upon the nail-bed ; the lateral and posterior edges lie in a deep groove,
the nail-groove (fig. 296, ¢). The chorium under the nail is covered throughout its entire
extent by longitudinal rows of papille (fig. 296, d@). Above this there lies, as in the skin, many
layers of prickle cells like those in the rete
Malpighii (fig. 294, d), and above this again
-~1 is the substance of the nail (fig. 296, a).
[The stratum granulosum is rudimentary in
the nail-bed. The substance of the nail re-
presents the stratum lucidum, there being |
no stratum corneum (A/ein).] The poste-
rior part of the nail-groove and the half
moon, brighter part or lunule, form the root
of the nail. They are, at the same time,
the matrix, from which growth of the nail
SS ee takes place. The lunule is present in an
Fig. 295. isolated ve Aue is due to ee ap a
Papille of the skin, epidermis removed, blood- Parency © the posterior parvjeh the, DAU,

Pomel injected ; Saaasneain a Wagner’s touch- ile Ratha eee nee nagemtpeeeiey

corpuscle, a, the others a capillary loop. ah aoa Ob Tne Coun Or he reve Balpignas

Growth of the Nail.—According to Unna, the matrix extends to the front part of the lunule.
The nail grows continually from behind forwards, and is formed by layers secreted or formed
by the matrix. These layers run parallel to the surface of the matrix. They run obliquely
from above and behind, downwards
and forwards, through the thick-
ness of the substance of the nail.
The nail is of the same thickness
; from the anterior margin of the
lunule forwards to its free margin.
Thus the nail does not grow in
Pg thickness in this region. In the

% course of a year the fingers produce
about 2 grms. of nail substance,
and relatively more in summer than
Z in winter.

; Development. —1. From _ the
second to the eighth month of
foetal life, the position of the nail is
indicated by a partial but marked
horny condition of the epidermis on
the back of the first phalanx, the

ce . ” .
: : é eponychium.” The remainder
Transverse section of one-half of a nail. a, nail-substance; o¢ this substance is represented

b, more open layer of cells of the nail-bed ; c, stratum : :

Malpighii of the nail-bed; d, transversely divided pa- pattie elie ae Miss

pille ; ¢, nail-groove ; 7, horny layer of e¢ projecting over the future nail from the sarhoe ae

the nail; g, papille of the skin on the back of the fier the furrow. 2. The future nail is
formed under the eponychium, with its first nail-cells still in front of the nail-groove ; then the
nail grows and pushes forward towards the groove. At the seventh month, the nail (itself
covered by the eponychium) covers the whole extent of the nail-bed. 3. When, at a later
period, the oi he pe splits off, the nail is uncovered. After birth the papille are formed on
the bed of the nail, while simultaneously the matrix passes backwards to the most posterior
part of the groove (Unna).

Absence of Hairs.—The whole of the skin, with the exception of the palmar surface of the
hand, sole of the foot, dorsal surface of the third phalanx of the fingers and toes, outer
surface of the eyelids, glans penis, inner surface of the prepuce, and part of the labia is covered
with hairs, which may be strong or fine (lanugo). oe

A Hair (specific gravity 1°26) is fixed by its lower extremity (root) in a depression of the —
skin or a hair-follicle (fig. 294, I, ») which passes obliquely through the thickness of the skin, :

STRUCTURE OF A HAIR-FOLLICLE. 441

sometimes as far as the subcutaneous tissue. The structure of a hair-follicle is the following :
1. The outer fibrous layer (figs. 294, 1, 293), composed of interwoven bundles of connective-
tissue, arranged for the most part longitudinally, and provided with numerous blood-vessels
and nerves. [It is just the connective-tissue of the surrounding chorium.] 2. The inner
fibrous layer (figs. 294, 2, 297) consists of a layer of fusiform cells (? smooth muscular fibres)
arranged circularly. [It does not extend throughout the whole length of the follicle.] 3. In-
side this layer is a transparent, hyaline, glass-like basement membrane (figs. 292, 3, 297),
which ends at the neck of the hair-follicle ; while above it is continued as the basement
membrane which exists between the epidermis and chorium. In addition to these coverings, a
hair-follicle has epithelial coverings which must be regarded in relation to the layers of the
epidermis. Immediately within the glass-like membrane is the outer root-sheath (figs. 294, 4,
297, 298), which consists of so many layers of epithelial cells that it forms a conspicuous
covering. It is, in fact, a direct continuation of the stratum Malpighii, and consists of many
layers of soft cells, the cells of the outer layer being cylindrical. Towards the base of the hair-
follicle it becomes narrower, and is united to, and continues with the cells of the root of the

"hair itself, at least in fully developed hairs. The horny layer of the epidermis continues to

retain its properties as far down as the orifice of the seba-
ceous follicle; below this point, however, it is continued as
the inner root-sheath. ‘This consists of (1) a single layer
of elongated, flat, homogeneous, non-nucleated cells (figs.
294, 6, 297, f—Henle’s layer) placed next and within the
outer root-sheath. Within this lies (2) Hualey’s layer (figs.
294, 5, 297, g), consisting of nucleated elongated polygonal
cells (fig. 294, x, and 3), while the cuticle of the hair-follicle
is composed of cells analogous to those of the surface of the
hair itself. Towards the bulb of the hair these three layers
become fused together.

Neha of a hair-follicle arranged from without in-
wards—

(a) Longitudinally arranged fibrous tissue.
(6) Circularly arranged spindle cells.
2. Glass-like (hyaline) membrane.
Nee (a) Outer root-sheath. , p
3. Epes (6) Inner root-sheath. ea ch oe
yers, (c) Cuticle of the hair. J
4. The hair itself.

The arrector pili muscle (fig. 294, A) is a fan-like arrange-
ment of a layer of smooth muscular fibres, attached below
to the side of a hair-follicle and extending towards the
surface of the chorium ; as it stretches obliquely upwards,
it subtends the obtuse angle formed by the hair-follicle and Fig. 297.
the surface of the skin, [or, in other words, it forms an acute m, + —
angle with the hair-follicle, and between it and the follicle Sc easel eae pa
lies the sebaceous gland]. When these muscles contract, ana A. hilgodevesssles <6, 1aner
they raise and erect- the hair-follicles, producing the con- circularly disposed layer ah
dition of cutis anserina or gooseskin. As the sebaceots glass like layer ; ¢, outer tf g,
gland lies in the angle between the muscle and the hair- aa rooteheath f AOR
follicle, contraction of the muscle compresses the gland and jaye’ of the same (H onal
favours the evacuation of the sebaceous secretion. It also sheath). g, inner layer of the
compresses the blood-vessels of the papilla (Una). Baie (Huxley’s sheath); h

The hair with its large bulbous extremity—hair-bulb— Quticle- J. hair oe
sits upon, or rather embraces, the papilla. It consists of (1) hse ;
the marrow or medulla (fig. 294, 7), which is absent in woolly hair and in the hairs formed during
the first year of life. It is composed of two or three rows of cubical cells (H, c). (2) Outside
this lies the thicker cortex (2), which consists of elongated, rigid, horny, fibrous cells (H, /, /),
while in and between these cells lie the pigment granules of the hair. (3) The surface of the
hair is covered with a cuticle (x), and consists of imbricated layers of non-nucleated squames.

Grey Hair.—When the hair becomes grey, as in old age, this is due to defective formation of
pigment in the cortical part. The silvery appearance of white hair is increased when small air-
cavities are developed, especially in the medulla and to a less extent in the cortex, where they
reflect the light. Landois records a case of the hair becoming suddenly grey, in a man whose
hair became grey during a single night, in the course of an attack of delirium tremens.
Numerous air-spaces were found throughout the entire marrow of the (blond) hairs, while the
hair-pigment still remained.

ood-Pigment in Hairs,—The feelers of albino rabbits contain in some part of their sub-
stances blood-pigment (Sig. Mayer). ]

1. Fibrous layers,

442

DEVELOPMENT AND PROPERTIES OF HAIR.

Development of Hair.—According to Killiker, from the 12th to 13th week of intra-uterine
life, solid finger-like processes of the epidermis are pushed down into the chorium. The process
becomes flask-shaped, while the central cells of the cylinder become elongated and form a
conical body, arising as it were from the depth of the recess. It soon differentiates into an

inner darker part,

———<

—TF

=

—s— =

ee =:
ve ——
LI)

tek

th

faa

rm}
oe
———

See nner Mee

wo

which becomes the hair, and a thinner, clearer layer covering the former,

the inner root-sheath. The outer cells, i.¢., those lying
next the wall of the sac, form the outer root-sheath.
Outside this, again, the fibrous tissue of the chorium
forms a rudimentary hair-follicle, while one of the
papille grows up against it, indents it, and becomes
embraced by the bulb of the hair. This is the hair
papilla, which contains a loop of blood-vessels. The
cells of the bulb of the hair proliferate rapidly and thus

' the hair grows in length. The point of the hair is

thereby gradually pushed upwards, pierces the inner
root-sheath, and passes obliquely through the epidermis.
The hairs appear upon the forehead at the 19th week ;
at the 23rd to 25th week the lanugo hairs appear free,
and they have a characteristic arrangement on different
parts of the body.

Physical Properties. —Hair has very considerable
elasticity (stretching to 0°33 of its length), considerable
cohesion (carrying 3 to 5 lbs.), resists putrefaction for
a long time, and is highly hygroscopic. The last pro-

er perty is also possessed by epidermal scales, as is proved
dies by the pains that occur in old wounds and scars during

A

eT |
a pel

damp weather.

Growth of a hair occurs by proliferation of the cells on
the surface of the hair papilla, these cells representing
the matrix of the hair. Layer after layer is formed, and
gradually the hair is raised higher within its follicle.

Change of the Hair.—According to one view, when
the hair has reached its full length, the process of forma-
tion on the surface of the hair papilla is interrupted ;
the root of the hair is raised from the papilla, becomes
horny, remains almost devoid of pigment, and is gradu-
ally more and more lifted upwards from the surface of
the papilla, while its lower bulbous end becomes split
up like a brush. The lower empty part of the hair-
follicle becomes smaller, while on the old papilla a new
formation of a hair begins, the old hair at the same time
falling out (Unna). According to Stieda, the old papilla
disappears, while a new one is formed in the hair-follicle,
and from it the new hair is developed. According to
Kolliker, again, both processes obtain.

284, THE GLANDS OF THE SKIN.—The sebaceous

F 18: 298. _ glands (fig. 294, I, T) are simple acinous glands, which
Section of a hair-follicle while a hair open by a duct into the hair-follicles of large hairs near
is being shed. a, outer and middle their upper part; in the case of small hairs, they may
sheaths of hair-follicle; }, hyaline project Font the duct of the gland (fig. 299), In some
membrane ; ¢, papilla, with a capil- situations, the ducts of the glands open free upon the
lary ; d, outer, ¢, inner root-sheath ; surface, ¢.g., the glands of labia minora, glans, prepuce
J, cuticle of the latter ; g, cuticle of (Tyson’s glands), and the red margins of the lips. The
the hair; h, young non-medullated Jargest glands occur in the nose and in the labia; they
hair; 7, tip of new hair; 7, hair- are absent only from the vola manus and planta pedis.
knob of the shed hair, with &, the The oblong alveoli of the gland consist of a basement
remainder of the cast-off outer root- sicuteine Vad with small polyhedral nucleated granu-
sheath. lar secretory cells (fig. 294, ¢). Within this are other

polyhedral cells, whose substance contains numerous oil-globules ; the cells become more fatty
as we proceed towards the centre of the alveolus. The cells lining the duct are continuous
with those of the outer root-sheath. The detritus formed by the fatty metamorphosis of the
cells constitutes the sebum or sebaceous secretion. [If the “oil or coceygeal-gland” of a duck
be removed, it is found that, when the animal is submerged, it takes up between its feathers
about the same amount of water as an intact duck ; but it retains 2 to 24 times. as much water

in its feathers (Max Joseph). ]
The sweat-glands (fig. 294,

4,
I, %), sometimes called sudoriparous glands, consist of a long

cS

THE SWEAT-GLANDS. | A43

blind tube, whose lower end is arranged in the form of a coil placed in the areolar tissue under
the skin, while the somewhat smaller upper end or excretory portion winds in a vertical,
slightly wave-like manner, through the chorium, and in a cork-screw or spiral manner through
the epidermis, where it opens with a free, somewhat trumpet-shaped, mouth. The glands are
very numerous and large in the palm of the hand, sole of the foot, axilla, forehead, and around
the nipple; few on the back of the trunk, and are absent on the glans, prepuce, and margin of
the lips. The circumanal glands and the ceruminous glands of the external auditory meatus,
and Moll’s glands, which open into the hair-follicles of the eyelashes, are modifications of the
sweat-glands.

Each gland-tube consists of a basement membrane lined by cells; the excretory part or
sweat-canal of the tube is lined by several layers of cubical cells, whose surface is covered by a
delicate cuticular layer, a small central lumen being
left. Within the coil the structure is different. The
first part'of the coil resembles the above, but as the
coil is the true secretory part of the gland, its structure
differs from the sweat-canal. This, the so-called distal
portion of the tube, is lined by a single layer of moder-
ately tall clear nucleated cylindrical epithelium (fig.
294, S), often containing oil-globules. Smooth muscu-
lar fibres are arranged longitudinally along the tube in
the large glands (fig. 294, S, a). There is a distinct
lumen present in the tube. As the duct passes through
the epidermis, it winds its way between the epidermal
cells without any independent membrane lining it
(Heynold). A network of capillaries surrounds the
coil. Before the arteries split up into capillaries, they
form a true rete mirabile around the coil (Briicke). This
is comparable to the glomerulus of the kidney, which
may also be regarded as a rete mirabile. Numerous
nerves pass to form a plexus, and terminate in the
glands (Tomsa).

The total number of sweat-glands is estimated by
Krause at 24 millions, which gives a secretory surface
of nearly 1800 square metres. These glands secrete
sweat. Nevertheless, an oily or fatty substance is often
mixed with the sweat. In some animals (glands in
the sole of the foot of the dog, and in birds) this oily
secretion is very marked.

Numerous lymphatics occur in the cutis, some arise
by a blind end, and others from loops within the papilla
on a plane lower than the vascular capillary. [These
open into more or less horizontal networks of tubular
lymphatics in the cutis, and these again into the wide
lymphatics of the subcutaneous tissue, which are well : ’
provided with valves.] Special lymphatic spaces are Sebaceous gland, with % lanugo hair. a,
disposed in relation with the hair-follicles and their granular epithelium ; 6, rete Malpighii
glands (Newmann), [and also with the fat (K/ein). The ieee with a; c, fatty cells and
lymphatics of the skin are readily injected with Berlin free fat; d, acini; ¢, hair-follicle, with
blue by the puncture method]. a small hair, f.

The blood-vessels of the skin are arranged in several systems. There is a superficial system,
from which proceed the capillaries for the papille. There is a deeper system of vessels which
supplies special blood-vessels to (a) the fatty tissue ; (b) the hair-follicles, each of which has a
special vascular arrangement of its own, and in connection with this each sebaceous gland
receives a special artery ; (c) an artery goes also to each coil of a sweat-gland, where it forms a
dense plexus of capillaries ( Z’omsa).

285. THE SKIN AS A PROTECTIVE COVERING.—The subcutaneous
fatty tissue fills up the depressions between adjoisiing parts of the body and covers
projecting parts, so that a more rounded appearance of the body is thereby ob-
tained. It also acts as a soft elastic pad and protects delicate parts from external
pressure (sole of the foot, palm of the hand), and it often surrounds and _ protects
blood-vessels, nerves, &c. It is a bad conductor of heat, and thus acts as one of
the factors regulating the radiation of heat (§ 214, II., 4), and, therefore, the
temperature of the body. The epidermis and cutis vera also act in the same manner
(§ 212). Klug found that the heat-conduction is less through the skin and sub-

444 CUTANEOUS RESPIRATION : SEBUM—SWEAT.

cutaneous fatty tissue than through the skin alone; the epidermis conducts heat
less easily than the fat and the chorium.

The solid, elastic, easily movable cutis affords a good protection against external,
mechanical injuries; while the dry, impermeable, horny epidermis, devoid of
nerves and blood-vessels, affords a further protection against the absorption of
poisons, and at the same time it is capable of resisting, to a certain degree, thermal
and even chemical actions. A thin layer of fatty matter protects the free surface of
the epidermis from the macerating action of fluids, and from the disintegrating
action of the air. The epidermis is important in connection with the fluids of the
body. It exerts pressure upon the cutaneous capillaries, and, to a limited extent, |
prevents too great diffusion of fluid from the cutaneous vessels. Parts of the skin
devoid of epidermis are red and always moist. When dry, the epidermis and the
epidermal appendages are bad conductors of electricity (§ 326). Lastly, the exist-
ence of uninjured epidermis prevents adjoining parts from growing together.

As the epidermis is but slightly extensile it is stretched over the folds and papille of the cutis

vera, which becomes level when the skin is stretched, and the papille may even disappear with
strong tension (Lewinski).

286. CUTANEOUS RESPIRATION: SEBUM—SWEAT,—The skin, with a
surface of more than 1} square metre, has the following secretory functions :—

1. The respiratory excretion ;

2. The secretion of sebaceous matter ; and

3. The secretion of sweat.

[Besides this the skin is protective, contains sense-organs, is largely concerned
in regulating the temperature, and may be concerned in absorption. |

1. Respiration by the skin has been referred to (§ 131). The organs concerned are the tubes
of the sweat-glands, moistened as they are with fluids, and surrounded by a rich network of
capillaries. 1t is uncertain whether or not the skin gives off a small amount of N or ammonia.
Rohrig made experiments upon an arm placed in an air-tight metal box. According to him
the amount of CO, and H,O excreted is subject to certain daily variations ; it is increased by
digestion, increased temperature of the surroundings, the application of cutaneous stimuli, and
by impeding the pulmonary respiration. The exchange of gases also depends upon the vascu-
larity of certain parts of the skin, while the cutaneous absorption of O also depends upon the
number of coloured corpuscles in the blood.

In frogs and other amphibians, with a thin, always moist epidermis, the cutaneous respir-
ation is more considerable than in warm-blooded animals. In winter, in frogs, the skin alone
yields ? of the total amount of CO, excreted ; in summer, 3 of the same (Bidder) ; thus, in
these animals it is a more important respiratory organ than the lungs themselves.

Suppression of the cutaneous activity by varnishing or dipping the skin in oil, causes death
by asphyxia (frogs) sooner than ligature of the lungs. Varilahing the Skin.—When the skin
of a warm-blooded animal is covered with an impermeable varnish [such as gelatin] (Fourcault,
Becquerel, Brechet), death occurs after a time, probably owing to the loss of too much heat.
The formation of crystalline ammonio-magnesic phosphate in the cutaneous tissue of such
animals (Edenhuizen) is not sufficient to account for death, nor are congestion of internal
organs and serous effusions satisfactory explanations. The retention of the volatile substances
(acids) present in the sweat is not sufficient. Strong animals live longer than feeble ones ;
horses die after several days (Gerlach) ; they shiver and lose flesh. The larger the cutaneous
surface left unvarnished, the later does death take place. Rabbits die wheat of their surface
is varnished. When the entire surface of the animal is varnished, the temperature rapidly
falls (to 19°), the poe and respirations vary; usually they fall when the varnishing process is
limited ; increased frequency of respiration has been observed (§ 225). Pigs, dogs, horses, when
one-half of the body is varnished, exhibit only a temporary fall of the temperature, and show
signs of weakness, but do not die (Ellenberger and Hofmeister). [In extensive burns of the
skin, not only is there disintegration of the coloured blood-corpuscles (v. Lesser), but in some
cases ulcers occur in the duodenum. The cause of the ulceration, however, has not been ascer-

tained satisfactorily (Curling). ]

2. Sebaceous Secretion.—The fatty matter as it is excreted from the acini of
the sebaceous glands is fluid, but even within the excretory duct of the gland it
stagnates and forms a white fat-like mass, which may sometimes be expressed (at
the side of the nose) as a worm-like white body, the so-called comedo. The

THE SWEAT. A45

sebaceous matter keeps the skin supple, and prevents the hair from becoming too
dry. Microscopically, the secretion is seen to contain innumerable fatty granules,
a few gland-cells filled with fat, visible after the addition of caustic soda, crystals
of cholesterin, and in some men a microscopic mite-like animal (Demodex folli-
-¢eulorum). : |

Chemical Composition.—The constituents are for the most part fatty ; chiefly olezn (fluid)
and palmitin (solid) fat, soaps, and some cholesterin ; a small amount of albumin and unknown
extractives. Amongst the inorganic constituents, the insoluble earthy phosphates are most
abundant ; while the alkaline chlorides and phosphates are less abundant.

The vernix caseosa, which covers the skin of a new-born child, is a greasy mixture of seba-
ceous matter and macerated epidermal cells (containing 47°5 per cent. fat), A similar product
is the smegma preeputialis (52°8 per cent. fat), in which an ammonia soap is present.

The cerumen or ear-wax is a mixture of the secretions of the ceruminous glands of the ear
(similar in structure to the sweat-glands) and the sebaceous glands of the auditory canal. Besides
the constituents of sebum, it contains yellow or brownish particles, a bitter yellow extractive
substance derived from the ceruminous glands, potash soaps, and a special fat. The secretion
of the Meibomian glands is sebum.

[Lanoline,—Liebreich finds in feathers, hairs, wool, and keratin-tissues generally, a choles-
terin fat, which however is not a true fat, although it saponifies, but an ethereal compound of
certain fatty acids with cholesterin. In commerce it is obtained from wool, and is known by
the above name; it forms an admirable basis for ointments, and it is very readily absorbed by
the skin.] Thus, the fat-like substance for protecting the epidermis is partly formed along
with keratin in the epidermis itself.

3. The Sweat.—The sweat is secreted in the coil of the sweat-glands. As long
as the secretion is small in amount, the water secreted is evaporated at once from
the skin along with the volatile constituents of sweat ; as soon, however, as the
secretion is increased, or evaporation is prevented, drops of sweat appear on the
surface of the skin. The former is called insensible perspiration, and the latter
sensible perspiration. [Broadly, the quantity is about 2 lbs. in twenty-four
hours. |

The sensible perspiration varies greatly; as a rule, the right side of the body perspires more
freely than the left. The palms of the hands secrete most, then follow the soles of the feet,
cheek, breast, upper arm, and fore-arm (Peiper). It falls from morning to mid-day, and rises
again towards evening, reaching its maximum before midnight. Much moisture and cold in
the surrounding atmosphere diminish it, and so does diuresis. In children, the insensible per-
spiration is relatively great. The drinking of water favours it, alcohol diminishes it (H. Schmid).

Method. —Sweat is obtained from a man by placing him in a metallic vessel in a warm bath;
the sweat is rapidly secreted and collected in the vessel. In this way Favre collected 2560
grammes of sweat in 14 hour. An arm may be inclosed in a cylindrical vessel, which is fixed
air-tight round the arm with an elastic bandage (Schottii).

Amongst animals, the horse sweats, so does the ox, but to a less extent ; the vola and planta
of apes, cats, and the hedgehog secrete sweat ; the snout of the pig sweats (?), while the goat,
rabbit, rat, mouse, and dog are said not to sweat (Luchsinger). [The skin over the body and
the pad on the dog’s foot contain numerous sweat-glands, which open free on the surface of the
pad and into the hair-follicles on the general surface of the skin (W. Stirling).]

Microscopically.—The sweat contains only a few epidermal scales accidentally mixed with it,
and fine fatty granules from the sebaceous glands.

Chemical Composition.—Its reaction is alkaline, although it frequently is acid,
owing to the admixture of fatty acids from decomposed sebum. During profuse
secretion it becomes neutral, and lastly alkaline again (Z'riimpy and Luchsinger).
The sweat is colourless, slightly turbid, of a saltish taste, and has a characteristic
odour varying in different parts of the body ; the odour is due to the presence of
volatile fatty acids. The constituents are watér, which is increased by copious
draughts of that fluid, and solids, which amount to 1°180 per cent. (0°70 to 2°66 per
cent.—Funke), and of these 0-96 per cent. is organic and 0°33 inorganic. Amongst
the organie constituents are neutral fats (palmitin, stearin), also present in the
sweat of the palm of the hand, which contains no sebaceous glands, cholesterin,
volatile fatty acids (chiefly formic, acetic, butyric, propionic, caproic, capric acids),
varying qualitatively and quantitatively in different parts of the body.—These
acids are most abundant in the sweat first (acid) secreted. There are also traces

446 INFLUENCE OF NERVES ON THE SECRETION OF SWEAT.

of albumin (similar to casein) and urea, about 0°1 per cent. In uremic conditions
(anuria in cholera) urea has been found crystallised on the skin. When the
secretion of sweat is greatly increased, the amount of urea in the urine is diminished,
both in health and in uremia (Leube). The nature of the reddish-yellow pigment,
which is ‘extracted from the residue of sweat by alcohol, and coloured green by
oxalic acid, is unknown. Amongst inorganic constituents, those that are easily
soluble are more abundant than those that are soluble with difficulty, in the pro-
portion of 17 to 1 ; sodium chloride, 0-2 ; potassium chloride, 0°2 ; sulphates, 0:01
per 1000, together with traces of earthy phosphates and sodium phosphate. Sweat
contains CO, in a state of absorption and some N. When decomposed with free
access of air, it yields ammonia salts (Gorup-Besanez).

Excretion of Substances.—Some substances when introduced into the body reappear in the
sweat—benzoic, cinnamic, tartaric, and succinic acids are readily excreted ; quinine and potassic
iodide with more difficulty. Mercurie chloride, arsenious and arsenic acids, sodium and
potassium arseniate have also been found. After taking arseniate of iron, arsenious acid has
been found in the sweat, and iron in the urine. Mercury iodide reappears as a chloride in the
sweat, while the iodine occurs in the saliva.

Formation of Pigments.—The leucocytes furnish the material, and the pigment
is deposited in granules in the deeper layers, and, to a less extent, in the upper
layers, of the rete Malpighii. This occurs in the folds around the anus, scrotum,
nipple, {especially during pregnancy |, and everywhere in the coloured races. There
is a diffuse, whitish-yellow pigment in the stratum corneum, which becomes darker
in old age. The pigmentation depends on chemical processes, reduction taking
place, and these processes are aided by light. Granular pigment lies also in the
layers of prickle cells. The dark coloration of the skin may be arrested by free O
[hydric peroxide], while the corneous change is prevented at the same time
(Unna). .

Pathological.—To this belongs the formation of liver spots or cholasma, freckles, and the
pigmentation of Addison’s disease, [pigmentation round old ulcers, &c.] (§ 103, IV.). [The
curious cases of pigmentation, especially in neurotic women, ¢.g., in the eyelids, deserve further
study in relation to the part played by the nervous system in this process. ]

287. INFLUENCE OF NERVES ON THE SECRETION OF SWEAT.—
The secretion of the skin, which averages about z}, of the body-weight, 2.e., about
double the amount of water excreted by the lungs, may be increased or diminished.
The liability to perspire varies much in different individuals, The following con-
ditions influence the secretion—1. Increased temperature of the surroundings
causes the skin to become red, while there is a profuse secretion of sweat (§ 214,
II., 1). Cold, as well as a temperature of the skin about 50° C., arrests the secretion.
2. A very watery condition of the blood, ¢.g., after copious draughts of warm
water, increases the secretion. Increased cardiac and vascular activity, whereby
the blood-pressure within the cutaneous capillaries is increased, have a similar effect ;
increased sweating follows increased muscular activity. 3. Certain drugs favour
sweating, ¢.g., pilocarpin, Calabar bean, strychnin, picrotoxin, muscarin, nicotin,
camphor, ammonia compounds; while others, as atropin and morphia, in large doses,
diminish or paralyse the secretion. [Drugs which excite copious perspiration, so
that it stands as beads of sweat on the skin, are called sudorifics, while those that
excite the secretion gently are diaphoretics, the difference being one of degree.
Those drugs which lessen the secretion are called antihydrotics.| 4. It is import-
ant to notice the antagonism which exists, probably upon mechanical grounds,
between the secretion of sweat, the urinary secretion, and the evacuation of the
intestine. Thus copious secretion of urine (e.g., in diabetes) and watery stools
coincide with dryness of the skin. If the secretion of sweat be increased, the
percentage of salts, urea, and albumin is also increased, whilst the other organic
substances are diminished. The more saturated the air is with watery vapour, the
sooner does the secretion appear in drops upon the’ skin, while in dry air or air in

INFLUENCE OF NERVES ON THE SECRETION OF SWEAT. 447

motion, owing to the rapid evaporation, the formation of drops of sweat is prevented,
or at least retarded. [The complementary relation between the skin and kidneys
is well known. In summer, when the skin is active, the kidneys separate less
water; in winter, when the skin is less active, it is cold and comparatively
bloodless, while the kidneys excrete more water, so that the action of these two
organs is in inverse ratio. |

The influence of nerves upon the secretion of sweat is very marked.

I. Just as in the secretion of saliva (§ 145), vaso-motor nerves are usually in
action at the same time as the proper secretory nerves ; the vaso-dilator nerves
(sweating with a red congested skin) are most frequently involved. The fact that
secretion of sweat does occasionally take place when the skin is pale (fear, death-
agony) shows that, when the vaso-motor nerves are excited, so as to constrict the
cutaneous blood-vessels, the sweat-secretory nerve-fibres may also be active.

Under certain circumstances, the amount of blood in the skin seems to determine the
occurrence of sweating; thus, Dupuy found that section of the cervical sympathetic caused
secretion on that side of the neck of a horse; while Nitzelnadel found that percutaneous
electrical stimulation of the cervical sympathetic in man, limited the sweating.

[We may draw a parallel between the secretion of saliva and that of sweat. Both are formed
in glands derived from the outer layer of the embryo. Both secretions are formed from lymph
supplied by the blood-stream, and if the lymph be in sufficient quantity, secretion may take
place when there is no circulation, although in both cases secretion is most lively when the
circulation is most active and the secretory nerves of both are excited simultaneously ; both
glands have secretory nerves distinct from the nerves of the blood-vessels; both glands may be
paralysed by the action of the nervous system, or in disease (fever), or conversely, both are
paralysed by atropine and excited by other drugs, ¢.g., pilocarpin. In the gland cells of both,
histological changes accompany the secretory act, and no doubt similar electromotor pheno-
mena occur in both glands. ]

II. Secretory nerves, altogether independent of the circulation, control the
secretion of sweat. Stimulation of these nerves, even in a limb which has been
amputated in a kitten, causes a temporary secretion of sweat, 2.e., after complete
arrest of the circulation (Goltz, Kendall and Luchsinger, Ostroumow). In the intact
condition of the body, however, profuse perspiration, at all events, is always
associated with simultaneous dilatation of the blood-vessels (just as, in stimulation
of the facial nerve, an increased secretion of saliva is associated with an increased
blood-stream—S 145, A, I.). The secretory nerves and those for the blood-vessels
seem to lie in the same nerve-trunks.

The secretory nerves for the hind limbs (cat) lie in the sciatic nerve. Luch-
singer found that stimulation of the peripheral end of this nerve caused renewed
secretion of sweat for a period of half an hour, provided the foot was always wiped
to remove the sweat already formed. If a kitten, whose sciatic nerve is divided on
one side, be placed in a chamber filled with heated air, all the three intact limbs
soon begin to sweat, but the limb whose nerve is divided does not, nor does it do
so when the veins of the limb are ligatured so as to produce congestion of its
blood-vessels. [The cat sweats only on the hairless soles of the feet.| As to the
course of the secretory fibres to the sciatic nerve, some pass directly from the
spinal cord (Vulpian), some pass into the abdominal sympathetic (Luchsinger,
Nawrocki, Ostroumow), through the rami communicantes and the anterior spinal
roots from the upper lumbar and lower dorsal spinal cord (9th to 13th dorsal
vertebree—cat), where the sweat-centre for the lower limbs is situated.

The sweat-centre may be excited directly :—(1) By a highly venous condition
of the blood, as during dyspneea, ¢.g., the secretion of sweat that sometimes pre-
cedes death; (2) by overheated blood (45° C.) streaming through the centre ; (3)
by certain poisons (see p. 446). The-centre may be also excited reflexly, although
the results are variable, ¢.g., stimulation of the crural and peroneal nerves, as well
as the central end of the opposite sciatic nerve, excites it. [The pungency of
mustard in the mouth may excite free perspiration on the face. |

7

448 PATHOLOGICAL VARIATIONS.

Anterior Extremity.—The secretory fibres lie in the ulnar and median nerves,
for the fore-limbs of the cat ; most of them, or indeed all of them (Vawrockz), pass
into the thoracic sympathetic (Ggl. stellatum), and part (?) run in the nerve-roots
direct from the spinal cord (Luchsinger, Vulpian, Ott). A similar sweat-centre
for the upper limbs lies in the lower part of the cervical spinal cord. Stimulation
of the central ends of the brachial plexus causes a reflex secretion of sweat upon
the foot of the other side (Adamkiewicz). At the same time the hind feet also
perspire.

Pathological. —Degeneration of the motor ganglia of the anterior horns of the spinal cord
causes loss of the secretion of sweat, in addition to paralysis of the voluntary muscles of the

trunk. The perspiration is increased in paralysed as well asin cedematous limbs. In nephritis,
there are great variations in the amount of water given off by the skin.

Head.—The secretory fibres for this part (horse, man, snout of pig) lie in the
thoracic sympathetic, pass into the ganglion stellatum, and ascend in the cervical
sympathetic. Percutaneous electrical stimulation of the cervical sympathetic in
man, causes sweating of that side of the face and of the arm (IZ. Meyer). In the
cephalic portion of the sympathetic, some of the fibres pass into, or become applied
to, the branches of the trigeminus, which explains why stimulation of the infra-
orbital nerve causes secretion of sweat. Some fibres, however, arise directly from
the roots of the trigeminus (Luchsinger), and the facial (Vulpian, Adamkiewicz).
Undoubtedly the cerebrum has a direct effect either upon the vaso-motor nerves
(p. 447, I.) or upon the sweat-secretory fibres (II.), as in the sweating produced by
psychical excitement (pain, fear, &c.).

Adamkiewicz and Senator found that, in a man suffering from abscess of the motor region of
the cortex cerebri for the arm, there were spasms and perspiration in the arm.

Sweat-Centre.—According to Adamkiewicz, the medulla oblongata contains the
dominating sweat-centre (§ 373). When this centre is stimulated in a cat, all
the four feet sweat, even three-quarters of an hour after death (Adamkiewicz),

III. The nerve-fibres which terminate in the smooth muscular jibres of the sweat-
glands act upon the excretion of the secretion. 7

[Changes in the Cells during Secretion.—In the resting glands of the horse, the cylindrical
cells are clear with the nucleus near their attached ends, but after free perspiration they become
granular, and their nucleus is more central (Renaut). ]

If the sweat-nerves be divided (cat), injection of pilocarpin causes a secretion of sweat, even
at the end of three days. After a longer period than six days, there may be no secretion at all.
This observation coincides with the phenomenon of dryness of the skin in paralysed limbs.
Dieffenbach found that transplanted portions of skin first began to sweat when their sensibility
was restored. Ifa motor nerve (tibial, median, facial) of a man be stimulated, sweat appears
on the skin over the muscular area supplied by the nerve, and also upon the corresponding area
of the opposite non-stimulated side of the body. This result occurs when the circulation is
arrested as well as when it is active. Sensory and thermal stimulation of the skin always cause
a bilateral reflex secretion independently of the circulation. The area of sweating is inde-
pendent of the part of the skin stimulated.

288. PATHOLOGICAL VARIATIONS.—1. Anidrosis or diminution of the secretion of
sweat occurs in diabetes and the cancerous cachexia, and along with other disturbances of
nutrition of the skin in some nervous diseases, ¢.g., in dementia paralytica ; in some limited
regions of the skin, it has occurred in certain tropho-neuroses, ¢.g., in unilateral atrophy of the
face and in paralysed parts. In many of these cases it depends upon paralysis of the corre-
sponding nerves or their spinal sweat-centres.

2. Hyperidrosis, or increase of the secretion of sweat, occurs in easily excitable persons, in
consequence of the irritation of the nerves concerned (§ 288), ¢.g., the sweating which occurs in
debilitated conditions and in the hysterical (sometimes on the head and hands), and the so-
called epileptoid sweats (Zulenburg). Sometimes the increase is confined to one side of the head
(H. unilateralis), This condition is often accompanied with other nervous phenomena, partly
with the symptoms of paralysis of the cervical sympathetic (redness of the face, narrow pupil),
partly with symptoms of stimulation of the sympathetic (dilated pupil, exophthalmos). It may
occur without these phenomena, and is due perhaps to stimulation of the proper secretory fibres
alone. [Increased sweating is very marked in certain fevers, both during their course and at
the crisis in some; while the sweat is not only copious but acid in acute rheumatism. The
“* night-sweats ” of phthisis are very marked and disagreeable. ] ' ye

CUTANEOUS ABSORPTION. 449

3. Paridrosis or qualitative changes in the secretion of sweat, ¢.g., the rare case of ‘‘ sweating
of blood” (hematohidrosis), is sometimes unilateral. According to Hebra, in some cases this
condition represents a vicarious form of menstruation. It is, however, usually one of many
phenomena of nervous affections. Bloody sweat sometimes occurs in yellow fever. Bile-
pigments have been found in the sweat in jaundice; blue sweat from indigo (Bizio), from
pyocyanin (the rare blue colouring-matter of pus), or from phosphate of the oxide of iron (Osc.
Kollmann) is extremely rare. Such coloured sweats are called chromidrosis. Numerous micro-
organisms (which, however, are innocuous) live between the epidermal scales and on the hairs,
two varieties of Saccharomycetes ; in cutaneous folds Leptothrix epidermalis, various Schizo-
mycetes, and five kinds of Micrococci; and between the toes—-Bacterium graveoleus (Bordoni-
Uffreduzzi), which causes the odour of the sweat of the feet. Micro-organisms are also the
cause of yellow, blue, and red sweat ; the last is due to Micrococcus hematodes. .

Grape-sugar occurs in the sweat in diabetes mellitus; uric acid and cystin very rarely ; and
in the sweat of stinking feet, leucin, tyrosin, valerianic acid, and ammonia. Stinking sweat
(bromidrosis) is due to the decomposition of the sweat, from the presence of a special micro-
organism (Bacterium foetidum—Thin). Inthe sweating stage of ague butyrate of lime has been
found, while in the sticky sweat of acute articular rheumatism there is more albumin (Anseliino),
and the same is the case in artificial sweating (Lewbe); lactic acid is present in the sweat in
puerperal fever.

The sebaceous secretion is sometimes increased, constituting seborrhcea, which may be local
or general, It may be diminished (Asteatosis cutis). The sebaceous glands degenerate in old
people, and hence the glancing of the skin (Rémy). If the ducts of the glands are occluded the
sebum accumulates. Sometimes the duct is occluded by black particles or ultramarine (Uana)
from the blue used in colouring the linen. When pressed out, the fatty worm-shaped secretion
is called ‘‘ comedo.”

289. CUTANEOUS ABSORPTION—GALVANIC CONDUCTION. —After long immersion in
water the superficial layers of the epidermis become moist and swell up. The skin is unable to
absorb any substances, either salts or vegetable poisons, from watery solutions of these. This
is due to the fat normally present on the epidermis and in the pores of the skin. If the fat be
removed from the skin by alcohol, ether, or chloroform, absorption may occur in a few minutes
(Parisot). According to Rohrig, all volatile substances, ¢.g., carbolic acid and others, which
act upon and corrode the epidermis, are capable of absorption. While according to Juhl, such
watery solutions as impinge on the skin, in a finely divided spray, are also capable of absorption,
which very probably takes place through the interstices of the epidermis.

[Inunction.— When ointments are rubbed into the skin so as to press the substance into the
pores, absorption occurs, ¢.g., potassium iodide in an ointment so rubbed in is absorbed, so is
mercurial ointment. V. Voit found globules of mercury between the layers of the epidermis,
and even in the chorium of a person who was executed, into whose skin mercurial ointment had
been previously rubbed. The mercury globules, in cases of mercurial inunction, pass into the
hair-follicles and ducts of the glands, where they are affected by the secretion of the glands and
transformed into a compound capable of absorption, An abraded or inflamed surface (¢.g., after
a blister), where the epidermis is removed, absorbs very rapidly, just like the surface of a wound
(Endermic method). |

[Drugs may be applied locaily where the epidermis is intact—epidermic method—as when
drugs which affect the sensory nerves of a part are painted over a painful area to diminish the
pain. Another method, the hypodermic, now largely used, is that of injecting, by means of a
hypodermic syringe, a non-corrosive, non-irritant drug, in solution, into the subcutaneous
tissue, where it practically passes into the lymph spaces and comes into direct relation with
the lymph- and blood-stream ; absorption takes place with great rapidity, even more so than
from the stomach. ]

Gases. — Under normal conditions, minute traces of O are absorbed from the air; hydrocyanic
acid, sulphuretted hydrogen—CO, CO,, the vapour of chloroform and ether may be absorbed
(Chaussier, Gerlach, Rohrig). Ina bath containing sulphuretted hydrogen, this gas is absorbed,
while CO, is given off into the water (Réhrig).

Absorption of watery solutions takes place rapidly through the skin of the frog (Gutitmann,
W. Stirling, v. Wittich). Even after the circulation is excluded and the central nervous system
destroyed, much water is absorbed through the skin of thé frog, but not to such an extent as
when the circulation is intact (Spina).

Galvanic Conduction through the Skin.—If the two electrodes of a constant current be im-
pregnated with a watery solution of certain substances and applied to the skin, and if the
direction of thecurrent be changed from time to time, strychnin may be caused to pass through
the skin of a rabbit in a few minutes, and that in sufficient amount to kill the animal (H. JZunk).
In man, quinine and potassium iodide have been introduced into the body in this way, and
their presence detected in the urine. This process is called the cataphoric action of the con-
stant current (§ 328).

290, COMPARATIVE-—HISTORICAL,—In all vertebrates, the skin consists of chorium
; 3 | 2% 3

450 COMPARATIVE—HISTORICAL.

and epidermis. In some reptiles, the epidermis becomes horny, and forms large plates or scales.
Similar structures occur in the edentata among mammals. The epidermal appendages assume
yarious forms—such as hair, nail, spines, bristles, feathers, claws, hoof, horns, spurs, &e. The }
scales of some fishes are partly osseous structures. Many glands occur in the skin; in some
amphibia they secrete mucus, in others the secretion is poisonous, Snakes and tortoises are
devoid of cutaneous glands; in lizards the Rip-3: aageoct extend from the anus to the bend of
the knee. In the crocodile, the glands open under the margins of the cutaneo-osseous scales.
In birds, the cutaneous glands are absent; the ‘‘coccygeal glands” form an oily secretion for
lubricating the feathers. [This is denied by O. Liebreich, as he finds no cholesterin-fats in
their secretion.] The civet glands, at the anus of the civet cat, the preputial glands of the musk
deer, the glands of the hare, and the pedal glands of ruminants, are really greatly developed
sebaceous glands. In some invertebrata, the skin, consisting of epidermis and chorium, is
intimately united with the subjacent muscles, forming a musculo-cutaneous tube for the body
of the animal. The cephalopoda have chromatophores in their skin, 7.¢e., round or irregular
spaces filled with coloured granules. Muscular fibres are arranged radially around these spaces,
so that when these muscles contract the coloured surface is increased. The change of colour in
these animals is due to the play or contraction of these muscles (Briicke). Special glands ‘are
concerned in the production of the shell of the snail. The annulosa are covered with a chitin-
ous investment, which is continued for a certain distance along the digestive tract and the
trachee. It is thrown off when the animal sheds its covering. It not only protects the animal,
but it forms a structure for the attachment of muscles. In echinodermata, the cutaneous
covering contains calcareous masses; in the holothurians, the calcareous structures assuine the
form of calcareous spicules.

Historical.—Hippocrates (born 460 B.c.) and Theophrastus (born 371 B.c.) distinguished the
perspiration from the sweat; and, according to the latter, the secretion of sweat stands in a
certain antagonistic relation to the urinary secretion and to the water in the feces, According
to Cassius Felix (97 A.D.), a person placed in a bath absorbs water through the skin; Sanctorius
(1614) measured the amount of sweat given off; Alberti (1581) was acquainted with the hair-
bulb; Donatus (1588) described hair becoming grey suddenly; Riolan (1626) showed that the
colour of the skin of the negro was due to the epidermis.

Physiology of the

Motor Apparatus.

291. [CILIARY MOTION—PIGMENT CELLS].—(|(a) Muscular Move-
ment.— By far the greatest number of the movements occurring in our bodies is
accomplished through the agency of muscular fibre, which, when it is excited by a
stimulus, contracts, 2.e., it forcibly shortens, and thus brings its two ends nearer

together, while it bulges to a corresponding extent laterally.

traction takes place in a definite direction. |

In muscle, the con-

[(6) Amceboid Movement.— Motion is also exhibited by colourless blood-cor-

puscles, lymph-corpuscles, leucocytes, and some other corpuscles.

In_ these

structures we have examples of amceboid movement (§ 9), which is movement in

an indefinite direction. |

[(c) Ciliary Movement.—There is also a peculiar form of movement, known as

ciliary movement.

movement.
agents (fig. 300). |

There is a gradual transition between these different forms of
The cilia which are attached to the ciliated epithelium are the motor

[Ciliated epithelium—where found, —In the nasal mucous membrane, except the olfactory
region ; the cavities accessory to the nose; the upper half of the pharynx, Eustachian tube,

larynx, trachea, and bronchi; in the uterus,
except the lower half of the cervix ; Fallopian
tubes ; vasa efferentia to the lower end of epi-
didymis ; ventricles of brain (child) ; and the
central canal of the spinal cord. ]

[The cilia are flattened blade-like or hair-like

appendages attached to the free end of the ~

cells, They are about 355 inch in length, and

are apparently homogeneous and structureless.

They are planted upon a clear non-contractile
disc on the free end of the cell, and some ob-
servers state that they pass through the disc to
become continuous with the protoplasm of the
cell, or with the plexus of fibrils which pervades
the protoplasm, so that by some observers they

are regarded as prolongations of the intra-epi-

Ciliated a Clear
epithelium. \: dise,
Inter-
mediate
‘ea forms.
: Inner
Débove’s SA Oe layer
membrane, ae

Fig. 300.
Ciliated epithelium.

thelial plexus of fibrils. They are specially modified parts of an epithelial cell, and are con-
tractile and elastic. They are colourless, tolerably strong, not coloured by staining reagents,
and are possessed of considerable rigidity and flexibility’: They are always connected with the
protoplasm of cells, and are never outgrowths of the solid cell membranes. There may be 10
to 20 cilia distributed uniformly on the free surface of a cell (fig. 300).]

[In the large ciliated cells in the intestine of some molluscs (mussel), the cilia perforate the

clear refractile disc, which appears to consist’of small globules—basal pieces—united by their
edge, so that a cilium seems to spring from each of these, while continued downwards into the
protoplasm of the cell, but not attached to the nucleus, there is a-single varicose fibril—rootlet,
and the leash of these fibrils passes through the substance of the cell and may unite towards its

lower tailed extremity (Engelmann). ]
[Ciliary motion may be studied in the gill of a mussel, a small part of the gill being teased

452 FUNCTIONS OF CILIA.

in sea water ; or the hard palate of a frog, newly killed, may be scraped and the scraping ex-
amined in # p.c. salt solution. On analysing the movement, all the cilia will be observed to
execute a regular, periodic, to and fro rhythmical movement in a plane usually vertical to the
surface of the cells, the direction of the movement being parallel to the long axis of the organ.
The appearance presented by the movements of the cilia is sometimes described as a lashing
movement, or like a field of corn moved by the wind. Each vibration of a cilium consists of a
rapid forward movement or flexion, the tip moving more than the base, and a slower backward
movement, the cilium again straightening itself. The forward movement is about twice as rapid
as the backward movement. The amplitude of the movement varies according to the kind of
cell and other conditions, being less when the cells are about to die, but it is the same for all the
cilia attached to one cell, and is seldom more than 20° to 50°. There is a certain periodicity
in their movement—in the frog they contract about 12 times per second, The result of the
rapid forward movement is that the surrounding fluid, and any particles it may contain, are
moved in the direction in which the cilia bend. All the cilia of adjoining cells do not move at
once, but in regular succession, the movement travelling from one cell to the other, but how
this co-ordination is brought about we do not know. At least it is quite independent of the
nervous system, as ciliary movement goes on, in isolated cells, and in man it has been observed
in the trachea two days after death. Conditions for Movement.—In order that ciliary move-
ment may go on, it is essential that (1) the cilia be connected with part of a cell ; (2) moisture ;
(3) oxygen be present ; and (4) the temperature be within certain limits. ]

[A ciliated epithelial cell is a good example of the physiological division of labour. It is
derived from a cell which originally held motor, automatic, and nutritive functions all com-
bined in one mass of protoplasm, but in the fully developed cell, the nutritive and regulative *
functions are oontitiel to the protoplasm, while the cilia: alone are contractile. If the cilia
be separated from the cell, they no longer move. If, however, a cell be divided so that part of
it remains attached to the cilia, the latter still move. The nucleus is not essential for this act.
It would seem, therefore, that though the cilia are contractile, the motor impulse probably
proceeds from the cell. Each cell can regulate its own nutrition, for during life they resist the
entrance of certain coloured fluids. ]

[Effect of Reagents.—Gentle heat accelerates the number:and intensity of the movements,
cold retards them. <A temperature of 45° C. causes coagulation of their proteids, makes them
permanently rigid, and kills them, just in the same way as it acts on muscle, causing heat-
stiffening (§ 295, 1). Weak alkalies may cause them to contract after their movement is
arrested or nearly so (Virchow), and any current of fluid in fact may do so, Lister showed
that the vapour of ether and chloroform arrests the movements as long as the narcosis lasts,
but if the vapour be not applied for too long a time, the cilia may begin to move again. The
prolonged action of the vapour kills them. As yet we do not know any specific poison for
cilia—atropin, veratrin, and curara acting like other substances with the same endosmotic
equivalent (Zngelmann).]

[Functions of Cilia.—The moving cilia propel fluids or particles along the |
passages which they line. By carrying secretions along the tubes which they. line
towards where these tubes open on the surface, they aid in excretion. In the re-
spiratory passages, they carry outwards along the bronchi and trachea, the mucus
formed by the mucous glands in these regions. When the mucus reaches the
larynx it is either swallowed or coughed up. That the cilia carry particles upwards
in a spiral direction in the trachea has been proved by actual laryngoscopic investi-
gation, and also by excising a trachea and sprinkling a coloured powder on its
mucous membrane, when the coloured particles (Berlin blue or charcoal) are slowly
carried towards the upper end of the trachea. In bronchitis the ciliated epithelium
is shed, and hence the mucus tends to accumulate in the bronchi. They remove
mucus from cavities accessory to the nose, and from the tympanum, while the ova
are carried partly by their agency from the ovary along the Fallopian tube to the
uterus. In some of the lower animals they act as organs of locomotion, and in
others as adjuvants to respiration, by creating currents of water in the region of the
organs of respiration. ]

[The Force of Ciliary Movement.—Wyman and Bowditch found that the amount of work
that can be done by cilia is very considerable. The work was estimated by the weight which
a measured surface of the mucous membrane of the frog’s hard palate was able to carry up an
inclined plane of a definite slope in a given time. ]

[Pigment-cells belong to the group of contractile tissues, and are well developed in the frog,
ae iH

Pete ee

and-many other animals where their characters have been carefully studied. They are generally
regarded as comparable to branched connective-tissue corpuscles, loaded with pigmented ules

~

-
~
ad
a

- fluid with granules in suspension. In

. divided, the skin of the leg on that

STRUCTURE AND ARRANGEMENT OF MUSCLES. 453

of melanin. The pigment-granules may be diffused in the cell, or aggregated around the nucleus ;
in the former case, the skin of the frog appears dark in colour, in the latter, it is but slightly
pigmented (fig. 301). The question has been raised whether they are actual cells or merely
spaces, branched, and containing a 4

any case, they undergo marked changes
of shape under various influences. If
the motor-nerve to one leg of a frog be

side becomes gradually darker in colour
than the intact leg. A similar result
is seen in the curara experiment, when
all parts are ligatured except the nerve.
Local applications affect the state of
diffusion of the pigment, as v. Wittich
found that turpentine or electricity are
caused the cells of the tree-frog to con- «= i
tract, and the same effect is produced 5
by light. In Rana temporaria local % 2
irritation has little effect, but light, on Fig 301
the contrary, has, although the effect _. 2s eae od :
of light seems to be brought about Pigment-cells from the web of frog’s foot; a, cell with
through the eye, probably by a reflex pigment-granules diffused ; b, granules more concen-
mechanism (Lister). A pale-coloured trated; c, more concentrated still; d, cells with guanin-
frog, put in a dark place, assumes, after granules (Stirling).
a time, a different colour, as the pigment is diffused in the dark; but if it be exposed toa
bright light it soon becomes pale again. The same phenomenon may be seen on studying the
web of a frog’s leg under the microscope. The marked variations of colour—within a certain
range—in the chameleon is due to the condition of the pigmeht-cells:in its skin, covered as
they are by epidermis, containing a thin stratum of air (Briicke). When it is poisoned with
strychnin, its whole body turns pale; if it be ill, its body becomes spotted in a dendritic
fashion, and if its cutaneous nerves be divided, the area’supplied by the nerve changes to black.
The condition of its skin, therefore, is readily affected by the condition of its nervous system,
for psychical excitement also alters its colour. Ifthe sympathetic nerve in the neck of a turbot
be divided, the skin on the dorsal part of the head becomes black. It is notorious that the
colour of fishes is adapted to the colour of their environment. If the nerve proceeding from
the stellate ganglion in the mantle of a cuttle-fish be divided, the skin on one half of the body
becomes pale. |

{Guanin in Cells.—Besides the pigment-cells in the web of a frog’s foot (especi-
ally in Rana temporaria) there are other cells which contain granules of guanin
(fig. 301, d).. If the web of a frog’s foot be mounted in Canada balsam and
examined microscopically between crossed Nicol’s prisms, each guanin-cell is seen

to contain numerous very strongly doubly refractive granules of guanin (§ 283).]

292. STRUCTURE AND ARRANGEMENT OF MUSCLES.—| Muscular
Tissue is endowed with contractility, so that when it is acted upon by certain forms
of energy or stimuli, it contracts. There are two varieties of this tissue—

(1) Striped, striated (or voluntary) ; aren
_ (2) Non-striped, smooth, organic (or involuntary).

Some muscles are completely under the control of the will, and are hence called
“voluntary,” and-others are not directly subject to the control of the will, and are
hence called “involuntary ;” the former are for the most part striped, and the
latter non-striped; but the heart-muscle, although striped, is an involuntary
muscle. | . ;

1, Striped Muscles.—The surface of a muscle is covered with a connective-tissue envelope or
perimysium externum, from which septa, carrying blood-vessels and nerves, the perimysium
internum, pass into the substance of the muscle, so as to divide it into bundles of fibres or
fasciculi, which are fine in the eye-muscles and coarse in the glutei. In each such com-
partment or mesh, there lie a number of yuiseular fibres arranged more or less parallel to each
other, [The fibres are held together by delicate connective-tissue or endomysium, which sur-
rounds groups of the fibres ; each fibre being, as it. were, separated from its neighbour by
delicate fibrillar connective-tissue.] Each muscular fibre is surrounded with a rich plexus of
capillaries (which form an elongated meshwork, lying between adjacent fibres, but never pene-

454 STRUCTURE AND ARRANGEMENT OF MUSCLES.

i res, which, however, they cross (fig. 307). Ina contracted muscle, the capil-
Sites aay be slightly sinuous in their course, but when a muscle is on the stanieh shes? curves:
disappear. The capillaries lie in the endomysium, and near them ot feet ics]. aa?
muscular fibre receives a nerve-fibre. [Where found.—Striped muscular ig er in ae
skeletal muscles, heart, diaphragm, pharynx, upper part of pes pe muscles 0 e mi
ear and pinna, the true sphincter of the urethra, and external anal sp snc gat eta ee

A muscular fibre (fig. 302, 1) isa more or less cylindrical or polygonal fibre, bo 67
(x35 to zy in.] in diameter, and never longer than 3 to 4 centimetres [1 to 14 few ct ithin
short muscles, ¢.g., stapedius, tensor tympani, or the short muscles of a Og § e fibres are Cy
long as the muscle itself ; within longer muscles, however, the individual fibres are pointed,

Fig. 302.

Histology of muscular tissue. 1, Diagram of part of a striped muscular fibre ; S, sarcolemma ;
Q, transverse stripes; F, fibrille ; K, the muscle nuclei; N, a nerve-fibre entering it
with 4, its axis cylinder and Kiihne’s motorial end-plate, ¢, seen in profile ; 2, transverse
section of yet of a muscular fibre, showing Cohnheim’s areas, c; 3, isolated muscular fibrille ;

4, part of an insect’s muscle greatly magnified ; @ Krause-Amici’s line limiting the
muscular cases ; b, the doubly-refractive substance ; c, Hensen’s disc ; d, the singly-refrac-
tive substance ; 5, fibres cleaving transversely into discs ; 6, muscular fibre from the heart
of a frog; 7, development of a striped muscle from a human fcetus at the third month ;
8, 9, muscular fibres of the heart ; c, capillaries ; 6, connective-tissue corpuscles ; 10, smooth
muscular fibres ; 11, transverse section of smooth muscular fibres. :

and are united obliquely by cement-substance with a similar bevelled or pointed end of another
fibre lying in the same direction. Muscular fibres may be isolated by maceration in nitric acid
with excess of potassic chlorate or by a 36 per cent. solution of caustic potash.
{Each muscular fibre consists of the following parts :—
1, Sarcolemma, an elastic sheath, with transverse partitions, stretching across the fibre at
regular intervals—the membrane of Krause ; . .
2. The included sarcous substance ; . :
3. The nuclei or muscle corpuscles.] aye

STRUCTURE OF A MUSCULAR FIBRILLA. A55

‘Sarcolemma, —Each muscular fibre is completely enclosed by a thin colourless, structureless,
transparent elastic sheath (fig. 302, 1, 8), which, chemically, is midway between connective
and elastic tissue, and within it is the contractile substance of the muscle. [When a muscular
fibre is being digested by trypsin, Chittenden observed, at the beginning, the sarcolemma raised
from its sarcous contents as a folded tube, but it is ultimately di gested by trypsin. It is thus
distinguished from the collagen substance of connective- tissue, which is not digested by trypsin.
It is not dissolved by boiling, and it resists the action of acids and dilute alkalies, while it is
dissolved by concentrated alkalies. Thus, it differs from elastic fibres, and on the whole,
chemically, it seems to be most closely related to the membrana propria of glands. It has
much more cohesion than the sarcous substance which it encloses, so that sometimes, when
teasing fresh muscular tissue under the microscope, one may observe the sarcous substance torn
across, with the unruptured sarcolemma stretching between the ends of the ruptured sarcous
substance. If muscular fibres be teased in distilled water, sometimes fine clear blebs are seen
along the course of the fibre, due to the sarcolemma being raised by the fluid diffusing under
it. The sarcous substance, but not the sarcolemma, may be torn across by plunging a ” muscle
in water at 55° C., and keeping it there for some time (Ranvier). ]

Sarcous Substance.—The sarcous substance is marked transversely by alternate light and
dim layers, bands, stripes or discs (fig. 302, 1, Q), so that each fibre is said to be ‘‘ transversely
striped.” [The stripes do not occur in the sarcolemma, but are confined to the sarcous sub,
stance, and they involve its whole thickness. ]

[The animals most suited for studying the structure of the sarcous substance are some of the
insects. The muscles of the water-beetle, Dytiscus marginalis, and the Hydrophilus piceus are
well suited for this purpose. So is the crab’s muscle. In examining a living muscle micro-
scopically, no fluid except the muscle-juice should be added to the preparation, and very high
powers of the microscope are required to make out the finer details. ]

Bowman’s Discs.—If a muscular fibre be subjected to the action of hydrochloric acid (1 per
1000), or if it be digested by gastric juice, or if it be frozen, it tends to cleave transversely
into discs (Bowman), “which are artificial products, and resemble a pile of coins which has been
knocked over (fig. 302, 5).

Fibrillxs.—Under certain circumstances, a fibre may exhibit longitudinal striation. This
is due to the fact that it may be split up longitudinally into an immense number of (1 to 17
in diameter) fine, contractile threads, the primitive fibrille mM
(fig. 302, 1, F), placed side by side, each of which is also
transversely striped, and they are so ‘united to each other by
semi-fluid cement-substance, that the transverse markings of
all the fibrillee lie at the same level. Several of these fibrils
are united together owing to the mutual pressure,and prismatic
in form, so that when a transverse section of a perfectly fresh
muscular fibre is observed after it is frozen, the end of each
fibre is mapped out into a number of small polygonal areas
called Cohnheim’s areas (fig. 302, 2). [Each bundle of fibrils
or polygonal area represents what Kélliker called a ‘‘ Muscle-
Column.” :

Fibrille are easily obtained from insects’ muscles, while fj
those from a mammal’s muscle are readily isolated ‘by the
action of dilute alcohol, Miiller’s fluid [or, best of all, 4 per
cent. solution of chromic acid] (fig. 302, 3).

{In studying the structure of muscle, it is well to re-
member that there are considerable differences between the Sit
muscles of Vertebrates and those of Arthropoda. ] ‘ Soh i

[When a living unaltered vertebrate muscular fibre is §& ut
examined microscopically, in its own juice, we observe the
alternate dim and light transverse discs, Amici, Krause, and
- Dobie showed that a fine dark line runs across the light
disc, and divides it into two (fig. 303). Amici resolved it Tt TES
into a row of granules, and by others (¢.g., Krause) it is Fie. 303
regarded as due to the existence of a membrane,—hence rane
it is called Krause’s membrane,—which runs transversely
across the fibre, being attached all round to the sarcolemma, thus dividing each fibre into a
series of compartments placed end to end. Hensen described a dise or stripe in the centre of
the dim disc. ] ;

[On Krause’s theory, each muscular compartment contains (1) a broad dim disc, which is the
contractile part of the sarcous substance: It is doubly refractive (anisotropous), ‘and is com-
posed of Bowman’s sarcous elements, (2) On each end of this disc, and between it and Krause’s
membranes, is a narrower, clear, homogeneous, and but singly refractile (isotropous), soft or
fluid substance, which forms the lateral disc of Engelmann. In some insects it contains a row
of refractive granules, coustisuting the granular layer of Flégel. If a muscular fibre be

Human muscular fibre, x 300.

456 DISCS AND NUCLEI IN A MUSCULAR FIBRE,

stretched and stained with logwood, the central part of the dim dise appears lighter in colour
than the two ends of the same disc. This. has been described as a separate disc, and is called
the median dise of Hensen (fig. 302, 4, ¢).]

[In an unaltered fibre, the dim broad stripe may appear homogeneous, but after.a time it
cleaves throughout its entire extent in the long axis of the fibre into a number of prismatic
elements or fibrils, the sarcous elements of Bowman (fig. 302). These at first are prismatic, but
as ‘they solidify they shrink and seem to squeeze out of them a fluid, becoming at the same time
more constricted in the centre. This separation into bundles of fibrils with an interstitial matter
gives rise to the appearance seen on transverse section of a frozen muscle, and known as Cohn-
heim’s areas (fig. 802, 2, c). In all probability the cleavage also extends through the lateral
dises, and thus fibrils are formed by longitudinal cleavage of the fibre. ]

[Muscles of Arthropoda, —Engelmann showed that the muscles of these animals have a large
number of discs. In a muscle of an animal killed by being plunged into alcohol, according to
the position of the lens of the microscope, one sees :—

1. The broad dim disc, composed of two darker lateral portions or discs, and a lighter dise—
that of Hensen, between them. In fig, 304 the whole disc is marked Q, and Hensen’s disc is
distinguished as h. .

2. On both sides of this is a small, clear, slightly refractive stripe, J, corresponding to one of
Engelmann’s isotropous stripes.

3. On both sides there follows symmetrically a dark epg refractive stripe, N, corre-
sponding to Engelmann’s accessory stripe and Flogel’s granular layer.

4. Then on both sides there is a clear, feebly refractive disc, E.

5. Beyond E is a small, dark, highly refractive stripe, Z—usually the darkest—corresponding
to the Amici-Krause line. ]

[From Z, the stripes are repeated in the inverse order to Q, then in the same order to Z, and
soon. This is the appearance with a low position of the lens. Many muscles do not show all
these stripes, thus / is often absent. ]

[If the lens of the microscope be raised, to get a more superficial view of the fibre, the
distribution of the light is reversed (fig. 304, II), as all strongly refractive sections become

light, and all feebly refrac-
Z tive appear darker, while
with a deep position of the
lens, the reverse is the
case. }

E- gy puamananusnesosnaszonnuseinntt [Experiment shows that
HN ie the dim dise rapidly swells
‘AN = up in dilute acids, and also
“z that the dim discs (Q), the
accessory discs (N), and

the Amici-Krause line (K),

stain more deeply with log-
Z wood than the other dises,

and A less than the rest of

EY, Hee eee

a

to

Fs aaa Mineeneatsenessse

Por eeeeeeceneseeeeereneneees:

=

TTT et

ia

‘ Z Mit a muscle which has
; ee ee ae ey been some time in aleohol
Fig. 304. Fig. 305, be examined as to its longi-

Fig. 304.—Insect’s muscle; I, with a high position of the lens, tudinal striation, it will be
and II, with a deeper position. Fig. 305.—Muscular fibre of seen to consist of rods with
Carabus cancellatus, light intervals between

them (fig. 305). The rods
are thicker at their ends, and thinner and lighter at their middle. Rollett regards the clear
intervals between these rods as consisting of sarcoplasma, a body closely related to protoplasm,
and the rods as bundles of fibrille or ‘‘ muscle columns.”

[If a muscle be acted upon by certain acids the relative appearance of the muscle-columns and
the sarcoplasma is altered ; and the latter may appear in these and in gold preparations as a
plexus of fibrils with regular longitudinal and transverse meshes (Melland, Marshall, fig. 306).}

[Muscle Rods.—Schiifer describes the appearance differently :—-Double rows of granules are
seen lying in or at the boundaries of the light streaks (discs), and very fine longitudinal lines
may be detected running through the dark streak (dim disc) and uniting the minute granules,
_These fine lines, with their enlarged extremities, are ‘‘ muscle rods.”” They are most conspicuous
in insects. During the contraction of a living muscular fibre, Schiifer describes the ‘‘ reversal
of the stripes ’’ (§ 297) as follows :-—‘‘ When the fibres contract, the light stripes are seen, as
the fibre shortens and thickens, to become dark, an apparent reversal being thereby produced
in the strie. This reversal is due to the enlargement of the rows of dark dots and the formation
by their juxtaposition and blending of dark discs, whilst the muscular substances between these
dises has by contrast a bright appearance.” With polarised light in a living muscular fibre,

TENDON AND BLOOD-VESSELS OF A MUSCLE. 487

all the sarcous substance, except the muscle rod, is doubly refractive or anisotropous, so that it
appears bright on a dark field when the Nicol’s prisms are crossed, while under the same condi-
tions contracted muscle and dead muscle show alternate dark and light bands (Schéfer).]

The nuclei or muscle-corpuscles are found immediately under the sarcolemma in all
mammals, and their long axis lies in the long axis of the fibre (8 to 13 u long, 3 to 4 uw broad).

[In the muscles of the frog, reptiles, and some other animals, ¢e.g., the red muscles of the
rabbit and hare and in some muscles of birds, they lie in the substance of the fibre surrounded
by a small amount of protoplasm.] When they occur immediately under the sarcolemma they
are more or less flattened, and lie embedded in a small amount of protoplasm (fig, 302, 1 and 2,
K). They contain one or two nucleoli, and it is said that the protoplasm sends out fine
processes which unite with similar processes from adjoining corpuscles, so that, according to
this view, a branched protoplasmic network exists under the sarcolemma. [Hach nucleus has a
reticulated appearance due to the presence of a plexus of fibrils, consisting of chromatin ; in its
meshes lies an achromatic substance. The nuclei are specially large in Otiorrhynchus planatus,
one of the beetles. Mitotic figures indicating division of the nuclei have been observed. The
nuclei are not seen in a perfectly fresh muscle, because, until they have undergone some change,
their refractive index is the same as that of the sarcous substance.] They become specially
evident after the addition of acetic acid. Histogenetically, they are the remainder of the cells
from which the muscular fibres were developed (fig. 302, 7). According to M. Schultze, the
sarcous substance is an intercellular substance differentiated and formed by their activity.
Perhaps they are the centres of nutrition for the mus- —
cular fibres. In amphibians, birds, fishes, and reptiles,
they lie in the axis of the fibres between the fibrils,

It is said that the protoplasm of the muscle-corpuscles
forms a fine network throughout the whole muscular
fibre, the transverse branches taking the course of the ;
lines of Krause or Dobie, and ao
the longitudinal branches run-
ning in the interstices between
Cohnheim’s area (Retzius,
Bremer, Melland, fig. 306).

Fig. 306. | Fig. 307.
Fig. 306.—Network in a muscular fibre, Fig. 307.—Relation of a tendon, S, to its muscular
fibre. Fig. 308.—Injected blood-vessels of a human muscle, a, small artery; b, vein;

c, capillaries. x 250.

Relation to Tendons.—<According to Toldt, the delicate connective-tissue elements, which
cover the several muscular fibres, pass from the ends of the latter directly into the connective-
tissue elements of the tendon. The end of the muscular fibre is perhaps united to the smooth
surface or hollow end of the tendon by means of a special cement (Weismann—fig. 307, 8), In
arthropoda, the sarcolemma passes directly into and becomes continuous with the tendon (Leydig).
The tendon itself consists of longitudinally arranged bundles of white fibrous tissue with cells—
tendon cells—embracing them. There is a loose capsule or sheath of connective-tissue—the
peritendineum of Kollman—surrounding the whole and carrying the blood-vessels, lymphatics,
and nerves. The tendons move in the tendon-sheaths, which are moistened by a mucous fluid.
In most situations, muscular fibres are attached by means of tendons to some fixed point, but
* other situations (face) the ends terminate between the connective-tissue elements of the
skin,

[Blood-Vessels,—Muscles, being very active organs, are richly supplied with blood. The
blood-supply of a muscle differs from some organs in not constituting an actual vascular unit,

458 | “NERVES OF A MUSCLE, = > > 7

supplied only by one artery and one vein, thus being unlike the kidney, spleen, &c. Each,
muscle usually receives several branches from different arteries, and branches enter it at certain,
distances along its whole length. . The artery and vein usually lie together in the connective-
tissue of the perimysium, while the capillaries lie in the endomysium. The capillaries lie
between the muscular fibres, but outside the sarcolemma, where they form an elongated rich
plexus with numerous transverse branches (fig. 308). The lymph to nourish the sareous sub-
stance must traverse the sarcolemma to reach the former. In the red muscles of the rabbit.
(e.g., semitendinosus) the capillaries are more wavy, while on the transverse branches of some
of the capillaries, and on the veins, there are small, oval, saccular dilatations, which act as
reservoirs for blood (Ranvier). }

[Lymphatics.—We know very little of the lymphatics of muscle, although the lymphatics of
tendon and fascia have been carefully studied by Ludwig and Schweigger-Seidel. There are
lymphatics in the endomysium, of the heart, which are continuous with those under the peri-
cardium. This subject still requires further investigation. Compare the lymphatics of the
fascia lata of the dog (fig. 227, § 201.] mt

Entrance of the Nerve.—The ¢rwnk of the motor nerve, as a rule, enters the muscle at its
geometrical centre (Schwalbe); hence, the point of entrance in muscles with long, parallel, or
spindle-shaped fibres lies near its middle. If the muscle with parallel fibres is more than 2 to
8 centimetres [1-3 inches] in length, several branches enter its middle. In triangular muscles,
the point of entrance of the nerve is displaced more towards the strong tendinous point of con-
vergence of the muscular fibres. A nerve-fibre usually enters a muscle at the point where there
is the least displacement of the muscular substance during contraction.

Motor Nerve.—Every muscle-fibre receives a motor nerve-fibre (fig, 302, 1, N).

Each nerve does not contain originally as many motor nerve-fibres as there are

muscular fibres in the muscle

it enters; in the human eye-

muscles, there are only 3

nerve-fibres to 7 muscular

fibres; in other muscles

End- (dog), 1 nerve-fibre to 40 or

plate. 80 (Zergast). Hence, when

a nerve enters a muscle it

must divide, which occurs

dichotomously [at_Ranvier’s

Muscle nodes], the structure under-

“nucleus: going no change until there

are exactly as many nerve-

fibres as muscular fibres. In

warm-blooded animals each

Muscular fibres with motorial end-plates. muscular fibre has only one,

while cold-blooded animals

have several points of insertion of the nerve-fibre (Sandmann). A nerve-fibre enters

each muscular fibre, and where it enters it forms an eminence (Doyére, 1840), the
“‘ motorial end-plate ” (figs. 302, 1, e, 309, 310, 311). ayes : )

[The elaborate investigations of K. Mays on the exact distribution of nerve-fibres

in the muscles of the frog have conclusively proved—apart from experimental reasons

—that parts of muscles receive no nerve-fibres at all, large portions being free from
nerves. ‘This has been proved for all classes of vertebrates except osseous fishes. |

Nerve.

[The mode of termination of a motor nerve in a muscular fibre is not the same in all animals,
but in every case it . the sarcolemma, and its ultimate distribution has a distinct hypo-
lemmal character. The Doyére’s eminence is present in most mammals and reptiles, but in
amphibians and birds, the ending is flat on the musele-fibre. Most of the results known to us’
have been worked out by Kiihne. The nerve-endings, then, are confined to very small - $0
or areas on the muscular fibres, termed by Kiihne “fields of innervation.” Most nerve-fibres”
have only one such field, but very long fibres may have, at most, eight. One or more medul-
lated nerve-fibres pass—as pecterminal or epilemmal fibres—from the point of division of the
nerve-fibre to the muscular fibre, to pass into the nerve-endings. The nerve-endings consist
of divisions of the axial cylinder, which are distributed over the sarcous substance without
(so far as is known) forming any direct connection with it. 'The endings, however, lie in direet

NERVES OF A MUSCLE. 459

contact with it. This branched arrangement of the axis-cylinder under the sarcolemma, Kiihne
has called a ‘‘motor-spray ” (‘‘motorisches Geweih”), and the mode of distribution of the
branches varies in different classes of animals. In the frog (fig. 310), tailed amphibians, and
birds, the hypolemmal branches of the axis-cylinder form bayonet-like and branched endings.
In the lizard, snakes, and mammals, the branches are often curved or twisted, and possessed of
lobes, and as the division is very variable, there is every form from a simple hook-like bend to a
highly arborescent termination. ]

[Where a motor nerve enters a muscular fibre at the eminence of Doyére, the sheath of the
nerve-fibre, known.as the perineural or Henle’s sheath ($ 321), becomes

continuous with the sarcolemma. The eminence itself consists of a

mass of protoplasm—or sarcoplasm—called
by Kiihne sarcoglia—which contains gran-
ules and nuclei, the latter with a mem-
brane and peculiar nucleoli; the nuclei
themselves are the fundamental or basal
nuclei of the sarcoglia. The outer surface
of the eminence is covered by a mem-
brane called telolemma by Kiihne, but
which in reality consists of two mem-
branes, an outer
one, the epilemma,
continuous with
the perineural or
Henle’s sheath, and
an inner one, the
endolemma, the

CA a
Thi

200000

& Heel 4] continuation of the
i nics Hatalal3} j E/E | sheath of Schwann
Pp : FEIEIEIFIEEIEIEIBIELE IE 7424] of the nerve-fibre,
‘ ()-e LEE EEEERE all [44 both ultimately be-

ing connected with
cae thesarcolemma. As

Fig. 310. Fig. 311. the nerve pierces
the muscular fibre,
it loses its myeline,
and with it disap-
pears the keratin
sheath or axilemma
of theaxis-cylinder,
so that the spray-
like ending is ac-
companied only by
the telolemma (fig. 311). The telolemma contains nuclei which are derived from Henle’s
sheath (Kiihne). ]

[In some animals, such as the lizard, in order to see the nerve terminations, it is sufficient to
stain portions of fresh muscles with Delafield’s logwood. ]

0 TE gem a F

Fig. 310.—Motor nerve-ending in the frog (Kiihne). a, Profile. view of
entrance of the nerve ; 4, b, nuclei of the branches of the axial cylinder ;
c, ¢, c, nuclei of Henle’s sheath; ¢, muscle nuclei. Fig. 311.—Motor
nerve-ending in lizards, mammals, and man. Schematicafter Kiihne. A,
axis-cylinder ; A’A’, terminal branches of A ; a, a, myelin of nerves; 0,
perineural or Henle’s sheath, and its nuclei (c); d, nuclei of telolemma ;
B, bed; D, large granule in B; C, nuclei of the bed ; E, muscle nuclei ;
F, contractile substance.

[ Nerve-endings, then, are sublemmar, and the terminations of the nerves never
penetrate into the depth of the muscular fibre, but come into direct contact with
the contractile prism or cylinder moistened by the fluids of the muscle. In
many cases the striped substance is separated from the blunt nerve-endings by some
of the sarcoglia, which in some cases penetrate and traverse the other constituent
of the fibre. The latter Kiihne has called “‘rhabdia.” The antler-like division of
the axis-cylinder or spray, in contact with the muscular substance, serves to conduct
the excitation from the former to the latter, but excitation of the muscular sub-
stance is never transmitted in the reverse order to the nerve-ending (Azihne). |

Each muscular fibre of the cray fish is supplied by two nerve-fibrils arising from separate
axis-cylinders (Biedermann).

Sensory fibres also occur in muscles, and they are the channels for muscular
sensibility. They seem to be distributed on the outer surface of the sarcolemma,
where they form a branched plexus and wind round the muscular fibres (Arndt,
Sachs) ; but, according to Tschirjew, the sensory nerves traverse the substance of
the muscle, and after dividing dichotomously, end only in the aponeurosis, either

460 RED AND PALE MUSCLES.

suddenly or by means of a small swelling—a view confirmed by Rauber. The
existence of sensory nerves in muscles is also proved by the fact that stimulation
of the central end of a motor nerve, e.g., the phrenic, causes increase of the blood-
pressure and dilatation of the pupil (Asp, Kowalewsky, Nawrocki), as well as by the
fact that when they are inflamed they are painful. They of course do not de-
generate after section of the anterior root of the spinal nerves.

Red and Pale Muscles.—-In many fishes,(skate, plaice, herring, mackerel) (W. Stirling),
birds, and mammals (rabbits), there are two kinds of striped muscle (Krause), differing in
colour, histological structure (Ranvier), and physiological properties (Kronecker and Stirling).
Some are *‘red,”’ ¢.g., the soleus and semitendinosus of the rabbit, and others ‘‘ pale,”’ ¢.g.,
the adductor magnus. In the pale muscles the transverse striation is less regular, and their
nuclei fewer than in the red muscles (Ranvier); they contain less glycogen and myosin, [W.
Stirling finds that the red muscles in many fishes, ¢.g., the mackerel, contain granules of oil,
and present all the appearance of, muscle in a state of fatty degeneration, while the pale
muscles, lying side by side, contain no fatty granules. ] =

Julius Arnold found in human muscles an extensive distribution of pale fibres amongst |

the red ones, and indeed in the same muscle in the frog and mammals, red and pale fibres
occur together, in fact this is the case in almost every muscle (Griitzner).

[Spectrum. —The red colour of the ordinary skeletal muscle is due to hemoglobin in the sarcous
substance (Kiihne). This is proved by the fact that the colour is retained after all the blood
is washed out of the vessels, when a thin muscle still shows the absorption-bands of hemo-
globin when examined with the spectroscope. |

[Myo-hematin.—MacMunn points out that although most voluntary muscles owe their
colour to hemoglobin, it is accompanied by myo-hematin in most cases, and sometimes entirely
replaced by it. Myo-hematin is found in the heart of vertebrates, in the papillary muscles of
the human heart, and in abundance in the pectoral muscles of pigeons, and in some muscles
of vertebrates and invertebrates, ¢.g., certain beetles (Hydrophilus, Dytiscus), the common fly,
and other insects, spiders, crustaceans, and molluscs. ]

Muscular Fibres of the Heart.—The mammalian cardiac muscle has certain peculiarities
already mentioned (§ 43) :—(1) It is striped, but it is involuntary ; (2) it has no sarcolemma ;
(3) its fibres branch and anastomose ; (4) the transverse striation is not so distinct, and it is
sometimes striated longitudinally ; (5) the nucleus is placed in the centre of each cell (see
§ 43). [The cardiac muscle, viewed from a physiological point of view, stands midway between
striped and unstriped muscle. Its contraction occurs slowly and lasts for a long time (p. 86),
ale, although it is transversely striped, it is involuntary. ]

[Purkinje’s Fibres,—These fibres, which form a plexus of greyish fibres under the endo-
cardium of the heart of ruminants, have been described already (fig. 28) ; the cells have, as it
were, advanced only to a certain stage of development (§ 46). ]

Development.— ach muscular fibre is developed from a uni-nucleated cell of the mesoblast,
which elongates into the form of a spindle. As the cell elongates, the nuclei multiply. The
superficial or parietal part of the cell-substance shows transverse markings (fig. 302, 7), while
the nuclei with a small amount of protoplasm are continuous along the axis of the fibre, where
they remain in some animals, but in man they pass to the surface where they come to lie under
the sarcolemma, The muscles of {the young are smaller and have fewer fibres than those of
adults (Budge). In developing muscle, the number of fibres is increased by the proliferation
of the muscle-corpuscles, which form new fibres.

Striped muscle, besides occurring in the corresponding organs of vertebrata, occurs in the
iris and choroid of birds. The arthropoda have only striped muscle, the molluscs, worms,
and echinoderms chiefly smooth muscles; in the latter are muscles with double oblique striation
(Schwalbe). According to Paneth, in old individuals separate cells with aggregation of con-

tractile substance—so-called Sarcoplasts—unite to form new muscular fibres. Sig. Mayer regards .

these structures as retrogressive structures, and he calls them Sarcolytes (§ 103, II.).

2. Non-Striped Muscle.—[Distribution.—It occurs very widely distributed in the body, in
the muscular coat of the lower half of the human cesophagus, stomach, small and large intestine,
muscularis muscose of the intestinal tract, in the arteries, veins, and lymphatics, posterior part
of the trachea, bronchi, infundibula of the lung, muscular coat of the ureter, bladder, urethra,
vas deferens, vesicule seminales, and prostate; corpora cavernosa and spongiosa penis, ovary,
Fallopian tube, uterus, skin, ciliary muscle, iris, upper eyelid, spleen and capsule of lymphatic
glands, tunica dartos of the scrotum, gall-bladder, in ducts of glands, and in some other
situations. }

Structure.—Smooth muscular fibres consist of fusiform or spindle-shaped elongated cells,
with their ends either tapering to fine points or divided (fig. 312). These contractile fibre-cells
may be isolated by steeping a piece of the tissue in a 30 per cent. solution of caustic potash, or
a strong solution of nitric acid. They are 45 to 80 u [z45 to x45 in.] in length, and 4 to 104
[sve to xsyy in.] in breadth. Each cell contains a solid oval elongated nucleus, which wind?

_— ——

NON-STRIPED MUSCLE. 461

contain one or more nucleoli. It is brought into view by the action of dilute acetic acid, or by
staining reagents. The mass of the cell appears more or less homogeneous, [and is surrounded
by a thin elastic envelope]. In some places it shows longitudinal fibrillation. [Method.—This
fibrillation is revealed more distinctly thus :—Place the mesentery of a newt (K/ein) or the
bladder of the salamandra maculata (Flemming) in a 5 per cent. solution of ammonium
chromate, and afterwards stain it with picro-carmine. Each cell consists of a thin elastic
sheath (sarcolemma of Krause) enclosing a bundle of fibrils (F) which run in a longitudinal
direction within the fibre (fig. 313). They are continuous at the poles of the nucleus with the
plexus of fibrils which lies within the nucleus, and, according to Klein, they are the contractile
art, and when they contract the sheath becomes shrivelled transversely and exhibits what looks

ike thickenings (S). These fibrils have been observed by Flemming in the cells while living.
Sometimes the cells are branched, while in the frog’s bladder they are triradiate.

[Arrangement,—Sometimes the fibres occur singly, but usually they are arranged in groups,
forming lamelle, sheets, or bundles, or in a plexiform manner, the bundles being surrounded by
connective-tissue.] A very delicate elastic cement-substance unites the individual cells to each
other. [This cement may be demonstrated by the action of nitrate of silver. In transverse
section (fig. 312, 11) they appear oval or polygonal, with the delicate homogeneous cement
between them ; but, as the fibres are cut at various levels, the areas are unequal in size, and all
of them, of course, are not divided at the position of the nucleus. |

They vary in length from 44,5 to 33> of an inch; those in the middle coat of the arteries
are short, while they are long in the intestinal tract, and-especially in the pregnant uterus.
According to Engelmann, the separation of the smooth muscular substance into its individual
spindle-like elements is a post-mortem change of the tissue. Sometimes transverse thickenings
are seen, which are not due to transverse striation, but to a partial contraction. Occasionally
they have a tendinous insertion.

Blood-Vessels.—Non-striped muscle is richly supplied with blood-vessels, and the capillaries

|

Fig. 312. Fig. 313. Fig. 314.

Fig. 312.—Smooth muscular fibres (10); (11) transverse section. Fig. 313.—Smooth mus-
cular fibre from the mesentery of a newt (ammonium chromate), N, nucleus; F, fibrils;
S, markings in the sheath. Fig, 314.—Termination of nerve in non-striped muscle.

form elongated meshes between the fibres, [although it is not so vascular as striped muscle].
Lymphatics also occur between the fibres.

Motor Nerves.—According to J. Arnold, they consist of medullated and non-medullated
fibres [derived from the sympathetic system] which form a plexus—ground plexus—partly pro-
vided with ganglionic cells, and lying in the connective-tissue of the perimysium. [The fibres
are surrounded with an endothelial sheath.] Small branches [composed of bundles of fibrils]
are given off from this plexus, forming the intermediary plexus with angular nuclei at the noda]
points, It lies either immediately upon the musculature or in the connective-tissue between
the individual bundles. From the intermediary plexus, the finest fibrille (0°3 to 0°5 u) pass

> off, either singly or in groups, and reunite te form the intermuscular plexus (fig. 314, d), which
; lies in the cement substance between the muscle-cells, to end, according to Frankenhiuser, in
= the nucleoli of the nucleus, or in the neighbourhood of the nucleus (Lustig). According to J.
; Arnold, the fibrils traverse the fibre and the nucleus, so that the fibres appear to be strung upon
x a fibril passing through their nuclei. According to Lowit, the fibrils reach only the interstitial
‘

462 PHYSICAL AND. CHEMICAL PROPERTIES OF MUSCLE,

substance, while Gscheidlen also observed that the finest terminal. fibrils, one of which goes to
each muscular fibre, ran along the margins of the latter (fig. 314), The course of these fibrils
can only be traced after the action of gold chloride. [Ranvier has traced their terminations in
the stomach of the leech. ]

Nerves of Tendon.—Within the tendons of the frog, there is a plexus of medullated nerve-
fibres, from which brush-like divided fibres proceed, which ultimately end with a point in
nucleated plates, the nerve-flakes of Rollett. According to Sachs, bodies like end-bulbs occur
in tendons, while Rauber found Vater’s corpuscles in their sheaths ; Golgi found, in addition,
spindle-shaped terminal corpuscles, which he regards as a specific apparatus for estimating
tension.

293. PHYSICAL AND CHEMICAL PROPERTIES OF MUSCLE.—1.
The consistence of the sarcous substance is the same as that of living protoplasm,
e.g., of lymph-cells ; it is semi-solid, 7.¢., it is not fluid to such a degree as to flow
like a fluid, nor is it so solid that, when its parts are separated, these parts are
unable to come together to form a continuous whole. The consistence may be
compared to a jelly at the moment when it is dissolved (e.g., by heat). The power
of imbibition is increased in a contracted muscle (Ranke).

Proofs.—The following facts corroborate the view expressed above :—-(a) The analogy between
the function of the sarcous substance and the contractile protoplasm of cells (§ 9). (6) The
so-called Porret’s phenomenon, which consists in this, that when a galvanic current is conducted
through the living, fresh, sarcous substance, the contents of the muscular fibre exhibit a stream-
ing movement from the positive to the negative pole (as in all other fluids), so that the fibre
swells at the negative pole (Kiihne). (ce) By the fact that wave-movements have been observed
to pass along the muscular fibre. (d) Direct observation has shown that a small parasitic round
worm (Myoryctes Weismanni) moved freely in the sarcous substance within the sarcolemma,
while the semi-solid mass closed up in the tract behind it (Kiihne,' Eberth).

2. Polarised Light.—The contractile substance doubly refracts light, and is said to be aniso-
tropous, while the ground substance causes single refraction, and is isotropous, According
to Briicke, muscle behaves like a doubly refractive, positively uniaxial body, whose optical axis
lies in the long axis of the fibre. When a muscular fibre is examined under the polarisation
microscope, the doubly refractive substance is recognised by its appearing bright in the dark
field of the microscope when the Nicols are crossed (§ 297). During contraction of the mus-
cular fibre, the contractile part of the fibre becomes narrower, and at the same time broader,
whilst the optical constants do not thereby undergo any change. Hence, Briicke concludes
that the contractile discs are not simple bodies like crystals, but must consist of a whole series
of small, doubly refractive elements arranged in groups, which Sere their position during
contraction and relaxation, These small elements Briicke called disdiaclasts, According to
Schipiloff, Danielewsky, and O. Nasse, the contractile anisotropous substance consists of myosin,
which occurs in a crystalline condition and represents the disdiaclasts. According to Engel-
mann, however, all contractile elements are doubly refractive, and the direction of contraction
always coincides with the optical axis.

The investigations of v. Ebner have shown that during the process of growth of the tissue,
tension is produced—the tension of bodies subjected to imbibition—which results in double
refraction, and so gives rise to the condition called anisotropous. During a sustained con-
traction, the index of refraction of the muscular fibre increases (Exner).

[Reaction. —If a transverse section of a living excised muscle be pressed upon a strip of blue
litmus paper, the latter may assume a reddish tinge, and if upon a red litmus paper the latter
may assume a bluish tinge, but it will not alter violet litmus paper. This is the ampho-
chromatic or amphoteric reaction, indicating that the muscle.is neutral. It may, however,
give only an alkaline reaction. A living muscle plunged into boiling water still retains its
heutral or alkaline reaction ; but a muscle, which has been tetanised, or is in rigor mortis, is
decidedly acid. }

The chemical composition of muscle undergoes a great change after death,

, owing to the spontaneous coagulation of a proteid within the muscular fibres. As
frog’s muscles may be frozen and thawed, and still remain contractile, they

cannot, therefore, be greatly changed by the process of freezing. Kiihne bled

frogs, cooled their muscles to 10° or 7° C., pounding them in an iced mortar, and

expressed their juice through linen. The juice so expressed, when filtered in the

cold, forms a neutral, or alkaline, slightly yellowish, opalescent fluid, the so-called

“muscle-plasma,” Like blood-plasma, it coagulates spontaneously ; at first it is

like. a uniform soft jelly, but soon becomes opaque; doubly refractive fibres and

7

CHEMICAL COMPOSITION OF MUSCLE-SERUM. 463

specks, similar to the fibrin of blood, appear in the jelly, and as these begin to con-
tract, they squeeze out of the jelly an acid “‘muscle-serum.” [Halliburton finds
that the muscles of warm-blooded animals yield a similar muscle-plasma.| Cold
prevents or delays the coagulation of the muscle-plasma ; above 0°, coagulation
occurs very slowly, and the rapidity of coagulation increases rapidly as the tempera-
ture rises, while coagulation takes place very rapidly at 40° C. in cold-blooded
animals, or at 48° to. 50° C. in warm-blooded muscles. The addition of distilled
water or an acid to muscle-plasma causes coagulation at once. The coagulated
proteid, most abundant in muscle, and which arises from the doubly refractive
substance, is called “myosin” (W. Athne).

Myosin.-—It is a globulin (§ 245), and is soluble in strong (10 per cent.) solution of common
salt, and is again precipitated from such a solution by dilution with water, or by the addition
of very small quantities of acids (0°1 to 0°2 per cent. lactic or hydrochloric acid). It is soluble
in dilute alkalies or slightly stronger acids (0°5 per cent. lactic or hydrochloric acid), and also
in 13 per cent. ammonium chloride solution. [The more myosin is freed from salts (especially
of calcium) by washing, the more insoluble does it become, both in saline solutions and weak
hydrochloric acid. . When once precipitated from its solution, it can be redissolved, reprecipi-
tated, and again undergo coagulation a second or even a third time (Halliburton).] Like fibrin,
myosin rapidly decomposes hydric peroxide. When treated with dilute hydrochloric acid and
heat, it is very rapidly changed into syntonin (§ 245), Myosin may be extracted from muscle
by a 10 to 15 per cent. solution of NH,Cl, and if it be heated to 65°, it is precipitated again
(Danielewsky). Danielewsky succeeded in partly changing syntonin into myosin by the action
of milk of lime and ammonium chloride. Myosin occurs in other animal structures (cornea),
nay, even in some vegetables (0. Masse).

Muscle-serum, according to Kiihne, still contains three proteids (2°3 to 3 per
cent.), viz. :—1. Alkali-albuminate, which is precipitated on adding an acid, even
at 20° to 24°C. 2. Ordinary serum-albumin, 1:4 to 1:7 per cent. (§°32, a), which
coagulates at 73° C. 3, An albuminate which coagulates at 47° C.

[Halliburton finds, however, the following proteids in muscle-plasma.—

Name. ee by Saturation with NaCl or Na,SO,. |

|

Paramyosinogen, . , : ee es Causes precipitation. ) Proteids which go to |
Myosinogen, : , 56° ve ‘i form muscle-clot. |
: 56 . |
Myoglobulin, =. 4 Se se toh lL) “Broteids ofane 4
Albumin, . ‘ , é 73 No. | ea ies emia |
Myoalbumose, : . Not | No: |; J ; |

Although the first two go to form the clot of muscle or myosin, paramyosinogen is
not essential for coagulation, Besides these bodies there are hemoglobin and
also myo-hematin, which is not identical with the blood-pigment. It can be ex-
tracted by ether from muscle (e.g., the breast muscle of a pigeon), whereby the ether
becomes red. It can exist in an oxidised and reduced condition (MacMunn). |

The other chemical constituents of muscle have been referred to in treating of
flesh (§ 233). 1, Muscle-ferments.—Briicke found traces of pepsin and peptone
in muscle-juice, [the latter is denied by Halliburton]; Piotrowsky, a trace of a
diastatic ferment. [When muscle becomes acid, as in rigor mortis, the pepsin ata
suitable temperature (35° to 40° C.) acts on the proteids, and albumoses and peptones
are formed. Halliburton found a myosin-ferment which has the characters of an
albumose. 2. In addition to volatile fatty acids (formic, acetic, butyric), there are
two isomeric forms of lactic acid (C,H,O.) present in muscle with an acid reaction :
—(a) Ethylidene-lactic acid, in the modification known as right rotatory sarcolactic
or paralactye acid, which occurs only in muscles, and some other animal structures,
(6) Ethylene-lactic acid in small amount (§ 251, 3, ¢). It was formerly assumed
that lactic acid is formed by fermentation from the carbohydrates of the muscle
(glycogen, dextrin, sugar), and Maly has observed that paralactic acid is occa-
sionally formed when these bodies undergo fermentation, According to Bohm,

464 METABOLISM IN MUSCLE.

however, the glycogen of muscle does not pass into lactie acid, as during rigor
mortis, if putrefaction be prevented, the amount of glycogen does not diminish.
If muscle be suddenly boiled or treated with strong alcohol, the ferment is destroyed,
and hence the acidification of the muscular tissue is prevented (Du Bois-Reymond).
Acid potassium phosphate also. contributes to the acid reaction, 3, Carnin
(C;H,N,O,) which is changed by bromine or nitric acid into sarkin, occurs to the
extent of 1 per cent. in Liebig’s extract of meat (Werdel). 4. Urea, 0°01 per cent.
(Haycraft). [There is much urea in the muscles of the skate.] 5. Glycogen
occurs to the amount of over 1 per cent. after copious flesh feeding, and to 0°5
per cent. during fasting. It is stored up in the muscles, as well as in the liver,
during digestion, but it disappears during hunger. It is perhaps formed in the
muscles from proteids (§ 174, 2). 6. Lecithin, derived in part from the motor
nerve-endings (§ 23 and § 251). 7. The gases are CO, (15 to 18 vol. per cent.),
partly absorbed, partly chemically united ; some absorbed N, but no O, although
muscle continually absorbs O from the blood passing through it (L. Hermann).
The muscles contain a substance whose decomposition yields CO,. When muscles
are exercised, this substance is used up, so that severely fatigued muscles yield
less CO, (Stinzing). [All muscles have not the same chemical composition. |

994. METABOLISM IN MUSCLE.—{In living muscle we have to study the
transformations of energy, and the chemical changes on which these depend. But
as we cannot examine the chemical changes which occur during a contraction, we
are confined to a study of (1) the composition of a muscle before and after contrac-
tion, and (2) the effect of contraction on the medium surrounding or passing through
a muscle. We may observe the effect produced by a muscle upon air or other
gases to which an excised muscle is exposed, or we may investigate the changes
which the blood undergoes in passing through a muscle, and if the muscle be still
in situ, the effect upon the general excreta. These methods may be applied to
muscle in various conditions, passive or active, dead or dying, to excised muscles
or those still under normal circumstances. | ;

I. A passive muscle continually absorbs a certain amount of O from the blood
flowing through its capillaries, and returns a certain amount of CO, to the blood-
stream. The amount of CO, given off is less than corresponds to the amount of O
absorbed. Excised muscles freed from blood exhibit an analogous but diminished
gaseous exchange. As an excised muscle remains longer excitable in O or in air
than in an atmosphere free from O, or in indifferent gases, we must conclude that the
above-named gaseous exchange is connected with the normal metabolism, and is
a condition on which the life and activity of the muscle depend, [Resting
living muscles also exhale CO,, |

If a living muscle be excised, and if blood be perfused through its blood-vessels, the amount
of O used up is, within pretty wide limits, almost independent of temperature ; if the variations
of temperature be great, it rises and falls with the temperature. The CO, given off by muscular
tissue (less than the O used up) falls when the muscle is cooled, but it is not increased when
the muscle is subsequently warmed (Rubner).

This exchange of gases must be distinguished from the putrefactive phenomena due to the
development of living organisms in the muscle. These putrefactive phenomena are also con-
nected with the consumption of O and the excretion of CO,, and occur soon after death (Z.
Hermann). ,

II. In an active muscle the blood-vessels are always dilated (Ludwig and
Sczelkow, Gaskell)—a condition pointing to a more lively material exchange in the
organ, [The dilatation of the blood-vessels can be observed microscopically in the
contracting mylo-hyoid muscle of the frog.) Hence, the active muscle is distin-
guished from the passive one by a series of chemical transformations, :

1. Reaction.—The neutral or feebly alkaline reaction of a passive muscle (
of the non-striped variety) passes into an acid reaction during the activity of the
muscle, owing to the formation of paralactic acid (Du Bois-Reymond, 1859); the

METABOLISM. IN MUSCLE. 465

degree of acidity increases up to a certain extent, according to the amount of work
performed by the muscle (#. Heidenhain). The acidification is due, according to
Weyl and Zeitler, to the phosphoric acid produced by the decomposition of lecithin
and (? nuclein).

It is doubtful if the acidity is due to lactic acid, as Warren and Astaschewsky find that
there is less lactic acid in the active than in the passive muscle. Marcuse, however, supports
the lactic acid theory, while Moleschott and Battistini, agree that the passive muscle contains
acid, but the fatigued muscle contains more, especially ‘of ‘phosphoric acid and CQ,.

2. Production of CO,.—An active muscle excretes considerably more CO, than
a passive one :—(qa) active muscular exertion on the part of a man or of animals
increases the amount of CO, given off by the lungs (§ 127) ; (4) venous blood flow-
ing from a tetanised muscle of a limb contains more CO,, more CO, being formed
than corresponds to the O, which has simultaneously been absorbed (Ludwig and
Sczelkow). The same result is obtained when blood is passed through an excised
muscle artificially ; (c) an excised muscle caused to contract excretes more CO,,.
(Compare § 368.)

3. Consumption of epeeeoin active muscle uses up more O—(a) when
more muscular work is done, the body absorbs much more O (§ 217)—even 4 to 5
times as much (Regnault and Reiset) ; (6) venous blood flowing from an active
muscle of a limb contains less O (Ludwig, Sczelkow, and Al. Schmidt). Neverthe-
less, the increase of O used up by the active muscle i is not so great as the amount
of CO, given off (v. Pettenkofer and v. Voit), The increase of O used up may be
ascertained even during the period of rest directly following the period of activity,
and the same is the case with the CO, excreted (v. Wey).

As yet, it is not possible to prove by gasometric methods, that O is used up in
an excised muscle free from blood. Indeed, the presence of O does not seem to
be absolutely necessary for the activity of muscle during short periods, as an
excised muscle may continue to contract in a vacuum, or ina mixture of gases
free from O, and no O can be obtained from muscular tissue (LZ. Hermann). A
frog’s muscles rob easily reducible substances of their O; they discharge the colour
of a solution of indigo; muscles which have rested for a time, acting less
energetically than those which have been kept in a state of continued activity
(Griitzner, G'scheidlen).

4, Glycogen. —The amount of glycogen (0°43 per cent. in 1 the muscles of a frog
or rabbit) and grape-sugar is diminished in an active muscle (O. Vasse, Weiss), but
muscles devoid of glycogen do not lose their excitability and contractility. Hence,
glycogen is certainly not the direct source of the energy in an active muscle.
Perhaps it is to be sought for in an as yet unknown decomposition-product of
glycogen (Luchsinger). [There is more glycogen in the red than in the pale
muscles of a rabbit. |
5, Extractives.—An active muscle contains less extractive substances soluble in
water, but more extractives soluble in alcohol (v. Helmholtz, 1845); it also
contains less of the substances which form CO, (Ranke); less Laas acids

__.» (Sezetkow) ; less kreatin and kreatinin (v. Voit).

6. During contraction, the amount of water in the muscular tissue increases,

| while that of the blood. is correspondingly diminished (7. Ranke). The solid

substances of the blood are increased, while they (albumin) are diminished in the

~ lymph (Fano).

7. Urea.—The amount of urea excreted from the body is not materially
increased during muscular exertion (v. Voit, Fick and Wislicenus). According to
Parkes, however, although the excretion of urea is not increased immediately, yet
after 1 to 14 day there is a slight increase. The amount of work done cannot be
determined from the amount of albumin which is changed into urea.

[Relation of Muscular Work to Urea.—Ed. Smith, Parkes, and others have ety numerous

| 2G

466 , METABOLISM IN MUSCLE.

investigations on this subject. Fick and Wislicenus (1866) ascended the Faulhorn, and for
seventeen hours before and for six hours after the ascent no proteid food was taken—the diet
consisting of cakes made of fat, sugar, and starch, The urine was collected in three periods, as
follows :—

| , | Fick. | _ Wislicenus.

| 1. Urea of 11 hours before the ascent, . | 288°55 grs. 221°05 grs. ;
ae 8 ,, during :. | 109744 ,, be 103°46°,, ) : |
ce ee ee — go-aa 7” § 18977 | “zp.gg 7 ¢ 188°35

A hearty meal was taken after this period, and the urine of the next eleven hours after the
period of rest contained 159°15 grains of urea (Fick), and 176°71 (Wislicenus). All the experi-
ments go to show that the amount of urea excreted in the urine is far more dependent upon the
nitrogen ingested, z.e., the nature of the food, than upon the decomposition of the muscular
substance. <A vegetable dict diminishes, while an animal diet greatly increases, the amount of
urea in the urine. North’s researches confirm those of Parkes, but he finds that the disturbance
produced by severe muscular labour is considerable. The elimination of phosphates is not
affected, while the sulphates in the urine are increased. ] .

During the activity of a muscle, a// the groups of the chemical substances
present in muscle undergo more rapid transformations (J. Ranke). It is still a
matter of doubt, therefore, whether we may assume that the kinetic energy of a
muscle is chiefly due to the transformation of the chemical energy of the
carbohydrates which are decomposed or used up in the process of contraction. As
yet we do not know whether the glycogen is supplied by the blood-stream to the
muscles, perhaps from the liver, or whether it is formed within the muscles
themselves from some unknown derivative of the proteids. The normal circulation
is certainly one of the conditions for the formation of glycogen in muscle, as
glycogen diminishes after ligature of the blood-vessels (Chandelon).’ ‘A’ muscle in
which the blood circulates freely is capable of doing more work than one devoid of
blood, and even in the intact body, more blood is always supplied to the contracted
muscles. .

{Source of Muscular Energy.—The experiment of Fick and Wislicenus
definitely proved that the proteids are not the exclusive, or by any means the
chief source of muscular energy. As it is conclusively proved, that during
muscular work, there is a great increase in the amount of O absorbed, and CO,
given off, it is evident that the non-nitrogenous substances of the food must be
the chief sources of this energy. We turn naturally to the carbohydrates, and as
the latter are chiefly stored up in the form of glycogen in the muscles, it is
assumed that glycogen is the chief source of the energy. Glycogen in muscle
diminishes during muscular work, and is stored up during rest (Bernard). Kiilz
also found that in dogs the glycogen disappears from the liver during work, and
Voit found that the muscle-glycogen disappears before that in the liver. It
appears, therefore, that the carbohydrates are a source of muscular energy. But
they, again, are not the only source. It is highly probable that glycogen can be
formed from proteids, and it is allowable, therefore, to assume that proteids may
also serve as a source of muscular energy. If this be not so, it is difficult to
understand how carnivora can be fed and maintained in good health for long
periods on lean flesh. The fats are probably also another source. Hence, it would
appear that all three of the chief groups of food-stuffs—carbohydrates, proteids,
and fats—may serve as the source of muscular energy ; but that, so long as non-
nitrogenous elements are supplied in the food in sufticient quantity, or are stored
up in the body, the muscles do their work chiefly on these. After they are used up,
the proteids are, as it were, called up.] Ve

295, RIGOR MORTIS.—Cause.—Excised striped, or smooth muscles, and
also the muscles of an intact body, at a certain time after death, pass into a
condition of rigidity— cadaveric rigidity or rigor mortis. When all the muscles

;

CAUSE OF RIGOR MORTIS. 467

of a corpse are thus affected, the whole cadaver becomes completely stiff or rigid.
The cause of this phenomenon depends upon the spontaneous coagulation of a
proteid, viz., the myosin of the muscular fibres (Atihne). Under certain circum-
stances, the coagulation of the other proteids of the muscle may increase the
rigidity. During the process of coagulation, an acid is formed, heat is set free
(v. Walther, Fick—§ 223), owing to the passage of the fiuid myosin into the solid
condition, and also to the simultaneous and subsequently increased density of the
tissue.

Properties of a Muscle in Rigor Mortis.—It is shorter, thicker, and somewhat
denser (Schmulewitsch) ; stiff, compact, and solid; turbid and opaque (owing to
the coagulation of the myosin) ; incompletely elastic, less extensible, and more
easily torn or ruptured; it is completely inexcitable to stimuli; the muscular
electrical current is abolished, (or there is a slight current in the opposite direction) ;
its reaction is acid, owing to the formation of both forms of lactic acid (§ 293),
glycero-phosphoric acid (Diakanow); while it also develops free CO,. When
an incision is made into a rigid muscle, a fluid, the muscle-serum, appears
spontaneously in the wound (§ 293).

The first formed lactic acid converts the salts of the muscle into acid salts ; thus, potassium
lactate and acid potassium phosphate are formed from potassium phosphate. ‘The lactic acid,
which is formed thereafter, remains free and ununited in the muscle.

Amount of Glycogen.—The newest observations of Bohm are against the view that, during
rigor mortis, a partial or complete transformation of the glycogen into sugar and then into
lactic acid takes place. During digestion, a temporary storage of glycogen occurs in the muscles
as well as in the liver, so that about as much is found in the muscles as in the liver. There —
is no diminution of the glycogen when rigidity takes place, provided putrefaction be prevented ;
so that the lactic acid of rigid muscles cannot be formed from glycogen, but more probably it
is formed from the decomposition of the albuminates (Demant, Bohin).

The amount of acid does not vary, whether the rigidity occurs rapidly or slowly (J. Ranke) ;
when acidification begins, the rigidity becomes more marked, owing to the coagulation of the
alkali-albuminate of the muscle. Less CO, is formed from a rigid muscle, the more CO, it has
given off previously, during muscular exertion. <A rigid muscle gives off N, and absorbs O. In
a cadaveric rigid muscle, fibrin-ferment is present (Al. Schmidt and others). It seems to be a
product of protoplasm, and is never absent where this occurs (Rawschenbach). [The myosin-
ferment seems not to be identical with the fibrin-ferment (p. 463). ]

[Rigor Mortis and Coagulation of Blood.—Thus, there is a marked analogy
between the coagulation of the blood and that of muscle. In both cases, a fluid
body yields a solid body, fibrin from blood, and myosin from muscle ; the coagula-
tion of blood is prevented by neutral salts, and so is the coagulation of myosin ;
dilution of the salted plasma produces coagulation in both cases ; and perhaps the
coagulation in both is due to the action of a ferment, the one the fibrin-ferment
the other the myosin-ferment. There are, however, points of difference, for
myosin can be dissolved, reprecipitated, and coagulated several times, while fibrix
does not undergo recoagulation ; the formation of myosin from myosinogen, again,
is accompanied by the development of an acid, whereas that of fibrin from
fibrinogen is not; further, the formation of myosin is uot accompanied by the
formation of another globulin, whereas that of fibrin from fibrinogen is. |

Stages of Rigidity.—Two stages are recognisable in cadaveric muscles :—In
the first stage, the muscle is rigid, but still excitable ; in this stage the myosin
seems to be in a jelly-like condition. Restitution, is still possible during this stage.

‘In the second stage, the rigidity is well pronounced, with all the phenomena

above mentioned.

The onset, of the rigidity varies in man from ten minutes to seven hours [but as
a rule it is complete within four to six hours after death. The muscles of the jaws
are first affected, then those of the neck and trunk, afterwards (as a rule) the
lower limbs, and finally the. upper limbs]. Its duration is equally variable—one
to six days. After the cadaveric rigidity has disappeared, the muscles, owing to

468 STAGES OF CADAVERIC RIGIDITY.

further decompositions and an alkaline reaction, become soft, and the rigidity dis-
appears (Vysten). The onset of the rigidity is always preceded bya loss of nervous
activity. Hence, the muscles of the head and neck are first affected, and the other
muscles in a descending series (§ 352). Disappearance of the rigidity occurs first in
the muscles first affected (Vysten). Great muscular activity before death (e.g., spasms
of tetanus, cholera, strychnin, or opium poisoning) causes rapid and intense rigidity;
hence, the heart becomes rigid relatively rapidly, and strongly. Hunted animals
may become affected within a few minutes after death. Usually the rigidity lasts
longer the later it occurs. Rigidity does not occur in a foetus before the seventh
month. A frog’s muscle cooled to 0° C. does not begin to exhibit cadaveric
rigidity for four to seven days.

Stenson’s Experiment.—The amount of blood in a muscle has a marked effect
upon the onset of the rigidity. Ligature of the muscular. arteries causes at first in
all mammals an increase of the muscular excitability, and then a rapid fall of the
excitability (Schmulewitsch) ; thereafter stiffness occurs, the one stage following
closely upon the other (Swammerdam, Nic. Stenson, 1667). [If the ligature be
removed in the first stage, the muscle recovers, but in the later stages the rigidity
is permanent.] If the artery going toa muscle be ligatured, Stannius observed
that the excitability of the motor nerves disappeared after an hour, that of the
muscular substance after four to five hours, and then cadaveric rigidity set in.

Pathological.— When the blood-vessels of a muscle are occluded, by coagulation taking
place within them, rigidity of the muscles is produced (§ 102). True cadaveric rigidity may be
produced by too tight bandaging ; the muscles are paralysed, rigid, and break up into flakes,
while the contents of the fibre are afterwards absorbed (R. Volkmann). Occlusion of the blood-
vessels of muscles by infarcts, especially in persons with atheromatous arteries, may even cause
necrosis of the muscles implicated (Finch, Girandeau).

If the circulation be re-established during the first stage of the rigidity, the
muscle soon recovers its excitability (Stannius). When the second stage has set
in, restitution is impossible (Avihne). In cold-blooded animals, cadaveric rigidity
does not occur for several days after ligaturing the blood-vessels. Brown-Séquard,
by injecting fresh oxygenated blood into the blood-vessels, succeeded in restoring the
excitability of the muscles of a human cadaver four hours after death, z.¢., during
the first stage of cadaveric rigidity. Ludwig and Al. Schmidt found that the onset
of cadaveric rigidity was greatly retarded in excised muscles, when arterial blood
was passed through their blood-vessels. Blood deprived of ifs O did not produce
this effect. Cadaveric rigidity occurs relatively early after severe hemorrhage. If
a weak alkaline fluid be perfused through the blood-vessels of the dead muscles
of a frog, cadaveric rigidity is prevented (Schipilof’).

Section of Nerves.—Preliminary section of the motor nerves causes a later
onset of the rigidity in the corresponding muscles (Brown-Séquard, Heineke). [The
same result occurs after a hemi-section of the spinal cord or after removal of one
cerebral hemisphere (Bierfreund).| In fishes, whose medulla oblongata is suddenly
destroyed, cadaveric rigidity occurs much more slowly than in those animals that
die slowly (Blane).

[Other Influences. —Rigidity begins much later in the red (11 to 15 hours) than in pale muscles
(1 to 3 hours post-mortem) ; the rigor is complete in the white muscles in 10 to 14 hours, in
the red in 52 to 58 hours. The extent of shortening due to the rigor is 2 to 24 times as great
as in the white. In both muscles the resolution of the rigor begins 12 to 15 hours after the
completion of the rigidity, so that the red muscles are not completely rigid before the other
muscles appear to have passed from a state of rigidity. Temperature has a marked effect, but it
acts more on the resolution than on the onset of the rigor. At 60° C. the onset begins almost
at once, and is complete in a few minutes (Bierfrewnd). Ether and chloroform injected into the
blood-vessels cause almost instantaneous rigor (Kussmaut).]

Rigidity may be produced artificially by various reagents :—

1. Heat [‘ Heat-stiffening ”’] causes the myosin to coagulate at 40° C. in cold-
blooded animals, in birds about 53° C., and in mammals at 48° to 50° C. The

—_

’

EFFECT OF HEAT, WATER, AND ACIDS ON MUSCLE. 469

protoplasm of plants and animals, e.g., of the amceba, is coagulated by heat, giving
rise to heat rigor.

Schmulewitsch found that the longer a muscle had been excised from the body, the greater
was the heat required to produce stiffening. Heat-stiffening differs from cadaveric rigidity
thus :—a 13 per cent. solution of ammonium chloride dissolves out the myosin from a cadaveric
rigid muscle, but not from one rendered rigid by heat (Schipiloff). If the rigid cadaveric
muscles of a frog be heated, another proteid coagulates at 45°, and lastly at 75° the serum-
albumin itself. Hence, both processes together make the muscle more rigid (§ 295).

2. When a muscle is saturated with distilled water, it produces “ water-
stiffening ’—an acid reaction being developed at the same time.

Muscles rendered stiff by water still exhibit electromotive phenomena, while muscles
rendered rigid by other means do not (Biedermann). If the upper limb of a frog be ligatured,
deprived of its skin, and dipped in warm water, it becomes rigid. If the ligature be removed
and the circulation re-established, the rigidity may be partially set aside. If there be well-
marked rigidity, it can only be set aside by placing the limb in a 10 per cent. solution of com-
mon salt, which dissolves the coagulum of myosin (Preyer).

3. Acids, even CO,, rapidly produce ‘‘acid-stiffening,” which is probably
different from ordinary stiffening, as such muscles do not evolve any free CO,
(L. Hermann). The injection of 0°1 to 0°2 per cent. solutions of lactic or hydro-
chloric acid into the muscles of a frog produces stiffening at once, which may be
set aside by injecting 0°5 per cent. solution of an acid, or by a solution of soda, or
by 15 per cent. solution of ammonium chloride. The acids form a compound with
myosin (Schipiloff).

4. Freezing and thawing a part alternately, rapidly produce stiffening ; and it
is aided by mechanical injuries. |

Poisons.—Rigor mortis is favoured by quinine, caffein, digitalin, [a concentrated solution of
caffein or digitalin, applied to the muscle of a frog, produces rigor mortis], veratrin, hydrocyanic —
acid, ether, chloroform, the oils of mustard, fennel, and aniseed; direct contact of muscular
tissue with potassium sulphocyanide (Bernard, Setschenow), ammonia, alcohol, and metallic salts.

Position of the Body.—The attitude of the body during cadaveric rigidity is generally that
occupied at death ; the position of the limbs is the result of the varying tensions of the different
muscles. During the occurrence of rigor mortis, a limb, or more frequently the arm and fingers,
may move (Sommer). Thus, if stiffening occurs rapidly and firmly in certain groups of muscles,
this may produce movements, as is sometimes seen in cholera. If cadaveric rigidity occurs very
rapidly, the body may occupy the same position which it did at the moment of death, as some-
times happens on the battle-field. In these cases it does not seem that a contracted condition
of the muscle passes at once into rigor mortis; but between these two conditions, according to
Briicke, there is always a very short relaxation.

Muscles which have been plunged into boiling water do not undergo rigor mortis, neither do
they become acid (Du Bois- Reymond), nor evolve free CO, (L. Hermann).

Work done during Rigidity.—A muscle in the act of becoming stiff will lift a weight, but
the height to which it is lifted is greater with small weights, less with heavier weights, than
when a living muscle is stimulated with a maximal stimulus.

Analogy between Contraction and Rigidity.—L. Hermann has drawn attention
to the analogy which exists between a muscle in a state of contraction and one in
a state of cadaveric rigidity—both evolve CO, and the other acids from the same
source ; [both acts take place without the consumption of O]. The form of the
contracted and of the stiffened muscles is shorter and thicker; both are denser, less
elastic, and evolve heat ; in both cases, the muscular contents behave negatively
as regards their electromotive force, in reference to the unaltered, living, resting
substance. Hence, he is inclined to regard a muscular contraction as a temporary,
physiological, rapidly disappearing rigor. Rigor mortis is in a certain sense the
last flickering act of a living muscle, [and he regards contraction as partial
death of a muscle. But this is no explanation, and moreover there are important
points of difference. We have no proof of a coagulum being formed during con-
traction, while the extensibility is increased during contraction and much diminished
during rigor. | |

Disappearance of Rigidity.—When rigor mortis passes off, there is a consider-

470 MUSCULAR EXCITABILITY.

able amount of acid formed in the muscle, which dissolves the coagulated myosin.
After a time putrefaction sets in, accompanied by the presence of micro-organisms
and the evolution of ammonia and putrefactive gases (H,S, N, CO,—§ 184).
[Hermann and Birerfreund attach much importance to the resolution of rigor
mortis independently of putrefaction. | :

According to Onimus, the loss of excitability which precedes the onset of rigor mortis occurs
in the following order in man :—left ventricle, stomach, intestine (55 minutes); urinary bladder,
right ventricle (60 min.); iris (105 min.); muscles of face and tongue (180 min.); the extensors
of the extremities (about one hour before the flexors); the muscles of the trunk (five to six
hours). The cesophagus remains excitable for a long time (§ 325).

996. MUSCULAR EXCITABILITY.—By the term excitability or irrita-
bility of a muscle, is meant that property of a muscle in virtue of which it responds
to stimuli, at the same time becoming shorter and correspondingly thicker. The
condition of excitement is the active condition of a muscle produced by the applica-
tion of stimuli, and is usually indicated by the act of contraction. Stimuli are
simply various forms of energy, and they throw the muscle into a state of excite-
ment, while at the moment of activity the chemical energy of the muscle is trans-
formed into work and heat, so that stimuli act as “ liberating ” or ‘“ discharging
forces.” [These “discharging forces” may themselves be very feeble, but they
are capable of causing the manifestation of the transformation of a large amount
of energy.] The normal temperature of the body is most favourable for main-
taining the normal muscular excitability ; the excitability varies as the tempera-
ture rises or falls. . |

As long as the blood-stream within a muscle is uninterrupted, the first effect
of stimulation of a muscle is to increase its energising power, partly because the
circulation is more lively and the blood-vessels are dilated, but after a time, the
energising power is diminished. Even in excised muscles, especially when the
large nerve-trunks have already lost their excitability, the excitability is increased
after a stimulus, so that the application of a series of stimuli of the same strength
causes a series of contractions which are greater than at first (Wwndt). Hence,
we account for the fact that, although the first feeble stimulus may be unable to
discharge a contraction, the second may, because the first one has increased the
muscular excitability (/%ch).

Effects of Cold.—If the muscles of a frog or tortoise be kept in a cool place, they may remain
excitable for ten days, while the muscles of warm-blooded animals cease to be excitable after
one and a half to two and a half hours. (For the heart see § 55.) A muscle, when stimulated
directly, always remains excitable for a longer time when its motor nerve is already dead.

[Independent Muscular Excitability.—Since the time of Albrecht v. Haller, and
R. Whytt, physiologists have ascribed to muscle a condition of excitability which
is entirely independent of the existence of motor nerves, but is dependent on certain
constituents of the sarcous substance. Excitability, or the property of responding
to a stimulus, is a widely distributed function of protoplasm or its modifications.
A colourless blood-corpuscle or an amceba is excitable, and so are secretory and
nerve-cells, In the first case, the application of a stimulus results in motion in
an indefinite direction, in the second in the formation of a secretion, and in the
third in the discharge of nerve-energy. In the case of muscle, a stimulus causes
movement in a definite direction, called a contraction, and depending on the con-
tractility of the sarcous substance. There are many considerations which show, that
excitability is independent of the nervous system, although in the higher animals,
nerves are the usual medium through which the excitability is brought into action.
Plants however are excitable, and they contain no nerves. |

Numerous experiments attest the ‘independent excitability’ of muscle :—1.
There are chemical stimuli, which do not cause movement when applied to motor
nerves, but do so when they are applied directly to muscle ; ammonia, lime water,

ACTION OF CURARA. — 471
carbolic acid. 2. The ends of the sartorius of the frog, in which no nerve-termina-
tions are observable by means of the microscope, contract when they are stimulated
directly (Kuihne). 3. Curara paralyses the extremities of the motor nerves, while
the muscles themselves remain excitable (Cl. Bernard, Kélliker). The action of
cold, or arrest of the blood supply in an animal, abolishes the excitability of the
nerves, but not of the muscles at the same time. 4. After section of its nerve, a
muscle still remains excitable, even after the nerves have undergone fatty degenera-
tion (Brown-Séquard, Bidder). 5. Sometimes electrical stimuli act only upon the
nerves and not upon the muscle itself (Briicke). [6. The foetal heart contracts
rhythmically before any nervous structures are discoverable in it. |

[The Action of Curara.—Curara, woorali, urari, or Indian arrow poison of South America, is
the inspissated juice of the Strychnos crevauxi. A watery extract of the drug, when injected
under the skin or into the blood of an animal, acts chiefly upon the motor nerve-endings, and
does not affect the muscular contractility. An active substance, cwrarin, has been isolated
from it (p. 474). Poison a frog by injecting a few milligrammes into the dorsal lymph-sac. In
a few minutes after the poison is absorbed, the animal ceases to support itself on its fore-limbs;
it lies flat on the table, its limbs are paralysed, and so are the respiratory movements in the
throat. When completely under the action of the poison, the frog lies in any position, limp
and motionless, neither exhibiting voluntary nor reflex movements. If the brain be destroyed
and the skin removed, on faradising the sciatic nerve, no contraction of the muscles of the hind-
limb occurs, but if the electrical stimulus be applied directly to the muscles, they contract,
thus proving that curara poisons the motor connections and not the muscles. Ifthe dose be
not too large, the heart still continues to beat, and the vaso-motor nerves remain active. ]

[Methods.—(1) Local Application.—Bernard took two nerve-muscle prepara-
tions, put some solution of curara into two watch-glasses, and dipped the nerve
into one glass and the muscle of the other preparation |
into the other glass. The curara penetrated into both
preparations, and he found, on stimulating the nerve
which had been steeped in curara, that its muscle still
contracted, so that the curara had not acted on the motor
nerve-fibres ; while stimulation of the nerve of the other
preparation produced no contraction, although the corre-
sponding muscle contracted. In the latter case, the curara
had penetrated into the muscle and affected the intra-
muscular portions of the nerve. |

[(2) But it is the terminal or intra-muscular portions
of the nerves, not the nerve-trunk, which are paralysed.
Ligature the sciatic artery, or, better still, tie all the
parts of the hind-limb of a frog, except the sciatic nerve,
at the upper part of a thigh (fig. 315). Inject curara
into the dorsal lymph-sac. The poisoned blood will, of
course, circulate in every part of the body except the
ligatured limb. The shaded parts are traversed by the
poison. The animal can still, at a certain stage of the © —_—=*Fig. 815.
poisoning, pull up the non-poisoned limb, while it cannot frog with sciatic artery li-

; A. ‘ gatured. S.P., spinal cord
move the poisoned one. At this time, although poisoned Jith afforent and efferent
blood has circulated in the sacral and intra-abdominal nerves; P., poisoned, N.P.,
parts of the nerves, yet they are not paralysed, so that non-poisoned leg ; M
the poison does not act on this part of the trunk of the ttecnemius muscles.
nerve. But we can show that it does not act on any part of the extra-muscular
trunk of thenerve. This is done by ligaturing the arteries going to the gastrocnem-
ius muscle, and then poisoning the-animal. On stimulating the nerve on the
ligatured side, the gastrocnemius of that side contracts, although the whole length
of the nerve-trunk was supplied by poisoned blood. Therefore, it is the znéra-
muscular terminations of the nerves which are acted on.|

, gas-

472 ACTION OF CURARA.

[By means of the following arrangement we may prove that the terminal parts
of the nerve are paralysed. Ligature the sciatic artery of one leg of a frog, and
then inject curara into a lymph-sac. After the
animal is fully poisoned, expose the sciatic
nerve in both legs, leaving all the muscles
below the knee-joint, then clean and divide
the femur at its middle. Pin a straw flag to
each limb, and fix both femora in a clamp,
with the gastrocnemii uppermost, as in fig.
316. Place the two nerves, N, on electrodes
attached to two wires coming from a com-
mutator, C (fig. 316). From the opposite
binding screws of the commutator, two wires
pass to the gastrocnemii. The other two
binding screws of the commutator are con-
nected with the secondary coil of an induction
machine (§ 330). The bridge of the com-
mutator can be turned so as to pass the current
| either through both muscles or both nerves—
| the latter is the case in the diagram (H).
: When both nerves are stimulated, only the non-
poisoned leg (NP) contracts. Reverse the com-
mutator, and pass the current through both
muscles, when both contract. |

[Rosenthal’s Modification. —Pull the secondary coil
far away from the primary, and pass the current
through both muscles. Gradually approximate the
secondary to the primary coil, and in doing so, it will
be found that the non-poisoned leg contracts first,
but on continuing to push up the secondary coil, both limbs contract. Thus, the poisoned limb

Fig. 316.

Scheme of the curara experiment. — B,
battery; I, primary, II, secondary
spiral; N, nerves; F, clamp; NP,
non-poisoned leg; P, poisoned leg ;
C, commutator ; K, key.

norm
curare

Fig. 317. Fig. 318.

Fig. 317.—Curve showing the excitability in the sartorius of a frog in a normal and curarised
muscle, Fig. 318.—Distribution of nerves in the sartorius of a frog and the curve of ex-
citability in different parts of the muscle, 7.¢., the excitability is greatest where there are
most nerve-endings.

does not respond to'so feeble a faradic stimulus as the non-poisoned one, a result which is not
due‘to the action of the curara on the excitability of the muscle. The non-poisoned limb

“MUSCULAR STIMULI, 473

responds to a feebler stimulus because its motor nerve terminations are not paralysed, while the
poisoned leg does not do so, because the motor terminations are paralysed. A feebler induced
shock suffices to cause a muscle to contract when it is applied to the nerve, than when it is
applied to the muscle itself directly. In large doses, curara also affects the spinal cord (p. 474). ]

[On what structures does curara act?—These experiments prove that curara does not
paralyse the motor nerve-trunks, nor the muscular fibres, and that it acts on the motor termin-
ations within the muscles, but they do not enable us to state the precise part of the nerve-ending
so affected. It may act on (1) the nerve just before it pierces the sarcolemma, (2) the sub-lemmar
axis-cylinder, (3) the end-plates, (4) the terminal branches or spray. Kiihne and Pollitzer
have made it probable that, even when a muscle is thoroughly impregnated with curara, some
of the nervous apparatus is unaffected. The sartorius is most excitable where there are most
nerves (fig. 318), and even in a muscle profoundly poisoned with curara, the distribution of
excitability varies with the number of nerves in the several parts of the muscle (fig. 317) just
as in a normal muscle, with this difference, that the excitability of all the parts of the muscle
containing nerves is less than normal. That this variation in excitability is due to nervous
structures, is shown by using a polarising anelectrotonic current (§ 335), which depresses the
excitability of nerve-fibres, and then this difference of excitability disappears, the curve of ex-
citability running parallel with the abscissa, so that the difference does not seem to be due
to purely muscular causes. ]

[Pollitzer, speculating as to which part of the terminal nerve is affected, supposes that all
parts beyond the last node of Ranvier retain their functions, and he supposes that it is not the
axis-cylinders themselves, but the cement at the nodes, on which the drug exerts its specific
action.

Reet uiCulae Cells. —Even in the lower animals, ¢.g., Hydra and Meduse, there are uni-
cellular structures called ‘‘newro-muscular cells,” in which the nervous and muscular sub-
stances are represented in the same cell (Kleinenberg and Eimer). [The outer part of these
cells is adapted for the action of stimuli, and corresponds to the nervous receptive organ, while
the inner deeper part is contractile, and is the representative of the muscular part. ]

Muscular Stimuli.—Various stimuli cause a muscle to contract, either by
- acting upon its motor nerve, or upon the muscular substance itself (§ 324). [The
former is called indirect stimulation, the latter direct stimulation. |

1. Under ordinary circumstances, the normal stimulus exciting a muscle to
contract is the nerve impulse which passes along a nerve, but its exact nature is
unknown.

2. Chemical Stimuli.—All chemical substances which alter the chemical com-
position of a muscle with sufficient rapidity, act as muscular stimuli. Mineral
acids (HCl 01 per cent.), acetic and oxalic acids, the salts of iron, zinc, copper,
silver, and lead, bile, all act in weak solutions as muscular stimuli; they act upon
the motor nerve only when they are more concentrated. Lactic acid and glycerin,
when concentrated, excite only the nerve; when dilute, only the muscle. [The
lower end of the sartorius, which contains no nerves, may be dipped into glycerin,
and it will not contract, but if it be dipped deeper to where there are nerve-
endings, it will contract at once.| Neutral alkaline salts act equally upon nerve
and muscle; alcohol and ether act on both very feebly. When water is injected
into the blood-vessels, it causes fibrillar muscular contractions (v. Wettich), while a
06 per cent. solution of NaCl may be passed through a muscle for days without
causing contraction (Kdlliker, O. Nasse). |Carslaw, under Ludwig’s direction,
however, found that solutions containing 0°5 to 0°2 per cent. NaCl, when perfused
through the muscles of a frog, excite many short, powerful attacks of tetanus,
separated from each other by. periods of rest. Solutions containing 0°5 to 0-7 per
cent. NaCl, z:e., so-called “indifferent fluids” or “ normal saline,” are not without
influence, but of all known saline solutions, they injure a nerve-muscle preparation
least. Solutions of 1 to 2 per cent. rapidly kill the muscle.] Acids, alkalies, and
extract of flesh diminish the muscular excitability, while the muscular stimuli,
in small doses, increase it (Ranke). Gases and vapours stimulate muscle; they
cause either a simple contraction (e.g., HCl), or at once permanent contraction or
contracture (e.g., Cl). Long exposure to the gas causes rigidity. The vapour of
bisulphide of carbon stimulates only the nerves, while most vapours (e.g., HCl) kill
without exciting them (Kvihne and Jani). .

474 THERMAL AND MECHANICAL’ STIMULI.

Method. —In making experiments upon the chemical stimulation of muscle, it is inadvisable
to dip the transverse section of the muscle into the solution of the chemical reagent (Hering).
The chemical stimulus ought to be applied in solution to a limited portion of the uninjured
surface of the muscle; after a few seconds, we obtain a contraction or fibrillar twitchings of the:
superficial muscular layers (Hering). .

{Rhythrnical Contraction.—W hile rhythmical contractions are very marked in smooth muscle,
(especially if it is stretched or subjected to considerable internal pressure, as in the hollow
viscera), ¢.g., the intestine, uterus, ureter, blood-vessels, and also in the striped but involuntary
cardiac musculature (§ 48), they are not, as a rule, very common in striped voluntary muscle.
Chemical stimuli are particularly effective in producing them.] If the sartorius of a curarised
frog be dipped into a solution composed of 5 grms. NaCl, 2 grms. alkaline sodium phosphate,
and 0°5 grm. sodium carbonate in 1 litre of water, at 10° C., the muscle contracts rhythmically,
and may do so for several days, especially with a low temperature (Biedermann). This recalls
the rhythmical contraction of the heart. [Kiihne found a similar result. The rhythm is
arrested by lactic acid and restored by an alkaline solution of NaCl.] Rhythmical movements
may also be induced in the sartorius (frog), by the combined action of a dilute solution of sodic
carbonate and an ascending constant electrical current. Compare also the action of a constant
current on the heart (§ 58).

3. Thermal Stimuli.—If an excised frog’s muscle be rapidly heated to 28° C., a
gradually increasing contraction occurs, which, at 30° C., is more pronounced,
reaching its maximum at 45° C. If the temperature be raised, “ heat-stiffening ”
rapidly ensues. The smooth muscles of warm-blooded animals also contract when
they are warmed, but those of cold-blooded animals are elongated by heat (Grwn-
hagen). If a frog’s muscle be cooled to 0°, it is very excitable to mechanical
stimuli (Griinhagen) ; it is even excited by a temperature under 0° (Eckhard).

Cl. Bernard observed that the muscles of animals, artificially cooled, remained excitable many
hours after death (§ 225). Heat causes the excitability to disappear rapidly, but increases it
temporarily.

4. Mechanical Stimuli.—Every kind of sudden mechanical stimulus, provided
it be applied with sufficient rapidity to a muscle (and also to a nerve), causes a
contraction. If stimuli of sufficient intensity be repeated with sufficient rapidity,
tetanus is produced. Strong local stimulation causes a weal-like, long-continued
contraction at the part stimulated (§ 297, 3, a). Moderate tension of a muscle
increases its excitability.

5. Electrical Stimuli will be referred to when treating of the stimulation of
nerve (§ 324).

Other Actions of Curara.—When it is injected into a frog, either into the blood or sub-
cutaneously, it causes at first paralysis of the intra-muscular ends of the motor nerves (p. 471),
while the muscles themselves remain excitable. The sensory nerves, the central nervous system,
viscera, heart, intestine, and the blood-vessels are not affected at first (Cl. Bernard, Kélliker).
[If the skin be stimulated, the frog pulls up the ligatured leg reflexly, although the other leg
remains quiescent; this shows that the sensory nerve and nerve-centres are still intact; but

when the action of the drug is fully developed, no amount of stimulation of the skin or the
aan roots of the nerves will give rise to a reflex act, although the motor nerve of the

igatured limb is known to be excitable; hence, it is probable that the nerve-centres in the cord .

themselves are ultimately affected. If the dose be very large, the heart and blood-vessels are
affected.] In warm-blooded animals, death takes place by asphyxia, owing to paralysis of the
diaphragm, but of course there are no spasms. In frogs, where the skin is the most important
respiratory organ, if a suitable dose be injected subcutaneously, the animal may remain motion-
less for days and yet recover, the poison being eliminated by the urine (Kiihne). If the dose
be large, the inhibitory fibres of the vagus may be pereiiieed. In electrical fishes, the sensory
nerves, and in frogs, the lymph-hearts are paralysed. A dose sufficient to kill a frog, when in-
jected under its skin, will not do so if administered by the mouth, because the poison seems to
be eliminated as rapidly by the kidneys as it is absorbed from the gastric mucous membrane.
For the same reason the flesh of an animal killed by curara is not poisonous when eaten. If,
however, the ureters be tied, the poison collects in the blood, and poisoning takés place
(L. Hermann). [In this case the mammal may exhibit convulsions. Why? Curara

the respiratory nerves, so that asphyxia is produced from the venosity of the blood, it affects
the respiratory nerve-endings before those in the muscles generally, so that when the venous
blood stimulates the nerve-centres, the partially affected muscles respond by convulsions. Other
narcotics may excite convulsions indirectly by inducing a venous condition of the blood, while
the motor centres, nerves, and muscles are still unaffected.] Large doses, however, poison un-

CHANGES IN A MUSCLE DURING CONTRACTION. 475

injured animals even when given by the mouth. The nerves and muscles of poisoned animals
exhibit considerable electromotive force. [For the effect of curara on lymph-formation
($ 199, 6).]

Atropin appears to be a specific poison for smooth muscular tissue, but different muscles are
differently affected (Szpilmann, Luchsinger). [This is doubtful. A small quantity of atropin
seems to affect the motor nerves of smooth muscle in the same way that curara does those of
striped muscle; we must remember, however, that there are no end-plates proper in the former,
so that the link between the nerve-fibrils and the contractile substance is probably different in
the two cases. It is well known that the amount of striped and smooth muscle varies in the
cesophagus in different animals. Szpilmann and Luchsinger found that, after the action of
atropin, stimulation of the peripheral end of the vagus will still cause contraction of the striped
muscular fibres in the cesophagus, but not of the smooth fibres, although both forms of muscular
tissue respond to direct stimulation. ]

After section of the motor nerve of a muscle, the excitability undergoes remarkable changes ;
after three to four days the excitability of the paralysed muscle is diminished, both for direct
and indirect stimuli (p. 473); this condition is followed by a stage, during which a constant
current is more active than normal, while induced currents are scarcely or not at all effective
(§ 339, I.). The excitability to mechanical stimuli is also increased. The increased excitability
occurs until about the seventh week; it gradually diminishes until it is abolished towards the
sixth to the seventh month. Fatty degeneration begins in the second week after section of the
motor nerve, and goes on until there is complete muscular atrophy. Immediately after section
of the sciatic nerve, Schmulewitsch found that the excitability of the muscles supplied by it
was increased.

297. CHANGES IN A MUSCLE DURING CONTRACTION.—I. Macro-
scopic Phenomena.—1. When a muscle contracts, it becomes shorter and at the
same time correspondingly thicker.

The degree of contraction, which in very excitable frogs may be 65 to 85 per cent. (72 per
cent. mean) of the tctal length of the muscle, depends upon various conditions :—(a) Up toa
certain point, increasing the strength of the stimulus causes a greater degree of contraction ;
(6) as the muscular fatigue increases, 7.¢., after continued vigorous exertion, the stimulus
remaining the same, the extent of contraction is diminished ; (c) the temperature of the sur-
roundings has a certain effect. The extent of the contraction is increased in a frog’s muscle—
the strength of stimulus and degree of fatigue remaining the same—when it is heated to
33°C. Ifthe temperature be increased above this point, the degree of contraction is diminished
(Schmulewitsch).

2. The volume of a contracted muscle is slightly diminished (Swammerdam, +
1680). Hence, the specific gravity of a contracted muscle is slightly increased,
the ratio to the non-contracted muscle being 1062 : 1061 (Valentin) ; the diminu-
tion in volume is, however, only ;34-5, although this has recently been denied by
J. Ewald.

Methods.—(a) Erman placed portions of the body of a live eel in a glass-vessel filled with an
indifferent fluid. A narrow tube communicated with the glass-vessel, and the fluid rose in the
tube to a certain level. As soon as the muscles of the eel were caused to contract, the fluid in
the index-tube sank. (b) Landois demonstrates the decrease in volume by means of a mano-
metric flame. The cylindrical vessel containing the muscle is provided with two electrodes
fixed into it in an air-tight manner. The interior of the vessel communicates with the gas
supply, while there is a small narrow exit-tube for the gas, which is lighted. Every time the
muscle contracts, the flame diminishes. The same experiment may be performed with a con-
tracting heart.

3. Total and Partial Contraction.—Normally, all stimuli applied to a muscle or
its motor nerve cause contraction in all its muscular fibres. Thus, the muscle con-
ducts the state of excitement to all its parts. Under certain circumstances, how-
ever, this is not the case, viz. :—(a) when the muscle is greatly fatigued, or when
it is about to die, violent mechanical stimuli, as a vigorous tap with the finger or a
percussion hammer (and also chemical or electrical stimuli), cause a localised con-
traction of the muscular fibres. This is Schiff’s “idio-muscular contraction.” The
same phenomenon is exhibited by the muscles of a healthy man, when the blunt
edge of an instrument is drawn transversely over the direction of the muscular
fibres. (b) Under certain as yet but imperfectly known conditions, a muscle ex-
hibits so-called fibrillar contractions, 7.c., short contractions occur alternately in

476 TOTAL AND PARTIAL MUSCULAR CONTRACTION.

different bundles of muscular fibres. This is the case in the muscles of the tongue,
after section of the hypoglossal nerve ; and in the muscles of the face, after section
of the facial nerve.

[In some phthisical patients there is marked muscular excitability, so that if the pectoral
muscle Be percussed, a local contraction —idio-muscular—occurs, either confined to the spot, or
two waves may proceed outwards and return to the spot struck. ]

Cause of Fibrillar Contraction.—According to Bleuler and Lehmann, section of the hypo-
glossal nerve in rabbits is followed by fibrillar contractions after sixty to eighty hours ; these
contractions may continue for months, even when the divided nerve has healed and is stimu-
lated above the cicatrix so as to produce movements in the corresponding half of the tongue.
Stimulation of the lingual nerve increases the fibrillar contractions or arreststhem. This nerve
contains vaso-dilator fibres derived from the chorda tympani. Schiff is of opinion that the
increased blood-stream through the organ is the cause of the contractions. Sig. Mayer found
that, by compressing the carotids and subclavian, and again removing the pressure so as to per-
mit free circulation, the muscles of the face contracted. Section of the motor nerves of the
face did not abolish the phenomenon, but compression of the arteries did. The cause of the
phenomenon, therefore, seems to lie within the muscles themselves. This phenomenon may
be compared to the paralytic secretion of saliva and pancreatic juice which follows section of the
nerves going to these glands (pp. 214, 258). Similar fibrillar contractions occur in man under
pathological conditions, but they may also occur without any signs of pathological disturbance.
[Fibrillar contractions, due to a central cause, occur in monkeys after excision of the thyroid
gland (§ 103, III.). Some drugs cause fibrillar muscular contractions, ¢.g., aconitin, guanidin,
nicotin, pilocarpin, but physostigmin produces them in warm-blooded animals (not in frogs).
According to Brunton these drugs probably act by irritating the motor nerve-endings, as the
contractions are gradually abolished by curara. ]

II. Microscopic Phenomena.—1. Single muscular jibrille exhibit the same
phenomena as an entire muscle, in that they contract and become thicker. 2.
There is great difficulty in observing the changes that occur in the individual parts
of a muscular fibre during the act of contraction. This much is certain, that the
muscular elements become shorter and broader during contraction, and that the
transverse stric approach nearer to each other (Bowman, 1840). 3. There is great
difference of opinion as to the behaviour of the doubly refractive
(anisotropous) and the singly refractive media. q

Engelmann’s View.—Fig. 319, 1, on the left represents a ae mus-

cular element—from c to d is the doubly refractive contractile substance, 4 asa

° . ° A e . . oh Ba at it

with the median disc, a, b, in it ; A and g are the lateral discs. Besides C

these, in each of the singly refractive discs there is a clear dise—‘‘secondary ey
e

in the muscles of insects. Fig. 1, on the right, shows the same element in
polarised light, whereby the middle
area of the element, as far as the con-
tractile substance proper extends,
is, owing to its double refraction,
bright ; while the other part of the
muscular element, owing to its being
singly refractive, is black. Fig.
319, 2, is the transition stage, and
3 the proper stage of contraction of
the muscular element. In both
cases, the figures on the left are
viewed in ordinary light, and on the
right, in polarised light. During Fig. 319,

contraction (fig. 319, 3), the singl ; : ‘ ed
refractive disc Medel tae", whol. The microscopic appearances during a muscular contraction

- . in the individual elements of the fibrille. 1, 2, 3 (after
mae hap omtaaeedress bly aby porte Engelmann) ; 4, 5 (after Merkel),

certain Gegree of contraction (2), when viewed in ordinary light, may 4 so homogeneous and
but slightly striped transversely =the homogencous or transition stage. uring a greater degree
of contraction (3), very dark transverse stripes reappear, corresponding to the singly refractive
discs, At every stage of the contraction, as well as in the transition stage, the singly and
doubly refractive discs are sharply defined, and are recognised by the polariscope as uar
alternating layers (in 1, 2, and 3 on the right). These do not change places during the con- —
traction. The height of both discs is diminished during contraction, but the singly refractive —

disc” f and e, which is only slightly doubly refractive. This occurs only al 4

Gow aAacmpD obs

MUSCULAR CONTRACTION AND MYOGRAPHS. 477

do so more rapidly than the doubly refractive discs. The total volume of each element
does not undergo any appreciable alteration in volume during the contraction. Hence, the
doubly refractive discs increase in volume at the expense of the singly refractive. From this
it is concluded that, during the contraction, fluid passes from the singly refractive into the
doubly refractive discs ; the former shrink, the latter swell.

Merkel’s view is partially different. In fig. 319, 4, are two muscular elements at rest ; in (5),
two in a state of contraction, after Merkel. The grey punctuated areas are the doubly refrac-
tive substance, c, the median disc. According to Merkel, during contraction the dark substance
lying in the middle of the element changes its position—either in part or as a whole ; it leaves
the middle of the element (the two surfaces of Hensen’s median dises, 4, c), and places itself
at the lateral discs, 5 at e and d, while the clear substance leaves the lateral disc, 4, ¢ and d,
and applies itself to both surfaces of the median disc, 5, c. The clear substance of the isotrop-
ous discs is fiuid, and plays a more passive role ; during contraction it is in part absorbed by
the dark substance which thus swells up. This mutual exchange of place of the substances is
accompanied by an intermediate ‘‘stage of dissolution,” in which the whole contents of the
element appear equally homogeneous, in which, therefore, the fluid singly refractive substance
has uniformly penetrated the doubly refractive substance. At this moment only the lateral
discs are still visible.

[Ifa living portion of an insect’s muscle be examined in its own juice, contraction-waves
may be seen.to pass over the fibres. When a contraction-wave passes over part of the fibres,
the discs become shorter and broader; at the same time, in the fully contracted part, the dim
disc appears lighter than the centre of the light disc. There is said to be a ‘‘ reversal of the
stripes’ from what obtains in a passive muscle. Before this stage is reached, there is an inter-
mediate stage where the two bands are almost uniform in appearance. |

Methods.—These phenomena are best observed by ‘‘fixing” the different stages of rest or
contraction, by suddenly plunging the muscular fibrille of insect’s muscles into alcohol or
osmic acid, which coagulates the muscle-substance. The actual contraction may be observed
under the microscope in the transparent parts of the larvee of insects. _

Spectrum.—A thin muscle, ¢.g., the sartorius of the frog, when placed directly behind a
nalrow slit running at right angles to the course of the fibres, yields a diffraction-spectrum.
When the muscle contracts, as by me-
chanical stimulation, the spectrum “p K
broadens, a proof that the interspaces of (
the transverse stripes become narrower
(Ranvier).

298. MUSCULAR CON-
TRACTION. — Methods. — In
-order to determine the duration
of each phase of a muscular con-
traction, myographs of various
forms are used.

V. Helmholtz’s Myograph is shown
in fig. 320. A muscle, M—say the
gastrocnemius of a frog attached to the
femur—is fixed by the femur ina clamp,
K; its lower end is attached to a mov-
able lever carrying a scale-pan and
weight, W, the weight being varied at
pleasure. When the muscle contracts,
necessarily it raises the lever. At the Fis, 320..
free end of the lever is a movable style, %
F, which inscribes its movements on a

Scheme of v. Helmholtz’s myograph. M, muscle fixed
in aclamp, K ; F, writing style ; P, weight or counter-

revolving cylinder caused to rotate at a ‘ :
M4 poise for the lever; W, scale-pan for weights ; 8, 8,
uniform trate by means of clock-work. supports for the lever. ‘ :

The cylinder is covered with smoked “

enamelled paper in the flame of a turpentine lamp. When'the muscle contracts, it inscribes a
curve—the ‘‘ muscle-curve,” or ‘“‘myogram.” The abscissa of the curve indicates the duration
of the contraction, but of course the rate at which the cylinder is moving must be known. The
ordinates peptecae the height of contraction at any particular part of the curve.

The muscle-curve may be inscribed upon a*smoked glass plate attached to one limb of a
vibrating tuning-fork. Such a curve registers the time-units in all its parts. Suppose each
vibration of the tuning-fork = 0°01618 second, then the duration of any part of such a curve is
obtained by counting the number of vibrations and multiplying by 0:01613 second.

[Fick’s Pendulum Myograph.—A board fixed to the wall carries a heavy iron pendulum, P,

478 PENDULUM MYOGRAPH.

whose axis, A, A, moves on friction rollers (fig. 321). At the lower swinging end are two glass

plates, G and G’, fixed to a bearer, T. The plates can be adjusted by means of the screw, s, so

that several curves can be written one above the other. The plate, G’, on the posterior surface
is merely a compensator, so that, when G is elevated, G’ is lowered, and thus the duration of the ©
oscillation is not altered. The spring catches, H, H, which can be turned inwards or out-
wards, are used to fix the pendulum by the teeth, a, a, when it is drawn to one side. The
pendulum is drawn to one side and fixed, a, in H, so that when H is pulled down, it is liberated
- and swings to the other side, where it

fp is caught by H at the opposite side.

In the improved form, the catches, H,

are made to slide along a rod like the
are of a circle, so that the length of
the swing can be varied. As the pen-
dulum swings from one side to the
other, the projecting points, a, a, knock
© © over the contact key, }, and the cur-
rent is opened and a shock transmitted
to the muscle. The writing-lever to
which the muscle is attached is usually

a heavy one, and a style writes upon

the smoked surface of the glass. Of

course, when the pendulum swings, it
moves with unequal velocities at dif-
erent parts of its course. ]

[When using the pendulum myo-
graph to study a muscular contraction,
arrange it as in fig. 322. The frog’s
muscle is attached to a writing-lever,
which is very like the lever in fig. 321,
while the style inscribes its movements
on the blackened plate. ]

[The pendulum is fixed in the catch,
C, as shown in the figure ; the key,
K’, isclosed and placed in the primary
circuit, while two wires from the
secondary coil of an induction machine
- are attached to the muscle. When
the pendulum swings, the projecting
tooth, 8, knocks over the contact at.
K’, and breaks the primary circuit,
when a shock is instantly transmitted
through the muscle. Before stimu-
lating, allow the pendulum to swing .
to obtain an abscissa. The time is
recorded by a vibrating tuning-fork, of
known rate of vibration, connected
with a Dupré’s electric chronograph.

© Dupré’s chronograph is merely a small

@ electro-magnet with a fine writing 4

style attached, which vibrates when it }

is introduced in an electrical circuit, .

in which is placed a vibrating tuning-

tork. The signal vibrates just as often
Fig. 321. as the tuning-fork.] .

Fick’s pendulum myograph, as improved by v. Helm- [Du Bois Spring Myograph. —It
holtz (;', natural size), side and front view. consists of a glass plate fixed in a
frame, and moving on two polished

steel wires, stretched between the supports A and B (fig. 823), At bis a spring which, when it

is compressed between the upright, B, and the knob, b, drives the glass plate from B to A. As
the plate moves from one side to the other, a small tooth, d, on its under surface, opens the
key, 3 < _ * shock is eats to oH muscle, The arrangement otherwise is the same
as for the pendulum myo 4 e smoked glass plate is liberated by the projecting finger-
plate attached to the uptight A.] ee 2 Sith th paint

[Marey’s Simple Myograph.—The gastrocnemius is attached to a horizontal lever, which in-
scribes its movements on a revolving cylinder. This form of myograph, when provided with two
levers,is very useful for comparing the action of a poison on one limb, the other being unpoisoned,

[Pfliiger’s stationary form is simply a Helmholtz’s myograph (fig. 320) arranged to re

mi
Lh

{5

MYOGRAM OR MUSCLE-CURVE., 974

its movements on a stationary glass plate, so that the muscle merely makes a vertical line or
ordinate instead of a curve ; it thus merely indicates the height or extent of the contraction,

not its duration.]

A rapidly rotating disc was used by Valentin and Rosenthal for registering the muscle-

curve, while Harless used a plate which was
allowed to fall rapidly, the so-called ‘‘ Fall-
myograph. In all these experiments it is
necessary to indicate at the same time the
moment of stimulation.

Contraction Curve of Human Muscle.
—JIn man, another principle is adopted,
viz., to measure the increase in thickness
during the contraction, either by. means
of a lever or a compressible tambour, such
as is used in Brondgeest’s pansphygmo-
graph (fig. 36). [The thickening of the
adductor muscles of the thumb may be
registered by means of Marey’s pince
poe aur

I. Simple Contraction.—If a single
shock or stemulus of momentary duration be
applied to a muscle, a ‘‘ simple muscular
contraction ” [or shortly, a contraction or
twitch] is the result, ze, the muscle
rapidly shortens and quickly returns again
to its original relaxed condition.

Myogram or Muscle-Curve.—Suppose
a single stimulus be applied to a muscle
attached to a light writing-lever, which
is not “overweighted ” with any weight

up ll i

—it

K

Fig. 322.

Scheme of the arrangement of the pendulum
myograph. B, battery ; 7 primary, EL
secondary spiral of the induction machine:
S, tooth; K’, key; C, C, catches; K’ in
the corner, scheme of K’; K, key in primary
circuit.

attached to it, then, when the muscle contracts, the oe events take place :—

Sf

Fig. 323.
Spring myograph or “ shooter.”’
Bae A period or stage of latent stimulation (figs. 324, 325).
(2) A period of increasing energy or contraction.
(3) A period of decreasing energy or more rapid relaxation.
(4) A period of slow relaxation, or the elastic after-vibration. |

480 LATENT PERIOD OF A MUSCLE CURVE.

The muscle-curve proper is composed of 2, 3, and 4. )

1. The latent period (fig. 324, a, 6) consists in this, that the muscle does not
begin to contract precisely at the moment the stimulus is applied to it, but the
contraction occurs somewhat later, i.e, a short, but measurable interval, elapses
between the application of a
momentary stimulus and the
contraction (v. Helmholtz). If
the entire muscle be stimulated
by ‘a momentary stimulus, e.g.,
a single break induction shock,
the duration of the latent period
is about 0°01 second. In smooth
muscle, the latent period may

Fig. 324.
Muscle-curve produced by a single induction shock ap-
plied to a muscle. a-/, abscissa ; a-c, ordinate ; a 3, last for several seconds.
period of latent stimulation ; bd, period of increasing [Although no change be visible
energy ; @e, period of decreasing energy ; ¢ f, elastic |, 9 muscle during the latent

after-vibrations. ,
period, nevertheless we have

proof that some change does take place within the muscle-substance, for we know
that the electrical current of the muscle is diminished during this period, or we
have what is known as the negative variation of the muscle-current (Bernstein— °
§ 333). ]

In man, the latent period varies between 0°004 and 0°01 second. If the experiment be so
arranged that the muscle can contract as soon as the stimulus is applied to it, ¢.e., before time
is lost in making the muscle tense ; or to put it otherwise, if the muscle has not ‘‘ to take in
slack,” as it were, the latent period may fall below 0°004 second (Gad). If the muscle be still
attached to the body, protected as much as possible from external influences and properly
supplied with blood, the latent period may be reduced to 0°0033 or even 0°0025.

Modifying Influences.—The latent period is shortened by an increased strength of the
stimulus and by heat ; while fatigue, cooling, and increasing weight lengthen it (Lauterbach,
Mendelssohn, Yeo, Cash). The latent period of a break-contraction is longer than that of
a make-contraction. The red muscles have a longer latent period than the white. Before the
muscle contracts as a whole, the individual fibres within it must have contracted. We must,
therefore, conclude that the latency of the individual muscular elements is shorter than that of
the entire muscle (Gad, Tigerstedt).

2. The contraction or stage of increasing energy, 7.¢., from the moment the
muscle begins to shorten until it reaches its greatest degree of contraction (6b d).
At first the muscle contracts slowly, then more rapidly, and again more slowly, so
that the ascending limb of the curve has somewhat the form of an f. This stage
lasts 0°03 to 0°4 second. It is shorter when the contraction is shorter (weak
stimulus) and the less the weight the muscle has to lift. It also varies with the
excitability of the muscle, being shorter in a fresh, non-fatigued muscle.

3. Elongation or stage of decreasing energy.—After the muscle has con-
tracted up to its maximum for any particular stimulus, it begins to relax—at first
slowly, then rapidly—and lastly more slowly, so that an inverse of an fis obtained
(de). This stage is usually of shorter duration than 2. The duration varies with
the strength of the stimulus, being shorter than 2 with a weak stimulus, and
longer with a strong stimulus. It also depends upon the extent to which the
muscle is loaded during contraction.

t: The fourth stage has received various names—stage of elastic after-vibra-
tion [residual contraction or contraction-remainder (Hermann). The after-
vibrations (e 7), which disappear gradually, depend upon the elasticity of the
muscle. The duration of this stage is longest with a powerful contraction, and
when the weight attached to the muscle is small].

If the stimulus be applied to the motor nerve instead of to the muscle itself, the
contraction is greater (Pjliger), and lasts longer (Wundt) the nearer to the spinal
cord the stimulus is applied to the nerve.

METHOD OF MEASURING A MYOGRAM. 481

[In studying a muscle-curve, the more or less vertical character of the ascent
will indicate the
rapidity of the con-
traction, the height
above the base line,
itsextent, thelength
of the curve, the
duration, and the
line of descent, the
rate of its extensi-
bility. The form
of the muscle-curve

Fig. 325.

Pendulum myograph curve of a frog’s gastrocnemius. S, point of stimu-
; : lation; A, latent period; B, period of shortening, and C, of relaxation.
will vary with the 250 DV., tuning-fork vibrating 250 double vibrations per sec. The
kind of myograph dotted vertical lines are ordinates (Stirling).
used ; if it be stationary, then the muscle will merely record a vertical line ; if the
recording surface move quickly, the two parts
of the curve will form an acute angle (fig. 327) ;
and if it move with great rapidity, they will
have the form of fig. 325, that obtained with
a pendulum myograph. A vibrating tuning-
fork records time directly under the tracing,
whereby the duration of each part of the curve
is readily determined. |

[In measuring the myogram, all that is required is
to know the moment at which the stimulus was ap-
plied, and to note when the curve begins to leave the
base line or abscissa. Raise a vertical line or ordinate
from each of these points, and the interval between
these lines, as measured by the chronograph, indicates
the time (fig. 325). ]

[The time-relations of a simple muscular con-
traction caused by a single induction shock Fig. 326.
may be studied by means of the following Arrangement for estimating the time-
arrangement :—Attach a frog’s gastrocnemius tu relations during contraction of a
a lever, as in fig. 326, and through the frog’s muscle produced by a faradic shock.

muscle place two wires from the secondary coil
of an induction machine. A scale-pan with a
weight is attached to the lever. On the same
support adjust an electro-magnet with a writing-
style in the primary circuit, and in this circuit

also place a key (K) to make and break the current.

graph to the same support, and make
it vibrate by connecting it in circuit
with a tuning-fork of known rate of
vibration, and driven by a galvanic
battery. See that the points of all
three levers write exactly over each
other on the revolving cylinder. ' The
upper lever registers the contraction,
the electro-magnet the moment the

stimulus is applied to the muscle, and p05 mtiscle stim

the electrical chronograph the time. |
[Single make (closing) or break
(opening) induction shocks.

break (B) and make shock (M).
shows the same, but with the muscle fatigued.

A muscle or nerve may be stimulated either with

B, battery ; K, key in primary circuit ;
I, primary, II, secondary spiral; /,
muscle lever; ¢, electro-magnet in
primary circuit ; ¢, electric signal ; St?,
support; RC, revolving cylinder (after
Rutherford).

Fix also a Dupré’s chrono-

Fig. 327.
ulated alternately by a single

The lower curve

a “make” or “break” induction shock, but it is important to notice that the break

2H

482 OVERWEIGHTED MUSCLES.

shock is stronger than the make. In fig. 327, B shows the effect produced by a
single break induction shock, and M that of a single make shock. |

Overweighted Muscles.—The foregoing remarks apply to curves obtained by a light lever
connected with the muscle. If the muscle lever be ‘‘ overweighted,” or overloaded, i.c., if the
lever be loaded, so that when the muscle contracts it has to lift these weights, the course of the
curve varies according to the weight to be lifted. It is necessary, however, to support the lever
in the intervals when the muscle is at rest. As the weights are increased, the occurrence of the
contraction is delayed. This is due to the fact that the muscle, at the moment of stimulation,
must accumulate as much energy as is necessary to lift the weight. The greater the weight, the
longer is the time before it is raised. Lastly 1] cmuscle may be so ‘‘ loaded,” or ‘‘overloaded,”
that it cannot contract at all ; this is the limit of the mtscular or mechanical energy of the
muscle (v. Helmholtz).

Fatigue.—If a muscle be caused to contract so frequently that it becomes

“ fatigued,” the latent period is longer, the curve is not so high, because the

muscular contraction is less,

and the abscissa is longer, 7.e.,

the contraction is slower and

lasts longer (fig. 328). Cool-
ing a muscle has the same
effect. Soltmann finds that,
the fresh muscles of new-born
animals behave in a similar
manner. The myogram has

a flat apex and considerable

elongation in the descending

Fig. 328. linb of the curve.

I, Contraction of a fatigued frog’s muscle writing its contrac- Constant Current.—lIf the
tion on a vibrating plate attached to a tuning-fork. Each motor nerve of a muscle be
wtmation 02536 stcond Intent perils 6 stage stimulated by amake or break
most rapid writing movements of the right hand inscribed Shock of a constant current,
onavibrating plate. III, The most rapid trembling tetanic the resulting muscular con-
movements of the right fore-arm inscribed on the same traction corresponds exactly
piste to that already described. If,

however, the current be made or broken with the muscle itself directly in the

circuit, during the make shock, there is a certain degree of contraction which lasts
for a time, so that the curve
assumes the form of fig.

329, where S represents the

moment of closing or making

the current, and QO the
moment of opening or break-

Fig. 329,
Effect on a muscle of closing and opening a constant current. ;,,, +4 (g
ee ; * ing it (§ 336, D).
S, closing ; O, opening shock (Wundt). ing 1t (§ ’ D)

The investigations of Cash and
Kronecker show that individual muscles have a special form of muscle-curve ; the omohyoid

of the tortoise contracts more rapidly than the pectoralis. Similar differences occur in the
muscles of frogs and mammals. The flexors of the frog contract more rapidly than the extensors
(Griitener) Sometimes within one and the same muscle there are ‘‘ red ” (rich in glycogen) and
‘*nale” fibres (§ 292). The red fibres contract more slowly, are less excitable, and less easily
fatigued (Griitzner). The muscles of flying insects contract very rapidly, even more than 100
times per second.

oisons.—Very small doses of curara or quinine increase the height of the contraction
(excited by stimulation of the motor nerve), while larger doses diminish it, and finally abolish
it altogether, Guanidin has a similar action in large doses, but the maximum of contraction
lasts for a longer time. Suitable doses of veratrin also increase the contractions, but the stage
of relaxation is greatly strengthened (Rossbach and Clostermeyer). Veratrin, antiarin, and
digitalin, in large doses, act upon the sarcous substance in such a way that the contractions
become very prolonged, not unlike a condition of prolonged tetanus (Harless, 1862). The
latent period of muscl:s poisoned with veratrin and strychnin is shortened at first, and after-

CONTRACTION-REMAINDER. 483

wards lengthened. The gastrocnemius of a frog supplied by blood containing soda contracts
more rapidly (Gritzncv). Kunkel is of opinion that muscular poisons act by controlling the
imbibition of water by the sarcous substance. As muscular contraction depends on imbibition
(§ 297, II.), the form of the contraction of the poisoned muscle will depend upon the altered
condition of imbibition produced by the drug.

[Veratrin.—If a frog be poisoned with veratrin, and then be made to spring, it does so
rapidly, but when it alights again the hind legs are extended, and they are only drawn up after
a time. Thus, rapid and powerful contraction, with slow and prolonged relaxation, are the
character of the movements. Ina muscle poisoned with veratrin, the ascent is quick enough,
but it remains contracted for a long time, so that this condition has been called ‘‘contracture.”
A single stimulation may
cause a contraction lasting
five to fifteen seconds, ac-
cording to circumstances (fig,
330). Brunton and Cash
find that cold has a marked
effect on the action of veratrin
—in fact, its effect may be
permanently destroyed by
exposure to extremes of heat
or cold. The muscle-curve
of a brainless frog cooled
artificially, and then poison-

ed by veratrin, occasionally Fig. 330,
gives no indications of. the Lower curve is the normal muscle-curve (frog), upper one of the
action of the poison until its same muscle with veratrin (Stirling).

temperature is raised, and

this is not due to non- absor ption of the poison. Cold, therefore, abolishes or lessens the con-
tracture peculiar to a veratrin-curve. Similar results are obtained with salts of barium, and to
a less degree by those of strontium and calcium (Brunton and Cash). |

Smooth Muscles.—The muscle-curve of smooth or non-striped muscles is similar
to that of the striped muscles, but the duration of the contraction is visibly much
longer, and there are other points of difference. Some muscles stand midway
between these two, at least as far as the duration of their contractions is con-
cerned,

The ‘‘red” muscles of rabbits, the muscles of the tortoise, the adductors of the common
mussel, and the heart, all react in a similar manner.

Contraction-Remainder.—A contracted muscle assumes its original length only
when it is extended by sufficient traction, ¢.g., by means of a weight. Otherwise,
the muscle may remain partially shortened for a long time. This condition has
been called “contracture” (Tiegel), or, better, contraction-remainder (/ermann).
This condition is most marked in muscles that have been previously subjected to
strong, direct stimulation, and are greatly fatigued, which are distinctly acid, and
ready to pass into rigor mortis, or in muscles excised from animals poisoned with
veratrin (fig. 330).

Rapidity of Muscular Contraction.—In man, single muscular movements can
be executed with great rapidity. The time-relations of such movements can be
ascertained by inscribing the movements upon a smoked glass plate attached to a
tuning-fork. Fig. 328, II, represents the most rapid voluntary movements that
Landois could execute, as, ¢€.g., in writing the letters n, , and every contraction is
equal to about 3°5 vibravions (1 vibration =0-01613 second) =0:0564 second. In
III, the right arm was tetanised, in which case 2’ to 2°5 vibrations occur = 0°0323
to 0:0403 second.

V. Kries found that a simple muscular twitch, caused by a single induction shock,
is shorter than a momentary voluntary single movement. If the thickening caused
by a single voluntary contraction of a muscle be registered directly, the curve
shows that the contraction within the muscle lasts longer than the duration of the
movement produced in the passive motor apparatus itself. This paradoxical
phenomenon is due to the fact that, shortly after the primary voluntary muscular ©

484 EFFECT OF SUCCESSIVE STIMULI.

contraction, there is a contraction of the antagonistic muscles, whereby a part of
the intended movement is, as it were, cut off. During the most rapid voluntary
movement in human muscles, v. Kries found that 4 stimuli per second were active,
so that a voluntary contraction is really a short tetanus. -

Pathological.—In secondary degeneration of the spinal cord after apoplexy, atrophic muscular
anchylosis of the limbs, muscular atrophy, progressive ataxia, and paralysis agitans of long
standing, the latent period is lengthened ; while it is shortened in the contracture of senile chorea
and spastic tabes (J/endelssohn). The whole curve is lengthened in jaundice and diabetes
(Edinger). In cerebral hemiplegia, during the stage of contracture, the muscle-curve resembles
the curve of a muscle poisoned with veratrin, and the same is the. case in spastic spinal puaes
and amyotrophic lateral sclerosis ; in pseudo-hypertrophy of the muscles the ascent is short and
the descent very elongated. In muscular atrophy, after cerebral hemiplegia, and in tabes, the
latent period increases, while the height of the curve diminishes. In chorea, the curve is short
(Reaction of Degeneration, § 339). In rare cases in man, it has been observed that the execution
of spontaneous movements results in a very prolonged contraction (Thomsen’s disease).
such cases the muscular fibres are very broad, and the nuclei increased (Erb).

II. Action of Two Successive Stimuli.—Let two momentary stimuli be applied
successively to a muscle :—(A) If each stimulus or shock be of itself sufficient to
cause a maximal contraction, 7.¢., the greatest possible contraction which the
muscle can accomplish, then the effect will vary according to the time which
elapses between the application of the two stimuli. (a) If the second stimulus is
applied to the muscle after the relaxation of the muscle following upon the first
stimulus, we obtain merely two maximal contractions. (6) If, however, the second
stimulus be applied to the muscle during the time that the effect of the first is
present, z.e., while the muscle is in the phase of contraction or of relaxation ; in
this case the second stimulus causes a new maximal contraction, according to the
time of the particular phase of the contraction. (c) When, lastly, the second
stimulus follows the first so rapidly that both occur during the latent period, we
obtain only one maximal contraction (v. Helmholtz). It is to be specially noted
that a single maximal
stimulus never excites
the same degree of
shortening as tetanic
stimulation (III), but
only about 4 of the
height of the contrac-
tion in tetanus.

(B) If the stimuli
be not maximal, but
only such as cause a
medium or sub-max-

Fig. 381. imal contraction, the

I, two successive sub-maximal contractions; II, successive contrac- effects of both stimuli
tions produced by stimulating a muscle with 12 induction shocks are superposed, or
per second; III, curve produced with very rapid induction shocks there is a summation

(complete tetanus). : of the contractions (fig.
331). It is of no consequence at what particular phase of the primary contraction
the second shock is applied. In all cases, the second stimulus causes a contrac-
tion, just as if the phase of contraction caused by the first shock was the natural
passive form of the muscle, 7.¢., the new contraction (b, c) starts from that point as
from an abscissa (fig. 331, I, 6). Thus, under favourable conditions, the contraction
may be twice as great as that caused by the first stimulus. The most favourable
time for the application of the second stimulus is .j,th second atter the application
of the first (Sewall). The effects of both stimuli are obtained even when the
second stimulus is applied during the latent period (v. Helmholtz). .

TETANUS OF MUSCLE. 485

III. Tetanus—Summation of Stimuli.—If stimuli, each capable of causing a
contraction, and following each other with medium rapidity, be applied to a
muscle, the muscle has not sufficient time to elongate or relax in the intervals of
stimulation. Therefore, according to the rapidity of the successive stimuli, it
remains in a condition of continued vibratory contraction, or in a state of tetanus.
Tetanus is, however, not a continuous uniform condition of contraction, but it is a
discontinuous condition or form of the muscle, depending upon the summation or
accumulation of contractions. If the stimuli are applied with moderate rapidity,
the individual contractions appear in the curve (fig. 331, IL) ; if they occur rapidly,
and thus become superposed and fused, the curve appears continuous and unbroken
by elevations and depressions (fig. 331, III). As a fatigued muscle contracts
slowly, it is evident that such a muscle will become tetanic by a smaller number of
stimuli per second than will suffice for a fresh muscle (Marey). All muscular
movements of long duration occurring in our bodies are probably tetanic in their
nature (Hd. Weber).

[Summation of Stimuli.—If a stimulus, insufficient in itself to cause contraction
of a muscle, be repeatedly applied to a muscle in proper tempo and of sufficient
strength, at first a slight and then a stronger or maximal contraction may be
produced. This process of summation occurs also in nervous tissue (§ 360).|

[Staircase or ‘‘Treppe.” Bowditch showed that the cardiac contractions exhibited a ‘‘ stair-
case” character, 7.¢., the height of the second beat is greater than that of the first; and the third
than that of the second (p. 84). The same occurs in the case of the muscles of the frog ( Tegel,
Minot) and in mammals (Rossbach). Bohr showed that the successive ascending apices in a
tetanus-curve have really a staircase
character, and that its exact form is
that of a hyperbola. Bohr found
that. (1) this form—the muscle not
being fatigued—is independent of
the strength and frequency of the
stimuli. (2) The height of the series
of contractions in tetanus is inde-
pendent of the frequency of the
stimuli, increase of frequency merely Fig. 332.

causing the staircase to reach its Pony groups of contractions, interval of simulation 2

Fue ce say eee (3) The seconds, and 5 minutes pause between two groups
eight o e staircase increases— (Buckmaster).

within certain limits—with the

strength of the stimulus. Buckmaster has confirmed this for simple contractions, but as
shown in fig. 332, when the stimuli are minimal or sub-maximal, there is usually no staircase
character of the contractions, I

but maximal stimuli always ,
cause it. ]

A continued voluntary
contraction in man, consists
of a series of single con-
tractions rapidly following
each other. Every such
movement, on being carefully
analysed, consists of inter-
mittent vibrations, which
reach their maximum when

Minimal. Maximal. Sub-maximal. Maximal.

- a person shivers(Zd. Weber). Fig. 333.
—[Baxt found that the I., vibration obtained from the flexor brevis follicis; II., from
simplest possible voluntary the extensor digiti tertii. .

contractions, ¢.g., striking with the index finger, occupies on an average nearly twice
as long a time as a similar movement discharged by a single induction shock. |

The number of single impulses sent to our muscles during a voluntary move-
ment is tolerably variable, during a slow contraction =8 to 12, and during a rapid

486 NUMBER OF STIMULI.

contraction = 18 to 20 impulses per second. Fig. 333, I., represents a myogram of a
sustained contraction of the flexor brevis pollicis and abductor pollicis, recorded on
a vibrating plate. The wave-like elevations indicate the single impulses, each
tooth = 0:01613 second. II. is a similar curve registered by the extensor digiti tertii
(Landois). ([Schifer finds that a prolonged voluntary contraction in man is an
incomplete tetanus produced by 8 to 13 successive nervous impulses per second.
About 10 per second may be taken as the average. |

The requisite degree of shortening is obtained, by the summation of single stimuli applied to
the slowly contracting muscle, until the desired degree of shortening is obtained. In estimating
exactly the amount of movement, we generally oppose some resistance by contracting antagonistic
muscles, as is shown by observations on spare individuals (Briicke).

The tetanic contractions, which occur normally in an intact body, are proved to consist of
a series of successive contractions, because they can give rise to secondary tetanus (§ 332), which
may also be caused by muscles thrown into tetanus by strychnin poisoning (Lovén). The
muscle-sound cannot be regarded as a proof of the oscillatory movement in tetanus, [as Helmholtz
has shown that this sound coincides with the resonance sound of the ear (Hering and
Friedrich)}.

If a muscle be connected with a telephone, whose wires are brought into connection with two
needles, one placed in the tendon, and the other in the substance of the muscle, we hear a
sound when the muscle is thrown into tetanus, which proves that periodic vibratory processes,
i.e., successive contractions, occur in the muscle (Bernstein and Schinlein). The sound is most
distinct when the tetanising Neef’s hammer of anu induction machine vibrates about 50 times
per second (Wedenski and Kronecker).

The number of stimuli requisite to produce tetanus varies in different animals, and in
different muscles of the same animal. About 15 stimuli per second are required to produce
tetanus in the muscles of the frog (hyoglossus only 10, gastrocnemius 27); very feeble stimuli
(more than 29 per second) cause tetanus (Kronecker) ; the muscles of the tortoise become tetanic
with 2 to 3 shocks per second; the ved muscles of the rabbit by 10, the pale by over 20
(Kronecker and Stirling) ; muscles of birds not even with 70 (J/arey); muscles of insects 330
to 340 per second (Marey). Tetanic stimulation of the muscles of the crayfish (Astacus) and
also in hydrophilus, may cause rhythmical contractions (Richet), or rhythmically interrupted
tetanus (Schinlein). :

Curarised muscles sometimes pass into tetanus on the application of a momentary stimulus
(Kiihne, Hering).

O. Soltmann found that the pale muscles of new-born rabbits were rendered tetanic with 16
stimuli per second, so that tetanus was produced in them with the same number of shocks as in
fatigued adult muscles. This may serve
partly to explain the facility with which
spasms occur in new-born animals,

[The red and pale muscles of a
rabbit, as already shown, differ struc-
turally, and also in regard to their
- blood supply (p. 458). They also differ
physiologically and chemically (p. 460),
When both muscles are caused to con-
tract, by stimulating the sciatic nerve

Fig. 334. with a single induction shock, the

Curves obtained from red (upper) and pale (lower) Curves obtained are shown in fig. 334;
muscles of a rabbit, by stimulating the sciatic nerve the lower one from the pale, and the
with a single induction shock. The lowest line Upper from the red muscle, The latent
indicates time, and is divided into 4,5 second period is longer, while the duration of

(Kronecker and Stirling). . a simple contraction of a red muscle is

pe three times longer than that of a-pale
muscle, Four stimuli per second cause an incomplete tetanus, and 10 per second a nearly com-
plete tetanus in the red muscles of a rabbit, while the pale muscles require 20 to 30 stimuli per
second to be completely tetanised. Fig. 8335 shows the results produced by induction shocks
applied to both muscles at intervals of 4 second.]
he extent of shortening in a tetanically contracted muscle, within certain limits, is dependent
upon the strength of the individual stimuli—but not upon their frequency. The contraction-
remainder after tetanus is greater the stronger the stimuli; the longer they are applied, and
the feebler the muscle used (Bohr). For an unweighted muscle, the height of a contraction and
that of tetanus are the same (v. Frey). Only when a muscle is weighted is the height of a single
contraction less than by a tetanic contraction. Sometimes stimulus applied toa musele imme-

diately after tetanus produces a greater effect than it did before the tetanus (Rossbach, Bohr)... .

y
¥
I
a
“

TONE-INDUCTORIUM OF KRONECKER AND STIRLING. 487

Duration of Tetanus,—A tetanised muscle cannot remain contracted to the same extent for
an indefinite period, even if the stimuli are kept constant. It gradually begins to elongate,
at first somewhat rapidly, and then more slowly, owing to the occurrence of fatigue. If the

BE ea
Fig. 335.
Make and break induction shocks of 300 units, applied at intervals of a + second to the pale

(lower) and red (upper) muscles of a rabbit. The lowest line marks 4 second (Kronecker
and Stirling).

tetanic stimulation is arrested, the muscle does not regain its original position and shape at
once, but a contraction-remainder exists for a certain time, this being more evident after stimu-
lation with induction shocks.

IV. If very rapid induction shocks (224 to 360 per second) be applied to a
muscle, the tetanus after a so-called ‘ initial contraction ”’ (Bernstein) may cease
(Harless, Heidenhain). This occurs most readily when the nerves are cooled.
Kronecker and Stirling, however, found that stimuli following each other at greater
rapidity than 24,000 per second produced tetanus.

[Tone-inductorium of Kronecker and Stirling.—This apparatus (fig. 336), consists of a rod
of iron, d, fixed in an iron upright ata. The primary, s, and secondary spiral, s,, rest on
wooden supports, which can be pushed over both ends of the rod. One end of the rod lies

\ X,

+

Eee
ELS
Do

j=>

Fig. 336.
Tone-inductorium of Kronecker and Stirling. d, iron rod, clamped at a; s,, primary, s,,
secondary spiral, with a key, /; leather rollers, f and g, driven by wheels, h.

between leather rollers, f and g, which can be made to rub on the rod by moving the toothed
wheels, 2, In this way a tone is produced by the longitudinal vibrations of the rod, the
number of vibrations being proportional to the length of the rod, so that by means of this
instrument we can produce from 1000 to 24,000 alternating induction shocks per second. ]

Fick has recently investigated the changes—tension—undergone by a muscle when it is
stimulated, and when its length remains constant, and he calls this process an ‘‘ isometrical
muscular act.” He finds that a voluntary contraction in an isometrical act in man causes a
higher. tension than a contraction excited electrically, In the frog, the tension is nearly twice
as great during tetanus as during a single maximal muscular contraction ; in human muscles,
it may be ten times as great.

299. RAPIDITY OF TRANSMISSION OF A CONTRACTION.—1. If along

muscle be stimulated at one end, a contraction occurs at that point, and is rapidly

488 EFFECT OF VARIOUS CONDITIONS ON MUSCULAR CONTRACTION.

propagated in a wave-like manner through the whole length of the muscle, until
it reaches its other end. The condition of excitement or molecular disturbance is
communicated to each successive part of the muscle, in virtue of a special eonduc-
tive capacity of the muscle. The mean velocity of the contraction-wave is 3 to 4
metres per second in the frog (Bernstein, 3°869 metres) ; rabbit, 4 to 5 metres
(Bernstein and Steiner) ; lobster, 1 metre (Frédéricg and van de Velde) ; in smooth
muscle and in the heart, only 10 to 15 millimetres per second (§ 58, 4). These
results have reference only to excised muscles, the velocity of transmission being
much greater in the voluntary muscles of a living man, viz., 10 to 13 metres (Her-
mann, § 334, II.).

Methods.—Aeby placed writing-levers upon both ends of a muscle, the levers resting trans-
versely to the direction of the muscular fibres. The muscle was stimulated, and both levers
registered their movements, the one directly over the other on a revolving cylinder. On stimu-
lating one end of the muscle, the lever nearest to this point is raised by the contraction-wave,
and a little later the other lever. When we know the rate at which the cylinder is moving,
and the distance between the two elevations, it is easy to calculate the rapidity of transmission
of the contraction-wave.

Duration and Wave-Length.—The time, corresponding to the length of the
abscissa of the muscle-curve inscribed by each writing-lever, is equal to the dura-
tion of the contraction of this part of the muscle (according to Bernstein, 0°053 to
0-098 second). If this value be multiplied by the rapidity of transmission of the
muscular contraction-wave, we obtain the wave-length of the contractron-wave

= 206 to 380 millimetres).

Modifying Influences.—Cold (fig. 337), fatigue, approaching death, and many
poisons [veratrin, KCy] diminish the velocity and the height of the contraction-
wave, while the
strength of the stim-
ulus and the extent
to which the muscle
is loaded are without
any effect upon the
velocity of the wave
(Achy). In excised
muscles, the size of
the wave diminishes

Fig. 337. as it passes along the

Upper two curves, 2 and 1, obtained from a rabbit’s muscle by the muscle, but this is

above arrangement ; the lower two curves from the same muscle, not the case in the

when it was cooled by ice. muscles of living men

and animals. The contraction-wave never passes from one muscular fibre to a
neighbouring fibre.

[Fig. 337 shows the effect of cold on the muscles of a rabbit, in delaying the contraction-
wave. There is a longer distance between 1 and 2 in the lower than in the upper curves. ]

2. If a long muscle be stimulated locally near its middle, a contraction-wave is
propagated towards both ends of the muscle. If several points be stimulated
simultaneously, a wave movement sets out from each, the waves passing over each
other in their course (Schif’).

3. If a stimulus be applied to the motor nerve of a muscle, an impulse is com-
municated to every muscular fibre; a contraction-wave begins at the end-organ
[motorial end-plate], and must be propagated in both directions along the muscular
fibres, whose length is only 3 to 4 centimetres. As the length of the motor fibres
from the nerve-trunk to where they terminate in the motorial end-plates is unequal,
contraction of all the muscular fibres cannot take place absolutely at the same
moment, as the nerve impulse takes a certain time to travel along a nerve.

MUSCULAR WORK. Be 489

Nevertheless, the difference is so small that, when a muscle is caused to contract
by stimulation of its motor nerve, practically the whole muscle appears to contract
simultaneously and at once.

4. A complete, uniform, momentary contraction of all the fibres of a muscle can
only take place when all the fibres are excited at the same moment. This occurs
when the electrodes are placed at both ends of the muscle, and an electrical
stimulus of momentary duration passes through the whole length of the muscle.

300, MUSCULAR WORK.—Muscles are most perfect machines, not only
because they make the most thorough use of the substances on which their activity
depends (§ 217), but they are distinguished from all machines of human manufac-
ture by the fact that, by frequent exercise they become stronger, and are thereby
capable of accomplishing more work (Du Bois-Reymond).

The amount of work (W) which a muscle can perform is equal to the product
of the weight lifted (py) and the height to which it is lifted (A), we, W=ph
(Introduction). Hence, it follows that when a muscle is not loaded (where p=0),
then w must be=0, «¢., no work is performed. If, again, it be overloaded with
too great a load, so that it is unable to contract (k=0), here also the work is nil.
Between these two extremes an active muscle is capable of doing a certain amount
of ‘‘ work.”

I. Work with Maximal Stimulation.— When the strongest possible, or maximal
stimulus is applied—z.e., when the strength of the stimulus is such as to cause a
muscle to contract to the greatest possible extent of which it is capable, the amount
of work done increases more and more as the weight is increased, but only up to a
certain maximum. If the weight be gradually increased, so that it is lifted to a
less height, the amount of work diminishes more and more, and gradually falls to
be =0, when the weight is not lifted at all. .

Example of the work done by a frog’s muscle (Zd. Weber) :—-

Weight lifted in Grammes. Height in Millimetres. | Work done in Gramme-Millimetres.
5 27°6 138
15 25-1 | 376
25 11°45 | 286
= 7°3 | 220

[Suppose a muscle be loaded with a certain number of grammes, and then caused to contract,
we get a certain height of contraction. Fig. 338 shows the result of an experiment of this
kind. The vertical lines represent the height to which
the weights (in grammes) noted under them were raised,
so that, as a rule, as the weight increases the height to |
which it is raised decreases. ] |

Laws of Muscular Work.—1. A muscle can |
lift a greater load the larger its transverse section,
z.e., the more fibres it contains arranged parallel

to each other. 50 | |
2. The longer the muscle, the higher it can lift ane
a weight. wee a
3. When a muscle begins to contract, it can lift grammes.
the largest load ; as the contraction proceeds, it. Fig. 338.

can only lift a less and less load, and when it is
at its maximum of shortening, only relatively very
light loads. :'

4. By the term “‘ absolute muscular force ’’ is meant, according to Ed. Weber,
just the weight which a muscle undergoing maximal stimulation is no longer able
to lift (the muscle being in its normal resting phase), and without the muscle at
the moment of stimulation being elongated by the weight.

Height to which each of the weights
is raised.

490 TESTING INDIVIDUAL MUSCLES.

Comparative.—Comparing the absolute muscular force of different muscles, even in different
animals, it is usual to calculate it with reference to that of a square centimetre. The mean
transverse section of a muscle is obtained by dividing its volume by its length. The volume is
equal to the absolute weight of the muscles divided by its specific gravity=1058, The absolute
muscular force for 1 [ centimetre of a frog’s muscle=2°8 to 3 kilos. [6°6 lbs.] (J. Rosen-
thal); for 1 CO centimetre of human muscle=7 to 8 (Henke and Knorz), or even 9 to 10'kilos.
[20 to 23 lbs.] (Korster, Haughton). Insects can perform an extraordinary amount of work—
an insect can drag along sixty-seven times its body-weight ; a horse scarcely three times its
own weight.

5. During tetanus, when a weight is kept suspended, no work is done as long as
the weight is suspended, but of course work is done in the act of lifting the load.
To produce tetanus, successive stimuli are required, the muscular metabolism is in-
creased, and fatigue rapidly occurs. The potential energy in this case is converted
into heat (§ 302). Whena muscle is stimulated with a maximal stimulus, it can-
not lift so great a weight with one contraction as when it is stimulated tetanically
(Hermann). The energy evolved, even during tetanus, is greater the more frequent
the stimulation, at least up to 100 stimuli per second (Bernstein).

II. Medium Stimuli.—If a muscle be caused to contract by stimuli of moderate
strength, t.e., such as do not cause a maximal contraction, there are two possibilities:
—Either the feeble stimulus is kept constant whilst the load is varied, in which
case the amount of work done follows the same law as obtains for maximal stimula-
tion; or, the load may be kept the same, whilst the strength of the stimulus is
varied. In the latter case, Fick observed that the height to which the load was —
lifted increased in a direct ratio with the strength of the stimulus,

The stimulus which causes a muscle to contract must reach a certain strength or intensity
before it becomes effective, 7.¢., the ‘‘liminal intensity ’’ of the stimulus, but this is independ-
ent of the weight applied to the muscle. With minimal stimuli, a small weight is raised
higher than a large one, but as the stimulus is increased, the contractions also increase in a
larger ratio with an increased load (v. K7ies).

The blood-stream within the muscles of an intact body is increased during
muscular activity. The blood-vessels of the muscle dilate, so that the amount of
blood flowing through them is increased (Ludwig and Sczelkow), At the time that
the motor fibres are excited, so also are the vaso-dilator fibres, which lie in the
same nervous channels (§ 294, II.). [Gaskell found that faradisation of the nerve
of the mylohyoid muscle of the frog not only caused tetanus of the muscle, but.
also dilatation of its blood-vessels. |

Testing Individual Muscles.—In estimating the absolute force of the individual muscles or
groups of muscles in man, we must always pay particular attention to the physical relations,
z.¢., to the arrangement of the levers, direction
of the traction, degree of shortening, &c..(§ 306).
Dynamometer.—The absolute force of certain
groups of muscles is very conveniently, and
practically ascertained by means of a, dyna-
mometer (fig. 339). This instrument is very
useful for testing the difference between the
power of the two arms in cases of paralysis.
The patient grasps the instrument in his hand
and an index registers the force exerted.
Fig. 339 Quetelet has estimated the force of certain

D a f Mathj muscles—the pressure of both hands of aman
JRamomeyer oF Mathieu, to be=70 kilos.; while by pulling he can move

double this weight. The force of the female hand is one-third less, A man can carry more
than double his own weight ; a woman about the half of this, Boys can carry about one-third
more than girls. [Very convenient dynamometers are made by Salter of Birmingham, both
for testing the strength of pull and squeeze ; in testing the former, the instrument is held as
an archer holds his bow when in the act of drawing it, and the strength of pull is given by an
index ; in the latter another form of the instrument is used, Large numbers of observations
were made by means of these instruments by Francis Galton at the Health Exhibition, 1885.] _

Amount of Work Daily.—In estimating the work done by a man, we have to consider, not —
only the amount of work done at any one moment, but how often, time after time, he ¢

THE ELASTICITY OF MUSCLE. 491

succeed in doing work. The mean value of the daily work of a man working eight hours a
day is 10 (10°5 to 11 at most) kilogramme-metres per second, 7¢.e., a daily amount of work=
288,000 (300,000) kilogramme-metres.

. [Ergostat.—Sometimes it is desirable that patients—especially those who suffer from excessive
corpulence—-should do a certain amount of work daily ; this can be carried out by Gaertner’s
Ergostat, which resembles a winch, driven by a handle. The pressure upon the wheel can be
regulated by means of a strap, lever, and weights, and according to the weight and number of
revolutions of the wheel, can the amount of mechanical work be accurately regulated. This
instrument is recommended for therapeutical purposes. ]

Modifying Conditions.—Many substances, after being introduced into the body, diminish,
and ultimately paralyse the production of work—mercury, digitalin, helleborin, potash salts, &c.
Others increase the muscular activity—veratrin (Rossbach), glycogen, [caffein, and allied alka-
loids], muscarin (Klug and Fr. Hégyes), kreatin and hypoxanthin ; extract of meat rapidly
restores the muscles after fatigue (Kobert). [Those drugs which excite muscular tissue restore
it after fatigue. Kreatin is a waste product of muscle, and beet-tea and Liebig’s extract of
meat perhaps owe their restorative qualities partly to these extractives. ] .

301. THE ELASTICITY OF MUSCLE.—Physical.—Every elastic body has its ‘‘ natural
shape,” 7.¢., its shape when no external force (tension or pressure) acts upon it so as to distort
it. Thus, the passive muscle has a “natural form.” If, however, a muscle be extended
in the course of its fibres, the parts of the muscle are evidently pulled asunder. If the
stretching be carried only to a certain degree, the muscle, in virtue of its elasticity, will regain
its natural form. Such a body is said to possess ‘‘ complete elasticity,” 7.c., after being
stretched it regains exactly its original shape. By the term ‘‘ amount of elasticity ” (modulus)
is meant the weight (expressed in kilogrammes) necessary to extend an elastic body 1 ( milli-
metre in diameter, its own length, without the body breaking. Of course many bodies are
ruptured before this occurs. Fora passive muscle it is =0°2734 (Wundt) [that of bone = 2264
(Wertheim), tendon=1°6693, nerve=1°0905, the arterial walls=0°0726 (Wundt)]. Thus, the
amount of elasticity of a passive muscle is small, as it requires only a slight stretching force to
extend it to its own length. It has, therefore, no great amount of elasticity. The term
‘‘ coefficient of elasticity ” is applied to the fraction of the length of an elastic body, to which
it is elongated by the unit of weight applied to stretch it. It is large in a passive muscle. If
the tension be sufficiently great, the elastic body ruptures at last. The ‘“‘carrying capacity”
of muscular tissue, until it ruptures, is in the following ratios for youth; middle, and old age,
nearly 7:3: 2. [Instead of the word “elasticity,” Brunton suggests the use of extensibility
and retractibility, terms suggested by Marey, the one referable to the elongation on the:appli
cation of a weight, and the other to the shortening after its removal. ]

Curve of Elasticity.—In inorganic elastic bodies, the line of elongation, or the
extension, is directly proportional to the extending weight; in organic bodies, and
therefore in muscle, this is not the case, as the weight is continually increased by
equal increments—the muscle is less extended than at the beginning, so that the
extension is not proportional to the weight. If equal weights be added to a scale-

Fig. 340. Fig. 341. Fig. 342.
Fig. 340.—Curve of elasticity from an inorganic body (india-rubber). Fig. 341.—Curve of
elasticity from the sartorius of a frog, obtained by adding equal increments of weight at
A, B, C, &c. Fig. 342.—Curve of elasticity produced by continuous extension and recoil
of a frog’s muscle ; 0 , abscissa before, 2 after extension.
pan attached to a piece of india-rubber, with a writing-lever connected with it, and
writing its movements on a plate of glass that-can be moved with the hand, we
get such a curve as in fig. 340, while, if the same be done with the sartorius of a
frog, we get a result similar to fig. 341. A straight line joins the apices of the
former, while the curve of elasticity is a hyperbola, or something near it, in the
latter case. :

‘gS

492 ELASTIC AFTER-EFFECT.

Elastic After-Effect—At the same time, after the first elongation, correspond-
ing to the extending weight, is reached, the muscle may remain for days, and even
weeks, somewhat elongated. This is called the “elastic after-effect” (§ 65).
{Marey attached a lever to a frog’s muscle, and allowed the latter to record its
movements on a slowly revolving cylinder. To the lever was fixed a vessel into
which mercury slowly flowed. This extended the muscle, and when it had ceased
to elongate, the mercury was allowed slowly to run out again. The curve obtained
is shown in fig. 342. The abscisse, o x and «’, indicate the position of the writing-
style before and after the experiment, and we observe that x’ is lower than o 2, so
that the recoil is imperfect. There has been an actual elongation of the muscle,
so that the limit of its elasticity is exceeded. Although a frog’s gastrocnemius
may be loaded with 1500 grammes without rupturing it, 100 grammes will prevent
its regaining its original length. | |

Method.—In order to test the elasticity of a muscle, fix it to a support provided with a
graduated scale, and to the lower end of the muscle attach a scale-pan, in which are placed
various weights, measuring on each occasion the corresponding elongation of the muscle thereby
obtained (Hd. Weber). In order to obtain the curve of elongation or extensibility take as

abscisse the successive units of weight added, and the elongation corresponding to each weight
as ordinates. Example from the hyoglossus of the frog :—

| Length of the Muscle Extension.
Weight in Grammes. 3 rane — ae
= in Millimetres. in Millimatros. | pea
0°3 24°9 iy 7
2°3 32°3 2°3 | 7
3°3 33°4 a 1a | 3
4 5 34 2 0 “3 | 9
= 34°6 04 | 1

The elasticity of passive muscle is small, but very complete, and is comparable
to that of a caoutchouc fibre. Small weights greatly elongate the muscle. If the
weights be uniformly increased, there is not a uniform elongation; with equal
increments of weight, the greater the load, the increase in elongation always
becomes less; or, to express it in another way, the amount of elasticity .of the
passive muscle increases with its increased extension (Ed. Weber).

In inorganic bodies, the curve of extension is a straight line, but in organic
bodies, it more closely resembles a hyperbola (Wertheim). The elasticity of a

passive fatigued muscle does not differ essentially from that of a non-fatigued
muscle,

Muscles in the living body, and still in connection with their nerves and blood-vessels, are
more extensible than excised ones. Muscles, when quite fresh, are elongated (within certain
small limits as regards the weight) at first with a uniformly increasing weight, to an extent
proportional to the latter, just as with an inorganic body. hen heavy weights are used, we
must be careful to take into consideration the ‘* elastic after-effect” (§ 65).

The volume of a stretched muscle is slightly Jessthan an unstretched one, similar to the
contracted (§ 297, 2) and stiffened muscle (§ 295).

Dead muscles and muséles in rigor mortis have greater elasticity, 7.¢., they require a heavier
weight to stretch them than fresh muscles; but, on the other hand, the elasticity of dead

muscles is less complete, i.¢., after they are stretched, they only recover their original form.

within certain limits.

Elasticity of Intact Muscles.—Normally, within the body, the museles are
stretched to a very slight extent, as can be shown by the slight degree of retraction
which occurs when the insertion of a muscle is divided. This slight degree of
extension, or stretching, is important. If this were not so, when a muscle is about
to contract, and before it could act upon a bone as a lever, it would have to “ take
in so much slack.” The elasticity of muscles is manifested during the contraction

USES OF ELASTICITY. 493

of antagonistic muscles. The position of a passive limb depends upon the
resultant of the elastic tension of the different muscle groups.

The elasticity of an active muscle is less than that of a passive muscle, 7.¢., it
is elongated by the same weight to a greater extent than a passive muscle. For
this reason, the active muscle, as can be shown in an excised contracted muscle, is
softer; the apparently great hardness manifested by stretched contracted muscles
depends upon their tension. When the active muscle becomes fatigued, its
elasticity is diminished (§ 304). |

Method.—Ed. Weber took the hyoglossus muscle of a frog and suspended it vertically,
noticing its length when it was passive. It was then tetanised with induction shocks and its
height again noted. One after the other heavier weights were attached to it, and the length
of the passive and tetanised muscle observed for each weight. The extent to which the active
loaded muscle shortened from the position of the passive loaded muscle he called the ‘‘ height
of the lift” (or ‘‘ Hubhéhe”). The latter becomes less as the weight increases, and lastly,
the tetanised muscle may be so loaded that it cannot contract, 7.¢., the height of the lift is=0.

Weber’s Paradox.—The case may occur where, when a muscle is so loaded that it cannot
contract when it is stimulated, it may even elongate. According to Wundt, even in this
condition the elasticity is not changed. [The usual explanation given is that, as the elasticity
of a muscle is diminished during contraction, it is more extended with the same weight in the
contracted as compared with the passive or uncontracted state, so that a heavily weighted
muscle, when stimulated, may elongate instead of shorten.] According to Wundt, however,
as stated, there is no change in the elasticity of the muscle. In these experiments, the length
of the active loaded muscle is equal to the length of the passive muscle when similiarly loaded,
minus the ‘‘ height of the lift.”

Poisons.—Potash causes shortening of a muscle with simultaneous increase of its elasticity.
Digitalin produces other changes with increased elasticity. Physostigmin increases it, while
veratrin diminishes it, and interferes with its completeness (Rossbach and v. Anrep), and. tannin
makes a muscle less extensible, but more elastic (Lewin). Ligature of the blood-vessels
produces at first a decrease, and then an increase, of the elasticity ; section of the motor nerve
diminishes the elasticity (v. Anrep) ; heat increases it.

Eduard Weber concluded from his experiments that a muscle assumes two forms, the active
and the passive form. Each of these corresponds toa special naturalform. The passive muscle
is longer and thinner—the active-is shorter and thicker in form. The passive as well as the
active muscle strives to retain its form. If the passive muscle be set into activity, the passive
rapidly changes into the active form, in virtue of its elastic force. The latter is the energy
which causes muscular work. Schwann compared the force of an active muscle to a long,
elastic, tense spiral spring. Both can lift the greatest weight, only from that form in which
they are most stretched. The more they shorten, the less the weight which they can lift.

[Uses of Elasticity.—As already pointed out, all muscles are slightly on the
stretch, so that no time is lost nor energy wasted, in “ taking in slack,” as it were;
but the elasticity also lessens the shock of the contraction, so that it is developed
gradually, and muscles are not liable to be torn from their attachments. The
muscular energy is transmitted to the mass to be moved through an elastic and
easily extensible body (muscle), whereby the shock due to the contraction is
lessened, but, as Marey has shown, the amount of work is thereby considerably
increased. | | :

[Tonicity of Muscle (§ 362)—Sensibility of Muscle.—That muscles contain sensory fibres is
certain (§ 430). Section of inflamed muscles is painful, and during muscular cramp intense pain
is felt. Sachs discharged a reflex action by stimulating the central end of an intra-muscular

nerve-filament in a frog, while stimulation of the central end of the phrenic nerve raises the
blood-pressure (Muscular Sense, § 480).]

302. Formation of Heat in an Active Muscle.— After Bunzen, in 1805
(§ 209, 1, 6), showed that during muscular activity heat is evolved, v. Helmholtz
proved that an excised frog’s muscle, when tetanised for two to three minutes,
exhibited an increase of its temperature of 0°14° to 0°18° C. R. Heidenhain
succeeded in showing an increase of 0°001° to 0-005° C. for each single contraction.
The heart is warmer during every systole (Marey).

[Method.—The rise in temperature of a frog’s muscle may be estimated by placing the two
gastrocnemii of a frog’s muscle on the two junctions of a thermo-electric pile, connected with a

494 HEAT-FORMATION IN AN ACTIVE MUSCLE.

heat galvanometer. Of course, when the two muscles are at the same temperature, the needle
of the galvanometer is stationary ; but, if one muscle is made to contract, or is tetanised, then
an electrical current is set up which deflects the needle (§ 208, B). Lujankow has, by means of
a delicate thermometer placed between the thigh muscles of a dog, estimated the rise of tempera-
ture under different conditions of the muscle, while the latter was still in sitw and intact. }

The following facts have been ascertained with regard to the development of
heat :—

1. Relation to Work.—It bears a relation to the amount of work.

(a) If a muscle during contraction carries a weight which extends it again during
rest, no work is transferred beyond the muscle (§ 300). In this case all the
chemical potential energy during this movement is converted into heat. Under
these circumstances, the amount of heat evolved runs parallel with the amount of
work done, 7.¢., it increases as the load and the height increase up to a maximum
point, and afterwards diminishes as the load is increased. The heat-maximum
is reached with a less load sooner than the work-maximum (Hez/enhain).

(b) If, when the muscle is at the height of its contraction, the load be removed,
then the muscle has produced work referable to something outside itself; in this |
case the amount of heat produced is less (A. Fick). The amount of work produced,
and the diminished amount of heat formed, when taken together, represent the
same amount of energy, corresponding to the law of the conservation of energy.

(c) If the same amount of work is performed in one case by many but small
contractions, and in another by fewer but larger contractions, then, in the latter
case, the amount of heat is greater (Hezdenhain and Nawalichin). This shows that
larger contractions are accompanied by a relatively greater metabolism of the mus-
cular substance than small contractions, which is in harmony with practical experi-
ence ; thus the ascent of a tower with steep high steps causes fatigue more rapidly
(metabolism greater) than the ascent of a more gentle slope with lower steps.

(d) If the weighted muscle executes a series of contractions one after the other,
and at the same time does work, then the amount of heat it produces is greater than
when it is tetanic, and keeps a weight suspended. Thus, the transition of the
muscle into a shortened form causes a greater production of heat than the mainten-
ance of this form.

2. Relation to Tension.—The amount of heat evolved depends upon the tension
of the muscle ; it also increases as the muscular tension increases (Heidenhain). If
the-ends of a muscle be so fixed that it cannot contract, the maximum of heat is
obtained (Léclard), and this the more quickly the more rapidly the stimuli follow
each other (ck). Such a condition occurs during tetanus, in which condition the
violently contracted muscles oppose each other, and very high temperatures have
been registered by Wunderlich (§ 213, 7), while the same is true of animals that
are tetanised (Leyden). Dogs kept in a state of tetanus by electrical stimulation
die, because their temperature rises so high (44° to 45° C.) that life no longer can
be maintained (Aichet). In addition to the formation of heat, there is a consider-
able amount of acid, and of alcoholic extractives produced in the muscular tissue. |

3. Relation to Stretching.—Heat is also evolved during the elongation or
relaxation of a contracted muscle, e.g., by causing a muscle to contract without the
addition of any weight, and loading it when it begins to relax, whereby heat is
produced (Steiner, Schmulewitsch, and Westerman). If weights be attached to a —
muscle by means of an inextensible medium, and the weights be allowed to fall
from a height’so as to givea jerk to the muscle, then an amount of heat equivalent
to the work done by the drop, is set free in the muscle (Fick and Danilewsky),

_ 4. The formation of heat diminishes as the muscular fatigue increases,

5. In a muscle duly supplied with blood, the production of “heat (as well as the
mechanical work) is far more active than in a muscle whose blood-vessels are
ligatured or its blood-stream cut off. Recovery takes place more rapidly and com-

\.
4

THE MUSCLE SOUND. 495

pletely after fatigue, while, at the same time, there is a new increase in the produc-
tion of heat (Meade Smith).

The amount of work and heat in a muscle must always correspond to the transformation of
an equivalent amount of chemical energy. A greater part of this energy is manifested as work,
the greater the resistance that is offered to the muscular contraction. When the resistance 1s

great, $ of the chemical energy may be manifested as work, but when it is small, only a small
part of it is so converted.

It was stated that a nerve in action is #,° C. warmer (Valentin), but this is denied by
v. Helmholtz and Heidenhain.

In man, if the muscles be stimulated with electricity or contracted voluntarily, the produc-
tion of heat may be detected through the skin (v. Ziemssen). The venous blood flowing from
an actively contracting muscle is 0°6° C. warmer than the arterial blood (Meade Smith).

308. THE MUSCLE SOUND.—Muscle Sound.—When a muscle contracts,
and is at the same time kept in a state of tension by the application of sufficient
resistance, it emits a distinct sound or tone with a semi-musical quality, depend-
ing upon the intermittent variations of tension occurring within it (Wollaston).

Methods.—The muscle sound may be heard by placing the ear over tle tetanically contracted
and tense biceps of another person ; or we may insert the tips of our index fingers into our ears,
and forcibly contract the muscles of our arm; or the sound of the muscles that close the jaw
may be heard by forcibly contracting them, especially at night when all is still, and when the
outer ears are closed. V. Helmholtz found that this tone coincides with the resonance tone of
the ear, and he thought that the vibrations of the muscles caused this resonance tone. The
sound of an isolated frog’s muscle may be heard by placing one end of a rod in the ear, the other
ear beingclosed. To the other end of the rod is attached a loaded frog’s muscle kept in a tetanic
condition. The pitch of the note, 7.¢., the number of vibrations, may be estimated by com-
paring the muscle sound with that produced by elastic springs vibrating at a known rate.

When a muscle contracts voluntarily, 2.¢., through the will, it makes 19°5 vibra-
tions per second. [Schafer and others give the number as 10 successive nervous
impulses per second, p.486.] We do not hear this very low tone, owing to the number
of vibrations per second being too few, but what we actually hear is the first over-
tone, with double the number of vibrations. The muscle sound has 19°5 vibrations,
when the muscles of an animal are caused to contract, by stimulating its spinal cord
(v. Helmholtz), and also when the motor nerve-trunk is excited by chemical means
(Bernstein). If, however, tetanising induction shocks be applied to a muscle, then
the number of vibrations of the muscle sound corresponds exactly with the number
of vibrations of the vibrating spring or hammer of the induction apparatus, Thus,
the tone may be raised or lowered by altering the tension of the spring.

Loven found that the muscle sound was loudest, when the weakest currents capable of pro-
ducing tetanus were employed. The sound corresponded to the number of vibrations of the
octave just below it in the scale. With stronger currents the muscle-sound disappears, but it
reappears with the same number of vibrations as that of the interrupter of the induction ap-
paratus, if still stronger currents are used. |

If the induction shocks be applied to the nerve, the sound is not so loud, but it
has the same number of vibrations as the interrupter. With rapid induction
shocks, tones caused by 704 (Loven) and 1000 vibrations per second have been
produced (Bernstein).

The first heart-sound is partly muscular (§ 53).

A single induction shock is said to cause the muscle-sound in a contracting muscle. If this
be so, it is doubtful if the muscle-sound can be regarded as a sign that tetanus is due to a
series of single variations of the muscle (§ 298, III.).

304, FATIGUE AND RECOVERY OF MUSCLE.—Fatigue.—By the term
fatigue is meant that condition of diminished capacity for work which is produced
in a muscle by prolonged activity. This condition is accompanied in the living
person with a peculiar feeling of lassitude, which is referred to the muscles. A
fatigued muscle rapidly recovers in a-living animal, but an excised muscle recovers
only to a slight extent (Hd. Weber, Valentin).

[Waller recognises a certain resemblance between experimental fatigue and the natural decline
of excitability at death, in disease, and in poisoning. ]

496 MODIFYING CONDITIONS.

The cause of fatigue is probably partly due to the accumulation of decomposition-
prodtcts—“ fatigue stuffs ’’—in the muscular tissue, these products being formed
within the muscle itself during its activity. They are phosphoric acid, either free
or in the form of acid phosphates, acid potassium phosphate (§ 294), glycerin-
phosphoric acid (?) and CO,. If these substances be removed from a muscle, by
passing through its blood-vessels an indifferent solution of common salt (0°6 per
cent.), or a weak solution of sodium carbonate [or a dilute solution of permanganate
of potash (Avonecker)|, the muscle again becomes capable of energising (J. Ranke,
1863). The using up of O by an active muscle favours fatigue (v. Pettenkofer and
v. Voit). The transfusion of arterial blood (not of venous—Bichat) removes the
fatigue (Ranke, Kronecker), probably by replacing the substances that have been
used up in the muscle. Conversely, an actively energising muscle may be rapidly
fatigued by injecting into its blood-vessels a dilute solution of phosphoric acid, of
acid potassium phosphate, or dissolved extract of meat (Kemmerich). A muscle
fatigued in this way absorbs less O, and when so fatigued, it evolves only a small
amount of acids and CO,. The conditions which lead up to fatigue are connected
with considerable metabolism in the muscular tissue.

[Zabludowski found that if a frog’s muscles be systematically stimulated by maximum in-
duction shocks until they cease to contract, massage or kneading them rapidly restored their
excitability, while simple rest had little effect. Massage acts on the nerves, but chiefly by
favouring the blood- and lymph-streams which wash out the waste products from the muscle.

A similar result obtains in man, so that the ancient Roman practice of ‘‘rubbing”’ after a bath
and after exercise was one conducive to restoration of the power of the muscles. ]

Modifying Conditions.—In order to obtain the same amount of work from a
fatigued muscle, a much more powerful stimulus must be applied to it than toa
fresh one. A fatigued muscle is incapable of lifting a considerable load, so that
its absolute muscular force is diminished. If, during the course of an experiment,
an excised muscle be loaded with the same weight, and if the muscle be stimulated
at regular intervals with maximal stimuli (strong induction shocks), contraction
after contraction gradually and regularly diminishes in height, the decrease being a
constant fraction of the total shortening. Thus the fatigue-curve is represented by a
straight line [1.e., a straight line will touch the apices of all the contractions]. The
more rapidly the contractions succeed each other, the greater is the fall in the height
of the contraction [7.¢., if the zmterval between the contractions be short, the fatigue-
curve falls rapidly towards the abscissa], and conversely. After a certain number
of contractions, an excised muscle becomes exhausted.

This result occurs whether the stimuli are applied at short or long intervals
(Kronecker), and a similar result is obtained with sub-maximal stimuli (7Z%ege/).
A fatigued muscle contracts more slowly than a fresh one, while the latent period
is also longer during fatigue (p. 480). The fatigued muscle is said to be more
extensible (Donders and van Mansvelt). If a muscle be so loaded that, when it
contracts, it cannot lift the load, fatigue occurs even to a greater extent than when
the load is such that the muscle can lift it (Leber). The metabolism and the forma-
tion of acid are greater in a contracted muscle kept on the stretch, than in a con-
tracted muscle allowed to shorten (Heidenhain). Ifa muscle contract, but be not
required to lift any load, it becomes fatigued only very gradually. If a muscle be
loaded only during contraction, and not during relaxation, it is fatigued more
slowly than when it is loaded during both phases; and the same is true when
a muscle has to lift its load only during the course of its contraction, instead of at
the beginning of the contraction. Loads may be suspended to perfectly passive
muscles without fatiguing them (/arless, Leber). :

[Signs of Fatigue (fig. 343).—In the record of the series of contractions ; (1)
the contractions become more prolonged; (2) they decrease in height; (3) the
latent period becomes longer ; (4) if maximal shocks be used, the beginning of the

FATIGUE AND RECOVERY OF MUSCLES. 497

series exhibits a “‘staircase” character of its contractions just like the heart

(§ 57). ]

[While an excised frog’s muscle is fairly rapidly exhausted by single opening induction
shocks, at intervals of one second, human muscle in its normal relations may be almost in-
definitely so treated, and there is no change
in the record or any sensation of fatigue.
Waller regards this as favouring the view
that the ‘‘fatigue consequent upon pyro-
longed muscular exertion is normally cen-
tral rather than peripheral.” Such results,
however, do not harmonise with those of
Zabludowski on the kneading of :uscles, or
massage. Probably there are two factors,
one central, the other peripheral. ]

Blood Supply.—If the arteries of a mam-
mal be ligatured, stimulation of the motor Fig. 343,
nerves produces complete fatigue after 120 Fatigue-curve of a frog’s muscle. The sciatic nerve
to 240 contractions (in two to four minutes), was stimulated with maximal induction shocks
but direct muscular stimulation still causes and every fifteenth contraction recorded (Stir-
the muscles to contract. In both cases the ling).
fatigue-curve is in the form of a straight
line. If the blood supply to a mammalian muscle be normal, on stimulating the motor
nerve, the muscular contractions at first increase in height and then fall, their apices forming
a straight line (Rossbach and Harteneck). In persons who have used their muscles until fatigue
sets in, it is found that at the beginning the nerves and muscles react better to galvanic and
faradic stimulation, but afterwards always to a less degree (Orschanski). According to v. Kries,
a muscle tetanised and fatigued with maximal stimuli behaves like a fresh muscle tetanised
with sub-maximal stimuli ; both show an incomplete transition from the passive to the active
condition,

[Relation of End-Plates.—Muscle is fatigued far more rapidly than nerve, and the fatigue
begins in the muscle and not in the nerve, and it seems to be the weakest link in the chain
between nerve and muscle which is affected during excessive action, viz., the motor end-plate
(Waller). Ina nerve its conductivity is sooner atfected by fatigue than its direct excitability.
Waller finds that after death ‘‘ the excitability of a nerve persists when its action upon muscle
has ceased, such muscle being still excitable by direct stimulation.” Some link in the chain is
obviously affected, and it is perhaps the end-plates. ]

[Action of Drugs on Fatigue.—Waller finds, in a frog poisoned with veratrin, that if the
muscles be stimulated electrically, the characteristic elongation of the descent (§$ 298) gradually
disappears, but reappears
after a period of rest. In
this respect, strychnin in
its action on the spinal
cord behaves precisely
the same as veratrin on
muscle, viz., its effect is
dissipated by action and
restored by rest.] Curara
and the ptomaines cause
an irregular course of the
fatigue-curve (Guareschi iF

: ; ig. 344,
and Mosso). [If strychnin : ' Sie eens ;
be injected into a frog, Curves obtained by direct stimulation of the gastrocnemius of a frog
and the sciatic nerve on Poisoned with strychnin, the sciatic nerve divided on one side (upper
one side divided after the CUrve) and not on the other (lower or fatigue-curve). .

strychnin tetanus has lasted for a time, the leg muscles of the side with the nerve undivided
exhibit signs of fatigue, as shown by direct stimulation, of the muscles of both legs, when a
curve similar to fig. 344 is obtained. The higher one is the non-fatigued, the lower that of the
side with the nerve undivided (Wadler). ]

Recovery from the condition of fatigue is promoted by passing a constant electrical
current through the entire length of the muscle (Heidenhain), also by injecting
fresh arterial blood into its blood-vessel, or by very small doses of veratrin, [or
permanganate of potash], and by rest.

If the muscle of an intact animal be stimulated continuously (fourteen days or so), until
complete fatigue occurs, the muscular fibres become granular and exhibit a wagike degenera-

aI

498 MECHANISM OF THE BONES AND JOINTS.

tion. The transverse striation is still visible as long as the sarcous substance is in large masses,
but as soon as it breaks up into small pieces the transverse striation disappears completely
(O. Roth).

305. MECHANISM OF THE BONES AND JOINTS.—Bones exhibit in the
inner architecture of their spongiosa an arrangement of their lamelle and spicules
which represents the static result of those forces—pressure and traction—which act
on the developing bone (Structure of Bone, § 447). They are so arranged that,
with the minimum of material, they afford the greatest resistance as a supporting
structure or framework (H. v. Meyer, Culmann, Jul. Wolf).

I. The joints permit the freest movements of one bone upon another, [such as exist between
the extremities of the bones of the limbs. In other cases, sutures are formed, which, while
permitting no movement, allow the contents of the cavity which they surround to enlarge, as
in the case of the cranium]. The articular end of a fresh bone is covered with a thin layer or
plate of hyaline cartilage, which in virtue of its elasticity moderates any shocks or impulses
communicated to the bones. The surface of the articular cartilage is perfectly smooth, and
facilitates an easy gliding movement of the one surface upon the other. At the outer boundary
line of the cartilage, there is fixed the capsule of the joint, which encloses the articular ends of
the bones like a sac. The inner surface of the capsule is lined by a synovial membrane, which
secretes the sticky, semi-fluid, synovia, moistening the joint. The outer surface of the capsule
is provided at various parts with bands of fibrous tissue, some of which strengthen it, whilst
others restrain or limit the movement of the joint. Some osseous processes limit the movements

of particular joints, ¢.g., the coronoid process of the ulna, which
permits the fore-arm to be flexed on the upper arm only toa
certain extent ; the olecranon, which prevents over-extension
at the elbow-joint. The joint surfaces are kept in apposition
—(1) by the adhesion of the synovia-covered smooth articular
surface ; (2) by the capsule and its fibrous bands ; and (3) by
the elastic tension and contraction of the muscles.
(Structure of Articular Cartilage. —The thin layer of hyaline
Hyaline encrusting cartilage is fixed by an irregular surface upon the
curtilage. corresponding surtace of the head of the bone (fig. 345). Ina
vertical section through the articular cartilage of a bone which |
has been softened in chromic or other suitable acid, we observe .
that the cartilage cells are flattened near the free surface of the |
cartilage, and their long axes are parallel to the surface of the
joint ; lower down, the cells are arranged in irregular groups, |
and farther down still, nearer the bone, in columns or rows, 4
ee whose long axis is in the long axis of the bone. These rows
2] Calcifiea @re produced by transverse cleavage of pre-existing cells. In
: Jcy.| cartilage. the upper two-thirds or thereby the matrix of the cartilage is
if hyaline, but in the lower third, near the bone, the matrix is
granular and sometimes fibrillated. This is the calcified zone,
which is impregnated with lime salts, and sharply defined by
a nearly straight line from the hyaline zone above it, and by a
very bold wavy line from the osseous head of the bone.

Synovial Membrane.—Synovial membrane consists of bundles
of delicate connective-tissue mixed with elastic tissue, while on
its inner surface it is provided with folds, some of which con-
tain fat, and others blood-vessels (synovial villi)... The inner
surface peers with recaps i The pnp tn liga-

: : ‘ _ ments and cartilages are not covered by the synovial membrane,
cesar iy trie as car nor are they covered by endothelium. The synovia is a colour-
; . less, stringy, alkaline fluid, with a chemical composition closel
allied to that of transudations, with this difference, that it contains much mucin, together wit
albumin and traces of fat. ‘Excessive movement diminishes its amount, makes it more inspis-
sated, and increases the mucin, but diminishes the salts.

Joints may be divided into several classes, according to the kind of movement
which they permit :— |

1. Joints with movement around one axis: (a) The Ginglymus, or Hinge-Joint.—The one
articular surface represents a portion of a cylinder or sphere, to which the other surface is
adapted by a corresponding depression, so that, when flexion or extension of the joint takes
Place, it moves only on one axis of the cylinder or sphere. The joints of the fingers and toes are

inge-joints of this description. Lateral ligaments, which prevent a lateral displacement of
the articular surfaces, are always present. =

=) [=
2anP-> =

am® ©
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i) Bone.

SOCREW-HINGE JOINTS. 499

The Screw-hinge Joint is a modification of the simple hinge form (Langer, Henke), e.g., the
humero-ulnar articulation. Strictly speaking, simple flexion and extension do not take place
at the elbow-joint, but the ulna moves on the capitellum of the humerus like a nut on a bolt;
in the right humerus, the screw is a right spiral, in the left, a left spiral. The ankle-joint is
another example ; the nut or female screw is the tibial surface, the right joint is like a left-
handed screw, the left the reverse. (b) The Pivot-Joint (rotatoria), with a cylindrical surface,
é.g., the joint between the atlas and the axis, the axis of rotation being around the odontoid
process of the axis. In the acts of pronation and supination of the fore-arm at the elbow-
joint, the axis of rotation is from the middle of the cotyloid cavity of the head of the radius
to the styloid process of the ulna. The other joints which assist in these movements are above
the joint, between the circumferential part of the head of the radius and the sigmoid cavity of
the ulna, and below the joint, between the sigmoid cavity of the radius which moves over the
rounded lower end of the ulna.

2. Joints with movements around two axes.—(a) Such joints have two unequally curved
surfaces which intersect each other, but which le in the same direction, e.g., the atlanto-
occipital joint, or the wrist-joint, at which lateral movements, as well as flexion and extension,
take place. (0) Joints with curved surfaces, which intersect each other, but which do not lie
in the same direction. To this group belong the saddle-shaped articulations, whose surface is
concave in one direction, but convex in the other, ¢.g., the joint between the metacarpal bone
of the thumb and the trapezium. The chief movements are—(1) flexion and extension, (2)
abduction and adduction. Further, to a limited degree, movement is possible in all other
directions ; and, lastly, a pyramidal movement can be described by the thumb.

3. Joints with movement on a spiral articular surface (spiral joints), e.g., the knee-joint
(Goodsir). The condyle of the femur, curved from before backwards, in the antero-posterior
section of its articular surface, represents a spiral (Ed. Weber), whose centre lies nearer the
posterior part of the condyle, and whose radius vector increases from behind, downwards and
forwards. Flexion and extension are the chief movements. The strong lateral ligaments arise
from the condyles of the femur corresponding to the centre of the spiral, and are inserted into the
head of the fibula and internal condyle of the tibia. When the knee-joint is strongly flexed,
the lateral ligaments are relaxed—they become tense as the extension increases ; and when the
knee-joint is fully extended, they act quite like tense bands which secure the lateral fixation of
the joint. Corresponding to the spiral form of the articular surface, flexion and extension do not
take place around one axis, but the axis moves continually with the point of contact ; the axis
moves also in a spiral direction. The greatest flexion and extension cover an angle of about
145°. The anterior crucial ligament is more tense during extension, and acts as a check liga-
ment for too great extension, while the posterior is more tense during flexion, and is a check
ligament for too great flexion. The movements of extension and flexion at the knee are further
complicated by the fact that the joint has a screw-like movement, in that during the greater
extension the leg moves outwards. Hence, the thigh, when the leg is fixed, must be rotated
outwards during flexion. Pronation and supination take place during the greatest flexion to
the extent of 41° (Albert) at the knee-joint, while with the greatest extension it is nil. It
occurs because the external condyle of the tibia rotates on the internal. In all positions during
flexion, the crucial ligaments are fairly and uniformly tense, whereby the articular surfaces are
against each other. Owing to their arrangement, during increasing tension of the anterior
ligament (extension), the condyles of the femur must roll inore on to the anterior part of the
articular surface of the tibia, while by increasing tension of the posterior ligament (flexion), they
must pass more backwards.

4. Joints with the axis of rotation round one fixed point.—These are the freely movable
arthrodial joints. The movements can take place around innumerable axes, which all inter-
sect each other in the centre of rotation. One articular surface is nearly spherical, the other is
cup-shaped. The shoulder- and hip-joints are typical ‘‘ball-and-socket-joints.” We may
represent the movements as taking place around three axes, intersecting each other at right
angles. The movements which can be performed at these joints may be grouped as :—(1)
pendulum-like movements in any plane, (2) rotation round the long axis of the limb, and (3)
circumscribing movements [circumduction], such as are made round the circumference of a
sphere ; the centre is in the point of rotation of the joint, while the circumference is described
by the limb itself.

Limited arthrodial joints are ball joints with limited movements, and where rotation on the
long axis is wanting, ¢.g., the metacarpo-phalangeal joints.

5. Rigid joints or amphiarthroses are characterised by the fact that movement may occur in
all directions, but only to a very limited extent, in consequence of the tough and unyielding
external ligaments. Both articular surfaces are usually about the same size, and are nearly
plane surfaces, ¢.g., the articulations of the carpal and the tarsal bones.

II. Symphyses, synchondroses, and syndesmoses unite bones without the formation of a
proper articular cavity, are movable in all directions, but only to the slightest extent. Physio-
a they are closely related to amphiarthrodial joints.

I. Sutures unite bones without permitting any movement. The physiological importance

500 SPHINCTER AND OTHER MUSCLES.

of the suture is that the bones can still grow at their edges, which thus renders possible th
distension of the cavity enclosed by the bones (Herm. v. Meyer).

306. ARRANGEMENT AND USES OF MUSCLES.—The muscles form 45
per cent, of the total mass of the body, those of the right side being heavier than
those on the left. Muscles may be arranged in the following groups, as far as their
mechanical actions are concerned :— .

A. Muscles without a definite origin and insertion :—

1. The hollow muscles surrounding globular, oval, or irregular cavities, such
as the urinary bladder, gall-bladder, uterus, and heart ; or the walls of more or less
cylindrical canals (intestinal tract, muscular gland ducts, ureters, Fallopian tubes,
vasa deferentia, blood-vessels, lymphatics). In all these cases the muscular fibres
are arranged in several layers, e. g., in a longitudinal and a circular layer, and some-
times also in an oblique layer. All these layers act together and thus diminish the
cavity. It is inadmissible to ascribe different mechanical effects to the different
layers, ¢.g., that the circular fibres of the intestine narrow it, while the longitudinal
dilate it. Both sets of fibres rather seem to act simultaneously, and diminish the
cavity by making it narrower and shorter at the same time. The only case where
muscular fibres may act in partially dilating the cavity is when, owing to pressure
from without, or from partial contraction of some fibres, a fold, projecting into the
lumen, has been formed. When the fibres, necessarily stretching across the depres-
sion thereby produced, contract, they must tend to undo it, z.e., enlarge the cavity.
The various layers are all innervated from the same motor source, which supports
the view of their conjoint action. |

2. The sphincters surround an opening ora short canal, and by their action
they either constrict or close it, e.g., sphincter pupille, palpebrarum, oris, pylori,
ani, cunni, urethre.

B. Muscles with a definite origin and insertion :—

1. The origin is completely fixed when the muscle is in action. The course
of the muscular fibres, as they pass to where they are inserted, permits of the
insertion being approximated in a straight line towards their origin during con-
traction, ¢e.g., the attolens, attrahens, and retrahentes of the outer ear, and the
rhomboidei. ‘Some of these muscles are inserted into soft parts which necessarily
must follow the line of traction, e.g., the azygos uvule, levator palati niollis, and
most of the muscles which arise from bone and are inserted into the skin, such as
the muscles of the face, styloglossus, stylopharyngeus, «ce.

2. Both Origin and Insertion movable.—In this case the movements of both
points are inversely as the resistance to be overcome. ‘The resistance is often
voluntary, which may be increased either at the origin or insertion of the muscle,
Thus, the sternocleidomastoid may act either as a depressor of the head or as an
elevator of the chest; the pectoralis minor may act as an abductor and depressor
of the shoulder, or as an elevator of the 3rd to 5th ribs (when the shoulder-girdle
is fixed),

3. Angular Course.—Many muscles having a fixed origin are diverted from
their straight course; either their fibres or their tendons may be bent out of the
straight course. Sometimes the curving is slight, as in the occipito-frontalis and
levator palpebrz superioris, or the tendon may form an angle round some bony
process, whereby the muscular traction acts in quite a different direction, ¢.e., as if
the muscle acted directly from this process upon its point of insertion, e.g, the
obliquus oculi superior, tensor tympani, tensor veli palatini, obturator internus.

4. Many of the muscles of the extremities act upon the long bones as upon
levers:—(a) Some act upon a lever with one arm, in which case the insertion of
the muscle (power) and the weight lie upon one side of the fulcrum or point of
support, ¢.g., biceps, deltoid. The insertion (or power) often lies very close to
the fulcrum. In such a case, the rapidity of the movement at the end of the lever

VARIOUS KINDS OF LEVERS ACTED ON BY MUSCLES. 501

is greatly increased, but force is lost [7.e., what is gained in rapidity is lost in

power]. This arrangement has this advantage, that, owing to the slight contraction

of the muscle, little energy is evolved, which would be the case had the muscular
contraction been more considerable (§ 300, I., 3). (4) The muscles act upon the
bones as upon a lever with two arms, in which case the power (insertion of the
muscle) lies on the other side of the fulcrum opposite to the weight, e.g., the
triceps and muscles of the calf. In both cases, the muscular force necessary to
overcome the resistance is estimated by the principles of the lever: equilibrium is
established when the static moments (=product of the power in its vertical
distance from the fulcrum) are equal ; or when the power and weight are inversely
proportional, as their vertical distance from the fulcrum.

[The Bony Lever.—All the three orders of levers are met with in the body. Indeed, in the
elbow-joint all the three orders are represented. The annexed scheme shows the relative posi-
tions of P, W, and F (fig. 346). The first order represented by such a movement as nodding the
head, the second by raising the body on the tiptoes by the muscles
of the calf, and the third by the action of the biceps in raising the @ F

|
fore-arm. At the elbow-joint, the first order is illustrated by ex- W a 3 (1)
tending the flexed fore-arm on the upper arm, as in striking a blow Pe
on the table, where the triceps attached to the olecranon is the F & le 7
power, the trochlea the fulcrum, and the hand the weight. Ifthe 7 WwW P (2)
hand rest on the table and the body be raised on it, then the hand ; -
is the fulcrum, while the triceps is the power raising the humerus e t i (3)
and the parts resting on it (W). The third order has already been W A eae
referred to, ¢.g., flexing the fore-arm. ] Fig. 346.

_Direction of Action.—It is most important to observe the direc- The three orders of levers.
tion in which the muscular force and weight act upon the lever-arm.
Thus, the direction may be vertical to the lever in one position, while after flexion it may act
obliquely upon the lever. The static moment of a power acting obliquely on the lever-arm is
obtained by multiplying the power with the power acting in a direction vertical to the point
of rotation. |
Examples :—In fig. 347, I., B x represents the humerus, and x Z the radius; A y, the direc-
tion of the traction of the biceps. If the biceps acts at a right angle only, as by lifting
horizontally a weight (P) lying on the fore-arm or in the hand, then the power of the biceps
(= A) is obtained from the formula, Ay x= PaeZ,ie, A=(P x Z): y x. It is evident

P
| pO
Z Ty

Fig. 347. -
Scheme of the action of the muscles on bones.

that, when the radius is depressed to the position x C, the result is different ; then the force of »
the biceps = A, = (P, vz): 02. In fig. 347, II., TF is the tibia, F, the ankle-joint, MC,
the foot in a horizontal position. The power of the muscles of the calf ( = a) necessary
to equalise a force, p, directed from below against the anterior part of the foot, would be

500 SPHINCTER AND OTHER MUSCLES.

of the suture is that the bones can still grow at their edges, which thus renders possible th
distension of the cavity enclosed by the bones (Herm. v. Meyer). |

306. ARRANGEMENT AND USES OF MUSCLES.—The muscles form 45
per cent, of the total mass of the body, those of the right side being heavier than
those on the left. Muscles may be arranged in the following groups, as far as their
mechanical actions are concerned :—

A. Muscles without a definite origin and insertion :—

1. The hollow muscles surrounding globular, oval, or irregular cavities, such
as the urinary bladder, gall-bladder, uterus, and heart ; or the walls of more or less
cylindrical canals (intestinal tract, muscular gland ducts, ureters, Fallopian tubes,
vasa deferentia, blood-vessels, lymphatics). In all these cases the muscular fibres
are arranged in several layers, e. g., in a longitudinal and a circular layer, and some-
times also in an oblique layer. All these layers act together and thus diminish the
cavity. It is inadmissible to ascribe different mechanical effects to the different
layers, ¢.g., that the circular fibres of the intestine narrow it, while the longitudinal
dilate it. Both sets of fibres rather seem to act simultaneously, and diminish the
cavity by making it narrower and shorter at the same time. The only case where
muscular fibres may act in partially dilating the cavity is when, owing to pressure
from without, or from partial contraction of some fibres, a fold, projecting into the
lumen, has been formed. When the fibres, necessarily stretching across the depres-
sion thereby produced, contract, they must tend to undo it, z.e., enlarge the cavity.
The various layers are all innervated from the same motor source, which supports
the view of their conjoint action. |

2. The sphincters surround an opening ora short canal, and by their action
they either constrict or close it, e.g., sphincter pupillz, palpebrarum, oris, pylori,
ani, cunni, urethre.

B. Muscles with a definite origin and insertion :—

1. The origin is completely fixed when the muscle is in action. The course
of the muscular fibres, as they pass to where they are inserted, permits of the
insertion being approximated in a straight line towards their origin during con-
traction, ¢.g., the attolens, attrahens, and retrahentes of the outer ear, and the
rhomboidei. Some of these muscles are inserted into soft parts which necessarily
must follow the line of traction, e¢.g., the azygos uvule, levator palati niollis, and
most of the muscles which arise from bone and are inserted into the skin, such as
the muscles of the face, styloglossus, stylopharyngeus, &c.

2. Both Origin and Insertion movable.—In this case the movements of both
points are inversely as the resistance to be overcome. The resistance is often
voluntary, which may be increased either at the origin or insertion of the muscle,
Thus, the sternocleidomastoid may act either as a depressor of the head or as an
elevator of the chest; the pectoralis minor may act as an abductor and depressor
of the shoulder, or as an elevator of the 3rd to 5th ribs (when the shoulder-girdle
is fixed). |

3. Angular Course.—Many muscles having a fixed origin are diverted from
their straight course; either their fibres or their tendons may be bent out of the
straight course. Sometimes the curving is slight, as in the occipito-frontalis and
levator palpebre superioris, or the tendon may form an angle round some bony
process, whereby the muscular traction acts in quite a different direction, ¢.¢., as if
the muscle acted directly from this process upon its point of insertion, e.g, the
obliquus oculi superior, tensor tympani, tensor veli palatini, obturator internus.

4. Many of the muscles of the extremities act upon the long bones as upon
levers:—(a) Some act upon a lever with one arm, in which case the insertion of
the muscle (power) and the weight lie upon one side of the fulcrum or point of
support, e.g., biceps, deltoid. The insertion (or power) often lies very close to
the fulcrum. In such a case, the rapidity of the movement at the end of the lever

VARIOUS KINDS OF LEVERS ACTED ON BY MUSCLES. 501

is greatly increased, but force is lost [7.¢., what is gained in rapidity is lost in
power]. This arrangement has this advantage, that, owing to the slight contraction
of the muscle, little energy is evolved, which would be the case had the muscular
contraction been more considerable (§ 300, I., 3). (4) The muscles act upon the
bones as upon a lever with two arms, in which case the power (insertion of the
muscle) lies on the other side of the fulcrum opposite to the weight, e.g., the
triceps and muscles of the calf. In both cases, the muscular force necessary to
overcome the resistance is estimated by the principles of the lever: equilibrium is
established when the static moments (=product of the power in its vertical
distance from the fulcrum) are equal ; or when the power and weight are inversely
proportional, as their vertical distance from the fulcrum.

[The Bony Lever.—All the three orders of levers are met with in the body. Indeed, in the
elbow-joint all the three orders are represented. The annexed scheme shows the relative posi-
tions of P, W, and F (fig. 346). The first order represented by such a movement as nodding the
head, the second by raising the body on the tiptoes by the muscles
of the calf, and the third by the action of the biceps in raising the @ F

fore-arm. At the elbow-joint, the first order is illustrated by ex- Ww a 3 (1)
tending the flexed fore-arm on the upper arm, as in striking a blow 7

on the table, where the triceps attached to the olecranon is the F @ baw
power, the trochlea the fulcrum, and the hand the weight. Ifthe 7 Ww P (2)
hand rest on the table and the body be raised on it, then the hand : :

is the fulcrum, while the triceps is the power raising the humerus & | K (3)
and the parts resting on it (W). The third order has already been W A Pees
referred to, ¢.g., flexing the fore-arm. ] Fig. 346.

Direction of Action.—It is most important to observe the direc- The three orders of levers.
tion in which the muscular force and weight act upon the lever-arm.
Thus, the direction may be vertical to the lever in one position, while after flexion it may act
obliquely upon the lever. The static moment of a power acting obliquely on the lever-arm is
obtained by multiplying the power with the power acting in a direction vertical to the point
of rotation.

Examples :—In fig. 347, I., B x represents the humerus, and x Z the radius; A y, the direc-
tion of the traction of the biceps. If the biceps acts at a right angle only, as by lifting
horizontally a weight (P) lying on the fore-arm or in the hand, then the power of the biceps
(= A) is obtained from the formula, Ay x= PwZ, i.e, A=(P wx Z): ya. It is evident

B
T H
P
| aw; :
v i
Z v7" FE

Fig. 347. -
Scheme of the action of the muscles on bones.

that, when the radius is depressed to the position x ©, the result is different ; then the force of
the biceps = A, = (P, vx): 02. In fig. 847, II., TF is the tibia, F, the ankle-joint, MC,
the foot in a horizontal position. The power of the muscles of the calf ( = a) necessary
to equalise a force, p, directed from below against the anterior part of the foot, would be

502 SYNERGETIC AND ANTAGONISTIC MUSCLES.

a=(pMF): FC. Ifthe foot be altered to the position R S, the force of the muscles of ©
the calf would then be 0, = (py, MF): FC.

In muscles also, which, like the coraco-brachialis, are stretched over the angle of
a hinge, the same result obtains.

In fig. 347, III., H E is the humerus, E, the elbow-joint, E R, the radius, B R, the coraco-
brachialis. Its moment in this position is = A, aE. When the radius is raised to E R,,
then itis = A,a E. We must notice, however, that B R, < BR. Hence, the absolute
muscular force must be less in the flexed position, because every muscle, as it becomes shorter,
lifts less weight. What is lost in power is gained by the elongation of the lever-arm.

5. Many muscles have a double action; when contracted in the ordinary way
they execute a combined movement, e¢.g., the biceps isa flexor and supinator of
the forearm. If one of these movements be prevented by the action of other
muscles, the muscle takes no part in the execution of the other movement.

If the fore-arm be strongly pronated and flexed in this position, the biceps takes no part
therein ; or, when the elbow-joint is rigidly supinated, only the supinator brevis acts, not the
biceps. The muscles of mastication are another example. The masseter elevates the lower jaw,
and at the same time pulls it forward. If the depressed jaw, however, be strongly pulled back-
wards when the jaw is raised, the masseter is not concerned. The temporal muscle raises the
jaw, and at the same time pulls it backwards. If the depressed jaw be raised after being pushed
forward, then the temporal is not concerned in its elevation.

6. Muscles acting on two or more joints are those which, in their course from
their origin to their insertion, pass over two or more joints. Either the tendons
may deviate from a straight course, e.g., the extensors and flexors of the fingers
and toes, as when the latter are flexed ; or the direction is always straight, e.g., the
gastrocnemius. The muscles of this group present the following points of interest—
(a) The phenomenon of so-called “active insufficiency.” If the position of the
joints over which the muscle passes be so altered that its origin and insertion
come too near each other, the muscle may require to contract so much before
it can act on the bones attached to it, that it cannot contract actively any
further than to the extent of the shortening from which it begins to be active ; e.g.,
when the knee-joint is bent, the gastrocnemius can no longer produce plantar flexion
of the foot, but the traction on the tendo Achilles is produced by the soleus. (0)
‘“‘ Passive insufficiency ” is shown by many-jointed muscles under the following
circumstances :—In certain positions of the joint,a muscle may be so stretched
that it may act like a rigid strap, and thus limit or prevent the action of other
muscles, e.g., the gastrocnemius is too short to permit complete dorsal flexion of
the foot when the knee is extended. ‘The long flexors of the leg, arising from the
tuber ischii, are too short to permit complete extension of the knee-joint. when the
hip-joint is flexed at an acute angle. The extensor tendons of the fingers are too
short to permit of complete flexion of the joints of the fingers when the hand is
completely flexed.

7. Synergetic muscles are those which together subserve a certain kind of
movement, e.g., the flexors of the leg, the muscles of the calf, and others. The
abdominal muscles act along with the diaphragm in diminishing the abdomen
during straining, while the muscles of inspiration or expiration, even the different
origins of one muscle, or the two bellies of a biventral muscle, may be regarded
from the same point of view.

Antagonistic muscles are those which, during their action, have exactly the
opposite effect of other muscles, ¢.g., flexors and extensors—pronators and supina-
tors—adductors and abductors—elevators and depressors—sphincters and dilators—
inspiratory and expiratory.

When it is necessary to bring the full power of our muscles into action, we
quite involuntarily bring them beforehand into a condition of the greatest tension,
as a muscle in this condition is in the most favourable position for doing
work (§ 300, L., 3). Conversely, when we execute delicate movements requiring

GYMNASTICS, MASSAGE, AND CHANGES IN MUSCLE. 503

little energy, we select a position in which the corresponding muscle is already
shortened.

All the fasciz of the body are connected with muscles, which, when they contract, alter the
tension of the former, so that they are in a certain sense aponeuroses or tendons of the latter
(K. Bardeleben). [For the importance of muscular movements and those of fascie in connection
with the movements of the lymph, see § 201.]

307. GYMNASTICS; MOTOR PATHOLOGICAL VARIATIONS.—Gymnastic exercise is
most important for the proper development of the muscles and motor power, and it ought to
be commenced in both sexes at an early age. Systematic muscular activity increases the
volume of the muscles, and enables them to do more work. The amount of blood is increased
with increase in the muscular development, while at the same time the bones and ligaments
become more resistant. As the circulation is more lively in an active muscle, gymnastics favour
the circulation, and ought to be practised, especially by persons of sedentary habits, who are
apt to suffer from congestion of blood in abdominal organs (e.g., hemorrhoids), as it favours
the movement of the tissue juices [§ 201]. An active muscle also uses more O and produces
more CO,, so that respiration is also excited. The total increase of the metabolism gives rise
to the feeling of well-being and vigour, diminishes abnormal irritability, and dispels the
tendency to fatigue. The whole body becomes firmer, and specifically heavier (Jiége7).

By Ling’s, or the Swedish system, a systematic attempt is made to strengthen certain weak
muscles, or groups of muscles, whose weakness might lead to the production of deformities.
These muscles are exercised systematically by opposing to them resistances, which must either
be overcome, or against which the patient must strive by muscular action.

Massage, which consists in kneading, pressing, or rubbing the muscles, favours the blood-
stream ; hence, this system may be advantageously used fer such muscles as are so weakened by
disease that an independent treatment by means of gymnastics cannot be adopted. [The

importance of massage as a restorative practice in getting rid of the waste products of muscular

activity has been already referred to (§ 304).]

Disturbances of the normal movements may partly affect the passive motor organs (c.9.,
the bones, joints, ligaments, and aponeuroses), or the active organs (muscles with their
tendons, and motor nerves),

Passive Organs.—Fractures, caries and necrosis, and inflammation of the bones, which make
movements painful, influence or even make movement impossible. Similarly, dislocations,
relaxation of the ligaments, arthritis, or anchylosis interfere with movement. Also curvature of
bones, hyperostosis or exostosis; lateral curvature of the vertebral column (Scoliosis), back-

‘ward angular curvature (Kyphosis), or forward curvature (Lordosis), The latter interfere with

respiration. In the lower extremities, which have to carry the weight of the body, genu
valgum may occur in flabby, tall, rapidly-growing individuals, especially in some trades, e¢.g.,
in bakers, The opposite form, genu varum, is generally a result of rickets. Flat foot depends
upon a depression of the arch of the foot, which then no longer rests upon its three points of
support. Its causes seem to be similiar to those of genu valgum. The ligaments of the small
tarsal joints are stretched, and the long axis of the foot is usually directed outwards ; the
inner margin of the foot is more turned to the ground, while pain in the foot and malleoli
make walking and standing impossible. Club-foot (Talipes varus), in which the inner margin
of the foot is raised, and the point of the toes is directed inwards and downwards, depends
upon imperfect development during fcetal life. All children are born with a certain very
slight degree of bending of the foot in this direction. Talipes equinus, in which the toes,
and T. calcaneus, in which the heel touches the ground, usually depend upon contracture of
the muscles causing these positions of the foot, or upon paralysis of the antagonistic muscles.
Rickets and Osteomalacia.—If the earthy salts be withheld from the food, the bones
gradually undergo a change; they become thin, translucent, and may even bend under
pressure. In certain persistent defects of nutrition, the lime and other salts of the food are not
absorbed, giving rise to rachitis, or rickets, in children. If fully formed bones lose their lime-
salts to the extent of 4 to 4 (halisterisis), they become brittle and soft (osteomalacia). This
occurs to a limited extent in old age. :
Muscles.—The normal nutrition of muscle is intimately dependent on a proper supply of
sodium chloride and potash salts in the food, as these form integral parts of the muscular tissue
(Kemmerich, Forester). Besides the atrophic changes which occur in the muscles when these
substances are withheld, there are disturbances of the central nervous system and digestive appa-
ratus, and the animals ultimately die. The condition of the muscles during inanition is given
in § 237. If muscles and bones be kept. inactive, they tend to atrophy (§ 244). In atrophic
muscles, and in cases of anchylosis, thereis an enormous increase, or ‘‘ atrophic proliferation,”
of the muscle-corpuscles, which takes place at the expense of the contractile contents
(Cohnheim). A certain degree of muscular atrophy takes place in old age. The uterus, after
delivery, undergoes a great decrease in size and weight—from 1000 to 350 grammes—due
chiefly to the diminished blood supply to the organ. In chronic lead poisoning, the extensors

504 MOBILITY OF THE VERTEBRA.

and interossei chiefly undergo atrophy. Atrophy and degeneration of the muscles are followed
by shortening aud ehinniie of the bones to which the muscles are attached.

Section and paralysis of the motor nerves cause palsy of the muscle, thus rendering them
inactive, and they ultimately degenerate. Atrophy also occurs after inflammation or softening
of the multipolar nerve-cells in the anterior horn of the grey matter of the spinal cord, or the
motor nuclei (facial, spinal accessory, and hypoglossal of Stilling in the medulla oblongata), in
the muscles connected with these parts. Rapid atrophy takes piece in certain forms of spinal
paralysis and in acute bulbar paralysis (paralysis of the medulla oblongata), and in a chronic
form in progressive muscular atrophy and progressive bulbar paralysis. The muscles and their
nerves become small and soft. The muscles show many nuclei, the sarcous substance becomes
fatty, and ultimately disappears. According to Charcot, these areas are at the same time the
trophic centres for the nerves proceeding from them, as well as for the muscles belonging to
them. According to Friedreich, the primary lesion in progressive muscular atrophy is in the
muscles, and is due to a primary interstitial inflammation of the muscle, resulting in atrophy
and degenerative changes, while the nerve-centres are affected secondarily, just as after amputa-
tion of a limb, the corresponding part of the spinal cord degenerates.

In pseudo-hypertrophic muscular atrophy the muscular fibres atrophy completely, with
copious development of fat and connective-tissue between the fibres, without the nerves or spinal
cord undergoing degeneration. The muscular substance may also undergo amyloid or wax-like
degeneration, whereby the amyloid substance infiltrates the tissue (§ 249, VI.). Sometimes
atrophic muscles have a deep brown colour, due to a change of the hemoglobin ofthe muscle.
When muscles are much used they hypertrophy, as the heart in certain cases of valvular lesion
or obstruction (§ 40), the bladder, and intestine. [In true hypertrophy there is an increased
number or increase in the size of its tissue elements, throughout the entire tissue or organ,
without any deposit of a foreign body. Perhaps, in hypertrophy of the bladder, the thickened
muscular coat not only serves to overcome resistance, but it offers greater resistance to bursting
under the increased intra-vesical pressure. Mere enlargement is not hypertrophy, for this may
be brought about by foreign elements. In atrophy there is a diminution in size or bulk, even
when the blood-stream is kept up, the decrease being due to pressure. An atrophied organ may
be even enlarged, as seen in pseudo-hypertrophic paralysis, where the muscles are larger, owing
to the interstitial growth of fatty and connective-tissue, while the true muscular tissue is
diminished and truly atrophied. ]

308. STANDING.—The act of standing is accomplished by muscular action,
and is the vertical position of equilibrium of the body, in which a line drawn from

the centre of gravity of the body falls within the area of both feet placed upon the:

ground. In the military attitude, the muscles act in two directions—(1) to fix the
jointed body, as it were, into one unbending column ; and (2) in case of a variation
of the equilibrium, to compensate by muscular action for the disturbance of the
equilibrium.

The following individual motor acts occur in standing :—

1. Fixation of the head upon the vertebral column. The occiput may be moved in various
directions upon the atlas, as in the acts of nodding. As the long arm of the lever lies in front
of the atlas, necessarily when the muscles of the back of the neck relax, as in sleep or death,
the chin falls upon the breast. The strong neck muscles, which pull from the vertebral column
upon the occiput, fix the head in a firm position on the vertebral column. The chief rotatory
movement of the head on a vertical axis occurs round the odontoid process of the axis. The
articular surfaces on the pedicles, and part of the bodies of the 1st and 2nd vertebre, are con-
vex towards each other in the middle, becoming somewhat lower in front and behind, so that
the head is highest in the erect posture. Hence, when the head is greatly rotated, compression
of the medulla oblongata is prevented (Henke). In standing, these muscles do not require to
be fixed by muscular action, as no rotation can take place when the neck muscles are at rest.

2. Fixed Vertebral Column.—The vertebral column itself must be fixed, especially where it
is most mobile, 7.e., in the cervical and lumbar regions. This is bronght about by the pis.
muscles situate in these regions, ¢.g., the cervical spinal muscles, Extensor dorsi communis an
Quadratus lumborum.

Mobility of the Vertebrea.—The least movable vertebrae are the 8rd to the 6th dorsal ;
the sacrum is quite immovable. For a certain length of the column, the mobility depends
on (a) the number and height of the interarticular fibro-cartilages. They are most
numerous in the neck, thickest in the lumbar region, and relatively also in the lower
cervical region. They permit movement to take place in every direction. Collectively the
interarticular discs form one-fourth of the height of the whole vertebral column. They are
compressed somewhat by the pressure of the body; hence, the body is longest in the more
and after lying in the horizontal position. The smaller periphery of the bodies of the cervie
vertebre favours the mobility of these vertebrae compared with the larger lower ones. (b) The

STANDING AND SITTING. 505

position of the processes also influences greatly the mobility. The strongly depressed spines of
the dorsal region hinder hyperextension. The articular processes on the cervical vertebra are
so placed that their surfaces look obliquely from before and upwards, backwards, and down-
wards ; this permits relatively free movement, rotation, lateral and nodding movements. In
the dorsal region, the articular surfaces are directed vertically and directly to the front, the
lower directly backwards ; in the lumbar region, the position of the articular processes is almost
completely vertical and antero-posterior. In bending backwards as far as possible, the most
mobile parts of the column are the lower cervical vertebre, the 11th dorsal to the 2nd lumbar
and the lower two lumbar vertebre (ZL. H. Weber).

3. The centre of gravity of the head, trunk, and arms when fixed as above, lies in front of
the 10th dorsal vertebra. It lies further forward, in a horizontal plane, passing through the
xiphoid process, the greater the distension of the abdomen by food, fat, or pregnancy. A line
drawn vertically downwards from the centre of gravity passes behind the line uniting both hip-
joints. Hence, the trunk would fall backwards on the hip-joint, were it not prevented partly
by ligaments and partly by muscles. The former are represented by the ileo-femoral band and
the anterior tense layer of the fascia lata. As ligaments alone, however, never resist permanent
traction, they are aided, especially by the ileo-psoas muscle inserted into the small trochanter,
and in part, also, by the rectus femoris. Lateral movement at the hip-joint, whereby the one
limb must be abducted and the other adducted, is prevented especially by the large mass of the
glutei. When the leg is extended, the ileo-femoral ligament, aided by the fascia lata, prevents
adduction.

4, The rigid part of the body, head, and trunk, with the arms and legs, whose centre of
gravity lies lower and only a little in front, so that the vertical line drawn downwards inter-
sects a line connecting the posterior surfaces of the knee-joints, must now be fixed at the knee-
joint. Falling backwards is prevented by a slight action of the quadriceps femoris, aided by
the tension of the fascia lata. Indirectly it is aided also by the ileo-femoral ligament. Lateral
movement of the knee is prevented by the disposition of the strong lateral ligaments. Rotation
cannot take place at the knee-joint in the extended position (§ 305, I., 3).

5. A line drawn downwards from the centre of gravity of the whole body, which lies in the
promontory, falls slightly in front of a line between the two ankle-joints. Hence, the body
would fall forward on the latter joint. This is prevented especially by the muscles of the calf,
aided by the muscles of the deep layer of the leg (tibialis posticus, flexors of the toes, peroneus
longus et brevis).

Other Factors :—(a) As the long axis of the foot forms with the leg an angle of 50°, falling
forward can only occur after the feet are in a position more nearly parallel with their long axis.
(>) The form of the articular surfaces helps, as the anterior broad part of the astragalus must be
pressed between the two malleoli. The latter mechanism cannot be of much importance.

6. The metatarsus and phalanges are united by tense ligaments to form the arch of the foot,
which touches the ground at three points—tuber calcanei (heel), the head of the first metatarsal
bone (ball of the great toe), and of the fifth toe. Between the latter two points, the heads of
the metatarsal bones also form points of supports. The weight of the body is transmitted to
the highest part of the arch of the foot, the caput tali. The arching of the foot is fixed only by
ligaments. The toes play no part in standing, although, when moved by their muscles, they
greatly aid the balancing of the body. The maintenance of the erect attitude fatigues one
more rapidly than walking.

309. SITTING.—Sitting is that position of equilibrium whereby the body is supported
on the tubera ischii, on which a to and fro movement may take place (H. v. Meyer). The
head and trunk together are made rigid to form an immovable column, as in standing. We
may distinguish—(1) the forward posture, in which the line of gravity passes in front of the
tubera ischii; the body being supported either against a fixed object, ¢.g., by means of the arm
on a table, or against the upper surface of the thigh. (2) The backward posture, in which the
line of gravity falls behind the tubera. A person is prevented from falling backward either by
leaning on a support, or by the counter-weight of the legs kept extended by muscular action,
whereby the sacrum forms an additional point of support, while the trunk is fixed on the thigh
by the ileo-psoas and rectus femoris, the leg being kept extended by the extensor quadriceps.
Usually the centre of gravity is so placed that the heel also acts as a point of support. The
latter sitting posture is of course not suited for resting the muscles of the lower limbs. (3)
When ‘“‘ sitting erect” the line of gravity falls between the tubera themselves. The muscles of
the legs are relaxed, the rigid trunk only requires to be balanced by slight muscular action.
Usually the balancing of the head is sufficient to maintain the equilibrium.

310. WALKING, RUNNING, AND SPRINGING.—By the term walking
is understood progression in a forward horizontal direction with the least possible
muscular exertion, due to the alternate activity of the two legs,

Methods.—The Brothers Weber were the first to analyse the various positions of the body in
walking, running, and springing, and they represented them in a continuous series, which

506 WALKING.

represents the successive phases of locomotion. These phases may be examined with the
zoetrope (§ 398, 3). Marey estimated the time-relations of the individual acts, by transferring
the movements by means of his air-tambours to a recording surface. Recently, by means ofa
revolving camera. he has succeeded in photographing, in instantaneous pictures (x50 second),

the whole series of acts.
Of course this series, when
placed in the zoetrope,
represents the natural
movements. Figs. 349,
350, 351 represent these
acts.

In walking, the legs
are active alternately ;
while one—the “‘ sup-
porting” or “active”
leg—carries the trunk,
the other is “‘inac-
tive” or “passive.”
Each leg is alternately
in an active and a

Fig. 348. passive phase. Walk-
Phases of walking. The thick lines represent the active, the thin the ing may be divided
passive leg ; 2, the hip-joint ; 4, a, knee ae fag ankle ; c, d, heel; into the following

m, e, ball of the tarso-metatarsal joint ; , g, point of great toe. sp, ovements :—

I. Act (fig. 348, 2).—The active leg is vertical, slightly flexed at the knee, and it alone
supports the centre of gravity of the body. The passive leg is completely extended, and
touches the ground only with the tip of the great toe (z). This position of the leg corresponds
to a right-angled triangle, in which the active leg and the ground form two sides, while the
passive leg is the hypothenuse.

II. Act.—For the forward movement of the trunk, the active leg is inclined slightly from its
vertical position (cathetus) to an oblique and more forward (hypothenuse) position (3), In
order that the trunk may remain at the same height, it is necessary that the active leg be
lengthened. This is accomplished by completely extending the knee (3, 4, 5), as well as by
lifting the heel from the ground (4, 5), so that the foot rests on the balls or the heads of the

{ 0 0.50 1 1.50 2 2.50 3 Meter J

Fig. 349.

Phases of slow walking. Instantaneous photograph (Marey), only the side directed to the ob-
server isshown. From the vertical position of the right, active leg; (I.), all the phases of
this leg are represented in six pe (I. to VI.), while after VI. the vertical position is
regained. The Arabic numerals indicate the simultaneous position of the corresponding

left leg; thus 1=I., 2=TII., &c., so that during the position IV. of the right leg, at the
same time the left leg has the position as 1.

metatarsal bones, and, lastly, by elevating it on the point of the great toe (2, thin line).
During the extension and forward movement of the active leg, the tips of the toes of the passive
leg have left the ground (3). It is slightly flexed at the knee-joint (owing to the shortening),
it performs a ‘‘ pendulum-like movement ” (4, 5), whereby its foot is moved as far in front of
the active leg as it was formerly behind it. The foot is then placed flat upon the ground (1, 2,

WALKING, RUNNING, AND SPRINGING. 507

thick lines) ; the centre of gravity is now transferred to this active leg, which, at the same time,
is slightly flexed at the knee, and placed vertically. The first act is then repeated.

Simultaneous Movements of the Trunk.—During walking, the trunk performs certain
characteristic movements. (1) It leans every time towards the active leg, owing to the traction
of the glutei and the tensor fas¢iz late, so that the centre of gravity is moved, which in short
heavy persons with a broad pelvis leads to their ‘‘waddling” gait. (2) The trunk, especially
during rapid walking, is inclined slightly forward to overcome the resistance of the air. (3)
During the ‘‘ pendulum-like action,” the trunk rotates slightly on the head of the active femur.
This rotation is compensated, especially in rapid walking, by the arm of the same side as the
oscillating leg swinging in the opposite direction, while that on the other side at the same time
swings in the same direction as the oscillating limb.

Modifying Conditions: 1. Zhe Duration of the Step.—As the rapidity of the vibration of a
pendulum (leg) depends upon its length, it is evident that each individual, according to the
length of his legs, must have a certain natural rate of walking. The ‘‘dwration of a step”
depends also upon the time during which both feet touch the ground simultaneously, which, of
course, can be altered voluntarily. When ‘‘ walking rapidly” the time = O, #.¢., at the same
moment in which the active leg reaches the ground, the passive leg is raised. 2. The length
of the step is usually about 6 to 7 decimetres [23 to 27 inches], and it must be greater, the
more the length of the hypothenuse of the passive leg exceeds the cathetus of the active one.
Hence, during a long step, the active leg is greatly shortened (by flexion of the knee), so that
the trunk is pulled downwards. Similarly, long legs can make longer steps.

According to Marey and others, the pendulum movement of the passive leg is not a true
pendulum movement, because its movement, owing to muscular action, is of more uniform
rapidity. During the pendulum movement of the whole limb, the leg vibrates by itself at the
knee-joint (Luce, H. Vierordt}.

Fixation of the Femur.—According to Ed. and W. Weber, the head of the femur of the
passive leg is fixed in its socket chiefly by the atmospheric pressure, so that no muscular action
is necessary for carrying the whole limb. If all the muscles and the capsule be divided, the
head of the femur still remains in the cotyloid cavity. Rose refers this condition not to the
action of the atmospheric pressure, but to two adhesion surfaces united by means of synovia.

ee T si | |
E075 1. f25. 050-155 2 225 2.50 2.75 8 Meter
Fig. 350.
Instantaneous photograph of a runner (/arey). Ten pictures per second. The abscissa
indicates the length of the step in metres.

The experiments of Aeby show that not only the weight of the limb is supported by the
atmospheric pressure, but that the latter can support several times this weight. When traction
is exerted on the limb, the margins of the cotyloid ligament of the cotyloid cavity are applied
like a valve tightly to the margin of the cartilage of the head of the femur. According to the
Brothers Weber, the leg falls from its socket as soon as air is admitted by making a perforation
into the articular cavity.

Work done during Walking.—Marey and Demery estimate the amount done by a man
weighing 64 kilos. [10 stones], when walking slowly, as=6 kilogrammetres per second; rapid
running=56 kilogrammetres. The work done is due to the raising of the entire body and
extremities, to the velocity communicated to the body, as well as to the maintenance of the
centre of gravity.

In springing or leaping, the body is rapidly projected upwards by the greatest possible and
most rapid conttaction of the muscles, while at the same time the centre of gravity is maintained
by other muscular acts (fig. 351). , .

The. pressure upon the sole of the foot in walking is distributed in the following manner :—
The supporting leg always presses more strongly on the ground than the other ; the longer the
step the greater the pressure. The heel receives the maximum amount of pressure sooner than
the point of the foot (Carlet).

510 ARRANGEMENT OF THE LARYNX.

the cords rapidly return to their former position, and are again pushed asunder, and caused to

vibrate.
1. Thus, when a membrane vibrates, the air must be alternately condensed and rarefied.

The condensation and rarefaction are the chief cause of the tone or note (as in the siren), not so
much the membranes themselves (v. Helmholtz). :

2. The.air-tube or ‘‘ porte vente,” conducting the air to the membranes in man is the lower

rtion of the larynx, the trachea, and the whole bronchial system; the bellows are represented

v the chest and lungs, which are forcibly diminished in size by the expiratory muscles.

3. The cavities which lie above the membranes constitute ‘‘ resonators,” and consist of the
upper part of the larynx, pharynx, and also of the cavities of the nose and mouth, arranged,
as it were, in two stories, the one over the other, which can be closed alternately.

The pitch of the tone produced by a membranous apparatus depends upon the following
factors :—

(a) On the length of the elastic nembranes or plates. The pitch is inversely proportional to
the length of the elastic membrane, 7.¢., the shorter the membrane the higher the pitch, or the
greater the number of vibrations per second. Hence, the pitch of a child’s vocal cords (shorter)
is higher than that of an adult.

(o) The pitch of the tone is directly proportional to the square root of the amount of the
elasticity of the elastic membrane. In membranous reeds, and also with silk, it is directly pro-
portional to the square root of the extending weight, which in the case of the larynx is the
torce of the muscles rendering the cords tense.

(c) The tone of membranous reeds is not only strengthened by a more powerful blast, as the
amplitude of the vibrations is increased, but the pitch of the tone may also be raised at the same
time, because, owing to the great amplitude of the vibration, the mean tension of the elastic
membrane is increased.

(72) The supra-laryngeal cavities, which act as resonators, are also inflated when the larynx
is in action, so that the tone produced by these cavities is added to and blended with the sound
of the elastic membranes, whereby certain partial tones of the latter are strengthened (§ 415).
The characteristic timbre of the voice largely depends upon the form of the resonators.

(e) When vocalising, the strongest resonance takes place in the air-tubes, as they contain |
compressed air. It causes the vocal fremitus which is audible on placing the ear over the chest
(§ 117, 6).

(7) Narrowing or dilating the glottis has no effect on the pitch of the tone, only with a wide
glottis much more air must be driven through it, which, of course, greatly increases the work
of the thorax. :

313. ARRANGEMENT OF THE LARYNX.—I. Cartilages and Ligaments.
—The fundamental part of the larynx consists of the cricoid cartilage, whose small
narrow portion is directed forwards and the broad plate backwards. The thyroid
cartilage articulates by its inferior cornu with the posterior lateral portion of the
cricoid. This permits of the thyroid cartilage rotating upon a horizontal axis
directed through both of the articular surfaces, so that the upper margin of the
thyroid passes forward and downward, while the joint is so constructed as to
permit also of a slight upward, downward, forward, and backward movement of
the thyroid upon the cricoid cartilage. The triangular arytenoid cartilages
articulate at some distance from the middle line, with oval, saddle-like, articular
surfaces placed upon the upper margin of the plate of the cricoid cartilage. The
articular surfaces permit two kinds of movements on the part of the arytenoid
cartilages ; first, rotation on their base around their vertical long axis, whereby
either the anterior angle or processus vocalis, which is directed forwards, is rotated
outwards ; while the processus muscularis, which is directed outwards and projects
over the margin of the. cricoid cartilage, is rotated backwards and inwards, or
conversely. Further, the arytenoids may be slightly displaced upon their bases
either outwards or inwards.

The true vocal cords, or thyro-arytenoid ligaments, are in man about 15 milli-
metres, and in woman 11 millimetres in length, and consist of numerous elastic
fibres. They arise close to each other from near the middle of the inner angle of the
thyroid cartilage, and are inserted, each into the anterior angle or processus vocalis
of the arytenoid cartilages. The ventricles of Morgagni permit free vibration
of the true vocal cords, and separate them from the upper or false cords, which con-
sist of folds of mucous membrane. The false vocal cords are not concerned in

ACTION OF THE LARYNGEAL MUSCLES. 51!

phonation, but the secretion of their numerous mucous glands moistens the true
vocal cords.

The obliquely directed under-surface of the vocal cords causes the cords to come together very
easily when the glottis is narrow during respiration (e¢.g., in sobbing), while the closure may be
made more secure by respiration. The opposite is the condition of the false vocal cords, which,
when they touch, are easily separated during inspiration ; while during expiration, owing to the
dilatation of the ventricles of Morgagni, they easily come together and close (Wyllie, L. Brun-
ton and Cash).

II. Action of the Laryngeal Muscles.—These muscles have a double function :
—1l. One connected with respiration, in as far as the glottis is widened and

Fig. 352.

Fig. 352.—Larynx from the front, with the ligaments and the insertions of the muscles.
O.h., Os hyoideum; C.th., Cart. thyreoidea; Corp, trit., Corpus triticeum; C.c., Cart.
cricoidea ; C.t7., Cart. tracheales ; Lig. thyr.-hyoid. med., Ligamentum thyreo-hyoideum
medium ; Lig. th.-h. lat., Ligam. thyreo-hyoideum laterale ; Lig., cric. thyr. med., Ligam.
crico-thyreoideum medium ; Lig. cric.-trach., Ligam. crico-tracheale; M. St.-h., Muse.
sterno-hyoideus ; M.. th.-hyoid.,. Muse. thyreo-hyoideus ; JZ. st.-th., Muse. sterno-thyreo-
ideus ; MV. cr.-th., Muse. crico-thyreoideus. Fig, 353.—Larynx from behind after removal
of the muscles. #., Epiglottis cushion (W.); Z. ar.-ep., Lig. ary-epiglotticum ; J/m.,
Membrana mucosa; C.W., Cart. Wrisbergii; C.S., Cart. Santorini; C. aryt., Cart.
arytenoidea ; C.c., Cart. cricoidea ; P.m., Processus muscularis of Cart. aryten.; L. cr.-ar.,
Ligam. crico-arytean.; C.s., Cornu superius; C./., Cornu inferius Cart. thyreoidea.
L. ce.-cr. p. %., Lig. kerato-cricoideum. post. inf.; C.tr., Cart. tracheales ; P.m.tr., Pars
membranacea trachee. .

narrowed alternately during respiration ; further, when the glottis is firmly closed
by these muscles, the entrance of foreign substances into the larynx is prevented.
The glottis is closed immediately before the act of coughing (§ 120). 2. The
larnyngeal muscles give the vocal cords*the proper tension and other conditions for
phonation.

1. The glottis is dilated by the action of the posterior crico-arytenoid muscles.
When they contract they pull both processus musculares of the arytenoid cartilages

512 ACTION OF THE LARYNGEAL MUSCLES.

backwards, downwards, and towards the middle line (fig. 356), so that the processus
vocales (I, I) must go apart and upwards (II, II). Thus, between the vocal cords
(glottis vocalis), as well as between the inner margins of the arytenoid cartilages,
a large triangular space is formed (glottis respiratoria), and these spaces are so
arranged that their bases come together, so that the aperture between the cords and -
the arytenoid cartilages has a rhomboidal form. Fig. 356 shows the action of the
muscles. The vocal cords, represented by lines converging in front, arise from the
anterior angle of the arytenoid cartilages (I, I). When these cartilages are rotated

eI
MM A

Lu Y \.
iM / ' ad

| 4 i Ml
AN oll itd hy

Fig. 355.

Fig. '354.—Larynx from behind with its muscles. £., Epiglottis, with the cushion (W.) ;
C.W., Cart. Wrisbergii; C.S., Cart. Santorini; C.c., Cart. cricoidea. Cornu sup.—
Cornu inf., Cart. thyreoidex ; M. ar. tr., Musc. arytenoideus transversus ; Mdm. ar. obl.,
Musculi arytenoidei obliqui ; M. cr.-aryt. post., Musculus crico-arytenoideus posticus ; Pars
cart., Pars cartilaginea ; Pars memb., Pars membranacea trachee. Fig. 355.—Nerves of
the larynx. 0O.h., Os hyoideum ; C.th., Cart. thyreoidea; C.c., Cart. cricoidea; Z’7.,
Trachea; M. th.-ar., M. thyreo-arytenoideus; Jf. cr.-ar. p., M. crico-arytenoideus
posticus; J. er.-ar 1., M. crico-aryten. lateralis; J. cr.-th., M. crico-thyreoideus ;
N. lar. sup. v., N. laryngeus sup.; #./Z., Ramus internus ; #.#., Ramus ext.; NV. dar. rec. v., |
N. laryngeus recurrens; #.J.N.LZ.R., Ramus int.; AR. £.N.L.R., Ramus ext. nervi laryngei
recurrentis vagi.

into the position (II, IT), the cords take the position indicated by the dotted lines.

The widening of the respiratory portion of the glottis between the arytenoid carti-

lages is also indicated in the diagram,

Pathological.—When these muscles are paralysed, the widening of the glottis does not take
place, and there may be severe dyspnea Stine inspiration, although the voice is unaffected |
(Riegel, L. Weber). Ina larynx just excised, the dilators are the first to lose their excitability
(Semon and Horsley).

2. The entrance to the glottis is constricted by the arytenoid muscle (trans-
verse), which extends transversely between both outer surfaces of the arytenoids
along their whole length (fig. 357). On the posterior surface of this muscle is

ACTION OF THE LARYNGEAL MUSCLES, 513

placed the cross bundles (fig. 354) of the thyro-aryepiglotticus (or arytznoidei
obliqui); they act like the foregoing. The action of these muscles is indicated in
fig. 357 ; the arrows point to the line of traction.

; Pathological. —Paralysis of this muscle enfeebles the voice and makes it hoarse, as much air
Gg escapes between the arytenoid cartilages during phonation.
3 3. In order that the vocal cords be approximated to each other, which occurs

during phonation, the processus vocales of the arytenoid cartilages must be closely
apposed, whereby they must be rotated inwards and downwards. This result is
brought about by the processus musculares being moved in a forward and upward
direction by the thyro-arytenoid muscles, These muscles are applied to, and in
fact are imbedded in, the substance of the elastic vocal cords, and their fibres reach
to the external surface of the arytenoid cartilages. When they contract, they
rotate these cartilages so that the processus vocales must rotate inwards. The
glottis. vocalis is thereby narrowed to a mere slit (fig. 358), whilst the glottis
respiratoria remains as a broad triangular opening. The action of these muscles is
indicated in fig. 358.

The lateral crico-arytenoid muscle is inserted into the anterior margin of the
articular surface of the arytenoid cartilage; hence, it can only pull the cartilage

Fig. 356. Fig. 357. Fig. 358.

Fig, 356.—Schematic horizontal section of the larynx. I, Position of the horizontally divided
arytenoid cartilages during respiration ; from their anterior processes run the converging
vocal cords, The arrows show the line of traction of the posterior crico-arytenoid muscles ;
II, II, the position of the arytenoid muscles as a result of this action. Fig. 357.—
Schematic horizontal section of the larynx, to illustrate the action of the arytenoid muscle.
I, I, position of the arytenoid cartilages during quiet respiration. The arrows indicate the
direction of the contraction of the muscle ; II, II, the position of the arytenoid cartilages
after the arytenoideus contracts. Fig. 358.—Scheme of the closure of the glottis by the
thyro-arytenoid muscles. II, II, position of the arytenoid cartilages during quiet respira-
tion. The arrows indicate the direction of the muscular traction.—I, I, position of the
arytenoid cartilages after the muscles contract.

forwards; but some have supposed that it can also rotate the arytenoid cartilage in
L a manner similar to the thyro-arytenoid (?), with this difference, that the processus
vocales do not come so close to each other.

Pathological, —Paralysis of both thyro-arytenoid muscles causes loss of voice.

4. The vocal cords are rendered tense by their points of attachment being
removed from each other by the action of muscles. The chief agents in this action
are the erico-thyroid muscles, which pull the thyroid cartilage forwards and down-
wards. At the same time, however, the posterior crico-arytenoids must pull the
arytenoid cartilages slightly backwards, and also keep them fixed,

. The genio-hyoid and thyro-hyoid, when they contract, pull the thyroid upwards and forwards
towards the chin, and also tend to increase the tension of the vocal cords (C. Mayer, Griitzner).

Pathological. +Paralysis of the crico-thyroid causes the voice to become harsh and deep, owing
to the vocal cords not being sufficiently tense:

Position during Phonation.—The tension of the vocal cords brought about in
this. way is not of itself sufficient for phonation. The triangular aperture of the
glottis respiratoria between the arytenoid cartilages, produced by the unaided action

2K

514 | RELAXATION OF THE VOCAL CORDS.

of the internal thyro-arytenoid muscles (see 3) must be closed by the action of the
transverse and oblique arytenoid muscles. The vocal cords themselves must have
a concave margin, which is obtained through the action of the crico-thyroids and
posterior crico-arytenoids, so that the glottis vocalis presents the appearance of a
myrtle’ leaf (Zen/e), while the rima glottidis has the form of a linear slit (fig. 362).
The contraction of the internal thyro-arytenoid converts the concave margin of the
vocal cords into a straight margin. This muscle adjusts the delicate variations of
tension of the vocal cords themselves, causing more especially such variations as are
necessary for the production of tones of slightly different pitch. As these muscles
come close to the margin of the cords, and are securely woven, as it were, amongst
the elastic fibres of which the cords consist, they are specially adapted for the above-
mentioned purpose. When the muscles contract, they give the necessary resistance
to the cords, thus favouring their vibration. As some of the muscular fibres end
in the elastic fibres of the cords, these fibres, when they contract, can. render
certain parts of the cords more tense than others, and thus favour the modifications
in the formation of the tones. The coarser variations in the tension of the vocal
cords are produced by the separation of the thyroid from the arytenoid cartilages,
while the finer variations of tension are produced by the thyro-arytenoid muscles.
The value of the elastic-tissue of the cords does not depend so much upon its
extensibility, as upon its property of shortening without forming folds and creases.

Pathological.—In paralysis of these muscles, the voice can only be produced by forcible
expiration, as much air escapes through the glottis ; the tones are at the same time deep and
impure. Paralysis of the muscle of one side causes flapping of the vocal cord on that side
(Gerhardt).

5. The relaxation of the vocal cords occurs spontaneously when the stretch-
ing forces cease to act; the elasticity of the displaced thyroid and arytenoid carti-
lages comes into play, and restores them to their original position. The vocal
cords are also relaxed by the action of the thyro-arytenoid and lateral crico-arytenoid
muscles. .

It is evident, from the above statements, that tension of the vocal cords and
narrowing of the glottis are necessary for phonation. The tension is produced
by the crico-thyroids and posterior crico-arytenoids ; the narrowing of the glottis
respiratoria by the arytenoids, transverse and oblique, the glottis vocalis being
narrowed by the thyro-arytenoids and (? lateral crico-arytenoids), the former muscles
causing the cords themselves to become tense.

Nerves (§ 352, 5).—The crico-thyroid is supplied by the superior laryngeal
branch of the vagus, which at the same time is the sensory nerve of the mucous
membrane of the larynx. All the other intrinsic muscles of the larynx are supplied
by the inferior laryngeal.

The mucous membrane of the larynx is richly supplied with elastic fibres, and so is the
sub-mucosa. The sub-mucosa is more lax near the entrance to the glottis and in the ventricles
of Morgagni, which explains the enormous swelling that sometimes occurs in these parts in
cedema glottidis. A thin clear limiting membrane lies under the epithelium. The epithelium
is stratified, cylindrical, and ciliated with intervening goblet cells. On the true vocal cords
and the anterior surface of the epiglottis, however, this is replaced by stratified squamous
epithelium, which covers the small papille of the mucous membrane. Numerous branched
mucous glands occur over the cartilages of Wrisberg, the cushion of the epiglottis, and in the
ventricles of Morgagni; in other situations, as on the posterior surface of the larynx, the glands
are more scattered. The blood-vessels form a dense capillary plexus under the membrana
propria of the mucous membrane ; under this, however, there are other two strata of blood-
vessels, The lymphatics form a superficial narrow mesh-work under the blood-capillaries, with
a deeper, coarser plexus, The medullated nerves have ganglia in their branches, but their
mode of termination is unknown. [W. Stirling has described a rich sub-epithelial plexus of
medullated nerve-fibres on the anterior surface of the epiglottis, while he finds that there are
ganglionic cells in the course of the superior laryngeal nerve.] nie

Cartilages.—The thyroid, cricoid, and nearly the whole of the arytenoid cartilages conta
hyaline cartilage. The two former are prone to ossify. The apex and processus vocalis of

eed

f
es

LARYNGOSCOPY. 515

arytenoid. cartilages consist of yellow jibro-cartilage, and so do all the other cartilages of the
larynx.

_ The larynx grows until about the sixth year, when it rests for a time, but it becomes again
much larger at puberty (§ 434). ;

314. LARYNGOSCOPY.—Historical.—After Bozzini (1807) gave the first impulse towards
the investigation of the internal cavities of the body, by illuminating them with the aid of
mirrors, Babington (1829) actually observed the glottis in this way. The famous singer,
Manuel Garcia (1854), made investigations both on himself and other singers, regarding the
movements of the vocal cords, during respiration and phonation. The examination of the
larynx by means of the laryngoscope was rendered practicable chiefly by Tiirck (1857) and

/
7

Fig. 359.

Vertical section through the head and neck, to the Ist dorsal vertebra, «a, position of the
laryngoscope on observing the posterior part of the glottis, arytenoid cartilages, and upper
surface of the posterior wall of the larynx; 5, its position on observing the anterior angle
of the glottis. Large, a, and b, small laryngoscopic mirrors, |

Czermak, the latter observer being the first to use the light of a lamp for the illumination of
the larynx. Rhinoscopy was actually first practised by Baumés (1838), but Czermak was the
first person who investigated this subject systematically.

e goscope consists of a small mirror fixed to-a long handle, at an angle of 125° to
130° (fig. 359, a, b). When the mouth is opened, and the tongue drawn forward, the mirror is
introduced, as is shown in fig. 360. The position of the mirror must be varied, according to
the position of the larynx we wish to examine; in some cases, the soft palate has to be raised
by the back of the mirror, as in the position 6. A picture of the part of the larynx examined is
formed in the small mirror, the rays of light passing in the direction indicated by the dotted

516 7 THE LARYNGOSCOPE.

lines from the mirror ; they are reflected at the same angle through the mouth into the eye of
the observer, who must place himself in the direction of the reflected rays.

The illumination of the larynx is accomplished either by means of direct sunlight or by light
from an artificial source, ¢.g., an ordinary lamp, an oxyhydrogen lime-light, or the electric light,
The beam of light impinges upon a concave mirror of 15 to 20 centimetres focus, and 10 centi-
metres in width, ced from its surface the concentrated beam of light is reflected through the
mouth of the patient, and directed upon the small mirror held in the back part of the throat.
The beam of light is reflected at the same angle towards the larynx by the small throat mirror,
so that the larynx is brightly illuminated, The observer has now to direct his eye in the same

Fig. 360.
Method of examining the larynx,

(lirection as the illuminating rays, which can be accomplished by having a hole in the centre of |
the concave mirror, through which the observer looks, Practically, however, this is unnecessary ; |
all that is necessary is to fix the concave mirror to the forehead by means of a broad elastic .
band, so that the observer, by looking just under the margin of the concave mirror, can see the
picture of the larynx in the small throat mirror (fig. 360).
In order to examine the larynx, place the patient
immediately in front of you, and cause him to open his
mouth and protrude his tongue, <A lamp is placed at
the side of the head of the patient, and light from this
source is reflected from the concave mirror on the ob-
server's forehead, and concentrated upon the laryngo-
scopic mirror introduced into the back part of the
throat of the patient (fig. 360).
Oertel was able by means of a rapid intermittent 7
illumination of the larynx through a stroboscopic dise,
to study the movements of the vocal cords directly
with the eye. Simanowsky put a photographic camera
in the position of the eye, and photographed the move-
ments of the vocal cords of an artificial larynx. [Brown
and Behnke have photographed the human vocal cords. ]
Laryngeal Electrodes,—V. Ziemssen introduces long
narrow electrodes into the larynx, to stimulate the

~_- ss .

Fig. 361.

The larynx, as seen with the: laryngo- muscles and study their actions. Rossbach finds that

wei ; Ha tongue; #., epiglottis; V., the muscles and nerves of the interior of the larynx

va i oh aap ae L.v., true vocal may be stimulated by stimulating the skin, 4.¢.,

oes: pon Morgagni; L.v.s., pereutaneously. Those methods are used both for
alse vocal cords; P., position of physiological and therapeutical purposes.

Picture of the Larynx.—Fig. 361 shows the
following structures:—JZ., the root of the
tongue, with the ligamentum glosso-epiglotticum continued from its middle; on
each side of the latter are V.V., the so-called vallecul. The epiglottis (Z.) appears

pharynx j S., cartilage of Santorini ;
., of Wrisberg ; S.p.,sinus piriformes,

LARYNGOSCOPIC IMAGE. 517

like an arched upper lip; under it, during normal respiration, are the lancet-shaped
glottis (R.) and on each side of it the true vocal cords (L.v). The length of the
vocal cord in a child is 6 to 8 mm., in the female 10 to 15 mm. when they are.
relaxed, and 15 to 20 mm. when tense. In man, the lengths under the same con-
ditions are 15 to 20 mm. and 20 to 25.mm. The breadth varies from 2 to 5 mm.
On the external side of each vocal cord is the entrance to the sinus of Morgagni

Fig. 363.
Position of the vocal cords on uttering a View of the rings and bifurcation of
high note. trachea.

(S.M.), represented as a dark line. Further upwards and more external are (L.v.s.)
the upper or false vocal cords. [The upper or false vocal cords are red, the lower or
true, white.] On each side of P. are (S.S.), the apices of the cartilages of San-

torint, placed upon the apices of .
the arytenoid cartilages, while
immediately behind is the wall of
the pharynx, P. In the aryteno-
epiglottidean fold are (W.W.) the
cartilages of Wrisberg, while out-
side these are the depressions (S.p.)
constituting the s¢nus piriformes.

During normal respiration, the
glottis has the form of a lancet-
shaped slit between the bright,
yellowish-white, vocal cords (fig.
362). If a deep inspiration be
taken, the glottis is considerably
widened (fig. 363), and if the
mirror be favourably adjusted we
may see the rings of the trachea,
and even the birfurcation of the
trachea. |

If a high note be uttered, the
glottis is contracted to a very
narrow slit (fig. 362).

- Rhinoscopy.—If a small mirror, fixed
to a handle at an angle of 100° to 110°,
be introduced into the pharynx, as
shown in fig. 364, and if the mirror be ‘
directed upwards, certain structures are at Fig. 364, ;
with difficulty rendered visible (fig. 365). Position of the laryngoscopic mirror in rhinoscopy.
In the middle is the septum narium (S.7.), and on each side of it the long oval large posterior
nares (Ch.), below this the soft palate (P.m.), with the pendant uwvula (U.). In the posterior
nares are the posterior extremities of the lower (C.i.), middle (C.m.), and upper turbinated bones
(C.s.). At the upper part, a portion of the roof of the pharynx (0.R.) is seen, with the arched
masses of adenoid tissue lying between the openings of the Zustachian tubes (7.7), and called

by Luschka the pharyngeal tonsils. External to the openings of the Eustachian tube is the
tubular eminence (W.), and outside this is the groove of Rosenmiiller (R.).

518 CONDITIONS INFLUENCING THE LARYNGEAL SOUNDS,

Experiments on the Larynx.—Ferrein (§ 741) and Joh. Miiller made experiments upon the
excised larynx. A tracheal tube was tied into the excised human larynx, and air was blown
through it, the pressure being measured by means of a mercurial manometer, while various
arrangements were adopted for putting the vocal
cords on the stretch and for opening or closing the
glottis.

315. CONDITIONS INFLUENCING
THE LARYNGEAL SOUNDS.—tThe pitch
of the note emitted by the larynx depends
upon :—

a The Tension of the Vocal Cords, i.e.,
upon the degree of contraction of the crico-
thyroid and posterior crico-arytenoid muscles,
and also of the internal thyro-arytenoids
tesa TE ie ee 3 F

2. The Length of the Vocal Cords.—
(a) Children and females with short vocal
cords produce high notes. (6) If the ary-
tenoid cartilages are pressed together by the

Fig. 365.
Composite rhinoscopic view. S.n., Septum
narium ; C.i., C.im., C.s., lower, middle, : :
and upper turbinated bones; 7'., Eusta- action of the arytenoid muscles (transverse

chian tube; JV., tubulareminence; #., and oblique), so that the vocal cords alone
groove of Rosenmiiller; .m., soft can vibrate, while their intercartilaginous

DE MO. t 116 ome op ; . .
ie aa tae ae a portions lying between the processus vocales

do not, the tone thereby produced is higher (Garcia). In the production of low
notes, the vocal cords, as well as the margins of the arytenoid cartilages, vibrate.
At the same time the space above the entrance to the glottis is enlarged and the
larynx becomes more prominent. (c) Every individual has a certain medium pitch
of his voice, which corresponds to the smallest possible tension of the intrinsic
muscles of the larynx.

3. The Strength of the Blast.—That the strength of the blast from below raises
the pitch of the tones of the human larynx is shown by the fact, that tones of the
highest pitch can only be uttered by powerful expiratory efforts. With tones of
medium pitch, the pressure of the air in the trachea is 160 mm., with high pitch
200 mm., and with very high notes 945 mm., and in whispering 30 mm., of water
(Cagniard-Latour). These results were obtained in a case of tracheal fistula.

Accessory Phenomena, —The following as yet but partially explained phenomena are observed
in connection with the production of high notes :—(a) As the pitch of the note rises, the larynx
is elevated, partly because the muscles raising it are active, partly because the increased intra-
tracheal pressure so lengthens the trachea, that the larynx is thereby raised; the uvula is raised
more and more (Labus). (b) The upper vocal cords approximate to each other more and more,
without, however, coming into contact, or participating in the vibrations. (c) The epiglottis
inclines more and more backwards over the glottis. : :

4, The falsetto voice with its soft timbre and the absence of resonance or
pectoral fremitus in the air-tubes is particularly interesting. Oertel observed that,
during the falsetto voice, the vocal cords vibrated so as to form nodes across them,
but sometimes there was only one node, so that the free margin of the cord and
the basal margin vibrated, being separated from each other by a nodal line (parallel
to the margins of the vocal cord). During a high falsetto note, there may be three
such nodal lines parallel to each other. The nodal lines are produced probably by
a partial contraction of the fibres of the thyro-arytenoid muscle (p. 513), while at
the same time the vocal cords must be reduced to as thin plates as possible by
the action of the crico-thyroid, posterior arytenoid, thyro- and genio-hyoid muscles
(Oertel). The form of the glottis is elliptical, while with the chest-voice the vocal
cords are limited by straight surfaces ; the air also passes more freely through the
arynx. | : Poe

RANGE OF THE VOICE. 519

Oertel also found that during the falsetto voice the epiglottis is erect. The apices of the
arytenoid cartilages are slightly inclined backwards, the whole larynx is larger from before
backwards, .and narrower from side to side, the aryepiglottidean folds are tense with sharp
margins, and the entrance to the ventricles of Morgagni is narrowed. The vocal cords are
narrower, the processus vocales touch each other. The rotation of the arytenoid cartilages
necessary for this is brought about by the action of the crico-arytenoid alone, while the thyro-
arytenoid is to be regarded only as an accessory aid. The pitch of the note is increased solely by
increased tension of the vocal cords. In addition, there are a number of transverse and longi-
tudinal partial vibrations. During the chest-voice, a smaller part of the margin vibrates than
in the falsetto voice, so that in the production of the latter we are conscious of less muscular
exertion in the larynx. The uvula is raised to the horizontal position.

Production of Voice.—In order that voice be produced, the following conditions
are necessary :—(1) The necessary amount of air is collected in the chest; (2) the
larynx and its parts are fixed in the proper position; (3) air is then forced by an
expiratory effort either through the linear chink of the closed glottis, so that the
latter is forced open, or at first some air is allowed to pass through the glottis
without producing a sound, but as the blast of air is strengthened the vocal cords
are thrown into vibration. |

316, RANGE OF THE VOICE.—The range of the human voice for chest
notes is given in the following scheme :—

256 Soprano. 1024
nO | Alto. 684 m
| (ES eo ee Go eee e Si
EFGAB ecdefgab| ¢d@Vefgab| £ Ee
C = e [ r ]
E — — ——S
C | s = i
ry = ed | el de” f” or a"! pb” el”!
ee | | |
Seale BOA ie |
80 | Bass. 342
128 Tenor, 512

The accompanying figures indicate the number of vibrations per second in the corresponding
tone. It is evident that from ¢’ tof’ is common to all voices, nevertheless, they have a different
timbre. The lowest note or tone, which, however, is only occasionally sung by bass singers, is
the contra-F, with 42 vibrations—the highest note of the soprano voice is a”, with 1708
vibrations,

Timbre.—The voice of every individual has a peculiar quality, clang, or timbre,
which depends upon the shape of all the cavities connected with the larynx. In
the production of nasal tones, the air in the nose is caused to vibrate strongly, so
that the entrance to the nares must necessarily be open. :

317. SPEECH—-THE VOWELS.—The motor processes connected with the pro-
duction of speech occur in the resonating cavities, the pharynx, mouth, and nose,
and are directed towards the production of musical tones and noises.

Whispering and Audible Speech.—When sounds or noises are produced in the
resonating chambers, the larynx being passive, the vox clandestina, or whispering
is produced ; when the vocal cords, however, vibrate at the same time, ‘audible
speech” is produced. [Whispering, therefore, is speech without voice.] _ Whisper-
ing may be fairly loud, but it requires great exertion, 7.¢., a great expiratory blast,
for its production ; hence it is very fatiguing. It may be performed both with
inspiration and expiration, while audible speech is but temporary and indistinct, if
it is produced during inspiration. Whispering is caused by the sound produced by
the air passing over the obtuse margins of-the cords. During the production of
audible sounds, however, the sharp margins of the vocal cords are directed towards
the air by the position of the processus vocales, |

During speech the soft palate is in action; at each word it is raised, while at the same time,
Passavant’s transverse band is formed in the pharynx (§ 156). The soft palate is raised highest

520 THE FORMATION OF VOWELS.

when u andi are sounded, then with o and ¢, and least with a When sounding m and n it
does not move ; it is high (like mn) during the utterance of the explosives. With 1, s, and
especially with the gutteral r, it exhibits a trembling movement (Gentzen, Falkson).

Speech is composed of vowels and consonants.

A. Vowels (analysis and artificial formation, § 415).—A. During whispering,
a vowel is the musical tone produced, either during expiration or inspiration, by
the inflated characteristic form of the mouth, which not only has a definite pitch,
but also a particular and characteristic timbre. The characteristic form of the
mouth may be called “ vowel-cavity.”

I, The’ pitch of the vowels may be estimated musically. It is remarkable that the funda-
mental tone of the ‘‘ vowel-cavity” is nearly constant at different ages and in the sexes. The
different capacities of the mouth can be compensated for by different sizes of the oral aperture.
The pitch of the vowel-cavity may be estimated by placing a number of vibrating tuning-forks
of different pitch in front of the mouth, and testing them until we find the one which
corresponds with the fundamental tone of the vowel-cavity. This is known by the fact, that
the tone of the tuning-fork is intensified by the resonance of the air in the mouth, or the
vibrations may be transferred to a vibrating membrane and recorded on a smoked surface, as in
the phonautograph of Donders.

According to Konig, the fundamental tones of the vowel-cavity are for |
U = b, O = b’, A a Ds E = be. I — 9 has
If the vowels be whispered in this series, we find at once that their pitch rises.
The fundamental tone in the production of a vowel may vary within certain limits.
This may be shown by giving the mouth the characteristic position and then per-
cussing the cheeks (Auerbach); the sound emitted is that of the vowel, whose pitch
will vary accordingly to the position of the mouth.

When sounding A, the mouth has the form of a funnel widening in front (fig. 366, A). The |
tongue lies in the floor of the mouth, and the lips are wide open. The soft palate is moderately |
|

en

Fig. 366.
Section of the parts concerned in phonation. Z, tongue ; p, soft palate ; ¢, epiglottis ; 9,
glottis ; h, hyoid bone ; 1, thyroid, 2, 3 cricoid, 4, arytenoid cartilage.

raised (Czermak). It is more elevated successively with O, E, U, I. The hyoid bone appears
as if at rest, but the larynx is slightly raised. It is higher than with U, but lower than with I.
If we sound A to I, the larynx and the hyoid bone retain their relative position, but both are _
raised. In passing from A to U, the larynx is depressed as far as possible. The hyoid bone
passes slightly forward (Briicke). When sounding A, the space between the larynx, posterior
wall of the pharynx, soft palate, and the root of the tongue, is only moderately wide; it
becomes wider with E, and especially with I (Purkinje), but it is smallest with U. -
When sounding U (fig. 366), the form of the cavity of the mouth is like that of a capaci
flask with a short, narrow neck. The whole resonance apparatus is then longest. The lips are
fe ge as far as possible, are arranged in folds and sis leaving only a small openi
e larynx is depressed as far as possible, while the root of the tongue is approximated to
pee margin of the palatine arch. ‘
_ When sounding 0, the mouth, as in U, is like a wide-bellied flask with a short neck, but the

_DIPHTHONGS AND NASAL TIMBRE OF VOWELS. 521

latter is shorter and wider as the lips are nearer to the teeth. The larynx is slightly higher
than with U, while the resonance chambers also are shorter (fig. 366).

When sounding I, the cavity of the mouth, at the posterior part, is in the form of a small-
bellied flask with a long narrow neck, of which the belly has the fundamental tone, f, the
neck that of d’’. The resonating chambers are shortest, as the larynx is raised as much as
possible, while the mouth, owing to the retraction of the lips, is bounded in front by the teeth.
The cavity between the hard palate and the back of the tongue is exceedingly narrow, there
being only a median narrow slit. Hence, the air can only enter with a clear piping noise,
which sets even the vertex of the skull in vibration, and when the ears are stopped the sounds
seem very shrill, When the larynx is depressed and the lips protruded, as for sounding U, I
cannot be sounded.

When sounding E, which stands next to I, the cavity has also the form of a flask with a
small belly (fundamental tone, f’), and with a long, narrow neck (fundamental tone, b’”), . The
neck is wider, so that it does not give rise to a piping noise. The larynx is slightly lower
than for I, but not so high as for A.

Fundamentally, there are only three primary vowels—I, A, U, the others and the so-called
diphthongs standing between them (Briicke).

Diphthongs occur when, during vocalisation, we pass from the position of one
vowel into that of another. Distinct diphthongs are sounded only on passing from
one vowel with the mouth wide open to one with the mouth narrow; during the
converse process, the vowels appear to our ear to be separate (Briicke).

II. Timbre or Clang-Tint.—Besides its pitch, every vowel has a special timbre,
quality, or clang-tint.

The vocal timbre of U (whispering) has, in addition to its fundamental tone, b, a deep
piping timbre. The timbre depends upon the number and pitch of the partials or overtones of
the vowel sound (§ 415). ;

Nasal Timbre.—The timbre is modified in a special manner when the vowels are spoken with
a ‘‘nasal”’ twang, which is largely the case in the French language. The nasal timbre is
produced by the soft palate not cutting off the nasal cavity completely, which happens every
time a pure vowel is sounded, so that the air in the nasal cavity is thrown into sympathetic
vibration. When a vowel is spoken with a nasal timbre, air passes out of the nose and mouth
simultaneously, while with a pure vowel sound, it passes out only through the mouth.

When sounding a pure vowel (non-nasal), the shutting off of the nasal cavity from the mouth
is so complete, that it requires an artificial pressure of 30 to 100 mm. of mercury to overcome
it (Hartmann).

The vowels, a, i (s), 6 (ce), 0, e, are used with a nasal timbre—a nasal i does not occur in
any language. Certainly it is very difficult to sound it thus, because when sounding 1, the
mouth is so narrow that when the passage to the nose is open, the air passes almost completely
through the latter, whilst the small amount passing through the mouth scarcely suffices to
produce a sound.

In sounding vowels, we must observe if they are sounded through a previously closed glottis,
as is done in the German language in all words beginning with a vowel (spiritus lenis). The
glottis, however, may be previously opened with a preliminary breath, followed by the vowel
sound ; we obtain the aspirate vowel (spiritus asper of the Greeks).

B. If the vowels are sounded in an audible tone, 7.¢., along with the sound from
the larynx, the fundamental tone of the vocal cavity strengthens in a characteristic
manner the corresponding partial tones present in the laryngeal sound ( Wheatstone,
v. Helmholtz).

318. CONSONANTS.—The consonants are noises which are produced at
certain parts of the resonance chamber. [As their name denotes, they can only be
sounded in conjunction with a vowel. | 7

Classification.—The most obvious classification is according to—(I.) Their acoustic properties,
so that they are divided into—(1) liquid consonants, 7.¢e., such as are appreciable without a
vowel (m, n, 1, r, 8); (2) mutes, including all the others, which cannot be distinctly heard
without an accompanying vowel. (II.) According to their mechanism of formation, as well as
the type of the organ of speech, by which they are produced. They are divided into—

1. losives. —Their enunciation is accom sited. by a kind of bursting open of an obstacle,
or an explosion, occasioned by the confined.and compressed air which causes a stronger or weaker
noise ; or, conversely, the current of air is suddenly interrupted, while, at the same time, the
nasal cavities are cut off by the soft palate. .

2, Aspirates, in which one part of the canal is constricted or stopped, so that the air rushes
out through the constriction, causing a faint whistling noise. (The nasal cavity is cut off.) In

522 CLASSIFICATION OF CONSONANTS.

uttering L, which is closely related to the aspirates, but differs from them in that the narrow
passage for the rush of air is not in the middle, but at both sides of the middle of the closed
part. (The nasal cavity is shut off.) ;

3. Vibratives, which are produced by air being forced through a narrow portion of the canal,
so that the margins of the narrow tube are set in vibration. (‘The nasal cavity is shut off.)

4, Resonants (also called nasals or semi-vowels). The nasal cavity is completely free, while
the vocal canal is completely closed in the front part of the oral channel. According to the
position of the obstruction in the oral cavity, the air in a larger or smaller portion of the mouth
is thrown into sympathetic vibration.

We may also classify them according to the position in which they are produced
—the ‘‘articulation positions ” of Briicke. These are :—

A. Between both lips ; B, between the tongue and the hard palate ; C, between
the tongue and the soft palate ; D, between the true vocal cords.

A. Consonants of the First Articulation Position.

1, Explosive Labials.—b, the voice is sounded before the slight explosion occurs ; p, the
voice is sounded after the much stronger explosion has taken place (Kempelen). [The former
is spoken of as ‘‘ voiced” and the latter as ‘‘ breathed.’’]

2. Aspirate Labials.—f, between the upper incisor teeth and the lower lip (labiodental). It
is absent in all true Slavic words (Purkiie) ; v, between both lips (labial) ; w is formed when
the mouth is in the position for f, but instead of merely forcing in the air, the voice is sounded
at the same time. Really there are two different w—one corresponding to the labial f, as in
wiirde, and the labiodental, ¢.g., quelle (Briicke),

3. Vibrative Labials.—The burring sound, emitted by grooms, but inot used in civilised
language.

4, Resonant Labials. —m is formed essentially by sounding the voice whereby the air, in the
mouth and nose, is thrown into sympathetic vibration [‘‘ voiced ”’],

B. Consonants of the Second Articulation Position.

1. The explosives, when enunciated sharply and without the voice, are T hard (also dt and
th) ; when they are feeble and produced along with simultaneous laryngeal sounds (voice), we
have D soft.

2. The aspirates embrace §, including 8 sharp, written 88 or 8 z, which is produced without
any audible laryngeal vibration ; or soft, which requires the voice. Then, also, there are modi-
tications according to the position where the noises are produced. The sharp aspirates include
Sch, and the hard English Th ; to the soft belong the French J soft, and the English Th soft.
L, which occurs in many modifications, appears here, ¢.g., the L soft of the French. L may be
sounded soft with the voice, or sharp without it.

3. The vibrative, or R, which is generally voiced, but it can be formed without the larynx.

The resonants are N-sounds, which also occur in several modifications,

C. Consonants of the Third Articulation Position,

1. The explosives are the K-sounds, which are hard and breathed and not voiced ; G@-sounds,
which are voiced.

2. The aspirates, when hard and breathed but not voiced, the Ch, and when sounded softly
and not voiced, J is formed.

3. The vibrative is the palatal R, which is produced by vibration of the uvula (Briicke),

4, The resonant is the palatal N.

D. Consonants of the Fourth Articulation Position.

1. An explosive sound does not occur when the glottis is forced open, if a vowel is loudly
sounded with the glottis previously closed. If this occurs during whispering, a feeble short
noise, due to the sudden opening of the glottis, may be heard.

2. The aspirates of the glottis are the H-sounds, which are produced when the glottis is
moderately wide.

3. A glottis-vibrative occurs in the so-called laryngeal RB of lower Saxon (Briicke),

4, A laryngeal resonant cannot exist.

The combination of different consonants is accomplished by the successive movements neces-
sary for each- being rapidly executed. Compound consonants, however, are such as are formed
when the oral parts are adjusted simultaneously for two different consonants, so that a mixed
sound is formed from two, Examples: Sch—tsch, tz, ts—Ps (y)—Ks (Xz).

319, PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH.—Aphonia.—Paralysis of
the motor nerves (vagus) of the larynx by injury, or the pressure of tumours, causes aphonia or
loss of voice (Galen). In aneurism of the aortic arch, the left recurrent nerve may be paralysed
from pressure. -The laryngeal nerves may be temporarily paralysed by rheumatism, over-exer-

PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH. 523

tion, and hysteria, or by serous effusions into the laryngeal muscles. If the tensors are paralysed,
monotonia is the chief result: the disturbances of respiration in paralysis of the larynx are
important. As long as the respiration is tranquil, there may be no disturbance, but as soon as
increased respiration occurs, great dyspncea sets in, owing to the inability of the glottis to
dilate.

If only one vocal cord is paralysed, the voice becomes impure and falsetto-like, while we may
feel from without that there is less vibration on the paralysed side (Gerhardt). Sometimes
the vocal cords are only so far paralysed that they do not move during phonation, but do so
during forced respiration and during coughing (phonetic paralysis),

Diphthongia.—Incomplete unilateral paralysis of the recurrent nerve is sometimes followed
by a double tone, owing to the unequal tension of the two vocal cords. According to Tiirck
and Schnitzler, however, the double tone occurs when the two vocal cords touch at some part
of their course (¢.g., from the presence of a tumour, fig. 367), so that the glottis is divided into
two unequal portions, each of which produces its own sound.

Hoarseness is caused by mucus upon the vocal cords, by roughness, swelling, or laxness of
the cords. If, while speaking, the cords are approximated, and suddenly touch each other,
the ‘‘speech is broken,” owing to the formation of nodal
points (§ 352). Disease of the pharynx, naso-pharyngeal
cavity, and uvula may produce a change in the voice reflealy.

Paralysis of the soft palate (as well as congenital per-
foration or cleft palate) causes a nasal timbre of all vowels;
the former renders difficult the normal formation of con-
sonants of the third articulation position ; resonance is
imperfect, while the explosives are weak, owing to the escape
of the air through the nose.

Paralysis of the tongue weakens I; E and A (#) are less
easily pronounced, while the formation of consonants of the
second and third articulation position is affected. The term
eee Drees 0 a sui In ies ea oes Tumours on the vocal cords causing
Gee is followed by spasmodic movements of the tongue qouble tone from the larynx.

Y).
» In paralysis of the lips (facial nerve), and in hare-lip, regard must be had to the formation
of consonants of the first articulation position. When the nose is closed, the speech has a
characteristic sound. The normal formation of resonants is of course at an end. After excision
of the larynx, a metal reed, enclosed in a tube, and acting like an artificial larynx, is introduced
between the trachea.and the cavity of the mouth (Czerny).

Stammering is a disturbance of the formation of sounds. [Stammering is due to long-con-
tinued spasmodic contraction of the diaphragm, just as hiccough is (§ 120), and, therefore, it is
essentially a spasmodic inspiration. As speech depends upon the expiratory blast, the spasm
prevents expiration. It may be brought about by mental excitement or emotional conditions.
Hence, the treatment of stammering is to regulate the respirations. In stuttering, which is
defective speech due to inability to form the proper sounds, the breathing is normal. ]

_ 320. COMPARATIVE—HISTORICAL.—Speech may be classified with the ‘‘expression of
the emotions” (Darwin). Psychical excitement causes in man characteristic movements, in
which certain groups of muscles are always concerned, e.g., laughing, weeping, the facial ex-
pression in anger, pain, shame, &c. These movements afford a means whereby one creature can
communicate with another. Primarily in their origin, the movements of expression are reflex
motor phenomena; when they are produced for purposes of explanation, they are voluntary
imitations of this reflex. Besides the emotional movements, impressions upon the sense-organs
produce characteristic reflex movements, which may be used for purposes of expression (Geiger),
¢.g., stroking or painful stimulation of the skin, movements after smelling pleasant or unpleasant
or disagreeable odours, the action of sound and light, and the perception of all kinds of objects.

The expression of the emotions occurs in its simplest form in what is known as expression by
means of signs or pantomime or mimicry. Another means is the imitation of sounds by the
organ of speech, constituting onamatopoesy, e.g., the hissing of a stream, the roll of thunder,
the tumult of a storm, whistling, &c. The expression of speech is, of course, dependent upon
the process of ideation and perception.

The occurrence of different sownds in different languages is very interesting. Some languages
(¢.g., of the Hurons) have no labials; in some South Sea Islands, no laryngeal sounds are
spoken ; fis absent in Sanscrit and Finnish; the short e, 0, and the soft sibilants in Sanscrit ;
d, in Chinese and Mexican; s, in many Polynesian languages ; 7, in Chinese, &c.

Voice in Animals,—Animals, more especially the higher forms, can express their emotions
by facial and other gestures. The vocal organs of mammals are essentially the same as those
of man. Special resonance organs occur in the orang-outang, mandril, macacus, and mycetes
monkeys, in the form of large cheek pouches, which can be inflated with air, and open between
the larynx and the hyoid bone.

524 COMPARATIVE AND HISTORICAL.

Birds have an upper (larynx) and a lower larynx (syrinx); the latter is placed at the
bifurcation of the trachea, and is the true vocal organ. Two folds of mucous membrane (three
in singing birds) project into each bronchus, and are rendered tense by muscles, and are thus
adapted to serve for the production of voice.

Amongst reptiles, the tortoises produce merely a sniffing sound, which in the Emys has a
peculiar piping character. The blind snakes are voiceless, the chameleon and the lizards have
a very feeble voice; the cayman and crocodile emit a feeble roaring sound, which is lost in
some adults owing to changes in the larynx. The snakes have no special vocal organs, but by
forcing out air from their capacious lung, they make a peculiar hissing sound, which in some
species is loud. Amongst amphibians, the frog has a larynx provided with muscles, The
sound emitted without any muscular action is a deep intermittent tone, while more forcible
expiration, with contraction of the laryngeal constrictors, causes a clearer continuous sound.
The male, in Rana esculenta, has at each side of the angle of the mouth a sound-bag, which
can be inflated with air and acts as. a resonance chamber. The “‘croaking” of the male frog is
quite characteristic. In Pipa, the larynx is provided with two cartilaginous rods, which are
thrown into vibration by the blast of air, and act like vibrating rods or the limbs ofa tuning-
fork. Some fishes emit sounds, either by rubbing together the upper and lower pharyngeal
bones, or by the expulsion of air from the swimming bladder, mouth, or anus,

Some insects cause sounds partly by forcing the expired air through their stigmata provided
with muscular reeds, which are thus thrown into vibration (bees and many diptera). The
wings, owing to the rapid contraction of their muscles, may also cause sounds (flies, cockroach,
bees). The Sphinx atropos (death-head moth) forces air from its sucking stomach. In others,
sounds are produced by rubbing their legs on the wing-cases (Acridium), or the wing-cases on
each other (Gryllus, locust), or on the thorax (Cerambyx), on the leg (Geotrupes), on the abdomen
or the margin of the wing (Nekrophorus). In Cicadaciw, membranes are pulled upon by
muscles, and are thus caused to vibrate. Friction sounds are produced between the cephalo-
thorax and the abdomen in some spiders (Theridium), and in some crabs (Palinurus). Some
mollusca (Pecten) emit a sound on separating their shells.

Historical.—The Hippocratic School was aware of the fact that division of the trachea
abolished the voice, and that the epiglottis prevented the entrance of food into the larynx,
Aristotle made numerous observations on the voice of animals. The true cause of the voice
escaped him as well as Galen. Galen observed complete loss of voice after double pneumo-
thorax, after section of the intercostal muscles or their nerves, as well as after destruction of
part of the spinal cord, even although the diaphragm still contracted. He gave the cartilages
of the larynx the names that still distinguish them ; he knew some of the laryngeal muscles,
and asserted that voice was produced only when the glottis was narrowed. He compared the
larynx to a flute. The weakening of the voice, in feeble conditions, especially after loss of
blood, was known to the ancients. Dodart (1700) was the first to explain voice as due to the
vibration of the vocal cords by the air passing between them.

The production of vocal sounds attracted much attention amongst the ancient Asiatics and
Arabians—less amongst the Greeks. Pietro Ponce (+ 1584) was the first to advocate instruction
in the art of speaking in cases of dumbness. Bacon (1638) studied the shape of the mouth for
the pronunciation of the various sounds. Kratzenstein (1781) made an artificial apparatus for
the production of vowel sounds, by placing resonators of various forms over vibrating reeds.
Von Kempelen (1769 to 1791) constructed the first speaking-machine. Rob. Willis (1828)
found that an elastic vibrating spring gives the vowels in the series—U, O, A, E, I—according
to the depth or height of its tone ; further, that by lengthening or shortening an artificial
resonator on an artificial vocal apparatus, the vowels may be obtained in the same series. The
newest and most important investigations on speech are by Wheatstone, v. Helmholtz, Donders,
Briicke, &c., and are mentioned in the context. Hensen succeeded in showing exactly the
pitch of vocal tone, thus:—The tone is sung against a Kénig’s capsule with a gas flame.
Opposite the flame is placed a tuning-fork vibrating horizontally, and in front of one of its
limbs is a mirror, in which the image of the flame is reflected. When the vocal tone is of the
same number of vibrations as the tuning-fork, the flame in the mirror shows orfe elevation, if
double, z.¢., the octave, 2, and with the double octave, 4 elevations.

}
}
{
j

General Physiology of the Nerves and
hilectro-Physiology.

321. STRUCTURE OF THE NERVE ELEMENTS.—The nervous elements

present two distinct forms :—

. Non-medullated. Of various forms
I, Nerve-Fibres, | Modcilated. II, Nerve-Cells. Soak Pana Gae

An aggregation of nerve-cells constitutes a nerve-ganglion. The fibres represent
a conducting apparatus, and serve to place the central nervous organs in connection
with peripheral end-organs, The nerve-cells, however, besides transmitting impulses,
act as physiological centres for automatic or reflex movements, and also for the
sensory, perceptive, trophic, and secretory functions,

I. (1) The non-medullated nerve-fibres occur in several forms :—

1, Primitive Fibrils.—The simplest form of nerve-fibre, which is visible with a magnifying
power of 500 to 800 diameters linear, consists of primitive nerve-fibrils, They are very delicate
fibres (fig. 368, 1), often with small varicose swellings here and there in their course, which,
however, are due to changes post-mortem. They are stained of a brown or purplish colour by the
gold-chloride method, and they occur when a nerve-fibre is near its termination, being formed
by the splitting up of the axis-cylinder of the nerve-fibre, ¢.g., in the terminations of the corneal
nerves, the optic nerve-layer in the retina, the terminations of the olfactory fibres, and in a plexi-
form arrangement in non-striped muscle (p. 461), Similar fine fibrils occur in the grey matter
of the brain and spinal cord, and in the finely divided processes of nerve-cells.

2. Naked or simple axial cylinders (fig. 368, 2), which represent bundles of primitive fibrils
held together by a slightly granular cement, so that they exhibit very delicate longitudinal
striation with fine granules scattered in their course. The best example is the axial cylinder
process of nerve-cells (fig. 368, I, z). [The thickness of the axis-cylinder depends upon the
number of fibrils entering into its composition. ]

3. Axis-cylinders surrounded with Schwann’s sheath, or Remak’s fibres (3°8 to 6°8 wu broad),
the latter name being given to them from their discoverer (fig. 368, 3). [These fibres are also
called pale or non-medullated, and from their abundance in the sympathetic nervous system,
sympathetic.] They consist of a sheath, corresponding to Schwann’s sheath [neurilemma, or
primitive sheath, which encloses an axial cylinder; while lying here and there under the sheath,
and between it and the axial cylinder are nerve-corpuscles, These fibres are always fibrillated
longitudinally]. The sheath is delicate, structureless, and elastic. Dilute acids clear the
fibres without causing them to swell up, while gold chloride makes them brownish-red. They
are widely distributed in the sympathetic nerves, [e¢.g., splenic], and in the branches of the
olfactory nerves. All nerves in the embryo, as well as the nerves of many invertebrata, are of
this kind. [According to Ranvier, these fibres do not possess a sheath, but the nuclei are
merely applied to the surface, or slightly embedded in the superficial parts of the fibre, so that
they belong to the fibre itself. These fibres also branch and form an anastomosing net-work
(fig. 370). This the medullated fibres never do. These fibres, when acted on by silver nitrate,

- never show any crosses. The branched forms occur in the ordinary nerves of distribution, and

they are numerous in the vagus, but the olfactory nerves have a distinct sheath which is
nucleated. ] .

(2) Medullated fibres occur also in several forms :—

4, Axis-cylinders, or nerve-fibrils, covered only by a medullary sheath, or white substance
of Schwann, are met with in the white and grey matter of the central nervous system, in the

526 STRUCTURE OF NERVE-FIBRES.

optic and auditory nerves. These medullated nerve-fibres, without any neurilemma, often show
after death, varicose swellings in their course [due to the accumulation of fluid between the
medulla of myelin and the axis-cylinder]. Hence they are called varicose fibres. [The varicose
appearance is easily produced by squeezing a small piece of the white matter of the spinal cord
between a slide and a cover-glass. Nitrate of silver does not reveal any crosses, and there are
no nodes of Ranvier. When acted upon by coagulating reagents, ¢.g., chromic acid, the

Fig. 368.

1, Primitive fibrille ; 2, axis-cylinder; 3, Remak’s fibres; 4, medullated varicose fibre ; 5, 6,
medullated fibre, with Schwann’s sheath; c, neurilemma ; ¢, ¢, Ranvier’s nodes ; 6, white
substance of Schwann ; d, cells of the endoneurium ; a, axis-cylinder ; x," myelin drops ;
7, transverse section of nerve-fibres ; 8, nerve-fibre acted on with silver nitrate and show-
ing Fromann’s lines. I, multipolar nerve-cell from the spinal cord; z, axial cylinder
process; y, protoplasmic processes—to the right of it a bipolar cell. II, peripheral
ganglionic cell, with a connective-tissue capsule, III, ganglionic cell, with 0, a spiral,
and n, straight process ; m, sheath.

medullary sheath appears laminated, so that on transverse section, when the axis-cylinder is

stained, it is surrounded by concentric circles (fig. 869). :

5. Medullated Nerve-Fibres with Schwann’s Sheath (fig. 368, 5, 6).—These are the most
complex nerve-fibres, and are 10 to 22°6 uw [zehya tO xeyn inch] broad. They are most
they are also present in the sympathetic nerves. [When examined in the fresh and living con-
dition in situ, they appear refractive and homogeneous (Ranvier, Stirling); but if acted upon

numerous in, and in fact they make up the great mass of, the cerebro-spinal nertee, sone a

oo

=

if

STRUCTURE OF NERVE-FIBRES. | 527

by reagents, they are not only refractive, but exhibit a double contour, the margins being dark
and well defined.] Each fibre consists of-—

[1. Schwann’s sheath, neurilemma, or primitive sheath ;

2. White substance of Schwann, medullary sheath, or myelin;

3. Axis-cylinder composed of fibrils and surrounded by a sheath
called the axilemma ;

4, Nerve-corpuscles. |

A. The axis-cylinder, which occupies } to } of the breadth of the
fibre, is the essential part of the nerve, and lies in the centre of the
fibre. like the wick in the centre of a candle (fig. 368, 6, a). Its
usual shape is cylindrical, but sometimes it is flattened or placed
eccentrically—[this is most probably due to the hardening process
employed]. It is composed of fibrils
[united by cement or stroma; they
become more obvious near the termi-
nations of the nerve, or after the action
of reagents, which sometimes cause
the fibrils to appear beaded. It is
quite transparent, and stains deeply
with carmine or logwood], while dur-
ing life, its consistence is semi-fluid.
According to Kupffer, a fluid—“neuro-
plasma ’”—lies between the fibrils
{while, according to other observers,
the whole cylinder is enclosed in an
elastic sheath peculiar to itself and
composed of neuro-keratin. This
sheath is called by Kiihne, the axi-
lemma. Each axis-cylinder is'an enor-
mously long process of a ganglionic
cell].

Fromann’s Lines,—Chloroform and
collodion render it visible, while it is
most easily isolated as a solid rod, by

Node of
— Ranvier.

Primitive
Sheath.

Nerve-
Corpuscies.

Interannular Segment.

; de pide Axial
the action of nitric acid with excess Cylinder.
of potassium chlorate. When acted
on by silver nitrate, Fromann observed
transverse markings on it, but their
significance is unknown (fig. 368, 8).

B. The white substance of Schwann, :

A White
medullary sheath or myelin, surrounds Sanatance ot
the axis-cylinder, like an insulating Schwann.

Ons ze Ss
S ‘ ___ Node of
Ranvier.
Fig. 371.

Fig. 369.—Transverse section of the nerve-fibres of the spinal cord, the axis-cylinders like dots
surrounded by a clear space (myelin). Fig. 370.—Remak’s fibre from vagus of dog.
b, fibrils; n, nucleus; y, protoplasm surrounding it. Fig. 371.—Medullated nerve-fibre of

’ a rabbit aeted on by osmic acid, x 400.

medium around an electric wire. In the perfectly fresh condition it is quite homogeneous,
highly glistening, bright, and refractive ; its consistence is fluid, so that it oozes out of the
cut ends of the fibres in spherical drops (fig. 368, x), [myelin drops, which are always marked
by concentric lines, are highly refractive, and best seen when a fresh nerve is teased in salt
solution]. After death, or after the action of reagents, it shrinks slightly from the sheath, so

528 STRUCTURE OF NERVE-FIBRES,

that the fibres have a double contour, while the substance itself breaks up into smaller or larger
droplets, due not to coagulation (Pertik), but, according to Toldt, to a process like emulsifica-
tion, the drops pressing against each other. Thus, the fibre is broken up into masses, so that
it has a characteristic appearance (fig. 368, 6), It contains a large amount of cerebrin and
lecithin, which swell up to form myelin-like forms in warm
water. It also contains fatty matter, so that these fibres are
blackened by osmic acid, [while boiling ether extracts cholesterin
from them]. Chloroform, ether, and benzin, by dissolving the
fatty and some other constituents of the fibres, make them very
transparent. [Some observers describe a fluid lying between the
medulla and the axis-cylinder.]

C. The Sheath of Schwann, or the neurilemma, lies imme-
diately outside of and invests the white sheath (fig. 368, 6, c),
and is a delicate structureless membrane, comparable to the
sarcolemma of a muscular fibre.

D. Nerve-Corpuscles.—At fairly wide intervals under the
neurilemma, and lying in depressions between it and the
medullary sheath, are the nucleated nerve-corpuscles, which are
readily stained by pigments (fig. 371). [They may be compared
to the muscle-corpuscles, the nuclei being surrounded by a small
amount of protoplasm which sometimes contains pigment. They
are not so numerous as in muscle.] [Adamkiewicz describes
nerve-corpuscles, or ‘‘demilunes” under the neurilemma, quite
distinct from the ordinary nerve-corpuscles. They are stained
yellow by safranin, while the ordinary nerve-corpuscles are
stained by methylanilin. ]

Ranvier’s Nodes or Constrictions.—The neuri-
lemma forms in broad fibres at longer, and
in narrower ones at shorter intervals, the nodes
or constrictions of Ranvier (fig. 368, 6, t, ¢;
fig. 371; fig. 372, fs). They are constrictions
which occur at regular intervals along a nerve-
fibre ; at them the white substance of Schwann
is interrupted, so that the sheath of Schwann
lies upon the axis-cylinder [or its elastic sheath]
at the nodes. The part of the nerve lying
between any two nodes is called an_ ‘inter-
annular or inter-nodal segment, and each such
segment contains one or more nuclei, so that
; some observers look upon the whole segment
as equivalent to one cell.

The function of the nodes seems to be to
permit the diffusion of plasma through the outer ~
sheath into the axis-cylinder, while the decom-
position-products are similarly given off. [A
colouring-matter like picro-carmine diffuses into
the fibre only at the nodes, and stains the
axis-cylinder red, although it does not diffuse
through the white substance of Schwann.

Incisures (of Schmidt and Lantermann).— Fig. 373
Each interannular segment in a stretched nerve yy ,4n)Jated 18 fib th
shows, running across the white substance, a ~~ ulated nerve-tihnes (07s
379. number of oblique lines, which are called
llated wmisures (figs. 872, 373). They indicate that
the segment’is built up of a series of conical

a

<

be

osmic acid, a, axis-cylinder;
s, sheath of Schwann; 1”,
nucleus; p, p, granular sub-
stance at the poles of the
nucleus; 7, 7, Ranvier’s
nodes where the medullary
sheath is interrupted and

Fig
Med u

>». fibr ; z 5 ;
Mieskcaat a sections, each of which is bevelled at its ends,

apa and the bevels are arranged in an imbricate
ines ae men mn one one the other, while the slight
vawx?, nterval between them appears as an incisure. : F

oP e Each such section of the eis matter is called ce erty pes: un aoe: ;

: a cylinder cone (Kuhnt). t, £, doiptnes Ot Pheer

Neuro-Keratin Sheath,—According to Ewald and Kiihne, the axis-cylinder, as well as the
white substance of Schwann, is covered with an excessively delicate sheath, consisting of newro-
keratin, and the two sheaths are connected by numerous transverse and oblique fibrils, which
permeate the white substance. [The myelin seems to lie in the interstices of this mesh-work.]
[Rod-like Structures in Myelin.—If a nerve be hardened in amimoniwm chromate (or picric
acid), M‘Carthy has shown that the myelin exhibits rod-like structures, radiating from the

described. ]_

STRUCTURE OF NERVE-FIBRES.

axis-cylinder outwards, which are stained with logwood and carmine.
-not distinct from each other, but are perhaps part of the neuro-keratin network already

529

The rods are probably

Action of Nitrate of Silver.—When a small nerve, ¢.g., the intercostal nerve of a mouse, is
acted on by silver nitrate, it is seen to be covered by an endothelial sheath composed of flattened
endothelial cells (fig. 374), while the nerve-fibres themselves exhibit crosses along their course.

These crosses are due to the penetration of the silver solution
at the nodes, where it stains the cement-substance and also
part of the axis-cylinder, so that the latter sometimes exhibits
transverse markings called Fromann’s lines (fig. 368, 8).]
[New Methods.—Much progress has recently been made
in tracing the course of medullated nerve-fibres by the action
of new staining reagents; thus acid fuchsin stains the myelin
deeply, leaving the other parts unstained, at least it can be
so manipulated as to yield this result. Weigert’s Method
and its modifications have yielded most important results,
and proved that medullated nerve-fibres exist in many parts

of the central nervous system where they cannot be seen in

the ordinary way. The nerve-tissue is hardened in a solu-
tion of a chromium salt, and placed in a half-saturated
solution of cupric acetate; it is then stained with logwood,
and afterwards the elements are differentiated by steeping
the sections in a solution of ferricyanide of potash and
borax. The myelin is coloured a logwood tint. ]

In the spinal nerves, those fibres are thickest which have
the longest course before they reach their end-organ
(Schwalbe), while those ganglion-cells are largest which
send out the longest nerve-fibres (Pierret). [Gaskell finds
that the longest nerves are not necessarily the thickest, for
the visceral nerves in the vagus are small nerves, and yet
run a very long course. ] .

Division of Nerves. —Nerve-fibres run in the nerve-trunks
without dividing; but when they approach their termination
they often divide dichotomously [at a node], giving rise to
two similar fibres, but there may be several branches at a
node (fig. 376, ¢). [The divisions are numerous in motor

Fig. 374.

Intercostal nerve of a mouse (single
fasciculus of nerve-fibres) stained
with silver nitrate. Endothelial
sheath stained, and some nodes
of Ranvier indicated by crosses.

nerves to striped muscles.] In the electrical nerves of the malapterurus and gymnotus, there

is a great accumula- op »
tion of Schwann’s
sheaths roundanerve,
so that a nerve-fibre
is as thick asa sew-
ing-needle. Such a
fibre, when it divides,
breaks up into a
bundle of smaller
fibres.
[Nerve-Sheaths. —
A nerve-trunk con-
sists of bundles of
nerve - fibres. The
bundles are held to-
gether by a common \

sheath (fig. 375, ep),
the epineurium which
contains the larger
blood-vessels, lymph-
atics, and sometimes
fat and plasma cells.
Each bundle is sur-

rounded with its own 3 Fig. 375.

sheath or rineu- : }
rium (pe), which con- ‘Lrans. section of a nerve (median).

sists of lamellated

RS AK
Vy gee
NW @ ae SORROW oN ‘y Vee
connective-tissue ‘Yaa | Wasmcess ie scsoes sek aM li) I See ae

ep, epineurium ; pe, perineurium ;
ed, endoneurium.

connective-tissue disposed circularly, and between the lamelle are lymph spaces lined by
flattened endothelial a a These lymph spaces may be injected from and communicate with

oi

530 STRUCTURE OF NERVE-FIBRES.

the lymphatics (Axel Key and Retzius).] The nerve-fibres within any bundle are held together
by delicate connective-tissue, which penetrates between the adjoining fibres, constituting the
endoneurium (ed). It consists of delicate fibres with branched connective-tissue corpuscles
(fig. 868, 6, @), and in it lie the capillaries, which are not very numerous, and are arranged to
form elongated open meshes. ; sh ib aera chee soeie

[Henle’s Sheath.— When a nerve is traced to its distribution, it branches and becomes smaller,
until it may consist only of a few bundles or even a single bundle of nerve-fibres. As the bundle
branches, it has to give off part of its lamellated sheath or perineurium to each branch, so that,
as we pass to the periphery, the smaller bundles are surrounded by few lamelle. Ina bundle
containing only a few fibres, this sheath may be much reduced, or may consist only of thin,
flattened, connective-tissue corpuscles with a few fibres. A sheath surrounding a few nerve-
fibres is called Henle’s Sheath by Ranvier. ]

[Nervi Nervorum. —Marshall and v. Horsley have shown that the nerve-sheaths are provided
with special nerve-fibres, in virtue of which they are endowed with sensibility. ]

Development.—At first nerve-fibres consist only of fibrils, ¢.¢., of axis-cylinders, which
become covered with connective substance, and ultimately the white substance of Schwann is

Sa developed in some of them. The growth in length of the

Se fibres takes place by elongation of the individual “ inter-
annular” segments, and also by the new formation of these
(Vignal).

II. Ganglionic or Nerve-Cells. —1. Multipolar nerve-cells
(fig. 368, I) occur partly as large cells (100 u), and are visible
to the unaided eye as in the anterior horn of the spinal cord,
and in a different form in the cerebellum, and partly in a
smaller form (20 to 10 «) in the posterior horns of the spinal
cord, many parts of the cerebrum and cerebellum, and in the
retina. They may be spherical, ovoid, pyramidal [cerebrum],
pear- or flask-shaped [cerebellum], and are provided with
numerous branched processes which give the cells a char-
acteristic appearance. [Deiters isolated such cells from the
anterior horn of the grey matter of the spinal cord, so that
this special form of cell is sometimes called ‘‘Deiters’ cell”
(fig. 368, I).] They are devoid of a cell envelope, are of soft
consistence, and exhibit a fibrillated structure, which may
extend even into the processes. Fine granules lie scattered
throughout the cell-substance between the fibrils. Not unfre-
quently yellow or brown granules of pigment are also found,
either collected at certain parts in the cell or scattered through-
out it. The relatively large nwclews consists of a clear envelope
enclosing a resistant substance. It does not appear to have
a membrane in youth (Schwalbe). Within the nucleus lies the
nucleolus, which in the recent condition is angular, provided
with processes and capable of motion, but after death 1s highly
refractive and spherical. There is always one unbranched
process, constituting the axial cylinder process (I, z) which
remains unbranched, but it soon becomes covered with the
white substance of Schwann, and the other sheaths of a
medullated nerve, so that it becomes the axial cylinder of a
nerve-fibre. [Thus a nerve-fibre is merely an excessively long,
unbranched process of a nervé-cell pushed outwards towar
the periphery.] It is not definitely ascertained that the cerebral
cells have such processes. All the other processes divide very
frequently until they form a branched, root-like, complex
arrangement of the finest primitive fibrils. These are called
aa ary protoplasmic processes (I, y). By means of these processes,

Fig. 376. _ adjoining cells are brought into communication with each
Cell from the Gasserian ganglion. other, so that impulses can be conducted from one cell to

n, nuclei of the sheath; ¢, fibre another, Further, many of these fibrils approximate to each

dividing at a node of Ranvier. other and join together to form axis-cylinders of other nerve-
nar 4 Thanhoffer states that he has traced the axis-cylinder process to the nucleus and
nucleolus.

2. Bipolar cells are best developed in fishes, ¢.g., in the spinal ganglia of the skate, and in
the Gasserian ganglion of the pike. They appear to be nucleated, fusiform enlargements of
the axis-cylinder (fig. 368, on the right of I). The white substance often stops short on each
side of the enlargement, but sometimes the white substance and the sheath of Schwann pass
over the enlargement. pina

3. Nerve- with connective-tissue capsules occur in the peripheral ganglia of man (fig.

CHEMISTRY OF NERVOUS MATTER. 531

368, II), ¢.g., iv the spinal ganglia. The soft body of the cell, which is provided with several
processes, is covered by a thick, tough capsule composed of several layers of connective-tissue
corpuscles ;.while the inner surface of the composite capsule is lined by a layer of delicate
endothelial cells (fig. 376). The body of the cells in the spinal ganglia is traversed by a net-
work of fine fibrils (Flemming). The capsule is continuous with the sheath of the nerve-fibre.

- Rawitz and G. Retzius find that the cells of the spinal ganglia are wnipolar, the outgoing
fibre taking a half-turn within the capsule before it leaves the cell (fig. 376). Retzius [and
Ranvier] observed the process to divide like a T. . Perhaps this division corresponds to the
two processes of a pital cell. The jugular ganglion and plexus gangliiformis vagi in man
contain only unipolar cells, so that, in this respect, they may be compared to spinal ganglia.
The same is the case in the Gasserian ganglion; while the ciliary, spheno-palatine, otic, and
submaxillary ganglia structurally resemble the ganglia of the sympathetic.

4, Ganglionic cells with spiral fibres occur chiefly in the abdominal sympathetic of the frog
(Beale, J. Arnold). The body of the cell is usually pyriform in shape, and from it proceeds a
straight unbranched process (fig. 368, III, 2), which ultimately becomes the axis-cylinder of a
nerve. <A spiral fibre springs from the cell (?a network), emerges from it, and curves in a
spiral direction round the former (0). The whole cell is surrounded by a nucleated capsule (7).
We know nothing of the significance of the different fibres.

322. CHEMICAL AND MECHANICAL PROPERTIES OF NERVOUS
SUBSTANCE.—1. Proteids.—Albumin occurs chiefly in the axis-cylinder and in
the substance of the ganglionic cells. Some of this proteid substance presents
characters not unlike those of myosin (§ 293). Dilute solution of common salt
extracts a proteid from nervous matter, which is precipitated by the addition of
much water and also by a concentrated solution of common salt (Petrowsky).
Potash-albumin and a globulin-like substance are also present. Nuclein occurs
especially in the grey matter (§ 250, 2), while neuro-keratin, a body containing
much sulphur and closely related to keratin, occurs in the corneous sheath of nerve-
fibres (p. 528). If grey nervous matter be subjected to artificial digestion with
trypsin, both of these substances remain undigested (Kiihne and Ewald). Pure
neuro-keratin is obtained by treating the residue with caustic potash. The sheath
of Schwann does not yield gelatin, but a substance closely related to elastin
($ 250, 6), from which it differs, however, in being more soluble in alkalies. The
connective-tissue of nerves yields gelatin.

2. Fats and other allied substances soluble in ether, more especially in the white
_ matter :—(a) Cerebrin, free from phosphorus (§ 250, 3).

Cerebrin is a white powder composed of spherical granules soluble in hot alcohol and ether,
but insoluble in cold water. It is decomposed at 80° C., and its solutions are neutral. When
boiled for a long time with acids, it splits up into a left-rotatory body like sugar, and another
unknown product. Preparation.—Rub up the brain into a thin fluid with baryta water.
Extract the separated coagulum with boiling alcohol. The extract is frequently treated with
cold ether to remove the cholesterin (W. Miller). Parkus separated from cerebrin its
homologue, homocerebrin, which is slightly more soluble in alcohol, and the clyster-like body,
encephalin, which is soluble in hot water.

(6) Lecithin and its decomposition-products—-glycero-phosphoric acid and oleo-
phosphoric acid (§ 251).

_ Neurin (or Cholin=C,H,,;NO,) is a strongly alakaline, colourless fluid, forming crystalline
salts with acids. It is soluble in water and alcohol, and has been formed synthetically from
glycol and trimethylamin. Lecithin is a salt of the base neurin.

(c) Protagon, which contains N and P, is similar to cerebrin, and is, according

to its discoverer, the chief constituent of the brain (Ziebreich).
_ According to Hoppe-Seyler and Diaconow, it is a mixture of lecithin and cerebrin. [The
investigations of Gamgee and Blankenhorn have shown, however, that protagon is a definite
chemical body. They find that, instead of being unstable, it is a very stable body.] Itis a
glucoside, and crystalline, and can be extracted from the brain by warm alcohol, and when
boiled with baryta yields the decomposition-products of lecithin.

3. The following substances are extracted by water :—Xanthin and hypoxanthin (Scherer),
kreatin. (Lerch), inosit (W. Miller), ordinary lactic acid (Gscheidlen), acetic and formic acids,
uric acid (?), and volatile fatty acids ; leucin (in disease), urea (in uremia), and a substance

like starch in the human brain (Jafé). All these substances are for the most part products of
the regressive metabolism of the tissues.

532 METABOLISM OF NERVES.

Reaction.—Nervous substance, when passive, is neutral or feebly alkaline in
reaction, while active (? and dead) it is acid (Funke). The grey matter of the
brain, when quite fresh, is alkaline (Liebreich), but death rapidly causes it to
become acid (scheidlen).

The reaction of nerve-fibres varies during life. After introducing methyl-blue into the
body of a living animal, Ehrlich found that the axis-cylinder became blue, 7.¢., in those nerves

which have an alkaline reaction (cortex cerebri, cardiac, sensory, motor (non-striped), gustatory
and olfactory fibres), while the termination of motor (voluntary) nerves remained uncoloured.

The latter he regards as acid. .

The nerves after death have a more solid consistence, so that in all probability
some coagulation or change, comparable to the stiffening of muscle, occurs in them
after death, while at the same time a free acid is liberated (§ 295). Ifa fresh
brain be rapidly “broiled” at 100° C., it, like a muscle similarly treated, remains

alkaline ($ 295).

os

Chemical Composition. Grey Matter. White Matter.
Waters 16% ku 81°6 per cent. 68°4 per cent.
Solids, . : ; . : , : 18°4 i 31°6 *
The solids consist of —
Albumins and glutin, 55°4 re 24°7 Pe
Lecithin, é ; 17°2 a 9°9 o
Cholesterin and fats, L327 we 52°1 ;
Cerebrin, ; : : , O"d if 925 ns
Substances insoluble in ether. ma 67 . 3°3 rf
Salts, . ; : ; , ; ela ses “i 0°5 bs
| 100-0 100°0

In 100 parts of ash, Breed found potash 32, soda 11, magnesia 2, lime 0°7, NaCl 5, iron
phosphate 1:2, fixed phosphoric acid 39, sulphuric acid 0°1, silicic acid 0°4.

[Ptomaines (§ 166) are obtained from putrefying brain. They have an effect on the motor
nerves like curara, but in much less degree, while the phenomena last for a much shorter time
(Guareschi and Mosso). |

Mechanical Properties.—One of the most remarkable mechanical properties of
nerve-fibres is the absence of elastic tension according to the varying positions of |
the body. Divided nerves do not retract; such nerves exhibit delicate, microscopic, | .

transverse folds, [like watered silk] or Fontana’s transverse markings. .

The cohesion of a nerve is very considerable. When a limb is forcibly torn
from the body, as sometimes happens from its becoming entangled in machinery,
then erve not unfrequently remains unsevered, while the other soft parts are
ruptured. [Tillaux found that a weight of 110 to 120 lbs. was required to rupture
the sciatic nerve at the popliteal space, while to break the median or ulnar nerve
of a fresh body, a force equal to 40 to 50 lbs. was required. The toughness and
elasticity of nerves are often well shown in cases of injury or gun-shot wounds.
The median or ulnar nerve will gain 15 to 20 centimetres (6 to 8 inches) before
breaking. Weir Mitchell has shown that a healthy nerve will bear a very consider-
able amount of pressure and handling, and, in fact, the method of nerve-stretching
depends upon this property of a nerve-trunk. |

323. METABOLISM OF NERVES.—Influence of Blood-Supply.—We know
very little regarding the metabolic processes that occur in nerve-tissue. Some
extractives are obtained from nerve-tissue, and they may, perhaps, be regarded as
decomposition-products (p. 531). It has not been proved satisfactorily that during —
the activity of nerves there is an exchange of O and CO,. ‘That there is an
exchange of materials within the nerves is proved by the fact that, after com- —
pression of the blood-vessels of the nerves, the excitability of the nerves falls, —
and is restored again when the circulation is re-established. Compression of the
abdominal aorta causes paralysis and numbness of the lower half of the body,

MECHANICAL STIMULI AND NERVE-STRETCHING, 533

while occlusion of the cerebral vessels causes almost instantaneously cessation of
the cerebral functions. The metabolism of the central nervous organs is much
more active than that of the nerves themselves. [If the abdominal aorta of a
rabbit be compressed for a few minutes, the hind limbs are quickly paralysed, the
animal crawls forward on its fore-legs, drawing the hind limbs in an extended
position after it.] The ganglia form much lymph.

324. EXCITABILITY OF THE NERVES—STIMULI.—Nerves possess the
property of being thrown into a state of excitement by stimuli, and are, therefore,
said to be excitable or irritable. The stimuli may be applied to, and may act
upon, any part of the nerve. [The following are the various kinds of stimuli, z.e.,
modes of motion, which act upon nerves] :—

1. Mechanical stimuli act upon nerves when they are applied with sufficient
rapidity to produce a change in the form of the nerve-particles, e.g., a blow,
pressure, pinching, tension, puncture, and section. In the case of sensory nerves,
when they are stimulated, pain is produced, as is felt when a limb ‘‘sleeps,” or
when pressure is exerted upon the ulnar nerve at the bend of the elbow. Whena
motor nerve is stimulated, motion results in the muscle attached to the nerve. If
the continuity of the nerve-fibres be destroyed, or, what is the same thing, if the
continuity of the axial cylinder be interrupted by the mechanical stimulus, the
conduction of the impulse across the injured part is interrupted. If the molecular
arrangements of the nerves be permanently deranged, e.g., by a violent shock, the
excitability of the nerves may be thereby extinguished.

A slight blow applied to the radial nerve in the fore-arm, or to the axillary nerves in the
supraclavicular groove, is followed by a contraction of the muscles supplied by these nerves,
Under. pathological conditions, the excitability of a nerve for mechanical stimuli may be
increased enormously.

Tigerstedt ascertained that the minimal mechanical stimulus is represented by 900 milligram-
millimetres, and the maximwm by 7000 to 8000. Strong stimuli cause fatigue, but the fatigue
does not extend beyond the part stimulated. A nerve when stimulated mechanically does not
become acid. Slight pressure without tension increases the excitability, which diminishes after
a short time. The mechanical work produced by an excited muscle in consequence of a stimulus
was 100 times greater than the mechanical energy of the mechanical nerve-stimulus.

Continued pressure upon a mixed nerve paralyses the motor sooner than the
sensory fibres. If the stimulus be applied very gradually, the nerve may be
rendered inexcitable without manifesting any signs of its being stimulated
(Fontana, 1758). Paralysis, due to continuous pressure gradually applied, may
occur in the region supplied by the brachial nerves; the left recurrent laryngeal

“nerve also may be similarly paralysed from the pressure of an aneurism of the arch
of the aorta.

By increasing the pressure on a nerve by using a gradually increasing weight, there is at first
an increase and then a decrease of the excitability. Pressure on a mixed nerve abolishes reflex
conduction sooner than motor conduction (Kronecker and Zederbawm).

Nerve-stretching is employed for therapeutical purposes. If a-nerve be exposed and

stretched, or if it be made sufficiently tense, the nerve is stimulated. Slight tension increases

the reflex excitability (Schleich), while violent extension produces a temporary diminution or
abolition of the excitability (Valentin). The centripetal or sensory fibres of the sciatic nerve
are sooner paralysed thereby than the centrifugal or motor (Conrad). During the process of
extension, mechanical changes are produced, either in the nerve itself or in its end-organs,
causing an alteration of the excitability, but it may also affect the central organs. The
paralysis, which sometimes occurs after forcible stretching, usually rapidly disappears. There-
fore, when a nerve is in an excessively excitable condition, or when this is due to an inflam-
matory fixation or constriction of the nerve at some part of its course, nerve-stretching may
be useful, partly by diminishing the excitability, partly by breaking up the inflammatory
adhesions. In cases where stimulation of an afferent nerve gives rise to epileptic or tetanic
spasms, nerve-stretching may be useful by diminishing the excitability at the periphery, in
addition to the other effects already described. It has also been employed in some spinal
affections, which may not as yet have resulted in marked degenerative changes.

For physiological purposes, a nerve may be stimulated mechanically by means of Heiden-

534 THERMAL AND CHEMICAL STIMULI.

hain’s tetanomotor, which is simply an ivory hammer attached to the prolonged spring of a
Neef’s hammer of an induction machine. [A more delicate form of this instrument was used
by Tigerstedt (§ 335).] The rapid vibration of the hammer communicates a series of mechanical
shocks to the nerve upon which it is caused to beat. Rhythmic extension of a nerve causes
contractions and even tetanus,

2. Thermal Stimuli.—If a frog’s nerve be heated to 45° C., its excitability is
first increased and then diminished. The higher the temperature, the greater is .
the excitability, and the shorter its duration (Afanasief). If a nerve be heated to
50° C. for a short time, its excitability and conductivity are abolished. The frog’s
nerve alone regains its excitability on being cooled (Pickford). If the temperature
be raised to 65° C., the excitability is abolished without the occurrence of a con-
traction, while its medulla is broken up (Eckhard). Sudden cooling of a nerve to
5° C. acts as a stimulus, causing contraction in a muscle, while sudden heating to
40° or 45° C. produces the same result. If the temperature be increased still more,
instead of a single contraction a tetanic condition is produced. All such rapid
variations of temperature quickly exhaust the nerve and kill it. If a nerve be
frozen gradually, it retains its excitability on being thawed. The excitability lasts
long in a cooled nerve ; in fact, it is increased in a motor nerve, but the contractions
are not so high and more prolonged, while the conduction in the nerve takes place
more slowly. Amongst miammalian nerves, the afferent and vaso-dilator nerves at
45° to 50° C. exhibit the results of stimulation, while the others only show a change
in their excitability. When cooled to +5° C., the excitability of all the fibres is
diminished ((‘riitzner). .

3. Chemical Stimuli excite nerves when they act with a certain rapidity, and
thereby alter the condition of the nerve (p. 473). Most chemical stimuli act by
first increasing the nervous excitability, and then diminishing or paralysing it.
Chemical stimuli, as a rule, have less effect upon sexsory than upon motor fibres
(Eckhard). According to Griitzner, the inactivity of chemical stimuli, so often
observed when they are applied to sensory nerves, depends in great part upon the
non-simultaneous stimulation of all the nerve-fibres. Amongst chemical stimuli
are—(a) rapid abstraction of water by dry air, blotting paper, exposure in a
chamber containing sulphuric acid, or by the action of solutions which absorb
fluids, e.g., concentrated solutions of neutral alkaline salts (NaCl, excites only motor
fibres in mammals—Grvitzner), sugar, urea, concentrated glycerin (and ? some
metallic salts). The subsequent addition of water may abolish the contractions,
while the nerve may still remain excitable. The abstraction of water first increases
and afterwards diminishes the excitability. The dmbibition of water diminishes the
excitability. (%) Free alkalies, mineral acids (not phosphoric), many organic acids
(acetic, oxalic, tartaric, lactic), and most salts of the heavy metals. While the
acids act as stimuli, only when they are somewhat concentrated, the caustic alkalies
act in solutions of 0°8 to 0°1 per cent. (Kiihne). Neutral potash salts, in a concen-
trated form, rapidly kill a nerve, but they do not excite it nearly so strongly as the
soda compounds. Dilute solutions of the neutral potash salts first increase and
afterwards diminish it (Hanke), as can be shown by stimulation with an induction
shock (Biedermann). (c) Various substances, e.g., dilute alcohol, ether, chloroform,
bile, bile-salts, and sugar. ‘These substances usually excite contractions, and after-
wards rapidly kill the nerve. Ammonia, lime-water, some metallic salts, carbon
bisulphide, and ethereal oils kill the nerve without exciting it—at least without
producing any contraction in a frog’s nerve-muscle preparation. [The nerve of a
nerve-muscle preparation may be dipped into ammonia, but no contraction results,
while the slightest traces of ammonia applied to a muscle cause contraction.] —
Carbolic acid does the same, although when applied directly to the spinal cord
produces spasms. These substances excite the muscles when they are directly —
applied to them. Tannic acid does not act as a stimulus either to nerve or muscle.

PHYSIOLOGICAL AND ELECTRICAL STIMULI. 535

As a general rule, the stimulating solutions must be more concentrated when applied
- to a nerve than to muscle, in order that a contraction may be produced.

(Methods, —If a nerve-muscle preparation of a frog’s limb be made, and a straw flag (p. 472)
attached to the toes while the femur is fixed in a clamp, and its nerve be then dipped in a
saturated solution of common salt, the toes soon begin to twitch, and by and by the whole limb
becomes tetanic, and thus keeps the straw flag extended. The effect of fluid on a muscle or
nerve is easily tested by fixing the muscle in a 1 clamp, while a drop of the fluid is placed on a
greased surface, which gives it a convex form. The end of the muscle or nerve is then brought
into contact with the cupola of the drop (Kiihne). |

4. The Physiological or normal stimulus excites the nerves in the normal
intact body. Its nature is entirely unknown. The “nerve-motion” thereby set
up travels either in a “centrifugal” or outgoing direction from the central nervous
system, giving rise to motion, inhibition of motion, or secretion; or in a “ centri-
petal ” or ingoing direction from the specific end-organs of the nerves of the special
senses or the sensory nerves. In the latter case, the impulse reaches the central
organs, where it may excite sensation or perception, or it may be transferred to the
motor areas and be conducted in a centrifugal direction, constituting a “ reflex ”
stimulation (§ 360). A single physiological nerve-impulse travels more slowly than
that excited by the momentary application of an induction shock (Loven, v. Aries).
It is not a uniform process excited by varying intensity and greater or less frequency
of stimulation, but it is Pconaly a process varying considerably in duration, and
it may even last as long as } second (v. Aries).

5. Electrical Stimuli. ey The following forms of electrical stimuli may be
used :—

(1) A constant current, which may be made or broken (§ 328).
(2) Induction shocks, either make or break shocks (§ 329).
(3) An interrupted current (§ 329).

The electrical current acts most powerfully upon the nerves at the moment when
it is applied, and at the moment when it ceases (§ 336); in a similar way, any
increase or decrease in the strength of a constant current acts as a stimulus. If an
electrical current be applied to a nerve, and its strength be very gradually increased
or diminished, then the visible signs of stimulation of the nerve are very slight.
As a general rule, the stimulation is more energetic the more rapid the variations of
the strength of the current applied to the nerve, 7.¢., the more suddenly the
intensity of the stimulating current is increased or diminished (du Bots-Reymond).

An electrical current must have a certain strength or liminal intensity before it
is effective. By uniformly increasing the strength of the current, the size of the
contraction increases rapidly at first, “then more slowly (Zigerstedt and Willhard).

An electrical current, in order to vale a nerve, must have a certain duration,
it must act at least during 0:0015 second (fick, 1863); even with currents of
slightly longer duration, the opening shock may have no effect. If the duration of
the closing shock of a constant current be so arranged that it is just too short to
be active, “then it merely requires to last 1:3 to 2 times longer to produce ee most
complete effect (Grtinhagen).

The electrical current is most active when it flows in the long axis of the nerve ;
it is inactive when applied vertically to the axis of the nerve (Galvani). Similarly,
muscles are incomparably less excited by transverse than by longitudinal currents
(Giuffre).

The greater the length of nerve traversed by the current, the less the stimulus
that is required (Pfaf).

Constant Current.—If the constant current be used as a nervous stimulus, the
stimulating effect on the sensory nerves is most marked at the moment of making
and breaking the current ; during the time the current passes, only slight excite-
ment is perceived, but, even under these circumstances, very strong currents may
cause very considerable, and even. unbearable, sensations. . If a constant current be —

7

536 UNEQUAL EXCITABILITY.

applied to a motor nerve, the greatest effect is produced when the current is made
or closed [elosing or make contraction], and when it is broken or opened [opening
or break contraction]. But while the current is passing, the stimulation does not
cease completely, for, with a certain strength of stimulus, the muscle remains in a
state of tenanus (galvanotonus or “closing tetanus ”) (P/liger), For the same
effect on muscles, see p. 482. With strong currents this tetanus does not appear,
chiefly because the current diminishes the excitability of the nerves, and thus
develops resistance, which prevents the stimulus from reaching the muscle.
According to Hermann, a descending current applied to the nerve, at a distance
from the muscles, causes this tetanus more readily, while an ascending current
causes it more readily when the current is closed near the muscle. The constant
current is said by Griitzner to have no effect on vaso-motor and secretory fibres.

Over-maximal Contraction.—By gradually increasing the strength of the electrical stimulus
applied to a motor nerve, Fick observed that the muscular contractions (height of the lift) at
first increased proportionally to the increase of the stimulus, until a maximal contraction was
obtained. Ifthe strength of the stimulus be increased still further, another increase of the
contraction above the first reached maximum is obtained. This is called an ‘‘ over-maximal
contraction.” Occasionally between the first maximum and the second there is a diminution, or
indeed absence of, or gap or hiatus, in the contractions. The cause of this lies in the positive
pole, which with a certain strength of current is sufficient to prevent the further transmission
of the excitement (§ 335). On continuing to increase the induction current, ultimately a stage
is reached where the stimulation at the negative pole again becomes stronger than the inhibition
at the positive, and this overcomes the latter. The contractions before the gap are caused by
the occurrence of the induction current (their latent period is short); the contractions (long
latent period, like that after all opening shocks—Waller), after the gap, are caused by the
disappearance of the induction current, ¢.¢., by polarisation; this is added to the stimulation
proceeding from the negative pole, which after the gap overcomes the inhibition at the
positive pole, and excites the over-maximal contractions (TZ'igerstedt and Wilthard).

Tetanus.—If single shocks of short duration be rapidly applied after each other
to a nerve, tetanus in the corresponding muscle is produced (§ 298, III.).

A motor nerve has a greater specific excitability for electrical stimuli than the
muscle-substance. This is proved by the fact that, a feebler stimulus suffices to
excite a muscle when applied to the nerve than when it is applied to the muscle .
directly, as occurs when the terminations of the motor nerves are paralysed by
curara (Losenthal).

Soltmann found that the excitability of the motor nerves of new-born animals
for electrical stimuli is less than in adults. The excitability increases until the 5th
to 10th month. |

Unequal Excitability.— Under certain circumstances, the nearer the part of
the motor nerve stimulated lies to the central nervous system, the greater is the effect
produced (contraction) ; [or what is the same thing, the further the point of a nerve
which is stimulated is from the muscle, the stimulus being the same, the greater is
the contraction. This led Pfliiger to his “ avalanche-theory,” ¢.¢., that the ‘ nerve-
motion” increases in the nerve as it passes towards the muscles. This effect is
explained, however, by the unequal excitability of different parts of the same
nerve]. According to Fileischl, all parts of the nerve are equally excitable for
chemical stimuli. Further, it is said that the higher placed parts of a nerve are
more excitable only when the stimulating current passes in a descending direction;
the reverse is the case when the current ascends (Hermann). On stimulating a
sensory nerve, Rutherford and Hiillsten found that the reflex contraction was
greater, the nearer the stimulated point was to the central nervous system.

Unequal Excitability in the same Nerve.—Nerve-fibres, even when functionally
the same and included in the same nerve-trunk, are not all equally excitable. Thus,
feeble stimulation of the sciatic nerve of a frog causes contraction of the flexor
muscles, while it requires a stronger stimulus to produce contraction of the extensors
(Ritter, 1805, Follett). According to Ritter, the nerves for the flexors die first.

UNIPOLAR STIMULATION AND NORMAL NUTRITION. 537

Direct stimulation of the muscles in curarised animals shows that the flexors contract with a
feebler stimulus (but also fatigue sooner) than the extensors ; the pale muscles of the rabbit are
also more excitable than the red. Asarule, poisons affect the flexors sooner than the extensors.
In some muscles some pale fibres are present, and they are more excitable than the red
(Griitzner) (§ 298). If a frog’s nerve-muscle preparation be exposed to the action of ether,
on strong stimulation of the sciatic nerve, flexion oceurs (@riitzner, Bowditch), but, if the current
be made stronger, extension takes place. During deep ether-narcosis, strong stimulation of the
recurrent nerve causes dilatation, and with slight narcosis, narrowing of the glottis takes
place ; dilatation occurs on slight stimulation (Bowditch). The adductor muscle of the claw of a
crayfish is relaxed under a weak stimulus, but it contracts when a strong stimulus is applied
to it. The reversé is the case with the muscle which opens the claw (Biedermann).

Unipolar Stimulation.—If one electrode of an induction apparatus be applied
to a nerve, it may act as a stimulus. Du Bois-Reymond has called this ‘ unipolar
induction action.” Jt is due to the movement of the electrical current to and from
the free ends of the open induction current at the moment of induction. [ Unipolar
induction is more apt to occur with the opening than the closing shock, because
the former is more intense. |

Upon muscle, electrical stimuli act quite as they do upon nerves. Electrical
currents of very short duration have no effect upon muscles whose nerves are
paralysed by curara (Driicke), and the same is true of greatly fatigued muscles, or
muscles about to die or greatly weakened by diseased conditions (§ 399).

325. DIMINUTION OF THE EXCITABILITY—DEGENERATION AND
REGENERATION OF NERVES.—1. Normal Nutrition.—The continuance of
the normal excitability in the nerves of the body depends upon the maintenance of
the normal nutrition of the nerves themselves and a due supply of blood. Insuffi-
cient nutrition causes, in the first instance, increased excitability, and if the condi-
tion be continued the excitability is diminished (§ 339, I.).

When the physician meets with the signs of increased excitability of the nerves, under bad or
abnormal conditions of nutrition, this is to be regarded as the beginning of the stage of decrease
of the nerve-energy. Invigorating measures are required.

If the terminal nervous apparatus be subjected to a temporary disturbance of its
nutrition, the return of the normal nutritive process is heralded by a more or less
marked stage of excitement. The more excitable the nervous apparatus, the
shorter must be the duration of the disturbance of nutrition, eg., cutting off the
arterial blood supply or interfering with the respiration.

2. Fatigue.—Continued excessive stimulation of a nerve, without sufficient
intervals of repose, causes fatigue of the nerve, and by exhaustion rapidly
diminishes the excitability. A nerve is more slowly fatigued than a muscle
(Bernstein), but it recovers more slowly (§ 304). [Nerves of cold-blooded animals
( Widenskiz) and mammals (Bowditch) may be tetanised for hours without becoming
fatigued. |

[To show that a muscle is much more rapidly fatigued than a nerve, Bernstein arranged two
nerve-muscle preparations so that both nerves were tetanised simultaneously, but through one of
the nerves, a polarising constant current was passed by means of non-polarisable electrodes (§ 327),
so that the condition of anelectrotonus (§ 335) was set up in this nerve, and thus “blocked”
the propagation of impulses to the corresponding muscle. Only one muscle, therefore, was
tetanised. Both nerves were continuously stimulated until fatigue of the contracting muscle
took place, and on breaking the polarising current applied to the other nerve, the corresponding
muscle at once became tetanic. Now, as both nerves were equally stimulated, and the muscle
in connection with one nerve was fatigued, while the other muscle at once contracted, it is

evident that a muscle is much more rapidly fatigued than a motor nerve. In sensory nerves,
fatigue and recovery are analogous to the corresponding processes in motor nerves (Bernstein). ]

Recovery.—When a nerve recovers, at first it does so slowly, then more rapidly,
and afterwards again more slowly. If recovery does not occur within half an hour
after a frog’s nerve has been subjected to very long and intense stimulation, it will
not take place at all.

538 DEGENERATION OF NERVE-FIBRES.

3. Continued inaction of a nerve diminishes, and may ultimately abolish the
excitability.

Thus, the central ends of divided sensory nerves, after amputation of a limb, lose their
excitability, although the nerves are still connected with the central nervous system, because
the end-organs through which they were normally excited have been removed.

4. Separation from their Nerve-Centres.—The nerve-fibres remain in a con-
dition of normal nutrition, only when they are directly connected with their
centre, which governs the nutritive processes within the nerve. If a
nerve within the body be separated from its ‘‘ nutritive centre ”—either
by section of the nerve or compressing it—within a short time it loses its
excitability, and the peripheral end undergoes fatty degeneration, which
begins in four to six days in warm-blooded animals, and after a long
time in cold-blooded ones (Joh. Miiller). See also the changes of the
excitability during this condition, the so-called “Reaction of degener-
ation” (§ 339). If the sensory nerve-fibres of the root of a spinal nerve
be divided on the central side of the ganglion, the fibres on the peripheral
side do not degenerate, for thé ganglion is the trophic or nutritive centre

Fig. 377.

Degeneration and regeneration of nerves. A, sub-division of the myelin ; B, further disintegra-
tion thereof (osmic acid staining); C, interruption of the axial cylinder, which is
surrounded with the broken-up myelin ; D, accumulation of nuclei, with the remainder
of the myelin in a spindle-shaped fibre ; E, a new nerve-fibre, with a new sheath of
Schwann, sn, within the old sheath of Schwann, sw; F, a new nerve-fibre passing in a
curved course through an old nerve-fibre sheath.

for the sensory nerves; but the fibres still in connection with the cord degenerate
( Waller), 3

[Wallerian Law of Degeneration.—If a spinal nerve be divided, the peripheral. |

TRAUMATIC AND FATTY DEGENERATION. - 539

part of the nerve and its branches, including the sensory and motor fibres, degene-
rate completely (fig. 378, A), while the central parts of the nerve remain unaltered.
If the anterior root of a spinal nerve alone be divided before it joins the posterior
root, all the peripheral nerve-fibres connected with the anterior root degenerate
(fig. 378, B), so that in the nerve of distribution only the motor fibres degenerate.
The portion of the nerve-root which remains attached to the cord does not
degenerate. If the posterior root alone be divided, between the spinal cord and the
ganglion, the effect is reversed, the part of the nerve-root lying between the section
and the spinal cord degenerates, while the part of the nerve connected with the
ganglion does not degenerate (fig. 378, C). The central fibres degenerate because

A 8B C

uA

Fig. 378.

Diagram of the roots of a spinal nerve, showing the effect of section (the black y arts represent
the degenerated parts). A, section of the nerve-trunk beyond the ganglicn; B, of the
anterior root, and C, of the posterior; D, excision of the ganglion; a, anterior, »,
posterior root ; g, ganglion.

they are separated from the ganglion. If the ganglion be excised, or if separated,
as in fig. 378, D, both the central and peripheral parts of the posterior root
degenerate. These experiments of Waller show that the fibres of the anterior and
posterior rcots are governed by different centres of nutrition or ‘‘ trophic centres.”
As the anterior root degenerates when it is separated from the cord, and the
posterior when it is separated from its own ganglion, it is assumed that the trophic
centre for the fibres of the anterior root lies in the multipolar nerve-cells of the
anterior horn of the grey matter of the spinal cord, while that for the fibres of the
posterior root lies in the cells of the ganglion placed on it. The nature of this
supposed trophic influence is entirely unknown. |

Traumatic and Fatty Degeneration.—Both ends of the nerve at the point of section imme-
diately begin to undergo ‘‘ traumatic degeneration.” (In the frog on the 1st and 2nd day.)
After a time neither the myelin nor axis-cylinder is distinguishable (Schiff). According to
Engelmann, this condition extends only to the nearest node of Ranvier, and afterwards the so-
called ‘‘ fatty degeneration” begins. The process of ‘‘ fatty” degeneration begins simultane-
ously in the whole peripheral portion ; the white substance of Schwann breaks up into masses
(fig. 377, A), just as it does after death, in microscopic preparations; afterwards, the myelin
forms globules and round masses (B), the axial-cylinder is compressed or constricted, and is
ultimately broken across (C) in many places (7th day). The nerve-fibre seems to break up into
two substances—one fatty, the other proteid in constitution, the fat being absorbed (S. Mayer).
The nuclei of Schwann’s sheath swell up and proliferate (D—until the 10th day). According
to Ranvier, the nuclei of the interannular segments and their surrounding protoplasm
proliferate, and ultimately interrupt the continuity of the axis-cylinder and the myelin. They
then undergo considerable development with simultaneous disappearance of the medulla and
axis-cylinder, or at least fatty substances formed by their degeneration, so that the nerve-fibres
look like fibres of connective-tissue. [According to-this view, the process isin part an active
one, due to the growth of the nerve-corpuscles breaking up the contents of the neurilemma,
which then pltimately undergo chemical degenerative changes.] According to Ranvier,
Tizzoni, and others, leucocytes wander into the cut ends of the nerves, and also at Ranvier’s
nodes, insinuating themselves into the nerve-fibres, where they take myelin into their bodies,
and subject it to certain changes. [These cells are best revealed by the action of osmic acid,

which blackens any myelin particles in their interior.] Degeneration also takes place in the

540 TROPHIC CENTRES AND MODIFYING CONDITIONS.

motorial end-plates, beginning first in the non-medullated branches, then in the terminal 7. a
fibrils, and lastly in the nerve-trunks (Gessler). a ;
generation of Nerves.—In order that regeneration of a divided nerve may take place
(Cruickshank, 1795), the divided ends of the nerve must be brought into contact (§ 244), In
man this is done by means of sutures, About the middle of the fourth week, small clear
bands appear within the neurilemma, winding between the nuclei and the remains of the
myelin (E). They soon become wider, and receive myelin with incisures, and nodes, and a
sheath of Schwann (2nd to 3rd month—F). The regeneration process takes place in each
interannular segment, while the individual segments unite end to end at the nodes of Ranvier
($ $21, I., 5). On this view, each nerve-segment of the fibre corresponds to a ‘‘cell-unit”
(E. Neumann, Eichhorst). Thesame process oceurs in nerves ligatured in their course. Several
new fibres may be formed within one old nerve-sheath. The divided axis-cylinders of the
central end of the nerve begin to grow about the 14th day, until they meet the newly formed
ones, with which they unite. '

[Primary and Secondary Nerve Suture.—Numerous experiments on animals and man have
established the fact that, immediate or primary suture of a nerve, after it is divided, either
accidentally, or intentionally, hastens reunion and regeneration, and accelerates the restoration
of function. Secondary suture, z.c., bringing the ends together long after the nerve has been
divided, has been practised with success. Surgeons have recorded cases where the function
was restored after division had taken place for 3 to 16 months, and even longer, and in most
cases the sensibility was restored first, the average time being 2 to 4 weeks. Motion is
recovered much later. The ends of the nerve should be stitched to each other with catgut,
the muscles at the same time being kept from becoming atrophied by electrical stimulation and
the systematic use of massage (§ 307). After suture of a nerve, conductivity is restored in the
rabbit in 40 days, on the 31st in dogs, and 25th in fowls, but after simple division without
suture, not till the 60th day in the rabbit. Transplantation of nerve does not succeed (John-
son). }

Union of Nerves.—The central end of a divided motor nerve may unite with the peripheral
end of another, and still conduct impulses (Rava). [It is stated that sensory fibres will
reunite with sensory fibres, and motor fibres with motor fibres, and the regenerated
nerve will, in the former case, conduct sensory impulses, and the latter motor impulses,
There is very considerable diversity of opinion, however, as to the regeneration or union
of sensory with motor fibres. Paul Bert made the following experiment :—He stitched the
tail of a rat into the animal’s back, and after union had taken place, he cut the tail from the
body at the root, so that the tail, as it were, grew out of the animal’s back, broad end upper-
most. On irritating the end of the tail, which was formerly the root, the animal gave signs
of pain. This experiment was devised by Bert to try to show that nerve-fibres can conduct
impulses in both directions. One of two things must have occurred. Either the motor fibres,
which normally carried impulses down the tail, now convey them in the opposite direction,
and convey them to sensory fibres with which they have united ; or the sensory fibres, which
normally conducted impulses from the tip upwards, now carry them in the opposite direction.
If the former were actually what happened, it would show that nerve-fibres of different function
do unite (§ 349). Reichert asserts that he has succeeded in uniting the hypoglossal with the
vagus in the dog. According to Gessler the end-plate is the first to regenerate. ]

_ Trophic Centres.—The regeneration of the nerves seems to take place under the
influence of the nerve-centres, which act as their nutritive, or trophic centres.
Nerves permanently separated from these centres never regenerate.

During the regeneration of a mized nerve, sensibility is restored first, subsequently
voluntary motion, and lastly, the movements of the muscles, when their motor
nerves are stimulated directly (Schiff, Erb, v. Ziemssen).

_ Wallerian Method of Investigation.—As the peripheral end of a nerve undergoes degenera-
tion after section, we use this method for determining the course of nerve-fibres in a complex
arrangement of nerves. The course of special nerve-fibres may be ascertained by tracing the
degeneration tract (Wadler). If after section, reunion or regeneration of a motor nerve does
not take place, the muscle supplied by this nerve ultimately undergoes fatty degeneration.

_ 5. Modifying Conditions.—Under the action of various operations, e.g., compress-
ing a nerve [so as not absolutely to sever the physiological continuity], it has been
found that voluntary impulses or stimuli applied above the compressed spot, give
rise to impulses which are conducted through the nerve, and in the case of a motor
nerve, cause contraction of the muscles, whilst the excitability of the parts below
the injured spot is greatly diminished (Schif’). In a similar manner, it is found
that the nerves of animals poisoned with CO,, curara or coniin, sometimes even
the nerves of paralysed limbs in man, are not excitable to direct stimuli, while they

RITTER-VALLI LAW. AND ELECTRO-PHYSIOLOGY. 541

are capable of conducting impressions coming from the central nervous system
(Duchenne). The injured part of the nerve, therefore, loses its excitability sooner
than its power of conducting an impulse.

6. Certain poisons, such as veratrin, at first increase the excitability of the
nerves, and afterwards abolish it; with some other poisons, the abolition of
the excitability passes off very rapidly, e.g., curara. Conium, cynoglossum, iodide
of methylstrychnin, and iodide of ethylstrychnin have a similar action.

If the nerve or muscle of a frog be placed in a solution of the poison, we obtain a different
effect from that which results when the poison is injected into the body of the animal. Atropin
diminishes the excitability of a nerve-muscle preparation of the frog without causing any
previous increase, while alcohol, ether, and chloroform increase and then diminish the excita-
bility (Momsen).

7. Ritter-Valli Law.—If a nerve be separated from its centre, or if the centre
die, the excitability of the nerve is increased; the increase begins at the central
end, and travels towards the periphery—the excitability then fad/s until it disappears
entirely. This process takes place more rapidly in the central than in the peri-
pheral part of the nerve, so that the peripheral end of a nerve separated from its
centre remains excitable for a longer time than the central end.

The rapidity of the transmission of impulses in a nerve is increased when the excitability is
increased, but it is lessened when the excitability is diminished. In the latter condition, an
electrical stimulus must last longer in order to be effective ; hence rapid induction shocks may
not produce any effect.

The law of contraction also undergoes some modification in the different stages of the changes
of excitability (§ 336, II.).

8. Excitable Points.—Many nerves are more excitable at certain parts of their
course than at others, and the excitability may last longer at these parts. One of
these parts is the upper third of the sciatic nerve of a frog, just where a branch is
given off (Budge).

The motor and sensory fibres of the upper third of the sciatic nerve of a frog are more excit-
able for all stimuli than the lower parts (Griitzner and Elpon). Whether this arises from
injury during preparation, (a branch is given off there), or is due to anatomical conditions, ¢.4.,
more connective-tissue and more nodes in the lower part of the sciatic, is undetermined (Clara
Halperson).

This increased excitability may be due to injury to the nerve in preparing it for experiment.
After section or compression of a nerve, all electrical currents employed to stimulate the nerve
are far more active when the direction of the current passes away from the point of injury, than
when they pass in the opposite direction. This is due to the fact, that the current produced in
the nerve after the lesion is added to the stimulation current (§ 331, 5). Even in intact nerves
—sciatic of a frog—where the nerve ends at the periphery or at the centre, or where large
branches are given off, there are points which behave in the same way as those points where a
lesion has taken place (Griitzner and Moschner).

Death of a Nerve.—In a dead nerve the excitability is entirely abolished, death
taking place according to the Ritter-Valli Law, from the centre towards the
periphery. The reaction of a dead nerve has been found by some observers to be
acid (§ 322).

The functions of the brain cease immediately death takes place, while the vital functions of
the spinal cord, especially of the white matter, last for a short time; the large nerve-trunks
gradually die, then the nerves of the extensor muscles, those of the flexors after three to four
hours ; while the sympathetic fibres retain their excitability longest, those of the intestine even
for ten hours (Onimus). Compare § 295. The nerves of a dead frog may remain excitable for
several days, provided the animal be kept in a cool place.

Electro-Physiology.—Before beginning the study of electro-physiology, the
student ought to read and study carefully the following short preliminary remarks
on the physics of this question:— . |

326. PHYSICAL—THE GALVANIC CURRENT—RHEOCORD.—1. Electro-motive Force
—If two of the under-mentioned bodies be brought into direct contact, in one of them positive
electricity, and, in the other, negative electricity can be detected. The cause of this phenomenon
is the electro-motive.force. The electro-motive substances may be arranged in a series of the
first class, so that if the first-mentioned substance be brought into contact with any of the

542 OHM’S LAW, STRENGTH AND DENSITY OF GALVANIC CURRENTS.

other bodies, the first substance is negatively, the last positively, electrified. “This series is:
—carbon, platinum, gold, silver, copper, iron, tin, lead, zinc+.

The amount of the electro-motive force produced by the contact of two of these bodies is

greater, the further the bodies are apart in the series. The contact of the bodies may take place
at one or more points. If several of the bodies of this series be arranged in a pile, the electrical
tension thereby produced is just as great as if the two extreme bodies were brought into contact,
the intermediate ones being left out.

2. The nature of the two electricities is readily determined by placing one of the bodies of the
series in contact with a fluid. If zine be placed in pure or acidulated water, the zinc is+
(positive) and the water - (negative). If copper be taken instead of zinc, the copper is + but
the fluid—. Experiment shows that those metals, in contact with fluid, are negatively electri-
fied most strongly which are most acted on chemically by the fluid in which they are placed.
Each such combination affords a constant difference of tension or potential. The tension [or
power of overcoming resistance] of the amount of electricity obtained from both bodies depends
upon the size of the surfaces in contact. The fluids, e.g., the solutions of acids, alkalies, or salts
are called exciters of electricity of the second class, They do not form among themselves'a
definite series with different tensions. When placed in these fluids, the metals lying next the
+ end of the above series, especially zinc, are most strongly electrified negatively, and to a less
extent those lying nearer the — end of the series. .

3. Galvanic Battery.—If two different exciters of the first class be placed in fluid, without
the bodies coming into contact, e.g., zinc and eit ae the projecting end of the (negative) zinc
shows free negative electricity, while the free end of the (positive) copper shows free positive
electricity. Such a combination of two electro-motors of the first class with an electro-motor
of the second class is called a galvanic battery. As long as the two metals in this fluid are kept
separate, the circuit is said to be broken or open, but as soon as the free projecting ends of the
metals are connected outside the fluid, ¢.g., by a copper wire, the circuit or current is made
or closed, and a galvanic or constant current of electricity is obtained. The galvanic current
has resistance to encounter in its course, which is called ‘‘ conduction resistance” (W). It is
directly proportional—(1) to the length (7) of the circuit ; (2) and with the same length of
circuit, inversely as the section (q) of the same; and (3) it also depends on the molecular
properties of the conducting material (specific conduction resistance =s), so that the conduction
resistance, W=(s. 7): g. ‘The resistance to conduction increases with the increase of the
temperature of the metals, but diminishes under similar conditions with fluids.

Ohm’s Law.—The strength of a galvanic current (S), or the amount of electricity passing
through the closed circuit, is proportional to the electro-motive force (E)—-or the electrical
tension, but inversely proportional to the total resistance to conduction (L)—

So that S=E : L (Ohm’s Law, 1827).

The total resistance to conduction, however, in a closed circuit is composed of (1) the resist-
ance outside the battery (‘‘ extraordinary resistance ”) ; and (2) the resistance within the battery
itself (‘‘ essential resistance”). The specific resistance to conduction is very variable in different
substances : it is relatively small in metals (¢.g., for copper=1, iron=6'4, German silver=12),
but very great in fluids (e.g., for a concentrated solution of common salt 6,515,000, for a con-
centrated solution of copper sulphate 10,963,600).

Conduction in Animal Tissues.—It is also very great in animal tissues, almost a million
times greater than in metals. When a constant current is applied to the skin so as to traverse
the body, the resistance diminishes because of the conduction of water in the epidermis under
the action of the constant current (§ 290), and the congestion of the cutaneous blood-vessels in
consequence of the stimulation. But the resistance varies in different parts of the skin, the
least being in the palm of the hand and sole of the foot. The chief seat of the resistance is the
epidermis, for after its removal by means of a blister, the resistance is greatly diminished. Dead
tissue, as a rule, is a worse conductor than living tissues (Jol/y). When the current is passed
transversely to the direction of the fibres of a muscle, the resistance is nearly nine times as great
as when the current passes in the direction of the fibres—a condition which disappears in rigor
mortis (4ermann). In nerves, the resistance longitudinally is two and a half million times

greater than in mercury, transversely about twelve million times greater (Hermann). Tetanus —

and rigor mortis diminish the resistance in muscle (du Bois-Reymond).

Deductions.—It follows from Ohm’s law that—I. If there is very great resistance to the .

current outside the battery [7.¢., between the electrodes], as is the case when a nerve or a muscle
lies on the electrodes, the strength of the current can only be increased by increasing the
number of the electro-motive elements. II, When, however, the extraordinary resistance is
very small compared with that within the battery itself, the strength of the current cannot be
increased by increasing the number of the elements, but only by increasing the surfaces of the
plates in the battery. |
Strength and Density. —We must carefully distinguish the strength (intensity) of the current
from its density. As the same amount of electricity always flows through any given transverse

section of the circuit, then, if the size of the transverse section of the circuit varies, the elee-

\ :

RHEOCORD—GALVANOMETER. 543

tricity must be of greater density in the narrower parts, and it is evident that the density will
be less where the transverse section is greater. Let S=the strength of the current, and ¢ the
transverse section of the given part of the circuit, then the density (d) at the latter part is
d=S: ¢@.

If the galvanic current passing from the positive pole of a battery is divided into two or
more streams, which are again reunited at the other pole, then the sum of the strength of all
the streams is equal to the strength of the undivided stream. If, however, the different streams
are different as regards length, section, and material, then the strength of the current passing
in each of the streams is inversely proportional to the resistance to the conduction.

Du Bois-Reymond’s Rheocord.—This instrument, constructed on the principle of the
‘secondary ” or ‘short circuit,” enables us to graduate the strength of a galvanic current to
any required degree, for the stimulation of nerve and muscle.
From the two poles (fig. 379, a, 6) of a constant battery, there
are two conducting wires (a, ¢ and d, 6), which go to the
nerve of a frog’s nerve-muscle preparation (F). The portion
of nerve (c, d) introduced into this circuit (a, c, d, 0) offers
very great resistance. The second stream or secondary circuit °
(a A, b B) conducted from a@ and 6 passes through a thick
brass plate (A, B), consisting of seven pieces of brass (1 to 7)
placed end to end, but not in contact. They can all, with
the exception of 1 and 2, be made to form a continuous
conductor by placing in the spaces between them the brass
plugs (S, to S;). Evidently, with the arrangement shown
in fig. 879, only a minimal part of the current will pass
‘through the nerve (c, d), owing to the very great resistance
in it, while by far the greatest part will pass through the |
good conducting medium of brass(A, L, B). If new resist- | | 1
ance be introduced into this circuit, then the a, c, d, D
stream will be strengthened.” This resistance can be intro- |;
duced into the latter circuit by means of the thin wires 4 [b Ic
marked Ia, 1b, Ic, Il, V,X. Suppose all the brass plugs;
from S, to S,; to be removed, then the current entering at
A must traverse the whole system of thin wires. Thus,
there is more resistance to the passage of this current, so
that the current through the nerve must be strengthened.

t S2 Ss
Werle leereall ees

If only one brass plug be taken out, then the current passes
through only the corresponding length of wire. The resist-
ances offered by the different lengths of wire from I a to |: ti
X are so arranged that I a, I b, and Ic each represents a
unit of resistance; II, double; V, five times; and X, ten la
times the resistance. The length of wire, I @, can also be
shortened by the movable bridge (L) [composed of a small ¥!: eins L Hl | i
tube filled with mercury, through which the wires pass], G2 y b Shs
the scale (a, y) indicating the length of the resistance wires. Fig. 379
It is evident that, by means of the bridge, and by the , See ,
method of using the brass plugs, the apparatus can be Scheme of du Bois-Reymond’s
graduated to yield very variable currents for stimulating rheocord,
nerve or muscle. When the bridge (L) is pushed hard up to 1 and 2, the current passes
directly from A to B, and not through the thin wires (I @).

The rheostat is another instrument used to vary the resistance of a galvanic current
( Wheatstone).

32'7. ACTION OF THE GALVANIC CURRENT ON A MAGNETIC NEEDLE—GAL-
VANOMETER. —In 1820, Oerstedt of Copenhagen found that a magnetic needle, suspended in
the magnetic meridian, was deflected by a constant current of electricity passed along a wire
parallel to it. [The side to which the north pole is deflected depends upon the direction of the
current, and whether it passes above or below the needle. ]

Ampére’s Rule.—Ampére has given a simple rule for determining the direction. If an
observer be placed parallel to and facing the needle, and if the current be passing from his feet
to his head, then the north pole of the needle will always be deflected to the /¢ft, and the south
pole in the opposite direction. The effect exerted by the constant current acts always in a
direction towards the so-called electro-magnetic plane. The latter is the plane passing through
the north pole of the needle, and two points in the straight wire running parallel with the
needle. The force of the constant current, which causes the deflection of the magnetic needle,
is proportional to the sine of the angle between the electro-magnetic plane and the plane of
vibration of the needle.

Multiplicator.—The deflection of the needle caused by the constant current may be increased

544 GALVANOMETER.

by coiling the conducting wire many times in the same direction on a rectangular frame,
or merely around and in the same direction as the needle, [provided that each turn
of the wire be properly insulated from the other]. An instrument constructed on this
principle is sailed a multiplicator or multiplier. The greater the number of turns of the d
wire, the greater is the angle of deflection of the needle, although the deflection is not directly
proportional, as the several turns or coils are not at the same distance from, or in the same
position as, the needle. By means of the multiplier we may detect the presence [and also the
amount and direction] of feeble currents. [The instrument is now termed a galvanometer. }
Experience has shown that, when great resistance, (as in animal tissues), is opposed to the weak
galvanic currents, we must use a very large number of turns of thin wire roun the needle. If,
however, the resistance in the circuit is but small, e.g., in thermo-electrical arrangements, a few
turns of a thick wire round the needle are sufficient. The multiplier may be made more sensitive
by weakening the magnetic directive force of the needle, which keeps it pointing to the north.
“Galvanometer and Astatic Needles.—In the multiplier of Schweigger, used for physiological
purposes, the tendency of the needle to point to the north is greatly weakened by using the
astatic needles of Nobili. [A multiplier
or galvanometer with a single magnetic
needle always requires comparatively
strong currents to deflect the needle.
The needle is continually acted upon by
the directive magnetic influence of the
earth, which tends to keep it in the
magnetic meridian, and, as soon as it is
moved out of the magnetic meridian,
the directive action of the earth tends
to bring it back. Hence, such a simple
form of galvanometer is not sufficiently
sensitive for detecting feeble currents.
In 1827, Nobili devised an astatic com-
bination of needles, whereby the action
of the earth’s magnetism was dimin- ,
ished.] Two similar magnetic needles —
are united by a solid light piece of horn
[or tortoise shell], and are so arranged
that the north pole of the one is placed
over or opposite to the south pole of the
other (fig. 380). [If both needles are
equally magnetised, then the earth's
influence on the needle is neutralised,
so that the needles no longer adjust
themselves in the magnetic meridian ;
hence, such a system is called astatic. ]
Fig. 380. As it is impossible to make both needles

Te RAT ore ; Pee is of absolutely equal magnetic strength,
Scheme of the galvanometer. N, N, astatic needles 914 needle js always stronger than the

suspended by the silk fibre, G; P, P, non-polaris- oino, The difference, however, must
able electrodes, containing zinc sulphate solution, 15+ be so great that ike stronger neadle
s, and pads of blotting paper, 6, covered with clay, points to the north, but only that the

t, t, on which the muscle, M, is placed; II and III, ;
arrangement of the muscle on the electrodes; IV, palate ee Ve the caaaraealaaie

non-polarisable electrodes; Z, zinc wire; K, cork; siqian into which position the system

a, zinc sulphate solution ; ¢, ¢, clay points. always swings after it is deflected from
this position. This angular deviation of the astatic system towards the magnetic meridian is
called the ‘‘ free deviation.” The more perfectly an astatic condition is reached, the nearer does
the angle formed by the direction of the free deviation with the magnetic meridian become a
right angle. The greater, therefore, the astatic condition, the fewer vibrations will the astatic
system make in a given time, after it has been deflected from its position. The duration of
each single vibration is also very great. [Hence, when using a galvanometer, and adjusting its
needle to zero, if the magnets dance about or move quickly, then the system is not sensitive,
but a sensitive condition of the needles is indicated by a slow period of oscillation. ]

In making a galvanometer, the turns of the wire must have the same direction as the needles.
In Nobili’s galvanometer, as improved by du Bois-Reymond, the upper needle swings above a
card divided into degrees (fig. 380), on which the extent of its deflection may be read off. Even
the purest copper wire used for the coils round the needles always contains a trace of iron, which
exerts an influence upon the needles. Hence, a small fixed directive or compensatory et
(r) = evs pat one of the poles of the upper needle to compensate for the action of the iron
on the needles. ;

ELECTROLYSIS, POLARISATION, BATTERIES. . 545

328. ELECTROLYSIS, POLARISATION, BATTERIES. —Electrolysis.—Every galvanic
current which traverses a fluid conductor causes decomposition or electrolysis of the fluid. The
decomposition-products, called “ions,” accumulate at the poles (electrodes) in the fluid, the
positive pole (+ ) being called the anode [avd, up, 65ds, a way], the negative pole (— ) the cathode
(xard, down, 65ss, a way). The anions accumulate at the anode and the kations at the
cathode.

Transition Resistance.—When the decomposition-products accumulate upon the electrodes,
by their presence they either increase or diminish the resistance to the electrical current. This
is called transition resistance. Ifthe resistance within the battery is thereby increased, the
transition resistance is said to be positive; if diminished, negative.

Galvanic Polarisation.—The ions accumulated on the electrodes may also vary the strength
of the current, by developing between the anions and kations a new galvanic current, just as
occurs between two different bodies connected by a fluid medium. This phenomenon is called
galvanic polarisation. Thus, when water is decomposed, the electrodes being of platinum, the
oxygen (negative) accumulates at the + pole, and the hydrogen (positive) at the — pole. Usually
the polarisation current has a direction opposite to the original current; hence, we speak of
negative polarisation. When the two currents have the same direction, positive polarisation ob-
tains. Of course, transition resistance and polarisation may occur together during electrolysis.

Test.—Polarisation, when present, may be so slight as not to be visible to the eye, but it
may be detected thus :—After a time exclude the pri-
mary source of the current, especially the element con-
nected with the electrodes, and place the free projecting
end of the electrodes in connection with a galvano-
meter, which will at once indicate, by the deflection
of its needle, the presence of even the slightest polarisa-
tion.

Secondary Decompositions.—The ions excreted dur-
ing electrolysis cause, especially at their moment of
formation, secondary decompositions. With platinum
electrodes in a solution of common salt, chlorine ac-
cumulates at the anode and sodium at the cathode, but
the latter at once decomposes the water, and uses the
oxygen of the water to oxidise itself, while the hydro-
gen is deposited secondarily upon the cathode. The
amount of polarisation increases, although only to a
slight extent, with the strength of the current, while
it is nearly proportional to the increase of the tempera-
ture. The attempts to get rid of polarisation, which
obviously must very soon alter the strength of the
galvanic current, have led to the discovery of two im-
portant arrangements, viz., the construction of constant
galvanic batteries, and non-polarisable electrodes (du
Bois-Reymond).

Constant Batteries, Elements, or Cells.—A perfectly |
constant element produces f constant current, 7.é., one
remaining of equal strength, by the ions produced by :
the electrodes being got an of the mene they med Hg. ash:
formed, so that they cannot give rise to polarisation. Large Grove’s cell.

For this purpose, each of the substances from the tension series used is placed in a special
fluid (§ 326), both fluids being separated by a porous septum (porcelain cylinder).

Grove’s cell has two metals and two fluids (fig. 381). The zinc is in the form of a roll placed in
dilute sulphuric acid [1 acid to 7 of water, which is contained in a glass, porcelain, or ebonite vessel].
The platinum is in contact with strong nitric acid, [which is contained in a porous cell placed
inside the roll of zinc]. The O, formed by the electrolysis and deposited on the zinc plate, forms

‘zinc oxide, which is at once dissolved by the sulphuric acid. The hydrogen on the platinum
unites at once with the nitric acid, which gives up O and forms nitrous acid and water, thus—

[Platinum is the + pole, and zinc the — .]

[Grove’s battery is very powerful, but the nitrous fumes are very disagreeable and irritatin z;
hence these elements should be kept in a special well-ventilated recess in the laboratory, in an
evaporating chamber, or under glass. The fumies also attack instruments. ]

Bunsen’s cell is similar to Grove’s, only a piece of compressed carbon is substituted for the
platinum in contact with the nitric acid. '

[The carbon is the + pole, the zine the - .]

[Daniell’s cell consists of an outer vessel of glass or earthenware, and sometimes of metallic

2M

546 DANIELL, SMEE, GRENNET, AND LECLANCHE’S ELEMENT.

copper, filled with a saturated solution of cupric sulphate (fig. 382). A roll of copper, perforated
with a few holes, is placed in the copper solution, and in order that the latter be kept satwrated,
and to supply the place of the ad used up by the battery when in
action, there is a small shelf on the copper roll, on which are placed
crystals of cupric sulphate. A porous earthenware vessel containing
zine in contact with dilute sulphuric acid (1 : 7) is placed within the
copper cylinder. When the circuit is completed, the zinc is acted on,
(ml zine sulphate being formed, and hydrogen liberated. The hydrogen in
| statu nascendi passes through the porous cell, reduces the cupric sulphate
| to metallic copper, which is precipitated on the copper cylinder, so that
|K the latter is always kept bright and clean. The liberated sulphuric
SoS acid replaces that in contact with the zinc. Owing to the absence of
‘Guu polarisation, the Daniell is one of the most constant batteries, and is
SCTTTTTT mm cenerally taken as the standard of comparison. ]
Fig. 382. [The copper is the + pole, zine the — .]
Daniel's cell. [Smee’s cell contains only one fluid, viz., dilute sulphuric acid
(1: 7), in which the two metals, zinc and platinum, or zinc and platinised silver, are placed.
The platinum is the + pole, and zinc the — .]

[Grennet’s or the Bichromate cell consists of one plate of zinc and two plates of compressed
carbon in a fluid, containing bichromate of potash, sulphuric acid, and water. The fluid con-
sists of 1 part of potassium bichromate ™»
dissolved in 8 parts of water, to which |
one part of sulphuric acid is added. —|
Measure by weight. The cell consists
of a wide-mouthed glass bottle (fig.

J
——
et
INI ke |
INE)

Mm a

= C Ss -

i Hl HH | i
wt | | i
at ipa

Fig. 383. Fig, 384,
Fig. 383.—Grennet’s cell. A, glass vessel; K, K, carbon; Z, zinc; D, E, binding screws for
the wires; B, rod to raise the zine from the fluid; C, screw to fix B. "trig. 384,—
Leclanché’s cell. A, outer vessel ; T, porous cylinder, containing K, carbon; B,. binding
screw ; Z, zine; C, binding screw of negative pole. :

383); the carbons remain in the fluid, while the zine can be raised or depressed. When
not in action, the zinc, which is attached to a rod (B), is lifted out of the fluid. It is not a

very constant battery. When in action, the zinc is acted on by the sulphuric acid, hydrogen —
; ‘¢

being liberated, which reduces the hichromate of potash.
The carbon is the + pole, and the zinc the — .]

[Leclanché’s cell (fig. 384) consists of an outer glass vessel containing zinc in a solution of

REFLECTING GALVANOMETER AND SHUNT. . 547

ammonium chloride, while the porous cell contains compressed carbon in a fluid mixture of
_ black oxide of manganese and carbon. It is most frequently used for electric bells, as its feeble
current lasts for a long time.

The carbon is the + pole, and the zinc the — .]

Fig. 385 Fig. 386.
Fig. 385.—Non-polarisable electrode of du Bois-Reymond, Z, zinc; H, movable support ; C,
clay point—the whole on a universal joint. Fig. 386.—Brush electrodes of v. Fleischl.

nerve or muscle, by means of ordinary electrodes composed either of copper or platinum, of
course electrolysis must occur, and in consequence thereof

polarisation takes place. In order to avoid this, non-polaris-
able electrodes (figs. 380, 38%) are used. Such electrodes are
made by taking two pieces of carefully amalgamated, pure,
zinc wire (z, 2), and dipping these in a saturated solution of
zinc sulphate contained in tubes (a, w), whose lower ends are
closed by means of modeller’s clay (¢, ¢), moistened with 0°6
per cent. normal saline solution. The contact of the tissues
with these electrodes does not give rise to polarity. [The
brush electrodes of v. Fleisch] are very serviceable (fig. 386).
The lower end of the glass tube is plugged with a camel-hair
pencil, moistened with modeller’s clay, otherwise the arrange-
ment is the same as shown in fig. 380, IV.]

Arrangement for the Muscle- or Nerve-Current.—In order
to investigate the electrical currents of nerve or muscle, the
tissue must be placed on non-polarisable electrodes, which may
either be one of the forms described above, or the original form
used by du Bois-Reymond (fig. 380). The last consists of two
zinc troughs (p, p) thoroughly amalgamated inside, insulated on
vulcanite, and filled with a saturated solution of zinc sulphate
(s, s). In each trough is placed a thick pad or cushion of
white blotting paper (0, b) saturated with the same fluid [de-
riving cushions]. [The cushion consists of many layers, almost
sufficient to fill the trough, and they are kept together by a
thread. ‘To prevent the action of the zine sulphate upon the
tissue, each cushion is covered. with a thin layer of modeller’s
clay (¢, ¢), moistened with 0°6 per cent. saline solution, which
is a good conductor [clay guard]. The clay guard prevents
the action of the solution upon the tissue. Connected with
the electrodes are a pair of binding screws, whereby the appa-
ratus is connected with the galvanometer (fig. 380).

[Reflecting Galvanometer.—The form of galvanometer,
used in this country for physiological purposes, is that of Sir
William Thomson (fig. 387). In Germany, Wiedemann’s form
is more commonly used. In Thomson’s instrument, the

Fig. 387.

astatic needles are very light, and connected to each other Thomson’s reflecting galvano-

by a piece of aluminium, and each set of needles is surrounded Meter. «, upper, Z, lower coil ;
by a separate coil of wire, the lower coil (7) winding in a * %, levelling screws ; ™m, mag-
direction opposite to that of the upper (w). A small, round, net, on a brass support, 0.

light, slightly concave mirror is fixed to the upper set of needles. The needles are sus-
pended by a delicate silk fibril, and they can be raised or lowered as required by means of a

548 . REFLECTING GALVANOMETER AND SHUNT.

small milled head. When the milled head is raised, the system of needles swings freely.
The coils are protected by a glass shade, and the whole stands on a vulcanite base, which
is levelled by three screws (s, 8). On a brass rod (db) is a feeble magnet (m), which is used to
give an artificial meridian. The magnet (m) can be raised or lowered by means of a milled
head. ]

(Lamp and Scale.—When the instrument is to be used, place it so that the coils face east and

west. At 3 feet distant from the front of the galvanometer, facing west, is placed the lamp and .

scale (fig. 888). There is a small vertical slit in front of the lamp, and the image of this slit is
projected on the mirror attached to the upper needles, and by it
is reflected on to the paper scale fixed just above the slit. The

spot of light is focussed at zero by means of the magnet, m.
» The needles are most sensitive when the oscillations occur
slowly. The sensitiveness of the needles can be regulated by
means of the magnet. In every case the instrument must be
quite level, and for this purpose there is a small spirit-level in
the base of the galvanometer. ]

(Shunt.—As the galvanometer is very delicate, it is con-
venient to have a shunt to regulate to a certain extent the
amount of electricity transmitted through the galvanometer.
The shunt (fig. 389) consists of a brass box containing coils of
German silver wire, and is constructed on the same principle as
resistance coils or the rheocord (§ 326). On the upper surface
of the box are several plates of brass separated from each other,
Fi like those of the rheocord, but which can be united by brass

ip. o8e lugs. The two wires coming from the electrod ted

,_ plugs. 1e two wires coming from the electrodes are connecte
Lamp and scale for Thomson’s \ ith the two binding screws, and from the latter two wires are
galvanometer, led to the outer two binding screws of the galvanometer. By
placing a plug between the brass plates attached to the two binding screws in the figure, the
current is short-circuited. On removing both plugs, the whole of the current must pass
through the galvanometer. If one plug be placed between the central disc of brass and the
plate marked }, (the other being left out), then ;,th of the current goes through the galvano-
meter and ,°,ths to the electrodes. If the plug be placed as shown in
the figure opposite ;'5, then ;ijth part of the current goes to the gal-
vanometer, while ;°°,ths are short-circuited. If the plug be placed
ee abo, Only yj'55th part goes through the galvanometer. ]
ternal Polarisation of Moist Bodies.—Nerves and muscular fibres,
the juicy parts of vegetables and animals, fibrin, and other similar bodies
possessing a porous structure filled with fluid, exhibit the phenomena of
polarisation when subjected to strong currents—a condition termed
internal polarisation of moist bodies by du Bois-Reymond. It is assumed
that the solid parts in the interior of these bodies which are better
conductors, produce electrolysis of the adjoining fluid, just like metals
in contact with fluid. The ions produced by the decomposition of the
@ internal fluids give rise to differences of potential, and thus cause in-
ternal polarisation (§ 333).

Cataphoric Action.—If the two electrodes from a galvanic battery

be placed in the two compartments of a fluid, separated from each other

Fig. 389. by a porous septum, we observe that the fluid particles pass in the
Shunt for galvano- direction of the galvanic current, from the + to the — pole, so that
meter. after some time, the fluid in the one half of the vessel increases, while it

diminishes in the other. The phenomena of direct transference were
called by du Bois-Reymond the cataphoric action of the constant current. The introduction of
dissolved substances through the skin by means of a constant current depends upon this action
(§ 290), and so does the so-called Porret’s phenomenon in living muscle (§ 293, I., 5).

External Secondary Resistance.—This condition also depends on cataphoric action. If the
oe electrodes of a constant battery be placed in a vessel filled with a solution of cupric
su phate, and from each electrode there project a cushion saturated with this fluid, then, on
placing a piece of muscle, cartilage, vegetable tissue, or even a prismatic strip of coagulated
albumin across these cushions, we observe that, very soon after the circuit is closed, there is
a considerable variation of the current. If the direction of the current be reversed, it first
becomes stronger, but afterwards diminishes. By constantly altering the direction of the
current we cause the same changes in the intensity. Ifa prismatic strip of co ted albumin
be used for the experiment, we observe that, simultaneously with the enfeeblement of the
current in the neighbourhood of the + pole, the albumin loses water and becomes more
shrivelled, while at the — pole the albumin is swollen up and contains more water. If the
direction of the current be altered, the phenomena are also changed. The shrivelling and
removal of water in the albumin at the positive pole must be the cause of the resistance in the

INDUCED OR FARADIC ELECTRICITY. 549

circuit, which explains the enfeeblement of the galvanic current. This phenomenon is called
‘*external secondary resistance ” (du Bots-Reymond).

329, INDUCTION—EXTRA-CURRENT—MAGNETIC-INDUCTION.—Induction of the
Extra-Current.—If a galvanic element is closed by means of a short arc of wire, at the moment
the circuit is again opened or broken, a slight spark is observed. If, however, the circuit is
made or closed by means of a very long wire rolled in a coil, then on breaking the circuit there
is a strong spark. If the wires be connected with two electrodes, so that a person can hold one
in each hand, the current at the moment it is opened must pass through the person’s body,
then there is a violent shock communicated to the hand. This phenomenon is due to a current
induced in the long spiral of wire which Faraday called the extra-current. It is caused thus :
—When the circuit is closed by means of the spiral wire, the galvanic current passing along it
excites an electric current in the adjoining coils of the same spiral. At the moment of closing
or making the circuit in the spiral, the induced current is in the opposite direction to the
galvanic current in the circuit ; hence its strength is lessened, and it causes no shock. At
the moment of opening, however, the induced current has the same direction as the galvanic
stream, and hence its action is strengthened.

Magnetisation of Iron.—If a rod of soft iron be placed in the cavity of a spiral of copper
wire, then the soft iron remains magnetic as long as a galvanic current circulates in the
spiral. If one end of the iron rod be directed towards the observer, and the other away from
him, and if, further, the positive current traverse the spiral in the same direction as the
hands of a clock, then the end of the magnet directed towards the person is the negative pole
of the magnet. The power of the magnet depends upon the number of spiral windings, and on
the thickness of the iron bar. Assoon as the current is opened, the magnetism of the iron
rod disappears.

Induced or Faradic Current.—If a very long, insulated, wire be coiled into the form ofa
spiral roll, which we may call the secondary spiral, and if a similar spiral, the primary spiral,
be placed near the former, and the ends of the wire of the primary spiral be connected with
the poles of a constant battery, every time the current in the primary circuit is made (closed),
or broken (opened), a current takes place, or, as it is said, is induced in the secondary spiral.
If the primary circuit be kept closed, and if the secondary spiral be brought nearer to, or
removed further from, the primary spiral, a current is also induced in the secondary spiral
(Faraday, 1832). The current in the secondary circuit is called the induced or Faradic
current. When the primary circuit is closed, or when the two spirals are brought nearer to
each other, the current in the secondary spiral has a direction opposite to that in the primary
spiral, while the current produced by opening the primary circuit, or by removing the spirals
further apart, has the same direction as the primary. During the time the primary circuit is
closed, or when both spirals remain at the same distance from each other, there is no current in
the secondary spiral.

Difference between the Opening [break] and Closing [make] Shocks. —The opening and closing
shocks in the secondary spiral are distinguished from each other in the following respects (fig.
390) :—The amount of electricity is the same, during the opening, as during the closing shock,
but during the opening shock, the electricity rapidly reaches its maximum of intensity and
lasts but a short time, while during the closing shock, it gradually increases, but does not
reach the high maximum, and this occurs more slowly. [In fig. 390, P, and S, are the abscisse
of the primary (inducing) and induced currents respectively. The: vertical lines or ordinates
represent the intensity of the current, while the length of the abscissa indicates its duration.
Curve 1 indicates the course of the primary current, and 2, that in the secondary spiral
(induced) when the current is closed, while at I the primary current is suddenly opened, when
it gives rise to the induced current, 4, in the secondary spiral.] The cause of the difference is
the following :—When the primary circuit is closed, there is developed in it the extra-current,
which is opposite in direction to the primary current. Hence, it opposes considerable resistance
to the complete development of the strength of the primary current, so that the current, induced
in the secondary spiral must also develop slowly. But when the primary spiral is opened, the
extra-current in the latter has the same direction as the primary current—there is no extra
resistance. The rapid and intense action of the opening induction shock is of great physio-
logical importance.

Break or Opening Shock.--[On applying a single induction shock to a nerve or a muscle, the
effect is greater with the break or opening shock. If the secondary spiral be separated from the
primary, so that the induced currents are not sufficient to cause contraction of a muscle when
applied to its motor nerve, then, on gradually approximating the secondary to the primary
spiral, the break or opening shock will cause-a contraction before the closing one does so.] ©

Helmholtz’s Modification, —Under certain circumstances, it is desirable to equalise the make
and break shocks. This may be done by greatly weakening the extra-current, which may be
accomplished by making the primary spiral of only a few coils of wire. V. Helmholtz
accomplishes the same result by introducing a secondary circuit into the primary current. By
this arrangement the current in the primary spiral never completely disappears, but by

550 . UNIPOLAR INDUCTION.

alternately making and breaking this secondary circuit where the resistance is much less, it is
alternately weakened and strengthened. Jem ,

{In fig. 391 a wire is introduced between @ and f, while the binding screw, J, is separated
from the platinum contact, c, of Neef’s hammer, but, at the same time the screw, d, is raised so
that it touches Neef’s hammer. The current passes from the battery, K, through the pillar, a,

I»

i es .

Fig. 390. Fig. 391.

Fig. 390.—Scheme of the induced currents. Fis abscissa of the primary, and S,, of the secondary
current; A, beginning, and E, end of the inducing current; 1, curve of the primary
current weakened by the extra-current ; 3, where the primary current is opened; 2 and 4,
corresponding currents induced in the secondary spiral; P,, height, i.¢., the strength of
the constant inducing current; 5 and 7, the curve of the inducing current when it is
opened and closed during Helmholtz’s modification ; 6 and 8, the corresponding currents
induced in the secondary circuit. Fig. 391.—Helmholtz’s modification of Neef’s hammer.
As long as cis not in contact with d, yh remains magnetic ; thus c is attracted to d and
a secondary circuit, a, b, c, d, ¢ is formed; ¢ then springs back again, and thus the process
goes on. A new wire is introduced to connect a with 7K, battery.

to f in the direction of the arrow, through the primary spiral, P, to the coil of soft wire, g, and
back to the battery, through A and e. But gis magnetised thereby, and when it is so, it attracts
c and makes it touch the screw d. Thus a secondary circuit, or short circuit, is formed through
a, b, c, d, e, which weakens the current passing through the electro-magnet, g, so that the
elastic metallic spring flies up again and the current through the primary spiral is long-cireuited,
and thus the process is repeated. In fig. 390 the lines 1 and 7 indicate the course of the current
in the primary circuit at closing (a), and opening (¢). It must be remembered that in this
arrangement there is always a current passing through the primary spiral, P (fig. 391). The
dotted lines, 6 and 8, above and below S,, represent the course of the opening (a) and closing
shocks (c) in the secondary spiral. Even with this arrangement the opening is still slightly
stronger than the closing shock.] The two shocks, however, may be completely equalised by
slacing a resistance coil or rheostat in the short circuit, which increases the resistance, and thus
increases the current through the primary spiral when the short circuit is closed.

Unipolar Induction.—When there is a very rapid current in the primary spiral, not only is
there a current induced in the secondary spiral, when its free ends are closed, ¢.g., by being
connected with an animal tissue, but there is also a current when one wire is attached to a
binding screw connected with one end of the wire of the secondary spiral (p. 537), A muscle
of a frog’s leg, when connected with this wire, contracts, and this is called a unipolar induced
contraction. It usually occurs when the primary circuit is opened. The occurrence of these
contractions is favoured, when the other end of the spiral is placed in connection with the
ground, and when the frog’s muscle preparation is not completely insulated.

Magneto-Induction.—If a magnet be brought near to, or thrust into the interior of, a coil of
wire, it excites a current, and also when a piece of soft iron is suddenly rendered magnetic or
suddenly demagnetised. The direction of the current so induced in the spiral is exactly the
same as that with Faradic electricity, i.¢., the occurrence of the magnetism, on approximating
the A ag to a magnet, excites an induced current in a direction opposite to that supposed to
circulate in the magnet. Conversely, the demagnetisation, or the removal of the spiral from
the magnet, causes a current in the same direction. *

Acoustic Tetanus.—If a magnet be rapidly moved to and fro near a spiral, which can easily
be done by fixing a vibrating magnetic rod at one end and allowing the other end to swing

freely near the spiral, then the pitch of the note of the vibrating rod gives us the rapidity of the _
induction shocks. Ifa frog’s nerve-muscle preparation be stimulated, we get what Grossmann a

called ‘‘ acoustic tetanus.”

|
;
‘
:

DU BOIS-REYMOND’S INDUCTORIUM. 551

. 330. DU BOIS-REYMOND’S INDUCTORIUM—MAGNETO-INDUCTION APPARATUS. —
The inductorium of du Bois-Reymond, which is used for physiological purposes, is a modification
of the magneto-electromotor apparatus of Wagner and Neef. A scheme of the apparatus is
given in fig. 392. D represents the galvanic battery. The wire from the positive pole, a, passes
to a metallic column, S, which has a horizontal vibrating spring, F, attached to its upper end.
To the outer end of the spring a square piece of iron, ¢, is attached. The middle point of the
upper surface of the spring [covered with a little piece of platinum] is in contact with a movable
screw, 6. A moderately thick copper wire, c, passes from the screw, 0, to the primary spiral
or coil, x, x, which contains in its interior a number of pieces of soft iron wire, 7, 7, covered
with an insulating varnish. The copper wire which surrounds the primary spiral is covered
with silk. The wire, d, is continued from the primary spiral to a horse-shoe piece of soft iron,
H, around which it is coiled spirally, and from thence it proceeds, at f, back to the negative
pole of the battery, g. When the current in this circuit—called the primary circuit—is closed,
the following effects are produced :—The horse-shoe, H, becomes magnetic, in consequence of
which it attracts the movable spring or Neef’s hammer, e, whereby the contact of the spring,
F, with the screw, b, is broken. Thus the current is broken, the horse-shoe is demagnetised,
the spring, ¢, is liberated, and, being elastic, it springs upwards again to its original position in
contact with 6, and thus the current is re-established. The new contact causes H to be
remagnetised, so that it must alternately rapidly attract and liberate the spring, e, whereby the
primary current is rapidly made and broken between F and 0.

I

||
—)
—

. Fig. 392.

I, Scheme of du Bois-Reymond’s sledge induction machine. D, galvanic battery; a, wire
from + pole, (g) — pole; S, brass upright; F, elastic spring; 0, binding screw; ¢, wire
round primary spiral (#, x), containing (7, 7) soft iron wire; K, K, secondary spiral, with
board (p, p) on which it can be moved ; H, soft iron magnetised by current (d, /) passing
round it. II, key for secondary circuit, as shown it is short-circuited. III, electrodes
(r, r), with a key (K) for breaking the circuit.

A secondary spiral or coil (K, K) is placed in the same direction as the primary (x, x), but
having no connection with it. It moves in grooves upon a long piece of wood (p, »). The
secondary spiral consists of a hollow cylinder of wood covered with numerous coils of thin silk-
covered wire. The secondary spiral, moving in slots, can be approximated to or even pushed
entirely over the primary spiral, or can be removed from it to any distance desired.

[Fig. 393 shows the actual arrangement of du Bois-Reymond’s inductorium., The primary
coil (R’) consists of about 150 coils of thick insulated copper wire, the wire being thick to offer
slight resistance to the galvanic current. The secondary coil (R”) consists of 6000 turns of
thin insulated copper wire arranged on a wooden bobbin ; the whole spiral can be moved along
the board (B)to which ,a millimetre scale (I) is attached, so that the distance of the secondary
from the primary spiral may be ascertained. At the left end of the apparatus is Wagner’s
hammer, as adapted by Neef, which is just an automatic arrangement for opening and breaking
the primary circuit. When Neef’s hammer is used, the wires from the battery are connected
as in the figure; but when single shocks are required, the wires from the battery are connected
with a key, and this again with the two terminals of the primary spiral, S’ and S’”’. In the

552 , MAGNETO-INDUCTION.

improved form of this apparatus (fig. 394) the secondary spiral is equiposed over a pulley
with a back weight, so that it can move easily in a vertical direction to and from the primary
spiral. A. de Watteville has used a form similar to this for a long time. ] me
According to the law of induction (§ 329), when the primary circuit is closed, a current is in-
duced in the secondary circuit in a direction the reverse of that in the primary, while, when it
is opened, the induced current has the same direction. Further, according to the laws of
magneto-induction, the magnetisation of the iron rods (i, 7) within the primary spiral (x, x),
causes a reverse current in the secondary spiral (K, K), while the demagnetisation of the iron
rods, on opening the primary circuit, causes an induced current
in the same direction. Thus, we explain the much more powerful
action of the opening or break shock as compared with the closing
or make shock (p. 481). [The direction of the inducing current
remains the same, while the induced currents are constantly
reversed. | hae
The magneto-induction (R) apparatus of Pixil, as improved
by Stohrer, consists of a very powerful horse-shoe steel magnet
(fig. 395). Opposite its two poles (N and S$) is a horse-shoe-
shaped piece of iron (H), which rotates on a horizontal axis (4, 0).
On the ends of the horse-shoe are fixed wooden bobbins (c, @),
with an insulated wire coiled round them. When the horse-
shoe is at rest, as in the figure, it becomes magnetised by the

A

nA

A LN
AMT EET

————

Fig. 394.

Fig. 393.—Induction apparatus of du Bois-Reymond. R’, primary, R’, secondary spiral ; B,
board on which R” moves; I, scale; + -, wires from battery; P’, P’, pillars; H, Neef’s
hammer ; B’, electro-magnet ; 8’, binding screw touching the steel spring (H) ; 8S’ and
S”, binding screws to which to attach wires where Neef’s hammer is not required. Fig.
394.—-New form of du Bois-Reymond’s inductorium.

steel magnet, while in the wires of both bobbins (c and d@) an electric current is developed every
time the horse-shoe is demagnetised, and again magnetised. When the bobbins rotate in
front of the magnet, as each coil approaches one pole, a current is induced, and similarly when
it is carried past the pole of the magnet, so that four currents are induced in each coil by a single
rotation. By means of Stéhrer’s commutator (m, 7) attached to the spindle (a, 0), and the
divided metal plates (y, z) which pass to the electrodes, the two currents induced in the bobbins
are obtained in the same direction.

Keys, or arrangements for opening or closing a circuit, are of great use. Fig. 392, II, shows
a scheme of the friction key of du Bois-Reymond, introduced into the secondary circuit. It
consists of two brass bars (z and y) fixed to a plate of ebonite, and as long as the key is down
on the metal bridge (y, 7, z) it is ‘‘ short-circuited,” i.e., the conduction is so good through the
thick brass bars that none of the current goes through the wires leading from the left of the
key. When the bridge (7) is lifted the current is opened. [Fig. 396 shows the form of the
key, v being a screw wherewith to clamp it to the table.] Similarly the key electrodes (III)
may be used, the current being made as soon as the spring connecting-plate (e) is raised by
pressing upon k. This instrument is opened by the hand; a, 6 are the wires from the battery
or induction machine}; 7, 7, those going to the tissue ; G, the handle of the instrument.

[Plug Key. —Other forms of keys are in use, ¢.g., fig. 397, the plug key, the two brass plates
to which the wires are attached being fixed on a plate of ebonite. The brass plug is used to
connect the two brass plates. All these are dry contacts, but sometimes a fluid contact is used

VARIOUS FORMS OF KEYS. ‘we 553

as in the mercury key, which merely consists of a block of wood with a cup of mercury in its
centre. The ends of the wires from the battery dip into the mercury ; when both wires dip
into the mercury the circuit is made, and when one is out it is broken. |

[Capillary Contact Key.—Where an ordinary mercury key is used to open and close the

A

Fig. 395. Fig. 396.
Magneto-induction apparatus, with Stohrer’s Du Bois-Reymond’s friction key.
commutator.

®
primary circuit, the layer of oxide formed on the surface by the opening spark disturbs the con-
duction after a short time; hence, it is advisable to wash the surface of the mercury with a dilute
solution of alcohol and water (W. Stirling). A handy form of “ capillary contact” is shown in
fig. 398, such as was used by Kronecker and Stirling in their experiments on the heart. ‘A
glass T-tube is provided at the crossing point with a small opening (a). The vertical tube (0)

Fig. 397. Fig. 398.

Fig. 397.—Plug key. Fig. 398.—Capillary contact. ¢, vibrating platinum style adjustable
by fand g and dipping into mercury at a; b, bent tube filled with mercury, into which dips
a wire (d) ; a, opening in cross tube (¢),

is bent in. the form of a U, and filled so full-with mercury that the convex surface of the latter
projects within the lumen of the transverse tube (c). One end of ¢ is connected with a Mariotte’s
flask containing diluted alcohol, and the supply of the latter can be regulated by means of a
stop-cock, The fluid flows over the apex of the mercury and keeps it clean. The vibrating
platinum style (¢) is attached to the end of a rod, which in turn is connected with the positive

554 ELECTRICAL CURRENTS IN NERVE AND MUSCLE.

pole of the battery, while the platinum wire (d) is connected with the negative pole of the
**battery.’’]

331, ELECTRICAL CURRENTS in PASSIVE MUSCLE and NERVE—SKIN CURRENTS.
—Methods.—In order to investigate the laws of the muscle-current, we must use a muscle
composed-of parallel fibres, and with a simple arrangement of its fibres in the form of a prism
or cylinder (fig. 399, I and II). The sartorius muscle of the frog supplies these conditions, In
such a muscle, we distinguish the surface or the natural longitudinal section, its tendinous
ends or the natural transverse section ; further, when the latter is divided transversely to the
long axis, the artificial transverse section (fig. 399, I, c,d); lastly, the term equator (a, b-m, n)
is applied to a line so drawn as exactly to divide the length of the muscle into halves. As the
currents are very feeble, it is necessary to use a galvanometer with a periodic damped magnet
(figs. 380, I, and 387), ora tangent mirror-boussole similar to that used for thermo-electric
purposes (fig. 230). The wires leading from the tissue are connected with non-polarisable elec-
trodes (fig. 380, P, P).

The capillary-electrometer of Lippmann may be used for detecting the current (fig. 400).
A thread of mercury enclosed in a capillary tube and touching a conducting fluid, c.g., dilute
sulphuric acid, is displaced by
the constant current, in conse-
quence of the polarisation tak-
ing place at the point of contact
altering the constancy of the
capillarity of the mercury. The
displacement of the mercury
which the observer (B) detects
by the aid of the microscope
(M) is in the direction of the
positive current. R is a capil-
lary glass tube, filled. from
above with mercury, and from
below with dilute sulphuric
~ acid. Its lower narrow end
opens into a wide glass tube,
provided below with a platinum
wire. fused into it and filled
with Hg (q), and this again is
covered with dilute sulphuric
acid (s). The wires are con-
nected with noy-polarisable
electrodes applied to the + and
— surfaces of the muscle. On
closing the circuit, the thread
of mercury passes downwards
from c in the direction of the
Capillary electrometer, TOW. ;

R, mercury in tube; Compensation, —The
capillary tube ; s, sul- Strength of the current in ani-
2) phurie ‘acid; g, Hg; mal tissues is best measured by
| Fig. 399, B, observer: M mi. the compensation method of

Scheme of the muscle-current. croscope. ie Poggendorf and du Bois-Rey-

mond. <A current of known

strength, or which can be accurately graduated, is passed in an opposite direction through the

same galvanometer or boussole, until the current from the animal tissue is just neutralised or

compensated. [When this occurs, the needle deflected by the tissue-current returns to zero.

The principle is exactly the same as that of weighing a body in terms of some standard weights
placed in the opposite scale-pan of the balance. ] :

[Hermann calls the current obtained from an injured muscle, 7.e., one on which
an artificial transverse or other section has been made, a demarcation-current,
while the currents obtained when such a muscle contracts, he calls action-currents.
This section deals with demarcation-currents, or the muscle-current of du Bois-
Reymond. |

1. Perfectly fresh uninjured muscles yield no current, and the same is true of
dead muscle (LZ. Hermann, 1867).

2. Strong electrical currents are observed when the transverse section of a muscle

is placed on one of the cushions of the non-polarisable electrodes (fig. 380, I, M), —

ELECTRICAL CURRENTS IN NERVE AND MUSCLE. 555

while the surface is in connection with the other (Nobili, Matteucci, du Bois-
Reymond). The direction of the current is from the (positive) longitudinal section
to the (negative) transverse section in the conducting wires (¢.e., within the muscle
itself from the transverse to the longitudinal section (figs. 380, I, and 399, [)). .
This current is stronger the nearer one electrode is to the equator, and the other
to the centre of the transverse section; while the strength diminishes, the nearer
the one electrode is to the end of the surface, and the other to the margin of the
transverse section.

poe muscles also yield similar currents between their transverse and longitudinal surfaces
§ 334, IT.).

3. Weak electrical currents are obtained when—(a) two points at unequal
distances from the equator are connected ; the current then passes from the point
nearer the equator (+) to the point lying further from it (— ), but of course this
direction is reversed within the muscle itself (fig. 399, IT, ke and /e). (b) Similarly
weak currents are obtained by connecting points of the transverse section at
unequal distances from the centre, in which case the current outside the muscle
passes from the point lying nearer the edge of the muscle to that nearer the centre
of the transverse section (fig. 399, II, 2, ¢).

4. When two points on the surface are equidistant from the equator (fig. 399,
I, #, y, v, 4—I, 7, e), or two equidistant from the centre of the transverse section
(II, c) are connected, no current is obtained. [Because the points are iso-electrical,
that is of equal potential. |

5. If the transverse section of the muscle be oblique (fig. 399, III), so that the
muscle forms a rhomb, the conditions obtaining under III are disturbed. The
point lying nearer to the obtuse angle of the transverse section or surface is positive
to the one lying near to the acute angle. The equator is oblique (a,c). These
currents are called “deviation currents or inclination currents” by du Bois-Reymond,
and their course is indicated by the lines 1, 2, and 3.

The electro-motive force of a strong muscle-current (frog) is equal to 0°05 to 0°08 of a
Daniell’s element ; while the strongest deviation current may be 0°1 Daniell. The muscles of
a curarised animal at first yield stronger currents ; fatigue of the muscle diminishes the strength
of the current (Roeber), while it is completely abolished when the muscle dies, Heating a
muscle increases the current ; but above 40° C. it is diminished (Steiner).
Cooling diminishes the electro-motive force. The warmed living mus-
cular and nervous substance is positive to the cooler portions (Hev-
mann) ; while, if the dead tissues be heated, they behave practically
as indifferent bodies as regards the tissues that are not heated.

6. The passive nerve behaves like muscle, as far as 2, 3,
and 4 are concerned.

The electro-motive force of the strongest nerve-current, according
to du Bois-Reymond, is 0:02 of a Daniell. Heating a nerve from 15° to
25° C. increases the nerve-current, while high temperatures diminish
it (Steiner).

7. If the two transversely divided ends of an excised nerve,
or two points on the surface equidistant from the equator, be
tested, a current—the axial current-—flows in the nerve-fibre
in the opposite direction to the direction of the normal impulse
in the nerve ; so that in centrifugal nerves it flows in a cen-

Fig. 401.

; M ‘ ‘ : : . Nerve-muscle prepara-
tripetal direction, and in centripetal nerves in a centrifugal ~ 4:5, of a frog. F,

direction (Mendelssohn and Christiant). . femur; 8, sciatic

nerve ; I, tendo Ach-

The electro-motive force increases with the’ length of the nerve and ita

with the area of its trausverse section. Fatigue (e, g., tetanic stimula-

tion) weakens it, especially in motor nerves, yand to a less extent in centripetal nerves.
[Nerve-Muscle Preparation.—This term has been used on several occasions. It

is simply the sciatic nerve with the gastrocnemius of the frog attached to it (fig. 401).

556 SELF-STIMULATION OF THE MUSCLE.

The sciatic nerve is dissected out entire from the vertebral column to the knee; the
muscles of the thigh separated from the femur, and the latter divided about its
middle, so that the preparation can be fixed in a clamp by the. remaining portion
of the femur; while the tendon of the gastrocnemius is divided near to the foot.
If a straw flag is to be attached to the foot, do not divide the tendo Achilles. |

Rheoscopic Limb.—The existence of a muscle-current may be proved without
the aid of a galvanometer :—1. By means of a sensitive nerve-muscle preparation
of a frog, or the so-called “ physiological rheoscope.” Place a moist conductor on
the transverse and another on the longitudinal surface of the gastrocnemius of a
frog. On placing the sciatic nerve of a nerve-muscle preparation of a frog on these
conductors, so as to bridge over or connect their two surfaces, contraction of the
muscle connected with the nerve occurs at once ; and the same occurs when the
nerve is removed.

Make a transverse section of the gastrocnemius muscle of a frog’s nerve-muscle
preparation, and allow the sciatic nerve to fall upon this transverse section; the
limb will contract as the muscle-current from the longitudinal to the transverse
surface now traverses the nerve (Galvani, Al. v. Humboldt). These experiments
have long been known as “ contraction without metals.”

[Use a nerve-muscle preparation, or, as it is called, a physiological limb. Hold the prepara-
tion by the femur, and allow its own nerve to fall upon the gastrocnemius, and the muscle will
contract, but it is better to allow the nerve to fall suddenly upon the cross section of the muscle.
The nerve then completes the circuit between the longitudinal and transverse section of the
muscle, so that it is stimulated by the current from the latter, the nerve is stimulated, and through

it the muscle. That it is so, is proved by tying a thread round the nerve near the muscle, when
the latter no longer contracts. ]

2. Self-Stimulation of the Muscle.—We may use the muscle-current of an
isolated muscle to stimulate the latter directly and cause it to contract. If the
transverse and longitudinal surfaces of a curarised frog’s nerve-muscle preparation
be placed on non-polarisable electrodes, and the circuit be closed by dipping the
wires coming from the electrodes in mercury, then the muscle contracts. Similarly
a nerve may be stimulated with its own demarcation-current (du Bois-Reymond
and others). If the lower end of a muscle with its transverse section be dipped
into normal saline solution (0°6 per cent. NaCl), which is quite an indifferent fluid,
this fluid forms an accessory circuit between the transverse and adjoining longi-
tudinal surface of the muscle, so that the muscle contracts. Other indifferent
fluids used in the same way produce a similar result.

[Kithne’s Experiment (fig. 402).—The demarcation-current of the nerve of a
nerve-muscle preparation may be used
as the stimulus to that nerve on com-
pleting the circuit. On an earthenware
bowl (B) is fixed a glass plate (G), and
thin rolls of modeller’s clay (P P’) are
bent over G. <A nerve-muscle prepara-
tion is placed with its nerve (N) on the
clay, touching the latter with its trans-
verse and longitudinal surfaces. On
dipping the clay into a vessel containing
: normal saline (C), the muscle contracts,

Fig. 402. and on withdrawing the normal saline,
Kiihne’s nerve demarcation-current experiment. ” oe contracts, Tn this ‘case the
Miah nerve is stimulated by the completion
of the circuit of its own demarcation-current. ]

3. Electrolysis.—If the muscle-current be conducted through starch mixed with

potassie vodide, then the iodine is deposited at the + pole, where it makes the starch

blue.

ELECTRICAL CURRENTS OF ACTIVE MUSCLE. 557

Frog Current.—It is asserted that the total current in the body is the sum of the electrical
currents of the several muscles and nerves which, in a frog deprived of its skin, pass from the
tip of the toes toward the trunk, and in the trunk from the anus to the head. This is the
“‘corrente propria della rana” of Leopoldo Nobili (1827), or the ‘‘frog current” of du Bois-
Reymond. In mammals, the corresponding current passes in the opposite direction.

After death, the currents disappear sooner than the excitability (Valentin) ; they remain
longer in the muscle than the nerves, and in the latter they disappear sooner in the central
portions. If the nerve-current after a time become feeble, it may be strengthened by making
a new transverse section of the nerve. A motor nerve completely paralysed by curara gives a
current (Funke), and so does a nerve beginning to undergo degeneration, even two weeks after
it has lost its excitability. Muscles in a state of rigor mortis give currents in the opposite
direction, owing to inequalities, which take place during decomposition. The nerve-current is
reversed by the action of boiling water or drying.

Currents from Skin and Mucous Membranes.—In the skin of the frog the
outer surface is +, the inner is — (du Bois-Reymond), and the same is true of the
mucous membrane of the intestinal tract (Rosenthal), the cornea (Griinhagen), as
well as the xon-glandular skin of fishes (Zermann) and molluscs (Oeh/er). Currents
are also manifested by glands.

332. CURRENTS OF STIMULATED MUSCLE AND NERVE—ACTION-
CURRENTS.—1. Negative Variation of the Muscle-Current.-—If a muscle, which
yields a strong electrical current, be thrown into a state of tetanic contraction by
stimulating its motor nerve, then, when the muscle contracts, there is a diminution
of the muscle-current, and occasionally the needle of the galvanometer may swing
almost to zero. This is the ‘negative variation of the muscle-current” (du Bois-
Reymond). It is larger, the greater the primary deflection of the galvanometer
needle and the more energetic the contraction.

After tetanus, the muscle-current is weaker than it was before. If the muscle was so placed
upon the electrodes that the current was ‘‘ feeble,” equally during tetanus there is a diminution
of this current. In the inactive arrangement, the contraction of the muscle has no effect on

the needle. Ifthe muscle be prevented from shortening, as by keeping it tense, the negative
variation still takes place.

2. Current during Tetanus.—An excised frog’s muscle tetanised through its
nerve shows electro-motive foree—the so-called “action-current.” In a tetanised
frog’s gastrocnemius, there is a descending current. In completely uninjured human
muscles, however, thrown into tetanus by acting on their nerves, there is no such
current (ZL. Hermann); similarly, in quite uninjured frog’s muscles, as well as when
these muscles are directly and completely tetanised, there is no current.

3. Current during the Contraction-Wave.—If one end of a muscle be directly
excited with a momentary stimulus, so that the contraction-wave (§ 299) rapidly
passes along the whole length of the muscular fibres, then each part of the muscle,
successively and immediately before it contracts, shows the negative variation.
Thus, the “‘contraction-wave” is preceded by a ‘‘negative wave” of the muscle-
current, the latter occurring during the latent period. Both waves have the same
velocity, about 3 metres per second. The negative wave, which first increases and
then diminishes, lasts at each point only 0°003 second (Bernstein). |

4. During a Single Contraction.—A single contraction also shows a muscle-
current. [The electrical variation takes place during the latent period of the
muscular contraction, so that it precedes the latter. The variation begins -01” to
04” after excitation, while the contraction does not begin until ‘11” to 33”
(Waller). A frog’s muscle may be made to record its contraction, and simul-
taneously the variation of the electrical current, as ascertained by the capillary
electrometer, may be photographed (fig. 403), and the same may be done in the
case of the heart (fig. 404). The capillary electrometer may with advantage be
employed to measure this time-difference, the electrical and the mechanical events
being simultaneously recorded. |

The diphasic variation—Ist phase middle negative to end; 2nd phase and negative to
middle begins about ‘01” before the commencement of muscular contraction (Wadler).

558 ELECTRICAL CURRENTS OF ACTIVE MUSCLE.

The variation is diphasic—Ist phase base negative to apex ; 2nd phase apex negative to base
(Waller). The first phase begins 7” before the commencement of contraction,

One of the best objects for this purpdse is the contracting heart, which is placed
upon the non-polarisable electrodes connected with a sensitive galvanometer. Each

, beat of the heart causes a deflection of the needle, which
occurs before the contraction of the cardiac muscle
(Kolliker and H,. Miiller), The electrical disturbance
in the muscle causing the negative variation always
precedes the actual contraction (v. Helmholtz, 1545),
Still it lasts throughout the whole duration of the con-
traction (Lee). When the completely uninjured frog’s
gastrocnemius contracts by stimulating the nerve,
there is at first a descending and then an ascending
current (Sig. Mayer, § 334, IT.).

More exact observations on the electrical processes of the pul-
sating heart show that complicated phenomena occur. The apex
of the dog’s heart is negative to the base during systole. In
inany cases this is preceded, and in some it is followed, by an
opposite condition (Frédéricq), t.¢e., a diphasic variation. If the
heart be arrested in diastole by stimulation of the vagus (§ 369),
Fie, 403 there is a positive variation of the muscle-current (Gaskell,

5 : Fano). Waller has demonstrated a true electrical variation of
Frog. Gastrocnemius led off the human intact heart.

ae ae ees Patel ae | Heart.—Gaskell has shown that, when the vagus of
from the tendon. Contrac- & tortoise is stimulated so as to arrest its heart in diastole,
tion excited by a single the action of the inhibitory nerve is accompanied by a
ier ah ate locas positive electrical variation of the heart-current, while
’, electrometer; m, muscle; Stimulation of the sympathetic (augmentor) nerve causes
‘, time in th sec. (muscle an electrical variation of the same sign as that caused by
to H,SO,; tendon to Hg) a contraction in the non-beating tissue of the ventricle
CaN). of the toad. In both cases, the respective nerves can
produce their electrical effect after the heart has been brought to standstill by

the application of muscarin to the sinus. These experiments are of the utmost

t

dt

Fig. 404.
Frog’s heart. Spontaneous contraction. e, ¢, electrometer; , h, heart’s contraction ; t, ¢,
time in 5th sec. (apex to H,SO,, base to Hg) ( Waller).

importance in connection with the theory of the action of these nerves on the heart
(§ 370), and the mode of action of poisons on the heart itself. |

Secondary Contraction.—A nerve-muscle preparation may be used to demonstrate
the electrical changes that occur during a single contraction. If the sciatic nerve,
A, of such a preparation be placed upon another muscle, B, as. in fig. 405, then

SECONDARY CONTRACTION. 559

every time the latter, B, contracts, the frog’s muscle, A, connected with the nerve
also contracts. |

If the nerve of a frog’s nerve-muscle preparation be placed on a contracting
mammalian heart, then a contraction of the muscle occurs with every beat of the
heart (Matteucci, 1842). The diaphragm, even after
section of the phrenic nerve, especially the left, also con-
tracts during the heart-beat (Schiff). This is the
‘secondary contraction” of Galvani.

Secondary Tetanus.—Similarly, if a nerve of anerve- /%
muscle preparation be placed on a muscle which is /@
tetanised, then the former also contracts, showing
“secondary tetanus” (du Bois-Reymond). The latter
experiment is regarded as a proof that, during the pro-
cess of negative variation in the muscle, many successive
variations of the current must take place, as only rapid
variations of this kind can produce tetanus by acting on
a nerve—continuous variations being unable to do so.

Usually, there is no secondary tetanus in a frog’s nerve- Fig. 405. .
muscle preparation when it is laid upon a muscle which is Secondary contraction. The
tetanised voluntarily, or by chemical stimuli, or by poisoning sciatic nerve of A lies on B;
with strychnin (Hering, Kiihne); still, Loven has observed E, electrodes applied to the
secondary strychnin tetanus composed of six to nine shocks per Sciatic nerve of B.
second. Observations with a sensitive galvanometer, or Lippmann’s capillary electrometer (fig.
400), show that the spasms of strychnin poisoning, as well as a voluntary contraction, are dis-
continuous processes (Loven, p. 485).

Biedermann observed that striped muscle, under the influence of the vapour of ether, passes
into a condition in which it shows no obvious change of form or movement when it is
stimulated, whilst at the spot stimulated, there are galvanometric variations of the same strength
as occurred during stimulation before the action of the ether. Owing to the abolition of the
power of conductivity, they can only manifest themselves locally.

[Secondary Contraction from Muscle to Muscle (Avihne).—If 5 mm. of one end
of the sartorius of a curarised frog be laid upon a corresponding 5 mm. of the other
sartorius, so that both muscles are in line, and if the surfaces of contact be pressed
together, either by an ebonite press or other means, on stimulating the free end
of one of the muscles—either electrically, mechanically, or chemically—the other
muscle also contracts, and if the first one be tetanised, the second one also is thrown
into tetanus. The experiment may be repeated with five or six muscles in line.
The conduction is interrupted at once by ligature of the muscle. The second
muscle contracts, because it is stimulated directly by the action-currents of the
contracting muscular fibres. The effect is prevented by introducing, between the
overlapping ends of the muscle, a thin plate of gutta-percha, tinfoil, or any insulator.
This experiment of Kiihne’s shows us how important a rd/e electrical phenomena
play in connection with muscular contraction. Secondary contraction from nerve
has long been known. | |

Negative Variation in Nerve.—If a nerve be placed with its transverse section
on one non-polarisable electrode, and its longitudinal surface on the other, and if it
be stimulated electrically, chemically, or mechanically, the nerve-current is also
diminished (du Bois-Reymond). This negative variation is propagated towards
both ends of a nerve, and is composed of very rapid, successive, periodic, interrup-
tions of the original current, just as in a contracted muscle (Bernstein). Hering
succeeded in obtaining from a nerve, as from a muscle, a secondary contraction or
secondary tetanus. The amount of the negative variation depends upon the.
extent of the primary deflection, also upon the degree of nervous excitability, and
on the strength of the stimulus employed. The negative variation occurs on
stimulating with tetanic as well as with single shocks. The negative variation
is not observed in completely uninjured nerves. :

560 CURRENT IN THE SPINAL CORD.

Hering found that the negative variation of the nerve-current caused by tetanic stimulation
is followed by a positive variation, which occurs immediately after the former, 7.¢., it is
diphasic. It increases to a certain degree with the duration of the stimulation, as well as
with the strength of the stimulus, and with the drying of the nerve (Head). (Effect of Electro-
tonus, § 335, 1.).

Newative Variation of the Spinal Cord.—This is the same as in nerves generally. If a
current be conducted from the transverse and longitudinal surfaces of the upper part of the
medulla oblongata, we observe spontaneous, intermittent, negative variations, perhaps due to
the intermittent excitement of the nerve-centres, more especially of the respiratory centre.
Similar variations are obtained reflexly by single stimuli applied to the sciatic nerve, while
strong stimulation by common salt or induction shocks inhibits them.

Velocity.—The process of negative variation is propagated at a measurable velocity along
the nerve, most rapidly at 15° to 25° C. (Steiner), and at the same rate as the velocity of the
nervous impulse itself, about 27 to 28 metres per second. The duration of a single variation (of
which the process of negative variation is composed) is only 0°0005 to 0°0008 second, while the
exvedatett in the nerve is calculated by Bernstein at 18 mm. . 43H

Differential Rheotome.—J. Bernstein estimated the velocity of the negative variationjin a
nerve by means of a differential rheotome thus (fig. 406) :—A long stretch of a nerve (N ) is
so arranged that at one end of it (N) its transverse and longitudinal surfaces are connected with

Fig. 406.
Scheme of Bernstein’s differential rheotome ; N 7, nerve ; J, induction machine ; G, galvano-
meter, a, y, deflection of needle; E, battery and primary circuit with C for opening it
at ae ce, for closing galvanometer circuit; < z, electrodes in galvanometer circuit; S,
motor.

a galvanometer (G), while at the other end (n) are placed the electrodes of an induction
machine (J). A disc (B) rapidly rotating on its vertical axis (A) has an arrangement (C) at
one point of its circumference, by means of which the current of the primary circuit (E) is
rapidly opened and closed during each revolution. This causes, with ee § rotation of the dise,
an opening and a closing shock to be applied to the end of the nerve. At the diametrically
opposite part of the circumference is an arrangement (c) by which the galvanometer circuit is
closed and opened during each revolution. Thus, the stimulation and the closing of the
galvanometer circuit occur at the same moment. On rapidly rotating the disc, the galvano-
meter indicates a strong nerve-current, an excursion of the magnetic needle to y. - At the
moment of stimulation, the negative variation has not yet reached the other end of the nerve.
If, however, the arrangement which closes the galvanometer circuit be so displaced (to 0) along
the circumference, that the galvanometer circuit is closed somewhat later than the nerve is
stimulated, then the current is weakened by the negative variation (the needle passing back-
ward to x). When we know the velocity of rotation of the disc, it is easy to calculate the rate
ri whieh. ine impulse causing the negative variation passes along a given distance of nerve
rom Nn.

ate negative variation is absent in degenerated nerves as soon as they lose their excita-

_ nerve), and if the direction of this current coincide

ELECTRICAL CURRENTS DURING ELECTROTONUS. 561

Rectinal and Eye Currents.—If a freshly-excised eyeball be placed on the non-polarisable
electrodes connected with a galvanometer, and if light fall upon the eye, then the normal eye-
current from the cornea (+) to the transverse section of the optic nerve (-— ) is at first increased.
Yellow light is most powerful, and less so the other colours (Holmgren, M‘Kendrick and
Dewar), The inner surface of the passive retina is positive to the posterior, When the retina
is illuminated there is a double variation, a negative variation with a preliminary positive
increase ; while, when the light ceases, there is a simple positive variation. Retin, in which
the visual purple has disappeared owing to the action of ight, show smaller variations (Xihne
and Steiner),

Stimulation of the secretory nerves of the glandular membranes, besides causing secretion,
affects the current of rest (Roeber), This secretion-current passes in the same direction in the
skin of the frog and warm-blooded animals as the current of rest, although in the frog it is
occasionally in “the opposite direction (Hermann). If the current be conducted unifor mly from.
both hind feet of a cat, on stimulating the sciatic nerve of one side, not only is there a secretion
of sweat (§ 288), but a secretion-current is developed (Luchsinger and Hermann). If two
symmetrical parts of the skin in the leg or arm of a man be similarly tested, and the muscle of
one side be contracted, a similar current is developed. Destruction or atrophy of the glands
abolishes both the power of secretion and the secretion-current. There is no secretion-current
from skin covered with hairs, but devoid of glands (Bubnoj). [The secretion-current from the
submaxillary gland is referred to in § 145 (Bayliss and Bradford). |

333. ELECTROTONIC CURRENTS IN NERVE AND MUSCLE.—{ When a
constant current called the “ polarising current” is passed though a stretch of
nerve, the nerve is thrown into a peculiar condition, called the “ electrotonic con-
dition,” or briefly electrotonus. In this condition, the vital properties of the
nerve are modified, 2.¢.,

(1) Its electromotivity (§ 333).
(2) Its excitability (§ 335).

The former is considered in this section, and the latter in a subsequent section. |

1. Positive Phase of Electrotonus.—If a nerve be so arranged upon the
electrodes (fig. 407, I) that its transverse section
lies on one, and its longitudinal on the other elec-
trode, then the galvanometer indicates a strong
current. If now a constant current be transmitted
through the end of the nerve projecting beyond the
electrodes (the so-called “polarising” end of the

with that in the nerve, then the magnetic needle
gives a greater deflection, indicating an increase of
the nerve-current—“ the positive phase of elec-
trotonus.” The increase is greater the longer
the stretch of nerve traversed by the current, the
stronger the galvanic current, and the less the dis-
tance between the part of the nerve traversed by
the constant current and that on the electrodes,

2. Negative Phase of Electrotonus.—lIf in the
same length of nerve, the constant current passes
in the opposite direction to the nerve-current (fig. 3
407, II), there is a diminution of the electro- Fig. 407.

motive force of the latter—‘“‘ negative phase of Nerve-current in electrotonus. a,
electrotonus.” galvanometer; 0, electrodes; E,

3. Equator.—If two points of the nerve equi- constant current.

distant from the equator be placed on the electrodes (III), there is no deflection of
the galvanometer needle (p. 555, 4). Ifa constant current be passed through one
free projecting end of the nerve, then the galvanometer indicates an electro-motive
effect in the same direction as the constant current.
Electrotonus.—These experiments show that a constant current causes a change
of the theses madame force of the part of the nerve directly traversed by the constant
2N

562 THEORIES OF NERVE- AND MUSCLE-CURRENTS.

current, i.¢., in the intrapolar area, and also in the part of the nerve outside the
electrodes, i.e, in the extrapolar area. This condition is called electrotonus
(du Bois-Reymond, 1843).

The electrotonic current is strongest not far from the electrodes, and it may be twenty-five
times as strong as the nerve-current of rest ($ 331, 5) ; it is greater on the anode than on the
cathode side; it undergoes a negative variation like the resting nerve-current during tetanus ;
it occurs at once on closing the constant current, although it diminishes uninterruptedly at
the cathode (du Bois-Reymond). On the contrary, between the electrodes, besides the polarising
current itself, there is no obvious electrotonic increase of the current to be observed (Hermann).
These phenomena take place only as long as the nerve is excitable. If the nerve be ligatured
in the projecting part in the galvanometer circuit, the phenomena cease in the ligatured part.
The above-described galvanic electrotonic changes of the extra-polar part are absent in non-
medullated nerve-fibres, whilst, on the contrary, the physiological electrotonus is present.
The physiological electrotonus of medullated nerves can be set aside by treating medullated
nerves With ether, whilst the physical phenomena remain (Biedermann).

The negative variation (§ 332) occurs more rapidly than the electrotonic increase of the current,
so that the former is over before the electro-motive increase occurs. The velocity of the electro-
tonic change in the current is less than the rapidity of propagation of the excitement in: the
nerves—being only 8 to 10 metres per second (7'schirjew, Bernstein).

‘‘The secondary contraction from a nerve” depends upon the electrotonic state. If the
sciatic nerve of a frog’s nerve-muscle preparation be placed on an excised nerve, and if a con-
stant current be passed through the free end of the latter—non-electrical stimuli being inactive
—the muscles contract. This occurs because the electrotonising current in the excised nerve
stimulates the nerve lying on it. By rapidly closing and opening the current, we obtain
‘‘ secondary tetanus from a nerve” (p. 559).

{Paradoxical Contraction.—Exactly the same occurs when the current is applied
to one of the two branches into which the sciatic nerve of the frog divides. The
sciatic nerve of the frog divides at the lower end of the thigh into the peroneal and
tual branches. If the sciatic nerve be divided above, and the peroneal branch be
also divided and stimulated with interrupted induction shocks, the muscles supplied
by the tibial branch will contract. There is no contraction of the muscle if the
peroneal nerve be ligatured. | |

Polarising After-Currents.—When the constant current is opened, there are after-currents
depending upon internal polarisation (§ 328). In living nerves, muscle, and electrical organs
this internal polarisation current, when a strong primary current of very short duration is
used, is always positive, i.¢., has the same direction as the primary current. Prolonged dura-
tion of the primary current ultimately causes negative polarisation. Between these two is a stage
when there is no polarisation. Positive polarisation is especially strong in nerves when the
primary current has the direction of the impulse in the nerve ; in muscle, when the primary
current is directed from the point of entrance of the nerve into the muscle towards the end of
the muscle (§ 334, II.). 7

+. Muscle-Current during Electrotonus.—The constant current also produces
an electrotonic condition in muscle ; a constant current in the same direction in-
creases the muscle-current, while one in an opposite direction weakens it, but the
action is relatively feeble.

[Electrotonic Phenomena in Conductors.—Matteucci found that a metallic wire surrounded
by a moist conductor, when traversed by a galvanic current, exhibits currents possessing the
properties of electrotonic currents of nerves. He also found that the currents ceased if the
wire was of zinc, and the envelope a saturated solution of zinc sulphate. This shows that
these currents were due to: polarisation between the core and the fluid. Hermann finds that
the currents ony obtain when a polarisable core is present. A straw without. joints, if filled
with a saturated solution of common salt, or the tentacles of a lobster when moistened with
saline solution, and traversed by a constant current, exhibit similar electrotonic currents
(Hering).] . :

334, THEORIES OF MUSCLE- AND NERVE-CURRENTS.—I. Molecular
or pre-existence Theory.—To explain the currents in muscle and nerve, du Bois-
Reymond proposed the so-called: molecular theory. According to this theory, a
nerve- or muscle-fibre is composed of a series of small electro-motive molecules

arranged one behind the other, and surrounded by a conducting indifferent fluid. —
The molecules are supposed to have a positive equatorial zone directed towards the

d
f
‘
}
:

STREAMLESS FRESH MUSCLES. 563

surface, and two negative polar surfaces directed towards the transverse section.
Every fresh transverse section exposes new negative surfaces, and every artificial
longitudinal section new positive areas.

This scheme explains the strong currents,—when the + longitudinal surface is connected |
- with the — transverse surface, a current is obtained from the former to the latter,—but it does
not explain the feeble currents. To explain their occurrence we must assume that, on the one
hand, the electro-motive force of the molecules is weakened with varying rapidity at unequal
distances from the equator ; on the other, at unequal distances from the transverse section.
Then, of course, differences of electrical tension obtain between the stronger and the feebler

molecules.

Parelectronomy.—But the natural transverse section of a muscle, z.¢., the end of the tendon,
is not negative, but more or less positive electrically. To explain this condition, du Bois-
Reymond assumes that on the end of the tendon there is a layer of electro-positive muscle-
substance. He supposes that each of the peripolar elements of muscle consists of two bipolar
elements, and that a layer of this ha/f element lies at the end of the tendon, so that its positive
side is turned towards the free surface of the tendon. This layer he calls the ‘‘ parelectronomic
layer.” It is never completely absent. Sometimes it is so marked as to make the end of the
a : in relation to the surface. Cauterisation destroys it. [It is supposed to be favoured

cold. .
the negative variation is explained by supposing that, during the action of a muscle and
nerve, the electro-motive force of all the molecules is diminished. During partial contraction
of a muscle, the contracted part assumes more the characters of an indifferent conductor, which
now becomes connected with the negative zone of the passive contents of the muscular fibres.

The electrotonic currents beyond the electrodes in nerves must be explained. To explain the
electrotonic condition, it is assumed that the bipolar molecules are capable of rotation. The
polarising current acts upon the direction of the molecules, so that they turn their negative
surfaces towards the anode, and their positive surfaces to the cathode, whereby the molecules of
the intrapolar region have the arrangement of a Volta’s pile. In the part of the nerve outside
the electrodes, the further removed it is, the less precisely are the molecules arranged. Hence,
the swing of the needle is less, the further the extrapolar portion is from the electrodes.

II. Difference or Alteration Theory.—The difference theory was proposed by
L. Hermann, and, according to him, the four following considerations are sufficient
to explain the occurrence of the galvanic phenomena in living tissues :—(1) Proto-
plasm, by undergoing partial death in its continuity, whether by injury or by
(horny or mucous) metamorphosis, becomes negative towards the uninjured part.
(2) Protoplasm, by being partially excited in its continuity, becomes negative to
the uninjured part.. (3) Protoplasm, when partially heated in its continuity,
becomes positive, and by cooling negative, to the unchanged part. (4) Proto-
plasm is strongly polarisable on its surface (muscle, nerve), the polarisation
constants diminishing with excitement and in the process of dying.

Streamless Fresh Muscles.—It seems that passive, uninjured, and absolutely
fresh nerves, and muscles, are completely devoid of a current, ¢g., the heart
(Engelmann), also the musculature of fishes while still covered by the skin.

[According to Hermann, the currents obtained from muscle are due to injury of
the muscle-substance, whereby a difference of potential is set up, the injured part
being negative to the uninjured. In fact, it is impossible to isolate a muscle with-
out injuring it, owing to its connections. Frogs exhibit skin-currents after the
skin is destroyed ; the muscles still exhibit currents, but Hermann explains this by
the action of the irritant, used to destroy the skin, also affecting the muscle. In
fishes, however, there are no skin-currents, and if they be curarised, absolutely no
current is obtained from their uninjured muscles (Hermann). The heart also when
passive and uninjured gives no current, although it exhibits an action-current when
it contracts, and every injured part in it possesses a negative electrical potential
with reference to the rest. | j :

L. Hermann also finds that the muscle-current is always developed after a time, which is very
short, when a new transverse section is made. [By means of his ‘‘ Fall-rheotom,” an arrange-
ment whereby a weight, covered with shagreen, injured a muscle, and at the same time, closed
and opened a galvanometer circuit, Hermann was able to show that the current—demarcation-
current—took a certain time to develop. Had it been pre-existent, as supposed by du Bois-
Reymond, this ought not to have been the case. ]

564 ACTION-CURRENTS.

- Demarcation-Current.—Every injury of a muscle or nerve causes at the point of injury
(demarcation surface) a dying substance, which behaves negatively to the positive intact substance.
The current thus produced is called by Hermann the “‘demarcation-current.” If individual
rts of a muscle be moistened with potash salts or muscle-juice, they become negatively electrical ;
if these substances be removed these parts cease to be negative (Biedermann). shin
It appears that all living protoplasmic substance has a special property, whereb injury ofa
art of it makes it, when dying, negative, while the intact parts remain positively e ectrical.
hus, all transverse sections of living parts of plants are negative to their surface (Buff); and the
same occurs in animal parts, e.g., glands and bones. Engelmann made the remarkable observa-
tion that the heart and smooth muscle again lose the negative condition of their transverse
section, when the muscle-cells are completely dead, as far as the cement-substance of the nearest
cells ; in nerves, when the divided portion dies, as far as the first node of Ranvier, When all
these organs are again completely streamless, then the absolutely dead substance behaves
essentially as an indifferent moist conductor. Muscles divided subcutaneously and healed do
not exhibit a negative reaction of the surface of their section.

All these considerations go to show that the pre-eaxistence of a current in living
uninjured tissues can no longer be maintained.

Theoretical. —Griinhagen and L. Hermann explain the electrotonic currents as being due to
internal polarisation in the nerve-fibre between the conducting core of the nerve and the enclos-
ing sheaths. Matteucci found that, when a wire is surrounded with a moist conductor, and the
covering placed in connection with the electrodes of a constant current, currents similar to the
electrotonic currents in nerves, and due to polarisation, are developed. If either the wire or
the moist covering be interrupted at any part, then the | Sade current does not extend
beyond the rupture (p. 562). The polarisation developed on the surface of the wire by its
transition-resistance causes the conducted current to extend much beyond the electrodes.

Muscles and nerves consist of fibres surrounded by indifferent conductors. As soon as a con-
stant current is closed, on their surface, internal polarisation is developed, which produces the
electrotonic variation ; it disappears again on opening or breaking the current. Polarisation is
detected by the fact that, in living nerve, the galvanic resistance to conduction across a fibre is
about five times, and in muscles about seven times greater than in the longitudinal direction.

Action-Currents.—The term ‘‘action-current” is applied by L. Hermann to the currents
obtained during the activity of a muscle or nerve. When a single stimulation-wave (contrac-
tion) passes along muscular fibres, which are connected at two points with a galvanometer, then
that point through which the wave is just passing is negative to the other. Occasionally, in
excised muscles, local contractions occur, and these points are negative to the other passive
parts of the muscle (Biedermann). In order, therefore, to explain the currents obtained from
a frog’s leg during tetanus, we must assume that the end of the fibre which is negative partici-
pates less in the excitement than the middle of the fibre. But this is the case only in dying or
fatigued muscles.

According to § 336, D, the direct application of a constant current to a muscle causes con-
traction first at the cathode, when the current is closed, and when it is opened, at the anode.
This is explained by assuming that, during the closing contraction, the muscle is negative at
the cathode, while with the opening contraction the negative condition is at the anode.

If a muscle be thrown into contraction by stimulating its nerve, then the wave of excitement
travels from the entrance of the nerve to both ends of the muscle, which also behave negatively
to the passive parts of the muscle. According to the point at which the nerve enters the muscle,
the ascending or descending wave of excitement will reach the end (origin or insertion) of the
muscle sooner than the other. On placing such a muscle in the galvanometer circuit, then at
first that end of the muscle will be negative which lies nearest to the point of entrance of the
nerve (¢.g., the upper end of the gastrocnemius), and afterwards the lower end. Thus, there
appears rapidly tier each other, at first a descending, and then an ascending, current in the
galvanometer circuit, of course reversed within the muscle itself (Sig. Mayer) (§ 332, 4).

The same occurs in the muscles of the human fore-arm. When these were caused to contract
through their nerves, at first the point of entrance of the nerve (10 cm. above the elbow-joint)
was negative, and then followed the ends of the muscles when the contraction-wave, with a
velocity of 10 to 13 metres per second, reached them (ZL. Hermann) (§ 399, 1).

If a completely uninjured, streamless muscle be made to contract directly and in toto, then
neither during a single contraction, nor in tetanus, is there a current, because the whole of the
muscle passes at the same moment into a condition of contraction.

Nerve-Currents.—Hermann also supposes that the contents of dying or active nerves behave
negatively to the passive normal portions. .

Imbibition Currents.—When water flows through capillary spaces, this is accompanied by
an electrical movement in the same direction (Quincke, Zéllner). Similarly, the forward move-
ment of water in the capillary interspaces of non-living parts (pores of a porcelain plate) is also
connected with electrical movements, which have the same Mirortign as the current of water. a

. a

e
J

VARIATIONS OF THE EXCITABILITY DURING ELECTROTONUS. 565

The same effect occurs in the movement of water, which results in that condition known as
imbibition of a body. We must remember, that at the demarcation surface of an injured nerve
or muscle, imbibition takes place ; that also at the contracted parts of a muscle imbibition of
fluid occurs (§ 227, II.) ; and that during secretion there is a movement of the fluid particles.

In plants, electrical phenomena have been observed during the passive bending of vegetable
parts (leaves or stalks), as well as during the active movements which are associated with the
bending of certain parts, ¢.g., as in the mimosa and dionea (Burdon-Sanderson). These
phenomena are perhaps explicable by the movement of water which must take place in the
interior of the vegetable parts (A. G. Kunkel). The root cap of a sprouting plant is negative
to the seed coverings (Hermann) ; the cotyledons positive to the other parts of the seedling
(Miiller-Hettlingen). In the incubated hen’s egg, the embryo is + , the yelk — (Hermann and
v. Gendre),

335. ELECTRONIC ALTERATION OF THE EXCITABILITY.—Cause of
Electrotonus.—If a certain stretch of a living nerve be traversed by a constant
electrical (“‘ polarising ” ) current, it passes into a condition of altered excitability
(Ritter, 1802, and others), which du Bois-Reymond called the electrotonic condition,
or simply electrotonus. This condition of altered excitability extends not only over
the part actually traversed by the current, entrapolar portion, but it is communi-
cated to the entire nerve, 7.¢., to the extrapolar portions. Pfliiger (1859) discovered
the following laws of electrotonus :—

At the positive pole or anode (fig. 408, A) the excitability is diminished—this
is the region of anelectrotonus ; at the negative pole or cathode (K) it is increased
—this is the region of cathelectrotonus. The changes of excitability are most
marked in the regions of the poles themselves.

Indifferent Point.—In the intrapolar region a point must exist where the
anelectrotonic and cathelectrotonic regions meet, where therefore the excitability is
unchanged ; this is called the indifference or neutral point. This point lies
nearer the anode (7) with a weak current, but with a strong current nearer the
cathode (z,) ; hence, in the first case, almost the whole intrapolar portion is more
excitable ; in the latter, less excitable. [Expressed otherwise, a weak current
increases the area over which the negative pole prevails, while the reverse is the
case with a strong current. Or in the intrapolar region, the diminution of excita-
bility extends as the strength of the current increases, or to put it otherwise, with
an increasing strength of current, the indifferent point moves from the positive to
the negative pole.] Very strong currents greatly diminish the conductivity at the
anode, and indeed may make the nerve completely incapable of conduction at this
part.

At the cathode also, but only after the polarising current has passed for some time through
the nerve (Werigo), the excitability is diminished, and the nerve in this area is rendered
incapable of conduction (Griinhagen).

Extrapolar Region.—The extrapolar area, or that lying outside the electrodes,
is greater the stronger the current. Further, with the weakest currents, the extra-
polar anelectrotonic area is greater than the extrapolar cathelectrotonic. With
strong currents this relation is reversed. ;

Fig. 408 shows the excitability of a nerve (N, ) traversed by a constant current in the
direction of the arrow. The curve shows the degree of increased excitability in the neighbour-
hood of the cathode (X) as an elevation above the nerve, diminution at the anode (4) as a
depression. The curve m, 0, 7, p, 7, shows the degree of excitability with a strong current ;
e, J, t,, h, k, with a medium current; lastly, a, b, 7, c, d, with a weak current.

The electrotonic effect increases with the length of the nerve traversed by the current. The
changes of the excitability in electrotonus occur instantly when the circuit is closed, while
anelectrotonus develops and extends more slowly. Cold diminishes electrotonus (Hermann and
vo. Gendre). —

When the polarising current is opened or broken, at first there is a reversal of
the relations of the excitability, and then there follows a transition to the normal
condition of excitability of the passive nerve (Pfliiger). At the very first moment
of closing, Wundt observed that the excitability of the whole nerve was increased.

566 PROOF OF. ELECTROTONUS IN MOTOR NERVES.

L. Proof of Electrotonus in Motor Nerves.—To test the laws of electrotonus, take a frog's
nerve-muscle preparation (fig. 401). A constant current (p. 542) is applied to a limited part
of the nerve by means of non-polarisable electrodes. A stimulus, electrical, chemical (saturated
solution of common salt), or mechanical is applied either in the region of the anode or cathode ;
and we observe whether the contraction which results is greater when the polarising current is
opened or closed. We shall consider the following cases (ig. 409).

(a) Descending extrapolar anelectrotonus, With a escending current we have to test
the excitability of the extrapolar region at the anode. If the stimulus (common salt) applied
at R (while the circuit was open) causes in this case (A) moderately strong contractions in the

Qo

era,
.

-
-

Fig. 408.
Scheme of the electrotonic excitability.
limb, then these at once become weaker, or disappear as soon as the constant current is trans-
mitted through the nerve. After the circuit is opened, the contractions produced by the salt
again occur of the original strength.

(b) Descending extrapolar cathelectrotonous (A). The stimulus (salt) is at R,, and the
contractions thereby produced are at once increased after closing the polarising current. On
opening it they are again weakened.

(c) Ascending extrapolar anelectrotonus (B). The salt lies
at 7,; the moderately strong contractions excited by the salt

a

B before the current is made, become feebler after the current is
Wer made. 3
<| (d) Ascending extrapolar cathelectrotonus (B). The salt lies

at 7. In this case we must distinguish according to the strength

: of the polarising current :—(1) When the current is very weak,

) which can be obtained with the aid of the rheocord (fig. 379), on

closing the polarising current, there is an increase of the con-

traction produced by salt. (2) If, however, the current is stronger,

the contractions become either smaller or cease. This is due to

4 Bae the fact that with strong currents the conductivity of the nodes

is diminished or even abolished (p. 565). Although the salt

acts on the excitable nerve, there is no contraction of the muscle,

as the conduction of an impulse is prevented by the resistance in
the nerve.

The law of electrotonus may also be demonstrated on a com-
pletely isolated nerve. The end of the nerve is properly disposed
upon electrodes connected with a galvanometer, so as to obtain
a strong current. If the nerve, when the constant current is
closed, is stimulated in the anelectrotonic area, ¢.g., by an in-

Fi ' duction shock, then the negative variation is weaker than when
g. 409. th betaine oceans C ly: it laét Ke
Method of testing the excita- | e polarising circuit was open. Conversely, it is stronger when
bility in el it is stimulated in the cathelectrotonic area. The currents from
lity in electrotonus. R, the extrapolar areas of a nerve in a condition of electrotonus,
r, Ry, 7), where the com- exhibit the negative variation when the nerve is stimulated
mon salt (stimulus) is ap- (Bernstein). id
Plied. [Tigerstedt, instead of employing an electrical or chemical
stimulus to excite the electrotonic nerve, used an apparatus like Heidenhain’s tetanometer,
pie the nerve was beaten gently with a: small ivory hammer. He fully confirms Pfliiger’s
resu . beget <a
Proof in Man.—In performing this experiment it is important to remember the distribution
of the current in the body. If both electrodes, for example, be placed over the course of the —
ulnar nerve (fig. 410), the currents entering the nerve at the anode (+ @ a) must diminish q

Se ee nr? eee

<a

eee

PROOF OF ELECTROTONUS IN SENSORY AND INHIBITORY NERVES. 567

excitability ; only above and below the anode (atc c) the positive current emerges from the
nerve and excites cathelectrotonus at these points. Similarly, where the cathode is applied
(-—c¢ cc) there is increased excitability, but in higher and lower parts of the nerve, where (at a a)
the positive current (coming from +) enters the nerve, the excitability is diminished (anelec-
trotonus) (v. Helmholtz, Erb). If we desire to stimulate in the neighbourhood of an electrode,
then we cannot act upon that part of the nerve whose excitability is influenced by the electrode.
In order, therefore, to stimulate directly the same point on which the electrode acts, it is
necessary to apply the stimulus at the same time by the electrode itself, ¢.g., either mechani-
cally or by conducting the stimulating current through the polarising circuit (Waller and de
Wattevitlle).

II. Proof of Electrotonus in Sensory Nerves.—Isolate the sciatic nerve of a decapitated
frog. When this nerve is stimulated in its course with a saturated solution of common salt,
reflex movements are excited in the other leg, the spinal cord being intact. These disappear as
soon as a constant current is applied to the nerve, provided the salt lies in the anelectrotonic
area (Pfliiger and Zurhelle, Hallstén).

III. Proof of Electrotonus in Inhibitory Nerves.—To show this, proceed thus :—On causing
dyspnoea in a rabbit, the number of heart-beats is diminished, owing to the action of the
dyspneeic blood on the cardio-inhibitory centre in the medulla oblongata. If, after dividing
the vagus on one side, a constant descending current be passed through the other intact vagus,
the number of pulse-beats is again increased (descending extrapolar anelectrotonus). If, how-
ever, the current through the nerve be an ascending one, then with weak currents the number

Fig. 410.
Scheme of the distribution of an electrical current in the nerve on galvanising the
ulnar nerve.

of heart-beats increases still more (ascending extrapolar cathelectrotonus). Hence, the action of
inhibitory nerves in electrotonus is the opposite of that in motor nerves.

During the electrotonus of muscle, the excitability of the entrapolar portion is
altered. The delay in the conduction is confined to this area alone (v. Bezold)-—
compare § 337, 1.

336. ELECTROTONUS—LAW OF CONTRACTION.—Opening and Closing
Shocks.—A nerve is stimulated both at the moment of the occurrence and that of
disappearance of electrotonus (2.e., by closing and opening the current— Ritter) :—
(1) When the current is closed, the stimulation occurs only at the cathode, 7.c., at
the moment when the electrotonus takes place. (2) When the current is opened,
stimulation occurs only at the anode, 7.e., at the moment when the electrotonus
disappears. [This is Pfliiger’s well-known principle—“‘ A given tract of nerve is stimu-
lated by the appearance of cathelectrotonus and the disappearance of anelectrotonus—not,
however, by the disappearance of cathelectrotonus nor by the appearance of anelectro-
tonus.” From this principle can be deduced the law of contraction.| (3) The
stimulation at the occurrence of cathelectrotonus is stronger than that at the dis-
appearance of anelectrotonus (Pfliiger). :

Ritter’s Opening Tetanus,—That stimulation occurs only at the anode, when the current is
opened, was proved by Pfliiger by means of ‘‘ Ritter’s opening tetanus.” Ritter’s tetanus con-

sists in this, that when a constant current is passed for a long time through a long stretch of
nerve, on opening the current, tetanus. lasting for a considerable time results. If the current

568 THE LAW OF CONTRACTION,

was a descending one, then this tetanus ceases at once after section of the intrapolar area, a
proof that the tetanus resulted from the now separated anode. If the current was an ascending
one, section of the nerve has no effect on the tetanus.

Pfliiger and v. Bezold found a further proof that the closing or make contraction proceeds from
the cathode, and the opening or break contraction from the anode, by showing that with a descend-
ing current, the closing contraction in the muscle, at the moment of closing occurred earlier,
while the opening contraction at the moment of opening occurred later ; and, conversely, with
an ascending current the closing contraction occurred later, and the opening contraction
sooner. The difference in time corresponds to the time required for the propagation of the
impulse in the intrapolar region (§ 337). If a large part of the intrapolar region in a frog’s
nerve be rendered inexcitable by applying ammonia to it, then only the electrode next the

muscle stimulates, i.c., always on closing or making a descending current and on opening or
breaking an ascending one (Biedermann).

A. The law of contraction is valid for all kinds of nerves—I. The contraction
occurring at the closing or opening of a constant current varies with (a) the direc-
tion (Pfaf’), and (}) the strength of the current (Heidenhain).

(1) Very feeble currents, in conformity with the third of the above statements,
cause only a closing contraction, both with an ascending and a descending current.
The disappearance of electrotonus is so feeble a stimulus as not to excite the nerve.

(2) Medium currents cause opening or closing contractions both with an ascending
and descending current.

(3) Very strong currents cause only a closing contraction with a descending
current ; the opening shock does not occur, because, with very strong currents,
almost the whole of the intrapolar portion of the electrotonic nerve is incapable of
conducting an impulse (p. 565), Ascending currents cause only an opening contraction
for the same reason. With a certain strength of current, the muscle remains
tetanic while the current is closed (“closing tetanus”).

[The law of contraction is formulated :—R =rest ; C = contraction. |

Ascending. | Descending.

| Strength of Current. -
On Closing. | On Opening. On Closing. | On Opening.

Weds we oe. a Cc | R C | R

| Medium,. . . . C C C | C

| Strong, . ; : : R C C | R

II. In a dying nerve, losing its excitability, according to the Ritter-Valli law
(§ 325, 7), the law of contraction is modified. In the stage of increased excitability,
weak currents cause only closing contractions with both directions of the current.
In the following stage, when the excitability begins to diminish, weak currents cause
opening and closing contractions with both currents. Lastly, when the excitability
is very greatly diminished, the descending current is followed only by a closing
contraction, and the ascending by an opening contraction (Ritter, 1829). .

III. As the various changes in excitability occur in a centrifugal direction along
the nerve, we may detect the various stages simultaneously at different.parts along
the course of the nerve. According to Valentin and Fick, the living intact nerve
shows only a closing contraction with both directions of the current, and opening
contractions only with very strong currents.

Fleischl’s Law of Contraction.—V. Fleisch] and Stricker have stated a different law, in
respect to the fact, that the excitability varies at certain points in the course of a nerve. The
sciatic nerve is divided into three areas :—(1) Stretches from the muscle to the place where the
branches for the thigh muscles are given off; (2) from here to the intervertebral ganglion; (3
from here into the spinal cord. Each of these three areas consists of two parts (‘‘ upper an
lower pole”), which adjoin each other at an equator. In each upper pole, the excitability of —
the nerve is greater for descending currents, and in each lower pole for ascending ones. At
each equator the excitability of the nerve is the same for ascending and descending currents.
The difference in the activity, due to the direction of the current, is greater for each stretch of
nerve the greater this stretch is distant from the equator. The excitability is less at those
points of the nerve where the three areas join each other. +t

THE LAW OF CONTRACTION. 569

Eckhard observed that, on opening an ascending medium current applied to the hypoglossal
nerve of a rabbit, one-half of the tongue exhibited a trembling movement instead of a contrac-
tion, while on closing a descending current, the same result occurred (§ 297, 3). According to
Pfliiger, the molecules of the passive nerve are in a certain state of medium mobility. In
cathelectrotonus the mobility of the molecules is increased, in anelectrotonus diminished.

B. The law for inhibitory nerves is similar. Moleschott, v. Bezold, and
Donders have found similar results for the vagus, with this difference, that, instead
of the contraction of a muscle, there is inhibition of the heart.

C. For sensory nerves also the result is the same, but we must remember that
the perceptive organ lies at the central end of the nerve, while in a motor nerve it
is at the periphery (muscle). Pfliiger studied the effect of closing and opening
a current on sensory nerves by observing the reflex movement which resulted.
Weak currents cause only closing contractions ; mediwm currents both opening and
closing contractions ; strong descending currents only opening contractions ; and
ascending only closing contractions. Weak currents applied to the human ski
cause a sensation with both directions of the current only at closing ; strong descend-
ing currents a sensation only at opening; strong ascending currents a sensation
only at closing (Marianini, Matteucc’). When the current is closed, there is prickly
feeling, which increases with the strength of the current (Volta). Analogous
phenomena have been observed in the sense organs (sensations of light and sound)
by Volta and Ritter.

D. In muscle, the law of contraction is proved thus—by fixing one end of the
muscle, keeping it tense, so that it cannot shorten, and opening and closing the
current at this end. The end of the muscle, which is free to move, shows the same
law of contraction as if the motor nerve were stimulated (v. Bezold). On closing

‘the current, the contraction begins at the cathode; on opening, at the anode
(Engelmann). EK. Hering and Biedermann showed more clearly that both the
closing and opening contractions are purely polar effects; when a weak current
applied to a muscle is closed, the first effect is a small contraction limited to the
cathodic surface of the muscle. Increase of the current causes increased contraction
which extends to the anode, but which is weaker there than at the cathode ; at the
same time, the muscle remains contracted during the time the current is closed.
On opening, the contraction begins at the anode; even after opening, the muscle
for a time may remain contracted, which ceases on closing the current in the same
direction.

By killing the end of a muscle in various ways, the excitability is diminished near this part.
Hence, at such a place the polar action is feeble (van Loon and Engelmann, Biedermann).
Touching a part with extract of flesh, potash, or alcohol diminishes locally the polar action,
while soda salts and veratrin increase it (Biedermann),

Closing Continued Contraction.—The moderate continued contraction, which is sometimes
observed in a muscle while the current is closed (fig. 329, O), depends upon the abnormal pro-
longation of the closing contraction at the cathode when a strong stimulus is used, or during
the stage of dying, or in cooled winter frogs; sometimes the opening of the current is
accompanied by a similar contraction proceeding from the anode (Biedermann). This tetanus
is also due to the summation of a series of simple contractions (§ 298, III.). By acting on a
muscle with a 2 per cent. saline solution containing sodic carbonate, the duration of the con-
traction is increased considerably, and occasionally the muscle shortens rhythmically (§ 296)
(Biedermann).

If the whole muscle is placed in the circuit, the closing contraction is strongest
with both directions of the current; during the time the current is closed, a con-
tinued contraction is strongest when the current is ascending ( Wundt).

Inhibitory Action.—The constant current, when applied to a muscle in a con-
dition of continued and sustained contraction, has exactly the opposite effect to
that on a relaxed muscle. If a constant current be applied by means of non-
polarisable electrodes to a muscle in a state of continued contraction, eg., after
poisoning with veratrin or through the contracted ventricle, when the current is
closed, there is a relaxation beginning at the anode and extending to the other

570 RITTER’S OPENING TETANUS.

parts; on opening the current applied to muscle in continued contraction, the
relaxation proceeds from the cathode.

Corresponding to this remarkable phenomenon, Biedermann found as regards the currents
in the muscle-substance following the ordinary law, that every contracted part is negative to
every passive section of the muscle. Perhaps the experiment of Pawlow, who found nerve-fibres
in the adductor muscle of the mussel, whose stimulation caused relaxation of the muscular
contraction, may throw some light on this question.

Ritter’s Opening Tetanus.—If a nerve or muscle be traversed by a constant
current for some time, we often obtain a prolonged tetanus, after opening the
current (Ritter’s opening tetanus, 1798). It is set aside by closing the original |
current, while closing a current in the opposite direction increases it (“ Volta’s |
alternative ”). The continued passage of the current increases the excitability for
the opening of the current in the same direction, and for the closing of the reverse
current ; conversely, it diminishes it for the closing of the current in the same
direction, and for the opening of the reverse current (Volta).

According to Griitzner and Tigerstedt, the cause of the opening contraction is partly due to
the occurrence of polarising after-currents (§ 333), and according to Hermann toa diminution
of the anodic positive polarisation.

Engelmann and Griinhagen explain the occurrence of opening and closing tetanus, thus, as |
due to latent stimulations, drying, variations of the temperature of the prepared nerve, which of |
themselves are too feeble to cause tetanus, but which become effective if an increased excitability |

|

obtuins at the cathode after closure, and at the anode after opening the current.

Biedermann showed that, under certain conditions, two successive opening contractions can
be obtained in a frog’s nerve-muscle preparation, the second and later one corresponding to
Ritter’s tetanus. The first of these contractions is due to the disappearance of anelectrotonus
in Pfliiger’s sense ; the second is explained, like Ritter’s opening tetanus, in Engelmann and |
Griinhagen’s sense.

Simultaneous action of the constant current and the nerve-current.—Action of two currents.
In a nerve-muscle preparation used to prove the law of contraction, of course a demarcation-
current is developed in the nerve (§ 334, II.). If an artificial weak stimulating-current be
applied to such a nerve, we obtain an interference effect due to these two currents ; closing a
weak constant current causes a contraction, which, however, is not properly a closing contrac-
tion, but depends upon the opening (or derivation) of a branch of the demarcation-current ;
conversely, the opening of a weak constant current may excite a contraction, which is really due
to the closing of a side branch of the nerve-current, in a secondary circuit through the electrodes
(Hering, Biedermann, Griitzner). :

If two induction shocks be simultaneously applied to a motor nerve, two cases are possible. :
Either the one shock is so feeble that the nerve is not thereby sufficiently excited to cause a
contraction, while the other shock causes only a feeble contraction. In this case, the sub-
maximal shock plays the part of a weak constant current, and the size of the contraction
depends only upon whether the effective stimulus was applied in the area of the anode or the
cathode of the submaximal shock (Sewall, Griinhagen, Werigo). If, however, unequal, strong,
induction shocks, each of which is effective—but separated from each other on account of
the electrotonic action—be applied to a nerve, then the result is as if the stronger alone was
Ms Sa feebler wave of excitation passes completely into the stronger one (Griinhagen,

erigo).

337. TRANSMISSION OF NERVOUS IMPULSES.—1. If a motor nerve
be stimulated at its central end (1) a condition of excitation is set up, and (2)
an impulse is transmitted along the nerve to the muscle with a certain velocity.
The latter depends on the former and represents the function of conductivity.
The velocity is about 274 metres [about 90 feet] per second (v. Helmholtz), and for
the human motor nerves 33°9 [100 to 120 feet per second] (v. Helmholtz and Bazt).

The velocity is less in the visceral nerves, ¢.g., in the pharyngeal branches of the vagus 8°2
patho . aan (Chawveau); in the motor nerves of the lobster 6 metres [18 feet] (Prédéricg and
van elde). :

Modifying Conditions.—The velocity is influenced by various conditions :-—
Temperature.—It is lessened considerably by cold (v. Helmholtz), but both high
and low temperatures of the nerve (above or below 15° to 25° C.) lessen it (Steiner
and Trojtzky) ; also curara, the electrotonic condition (v. Bezold) ; or only anelectro-
tonus, while cathelectrotonus increases it (Rutherford, Wundt). It varies also with

"ApS Re

duration, the extent of the

NERVE-IMPULSE IN SENSORY NERVES AND REACTION TIME. 571

the length of the conducting nerve, but it increases with the strength of the stimulus
(v. Helmholtz and Baxt), although not at first (v. Vintschgau).

Methods.—1. V. Helmholtz (1850) estimated the velocity of the nerve-impulse in a frog’s
motor nerve after the method of Pouillet. The method depends upon the fact that, the needle
of a galvanometer is deflected
by a current of very short

deflection being proportional
to the duration and strength
ofthe current. ‘The apparatus
is so arranged that the ‘‘ time-
marking current” is closed at
the moment the nerve is stimu-
lated, and opened again when
the muscle contracts. If the
nerve attached to a muscle be
now stimulated at the further
point from the muscle, and a
second time near its entrance
to the muscle, then in the
latter case the time between
the application of the stimulus
and the beginning of the con-
traction of the muscle, 7.¢., the
deflection of the galvanometer,
will be less than in the former
case, as the impulse has to
traverse the whole length of
the nerve to reach the muscle.
The difference between the two
times is the time required by
the impulse to traverse a given Fig. 411.

distance of nerve. Fig. 411 V. Helmholtz’s method of estimating the velocity of a
shows in a diagrammatic man- ‘ nerve-pulse.

ner the arrangement of the ex-

periment. The galvanometer, G, is placed in the time-marking circuit (open at first), a, 0b
(element), ¢ (piece of platinum on a key, W), introduced into the time-marking circuit, d, e,
f,h. The circuit is made by closing the key, 8, when d depresses the platinum plate of the
key, W. At once when the current
is closed, the magnetic needle is
deflected, and its extent noted. At
the same moment in which the cur-
rent between c and d is closed, the
primary circuit of the induction
machine is opened, the circuit being
i, k, ¢ (element), m, O (primary
spiral), p. Thereby an opening shock
is induced in: the secondary spiral,
R, which stimulates the nerve of the
frog’s leg at n. Thus, the closing
of the galvanometer circuit exactly
coincides with the stimulation of the
nerve. The impulse is propagated
through the nerve to the muscle, M, -
and the latter contracts when the im- ~ \_ jw
pulse reaches it, at the same time ae
opening the time-measuring circuit

at the double contact, ¢ and f, by

GIG Nk

Wa

raising the lever, H, which rotates Scheme for measuring the velocity of nerve energy. /,

onz. Atthe moment of opening, the clamp for femur; m, muscle; N, nerve; a, near, 6, re-
further deflection of the magnetic moved from, C, commutator; II, secondary; I, primary —
needle ceases. The contact at f is Spiral of induction machine; B, battery; 1, 2, key ;
made by a pointed cupola of mercury. 3, tooth on the smoked plate P.

When the lever, H, falls after the contact of the muscle, so that the point, ¢, comes into contact
with the underlying solid plate, y, the contact at / still remains open; ¢.e., through the gal-
vapometer circuit. If the nerve be stimulated with the opening shock, first atm, and then

572 METHOD OF ESTIMATING RAPIDITY OF A NERVE-IMPULSE.

at N, the deflection of the needle is greater in the former than in the latter case. From the
difference, we calculate the time for the conduction of the impulse in the stretch of the nerve
between 7 and N.

[2. A simpler method is that shown in the scheme, fig. 412. Use a pendulum
or spring myograph (fig. 323), and suspend in a suitable manner a frog’s gastro-
cnemius (m), with a long portion of the sciatic nerve (N) dissected out, by fixing

the femur in a clamp (jf), while the tendo Achilles is fixed to a lever, which.

inscribes its movements on the smoked glass plate (P) of the myograph ; place the
key of the myograph (2) in the circuit with the battery (B), and the primary
circuit of the induction machine (I). To the secondary coil (II) attach two wires,
and connect them with a commutator without cross-bars (C). Connect the other
binding screws of the commutator with two pairs of wires, arranged so that one
pair can stimulate the nerve near the muscle (a), and the other at a distance from
it (b). When the glass plate flies from one side to the other, the tooth (3) on
its framework opens the key (2) in the primary circuit, and if the commutator be
in the position indicated, then the induced current will stimulate the nerve at a,
and a curve will be obtained on the glass plate. Rearrange the pendulum as before,
but turn the handle of the commutator, and allow the glass plate to fly again.
This time the induced current will stimulate the nerve at 6, and a second con-
traction, a /ittle /ater than the first one, will be obtained. Register the velocity of
the glass plate by means of a tuning-fork, and the curve obtained will be something
like fig. 413, although this curve was obtained on a cylinder travelling at a uniform

Fig. 418.
1, curve obtained on stimulating a nerve (man) near the muscle ; 2, when the stimulus was
applied to the nerve at a distance from the muscle ; D, vibrations of a tuning-fork (250
per second).

rate. The difference between the beginning of the a and 6 curves indicates the
time that the nerve-impulse took to travel from 4 toa. This time is measured by
the tuning-fork, and if the distance between the points a and 6 is known, then the
calculation is a simple one. Suppose the stretch of nerve between a and b to be 2
inches, and the time required by the impulse to travel from a to 6 to be 745 second,
then we have the simple calculation—2 inches : 12 inches: : z}9”: yy”, or 80
feet per second. In fig. 413 the experiment was made on man; the curve 1 was
obtained by stimulating the nerve near the muscle, and 2 when the nerve was
stimulated at a distance of 30 centimetres. The interval between the vertical lines
corresponds to ;$5 second, 7.¢., the time required by the nerve-impulse to pass
along 30 centimetres of nerve, which is equal to a velocity of 30 metres (90 feet)
per second. |

In man, v. Helmholtz and Baxt estimated the velocity of the impulse in the median nerve
by causing the muscles of the ball of the thumb to write off their contractions on a rapidly
revolving cylinder. [In this case the ‘‘pince myographique” of Marey may be used (§ 708).
The ends of the pince are applied so as to embrace the ball of the thumb, so that when the
muscles contract, the increase in thickness of the muscles expands the pince, which acts on a
Marey’s tambour, by which the movement is transmitted to another tambour provided with a
writing-style, and inscribing its movements upon a rapidly moving surface, either rotatory
or swinging.] The nerve is stimulated at one time in the axilla and again at the wrist. Two
eurves are obtained, which, of course, do not begin at the same time. The difference in time
between the beginning of the two curves is the time taken by the impulse to traverse the above-

i in

NERVE-IMPULSE IN SENSORY NERVES AND REACTION TIME. 573

mentioned length of nerve. [The time is easily ascertained by causing a tuning-fork of a
known rate of vibration to write its movements under the curves, ]

3. In the sensory nerves of man, the velocity of the impulse is probably about
the same as in motor nerves. The rates given vary between 94 to 30 metres [280
to 90 feet] per second (v. Helmholtz).

Method.—Two points are chosen as far apart as possible, and at unequal distances from the
brain, and they are successively excited by a momentary stimulus, ¢.g., an opening induction
shock applied successively to the tip of the ear and the great toe. The moment of the applica-
tion of the stimulus is indicated on the registering surface. The person experimented on is
provided with a key attached to an electric arrangement, by which he can mark on the register-
ing surface the moment he feels the sensation in each case.

Reaction Time.—The time which elapses between the application of the stimulus and the
reaction is called the ‘‘ reaction time.” It is made up of the time necessary for conduction in
the sensory nerve, that for the process of perception in the brain, for the conduction in the
motor nerves to the muscles, by which the signs on the registering surface were made, and
lastly by the latent period (p. 480). The reaction time is usually about 0°125 to 0°2 second
(§ 374).

Pathological.—The conduction in the cutaneous nerves is sometimes greatly delayed, in
alterations of the cutaneous sensibility, in certain diseases of the spinal cord (§ 364). The
sensation itself may be unchanged. Sometimes only the conduction for painful impressions is
retarded, so that a painful impression on the skin is first perceived as a tactile sensation, and
afterwards as pain, or conversely. When the interval of time between these two sensations is
long, then there is a distinctly dowble sensation (Naunyn). It is rarely that voluntary move-
ments are executed much more slowly from causes depending on the motor nerves, but
occasionally the time between the voluntary impulse and the contraction is lengthened, but
there may be in addition slower or longer continued contraction of the muscle. In tabes
dorsalis or locomotor ataxia, the discharge of reflex movements is delayed ; it is slower with
thermal stimuli (60°) than with cold ones (0°52° C., Zwald).

338. DOUBLE CONDUCTION IN NERVES.—Conductivity is that property
of a living nerve in virtue of which, on the application of a stimulus, it transmits
an impulse. [The nature of a nerve-impulse is entirely unknown ; we may con-
veniently term the process nerve-motion, but there is some reason to believe that
nerve energy is transmitted by some sort of molecular vibration.]| The conductivity
is destroyed by all influences or conditions which injure the nerve in its continuity
(section, ligature, compression, destruction by chemical agents) ; or which abolish
the excitability at any part of its course (absolute deprival of blood ; certain
poisons, ¢.g., curara for motor nerves ; also strong anelectrotonus, § 335).

Law of Isolated Conduction.—Conduction always takes place only in the con-
tinuity of fibres, the impulse never being transferred to adjoining nerve-fibres.

Double Conduction.—Although apparently conduction in motor nerves takes
place only in a centrifugal direction towards the muscles, and in sensory nerves in a
centripetal direction, 7.e., towards the centre ; nevertheless, experiment has proved
that a nerve conducts an impulse in both directions, just as in a non-living con-
ductor. Ifa pure motor or sensory nerve be stimulated in its course, an impulse
is propagated at the same time in a centrifugal and in a centripetal direction.
This is the phenomenon of ‘‘ double conduction.”

Proofs.—1. If a nerve be stimulated, its electro-motive properties are affected
both above and below the point of stimulation (see Wegative Variation in Nerves,
§ 332).

2. ‘tectrical Nerves.—If the posterior free-end of the electrical centrifugal
nerves of the malapterurus be stimulated, the branches given off above the point
of stimulation are also excited, so that the whole electrical organ discharges its
electricity (Babuchin, Mantey). :

3. Kiihne’s Experiments.—The sartorius of the frog has no nerve-fibres at its
upper and lower ends. If the lower end be cut off, and if the lower third of the
muscle be suspended and divided vertically, on stimulating mechanically one apex
of the muscle, then the impulse passes in the motor nerves centripetally to the place

574 PROOFS OF DOUBLE CONDUCTION IN NERVES,

where the nerve-fibre bifurcates in the muscle, and from thence centrifugally into
the other or non-stimulated apex, and causes it to contract.
[The Gracilis of the frog is divided into a larger and smaller portion (L) by a
tendinous inscription (K) running across it (fig. 414). The nerve (N) enters at
; the hilum in the larger portion, bifurcates, and gives a branch (k) to

the smaller portion and another to the larger portion of the muscle.
Let the muscle be cut as shown in fig. 414, avoiding injury to the
nerves, so that only the nerve-twig (4) connects the larger and smaller
portions of the muscle. If the tongue or tip of muscle (Z) with
its nerves be stimulated. contraction occurs both in L and M, which .
is due to centripetal conduction in the motor nerve. The nerve-fibres |
divide dichotomously above where the nerves are given off to the 7
portions L and M. | | |
[If the inscription be left, and the lower tip of the muscle (which |

is devoid of nerves) be stimulated, only the lower and not the upper |
Kiihne’s Gracilis part twitches; but if a part of the muscle containing nerves common |
experiment. to both parts be stimulated, then both parts of the muscle contract. |
This also proves that pure muscular excitation does not travel backwards from the |
muscle to the nerves. How this comes about, we are entirely ignorant. | |
|

|

The following experiments used to be cited as proofs, but they do not stand the
test of criticism.

4. Union of Motor and Sensory Nerves.—If the hypoglossal and lingual nerves be divided in
a dog, and if the peripheral end of the hypoglossal be stitched, so as to unite with the central
2 end of the litigual (Bidder), then,
several months after the union and
restitution of the nerves, stimula-
tion of the central end of the
lingual causes contraction in the
corresponding half of the tongue.
Hence, it has been assumed that
the lingual, which is the sensory
nerve of the tongue, must conduct
the impulse in a peripheral direc-
tion to the end of the hypoglossal. 7
This experiment is not conclusive,
as the trunk of the lingual receives
high up the centrifugal fibres from ;
the seventh, viz., the chorda tym- .
pani, which may unite with those
of the hypoglossal. Further, ifthe
chorda be divided and allowed to
degenerate before the above de-
scribed experiment is made, then
no contractions occur on stimu-
lating the lingual above the point
of union (§ 349). _ . ;
5. Bert’s Experiment. — Paul
Bert removed the .skin from the
tip of the tail of a rat, and stitched
it into the skin of the back of the
animal, where it united with the
tisanes Afee the ft Hee ine
Fig. 415. Fig. 416. Fig 417. taken place, the tail was then di-
: . vided at its base, so that the tail,
Double sponge kids Disc rheophore. Metallic brush. as it were, grew out of thé'ekin 6m
the back of the animal. On stimulating the tail, the animal exhibited signs of sensation. For
the explanation of this experiment, see § 325. :

339, ELECTRO-THERAPEUTICS—REACTION OF DEGENERATION. —Electricity is fre-
_ quently employed for therapeutical purposes, the ep interrupted current of the induction
machine, or Faradic current, being frequently used (especially since Duchenne, 1847), the .

THERAPEUTICAL USES OF ELECTRICITY—-RHEOPHORES. 575

magneto-electrical apparatus, and the extra-cwrrent apparatus.

The constant or galvanic current
is also used, especially since Remak’s time, 1855 (§ 330).
N. radialis, M. triceps (caput ext.)
re M. triceps
‘ M. brachial. intern. / (caput long.)

M. supinator iong.
; M. radial. ext. long.
' M. radia’. ext. brev. /

| M. deltoideus
(post. half). ‘
(N. axillaris).

M. ulnar. ext. \

M. extens. digit. communis. M. supinat. brev. /

M. extens. digit. min. i /
M. extens. ee L
\

M. abduct. pollic. long.

M. extens. pollic. brev,
M. extens. poll. long. ,

y
M. abduct. digit. min. (N. ulnaris.)

Mm. inteross. dorsal. I, IL, 1II, et [V.
(N. ulnaris.)

Fig. 418.
- Motor points of the radial nerve and the muscles supplied by it ; dorsal surface.
1. In paralysis, Faradic currents are applied, either to the muscles themselves (Duchenne),
or the points of entrance of the motor nerves, by means of suitable electrodes, or rheophores
covered with sponge, &c., and moistened (v. Ziemssei).

M. deltoideus (ant. half) N. axillaris.
N. musculo-cutaneus.
M. biceps brachii.

M. brach. anticus.

N. medianus.

M. pronator teres
ss : M. abductor pollic. brev.
M. flex. digitor. commun. profund. sapere

M. opponens pollicis.
M. flex. carpi radialis. | ie Os
. flex. digitor. sublim. - flex. poll. brev.
i M, flex. dig subl. M. abductor pollic. brev.
| - (dig. ind. et min.)

Man, lumbrica!es
M. flex poll. Tetdn

|
|

Mm. lumbri-
calesIII et IV.

ae M. opponens digit. min.
Saat, M. flexor digit. min.
= M. abductor digit. min.

‘ : if MaiiaGiy ont -- --L.. ~ M, palmaris brev,
M. flexor carpi Unaris.s | .. ~N. ulnaris.

| Bea GS O88 20 Betirin,

_ Motor points of the median and ulnar. nerves, with the muscles supplied by them.
[Rheophores,—Many different forms are used, saccording to the organ or'part to be stimu-

N. ulnaris.

Wid si

576 EFFECT OF THE CONSTANT CURRENT,

lated, or the effect desired. When electricity is applied to the skin to remove anesthesia,
hyperesthesia, or altered sensibility, and we desire to limit the effect to the skin alone, then
the rheophores are applied dry, and are usually made of metal. If, however, deeper-seated
structures, as muscles or nerve-trunks, are to be affected, the skin must be well moistened and
-softened by sponging with warm water, while the rheophores are fitted with sponges moistened
with contmon salt and water, which diminishes the resistance of the skin to the passage of
electricity (figs. 415-417). ] ae ac.

In faradising the paralysed muscle, the object is to cause artificial movements in it, and thus

prevent the degeneration which it would otherwise undergo, merely from inaction. If, in»

addition to the motor nerves, its trophic nerves are also paralysed, then a muscle atrophies,

__--— N. cruralis, \
M. tensor fascize late
Peet (Nn. glut. sup.)
Ye
a
5 N. obturator. — A
a M. pectineus. M, quadriceps femoris 8
=} —— (general centre). 4
~
2
ro M. adductor magnus. - scat H °
= _—— M. rectus femoris. z
E M. adduct. longus. ©
I __-— M. cruralis. e
z, .
M. vastus externus.
a M. vastus internus.
N. peroneus. M, gastrocnem. extern.
M. tibial. antic.
; M. soleus.
M. exten. dig. com. long. —————
z M. peroneus longus. ee” 2
5 M brevi 5
. peroneus brevis.
3 P : . _— M. flexor hallucis long. 4
7 M. extens. hallucis long. ..—— ) st
ca
3 ra M. abductor digiti. min, E
Zz g .
M. extens. digit. comm.
brevis al ee
v ss — -
re Mm, interossei dorsales.

Fig, 420,
Motor points of the peroneal and tibial Deere on the front of the leg; the peroneal on the
left, the tibial on the right (after Hichhorst),

notwithstanding the faradisation’ (§ 325, 4). The use of the induced current also improves a
paralysed muscle, as it increases the blood-stream through it, while it affects the metabolism
of the muscle reflexly. In addition, weak currents may restore the excitability of enfeebled
nerves (v. Bezold, Engelmann).

The figs. 418, 419, 420, 421 indicate the positions of the motor points of the extremities,
where, by stimulating at the entrance of the nerve, each muscle may be caused to contract
singly. In § 349 the motor points of the face, and in § 347 those of the neck, are indicated.

The constant current may be employed as a stimulus, when it is closed and opened, in the
form of an interrupted current, by altering its direction and increasing or diminishing its
intensity, but it also causes a polar action, On closing the current, the nerve at the cathode is

REACTION OF DEGENERATION. 5/7

stimulated ; similarly, on opening the current, at the anode (§ 336). Thus, when the current
is closed, the excitability of the nerve is increased at the cathode (§ 335), which may act
favourably upon the nerve. Increased excitability in electrotonus at the anode, although
feebler, has been observed during percutaneous galvanisation in man. This is especially the
case by repeatedly reversing the current, sometimes also by opening and closing, or even with
a uniform current. If the increase of the excitability is obtained, then the direction of the
current increases the excitability on closing the reverse current, and on opening the one in the
same direction.

Restorative Effect.—Further, in using the constant current, we have to consider its restor-
ative effects, especially when it is ascending. R. Heidenhain found that feeble and fatigued
muscles recover after the passage of a constant current through them.

M. gluteus maximus
(great sciatic).

N. ischiadicus.

M, biceps fem. (cap. long.)

(grt. sciat.). M.adduct.magnus (n.obt.)

M. semitendinosus (grt.

—

M. biceps fem. (cap. brev.)

sciat.).
M. semimembranosus
(grt. sciat.). (grt. sciat.).

N, tibialis.

Nervus peroneus.

N. peroneus.

M. gastrocnem.(cap.extr.).

M. gastrocnem. (cap. int.).

‘STTBIQI} SNAION

M. soleus.

M. flex. dig. comm. long.

M. flexor hallucis longus.

N. tibialis.

Fig. 421.
Motor points of the sciatic nerve and its branches; the peroneal and tibial nerves.

Lastly, the constant current may be useful from its catalytic or cataphoric action (§ 328).
The effect is directly upon the tissue elements. It may also act directly or reflexly upon the
blood- and lymph-vessels.

Faradisation in Paralysis, —If the primary cause of the paralysis is in the muscles themselves,
then the induced current is generally applied directly to the muscles themselves by means of
sponge electrodes (fig. 415) ; while, if the motor nerves are the primary seat, then the electrodes
are applied over them. The current used must be only of very moderate strength ; strong
tetanic contractions are injurious, and so is too prolonged application (Zulenburg).

The galvanic current may also be applied to-the muscles or to their motor nerves, or to the
centres ofthe latter, or to both muscle and nerve simultaneously, As a rule, the cathode is
placed nearer the centre, as it increases the excitability. When the electrode is moved along
the course of the nerve, or when the strength of the current is varied, the action is favoured,
If the seat of the lesion is in the central nervous system, then the electrodes are applied along
the vertebral column, or on the vertebral column, and the course of the nerves at the same

20

578 REACTION OF DEGENERATION.

time, or one on the head and the other on a point as near as possible to the supposed seat of
the lesion. The current must not be too strong nor applied too long. .

Induced v. Constant Current: Reaction of Degeneration.—Paralysed nerves and muscles
behave quite differently as regards the induced (rapidly interrupted) and the constant current.
This is called the ‘‘ reaction of degeneration.” We must remember the physiological fact that
a dying nerve attached to a muscle ($ 325), and also the muscles of a curarised animal, react
much less strongly to rapidly interrupted currents than fresh non-curarised muscles. Baierlacher,
in 1859, found that, in a case of facial paralysis, the facial muscles contracted but feebly to the
induced current, but very energetically on the constant current being used. The excitability
for the constant current may be abnormally increased, but may disappear on recovery taking
place. According to Neumann, it is the longer duration of the constant current as opposed to
the momentary closing and opening of the induced current which makes the contraction of the
muscle possible. If the constant current be broken as rapidly as the Faradic current is broken,
then the constant current does not cause contraction. Conversely, the induced current may be
rendered effective by causing it to last longer. We may also keep the primary circuit of the
induction machine closed, and move the secondary spiral to and fro along the slots. Thus we
obtain slow gradations of the induced current which act energetically upon curarised muscles
(Briicke). Hence, in stimulating a muscle or nerve, we have to consider not only the strength,
but also the duration, of the current, just us the deflection of the magnetic needle depends upon
these two factors.

[Galvanic excitability is the term applied to the condition of a nerve or muscle, whereby it
responds to the opening or closing of a continuous current. The effects differ according as the
current is opened or closed, and according to its strength. Asa rule, the cathode causes a con-
traction chiefly at closure, the anode at opening the current, while the cathode is the stronger
stimulus. With a weak current, the cathode produces a simple contraction on closing the current,
but no contraction from the anode. With a medium current, we get with the cathode a strong
closing contraction but no opening contraction, while the anode excites feeble opening and
closing contractions. With a strong current, we get with the cathode a tetanic contraction at
closure, and a perceptible contraction at opening, while with the anode there is contraction both
at opening and closing. ]

[The law of contraction is usually expressed by the following formula (Z7b) :—An=anode,
Ca=cathode, C=contraction, c=feeble contraction, C’=strong contraction, S=closure of
current, O=opening of current, Te=tetanic contraction—so that, expressing the above state-
ments briefly, we have—

Weak currents produce Ca S C ;
Medium ,, CaS OC’, AnSc, AnOc;
Strong ,, : CaS Te, AnSC, AnOC.CaOc] -

[Typical Reaction of Degeneration.—When the reaction of the nerve and muscle
to electrical stimulation is altered both qualitatively and quantitatively, we have
the reaction of degeneration, which is characterised essentially by the following
conditions] :—The excitability of the muscles is diminished or abolished for the
Faradic current, while it is increased for the galvanic current from the 3rd to 58th
day ; it again diminishes, however, with variations, from the 72nd to 80th day ; the
anode closing contraction is stronger than the cathode closing contraction. The con-
tractions in the affected muscles occur slowly in a peristaltic manner, and are local,
in contrast with the rapid contraction of normal muscle. The diminution of the
excitability of the nerves is similar for the galvanic and Faradic currents. If the
reaction of the nerves be normal, while the muscle during direct stimulation with
the constant current exhibits the reaction of degeneration, we speak of “ partial
reaction of degeneration,” which is constantly present in progressive muscular
atrophy (£7b).

[The “reaction of degeneration” may occur before there is actual paralysis, as in lead
poisoning. When it occurs we have to deal with some affection of the nerve-fibres, or of the
trophic nerve-cells. When it is established, (1) stimulation of the nerve with Faradie and
galvanic electricity does not cause contraction of the muscle ; (2) direct Faradic stimulation
the muscles does not cause contraction ; (3) the galvanic current usually excites contraction
more readily than ina normal muscle, so that the muscle responds to much feebler currents
than act on healthy muscles, but the contraction is longer and more of a tonic character, and
shows a tendency to become tetanic. The electrical excitability is generally unaffected in
paralysis of cerebral origin, and in some forms of spinal paralysis, as primary lateral sc
and transverse myelitis, but the ‘‘ reaction of degeneration” occurs in traumatic paralysis, d
to injury of the nerve-trunks, neuritis, rheumatic facial paralysis, lead palsy, ot ie affections

-

APPLICATIONS OF ‘ELECTRICITY IN DISEASE. 579

of the nerve-cells in the anterior cornu of the grey matter of the spinal cord.] In rare cases
the contraction of the muscles, caused by applying a Faradic current to the nerve, follows a
slow peristaltic-like course—‘‘ Faradic reaction of degeneration” (E. Remak, Erb).

II. In Various Forms of Spasm (spasins, contracture, muscular tremor) the constant current
is most effective (Remak). By the action of anelectrotonus, a pathological increase of the
excitability is subdued. Hence, the anode ought to be applied to the part with increased
excitability, and if it be a case of reflex spasm, to the points which are the origin or seat of the
increased excitability. Weak currents of uniform intensity are most effective. The constant
current may also be useful from its cataphoric action, whereby it favours the removal of irritants
from, the seat of the irritation. Further, the constant current increases the voluntary control
over the affected muscles. In spasms of central origin, the constant current may be applied to
the central organ itself. Faradisation is used in spasmodic affections to increase the vigour of
enfeebled antagonistic muscles. Muscles in a condition of contracture are said to become more
extensible under the influence of the Faradic current (Remak), as a normal muscle is more
excitable during active contraction (§ 301).

In Cutaneous Anesthesia, the Faradic current applied to the skin by means of hair-brush
electrodes is frequently used (fig. 417). When using the constant current, the cathode must be
applied to the parts with diminished sensibility. The constant current alone is applied to the
central seat of the lesion, and care must be taken to what extent the occurrence of cathelectro-
tonus in the centre affects the occurrence of sensation.

III. In Hyperesthesia and Neuralgias, Faradic currents are applied with the object of
over-stimulating the hyper-sensitive parts, and thus to benumb them. Besides these powerful
currents, weak currents act reflexly and accelerate the blood-stream, increase the heart’s action,
and constrict the blood-vessels, while strong currents cause the opposite effects (O. Nawmann).
Both may be useful. In employing the constant current in neuralgia (Remak), one object is
by exciting anelectrotonus in the hyper-sensitive nerves, to cause a diminution of the excita-
bility. According to the nature of the case, the anode is placed either on the nerve-trunk, or
even on the centre itself, and the cathode on an indifferent part of the body. The catalytic and
cataphoric effects also are most ‘important, for by means of them, especially in recent rheumatic
neuralgias, the irritating inflammatory products are distributed and conducted away from the
part. A descending current is transmitted continuously for a time through the nerve-trunk,
and in recent cases its effects are sometimes very striking. Lastly, of course, the constant
current may be used as a cutaneous stimulus, while the Faradic current also acts reflexly on the
cardiac and vascular activity. PRY ee eee
_ Recently, Charcot and Ballet have used the electric spark from an electrical machine in cases
of anesthesia, facial paralysis, and paralysis agitans. In some cases of spinal paralysis, muscles
can be made to contract with the electric spark, which do not contract to a Faradic current.
[Electricity is sometimes used to distinguish real from feigned disease, or to distinguish death
from a condition of trance. ] _ ;

,Galvano-Cautery.—The electrical current is used for thermal purposes, as in the-galvano-
cautery. . ae ria §

Galvano-Puncture.—The electrolytic properties of electrical currents are employed to cause
coagulation in aneurisms or varix. [If the electrodes from a constant battery in action be
inserted in an aneurismal sac, after a time the fibrin of the ,blood is deposited in the sac,
whereby the cavity of the aneurism is gradually filled up.. A galvanic current passed through
defibrinated blood causes the formation of a coagulum of proteid matter at the positive pole and
bubbles of gas at the negative. ] Poe caren ine

340. ELECTRICAL CHARGING OF THE BODY.—Saussure investigated by means of the
electroscope the ‘‘ charge” of a person standing on an insulated stool. The phenomena observed
by him, which were always inconstant, were due to the friction of the clothes upon the skin.
Gardini, Hemmer, Ahrens (1817), and Nasse regarded the body as normally charged with
positive electricity, while Sjosten and others regarded it as negatively charged.- Most probably
all these phenomena are due to friction, and are modified effects of the air in contact with the
heterogeneous clothing (Hankel). A strong charge resulting in an actual spark has frequently
been described. Cardanus (1553) obtained sparks from the -tips of the hair of the head.
According to Horsford (1837), long sparks were obtained from the-tips of-the fingers of a
nervous woman in Oxford, when she stood upon an insulated carpet. -Sparks have often been
observed on combing the hair or stroking the back of a cat in the dark. Freshly voided wrine
is negatively electrical (Vasalli-Eandi, Volta); so is the freshly formed web of a spider, while
the blood is positive. teh

341. COMPARATIVE—HISTORICAL.—HElectrical Fishes.—Some of the most interesting
phenomena connected with animal electricity are obtained in electrical fishes, of which there are
about fifty species, including the electrical eel, or Gymnotus electricus, of the lagoons of the region
of the Orinoco in South America—it may measure over 7 feet in length—the Torpedo marmorata
and some allied species, 30 to 70 centimetres [1 to 24 feet], in the Adriatic and Mediterranean, the
Malapterurus electricus of the Nile, and the Mormyrus also of the same river. By means of

580 COMPARATIVE—HISTORICAL,

special electrical organs (Hedi, 1666), these animals can in part voluntarily (gymnotus and
malapterurus), and in part reflexly (torpedo), give a very powerful electrical shock. The
electrical organ consists of ‘‘ compartments” of various forms, separated from each other by con-
nective-tissue, and filled with a jelly-like substance, which the nerves enter on one surface and
ramify to‘produce a plexus, From this plexus there proceed branches of the axial arenes
which ee in a nucleated plate, the ‘‘electrical plate” (Billharz, M. Schulze), When the
*‘ electrical nerves ’’ proceeding to the organ are stimulated, an electrical discharge is the result.

In Gymnotus, the electrical organ consists of several rows of columns arranged along both
sides of the spinal column of the animal, under the skin as far as the tail. It receives on the
anterior surface several branches from the intercostal nerves. Besides this large organ there is
a smaller one lying on both sides above the anal fins, Here the plates are vertical, and the
direction of the electrical current in the fish is ascending, so that of course it is descending in
the surrounding water (Faraday, du Bois-Reymond).

In Malapterurus, the organ surrounds the body like a mantle, and receives only one nerve-
fibre (p. 529), whose axis cylinder arises near the medulla oblongata from one gigantic ganglionic -
cell (Billharz), and is composed of protoplasmic processes (Fritsch), The plates are also vertical,
and receive their nerves from the posterior surface. The direction of the current is descending
in the fish during the discharge (du Bois-Reymond).

In the Torpedo, the organ lies immediately under the skin laterally on each side of the head,
reaching as far as the pectoral fins. It receives several nerves which arise from the lobus
electricus, between the corpora quadrigemina and the medulla oblongata, The plates, which do
not increase in number with the growth of the animal (Delle Chiaje, Babuchin), lie horizontally,
while the nerve-fibres enter them on their dorsal surfaces, the current in the fish being from the
abdominal to the dorsal surface (Galvani). :

It is extremely probable that the electric organs are modified muscles, in which the nerve
terminations are highly developed, the electrical plates corresponding to the motorial end-plates
of the muscular fibres, the contractile substance having disappeared, so that during physiological
activity the chemical energy is changed into electricity alone, while there is no ‘‘ work”. done.
This view is supported by the observation of Babuchin, that during development the organs are
originally formed like muscles; further, that the organs when at rest are neutral, but when
active or dead, acid ; and lastly, they contain a substance related to myosin which coagulates
after death (§ 295—Weyl), The organs manifest fatigue; they have a ‘“‘latent period” ~
of 0016 second, while one shock of the organ (comparable to the current in an active muscle)
lasts 0°07 second, About twenty-five of these shocks go to make a discharge, which lasts
about 0°23 second. The discharge, like tetanus, is a discontinuous process (Marey),
Mechanical, chemical, thermal, and electrical stimuli cause a discharge; a single induction
shock is not effective (Sachs). During the electrical discharge the current traverses
the muscles of the animal itself; the latter contract in the torpedo, while they do not
do so in the gymnotus and malapterurus during the discharge (Steiner). A torpedo can
give about fifty shocks per minute; it then becomes fatigued, and requires some time to
recover itself, It may only partially discharge its organ (Al. v, Humboldt, Sachs), Cooling
makes the organ less active, while heating it to 22° C. makes it more so, The organ becomes
tetanic with strychnin (Becquerel), while curara paralyses it (Sachs), Stimulation of the
electrical organ of the torpedo causes a discharge (Matteucci); cold retards it, while section of
the electrical nerves paralyses the organ, The electrical fishes themselves are but slightly
affected by very strong induction shocks transmitted through the water in which they are
swimming (du Bois-Reymond), The substance of the electrical organs is singly refractive ;
excised portions give a current during rest, which has the same direction as the shock ; tetanus
of the organ weakens the current (Sachs, dw Bois-Reymond). Perhaps the electrical organs of
malapterurus is evolved from modified cutaneous glands (Fritsch). .

Historical.—Richer (1672) made the first communication about the gymnotus. Walsh
(1772) made investigations on the torpedo, on its discharge, and its power of communicating a
shock. J. Davy magnetised particles of steel, caused a deflection of the magnetic needle, and
obtained electrolysis with the electrical discharge, Becquerel, Brechet, and Matteucci studied
the direction of the discharge. Al, vy Humboldt described the habits and actions of the :
notus of South America, Hausen (1743) and de Sauvages (1744) supposed that electricity
was the active force in nerves. The actual investigations into animal electricity began with G,
Aloisio Galvani (1791), who observed that frogs’ legs connected with an electrical machine con-
tracted, and also when they were touched with two different metals. He believed that ner Aa
and muscles generated electricity. Alessandro Volta ascribed the second experiment to then
electrical current produced by the contact of dissimilar metals, and therefore outside the tissues” 2
of the frog. The contraction without metals described by Galvani was confirmed by Alex. v.
Humboldt (1798). Pfaff (1793) first observed the effect of the direction of the current upon th
contraction of a frog’s leg obtained by stimulating its nerve. Bunzen made a galvanic pile:
frogs’ legs, The whole subject entered on a new phase with the construction of the galvans
meter and since the introduction of the classical methods devised by du Bois-Reymond, 4,
from 1843 onwards. ; i

A oe ——

a a ae

Physiology of the Peripheral Nerves.

342. FUNCTIONAL CLASSIFICATION OF NERVE-FIBRES.-— As nerve-
fibres, on being stimulated, are capable of conducting impulses in both directions
(§ 338), it is obvious that the physiological position of a nerve-fibre must depend
essentially upon its relations to the peripheral end-organ on the one hand, and its
central connection on the other. Thus, each nerve is distributed to a special area
within which, under normal circumstances, in the intact body, it performs its
functions. This function of the individual nerves, determined by their anatomical
connections, is called their ‘specific energy.” |

I. Centrifugal or Efferent Nerves.—(a) Motor.—Those nerve-fibres whose
peripheral end-organ consists of a muscle, the central ends of the fibres being
connected with nerve-cells :— _

1. Motor fibres of striped muscle (§§ 292 to 320).

2. Motor nerves of the heart (§ 57).

3. Motor nerves of smooth muscle, ¢.g., the intestine (§ 171). The vaso-motor nerves are
specially treated of in § 371.

(b) Secretory.—Those nerve-fibres whose peripheral end-organ consists of a
secretory cell, the central ends of the fibres being connected with nerve-cells.

Examples of secretory nerves are the secretory nerves for saliva (§ 145) and those for sweating
(§ 289, 1I.). It is to be remembered, however, that these fibres not unfrequently lie in the
same sheath with other nerve-fibres, so that stimulation of a nerve may give rise to several
results, according to the kind of nerve-fibres present in the nerve. Thus, the secretory and
vaso-motor nerves of glands may be excited simultaneously.

(c) Trophic.—The end-organs of these nerve-fibres lie in the tissues themselves,
and are as yet unknown. These nerves are called trophic, because they are
supposed to govern or control the normal metabolism of the tissues,

In some tissues, we know of a direct connection of their elements with nerve-fibres, which
may influence their nutrition. Nerves are connected with the corneal corpuscles (§ 201, 7),
with the pigment-cells of the frog’s skin (Ehrmann), the connective-tissue corpuscles of the
serous membrane of the stomach of the frog, and the cells around the stomata of lymphatic
surfaces (§ 196, 5) (Z. F.- Hoffmann). :

Trophic Influence of Nerves.—The trophic functions of certain nerves are referred to as
under :—On the influence of the trigeminus on the eye, the mucous membrane of the mouth
and nose, the face (§ 347); the influence of the vagus on the lungs (§ 352); motor nerves on
muscle (§ 307); nerve-centres on nerve-fibres (§ 325, 4) ; certain central organs upon certain
viscera (§ 379).

Section of certain nerves influences the growth of the bones. H. Nasse found that, after
section of their nerves, the bones showed an absolute diminution of all their individual con-
stituents, while there was an increase of the fat. Section of the spermatic nerve is followed by
degeneration of the testicle (Nélaton, Obolensky). After extirpation of their secretory nerves,
there is degeneration of the sub-maxillary glands (p. 213). Section of the nerves of the cock’s-
comb interferes with the nutrition of that organ (Legros, Schiff). After section of the 2nd
cervical nerve in rabbits and cats, the hair falls off the ear on that side (Joseph). Section of the

582 TROPHIC NERVES AND TROPHONEUROSES.

cervical sympathetic nerve in young, growing animals is followed by a more rapid growth of the

ear oes side (Bidder, Stirling, Stricker), also of the hair on that side (Schiff, Stirling) ; .

while it is said that the corresponding half of the brain is smaller, which, perhaps, is due to

the pressure from the dilated blood-vessels (Brown-Séquard). ;
ood-Vessels.—Lewaschew found that prolonged uninterrupted stimulation of the sciatic

nerve of dogs, by means of chemical tail [threads dipped in sulphuric acid), caused hyper-

trophy of the lower limb and foot, together with the formation of aneurismal dilatations upon

the blood-vessels.

Skin and Cutaneous Appendages. —In man, stimulation or paralysis of nerves, or degeneration
of the grey matter of the spinal cord, is not unfrequently followed by changes in the pigmenta-
tion of the skin, in the nails, in the hair and its mode of growth and colour (Jarisch). [Injury
to the brain, as by a fall, sometimes results in paralysis of the hair follicles, so that, after such
an injury, the hair is lost over nearly the whole of the body.] Sometimes there may be erup-
tions upon the skin, apparently traumatic in their origin (v. Bérensprung). Sometimes there is
a tendency to decubitus (§ 379), and in some rare cases of tabes, there is a peculiar degeneration
of the joints (Charcot’s disease). The changes which take place in a nerve separated from its
centre are described in § 325.

[Trophoneuroses.—Some of the chief data on which the existence of trophic nerves is assumed
are indicated above. There are many pathological conditions referable to diseases or injuries of
nerves,

arene =e is well known, paralysis of a motor nerve leads to simple atrophy of the
corresponding muscle, provided it be not exercised ; but when the motor ganglionic cells of the
anterior horn of grey matter, or the corresponding cells in the crus, pons, and medulla, are
saralysed, there is an active condition of atrophy with proliferation of the muscular nuclei.
Piosreaive muscular atrophy, or wasting palsy, is another trophic change in muscle, whereby
either individual muscles, or groups of muscles, are one after the other paralysed and become
atrophied. In pseudo-hypertrophic paralysis, there is cirrhosis or increased development of
the connective-tissue, with a diminution of the true muscular elements, so that although the
muscles increase in bulk their power is diminished. ]

Cutaneous Trophic Affections.—Amongst these may be mentioned the occurrence of red
patches or erythema, urticaria or nettle-rash, some forms of lichen, eczema, the bull or blebs
of pemphigus, and some forms of ichthyosis, each of which may occur in limited areas after
injury toa nerve or its spinal or cerebral centre. The relation between the cutaneous eruption
aud the distribution of a nerve is sometimes very marked in herpes zoster, which frequently
follows the distribution of the intercostal and supraorbital nerves. Glossy skin (Paget, Weir
Mitchell) is a condition depending upon impaired nutrition and circulation, and due to injuries
ofnerves. The skin is smooth and glossy in the area of distribution of certain nerves, while
the wrinkles and folds have disappeared. In myxcedema, the subcutaneous tissue and other
organs are infiltrated with, while the blood contains, mucin. The subcutaneous tissue is
swollen, and the patient looks as if suffering from renal dropsy. There is marked alteration
of the cerebral faculties, and a condition resembling a ‘‘cretinoid state” occurs after the
excision of the thyroid gland. Victor Horsley has shown that a similar condition occurs in
monkeys after excision of the thyroid gland (§ 103, III.). [Laycock described a condition of
nervous edema which occurs in some cases of hemiplegia, and apparently it is independent of |
renal or cardiac disease. ] .

[There are alterations in the colour of the skin depending on nervous affections, including
localised leucoderma, where circumscribed patches of the skin are devoid of pigment. The
pigmentation of the skin in Addison’s disease or bronzed skin, which occurs in some cases of
disease of the suprarenal capsules, may be partly nervous in its origin, more especially when we
consider the remarkable pigmentation that occurs around the nipple and some other parts of
the body during pregnancy, and in some uterine and ovarian affections. ;

In anesthetic leprosy, the anesthesia is due to the disease of the nervous structure, which
results in disturbance of motion and nutrition. Amongst other remarkable changes in the
skin, perhaps due to trophic conditions, are those of symmetrical and local gangrene, and
acute decubitus or bed-sores.] : | .

[Bed-Sores.— Besides the simple chronic form, which results from over-pressure, bad nursing,
and inattention to. cleanliness, combined with some defect of the nervous conditions, there is
another form, acute decubitus, which is due directly to nerve influence (Charcot). The latter
usually appears within a few hours or days of the cerebral or spinal lesion, and the whole cycle
of changes—from the appearance of the erythematous dusky patch to inflammation, ulceration,
and gangrene of the buttock—is completed in a few days. An acute bed-sore may form
when every attention is paid to the avoidance of pressure and other unfavourable conditions.
When it depends on cerebral affections, it begins and develops rapidly in the centre of the
gluteal region on the paralysed side, but when it is due to disease of the spinal cord, it forms
more in the middle line in the sacral region; while in unilateral spinal lesions it occurs not on

rx

the paralysed, but on the anesthetic side, a fact which seems to show that the trophic, like the
sensory fibres, decussate in the cord (Ross) 1 oa a 2 a

INHIBITORY AND AFFERENT NERVES. 583

[There are other forms due to nervous disease, including symmetrical gangrene and local
asphyxia of the terminal parts of the body, such as toes, nose, and external ear, caused perhaps
by spasm of the small arterioles (Raynaud’s disease) ; and the still more curious condition of
perforating ulcer of the foot. Hemorrhage of nervous origin sometimes occurs in the skin,
including those that occur in locomotor ataxia after severe attacks of pain, and hematoma
aurium, or the insane ear, which is specially common in general paralytics. ]

(d) [Inhibitory nerves are those nerves which modify, inhibit, or suppress a
motor or secretory act already in progress. |

Take as an example the effect of the vagus upon the action of the heart. Stimulation of the
peripheral end of the vagus causes the heart to stand still in diastole (§ 85); see also the
effect of the splanchnic upon the intestinal movements (§161). The vaso-dilator nerves, or those
whose stimulation.is followed by dilatation of the blood-vessels of the area which they supply,
are referred to especially in § 237.

[There is the greatest uncertainty as to the nature and mode of action of inhibitory nerves,
but take as a type the vagus, which depresses the function of the heart, as shown by the slower
rhythm, diminution of the contractions, relaxation of the muscular tissue, lowering of the
excitability and conduction. These phenomena are not due to exhaustion. Gaskell points out
that the action is beneficial in its after effects, so that this nerve, although it causes
diminished acitivity, is followed by repairjof function ; hence, he groups it as anabolic nerve,
the outward symptoms of cessation of function indicating that constructive chemical changes
are going on in the tissue. ]

(e) Thermic and electrical nerves have also been surmised to exist.

[Gaskell classifies the efferent nerves differently. Besides motor nerves to striped muscle,
he groups them as follows :—

1.. Nerves to vascular muscles.
(a) Vaso-motor, 7.€., vaso-constrictor, accelerators and augmentors of the heart.
(b) Vaso-inhibitory, t.¢., vaso-dilators and inhibitors of the heart.
2. Nerves of the visceral muscles.
(a) Viscero-motor.
_(b) Viscero-inhibitory.

3. Glandular nerves. ]

[Other terms are applied to nerves with reference to the chemical changes
they excite in a tissue in which they terminate. The ordinary metabolism is the
resultant of two processes—one constructive, the other destructive, or of assimila-
tion and dissimilation respectively. The former process is anabolism, the latter
katabolism. A motor nerve excites chemical destructive changes in a muscle, and
is so far the katabolic nerve of that tissue; in the same way the sympathetic to
the heart, by causing more rapid contraction, is also a katabolic nerve, while the
vagus, as it arrests the heart’s action, and brings about a constructive metabolism
of the cardiac tissue, is an anabolic nerve (‘askel/). |

II. Centripetal or Afferent Nerves.—(a) Sensory Nerves (sensory in the
narrower sense), which by means of special end-organs
conduct sensory impulses to the central nervous system.

(b) Nerves of Special Sense.

(c) Reflex or Excito-motor Nerves.—When the
periphery of one of these nerves is stimulated, an im-
pulse is set up which is conducted by them to a nerve-
centre, from whence it is transferred to a centrifugal or
efferent fibre, and the mechanism (I, a, b, c, d) in con-
nection with the peripheral end of this efferent fibre is
set in action; thus, there are—-Reflex motor, Reflex
secretory, and Reflex inhibitory fibres. [Fig. 422
shows the simplest mechanism necessary for a reflex Scheme of a reflex motoract. S,
motoract. The impulse starts from the skin, S, travels kim; %, afferent nerve ; N,

nerve-cell ; ef, efferent fibre.
up the. nerve, af, to the nerve-centre or nerve-cell, N,
situate in the spinal cord, where it is modified and transferred to the outgoing fibre,
ef, and conveyed by it to the muscle, M. |

IIT, Intercentral Nerves.—These fibres serve to connect ganglionic centres

584 OLFACTORY AND OPTIC NERVE.

with each other, as, for example, in co-ordinated movements, and in extensive reflex
acts.

THE CRANIAL NERVES.

343. L NERVUS OLFACTORIUS.—Anatomical.—The three-sided prismatic tractus olfac-
torius, lying in a groove on the under surface of the frontal lobe, arises by means of an inner,
outer, and middle root, from the tuber olfactorium (fig. 428, I). The tractus swells out upon
the cribriform plate of the ethmoid bone, and becomes the bulbus olfactorius, which is the
analogue of the special portion of the brain, existing in different mammals with a well-developed
sense of smell (Gratiolet). From twelve to fifteen olfactory filaments pass through the foramina
in the cribriform plate of the ethmoid bone. At first they lie between the periosteum and the
mucous membrane, but in the lower third of their course they enter the mucous membrane of
the regio olfactoria. The bulb consists of white matter below, and above of grey matter mixed
with small spindle-shaped ganglionic cells. Henle describes six, and Meynert eight layers, of
nervous matter seen on transverse section. [The centre for smell lies in the oP of the uncinate
gyrus on the inner surface of the cerebral hemisphere (Ferrier).] According to Gudden, removal
of the olfactory bulb is followed by atrophy of the gyrus uncinatus on the same side. Accord-
ing to Hill, the three roots of the olfactory bulb stream backwards, the inner one is small, the
middle one is a thick bundle, which grooves the head of the caudate nucleus, curves inwards
to the anterior commissure, and crosses vid this commissure where it decussates,‘and passes’ to
the extremity of the temporo-sphenoidal lobe. The outer roots pass transversely into the
pyriform lobe, thence vid the fornix, corpora albicantia, the bundle of Vicq d’Azyr into the
anterior end of the optic thalamus. Hill also points out that the elements contained in the
olfactory bulb are identical with those contained in the four outer layers of the retina. Flechsig
traces its origin (1) to the gyrus fornicatus, (2) through the lamia perforata anterior to the
internal capsule (sensory part), and to the gyrus uncinatus (sensory area of the cerebrum) (§ 378,
IV.). Probably the fibres at their origin cross to the cerebrum. There is a connection between
the olfactory bulbs in the anterior commissure. [Each nerve is related to both hemispheres. ]

Function.—It is the only nerve of smell. Physiologically, it is excited only by |
gaseous odorous bodies—(Sense of Smell, § 420). Stimulation of the nerve, by any
other form of stimulus, in any part of its course, causes a sensation of smell. [It |
also conveys those impressions which we call flavours, but in this case the sensation |
is combined with impressions from the organs of taste. In this case also the stimulus |
reaches the nerve by the posterior nares.] Congenital absence or section of both
olfactory nerves abolishes the sense of smell (easily performed on young animals—
Bifi)

Pathological.—_The term hyperosmia is applied to cases where the sense of smell is
excessively and abnormally acute, as in some hysterical persons, and in cases where there is a
purely subjective sense of smell, as in some insane persons. The latter is perhaps due to an
abnormal stimulation of the cortical centre (§ 378, IV.). Hyposmia and anosmia (i.¢.,
diminution and abolition of the sense of smell) may be due to mechanical causes, or to over- '
stimulation. Strychnin sometimes increases, while morphia diminishes, the sense of smell.
{Method of Testing, § 421.]

344. I. NERVUS OPTICUS.—Anatomical.—The tractus opticus (fig. 428, II) arises from
the anterior corpora quadrigemina, the corpus geniculatum externum, and the thalamus opticus
(fig. 428), as well as from the grey matter which lines the third ventricle (Zartuferi). <A
broad bundle of fibres passes from the origin of the optic tract to the cortical visual centre,
at the apex of the occipital lobe on the same side ( Wernicke—§ 879, IV.). Fibres pass from
the cerebellum through the crura.

The optic tract bends round the pedunculus cerebri, where it unites with its fellow of the
opposite side to form the chiasma, and from the opposite side of this the two optic nerves
spring.

[Connections of Optic Tract.—There is very considerable difficulty in ascertaining the exact
origin of all the fibres of the optic tract. Although as yet the statement of Gratiolet is not
proved that the optic tract is directly connected with every part of the cerebral hemisphere in
man, from the frontal to the occipital lobe, still the researches of D. J. Hamilton have shown
that its connections are very extensive. It is certain that some of them are ganglionic, 4.¢.,
connected with the ganglia at the base of the brain, while others are cortical, and form connec-
tions with the cortex cerebri.. The ganglionic fibres arise from the corpora geniculata, pulvinar,
and anterior corpora quadrigemina, and probably also from the substance of the thalamus. The
cortical fibres pe the ganglionic to form the optic tract. According to D. J. Hamilton, the
connection with the cortex in the frontal region is brought about by ‘* Meynert’s commissure.”
The latter arises directly from the lenticular-nucleus-loop, decussates in the lamina cinerea, and

—oo

OPTIC RADIATION AND CHIASMA. 585

asses into the optic nerve of the opposite side. The lenticular-nucleus-loop is formed below the
enticular nucleus by the junction of the strie medullares ; the strize medullares form part of the
fibres of the internal capsule, and the inner capsule is largely composed of fibres descending
from the cortex. Hamilton also asserts that other cortical connections join the tract as it winds
round the pedunculus cerebri, and they include (a) a large mass of fibres coming from the motor
areas of the opposite cerebral hemisphere, crossing in the corpus callosum, entering the outer
capsule, and joining the tract directly ; (0) fibres uniting it to the temporo-sphenoidal lobe of
the same side, especially the first and second temporo-sphenoidal convolutions; (c) fibres to the
gyrus hippocampi of the same side; (@) a large leash of fibres forming the ‘‘ optic radiation ”
of Gratiolet, which connect it directly with the tip of the occipital lobe. There are probably
also indirect connections with the occipital region through some of the basal ganglia. Although
some observers do not admit the connections with the frontal and sphenoidal lobes, all are
agreed as to its connection with the occipital by means of the ‘‘ optic radiation.’’]

[The optic radiation of Gratiolet is a wide strand of fibres expanding and terminating in the
occipital lobes. It is composed of, or, stated otherwise, gives branches to (a) the optic tract
directly, (5) the corpus geniculatum internum and externum, (c) to the pulvinar and substance
of the thalamus, (d) a direct sensitive band (Meynert’s “ Sensitive band ’’) to the posterior third
of the posterior limb of the inner capsule, (¢) fibres which run between the island of Reil and
the tip of the occipital lobe (D. J. Hamilton). ]

Chiasma.—The extent of the decussation of the optic fibres in the chiasma is
subject to variations. Asa rule, rather more’ than half of the fibres of one tract
cross to the optic nerve of the opposite side (fig. 423), so that the left optic tract

Fig. 423, Fig. 424.

Fig. 423.—Scheme of the semi-decussation of the optic nerves. JZ.A., left eye; #.A., right
eye. Fig. 424.—Diagram of the relation of the field of vision, retina, and optic tracts.
RF, LF, right and left fields of vision—the asterisk is at the fixing point; RR, LR,
right and left retina—the asterisk is at the macula lutea; /.2., 7.2., left halfand right half of
each retina, receiving rays from the opposite half of the field; RN, LN, right and left
optic nerves; Ch, chiasma; RT, LT, right and left optic tracts; below, the halves of the
fields from which impressions pass by each optic tract are superimposed (Gowers).

sends fibres to the left half of both eyes, while the right tract supplies the right
half of both eyes (§ 378, IV.). [Thus, the corresponding regions of each retina are
brought into relation with one hemisphere. The fibres which cross are from the
nasal half of each retina (fig. 424). ]

Hence, in man, destruction of one optic tract (and its central continuation in the occipital
lobe of the cerebrum) produces ‘‘ equilateral or homonymous hemianopia.” In the cat there
is a semi-decussation ; hence, in this animal extirpation of one eyeball causes atrophy and
degeneration of, half of the nerve-fibres in both optic tracts (@udden). Baumgarten and Mohr
have observed a similar result in man. A sagittal section of the chiasma in the cat produces
partial: blindness of both eyes (Nicati). According to Gudden, the fibres which decussate are
more numerous than those which do not, although J. Stilling maintains that they are only
slightly more numerous. According to J. Stilling, the decussating fibres lie in the central_axis
of the nerve, while those which do not decussate form a layer around the former.

586 HEMIANOPIA AND HEMIANOPSIA:

Other observers maintain that there is complete decussation of all the fibres in the chiasma,
Hence, section of one optic nerve causes dilatation of the pupil and blindness on the same side,
while section of one optic tract causes dilatation of the pupil and blindness of the opposite eye
(Knoll). In osseous fishes, both optic nerves are isolated and merely cross over each other, while
in the cyclostomata they do not cross at all, [Total decussation occurs-in those ‘animals where
the eyes do not act together. ]

Injury of the external geniculate body and section of the anterior brachium have the same
effect as section of the optic tract of the same side (§ 359—Bechterew).

In very rare cases the decussation is absent in man, so that the right tract passes directly into
the right eyeball, and the left into the left eyeball (Vesalius, Caldani), the sight not being
interfered with.

It is quite certain that the individual fibres do not divide in the chiasma, Two commissures,
the inferior commissure (Gudden) and Meynert’s commissure, unite both optic tracts further
back.

A special commissure (C, inferior) extends in a curved form across the posterior angle of the
chiasma (Gudden). It does not degenerate after enucleation of the eyeballs, so that it is
regarded as an intercentral connection. After excision of an eye, there is central degeneration
of the fibres of the optic nerve entering the eyeball (Gudden), and in man about the half of the
fibres in the corresponding optic tract (Baumgarten, Mohr). After section of both optic nerves,
or enucleation of both eyeballs, there is a degeneration, proceeding centrally, of the whole optic
tract. The degeneration extends to the origins in
the corpora quadrigemina, corpora geniculata, and
pulvinar, but not into the conducting paths lead-
ing to the cortical visual centre (v. Monakow) (§
378, LV, 13).

[Hemianopia and Hemianopsia.— When one
optic tract is interfered with or divided, there is
interference with or loss of sight in the lateral
halves of both retin, the blind part being
separated from the other half of the field of vision
by a vertical line. When it is spoken of as
paralysis of one-half of the retina, the term
hemiopia, or preferably hemianopia, is applied
to it; when with reference to the field of vision,
the term hemianopsia is used (see Lye). Suppose
the left optic tract to be divided or pressed upon
by a tumour at K (fig. 425), then the outer half
of the left and the inner half of the right eye are
blind, causing right lateral hemianopsia, i.e., the
two halves are affected which correspond in ordi-
nary vision, so that the condition is spoken of
homonymous hemianopsia. Suppose the lesion
to be at T (fig. 425), then there is paralysis of the
inner halves of both eyes, causing double temporal

Fig. 425.
Diagram of the decussation of the optic tracts, emianopsia. When there are two lesions at NN,

T, semi-decussation in the chiasma; TQ,
decussation of fibres behind the ext. geni-
culate bodies (CG); a’b, fibres which do not
decussate in the chiasma ; b’ a’, fibres pro-
ceeding from the right eye, and coming
together in the left hemisphere (LOG) ;
LOG, K, lesion of the left optic tract pro-
ducing right lateral hemianopsia ; 4, lesion

which is very rare, the owter halves of both retine
are paralysed, so that there is dowble nasal hemi-
anopsia. In order to explain some of the eye
symptoms that occasionally occur in cerebral
disease, Charcot has supposed that some of the
fibres which pass from the external geniculate
body to the visual centres in the occipital lobe
cross behind the corpora quadrigemina, and this

in the left hemisphere producing crossed is represented in the diagram as occurring at
amblyopia (right eye); T, lesion producing TQ, in the corpora quadrigemina. On this view,

temporal hemianopsia ; NN, lesion pro-
ducing nasal hemianopsia.

view, however, by no means explains
the point of central v

only ; of the middle of the chiasma,
the chiasma and occipital cortex, hemi

cause

all the occipital cortical fibres from one eye
would ultimately pass to the cortex of the occi-
pital lobe of the opposite hemisphere. This

nN 1s all the facts, for in cases of homonymous hemianopsia
ision on both sides, 7.¢.,

it is assumed that each macula lutea is connected with both hemispheres.
suggested by Charcot probably does not occur.
eyeball and the chiasma, i.¢c., in the orbit, optic foramen, or wit

both macule lutee are always unaffected, so that
The second crossing
Affections of the optic nerve, ¢.g., between the

bin the skull, affect one eye
temporal: hemiopia ; of the optic tract, between

opia, which is always symmetrical (Gowers).

Fig. 424, reduced from that of Gowers, shows the relation of the fields of vision of the retina,

tracts, and the cerebral optic centre.

FUNCTIONS OF THE THIRD CRANIAL NERVE. 587

Function.—The optic nerve is the nerve of sight ; physiologically, it is excited
only by the transference of the vibrations of the ether to the rods and cones of the
retina (§ 383). Every other form of stimulus, when applied to the nerve in its
course or at its centre, causes the sensation of light. Section or degeneration of
the nerve is followed by blindness. Stimulation of the optic nerve causes a reflex
contraction of the pupils, the efferent nerve being the oculomotorius or third cranial
nerve. If the stimulus be very strong, the eyelids are closed and there is a
secretion of tears. The influence of light.upon the general metabolism is stated at
S:h27, 9;

As the optic nerve has. special and independent connections with the so-called
visual centre (§ 378, IV.), as well as with the centre for narrowing the pupil (§ 345),
it is evident that, under pathological circumstances, there may be, on the one hand,
blindness with retention of the action of the iris, and on the other loss of the
movements of the iris, the sense of vision being retained (Wernicke).

Pathological. —Stimulation of almost the whole of the nervous apparatus may cause excessive
sensibility of the visual apparatus (hyperesthesia optica), or even visual impressions of the
most varied kinds (photopsia, chromatopsia), which in cases of stimulation of the visual
centre may become actual visual hallucinations (§ 378, IV.). Material change in, and
inflammation of, the nervous apparatus are often followed by a nervous weakness of vision
(amblyopia), or even by blindness (amaurosis). Both conditions, however, may be the signs
of disturbances of other organs, 7.¢., they are ‘‘sympathetic” signs, due it may be to changes
in the movement of the blood-stream, depending upon stimulation of the vaso-motor nerves.
The discovery of the partial origin of the optic nerve from the spinal cord explains the
occurrence of amblyopia with partial atrophy of the optic nerve, in disease of the spinal cord,
especially in tabes. Many poisons, such as lead and alcohol, disturb vision. There are
remarkable intermittent forms of amaurosis known as day-blindness or hemeralopia, which
occurs in some diseases of the liver and is sometimes associated with incipient cataract. [The
person can see better in a dim light than during the day or in a bright light. In night-
blindness or nyctalopia, the person cannot see at night or in a dim light, while vision is good
during the day or in a bright light. It depends upon disorder of the eye itself, and is usually
associated with imperfect conditions of nutrition. ]

345, III. NERVUS OCULOMOTORIUS.—Anatomical.—It springs from the oculomotorius
nucleus (united with that of the trochlearis), which is a direct continuation of the anterior
horn of the spinal cord, and lies under the aqueduct of Sylvius (fig. 428). [The motor nucleus
(fig. 427) gives origin to three sets of fibres, for (1) the most of the muscles of the eyeballs, (2)
the sphincter pupille, (8) ciliary muscle. The nucleus of the 3rd and 4th nerves is also con-
nected with that of the 6th under the iter, so that all the nerves to the ocular muscles are thus
co-related at their centres. ]

The origin is connected with the corpora quadrigemina, to which the intraocular fibres may
be traced, and also with the opposite half of the brain to the angular gyrus (§ 378, I.) through
the pedunculus cerebri. Beyond the pons, it appears on the inner side of the cerebral peduncle,
between the superior cerebellar and posterior cerebral arteries (fig. 428, III).

Function.—It contains—(1) the voluntary motor fibres for all the external
muscles of the eyeballs—except the external rectus and superior oblique—and for
the levator palpebre superioris. . The co-ordination of the movements of both eye-
balls, however, is independent of the will. (2) The fibres for the sphincter pupille,
which are excited reflexly from the retina. (3) The voluntary fibres for the muscle
of accommodation, the tensor choroidee or ciliary muscle. The intrabulbar fibres of
2 and 3 proceed from the branch for the inferior oblique muscle, as the short. root
of the ciliary ganglion (fig. 429), They reach the eyeball through the short: ciliary

‘nerves of the ganglion. V. Trautvetter and others observed that stimulation of
the nerve caused changes in the eye similar to those which accompany near vision.
The three centres for the muscle of accommodation, the sphincter pupille, and the
internal rectus muscle, lie directly in relation with each other, in the most posterior
part of the floor of the third ventricle (Hensen and Volckers). . ~ oe

The centre for the reflex stimulation of the sphincter fibres by light was said
to be in the corpora quadrigemina, but newer reséarches locate it in the medulla
oblongata (§§ 379, 392). The narrowing of the pupil, which accompanies the act

eS a ae
2 % . *

588 FUNCTIONS OF THE THIRD CRANIAL NERVE.

of accommodation for a near object, is to be regarded as an associated movement
(§ 392, 5). trate

Anastomoses.—In man, the nerve anastomoses on the sinus cavernosus with the ophthalmic
branch of the trigeminus, whereby it receives sensory fibres for the muscles to which it is distri-
buted (Valentin, Adamik), with the sympathetic through the carotid plexus, and (?) indirectly
through the abducens, whereby it receives vaso-motor fibres (?). ; :

Varieties.—In some rare cases, the pupillary fibres for the sphincter run in the abducens
(Adamiik), or even in the trigeminus (Schiff, v. Grdfe).

Atropin paralyses the intrabulbar fibres of the oculomotorius, while Calabar bean
stimulates them (or paralyses the sympathetic, or both—compare § 392).

Stimulation of the nerve, which causes contraction of the ai is best demonstrated on the
decapitated and opened head ofa bird. The pupil is dilated in paralysis of the oculomotorius,
in asphyxia, sudden cerebral anemia (¢.9., by ligature of the carotids, or beheading), sudden
venous congestion, and at death.

Pathological.—Complete paralysis of the oculomotorius is followed by—(1) drooping of the
upper eyelid (ptosis paralytica) ; (2) immobility of the eyeball ; (3) squinting (strabismus) out-
wards and downwards, and consequently there is double vision (diplopia) ; (4) slight protrusion
of the eyeball, because the action of the superior oblique muscle in pulling the eyeball forward
is no longer compensated by the action of three paralysed recti muscles. In animals provided
with a retractor bulbi muscle, the protrusion of the eyeball is more pronounced ; (5) moderate
dilatation of the pupil (mydriasis paralytica); (6) the pupil does not contract to light; (7) in-
ability to accommodate for a near object. It is to be noted, however, that the paralysis may
be confined to individual branches of the nerve, z.e., there may be incomplete paralysis.

[Squinting.—In paralysis of the superior rectus, the eye cannot be moved upwards, and
especially upwards and outwards. There is diplopia on looking u wards, the false image being
above the true, and turned to the right when the left eye is affected (fig. 426, 3). Inferior
Rectus. —Defect of downward, and especially downward and outward movement, the eye being
directed upwards and outwards. Diplopia with crossed images, the false one is below the true
image and placed obliquely, being turned to the left when the left eye is affected. Diplopia is

WOOO!

Internal External Superior Inferior Inferior Superior
rectus. rectus. rectus. oblique. rectus. oblique.

Fig. 426.

The black cross represents the true image, the thin cross the false image. The left eye is
represented as affected in all cases (Bristow).

most troublesome when the object is below the line of vision (fig. 426, 5). Internal Rectus.—
Defective inward movement, divergent squint, and diplopia, the images being on the same plane,
the false one to the patient’s right when the left eye is affected. The head is turned to the
healthy side, when looking at an object, while there is secondary deviation of the healthy eye
outwards (ig. 426, 1). Inferior oblique is rare, the eye is turned slightly downwards and in-
wards, and defective movement upwards. Diplopia with the false image above the true one,
especially on looking upwards ; the false image is oblique, and directed to the patient’s left
when the left eye is affected (fig. 426, 4).]

Stimulation of the branch supplying the levator palpebre in man causes lagophthalmus
spasticus, while stimulation of the other motor fibres causes a corresponding strabismus spas-
ticus, The latter form of squinting may be caused also reflexly—e.g., in teething, or in cases
of diarrhcea in children ; [the presence of worms or other source of irritation in the intestines of
children is a frequent cause of squinting]. Clonic spasms occur in both eyes, and also as in-
voluntary movements of the eyeballs constituting nystagmus, which may be produced by
stimulation of the corpora quadrigemina, as well as by other means. Tonic contraction of the
year pupille is called myosis spastica, and clonic contraction, hippus. Spasm of the muscle
of accommodation (ciliary muscle) is sometimes observed ; owing to the imperfect judgment of
distance, this condition is not unfrequently associated with macropia.

[Conjugate Deviation.—Some movements are produced by non-corresponding muscles; thus,
on looking to the right, we use the right external rectus and left internal rectus, and the same _
is the case in turning the head to the right, ¢.g., the inferior oblique, some muscles of the ight —
side act along with the left sterno-mastoid. In hemiplegia, the muscles on one side are Pees sed,
so that the head and often the eyes are turned away from the paralysed side, é.¢., to the side ¢

‘ FUNCTIONS OF THE FOURTH CRANIAL NERVE. 589

the brain on which the lesion occurs. This is called ‘‘ conjugate deviation” of the eyes, with
rotation of the head and neck, If the right external rectus be paralysed from an affection of
the sixth nerve, on telling the patient to look to the right it will be found that the left eye will
squint more inwards even than the right eye, i.e, owing to the strong voluntary effort, the
muscle, the left internal rectus which usually acts along with the right external rectus, con-
tracts vigorously, and so we get secondary deviation of the sound eye. Similar results occur
in connection with paralysis of other ocular muscles. ]

Conarium or pineal gland.
Pulvinar ~_

ee) Brachium conjunctivum anticum

=
_———_ Brachium conjunctivum
posticum.,

Sea a :
es ee emaiaat
e
Corpus if anticum
quadri- : NTs: ll SO eas oe
geminun | osticum oar \ MH Wifi Uf Pedunculus cerebri,

Locus coeruleus —

ad corpora quadri-
gemina, or
——-- superior cerebellar
peduncle.

Crus
-~ ad medullam oblon- | Cerebellé

Eminentia teres

Crus cerebelli

gatam, or interior
ad ae cerebellar
eduncle,
Middie cerebellar Dp ncle

peduncle.

Clava

Funiculus cuneatus
(Part of restiform body).

Funiculus gracilis ~~

(Posterior pyramid),

Medulla oblongata, with the corpora quadrigemina, The numbers J/—XJI indicate the
superficial origins of the cranial nerves, while those (3-12) indicate-their deep origin, 4.¢.,
the position of their central nuclei; ¢, funiculus teres.

. 346. IV. NERVUS TROCHLEARIS,—Anatomical.—It arises from the valve of Vieussens,
t.€., behind the fourth ventricle, but its fibres pass to the oculomotorius from the trochlearis
nucleus, which is to a certain extent a continuation of the anterior horn of the spinal cord (fig.
427). It passes to the lower margin of the corpora quadrigemina, pierces the roof of the
aqueduct of Sylvius, then into the velum.medullare superius, and after decussating with the
root of the opposite side behind the iter, it pierces the crus at the superior and external border
(fig. 428), Its fibrescross between its nucleus and its distribution. It has also an origin from
the locus eceruleus. The root of the ‘nerve receives some fibres.from the nucleus of the abducens
of the opposite side. Physiologically, there is a necessity for a connection between the centre
and the cortical motor centre for the eye muscles.

599

Function.—It is the voluntary motor nerve of the superior oblique muscle.“ (In

Fig. 428.
Part of the base of the brain, with the origins of the cranial
nerves ; the convolutions of the island of Reil on the

right side, but removed on the left. I’, olfactory tract
cut short ; II, left optic nerve ; II’, right optic tract ;
Th, cut surface of the left optic thalamus ; C, central
lobe, or island of Reil ; Sy, fissure of Sylvius; XX, the
locus perforatus anticus ; ¢, the external, and 7, the in-
ternal corpus geniculatum ; h, hypophysis cerebri ; tc,
tuber cinereum, with the cagaaibalare ; @, points to one
of the corpora albicantia ; P, the cerebral peduncle; /,
the fillet ; IIL, left oculomotor nerve ; X, the locus per-
foratus posticus ; PV, pons Varolii ; V, the greater part
of the fifth nerve ; +, the lesser root (on the right side
this mark is placed on the Gasserian ganglion and points
to the lesser root); 1, ophthalmic division of the fifth ;
VII a, facial, VII 4, auditory ; VIII, vagus; VIII a,
glosso-pharyngeal ; VIII b, spinal accessory; IX, hypo-
lossal ; fi, flocculus ; fh, horizontal fissure of the cere-

llum (Ce) ; am, amygdala ; pa, anterior pyramid ; 0,
olivary body; e¢, restiform y; d@, anterior median
fissure ; cl, the lateral column of the spinal cord ; CI,
the sub-oecipital or first cervical nerve.

the cerebellum, through the crura cerebelli. The origins of the sensory root anastomose-with’

THE NERVUS TRIGEMINUS.

co-ordinated movements, how-
ever, it is involuntary.)
Anastomoses, — Its connections
with the plexus caroticus sympa-
thici, and with the first branch of
the trigeminus, have the same sig-
nificance as similar branches of the
oculomotorius.
Pathological.—Paralysis of the
trochlearis nerve causes a very slight
loss of the mobility of the eyeball
outwards and downwards. There
is slight squinting inwards and
upwards, with diplopia or double
vision. The images are placed
obliquely over each other [the false_
image being the lower, and directe!
to the patient’s right when the left
eye is affected (fig. 426, 6)]; they
approach each other when the head
is turned towards the sound side,
and are separated when the head is
turned towards the other side. The
patient at first directs his head for-
wards, later he rotates it round a
vertical axis towards the sound side.
In rotating his head (whereby the
sound eye may retain the primary
osition), the eye rotates with it.
Saat of the trochlearis causes
squinting outwards and downwards.
347. V. NERVUS TRIGEMI-
NUS.—Anatomical.—The trigemi-
nus (fig. 429, 5), arises like a spinal
nerve by two roots (fig. 428, V.)
The smaller, anterior, motor root
proceeds from the ‘‘motor tri-
geminal nucleus” (5), which is
provided with many multipolar
nerve-cells, and lies in the floor of
the medulla oblongata, not far from
the middle line. Fibres connect
this nucleus with the cortical motor
centres on the opposite side of the
cerebrum. Besides this the ‘‘ de-
scending root”’ also supplies motor
fibres. It extends, laterally from
the corpora quadrigemina along the
aqueduct of Sylvius downwards to
the exit of the nerve (Henle, Forel).
The large posterior sensory root
receives fibres :—(1) From the small
cells of the ‘‘sensory trigeminal
nucleus” which lies at the level of
the pons, and is the analogue of the
posterior horn of the grey matter of
the spinal cord. (2) From the grey
matter of the posterior horn of the
spinal cord, downwards as far as the
second cervical vertebra. These
fibres run into the posterior column
of the cord and then appear as_ the
‘‘ascending root” in the trige-
minus. (3) Some fibres come from

THE OPHTHALMIC BRANCH OF THE FIFTH. — 591

thé motor nuclei of all the nerves arising from the medulla oblongata, with the exception of
the abducens. This explains the vast number of reflex relations of the fifth nerve. The thick
trunk appears on each side of the pons (fig. 428), when its posterior root (perhaps in connection
with some fibres from the anterior) forms ‘the Gasserian ganglion, upon the tip of the petrous
part of the temporal bone (fig. 429). Fibres from the sympathetic proceed from the plexus caver-
nosus to the ganglion. The nerve divides into three large branches.

I. The ophthalmic division (fig. 429, d) receives sympathetic fibres (vaso-motor
nerves) from the plexus cavernosus ; it passes through the superior orbital fissure
[sphenoidal] into the orbit. Its branches are :—

1. The’ small recurrent nerve which gives sensory branches to the tentorium
cerebelli. Fibres—the vaso-motor nerves for the dura mater—proceed along with
it from the carotid plexus of the sympathetic.

2. The lachrymal nerve gives off—(a) Sensory branches to the conjunctiva, the
upper eyelid, and the neighbouring part of the skin over. the temple (fig. 429, a) ;
(b) true sensory fibres to the lachrymal gland (?). Stimulation of this nerve is said
to cause a secretion of tears, while its section prevents the reflex secretion excited
through the sensory nerves of theeye. After a time, section of the nerve is followed
by a paralytic secretion of tears (Herzenstein and Wolferz), although the statement
is contested by Reich. The secretion of tears may be excited reflexly, by strong
stimulation of the retina by light, by stimulation of the first and second branches
of the trigeminus, and through all the sensory cranial nerves (Demtschenko) (§ 356,

8).

"3. The frontal (f) gives off the supratrochlear, which supplies sensory fibres to
the upper eyelids, brow, glabella, and those which excite the secretion of tears
reflexly ; and by its supraorbital branch (0), analogous branches to the upper
eyelid, skin of the forehead, and the adjoining skin over the temple as far as the
vertex.

4. The naso-ciliary nerve (nc), by its infratrochlear branch supplies fibres,
similar to those of 3, to the conjunctiva, caruncula, and saccus lacrimalis, the
upper eyelid, brow, and root of the nose. Its ethmoidal branch supplies the tip
and ale of the nose, outside:and inside, with sensory branches, as well as the upper
part of the septum and the turbinated bones with sensory fibres, which can act as
afferent nerves in the reflex secretion of tears ; while it is probable that vaso-motor
fibres are supplied to these parts through the same channel. (These fibres may be
derived from the anastomosis with the sympathetic (?).) The naso-ciliary nerve
gives off the long root (/) of the ciliary ganglion (c), and 1 to 3 long ciliary nerves.

The ciliary ganglion (fig. 429, c), which, according to Schwalbe, perhaps belongs
rather to the third than the fifth nerve, has three roots—(«) the short or oculomo-
torius (3—see § 345); (b) the long (/), from the naso-ciliary ; and (c) the sympa-
thetic (s) sometimes united with 6, from the carotid plexus. The short ciliary
nerves (¢), six to ten in number, proceed from the ganglion, along. with the long. -
ciliary nerves, to near the entrance of the optic nerve, where they perforate the
sclerotic coat and run forwards between it and the choroid. ©

Ciliary Nerves.— Physiologically, these nerves contain :— ‘

1. The motor fibres for the aurea pupille and the tensor choroidew from
the root of the oculomotorius (§ 345, 2, 3).

2. Sensory fibres for the cornea, which are distributed as extosaively fine ‘fibrils
between the epithelium of the conjunctiva bulbr; they perforate the sclerotic.
These fibres cause a reflex secretion of tears (N. lacrimalis) and closure of the
eyelids (N. facialis). Sensory fibres are supplied to the iris (pain in iritis and in
operations on the iris), the choroid (painful tension when the ciliary muscle is
strained), and the sclerotic.

3. Vaso-motor nerves for the blood-vessels of the iris, choroid, and retina. They
arise in part from the sympathetic root, and the anastomosis of the sympathetic

Semi-diagrammatic representation of the nerves of the eyeball, the connections of the trigeminus and
its ganglia, together with the facial and glosso-pharyngeal nerves. 3, Branch to the inferior oblique
muscle from the oculomotorius, with the thick short root, to the ciliary ganglion (c); ¢, ciliary
nerves; 7, long root to the ganglion from the naso-ciliary (nc) ; s, sympathetic root from the sym-
pathetic plexus (Sy) surrounding the internal carotid (G) ; d, first or ophthalmic division of the
trigeminus (5), with the naso-ciliary (nc), and the terminal branches of the lachrymal (@), supra-
orbital (4), and frontal (/); e, second or superior maxillary division of the nigemiane ; R, infra-
orbital ; m, spheno-palatine (Meckel’s) ganglion with its roots ; j, from the facial, and v, from the
sympathetic ; N, the nasal branches, and pp,, the palatine branches of the ganglion ; g, third or
inferior maxillary division of the trigeminus ; &, lingual ; 7 7, chorda tympani; m, otic ganglion,
with the roots from the tympanic plexus, the carotid plexus, and from the 3rd branch, and with its
branches to the auriculo-temporal (A), and to the chorda (i 4); L, sub-maxillary ganglion with its”
roots from the tympanico-lingual, and the sympathetic plexus on the external artery (q). 7, Facial
nerve—j, its great superficial petrosal branch ; a, gang. geniculatum ; f, branch to the tympanic
plexus ; y, branch to the stapedius ; 3, anastomatic twig to the auricular branch of the \ 3 v4,
chorda tympani ; 8, stylo-mastoid foramen. 9, Glosso-pharyngeal—a, its tympanic branch ; @ an
e, connections with the facial; U, terminations of the gustatory fibres of 9 in the circumyallat
papille ; Sy, sympathetic with Gg, s, the superior cervical ganglion; J, J, IJ, 1V, the four upper
cervical nerves ; P, parotid, M, sub-maxillary gland. ; . “i. a

*

_BRANCHES AND CONNECTIONS OF THE TRIGEMINUS. 593

with the ophthalmic division of the trigeminus (Wegner). The iris and retina
receive most of their vaso-motor nerves from the trigeminus itself (Rogow), and few
from the sympathetic ; according to Klein and Svetlin, the retinal vessels are not
influenced either by stimulation or division of the sympathetic. | .
4. Motor fibres for the dilator pupille, which for the most part are derived from
the sympathetic (Petit, 1727), through the sympathetic root of the ganglion, and the
anastomosis of the sympathetic with the trigeminus (Balogh, Oehl). Some observers
deny: altogether the existence of a dilator pupillz muscle (§ 384). The ophthalmic
division contains independent fibres for the dilatation of the pupil (Sch), which
arise in the medulla oblongata and proceed directly into the ophthalmic (? or arise

from the Gasserian ganglion—Oeh/).

It is not conclusively determined whether in man dilator fibres also proceed through the
sympathetic root of the ciliary ganglion, and reach the iris through the ciliary nerves. In the
dog and cat these fibres do not pass through the ciliary ganglion, but go directly along the
optic nerve to the eye (Hensen and Volckers) through the Gasserian ganglion, to its ophthalmic
branch and through the long ciliary nerves (Jegorow). In birds, the dilator fibres run only in
the fifth (Zeglinski). For the centre (§ 367, 8).

After section of the trigeminus, the pupil becomes contracted after a short period
of dilatation (rabbit, frog), but this effect is not permanent.’ After excision of the
superior cervical ganglion of the sympathetic, the power of dilatation of the pupil
is not completely abolished. The narrowing of the pupil which follows section of
the trigeminus in the rabbit, and which rarely lasts more than half an hour, may
be regarded as due to a reflex stimulation of the oculomotorius fibres of the
sphincter, in consequence of the painful stimulation caused by section of the

trigeminus. | ,

Stimulation of the Sympathetic.—Hither in the neck, or in its course to the eye, when the
peripheral end of the cervical sympathetic is stimulated, besides the effect on the blood-vessels,
there is dilatation of the pupil, as well as contraction of the smooth muscular fibres in the orbit
and eyelids. ‘The membrana orbitalis, which separates the orbit from the temporal fossa in
animals, contains numerous smooth muscular fibres (muscular orbitalis). The corresponding
membrane of the inferior orbital fissure [spheno-maxillary fissure] in man has a layer of smooth
muscle, one millimetre thick, and arranged for the most part longitudinally. Both eyelids
contain smooth muscular fibres which serve to close them; in the upper lid they lie as if they
were a continuation of the levator palpebre superioris, in the lower lid they lie close under the
conjunctiva. Zenon’s capsule also contains smooth muscular fibres. The sympathetic nerve
supplies all these muscles (Heinr. Miller)—(the orbital muscle is partly supplied from the
spheno-palatine ganglion); in animals, the retractor of the third eyelid at the inner angle of the
eye is similarly supplied. Hence, stimulation of the sympathetic causes dilatation of the pupil
and of the palpebral fissure, with protrusion of the eyeball. This result may be caused reflexly
by strong stimulation of sensory nerves. Strong stimulation of the nerves of the sexual organs
is followed by similar phenomena in the eye. The dilatation of the pupil, which occurs in chil-
dren affected with intestinal worms, is perhaps an analogous phenomenon. The pupil is dilated
when the spinal cord is stimulated (at the origin of the sympathetic), as in tetanus.

Section of the sympathetic, besides other etfects, causes narrowing of the fissure between th
eyelids, the eyeball sinks in its socket (and in animals, the third eyelid is relaxed and _ pro-
truded). In dogs, section causes internal squint, as the external rectus receives some motor
fibres from the sympathetic. (Origin of these fibres from the cilio-spinal region. Spinal Cord,
§ 362, 1.) . i,

5. It is probable that trophic fibres occur in the trigeminus, and pass through
the ciliary nerves to reach the eye. If the trigeminus be divided within the
cranium, after six to eight days, inflammation, necrosis of the cornea, and ulti-
mately complete destruction of the eyeball take place, constituting panophthalmia
(fodéra, 1823 ; Magendie).

Trophic Fibres.—In weighing the evidence for and against the existence of trophic fibres, we
must bear in mind the following considerations :—1. Section of the trigeminus makes the
whole eye insensible ;-the animal is therefore unconscious of direct injury to its eye, and can-
not therefore remove any offending body. Dust or mucus, which may adhere to the eye, is no
longer removed by the reflex closing of the eyelids ; while, owing to the absence of the reflex,
the eye is more open and is therefore subject to more injuries; the reflex secretion of tears is
also arrested. Snellen (1857) tixed the ear of a rabbit in front of its eye so as “2 protect the

; 2

594 TROPHIC NERVES IN THE TRIGEMINUS,

latter and shield it from injuries, and he found that the inflammation and other events occurred _
at a later date, while, according to Meissner and Biittner, if the eye be protected by means of a
complete capsule, the inflammation does not occur at all. There can be no doubt that the loss
of the sensibility of the eye favours the occurrence of inflammation. But Meissner, Biittner,
and Schiff observed that inflammation of the eye occurred when the trophic (most internal) fibres
alone wete divided, the eye at the same time retaining its sensibility this would seem to
indicate the existence of trophic fibres, but Cohnheim and Senftleben dispute the statement,
Conversely, the sensibility of the eye may be abolished by partial section of the nerve, yet the
eye does not become inflamed (Schif). Ranvier, who denies the existence of trophic nerves,
made a circular incision round the margin of the cornea through its superficial layers, so as to
divide all the corneal nerves. Insensibility of the cornea was thereby produced, but never
keratitis. Further, in man and animals, when they are unable to close their eyelids, there is
redness with secretion of tears, or slight dryness and opacity of the surface of the eyeball
(xerosis), but never the inflammation already described (Samuel). 2. We must also take into
consideration the following :—Section of the trigeminus paralyses the vaso-motor nerves in the
interior of the eyeball, which must undoubtedly cause a disturbance in the intraocular circula-
tion. According to Jesner and Griinhagen, the trigeminus also contains vaso-dilator fibres,
whose stimulation is followed by increased flow of blood to the eye, with consecutive excretion
of the fibrin-factors and increase in the amount of albumin of the aqueous humour. 3. After
section of the nerve, the intraocular tension is diminished (while stimulation of the nerve is
followed by increase of the intraocular pressure) (Hippell, Griinhagen). This diminution of the |
nornial tension necessarily must alter the normal relation of the filling of the blood- and lymph-
vessels, and also the movement of the fluids, upon which the normal nutrition is largely |
dependent. 4 Kiihne observed that stimulation of the corneal nerves was followed by con- {
traction of the so-called corneal-corpuscles. Perhaps the movements of these corpuscles may
influence the normal movement of the lymph in the canalicular system of the cornea (§ 384);
these movements, however, would seem to depend upon the nervous system, so that its destruc-
tion is likely to produce disturbance of nutrition.

[There are three conditions on which the changes may depend—(1) mere loss of sensibility,
which alone is not sufficient to explain the phenomena ; (2) vaso-motor disturbance, which is |
excluded by the above facts, and also by the other consideration that, if the fifth nerve be
divided and the superior cervical ganglion excised simultaneously, ophthalmia does not occur,
and, in fact, excision of this sympathetic ganglion may modify the results of section of the
fifth (Sinitzin). Thus, we are forced to (3) the theory of trophic fibres, whose centre is the
Gasserian ganglion. ] ,

Pathological, —In cases of anesthesia of the trigeminus in man, and, more rarely, in severe
irritation of this nerve, inflammation of the conjunctiva, ulceration and perforation of the cornea,
and finally panophthalmia, have been observed (Charles Bell), This condition has been called
ophthalmia neuroparalytica, Samuel found that a similar result was produced by electrical
stimulation of the Gasserian ganglion in animals. 4

There are other affections of the eye depending upon disease of the vaso-motor nerves, which
are sue different from the foregoing, as they never lead to degenerative changes. Such is
opht ia intermittens (due to malaria), a unilateral, intermittent, excessive filling of the
blood-vessels of the eye, accompanied by the secretion of tears, photophobia, often accompanied
by iritis and effusion of pus into the chambers of the eye. This condition is regarded as a vaso-
neurotic affection of the ocular blood-vessels by Eulenburg. Pathological observations, as well
as experiments upon animals, have shown that there is an intimate physiological connection
between the vascular areas of both eyes, so that affections of the vascular area of one eye are
apt to induce similar disturbances of the opposite eye. This serves to explain the fact that
inflammatory processes in the interior of one eyeball are apt to produce a similar condition in
the other eye. This is the so-called “sympathetic ophthalmia,” Thus, stimulation of the
ciliary nerves, or the fifth on one side, causes dilatation of the blood-vessels not only on its own
side but also on the other side as well (Jesner and Griinhagen). The pathological condition of
glaucoma simplex, where the intraocular tension is greatly increased, is ascribed by Donders to
irritation of the trigeminus, [Increased intraocular tension may be produced by irritation of
the secretory fibres contaitied in the fifth nerve (Donders), by stimulating the nucleus of the
trigeminus in the medulla oblongata (Hippell and Griinhagen), and also reflexly my irritation of

co
it

MECKEL’S GANGLION AND ITS CONNECTIONS, 595

2, The subcutaneous malar or orbital (0) supplies by its temporal and orbital
branches sensibility to the lateral angle of the eye and the adjoining area of skin
of the temple and cheek. Certain fibres are said to be the true secretory nerves for
tears. Compare N. lacrimalis, p. 591.

3. The dental, anterior, posterior, and median, and with them the anterior fibres
from the infraorbital nerve, supply sensory fibres to the teeth in the upper jaw,
the gum, periosteum, and the cavities of the jaw (p. 592). The vaso-motor nerves
of all these parts are supplied from the upper cervical ganglion of the sympathetic.

4, The infraorbital (R), after its exit from the infraorbital foramen, supplies
sensory nerves to the lower eyelid, the bridge and sides of the nose, and the upper
lip as far as the angle of the mouth. The accompanying artery receives its vaso-
motor fibres from the superior cervical ganglion of the sympathetic. For the
sweat-secreting fibres which occur in it (pig) see § 288.

The spheno-palatine ganglion (Meckel’s—z) forms connections with the second
division, ‘To it pass two short sensory root-fibres from the second division itself,
which are called spheno-palatine. Motor fibres enter the ganglion from behind,
through the large superficial petrosal branch of the facial (j); and grey vaso-
motor fibres (v) from the sympathetic plexus on the carotid (the deep large petrosal
nerve), The motor and vaso-motor fibres from the Vidian nerve, which reach the
ganglion through the canal of the same name.

Branches of the Ganglion.—(1) The sensory fibres (N) which supply the roof,
lateral walls, and septum of the nose (posterior and superior nasal); the terminal
fibres of the naso-palatine pass through the canalis incisivus to the hard palate,
behind the incisor teeth. The sensory inferior and posterior nasals for the lower
and middle turbinated bones, and both lower nasal ducts, are derived from the
antertor palatine branch of the ganglion, which descends in the palato-maxillary
canal. Lastly, the sensory branches for the hard (p) and soft palate (p,), and the
tonsils arise from the posterior palatine nerve. All the sensory fibres of the nose
(see also the Hthmoidal nerve), when stimulated, cause the reflex act of sneezing
(§ 120). Preparatory to the act of sneezing, there is always a peculiar feeling of
tickling in the nose, which is perhaps due to dilatation of the nasal blood-vessels.
This dilatation is rapidly caused by cold, more especially when it is applied directly
to the skin. The dilatation of the vessels is followed by an increased secretion of
watery fluid from the nasal mucous membrane. Stimulation of the nasal nerves
also causes a reflex secretion of tears, and it may also cause stand-still of the
respiratory movements in the expiratory phase (Hering and Kratschmer)—(compare
Respiratory centre, § 368). (2) The motor branches descend in the posterior palatine
nerve through the small palatine canal, and give off (4) motor branches to the
elevator of the soft palate and azygos uvulze (WVuhn). The sensory fibres for these
muscles are supplied by the trigeminus, According to Politzer, spasmodic con-
traction of these muscles occasionally causes crackling noises in the ears. (3) The
vaso-motor nerves of this entire area arise from the sympathetic root, z.e., from the
upper cervical ganglion. (4) The root of the trigeminus supplies the secretory
nerves of the mucous glands of the nasal mucous membrane. Stimulation excites
secretion, while section of the trigeminus diminishes it with simultaneous atrophic
degeneration of the mucous membrane. Thus, trophic functions for the mucosa
have been ascribed to the trigeminus (Aschenbrandt).

Stimulation of the Ganglion.—Feeble electrical stimulation of the exposed ganglion causes a
copious secretion of mucus and an increase of the temperature in the nose (Prévost), with dila-
tion of the vessels (Aschenbrandt), [Meckel’s ganglion has been excised in certain cases of
neuralgia (Valsham). | :

III. Inferior Maxillary (g).—It contains all the motor fibres of the fifth, along
with a number of sensory fibres ; it gives off —

1, The recurrent, which springs by itself from the sensory root, enters the skull

596 .. . INFERIOR MAXILLARY DIVISION.

through the foramen spinosum, and, along with the nerve of the same name from
the II. division, supplies sensory fibres to the dura mater. Fibres proceed from it
through the petroso-squamosal fissure to the mucous membrane of the cells of the.
mastoid process. ; .

2. Motor fibres for the muscles of mastication, viz., the masseteric, the two deep
temporal nerves, and the internal and external pterygoid nerves. The -sensory
fibres for the muscles are supplied by the sensory fibres. .

3. The buceinator is a sensory nerve for the mucous membrane of the cheek,
and the angle of the mouth as far as the lips.

According to Jolyet and Laffont, it contains, in addition, vaso-motor fibres for the mucous
membrane of the cheek, lower lip, and their mucous glands; but these fibres are probably
derived from the sympathetic. .

Trophic Fibres. —As this region of the mucous membrane of the mouth ulcerates after section
of the trigeminus, sorne have supposed that the buccinator nerve contains trophic fibres. But,
as Rollett pointed out, section of the inferior maxillary nerve paralyses the muscles of mastica-
tion on the same side, and hence the teeth do not act vertically upon each other, but press
against the cheek. Owing to the loss of the sensibility of the mouth, food passes between the
gum and the cheek, where it may remain attached, undergo decomposition, and perhaps
chemically irritate the mucous membrane. At a later stage, owing to the wearing away of the
teeth in an oblique manner, ulcers begin to form on the sownd side. Hence, there is no necessity
for assuming the existence of trophic fibres in this nerve. After section of the trigeminus, the
nasal mucous membrane on the same side becomes red and congested. This is due to the fact
that dust or mucus, not being removed from the nose by the usual reflex acts, remains there,
irritates, and ultimately causes inflammation. |

4. The lingual (4) receives at an acute angle the chorda tympani (7 2), a branch
of the facial coming from the tympanic cavity. The lingual does not contain any
motor fibres ; it is the sensory and tactile nerve of the anterior two-thirds of the |
tongue, of the anterior palatine arch, the tonsil, and the floor of the mouth. . These,
as well as all the other sensory fibres of the mouth, when stimulated, cause a reflex
secretion of saliva (compare § 145). The lingual is accompanied by the nerve of
taste (chorda) for the tip and margins of the tongue (7.e., the parts not supplied by
the glosso-pharyngeal). After section of the lingual nerve in man, Busch, Inzani,
and Lusanna found that the tactile sensibility was lost in the half of the tongue,
and there was loss of taste in the anterior part [two-thirds] of the tongue. The
fibres which administer to the sense of taste do not as a rule belong to the lingual
itself, but are derived from the chorda tympani (p. 600). According to Schiff, the —
lingual nerve is the gustatory nerve, and some cases of Erb and Senator support
this view. Such cases, however, seem to be exceptions to the general rule. The
lingual nerve in the substance of the tongue is provided with small ganglia
(Lemak, Stirling). Schiff observed that section of the lingual (and also of the
hypoglossal) caused redness of the tongue, so that vaso-motor fibres are present. in
its course. It is unknown whether these are derived from the anastomoses of the
Gasserian ganglion with the sympathetic. The lingual appears to receive vaso-
dilator fibres from the chorda for the tongue and gum (§ 349).

After section of the trigeminus, animals frequently bite their tongue, as they cannot feel the
position and movements of this organ in the mouth.

5. The inferior dental is the sensory branch to the teeth and gum; the vaso-
motor fibres reach it from the superior cervical ganglion. Before it passes into the
canal in the lower jaw, it gives off the mylo-hyoid nerve, which supplies motor
fibres to the mylo-hyoid and the anterior belly of the a, pa and also some fibres
to the triangularis menti and the platysma ; the muse sensory nerves also lie
in these branches. The mental nerve, which issues from the mental foramen, is the —
sensory nerve for the chin, lower lip, and the skin at the margin of the jaw. a

6. The auriculo-temporal gives sensory branches to the anterior wall of the
external auditory meatus, the tympanic membrane, the anterior part of the ear,
the adjoining region of the temple, and to the maxillary articulation. Ae

THE OTIC GANGLION AND ITS CONNECTIONS. 597

Fig. 430 shows the distribution of the branches of the trigeminus on the head, and the
ne 0% hates so that the distribution of anesthetic and hyperesthetic areas may easily be
made out.

The otic ganglion (m) lies beneath the foramen ovale on the inner side of the
third division. Its roots are—(1) short motor fibres from the third division ; (2)
vaso-motor from the plexus around the middle meningeal artery (ultimately
derived from the cervical ganglion of the sympathetic) ; (3) fibres (A) run from the
tympanic branch of the glosso-pharyngeal to the tympanic plexus, and from thence
through the canaliculus petrosus in the small superficial petrosal in the cranium,
then through a small canal between the apex of the petrous bone and the sphenoid,

Muse, temporalis.

Muse. masseter

fr :
N. hypoglossus, Lfuse. splenius.

Muse. sternocleid toid

N. accessorius,
= 2 oe. Muse. levator anguli scapulae.

Muse. cucullaris or trapezius.

N. dorsalis scapulae.

Platysma myoide:.
Muse. sternohyoideus,
Musc, sternothyreoideus,

Musc. omohyoideus.

Nn. thoracici anteriores.

N. axillaris.

i Ss.) eegehete N. thoracicus longus,

Erb’s Plexus
Supraclavicular- brachialis.
point.
ie Fig. 430. .
Distribution of the sensory nerves on the head as well as the position of the motor points on
i the neck. SO, area of distribution of the supraorbital nerve; $7’, supratrochlear; J7’,
infratrochlear; Z, lachrymal; N, ethmoidal; JO, infraorbital; B, buccinator; SJ,
subcutaneus male; AZ’, auriculo-temporal; AWM, great auricular; OM, great occipital ;
¥ OMi, lesser occipital ; C3, three cervical nerves ; C'S, cutaneous branches of the cervical
nerves ; CW, region of the central convolutions of the brain; SC, region of the speech-
- centre (third left frontal convolution). |

oN phrenicus.

be to reach the otic ganglion. Through the chorda tympani the facial nerve is con-
i stantly connected with the ganglion (fig. 430). :

The branches of the otic ganglion are—(1) motor twigs for the tensor tympani
; and tensor of the soft palate (these fibres are mixed with muscular sensory fibres—
Ludwig and Politzer) ; (2) one or more branches connecting the ganglion with the

598 THE SUB-MAXILLARY GANGLION AND ITS CONNECTIONS.

auriculo-temporal are carried by the roots 2 and 3 from the sympathetic and glosso-
pharyngeal, which the auriculo-temporal nerve (A), as it passes through the parotid
gland (P), gives off to the gland. These are the secretory fibres for the parotid;
their functions are stated in § 145.

Section of the trigeminus is followed by inflammatory changes in the tympanic cavity
(rabbit); the degree of inflammation varies much (Berthold and Griinhagen). Section of the
sympathetic or glosso-pharyngeal has no effect.

The sub-maxillary ganglion (fig. 429, L) lies close to the convex arch of
the tympanico-lingual nerve and the excretory duct of the sub-maxillary gland
(M). Its roots are—(1) branches of the chorda tympani, 2», which undergo
fatty degeneration after section of facial nerve. This root supplies secretory
fibres to the sub-maxillary and sub-lingual glands, but it also supplies vaso-dilator |
fibres for the blood-vessels of the same glands (§ 145). In addition, fibres are |
supplied to the smooth muscular fibres in Wharton’s duct. All the fibres of the |
chorda do not pass into the gland; some pass along with the lingual nerve into |
the tongue (see Chorda, under Facial Nerve). (2) The sympathetic root of the .
ganglion arises from the plexus around the submental branch of the external
maxillary artery (7), 7.e., ultimately from the superior cervical ganglion ; it passes
to the gland, and contains secretory fibres, whose stimulation is followed by the
secretion of thick concentrated saliva (trophic nerve of the gland). It also carries
the vaso-constrictor nerves to the gland (p. 212). (3) The sensory root springs
from the lingual. Some of the fibres, after passing through the ganglion, supply
the gland and its excretory ducts, while a few issue from the ganglion, and again
join the tympanico-lingual nerve to reach the tongue.

Pathological.—Trismus, or spasm of the muscles of mastication, supplied by the third division,
is usually bilateral ; it may be clonic in its nature (chattering of the teeth), or tonic, when it
constitutes the condition of lock-jaw or trismus. The spasms are usually individual symptoms
of more extensive convulsions ; more rarely when they occur alone, they are symptomatic of
disease of the cerebrum, medulla, pons, and cortex of the motor convolutions (Lulenburg). The
spasins may be caused reflexly, ¢.g., by stimulation of the sensory nerves of the head.

Paralysis.—_Degeneration of the motor nuclei, or an affection of the intracranial root of the
nerve, causes paralysis of the muscles of mastication, which is very rarely bilateral. Paralysis
of the tensor tympani is said to cause difficulty of hearing (Romberg), ov buzzing in the ears
(Benedict). We require further observations upon this point, as well as upon paralysis of the :
tensor of the soft palate.

Neuralgia may occur in all the branches of the fifth. It consists of severe attacks of pain
poo into the expansions of the nerves. It is usually unilateral, and in fact is often
confined to one branch, or even to a few twigs of one branch. The point from which the pain
proceeds is frequently the bony canal through which the branch issues. The ear, dura mater,
and tongue are rarely attacked. The attack is not unfrequently accompanied by contractions ;
or twitchings of the corresponding group of the facial muscles. The twitchings are either reflex,
or are due to direct peripheral irritation of the fibres of the facial nerve, which are mixed with
the terminal branches of the trigeminus. The reflex twitchings may be extensively distributed,
involving even the muscles of the arm and trunk.

ess or congestion of the affected part of the face is not an unfrequent symptom in
neuralgia, and it may be accompanied by increased_or diminished secretion ton the nasal and
buccal mucous membranes. This is a reflex phenomenon, the sympathetic being affected.
Reflex stimulation of the vaso-motor nerves frequently gives rise to disturbance of the cerebral
activities, owing to changes in the distribution of the blood in the head. Ludwig and Dittmar
found that stimulation of sensory nerves caused a reflex contraction of the arterial blood-vessels,
and increase of the blood-pressure in the cerebral vessels. Sometimes there is melancholy or
hypochondriasis, and in one case of violent pain in the inferior maxillary nerve, the attack was
accompanied by hallucinations of vision. . |

The trophic disturbances which sometimes accompany affections of the trigeminus are parti- __
cularly interesting. They are: a brittle character of the hair, which frequently becomes grey, _
or may fall out; circumscribed areas of inflammation of the skin, and the appearance of a
vesicular eruption upon the face [often following the distribution of certain nerves], and con-
stituting herpes, which may also occur on the cornea, constituting the neuralgic herpes cornes a
of Schmidt-Rimpler. Lastly, there is the progressive atrophy of the face which is usually con-
fined to one side, but may occur on both sides (Eulenburg). It is caused very probably by a —
trophic affection of the trigeminus, although the vaso-motor nerves may also be affected reflexly, —

NERVUS ABDUCENS. 599

Landois found that in the famous case of Romberg, a man named Schwahn, the sphygmo-
graphic tracing of the carotid pulse of the atrophied side was distinctly smaller than on the
Plpeeaitechitech made the remarkable observation that stimulation of the branches of the
trigeminus, especially those going to the ear, caused an increase of the sensation of light in the
person so stimulated. Blowing upon the cheeks or nasal mucous membrane, electrical stimula-
tion, the use of snuff, smelling strong perfumes—all temporarily increase the sensation of light.
The senses of taste and smell, as well as the sensibility of certain areas of the skin, can all be
exalted reflexly by gentle stimulation of the trigeminus. In intense affections of the ear, whereby
the fibres of the trigeminus are often affected sympathetically, these sensory functions may be
diminished. As the ear-malady begins to improve, the excitability of these sense organs also
again begins to improve.

[Complete section of the trigeminus results in loss of sensibility in all the parts
supplied by it (fig. 430), including one side of the face, temple, part of the ear, the
fore part of the head, conjunctiva, cornea, mouth, gums, Schneiderian mucous
membrane, anterior two-thirds of the tongue, and part of pharynx. In drinking
from a vessel, the patient feels as if one side of it were cut away. The muscles of
mastication are paralysed on that side, food is not chewed on one side, and fur
accumulates on the tongue on that side. The mucous membranes tend to ulcerate,
that of the mouth being chafed by the teeth, the gums get spongy, the nasal
mucous membrane tends to ulcerate, so that smelling is interfered with, and
ammonia excites no reflex acts, while the eye undergoes panophthalmia. |

[Gowers is of opinion that the sensation of taste on the posterior part of the tongue, soft
palate, and palatine arch depends on the fifth nerve and not on the glosso-pharyngeal nerve. ]

348. VI. NERVUS ABDUCENS.—Anatomical.—It arises slightly in front of and partly
from the nucleus of the facial nerve (which corresponds to the anterior horn of the spinal cord),
from large-celled ganglia in the deeper part of the anterior region of the fourth ventricle,
(emenentia teres, fig. 427). [Its nucleus is connected with the nucleus of the third nerve of
the opposite side. It appears at the posterior margin of the pons (fig. 428, VI.). This nerve
has a very long course before it enters the orbit, and as it bends over the posterior margin of
the pons, it is liable to be compressed there or from pressure upon the tentorium cerebelli, so
that both nerves are very liable to paralysis. ]

Function.—It is the voluntary nerve of the external rectus muscle. In co-
ordinated movements of the eyeballs, however, it is involuntary.

Anastomoses.—Branches reach it from the sympathetic upon the cavernous sinus (fig. 429).
A few come from the trigeminus, and their function is analogous to similar fibres supplied to
the trochlearis and oculomotorius.

Pathological.—Complete paralysis causes squinting inwards [or convergent squint] and con-
sequent diplopia. [The eye cannot be rotated outwards beyond the middle line, the double
images are in the same horizontal plane and vertical, the false one is to the left of the patient’s
eye when the left eye is affected (fig. 426, 2). The feeling of giddiness is often severe. There
is secondary deviation to the inner side, and the head is turned towards the affected side.] In
dogs, section of the cervical sympathetic causes a slight deviation of the eyeball inwards (Petit).
This is explained by the fact that the abducens receives a few motor fibres from the cervical
sympathetic. Spasm of the abducens causes external squint. . net

Squint.—In addition to paralysis or stimulation of certain nerves producing squint, it is to
be remembered that it may also be caused by a primary affection of the muscles themselves,
é.g., congenital shortness, contracture, or injuries of these muscles. It may also be brought
about owing to opacities of the transparent media of the eye; a person with, say an opacity
of the cornea, rotates the affected eye involuntarily, so that the rays of light may enter the eye
through a clear part of the media.

349, VII. NERVUS FACIALIS,—Anatomical,—This nerve consists entirely of efferent fibres,
and arises from the floor of the fourth ventricle from the ‘‘ facial nucleus” (fig. 427, 7), which
lies behind the origin of the abducens, and also by some fibres from the nucleus of the abducens
[although Gowers’ observations do not confirm this (§ .866)]. Other fibres arise from the
cerebrum of the opposite side (§ 378, I.). It consists of two roots, the smaller—portio inter-
media of Wrisberg—forms a connection with the auditory nerve (see § 350).. The original
fibres of the portio intermedia are developed from the glosso-pharyngeal nucleus (Sapolini). It
would thus appear that the sensory and gustatory fibres which are present in the chorda tympani
enter it through these fibres (Duval, Schultze, Vulpian), so that the portio intermedia is a special
part of the nerve of taste, which becomes conjoined with the facial, and runs to the tongue in
the chorda. Along with the auditory nerve, it traverses the porus acusticus internus, where it

600 THE CHORDA TYMPANI AND TASTE.

into the facial or Fallopian canal. At first it has a transverse direction as far as the

iatus of this canal; it then bends at an acute angle at the “knee” (a) above the tympanic
cavity, to descend in an osseous canal in the posterior wall of this space (fig. 429). It emerges -

from the stylo-mastoid foramen, pierces the parotid gland, and is distributed in a fan-shaped

manner (pes anserinus major). [The superficial origin is at the lower margin of the pons, in

the depression between the olivary body and the restiform body, as indicated in fig. 428,

Vil a.] |

Its branches are:—l. The motor large superficial petrosal (j). It arises |
from the “knee” or geniculate ganglion within the Fallopian canal, in the cavity »
of the skull, runs upon the anterior surface of the temporal bone, traverses the
foramen lacerum medium on the under surface of the base of. the skull, and passes
through the Vidian canal to reach the spheno-palatine ganglion (p. 595). It is
uncertain whether this nerve conveys sensory branches from the second division of
the trigeminus to the facial.

2. Connecting branches (8) pass from the geniculate ganglion to the otic ganglion.
For their course and function, see Otic ganglion (p. 597).

3. The motor branch to the stapedius muscle (y).

4. The chorda tympani (77) arises from the facial before it emerges at the
stylomastoid foramen (s), runs through the tympanic cavity (above the tendon of
the tensor tympani, between the handle of the malleus and the long process of
the incus), passes out of the skull through the petro-tympanic fissure, and then
joins the lingual nerve at an acute angle (p. 596, 4). Before it unites with. this
nerve, it exchanges fibres with the otic ganglion (m). Thus, sensory fibres can
enter the chorda from the third division of the trigeminus, which may run
centripetally to the facial to be distributed along with it. In the same way, sensory
tibres may pass from the lingual nerve through the chorda into the facial (Longet).
Stimulation of the chorda—which even in man may be done in cases where the
tympanic membrane is destroyed—causes a prickling feeling in the anterior margins
and tip of the tongue (T7réltsch). O. Wolfe found that the section of the chorda in
man abolished the sensibility for tactile and thermal stimuli upon the tip of the
tongue ; and the same was true of the sense of taste in this region. It is supposed
by Calori, that these fibres enter the facial nerve at its periphery (especially through
the auriculo-temporal into the branches of the facial), that they run in a centripetal
direction in the facial, and afterwards pursue a centrifugal course in the chorda.
[It is possible that sensory fibres pass from the spheno-palatine ganglion of the
fifth through the Vidian nerve and large superficial petrosal to enter the facial.
These fibres may be those that appear in the seventh as the chorda fibres which
administer to taste. Bigelow asserts that the chorda tympani is not a branch of the
facial, but the continuation of the nervus intermedius of Wrisberg.] The chorda
also contains secretory and vaso-dilator fibres for the sub-maxillary and sub-lingual
glands (§ 145). .

Gustatory Fibres.—The chorda also contains fibres administering to the sense of
taste, for the margin and tip of the tongue (anterior two-thirds), which are conveyed —
to the tongue along the course of the lingual. Urbantschitsch made observations
upon a man whose chorda was freely exposed, and in whom its stimulation in the
tympanic cavity caused a sensation of taste (and also.of touch) in the margins and
tip of the tongue.

It would seem, therefore, that the gustatory fibres of the chorda have their
origin in the glosso-pharyngeal nerve. They may reach the chorda:—1, Through
the portio intermedia of Wrisberg, as already mentioned. : |

2, There is achannel beyond the stylomastoid foramen, viz., through the ramus communicans
cum glosso-pharyngeo (fig. 429), which passes from the last mentioned nerve in that branch of
the facial which contains the motor fibres for the stylohyoid and posterior belly of the digastric
muscle (Henle’s N, styloideus). This nerve also supplies muscular sensibility to the stylohyoid

and posterior belly of the digastric muscles. It is also assumed that, by means of these anasto-
moses, motor fibres are supplied by the facial to the glosso-pharyngeal nerve. . 3. A union of the

PARALYSIS OF THE FACIAL, 601

glosso-pharyngeal and facial nerves occurs in the tympanic cavity. The tympanic branch of

the glosso-pharyngeal (A) passes into this cavity, where it unites in the tympanic plexus with
7 the small superficial petrosal nerve (8), which springs from the knee on the facial. The
gustatory fibres may first pass into the otic ganglion, which is always connected with the
chorda (Otic ganglion, p. 597, 3). Lastly, a connection is described through a twig (7) from the
petrous ganglion of the glosso-pharyngeal, direct to the facial trunk within the Fallopian canal
(Garibaldi).

According to some observers, the chorda contains vaso-dilator fibres for the
anterior two-thirds of the tongue (Vulpzan).

Pseudo-motor Action.—From one to three weeks after the section of the hypoglossal nerve,
stimulation of the chorda causes movements in the tongue (Philippeaux and Vulpian). These
movements are not so energetic as, and occur more slowly than, those caused by stimulation of
the hypoglossal. NVicotin first excites, then paralyses, the motor effect of the chorda. Even after
cessation of the circulation, stimulation of the chorda causes movements, Heidenhain supposes

. frontalis.

- corrugator supercilii.
. orbicular palpebr.

. compressor nasi et pyram nasi
. levator lab. sup. alaque nasi.

. levator lab. sup. propr.

. zygomatic minor.

. dilatat. narium.

. zygomatic. major.

Upper branches of the Facial.
Trunk of the Facial.

Mm. retrahens et attolens auricul.
Muse. occipitalis. =

Middle branches of the Facial.

M. stylohyoideus.

sM. digastricus.

. orbicularis oris.

. levator menti.
- quadratus menti.

Lower branches of the Facial. - triangularis menti.

| Fig. 431.
Motor points of the facial nerve and the facial muscles supplied by it.

that, owing to the stimulation of the chorda, there is an increased secretion of lymph within

the musculature, which acts as the cause of the muscular contraction. He called this action

**pseudo-motor.” ;

f (If, after the union of the central end of the lingualis and the peripheral end of the hypo-
G glossal nerve, the lingualis be stimulated, there is a genuine contraction of the musculature of
bi the tongue, on that side. A pseudo-motor contraction is easily distinguished from a true
contraction, for when a telephone is connected with the tongue, on stimulating the hypoglossal
the tone of the tetanus thereby produced is heard, but on stimulating the lingual, although
the pseudo-motor contractions occur, no sourid is heard (Rogowicz).]

5. Connection with Vagus.—Before the chorda is given off, the trunk of the facial comes
into direct relation with the auricular branch of thé vagus (8), which. crosses it in the mastoid
canal, and supplies it with sensory nerves (see Vagus). ‘Tae:

6. Peripheral Branches.—After the facial issues: from its canal, it supplies

602 UNILATERAL AND DOUBLE PARALYSIS OF THE FACIAL.

motor fibres to the stylohyoid and posterior belly of the digastric, occipitalis, all the
muscles of the external ear, the muscles of expression, buccinator and platysma.
The facial also contains secretory fibres for the face (compare § 288). ;

Although most of the branches of the facial are under the influence of the will, yet most men
cannot voluntarily move the muscles of the nose and ear.

Anastomoses.—The branches of the seventh nerve on the face anastomose with
those of the trigeminus, whereby sensory fibres are conveyed to the muscles of
expression. The sensory branches of the auricular branch of the vagus, and the |
great auricular, enter the peripheral ends of the facial, and supply sensibility to the
muscles of the ear; while the sensory fibres of the third cervical nerve similarly
supply the platysma with sensibility. Section of the facial at the stylomastoid
foramen is painful, but it is still more so if the peripheral branches on the face are
divided (Recurrent sensibility, § 355).

Pathological. —In all cases of paralysis of the facial, the most important point to determine
is whether the seat of the affection is in the periphery, in the region of the stylomastoid
foramen, or in the course of the long Fallopian canal, or is central (cerebral) in its origin. This
point must be determined by an analysis of the symptoms. Paralysis .at the stylomastoid
foramen is very frequently rheumatic, and probably depends upon an exudation compressing
the nerve; the exudation probably occupying the lymph-space described by Riidinger on the
inner side of the Fallopian canal, between the periosteum and the nerve, and which is a
continuation of the arachnoid space. Other causes are—inflammation of the parotid gland,
direct injury, and pressure from the forceps during delivery. In the course of the canal, the
causes are—fracture of the temporal bone, effusion of the blood into the canal, syphilitic
effusions, and caries of the temporal bone ; the last sometimes occurs in inflammation of the
ear. Amongst intracranial causes are—affections of the membranes of the brain, and of the
base of the skull in the region of the nerve, disease of the ‘‘ facial nucleus”; lastly, affection
of the cortical centre of the nerve and its connections with the nucleus. . [No nerve is so liable
as the seventh to be paralysed independently. ]

Symptoms of Unilateral Paralysis of the Facial [or Bell’s Paralysis].—1. Paralysis of the
muscles of expression: The forehead is smooth, without folds, the eyelids remain open
(lagophthalmus paralyticus), the outer angle being slightly lower. The anterior surface of the |
eye rapidly becomes dry, the cornea is dull, as, owing to the paralysis of the orbicularis, the |
tears are not properly distributed over the conjunctiva, and, in fact, in consequence of the
dryness of the eyeball, there may be temporary inflammation (keratitis xerotica), In order .
to protect the eyeball from the light, the patient turns it upwards under the upper eyelid
(Bell), relaxes the levator palpebre, which allows the lid to fall somewhat (Hasse). The nose
is immovable, while the naso-labial fold is obliterated. As the nostrils cannot be dilated, the
sense of smell is interfered with. The impairment of the sense of smell depends more,
however, upon the imperfect conduction of the tears, owing to paralysis of the orbicularis
palpebrarum and Horner’s muscle, thus causing dryness of the corresponding side. of the nasal
cavity. Horses, which distend the nostrils widely during respiration, after section of both
facial nerves, are said by Cl. Bernard to die from interference with the respiration, or at least
they suffer from severe dyspncea (Ellenberger). The face is drawn towards the sound side, so that
the nose, mouth, and chin are oblique. Paralysis of the buccinator interferes with the proper
formation of the bolus of food; the food collects between the cheek and the gum, from which it
is usually removed by the patient with his fingers ; saliva and fluids.escape from the angle of
the mouth. During vigorous expiration, the cheeks are puffed outwards like a sail. . The speech
may be affected owing to the difficulty of sounding the labial consonants, (especially in double
persiyn) and the vowels, u, ii (ue), 6 (oe) ; while the speech, in paralysis of the branches to

th sides of the palate, becomes nasal (§ 628). The acts of whistling, sucking, blowing, and
spitting are interfered with, In double paralysis, many of these symptoms are greatly in-
tensified, while others, such as the oblique position of the features, disappear, The features
are completely relaxed ; there is no mimetic play of the features, the patients weep and laugh,

as it were, behind a mask” (Romberg). 2. In paralysis of the palate, when the uvula is
directed towards the sound side, and the paralysed half of the palate hangs down and cannot be
raised (large superficial petrosal nerve), it is not autora to what extent this condition
influences the act of deglutition and the formation of the consonants. 8. Taste is interfered
with; either it is absent on the anterior two-thirds of the tongue, or the sensation is delayed
and altered, This is due to an affection of the chorda. 4. Diminution of saliva on the affected
side was first described by Arnold; still, we must determine to what extent a simultaneous
affection of the sense of taste may cause a reflex interference with the secretion of saliva, or
whether rapid removal of the saliva through the opened lips and angle of the mouth may cause
the dryness on the affected side of the mouth. 5. Roux pointed out that hearing is affected,

‘
4
’ ’ D

STIMULATION OF THE FACIAL. 603

the sensibility to sounds being increased (oxyakoia, hyperakusis willisiana). The paralysis of
the stapedius muscle makes the stapes loose in the fenestra ovalis, so that all impulses from the
tympanum act vigorously upon the stapes, which consequently excites considerable vibrations in
the fluid of the inner ear. More rarely, in paralysis of the stapedius, it has been observed that
low notes are heard at a greater distance than on the sound side (Lucae, Mow). 6. As the
facial in man appears to contain fibres for the secretion of sweat, this explains the loss of the
power of sweating in the face when the nerve begins to atrophy (Strauss, Bloch).

Section of the facial in young animals causes atrophy of the corresponding muscles. The
facial bones are also imperfectly developed ; they remain smaller, and hence the bones of the
sound side of the face grow towards, and ultimately across, the middle line towards the affected
side (Brown-Séquard). The salivary glands also remain smaller.

Stimulation—or irritation in the area of the facial—causes partial or extensive, either direct
or reflex, tonic or clonic spasms. The extensive forms are known as ‘‘ mimetic facial spasm.”’
Amongst the partial forms are tonic contraction of the eyelid (blepharospasm), which is most
common ; and is caused reflexly by stimulation of the sensory nerves of the eye, ¢.g., in scrofulous
ophthalmia, or from excessive sensibility of the retina (photophobia). More rarely, the excite-
ment proceeds from some more distant part, ¢.g., in one cause recorded by v. Grife, from
inflammatory stimulation of the anterior palatine arch. The.centre for the reflex is the facial
nucleus. The clonic form of spasm—spasmodic winking (spasmus nictitans)—is usually of
reflex origin, due to irritation of the eye, the dental nerves, or even of more distant nerves.
In severe cases, the atfection may be bilateral, and the spasms may extend to the muscles of
the neck, trunk, and upper extremities. Contraction of the muscles of the lip may be excited
by emotions (rage, grief), or reflexly. Fibrillar contractions occur after section of the facial as
a ‘‘degeneration-phenomenon” (p. 476). [If the facial be torn out at the stylomastoid
foramen, there is paralytic oscillation of the lip muscles (Schiff). If, in such an animal, the
posterior root of the annulus of Vieussens be stimulated electrically, as it contains vaso-dilator
fibres (Dastre and Morat), not only do the blood-vessels of the cheek and lips dilate, but the
veins pulsate and florid blood escapes from the veins, just as occurs in the sub-maxillary gland
when the chorda is stimulated. On stimulating the ansa, after section of the seventh, there is
a pseudo-motor effect on the muscles of the cheek and lips, so that there is an analogy between
the chorda and the ansa (Rogowicz).] Intracranial stimulation of the most varied description
may cause spasms. Lastly, facial spasm may be part of a general spasmodic condition, as in
epilepsy, chorea, hysteria, tetanus. Aretaeus (81 A.D.) made the interesting observation that
the muscles of the ear contracted during tetanus. Very rarely have spasmodic elevation of the
palate and increased salivation been described as the result of irritation of the facial (Lewbe).
Moos observed a profuse secretion of saliva on stimulating the chorda during an operation on
the tympanic cavity.

350. VIII. NERVUS ACUSTICUS.—Arises by two roots (Stieda) ; a larger anterior and a
smaller posterior one. From the former proceeds the vestibular nerve, and from the latter the
cochlear nerve; these are separated in the sheep and horse (Horbaczewski). Each root springs
from a median and a lateral nucleus, so that there are four nuclei. Some fibres come from the
cerebellum, and these may be connected with equilibration. The chief mass of the posterior
ganglion fibres of the cochlear nerve cross and pass to the corpora quadrigemina, the internal
geniculate, and finally to the temporo-sphenoidal lobe (§ 378, IV., 2). After extirpation of the
temporo-sphenoidal lobe, these fibres atrophy into the internal capsule and internal geniculate
body (v. Monakow). ‘The stris acustice form a second decussating projection system. The
origin of both acoustic nerves are connected by commissures in the brain (fechsiq).

In the course of the internal auditory meatus, the auditory and portio intermedia of the facial
exchange fibres, but the physiological significance of this is unknown.

Function.—The acusticus or auditory nerve has a double function :—1. It is
the nerve of hearing ; when stimulated, either at its origin, in its course, or at its
peripheral terminations, it gives rise to sensations of sound. Every injury, accord-
ing to its intensity and extent, causes hardness of hearing or even deafness.

2. Quite distinct from the foregoing is the other function, which depends upon
the semicircular canals, viz., that stimulation of the peripheral expansions in the
ampullz influences the movements necessary for maintaining the equilibrium of
the body.

_ Brenner’s Formula.—The relation of the auditory nerve to the galvanic current is. very
important. In healthy persons, when there is closure at the cathode, there is the sensation of
a clang (or tone) in the ear, which continues with variations while the current is closed. When
the anode is opened, there is a feebler tone (Brenner’s Normal Acoustic Formula). This clang

ses exactly with the resonance fundamental tone of the sound-conducting apparatus of the
ear itself,

604 THE SEMICIRCULAR CANALS,

Pathological. —Jncreaséd sensibility of the auditory nerve in any part of its course, its centre,
or peripheral expansions causes the condition known as hyperakusis, which usually is a sign of
eatly increased nervous excitability, as in hysteria. When excessive, it may give rise to
istinctly painful impressions, which condition is known as acoustic. hyperalgia (Lulenburg).
Stimulation of the parts above-named causes sensations of sound, the most common being the
sensation of singing in the ears, or tinnitus. This condition is often due to changes in the
amount of blood in the blood-vessels of the ear—either anemic or hyperemic stimulation,
There is well-marked tinnitus after large doses of quinine or salicin, due to the vaso-motor
effect of these drugs upon the vessels of the labyrinth (Kirchner). Not unfrequently, in cases
of tinnitus, the reaction due to the galvanic current is often increased, More rarely there is
the so-called ‘‘ paradoxical reaction” —i.e., on applying the galvanic current to one ear, in
addition to the reaction in this ear, there is the opposite result in the non-stimulated ear. In
other cases of disease of the auditory nerve, noises rather than musical notes are produced by
the current ; stimulation, especially of the cortical centre of the auditory nerve, chiefly in
lunatics, may cause auditory delusions (§ 378, IV.). According as the excitability of the
auditory nerve is diminished or abolished, there is the condition of nervous hardness of hearing
(hypakusis), or nervous deafness (anakusis). .
The Semicircular Canals of the Labyrinth.—Section or injury to these canals
does not interfere with hearing, but other important symptoms follow their injury,
such as disturbances of equilibrium due to a feeling of giddiness, especially when
the injury is bilateral (//owrens). This does not occur in fishes (Kteselbach). The
pendulum-like movement of the head, in the direction of the plane of the injured
canal, is very characteristic. If the hvrizontal canal be divided, the head (of the
pigeon) is turned alternately to the right and left. The rotation takes place, especially
when the animal is about to execute a movement : when it is at rest, the movement
is less pronounced. The phenomenon may last for months, and injury to the
posterior vertical canals causes a well-marked up and down movement or nodding of
the head, the animal itself not unfrequently falling forwards or backwards. Injury
to the superior vertical canals also causes pendulum-like vertical movements of the
head, while the animal often falls forwards. When all the canals are destroyed,
various pendulum-like movements are performed, while standing is often impossible.
Breuer found that electrical stimulation of the canals caused rotation of the head,
while Landois, on applying a solution of salt to the canals, observed pendulum-
like movements, which, however, disappeared after a time. A 25 per cent. solu-
tion of chloral dropped into the ear of a rabbit causes, after fifteen minutes, a
similar destruction of the canals (Vulpian). Section of the acoustic nerves within
the cranium has the same result (Bechterew).

Explanation.—Goltz regards the canals as organs of sense for ascertaining the equilibrium or
position of the head in space; Mach, as an organ for ascertaining the movements of the head.
According to Goltz’s statical theory, every position of the head causes the endolymph to exert
the greatest pressure upon a certain part of the canals, and thus excites in a varying degree the
nerve-terminations in the ampulla, According to Breuer, when the head is rotated, currents
are produced in the endolymph of the canals, which must have a fixed relation to the direction
and extent of the movements of the head, and these currents, therefore, when they are perceived,
afford a means of determining the movement of the head. The nervous end-organs of the
ampulle are arranged for ascertaining this perception. If the semicircular canals are an appa-
ratus-—in fact, ‘‘sense-organs ”—for the sensation of the equilibrium, and if their function is
to determine the position or movements of the head, necessarily their destruction or stimulation
must alter these perceptions, and so give rise to abnormal movements of the head. Vulpian
regards the rotation of the head as due to strong auditory perceptions (?) in consequence of
affections of the canals. Béttcher, Tomaszewicz, and Baginsky regard the injury to the cere-

bellum as the cause of the phenomena, The pendulum-like movements, however, ate sO

characteristic that they cannot be confounded with disturbances of the equilibrium which result
from injury to the cerebellum.
[Kinetic Theory.—In 1875 Crum Brown pointed out that, if a person be rotated: passively,
his eyes being bandaged, he can, up to acertain point, indicate pretty accurately the amount
of movement, but after a time, this cannot be done, and if the rotation, as on a potter’s wheel
be stopped, the sense of rotation continues. Crum Brown su ted that currents were roduced
in the Koa Aaanse while the terminal hair-cells lagged behind, and were, in fact, flags throug
the fluid, He pointed out that the right posterior canal is in line with the left superior, anc
the left posterior with the right superior, a fact which is readily observed by looking from

. \

GIDDINESS, NYSTAGMUS, MENIERE’S. DISEASE. 605

behind at a skull, with the semicircular canals exposed (fig. 432). He assumes that the canals
are paired organs, and that each pair is connected with rotation or movement of the head in a
particular direction. ]

Giddiness.—This feeling of false { impressions as to the relations of the surround-
ings and consequent movements of the body, occurs especially during Bena
changes in the normal movements of the eyes, whether ,,9

due to involuntary to and fro movements of the eye-
balls (nystagmus), or to paralysis of some eye muscle.
Active or passive movements of the head or of the

body are normally accompanied by simultaneous move-

ments of both eyeballs, which are characteristic for
every position of the body. The general character of
these ‘‘ compensatory ” bilateral movements of the eyes

consists in this, that during the various changes in the 5
position of the head and body, the eyes strive to main- © Fi
ig. 432.
tain their primary passive position. Section of the , see ane

: Diagram of the disposition of
aqueduct of Sylvius at the level of the corpora qua- the semicircular canals. RS
drigemina, of the floor of the fourth ventricle, of and LS, right and left supe-
- the auditory nucleus, both acustici, as well as de- ‘ior; LP and RP, right and
struction of both membranous labyrinths, causes dis- left posterior ; LE and RE,

: right and left external.
appearance of these movements; while, conversely,
stimulation of these parts is followed by bilateral associated movements of the
eyeballs.

Compensatory movements of the eyeballs, under “ioral circumstances, may be
caused reflexly from the membranous labyrinth. Nerve channels, capable of excit-
ing reflex movements of both eyes, proceed from both labyrinths, and, indeed, both
eyes are affected from both labyrinths. These channels pass through the auditory
nerve to the centre (nuclei of the 3rd, 4th, 6th, and 8th cranial nerves), and from
the latter efferent fibres pass to the muscles of the eye ({égyes).

Cyon found that stimulation of the horizontal semicircular canal was followed by horizontal
nystagmus; of the posterior, by vertical, and of the anterior canal, by diagonal nystagmus.
Stimulation of one auditory nerve is followed by rotating nystagmus, and rotation of the body
of the animal on its axis towards the stimulated side.

Poisons.—-Chloroform and other poisons enfeeble the compensatory movements of the eye-
balls, while nicotin and asphyxia suppress them, owing to their action on their nerve-centre.

It is probable that the disturbances of equilibrium and the feeling of giddiness
which follow the passage of a galvanic current through the head between the mastoid
processes, are also due to an action upon the semicircular canals of the labyrinth
(§ 300). Deviation of the eyeballs is produced by such a galvanic current (Hitziq).
The same result is produced when the two electrodes are placed in the external
auditory meatuses.

Pathological. —Meniere’s Disease. —The feeling of giddiness, not unfrequently accompanied
by tinnitus, which occurs.in Meniére’s disease, must be referred to an affection of the nerves of
the ampullz or their central organs, or of the semicircular canals themselves. By injecting fluid
violently into the ear of a rabbit, giddiness, with nystagmus and rotation of the head towards
the side operated on, are produced (Baginsky). . In cases in man, where the tympanic membrane
was defective, Luce, when employing the so- called ear-air-douche at 0°1 atmosphere, observed
abduction of the eyeball with diplopia, giddiness, darkness in front of the eyes, while the
respiration was deeper and accelerated. These phenomena must be due to stimulation or ex-
haustion of the vestibular branch of the auditory nerve (Hégyes). In chronic gastric catarrh,
a tendency to giddiness is an occasional symptom (Trousseau’s gastric giddiness). This may,
perhaps, be caused by stimulation of the gastric nerves exciting the vaso-motor nerves of the

byrinth, which must affect the pressure of the endolymph. Analogous giddiness is excited
from the larynx (Charcot), and from the urethra (Zrlenmeyer).

__ [Vertigo or giddiness is a very common symptom in disease, and may be produced by a great

many different conditions. It literally means ‘“‘a turning.” As Gowers points out, the most
comnion symptom is that the patient himself has a sense of movement in one or other direction;
or objects may appear to move before him; and more rarely there is actual movement “ com-

606 THE GLOSSO-PHARYNGEAL NERVE.

monly in the same direction as the subjective sense of movement.” It is sometimes due to a

want of harmony between the impressions derived from different sense-organs or ‘‘ contra-
dictoriness of sensory impressions (Grainger Stewart), as is sometimes felt on aseending or

descending a stair, or by some persons while standing on a high tower, constituting tower or

cliff giddiness. One of the most remarkable conditions is that called “ agoraphobia” (Benedikt,
Westphal). » The person can walk quite well in a narrow lane or street, but when he attempts
to cross a wide square, he experiences a feeling closely allied to giddiness, The giddiness of
sea-sickness is proverbial, while some persons get giddy with waltzing or swinging. Besides
occurring in Menitre’s disease, it sometimes occurs in locomotor ataxia, and some cerebral and
cerebellar affections, including cerebral anemia, Very distressing giddiness and headache are
often produced by paralysis of some of the ocular muscles, ¢.g., the external rectus. Defective
or perverted ocular impressions, as well as similar auditory impressions, may give rise to vertigo ;
in the latter or labyrinthine form the vertigo may be very severe, Severe vertigo is often ac-
companied by vomiting. A hard plug of ear-wax may press on the membrana tympani and
cause severe giddiness. The forms of dyspeptic giddiness and the toxic forms due to the abuse
of alcohol, tobacco, and some other drugs are familiar examples of this condition. ]

[Tinnitus Aurium, or subjective noises in the ear, is a very common symptom in disease of .

the ear; the noise may be continuous or discontinuous, be buzzing, singing, or rumbling in
character. ]

351. IX. NERVUS GLOSSO-PHARYNGEUS, —Anatomical.-—This nerve (fig. 429, 9) arises
from the nucleus of the same name, which consists partly of large cells (motor) and partly of
small cells (belonging to the gustatory fibres). The nucleus lies in the lower half of the fourth

ventricle, deep in the medulla oblongata, near the olive (fig. 427), and posteriorly it abuts on -

that of the vagus, The anterior part of the central nucleus is regarded as the root of the portio
intermedia of the facial (§ 349). The nerve also receives fibres from the vagal centres. The
fibres collect into two trunks, which afterwards unite and leave the medulla oblongata in front
of the vagus. In the fossula petrosa it has on it the petrous ganglion, from which, occasion-
ally, a special part on the posterior twig is separated within the skull as the ganglion of Ehren-
ritter. Communicating branches are sent from the petrous ganglion to the trigeminus, facial
(« and ), vagus and carotid plexus, From this ganglion also the tympanic nerve (A) ascends
vertically in the tympanic cavity, where it unites with the tympanic plexus, This branch
($ 349, 4) gives sensory fibres to the tympanic cavity and the Eustachian tube; while, in the
dog, it also carries secretory fibres for the parotid into the small superficial petrosal nerve
(Heidenhain—§ 145),

Function.—1. It is the nerve of taste for the posterior third of the tongue, the
lateral part of the soft palate, and the glosso-palatine arch (compare § 422), [This
is denied by Gowers (p. 600). ]

The nerve of taste for the anterior two-thirds of the tongue is referred to under the lingual
($ 347, III., 4) and chorda tympani nerves (§ 349, 4). The glossal branches are provided with
ganglia, especially where the nerve divides at the base of the circumvallate papille (Remak,
Kolliker, Stirling). The nerve ends in the circumvallate papille (fig. 429, U), and the end-
organs are represented by the taste bulbs (§ 422),

2. It is the sensory nerve for the posterior third of the tongue, the anterior
surface of the epiglottis, the tonsils, the anterior palatine arch, the soft palate, and
a part of the pharynx. From this nerve there may be discharged reflexly, move-
ments of deglutition, of the palate and pharynx, which may pass into those of
vomiting ($158). These fibres, like the gustatory fibres, can excite a reflex secre-
tion of saliva (§ 145).

3. It is motor for the stylo-pharyngeus and middle constrictor of the pharynx

(Volkmann) ; and, according to other observers, to the (t) glosso-palatinus (Hein)
and the (/?) levator veli palatini and azygos uvule (compare Spheno-palatine
ganglion, § 347, I1.). It is doubtful whether the glosso-pharyngeal nerve is really
a motor nerve at its origin—although Meynert and others have described a motor
nucleus—or whether the motor fibres reach the nerve at the petrous ganglion,
through the communicating branch from the facial.

4, A 4s Sys ar wena the lingual artery ; this nerve, perhaps, is vaso-dilator for the lingual

blood-vesse
Pathological. —There are no satisfactory observations on man of uncomplicated affections of
the glosso-pharyngeal nerve, ;

352, X. NERVUS VAGUS.—Anatomical,—The nucleus from which the y

' f

along with the 9th and 11th nerve is in (1) the ala-cinerea in the lower half of A calamus

PF i a

Ae te

THE CONNECTING AND OTHER BRANCHES OF THE VAGUS, 607

scriptorius Ga. 427, 10) [and it is very probably the representative of the cells of the vesicular
column of Clarke (§ 366)]. (2) Other fibres come from the ‘longitudinal bundle” or

' “respiratory bundle” lying outside the nucleus, and reaching down into the cervical enlarge-

ment. (3) A motor nucleus—the nucleus ambiguus—a prolongation of some of the cells of the
anterior horn of the spinal cord, gives some motor fibres. It leaves the medulla oblongata by
10 to 15 threads behind the 9th nerve, between the divisions of the lateral column, and has a
ganglion (jugular) upon it in the jugular foramen (fig. 428, VIII). Its branches contain
fibres which subserve different functions.

1. The sensory meningeal branch from the jugular ganglion accompanies the
vaso-motor fibres of the sympathetic on the middle meningeal artery, and sends
fibres to the occipital and transverse sinus,

When it is irritated, as in congestion of the head and inflammation of the dura mater, it gives
rise to vomiting.

2. The auricular branch (fig. 433, au.) from the jugular ganglion receives a
communicating branch from the petrous ganglion of the 9th nerve, traverses the
canaliculus mastoideus, crossing the course of the facial, with which it exchanges
fibres whose function is unknown. On its course, it gives sensory branches to
the posterior part of the auditory meatus, and the adjoining part of the outer eavr.
A branch runs along with posterior auricular branch of the facial, and confers
sensibility on the muscles, |

When this nerve is irritated, either through inflammation or by the presence of foreign
bodies in the outer ear passage, it may give rise to vomiting. Stimulation of the deep part “of
the external auditory meatus in the region supplied by the auricular branch causes coughing
reflexly [e.g., from the presence of a pea in the ear]. Similarly, contraction of the blood-vessels
of the ear may be caused reflexly (Snellen, Loven).

The nerve is the remainder of aconsiderable branch of the vagus which exists in fishes and
the larvee of frogs, and runs under the skin along the side of the body,

3. The connecting branches of the vagus are :—(1) A branch which directly
connects the petrous ganglion of the 9th with the jugular ganglion of the 10th;
its function is unknown. (2) Directly above the plexus gangliiformis vagi, the
vagus is joined by the whole inner half of the spinal accessory. This nerve conveys
to the vagus the motor fibres for the larynx, and the cervical part of the esophagus
(which according to Steiner lie in the inner part of the nerve-trunk), as well as the
inhibitory jibres for the heart (Cl. Bernard). (3) The plexus gangliiformis fibres,
whose function is unknown, join the trunk of the vagus from the hypoglossal,
superior cervical ganglion of the sympathetic, and the cervical plexus,

4, Pharyngeal Plexus.—The vagus sends one or two branches (fig. 433, 2) from
the upper part of the plexus gangliiformis to the pharyngeal plexus, where at the
level of the middle constrictor of the pharynx, it is joined by the pharyngeal branches
of the 9th nerve and those of the upper cervical sympathetic ganglion, near the
ascending pharyngeal artery, to form the pharyngeal plexus, The vagal fibres in
this plexus supply the three constrictors of the pharynx with motor jibres, while the
tensor palati (Otic ganglion, § 347, III.) and levator of the soft palate (compare
Spheno-palatine ganglion, § 347, II.) also receive motor (? sensory) fibres. Sensory
fibres of the vagus from the pharyngeal plexus supply the pharynx from the part
beneath the soft palate downwards, ‘These fibres excite the pharyngeal constric-
tors reflexly, during the act of swallowing (§ 156). If stimulated very strongly,
they may cause vomiting. (The sympathetic fibres of the cesophageal plexus give
vaso-motor nerves to the cesophageal vessels ; for the eoreee branches of the
9th nerve see above.) .

5. The vagus supplies two branches to the larynx, the superior and inferior
laryngeal.

(a) The superior laryngeal (fig. 433, 3) receives vaso-motor fibres from the
superior cervical ganglion of the sympathetic, It divides into two branches, external
and internal :—(1) The external branch receives vaso-motor fibres from the same
source (they, accompany the superior thyroid artery), and supply the crico-thyroid

recurrens

accelerans

NX
S$
a
ry
<
©
Ss

Zi

Ie Wd
Uf O

Fig. 433. G8
I. Scheme of the distribution of the vagus and accessorius.—10, Exit of left vagus from the skull ;
10,, right vagus; 9, glosso-pharyngeal ; 7, facial ; 1, deep post-auricular from the facial ;

SUPERIOR AND INFERIOR LARYNGEAL NERVES. 609

muscle with motor fibres, and sensory fibres to the lower lateral portion of the
laryngeal mucous membrane. (2) The internal branch gives off sensory branches
only to the glosso-epiglottidean fold, and the adjoining lateral region of the root of
the tongue, the aryepiglottidean fold, and to the whole anterior part of the larynx,
except the part supplied by the external branch (Zonget). Stimulation of any of
these sensory fibres causes coughing reflexly. Coughing is produced by stimula-
tion of the boundaries of the glottis respiratoria, but not of the vocal cords, and
by stimulation of the sensory branches of the vagus to the tracheal mucous mem-
brane, especially at the bifurcation, and also from the bronchial mucous membrane
(Kohts). Coughing is also caused by stimulation of the auricular branch of the
vagus, especially in the deep part of the external auditory meatus, of the pulmonary
tissue, especially when altered pathologically ; in pathological conditions (inflamma-
tion) of the pleura (? certain changes in the stomach [stomach-cough]), of the liver
and spleen (Vaunyn). The coughing centre is said to lie on each side of the
raphe, in the neighbourhood of the ala cinerea (Kohts). Cases of violent coughing
may, owing to stimulation of the pharynx, be accompanied by vomiting as an asso-
ciated movement (§ 120).

In many individuals, coughing can be excited by stimulation of distant sensory nerves (§ 120,1),
e:g., from the outer ear (auricular nerve), nasal mucous membrane, liver, spleen, stomach,
intestine, uterus, mamme, ovaries, and even from certain cutaneous areas (Hbstein). It is un-
certain if these conditions act directly upon the coughing centre, or first of all affect the vascu-
larisation and secretion of the respiratory organs, which in their turn affect the coughing centre.

The cough (dog, cat) caused by stimulation of the trachea and bronchi occurs at once, and
lasts as long as the stimulus lasts ; in stimulation of the larynx, the first effect is inhibition
of the respiration accompanied by movements of deglutition, while the cough occurs after the
cessation of the stimulation (Kandarazky).

The superior laryngeal contains afferent fibres which, when stimulated, cause arrest of the
respiration and closure of the rima glottidis (Rosenthal)—(see Respiratory centre, § 368). Lastly,
fibres which are efferent and serve to excite the vaso-motor centre, and are in fact ‘‘ pressor
Jjibres””—(see Vaso-motor centre, § 371, II.).

(6) The inferior laryngeal or recurrent bends on the left side around
the arch of the aorta, and on the right around the subclavian, and ascends in the
groove between the trachea and cesophagus, giving motor fibres to these organs,
and the lower constrictors of the pharynx, and passes to the larynx, to supply
motor fibres to all its muscles, except the cricothyroid. It also has an inhibitory
action upon the respiratory centre (see § 368).

A connecting branch runs from the superior laryngeal to the inferior (the anastomosis of
Galen), which occasionally gives oif sensory branches to the upper half of the trachea (sometimes
to the larynx ?) ; perhaps also to the cesophagus (Zonget), and sensory fibres (?) for the muscles
of the larynx supplied by the recurrent laryngeal. According to Frangois Franck, sensory fibres
pass by this anastomosis from the recurrent into the superior laryngeal. According to Waller
and Burckhard, the motor fibres of both laryugeal nerves are all derived from the accessorius ;
while Chauveau maintains that the cricothyroid is an exception.

Stimulation of the superior laryngeal is painful, and causes contraction of

2, pharyngeal branches of vagus; 6, pharyngeal branch of the glosso-pharyngeal ; 3,
superior laryngeal, with its anastomoses, 7, with the sympathetic and its division, 4, into
its internal, v, and external branches, ¢; 5, inferior or recurrent laryngeal ; aw., auricular
branch of vagus. Cardiac nerves :—g, cardiac branches from the vagus and superior laryn-
geal ; 7, h, the three cardiac branches from the upper, g, middle, x, and lower, y, cervical
ganglion of the sympathetic ; %, ring of Vieusses ; /, cardiac branch from the recurrent
aryngeal ; Z, lung with the anterior and posterior pulmonary plexuses ; 7, cesophageal
plexus ; 00, gastric branches, and near them the hepatic branches, 7 ; m, cceliae plexus ;
k, splanchnic entering former; 11, accessory nerve sending its inner branch into- the
gangliform, plexus of the vagus—its outer branch, ac, supplies the sternomastoid, S¢ and
ac,, and the trapezius, Cc; O, external’auditory meatus; Oh, hyoid bone; K, thyroid
cartilage ; 7’, trachea; H, heart; P, pulmonary artery ; A A, aorta; c¢, right carotid ;
¢,, left carotid ; s and s,, right and left vibolavian artery; ZZ, diaphragm ; N, kidney ; Nn,
suprarenal capsule; M/, stomach; m, spleen; ZZ, lung and liver. II. Scheme of the
course of the depressor and accelerans in the cat. '

2Q

610 THE DEPRESSOR NERVE.

the cricothyroid muscle (while the other laryngeal muscles contract reflexly).
Section of both nerves, owing to paralysis of the cricothyroids, causes slight :
slowing of the respirations (Sklarek).. In dogs, the voice becomes, deeper and
hoarser, owing to diminished tension of the. vocal cords (Longet). The larynx
becomes insensible, so that saliva and particles of food pass into the trachea and
lungs, without causing reflex contraction of the glottis or coughing. This excites
‘traumatic pneumonia,” which results in death (Frvedldnder). .
Stimulation of the recurrent nerves causes spasm of the glottis, Section 7
of these nerves paralyses the laryngeal muscles supplied by them, the voice becomes |
husky and hoarse (in the pig—Galen, Riolan, 1618) in man, dog, and cat ; while |
rabbits retain their shrill cry. The glottis is small, with every inspiration, the |
vocal cords approximate considerably at their anterior parts,
| pp while, during expiration, they are relaxed and are separated
from each other. Hence, the inspiration, especially in young
individuals whose glottis respiratoria is narrow, is difficult
M and noisy (Legallois) ; while the expiration takes place easily.

After a few days, the animal (carnivore) becomes more quiet, .
it respires with less effort, and the passive vibratory move-
ments of the vocal cords become less. Even after a con-
siderable interval, if the animal be excited, it is attacked with
severe dyspncea, which disappears only when the animal has
become quiet again. Owing to paralysis of the laryngeal
muscles, foreign bodies are apt to enter the trachea, while
the paralysis renders difficult the first part of the process of
swallowing in the cesophageal region. Broncho-pneumonia
may be produced (Arnsperger).

6. The depressor nerve, which in the rabbit arises by one
branch from the superior laryngeal, and usually also by a.
second root from the trunk of the vagus itself [runs down |
the neck in close relation with the vagus, sympathetic, and
carotid artery, enters the thorax], and joins the cardiac plexus
(fig. 434, sc). It is an afferent nerve, and when its central
end is stimulated [provided both vagi be divided], it dimin-
ishes the energy of the vaso-motor centre, and thus causes a
fall of the blood-pressure (hence the name given to it by Cyon

Fig. 434. and Ludwig, § 371, IL). At the same time, [if the vagus
Scheme of the cardiac 02 the opposite side be intact], its stimulation affects the
nerves in the rabbit, Ca7dto-inhibitory centre, and thus reflexly diminishes the num-

P, pons ; M, medulla ber of heart-beats. [Its stimulation also gives rise to pain,

oblongata ; VAG, va- so that it is the sensory nerve of the heart. If in a rabbit

inet rnd aanecal ’ the vagi be divided in the middle of the neck, and the central

se, superior cardiac or €0d of the depressor nerve, which is the smallest of the three

depressor ; ic, inferior nerves near the carotid, be stimulated, after a short time there

cardiac or cardio-in- js no alteration of the heart-beats, but there is steady fall of

hibitory ; H, heart. the blood-pressure (fig. 106), which is due to a reflex inhibi-
tion of the vaso-motor centre, resulting in a dilatation of the blood-vessels of the
abdomen. Of course, if the vagi be intact, there is a reflex inhibitory effect on the
heart. It is doubtful if the depressor comes into action when the heart is over-
distended, If it did, of course the blood-pressure would be reduced by the reflex
dilatation of the abdominal blood-vessels. ] :

_ The depressor nerve is present in the cat ($ 370), hedgehog (Aubert, Rover), rat and mouse;
in the horse and in man, fibres analogous to the depressor re-enter the trunk of the vagus
(Bernhardt, Kreidmann). Depressor fibres are also found in the rabbit in the trunk of the

vagus (Dreschfeldt, Stelling). . as} =) oy sell

CARDIAC AND PULMONARY BRANCHES OF THE VAGUS, O11

7, The cardiac branches (fig. 433, g, 7), as well as the cardiac plexus, have been
described in § 57. These nerves contain the inhibitory jibres for the heart (fig. 434,
ic—cardio-inhibitory—Zdward Weber, November, 1845; Budge, independently
in May 1846), also sensory fibres for the heart [in the frog (Budge), and partly
in mammals ((oltz)]. Lastly, in some animals the heart receives some of the
accelerating fibres through the trunk of the vagus. Feeble stimulation of the vagus
occasionally causes acceleration of the beats of the heart (Schiff). [This occurs
when the vagus contains accelerator fibres.] In an animal poisoned with nicotin,
or atropin, which paralyses the inhibitory fibres of the vagus, stimulation of the
vagus is followed by acceleration of the heart-beats (Schiff, Schmiedeberg) [owing to
the unopposed action of any accelerated fibres that may be present in the nerve, ¢.¢.,
of the frog]. |

8. The pulmonary branches of the vagus join the anterior and _ posterior
pulmonary plexuses. The anterior pulmonary plexus gives sensory and motor
fibres to the trachea, and runs on the anterior surface of the branches of the bronchi
into the lungs (LZ). The posterior plexus is formed by three to five large branches
from the vagus, near the bifurcation of the trachea, together with branches from
the lowest cervical ganglion of the sympathetic and fibres from the cardiac
plexus. The plexuses of opposite sides exchange fibres, and branches are given off
which accompany the bronchi in the lungs. Ganglia occur in the course of the
pulmonary branches in the frog (Arnold, W. Stirling) [newt—W. Stirling ; and in
mammals (Remak, Egorow, W. Stirling)|, in the larynx [Cock, W. Stirling], in the
trachea and bronchi [W. Stirling, Kandarazki]. Branches proceed from the
pulmonary plexus to the pericardium and the superior vena cava (Luschka,
ZLuckerkandl). ;

The functions of the pulmonary branches of the vagus are—(1) they supply
motor branches to the smooth muscles of the whole bronchial system (§ 106) ;
(2) they supply a small part of the vaso-motor nerves of the pulmonary vessels
(Schif’), but by far the largest number of these nerves (? all) is supplied from the
connection with the sympathetic (in animals from the first dorsal ganglion) —(Brown-
Séquard, A. Fick, Badoud, Lichtheim) ; (3) they supply sensory (cough-exciting)
fibres to the whole bronchial system, and to the lungs; (4) they give afferent
fibres, which, when stimulated, diminish the activity of the vaso-motor centre, and
thus cause a fall of the blood-pressure during forced expiration ; (5) similar fibres
which act upon the inhibitory centre of the heart, and so influence it as to accelerate
the pulse-beats (§ 369, II.). Simultaneous stimulation of 4 and 5 alters the pulse
rhythm (Sommerbrodt) ; (6) they also contain afferent fibres from the pulmonary
parenchyma to the medulla oblongata, which stimulate the respiratory centre. [These
fibres are continually in action], and consequently section of both vagi is followed by
diminution of the number of respirations; the respirations become at the same time
deeper, while the same volume of air is changed ( Valentin). Stimulation of the central
end of the vagus again accelerates the respirations (Z’raube, J. Rosenthal). Thus,
laboured and difficult respiration is explained by the fact that the influences
conveyed by these fibres which excite the respiratory centre reflexly are cut off ; so
it is evident, that centripetal or afferent impulses proceeding upwards in the vagus
are intimately concerned in maintaining normal reflex respiration ; after these
nerves are divided, conditions exciting the respiratory movements must originate
directly, especially in the medulla oblongata itself (§ 368).

Pneumonia after Section of both Vagi.—The inflammation which follows section of both
vagi has attracted the attention of many observers since the time of Valsalva, Morgagni (1740),
and Legallois (1812). In attempting to explain this phenomenon, we must bear in mind the
following considerations :—(a) Section of both vagi is followed by loss of motor power in the
muscles of the larynx, as well as the sensibility of the larynx, trachea, bronchi, and the lungs,
provided the section be made above the origin of the superior laryngeal nerves. Hence, the
glottis is not closed during swallowing, nor is it. closed reflexly when foreign bodies (saliva,

612 (ESOPHAGEAL AND GASTRIC PLEXUSES.

rticles of food, irrespirable gases) enter the respiratory passages. Even the reflex act of cough-
ae. which, under oon eosiniese would get rid of the offending bodies, is abolished.
Thus, foreign bodies may readily enter the lungs, and this is favoured by the fact that, owing to
the simultaneous paralysis of the cesophagus, the food remains in the latter for a time, and
may therefore easily enter the larynx. ‘That this constitutes one important factor was proved
by Traube, who found that the pneumonia was prevented when he caused the animals to respire
by means of a tube inserted into the trachea through an aperture in the neck, If, on the con-
trary, only the motor recurrent nerves were divided and the cesophagus ligatured, so that in
the process of attempting to swallow, food must necessarily enter the respiratory passages,
“traumatic pneumonia”’ was the invariable result (Zraube, O. Frey). (b) A second factor
depends on the circumstance that, owing to the laboured and difficult. respiration, the Jungs
become surcharged with blood, because during the lung time that the thorax is distended, the
pressure of the air within the lungs is abnormally low. This condition of congestion, or abnormal |
tilling of the pulmonary vessels with blood, is followed by serous exudation (pulmonary cedema), |
and even by exudation of blood and the formation of pus in the air-vesicles (Frey). This same ;
circumstance favours the entrance of fluids through the glottis (§ 352, 6). The introduction
of a tracheal cannula will prevent the entrance of fluids and the occurrence of inflammation. It
is probable that a partial paralysis of the pulmonary vaso-motor nerves may be concerned in the
inflammation, as this conduces to an engorgement of the pulmonary capillaries. (c) Lastly,
it is of consequence to determine whether trophic fibres are present in the vagus, which may
influence the normal condition of the pulmonary tissues. According to Michaelson, the
pneumonia which takes place immediately after section of the vagi occurs especially in the lower
and middle lobes ; the pneumonia which follows section of the recurrents occurs more slowly,
and causes catarrhal 7 en RN especially in the upper lobes. Rabbits, as a rule, die within
twenty-four hours, with all the symptoms of pneumonia; when the above-mentioned precautions
are taken, they may live for several days. Dogs may live foralong time. If the 9th, 10th, and
12th nerves be torn out on one side in a rabbit, death takes place from pneumonia (Griinhagen).
In birds, bilateral section of the vagi is not followed by pneumonia (Blainville, Bililroth),
because the upper larynx remains capable of closing firmly—death takes place in eight to ten days
with the symptoms of inanition (Einbrodt, Zander, v. Anrep), while the heart undergoes fatty
degeneration (Hichhorst), and so do the liver, stomach, and muscles (v. Anrep). According to
Wassilieff, the heart shows cloudy swelling and slight wax-like degeneration. Frogs, which at
every respiration open the glottis, and close it during the pause, die of asphyxia. Section of
the pulmonary branches has no injurious effect (Bidder). [Unilateral section of the vagus in
rabbits is followed within forty-eight hours by the appearance of yellowish-white spots on the |
myocardium, especially near the interventricular septum, on the papillary muscles, and |
along the furrows for the coronary arteries. The muscular fibres exhibit retrogressive changes,
whereby their strie disappear ; they become swollen up and filled with albuminous granules.
After eight to ten days, the interstitial tissue of these foci becomes infiltrated with small round .
granular cells, especially near the blood-vessels. At a later stage, the interstitial connective- |
tissue increases in amount, and the muscle atrophies. No effect is produced by section of
the depressor or sympathetic, and Fantino concludes that some of the fibres of the vagus exert a .
trophic action on the myocardium. } |

9. The cwsophageal plexus (fig. 434, 7) is formed principally by branches
from the vagus above the inferior laryngeal, from the pulmonary plexus, and below
from the trunk itself. This plexus supplies the csophagus with motor power
(§ 156), the sensibility which is present only in the upper part, and it also supplies
fibres capable of exciting reflex actions.

10. The gastric plexus (00) consists of (a) the anterior (left) termination of
the vagus, which supplies fibres to the cesophagus and courses along the small
curvature, and sends a few fibres through the portal fissure into the liver ; (6) the
posterior (right) vagus, after giving off a few fibres to the oesophagus, takes part in
the formation of the gastric plexus to which (c) sympathetic fibres are added at the
pylorus. Section of the vagi is followed by hyperemia of the gastric mucous
membrane (Panum, Pincus), but it does not interfere with digestion (Bidder and
Schmidt), even when it is performed at the cardia (Kritzler, Schiff). |

11. About two-thirds of the right vagus on the stomach joins the celiac
plexus, and from it branches accompany the arteries to the liver, spleen, pancreas,
duodenum, kidney, and suprarenal capsules. The vagus supplies motor fibres to the
stomach, which belong to the root of the vagus itself and not to the accessorius

4

(Stilling, Bischof). The gastric branches also contain afferent fibres, which, when
stimulated, cause reflexly a secretion of saliva (§ 145). It is undetermined whether —
i :

REFLEX EFFECTS OF STIMULATION OF THE VAGUS. 613

they also cause vomiting. For the effect of the vagus upon the movements of the
intestine (see § 161). According to some observers, stimulation of the vagus is
followed by movement of the large as well as of the small intestine (Stzdling,
Kupfer, C. Ludwig, Remak). Stimulation of the peripheral end of the vagus causes
contraction of the smooth muscular fibres in the capsule and trabecule of the spleen
(in the rabbit and dog, § 103). Stimulation of the vagus at the cardia causes in-
crease in the secretion of urine with dilatation of the renal vessels, while the blood of
the renal vein becomes more arterial (Cl. Bernard). According to Rossbach and
Quellhorst, a few vaso-motor fibres are supplied by the vagus to the abdominal
organs, whilst the greatest number comes from the splanchnic.

12. Reflex Effects.—The vagus and its branches contain fibres, some of which
have been referred to already, which act reflexly (afferent) upon certain nervous
mechanisms.

(a) On the vaso-motor centre there act (a) pressor fibres (especially in both laryngeal nerves),
whose stimulation is followed by a reflex contraction of the arterial blood-channels, and thus
cause a rise of the blood-pressure; (8) depressor fibres (in the depressor or the vagus itself),
which have exactly an opposite effect. (This subject is specially referred to under the head of
the Vaso-motor nerve-centre, § 371.)

(b) On the respiratory centre there act (a) fibres (pulmonary branches) whose stimulation is
followed by acceleration of the respiration ; and (8) inhibitory fibres (in both laryngeals), whose
stimulation is followed by slowing or arrest of the respiration. (See Respiratory centre, § 368.)

(c) On the cardio-inhibitory system.—[Wher. the central end of one vagus is stimulated,
provided the other vagus is intact, the heart may be arrested reflexly in the diastolic phase. ]
Mayer and Pribram observed that sudden distension of the stomach caused slowing and even
arrest of the heart, while, at the same time, there was contraction of the arteries of the medulla
oblongata and increase of the blood-pressure.

(Zz) On the vomiting centre.—This centre may be affected by stimulation of the central end
of the vagus, and, as already mentioned, by stimulation of many afferent fibres in the vagus
(§ 158).

(e) On the pancreatic secretion.—Stimulation of the central end of the vagus is followed by
arrest of this secretion (§ 171).

(f) According to Cl. Bernard, there are fibres present in the pulmonary nerves, which, when
they are stimulated, increase reflexly the formation of sugar in the liver, perhaps through the
hepatic branches of the vagus.

Unequal Excitability.—The various branches of the vagus are not all endowed with the same
degree of excitability. If the peripheral end of the vagus be stimulated, first of all with a weak
stimulus, the laryngeal muscles are first affected, and afterwards the heart is slowed (Ruther-

ford). Ifthe central end be stimulated with feeble stimuli, the ‘‘ excito-respiratory ” fibres are

exhausted before the ‘‘inhibito-respiratory” (Burkart), According to Steiner, the variovs
fibres are so arranged in the vagus that the afferent fibres lie in the outer, and the efferent in
the inner, half of the trunk, in the cervical region.

Pathological.—Stimulation or paralysis in the area of the vagus must necessarily present a
very different picture according as the affection is referred to the whole trunk or only to some
of its branches, or whether the affection is unilateral or bilateral. Paralysis of the pharynx
and cesophagus, which is usually of central or intracranial origin, interferes with or abolishes
deglutition, so that when the cesophagus becomes filled with food there is difficulty of breathing,
and the food may even pass into the nasal cavities, A peculiar sonorous gurgling is occasionally
heard in the relaxed canal (deglutatio sonora). In incomplete paralysis, the act of deglutition
is delayed and rendered more difficult, while large masses are swallowed more easily than small
ones. Increased contraction and spasmodic stricture of the cesophagus are referred to under the
phenomena of general nervous excitability (§ 186).

Spasm of the laryngeal muscles causes spasmodic closure of the glottis (Spasmus glottidis).
This condition is most apt to occur in children, and takes place in paroxysms, with symptoms
of dyspneea and crowing inspiration ; if the case be very severe, there may be muscular con-
tractions (of the eye, jaw, digits, &c.). The symptoms are very probably due to the reflex
spasms which may be discharged from the sensory nerves of several areas (teeth, intestine, skin).

e impulse is conducted along the sensory nerves proceeding from these areas to the medulla
oblongata, where it causes the discharge of the reflex mechanism which produces the above-
mentioned results. There may be spasm-of the dilators of the glottis and other laryngeal
muscles (Frénézel).

Stimulation of the sensory nerves of the larynx, as is well known, produces coughing. If
the stimulation be very intense, as in whooping-cough, the fibres lying in the laryngeal nerves,
which inhibit the respiratory centre, may also be stimulated ; the number of respirations is

614 PATHOLOGICAL CONDITIONS OF THE VAGUS.

diminished, and ultimately the respiration ceases, the diaphragm being relaxed : while, with
the most intense stimulation, there may be spasmodic expiratory arrest of the respiration with
closure of the glottis, which may last for fifteen seconds. Paralysis of the laryngeal nerves,
which causes disturbances of speech, has been referred to in § 313. In bilateral paralysis of the
recurrent nerves, in consequence of tension upon them due to dilatation of the aorta and the
subclavian artery, a panes aoe Ni amount of air is breathed out, owing to the futile efforts which
the patient makes in trying to speak; expectoration is more difficult, while violent coughing is
impossible (v. Ziemssen). Attacks of dyspnoea occur just as in animals, if the person make
violent efforts. Some observers (Salter, Bergson) have referred the paroxysms of nervous
asthma, which last for a quarter of an hour or more, and constitute asthma bronchiale, to
stimulation of the pulmonary plexus, causing spasmodic contraction of the bronchial muscle (§
106). Physical mvestigation during the phan doe reveals nothing but the existence of some
rhonchi ($117). If this condition is really spasmodic in its nature (? of the vessels), it must be ~
usually of a reflex character ; the afferent nerves may be those of the lung, skin, or genitals (in:
hysteria). Perhaps, however, it is due to a temporary paralysis of the pulmonary nerves
(afferent), which excite the respiratory centre (excito-respiratory).

Stimulation of the cardiac branches of the vagus may cause attacks of temporary suspension
of the cardiac contractions, which are accompanied by a feeling of great depression and of
impending dissolution, with occasionally pain in the region of the heart. Attacks of this sort
may be produced reflexly, ¢.g., by stimulation or irritation of the abdominal organs (as in the
experiment of Goltz of tapping the intestines). Hennoch and Silbermann observed slowing of
the action of the heart in children suffering from gastric irritation. Similarly, the respiration
may be affected reflexly through the vagus, a condition described by Hennoch as asthma
dyspepticum. In cases of intermittent paralysis of the cardiac branches of the vagus, we rarely
tind acceleration of the pulse above 160 (Riegel), 200 (Tuczek, L. Langer); even 240 pulse-beats
per minute have been recorded (Kuppert), and in such cases, the beats vary much in rhythm
and force, and they are very irregular. These cases require to be more minutely analysed, as it
is not clear how much is due to paralysis of the vagus and how much to the action of the
accelerating mechanism of the heart. Little is known of affections of the intra-abdominal
fibres of the vagus. It seems that the sensory branches of the stomach do not come from the
vagus. If the trunk of the vagus or its centre be paralysed, there are laboured, deep, slow
respirations, such as follow the section of both vagi (Guttmann).

353. XI. NERVUS ACCESSORIUS WILLISII.—Anatomical.—This nerve arises by two
completely separate roots; one from the accessorius nucleus of the medulla oblongata
(fig. 427, 11), which is connected with the vagus nucleus ; while the other root arises between
the anterior and posterior nerve-roots from the spinal cord, usually between the 5th and 6th
cervical vertebre. In the spinal cord, its tibres can be traced to an elongated nucleus lying on
the outer side of the anterior cornu, as far downwards as the 5th cervical vertebra. ear the
jugular foramen both portions come together, but do not exchange fibres (Holl) ; both roots
afterwards separate from each other to form two distinct branches, the anterior (inner), which
arises from the medulla oblongata, passing en masse into the plexus gangliiformis vagi. This
branch supplies the vagus with most of its motor fibres (compare § 352, 3), and also its cardio- _
inhibitory fibres (fig. 433). [The upper cervical metameres or segments give origin not only to
the anterior and posterior roots of the corresponding nerve-roots, but between these roots arise the
roots of the spinal accessory nerve. This nerve contains /arge medullated nerve-fibres, and fine
medullated fibres ‘such as characterise the visceral branches of the thoracic and sacral regions
(§ 356). The nerve passes by the jugular ganglion of the vagus, then divides into the external and
internal branch. All the large fibres pass into the external branch, which, along with branches
from the cervical plexus, supply the sternomastoid and trapezius. The internal branch, com-
posed of small fibres, passes into the ganglion of the trunk of the vagus. Gaskell therefore
regards the internal branch ‘“‘as foaned by the rami viscerales of the upper cervical and v.
nerves.’ These fine medullated nerve-fibres probably arise from the cells of the posterior vesicular
column of Clarke. The motor fibres to the trapezius and sternomastoid arise from the cells
of the lateral horn of grey matter. ]

If the accessorius be pulled out by the root in animals, the cardio-inhibitory
fibres undergo degeneration. If the trunk of the vagus be stimulated in the neck
four to five days after the operation, the action of the heart is no longer arrested |
thereby [owing to the degeneration of the cardio-inhibitory fibres] (Waller, Schiff,
Daszkvewicz, Heidenhain) ; according to Heidenhain, the heart-beats are accelerated _
immediately after pulling out the nerve. 17 aia

The external branch arises from the spinal roots. This nerve communicates aa
with the sensory branches of the posterior root of the lst, more rarely of the 2nd
cervical nerve, and these fibres supply sensibility to the muscles ; it then turns

THE HYPOGLOSSAL NERVE. - 615

backwards above the transverse process of the atlas, and terminates as a motor
nerve in the sternomastoid and trapezius (fig. 433), The latter muscle usually
receives motor fibres also from the cervical plexus (fig. 429).

The external branch communicates with several cervical nerves. These fibres either partici-
pate in the innervation of the above-named muscles, or the accessorius returns part of the
sensory fibres supplied by the posterior roots of the two upper cervical nerves.

Pathological. —Stimulation of the outer branch causes tonic or clonic spasm of the above-
named muscles, usually on one side. If the branch to the sternomastoid be affected alone, the
head is moved with each clonic spasm. If the affection be bilateral, the spasm usually takes
place on opposite sides alternately, while it is rare to have it on both sides simultaneously. In
spasm of the trapezius the head is drawn backwards and to the side. Tonic contraction of the
flexors of the head causes the characteristic position of the head known as caput obstipum
(spasticum) or wryneck. In paralysis of one of these muscles, the head is drawn towards the
sound side (torticollis paralyticus). Paralysis of the trapezius is usually only partial.

Paralysis of the whole trunk of the spinal accessory (usually caused by central conditions),
besides causing paralysis of the sternomastoid and trapezius, also paralyses the motor branches
of the vagus already referred to (rb, Frankel).

354, XII. NERVUS HYPOGLOSSUS. —Anatomical.—It arises trom two large-celled nuclei
within the lowest part of the calamus scriptorius, and one adjoining small-celled nucleus (Roller),
while additional fibres come from the brain (§$ 378), and also perhaps from the olive (fig. 427, 12).
It springs by 10 to 15 twigs in a line with the anterior roots of the spinal nerve (fig. 420, IX.).
In its development part of the hypoglossal behaves as a spinal nerve (Fvoriep).

Function.—It is motor to all the muscles of the tongue, including the
geniohyoid and thyrohyoid.

Connections.—The trunk of the hypogiossal is connected with—(1) the superior cervical
ganglion of the sympathetic, which supplies it with vaso-motor fibres for the blood-vessels of the
tongue. After section of the hypoglossal and lingual nerves, the corresponding half of the
tongue becomes red and congested (Schif?), (2) There is also a branch from the plexus ganglii-
formis vagi, its small lingual branch to the commencement of the hypoglossal arch. These
fibres supply the hypoglossal with sensory fibres-for the muscles of the tongue, for even after
section of the lingual the tongue still possesses dull sensibility. It is uncertain whether fibres
with a similar function are partly derived from the cervical nerves or from the anastomosis
which takes place with the lingual. (3) It is united with the wpper cervical nerves by means
of the loops known as the ansa hypoglossi. These connecting fibres run in the descendens noni
to the sternohyoid, omohyoid, and sternothyroid. Cervical fibres do not, as a rule, enter the
tongue ; stimulation of the root of the hypoglossal acts upon the above-named muscles only
very rarely and to a very slight extent (Volkmann). (Compare § 297, 8, and § 336, III.),

Bilateral section of the nerve causes complete motor paralysis of the tongue.
Dogs can no longer lap, they bite the flaccid tongue. Frogs, which seize their
prey with the tongue, must starve; when the tongue hangs from the mouth, it
must prevent the closure of the mouth, so that these animals must die from
asphyxia, as air is pumped into the lungs only when the mouth is closed.

Pathological.—Paralysis of the hypoglossal (glossoplegia), which is usually central in its
origin, causes disturbance of speech (§ 319). [In unilateral palsy, the tongue lies in the mouth
in its normal position, but the base is more prominent on the paralysed side. When the
tongue is protruded, it passes to the sound side by the genio-hyoglossus (§ 155).] Paralysis of
the tongue also interferes with mastication, the formation of the bolusin the mouth, and degluti-
tion in the mouth. Owing to the imperfect movements of the tongue, taste is imperfect, and
the singing of high notes and the falsetto voice, which require certain positions of the tongue,
appear to be impossible (Bennatz).

pasm of the tongue, which causes aphthongia (§ 318), is usually reflex in its origin, and is
extremely rare. Idiopathic cases of spasm of the tongue have been described ; the seat of the
irritation lay either in the cortex cerebri or in the oblongata (Berger, E. Remak). For Pseudo-
motor Action, p. 601. .

355, THE SPINAL NERVES.—Anatomical.—The thirty-one pairs of spinal nerves arise
by means of a posterior [superior, gangliated] root (consisting of a few large rounded bundles),
from the suleus between the posterior and lateral columns of the spinal cord, and by means of
an anterior [inferior, non-gangliated] root (consisting of numerous fine flat strands), from the
furrow between the anterior and lateral columns, fig. 435. The posterior roots, with the
exception of the Ist cervical nerve, are the larger. Occasionally the roots on opposite sides are
not symmetrical ; one or other root, or even a whole nerve, may be absent from the dorsal
region (Adamkiewicz). On the posterior root is the spindle-shaped spinal ganglion (§ 821, II.,

616 MORPHOLOGY OF A SPINAL NERVE.

3), which is occasionally double on the lumbar and sacral nerves, Beyond the ganglion, the
two roots unite to form within the spinal canal the mixed trunk of a spinal nerve. The
branches of the nerve-trunk invariably contain fibres coming from both roots. The number of
fibres in the nerve-trunk is exactly the same as in the two roots ; hence, we must conclude that
the nerve-cells in the spinal ganglion are intercalated in the course of the fibres (Gawle and
Birge). : ;

Varieties. —The spinal ganglion is sometimes double, and according to Hyrtl, isolated
ganglionic cells frequently occur in the posterior root, between the ganglion and the cord.
Occasionally the roots are somewhat unsymmetrical on opposite sides ; in the dorsal part one
or other, or both roots of a spinal nerve are sometimes absent (Adamkiewicz).

(Morphology of the Spinal Nerves and Limb-Plexuses.—A typical segmental spinal nerve
(fig. 435) divides, after its formation, into three parts, a dorsal branch, or superior primary
division, distributed to the back, a soma-
tic branch, or inferior primary division,
supplying the body-wall or limbs; and
a splanchnic or visceral branch, or ramus
communicans, connected with the sym-
pathetic gangliated cord, and distributed
to the large vessels and viscera. The
somatic branch is the largest, and is
generally, by human anatomists, spoken
of as the ‘‘anterior primary division.”
In the thoracic and upper lumbar regions,
the distribution of this nerve is simple.
It divides into an external (or lateral)
branch, and an internal (or anterior)
branch, which supply respectively the
lateral and anterior portions of the tho-
racic and abdominal walls. }

[In the region of the neck, and in re-
lation to the limbs, the arrangement of
thesomatic branches becomes complicated
by the formation of the plexuses. In
Fig. 435. the embryo, however, the distribution of

the nerves is simpler, and a comparison
can be made both with the adult arrange-
ment, and with the typical nerve as seen
in the thoracic region. In the embryo,
the neck as such does not exist, and the
upper limb sprouts out directly beyond the segmented visceral arches. In this state, the
somatic branch ig distributed as in the thoracic region ; the nerve divides into an external and
an internal branch, distributed to the side and front of the corresponding part of the arches
in the neck, in the regions where the limbs are appearing as two flattened buds from the ventro-
lateral aspect of the body. The somatic branch sweeps round into the blastema forming the
limb, and divides into its two branches, external and internal, or dorsal and ventral, which
are distributed to the outer (dorsal) and inner (ventral) surfaces, respectively, of the primitive
limb.. At this time, the cartilaginous and muscular elements of the limb have not become
differentiated. While this is occurring, the dorsal and ventral parts of the somatic branches
of the nerves entering the limb unite with adjacent dorsal and ventral branches, in various com-
binations, so as to produce the limb-plexuses, The nerves resulting from these combinations
are distributed to the primitive, dorsal, and ventral surfaces of the limbs. Thus, the plexuses
are formed, and the peripheral distribution of the nerves has taken place before the period of
flexion and angulation of the limbs. These processes mark the conditions in the adult; but
even then it is easy to make out that the nerves in the upper limb derived from the posterior
(dorsal) cords of the brachial plexus supply the scapular region, extensor surface of the arm
and fore-arm, and the back of the hand,—parts which are derived from the dorsal surface of
the primitive limb; while the nerves produced from the anterior (ventral) cords supply the
see seing region, front of the arm, fore-arm, and hand,—parts representing the primitive ventral
surface.

[In the lower limb, the nerves derived from a union of the posterior branches are the external
cutaneous, anterior crural, gluteal, and external popliteal. These supply the iliac surfaces, the
front of the thigh, leg, and foot,—belonging to the primitive dorsal surface of the limb.
he nerves formed by the union of anterior branches,—genitocrural, obturator, and internal
popliteal, in like manner supply the parts of the limb corresponding to the ventral surface,—
ne peor and back of the thigh, the back of the leg, and the sole of the foot (4. &M.

aterson).

[Structure of a Spinal Ganglion. —The ganglion is invested by a thin, firmly adherent, sheath

Diagram of a spinal nerve; C, spinal cord; pr, ar
posterior and anterior roots; SPD, IPD, superior
and inferior primary divisions; d, v, dorsal and
ventral branches ; sv, sympathetic root (Loss).

»

a. 4

THE SPINAL NERVES. 617

of connective-tissue, which sends processes into the swelling, and is continuous with the sheaths
of the nerve entering and leaving the ganglion (fig. 436, c). In mammals, ¢.g., rabbit, a longi-
tudinal section of such a ganglion exhibits the cells
arranged in groups, with strands of nerve-fibres coursing
longitudinally between them (fig. 436, a, 0). The nerve-
cells are usually globular in form, with a distinct capsule
lined with epithelium, and the cell-substance itself con-
tains a well-defined nucleus with a nuclear envelope and
a nucleolus. The capsule of the cell is continuous with
the sheath of Schwann of a nerve-fibre. The exact relation
between the nerve-fibres and the nerve-cells is difficult to
establish, but it is probable that each nerve-cell is con-
nected with one nerve-fibre, z.¢., they are unipolar. In
the spinal ganglia of the vertebrates above fishes, and also
in the Gasserian ganglion, cells are found with a single
process or fibre attached to them, the nerve-fibre process
not unfrequently coiling a few times within the capsule.
This process, after emerging from the capsule, becomes
coated with myelin, and usually soon divides at a node of
Ranvier (fig. 341, ¢). Ranvier, who first observed this
arrangement, describes it as a T-shaped fibre. These
nerve-cells with T-shaped fibres have been observed in the {i-¢
spinal ganglia of all vertebrates above fishes, in the Gas- WWG*/%
serian and geniculate: ganglia, as well as in the jugular
and cervical ganglia of the vagus. In fishes, the nerve-
cells of the spinal ganglia are bipolar (fig. 868, 4). There
is a rich plexus of capillaries in these ganglia, and each
cell is surrounded by a mesh-work of capillaries, which
never penetrate the cell capsules. ]

Bell’s Law.—Sir Charles Bell discovered (1811)
that the anterior roots of the spinal nerves are
motor, the posterior are sensory.

Recurrent Sensibility.— Magendie discovered
(1822) the remarkable fact that sensory jibres are
also present in the anterior roots, so that their he '
stimulation causes pain. This is due to the fact Longitudinal section of a spinal gan-

; : glion. a,nerve-fibre; 6, nerve-cells;
that sensory fibres pass into the anterior root after @ capsule.
the two roots have joined, and these fibres run in
the anterior root in a centripetal direction (Schiff, Cl. Bernard). The sensibility of
the anterior root is abolished at once by section of the posterior root. This condition
is called “recurrent sensibility ” of the anterior root. When the sensibility of the
anterior root is abolished, so is the sensibility of the surface of the spinal cord in the
neighbourhood of the root. A long time after section of the anterior, and when the
degeneration phenomena have had time to develop (§ 325), a few non-degenerated
sensory fibres are always to be found in the central stump (Schiff, Vulpian).
Schiff found that, in cases where the motor fibres had undergone degeneration,
there were always non-degenerated fibres to be found in the anterior root, which
passed into the membranes of the spinal cord. The sensory fibres pass into the
motor root, either at the angle of union of the roots, or in the plexus, or in the
region of the peripheral terminations. Sensory fibres enter many of the branches
of the motor cranial nerves at their periphery, and afterwards run in a centripetal
direction (p. 602). Even into the trunks of sensory nerves, sensory branches of
other sensory nerves may enter. This explains the remarkable observation, that
after section of a nerve trunk (e.g., the median), its peripheral terminations still
retain their sensibility (Arloing and Tripier). - The tissue of the motor and sensory
nerves, like most other tissues of the body, is provided with sensory nerves (Verv
nervorum, p. 530). ;

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[It does not follow that section of a peripheral cutaneous nerve will cause anesthesia in the
part to which it is distributed ; in fact, one of the principal nerve trunks of the brachial plexus

618 BELL'S LAW AND DEDUCTIONS THEREFROM.

may be divided without giving rise to complete anesthesia in any part of the area of distribu-
tion of the sensory branches of the nerve, and even if there be partial or complete cutaneous
anesthesia, it is much less in extent than corresponds to the anatomical area of distribution.
The anesthetic area tends to become smaller in extent (Ross). Thus, there is not complete
independence in the distribution of these nerves. These results are explained by the anas-
tomosis between branches of nerves, the exchange of fibres in the terminal networks, while some
sensory fibres enter the peripheral parts of a nerve and run centripetally, perhaps being distri-
buted to the skin and conferring recurrent sensibility on the peripheral part of the nerve. ]
Relative Position of Motor and Sensory Fibres.—In embryos (rabbit) the motor fibres stain
more deeply with carmine than the sensory fibres, so that their position in the peripheral nerves
of distribution may thereby be made out. In the
A B anterior branch of a spinal nerve, the sensory fibres
lie in the outer part of the branch, the motor in the
inner part ; while this relation is reversed in the
posterior root (L. Léwe). |
Deduction from Bell’s Law.—Careful ob-
servations of the effects of section of the roots |
of the spinal nerves (Magendie, 1822), as well .
as the discovery of the reflex relation of the |
stimulation of the sensory roots to the ante-
rior, constituting reflex movements (Marshall .
Hall, Johannes Miller, 1832), enable us to
deduce the following conclusions from Bell’s |
law :—1l. At the moment of section of the |
anterior root, there is a contraction in. the
muscles supplied by this root. 2. There is at
the same time a sensation of pain due to the
“recurrent sensibility.” 3. After the section,
the corresponding muscles are paralysed. 4.
Stimulation of the peripheral trunk of the
anterior root (immediately after the operation)
causes ccntraction of the muscles, and eventu-
ally pain, owing to the recurrent sensibility.
5. Stimulation of the central end is without =
effect. 6. The sensibility of the paralysed
parts is retained completely. 7. At the mo-
ment of section of the posterior root, there
is severe pain. 8. At the same time move-
er ments are discharged reflexly. 9. After the
Fig. 437. section, all parts supplied by the divided roots
Distribution of the cutaneous nervesof the Te devoid of sensibility. 10. Stimulation of
arm. A, Dorsal surface—J sc, supra- the peripheral trunk of the divided nerve is
yaitenel ‘ ei pers o cps, se without effect. 11. Stimulation of the central
erlor Cutaneous ; 4 cmd, median }
cutaneous ; 4 cpi, inferior posterior cu- end causes pain and reflex movements. ‘12.
taneous; 6 cm, median cutaneous; 7 Lhe central end ultimately degenerates. 13.
cl, lateral cutaneous ; 8 u, ulnar; 97a, Movement is retained completely in the para-
one i ie ae S volar sur- lysed parts, ¢.g., in the extremities. :
— : ra-clavicular; 2 az, : :
axillary ; 3 cmd, internal cutaneous ; 4 The ultimate he ffect, known i Wallerian
cl, lateral cutaneous; 5 em, cutaneous Gegeneration, which follows section of the
medius ; 6 me, median ; 7 wv, ulnar. nerve or its roots, is referred to in § 325.
Recently, Joseph has slightly modified the
statements of Waller on the degeneration in the posterior roots. According tohim,
the spinal ganglion is the nutritive centre for by far the largest number of the fibres
of this root ; but individual fibres traverse the ganglion without forming connec-
tions with its cells, so that the nutritive or trophic centre for this small number of
nerve-fibres is in the spinal cord. | : i

- eGift

FUNCTIONS OF THE ANTERIOR SPINAL ROOTS.

619

Inco-ordinated Movements of Insensible Limbs.—After section of the posterior roots, ¢.g.,
of the nerves for the posterior extremities, the muscles retain their movements, nevertheless

there are characteristic disturbances of their motor power.

This is expressed in the awkward

manner in which the animal executes its movement—it has lost toa large extent its harmony

and elegance of motion. This is due to the fact
that, owing to the absence of the sensibility of the
muscles and skin, the animal is no longer conscious
of the resistance which is opposed to its movements.
Hence, the degree of muscular energy necessary for
any particular effort cannot be accurately gradu-
ated. Animals which have lost the sensibility of
their extremities often allow their limbs to lie in
abnormal positions, such as a healthy animal would
not tolerate. In man also, when the peripheral
ends of the cutaneous nerves are degenerated, there
are ataxic phenomena (§ 364, 3).

Increased Excitability. —Harless (1858), Ludwig,
and Cyon (controverted by v. Bezold, Uspensky,
Griinhagen, and G. Heidenhain) observed that the
anterior root is more excitable as long as the pos-
terior roots remain intact and are sensitive, and
that their excitability is diminished as soon as the
posterior roots are divided. In order to explain
this phenomenon, we must assume that, in the
intact body, a series of gentle impulses (impres-
sions of touch, temperature, position of limbs, &c.)
are continuously streaming through the posterior
roots to the spinal cord, where they are transferred
to the motor roots, so that a less stimulus is required
to excite the anterior roots than when these reflex
impulses of the posterior root, which increase the
excitability, are absent. Clearly, a less stimulus
will be required to excite a nerve already in a gentle
state of excitement than in the case of a fibre which
is not so excited. In the former case, the dis-
charging stimulus becomes as it were superposed on
the excitement already present. (Compare § 362.)

The anterior roots of the spinal nerves
supply efferent fibres to—

1. All the voluntary muscles of the trunk
and extremities.

Every muscle always receives its motor fibres from
several anterior roots (not from a single nerve-root).
Hence, every root supplies branches to a particular
group of muscles (Preyer, P. Bert, Gad). The ex-
periments of Ferrier and Yeo show that stimulation
of each of the anterior roots in apes (brachial and
lumbo-sacral plexuses) caused a complex co-ordi-
nated movement. Section of one root did not cause
complete paralysis of the muscles concerned in
these co-ordinated movements, although the force
of the movement was impaired. These experiments
confirm the results of clinical observation on man.
The fibres for groups of muscles of different func-
tions (¢.g., for flexors, extensors) arise from special
limited areas of the spinal cord. The cervical and
lumbar enlargements of the spinal cord are great
centres for highly co-ordinated muscular move-
ments,

2. The anterior roots also supply motor

Fig. 438.
Distribution of the cutaneous nerves of the

leg (after Henle). A, Anterior surface
—l, crural nerve; 2, external lateral
cutaneous ; 3, ilio-inguinal ; 4, lumbo-
inguinal ; 5, external spermatic ; 6, pos-
terior cutaneous ; 7, obturator ; 8, great
saphenous; 9, communicating peroneal ;
10, superficial peroneal; 11, deep peroneal;
12, communicating tibial. B, Posterior
surface—l, posterior cutaneous ; 2, ex-
ternal femoral cutaneous ; 3, obturator ;

4, median posterior femoral cutaneous ;

5, communicating peroneal ; 6, creat
saphenous ; 7, communicating tibial ; 8,
plantar cutaneous ; - 8) median plantar ;

~ 10, lateral plantar. ©

fibres for a number of organs provided with smooth muscular fibres, e.g., the bladder
(§ 280), ureter, uterus. [These are the viscero-motor nerves of Gaskell, and from

them come also viscero-inhibitory nerves. |

3. Motor fibres for the smooth muscular fibres of the blood-vessels, the vaso-

620 THE SYMPATHETIC NERVE.

motor, Vaso-constrictor, or vaso-hypertonic nerves [also accelerator or augmentor
nerves of the heart]. They run in the sympathetic for a part of their course

371).
4, Denibitory fibres for the blood-vessels. These are but imperfectly known.

They are also called vaso-dilator or vaso-hypotonic nerves (§ 372). [Also inhibitory

nerves for the heart, which leave the spinal axis in the vagus. |
5. Secretory fibres for the sweat-glands of the skin (§ 289). Fora part of their

course they run in the sympathetic. |
6. Trophic fibres of the tissues (§ 342, I., c). |
The posterior roots contain all the sensory nerves of the whole of the skin and

the internal tissues, except the front part of the head, face, and the internal part of

the head. They also contain the tactile nerves for the areas of the skin already

mentioned. Stimuli which discharge reflex movements are conducted to the spinal

cord through the posterior roots. The sensory fibres of a mixed nerve-trunk supply

the cutaneous area, which is moved by those muscles (or whieh covers those muscles)

to which the same branch supplies the motor fibres. The special distribution

of the motor and sensory nerves of the body belongs to anatomy (figs. 429, 430,

437, 438)

[Physiology of the Limb-Plexuses.—The idea that the nerve-strands become rearranged in the
limb-plexuses so as to connect nerves derived from different parts of the spinal cord with
particular groups of muscles, in order to allow of ‘‘ co-ordination of muscular action,” does not
seem to be borne out by more extended observation. Herringham has shown by dissection (and
the same is seen in cases of paralysis of motion and sensation) that a given muscle or part of a
muscle, and a given spot of skin, are supplied by particular branches of individual spinal nerves
proceeding directly from the spinal cord. The reason that the plexuses exist is, apparently, not
a physiological one. Co-ordination cannot be effected in the plexus, where the axis-cylinders
of the nerves do not divide; but only in the spinal cord and central nervous system, and
through the intervention of nerve-cells. The existence of the plexuses is due to the fact that
embryologically the limb consists of a flattened lappet, or bud, derived from certain somites, but
at first presenting no signs of segmentation, with a preaxial and a postaxial border, and outer
(dorsal) and inner (ventral) surfaces of skin, covering a double layer of muscle on each surface.
The dorsal and ventral branches of the nerves supply these respective surfaces ; and after the
nerves have grown out, the simple muscular strata become split up into individual muscles,
which contain elements derived from one or more segments represented in the primitive limb.
Each nerve is segmental, and, therefore, supplies a muscle derived, for example, from the
elements of two segments ; the nerve of distribution must contain corresponding parts of two
segmental nerves. The plexuses appear, therefore, from an embryological cause, and have no
direct physiological significance (4. M. Paterson).]

356. THE SYMPATHETIC NERVE.—[Anatomical.—The sympathetic nervous system
contains a large number of non-medullated or Remak’s fibres, and consists of a series of ganglia — .
lying on each side of the vertebral column and connected with each other by inter-ganglionic |
fibres. The typical distribution obtains in the thoracic region, where the lateral or vertebral

nglia lie close on the vertebre. In front of this is a second series of ganglia, which do not

orm a double line, but are connected with the former and with each other. They are the pre-
vertebral or collateral ganglia, e.g., semilunar, inferior mesenteric, &c., the nerves connecting
them with the former being called rami efferentes. From these, fibres proceed to connect them
with ganglia lying in or about tissues or organs—the terminal ganglia (Gaskell). ]

{Each spinal nerve in this region is connected with its corresponding sympathetic ganglion
? the ramus communicans, which is formed by fibres both from the anterior and posterior roots
of a spinal nerve. It corresponds to the visceral nerve of the morphologist, and is composed of
two parts—a white and a grey ramus. The white ramus is composed entirely of medullated
fibres, and coming from the anterior and posterior roots of a spinal nerve, passes into the lateral
and collateral ganglia. These white rami occur in the dog only from the 2nd thoracic to the

2nd lumbar nerve (fig. 439). Above and below this, the rami are all and composed of non-
medullated nerve-fibres (Gaskell). ] + oye -

[In man, the four upper rami communicantes from the four upper cervical nerves all join the
superior cervical ganglion (fig. 428, G g, s), the 5th and 6th join the middle cervical, the 1m
and 8th the inferior cervical ganglion. The lowest pair of ganglia are generally united by
pth. ve front of the first coceygeal vertebra, aha they lie in relation with the eoccygeal

glion. oi

voi

[Cephalic Portion.—As the sympathetic ascends to the head it forms connections with many

THE SYMPATHETIC NERVE. 621

of the cranial nerves, and there is a free exchange of fibres between these nerves. (The function
and significance of these exchanges are referred to under the physiology of the cranial nerves). ]

[Dorsal and Abdominal Portion.—Numerous fibres pass from these parts chiefly to the thoracic
and abdominal cavities, where they form large gangliated plexuses, from which functionally
different fibres proceed to the different organs. ]

[In the dog, the 2nd, 3rd, 4th, and 5th thoracic pass upwards into the cervical sympathetic,
those in the dorsal region being directed downwards trom the lateral ganglia to form the
splanchnics (fig. 439). The grey non-medullated nerve-fibres of each grey ramus are connected
with the cells of its ganglion (lateral) ; the fibres do not go beyond the ganglion, but really run
to the corresponding spinal nerve to ramify in the sheaths of the nerves, the connective-tissue
on the vertebre and the dura mater, and perhaps the other spinal membranes ; so that, accord-
ing to Gaskell, no non-medullated nerves leave the central nervous system by the spinal nerve-
roots. Thus, the white rami communicantes alone constitute the rami viscerales of the morpho-
logist, and all the visceral nerves passing out from the central nervous system into the sympa-
thetic system pass out by them alone. All the nerves in the white ramus are of small calibre
(1°8 w to 2°7 w) and medullated, while the true motor fibres are much larger (14°4 uw to 19 y).
The small, white fibres can be traced upwards as medullated fibres into the superior cervical
ganglion, and in the thorax over the lateral ganglia to form the splanchnics into the collateral
ganglia, beyond which they cease to be medullated. By the 2nd and 3rd sacral nerves some
tibres of smallest calibre issue to form the nervi erigentes, which pass over and do not com-
municate with the lateral ganglia, but enter the hypogastric plexus, whence they send branches
upwards to the inferior mesenteric plexus and downwards to the bladder, rectum, and generative
organs. Gaskell pee to call them the pelvic splanchnic nerves (fig. 439). ]

[In the cervical region, there is no white ramus, and the nerve-roots contain no nerve-fibres
of small calibre. But in this region rises the spinal accessory nerve, between the anterior and
posterior roots. It contains small and large nerve-fibres; the former pass into the internal
division of this nerve and join the ganglion of the trunk of the vagus, while the large motor
fibres form its external branch and supply the sternomastoid and trapezius muscles. ]

[All the vaso-motor nerves arise in the central nervous system, and they leave the spinal
cord as the finest medullated fibres in the anterior roots of all the spinal nerves between the 2nd
thoracic and 2nd lumbar (dog) ‘‘along the corresponding ramus visceralis, enter the lateral or
main sympathetic chain of ganglia, where they become non-medullated, and are thence distri-
buted either directly or after communication with other ganglia” (Gaskell). ]

[The vaso-dilator nerves leave the central nervous system among the fine medullated fibres,
which help to form the cervico-cranial and sacral rami viscerales, and pass without altering their
character into the distal ganglia” (Gaskell). ]

[‘‘ The viscero-motor nerves. upon which the peristaltic contraction of the thoracic portion
of the esophagus, stomach, and intestines depends, leave the central nervous system in the out-
flow of fine medullated nerves which occurs in the upper part of the cervical region, and pass
by way of the rami viscerales of the accessory and vagus nerves to the ganglion trunci vagi,
where they become non-medullated ” (Gaskel?). ]

[‘‘ The inhibitory nerves of the circular muscles of the alimentary canal and its appendages
leave the central nervous system in the anterior roots, and pass out among the fine medullated
fibres of the rami viscerales into the distal ganglia without communication with the proximal
ganglia” (Gaskell).]

[Structure of a Ganglion.—The structure of the sympathetic nerve-fibres and nerve-cells has
already been described in § 321. On making a section of a sympathetic ganglion, ¢.g., the
human superior cervical, we observe groups of cells with bundles of nerve-fibres—chiefly non-
medullated—running between them, and the whole surrounded by a laminated capsule of con-
nective-tissue, which sénds septa into the ganglion. The nerve-cells have many processes, and
are, therefore, multipolar, and each cell is surrounded by a capsule with nuclei on its inner
surface (fig. 368, II). The processes pierce the capsule, and one of them certainly—and perhaps
all the processes—are connected with a nerve-fibre. Ranvier states that each cell has a
fibrillated outer portion and a more granular inner part. Each of the processes becomes con-
tinuous with a fibre of Remak. Not unfrequently yellowish-brown pigment is found in the
cell-substance. Similar cells have been found in the ophthalmic, sub-maxillary, otic, and
spheno-palatine ganglia. The number of medullated nerve-fibres diminishes as the sympathetic
nerves are traced towards their distribution. Ranvier states that it is possible in the rabbit to
trace the conversion of a medullated fibre into a branched fibre of Remak. The blood-vessels of
the sympathetic ganglia in mammals are peculiar. The arteries are small, and after sub-
division form a capillary network, each mesh of which encloses several ganglionic cells. The
veins on the contrary are very large, tortuous, varicose, and often terminate in culs-de-sac,
into which several capillaries open. The arrangement of the veins is spoken of as the venous
sinuses of these ganglia, being compared by Ranvier to the sinuses of the dura mater and
venous plexuses of the spinal canal. }

Functions.—The following is merely a general summary :—

622

I. Independent F

which remain after a

FUNCTIONS OF THE CERVICAL SYMPATHETIC,

unctions of the sympathetic are those of certain nerve plexuses
ll the nervous connections with the cerebro-spinal branches

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the direction of inhibition or stimula-
tion—through fibres reaching them
from the cerebro-spinal nerves.

To these belong :—

1. The automatic ganglia of the
heart (§ 58).

2. The mesenteric plexus of the in-
testine (§ 161),

3. The plexuses of the uterus, Fal-

lopian tubes, ureters (also of the blood- ,

and lymph-vessels).

II. Dependent Functions.—Fibres
run in the sympathetic, which (like
the peripheral nerves) are active only
when their connection with the central
nervous system is maintained, e.g., the
sensory fibres of the splanchnic. Others
again convey impulses from the central
nervous system to the ganglia, while
the ganglia in turn modify the impulses
which inhibit or excite the movements
of the corresponding organs.

The following statement is a reswmé of the

functions of the sympathetic, according to
the anatomical arrangement :—

A. Cervical Part of the Sympa-
thetic. —1. Pupil-dilating fibres (com-
pare Ciliary ganglion, § 347, I, and
Tris, § 392), According to Budge,
these fibres arise from the spinal cord,

and run through the upper two dorsal .

and lowest two cervical nerves into the
cervical sympathetic, which conveys
them to the head. Section of the cer-
vical sympathetic or its rami communi-
cantes causes contraction of the pupil.
(The central origin of these fibres is
referred to in § 362, 1, and §.367, 8.)

2. Motor fibres for Miiller’s smooth
muscle of the orbit, and partly for the
external rectus muscle (§ 348).

3. Vaso-motor branches for the
outer ear and the side of the face (CZ.
Bernard), tympanum (Prussak), con-
junctiva, iris, choroid, retina (only in
part—see Ciliary ganglion, § 347, L.),

nx, thyroid gland—fibres for the vessels of the

brain and its membranes (Donders and Callenfels).

4. In the cervical portion are afferent fibres which excite the vaso-motor centre

in the medulla (Awbert).

5. Secretory (trophic) and vaso-motor fibres for the salivary glands (§ 145).

THORACIC AND ABDOMINAL SYMPATHETIC. 623

6. Sweat-secretory fibres (see § 288, IT.).

7. According to Wolferz and Demtschenko the lachrymal glands receive sympa-
thetic secretory fibres (?).

B. Thoracic and Abdominal Sympathetic.—First of all there is—

1. The sympathetic portion of the cardiac plexus (§ 57, 2), which receives
accelerating or augmentor fibres for the heart from the lower cervical and 1st
thoracic ganglion (Cl. Bernard, v. Bezold, Cyon, Schmiedeberg). The fibres arise
partly from the sympathetic and partly from the plexus around the vertebral artery
(v. Bezold, Bever). (Compare § 370.)

2. For the vaso-motor fibres passing through the sympathetic to the extremities,
skin of the trunk, and lungs (see § 371). For vaso-dilators (§ 472).

3. The cervical sympathetic and the splanchnic contain fibres which, when their
central ends are stimulated, excite the cardio-inhibitory system in the medulla
oblongata (Bernstein).

4, The functions of the splanchnic are referred to in §§ 164, 175, 276, and 371.
_ 5. The functions of the coeliac and mesenteric plexuses are referred to in
§§ 183 and 192. After extirpation of the cceliac ganglion, Lamansky observed
temporary disturbance of digestion, undigested food being passed per anum.

6. For the secretory fibres for sweating, see § 289, II.

7. Lastly, the abdominal portion of the sympathetic contains motor and vaso-
motor fibres for the spleen, the large intestine (accompanying its arteries), bladder
(§ 280), ureters, uterus (running in the hypogastric plexus), vas deferens, and
vesiculz seminales. Stimulation of all cf these nerve channels causes increased
movement of the organs, but it must be remembered that the diminished supply of
blood thereby produced also acts as a stimulus (§ 161). Section of these nerves is
followed by dilatation of the blood-vessels, with subsequent derangement of the
circulation, and ultimately of the nutrition. The relation of the suprarenal
bodies to the sympathetic is referred to in § 103, IV. The renal plexus is referred
to in § 276, while the cavernous plexus is treated of in § 436.

Pathological.— Considering the numerous connections of the sympathetic, we would naturally

suppose that it offers an extensive area for pathological changes. Affections involving the vaso-
motor system are referred to in § 371.

The cervical sympathetic is most frequently paralysed or stimulated by traumatic conditions,
wounds by bullets or knives, tumours, enlarged lymph-glands, aneurisms, inflammation of the
apices of the lungs and the adjacent pleure, while exostoses of the vertebrae may stimulate it in
part or paralyse it in part. The phenomena so produced have been partly analysed in treating
of the ciliary ganglion (§ 347, I.), Stimulation of the cervical sympathetic in man causes
dilatation of the pupil (mydriasis spastica), palor of the face, and occasionally hyperidrosis or
profuse sweating (§ 289, 2, and § 288); disturbance of vision for near objects, as the pupil
cannot be contracted (see Accommodation), and hence the spherical aberration of the lens
(§ 391) must also interfere with vision; protrusion of the eyeball with widening of the palpebral
fissure. Paralysis or section of the cervical sympathetic causes increased fulness of the blood-
vessels of the side of the head, with occasional anidrosis ; contraction of the pupil (myosis
paralytica), which undergoes changes in its diameter during accommodation, but not as the
effect of the stimulation of light—atropin dilates it slightly. The slit between the eyelids is.
narrowed, the eyeball retracted and sunk in the orbit, the cornea somewhat flattened, and the
consistence of the eyeball diminished. Stimulation of the sympathetic is followed by an
increased secretion of saliva (§ 145). The above described symptoms have been occasionally

accompanied by unilateral atrophy of the face.

[Section of the Cervical Sympathetic.—This experiment is easily done on a
rabbit, preferably an albino one. Divide the nerve in the neck, and immediately
thereafter (1) the ear and adjoining parts on that side become greatly congested
with blood, blood-vessels appear that were formerly not visible, and as a result of
the increased quantity of blood in the ear (hyperzmia), there is (2) a rise of the
temperature amounting to even 4° to 6° C. (Cl. Bernard). These are the vaso-
motor changes. (3) The pupil is contracted, the cornea flattened, and there is
retraction of the eyeball and consequent narrowing of the palpebral fissure. These

624 COMPARATIVE—HISTORICAL.

are the oculo-pupillary symptoms. Stimulation (electrical) of the peripheral end
produces the opposite results,—pallor of the ears, owing to contraction of the blood-
vessels, with consequent fall of the temperature ; dilatation of the pupil, bulging of
the cornea, protrusion of the eyeball (exophthalmos), and widening of the palpebral
fissure. At the same time, the blood-vessels to the salivary glands are contracted,
and there is a secretion of thick saliva. The last results are due to the vaso-
constrictor and secretory fibres. The vaso-motor and oculo-pupillary fibres, although
they lie in the same trunk in the neck, do not issue from the cord by the same
nerve-roots ; the latter come out of the cord with the anterior roots of the Ist and
2nd dorsal nerves (dog), while section of the cord between the 2nd and 4th dorsal
vertebrae produces the vaso-motor changes only. The nasal mucous membrane and
lachrymal gland are influenced by the sympathetic. |

(Division of the cervical sympathetic in young, growing, animals results in hypertrophy of
the ear, and increased growth of the hair on that side (Bidder, W. Stirling). ] 9

(The vago-sympathetic nerve (dog) in the neck contains vaso-dilator fibres (really in the
sympathetic) for the skin and mucous membranes of that side of the head. Weak stimulation
of the central end of the sympathetic causes dilatation of the blood-vessels of these parts. The
vaso-dilator fibres of the superior maxillary nerve probably come from the same source. The
centre for these nerves is in the dorsal region of the cord between the Ist and 5th dorsal
vertebra, where the fibres pass out with the rami communicantes to enter the cervical sympathetic
(Dastre and Morat). The vaso-dilator fibres occur in the posterior segment of the ring of
Vieussens, and when they are stimulated after section of the 7th cranial nerve, there is a
‘* pseudo-motor ” effect on the muscles of the cheek and lip (§ 349). ]

Irritation in the area of the splanchnic, as occurs occasionally in lead poisoning, is
characterised by violent pain (lead colic), inhibition of the intestinal movements, (hence
the persistent constipation), slowing of the heart’s action, brought about reflexly, just as. in
Goltz’s ‘‘tapping” experiment (§ 369). Irritation in the area of the sensory nerves of the
sympathetic may give rise to that condition which is called by Romberg neuralgia hypogastrica,
a painful affection of the lower abdominal and sacral regions, hysteralgia, neuralgia testis,
which are localised in the plexuses of the sympathetic. In affections of the abdominal
sympathetic, there may be severe constipation, with diminished or increased secretion of the
intestinal glands (§ 186).

357, COMPARATIVE—HISTORICAL.—Comparative.—Some of the cranial nerves may
be absent, others, again, may be abortive, or exist as branches of other nerves. The facial
nerve, which supplies the muscles of expression in man, and is, at the same time, the nerve for
facial respiratory movements, diminishes more and more in the lower classes of the vertebrata,
pari passu, with the diminution of the facial muscles. In birds and reptiles, it supplies the
muscles of the hyoid bone, or the superficial cervical muscles of the nape of the neck. In
amphibians (frog), the facial no longer exists as a separate nerve, the nerve which corresponds
to it springing from the trigeminus. In fishes, the 5th and 7th nerves fourm a joint complex
nerve. The part corresponding to the facial (also called ramus opercularis trigemini) is the chief
motor nerve of the muscles of the gill-cover, and is, therefore, the respiratory nerve. In the
cyclostomata (lamprey) there is an independent facial. The vagus is present in all vertebrata;
in fishes it gives off a large nerve, the lateral nerve of the body (N. lateralis), which runs along
each side of the body close to the lateral canal. It is also present in the tadpole. Its
rudimentary representative in man is the auricular branch. In the frog the 9th, 10th, and
11th arise together from one trunk, and the 7th and 8th from another. In fishes and amphibia,
the hypoglossal is the first cervical nerve. In amphioxus, the cerebral and spinal nerves are
not distinct from each other. The spinal nerves are remarkably similar in all classes of the
vertebrata, The sympathetic is absent in the cyclostomata, where it is represented by the
vagus. Its course is along the vertebral column, where it receives the rami communicantes of
the spinal nerves. In the region of the head its connections with the 5th and 10th nerves are
specially developed. In frogs, and still more so in birds, the number of connections with the
cranial nerves increases.

rical.—The vagus and sympathetic were known to the Hippocratic School. According
to Erasistratus, all the nerves proceed from the brain and spinal cord ; Herophilus was the first
to distinguish the nerves from the tendons, which Aristotle confounded with each other.
Marianus (80 A.D.) recognised seven pairs of cranial nerves. Galen was in possession of a wide
range of important facts in the physiology of the nervous system (§ 140) ; he observed that loss
of voice followed ligature of the recurrent nerves ; and he was acquainted with the accessorius,
and the ganglia on the abdominal nerves, The cauda equina is referred to in the Talmud ;
Coiter (1573) described exactly the anterior and posterior spinal nerve-roots. Van Helmont
(+ 1644) states that the peripheral motor nerves also give rise to impressions of pain, an

PHYSIOLOGY OF THE NERVE-CENTRES. 625

Cesalpinus (1571) remarks that interruption of the blood-stream makes the parts insensible.
Thomas Willis described the chief ganglia (1664), In Des Cartes there is the first indication of
reflex movements; Stephen Hales and. Robert Whytt showed that the spinal cord was
necessary for such acts. Prochaska described the reflex channels, [while Marshall Hall
established the doctrine of reflex, or, as he called them, ‘‘ diastaltic” actions]. Duverney
(1761) discovered the ciliary ganglion. “Gall traced more carefully the course of the 3rd and
6th nerves, and also the spinal nerves into the grey matter. Hitherto only nine nerves of
the brain had been enumerated ; Sommerring (1791) separated the facial from the auditory
nerve, Andersch (1797) the 9th, 10th, and 11th nerves.

Physiology of the Nerve-Centres.

358. GENERAL.—(The nerve-fibres and nerve-cells constitute the elements
out of which nerve-centres are formed, being held together by connective-tissue.
In the process of evolution, groups of nerve-cells with connecting fibres are arranged
to constitute nervous masses, whereby there is a corresponding integration of
function. Thus, with structural integration there is a functional integration.
When the structure suffers so also does the function, and those parts which are
most evolved, as well as those actions which have to be learned by practice, are the
first to suffer during the dissolution of the nervous system. |

General Functions.—The central organs of the nervous system are in general
characterised by the following properties :—

1. They contain nerve-cells, which are either arranged in groups in the interior
of the central organs of the nervous system, or embedded in the peripheral branches
of the nerves. | Nerve-cells are centres of activity, originate impulses and conduct
saa as well, while nerve-fibres are chiefly conductors. |

. The nerve-centres are capable of discharging reflexes, ¢.7., reflex-motor, reflex-
perenne, and reflex-inhibitory acts.

3. The centres may be the seat cf automatic excitement, i.c., - they may
manifest phenomena, without the application of any apparent: external stimulus.
The energy so liberated may be transferred to act.upon other organs. This
automatic state of excitement or stimulation may be continwous, v.e., may be
continued without interruption, when it is called tonic automatic or tonus ; or it
inay be ¢ntermittent, and occur with a certain rhythm (rhythmical automatic).

4, The central organs are trophic centres for the nerves proceeding from them ;
they may also perform similar functions for the tissues innervated by them.

5. The psychical activities are dependentupen an intact condition of the gangli-
onic central organs. These various functions are distributed over different centres.

[The term ‘‘centre” is merely applied to an aggregation of nerve-cells so related to each
other as to subserve a certain function, but, inasmuch as these cells are connected to each other
and with other cells in many ways, various combinations of them may result; again, we have
also to take into account the greater or less resistance in some paths than in others, so that
the.variety of combinations which these cells may subserve is enormous. These cells give off
processes which branch, and anastomose with processes from other cells. ‘Thus, innumerable
ways are opened up to nervous impulses by these combinations, so that .in,a certain. way
we may regard a cell as.a junction of these conducting fibres, or a ‘‘ shunt” whereby an impulse
may be-shunted on‘to ‘one or other branch in the direction’ of east: resistance, or in the best
beaten path as it were; while there may be a ‘‘ block” in other directions. ] ° |

{In connection with the histology of the centr al nervous system we have to 5 tua _—

A. The nervous constituents. B. Non-nervous constituents. .
(1) "Nerve-fibres-- -) :- © 0% (1) Vessels. (blobd and lymph). -

* (2) Nerve-cells. ““~ °°. 7 > (2). Epithelium.
ete liter hit. 1445 | (3) Sustentacular tissue. —
(a) Connective-tissue.
(>) Neuroglia. |.
| 2R

626 STRUCTURE OF THE SPINAL CORD,

The Spinal Cord.
359. STRUCTURE OF THE SPINAL CORD.—{The key to the study of

the central nervous system is to remember that it begins as an involution of the |
epiblast, and is originally tubular, with a central canal, dilated in the brain-end |
into ventricles. In the spinal cord there are three concentric parts: first, the |
columnar ciliated epithelium, outside this the central grey tube, and covering in all, |
the outer white conducting fibres (//7//). |

Structure.—The spinal cord consists of white matter externally and grey matter internally.
[It is invested by membranes—the pia mater, composed of two layers and consisting of con-
nective-tissue with blood-vessels, being firmly adherent to the white matter and sending septa
into the substance of the cord. Both layers dip into the anterior median fissure, and only the
inner one into the posterior median groove. The arachnoid is a more delicate membrane and
non-vascular, while the dura mater is a tough membrane lining the vertebral canal, and
forming a theca or protective coat for the cord (§ 381).] The grey mater has the form
of two crescents )=( placed back to back [or a capital H], in which we can distinguish an
anterior («) and a posterior horn (py), a middle’ part, and a grey commissure connecting the two
crescents. In the centre of this grey commissure is a canal—central canal—which runs from
the calamus ene downwards ; it is lined throughout by a single layer of ciliated
cylindrical epithelium, [in the fcetus, the cilia not being visible in the adult], and the canal
itself is the representative of the embryonal ‘‘ medullary tube ” (figs. 440, 446). [The part of

A A

|
|

p P P oP
Fig. 440.
Transverse section of the spinal cord ; in the centre is the butterfly form of the grey matter
surrounded by white matter. , posterior, and a, anterior, horns of the grey matter ; PR,

aeseecpag roots ; AR, anterior roots of a spinal nerve ; A, A, the white anterior; L, L, the
teral ; P, P, the posterior columns.

the grey commissure in front of this canal is called the anterior, and the part behind, the

ey commissure, In front of the grey commissure, and between it and the base of
the anterior median fissure, are bundles of white nerve-fibres passing in a horizontal or oblique
direction from the anterior column of one side to the grey matter of the anterior cornu of the
opposite side (fig. 440). These decussating fibres constitute the white commissure.

e white matter surrounds the grey, and is arranged in several columns [an , lateral,
and posterior—by the passage of the nerve-roots to the cornua (figs. 440, 446)]. Along the
anterior surface of the cord there runs a well-marked fissure, which dips into the cord itself,
but does not reach the grey matter, as a mass of white matter—the white commissure—runs
from one side of the cord to the other. Between this fissure, known as the anterior : n
fissure, and the line of exit of the anterior roots of the spinal nerves, lies the anterior colum: 7

’

STRUCTURE OF THE WHITE AND GREY MATTER. 627

(A); the white matter lying laterally between the origin of the anterior and posterior roots of the
spinal nerves is the lateral column (L), while the white matter lying between the line of origin
of the posterior roots and the so-called posterior median fissure, is the posterior column (P).
[The posterior median fissure is not a real fissure, but is filled up with the inner layer of the pia
mater, which dips down from the under. surface of this membrane quite to the grey matter of
the posterior commissure.] Each posterior i
column, in certain regions of the cord, may
be subdivided into an inner part lying next
the fissure, the postero-median or Golli’s
column, or the inner root-zone (Charcot, fig.
454, c); and an outer larger part next the
posterior root, known as the postero-exter-
nal or Burdach’s column, or the outer root-
zone (Charcot, fig. 454, d).

Fig. 441, Fig. 442.

Fig. 441.—Transverse section of the white matter of the cord; x150. a, peripheral layer.
Besides the transverse sections of the nerve-fibres, large and fine, there are three branched
connective-tissue corpuscles (c). Fig. 442.—Multipolar nerve-cells from the grey matter of
the anterior horn of the spinal cord (ox), a, nerve-cell ; 0, axis-cylinder; c, grey matter ;
d, white matter of column ; ¢é, e, branches of cells,

The white matter consists chiefly of medullated fibres without the sheath of Schwann and
Ranvier’s nodes, but provided with the neuro-keratin sheaths of Kiihne and Ewald (§ 321), the
fibres themselves being chiefly arranged longitudinally. [The incisures of Schmidt exist in these
fibres, and can be demonstrated by the interstitial injection of osmic acid (Ranvier).] The
nerve-fibres of the nerve-roots, as well as those that pass from the grey matter into the columns,
have a transverse or oblique course. There are also decussating fibres in the anterior or white
commissure. [In a transverse section of the white matter of the spinal cord, the nerve-fibres
are of different sizes, and appear like small circles with a rounded dot in their centre—the axis-
cylinder—the latter may be stained with carmine or other dye (fig. 441). They are smallest in
the postero-median or Goll’s column, and largest in the crossed and direct pyramidal tracts,
which are motor. The white substance of Schwann, especially in preparations hardened in
salts of chromium, often presents the appearance of concentric lines. Fine septa of connective-
tissue carrying blood-vessels lie between groups of the nerve-fibres, while here and there between
the nerve-fibres may be seen branched neuroglia corpuscles, Immediately underneath the pia
mater there is a
pretty thick lay-
er of neuroglia,
which invests the
prolongations of
the pia into the
cord. ]

[The grey mat-
ter differs in : vases?
shape im the dif- 7 meyer eES . Albs
ferent regions of ! IV iT Il y d er | XY JX Vil Vil VI Wimioart vaaiwvvy Wi il
the cord, and so Sacral : Dorsal Cervical
does the ey ,
commissure ‘tic. Fig. 443.

444). The latter Diagram of the absolute and relative extenc of the grey matter, and of the
is thicker and white columns in successive sectional areas of the spinal cord, as well as the
shorter in the sectional areas of the several entering nerve-roots. NR, nerve-roots ; AC
cervical than in LC, PC, anterior, lateral, and posterior columns ; Gr, grey matter,

the dorsal re-

gion, while it is very narrow in the lumbar region. The amount of grey matter undergoes a
great increase opposite the origins of the large nerves, the increase being most marked opposite

628 ARRANGEMENT OF NERVE-CELLS.

the cervical and lumbar enlargements. Ludwig and Worschiloff constructed a series of curves
from measurements by Stilling of the sectional areas of the grey and white matter of the
cord, as well as of the several nerve-roots. ‘These curves have been arranged in the annexed
convenient form by Schiifer after Woroschiloff (fig. 443)] :— ;

[In the cervical region, the lateral white columns are large, the anterior cornu of the grey
matter is wide and large, while the posterior cornu is narrow ; Goll’s column is marked off by a
depression and a prolongation of the pia mater ; the cord itself is broadest from side to side. In
the dorsal region, the grey matter is small in animals, and both cornua are narrow and of near]
equal breadth, while the cord itself is smaller and cylindrical. In it the intermedio-late
and posterior vesicular groups of cells are distinct.. They have probably relations to viscera.
The commissure lies well forward between the crescents. In the lumbar region, the
matter is relatively and absolutely greatest, while the white
lateral columns are small, the central canal in the com-
missure being nearly in the middle of the cord. In the
conus medullaris, the grey matter makes up the great mass
of it, with a few white fibres externally (fig. 444).]

The anterior cornu of the grey matter is shorter and
broader, and does not reach so near to the surface as the
posterior ; moreover, each anterior nerve-root arises from
it by several bundles—it contains several groups of large
multipolar ganglionic cells (fig. 442) ; the posterior cornu
is more pointed, longer, and narrower, and reaches nearer
to the surface, the posterior root arising by a single bundle
at the postero-lateral fissure ; while the cornu itself contains
a few fusiform nerve-cells, and is covered by the-substantia
gelatinosa of Rolando, which is in part an accumulation of
neuroglia. ar

[The substantia gelatinosa on the posterior cornu is
marked by striation where the posterior root-fibres traverse
it. It contains some connective-tissue cells and some fusi-
form nerve-cells, especially near the margins. The substance
itself stains deeply with carmine. ] .

[The outer margin of the grey matter near its middle is
not so sharply defined from the white matter as elsewhere ;
and, in fact, a kind of anastomosis of the grey matter pro-
jects into the lateral column, especially in the cervical
region, constituting the processus reticularis (fig. 446). ]

[Arrangement of Nerve-Cells.—The nerve-cells are ar-
ranged in four groups, forming columns more or less con-
tinuous. There are those of the anterior and posterior
horns, those of the lateral column (intermedio-lateral), and
the posterior vesicular column of Clarke. The anterior and
posterior groups exist as continuous columns along the en-

tire cord. The cells in the anterior cornu are subdivided
Fig. 444, into smaller groups, which vary in the different regions of

7 the cord. There isan inner or median group near the
anterior angle of the cornu. It is the. smallest group, and
is absent in the lumbar region. Near the ‘anterior edge is
ey anterior group, and in Oe Sight part of the mite is

: the antero-lateral group. ese two groups are often

cre Pier! Rastp x united, as in the mid-cervical region. There is usually a

at the 5th sacral vertebra: F’ third large group—the external or postero-lateral in the

at coceyx; A, B, C, enlarged Posterior outer angle of the anterior comu—the cells of the
twice; D. EF Shrtan oo anterior horn being very large (67 to 135 u), while the fusi-
anterior p posterior neo Bh Bay form cells of the posterior horn are 18 » in diameter.
pri : Those of the lateral column are distinct, except in the lum-

bar and cervical enlargements, where they blend with the anterior horn. The column of Clarke
(cells 40 to 90 u) is discontinued, and is limited to i ion, (2) cervico-cranial
region, (3) sacral region, being most conspicuous in (1), where it corresponds absolutely to the
outflow of visceral nerves (Gaskell). ’ In‘the sacral region it corresponds to the :*‘ sacral nucleus
of Stilling,” while in the cervical region it begins in the dog at the 2nd cervical nerve, forming
the cervical nucleus, being continued above into the nuelei of" the vagus and zltkto- Shaya
nerves. The cells of this column give rise-to small miedullated nerve-fibres or-the leucenteric
fibres of Gaskell. } wy 194 us watalak posi a i sinc? leatviee

The multipolar ganglion cells are largest, and arranged in groups in the anterior horns 9
the grey matter (fig. 446—‘‘motor ganglionic cells”), - [They also occur in the lateral proc
and in the processus reticularis. It is-to be noted that the cells become more branched as 1

Transverse sections of the spinal —
cord in different regions. A,
through the middle of the
cervical; B, the dérsal; ©, the

seat

’

GERLACH’S NETWORK AND MULTIPOLAR CELLS. 629

proceed upwards amongst the vertebrata. -These cells usually contain pigment-granules, and,
according to Pierret, their size has a direct relation to the length of the nerve-fibre proceeding
from them ; so that they are largest in the lumbar enlargement, smaller in the cervical enlarge-
ment, and smallest in the dorsal region. Smaller spindle-shaped (**sensory’’) cells occur in
much smaller numbers in the grey matter of the posterior horn. The cells of Clarke’s column
(fig. 445) are smaller (30-60 u), and are usually arranged with their long axis in the long axis of
the cord. The processes are fewer, but one is generally directed towards the head, and some
towards the caudal end of the body. They usually contain much pigment, which is generally
disposed towards the cerebral pole of the cell. ]

{In a longitudinal section of the cord (fig. 447), these cells are seen to be arranged in columns,
the large multipolar cells in the anterior horn (m); in the same section are shown, the longi-
tudinal direction of the nerve-fibres in the anterior (a) and posterior white columns (c), the
horizontal direction of the fibres of the anterior and posterior nerve-roots (b and /). ,

The grey matter contains an exceedingly delicate tibrous network of the finest nerve-fibrils
(Gerlach), which is produced by the repeated division of the protoplasmic processes of the

nt

Te es Ran
t is a AS
4 ; 8,

NY

Fig. 445. Fig. 446.

Fig. 445.—Nerve-cell from Clarke’s column (horse). The arrow indicates the cerebral end. Fig.
446.—Transverse section of the spinal cord (lower dorsal). A, L, P, anterior, lateral, and
posterior columns; A.M.F., P.M.F., anterior and posterior median fissures; a, 0, c, ceils
of the anterior horn; d, posterior cornu and substantia gelatinosa; ¢, central canal ; /,
veins ; g, anterior root bundles ; 2, posterior root bundles ; 7, white commissure ;./, grey
commissure ; 7, reticular formation.

multipolar ganglionic cells. Medullated nerve-fibres traverse and divide in the grey matter
and become non-medullated; some of them merely pass through the grey matter of the non-
medullated fibres and terminate in Gerlach’s network. Fibres pass from the grey matter of one
side to that of the other through the commissures in front of and behind the central canal.

[By means of Weigert’s method of staining medullated nerve-fibres (p. 529), it has been
proved that numerous, fine, medullated nerve-fibres exist in the grey substance. ]

Gerlach’s Theory. —According to Gerlach,.the connection of the fibres and cells is as follows :
—The fibres of the anterior root proceed difectly to the ganglionic cells of the anterior horn,
with which they form direct communications by means of the unbranched axial cylinder pro-
cesses (fig. 448, z).. The grey network of protoplasmic processes, produced by the repeated
branchings of the fibres of these cells, gives origin to broad fibres. A part of the latter (the
median bundle) passes through the anterior white commissure to the other side, and then ascends

his

630 THE NEUROGLIA AND BLOOD-VESSELS OF THE CORD.

in the'anterior column of the opposite side. Other fibres (the lateral bundle) pass into the

Fig. 447. Fig. 448,

Fig.*447.—Longitudinal section of the human spinal cord. «@, anterior, ¢, posterior, d, lateral
white columns ; 8, anterior, c, posterior nerve-roots ; /, horizontal (pyramidal) fibres passing
to m, cells of anterior cornu; 2, oblique fibres of posterior root. Fig, 448.—Mu tipolar
nerve-cell, from the anterior horn of the spinal cord. z, axis-cylinder process ; y, branched
processes,

lateral column of the same side, and ascend in it as far as-the decussation of the pyramids, .
where they cross in the medulla to the other
side. The fibres of the posterior root enter the
? posterior horn, and, after dividing, terminate
in the nervous protoplasmic network of the
grey matter. By means of this network they
are connected indirectly with the ganglionic
cells of the posterior horn, which are said not ~
to have an axial cylinder process. The grey
network, which connects the ganglia of the
anterior and posterior horns with each other,
also sends fibres, which pass to the other side |
of the cord in front of and behind the central
canal. They then take a backward course, to
ascend partly in the posterior horns and partly
in the lateral columns. “

[The anterior root enters in several bundles
of coarse fibres which diverge before they reach
the grey matter. Most, or perhaps all, the
fibres end in the large motor nerve-cells in the
anterior cornu or its lateral process (fig. 449,
a, b, c, d, e). But the fibres diverge in all
directions, some of the fibres of the bundle
nearest the middle line (8) end in the laterally
placed cells (c) ; a.part (4) crosses the anterior
commissure to end in cells on the opposite side
(zd). Some of them (6) run upwards to become
connected with motor cells lying further up
the cord. ] ‘

[The posterior root entersasasingle bundle, —

Fig. 449. oo osed of 9 et with Beevoes OF

Scheme of the course of the fibres in the spinal thicker ones. The finest fibres, which are usu-

cord. The longitudinal fibres are indicated by ally placed most laterally (7), or outer radi-
small circles ; while the nerve-cells are black, C™/r fibres, curve into the longitudinal fib

F ; ; so that they are cut across in a transverse sec- _

tion, but they again take a horizontal course and enter the substantia gelatinosa. The remainder

}
j

THE NEUROGLIA AND BLOOD-VESSELS OF THE CORD. 631

of the fibres split into an outer and inner part. The lateral smaller part or central fibres (8 to
10) passes into the substantia gelatinosa, where it divides into several strands, some of which
pass into the central part of the grey matter (10), while others (8) pass upwards and downwards in
a longitudinal direction. Some of the fibres (9) perhaps end in the nerve-cells (7) in the posterior
cornu. The median, inner or internal radicular fasciculus (11 to 14), sweeps through the

_postero-external column, and, after running a longitudinal course in the white matter, enters the

grey substance of the posterior cornu. Some fibres (11) pass to the small fusiform cells (9) ;
and others (13) pass to be connected with the cells of Clarke’s column (), when it is present.
From the cells of Clarke’s column, fibres seem to pass to the direct cerebellar tract (20). Some
of the fibres (12) pass into the posterior grey commissure, to reach the opposite side. This so
far only accounts for a part of the fibres. Some of them (8 to 10) are concerned in the formation
of the fine nerve-plexus in the grey matter, whereby, perhaps, they become connected with the
cells in the anterior cornu. It is asserted that some of the fibres (14) ultimately pass into
Goll’s column. Many of the fibres in the posterior root have been proved to be directly con-
nected with nerve-cells, ¢.g., in Petromyzon by Freund, and in the Proteus by Klaussner, so
that it is very doubtful if, in the higher animals, the fibres of the posterior root are directly
connected with the plexus of grey fibres as suggested by Gerlach (p. 629). ]

Neuroglia.—The connective-tissue of the spinal cord arises in part from the pia mater and
passes into the white matter, carrying with it blood-vessels, and forming septa, which separate
the nerve-fibres into bundles. [The connective-tissue of the central nervous system is so far
peculiar, that the intercellular substance is reduced to a minimum. It consists of a reticulated
connective-tissue composed of fine fibres, which form a network. Fig. 450 shows one of the
. cells, ‘‘ glia-cells,” iso-

lated. It consists of a

x ( small, granular, nucle-
ated body, with numer-

ous excessively fine,
slightly branched, stiff
processes. The pro-
cesses form a sustenta-

Fig, 450. | Fig. 451.

Fig. 450.—Isolated connective-tissue corpuscle or ‘‘glia-cell” from the human spinal cord ;
x 800. Fig. 451.—Longitudinal section of the spinal cord. a, white, , grey matter; c,
crystals of mercuric chloride. Prepared by Golgi’s mercuric chloride method ; x 80.

cular tissue for the nerve-fibres and blood-vessels, The arrangement and distribution of these
cells is best seen in sections of a cord hardened by Golgi’s method in corrosive sublimate solution
(fig. 451). In some situations, ¢e.g., the white matter of the cerebrum and cerebellum, the cells
are smaller and more angular, and the processes are often connected with the outer coat of the
blood-vessels. On the whole, the connective-tissue is much finer.in the brain than in the
cord. The central canal is surrounded with a denser layer of this tissue, known as the
‘*central ependyma,” which stains deeply with carmine, and is very like the substantia
gelatinosa in its structure (p. 628), We must distinguish from this form of connective-tissue
that special form in the grey matter to which Virchow gave the name of neuroglia, It is
epoca!) adapted to fill up the spaces left by the other elements, and without interfering with
the exchange of fluids serves to hold the elements together. It is an excessively finely granular
ground-substance in the grey matter. It is also an intercellular substance, but in the adult the
cells to which it owes its origin are no longer to be found. It is doubtful, from its chemical
nature, if it is really to be reckoned along with the connective-tissues. It seems to be rather a
tissue sui generis, belonging to the nervous system, and it is present in very small amount. ]

632 BLOOD-VESSELS OF THE SPINAL CORD.

The neuroglia is also abundant on the sides and apex of the posterior horns, where it is called
the gelatinous substance of Rolando. ft 1(EF ORE 4
[Blood-Vessels.—The spinal cord is partly supplied with blood by arteries from
the vertebrals, and partly by branches of the intercostal, lumbar, and sacral
arteries, which reach it through the intervertebral foramina, and pass to the cord
along the anterior and posterior roots. |
[Blood-Vessels.—The anterior median (or anterior spinal) (fig. 452) artery gives off
branches, which dip into the fissure of the same name, pass to. Its base, and, after perforatin
the anterior commissure, divide into two branches, one for each mass of grey matter, and eac
branch in turn splits into three, which supply part of the anterior, median, and posterior grey
matter. The arteries lying in the sulci are called arterie sulci (s) by Adamkiewicz. In the
grey matter, there is usually a special branch to Clarke’s column (c/). a he vaso-coronary arteries
ae include all those arterial branches’ which proceed
from the periphery into the white matter; the
finer branches pass only into the white matter,
but the larger into the grey substance. The largest
branch is the artery of the posterior fissure (/’p),
which passes along the posterior septum and reaches
almost to the commissure, giving branches in its
course, There isa large artery between the column
of Goll and the postero-external column, viz., the

a A.M.F.

vil
bg tana
f

Fig. 452.
Fig. 452.—Semi-diagrammatic arrangement of the arteries in the spinal cord. Spa, anterior
spinal; s, sulcine artery ; sc, sulco-commissural; an, its anastomosing branch; cl,. to
Clarke’s column ; Fy, posterior fissure; 7a, rp, branches along anterior and posterior roots;
cp, for post. cornu ; 7f, interfunicular ; Za, lm, lp, anterior, median, and posterior lateral.
Fig. 453.—Injected blood-vessels of the spinal cord. A?

interfunicular artery (if). Arteries enter along the anterior and posterior roots (7a, 7p). \ There
are also a median lateral artery (7m), and an anterior and posterior lateral (Jp, la), which
enter the lateral column. The general result is that the grey matter is much more vascular
than the white, as is shown in fig. 453. Some small vessels come from the pia and. send
branches to the white matter, and unbranched arteries to the grey matter, where they form
a capillary plexus. The blood-vessels are surrounded by perivascular lymph-spaces (His).]
[With regard to the blood-véssels supplying the cord as a whole, Moxon has pointed out that,
owing to the cord not being as long as the vertebral canal; the lower nerves have to run down
within the vertebral canal, before they emerge from the appropriate intervertebral foramina,’ As
re-enforcing arteries enter the cord along the course of these nerves, necessarily the branches
entering along the course of the lumbar and lower dorsal nerves are long, and this, together with
their small size, offers considerable resistance to the blood-stream. Hence, perhaps, the reason
why the lower part of the cord is so apt to be affected by various pathaldgtngt conditions. ]
[Functions of the Spinal Cord.—(1) It is a great conducting medium, con-
ducting impulses upwards and downwards, and within itself from side to side;
(2) the great reflex centre, or rather series of so-called centres; (3) impulses

originate within it. | ‘

é
FLECHSIG’S SYSTEMS OF CONDUCTING FIBRES. 633

~ Conducting Systems.—The whole of the longitudinal fibres of the spinal cord

may be arranged systematically in special bundles, according to their function.
[Methods.—The course fof the fibres and their division into so-called systems has been
ascertained. partly by anatomical-and embryological, partly by physiological and patho-
logical means. Apart from experimental methods, such as dividing one column of the cord
and observing the results, we have the following methods of investigation :—(1) Tiirck found
that injury or disease of certain parts of the brain was followed by a degeneration downwards,
or secondary descending degeneration of certain of the nerve-fibres connected with the seat
of injury, 7.¢., they were separated from their trophic centres and underwent degeneration.
(2) P. Schieferdecker found also, after section of the cord, that above and below the level of the
section, certain definite tracts of--white matter underwent degeneration [thus showing that
certain tracts had their trophic centre below ; this constitutes secondary ascending degenera-
tion]. [(3) Gudden’s Method.—He showed, as regards the brain, that excision of a sense-
organ in a young growing animal was followed by atrophy of the nerve-fibres and some other
parts connected with it. Thus, the optic nerve and anterior corpora quadrigemina atrophy
after excision of the eyeball in young rabbits.] (4) Embryological.—Flechsig showed that the
fibres of the cord [and the brain also] oune development became covered with myelin at
different periods, those fibres becoming medullated latest which had the longest course. In
this way he mapped out the following systems :— is
Flechsig’s Systems of Fibres.—1. In the anterior column lie (a) the uncrossed,

anterior, or direct pyramidal tract [also called the Column of Tiirck|; and ex-
ternal to it is (b) the anterior ground bundle, ~ cece : ee
or anterior radicular zone (fig. 454) [The Sa Db
direct. pyramidal tract varies in size, and it ee tag.
generally extends downwards-in the cord to
about the middle of the dorsal region, dimin-
ishing.steadily in its course; so that it would
seem that this tract contains chiefly fibres for
the arm. We do not know, exactly, how these.
fibres end, whether they cross to the opposite
side, or remain on the same side, but most prob-
ably most of them pass through the anterior
commissure to the grey matter.of the opposite
side. | ee nn rae ee a:

_ 2. In the posterior column he distinguishes re
(c) Goll’s column, or the postero-median (pos-

Fig, 454. » .
tero-internal) column; and (d) the funiculus Scheme of. the conducting paths in the

cee «jn Spinal cord at the 3rd dorsal nerve.
cuneatus, burdach’s column, or the posterior Rie blade ptember y witlen 1,

radicular zone, or the postero-eaternal column. anterior, hw, posterior, root; a,
3. In the lateral column are (e) the antero- direct, and g, crossed, pyramidal tracts;
lateral tract and (f) the lateral mixed 4%, anterior column ground: bundle ; ¢,
paths, or lateral limiting tract, (g) the lateral Gall’s columa . Lees anne ao:
or crossed pyramidal tract, and (4) the direct}, direct cerebellar tracts. eae
cerebellar tract. - | . nee
[All the impulses from the central convolutions or motor areas of the cerebrum, by
means of which voluntary movements are executed, are conducted by the pyramidal
tracts a and g (§ 365). . The fibres in these tracts descend from the central con-
volutions, z.¢., the motor areas pass through the white matter of the cerebrum, con-
verging like the rays of a fan to the internal capsule, where they lie in the knee
and anterior two-thirds of its posterior segment (the fibres for the face at the knee,
and behind this in order those for the arm and leg), they then enter the middle-third
of the crusta (fig. 502, Py), pass through the pons into the anterior pyramids of the
medulla oblongata, where the great mass crosses over to the lateral column of the
opposite side of the cord (crossed pyramidal tract), a small part descending in the
cord on the same side as the antero-median tract (direct pyramidal tract, «). The
crossed pyramida! tract lies external to the posterior half of the grey matter in the
lateral column (fig. 454, g), and it extends throughout the length of the cord. In

634 SECONDARY DEGENERATION OF TROPHIC CENTRES.

the greater part of its course, it is separated from the surface by the direct cerebellar
tract, but where the latter lies further forward, as at the third cervical segment and
lower dorsal region, its posterior surface reaches the surface, while from the last dorsal
segment, throughout the lumbar region, it comes quite to the surface, as the direct
cerebellar tract ceases at the first lumbar vertebra. The pyramidal tract diminishes |
from above downwards, and its fibres pass into the grey matter of the anterior
cornu, and in all probability they subdivide to form fine fibrils, which become con-
nected with the dense plexus of fine fibrils produced by the subdivision of the
processes of the multipolar nerve-cells. From each multipolar nerve-cell, a nerve-
fibre proceeds and passes into the anterior root. The direct cerebellar tract (h)
begins about the first lumbar nerve, and increases somewhat in thickness from
below upwards, but most of its fibres enter it at the first lumbar and lowest dorsal
nerves. It forms a thin layer on the surface of the cord. Its fibres very probably
arise in the cells of Clarke’s column. As Clarke’s column is connected with some
of the fibres of the posterior root (for the trunk of the body), it follows that this tract
connects certain parts of the posterior roots with the cerebellum. The fibres pass
up through the cord and restiform body to the cerebellum. When it is divided, it
degenerates upwards, so that it conducts impulses in a centripetal direction.] The
anterior (e) and lateral paths (/) and the anterior ground bundle (0) represent the
channels which connect the grey matter of the spinal cord and that of the medulla
oblongata ; they represent the channels for reflex effects, and they also contain
those fibres which are the direct continuation of the anterior spinal nerve-roots,
which enter the cord at different levels and penetrate into the grey matter. In e
and f there are some sensory paths. Lastly, c unites the posterior roots with the
grey nuclei of the funiculi graciles of the medulla oblongata; d connects some of
the posterior nerve-roots through the restiform body with the vermiform process of ~
the cerebellum (/Vechsig). The direction of conduction in the posterior columns,
which are continuations of some of the fibres of the posterior roots, is upwards, as
part of them degenerates upwards after section of the posterior root. Of the fibres
of each posterior root, some pass directly into the posterior horn, another part
ascends in the posterior column of the same side, and gradually as it ascends, it
comes nearer the posterior median fissure. Some of these fibres enter the grey
matter of the posterior horn at a higher level. The fibres of the posterior columns
run upwards as far as the interolivary layer and the decussation of the pyramids,
where they seem to end, or at least form connections with the nerve-cells of the
funiculi graciles [clava] and cuneati [triangular nucleus], A small part as arcuate
fibres join the restiform body, and thus the cerebellum is connected with the
posterior columns,

Further, the transverse sectional area of the direct and crossed pyramidal tracts (a and g), ~
the lateral cerebellar tract (2), and Goll’s column (c) gradually diminish from above downwards;
they serve to connect intracranial central parts with the ganglionic centres distributed along
the a cord, The anterior root bundle (b), the funiculus cuneatus (d), and the anterior
mixed lateral tracts (ec) vary in diameter at different parts of the cord, corresponding to the
number of nerve-roots. It has been concluded from this that these tracts serve to connect the
grey matter at different levels in the cord with each other, and ultimately with the medulla
oblongata, so that they do not pass directly to the higher parts of the brain (fig. 443).

Nutritive Centres of the Conducting Paths.—Tiirck observed that the
destruction of certain parts of the brain caused a secondary degeneration of certain
parts of the cord, corresponding to the parts called pyramidal tracts by Fleschig
(fig. 455). P. Schieferdecker found the same effects below where he divided the
spinal cord in a dog. Hence, it is concluded that the nutritive or trophic centre of
the pyramidal tracts lies in the cerebrum. [Section of the cord, or an injury com-
pressing the cord, besides giving rise to loss of certain functions (p. 648), results
in structural changes in certain limited areas of the cord itself. Below the section gi

SECONDARY DEGENERATION OF TROPHIC CENTRES. 635

after a time, the direct and crossed pyramidal tracts (fig. 455, 1, 1’, 2, 2°) degenerate
downwards, i.e., they undergo descending secondary degeneration, because they
are cut off from their nutritive
or trophic centres, which are
situated above in the pyramidal
cells of the motor areas of the
brain (§ 378). The trophic
centre for the fibres of the
anterior root lies in the multi-
polar nerve-cells of the anterior
cornu of the grey matter of the
cord. After section of the
spinal cord, Goll’s column and
the direct cerebellar tracts de-
generate wpwards, 1.¢, they
undergo ascending secondary
degeneration. Ifthe posterior
columns even be divided, Goll’s
column degenerates upwards
towards the medulla oblongata, Fig. 455.
and the degeneration ends in Transverse section of the spinal cord, showing the secondary
the posterior pyramidal nucleus degeneration tracts. AR, anterior, TR, posterior root ;
or clava. The same .result 1, 1’ (CPT), region of the crossed pyramidal tract ; 2, 2’
occurs if the posterior nerve- (DPT), direct pyramidal tract; PEC, postero-external
roots of the cauda equina be column ; LC, lateral column.
injured. Hence, fibres seem to pass from the posterior root into these columns, and
the nerve-cells in the clava must also have an important relation to these nerve-fibres
and the parts whence they are derived. The postero-external column remains un-
degenerated, so that there is a very sharp distinction between the two parts of the
posterior column. As Goll’s column degenerates upwards, it points to its fibres
conducting impulses in a centripetal direction, and to the nutritive centre for its
nerve-fibres being below. The trophic centre is probably in the spinal ganglion of
the posterior root. |

; [If the cord be divided above the junction of the dorsal and lumbar regions, the ©
direct cerebellar tract undergoes ascending degeneration, which extends through
the restiform body to the cerebellum. Its trophic centre is probably in the cells of
Clarke's column.] Those fibres of the spinal cord which do not degenerate after
section of the cord, especially numerous in the lateral and anterior columns
{anterior ground bundle, the anterior and lateral mixed zones of the lateral column,
and the postero-external part of the posterior column], are commissural in function,
connecting ganglionic cells with each other, and are, therefore, provided with a
trophic centre at both ends,

_ Time of Development.—With regard to the time of development of the individual systems,
Flechsig finds that the first formed paths are those between the periphery and the central grey
matter, especially the nerve-roots, i.¢., they are the first to be covered with the myelin. Then
fibres which connect the grey matter at different levels are formed—the fibres which connect
the grey matter of the cord with the cerebellum, and also the former with the tegmentum of the
cerebral peduncle. At last the fibres which connect the ganglia of the pedunculus cerebri, and
perhaps also the grey matter of the cortex cerebri with the grey matter of the cord are formed.
In cases of anencephalous foetuses, 7.¢., where the cerebrum is absent, neither the pyramidal
tracts nor the'pyramids are developed. In the brain before birth, medullated nerve-fibres are
formed in the paracentral, central, and oceipital convolutions, and in the island of Reil, and
last of all in the frontal convolutions (Z'wezek).

360. SPINAL REFLEXES.—By the term reflex. movement is meant a
movement caused by the stimulation of an afferent (sensory) nerve. The stimulus,

636 SPINAL REFLEX ACTIONS AND SPASMS.

on being applied to an afferent nerve, sets up a state of excitement (nervous
impulse) in that nerve, which state of excitement 1s transmitted or conducted in a
centripetal direction along the nerve to the centre (spinal cord: in this case) ; where
the nerve-cells represent the nerve-centre in the cord, the impulse is transferred
to the motor, efferent or centrifugal channel. Three factors, therefore, are essential
for a reflex motor act—a centripetal or afferent fibre, a transferring centre, a centri-
fugal or efferent fibre ; these together constitute a reflex are (fig. 456). Ina purely
retlex act, all voluntary activity is excluded. =~ ae ast oh ¢

Reflex movements may be divided into the three followmg groups:—

I. The simple or partial reflexes, which are characterised; by. ‘the fact that

stimulation of a sensory area discharges movement in one muscle only, or at :least

Fig. 456. 2 ‘Fig. 457.

s

Fig. 456.—Scheme of a reflex arc. S, skin; M, muscle; N, nerve-cell, with af, afferent, and
ef, efferent fibres. Fig. 457.—Section of a spinal segment, showing a unilateral and crossed
reflex act. A, anterior, and P, posterior surface; M, muscle ; S, skin ;.G, ganglion.

in one limited group of muscles. Examples :—A blow upon the knee causes.a
contraction in the quadriceps extensor cruris; contact with the conjunctiva causes
closure of the eyelids. In the former case, the afferent channels arise in the tendon
of the quadriceps, and the efferent channels lie in the nerve which supplies. the
quadriceps ; in the latter case, the afferent nerve is the 5th and the efferent the, 7th
cranial nerve. In the former case the centre is in the lumbar region of the cord ;
in the latter, in the grey matter of the medulla oblongata. ' ult

II. The extensive inco-ordinate reflexes, or reflex spasms.—These movements
occur in the form of clonic or tetanic contractions; individual. groups of muscles,
or all the muscles of the body may be implicated.. Causes :—A reflex spasm
depends upon a double cause—(a). Either the grey matter or the spinal. cord is in a
condition of exalted excitability, so that the nervous impulse, after having reached
the centre, is easily transferred to the neighbouring centres. This excessive
excitability is produced by certain poisons, more especially by strychnin, brucia,
caffein, atropin, nicotin, carbolic acid, &c. The slightest, touch applied to an
animal poisoned with strychnin is sufficient to throw the animal at once into spasms.
Pathological conditions may cause a similar result; thus, there is excessive
excitability in hydrophobia and tetanus. On the other hand, the central organ
may be in such a condition that extensive reflexes cannot take place ; thus, in the
condition of apnoea, the spasms that occur in poisoning with strychnin do not take
place (J. Rosenthal and Leube), and the same result is brought about by passive
artificial respiratory movements (§ 361, 3). ‘The performance of other passive
periodic movements in various parts of the body also produces a similar condition
(Buchheim). If the spinal cord be cooled very considerably, reflex spasms may not
occur (Kunde). (b) Extensive reflex movements may also take place when the
discharging stimulus is very strong. Examples of this condition occur in man,
thus—intense neuralgia may be accompanied by extensive spasmodic movements. —

REFLEX SPASMS AND SUMMATION OF STIMULI. 637

[Fig. 458 shows the mechanism of simple and complex reflex movements. Suppose the skin
to be stimulated at P, an impulse is sent to A and from it to a muscle 1 on the same side, result-
ing in a unilateral simple reflex movement—the resistance being less in this direction than in
the.other channels. If the impulse be stronger, or the transverse resistance in the cord dimin-
ished, the impulse may pass to B, thence to 2, resulting in a symmetrical reflex movement on
both sides. But if a very strong impulse reach the cord, or if the excitability of the grey
matter be increased, ¢.g., by strychnin, the resistance to the diffusion of the impulse is dimin-
ished, and it passes upward to C and D, resulting in more complex movements—-thus there is
irradiation—or it may even affect the centres in the medulla oblongata, E, giving rise to
general convulsive movements. ]

General spasms usually manifest themselves as “extensor tetanus,” because the extensors
overcome the flexor muscles. Nerves which arise from the medulla oblongata may be excited
through the stimulation of distant afferent nerves, without general spasms being produced.

Strychnin is the most powerful reflex-producing poison we possess, and it acts upon the grey
matter of the spinal cord. [An animal poisoned
with strychnin exhibits tetanic spasms on the
application of the slightest stimulus. All the
inuscles become rigid, but the extensors overcome
the flexors.] If the heart of a frog be ligatured,
and the poison afterwards applied directly to the
spinal cord, reflex spasms are produced, proving
that strychnin acts upon the spinal cord. During
the spasm the heart is arrested in diastole, owing
to the stimulation of the vagus, while the arterial
blood-pressure is greatly increased, owing to stimu-
lation of the central vaso-motor centres of the me-
dulla oblongata and spinal cord. Mammals may
die from asphyxia during the attack ; and, after
large doses, death may occur, owing to paralysis
of the spinal cord, due to the frequently recurring
spasms. Fowls are unaffected by comparatively
large doses. [We can prove that strychnin does
not produce spasms by acting on the brain,
muscle, or nerve. Destroy the brain of a frog,
divide one sciatic nerve high up, and inject a small
dose of strychnin into the dorsal lymph-sac ; in
a few minutes all the muscles of the body, except
those supplied by the divided nerve, will be in
spasms, showing that, although the poisoned blood
has circulated in the nerves and muscles of the
leg, it does not act on them. Destroy the spinal
cord, and the spasms cease at once. ] ;

Summation of Stimuli.—By this term
is meant, that a single weak stimulus, . Fig. 458.
which in itself is incapable of discharging Scheme of mode of propagation of reflex
a reflex act, may, if repeated sufficiently ea as date ao as ; 2a B, C, D, Ne
often, produce this act. The single im-. “ °™™ SPA core; ia Re heii
pulses are conducted to the spinal cord, in which the process of ‘summation ”
takes place. According to J. Rosenthal, 3 feeble stimuli per second are capable
of ‘producing this effect, although 16 stimuli per second are most effective. On
increasing the number of stimuli per second, no further increase of the reflex act is
possible. Other observers (Stirling, Ward) have found that stimuli, such as. in-
duction shocks, are active within much wider limits; ¢g., from 0°05 to 0°4 second
interval. W. Stirling has shown it to be extremely probable that all reflex acts
are due to the repetition of impulses in the nerve-centres.
- [Strychnin interferes with the summation of stimuli, but the reflex excitability is so greatly
éxalted that a minimal stimulus is at the same time a maximal one.] _—- —- :
--Pfliiger’s Law of Reflex Actions. —(1).The reflex.movement: occurs on the same side on which
the sensory nerve is stimulated ; while only those muscles contract whose nerves arise from the
same segment of the spinal cord. (2) If the reflex occur on the other side, only the corre-
sponding muscles contract. (3) If the contractions be unequal upon the two sides, then the

most vigorous contractions always occur on the side which is stimulated. (4) If the reflex
excitement extend to other motor nerves, those nerves are always affected which lie in the

638 EFFECT OF DRUGS ON REFLEX ACTION.

direction of the medulla oblongata. Lastly, all the muscles of the body may be thrown into

contraction. : cuit
Crossed Reflexes. —There are exceptions to these rules, If the region of the eye be irritated

in a frog whose cerebrum is removed, there is frequently a reflex contraction in the hind limb
of the oppasite side (Luchsinger, Langendorff). In beheaded tritons and tortoises, and in deeply
safuotionl dogs and cats, tickling one fore limb is frequently followed by a movement of the

This phenomenon is called a ‘‘ crossed reflex ”

hind limb of the opposite side (Luchsinger). : é
(fig. 457). Ifthe spinal cord be divided along the middle line throughout its entire extent,
then of course the reflexes are confined to one side only (Schiff).

III. Extensive co-ordinated reflexes are due to stimulation of a sensory nerve,
causing the discharge of complicated reflex movements in whole groups of different
muscles, the movements being ‘‘purposive ” in character, 2¢., as if they were
intended for a particular purpose.

Methods.—The experiments are made upon cold-blooded animals (decapitated or pithed frogs,
tortoises, or eels) or upon mammals. In the latter, artificial respiration is kept up, and the
four arteries going to the head are ligatured, in order to eliminate the action of the brain (Sig,
Mayer, Luchsinger). The reflexes of the lower part of the spinal cord may be studied on animals
(or men), in cases where the spinal cord is divided transversely in the upper dorsal region, In
such cases, some time must elapse in order that the primary effect of the lesion (the so-called
shock), which usually causes a diminution of the reflexes, may pass off. Very young mammals
exhibit reflexes for a considerable time after they are beheaded.

Examples:—1. The protective movements of pithed or decapitated frogs. [If
a drop of a dilute acid be applied to the skin of such a frog, immediately it strives
to get rid of the offending body, and it generally succeeds in doing so.] Similarly,
it kicks against any fixed body pushed against it. These movements are so
purposive in their character, and the actions of groups of muscles are so adjusted to
perform a particular act, that Pfliiger regarded them as directed by, and due to
“consciousness of the spinal cord.” If a flame be applied to the side or part of the
body of an eel, the body is moved away from the flame. The tail of a decapitated
triton, tortoise, newt, eel, or snake is directed towards a gentle stimulus, but if a
violent stimulus is used, it is directed away from it (Luchsinger).

2. Goltz’s Croaking Experiment.—A pithed (male) frog, @e¢., one with its
cerebral lobes alone removed (or one with its eyes or ears destroyed—Langendorf),
croaks every time the skin of its back or flanksis gently stroked. [Some male
frogs, when held up by the finger and thumb immediately behind the fore legs,
croak every time gentle pressure is made on their flank. ]

3. Goltz’s ‘Embrace Experiment.”—During the breeding season in spring, the
part of the body of the male frog between the skull and the fourth vertebra,
embraces every rigid object, which is brought into contact with, and gently
stimulates, the skin over the sternum.

In the intact animal, the exciting stimulus lies in the degree of filling of the male seminal organ
(Tarchanof). The reflex ceases at once on gently stimulating the optic lobes (Alberton).

4. In mammals (dogs), the following reflex acts are performed by the posterior
part of the spinal cord, even after it is separated from the rest of the cord :—
Scratching with the hind feet a part of the skin which has been tickled (just as in
intact animals); the movements necessary for emptying the bladder and for
defeecation, as well as those necessary for erection ; the movements necessary for
parturition (Goltz, Freusberg and Gergens). Co-ordinated movements do not, as a
rule, occur simultaneously in portions of the spinal cord lying widely apart after
removal of the medulla oblongata. According to Ludwig and Owsjannikow, the
medulla oblongata perhaps contains a reflex organ of a higher order, which forms,
as it were, a centre for combining, through the medium of the nerve-fibres, the
various reflex provinces in the spinal cord. * ait}

5, Co-ordinated reflexes may occur in man during sleep, and during pathological
comatose conditions. ne

Most of the movements which we perform while we are awake, and which we execute uncon-

a

ha?

—
~~ --<-

REFLEX TIME AND INHIBITION OF REFLEXES. 639

sciously—or even when our psychical activities are concentrated upon some other object—really
belong to the category of co-ordinated reflexes. Many complicated motor acts must first be
learned—e. g., dancing, skating, riding, walking—before unconscious harmonious co-ordinated
reflexes can again be discharged. The co- ordinated reflex movements of coughing, sneezing,
and vomiting depend upon the spinal cord, together with the medulla oblongata. ;

The following facts are also important :—

1. Reflexes are more easily and more completely discharged, when the specific
end-organ of the afferent nerve is stimulated, than when the trunk of the nerve is
stimulated in its course (Marshall Hall, 1837). [Thus, by gently tickling the
skin, it is easy to discharge a reflex act, while it requires a strong stimulus to be
applied to an exposed sensory nerve in order to do so. |

2. A stronger stimulus is required to discharge a reflex movement than for the
direct stimulation of motor nerves.

3. A movement produced reflexly is of shorter duration than the corresponding
movement executed voluntarily. Further, the occurrence of the movement after
the moment of stimulation is distinctly delayed. In the frog, a period nearly
twelve times as long elapses before the occurrence of the contraction, than is
occupied in the transmission of the impulse in the sensory and motor nerves
(Helmholtz, 1854). Thus, the spinal cord offers resistance to the transmission of
impulses through it.

The term ‘‘reflex time” is applied to the time necessary for transferring the impulse from
the afferent fibre to the nerve-cells of the cord, and from them to the efferent fibre. In the
frog it is equal to 0°008 to 0°015 second. The time, however, is increased by almost one-third,
if the impulse pass to the other side of the cord, or if it pass along the cord, ¢.g., from the
sensory nerves of the anterior extremity to the motor roots of the posterior limb. Heat dimi-
nishes the reflex time and increases the reflex excitability. Lowering the temperature (winter
frogs), as well as the reflex-exciting poisons already mentioned, lengthens the reflex time, whilst
the reflex excitability is simultaneously increased. Conversely, the reflex time diminishes as
the strength of the stimulus increases, and it may even become of minimal duration (J,
Rosenthal). The reflex time is determined by ascertaining the moment at which the sensory
nerve is stimulated, and the subsequent contraction occurs. Deduct from this the time of
latent stimulation (§ 298, I.), and the time necessary for the conduction of the impulse (§ 298)
in the afferent and efferent nerves (v. Helmholtz, J. Rosenthal, Exner, Wundt).

[Influence of Poisons. —The latent period and reflex time are influenced by a large number
of conditions. Ina research as yet unpublished, W. Stirling finds that the latent period may
remain nearly constant in a pithed frog for nearly two days, when tested by Tiirck’s method.
Sodic chloride does not influence the time, nor does sodic bromide or iodide. Potassic chloride,
however, lengthens it enormously, or even abolishes reflex action after a very short time, and
so do potassic bromide, ammonium chloride and bromide, chloral and croton-chloral. The
lithia salts also lengthen the reflex time, or abolish the reflex act after a time. ]

361. INHIBITION OF THE REFLEXES.—Within the ‘body there are
mechanisms which can suppress or wmhibit the discharge of reflexes, and they may
therefore be termed mechanisms inhibiting the reflexes. These are :—

1. Voluntary Inhibition.—Reflexes may be inhibited voluntarily, both in the
region of the spinal cord and brain. Examples :—Keeping the eyelids open when
the eyeball is touched ; arrest of movement when the skin is tickled. We must
cbserve, however, that the suppression of reflexes is possible only up to a certain
point. . If the stimulus be strong, and repeated with sufficient frequency, the reflex
impulse ultimately overcomes the voluntary effort. It is impossible to suppress
those reflex movements which cannot at any time be performed voluntarily. Thus,
erection, ejaculation, parturition, and the movements of the iris, are neither direct
voluntary acts, nor can they, when they are excited reflexly, be suppressed by the
will.

2. Setschenow’s inhibitory centre is another cerebral apparatus, which in the
frog is placed in the optic lobes. If the optic lobes be separated from the rest of
the brain and spinal cord, by a section made below it, the reflex excitability is
increased. If the lower divided surface of the optic lobes be stimulated with a

640 EXAMPLES AND NATURE OF INHIBITION.

crystal of common salt or blood, the reflex movements are suppressed, The same
results obtain when only one side is operated on. Similar organs are supposed to
be present in the corpora quadrigemina and medulla oblongata of the higher verte-
brates. From 1 and 2 we may explain why reflex movements occur more regularly
and more readily after separation of the brain from the spinal cord. _

[Quinine greatly diminishes the reflex excitability in the frog, but if the medulla oblongata
be divided, the reflex excitability of the cord is restored. The depression is ascribed by Chaperon
to the action of the quinine on Setschenow’s centres. }

3. Strong stimulation of a sensory nerve inhibits reflex movements. The
reflex does not take place if an afferent nerve be stimulated very powerfully (Goltz,
Lewisson). Examples :—Suppressing a sneeze by friction of the nose, [compressing
the skin of the nose over the exit of the nasal nerve]; suppression of the move-
ments produced by tickling, by biting the tongue. Very violent stimulation may
even suppress the co-ordinated reflex movements usually controlled by voluntary
impulses. Violent pain of the abdominal organs (intestine, uterus, kidneys, bladder,
or liver) may prevent a person from walking or even from standing. To the same |
category belongs the fact that persons fall down when internal organs richly |
supplied with nerves are injured, there being neither injury of the motor nerves nor |
loss of blood to account for the phenomenon. Excitement of the central organs
through other centripetal channels (nerves of special sense, and those of the
generative organs) diminishes the reflexes in other channels. |

4. It is important to note that in the suppression of reflexes, antagonistic muscles are often
thrown into action, whether voluntarily or by the stimulation of sensory nerves, 7.¢., reflexly.
In some cases, in order to cause suppression of the reflex, it appears to be sufficient to direct our
attention to the execution of such a complicated reflex-act. Thus, some persons cannot sneeze
when they think intently upon this act itself (Darwin). The voluntary impulse rapidly reaches
the reflex centre, and begins to influence it so that the normal course of the reflex stimulation,
due to an impulse from the periphery, is interfered with (Schlésser).

5. Poisons.—Chloroform diminishes the reflex excitability by acting upon the
centre, and a similar effect is produced by picrotoxin, morphia, narcotin, thebain,
aconitin, quinine, hydrocyanic acid. [W. Stirling finds that chloral, potassic
bromide and chloride, ammonium chloride, but not sodium chloride, greatly diminish
the reflex excitability. .Nicotin increases it in frogs (Freusberg).|.

A constant current of electricity passed longitudinally through the cord
diminishes the reflexes (Ranke), especially if the direction of the current is from
above downwards (Legros and Onimus, Uspensky), =

[Some drugs affect the reflex excitability directly by acting on the spinal cord, ¢.g.,
methylconine, but other drugs may produce the same result indirectly by affecting the heart
and the blood-supply to the cord. If the abdominal aorta of a rabbit be compressed for a few
sac neg cut off the supply of blood to the cord and lower limbs, temporary paraplegia is
produced.] - : Sree ee te

If frogs be asphyxiated in air deprived of all-its O, the brain and spinal cord become
completely unexcitable, and can no longer discharge reflex acts; The motor nerves and the
muscles, however, suffer very. little, and may retain their excitability. for many days (Aubert). .

[Nature of Inhibition.—The forpening. wiew assumes the existence of inhibitory centres, but
it is important to point out that-it has been attempted to explain this phenomenon: without
postulating the existence of inhibitory centres. During inhibition the fiinetion- of an organ is
restrained—during paralysis it is abolished, sa that there is a sharp distinction’ between the two
conditions, The analogy between inhibitory phenomena and’ the.effects of interference of
waves of light or sound has been pointed out by Bernard and Romanes, while Lauder Branton
has tried to explain the question on a physical basis, indicating that inhibition is not dependent
on-the existence of special inhibitory centres, but that stimulation and inhibition are‘di E.
phases of excitement, the two terms being relative conditions depending on the length of the
path along which the impulse has to travel and the rate of its transmission... _Bruntom points
out that the known facts are more consistent with an hypothesis of the interference of way
one with another, than with the supposition that there are inhibitory centres for every s0-
inhibitory act in the body. In discussing this question great regard-must be had “to the action
of the vagus on the heart (§ 369).}° 5. ° |. . yiv ih. ! }] . Deaaspae aes

_—

TURCK’S METHOD—THEORY OF REFLEX ACTION. O41

Tiirck’s method of testing the reflex excitability of a frog is the following :—A
frog is pithed, and after it has recovered from the shock, its foot is dipped into
dilute sulphuric acid [2 per 1000]. The time which elapses between the leg being
dipped in and the moment it is withdrawn is noted. [The time may be estimated
by means of a metronome, or the movements may be inscribed upon a recording
surface. The time which elapses is known as the “ period of latent stimulation.” |

This time is greatly prolonged after the optic lobes have been stimulated with a crystal of
common salt or blood, or after the stimulation of a sensory nerve.

Setschenow distinguished tactile reflexes, which are discharged by stimulation of the nerves
of touch ; and pathic, which are due to stimulation of sensory (pain-conducting) fibres. He and
Paschutin suppose that the tactile reflexes are suppressed by voluntary impulses, and the pathic
by the centre in the optic lobes.

Theory of Reflex Movements.—The following theory has been propounded to account for the
phenomena already described :—It is assumed that the afferent fibre within the grey matter of
the spinal cord joins one or more nerve-cells, and thus is placed in communication in all direc-
tions with the network of fibres in the grey substance. Any impulse reaching the grey matter
of the cord has to overcome considerable resistance. The least resistance lies in the direction
of those efferent fibres which emerge in the same plane aud upon the same side as the entering
fibre. Thus, the feeblest stimulus gives rise to a simple reflex, which generally is merely a
simple protective movement for the part of the skin which is stimulated. Still greater resist-
ance is opposed in the direction of other motor ganglia. If the reflex impulse is to pass to
these ganglia, either the discharging st?mudus must be considerably increased, or the resistance
within the connections of the ganglia of the grey matter must be diminished. The latter
condition is produced by the action of the above-named poisons, as well as during general
increased nervous excitability (hysteria, nervousness). Thus, extensive reflex spasms may be
produced either by increasing the stimulus, or by diminishing the resistance to conduction in
the spinal cord. Those conditions which render the occurrence of reflexes more difficult, or
abolish them altogether, must be regarded as increasing the resistance in the reflex arc in the
cord. The action of the reflex inhibitory mechanism may be viewed in a similar manner.

The fibres of the reflex arc must have a connection with the reflex inhibitory paths; we must
assume that equally by the reflex inhibitory stimulation resistance is introduced into the reflex
arc. The explanation of extensive co-ordinated movements is accompanied with difficulties. It
is assumed, that by use and also by heredity, those ganglionic cells which are the first to receive
the impulse are placed in the path of least resistance in connection with those cells which
transfer the impulse to the groups of muscles, whose contraction, resulting in a co-ordinated
purposive movement, prevents the body or the limb trom being affected by any injurious
influences.

Pathological.—Anomalies of reflex activity afford an important field to the physician in the
investigation of nervous diseases. Enfeeblement, or even complete abolition of the reflexes
may occur :—(1) Owing to diminished sensibility or complete insensibility of the afferent fibres ;
(2) in analogous affections of the central organ; (3) or, lastly, of the efferent fibres. Where
there is general depression of the nervous activity (as after shocks, compression or inflammation
of the central nervous organs; in asphyxia, in deep coma, and in consequence of the action of
many poisons), the reflexes may be greatly diminished or even abolished.

[Reflexes.—The physician, by studying the condition of the reflexes, can form an
idea as to the condition of practically every inch of the spinal cord. There are
three groups of reflexes, (a) the superficial, (4) the deep or tendon, (c) the organic
reflexes. | |

[The superficial or skin reflexes are excited by stimulating the skin, ¢.g., by
tickling, pricking, scratching, &c. We can obtain a series of reflexes from below
as far up as the lower part of the cervical region. The plantar reflex is obtained
by tickling the soles of the feet, when the leg on that side, or, it may be, both legs
are drawn up. It is always present in health, and its centre is in the lumbar
enlargement of the cord. The cremasteric reflex is well marked in boys, and is
easily produced by exciting the skin on the inner side of the thigh, when the
testicle on that side is retracted. The gluteal reflex consists in a contraction of
the gluteal muscles, when the skin over the buttock is stimulated. The abdominal
reflex consists in a similar contraction of the abdominal muscles, when the skin
over the abdomen in the mammary line is stimulated. The epigastric reflex is
obtained by stimulating the skin in front between the fourth and sixth ribs. The
interscapular reflex results in a contraction of the muscles attached to the scapula,

| , 28

642 THE SUPERFICIAL REFLEXES..

when the skin between the scapule is stimulated. Its centre corresponds to the

lower cervical and upper dorsal region. |
[The following table, after Gowers, shows the relation of each reflex to the spinal segment or

segments on which it depends:—

Cervical, * . ; : 6) Lumbar, . , : 3 i aig
yg pinterseapular, | gf Knee Refler.
Dore: , , : t ; ; ‘ : \ Gluteal.
as : a‘ : oa Rot ; - om : : ; pee e
a 6 pigastric. acral, P ‘ &
' A eas Ba erm Se ea 218 =} Plantar,
ss 8 ) nee : : : 3) N58 | Vesical.
Gs 9 | ae : : 4 Rectal.
a 10 } Abdominal. ow : ; ; 5 Sexual.]
99 i 1
12)

9?

Another important diagnostic reflex is the ‘‘ abdominal reflex,” which consists
in this, that when the skin of the abdomen is stroked, e.g., with the handle of a
percussion-hammer, the abdominal muscles contract. When this reflex is absent
on both sides in a cerebral affection, it indicates a diffuse disease of the brain ; its
absence on one side indicates a local affection of the opposite half of the brain.
The cremasteric, conjunctival, mammillary, pupillary, and nasal reflexes may also
be specially investigated. In hemiplegia complicated with cerebral lesions, the
reflexes on the paralysed side are diminished, whilst not unfrequently the patellar
reflex may be increased. In extensive cerebral affections accompanied by coma the
reflexes are absent on both sides, including of course those of the anus and bladder
(O. Rosenbach).

[ Horsley finds that in the deepest narcosis produced by nitrous oxide gas the superficial reflexes
(e.g., plantar, conjunctival) are abolished, while the deep (knee-jerk) remain. Anemia of the
lumbar enlargement (compression of the abdominal aorta) causes disappearances of both reflexes
(Prévost). Chloroform and asphyxia abolish the deep as well as the superficial reflexes. Horsley
regards the so-called deep reflex or knee-jerk not as depending on a centre in the cord, but the
ee aaa of the rectus femoris is due to local irritation of the muscle from sudden elonga-
tion.

Deep or Tendon Reflexes.—Under pathological conditions, special attention is
directed to the so-called tendon reflexes, which depend upon the fact, that a blow
upon a tendon (e.g., the quadriceps femoris, tendo Achilles, &c.) discharges a
contraction of the corresponding muscle (Westphal, Erb, 1875). The patellar
tendon reflex (also called “knee phenomenon”) or simply ‘“ knee-reflex,” or “ knee-
jerk,” is invariably absent in cases of ataxic tabes dorsalis, while in spastic spinal
paralysis it is abnormally strong and extensive (#7rb). [The “knee-jerk” is
elicited by percussing the ligamentum patelle, and is due to a single spasm of the
rectus. The latent period is 0-03 to 0°04 second, and it is argued by Waller and
others that it is doubtful if this tendon-reflex is subserved by a spinal nervous arc,
while admitting the effect of the spinal cord in modifying the response of the
muscle.] Section of the motor nerves abolishes the patellar phenomenon in rabbits
(Schultz), and so does section of the cord opposite the 5th and 6th lumbar vertebrae
(T'schirjew). Landois finds that in his own person the contraction occurs 0°048
second after the blow upon the ligamentum patella. According to’ Waller, the
patellar reflex and the tendo Achilles reflex occur 0°03 to 0°04 second, and
according to Eulenburg, 0-032 second after the blow. According to Westphal, these
phenomena are not simple reflex processes, but complex conditions intimately
dependent upon the muscle tonus, so that when the tonus of the quadriceps
femoris is diminished, the phenomenon is abolished. In order that the phenomenon
may take place, it is necessary that the outer part of the posterior column of the
spinal cord remain intact (Westphal). [The knee-jerk can be increased or reinforced _

PATELLAR REFLEX AND ANKLE CLONUS. 643

by volitional acts directed to other parts of the body, e.g., by exercising voluntary
pressure with the hand (Jendrdssik).| [A “jaw-jerk” is obtained by suddenly
depressing the lower jaw (Gowers, Beevor, and De Watteville), and the last ob-
server finds that the latent period is 0°02 second, and if this be the case, it is an
argument against these so-called ‘‘ tendon reflexes ” being true reflexes, and that they
are direct contractions of the muscles due to sudden stimulation by extension. |

{Method.—The knee-jerk is easily elicited by striking the patellar tendon with
the edge of the hand or a percussion-hammer when the leg is semi-flexed, as when
the legs are hanging over the edge of a table or when one leg is crossed over the
other. It is almost invariably present in health, but it becomes greatly exaggerated
in descending degeneration of the lateral columns and lateral sclerosis. |

{Ankle clonus is another tendon reflex, and it is never presentin health. If the
leg be nearly extended, and pressure made upon the sole of the foot so as suddenly
to flex the foot at the ankle, a series of (5 to 7 per second) rhythmical contractions
of the muscles of the calf takes place. Gowers describes a modification elicited by
tapping the muscles of the front of the leg, the ‘‘front-tap contraction.” Ankle
clonus is excessive in sclerosis of the lateral columns and spastic paralysis. |

[In ‘‘ankle clonus” excited by sudden passive flexion of the foot, there is a multiple spasm
of the gastrocnemius. Here also the latent period is about 0°03 to 0°04 second, and the rhythm
8 to 10 per second. This short latent period has led some observers to doubt the essentially
reflex nature of this act.] ;

When we are about to sleep (§ 374), there is first of all a temporary increase of the reflexes ;
in the first sleep the reflexes are diminished, and the pupils are contracted. In deep sleep the
abdominal, cremasteric, and patellar reflexes are absent ; while tickling the soles of the feet and

the nose onlyacts when the stimulus is of a certain intensity. In narcosis, ¢.g., chloroform or
morphia, the abdominal, then the conjunctival and patellar reflexes disappear; lastly, the pupils

_ contract (O. Rosenbach).

Abnormal increase of the reflex activity usually indicates an increase of the excitability of
the reflex centre, although an abnormal sensibility of the afferent nerve may be the cause. As
the harmonious equilibrium of the voluntary movements is largely dependent upon and regulated
by the reflexes, it is evident that in affections of the spinal cord, there are frequent disturbances
of the voluntary movements, ¢.g., the characteristic disturbance of motion in attempting to
walk, and in grasping movements exhibited by persons suffering from ataxic tabes dorsalis [or,
as it is more generally called, locomotor ataxia]. ae

[The organic reflexes include a consideration of the acts of micturition, erection,
ejaculation, defecation, and those connected with the motor and secretory digestive
processes, respiration, and circulation. | 3

362. CENTRES IN THE SPINAL CORD.—Centres capable of being
excited reflexly, and which can bring about the discharge of certain complicated,
yet well-co-ordinated, motor acts exist in various parts of the spinal cord. They
still retain their activity after the spinal cord is separated from the medulla
oblongata ; further, those centres lying in the lower part of the spinal cord still
retain their activity after being separated from the higher centres, but in the normal
intact body, they are subjected to the control of higher reflex centres in the medulla
oblongata. Hence, we may speak of them as subordinate spinal centres. The
cerebrum also, partly by the production of perceptions, and partly as the organ of
volition, can excite or suppress the action of certain of these subordinate spinal
centres. (For the significance of the term “Centre,” see p. 625. ] :

1. The cilio-spinal centre connected with the dilatation of the pupil lies in
the lower cervical part of the cord, and extends downwards to the region of the Ist
to the 3rd dorsal vertebra. It is excited by diminution of light ; both pupils always
react simultaneously, when one retina is shaded. Unilateral extirpation of this part
of the spinal cord causes contraction of the pupil on the same side. The motor
fibres pass out by the anterior roots of the two lower cervical and two upper dorsal
nerves, into the cervical sympathetic (§ 392). Even the idea of darkness may some-
times, though rarely, cause dilatation of the pupil (Budge).

644 CENTRES IN THE SPINAL CORD.

In goats and cats, this centre, even after being separated from the medulla oblongata, can be
excited directly by dyspneic blood, and also reflexly by the stimulation of sensory nerves, ¢.g.,
the median, especially when the reflex excitability of the cord is increased by the action of
strychnin or atropin (Luchsinger). For the dilator centre in the medulla oblongata, see

§ 367, 8.

2. The ano-spinal centre, or centre controlling the act of defecation. The
afferent nerves lie in the hemorrhoidal and inferior mesenteric plexuses, the centre
at the 5th (dog) or 6th to 7th (rabbit) lumbar vertebra; the efferent fibres arise
from the pudendal plexus and pass to the sphincter muscles. For the relation of
this centre to the cerebrum see § 160. After section of the spinal cord [in dogs],
Goltz observed that the sphincter contracted rhythmically upon the finger intro-
duced into the anus; the co-ordinated activity of the centre therefore would seem
to be possible only when the centre remains in connection with the brain.

3. The vesico-spinal centre for regulating micturition, or Budge’s vesico-spinal
centre. The centre for the sphincter muscle lies at the 5th (dog) or the 7th (rabbit)
lumbar vertebra, and that for the muscles of the bladder somewhat higher. The
centre acts only in a properly co-ordinated way in connection with the brain
(§ 280).

; 4. the erection centre also lies in the lumbar region (§ 436). The afferent
nerves are the sensory nerves of the penis; the efferent nerves for the deep artery
of the penis are the vaso-dilator nerves, arising from the lst to 3rd sacral nerves,
or Eckhard’s nervi erigentes—while the motor nerves for the ischio-cavernosus
and deep transverse perineal muscles arise from the 3rd to 4th sacral nerves (§ 356).
The latter may also be excited voluntarily, the former also partly by the brain, by
directing the attention to the sexual activity. Eckhard observed erection to take
place after stimulation of the higher regions of the spinal cord, as well as of the
pons and crura cerebri.

5. The ejaculation centre. The afferent nerve is the dorsal of the penis, the
centre (Budge’s genito-spinal centre) lies at the 4th lumbar vertebra (rabbit) ; the
motor fibres of the vas deferens arise from the 4th and 5th lumbar nerves, which
pass into the sympathetic, and from thence to the vas deferens. The motor fibres
for the bulbo-cavernosus muscle, which ejects the semen from the bulb of the
urethra, lie in the 3rd and 4th sacral nerves (perineal).

6. The parturition centre lies at the 1st and 2nd lumbar vertebree (§ 453); the
afferent fibres come from the uterine plexus, to which also the motor fibres proceed
(Korner). Goltz and Freusberg observed that a bitch became pregnant after its
spinal cord was divided at the 1st lumbar vertebra.

7. Vaso-motor Centres.—Both vaso-motor and vaso-dilator centres are dis-
tributed throughout the whole spinal axis. To them belongs the centre for the
spleen, which in the dog is opposite the 1st to 4th cervical vertebrae (Bulgak). They
can be excited reflexly, but they are also controlled by the dominating centre in
asin. oblongata (§ 371). Psychical disturbance (cerebrum) influences them
(3

[8. Perhaps there are vaso-dilator centres (§ 372).] :
( oe 8) sweat centre is perhaps distributed similarly to the vaso-motor centre

The reflex movements discharged from these centres are orderly co-ordinated reflexes, and
may thus be compared to the orderly reflexes of the trunk and extremities, ; wel
Muscle Tonus.—Formerly automatic functions were ascribed to the spinal cord, one of these
being that it caused a moderate active tension of the muscles—a condition that was term
muscle tone, or tonus. The existence of tonus in a striped muscle was thought to be proved by
the fact that, when such a muscle was divided, its bi retracted. This is due merely to the
fact that all the muscles are stretched slightly beyond their normal length (§ 301). Even
paraiyecc muscles, which have lost their muscular. tone, show the same phenomenon.
ormerly, the stronger contraction of certain muscles, after paralysis of their antagonists, and
the retraction of the facial muscles to the sound side, after paralysis of the facial nerve, were —

EXCITABILITY OF THE SPINAL CORD. 645

also regarded as due to tonus. This result is due to the fact that, during the activity of the
intact muscles, the other ones have not sufficient power to restore the parts to their normal
median position. The following experiment of Auerbach and Heidenhain is against the
assumption of a tonic contraction :—If the muscles of the leg of a decapitated frog be stretched,
it is found that they do not elongate after section of the sciatic nerve, or-after it is paralysed by
. touching it with ammonia or carbolic acid.

Reflex Tonus.—If, however, a decapitated frog be suspended in an abnormal position, we
observe, after section of the sciatic nerve, or the posterior nerve-roots on one side, that the
leg on that side hangs limp, while the leg of the sound side is slightly retracted. The sensory
nerves of the latter are slightly and continually stimulated by the weight of the limb, so that
a slight reflex retraction of the leg takes place, which disappears as soon as the sensory nerves
of the leg are divided. If we choose to call this slight retraction tonus, then it is a reflex tonus
(Brondgeest). (See the experiments of Harless, C. Ludwig, and Cyon—§ 355.)

363. EXCITABILITY OF THE SPINAL CORD.—Even at the present
time observers are by no means agreed whether the spinal cord, like peripheral
nerves, is excitable, or whether it is distinguished by the remarkable peculiarity that
most of its conducting paths and ganglia do not react to direct electrical and
mechanical stimuli.

It is contended by some observers that if stimuli be cautiously applied either to white or
grey matter, there is neither movement nor sensation (Van Deen (1841), Brown-Séquard). Care
must be taken not to stimulate the roots of the spinal nerves, as these respond at once to
stimuli, and thus may give rise to movements or sensations. As the spinal cord conducts to
the brain impulses communicated to it from the stimulated posterior roots, but does not itself
respond to stimuli which produce sensations, Schiff has applied to it the term ‘‘ esthesodic.”’
Further, as the cord can conduct both voluntary and reflex motor impulses, without, however,
itself being affected by motor impulses applied to it directly, he calls it ‘‘ kinesodic.”

Schiff’s views are as follows :—

1. In the posterior columns the sensory root-fibres of the posterior root
which traverse these columns give rise to painful impressions, but the proper paths
of the posterior columns themselves do not do so. The proof that stimulation of
the posterior column produces sensory impressions, he finds in the fact that dilata-
tion of the pupil occurred with every stimulation (§ 292). Removal of the posterior
column produces anesthesia (loss of tactile sensation). Algesia [or the sensation of
pain] remains intact, although at first there may even be hyperalgesia.

2. The anterior columns are non-excitable, both for striped and non-striped
muscle, as long as the stimuli are applied only to the proper paths of this column.
But movements may follow, either when the anterior nerve-roots are stimulated, or
when, by the escape of the current, the posterior columns are affected, whereby
reflex movements are produced.

According to Schiff, therefore, all the phenomena of irritation, which occur when an uninjured
cord is stimulated (spasms, contracture), are caused either by simultaneous stimulation of the
anterior roots, or are reflexes from the posterior columns alone, or simultaneously from the
posterior columns and the posterior roots. Diseases affecting only the anterior and lateral
columns alone never produce symptoms of irritation, but always of paralysis. In complete
anesthesia and apncea, every form of stimulus is quite inactive. According to Schiff’s view, all
centres, both spinal and cerebral, are inexcitable by artificial means.

Direct Excitability.—Many observers, however, oppose these views, and contend that the
spinal cord is excitable to direct stimulation. Fick observed movements to take place when
he stimulated the white columns of the cord of a frog, isolated for a long distance so as to avoid
the escape of the stimulating currents. Sirotinin, also, who stimulated the transverse section
of the frog’s cord from point to point, obtained contraction of the muscles both by mechanical
and electrical stimuli. Biedermann comes to the following conclusions:—The transverse
section of a motor nerve is most excitable. Weak stimuli (descending opening shocks) excite
the cut surface of the transversely divided spinal cord, but do not act when applied further
down. Luchsinger asserts that, after dipping the anterior part of a beheaded snake into warm
water, the reflex movements of the upper part of the cord are abolished, while the direct excita-
bility remains, _

3. Excitability of the Vaso-motors.—The vaso-constrictor nerves, which pro-
ceed from the vaso-motor centre and run downwards in the lateral columns of the
cord, are excitable by all stimuli along their whole course; direct stimulation of

646 HYPERASTHESIA.

any transverse section of the cord constricts all the blood-vessels below the point of
section (C. Ludwig and Thiry). In the same way, the fibres which ascend in the
cord, and increase the action of the vaso-motor centre—pressor fibres, are also
excitable (C. Ludwig and Dittmar—§ 364, 10). Stimulation of these fibres,
although it affects the vaso-motor centre reflexly, does not cause sensation. —

4. Chemical stimuli such as the application of common salt, or wetting the
cut surface with blood, appear to excite the spinal cord.

5. The motor centres are directly excited by blood heated above 40° C., or by
asphyxiated blood, or by sudden and complete anwmia of the cord produced by
ligature of the aorta (Sigm. Mayer) ;} and also by certain polsons—picrotoxin,
nicotin, and compounds of barium (Luchsinger).

Action of Blood and Poisons.—In experiments of this kind, the spinal cord ought to be
divided at the 1st lumbar vertebra, at least twenty hours before the experiment is begun. Itis
well to divide the posterior roots beforehand to avoid reflex movements. If, in a cat thus
operated on, dyspnea be produced, or its blood overheated, then spasms, contraction of the vessels,
and secretion of sweat occur in the hind limbs, together with evacuation of the contents of
the bladder and rectum, while there are movements of the wterus and the vas deferens. Some
poisons act in a similar manner. In animals with the medulla oblongata divided, rhythmical
respiratory movements may be produced if the spinal cord has been previously rendered very
sensitive by strychnin or overheated blood (P. v. Rokitansky, v. Schroff—§ 368).

The ganglion-cells of the anterior cornu can be excited mechanically (Birge),
and, according to Biedermann, the grey matter also responds to electrical stimuli.

Hyperesthesia.— After unilateral section of the cord, or even only of the
posterior or lateral columns, there is hyperasthesia on the same side below the
point of section (Yodéra, 1823, and others), so that rabbits shriek on the slightest
touch. The phenomenon may last for three weeks, and then give place to normal
or sub-normal excitability. On the sound side the sensibility remains permanently
diminished. A similar result has been observed in cases of injury in man. An
analogous phenomenon, or a tendency to contraction in the muscles below the
section (hyperkinesia), has been observed by Brown-Séquard after section of the
anterior columns.

The excitability of the cord is intimately dependent on the continuance of the
circulation, for ligature of the abdominal aorta rapidly paralyses the lower
extremities (Stenson, 1667), due to anemia of the cord (Schiffer). Later, the
anterior roots of the spinal nerves, and the anemic part of the grey matter of the
cord, undergo degeneration.

364. THE CONDUCTING PATHS IN THE SPINAL CORD.—( Posterior
Root.—(a) The inner part, or internal radicular fasciculus is supposed to convey
the impressions from tendons and those for touch and locality. . When the postero-
external column is diseased, as in locomotor ataxia, the deep reflexes, especially the
patellar tendon reflex, are enfeebled, or it may be abolished, while the implication
of the fibres of the internal fasciculus gives rise to severe pain. (b) The outer
radicular fibres enter the grey matter of the posterior horn, and are supposed to
convey the impressions for cutaneous reflexes and temperature. (c) The central
fibres pass directly into the grey matter, and are supposed to conduct painful
impressions into the grey matter (fig. 449).] | ae

1. Localised tactile sensations (temperature, pressure, and the muscular sense
impressions) are conducted upwards through the posterior roots to the ganglia of
the posterior cornu, and lastly into the posterior column of the same side.

In man, the conducting path from the legs runs in Goll’s column, while those for the arms )

run in the ground-bundle (fig. 454) (Flechsig). In rabbits, the path of localised tactile impres-
sions lies in the lower dorsal region in the lateral columns (Ludwig and Woroschilof, Ott and
Meade-Smith), | “eet

Anesthesia.—Section of individual pauls of the lateral columns abolishes the sensibility for
the parts of the skin connected with t

e part destroyed, while total section produces the same

|

|
q
|

|
~7

i
ae
- '

CONDUCTING PATHS’ IN SPINAL CORD. 647

result for the whole of the opposite side of the body below the section. The condition where
tactile and muscular sensibility is lost is known as anesthesia.

2. Localised voluntary movements in man are conducted on the same side
through the anterior and lateral columns (S§ 358 and 365), in the parts known as the
pyramidal tracts. The impulses then pass into the cells of the anterior cornu, and
thence to the corresponding anterior: nerve-roots to the muscles. The exact section
experiments of Ludwig and Woroschiloff showed that, in the lower dorsal region of
the rabbit, these paths were confined to the lateral columns. Every motor nerve-
fibre is connected with a nerve-cell in the anterior horn of the frog’s spinal cord
(Gaule and Birge). Section of one lateral column abolishes voluntary movement
in the corresponding individual muscles below the point of section. It is obvious,
from the conduction in 1 and 2, that the lateral columns must increase in thickness
and number of fibres from below upwards (Stling, Woroschilof ) [see fig. 443].

3. Tactile reflexes (extensive and co-ordinated).—The fibres enter by the
posterior root, and proceed to the posterior cornu. The groups of ganglionic cells,
which control the co-ordinated reflexes, are connected together by fibres which run
in the anterior tracts, the anterior ground bundle and (?) the direct cerebellar tracts
(p. 633). The fibres for the muscles which are contracted pass from the motor
ganglia outwards through the anterior roots.

In ataxic tabes dorsalis, or locomotor ataxia, there is a degeneration of the posterior columns,
characterised by a peculiar motor disturbance. The voluntary movements can be executed with
full and normal vigour, but the finer harmonious adjustments are wanting or impaired, both in
intensity and extent. These depend in part upon the normal existence of tactile and muscular
impressions, whose channels*lie in the posterior columns. After degeneration of the latter,
there is not only anesthesia, but also a disturbance in the discharge of tactile reflexes, for which
the centripetal are is interrupted. But a simultaneous lesion of the sensory nerves alone may
in a similar manner materially influence the harmony of the movements, owing to the analgesia
and the disappearance of the pathic reflexes (§ 355). As the fibres of the posterior root traverse
the white posterior columns, we can account for the disturbances of sensation which characterise
the degenerations of these parts (Charcot and Pierret). But even the posterior roots themselves
may undergo degeneration, and this may also give rise to disturbances of sensation (p. 618).
The sensory disturbances usually consist in an abnormal increase of the tactile or painful sensa-
tions, with lightning pains shooting down the limbs, and this condition may lead to one
where the tactile and painful sensations are abolished. At the same time, owing to stimu-
lation of the posterior columns, the tactile sensibility is altered, giving rise to the sensation of
formication, or a feeling of constriction [‘‘girdle sensation’’]. The conduction of sensory
impressions is often slowed (§ 337). The sensibility of the muscles, joints, and internal parts
is altered.

The maintenance of the equilibrium is largely guided by the impulses which travel inwards
to the co-ordinating centres through the sensory nerves, special and general, deep and super-
ficial. In many cases of locomotor ataxia, if the patient place his feet close together and close
his eyes, he sways from side to side and may fall over, because by cutting off the guiding
sensations obtained through the optic nerve, the other enfeebled impulses obtained from the
skin and the deeper structures are too feeble to excite proper co-ordination.

4, The inhibition of tactile reflexes occurs through the anterior columns; the
impulses pass from the anterior column at the corresponding level into the grey
matter, where they form connections with the reflex conducting apparatus.

5. The conduction of painful impressions occurs through the posterior roots, and
thence through the whole of the grey matter. There is a partial decussation of
these impulses in the cord, the conducting fibres passing from one side to the other.
The further course of these fibres to the brain is given in § 365.

If all the grey matter be divided, except a small connecting portion, this is sufficient to
conduct painful impressions. In this case, however, the conduction is slower (Schiff). Only
when the greymatter is completely divided, is the conduction of painful impressions from below
completely interrupted. This gives rise to the condition of analgesia, in which, when the
posterior columns are still intact, tactile impressions are still conducted. This condition is
sometimes observed in man during incomplete narcosis from chloroform and morphia ( Thiersch).

Those poisons act sooner on the nerves which administer to painful sensations than on those
for tactile impressions, so that the person operated on is conscious of the contact of a knife, but

648 CONDUCTION IN THE SPINAL CORD.

not of the painful sensations caused by the knife dividing the parts. As painful impressions
are conducted by the whole of the grey matter, and as the impressions are more powerful the
stronger the painful impression, we may thus explain the so-called irradiation of painful
impressions. During violent pain, the pain seems to extend to wide areas; thus, in violent
toothache, proceeding from a particular tooth, the pain may be felt in the whole jaw, or it may

be over one side of the head. ; ; ; wu \
According to Bechterew, the paths for the conduction of painful impressions lie in the anterior

rt of the lateral column (dog, rabbit). wee
PThe sepetiments of Weiss on dogs, by dividing the lateral column at the limit of the dorsal

and lumbar regions, showed that each lateral column contains sensory fibres for both sides, The
chief mass of the motor fibres remains on the same side. Section of both lateral columns
abolishes completely sensibility and motility on both sides. The anterior columns and the grey
matter are not sufficient to maintain these.

6. The conduction of spasmodic, involuntary, inco-ordinated movements takes
place through the grey matter, and from the latter through the anterior roots. |

It occurs in epilepsy, poisoning with strychnin, uremic poisoning, and tetanus (§ 360, II.).
The anemic and dyspneeic spasms are excited in and conducted from the medulla oblongata, and
communicated through the whole of the grey matter.

7. The conduction of extensive reflex spasms takes place from the posterior

roots, perhaps to the cells of the posterior cornu and then to the cells of the anterior
cornu, above and below the plane of the entering impulse (fig. 458), and, lastly,
into the anterior roots, under the conditions already referred to in § 360, II.

8. The inhibition of pathic reflexes occurs through the anterior columns
downwards, and then into the grey matter to the connecting channels of the reflex
organ, into which it introduces resistance.

9. The vaso-motor fibres run in the lateral columns (Dittmar), and, after they
have passed into the ganglia of the grey matter at the corresponding level, they
leave the spinal cord by the anterior roots. They reach the muscles of the blood-
vessels either through the paths of the spinal nerves, or they pass through the rami
communicantes into the sympathetic, and thence into the visceral plexuses
(§ 356).

Section of the spinal cord paralyses all the vaso-motor nerves below the point of section ; while
stimulation of the peripheral end of the spinal cord causes contraction of all these vessels. [Ott’s
experiments on cats show that the vaso-motor fibres run in the lateral columns, and that they as
well as the sudorific nerves decussate in the cord. ]

10. Pressor fibres enter in the posterior roots, run upwards in the lateral columns,
and undergo an incomplete decussation (Ludwig and Miescher),

They ultimately terminate in the dominating vaso-motor centre in the medulla oblongata, which
they excite reflexly. Similarly, depressor fibres must pass upwards in the spinal cord, but we
know nothing as to their course.

11. From the respiratory centre in the medulla oblongata, respiratory nerves
run downwards in the lateral columns on the same side, and after forming connec-
tions with the ganglia of the grey matter pass through the anterior roots into the
motor nerves of the respiratory muscles (Schif'). :

Unilateral, or total destruction of the spinal cord, the higher up it is done, accordingly
paralyses more and more of the respiratory nerves, on the same or on both sides. Section of the
cord above the origin of the phrenic nerves causes death, owing to the paralysis of these nerves
of the diaphragm (§ 113).

In pathological cases, in degeneration of, or direct injury to, the spinal cord or its individual
parts, we must be careful to observe whether there may not be present simultaneously paralytic
and irritative phenomena, whereby the symptoms are obscured.

[Complete transverse section of the cord results immediately in complete
paralysis of motion and sensation in all the parts supplied by nerves below the seat
of the injury, although the muscles below the injury retain their normal trophic
and electrical conditions. There is a narrow hyperesthetic area at the upper limit
of the paralysed area, and when this occurs in the dorsal region, it gives rise to the
feeling of a belt tightly drawn round the waist, or the “girdle sensation.” There
is also vaso-motor paralysis below the lesion, but the blood-vessels soon regain their

EFFECTS OF SECTION OF THE CORD. 649
tone, owing to the subsidiary vaso-motor centres in the cord. The remote effects
come on much later, and are secondary descending degeneration in the crossed and
direct pyramidal tracts and ascending degeneration in the postero-internal columns
(fig. 455). According to the seat of the lesion, the functions of the bladder and
rectum may be interfered with. Injury to the upper cervical region sometimes
causes hyperpyrexia. |

[Unilateral section results in paralysis of voluntary motion in the muscles
supplied by nerves given off below the seat of the injury, although the muscles
do not atrophy, but when secondary descending degeneration
occurs they become rigid, and exhibit the ordinary signs of
contracture. There is vaso-motor paralysis on the same side,
although this passes off below the injury, while the ordinary and
muscular sensibility are diminished on both sides (fig. 459).
There is bilateral anzesthesia. On the opposite side there is
total anesthesia and analgesia below the lesion, but on the same
side in the dorsal region there is a narrow circular anzsthetic
zone (fig. 459, b), corresponding to the sensory nerve-fibres
destroyed at the level of the section. The sensory nerves
decussate shortly after they enter the cord, hence the anes-
thesia on the opposite side, but they do not cross at once, but
run obliquely upwards before they enter the grey matter of the
opposite side, so that a unilateral section will involve some
fibres coming from the same side, and hence the slightly dimin-
ished sensibility in a circular area on the same side. ‘There is
a narrow hyperesthetic area on the same side as the lesion, at
the upper limit of the paralysed cutaneous area (fig. 459, c), due
perhaps to stimulation of the cut ends of the sensory fibres on

that side. In man there is hyperesthesia (to touch, tickling, —-Fi8- 459.
pain, heat, and cold) on the parts below the lesion on the same pagent ae
side, but the cause of this is not known. The remote effects fF the loft half of the

are due to the usual descending and ascending degeneration
which set in.]

spinal cord in the
dorsal region. (qa)

[In monkeys, after hemi-section of the cord in the dorsal region,
there is paralysis of voluntary motion and retention of sensibility with
vaso-motor paralysis of the same side, and retention of voluntary motion
with anesthesia and analgesia on the opposite side.
hyperesthesia on the side of the lesion is not certain in these animals,

The existence of

oblique lines, motor
and vaso-motor para-
lysis; (b, d), com-
plete anesthesia ; (a,
c), hypereesthesia of
the skin.

but there is no doubt of itin man. Ferrier also finds (in opposition to
Brown-Séquard) that the muscular sense is paralysed as well as all other forms of sensibility, on
the side opposite to the lesion, but unimpaired on the side of the lesion. The muscular sense,
in fact, is entirely separable from the motor innervation of muscle (Ferrier). The power of
emptying the bladder and rectum was not affected. ]

The Brain.

365, GENERAL SCHEMA OF THE BRAIN.—In an organ so complicated in its structure
as the brain, it is necessary to have a general view of the chief arrangements of its individual
parts. Meynert gave a plan of the general arrangement of this organ, and although this plan
may not be quite correct, still it is useful in the study of brain function. The weight of the
brain is in man about 1358 grammes, and in woman 1220 grammes (Bischoff).

[A special layer of grey matter of the cerebrum is placed externally and spread as a thin
coating over the white matter or centrum.ovale—which lies*internally, and consists of nerve-
% fibres or the white matter. That part lying in each hemisphere is the centrum semi-ovale. The
grey matter is folded into gyri or convolutions separated from each other by fissures or sulci,
Some of the latter are very marked, and serve to separate adjacent lobes, while the lobes
themselves are further subdivided by sulci into convolutions. For a description of the lobes
see § 375. Some masses of grey matter are disposed at the base of the brain, forming the

‘

;

650 THE BRAIN—STRUCTURE OF THE CEREBRUM.

corpus striatum (projecting into the lateral ventricles), which in reality is composed of two
rts, the nucleus caudatus and lenticular nucleus (fig. 460, 6), the optic thalamus which lies
hind the former, and bounds the 3rd ventricle (fig. 460, d), the corpora quadrigemina lying on

the upper surface of the crura cerebri (fig. 480, hi); within the tegmentum of the crura cerebri

are the red nucleus and locus niger (fig. 502). Lastly, there is the continuation of the grey

matter of the cord up through the medulla, pons, and around the iter, forming the central |

grey tube and terminating anteriorly at the tuber cinereum. These various parts are connected

in a variety of ways with each other, some by transverse fibres stretching between the two sides

of the brain, while other longi-

tudinal fibres bring the hinder |

and lower parts into relation with |

the fore parts. ]

[Under cover of the occipital
lobes, but connected with the
cerebrum in front, and the spinal
cord below, is the cerebellum,
which has its grey matter ex-
ternally and its white core inter-
nally. Thus we have to consider
cerebro-spinal and cerebello-spinal
connections. ]

Meynert’s Projection Systems.
—The cortex of the cerebrum
consists of convolutions and sulci,
the ‘‘ peripheral grey matter”
(fig. 461, C), which is recognised
as a nervous structure, from the
presence in it of numerous gan-
glionic cells (§ 358, 1). From it
proceed all the motor fibres which
ure excited by the will, and to it
proceed all the fibres coming from
the organs of special sense and
sensory organs, which give rise to
the psychical perception of. ex-
ternal impressions. [In fig. 461
the decussation of the sensory
fibres is represented as occurring
near the medulla oblongata. It
is more po that a large
Fig. 460. number of the sensory fibres de-

Dissection of the brain from above, showing the lateral, 3rd, beaees ena Eekest! Cee vs
> nd

and 4th ventricles, with the basal ganglia, and surrounding 4¢3 ~ gome observers assert that
parts. a, knee of the corpus callosum; ), anterior part of 5 eof the sensory fibres decussate
the right corpus striatum ; b’, grey matter dissected off to . y

raping Seer ; : i! : in the medulla oblongata. ]

show white fibres; c, points to tenia semicircularis ; d, First Projection System.—The
optic thalamus ; e, anterior pillars of fornix, with 5th ven- channels A pis Hide from {thes
tricle in front of them, between the two lamine of the cortex cerebri, some of then ean
septum lucidum ; f, middle or soft commissure; g, 3rd aA EE TNS basal gangile or game
Ms late tie corpora quadrigemina ; k, superior cere- glia af the ASE in Mi olbae

ar peduncle ; 7, hippocampus major ; ™, posterior cornu %.
of lateral ventricle ; ig pase seh collatersita: o, 4th ven- striatum (C.s) (composed of Bae

a Pe é ; caudate nucleus and lenticular
aoe ; p, medulla oblongata ; s, cerebellum, with 7, arbor | a cleus (N.2),) optic thalamus

(T.0), and corpora quadrigemina
—some fibres form connections with cells within this central grey matter. The fibres which
proceed from the cortex through the corona radiata in a radiate direction constitute Meynert’s
Jirst projection system. Besides these, the white substance also contains two other systems of
fibres :—(a) Commissural fibres, such as the corpus callosum and the anterior commissure (¢, ¢),
which are supposed to connect the two hemispheres with each other; and (b) a connecting or
association system, whereby two.different areas of the same side are connected together (a, @).
The ganglionic grey matter of the basal ganglia forms the first stage in the course of a lar,
number of the fibres. When they enter the central grey matter, they are interrupted in their
course. According to Meynert, the corona radiata contains bundles of fibres from the co
striatum (1, 1), lenticular nucleus (2, 2), optic thalamus (3, 8), and corpora quadrigemina (4, 4).
The second projection system consists of longitudinal bundles of fibres, which proceed down-
wards and reach the so-called “ central grey tube,” which is the ganglionic grey matter reaching

SCHEME OF THE CENTRAL NERVOUS SYSTEM. 65 I

from the 3rd ventricle through the aqueduct of Sylvius, and the medulla oblongata, to the
lowest. part of the grey matter of the spinal cord. It lines the inner surface of the medullary
tube. It is the second stage in the course of the fibres extending from the basal ganglia to the

Fig. 461.

I, Scheme of the brain.—C, C, cortex cerebri; C.s, corpus striatum; N./, nucleus lenti-
cularis; T.o,. optic thalamus; v, corpora quadrigemina; P, pedunculus cerebri; H,
tegmentum ; and g, crusta ; 1, 1, corona radiata of the corpus striatum ; 2, 2, of the lenti-
_ cular nucleus ; 3, 3, of the optic thalamus ; 4, 4, of the corpora quadrigemina ; 5, pyramidal
i fibres from the cortex cerebri (Flechsig) ; 6, 6, fibres from the corpora quadrigemina to the
tegmentum ; m, further course of these fibres; 8, 8, fibres from the corpus striatum and
lenticular nucleus to the crusta of the pedunculus cerebri ; M, further course of these; S, S,
course of the sensory fibres; R, transverse section of the spinal cord ; v. W, anterior, and
_h.W, posterior roots; a, a, association system of fibres; c, c, commissural fibres. IT,
Transverse section through the posterior pair of the corpora quadrigemina and the pedunculi
cerebri of man.—v, crusta of the peduncle ; s, substantia nigra; v, corpora quadrigemina,
with a section of the aqueduct. IIJ, The same of the dog; IV, of an ape; V, of the
guinea-pig. [See p. 650.] 3
central tubular grey matter. The fibres of this system must obviously vary greatly in length ;
some fibres end in the central grey matter above the medulla oblongata, ¢.g., in the oculomotor
nucleus, while others reach to the level of the last spinal nerves. In the central grey matter,

a SS

652 CEREBELLO-SPINAL CONNECTIONS.

not only is the course of the fibres interrupted, but there is in it an increase in the number of
fibres, for far more fibres proceed peripherally from the grey matter of the medulla and spinal
cord, than are sent to it from the central grey matter of the brain. ;

As to the arrangement of the fibres in this second system, the fibres descending from the
caudate and lenticular nucleus (8, 8) are grouped into a special channel, which descends
through the crusta of the cerebral peduncle, and enters the medulla oblongata, or (according to
Flechsig) the pons. In the same way there proceeds from the thalamus (S) and corpora quad-
rigemina (6, 6) a bundle which descends through the tegmentum (H) of the cerebral peduncle.
Both sets of fibres—those in the crusta and in the tegmentum—come together in the cord.

According to Wernicke, the lenticular nucleus and caudate nucleus are not the parts of the
brain into which, from the cerebral cortex and through the corona, radiate fibres enter; but
they are independent parts, analogous to the cortex, and from them fibres proceed. These
fibres pass into the crusta and run along with those fibres proceeding from the thalamus and
corpora quadrigemina.

According to Meynert, the fibres which pass from the thalamus and corpora quadrigemina,
through the tegmentum of the cerebral peduncle, are reflex channels; so that these portions of
the brain are centres for certain extensive, co-ordinated reflexes. This is shown by the fact
that, after destruction of the voluntary motor paths, in animals, the technical completeness of
movements, so far as these are discharged
reflexly, is still intact. These channels
run in the spinal cord, at first on the
side (m), and probably ultimately cross in
the spinal cord itself.

The Third Projection System.—Lastly,
from the central tubular grey matter there
proceeds the third system, or the peri-
pheral nerves, motor and sensory. These
are more numerous than the fibres of the
second system.

[While there are three concentric tubes
in the spinal cord (§ 359), in the part
which forms the brain an extra layer of
grey matter is added—the peripheral
grey tube—constituting the cortex of the

the corpora quadrigemina. Thus, the
white matter lies between two concentric
masses of grey matter (Hl). ]
Connections of the Cerebellum.—The
cerebellum consists of two somewhat flat-
tened hemispheres connected across the
middle line by the middle lobe or vermi-
form process which is the fundamental
portion of the organ, as it is best de-
veloped in lower animals, while as yet
the ial lobes are but small or absent,
e.g.,in birds. The surface is furrowed by
sulci so as to cause it to resemble a series
of folia, leaflets or lamins; larger fissures
divide it into lobes, Peduncles,—The
two superior peduncles connect it with
the corpora quadrigemina and the crura
cerebri. The fibres come from the lower
part of the cerebellum and from its dentate
nucleus, and a number of these fibres decussate in the upper part of the pons and the tegmen-
tum, some of them becoming connected with the red nucleus in the tegmentum of the opposite
side. Some of the fibres seem to connect the cerebellum with the frontal lobes, constituting a
fronto-cerebellar tract, and they are also crossed (Gowers). When the cerebellum is congeni-
tally absent, these fibres are absent (Flechsig). By the two inferior peduncles or restiform
bodies, it is connected with all the columns of the spinal cord, and it is to be noted that some of
the fibres forming these peduncles are connected with the olivary body of the opposite side, so
that they decussate. The middle peduncle is formed by the transverse fibres of the pons (figs.
462, 503). It is evident that there is a cerebello-spinal, as well as a cerebro-spinal connection
to be considered. ] i seo
[The grey matter is external and the white internal, and on section the foliated branched
appearance of the cerebellum constitutes the arbor vite. Within each lateral lobe is a folded,
mass of grey matter like that in the olivary body, called the corpus dentatum, and from its

Fig. 462.

Floor of the 4th ventricle and the connections of the
cerebellum. On the left side the three cerebellar
peduncles are cut short ; on the right the connec-
tions of the superior and inferior peduncles have
been preserved, while the middle one has been cut
short. 1, median groove of the 4th ventricle with
the fasciculi teretes ; 2, the strie of the auditory
nerve on each side emerging from it ; 3, inferior
peduncle ; 4, posterior pyramid and clava, with
the calamus scriptorius above it; 5, superior
peduncle ; 6, fillet to the side of the crura cerebri ;
8, corpora quadrigemina,

cerebral hemispheres and cerebellum, and’

Eo

—— hl OOO OOOO

CEREBRO-SPINAL CONNECTIONS. 65 3

interior white fibres proceed. Stilling describes in the front part of the middle lobe roof-nuclei
—so called because they lie in the roof of the 4th ventricle. As is shown in fig. 462, the white
fibres of the superior peduncle pass to the grey matter on the inferior surface of the cerebellum,
while the inferior peduncular fibres pass to the superior surface, chiefly of the median part ;
but both are said to form connections with the corpus dentatum; the middle peduncle is con-
nected with the grey matter of the lateral lobes. The minute structure is described in § 380. ]

The distribution of the blood-vessels of the brain is of much practical importance. The
middle cerebral artery of the Sylvian fissure supplies the motor areas of the brain in’ animals ;
in man, the paracentral lobule is supplied by the anterior cerebral artery (Duret). The region
of the third left frontal convolution, which is the speech-centre, is supplied by a special branch
of the middle cerebral. According to Ferrier, that part of the brain, any injury to which
causes disturbance of intelligence, is supplied by the anterior cerebral; while those regions,
where injury is followed by hemi-anesthesia, are supplied by the posterior cerebral. It is stated
that anemia of isolated parts of this area of the brain is associated with melancholia in man.

Conduction to and from cerebrum—Voluntary motor fibres.—The course
of the fibres which convey impulses for voluntary motion—the pyramidal tracts
—proceeds from the motor regions of the cerebrum (§§ 375, 378, I.), passing
into and through the white matter of the cerebrum through the corona radiata,
and converges to the internal capsule, which lies between the nucleus
caudatus and opticus thalamus internally and the lenticular nucleus externally
(fig. 500). [The motor fibres for the face and tongue occupy the knee of the
capsule (F), those for the arm the anterior third of the posterior segment or limb
(A), and those for the leg the middle third (L). They pass beneath the optic
thalamus, enter the crusta of the cerebral peduncle, and occupy its middle third, or
two-fifths, extending almost to the substantia nigra, the fibres for the face being
next the middle line, and those for the leg most external, the fibres for the arm
lying between the two. They pass into the pons on the same side, where the fibres
for the face (and tongue) cross to the opposite side, to become connected with the
nuclei from which the facial and hypoglossal nerves arise. The fibres for the arm,
and leg (and trunk) continue their course to the medulla oblongata, where they
forma the anterior pyramids. In the pons, the pyramidal tracts are broken up into
bundles lying between its superficial and deep transverse fibres, and surrounded by
grey matter (fig. 503); but they have no connection with the grey matter of the pons.
By far the greater proportion of the fibres cross at the decussation of the pyramids
to form the crossed pyramidal tracts, or lateral pyramidal tracts, of the lateral
column of the opposite side. The small uncrossed portion is continued as the
direct pyramidal tract on the same side. The latter fibres, perhaps, supply
those muscles of the trunk (e.g., respiratory, abdominal, and perineal), which always
act together on both sides. According to other observers, however, they cross to
the other side of the cord through the anterior white commissure, and descend in
the crossed pyramidal tract or pyramidal tract of the lateral column. The fibres of
the pyramidal tracts split up into fine fibrils, which form connections with the
fibrils produced by the subdivision of the processes of the multipolar nerve-cells.
Thus, fibres form connections with the multipolar ganglionic cells of the anterior
cornu of the grey matter of the spinal cord at successively lower levels, and from
each multipolar cell is directed peripherally a single unbranched process, which
ultimately becomes a nerve-fibre. The pyramidal tracts thus end in the multipolar
nerve-cells of the grey matter of the spinal cord, from which the anterior roots of
the spinal nerves arise. sot

[The course of the pyramidal tracts and the decussation of these fibres in the
medulla oblongata, explain why a hemorrhage involving the cerebral motor centres,
or affecting these fibres in any part of their course above the decussation, results in
paralysis of the muscles supplied by the fibres so involved on the opposite side of
the body. In their passage through the brain,‘the paths for direct motor impulses
are not interrupted anywhere in their course by ganglion cells, not even in the
corpus striatum or pons. They pass in a direct uninterrupted line, until each fibre

654 COURSE OF THE SENSORY NERVES.

becomes connected with a multipolar nerve-cell in the anterior horn of the grey
matter of the spinal cord, so that they have the longest course of any fibres in the

pi irene sere —There are variations as to the number of fibres which cross at
the pyramids (Flechsig). In some cases the usual arrangement is reversed, and in some rare
instances there is no decussation, so that the pyramidal tracts from the brain remain on the
same side, In this way we may explain the very rare cases where paralysis of the voluntary
movements takes place on the same side as the lesion of the cerebrum (Morgagni, Pierret).
This is direct paralysis. [Usually about 90 per cent. of the fibres decussate. ] .

The motor cranial nerves have the centres through which they are excited
voluntarily in the cortex cerebri (§ 378). The paths for such voluntary impulses |
also pass through the internal capsule and the crusta of the cerebral peduncle.
[In the internal capsule, the fibres for the face (and tongue) lie in the knee, while
they occupy the part of the middle of the crusta next the middle line. Their.
course is then directed across the middle line to their respective nuclei, from which
fibres proceed to the muscles supplied by these nuclei.] ‘The exact course of many
of the fibres is still unknown. The hypoglossal nerve runs with the pyramidal
tracts, and behaves like the anterior root of a spinal nerve (S§ 354, 357).

[Sensory Paths.—Our knowledge is by no means precise. Sensory impulses,
passing into the cord, enter it by the posterior nerve-roots, and may pass to the
cerebrum or cerebellum. If to the cerebellum, the course, probably, is partly
to the direct cerebellar tract and posterior column to the restiform body, thence to
the cerebellum. If to the cerebrum, they c7oss the middle line in the cord not
far above where they enter and pass to the lateral column, in front of the pyramidal
tract. Some enter the posterior column, and others ascend in the grey matter to
pass upwards. As the two subdivisions of the posterior column terminate above
in the nuclei of the funiculus gracilis and funiculus cuneatus, and this column
contains fibres from the posterior root, it is suggested that above the clava and
cuneate nucleus the fibres cross in the superior pyramidal decussation to reach the
pons and tegmentum. In the medulla, it is probable that those fibres which do not
decussate there do so in the pons, the impulses perhaps travelling upwards in the
formatio reticularis, thence, into the posterior half of the pons, into the tegmentum
of the crus under the corpora quadrigemina, to enter the posterior third of the
posterior limb of the internal capsule (fig. 500, 8). But, of course, the sensory
fibres from the face have to be connected with the sensory centres in the cerebrum,
so that the sensory paths from the cord, 7.e., from the trunk and limbs, are joined
by those from the face in the pons, and they also occupy part of the posterior third
of the posterior segment of the internal capsule, so that this important part of the
internal capsule conducts sensory impulses from the opposite half of the body.
Some of the fibres pass into the optic thalamus, and others enter the white matter
of the cerebrum, but their exact course is very uncertain. The sensory fibres
derived from the organs of special sense, ¢.g., the ear, go to the superior temporo-
sphenoidal convolution, but whether directly or indirectly we do not know ; perhaps
some of those for vision traverse the optic thalamus. Some of the afferent fibres
perhaps go to the occipital region, and Gowers asserts that some of them go to the
parietal and central regions, 7.¢., to the “ motor” regions, for he holds “ that disease
of the motor cortex often causes impairment of the tactile sensibility.”]

[Charcot has called the posterior third of the posterior segment of the internal
capsule, lying between the posterior part of the lenticular nucleus and the optic
thalamus, the “carefour sensitiv” or “sensory crossway” (fig. 500, S). If it
be divided there is hemi-anzsthesia of the opposite side. ] | :

Sensory Decussation in Cord.—As the greater part of the sensory fibres
from the skin decussate in the spinal cord, and thus pass to the opposite side of the .
cord (fig. 463), unilateral section of the spinal cord in man (and monkey—Jerrier)

SENSORY IMPULSES AND THE MEDULLA OBLONGATA.

abolishes sensibility on the opposite side below the lesion.
of the parts below the seat of the section on the side of the injury (§ 363).

655
There is hyperzesthesia
From

experiments on mammals, Brown-Séquard concludes that the decussating sensory

nerve-fibres pass to the opposite side within the cord
at different levels, the lowest being the fibres for
touch, then those for tickling and pain, and, highest
of all, those which administer to sensations of tem-
perature.

All the fibres, therefore, which connect the spinal
cord with the grey matter of the brain, undergo a
complete decussation in their course. Hence, in man
a destructive affection of one hemisphere usually causes
complete motor paralysis and loss of sensibility on the
opposite side of the body. The fibres proceeding from
the nuclei of origin of the cranial nerves also cross
within the cranium.

Not unfrequently the motor paralysis and anesthesia occur
on the same side of the head, in which case the lesion (due to
pressure or inflammation) involves the cranial nerves lying at
the base of the brain.

The positions of decussation are (1) in the spinal cord, (2)
in the medulla oblongata, and lastly (3) in the pons. The
decussation is complete in the peduncle.

Alternate Paralysis.—Gubler observed that unilateral in-
jury to the pons caused paralysis of the facial nerve on the
same side, but paralysis of the opposite half of the body. He
concluded that the nerves of the trunk decussate before they
reach the pons, while the facial fibres decussate within the
pons. ‘To these rare cases the name ‘‘alternate hemiplegia”
is given. [When hemorrhage takes place into the lower part
of the lateral half of the pons, there may be alternate para-
lysis, but when the upper part of the lateral half is injured,
the facial is paralysed on the same side as the body, § 379.]

The olfactory nerve is said not to decussate (?), while the
optic nerve undergoes a partial decussation at the chiasma
(§ 344). Some observers assert that the fibres of the troch-
learis decussate at their origin.

366. THE MEDULLA OBLONGATA.—{Structure.—In
the medulla oblongata, the fibres from the cord are rearranged,
the grey matter is also much changed, while new grey matter
is added. Each half of the medulla oblongata consists of the
following parts, from before backwards :—The anterior pyra-
mid, olivary body, restiform body, and posterior pyramid,
or funiculus gracilis (figs. 464, 465, 466). By the divergence
of the posterior pyramids and the restiform bodies, the floor
of the 4th ventricle is'exposed. As the central canal of the
cord gradually comes nearer to the posterior surface of the
medulla, it opens into the 4th ventricle. At the lower end
of the medulla oblongata, on separating the anterior pyra-

03 UD
nn 8

NY
¥% 2

Fig. 463.
Diagram of a spinal segment as
a spinal centre and conduct-

ing medium. B, right, B,

‘left cerebral hemisphere ; MO,

lower end of medulla oblon-
gata; 1, motor tract from the
right hemisphere, the larger
part decussating at MO, and
passing down the lateral column
of the cord on the opposite side
to the muscles M and M’; 2,
motor tract from the left hem1-
sphere ; S, 8’, sensitive areas
on the left side of the body ;
3’, 38, the main sensory tract
from the left side of the body
—it decussates shortly after
entering the cord ; S*, S%, sen-
sitive areas, and 4’, 4, tracts
from the right side of the body.
The arrows indicate the direc-
tion of theimpulses( Bramwell).
[Here all the sensory fibres are
shown as crossing in the cord. ]

mids, we may see the decussation of the pyramids, where the fibres cross over to the lateral
columns of the cord. The anterior pyramid receives the direct pyramidal tract of the anterior
column of the cord from its own side, and the crossed pyramidal tract from the lateral column
of the cord of the opposite side (fig. 464). The decussating fibres (crossed pyramidal tract) of
the lateral column pass across in bundles to form the decussation of the pyramids. Most of the
poronidel fibres pass through the pons directly to the cerebrum, a few fibres pass to the cere-

voor 0m some join fibres proceeding from the olivary body to form the olivary fasciculus
or fillet.

(Thus, only a part of the anterior column of the cord—direct pyramidal tract—is continued
into the anterior pyramid, where it lies external to the fibres which pass to the lateral column
of the opposite side. The remainder of the anterior column—the antero-external fibres—are
continued upwards, but lie deeper under cover of the anterior-pyramid, where they serve to form
part of the formatio reticularis (p. 658).] .

656 THE SUBDIVISIONS OF THE MEDULLA OBLONGATA.

[Of the fibres of the Jateral column of the cord, some, the direct cerebellar tract, pass back-
wards to join the restiform body and go to the cerebellum, These fibres lie as a thin layer on
the surface of the restiform body, The crossed pyramidal fibres cross obliquely, at the lower
end of the medulla, to the anterior pyramid of the opposite side, and in their course they
traverse the grey matter of the anterior cornu (fig. 464, py). These fibres form the larger and
mesial portion of the anterior pyramid. The remaining fibres of the lateral columns are con-
tinued upwards, and pass beneath the olivary body, where they are concealed by this structure
and also by the arcuate fibres, but they appear in the floor of the medulla oblongata and are
here known as the fasciculus teres, which goes to the cerebrum. As they pass upwards, they
help to form the lateral part of the formatio reticularis. ] ; ;

(The posterior pyramid of the oblongata is merely the upward continuation of the postero-
median column, or funiculus gracilis of the cord. As it passes upwards at the medulla it broadens

Fig. 464

Section of the decussation of the pyramids. fla, anterior median fissure, displaced laterally by
the fibres decussating at d ; V, anterior column ; Ca, anterior cornu, with its nerve-cells,
a, b; cc, central canal; S, lateral column ; /r, formatio reticularis ; ce, neck, and g, head
of the posterior cornu ; rpCJ, posterior root of the 1st cervical nerve ; zc, first indication
of the nucleus of the funiculus cuneatus ; 2g, nucleus (clava) of the funiculus gracilis ; H’,
funiculus gracilis; H?, funiculus cuneatus ; slp, posterior median fissure; x, groups of
ganglionic cells in the base of the posterior cornu. x6.

out, forming the clava, which tapers away above. The clava contains a mass of grey matter—
the clavate nucleus. ]

[The restiform body consists chiefly of the upward continuation of the postero-external column.
or funiculus cuneatus of the cord. It contains a mass of grey matter, called the cuneate or
triangular nucleus. Above the level of the clava, the funiculus cuneatus forms part of the
lateral boundary of the 4th ventricle. Immediately outside this, ¢.¢., between it and the con-
tinuation of the posterior nerve-roots, is a longitudinal prominence, which Schwalbe has called,
the funiculus of Rolando, It is formed by the head of the posterior cornu of grey matter
coming nearer the surface. It also forms part of the restiform body. Some arcuate fibres issue
from the anterior median fissure, turn transversely outwards over the anterior pyramids and
olivary body, and pass along with the funiculus cuneatus, the funiculus of Rolando, and the
direct cerebellar fibres, to enter the corresponding lateral lobe of the cerebellum, all these,
structures forming its inferior peduncle. Some observers suggest that the funiculus cuneatus
and funiculus of Rolando do not pass into the cerebellum. ]

[The olivary body forms a well-marked oval or olive-shaped body, which does not extend,
the whole length of the medulla (fig. 466, 0). Above, it is separated from the pons by a groove
from which the 6th nerve emerges, In the groove between it and the anterior acute arise,

STRUCTURE OF THE MEDULLA OBLONGATA. 657

the strands of the hypoglossal nerve, while in a corresponding groove along its outer surface is
the line of exit of the vagus, glosso-pharyngeal, and spinal accessory nerves, It is covered on
its surface by longitudinal and arcuate fibres, while in its interior jit contains the dentate
nucleus.

[The Rates of the olivary bodies are quite unknown, but it is important to remember
that they are connected by fibres with the dentate nuclei of the cerebellum. Fibres pass into
the olivary body from the posterior column of the cord of the opposite side, and it is also con-
nected with the dentate body of the opposite side, while, as we know, the dentate body is
connected with the tegmentum, so that through the left dentate body of the opposite side, the
tegmentum of, say, the right crus, is connected with the right olivary body (Gowers).]

[Decussation of the pyramids is the term given to those fibres which cross obliquely in
several bundles, at the lower part of the medulla, from the anterior pyramid of the medulla

=
i
x

t
SS =

Ss
: —s
*@

Fig. 465. Fig, 466.

Fig. 465,—Section of the medulla oblongata at the so-called upper decussation of the pyramids.
fla, anterior, slp, posterior median fissure ; »XJ, nucleus of the accessorius vagi ; nXJZ,
nucleus of the hypoglossal ; da, the so-called superior or anterior decussation of the pyra-
mids ; py, anterior pyramid; 2.ar, nucleus arciformis ; O!, median parolivary body ; 0,
beginning of the nucleus of the olivary body; 2/, nucleus of the lateral column; F’,
formatio reticularis ; g, substantia gelatinosa, with (aV) the ascending root of the trige-
minus; 2c, nucleus of the funiculus cuneatus; nc!, external nucleus of the funiculus
cuneatus ; ng, nucleus of the funiculus gracilis (or clava); H4, funiculus gracilis; H?,
funiculus cuneatus ; cc, central canal; fa, fa’, fa”, external arciform fibres x 4. Fig. 466.—
Section of the medulla oblongata through the olivary body. nxXJJ, nucleus of the hypo-
glossal ; »X, nX1, more or less cellular parts of the nucleus of the vagus ; XJZ, hypoglossal
nerve; X, vagus; n.am, nucleus ambiguus; nl, nucleus lateralis; 0, olivary nucleus ;
oal, external, and oam, internal parolivary body ; 7s, the round bundle, or funiculus soli-
tarius ; Cr, restiform body ; p, anterior pyramid, surrounded by arciform fibres ; fae, pol,
fibres proceeding from the olive to the raphe (pedunculus olive); 7, raphe. x 4.

into the lateral column of the cord of the opposite side (fig. 464, d) to form its lateral pyramid
tracts, or crossed pyramidal tracts, The number of fibres which decussate varies, and in some
cases all the fibres may cross. ]

[The grey matter of the medulla is largely a continuation of that of the cord, although it is
arranged differently. As the fibres from the lateral column of the cord pass over to form part
of the anterior pyramid of the medulla on the opposite side, they traverse the grey matter, and
thus cut off the tip of the anterior cornu, which is also pushed backwards by the olivary body,
and exists as a distinct mass, the nucleus lateralis (fig. 465, nl), Part of the anterior grev
matter also appears in the floor of the 4th ventricle as the eminence of the fasciculus teres, and
from part of it springs the hypoglossal nerve (fig. 466, XZZ), The neck joining the modified
anterior and posterior cornua is much broken up by the passage of longitudinal and transverse

aT

658 THE GREY MATTER OF THE MEDULLA OBLONGATA.

fibres through it, so that it forms a formatio reticularis, separating the two cornua (fig. 465, fr).
The caput cornu posterioris comes to be covered higher up by the ascending root of the 5th
nerve (fig. 465, ay), and arcuate fibres passing'to the restiform body. The posterior cornu 1s
also broken up and is thrown outwards, its caput giving rise to part of the elevation seen on the
surface and described as the funiculus of Rolando, while part of the base now greatly enlarged
forms the grey matter in the funiculus gracilis [clavate nucleus] (fig. 464, xg) and funiculus
cuneatus [cuneate or triangular nucleus] (fig. 464, 7). Nearer the middle line, the grey matter
of the posterior grey cornu appears in the floor of the 4th ventricle, above the point where the
central canal opens into it, as the nuclei of the spinal accessory, vagus, and glosso-pharyngeal
nerves.

{In a floor of the 4th ventricle near the raphe, and quite superficial, is a longitudinal mass
of large multipolar nerve-cells, derived from the base of the anterior cornu from which spring
the several bundles forming the hypoglossal nerve ; it is the hypoglossal nucleus (fig. 466, nXI1),
the nerve-fibres passing obliquely outwards to appear between the anterior pyramid and the
olivary body. Internal to it, and next the median groove, is a small mass of cells continuous
with those in the raphe, and called the nucleus of the funiculus teres (fig. 466, nt). Around
the central canal at the lower part of the medulla is a group of cells (fig. 466, nXJ), which
becomes displaced laterally as it comes nearer the surface in the floor of the medulla oblongata,
where it lies outside the hypoglossal nucleus, and corresponds to the prominence of the ala
cinerea (fig. 466, 2X); and from it and its continuation upwards arise from below upwards part
of the spinal accessory (11th), and the vagus (10th, corresponding to the position of the
eminentia cinerea—fig. 466, X), so that this column of cells forms the vago-accessorius
nucleus, External to and in front of this is the nucleus for the glosso-pharyngeal nerve.
Further up in the medulla, on a level with the auditory strie and outside the previous column,
is a tract of cells from which the auditory nerve (8th) in great part arises; it is the principal
auditory nucleus, and lies just under the commencement of the inferior cerebellar peduncle
(fig. 427, 8’, 8”, 8”). It consists of an outer and inner nucleus, which extend to the mi dle line.
It forms connections with the cerebellum, and some fibres are said to enter the inferior cerebellar
peduncle. This is an een relationship, as we know that the vestibular branch of the
auditory nerve comes partly from the semicircular canals, so that in this way these organs may
be connected with the cerebellum. }

| Superadded Grey Matter.—There is a superadded mass of grey matter not represented in
the cord, that of the olivary body, enclosing a nucleus, the corpus dentatum, with its wavy
strip of grey matter containing many small multipolar nerve-cells embedded in neuroglia, The
yrey matter is covered on the surface by longitudinal and transverse fibres. It is open towards
the middle line (hilum), and into it run white fibres forming its pedunele (fig. 466, p, 9, /).
These fibres diverge like a fau, some of them ending in connection with the small multipolar
cells of the dentate body, while others traverse the lamina of grey matter and pass backwards
to appear as arcuate fibres which join the restiform body ; others, again, pass directly through
to the surface of the olivary body, which they help to cover as the superficial arcuate fibres.
The accessory olivary nuclei (fig. 465, 0’, 0’) are two small masses of grey matter similar to the
last, and looking as if they were detached from it, one lying above and external, sometimes
called the parolivary body, and the other slightly below and internal to the olivary nucleus,
the latter being separated from the dentate body by the roots of the hypoglossal nerve. The
latter is sometimes called the internal parolivary body, or nucleus of the pyramid.] )

(The formatio reticularis occupies the greater part of the central and lateral parts of the
medulla, and is produced by the intercrossing of bundles of fibres running longitudinally and
more or less transversely in the medulla (fig. 465, fr). In the more lateral portions are lar,
multipolar nerve-cells, perhaps continued upwards from part of the anterior cornu, while the
part next the raphe has no such cells. The longitudinal Abies consist of the upward prolonga-
tion of the antero-external columns of the cord, while some seem to arise from the clavate nuclei
and olives as arcuate fibres passing upwards. In the lateral portions, the longitudinal fibres
are the direct continuation upwards of Flechsig’s antero-lateral mixed tracts of the lateral
columns (p. 633). The horizontal fibres are formed by arcuate fibres, some of which run more
or less transversely outwards from the raphe. The superficial arcuate fibres (fig. 466, f, a, ¢)
ap in the anterior median fissure, and perhaps come through the raphe from the opposite.
side of the medulla, curve round the anterior pyramids, form a kind of capsule for the olives,
and join the restiform body (p. 656), but baa! are reinforced by some of the deep arcuate fibres
which traverse the olivary body (p. 656). The deep arcuate fibres run from the clavate and
triangular nuclei horizontally inwards to the raphe, and cross to the other side; others pass —
iy eH 0 oe Lejinih may, and through it to the restiform body. In the ra 4

erve-cells, some fibres ru itudi a a
before backw ag J , n transversely, others longitudinally, and others from
_ (Other Nerve Nuclei—Sixth Nerve.—Under the elevation called eminentia teres (fig, 427)
in front of the auditory strix, close to the middle line, is a tract of large multipolar ae alls.
It was once thought to be the common nucleus of the 6th and 7th facial nerves, but Gowers —
has shown that “ the facial ascends to-this nucleus, forms a loop round it (some fibres indeed

FUNCTIONS OF THE MEDULLA OBLONGATA. 659

ge through it), and then passes downwards, for wards, and outwards, to a column of cells more
eeply ened in the medulla than any other nucleus in the lower part.” But the 7th has no
real origin from this nucleus. Facial Nerve.—The nucleus lies deep in the formatio reticularis
of the pons under the floor of the 4th ventricle, but outside the position of the nucleus of the
6th (fig. 427, 7). It extends downwards about as far as the auditory striz, or a little lower.
The fifth nerve arises from its motor nucleus (with large multipolar cells), which lies more
superficially above and external to the 6th (fig, 427, 5)... The fibres run backwards, where they
are joined by fibres from the upper sensory nucleus, but another sensory nucleus extends down
nearly to the lower end of the medulla (5”). Doubtless this extensive origin brings this nerve
into intimate relation with the other cranial nerves, and accounts for the numerous reflex acts
which can be discharged through the fifth nerve. Some sensory fibres are said to pass up
beneath the corpora quadrigemina (Gowers). The fourth nerve arises from the valve of
Vieussens, 7.¢., the lamina of white and grey matter which stretches between the superior
cerebellar peduncles. It arises, therefore, behind the 4th ventricle, but some of the fibres spring
from nerve-cells at the lower part of the nucleus of the 3rd nerve. Some fibres also descend in
the pons to form a connection with the nucleus of the 6th nerve. The fibres decussate behind
the aqueduct, so that in it alone, of all the cranial nerves, decussation occurs between its
nucleus and its superficial origin (Gowe7s). The third nerve arises from a tract of cells beneath
the aqueduct and near the middle line, and the fibres descend through the tegmentum to appear
at the inner side of the crus cerebri. - Gowers points out that, in reality, there are three distinct
functional centres, (1) for accommodation (ciliary muscle), (2) for the light reflex of the iris,
and (3) most of the external muscles of the eyeball. It is important to notice the connection
between the nuclei of the 3rd, 4th, and 6th nerves, in relation to the innervation of the ocular
muscles. |

Functions.—The medulla oblongata, which connects the spinal cord with the
brain, has many points of resemblance with the former. [Like the cord it is
concerned (1) in the, conduction of impulses.]| (2) In it, numerous reflex
centres are present, ¢.g., for semple reflexes similar to the nerve-centres in the spinal
cord, e.g., closure of the eyelids, [so that they subserve the transference of afferent
into efferent impulses]. There are other centres present which seem to dominate
or control similar centres placed in the cord, e.g., the great vaso-motor centre, the
sweat-secreting, pupil-dilating centres, and the centre for combining the reflex move-
ments of the body. Some of the centres are capable of being excited reflexly
(§ 358, 2). (3) It is also said to contain automatic centres (§ 358, 3). The
normal functions of the centres depend upon the exchanges of blood-gases, effected
by the circulation of the blood through the medulla. If this gaseous exchange be
interrupted or interfered with, as by asphyxia, sudden anzemia, or venous congestion,
these centres are first excited, and exhibit a condition of increased excitability, and
at last, if they are over-stimulated, they are paralysed. An excessive temperature
also acts as a stimulus. All the centres, however, are not active at the same time,
and they do not all exhibit the same degree of excitability. Normally, the
respiratory centre and the vaso-motor centre are continually ina state of rhythmical
activity. In some animals, the inhibitory centre of the heart remains continually
non-excited ; in others, it is stimulated very slightly under normal conditions,
simultaneously with the stimulation of the respiratory centre, and only during
inspiration. The spasm centre is not stimulated under normal conditions; and
during intra-uterine life, the respiratory centre remains quiescent. The, medulla.
oblongata, therefore, contains a collocation of nerve-centres which are essential for
the maintenance of life, as well as various conducting paths of the utmost.
importance, We shall treat of the reflex, and afterwards of the automatic centres.

367. REFLEX CENTRES OF THE MEDULLA OBLONGATA.—The
medulla oblongata contains a number of reflex centres, which minister to the
discharge of a large number of co-ordinated movements.

1. Centre for closure of the eyelids. The sensory branches of the 5th cranial
nerve tothe cornea, conjunctiva, and the skin in the region of the eye, are: the.
afferent nerves. They conduct impulses to the medulla oblongata, where they
are transferred to, and excite part of, the centre of the facial nerve, whence, through

660 REFLEX CENTRES OF THE MEDULLA OBLONGATA.

branches of the facial, the efferent impulses are conveyed to the orbicularis
palpebrarum. The centre extends from about the middle of the ala cinerea
upwards to the posterior margin of the pons (Nickell).

The reflex closure of the eyelids always occurs on both sides, but closure may be produced volun-
tarily on one side (winking). When the stimulation is strong, the corrugator and other groups of
muscles which raise the cheek and nose towards the eye may also contract, and so form a more
perfect protection and closure of the eye. Intense stimulation of the retina causes closure of the
eyelids [and in this case the shortest reflex known, the latent period, is 0°05 second ( Wadler)).

2. Sneezing centre.—The afferent channels are the internal nasal branches of
the trigeminus and the olfactory, the latter in the case of intense odours. The
efferent or motor paths lie in the nerves for the muscles of expiration (§§ 120, 3,
and 347, II.). Sneezing cannot be performed voluntarily, [but it may be inhibited
by compressing the nasal nerve at its exit on the nose].

3. Coughing centre.—According to Kohts, it is placed a little above the —
inspiratory centre; the afferent paths are the sensory branches of the vagus
(§ 352, 5, a). The efferent paths lie in the nerves of expiration and those that
close the glottis (§ 120, 1).

4. Centre for sucking and mastication.—The afferent paths lie in the sensory
branches of the nerves of the mouth and lips (2nd and 3rd branches of the
trigeminus and glosso-pharyngeal). The efferent nerves for sucking are (§ 152) :—
Facial for the lips, hypoglossal for the tongue, the inferior maxillary division of the
trigeminus for the muscles which elevate and depress the jaw. For the movements
of mastication, the same nerves are in action (§ 153); but when food passes within
the dental arch, the hypoglossal is concerned in the movements of the tongue, and
the facial for the buccinator.

5. Centre for the secretion of saliva (p. 215) lies in the floor of the 4th
ventricle. Stimulation of the medulla oblongata causes a profuse secretion of
saliva when the chorda tympani and glosso-pharyngeal nerves are intact, a much
feebler secretion when the nerves are divided, and no secretion at all when the
cervical sympathetic is extirpated at the same time (Grvitzner).

6. Swallowing centre lies in the floor of the 4th ventricle (§ 156).—The afferent
paths lie in the sensory branches of the nerves of the mouth, palate, and pharynx
(2nd and 3rd branches of the trigeminus, glosso-pharyngeal, and vagus); the
efferent channels, in the motor branches of the pharyngeal plexus (§ 352, 4).
Stimulation of the glosso-pharyngeal nerve does not cause deglutition ; on the
contrary, this act is inhibited (p. 228), |

According to Steiner, every time we swallow there is a slight stimulation of the respiratory
centre, resulting in a contraction of the diaphragm, [Kronecker has shown that if a glass of
water be sipped slowly, the action of the cardio-inhibitory centre is interfered with reflexly, so

that the heart beats much more rapidly, whereby the circulation is accelerated, hence probably

the reason why sipping an alcoholic drink intoxicates more rapidly than when it is quickly
swallowed (p. 668). ]

7. Vomiting centre (¢ 158).—The relation of certain branches of the vagus to
this act are given at § 352, 2, and 12, d.!
8. The upper centre for the dilator pupille muscle, the smooth muscles of the
orbit, and the eyelids lies in the medulla oblongata. The fibres pass out partly in
the trigeminus (§ 347, I., 3), partly in the lateral columns of the spinal cord as far
down as the cilio-spinal region, and proceed by the two lowest cervical and the two
upper dorsal nerves into the cervical sympathetic (§ 356, A, 1). The centre is
normally excited reflexly by shading the retina, i.e., by diminishing the amount of
light admitted into the eye. It is directly excited by the circulation of dyspneeic
wie ts , medulla. (The centre for contracting the pupil is referred to at & 345
n ‘ : at ‘Oly Of Seam
The centre may be excited reflexly by stimulation of Je, iatic. These x fs
afferent fibres pass upwards through both lateral cobain to:thelv colitre lic oncoloontgn 3s a ae

POSITION OF THE RESPIRATORY CENTRE. 661

9. There is a subordinate centre in the medulla oblongata, which seems to be
concerned in bringing the various reflex centres of the cord into relation with each
other. Owsjannikow found that, on dividing the medulla 6 mm. above the calamus
scriptorius (rabbit), the general reflex movements of the body still occurred, and
the anterior and posterior extremities participated in such general movements. If,
however, the section was made 1 mm. nearer the calamus, only local partial reflex
actions occurred (§ 360, III., 4); [thus, on stimulating the hind-leg, the fore-legs
did not react—the transference of the reflex was interfered with]. The centre
reaches upwards to slightly above the lowest third of the oblongata.

The medulla in the frog also contains the general centre for movements from place to place.
Section of this region abolishes the power to move from place to place; when external stimuli
are applied, there remains only simple reflex movements (Steiner).

Pathological. —The medulla oblongata is sometimes the seat of a typical disease, known as
bulbar paralysis, or glosso-pharyngo-labial paralysis (Duchenne, 1860), in which there is a
progressive invasion of the different nerve-nuclei (centres) of the cranial nerves which arise
within the medulla, these centres being the motor portions of an important reflex apparatus.
Usually, the disease begins with paralysis of the tongue, accompanied by fibrillar contractions,
whereby speech, formation of the food into a bolus, and swallowing are interfered with (§ 354).
The secretion of thick, viscid saliva points to the impossibility of secreting a thin watery facial
saliva (§ 145, A), owing to paralysis of this nerve-nucleus. Swallowing may be impossible,
owing to paralysis of the pharynx and palate. This interferes with the formation of consonants
[especially the linguals, 7, ¢, s, 7, and, by and by, the labial explosives b, p] (§ 318, C); the
speech becomes nasal, while fluids and solid food often pass into the nose. Then follows
paralysis of the branches of the facial to the lips, and there is a characteristic expression of the
mouth ‘‘as if it were frozen.” ‘All the muscles of the face may be paralysed ; sometimes the
laryngeal muscles are paralysed, leading to loss of voice and the entrance of food into the
windpipe. The heart-beats are often retarded, pointing to stimulation of the cardio-inhibitory
fibres (arising from the accessorius). Attacks of dt yspnrea, like those following paralysis of the
recurrent nerves (§ 313, II., 1, and § 352, 5, b), and death may occur. Paralysis of the muscles
of mastication, contraction of the pupil, and paralysis of the abducens are rare. [This disease
is always bilateral, and it is important to note that it affects the nuclei of those muscles that
guard the orifices of the mouth, including the tongue, the posterior nares including the soft
palate, and the rima glottidis with the vocal cords. ]

368. RESPIRATORY CENTRE. INNERVATION OF THE RESPIRA-
TORY ORGANS.—The respiratory centre lies in the medulla oblongata (Legallovs,
1811), behind the superficial origin of the vagi, on both sides of the posterior
aspect of the apex of the calamus scriptorius, between the nuclei of the vagus and
accessorius, and was named by Flourens the vital point, or neud vital. The centre
is double, one for each side, and it may be separated by means of a longitudinal
incision (Longet, 1847), whereby the respiratory movements continue symmetrically
on both sides. Section of Vagi.—If one vagus be divided, respiration on that
side is slowed. If both vagi be divided, the respirations become much slower and
deeper, but the respiratory movements are symmetrical on both sides. Stimulation
of the central end of one vagus, both being divided, causes an arrest of the
respiration only on the same side, the other side continues to breathe. The same
result is obtained by stimulation of the trigeminus on one side (Langendorf’). When
the centre is divided transversely on one side, the respiratory movements on the
same side cease (Schiff). Most probably the dominating respiratory centre lies
in the medulla oblongata, and upon it depend the rhythm and symmetry of the
respiratory movements ; but, in addition, other and subordinate centres are placed in
the spinal cord, and these are governed by the oblongata centre. If the spinal cord
be divided in newly-born animals (dog, cat) below the medulla oblongata, respira-
tory movements of the thorax are sometimes observed (Brachet, 1835).

{If the cord be divided below the medulla, or the cranial arteries ligatured (rabbit), there
may still be respiratory movements, which become more distinct if strychnin be previously
administered, so that Langendorff assumes the existence of a spinal respiratory centre, which
he finds is also influenced by reflex stimulation of sensory nerves. ]

Nitschmann, by means of a vertical incision into the cervical cord, divided the spinal centre

662 CEREBRAL RESPIRATORY CENTRE.

‘hich acted on both sides of the diaphragm after the medulla
etre ler eeepnesries The spinal centres must, therefore, be con-

tre can be excited or inhibited

into two 2
was divided just below the calamus scriptorius. ‘
nected with each other in the cord. The spinal respiratory cen

flexly (Wertheimer). :
ns paceenioal yaaness locates the respiratory centre near the lateral margins of the grey matter

in the floor of the 4th ventricle, but not reaching so far backwards as the ala jcinerea.
According to Gierke, Heidenhain, and Langendorff, those parts of the medulla oblongata whose
destruction causes cessation of the respiratory movements are single or double strands of
nervous matter, containing grey nervous substance with small ganglion cells, and running
downwards in the substance of the medulla oblongata. These strands are said to arise partly
from the roots of the vagus, trigeminus, spinal accessory, and glosso-pharyngeal (Meynert),
forming connections by means of fibres with the other side, and descending as far downwards
as the cervical enlargement of the spinal cord (Gold). According to this view, this strand
represents an inter-central band connecting the spinal cord (the place of origin of the motor
respiratory nerves) with the nuclei of the above-named cranial nerves.

Cerebral Inspiratory Centre.—According to Christiani, there is a cerebral |
inspiratory centre in the optic thalamus in the floor of the 3rd ventricle, which is
stimulated through the optic and auditory
nerves, even after extirpation of the cere-
brum and corpora striata; when it is stimu-
lated directly, it deepens and accelerates the
inspiratory movements, and may even cause
a standstill of the respiration in the inspira-
tory phase. This inspiratory centre may be
extirpated. After this operation, an expira-
tory centre is active in the substance of the
anterior pair of the corpora quadrigemina,
not far from the aqueduct of Sylvius. Martin
and Booker describe a second cerebral in-
spiratory centre in the posterior pair of the
corpora quadrigemina. These three centres
are connected with the centres in the medulla
oblongata.

The respiratory centre consists of two
centres, which are in a state of activity alter-
nately—an inspiratory and an expiratory
centre (fig. 467), each one forming the
Fig. 467. motor central point for the acts of inspira-

Scheme of the chief respiratory nerves. tion and expiration (§ 112). The centre is
ins, inspiratory, and exp, expiratory centre automatic, for, after section of all the sen-
sarekare gikbed bsg Deca ae ae sory nerves which can act reflexly upon the
muscles, ab; to muscles of back, do. In- centre, it stl ll ret ains 1ts activit y: The de-
spiratory motor nerves. ph, phrenic to tee of excitability and the stimulation of
diaphragm, d; int, intercostal nerves; the centre depend upon the state of the

Sp eeu rent eat as Le dene nare blood, and chiefly upon the amount of the

centre ; a palmacars fibres hat cite blood-ga ses, the O and CO, (J. Rosenthal).

expiratory centre; cz’, fibres of sup. According to the condition of the centre, there
laryngeal that excite expiratory centre; are several well-recognised respiratory con-
_ inh, fibres of sup. laryngeal that inhibit ditions :—

oe ape vitae = 1. Apnea.—Complete cessation of the
respiration constitutes apnea, i.e., cessation of the respiratory movements, owing
to the absence of the proper stimulus, due to the blood being saturated with O and
poor in CQ,. Such blood saturated with O fails to stimulate the centre, and hence
the respiratory muscles are quiescent. This seems to be the condition in the foetus
during intrauterine life. If air be vigorously and rapidly forced into the lungs of
an animal by artificial respiration, the animal will cease to breathe for a time, after

APNEIC BLOOD, EUPNGA, AND DYSPNEA. 663

cessation of the artificial respiration (Hook, 1667), the blood being so arterialised
that it no longer stimulates the respiratory centre. If a person takes a series of
rapid, deep respirations his blood becomes surcharged with oxygen, and long
‘“‘apnoeic pauses ’’ occur.

Apneeic Blood.—A. Ewald found that the arterial blood of apneic animals was completely
saturated with O, while the CO, was diminished ; the venous blood contained less O than normal
—this latter condition being due to the apneeic blood causing a considerable fall of the blood-
pressure and consequent slowing of the blood-stream, so that the O can be more completely
taken from the blood in the capillaries (Pfliiger). The amount of O used in apnea on the whole
is not increased (§ 127). Gad remarks that during forced artificial respiration, the pulmonary
alveoli contain a very large amount of atmospheric air; hence, they are able to arterialise the
blood for a longer time, thus diminishing the necessity for respiration. According to Gad and
Knoll, the excitability of the respiratory centre is reduced during apncea, and this is caused
reflexly during artificial respiration by the distension of the lungs stimulating the branches of
the vagus. In quite young mammals apneea cannot be produced (Runge).

[Drugs.—If the excitability of the respiratory centre be diminished by chloral, apncea is
readily induced, while, if the centre be excited, as by apomorphine, it is difficult to produce it. ]

2. Eupnea.—The normal stimulation of the respiratory centre, ewpnea, is
caused by the blood, in which the amount of O and CO, does not exceed the normal
limits (§§ 35 and 36).

3. Dyspnea.—All conditions which diminish the O and increase the CO, in
the blood circulating through the medulla and respiratory centre cause acceleration
and deepening of the respirations, which may ultimately pass into vigorous and
laboured activity of all the respiratory muscles, constituting dyspnea, when the
difficulty of breathing is very great (§ 134). [Changes in the rhythm, § 111.]

During normal respiration, and with the commencement of the need for more air, according
to Gad, the gases of the blood excite only the inspiratory centre; while the expiration follows
owing to reflex stimulation of the pulmonary vagus by the distension of the lungs (p. 666). He
is also of opinion that the normal respiratory movements are excited by the CO,.

[Muscular work, as is well-known, increases the respirations and may even cause dyspncea.
This is not due to the nervous connections of the muscles or other organs with the respiratory
centre, but to changes in the blood. Geppert and Zuntz have shown, however, that the result
cannot be explained by changes in the blood caused either by diminution of O or increase of
CO,. It seems to be due to the blood taking up some as yet unknown products from the con-
tracting muscle, and carrying them to the respiratory centre, which is directly excited by them.
The nature of these substances is unknown. It has been shown that the alkalinity of the
blood is reduced by the formation of an acid. The substances, whatever they may be, are not
excreted by the urine, and are, therefore, perhaps readily oxidised (Loewy). C. Lehmann has
proved that, in rabbits, the acidification of the blood produced by muscular exertion plays an
important part in the stimulation of the respiratory centre. ]

4. Asphyxia.—If blood, abnormal as regards the amount and quality of its
gases, continue to circulate in the medulla, or if the condition of the blood become
still more abnormal, the respiratory centre is over-stimulated, and ultimately
exhausted. 'The respirations are diminished both in number and depth, and they
become feeble and gasping in character; ultimately the movements of the
respiratory muscles cease, and the heart itself soon ceases to beat. This constitutes
the condition of asphyxia, and if it be continued, death from suffocation takes
place. (Langendorff asserts that in asphyxiated frogs the muscles and grey
nervous substance have an acid reaction.) If the conditions causing the abnormal
condition of the blood be removed, the asphyxia may be prevented under favourable
circumstances, especially by using artificial respiration (§ 134); the respiratory
muscles begin to act and the heart begins to beat, so that the normal eupneeic
stage is reached through the condition of dyspnoea. If the venous condition of the
blood be produced slowly and very.gradually, asphyxia may occur without there
being any symptoms of dyspnoea, as happens when death takes place quietly and
very gradually (§ 324, 5). |

Causes of Dyspnoea,—(1) Direct limitation of the activity of the respiratory organs ;
diminution of the respiratory surface by inflammation, acute cedema (§ 47), or collapse of the

664 CONDITIONS ACTING ON THE RESPIRATORY CENTRE.

i ocelusion of the capillaries of the alveoli, compression of the lungs, entrance of air into
ge obstruction or ‘diene of the Age: (2) Obstruction to the entrance of
the normal amount of air by strangulation, or enclosure in an insufficient space. (3) En-
feeblement of the circulation, so that the medulla oblongata does not receive a sufficient amount
of blood ; in degeneration of the heart, valvular cardiac disease ; and artificially by ligature of
the carotid and vertebral arteries (Kussmaul and Tenner), or by preventing the free efflux of
venous blood from the skull, or by the ra ag of a large quantity of air or indifferent particles
into the right heart. (4) Direct loss of blood, which acts by arresting the exchange of gases
in the medulla (J. Rosenthal). This is the cause of the ‘‘ biting or snapping at the air” mani-
fested by the decapitated heads of young animals, ¢.g., kittens. [The phenomenon is well marked
in the head of a tortoise separated from the body (W. Stirling).] a

If we study the rapidly fatal effects of these factors on the respiratory activity, we observe
that at first the respirations become quicker and deeper, then after an attack of general con-
vulsions, ending in expiratory spasm, there follows a stage of complete cessation of respiration.
Before death takes place, there are usually a few ‘‘snapping” or gasping efforts at inspiration
(Hogyes, Sigm. Mayer—§ 111). ; rt _

Condition of the Blood-Gases.—As a general rule, in the production of dyspneea, the want
of O and the excess of CO, act simultaneously (Pfliiger and Dohmen), but each of these alone
may act as an efficient cause. According to Bernstein, blood containing a small amount of O
acts chiefly upon the inspiratory centre, and blood rich in CO, on the expiratory centre. (1)
Dyspnea, from want of O, occurs during respiration in a space of moderate size (§ 133), in
spaces where the tension of the air is diminished, and by breathing indifferent gases or those
containing no free O. When the blood is freely ventilated with N or H, the amount of CO,
in the blood may even be diminished, and death occurs with all the signs of asphyxia (Pfliger).
(2) Dyspnea, from the blood being overcharged with CO,, occurs by breathing air containing
much CO, (§ 133). Air containing much CO, may cause dyspneea, even when the amount of O
in the blood is greater than that in the atmosphere (Zhiry). The blood may even contain more
O than normal (Pfliiger).

Heat Dyspnea.—An increased temperature increases the activity of the respiratory centre
(§ 214, II., 3). This occurs when blood warmer than natural flows through the brain, as Fick
and Goldstein observed when they placed the exposed carotids in warm tubes, so as to heat the
blood passing through them. In this case the heated blood acts directly upon the brain, the
medulla, and the cerebral respiratory centres (Gad). Direct cooling diminishes the excitability
(Frédéricq). When the temperature is increased, vigorous artificial respiration does not produce
apnoea, although the blood is highly arterialised (Ackermann). Emetics act ina similar manner
(Hermann and Grimm).

Electrical stimulation of the medulla oblongata, after it is separated from the brain,
discharges respiratory movements or increases those already present (Kronecker and Marck-
wald). Langendorff found that electrical, mechanical, or chemical (salts) stimulation usually
caused an expiratory effect, while stimulation of the cervical spinal cord (subordinate centre)
gave an inspiratory effect. According to Laborde, a superficial lesion in the region of the
calamus scriptorius causes standstill of the respiration for a few minutes. If the peripheral
end of the vagus be stimulated, so as to arrest the action of the heart, the respirations also
cease after a few seconds. Arrest of the heart’s action causes a temporary anemia of the
medulla, in consequence of which its excitability is lowered, so that the respirations cease for
a time (Langendorff), _

Action on the Centre.—The respiratory centre, besides being capable of
being stimulated directly, may be influenced by the will, and also reflexly by
stimulation of a number of afferent nerves.

1, By a voluntary impulse we may arrest the respiration for a short time,
but only until the blood becomes so venous as to excite the centre to increased
action. ‘The number and depth of the respirations may be voluntarily increased for
a long time, and we may also voluntarily change the rhythm of respiration.

2. The respiratory centre may be influenced reflexly both by fibres which excite
it to increased action and by others which inhibit its action. (a) The exciting
fibres lie in the pulmonary branches of the vagus, in the optic, auditory, and
cutaneous nerves; normally their action overcomes the action of the inhibitory
fibres. Thus, a cold bath deepens the respirations, and causes a moderate accelera-
tion of the pulmonary ventilation (Speck).

Section of both vagicauses slower and deeper respiratory movements, owing
to the cutting off of those impulses which under normal conditions pass from the _
lungs to excite the respiratory centre (p. 661). The amount of air taken in the _

CONDITIONS ACTING ON THE RESPIRATORY CENTRE. 665

CO, given off, however, is unchanged, but the inspiratory efforts are more vigorous
and not so purposive (Gad), Weak tetanising currents applied to the central end
of the vagus, cause acceleration of the respirations, while, at the same time, the
efforts of the respiratory muscles may be increased, or diminished, or remain un-
changed (Gad). Strong tetanising currents cause standstill of the respiration in
the inspiratory phase (Z’vraube), or especially in fatigue of the nerves, in the
expiratory phase (Budge, Burkart). Single induction shocks have no effect
(Marckwald and Kronecker).

[Marckwald, while admitting that the respiratory centre is automatically active, as well as
capable of being affected reflexly, comes to the conclusion, that, when the centre is
separated from all nerve-channels by which afferent impulses can be conveyed to it, it is
incapable of discharging rhythmical respiratory movements. He also asserts that the normal
thythmical respiration is a reflex act discharged chiefly through the vagi, and that the normal
excitant of the respiratory centre is not dependent on the condition of the blood, either on the
diminution of O, or the increase of CO, These results are opposed to the usually accepted
view, and they are controverted by Loewy. Division of the medulla oblongata above the
respiratory centre, so as to cut off all cerebral channels of communication, has very little
effect on the respirations. If, after this, one, or both vagi be divided, there is—(1) an eatra-
ordinary slowing of the respiration ; the number of respirations may fall in the rabbit, from
20 to 2 or 4 per minute ; (2) the rhythm is changed, in some cases the inspiration may be
twice or thrice as long as the expiration, but, whatever the ratio of inspiration to expiration,
the respiration is rhythmical ; (3) the volwme of air respired is diminished (p. 664), but the
volume for each respiration is deeper; (4) the intra-thoracic pressure is increased, during
inspiration, and during expiration it is the same as before the vagotomy. ]

Before Vagotomy.., 1 After Vagotomy.
. A | : pom) : c|

o Se > ee lee a pm | O48 mo Sz [ma og
& = 5 2a | on 52 Sida as ee log) ge .
5 22 2 | Be 18s 22 &| Se | 35 | #3 |Bs| fs
e Ba 2 ao am SA 2° 3A So oe Es oa! Som
& = <3) > > = em [om > =) > =

mm. c.cm. c.cm. c.cm. “ihe fae
1 | —30to —40| 20 | 310-350] 16 || -60 to —70]| 4 3 130-140] 59 33 | 100
2 | —22to —24/| 32 | 5380-540/ 16 || —50to —60| 24 4 105-120} 79°5 | 40 | 150

[The above table (from Loewy) shows the result. Loewy finds that, if the centre be separated
from all centripetal channels, it still discharges respiratory movements, which are rhythmical,
and he has shown that these rhythmical discharges are due to the condition of the blood. ]

[If one lung be made atelectic, 7.¢., devoid of air, e.g., by plugging its bronchus with a
sponge-tent, then the pulmonary fibres of the vagus from this lung are no longer excited during
respiration, and their section has no effect on the respiration. Section of the vagus on the
sound side, however, has the same consequence as double vagotomy (Loewy). |

Wedenski and Heidenhain find that a temporary, weak, electrical stimulus applied to the
central end of the vagus, at the beginning of inspiration (rabbit), affects the depth of the
succeeding inspirations, while a similar strong stimulus affects also the depth of the following
expirations. If the stimulus be applied just at the commencement of expiration, stronger
stimuli being required in this case, there is a diminution of the expiration and of the following
inspiration. Continued tetanic stimulation of the vagus may cause decrease in the depth of
the expirations, or at the same time alteration in the depth of the inspirations, without
affecting the respiratory rhythm; when the stimulation is stronger, inspiration and expiration
are diminished with or without alteration of the frequency, and with the strongest stimuli,
respirations cease either in the inspiratory or expiratory phase.

(6) The inhibitory nerves which affect the respiratory centre run in the superior
laryngeal nerve (osenthal), and also in the inferior (Pfliiger and Burkart, Hering,
Breuer), to the respiratory centre (fig. 467, ih).

According'to Langendorff, direct electrical, mechanical, or chemical stimulation of the centre
may arrest respiration, perhaps in consequence of the stimulus affecting the central ends of
these inhibitory nerves where they enter the ganglia of the respiratory centre. During the
reflex inhibition of the respiration in the expiratory phase, there is a suppression of the motor
impulse in the inspiratory centre ( Wegete).

Stimulation of the superior or inferior laryngeal nerves (6) or their central ends

666 STIMULATION AND REGULATION OF THE RESPIRATORY CENTRE.

causes slowing, and even arrest of the respiration (in expiration— Rosenthal).
Arrest of the respiration in expiration is also caused by stimulation of the nasal
(Hering and Kratschmer) and ophthalmic branches of the trigeminus (Christiant),
of the olfactory, and glosso-pharyngeal (Marckwald). [Kratschmer found that
tobacco-smoke blown into a rabbit’s nostrils, or puffed through a hole in the
trachea into the nose, by stimulating the nasal branch of the fifth nerve, arrested
the respiration in the expiratory phase ; while it had no effect when blown into the
lungs. Ammonia vapour applied to the nostrils arrests it in the same way. If
ammonia vapour be blown into the lungs (the nasal cavity being protected from its
action), the respiration may be accelerated, or deepened, or arrested occasionally in
expiration, «.¢., according to the fibres of the vagus acted on by the vapour in the
lungs (Knoll).| Stimulation of the pulmonary branches of the vagus by breathing
irritating gases (Knoll) causes standstill in expiration, although some other gases
cause standstill in inspiration. Chemical stimulation of the trunk of the vagus,—
by dilute solutions of sodic carbonate,—causes expiratory inhibition of the respira-
tion; and mechanical stimulation,—rubbing with a glass rod,—inspiratory inhibition
(Knoll). The stimulation of sensory cutaneous nerves, especially of the chest and
abdomen (as occurs on taking a cold douche), and stimulation of the splanchnics,
cause standstill in expiration, the first cause often giving rise to temporary clonic
contractions of the respiratory muscles. The respirations are often slowed to a very
great extent by pressure upon the brain, [whether the pressure be due to a
depressed fracture or effusion into the ventricles and subarachnoid space]. The
respiration may be greatly oppressed and stertorous. |

The amount of work done by the respiratory muscles is altered during the reflex slowing of
the respiratory muscles, the work being increased during slow respiration, owing to the
ineffectual inspiratory efforts (Gad). The volume of the gases which passes through the lungs
during a given time remains unchanged (Valentin), and the gaseous exchanges are not altered
at first (Voit and Rauber).

Automatic Regulation.— Under normal circumstances, it would seem that the
pulmonary branches of the vagus act upon the two respiratory centres, so as to set
in action what has been termed the self-adjusting mechanism ; thus, the inspiratory
dilatation of the lungs stimulates mechanically the fibres which reflexly excite the
expiratory centres, while the diminution of the lungs during expiration excites the
nerves which proceed to the inspiratory centre (Hering and Breuer, Head). ['Thus,
blowing into the lungs excites the act of expiration, and sucking air out of them
excites inspiration. | :

In this way we may explain the alternate play of inspiration and expiration. In deep
narcosis, however, dilatation of the thorax in animals is followed first by cessation of the
respiratory movements, and then by inspiration (P. Guttmann).

Discharge of the First Respiration.—The foetus is in an apnovic condition
until birth, when the umbilical cord is cut. During intrauterine life, O is freely
supplied to it by the activity of the placenta. All conditions which interfere with
this due supply of O, as compression of the umbilical vessels and prolonged labour
pains, cause a decrease of the O and an increase of the CO, in the blood, so that
the condition of the foetal blood is so altered as to stimulate the respiratory centre,
and thus the impulse is given for the discharge of the first respiratory movement
(Schwartz). A foetus, still within the unopened foetal membranes, may make
respiratory movements (Vesalius, 1542). If the exchange of gases be interrupted
to a sufficient extent, dyspnoea and ultimately death of the foetus may occur. If,
however, the venous condition of the mother’s blood develops very slowly, as in
cases of quiet slow death of the mother, the medulla oblongata of the foetus may
gradually die without any respiratory movement being discharged (§ 324, 5).

According to this view, the respiratory movements are due to the direct action of the

dyspneeic blood upon the medulla oblongata. [The excitability of the respiratory centre is less

DIRECT STIMULATION OF THE CARDIO-INHIBITORY CENTRE. 667

in the feetus than in the newly born, and it increases from day to day after birth. Amongst
the causes of the diminished excitability are the small amount of O in fetal blood, and the slow
velocity of the circulation. If an inspiration is discharged in the fcetus, it is at once inhibited
by fluid passing into the nostrils and inhibiting the act reflexly. The chief cause of the first
respiration after birth, is undoubtedly the increasing venosity of the blood, and also the dis-
appearance of the above-named reflex inhibitory process.] Death of the mother acts like
compression of the umbilical cord. In the former case, the maternal venous blood robs the
foetal blood of its O, so that death of the foetus occurs more rapidly (Zuntz). If the mother be
rapidly poisoned with CO (§ 17), the foetus may live longer, as the CO-hemoglobin of the
maternal blood cannot take any O from the fcetal blood (§ 16—Hogyes). In slow poisoning the
CO passes into the foetal blood (Gréhant and Quinquand).

In many cases, especially in cases of very prolonged labour, the excitability of the respiratory
centre may be so diminished, that after birth, the dyspneic condition of the blood alone is not
sufficient to excite respiration in a normal rhythmical manner. In such cases stimulation of
the skin also acts, e.g., partly by the cooling produced by the evaporation of the amniotic fluid
from the skin. When air has entered the lungs by the first respiratory movements, the air
within the lungs also excites the pulmonary branches of the vagus (Pfliiger), and thus the
respiratory centre is stimulated reflexly to increased activity. According to v. Preuschen’s
observations, stimulation of the cutaneous nerves is more effective than that of the pulmonary
branches of the vagus. In animals which have been rendered apneic by free ventilation of
their lungs, respiratory movements may be discharged by strong cutaneous stimuli, ¢.g., dashing
on of cold water. The mechanical stimulation of the skin by friction or sharp blows, or the
application of a cold douche, excites the respiratory centre. When the placental circulation is
intact, cutaneous stimuli do not discharge respiratory movements (Zuntz and Cohnstein), (Arti-
ficial respiration, § 134).

[Action of Drugs on the Respiratory Centre.—Ammonia, salts of zinc and copper, strychnin,
atropin, duboisin, apomorphin, emetin, the digitalis group, and heat increase the rapidity and
depth of the respirations, while they become frequent and shallower after the use of alcohol,
opium, chloral, chloroform,’ physostigmin. The excitability of the centre is first increased and
then diminished by caffein, nicotin, quinine, and saponin (Brunton). ]

369. CENTRE FOR THE INHIBITORY NERVES OF THE HEART—
(CARDIO-INHIBITORY).—tThe fibres of the vagus, when moderately stimulated,
diminish the action of the heart; when strongly stimulated, however, they arrest
its action and cause it to stand still in diastole (§ 352, 7); they are supplied to the
vagus through the spinal accessory nerve, and have their centre in the medulla
oblongata (§ 353).

[Gaskell has shown that stimulation of the vagus not only influences the rhythm
of the heart’s action, but modifies the other functions of the cardiac muscle.
Stimulation of the vagus influences—(a) the automatic rhythm, 2.e., the rate at
which the heart contracts automatically ; (6) the force of the contractions, more
especially the auricles, although in some animals, ¢.g., the tortoise, the ventricles
are not affected; (c) the power of conduction, v.¢., the capacity for conducting the
muscular contractions. According to Gaskell, the vagus acts upon the rhythmical
power of the muscular fibres of the heart. |
_ This centre may be excited directly in the medulla, and also reflexly, by stimu-
lating certain afferent nerves,

Many observers assume that this centre is in a state of tonic excitement, 7.c., that there is
a continuous, uninterrupted, regulating, and inhibitory action of this centre upon the heart
through the fibres of the vagus. According to Bernstein, this tonic excitement is caused
reflexly through the abdominal and cervical sympathetic. .

I. Direct Stimulation of the Centre.—This centre may be stimulated directly,
by the same stimuli that act upon the respiratory centre. (1) Sudden anemia of
the oblongata, ligature of both carotids or both subclavians, or decapitating a
rabbit, the vagi alone being left undivided, cause slowing and even temporary
arrest of the action of the heart. (2) Sudden venous hyperemia acts in a similar
manner, ¢.g., by ligaturing all the veins returning from the head. (3) Increased
venosity of the blood, produced either by direct cessation of the respiraticns (rabbit),
or by forcing into the lungs a quantity of air containing much CO, (Zvaube). As
the circulation in the placenta (the respiratory organ of. the foetus) is interfered

668 STIMULATION OF THE TRUNK OF THE VAGUS.

with during severe labour, this sufficiently explains the enfeeblement of the action
of the heart which occurs during protracted labour ; it is due to stimulation of the
central end of the vagus by the dyspnaic blood (B. S. Schultze). (4) At the
moment the respiratory centre is excited, and an inspuration occurs, there. is a |
variation in the inhibitory activity.of the cardiac centre (Donders, Pjliger, Frédéricq
—$ 74, a. 4). (5) The centre is excited by increased blood-pressure within the |

cerebral arteries. ;

II. The centre may be excited reflexly by—(1) Stimulation of sensory nerves
(Loven). (2) Stimulation of the centralend of one vagus, provided the other vagus
is intact. (3) Stimulation of the sensory nerves of the intestines, by tapping upon
the belly (Goltz’s tapping experiment), whereby the action of the heart is arrested.
Stimulation of the splanchnic directly (Asp and Ludwig), or of the abdominal or
cervical sympathetic, produces the same result. Very strong stimulation of
sensory nerves, however, arrests the above-named reflex effects upon the vagus |
(§ 361, 3).

Tapping Experiment.—Goltz’s experiment succeeds at once, by tapping the intestines of a
frog directly, say, with the handle of a scalpel, especially if the intestine has been exposed to
the air for a short time, so as to become inflamed (Zarchanoff). Stimulation of the stomach of 4
the dog causes slowing of the heart-beat (Sig. Mayer and Pribram). [M‘William finds that the
action of the heart of the eel may be arrested reflexly with very great facility. The reflex
inhibition is obtained by slight stimulation of the gills (through the branchial nerves), the
skin of the head and tail, and parietal peritoneum, by severe injury of almost any part of the
animal, except the abdominal organs. ]

[Effect of Swallowing Fluids.—Kronecker has shown that the act of swallowing interferes
with or abolishes temporarily the cardio-inhibitory action of the vagus, so that the pulse-rate is
greatly accelerated. Merely sipping a wine-glassful of water may raise the rate 30 per cent.
Hence, sipping cold water acts as a powerful cardiac stimulant. ]

According to Hering, the excitability of the cardio-inhibitory centre is diminished by
vigorous artificial ventilation of the lungs with atmospheric air. At the same time, there is a
considerable fall of the blood-pressure (§ 352, 8, 4). In man, a vigorous expiration, owing to
the increased intra-pulmonary pressure, causes an acceleration of the heart-beat, which
Sommerbrodt ascribes to a diminution of the activity of the vagi. At the same time the
activity of the vaso-motor centre is diminished (§ 60, 2).

Stimulation of the trunk of the vagus from the centre downwards, along its
whole course, and also of certain of its cardiac branches [inferior cardiac], causes
the heart either to beat more

. ee slowly, or arrests its action in
VIN OI diastole. The result depends

Heart Beat. upon the strength of the stimulus

TOTP TTT TT TT TTT TT TTT TT TTT TT TTT eT bs 9 OG Ye GT Rn employed ; feeble stimuli slow
: A Secs. : °

7 meme: the action of. the heart, while

| — Stimulation strong stimuli arrest it in dias-

Fig. 468. tole. The frog’s heart may be

Beating of a frog’s heart taken by means of a lever rest- arrested by stimulating the fibres

ing on the heart. The lowest curve shows when the of the vagus upon the sinus ve-

vagus was stimulated and the consequent arrest of th i i
Beare beat (Sig tine, q of the nosus [or by stimulating the

y ghd vagus in its course as in fig.
468]. If strong stimuli be applied, either to the centre or to the course of the nerve,
for a long time, the part stimulated becomes fatigued and the heart beats more
rapidly in spite of the continued stimulation, If a part of the nerve lying nearer
the heart be stimulated, inhibition of the heart’s action is brought about, as the
stimulus acts upon a fresh portion of nerve. |

The following points have also been ascertained regarding the stimulation of the inhibitory q

1. The experiments of Liwit on the frog’s heart, confirmed by Heidenhain, showed that
electrical and chemical stimulation of the vagus produce different cova: as regards the extent
of the ventricular systole, as well as the number of heart-beats ; the contractions either become

te al

DIFFERENCE IN ANIMALS. 669

smaller, or less frequent, or they become smaller and less frequent simultaneously, Strong
stimuli cause, in addition, well-marked relaxation of the heart-muscle during diastole.

2. In order to cause inhibition of the heart, a continwous stimulus is not necessary. <A
rhythmically interrupted moderate stimulus suffices (v. Bezvld) ; 18 to 20 stimuli per second are
required for mammals, and 2 to 3 per second for cold-blooded animals,

3..Donders, with Prahl and Niiel, observed that arrest of the heart’s action did not take
place immediately the stimulus was applied to the vagus; but about é of a second—period of
latent stimulation—elapsed before the effect was produced on the heart.

4, If the heart be arrested by stimulation of the vagus, it can still contract, if it be excited

- directly, e.g., by pricking it with a needle, when it executes a single contraction. [This holds

good only for some animals, ¢.g., frog, tortoise, birds and mammals, In fishes, only the
ventricle responds to stimulation during marked inhibition ; in the newt, only the bulbus
arteriosus, In the newt’s heart, the sinus, auricles, and ventricle are all inexcitable to direct
stimulation during strong inhibition. ]

5. According to A. B. Meyer, inhibitory fibres are present only in the right vagus in the
turtle, It is usually stated that the right vagus is more effective than the left in other animals,
¢.g., rabbit (Masoin) ; but this is subject to many exceptions (Landois and Langendorf’). [In
the newt, the right vagus acts more readily on the ventricle than on the other parts of the
heart ; slight stimulation of the right vagus can arrest the ventricle, while the sinus and auricles

. go on beating. ]

6. The vagus has been compressed by the finger in the neck of man (Czermak, Concato); but
this experiment is accompanied by danger, and ought not to be undertaken, The electrotonic
condition of the vagus is stated in § 335, III.

7. Schiff found that stimulation of the vagus of the frog caused acceleration of the heart-beat,
when he displaced the blood of the heart with saline solution, If blood-serum be supplied to
the heart, the vagus regains its inhibitory action,

8. Many soda salts in a proper concentration arrest the inhibitory action of the vagus, while
potash salts restore the inhibitory function of the vagi suspended by the soda salts. If, how-
ever, the soda or potash salts act too long upon the heart, they produce a condition in which,
after the inhibitory function of the vagi is abolished, it is not again restored. The heart’s
action in this condition is usually arhythmical (Léwit).

9, If the intracardial pressure be greatly increased, so as to accelerate greatly the cardiac
pulsations, the activity of the vagus is correspondingly diminished (J. M. Ludwig and
Luchsinger).

[Differences in Animals,—Perhaps the most remarkable fact in connection with the influence

~ of the vagus on the eel’s heart and that of all other fishes examined, is, that vagus-stimulation

causes the sinus and auricle to be entirely inexcitable to direct stimulation during strong
inhibition. Nerve-stimulation has in this case the very peculiar effect of rendering the
muscular tissue temporarily incapable of responding to even the strongest direct stimuli, ¢.g.,
powerful induction shocks. This would appear to be decisive evidence that the vagus acts on
muscle directly, and not simply on automatic motor ganglia, as was held according to the old

~ view (M*‘ William). |

Poisons.— Muscarin stimulates the terminations of the vagus in the heart, and causes the
heart to stand still in diastole (Schmiedeberg and Koppe). [See p. 85 for Gaskell’s views.] If
atropin be applied in solution to the heart, this action is set aside, and the heart begins to beat
again. [Atropin abolishes completely the inhibitory action of the vagus on the heart. If it
be injected into the jugular vein of a rabbit, the pulse-beats are increased 27 per cent.,
in the dog, they may be trebled, and in a man under its full influence the pulse-beats
may rise from 70 to 150 or more. After atropin, it is impossible to arrest the action of the
heart by stimulation of the vagus, and in the frog this cannot be done even by stimulation of
the inhibitory centre in the heart itself, so that atropin must be regarded as paralysing the
intracardiac terminations of the vagus.] Digitalin diminishes the number of heart-beats
by stimulating the cardio-inhibitory centre (vagus) in the medulla.- Large doses diminish the
excitability of the vagus centre, and increase at the same time the accelerating cardiac ganglia,
so that the heart-beats are thereby increased. In small doses, digitalin raises the blood-
pressure by stimulating the vaso-motor centre and the elements of the vascular wall (Klug).
Nicotin first excites the vagus, then rapidly paralyses it. Hydrocyanic acid has the same
effect (Preyer). Atropin (v. Bezold) and curara (large dose—Cl. Bernard and Kélliker)
paralyse the vagi, and so does a very low temperature or high fever.

370. CENTRE FOR THE ACCELERATING CARDIAC NERVES.—
Nervus Accelerans.—It is more than probable that a centre exists in the medulla
oblongata, which sends accelerating fibres to the heart. These fibres pass from the
medulla oblongata—but from which part thereof has not been exactly ascertained
—through the spinal cord, and leave the cord through the rami communicantes of
the lower cervical and upper six dorsal nerves (Stricker), to pass into the sympathetic

670 THE NERVUS ACCELERANS AND THE CARDIAC PLEXUS.
/ . Ve

nerve. Some of these fibres, issuing from the spinal cord, pass through the pormeatgn
sympathetic ganglion and the ring of Vieussens, to Join the ramet plexus (figs. ld
470). [These fibres, proceeding from the spinal cord, frequent y accompany | a
nerve running along the vertebral artery], and they constitute the N ervus accelerans
cordis. (Fig. 470 shows the accelerator fibres passing through the ganglion stellatum
of the cat to join the cardiac plexus.] If the vagi of an animal be divided, stimu-
lation of the medulla oblongata, of the lower end of the divided cervical spinal cord,

Fig. 469. Fig. 470.

469.—Scheme of the course of the accelerans fibres. P, pons; MO, medulla oblongata ;
C, spinal cord ; V, inhibitory centre for heart ; A, accelerans centre ; Vac., vagus; SL,
superior, IL, inferior laryngeal ; SC, superior, IC, inferior cardiac ; H, heart; C, cerebral
impulse; S, cervical sympathetic ; a, a, accelerans fibres. Fig 470.—Cardiac plexus, and
ganglion stellatum of the cat. R, right, L, left x14; 1, vagus; 2’ cervical. sympathetic,
and in the annulus of Vieussens; 2, communicating branches from the middle cervical gan-
glion and the ganglion stellatum; 2’, thoracic sympathetic; 8, recurrent laryngeal ; 4,
depressor nerve ; 5, middle cervical ganglion ; 5’, communication between 5 and the vagus;
6, ganglion stellatum (1st thoracic ganglion) ; 7, communicating branches with the vagus ;
8, nervus accelerans ; 8, 8’, 8’, roots of accelerans ; 9, branch of the ganglion stellatum.

*

Fig.

even of the lower cervical ganglion, or of the upper dorsal ganglion of the
sympathetic (Gang. stellatum), causes acceleration of the heart-beats in the dog and
rabbit, without the blood-pressure undergoing any change (Cl. Bernard, v. Bezold,
Cyon).

On stimulating the medulla oblongata or the cervical portion of the spinal cord, the vaso-
motor nerves are, of course, simultaneously excited. The consequence is that the blood-vessels,
supplied by vaso-motor nerves from the spot which is stimulated, contract, and the blood-
pressure is greatly increased. Again, a simple increase of the blood-pressure accelerates the
action of the heart ; this experiment does not prove directly the existence of accelerating fibres
lying in the upper part of the spinal cord. If, however, the splanchnic nerves be divided
beforehand (when, as they supply the largest vaso-motor area in the body, the result of their
division is to cause a great fall of the blood-pressure), then on stimulating the above-named

ACCELERANS IN THE FROG. 671

parts, after this operation, the heart-beats are still. increased in number, so that this increase
cannot be due to the increased blood-pressure. Indirectly it may be shown, by dividing or
extirpating all the nerves of the cardiac plexus, or at least all the nerves going to the heart,
that stimulation.of the medulla oblongata, or cervical part of the spinal cord, no longer
causes an increased frequency of the heart’s action to the same extent as before division of
these nerves. The slightly increased frequency in this case is due to the increased blood-
pressure.

The accelerating centre is certainly not continually in a state of tonic excitement,
as section of the accelerans nerve does not cause slowing of the action of the heart ;
the same is true of destruction of the medulla oblongata or of the cervical spinal
cord. In the latter case, the splanchnic nerves must be divided beforehand, to
avoid the slowing effect on the action of the heart produced by the great fall of the
blood-pressure consequent upon destruction of the cord, otherwise we might be apt
to ascribe the result to the action of the accelerating centre, when it is in reality
due to the diminished blood-pressure (Cyov).

According to the results of the older observers (v. Bezold and others), some
accelerating fibres run in the cervical sympathetic. A few fibres pass through the
vagus to reach the heart (§ 352, 7), and when they are stimulated, either the heart-
beat is accelerated or the cardiac contractions strengthened (//e:denhain and Liwit),
or the latter alone occurs (Pawlow). The inhibitory fibres of the vagus lose their
excitability more readily than the accelerating fibres, but the vagus fibres are more
excitable than those of the accelerans.

Tarchanoff has described some very rare cases of individuals who, by a merely voluntary effort,
and while at rest, the respirations remaining unaffected, could nearly double the number of
their pulse-beats.

Modifying Conditions.—When the peripheral end of the nervus accelerans is stimulated, a
considerable time elapses before the effect upon the frequency of the heart takes place, ¢.e., it
has a long latent period. Further, the acceleration thus produced disappears gradually. If
the vagus and accelerans fibres be stimulated simultaneously, only the inhibitory action of the
vagus is manifested. If, while the accelerans is being stimulated, the vagus be suddenly excited,
there is a prompt diminution in the number of the heart-beats ; and if the stimulation of the
vagus is stopped, the accelerating effect of the accelerans is again rapidly manifested (C. Ludwig
with Schmiedebery, Bowditch, Baxt). According to the experiments of Stricker and Wagner
on dogs, with both vagi divided, a diminution of the number of the heart-beats occurred

when both accelerantes were divided. This would indicate a tonic innervation of the latter
nerves. .

[Accelerans in the Frog.—Gaskell showed that stimulation of the vagus
might produce two opposing effects ; the one of the nature of inhibition, the other
of augmentation. In the crocodile, the accelerans fibres leave the sympathetic
chain at the large ganglion corresponding to the ganglion stellatum of the dog, and
run along the vertebral artery up to the superior vena cava, and, after anastomosing
with branches of the vagus, pass to the heart. ‘‘Stimulation of these fibres in-
creases the rate of the cardiac rhythm, and augments the force of auricular con-
tractions ; while stimulation of the vagus slows the rhythm, and diminishes the
strength of the auricular contractions.” The strength of the ventricular contraction,
both in the tortoise and crocodile, does not seem to be influenced by stimulation of
the vagus, and probably also it is unaffected by the sympathetic. The so-called
vagus of the frog, in reality, consists of pure vagus fibres and sympathetic fibres,
and is in fact a vago-sympathetic. Gaskell finds that stimulation of the sympathetic,
before it joins the combined ganglion of the sympathetic and vagus, produces purely
augmentor or accelerating effects ; while stzmulation of the vagus, before it enters
the ganglion, produces purely inhibitory effects. The two sets of fibres are quite
distinct, so that in the frog, the sympathetic is a purely augmentor (accelerator),
and the vagus a purely inhibitory nerve. Acceleration is merely one of the effects
produced by stimulation of these nerves ; hence, Gaskell suggests that they ought
to be called “‘ augmentor,” or simply cardiac sympathetic nerves. |

{In his more recent researches Gaskell asserts that vagus stimulation produces first an inhibi-

672 POSITION OF THE VASO-MOTOR CENTRE.

it ultimately improves the condition of the heart as regards

Md ssi fT ft; b t that .
tory or depressing effect, bu lof these. He regards it as a true anabolic nerve (§ 342, d).]

force, rate, or regularity—one or al

3'71. VASO-MOTOR CENTRE AND VASO-MOTOR NERVES,.—Vaso-motor
Centre.—The chief dominating or general centre, which supplies all the non-
striped muscles of the arterial system with motor nerves (Vaso-motor, vaso-con-
strictor, vaso-hypertonic nerves), lies in the medulla oblongata, at a point which
contains many ganglionic cells (Ludwig and Thiry). Those nerves which pass to
the blood-vessels are known as vaso-motor nerves. The centre (which is 3
millimetres long and 1} millimetre broad in the rabbit) reaches from the region of
the upper part of the floor of the medulla oblongata to within 4 to 5 mm. of the
calamus scriptorius. Each half of the body has its own centre, placed 23 milli-
metres from the middle line on its own side, in that part of the medulla oblongata
which represents the upward continuation of the lateral columns of the spinal cord -
according to Ludwig, Owsjannikow, and Dittmar, in the lower part of the superior
olives. Stimulation of this central area causes contraction of all the arteries, and,
in consequence, there is great increase of the arterial blood-pressure, resulting in
swelling of the veins and heart. Paralysis of this centre causes relaxation and
dilatation of all the arteries, and consequently there is an enormous fall of the
blood-pressure. Under ordinary circumstances, the vaso-motor centre is in a condi-
tion of moderate tonic excitement (§ 366). Just as in the case of the cardiac and
respiratory centres, the vaso-motor centre may be excited directly and reflexly.

[Position—How ascertained.—As stimulation of the central end of a sensory
nerve, ¢.y., the sciatic, in an animal under the influence of curara, causes a rise in
the blood-pressure, even after removal of the cerebrum, it is evident that the centre
is not in the cerebrum itself. For the effect of chloral, under the same conditions,
see p. 674. By making a series of sections from above downwards, it is found
that this reflex effect is not affected until a short distance above the medulla
oblongata is reached. If more and more of the medulla oblongata be removed from
above downwards, then the reflex rise of the blood-pressure becomes less and less,
until, when the section is made 4 to 5 mm. above the calamus scriptorius, the
effect ceases altogether. This is taken to be the lower limit of the general vaso-
motor centre. The bilateral centre corresponds to some large multipolar nerve-
cells, described by Clarke as the antero-lateral nucleus. |

I. Direct Stimulation of the Centre.—The amount and quality of the gases
contained in the blood flowing through the medulla are of primary importance. In
the condition of apnoea (§ 368, 1), the centre seems to be very slightly excited, as
the blood-pressure undergoes a considerable decrease. When the mixture of blood-
gases is such as exists under normal circumstances, the centre is in a state of
moderate excitement, and running parallel with the respiratory movements are
variations in the excitement of the centre (Traube-Hering curves—§ 85), these
variations being indicated by the rise of the blood-pressure. When the blood is
highly venous, produced either by asphyxia or by the inspiration of air containing
a large amount of CO,, the centre is strongly excited, so that all the arteries of the
body contract, while the venous system and the heart become distended with blood
(Thiry). At the same time, the velocity of the blood-stream is increased
(Heidenhain). The same result is produced by ligature of both the carotid and
- subclavian arteries, thus causing sudden anemia of the medulla oblongata; and,
no doubt, also by the sudden stagnation of the blood in venous hyperemia. t

Emptiness of the Arteries after Death.—The venosity of the blood which occurs after death
always produces an energetic stimulation of the vaso-motor centre, in consequence of which the
arteries are firmly contracted. The blood is thereby forced towards the capillaries and veins,
and thus is explained the “ arenes of the arteries after death.” | ia

Effect on Hemorrhage.—blood flows much more freely from large wounds, when the vast
motor centre is intact, than if it be destroyed (frog). As psychical excitement undoubtedly

COURSE OF THE VASO-MOTOR FIBRES. 673

influences the vaso-motor centre, we may thus explain the influence of psychical excitement
(speaking, &c.) upon the cessation of hemorrhage. If the hemorrhage be severe, stimulation
of the medulla oblongata, due to the anemia, may ultimately cause constriction of the small
arteries, and thus arrest the bleeding. Thus, surgeons are acquainted with the fact that
dangerous hemorrhage is often arrested as soon as unconsciousness, due to cerebral anemia,
occurs. If the heart be ligatured in a frog, all the blood is ultimately forced into the veins,
and this result is also due to the anemic stimulation of the oblongata (Goltz). In mammals,
when the heart is ligatured, the equilibration of the blood-pressure between the arterial and
venous systems takes place more slowly when the medulla oblongata is destroyed than when it
is intact (v. Bezold, Gscheidlen).

[Effect of Destruction of the Vaso-motor Centre.—If two frogs be pithed and their hearts ex-
posed, and both be suspended, then the hearts of both will be found to beat rhythmically and
fill with blood. Destroy the medulla oblongata and spinal cord of one of them, then immedi-
ately in this case, the heart, although continuing to beat with an altered rhythm, ceases to be
filled with blood ; it appears collapsed, pale, and bloodless. There is a great accumulation of
the blood in the abdominal organs and veins, and it is not returned to the heart, so that the
arteries are empty. This experiment of Goltz is held to show the existence of venous tonus
depending on a cerebro-spinal centre. Ifa limb of this frog be amputated, there is little or no
hemorrhage, while in the other frog the hemorrhage is severe. The bearing of this experi-
ment on conditions of ‘‘shock”’ is evident. ]

Action of Poisons.-—Strychnin stimulates the centre directly, even in curarised dogs, and so
do nicotin and Calabar bean.

Direct Electrical Stimulation.—On stimulating the centre directly in animals, it is found that
single induction shocks only become effective when they succeed each other at the rate of 2 to
3 shocks per second. Thus there is a ‘‘summation”’ of the single shocks. The maximum
contraction of the arteries, as expressed by the maximum blood-pressure, is reached when 10 to 12
strong, or 20 to 25 moderately strong shocks per second are applied (Kronecker and Nicolaides).

Course of the Vaso-motor Nerves,—From the vaso-motor centre fibres proceed directly through
some of the cranial nerves ta their area of distribution ; through the trigeminus partly to the
interior of the eye (§ 347, I., 2), through the lingual and hypoglossal to the tongue (§ 347, III.,
4), through the vagus to a limited extent to the lungs (§ 352, 8, 2), and to the intestines
(§ 352, 11).

All the other vaso-motor nerves descend in the lateral columns of the spinal cord (§ 364, 9) ;
hence, stimulation of the lower cut end of the spinal cord causes contraction of the blood-vessels
supplied by the nerves below the point of section (Pfliiger). In their course through the cord,
these fibres form connections with the subordinate vaso-motor centres in the grey matter of the
cord (§ 362, 7), and then leave the cord either directly through the anterior roots of the spinal
nerves to their areas of distribution, or pass through the rami communicantes into the sympa-
thetic, and from them reach the blood-vessels to which they are distributed (§ 356) [see fig. 439].

The following is the arrangement of these nerves in the region of the head :—The cervical
portion of the sympathetic supplies the great majority of the blood-vessels of the head (see
Sympathetic, § 356, A, 3). In some animals, the great awricular nerve supplies a few vaso-
motor fibres to its own area of distribution (Schiff, Lovén, Moreau). The vaso-motor nerves to
the upper extremities pass through the anterior roots of the middle dorsal nerves into the
thoracic sympathetic, and upwards to the lst thoracic ganglion, and from thence through the
rami communicantes to the brachial plexus (Schiff, Cyon). The skin of the trunk receives its
vaso-motor nerves through the dorsal and lumbar nerves. The vaso-motor nerves to the lower
extremities pass through the nerves of the lumbar and sacral plexuses into the sympathetic,
and from thence to the lower limbs (Pfliiger, Schiff, Cl. Bernard). The lungs, in addition to a
few fibres through the vagus, are supplied from the cervical spinal cord through the 1st thoracic
ganglion (Brown-Séquard, Fick and Badoud, Lichtheim). The splanchnic is the gréatest vaso-
motor nerve in the body, and supplies the abdominal viscera (§ 356, B—v. Bezold, Ludwig and
Cyon). The vaso-motor nerves of the liver (§ 173, 6), kidney (§ 276), and spleen (§ 103) have
been referred to already. According to Stricker, most of the vaso-motor nerves leave the spinal
cord between the 5th cervical and the 1st dorsal vertebre. [Gaskell finds that in the dog (fig.
439) they begin to leave the cord at the 2nd dorsal nerve (§ 366). ]

As a general rule, the blood-vessels for the skin of the trunk and extremities are innervated
from those nerves which give other fibres (¢.g., sensory) to those regions. The different vascular
areas behave differently with regard to the intensity of the action of the vaso-motor nerves.
The most powerful vaso-motor nerves are those that act upon the blood-vessels of peripheral
Farts, e.g., the toes, the fingers, and ears; while those that act upon central parts seem to be
e

o é.

ss active (Lewaschew), ¢.g., on the pulmonic circulation (§ 88).

IL. Reflex Stimulation of the Centre.—There are fibres contained in the
different afferent nerves, whose stimulation affects the vaso-motor centre. There
are nerve-fibres whose stimulation excites the vaso-motor centre, thus causing a

2uU

674 REFLEX STIMULATION OF THE VASO-MOTOR CENTRE.

stronger contraction of the arteries, and consequently an increase of the arterial
blood-pressure. These are called “pressor” fibres. Conversely, there are other
fibres whose stimulation reflexly diminishes the excitability of the vaso-motor
centre, These act as reflex inhibitory nerves on the centre, and are known as

“depressor ” fibres, : j

Pressor, or excito-vaso-motor nerves, have already been referred to in connection
with the superior and inferior laryngeal nerves (§ 352, 12, a), in the trigeminus,
which, when stimulated directly (§ 347), causes a pressor action, as well as when
stimulating vapours are blown into the nostrils (Hering and Kratschmer). — [The
rise of the blood-pressure in this case, however, is accompanied by a change in the
character of the heart’s beat and in the respirations. Rutherford has shown that
in the rabbit the vapour of chloroform, ether, amyl nitrite, acetic acid, or ammonia
held before the nose of a rabbit, greatly retards or even arrests the heart’s action,
and the same is true if the nostrils be closed by the hand. This arrest does not
occur if the trachea be opened, and Rutherford regards the result as due not to the
stimulation of the sensory fibres of the trigeminus, but to the state of the blood
acting on the cardio-inhibitory nerve apparatus.] Hubert and Roever found pressor
tibres in the cervical sympathetic ; S. Mayer and Pribram found that mechanical
stimulation of the stomach, especially of its serosa, caused pressor effects (§ 352,
12, c). According to Loven, the jirst effect of stimulating every sensory nerve is a
pressor action.

[1f a dog be poisoned with curara, and the central end of one sciatic nerve be
stimulated, there is a great and steady rise of the blood-pressure, chiefly owing to
the contraction of the abdominal blood-vessels, and at the same time there is no
change in the heart-beat. If, however, the animal be poisoned with chloral, there
is a fall of the blood-pressure resembling a depressor effect. |

O, Naumann found that weak, electrical stimulation of the skin caused at first contraction
of the blood-vessels, especially of the mesentery, lungs, and the web, with simultaneous excite-
ment of the cardiac activity and acceleration of the circulation (frog). Strong stimuli, however,
had an opposite effect, 7.¢., a depressor effect, with simultaneous decrease of the cardiac activity,
Griitzner and Heidenhain found that contact with the skin caused a pressor effect, while pain-
ful impressions produced no effect. The application of heat and cold to the skin produces
reflexly a change in the lumen of the blood-vessels and in the cardiac activity (Rohrig, Winter-
nitz). Pinching the skin causes contraction of the vessels of the pia mater of the rabbit
(Schiiller), and the same result was produced by a warm bath, while cold dilated the vessels,
These results are due partly to pressor and partly to depressor effects, but the chief cause of the
dilatation of the blood-vessels is the increased blood-pressure due to the cold constricting the
cutaneous vessels. Heat, of course, has the opposite effect. In man, most stimuli applied to
sensory nerves produce an effect :—feeble cutaneous stimuli, tickling (even unpleasant odours,
bitter or acid tastes, optical and acoustic stimuli) at the parts where they are applied, cause a fall
of the cutaneous temperature, and diminution of the volume of the corresponding limb, some-
times increase of the general blood-pressure and change of the heart-beat. The opposite effects
are produced by painful stimulation, the action of heat (and even by pleasant odours and sweet
tastes). The former cause simultaneously dilatation of the cerebral vessels and increase
the vascular contents of the skull,—the latter cause the opposite results (Jstominow and
Tarchanof ),

Depressor fibres, i.¢., fibres whose stimulation diminishes the activity of the
vaso-motor centre, are present in many nerves. They are specially numerous in
the superior cardiac branch of the vagus, which is known as the depressor nerve
(§ 352, 6). The trunk of the vagus below the latter also contains depressor fibres
(v. Bezold), as well as the pulmonary fibres (dog). The latter also act as depressors,
during strong expiratory efforts (§ 74) ; while Hering found that inflating the lungs:
(to 50 mm. Hg pressure) caused a fall of the blood-pressure (and also accelerated
the heart beats—§ 369, IL). Stimulation of the central end of sensory nerves,
especially when it is intense and long-continued, causes dilatation of the blood-
vessels in the area supplied by them (Loven). According to Latschenberger and oa
Deahna, all sensory nerves contain both pressor and depressor fibres. toes

(
Maes =
a

CONDITIONS INFLUENCING THE BLOOD-VESSELS. — 675

|If a rabbit be poisoned with curara, and the central end of the great auricular
nerve be stimulated, there is a double effect—one local and the other general ; the
blood-vessels throughout the body, but especially in the splanchnic area, contract,
so that there is a general rise of the blood-pressure, while the blood-vessels of the
ear are dilated. If the central end of the tibial nerve be stimulated, there is a rise
of the general blood-pressure, but a local dilatation of the saphena artery in the
limb of that side (Zovén). Again, the temperature of one hand and the condition
of its blood-vessels influence that of the other. If one hand be dipped in cold
water, the temperature of the other hand falls. Thus, pressor and depressor effects
may be obtained from the same nerve. The vaso-motor centre, therefore, primarily
regulates the condition of the blood-vessels, but through them it obtains its
importance by regulating and controlling the blood supply according to the needs
of an organ. | .

The central artery of a rabbit’s ear contracts regularly and rhythmically 3 to 5 times per
minute. Schiff observed that stimulation of sensory nerves caused a dilatation of the artery,
which was preceded by a slight temporary constriction.

Depressor effects are produced in the area of an artery on which direct pressure is made, as
occurs, for example, when the sphygmograph is applied for a long time—the pulse-curves
become larger, and there are signs of diminished arterial tension (§ 75).

Rhythmical Contraction of Arteries.—In the intact body slow alternating contraction and
dilatation, without a uniform rhythm, have been observed in the arteries of the ear of the
rabbit, the membrane of a bat’s wing, and the web of a frog’s foot. This arrangement, observed
by Schiff, supplies more or less blood to the parts according to the action of external conditions.
It has been called a ‘‘ periodic regulatory vascular movement.’”’ This movement may be use-
ful when a vessel is occluded, as after ligature, and may help to establish more rapidly the

collateral circulation. Stefani has shown that this occurs with more difficulty after section of
the nerves.

Direct, local, applications may influence the lumen of the blood-vessels ; cold and moderate
electrical stimuli cause contraction; while, conversely, heat.and strong mechanical or
electrical stimuli cause dilatation, although with the last two there is usually a preliminary
constriction.

Poisons.—Almost all the digitalis group of substances cause constriction ; quinine and
salicin a the splenic vessels, The other febrifuges dilate the vessels (7homson).
See p. 95.

Effect on Temperature.—The vaso-motor nerves influence the temperature, not
only of individual parts, but of the whole body.

1. Local Effects.—Section of a peripheral vaso-motor nerve, eg., the cervical
sympathetic, is followed by dilatation of the blood-vessels of the parts supplied
by it (such as the ear of the rabbit), the intra-arterial pressure dilating the paralysed
walls of the vessels. Much arterial blood, therefore, passes into and causes
congestion and redness of the parts, or hyperzemia, while, at the same time, the
temperature is increased. There is also increased transudation through the dilated
capillaries within the dilated areas; the velocity of the blood-stream is of course
diminished, and the blood-pressure increased. The pulse is also felt more easily,
because the blood-vessels are dilated. Owing to the increase of the blood-stream, the
blood may flow from the veins almost arterial (bright red) in its characters, and the
pulse may even be propagated into the veins, so that the blood spouts from them
(Cl. Bernard). Stimulation of the peripheral end of a vaso-motor nerve causes
the opposite results—pallor, owing to contraction of the vessels, diminished
transudation, and fall of the temperature on the surface. The smaller arteries
may contract so much that their lumen is almost obliterated. Continued stimulation
ultimately exhausts the nerve, and causes at the same time the phenomena of
paralysis of the vascular wall. .
‘Secondary Results.—The immediate results of paralysis of the vaso-motor nerves lead to
other effects ; the paralysis of the muscles of the blood-vessels must lead to congestion of the
blood in the part ; the blood moves more slowly, so that the parts in contact with the air cool

more easily, and hence the first stage of increase of the temperature may be followed by a fall
of the temperature. The ear of a rabbit with the sympathetic divided, after several weeks

676 LOCAL AND SECONDARY RESULTS OF VASO-MOTOR ACTION.

than the ear on the sound one. If in man the motor muscular nerves, as well

ee cone fibres, are paralysed, then the paralysed limb becomes cooler, because the
paralysed muscles no longer contract to aid in the production of heat (§ 338), and also because
the dilatation of the muscular arteries, which accompanies a muscular contraction, is absent.
Should atrophy of the paralysed muscles set in, the blood-vessels also become smaller. Hence,
ralysed limbs in man generally become cooler as time goes on. The primary effect, however,
in a limb, e.g., after section of the sciatic or lesion of the brachial plexus, is an increase of the

€
temperature. ; |

If, at the same time, the vaso-motor nerves of a large area of the skin be
paralysed, ¢.g., the lower half of the body after section of the spinal cord, then so
much heat is given off from the dilated blood-vessels that, either the warming of the 7
skin lasts for a very short time and to a slight degree, or there may be cooling
at once. Some observers (T'schetschichin, Naunyn, Quincke) observed a rise of the
temperature after section of the cervical spinal cord, but Riegel did not observe this
increase.

2. Effect on the Temperature of the Body.—Stimulation or paralysis of .
the vaso-motor nerves of a small area has practically no effect on the general
temperature of the body. If, however, the vaso-motor nerves of a considerable area
of the skin be suddenly paralysed, then the temperature of the entire body falls,
because more heat is given off from the dilated vessels than under normal circum-
stances. This occurs when the spinal cord is divided high up in the neck. The
inhalation of a few drops of amyl nitrite, which dilates the blood-vessels of the
skin, causes a fall of the temperature (Sassetzki and Manassein). Conversely,
stimulation of the vaso-motor nerves of a large area increases the temperature,
because the constricted vessels give off less heat. The temperature in fever may
be partly explained in this way (§ 220, 4).

The activity of the heart, z.c., the number and energy of the cardiac con-
tractions, is influenced by the condition of the vaso-motor nerves. When a large
vaso-motor area is paralysed, the blood-channels are dilated, so that the blood does
not flow to the heart at the usual rate and in the usual amount, as the pressure is
considerably diminished. Hence, the heart executes extremely small and feeble
contractions. Stricker observed that the heart of a dog ceased to beat on extirpat-
ing the spinal cord from the 1st cervical to the 8th dorsal vertebra. Conversely,
we know that stimulation of a large vaso-motor area, by constricting the blood-
vessels, raises the arterial blood-pressure considerably. As the arterial pressure
affects the pressure within the left ventricle, it may act as a mechanical stimulus
to the cardiac wall, and increase the cardiac contractions both in number and
strength. Hence, the circulation is accelerated (Herdenhain, Slavjansky).

Splanchnic.—By far the largest vaso-motor area in the body is that controlled by the
splanchnic nerves, as they supply the blood-vessels of the abdomen (§.161) ; hence, stimulation
of their peripheral ends is followed by a great rise of the blood-pressure. When they are
divided, there is such a fall of the blood-pressure that other parts of the body become more
or less anemic, and the animal may even die from ‘“‘ being ied into its own belly,” ¢.¢., from
what has been called ‘‘intravasc hemorrhage.” Animals whose portal vein is ligatured
die for the same reason (C. Ludwig and Thiry) [see § 87]. The capacity of the vascular system,
depending as it does in part upon the condition of the vaso-motor nerves, influences the body-
weight. Stimulation of certain vascular areas may cause the rapid excretion of water, and we
may thus account in part for the diminution of the body-weight, which has been sometimes
observed after an epileptic attack terminating with polyuria.

c disturbances sometimes occur after affections of the vaso-motor nerves (§ 342, L., ¢).
Paralysis of the vaso-motor nerves not only causes dilatation of the blood-vessels and local
increase of the blood-pressure, but it may also cause increased transudation through the capil-
laries [§ 203]. When the active contraction of the muscles is abolished, the blood-stream at
the same time becomes slower, and in some cases, the skin becomes livid, owing to the venous
congestion. There is a diminution of the normal transpiration, and the operas may be d

and peel off in seales. The growth of the hair and nails may be affected by the congestion
blood, # and other tissues may also suffer. fi 7 te 7

Vaso motor Centres in the Spinal Cord.—Besides the dominating centre. €

a

ys

iT)

CONDITIONS AFFECTING THE VASO-MOTOR CENTRE. 67 7.

in the medulla oblongata, the blood-vessels are acted upon by local or subordinate
vaso-motor centres in the grey matter of the spinal cord, as is proved by the follow-
ing observations :-—If the spinal cord of an animal be divided, then all the blood-
vessels supplied by vaso-motor nerves below the point of section are paralysed, as
the vaso-motor fibres proceed from the medulla oblongata. If the animal lives,
the blood-vessels regain their tone and their former calibre, while the rhythmical
movements of their muscular walls are ascribed to the subordinate centres in the
lower part of the spinal cord (aster, Goltz—§ 362, 7).

The subordinate spinal centres may, further, be stimulated directly by dyspneic blood, and
also reflexly, in the rabbit and frog ( Ustimowitsch). After destruction of the medulla oblongata,
the arteries of the frog’s web still contract reflexly when the sensory nerves of the hind leg are
stimulated (Putnam, Nussbaum, Vulpian). Inthe dog, opposite the 3rd to 6th dorsal nerve is a
spinal vaso-motor centre (origin of the splanchnic), which can be excited reflexly (Smirnow),
and there is a similar one in the lower part of the spinal cord (Vulpian).

If the lower divided part of the cord be crushed, the blood-vessels again dilate,
owing to the destruction of the subordinate centres. In animals which survive this
operation, the vessels of the paralysed parts gradually recover their normal diameter
and rhythmical movements. ‘This effect is ascribed to ganglia, which are supposed
to exist along the course of the vessels. [It is to be recollected that the existence
of these peripheral nervous mechanisms has not been proved.| ‘These ganglia [or
peripheral nervous mechanisms] might be compared to the ganglia of the heart, and
seem by themselves capable of sustaining the movements of the vascular wall.
Even the blood-vessels of an excised kidney exhibit periodic variations of their
calibre (C. Ludwig and Mosso). It is important to observe that the walls of the
blood-vessels contract as soon as the blood becomes highly venous. Hence, the
blood-vessels offer a greater resistance to the passage of venous than of arterial
blood (C. Ludwig). Nevertheless, the blood-vessels, although they recover part of
their tone and mobility, never do so completely.

The effects of direct mechanical, chemical, and electrical stimuli on blood-vessels may be due
to their action on these peripheral nervous mechanisms. The arteries may contract so much
as almost to disappear, but sometimes dilatation follows the primary stimulus.

Lewaschew found that limbs, in which the vaso-motor fibres had undergone degeneration,
reacted like intact limbs to variations of temperature ; heat relaxed the vessels, and cold con-
stricted them. It is, however, doubtful if the variations of the vascular lumen depend upon

the stimulation of the peripheral nervous mechanisms. Amy] nitrite and digitalis are supposed
to act on those hypothetical mechanisms.

The pulsating veins in the bat’s wing still continue to beat after section of all their nerves,
which is in favour of the existence of local nervous mechanisms (Luchsinger, Schiff).
,» Influence of the Cerebrum.—The cerebrum influences the vaso-motor
‘entre, as is proved by the sudden pallor that accompanies some psychical con-
ditions, such as fright or terror. There is a centre in the grey matter of the
cerebrum where stimulation causes cooling of the opposite side of the body.

Although there is one general vaso-motor centre in the medulla oblongata, which
influences a// the blood-vessels of the body, it is really a complex composite centre,
consisting of a nwmber of closely aggregated centres, each of which presides over a
particular vascular area. We know something, ¢.¢., ‘of the hepatic (§ 175) and renal
ceutres (§ 276).

Many poisons excite the vaso-motor nerves, such as ergotin, tannic acid, copaiba, and aerials
others first excite, and then paralyse, e.g., chloral hydrate, morphia, "laudanosin, veratrin,
nicotin, Calabar bean, alcohol: others rapidly paralyse them, ¢.g., amyl nitrite, CO (§ 17),
atropin, muscarin. The paralytic action of the poison is proved by the fact that, ‘after section
of the vagi and accelerantes, neither the pressor nor the depressor nerves, when stimulated,
produce any effect. Many pathological infective agents affect the vaso-motor nerves.

The veins are also influenced by vaso-motor nerves, and so are er e lymphaties,
but we know very little about this condition.

Pathological.—_The angio-neuroses, or nervous affections of blood: vessels, form a most
important group of diseases. The parts primarily affected may be either the peripheral nervous

678 PATHOLOGICAL VASO-MOTOR PHENOMENA.

mechanisms, the subordinate centres in the cord, the dominating centre in the medulla, or the —

grey matter of the cerebrum. The effect may be direct or reflex. The dilatation of the vessels
may also be due to stimulation of vaso-dilator nerves, and the physician must be careful to
distinguish whether the result is due to paralysis of the vaso-constrictor nerves or stimulation
of the vaso-dilator fibres. : ;
Angio-neuroses of the skin occur in affections of the vaso-motor nerves, either as a diffuse
redness or pallor ; or there may be circumscribed affections. Sometimes, owing to the stimula-
tion of individual vaso-motor nerves, there are local cutaneous arterio-spasms (Nothnagel). In
certain acute febrile attacks— after previous initial violent stimulation of the vaso-motor nerves,
especially during the cold stage of fever—there may be different forms of paralytic phenomena
of the cutaneous vessels. In some cases of epilepsy in man, Trousseau observed irregular, red,
angio-paralytic patches (ataches cérébrales). Continued strong stimulation may lead to
interruption of the circulation, which may result in gangrene of the skin and deeper-seated
parts ( /Veiss). ;
Hemicrania, due to unilateral spasm of the branches of the carotid on the head, is accom-

panied by severe headache (Du Bois-Reymond). The cervical sympathetic nerve is intensely

stimulated—a pale, collapsed, and cool side of the face, contraction of the temporal artery like
a firm whip-cord, dilatation of the pupil, secretion of thick saliva, are sure signs of this affec-
tion. This form may be followed by the opposite condition of paralysis of the cervical sympa-
thetic, where the effects are reversed. Sometimes the two conditions may alternate. '

Basedow’s disease is a remarkable condition, in which the vaso-motor nerves are concerned ;
the heart beats very rapidly (90 to 129-200 beats per minute), causing palpitation ; there is
swelling of the thyroid gland (struma), and projection of the eyeballs (exophthalmos), with
a palaekd co-ordinated movements of the upper eyelid, whereby the plane of vision is raised
or lowered. Perhaps in this disease we have to deal with a simultaneous stimulation of the
accelerans cordis (§ 370), the motor fibres of Miiller’s muscles of the orbit and eyelids (§ 347, I.),
as well as of the vaso-dilators of the thyroid gland. The disease may be due to direct stimula-
tion of the sympathetic channels or their spinal origins, or it may be referred to some reflex cause.
It has also been explained, however, thus, that the exophthalmos and struma are the conse-
quence of vaso-motor paralysis, which results in enlargement of the blood-vessels, while the
increased cardiac action is a sign of the diminished or arrested inhibitory action of the vagus.
All these eee may be caused, according to Filehne, by injury to the upper part of both
restiform bodies in rabbits.

Visceral Angio-neuroses.—The occurrence of sudden hyperemia with transudations and
ecchymoses in some thoracic or abdominal organs may have a neurotic basis. As already
mentioned, injury to the pons, corpus striatum, and optic thalamus may give rise to hyperemia,
and ecchymoses in the lungs, pleure, intestines, and kidneys. According to Brown-Séquard,
compression or section of one-half of the pons causes ecchymoses, especially in the lung of the
opposite side ; he also observed ecchymoses in the renal capsule after injury of the lumbar
portion of the spinal cord (§ 379).

The dependence of diabetes mellitus upon injury to the vaso-motor nerves is referred to in
§ 175 ;. the action of the vaso-motor nerves on the secretion of urine in § 276; and fever in § 220.

372. VASO-DILATOR CENTRE AND NERVES.— Although a vaso-dilator
centre has not been definitely proved to exist in the medulla, still its existence there
has been surmised. Its action is opposite to that of the vaso-motor centre. The
centre is certainly not in a continuous or tonic state of excitement. The vaso-dilator
nerves behave in their functions similarly to the cardiac branches of the vagus ;
both, when stimulated, cause relaxation and rest ( Schif, Cl. Bernard).. Hence,
these nerves have been called waso-inhibitory, vaso-hypotonic, or vaso-dilator
nerves. LDyspnceic blood stimulates this centre as well as the vaso-motor centre,
so that the cutaneous vessels are dilated, while simultaneously the vessels of the
internal organs are contracted and the organs anemic, owing to the stimulation of
their vaso-motor centre (Dastre and Morat). Nicotin is a powerful excitant of the
vaso-dilator nerves (Ostroumoff) ; it raises the temperature of the foot (dog), and
increases the formation of lymph (Rogowicz),

[The existence of vaso-dilator nerves is assumed in accordance with such facts as
the following :—If the chorda tympani be divided, there is no change in the
blood-vessels of the sub-maxillary gland ; but if its peripheral end be stimulated, in

addition to other results (§ 145), there is dilatation of the blood-vessels of the sub-.

maxillary gland, so that its veins discharge bright florid blood, while they spout

like an artery. Similarly, if the nervi erigentes be divided, there is no effect on

i *

COURSE OF THE VASO-DILATOR NERVES. 679

the blood-vessels of the penis (§ 362, 4); but if their peripheral ends be stimulated
with Faradic electricity, the sinuses of the corpora cavernosa dilate, become filled
with blood, and erection takes place (§ 436). Other examples in muscle and else-
where are referred to below. |

Course of the Vaso-dilator Nerves.—To some organs they pass as special nerves—to other
parts of the body, however, they proceed along with the vaso-motor and other nerves. Accord-
ing to Dastre and Morat, the vaso-dilator nerves for the bucco-labial region (dog) pass out from
the cord by the 1st to the 3rd dorsal nerves, and go through the rami communicantes into the
sympathetic, then to the superior cervical ganglion, and lastly through the carotid and inter-
carotid plexus into the trigeminus. [The fibres occur in the posterior segment of the ring of
Vieussens, and if they be.stimulated there is dilatation of the vessels in the lip and cheek on
that side (p. 624).] The maxillary branch of the trigeminus, however, also contains vaso-
dilator fibres proper to itself (Zaffont). In the grey matter of the cord, there is a special
subordinate ceutre for the vaso-dilator fibres of the bucco-labial region. This centre may be
acted on reflexly by stimulation of the vagus, especially its pulmonary branches, and even by
stimulating the sciatic nerve. The ear receives its nerves from the 1st dorsal and lowest cervical
ganglion, the upper limb from the thoracic portion, and the lower limb from the abdominal
portion of the sympathetic. The vaso-dilator fibres run to the sub-maxillary and sub-lingual
glands in the chorda tympani (§ 349, 4), while those for the posterior part of the tongue run
in the glosso-pharyngeal nerve (§ 351, 4—Vulpian). Perhaps the vagus contains those for the
kidneys (§ 276). Stimulation of the nervi erigentes proceeding from the sacral plexus causes
dilatation of the arteries of the penis, together with congestion of the corpora cavernosa (§ 436)
(Eckhard, Loven). Eckhard found that erection of the penis can be produced by stimulation of
the spinal cord and of the pons as far as the peduncles, which may explain the phenomenon of
priapism in connection with pathological irritations in these regions. The muscles receive
the vaso-dilator fibres for their vessels through the trunks of the motor nerves. Stimulation
of a motor nerve or the spinal cord causes not only contraction of the corresponding muscles,
but also dilatation of their blood-vessels (§ 294, II1.—C. Ludwig and Sczelkow, Hafiz, Gaskell)-—
the dilatation of the vessels taking place even when the muscle is prevented from shortening.
[Gaskell observed under the microscope, the dilatation produced by stimulation of the nerve to
the mylohyoid muscle of the frog.] The vaso-dilators remain medullated up to their terminal
ganglion (Gaskell).

The vaso-dilators (like the vaso-motors, p. 676) also have subordinate
centres in the spinal cord; e¢.., the fibres of the labio-buccal region at the
lst to 3rd dorsal vertebra. This centre may be influenced reflexly through the
pulmonary fibres of the vagus, and also through the sciatic (Laffont, Smirnow).
According to Holtz, a similar centre lies in the lowest part of the cord.

Goltz showed that, in the nerves to the limbs (e.g., in the sciatic nerve), the vaso-motor
and vaso-dilator fibres lie side by side in the same nerve. If the peripheral end of this nerve
be stimulated immediately after it is divided, the action of the vaso-constrictor fibres overcomes
that of the dilators. Ifthe peripheral end be stimulated 4 to 6 days after the section, when the
vaso-constrictors have lost their excitability, the blood-vessels dilate under the action of the
vaso-dilator fibres. Stimuli, which are applied at long intervals to the nerve, act especially on
the vaso-dilator fibres ; while tetanising stimuli act on the vaso-motors. The latent period of
the vaso-dilators is longer, and they are more easily exhausted than the vaso-motors (Bowditch and
Warren). The sciatic nerve receives both kinds of fibres from the sympathetic. It is assumed
that the peripheral nervous mechanisms in connection with the blood-vessels are influenced by
both kinds of vascular nerves ; the vaso-motors (constrictors) increase, while the vaso-dilators
diminish the activity of these mechanisms or ganglia. [It is, however, possible to explain their
effects by supposing that they act directly upon the muscular fibres of the blood-vessels, without
the intervention of any nervous ganglionic structures. ]

[Section of the spinal cord high up in the neck causes, of course, a great fall of the blood-
pressure, owing to the division of the vaso-motor nerves. In the dog the pressure may fall
to 30-40 mm. Hg. After isolation of the cord, in rabbits alone, stimulation of the central
end of a sensory nerve causes a rise of the blood-pressure; in dogs, however, under the same
conditions, the blood-pressure falls. Dyspneeie blood also causes a rise of the blood-pressure,
which is preceded by a fall (Ustimowitch). This reflex fall of the blood-pressure takes place
after section of the splanchnics, and the nerves to the extremities, but it does not take place if
the spinal-cdérd be divided at the lumbar or lower dorsal region. If the cord be divided in the
lower dorsal region, stimulation of the brachial plexus has no effect, while the fall occurs after
stimulation of the central end of the sciatic. These experiments indicate that the vaso-dilator
nerves which cause the fall of the blood-pressure arise in the lower part of the spinal cord
(lumbar), and that they are probably contained in the visceral nerves and not in those for the
extremities (Thayer and Pal). | it

680 SPASM AND SWEAT CENTRE.

In the muscles of the face, paralysed by extirpation of the facial nerve, stimula-
tion of the ring of Vieussens causes pseudo-motor contractions of these muscles,
just as stimulation of the chorda tympani causes such contractions in the paralysed
tongue ($349, 4), after section of the hypoglossal nerve (Rogowicz).

In analysing the vascular phenomena resulting from experiments on these nerves, we must
be very careful to determine, whether the dilatation is the result of stimulation of the vaso-
dilators, or a consequence of paralysis of the vaso-constrictors. Psychical conditions act upon
the vaso-dilator nerves—the blush of shame, which is not confined to the face, but may even
extend over the whole skin, is probably due to stimulation of the vaso-dilator centre. _

Influence on Temperature. —The vaso-dilator nerves obviously have a considerable influence
on the temperature of the body and on the heat of the individual parts of the body. Both
vascular centres must act as important regulatory mechanisms for the radiation of heat through
the cutaneous vessels (§ 214, II.). Probably they are kept in activity reflexly by sensory nerves.
Disturbances in their function may lead to an abnormal accumulation of heat, as in fever (§ 220),
or to abnormal cooling (§ 218, 7). Some observers, however, assume the existence of an in-.
tracranial ‘‘ heat-re ting centre ” (7'schetschichin, Naunyn, Quincke). Accordin to Wood,
separation of the medulla oblongata from the pons causes an increased radiation and a iminished
production of heat, due to the cutting off of the influences from the heat-regulatiug centre (§ 377).

373. SPASM-CENTRE — SWEAT-CENTRE, — Spasm-Centre. —In the
medulla oblongata, just where it joins the pons, there is a centre, whose stimulation
causes general spasms. The centre may be excited by suddenly producing a highly
venous condition of the blood (“asphyxia spasms”), in cases of drowning in
mammals (but not in frogs), sudden anemia of the medulla oblongata, either in
consequence of hemorrhage or ligature of both carotids and subclavians (Auwssmaul
and Tenner), and lastly, by sudden venous stagnation caused by compressing the veins
coming from the head. In all these cases, the stimulation of the centre is due to
the sudden interruption of the normal exchange of the gases. When these factors act
quite gradually, death may take place withoat convulsions. Direct stimulation by
means of chemical substances (ammonia carbonate, potash, and soda salts, dc.) applied
to the medulla, quickly causes general convulsions (Papellier). Intense direct
mechanical stimulation of the medulla, as by its sudden destruction, causes general
convulsions.

Position.—Nothnagel attempted by direct stimulation to map out the position of the spasm- -
centre in rabbits ; it extends from the area above the ala cinerea upwards to the corpora quad-
rigemina. It is limited externally by the locus cceruleus and the tuberculum acusticum, In
the frog, it lies in the lower half of the 4th ventricle (Hewbel). The centre is affected in exten- ;
sive reflex spasms (§ 364, 6), e.g., in poisoning with strychnin and in hydrophobia.

Poisons.—Many inorganic and organic poisons, most cardiac poisons, nicotin, picrotoxin,
ammonia (§ 277), and the compounds of barium cause death after producing convulsions, by
acting on the spasm-centre (Réber, Heubel, Bohm).

If the arteries going to the brain be ligatured so as to paralyse the medulla oblongata, then, 4
on ligaturing the abdominal aorta, spasms of the lower limbs occur, owing to the anemic
stimulation of the motor ganglia of the spinal cord (Sigm. Mayer). |

Pathological—Epilepsy.—Schrieder van der Kolk found the blood-vessels of the oblongais
dilated and increased in cases of epilepsy. Brown-Séquard observed that injury to the cent
or peripheral nervous system (spinal cord, oblongata, peduncle, corpora quadrigemina, sciatic
nerve) of guinea-pigs produced epilepsy, and this condition even became hereditary, Stimula-
tion of the cheek or of the face ‘‘ epileptic zone,” on the same side as the injury (spinal cord),
caused at once an attack of epilepsy; but when the peduncle was injured, the opposite side
must be stimulated. Westphal made guinea-pigs epileptic by repeated light blows on the skull,
and this condition also became hereditary. In these cases, there was effusion of blood in the
medulla oblongata and upper part of the spinal cord (§§ 375 and 378, I.). Direct stimulation
of the cerebrum also produces epileptic convulsions. Strong electrical stimulation of the motor —
areas of the cortex cerebri is often followed by an epileptic attack (§ 375). [It is no anfreqnens :
occurrence while one is stimulating the motor areas of the cortex cerebri of a dog, to find the
animal exhibiting symptoms of local or general epilepsy. ]

Sweat-Centre.-A dominating centre for the secretion of the sweat of ‘the

entire surface of the body (§ 289, II.)—with subordinate spinal centres (§ 362, 8)—
occurs in the medulla oblongata (Adamkiewicz, Marmé, Nawrocki). It is double

a

‘
i &
i)

_ PSYCHICAL FUNCTIONS OF THE BRAIN. 681

and in rare cases the excitability is unequa! on the two sides, as is manifested by
unilateral perspiration (§ 289, 2).

Poisons.—Calabar bean, nicotin, picrotoxin, camphor, and ammonium acetate, cause a
secretion of sweat by acting directly on the sweat-centre. Muscarin causes local stimulation of
the peripheral sweat-fibres—it causes sweating of the hind limbs after section of the sciatic
nerves. Atropin arrests the action of muscarin (Ott, Wood, Field, Nawrocki).

[Regeneration of the Spinal Cord.—In some animals, true nervous matter is reproduced after
part of the spinal cord has been destroyed, at least this is so in tritons and lizards (H. Miiller’).
In these animals, when the tail is removed, it is reproduced, and Miiller found that a part of
the spinal cord corresponding to the new part of the tail is reproduced. Morphologically, the
elements were the same, but the spinal nerves were not reproduced, while physiologically, the
new nerve substance was not functionally active ; it corresponds, as it were, to a lower stage of
development. According to Masius and Vanlair, an excised portion of the spinal cord of a frog
is reproduced after six months; while Brown-Séquard maintains that re-union of the divided
surfaces of the cord takes place in pigeons after six to fifteen months. A partial re-union is
asserted to occur in dogs by Dentan, Naunyn, and Eichhorst, although Schieferdecker obtained
only negative results, the divided ends being united only by connective-tissue (Schwalbe). |

374. PSYCHICAL FUNCTIONS OF THE BRAIN.—-The hemispheres of
the cerebrum are usually said to be the seat of all the psychical activities. Only
when they are intact are the processes of thinking, feeling, and willing possible.
After they are destroyed, the organism comes to be like a complicated machine, and
its whole activity is only the expression of the external and internal stimuli which
act upon it. The psychical activities appear to be located in both hemispheres, so
that after destruction of a considerable part of one of them, the other seems to act
in place of the part destroyed. [Objection has been taken to the term the “seat
of” the will and intelligence, and undoubtedly it is more consistent with what we
know, or rather do not know, to say, that the existence of volition and intelligence
is dependent on the connection of the cerebral cortex with the rest of the brain. |

[That a certain condition of the cerebral hemispheres is necessary for the manifestation of the
intellectual faculties, is admitted on all hands ; for, compression of the brain, ¢.g., by a depressed
fracture of the skull, and sudden cessation of the supply of blood to the brain, abolish conscious-
ness. The intellectual faculties are affected by inflammation of the meninges involving the
surface of the brain, the action of drugs affects the intellectual and other faculties; but while
all this is admitted we cannot say precisely upon what parts of the brain ideation depends. The
pre-frontal area, or the convolutions in front of the ascending frontal supplied by the anterior
cerebral artery, are sometimes regarded as the anatomical substratum of certain mental acts.
At any rate, electrical stimulation of these parts is not followed by muscular motion, and,
according to Ferrier, if this region be extirpated in the monkey, there is no motor or sensory
disturbance in this animal ; it still exhibits emotional feeling, all its special senses remain, and
the power of voluntary motion is retained ; but, nevertheless, there is a decided alteration in
the animal’s character and behaviour, so that it exhibits considerable psychological alterations,
and, according to Ferrier, “it has lost to all appearance the faculty of attention and intelligent
observation. ’”’}

Observations on Man.—Cases in which considerable wnilateral lesions or destruction of one
hemisphere have taken place, without the psychical activities appearing to suffer, sometimes
occur. The following is a case communicated by Longet :—A boy, 16 years of age, had his
parietal bone fractured by a stone falling on it, so that part of the protruding brain-matter had
to be removed. On reapplying the bandages, more brain-matter had to be removed. After 18
days he fell out of bed, and more brain-matter protruded, which was removed. On the 35th
day he got intoxicated, tore off the bandages, and with them a part of the brain-matter. After
his recovery, the boy still retained his intelligence, but he was hemiplegic. Even when both
hemispheres are moderately destroyed, the intelligence appears to be intact ; thus, Trousseau
describes the case of an officer whose fore-brain was pierced transversely by a bullet. There
was scarcely any appearance of his mental or bodily faculties being affected. In other cases,
destruction of parts of the brain peculiarly alters the character. We must be extremely careful,
however, in forming conclusions in all such cases. [In the celebrated ‘‘ American crow-bar
case” recorded by Bigelow, a young man was hit by a bar of iron 1} inch in diameter, which
traversed the anterior part of the left hemisphere, going clean out at the top of his head. This
man lived for thirteen years without any permanent alterations of motor or sensory functions ;
but ‘‘the man’s disposition and character were observed to have undergone a serious change.
There were, however, some changes which might be referable to injury to the frontal region.”
In all cases it is most important to know both the exact site and the extent of the lesion. Ross

682 REMOVAL OF THE CEREBRUM.

points out that the characteristic features of lesions in the pre-frontal cortical region are
afforded by “ psychical disturbances, consisting of dementia, apathy, and somnolency.”

Imperfect development of the cerebrum. -Microcephalia and hydrocephalus yield every
result between diminution of the psychical activities and idiocy. Extensive inflammation,
degeneration, pressure, anemia of the blood-vessels, and the actions of many poisons produce
the same effect. ,

Flourens’ Doctrine.—Flourens assumed that the whole of the cerebrum is concerned in
every psychical process. From his experiments on pigeons, he concluded that, if a small part
of the hemispheres remained intact, it was sufficient for the manifestation of the mental
functions ; just in proportion as the grey matter of the hemispheres is removed, ali the
functions of the cerebrum are enfeebled, and when all the grey matter is removed, all the
functions are abolished. According to this view, neither the different faculties nor the different
ea are localised in special areas. Goltz holds a somewhat similar view to that of

lourens. He assumes that if an uninjured part of the cerebrum remain, it can to a certain
extent perform the functions of the parts that have been removed. This Vulpian has called
the law of ‘‘functional substitution” (loi de suppléance).

The Phrenological doctrine of Gall (+ 1828) and Spurzheim assumes that the different —
mental faculties are located in different parts of the brain, and it is assumed that a large
development of a particular organ may be detected by examining the external configuration of —
the head (Cranioscopy).

Removal of the Cerebrum.—After the removal of both cerebral hemispheres,
in most animals, every voluntary movement and all conscious impression and
sensory perception entirely cease. On the other hand, the whole mechanical move-

ments and the maintenance of the equilibrium of the movements are retained.
The maintenance of the equilibrium depends upon the mid-brain, and is regu- |
lated by important reflex channels (§ 379).

Sudden cessation of the circulation in the brain, e.g., by decapitation, is followed at once by
cessation of the mental faculties. When Hayem and Barrier perfused the blood of a horse
through the carotids of a decapitated dog’s head, the head showed signs of consciousness, and
will for 10 seconds, but not longer. |

The mid-brain (corpora quadrigemina) is connected not only with the grey matter
of the spinal cord and medulla oblongata, the seat of extensive reflex mechanisms
(S 367), but it also receives fibres coming from the higher organs of sense, which
also excite movements reflexly. The corpora quadrigemina are also supposed to
contain a reflex inhibitory apparatus (§ 361, 2). The joint action of all these
parts makes the corpora quadrigemina one of the most important organs for the
harmonious execution of movements, and this even in a higher degree than the
medulla oblongata itself (Goltz). Animals with their corpora quadrigemina intact
retain the equilibrium of their bodies under the most varied conditions, but they
lose this power as soon as the mid-brain is destroyed (Goltz). Christiani locates the
co-ordinating centre for the change of place and the maintenance of the equilibrium,
in mammals, in front of the inspiratory centre in the 3rd ventricle (§ 368).

That impressions from the skin and sense-organs are concerned in the maintenance of the
equilibrium, is proved by the following facts :—A frog without its cerebrum at once loses its

wer of balancing itself as soon as the skin is removed from its hind limbs. The action of
impressions communicated through the eyes is proved by the difficulty or impossibility of
maintaining the equilibrium in nystagmus (§ 350), and by the vertigo which often accompanies
paralysis of the external ocular muscles. In persons whose cutaneous sensibility is diminished
the eyes are the chief organs for the maintenance of the equilibrium ; they fall over when the
eyes are closed. [This is well-illustrated in cases of locomotor ataxia (p. 647). ] .

Frog.—A frog with its cerebrum removed retains its power of maintaining its
equilibrium. It can sit, spring, or execute complicated co-ordinated movements
when appropriate stimuli are applied ; when placed on its back, it immediately
turns into its normal position on its belly; if stimulated it gives one or two
springs, and then comes to rest; when thrown into water, it swims to the margin
of the vessel, and it may crawl up the side, and sit passive upon the edge of the
vessel. When incited to move, it exhibits the most complete harmony and unity
in all its movements. Unless it is stimulated, it never makes independent,
voluntary, purposive movements, It sits in the same place continually as if in

‘

ee

REMOVAL OF THE CEREBRUM FROM A FROG. 683

sleep, it takes no food, it has no feelings of hunger and thirst, it shows no symptoms
of fear, and ultimately, if left alone, it becomes desiccated like a mummy on the
spot where it sits. [If the flanks of such a frog be stroked, it croaks with the
utmost regularity according to the number of times it is stroked. Langendorff has
shown that a frog croaks under the same circumstances, when both optic nerves
are divided. It seems to be influenced by light; for, if an object be placed in
front of it so as to throw a strong shadow, then on stimulating the frog it will
spring not against the object, a, but in the direction, > (fig. 471). Steiner finds
that if a glass plate be substituted a ;

for an opaque object like a book, Bava RA =H

the frog always jumps against this F

obstacle. Its balancing move- bee

ments on a board are quite re-

markable and acrobatic in charac-

ter. If it be placed on a board, —

and the board gently inclined (fig. Rig, 471. Fig. 472.

472), it does not fall off, as a frog Fig. 471.—Frog without its cerebrum avoiding an ob-
with only its spinal cord will do, ject placed in its path. Fig. 472.—Frog without its
but as the board is inclined, so as cerebrum moving on an inclined board (Goltz).
to alter the animal’s centre of gravity, it slowly crawls up the board until its equi-
librium is restored. If the board be sloped as in fig. 472, it will crawl up until it
sits on the edge, and if the board be still further tilted, the frog will move as indi-
cated in the figure. It only does so, however, when the board is inclined, and it
rests as soon as its centre of gravity is restored. It responds to every stimulus
just like a complex machine, answering each stimulus with an appropriate action. |

A pigeon without its cerebral hemispheres behaves in a similar manner (fig.
473). When undisturbed it sits continuously, as if in sleep, but when stimulated,
it shows complete harmony of all its
movements ; it can walk, fly, perch, and
balance its body. The sensory nerves
and those of special sensation conduct
impulses to the brain; they only dis-
charge reflex movements, but they do
not excite conscious impressions. Hence,
the bird starts when a pistol is fired close
to its ear; it closes its eyes when it is
brought near a flame, and the pupils con-
tract ; it turns away its head when the
vapour of ammonia is applied to its nos- “zs
trils. All these impressions are not per- g. 473.
ceived as conscious perceptions. The Pigeon with its cerebral hemispheres removed.
perceptive faculties—the will and memory—are abolished ; the animal never takes
food or drinks spontaneously. But if food be placed at the back part of its throat
it is swallowed [reflex act], and in this way the animal may be maintained alive
for months (/lowrens).

Fish appear to behave differently. A carp with its cerebrum removed (fig. 483,
VI. 1) can see and may even select its food, and seems to execute its movements

_ voluntarily (Steiner, Vulpian).

Mammals (rabbit), owing to the great loss of blood consequent on removal of the
cerebrum, are not well suited for experiments of this kind. Immediately after the
operation they show great signs of muscular weakness. When they recover, they
present the same general phenomena; only when they are stimulated they run,
as it were, blindfold against an obstacle. Vulpian observed a peculiar shriek or
ery which such a rabbit makes under the circumstances. Sometimes even in man

684 REMOVAL OF THE CEREBRUM.

a peculiar cry is emitted in some cases of pressure or inflammation rendering the
cerebral hemispheres inactive. :

Observations on somnambulists show that in man, also, complete harmony
of all movements may be retained, without the assistance of the will or conscious
impressions and perceptions. Asa matter of fact, many of our ordinary movements
are accomplished without our being conscious of them. They take place under the
guidance of the basal ganglia.

The degree of intelligence in the animal kingdom is in relation to the size of the cerebral
hemispheres, in proportion to the mass of the other parts of the central nervous system. Taking
the brain alone into consideration, we observe that those animals have the highest intelligence
in which the cerebral hemispheres greatly exceed the mid-brain in weight. The mid-brain is
represented by the optic lobes in the lower vertebrates, and by the corpora quadrigemina
in the higher vertebrates. In fig. 483, VI, represents the brain of a carp; V, of a frog ;
and IV, of a pigeon. In all these cases 1 indicates the cerebral hemispheres ; 2, the optic.
lobes ; 3, the cerebellum; and 4, the medulla oblongata. In the carp, the cerebral hemi-
spheres are smaller than the optic lobes; in the frog, they exceed the latter in size. In
the pigeon, the cerebrum begins to project backward over the cerebellum. The degree of
intelligence increases in these animals in this proportion. In the dog’s brain (fig. 483, II)
the hemispheres completely cover the corpora quadrigemina, but the cerebellum still lies
bebind the cerebrum. In man the occipital lobes of the cerebrum completely overlap the
cerebellum (fig. 479). [The projection of the occipital lobes over the cerebellum is due to the
development of the frontal lobes pushing backwards the convolutions that lie behind them,
and not entirely to increased development of the occipital lobes. ]

Meynert’s Theory.—According to Meynert, we may represent this relation in another way.
As is known, fibres proceed downwards from the cerebral hemispheres, through the crusta or
basis of the cerebral peduncle. These fibres are separated from the upper fibres or tegmentum
of the peduncle by the locus niger, the tegmentum being connected with the corpora quadrige-
mina and the optic thalamus. The larger, therefore, the cerebral hemispheres, the more
numerous will be the fibres proceeding from it. In fig. 461, II, is a transverse section of the
posterior corpora quadrigemina, with the aqueduct of Sylvius and both cerebral peduncles of an
adult man ; p, p, 1s the crusta of each peduncle, and above it lies the locus niger, s, Fig. 461,
IV, shows the same parts ina monkey; III, in a dog; and V, in a guinea-pig. The crusta
diminishes in the above series. There is a corresponding diminution of the cerebral hemi-
spheres, and, at the same time, in the intelligence of the corresponding animals.

Sulci and Gyri.—The degree of intelligence also depends upon the number and depth of the
convolutions. In the lowest vertebrates (fish, frog, bird) the furrows or sulci are absent (fig.
461, IV, V, VI); in the rabbit there are two shallow furrows on each side (III). The dog has
a completely furrowed cerebrum (I, II). Most remarkable is the complexity of the sulci and
convolutions of the cerebrum of the elephant, one of the most intelligent of animals. Never-
theless, some very stupid animals, as the ox, have very complex convolutions.

The absolute weight of the brain cannot be taken as a guide to the intelligence. The
elephant has absolutely the heaviest brain, but man has relatively the heaviest brain. [We
ought also to take into account the complexity of the convolutions and the depth of the grey
matter, its vascularity, and the extent of anastomoses between its nerve-cells. ]

Time an Element in all Psychical Processes.—Every psychical process requires

a certain time for its occurrence—a certain time always elapses between. the
application of the stimulus and the conscious reaction. ; ve |

Nature of Stimulus. | Reaction Time. Name of Observer.
Shock on left hand, . , : : ; ad :
| Shock on forehead, pos. : . ee | “Dol
Shock on toe of left foot, . ; : fal 17 Do.
| Sudden noise, - ‘ ‘ ‘ ; ; 13 Do.
| Visual impression of electric spark, . aa 15 Do.

Hearing a sound, ; : P : ; ol 16 Donders. .
Current to tongue causing taste, . . . 16 v. Vintschgau and
Hon ed.
Saline taste, f : : : : ; ‘ 15 Os); 7
Taste of sugar, . ; eae ; ‘ 16 en me, |
fay Ee ne es. OA Es 16 | "Do. Tote

5, quinine, Pati eo tl pe eon sili 23 Do. & G ma
: se “i bes , aes ;

REACTION TIME. 685

_ Reaction Time.—This time is known as “ reaction time,” and is distinctly longer than the
simple reflex time required for a reflex act. It can be measured by causing the person experi-
mented on to indicate by means of an electrical signal the moment when the stimulus; is
applied. The reaction time consists of the following events :—(1) The duration of perception,
z.€., when we become conscious of the impression ; (2) the duration of the time required to
direct the attention to the impression, 7.¢., the duration of apperception ; and (3) the dwration of
the voluntary impulse, together with (4) the time required for conducting the impulse in the
afferent nerves to the centre, and (5) the time for the impulse to travel outwards in the motor
nerves. If the signal be made with the hand, then the reaction time for the impression of
sound is 0°136 to 0°167 second ; for taste, 0°15 to 0°23; touch, 0°133 to 0°201 second (Horsch,
v. Vintschgau and Hénigschmied); for olfactory impressions, which, of course, depend upon
many conditions (the phase of respiration, current of air), 0°2 to 0°5 second. Intense stimula-
tion, increased attention, practice, expectation, and knowledge of the kind of stimulus to be
applied, all diminish the time. Tactile impressions are most rapidly perceived when they are
applied to the most sensitive parts (v. Vintschgau). The time is increased with very strong
stimuli, and when objects difficult to be distinguished are applied (v. Helmholtz and Bazt).
The time required to direct the attention to a number consisting of 1 to 3 figures, Tigerstedt
and Bergquist found to be 0°015 to 0°035 second. Alcohol and the anesthetics alter the time ;
according to their degree of action they shorten or lengthen it (Kraplin). In order that two
shocks applied after each other be distinguished as two distinct impressions, a certain interval
must elapse between the two shocks—for the ear, 0°002 to 0°0075 second ; for the eye, 0°044 to
0°47 second ; for the finger, 0°277 second.

[The Dilemma.—When a person is experimented on, and he is not told whether the right or
left side is to be stimulated, or what coloured disc may be presented to the eye, then the time
to respond correctly is longer. ]

[Drugs and other conditions affect the reaction time. Ether and chloroform lengthen it,
while alcohol does the same, but the person imagines he really reacts quicker. Noises also
lengthen it. ]

In sleep and waking, we observe the periodicity of the active and passive conditions of the
brain. During sleep, there is diminished excitability of the whole nervous system, which is
only partly due to the fatigue of afferent nerves, but is largely due to the condition of the
central nervous system. During sleep, we require to apply strong stimuli to produce reflex acts.
In the deepest sleep the psychical or mental processes seem to be completely in abeyance, so
that a person asleep might be compared to an animal with its cerebral hemispheres removed.
Towards the approach of the period when a person is about to waken, psychical activity
may manifest itself in the form of dreams, which differ, however, from normal mental
processes. They consist either of impressions, where there is no objective cause (hallucinations),
or of voluntary impulses which are not executed, or trains of thought where the reasoning and
judging powers are disturbed. Often, especially near the time of waking, the actual stimuli
may so act as to give rise tou impressions which become mixed with the thoughts of a dream.
The diminished activity of the heart (§ 70, 3, c), the respiration (§ 127, 4), the gastric and
intestinal movements (§ 213, 4), the formation of heat (§ 216, 4), and the secretions, point to
a diminished excitability of the corresponding nerve-centres, and the diminished reflex excita-
bility to a corresponding condition of the spinal cord. The pupils are contracted during sleep,
the deeper the latter is; so that in the deepest sleep they do not. become contracted on the
application of light. The pupils dilate when sensory or auditory stimuli are applied, and the
lighter the sleep, the more is this the case; they are widest at the moment of awaking (Plotke).
[Hughlings Jackson finds that the retina is more anemic than in the waking state.] During
sleep, there seems to be a condition of increased action of certain sphincter muscles—those for
contracting the pupil and closing the eyelids (Rosenbach). The soundness of the sleep may be
determined by the intensity of the sound required to waken a person. Kohlschiitter found that
at first sleep deepens very quickly, then more slowly, and the maximum is reached after one
hour (according to Ménninghoff and Priesbergen after 17 hour) ; it then rapidly lightens, until
several hours before waking it is very light. External or internal stimuli may suddenly diminish
the depth of the sleep, but this may be followed again by deep sleep. The deeper the sleep,
the longer it lasts. [Durham asserts that the brain is anemic, that the arteries and veins of
the pia mater are contracted during sleep and the brain smaller ; but is this cause or effect ?]

The cause of sleep is the using up of the potential energy, especially in the central nervous
system, which renders a restitution of energy necessary. Perhaps the accumulation of the de-
composition-products of the nervous activity may also act as producers of sleep (? lactates—
Preyer). Sleep cannot be kept up for above a certain time, nor can it be interrupted voluntarily.
Many narcotics rapidly produce sleep. [The “diastolic phase of cerebral activity,” as sleep has
been called, is largely dependent on the-absence of stimuli. We must suppose that there are
two factors, one central, represented by the excitability of the cerebrum, which will vary under
different conditions, and the other external, represented by the impulses reaching the cerebrum
through the different sense-organs. We know that a tendency to sleep is favoured by removal
of external stimuli, by shutting the eyes, retiring toa quiet place, &c. The external sensory

686 ‘STRUCTURE OF THE CEREBRUM.

impressions, indeed, influence the whole metabolism. Strumpell describes the case of a boy
whose sensory inlets were all paralysed except one eye and one ear, and when these inlets were
closed the boy fell asleep, showing how intimately the waking condition is bound up with
sensory afferent impulses reaching the cerebral centres.) Mod:

Leda such as opium, morphia, KBr, chloral, are drugs which induce sleep. ]

ypnotisin, or Animal Magnetism, —{ Most important observations on this subject were made

by Braid of Manchester, whose results are confirmed by many of the recent re-discoveries of
Weinhold, Heidenhain, and others.] Heidenhain assumes that the cause of this condition is
due to an inhibition of the ganglionic cells of the cerebrum, pacer by continuous feeble
stimulation of the face (slightly stroking the skin or electrical applications), or of the optic
nerve (as by gazing steadily at a small brilliant object), or of the auditory nerve (by uniform
sounds) ; while sudden and strong stimulation of the same nerves, especially blowing upon the
face, abolishes the condition. Berger attributes great importance [as did Carpenter and Braid
long ago] to the psychological factor, whereby the attention was directed to a particular part of
the body. The facility with which different persons become hypnotic varies very greatly.
When the hypnotic condition has been produced a number of times, its subsequent occurrence
is facilitated, ¢.g., by merely pressing upon the brow, by placin the body passively ina certain —
josition, or by stroking the skin. In some people the mere idea of the condition suffices, | A
hepuatned person is no longer able to open his eyelids when they are pressed together, This
is followed by spasm of the apparatus for accommodation in the eye, the range of accommodation
is diminished, and there may be deviation of the position of the eyeballs ; then follow phenomena
of stimulation of the sympathetic in the oblongata; dilatation of the fissure of the eyelids and
the pupil, exophthalmos, and increase of the respiration and pulse. At a certain stage, there
may be a great increase in the sensitiveness of the functions of the sense-organs, and also of the
muscular sensibility. Afterwards there may be analgesia of the part stroked, and loss of taste ;
the sense of temperature is lost less readily, and still later that of sight, of smell, and of hearing.
Owing to the abolition or suspension of consciousness, stimuli applied to the sense-organs do
not produce conscious impressions or perceptions. But stimuli applied to the sense-organs of a
hypnotised person cause movements, which, however, are unconscious, although they simulate
voluntary acts. In persons with greatly increased reflex excitability, voluntary movements
may excite reflex spasms; the person may be unable to co-ordinate his organs for speech.

Types.—According to Griitzner, there are several forms of hypnotism :—(1) Passive sleep,
where words are still understood, which occurs especially in girls ; (2) owing to the increased
reflex excitability of the striped muscles, certain groups of muscles may be contracted—a condi-
tion which may last for days, especially in strong people ; at the same time ataxia may occur,
and the muscles may fail to perform their functions (artificial katalepsy). During the stage of
lethargy in hysterical persons, the tendon reflexes are often absent (Charcot and Richer) ; (3)

autonomy at call, i.e., the hypnotised person—in most cases the consciousness is still retained— j
obeys a command, in his condition of light sleep. When the hand is grasped or the head stroked, 4
he executes involuntary movements—runs about, dances, rides on a stool, and the like; (4)
hallucinations occur only in some individuals when they waken from a deep sleep, the hallucina-
tions (usually consisting of the sensation of sparks of fire or odours) being very strong and well-

the finer movements occur rarely. The ‘‘echo-speech” is produced by pressure upon the neck,
speaking into the throat, or against the abdomen. Pressure over the right eyebrow often ushers
in the speech, Colour-sensation is suspended by placing the warm hand on the eye, or by
stroking the opposite side of the head (Cohn). Stroking the limbs in the reverse direction
gradually removes the rigidity of the limbs and causes the person to waken. Blowing on a part
does so at once. Insane persons can be hypnotised. Disagreeable results follow only when the
condition is induced too often and too continuously.

Hypnotism in Animals.—A hen remains in a fixed position when an object is suddenly placed
before its eyes, or when a straw is placed over its beak, or when the head of the animal is pressed
on the ground and a chalk line made before its beak (Kircher’s experimentum mirabile, 1644),
[Langley has hypnotised a crocodile.] Birds, rabbits, and frogs remain passive for a time after
they have been gently stroked.on the back. Crayfish stand on their head and claws (Czermak). :

375, STRUCTURE OF THE CEREBRUM—MOTOR CORTICAL CENTRES, —[Cerebral Con-
volution.—A vertical section of a cerebral convolution consists of a thin layer of grey matter
externally enclosing a white core (fig. 478). The cortex consists of cells and fibres embedded
in a matrix, and to the nerve-cells nerve-fibres proceed from the white matter, The nerve-cells
of the cortex vary in size, form, and distribution in the different layers and also in different
convolutions. Taking such a convolution as the ascending frontal or motor-area type, we get
the appearances shown in fig. 474. It is covered on its surface by the pia mater, (1) The
most superficial layer is narrow, and consists of much neuroglia, a network of branched nerve-
fibrils, a few scattered small multipolar nerve-cells, and a layer of very small medullated nerve-
fibres ; (2) a layer of close-set small, angular, or short pyramidal nerve-cells ; (3) the thickest —
layer or formation of the cornu ammonis, consisting of many layers of larger pyramidal cells, —

pronounced; (5) imitation is rare, ordinary movements, such as walking, are easily imitated, |
\
a

MOTOR CORTICAL CENTRES. 687

which are larger in the deeper than in
the more superficial layers. They are
not so closely packed together, as many
granules lie between them. At the
lowest part of this layer, the cells are
larger than elsewhere, presenting some
resemblance to the cells of the anterior
cornu of the grey matter of the spinal
cord. By some it is described as a
special layer, and termed the ganglion-
cell layer. This layer is specially well
marked in those convolutions which
are described as containing motor
centres. Amongst the large cells area
few small angular-looking cells, which
become more numerous lower down,
and from (4) a narrow layer of numer-
ous small, branched, irregular, gangli-
onic cells—the “granular formation”
of Meynert. In the motor areas mixed
with these are large pyramidal cells,
disposed in groups called ‘‘cell-clus-
ters.” (5) A layer of spindle-shaped
fusiform branched cells—the claustral
formation of Meynert—lying for the
most part parallel to the surface of the
convolution. No layer is composed
exclusively of one form of cell. The
above represents the motor type. Then
follows the white matter (7), consisting
of medullated nerve-fibres, which run
in groups into the grey matter, where
they lose their myelin. The fibres are
somewhat smaller than in the other
parts of the nervous system (diameter
avon inch), and between them lie a few °
nuclear elements. |

[In the sensory type, as in the occi-
pital lobe (fig. 475), the first and second
layers are not unlike the corresponding
layers in the motor type, and the fusi-
form cells in the seventh layer also
resemble the latter. The layer of pyra-
midal cells (3) is not so large, while its
deeper part, sometimes called the “gan-
glion-cell layer,” contains no large
cells. (5) Between the two is (4) a
layer with numerous angular granule-
like bodies or cells, called the “ granule-
layer.””]

[The hippocampus major contains,
besides a layer of neuroglia and some
white matter on the surface, a regular
series of pyramidal cells, which give it
a characteristic appearance. This is the
part which varies most. It is to be re-

Fig. 474. membered that the transition from one .
‘Cortex of motor area type to the other takes place gradually. ] Pee
of brain of monkey [Pyramidal Cells of the Cortex.— Fig. 470.
(x 150). 1, super- Each cell is more or less pyramidal in Cortex of occipital lobe. 1,

ficial layer; 2, small shape, giving off several processes—(a) superficial layer; 2, small
angular cells; 38, py- an apical process, which is often very angular cells; 3, 5, pyra-
ramidal cells; 4, gan- long, and runs towards the surface of midal cells; 4, granule
glionic cells and cell- the cerebrum, where it is said to ter- layer; 6, granules and
clusters; 5, fusiform minate in an ovoid corpuscle, closely ganglionic layer; 7,
cells( Ferrier, after Bevan resembling those in which the ultimate —_spindle-cells (Ferrier,
Lewis), EN) branches of Purkinje’s cells of the cere- after Bevan Lewis),

688 STRUCTURE OF THE CEREBRUM.

. (b) the unbranched median basilar process, which is an axial cylinder process, and
rc scn7 post bet with the axial cylinder of a nerve-fibre of the white matter. It ultimately
becomes invested by myelin. (c) The lateral processes are given off chiefly near the base of

the cell, and they soon branch to
_@ form part of the ground plexus of
<2 [§ B fibrils which everywhere pervades @ See
7 the grey matter. ] , 3s
Each cell is surrounded by a Cc
lymph-space, and so are the blood-
vessels, in the latter case forming
¢ , a perivascular space, which com- d.
-G municates with the pericellular
lymph-space, as in fig. 476.
Soe [Nerve-fibres in the Cortex.—
| ae The ordinary methods of hardening
Fig. 476. the brain do not enable us to detect
y» the enormous number of medul- e
lymph-spaces. a, capillary lated nerve-fibres in the grey
with a lymph-space communi- matter. By using Exner sbeiogre ts
cating with the pericellular acid method, or Weigert's or Pal’s
lymph-space }, round the cell method, we obtain such a result
a lymph-space c, containing 4838 shown in fig. 477. Under the
two lymph-corpuscles. x 150, P14 (P) is a layer of connective-

Perivascular and _ pericellula

tissue (a) devoid of nerve-fibres.
Beneath it is a layer (b) occupying about the half of the outer I
layer, which is almost entirely taken up by medullated uerve-fibres ;
most of these are fine, but a few of them are coarse, and run parallel
to the surface and tangential to the arc of the outer contour of the
convolution. Internal to this is a layer of medullated fibres (¢),
which cross each other in various directions ; while a similar net- h »
work (d) occurs in the small-celled layer. (2) In the layer of large
pyramidal cells (3) there are bundles of medullated fibres, running
radially (ce); but at the lower part of this layer there is a very dense
network (f), forming (in a Weigert’s preparation) a dense, dark
band, corresponding to the outer layer of Baillanger. In the layers
marked (g and h), which are partly in the third and partly in the
fourth cortical layer, the radial arrangement is more marked and
more compact, and the thick fibres are more numerous. In the
middle is (k) a narrow dense network corresponding to Baillanger’s
inner layer. The lower part of the fourth layer, and the whole of le
the fifth, are occupied by 7. It is to be remembered, that all the
convolutions do not present exactly the same structure and arrange-
ment (Obersteiner). |
SD auaecrara ees grey matter differs in different parts of the

rain. In the grey matter of the cornu ammonis, the large pyra- . .

midal cells of (3) make up the chief mass; in the laneteage (4) is Nereis ew i —o
most abundant. In the central convolutions (ascending frontal st ara a 50 ( Pet a
and parietal), according to Betz, Mierzejewski, and Bevan Lewis, se th = y 5 Sve lav Pt
very large pyramidal cells are found in the lower part of the third Me ot t Masts oy thal
layer. Similar cells have been found in the posterior extremities spe f > eet: ata
of the frontal convolutions in some animals—the posterior parietal chee minpures ct
lobule, and para-central lobule, all of which have motor functions. fe : rattan rd leyers
In those convolutions which are regarded as subserving sensory fb ve 4 hit rood
functions, a somewhat different type prevails, ¢.g., the occipital pres 5 ee
gyri or annectant convolution (B. Lewis). The very large pyramidal cells are absent, while
the granule layer exists as a well-marked layer between the layer of large pyramidal cells and the
ganglion cell-layer (fig. 475).]

[Fuchs finds that there are no medullated fibres either in the cortex or medulla until the end
of the first month of life. The medullated fibres appear in the uppermost layer at the fifth
month, and in the second at the end of the first year, the radial bundles in the deeper layers at
the second month. The medullated fibres increase until the seventh or eighth year, when they
have the same arrangement as in the adult. ]

[Blood-Vessels.—The adventitia of the small cerebral vessels contains pigment and granular
cells, filled with oil-granules. In the new-born child, the blood-vessels of the brain are beset —
with cells, filled wit patty granules. Perhaps the granules suppl of the material for the
formation of the myelin sheath on the nerve-fibres. About the I saan the fat is replaced
bya yellow pigment. In adults, yellow or brown glancing pigment-granules are found in the —

BLOOD-VESSELS. OF THE CEREBRUM. 689 —

adventitia of the arteries. In the adventitia of the veins there is no. pigment, but generally
some fat. The grey matter is much more vascular than the white, and when injected, a
section of a convolution presents the. appearance. shown in fig. 478. The nutritive arteries
consist of—(a) the long medullary arteries (1) which pass from the pia mater'through the grey
matter into the central white matter or centrum ovale. They are terminal arteries, and do not
communicate with each other in their course ; thus, they supply independent vascular areas ;
nor do they anastomose with any of the arteries derived from the ganglionic system of blood-
vessels ; 12,to 15 of them are seen in a section ofaconvolution. (b) Theshort cortical nutritive
arteries (2) are smaller and shorter than the foregoing. Although some of them enter the
white matter, they chiefly supply the cortex, where they form an open meshed plexus in the first
layer (a), while in the next layer (b) the plexus of capillaries is dense, the plexus again being
wider in the inner layers (c). |

[Central or Ganglionic Arteries.—From the trunks constituting the circle of Willis (fig. in
§ 381), branches are given off, which pass upwards and enter the brain to supply the basal ganglia
with blood. They are arranged in .

several groups, but they are all ter- ; STALK
minal, ack ou supplying its ik meg a 4 al Nea oda
area, nor do they anastomose wit A Nh a Ra NN AN Kee Ay) Al a) ain ~
the arteries of the cortex. | ty aS wl ae Wieiats al | Al man
Cerebral Arteries.—From a prac- ! RRO hf best iG ll dA ss
- h ey Stab P P B ipso Wats it AY ik ving ! | i Ei Weed Mec AN RS
tical point of view, the distribution SSN TE ij mt a ! Han Uh a
P 4 LiL SA ‘ | Hy} AA 2 i Ay <P it q TNS
of the blood-vessels of the brain is INA ORC E i a) ey Oe a
. xt in tah I . sheep iy
important. The artery of the Syl- iu ROAR i Wi gael \
fi ee if sl

|
vian fissure supplies the mofor areas @.. lh <A
of the brain in animals; in man, Z—~+ Mises
the precentral lobule is supplied by ——-
a branch of the anterior cerebral € US Oi

artery (Duret). The region of the LEN A
third left frontal convolution, which d | ines a 4
is connected with the \fimction of | Re
speech, is supplied by a Special nN a

: Ret
UR ‘ Hi Mi

(iA
‘pst “eat
branch of the Sylvian artery. Those 2 De
oa

areas of the frontal lobes whose in- jean Nill a

jury results in disturbance of the eo ‘eh jit :

intelligence, are supplied by the Bie Nett | | is

anterior cerebral artery. Those linge, a, \

regions of the cortex cerebri, whose PS | .

injury, according to Ferrier, causes jaan ul A

hemianesthesia, are supplied by the inne wan i %

posterior cerebral artery. ee aa i f
[In connection with the localisa- Soa

tion of the centres in the cortex, it oa!

is important to be thoroughly ac- 7, j ty

quainted with the arrangement of Fig. 478.

the cerebral convolutions, Each
half of the outer cerebral surface is
divided by certain fissures into five

1, 1, medullary‘arteries ; and 1’, 1’, in groups between the
convolutions ; 2, 2, arteries of the cortex cerebri ; a, large
: a meshed plexus in first layer; 6, closer plexus in middle
saa EH ek parietal, occipital, layer ; ee opener plexus in the grey wintice next the white
poro-sphenoidal, and central, ake sehiitta Is (d) ;
or island of Reil (fig.: 481). <The -*U0S*#R0e, WIEN 118 Vessels (a). | A
frontal lobe (fig. 479) consists of three convolutions, with numerous secondary folds running
nearly horizontal, named superior (F,), middle (F,), and inferior (F,) frontal -convolutions.
Behind these is a large convolution, the ascending frontal (A), which ascends almost vertically,
immediately behind these—separated from them, however, by the precentral fissure (7/3), and
pe rped off behind by the fissure of Rolando, or the central sulcus (c). ]

[The parietal lobe (fig. 479, P) is limited in front by the fissure of Rolando, below in part by
the Sylvian fissure, and behind by the parieto-occipital fissure. It consists of the ascending
pale (posterior central) convolution (fig. 479, B),; which ascends just behind the fissure of
Rolando, and parallel to the ascending frontal, with which it is continuous below ; above, it
becomes continuous with the superior parietal lobule (P,), while the latter is separated from the
inferior parietal lobule (‘‘ pli courbe”’) by the interparietal sulcus. The inferior parietal lobule
consists of (a) a part arching over the upper end of the Sylvian fissure, the supra-marginal
convolution (P,), which is continuous with the superior temporo-sphenoidal convolution.
Behind is (6) the angular gyrus (P,'), which arches round the posterior end of the parallel
fissure, and becomes connected with the middle temporo-sphenoidal convolution. ] —

_ [The temporo-sphenoidal or temporal lobe (fig. 479, T) consists of three horizontal convolu-

690 CONVOLUTIONS OF THE CEREBRUM.

tions—superior, middle, and inferior—the two former being separated by the parallel sulcus,
while the whole lobe is mapped off from the frontal by the Sylvian fissure (S).] .
e occipital lobe (fig. 479, O) is small, forms the rounded posterior end of the cerebrum,

and is separated from the parietal lobe by the parieto-occipital fissure, which fissure is bridged
over at the lower part by the four annectant gyri (plis de passage of Gratiolet). It has three
convolutions—superior (O,), iddle (O,), and inferior (O;)—on its outer surface. | '
(The central lobe or island of Reil, consists of five or six short, straight convolutions (gyri
operti—fig. 481), radiating outwards and backwards from near the anterior perforated spot,
and can only be seen when the margins of the Sylvian fissure are pulled asunder. The
operculum, consisting of the extremities of the inferior frontal, ascending parietal, and frontal
convolutions, lie outside it, cover it, and conceal it from view. |
(On the inner or mesial surface of the cerebrum are—the gyrus fornicatus (fig. 480, Gf), or
convolution of the corpus callosum, which runs parallel to and bends round the anterior and

Fig. 479,

Left side of the human brain (diagrammatic). F, frontal; P, parietal; O, occipi ft
rae : cipital ;
temporo-sphenoidal lobe ; S, fissure of Sylvius ; 8’, honeoutal ascending Bea of g ;
¢, sulcus centralis, or fissure of Rolando; A, ascending frontal, and B, ascending parie
serolusion ; F,, superior, F,, middle, and F;, inferior frontal convolutions ; f;, superior,
me J», inferior frontal fissures ; f3, sulcus precentralis ; P, superior parietal lobule ; Ps,
nieeiog. parietal lobule, consisting of P,, supra-marginal gyrus, and P,’, angular rus ; ip,
= cus interparietalis ; cm, termination of calloso-marginal fissure ; Oj, first, Oo, secon
Me third occipital convolutions ; yo, parietal-occipital fissure; 0, transverse occipi
“eh oy inferior longitudinal occipital fissure ; T,, first, T,, second, T;, third temporo-
sphenoidal convolutions ; ¢,, first, tg, second temporo-sphenoidal fissures. it injoiaall

posterior extremities of the corpus callosum, terminating posteriorly in the gyrus vificdnatttin’ Be
gyrus hippocampi (fig. 480, H), and ending anteriorly Tae ence extremity, the subiculum
mates egy oe (fig. 480, U). Above it is the calloso-marginal fissure (fig. 480, em), and
rp ing en el to it is the marginal convolution (fig. 480), which lies between the latter
th iri and the margin of the longitudinal fissure ; it is, however, merely the mesial aspec we
on rontal and parietal convolutions. The quadrate lobule or precuneus lies (fig. 480,

t tween the posterior extremity of the calloso-marginal fissure and the parieto-occipital fissuz
it is merely. the mesial aspect of the ascending parietal convolution. The parieto-oc

CONVOLUTIONS OF THE CEREBRUM. 691

fissure terminates below in the calcarine fissure (fig. 480, oc), and the latter runs backwards in
the occipital lobe dividing it into two branches, oc’, oc’. Between the parieto-occipital and
calearine fissures lies the wedge-shaped lobule termed the cuneus (fig. 480, Oz). The calcarine
fissure indicates on the surface the position of the calcar avis or hippocampus minor, in the
posterior cornu of the lateral ventricle. The dentate fissure or swlcws hippocampi (fig. 480, h)
marks the position of the elevation of the hippocampus major, or cornu ammonis, in the lateral
ventricle. The temporo-sphenoidal lobe terminates anteriorly in the uncinate gyrus, while,
running along the former and the occipital lobes, is the collateral fissure (occipito-temporal
sulcus), which marks the position of the eminentia collateralis in the descending cornu of the
lateral ventricle, while it also separates the superior from the inferior temporo-occipital con-
volutions (T, and T;).]

Motor Centres.—In 1870 Fritsch and Hitzig discovered a series of circum-
scribed regions on the surface of the cerebral convolutions, whose stimulation

Gf
Lie

. Fig. 480.

Median aspect of the right hemisphere. CC, corpus callosum divided longitudinally ; Gf,
gyrus fornicatus ; H, gyrus hippocampi; /, sulcus hippocampi; U, uncinate gyrus; em,
calloso-marginal fissure; F, first frontal convolution ; c, terminal portion of fissure of
Rolando ; A, ascending frontal ; B, ascending parietal convolution and paracentral lobule ;
P,’, precuneus or quadrate lobule; Oz, cuneus; Po, parieto-occipital fissure; 0), trans-
verse occipital fissure ; oc, calcarine fissure; oc’, superior, oc’, inferior ramus of the same ;
D, gyrus descendens; T,, gyrus occipito-temporalis lateralis (lobulus fusiformis); T;,
gyrus occipito-temporalis medialis (lobulus lingualis). —

by means of electricity causes co-ordinated movements in quite distinct groups of
muscles of the opposite side of the body (fig. 483, I, II).

Methods—Stimulation.—The surface of the cerebrum is exposed in an animal (dog, monkey)
by removing a part of the skull covering the so-called motor convolutions and dividing the
dura mater. When the convolutions are fully exposed, a pair of blunt non-polarisable (§ 328)
needle electrodes are applied near each other to various parts of the cerebral surface. We may
_ employ the closing or opening shock of a constant current, or the constant current may be
rapidly interrupted, the current being of such a strength as to be distinctly perceived when it is
+ hier to the tip of the tongue (Fritsch and Hitzig). Or, the induced current may be used,
also of such a strength that it is readily felt when applied to the tip of the tongue (Ferrier,
1873). The cerebrum is completely insensible to severe operations made upon tt.

The areas of the cerebral cortex, whose stimulation discharges the characteristic
movements, are regarded by some as-actual centres, because the reaction-time after
stimulation of the centres and the duration of the muscular contraction are longer
than when the subcortical fibres which lead towards the deeper parts of the brain

are stimulated. Another circumstance favouring this view is, that the excitability

692 CONDITIONS AFFECTING THE MOTOR CENTRES.

of these areas is influenced by the stimulation of afferent nerves (Bubnof’ and
Heidenhain). It may be that these centres are acted upon by voluntary impulses in
the execution of voluntary movements. " Hence, they have been called “ psychomotor
centres.” [At any rate, these areas have a definite relation to certain motor acts,

; and perhaps it is well to speak of them as
“areas of representation” of the function to
which they are related.] The motor areas
of the cerebrum (dog, cat, sheep) are charae-
terised by the presence of specially large
pyramidal cells (Betz, Merzejewsky, Bevan
Lewis) ; while similar cells were found by
Obersteiner in the areas marked 4 and 8 (fig.
483), and Betz found them in the ascending
frontal convolution of man, in the third
frontal convolution, and in the island of
Reil. ©. Soltmann found that stimulation
of the motor areas in newly-born animals is
without result, while only the deeper fibres
of the corona radiata are excitable.

Modifying Conditions. —-In the condition of deep
narcosis produced by chloroform, ether, chloral,
morphia, or in apneea, the excitability of the centres
is abolished (Schiff), whilst the subcortical con-
ducting paths still retain their excitability (Bubnof*
and Heidenhain). Small doses of these poisons
and also of atropin at first increase the excitability
of the centres. Moderate loss of blood excites
them, while a great loss of blood diminishes and
then abolishes the excitability (Munk and Orschan-

Fig. 481. sky). Slight inflammation increases, while cooling

Orbital surface of the left frontal lobe and diminishes, the excitability. If the cortex cerebri
the island of Reil, the tip of the temporo- be removed in animals, the excitability of the
sphenoidal lobe removed to show the fibres of the corona radiata is completely abolished
latter. 17, convolution of the margin of about the fourth day, just as in the case of a peri-

the longitudinal fissure ; O, olfactory fis- sage ss nase hl its centre (Albertont,

sure, W ; d

Te ete Rey ee Tne} Stimulation of Subcortical Parts.—As the fibres

volutions on the orbital surface; 1,1,1,1, of the corona radiata converge towards the centre

ander girtace of theéinforactrontal con. 0bane hemisphere, it is evident that, after removal

volution; 4, undersurface of the ascendin of the cortex, stimulation of these fibres in the

frontal, and 5 of the ascending varietal deeper parts of the hemisphere is followed by the

convolutions ; C, central lobe or island. S4™me motor results (Gliky and Eckhard). The

stimulus is applied merely to a deeper part of the

motor path. Ifthe stimulus be applied to parts situated still more deeply, as for example to
the internal capsule, general contraction of the muscles on the opposite side is the result.

Time Relations of the Stimulation.—According to Franck and Pitres, the time which elapses
between the moment of stimulation of the cortex and the resulting movement, after de-
ducting the period of latent stimulation for the muscles, and the time necessary for the con-
duction of the impulse through the cord and nerves of the extremities, is 0°045 second.
Heidenhain and Bubnoff found that, during moderate morphia narcosis, when the stimulating
current was increased in strength, the muscular contraction and the reaction-time became
shorter. After removal of the cortex, the occurrence of the muscular contraction from the
moment of stimulation of the white matter is diminished } to 4. The form of the muscular ~
contraction is longer and more extended when the cortex, than when the subcortical paths, are .
stimulated. If the animal (dog) be in a state of high reflex excitability, these differences dig. (are
appear ; in both cases the contraction follows very rapidly (Bubnoff and Heidenhain). If the 4
stimulus be very strong the muscles of the same side may contract, but somewhat later than
those of the opposite side. If the motor areas for the fore and hind limbs be stimulated
simultaneously, the latter contract somewhat after the former. ) aoe

Number of Stimuli. —If 40 stimuli per second be applied to a motor area, then the corre-
sponding muscles Phere: 40 single contractions ; while with 46 single stimuli per second
results a continued complete contraction (Franck and Pitres). In one and the same anim

.

CONDITIONS AFFECTING THE MOTOR CENTRES. 693

the same number of stimuli is required to produce a continuous contraction, whether the cortical
centre, the motor nerve, or even the muscle itself be stimulated. With very feeble stimuli,
summation of stimuli takes place, for the muscular contraction only begins after several in-
effective stimuli have been applied. [It is generally held that the rhythm of a contracting
muscle is the same as the rhythm of the stimuli applied to its motor nerve, but Schiifer and
Horsley contend that this holds good for rates of stimuli to about 10 or 12 per second. They
find that the same is true for the cortex cerebri, corona radiata, and medulla spinalis, viz., that
the muscular response does not vary with the rhythm, 7.e., number of stimuli per sec.), but
that the rhythm is constant—about 10 per sec.—and independent of the number of stimuli per
sec., provided they are above 10 per sec. applied to these parts, Indeed, all voluntary contrac-
tions show a similar rate of undulation in the muscle-curve. Perhaps the rhythm of the
efferent impulses is modified in the motor nerve-cells of the spinal cord. }

[The matter, as regards electrical stimulation of the cortex cerebri, resolves itself
into this, that stimulation of certain cortical areas always causes contraction in

View of the brain from above (semi-diagrammatic). ,, end of ramus of the Sylvian fissure.
The other letters refer to the same parts as in fig. 479.

definite muscles or groups of muscles, resulting in definite co-ordinated movements
on the opposite side of the body ; the areas have been called “motor areas.” They
have been mapped out and ascertained in a large number of animals, and the
question comes to be—Are there similar areas.in man ?]

Primary Fissures and Convolutions of the Dog’s Brain.—The wosition of the motor centres in
the dog’s brain is indicated in fig. 483, I and II. The dog’s brain is marked by two “‘ primary
fissures,” viz., the sulcus cruciatus (S), which intersects the longitudinal fissure at a right
angle at the junction of its anterior with its middle third. This ‘fissure has been called the
sulcus frontalis, or the fissura coronalis. The second primary fissure is the fossa Sylvii (F).

‘

694 MOTOR POINTS IN THE CEREBRUM OF THE DOG.

’ in addition, are arranged with reference to these primary fissures.

Four ‘‘ primary convolutions,’
in the form of a sharply curved knee, embraces the fossa

The first primary convolution (I),

a 8
Fig. 483.
I, Cerebrum of the dog from above ; II, from the side ; I, II, Il], IV i
“tant ; ; uae ae : the four primary con-
volutions, —S, aus cruciatus ; F, Sylvian fossa; 0, olfactory lobe 3D open my 1,
— area for the muscles of the neck ; 2, extensors aud abductors of the fore limb; 3, | .
as and rotators of the fore limb; 4, the muscles of the hind limb; 5, the facial ‘
pee 6, lateral switching movements of the tail ; 7, retraction and abduction of the
fore a ; 8, elevation of the shoulder and extension of fore limb (movements as in -
ing) : Ad orbicularis palpebrarum, zygomaticus, closure of the eyelids. II, a, a, retrac-
- n — elevation of the angle of the mouth ; }, opening of the mouth and movements of —
S ri — centre ; c, c, platysma ; d, opening of the eye ; I, ¢, thermic centre, according to -
wulen nrg ane Landois. III, cerebrum of the rabbit from above ; IV, cerebrum of the
Figo, —. ore y MO gr ag of the frog from above; VI, cerebrum of the carp from
a ate aise as is the olfactory lobe ; 1, cerebrum ; 2, optic lobe ;.3, coreballnma:

Sylvii (F). The second convolution (II) runs nearly parallel to the first. The fourth prise

%
~
ie
“
“

&

POSITION OF THE MOTOR CENTRES IN THE DOG. 695

convolution (IV) bounds the longitudinal fissure, and is separated from its fellow of the opposite
side by the falx cerebri ; anteriorly.it embraces the sulcus cruciatus (S), so that it is divided
into two parts by this sulcus, a part, the gyrus precruciatus or prefrontalis, lying in front of
the sulcus, and the gyrus postcruciatus (postfrontalis) lying behind it. The third primary con-
volution (III) runs parallel. to the fourth. Some authors count the convolutions from the
longitudinal tissure outwards. In fig. 483, I and II, the motor arcas or centres are indicated
by dots on the individual primary convolutions. We must remember, however, that the
_ centres are not mere points, but that they vary in size from that of a pea upwards, according to
the size of the animal. Motor areas have been mapped out in the brain of the monkey, rabbit,
rat, bird, and frog.

Position of the Motor Centres (Dog).— Fritsch and Hitzig, in 1870, mapped out the following
motor areas, whose position may be readily found on referring to fig. 483 :—1, is the centre for
the muscles of the neck ; 2, for the extensors and adductors of the fore limb ; 3, for the flexion
and rotation of the fore leg; 4, for the movements of the hind limb, which Luciani and
Tamburini resolved into two antagonistic centres ; 5, for the muscles of the face, or the facial
centre. In 1873 Ferrier discovered the following additional centres :—6, for the lateral switch-
ing movements of the tad/; 7, for the retraction and abduction of the fore limb ; 8, for the
elevation of the shoulder and extension of the fore limb, as in walking; the area marked
9, 9, 9, controls the movements of the orbicularis palpebrarum, and of the zygomaticus (closure
of the eyelids), together with the upward movement of the eyeball and narrowing of the pupil.
Stimulation of the areas a, a (fig. II) is followed by retraction and elevation of the angle of
the mouth, with partial opening of the mouth ; at 6, Ferrier observed opening of the mouth
with protrusion and retraction of the tongue, while the dog not unfrequently howled. He
called this centre the ‘‘oral centre.” Stimulation of ¢c causes retraction of the angle of the
mouth, owing to the action of the platysma, while c’ causes elevation of the angle of the mouth
and of one-half of the face, until the eye may be closed, just as in 9. Stimulation of d is
followed by opening of the eye and dilatation of the pupil, while the eyes and head are turned
towards the other side. According to H. Munk, the prefrontal region has an influence upon
the attitude of the body (?)} The perineal muscles contract when the gyrus postcruciatus is
stimulated. Stimulation of the gyrus precruciatus on its anterior and sloping aspect causes
movements in the pharynx and larynx.

The position of the individual motor areas may vary somewhat, and they may be
slightly different on the two sides (Luctant and Tamburini).

Strong Stimuli.—tIf the stimulation be very strong, not only the muscles on
the opposite side, but those on the same side, may contract. These latter move-
ments belong to the class of associated movements, and are due to conduction
through commissural fibres. Those muscles, which usually (muscles of mastication)
or always (muscles of eye, larynx, and face) act together, appear to have a centre
. not only in the opposite but also in the hemisphere of the same side (Zener). [All
observers have found that stimulation of the facial centre causes identical (associated)
movements on both sides of the face, so that both sides of the face seem to be
represented in each hemisphere. Schifer and Horsley’s experiments make it very
probable that some other muscles, ¢.g., some of the trunk muscles, pectorals, and
recti abdominis, are represented bilaterally in the hemispheres. This is an
important point, in relation to recovery after the supposed destruction of a centre,
and has an intimate bearing on the question of “Substitution,” in reference to the
restoration of nerve-function (p. 682). | |

Mechanical stimulation, ¢.g., scraping the motor areas for the limbs, produces
movements in these parts (Luciant). :

Cerebral Epilepsy.—It is of great practical diagnostic importance to ascertain if
stimulation of the motor areas in man, due to local diseases (inflammation, tumours,
softening, degenerative irritation), causes movements. [Hughlings-Jackson has
shown that local diseases of the cortex may cause spasmodic contractions in certain
groups of muscles, a condition known as “Jacksonian Epilepsy,” and he explains
in this way the occurrence of unilateral local epileptiform spasms, which were
observed by Ferrier and Landois to occur after inflammatory irritation.] Luciani
observed these spasms in dogs, and sometimes they were so violent and general as
to constitute an attack of epilepsy. - This condition became hereditary, and the
animals ultimately died from epilepsy (§ 373). According to Eckhard, epileptic

696 EFFECT OF STIMULI ON ‘THE MOTOR CENTRES, —

attacks are never produced by stimulation of the surface of the posterior convolu-
tions. |
_ Strong stimulation of the motor regions may give rise in dogs to a complete general convul-
sive ailptie attack, which usually begins with contractions of the groups of museles specially
related to the stimulated centre (Ferrier, Eulenburg and Landois, Alberton, Luciuni and
Tamburini); then often passes to the corresponding limb of the opposite side (associated move-
ments) ; and lastly, aJl the muscles of the body are thrown into tonic and then into clonic
spasms. The opposite side of the body has been observed to pass into spasm from below up-
wards, after the contractions were developed in the other side. The spasmodic excitement
passes from centre to centre, an intermediate motor region never being passed over. After this
condition has once been produced, the slightest stimulation may sultice to bring on a new
epileptic attack (§ 378). uring the attack, the cerebral circulation is accelerated. According
to Eckhard and Danillo, epileptic attacks cannot be discharged from the posterior part of the
cerebrum by means of weak currents. Stimulation of the subcortical white matter causes
epilepsy, which, however, begins in the muscles of the same side (Bubnof and Heidenhain),
These contractions are due to an escape of the electrical current, which thus reaches the medulla -
oblongata (§ 373). - ,
If certain motor areas are extirpated, the epileptic attack is absent from the muscles con-
trolled by these areas (Luciani). Separation of the motor cortical area by means of a horizontal.
section during an attack cuts short the latter (Afunk), During an epileptic attack it is possible
to excise the motor area of one extremity, and thus exclude this limb from the attack whilst the
rest of the body is convulsed. :
Drugs. —The continued use of potassium bromide prevents the production of epilepsy on stimu-
lating the cortical areas.

Chemical Stimulation.—Substances such as occur in urine, e¢.g., kreatinin,
kreatin, acid potassic phosphate, and sediment of urates, when sprinkled on. the
motor areas of the dog, cause pronounced eclampsic, clonic convulsions, which recur
spontaneously, and are followed by deep coma. These symptoms are like.those of
uremic poisoning. The sensory centres, especially that for vision, seem also to be
affected. by chemical stimulation (Landovs). | a

{Motor Centres in the Monkey.—Ferrier has mapped out a large number
of centres on the outer surface of the brain in the monkey, and to each centre he
has given a number. These numbers have been transferred to corresponding con-
volutions on the human brain, numbered accordingly. These areas are specially
distributed on the convolutions around the fissure of Rolando, including in the
monkey, the posterior extremities of the posterior and middle frontal convolutions, —
the ascending frontal, ascending parietal, and part of the parietal lobule. |

[Fig. 484 represents these areas transferred to the corresponding areas in man, (1) On the
superior parietal lobule (advance of the opposite hind limb, as in walking). (2), (3), (4) Around
the upper extremity of the fissure of Rolando, (complex movements of the opposite leg and arm, .
and of the trunk, as in swimming). (a), (5), (c), (d), On the ascending parietal or posterior
central convolution (individual and combined movements of the fingers and wrist of the opposite
hand or prehensile movements). (5) Posterior end of the superior frontal convolution (exten-
sion forward of the opposite arm and hand). (6) Upper part of the ascending frontal or anterior
central convolution (supination and flexion of the opposite fore-arm). (7) Middle of the same
convolution (retraction and elevation of the opposite angle of the mouth). (8) At the lower
end of the same convolution (elevation of the ala nasi and upper lip, and depression of the
lower lip on the opposite side), (9), (10) Broca’s convolution (opening of the mouth with pro-
trusion and retraction of the tongue—aphasic region). (11) Between 10 and the lower end of
the ascending parietal convolution (retraction of the opposite angle of the mouth, the head
turns towards one side), (12) Posterior part of the superior and middle frontal conyolu- —
tions (the eyes open widely, the pupils dilate, and the head and eyes turn towards the
opposite side). (13), (13’) Supra-marginal and angular gyrus (the eyes move towards the’
opposite side, and upwards or downwards—centre of vision). (14) Superior temporo-sphenoidal a
convolution (pricking of the opposite ear, pupils dilate, and the head and eyes turn to the _
opposite side—hearing centre). . Ms hes ‘4

i '
Hh}

[Experiments on Monkeys.—Electrical stimulation of the anterior part of the
frontal lobes yields negative results; but behind the anterior end of the sagittal
limb of the precentral sulcus, there are lateral movements of the head and eyes:
If the anterior third or fourth be removed, Schiifer and Horsley observed no ae

.

MOTOR CENTRES IN THE MARGINAL CONVOLUTION. 697

paralysis nor any deficiency of general or special sensibility..~ Excitation of the
external surface (motor area) led Ferrier to map out the areas named on p. 695.
Schifer and Horsley’s experiments agree with Ferrier’s, andjthey map out the

Ne

J

Ad ss

Ka

a

es

NN. ; Ye.

NW ANS
N
AY

Fig. 484.

The brain with the chief convolutions (after Ecker). See also figs. 498, 499 in their relation to
the skull, The numbers 1 to 14, and the letters a to d, indicate cortical areas (p. 696).
S, Sylvian fissure ; C, central sulcus, or fissure of Rolando ; A, anterior, and B, posterior
central convolutions ; F,, upper, F,, middle, and F,, lowest frontal convolutions ; /,,
superior, and f,, inferior frontal fissure ; 73, sulcus precentralis; P,, superior, P,, inferior
parietal lobe, with P,, gyrus supra-marginalis ; P,', gyrus angularis; ip, sulcus inter-
parietalis ; cm, end of calloso-marginal fissure; O,, O,, Os, occipital convolutions ; po,
parieto-occipital fissure ; T,, T,, T3, temporo-sphenoidal convolutions; K,, K,, Ky, points in
the coronal suture ;-4,, 4,, in the lambdoidal suture,

motor area into a number of main areas, each of which is particularly concerned
with the movement of a particular part or limb, and in some of which, centres con-
cerned with more specialised movements may be marked out. The arm-area is
roughly triangular (fig. 485), and “occupies most of the upper half of the ascend-
ing parietal and ascending frontal gyri, from a little beneath the level of the sagittal
part of the precentral fissure below, nearly to the margin of the hemisphere above,
together with the adjacent part of the frontal lobe below the small antero-posterior
| _ suleus.” It bends round and is continuous with a part of the marginal gyrus.
; The special movements of the arm are indicated in fig. 485.]
_ [The face-area gives rise not only to movements’ of the facial-muscles, but also of
p . the whole of the upper end of the alimentary tube. It comprises the whole of the

698 MOTOR CENTRES IN THE MARGINAL CONVOLUTION.

ascending parietal and frontal convolutions below the arm-area, down to the fissure
of Sylvius, and including the external surface of the operculum. |

(The head-area, or area for visual direction, comprises part of the frontal lobe
from the margin of thé hemisphere to the face-area. In front it 1s bounded by the
non-excitable part of the frontal lobe. Its stimulation gives the results obtained
by Ferrier on stimulating his No. 12 centre. The leg-area is partly situate on
the mesial surface, but it extends over to the external surface from the parieto-
occipital fissure nearly to the level of the anterior end of the small sulcus marked
y. The trunk-area scarcely extends over the margin to reach the external
surface.

saatee and Horsley have extended Ferrier’s researches, and shown that motor
centres exist in the marginal convolution (fig. 486), which is excitable only in
that portion corresponding in extent (antero-posteriorly) to the excitable portion

OVEMENTS OF FLEXION AT.
TOES AND KNEE
oor x SYARSIA

"wp
Tow Soi (Luray
AND

A

Ny
{h

;
Es N OVENE
r Nea
JREAY
. =
ily Hi
D

Fig. 485. Fig. 486.

Fig. 485.—Diagram of the motor areas on the outer surface of a monkey’s brain (Horsley and
Schafer). Fig. 486.—Diagram of the motor areas on the marginal convolution of a
monkey’s brain!(Horsley and Schéfer).

of the outer surface of the hemisphere. Anteriorly it reaches forward to a line

which is opposite the junction of the posterior and middle thirds of the superior

frontal convolution (centre 12), while posteriorly it extends backwards opposite to
the parietal lobule, including the paracentral lobule, which contains large multipolar
pyramidal motor cells. The rest of the mesial surface is excitable. They find that
the centres are arranged from before backwards in the following order :—(1)

Movements of the head—this area is very small, and belongs to the large head- —

area on the external surface ; (2) of the fore-arm and hand; (3) of the arm at the
shoulder ; (4) of the upper dorsal part of the trunk ; (6) of the leg at the hip; (7)
of the lower leg at the knee ; (8) of the foot and toes. | !

Excitation of the Area AS produces movements of the arm (fig. 489). These vary accordin
to the spot stimulated, but towards the anterior part of the area, movements of the wrist sae
fore-arm, towards the posterior part movements of the arm and shoulder, are more frequently
the result of the excitation. Excitation of Tr produces movements of the trunk, generally
arching and rotation. ‘Those movements which are called forth by stimulating the anterior
part of the area are usually contined to the upper part of the trunk (thoracic region), and are:
often associated with movements of the shealias and arm; those called forth by stimulating
the posterior part are movements of the abdominal and pelvic regions and of the tail, and are
often associated with movements of the hip and leg. Excitation of the area L produces move-
ments in the lower limb. These vary according to the part stimulated, extension of the hip

being especially associated with excitation of the anterior part of the area, and contraction of

the hamstrings with excitation of the middle part.]

_ (Do similar Centres exist in Man?—The results of clinical and pathological
investigations show, that similar although not absolutely identical areas exist in —
man. ‘The motor areas, or those which have a special relation to voluntary motion —

a’

Ww

MOTOR CENTRES IN MAN.” © 699

in man, exist in part on the convolutions bounding the fissure of Rolando, and
occupy the “central” convolutions, ze, the ascending frontal and ascending
parietal convolutions along with the superior parietal lobule, and along the mesial
surface of the hemisphere, the paracentral lobule and precuneus (fig. 488). In this
region, the upper third of the ascending frontal and parietal convolutions along
with the superior parietal are the leg area (fig. 488, dey), the middle third of the
ascending parietal and ascending frontal for the arm, and the upper part of the
lowest third of these convolutions for the face, while the very lowest part of the
ascending frontal convolution is the area for the movements of the lips (L) and
tongue (T). (Compare figs. 485, 490.) The last area, with the posterior extremity
of the third left frontal convolution, is the centre for voluntary speech. We can-
not say whether these “centres” are sharply mapped off from each other. In any
case a very strong stimulation of one centre may involve an adjacent area. So far
as is yet known, centres Nos. 5 and 12, as represented on the monkey’s brain—
those on the posterior extremity of the superior and middle frontal convolutions,—
(5) for extension forward of the arm and hand, and (12) for opening the eyes and
turning the head towards the opposite side (as in surprise), are not represented in
the human brain. So accurately have certain of these areas been located, that
surgeons, in suitable cases, have been able to excise a tumour causing certain
symptoms, with relief of those symptoms. | :

[We may, therefore, assert as a general proposition that the muscles of one
lateral half of the body are regulated by certain areas in the opposite cerebral
hemisphere. | |

a

[Gowers maintains that the motor region is not exclusively motor, but that destruction of this
area also leads to some loss of sensation. Starr also asserts that perceptions occur in the grey
matter of the cortex of the ‘‘central” region and parietal convolutions, and that the various sensory
areas for the various parts of the body lie about, and coincide to some extent with, the motor
various areas for similar parts, but the sensory area is more extensive than the motor area,
extending into the parietal behind the motor area, which is confined to the ascending frontal
and parietal convolutions. ] .

II. Method of Destruction or Ablation of Parts of the Cortex.—Much confusion in this
matter has arisen from comparing the results obtained on animals of different species. [It seems
quite certain that the results obtained in the dog are quite different from those in the monkey.
The motor areas may be simply excised with a knife, or the surface of the brain may be washed
away with a stream of water, as was done by Goltz in dogs. ]

[In the dog, the areas which are described as motor may be removed either by the knife
(Hermann) or by means of a stream of water so directed as to wash away the grey matter
(Goltz). .In both cases, although there was some paralysis on the opposite side of the body,
this was but temporary, for the paralysis disappeared within a few days, the animals having
very decided control over their muscles, although Goltz admits that certain acts, especially
those which the dogs had been trained to execute, ¢.g., giving a paw, were executed “ clumsily,”
indicating some failure of complete control, which Goltz ascribed to loss of tactile sensibility.
Goltz thinks that the extent of the injury has more to do with the result than the locality.
The restoration of motion was not due to the action of the corresponding centre of the opposite
side, as destruction of this centre, although it produced the usual symptoms on the side which
it governed, had no effect on the previous result (Carville and Duvet). ]

{In the monkey, there can be no doubt from the experiments of Ferrier that
destruction of a motor centre, ¢e.g., that for the arm, results in permanent paralysis
of the arm of the opposite side, and if the centres for the arm and leg are destroyed,
there is permanent hemiplegia of the opposite side. ‘In order that the hemiplegia
or paraplegia produced by cortical ablation shall be complete, it is necessary to
include the part of the marginal gyrus corresponding in longitudinal extent to the
excitable areas of the external surface.” The amount. of paralysis produced by
ablation of the marginal gyri alone~is as great as that caused by removal of the
much more extensive external areas; but the complexity of the muscular move-
ments which are governed from these areas is much greater than in those governed
from the marginal gyrus (Schafer and Horsley). |

700 EXTIRPATION OF THE MOTOR CENTRES,

[In man, records of destructive lesions of the motor areas in whole or part have
now accumulated to such an extent as to leave no doubt, that if there be, say, a
destructive lesion of the middle third of the cortex of the ascending frontal and
ascending parietal convolutions, there will be paralysis of the arm of the opposite
side ; and*the same is true for the other centres. } ;

[In extirpation or ablation of the motor centres, again, much confusion
has arisen from comparing the results obtained on different animals. In the dog,
there is no permanent motor paralysis, in the monkey and man there is. The
difference is this, that in the dog the lower centres, perhaps the basal ganglia, are
‘able to subserve the execution of those co-ordinated movements required for stand-
ing, progression, d&c. As we proceed higher in the animal scale, the motor cortical
centres assume more and more of the functions subserved by the basal ganglia in
lower animals. There is, as it were, a gradual displacement of motor centres to
the cortical region, as we ascend in the zoological scale. ] .

Differences in Animals.—The higher the development of the intelligence of animals, the
more have their movements been learned, and the more have they gradually come to be con-
trolled by the will; in them the disturbance of the motor phenomena becomes more pronounced
and persistent after destruction of the cortical psychomotor centres. Whilst in the lower
vertebrates, including the birds, extirpation of the whole hemispheres does not materially
interfere with movements, the pagal Fa oe, reflex movements being sufficient—in dogs
occasionally, but exceptionally, extirpation of several motor areas produces visible permanent
disturbance of motor acts—and in monkeys and man (§ 378), the paralytic phenomena may be |
intense and persistent. |

Acquired Movements.— Among the movements performed by men are many which have been
acquired after much practice, and have been subjected to voluntary control, e.g., the move-
ments of the hands for many manual occupations. _ After aelesion of certain motor areas, such
movements are reacquired only very slowly and incompletely, or it may be not at all. [The
interference with these finer acquired movements sometimes becomes very marked in lesions of
the motor areas produced by hemorrhage, and in some cases of hemiplegia.] Those move-
ments, however,!which are, as it were, innate [or as they are sometimes termed fundamental
in opposition to acquired], and are under the control of the will without much practice—such
as the associated movements of the eyes, face, some of those of the limbs—are either rapidly
restored after the lesion, or they appear to suffer but slightly after a lesion of the cerebral cortex;
the facial muscles are never so completely paralysed as from a lesion of the trunk of the facial
nerve ; usually the eye can be closed in the former case. The movements necessary for sucking
have been performed by hemicephalic infants.

Theoretical, —Hitzig ascribes the disturbance of movement, after the removal of the motor
centres, to the loss of the ‘‘ muscular sensibility.” Schiff refers it to the loss of tactile sensibility.
According to Ferrier, the tactile and sensory impressions are not appreciably diminished or
altered. The descending degeneration of the pyramidal tracts in the lateral columns, according
to Schiff, occurs after section of the posterior half of the cervical spinal cord, or even after
section of the posterior part of the lateral columns. After dividing the latter, and allowing
secondary degeneration to take place, it is not possible to discharge movements by stimulating
the cortex cerebri. [Schiff divided the posterior column of the cord, and found that stimula-
tion of the opposite motor cortex failed to excite movements in the opposite fore limbs. He
supposed that this result was due to ascending degeneration. Horsley finds, however, that,
Schiff’s results are due to transverse aseptic myelitis at the seat of operation, thus causing a
“block” there in the motor tract.] The posterior columns, and their continuation upwards
to the brain, are supposed to carry the impulses upwards to the cerebrum (ascending the
limb of the reflex arc), where, after ook modified in the centres, they are carried outwards by the
pyramidal tracts (descending limb of the reflex arc). [Some hold that the posterior columns
are directly connected with the cortical motor area, while others think that a sensory perceptive
centre is interposed between the afferent and efferent impulses.] Between, but deeper in the
brain, lie the centres for tactile sensibility. Landois He Eulenburg observed in a dog, from
which the motor centres for the extremities had been removed on both sides, that the move-
ments became completely ataxic, i.e., the animal could not execute such co-ordinated move-
ments as walking, standing, &c. Goltz regards the disturbances of movement after injury of
the cortex as due to inhibition. Schiff maintains that when the cortex-cerebri is stimuleienla we
do not stimulate a cortical centre, but only the sensory channels of a reflex arc, the continua-
tion of the posterior columns, so that on this supposition the movements resulting from
stimulation of the motor points would be reflex movements, The centres lie deeper in the
brain. This view is not generally entertained. Src pn

Modifying Conditions.—The excitability of the motor centres is capablevof :

7
=
zs

CONDITIONS AFFECTING THE MOTOR CENTRES. 7Ol

being considerably modified. Stimulation of sensory nerves diminishes it; thus,
the curve of contraction of the muscles becomes lower and longer, while the
reaction-time is lengthened simultaneously. Only when, owing to strong stimula-
tion, the reflex muscular contractions are vigorous, the excitability of the cortical
centres appears to be increased. Specially noteworthy is the fact that, in a certain
stage of morphia-narcosis, a stimulus which is too feeble to discharge a contrac-
tion becomes effective at once, if immediately before the stimulus is applied to the
cortical centre, the skin of certain cutaneous areas be subjected to gentle tactile
stimulation. When strong pressure is applied to the foot, the contractions become
tonic in their nature, so that all stimuli, which under normal conditions produce only
temporary stimulation, now stimulate these centres continuously. If, during the
tonic contraction, one gently strokes the back of the foot, blows on the face, gently
taps the nose, or stimulates the sciatic nerve, suddenly relaxation of the muscles
again occurs. These phenomena call to mind the analogous observations in
hypnotised animals (§ 374). Another very remarkable observation is, that when
either owing to a reflex effect, or to strong electrical stimulation of a cortical centre,
contraction of the corresponding muscles is produced, then feeble stimulation of the
same centre, but also of other centres, suppresses the movement. Thus, we have
the remarkable fact that, according to the strength of the stimulus applied to the
motor apparatus, we can either produce movement or suppress a movement already
in progress (Bubnof and Heidenhain). |
[Excision of the Thyroid affects the nerve-centres. After thyroidectomy (twenty-four hours)
the tetanus obtained by stimulating the cortex is greatly changed. It ceases when the stimu-
lating current is shut off, as suddenly as that observed on stimulating the corona radiata. In
more advanced cases, the tetanus is soon exhausted, and is often followed by clonic epileptoid

spasms. In the latter stages, after thyroidectomy, there may be only a feeble tetanus, or none
at all, on stimulating the motor areas, so great is the state of depression of function of these
centres (Horsley). |

[Warner has directed attention to visible muscular movements apart from: those studied in
epilepsy, chorea, athetosis—and including attitude, gait, movements of the eyeballs, position of
the hand, and posture in general, &c.—as expressive of states of the brain and nerve-centres. |

376. SENSORY CORTICAL CENTRES.—[There must be some connection
between the surface of the brain and the afferent channels through which sensory
impulses pass inwards, and although the channels for sensory impulses are, perhaps,
not so definitely localised as those for voluntary motion, still we know that sensory
impulses for the opposite half of the body travel upwards through the posterior
third of the posterior limb of the internal capsule (fig. 500, S), to radiate in all
probability into the occipital and temporo-sphenoidal lobes. Parts of these convolu-
tions are sometimes spoken of as “ sensory centres” or “ psycho-sensorial ” areas. |

[The same methods have been applied to the investigation of these centres, viz., stimulation
and extirpation. Stimulation.—Ferrier found that electrical stimulation of the angular gyrus
(monkey) caused movements of the eyeballs towards the side, with sometimes associated move-
ments of the head, but he regarded these as reflex movements, so that for this and other reasons
he, in his earliest contributions, considered the angular gyrus and adjacent parts as the ‘‘ centre
for vision.” On stimulating the first temporo-sphenoidal convolution, the monkey pricked the
opposite ear, the pupils dilated, while the head and ears turned to the opposite side, it.exhibited
movements similar to those caused by a loud sound; these movements are also reflex pheno-
mena, so that he located the ‘‘ auditory centre” in this region, and on somewhat similar
grounds. As the result of inferences from the stimulation and extirpation of other parts, he
referred the centres for smell and taste to the tip of the temporo-sphenoidal lobe, and for touch
to the hippocampus major, but all these statements have not been confirmed.] .

[Goltz experimented on dogs by washing away the cortex cerebri, and found that when a_
sufficient amount of the grey matter is removed, and after recovery from the immediate effects
of the operation, there is a peculiar defect’of vision and other sensory defects, but so far Goltz
has not found that there is any difference in this respect between removal of the anterior and
posterior lobes of the dog’s brain. The dog is not blind, as it can see and use its eyes to avoid
obstacles, but it seemed as if the animal failed to recognise food or flesh as such, when placed
before it ; while exhibitions, which, before the operation, greatly excited: the dog, ceased to do

7O2 SENSORY CORTICAL CENTRES.

so. Goltz caused his servant to dress himself in a mummer’s red coloured garb, which

reyiously had greatly excited the dog, but after the operation the dog, although it was not
blind, was no longer excited thereby. Nor was it afterwards cowed by the appearance of a
whip. After a time there was recovery to a certain extent if the animal was trained, whether
by the deposition of new impressions, or by opening up new channels, or by the partial
recovery of some parts of the grey matter not removed, it is impossible to say. ]

[Munk has mapped out the surface of the brain into a series of ‘‘ sensory ” or psycho-sensorial
centres, but he distinguishes between complete and total extirpation of these centres and the
phenomena which follow these operations. }

When these centres are partially disorganised, the mechanism of the sensory
activity may remain intact, but “the conscious link is wanting.” A dog with its

centres thus destroyed, sees, hears, or smells, but it no longer knows what it sees, «

hears, or smells. These centres are in a certain sense the seat of experience that
has been acquired through the organs of sense. Stimulation of these centres

may give rise to movements, such as occur when sudden intense sensory impressions

are produced. These movements, therefore, are to be regarded as reflex, partly as
extensive co-ordinated reflex movements, and are in no way to be confounded with
the movements which result from direct stimulation of the motor cortical centres.
To this belongs dilatation of the pupil and the fissure of the eyelids, as well as
lateral movements of the eyeball.

1, The ‘visual area,” according to Munk, embraces the outer convex part of
the occipital lobe of the dog’s brain. [This area and its connections are represented

in fig. 487. It is, therefore, in the area supplied by .

the posterior cerebral artery.| If the occipital lobes be
completely destroyed, the dog remains permanently
blind (“cortical or absolute blindness”). If, how-
ever, only the central circular area be destroyed, there
is loss of the conscious visual sensation, which may be
called “psychical blindness” (J/unk) [a condition of
visual defect like that observed by Goltz in the dog, in
which the dog saw an object, e.g., its food, but failed
to recognise it as such. There is a certain amount of
recovery if the whole visual area be not removed,
According to Schafer, the visual area of the cerebral
cortex in the monkey comprises the whole of the oc-
cipital lobe, and perhaps a part of the angular gyrus.
He finds, with Munk, that removal of one occipital
lobe is followed by hemianopia, 7.c., blindness in the
lateral half of each retina corresponding to the side
operated on. ‘The blindness passes off. Removal of
both occipital lobes is said to produce total and per-
Fig. 487. manent blindness, whereas destruction of the cortex of
Eininie if’ the peycho-opklc both angular gyri is not followed by any appreciable
fibres (after Munk). permanent defect of vision. Ferrier, however, does not
accept these statements. |
[Ferrier and Yeo find that after operations conducted antiseptically, removal of
both occipital lobes (monkeys) does not cause any recognisable disturbance of
_ Vision, or other bodily or mental derangement, provided the lesion does not. extend
beyond the parieto-occipital fissure. Nor does destruction of both angular gyri
cause permanent loss of vision ; such loss of vision lasts only three days, so that in
Ferrier’s original experiments, the animals lived for too short a time after the
operation, to enable a just conclusion to be arrived at. Destruction of both

angular gyri and occipital lobes causes total and permanent blindness in both eyes —

in monkeys, without any impairment of the other senses or motor power. This

region Ferrier calls the “ occipito-angular region.” _ (or pide ae

THE VISUAL CENTRE. 703

[Stimulation of the angular gyrus causes movements of the eyes to the
opposite side, with closure of the eyelids and contraction of the pupil. The eye-
balls were directed upwards or downwards according as the electrodes were applied
to the anterior or posterior limb of the angular gyrus (Ferrier). Stimulation of
‘ the whole of the cortex of the occipital lobe, including its mesial and under
surfaces, causes conjugate deviation of the eyes to the opposite side, the direction
of movement varying with the position of the electrodes. |

Mauthner denies the existence of cortical. blindness, and believes that, after destruction of
the middle of the visual centre, the reason why the dog does not recognise the object with the
opposite eye is because, owing to there being only indirect vision, there is no distinct impression
on the retina. The ‘position of the visual centre has been variously stated by different
observers. According to Ferrier, in the dog it lies in the occipital part of the III primary con-
volution, near the spot marked ¢, e, e, in fig. 483; according to his newer researches, in the
occipital lobe and gyrus angularis.

Connection with the Retina. —Munk asserts that in dogs loth retin are connected with each
visual cortical centre, and in such a manner that the greatest part of each retina is connected
_ with the opposite cortical centre, and only by its most external lateral marginal part with the
centre of the same side (fig. 487). If we imagine the surface of one retina to be projected upon
the centres, then the most external margin of the first is connected with the centre of the same
side, the inner margin of the retina with the inner area of the opposite centre, the upper Margin
with the anterior area, and the lower marginal part of the retina with the posterior area of the
opposite side. The (shaded) middle of the centre corresponds to the position of direct vision of
the retina of the opposite side (compare § 344).

Stimulation of the visual centre in dogs causes movements of the eyes
towards the other side, sometimes with similar movements of the head and con-
traction of the pupils. If one eye be excised, from new-born dogs, the opposite
visual centre, after several months, is less dev eloped (Munk). After extirpation
of the visual centre in young dogs, the channels which connect it with the optic
nerve undergo degeneration (Monakow) (§ 344).

In monkeys; the centre occupies the occipital lobe. Unilateral destruction causes temporary
blindness of the halves of both retine, 7.¢., hemianopia on the side of the injury. The visual
centre in pigeons (fig. 483, IV, where 1 is placed) lies somewhat behind and internal to the
highest curvature of the “hemispheres (M‘Kendrick, Ferrier, Musehold). The visual centre
in the frog lies in the optic lobe (Blaschko).

[The visual path is along the optic nerve to the chiasma, where the fibres from the nasal half
of each retina cross to the optic tract, some of the fibres perhaps becoming connected with the
- external corpora geniculata, and some with the pulvinar of the optic thalamus and corpora
quadrigemina, while the great ass sweeps backwards to the occipital lobes as the optic expan-
sion of Gratiolet. Destruction of this path behind the chiasma causes hemiopia or hemianopia,
and certain diseases of the occipital cortex cause a similar result. . Perhaps, however, there is
another centre in the angular gyrus (and supra-marginal lobe), for in eases of word- ‘plindness
disease has been found in these regions. Sometimes flashes of light or the appearance of a ball
of fire form the aura in epilepsy, and Hughlings Jackson thinks that discharging lesions of the
right occipital lobe cause coloured vision more frequently than on the left.]

2. The centre for hearing, or “auditory area,” lies in the dog, according to
Ferrier, in the region of the second primary convolution at f, f, f (fig. 483, IT),
while in the monkey and man it is in the first temporal or temporo-sphenoidal
gyrus (Ferrier’s centre, No. 14).* Munk locates it in the same region. According
to Munk, destruction of the entire region causes deafness of the opposite ear, while
destruction of the middle shaded part alone causes “‘ psychical deafness ” (“‘ Seelen-
taubheit”). Electrical irritation of the upper two-thirds of the superior temporal
convolution is followed by a reaction which closely resembles that produced by a
sudden fright, or that produced by a sudden unexpected noise. [There is a quick
retraction of the opposite ear, i.e. “pricking” of the ear as if toward the supposed
origin of the sound, combined generally with turning of the head and eyes to that
side, and dilatation of the pupil.].~Ferrier locates the centre for hearing in the
monkey in the swperior temporo-sphenoidal convolution, and he finds that,. when the
centres on both sides are extirpated, the animal is absolutely deaf; it takes no
cognisance of a pistol fired in its neighbourhood. [From his experiments on monkeys,

704. OLFACTORY AND TACTILE CENTRES.

Schiifer denies absolutely the conclusionsof the above-named experiments. Schiifer
points out that it is not difficult to substantiate hearing in monkeys ; it is difficult
to substantiate deafness, for quite normal monkeys will often fail to pay the least
attention to loud sounds. In six monkeys, Schiifer,asserts that after more or less —
complete destruction of the superior temporal gyrus-on both sides, hearing was not
perceptibly affected. In one case, both temporal lobes were completely removed
without any permanent diminution in the-acateness of hearing. These results are
opposed to the ordinary clinical teaching on this subject.] In man, injuries to the
first and second temporo-sphenoidal convyolutions on one side do not appear to
cause complete deafness of one ear, as it seems that the sense of hearing for each
ear is perhaps represented on both sides. Bilateral lesions of these conyolutions
in man cause complete deafness. Disease of these two convolutions is associated
with word-deafness (p. 713). Wernicke cites the case of a person first affected
with word-deafness, who afterwards became completely deaf; and after death, a
bilateral lesion was found in the first temporo-sphenoidal convolution. . These con- a
|
:

volutions are supplied with blood by the middle cerebral or Sylvian artery.

(The auditory paths are from the auditory nuclei in the medulla oblongata
through the pons, where they perhaps cross into the tegmentum, thence into the
“sensory crossway,” and onwards to the auditory centre. |

[Auditory Aur». —Equally important with these effects of disease are the sensory impressions,
or ‘‘aure,” which sometimes usher in an attack of epilepsy ; sometimes:these aure consist of
sounds or noises, and in these cases the seat of the disease isjoften in the first temporo-sphenoidal
convolution. ] .

(3. The olfactory centre has not been so definitely located as some of the
others. There is strong presumptive evidence that it is situated in the hippo-
campal region of the temporal lobe, at its lower extremity. This view is strength-
ened by the anatomical relations of this region to the olfactory tract and anterior
commissure (Ferrier). M‘Lane Hamilton has recorded a case of epilepsy ushered
in by an aura of a disagreeable odour, in which there was atrophy of the grey
matter of the right uncinate gyrus. | |

[Olfactory Path,—Although the outer root of the olfactory tract runs direct to the uncinate
gyrus, in hemianesthesia resulting from injury to the ‘‘ sensory crossway,” smell is lost on the

opposite side, while it is lost on the same side when the uncinate gyrus is involved. It may be
that the impulses go. first to their own side, and cross afterwards. ] rs

[4. We do not’ know the centre for taste, and even the course of the nerve of
taste is disputed. © Ferrier places it close to that of smell. |

On stimulating the subiculum in monkeys, dogs, cats, and rabbits, he observed peculiar
movements of the lips and partial closure of the nostrils on the same side (§ 365). _In man,
subjective olfactory and gustatory perceptions are regarded as irritative phenomena, while loss
of these sensory activities, often complicated with other cerebral phenomena, is regarded as a
ayreon of their paralysis. 1 oti

(The gustatory path crosses in the posterior part of the posterior segment of the internal cap-
sule. While Gowers admits that the chorda tympani is the nerve of taste for the anterior two-
thirds of the tongue, he thinks that it reaches the facial nerve from the spheno-palatine ganglion
through the Vidian nerve. He denies that the glosso-pharyngeal is concerned in, taste, and
‘‘ he believes that taste impressions reach the brain solely by the roots of the 5th nerve.” He
admits that the nerves of taste to the back part of the tongue may be distributed with the
glosso-pharyngeal, reaching them through the otic ganglion by the small superficial ‘petrosal and
tympanic plexus,] - Pa ) og ‘

[5. Ferrier places the centre for tactile sensation in the hippocampal region, close
to the distribution of part of the posterior cerebral artery ; so far this has not been
confirmed, The centre for the sensation of pain has not been defined ; probably it
is very diffuse. The limbic lobe, according to Broca, includes the hippocampal
convolution and the gyrus fornicatus. Ferrier found that removal of the hippo-
campal region resulted in a diminution of the sensibility of the opposite side of the

t
;
t
H
{
ls
H
‘
j
‘
;

THERMAL CORTICAL CENTRES. 705

body. Horsley and Schifer observed only a temporary hemianesthesia, but they
found that an extensive lesion of the gyrus fornicatus was followed by hemianes-
thesia, more or less marked and persistent. From their experiments, these observers
conclude that the limbic lobe ‘is largely, if not exclusively, concerned in the appreci-

ation of sensations, painful and tactile.” ]

6. Munk is of opinion that the surface of the cerebrum in the region of the motor centres acts
at the same time as ‘‘sensory areas”’ (‘‘ Fiihlsphire’’), t.e., they serve as centres for the tactile
and muscular sensations and those of the innervation of the opposite side. He asserts that after
injury to these regions the corresponding functions are affected.

According to Bechterew, the centres for the perception of tactile impressions, those of inner-
vation, of the muscular sense, and painful impressions are placed in the neighbourhood of
the motor areas (dog) ; the first immediately behind and external to the motor areas, the others
in the region close to the origin of the Sylvian fissure. [So far this agrees with the views of
Starr (p. 699). ] :

Goltz, who first accurately described the disturbances of vision following upon injuries to the
cortex in dogs, is opposed to the view of sensory localisation. He believes that each eye is
connected with both hemispheres. He asserts that the disturbance of vision, after injury to
the brain, consists merely in a diminished colour- and space-sense. The recovery of the visual
perception of one eye after injury of one side of the cortex cerebri, he explains by supposing
that this injury merely causes a temporary inhibition of the visual activity in the opposite eye,
which disappears at a later period. Instead of psychical blindness and deafness he speaks of a
‘* cerebro-optical ” and ‘‘cerebro-acoustical weakness.”

377. THERMAL CORTICAL CENTRES.—Euleuberg and Landois discovered an area on
the cortex cerebri, whose stimulation produced an undoubted effect upon the temperature and
condition of the blood-vessels of the opposite extremities. This region (fig. 483, I, ¢) generally
embraces the area in which, at the same time, the motor centres for the flexors and rotators of
the fore limb (3), and for the, muscles of the hind limb (4) are placed. The areas for the anterior
and posterior limbs are placed apart, that for the anterior limb lies somewhat more anteriorly,
close to the lateral end of the crucial sulcus. Destruction of this region causes increase of the
temperature of the opposite extremities; the temperature may vary considerably (1°5° to 2°,
and even rising to 13° C.). This result has been confirmed by Hitzig, Bechterew, Wood, and
others. This rise of the temperature is usually present for a considerable time after the injury,
although it may undergo variations. Sometimes it may last three months, in other cases
it gradually reaches the normal in two or three days. In well-marked cases, there is a dimin-
ution of the resistance of the wall of the femoral artery to pressure, and the pulse-curve
is not so high (Reinke). Local electrical stimulation of the area causes a slight temporary
cooling of the opposite extremities, which may be detected by the thermo-electric method.
Stimulation by means of common salt acts in the same way, but in this case the phenomena of
destruction of the centre soon appear. As yet, it has not been proved that there is.a similar area
for each half of the head. The cerebro-epileptic attacks (§ 375) increase the bodily temperature,
partly owing to the increased production of heat by the muscles (§ 302), partly owing to dimin-
ished radiation of heat through the cutaneous vessels, in consequence of stimulation of the
thermal cortical nerves. The experiments led to no definite results when performed on rabbits.
According to Wood, destruction of these centres occasions an increased production of heat that
can be measured by calorimetric methods, while stimulation causes the opposite result.

These experiments explain how psychical stimulation of the cerebrum may have an effect
upon the diameter of the blood-vessels and on the temperature, as evidenced by sudden paleness
and congestion (§ 378, ITI.).

[Heat Production.—Injury to the fore-brain has no effect on the temperature. If the brain
of a rabbit be punctured through the large fontanelle, and the stylette be forced through the
grey matter on the surface, white matter, and the median portion of the corpus striatum right
to the base of the brain, there is a rapid rise of the temperature which may last several days.
Injury to the grey cortex does not affect the temperature. After puncture of the corpus stri-
atum, the highest temperature is reached only after twenty-four to seventy hours, but when
the puncture reaches the base of the brain this result occurs in two to four hours. Electrical
stimulation of these areas causes the same effect on the temperature. Direct injury to certain
parts of the brain is followed by a rise of the temperature—or fever. See also, p. 329, for further
evidence of the existence of thermal centres. There is at the same time an increase of the O
taken in, the CO, given off and a decided increase of the N given off, indicating an increase in
the proteid metabolism, which points to an increased production of heat (Aronsohn and Sachs,
Richet, Wood).} .

General and Theoretical. —Goltz’s View. —-Goltz uses a different method to remove the cortex
cerebri—he makes an opening in the skull of a dog, and by means of a stream of water washes
away the desired amount of brain-matter. He describes, first of all, inhibitory phenomena,
which are temporary and due to a temporary suppression of the activity of the nervous

2¥

706 TOPOGRAPHY OF THE MOTOR CENTRES.

a tus, which, however, is not injured anatomically; this may be explained in the same way
- a od ression of reflexes by sie stimulation of sensory nerves (§ 361, 3). In addition,
there are the permanent phenomena, due to the disappearance of the activity of the nervous
apparatus, which is removed by the operation. A dog, with a large mass of its cerebral cortex
removed, may be compared to an eating, complex, reflex machine. It behaves like an intensely
stupid dog, walks slowly, with its head hanging down ; its cutaneous sensibility is diminished
in all its qualities—it is less sensitive to pressure on the skin; it takes less cognisance of
variations of temperature, and does not comprehend how to feel; it can with difficult
accommodate itself to the outer world, especially with regard to seeking out and taking its food.
On the other hand, there is no paralysis of its muscles. The dog still sees, but it does not
understand what it does see; it looks like a somnambulist, who avoids obstacles without
obtaining a clear perception of their nature. It hears, as it can be wakened from sleep by a
call, but it hears like a person just wakened from a deep sleep by a voice—such a person does
not at once obtain a distinct perception of the sound. The same is the case with the other
senses. It howls from hunger, and eats until its stomach is filled ; it manifests no symptoms
of sexual excitement. os : ca ;

Goltz supposes that every part of the brain is concerned in the functions of willing, feeling, -
perception, and thinking. Every section is, independently of the others, connected by con-
ducting paths with all the voluntary muscles, and, on the other hand, with all the sensory nerves
of the body. He regards it as possible that the individual lobes have different functions.

After removal of the anterior or frontal convolutions and the motor areas, there is at first
unilateral motor and sensory paralysis and affection of vision. After some months, there remains
only the loss of the muscular sense. If the operation be bilateral, the phenomena are more
marked ; there are innumerable purposeless associated movements, and the dogs become
vicious. Marked and permanent disturbance in the capacity to utilise the impressions from the
sense-organs is not a necessary consequence of removal of the frontal convolutions.

Removal of the occipital lobes interferes most with vision. Bilateral removal makes the
animal almost blind. The dog remains obedient and lively. There is no disturbance of motion
or of the muscular sense.

Inhibitory Phenomena, —Injury to the brain also causes inhibitory phenomena, such as the
disturbances of motion, the complete hemiplegia which is ge gpl observed after large
unilateral injuries of the cortex cerebri; these are regarded by Goltz as inhibitory phenomena,
due to the injury acting on lower infra-cortical centres, whose action inhibits movement, but
these movements are recovered as soon as the inhibitory action ceases.

378. TOPOGRAPHY OF THE CORTEX CEREBRI.—A short resumé of
the arrangement of convolutions, according to Ecker, is given in § 375.
I. The cortical motor areas for the face and the limbs are grouped around the

;

. Fig. 488, “ Fig. 489. .
Fig. 488.—Motor areas in man shaded—outer surface of the left side of human brain. Dotted
area, the aphasic region (modified from Gowers). Fig. 489.—Inner surface of right hemi-
sphere. AS, area governing the movements of the arm and shoulder ; 7’, of the trunk ;

leg, those of the leg; Gf, gyrus fornicatus : CC! : i 3 0.
poinited lobe. 8; Gf, gy atus ; CC, corpus callosum ; U, uncinate gyrus ; 0,

fissure of Rolando, including the ascending frontal, ascending parietal, and part of
the parietal lobule (fig. 488). The centre for the face occupies the lowest third of —

the ascending frontal convolution, and reaches also to the lowest fifth of the ascend- —
ing parietal. The arm centre occupies the middle third of the ascending frontal and ‘Me

ee

TOPOGRAPHY -OF THE MOTOR CENTRES. 707

middle three-fifths of the ascending parietal convolutions, while the leg centre lies
at the upper end of the sulcus and extends backwards into the parietal lobule (and

perhaps on to the superior frontal convolution) (fig. 488). The leg centre is con-

tinued over on to the paracentral lobule, opposite the upper end of the fissure of
Rolando, in the marginal convolution on the mesial aspect of the hemisphere (fig.
490), where the centres for the muscles of the trunk also exist (p. 698). The centre
for speech is in the posterior part of the third left frontal convolution (fig. 488).

Blood Supply.—These convolutions are supplied with blood from 4 to 5 branches of the
Sylvian artery, which may sometimes be plugged with an embolon. When a clot lodges in
this artery, the branches to the basal ganglia may remain pervious, whilst the cortical branches
may be plugged (Duret, Heubner) (§ 381).

[Hemiplegia consists of motor paralysis of one-half of the body, although, as a
rule, all the muscles are not paralysed to the same extent ; in some there may be
complete paralysis, z.¢., they are entirely removed from voluntary control, while in
others, there is merely impaired voluntary control. It may be caused by affections
of the cortical areas or by lesion of the motor tracts above the medulla, and the
paralysis is always on the side
opposite to the lesion, owing to
the decussation of the motor paths
in the medulla. If the case be a
severe one, we have what Charcot
terms hémiplégie centrale vulgare,
or ‘complete hemiplegia,” due to
lesion of the cortical centres for
the face, arm, and leg. .While the
arm and leg are completely para-
lysed, the lower part of the face is

Fig. 490.

Fig. 490.—Transverse section of a cerebral hemisphere. CCa, corpus callosum ; NC, caudate

nucleus ; NL, lenticular nucleus ; IC, internal capsule ; CA, internal carotid artery; aSL,

lenticulo-striate artery ; (‘‘ Artery of hemorrhage”); F, A, L, T, position of motor areas

governing the movements of the face, arm, leg, and trunk muscles of the opposite side
(Horsley). Fig. 491.—Scheme of the innervation of bilaterally associated muscles (Loss).

more affected than the upper half, which is usually not much affected. All those
movements under voluntary control, and especially those that have been learned,
are abolished, whilst the associated and bilateral movements, which even animals
can execute immediately after birth, remain more or less unaffected. Hence, the
hand is more: paralysed than the arm; this, again, than the leg; the lower facial
branches more than the upper; thenerves of. the trunk scarcely at all (/errver).
When an extraordinary effort is made, it will be found that there is some impair-
ment of the power of the muscles of mastication and respiration, although the
muscles on opposite sides act together (Gowers). The trunk-muscles, as a rule, are

708 HEMIPLEGIA.

but slightly affected, or not at all, as their centre is elsewhere. There may be
alterations of sensibility and of the reflexes. ]

[Conduction through the whole of the econ fibres coming from one hemisphere may be
interrupted, and yet all the muscles on the opposite side of the body are not paralysed. The
muscles which are comparatively unaffected are those associated in their action with the muscles
of the opposite side, ¢.g., the respiratory muscles. Broadbent assumes that such muscles haye
a bilateral representation in the motor areas. Suppose in fig. 491, B, B’, to represent the cerebral
cortex: M, M, motor centres in it; N, N’, nerve nuclei in the spinal cord or medulla oblongata ; :
P, P’, the pyramidal tracts passing to spinal nuclei N, N’; m, m’, nerves proceeding from the last.
1, 2, 3, 4, 5, represent different lesions. In the case of muscles on opposite sides of the body,
which act independently, ¢.g., those of the hand, this is all the mechanism, but in bilaterally
associated muscles there is another mechanism, viz., commissural fibres between the nerve
nuclei, the one c conducting from right to left, and c’ from left to right. When there is an ‘
injury at 1 or 3, impulses can still pass from the uninjured side M to N’ and through ¢’ to the
muscles i, m’. In this way, both muscles receive motor impulses from one hemisphere (Zoss).]

Conjugate deviation of the eyes, with rotation of the head, is frequently present in the early:
period of hemiplegia, although it usually disappears. When a person turns his head to one side,
there is an associated movement of certain of the ocular muscles with those of the neck. The
head and eyes are usually turned to the side of the lesion ; this is termed “ conjugate deviation,”
so that the power of voluntarily moving the eyes and head to the paralysed side is temporarily
lost. The unopposed muscles rotate the head and eyes to the sound side. If the lesion be in
the posterior part of the pons, the deviation is to the paralysed side (Prévost). _

[Subsequent Effects.—If there be a hemorrhage, say into these motor regions, or from the
lenticulo-striate artery, so as to compress the pyramidal fibres in the knee and anterior two-
thirds of the posterior segment of the internal capsule, then there is usually tonic or persistent
contraction of the muscles affected. These tonic spasms may accompany the hemorrhage, or
come on a few days after it, and set up the condition of early rigidity. The contraction or
spasm—if any—accompanying the hemorrhage, is due to direct irritation of the pyramidal
fibres, while that which comes on a few days later, and usually lasts a few weeks, is also due
to irritation of these fibres, probably produced by inflammatory action in and around the seat
of the lesion. The affected limb is stiff and resists passive movement. After a few weeks, late
rigidity sets in and is persistent, and it is characterised by structural changes in the pyramidal
paths which lead to other results. There is secondary descending degeneration in the pyramidal
tracts, which causes ‘‘contracture” in the paralysed limbs, while at the same time, the deep |
or tendinous and periosteal reflexes (ankle-clonus, rectus-clonus, and the deep reflexes of the
arm-tendons, are exaggerated). The spastic rigidity is usually more marked in the arm than in
the leg, and it generally affects the flexors more than the extensors, so that the upper arm is
drawn close to the trunk, the elbow, arm, and fingers flexed; in the leg, the extensors of the
leg overcome the peronei. Hitzig has pointed out that the contracture is less during sleep, and
after rest. The muscles at first can be stretched by sustained pressure, but after months or
years, structural changes occur in the muscles, ligaments, and tendons, and the limbs assume a
permanent and characteristic attitude. ]

In hemiplegic persons, the power of the unparalysed side is sometimes diminished, which: is
not sufficiently explained by the fact that some bundles of the pyramidal tracts remain on the
same side (Brown Séquard, Charcot).

Acquired Movements.—Some movements performed by man are learned only after much
practice, and are only completely brought under the influence of the will after a time, such as
the movements of the hand in learning a trade. Such movements are reacquired only very
slowly, or not at all, after injury to the motor areas in which they are represented. Those
movements, however, which the body performs without previous training, such as the associated
movements of the eyeballs, the face, aud some of those of the legs, are rapidly recovered after
such an injury, or they suffer but little, if at all. Thus, the facial muscles seem never to be so
iy aac paralysed after a lesion of the facial cortical centre, as in affections of the trunk of

the facial nerve; the eye especially can be closed. Sucking movements have been observed in
hemicephalous fetuses.

Degeneration of the Pyramidal Tracts.—After destruction of the cortical
motor areas, descending degeneration of the cortico-motor paths, or “pyramidal
tracts,” takes place (§ 365). Degenerative changes have been found to occur within
the white matter under the cortex in the anterior two-thirds of the posterior segment
of the internal capsule, [in the middle third of the crusta (figs. 492, *, 493, L], pons,
in the anterior pyramids of the medulla oblongata (fig. 492), and thence they have
been traced into the pyramidal paths (direct and crossed) of the spinal cord (Charcot,
Singer). It is evident that lesions of these tracts at any part of their course must

DEGENERATION OF THE PYRAMIDAL TRACTS. 709

_have the same result, viz., to produce hemiplegia. (For the subsequent effects, see
p. 649.) Ina case of congenital absence of the left fore-arm, Edinger found that
the right central convolutions were less developed.

Ot rT

i. AWN “a
—ES
~ :

Fig. 492. Fig. 493.
Fig. 492.—Secondary descending degeneration in middle third of nee crus and medulla, after
destruction of the cortical motor centres on the right side. Fig. 493. —Horizontal section

of the cerebral peduncle in secondary degeneration ‘of the pyramidal tracts, where the lesion
was limited to the middle third of the posterior segment of the internal capsule. F, healthy
crusta ; L, locus niger; P, internal third of the crusta on the diseased side; D, secondary
degeneration in the middle third of the crusta ; CQ, corpora quadrigemina with the iter
below them.

It is doubtful if the muscular sense is represented in the motor areas ; Nothnagel supposes it
to be located in the temporal parietal lobes. It is to be noted, however, that in man there may
be general loss of the muscular sense or of motor repr esentations, and, on the other hand, a pure
motor paralysis without loss of the former.

Ataxic motor conditions, similar to those that occur in animals (p. 700), take place in man,
and are known as cerebral ataxia.

The position of the centres is given at p. 696.

[But we may have localised lesions affecting one or more of the cortical motor
areas ; these are called monoplegiz. Cases in man are now sufficiently numerous
to permit of accurate diagnosis.] Crural monoplegia [rare lesions recorded in the
convolutions at the upper end of the fissure of Rolando, and the continuation of
this area on to the paracentral lobule of the marginal convolution |,—brachio-
crural, more common, in the upper and middle thirds of the ascending frontal and
ascending parietal convolutions—brachial, brachio-facial—facial, the last in the
lowest part of the central convolutions.

Paralysis of the muscles of the neck and throat indicates a lesion of the central convolutions,
and so does paralysis of the muscles of the eye. Lesions of the cortex always cause simultaneous

_ movements of the head and eyeballs.

Irritation of the Motor Centres.—If the motor centres are irritated by patho-
logical processes, such as hyperemia, or inflammation in a syphilitic diathesis—
more rarely by tumours, tubercle, cysts, cicatrices, fragments of bone—there arise
spasmodic movements in the corresponding muscle-groups. This condition of a
sudden discharge of the grey matter resulting in local spasms is called “‘ Jacksonian,
or cerebral epilepsy.”

[Convulsions and spasms may be discharged from motor cortical lesions, and

710 POSITION OF THE MOTOR CENTRES.

these, whether they affect the general or localised areas, give rise to unilateral con-

volutions and monospasm respectively. re

Be Pee re 1e seat of the spasm, it is called facial, brachial, crural mono-
eee ager Earache bees may affect several groups of muscles. Bartholow and
Sciamanna have stimulated the exposed human brain successfully with electricity.

Cerebral Epilepsy.—Very powerful stimulation of one side may give rise to
bilateral spasms, with loss of consciousness. In this case,'impulses are conducted
to the other hemisphere by commissural fibres (§ 379).

Movements of the Eye.—Nothing definite is known regarding the centre in the cortex for
voluntary combined movements of the eyeballs in man. In paralytic affections of the cortex and
of the paths proceeding from it, we occasionally find both eyes with a lateral deviation. If the
paralytic affection lies in one cerebral hemisphere, the conjugate deviation of the eyeballs is
towards the sound side (p. 588). If it is situated in the conducting paths, after these have
decussated, viz., in the pons, the eyes are turned towards the paralysed side (Prévost).

If the part be irritated so as to produce spasms in the opposite half of the body, of course the
eyes are turned in the direction opposite to that in pure paralysis. Instead of the lateral
deviation of the eyeballs already described, there is occasionally in cerebral paralysis merely a
weakening of the lateral recti muscles, so that during rest the eyes are not yet turned towards
the sound side, but they cannot be turned strongly towards the affected side (Leichtenstern,
Hunnius). The centre for the levator palpebre superioris appears to be placed in the angular
gyrus (Grasset, Landouzy).

II. The Centre for Speech.—The investigations of Bouilland [1825], Dax
ee Broca [1861], Kussmaul, Broadbent, and others have shown that the third

eft frontal convolution of the cerebrum (figs. 484, F3, and 488) is of essential
importance for speech, while probably the island of Reil also is concerned. The
island is deeply placed, and is seen on lifting up the overhanging part of the brain
called the operculum, lying between the two branches of the Sylvian fissure (8).
The motor centres for the organs of speech (lips, tongue) lie in this region, and
here also the psychical processes in the act of speech are completed. In the great
majority of mankind, the centre for speech is located in the left hemisphere. The
fact that most men are right-handed also points to a finer construction of the motor
apparatus for the upper extremity, which must also be located in the left hemisphere.
Men, therefore, with pronounced right-handedness (“droiters”) are evidently /eft-
brained (“ gauchers du cerveau”—JSroca). By far the greater number of mankind
are ‘‘left-brained speakers” (Kussmaul); still there are exceptions. As a matter
of fact, cases have been observed of left-handed persons who lost their power of
speech after a lesion of the vight hemisphere (Ogle). Investigations on the brains
of remarkable men have shown that in them the third frontal convolution is more
extensive and more complex than in men of a lower mental calibre. In deaf-mutes
it is very simple; microcephales and monkeys possess only a rudimentary third
frontal (Ridinger).

The motor tract for speech passes along the upper edge of the island’of Reil, then into the
substance of the hemispheres internal to the posterior edge of the knee of the internal capsule ;
from thence, through the crusta of the left cerebral peduncle into the left half of the pons,
where it crosses, then into the medulla oblongata, which is the place where all the motor nerves
(trigeminus, facial, hypoglossal, vagus, and the respiratory nerves) concerned in speech arise,
Total destruction of these paths, therefore, causes total aphasia; while partial destruction.
causes a greater or less disturbance of the mechanism of articulation, which has been called
. anazthris by Leyden and Wernicke.

Conditions.—Three activities are required for speech—(1) the normal movement
of the vocal apparatus (tongue, lips, mouth, and respiratory apparatus); (2) a ‘
knowledge of the signs for objects and ideas (oral, written and imitative or mimetic
signs) ; (3) the correct union of both. |

Aphasia (4 priv. and ddois speech).—Injury of the speech-centre causes either a ~
loss or more or less considerable disturbance of the power of speech. The loss of
the power of speech is called “aphasia.” [Aphasia, as usually understood, means
the partial or complete loss of the power of articulate speech from cerebral causes. |

ae oe

APHASIA. 711

The following forms of aphasia may be distinguished : —

1. Ataxic aphasia (or the oro-lingual hemiparesis of Ferrier), z.¢., the loss of speech owing
to inability to execute the various movements of the mouth necessary for speech. Whenever
such a person attempts to speak, he merely executes inco-ordinated grimaces and utters inarti-
culate sounds. [The muscles concerned in articulation, however, are not paralysed, but there
is an absence of co-ordination of these muscles due to disease of the cortical centre.] Hence, the
patient cannot repeat what is said to him. Nevertheless, the psychical processes necessary for
speech are completely retained, and all words are remembered ; and hence, these persons can
still give expression to their thoughts graphically or by writing. If, however, the finely
adjusted movements necessary for writing are lost, owing to an affection of the centre for the
hand, then there arises at the same time the condition of agraphia, or inability to execute those
movements necessary for writing. Such a person, when he desires to express his ideas in
writing, only succeeds in making a few unintelligible scrawls on the paper. Occasionally such
patients suffer from loss of the power of imitation or the execution of particular movements of
the limbs and body constituting pantomime speech or amimia (Kussmaul).

2. Amnesic Aphasia, or Loss of the Memory of Words.—Shonld the patient, however, hear
the word, its significance recurs to him. The movements necessary for speech remain intact ;
hence, such a patient can at once repeat or write down what is said to him. Sometimes only
certain kinds of words are forgotten, or it may be even only parts of certain words, so that only
part of these words is spoken. [Nouns and proper names usually go first.] Cases of amnesic
aphasia, or the mixed ataxic-amnesic form of disturbance of speech, point to a lesion of thé
third frontal convolution and of the island of Reil on the deft side. Another form of amnesic
aphasia consists in this, that the words remain in one’s memory but do not come when they
are wanted, 7.¢., the association between the idea and the proper word to give expression to it
is inhibited (Kussmaul). It is common for old people to forget the names of persons or proper
names ; indeed, such a phenomenon is common within physiological limits, and it may ulti-
mately pass into the pathological condition of amnesia senilis, Amongst the disturbances of
speech of cerebral origin, Kussmaul reckons the following :—

3. Paraphasia, or the inability to connect rightly the ideas with the proper words to express
these ideas, so that, instead of giving expression to the proper ideas, the sense may be inverted,
or the form of words may be unintelligible. It is as if the person were continually making a
‘“slip of the tongue.”

4, Agrammatism and ataxaphasia, or the inability to form the words grammatically and to
arrange them synthetically into sentences. Besides these, there is—

5. A pathological slow way of speaking (bradyphasia), or a pathological and stuttering way
of reading (tumultus sermonis), both conditions being due to derangement of the cortex
(Kussmaul). The disturbances of speech depending essentially upon affections of the peripheral
nerves, or of the muscles of the organs of the voice and speech, are already referred to in
§§ 319, 349, and 354.

[In word-blindness, the person cannot name a letter or a word, so that he can-
not understand symbols, such as printed or written words, or it may be any familiar
object, although he can
see quite well, while he
can speak fluently and
write correctly. |

[In word-deafness,
the person hears other
sounds and is not deaf,
but he does not hear
words. |

[The study of aphasia
in its various forms is
simplified by a study of
the mode of acquisition of

language byachild. The _. Fig. 494, . Fig. 495.
child hears spoken words Figs. 494, 495.—Schemes of aphasia. A, centre for auditory images;
and obtains auditory me- M, for motor images; B, perception centre; Oc, eye; E, reading

mories or impressions of centre ; 1 to 7, lesions (Lichtheim).

these sounds (called by Lichtheim ‘‘anditory word-representations”’), and this must form
the starting-point of language, and by and by it begins to co-ordinate its muscles to pro-
duce sounds imitative of these. Thus we have two centres, one for ‘‘auditory images”
(fig. 494, A), and the other for ‘‘motor images” (fig. 494, M), and these two must be con-
nected, thus establishing a reflex arc. There is a receptive and an emissive department as

712 ? APHASIA.

represented in the scheme. We must assume the existence of a ee oe (B), “in which
concepts are elaborated,” where these sounds become intelligible. Volitional language requires
a connection between B and M, as well as between A and M. But we have also reading and
writing. Suppose O to represent a centre for visual impressions (printed words or writing) >
these we can understand through the connection between such visual impressions and auditory
impressions, whereby a path is established through OA (fig. 495). In reading aloud, however,
the oro-lingual muscles must be co-ordinated, so we have the path OAM opened up. In
writing, or copying written characters, the movements of the hand are special, and perhaps
require a special centre, or at least a special arrangement of the channels for impulses in the
centre ; the movements are learned under the guidance of ocular impressions, so we connect O
and E, E being the centre guiding the movements in writing. As to volitional writing, the
impulse passes through M—but does it pass directly to E, or indirectly through A? Lichtheim
assumes that it goes direct from M to E. It is evident that there are seven channels which
may be interrupted, each one giving rise to a different form of aphasia (1 to 7).]

[Looked at from another point of view, either the ingoing (a) or outgoing (m) channels or
centres, or the commissural fibres between both, may be affected. If the motor centre is
affected, we have Wernicke’s ‘‘ motor aphasia”; if the sensory, his ‘‘sensory aphasia. ”’]

(In the most common form, or ataxic aphasia (Kussmaul), which was that described by
Broca, or the ‘‘ motor aphasia” of Wernicke, the lesion is in fig. 494, in M, i.e., in the motor,
or what Ross calls the emissive department. In such a case, it is obvious that there will be
loss of (1) volitional speech, (2) repetition of words, (3) reading aloud, (4) volitional writing,
and (5) writing to dictation ; while there will exist (2) understanding of spoken words, (0) also
of written words, .(c) and the faculty of copying.
If the lesion be in A,‘ we have the ‘‘sensorial aphasia”
of Wernicke, z.e., in the acoustic word-centre ; we
find loss of (1) understanding of spoken language,
(2) also of written language, (3) faculty of repeating
words, (4) and of writing to dictation, (5) and of
reading aloud; there will exist (a) the faculty of
writing, (b) of copying words, and (c) of volitional
speech, but the volitional speech is imperfect, the
wrong word being often used, so that there is the
condition of |‘ paraphasia.” If the connection be-
tween A and M be destroyed, other results will
follow, and such cases of ‘‘commissural” aphasia
have been described by Wernicke. If the interrup-
tion be between B and M, we have a not uncommon
variety of motor aphasia (4), where there is loss of
(1) volitional speech, and (2) volitional writing, and
there exist (a) understanding of spoken language, (db)
of written language, (c) and the faculty of copying;
but it differs from Broca’s aphasia in that there also

exists the faculty (d) of repeating words, (e) of writ-
| ; ing to dictation, (f), and of reading aloud. If the

lesion is in Mm (5), the symptoms will be those of
Broca’s ser but there will exist (1) the faculty of
volitional writing, and (2) of writing to dictation.
Many examples of this occur where patients have
lost the faculty of speaking, but can express their
thoughts in writing. In lesions of the path AB (6),
there will be loss of (1) understanding of spoken
language, and (2) of written language, and there will
exist (a) volitional speech (but it will be para-
> (b) Mfc eng (but it will have the
. characters of par: ia), (c) the faculty of repeat-
Fig. = ing words, (dreading. aloud, (¢c) writing to dictatog
and (f) power of copying words. The person will be quite unable to understand what he
repeats, reads aloud, or copies. ]

[Fig. 496 shows diagrammatically the conditions in motor and sensory aphasia, From
the eye and ear centripetal fibres (v and a) ascend to terminate in the visual (V) and audito
centres (A), in the cortex, while afferent fibres (s, s’, s”), indicated by dotted lines, also
from the articulations, muscles of the hand, and orbit to the cerebrum. The dotted lines on the
surface of the cortex represent the association system of fibres which connects the centres
with each other. The centres for vocal (V) and written expression (W) are connected by centri-
ne fibres, m and m’, with the hand and larynx respectively (Ross).] pe

. The thermal centre for the extremities is associated with the motor areas (§ 377). I jury,
or degeneration of these areas causes inequality of the temperature on both sides (Bechiterew). a 2

—_——

THE AUDITORY, GUSTATORY, AND OLFACTORY CENTRES. 713

IV. The sensory regions are those areas in which conscious perceptions of
the sensory impressions are accomplished. Perhaps they are the substratum of
sensory perceptions, and of the memory of sensory impressions.

1. The visual centre, according to Munk, includes the occipital lobes (fig. 484,
01, 02, 08), while, according to Ferrier, it also includes the angular gyrus. Huguenin
observed, in a case of long-standing blindness, consecutive disappearance of the
occipital convolutions on both sides of the parieto-occipital fissure, while Giovanardi,
in a case of congenital absence of the eyes, observed atrophy of the occipital lobes,
which were separated by a deep furrow from the rest of the brain. Stimulation of
the centre gives rise to the phenomena of light and colour. Injury causes disturb-
ance of vision, especially hemiopia of the same side (§ 344— Westphal). When
one centre is the seat of irritation, there is photopsia of the same halves of both
eyes (Charcot). Stimulation of both centres causes the occurrence of the phenomena
of light or colour, or visual hallucinations in the entire field of vision. Cases of
injury to the brain, where the sensations of light and space are quite intact, and
where the colour sense alone is abolished, seem to indicate that the colour sense
centre must be specially localised in the visual centre (Samelsohn). After injury of
certain parts, especially of the lower parietal lobe, “‘ msychical blindness” may occur.
A special form of this condition is known as ‘“ word-blindness” or alexia
(Coecitas verbalis), which consists in this that the patient is no longer able to
recognise ordinary written or printed characters (p. 711).

Charcot records an interesting case of psychical blindness. After a violent paroxysm of rage,
an intelligent man suddenly lost the memory of visual impressions ; all objects (persons, streets,
houses) which were well known to him appeared to be quite strange, so that he did not even
recognise himself in a mirror. Visual perceptions were entirely absent from his dreams.

Clinical observations on hemianopia (§ 344) show that the field of vision of each eye is
divided into a larger outer and a smaller inner portion, separated from each other by a vertical
line passing through the macula lutea. Each right or left half of both visual fields is related
to one hemisphere ; both left halves are projected upon the left occipital lobes, and both right

upon the right occipital lobes (fig. 487). Thus, in binocular vision, every picture (when not
too small) must be seen in two halves; the left half by the left, the right half by the right

hemisphere ( Wernicke).

As a result of pathological stimulation of the visual centre, especially in the insane, visual
spectres may be produced. Pick observed a case where the hallucinations were confined to the
right eye. Celebrated examples of ocular spectra occurred in Cardanus, Swedenborg, Nicolai,

J. Kerner, and Holderlin.
After degeneration of the cortical centre, the fibres which connect the occipital lobes with the

external geniculate body, the anterior corpora quadrigemina, pulvinar, these structures them-
selves, and the origin of the optic tract undergo degeneration (v. Monakovw).

2. The auditory centre lies on both sides (crossed) in the temporo-sphenoidal
lobes [according to Ferrier in the superior temporal convolution]; when it is com-
pletely removed, deafness results, while partial (left side) injury causes psychical
deafness. [See p. 704 for contradictory results.] Amongst the phenomena caused
by partial injury is swrditas verbalis (word-deafness), which may occur alone or in
conjunction with coecitas verbalis. Wernicke found in all cases of word-deafness
softening of the first left temporo-sphenoidal convolution (p. 704). In left-handed
persons, the centre lies perhaps in the right temporo-sphenoidal lobes ( Westphad).

Clinical.—We may refer word-blindness and word-deafness to the aphataxic group of diseases,
in so far as they resemble the amnesic form. A person word-blind or word-deaf resembles one
who in early youth has learned a foreign tongue, which he has completely forgotten at a later
period. He hears or reads the words and written characters ; he can even repeat or write the
words, but he has completely lost the significance of the signs. While an amnesic aphasic
person has only lost the key to open his vocal treasure, in a person who is word-blind or word-
deaf even thisis gone. From a case of recovery it is known that to the patient the words sound
like a confused noise. Huguenin found-atrophy of the temporo-sphenoidal lobes after long-
continued deafness. ;,

3. Gustatory and Olfactory Centre.—In the uncinate gyrus on the znner side
of the temporo-sphenoidal lobe (especially on the inner side of that marked U in

714 THE PSYCHO-SENSORIAL PATHS.

fig. 480), Ferrier locates the joint centres for smell and taste. These two centres
do not seem to be distinct locally from each other.

4. Tactile Areas.—According to Tripier and others, all the tactede cerebral
fields from different parts of the body coincide with the motor cortical centres for
these parts [compare p. 705].

Occasionally, in epileptics, strong stimulation of the sensory centres, as expressed in the
excessive subjective sensations, accompanies the spasmodic attacks (compare § 393, 12), Such
epileptiform hallucinations, however, occur without spasms, and are accompanied only by dis-
turbances of consciousness of very short duration (Berger).

Course of the Sensory Paths.—The nerve-fibres which conduct impulses from the
sensory organs to the sensory cortical centres pass through the posterior third of the
posterior limb of the internal capsule between the optic thalamus and the lenticular
nucleus (fig. 500, 8S). Hence, section of this part of the internal capsule causes
hemianesthesia of the opposite half of the body (Charcot). In such a case,
sensory functions are abolished—only the viscera retaining their sensibility. There
may also be loss of hearing, smell, and taste,—and hemiopia (Bechterew).

Pathological.—In cases where there is more or less injury or degeneration of these paths,
there is a corresponding greater or less pronounced loss of the pressure and temperature sense,
of the cutaneous and muscular sensibility, of taste, smell, and hearing. The eye is rarely quite
blind, but the sharpness of vision is interfered with, the field of vision is narrowed, while the
colour sense may be partially or completely lost. The eye on the same side may suffer to a
slight extent.

V. Numerous cases of injury of the anterior frontal region, without interference
with motor or sensory functions, have been collected by Charcot, Ferrier, and
others. On the other hand, en-
feeblement of the intelligence
and idiocy are often observed in
acquired or congenital defects of
the prefrontal region. In highly
intellectual men, Riidingerfound
in addition a considerable de-
velopment of the temporo-sphe-
noidal lobe. According to
Flechsig, there is no doubt that
the frontal lobes and the tem-
poro-occipital zone are related
to intellectual processes, more
especially the “‘ higher” of these.

Topography of the Brain.—The
relationsof the chief fissures and con-
volutions of the brain to the surface
of the skull are given in ng. 484,
the brain being represented after
Ecker, [Turner and others have
given minute directions for finding
the position of the different con-
volutions by reference to the sutures
and other prominent parts of the
skull. The annexed diagram by
R. W. Reid shows the relation of
the convolutions to certain fixed

Fig. 497.
Relation of the fissures and convolutions to the surface of 1:
the scalp. +, most prominent part of the parietal emi- ms ree of the fissure of

nence ; a, convex line bounding parietal lo below ; 3, i joi
peeves line bounding the temporo-sphenoidal lobe behind oe Tenetbattol aaean is obs
Rem “ on ) : tained by measuring on the scalp K
in the middle line the distance between the glabella and the external occipital protuberance, or
the inion, which, in ordinary heads, varies from 11 to 13 inches (fg. 499). Measured ie ae
before backwards, along this line, the distance from the glabella to the top of the fissure is. Si SS

THE BASAL’ GANGLIA. x15

per cent. of the length of the whole line. The direction of the fissure is downwards and for-
wards, and the long axis of the fissure forms, with the average mesial line, an angle of 67°,

the angle opening forwards. Its
average length is 3% inches. ]

[The fissure of Slyvius is found
by drawing a line from the ex-
ternal angular process of the frontal
bone backwards to the occipital
protuberance, taking the nearest
route between these two points.
A point, 14 inch backwards from
the angular process along this line,
marks the origin of the fissure ;
while a straight line drawn to the
centre of the parietal eminence
marks the course of its posterior
limb. The parieto-occipital fissure
will be two inches behind the upper
end of the Rolandic fissure (4. W.
Hare).

[Corpus Callosum.—It is usually
stated that the corpus callosum
connects the convolutions of one
side of the brain with those on the
other, 7.e., that it is an inter-
hemispherical commissure. D. J.
Hamilton, however, is of opinion
that it is not an inter-hemispheric
commissure, but is due to-cortical
fibres coming from the cortex
cerebri to be connected with the
basal ganglia of the opposite side.
On this view, the ‘‘corona radiata,”’
as usually understood, consists only
of the fibres which pass from the
cerebral peduncle directly up to the
cortex on the same side, and are
contained in the posterior division
and knee of the internal capsule.
They correspond to the motor
pyramidal tracts. Hamilton main-
tains that all the other fibres of
the internal capsule pass into the
crossed callosal tract, and, instead
of running directly up to the cortex
on the same side, cross in the
corpus callosum to the cortex of
the opposite side. Beevor, relying
on the examination of the brain of
monkeys, by Weigert’s method,
denies that any fibres of the corpus
callosum pass into the external or

the old view that the corpus cal-
losum is a commissure between the
two hemispheres. ]

Erb observed a case of its almost
complete destruction without any
considerable effect on motility,
co-ordination, sensibility, !reflexes,
senses, speech, or any marked im-
pairment of intelligence.

379. BASAL GANGLIA

Fig. 499.

internal capsules, and he supports Fig. 498.—The fissures of Rolando and Sylvius are marked

as broad dark lines. The shaded circles mark approxi-
mately the motor areas. 1, lower extremity; 2, 3, 4, 5, 6,
and a, b, c, d, upper extremity; 7, 8, 9, 10, 11, oro-
lingual muscles (4. W. Hare). Fig. 499.—Head, skull,
and cerebral fissures. OPvr, occipital protuberance ; EAP,
external angular process; SF, Sylvian fissure; <A, its
ascending limb; FR, fissure of Rolando; PE, parietal
eminence; MMA, middle meningeal artery; TS, tip of
temporo-sphenoidal lobe; B, Broca’s convolution; IF,
inferior frontal sulcus; POF, parieto-occipital fissure ;
IPF, intra-parietal sulcus (4. W. Hare).

—MID BRAIN.—|The corpus striatum consists of two parts, an intra-ventricular
portion projecting into the lateral ventricle, the caudate nucleus, and an extra-

716 THE BASAL GANGLIA.

ventricular portion, the lenticular nucleus. Between the head of the caudate
nucleus internally, and the lenticular nucleus externally, lies the anterior division
of the internal capsule. The fibres which pass between these ganglia do not
seem to form connections with them. The expanded head of the caudate nucleus
is in front, and lies inside and around the front, of the lenticular nucleus, with
which and the anterior perforated space it is continuous; it sweeps backwards
into a tailed extremity, which nearly surrounds the lenticular nucleus like a loop.
The lenticular nucleus is biconvex in a horizontal section, but triangular and
subdivided into three divisions when seen in a vertical section (fig. 501). The
older observations on the corpora striata in man may be dismissed, as a distinction
was not drawn between injury to its two parts ou the one hand and the internal
capsule on the other. ]

[The caudate nucleus and lenticular nucleus in their development are co-
ordinate with the development of the cortex cerebri. Electrical stimulation of
these ganglia causes general muscular contractions in the opposite half of the body,
which are due to simultaneous stimulation of the neighbouring cortico-muscular
paths. The same result is obtained as if all the motor cortical centres were stimu-
lated simultaneously. |

Gliky did not observe movements on stimulating the corpus striatum in rabbits ; it would
seem that, in these animals the motor paths do not traverse these ganglia, but merely pass along-
side of them.

(Lesions of the lenticular nucleus or of the caudate nucleus do not seem to give
rise to any permanent symptoms, provided the internal capsule be not injured.]}
Destruction of the internal capsule, however, causes paralysis of motion or
sensibility, or both, on the opposite side of the body, according to the part of it
which is injured. The corpus striatum is quite insensible to painful stimulation
(Longet).

Pathological.—In man, a lesion, not too small, destroying the anterior part of the corpus
striatum is followed by permanent paralysis of the opposite side, provided the internal capsule
is injured, but the paralysis gradually disappears, if the lenticular and caudate nucleus only are
affected (compare § 365). Sometimes there is dilatation of the blood-vessels in consequence of
vaso-motor paralysis (§ 377) if ,the posterior part is injured (Nothnagel) ; redness and a slightly
increased temperature of the paralysed extremities, at least for a certain time; swelling or
vedema of the extremities ; sweating ; anomalies of the pulse detectable by the sphygmograph ;
decubitus acutus on the paralysed side ; abnormalities of the nails, hair, skin ; acute inflamma-
tions of joints, especially of the shoulder. Later, contracture or permanent contraction of the
paralysed muscles takes place (Huguenin, Charcot). In some cases there is cutaneous anesthesia,
and occasionally safecblcihent of the sense-organs of the paralysed side, and both when the

vosterior third or sensory crossway of the posterior section of the internal capsule is affected.
sually, however, hemiplegia and hemianesthesia occur together.

Optic Thalamus.—-errier did not observe any movements on stimulating the
optic thalami with electricity. As the pulvinar, or posterior extremity of the optic
thalamus, is in part the origin of the optic nerve, and is also connected by fibres
with the cortex cerebri, it is probably related to the sense of sight. Injury to its
posterior third in man, results in disturbance of vision (Nothnagel). Ferrier
surmises that the sensory fibres pass through the optic thalami on their way to the
cortex, so that when they are destroyed, insensibility of the opposite half of the
body is produced. Removal of the optic thalamus, or destruction of the part in
the neighbourhood of the inspiratory centre in the wall of the third ventricle,
influences the co-ordinated movements in the rabbit (Christiant).

We know very little definitely as to the functions of these organs. After injury to one
thalamus, there has been observed enfeeblement or paralysis of the muscles of the opposite side, —_
together with mouvements de mange; and sometimes hemianesthesia of the opposite side, A
with or without affections of the motor areas, have been recorded. Extirpation of certain
cortical areas (rabbit) is followed by atrophy of certain parts of the thalamus (v. Monakow).—

’

[Internal Capsule.—In connection with the functions of the basal ganglia, it
most important to remember their relation to the internal capsule. The corpus

THE INTERNAL CAPSULE. 717

striatum consists of an intra-ventricular part, the caudate nucleus; and an extra-
ventricular part, the lenticular nucleus. The lenticular nucleus consists of three
parts, best seen in a vertical section (fig. 501, 1, 2, 3), with white matter between
them, the strie medullares. The anterior limb of the internal capsule sweeps

Gyrus fornicatus

Corpus callosum
Cornu anticum.

Septum: lucidum.
Caput nuclei caudati.

Columnae fornicis
i Capsula interna
aga (anterior limb).
Capsula externa.
Island of Reil.

Nucleus lentiformis.

Stria terminalis.
Claustrum.

Thalazins opticus. _ ! i. : :
: VY /, Y Y SS Capsula interna
Yj Y | aN ¢ romsiy «8 pare \ (posterior limb).
Bs” : ee — Thalamus optics.

Corpus genicula-

Pulvinar. .
tuu mnediale.

Caucate nucleus.

Biachium eonjunc-
tivum anticum.

Pedunculus cerebri.

{ ad corpora
quadrige-
mina.
Crus ad medullam t;
eerevelli oblongata. VA ;
fy, /

f~

\\\

ad pontem.

41a cinerese

Obex. -
Funiculus cuneatus
Funiculus gracilis.
Fig. 500.

Human brain, with the hemispheres removed by a horizontal incision on the right side. 4,
trochlear ; 8, acoustic nerve ; 6, origin of the abducens; F, A, L, position of the pyramidal

(motor) fibres for the face, arm, and leg; S, sensory fibres.

between the caudate and lenticular nucleus, while the posterior segment lies between
the optic thalamus and the lenticular nucleus (fig. 500). External to the first
division of the lenticular nucleus is the external capsule (figs. 500, 501), whose
function is unknown. External to this is the claustrum, whose function is also

718 PEDUNCLE AND PONS.

unknown. It is evident that hemorrhage into or about the basal ganglia is apt
to involve the fibres of the internal capsule. [When the lenticulo-striate artery,
or as it is called the “artery of hemorrhage,” ruptures (fig. 490, aSL), it may not
only destoy the lenticular nucleus, but the internal capsule will be compressed ;
and the same is the case with the lenticulo-optic artery—the external capsule will
tend to force the blood inwards. We know that, in the posterior segment of the
capsule, the volitional or pyramidal fibres lie in the following order from before
backwards—those for the face (and tongue) in the knee, in the anterior third
those for the arm and hand, and in the middle third for the leg, and perhaps behind
these those for the trunk (fig. 500, F, A, L), so that a very small lesion in this
region will affect a large number of these fibres, converging as they do like the
rays of a fan from the motor cortical areas, where the arrangement of these centres
js a supero-inferior one (fig. 488), to become an antero-posterior one in the knee
| and posterior limb of the
internal capsule (fig. 500).
The posterior third of this
limb is sensory and is the
“sensory crossway.” |

Nucleus
caudatus. ~*,
‘

Corpus [Horsley points out that he-

callosum : :
morrhage trom the lenticulo-
Pillars of striate artery affects in order the
the fornix muscles of the face, arm, leg, and
trunk, while recovery is in the

inverse order. ]

Internal 7 :
capsule. [The crura cerebri (fig.
Optic 461, P), or cerebral pe-
thalamus. duncles, are two thick
Saikconi- strands as they emerge
miesure. above the pons, and as they
External — are much larger than the
is haa pyramidal tracts, they must
Claustrum. ~~~ receive many fibres within

the pons. <A transverse sec-
tion (fig. 502) shows that,
on them posteriorly and con-
necting them, are the cor-
pora quadrigemina (CQ).
The crus proper is divided
by the substantia nigra (SN)
into a lower part, the crusta
or basis, and an upper part, or tegmentum. The crusta is composed of ascending
and descending nerve-fibres ; but the tegmentum, in addition to many nerve-fibres,

Fig. 501.
Frontal section through the right cerebral hemisphere in front
of the soft commissure (posterior surface of the section).

contains much grey matter with nerve-cells. Near the middle is the ‘red nucleus ”

or “tegmental nucleus” (RN). Outside this is the fillet (F), a well-defined bundle
of nerve-fibres running upwards from the pons. Above the nucleus, near the middle
line, is the “‘ posterior longitudinal bundle ” (p. 1. b.), which is triangular in section.
Above the tegmentum lie many nerve-cells, the origin of the third nerve (III), and
arranged around the iter is much grey matter. ]

Injury to one cerebral peduncle causes, in the first place, violent pain and spasm
of the opposite side, while the blood-vessels on that side contract, and the salivary
glands secrete. These phenomena of irritation are followed by paralytic symptoms
of the opposite side, viz., anesthesia (§ 365) and paresis, or incomplete voluntary
control over the muscles, as well as paralysis of the vaso-motor nerves. In

affections of the cerebral peduncle in man, we must remember the relation of

PONS VAROLII. 719
the oculomotorius to it, as the latter is often paralysed on the same side | while
the extremities, tongue, and half the face are paralysed on the opposite side from
the lesion |. | |

The middle third of the crusta of the cerebral peduncle (fig. 502) includes the direct pyramidal
tracts (S$ 365, 378). The fibres of the inner third connect the frontal lobes with the cerebellum
through the superior cerebellar peduncles. In the
outer third are fibres which connect the pons with
the temporal and occipital cerebral lobes (flech-
sig). The fibres which pass from the tegmentum
into the corona radiata conduct sensory impulses
(Flechsiq).

[The pons varolii contains ascending and
descending fibres, as well as transverse ones,
and, in addition, the continuation upwards
of grey matter from the medulla, special
masses of grey matter, and the nuclei of
certain cranial nerves. Its appearance in
section necessarily varies with the region
where the section is made. Fig. 503 is
a transverse section through part of the
seventh nerve. The lower part shows the

Fig. 502.

Scheme of transverse section of the cerebral
peduncles. CQ, corpora quadrigemina; Aq,

superficial (s.t.f.) and deep (d.t.f.) trans-
verse fibres, with the pyramidal fibres (Py)
between them. |

Stimulation or section of the pons causes
pain and spasms; after the section, there
may be sensory, motor, and vaso-motor

aqueduct; p.l.b., posterior longitudinal
bundle; F, fillet or lemniscus; RN, red
nucleus ; SN, substantia nigra; III, third
nerve ; Py, pyramidal tracts; FC, fronto-
cerebellar; and TOC, temporo-occipital
fibres of the crusta ; CC, caudate-cerebellar
fibres in upper part of crusta (after Wernicke
and Gowers). |

paralysis, together with forced movements.

For diagnostic purposes in man, it is important to observe if alternate hemiplegia be
present.

[In lesions situated in the lower half of one side of the pons, there is facial paralysis on the

P.TAF. FAP.T.
ae F
/ D
pes Sle ent
M.0.
D.XP.
Fig. 503. Fig. 504,
Fig. 503.—Transverse section of the pons through part of the seventh nerve. x2. F.R., for-

matio reticularis; VII, seventh nerve; Va, ascending root, and Vm, motor root of the
fifth nerve ; F, fillet; s.o., superior olive; s.l.b., superior longitudinal bundle; Py, pyra-
midal fibres ; R, restiform body ; M.P., middle peduncles of cerebellum; d.t.f. and s.t.f.,
deep and transverse superficial fibres of the pons (after Wernicke). Fig. 504.—Scheme of
the fibres in the pons; PT, pyramidal tracts; F, facial fibres ; w, upper, 7, lower lesion ;
MO, medulla oblongata ; DP, decussation of pyramids. |

same side as the lesion and paralysis (motor and sensory, and more or less complete) on the
opposite side of the body—this is called alternate paralysis ; while, if the lesion be in the upper

a

720 CORPORA QUADRIGEMINA,
the facial paralysis is on the same side as the paralysis of the body.

i th ) Pag c
ar on metrogel a ge 1e 5th and 6th nerves may also be involved. This is explained by

But the parts supplied by the 5th
fig. 504, where the upper facial fibres cross in the pons. er sions of th
pons are frequently associated with hyperpyrexia, the temperature often rising rapidly within
an hour, perhaps from the grey matter in the floor of the 4th ventricle being affected ; but
whether it is due to some effect on a heat-regulating or heat-producing centre is uncertain.
Tumours of considerable size may press on the pons without producing very marked 4 PO pe
as tumours tend to push aside tissues, unless re infiltrating in their character, Lesions of
the transverse superficial fibres (middle cerebellar peduncles) often give rise to involuntary

forced movements, there being a tendency to move to one side or the other. ]

The Corpora Quadrigemina.—Destruction of these bodies on one side in
mammals (or their homologues, the optic lobes in birds, amphibians, and fishes)
causes actual blindness, which may be on the same or the opposite side, according
to the relation of the fibres crossing at the optic chiasma (§ 344). 7'otal destruction
causes blindness of both eyes. At the same time, the reflex contraction of the
pupil, due to stimulation of the retina with light, no longer takes place (Flourens),
where the optic is the afferent and the oculomotorius the efferent nerve (§ 345).
If the cerebral hemispheres alone be removed, the pupil still contracts to light, as
well as after mechanical stimulation of the optic nerve (7. Mayo). Destruction of
the corpora quadrigemina interferes with the complete harmony of the motor acts ;
disturbance of equilibrium and inco-ordination of movements occur (Serres). In
frogs, Goltz observed not only awkward clumsy movements, but at the same
time the animals have to a large extent lost the power of completely balancing the
body (p. 683). A similar result was observed in pigeons (‘Kendrick) and
rabbits (Ferrier). Extirpation of the eyeball is followed by atrophy of the opposite

anterior corpus quadrigeminum (G'udden).

According to Bechterew, the fibres of one optic tract pass through the anterior brachium (fig.
500) into the anterior pair (nates) of the corpora quadrigemina ; while those fibres which cross
in the chiasma (fig. 425) pass into the posterior pair (testes). According to this arrangement
we have partial blindness, according as one or other pair of these bodies is destroyed.

(In man, very little is known regarding the etfects of disease of the corpora quadrigemina,
interference with the ocular muscles being the most marked symptom ; but the inco-ordination
of movement which has been observed may be due to pressure upon the superior cerebellar
peduncle, while it is by no means certain that the defects of vision are directly due to lesions of
these bodies. ]

Stimulation of the Corpora Quadrigemina.—The corpora quadrigemina react to electrical,
chemical, and mechanical stimuli. The results of stimulation are very variously stated.
According to some observers, there is dilatation of the pupil.on the same side ; according to
Ferrier, 1t may be the pupil on the opposite or on the same side. The stimulation may
be conducted from the corpora quadrigemina to the medulla oblongata, and to the origin of the
sympathetic, for, after section of the sympathetic nerve in the neck, dilatation of the pupil no
longer takes place. According to Knoll, the contraction of the pupil observed by the older
experimenters occurs ouly when the adjoining optic tract is stimulated. Stimulation of the
right anterior corpus quadrigeminum causes deviation of both eyes to the left (and conversely) ;
on continuing the stimulation, the head is turned to this side. On dividing the corpora quad-
rigemina by a vertical median incision, stimulation of one side causes the result to take place
only on one side (Adamiik). Ferrier observed signs of pain on stimulating these organs in
mammals, Carville and Duret conclude from their experiments, that these organs are centres
for the extensor movements of the trunk. Ferrier found, on stimulating one optic lobe in a
pigeon, dilatation of the opposite pupil, turning of the head towards the other side and back-
wards, movement of the opposite wing and leg; strong stimulation caused flapping movements
of both wings. Danilewsky, Ferrier, and Lauder Brunton observed a rise of the blood-pressure

and slowing of the heart-beat, together with deeper inspiration and expiration. |
_ Bechterew ascribes all the phenomena, except those of vision itself, which accompany injury
or stimulation of these bodies, to affections of deeper seated parts. He asserts that the corpora
quadrigemina contain neither the centre for the movements of the pupils nor that for the
combined movements of the eyeballs ; not even the centre for maintaining the equilibrium of
the body. Stimulation of these bodies causes the animals to perform marked movements.
Reflex phenomena, nystagmus, forced movements, and unsteadiness of the gait only occur,
however, when the deeper parts are injured. |

Pathological.—Lesions of the anterior pair in man, according to the extent of the lesion,
cause disturbance of vision, failure of the pupil to contract to li “ht, and even blindness; there

Sudden and extensive lesions of the -

7

FORCED MOVEMENTS—NYSTAGMUS. 721

may be joie age of the oculomotorii on both sides. Disease of the posterior pair may be
associated with disturbances of co-ordination (Nothnagel),

Forced Movements.—It is evident from what has been said regarding the
importance of the corpora quadrigemina for the harmonious execution of movements,
that wnilateral injury of such parts as are connected with them by conducting
channels, must give rise to peculiar unilateral disturbance of the equilibrium,
causing variations from the symmetrical movements of both sides of the body.
These movemeuts are called forced movements. To this class belong the ‘“ mouve-
ments de manége,” where the animal, instead of moving in a straight line, runs round
in a circle; index movements, where the anterior part of the body is moved
round the posterior part, which remains in its place, just like the movements of an
index round its axis ; and rolling movements, when the animal rolls on its long axis.
All these forms of movement may pass into each other, and they are, in fact, merely
different varieties of the same kind of movement. The parts of the nervous system
whose injury produces these movements are the corpus striatum, optic thalamus,
cerebral peduncle, pons, middle cerebellar peduncles, and certain parts of the
medulla oblongata. Eulenburg observed index movements in the rabbit, after
injury to the surface of the brain, and Bechterew observed the same in dogs.
Forced movements, together with nystagmus and rotation of the eyeballs, are
caused by injury to the olives (Bechterew). 'The statements of observers vary as to
the direction and kind of movement produced by injuring individual parts. The
following observations have been made :—Section of the anterior part of the pons,
and of the crura cerebelli causes index, or, it may be, rolling movements towards
the other side; section of the posterior part of the same regions causes rolling move
ments towards the same side, while the same result is caused by a deeper puncture
into the tuberculum acusticum, or into the restiform body. Section of one cerebral
peduncle causes mouvements de manége, while the body is curved with the con-
vexity towards the same side. The nearer to the pons the section is made, the
smaller is the circle described ; ultimately index movements occur. Injury to one
optic thalamus produces results similar to puncture of the anterior part of the
cerebral peduncle, because the latter is injured along with it at the same time.
Injury to the anterior part of one optic thalamus causes the opposite kind of forced
movement, viz., with the concavity of the body towards the injured side. Injury -
to the spinal portion of the medulla oblongata is followed by bending of the head
and vertebral column, with the convexity towards the injured side, along with
movements in a circle. When the anterior end of the calamus and the part above
it are injured, the movements are towards the sound side.

Strabismus and Nystagmus.—Amongst the forced movements may be reckoned
deviation of the eyeballs, strabismus or squinting, and involuntary oscillation of the
eyeballs, constituting nystagmus. The latter condition occurs after superficial
lesions of the restiform body, as well as of the floor of the 4th ventricle. A
unilateral, deep, transverse injury, from the apex of the calamus upwards as far as
the tuberculum acusticum, causes the eye of the same side to squint downwards
and forwards, that of the other side backwards and upwards. Section of both sides
causes this condition to disappear (Schwahn). Hence, Eckhard assumes that the
medulla oblongata is the seat of an apparatus controlling the movements of the
eyes (Eckhard), which can be excited by sudden anzmia, e.g., ligature of the
cephalic arteries in a rabbit.

In pathological degeneration of the olivary body of the medulla oblongata in man, Meschede
observed intense rotatory movements towards the same side.

Theory.—In order to explain the occurrence of forced movements, it is suggested that there
is unilateral incomplete paralysis (Lafarque), so that the animal in its efforts to move onwards
leaves the paralytic side slightly behind the other, and hence there is a variation from the

symmetry of the movements. Brown-Séquard regards the matter in exactly an opposite light,
viz., as due to stimulation from injury, causing an excessive activity of one-half of the body.

22

722 PINEAL AND PITUITARY BODIES.

Henle ascribes the movements to vertigo, or a feeling of giddiness caused by the injury. In all a
operations on the central nervous system, where the equilibrium is deeply affected, there is a
considerable increase in the number and depth of the respirations (Landois). yLo®
Other Effects.—Some observers noticed variations of the blood-pressure and a change in the
number of heart-beats after stimulation of the cortex cerebri, ¢.g., after electrical stimulation of the
motor areas for the extremities (Bochefontaine). Balogh observed acceleration of the pulse, on
stimulating several points on the cortex cerebri of a dog, and from one point sowing of the pulse.
Eckhard stimulated the surface of the brain in rabbits, and, as a rule, he observed that, as long as
single crossed movements occurred in the anterior extremities, there was no effect upon the heart,
but that the heart became affected as soon as other movements occurred. This consists in slow
strong pulse-beats, with occasional weaker beats, while at the same time the blood-pressure is
slightly increased (Bochefontaine). If the vagi be divided beforehand, the effect upon the pulse
disappears, while the increase of the blood-pressure remains. That psychical processes affect the
action of the heart was known to Homer and Chrysipp. Bochefontaine and Lepine, on stimulat-
ing several points, especially in the neighbourhood of the sulcus cruciatus in the dog, observed
increased secretion of saliva, slowing of the movements of the stomach, peristalsis of the
intestine, contraction of the spleen, of the uterus, of the bladder, and increased respirations.
Bufalini, on stimulating those parts of the cortex which cause movements of the jaw, observed
secretion of gastric juice with increase of the temperature of the stomach. Schiff, Brown-
Sequard, Ebstein, Klosterhalfen, and others have observed that injury to the pons, corpus
striatum, thalamus, cerebral peduucle, and medulla oblongata often causes hyperemia and
hemorrhage into the lung (according to Brown-Séquard, especially after injury to one side of
the pons, which affects the opposite lung), under the pleura, in the stomach, intestine, and

kidneys. Gastric hemorrhage is common after injury to the pons just where the cerebral
Pe join it. Similar phenomena have been observed in man after apoplexy or cerebral
emorrhage.

Specially interesting is the cerebral wnilateral decubitus acutus or bed-sore, described by
Charcot, which always occurs on the paralysed side of the body, i.c., on the side opposite to

‘Sp F

: ak Co

the cerebral injury. It begins on the
second or third day, rapidly causes enor-
mous destruction and sloughing of the
tissues on the back and lower extremities,
and death soon takes place. The decu-
bitus which occurs after spinal injuries,
usually begins in the middle line of the
buttocks, and extends symmetrically on
both sides. In cases of unilateral injury
to the spinal cord, the decubitus occurs
on the corresponding side of the sacral
region (p. 508).

[The Pineal Gland or epiphysis cerebri
lies on the back of, and is connected
with, the third ventricle (fig. 505, Z).
It projects backwards between the cor-
Lore quadrigemina. It is originally

eveloped as a hollow outgrowth from
that part of the embryonic brain which
becomes the third ventricle. The hollow
centre usually disappears, while the distal

Fig. 505.

Longitudinal section of an adult human brain. Aq,
aqueduct of Sylvius ; B, corpus callosum; Ca, ante-
rior commissure ; Cm, middle commissure ; Col,
lamina terminalis ; Cp, posterior commissure ; FM,
foramen of Munro; G, Fenix ; H, pituitary body ;
HH, cerebellum ; MH, corpora quadrigemina ; JH,

medulla oblongata; P, pons Varolii; 2, spinal cord;

SP septum lucidum ; J, infundibulum ; Zh, tela
oroidea ; Zo, optic thalamus ; VH, cerebrum ; Z,

pineal gland ; J, olfactory lobe and nerve ; JJ, optic

nerve,

posterior lobe is developed as a hollow
nected with the third ventricle.

the infundibulum. The anterior

the upper end e
with the anterior lo

outgrowth from the part of the embryonic brain con-
with | It loses its cavity and its nervous tissue ; is ermeated 1
connective-tissue and blood-vessels ; and is connected with the floor of the third

lobe is developed as a tubular invagination of the stor
i.e., from the ectoderm of the buccal cavity ; but it soon loses its connection with this ca
, and the stalk atrophies. In mammalia, ny
to form the pituitary body. For the effects of its removal, see § 108, V

ortion becomes enlarged and is often
obulated. Its distal portion may ter-
minate outside the skull ; and in some
animals there is developed in the median
line of the skull an eye—pineal eye—
arranged on the invertebrate plan, as in
ainern Hatteria, &c. (De Graaf, Spencer)
(¢ 405).

[The pituitary body or hypophysis
cerebri consists of two lobes, different in
origin and structure (fig. 505, H). The

ventricl

the upper expanded end um

STRUCTURE AND FUNCTIONS OF THE CEREBELLUM. 723

380. STRUCTURE AND FUNCTIONS OF THE CEREBELLUM.—{Structure.—On examin-
ing a vertical section of a cerebellar leaflet, we observe the following microscopic appearances : -
—Externally, is the pia mater with its blood-vessels (fig. 506, a), which penetrate into the
grey matter ; within is the medulla, composed of white fibres. The grey matter consists of b,
a broad outer or molecular layer, largely composed of branched fibrils ; and internal to it is d,
the “ granular,” nuclear, or rust-coloured layer. On the boundary line between these two, is
‘the layer of Purkinje’s cells, c. The cells of Purkinje form a single layer of large multipolar
flask-shaped nerve-cells, which have been
compared to the branched antlers of a stag
(fig. 507). From their outer surface is given
off a process which rapidly divides, and gives
rise to a large number of smaller processes
running outwards in the outer grey layer.
Some of these processes form part of the
ground-plexus of fibrils in this layer; An
unbranched axial cylinder process is sent
inwards to the granular layers, where it be-
comes continuous with a nerve-fibre—every
cell of Purkinje being continuous with a
straight unbranched medullated nerve-fibre.
The wnbranched fibres run straight from the
medulla through the granular layer, forming
no connection with its granules. A second
set of branched or anastomosing, often vari-
cose, nerve-fibres, finer than the foregoing,
pass from the medulla into the granular
layer, where they form a network which is

Fig. 507. |

Fig. 506.—Vertical section of the cerebellum. a, pia mater; 0, external layer ; c, layer of
Purkinje’s cells ; d, inner layer ; e, medullary white matter. Fig. 507.— Purkinje’s cell,
sublimate preparation. x 120,

continued into the molecular layer. The granular layer is composed of closely packed
granules of two kinds; one is stained by hematoxylin, and the other with eosin (Denissenko).
The hematoxylin stained cells are most numerous; they consist of a nucleus surrounded
by protoplasm, and are what were formerly called granules. The eosin-stained cells, which
are also stained by nigrosin (Beevor), are interposed in the course of medullated nerve-
fibres. The hematoxylin cells, called glia-cells by Beevor, have processes, and form a -net-
work throughout the granular layer, which also extends into the molecular layer. This net-
work is regarded as the continuation of the modified myelin of the nerve-fibres, and it forms
a capsule for the cells of Purkinje. The molecular layer consists of a ground substance, com-
posed of a spongy network of fine fibrils, which seem to be of the nature of neuro-keratin,
strengthened here and there by stronger fibres. In the meshes lies a homogeneous substance.

Lal ek -
724 FUNCTIONS OF THE CEREBELLUM.

Some of this substance is more condensed to form a limitans externa on the surface of the
cerebellum, while on the boundary line next the granular layer the branches of the glia-cells
form a limitans interna, and between the two stretches the neuro-keratin network. Some
small varicose nerve-fibres exist in this layer continuous with those in the granular layer, The
branched process of the cells of Purkinje is fibrillated, and the finer processes are composed
also of fibrils, which are gradually distributed until they become isolated. It is suggested by
Beevor that these fibrils bend at a right angle in a plane parallel to the surface, and rearran
themselves as fibres surrounded by a medullated sheath, and that these fibres run inwards
through the molecular and granular layers—as the branched fibres—to the medulla.]

Function.—Injuries of the cerebellum cause disturbances in the harmony of the
movements of the body. Most probably, the cerebellum is a great and important
central organ for the finer co-ordination and integration of movements. The fact
that it is connected with all the columns of the spinal cord and with all the central
ganglionic masses, renders this very probable. The direct cerebellar tracts from the
lateral column of the cord conduct sensory impressions to the cerebellum, and thus
indicate the posture of the trunk. The cerebellum may affect the motor nerves of
the cord through fibres which pass downward in the lateral columns of the cord
from the restiform bodies (/lechsig). Injury of the cerebellum neither produces
disturbance of the psychical activities, nor does it interfere with the will or
consciousness. Injuries to the cerebellum itself do not give rise to pain.

According to Schiff, the cerebellum does not actually regulate the co-ordination of movements.
According to him, there is a mechanism on both sides of the middle line, which increases all
the complicated muscular movements—not only those for powerful contractions, but also the
peculiar fine movements which fix the limbs and joints. Luciani asserts that destruction of
the cerebellum produces a condition of incomplete tonus, there being a want of energy to control
the voluntary muscles. Each half of the organ acts on both halves of the body. 3

Injury or Removal of Cerebellum.—The immediate results produced by injury to
or removal of the cerebellum have been admirably described by Flourens (fig. 508).
On removing the most superficial layers
in a pigeon, the animal merely showed
signs of weakness and interference with
the uniformity of its movements. On
removing more of the cerebellum, the
animal became greatly excited, and made
violent irregular movements, which did
not partake of the character of con-
vulsions. The sensorium was unaffected,
while vision and hearing were intact.
Co-ordinated movements, such as walk-
ing, flying, springing, and turning, could
be executed but imperfectly. After re-
moval of the deepest layers, the power of
executing the above-named movements
was completely abolished. On placing
the pigeon on its back, it could not get on its legs; at the same time it made con-
tinually the greatest exertions in its movements, but these were always inco-ordinated,
and therefore without any satisfactory result. The will, intelligence, and percep-
tion remained intact ; the animal could see and hear, and sought to avoid obstacles
placed in its way. It gradually exhausted itself in fruitless efforts to get on its
legs, and ultimately remained in its abnormal position, quite exhausted. Flourens
concluded from these experiments that the cerebellum is the centre for co-ordinating
voluntary movements. Lussana and Morganti regard the cerebellum as the seat of
the muscular sense. | | i

[Extirpation in Mammals.—The dangers attending this operation are so great, that but few
animals survive. Luciani, however, by using antiseptic and other precautions, has been at
to operate so that complete cicatrisation was obtained, the animal (young bitch) being restor

to health for a few months. The cerebellum alone was removed, but not its peduncles,

Pigeon with its cerebellum removed,

)

_—

i

EXTIRPATION OF THE CEREBELLUM. 725

all other similar operations, we must distinguish sharply the phenomena manifested during re-
covery from those after complete recovery. During the first period of six weeks, from the time
of the operation until complete recovery, the symptoms are those of injury and irritation of the
divided peduncles, along with those resulting from the removal of the organ. They are clonic
contractions of the muscles of the fore limb, neck, and back, passing into tonic contractions
when the animal attempts to move, and also weakness of the hind legs, so that all the normal
voluntary movements are interfered with, 7.¢., inco-ordinated, although these symptoms may
be explained by the injury to adjoining parts. There was no sensory disturbance or loss of the
muscular sense, although closing the eyes rendered standing impossible. As recovery takes
place, these symptoms disappear, and the animal enters on the second period, where the
symptoms depending on the actual loss of the organ are pronounced. The contracture and
pseudo-paralytic weakness disappear, while there are alterations in the tone of the individual
muscles, producing a sort of ‘‘cerebellar ataxy.” The dog could swim in quite a normal
manner, its power of equilibration was not interfered with, but acts requiring a greater develop-
ment of muscular energy could not be properly executed. This period lasted four to five months.
After this time its health gave way, there was otitis, conjunctivitis, articular and cutaneous
inflammations, while a peculiar form of marasmus set in, the animal dying after eight months. .
In fishes also, the removal of the cerebellum does not affect their power of locomotion
(Bandelot). ]

Duration of the Phenomena.—After superficial lesions, or after a deep incision,
the disturbances of co-ordination soon pass away (fourens). If the injury affects
the lowest third of the cerebellum, the motor disturbances remain permanently.
Symmetrical lesions do not disturb co-ordination (Schif’). After removing the
greater portion of the cerebellum in birds, Weir-Mitchell has observed that the
original disturbances gradually disappear; and after months only slight weakness
and a condition of rapid fatigue remain. .

After ablation of the cerebellum, secondary degeneration occurs in the part of the pons
around the pyramids, the lower olives, all the cerebellar peduncles and the direct cerebellar
tract, usually on the same side (Flechsig). It is found also in individual fibres in all the
cranial nerves and the anterior roots of the spinal nerves (Marchi).

In the dog, superficial injuries of the vermiform process, or of one-half of the organ, produce
merely temporary disturbances; while deep injuries to the vermiform process, or removal of one
hemisphere and a part of the vermiform process, cause permanent rigidity of the legs and shaking
of the head ; if the worm and both halves are destroyed, there follows permanent pronounced
disturbance of co-ordination (v. Mering). According to Baginsky, destruction of a large part
of the vermiform process alone causes in mammals permanent disturbance of co-ordination.
Ferrier found that a vertical section of the cerebellum in monkeys, produced only inconsiderable
disturbances of equilibrium ; after injury of the anterior part of the middle lobe, the animal
often tumbles forward; while, when the posterior part is injured, it falls backward. After
injury of the lateral lobe, the animal is drawn towards the affected side (Schiff, Vulpian,
Ferrier, Hitzig). If the middle commissure be injured, the animal rolls violently on its long
axis towards the injured side (Magendie). Paralysis never occurs after injuries of the cerebellum,
nor is there ever disturbance of sensation or of the sense of touch. Luciani found that, in
animals with the cerebellum extirpated, marasmus ultimately set in. In frogs, an important
organ concerned with motion lies at the junction of the oblongata with the cerebellum (Eckhard).
After it is removed the animal can no longer execute co-ordinated jumping movements, nor can
it crawl (Goltz),

[In man, the cerebellum is connected with the maintenance of the equilibrium. There may
be a lesion of the hemispheres without any marked symptoms; but if the middle lobe be injured
or pressed on by a tumour, there is usually a reeling or staggering gait, like that of a drunken
man. Ross points out that, if the tumour affect the upper part of this lobe, the tendency is to
fall backwards, and if in the lower part, to fall forwards or to revolve round a horizontal axis.
Vomiting is frequently persistent and well marked, while there may be nystagmus and tonic
retraction of the head. |

After injuries of the cerebellum, involuntary oscillations of the eyeballs or nystagmus, as
well as squinting (Magendie, Hertwig), have been observed; while Ferrier observed movements
of the eyeballs after electrical stimulation. According to Curschmann, Eckhard, and Schwann,
this occurs only when the medulla oblongata is involved (§ 379).

Effects of Electricity and Vertigo.—If an electrical current be passed through the head, by
placing the electrodes in the mastoid fossa. behind both ears, with the + pole behind the right
and the — pole behind the left ear, then on closing the current, there is severe vertigo, and the
head and body lean to the + pole, while the objects around seem to be displaced to the left.
If the eyes be closed, while the current is passing, the movements appear to be transferred to
the person himself, so that he has a feeling of rotation to the left (Purkinje). At the moment

726 PROTECTIVE AND NUTRITIVE APPARATUS OF THE BRAIN,

the head leans towards the anode, the eyes turn in that direction, and often exhibit nystagmus.
The electrical current probably stimulates the nerves of the ampullz, as we know that affections
of these bodies cause vertigo (§ 350). The cerebellum has no relation to the sexual activities,
as was maintained by Gall. The contractions of the uterus observed by Valentin, Budge, and
Spiegelberg, after stimulation of the cerebellum, are as yet unexplained. ; ;
Pathological. —Lesions of one hemisphere may give rise to no symptoms ; but if the middle
lobe is involved, there is inco-ordination of movement, especially a tendency to fall, unsteady
gait, and pronounced vertigo. Irritative lesions of the middle peduncle cause complete gyrating
movements of the body around its axis, together with rotation of the eyes and head (Nothnagel),

38], PROTECTIVE APPARATUS OF THE BRAIN.—The Membranes,—The dura mater
cerebralis is intimately united to the periosteum of the cavity of the skull, while the spinal
Jura mater forms around the spinal cord a freely suspended long sac, fixed only on its anterior
surface, It isa fibrous membrane, consisting of firm bundles of connective-tissue intermixed
with numerous elastic fibres, and
provided with flattened connective-
tissue comput and Waldeyer’s
plasma cells. The smooth, inner
. surface is covered with a layer of
endothelium. It is but slightly
supplied with blood-vessels, although
they are more numerous in the outer
layers; the pape are numerous,
while nerves whose terminations are
unknown give to the dura its ex-
quisite sensibility to painful opera-
tions on it. Pacinian corpuscles
have been found in the dura over
the temporal bone. The lymphatic
subdural space (Key and Retzius)
lies between the dura and the arach-

- noid, and between the pia and arach-
Fig. 509. noid is the subarachnoid space (fig.

aus : : , 509). hese two spaces do n
Vertical section of the cortex cerebri and its membranes cer lea cue : The delicate

x 24. co, cortex cerebri; p, intima pie dipping into the prachnoid. thin and partially per-
sulci ; a, arachnoid, connected with p by means of the gosated. poor in ea eulente: el
loose subarachnoid trabecule in the subarachnoid space, without ct is covered on both
sa; v, v, blood-vessels ; d, dura ; sd, subdural space. eager

surfaces with squamous endothelium,
Only on the spinal cord is it separated from the pia, so that between the two lies the lymphatic
subarachnoid space ; over the brain, the two membranes are for the most part united together,
except the parts bridging over the sulci between adjacent convolutions. The arachnoid passes
from convolution to convolution without dipping into the sulci, while the pia dips into each
suleus (fig. 509, a). The ventricles of the brain communicate freely with the lymphatic
subarachnoid space, but not with the subdural space. The pia consists of delicate bun les of
connective-tissue without any admixture of elastic fibres; it is richly supplied with blood-
vessels and lymphatics, and carries nerves which accompany the blood-vessels into the substance
of the brain. The py baNcs open into the subarachnoid space (§ 196).
(Subarachnoid Fluid, or cerebro-spinal fluid, lies in the subarachnoid space, which is
traversed by trabecule of connective-tissue. Within the brain are a series of. cavities called
ventricles, which communicate one with another in a definite way. The fourth ventricle is
lined by a layer of columnar epithelium, and covered in dorsally by a membrane and continua-
tion of the pia mater, from the middle of which there hangs into the roof of the fourth ventricle
two vascular processes composed of capillaries—the choroid plexuses of the fourth ventricle,
which are comparable to the larger plexuses of the lateral ventricles. In this membrane is the
foramen of Magendie and tivo other smaller foramina, whereby the fluid in the subarachnoid
space communicates with that in the fourth ventricle ; but the lymphatics of the nerve-sheaths
ean be injected from the subarachnoid space, so that there is direct continuity of the flaid in
the ventricles of the brain with that in the subarachnoid space, perivascular spaces of the
cerebral substance, and the perineural lymphatics of nerves. The average quantity is about 2
ounces, and if it be suddenly withdrawn, epilepsy or convulsions may be produced ; or, if it be
rapidly increased in amount, coma may be produced. The middle and posterior parts of the
brain and the medulla oblongata do not rest directly on bone, but are separated by a distinct
interval from their osseous case, an interval occupied by the cerebro-spinal fluid and trave $e
by trabecule, so that, as Hilton expresses it, this fluid forms’a perfect water-bed for those’ arts,
being sustained by the venous circulation and the elasticity of the dura. It has impe
mechanical functions, protecting delicate parts of the brain from injury; by distribut

PACCHIONIAN BODIES AND MOVEMENTS OF THE BRAIN. 727.

vibratory impulses it insulates the nerve-roots, and has important relations to the quantity of
blood in the brain and the cerebral circulation (Chemical Composition, § 198). ]

[Spina bifida.—Sometimes the lamine of the vertebre in the lumbar or other region of the
spinal column are imperfectly developed, in which case the membranes project through as
a tumour distended by cerebro-spinal fluid and covered by skin. The effects of rapid tapping
or de pert d the sac are readily studied in such cases. ]

The Pacchionian bodies, or granulations, are connective-tissue villi, which serve for the out-
flow of lymph from the subdural and subarachnoid spaces into the sinuses of the dura mater,
especially the longitudinal sinus. The subarachnoid space also communicates with the spaces in
the spongy bone of the skull, and with the veins of the skull and surface of the face (Kollmann).
The subdural space also communicates with the lymphatic spaces in the dura, while the
latter communicate directly with the veins of the dura. Both the subdural and subarachnoid
lymphatic spaces communicate with the lymphatics of the nasal mucous membrane. The space
outside the dura of the spinal cord is called the epidural space, and may be regarded as
lymphatic in its nature ; the pleural and peritoneal cavities may be filled from it; but it does
not communicate with the cavity of the skull. The plexuses of blood-vessels are surrounded
by undeveloped connective-tissue. The tele choroideze in the new-born are still covered with
ciliated epithelium.

Movements of the Brain.—The pulsations of the large basal cerebral vessels
communicate their pulsatile movements (§ 79, 6) to the brain—the respiratory
movements also affect it, so that the brain rises during expiration and sinks during
inspiration. Lastly, there are slight alternating vascular elevations and depressions,
occurring 2 to 6 times per minute, due to the periodic dilatation and contraction of
the blood-vessels (§ 371). Psychical excitement influences these, and they are most
regular during sleep. The movements are best seen especially where the membranes
of the brain offer little resistance, ¢.g., over the fontanelles in children, and where
the membranes have been exposed by trephining. The presence of the cerebro-
spinal fluid is most important for the occurrence of these movements, as it propa-
gates the pressure uniformly, so that every systolic and expiratory dilatation of the
blood-vessels is concentrated upon those parts of the cerebral membrane which do
not offer any resistance (Donders). When the fluid escapes, the movements may
almost disappear.

Mental excitement increases the pulsations of the brain. At the moment of awaking, the
amount of blood in the brain diminishes ; sensory stimuli applied during sleep, so that the
sleeper does not awake, increase the amount of blood. As the arteries within the rigid skull-
case change their volume with each pulse-beat, the veins (sinuses) exhibit at every beat a
pulsatile variation in volume, the opposite of that occurring in the arteries (4/osso).

The Cerebral Blood-Vessels.—-The blood-vessels of the pia, of course, are regulated by the
vaso-motor nerves (§ 356, A, 3), and their calibre may also be influenced by the stimulation of
more distant parts of the body (§ 347). Donders trephined the skull so as to make a round
hole, and filled it with a piece of glass, so that with a microscope he could observe changes in
the calibre of the blood-vessels. Paralysis of the vaso-motor nerves and narcotics dilate the
blood-vessels ; they become greatly contracted at death (§ 373, I.). The blood-vessels are
dilated during cerebral activity (§ 100, A), as well as during sleep. Increased pressure within
the skull causes great derangement of the cerebral activity—laboured respiration (§ 368, B),
unconsciousness even to coma, and paralytic phenomena—all of which may in part be referable
to disturbances of the circulation. If all the cranial arteries be ligatured suddenly, there is
immediate loss of consciousness, together with strong stimulation of the medulla oblongata and
its centres, and death takes place rapidly with convulsions (compare § 373).

By the free anastomosis which takes place at the base of the brain, forming the circle of
Willis (fig. 510), the individual parts of the brain are preserved from want of blood, when one
or other blood-vessels is compressed or ligatured. Wéthin the brain, the arteries are distributed
as “terminal ” arteries, z.¢c., the terminal branches of any one artery end in their own area, and
do not anastomose with those of adjoining areas (Cohnheim). On the other hand, the peripheral
arteries (arteries of the corpus callosum, Sylvian fissure, and deep cerebral) which run externally
on the brain, form free anastomoses (Tichomirow).

[The nutrient or ganglionic arteries for the central ganglia arise in groups from the circle
of Willis, or from the first two centimetres of its trunks. The antero-median group (1) supplies
the anterior part of the head of the caudate nucleus. The postero-median (2) enter the
posterior perforated space and supply the internal surface of the optic thalami and the walls of
the third ventricle. The antero-lateral groups (3, 3) from the middle cerebral enter the
anterior perforated space, supply the corpora striata, the anterior part of the optic thalamus,
and the internal capsule. These branches are apt to rupture. The postero-lateral (4, 4)

728 THE GANGLIONIC CEREBRAL ARTERIES,

upply a large part of the optic thalami (Charcot). A line drawn at a distance of two centi-
ie Satie te circle of NVillis, encloses the ganglionic area, The cerebral convolutions
are supplied by the large branches of the circle of Willis. The anterior cerebral curves round
the corpus callosum, and supplies the gyrus rectus and the supraorbital, the first and second
frontal convolutions, the upper part of the ascending frontal, and the inner surface of the
hemisphere as far as the quadrate lobule (fig. 510, I). The posterior cerebral goes to the
region of the occipital lobe and the inferior aspect of the temporal lobe; the middle cerebral
er Sylvian artery divides into four branches, which go to the posterior part of the frontal lobe,
ascending frontal, and to all the

\ parietal lobes, ¢.¢., chiefly to the
motor areas (III), the angular

CA gyrus, and to the first temporo-
cet sphenoidal lobule. The terminal

ry De branches of these ganglionic

arteries do not anastomose with
a the cortical system. Fig. 511
WS IE . shows the ganglionic arteries
i Ne piercing the basal ganglia. Ob-
Wt viously, when hemorrhage of
the lenticulo-striate artery or
‘‘artery of hemorrhage ” (4, 4)
occurs, it will compress the len-
ticular nucleus, or tear it up, and
may even injure the parts out-
side, such as the external cap-
sule, claustrum (T), and island
of Reil (R), or those inside, e.g.,
the internal capsule. ]
[Thus, the anterior cerebral
supplies the prefrontal area and ©

es eS: : wt a small part of the motor area,
= — that for the leg-centre in the
a paracentral lobule and upper end

of the ascending frontal (and
perhaps that for the trunk), The
posterior cerebral supplies the
Vv centre for vision, and that con-
nected with the course of the
posterior part of the optic ex-
pansion, and also the sensory
Fig. 510. part of the internal capsule. The

Arteries of the base of the brain, or circle of Willis. C, C, in- aOrogien ee fee sce
ternal carotids; CA, anterior cerebral; S,S, Sylvian arteries; art of the leg-centre aia the
V, V, vertebrals; B, basilar; CP, posterior cerebrals; 1, 2, one anolia Soin cents
3, 3, 4, 4, groups of nutrient arteries. The dotted line shows seed ecay vORY’ ’

aa “cnet pee and that for speech. ]
the limit of the ganglionic area. [The cerebral circulation has

many peculiarities, The curves on the arteries serve to modify the effect of the cardiac shock,
the circle of Willis permits within limits a free circulation ; but, in as far as the skull is largely
a ri d box, it was at one time taught that, as the brain substanee and its fluids were prac-
tically incompressible, it was impossible to alter the amount of blood in the brain, This is a
mistake. The amount of blood undergoes an alteration in this -way, that when more blood
es in, some cerebro-spinal fluid moves out, and vice versd, so that there is an intimate relation
tween these fluids. In the developing skull, the cerebro-spinal fluid ma accumulate in large
amount within the ventricles, and greatly distend both them and the yielding skull-case from
internal —- as in acute hydrocephalus, The peculiarities and independence of the cortical
and ganglionic arteries have already been referred to. Plugging by means of a clot, vegetation,
or wart, carried from the heart, is common in the left middle cerebral artery.—Why 1—When
the plug is washed away by the blood-stream, owing to the left carotid springing from the aorta
nearly in line with the blood-current, the plug readily passes into the carotid and so into the
left middle cerebral which is in line with the internal carotid. In such a case, the convolutions —
and supplied by it are suddenly deprived of blood with immediate and serious results.] —
[The venous eittniation is peculiar. The sinuses are really spaces between the layers of the
tough dura mater, and partly bounded by bone. The blood moves in the longitudinal sinus
from before backwards, but most of the cortical veins open into it in a forward direction, so
that their stream is opposed to that in the sinus. Thus, the blood which enters the brain

ascending arteries reaches the sinuses by ascending veins, the reverse of what obtains elsewh

2
(/
(

in
ce lll

a

f 5

Wee

))

——-
tie a ee a

7

ia

EFFECTS OF PRESSURE ON THE BRAIN. 729

in parts where ascending veins convey blood from descending arteries, whereby the hydrostatic
pressure and gravity aid the circulation, but here gravitation is opposed to the flow of blood in the
cerebral veins. This will help to explain the occurrence of thrombosis in these vessels. Some
of the veins on the surface communicate with intracranial veins, ¢.g., those of the nose, the
facial through the ophthalmic, mastoid veins, and veins of the diploce. Hence, morbid processes
affecting the scalp (erysipelas), ear (caries), or face (carbuncle) may readily affect intracranial
structures (Gowers). }

If a person who has been in bed fora long time, and whose blood is small in amount, be
suddenly raised into the erect position, cerebral anemia is not unfrequently produced, owing to
hydrostatic causes. At the same time, there may be loss of consciousness and impairment of
the senses. Liebermeister regards the thyroid gland as a collateral blood-reservoir which
empties its blood towards the head during such changes of the position of the body. Perhaps
this may explain the swelling of the thyroid as a compensatory act, when the heart beats
violently, and the brain is surcharged with blood (§§ 103, III., and 371). Very violent
muscular exertion, as well as marked activity of other organs, causes a very considerable fall of
the blood-pressure in the carotid.

_Pressure on the Brain.—The brain and the fluid surrounding it are constantly subjected to
a certain mean pressure, which must ultimately depend upon the blood-pressure within the
vascular system, The investigations of Naunyn and Schreiber on the cerebral pressure (or
cerebro-spinal pressure) showed that the pressure must be slightly less than the pressure
within the carotid, before the symptoms proper to pressure on the brain occur. These are,
sudden attacks of headache, with vertigo, or it may be loss of consciousness, vomiting, slowing
of the pulse, slow and shallow respiration, convulsions—while the pressure of the cerebro

ep enn F: ge p

\t
\
~

Fig. 511.

Transverse section of the cerebrum behind the optic chiasma. Arteries of the corpus striatum.
Ch, optic chiasma; B, section of optic tract ; L, lenticular nucleus; I, internal capsule ;
C, caudate nucleus ; E, external capsule; T, claustrum ; R, convolutions of the island of
Reil; V, V, section of the lateral ventricles; P, P, pillars of the fornix; O, grey substance
of the third ventricle. Vascular areas—I, anterior cerebral artery ; II, Sylvian artery ;
III, posterior cerebral artery ; 1, internal carotid ; 2, Sylvian, 3, anterior cerebral artery ;
4, 4, lenticulo-striate arteries ; 5, 5, lenticular arteries.

tte fluid is increased. The cause of these phenomena lies in the anemia of the brain. If
the pressure is moderate, the above-named symptoms may remain latent; nevertheless,
disturbances of the nutrition of the brain occur, with consecutive phenomena, such as
persistent slight headache, feeling of vertigo, muscular weakness, and disturbances of vision
(owing to neuro-retinitis with choked disc). Increase of the blood-pressure diminishes the
symptoms, while diminution of the blood-pressure causes more pronounced phenomena of
cerebro-spinal pressure. In the dog, pain begins with a pressure of 70 to 80 mm. Hg.
Consciousness is abolished when the pressure is higher, and at 80 to 100 mm. spasms take place.
A pressure of, 100 to 120 mm. causes slowing of the pulse, owing to stimulation of the vagus at
its origin ; the respirations are temporarily accelerated and then diminish. Long-continued
severe compression always, sooner or later, ends fatally. The blood-pressure at first is increased,
owing to reflex stimulation of the vaso-motor centre from the pressure stimulating the sensory
nerves ; ultimately, the blood-pressure falls, and the pulse becomes very slow. Irregular
variations in the blood-pressure point to a direct central stimulation of the vaso-motor centre

730 COMPARATIVE AND HISTORICAL.

by pressure. The application of continued slowly increasing pressure compresses the brain
(Adamkiewicz).

382. COMPARATIVE—HISTORICAL, —Comparative.—Nerves are absent in the protozoa.
Neuro-muscular cells occur in the cwlenterata, in the hydroida and meduse, and they are the
first indications of a nervous apparatus (§ 296}. The umbrella of the medusa is covered with
a plexus of nerve-fibrils, which at various parts along its margin is provided with small
cellular thickenings corresponding to ganglia, and from these, nerve-fibres proceed to the
sense organs. Many of the worms possess a nervous ring in the cephalic portion, and in those
provided with an intestine a single or double nervous cord, in the form of a ring, surrounds
the pharynx. Branches (often two) pass from this into the elongated body, and usually these
carry ganglia corresponding to each ring of the body of the animal. In the leech, only one
gangliated cord is present. In the echinodermata, a large nerve-ring surrounds the mouth ;
and from it large nerves proceed, corresponding to the chief trunks of the water-vascular
system. At the points where the nerves are given off, the nervous ring is provided with the
so-called ‘‘ambulacral brains.” The arthropoda are provided with a large cephalic ganglion
placed above the pharynx, from which nerves pass to the sense organs. Another ganglion lies _
on the under surface of the pharynx, and is connected with the former by commissures. The
pharynx is thus embraced by a gangliated ring, and from it proceeds the abdominal gangliated
double chain, along the ventral surface of the body, through the thorax and abdomen. Some-
times several ganglia unite to form a large compound ganglion, while, in other cases, each
segment of the body contains its own ganglia. In the mollusca, the cesophageal nervous ring
is present, although the ganglionic masses vary much in position within it. A number of
compound ganglia lie scattered in different parts of the body, and are united by nerves to the
former. They represent the sympathetic system. In the cephalopoda, the cesophageal ring
has almost no commissure, and a part of the ganglionic matter is enclosed in a cartilaginous
capsule, and is often spoken of asa ‘‘ brain.” Additional ganglia are found in the mantle,
heart, and stomach. In vertebrates, the nervous system invariably lies on the dorsal aspect
of the body. In the amphioxus, there is no separation into brain and spinal cord. (See
§$ 374 and 375.)

Historical.—Alkmiion (580 B.c.) placed the seat of consciousness in the brain; Galen
(131-203 A.p.) regarded it as the seat of the impulses for voluntary movements. Aristotle
(384 B.c.) ascribed the relatively largest brain to man; he stated that it was inexcitable to
stimuli (insensible). One of the functions he ascribed to the brain was to cool the heat -
ascending from the heart. Herophilus (300 B.c.) gave the name calamus scriptorius ; and he
regarded the 4th ventricle as the most important organ for the maintenance of life. Even in
Homer there are repeated references to the dangers of injuries of the neck, Aretaeus and
Cassius Felix (97 A.D.) were aware of the fact that lesion of one cerebral hemisphere caused
paralysis on the opposite side of the body. Galen was acquainted with the path in the spinal
cord connected with movement and sensation. Vesalius (1540) described the five ventricles of
the brain. R. Colombo (1559) observed the movements of the brain isochronous with the
action of the heart. A more careful description of these movements was given by Riolan
(1618), Coiter (1573) discovered that an animal can live after removal of its cerebrum. About
the middle of the 17th century, Wepfer discovered the hemorrhagic nature of apoplexy.
Schneider (1660) estimated the weight of the brain in different animals. Mistichelli (1709)
and Petit (1710) described the decussation of the fibres of the spinal cord below the pons.
Gall discovered the partial origin of the optic nerve from the anterior pair of the corpora
quadrigemina, and by dissecting the brain from below, he attempted to trace the course of the
nerve-fibres to the convolutions (1810). Rolando described more accurately the form of the
grey matter of the spinal cord. Carus (1814) discovered the central canal. The most
compendious work on the brain was written by Burdach (1819-1826). The more recent
observations are referred to in the text.

Physiology of the Sense Organs.

383. INTRODUCTORY OBSERVATIONS.—Requisite Conditions.—The
sense organs have the function of transferring to the sensorium impressions of the
various phenomena of the external world; they are, in fact, the intermediate
instruments of sensory perceptions. In order that this may occur, the following
conditions must be fulfilled :—(1) The sense organ, provided with its specific end-
organ, must be anatomically perfect, and capable of acting physiologically. (2)
A. “specific stimulus” must be present, which under normal conditions acts upon
the end-organ. (3) The sense organ must be connected with the cerebrum by
means of a nerve, and the conduction through this path must be uninterrupted.
(4) During the act of stimulation, the psychical activity (attention) must be
directed to the process, and then the sensation results, e.g., of light or sound,
through the sense organ. (5) Lastly, when, by a psychical act, the sensation is
referred to the external cause, then there is a conscious sensory perception. Often,
however, this relation is completed as an unconscious conclusion, as it is essentially
a deduction from previous experience.

Stimuli.—With regard to the stimuli which are applied to the sensory apparatus, we dis-
tinguish :—(1) Adequate or homologous stimuli, 7.¢., stimuli for whose action the sense organs
are specially adapted, such as the rods and cones of the retina for the vibrations of the ether.
Thus, each sense organ has a specific form of stimulus best adapted to act upon it. This is
what Johannes Miiller called the ‘‘law of specific energy.”” (2) There are many other forms
of stimuli (mechanical, thermal, chemical, electrical, internal somatic) which act upon the sense
organs, producing the flash of light beheld when the eye is struck ; singing in the ears’ when
there is congestion of the head. These heterologous stimuli act upon the nervous elements of
the sensory apparatus along their entire course, from the end-organ to the cortex cerebri. The
homologous stimuli, on the other hand, act only on the end-organ, 7.¢., light has no effect
whatever upon the trunk of the exposed optic nerve.

Strength and Liminal Intensity.—Homologous stimuli act upon the sensory
organs only within certain limits as to strength. Very feeble stimuli at first
produce no effect. That strength of stimulus which is just sufficient to cause the
first trace of a sensation is called by Fechner the “liminal intensity” of the
sensation. As the strength of the stimulus increases, so also do the sensations, but
the sensations increase equally when the strength of the stimulus increases in
relative proportions. Thus, we have the same sensation of equal increase of light
when, instead of 10 candles, 11, or instead of 100 candles, 110 are lighted—the
proportion of increase in both cases is equal to one-tenth. As the logarithm of the
numbers increases in an equal degree, when the numbers increase in the same relative
proportion, the law may be expressed thus :—‘‘ The sensations do not increase with
the absolute strength of the stimuli, but nearly as the logarithm of the strength of
the stimulus.” This is Fechner’s “psycho-physical law,” but its accuracy has
recently been challenged by E. Hering. [It holds good only with regard to stimuli

732 FECHNER’S LAW.

of medium strength.] If the specific stimulus be too intense, it gives rise to
peculiar painful sensations, e.g., a feeling of blindness or deafness, as the case may
be. The sense organs respond to adequate stimuli, but only within certain limits
of the stimulus, e.g., the ear responds only to vibrating bodies emitting a certain
range of vibrations per second ; the retina responds only to the vibrations of the
ether between red and violet, but not to the so-called heat vibrations or to the
chemically active vibrations.

[It was Weber who worked out the relation between the intensity of stimuli and the changes
in the quantity of the resulting sensations. He used the method of “least observable differ-
ences,” as applied to sensations of pressure and the measurements of lines by the eye. Hence,
it is called Weber's Law; but Fechner expanded it and assumed that all just observable differ-
ences are equally great, and so the law is sometimes called by his name. ]

[Fechner’s Law.—Expressed in another way, the result depends on (1) the strength of the
stimulus, and (2) the degree of excitability. Supposing the latter to be constant, while the

former is varied, it is found that if the stimulus be doubled, tripled, or quadrupled, the sensa-.

tion increases only as the logarithm of the stimulus. Suppose the stimulus to be increased 10,
100, or 1000 times, then the sensation increases only as 1, 2, or 3. Just as there is a lower
limit of excitation liminal intensity (or threshold), so there is an upper limit or maximum of
excitation or height of sensibility, when any further increase produces no appreciable increase
in the sensation. Thus, we do not notice any difference between the central and peripheral
portion of the sun’s disc, though the difference of light intensity is enormous (Sully). Between
these two is the range of sensibility (Wundt). There is always a constant ratio between the
strength of the stimulus and the intensity of the sensation. The stronger the stimulus already
applied, the stronger must be the increase of the stimulus in order to cause a perceptible increase
of the sensation (Weber’s Law). The necessary increment is proportional to the intensity of
the stimulus, and it varies for each sense organ. Ifa weight of 10 grammes be placed in the hand,
it is found that 3°3 grammes must be added or removed before a difference in the sensation is
perceptible ; if 100 grammes are held, 33°3 grammes must be added or removed to obtain a per-
ceptible difference in the sensation. The magnitude of the fraction indicating the increment of
stimulus necessary to obtain a perceptible difference of the sensation, is spoken of as the constant
proportion or the discriminative sensibility. In the above case it is 1:8. The following table
gives approximately the constant proportion for each sense :—

Tactile Sensation, : Siam ee Muscular Sensation, . 6: 100.785
Thermal __,, : me ae eer Visual oe ~» 1: 100.445.)
Auditory __,, - <b Bee

[The application of the law to temperature sensations is beset with great difficulties, while
for taste and smell we do not know that it is really applicable. From an experimental point
of view, it cannot be said to be proved, and its application is obviously somewhat restricted to
certain sensations, and to these, only within a certain range. It certainly does not hold good
for sensations of pressure, and muscular sense, near the lower limits for these senses. *SAt
best it is only an approximately correct statement of what holds true of the relative intensity
of certain sensations of light and hearing, and less exactly of pressure and the muscular sense,
when these sensations are of moderate strength ” (Ladd). ]

The term after-sensation is applied to the following phenomenon, viz., that, as
a rule, the sensation lasts longer than the stimulus producing it ; thus, there is an
after-sensation, after pressure is applied to the skin. Subjective sensations

occur when stimuli due to internal somatic causes excite the nervous apparatus of —

the sense organ. The highest degrees of these, depending mostly upon pathological
stimulation of the sensory cortical centres, are characterised as hallucinations,
e.g., When a delirious person imagines he sees figures or hears sounds which have no
objective reality. In Opposition to this condition, the term illusion is applied to
modifications by the sensorium of sensations actually caused by external objects,
é.g., when the rolling of a waggon is mistaken for thunder. ns

In a new-born child, the sense of touch is strongly developed, that of pain slightly, muscular
sensations are undoubtedly present, while smell and taste are frequently confounded. - Auditory
stimuli are heard from the second day onwards, the stimulus of light immediately after birth,
but a peripheral field of vision does not yet exist (Cwignet). Towards the fourth to fifth week,
the movements of convergence and accommodation are noticable, while after four months,

colours are distinguished. The various stimuli are not perceived simultaneously—a reflex
inhibitory centre is not yet developed (Genzmer). 208

ANATOMICO-HISTOLOGICAL OBSERVATIONS. 733

The Visual Apparatus—The Eye.
384. HISTOLOGICAL OBSERVATIONS.—In the following remarks it is

assumed that the student is familiar with the anatomical structure of the eye :—

The cornea, for the sake of simplicity, is regarded as uniformly spherical, although, properly
speaking, it differs slightly from this form. It is more like a vertical section of a somewhat
oblique ellipsoid, which we must suppose to be formed by rotating an ellipse around its long
axis (Briicke), Itis nearly of uniform thickness throughout, only in the infant it is slightly
thicker in the centre, and in the adult slightly thinner. The cornea consists of the following
layers :—

[1. Anterior stratified epithelium, 4, Posterior elastic lamina.
2. Anterior elastic lamina, 5. Single layer of epithelium. ]
3. Substantia propria,

1, The anterior epithelium, stratified and nucleated, consists of many layers of cells (fig, 514,
a), The deepest cells are more or less columnar, are arranged side by side, and are called
supporting cells, The cells of the middle layers are more arched, and dip with finger-shaped
processes into corresponding spaces between their neighbours, The most superficial cells are
flat, perfectly smooth, hard, keratin-containing squamous epithelium. 2, The epithelial layer
rests upon the anterior elastic membrane (Bowman’s elastic lamina), a structureless clear base-

Fig, 513.

Fig. 512.—Cornea of the frog treated with chloride of gold, showing the corneal corpuscles
stained, and a few nerve-fibrils. Fig. 513.—Cornea of the frog treated with silver nitrate ;
the ground substance is stained, while the spaces for the corneal corpuscles are left
unstained.

ment-like membrane (b), whose existence is denied by Briicke. 3. The substantia propria of
the cornea consists of (chondrin-yielding) fibres composed of delicate fibrils of connective-tissue.
The fibres are arranged in mat-like thin lamelle (2), more or less united together, and are
placed in layers over each other. Towards the anterior elastic lamina, the fibres bend round
and perforate the superficial lamelle, thus serving as supporting fibres. [These perforating
fibres are comparable to Sharpey’s fibres in bone.] Between the lamelle are a series of inter-
communicating spaces lined by endothelium. These spaces are really lymph-spaces, and they
communicate with the lymphatics of the conjunctiva, The fixed corneal corpuscles lie in these
spaces (c),.and are provided with numerous processes, which anastomose with the processes of
corpuscles lying between the lamell# above and below, and on either side of them. Kiihne
observed that stimulation of the corneal nerves was followed by contraction of these cells (§ 201,
7), while Kiihne and Waldeyer maintair that they are connected with the corneal nerve-fibrils.

[The corneal corpuscles are looked upon as branched connective-tissue corpuscles lying in
and not quite filling the branched spaces between the lamelle. The processes anastomose
freely with similar cells in the same plane, and to a less extent with the processes of cells in

734 THE NERVES OF THE CORNEA.

i iately and below them. In a section stained with gold chloride, they
rman yeni A wien in fig. 512. In a vertical section of the cornea, they appear
fusiform and parallel to the free surface of the cornea (fig. 514). If the — “at a fa Fem
yencilled with silver nitrate, the cement-substance between the lamelle is blackened, an =
ranched cell-spaces remain clear, as 1n “e 513. The one figure represents, as 1t were, the

itive e other the negative image. ;
as pal ye pass into ihe lymph-spaces or juice-canals. The ni Sid pes of a
leucocytes in inflammation is referred to in § 200. 4. The transparent, structure “mag port 09
elastic membrane (d), the membrane of Descemet or Demours, is in many animals ¥ ated,
and shows evidence of stratification, while towards the margin of the cornea there mr
occasionally slight conical elevations. This membrane is very tough and very pemiatar (0
great importance in inflammation). If it be removed, it rolls up towards the convex side. At
its ater, ake it becomes continuous with the fibro-elastic reticulated ligamentum pectinatum
iridis, whose trabeculw are covered by epithelium. 5. The posterior single layer of epithelium

ACG OF 2,
= S x.
Pex ROGUES

——-
_ ————__-

Fig. 514.

Antero-posterior section at the junction of the cornea with the sclerotic. a, anterior corneal
epithelium ; >, Bowman’s lamina; c, corneal corpuscles; 7, corneal lamelle (the whole
thickness lying between ) and d is the substantia propria cornee) ; d, Descemet’s mem-
brane ; ¢, its epithelium ; /, junction of cornea with the sclerotic ; g, limbus conjunctive ;
h, conjunctiva ; 7, canal of Schlemm ; k, Leber’s venous plexus (is regarded by Leber as
belonging to 7); m, m, meshes in the tissue of the lig. iridis pectinatum ; n, attachment
of the iris; 0, longitudinal, p, circular (divided transversely) bundles of fibres of the
sclerotic ; g, perichoroidal space ; s, meridional [radiating], ¢, equatorial (circular) bundles
of the ciliary muscle ; w, transverse section of a ciliary artery ; v, epithelium of the iris (a
continuation of that on the posterior surface of the cornea) ; w, substance of the iris; 2,
pigment of the iris ; z, a ciliary process, ae

consists of flat, delicate, nucleated cells (e), which are continued from the margin of the cornea

on to the anterior surface of the iris(v). Fine juice-canals exist in the spaces between the indi-
vidual cells (v. Recklinghausen). These spaces communicate with a system of fine tubes under

THE NERVES OF THE CORNEA. | 735

the epithelium, perforate Descemet’s membrane, and thus communicate with the corneal
spaces,

Pioeavean's tubes are artificial productions, formed by forcing air or a coloured fluid between
the lamellz, when it passes between the bundles of fibrils, forming a series of tubes with dilata-
tions on them and running at right angles to one another between the lamelle. ]

The nerves of the cornea, which are derived from the long and short ciliary nerves (§ 347),
are partly sensory in function. They enter the cornea at its margin as medullated fibres, but
the myelin soon disappears, while the axial cylinders split up into tibrils. [The axial cylinders
branch and form a plexus between the lamelle, especially near the anterior surface, the funda-
mental or ground plexus (fig. 515, n). There are triangular nuclei at the nodal points, but
they probably belong to the sheath of flattened cells which cover the larger branches. There
is a finer and denser plexus of fibrils immediately under the anterior epithelium, sub-epithelial
plexus, which is derived from the former, the fibrils arising in pencils or groups (fig. 516). Some
fibrils perforate the anterior elastic lamina, rami perforantes, and pass between the anterior
epithelial cells to form the intra-epithelial network (fig. 515, b, »). Some observers suppose
that they terminate in free, : j
pointed, or bulbous ends. _ ee el ee en
There is also a fine plexus of SQ = Rane aay Oe ==
fibrils in the posterior layers
of the cornea, near Descemet’s
membrane. It gives off nu-
merous fine fibrils, which come
into intimate, if not direct,
anatomical relation with the
corneal corpuscles. The trophic
fibres of the cornea (§ 347) are,
perhaps, those deeper branches
which are connected with the
corneal corpuscles. ]

[Method.—These fibrils are
best revealed by staining a
cornea with chloride of gold, _ ;
which tingesthemofapurplish = * 2
line after exposure to light Fig. 515.

(Cohnheinr). ] _ Vertical section of the cornea stained with gold chloride. x,

Blood-vessels occur only in perve-fibrils ; a, perforating branch; 7, nucleus ; p, b, inter-

the outer margin of the cornea epithelial termination of fibrils ; s, anterior elastic lamina.
(fig. 518, v), and extend 2 mm.

over the cornea above, 1°5 mm. below, and 1 mm. laterally—the most external capillaries form
arched loops, and thus turn on themselves. The cornea is nourished from the blood-vessels in
its margin. Opacities of the cornea give rise to many forms of visual defects.

The sclerotic is a thick fibrous membrane, composed of, p, circular (equatorial) and, 0, longi-
tudinal (meridional) bundles of connective-tissue woven together (fig. 514). The spaces between
the bundles contain colourless and pigmented connective-tissue corpuscles and also leucocytes.
It is thickest posteriorly, thinner at the equator, while in front of this it again becomes thicker,
owing to the insertion of the tendons of the straight muscles of the eyeball. It contains few
blood-vessels, which form a wide-meshed capillary plexus, immediately under its deep surface.
Other vessels form an arterial ring around the entrance of the optic nerve. It rarely is quite
spherical ; it rather resembles an ellipsoid, which we might imagine to be formed by the rota-
tion of an ellipse around its short axis (short eyes) or around its long axis (long eyes). Above
and below, the sclerotic overlaps like a fold the clear margin of the cornea; hence, when the
cornea is viewed from before, it appears transversely elliptical, when seen from behind, it
appears circular. Following the margin of the cornea, but lying still within the substance of
the sclerotic, is the circular canal of Schlemm (7), which communicates with other anastomosing
veins, the venous plexus of Leber (). Schwalbe and Waldeyer regard Schlemm’s canal as a
lymphatic. Posteriorly, the sclerotic becomes continuous with the fibrous covering of the optic

nerve derived from the dura mater. The sclerotic is provided with nerves, which are said to

terminate in the cells of the scleral substance (Helfreich).

The tunica uvea, or the uveal tract, is composed of the choroid, the ciliary part of the choroid,
and the iris.

The choroid is composed of the following layers (fig. 517) :—(1) Most internally is the
transparent limiting membrane, 0°7 uw in thickness; but it is slightly thicker anteriorly. (2)
The very vascular capillary network of the ¢horio-capillaris, or membrane of Ruysch, embedded
in a homogeneous layer. Then follows—(3) a layer of a thick elastic network, covered on
both surfaces by endothelium (Sattler). (4) The choroid proper consists of a layer with
pigmented connective-tissue corpuscles, together with a thick elastic network, containing
the numerous venous vessels as well as the arteries. The pigmented layers are known as the

736 THE IRIS.

supra-choroidea, or lamina fusca, which surrounds the large lymphatic space lined with
endothelium and called the perichoroidal space, g. In new-born infants, which according to
Aristotle have the iris dark blue, the uveal tissue is devoid of pigment ; in brunettes it is
developed later, and in blondes not at all.

In the ciliary part of the choroid, the pigmented connective-tissue corpuscles are not so
numerous, The ciliary muscle (tensor choroidez, or muscle of accommodation) is placed in
this region. It arises (s), by means of a branched, reticulated, connective-tissue origin, from
the inner side of the junction of the cornea and sclerotic, near the canal of Schlemm, and
passes backwards to be inserted into the choroid. This constitutes the radiating fibres.
Other fibres lying internal to these are arranged circularly, ¢, in bundles in the ciliary margin.
These circular fibres are sometimes called Heinrich Miiller’s muscle. The muscle consists of
smooth muscular fibres, and is supplied by the oculomotorius (§ 345, 3).

The iris consists of the following parts from before backwards :—a layer of epithelial cells (v)
continuous with those covering the posterior surface of the cornea, a layer of reticulated

Fig. 516. Fig. 517.

Fig. 516. —Nerve-plexus in the cornea after gold chloride. 2, nerve; a, fibrils. Fig. 517.—Ver-
tical section of the choroid and a part of the sclerotic. (1) sclerotic ; (2) lamina supra-
choroidea ; (3) layer of large vessels ; (4) limiting layer ; (5) chorio-capillaris ; (6) hyaline
pape ; (7) pigment epithelium ; (g) large blood-vessels ; (p) pigment-cells; (¢c) sections

ries,

connective-tissue, the layer of blood-vessels, and lastly a posterior limiting membrane, which
contains the pigmentary epithelium (x) (Michel). In brunettes, the texture of the iris contains
pigmented connective-tissue corpuscles. The iris in some animals is described as containing
two muscles composed of smooth muscular fibres—one set constituting the sphincter pupille —
(circular—fig. 533), which surrounds the pupil, and lies nearer the posterior than the anterior
eaters of the iris (§ 392), Its nerve of supply is derived from the oculomotorius (§ 345, 2).
ae other fibres constitute the dilator pupille (radiating), which consists of a thinner layer of
res arranged in a radiate-manner, Some of the fibres reach to the margin of the pu il
while others bend into the sphincter. [The existence of a dilator pupille in man is denied
(§ 392).] At the outer margin of the iris, the radial bundles are arranged in anastomosing
ae, and form a circular muscular layer (Merkel). The chief nerve of supply for the dilator
seg is the sympathetic (§ 847, 3). Ganglia occur in the ciliary nerves in the choroid, [and
: a ee found also in the iris]. Gerlach has recently applied the term ligamentum annuare
: wf i ber eh er ee eae es which surrounds the iris, and at the same time forms
juni not the cornea saa? pe rit Age iris, ciliary muscle, sinus venosus iridis, and the line of
e choroidal vessels are of great importance in connection with the nutrition of the.

According he Leber, they are arranged as follows :—The arteries are—l, The short Bere : 4
ciliary, which are about twenty in number and perforate the sclerotic near the optic nerve

4

BLOOD-VESSELS OF THE EYEBALL, 737

(fig. 518, a, a). They terminate in the vascular network of the chorio-capillaris (m), which
reaches as far-as the ora serrata. 2, The long posterior ciliary ; one of these lies on the nasal
and the other on the temporal side, and they run (5) to the ciliary part of the choroid, where

they divide dichotomously, and penetrate
into the iris, where they help to form the
circulus arteriosus iridis major (p). 3. The
anterior ciliary (c), which arise from the
muscular branches, perforate the sclerotic
anteriorly, and give branches to the ciliary
part of the choroid and to the iris. About
twelve branches run backwards (0) from
them to the chorio-capillaris.

Veins,—-1. The anterior ciliary veins .(c)
receive the blood from the anterior part of |
the uvea and carry it outwards. These
branches areconnected with Schlemm’scanal
and Leber’s venous plexus, They do not
receive any blood from the iris.. 2. The
venous plexus of the ciliary processes (7)
receives the blood from the iris (qg), and
passes backwards to the choroidal veins.
3. The large vasa vorticosa Stenonis (i)
perforate the sclerotic behind the equator
of the bulb.

The inner margin of the iris rests upon
the anterior surface of the lens ; the poste-
rior chamber is small in adults, and in the
new-born child it may be said scarcely to
exist—it is so small, When.Berlin blue is
injected into the anterior chamber of the

-eye, it generally passes into the anterior

ciliary veins (Schwalbe), Even in living
animals, carmin also behaves in a similar
manner (Heisrath) ; hence, these observers
conclude that there is a direct communica-
tion between the veins and the aqueous
chamber, as these substances do not diffuse
through membranes.

layer of hexagonal cells (0'0135 to 0°02
mm. in breadth) filled with crystalline pig-
ment. This layer really belongs to the
retina. It consists of a single layer of cells
as far as the ora serrata—it is continued on
to the ciliary processes and the posterior
surface of the iris, where it forms several
layers (fig. 514, 2). In albinos it is devoid
of pigment ; on the other hand, the upper-
most cells, which lie on the ridges of the
ciliary processes, are always devoid of pig-
ment. [The processes of these cells vary in
length with the nature and kind of light
acting on the retina (§ 398). ]

The retina externally is in contact with
the layer of hexagonal pigment-cells (P%),
which in its development and functions
really belongs to the retina. The cells are
not flat, but they send pigmented processes
into the space between the ends of the rods,

0

= U

wJuJe]mTu Tux

Fig. 518.
Internal to the choroid, lies the single Diagram of the blood-vessels of. the eye (horizontal

view, veins black, arteries light, with a double
contour). a, a, short posterior ciliary ; 6, long
posterior ciliary ; ¢, c’, anterior ciliary artery and
vein ; d, d’, artery and vein of the conjunctiva ;
é, e’, central artery and vein of retina ; 7, blood-
vessels of the inner, and g, of the outer optic
sheath ; h, vorticose vein ; 7, posterior short cili-
ary vein confined to the sclerotic ; %, branch of
the posterior short ciliary artery to the optic
nerve ; 7, anastomosis of the choroidal vessels
with those of the optic ; m, chorio-capillaris ; ,
episcleral branches; 0, recurrent choroidal artery ;°
p, great circular artery of iris (transverse section);
q; blood-vessels of the iris; 7, ciliary process ; s,
branch of a vorticose vein from the ciliary muscle ;
t, branch of the anterior ciliary vein to the ciliary
muscle ; uw, circular vein ; v, marginal loops of
vessels on the cornea ; w, anterior artery and vein
of the conjunctiva.

In some animals (rabbit) the cells contain fatty

_ granules and other substances. The cells are larger and darker at the orra serrata (Kiihne).

The retina is composed of the following layers, proceeding from without inwards :—

[1. Layerof pigment-cells.

2. Rods and cones.

3. Haternal limiting membrane.
4. Outer nuclear layer.

-

5. Outer molecular (granular or in-

ternuclear) layer.

6. Inner nuclear layer.
7. Inner molecular (granular) layer.
8. Layer of nerve-cells (ganglionic)
layer.
9. Layer of nerve-fibres.
10. Internal limiting membrane.]

3A

738 THE RETINA.

1. The hexagonal pigment-cells already described. 2. The layer of rods and cones (St) or .
neuro-epithelium of Schwalbe [bacillary layer, or the visual cells, or visual epithelium of Kiithne} i
(fig. 520). These lie externally next the choroid, but they are absent at the entrance of the |
optic nerve. Then follows the external limiting membrane (Le), which is perforated by the
bases of the rods and cones. 3. The external nuclear layer (du. K) ; this and all the succeed-
ing layer’ are called ‘‘ brain layers” by Schwalbe. 4. The external granular (édw.gr), or inter-
nuclear layer, which is perforated by the fibres which proceed inwards from the nuclei of 3 to
reach 5, the nuclei of the internal nuclear layer (inX). The nuclei of this layer, which are
connected by fibres with the rods and cones, are marked by transverse lines in the macula lutea
(Krause, Denissenko). 6. The finely granular interna
granular layer (in.gr), through which the fibres proceeding
from the inner nuclear layer cannot be traced. It would
seem as if these fibres break up into the finest fibrils, into
which also the branched processes of the ganglionic cells

aie) =
= 5

if
BAe ,
V2 rr
:
}
4, 4
eae
§
Ad)
te ppeny

Fig. 520.

Fig. 519.—Vertical section of human retina. a, rods and cones ; 5, ext., and j, int. limit.
memb. ; c, ext., and f, int. nucl. layers ; ¢, ext., and g, int. gran. layers ; h, blood-vessel
and nerve-cells ; i, nerve-fibres. ds 520.—Layers of the retina. Pi, hexagonal pigment-
cells ; St, rods and cones ; Le, ext. imiting membrane ; dw.K, ext. nuclear layer ; dw.
ext. granular layer ; inX, int. nuclear ; in.gr, int. granular ; @gl, ganglionic apne eat if
0, fibres of optic nerve ; Zi, int. limit. membrane ; Rk, fibres of Miiller; K, nuclei; Sy
spaces for the nervous-elements. are Hh

of 7, the ganglionic layer, extend. According to v. Vintschgau, the proce .
glionic cells are connected with the fibres. 8. ‘The next, or aeeais eee pearin of ee a
of the optic nerve (0), and most internally is the internal limiting membrane (Zi). Accord-
ing to W. Krause, there are 400,000 broad, and as many narrow, optic fibres, so that for every
fibre there are 7 cones, about 100 rods, and 7 pigment-cells. The optic fibres are absent from
the macula lutea, where, however, there are numerous ganglionic cells. Between the two
homogeneous limiting membranes (Le aud Li) lies the connective-tissue substance of the ¥
retina. It contains the perforating fibres, or Miiller’s fibres, which run in a radiate manner
between the two membranes, and hold the various layers of the retina together. They beg

by a wing-shaped expansion at the internal limiting membrane (2), and in their course out-
wards contain nuclei (k). They are absent at the yellow spot. The supporting tissue forms a

ae

.
:

THE RETINA. — 730

network in all the layers, holes being left for the nervous portions (Sg). The inner segments
‘of the rods and cones are also surrounded by a sustentacular substance. As the retina passes
forward to the ora serrata, it becomes thinner and thinner, gradually becoming richer in con-
nective-tissue elements and poorer in nerve elements, until, in the ciliary part, only the cylin-
drical cells remain (fig. 519).

[Macula Lutea and Fovea Centralis.—There are no rods in the fovea, while the cones are
longer and narrower than in the other parts of the retina (fig. 521). The other layers also are
thinner, especially at the. macula lutea, but they become thicker towards the margins of the
fovea, where the ganglionic layer consists of several rows of bipolar cells. The yellow tint is
due to pigment lying between the layers composing the yellow spot. ]

The blood-vessels of the retina lie in the inner layers near the inner granular layer. Only
near the entrance of the optic nerve are they connected by fine branches with the choroidal
vessels ; they are surrounded by perivascular lymph-spaces. The greatest number of capillaries
runs in the layers external to the inner.granular layer (Hesse). The fovea centralis is devoid
of blood-vessels (Wettleship, Becker). Except in mammals, the eel (Denissenko), and some
tortoises (H. Miiller), the retina receives no blood-vessels. Destruction of the retina is followed
by blindness.

[Retinal Epithelium.—The single layer of pigmentary cells containing granules of melanin
sends processes downwards, like the hairs of a brush, between the rods and cones (§ 398).
Kiihne has shown that the nature and amount of light influence the condition of these processes

}

Bi/\{A
\
] Hi HU /

ji) CY A
Ca wi | i) i) iy { i till \ i 3) } |} h | Lhe : |

Fig. 521.

Section of the fovea centralis. a, cones; 6 and g, int. and ext. limit. memb. ; c, ext., and e,
nuclear layer ; d, fibres ; 7, nerve-cells.

(fig. 563). The protoplasm of these cells in a frog kept for several hours in the dark, is
retracted, and the pigment-granules lie chiefly in the body of the cell and in the processes near
the cell. In a frog kept in bright daylight, the processes loaded with pigment penetrate down-
wards between the rods and cones as far as the external limiting membrane. ]

Each rod and cone consists of an outer and an inner segment. During life, the outer
segment contains a reddish pigment or the visual purple (Boll). -

Visual purple [or rhodopsin] may be preserved by keeping the eye in darkness; but it is
soon bleached by daylight, while it is again restored when the eye is placed in darkness. It
can be extracted from the retina by means of a 2°5 per cent. solution of the bile acids, especially
from eyes that have been kept in 10 per cent. solution of common salt (Ayres). The rods are
0:04 to 0:06 mm. high and 0°0016 to 0°0018 mm. broad, and exhibit longitudinal striation,
produced by the presence of fine grooves ; a fine fibril runs in their interior (Ritter), The
external segment occasionally cleaves transversely into a number of fine transparent discs. [It
is a very resistant structure, and in this respect resembles neuro-keratin.] Krause found an
ellipsoidal body, the “rod ellipsoid,” at the junction of the inner and outer segments of the
rods. The cones are devoid of visual purple, but their outer segment is striated longitudinally,
and it also readily breaks across into thin discs. Only cones are present in the macula lutea.
In the neighbourhood of the vellow spot, each cone is surrounded by a ring of rods. The cones
become less numerous towards the periphery of the retina. In nocturnal animals, such as the
owl and bat, there are either no cones or imperfect ones. The retine of birds contain many
cones, that of the tortoise only cones. The rods and cones rest on the sieve-like perforated
external limiting membrane (Le). Both send processes through the membrane, the cones to
the larger and higher-placed nuclei, the rods to the nuclei, with transverse markings in the
external nuclear ah [The cones are particularly large in some fishes, ¢.g., the cod, while

740 STRUCTURE OF THE LENS.

the skate has no cones, but only rods, The same is the case in the shark and sturgeon,

nd mole. :

elastin es Regeneration of Rhodopsin,—Keep a rabbit in the dark for some time,
kill it, remove its eyeball, and examine its retina by the aid of monochromatic (sodium) light,
The retina will be purple-red in colour, all except the macula lutea and a small part at the ora
serrata. The pigment is confined to the outer segments of the rods, It is absent in pigeons,
hens, and one bat, although the last-has only rods. It is found both in nocturnal and diurnal
animals, Its colour is quickly bleached by light, and it fades rapidly at a temperature of 50
to 76° C., while trypsin, alum, and ammonia do not affect, it, It is restored in the retina by
the action of the retinal epithelium, If the retinal epithelium or choroid be lifted off from an
excised eye exposed to light, the pope is destroyed ; but if the eye be placed in darkness and
the retinal epithelium replaced, the colour is restored. ] ; Ek

Chemistry of the retina. —The reaction of the retina, when quite fresh, is acid, and becomes
alkaline in darkness. The rods and cones contain albumin, neuro-keratin, nuclein, and in the
cones are the pigmented oil globules, the so-called “ chromophanes,” The other layers contain
the constituents of the grey matter of the brain. ;

[Cones. —There is no colouring matter in the outer segment of the cones, but in fishes, co
tiles, and birds the inner segment contains a globular-coloured body often red and yellow, the
pigment being held in solution by a fatty body. Kiihne has separated a green (chlorophane),
a yellow (xanthophane), and a red (rhodophane) pigment. They all give a blue with iodine,
and are bleached by light (Schwalbe). ]

The crystalline lens is enclosed in a transparent capsule, thicker anteriorly than posteriorly,
and it is covered on the inner surface of the anterior wall by a layer of low epithelium, Towards
the margin of the lens, these cells elongate into nucleated fibres, which all bend round the

margin of the lens, and on both sides of the lens abut with

their ends against each of the triradiate figures. The lens

fibres contain globulin enclosed in a kind of membrane,

Owing to mutual pressure, they are hexagonal when seen in
transverse section (fig. 522, 2), while in many animals, especi-
ally fishes, their margins are serrated [the teeth dovetail
into each other]. For the sake of simplicity, we may regard
the lens as a biconvex body with spherical surfaces, the -
posterior surface being more curved, As a matter of fact,
the anterior part is part of an ellipsoid formed by rotation
on its short axis. The posterior surface resembles the section
of a paraboloid, z.e., we might regard it as formed by the
rotation of a parabola on its axis (Briicke). The outer layers
of the lens have less refractive power than the more internal
layers. The central part of the lens or nucleus is, at the
same time, firmer, and more convex than the entire lens.
The margin of the lens is always separated from the ciliary
processes by an intermediate space,

(Chemistry.—The lens contains about two-thirds of its

_———
SS

weight of water, while its chief solid is a gl called by
Berzelius crystallin (24°6 per cent.), with a little serum-
Fig. 522. albumin, salts, cholesterin, and fats. ]

itcue chase ot [Cataract.—Sometimes the lens becomes more or less
1, Fibres of the eet , Prenih a opaque, the opacity beginning either in the middle or outer
sections of the lens fibres. parts of the lens. This is generally due to fatty degenera-
tion of the fibres, cholesterin being deposited. An opaque, cataractous condition of the lens
may be produced in frogs, by injecting a solution of some salts or sugar into the lymph-sacs ;
the result is that these salts absorb the water from the lens, and thus make it opaque. The
cataract of diabetes is probably produced from the presence of grape-sugar in the blood. ]

The zonule of Zinn, at the ora serrata, is applied as a folded mam Vrene to the ciliary part of
the uvea, so that the ciliary aksaienai are pressed into its folds, and are united to it, It passes
to the margins of the lens, where it is inserted by a series of folds into the anterior part of the
capsule of the lens. Behind the zonule of Zinn, and reaching as far as the vitreous humour, is
the canal of Petit. The zonule isa fibrous perforated membrane. According to Merkel, the
canal of Petit is enclosed by very fine fibres, so that it is really not a canal but a complex com-
municating system of spaces (Gerlach). Nevertheless, the zonule represents a stretched mem-
pipet oe the lens in position, and may therefore be regarded as the suspensory ligament
of the lens,

Opacity or cloudiness of the lens (grey cataract) hinders the passage of light into the eye.
Aphakia, or the absence of the lens (as after operations. for maitecty may be remedied Secs
— - strong convex spectacles, Of course, such an eye does not possess the power of accom-
modation. win TH

The vitreous humour, as far as the ora serrata, is bounded by the internal limiting membrane

THE VITREOUS HUMOUR. ~ 741

of the retina (Henle, Iwanof’). From here forwards lying between both, are the meridional
fibres of the zonule, which are united with the surface of the vitreous and the ciliary processes.
A part of the fibrous layer bends into the saucer-shaped depression, and bounds it. A canal,
2mm. in diameter, runs from the optic papilla to the posterior surface of the capsule of the
lens ; it is called the hyaloid canal, and was formerly traversed by blood-vessels. The peri-
pheral part of the vitreous humour is laminated like an onion, the middle is homogeneous ; in
the former, especially in the foetus, are round fusiform or branched cells of the mucous tissue
of the vitreous, while in the centre there are disintegrated remains of these cells (Jwanoff). The
vitreous humour contains a very small percentage of solids, 1°5 per cent. of mucin, [and,
according to Picard, there is 0°5 per cent. of urea, and about ‘75 of sodic chloride].
[Structure.—The vitreous humour consists essentially of mucous tissue, in whose meshes lies
a very watery fluid, containing the organic and inorganic bodies in solution. According to

ACEY
al
yey

3 SY

—
i)

==

ZY eoeeente
ff ; —
Os = a
sports
ipl
4
} WF il
eT BY |
ih |
Ui i /
WA ta
Yi

Fig. 523.

Horizontal section of the entrance of the optic nerve and the coats of the eye. a, inner, 8,
outer layers of the retina ; ¢, choroid ; d, sclerotic ; ¢, physiological cup ; 7, central artery
of retina in axial canal; g, its point of bifurcation ; A, lamina cribrosa ; /, outer (dural)
sheath ; m, outer (subdural) space ; ”, inner (subarachnoid) space; 7, middle (arachnoid)
sheath ; p, inner (pial) sheath ; 7, bundles of nerve-fibres ; %, longitudinal septa of con-
nective-tissue.

Younan, the vitreous contains two types of cells—(1) amoeboid cells of various shapes and
sizes. They lie on the. inner surface of the lining hyaloid membrane and the other mem-
branes in the cortex of the vitreous ; (2) large branching multipolar cells. ‘The vitreous is
_ permeated by a large number of transparent, clear, homogeneous hyaloid membranes, which

are so disposed as to give rise to a concentric lamination. The canal of Stilling represents in
the adult the situation of the hyaloid artery of the foetus. It can readily be injected by a
coloured fluid. ] eat

The lymphatics of the eye consist of an anterior and a posterior set. The anterior consist of
the anterior and posterior chambers of the eye (aqueous), which communicate with the lym-
phatics of the iris, ciliary processes, cornea, and conjunctiva. The posterior consist of the
pepinoroida space between the sclerotic and the choroid (Schwalbe). This space is connected
y means of the perivascular lymphatics around the trunks of the vasa vorticosa, with the large
lymph-space of Tenon, which lies between the sclerotic and Tenon’s capsule. Posteriorly, this
is continued into a lymph-channel, which invests the surface of the optic nerve ; while
anteriorly it communicates directly with the sub-conjunctival lymph-spaces of the eyeball.
The optic nerve has three sheaths—(1) the dural ; (2) the arachnoid ; and (3) the pial sheath,
derived from the corresponding membranes of the brain. Two lymph-spaces lie between these
three sheaths—the subdural space between 1 and 2, and the subarachnoid space between 2 -
and 8 (fig. 509). Both spaces are lined by endothelium ; and the fine trabecule passing from

/

742 INTRAOCULAR PRESSURE.

one wall to the other are similarly covered. According to Axel Key and Retzius, these lymph-
spaces communicate anteriorly with the perichoroidal space. natal

The aqueous humour closely resembles the cerebro-spinal fluid, and contains albumin and
sugar ; the former is increased, and the latter disappears after death. The same occurs in the
vitreous. The albumin increases when the difference between the blood-pressure and the intra-
ocular pressure rises. Such variations of pressure, and also intense stimuli applied to the
eye, cause the production of fibrin in the anterior chamber (Jesner and Griinhagen).

Intraocular ure.—The cavity of the bulb is practically filled with watery fluids, which,
during life, are constantly subjected to a certain pressure, the ‘intraocular pressure.” Ulti-
mately, this depends upon the blood-pressure within the arteries of the retina and uvea, and
must rise and fall with it. The pressure is determined by pressing upon the eyeball, and
ascertaining whether it is tense, or soft and compressible. Just as in the case of the arterial
pressure, the intraocular pressure is influenced by many circumstances ; it is increased at every
pulse-beat and at every expiration, while it is decreased during inspiration. The elastic tension
of the sclerotic and cornea regulates the increase of the arterial pressure by acting like the air-
chamber in a fire-engine ; thus, when more arterial blood is pumped into the eyeball, more
venous blood is also expelled. The constancy of the intraocular pressure is also influenced by
the fact that, just as the aqueous humour is removed, it is secreted, or rather formed, as rapidly
as it is absorbed (§ 392). [Fick has invented an instrument for the direct measurement of the
intraocular pressure, a small plate of known size is pressed against the eyeball, and the pressure
exerted is registered by means of a spring and index. ]

The secretion of the aqueous humour occurs pretty rapidly, as may be surmised from the
fact, that hemoglobin is found in the aqueous humour half an hour after dissolved blood (lamb’s)
is injected into the blood-vessels of a dog. It is rapidly reformed, after evacuation, through a
wound in the cornea. According to Knies, the watery fluid within the eyeball is secreted,
especially from the chorio-capillaris, and reaches the suprachoroidal space, in the lymph-sheaths
of the optic nerve, and partly through the network of the sclerotic. It saturates the retina
vitreous, lens, and for the most part passes through the zonula ciliaris into the posterior
chamber, and through the pupil into the anterior chamber. The movements of the fluid with-
in the eyeball have been recently studied by Ehrlich, who used fluorescein, an indifferent sub-
stance, which, on being introduced into the body, passes into the fluids of the eyeball, and in a
very dilute solution may be recognised by its green fluorescence in reflected light. From obser-
vations on the entrance of this substance into the eye, Schéler and Uhthoff regard the posterior
surface of the iris and the ciliary body as the secretory organs for the aqueous humour. It
passes through the pupil into the anterior chamber}; some passes into the lens, and along the
canal of Petit into the vitreous humour (Pfliiger). Section of the cervical sympathetic, and still
more of the trigeminus, accelerates the secretion of the aqueous, but its amount is diminished.
If the substance is dropped into the conjunctival sac, it percolates towards the centre of the
cornea, and through the latter into the anterior chamber (Pfliiger).

A current passes forwards from the vitreous humour around the lens, and there is an outflow
ce the central artery of the retina backwards through the optic nerve to the cavity of the
ole ih ae The current in the spaces between the sheaths flows from the brain to the eye

The outflow of the aqueous humour, according to Leber and Heisrath, takes place chiefly
between the meshes of the ligamentum pectinatum iridis (fig. 514, m m) and the canal of
Schlemm (7, &), into the anterior circular veins (p. 737). A small part of the aqueous humour
diffuses into the posterior Jayers of the cornea, to nourish it (Leber). None of the water is
conducted from the eyeball by any special efferent lymphatics (Leber). Under normal cireum-
stances, the pressure is nearly the same in the vitreous and aqueous chambers, but atro
seems to diminish the pressure in the former and to increase it in the latter whilst Colekae
bean has an opposite action (Ad. Weber). Arrest of the outflow of the venous blood often
increases the pressure in the vitreous, and diminishes that in the aqueous chamber. Compres-
sion of the bulb from without causes more fluid to pass out of the eye temporarily than enters —
it. The diminution of the intraocular pressure is well-marked after section of the trigeminus,
while it rises when this nerve is stimulated. The statements of observers regarding the effect
- the sympathetic nerve upon the pressure vary. Interruption to the venous outflow increases
: od gag ca - imperfect supply of blood, the outflow being normal, diminishes the pres-

, ion of the blood-vessels of the eye is referred to at § 347. eons

385, DIOPTRIC OBSERVATIONS.—'The e i i
ar .—The eye as an optical instrument is comparable to a ‘|
hese Spacere 2 Res iste an inverted diminished image of the objects of the isteeand world —
, wp a background, the field of projection. Instead of the single lens of the camera,
Pathos e eye has several refractive media placed behind each other— coleman aqueous
proms pole ose individual parts—capsule, cortical layers, and nucleus, all possess different
pig chide ces), and vitreous humour. Every two of these adjacent media are bound
s Psy ison mae e,” which may be regarded as spherical. The field of projection of the |
e retina, which is coloured with .the visual purple (Boll, Kiihne), Ks this substance

ACTION OF LENSES ON LIGHT. — 743

bleached chemically by the direct action of light, so that the pictures may be temporarily fixed
upon the retina, the comparison of the eye with the camera of the photographer becomes more
striking. In order that the passage of the rays of light through the media of the eye may be
rightly understood, we must know the following factors :—(1) the refractive indices of all the
media ; (2) the form of the refractive surfaces ; (3) the distance of the various media from each
other and from the field of projection or retina.

Action of a converging lens.—We must know how a convex lens acts upon light. In a
convex lens we distinguish the centre of curvature, 7.e., the centre of both spherical surfaces
(fig. 524, I, m, m,). The line connecting both is called the chief axis ; the centre of this line is
the optical centre of the lens (0). All rays which pass through the optical centre of the lens
pass through unbent, or without being refracted ; they are called the chief or principal rays
(2, 24) The following are the laws regulating the action of a convex lens upon rays of light :—

D> Sse
Fig.. 524. ,
Figures illustrating the action of lenses upon rays of light passing through them.

1, Rays which fall upon the lens, parallel with the principal axis (II, f, a), are so refracted
that they are collected on the other side of the lens, at a point called the focus or principal
focus (f). ‘The distance of this point from the central point (0) of the lens, is called the focal
distance of the lens (/, 0). The converse of this condition is evident, viz., rays which diverge
from a focus and reach the lens, pass through it to the other side, parallel with the principal
axis, without again coming together.

2. Rays of light proceeding from a source of light (IV, 7) in the prolonged principal axis, but
beyond the focal point (f), again converge to a point on the other side of the lens. The follow- —
ing cases may occur :—(a) When the distance of the light from the lens is equal to twice the
focal distance, the focus or point of convergence lies at the same distance on the other side of
the lens, i.e., twice the focal distance, (b) If the luminous point be moved nearer to the
focus, then the focal point is moved farther away. (c) If the light is still farther from the lens
than twice the focal distance, then the focal point comes correspondingly near to the lens.

3. Rays proceeding from a point of the chief axis (III, 2) within the focal distance, pass out
at the other side less divergent, but do not come to a focus again. Conversely, rays which are
eparergent, and pass through a collecting lens, have their focal point within the focal distance,

4. If the luminous point (V, a) is placed in the secondary ray (a, b), the same laws obtain,
provided the angle formed by the secondary ray with the principal axis is small.

Formation of images by convex lenses.—After what has been stated, regarding the position
of the point of convergence of rays proceeding from. a luminous point, the construction of the
image of any object by a convex lens is easily accomplished, This is done simply by projecting
images of the various parts of the object. Thus, evidently (in V), bis the focal point of the
object, a, while v is the focal point of the object 7. The picture is inverted. Collecting lenses
form an inverted and real-image (i.e, wpon.a screen) only of such objects as are placed beyond
the focal point of the lens, : ee oe pr

744 FORMATION OF IMAGES BY CONVEX LENSES.

With regard to the size and distance of the image from the lens, there are the following
commetn If the object be placed at twice the focal distance from the lens, the ig, of the
same is just the same size and at the same distance from the lens as the object is. (6) If the
object be nearer than the focus, the image recedes and at the same time becomes larger. (c) If

$ : f°

peat '

Fig. 525. Fig. 526.
the object be farther removed from the lens than twice the focal distance, then the image is
nearer to the lens and at the same time becomes smaller.
Position of the focal point.—The distance of the focal point from the lens is readily calcu-
lated according to the following formula :—Where /= the distance of the luminous point, =the
|

A : ; jee | 1
distance of the image, and f=the focal distance of the lens: a ae , or ar 2

Example.—Let /=24 centimetres, f=6 cm. Then i- = - ry = - so that b=8 cm., i.¢., the

image is formed 8 cm. behind the lens. Further, let 7=10 em., f=5 em. (i.¢.,7=2f). Then
1 ‘
eee ace ; so that b=10, i.¢., the image is placed at twice the focal distance of the lens.

Lastly, let 7=oo. Then r= we = so that b=f, z.¢., the image of parallel rays coming from

infinity lies in the focal point of the lens.
Refractive Indices.—A ray of light, which passes in a perpendicular direction from one
medium into another medium of different density, passes through the latter without changing
its course or being refracted. In fig. 525, if G D, is | A B, then so is D D, } AB; for a plane
surface A B is the horizontal, and G D the vertical line. If the surface be spherical, then the -
vertical line is the prolonged radius of this sphere. If, however, the ray of light fall obliquely
upon the surface, itis “refracted,” 7.¢., it is bent out of its original course. e incident and
the refracted ray nevertheless lie in one plane. When the oblique incident ray passes from a
less dense nedium (e.g., air) into one more dense (e.g., water), the refracted or excident ‘ray is
bent towards the perpendicular. _ If, conversely, it pass from a more dense to a less dense medium, |
it is bent away from the ag sei The angle (i,G D S) which the incident ray (S D) forms
with the perpendicular (@ D) is called the angle of incidence, the angle formed by the refracted -q
ray (D S,) with the prolonged perpendicular (D D) is called the angle of refraction, D D S;
(r). ‘The refractive power is expressed as the refractive index. ‘The term refractive index
(m) means, that number which shows for a certain substance, how many times the sine of the
angle of incidence is greater than the sine of the angle of refraction, when a ray of light passes
from the air into that substance. Thus, »=sin. i: sin. r=ab, : cd. On comparing the refractive
indices of two media, we always assume that the ray passes from air into the medium, On
passing from the air into water, the ray of light is so refracted that the sine of the angle of .
ineidence is to the sine of the angle of refraction, as 4 : 3; the refractive index = 4 (or more
exactly =1°336). With glass the proportion is=3 : 2 (=1°535—Snellius, 1620; Desi wa! ¢
aie sine of the incident and refractive-angles are related as the velocity of light with both
m ia. i tore
The construction of the refracted ray, the refractive index being given, is simple :—Exa
—Suppose in fig. 526, L=the air, G=a dense medium (glass) with a spherical surface, zy, and

Soe

ACTION OF A CONVEX LENS. 745

with its centre at m; po=the oblique incident ray the m Z is the perpendicular <) = the
angle of incidence. The refractive index given is 5 ; the object is to find the direction of the

refracted way. From o as centre describe a circle with a radius of any length; from a draw a
perpendicular, a 6 to m Z; then @ d is the sine of the angle of incidence, 7. Divide the line a b
into three equal parts, and prolong it to the extent of two of these parts, viz., top. Draw the

line p parallel tom 7. The line joining o to 7 is the direction of the refracted ray. On mak-
ing a line, ns, perpendicular to m Z,n s=bp. Further, n s=sine <)=r. Sothatab: sn
or: bp)=3: 2orsin. 7? : sin. 7= =.

Optical cardinal point of a simple collecting system.—Two refractive media (fig. 527, L and

A E c

Fig. 527.

G), which are separated from each other by a spherical surface (a, b) form a simple collecting
system. It is easy to estimate the construction of an incident ray coming from the first
medium (L) and falling obliquely upon the surface (a, b) separating the two media, as well as
to ascertain its direction in the second medium, G, and also from the position of a luminous
point in the-first medium, to estimate the position of the corresponding focal point in the
second medium. The factors required to be known are the following :—L (fig. 527) is the
first, and G the second medium, a, b=the spherical surface whose centre is m. Of course, all
the radii drawn from m to ab (ma, m 1) are perpendiculars, so that all rays falling in the
direction of the radii must pass unrefracted through m. All rays of this sort are called rays or
lines of direction ; m, as the point of intersection of all these, is called the nodal point. The
line which connects m with the vertex of the spherical surface, x, and which is prolonged in
both directions, is called the optic axis, 0 Q. A plane (EK, F) in x, perpendicular to O Q, is
called the principal plane, and in it zis the principal point. The following facts have been
ascertained :—(1) All rays (a to a;), which in the first medium are parallel with each other and
with the optic axis, and fall upon a 8, are so refracted in the second medium that they are all
again united in one point (p,) of the second medium. This is called the second principal focus.
A plane in this point perpendicular to O Q is called the second focal plane (C D). (2) All rays
(c to c,), which in the first medium are parallel to each other, but not parallel to O Q, reunite
in a point of the second focal plane (r), where the non-refracted directive ray (¢,, m 7) meets
this. (In this case, the angle formed by the rays ¢ to c, with C Q must be very small.) The
propositions 1 and 2 of course may be reversed; the divergent rays proceeding trom p towards
a b pass into the first medium parallel to each other, and also with the axis C Q (a to a;); and
the rays proceeding from 7 pass into the first medium parallel to each other, but not parallel
to the axis O Q (ase toc,). (8) All rays,“which in the second medium are parallel to each
other (0 to b,) and with the axis O Q, reunite in a point in the first medium (p) called the jirst
Socal point ; of course the converse of this is true. A plane in this point perpendicular to O Q
is called the first focal plane (A, B). The radius of the refractive surface (m, x) is equal to the
difference of the distance of both focal points (p and p,) from the principal focus (x); thus m «=
Pp, x-p x. From these comparatively simple propositions it is easy to determine the following
points :— . .

1. The construction of the refracted ray.—Let A be the first (fig. 528); B, the second

medium; ¢ d, the spherical surface separating the two; a b, the optical axis; %, the nodal

point ; y, the first and p, the second principal focus; C, D, the second focal plane. Suppose
x y to represent the direction of the incident ray, what is the construction of the refracted ray

7406 ACTION OF A CONVEX LENS.

in the second medium?! Prolong + opty ghey ray, P, k, Q parallel to x, y, then y, Q is the
‘rection of the refracted ray (according to 2).

Construction of the image for a given object.—In fig. 529, B, ¢, d, a, b, k, p, and p,,

C, D are as before. Suppose

C a luminous point (0) in the first .

i medium, what is the position of

the image in the second me-
dium? Prolong the unre-
fracted ray (0, k, P), and draw
the ray (0, x) parallel to the:axis
(a, b). The parallel rays (a, ¢
and o, x) reunite in p (accord-
ing to proposition 1). Prolong
2, p, until it intersects the ray
(o, P), then the image of o is
at P, the rays of light (0 x and
o k) proceeding from the lumi-
Fig. 528. nous point (0) reunite in P.

Construction of the refracted ray and the image in several refractive media,—lIf several

refractive media be placed behind each other, we must proceed from medium to medium with

Fig. 529. P

the same methods as above described. This would be very tedious, especially when dealing
with small objects. Gauss (1840) calculated that in such cases the method of construction is

= 0
h h, fF : i
Fig, 580.

very simple. If the several media are “centred,” i.c., if all have the same optic axis, then’'tl
refractive indices of such a centred system may be represented by two equal, strong, re uc
surfaces at a certain distance. The rays falling upon the first surface are not refracted by 1

CARDINAL OPTICAL POINTS. waa

but are essentially projected forwards parallel with themselves to the second surface. Refraction
takes place first at the second surface, just as if only one refractive surface was present. In
order to make the calculation, we must know the refractive indices of the media, the radii of
the refractive surfaces, and the distance of the refractive surfaces from each other.

Construction of the refracted ray is accomplished as follows :—Let a 6 represent the optical
axis (fig. 530, I.) ; H, the first focal point determined by calculation ; h h,}the principal plane ;
H, the second focal point ; 2,, h;, the second principal plane; %, the first, and &, the second
nodal point ; F, the second focal point ; and F,, F,, the second focal plane. Make the ray of
direction p k, parallel to m,, n;. According to proposition 2, p, k, and m,, n, must meet in a
point of the plane F, F,. As p %, passes through unrefracted, the ray from 2, must fall at 7 ;
n, r is, therefore, the direction of the refracted ray.

Construction of the focal point.—Let o be a luminous point (fig. 530, II.), what is the
position of its image in the last medium? Prolong from o the ray ot direction 0 k, and make
0, x parallel to ab, Both rays are prolonged in a parallel direction to the second focal plane.
The ray parallel to a b goes through F; m, #, as the ray of direction passes through unrefracted.
O, where n, F, and m &, intersect each other, is the position of the image of o.

386. DIOPTRICS—RETINAL IMAGE—OPHTHALMOMETER.—Position
of the cardinal points.—The eye surrounded with air on the anterior surface of the
cornea, represents a concentric system of refractive media with spherical separating
surfaces. In order to ascertain the course of the rays through the various media
of the eye, we must know the position of both principal foci of both nodal points
as well as the two principal focal points. Gauss, Listing, and v. Helmholtz have
calculated the position of these points. In order to make this calculation, we
require to know the refractive indices of the media of the eye, the radii of the
refractive surfaces, and the distance of the latter from each other. These will be
referred to afterwards. (1) The first principal point is 21746 mm.; and (2): the
second principal point is 2°5724 mm. behind the anterior surface of the cornea.
(3) The first nodal point, 0°7580 mm. ; and (4) the second nodal point, 0:3602 mm.
in front of the posterior surface of the lens. (5) The second principal focus,
14-6470 mm. behind the posterior surface of the lens; and (6) the jirst principal
focus, 12°8326 in front of the anterior surface of the cornea.

Listing’s reduced eye.—The distance between the two principal points, or the two

nodal points, is so small (only 0°4 mm.), that practically, without introducing any

Fig. 581.

great error in the construction, we may assume ove mean nodal or principal point
lying between the two nodal or principal points. By this simple procedure we gain
one refractive surface for all the media of the eye, and only one nodal point,
through which all the rays of direction from without must pass without being
refracted. This schematic simplified eye is called “the reduced eye” of Listing.
Formation of the retinal image.—Thus, the construction of the image on the
retina becomes very simple. In distinct vision, the inverted image is formed on
the retina. Let A B represent an object placed vertically in front of the eye (fig.
531). A pencil of rays passes from A into the eye; the ray of direction, A d,

748 THE OPHTHALMOMETER.

passes without refraction through the nodal point, k. Further, as the focal point
for the luminous point, A, is upon the retina, all the rays proceeding from A must
reunite in d. The same is true of the rays proceeding from B, and, of course, for
rays sent out from an intermediate point of the body, AB. The retinal image is,
as it were; a mosaic, composed of innumerable foci of the object. | As all the rays
of direction must pass through the common nodal point, 4, this is also called the
© point of intersection of the visual rays.”

The inverted image on the retina is easily seen in the excised eye of an albino rabbit, by hold-
ing up any object in front of the cornea and observing the inverted image through the trans-
parent coats of the eyeball. : ;

The size of the retinal image may also be calculated, provided we know the size of the
object, and its distance from the cornea. As the two triangles, A B & and cd & are similar,
AB: cd=fk:kg, sothatcd=(A B, kg): fk. All these values are known, viz., k g=15°16
mm.; further, fk=a k x a, f, where af is measured directly, and a k=7'44 mm. The size
of A B is measured directly.

The angle, A & B, is called the visual angle, and of course it is equal to the
angle c k d. It is evident that the nearer objects, ~ y, and r s, must have the
same visual angle. Hence, all the three objects, A By wy; and r s, give a retinal
image of the same size. Such objects, whose ends when united with the nodal
point form a visual angle of the same size, and consequently form retinal images
of the same size, have the same “ apparent size.”

In order to determine the optical cardinal points by calculation, after the
method of Gauss, we must know the following factors :—

1. The refractive indices: for the cornea, 1:377 ; aqueous humour, 1°377 ; lens,
1:454 (as the mean value of all the layers) ; vitreous humour, 1336 ; air being
taken as 1, and water 1°33).

2. The radii of the spherical refractive surfaces: of the cornea, 7°7 mm.; of
the anterior surface of the lens, 10°3 ; of the posterior, 6:1 mm.

3. The distance of the refractive surfaces: from the vertex of the cornea to
the anterior surface of the lens, 3°4 mm. ; from the latter to the posterior ‘surface
of the lens (axis of the lens), 4 mm. ; diameter of the vitreous humour, 14°6 mm. .
The total length of the optic axis is 22°0 mm.

[Kiihne's Artificial Eye.—The formation of an inverted image, and the other points in the
dioptrics of the eye can be studied most effectively on Kiihne’s artificial eye, the course of the
rays of light being visible in water tinged with eosine. ]

Ophthalmometer.—This is an instrument to enable us to measure the radii of the refractive
media of the eye. As the normal curvature cannot be accurately measured on the dead eye,
owing to the rapid collapse of the ocular tunics, we have recourse to the process of Kohlrausch,
for calculating the radii of the refractive surfaces from the size of the reflected images in the
livingeye. The size of a luminous body is to the size of its reflected image, as the distance of both
to half the radius of the convex mirror. Hence, it is necessary to measure the size of the re-

Fig. 532.
Scheme of the ophthalmometer of Helmholtz.
flected image. This is done by means of the ophthalmometer of Helmholtz (fig. 582).
The apparatus is constructed on the following principle :—-If we observe an object
through a glass plate placed obliquely, the object appears to be displaced laterally ; the
displacement becomes greater, the more obliquely the plate is moved. oppo the observer,
ery

A, to look through the telescope, F, which has the plate, G, placed obliquely in front of the
upper half of its objective, he sees the corneal reflected image, a b, of the eye, B, and the —

ACCOMMODATION OF THE EYE. 749

image appears'to be displaced laterally, viz., toa’ b’, If asecond plate, G, be placed in front
of the lower half of the telescope, but placed in the opposite direction, so that both plates,
corresponding to the middle line of the objective, intersect at an angle, then the observer sees
the reflected image, a b, displaced laterally to a’ 6’. As both glass plates rotate round their
point of intersection, the position of both is so selected, that both reflected images just touch
each other with their inner margins, (so that 0’ abuts closely upon a”). The size of the reflected
image can be determined from the size of the angle formed by both plates, but we must take
into calculation the thickness of the glass plates and their refractive indices. The size of the
corneal image, and also that in the lens, may be ascertained in the passive eye, and also in the
eye accommodated for a near object, and the length of the radius of the curved surface may be
calculated therefrom (Helmholtz and others).

Fluorescence, —A1] the media of the eye, even the retina, are slightly fluorescent; the lens
most, the virteous humour least (v. Helmholtz).

Erect Vision.—As the retinal image is inverted, we must explain how we see
objects upright. By a psychical act, the impulses from any point of the retina are
again referred to the exterior, in the direction through the nodal point; thus the
stimulation of the point d is referred to A, that of ¢ to B (fig. 531). The reference
of the image to the external world happens thus, that all points appear to lie in a
surface floating in front of the eye, which is called the field of vision. The field of
vision is the inverted surface of the retina projected externally ; hence, the field of
vision appears erect again, as the inverted retinal image is again projected externally
but inverted (fig. 531), |

That the stimulation of any point is again projected in an inverse direction through the
nodal point, is proved by the simple experiment, that pressure upon the outer aspect of the
eyeball is projected or referred to the inner aspect of the field of vision. The entoptical phe-
nomena of the retina are similarly projected externally and inverted ; so that, e¢.g., the entrance
of the optic nerve is referred externally to the yellow spot (see § 393), All sensations from the
retina are projected externally.

387. ACCOMMODATION OF THE EYE.—dAccording to No. 2. (p. 743), the rays of light
proceeding from a luminous point, ¢.g., a flame, and acted upon by a collecting (convex) lens,
are brought to a focus or focal point, which has always a definite relation to the luminous
object. If a projection-surface or screen be placed at this, distance from the lens, a real and
inverted image of the object is obtained upon the screen. If the screen be placed nearer to the
lens (fig. 524, IV, a, b), or farther away from it (c, d), no distinct image of the object is formed,
but diffusion circles are obtained ; because, in the former case, the rays have not united, and
in the latter, because the rays, after uniting, have crossed each other and become divergent.
If the luminous point be brought nearer to, or removed farther from, the lens, in order to
obtain a distinct image, in every case, the screen must be brought nearer, or removed from the
lens, to keep the same distance between the lens and the screen. If, however, the screen be
fixed permanently, whilst the distance between the luminous point and the lens varies, a
distinct image can only be obtained upon the screen, provided the lens, as the luminous point
approaches it, becomes more convex, 7.¢., refracts the rays of light more strongly—conversely,
when the distance between the luminous point and the lens becomes greater, the lens must
become less curved, 7.¢,, refract less strongly.

In the eye, the projection surface or screen is represented by the retina, which is permanently
fixed at a certain distance ; but the eye has the power of forming distinct images of near and
distant objects upon the retina, so that the refractive power, z.¢., the form of the crystalline
lens in the eye, must undergo a change in curvature corresponding in every case to the distance
of the object. [It is important to remember, that we cannot see a near object and a distant
one with equal distinctness at the same time, and hence arises the necessity for accom-
modation. ]

Accommodation.—By the term “ accommodation of the eye,” is understood that
property of the eye, whereby it forms distinct images of distant as well as near
objects upon the retina. This power depends upon the fact, that the crystalline
lens alters its curvature, becoming more convex (thicker), or less curved
(flatter), according to the distance of the object. When the lens is absent from the
eyeball, accommodation is impossible (7h. Young, Donders—p. 740):

During rest [or negative accommodation], or when the eye is passive, it is
accommodated for the greatest distance, i.¢., images of objects placed at an infinite
distance (¢.g., the moon) are formed upon the retina. In this case, rays coming

750 ACCOMMODATION.

from such a distance are practically parallel, and when they enter the eye, are in

the passive normal eye (emmetropic) brought to a focus on the retina. When

looking at a distant object, a distinct image 1s

~ formed on the retina without the aid of any
muscular action.

That distant objects are seen without the aid of any
muscular action is shown by the following considera-
tions:—(1) With the
normal, or emmetropic
eye, we can see distant
objects clearly and dis-
tinctly, without expe-
riencing any feeling of
effort. On opening the
eyelids afteralong period
of rest, the objects at a
distance are at once dis-

RAMA’,
Bones \
Anterior quadrant of a horizontal section of the eyeball, cornea, and lens. WY
a, substantia propria of the cornea; b, Bowman’s elastic membrane ; c,
anterior corneal epithelium ; ¢d, Descement’s membrane ; ¢, its epithe-
lium ; f, conjunctiva ; g, sclerotic ; h, iris; 7, sphincter iridis; j, liga-
mentum pectinatum iridis, with the adjoining vacnolated tissue ; 4, canal
of Schlemm ; 7, longitudinal, m, circular muscular fibres of the ciliary
muscle ; 2, ciliary process ; 0, ciliary part of the retina ; q, canal of Petit,
with Z, zonule of Zinn in front of it ; and p, the posterior layer of the hyaloid membrane ;
r, anterior, s, posterior part of the capsule of the lens; ¢, choroid ; «, perichoroidal space ;
T, pigment epithelium of the iris ; z, margin of the lens.

tinctly visible in the field of vision. (2) If, in consequence of paralysis of the mechanism of
accommodation (e.g., through paralysis of the oculomotor nerve—§ 345, 7), the eye is unable to
focus images of objects placed at ditferent distances, still distinct images are obtained of distant
objects. Thus, paralysis of the mechanism of accommodation is always accompanied by inability
to focus a near object, never a distant object. A temporary paralysis occurs with the same
results when a solution of atropin or duboisin is dropped into the eye, and also in poisoning
with these drugs (§ 392).

When the eye is accommodated for a near object, [positive accommodation],
the lens is thicker, its anterior surface is more curved (convex), and projects
farther into the anterior chamber of the eye (Cramer, 1851, v. Helmholtz, 1853).
The mechanism producing this result is the following :— During rest, the lens is kept
somewhat flattened against the vitreous humour lying behind it, by the tension of the
stretched zonule of Zinn, which is attached round the margin of the lens (fig. 533, Z).
When the muscle of accommodation, the ciliary muscle (/, m), contracts, it pulls
forward the margin of the choroid, so that the zonule of Zinn in intimate relation
with it is relaxed. [When we accommodate for a near object, the ciliary muscle
contracts, pulls forward the choroid, relaxes the zonule of Zinn, and this in turn
diminishes the tension of the anterior part of the capsule of the lens.| The lens
assumes a more curved form, in virtue of its elasticity, so that it becomes more
convex as soon as the tension of the zonule of Zinn, which keeps it flattened, is
diminished (fig. 534). As the posterior surface of the lens lies in the saucer-shaped
unyielding depression of the vitreous humour, the anterior surface of the lens in
becoming more convex must necessarily protrude more forwards. i

Nerves.— According to Hensen and Vilckers, the origin of the nerves of accom-

NERVES. | | 701

modation lies in the most anterior root-bundles of the oculomotorius. Stimulation
of the posterior part of the floor of the third ventricle causes accommodation ; if a
_ part lying slightly posterior to this be stimulated, contraction of the pupil occurs.
On stimulating the limit between the third ventricle and the aqueduct, there results

Fig. 534,

Scheme of accommodation for near and distant objects. The right side of the figure represents
the condition of the lens during accommodation for a near object, and the left side when
the eye is at rest. The letters indicate the same parts on both sides ; those on the right
side are marked with a dash ; J, left, B, right half of the lens ; C, cornea; S, sclerotic ;
C.S., canal of Schlemm ; V.X., anterior chamber ; J, iris; P, margin of the pupil; V,
anterior surface ; H, posterior surface of the lens; #, margin of the lens; /, margin of
the ciliary processes ; a@ and b, space between the two former ; the line 7, X, indicates the
thickness of the lens during accommodation for a near object ; Z, Y, the thickness of the
lens when the eye is passive.

contraction of the internal rectus muscle, while stimulation of the other parts around
the cer causes contraction of the superior rectus, levator palpebre, rectus inferior,
and inferior oblique muscles.

Proofs.—That the lens undergoes an alteration in its curvature, during accommodation, is
proved by the following facts :—

1. Purkinje-Sanson’s Images.—If a lighted candle be held at one side of the eye, or if light
be allowed to fall on the eye through two triangular holes, placed above each other and cut in
a piece of cardboard, in the latter case the observer will see three pairs of reflected images [in
the former, three images]. The brightest’and most ©
distinct image (or pair of images) is erect and is
produced by the anterior surface of the cornea (fig.
535, a). The second image (or pair of images) is
also erect. It is the largest, but it is not so bright
(b), and it is reflected by the anterior surface of
the lens. (The size of a reflected image from a
convex mirror is greater, the longer the radius of
curvature of the reflecting surface.) The latter
image lies 8 mm. behind the plane of the pupil. f
The third image (or pair of images) is of medium Fig, 535.
size and. medium brightness—it is inverted and lies
nearly in the plane.of the pupil (¢). The posterior
capsule of the lens, which reflects the last image,
acts likea concave mirror. Ifa luminous object be
placed at a distance from a concave mirror, its inverted, diminished, rea/ image lies close to the
focus towards the side of the object. If the images be studied when the observed eye is passive,
i.¢., in the phase of negative accommodation, on asking the person experimented upon to accom-
modate his eye for a near object, at once a change-in the relative position and size of some of
the images is apparent. The middle pair‘of images reflected by the anterior surface of the lens
diminish in size and approach each other (d), which depends upon the fact that the anterior
surface of the lens has become more convex. At the same time, the image (or pair of images)
comes nearer to the image formed by the cornea (a, and c,) as the anterior surface of the lens lies
nearer to the cornea. The other images (or pairs of images) neither change their size nor, posi-

Sanson-Purkinje’s images. a, b, c, during
negative, and a,, b,, ¢, positive accommo-
dation.

752 THE PHAKOSCOPE,

tion, Helmholtz, with the aid of the ophthalmometer, has measured the diminution of the
radius of curvature of the anterior surface of the lens during accommodation for a near object.

[Phakoscope.— These images may be readily shown by
means of the phakoscope of v. Helmholtz (fig. 586). It
consists of a triangular box with its angles cut off and
blackened inside. The observer’s eye is placed at a, while
on the opposite side of the box are two prisms, 6, D';
b the observed eye is placed at the side of the box opposite
to C. When a candle is held in front of the prisms, }
h and J, three pairs of images are seen in the observed
_ eye, Ask the person to accommodate for a distant ob-

ject, and note the position of the images. On pushing
up the slide C with a pin attached to it, and asking him
to accommodate for the pin, z.¢., for a near object, the
position and size of the middle images chiefly will be
seen to alter as described above. ]

2. In consequence of the increased curvature of the
lens during accommodation for a near object, the re-
fractive indices within the eye must undergo a change.
According to v. Helmholtz the annexed measurements
obtain in negative and positive accommodation respec-
tively.

3. Tato View of the Pupil.—If the passive eye be
looked at from the side, we observe only a small black
strip of the pupil, which becomes broader as soon as the
person experimented on accommodates for a near object,
as the whole pupil is pushed more forwards.

Fig. 536. 4. Focal Line. —If light be admitted through the cor-
Phakoscope of Helmholtz. nea into the anterior chamber, the ‘‘ focal line” formed

by the concave surface of the cornea falls upon the iris.

If the ren be made upon a person whose eye is accommodated for a distant object, so

that the line lies near the margin of the pupil, it gradually recedes towards the scleral margin
Accommodation. Negative—Mm. Positive—Mm,
| Radius of the cornea, ‘ ; : : ‘ ; ; 8 8
| Radius of anterior surface of lens, . : : : ’ 10 6
Radius of aes ea surface of lens, . ; ‘ ‘ ; 6 5°5
| Position of the vertex of the outer surface of the lens be- : :
hind the vertex of the cornea, . ‘ : 36 ne
| Position of the posterior vertex of the lens, .. ; 2 7°2
Position of the anterior focal point, ; ‘ . : 12°9 11°24
- Position of the first principal point, : ‘ ° ° 1°94 2°03
Position of the second principal point, . : ; ; 6°96 6°51
' Position of the posterior focal point behind the anterior
vertex of the cornea, , : : a or

of the iris, as ‘soon as the person accommodates for a near object, because the iris becomes more
oblique as its inner margin is pushed forward.

5. Change in Size of Pupil.—On accommodating for a near object, the pupil contracts,
while in accommodation for a distant object, it dilates (Descartes, 1637). The contraction takes
place slightly after the accommodation (Donders). This phenomenon may be regarded as an
associated movement, as both the ciliary muscle and the sphincter pupille are supplied by the
oculomotorius (§ 345, 2, 3). A reference to fig. 533 shows that the latter also directly supports
the ciliary muscle; as the inner margin of the iris passes inwards (towards 7), its tension tends
to be propagated to the ciliary margin of the choroid, which also must pass inwards, The
ciliary processes are made tense, chiefly by the ciliary muscle (tensor choroida), _Accommoda-
tion can still be performed, even thou!) the iris be absent or cleft.

6, Internal Rotation of the Eye.—On rotating the eyeball inwards, accommodation for a
near object is performed involuntarily. As rotation of both eyeballs inwards takes place when
the axes of vision are directed to a near object, it is evident that this must be accompanied
involuntarily by an accommodation of the eye for a near object, ,

7. Time for Accommodation.—A person can accommodate from a near to a distant object
(which depends upon relaxation of the ciliary muscle) much more rapidly than conversely, from
a distant to a near pact (Vierordt, Aeby). The process of accommodation requires a longer
time, the nearer the object is brought to the eye (Vierordt, Vilckers and Hensen), The time

SO

SCHEINER’S EXPERIMENT. 753

necessary for the image reflected from the anterior surface of the lens to change its place during
accommodation, is less than that required for subjective accommodation (Aubert and
Angelucci). .

8. Line of Accommodation.— When the eye is placed in a certain position during accommo-
. dation, we may see not one point alone distinctly, but a whole series of points behind each
other: Czermak called the line in which these points lie the line of accommodation. The more
the eye is accommodated for a distant object, the longer does this line become. All objects
placed at a greater distance from the eye than 60 to 70 metres appear equally distinct to the
eye.. The line becomes shorter the more we accommodate for a near object—i.e., when we
accommodate as much as possible for a near object, a second point can only be seen indistinctly
at a short distance behind the object looked at.

9. The nerves concerned in the mechanism of accommodation are referred to under Ocu/o-
motorius (§ 345, and again in § 704). |

Scheiner’s Experiment.—The experiment which bears the name of Scheiner
(1619) serves to illustrate the refractive action of the lens during accommodation
for a near object, as well as for a distant object. Make two small pin-holes (S, d)
in a piece of cardboard (fig. 537, K, K,), the holes being nearer to each other than
the diameter of the pupil. On looking ;
through these holes, S, d, at two needles : R
(p and 7) placed behind each other, then E
on accommodating for the near needle (p), i
the far needle (7) becomes double and in- ii
verted. On accommodating for the near ii
needle (py), of course the rays proceeding ii
from it fall upon the retina at the focus
(p,); while the rays coniing from the far Po
needle (7) have already united and crossed ae
in the vitreous humour, whence they di-
verge more and more and form two pictures
(7, 7,,) on the retina. If the right hole in
the cardboard (d) be closed, the eft picture
on the retina (7,) of the double images
of the far needle disappears. An analo-
gous result is obtained on accommodating
for the far needle (R). The near needle
(P) gives a double image (P,, P_,), because
the rays from it have not yet come to a
focus. On closing the right hole (d,), the
right double image (P.,) disappears (Porter-
jield). When the eye of the observer is
accommodated for the near needle, on
closing one aperture the double image of Fig. 537.
the distant point disappears on that side ; Scheiner’s experiment.
but if the eye is accommodated for the distant needle, on closing one hole the
crossed image of the near needle disappears.

388. REFRACTIVE POWER OF THE EYE—ANOMALIES OF RE-
FRACTION.—The limits of distinct vision vary very greatly in different eyes.
We distinguish the far point [p.r., punctum remotum] and the near point [p.p.,
punctum proximum|]; the former indicates the distance to which an object may
be removed from the eye, and may still be seen distinctly ; the latter, the distance
to which any object may be brought to the eye, and may still be seen distinctly.
The distance between these two points is called the range of accommodatior.
The types of eyeball are characterised as follows— |

1. The normal or emmetropic eye is so arranged when at vest that parallel rays
(fig. 538, 7, 7) coming from the most distant objects can be focussed on the retina

3B

754 EMMETROPIC AND MYOPIC EYES. ,

(r,). The far point, therefore, is = o (infinity). When accommodating as much
as possible for a near object, whereby the convexity of the lens is increased (fig.
538, a), rays from a luminous point placed at a distance of 5 inches are still focussed
on the retina, z.¢., the near pont
is=5 inches (1 inch=27 mm.).
The range of accommodation, or
[‘‘the range of distinct vision”
therefore, is from 5 inches (10-12
cm.) tow.

2. The short-sighted, myopic
eye (or long eye) cannot, when at
rest, bring parallel rays from in-
finity to a focus on the retina (fig.
539). These rays decussate within
the vitreous humour (at O), and
after crossing form diffusion circles
upon the retina. The object must
be removed from the passive eye

Fig. 588, to a distance of 60 to 120 inches
Condition of refraction in the normal passive eye and (to fr), in order that the rays may
during accommodation. he focssed on the retinas; The
passive myopic eye, therefore, can only focus divergent rays upon the retina. The
far point, therefore, lies abnormally near. With an intense effort at accommodation,
objects at a distance of 4 to
2 inches, or even less, from
the eye may be seen dis-
tinctly. The near point,
therefore, lies abnormally
near; the range of accom-
modation is diminished,

Short-sightedness, or myopia,
usually depends upon congenital,
and frequently hereditary, elon-
Fic. 539. gation of the eyeball. This

a anomaly of the refractive media
is easily corrected by using a
diverging lens (concave), which makes parallel rays divergent, so that they can then be brought
to a focus on the retina. It is remarkable that most children are myopic when they are born.
This myopia, however, depends upon a too-curved condition of the cornea and lens, and on the
lens being too near to the cornea. As the eye grows, this short-sightedness disappears,

The cause of myopia in children is ascribed
to the continued activity of the ciliary muscle
in reading, writing, &c., or the continued
convergence of the eyeballs, whereby the
external pressure upon the eyeball is in-
creased,
pap 3. The long-sighted, hyperme-
tropic eye, hyperoptic (flat eye) when
at rest, can only cause convergent rays
to come to. a focus on the retina (fig,
540). Distinct images can only be *
Fi formed when the rays proceeding from

g. 540. é

objects are rendered convergent by
means of a convex lens, as parallel rays
would come to a focus behind the retina (at f), All rays proceeding from natural
objects are either divergent, or at most nearly parallel, never convergent. Hence,

Myopic eye.

Hypermetropie eye.

THE POWER OR FORCE OF ACCOMMODATION. _ 755

a long-sighted person, when the eye is passive, 1.¢., 1s negatwely accommodated,
cannot see distinctly without a convex lens. When the ciliary muscle contracts,
slightly convergent, parallel, and even slightly divergent rays may be focussed,
according to the increasing degree of the accommodation. The far point of the
eye is negative, the near point abnormally distant (over 8 to 80 inches), while the
range of accommodation is infinitely great.

The cause of hypermetropia is abnormal shortness of the eye, which is generally due to
imperfect development in all directions. It is corrected by using a convex lens.

[Defective Accommodation.—In the presbyopic eye, ot long-sighted eye of old
people, the near point is farther away than normal, but the far point is still
unaffected. In such cases, the person cannot see a near object distinctly, unless it
be held at a considerable distance from the eye. It is due to a defect in the
mechanism of accommodation, the lens becoming somewhat flatter, less elastic, and
denser with old age, while the ciliary muscle becomes weaker. In hypermetropia,
on the contrary, the mechanism of accommodation may be perfect, yet from the
shape of the eye the person cannot focus on his retina the rays of light from a near
object. In presbyopia the range of distinct vision is diminished. The defect is
remedied by weak convex glasses. The defect usually begins about forty-five
years of age. ]

Estimation of the Far Point—Snellen’s Types.—In order to determine the far point of an
eye, gradually bring nearer to the eye objects which form a visual angle of 5 minutes (e.y.,
Snellen’s small type letters, or the mediwm type, 4 to 8, of Jaeger), until they can be seen dis-
tinctly. The distance from the eye indicates the far point. In order to determine the far point
of a myopic person, place at 20 inches distant from the eye the same objects which give a visual
angle of 5 minutes, and ascertain the concave lens which will enable the person to see the objects
distinctly. To estimate the newr point, bring small objects (¢.g., the finest print) nearer and
nearer to the eye, until it finally becomes indistinct. The distance at which one can still see
distinctly indicates the far point.

Optometer.—The optometer may also be used to determine the near and far points. A small
object, e.g., a needle, is so arranged as to be movable along a scale, along which the eye to be
investigated can look as a person looks along the sight of a rifle. The needle is moved as near
as possible, and then removed as far as possible, in each case as long as it is seen distinctly.
The distance of the near and far point and the range of accommodation can be read off directly
upon the scale (Grééfe),

389. FORCE OF ACCOMMODATION.—Force.—The range of accommodation, which is
easily determined experimentally, does not by itself determine the proper ower or force of
accommodation. The measure of the latter depends upon the mechanical work done by the
muscle of accommodation, or the ciliary muscle. Of course this cannot be directly determined
in the eye itself. Hence, this force is measured by the optical effect, which results in consequence
of the change in the shape of the lens, brought about by the energy of the contracting muscle.

In the normal eye, during the passive condition, the rays coming from infinity, and there-
fore parallel (which are dotted in fig. 541), are focussed upon the retina at /. If rays coming
from a distance of 5 inches (p. 756)
are to be focussed, the whole avail-
able energy of the ciliary muscle must
be brought into play to allow the lens
to become more convex, so that the
rays may be brought to a focus at
* The energy of accommodation,
therefore, produces an optical effect in
as far as it increases the convexity
of the anterior surface of the passive
lens (A), by the amount indicated by Fie. 541
B. Practically, we may regard the Soh
matter as if a new convex lens (B) were added to the existing convex lens(A). What, therefore,
must be the foeal distance of the lens (B), in order that rays coming from the near point (5 inches)
may be focussed upon the retina at f? Evidently the lens B must make the diverging rays coming
from p, parallel, and then A can focus them at. Convex lenses cause those rays proceeding from
their focal points to pass out at the other side as parallel rays (§ 385, I.). Hence, in our case,
the lens must have a focal distance of 5 inches. The normal eye, therefore, with the far point
=o, and the near point=5 inches, has a power of accommodation equal to a lens of 5 inches

756 SPECTACLES.

i _ When the lens by the energy of accommodation is rendered more powerfully re-
Rees das tacrense (B) can seaily be eliminated by placing before the eye a concave lens
which possesses exactly the opposite optical effect of the increase of accommodation (B), Hence,
it is possible to indicate the power (force) of accommodation of the eye by a lens of a definite
focal distance, i.c., by the optical effect produced by the latter. Therefore, according to
Donders, the measure of the force of accommodation of the eye is the reciprocal value of the
focal distance of a concave lens, which, when placed before the accommodated eye, so refracts
the rays of light coming from the near point (p) as if they came from the far point.

Example.—We may calculate the force of the accommodation according to the following for-

mula a oo = i.c., the-force of accommodation, expressed as the dioptric value of a lens (of
x ? .

x inch focal digs neek is equal to the difference of the reciprocal values of the distances of the

near point (p) and of the far point (7) of the eye. In the emmetropic eye, as already mentioned,

: et at | res
p=5, r=. Its force of accommodation is therefore hal ag so that x=5, i.e., it is equal

: : : ae eae eae
to a lens of 5 inches focal distance. In a myopic eye, p=4, r=12, so that a ea 1.0.,¢=
6. Inanother myopic eye, with p=4 and r=20, then a~=5, which is a normal force of accom-
modation. Hence, it is evident that two different eyes, possessing a very different range of
accommodation, may nevertheless have the same force of accommodation. Example.—The one

: es |
eye has p=4, r=, the other, p=2, r=4. In both cases, ee |
modation of both eyes is equal to the dioptric value of a lens of 4 inches focal distance. Con-
versely, two eyes may have the same range of accommodation, and yet their force of accommo-
dation be very unequal. Example.—The one eye has p=3, r=6 ; the other p=6, r=9. Both,
therefore, have a range of accommodation of 3 inches. For these, the force of accommodation,

on ee x=6; and kee x= 18.
x 6

so that the force of accom-

Relation of range to force of accommodation.—The general law is, that, the ranges of
accommodation of two eyes being equally great, then their forces of accommodation are equal,
provided that their near points are the same. If the ranges of accommodation for both eyes
are equally great, but their near points unequal, then the forces of accommodation are also un-
equal—the latter being greater in the eyes with the smallest near point. This is due to the
fact that every difference of distance meav a lens has a much greater effect upon the image as
compared with differences in the distance far from a lens. The emmetropic eye can see dis-
tinctly objects at 60 to 70 metres, and even to infinity, without accommodation.

While p and r may be directly estimated in the emmetropic and myopic eyes, this is impos-
sible with the hypermetropic (long-sighted) eye. The far point in the latter is negative ; indeed,
in very pronounced hypermetropia even the near point may be negative. The far point may
be estimated by making the hypermetropic eye practically a normal eye by using suitable
convex lenses. The relative near point may then be determined by means of the lens.

Even from the 15th kis onwards, the power of accommodation is generally diminished for
near objects—perhaps this is due to a diminution of the elasticity of the lens (Donders).

390. SPECTACLES. —The focal distance of concave (diverging), as well as convex (converg-
ing) spectacles, depends upon the refractive index of the glass (usually 3 : 2), and on the length
of the radius of curvature. If the curvature of both sides of the lens is the same (biconcave or
biconvex), then, with the ordinary refractive index of glass, the focal distance is the same as the
radius of curvature. If one surface of the lens is plane, then the focal distance is twice as
great as the radius of the spherical surface. Spectacles are arranged according to their focal
distance in inches, but a lens of shorter focal distance than 1 inch is generally not used. They
may also be arranged according to their refractive power. In this case, the refractive power of
a lens of 1 inch focus is taken as the unit. A lens of 2 inches focus refracts light only
half as much as the unit measure of 1 inch focus; a lens of 3 inches focus refracts $ as
strongly, &c. This is the case both with convex and concave lenses, the latter, of course,
having a negative focal distance ; thus, ‘

eer! are es hee as strongly as the concave lens of 1 inch (negative) focal distance.

es.—Having determined the near point in a myopic eye, of course we
require to render parallel the divergent rays coming from the far point, just as if they came
from infinity. This is done by selecting a concave lens of the focal distance of the far point.
The greatest distance is the far point of the emmetropic eye. Suppose a myopic eye with a far

point of 6 inches, then such a Pte requires a concave lens of 6 inches focus to enable him to
see distinctly at the test di

at tl tance. Thus, in a myopic eye, the distance of the far point
from the eye is directly equal to the focus of the (weakest) concave lens, which enables one to
see distinctly objects at the greatest distance. These lenses generally have the same num

as the spectacles required to correct the defect. Example,—A myopic eye with a far point of

concave—4,” indicates that a concave lens diverges

i

DIOPTRIC—CHROMATIC ABERRATION. | 757

8 inches requires a concave lens of 8 inches focus, 7.¢., the concave spectacles No. 8. For the
hypermetropic (long-sighted) eye, the focal distance of the strongest convex lens, which enables
the hypermetropic eye to see the most distant objects distinctly, is at the same time the distance

' of the far point from the eye. Example.—A hypermetropic eye which can see the most distant

objects with the aid of a convex lens of 12 inches focus has a far point of 12; the proper

spectacles are convex No. 12. ee

[Diopter or Dioptric.—The focal length of a lens used to be expressed in inches ; and as the
unit was taken as 1 inch, necessarily all weaker lenses were expressed in fractions of an inch.
In the method advocated by Donders, the standard is a lens of a focal distance of 1 metre
(39°370 English inches, about 40 inches), and this unit is called a dioptric. Thus, the standard
is a weak lens, so that the stronger lenses are multiples of this. Hence, a lens of 2 dioptrics=
one of about 20 inches focus ; 10 dioptrics=4 inches focus ; and so on. The lenses are num-
bered from No. 1, z.¢., 1 dioptric onwards. It is convenient to use signs instead of the words
convex and concave. For convex the sign plus + is used, and for concave the sign minus —.
Thus a + 4°0 means a convex lens of 4 dioptrics, and a — 4°0=a concave lens of 4 dioptrics. ]

In all cases of myopia or hypermetropia, the person ought to wear the proper spectacles. In
a myopic eye, when the far point is still more than 5 inches, the patient ought always to wear
spectacles ; but generally the working distance, ¢.g., for reading, writing, and for handicrafts, is
about 12 inches from the eye. If the person desires to do finer work (etching, drawing), requir-
ing the object to be brought nearer to the eye, so as to obtain a larger image upon the retina,
then he should either remove the spectacles altogether or use a weaker pair.

The hypermetropic person ought to wear his convex spectacles when looking at a near object,
and especially when the illumination is feeble, because then, owing to the dilatation of the
pupil, the diffusion circles of the eye tend to become very pronounced. It is advisable to wear
at first convex spectacles, which are slightly too strong. Cylindrical lenses are referred
to under Astigmatism. Spectacles provided with dull-coloured or blue glasses are used to
protect the retina when the light is too intense. Stenopaic spectacles are narrow diaphragms
placed in the front of the eye, which cause it to move in a definite direction in order to see
through the opening of the diaphragm.

391. CHROMATIC AND SPHERICAL ABERRATION, ASTIGMATISM.
—Chromatic Aberration.—All the rays of white light, which undergo refraction,
are at the same time broken up by dispersion into a bundle of rays which, when
they are received on a screen, form a spectrum. ‘This is due to the fact that the
different colours of the spectrum possess different degrees of refrangibility. The
violet rays are refracted most strongly ; the red rays least.

A white point on a black ground does not form a sharp simple image on the retina, but many
coloured points appear after each other. If the eye is accommodated so strongly as to focus
the violet rays to a sharp image, then all the other colours must form concentric diffusion
circles, which become larger towards the red. In the centre of all the circles, where all
the colours of the spectrum are superposed, a white point is produced by their mixture,
while around it are placed the coloured circles. The distance of the focus of the red rays
from that of the violet in the eye=0°58 to 0°62 mm. The focal distance for red is, accord-
ing to v. Helmholtz, for the reduced eye, 20°524 mm.; for violet, 20°'140 mm. Thus, the
near and far points for violet light are nearer each other than in the case of red light ; white
objects, therefore, appear reddish when beyond the far point, but when nearer than the near
point they are violet. Hence, the eye must accommodate more strongly for red rays than for
violet, so that we judge red objects to be nearer us than violet objects placed at an equal
distance (Briicke).

Monochromatic, or Spherical Aberration.—Apart from the decomposition or dispersion of
white light into its components—the rays of white light, proceeding from a point if transmitted
through refractive spherical surfaces—we find.that, before the rays are again brought to a focus,
the marginal rays are more strongly refracted than those passing through the central parts of
the lens. Hence, there is not one focus butmany. In the eye this defect is naturally corrected
by the iris, which, acting as a diaphragm, cuts off the marginal rays (fig. 531), especially when
the lens is most convex, when the pupil also is most contracted. In addition, the margin of
the lens has less refractive power than the central substance ; lastly, the margins of the refractive
spherical surfaces of the eye are less curved towards their margins than the parts lying nearer
to the optical axis. Compare the form of the cornea (p. 733) and the lens (p. 740).

Imperfect Centring of the Refractive Surfaces.—-The sharp projection of an image is some-
what interfered with by the fact that the refractive surfaces are not exactly centred (Briicke),
Thus, the vertex of the cornea is not exactly in the termination of the optic axis ; the vertices
of both surfaces of the lens, and even the different layers of the lens itself, are not exactly in
the or axis. The variations, however, and the disturbances produced thereby are very small
indeed.

758 ASTIGMATISM.

Astigmatism. —When the curvature of the refractive surfaces of the eye is unequally
great in its different meridians, of course the rays of light cannot be united or focussed in one .
int. Generally, in such cases, the cornea is more curved in its vertical meridian and least in .
the horizontal (as is shown by ophthalmometric measurements, p. 748). The rays ing |
through the vertical meridian come to a focus, first, in a horizontal focal line ; while the rays
entering horizontally unite afterwards in a vertical line. |, There is thus no common focus for
the light rays in the eye ; hence the name “‘astigmatismn. The lens also is unequally curved
in its meridians, but it is the reverse of the cornea ; consequently, a part of the inequality of
the curvature of the cornea is thereby compensated, and only a part of it affects the rays of
light. The emmetropic eye has a very slight degree of this inequality (normal astigmatism).
If two very fine lines of equal thickness be drawn on white paper, so as to intersect each other
at right angles, it will be found that, in order to see the horizontal line quite sharply, the paper
must be brought slightly nearer to the eye, than when we focus the vertical line. When the
inequality of curvature of the meridians 1s considerable, of course exact vision is no longer
ssible.
M TFig. 542 shows the effect of an astigmatic surface on the rays of light. Let a b cd be such
a surface, and suppose diverging rays to proceed from f. The rays passing through ¢ d come to

&------

oa i
Fig. 542.
Action of an astigmatic surface on a cone of light (Fost).

a focus at /,, while those passing through the vertical meridian are focussed at f, The outline \
of the cone of rays between a bc d and f, varies, as shown in the figure. Ata certain part it
is oval, with its axis vertical, at another the long axis of the oval is horizontal, while at other
places it is circular, or the rays are focussed in a horizontal or vertical line. ]

Correction.—This condition is corrected by a cylindrical lens, 7.¢., a lens so cut as to be
without curvature in one direction, while in the other direction (vertical to the former) it is
curved. The lens is placed in front of the eye, so that the direction of its curvature coincides
with the direction of least curvature of the eye (v. Helmholtz, Knapp, Donders).
The section C a hed of the cylindrical lens (fig. 543) represents a plano-con-
vex, the section C a B y 5, a concavo-convex lens.

[Test.—Draw two lines of equal thickness at right angles to each other. An
astigmatic person cannot see both lines with equal distinctness at the same
time, one line will appear thicker than the other. Or, a series of lines radiatin
from a centre may be used (astigmatic clock) when that line which is paralle
~| to the astigmatic meridian will be seen most distinctly ; while, with the ver-

ee

:

ra Me

Cc} | tical meridian most curved, it would be the vertical line. ]
Irregular Astigmatism.—Owing to the radiate arrangement of the fibres in
the interior of the crystalline lens, and in consequence of the unequal course
ad | is of the fibres within the different parts of one and the same neridian of the lens,

the rays of light passing through one meridian of the lens, cannot all be
brought to one focus. Hence, we do not obtain a distinct sharp image of
distant luminous points, such as stars or street lamps, but we see a radiate
c jagged figure provided with rays. The same obtains on holding a piece of card-
Fig. 543. yard with a small hole in it towards the light, at a distance from the eye
Cylindrical slightly greater than the far point. Slight degrees of this irregular astigma-
glasses for a- tism are normal, but when it is highly developed it greatly interferes with
stigmatism. Vision, by forming several foci of an object instead of one (Polyopia monocu-
laris), Of course this condition cannot obtain in an eye devoid of a lens,

392. IRIS.—Functions.—1. The iris acts like a diaphragm in an optical
apparatus by cutting off the marginal rays, which, if they entered the eye, would
cause spherical aberration, and thus produce indistinct vision (fig. 531). co
_ 2. As the pupil contracts strongly in a bright light, and dilates when the light
is feeble, it regulates the amount of light entering the eye ; thus, fewer rays enter
the eye when the light is strong than when it is feeble. Josie

=
S wa 4

MOVEMENTS OF THE IRIS. 759

3. To a certain extent it supports the action of the ciliary muscle.

Muscles and Nerves.—The iris is usually described as being provided with two
sets of muscular fibres—the sphincter, which immediately surrounds the pupil and
is supplied by the oculomotorius (§ 345, 2), and the dilator pupille (p. 736),
supplied chiefly by the cervical sympathetic (§ 356, A, 1), and the trigeminus
(§ 347, 3). Both muscles stand in an antagonistic relation to each other (§ 345),
the pupil dilates moderately after section or paralysis of the oculomotorius, owing
to the contraction of the dilator fibres which are supplied by the cervical sym-
pathetic ; conversely, the pupil contracts when the sympathetic is divided or
extirpated (Petit, 1727). When both nerves are stimulated simultaneously, the
pupil contracts, so that the excitability of the oculomotorius overcomes the sym-
pathetic.

[The existence of a dilator pupille muscle is not universally recognised, and in fact some
observers doubt its existence. The muscular nature of the radial fibres in the posterior limiting
membrane of the iris is denied by Griinhagen, while Koganei regards these as in no case
muscular, and the dilating fibres as represented by fibres radiating from the iris. These fibres
are well-developed in birds and the otter, exist in traces in the rabbit, and are absent in man.
Gaskell points out that in this case the size of the pupil must in part depend on the elasticity
of the radial fibres of the iris, while the dilator nerve-fibres must act on the sphincter fibres,
causing them to relax. Gaskell groups the sphincter of the iris with those muscles ‘‘ supplied
by two nerves of opposite character, the one motor, the other inhibitory.” The dilatation of
the pupil caused by stimulation of the cervical sympathetic is usually explained by the
hypothesis that this nerve contains motor fibres, which act on the dilator fibres. Griinhagen
thought that it might be due chiefly to the constriction of the blood-vessels of the iris;
Gaskell suggests that the nerve acts on the sphincter muscle, and is the inhibitory nerve of
that muscle, dilatation taking place because the sphincter is normally in a condition of tonic
contraction, and also because the posterior limiting membrane is elastic. ]

Nerves.—Arnstein and A. Meyer have studied the mode of termination of the nerve-fibres in
the iris. All the medullated nerve-fibres lose their white sheaths after a time ; most of the
fibres (motor) in the region of the sphincter consist of naked bundles of fibrils. A network of
very delicate sensory nerves lies under the anterior epithelium. Numerous fibrils pass to the
capillaries and arteries as vaso-motor nerves. [Many ganglionic cells are intercalated in the
course of the fibres. ]

Movements of the iris occur under the following conditions :—

1, Action of light on the retina causes, (according to its intensity and amount), a correspond-
ing contraction of the pupil; the same effect is produced by stimulation of the optic nerve
itself (Herbert Mayo, + 1852). This movement is a reflex act, [the afferent nerve being the
optic and the efferent the oculomotorius ; the impulse is transferred from the former to the
latter in a centre situated somewhere below the corpora quadrigemina (fig. 544, C)]. The
older observers locate the centre in the corpora quadrigemina, the recent observers in the
medulla oblongata (p. 660). Both pupils always react, although only one retina be stimulated ;
generally under normal circumstances both contract to the same extent (Donders), owing to
the intercentral communication [coupling] of the two pupillo-constricting centres. [This is
called consensual contraction of the pupil.] After section of the optic nerve the pupil dilates,
en te section of the oculomotorius no longer produces any further dilatation

noll), .

2. The centre for the dilator fibres of the pupil (pupillo-dilating centre) is excited by
dyspneic blood (§ 367, 8). If the dyspnea ultimately’ passes into asphyxia, the dilatation of

the pupil diminishes. Of course, if the peripheral dilating fibres (§ 247, 3) [e.g., the ,
_ sympathetic nerve in the neck] be previously divided, this effect cannot take place, as the

dyspneeic blood acts on the centre and not on the nerve-fibres.

3. The centre, as well as the subordinate ‘‘ cilio-spinal region”’ of the spinal cord (§ 362, 1),
is also capable of being excited reflexly ; painful stimulation of sensory nerves, in addition to
causing protrusion of the eyeballs (§ 347), a fact proved in the case of persons subjected to
torture, produces dilatation of the pupils (Arndt, Bernard, Westphal, Luchsinger); while a
similar effect is caused by labour pains, a loud call in the ear, stimulation of the nerves of the
sexual organs, and even by slight tactile impressions (Fod and Schiff). According to Bechterew,
the foregoing results are due to inhibition of the light-reflex in the sense expressed in § 361, 3.

4. The condition of the blood-vessels of the iris influences the size of the pupil ; all condi-
tions causing injection or congestion of these vessels contract the pupil, all Sots diminish-

return of venous blood from the head, momentarily by every pulse-beat, owing to the diastolic
filling of the arteries ; diminution of the intraocular pressure, e.g., after puncture of the anterior

ae

- ing them dilate it. .The pupil, therefore, is contracted by forced expiration, which prevents the |

760 ACTION OF DRUGS ON THE PUPIL.

, because, owing to the diminished intraocular pressure, there is less resistance to the
ona h blood into ihe blood-vessels of the iris (Hensen and Véolckers); paralysis of the vaso- .
motor fibres of the iris (§ 347, 2). Conversely, the pupil is dilated by conditions the reverse of
“those already mentioned, and also by strong muscular exertion, whereby blood flows freely into
the dilated muscular blood-vessels ; also, when death takes place. The condition of the filling
of the bleod-vessels also explains the fact, that the pupil dilated with atropin becomes smaller
when a part of the sympathetic in the upper cervical ganglion, carrying the vaso-motor fibres
of the iris, is excised ; also, that after extirpation of this ganglion, atropin always causes a less
diminution of the pupil on this side. The fact that when the pupil is amend | dilated by
stimulation of the sympathetic, it is further dilated by atropin, is due to a diminished injection
of the blood-vessels of the iris. If an animal with its pupils dilated with atropin be rapidly
hled, the pupils contract, owing to the anemic stimulation of the origin of the oculomotorius
(Moriggia). The dilatation of the pupils observed in cases of neuralgia of the trigeminus, is
partly due to the stimulation of the dilating fibres, partly to the stimulation of the vaso-motor
fibres of the iris (§ 347, 2).

5. Contraction of the pupil occurs as an associated movement, during accommodation for a
near object (p. 752, 5), and when the eyeballs are rotated inwards, which is the case during
sleep (p. 685). Conversely, intense movements of the iris, caused by variations in the bright-
ness of dazzling illumination, ¢.g., of the electric light, are followed by disturbing associated
movements of the ciliary muscle (Ljubinsky). In certain movements discharged from the
medulla oblongata (forced respiration, chewing, swallowing, vomiting), dilatation of the pupil
occurs as a kind of associated movement.

[Argyll Robertson Pupil.—In this condition the pupil does not contract to light, mies.
it contracts when the eye is accommodated for a near object, vision usually being normal. The
lesion is situated in those structures connecting
the afferent and efferent fibres at their central
ends (at A in fig. 544), 7@.e., the connection
between the corpora quadrigemina and the oculo-
motorius. It is most frequently found in loco-
motor ataxia, although it also occurs in progres-
sive paralysis of the insane. ]

Direct stimulation at the margin of the cornea
causes dilatation of the pupil (2. H. Weber); in
fact, direct stimulation of circumscribed areas of
the margin of the iris causes partial contraction
of the dilator fibres (Bernstein and Dogiel).
Stimulation near the centre of the cornea con-
‘ tracts the pupil (Z. H. Weber). In addition,
we must assume that the iris itself contains ele-
ments that influence the diameter of the pupil
(Sig. Mayer and Pribram).

Our knowledge of the action of poisons on the

iris is still very obscure. Those substances which

\ ne dilate the pupil are called mydriatics, ¢.g.,

M atropin, homatropin, duboisin, daturin, and hyo-

scyamin. They act chiefly by paralysing the

oculomotorius. But, in addition, there must be

N also an effect upon the dilating fibres, for after

uv complete paralysis (section) of the oculomotorius,

Fig, 544. the moderate dilatation of the pupil thereby

= produced (§ 345, 5) is still further increased by

atropin. Minimal doses of atropin contract the

pupil, owing to stimulation of the pupillo-
H, oculomotor (sphincter) roots; I, sym- constrictor fibres ; enormous doses cause m erate —
athetio. (dilator): ‘Ki aubetiot cools dilatation of the pupil in consequence of paralysis

+ N.O posterior Sontat Al meat Vaio of the dilating as well as of the constricting

; ausing pupillary immobility ea probable nerve-fibres. Atropin acts after destruction of

seat of lesion, causing myosis : the ciliary [ophthalmic] ganglion (Hensen and

: — Volckers) [and division of all the nerves except
the optic], and in the excised eye (De Ruyter), [so that atropin is a local mydriatic.
In moderate doses it paralyses the nervous terminations of the 3rd nerve (but not in birds
whose iris contains striped muscle), and in larger doses it also paralyses the muscular fibres].
(Cocaine, or cucaine, is obtained from the leaves of Erythroxylon coca. When applied locally
it acts as a powerful local anesthetic, and hence it is very useful for operations about |
the muco-cutaneous orifices. A 4 per cent. solution dro ped into the eye produces complete
insensibility of the cornea in a few minutes, It causes dilatation of the pupils, though i
react to light and to the movements of accommodation. It also causes temporary pant wale :

-
te nyt anal

o?s
0 oe nes,
op Hf
,
~ ao?

~, f
“y---ed
Ay .
oe

Scheme of the nerves of the iris. B, centrum
optici; C, oculomotor centre; D, dilator
centre (spinal); E, iris; G, optic nerve ;

aa

GORHAM’S PUPIL PHOTOMETER. 761

accommodation, a sensation of heaviness and coldness of the eyeball, enlargement of the
9g nae fissure, constriction of the small peripheral vessels, and slight lachrymation. ]

yotics are those substances which contract the pupil :—Physostigmin (= Eserin, the alka-
loid of Calabar bean), nicotin, pilocarpin, muscarin, morphia, according to some observers
(Griinhagen) cause stimulation of the oculomotorius, while others say they paralyse the sym-
pathetic. As these substances cause spasm of the ciliary muscle, it is supposed that the first of
these has an analogous action on the sphincter. It is probable that they paralyse the dilator
fibres and stimulate the oculomotor fibres. [Amongst local myotics, 7.¢., those which act on
the eye, some act on the muscular fibres of the iris, e.g., physostigmin or eserin, while others
act on the peripheral terminations of the 3rd nerve, ¢.g., pilocarpin, muscarin. Muscarin causes
very great contraction of the pupil from spasm of the circular fibres, due to its action on the
3rd nerve ; eserin, on the other hand, although contracting the pupil, also affects the dilator
fibres. The contraction of the pupil due to opium is central in its cause. ]

If the one pupil be contracted or dilated by these substances, the other pupil, conversely, is
dilated or contracted, owing to the change in the amount of light admitted into the eye into
which the poison has been introduced. The anesthetics (ether, chloroform, alcohol, &c.),
when they begin to cause stupor, contract the pupil, and when their action is intense they dilate
it (Dogiel). Chloroform, during the stage when it causes excitement (preceding the narcosis),
stimulates the centre for the dilatation of the pupil; after a time this centre is paralysed, so
that the pupil no longer dilates on the application of external stimuli. Thereafter the pupillo-
constrictor centre is stimulated, whereby the pupil may be contracted to the size of a pin’s
head ; ultimately this centre is paralysed, and the pupil becomes dilated.

Time for Movements of Iris.—The reflex dilatation of the pupil occurs slightly later than the
reflex contraction, the time in the two cases being 0°5 and 0°3 second respectively, after stimu-
lation by light (v. Vintschgaw). A certain time always elapses, until the iris, corresponding to
the strength of the stimulus of light exciting the retina, ‘‘adapts ” itself to produce a suitable
size of the pupil (Aubert). Contraction of the pupil occurs very rapidly after stimulation of the
oculomotorius in birds; in rabbits 0°89 second elapses after stimulation of the sympathetic,
until the dilatation begins (47/t).

Excised Eye.—Light causes contraction of the pupil in the excised eye of amphibians and
fishes (A7nold). Even the iris of the eel, when cut out and placed in normal saline solution,
contracts to light (Arnold), the green and blue rays being most active. Jncrease of the tempera-
twre causes mydriasis in the excised eye of the frog or eel, while cooling causes myosis (H.
Miiller),

[Size of the Pupil. —Jonathan Hutchinson recommends a pupilometer, consisting of a metal
plate perforated with a series of holes of different sizes. The smallest hole measures about } of
a line, and the largest is 44 lines. The plate is placed just below the patient’s eye, and the
hole is selected which corresponds with the size of the pupil. ]

[Gorham’s Pupil Photometer.—This ingenious instrument may be used as a pupilometer,
and also as a photometer. It consists of a piece of bronzed tubing 1°9 in. long and 1°5 in.
diameter (figs. 545 and 546). One end is closed by a disc or cap, which is pierced in its radii by

Fig, 545, Fig. 546.

Gorham’s pupil photometer. Fig. 545 shows the dise with a slot and two holes. Fig. 546
gives a side view with the diameter of the pupil marked on it. The upper end is closed by
the disc, while the lower end is open.

a series of holes at distances varying from ‘05 in. to ‘28 in. There isa slot in the cap which
allows one pair of holes to be visible at atime, while on the cylinder is engraved the linear
distance of each pair of holes. In using the instrument as a pupilometer, look through the
open end of the tube (the bottom in fig. 546), with both eyes open, towards a sheet of white
paper or the sky, when two dics of light will be seen. Then reyolve the lid or cap slowly until
the two white dics just touch one another at their edges. The decimal fraction opposite the two

762 ENTOPTICAL PHENOMENA.

apertures seen on the scale outside indicates the diameter of the pupil in 100ths. . an _
When using it as a photometer, it is assumed that the size of the pupil gives an index of the
intensity of the amount of light which influences the diameter of the pupil. ] sil

Intraocular Pressure.—The movements of the iris are always accompanied by variations of
the intraocular pressure. The muscles of the iris affect the intraocular aarp that om
dilatation of the pupil increases it, while contraction of the pupil diminishes it. The increased
or diminished tension can be felt when two fingers are pressed on the a of
the sympathetic increases, while its section diminishes the pressure. ree off rugs. er
dropped into the eye, after producing a short temporary diminution of t 1e ing: hor gay it;
eserin, after a primary increase, causes a diminution of the pressure (Graser ar dlzke).

393. ENTOPTICAL PHENOMENA. —Entoptical phenomena depend upon
the perception of objects present within the eyeball itself.

1. Shadows are formed upon the retina by different opaque bodies. In order to see them in
one’s own eye, proceed thus :—By means of a strong convex lens project a small we of a flame
pon a paper screen, prick a small opening through the image of the flame, and place one eye
at the other side of the screen, so that the illuminated puncture lies in the anterior focus of the
eve, i.¢., about 13 mm. in front of the cornea, As the rays proceeding from this point pass
parallel through the media of the eye, a diffuse bright. field of vision, surrounded by the black
inargins of the iris, is obtained. All dark bodies which lie in the course of the rays of light

Fig. 547.

Entoptical Shadows.

throw a shadow upon the retina, and appear as specks. There are various forms of these shadows
(fig. 547) :—

(a) The spectrum mucro-lacrimale, especially upon the margin of the eyelids, depending
upon particles of mucus, fat globules from the Meibomian glands, dust mixed with tears, causing
cloudy or drop-like retinal shadows, which are removed by winking.

(b) Folds in the cornea.—If the cornea be pressed laterally with the finger, wrinkled shadows,
due to temporary wrinkles in the cornea, are produced.

(c) Lens’ shadows. —Bead-like or dark specks, bright and star-like figures, the former due to
deposits on and in the lens, the latter to the radiate structure of the lens.

(d) Musce volitantes (J)cchales, 1690), like strings of beads, circles, groups of balls or pale
stripes, depend upon opaque particles (cells, disintegrating cells, granular fibres) in the vitreous
humour. They move about when the eye is moved rapidly. Listing (1845) showed that one may
determine pretty accurately the position of these objects. Whilst making the observation upon
one’s own eyes, raise or depress the source of light ; those shadows which are caused by bodies
on a level with the pupil retain their relative positions in the bright fields of vision. Shadows
which appear to move in the same direction as the source of light are caused by bodies which
lie in front of the plane of the pupil—those, however, which appear to move in the opposite
direction depend upon objects behind the plane of the pupil.

2. Purkinje’s figtre (1819) depends upon the blood-vessels within the retina, which cast a
shadow upon the most external layer of the retina, viz., upon the rods and cones, these being
the parts acted upon by light. In ordinary vision we do not observe these shadows. Accord-
ing to v. Helmholtz, this is due to the fact that the sensibility of the shaded parts of the retina
is greater, and their excitability is less exhausted, than all the other parts of the retina. As
soon, however, as we change the position of the shadow of the blood-vessels, instead of being
directly behind, so that the blood-vessels come to lie more Jaterally and behind them, #.¢., upon
places which do not receive shadows from the blood-vessels when the rays of light pass through
the eye in the ordinary way, then the figure of the blood-vessels becomes apparent at once. All
that is necessary is to cause the light to enter the eyeball obliquely. Method. (1) This may
be done by passing an intense light through the sclerotic, e.g., by throwing upon the sclerotic
a small, bright, luminous image from a source of light. On moving the source of light, the

—— —— a

ENTOPTICAL PHENOMENA. 763

figure of the blood-vessels moves in the same direction. (2) Look directly upwards to the sky,
wink with the upper eyelid drooping, so that for a moment, corresponding to the act of winking,
rays of light enter obliquely the lowest part of the pupils. (3) Look through a small aperture
towards a bright sky, and move the aperture rapidly to and fro, so that from both sides of the
blood-vessels shadows fall rapidly upon the nearest series of rods and cones. (4) In a darkened
room look straight ahead, and move a light to and fro close under the eyes. Occasionally,
whilst performing this experiment, one may see the macula lutea as a non-vascular shaded de-
pression, and, owing to the inversion of the objects, it lies on the inner side of the entrance of
the optic nerve.

3. Movements of the blood-corpuscles in the retinal capillaries.—-On looking, without
accommodating the eye, towards a large bright surface, or through a dark blue glass towards
the sun, we see bright spots, like points, forming longer or shorter chains, moving in tortuous
paths. The phenomenon is, perhaps, caused by the red blood-corpuscles (in the capillaries
posterior to the external granular layer) acting as small light-collecting concave discs, concen-
trating the light falling upon them from bright surfaces, and throwing it upon the rods of the
retina. Each corpuscle must be in a special position; should it rotate, the phenomenon
disappears. Vierordt, who projected the movement upon a screen, calculated, from the
velocity of their motion, the velocity of the blood-stream in the retinal capillaries as equal to
0°5 to 0°75 mm. in a second, which corresponds very closely with the results obtained directly
in other capillaries by E. H. Weber and Volkmann (§ 90, 4). When the carotids are com-
pressed, the movement is slower on freeing them from the compression ; during short forced
expirations the movement is accelerated (Landois).

4. The entoptical pulse (§ 79, 2) depends upon the pulsating arteries irritating mechanically
the rods lying outside them.

5. Pressure Phosphenes.—Pressure applied to the eye causes a series of phenomena :—(q@)
Partial pressure upon the eyeball causes the so-called illuminated ‘‘pressure-picture” or
phosphene, which was known to Aristotle. As the impression upon the retina is referred to
something outside the eye, the phosphene is always perceived on the side of the field of vision
opposite to where the pressure, affects the retina, ¢.g., pressure upon the outer surface of the
eyeball causes the flash of light to appear on the inner side. If the retina is not well lighted,
the phosphene appears luminous; if the retina is well lighted, it appears as a dark speck,
within which the visual perception is momentarily abolished. (0) If a uniform pressure be
applied to the eyeball continuously from before backwards, as Purkinje pointed out, after some
time there appear in the field of vision very sparkling variable figures, which perform a wonderful
fantastic play, and often resemble the sparkling effects obtained in a kaleidoscope (v. Helm-
holtz), and are probably comparable to the feeling of formication produced by pressure upon sen-
sory nerves (‘‘sleeping of the limbs”). (c) By applying equable and continued pressure,
Steinbach aud Purkinje observed a network with moving contents of a bluish-silvery colour,
which seemed to correspond to the retinal voins. Vierordt and Laiblin observed the branching
of the blood-vessels of the choroid as a red network upon a black ground. (d) According to
Houdin, we may detect the position of the yellow spot by pressure upon the eyeball.

6. The entrance of the optic nerve may be detected on moving the eyes rapidly backwards,
and especially inwards, as a fiery ring or semicircle about the size of a pea. Probably, owing
to the movement of the retina, the entrance of the optic nerve is stimulated mechanically by
the rapid bending. Purkinje and others observed that the ring remained persistent on turning
the eye strongly inwards. If the retina be brightly illuminated, the ring appears dark, and
when the field of vision is coloured, the ring has a different tint. If Purkinje’s figure be pro-
duced at the same time, one may observe that the vascular trunk proceeds trom this ring—a
proof that the ring corresponds to the entrance of the optic nerve (Landois).

7, Accommodation Spot.—On accommodating the eye strongly towards a white surface,
there appears in the middle a small, bright, trembling shimmer, and in its centre a coarse
brown speck, about the size of a pea, is seen (Purkinje). If pressure be applied externally to
the eyeball, this speck becomes more distinct. After having once observed the phenomenon,
occasionally on pressing laterally upon the opened eye we may see it as a bright speck ‘in the
field of vision—another proof that the intraocular pressure is increased during accommodation.

8. Mechanical Optical Stimulation.—On dividing the optic nerve in man, as in extirpation
of the eyeball, a flash of light is observed at the moment of section by the person operated on.
The section of the nerve-fibres themselves is painless, but section of the sheaths is painful.

9. The accommodation phosphene is the occurrence of a fiery ring at the periphery of the
field of vision, seen on suddenly bringing the eyes to rest after accommodating for a long time
in the dark (Purkinje). The sudden tension of the zonule of Zinn resulting from the relaxation
causes a mechanieal stretching of the outermost part of the margin of the retina, or it may be of
a part of the retina behind this. Purkinje observed the phenomenon after suddenly relaxing
the pressure on the eye.

10. Electrical Phenomena.—Electrical currents, when applied to the eye, cause a strong
flash of light over the whole field of vision. One pole of the battery may be placed on the
under eyelid and the other on the neck. The flash at closing [making] the current is strongest

764 ILLUMINATION OF THE EYE.

with an ascending current, that with opening [breaking] the current with a descending current.
If a uniform continuous ascending current be transmitted through the closed eyes, the dark dise
of the elevation at the entrance of the optic nerve appears in a whitish-violet field of vision ;
with a descending current, the field of vision is reddish and dark, in which the position of the
optic nerve appears light blue (v. Helmholtz). If external colours are looked at simultaneously,
these colours blend to form a violet or yellow with the colours looked at (Schelske). During
the passage of the ascending current we see external objects indistinctly and smaller when the
eyes are open; while with the descending current they are /arger and more distinct (Ritter).
Sometimés the position of the macula lutea appears dark on a bright ground, or the reverse,
according to the direction of the current. If the current be opened [broken] the phenomena
are reversed (§ 335), and the eye soon returns to rest.

11. The yellow spot appears sometimes as a dark circle when there is a uniform blue illumi-
nation. In a strong light the position of the yellow spot is surrounded by a bright area, twice
or thrice as large, called ‘‘ Léwe’s ring.” [Clerk-Maxwell’s Experiment.—On looking through
a solution of chrome-alum in a bottle or vessel with parallel glass sides, we observe an oval
purplish spot in-the greenish colour of the alum. ‘This is due to the pigment of the yellow spot. ]

Haidinger’s Brushes, —On directing the eye towards a source of polarised light, ‘‘ Haidinger’s
polarised brushes” appear at the point of fixation. They are seen on looking through a Nicol’s
prism at a bright cloud (v. Helmholtz). They are bright and bluish on a surface, bounded by
two neighbouring hyperbola on a white field ; the dark bundle ne them is smallest in
the centre and yellow. Of the various colours of homogeneous light, blue alone shows the
brushes (Stokes). According to v. Helmholtz the seat of the phenomenon is the yellow spot,
and is due to the yellow-coloured elements of the yellow spot being slightly doubly refractive,
while at one part they absorb more, at another less, of the rays entering the eye.

12. Lastly, there are the visual sensations depending on internal causes, ¢.g., increased
bounding of the blood through the retina, as during violent coughing, increased intraocular
pressure. Stimulation of the visual areas (§ 378, IV.) may produce spectra, which Cardanus
(1550), Goethe, Nicolai, and Johannes Miiller could produce voluntarily.

394. ILLUMINATION OF THE EYE._OPHTHALMOSCOPE.—The light
which enters the eye is partly absorbed by the black uveal pigment, and partly
again reflected from the eye, and always in the same direction in which the rays
entered the eye. By placing oneself in front of the eye of another person, of course
the head, being an opaque body, cuts off a large number of rays. Owing to the

position of the head, no rays of light can enter
x the eye; and of course none can be reflected
| back to the eye of the observer. Hence, the
@ eye of the person being examined always appears
black, because those rays which alone could be
reflected in the direction of the eye of the ob-

Fig. 548,
Arrangement for examining the eye of B. A, eye of observer ; x, source of light; S, 8, plate |
of glass directed obliquely, reflecting light into B. i
server are cut off. As soon, however, as we succeed in causing rays of light to
enter the eye at the same time and in the same direction in which we observe the

eye of another person, the fundus of the eye appears brightly illuminated. ‘
The following simple arrangement is sufficient for the purposes (fig. 548) :—Let B be the eye. <

Me Sy

THE OPHTHALMOSCOPE. 765.

of the patient, A that of the observer, and let a flame be placed at 2. The rays of light pro-
ceeding from 2 impinge upon the obliquely placed plate of glass (S,S), and are reflected in the
direction of the dotted lines into the eye (B). The fundus of the eye appears in this position
to be brightly illuminated in diffusion circles around b. As the observer (A) can see through

Fig. 549.

the obliquely placed glass plate (S, S), and in the same direction as the reflected rays (x, y), he
sees the retina around 0 brightly illuminated.

In order that this method be made available for practical purposes, we must, of course, be
able to distinguish the details, such as the blood-vessels of the fundus of the eye, the macula

P ce A
S1
a SR a [ A
Tt T
Ss
>
Fig. 550.

lutea, the entrance of the optic nerve, abnormalities of the retina, and the choroidal pigment,
&c. The following considerations show us how to proceed in order to accomplish this. As
already mentioned, and as fig. 531 shows, a small inverted image is formed on the retina (c, d@)
when we look at an object (A, B); conversely, according to the same dioptric law, an enlarged
inverted real image of a small distinct area of the retina (c, d—depending on the distance for
which the eye was accommodated) must be formed outside the eye (A, B).

P a

Fig. 551. _
‘i If ne fundus of this eye be sufficiently illuminated, this aerial image will be correspondingly
right. aa
In order to see the.individual parts of the retinal picture more distinctly, the observer must
accommodate his own eye for the position of this image. In such circumstances the eye of the
observer would be too near the observed eye. His eye when so accommodated is removed from

766 THE OPHTHALMOSCOPE,

the eye of the patient by his own visual distance, and by the visual distance of the patient. As
this distance is considerable, the individual small details of the fundus cannot be seen distinctly.
Further, owing to the contraction of the pupil of the patient, only a small area of the fundus
can be seen, and this only under a small visual angle, quite apart from the fact that it is often
impossible to accommodate for the real image of the fundus of the patient.

ence, the eye of the observer must be brought nearer to the eye of the patient. This may
be done in two ways :—(1) Either by placing in front of the eye of the patient a strong convex
lens (of 1 to 3 inches focus—fig. 549, C). This causes the retinal image to be nearer to the eye
(at B), owing to the strong lens refracting the rays of light. The observer (M) can come nearer
to the eye, and can still accommodate for the image of the fundus of the eye. (2) Ora concave
lens is placed immediately in front of the eye of the patient (fig. 550, 0). The rays of light
emerging from the eye of the patient (P) are either made parallel by the concave lens (0), and
are brought to a focus on the retina of the emmetropic observer (A); or, if the lens causes the
rays to diverge (fig. 551), an erect, virtual image is formed at a distance behind the eye of the
patient (at R). In these cases, also, the observer can go much nearer to the eye of the patient.

The ophthalmoscope invented by v. Helmholtz enables us to examine the whole
of the fundus of the eye.

[Direct Method.—Use a concave mirror of 20 centimetres focal distance, with a central open-
ing. Reflect a beam of light into the patient’s eye, where the rays cross in the vitreous and

Fig. 552. Fig. 553.

Fig. 552, —The entrance of the optic nerve with the adjacent parts of the fundus of the normal
by a, ring of connective-tissue ; b, choroidal ring; c, arteries ; d, veins; g, division of
the central artery ; h, division of the central vein ; L, lamina cribrosa ; t, temporal (outer)
side ; n, nasal (inner) side. Fig. 553.— Morton’s ophthalmoscope.

illuminate the fundus of the eye. These rays again pass out of the eye and reach the observer’s
eye through the central hole in the mirror. If the observer be emmetropic they come to a focus
on his retina. In this way all the parts of the retina are seen in their normal position, but
enlargéd. Hence, it is sometimes called the examination of the upright image. The eye of
the patient and observer must be at rest, i.¢., be negatively accommodated, while the mirror
‘must be brought as near as possible to the eye of the patient. ]
_ [Indirect Method, by which a more general view of the fundus is obtained. Throw the light
into the patient’s eye by an ophthalmoscopic mirror as above, but held ata distance of about 50
cm. (10 inches) from the patient’s eye. Hold a biconvex lens of 14 dioptrics focal length
vertically between the mirror and the patient’s eye (fig. 549), the observer looking through the
hole of the mirror, What he does see is an inverted aerial image at B. Only a small part of
the fundus oculi can be seen at one time.]

[The ophthalmoscope, besides being used for examining the interior of the eyeball, is of the
utmost use in determining the existence and amount of anomalies of refraction in the refrac-
tive media. For this purpose an ophthalmoscope requires to be provided with plus and sinus

lenses, which can be readily brought before the eye of the observer. This is readily done He =

an ingenious mechanism devised by Couper, and made use of in the handy students’ oph
moscope of Morton (fig. 553). The lenses are moved by a dvivinig: Whee! ‘ol the left. igure,

RETINOSCOPY. 767

while at the same time is indicated at a certain aperture the lens presented at the sight hole.
The instrument is also provided with a movable arrangement carrying a concave mirror at
either end. One of these mirrors is 10 inches in focus, and is used for indirect examination
and retinoscopy, while the other is of 3 inches focus for direct examination, and is fixed at an

le of 25°.
go vedas Oi ophthalmoscope is used also for this purpose. A beam of light is
reflected into the eye by the ophthalmoscopic mirror, and the play of light and shade on the
fundus oculi observed. A study of this is important in determining anomalies of refraction.
For the method, the student is referred to a text-book on ‘‘ Diseases of the Eye.’’] Rar

[Artificial Eye.—The student may practise the use of the ophthalmoscope on an artificial
eye, such as that of Frost (fig. 554) or Perrin.]_

Illumination.—In order to illuminate the interior of the eye, v. Helmholtz used several
plates of glass, placed behind each other, in the position of S, S, in fig. 548. Afterwards he
used a plane or concave mirror of 7 inches focus (fig. 549), with a hole in the centre. _ Fig. 552
shows the appearance of the fundus of the eye, as seen with the ophthalmoscope. In albinos
the fundus of the eye appears red, because light passes into the eye through the sclerotic and

ris

ieee eee
125 cepa
Fig. 554. Fig. 555,
Frost’s artificial eye, Action of the orthoscope.

uvea, which are devoid of pigment. Ifa diaphragm be placed over the eye, so that the pupil
alone is free, the eye appears black (Donders), ; .

Tapetum.—In many animals the eyes have a bright green lustre. These eyes have a special
layer, the tapetum, or the membrana versicolor of Fielding ; in carnivora it consists of cells,
in herbivora of fibres, placed between the capillaries of the choroid and the stroma of the uvea.
These structures exhibit interference-colours and reflect much light, so that the coloured lustre
appears in the eye.

blique illumination is used with advantage for investigating the anterior chamber. A
bright beam of light, condensed by a convex lens, is thrown laterally upon the cornea into the
eye, and so directed upon the point to be investigated as to illuminate it. A point so illumi-
nated, ¢.g., a part of the iris, may be examined from a distance by means of a lens, or even by
a microscope (Liebreich). | "

The Orthoscope,—Czermak constructed this instrument, in which the eye is placed under
water (fig. 555). It consists of a small glass trough with one.of its walls removed. The
margins of the open side are pressed firmly against the region of the eye. The eye and its sur-
roundings form, as it were, the sixth side of the trough, which is filled with water, so that the

768 EXPERIMENTS ON THE RETINA.

cornea is bathed therewith. As the refractive index of water is almost the same as the refrac-
tive index of the media of the eye, the rays of light pass into the eye in astral tht direction
without being refracted. Hence, objects in the anterior chamber can be seen directly, as if
they were not within the eye at all. Another advantage is that the objects can be brought
nearer to the eye of the observer. The rays of light emerging from the point (a) of the fundus,
if the eye were surrounded by air, would leave the eye as the parallel lines, d, c, b,c. Under
water, these rays, a, 6, continue in the direction a, b, as far as b, d, where they emer from
the water, and are bent from the perpendicular to d, e, d, e. The eye of the observer, looking
in the direction e, d, sees the point, a, nearer, viz., in the direction e, d, a’, lying at a.

395. ACTIVITY OF THE RETINA IN VISION.—I. Blind Spot.—The
rods and cones alone are the parts of the retina sensitive to light, they alone are
excited by the vibrations of the ether. This is confirmed by Mariotte’s experiment
(1688), which proves that the entrance of the optic nerve, where rods and cones
are absent, is devoid of visual sensibility. Hence it is spoken of as the “ blind
spot.”

: [Mariotte’s Experiment.—Make two marks, about 3 inches apart, upon paper
(fig. 556). Look at the cross with the right eye, keeping the left eye closed, and
hold the paper about a foot from the eye, when both the cross and the circle will

—

Fig. 556.

be seen. Gradually approximate the paper to the eye, keeping the open eye
steadily fixed on the cross ; at a certain moment the circle will disappear, and on
bringing the paper nearer to the eye it will reappear. The moment when the circle
disappears is when its image falls upon the entrance of the optic nerve. |

Position and Size.—The entrance of the optic nerve lies about 3°5 mm. internal to the
visual axis of the eyeball, in the retina. Its diameter is 1°8 mm. The apparent diameter of
the blind spot in the field of vision is in a horizontal direction 6° 56’—this lies 12° 35’ to
18° 55’ horizontally from the fixed point. Eleven full moons placed side by side would dis-
appear on the surface, and so would a human face at a distance of over 2 metres.

roofs.—The following facts prove that the entrance of the optic nerve is insensible to
light :—(1) Donders projected, by means of a mirror, the small image of a flame upon the
entrance of the optic nerve of another person, and the person had no sensation of light. But
a sensation of light was experienced, when the image of the flame was projected upon the
neighbouring parts of the retina. (2) On combining with Mariotte’s experiment the experiment
which causes entoptical phenomena at the entrance of the optic nerve, this coincides with the
blind spot (§ 393, 6 and 7).

Form of Blind Spot.—In order to determine the form and apparent size of the blind spot in
one’s own eye, fix the head at about 25 centimetres from a surface of white paper ; select a
small point on the latter and keep the eye directed towards it; then, starting from the
position of the blind spot, move a white feather in all directions over the paper ; whenever the
tip of the feather becomes visible, make a mark at this spot. The blind spot may be mapped
out in this way. It has an irregular, elliptical form from which processes proceed, due to the
equally non-sensitive origins of the large blood-vessels of the retina (Hweck). (Mariotte
concluded from his experiment that the choroid, which is perforated by the optic nerve, is the
membrane sensitive to light, as the nerves are nowhere absent from the retina.)

The blind spot causes no appreciable gap in the field of vision.—As this area is not excited .
74 light, a black spot cannot appear in the field of vision, for the sensation of black implies
the presence of retinal elements, which, however, are absent from the blind spot. The
circumstance, however, that in spite of the existence of, an inexcitable spot during vision, no
part of the field of vision appears to be wnoccupied, is due to a psychical action. The
unoceupied area of the field of vision, corresponding to the blind spot, is filled in according to
probability by a psychical process (Z. H. Weber). Hence, when a white point disa pears:
from a black surface, the whole surface appears to us black; a white surface, from which a
black poiut falls on the blind spot, appears quite white ; a page of print, grey throughout, &c.
According to the probabilities, certain parts are supplied—parts of a circle, the middle parts of
a long line, the central part of a cross. Such images, Towevel: as cannot be constructed

IMAGES FALLING ON THE RODS AND CONES. 769

according to the probabilities, are not perfected, ¢.g., the end of a line or a human face. In
other cases the condition known as “‘ contraction” of the field of vision tends to fill up the gap.
This will be evident on looking at the nine adjoining letters, so that

é disappears ; we no longer see the three letters on each side of it in b

straight lines, but 6, f, A, d are turned in towardse. The adjoining a C
parts of the field of vision seem to extend over and around the blind

spot, and thus help to compensate for the blind spot.

II. Optic Fibres Inexcitable to Light.—The layer of the Q (@) ff
Jibres of the optic nerve in the retina is not sensitive to light.

This is proved by the fact that, in the fovea centralis, which :
is the area of most acute vision, there are no nerve-fibres. g h 1
Further, Purkinje’s figure proves that, as the arteries of the

retina lie behind the optic fibres, the latter cannot be concerned in the perception
of the former.

III. Rods and Cones.—The outer segments of the rods and cones have rounded
outlines, and are packed close together ; but natural spaces must exist betweeu
them, corresponding to the spaces that must exist between groups of bodies with a
circular outline. These parts are insensible to light, so that a retinal image is com-
posed like a mosaic of round stones. The diameter of a cone in the yellow spot is
2 to 2°5 pw (M. Schultze). If twoimages of two small points, placed very near each
other, fall upon the retina, they will still be distinguished as distinct images, pro-
vided that both images fall upon two different cones. The two images on the
retina need only be 3-4-5°4 pw apart, in order that each may be seen separately,
for then the images still fall upon ¢wo adjoining cones. If the distance be dimin-
ished so very much that both images fall upon one cone, or one upon one cone and
the other upon the intermediate or cement substance, then only one image is per-
ceived. The images must be further apart in the peripheral portion of the retina ©
in order that they may be separately distinguished.

As the rounded end-surfaces of the cones do not lie exactly under each other, but are so
arranged that one series of circles is adapted to the interstices of the following series, this
explains why fine dark lines lying near each other appear to have alternating twists upon them,
. ap we images of these must fall upon the cones, at one time to the right, at another to the

eft.

IV. The fovea centralis is the region of most acute vision, where only cones are
present, and where they are very numerous and closely packed (fig. 521). The
cones are less numerous in the peripheral areas of the retina, and consequently vision
is much less acute in these regions. We may therefore conclude that the cones are
more important for vision than the rods. When we wish to see an object distinctly,
we involuntarily turn our eyes so that the retinal image falls upon the fovea
centralis. In doing this, we are said to “fiz” our eyes upon an object. The line
drawn from the fovea to the object is called the axis of vision (fig. 557, Sr). It
forms an angle of only 3°5-7° with the ‘optical axis” (O A), which unites the
centres of the spherical surfaces of the refractive media of the eye. The point of
intersection, of course, lies in the nodal point (An) of the lens (p. 770). The term
“direct vision ” is applied to vision when the direction of the axis of vision is in
line with the object, [7.¢., when the image of the object falls directly on the fovea
centralis. |

‘Indirect vision” occurs when the rays of light from an object fall upon the
peripheral parts of the retina. Indirect vision is much less acute than the direct.

To test the acuity of direct vision, draw two fine parallel lines close to each other, and
gradually remove them more and more from the eye, until both appear almost to unite and
form one line. . The size of the retinal image may be-ascertained by determining the distance
of the two lines from each other, and the distance of the lines from the eye, or, from the cor-
responding visual angle, which is generally from 60 to 90 seconds,

erimetry.—In order to test indirect vision, we may use the perimeter of Aubert and

Forster. The eye is placed opposite a fixed point, from which a semicircle proceeds, so that

the eye lies in the centre of it, As the semicircle rotates round the fixed point, on rotating the
“a 3.C

770 - M*HARDY’S PERIMETER.

former we can circumscribe the surface of a hemisphere, in the centre of which the eye is placed.
Proceeding from the fixed point, objects are placed upon semicircles, and are gradually pushed
more and more towards the periphery of the field of vision, until the object becomes indistinct,
and finally disappears. The process of testing is continued by placing the are successively in
the different meridians of the field of vision.

[M‘Hardy’s perimeter is a very convenient form (fig. 558). It consists of two uprights (C
and D), which are fixed to the opposite ends of a flat basal plate (A). C carries an arrangement
for supporting the patient’s head, while D carries the automatic arrangement for the perimetric

Fig. 557.

Horizontal section of the right eye. a, cornea; b, conjunctiva; ¢, sclerotic ; d, anterior
chamber containing the aqueous humour ; ¢, iris; ff’, pupil; g, posterior chamber ; J,
Petit’s canal; j, ciliary muscle; , corneo-scleral limit; 7, canal of Schlemm ; m, choroid ;
oo Be apie ore raat y ve optic nerve; g, nerve-sheaths ; p, nerve-fibres ; Ze,

ina cribrosa, e line indicates the optic axis; i ision ;
position of the fovea centralis. plc axis; Ar the arty Gene am

record, Both of these can be raised or depressed by the screws (G and 6), The patient’s chin
rests on the chin-rest (E), while in the mouth is iewed tandolt's biting fixation (1) which is
detachable. The position of the head can be altered by sliding F on L, which can be fixed in
any position by the screw (0). The porcelain button (i) just below the patient’s eye (7) is con-
nected with the adjustment of the ‘fixation point.” The automatic recording a

consists of a revolving quadrant (4, h), which describes a hemisphere round a horizontal .
passing ee the centre of the hollow male axle, turning in the female end of a, which is
ae rted by D. The quadrant can be fixed at any point by g. On the front concave surface
of the quadrant is fixed a circular white piece of ivory, representing the *‘ fixation vant, treat

, :

PRIESTLEY SMITH’S PERIMETER. 77%

which a needle projects, and which is the zero of the instrument. A carriage (7), in which the
test objects are placed, can be moved in the concave face of the quadrant by means of the milled
head (j), which moves the carriage by means of a tooth and pinion wheel. |

[When the milled head (7) is turned, it moves the carriage and two slides (& and /), the two
slides moving in the ratio of 2to1. The rate of the carriage is so adjusted that it travels ten
times faster than /, and five times faster than %. The pointer (p) is connected with these slides,
so that it moves when they move, and records its movements by piercing the record chart,
which is fixed in the double-faced frame (e). The frame for the record chart is hinged near c
to the upright (D). The frame, when upright, comes so near the pointer that the latter can
pierce a chart placed in the frame. The patient is directed to look at the “fixation point,”
which is merely a small ivory button placed in the imaginary axis of the hemisphere on the

cl

| | : ge es

NM
Fig. 558.

M‘Hardy’s perimeter. I, porcelain button; M, bit; E, for fixing the head; g, h, quadrant ;
0, fixation point ; p, pointer for piercing the record chart held in the frame (e) which moves
onc; D, upright supporting the quadrant and the automatic arrangement of slides (% and
1), which are moved by /.

front of the centre of the concave surface of the quadrant; the projecting needle-point (0) indi-
cates its position. This is the zero of the quadrant, and on each side of it the quadrant is
divided into 90°. ]

[In testing the field of vision, place the carriage so as to cover zero, adjust the eye for the
fixation point, and look steadily at it, when, if all is right, the pointer (py) ought to pierce the
centre of the chart. Move the carriage along the quadrant by 7 until it disappears from the
field of vision, and when it does so the pointer is made to pierce the chart. Make another
observation in another direction by altering the position of the quadrant, and go on doing so
until a complete record is obtained of the field of vision. Test the other eye in the same way.
The colour-field may be tested by using coloured papers in the carriage. }

[Priestley Smith’s perimeter (fig. 559).—The wooden knob on the left of the figure is placed
under the eyeof the patient, who stares at the fixed. point in the axis of the quadrant, which
can be moved in any meridian. The test object is a square piece of white paper, which is moved
along the quadrant. The chart is placed on the posterior surface of the hand-wheel and moves
with it, so that the meridians of the chart move with the quadrant. There is a scale behind
the hand-wheel corresponding with the circles on the chart, so that the observer can prick off
his observations directly. ]

772 PERIMETRIC CHARTS.

[Scotoma is the term applied to dimness or blindness in epee ye of the field of vision, |

which may be cen marginal, or in patches. }

The capacity for distinguishing colours <i-
minishes more rapidly at the periphery of the
retina, than that for distinguishing differences in
the brightness or intensity of light. — In fact, the
veriphery of the retina is slightly red blind.

he diminution is greater in the vertical meridian
of the eye than in the horizontal, and it dimin-
ishes with the distance from the fixation point
(Aubert and Forster). These observers also
state that, during accommodation for a distant
object, the diminution of the capacity to distin-
guish brightness and colour towards the peri-
phery of the lens, occurs more rapidly than with
near vision. The excitability of the retina for
colours and brightness is greater at a point
equally distant from the fovea centralis on the
temporal than on the nasal side of the eye
(Schon).

Perimetric Chart. —If the arc of the perimeter
(fig. 559) be divided into 90 degrees, beginning at
the fixation point (central point), and proceeding
to L and M (fig. 560); and if a series of con-
centric circles be inscribed on this, with the
point of fixation as their centre, we can con-
struct a topographical chart of the visual capa-
———— — city of the normal or healthy eye from the data
5Q __Priog 5 een obtained by the examination of the retina.

Doe Peo Ma nets pepeetee Fig. 560 is an example; the thick lines indi-
cate a diseased eye the corresponding thin lines a healthy eye. The continuous line indicates

en Gj

Fi

ao
>

Fig. 560.
Perimetric chart of a healthy and a diseased eye.

the limits for the perception of white; the interrupted line that for blue; the punctuated and

* —

RETINAL STIMULATION—OPTOGRAM. 773

interrupted line that for red; mis the blind spot. In the normal eye the limits for the perception
of colours are as under:—

White. Blue. | Red. Green.
Externally, : . , ; : . | 70°-88° 65° 60° 40°
Internally, . ‘ : : ; : . | 50°-60° 60° 50° 40°
Upwards, . : : : ; : . | 45°-55° 45° 40° 30°-35°
Downwards, : , : ; 3 : 65°-70° 60° 50° 35°

V. Specific Energy.—The rods and cones alone are endowed with what Johannes
Miiller called ‘‘ specific energy,” 2.e., they alone are set into activity by the ethereal
vibrations, to produce those impulses which result in vision. Mechanical and
electrical stimuli, however, when applied to any part of the course of the nervous
apparatus, produce visual phenomena. Mechanical stimuli are more intense stimuli
than light rays, as is shown by performing the dark pressure figure with the eyes
open (§ 393, 5, a), whereby the circulation in the retina is interfered with ; in the
region of pressure, we cannot see external objects which affect the retina uniformly
and continuously.

VI. The duration of the retinal stimulation must be exceedingly short, as the
electrical spark lasts only 0°000000868 second ; still, as a general rule, a shorter
time is required, the larger and brighter the object looked at. Alternate stimu-
lation with light, 17 to 18 times per minute, is perceived most intensely (Lriicke).
Further, an increase or diminution of 0°01 part of the intensity of the light is
perceptible (§ 383). A shorter time is required to perceive yellow than is required
for violet and red (Vierordt). The retina becomes more sensitive to light, after a
person has been kept in the dark for a long time, and also after repose during the
night. If light be allowed to act on the eyes for a long time, and especially if it
be intense, it causes fatigue of the retina, which begins sooner in the centre than
in the periphery of the organ (Aubert). At first the fatigue comes on rapidly and
afterwards develops more slowly—it is most marked in the morning (A. Jick).
The periphery of the retina is specially characterised by its capacity for distinguish-
ing movements (Lxner). |

VII. Visual Purple.—The mode of the action of light upon the end-organs of
the retina has already been referred to (p. 739) in connection with the “visual purple”
or rhodopsin (Boll, Kiihne). Kiihne showed that, by illuminating the retina, actual
pictures (e.g., the image of a window) could be produced on the retina, but they
gradually disappeared. From this point of view we might regard the retina as
comparable, to a certain extent, to the sensitive plate of a photographic apparatus.

Optogram.—The visual purple is formed by the pigment-epithelium of the retina. Perhaps
we might compare the process to a kind of secretion. The visual purple may be restored in a
retina by laying the latter upon living choroidal epithelium. The pigment disappears from
the mammalian retina by the action of light 60 times more rapidly than from the retina of the
frog. In a rabbit’s eye, whose pupil was dilated with atropin, Ewald and Kiihne obtained a
sharp picture or optogram of a bright object placed at a distance of 24 cm. from the eye—the
image was ‘‘ fixed” bya 4 per cent. solution of alum. Visual purple withstands all the oxidising
reagents ; zinc chloride, acetic acid, and corrosive sublimate change it into a yellow substance
—it becomes white only through the action of light; the dark heat-rays are without effect,
while it is decomposed above a temperature of 52°C. [As visual purple is absent from the
cones, and cones only are present in the fovea centralis, we cannot explain vision by optograms
formed by the visual purple. ]

VIII. Destruction of the rods and cones of the retina causes corresponding
dark spots in the field of vision.

396. PERCEPTION OF COLOURS. —Physical.—The vibrations of the light-ether are per-
ceived by the retina only within distinct limits. If a beam of white light, ¢.g., from the sun,
be transmitted through a prism, the light rays are refracted and dispersed, and a ‘‘ prismatic
spectrum” is obtained (fig. 17). White light contains rays of very different wave-lengths or
periods of vibration. The dark heat-rays, whose wave-length is 0°00194'mm., are refracted least
(Fizeau). ‘They do not act upon the retina, and are therefore invisible. They act, however,

774 PERCEPTION OF COLOURS.

r cent. of these rays is absorbed by the media of the eye
rauenhofer’s line, A, onwards, the oscillations of the light-
r :—Red with 481 billions of vibrations per second,
607, blue with 6538, indigo with 676, and violet
with 764 billion vibrations per second. The sensation of colour therefore depends on the
number of vibrations of the light-ether, just as the pitch of a note depends on the number of
vibrations of the sounding body (Newton, 1704; Hartley, 1772). Beyond the violet lie the
chemically active [actinic] rays of the spectrum. After cutting out all the spectrum, including |
the violet rays, v. Helmholtz succeeded in seeing the ultra-violet rays, w ich had a feeble
greyish-blue colour, The heat-rays in the coloured part of the spectrum are transmitted by the
media of the eye in the same way as through water. The existence of the ultra-violet rays is
best ascertained by the phenomenon of fluorescence. Von Helmholtz, on illuminating a solution
of sulphate of quinine with the ultra-violet rays, saw a bluish-white light proceeding from all
parts of the solution which were acted on by the ultra-violet rays. As the media of the eye them-
selves exhibit fluorescence (v. Helmholtz), they must increase the power of the retina to distin-
guish these rays. The ultra-violet rays are not largely absorbed by the media of the eye (Briicke).

In order that a colour be perceived, it is essential that a certain amount of light fall upon the
retina. Blue, when at the lowest degree of brightness, gives a colour sensation with an amount
of light which is sixteen times less than that required for red (Dobrowlosky).

Intensity of the Impression of Light.—While light of different periods of vibration applied
to the eye excites the different sensations of colour, the amplitude of the vibrations (height of
the waves) determines the intensity of the impression of light; just as the loudness of a note
(lepends on the amplitude of the vibrations of the sounding body. The sun’s light contains all
the rays which excite the sensation of colour in us, and when all these rays fall simultaneously .
upon the retina we experience the sensation of white. If the colours of the spectrum obtained
by means of a prism be reunited, white light is again obtained. If no vibrations of the light-
ether reach the retina, every sensation of light and colour is absent, but we can scarcely apply the
term black to this condition. It is rather the absence of sensation, such as, for example, is
the case when a beam of light falls on the skin of the back. This does not give the sensation
of black, but rather that of no sensation of light.

Simple and Mixed Colours.—We distinguish simple colours, ¢.g., those of the
spectrum. In order to perceive these, the retina must be excited (set into ae
by a distinct number of oscillations (see above). Further, we distinguish “ mixe
colours,” whose sensations are produced when the retina is excited by two or more |
simple colours, simultaneously or rapidly alternating. The most complex mixed }
colour is white, which is composed of a mixture of all the simple colours of the
spectrum, ;

_The “ complementary colours” areimportant. Any two colours which together |
give the sensation of white are complementary to each other. The “contrast colours ” |
are mentioned here merely to complete the list. They are closely related to the
complementary colours. Any two colours which, when mixed, supplement the
generally prevailing tone of the light, are contrast colours. When the sky is blue,
the two contrast colours must be bluish-white : with bright gaslight they must be
yellowish-white, and in pure white light of course all the complementary are the
same as the contrast colours (Briicke).

Methods of Mixing Colours,—1, Two solar spectra are projected upon a screen, and the
spectra are so arranged as to cause any one part of one spectrum to cover any part of. the other.
2. Look obliquely through a vertically arranged glass plate at a colour placed ‘behind. it.
Another colour is placed in Jront of the glass plate, so that its image is also reflected into the
eye of the observer ; thus, the light of one colour transmitted through the glass plate and the
reflected light from the other colour reach the eye simultaneously. [ bert’s Method. —This
is easily done by Lambert's method. Use coloured wafers and a slip of glass; place a red wafer
so a sheet of black paper, and about 3 inches behind it another blue one. Hold the plate of
glass midway and vertically between them, and so incline the glass that, while looking.t rough
it at the red wafer, a reflected image of the blue one will be projected into the eye in the same
direction as that of the red image, when we have the sensation of purple. ] elites
< A rotatory disc, with sectors of various colours, is rapidly othtnd in front of the eyes. On
roa dly rotating the coloured dise, the impressions produced by the individual colours are united
oman wast ae haere is If vine sotading disc, which yields, let us suppose, white, on mixin
ports BSayes eth ected in a rapidly rotating mirror, then the indi og

4, Place in front of each of the small holes in the cardboard used for Scheiner’s experiment i

upon sensory nerves. About 90
(Briicke and Knoblauch). From
ether excite the retina in the following orde
orange with 532, yellow with 563, green with

GEOMETRICAL COLOUR TABLE.

775

(fig. 537) two differently coloured pieces of glass ; the coloured rays of light passing through

‘the holes unite on the retina, and produce a mixed colour (Czermak).

Complementary Colours. —Investigation shows that the following colours of the spectrum are
complementary, 7.¢., every pair gives rise to white :—

Red and greenish-blue,
Yellow and indigo-blue,

Orange and Cyan-blue,

Greenish-yellow and violet,

while green has the compound complementary colour, purple (v. Helmholtz). —

The mixed colours may be determined from the following table.

At the top of the vertical

and horizontal columns are placed the simple colours ; the mixed colours occur where they
intersect the corresponding vertical and horizontal columns (Dk. =dark ; wh. = whitish) :—

Violet. Indigo. Cyan-blue. ee Green. | ace Yellow.
Red Purple Dk.-rose Wh.-rose White Wh.-yellow | Gold-yellow | Orange
Orange °* Dk.-rose Wh.-rose White Wh.-yellow | Yellow Yellow ies
r Yellow Wh.-rose White Wh.-green | Wh.-yellow | Gr.-yellow ae
Gr.-yellow White Wh.-green Wh.-green | Green. Ss
Green White-blue | Water-blue | Bl.-green ios
Bluish-green | Water-blue | Water-blue “Ss
Cyan-blue Indigo coe

The following results have been obtained from observations on the mixture of
colours :—

1. If two simple, but non-complementary, spectral colours be mixed with each
other, they give rise to a colour sensation, which may be represented by a colour
lying in the spectrum between both, and mixed with a certain quantity of white.
Hence we may produce every impression of mixed colours by a colour of the spec-
trum + white (Grassmap).

2. The less white the colours contain, the more “saturated ” they are said to
be ; the more white they contain, the more unsaturated do they appear. The
saturation of a colour diminishes with the intensity of the illumination.

Geometrical Colour Table.—Since the time of Newton, attempts have been made to construct
a so-called ‘‘ geometrical colour table,” which will enable any mixed colour to be readily found.
Fig. 561 shows such a colour table;
white is placed in the middle, and from Gr.
it to every point in the curve,—which is
marked with the names of the colours,
—suppose each colour to be so placed
that, proceeding from white, the colours
are arranged, beginning with the bright-
est tone, always followed by the most
saturated tone, until the pure saturated
spectral colour lies in the point of the
curve marked with the name of the
colour. The mixed colour, purple, is
placed between violet and red. In order
to determine from this table the mixed
colour of any two spectral colours, unite
the points of these colours by a straight
line. Suppose weights corresponding to
the units of intensity of these colours,
to be placed on both points of the curve
indicating colours, then the position of
the centre of gravity of both in the line
connecting the colours indicates the posi-
tion of the mixed colour in the table. The mixed colour of two spectral colours always lies in
the colour table in the straight line connecting the two colour points. Further, the impression
of the mixed colour corresponds to an intermediate spectral colour mixed with white. The
gor plementary colour of any spectral colour is found at once by making a line from the point
of this colour'through white, until it intersects the opposite margin of the colour table; the
point of intersection indicates the complementary colour. If pure white be produced by mixing
two complementary colours, the colour lying nearest white on the connecting line must be
specially strong, as then only would the centre of gravity of the lines uniting both colours lie
in the point marked white.

Fig. 561.
Geometrical colour cone or table.

776 YOUNG-HELMHOLTZ THEORY OF COLOUR SENSATION,

By means of the colour table we may ascertain the mixed colour of three or more colours.
For example, it is required to find the mixed colour resulting from the union of the point, a
(pale yellow), } (fairly saturated bluish-green), and ¢ (fairly saturated blue). On the three
points place weights corresponding to their intensities, and ascertain the centre of gravity of the
weight, a, b,c; it willlie at p. It is obvious, however, that the impression of this mixed
colour, whitish green-blue, can be produced by green-blue + white, so that p may be also the
centre of gravity of two ie pa which lie in the line connecting white and green-blue.

We may describe a triangle, V, Gr, R, about the colour table so as to enclose it completely.
The three fundamental or primary colours lie in the angles of this triangle, red, green, violet.
It is evident that each of the coloured impressions, 7.¢., any point of the colour table, may be
determined by placing weights corresponding to the intensity of the primary colowrs at the
angles of the triangle, so that the point of the colour table, or what is the same thing, the
desired mixed colour, is the centre of gravity of the triangle with its angles weighted as above.
The intensity of the three primary colours, in order to produce the mixed colour, must be re-
presented in the same proportion as the weights.

Theories.— Various theories have been proposed to account for colour sensation.

1. According to one theory, colour sensation is produced by one kind of element present in
the retina, being excited in different ways by light of different colours (oscillations of the light-
ether of different wave-lengths, number of vibrations, and refractive indices).

2. Young-Helmholtz Theory.—The theory of Thomas Young (1807) and v.
Helmholtz (1852) assumes that three different kinds of nerve-elements, correspond-
ing to the three primary colours, are present in the retina,. Stimulation of the
first kind causes the sensation of red, of the second green, and of the third violet.

The elements sensitive to red are most strongly excited by light with the longest wave-
length, the red rays ; those for green by medium wave-lengths, green rays ; those for violet by
the rays of shortest wave-length, violet rays. Further, it is assumed, in order to explain a
number of phenomena, that every colour of the spectrum excites all the kinds of fibres, some of

amas (a

Fig. 562.

them feebly, others strongly. Suppose in fig. 562 the colours of the spectrum are arranged in their
natural order from red to violet horizontally, then the three curves raised upon the abscissa
might indicate the strength of the stimulation of the three kinds of retinal elements. The
continuous curve corresponds to the rays producing the sensation of red, the dotted line that
of green, and the broken line that of violet. Pure red light, as indicated by the height of the
ordinates in R, strongly excites the elements sensitive to red, and feebly the other two kinds
of terminations, resulting in the sensation of red. Simple yellow excites moderately the
elements for red and green, and feebly those for violet =sensation of yellow. Simple green
excites strongly the elements for green, but much more feebly the two other kinds=sensation
of green. Simple blue excites toa moderate extent the elements for green and violet ; more
feebly those for red=sensation of blue. Simple violet excites strongly the corresponding
elements, feebly the others=sensation of violet, Stimulation of any two elements excites the
impression of a mixed colour; while, if all of them be excited in a nearly equal degree, the
sensation of white is produced. As a matter of fact, the Young-Helmholtz theory gives a
simple explanation of the phenomena of the physiological doctrine of colour. It has been
attempted to make the results obtained by examination of the structure of the retina accord
with this view. According to Max Schultze, the cones alone are end-organs connected with
the perception of colour. The presence of longitudinal striation in their outer segments is
regarded as constituting them multiple terminal end-organs. Our power of colour sensation,
8? far as it depends on the retina, would, on this view of the matter, bear a relation to the
number of cones. The degree of colour sensation is most developed in the macula lutea, which
contains only cones, and diminishes as the distance from the point increases, while it is absent
in the peripheral parts of the retina. The rods of the retina are said to be concerned only with
the copectey to distinguish between quantitative sensations of light.

8, Hering’s Theory.—Ew. Hering, in order to explain the sensation of light, proceeds from
the axiom stated under 1, p. 775. What we are conscious of, and call a visual sensation, is
the physical expression for the metabolism in the visual substance (‘‘ Sehsubstanz”’), %.¢.,

in those nerve-masses which are excited in the process of vision. Like every other corporeal a

is

oe a a oe

aa

HERING’S THEORY. FIG

matter, this substance during the activity of the metabolic process undergoes decomposition or
‘*disassimilation” ; while during rest it must be again renewed, or ‘‘assimilate’’ new

material. Hering assumes that for the perception of white and black, two different qualities

of the chemical processes take place in the visual substance, so that the sensation of white
corresponds to the disassimilation (decomposition), and that of black to the assimilation
(restitution) of the visual substance. According to this view, the different degrees of distinct-
ness or intensity with which these two sensations appear, occur in the several transitions between
pure white and deep black; or, the proportions in which they appear to be mixed (grey),
correspond to the intensity of these two psycho-physical processes. Thus, the consumption
and restitution of matter in the visual substance are the primary processes in the sensation of
white and black. In the production of the sensation of white, the consumption of the visual
substance is caused by the vibrating ethereal waves acting as the discharging force or stimulus,
while the degree of the sensation of whiteness is proportional to the quantity of the matter
consumed. The process of restitution discharges the sensation of black; the more rapidly it
occurs, the stronger is the sensation of black. The consumption of the visual substance at one
place causes a greater restitution in the adjoining parts. Both processes influence each other
simultaneously and conjointly. [In the production of a visual sensation, it is important to
remember that the condition of one part of the retina influences contemporaneously the
condition of adjoining parts of the retina, z.¢., ‘‘the sensation which arises through the
stimulation of any given point of the retina, is also a function of the state of other immediately
contiguous points.”] This explains physiologically the phenomenon of contrast of which the
old view could give only a psychical interpretation (p. 782).

Similarly, colour sensation is regarded as a sensation of decomposition (disassimilation) and
of restitution (assimilation) ; in addition to white, red and yellow are the expression of
decomposition ; while green and blue represent the sensation of restitution. Thus, the visual
substance is subject to three different ways of chemical change or metabolism. We may
explain in this way the colowred phenomena of contrast and the complementary after-images.
The sensation of black-white may occur simultaneously with all colours; hence, every colour
sensation is accompanied by that of dark or bright, so that we cannot have an absolutely pure
colour. There are three different constituents of the visual substance ; that connected with
the sensation of black-white (colourless), that with blue-yellow, and that with red-green.
All the rays of the visible spectrum act in disassimilating the black-white substance, but the
different rays act in different degrees. The blue-yellow or the red-green substances, on the
other hand, are disassimilated only by certain rays, some rays causing assimilation, whilst
others are inactive. Mixed light appears colourless when it causes an equally strong dis-

assimilation and assimilation in the blue-yellow and in the red-green substance, so that the |

two processes mutually antagonise each other, and the action on the black-white substance
appears pure. Two objective kinds of light, which together yield white, are not to be
regarded as complementary, but as antagonistic, kinds of light, as they do not supplement
each other to produce white, but only allow this to appear pure, because, being antagonistic,
they mutually prevent each other’s action.

The imperfection of the Young-Helmholtz theory of colour sensation is that it recognises
only one kind of excitability, excitement, and fatigue (corresponding to Hering’s disassimilation),
and that it ignores the antagonistic relation of certain light rays to the eye. It does not regard
white as consisting of complementary light rays, which neutralise each other by their action on
the coloured visual substance, but as uniting to form white (Hering).

[While it suffices to explain a great many of the phenomena of light and colour, ¢.g., the
mixing of colours and complementary colours, it does not satisfactorily explain contrast or
colour-blindness. Fick admits that it does not explain the following important fact :—Every
ray of light, while exciting a colour sensation if it falls on a sufficient area of the posterior
polar part of the eyeball, provided it acts on an extremely limited part of the retina, even if
it be coloured light, produces a whitish impression. This is exactly the opposite of what we
should expect, viz., the smaller the area of retina acted on, the more readily should the parti-
cular nerve-ending be excited and a pure colour sensation result. ]

In applying this theory to colour-blindness (§ 397), we must assume that those
who are red-blind want the red-green visual substance ; there are but two partial
spectra in their solar spectrum, the black-white and the yellow-blue. The position
of green appears to such an one to be colourless ; the rays of the red part of the
spectrum are visible, so far as the sensation of yellow and white produced by these
rays is strong enough to excite the retina. Hering divides his spectrum into a
yellow anda blue half. A violet-blind person wants the yellow-blue visual substance ;
in his spectrum there are only two partial spectra, the black-white and the red-green.
In cases‘ of complete colour-blindness, the yellow-blue and red-green substances
are absent. Hence, such a person has only the sensation of bright and dark. .The

JS A

778 COLOUR-BLINDNESS.

sensibility to light and the length of the spectrum are retained ; the brightest part
in this case, as in the normal eye, is in the yellow (Hering).

397. COLOUR-BLINDNESS AND ITS PRACTICAL IMPORTANCE —
Causes. —By the term colour-blindness (dyschromatopsy) is meant a pathological
condition in which some individuals are unable to distinguish certain colours.
Huddart (1777) was acquainted with the condition, but it was first accurately
described by Dalton (1794), who himself was red-blind. The term colour-blindness
was given to it by Brewster.

The supporters of the Young-Helmholtz theory assume that, corresponding to the paralysis
of the three colour-perceiving elements of the retina, there are the following kinds of colour-
blindness: | Red-blindness, 2. Green-blindness, 3, Violet-blindness,

The highest degree being termed complete colour-blindness,
MT he eaten: of E. Herings theory of colour sensation distinguish the following kinds :—

1. Complete Colour-blindness (Achromatopsy).—The spectrum appears achromatic ; the
position of the greenish-yellow is the brightest, while it is darker on both sides of it. A
coloured picture appears like a photograph or an engraving. Occasionally the different degrees
of light intensity are perceived in one shade of colour, ¢.g., yellow, which cannot be compared
with any other colour. O. Becker and v. Hippel observed cases of unilateral congenital com-
plete colour-blindness, whilst the other eye was normal for colour-perception.

2. Blue-yellow Blindness.—The spectrum is dichromatic, and consists only of red and green.
The blue-violet end of the spectrum is usually greatly shortened. In pure cases only the red
and green are correctly distinguished (Mauthner’s erythrochloropy), but not the other colours.
Unilateral cases have been observed.

3. Red-green Blindness.—The spectrum is also dichromatic. Yellow and blue are correctly
distinguished ; violet and blue are both taken for blue. The sensations for red and green are
absent altogether. There are several forms of this—(a) Green-blindness, or the red-green
blindness, with undiminished spectrum (Mauthner’s xanthokyanopy), in which bright-green and
dark-red are confounded. In the spectrum yellow abuts directly on blue, or between the two,
at most, there is a strip of grey. The maximum of brightness is in the yellow. It is often
unilateral and often hereditary. () Red-blindness (or the red-green blindness with undi-
minished spectrum, also called Daltonism), in which bright-red and dark-green are confounded.
The spectrum consists of yellow and blue, but the yellow lies in the orange. The red end of
the spectrum is uncoloured, or even dark. The greatest brightness, as well as the limit between
yellow and blue, lies more towards the right.

4. Incomplete colour-blindness, or a diminished colour sense, indicates the condition in
which the acuteness of colour perception is diminished, so that the colours can be detected only
in large objects, or only when they are near, and when they are mixed with white they no
longer appear as such. A certain degree of this form is frequent, in as far as many persons are
unable to distinguish greenish-blue from bluish-green.

Acquired colour-blindness occurs in diseases of the retina and atrophy of the optic nerve in
commencing tabes, in some forms of cerebral disease (p. 713), and intoxications. At first
green-blindness occurs, which is soon followed by red-blindness. The peripheral zone of the
retina suffers sooner than the central area. In hysterical persons there may be intermittent
attacks of colour-blindness (Charcot) ; and the same occurs in hypnotised persons (p. 686).

H. Cohn found that, on heating the eyeball of some colour-blind persons, the colour-blind-
ness disappeared i ag Occasionally in persons without a lens red vision is present, and is
(ue to unknown causes. Percentage.—Holmgren found that 2°7 per cent. of persons were
colour-blind, most being red and green blind, and very few violet blind.

Limits of Normal Colour-blindness.—The investigations on the power of colour perception
in the normal retina are best carried out by means of Aubert-Férster’s perimeter, or that of
M ‘Hardy (§ 395). It is found that our colour perception is. complete only in the middle of the
Jield of vision. Around this is a middle zone, in which only blue and yellow are perceived, in
which, therefore, there is red blindness. Outside this zone, there is a peripheral girdle, where
there is complete colour-blindness ($ 395). Hence a red-blind person is distinguished from a
person with normal vision, in that the central area of the normal field of vision is absent in the
former, this being rather included in the middle zone. The field of vision of a green-blind
person differs from that of a person with normal vision, in that his peripheral zone corresponds
to the intermediate and peripheral zones of the normal eye. The violet-blind person is dis-
tinguished by the complete absence of the normal peripheral zone. The incomplete colour-
blindness of these two kinds is characterised by a uniformly diminished central field. [When

very intense colours are used, such as those of the solar spectrum, the retina can distinguish —
them quite up to its margin (Landolt). ] . Dales?

a ee

STIMULATION OF THE RETINA. 779

In poisoning with santonin, violet-blindness (yellow vision) occurs in consequence of the
paralysis of the violet perceptive retinal elements, which not unfrequently is preceded by stimu-
lation of these elements, resulting in violet vision, 7.¢., objects seem to be coloured violet
(Hiifner). Such is the explanation of this phenomenon given by Holmgren. Max Schultze,
however, referred the yellow vision, 7.¢., seeing objects yellow, to an increase of the yellow
pigment in the macula lutea.

When coloured objects are very small, and illuminated only for a short time, the normal eye
first fails to perceive red (Aubert) ; hence, it appears that a stronger stimulus is required to
excite the sensation of red. Briicke found that very rapidly intermittent white light is per-
ceived as green, because the short duration of the stimulation fails to excite the elements of
the retina connected with the sensation of red.

[The practical importance of colour-blindness was pointed out by George Wilson, and again
more recently by Holmgren.] No person should be employed in the marine or railway service
until he has been properly certified as able to distinguish red from green.

Methods of Testing Colour-blindness.—Following Seebeck, Holmgren used small skeins of
coloured wools as the simplest material, in red, orange, yellow, greenish-yellow, green, greenish-
blue, blue, violet, purple, rose, brown, grey. There are five finely graduated shades of each of
the above colours. When testing a person, select only one skein—e.g., a bright red or rose—
from the mass of coloured wools placed in front of him, and place it aside, asking him to seek
out those skeins which he supposes are nearest to it in colour.

Macé and Nacati have measured the acuteness of vision by illuminating a small object with
different parts of the spectrum. They compared the observations on red and green-blind
persons with their own results, and found that a red-blind person perceives green light as much
brighter than it appears to a normal person. The green-blind had an excessive sensibility for
red and violet. It appears that what the colour-blind lose in perceptive power for one colour
they gain for another. They have also a keen sense for variations in brightness.

398. STIMULATION OF THE RETINA.—As with every other nervous
apparatus, a certain but determinable time elapses after the rays of light fall upon
the eye before the action of the light takes place, whether the light acts so as to
produce a conscious impression, or produces merely a reflex effect npon the pupil.
The strength of the impression produced depends partly and chiefly upon the
excitability of the retina and the other nervous structures. If the light acts for a
long time with equal intensity, the excitation, after having reached its culminating
point, rapidly diminishes again, at first more
rapidly, and afterwards more and more slowly.

[When the retina is stimulated by light,
there is (1) an effect on the rhodopsin (p. 740). |
(2) The electro-motive force is diminished
(§ 332). (3) The processes of the hexagonal
pigment-cells of the retina dipping between
the rods and cones are affected; thus they are
retracted in darkness, and protruded in the
light (fig. 563). (4) Engelmann has shown
that the length and shape of the cones vary
with the action of light. The cones are re-
tracted in darkness and protruded under the
influence of light (fig. 563). This alteration

in the shape of the cones takes place even if L Fig. 563, 2.
the light acts on the skin, and not on the eye- The cones of the retina and pigment-cells
ball at all. | (of the frog) as affected by light and

After-Images.—If the light acts on the darkness: 1. after two days in dark-
eye for some time so as to excite the retina, SS: 2. after ten minutes in daylight.
and if it be suddenly withheld, the retina still remains for some time in an excited
condition, which is more intense and lasts longer, the stronger and the longer the
light may have been applied, and the more excitable the condition of the retina.
Thus, after every visual perception, especially if it is very distinct and bright,
there remains a so-called “ after-image.” We distinguish a “positive after-
image,” which is an image of similar brightness, and a similar colour.

780 AFTER-IMAGES.

“That the impression of any picture remains for some time upon the eye is a physio-
logical phenomenon; when such an impression can be seen for a long time, it becomes patho-
logical. The weaker the eye is, the longer the image remains upon it. The retina does not
recover itself so quickly, and we may regard the action as a kind of paralysis. This is not to
be wondered at in the case of dazzling pictures. After looking at the sun, the image may
remain on the retina for several days. A similar result sometimes occurs with pictures whic
are not dazzling. Busch records that the impression of an engraving, with all its details,
remained on his eye for 17 minutes ”’ (Goethe). ads ten

Experiments and Apparatus for Positive After-Images. —1. When a burning stick is rapidly
rotated, it appears as a fiery circle.

2. The phanakistoscope (//luteaw) or the stroboscopic discs (Stampfer). Upon a disc or
cylinder, a series of objects is so depicted that successive drawings represent individual factors
of one continuous movement. On looking through an opening at such a disc rotated rapidly,
we see pictures of the different phases moving so quickly that each rapidly follows the one in
front of it. As the impression of the one picture remains until the following one takes its
place, it has the appearance as if the successive eee of the movement were continuous, and
one and the same figure. The apparatus under the name of zoetrope, which is extensively used
as a toy, is generally stated to have been invented in 1832. It was described by Cardanus in
1550. It may be used to represent certain movements, ¢.g., of the spermatozoa and ciliary
motion, the movements of the heart and those of locomotion.

3. The colour top contains on the sectors of its disc the colours which are to be mixed. As
the colour of each sector leaves a condition of excitation for the whole duration of a revolution,
all the colours must be perceived simultaneously, ¢.e., as a mixed colour.

[Illusions of Motion.—Silvanus P. Thompson points out that if a series of concentric circles
in black and white be made on paper, and the sheet on which the circles are drawn be moved
with a motion, as if one were rinsing out a pail, but with a very minute radius, then all the
circles appear to rotate with the same angular velocity as that imparted. Professor Thompson

has contrived other forms of this illusion, in the form of strobic discs. ]

Negative After-Images.—Occasionally, when the stimulation of the retina is
strong and very intense, a ‘‘ negative,” instead of a positive after-image, appears. In
a negative after-image, the bright parts of the object appear dark, and the coloured .
parts in corresponding contrast colours (p. 774).

Examples of Negative After-Images.—After looking fora long time at a dazzlingly-illuminated
white window, on closing the eyes we have the impression of a bright cross, or crosses, as the
case may be, with dark panes.

Negative coloured after-images are beautifully shown by Norrenberg’s apparatus. Look
steadily at a coloured surface, ¢.g., a yellow board with a small blue square attached to the
centre of its surface. A white screen is allowed to fall suddenly in front of the board—the white
surface now has a bluish appearance, with a yellow square in its centre.

The usual explanation of dark negative after-images is that the retinal elements are fatigued
by the light, so that for some time they become less excitable, and consequently light is but
feebly perceived in the corresponding areas of the retina; hence, darkness prevails.

_Hering explains the dark after-images as due to a process of assimilation in the black-white
visual substance. In a worsen? coloured after-images, the Young-Helmholtz theory assumes
that, under the action of the hght waves, e.g., red, the retinal elements connected with the
perception of this colour are paralysed. On now looking suddenly on a white surface, the
mixture of all the colours appears as white minus red, i.e., the white appears green. In bright
daylight the contrast colour lies very near the complementary colour. According to Hering,
the contrast after-image is explained by the assimilation of the corresponding coloured visual
substance, in this case, of the “red-green” (§ 397). From the commencement of a momentary
illumination until the appearance of an after-image, 0°344 sec. elapses (v. Vintschgau and

Lustig).

Not unfrequently, after intense stimulation of the retina, positivé and negative
after-images alternate with each other until they gradually fuse. After looking at
the dark-red setting sun we see alternate discs of red and green.

The phenomena of contrast undergo some modification in the peripheral areas of
the retina, owing to the partial colour-blindness which occurs in these areas
(Adamiick and Woinow). r

Irradiation is the term applied to certain phenomena where we form a false
estimate of visual impressions, owing to inexact accommodation. Tf, from inexact
accommodation, the margins of the object are projected upon the retina in diffusion
circles, the mind tends to add the undefined margin to those parts of the visual

SIMULTANEOUS CONTRAST. 78 I

image which are most prominent in the image itself. What is bright appears
larger and overcomes what is dark, while an object, without reference to brightness
or colour, has the same relation to its background
(fig. 564). When the accommodation is quite
accurate, the phenomenon of irradiation is not

Fig. 564. Fig. 565.
For irradiation. For irradiation.

present. [On looking at fig. 565 from a distance, the white squares appear larger
and as if they were united by a white band. |

“A dark object appears smaller than a bright one of the same size. On looking at the same
time from a certain distance at two circles of the same size, a white one on a black background,
and a black on a white background, we estimate the latter to be about one-fifth less than the
former (fig. 564). On making the black circle one-fifth larger they will appear equal. Tycho
de Brahe remarks that the moon, when in conjunction (dark), appears to be one-fifth smaller
than in opposition (full, bright). The first lunar crescent appears to belong to a larger disc
than the dark one adjoining it, which can occasionally be distinguished at the time of the new
light. Black clothes make persons appear to be much smaller than light clothes. A light seen
behind a margin gives the appearance of a cut in the margin. A ruler, behind which is placed
a lighted candle, appears to the observer to have a notch in it. The sun, when rising and
setting, appears to make a depression in the horizon” (Goethe).

[Contrast.—The fundamental phenomena are such as these, that a bright object
looks brighter surrounded by objects darker than itself; and darker with surround-
ings brighter than itself. There may be contrasts either with bright or dark objects
or with coloured ones. |

Simultaneous Contrast.—By this term is meant a phenomenon like the follow-
ing :—When bright and dark parts are present in a picture at the same time, the
bright (white) parts always appear to be more intensely bright the less white there
is near them, or, what is the same thing, the darker the surroundings, and, con-
versely, they appear less bright the more white tints that are present near them.
A similar phenomenon occurs with coloured pictures. A colour in a picture appears
to us to be more intense the less of this colour there is in the adjoining parts, that
is, the more the surroundings resemble the tints of the contrast colour. Simultane-
ous contrast arises from simultaneous impressions occurring in two adjoining and
different parts of the retina.

Examples of Contrast for Bright and Dark.—1. Look at a white network on a black ground ;
the parts where the white lines intersect appear darker, because there is least black near them.

2. Look at a point of a small strip of dark grey paper in front of a dark black background.
Push a large piece of white paper between the strip and the background; the strip on the white
ground now appears to be much darker than before. On again removing the white paper, the
strip at once again appears bright (Hering).

3. Look with both eyes towards a greyish-white surface, ¢.g., the ceiling of a room. After
gazing for some-time, place in front of the eye a paper tube eight inches long, and an inch to
an inch and a quarter in diameter, blackened in the inside. The part of the ceiling seen
through the tube appears as a round: white spot (Landois).

Examples for Colours.—1. Place a piece of. grey paper on a red, yellow, or blue ground; the
contrast colours appear at once, viz., green; blue, or yellow. The phenomenon is made still
more distinet by covering the whole with transparent tracing paper (Herm. Meyer). . Under
similar circumstances, printed matter on a coloured ground appears in its complementary colour
(W. v. Bezold).

782 EXAMPLES OF CONTRAST.

2. An air-bubble in the strongly tinged field of vision of a thick microscopical preparation

ap with an intense contrast colour (Landois), ’ . |

. Paste four green sectors upon a rotatory white disc, leave a ring round the centre of the
dise uncovered by green, and cover : with a black strip. On rotating such a disc the black
-ars red and not grey (Briicke). ; ‘ae

a ; Tok with both mercedes a Ser iahaehkts surface, and place in front of one eye a tube
about the length and breadth of a finger, composed of transparent oiled paper, gummed together

to such thickness as will permit light to pass through its walls. The part of the surface seen
through the tube appears in its contrast colour. The experiment also shows the contrast in the
intensity of the illumination (Landois). A white piece of paper, with a round black spot in its
centre, when looked at through a blue glass appears blue with a black spot. Ifa white spot of

the same size on a black ground be placed in front, so that it is reflected in the glass plate and

just covers the black spot, it shows the contrast colour yellow (Ltagona Scina). :

5. The coloured shadows also belong to the eroup of simultaneous contrasts. ee Two condi-
tions are necessary for the production of coloured shadows—firstly, that the light gives some
kind of a colour to the white surface; second, that the shadow is illuminated, to a certain
extent, by another light. During the twilight, place a short lighted candle on a white surface,
between it and the fading daylight hold a pencil vertically, so that the shadow thrown by the
candle is illuminated, but not abolished, by the feeble daylight ; the shadow appears of a
beautiful blue. The blue shadow is easily seen, but it requires a little attention to observe that
the white paper acts like a reddish-yellow surface, whereby the blue colour apparent to the eye
is improved. One of the most beautiful cases of coloured shadows is seen in connection with
the full moon. The light of the candle and that of the moon can be completely equalised.

Both shadows can be obtained of equal strength and distinctness, so that both colours are
completely balanced. Place the plate opposite the light of the moon, the lighted candle a little
to one side at a suitable distance. In front of the plate hold an opaque body, when a double
shadow appears, the one thrown by the moon and lighted by the candle being bright reddish-
yellow ; and, conversely, the one thrown by the candle and lighted by the moon appears of a
beautiful blue. Where the two shadows come together and unite is black” (Goethe).

6. ‘‘ Take a plate of green glass of considerable thickness and hold it so as to get the bars of
a window reflected in it, the bars will be seen double, the image formed by the under surface
of the glass being green, while the image coming from the under surface of the glass, and which
ought really to be colourless, appears to be purple. The experiment may be performed with a ~
vessel filled with water, with a mirror at its base. With pure water colourless images are
obtained, while by colouring the water coloured images are produced ” (Goethe).

Explanation of Contrast.—Some of these phenomena may be explained as due to an error of
judgment. During the simultaneous action of several impressions, the judgment errs, so that
when an effect occurs at one place, this acts to the slightest extent in the neighbouring parts.

When, therefore, brightness acts upon a part of the retina, the judgment ascribes the smallest
possible action of the brightness to the adjoining parts of the retina. It is the same with
colours. It is far more probable that the phenomena are to be referred to actual physiological
processes (Hering). Partial stimulation with light affects not only the part so acted on, but also

the surrounding area of the retina (p. 782); the part directly excited undergoing increased dis-
assimilation, the (indirectly stimulated) adjoining area undergoing increased assimilation ;

the increase of the latter is greatest in the immediate neighbourhood of the illuminated .
portion, and eee diminishes as the distance from it increases. By the increase of the
assimilation in those parts not acted on by the image of the object, this is prevented, so that
the diffused light is perceived. The increase of the assimilation in the immediate neighbourhood
of the illuminated spot is greatest, so that the perception of this relatively stronger different
light is largely rendered impossible (Hering).

{Helmholtz thus giceined an phenomena of contrast to psychical conditions, ¢.¢., errors of
judgment, but this explanation is certainly not complete. A far more satisfactory solution of the
problem is that of Hering, that stimulation of one part of the retina affects the condition of
adjoining parts. Ifa white disc on a black background be looked at for a time, and then the
eyes be closed, a negative after-image of the disc appears, but it is darker and blacker than the
visual area, and it has a light area around, brightest close to the disc, i.¢., the adjacent part of
the retina is affected. This Hering has called successive light induction, ]

Successive Contrast.—Look for a long time at a dark or bright object, or at a coloured (¢.g.,
red) one, and then allow the effect of the contrast to occur on the retina, i.é., With reference
to the above, bright and dark, or the contrast colour green, then these become very intense,
This phenomenon has also been called “successive contrast.” In this case the negative after-
image obviously plays a part.

(Some drugs cause subjective visual sensations, but these do so by acting on the brain, eg.,
ry sim - delirium tremens, cannabis indica, sodic salicylate, and large doses of digitali

ru .

399, MOVEMENTS OF THE EYEBALLS—EYE MUSCLES.—The globular _

MOVEMENTS OF THE EYEBALLS. 783

eyeball is capable of extensive and free movement on the correspondingly excavated
fatty pad of the orbit, just like the head of a long bone in the corresponding socket
of a freely movable arthroidal joint. The movements of the eyeball, however, are
limited by certain conditions, by the mode in which the eye-muscles are attached
to it. Thus, when one muscle contracts, its antagonistic muscle acts like a bridle,
and so limits the movement; the movements are also limited by the insertion of
the optic nerve. The soft elastic pad of the orbit on which the eyeball rests is
itself subject to be moved forward or backward, so that the eyeball also must
participate in these movements.

Protrusion of the eyeball takes place—l. By congestion of the blood-vessels, especially of
_ the veins in the orbit, such as occurs when the overflow of the venous blood from the head is
interfered with, as in cases of hanging. 2. By contraction of the smooth muscular fibres in
Tenon’s capsule, in the spheno-maxillary fissure, and in the eyelids ($ 404), which are inner-
vated by the cervical sympathetic nerve. 3. By voluntary forced opening of the palpebral
fissure, whereby the pressure of the eyelids acting on the eyeball is diminished. 4. By the
action of the oblique muscles, which act by pulling the eyeball inwards and forwards. If the
superior oblique be contracted when the eyelids are forcibly opened, the eyeball may be pro-
truded about 1 mm. When protrusion of the eyeball occurs pathologically (as in 1 and 2), the
condition is called exophthalmos,

Retraction of the eyeball is the opposite condition, and is caused—l. By closing the eye-
lids forcibly. 2. By an empty condition of the retrobulbar blood-vessels, diminished succulence,
or disappearance of the tissue of the orbit. 3. Section of the cervical sympathetic in dogs
causes the eyeball to sink somewhat in the orbit. The smooth muscular fibres of Tenon’s
capsule are perhaps antagonistic in their action to the four recti when acting together, and thus
prevent the eyeball from being drawn too far backwards. Many animals have a special

retractor bulbi muscle, ¢.g., amphibians, reptiles, and many mammals; the ruminants have
four. .

The movements of the eyes are almost always accompanied by similar movements

of the head, chiefly on looking upwards, less so on looking laterally, and least of
all when looking downwards.

’ The difficult investigations on the movements of the eyeballs have been carried out, especially
by Listing, Meissner, Helmholtz, Donders, A. Fick, and E. Hering.

Axes.—A1l the movements of the eyeball take place round its point of rotation (fig. 566, O),
which lies 1°77 mm. behind the centre of the visual axis, or 10°957 mm. from the vertex of the
cornea (Donders). In order to determine more carefully the movements of the eyeball, it is
necessary to have certain definite data :—1. The visual axis (S, 8,), or the antero-posterior axis
of the eyeball, unites the point of rotation with the fovea centralis, and is continued straight
forwards to the vertex of the cornea. 2. The transverse, or horizontal axis (Q, Q,), is the
straight line connecting the points of rotation of both eyes and its extension outwards. Of
course, it is at right angles to 1. 3. The vertical axis passes vertically through the point of
rotation at right angles to 1 and 2. These three axes form a co-ordinate system. We must
imagine that in the orbit there is a fixed determinate axial system, whose point of intersection
corresponds with the point of rotation of the eyeball. When the eye is at rest (primary
position), the three axes of the eyeball completely coincide with the three axes of the co-ordinate
system in the orbit. When the eyeball however is moved, two or more axes are displaced from
this, so that they must form angles with the fixed orbital system.

Planes of Separation.—In order to be more exact, and also partly for further estimations, let
us suppose three planes passing through the eyeball, and that their position is secured by any
two axes. 1. The horizontal plane of separation divides the eyeball into an upper and lower
half ; it is determined by the visual transverse axis. In its course through the retina it forms
the horizontal line of separation of the latter; the coats of the eyeball itself cut it in their.
horizontal meridian. 2. The vertical plane divides the eyeball into an inner and outer half ;
it is determined by the visual and vertical axes. It cuts the retina in the vertical line of
separation of the latter and the periphery of the bulb in the vertical meridian of the eyeball.
3. The equatorial plane divides the eyeball into an anterior and posterior half; its position is
determined by the vertical and transverse axes, and it cuts the sclerotic in the equator of the
eyeball. The horizontal and vertical lines of separation of the retina, which intersect in the
fovea centralis, divide the retina into four quadrants. -

In order to define more precisely the movements of the eyeball, v. Helmholtz has introduced
the following terms :—He calls the straight line which connects the point of rotation of the eye
with the fixed point in the outer world, the visual line (“Blicklinie”), while a plane passing
through these lines in both eyes he called the visual plane; the ground line of this plane is the
line uniting the two points of rotation, viz., the transverse axis of the eyeball. Suppose a

784 POSITIONS OF THE EYEBALL.

i i o-posterior) to be made through the head, so as to divide the latter into a
o*Gut and left belt, then this a. would halve the ground line of the visual plane, and when
prolonged forward would intersect the visual plane in the median line, The visual point of the
eve can be (1) raised or lowered—the field which it traverses being called the visual field
(* Blickfeld”) ; it is part of a spherical surface with the point of rotation of the eye in its
centre, . Proceeding from the primary position of both eyes, which is characterised by. both
visual lines being parallel with each other and horizontal, then the elevation of the visual plane
can be determined by the angle which this forms with the plane of the primary position. This
angle is called the angle of elevation—it is positive when the visual plane is raised (to the fore-
head), and negative when it is lowered (chinwards), (2) From the primary position, the visual
line can be turned laterally in the visual plane. The extent. of this lateral deviation is measured
by the angle of lateral rotation, %.c., by the angle which the visual line forms with the
median line of the visual plane ; it is said to be positive when the posterior part of the visual
line is turned to the right, negative when to the left. The following are the positions of the

eyeball :—

1. Primary position [or “ position of rest”], in which both the lines of vision
are parallel with each other, and the visual planes are horizontal. The three axes of
the eyeball coincide with the three fixed axes of the co-ordinate system in the orbit.

2. Secondary positions are due to movements of the eye from the primary post-
tion. There are two different varieties—(a) where the visual lines are parallel,
but are directed upwards or downwards. The transverse axis of both eyes remains
the same as in the primary position ; the deviations of the other two axes expressed
by the amount of the angle of elevation of the ine of vision. (6) The second
variety of the secondary position is produced by the convergence or divergence of the
lines of vision. In this variety the vertical axis, round which the lateral rotation
takes place, remains as in the primary position ; the other axes form angles ; the
amount of the deviation is expressed by the “ angle of lateral rotation.” The eye,
when in the primary position, can be rotated from this position 42° outwards, 45°
inwards, 34° upwards, and 57° downwards (Schuurmann).

3. Tertiary position is the position brought about by the movements of the eye,
in which the lines of vision are convergent, and are at the same time znclined up-
wards or downwards.

[Listing’s Law is that which expresses the movements of the eyeball. When the eyeball
moves from the primary position, or position of rest, the angle of rotation of the eye in the
second position is the same as if the eye were turned about a fixed axis perpendicular to both
the first and the second positions of the visual line (Helmholtz). ]

All the three axes of the eye are no longer coincident with the axes in the primary
position. The exact direction of the visual lines is determined by the amount of
the angle of lateral rotation and the angle of elevation. There is still another
important point. The eyeball is always rotated at the same time round the line
of vision and round its axis (Volkmann, Hering). As the iris rotates round the
visual line like a wheel round its axis, this rotation is called “ circular rotation ”
(‘‘ Raddrehung”) of the eye, which is always connected with the tertiary positions.
Even oblique movements may be regarded as composed of—(1) a rotation round
the vertical axis, and (2) round the transverse axis ; or it may be referred to rota-
tion round a single constant axis placed between the above-named axes, passing
through the point of rotation of the eyeball, and at right angles to the secondary
and primary direction of the visual axis (line of vision)—(Listing). The amount
of circular rotation is measured by the angle which the horizontal separation line of
the retina forms with the horizontal separation of the retina of the eye in the primary
position. This angle is said to be positive, when the eye itself rotates in the same
direction as the hand of a watch observed by the same eye, z.e., when the upper end
of the vertical line of separation of the retina is turned to the right. “Fr

According to Donders, the angle of rotation increases with the angle of elevation and the
angle of lateral rotation—it may exceed 10°. With equally great elevation or pd ap of

the visual plane, the rotation is greater, the greater the elevation or depression of the line of
vision, ¢s ‘ . 1S QUITE

Jala

THE OCULAR MUSCLES. 785

On looking upwards in the tertiary position, the upper ends of the vertical lines of separation
of the retina diverge ; on looking downwards they converge. If the visual plane be raised, the
eye, when it deviates laterally to the right, makes a circular rotation to the left. When the
visual plane is depressed, on deviating the eye to the right or left, there is a corresponding
circular rotation to the right or left. Or we may express the result thus:—When the angle of
elevation and the angle of deviation have the same sign (+ or — ), then the rotation of the eye-
ball is negative ; when, however, the signs are unequal, the rotation is positive. In order to
make the circular rotation visible in one’s own eye, accommodate one eye for a surface divided
by vertical and horizontal lines until a positive after-image is produced, and then rapidly rotate
the eye into the third position. The lines of the after-image then form angles with the lines
of the background. As the position of the vertical meridian of the eye is important from a
practical point of view, it is necessary to note that, in the primary and secondary positions of
the eyes, the vertical meridian retains its vertical position. On looking to the left and up-

%..
wr) %

Fig. 566.
Scheme of the action of the ocular muscles.

wards, or to the right and downwards, the vertical meridians of both eyes are turned to the

left ; conversely, they are turned to the right on looking to the left ‘and downwards, or to the
right and upwards.

In the secondary positions of the eye, rotation of the axis of the eye never occurs (Listing).
Very slight rolling of the eyes occurs, however, when the head is inclined towards the shoulder,
and in the direction opposite to that of the head, it is about 1° for every 10° of inclination of
the head (Skrebitzk).

Ocular Muscles.—The movements of the eyeball are accomplished by means of
the four straight and two oblique ocular muscles. In order to understand the .
action of each of these muscles, we must know the plane of traction of the muscles

3D

786 ACTION OF THE OCULAR MUSCLES.

and the axis of rotation of the eyeball. The plane of traction is found by the
plane lying in the middle of the origin and insertion of the muscle and the point
of rotation of the eyeball. The axis of rotation is always at right angles to the
plane of traction in the point of rotation of the eyeball.

1. The rectus internus (I) and externus (E) rotate the eye almost exactly inwards
and outwards (fig. 566). The plane of traction lies in the plane of the paper ; Q,
E, is the direction of the traction of the external rectus,’Q,, I, that of the internal.
The axis of rotation is in the point of rotation, O, at right angles to the plane of
the paper, so that it coincides with the vertical axis of the eyeball. 2. The axis
of rotation of the R. superior and inferior (the dotted line, R. sup., R. inf.),
lies in the horizontal plane of separation of the eye, but it forms an angle of about
20° with the transverse axis (Q, Q,) ; the direction of the traction for both muscles
is indicated by the line, s, 7. By the action of these muscles, the cornea is turned
upwards and slightly inwards, or downwards and slightly inwards. 3. The axis
of rotation of both oblique muscles (the dotted lines, Obl. sup. and Obl. inf.) also lies
in the horizontal plane of separation of the eyeball, and it forms an angle of 60° with
the transverse axis. The direction of the traction of the eferior oblique gives the
line, a, b; that of the superior, the line, c, d. The action of these muscles, there-
fore, is in the one case to rotate the cornea outwards and upwards, and in the other
outwards and downwards. ‘These actions, of course, only obtain when the eyes are in
the primary position—in every other position the axis of rotation of each muscle
changes.

When the eyes are at rest, the muscles are in equilibrium. Owing to the power
of the internal recti, the visual axes converge and would meet, if prolonged 40
centimetres in front of the eye. In the movements of the eyeball, one, two, or
three muscles may be concerned. One muscle acts only when the eye is moved
directly outwards or inwards, especially the internal and external rectus. Zwo
muscles act when the eyeball is moved directly upwards (superior rectus and inferior
oblique) or downwards (inferior rectus and superior oblique). Zhree muscles are
in action when the eyeballs take a diagonal direction, especially for inwards and
upwards, by the internal and the superior rectus and inferior oblique ; for inwards
and downwards, the internal and inferior rectus and superior oblique ; for outwards
and downwards, the external and inferior rectus and superior oblique ; for outwards
and upwards, the external and superior rectus and inferior oblique.

[The following table shows the action of the muscles of the eyeball :—

Inwards, : Rectus internus. Rectus internus.

Outwards, . Rectus externus,

{ Rectus superior.

| Obliquus inferior.
Rectus inferior. Rectus"superior.
Obliquus superior. Obliquus inferior.

Taards ane | Recta internus. Dianirds aad Rectus externus.

Inwards and

ectus inferior.
downwards, Rec

Obliquus superior.

Upwards
P , Rectus externus.

Outwards and

Downwards, . upwards,

ne Rectus superior. Rectus inferior.
Sai Obliquus inferior, dovwmivaras, Obliquus superior. ]

Ruete imitated the movements of the eyeballs by means of a model, which he called the
ophthalmotrope.

The size of the eyeball and its length diminish with age. The mobility is less in the vertical
than in the lateral direction, and less upwards than downwards. The normal and myopic eye
can be moved more outwards, and the long-sighted eye more inwards, the external and internal
recti act most when the eye is moved outwards, the obliqui when it is rotated inwards, 4
eye can be turned inwards to a greater extent when the other eye at the same time is turned
outwards than when the other is turned inwards. During near vision, the right eye can be
turned less to the right, and the left to the left, than during distant vision (Hering).

Simultaneous Ocular Movements.—Both eyes are always moved simultaneously.

Even when one eye is quite blind, the ocular muscles move when the whole eyeball
is excited, When the head is straight, the movements always take place so that

;
;

BINOCULAR VISION. 787

both visual planes (visual axes) lie in the same plane. In front both visual axes
can diverge only to a trifling extent, while they can converge considerably. If
individual ocular muscles are paralysed, the position of the visual axis in the same
place is disturbed, and squinting results, so that the patient no longer can direct
both visual axes simultaneously to the same point, but he directs the one eye after
the other. Even nystagmus (p. 721) occurs in both eyes simultaneously, and in
the same direction. The innate simultaneous movement of ‘both eyes is spoken of
as an associated movement (Joh. Miller). E. Hering showed that in all ocular
movements there is a uniformity of the innervation as well. Even during such
movements, in which one eye apparently is at rest, there is a movement, due to the
action of two antagonistic forces, the movements resulting in a slight to and fro
motion of the eyeball.

The motor nerves of the ocular muscles are the oculomotorius (§ 345), the trochlearis (§ 346),
and the abducens (§ 348). The centre lies in the corpora quadrigemina, and below it (§ 379),
and partly in the medulla oblongata (§ 379).

400. BINOCULAR VISION.—Advantages.—Vision with both eyes affords
the following advantages :—(1) The jield of vision of both eyes is considerably
larger than that of one eye. (2) The perception of depth is rendered easier, as the
retinal images are obtained from two different points. (3) A more exact estimate
of the distance and size of an object can be formed, in consequence of the perception
of the degree of convergence of both eyes. (4) The correction of certain errors in
the one eye is rendered possible by the other.

When the position of the head is fixed, we can easily form a conception as to the form of the
entire field of vision if we close one eye and direct the open eye inwards. We observe that it is
pear-shaped, broad above and smaller below, the silhouette, or profile of the nose, causes the
depression between the upper and lower part of the field.

401. IDENTICAL POINTS—HOROPTER.—Identical Points.—If we
imagine the retine of both eyes to be a pair of hollow saucers placed one within the
other, so that the yellow spots of both eyes coincide, and also the similar quadrants of
the retinz, then all those points of both retinze which coincide or cover each other are
called ‘‘ identical” or ‘‘ corresponding points” of the retina. The two meridians
which separate the quadrants coinciding with each other are called the “lines of
separation.” Physiologically, the identical points are characterised by the fact
that, when they are both simultaneously excited by light, the excitement proceeding
from them is, by a psychical act, referred to one and the same point of the field of
vision, lying, of course, in a direction through the nodal point of each eye. Stimu-
lation of both identical points causes only one image in the field of vision. Hence
all those objects of the external world, whose rays of light pass through the nodal
points to fall upon identical points of the retina, are seen singly, because their
images from both eyes are referred to the same point of the field of vision, so that
they cover each other. All other objects whose images do not fall upon identical
points of the retina cause double vision, or diplopia.

Proofs.—If we look at a linear object with the points 1, 2, 3, then the corresponding retinal
images are 1, 2, 3 and 1, 2, 3, which are obviously identical points of the retine (fig. 567). If,
while looking at this line, there be a point, A, nearer the eyes, or B, further from them, then,
on focussing for 1, 2, 3, neither the rays (A, a, A, a) coming from A, nor those (B, 0, B, 6) from
B, fall upon identical points ; hence A and B appear double.

Make a point (¢.g., 2) with ink on paper ; of course the image will fall upon both fovee cen-
trales of the retine (2, 2), which of course are identical points. Now press laterally upon one
eye, so as to displace it slightly, then two points at once appear, because the image of the point
no longer falls upon the fovea centralis of the displaced eye, but on an adjoining non-identical
part of the retina. When we squint voluntarily all objects appear double. :

The vertical surfaces of separation of thé retina do not exactly coincide with the vertical
meridians. There is a certain amount of divergence (0°5°-3°), less above, which varies in
different individuals, and it may be in the same individual at different times (Hering). The
horizontal lines of separation, however, coincide. Images which fall upon the vertical lines of

788 THE HOROPTER.

i ical to those on the horizontal lines, although they are not actually
mg og eae tase of separation are the apparent vertical meridians. Some
observers regard the identical points of the retina as an acquired arrangement ; others regard it
as normally innate. Persons who have had a squint from their birth see singly; in these
cases, the identical points must be differently disposed.

The ‘horopter represents all those points of the outer world from which rays of

Fig. 567. Fig. 568.
Scheme of identical and non-identical points Horopter for the secondary position, with
of the retina. convergence of the visual axes.

light passing into both eyes fall upon identical points of the retina, the eyes being
in a certain position. It varies with the different positions of the eyes.

1. In the primary position of both eyes with the visual axes parallel, the rays of direction
proceeding from two identical points of the two retine are parallel and intersect only at
infinity. Hence for the primary position the horopter is a plane in infinity.

2. In the secondary position of the eyes with converging visual axes, the horopter for the
transverse lines of separation is a circle which passes through the nodal points of both eyes (fig.
568, K, K), and through the fixed points I, II, III. The horopter of the vertical, lines of
separation is in this position vertical to the plane of vision.

8. In the symmetrical tertiary position, in which the horizontal and vertical lines of
separation form an angle, the horopter of the vertical lines of separation is a straight line
inclined towards the horizon. There is no horopter for the identical points of the horizontal
ane rhe wabdony as the lines of direction prolonged from the identical points of these points
do not intersect.

4. In the unsymmetrical tertiary position (with rolling) of the eyes, in which the fixed point

lies at unequal distances from both nodal points, the horopter is a curve of a complex form.

All objects, the rays proceeding from which fall upon non-identical points 01 the
retinw, appear double. We can distinguish direct or crossed double images, accord-

ing as the rays prolonged from the non-identical points of the retina intersect a
front of or behind the fixed point.

Experiment.—Hold two fingers—the one behind the other—before both eyes. Accommo-
date for the far one and then the near one appears double, and when we accommodate for the
near one the far one appears double. If, when accommodating for the near one, the right eve
be closed, the left (crossed) image of the far finger disappears. On accommodating for the
far finger and closing the right eye, the right (direct) double image of the near finger
disappears. .
_ Double images are referred to the proper distance from the eyes, just as single
images are. \ 7a

,

STEREOSCOPIC VISION. 7809

Neglect of Double Images.— Notwithstanding the very large number of double
images which must be formed during vision, they do not disturb vision. As a
general rule they are “neglected,” so that the attention must, as a rule, be directed
to them before they are perceived. This condition is favoured thus :—

1. The attention is always directed to the point of the field of vision which is accommodated

for at the time. The image of this part is projected on to both yellow spots, which are
identical points of the retina.

2. The form and colour of objects on the lateral parts of the retina are not perceived so
sharply.

8. The eyes are always accommodated for those points which are looked at. Hence,
‘indistinct images with diffusion circles are always formed by those objects which yield double
images, so that they can be more readily neglected.

4, Many double images lie so close together that the greater part of them, when the images
are large, covers the other.

5. By practice images which do not exactly coincide may be united.

402. STEREOSCOPIC VISION.—On looking at an object, both eyes do not
yield exactly similar images of that object—the images are slightly different,
because the two eyes look at the object from two differ- ae :
ent points of view. With the right eye we can see
more of the side of the body directed towards it, and EG ¢. 6g
the same is the case with the left eye. Notwithstand-
ing this inequality, the two images are united. How

two different images are combined is best understood Fou eee

by analysing the stereoscopic images. B Db d
Let, in fig. 569, L and R represent two such images as are L R

obtained with the left and right eyes. These images, when Fig. 569.

seen with a stereoscope, look like a truncated pyramid, which Two stereoscopic drawings.
projects towards the eye of the observer, as the points indicated

by the same signs cover each other. On measuring the distance of the points, which coincide
or cover each other in both figures, we find that the distances A, a, B, 6, C, c, D, d are equally
great, and at the same time are the widest of all the points of both figures ; the distances E, e,
F, 7, G, g, H, h are also equal, but are smaller than the former. On looking at the coincid-
ing lines (A, E, a, e, and B, F, 0, f), we observe that all the points of this line which lie nearer
to Aa and B dare further apart than those lying nearer E ¢ and Ff.

Comparing these results with the stereoscopic image, we have the following laws
for stereoscopic vision:—1. All those points of two stereoscopic images, and of
course of two retinal images of an object, which in both images are equally distant
from each other, appear on the same plane. 2. All points which are nearer to each
other, compared with the distance of other points, appear to be nearer to the

observer. 8. Conversely, all points which lie further apart from each other appear
perspectively in the background.

The cause of this phenomenon lies in the fact that, “in vision with both eyes

we. constantly refer the position of the individual images in the direction of the
visual axis to where they both intersect.”

Proofs.—The following stereoscopic experiment proves this (fig. 570).:—Take both images of
two pairs of points (a, 6, and a, 8), which are at unequal distances from each other on the
surface of the paper. By means of small stereoscopic prisms cause them to coincide, then the
combined point, A of a, and « appears at a distance on the plane of the paper, while the other
point, B, produced by the superposition of } and 8, floats in the air before the observer. Fig.
570 shows how this occurs. The following experiment shows the same result :—Draw two
figures, which are to be superposed similar to the lines B, A, A, E, 4, a, and a, e, in fig. 569.
In the lines B, A, and 8, a, all the points which are to be superposed lie equally distant from
each other, while, on the contrary, all the points in A, E, and a, ¢, which lie nearer E and e,
are constantly nearer to each other. When looked at with a stereoscope, the superposed
verticals, A, ¢, and B, 0, lie in the plane of the paper, while the superposed lines, A, a, and E,
e, project obliquely towards the observer from the plane of the paper. From these two

fundamental experiments we may analyse all pare of stereoscopic pictures. Thus, in fig. 569,
if we exchange the two pictures, so that R lies in the place of L, then we must obtain the
impression of a truncated hollow pyramid. ©

79° THEORY OF STEREOSCOPIC VISION.

reoscopic pi i so constructed that the one contains the body from the
Phir at “omng a “the « ag ee the front and below (suppose in fig. 569 the lines A B,
and a b, were the ground lines), can never be superposed by means of the stereoscope,

This process has been explained in another way. Of the two figures, R and L
(fig. 569), only A B C D, anda bc d, fall upon identical points of the retina, hence
these alone can be superposed ; or, when there 1s a different convergence of the.
visual axis, only E F GH, and ef g h, can be superposed for the same reason.
Suppose the square ground surfaces of the figures are first superposed, in order to
explain the stereoscopic impression, it is further assumed that both eyes, after

superposition of the ground squares, are rapidly moved towards the apex of the

A a L ——_ B
N He ‘
is ms “ze
‘ ae. ry |
os iN oo
as soy “4
' . ‘

oxy

-
-
-
aor]
x
~

Fig. 570. , Fig. 571.

., Wheatstone’s stereoscope. Scheme of Brewster’s stereoscope.
pyramid. As the axis of the eyes must thereby converge more and more, the apex
of the pyramid appears to project ; as all points which require the convergence of
the eyes for their vision appear to us to be nearer (see below). Thus, all corre-
sponding parts of both figures would be brought, one after the other, upon identical
points of the retina by the movements of the eyes (Briicke).

It has been urged against this view that, the duration of an electrical spark
suffices for stereoscopic vision (Dove)—a time which is quite insufficient for the
movements of the eyes. Although this may be true for many figures, yet in the
correct combination of complex or extraordinary figures, these movements of the
visual axes are not excluded, and in many individuals they are distinctly advan-
tageous. Not only the actual movements necessary for this act, but the sensa-
tions derived from the muscles are also concerned.

When two figures are momentarily combined to form a stereoscopic picture, there
being no movement of the eyes, clearly many points in the stereoscopic pictures are
superposed which, strictly speaking, do not fall upon identical points of the retina.
Hence we cannot characterise the identical points of the retina as coinciding
mathematically ; but from a physiological point of view we must regard such points
as identical, which, as a rule, by simultaneous stimulation, give rise to a single
image. The mind obviously plays a part in this combination of images. There
is a certain psychical tendency to fuse the double images on the retinz into on
image, in accordance with the fact that we, from experience, recognise :
existence of. a single object. If the differences between two stereoscopic pictures

THE STEREOSCOPE. 791

be too great, so that parts of the retina too wide apart are excited thereby, or
when new lines are present in a picture, and do not admit of a stereoscopic effect,
or disturb the combination, then the stereoscopic effect ceases.

The stereoscope is an instrument by means of which two somewhat similar pictures drawn
. in perspective may be superposed so that they appear single. Wheatstone (1838) obtained this
result by means of two mirrors placed at an angle (fig 570); Brewster (1843) by two prisms (fig.
571). The construction and mode of action are obvious from the illustrations.

Some pairs of two such pictures may be combined, without a stereoscope, by directing the
visual axis of each eye to the picture held opposite to it.

Two completely identical pictures, 7.¢.,in which all corresponding points have exactly the
same relation to each other as the same sides of tivo copies of a book, appear quite flat under
the stereoscope ; as soon, however, as in one of them one or more points alters its relation to
the corresponding points, this point either projects or recedes from the plane.

Telestereoscope.— When objects, placed at a great distance, are looked at, ¢.g., the most
distant part of a landscape, they appear to us to be flat, as in a picture, and do not stand out,
because the slight differences of position of our eyes in the head are not to be compared with
the great distance. In order to obtain a stereoscopic view of such objects, v. Helmholtz
constructed the telestereoscope (fig. 572), an apparatus which by means of two parallel mirrors,
places, as it were, the point of view of both eyes wider apart.
Of the mirrors, L and R each projects its image of the landscape

upon 7 and 7, to which both eyes, O, 0, are directed. Accord-
- ing to the distance between L and R the eyes, O, 0, as it were,
are displaced to O, 0, The distant landscape appears like a
stereoscopic view. In order to see distant parts more clearly
and nearer, a double telescope or opera-glass may be placed in
front of the eyes.

Take two corresponding stereoscopic pictures, with the surfaces
black in one case and light in the other. Draw two truncated
pyramids like fig. 569, make one figure exactly like L, ic.,

Fig. 572. Fig. 573.
Telestereoscope of v. Helmholtz. Wheatstone’s Pseudoscope.

with a white surface and black lines, and the other with white lines and a black surface, then
under the stereoscope such objects glance. The cause of the glancing condition is that the
glancing body at a certain distance reflects bright light into one eye and not into the other,
because a ray reflected at an angle cannot enter both eyes simultaneously (Dove).

Wheatstone’s Pseudoscope consists of two right-angled prisms (fig. 573, A and B) enclosed
in a tube, through which we can look in a direction parallel with the surfaces of the
hypothenuses. If a spherical surface be looked at with this instrument, the image formed in
each eye is inverted laterally. The right eye sees the view usually obtained by the left eye,
and conversely; the shadow which the body in the light throws upon a light ground is reversed.
Hence the ball appears hollow. :

Struggle of the Fields of Vision.—The stereoscope is also useful for the following purpose :—
In vision with both eyes, both eyes are almost never active simultaneously and to the same
extent ; both undergo variations, so that first the impression on the one retina and then that on
the other is stronger. If two different surfaces be placed in a stereoscope, then, especially when
they are luminous, these two alternate in the general field of vision, according as one or other
eye is active (Panum). Take two surfaces with lines ruled on them, so that when the surfaces
are superposed the lines will cross each other, then either the one or the other system of lines is
more prominent (Panwm). The same is true with coloured stereoscopic figures, so that there is
a contest or struggle of the coloured fields of vision.

403. ESTIMATION OF SIZE AND DISTANCE.—Size.— We estimate the
size of an object—apart from all other factors—from the size of the retinal image ;
thus the moon is estimated to be larger than the stars. If, while looking at a

792 ESTIMATION OF SIZE AND DISTANCE.

distant landscape, a fly should suddenly pass across our field of vision, near to our
eye, then the image of the fly, owing to the relatively great size of the retinal
image, may give one the impression of an object as large as a bird. If, owing to
defective accommodation, the image gives rise to diffusion circles, the.size may
appear to be even greater. But objects of very unequal size give equally large
retinal images, especially if they are placed at such a distance that they form the
same visual angle (fig. 531); so that in estimating the actual size of an object,
as opposed to the apparent size determined by the visual angle, the estimate of
distance is of the greatest importance.

As to the distance of an object, we obtain some information from the feeling of
accommodation, as a greater effort of the muscle of accommodation is required for
exact vision of a near object than for seeing a distant one. But, as with two
objects at unequal distances giving retinal images of the same size, we know from
experience that that object is smaller which is near, then that object is estimated
to be the smaller for which, during vision, we must accommodate more strongly.

In this way we explain the following :—A person beginning to use a microscope always ob-
serves with his eyes accommodated for a near object, while one used to the microscope looks
through it without accommodating. Hence beginners always estimate microscopic objects as
too small, and on making a drawing of them it is too small. If we produce an after-image in
one eye, it at once appears smaller on accommodating for a near object, and again becomes
larger during negative accommodation. If we look with one eye at a small body placed as near
as possible to the eye, then a body lying behind it, but seen only indirectly, appears smaller.

Angle of Convergence of Visual Axes.—In estimating the size of an object,
and taking into account our estimate of its distance, we also obtain much more
important information from the degree of convergence of the visual axes. We refer
the position of an object, viewed with both eyes, to the point where both visual axes
intersect. The angle formed by the two visual axes at this ‘point is called the -
‘angle of convergence of the visual axes” (“‘ Gesichtswinkel”). The larger, there-
fore, the visual angle, the size of the retinal image remaining the same—we judge
the object to be nearer. The nearer the object is, it may be the smaller, in order
to form a “visual angle” of the same size,
such as a distant large object would give.
Hence, we conclude, that with the same appa-
rent size (equally large visual angle, or retinal
images of the same size) we judge that object
to be smallest which gives the greatest con-
vergence of the visual axes during binocular
vision. As to the muscular exertion necessary
for this purpose, we obtain information from
the muscular sense of the ocular muscles.

Experiments and Proofs—The chess-board pheno-
menon of H. Meyer.—1. If we look at a uniform
chess-board-like pattern (tapestry or carpet), then,
when the visual axes are directed directly forwards,
the spaces on the pattern appear of a certain size, Tf,
now, we look at a nearer object, we may cause the
visual axes to cross, when the pattern apparently moves
towards the plane of the fixed point, so that the crossed
double images are superposed, and the pattern at once

Fig. 574, appears smaller. é .
Rallett’s glass platé a 2. Rollett looks at an object through two thick
pparatus. apa pr of glass ee at an angle. The plates are at
directed towards the observer (fig. 574, II), at aiiother in the ino Fale 1 if toieeek
f and i, are to see the object a, in I, then as the glass plates so displace the rays, a, c, and a, 9
as to make them parallel with the direction of these rays, viz., ¢ J, and h ‘i, then the eyes
must converge more than when they are turned directly towards a. Hence the object appears
nearer and smaller, as at a, In II, the rays, b, k, and 6, 0, from the nearer object b,, fall upon

.

THE EYELIDS. 793

the glass plates. In order to see 0, the eyes (x and g) must diverge more, so that b appears
more distant and larger.

3. In looking through Wheatstone’s reflecting stereoscope (fig. 571), it is obvious that the more
the two images approach the observer, the more must the observer converge his visual axes,
because the angles of incidence and reflexion are greater. Hence the compound picture now
appears to him to be smaller. If the centre of the image, R, recedes to R,, then of course the
angle, S,,, 7p, is equal to S,, 7R,, and the same on the left side.

4. In using the telestereoscope, the two eyes are, as it were, separated from each other, then
of course in looking at objects at a certain distance the convergence of the visual axes must be
greater than in normal vision. Hence, objects in a landscape appear as in a small model. But
as we are accustomed to infer that such small objects are at a great distance, hence the objects
themselves appear to recede in the distance.

Estimation of Distance.—When the retinal images are of the same size, we
estimate the distance to be greater the less the effort of accommodation, and con-
versely. In binocular vision, when the retinal images are of the same size, we
infer that that object is most distant for which the optic axes are least converged,
and conversely. Thus, the estimation of size and distance go hand in hand, in
great part at least, and the correct estimation of the distance also gives us a correct
estimate of the size of objects (Descartes). A further aid to the estimation of
distance is the observation of the apparent displacement of objects, on moving our
head or body. In the latter, especially, lateral objects appear to change their
position toward the background, the nearer they are to us. Hence, when travel-
ling in a train, in which case the change of position of the objects occurs very
rapidly, the objects themselves are regarded as nearer, and also smaller (Dove).
Lastly, those objects appear to us to be nearest which are most distinct in the field
of vision.

Example.—A light in a dark landscape, and a dazzling crown of snow on a hill, appear to be
near to us; looked at from the top of a high mountain, the silver glancing curved course of a
river not unfrequently appears as if it were raised from the plane.

False Estimates of Size and Direction.—1. A line divided by intermediate points appears
longer than one not so divided. Hence the heavens do not appear to us as a hollow sphere,
but as curved like an ellipse; and for the last reason the disc of
the setting sun is estimated to be larger than the sun when it is in
the zenith. 2. If we move a circle slowly to and fro behind a slit,
it appears as a horizontal ellipse; if we move it rapidly, it appears
as a vertical ellipse. 3. If avery fine line be drawn obliquely across
a vertical thick black line, then the direction of the fine line be-
yond the thick one appears to be different from its original
direction. 4, Zollner’s Lines.—Draw three parallel horizontal
lines 1 centimetre apart, and through the upper and lower ones
draw short oblique parallel lines in the direction from above and
the left to below and the right; through the middle line draw
similar oblique lines, but in the opposite direction, then the three
horizontal-lines no longer appear to be parallel. [Fig. 575 shows
-a modification of this. The lines are actually parallel, although Fig. 575.
some of them appear to converge and others to diverge.] If we Zoéllner’s Lines.
look in a dark room at a bright vertical line, and then bend the
head towards the shoulder, the line appears to be bent in the opposite direction (Aubert).

404. PROTECTIVE ORGANS OF THE EYE.—I. The eyelids are represented in section in
fig. 576. The tarsus is in reality not a cartilage, but merely a rigid plate of connective-tissue,
in which the Meibomian glands are imbedded; acinous sebaceous glands moisten the edges of
the eyelids with fatty matter. At the basal margin of the tarsus, especially of the upper one,
close to the reflection of the conjunctiva, open the acino-tubular glands of Krause. ‘The con-
junctiva covers the anterior surface of the bulb as far as the margin of the cornea, over
which the epithelium alone is continued. On the posterior surface of the eyelid, the conjunctiva
is partly provided with papilla. Itis covered by stratified prismatic epithelium. Coiled glands
occur in ruminants just outside the margin of the cornea, while outside this, towards the outer
angle of the eye in the pig, there are simple glandular sacs. Waldeyer describes modified
sweat glands in the tarsal margins in man. Small lymphatic sacs in the conjunctiva are called
trachoma glands. Krause found end-bulbs in the conjunctiva bulbi (§ 424). The blood-vessels
in the conjunctiva communicate with the juice-canals in the cornea and. sclerotic (p. 737).

794 THE LACHRYMAL APPARATUS.

The secretion of the conjunctiva, besides some mucus, consists of tears, which may be as

abundant as that formed in the lachrymal glands.

Closure of the eyelids is effected by the orbicularis palpebrarum (facial nerve,

Vertical section through the upper eyelid. .4, cutis;
1, epidermis ; 2, chorium; B and 3, subcutaneous
conuective-tissue ; C and 7, orbicularis muscle; D,
loose sub-muscular connective-tissue ; Z, insertion

of H. Miuller’s muscle ; F, tarsus ; G, conjunctiva ;

J, inner, X, outer edge of the lid; 4, pigment-cells ;

5, sweat glands; 6, hair follicles; 8 and 23, sections

of nerves; 9, arteries; 10, veins; 11, cilia; 12, modi-

fied sweat glands; 13, circular muscle of Riolan ;

14, Meibomian gland; 15, section of an acinus of

the same ; 16, posterior tarsal glands ; 18 and 19,

tissue of the tarsus; 20, pretarsal or sub-muscular

connective-tissue ; 21 and 22, conjunctiva, with its
epithelium ; 24, fat; 25, loosely woven posterior
end of the tarsus; 26, section of a palpebral artery.

§ 349), whereby the upper lid falls

9 in virtue of its own weight. This

muscle contracts—(1) voluntarily ;
(2) involuntarily (single contrac-
tions); (3) reflexly by stimulation
of all the sensory fibres of the tri-
geminus distributed to the bulb and
its immediate neighbourhood (§ 347),
also by intense stimulation of the
retina by light; (4) continued in-
voluntary closure occurs during
sleep.

Opening of the eyelids is brought
about by the passive descent of the
lower one, and the active elevation
of the upper eyelid by the levator
palpebrze superioris (§ 345). The
smooth muscular fibres of the eye-

lids also aid (p. 593). In looking

downwards, the lower eyelid is
pulled downwards by bands of con-
nective-tissue which run from the
inferior rectus to the inferior tarsal
cartilage (Schwalbe).

II. The lachrymal apparatus consists
of the lachrymal glands, which in struc-
ture closely resemble the parotid, their
acini being lined by low cylindrical granu-
lar epithelium. Four to five larger, and
eight to ten smaller excretory ducts con-
duct the tears above the outer angle of
the lid into the fornix conjunctive. The
tear ducts, beginning at the puncta
lachrymalis, are composed of connective
and elastic-tissue, and are lined by
stratified squamous epithelium. Striped
muscle accompanies the duct, and by its
contraction keeps the duct open. Toldt
found no sphincter surrounding the
puncta lachrymalia, while Gerlach found
an incomplete circular musculature, The
connective-tissue covering of the tear sac
and canal is united with the adjoining
periosteum. The thin mucous membrane,
which contains much adenoid tissue and
lymph-cells, is lined by a single layer of
ciliated cylindrical epithelium, which
below passes into the stratified form. The
opening of the duct is often provided
with a valve-like fold (Hasner’s valve),

The conduction of the tears oc-
curs between the lids and the bulb
by means of capillarity, the closure
of the eyelids aiding the process.

The Meibomian secretion prevents the overflow of the tears [just as greasing the

\

a

THE SECRETION OF TEARS. 795

edge of a glass vessel prevents the water in it from overflowing]. The tears are
conducted from the puncta through the duct, chiefly by a siphon action. Horner’s
muscle (also known to Duvernoy, 1678) likewise aids, as every time the eyelids are
closed it pulls upon the posterior wall of the sac, and thus dilates the latter, so
that it aspirates tears into it (Henke).

E. H. Weber and Hasner ascribe the aspiration of the tears to the diminution of the amount
of air in the nasal cavities during inspiration. Arlt asserts that the tear sac is compressed by
the contraction of the orbicularis muscle, so that the tears must be forced towards the nose.
Lastly, Stellwag supposes that when the eyelids are closed the tears are simply pressed into the

uncta, while Gad denies that there is any kind of pumping mechanism in the nasal canal.
andois points out that the tear ducts are surrounded by a plexus of veins, which according to
their state of distension may influence the size of these tubes.

The secretion of tears takes place only by direct stimulation of the lachrymal
nerve (§ 347, I., 2), subcutaneous malar (§ 347, IL, 2), and cervical sympathetic
(§ 356, A, 6), which have been called secretory nerves. Secretion may also be
excited reflexly (p. 591) by stimulation of the nasal mucous membrane only on the

same side (Herzensten). The ordinary secretion in the waking condition is really

a reflex secretion produced by the stimulation of the anterior surface of the bulb
by the air, or by the evaporation of tears. A very bright light also causes a
reflex secretion of tears, the optic being the afferent nerve. The centre in the
rabbit does not extend forward beyond the origin of the fifth nerve, but it extends
downwards to the fifth vertebra (Hckhard). During sleep all these factors are
absent, and there is no secretion. Histological changes.—Reichel found that in
the active gland (after injection of pilocarpin) the secretory cells became granular,
turbid, and smaller, while the outlines of the cells became less distinct, and the
nuclei spheroidal. In the resting gland, the cells are bright and slightly granular
with irregular nuclei. Intense stimulation by /ight acting on the optic nerve causes
a reflex secretion of tears. The flow of tears accompanying certain violent emotions,
and even hearty laughing, is still unexplained. During coughing and vomiting
the secretion of tears is increased partly reflexly, and partly by the outflow being
prevented by the expiratory pressure. }

Function.—The tears moisten the bulb, protect it from drying, and float away
small particles, being aided in this by the closure of the eyelids. Atropin
diminishes the tears (Mogaard).

Composition.—The tears are alkaline, saline to taste, and represent a “ serous”
secretion. Water 98-1 to 99; 1°46 organic substances (0°1 albumin and mucin,
0-1 epithelium) ; 0°4 to 0°8 salts (especially NaCl) .

[Action of Drugs.—Essential volatile oils and eserin increase the secretion of tears, atropin
arrests it, while eserin antagonises the effect of atropin and causes an increased secretion. ]

405, COMPARATIVE—HISTORICAL.—Comparative.—The simplest form of visual appa-
ratus is represented by aggregations of pigment-cells in the outer coverings of the body, which
are in connection with the termination of afferent nerves. The pigment absorbs the rays of
light, and in virtue of the light-ether discharges kinetic energy, which excites the terminations
of the nervous apparatus. Collections of pigment-cells, with nerve-fibres attached, and pro- °
vided with a clear refractive body, occur on the margin of the bell of the higher medusz, while
the lower forms have only aggregations of pigment on the bases of their tentacles. Also, in
many lower worms there are pigment spots near the brain. In others, the pigment lies as a
covering round the terminations of the nerves, which occur as ‘“‘ crystalline rods” or ‘‘ crystal-
line spheres.” In parasitic worms, the visual apparatus is absent. In star-fishes, the eyes are .
at the tips of the arms, and consist of a spherical crystal organ surrounded with pigment, with
a nerve going to it. In all other echinodermata there are only accumulations of pigment.
Amongst the annulosa there are several grades of visual apparatus—(1) Without a cornea, there

_Inay be only one crystal sphere (nervous end-organ) near the brain, as in the young of the crab ;

or there may be several crystal spheres forming a compound eye, as in the lower crabs, (2)
With a cornea, consisting of a lenticular body formed from the chitin of the outer integument,
the eye itself may be simple, merely consisting of one crystal rod, or it may be compound. The
compound eye consists of only one large lenticular cornea, common to all the crystal rods, as in
the spiders ; or each crystal rod has a special lenticular cornea for itself. The numerous rods

796 COMPARATIVE—HISTORICAL.

8 nded by pigment are closely packed together, and are arranged upon a curved surface, so
that their free satis also form a for of a sphere. The chitinous investment of the head is
facetted, and forms a small corneal lens on the free end of each rod. According to one view,
each facette, with the lens and the crystal sphere, is a special eye, and just as man has two eyes
so insects have several hundred. Each eye sees the picture of the outer world in toto. This
view is supported by the following experiment of van Leeuwenhoek :—If the cornea be sliced
off, each facette thereof gives a special image of an object. If a cross be made on the mirror of
a microscope, while a piece of the facetted cornea is placed as an object upon the stage, then we
see an image of the cross in each facette of the cornea, Thus for each rod (crystal sphere) there
would be a special image. Each corneal facette, however, forms only a part of the image of the
outer world, so that we must regard the image as composed like a mosaic. Amongst mollusca,
the fixed brachiopoda have two pigment spots near the brain, but only in their larval condition ;
while the mussel has, under similar conditions, pigment spots with a refractive body. The
adult mussel however, has pigment spots (ocelli) only in the margin of the mantel, but some
molluscs have stalked and highly deve H ip eyes. Some of the lower snails have no eyes, some
have pigment spots on the head, while the (poe snail has stalked eyes provided with a cornea,
an optic nerve with retina and pigment, and even a lens and vitreous body. Amongst cepha-
aoa, the nautilus has no cornea or lens, so that the sea-water flows freely into the orbits.
Others have a lens and no cornea, while some have an opening in the cornea (Loligo, Sepia,
Octopus). All the other parts of the eye are well developed. Amongst vertebrata, Amphioxus
has no eyes. They exist in a degenerated condition in Proteus and the mammal Spalax. In
many fishes, amphibians, and reptiles, the eye is covered by a piece of transparent skin.
[Pineal or Epiphysial Eye.—Some lizards, ¢.g., Hatteria, have a rudimentary median eye in the
median line of the head, and lodged in the parietal foramen. It is developed from the pineal
body, and its lens is formed from the optic cup, so that light falls upon the retina without
penetrating the fibres of the optic nerve. Thus, it is an invertebrate type of eye, where the
retina and lens are developed from epidermal structures, while in the vertebrate eye, the retina
is developed from the cerebrum.] Some hag-fishes, the crocodile, and birds have eyelids, and a
nictitating membrane at the inner angle of the eye. Connected with it is the Harderian
gland. In mammals the nictitating membrane is represented only by the plica semilunaris.
There is no lachrymal apparatus in fishes. The tears of snakes remain under the watch-glass-
like cutis with which the eyes are covered. The sclerotic often contains cartilage which may .
ossify. A vascular organ, the processus falciformis, passes from the middle of the choroid into
the interior of the vitreous body in osseous fishes, its anterior extremity being termed the
campanula Halleri. Similarly, thats is the pecten in birds, but it is provided with muscular
fibres. In birds the cornea is surrounded by a bony ring. The whale has an enormously thick
sclerotic. In aquatic animals, the lens is nearly spherical. The muscles of the iris and
choroid are transversely striped in birds and reptiles. The retinal rods in all vertebrates are
directed from before backwards, while the analogous elements (crystal rods and spheres) in
invertebrata are directed from behind forward.

Historical.—The Hippocratic School were acquainted with the optic nerve and lens. Aristotle
(384 B.c.) mentions that section of the optic nerve causes blindness—he was acquainted with
after-images, short and long sight. ae uae (307 B.c.) discovered the retina, and the ciliary
processes received their name in his school. Galen (131-208 a.p.) described the six muscles of
the eyeball, the puncta lachrymalia, and tear duct. Aerengar (1521) was aware of the fatty
matter at the edge of the eyelids. Stephanus (1545) and Casseri (1609) described the Meibomian
glands, which were afterwards redescribed by Meibom (1666). Fallopius described the vitreous
membrane and the ciliary ligament. Plater (1583) mentions that the posterior surface of the
lens is more curved. Aldrovandi observed the remainder of the pupillary membrane (1599).
Observations were made at the time of Vesalius (1540) on the refractive action of the lens.
Leonardo da Vinci compared the eye to a camera obscura. Maurolykos compared the action of
the lens to that of a lens of glass, but it was Kepler (1611) who first showed the true refractive
index of the lens and the formation of the retinal image, but he thought that during accommo- ©
dation the retina moved forward and backward. The J esuit, Scheiner (+ 1650), mentions, how-
ever, that the lens becomes more convex by the ciliary processes, and he assumed the existence
of muscular fibres in the uvea. He referred long and short sight to the curvature of the lens,
and he first showed the retinal image in an excised eye. With regard to the use of spectacles
there is a reference in Pliny. It is said that at the beginning of the 14th century the Floren-
tine, Salvino d Armato degli Armati di Fir (+1817), and the monk, Alessandro de Spina (+1313),
invented spectacles. Kepler (1611) and Descartes (1637) described their action. ays (+1852)
described the 3rd nerve as the constrictor nerve of the pupil. Zinn contributed considerably
to our Fonte“ of the structure of the eye. Ruysch described muscular fibres in the iris, and.
Monro described the sphincter of the pupil (1794). Jacob described the bacillary layer of i»
retina—Scemmering (1791) the yellow spot. Brewster and Chossat (1819) tested the
indices of the optical media. Purkinje (1819) studied subjective vision. 1

q

j SS
i NUS ;

re | a

Hearing.

406. THE ORGAN OF HEARING.—Stimulation of the Auditory Nerve.
—The normal manner in which the auditory nerve is excited, is by means of
sonorous vibrations, which set in motion the end-organs of the acoustic nerve,
which lie in} the endolymph of the labyrinth of the inner ear, on membranous

expansionsof the cochlea
and semicircular canals.
Hence, the sonorous vi-
brations are first trans-
mitted to the fluid in
the labyrinth, and this,
in turn, is thrown into
waves, which set the end-
organs into vibration.
Thus, the excitement of
the auditory nerves is
brought about by the
mechanical stimulation
of the wave-motion of the
lymph of the labyrinth.
The fluid or lymph
of the labyrinth is sur-
rounded by the exceed-
ingly hard osseous mass
of the temporal bone (fig.

577). Only at one small gcheme of the organ of hearing.

- roundish and _ slightly
triangular area, the fe-
nestra rotunda (7), the
fluid is bounded by a
delicate yielding mem-

brane, which is in con- .

tact with the air in the
middle ear or tympanum

(P). Not far from the fenestra rotunda is the fenestra ovali
base of the stapes (s) is fixed by means of a yielding membranot
surface of this also is in contact with thé air in the middle ear,

Fig. 577.

AG, external auditory meatus;
T, tympanic membrane; K, malleus with its head (%), short
process (Xf), and handle (m); @, incus, its short process (a), and
its long process united to the stapes (s) by means of the Sylvian
ossicle (z); P, middle ear; 0, fenestra ovalis; 7, fenestra rotunda;
x, beginning of the lamina spiralis of the cochlea; pt, scala
tympani, and vé, scala vestibuli; V, vestibule; S, saccule; U,
utricle; H, semicircular canals; TE, Eustachian tube. The
long arrow indicates the line of traction of the tensor tympani;
the short curved one, that of the stapedius,

§ (0), in which the
S$ ring. The outer
- As the perilymph

of the inner ear is in contact at these two places with a yielding boundary, it is
clear that the lymph itself may exhibit oscillatory movements, as it must follow the
movements of the yielding boundaries. ia

798 CONDUCTION OF SOUND TO THE LABYRINTH.
The sonorous vibrations may set the perilymph in vibration in three different

ways :— : .
: i Conduction through the Bones of the Head.—This occurs especially when
the vibrating solid body is applied directly to some part of the head, e.g., @ tuning-
fork placed on the head, the sound being propagated most intensely in the
direction of the prolongation of the handle of the instrument—also when the sound
+s conducted to the head by means of fluid, as when the head is ducked under
water. Vibrations of the air, however, are practically not transferred directly to
the bones of the head, as is shown by the fact that we are deaf when the ears are

stopped.

The soft parts of the head, which lie immediately upon bone, conduct sound best, and of the
projecting part, the best conductor is the cartilaginous portion of the external ear. But even
under the most favourable circumstance, conduction through the bones of the head is far less
effective than the conduction of the sound-waves through the external auditory meatus. If a
tuning-fork be made to vibrate between the teeth until we no longer hear it, its tone may still
be heard on bringing it near the ear (Rinne). The conduction through the bones is favoured
when the oscillations are not transferred from the bones to the tympanic membrane, and are
thus transferred to the air, in the outer ear. Hence, we hear the sound of a tuning-fork applied
to the head better when the ears are stopped, as this prevents the propagation of the sound-
waves through the air in the outer ear. If, in a deaf person, the conduction is still normal
through the cranial bones, then the cause of the deafness is not in the nervous part of the ear,
but in the external sound-conducting part of the apparatus.

2. Normal hearing takes place through the external auditory meatus. The
enormous vibrations of the air first set the tympanic membrane in vibration (fig.
577, T); this moves the malleus (4), whose long process is inserted into it; the
malleus moves the incus (a), and this the stapes (s), which transfers the movements
of its plate to the perilymph of the labyrinth.

3. Direct Conduction to the Fenestra.—In man, in consequence of occasional disease of the _
middle ear, whereby the tympanic membrane and auditory ossicles may be destroyed, the
auditory apparatus may be excited, although only in a very feeble manner, by the vibrations of
the air being directly transferred to the membrane of the fenestra rotunda (7), and the parts
closing the fenestra ovalis (0). The membrane of the fenestra rotunda may vibrate alone, even
when the oval window is closed with a rigid body ( Weber-Liel).

407. PHYSICAL INTRODUCTION.—Sound is produced by the vibration of elastic bodies
capable of vibration. Alternate,condensation and rarefaction of the surrounding air are thus
produced ; or, in other words, sound-waves in which the particles vibrate longitudinally or in
the direction of the propagation of the sound are excited. Around the point of origin of the
sound, these condensations and rarefactions occur in equal concentric circles, which conduct
the sound vibrations to our outer ear. The vibrations of the sounding body are so called
‘« stationary vibrations,” i.¢., all the particles of the vibrating body are always in the same
phase of movement, in that they pass into movement simultaneously, they reach the maximum
of movement simultaneously, ¢.g., in the particles of a sounding vibrating metal rod. Sound
is produced by the stationary vibrations of elastic bodies ; it is propagated by progressive
wave-motion of elastic media, generally the air. The wave-length of a tone, 1.¢., the istance
of one maximum of condensation to the next one in the air, is proportional to the duration of
the vibration of the body, whose vibrations produce the sound-waves.

If A is the wave-length of a tone, ¢ in second the durations of a vibration ‘of the body.
producing the wave, then A= t, where n=3840°88 metres, which is the rate per second of
propagation of sound-waves in the air. The rapidity of the transmission of sound-waves in
water = 1435 metres per second, i.¢., nearly four times as rapid as in air; while, in solids
capable of vibration, it is sy from seven to eighteen times faster than in the air.
Sound-waves are conducted best through the same medium; when they have to pass through
several media they are always weckened. ;

Reflection of the sound-waves occurs when they impinge upon a solid obstacle, in which case
the angle of reflection is always equal to the angle of ada |

Wave Movements.—We distinguish—I. Progressive wave movements which occur in tw
forms—{1) As longitudinal waves, in which the individual particles of the vibrating body
vibrate around their centre of gravity in the direction of the propagation of the wave ; examples
are the waves in water and air. This movement causes an accumulation of the particles at
certain oT €.9., ON the crests of the waves in water-waves, while at other places they
diminished. This kind of wave is called a wave of condensation and rarefaction. — (2) Ih
however, each particle in the progressive wave moves vertically up and down, %.e., tra

THE EAR MUSCLES AND EXTERNAL AUDITORY MEATUS. 799

to the direction of the propagation of the wave, then we have the simple transverse waves, or
progressive waves, in which there is no condensation or rarefaction in the direction of propaga-
tion, as each particle is merely displaced laterally. An example of this is the progressive waves
in @ rope.

II. Stationary Flexion Waves,—When all the particles of an elastic vibrating body so
oscillate that all of them are always in the same phase of movement as the limbs of a vibrating
tuning-fork or a plucked string, then this kind of movement is described as stationary flexion
waves. As bodies, whose expansion in the direction of oscillation is very slight, vibrate to and
fro in the stationary flexion wave, so we see that the small parts of the auditory apparatus
{tympanic membrane, ossicles, lymph of the labyrinth) oscillate in stationary flexion waves.

408. EAR MUSCLES—EXTERNAL AUDITORY MEATUS.—When the external ear is
absent, little or no impairment of the hearing is observed ; hence, the physiological functions
of these organs are but slight. Boerhaave thought that the elevations and depressions of. the
outer ear might be connected with the reflection of the sound-waves, Numerous sound-waves,
however, must be again reflected outwards ; and those waves which reach the deep part of the
concha are said to be reflected towards the tragus, to be reflected by it into the external
auditory meatus. According to Schneider, when the depressions in the ear are filled up with
wax, hearing is impaired ; other observers, however, have found the hearing to be unaffected.
Mach points out that the dimensions of the external ear are proportionally too small to act as
reflecting organs for the wave-lengths of noises.

Muscles of the External Ear.—(1) The whole ear is moved by the retrahentes, attrahens, and
attollens. (2) The form of the ear may be altered by the tragicus, antitragicus, helicis major
and minor internally ; and by the transversus and obliquus auricule externally. Persons who
can move their ears do not find that the hearing is influenced during the movement. The Mm.
helicis major and minor are regarded as elevators of the helix, the transversus and obliquus
auricule as dilators of the concha; the tragicus and antitragicus as constrictors of the meatus.
In animals, the external ear and the action of its
muscles have a marked effect upon hearing. The
muscles point the ear in the direction of the sound,
while other muscles contract or dilate the space within
the externalear. In many diving animals, the meatus
can be closed by a kind of valve.

The external meatus is 3 to 3:25 cm. long
[14 to 14 inch], 8 to 9 mm. high, and 6 to 8 7
mm. broad at its outer opening (fig. 578). It (/ Nee,
is the conductor of the sound-waves to the Net RY. 5er
tympanic membrane, so that almost all the a SS hin,
sound-waves first impinge upon its wall, and 3
are then reflected towards the tympanic mem-
brane. To see well down into the meatus, we
must pull the auricle upwards and backwards.
Occlusion of the meatus, especially by a plug
of inspissated wax (§ 287), of course interferes :
with the hearing, [and when it presses on the Fig, 578.

|
a

—~

membrana tympani may give rise to severe The external auditory meatus and the
vertigo]. tympanic cavity. M, osseous spaces in

: the temporal bone; Pe, cartilaginous
409. TYMPANIC MEMBRANE.—The part of the meatus ; L, membranous
tympanic membrane, which is tolerably laxly Union between both ; F, auricular sur-
fixed in a special osseous cleft, with a thickened £#¢¢ for the condyle of the lower jaw.
margin, is an elastic, unyielding, and almost non-extensible membrane of about 0:1
mm. in thickness, and with a superficial area of 50 square millimetres (fig. 581).
It is elliptical in form, its greater diameter being 9:5 to 10 mm., and its lesser 8
mm., and it is fixed in the floor of the external meatus obliquely, at an angle of
40°, being directed from above and outwards, downwards and inwards. Both
tympanic membranes converge anteriorly, so that if both were prolonged they
would meet to form an angle of 130° t0 135°. The oblique position enables a larger
surface to be presented than would be obtained if it were stretched vertically, so
that more sound-waves can fall vertically upon it. 'The membrane is not stretched
flat, but a little under its centre (umbilicus) it is drawn slightly inwards by the

800 THE MEMBRANA TYMPANI.

handle of the malleus, which is attached to it 5 while the short process of the
allot slightly bulges out the membrane near its upper margin (figs. 577, 584).

: : i :—(1) The membrana propria
Structure.—The tympanic membrane consists of three layers :—(1)
is a fibrous membrane with radial fibres on its outer surface, and Paqurenen nee a linae
$ surface directed towards the
meatus is covered with a thin
and semi-transparent part of
the cutis. (3) The side to-
wards the tympanum is cover-
ed with a delicate mucous
membrane, with simple squa-
mous epithelium. Numerous
nerves and lymph-vessels, as
well as inner and outer blood-
vessels, occur in the mem-
brane.

[The middle layer, or
substantia propria, is fixed
to a ring of bone, which
is deficient above. It is
filled up by a layer com-
posed of the mucous and
Fig. 581. Fig. 580. cutaneous layers called

Fig. 579.—Tympanic membrane with the auditory ossicles (left) the membrana Jlaccida, or
seen from within. Cv, incus; Cm, malleus ; Ch, chorda tym- Shrapnell’s membrane. |
pani; 7, pouch-like depression (after Urbantschitsch). Fig. [Examination,— Wh
580.—Tympanic membrane and the auditory ossicles (left) seen re h ae en ae
from within, i.e., from the tympanic cavity. M, manubrium 4™nIng the outer ear an
or handle of the malleus ; T, insertion of the tensor tympani ; membrana tympani, ull the
h, head; JF, long process of the malleus; a, incus, with the sears apres a back-
short (K) and the long (/) process; S, plate of the stapes; WA!CS. e membrana tym-
Az, Az, is the common axis of rotation of the auditory ossicles ; P@! 1S examined by means of
S, the pinion-wheel arrangement between the malleus and 42 ear specw um (fe. ies
incus. Fig. 581.—Tympanic membrane of a new-born child The speculum is placed in
seen from without, with the handle of the malleus visible on it. the: ear, and light is re-
At, tympanic ring with its anterior (v) and posterior (/) ends. flected into it by means of a

coucave mirror, perforated in
the centre, and having a focal distance of four or five inches. It is convenient to have the
mirror fixed to a band placed round the head, as in the case of the laryngoscopic reflector

(fig. 359). It is important to remember that the membrane is placed obliquely, so that the

posterior and upper parts are nearer the surface. The membrane in health is greyish in colour

and transparent, so that the handle of the malleus is seen running from
above downwards and backwards, while at the anterior and inferior part
there is a cone of light with its apex directed inwards. ]

Function.—The tympanic membrane catches up the sound-
waves which penetrate into the external meatus, and is set into
vibration by them, the vibrations corresponding in number and

0 amplitude to the vibrating movements of the air. Politzer
connected the auditory ossicles fixed to the tympanic membrane
of a duck with a recording apparatus, and could thus register
the vibrations produced by sounding any particular tone. Owing
to its small dimensions, the tympanic membrane can vibrate
in toto, to and fro in the direction of the sound-waves correspond-
ing to the condensations and rarefactions of the vibrating air, and
therefore executes transverse vibrations, for which it is specially
Ear specula of adapted, owing to the relatively slight resistance.
various sizes. Fundamental Note.—Stretched strings and membranes are

generally only thrown into actual and considerable sympathetic vibration when
they are affected by tones which correspond with their own fundamental tone, or

FUNCTIONS OF THE OUTER EAR. SOI

whose number of vibrations is some multiple of the number of vibrations of the
same, as the octave. When other tones act on them, they exhibit only inconsider-
able sympathetic vibration. Ifa membrane be stretched over a funnel or cylinder,
and if a nodule of sealing wax attached to a silk thread be made just to touch the
centre of the membrane, then the sealing wax remains nearly at rest when tones or
sounds are made in the neighbourhood ; as soon, however, as the fundamental or
proper tone of this arrangement is sounded, the nodule is propelled by the strong
vibrations of the membrane." | :

If we apply this to the tympanic membrane, then it also should exhibit very
great vibrations when its own fundamental note is sounded, but only slight
vibrations when other tones are produced. This, however, would produce great
inequality in the audible sounds. There isan arrangement of the membrane where-
by this is prevented. (1) Great resistance is offered to the vibrations of the
tympanic membrane, owing to its union with the auditory ossicles. These act as a
damping apparatus, which provides, as in damped membranes generally, that the
tympanic membrane shall not exhibit excessive sympathetic vibrations for its own
fundamental note. But the damping also makes the sympathetic vibrations less
for all the other tones. In this way, al/ vibrations of the tympanic membrane are
modified ; especially, however, is the excessive vibration diminished during the
sounding of its fundamental tone. The membrane is at the same time rendered
more capable of responding to the vibrations of different wave-lengths. The damp-
ing also prevents after-vibrations, (2) Corresponding to the small mass of the
tympanic membrane, its sympathetic vibrations must also be small. Nevertheless,
these slight elongations are quite sufficient to convey the sonorous movements to
the most delicate end-organs of the auditory nerve ; in fact, there are arrangements
in the tympanum which still further diminish the vibrations of the
tympanic membrane. °

As v. Helmholtz has shown, the strong sympathetic vibrations of the tym-
panic membrane are not completely set aside by this damping arrangement.
The painful sensations produced by some tones are, perhaps, due to the sympa-
thetic vibration of the membrana tympani, According to Kessel, certain parts
of the membrane vibrate to certain. tones; the shortest radial fibres at the
upper part of the anterior and upper segment vibrate with the highest tones,
the longest fibres at the posterior segment with the deepest tones, At the
upper part of the posterior segment noises are transmitted.

According to Fick, the tympanic membrane, besides possessing the property

of taking up all vibrations with nearly equal intensity, has also the properties
of a resonance apparatus ; 7.¢., it causes a summation of the energy of suc- a
cessive vibrations. This is due to the funnel-shape of the membrane, and to :

the radial, rigid insertion of the handle of the malleus. Fig. 583.

Pathological. —Thickenings or inequalities of the tympanic membrane inter- Toynbee’s artifi-
fere with the acuteness of hearing, owing to the diminished capacity for vibra- cial membrana
tion ‘thereby produced. Holes in and loss of its substance act similarly. In tympani.
extensive destruction, an artificial tympanum is placed in the external meatus,
and its vibrations, to a certain extent, replace those of the lost membrane (Toynbee). [Fig.
583 shows an artificial tympanic membrane. ] ;

410. AUDITORY OSSICLES AND THEIR MUSCLES.—The auditory
ossicles have a double function.—(1) By means of the “chain” which they form,
they transfer the vibrations of the tympanic membrane to the perilymph of the
labyrinth. (2) They also afford points of attachment for the muscles of the middle
ear, which can alter the tension of the membrana tympani, and the pressure on the
lymph of the labyrinth.

Mechanism.—The form and position of the ossicles are given in figures 584 and
585. They form a jointed chain which connects the tympanic membrane, M, by
means of the malleus, /, incus, a, and stapes, 8, with the perilymph of the labyrinth.
The mode of movement of the ossicles is of special importance. The handle of
the malleus is firmly united to the fibres of the tympanic membrane (fig. 585, 7).

802 MECHANISM OF THE AUDITORY OSSICLES.

Besides this, the malleus is fixed by Zigaments which prescribe the direction of its
movements. Two ligaments—the lig. mallei anticum (passing from the processus
Folianus) and the posticum (froma small crest on the neck)—together form a com-
mon axial band (v. Helmholtz), which acts in the direction from behind forwards, 2.¢.,
parallel:to the surface of the tympanic membrane. The neck of the malleus lies
between the insertions of both ligaments. The united ligament determines the

eae ee movement of the malleus.

cs a When the handle of the
“— malleus is drawn inwards, of

course its head moves in the

opposite direction, or outwards,
Cara rtie The ¢ncus, a, is only partially

Aa See fixed by a ligament, which.at-
ebony SER

Fig. 585. Fig. 584.

Fig. 584.—The auditory ossicles (right). C.m, head; C, neck; Pbr, short process ; Pri, long
process ; M, handle of the malleus; Ci, body ; G, articular surface ; 4, short, and v, long
process of the incus; 0.S, so-called lenticular ossicle ; C.s, head ; a, anterior, and p, poste-
rior limb; P, plate of the stapes. Fig. 585.—Tympanum and auditory ossicles (left) mag-
nified. A.G., external meatus ; M, membrana tympani, which is attached to the handle of
the malleus, 7, and near it the short process, p; h, head of the malleus; a, incus; &, its
short process with its ligament; J, long process; s, Sylvian ossicle ; 8, stapes ; Ax, Aa,
is the axis of rotation of the ossicles, it is shown in perspective, and must be imagined to

- penetrate the plane of the paper; ¢, line of traction of the tensor tympani. The other
arrows indicate the movement of the ossicles when the tensor contracts.

taches its short process to the wall of the tympanic cavity, in front of the entrance
to the mastoid cells, k. The not very tense articulation joining it to the head
of the malleus, 4, which lies with its saddle-shaped articular surface in the hollow
of the incus, is important. The lower margin of the incus (fig 584, S) acts like
a tooth of a cog-wheel. Thus, when the handle of the malleus moves inwards

to the tympanic cavity, the incus, and its long process, 6, which is. parallel to ©

the handle of the malleus, also pass inwards. The incus forms almost a right
angle with the stapes, 8, through the intervention of the Sylvian. ossicle, sy » If,
however, as by condensation of the air in the tympanum, the membrana tympani
and the handle of the malleus move outwards, the long process of the incus does
not make a similar movement, as the malleus moves away from this margin of the
ineus. Hence, the stapes is not liable to be torn from its socket. The malleus and
incus form an angular lever, which moves round a common axis (fig. 581 and fig,
585, Aa, Ax). In the inward movement, the malleus follows the incus, as if both
formed one piece. The common avis (fig. 580) is not, however, the axial ligament
of the malleus, but it is formed anteriorly by the processus Folianus, LF, direc
forwards, and posteriorly by the short process of the incus directed backwat

The rotation of both ossicles around this axis occurs in a plane vertical to the p ne

“axis of rotation” of the

MOVEMENTS OF THE AUDITORY OSSICLES. 803

of the membrana tympani. During the rotation, of course the parts above this
axis (head of the malleus and upper part of the body of the incus) take a direction
opposite to the parts lying below it (the handle of the malleus and the long process
of the incus), as is indicated in fig. 585 by the direction of the arrows. The
movement of the handle of the malleus must follow that of the membrana tympani,
and vice versd, while the movement of the stapes is connected with the movement
of the long process of the incus, As the long process of the incus is only two-
thirds of the length of the handle of the malleus (figs. 577, 581, 585), of course the
excursion of the tip of the former, and with it of the stapes, must be correspond-
ingly Jess than the movement of the tip of the handle of the malleus ; while, on the
other hand, the force of the movement of the tip of the handle of the malleus,
corresponding to the diminution of the excursion, will be increased.

Mode of Vibration.—Thus, the movement of the membrana tympani inwards
causes a less extensive but a more powerful movement of the foot of the stapes
against the perilymph of the labyrinth. V. Helmholtz and Politzer calculated the
extent of the movement to be 0°07 mm. The mode in which the vibrations of the
membrana tympani are conveyed to the lymph of the labyrinth, through the chain
of ossicles, is quite analogous to the mechanism of these parts already described.
Long delicate glass threads have been fixed to these ossicles, and their movements
were thus graphically recorded on a smoked surface ( Polztzer, Hensen). Or, strongly
refractive particles are fixed to the ossicles, while the beam of light reflected from
them can be examined by means of a microscope (Buck, v. Helmholtz). All the
experiments showed that the transference of the sound-waves is accomplished by
means of the mechanism*of the angular lever, composed of the auditory ossicles
already described. As the vibrations of the membrana tympani are conveyed to
the handle of the malleus, they are weakened to about one-fourth of their original
strength (Politzer). [The membrana tympani is many times (30) larger than the
fenestra ovalis, and the relation in size might be represented by a funnel. The
arm of the malleal end of the lever where the power acts is 94 mm. long, while the
short or stapedial arm is 6} mm., so that the latter moves less than the former,
but what is lost in extent is gained in force. |

[Methods.—Politzer attached small, very light levers to each of the ossicles, and inscribed
their movements on a revolving cylinder. An organ-pipe was sounded, and when the levers
were of the same length, the malleus made the greatest excursion and the stapes the least.
Buck attached starch grains to the ossicles, illuminated them, and observed the movements of
the refractive starch granules by means of a microscope provided with a micrometer. ]

[The ossicles move en masse, and not in the way of propagating molecular
vibrations.]| As the excursions of the ossicles during sonorous vibrations are, how-
ever, only nominal, there is practically no change
in the position of the joints with each vibration.
The latter will only occur when extensive move-
ments take place by means of the muscles.

The muscles of the auditory ossicles alter the
position and tension of the membrana tympani, as
well as the pressure of the lymph of the labyrinth.
The tensor tympani, which lies in an osseous groove
above the Eustachian tube, has its tendon deflected
round an osseous projection [processus cochleari-
formis], which lies external to it, almost at right 7@ |
angles to the groove above it, and is inserted imme- =” fig. 586,
diately above the axes of rotation of the malleus Tensor tympani—the Eustachian
(fig. 580, M). When the muscle contracts in the tube (left).
direction of the arrow, ¢, then the handle of the malleus (m) pulls the membrana
tympani (M) inwards and tightens it (fig. 585). This also causes a movement

804 ACTION OF THE STAPEDIUS.

of the incus and stapes (S) which must be pressed more deeply into the fenestra
ovalis as already described. When the muscle relaxes, then owing to the elasticity
of the rotated axial ligament and the tense membrana tympanl itself, the position
of equilibrium is again restored. The motor nerve of this muscle arises from the
trigeminus, and passes through the otic ganglion (p. 597). C. Ludwig and Politzer
observed that stimulation of the fifth nerve within the cranium [dog] caused the
above mentioned movement.

Use of the tension.—The tension of the membrana tympani caused. by the
tensor tympani has a double function (Joh. Miiller)—1. The tense membrane offers
very great resistance to sympathetic vibrations when the sound-waves are very in-
tense, as it is a physical fact that stretched membranes are more difficult to throw
into sympathetic vibrations the tenser they are. Thus, the tension so far protects
the auditory organ, as it prevents too intense vibrations applied to the membrana
tympani from reaching the terminations of the nerves. 2. The tension of the
membrana tympani must vary according to the degree of contraction of the tensor.
Thus, the membrana for the time being has a different fundamental tone, and is
thereby capable of vibrating to the correspondingly higher tone, it, as it were, being
in a certain sense accommodated for.

Comparison with Iris.—The membrana tympani has been compared with the iris. Both
membranes prevent by contraction—narrowing of the pupil and tension of the membrana
tympani—the too intense action of the specific stimulus from causing too great stimulation, and
both adapt the sensory apparatus for the action of moderate or weak stimuli. This movement
in both membranes is brought about reflealy, in the ear through the N. acusticus, which causes
a reflex stimulation of the motor fibres for the tensor tympani.

Effect of Tension.—That increased tension of the membrana tympani renders it less sensitive
to sound-waves is easily proved, thus :—Close the mouth and nose, and make either a forced
expiration, so that the air is forced into the Eustachian tube, which bulges out the membrana
tympani, or inspire forcibly, whereby the air in the tympanum is diminished, so that the -
membrana bulges inwards. In both cases, hearing is interfered with, as long as the increased
tension lasts. If a funnel with a small lateral opening, and whose wide end is covered by a
membrane, be placed in the external meatus, hearing becomes less distinct when the membrane
is stretched (Joh. Miller). If air be blown into the external auditory meatus, both tensores
tympani contract, and in consequence of this the hearing of the other ear is temporarily
affected (Gelleé).

Normally, the tensor tympani is excited reflexly. The muscle is not directly and by itself
subject to the control of the will. According to L. Fick, the following phenomenon is due to
an ‘‘associated movement ” of the tensor :—When he pressed his jaws firmly against each other,
he heard in his ear a piping, singing tone, while a capillary tube, which was fixed air-tight into
the meatus, had a drop of water which was in it rapidly drawn inwards. During this experi-
ment, a person with normal hearing hears all musical tones as if they were louder, while all the
highest non-musical tones are enfeebled (Lucae). When yawning, v. Helmholtz and Politzer
found that hearing was enfeebled for certain tones,

Contraction of the tensor.—Hensen showed that the contraction of the tensor
tympani during hearing is not a continued contraction, but what might be termed
a “twitch.” A twitch takes place at the beginning of the act of hearing, which
favours the perception of the sound, as the membrana tympani thus set in motion
vibrates more readily to higher tones than when it is at rest. On
exposing the tympanum in cats and dogs, it was found that this
contraction or twitch occurs only at the beginning of the sound,
and that it soon ceases, although the sound may continue.

Action of the Stapedius——The muscle arises within the emi-
nentia pyramidalis, and is inserted into the head of the stapes and
' _ Sylvian ossicle (fig. 583); when it draws upon the head of the

Fig. 587. stapes, as indicated in fig. 577, by the small curved arrow, it must
Right stapedius place the bone obliquely, whereby the posterior end of the plate of

— the stapes is pressed somewhat deeper inwards into the fenest
ovalis, while the anterior is, as it were, displaced somewhat outwards. The stapes
is thereby more fixed, as the fibrous mass [annular ligament] which surrounds the -

THE EUSTACHIAN TUBE. 805

fenestra ovalis and keeps the stapes in its place becomes more tense. ‘The activity
of this muscle, therefore, prevents too intense shocks, which may be communicated
from the incus to the stapes, from being conveyed to the perilymph. It is supplied
by the facial nerve (§ 349, 3).

The stapedius in many persons executes an associated movement, when the eyelids are forcibly
closed (§ 349). Some persons can cause it to contract reflexly by scratching the skin in front
of the meatus, or by gently stroking the outer margin of the orbit (Henle). It seems to be
excited reflexly in many diseases of the ear when the tympanum is being syringed.

Other Views.—According to Lucae, when the stapes is displaced obliquely, its head forces the
long process of the incus, and also the membrana tympani, outwards, so that it is regarded as an
antagonist of the tensor tympani. Politzer observed that the pressure within the labyrinth
fell, when he stimulated the muscle. According to Toynbee, the stapedius acts as a lever and
moves the stapes slightly out of the fenestra ovalis, thus making it more free to move, so that
it is more capable of vibrating. Henle supposes that the stapedius is more concerned in fixing
than in moving the stapes, and that it comes into action when there is danger of too great move-
ment being communicated to the stapes from the incus. lLandois agrees with this opinion, and
compares the stapedius with the orbicularis palpebrarum, both being protective muscles.

Pathological. —Immobility of the auditory ossicles, either by adhesions or anchyloses, causing
diminished vibrations, interferes with hearing ; while the same result occurs when the stapes is
firmly anchylosed into the fenestra ovalis. The tendon of the tensor tympani has been divided
in cases of contracture of the muscles. For paralysis of the tensor, see p. 598, and for the
stapedius, p. 603.

411. EUSTACHIAN TUBE—TYMPANUM.—The Eustachian tube [4 centi-
metres in length, 12 in.| is the ventilating tube of the tympanic cavity. It keeps
the tension of the air-within the tympanum the same as that within the pharynx
and outer air (figs. 577, 586). Only when the tension of the air is the same out-
side and inside the tympanum, is the normal vibration of the membrana tympani
possible. The tube is generally closed, as the surfaces of the mucous membrane -
lining it come into apposition. During swallowing, however, the tube is opened,
owing to the traction of the fibres of the tensor veli palatini [spheno-salpingo-
staphylinus sive abductor tubae (v Z'réltsch), sive dilator tubae (Riidinger)]| inserted
into the membrano-cartilaginous part of the tube (Zoynbee, Politzer). (Compare
§ 139, 2.) When the tube is closed, the vibrations of the membrana tympani are
transferred in a more undiminished condition to the auditory ossicles than when it
is open, whereby part of the vibrating air is forced through the tube (Mach and
Kessel). If, however, the tympanic cavity is closed permanently, the air within it
becomes so rarefied (§ 139) that the membrana tympani, owing to the abnormally
low tension, becomes drawn inwards, thus causing difficulty of hearing. As the
tube is lined by ciliated epithelium it carries outwards to the pharynx the secre-
tions of the tympanum (p. 452).

Noise in the Tube.—A sharp hissing noise is heard in the tube during swallowing, when we
swallow slowly and at the same time contract the tensor tympani, due to the separation of the
adhesive surfaces of its lining membrane. Another person may hear this noise by using a
stethoscope or his ear. .

In Valsalva’s experiment (§ 60), as soon as the pressure of the air reaches 10 to 40 mm..
Hg, air enters the tube. The sound is heard first, and then we feel the increased tension of
the tympanic membrane, owing to the entrance of air into the tympanum. During forced
inspiration, when the nose and mouth are closed, air is sucked out, while the tympanum is
ultimately drawn inwards.

The M. levator veli palatini, as it passes under the base of the opening of the tube into the
pharynx, forms the levator-eminence or cushion (fig. 8354, W). Hence, when this muscle con-
tracts and its belly thickens, as at the commencement of the act of deglutition and during
phonation, the lower wall of the pharyngeal opening is raised, and the opening thereby
narrowed (Lucae). The contraction of the tensor, occurring during the later part of the act of.
deglutition, dilates the tube.

her Views.—According to Riidinger, thie tube is always open, although only bya very
narrow passage in the upper part of the canal, while the canal is dilated during swallowing.
According to Cleland, the tube is generally open, and is closed during swallowing.

{Practical Importance.—The tympanic cavity forms an osseous box, and there-
fore a protective organ for the auditory ossicles and their muscles, while the

806 CONDUCTION OF SOUND IN THE LABYRINTH.

increased air space, obtained by its communication with the mastoid cells, permits
free vibration of the membrana tympani. The six sides of the tympanum have

important practical relations. It is about half an inch in height, and one or two.

lines in breadth, i.e., from without inwards. Its roof is separated from the cavity

of the brain by a very thin piece of bone, which is sometimes defective, so that

encephalitis nay follow an abscess of the middle ear. The outer wall is formed by

the membrana tympani, while on the inner wall are the fenestra ovalis and rotunda,

the ridge of the aqueductus Fallopii, the promontory, and the pyramid. The floor

consists of a thin plate of bone, which roofs in the jugular fossa and separates it

from the jugular vein. Fractures of the base of the skull may rupture the carotid

artery or internal jugular vein ; hence, hemorrhage from the earsis a bad symptom

in these cases. Caries of the ear may extend to other organs. The anterior wall

is in close relation with the carotid artery, while the posterior communicates with

the mastoid cells, so that fluids from the middle ear sometimes escape through the

mastoid cells. |

That the air in the tympanum can communicate its vibrations to the membrane of the fenestra

rotunda is true (p. 797, 3), but normally this is so slight, when compared with the conduction
through the auditory ossicles, that it scarcely need be taken into account.

Structure.—The tube and tympanum are lined by a common mucous membrane, covered by

ciliated epithelium, while the membrana is lined by a layer of squamous epithelium. Mucous

glands were found by Troéltsch and Wendt in the mucous membrane.

[The VO covering the ossicles and tensor tympani is not ciliated. ]

Pathological.—The tube is often occluded, owing to chronic catarrh

and narrowing from cicatrices, hypertrophy of the mucous membrane,

or the presence of tumours. The deafness thereby pees may often

be cured by catheterising the tube from the nose (fig. 588). Effusions

into or suppuration within the tympanum of course paralyse the sound-

conducting mechanism, while inflammation often causes subsequent

affections of the plexus tympanicus. If the temporal bone be destroyed

Krohne é; Sesemant-

Fig. 588. Fig. 589.
Eustachian catheter. Politzer’s ear bag.

by progressive caries within the tympanum, inflammation of the neighbouring cerebral struc-
tures may occur and cause death.

(Methods, —Not unfrequently the aurist is called upon to dilate the Eustachian tube, which
in certain cases requires the use of a Eustachian catheter introduced into the tube along the
floor of the nose (fig. 588). At other times he requires to fill the tympanic cavity with air,
which is easily done by means of a Politzer’s bag (fig. 589). The nozzle is introduced into one
nostril, while the other nostril is closed, and the patient is directed to swallow, while at the
same moment the surgeon compresses the bag, and the patient’s mouth being closed, air is
forced through the open Eustachian tube into the middle ear. Sometimes a small curved
narrow manometer, containing a drop of coloured water, is placed in the outer ear (Politzer).
Normally, when the patient swallows, the fluid ought to move in the tube. ]

412. CONDUCTION OF SOUND IN THE LABYRINTH.—The vibrations
of the foot of the stapes in the fenestra ovalis give rise to waves in the perilymph
within the inner ear or labyrinth. These waves are so-called “flexion waves,” 1.¢.,
the perilymph moves in mass before the impulse of the base of the stapes. This is
only possible from the existence of a yielding membrane—that filling the fenestra
rotunda, and sometimes called the membrana secundaria, which during rest bulges

ite Oe Mel

METHOD OF TESTING SOUND-CONDUCTION. 807

inwards to the scala tympani, and can be bulged outwards towards the tympanic
cavity by the impulse communicated to it by the movement of the perilymph
(fig. 577, vr). The flexion waves must correspond in number and intensity to the
vibrations of the auditory ossicles, and must also excite the free terminations of
the auditory nerve, which float free in the endolymph.

As the endolymph of the saccule and utricle lying in the vestibule receives the
first impulse, and as these communicate anteriorly with the cochlea, and posteriorly
with the semicircular canals, consequently the motion of the
perilymph must be propagated through these canals. To
reach the cochlea, the movement passes from the saccule
(lying in the fovea hemispherica) along the scala vestibuli to
the helicotrema, where it passes into the scala tympani, where
it reaches the membrane of the fenestra rotunda, and causes it
to bulge outwards. From the wtricle (lying in the fovea hemi-

Sade ‘ ce : Fig. 590.
elliptica), in a similar manner the movement is propagated Havotinlapeatince of

through the semicircular canals. Politzer observed that the the labyrinth, fenes-
endolymph in the superior semicircular canal rose when he _ tra ovalis, cochlea to

caused contraction of the tensor tympani by stimulating the *he left, and (7) the
upper, (2) horizon-

trigeminus, just as the base of the stapes must be forced a) and (s) posterior
against the perilymph with every vibration of the membrana semicircular canal
tympani. (left).
[Practical.—It is well to view the organ of hearing as consisting of two
mechanisms :— ;
1. The sound-conducting apparatus.
2. The sound-perceiving apparatus.

The former includes the outer ear, with its auricle and external meatus; the
middle ear and the parts which bound it, or open into it. The latter consists of
the inner ear with the expansion of the auditory nerve in the labyrinth, the nerve
itself, and the sound-perceiving and interpreting centre or centres in the brain
(p. 703).

rrestite the Sound-conduction.—In any case of deafness, it is essential to
estimate the degree of deafness by the methods stated at p. 798, and it is well to
do so both for such sounds as those of a watch and conversation. We have next to
determine whether the sownd-conducting or the sound-perceiving apparatus is affected.
If a person is deaf to sounds transmitted through the air, on applying a sounding
tuning-fork to the middle line of the head or teeth, if it be heard distinctly,
then the sound-perceiving apparatus is intact, and we have to look for the cause of
deafness in the outer or middle ear. In a healthy person, the sound of the tuning-
fork is heard of equal intensity in both ears. In this case the sound is conducted
directly to the labyrinth by the cranial bones. In cases of disease of the sound-
conducting mechanism, the sound of the tuning-fork is heard loudest in the deafer
ear. Ed. Weber pointed out that, if one ear be stopped and a vibrating tuning-
fork placed on the head, the sound is referred to the plugged ear, where it is heard
loudest, It is assumed that when the ear is plugged, the sound-waves transmitted
by the cranial bones are prevented from escaping (J/ach). If, on the contrary, the
sound be heard loudest in the good ear, then in all probability there is some affection
of the sound-perceiving apparatus or labyrinth, although there are exceptions to
this statement, especially in elderly people. Another plan is to connect two tele-
phones with an induction machine, provided with a vibrating Neef’s hammer. The
sounds of the vibrations of the latter are reproduced in the telephones, and if they
be placed to the ears, then the healthy ears hear only one sound, which is referred
to the middle line, and usually to the back of the head. In diseased conditions
this is altered—it is referred to one side or the other. ]

808 . STRUCTURE OF THE COCHLEA.

413. LABYRINTH AND AUDITORY NERVE.—Scheme.—The vestibule (fig. 591, III)
contains two separate sacs; one of them, the saceule, s (round sac or 8, hemis heericus), com-
municates with the ductus cochlearis, Cc, of the cochlea ; the other, the utricle, U (elliptical
sac, or sacculus hemiellipticus), communicates with the semicircular canals, Cs, Cs.

The cochlea consists of 24 turns of a tube disposed round a central column or modiolus, The
tube is divided into two compartments by a horizontal septum, partly osseous and partly
membranous, the lamina spiralis ossea and membranacea (fig. 595; fig. 591, I). The lower
compartment is the scala tympani, and is separated from the cavity of the tympanum by the

) of the fenestra rotunda.
Da aies compartment is the scala vestibuli, which communicates with the vestibule of
the labyrinth (fig. 591, I). These two compartments communicate directly by a small opening
at the apex of the cochlea, a sickle-shaped edge [“‘ hamulus ”) of the lamina spiralis yoy
the helicotrema (fig. 577). The scala vestibuli is divided by Reissner’s membrane (fig. 591, 1),

ae ead
FV pw ON
ee

Org. Corti
mb. basilaris

rs

psa é
Vee, Scala tympani : aE

Fig. 591.

I, transverse section of a turn of the cochlea ; II, A, ampulla of a semicircular canal with the
crista acustica; a, p, auditory cells; p, provided with a fine hair; T, otoliths ;’ III,
scheme of the human labyrinth ; IV, scheme of a bird’s labyrinth; V, scheme of a fish’s
labyrinth.

which arises near the outer part of the lamina spiralis ossea, and runs obliquely outwards to
the wall of the cochlea so as to cut off a small triangular canal, the ductus or canalis cochlearis,
or scala media, Cc, whose floor is formed for the most part by the lamina spiralis membranacea,
and on which the end-organ of the auditory nerve—Corti’s organ—is placed. The lower end .
of the canalis cochlearis is blind, III, and divided towards the saccule, with which it com- .
municates by means of the small canalis reuniens, Cr (Hensen). The utricle (fig. 591, 111, U)
communicates with the three semicircular canals, Cs, Cs—each by means of an ampulla, 7
within which lie the terminations of the ampullary nerves, but as the posterior and the
superior canals unite, there is only one common ampulla for them. The membranous semi-
circular canals lie within the osseous canals, perilymph lying between the two. Perilymph also
fills the scala vestibuli and tympani, so that all the spaces within the labyrinth are filled by
fluid, while the spaces themselves are lined by short cylindrical epithelium.

_ The system of spaces, filled by endolymph, is the only part containing the nervous end-organs
for hearing. All these spaces communicate with each other; the semicircular canals -directl;
with the utricle, the ductus cochlearis with the saccule through the canalis reuniens; and
lastly, the saccule and utricle through the ‘‘saccus endolymphaticus,” which springs by an
isolated limb from each sac; the limbs then unite, as in the letter Y, and puss through the ~
osseous aqueductus vestibuli to end blindly in the dura mater of the brain (fig. III, R—Bottcher,
Retzius). The aqueductus cochlee is another narrow peeks, which begins in the scala fs ani,

iy t:

immediately in front of the fenestra rotunda, and opens close to the fossa jugularis.

a direct means of communication between the perilymph of the cochlea and the su
space, anblcs
Semicircular Canals and Vestibular Sacs.—The membranous semicircular canals do not
the ne osseous canals conte but are separated from them by a pretty w
space, which is filled with perilymph (fig. 592). At the concave margin they are fixed by ¢

~~

_

CRISTA ACUSTICA AND COCHLEA. 809

“nective-tissue to the osseous walls. The ampulle, however, completely fill the corresponding

osseous dilatations. The canals and ampulle consist externally of an outer, vascular, connec-
tive-tissue layer, on which there rests a well-marked hyaline layer, bearing a single layer of
flattened epithelium.

Crista Acustica.—The vestibular branch of the auditory nerve sends a branch to each ampulla
and to the saccule and utricle (fig. 593). In the ampulle (fig. 591, II, A), the nerve (c) ter-

Fig. 592. Fig. 593.

The interior of the right labyrinth with its membranous canals and nerves. In fig. 592, the
outer wall of the bony labyrinth is removed to show the membranous parts within—l,
commencement of the spiral tube of the cochlea; 2, posterior semicircular canal, partly
opened; 3, horizontal; 4, superior canal; 5, utricle; 6, saccule; 7, lamina spiralis; 7’,
scala tympani; 8, ampulla of the superior membranous canal; 9, of the horizontal; 10, of
the posterior canal. Fig. 593 shows the membranous labyrinth and nerves detached—1,
facial nerve in the internal auditory meatus; 2, anterior division of the auditory nerve
giving branches to 5, 8, and 9, the utricle and the ampulle of the superior and horizontal
canals; 3, posterior division of the auditory nerve, giving branches to the saccule, 6, and
posterior ampulla, 10, and cochlea, 4; 7, united part of the posterior and superior canals ;
11, posterior extremity of the horizontal canal.

minates in connection with the crista acustica, which is a yeilow elevation projecting into the
equator of the ampulla. The medullated nerve-fibres, x, form a plexus in the connective-tissue
layer, lose their myelin as they pass to the hyaline basement mem-
brane, and each ends in a cell provided with a rigid hair (0, p) 90 »
in length, so that the crista is largely covered with these hair-cells,
but between them are supporting cells like cylindrical epithelium
(a), and not unfrequently containing granules of yellow pigment.
The hairs or ‘‘ auditory hairs” (M. Schultze) are composed of many
fine fibres (Retzivs). An excessively fine membrane (membrana
tectoria) covers the hairs (Pritchard, Lang).

Macule Acustice.—The nerve-terminations in the macule acus-
ticee of the saccule and utricle are exactly the same as in the am-
pull, only the free surface of their membrana tectoria is sprinkled
with small white chalk-like crystals or otoliths (II, T), composed
of calcic carbonate, which are sometimes amorphous and partly in
the form of arragonite, lying fixed in the viscid endolymph. The
non-medullated axis-cylinders of the saccular nerves enter directly
into the substance of the hair-cells. The terminations of the nerves
have been investigated, chiefly in fishes, in the rays. .

[Fig. 594 is a vertical section of a macula acustica of the rabbit.
The medullated nerves (7) lose their myelin at the external limiting
membrane, become non-medullated, pierce this membrane, and
form a basal plexus (pb) between (7) the epithelial cells, and finally
terminate in the sensory ciliated cells (rv). The epithelium itself
consists of basal cells (cb), fusiform or supporting cells (f), and the
ciliated neuro-epithelium (7), each cell being provided with a cilinm,
which perforates the external limiting membrane (a). There is Vertical section of the ma-
thus a remarkable likeness to the olfactory epithelium. ] | eula acustica of a rabbit.

Cochlea,—The terminations of the cochlear branch of the audi-
tory nerve lie in connection with Corti’s organ, which is placed in the canalis or ductus coch-
learis (fig. 591, I, Cc, and III, Cc, and fig. 595), the small triangular chamber [or scala media, ]
cut off from the scala vestibuli by the membrane of Reissner. Corti’s organ is placed on the
lamina spiralis membranacea, and consists of a supporting apparatus composed of the so-called
Corti’s arches, each of which consists of two Corti’s rods (z, y), which lie upon each other like.

810 MEMBRANA RETICULARIS.

the beams of a house. But every two rods do not form an arch, as there are always three inner
to two outer rods (Claudius). There are about 4500 outer rods ( Waldeyer).

The ductus cochlearis becomes larger towards the apex of the cochlea, and the rods also
become longer ; the inner ones are 30 yu long in the first turn, and 34 uw in the upper, the
outer rods 47 » and 69 uw respectively. The span of the arches also increases (Hensen), [The

—_

o> > BX. =
ZZ apr ane basilaris

Fig. 595.

Scheme of the ductus cochlearis and the organ of Corti. N, cochlear nerve; K, inner, and P,
outer hair-cells; 2, nerve-fibrils terminating in P; a, a, supporting cells; d, cells in the
sulcus spiralis; z, inner rod of Corti; Mb. Corti, membrane of Corti, or the membrana
tectoria; 0, the membrana reticularis; H, G, cells filling up the space near the outer wall.

arches leave a triangular tunnel beneath them.] The proper end-organs of the cochlear nerve
are the cylindrical ‘‘ hair-cells” (Kélliker) previously observed by Corti, which are from
16,400 to 20,000 in number (Hensen, Waldeyer). There is one row of inner cells (¢), which
rests on a layer of small granular cells (K) (Bottcher, Waldeyer) ; the outer cells (a, a) number
12,000 in man (Retzius), and rest upon the basement membrane, being disposed,in three or
even four rows. Between the outer hair-cells there are other cellular structures, which are
either regarded as special cells (Deiter’s cells), or are regarded merely as processes of the hair-
cells (Lavdowsky). [The cochlear branch of the auditory nerve enters the modiolus, and runs
upwards in the osseous channels there provided for it, and as it does so gives branches to the
lamina spiralis, where they run between the osseous plates which form the lamina.] The
fibres (N) come out of the lamina spiralis after traversing the ganglionic cells in their course
(figs. 591, 595, I, G), and end by fine varicose fibrils in the hair-cells (fig. 595) (Waldeyer,
Gottstein, Lavdowsky, Retzius).

Membrana Reticularis.—Corti’s rods and the hair-cells are covered by a special membrane
(o), the membrana reticularis of Koélliker. The upper ends of the hair-cells, however, project
through holes in this membrane, which consists of a kind of a cement-substance holding these
parts together (Lavdowsky). [Springing from the outer end of the lamina spiralis, or crista
spiralis, is the membrana tectoria, sometimes called the membrane of Corti. It is a‘ well-
defined structure, often fibrillated in appearance, and extends outwards over the organ of Corti.]
Waldeyer regercs it as a damping apparatus for this organ (fig. 595, Mb. Corti).

(Basi ilar embrane.—lIts breadth increases from the base to the apex of the cochlea. This
fact is important in connection with the theory of the perception of tone. It is supposed that
high notes are appreciated by structures in connection with the former, and low notes by the
upper parts of the basilar membrane. In one case, recorded by Moos and Steinbrugge, a
patient heard low notes only iti the right ear, and after death it was found that the sullacky
nerve in the first turn of the cochlea was atrophied. ]

Intra-Labyrinthine Pressure.—The lymph within the labyrinth is under a certain pressure.
Every diminution of the pressure of the air in the tympanum is accompanied by a correspond-
ing diminution of the intra-labyrinthine pressure, while conversely every increase of pressure
is accompanied by an increase of the lymph-pressure (F. Bezold). S109

MUSICAL TONES AND NOISES. SII

The perilymph of the inner ear flows away chiefly through the aqueductus coch-
lez, in the circumference of the foramen jungulare, into the peripheral lymphatic
system, which also takes up the cerebro-spinal fluid of the subarachnoid space,
while a small part drains away to the sub-dural space through the internal auditory
meatus. The endolymph flows through the arachnoid sheath of the N. acusticus
into the subarachnoid space (C. Hasse).

414. AUDITORY PERCEPTIONS.— Every normal ear is able to distinguish
musical tones and noises. Physical experiments prove that tones are produced
when a vibrating elastic body executes periodic movements, 7.e., when the sound-
ing body executes the same movement in equal intervals of time, as the vibrations
of a string which has been plucked. A noise is produced by non-periodic move-
ments, z.¢., when the sounding body executes unequal movements in equal intervals
of time. [The non-periodic movements clash together on the ear, and produce dis-
sonance; as when we strike the key-board of a piano at random.| This is readily
proved by means of the szren. Suppose that there are forty holes in the rotatory
disc of this instrument, placed at exactly the same distance from each other-—on
rotating the disc and directing a current of air against it, obviously with every
rotation the air will be rarefied and condensed exactly forty times. Every two
condensations and rarefactions are separated from each other by an equal interval
of time. This arrangement yields a characteristic musical tone or note. If a
similar disc with holes perforated in it at wnequal distances be used, on air being
forced against it, a whirring non-musical nozse is produced, because the movements
of the sounding body (the condensations and rarefactions of the air) are non-pertodic.
[The double siren of v. Helmholtz is an improved instrument for showing the same
facts. |

The normal ear also distinguishes in every tone three distinct factors :—

[(1) Intensity or force ; (2) Pitch; (3) Quality, timbre or “klang.”|

1. The intensity of a tone depends upon the greater or lesser amplitude of the
vibrations of the sounding body. It is well known that a vibrating string emits
a feebler sound when its excursions are smaller. (The intensity of a sound corre-
sponds to the degree of illumination or brightness in the case of the eye.)

2. The pitch depends upon the number of vibrations which occur in a given
time [or the length of time occupied by a single vibration]. This is proved by
means of the siren. If the rotating disc have a series of forty holes at equal
intervals, and another series of eighty equidistant from each other, on blowing a
stream of air against the rotating disc we hear two sounds of unequal pitch, one
being the octave of the other. (The perception of pitch corresponds to the sensation
of colour in the case of the eye.)

3. The quality or timbre (‘“ Klangfarbe”) is peculiar to different sonorous
bodies. [It is the peculiarity of a musical tone by which we are enabled to dis-
tinguish it as coming from a particular instrument, or from the human voice.
Thus, the same note struck on a piano and sounded on a violin differs in quality
or timbre.| It depends upon the peculiar form of the vibration, or the form of the
wave of the sonorous body. (There is no analagous sensation in the case of light.)

I. Perception of Pitch.—By means of the organ of hearing, we can determine that different
tones have a different pitch. In the so-called musical scale, or gamut, this difference is very
marked to a normal ear. But in the scale there are again four tones, which, when they are
sounded together, cause in a normal ear the sensation of an agreeable sound, which once heard
ean readily be reproduced. This is the tone of the so-called accord, Triad, or Common Chord,
consisting of the 1st, 3rd, and 5th tones of the scale, to which the 8th tone or octave is added.
We have next to determine the pitch of the tones of the chord, and then that of the other
tones of the scale. The siren is used for the fundamental experiment, from which the others
can easily be calculated. Four concentric circles are drawn upon the rotatory disc of the siren ;

the inner circle contains 40 holes, the second 50, the third 60, and the outer 80—all the holes
being at equal distances from each other. If the dise be rotated, and air forced against each

812 PERCEPTION OF PITCH.

series of holes in turn, we distinguish successively the four tones of the accord (major chord
with its octave) ; when all the four series are blown upon simultaneously, we hear in complete
purity the major chord itself. The relative nwmber of the holes in the four series indicates in
the simplest manner the relative pitch of the tones of the major chord. While one revolution
of the disc is necessary to produce the fwnddmental grownd-tone (key-note or tonic) with 40
condensations and rarefactions of the air—in order to produce the octave, we must have
double the number of condensations and rarefactions during one revolution in the same time.
Thus, the relation of the number of vibrations of the Ground-tone or Tonic to the Octave next
above it, is 1:2. In the second series we have 50 holes, which causes the pitch of the third ;
hence, the relation of the Ground-tone to the Third in this case is 40 : 50, or 1: 13=4, @.¢., for
every vibration of the Ground-tone there are $ vibrations in the Third. In the third series are
60 holes, which, when blown upon, yield the fifth ; hence, the ratio of the Ground-tone to the
Fifth in our dise is 40 : 60, or 1: 14—%. In the same way we can estimate the pitch of the
Fourth tone, and we find that the number of vibrations of the First, Third, Fifth, and Octave
are to each other as 1: 3: $: 2.

The minor chord is quite as characteristic to a normal ear as the major. It is distinguished
essentially from the latter by its Third being half a tone lower. We can easily imitate it by -
the siren, as the Minor Third consists of a number of vibrations which stand to the -Ground-
tone as 6: 5, i.e., if 5 vibrations occur in a given time in the Ground-tone, then 6 occur in the
Minor Third ; its vibration number, therefore, is $.

From these relations of the Major and Minor common chords, we may calculate the relative
tones in the scale, and we must remember that the Octave of a tone always yields the fullest
and most complete harmony. It is evident that as the Major Third, and Minor Third, and the
Fifth harmonise with the fundamental Ground-tone or key-note, they must also harmonise with
the Octave of the key-note. We obtain from the Major Third with the number of vibrations
*, the Minor Sixth §, from the Minor Third with $, the Major Sixth =(,% =) #; from the Fifth
with 3, the Fourth=#. These’relations are known as the ‘‘ Inversions of the intervals.” These
relations of the tones are, collectively, the consonant intervals of the scale. The dissonant
stages, or discords, of the scale can be obtained as follows :—Suppose that we have the Ground-
tone or key-note C, with the number of vibrations=1, the Third E=§, the Fifth G=$, and the
Octave=2, we then derive from the Fifth or Dominant G a Major chord—this is G, B, D'.
The relative number of vibrations of these 3 tones is the same as in the Major chord of C,, C, E, .
G. Hence, the number of vibrations of G: Bis as C:E. When we substitute the values we
obtain $ : B=1: §-7.c.,, B=15. But D': B=G: E; so that D: 3 =%: §, 4¢, Di=4$, or
an octave lower, we have D=%. Deduce from F (subdominant) a Major chord, F, A, C!. The
relation of A: C'=E:G, or A: 2—§: 4, i.e, A=§. Lastly, F: A=C:E, or F: $=1: 4,
i.e., F= 4. So that all the tones of the scale have the following number of vibrations :—I., |
C=1; Il., D=§%; III., E=4; IV., F=4; V., G=$; VI.; A=§; VIL, B=¥; VIIL, Cle 2.
_ Conventional Estimate of Pitch.—Conventionally, the pitch or concert-pitch of the note, a,
is taken at 440 vibrations in the second (Scheibler, 1834), although in France it is taken at 485
vibrations per second. From this we can estimate the absolute number of vibrations for the,
tones of the scale :—C=33, D=37°125, E=41'25, F=44, G=49'5, A=55, B=61°'875 vibra-
tions. The number of vibrations of the next highest octave is found at once by multiplying
these numbers by 2.

_ Musical Notes.—The lowest notes used in music are the double-bass, E, with 41°25 vibra-

tions, pianoforte C with 33, grand piano A! with 27°5 and organ C! with 16°5. The highest
notes in music are the pianoforte cY with 4224, and dv on the piccolo-flute, with
4752 vibrations per second.

Limits of Auditory Perception.—According to Preyer, the limit of the
perception of the lowest audible tone lies between 16 and 23 vibrations
per second, and e” with 40,960 vibrations as the highest audible tone ;
so that this embraces about 114 octaves.

(Audibility of Shrill Notes.—This varies very greatly in different persons (Wol-

laston). , There is a remarkable falling off of the power as age advances (Galton).

For testing this Galton uses a small whistle made of a brass tube, with a diameter

of less than yyth of an inch (fig. 596). A plug is fitted at the lower end to lengthen

or shorten the tube, whereby the pitch of the note is altered. Amongst animals

Galton finds none superior to cats in the power of hearing shrill sounds, and he

Fig. 596, attributes this ‘‘to differentiation by natural selection amongst these animals until

Galton’s they have the power of hearing all the high notes made by mice and other little

Whistle, c"eatures they have to catch.”] HW

Variations in Auditory Perception.—It is rare to find that tones produced by

more than 35,000 vibrations per second are heard. When the tensor tympani is contracted, the
reeption may be increased for tones 3000 to 5000 vibrations higher, but rarely more. Pe

fopically, the perception for high notes may be abnormally acute—(1) When the tension of th

.

PERCEPTION OF QUALITY. 813

sound-conducting apparatus generally is increased. (2) By elimination of the sound-conducting
apparatus of the middle ear, which offers greater or less resistance to the propagation of very
high notes, as perforation of the membrane tympani, or loss of the incus and malleus. In these
cases, the stapes is directly set in vibration by the sound-waves, when tones up to 80,000 vibra-
tions have been perceived. Diminished tension of the sound-conducting apparatus causes
diminution of the perception for high tones (Blake).

A smaller number of vibrations than 16 per second (as in the organ) are no longer heard as a
tone, but as single dull impulses. The tones that are produced beyond the highest audible
note, as by stroking small tuning-forks with a violin bow, are also no longer heard as tones,
but they cause a painful cutting kind of impression in the ear. In the musical scale the range
is, approximately, from C of the first octave with 16°5 vibrations to e, the eighth octave.

Comparison of Ear and Eye.—In comparing the perception of the eye with that of the ear,
we see at once that the range of accommodation of the ear is much greater. Red has 456 billions
of vibrations per second, while the visible violet has but 667, so that the eye only takes cognis-
ance of vibrations which do not form even one octave.

Lowest Audible Tone.—As to the smallest number of successive vibrations which
the ear can perceive as a sensation of tone, Savart and Pfaundler considered that
two would suffice. If, however, we exclude in our experiments the possibility of
the occurrence of overtones, 4 to 8 (Mach) or even 16 to 20 vibrations (7. Auerbach,
Kohlrausch) are necessary to produce a characteristic tone.

When tones succeed each other rapidly, they are still perceived as distinct, when
at least 0-1 second intervenes between two successive tones (v. Helmholtz); if they
follow each other more rapidly, they fuse with each other, although a short-time
interval is sufficient for many musical tones.

By the term, “fineness of the ear,” or, as we say, a “good ear,” is meant the
capacity of distinguishing from each other, as different, two tones of nearly the
same number of vibrations. This power can be greatly increased by practice, so
that musicians can distinguish tones that differ in pitch by only =35, or even
aap of their vibrations.

With regard to the time-sense, it is found that beats are more precisely perceived
by the ear than by the other sense-organs (Héring, Mach).

Pathological.—According to Lucae, there are some ears that are better adapted for hearing
low notes and others for high notes. Both conditions are disadvantageous for hearing speech.
Those who hear low notes best hear the highest consonants imperfectly. The low notes are
heard abnormally loud in rheumatic facial paralysis, while the high tones are heard abnormally
loud in cases of loss of the membrana tympani, incus, and malleus. The stapedius is in full
action, whereby the highest tones are heard louder at the expense of the lower notes. Many
persons with normal hearing hear a tone higher with one ear than with the other. This con-
dition is called diplacusis binauralis. In rare cases, sudden loss of the perception of certain
tones has been observed, ¢.g., the bass-deafness of Moos. In a case described by Magnus, the
tones d', b!, were not heard (§ 316).

II. Perception of the Intensity of Tone.—The intensity of a tone depends upon the ampli-
tude of the vibrations of the sounding body. The intensity of the tone is proportional to the
square of the amplitude of vibration of the sounding body, 7.¢., with 2, 3, or 4 times the ampli-
tude the intensity of the tone is 4, 9, 16 times as strong. As sonorous vibrations are com-
municated to our ears by the wave-movements of the air, it is evident that the tones must
become less and less intense the further we aré from the source of the sound. The intensity of
the sound is inversely proportional to the square of the distance of the source of the sound from
the ear.

Tests.—1. Place a watch horizontally near the ear, and test how close it may be brought to
the ear, and also how far it may be removed, and still its sounds be heard. Measure the dis-
tance. 2. Itard uses a small hammer suspended like a pendulum, and allowed to fall upon a
hard surface. 3. Balls of different weights are allowed to fall from varying heights upon a plate.
In this case the intensity of the sound is proportional to the product of the weight of the ball
into the height it falls.

As to the limits of the perception of the intensity of a tone, it is found that a spherule weigh-
ing 1 milligram, and falling from a height of 1 mm. upon a glass plate, is heard at a distance
of 5 centimetres\(Schafhdult). \

415. PERCEPTION OF QUALITY—VOWELS.—By the term quality (‘‘ Klangfarbe ”’),
musical colour or timbre, is understood a peculiar character of the tone, by which it can be
distinguished apart from its pitch and intensity. Thus, a flute, horn, violin, and the human
voice may all sound the same note with equal intensity, and yet all the four are distinguished

814 VIBRATION CURVE OF A MUSICAL TONE.

at once by their specific quality. Wherein lies the essence (“ Wesen”’) of tone-colour? The
investigations of v. Helmholtz have proved that, amongst mechanisms which produce tones,
only those that produce pendulum-like vibrations, 1.¢., the to-and-fro vibrations of a metallic
rod with one end fixed, and tuning-forks, execute simple pendulum-like vibrations. This can
be shown by making a tuning-fork write off its vibrations on a recording surface, when a com-
letely uniform wave-line, with equal elevations and depressions 1s noted, The term ‘‘ tone ”
is restricted to those sounds, hardly ever occurring in nature, which are due to simple pen-
dulum-like vibrations. ;
Other investigations have shown that the tones of musical instruments and of the human
voice, all of which have a characteristic quality of their own, are com osed of many single
simple tones. Amongst these one is characterised by its intensity, anc at the same time it
determines the pitch of the whole compound musical “tone-picture.” This is called the
fundamental tone or key-note. The other weaker tones which, as it were, spring from and
are mingled with this, vary in different instruments both in intensity and number. They
are ‘upper tones,” and their vibrations are always some multiple—2, 3, 4, 5.... times—of
the fundamental tone or key-note. In general,

embrace numerous strong upper tones, especi-
ally of high pitch, in addition to the funda-
mental tone, are characterised by a_ sharp,
piercing, and rough quality, such as emanates
trom a trumpet or clarionet, and that conversely
the quality is characterised by mildness and
softness when the overtones are few, feeble, and
low, ¢.g., such as are produced by the flute. It
requires a well-trained musical ear to dis-

tones apart from the fundamental tone. But
this is very easily done with the aid of resonators
(fig. 600). These consist of spherical or funnel-
shaped hollow bodies, made of brass or some
other substance, which, by means of a short

resonator be placed in the ear, we can hear the
feeblest overtone of the same number of vibra-
tions as the fundamental tone. Thus, musical
instruments are distinguished by the number,

(Fig. 597.

Curves of a musical tone obtained by com- intensity, and pitch of the overtones which they
pounding the curve of a fundamental tone eee A vibrating metallic rod and a tuning-

with that of its overtones. ork have no overtones; they only give the
fundamental tone. As already mentioned, the term simple tone is applied to sounds due to
simple pendulum-like vibrations, while a sound composed of a fundamental tone and overtones
is called a ‘‘klang”’ or compound musical tone.

Vibration Curve of a Musical Tone.— When we remember that a musical tone or clang con-
sists of a fundamental tone, and a number of overtones of a certain intensity, which determine
its quality, then we ought to be able to construct geometrically the vibration curve of the
musical tone. Let A represent the vibration curve of the fundamental tone, and B that of the
first moderately weak overtone (fig. 597). The combination of these two curves is obtained
simply by computing the height of the ordinates, whereby the ordinates of the overtone curve,
lying above the abscissa or horizontal line, are added to the fundamental tone curve, while those
of the ordinates below the line are subtracted from it. Thus we obtain the curve C, which is
not a simple pendulum-like curve, but one which corresponds to an unsteady movement. A new
curve of the second overtone may be added to C, and soon. The result of all these combina-
tions is that the vibration curves corresponding to the compound musical tones are unsteady
periodic curves. All these curves must, of course, vary with the number and pitch of the
compounded overtone curves.

ment of the Phases.—The form of the vibration of one and the same musical tone
may vary very greetly if, in compounding the curves A and B, the curve B is only slightly
displaced laterally. If B is displaced so that the hollow of the wave 7 falls under A, the
addition of both curves yields the curve 7, 7, 7, with small elevations and broad valleys, If B
be displaced still further, until the elevation of the wave, #, coincides with A, we obtain still
another form, so that Mi displacement of the phases of the wave-motions of the compounde
simple pendulum-like vibrations, we obtain numerous different forms of the same musical tone.
The displacement of the phases, however, has no effect on the ear. ear

The general result of these observations, and those of Fourier, is that the quality of a musical
tone depends upon the characteristic form of the vibratory movement. , t

Analysis of Vowels.—The human voice represents a reed instrument with vibrating elastic

we say that all those outbursts of sound which

tinguish, in an instrumental burst, the over-.

tube, can be placed in the outer ear. If a~

ante

ARTIFICIAL VOWELS. 815

membranes, the vocal cords (§ 312). In uttering the various vowels the mouth assumes a
characteristic form, so that its cavity has a certain fundamental tone peculiar to itself. Thus,
to the fundamental tone of a certain pitch produced within the larynx, there are added certain
overtones, which communicate to the laryngeal tone the vocal or vowel quality. Hence, a
vowel is the timbre or quality of a musical tone which is produced in the larynx. The quality
depends upon the number, intensity, and pitch of the overtones, and the latter, again, depend
on the configuration of the ‘‘ vocal cavity” in uttering the different vowels (§ 317).

Suppose a person to sing the vowels one after the other on a special note, e.g., b 9, we can,
with the aid of resonators determine the overtones, and in what intensity they are mixed with
the fundamental tone, b 2, to give the characteristic quality. According to v. Helmholtz,
when we sound the vowels on b 9, for cach ‘of the three vowels, one overtone is specially
characteristic for A-b!! b; for O-b!'; for U-f. The other vowels and the diphthongs have
each two specially characteristic overtones, because in these cases the mouth is so shaped that
the posterior larger cavity, and also the anterior narrower part, each yields a special tone
{§ 316, I. and E). These two overtones are for E-B'!| ) and f!; for I-div and f; for A-g'!! and
d'!; for O-c'!! f and fi; for U-g'!! and f. These, however, are only the special upper tones.
There are many more upper tones, but they are not so prominent.

Artificial Vowels.—Just as it is possible to analyse a vowel into its fundamental tone and its
upper tones, it is possible to compound tones to produce the vowels by simultaneously sounding
the fundamental tone and the corresponding upper tones. (1) A vowel is produced simply by
singing loudly a vowel, ¢.g., A, upon a certain note against the free strings of an open piano,
whilst by the pedal the damper is kept raised. As soon as we stop singing, the characteristic
vowel is sounded by the strings of the piano. The voice sets into sympathetic vibration all
those strings whose overtones (in addition to the fundamental tone) occur in the vocal com-
pound tone, so that they vibrate for a time after the voice ceases (v. Helmholtz). (2) The
vowel apparatus devised by v. Helmholtz consists of numerous tuning-forks, which are kept
vibrating by means of electro-magnets. The lowest tuning-fork gives the fundamental tone,
B b, and the others the overtones. A resonator is placed in front of each tuning-fork, and
the distance between the two can be varied at pleasure. The resonators can be opened and
closed by a lid passing in front of their openings. When the resonator is closed, we cannot
hear the tone emitted by the tuning-fork placed in front of it; but when one or more resonators
are opened the tone is heard distinctly, and it is louder the more the resonator is opened. By
means of a series of keys, like the keys of a pianoforte, we can rapidly open and close the re-
sonators at will, and thus combine various overtones with the fundamental tone so as to pro-
duce vowels with different qualities. V. Helmholtz makes the following compositions :—
U=B D with b D weak and f ; O=damped B D with b! b strong and weaker b p, fi, d'; A=bh
(fundamental tone) with moderately strong b! b and f'!, and strong b'! p and d''; A=b hb
(fundamental tone) with b' P and f'! somewhat stronger than for A, d strong, b' b weaker, d!'!
and f'!| as strong as possible ; E=b D (as fundamental tone) moderately strong, with b' D and fi
moderate also, and f'!!, a!!! ), and b''! h, as strong as possible; I could not be produced.

In Appunn’s apparatus, the fundamental tone and the overtones are produced by means of
organ pipes, whose notes can be combined to produce the vowels, but it is not so good as the
tuning-forks, since the organ pipes do not yield simple tones, but nevertheless some of the
vowels can be admirably reproduced with this apparatus.

Edison’s Phonograph.—If we utter the vowels against a delicate membrane stretched over
the end of a hollow cylinder, and if a writing style be fixed to the centre of the membrane, and
the style be so arranged that it can write or record its movements on a piece of soft tinfoil
arranged on a revolving apparatus, then the vowel curve is stamped as it were upon the tinfoil.
If the style now be was to touch the tinfoil while the latter is moved, then the style is moved—
it moves the membrane, and we hear distinctly by resonance the vowel sound reproduced.

[Koenig’s Manometric Flames.—By means of this apparatus the quality of the vowel sounds
is easily shown. It consists of a small wooden capsule, A, divided into two compartments by
a piece of thin sheet india-rubber. Ordinary gas passes into the chamber on one side of the
membrane, through the stop-cock, and it is lighted at a small burner. To the other compart-
ment is attached a wider tube with a mouthpiece. The whole is fixed on a stand, and near it
is placed a four-sided rotating mirror, M, as suggested by Wheatstone (fig. 598). On speaking
or singing a vowel into the mouthpiece, and rotating the mirror, a toothed or zigzag flame-
picture is obtained’ in the mirror. The form of the flame-picture is characteristic for each
vowel, and varies of course with the pitch.] [Fig. 599 shows the form of the flame-picture
obtained in the rotating mirror when the vowels, ov, 0, A, are sung at a pitch of wt,, sol,, and
uty. This series shows how they differ in quality. ] |

[Koenig has also invented the apparatus for analysing any compound tone whose funda-
mental tone is UT, (fig, 600). It consists of a series of resonators, from UT, to UT;, fixed in an
iron frame. Each resonator is connected With its special flame, which is pictured in a long
narrow, square rotating mirror. Ifa tuning-fork UT, be sounded, only the flame UT, is affected,
and so on with each tuning-fork of the harmonic series. Suppose a compound note containing
the fundamental tone uT,, and its harmonics be sounded, then the flame of uT,, and those of

816 KOENIG’S MANOMETRIC APPARATUS.

the other harmonics in the note are also affected, so that the tone can be analysed optically.
The same may be done with the vowels. ]

Fig. 598.
Koenig’s manometric capsule (A) and mirror (M)—( Koenig).

~

0 a DP MB spb sable stb sub

Ry [RW Basses Mb sasec. By

TF = =—

Fig. 599.
Flame-pictures of the vowels ov, 0, and a (Koenig).

_ 416. LABYRINTH DURING HEARING.—If we ask what réle the ear plays
in the perception of the quality of sounds, then we must assume that, just as with

ACTION OF THE LABYRINTH DURING HEARING. 817

the help of resonators a musical note can be resolved into its fundamental tone and
overtones, so the ear is capable of performing such an analysis. The ear resolves
the complicated wave-forms of musical tones into their components. These com-
ponents it perceives as tones harmonious with each other; with marked attention
each is perceived singly, so that the ear distinguishes as different tone-colours only
different combinations of these simple tone-sensations. The resolution of complex
vibrations, due to quality, into simple pendulum-like vibrations is a characteristic
function of the ear. What apparatus in the ear is capable of doing this? If we
sing vigorously—e.g., the musi- _
cal vowel A on a definite note,
say b —against the strings of
an open pianoforte while the
damper is raised, then we cause
all those strings, and only those,
to vibrate sympathetically,
which are contained in the
vowel so sung. We. must,
therefore, assume that an ana-
logous sympathetic apparatus
occurs in the ear, which is tuned,
as it were, for different pitches,
and which will vibrate sympa-
thetically like the strings of a
pianoforte. ‘If we could so
connect every string of a piano
with a nerve-fibre that the nerve-
fibre would be excited and per-
ceived as often as the string
vibrated, then, as is ac-
tually the case in the
ear, every musical note

strument would excite
a series of sensations
exactly corresponding to
the pendulum-like vi-
brations into which the " Fig. 600.

original movements of XK enig’s apparatus for analysing a compound tone with the

the air can be resolved ; fundamental tone UT,.

and thus the existence

of each individual overtone would be exactly perceived, as is actually the case with
the ear. The perception of tones of different pitch, would under these circum-
stances depend upon different nerve-fibres, and hence would occur quite inde-
pendently of each other. Microscopic investigation shows that there are somewhat
similar structures in the ear. The free ends of all the nerve-fibres are connected
with small elastic particles which we must assume are set into sympathetic vibra-
tion by the sound-waves” (v. Helmholtz).

Resolution by the Cochlea.—Formerly v. Holmholtz considered the rods of Corti
to be the apparatus that vibrated and stimulated the terminations of the nerves.
But, as birds and amphibians, which certainly can distinguish musical notes, have
no rods (Hasse), the stretched radial fibres of the membrana basilaris, on which the
organ of Corti is placed, and which are shortest in the first turn of the cochlea,
becoming longer towards the apex of the cochlea, are now regarded as the vibrating

: 3F

818 HENSEN’S EXPERIMENTS ON MYSIS.

threads (Hensen). Thus, a string-like fibre of the membrana _basilaris, which is
capable of vibrating, corresponds to every possible simple tone. According to
Hensen, the hairs of the labyrinth, which are of unequal length, may serve this
purpose. Destruction of the apex of the cochlea causes deafness to deeper tones
insky).

itciess i Experiments.—That the hairs in connection with the hair-cells vibrate
to a particular note is also rendered probable by the experiments of Hensen on the
crustacean Mysis. He found that certain of the minute hairs (auditory hairs) in
the auditory organ of this animal, situate at the base of the antenna, vibrated when
certain tones were sounded on a keyed horn. The movements of the hairs were
observed by a low-power microscope. In mammals, however, there is a difficulty,
as the hairs attached to the cells appear to be all about the same length. We must
not forget that the perception of sound is a mental act. |

This assumption also explains the perception of novses. ty

Of noises in the strictly physical sense, it is assumed that they, like single
impulses, are perceived by the aid of the saccules and the ampulle.

It is assumed that the saccules and the ampulle are concerned in the general
perception of hearing, ¢.e., of shocks communicated to the auditory nerve (by
impulses and noises); while by the cochlea we estimate the pitch and depth of the
vibrations, and musical character of the vibrations produced by tones.

The relation of the semicircular canals to the equilibrium of the body is referred
to in § 350.

417. SIMULTANEOUS ACTION OF TWO TONES—HARMONY-—BEATS
—DISCORDS—DIFFERENTIAL TONES.—When ¢wo tones of different pitch
fall upon the ear simultaneously, they cause different sensations according to the
difference in pitch.

1. Consonance.—If the number of vibrations of the two tones is in the ratio of
simple multiples, as 1 : 2: 3:4, so that when the low notes make one vibration the
higher one makes 2:3 or 4... . then we experience a sensation of complete
harmony or concord. io

2. Interference.—If, however, the two tones do not stand to each other in the
relation of simple multiples, then when both tones are sounded simultaneously
interference takes place. The hollows of the one sound-wave can no longer coincide
with the hollows of the other, and the crests with the crests, but, corresponding to

the difference of number of vibrations of both curves, sometimes a wave-crest must *

coincide with a wave-hollow. Hence, when wave-crest meets wave-crest, there
must be an increase in the strength of the tone, and when a hollow coincides with
a crest, the sound must be weakened. Thus we obtain the impression of those
variations in tone intensity which have been called “ beats.”

_ The number of vibrations is of course always equal to the difference of the number of vibra-
tions of both tones. The beats are perceived most distinctly when two organ tones of low
pitch are sounded together in unison, but slightly out of tune. Suppose we take two organ
pipes with 33 vibrations per second, and so alter one pipe that it gives 34 vibrations per second,
then one distinct beat will be heard every second. The beats are heard more frequently the
greater the difference between the number of vibrations of the two tones.

Successive Beats.—The beats, however, produce very different impressions upon
the ear according to the rapidity with which they succeed each other. .

1. Isolated Beats.—When they occur at long intervals, we may perceive them
as completely isolated, but single intensifications of the sound with subsequent
enfeeblement, so that they give rise to the impression of isolated beats.

2. Dissonance.— When the beats occur more rapidly they cause a continuous
disagreeable whirring impression, which is spoken of as dissonance, or an unhar-

monious sensation. The greatest degree of unpleasant painful dissonance occurs
when there are 33 beats per second. ae

PERCEPTION OF THE DIRECTION OF SOUNDS. 819

3. Harmony.—If the beats take place more rapidly than 33 times per second,
the sensation of dissonance gradually diminishes, and it does so the more rapidly
the beats occur. The sensation passes gradually from moderately inharmonious
relations (which in music have to be resolved by certain laws) towards consonance
or harmony. The tone relations are successively the Second, Seventh, Minor Third,
Minor Sixth, Major Third, Major Sixth, Fourth, and Fifth.

4. Action of the Musical Tones (“ A/dnge”).—Two musical “klangs,” or com-
pound tones, falling on the ear simultaneously, produce a result similar to that of
two simple tones ; but in this case we have to deal not only with the two funda-
mental tones ; but also with the overtones. Hence the degree of dissonance of
two musical tones is the more pronounced the more the fundamental tones and the
overtones (and the “ differential” tones) produce beats which number about 33
per second.

5. Differential Tones.—Lastly two ‘“klangs,” or’ two simple musical tones
sounding simultaneously, may give rise to new tones when they are uniformly and
simultaneously sounding in corresponding intensity. We can hear, if we listen
attentively, a third: new tone, whose number of vibrations corresponds to the
difference between the two primary tones, and hence it is called a “differential
tone.” :

Summational Tones.—It was formerly supposed that new tones could arise from the sum-

mation or addition of their number of vibrations, but it has been shown that these tones are in
reality differential tones of a high order (Appunn, Preyer).

418. PERCEPTION OF SOUND — OBJECTIVE AND SUBJECTIVE
AUDITION—AFTER-SENSATION.—Objective and Auditory Perceptions.—
When the stimulation of the terminations of the nerves of the labyrinth is referred
to the outer world, then we have objective auditory perceptions. Such stimulations
are only referred to the outer world as are conveyed to the membrana tympani by
vibrations of the air, as is shown by the fact that if the head be immersed in water,
and the auditory meatuses be filled thereby, we hear all the vibrations as if they
occurred within our head itself (Hd. Weber), and the same is the case with our own
voice, as well as with the sound-waves. conducted through the bones of the head,
when both ears are firmly plugged.

Perception of Direction.—A<As to the perception of the direction whence sound
comes, we obtain some information from the relation of both meatuses to the
source of the sound, especially if we turn the head in the supposed direction of the
sound. We distinguish more easily the direction from which noises mixed with
musical tones come than that of tones (Rayleigh). When both ears are stimulated
equally, we refer the source of the sound to the middle line anteriorly, but when
one ear is stimulated more strongly than the other, we refer the source of the
sound more to one side (Kessel). The position of the ear-muscles, which perhaps
act like an ear-funnel, is important. According to Ed. Weber, it is more difficult
to determine the direction of sound when the ears are firmly fixed to the side of
the head. Further, if we place the hollow of both hands in front of the ear, so as
to form an open cavity behind them, we are apt to suppose that a sounding body
placed in front is behind us. The semicircular canals are said also to be concerned,
as sound coming from a certain direction must always excite one canal more than the
others. Thus, the left horizontal canal is most stimulated by horizontal sound-
_ waves coming from the left (Preyer). Other observers assert that the membrana
tympani localises the sound, as only certain parts of it are affected by the sound-
waves. :

The distance of a sound is judged of partly by the intensity or loudness of the
sound, such as we have learned to estimate from sound at a known distance. But
still we are subject to many misconceptions in this respect.

820 AUDITORY AFTER-SENSATIONS AND COLOUR ASSOCIATIONS.

subjective auditory sensations are the after-vibrations, especially of intense and
scatnaey ioemeat tones ; the tinnitus aurium (p. 606), which often accompanies abnormal
movements of the blood in the ear, al ae to a mechanical stimulation of the auditory
aps by the blood-stream (Brenner). By dc.
a Dee anche indica seems to act on the hearing centre, giving rise to subjective sounds ;
the hearing is rendered more acute by strychnin ; while quinine and sodic salicylate in large
doses cause ringing in the ears (Brunton). ] bse ,

Entotical perceptions, which are due to causes within the ear itself, are such as hearing the
pulse-beats in the surrounding arteries, and the rushing sound of the blood, which is especially
strong when there is increased resonance of the ear (as when the meatus or tympanum is closed,
or when fluid accumulates in the latter), during increased cardiac action, or in hyperesthesia
of the auditory nerve (Brenner). Sometimes there is a cracking noise in the maxillary
articulation, the noise produced by traction of the muscles on the Eustachian tube (§ 411), and
when air is forced into the latter, or when the membrana tympani is forced outwards or
inwards (§ 350). , :

Fatigue.—The ear after a time becomes fatigued, either for one tone or for a series of tones
which have acted on it, while the perceptive activity is not affected for other tones. Complete.
recovery, however, takes place in a few seconds (Urbantschitsch). —

Auditory After-Sensations. —(1) Those that correspond to positive after-sensations, where the
after-sensation is so closely connected with the original tone that both appear to be continuous.
(2) There are some after-sensations, where a pause intervenes between the end of the objective
and the beginuing of the subjective tone (Urbantschitsch). (3) There seems also to be a form
corresponding to negative after-images. ieee

In some persons, the perception of a tone is accompanied by the occurrence of subjective colours,
or the sensation of light, ¢e.g., the sound of a trumpet, accompanied by the sensation of yellow.
More seldom visual sensations of this kind are observed when the nerves of taste, smell, or
touch are excited (Vussbaumer, Lehmann and Bleuler). It is more common to find that an
intense sharp sound is accompanied by an associated sensation of the sensory nerves. Thus
many people experience a cold shudder when a slate pencil is drawn in a peculiar manner
across a slate.

(Colour Associations.—Colour is in some persons instantaneously associated with sound, and
Galton remarks that it is rather common in children, although in an ill-developed degree, and
the tendency seems to be very hereditary. Sometimes a particular colour is associated with a
particular letter, vowel sounds particularly evoking colours. Galton has given coloured
representations of these colour associations, and he points out their relation to what he calls
number-forms, or the association of certain forms with certain numbers. |

An auditory impulse communicated to one ear at the same time often causes an increase in
the auditory function of the other ear, in consequence of the stimulation of the auditory centres
of both sides (Urbantschitsch, Eitelbery). ;

Other Stimuli.—The auditory apparatus, besides being excited by sound-waves, is also
affected by heterologous stimuli. It is stimulated mechanically by a sudden blow on the ear.
The effects of electricity and pathological conditions are referred to in § 350.

419, COMPARATIVE—HISTORICAL. —The lowest fishes, the cyclostomata (Petromyzon),
have a saccule provided with auditory hairs containing otoliths, and communicating with two
semicircular canals, while the myxinoids have only one semicircular canal. Most of the other
fishes, however, have a utricle communicating with three semicircular canals. In the carp,
prolongations of the labyrinth communicate with the swimming-bladder. In amphibia, the
structure of the labyrinth is somewhat like that in fishes, but the cochlea is not typically
developed. Most amphibia, except the frog, are devoid of a membrana tympani. Only the
fenestra ovalis (not the rotunda) exists, and it is connected in the frog by three ossicles with
the freely-exposed membrana tympani. Amongst reptiles the appendix to the saccule, corre-
sponding to the cochlea, begins to be prominent. In the tortoise it is saccular, but in the
crocodile it is longer, and somewhat curved and dilated at the end. In all reptiles the
fenestra rotunda is developed, whereby the cochlea is connected with the labyrinth. In
crocodiles and birds, the cochlea is divided into a scala vestibuli and S. tympani. Snakes are
devoid of a tympanic cavity.’ In birds both saccules (fig. 591, IV, U 8S’) are united (Hasse),
the canal of the cochlea (U C), which is connected by means of a fine tube (C) with the
saccule, is larger, and shows indications of a spiral arrangement, and has a flask-like blind
end, the lagena (L). The auditory ossicles in reptiles and birds are reduced to one column-like
rod, corresponding to the stapes, and called the columella, The lowest mammals (Echidna)
have structures very like those of birds, while the higher mammals have the same type as in
man (fig. 591, I]1). The Eustachian tube is always open in the whale.

Amongst invertebrata, the auditory or is very simple in medusve and mollusca. It is

merely a bladder filled with fluid, with the srultory nerves provided with the ganglia in its —
t *

walls. Hair-cells occur in the interior, provided with one or more otoliths. Hensen observed

that in some of the annulosa, when sound was conducted into the water, some of the auditory

-a

THE SENSE OF SMELL. 821

bristles vibrated, being adapted for special tones. In cephalopoda, we distinguish the first
differentiation into a membranous and cartilaginous labyrinth.
Historical.—Empedocles (473 B.c.) referred auditory impressions to the cochlea. The
Hippocratic School was acquainted with the tympanum, and Aristotle (384 B.c.) with the
- Eustachian tube. Vesalius (1561) described the tensor tympani ; Cardanus (1560) the conduc-
tion through the bones of the head ; while Fallopius (1561) described the vestibule, the semi-
circular canals, chorda tympani, the two fenestre, the cochlea, and the aqueduct. Eustachius
(+ 1570) described the modiolus, the lamina spiralis of the cochlea, the Eustachian tube, as
well as the muscles of the ear ; Plater the ampulle (1583) ; Casseri (1600) the lamina spiralis
membranacea. Sylvius (1667) discovered the ossicle called by his name; Vesling (1641) the
stapedius. Mersenne (1618) was acquainted with overtones; Gassendus (1658) experimented
on the conduction of sound. Acoustics were greatly advanced by the work of Chladni (1802).
The most recent and largest work on the ear in vertebrates is by G. Retzius (1881-84).

The Sense of Smell.

420. STRUCTURE OF THE ORGAN OF SMELL.—Regio Olfactoria.—The area of the
distribution of the olfactory nerve is the regio olfactoria, which embraces the upper part of the
septum, the upper, and part of the middle (Cm) turbinated bone (fig. 601, Cs). All the
remainder of the nasal cavity is called the regio respiratoria. These two regions are distin-
guished as follows :—(1) The regio olfactoria has a thicker mucous membrane. (2) It is covered
by a single layer of cylindrical epithelium, the cells being often branched at their lower ends,
and contain a yellow or brownish-red pigment (figs. 602, 603, E). (3) It is coloured by this
pigment, and is thereby distinguished from the uncoloured regio respiratoria, which is covered

Epithe-
lium.

Mucous
Mem-
brane.

Fig, 601. Fig. 602. .

Fig, 601.—Nasal and pharyngo-nasal cavities. JZ, levator elevation; P.s.p., plica salphingo-
palatina ; Cs, Cm, Ci, the three turbinated bones (Urbantschitsch). Fig. 602.—Vertical
section of the olfactory region (rabbit), x 560. 9s, disc; zo, zone of oval, and zr of spherical
nuclei ; 6, basal cells ; dr, part of a Bowman’s gland ; , branch of the olfactory nerve.

by ciliated epithelium. (4) It contains peculiar tubular glands (Bowman’s glands), described
as ‘‘mixed glands” by Paulsen (§ 142), while the rest of the mucous membrane contains numer-
ous acinous serous glands (Heidenhain); but in man the latter are said to be mixed glands
(Stohr) (fig. 602). Lymph-follicles lie in the mucous membrane, and from them numerous
leucocytes pass out on to free surface (Stdhr). (5) Lastly, the regio olfactoria embraces the

822 STRUCTURE OF THE OLFACTORY ORGAN.

end-organs of the olfactory nerve. The long narrow olfactory cells (fig. 603, N) are distri-
buted prea the ordinary cylindrical epithelium (E) covering the regio olfactoria. The
body of the cell is spindle-shaped, with a large nucleus containing nucleoli, and it sends
upwards between the cylindrical cells a narrow (0°9 to 1°84) smooth
f rod, quite up to the free surface of the mucous membrane. In the frog
\ (n) the free end carries delicate projecting hairs or bristles. In the

become continuous with, varicose fine nerve-fibres, which pass into the
olfactory nerve (§ 321, I., 1). According to C. K. Hoffmann and Exner,
after section of the olfactory nerve, the specific olfactory end-organs
become changed into cylindrical epithelium (frog), and in warm-blooded
animals they undergo fatty degeneration, even on the 15th day. V.
Brunn found a homogeneous limiting membrane, which had holes in it
for transmitting the processes of the olfactory cells only. Do:

(The respiratory part of the nasal mucous membrane is lined by cili-
ated epithelium stratified like that in the trachea and resting on a base-
ment membrane. Below this there are many lymph-corpuscles ard
aggregations of adenoid tissue. |

[The organ of Jacobson is present in all mammals, and consists of two
narrow tubes protected by cartilage, and placed in the lower and anterior
part of the nasal septum. Each tube terminates blindly behind, but
anteriorly it opens into the nasal furrow or into the naso-palatine canal
(dog). The wall next the middle line is covered by olfactory epithelium,
and receives olfactory nerves (rabbit, guinea-pig), and it contains glands
similar to those of the olfactory region ; the outer wall is covered by
Fig. 603. columnar epithelium ciliated in some animals (K7ein).]

N; olfactory cells (it~ 491, OLFACTORY SENSATIONS.—Olfactory sensations
frog ; E, epithelium are produced by the action of gaseous, odorous substances, being
of the regio olfac- brought into direct contact with the olfactory cells, during
toria. the act of breathing. The current of air is divided by the

anterior projection of the lowest turbinated bone, so that a part above the latter

is conducted to the regio olfactoria. Odorous bodies taken into the mouth and then
expired through the posterior nares are said not to be smelt (Bidder). [This is
certainly not true, as kas been proved by Aronsohn. |

[It is usually stated that only odorous particles suspended in air excite the sensation of smell.
This is certainly not the whole truth—otherwise, how do aquatic animals, like fish, smell? More-
over the mucous membrane is always moist, and in some cases where there is a profuse secretion
from the olfactory mucous membrane, there is no impairment of the sense of smell. ]

During inspiration, the air streams along close to the septum, while little of it passes through
the nasal passages, especially the superior (Paulsen and Exner). [The expired air takes almost
the same course as the inspired air. ]

The first moment of contact between the odorous body and the olfactory mucous
membrane appears to be the time when the sensation takes place, as, when we wish
to obtain a more exact perception, we sniff’ several times, 7.¢., a series of rapid in-
spirations are taken, the mouth being kept closed. During sniffing, the air within
the nasal cavities is rarefied, and as air rushes in to equilibrate the pressure, the
air, laden with odorous particles, streams over the olfactory region. Odorous
fluids are said not to give rise to the sensation of smell when they are brought into
direct contact with the olfactory mucous membrane, as by pouring eau de Cologne
into the nostrils (Tourtual, 1827; £. H. Weber, 1847). [Aronsohn has, however,

shown that these experiments are not accurate, for one can smell eau de Cologne,

clove oil, &c., when a mixture of these bodies with ‘73 per cent. NaCl is applied to
the olfactory mucous membrane; the most suitable medium is -73 per cent, NaCl
and its temperature 40-43° C.] Even water alone temporarily affects the cells.
We know practically nothing about the nature of the action of odorous bodies,
but many odorous vapours have a considerable power of absorbing heat (Tyndall).
[Odorous bodies diminish the number of respirations (Goursen)| it

The intensity of the sensation depends on—1. The size of the olfactory surface,

as animals with a very keen sense of smell are found to have complex turbinated —

hye. deeper part of the mucous membrane, the olfactory cells pass into, and.

he

ht

OLFACTORY SENSATIONS. 823

bones covered by the olfactory mucous membrane. 2. The cencentration of the
odorous mixture of the air. Still, some substances may be attenuated enormously
(e.g., musk to the two-millionth of a milligramme), and still be smelt. 8. The
frequency of the conduction of the vapour to the olfactory cells (sniffing).

[The acuteness of the sense of smell is greatly improved by practice. A boy
named James Mitchell, who was deaf, dumb, and blind, used his sense of smell,
like a dog, to distinguish persons and things. |

[As in the case of sight and hearing, it has been sought to connect the quality of taste and
smell with the kind of vibrating stimulus. Ramsay showed that many facts pointed to the
dependence of smell upon the vibratory motion of odorous particles; thus, many gases and
vapours of low specific gravity—/.e., with a very rapid vibration of their molecules—are per-
fectly odourless, while such substances as the alcohols and fatty acids, alike in chemical and
physical properties, can excite generic smells, the higher members of the group being more
powerful in this respect than the lower ones. Taking the elements as arranged in a ‘‘ Natural
Classification” by Mendelejeff, Haycraft has shown that elements in the same group are capable
_ of producing similar or related tastes, and the same seems to be true for smell (Haycra/t). ]

We can smell the following substances in the following proportions :—Bromine 3535;, sul-
phuretted hydrogen spo/555 milligramme in 1 c.cm. of air (Valentin) ; also ggph555 Of a milli-
gramme of chlorphenol, and ggpatuoo0 Of a milligramme of mercaptan (#. Fischer and Penzoldt).

Electrical stimuli give rise to olfactory sensations. [Althaus found that electrical stimula-
tion of the olfactory mucous membrane gave rise to the sensation of the smell of phosphorus,
and Aronsohn found that he smelt on making the current when the cathode—and on breaking
the current when the anode—was in the nose.

The variations are referred to in § 343. If the two nostrils are filled with different odorous
substances there is no mixture of the odours, but we smell sometimes the one and sometimes
the other (Valentin). [Some substances appear to affect some regions of the olfactory mem-
brane, while others affect other parts.] The sense of smell, however, is very soon blunted, or
even paralysed. [It can be blunted or fatigued in a few minutes ; but after it is completely
fatigued it can recover in a minute.] Morphia, when mixed with a little sugar and taken as
snuff, paralyses the olfactory apparatus, while strychnin makes it more sensitive (Lichtenfels
and Frohlich).

The sensory nerves of the nasal mucous membrane (§ 347, II.) [¢.e., those supplied from the
fifth cranial nerve] are stimulated by irritating vapours, and may even cause pain, ¢,g., ammonia
and acetic acid. Ina very diluted condition they may even act on the olfactory nerves. The
nose is useful as a sentinel for guarding against the introduction of disagreeable odours and
foods. The sense of smell is aided by the sense of taste, and conversely.

[Flavour depends on the sense of smell, and, to test it, use substances, solid or fluid, with an
aroma or bouquet, such as wine or roast beef. ]

[Method of Testing. —In doing so, avoid the use of pungent substances like ammonia, which
excite the fifth nerve. Use some of the essential volatile oils, such as cloves, bergamot, and the
feetid gum resins, or musk and camphor. Electrical stimuli are not available. Action of
Drugs, § 343.]

Comparative.—In the lowest vertebrata, pits, or depressions provided with an olfactory
nerve, represent the simplest olfactory organ. Amphioxus and the cyclostomata have only one
olfactory pit ; all other vertebrates have two. In some animals (frog) the nose communicates
with the mouth by ducts. The olfactory nerve is absent in the whale.

Historical.—Rufus Ephesius (97 A.D.) described the passage of the olfactory nerve through
the ethmoid bone. Rudius (1600) dissected the body of a man with congenital anosmia, in
whom the olfactory nerves were absent. Majendie originally supposed that the nasal branch of
the fifth was the nerve of smell, a view successfully combated by Eschricht.

The Sense of Taste. |
422. STRUCTURE OF THE GUSTATORY ORGANS.—Gustatory Region.

—There is considerable difference of opinion as to what regions of the mouth are
endowed with taste:—(1) The root of the tongue in the neighbourhood of the
circumyallate papill, the area of distribution of the glosso-pharyngeal nerve, is un-
doubtedly endowed with taste (§ 351). (2) The tip and margins of the tongue are
gustatory, but there are very considerable variations. (3) The lateral part of the soft
palate and the glosso-palatine arch are endowed with taste from the glosso-pharyn-

824 STRUCTURE OF THE ORGANS OF TASTE.

geal nerve. (4) It is uncertain whether the hard palate and the entrance to the
larynx are endowed with taste (Drielsma). The middle of the tongue is not gustatory.

ongue—Mucous membrane.—The structure of the tongue, as a muscular organ covered with
ann pl wi has already been described (§ 155). The dorsal surface of the tongue, in
front of the blind foramen, is beset with elevations of the mucous membrane, which extend to
its tip and borders. These elevations, or papillw, are of three kinds ;—filiform, fungiform,
and circumvallate. They consist of elevations of the mucous membrane, visible to the naked
eye, and covered by stratified squamous epithelium, while the central core of connective-tissue
contains blood- and lymph-vessels and nerves. The filiform papille occur over the whole tongue,
and are smallest and most numerous. They are conical eminences covered by stratified squamous

1

Epithelium. 2

Epithelium. 3
Li trot Tunica

propria. 4

Tunica
propria.

Fig. 605.

Fig. 604.—Longitudinal section of the dorsum of the human tongue. 1, section of two filiform
papille, with secondary papille (2); 3, double, 4, single process of epithelium with loose
epithelial scales, x30. Fig. 605.—Longitudinal section of the human tongue. 1, second- ~
ary papille on 2, the fungiform papilla ; 3, base of 2; 4, small filiform papilla. x 30,

epithelium, and often beset with secondary papille (fig. 604). The fungiform papille occur
chiefly over the middle and front part of the tongue, and are not so numerous as the last. They
are club-shaped, with a narrow base, and broad expanded rounded head. They also have
secondary papille. They are generally brighter red than the others (fig. 605). The cireum-
vallate peralla 8 to 12 in number, diverge from the foramen cecum at the back part of the

Fig. 606.

I, Tranverse section of a circumvallate papilla; W, the papilla ; v,, v,, the wall in section ;
R, R, the circular slit or fossa ; K, K, the taste-bulbs in position ; N, N, the nerves. II,
Isolated taste-bulb ; D, supporting or protective cells; K, under end; E, free end, open,
wane : projecting apices of the taste-cells, III, Isolated protective cell (d) with a taste-
cell (e),

tongue in two rows in the form of a wide V, the open angle of the V being directed forwards,
They are large, with a broad expanded top, and are lodged in a depression of the mucous mem-
brane, being surrounded by a wall of mucous membrane, and separated from it by a circular
trench, into the base of which gland-ducts often open. They have numerous secondary papillae,
and in them are taste-buds, fig. 606, I.] : 3 obey

Jour different gustatory qualities,

GUSTATORY SENSATIONS. 825

Taste-bulbs,—The end-organs of the gustatory nerves are the taste-bulbs or taste-buds dis-
covered by Schwalbe and Lovén (1867). They occur on the lateral surfaces of the circumvallate
papille (fig. 606, I), and upon the opposite side, K, of the fossa or capillary slit, R, R, which
surrounds the central eminence or papilla; they occur more rarely on the surface. They also
occur on the fungiform papille, in the papille of the soft palate and uvula (4A. Hoffmann), on
the under surface of the epiglottis, the upper part of the posterior surface of the epiglottis, and
the inner side of the arytenoid cartilages (Verson, Davis), and on the vocal cords (Simanowsky).
Many buds or bulbs disappear in old age.

[In the rabbit and some other animals, there is a folded laminated organ on each side of the
posterior part of the tongue, called the papilla foliata ; the folds have on each side of them
numerous taste-buds (fig. 607). ]

Structure of the taste-bulbs. —They are 81 u high and 33 » thick, barrel-shaped, and embedded
in the thick stratified squamous epithelium of the tongue. Each bulb consists of a series of
lancet-shaped, bent, nucleated, outer supporting or protective cells, arranged like the staves
of a barrel (fig. 606, II, D, insolated in III, a). They are so arranged as to leave a small
opening, or the ‘‘ gustatory pore,” at the free end of the bulb. Surrounded by these cells,
and lying in the axis of the bud, are 1 to 10 gustatory cells (II, E), some of which are provided
with a delicate process (III, ¢) at their free ends, while their lower fixed ends send out basal
processes, which become continuous with
the terminations of the nerves of taste,
which have become non-medullated.
After section of the glosso-pharyngeal,
the taste-buds degenerate, while the
protective cells become changed into
ordinary epithelial cells within four
months (v. Vintschgau and Hénig-
schmied). Very similar structures were
found by Leydig in the skin of fresh-
water fishes. The glands of, the tongue
and their secretory fibres from the 9th
cranial nerve are referred to in § 141
(Drasch).

423. GUSTATORY SENSA-
TIONS. — Varieties.— There are

Epithelium.

the sensations of 1. Sweet; 2.
Bitter ; 3. Acid; 4. Saline. Acid
and saline substances at the same
time also stimulate the sensory
nerves of the tongue, but when
greatly diluted, they only excite the Vertical section of two septa of the papilla foliata
Steve soe eat ate oe
ete ope sas are areata! Bal and oe) of its duct, a; M, muscular fibres of
nerve-fibres for each different gusta- the tongue.

tory quality (v. Vintschgau).

Conditions.—Sapid substances, in order that they may be tasted, require the
following conditions :—They must be dissolved in the fluid of the month, especially
substances that are solid or gaseous. The intensity of the gustatory sensation
depends on :—1, The size of the surface acted on. Sensation is favoured by rub-
bing in the substance between the papille, in fact, this is illustrated in the rubbing
movements of the tongue during mastication (§ 354). 2. The concentration of the
sapid substance is of great importance. Valentin found that the following series
of substances ceased to be tasted in the order here stated, as they were gradually
diluted—syrup, sugar, common salt, aloes, quinine, sulphuric acid. Quinine can
be diluted 20 times more than common salt and still be tasted (Camerer). 3. The
time which elapses between the application of the sapid substance and the produc-
tion of the sensation varies with different substances. Saline substances are tasted
most rapidly (after 0°17 second, according to v. Vintschgaw), then sweet, acid and
bitter (quinine after 0°258 second, v. Vintschgau). This even occurs with a
mixture of these substances (Schirmer). The last-named substances produce the most

826 PATHOLOGICAL—COMPARATIVE—HISTORICAL.

persistent “after-taste.” 4. The delicacy of the sense of taste is partly congenital,
but it can be greatly improved by practice. If a person continues to taste the
same sapid substance, or a nearly related one, or even any very intensely sapid
substance, the gustatory sense is soon affected, and it becomes impossible.to give a
correct judgment as to the taste of the sapid body. 5. Taste is greatly aided by the
sense of smell, and in fact we often confound taste with smell; thus, ether, chloro-
form, musk, and assafcetida only affect the organ of smell. [The combined action
of taste and smell in some cases gives rise to flavour (p. 823).] The eye even may
aid the determination, as in the experiment where in rapidly tasting red and white
wine one after the other, when the eyes are covered, we soon become unable to
distinguish between the one and the other. 6. The most advantageous temperature
for taste is between 10° to 35° C.; hot and cold water temporarily paralyse taste. .
Ice placed on the tongue suppresses, sometimes entirely, the whole gustatory apparatus ;
cocain alone, bitter tastes, at water containing 2 per cent. of H,SO,, excite afterwards a
sweet taste (Aducco and Mosso).
Electrical Current.—The constant current, when applied to the tongue, excites, both
during its passage and when it is opened or closed, a sensation of acidity at the+ pole, and at
the — pole an alkaline taste, or, more correctly, a harsh burning sensation (Siwlzer, 1752). This
is not due to the action of the electrolytes of the fluid in the mouth, for even when the ia *
is moistened with an acid fuid the alkaline sensation is experienced at the — pole (Volta). e
cannot, however, set aside the supposition that perhaps electrolytes, or decomposition-products,
may be formed in the deeper parts and excite the gustatory fibres. Rapidly interrupted
currents do not excite taste (Griinhagen). V. Vintschgau, who has only incomplete taste on
the tip of the tongue, finds that when the ¢zp of the tongue is traversed by an electrical current,
there is never a gustatory sensation, but always a distinct tactile one. In experiments on
Honigschmied, who is possessed of normal taste in the tip of the tongue, there was often
a metallic or acid taste at the + pole on the tip of the tongue, while at the — pole taste was often
absent, and when it was present it was almost always alkaline, and acid only exceptionally. After
interrupting the current there was a metallic after-taste with both directions of the current.

[Testing Taste.—-Direct the person to put out his tongue and close his eyes, and
after drying the tongue apply the sapid substance by means of a glass rod or a
small brush. Try to confine the stimulus as much as possible to one place, and
after each experiment rinse the mouth with water. A wine-taster chews an olive
to “clean the palate,” as he says. For testing Jitter taste use a solution of quinine
or quassia ; for sweet, sugar, [or the intensely sweet substance “ saccharine” obtained
from coal tar]; saline, common salt; and acid, dilute citric or acetic acid. The
galvanic current may also be used. ]

Pathological. —Diseases of the tongue, as well as dryness of the mouth caused by interference
with the salivary secretion, interfere with the sense of taste. Subjective gustatory impressions
are common amongst the insane, and are due to some central cause, perhaps to irritation of the
centre for taste (§ 378, IV., 3). After oisoning with santonin, a bitter taste is experienced,
while after the subcutaneous injection of. morphia, there is a bitter and acid taste. The terms
hypergeusia, hypogeusia, and ageusia are applied to the increase, diminution, and abolition
of the sense of taste. Many tactile impressions on the tongue are frequently confounded with
gustatory sensations, ¢.g., the so-called biting, cooling, prickling, sandy, mealy, astringent,
and harsh tastes.

Comparative. —About 1760 taste-bulbs occur on the circumvallate papille of the ox. The
term papilla foliata is applied to a large folded gustatory organ placed laterally on the side of the
tongue (fig. 607), especially of the rabbit (Rapp, 1832); which in man is represented by analo-
gous organs, i of longitudinal folds, lying in the fimbrie lingua on each side of the
osterior part of the tongue (Krause, v. Wyss). Taste-bulbs are absent in reptiles and birds.
They are numerous in the gill-slits of the tadpole (F. Z. Schultze), while the tongue of the fro
is covered with epithelium aeeperies gustatory cells (Billroth, Axel Key). The blet-shaped
organs in the skin of fishes and oe es have a structure similar to the taste-bulbs, and may
perhaps have the same function. There are taste-bulbs in the mouth of the carp and ray.

torical.—Bellini regarded the Papille as the organs of taste (1711). Richerand, Mayo,
and Fodera thought that the lingual was the only nerve of taste, but Majendie proved that,
after it was divided, the posterior part of the tongue was still endowed with taste. Panizza

(1834) described the glosso-pharyngeal as the nerve of taste, the gustatory as the nerve of touch
and the hypoglossal as the motor nerve of the tongue. Fe “yf at ; Sik f

x .

STRUCTURE OF THE ORGANS OF TOUCH. 827

The Sense of Touch.

424, TERMINATIONS OF SENSORY NERVES.—1. The touch-corpuscles of Wagner and
Meissner lie in the papille of the cutis vera (§ 283), and are most numerous in the palm of the
hand and the sole of the foot, especially in the fingers and toes, there being abont 21 to
every square millimetre of skin, or 108 to 400 of the papille containing blood-vessels. They
are less abundant on the back of the hand and foot, mamma, lips, and tip of the tongue, rare
on the glans clitoridis, and occur singly and scattered on the volar side of the fore-arm, even in
the anthropoid apes. They are oval or elliptical bodies, 40-200 uw long [34, in.], and 60-70 u
broad [5$5 to sty in.], and are covered externally by layers of connective-tissue arranged
transversely in layers, and within is a granular mass with elongated striped nuclei (figs. 608,
609, ¢). One to three medullated
nerve-fibres pass to the lower
end of each corpuscle, and sur-
round it in a spiral manner two

S or three times; the fibres then
= lose their myelin, and, after
el dividing into 4 to 6 fibrils, branch
C within the corpuscle. The exact
o--BS an MN
: co)
Mill | i,
; | SNL NIMH ett
6b: | Wize: (0) Ne
f pik CNA Ve) I =
pa i in ! i Oe Qa \

i mY, ii iW
( (Oge7 |
No
; i

wn

l Va ie

aA |
WI i JANN Me Dara
he | ‘ i Ff, et faa

F
A
il

SS

Z ————
ee

EE

==

>.

ca Se

il
i

‘:

A

) AMA

Fig. 608. . Fig. 609.

Fig. 608.—Vertical section of the skin of the palm of the hand. a, blood-vessels ; b, papilla
of the cutis vera; c, capillary ; d, nerve-fibre ‘passing to a touch-corpuscle ; jf, nerve-
fibre divided transversely ; e, Wagner’s touch-corpuscle ; g, cells of the Malpighian layer
of the skin. Fig. 609.—Wagner’s touch-corpuscle from the palm, treated with gold

. fo] . .
chloride ; », nerve-fibres; a, a, groups of glomeruli.

mode of termination of the fibrils is not known. Some observers suppose that the transverse
fibrillation is due to the coils or windings of the nerve-fibrils; while according to others,
the inner part consists of numerous flattened cells lying one over the other, between which
the pale terminal fibres end either in swellings or with disc-like expansions, such as occur in
Merkel’s corpuscles.

[These do not contain a soft core such as exists in Pacini’s corpuscles. The corpuscles appear
to consist of connective-tissue with imperfect septa maga: into the interior from the fibrous
capsule. After the nerve-fibre enters it loses its myelin, and then branches, while the branches
anastomose and follow a spiral course within the corpuscle, finally to terminate in slight
enlargements. According to Thin, there are simple and compound corpuscles, depending on
the number of nerve-fibres entering them. ] :

Kollmann deseribes three special tactile areas in the hand :—(1) The tips of the fingers with
24 touch-corpuscles in a length of 10 mm. ; (2) the three eminences lying on the palm behind
the slits between the fingers, with 5°4-2°7 touch-corpuscles in the same length; and (3) the
ball of the thumb and little finger with 3°1-3°5 touch-corpuscles. The first two areas also
contain many of the corpuscles of Vater or Pacini, while in the latter these corpuscles are fewer
— and soattenets In the other parts of the hand the nervous end-organs are much less developed.

828 PACINI'S CORPUSCLES.

2. Vater’s (1741) or Pacini’s corpuscles are oval bodies (fig. 610), 1-2 mm. long, lying in
the subcutaneous tissue on the nerves of the fingers and toes (600-1400), in the neighbourhood
of joints and muscles, the sympathetic abdominal plexuses, near the aorta and fan ae gland
on the dorsum of the penis and clitoris, and in the mesocolon [and mesentery] o! the cat.
[They also occur in the course of the intercostal and periosteal nerves, and Stirling has
seen them in the capsule of lymphatic glands. They are attached to the nerves of the hand
and feet, and are so large as to be visible to the naked eye, both in these regions and between
the layers of the mesentery of the cat. They are whitish or somewhat transparent, with a
white line in the centre (cat); in man, they are y, to 75 inch long, and 3s to dy inch broad,
aud are attached by a stalk or pedicle (fig. 610, a) to the nerve.] They consist of numerous
nucleated connective-tissue capsules or lamelle lined by endothelium, separated from each other
by fluid, and lying one within the other like the coats of an onion, while in the axis is a
’ ; central core. A medullated nerve-fibre pangs to each,
where its sheath of Schwann unites with the capsule. It
loses its myelin, and passes into the interior as an axial
eylinder (fig. 610, e), where it either ends in a small knob
or may divide dichotomously (fig. 610, 7), each branch
terminating in a small pear-shaped enlargement. [Each
large corpuscle is covered by 40-50 lamelle, or tunics,
which are thinner and closer to each other (fig. 610, d)
internally than in the outer part, where they are thicker
and wider apart. The lamelle are like the laminz in the
lamellated sheath of a nerve, and are composed of an elastic
basis mixed with white fibres of connective-tissue, while
the inner surface of each lamella is lined by a single con-
tinuous layer of endothelium continuous with that of the

erineurium. It is easily stained with silver nitrate.
he efferent nerve-fibre is covered with a thick sheath of
lamellated connective-tissue (sheath of Henle), which be-
comes blended with the outer lamelle of the corpuscle.
The medullated nerve is sometimes accompanied by a

myelin until it reaches the core, where it terminates as
already described. ]

Fig. 610. Fig. 611. Fig, 612.

Fig. 610.—Vater’s or Pacini’s corpuscle. a, stalk; b, nerve-fibre entering it; ¢, d, connective-
tissue envelope ; ¢, axis-cylinder, with its end divided at J. Fig. 611.—End-bulb from
human conjunctiva, 4, nucleated capsule ; 6, core; ¢, fibre entering and branching, ter-
minating in core at d. Fig. 612.—Tactile corpuscles, clitoris of rabbit.

8, Krause’s end-bulbs very probably occur as a regular mode of nerve-termination in the
cutis and mucous membranes of all mammals (fig. 611), They are elongated, oval, or round
bodies, 0°075 to 0°14 mm. long, and have been found in the Saat layers of the conjunctiva
bulbi, floor of the mouth, margins of the lips, nasal mucous membrane, epiglottis, fungiform
and circumvallate papille, glans penis and Uitoris, volar surface of the toes of the guinea-pig,
ear and body of the mouse, and in the wing of the bat. [In the calf, the “eylindrical
bulbs” are oval, with a nerve-fibre terminating within them. The sheath of Henle becomes

continuous with the nucleated capsule, while the axial op titan, devoid of its men, : 3con-

tinued into the soft core. In man the end-bulbs are “ sp

eroidal,” and consist of an

.

blood-vessel, and pierces the various tunics, retaining its.

ee aie — :

ae

TERMINATIONS OF SENSORY NERVES. 829

connective-tissue capsule continuous with Henle’s sheath of the nerve, and enclosing many cells,
amongst which the axis-cylinder which enters the bulb branches and terminates.] The spheroidal
end-bulbs occur in man, in the nasal mucous membrane, conjunctiva, mouth, epiglottis, and
the mucous folds of the rectum. According to Waldeyer and Longworth, the nerve-fibrils
terminate in the cells within the capsule. These cells are said to be comparable to Merkel’s
tactile cells (Waldeyer). ;

The genital corpuscles of Krause, which occur in the skin and mucous membrane of the
glans penis, clitoris, and vagina, appear to be end-bulbs more or less fused together (fig. 612).

The articulation nerve-corpuscles occur in the synovial mucous membrane of the joints of
the fingers. They are larger than the end-bulbs, and have numerous oval nuclei externally,
while one to four nerve-fibres enter them.

4, Tactile or touch-corpuscles of Merkel, sometimes also called the corpuscles of Grandry,
occur in the beak and tongue of the duck and goose, in the epidermis of man and mammals,
and in the outer root-sheath of tactile hairs or feelers (fig. 613). They are small bodies com-
posed of a capsule enclosing two, three, or more large, granular, somewhat flattened nucleated
and nucleolated cells, piled one on the other in a vertical row like a row of cheeses. Each
corpuscle receives at one side a medullated nerve-fibre which loses its myelin, and branches, to
terminate, according to some observers (Merkel), in the cells themselves, and according to others
(Ranvier, Izquierdo, Hesse) in the protoplasmic transparent substance or disc lying between
the cells. [This intercellular disc is the ‘‘dise tactil” of Ranvier, or the ‘‘ Tastplatte” of
Hesse.] When there is a great aggre-
gation of these cells, large structures are
formed which appear to form a kind of
transition between these and touch-
corpuscles. [According to Klein, the
terminal fibrils end neither in the touch-

Fig. 613. Fig. 614.

Fig. 613.—Tactile corpuscles from the duck’s tongue. A, composed of three cells with two
interposed discs, with axis-cylinder, x, passing into them. B, two tactile cells and one
disc. Fig. 614.—Bouchon epidermique from the groin of a guinea-pig, after the action of
gold chloride. m, nerve-fibre ; a, tactile cells; m, tactile discs ; c, epithelial ceils.

swellings in the interstitial substance between the touch-cells, in a manner very similar to that
occurring in the end-bulbs. ]

[According to Merkel, tactile cells, either isolated or in groups, but in the latter case never
forming an independent end-organ, occur in the deeper layers of the epidermis of man and
mammals and also in the papille. They consist of round or flask-shaped cells, with the lower
pointed neck of the flask continuous with the axis-cylinder of a nerve-fibre. They are regarded
by Merkel as the simplest form of a tactile end-organ, but their existence is doubted by some
observers. |

Amongst animals there are many other forms of sensory end-organs. [Herbst’s corpuscles
occur in the mucous membrane of the tongue of the duck, and resemble small Vater’s corpuscles,
but their lamelle are thinner and nearer each other, while the axis-cylinder within the central
core is bordered on each side by a row of nuclei.] In the nose of the mole there is a peculiar
end-organ (Himer), while there are ‘‘ end-capsules” in the penis of the hedgehog and the tongue
of the elephant, and ‘‘ nerve-rings” in the ears of the mouse.

5. [Other Modes of Ending of Sensory Nerves.—Some sensory nerves terminate not by means
of special end-organs, but their axis-cylinder splits up into fibrils to form a nervous network,
from which fine fibrils are given off to terminate in the tissue in which-the nerve ends. These
fibrils, as in the cornea (§ 384), terminate by means of free ends between the epithelium on the
anterior surface of the cornea, and some observers state that the free ends are provided with
small enlargements (‘‘ bowtons terminals’”’) (fig..614, a). These enlargements or ‘‘ tactile cells”
occur in the groin of the guinea-pig and mole. A similar mode of termination occurs between
the cells of the epidermis in man and mammals (fig. 293).] |

6. Tendons, especially at their junction with muscles, have special end-organs (Sachs, Rollett,
Golgi), which assume various forms ; it may be a network of primitive nerve-tibrils, or flattened

830 SENSORY AND TACTILE SENSATIONS.

end-flakes or plates in the sterno-radial muscle of the frog, or elongated oval end-bulbs, not un-
like the end-bulbs of the conjunctiva, or small simple Pacinian corpuscles. } Hise

Prus found ganglion cells more frequently in the subcutaneous tissue than in the corium,
and they appeared to have some relation to the blood-vessels and sweat-glands,

425. SENSORY AND TACTILE SENSATIONS.—In the sensory nerve- ©
trunks there are two functionally different kinds of nerve-fibres :—(1) Those which
administer to painful impressions, which are sensory nerves in the narrower sense of
the word ; and (2) those which administer to tactile impressions and may therefore be
called tactile nerves. The sensations of temperature and pressure are also reckoned
as belonging to the tactile group. It is extremely probable that the sensory and
tactile nerves have different end-organs and fibres, and that they have also special
perceptive nerve-centres in the brain, although this is not definitely proved. This
view, however, is supported by the following facts :—

1. That sensory and tactile impressions cannot be discharged at the same time
from all the parts which are endowed with sensibility. Tactile sensations, includ-
ing pressure and temperature, are only discharged from the coverings of the skin,
the mouth, the entrance to and floor of the nose, the pharynx, the lower end of the
rectum and genito-urinary orifices ; feeble indistinct sensations of temperature are
felt in the cesophagus. Tactile sensations are absent from all internal viscera, as
has been proved in man in cases of gastric, intestinal, and urinary fistule. Pain
alone can be discharged from these organs. 2. The conduction channels of the
tactile and sensory nerves lie in different parts of the spinal cord (§ 364, 1 and 5).
This renders probable the assumption that their central and peripheral ends also
are different. 3. Very probably the reflex acts discharged by both kinds of ‘nerve
fibres—the tactile and pathic—are controlled, or even inhibited, by special central
nerve-organs (§ 361—?). 4, Under pathological conditions, and under the action of
narcotics, the one sensation may be suppressed while the other is retained (§ 364, 5). —

Sensory Stimuli.—In order to discharge a painful impression from sensory
nerves, relatively strong stimuli are required. The stimuli may be mechanical,
chemical, electrical, thermal, and somatic, the last being due to inflammation or
anomalies of nutrition and the like.

Peripheral Reference of the Sensations.—These nerves are excitable along their
entire course, and so is their central termination, so that pain may be produced by
stimulating them in any part of their course, but this pain, according to the “law
of peripheral perception,” is always referred to the periphery.

The tactile nerves can only discharge a tactile impression or sensation of contact
when moderately strong mechanical pressure is exerted, while thermal stimuli are
required to produce a temperature sensation, and in both cases, the results are
obtained only when the appropriate stimuli are applied to the end-organs. If
pressure or cold be applied to the course of a nerve-trunk, e.g., to the ulna at the
inner surface of the elbow-joint, we are conscious of painful sensations, but never of
those of temperature, referable to the peripheral terminations of the nerves in the
inner fingers. All strong stimuli disturb normal tactile sensations by over-stimula-
tion, and hence cause pain,

The law of the specific energy of nerves leads us to assume that the cutaneous
nerves contain different kinds of nerve-fibres with different kinds of end-orgat
which subserve different kinds of impressions, ¢ t t d at
Blix and Goldscheider have found such differanecs’ Electrical stimulation eonses

ave found such differences. Electrical stimulation causes
different sensations according to the part of the skin where it is applied; at one
spot, pain only is produced, at another a sensation of cold, at a third a sensation of
heat, and at a fourth, a sensation of pressure, At every temperature point or spot,
ia is Insensibility for pain or pressure, The “ pressure-points ” or pressure-spots
te much closer together, and are more numerous than the temperature-points,
There are special “pain-spots” and even “tickling-spots.” These spots are -

THE SENSE OF LOCALITY. 831

arranged in a linear chain, which usually radiates from the hair-follicles. The
** tickling-spots ” coincide with the pressure and pain-spots. The feeling of tickling
corresponds to the feeblest stimulation of a nerve-fibre, and pain to the strongest.
The pain-spots can be isolated by means of a needle, or electrically, especially in
the cutaneous furrows, in which the pressure-sense is absent.

Goldscheider removed from his own body small pieces of skin, in which he had previously
ascertained the presence of these ‘‘ spots,” and then investigated the excised skin microscopic-
ally. At each such spot he found a rich supply of nerves ; at the pressure-spots, there were
no touch-corpuscles, .

[By means of the skin, impressions are supplied also to the brain, whereby we become con-
scious of the amount and direction of a body moved in contact with the skin. Indeed, the
discriminative sensibility is more acute for motion than for touch ; but the liability to error in
judging of the distance and direction is great (Haid). ]

[Very complex sensations are obtained by means of the combined action of the skin and
muscles, ¢.g., those known as ‘‘feelings of double contact.’’ These sensations are of the
greatest advantage in acquiring the use of instruments and tools. If we touch an object with
a rod, we seem to feel the object at the point of the rod, and not in the hand where the cutaneous
nerves are actually stimulated. With a walking stick, we feel the ground
at the end of the stick. Touch the tips of the hair, or a tooth, and the
sensation is referred to the tips of the hair in the one case, and the crown
of the tooth in the other (Ladd). ]

426. SENSE OF LOCALITY.—We are not only able to
distinguish differences of pressure or temperature by our sensory
nerves, but we are able to distinguish the part which has been
touched. This capacity is spoken of as the sense of space or
locality. ‘

Methods of Testing.—1. Place the two blunted points of a pair of com-
passes (fig. 615) upon the part of the skin to be investigated, and determine
the smallest distance at which the two points are felt only as one impres-
sion. Sieveking’s esthesiometer may be used instead (fig. 616) ; one of the
points is movable along a graduated rod, while the other is fixed. 2.
The distance between the points of the instrument being kept the same,
touch several parts of the skin, and ask if the person feels the impression
of the points coming nearing to or going wider apart. 3. Touch a part of Fig. 615.
the skin with a blunt instrument, and observe if the spot touched is cor-
rectly indicated by the patient. 4. Separate the points of two pairs of
compasses unequally, and place their points upon different parts of the skin, and ask the person
to state when the points of both appear to be equally far apart. A distance of 4 lines on the ©

+ TM Line

Th ©

|

ksthesiometer.

Fig 616.
Esthesiometer of Sieveking

forehead appears to be equal to a distance of 2°4 lines on the uppe: lip. This is Fechner’s
‘‘methods of equivalents,”

The following results have been obtained. The sense of locality of a part of the
skin is more.acute under the following conditions :—

1. The greater the number of tactile’nerves in the corresponding part of the skin.

2. The greater the mobility of the part, so that it increases in the extremities
towards the fingers and toes. The sense of locality is always very acute in parts of
the body that are very rapidly moved (Vierordt).

832 MODIFYING CONDITIONS.

3. The sensibility of the limbs is finer in the transverse axis than in the long axis
of the limb, to the extent of 4th on the flexor surface of the upper limb, and jth
on the extensor surface.

4. The mode of application of the points of the esthesiometer :—(a) According
as they.are applied one after the other, instead of simultaneously, or as they are
considerably warmer or colder than the skin (A/ug), a person may distinguish a
less distance between the points. (+) If we begin with the points wide apart and
approximate them, then we can distinguish a less distance than when we proceed
from imperceptible distances to larger ones. (c) If the one point 1s warm and the
other cold, on exceeding the next distance we feel two impressions, but we cannot
rightly judge of their relative positions (Czermak). _ :

5. Exercise greatly improves the sense of locality; hence the extraordinary
acuteness of this sense in the blind, and the improvement always occurs on both
sides of the body ( Volkmanzn). .

(Fr. Galton finds that the reputed increased acuteness of the other senses in the case of the
blind is not so great as is generally alleged. He tested a large number of boys at an educational
blind asylum, with the result that the performances of the blind boys were by no means superior
to those of other boys. He points out, however, that ‘‘the guidance of the blind depends
mainly on the multitude of collateral indications, to which they give much heed, and not in their
superiority in any one of them.’’]

6. Moistening the skin with indifferent fluids increases the acuteness. If, how-
ever, the skin between two points, which are still felt as two distinct objects, be
slightly tickled, or be traversed by an imperceptible electrical current, the impres-
sions become fused (Suslowa). The sense of locality is rendered more acute at the
cathode when a constant current is used (Suslowa), and when the skin is congested
by stimulation (Klinkenberg), and also by slight stretching of the skin (Schmey);
further, by baths of carbonic acid (v. Basch and v, Dretl), or warm common salt,
and temporarily by the use of caffein (umpf).

7. Anemia, produced by elevating the limbs, or venous hyperemia (by compress-
ing the veins), blunts the sense, and so does too frequent testing of the sense of
locality, by producing fatigue. The sense is also blunted by cold applied to the
skin, the influence of the anode, strong stretching of the skin, as over the abdomen
during pregnancy, previous exertion of the muscles under the part of the skin

tested, and some poisons, ¢.g., atropin, daturin, morphin, strychnin, alcohol,

potassium bromide, cannabin, and chloral hydrate.
Millimetres. Millimetres.

1°1 [1°1) | Eyelid, ‘ : : : . 113 [9°]
Centre of hard palate, ; . 13°5 [11°3]
2°-2°3 [1°7] | Lower third of the fore-arm, vola

Tip of tongue, . ° . ;
Third phalanx of finger, volar
surface, . P :

Red part of the lip, . ; ; 4°5 [3°9] surface, . ; ; j » Te

Second phalanx of finger, volar In front of the zygoma,_ . . 15°8 [11°3]
surface, . : . ; . 4-4°5[3°9] | Plantar surface of the great toe,. 15°8 [9°]

First phalanx of finger, volar | Inner surface of the lip, . 20°3 [13°5]
surface, . , : : ~ 5-6°5 Behind the zygoma, . °22°6 (15°8]

Third phalanx of finger, dorsal Forehead, . : 226 [18°]
surface, . . ; ; ; 6°8 Occiput, . i 27°1 [22°6]

Tip of nose, : ; ;
Head of metacarpal bone, volar, 5°-6°8

Ball of thumb, . 6°5-7 Vertex, 33°8 [22°6
Ball of little finger, . ‘ . 5°5+6° Knee, ; é ’ 36°1 [31°6.
Centre of palm, : : . 8-9: Sacrum, gluteal region, 44°6 [33°8]
Dorsum and side of tongue, white Fore-arm and leg, 45:1 [83°8]
of the lips, metacarpal part of Neck, at ty ; : . 54:1 [8671]
the thumb, . ‘ ; . 9° [6°8] | Back at the fifth dorsal vertebra,
Third phalanx of the great toe, lower dorsaland lumbar region, 54°1 .
plantar surface, . ; - 11°3 [6°8] | Middle of the neck, . - o,, Osee
Second phalanx of the fingers, bt arm, thigh, and centre of eal
dorsal surface, 118 (e] the back, . . . 67°7 [31°6-40°6]
Bey 5: PR ke. Shh

Back of the hand,
Under the chin, .

31°6 [22°6]
33°8 [22°6]

| ASTHESIOMETRY. | 833

Smallest Appreciable Distance.—The preceding statement gives the smallest
distance, in millimetres, at which two points of a pair of compasses can still be dis-
tinguished as double by an adult. The corresponding numbers for a boy twelve
years of age are given within brackets. .

‘Illusions of the sense of locality occur very frequently ; the most marked are :—(1) A uni-
form movement over a cutaneous surface appears to be quicker in those places which have the
finest sense of locality. (2) If we merely towch the skin with the two points of an esthesio-
meter, then they feel as if they were wider apart than when the two points are moved along the
skin (Fechner). (3) A sphere, when touched with short rods, feels larger than when long rods
are used (Zourtual). (4) When the fingers of one hand are crossed, a small pebble or sphere
placed between them feels double (Aristotle’s experiment). [When a pebble is rolled between
the crossed index and middle finger (fig. 617, B), it feels as if two balls were present, but with
the fingers uncrossed single.] (5) When pieces of skin
are transplanted, ¢.g., from the forehead, to form a
nose, the person operated on feels, often for a long
time, the new nasal part as if it were his forehead.

Theoretical.—Numerous experiments were made by
E. H. Weber, Lotze, Meissner, Czermak, and others
to explain the phenomena of the sense of space.
Weber’s theory goes upon the assumption, that one
and the same nerve-fibre proceeding from the brain
to the skin can only take up one kind of impression,
and administer thereto. He called the part of the
skin to which each single nerve-fibre is distributed
a ‘‘circle of sensation.” When two stimuli act
simultaneously upon the tactile end-organ, then a
double sensation is felt, when one or more circles of
sensation lie between the tyo points stimulated.
This explanation, based upon anatomical considera- :
tions, does not explain how it is that, with practice, Fig. 617.
the circles of sensation become smaller, and also how Aristotle’s experiment.
it is that only one sensation occurs, when both points
of the instruments are so applied, that both points, although further apart than the diameter of
a circle of sensation, at one time lie upon two adjoining circles, at another between two others
with another circle intercalated between them.

Wundt’s Theory. —In accordance with the conclusions of Lotze, Wundt proceeds from a
psycho-physiological basis, that every part of the skin with tactile sensibility always conveys
to the brain the locality of the sensation. Every cutaneous area, therefore, gives to the tactile
sensation a ‘‘local colour” or quality, which is spoken of as the local sign. He assumes
that this local colour diminishes from point to point of the skin. This gradation is very sudden
in those parts of the skin where the sense of space is very acute, but occurs very gradually

where the sense of space is more obtuse. Separate im- Saeee

pressions unite into a common one, as soon as the gra- ,-,3:+ ++ Bega alec! oo hee s,
dation of the local colour becomes imperceptible. By °* Ve.2t 00 trotters "s seis"
practice and attention differences of sensation are expe- W1n."+. °° Sel ctelt Hepes
rienced, which ordinarily are not observed, so that he 7+". ‘31 “+ Ceres ise
explains the diminution of the circles of sensation by :

practice. The circle of sensation is an area of the skin, a b c
within which the local colour of the sensation changes so Fig. 618.

little that two separate impressions fuse into one. Pressure-spots. a, middle of the sole

: of th : <i Zyo :
427. PRESSURE SENSE.—By the sense of ae aoe A of zygoma ;
pressure we obtain a knowledge of the amount of | |
weight or pressure which is being exercised at the time on the different parts of
the skin.

A specific end-apparatus arranged in a punctated manner is connected with the
pressure sense (fig. 618). These points or spots are called ‘“ pressure-spots” or
“pressure-points ” (Bli), and are endowed with varying degrees of sensibility;
at some places (back, thigh) they are distinguished by a markedly pronounced after-
sensation. The arrangement of the pressure-spots follows the type of the arrange-
ment of the temperature-spots. The pressure-spots have usually another direction
than that of hot and cold spots, as a rule, they are denser. The minimal distance
at which two pressure-spots, when simultaneously stimulated, are felt as double, is

3G

8 34 THE PRESSURE SENSE.

—on the back, 4 to 6 mm. ; breast, 0°8 ; abdomen, 1°5 to 2; cheek, 0°4 to 06;
upper arm, 0°6 to 0°8 ; fore-arm, 0°5; back of the hand, 0°3 to 0°6 ; palm, 0:1 to
0°5 ; leg, 0°8 to 2; back of foot, 0°8 to 1; sole of foot, O8tolmm. |
Methods.—1. Place, on the part of the skin to be investigated, different weights, one after
the other, and ascertain what perceptions they give rise to, and the sense of the difference of
pressuré to which they give rise. We must be careful to exclude differences of temperature and
prevent the displacement of the weights—the weights must always be placed on the same spot,
and the skin should be covered beforehand with a disc, while the muscular sense must be
eliminated (§ 430). [This is done by supporting the hand or part of the skin which is being
tested, so that the action of all the muscles is excluded.] 2. A process is attached to a balance
and made to touch the skin, while by placing weights in the scale-pan or removing them, we

/
ee

ms)

ETUTETIUSTVI Ter ty V Eres yy gS

_

Fig. 619.
Landois’ mercurial balance for testing the pressure sense.

test what differences in weight the person experimented on is able to distinguish rey acs

In order to avoid the necessity of changing the weights, A. Eulenburg invented his bares-
thesiometer, which is constructed on the as princi fe as a spiral sprin S pakeleceta or balance.
There is a small button which rests on the skin mea is depressed by fhe spring. An index
shows at once the pressure in grammes, and the instrument is so arranged that the presssure
can be very easily varied. 4. Goltz uses a pulsating elastic tube, in which he can produce
waves of different height. He tested how high the latter must be before they are experienced
. pulse-waves, when the tube is placed upon the skin. 5. Landois uses a marential balance
( g. 619). The beam of a balance (W) moves upon two knife-edges (O, O), and is carried on the
meaty arm (>) of a heavy Support (T). One arm of the beam is provided with a screw (m)
eke ich an equilibratin weight (6) can be moved. The other arm (d) passes into a vertical
calibrated tube (R). Below this is the pressure-pad (P), which can be loaded as desired by a

weight (G), and which can be placed upon the part of the skin to be tested (H). From an
oaioining burette (B) held in a clamp (A), mercury can pass through a tube in the direction of —
© arrows, to one part of the balance and into the tube (R). On the stop-cock () being 5
a fy

RESULTS OF THE PRESSURE SENSE. 835

closed, whenever pressure is exerted on the tube (D, D), the mercury rises through d into R,
and increases the pressure on P. We measure the weight of the mercury corresponding to
each division of the tube (R). This instrument enables rapid variations of the weight to be
made without giving rise to any shock. In estimating both the pressure sense and temperature
sense, it is best to proceed on the principle of ‘‘ the least perceptible difference,” 7.¢., the
different pressures or temperatures are graduated, either beginning with great differences, or
proceeding from the smallest difference, and determining the limit at which the person can dis-
tinguish a difference in the sensation.

Results.—1. The smallest perceptible pressure, when applied to different parts of
the skin, varies very greatly according to the locality. The greatest acuteness of
sensibility is on the forehead, temples, and the back of the hand and fore-arm,
which perceive a pressure of 0:002 grm.; the fingers first feel with a weight of
07005 to 0°015 grm.; the chin, abdomen, and nose with 0:04 to 0°05 grm. ;
the finger nail 1 grm. (Kammler and Aubert).

The greater the sensibility of the skin, the more rapidly can stimuli succeed each other, and
still be perceived as single impressions ; 52 stimuli per second may be applied to the volar side
of the upper arm, 61 on the back of the hand, 70 to the tips of the fingers, and still be fel*
singly (Bloch).

2. Intermittent variations of pressure, as in Goltz’s tube, are felt more acutely by
the tips of the fingers than with the forehead.

3. Differences between two weights are perceived by the tips of the fingers when
the ratio is 29 : 30 (in the fore-arm as 18:2: 20), provided the weights are not too
light or too heavy. In passing from the use of very light to heavy weights, the
acuteness or fineness of the perception of difference increases at once, but with
heavier weights, the power of distinguishing differences rapidly diminishes again
(ZL. Hering, Biedermann). This observation is at variance with the psycho-physical
law of Fechner (§ 383). |

4, A. Eulenburg found the following gradations in the fineness of the pressure
sense :—The forehead, lips, dorsum of the cheeks, and temples appreciate differences
of 7, to s'5 (200 : 205 to 300: 310 grm.). The dorsal surface of the last phalanx
of the fingers, the fore-arm, hand, Ist and 2nd phalanx, the volar surface of the
hand, fore-arm, and upper arm, distinguish differences of 4, to #5 (200: 220 to
220: 210 grm.). The anterior surface of the leg and thigh are similar to the fore-
arm. Then follow the dorsum of the foot and toes, the sole of the foot, and the
posterior surface of the leg and thigh. Dohrn determined the smallest additional
weight, which, when added to 1 grm. already resting on the skin, was appreciated
as a difference, and he found that for the 3rd phalanx of the finger it was 0°499
grm. ; back of the foot, 0°5 grm.; 2nd phalanx, 0°771 grm.; Ist phalanx, 0-02
grm.; leg, 1 grm.; back of the hand, 1°156 grm. ; palm, 1°018 grm. ; patella, 1°5
grm.; fore-arm, 1:99 grm.; umbilicus, 3°5 grms. ; and the back, 3°8 grms.

5. Too long time must not elapse between the application of two successive
weights, but 100 seconds may elapse when the difference between the weights is
4:5 (£. H. Weber).

6. The sensation of an after-pressure is very marked, especially if the weight i
considerable and has been applied for a length of time. But even light weights,
when applied, must be separated by an interval of at least 4, to g45 second, in
order to be perceived. When they are applied at shorter intervals, the sensations
become fused. When Valentin pressed the tips of his fingers against a wheel
provided with blunt teeth he felt the impression of a smooth margin, when the teeth
were applied to the skin at the intervals above mentioned ; when the wheel was
rotated more slowly, each tooth gave rise to a distinct impression. Vibrations of
strings are distinguished as such when ‘the number of vibrations is 1506 to 1552
per second (v. Wittich and G'riinhagen). |

7. It is remarkable that pressure produced by the uniform compression of a part
of the body, eg., by dipping a finger or arm in mercury, is not felt as such; the

836 THE TEMPERATURE SENSE.

sensation is felt only at the Limit of the fluid, on the volar surface of the finger, at —

the limit of the surface of the mercury.

428. TEMPERATURE SENSE.—The temperature sense makes us aquainted
with the variations of the heat of the skin. ;

A specific end-apparatus arranged in a punctated manner 18 connected with the
temperature sense. ’ ; ; i {

These “ temperature-spots ” are arranged in a linear manner or in chains, which
are usually slightly curved (figs. 620, 621). They generally radiate from certain
points of the skin, usually the hair-roots. The chain of the ‘ cold-spots ” usually
does not coincide with those of the “ hot-spots,” although the point from which they
radiate may be the same. Frequently, these punctated lines are not complete, but
they may be indicated by scattered points, between which, not unfrequently, points
or spots for other qualities of sensation may be intercalated. Near the hairs there
are almost always temperature-spots. In parts of the skin, where the temperature
sensibility is slight, the temperature-points are present only near the hairs.

The sensation of cold occurs at once, while the sensation of heat develops
gradually. Mechanical and electrical stimulation also excite the sensation of

Ba os
; CL, ie
eoitiaw He > Sect eue 2 2 cee 0 Mes,
. ‘; igs oe 5 era Sa a
Sra sim se rt ae CT ee
° Tikal tesa Pane fee
see ot is Seotiee st A
Mee Se ee ee ote s.
BFS Sess. ee
A C
Fig. 620. Fig. 621.

Fig. 621.—A, cold-spots, B, hot-spots, from the volar surface of the terminal phalanx of the
index-finger to the margins of the nail. Fig. 622.—C, cold-spots, and D, warm-spots of the
radial half of the dorsal surface of the wrist. The arrow indicates the direction in which
the hair points.

temperature. A gentle touch of the temperature-spots is not perceived ; these
points seem to be anesthetic towards pressure and pain. Asa general rule, the
cold-spots are more abundant over the whole body—there are more of them in a
given area—while the hot-spots may be quite absent. The hot-spots are, as a rule,
perceived as double at a greater distance apart than the cold-spots. The minimal
distance on the forehead is 0°8 mm. for the cold-spots and 4 to 5 mm. for the
warm-spots ; on the breast the corresponding numbers are 2 and 4 to 5; back, 1°5
to 2 and 4 to 6; back of hand, 2 to 3 and 3 to 4; palm, 0°8 to 2; thigh and leg,
2 to 3 and 3 to 4 mm.
Method.—To test the hot- and cold-spots, use a hot or cold metallic rod ; at the cold-spots,

when they are lightly touched, only the sensation of cold will be felt, and a corresponding effect

with a ae rod at the hot-spots. Both spots are insensible to objects of the same temperature
as the skin.

According to E. Hering, what determines the sensation of temperature is the
temperature of the thermic end-apparatus itself, z.¢., its zero-temperature. As often
as the temperature of a cutaneous area is above its zero-temperature, we feel it as
warm; in the opposite case, cold. The one or the other sensation is more marked,
the more the one or other temperature varies from the zero-temperature, The zero-
temperature can undergo changes within considerable limits, owing to external
conditions, |

Methods,—To the surfaceof the skin objects of the same size and with the same the
conductivity are applied successively at different temperatures :-—1. Nothnagel uses”

THE TEMPERATURE SENSE. 837

wooden cups with a shetallio base, and filled with warm and cold water, the temperature being
registered by a thermometer placed in the cups. [2. Clinically, two test-tubes filled with
cold and warm water, or two spoons, the one hot and the other cold, may be used. ]
_ Results.—1. As a general rule, the feeling of cold is produced when a body
applied to the skin robs it of heat ; and, conversely, we have a sensation of warmth

when heat is communicated to the skin. ©

2. The greater the thermal conductivity of the substance touching the skin, the
more intense is the feeling of heat or cold (§ 218).

3. At a temperature of 15°5°-35° C., we distinguish distinctly differences of
temperature of 0-2°-0:16° R. with the tips of the fingers (Z. H. Weber). Tem-

ev @ @ 4

ily oe -s ee rs ° °
Ui
un

ti ae
i q
a ft ef : es i a |
TI ee Ball Ie sh + en

Tn

| i i
)

Fig. 622.

Cold- and hot-spots from the same part of the anterior surface of the fore-arm. a, cold-spots ;
b, hot-spots. The dark parts are the most sensitive, the hatched the medium, the dotted
the feebly, and the vacant spaces the non-sensitive.

peratures just below that of the blood (33°-27° C.—Wothnagel) are distinguished
most distinctly by the most sensitive parts, even to differences of 0°05° C. (Linder-
mann). Differences of temperature are less easily made out when dealing with
temperatures of 33°-39° C., as well as between 14°-27° C. A temperature of
55° C., and also one a few degrees above zero (2°8° C.), cause distinct pain in
addition to the sensation of temperature.

4, The sensibility for cold is generally greater than for warmth,—that of the left
hand is greater than the right (Goldscheider). The different parts of the skin also
vary in the acuteness of their thermal sense, and in the following order :—Tip
of the tongue, eyelids, cheeks, lips, neck, and body. The perceptible minimum
Nothnagel found to be 0°4° on the breast ; 0°9° on the back ; 0°3°, back of the
hand; 0°4°, palm; 0°2°, arm; 0°4°, back of the foot; 0°5°, thigh; 0°6°, leg;
0:4°-0°2°, cheek ; 0°4°-0°3° C., temple. The thermal sense is less acute in the
middle line, C.Juy the nose, than on each side of it (Z. H. Weber). Fig. 622 shows
that in one and the same portion of skin, the cold- and hot-spots are differently
located, 7.¢., their different topography.

If the mucous membrane of the mouth be. pencilled with a 10 per cent. solution of cocain; the
sensibility for heat is abolished ; the cooling sensation of menthol depends upon its stimu-
lation of the cold nerves; CO, applied to the skin excites the heat nerves (Goldscheider).

. 5. Differences of temperature are most easily perceived when the same part of the
skin is affected successively by objects of different temperature. If, however, two

838 COMMON SENSATION—PAIN.

different temperatures act simultaneously and side by side, the impressions are apt
to become fused, especially when the two areas are very near each other. .

6. Practice improves the temperature sense ; congestion of venous blood in the
skin diminishes it ; diminution of the amount of blood in the skin improves it (M.
Alsherg). When large areas of the skin are touched, the perception of differences
is more acute than with small areas. Rapid variations of the temperature produce
more intense sensations than gradual changes of temperature. Fatigue occurs soon.

Illusions are very common :—1. The sensations of heat and cold sometimes alternate in a
yaradoxical manner. When the skin is dipped first into water at 10° C. we feel cold, and if it
bs then dipped at once into water at 16° C., we have at first a feeling of warmth, but soon again
of cold. 2 The same temperature applied to a large surface of the skin is estimated to be
greater than when it is aopliel to a small area, ¢e.g., the whole hand when placed in water at
29°5° C. feels warmer than when a finger is dipped into water at 32°C. 8. Cold weights are
judged to be heavier than warm ones. .

Pathological.—Tactile sensibility is only seldom increased (hyperpselaphesia), but great
sensibility to differences of temperature is manifested by areas of the skin whose epidermis is

artly removed or altered by vesicants or herpes zoster, and the same occurs in some cases of
[abot tor ataxia ; while the sense of locality is rendered more acute in the two former cases and
in erysipelas. An abnormal condition of the sense of locality was described by Brown-Séquard,
where three points were felt when only two were applied, and two when one was applied to the
skin. Landois finds that in himself pricking the skin of the sternum over the angle of
Ludovicus is always accompanied by a sensation in the knee. [Some persons, when cold water
is applied to the scalp, have a sensation referable to the skin of the loins (Stirling).] A
remarkable variation of the sense of locality occurs in moderate poisoning with ced ios
where the person feels himself abnormally large or greatly diminished. In degeneration of the
»osterior columns of the cord, Obersteiner observed that the patient was unable to say whether

is right or left side was touched (‘‘allochiria”), Ferrier observed a case where a stimulus
applied to the right side was referred to the left, and vice versa.

Diminwtion and paralysis of the tactile sense (Hypopselaphesia and Apselaphesia) occur
either in conjunction with simultaneous injury to the sensory nerves, or alone. It is rare to
find that one of the qualities of the tactile sense is lost, ¢.g., either the tactile sense or the
sense of temperature—a condition which has been called ‘‘ partial tactile paralysis.” Limbs
which are ‘‘ sleeping” feel heat and not cold (Herzen).

429. COMMON SENSATION—PAIN.—By the term common sensation we
understand pleasant or unpleasant sensations in those parts of our bodies which are
endowed with sensibility, and which are not referable to external objects, and
whose characters are difficult to describe, and cannot be compared with other
sensations. Each sensation is, as it were, a peculiar one. To this belong pain,
hunger, thirst, malaise, fatigue, horror, vertigo, tickling, well-being, illness, the
respiratory feeling of free or impeded breathing.

Pain may occur wherever sensory nerves are distributed, and it is invariably
caused by a stronger stimulus than normal being applied to sensory nerves. Every
kind of stimulation, mechanical, thermal, chemical, electrical, as well as somatic
(inflammation or disturbances of nutrition), may excite pain. The last appears. to
be especially active, as many tissues become extremely painful during inflammation
(¢.g., muscles and bones), while they are comparatively insensible to cutting. Pain
may be produced by stimulating a sensory nerve in any part of its course, from its
centre to the periphery, but the sensation is invariably referred to the peripheral
end of the nerve. This is the law of the peripheral reference of sensations,
Hence, stimulation of a nerve, as in the scar of an amputated limb, may give rise
to a sensation of pain which is referred to the parts already removed. ‘Too violent
stimulation of a sensory nerve in its course may render it incapable of conducti
impressions, so that peripheral impressions are no longer perceived. If a sufficient
stimulus to produce pain be then applied to the central part of the nerve, such an
impression is still referred to the peripheral end of the nerve, Thus we explain the
paradoxical angsthesia dolorosa. In connection with painful impressions, the
patient is often unable to localise them exactly. This is most easily done when a
small injury (prick of a needle) is made on a peripheral part. When, however, the

METHOD OF TESTING PAIN—THE MUSCULAR SENSE. 839

stimulation occurs in the course of the nerve, or in the centre, or in nerves whose
peripheral ends are not accessible, as in the intestines, pain (as belly-ache), which
cannot easily be localised, is the result.

Irradiation.—During violent pain there is not unfrequently irradiation of the
pain (§ 364, 5), whereby localisation is impossible. It is rare for pain to remain

continuous and uniform; more generally there are exacerbations and diminutions

of the intensity, and sometimes periodic intensification, as in some neuralgias.

The intensity of the pain depends especially upon the excitability of the sensory
nerves. There are considerable individual variations in this respect, some nerves,
e.g., the trigeminus and splanchnic, being very sensitive. The larger the number
of fibres affected the more severe the pain. The duration is also of importance, in
as far as the same stimulation, when long continued, may become unbearable. We
speak of piercing, cutting, boring, burning, throbbing, pressing, gnawing, dull, and

‘other kinds of pain, but we are quite unacquainted with the conditions on which

such different sensations depend. Painful impressions are abolished by anesthetics
and narcotics, such as ether, chloroform, morphia, é&c. (§ 364, 5).

Methods of Testing.—To test the cutaneous sensibility, we usually employ the constant or
induced electrical current. Determine first the minimwm sensibility, z.e., the strength of the
current which excites the first trace of sensation, and also the minimum of pain, z.e., the
feeblest strength of the current which first causes distinct impressions of pain. The electrodes
consist of thin metallic needles, and are placed 1 to 2 cm. apart.

Pathological.-—When the excitability of the nerves which administer to painful sensations is
increased, a slight touch of the skin, nay, even a breath of cold air, may excite the most violent
pain, constituting cutaneous hyperalgia, especially in inflammatory or exanthematic conditions
of the skin. The term cutaneous paralgia is applied to certain anomalous, disagreeable, or
painful sensations which are frequently referred to the skin—itching, creeping, formication,
cold, and burning. In cerebro-spinal meningitis, sometimes a prick in the sole of the foot
produces a double sensation of pain and a double reflex contraction. Perhaps this condition
may be explained by supposing that in a part of the nerve the condition is delayed (§ 337, 2).
In neuralgia there is severe pain, occurring in paroxysms, with violent exacerbations and pain
shooting into other parts (p. 598). Very frequently excessive pain is produced by pressure on
the nerve where it makes its exit from a foramen or traverses a fascia.

Valleix’s Points Douloureux (1841).—The skin itself to which the sensory nerve runs,
especially at first, may be very sensitive; and when the neuralgia is of long duration the
sensibility may be diminished even to the condition of analgesia (7Z'irck); in the latter case there
may be pronounced anesthesia dolorosa (p. 838).

Dimi inution or paralysis of the sense of pain (hypalgia and analgia) may be due to affections
of the ends of the nerves, or of their course, or central terminations.

Metalloscopy.—In hysterical patients suffering from hemianesthesia, it is found that the
feeling of the paralysed side is restored, when small metallic plates or larger pieces of different
metals are applied to the affected parts (Burcqg, Charcot). At the same time that the affected
part recovers its sensibility the opposite limb or side becomes anesthetic. This condition has
been spoken of as transference of sensibility. The phenomenon is not due to galvanic currents
developed by the metals ; but it may be, perhaps, explained by the fact that, under physio-
logical conditions, and in a healthy person, every increase of the sensibility on one side of
the body, produced by the application of warm metallic plates or bandages, is followed by a
diminution of the sensibility of the opposite side. Conversely, it is found that when one side
of. the body is rendered less sensitive by the application of cold plates, the homologous part of
the other side becomes more sensitive (Rwmp/f). :

430. MUSCULAR SENSE.—Muscular Sensibility.—The sensory nerves of
the muscles (§ 292) always convey to us impressions as to the activity or non-
activity of these organs, and in the former case, these impressions enable us to
judge of the degree of contraction. Italso informs us of the amount of the con-
traction to be employed to overcome resistance. Obviously, the muscular sense
must be largely supported and aided by the sense of pressure, and conversely.
E. H. Weber showed, however, that the muscle sense is finer than the pressure
sense, as by it we can distinguish weights in the ratio of 39 : 40, while the
pressure sense only enables us to distinguish those in the ratio of 29 : 30. In
some cases there has been observed total cutaneous insensibility, while the

840 METHOD OF TESTING THE MUSCULAR SENSE, »

muscular sense was retained completely. A frog deprived of its skin can spring
without any apparent disturbance. The muscular sense 1s also greatly aided by
the sensibility of the joints, bones, and fascia. — Many muscles, ¢.g., those of respira-
tion, have only slight muscular sensibility, while it seems to be absent normally in
the heart and non-striped muscle.

[The muscular sense stands midway between special and common sensations, and
by it we obtain a knowledge of the condition of our muscles, and to what extent
they are contracted ; also the position of the various parts of our bodies and the
resistance offered by external objects. Thus, sensations accompanying muscular
movement are two-fold—(a) the movements in the unopposed muscles, as the
movements of the limbs in space; and (b) those of resistance where there is
opposition to the movement, as in lifting a weight. In the latter case the sensa-
tions due to innervation are important, and of course in such cases we have also 1
take into account the sensations obtained from mere pressure upon the skin, O
sensations derived from muscular movements depend on the direction and duration
of the movements. On the sensations thus conveyed to the sensorium, we form
judgments as to the direction of a point in space, as well as of the distance between
two points in space. This is very marked in the case of the ocular muscles. It is
also evident that the muscular sense is intimately related to, and often combined
with, the exercise of the sensation of touch and sight (Sully). |

Methods of Testing.—Weights are wrapped in a towel and suspended to the part to be
tested. The patient estimates the weight by raising and lowering it. The electro-muscular
sensibility also may be proved thus: cause the muscles to contract by means of induction shocks,
and observe the sensation thereby produced. [Direct the patient to place his feet together
while standing, and then close his eyes. A healthy person can stand quite steady, but in one

with the muscular sense impaired, as in locomotor ataxia, the patient may move to and fro, or

even fall (p. 647). Again, a person with his muscular sense impaired may not be able to touch
accurately and at once some part of his body, when his eyes are closed. }

A healthy person ee a weight of 1 gramme applied to his upper arm; when a weight of
15 grms, is applied, he perceives an addition of 1 grm. If the original weight be 50 grms., he
will detect the addition of 2 grms.; if the original weight be 100 grms., he will detect 3 grms.
The weight detectable by the individual finger varies. With the leg, when the weight is
applied at the knee, the individual may detect 30 to 40 grms.; but sometimes only a greater
weight. Often one can detect a difference of 10 to 20, or 30 to 70 grms.,

Section of a sensory nerve causes disturbance of the fine graduation of move-
ment (p. 619). Meynert supposes that the cerebral centre for muscular sensibility
lies. in the motor cortical centres, the muscles being connected by motor and
sensory paths with the ganglionic cells in these centres.

Too severe muscular exercise causes the sensation of fatigue, oppression, and
weight in the limbs (§ 304). ,

Pathological.—Abnormal increase of the muscular sense is rare (muscular hyperalgia and
hyperesthesia), as in anxictas tibiarum, a painful condition of unrest which leads to a continual
change in the position of the limbs. In cramp there is intense pain, due to stimulation of the
sensory nerves of the muscle, and the same is the case in inflammation. Diminution of the
muscular sensibility occurs in some choreic and ataxic persons (§ 364, 5). In locomotor ataxia
the muscular sense of the wi ea extremities may be normal or weakened, while it is usually con-
siderably diminished in the legs. [The muscular sense is said to be increased in the hypnotic
condition, and in somnambulists, ]

-

Reproduction and Development.

431. FORMS OF REPRODUCTION.—I. Abiogenesis (Generatio aequivoca, sive spontanea,
spontaneous generation).—It was formerly assumed that, under certain circumstances, non-
living matter derived from the decomposition of organic materials became changed spontaneously
into living beings. While Aristotle ascribed this mode of origin to insects, the recent observers
who advocate this form of generation restrict its action solely to the lowest organisms. Experi-
mental evidence is distinctly against spontaneous generation. If organised matter be heated to
a very high temperature in sealed tubes, and be thus deprived of all living organisms or their
spores, there is no generation of any organism. Hence, the dictum ‘‘Omne vivum ex ovo”
(Harvey, or, ex vivo). Some highly organised invertebrate animals (Gordius, Anguillula, Tardi-
grada, and Rotatoria) may be dried, and even heated to 140° C., and yet regain their vital
activities on being moistened (Anabiosis).

II, Division or fission occurs in many protozoa (amceba, infusoria). The organism, just as is
the case with cells, divides, the nucleus when present taking an active part in the process, so
that two nuclei and two masses of protoplasm
forming two organisms are produced. The
Ophidiasters amongst the echinoderms divide
spontaneously, and they are said to throw off
an arm which may develop into a complete
animal. According to Trembley (1744), the
hydra may be divided into pieces, and each
piece gives rise to a new individual [although
under normal circumstances the hydra gives off
buds, and is provided with generative organs].

[Division of Cells.—Although a cell is de-
fined as a ‘‘nucleated mass of living proto-

OES =

et SS f.

Si ee Ox os eo}
= patra ORR
<2 =e + ee

“Cy Z¢ > J, if _ “IN

Sy q fh } iS \ i \

AS) City Sie). NW
Fig. 623. Fig. 624.

Fig. 623.—Changes in a cell nucleus during karyokinesis. Fig. 624.—Typical nucleated cell of

- the intestinal epithelium. of a flesh-maggot. mc, membrane of cell; mn, membrane of

nucleus ; pe, cellular protoplasm, with the radiating re¢iculwm, and the enchylema enclosed
in its meshes ; pn, plasma of nucleus ; bn, nuclear filament showing numerous twists.

plasm,” recent researches have'shown that, from a histological as well as from a chemical point of
view, a cell is really a very complex structure. The apparently homogeneous cell-substance is
traversed by a fine plexus of fibrils, witha homogeneous substance in its meshes, while a
similar network of fibrils exists within the nucleus itself (fig. 623).] . a

[The nucleus of a typical cell is a spherical vesicle, consisting of a membrane containing what
is called ‘‘achromatin,” because it is not readily stained by staining reagents. Flemming has
also called it nuclear fluid, or intermediate substance. The achromatin substance is permeated

842 DIVISION OF CELLS.

by a delicate reticular network, or plexus of fibrils, which has been called “ chromatin,”
‘““nucleoplasm,” “karyoplasma,” and ‘‘karyomiton.” The network stains readily with pigments,
hence the name “chromatin” given to it by Flemming. The nodal points of the network
give a dotted or granular appearance to the nucleus, especially when it is examined with a low
power. The nuclear membrane also consists of chromatin (fig. 624). _ In the meshes of the net-
work lie nucleoli, which seem to differ in constitution, and perhaps in function. According to
Flemming, there are principal and accessory nucleoli in some nuclei. In Carnoy’s nomenclature
the several parts are spoken of asa fine reticulum of fibrils, enclosing in its meshes a fluid—the
enchylema—which contains various particles in suspension. ] ;

(Direct Cell-Division.—A cell may divide directly, as it were, by simple cleavage, and in
the process the nucleus usually divides before the cell protoplasm. The nucleus becomes con-
stricted in the centre, has an hour-glass shape, and soon divides into two. ]

(*

100

Fig. 625.

Mitosis. A, nuclear reticulum, resting state ; B, preparing for division ; C, wreath stage ; D,
monaster stage ; E, barrel stage; F, diaster stage ; G, daughter wreath stage; H, daughter
cells, passing to resting stage.

[Indirect Cell-Division.—Recent observations, confirmed by a great number of investi-

gators, conclusively prove that the process of division in cells is a very complicated one, the
changes in the nucleus being very remarkable. The terms karyokinesis, mitosis, or i

division have been applied to this process. Figs. 623, 625 show the changes that take place in
the nucleus. The chromatin or intranuclear network (a, B) passes into a convolution of
fibrils, while the nuclear envelope becomes less distinct, the fibrils at the same time becoming
thicker and forming loops, which gradually arrange themselves around a centre (c and d) in the
form of a wreath, rosette, or spirem (C). The fibres curve round both at the periphery and the
centre and form loops; but when their peripheral connections are severed or dissolved, we
obtain a star-shaped form or aster (D), composed of single loops radiating from the centre (e).
The loops divide in the direction of their length ; their number is doubled, but they are

thinner. By this further subdivision, the whole is composed of fine radiating fibrils (f), which

gradually arrange themselves around two poles, or new centres, to form the barrel-form or
pithode (E) ; the two groups of loops then separate still further, and arrange themselves so as
to form a diaster, or double star (g), the two groups being separated by a substance called the
equatorial plate. Each of the groups of fibrils becomes more elongated, and forms a nuclear
spindle, which indicates the position of a new nucleus. The protoplasm separates into two
parts. In each of these parts the chromatin rearranges itself into an irregular coil, and the whole
is called dispirem (G), and when division is complete, the chromatin filaments assume the form
seen in a resting nucleus. This whole complex process may be accomplished in 1 to 4 hours,
The separate groups of fibrils again become convoluted, each group gets a nuclear membrane,
while the cell protoplasm divides, and two daughter nuclei are obtained from the original cell. }

The following scheme represents some of the more important changes :— .

Mother nucleus, Daughter nuclei.
1. Network. 8. Network.
2. Convolution, 7. Convolution,
3. Wreath or Spirem. 6. Dispirem.
4. Aster, 5. Diaster,

Equatorial grouping of chromatin.
_ Til. Budding or gemmation occurs in a well-marked form among the polyps and in some
infusorians (Vorticella), A bud is given off by the parent, and gradually comes more and more
to resemble the latter, The bud either remains permanently attached to the parent, so that a
complex organism is produced, in which the digestive organs communicate with each other
directly, or in some cases there may be a ‘‘ colony” with a common nervous system, such as the

ee ee

FORMS OF REPRODUCTION. 843

polyzoa. In some composite animals (siphonophora) the different polyps perform different
functions. Some have a digestive, others a motor, and a third a generative function, so that
there is a physiological division of labour. Buds which are given off from the parent are formed
internally in the rhizopoda. In some animals (polyps, infusoria), which can reproduce them-
selves by buds or division, there is also the formation of male and female elements of generation,
so that they have a sexual and a non-sexual mode of reproduction...

IV. Conjugation is a form of reproduction which leads up to the sexual form. It occurs in
the unicellular Gregarine. The anterior end of one such organism unites with the posterior
end of another ; both become encysted, and form one passive spherical body. The conjoined
structures form an amorphous mass, from which numerous globular bodies are formed, and in
each of which numerous oblong structures—the pseudo-navicelli—are developed. These bodies
become, or give rise to an ameeboid structure, which forms a nucleus and an envelope, and
becomes transformed into a gregarina.

Sexual reproduction requires the formation of the embryo from the conjunction of the male
and female reproductive elements, the sperm-cell and the germ-cell, These products may be
formed either in one individual (hermaphroditism, as in the flat worms and gasteropods), or in
two separate organisms (male or female). Sexual reproduction embraces the following
varieties:— |

V. Metamorphosis is that form of sexual reproduction in which the embryo from an early
period undergoes a series of marked changes of external form, e.g., the chrysalis stage, and the
pupa stage, and in none of these stages is reproduction possible. Lastly, the final sexually
developed form (the imago stage in butterflies) is pro-
duced, which forms the sexual products whose union
gives rise to organisms which repeat the same cycle
of changes. Metamorphosis occurs extensively
amongst the insects; some of them have several
stages (holo-metabolic), and others have few stages
{hemi-metabolic).. It also occurs in some arthropoda,
and worms, ¢.g., trichina; *the sexual form of the
animal occurs in the in-
testine, the numerous
larve. wander into the
muscles, where they be-
come encysted, and form
undeveloped sexual or-
gans, constituting the
pupa stage of the muscu-
lar trichina. When the
encysted form is eaten by
anotheranimal, thesexual
organs come into activity,
a new brood is formed, f
and the cycle is re- fq
peated. Metamorphosis °

Fig. 626.
A ripe egg taken from the

uterus of Tenia solium.
a, Albuminous envelope;
b, remains of the yelk ;
c, covering of the embryo;

d, embryo with
bryonal hooklets.

em-

also occurs in the frog
and in _ petromyzon.
[This is really a condition
in which the embryo un-
dergoes marked changes
of form before it becomes

Fig. 627.
Encapsuled cysticercus from Tenia

solium embedded in a human
sartorius. Natural size.

sexually mature. ]

VI. Alternation of Generations (Stcenstrup).—In this variety some of the members of the
cycle can produce new beings non-sexually, while in the final stage reproduction is always sexual.
From a medical point of view, the life-history of the tape-worm or Tenia is most important.
The segments of the tape-worm are called proglottides (fig. 631), and each segment is herma-
phrodite, with testes, vas deferens, penis, ovary, &c., and numerous ova. The segments are
evacuated with the feces. The eggs are fertilised after they are shed (fig. 626), and from them
is developed an elliptical embryo, provided with six hooklets, which is swallowed by another
animal, the host. These embryos bore their way into the tissues of the host, where they
undergo development, forming the encysted stage (Cysticercus (fig. 627), Coenurus, or Echino-
coceus (fig. 630). The encysted capsule may contain one (cysticercus) or many (coenurus)
sessile heads of the tenia. In order to undergo further development, the cysticercus must be
eaten alive by another animal, when the head or scolex fixes itself by the hooklets and suckers
to the intestine of its new host (fig. 629), where it begins to bud and produce a series of new
segments between the head and the last-formed segment, and thus the cycle is repeated.

"The most important flat-worms are :—Tenia solium, in man ; the Cysticercus cellulose (fig.
628), in the pig, when it constitutes the measle in pork ; Tenia mediocanellata (fig. 631), the

844 yore TESTIS. —

cysted stage, in the ox; Tenia coenurus, in the dog’s intestine ; the encysted stage, or
emia saraken\ls, in the brain of the sheep, where it gives rise to the condition of
‘Ks ”. Tenia echinococcus, in the dog’s intestine ; the embryos or scolices occur in the
liver of man as ‘‘ hydatids,” ;

The meduse also exhibit alternation of generations, and so do some insects, especially the
nt liee or aphides. +!
PIL Parthenogeneais (Owen, v. Siebold).—In this variety, in addition to sexual reproduction,
new individuals may be produced without sexual union. The non-sexually produced brood is
always of one sex, asin the bees. A bee- Liv
hive contains a queen, the workers, and the
drones or males. During the nuptial flight,
the queen is impregnated by the males, and
the seminal fluid is stored up in the re-
ceptaculum seminis of the queen, and it

Fig. 628. Fig. 629. Fig. 630.

Fig. 628.—Cysticerci from Tenia solium removed from their capsule. 1, natural size; 2,
magnified. a, embryo-sac; 0, cavity produced by budding of the embryo-sac; ¢,
suctorial discs and hooklets. Fig. 629.—Cysticercus of Tenia solium, with its head and
segments protruded. a, caudal-sac ; b, head of the tape-worm, with discs and hooklets

(scolex); c, neck. Fig. 630.—Part of an Echinococcus capsule, with developing buds. .

a, sheath ; b, parenchymatous layer ; c, germinating capsule filled with scolices.

Le that the queen may voluntarily permit the contact of this fluid with the ova or with-
hold it

All fertilised eggs give rise to female, and all unfertilised ones to male bees,
VUI. Sexual reproduction without any intermediate stages occurs in, besides man, mammals,
birds, reptiles, and most fishes.

432, TESTIS—SEMINAL FLUID.—{Testis.—In the testis or male reproductive organ,
the seminal fluid which contains the male element or spermatozoa is formed. The framework
of the gland consists of a thick strong white fibrous covering, the tunica albuginea, composed
chiefly of white interlacing fibrous tissue. Externally, this layer is covered by the visceral

een 8864

Fig. 631.—Tenia mediocanellata. Natural size.

layer of the serous membrane, or the tunica vaginalis, which invests the testis and epididymis.
e tunica albuginea is prolonged for some distance as a vertical septum into the posterior
part of the testis, to form the mediastinum testis or corpus Highmori, Septa or trabecule—
more or less complete—stretch from the under surface of the T. albuginea towards the medias-
tinum, so that the organ is subdivided thereby into a number of compartments or lobules,
with their bases directed outwards and their apices towards the mediastinum. From these,
finer sustentacular fibres pass into the compartments to support the structures lying in -
compartments. ] ~ eg

STRUCTURE OF A SEMINAL TUBULE. 845

[Arrangement of Tubules.—Each compartment contains several seminal tubules, long
convoluted tubules (4,5 in. in diam.) which rarely branch except at their outer end; they are
about 2 feet in length and exceed 800 innumber. These tubules run towards the mediastinum,
those in one compartment uniting at an acute angle with each other, to form a smaller number
of narrower straight tubules—tubuli recti (fig. 632). These straight tubules open into a net-
work of tubules in the mediastinum to form the rete testis, a dense network of tubules of
irregular diameter (fig. 632). From this network there proceed 12 to 15 wider ducts,—the
vasa efferentia—which after emerging from the testis are at first straight, but soon become
convoluted—and form a series of coni- :
cal eminences—the coni vasculosi— T. albuginea.
which together form the head of the
epididymis, These tubes gradually
unite with each other and form the
body and globus minor of the epi-
didymis, which, when unravelled, is
a tube about 20 feet long terminat-
ing in the vas deferens (2 feet long),
which is the excretory duct of the
testis, ]

[Structure of a Tubule, — The
seminal tubules consist of a thick
well-marked basement membrane,
composed of flattened nucleated cells pyoog-
arranged like membranes (fig. 637). vessels, . 7
These tubes are lined by several
layers of more or less cubical cells ;
there is an outer row of such cells
next the basement membrane, and
often showing a dividing large

nucleus. Internal to these are Bcc Z0. NN \ \ 8 Ty

several layers of inner large clear (iS SNR oe ae
cells, with nuclei often dividing, so AL Ree VATA ee
that they form many daughter cells
which lie internal to them and next
the lumen. From these daughter
cells are formed the spermatozoa,
and they constitute the sperma-
toblasts. These several layers of
cells leave a distinct lumen. The
tubuli recti are narrow in diameter,
and lined by a single layer of
squamous or flattened epithelium
(fig. 633). The rete testis consists
merely of channels in the fibrous
stroma without a distinct membrana
propria, but lined by flattened epi-
thelium. The vasa efferentia and
coni vasculosi have circular smooth
muscular fibres in their walls, and
are lined by a layer of columnar
ciliated epithelium with striated pro-
toplasm. At the bases of these cells
in some parts is a layer of smaller ete
granular cells. These tubules form :

Seminal
tubules
cut
across.

Straight
tubules,

the epididymis, whose tubules have Fig. 632.
the same structure (fig. 634). In the. Transverse section of the testis (low
sheep, pigment cells are often found power view).

in the basement membrane. The vas

deferens is lined by several layers of columnar epithelium resting on a dense layer of fibrous
tissue—the mucosa, Outside this is the muscular coat, a thick layer of non-striped muscle
composed of a thick inner circular, and thick outer longitudinal layer, a thin submucous coat
connecting the muscular and mucous coats together ; outside all is the fibrous adventitia. ]

“ [The interstitial tissue (fig. 632), supporting the seminal tubules, is laminated and covered
by endothelial plates, with slits or spaces between the lamellv, which form the origin of the
lymphatics. These lymph-spaces are easily injected by the puncture method. In fact, if
Berlin blue be forced into the testis, the lymphatics of the testis and spermatic cord are readily.
filled with the injection. In some animals (boar), and to a less extent in man, dog, there are

4

846 CHEMICAL COMPOSITION OF THE SEMINAL FLUID.

also fairly large polyhedral interstitial cells, often with a large nucleus and sometimes
pigmented. The represent the residue of the epithelial cells of the Wolffian bodies (K/ein),
or, according to Waldeyer, they are plasma cells. The blood-vessels are numerous, and form
a dense plexus outside the basement membrane of the seminal tubules. ]

End of
convol
uted Blood-vessel.
tube.
Narrow
ial Transverse
section of a
tube of epi-
didymis.
Tubulus
rectus Ciliated
cylindrical
epithelium.
Blood-vesse] SSSA
ft N= ry
Wy) Ly OO
Interstitial 7 a z/ é
y connective- yf. / | |
‘Sy tissue. / i iN
Pip \\
n i) g— Rete
4G Natl testis.
ay pa)
Fig. 633. Fig. 634.

Fig. 633.—Convoluted seminal tubule 2 we into a narrow straight tubule. Fig. 634.— _
Transverse section of the tubules of the epididymis.

Chemical Composition.—The seminal fluid, as discharged from the urethra, is
mixed with the secretion of the glands of the vas deferens, Cowper’s glands, and
those of the prostate, and with the fluid of the vesiculz seminales. Its reaction
is neutral or alkaline, and it contains 82 per cent. of water, serum-albumin, alkali-
albuminate, nuclein, lecithin, cholesterin, fats (protamin ?), phosphorised fat, salts
(2 per cent.), especially phosphates of the alkalies and earths, together with sul-
phates, carbonates, and chlorides. The odorous body, whose nature is unknown,
was called “ spermatin” by Vauquelin. “

Seminal Fluid.—The sticky, whitish-yellow seminal fluid, largely composed of a mixture of
the secretions of the above-named glands, when exposed to the air, becomes more fluid, and on
adding water it becomes gelatinous, and from it separate whitish transparent flakes. When
long exposed, it forms rhomboidal crystals, which, according to Schreiner, consist of phosphatic
salts with an organic base (C,H,;N). These crystals (fig. 635) are said to be derived, from the
prostatic fluid, and are identical with the so-called Charcot’s crystals (fig. 149, c, and § 138).
The prostatic fluid is thin, milky, amphoteric, or of slightly acid reaction, and is possessed of
the seminal odour. The phosphoric acid necessary for tis formation of the crystals is obtained
from the seminal fluid. A somewhat similar odour occurs in the albumin of eggs not quite
fresh. The non-poisonous ptomain, cadaverin (pentamethyldiamin of Ladenburg), isolated by
Brieger from dead bodies, has a similar odour. ‘The secretion of the vesicule seminales of the
guinea-pig contains much fibrinogen (p. 376). . |

The spermatozoa are 50, long, and consist of a flattened pear-shaped head
(fig. 636, 1 and 2, &), which is followed by a rod-shaped middle piece, m
(Schweigger-Seidel), and a long tail-like prolongation or cilium, f. The sperma-
tozoon is propelled forwards by the to-and-fro movements of the tail at the rate
of 0°05 to 0°5 mm. per second; the movement is most rapid immediately after
the fluid is shed, but it gradually becomes feebler. | RR

Finer Structure.—The observations of Jensen have shown that the middle piece and
head are still more complex, although this is not the case in human spermatozoa and those

SPERMATOZOA. 847

of the bull (G. Retzius). - These consist of a flattened, long, narrow, transparent, proto-
plasmic mass, with a fibre composed of many delicate threads in both margins. At the tip
of the tail both fibres unite into one. The fibre of the one margin is generally straight
the other is thrown into wave-like folds, or
winds in a spiral manner round the other
(W. Krause, Gibbes). G. Retzius describes a
special terminal filament (fig. 636, ¢). An
axial thread surrounded by an envelope of
protoplasm, traverses the middle piece and
the tail (Eimer, v. Braun). [Leydig showed
that in the salamander there is a delicate mem-
brane attached to the tail, and Gibbes has
described a spiral thread attached to the head
(newt) and connected with the middle piece
by a hyaline membrane. ]

Motion of the Spermatozoa.—[After the
discharge of the seminal fluid, the spermatozoa
exhibit spontaneous movements for many
hours or days.] The movements are due to
the lashing movements of the tail, which
moves in a circle or rotates on its long axis,
the impulse to movement proceeding from
the protoplasm of the middle piece and the
tail, which seem to be capable of moving when

they are detached (HZimer). These move- Fie. 635
ments are comparable to those that occur in tne fluid
cilia (§ 292), and there are transition forms Crystals from spermatic fluid.

between ciliary and amceboid movements, as in the Monera. Reagents.—Within the testis
they do not exhibit movement, as the fluid is not sufficiently dilute to permit them to move.
Their movements are specially lively in the normal secretion of the female sexual organs
(Bischoff), and they move pretty freely, and for a long time, in all normal animal secretions
except saliva. Their movements are paralysed by water, alcohol, ether, chloroform, creosote,
gum, dextrin, vegetable mucin, syrup of grape-sugar, or very alkaline or acid uterine or vaginal
mucus (Donné), acids and metallic salts, and a too high or too low temperature. The narcotics,
as long as they are chemically indifferent, behave as indifferent fluids, and so do medium solu-
tions of urea, sugar, albumin, common salt, glycerin, amygdalin, &c.; but if these be too dilute
or too concentrated, they alter the amount of water in the spermatozoa and paralyse them.
The quiescence produced bytwater may be set aside by dilute alkalies (Virchow), as with cilia
(p. 452). Engelmann finds that minute traces of acids, alcohol, and ether excite movements.
The spermatozoa of the frog may be frozen four times in succession without killingthem. They
bear a heat of 43°75° C., and they will live for 70 days when placed in the abdominal cavity of
another frog (Mantegazza).

Resistance.—Owing to the large amounts of earthy salts which they contain, when dried
upon a microscopical slide, they still retain their form (Valentin). Their form is not destroyed
by nitric, sulphuric, hydrochloric, or boiling acetic acid, or by caustic alkalies; solutions of
NaCl and saltpetre (10 to 15 per cent.) change them into amorphous masses. Their organic
basis resembles the semi-solid albumin of epithelium.

Seminal fluid, besides spermatozoa, also contains seminal cells, a few epithelial cells from the
seminal passages, numerous lecithin granules, stratified amyloid bodies (inconstant), granular
yellow pigment, especially in old age, leucocytes, and sperma crystals (Fiirbinger).

Development of Spermatozoa.—The walls of the seminal tubules, », which are
made up of spindle-shaped cells, are lined by a nucleated, protoplasmic layer (fig.
637, I, 6, and IV, h), from which there project into the lumen of the tube long
(0°053 mm.) column-like prolongations (I, c, and II, III, IV), which break up at
their free end into several round or oval lobules (II.)—the spermatoblasts
(v. Ebner); these consist of soft finely granular protoplasm, and usually have an
oval nucleus in: their lower part. During development, each lobule of the sper-
matoblast elongates into a tail (IV, 7), while the deeper part forms the head and
middle pieces of the future spermatozoon (IV, 4). At this stage the spermatoblast
is like a greatly enlarged, irregular, cylindrical epithelial cell. When development
is complete, the head and middle piece are detached (III, ¢), and ultimately the
remaining part of the spermatoblast undergoes fatty degeneration. Not unfre-
quently in spermatozoa we may observe a small mass of protoplasm adhering to the

848 DEVELOPMENT OF SPERMATOZOA.

tail and the middle piece (III, ¢). Between the spermatoblasts are numerous round
amceboid cells devoid of an envelope, and connected to each other by processes.

OQ Ne
Wm
3

1 ij

)

7 8

é

\

Fig. 636,

Spermatozoa. 1, human (x 600), the head seen from the side ; 2, on edge; k, head; m, middle
jiece ; f, tail; e, terminal filament; 3, from the mouse; 4, bothriocephalus latus; 5,
lear: 6, mole; 7, green woodpecker ; 8, black swan ; 9, from a cross between a goldfinch
(M) and a canary (F); 10, from cobitis.

They seem to secrete the fluid part of the semen, and they may therefore be called
seminal cells (I, s, II, III, IV, p). A spermatozoon, therefore, is a detached

Fig, 637.

Semi-diagrammatic spermatogenesis : I, transverse section of a seminal tubule—a, membrane ;
b, protoplasmic inner lining ; c, spermatoblast ; s, seminal cells. II, Unripe spermatoblast
—/, rounded clavate lobules ; y, seminal cells. IV, spermatoblast, with ripe spermatozoa
(%) not yet detached ; tail, 7; », wall of the seminal tubule; /, its protoplasmic layer. III.
spermatoblast with a spermatozoon free, ¢, RY. | .

irs

independently mobile cilium of an enlarged epithelial cell.” Some observers adhere

STRUCTURE OF THE OVARY. 849

to the view that the spermatozoa are, in part at least, formed within round cells,
by a process of endogenous development,

According to Benda and v. Ebner, the spermatoblasts are formed by the coalescence (copula-
tion) of a group of seminal cells with the lower part of the foot-plate and stalk of the spermato-
blasts, Each seminal cell forms from
its nucleus the head, and from its pro-
toplasm the tail of a spermatozoon.
For the complete formation of these
parts, there must be a coalescence of
the seminal cells with the spermato-
blasts,

Shape.—The spermatozoa of most
animals are like cilia with larger or
smaller heads, The head is elliptical
(mammals), or pear-shaped (mammals),
or cylindrical (birds, amphibians, fish),
or cork-screw (singing birds, paludina),
or merely like hairs (insects—fig. 636).
Immobile seminal cells, quite different
from the ordinary forms, occur in
myriapoda and the oyster.

433. THE OVARY — OVUM — Fig. 638, ;

UTERUS. —[Structure of the Ovary. gection of a cat’s ovary, The place of attachment

—The ovary consists of a connective- “oy hilum is below. On the left is a corpus luteum,
tissue framework, with blood-vessels,

nerves, lymphatics, and numerous non-striped muscular fibres. The ova are embedded in this
matrix (fig. 638). The surface of the ovary is covered with a layer of columnar epithelium
(fig. 639, ¢e), the remains of the |
germ-epithelium, The most
superficial layer is called the
albuginea ; it does not contain
any ova. Below it is the corti-
cal layer of Schroén, which
contains the smallest Graafian
follicles (<$5 inch —fig. 638),
while deeper down are the
larger follicles (4, to x45 inch).
There are 40,000 to 70,000
follicles in the ovary of a female
infant. Each ovum lies within
its follicle or Graafian vesicle, |

Structure of an Ovum,—
The human ovum (C. £. v.
Baer, 1827) is 0°18 to 0°2 mm.
[x4y in.] in diameter, and is
a spherical cellular body with
a thick, solid, elastic envelope,
the zona pellucida, with

CO
radiating strie (fig. 640). ' The Bo
zona pellucida encloses the ea nee F LG, Ml:

cell-contents represented by Fig. 639.

h t i 1 : inks ; J
Boceens pee, Se elie Section ofan ovary. ¢, germ-epithelium ; 1, large sized follicles;

hich. i ins th 2, 2, middle sized and 3, 3, smaller sized follicles; 0, ovum
Bs a ea within a Graafian follicle ’ v, v, blood-vessels of the stroma ;
nucleus or germinal vesicle % cells of the membrana granulosa.
(40-50 « —Purkinje, 1825; Coste, 1834). The germinal vesicle contains the nucleolus
or germinal spot (5-7 4 —R. Wagner, 1835). The chemical composition is given in § 232,

[Ovum, Cell.
Zona pellucida corresponds tothe Cell-wall.
Vitellus oF », Cell-contents.
Germinal vesicle __,, », Nucleus.
Germinal spot re », | Nucleolus,]

_ [This arrangement shows the corresponding parts in a cell and the ovum, and in fact the
ovum represents a typical cell.]
3H

850 DEVELOPMENT OF THE OVA.

zona ucida (figs. 640, 641, V, Z), to which cells the Graafian follicles are often _ad-
Rcd isa a Sonar ih EA formed secondarily by the follicle (Pfliiger). According to Van
Beneden, it is lined by a thin membrane next the vitellus, and he regards the thin membrane
as the original cell-membrane of the ovum. The fine radiating strie in the zona are said to be
Cells of discus proligerus. due to the existence of nume-
; rous canals bere + : a
nee Sehlen). It is still undecided |
oe weeks re CERO ye whether there is a_ special
SAE micropyle or hole for the

entrance of the spermatoza.
A micropyle: has been
observed in some ova (holo-
thurians, many fishes, mus-
sels). The ova.of some
animals (many insects, ¢.g.,
the flea) have porous canals
in some part of their zona,
and these serve both for the
. Zona entrance of the spermatozoa
pellucida. and for the respiratory ex-

changes in the ovum.

The development of
the ova takes place in the
following manner:—The
surface of the ovary is
= covered with a layer of

Accessory
nucleoli, -
also

ah

‘Germinal vesicle

Fig. 640. cylindrical epithelium—
Ripe ovum of rabbit. the so-called “ germ-epi-

thelium ”—and between these cells lie somewhat spherical “primordial ova”
(fig. 641, I, a, a). The epithelium covering the surface dips into the ovary ©
at various places to form “ovarian tubes” (fig. 683). These tubes, from and
in which the ova are developed (Waldeyer), become deeper and deeper, and they
contain, in their interior, large single spherical cells with a nucleus and a nucleolus,
and other smaller and more numerous cells lining the tube. The large cells are
the cells (primordial ova) that are to develop into ova, while the smaller cells are
the epithelium of the tube, and are direct continuations of the cylindrical epithelium
on the surface of the ovary. The upper extremities of the tubes become closed,
while the tube itself is divided into a number of rounded compartments—snared
off, as it were, by the ingrowth of the ovarian stroma (I, c). Each compartment
so snared off usually contains one, or at most two, ova (IV, 0, 0), and becomes
developed into a Graafian follicle. The embryonic follicle enlarges, and fluid
appears within it ; while its lateral small cells become changed into the epithelium
lining the Graafian follicle itself, or those of the membrana granulosa. The cells
of the membrana granulosa form an elevation at one part—the discus proligerus
—by which the ovum is attached to the membrana granulosa. The follicles are at
first only 0°03 mm. in diameter, but they become larger, especially at puberty.
[The smaller ova are near the surface of the ovary, the larger ones deeper in its
substance (fig. 639).] When a Graafian follicle with its ovum is about to ripen
(IV), it sinks or passes downwards into the substance of the ovary, and enlarges at
the same time by the accumulation of fluid—the liquor folliculi—between the
tunica and membrana granulosa. It is covered by a vascular outer membrane—
the theea folliculi—which is lined by the epithelium constituting the membrana
granulosa (IV, 7). When a Graafian follicle is about to burst, it again rises to
the surface of the ovary, and attains a diameter of 1-0 to 15 mm., and is now ready
to burst and discharge its ovum. [The tissue between the enlarged Graafian
follicle and the surface of the ovary gradually becomes thinner and thinner and less
vascular, and at last gives way, when the ovum is discharged and caught by the

DEVELOPMENT OF THE OVA, 851°

fimbriated extremity. of the Fallopian tube embracing the ovary, so that the ovum
is shed into the Fallopian tube itself.| Only a small number of the Graafian
follicles undergo development normally, by far the greatest number atrophy and
never ripen. (The study of the development of the ova and ovary was advanced
particularly by Martin Barry, Pfliiger, Billroth, Schrén, His, Waldeyer, Kdolliker,
Koster, Lindgren, Schulin, Foulis, Balfour, and others.)

According to Waldeyer, the mammalian ovum is not a simple cell, but a compound structure.
The original primitive ovum is, according to him, formed only of the germinal vesicle and
germinal spot, with the surrounding membranous clear part of the vitellus (fig. 641, III). The
remainder of the vitellus is developed by the transformation of granulosa cells, which also form
the zona pellucida.

Holoblastic and Meroblastic Ova.—The ova of frogs and cyclostomata have the same type as
mammalian ova; they are called holoblastic ova, because all their contents go to form cells
which take part in the formation of the embryo. In contrast with these, the birds, the mono-
tremes alone amongst the mammals (Caldwell), the reptiles and the other fishes have meroblastic

Fig. 641.

I, An ovarian tube in process of development (new-born girl). @, a, young ova between the
_ epithelial cells on the surface of the ovary; }, the ovarian tube with ova and epithelial
cells; c, a small follicle cut off and enclosing an ovum. II, Open ovarian tube from a
bitch. III, Isolated primordial ovum (human). IV, Older follicle with two ova (0, 0)
and the tunica granulosa (g) of a bitch. V, Part of the surface of a ripe ovum of a rabbit
—z, zona pellucida ; d, vitellus ; ¢, adherent cells of the membrana granulosa. VI, First
polar globule formed. VII, Formation of the second polar globule (/0/).

ova (Reichert). The latter, in addition to the white or formative yelk, which corres onds to
the yelk of the holoblastic eggs, and gives rise to the embryonic cells, contains the food-yelk
(yellow in birds), which during development is a reserve store of food for the developing
mbryo.- \
I Hen’s Egg.—The small, white, round, finely granular speck, the cicatricula, blastoderm,
or tread, which is 2°5-3°5 mm. broad and 0°28-0°37 thick, lying upon the surface of the yellow
yelk, corresponds to the contents of the mammalian ovum, and is, therefore, the formative yelk.
In the cicatricula lie the germinal vesicle and spot (fig. 642). From the tread in which lie the

852 STRUCTURE OF A HEN’S EGG,

haracteristic white yelk elements, processes pass into the yellow yelk. A part passes as an
cae ly thin Ee round the vali. or cortical protoplasm. [The cicatricula in an unincubated
ileays uppermost whatever the position of the egg, provided the contents can rotate

fal: and this is due to the lighter specific gravity of that part of the yelk in connection with
ta has a white _ (the area opaca), sur-
, containing an opaque

a

freely, e gray
the aatitania. In a fecundated egg the cicatricu ;
rounding:a clear transparent area, the beginning of the area pelluci

Germinal Blastoderm.
vesicle co =
and spot. 7 M

2

----Its processes.

Marginal
~~~" protoplasm,

Vitelline
aa natn membrane.

Fig. 642.
Scheme of a meroblastic egg. a, White; b, yellow yelk granules,
spot in its centre. If an egg be boiled very hard and a section made of the yelk, it will be found
to consist of alternating layers of white and yellow yelk. The outermost layer is a thin layer
of white yelk, which is slightly thicker at the margin of the cicatricula, Within the centre of
the yelk is a flask-shaped mass of white yelk, the neck of the flask being connected with the
white yelk outside. This flask-shaped mass does not become so hard on being boiled, and its
upper expanded end is known as the ‘‘nucleus of Pander.’”” The great mass of the yelk is
made up, however, of yellow yelk.] Microscopically, the yellow yelk consists of soft yellow
spheres, of from 23-100 % in diameter, and they are often polyhedral from mutual pressure (fig.
643, 4). [They are very delicate and non-nucleated, but filled with fine granules, whisk are, per-
haps, proteid in their nature, as they are insoluble in ether and alcohol. They are devalonee by
the proliferation of the granulosa cells of the Graafian follicle, which also seem ultimately te
form the granulo-fibrous double envelope or the vitelline membrane (Himer). The whole yelk
of the hen’s egg is regarded by some observers as equivalent to the mammalian ovum plus the
corpus luteum. Microscopically, the white
ra yelk consists of small vesicles (5-75 «) con-
e taining a refractive substance and larger
spheres containing several smaller spherules
(fig. 643, a). The whole yelk is enveloped by
the vitelline membrane, which is transparent,
pas but possesses a fine fibrous structure, and it
Pg d seems to be allied to elastic tissue. ]
ye i When the yelk is fully developed within the
| hia . Graafian follicles of the hen’s ovarium, the
follicle bursts and discharges the yelk, which
passes into the oviduct, what in its pas it
rotates, owing to the direction of the folds of
the mucous membrane of the oviduct. . The
numerous glands of the oviduct secrete the
albumin, or white of the egg, which is deposited
< in layers around the yelk in its passage along
Fig. 644, the duct, othech at the anterior te =
Fowl’s egg after thirty hours incubation. RRS e chalazae are two twisted cords
shell eS shell- membrane 5 Os inammanber composed of twisted layers of the ousehsaemaas
¢, boundary between outer and middle portion part of the albumin. . They extend from Me
of albumin; d, more fluid albumin: ¢ P0lesof the yelk not quite to the outer par
chalazae ; v, yelk ; av, area opaca; ao, aren the albumin.] [The albumin is invested by th
vasculosa, and in its centre is the embryo, pipet get pa eanelhments cater ‘aes .
and an inner thinner one (fig. 644). Over the greater of the albumin these two layers

are united, but at the broad end of the hen’s egg they ten to separate, and air passing through

e av 20

FALLOPIAN TUBES. 853

the porous shell separates them more and more as the fluid of the egg evaporates. This air-
space is not found in fresh-laid eggs.] The layers consist of spontaneously coagulated keratin-
like fibres arranged in a spiral manner around the albumin (Lindvall and Hamarsten). [Ex-
ternal to this is the test, or shell, which consists of an organic matrix impregnated with lime
salts.] The shell consists of albumin impregnated with lime salts, which form a very porous
mortar. [The shell is porous, and its inner layer is perforated by vertical canals, through
which the respiratory exchange of the gases can take place.] In the eggs of some birds
there is an outer structureless, porous, slimy, or fatty cuticula. The shell is secreted in the
lower part of the oviduct. The shell is partly used up for the development of the bones of
the chick (Prout, Gruwe, although this is denied by Polt and Preyer). The pigment which
often occurs in many layers of the surface of the eggs of some birds appears to be a derivative of
hemogloblin and biliverdin.

Chemical Composition.—The yellow yelk is alkaline, and coloured yellow owing to the pre-
sence of lutein, which contains iron. It contains several proteids [including a globulin body
called vitellin (p. 376)], a body resembling nuclein, lecithin, vitellin, glycerin-phosphoric acid,
cholesterin, olein, palmitin, dextrose, potassic chloride, iron, earthy phosphates, fluoric and
silicic acids. The presence of cerebrin, glycogen, and starch is uncertain. [Dareste states that
starch is present. ]

[The albumin of egg contains—water, 86 per cent.; proteids, 12; fat and extractives, 1°5;
saline matter, including sodic and potassic chlorides, phosphates, and sulphates, °5 per cent. ]

[The uterus, a thick hollow muscular organ, is covered externally by a serous coat, and
lined internally by a mucous membrane,
while between the two is the thick mus-
cular coat composed of smooth muscular
fibres arranged in a great numberof layers
and in different directions. The mucous
membrane of the body of the uterus in
the unimpregnated condition hasnofolds,
while the muscularis mucose is very well
developed, and forms a great part of
uterine muscular wall. The mucous
membrane is lined by a single layer of
columnar ciliated epithelium. <A vertical
section shows the mucous membrane to
contain’ numerous tubular glands (fig.
645)—the uterine glands—which branch
towards their lower ends. They have a
membrana propria, and are lined by a
single layer of ciliated epithelium, a
small lumen being left in the centre.
The utricular glands are not formed dur-
ing intra-uterine life (Zurner), nor are
there any glands in the human uterus at
birth (G. J. Engelmann). There are.
numerous slit-like /ymphatic spaces in
the mucous membrane (Leopold), which
communicate with well-marked lymphatic
vessels existing in this and the other
layers of the organ. In the cervix, the
mucous membrane is folded, presenting
in the virgin the appearance known as _ e
the arbor vite. The external surface of Fig. 645.

the vaginal part of the neck is covered Vertical section of the mucous membrane of the human
by stratified squamous epithelium, like yterus, e, columnar epithelium, the cilia absent ;
the vagina. ] gg, utricular glands ; cf, intra-glandular connective-

[The Fallopian tubes are really the tissue ; vv, blood-vessels ; mm, muscularis mucose.
ducts of the ovaries (fig. 646). They

consist of a serous, muscular (an external, longitudinal, and an internal circular) layer of non-
striped muscle, and a mucous layer thrown into many folds and lined by a single layer of
ciliated columnar epithelium, but no glands (fig. 647).

434. PUBERTY.—The term puberty is applied to the period at which a
human being becomes capable of procreating, which occurs from the 13th to 15th
years in the female, and the 14th to 16th in the male. In warm climates, puberty
may occur in girls even at 8 years of age. Towards the 40th to 50th year, the
procreative faculty ceases in the female with the cessation of the menses; this con-

oS

854 PUBERTY.

stitutes the menopause or grand climacteric, whilst in man the formation: of
seminal fluid has been observed up to old age. From the period of puberty

Fig. 646.

Left broad ligament, Fallopian tube, ovary, and parovarium.
tube ; c, ampulla; g, fimbriated end of the tube, with the parovarium to its right; ¢,
ovary ; f, ovarian ligament.

onwards, the sexual appetite occurs, and the ripe ova are discharged from the

a, uterus ; b, isthmus of Fallopian

ovary. [But ova are discharged even before puberty or menstruation has gest

At puberty, the interna
and external generative
organs and their annexes
become more vascular and
undergo development; the
pelvis of the female as-
sumes the characteristic

female shape. For the .

across,

Fig. 647.
Transverse section of the Fallopian tube.

7s | cout eR, DONNY HAR ;
ESSAI connective. Changes in the mamme
x ¢2)))\ i ( tissue, see § 230. At the same

i x alt i Ciliated time hair is developed on

SHE) as SED NTMI 5 F
ee y Wy Wy “pithelium. the pubes and axilla, and
TEI Ae AMY Circular °

QI Se yma muscular in the male on the face,
< Sa Wy y Bure: while the sebaceous glands
—— y become larger and more
F Z ; Muscular A

— fibres cut active.

Other changes occur, espe-
cially in the larynx. In the
boy the larynx elongates in
its antero-posterior diameter,

the thyroid, or Adam’s apple, becomes more prominent, while the vocal cords lengthen, so that
the voice is hoarse, or husky, or ‘‘ breaks,” the voice being lowered at least an octave. In the
female the larynx becomes longer, while the compass of the voice is increased. The vital capa-
city (§ 108), corresponding to the increase in the size of the chest, undergoes a considerable
increase ; the whole form and expression assume the characteristic sexual appearance, while the
psychical energies also receive an impulse.

435. MENSTRUATION. —External Signs.—At regular intervals of time,
of 274-28 days in a mature female, there is a rupture of one or more ripe
Graafian follicles, while at the same time there is a discharge of blood rae

SIGNS OF MENSTRUATION, 855

external genitals. This is known as the process of menstruation (or menses, cata-
menia, or periods). . Most women menstruate during the first quarter of the moon,
and only a few at new and full moon (Stroh/). In mammals, the analogous condition
is spoken of as the period of heat [or the “rut” in deer]. There is a slightly bloody
discharge from the external genitals in carnivora, the mare, and cow (Aristotle),
while apes in their wild condition have a well-marked menstrual discharge (Neubert).
[Observations on cases where abdominal section has been performed have shown
that the Graafian follicles mature and burst at any time (Lawson Tait, Leopold). |

The onset of menstruation is usually heralded by constitutional and local phenomena—
there is an increased feeling of congestion in the internal generative organs, pain in the back
and loins, tension in the region of the uterus and ovaries, which are sensitive to pressure
fatigue in the limbs, alternate feeling of heat and cold, and even a slight increase of the tem-
perature of the skin (Kersch). There may be retardation of the process of digestion and varia-
tions in the evacuation of the feces and urine, and in the secretion of sweat. The discharge is
slimy at first, and then becomes bloody, lasting three to four days; the blood is venous, and
shows little tendency to coagulate, provided it is
mixed with much alkaline mucus from the genital
passages ; but, if the hemorrhage be free, the
blood may be clotted. The quantity of blood is
100 to 200 grms. [The blood contains many
white blood-corpuscles and epithelial cells.] After
cessation of the discharge of blood there is a
moderate amount of mucus given off.

The characteristic internal phenomena
which accompany menstruation are :—(1)
The changes in the uterine mucous mem-
brane ; and (2) the rupture of the Graafian
follicle.

1. Changes in the uterine mucous mem-
brane.—The uterine mucous membrane is
the chief source of the blood. The ciliated
epithelium of the congested, swollen, and
folded, soft, thick (3 to 6 mm.) mucous
membrane is shed. The orifices of the
numerous mucous glands of the mucous
membrane are distinct, the glands enlarge,
and the cells undergo fatty degeneration,
and so do the tissue and the blood-vessels Fig. 648. Fig. 649.
lying between the glands. The tissue con- Fig. 648.—Diagram of the uterus just before
tains more leucocytes than normal. This aa aes Pamewens ti: aaa
fatty degeneration and the excretion of the Uterus when menstruation has just ceased,
degenerated tissue occur, however, only in showing the cavity of the body deprived
the superficial layers of the mucosa, whose 0f mucous membrane (J. Williams).
blood-vessels, when torn across, yield the blood. The deeper layers remain intact,
and from them, after menstruation is over, the new mucous membrane is developed
(Kundrat and G. J. Engelmann). [Leopold denies the existence of this fatty
degeneration. According to Williams, the entire mucous membrane is removed
at each menstrual period, and it is regenerated from the muscular coat (fig. 649).
The mucous membrane of the cervix remains free from these changes. |

2. Ovulation.—The second important internal phenomenon is ovulation, in
which process the ovary becomes more vascular—the ripe follicle is turgid with
fluid, and in part projects above the surface of the ovary. The follicle ultimately
bursts, its membranes, and the epithelium covering of the ovary are torn or give
way under the pressure, the bursting being accompanied by the discharge of a
small amount of blood. At the same time, the congested, turgid, and erected
fimbriated extremity of the Fallopian tube is applied to the ovary, so that the

856 THEORIES OF OVULATION.

discharged ovum, with its adherent granulosa cells, and the liquor folliculi, are
caught by the funnel-shaped extremity of the tube (fig. 646). The ovum, when
discharged, is carried towards the uterus by the ciliated epithelium (§ 433) of the
tube, and perhaps also partly by the contraction of its muscular coat. Ducalliez
and Kiiss found that, by fully injecting the blood-vessels, they could imitate the
erection of the Fallopian tube. Rouget points out that the non-striped muscle of
the broad ligaments may cause constriction of the vessels, and thus secure the
necessary injection of the blood-vessels of the Fallopian tube.

Pfliiger's Theory.—There are two theories as to the connection between ovulation or the
discharge of an ovum and the escape of blood from the uterine mucous membrane. Pfliiger
regards the bloody discharge from the superficial layers of the uterine mucous membrane as a
physiological preparation or ‘‘ freshening” of the tissue (in the surgical sense), by which it
will be prepared to receive the ovum when the latter reaches the uterus, so that union can
take place between the ovum and the freshly-exposed surface of the mucous membrane, and
thus the ovum will receive nourishment from a new surface. ie ;

Reichert’s Theory.—-This view is opposed to that of Reichert, Engelmann, Williams, and
others. According to Reichert’s theory, before an ovum is discharged at all there is a sympa-
thetic change in the uterine mucous membrane, whereby it becomes more vascular, more
spongy, and swollen up. The mucous membrane so altered is spoken of as the membrana
decidua imenstrualis, and from its nature it is in a proper condition to receive, retain, and
nourish a fertilised ovum which may come into contact with it. Ifthe ovum, however, be not
fertilised, and escape from the genital passages, then the uterine mucous membrane degener-
ates, and blood is shed as above described. According to this view, the hemorrhage from the
uterine mucous membrane is a sign of the
non-occurrence of pregnancy; the mucous
membrane degenerates because it is not re-
quired for this occasion ; the menstrual blood
Vessels between outer 1S an external sign that the ovum has not
f layer and tunica propria, been impregnated. So that pregnancy, i.e.,
the development of the embryo in utero, is
y/_ Folded and thickened _ to be calculated, not from the last menstru-
tunica propria. ation, but from some time between the last

menstruation and the period which does not
occur.
In some cases the ovulation and the for-

Fresh corpus luteum. mation of the decidua menstrualis occur

separately, so that there may be menstrua-
tion without ovulation, and ovulation without menstruation.

Corpus Luteum.—When a Graafian follicle bursts, it discharges its contents and collapses ;
in the interior are the remains of the membrana granulosa and a small effusion of blood, which

soon coagulates. The small rup-
ture soon heals, after the serum
is absorbed. The vascular wall
Corpus of the follicle swells up. Villous
luteum prolongations or granulations of
Heart young connective-tissue, rich in
centre, Capillaries and cells, grow into the
interior of the follicle (fig. 651).
Colourless blood-corpuscles also
wander into the interior. At the
same time the cells of the granu-
losa proliferate, and form several
layers of cells, which ultimately,

Fig. 651. Fig. 652.
' Corpus luteum of cow (x 14), Lutein cells from the corpus luteum of cow.
after the disap nce of a numberof blood-vessels, undergo fatty degeneration, lutein, and
matter being formed, and it is this mass which gives the corpus luteum its yellow colour (fig.

ERECTION OF THE PENIS. 857

652). The capsule becomes more and more fused with the ovarian stroma. If pregnancy does
not take place after the menstruation, then the fatty matter is rapidly absorbed, and the effused
blood is changed into hematoidin (§ 20) and other derivatives of hemoglobin, while there is a
gradual shrivelling of the whole mass, which is complete in about four weeks, only a very
smal] remainder being left. Such-a corpus luteum, 7.¢., one not accompanied by pregnancy, is
called a false corpus luteum. If, however, pregnancy occurs, then the corpus luteum, instead
of shrivelling, grows and becomes a large body, especially at the third and fourth month, the
walls are thicker, the colour deeper, so that the corpus luteum at the period of delivery may be
6 to 10 mm. in diameter, and its remains may be found in the ovary fora very long time thereafter
(fig. 651). This form is sometimes spoken of as a true corpus luteum. [We cannot draw a sharp
distinction between these two forms.] Only a very small number of the ova in the ovary
undergo development and are discharged ; by far the greater number degenerate (Slavjansky).

436, PENIS—ERECTION.—Penis.—[The penis is composed of the two long cylindrical
corpora cavernosa, the corpus spongiosum, which lies between and below them, and sur-
rounds the urethra; these are held together by fibrous and muscular sheaths, and are
composed of erectile tissue.] Our knowledge of the distribution of the blood within the
penis is chiefly due to C. Langer’s researches. The albuginea of the corpus spongiosum con-
sists of tendinous connective-tissue, containing thickly-woven elastic tissue and smooth
muscular fibres, which together form a solid fibrous envelope, from which numerous interlacing
trabecule pass into the interior, so that the corpus spongiosum comes to resemble a sponge.
The anastomosing spaces bounded by these trabecule form a series of inter-communicating
venous spaces or sinuses filled
with blood and lined by a layer
of endothelium constituting erec-
tile tissue (fig. 653). The largest
sinuses lie in the lower and
external part of the corpus caver-
nosum, while they are less nume-
rous and smaller in the upper
part. The small arteries arise
from the A. profunda penis, which
runs along the septum, and pass
to the trabecule after following a
very sinuous course. At the outer ~
part of the corpus spongiosum,
some of the small arteries become
directly continuous with the larger
venous sinuses; some of them,
however, terminate in capillaries
both in the outer part and within
the corpus spongiosum, the capil-
laries ultimately terminating in
the venous sinuses. The helicine
arteries of the penis described
by Joh. Miiller are merely much
twisted arteries. The deep veins

oe oa hice oe gree oes Erectile tissue. a, trabecule of connective-tissue with elastic
?

while the veins proceeding from fibres and smooth muscle (c) ; 0, venous spaces.

the cavernous spaces pass to the dorsum of the penis to form the vena dorsalis penis. As these
vessels have to traverse the meshes of the vascular network in the cortex of the corpora
cavernosa penis, it is evident that, when the network is congested by being filled with blood,
it must compress the outgoing venous trunks. The corpus cavernosum urethre consists for
the most part’ of an external layer of closely packed anastomosing veins, which surround the
longitudinally directed blood-vessels of the urethra.

In the dog, all the arteries of the penis run at first towards the surface, where they divide
into penicilli. The veins arise from the capillary loops in the papille, and they empty their
blood into the cavernous spaces. Only a small part of the blood passes to the cavernous spaces
through the internal capillaries and veins, but arterial blood never flows directly into these
spaces (MZ. v. Frey).

Mechanism. of Erection.—Erection is due to the overfilling of the blood-
vessels of the penis with blood, whereby the volume of the organ is increased
four or five times, while, at the same time, there are also a higher temperature,
increased blood-pressure (to 4 of that in the carotid—AZckhard), with at first a
pulsatile movement, increased consistence, and erection of the organ.

858 MECHANISM OF ERECTION.

er de Graaf obtained complete erection of the penis by forcibly injecting its blood-
vessels (1668). ; :

The preliminary phenomena consist in a considerable increase of the arterial
blood-supply, the arteries being dilated and pulsating strongly. The arteries are
controlled by the nervi erigentes. The nervi erigentes [called by Gaskell the
pelvic splanchnics (fig. 439] arise chiefly from the second (more rarely the third)
sacral nerves (dog), and have ganglionic cells in their course (Loven, Nikolsky).
These nerves contain vaso-dilator fibres, which can be excited in part reflexly
from the sensory nerves of the penis, the transference centre being in the centre
for erection in the spinal cord (§ 372, 4). Sensory impressions produced by
voluntary movements of the genital apparatus (by the ischio- and bulbo-cavernosi
and cremaster muscles) can also dis-
charge this reflex ; while the thought
of sexual impulses, referable to the
penis, tends to induce erection. The
nervi erigentes also supply the longi-
tudinal fibres of the rectum (/ed/ner).

The centre for erection in the
spinal cord (§ 362, 2) is, however,
controlled by the dominating vaso-
dilator centre in the medulla oblon-
gata (§ 372), and the two centres are
connected by fibres within the cord ;
hence stimulation of the upper part
of the cord, as by asphyxiated blood
(§ 362, 5) or muscarin, may also be -
followed by erection(Nikolsky). [The
seminal fluid is frequently found dis-
charged in persons who have been
hanged. |

The psychical activity of the cere-
brum has a decided influence on the
genital vaso-dilator nerves. Just as
the psychical disturbance which ac-

Fig. 654. companies anger or shame is followed
Anterior wall of the pelvis with the urogenital sep- by dilatation of the blood-vessels of

tum seen from the front. The corpuscavernosum the head, owing to stimulation of the

“) Rds ue meee (3) hak ay er a vaso-dilator fibres, so when the atten-

xit from ras VBy teh aes Pee

abel vela a the penis ; 5 cart at the bulbo- tion vid directed to the sexual centres

cavernosus ; ¢, deep transversus perinei with its there is an action upon the nervi eri-

fascia (f) ; 6, vena profunda penis ; 7, arteryand gentes. This action of the brain is

vein of the bulbo-cavernosus. more comprehensible, since we know
that the diameter of the blood-vessels is affected by the cortex cerebri (§ 377). The
fibres probably pass from the cerebrum through the peduncles of the cerebrum and
the pons; as a matter of fact, if these parts be stimulated erection may take place
(§ 362, 4) (Eckhard).

When the‘impulse to erection is obtained by the increased supply of arterial
blood, the full completion of the act is brought about by the activity of the follow- —
ing transversely striped muscles :—(1) The ¢schio-cavernosus arises from the coccy
and by its tendinous union surrounds the root of the penis (fig. 172). When it
contracts, it compresses the root of the penis from above and laterally, so that the
outflow of blood from the penis is hindered. It has no action on the dorsal vein
of the penis, as this vessel lies in a groove on the dorsum of the penis, and is
therefore protected from compression by the tendon. (2) The deep transver

EJACULATION AND RECEPTION OF THE SEMEN, 859

pertnet is perforated by the venze profunde penis, which come from the corpora
cavernosa, so that when it contracts it must compress these veins between the
tense horizontal fibres (fig. 654, 6). The deep veins of the penis join the common
pudendal vein and the plexus Santorini. (3) Lastly, the bulbo-cavernosus is con-
cerned in the hardening of the urethral corpus spongiosum, as it compresses the
bulb of the urethra (figs. 654, 5, 172). All these muscles are partly under the
control of the will, whereby the erection may be increased. Normally, however,
their contraction is excited reflexly by stimulation of the sensory nerves of the
penis (§ 362, 4).

The congestion of blood is not complete, else, in pathological cases, continuous erection, as
in satyriasis, would give rise to gangrene. The accumulation of the blood in the penis is
favoured by the fact that the origins of the veins of the penis lie in the corpus cavernosum,
which, when it enlarges, must compress them. There are also trabecular smooth muscular
fibres, which compress the large venous plexus of Santorini.

That erection is a complex motor act depending on the nervous system, is proved by an
experiment of Hausmann, who found that section of the nerves of the penis prevented erection
in a stallion. The imperfect erection which occurs in the female is confined to the corpora
cavernosa clitoridis and the bulbi vestibuli. During erection, the passage from the urethra to
the bladder is closed, partly by the swelling of the caput gallinaginis, and partly by the action
of the sphincter urethre, which is connected with the deep transversus perinei.

43'7. EJACULATION—RECEPTION OF THE SEMEN.—In connection
with the ejaculation of the seminal fluid, we must distinguish two different factors
—(l1) its passage from the testicles to the vesicule seminales; (2) the act of
ejaculation itself. The former is caused by the newly secreted fluid forcing on that
in front of it, by the action of the ciliated epithelium (which lines the epididymis
to the beginning of the vas deferens), and also by the peristaltic movements of the
smooth muscular fibres of the vas deferens. Ejaculation, however, requires strong
peristaltic contractions of the vasa deferentia and the vesicule seminales, which are
brought about by the reflex stimulation of the ejaculation centre in the spinal cord
(§ 362, 5). As soon as the seminal fluid reaches the urethra, there is a rhythmical
contraction of the bulbo-cavernosus muscle (produced by the mechanical dilatation
of the urethra), whereby the fluid is forcibly ejected from the urethra. Both vasa
deferentia and vesiculz do not always eject their contents into the urethra simul-
taneously. With moderate excitement the contents of only one may be dis-
charged. The ischio-cavernosus and deep transversus perinei contract at the same
time as the bulbo-cavernosus, although the former have no effect on the act of
ejaculation. In the female also, under normal circumstances, at the height of the
sexual excitement there is a reflex movement corresponding to ejaculation. It con-
sists of a movement analogous to that in man. At first there is a reflex peristaltic
movement of the Fallopian tube and uterus, proceeding from the end of the tube
towards the vagina, and produced reflexly by the stimulation of the genital nerves.
Dembo observed that stimulation of the anterior upper wall of the vagina in
animals caused a gradual contraction of the uterus. By this movement, correspond-
ing to that of the vasa deferentia in man, a certain amount of the mucus normally
lining the uterus is forced into the vagina.

This is followed by the rhythmical contraction of the sphincter cunni (analogous
to the bulbo-cavernosus), also of the ischio-cavernosus, and deep transversus perinei.
The uterus is erected by the powerful contraction of its muscular fibres and round
ligaments, while at the same time it descends towards the vagina, its cavity is more
and more diminished, and its mucous contents are forced out. When the uterus
relaxes after the stage of excitement, it aspirates into its cavity the seminal fluid
injected into the vestibule (Aristotle, Bischof). :

— But the suction of the greatly excited uterus is not necessary for the reception of the semen

(Aristotle). The spermatozoa may wriggle by their own movements from the vagina into the
orifice of the uterus (Kristeller). The 4 of pregnancy where from some pathological causes

860 FERTILISATION OF THE OVUM.

rtial closure of the vagina or vulva), the penis has not passed into the vagina during coition,
a that the erristesaa can traverse the whole length of the vagina, and pass into the
uterus,

438. FERTILISATION OF THE OVUM.—The ovum is fertilised by one
spermatozoon passing into it. |

Swammerdam (+ 1685) proved that contact of the semen with the ovum was necessary for
fertilisation. Spallanzani (1768) proved that the fertilising agent was. the spermatozoa, and
not the clear filtered fluid part of the semen, and that the spermatozoa, even after being
enormously diluted, were still capable of action. Martin Barry (1850) was the first to observe
the entrance of a spermatozoon into the ovum of the rabbit. This occurs pretty rapidly, by a
boring movement through the vitelline membrane (Lewckhart). The entrance is effected either
through the porous canals or the micropyle (Keber, p. 850).

Theories. —As to the manner in which the spermatozoon affects the ovum, there are great
differences of opinion. Aristotle compared it to an action like that of rennet on milk ; Bischoff,
to that of yeast on a fermentable mass, i.c., to a catalytic action. These theories, however, are
quite unsatisfactory, as we know that the unfertilised ova of the hen, rabbit (Hensen), pig
(Bischoff), salpa (Kuppfer) (but not the frog—Pfliiger) can undergo the initial stages of develop-
ment as far as the stage of cleavage, and the star-fishes even as far as the larval form (@ree/).

Place of Fertilisation.—The place where fertilisation occurs is either the ovary,
as indicated by the occurrence of abdominal pregnancy, or the Fallopian tube, and
the numerous recesses in the latter afford a good temporary nidus for the sperma-
tozoa. This view is supported by the occurrence of tubal pregnancy. Thus, the
spermatozoa must be able to pass through the Fallopian tube to the ovary, which
is probably brought about chiefly by the movements proper to the spermatozoa
themselves. It is uncertain whether the peristaltic movements of the uterus and
Fallopian tube are concerned in this process ; certainly ciliary movement is not con- -
cerned, as the cilia of the Fallopian tube act from above downwards. When once
the ovum has passed unfertilised into the uterus, it is not fertilised in the uterus. -
It is assumed that the ovum reaches the uterus within 2 to 3 weeks (in the bitch,
8 to 14 days).

Twins occur in 1 in 87 pregnancies, but oftener in warm climates; triplets,
1:7600; four at a birth, 1: 330,000. More than six at a time have not been
observed. The average number of pregnancies in a woman is 44.

Superfecundation.—By this term is understood the fertilisation of two ova at the same
menstruation, by two different acts of coition. Thus, a mare may throw a foal and a mule,

after being covered first by a stallion and then by an ass. A white and a black child have been
born as twins by a woman.

_ Superfoetation is when a second impregnation takes place at a later period of pregnancy, as
in the second or third month. This, however, is only possible in a double uterus, or when

pcraination persists until the time of the second impregnation. It is said to occur frequently
in the hare,

Hybrids are produced when there is a cross between different species (horse, ass, zebra—dog,
jackal, wolf—goat, ibex—goat, sheep—species of llama—camel, dromedary—tiger, lion—species
of pheasant —goose, swan—carp, crucian—species of butterflies). Most hybrids are sterile,
especially as regards the formation of properly formed spermatozoa ; while the hybrid females
are for the most part fertile with the male of both parents, ¢.g., the mule; but the characters
of the offspring tend to return to those of the species of the parents. Very few hybrids are
fertile when crossed by hybrids. In many species of frogs the absence of hybrids is accounted

for by the mechanical obstacles to fertilisation of the ova.

_Tabal Migration of the Ovum.—Under exceptional circumstances, the ovum
discharged from a ruptured Graafian follicle passes into the Fallopian tube of the
other side, as is proved by the occurrence of tubal pregnancy and pregnancy of an
abnormal rudimentary horn of the uterus, in which case the true corpus luteum
is found on the other side of the ovary. This is spoken of as “external migration”
(Kussmaul, Leopold). This observation coincides with experiment, as granular
fluids, ¢.g., China-ink, when injected into the peritoneal cavity, pass into both
Fallopian tubes, and are carried by the ciliated epithelium to the uterus (Pinner
In animals, with a double uterus with two orifices, the ova may migrate oak

,

IMPREGNATION—CLEAVAGE OF THE YELK. 861

the os of the one into the other uterus, a condition which is spoken of as “ internal
migration.”

439. IMPREGNATION—CLEAVAGE—LAYERS OF THE EMBRYO.—
Maturation of the Ovum.—In birds and mammals, important changes occur in
the ovum before impregnation. The germinal vesicle comes to the surface and dis-
appears from view, while the germinal spot also disappears. In place of the
germinal vesicle, a spindle-shaped body appears. The granular elements of the
protoplasmic vitellus arrange themselves around each of the two poles of the spindle,
in the form of a star, the double-star, or diaster of Fol—nuclear spindle (figs. 655,
656). When this takes place, the peripheral pole of the nucleus or altered ger-
minal vesicle, along with some of the cellular substance of the ovum, protrudes
upon the surface of the vitellus, where they are nipped off from the ovum in the
form of small corpuscles just like an excretory product (fig. 657). These bodies,
which are not made use of in the further development and growth of the ovum,
are called polar or directing globules (/ol, Biitschli, O. Hertwig), although the
elimination of small bodies from the yelk was known to Dumortier [1837], Bis-
choff, P. J. van Beneden, Fritz Miiller [1848], Rathke, and others. The remaining
part of the germinal vesicle stays within the vitellus and travels back towards the
centre of the ovum, to form the female proneucleus (0. Hertwig, Fol, Selenka, EL.
van Beneden). [Before, however, the altered germinal vesicle travels downwards
again into the substance of the ovum, it divides again as before, and from it is
given off the second polar globule, and then the remainder of the germinal vesicle

Fig. 655. Fig. 656,

Fig.~655.—Formation of polar globules in a star-fish (Asterias glacialis), A, ripe ovum with
excentric germinal vesicle and spot; B-E, gradual metamorphosis of germinal vesicle
and spot, as seen in the living egg, into two asters ; F, formation of first polar globule, and
withdrawal of the remaining part of the nuclear spindle within the ovum; G, surface
view of living ovum with view of first polar globule; H, formation of second polar
globule; I, a later stage, showing the remaining internal part of the spindle in the form
of two clear vesicles ; K, ovum with two polar globules and radial strie around the female
pronucleus ; L, extrusion of polar globule. (Geddes: A-K, after Fol; L, after 0. Hertwiy.)
Fig. 656.—Egg of Scorpaena scrofa. The germinal vesicle is extruding a polar globule,
and withdrawing towards the centre of the ovum. Near it is the male pronucleus.

forms the female proneucleus (fig. 655). At the same time the vitellus shrinks
somewhat within the vitelline membrane. | :

Impregnation.—As a rule, only one spermatozoon penetrates the ovum, and as
it does so, it moves towards the female pronucleus, while its head becomes sur-
‘rounded with a star; it then loses its head and eilium, or tail, the latter only
serving as a motor organ, while the remaining middle piece swells up to form a
second new nucleus, the male pronucleus (ol, Selenka). According to Flemming,
it is the anterior part of the head, and according to Rein and Eberth, it is the
head which is so changed. Thereafter, the male and female pronucleus unite,
undergoing amceboid movements at the same time, to form the new nucleus of the
fertilised ovum. The female pronucleus receives the male pronucleus in a little
depression on its surface. Thereafter the yelk assumes a radiate appearance (fein).

862 CLEAVAGE OF THE YELK.

[The union of the representatives of the male and female elements forms the first
embryonic segmentation sphere or blastosphere, which divides into two. cells, and
these again into four, and so on (fig. 658). |
In Echinoderms, O. Hertwig and Fol observed that
several embryos were formed when, under abnormal con-
ditions, several spermatozoa penetrated an ovum. The
male pronuclei, formed from the several spermatozoa,
then fused each with a fragment of the female pro-
nucleus. Under similar circumstances, Born observed
in amphibians abnormal cleavage, but no further de-
velopment. :
Cleavage of the Yelk.—In an ovum so fer-
ae tilised the yelk contracts somewhat around the
Fig. 657. newly-formed nucleus, so that it becomes slightly
Egg of a Star-fish (Asteracanthion) with separated from the vitelline membrane, and for
two extruded polar globules. Male the first time the nucleus and the yelk divides
and female pronuclei near each other. . ° ‘
into two nucleated spheres. This process is

spoken of as a complete cleavage or /jission (fig. 658). Each of these two cells
azain divides into two, and the process is repeated, so that 4, 8, 16, 32, and so on,

Fig. 658.

Segmentation of a rabbit’s ovum. a, two-celled stage; 5b, four-celled stage; c, eight-celled
stage ; de, ae blastomeres showing the more rapid division of the outer-layer cells, and
0

the gradual enclosure of the pa sh cells ; ect, outer-layer cells ; ent, inner-layer cells ;
pg!, polar globules ; zp, zona pellucida.

spheres are formed (fig. 659). This constitutes the cleavage of the yelk, and the
process goes on until the whole yelk is subdivided into numerous small, nucleated
spheres, the ‘mulberry mass” or “ seg-

mentation spheres” or “morula,” or the

protoplasmic primordial spheres (20 to 25
) which are devoid of an envelope. [Each

cell divides by a process of karyokinesis.

' According to Van Beneden, the segmenta-

Fig. 659. tion begins in 1-2 hours after the union
Cleavage of the yelk of the e88 of Anchylo- of the pronuclei, and the process is com-
stomum duodenale. plete in about 75 hours. These primi-

tat en ae which all the tissues of the ad eae . - ora are pe)

q
~

STRUCTURE OF THE BLASTODERM. 863

Variation of Lines of Cleavage.—According to the observations of Pfluger, the ova of the
frog can be made to undergo cleavage in very different directions, according to the angle between
the axis of the egg and the line of gravitation. This of course we can alter as we please, by
erie the eggs at any angle to the line of gravitation. By the axis of the ovum is meant a
ine connecting the centre of the black surface and the middle of the white part, which, in the
fertilised ovum, is always vertical. In such cases of abnormal cleavage the deposition of the
organs takes place from other constituents of the egg than those from which they are formed
under normal conditions. Under normal circumstances, according to Roux, the first line of
cleavage in the frog is in the same direction as the central nervous system. The second inter-
sects the first at a right angle, so as to divide the mass of ovum into two unequal parts, the
larger of which forms the anterior part of the embryo.

Blastoderm.—During this time the ovum is enlarging by absorption of fluid
into its interior. All the cells, from mutual pressure against each other, become
polyhedral, and are so arranged as to form a cellular envelope or bladder, the
blastoderm or germinal membrane, which lies on the internal surface of the
vitelline membrane (De Graaf, v. Baer, Bischoff, Coste). A small part of the cells
not used in the formation of the blastoderm is found on some part of the latter.
[In the ovum of the bird, where there is only partial segmentation, the blastoderm
is a small round body resting on the surface of the yelk, under the vitelline
membrane, so that it does not completely surround the yelk, or a hollow cavity, as

Fig. 660. Fig. 661.
Fig. 660.—Blastodermic vesicle of a rabbit. ect, ectoderm, or outer layer of cells; ent, inner
layer of cells. Fig. 661.—Pr, primitive streak ; #, medullary groove; JU, first proto-
vertebra.

in mammals. In mammals, this cavity is called the segmentation cavity.| The
hollow sphere, composed of cells, is called the blastodermic vesicle by Reichert
(fig. 660), and in the human embryo it is formed at the 10th to 12th day, in the
rabbit at the 4th, the guinea-pig at the 34, the cat 7th, dog 11th, fox 14th,
ruminantia at the 10th to 12th day, and the deer at the 60th day.

When the blastoderm grows to 2 mm. (rabbit), whereby the vitelline membrane
is distended to a very thin delicate membrane, then at one part of it there appears
the germinal area, the area germinativa, or the embryonal shield (Coste, Kéllcker),
as a round white spot, in which the blastoderm, owing to the proliferation of its
cells, becomes double. The upper layer is called the ectoderm or epiblast, and in
some animals it consists of several layers of cells, while the lower layer is the
endoderm or hypoblast. ‘he hypoblast continues to grow at its edges, so that it
ultimately forms a completely closed sac, on which the epiblast is applied concen-
trically. The embryonal area soon becomes more pear-shaped, and afterwards
biscuit-shaped. At the same time the surface of the zona pellucida develops
numerous small, hollow, structureless villi, and is called the primitive chorion.

_ At the posterior part, or narrow’end, of the embryonic shield, the primitive
streak (fig. 661, I, Pr) appears at first as an elongated opaque circular thickening,
and later as a longer streak or groove, the primitive groove. [The opacity is due

864 STRUCTURE OF THE BLASTODERM.

to the fact that there are several layers of cells in this region (fig. 662). In a
transverse section through the primitive streak, three layers of cells are seen,
They form part of the middle layer or mesoblast, and are originally derived from
the hypoblast. These cells fuse with those of the epiblast. The remainder of the
hypoblastic cells retain their steliate character.] At the same time a new layer of

ye Fig. 662,
Transverse section of the poe streak of a fowl’s blastoderm. ep, epiblast ; hy, hypoblast.;
m, mesoblast ; pv, primitive groove ; yh, yoke of germinal wall.
cells is developed between the epiblast and hypoblast, the mesoderm or mesoblast
(tig. 662, I), which soon extends over the embryonal area, and into the blastoderm.
[There has been much discus-
: vial ‘dae Oo To se hlolol | np. sion as tu the origin of the

Lot Li ys Gh Gov : pass mesoblast, but in vertebrates
WSL (<) ZeJr)\ | Tea eons / ep. it seems to be originally de-

‘Je: som, Veloped from the hypoblast.

oz oy lanhy UON~s Fig. 663 shows a portion of
LS Yo >-spm. the hypoblast in its axial part,
Af @ ‘ rage Sessa Sa in process of forming the noto-
hy chord, which is described as

Fig. 663. mesoblastic.]| Blood - vessels

Transverse section of an embyro newt. a, mesenteron; pre formed within the meso-
ax. hy, axial hypoblast, forming the notochord ; be, celom ae
or body-cavity ; ep, epiblast ; hy, digestive hypoblast ; blast, and are distributed over
som, somatic mesoblast ; sym, splanchnic mesoblast ; np, the blastoderm to form th
neural plate. area vasculosa. .
Medullary Groove.—A longitudinal groove, the medullary groove, is formed at
the anterior part of the embryonal shield, but it gradually extends posteriorly,
embracing the anterior part of the primitive streak with its divided posterior end,
while the primitive streak itself gradually becomes relatively and absolutely smaller
and less distinct, until it disappears altogether (fig. 661, I, and II, Pr). |
The position of the embryo is indicated by the central part becoming more
transparent,—the area pellucida,—which is surrounded by a more opaque part—
the area opaca. [The area opaca rests directly upon the white yelk in the fowl,
and it takes no share in the formation of the embryo, but gives rise to structures
which are temporary, and are connected with the nutrition of the embryo. The
embryo is formed in the area pellucida alone.
From the epiblast [neuro-epidermal layer| are developed the central nervous
system and epidermal tissues, including the epithelium of the sense-organs. ,
From the mesoblast are formed most of the organs of the body [including the
vascular, muscular, and skeletal systems, and, according to some, the connective-
tissue, It also gives rise to the generative glands and excretory organs], =
From the hypoblast epithelio-glandular layer [which is the secretory layer], arise

STRUCTURES FORMED FROM THE EPIBLAST. 865

the intestinal epithelium, and that of the glands which open into intestine. The
notochord is also formed from its axial portion. [The mouth and anus being
formed by an inpushing of the epiblast, are lined by epiblast, and are sometimes
called the stomodeum and proctodeum respectively. |

[Structure of the Blastoderm (fig. 664).—Originally it is composed of only two
layers, and in a vertical section of it the epiblast consists of a single row of
nucleated granular cells,
arranged side by side,
with their long axes placed
vertically. The hypoblast
consists of larger cells
than the foregoing, al-
though they vary in size.
They are spherical and
very granular, so that no
nucleus is visible in them. Fig. 664.
The cells form a kind of Vertical section of part of the unincubated blastoderm of a hen,
network, and occur in 4, epiblast; 0, hypoblast ; c, formative cells resting on white
more than one layer, espe- yelk ; f, archenteron.
cially at the periphery. It rests on white yelk, and under it are large spherical
refractive cells, spoken of as formative cells (c). |

The cells of the epiblast, and especially those of the hypoblast, nourish themselves by the
direct absorption and incorporation of the constituents of the yelk into themselves. The

amceboid movements of these cells play a part in the process of absorption. The absorbed
particles are changed, or, as ‘it were, digested within the cells, and the product used in the

processes of growth and development (Kollmann).

440. STRUCTURES FORMED FROM THE EPIBLAST.—Lamine Dor-
sales.—The medullary groove upon the epiblast (also called outer, serous, sensorial,
corneal, or animal layer) becomes deeper (fig. 665, II). The two longitudinal
elevations or lamine dorsales consist of a thickening of the epiblast, and grow up
over the medullary groove, to meet each other and coalesce by their free edges in
the middle line posteriorly. Thus, the open groove is changed into a closed tube
—the medullary or neural tube (III). The cells next the lumen of the tube
ultimately become the ciliated epithelium lining the central canal of the spinal
cord, while the other cells of the nipped-off portion of the epiblast form the
ganglionic part of the central nervous system and its processes.

Primary Cerebral Vesicles.—|The laminz dorsales unite first in the region of the
neck of the embryo, and soon this is followed by the union of those over the future
head.| The medullary tube is not of uniform diameter, for at the anterior end it
becomes dilated and mapped out by constrictions into the primary vesicles of the
brain, which at first are arranged, one behind the other, in the following order,
each one being smaller than the one in front of it :—the fore-brain (representing
the structures from which the cerebral hemispheres are developed) ; the mid-brain
(corpora quadrigemina); the hind-brain (cerebellum); and the after-brain
(medulla oblongata), which is gradually continued into the spinal cord (IV and V).
The posterior part of the medullary tube has a dilatation at the lumbar enlarge-
ment. In birds, the medullary groove remains open in. this situation to form a
lozenge-shaped dilatation, the sinus rhomboidalis.

Cranial Flexures.—The anterior part of the medullary tube curves on itself,
especially at the junction of the spinal cord and oblongata, between the mid-brain
and hind-brain, and again almost at right angles between the fore-brain and mid-
brain, [Thus, a displacement of the-primary vesicles is produced, and the head of
the future embryo is mapped off.| At first all the cerebral vesicles are devoid of
convolutions and sulci. On each side of the fore-brain there grows out a stalked

ol

866 STRUCTURES FORMED FROM THE EPIBLAST.

hollow vesicle (VI), the primary optic vesicle. The remainder of the epiblast
Sotti the orale covering of the body. At an early period we can distinguish
the stratum corneum and the Malpighian layer of the skin (§ 283); from the
former are developed the hairs, nails, feathers, dc, !

ti i irds and in mero-
artial Cleavage.—Only a partial cleavage takes place in the eggs of birds and

Pik ova, 7.¢., aly the Y hite yelle in the neighbourhood of the cicatricula divides into nume-
rous segmentation spheres (Coste, 1848). The cells arrange themselves in two layers lying one

Fig. 665.

I, The three layers of the blastoderm of a mammalian ovum—2Z, zona pellucida; E, epiblast ;'m,
mesoblast ; ¢, hypoblast. II, Section of an embryo, with six protovertebre at the 1st day
—M, medullary groove ; h, somatopleure ; U, protovertebra ; c, chorda dorsalis ; 8, the
lateral plates divided into two ; ¢, hypoblast. I, Section of an embryo chick at the 2nd
day in the region behind the heart—M, medullary groove ; h, outer part of somatopleure ;
u, protovertebra ; c, chorda ; w, Wolffian duct ; K, celom ; 2, inner part of somatopleure;
y, inner part of splanchnopleure ; A, amniotic fold; a, aorta; e, hypoblast. IV, Scheme
of a longitudinal section of an early embryo. V, Scheme of the formation of the head- and
tail-folds—7, head-fold ; D, anterior extremity of the future intestinal tract ; S, tail-fold,
first rudiment of the cavity of the rectum. VI, Scheme of a longitudinal section through
an embryo after the formation of the head- and tail-folds—A 0, omphalo-mesenteric arteries;

-

m
'

a

Ls

STRUCTURES FORMED FROM THE MESOBLAST. 867

V o, omphalo-mesenteric veins ; @, position of the allantois; A, amniotic fold. VII,
Scheme of a longitudinal section through a human ovum—2Z, zona pellucida ; S, serous
cavity ; 7, union of the amniotic folds ; A, cavity of the amnion; a, allantois; N, um-
bilical vesicle ; m, mesoblast; #, heart; U, primitive intestine. VIII, Schematic trans-
verse section of the pregnant uterus during the formation of the placenta ; U, muscular
wall of the uterus ; py, uterine mucous membrane, or decidua vera ; 6, maternal part of the
placenta, or decidua serotina ; 7, decidua reflexa ; ch, chorion; A, amnion; », umbilicai
cord; a, allantois, with the urachus ; N, umbilical vesicle, with D, the omphalo-mesen-
teric duct ; ¢ ¢, openings of the Fallopian tubes ; G, canal of the cervix uteri. IX, Scheme
of a human embryo, with the visceral arches still persistent—A, amnion ; V, fore-brain ;
M, mid-brain ; H, hind-brain ; N, after-brain; U, primitive vertebre ; a, eye ; p, nasal
pits ; S, frontal process ; y, internal nasal process ; n, external nasal process ; 7, superior
maxillary process of the 1st visceral arch ; 1, 2, 3, and 4, the four visceral arches, with the
visceral clefts between them ; 0, auditory vesicle ; h, heart, with ¢, primitive aorta, which
divides into five aortic arches ; 7, descending aorta ; om, omphalo-mesenteric artery ; b, the
omphalo-mesenteric arteries on the umbilical vesicle ; c, omphalo-mesenteric vein ; L, liver,
with vene advehentes and revehentes; D, intestine ; 7, inferior cava; T, coccyx ; all,
allantois, with z, one umbilical artery, and #, an umbilical vein.

over the other. The upper layer or epiblast is the larger, and contains small pale cells; the
lower layer, or hypoblast, which at first is not a continuous layer, ultimately forms a continuous
layer, but its periphery is smaller than
the upper layer, while its cells are
larger and more granular.

Between the epiblast and hypoblast
there is formed, from the primitive
streak as a product of cell-proliferation,
the mesoblast, which is said by Kol-
liker to be due to the division of the
cells of the epiblast. It gradually ex-
tends in a peripheral direction between
the two other layers. All the three
layers grow at their periphery. In
the mesoblast blood-vessels are de-
veloped. All the three layers, as they
grow, come ultimately to enclose the
yelk, so that their margins come to-
gether at the opposite pole of the yelk.

441. STRUCTURES FORM-
ED FROM THE MESOBLAST
AND HYPOBLAST.—Themeso-
blast (vascular layer or middle
layer) forms immediately under
the medullary groove, a cylindri-
cal cellular cord, the chorda dor-
salis, or notochord, which is
thicker at the tail than at the
cephalic end (fig. 665, II, ITI, c).
It is present in all vertebrata, and
also in the larval form of the
ascidians, but in the latter it dis-
appears in the adult form (Kowa-

lewsky). In man it is relatively
; Embryo fowl of the 2nd day, x 50. Ao, area opaca ; Ap,
small. It forms the basis of the “grea pellucida ; Hh, hindbrain ; Mh, mid brain : Wh
bodies of the vertebra, and around _ fore-brain ; om, omphalo-mesenteric veins ; omr, point
it, as a central core, the substance where the closure of the neural groove is travelling
of the bodies of the-vertebree is ppinetar tides the Protester 3 yy muscle pas
: , posterior part of widely-open neural groove ; Rw,
deposited, so that they are strung penial ridge ; vA, Aiibottbe danwictis fold” :
on it, as it were, like beads ona

string. After it is formed, it becomes surrounded by a double sheath-like covering
(Gegenbaur, Kolliker).

868 STRUCTURES FORMED FROM THE MESOBLAST.

The recent observations of L. Gerlach and Strahl] show that the chorda dorsalis is derived
from the hypoblast (fig. 663). It does not contain chondrin or glutin, but albumin (Retzius).

Protovertebre.—The cells of the mesoblast, on each side of the chorda,
arrange themselves into cubical masses, always disposed in pairs behind each other,
the protovertebre (fig. 665, U and «). The first pair correspond to the atlas.
At a later period each protovertebra shows a marginal cellular area and a nuclear
area (fig. 665). Only part of it goes to form a future vertebra. The part of the
mesoblast lying external to the protovertebre, the lateral plates (fig. 665, II, s),
splits into two layers, an upper one and a lower one, which, however, are united
by a median plate at the protovertebre. The space between the two layers of the
mesoblast is called the pleuro-peritoneal cavity, or the ceelom of Haeckel (III, K).
The upper layer of the lateral plate becomes united to the epiblast, and forms
the cutaneo-muscular plate of German authors, or the somatopleure (fig. 665,
III, x; fig. 667, so), while the inner one unites with the hypoblast to form the
intestinal plate of German authors, or the splanchnopleure (fig. 665, III, v7; fig.
667, sp). On the surfaces of these plates, which are directed towards each other,
the endothelium lining the pleuro-peritoneal cavity is developed. On the surface

Sp.c

=
. > — oe
ERS hee -
BO/S > tN
2, >i mS Cay
=
=

—J we
z=
H 1S

eo oO

<>

Fig. 667.

Transverse section of an embryo duck. am, amnion ; ao, aorta ; ca.v, cardinal vein ; ch, noto-
chord ; hy, hypoblast ; ms, muscle-plate ; so, somatopleure ; sp, splanchnopleure ; sp.e,
spinal cord ; sp.g, spinal ganglion ; st, segmental tube ; wd, Wolffian (segmental) duct.

of the median plate, directed towards the ccelom, some cylindrical ‘cells, the

“germ-epithelium” of Waldeyer, remain, which form the ovarian tubes and the

ova (§ 438). :

According to Remak, the skin, the muscles of the trunk, and the blood-vessels, and according
to His, only the musculature of the trunk, are derived from the somatopleure. Both observers
agree that the splanchnopleure furnishes the musculature of the intestinal tract. ye

Parablastic and Archiblastic Cells.—According to His, the blood-vessels,
blood, and connective-tissue are not developed from true mesoblastic cells, but he
asserts that for this purpose certain cells wander in from the margins of the blasto:
derm between the epiblast and hypoblast, these cells being derived from outside the
position of the embryo, from the elements of the white yelk. His calls these struc

tures parablastic, in opposition to the archiblastic, which belong to the three -layers _

of the embryo. Waldeyer also adheres to the parablastic structure: of blood and

————

msi tl il

HEAD- AND TAIL-FOLDS—HEART. 869

connective-tissue, but he assumes that the material from which the latter is formed
is continuous protoplasm, and of equal value with the elements of the blastoderm.

The hypoblast does not undergo any change at this time; it applies itself to
the inner layer of the mesoblast, as a single layer of cells, to form the splanchno-
pleure.

442, FORMATION OF EMBRYO, HEART, PRIMITIVE CIRCULATION.
—Head- and Tail-Folds.—Up to this time the embryo lies with its three layers
in the plane of the layers themselves. The cephalic end of the future embryo is
first raised above the level of this plane (fig. 665, V). In front of, and under the
head, there is an inflection or tucking-in of the layers, which is spoken of as the
head-fold (V, 7). [It gradually travels backwards, so that the embryo is raised
above the level of its surroundings.| The raised cephalic end is hollow, and it
communicates with the space in the interior of the umbilical vesicle. The cavity
in the head is spoken of as the head-gut or fore-gut (V, D). The formation of
the fore-gut, by the elevation of the head from the plane of the three layers, occurs
on the second day in the chick, and in the dog on the 22nd day. The tail-fold is
formed in precisely the same way, in the chick on the 3rd day, and in the dog
on the 22nd day. The tail-fold, S, also is hollow, and the space within it is
the hind-gut, d. Thus, the body of the embryo is supported or rests on a hollow
stalk, which at first is wide, and communicates with the cavity of the umbilical
vesicle. This duct or communication is called the omphalo-mesenteric duct, or
the vitello-intestinal or vitelline duct. The saccular vesicle attached to it in
mammals is called the umbilical vesicle (VII, N), while the analogous much
larger sac in birds, which contains the yellow nutritive yelk, is called the yelk-sac.
The omphalo-mesenteric or vitelline duct in course of time becomes narrower, and
is ultimately obliterated in the chick on the 5th day. The point where it is con-
tinuous with the abdominal wall is the abdominal umbilicus, and where it is in-
serted into the primitive intestine, the intestinal umbilicus.

[Sometimes part of the vitelline duct remains attached to the intestine, and may prove
dangerous by becoming so displaced as to constrict a loop of intestine, and thus cause strangu-
lation of the gut.]

Heart.—Before this process of constriction is complete, some cells are mapped
off from that part of the splanchnopleure which lies immediately under the head-
gut ; this indicates the position of the heart, which appears in the chick at the end
of the first day, as a small, bright red, rhythmically contracting point, the punctum
saliens, or the oriypn kivovpévy of Aristotle. In mammals it appears much later.

The heart, VI, begins first as a mass of cells, some of which in the centre dis-
appear to form a central cavity, so that the whole looks like a pale hollow bud
(originally a pair) of the splanchnopleure. The central cavity soon dilates; it grows,
and becomes suspended in the ccelom by a duplicature like a mesentery (meso-
eardium), while the space which it occupies is spoken of as the fovea cardica. The
heart now assumes an elongated tubular form, with its aortic portion directed
forwards, and its venous end backward; it then undergoes a slight f-shaped curve
(fig. 675, 1). From the middle of the 2nd day, the heart begins to beat in the
chick, at the rate of about 40 beats per minute. [It is very important to note
that at first, although the heart beats rhythmically, it does not contain any nerve-
cells.

thie the anterior end of the heart, there proceeds from the bulbus aortz, the
aorta which passes forward and divides into two primitive aorte, which then
curve and pass backwards under the cerebral vesicles, and run in front of the proto-
vertebree. Opposite the omphalo-mesenteric duct, each primitive aorta in the
chick sends off one, in mammals several (dog 4 to 5), omphalo-mesenteric arteries
(VI, A, 0), which spread out to forma vascular network within the mesoblast of the

870 FORMATION OF THE BODY.

umbilical vesicle. From this network, there arise the omphalo-mesenteric veins, .
which run backwards on the vitelline duct, and end by two trunks in the venous end
of the tubular heart. In the chick, these veins arise from the sinus terminalis of the
future vena terminalis of the area vasculosa. Thus, the first or primitive circu-
lation is a closed system, and functionally it is concerned in carrying nutriment and
oxygen to the embryo. In the bird, the latter is supplied through the porous shell,
and the former is supplied up to the end of incubation by the yelk. In mammals,
both are supplied by the blood-vessels of the uterine mucous membrane to the ovum.
In birds, owing to the absorption of the contents of the yelk-sac, the vascular area
steadily diminishes, until ultimately, towards the end of the period of incubation,
the shrivelled yelk-sac slips into the abdominal cavity. In mammals, the circula-
tion on the umbilical vesicle, z.e., through the omphalo-mesenteric vessels, soon
diminishes, while the umbilical vesicle itself shrivels to a small appendix, and the
second circulation is formed to replace the omphalo-mesenteric system. The first
blood-vessels are formed in the chick, in the area vasculosa, outside the position
of the embryo, at the last quarter of the first day, before any part of the heart is
visible. The blood-vessels begin in vaso-formative cells [constituting the “ blood-
islands” of Pander]. At first they are solid, but they soon become hollow (§ 7, A).

A narrow-meshed plexus of Zymphatics is formed in the area vasculosa of the chick (His), and
it communicates with the amniotic cavity (4. Budge).

443. FORMATION OF THE BODY.—Body-Wall—(1) The cclom, or
pleuro-peritoneal cavity, becomes larger and larger, while at the same time, the
difference between the body-wall and the wall of the intestine becomes more pro-
nounced. The latter becomes more separated from the protovertebre,'as the
middle plate begins to be elongated to form a mesentery. The body-wall, or
somatopleure, composed of the epiblast and the outer layer of the cleft mesoblast,
becomes thickened by the ingrowth into it of the muscular layer from the muscle-
plate, and the position of the bones and the spinal nerves from the protovertebre.
These grow between the epiblast and the outer layer of the mesoblast (Zemak).
[The somatopleure, or parietal lamina, from each side grows forward and towards
the middle line, where they meet to form the body-wall, while at the same time,
the splanchnopleure, or visceral lamina, on each side also grow and meet in the
middle line, and when they do so, they enclose the intestine. Thus, there is one
tube within the other, and the space between is the pleuro-peritoneal cavity. ]

(2) Vertebral Column.—A dorsally placed structure, called the muscle-plate
(fig. 667, ms.), is differentiated from each of the protovertebre ; the remainder of
the protovertebra, the protovertebra proper, coalesces with that on the other side,
so that both completely surround the chorda, to form the membrana reuniens
inferior, in the chick on the 3rd, and in the rabbit on the 10th day, while, at the
same time, they close over the medullary tube dorsally, in the chick at the 4th
day, to form the membrana reuniens superior (Zeichert). Thus, there is a union
of the masses of the protovertebree in front of the medullary tube, which encloses
the chorda, and represents the basis of the bodies of all the vertebrae, whilst the
membrana reuniens superior, pushed between the muscle-plates and the epiblast on
the one hand and the medullary tube on the other, represents the position of the
entire vertebral /amine as well as the intervertebral ligaments between them. In
some rare cases the membrana reuniens superior is not developed, so that the
medullary tube is covered only by the epiblast (epidermis), either throughout its
entire extent, or at certain parts. This constitutes the condition of spina bifida,
or, when it occurs in the head, hemicephalia. The vertebral column at this
membranous stage is in the same condition as the vertebral column of the cyclo-.
stomata (Petromyzon). The membranes of the spinal cord, the spinal ganglia, and
spinal nerves are formed from the membrana reuniens superior, Lv}

4

VISCERAL CLEFTS AND ARCHES. 87 I

Lastly, parts of the somatopleures also grow towards the middle line of the back,
and insinuate themselves between the muscle-plate and the epiblast ; thus, the
dorsal skin is formed (Remak).

In the membranous vertebral column, there are formed the several cartilaginous
vertebrze, the one behind the other, in man at the 6th to 7th week, although at
first they do not form closed vertebral arches ; the latter are closed in man about
the 4th month. Each cartilaginous vertebra, however, is not formed from a pair
of protovertebra, 7.¢., the 6th cervical vertebra from the 6th pair of protovertebre,
but there is a new subdivision of the vertebral column, so that the lower half of
the preceding protovertebra and the upper half of the succeeding protovertebra
unite to form the final vertebra. While the bodies are becoming cartilaginous the
chorda becomes smaller, but it still remains larger in the intervertebral discs. The
body of the first vertebra or atlas unites with that of the axis to form its odontoid
process, and in addition it forms the arcus anterior atlantis and the transverse
ligament (Hasse). The chorda can be followed upwards through the ligamentum
suspensorium dentis as far as the posterior part of the sphenoid bone.

The histogenetic formation of cartilage from the indifferent formative cells takes place by
division and growth of the cells, until they ultimately form clear nucleated sacs. The cement
substance is probably formed by the outer parts of the cells (parietal substance) uniting and

secreting the intercellular substance. It is supposed by some that the latter contains fine
canals, which connect the protoplasm of the adjoining cells.

Visceral Clefts and Arches.—Each side of the cervical region contains four
slit-like openings—the visceral clefts or branchial openings (Rathke); in the chick,
the upper three are formed at the 3rd, and the fourth on the 4th day. Above the
slits are thickenings of the lateral wall, which constitute the visceral or branchial
arches (fig. 671). The clefts are formed by a perforation from the fore-gut, but
this, perhaps, does not always occur in the chick, mammal, and man (//is), and
they are lined by the cells of the hypoblast. On each side in each visceral arch,
2.e., above and below each cleft, there runs an aortic arch, five on each side
(fig. 665, IX). These aortic arches persist in fishes. In man, all the slits close,
except the uppermost one, from which the auditory meatus, the tympanic cavity, and
the Eustachian tube are developed. The four visceral arches are for the most part
made use of later for other formations (p. 879).

Primitive Mouth and Anus.—Immediately under the fore-brain, in the middle
line, is a thin spot, where there is at first a small depression, and ultimately a
rupture, forming the primitive oral aperture, which represents both the mouth
and the nose. Similarly, there is a depression at the caudal end, and the depres-
sion ultimately deepens, thus communicating with the hind-gut to form the anus.
When the latter part of the process is incomplete, there is atresia ani, or imper-
forate anus. Several processes are given off from the primitive intestine, including
the hypoblast and its muscular layers, to form the lungs, the liver, the pancreas,
the czecum (in birds), and the allantois.

The extremities appear at the sides of the body as short unjointed stumps or
projections at the 3rd cr 4th week in the human embryo.

444. AMNION AND ALLANTOIS.—Amnion.—During the elevation of the
embryo from its surroundings, immediately in front of the head (at the end of the
2nd day in the chick), there rises up a fold consisting of the epiblast and the outer
layer of the mesoblast, which gradually extends to form a sort of hood over the
cephalic end of the embryo (fig. 665, VI, A). In the same way, but somewhat
later, a fold rises at the caudal end, and between both along the lateral borders
similar elevations occur, the lateral folds (fig. 665, III, A). All these folds grow
over the back of the embryo to meet over the middle line posteriorly, where they
unite at the 3rd day, in the chick, to form the amniotic sac. Thus, a cavity which

872 FORMATION OF THE AMNION AND ALLANTOIS.

becomes filled with fluid—the amniotic fluid—is developed around the embryo
[so that the embryo really floats in the fluid of the amniotic sac]. In mammals
also, the amnion is developed very early, just as in birds (fig. 665, VII, A).
From the middle of pregnancy onwards, the amnion is applied directly to the
chorion; and united to it by a gelatinous layer of tissue, the tunica media of

Bischoff. :

Amniotic Fluid.—The amnion, and the allantois as well, are formed only in mammals,
birds, and reptiles, which have hence been called amniota, while the lower vertebrates, which
are devoid of an amnion, are called anamnia, Composition.—The amniotic fiuid is a clear,
serous, alkaline fluid, specific gravity 1007 to 1011, containing, besides epithelium, lanugo
hairs, 4 to 2 per cent. of fixed solids. Amongst the latter are albumin (#5 to 3 per cent. )
mucin, globulin, a vitelline-like body, some grape-sugar, urea, ammonium carbonate, very
probably derived from the decomposition of urea, sometimes lactic acid and kreatinin, calcic
sulphate and phosphate, and common salt. About the middle of pregnancy, it amounts to
about 1-1°5 kilo. [2°2-3°3 lbs.], and at the end about 0°5 kilo. The amniotic fluid is of feetal
origin, as is shown by its occurrence in birds, and is, perhaps, a transudation through the
foetal membranes. In mammals, the urine of the foetus forms part of it sari the second
half of pregnancy (Gusserow). In the pathological condition of hydramnion, the blood-vessels
of the uterine mucous membrane secrete a watery fluid. The fluid preserves the foetus, and also
the vessels of the fcetal membranes from mechanical injuries ; it permits the limbs to move
freely, and protects them from growing together ; and, lastly, it is important for dilating the
os uteri during labour. The amnion is capable of contraction at the 7th day in the chick; and
this is due to the smooth muscular fibres which are developed in the cutaneous plate in its
mesoblastic portion, but nerves have not been found.

Allantois.—From the anterior surface of the caudal end of the embryo, there
grows out a small double projection, which becomes hollowed out to form a sac
projecting into the cavity of the ceelom or pleuro-peritoneal cavity (fig. 665); it
constitutes the allantois, and is formed in the chick before the 5th day, and in
man, during the 2nd week. Being a true projection from the hind-gut, the
allantois has two layers, one from the hypoblast, and the other from the muscular
layer, so that it is an offshoot from the splanchnopleure. From both sides, there
pass on to the allantois the umbilical arteries from the hypogastric arteries, and
they ramify on the surface of the sac. The allantois grows, like a urinary bladder
gradually being distended, in front of the hind-gut in the pleuro-peritoneal cavity
towards the umbilicus ; and lastly, it grows out of the umbilicus, and projects
beyond it alongside the omphalo-mesenteric or vitelline duct, its vessels growing
with it (fig. 665, VII, a); but, after this stage, it behaves differently in birds and
mammals.

In birds, after the allantois passes out of the umbilicus, it undergoes great development, so
that within a short time it lines the whole of the interior of the shell as a highly vascular and
saccular membrane. Its arteries are at first branches of the primitive aorte, but with the
development of the posterior extremities they appear as branches of the hypogastric arteries,
Two allantoidal, or umbilical veins, proceed from the numerous capillaries of the allantois.
They pass backward aba the umbilicus, and at first unite with the omphalo-mesenteric
veins to join the venous end of the heart. In birds this circulation on the allantois, or second
circulation, is respiratory in function, as its vessels serve for the exchange of gases through the
porous shell. The circulation gradually assumes the respiratory functions of the umbilical
vesicle, as the latter gradually becomes smaller and smaller, and ceases to be a sufficient
respiratory organ. Towards the end of the period of incubation the chick may breathe and
cry within the shell (Aristotle)—a proof that the respiratory funetion of the allantois is partly
taken over by the lungs. The allantois is also the excretory organ of the urinary constituents,
Into its cavity in mammals the ducts of the primitive kidneys, or the Wolffian ducts, open, but
in birds and reptiles, which possess a cloaca, these open into the posterior wall of the cloaca.
The primitive kidneys, or Wolffian bodies, consist o many glomeruli, and empty their secre-
tion through the Wolffian ducts into the allantois (in birds into the cloaca), and the secretion
Sse through the allantois, per the umbilicus, into the peripheral part of the urinary sac.

mak found ammonium and sodium urate, allantoin, grape-sugar, and salts in the contents of
the allantois, From the 8th day onwards, the allantois of the chick is contractile (Vulpian),
owing to the presence of smooth fibres derived from the splanchnopleure. Lymphatics accom-
pany the branches of the arteries (4. Budge). . > Te

Allantois in Mammals.—In mammals and man, the relation of the allantois is

F@:TAL MEMBRANES. 873

somewhat different. The first part or its origin forms the urinary bladder, and
from the vertex of the latter there proceeds through the umbilicus a tube, the
urachus, which is open at first (fig. 665, VIII, a). The blind part of the sac of
the allantois outside the abdomen is in some animals filled with a fluid like urine.
In man, however, this sac disappears during the 2nd month, so that there remains
only the vessels which lie in the muscular part of the allantois. In some animals,
however, the allantois grows. larger, does not shrivel, but obtains through the
urachus from the bladder an alkaline turbid fluid, which contains some albumin,
sugar, urea, and allantoin. The relations of the umbilical vessels will be described
in connection with the foetal membranes.

445. FETAL MEMBRANES, PLACENTA, FETAL CIRCULATION.—
Decidua.—When a fecundated ovum reaches the uterus, it becomes surrounded by
a special covering, which William Hunter (1775) described as the membrana
decidua, because it was shed at birth. We distinguish the decidua vera (fig. 665,
VIII, p), which is merely the thickened, very vascular, softened, more spongy, and
somewhat altered mucous membrane of the uterus. [Sometimes in a diseased con-
dition, as in dysmenorrhcea, the superficial layer of the uterine mucous membrane is
thrown off nearly en masse in a
triangular form (fig. 668). This
serves to show the shape of the
decidua, which is that of the
uterus.]} When the ovum
reaches the uterus, it is caught
in a crypt or fold of the de-
cidua, and from the latter there
grow up elevations around the
ovum; but these elevations are
thin, and soon meet over the
back of the ovum to form the
decidua reflexa (fig. 665,
VIII, 7). At the 2nd to 3rd
month, there is still a space in
the uterus outside the reflexa ;
in the 4th month, the whole
cavity is filled by the ovum.
At one part the ovum lies ee
directly upon the d. vera [and Fig. 668.
that part is spoken of as the A dysmenorrhceal membrane laid open.
decidua serotina], but by far the greatest part of the surface of the ovum is in
contact with the reflexa. In the region of the d. serotina the placenta is ulti-
mately formed.

‘Structure of the Decidua Vera.—-The d. vera at the 8rd month is 4 to 7 mm. thick, and —
at the 4th only 1 to 3 mm., and it no longer has any epithelium; but it is very vascular, and
is possessed of lymphatics around the glands and blood-vessels (Leopold), and in its loose sub-
stance are large round cells (decidua cells—Kélliker), which in the deeper parts become changed
into fibre cells—there are also lymphoid cells. The uterine glands, which become greatly
developed at the commencement of pregnancy, at the 3rd to the 4th month form non-cellular,
' wide, bulging tubes, which become indistinct in the later months, and in which the epithelium
disappears more and more. The d. reflexa, much thinner than the vera from the middle of
pregnancy, is devoid of epithelium, and is without vessels and glands. Towards the end of
pregnancy both decidu unite. .

The ovum, covered at first with small hollow villi, is surrounded by the decidua.
From the formation of the amnion it follows that, after it is closed, a completely
closed sac passes away from the embryo to lie next the primitive chorion. This
membrane is the “serous covering” of v. Baer (fig. 665, VII, s),.or the false

874 THE PLACENTA.

amnion. It becomes closely applied to the inner surface of the chorion, and
extends even into its villi The allantois proceeding from the umbilicus
comes to lie directly in contact with the foetal membrane ; its sac disappears about
the 2nd month in man, but its vascular layer grows rapidly and lines the whole of
the inner surface of the chorion, where it is found on the 18th day (Coste). From
the 4th week the blood-vessels, along with a covering of connective-tissue, branch
and penetrate into the hollow cavities of the villi, and completely fill them. At
this time the primitive-chorion disappears. Thus, we have a stage of general vascu-
larisation of the chorion. In the place of the derivative of the zona pellucida we
have the vascular villi of the allantois, which are covered by the epiblastic cells
derived from the false amnion. This stage lasts only until the 3rd month, when
the chorionic villi disappear all over that part of the surface of the ovum which is
in contact with the decidua reflexa. On the other hand, the villi of the chorion,
where they lie in direct contact with the decidua serotina, become larger and more
branched. Thus, there is distinguished the chorion laeve and c. frondosum.

The chorion laeve, which consists of a connective-tissue matrix covered externally by several
layers of cells, has a few isolated villi at wide intervals. Between the chorion and the amnion
is a gelatinous substance (membrana intermedia) or undeveloped connective-tissue,

Placenta.—The large villi of the chorion frondosum penetrate into the tissue of
the decidua serotina of the uterine mucous membrane. [It was formerly supposed
that the chorionic villi entered the mouths of the uterine glands, but the researches
of Ercolani and Turner have shown that, although the uterine glands enlarge during
the early months of utero-gestation, the villi do not enter the glands, _ The villi
enter the crypts of the uterine mucous membrane. The glands of the inner layer
of the decidua serotina soon disappear.] As the villi grow into the decidua

serotina, they push against
the walls of the large blood-
vessels, which are similar to
capillaries in structure, so that
the villi come to be bathed by
the blood of the mother in the
uterine sinuses, or they float
in the colossal decidual capil-
_ laries (fig. 665, VII, 6). The
villi do not float naked in the
maternal blood, but they are
covered by a layer of cells
derived from the decidua.
Some villi, with bulbous ends,
unite firmly with the tissue of
the uterine part of the placenta
to form a firm bond of connec-
tion. [The placenta is formed
by the mutual intergrowth of
the chorionic villi and the de-
cidua serotina.| Thus, it con-
sists of a foetal part, includin
all the villi, and a mate
or uterine part, which is the

Fig. 669.

Human placental villi. Blood-vessels black,
very vascular decidua serotina. At the time of birth, both parts are so firmly
united that they cannot be separated. Around the margin of the placenta is a
large venous vessel, the marginal sinus of the placenta. [Friedlinder found the
uterine sinuses below the placental site blocked by giant cells after the 8th month
of pregnancy. Leopold confirms this, and found the same in the serotinal veins, |

7
oo ——,

UTERINE MILK. 875

Functions.—The placenta is the nutritive, excretory, and respiratory organ of
the foetus (§ 368) ; the latter receives its necessary pabulum by endosmosis from
the maternal sinuses through the coverings and vascular wall of the villi in which
the foetal blood circulates. [The placenta also contains glycogen. |

[Structure.—A piece of fresh placenta teased in normal saline solution, shows the villi pro-
vided with iateal offshoots, and consisting of a connective-tissue framework, containing a
capillary network with arteries and veins, while the villi themselves are covered by a layer of
somewhat cubical epithelium (fig. 669). ]

Uterine Milk.—Between the villi of the placenta there is a clear fluid, which
contains numerous small, albuminous globules, and this fluid, which is abundant
in the cow, is spoken of as the uterine milk. It seems to be formed by the breaking
up of the decidual cells. It has been supposed to be nutritive in function. [The
maternal placenta, therefore, seems to be a secreting structure, while the foetal part
has an absorbing function. The uterine milk has been analysed by Gamgee, who
found that it contained fatty, albuminous, and saline constituents, while sugar and
casein were absent. |

The investigations of Walter show, that after poisoning pregnant animals with strychnin,
morphia, veratrin, curara, and ergotin, these substances are not found in the foetus, although
many other chemical substances pass into it.

[Savory found that strychnin injected into a foetus in utero caused tetanic convulsions in the
mother (bitch), while syphilis may be communicated from the father to the mother through the
medium of the foetus (Hutchinson). A. Harvey’s record of observations on the crossing of breeds
of animals—chiefly of horses and allied species—show that materials can pass from the feetus to
the mother. ]

On looking at a placenta, it is seen that its villi are distributed on large areas s separated from
each other by depressions. This complex arrangement might be compared with the cotyledons
of some animals.

The position of the placenta is, as a rule, on the anterior or posterior wall of the uterus, more
rarely on the fundus uteri, or laterally from the opening of the Fallopian tube, or over the
internal orifice of the cervix, the last constituting the condition of placenta praevia, which is
a very dangerous form of placental insertion, as the placenta has to be ruptured before birth
can take place, so that the mother often dies from hemorrhage. The umbilical cord may be
inserted in the centre of the placenta (insertio centralis), or more towards the margin (ins.
marginalis), or the chord may be fixed to the chorion laeve. Sometimes, though rarely, there
are small subsidiary placente (pl. succentwriata), in addition to the large one. When the
placenta consists of two halves, it is called duplex or bipartite, a condition said by Hyrtl to be
constant in the apes of the old world.

Structure of the Cord.—The umbilical cord (48 to 60 cm. [20 to 24 inches] long,
11 to 13 mm. thick) is covered by a sheath from the amnion. The blood-vessels
make about forty spiral turns, and they begin to appear about the 2nd month.
|The cause of the twisting is not well understood, but Virchow has shown that
capillaries pass from the skin for a short distance on the cord, and they do so
unequally, and it may be that this may aid in the production of the torsion.] It
contains two strongly muscular and contractile arteries, and one umbilical vein.
The two arteries anastomose in the placenta (yrtl). In addition, the cord contains
the continuation of the urachus, the hypoblastic portion of the allantois (fig. 665,
VIII, a), which remains until the 2nd month, but afterwards is much shrivelled.
The omphalo-mesenteric duct of the umbilical vesicle (N) is reduced to a thread-
like stalk (fig. 665, VIII, D). Wharton’s jelly surrounds the umbilical blood-
vessels. Wharton’s jelly is a gelatinous-like connective-tissue, consisting of
branched corpuscles, lymphoid cells, some connective-tissue fibrils, and even elastic
fibres. It yields mucin. It is traversed by numerous juice-canals lined by endo-
thelial cells, but other blood- and lymphatic-vessels are absent. Nerves occur
3—8-11 cm. from the umbilicus (Schott, Valentin). |

The foetal circulation, which is established after the detsio nares of the
allantois, has the following course (fig. 670) :—-The blood of the foetus passes from
the hypogastric arteries through the two umbilical arteries, through the umbilical
cord to the placenta, where the arteries split up into capillaries. The blood is

876 THE FETAL CIRCULATION.

returned from the placenta by the umbilical vein, although the colour of the blood
cannot be distinguished from the venous or impure blood in the umbilical arteries.
The umbilical vein (fig. 673, 3, «) returns to the umbilicus, passes upwards under
the margin of the liver, gives a branch to the vena porta (a), and runs as the
: ductus venosus into the inferior vena
cava, which carries the blood into the
right auricle. Directed by the Eusta-.
chian valve and the tubercle of Lower
(fig. 675, 6, ¢Z), the great mass of the
blood passes through the foramen ovale
into the left auricle, owing to the pre-
sence of the valve of the foramen ovale.
From the left auricle it passes into the
left ventricle, aorta, and hypogastric
arteries, to the umbilical arteries. The
blood of the superior vena cava of the
foetus passes from the right auricle into
the right ventricle (fig. 675, 6, Cs).
From the right ventricle it passes into
the pulmonary artery (fig. 675, 7, p),
and through the ductus arteriosus of.
Botalli (4) into the aorta. There are,
therefore, two streams of blood in the
right auricle which cross each other, the
descending one from the head through
the superior vena cava, passing in front
of the transverse one from the inferior
vena cava to the foramen ovale.] Only
a small amount of the blood passes
through the as yet small branches of the
pulmonary artery to the lungs (fig. 675,
7,1, 2). The course of the blood makes
it evident that the head and upper limbs
Fig. 670. of the foetus are nourished by purer
Course of the fcetal circulation (Cleland). blood than the remainder of the trunk,
which is supplied with blood mixed with the blood of the superior vena cava.
After birth, the umbilical arteries are obliterated, and become the lateral ligaments
of the bladder, while their lower parts remain as the superior vesical arteries. The
umbilical vein is obliterated, and remains as the ligamentum teres, or round
ligament of the liver, and so is the ductus venosus Arantii. Lastly, the foramen
ovule is closed, and the ductus arteriosus is obliterated, the latter forming the lig.
arteriosus.

The condition of the membranes where there are more foetuses than one :—(1) With twins
there are two completely separated ova, with two placente and two decidue reflexe. (2) Two
completely separated ova may have only one reflexa, whereby the placente grow together, while
their blood-vessels remain distinct. The chorion is actually double, but cannot be separated
into two lamellw at the point of union. (3) One reflexa, one chorion, one placenta, two
umbilical cords, and two amnia, The vessels anastomose in the placenta. In this case there

is one ovum with a double yelk, or with two germinal vesicles in one yelk. (4) As in (3), but
only one amnion, caused by the formation of two embryos in the same blastoderm of the same
germinal vesicle. she
Formation of the footal membranes.—The oldest mammals have no placenta or umbilical
vessels ; these are the Mammalia implacentalia, including the monetremata and marsupials.
The second group includes the Mammalia placentalia, Amongst these (a) the non-decidua
possess only chorionic villi supplied by the umbilical vessels, which project into the depression
of the uterine mucous membrane, and from which they are pulled out at birth (Pl. diffusa, e.g.

a
,
:

CHRONOLOGY OF HUMAN DEVELOPMENT. 877

pachydermata, cetacea, solidungula, camelide). In the ruminants, the villi are arranged in
groups or cotyledons, which grow into the uterine mucous membrane, from which they are
pulled out at birth. (b) In the deciduata, there is such a firm union between the chorionic
villi with the uterine mucous membrane, that the uterine part of the placenta comes away
with the foetal part at birth. In this case the placenta is either zonary (carnivora, pinnipedia,
elephant) or discoid (apes, insectivora, edentata, rodentia).

446, CHRONOLOGY OF HUMAN DEVELOPMENT.—Development during the 1st Month.
—At the 12-13th day the ovum is saccular (5°5 mm. and 3 mm. in diameter) ; there is simply
the blastodermic vesicle, with the blastoderm at one part, consisting of two layers ; the zona
pellucida beset with small villi (Reichert). At the 15th-16th day the ovum (5-6 mm.) is
covered with simple cylindrical villi. The zona pellucida consists of embryonic connective-
tissue covered with a layer of flattened epithelium. The primitive groove and the lamine
dorsales appear. Then follows the stage when the allantois is first formed. At the 15th-18th
day Coste investigated an ovum. It was 13°2 mm. long, with small branched villi; the
embryo itself was 2°2 mm. long, of a curved form, and with a moderately enlarged cephalic end.
The amnion, umbilical vesicle with a wide vitelline duct,.and the allantois were developed, the
last already united to the false amnion. The S-shaped heart lies in the cardiac cavity, shows a
cavity and a bulbus aorte, but neither auricles nor ventricles. The visceral arches and clefts
are indicated, but they are not perforated. The omphalo-mesenteric vessels forming the first
circulation on the umbilical vesicle are developed, the duct (vitelline) is still quite open, and
two primitive aorte run in front of the protovertebre. The allantois attached to the foetal
membranes is provided with blood-vessels. The two omphalo-mesenteric veins unite with the
two umbilical veins, and pass to the venous end of the heart. The mouth is in process of
formation. The limbs and sense-organs absent ; the Wolffian bodies probably present.

At the 20th day all the visceral arches are formed, and the clefts are perforated. The mid-
brain forms the highest part of the brain, while the two auricles appear in the heart. The con-
nection with the umbilical vesicle is still moderately wide. The embryo is 2°6-3°3-4 mm.
long, while the head is turned to one side (His). Ata slightly later period the temporal and
cervical flexures take place, and the hemispheres appear more prominently ; the vitelline duct
is narrowed, the position of the liver is indicated, while the limbs are still absent (His).

At the 21st day the ovum is 13 mm. long and the embryo 4-4'5 mm.; the umbilical vesicle
2°2 mm., and the intestine almost closed. Three branchial clefts, Wolffian bodies laid down,
and the first appearance of the limbs, three cerebral vesicles, auditory capsules present (R.
Wagner). Coste also observed, in addition, the nasal pits, eye, the opening for the mouth,
with the frontal and superior maxillary processes, the heart with two ventricles and two
auricles.

End of the 1st Month.—The embryos of 25-28 days are characterised by the distinctly
stalked condition of the umbilical vesicle and the distinct presence of limbs. Size of the ovum,
17°6 mm.; embryo, 13 mm.; umbilical vesicle, 5°5 mm., with blood-vessels.

2nd Month.—The embryos of 28-35 days are more elongated, and all the branchial clefts are
closed except the first. The allantois has now only three vessels, as the right umbilical vein
is obliterated. At the 5th week the nasal pits are united with the angle of the mouth by
furrows, which close to form canals at the 6th week (Toldt). At 35-42 days the nasal and oral
orifices are separated, the face is flat, the limbs show three divisions, the toes are not so sharply
defined as the fingers. The outer ear appears as a low projection at the 7th week. The
Wolffian bodies are much reduced in size. Length of body at 7th to 8th week, 1°6-4°1 em.

End of the 2nd Month.—Ovum, 64 cm.; villi, 1°3 mm. long; the circulation on the
umbilical vesicle has disappeared ; embryo, 26 mm. long, and weighs 4 grammes. Eyelids and
nose present, umbilical cord 8 mm. long, abdominal cavity closed, ossification beginning in the
lower jaw, clavicle, ribs, bodies of the vertebre ; sex indistinct, kidneys laid down.

3rd Month. —Ovum as large as a goose’s egg, beginning of the placenta, embryo 7-9-cm.,
weighing 20 grammes, and is now spoken of asa foetus, External ear well formed, umbilical
cord 7 cm. long. Beginning of the difference between the sexes in the external genitals,
umbilicus in the lower fourth of the linea alba.

4th Month.—Fcetus, 17 cm. long, weighing 120 grammes, sex distinct, hair and nails begin-
ning to be formed, placenta weighs 80 grammes, umbilical cord 19 cm. long, umbilicus above
the lowest fourth of the linea alba, contractions or movements of the limbs, meconium in the
intestine, skin with blood-vessels shining through it, eyelids closed.

5th Month. —Fcetus, length of body, 9°7-14°7 cm., total length 18 to 28 cm., weighing 284
grammes ; hair on the head and lanugo distinct ; skin still somewhat red and thin, and covered
with vernix caseosa (§ 287, 2), is less transparent ; weight of placenta, 178 grammes ; umbilical
cord, 31 em. long. é tai

6th Month.—Fetus, length of body, 15-18°7, total length, 29-37 cm., weighing 634
grammes ; lanugo more abundant ; vernix more abundant ; testicles in the abdomen ; pupillary

‘membrane and eyelashes present ; meconium in the large intestine.

7th Month,—Feetus, length of body, 18-22°8, total length, 35-38 cm., weighing 1218

878 CHRONOLOGY OF HUMAN DEVELOPMENT.

he descent of the testicles begins—one testicle in the inguinal canal, the eyes open,
the pupillary membrane often absorbed at its centre in the 28th week. 1 In the brain other
fissures are formed besides the primary ones. The foetus is capable of living independently.
At the beginning of this month there is a centre of ossification in the os calcis.

8th Month. —Fcetus, length of body, 24-27°8, total length 42 cm., wei hing 1°5 to 2 kilos,
(3°3 to 44 lbs.), hair of the head abundant, 1°3 cm. long, nails with a small margin, umbilicus
below the middle of the linea alba, one testicle in the scrotum. ;

9th Month. —Fcetus, length of body, 30-87, total length, 47-67 cm., weighing 2234 grammes,
and is not distinguishable from the child at the full period.

Fotus at the Full Period.—Length of body, 51 cm. [20 inches], weight, 3} kilos. [7 lbs.],
lanugo present only on the shoulders, skin white. The nails of the fingers project beyond the
tips of the fingers, umbilicus slightly below the middle of the lineaalba. The centre of ossifica-
tion in the lower epiphysis of the femur is 4 to 8 mm. broad. ;

Period of Gestation or Incubation (Schenk),

grammes, t

Days. | Days. Weeks. Weeks.
Coluber, ; 12 | Rabbit, : 32 Dog, . ' Sheep, ; 21
Hen, . - Loy Hare, ,. : Hox. x ; y | Goat, . : 22°
Duck, . ae | Weeks.| Foumart, . Roe, . ; 24
Goose, . ; 29 | Rat, . : 5 | Badger, ; 19 | Bear, - ; 39
Stork, . ; 42 | Guinea-pig, . fA WO. x j Small apes, . \
Cassowary, . 65 | Cat, . : 8 | Lion, 14 | Deer, . . 86-40
Mouse, . ; 24 | Marten, as | Pig, 17 | Woman, .- 40

Horse, Camel, 13 months ; Rhinoceros, 18 months ; and the Elephant, 24 months,
Limitation of the supply of O to eggs, during incubation, leads to the formation of dwarf chicks,

447. FORMATION OF THE OSSEOUS SYSTEM. —Vertebral Column.—The ossification of
the vertebre begins at the 8th to the 9th week, and first of all there is a centre in each verte-
bral arch, then a centre is formed in the body behind the chorda, which, however, is composed
of two closely res centres. At the 5th month the osseous matter has reached the surface,
the chorda within the body of the vertebra is compressed ; the three parts unite in the 1st
year. The atlas has one centre in the anterior arch and two in the posterior ; they unite at the
3rd year. The epistropheus has a centre at the 1st year. The three points of the sacral verte-
bre unite or anchylose between the 2nd and the 6th year, and all the vertebree (sacral) become
united to form one body between the 18th and 25th years. Each of the four coccygeal vertebrae
has a centre from the lst to 10th year. The vertebree in later years produce 1 to 2 centres in
each process ; 1 to 2 centres in each transverse process ; 1 in the mamillary process of the
lumbar vertebre ; and 1 in each articular process (8 to 15 years). Of the upper and under
surfaces of the body of a vertebra each forms an epiphysial thin osseous plate, which may still
be visible at the 20th year. Gree of the cells of the chorda are still to be found within the
intervertebral discs. As long as the coccygeal vertebra, the odontoid process, and the base of
the skull are cartilaginous, they still contain the remains of the chorda (H. Miiller). The
coocygeal vertebre form the tail, and they originally project in man like a tail (fig. 665, IX, T),
which is ultimately covered over by the growth of the soft parts (7s).

The ribs bud out from the protovertebre, and are represented on each vertebra. The thoracic
ribs become cartilaginous in the 2nd month and grow forwards into the wall of the chest,
whereby the seven upper ones are united by a median portion (Rathke), which represents the
position of one-half of the sternum, and when the two halves meet in the middle line the
sternum is formed. When this does not occur we have the condition of the cleft sternum,
At the 6th month there is a centre of ossification in the manubrium, then 4 to 13 in pairs in
the body, and 1 in the ensiform process. Each rib has a centre of ossification in its body at
the 2nd month, and at the 8th to 14th one in the tubercle and another in the head. These
anchylose at the 14th to 25th year. Sometimes cervical ribs are present in man, and they are
name y developed in birds.

he skull.—'T'he chorda extends forwards into the axial part of the base to the sphenoid bone.
The skull at first is membranous, or the primordial cranium ; at the 2nd month the basal
portion becomes cartilaginous, including the occipital bone, except the upper half, the anterior
and posterior part and wee of the sphenoid bone, the petrous part and mastoid process of the
temporal bone, the ethmoid with the nasal septum, and the cartilagintts part of the nose. The

other parts of the skull remain membranous, so that there is a cartilaginous and membranous

rimordial cranium.
I, The occipital bone has a centre of ossification in the basilar part at the 3rd month, and
one in the condyloid part and another in the fossa cerebelli, while there are two centres in the
membranous cerebral fosse. The four centres of the body unite during intra-uterine life. All
the other parts unite at the 1st to 2nd year. '
Il. The henoid.—From the 8rd month it has two centres in the sella turcica, two in

the suleus caroticus, two in both great wings, which also form the lamina externa of the ptery-

DEVELOPMENT OF THE OSSEOUS SYSTEM. 879

goid process, while the non-cartilaginous and previously formed inner lamina arises from the
superior maxillary process of the first branchial arch. During the first half of foetal life these
centres unite as far as the great wings ; the dorsum selle and the clinoid process, as far as the
synchondrosis spheno-occipitalis, are still cartilaginous, but they ossify at the 13th year.

III, The pre-sphenoid at the 8th month has two centres in the small wings and two in the body,
At the 6th month they unite, but cartilage is still found within them even at the 13th year.

IV. The ethmoid has a centre in the labyrinth at the 5th month, then in the 1st yeara centre
in the central lamina. They unite about the 5th or 6th year.

V. Amongst the membranous bones are the inner lamina of the pterygoid process (one
centre), the upper half of the tabular plate of the occipital (two points), the parietal bone (one
centre in the parietal eminence), the frontal bone (one double centre in the frontal eminence),
three small centres in the nasal spine, spina trochlearis and zygomatic process, nasal (one
centre), the edges of the parietal bones (one centre), the tympanic ring (one centre), the
lachrymal, vomer, and intermaxillary bone.

The facial bones are intimately related to the transformations of the branchial arches and
branchial clefts (fig. 671). The median end of the first branchial arch projects inwards from
each side towards the large oral aperture. It has two pro-
cesses, the superior maxillary process which grows more
laterally towards the side of the mouth, and the inferior
maxillary process, which surrounds the lower margin of
the mouth (fig. 665, 1X). From above downwards there
grows as an elongation of the basis cranii the frontal pro-
cess (s), a broad process with a point (y) at its lower and
outer angle, the inner nasal process. The frontal and the
superior maxillary processes (7) unite with each other in
such a way that the former projects between the two latter.
At the same time there is anchylosed with the superior
maxillary process the small external nasal process (7), a
prolongation of the lateral part of the skull, and lying
above the superior maxillary process. Between the latter
and the outer nasal process is a slit leading to the eye (a).
Thus the mouth is cut off from the nasal apertures which
lie above it. But the separation is continued also within
the mouth ; the superior maxillary process produces the
upper jaw, the nasal process, and the intermaxillary pro-
cess (Goethe)—the latter is present in man, but is united ;
to the upper jaw. The intermaxillary bone, which in (%*12). 4, eye; at, atrium or
many animals remains as a separate bone (os incisivum), Primitive auricle of heart ; b, aortic
carries the incisor teeth. At the 9th week the hard palate bulb ; K’, K”, K’”, first (mandi-
is closed, and on it rests the septum of the nose, descend- bular), second (hyoid), third (1st
ing vertically from the frontal process. ‘The lower jaw is branchial) visceralarch; m,mouth;
formed from the inferior maxillary process. Atthecircum- % Superior, and w, inferior max-
ference of the oral aperture the lips and the alveolar walls illary process ; s, mid-brain ; ¥,
are formed. The tongue is formed behiud the point of the part of head and fore-brain ; 2,
union of the second and third branchial arches (His); while, Ventr icle of heart.
according to Born, it is formed by an intermediate part between the inferior maxillary processes.

These transformations may be interrupted. If the frontal process remains separate from the

Head of embryo rabbit of 10 days

Fig. 672. Fig, 673.
Fig. 672.—Hare lip on the left side. Fig. 673.—Inner view of the lower jaw of an embryo pig
3 inches long (x34). mk, Meckel’s cartilage ; d, dentary bone ; cr, coronoid process; a7,
articular process (condyle) ; ag, angular process ; m/, malleus ; mb, manubrium.

superior maxillary processes, then the mouth is not separated from the nose, . This separation
may occur only in the soft parts, constituting hare-lip (fig. 672) ; or it may involve the hard

880 THE BRANCHIAL CLEFTS AND THEIR RELATION TO NERVES.

nstituting cleft te. Both conditions may occur on one or both sides. From the
sores Raper of the first Fe nchial arch are formed the madleus (ossified at the 4th month), and

eckel’s cartilage (fig. 673), which proceeds from the latter behind the tympanic ring as a
long cartilaginous process, extending along the inner side of the lower jaw, almost to its middle.
It disappears after the 6th month ; still its posterior part forms the internal lateral ligament of
the maxillary articulation. Near where it leaves the malleus is the processus Folii (Baumiiller),
A part of its median end ossifies, and unites with the lower jaw. The lower jaw is laid down in
inembrane from the first branchial arch, while the angle and condyle are formed from a
cartilaginous process. The union of both bones to form the chin occurs at the 1st year. From
the superior maxillary process are formed the inner lamella of the pterygoid process, the palatine
process of the upper jaw, and the palatine bone at the end of the 2nd month, and lastly the
inalar bone. : ;

The second arch [hyoid], arising from the temporal bone, and running parallel with the
tirst arch, gives rise to the stapes (although according to Salensky, this is derived from the first
arch), the eminentia pyramidalis, with the stapedius muscle, the incus, the styloid process of
the temporal bone, the (formerly cartilaginous) stylohyoid ligament, the smaller cornu of the
liyoid bone, and lastly the glosso-palatine arch (His). : |

“The third arch (thyro-hyoid) forms the greater cornu and body of the hyoid bone and the
pharyngo-palatine arch (//7s).

The fourth arch gives rise to the thyroid cartilage (Hs).

Branchial Clefts.—The first branchial or visceral is represented by the external auditory
meatus, the tympanic cavity, and the Eustachian tube ; all the other clefts close. Should one
or other of the clefts remain open, a condition that is sometimes hereditary in some families, a
cervical fistula results, and it may be formed either from without or within. Sometimes only
a blind diverticulum remains. Branchiogenic tumours and cysts depend upon the branchial
arches (2. Volkmann).

(Relation of Branchial Clefts to Nerves.—It is important to note that the clefts in front of
the mouth (pre-oral), and those behind it (post-oral), have a relation to certain nerves. The
lachrymal slit between the frontal and nasal processes is supplied by the first division of
the trigeminus. The nasal slit between the’superior maxillary process and the nasal process is
supplied by the bifurcation of the third nerve. The oval cleft, between the superior maxillary
processes and the mandibular arch, is supplied by the second and third divisions of the trige-
minus. The first post-oral or tympanic-Eustachian cleft, between the mandibular arch (1st) ~
and the hyoid arch, is supplied by the portio dura. The next cleft is supplied by the glosso-
pharyngeal, and the succeeding clefts by branches of the vagus. ]

The thymus and thyroid glands are formed as paired diverticula from the epithelium cover-
ing the branchial arches. The epithelium of the last two clefts does not disappear (pig), but
proliferates and pushes inwards cylindrical processes, which develop into two epithelial vesicles,
the paired commencement of the thyroid glands. These vesicles have at first a central slit,
which communicates with the pharynx (Wdlfler). According to His, the thyroid gland appears
as an epithelial vesicle in the region of the 2nd pair of visceral arches in front of the tongue—
in man at the 4th week. Solid buds, which ultimately become hollow, are given off from the
eavity in the centre of the embryonic thyroid gland. The two glands ultimately unite together.
The only epithelial part of the thymus which remains is the so-called concentric corpuscles
(p. 154). According to Born, this gland is a diverticulum from the 3rd cleft, while His ascribes
its origin to the 4th and 5th aortic arches in man at the 4th week. The carotid gland is of
epithelial origin, being a variety of the thyroid (Stieda).

The Extremities.—The origin and course of the nerves of the brachial plexus (p. 616) show
that the upper extremity was originally placed much nearer to the cranium, while the position
of the posterior pair corresponds to the last lumbar and the 3rd or 4th sacral vertebree (His).

The clavicle, according to Bruch, is not a membrane bone, but is formed in cartilage like
the furculum of birds (Gegenbaur). At the 2nd month it is four times as large as the upper
limb ; it is the first bone to ossify at the 7th week. At puberty a sternal epiphysis is formed.
Episternal bones must be referred to the clavicles (Gétte). Ruge regards pieces of cartilages
existing between the clavicle and the sternum as the analogues of the episternum of animals.
The clavicle is absent in many mammals (carnivora) ; it is very large in flying animals, and in
the rabbit is half membranous. The furculum of birds represents the united clavicles.

The scapula at first is united with the clavicle (Rathke, Géotte), and at the end of the 2nd
month it has a median centre of ossification, which rapidly extends. Morphologically, the
accessory centre in the coracoid process is interesting ; the latter also forms the upper part of
the articular surface. -In birds the corresponding structure forms the coracoid bone, and is
united with the sternum; while in man pea a membranous band stretches from the tip of the
coracoid process to the sternum. The long, basal, osseous strip corresponds to the supra-
scapular of many animals. The other centres of ossification are—one in the lower angle,
two or three in the acromion, one in the articular surface, and an inconstant one in the spine.
Complete consolidation occurs at puberty. ! Sey G7 1 ToLteqee

The humerus ossifies at the 8th to the 9th week in its shaft. The other centres ‘are—one in

DEVELOPMENT OF THE BONES OF THE LIMBS. 881

the upper epiphysis, and one in the capitellum (1st year) ; one in the great tuberosity and one
in the small tuberosity (2nd year) ; two in the condyles (5th to 10th year) ; one in the trochlea
(12th year). The epiphyses unite with the shaft at the 16th to 20th year.

The radius ossifies in the shaft at the 3rd month. The other centres are—one in the lower
epiphysis (5th year), one in the upper (6th year), and an inconstant one in the tuberosity, and
one in the styloid process. They unite at puberty.

The ulna also ossifies in the shaft at the 3rd month. There is a centre in the lower end
(6th year), two in the olecranon (11th to 14th year), and an inconstant one in the coronoid
process, and one in the styloid process. They consolidate at puberty.

The carpus is arranged in mammals in two rows. The first row contains three bones—the
radial, intermediate, and ulnar bones. In man these are represented by the scaphoid, semi-
lunar, and cuneiform bones; the pisiform is only a sesamoid bone in the tendon of the
flexor carpi ulnaris. The second row really consists of as many bones as there are digits (e.9.,
salamander). In man the common position of the 4th and 5th fingers is represented by the
unciform bone. Morphologically, it is interesting to observe that an os centrale, corresponding
to the os carpale centrale of reptiles, amphibians, and some mammals, is formed at first, but
disappears at the 3rd month, or unites with the scaphoid. Only in very rare cases is it
persistent. All the carpal bones are cartilaginous at birth. They ossify as follows :—Os
magnum, unciform (lst year), cuneiform
(3rd year), trapezium, semilunar (5th year),
seaphoid (6th year), trapezoid (7th year),
and pisiform (12th year).

The metacarpal bones have a centre in
their diaphyses at the end of the 8rd
month, and so have the phalanges. All
the phalanges and the first bone of the
thumb have their cartilaginous epiphyses
at the central end, and the other metacarpal
bones at the peripheral end,-so that the
first bone of the thumb is to be regarded
as a phalanx. The epiphyses of the meta-
carpal bones ossify at the 2nd, and: those
of the phalanges at the 8rd year. They
consolidate at puberty.

The innominate bone, when carti-
laginous, consists of two parts—the pubis
and the ischium (Rosenberg). Ossification
begins with three centres—one in the ilium
(3rd to 4th month), one in the descending
ramus of the ischium (4th to 5th month),
one in the horizontal ramus of the pubis
(5th to 7th month). Between the 6th to
the 14th year, three centres are formed
where the bodies of the three bones meet
in the acetabulum, another in the super-
ficies auricularis, and one in the symphysis.

Other accessory centres are :—One in the Fic. 674

anterior inferior spine, the crests of the ; sigs a4 :

ilium, the tuberosity and the spine of the Centres of ossification of the innominate bone.
ischium, the tuberculum: pubis, eminentia iliopectinea, and floor of the acetabulum. At first
the descending ramus of the pubis and the ascending ramus of the ischium unite at the 7th
to 8th year; the Y-shaped suture in the acetabulum remains until puberty (fig. 674). See

The femur has its middle centre at the end of the 2nd month. At birth, there is a centre in
the lower epiphysis; slightly later in the head. In addition, there is one in thé great
trochanter (3rd to 11th year), one in the lesser trochanter (13th to 14th year), two in the con-
dyles (4th to 8th year); all unite about the time of puberty. The patella is a sesamoid bone in
the tendon of the quadriceps femoris. It is cartilaginous at the 2nd month, and ossifies from
the 1st to the 3rd year.

The tarsus generally resembles the carpus. The os calcis ossifies at the beginning of the 7th
month, the astragalus at the beginning of the 8th month, the cuboid at the end of the 10th,
the scaphoid (1st to 5th year), the I. and II. cuneiform (8rd year), and the III. cuneiform (4th
year). An accessory centre is formed in the heel of the caleaneum at the 5th to 10th year,
which consolidates at puberty. :

The metatarsal bones are formed like the metacarpals, only later.

[Histogenesis of Bone.—The great majority of our bones are laid down in cartilage, or are
preceded by a cartilaginous stage, including the bones of the limbs, backbone, base of the skull,
sternum, and ribs. These consist of solid masses of hyaline cartilage covered by a membrane,

3K

882 DEVELOPMENT AND GROWTH OF BONE,

ich is i i ‘th and ultimately becomes the periosteum. ‘The formation of bone, when
eeented 94 pore fai is called cadechoutval bone, Bans bones, such as the tabular bones of
the vault of the cranium, the facial bones, and part of the lower jaw, are not preceded by
cartilage. In the latter there is merely a membrane present, while from and in it the future bone
is formed. It becomes the future periosteum as well, This is called the intra-membranous

or periosteal mode of formation. ]

[Endochondral Formation. —(1) The cartilage has the shape of ‘the future bone only in

iniature, and it is covered with periosteum. In the cartilage an opaque spot or centre of
sasifieation appears, due to the deposition of lime-salts in its matrix. The cartilage cells
proliferate in this area, but the first bone is formed under the periosteum in the shaft, so
that an osseous case like a muff surrounds the cartilage. This bone is formed by the sub-
periosteal osteoblasts. (2) Blood-vessels, accompanied by osteoblasts and connective-tissue,
grow into the cartilage from the osteogenic layer of the periosteum (periosteal processes of
Virchow), so that the cartilage becomes channelled and vascular, As these channels extend they
open into the already enlarged cartilage lacune, absorption of the matrix taking place, while
other parts of the cartilaginous matrix become calcified. Thus a series of cavities, bounded by
calcified cartilage—the primary medullary cavities—are formed. They contain the primary-or
cartilage marrow, consisting of blood-vessels, osteoblasts, and osteoclasts, carried in from the osteo-
genic layer of the periosteum, and of course the cartilage cells that have been liberated from their
Jacune. (3) The osteoblasts are now in the interior of the cartilage, where they dispose them-
selves on the calcified cartilage, and secrete or form around them an osseous matrix, thus enclosing
the calcified cartilage, while the osteoblasts themselves become embedded in the products of their
own activity and remain as kone-corpuscles, Bone therefore is at first spongy bone, and as the
primary medullary spaces gradually become filled up by new osseous matter it becomes denser,
while the calcified cartilage is gradually absorbed. It is to be remembered that, part passwu
with the deposition of the new bone, bone and cartilage are being absorbed by the osteoclasts. ]

Chemical Composition of Bone.—Dry bone contains § of organic matter or ossein, from which
gelatin can be extracted by prolonged boiling ; and about % mineral matter, which consists of
neutral calcic phosphate, 57 per cent.; calcic carbonate, 7 per cent.; magnesic phosphate, 1 to
2 per cent.; calcic fluoride, 1 per cent., with traces of chlorine; and water, about 23 per cent
The marrow contains fluid fat, albumin, hypoxanthin, cholesterin, and extractives, The red
marrow contains more iron, corresponding to its larger proportion of hemoglobin (Nasse).

[The medullary cavity of a long bone is occupied by yellow marrow, which contains about
96 per cent. of fat. The red marrow occurs in the ends of long bones, in the flat bones of the
skull, and in some short bones. It contains very little fat, and is really lymphoid in its
characters, being, in fact, a blood-forming tissue (p. 12).]

Growth of capper a, Sane grow in thickness by the deposition of new bone from the
periosteum, the osteoblasts becoming embedded in the osseous matrix to form the bone-corpuscles.
Some of the fibres of the connective-tissue, which are caught up, as it were, in the process,
remain as Sharpey’s fibres, which are calcified fibres of white fibrous tissue, bolting together the
ae ea lamelle. [Miiller and Schifer have shown that there are also fibres in the peripheric
amelle, comparable to yellow elastic fibres ; they branch, stain deeply with magenta, and are
best developed in the bones of birds. ]

[At the same time that bone is being deposited on the surface, it is being absorbed in the
marrow cavity by the action of the osteoclasts, so that a metallic ring placed round a bone ina
young animal ultimately comes to lie in the medullary cavity (Duhamel). The. growth in
length takes place by the continual growth and ossification of the epiphysial cartilage. The
cartilage is gradually absorbed from below, but it proliferates at the same time, so that what is
lost in one direction is more than made up in the other (J. Hunter).

When the growth of bone is at an end, the epiphysis becomes united to the diaphysis, the
epiphysial cartilage itself becoming ossified. It is not definitely proved whether there is an
eae expansion or growth of the true osseous substance itself, as maintained by Wolff

, 9).

[Howship’s Lacunse.—The osteoclasts or myeloplaxes are large multinuclear giant-cells,
which erode bone. They can be seen in great numbers lying in small depressions porreaponiaas
to them—Howship’s lacune—on the fang of a temporary tooth, when it is being absorbed.
They are readily seen in a microscopical section of spongy bones with the soft parts preserved. ]

The form of a bone is influenced by external conditions. The bones are stronger the greater
the activity of the muscles acting on them, If pressure acting normally upon a bone be
removed, the bone develops in the direction of least resistance, and becomes thicker in that
direction. Bone develops more slowly on the side of the greatest external pressure, and it is
curved by unilateral pressure (Lessha/t).

448. DEVELOPMENT OF THE VASCULAR SYSTEM.—Heart.—{The heart appears as &
solid mass of cells in the splanchnopleure, at the front end of the embryo, immediately under

the ‘‘ fore-gut.” hy soon a cavity appears in this mass of cells ; some of the latter float free
in the fluid, while t

e cellular wall begins to pulsate. rhythmically. ‘This hollow cellular

a “a1

DEVELOPMENT OF THE HEART, 883

structure elongates into a tube, which very soon assumes a shape somewhat like an S (fig. 675,1)],
and there are indications of its being subdivided into (a) an upper aortic part with the bulbus
arteriosus ; (b) a middle or ventricular part; and (v), a lower venous or auricular part. The
heart then curves on itself in the form of a horse-shoe (2), so that the venous end (4) comes to
lie above and slightly behind the arterial end, On the right and left side, respectively, of the
venous part is a blind hollow outgrowth, which forms the large auricle on each side (8, 0, 0;).
The flexure of the body of the heart corresponding to the great curvature (2, V) is divided into
two large compartments (3), the division being indicated by a slight depression on the surface.
The large truncus venosus (4, v), which joins with the middle of the posterior wall of the
auricular part, is composed of the superior and inferior vene cave. This common trunk is
absorbed at a later period into the enlarging auricle, and thus arise the separate terminations
of the superior and inferior vene cave. . In man, the heart soon comes to lie in a special cavity,
which in part is bounded by a portion of the diaphragm (His). At the 4th to 5th week, the heart
begins to be divided into a right and a left half. Corresponding to the position of the vertical
ventricular furrow, a septum grows upwards vertically in the interior of the heart, and divides

Fig. 675.

Development of the heart. 1, Early appearance of the heart—a, aortic part, with the bulbus,
b; v, venous end. 2, Horse-shoe shaped curving of the heart—a, aortic end, with the
bulbus, b; V, ventricle; A, auricular part. 38, Formation of the auricular appendages,
0, 0,, and the external furrow in the ventricle. 4, Commencing division of the aorta,
p, into two tubes, @ 5, View from behind of the opened auricle, v, v, into the Z, and
£, ventricles, and between the two latter the projecting ventricular septum, while the aorta
(2) and pulmonary artery (p) open into their respective ventricles. 6, Relation of the
orifices of the superior (Cs) and inferior vena cava (CZ) to the auricle (schematic view from
above)—2, direction of the blood of the superior vena cava into the right auricle ; y,.that of
the inferior cava to the left auricle ; ¢Z, tubercle of Lower. 7, Heart of the ripe foetus—AR,
right, Z, left ventricle ; a, aorta, with the innominate, C, ¢, carotid, c, and left subclavian
artery, s; B, ductus arteriosus ; y, pulmonary artery, with the small branches Z and 2, to

the lungs,

the ventricular part into a right and left ventricle (5, R, Z). There is a constriction in the
heart, between the auricular and ventricular portions, forming the canalis auricularis, It
contains a communication between the auricle and both ventricles, lying between an anterior
and posterior projecting lip of endothelium, from which the auriculo-ventricular valves . are
formed (F. Schmidt). The ventricular septum grows upwards towards the canalis auricularis,
and is complete at the 8th week. ‘Thus, the large undivided auricle communicates by a right
and left auriculo-ventricular opening with the corresponding ventricle (5). At the same time
two septa (4, p a) appear in the interior of the truncus arteriosus (4, y), which ultimately meet,
and thus divide this tube into two tubes (5, a p), the latter forming the aorta and pulmonary

884 DEVELOPMENT OF THE AORTIC ARCHES.

> and are disposed towards each other like the tubes in a double-barrelled gun. The
canes pooeties Seanwigde until it meets the ventricular septum (5), so that the right ventricle
comes to be connected with the pulmonary artery, and the left with the aorta. The division of
the truncus arteriosus, however, takes place only in the first part of its course. The division

does not take place above, so that the pulmonary artery and aorta unite in one common trunk

above. ‘This communication between the pulmonary artery and the aorta is the ductus
josus Botalli (7, B). ; oe! 1 F
ab the auricle nn grows from the front and behind, ending internally with a concave
margin. The vena cava superior (6, Cs) terminates to the right of this fold, so that its blood
will tend to go towards the right ventricle, in the direction of the arrow in 6, x, The cava
inferior, on the other hand (6, Ci), opens directly opposite the fold. On the left of its orifice
the valve of the foramen ovale is formed by a fold growing towards the auricular fold, so that
the blood-current from the inferior vena cava goes only to the left, in the direction of the
arrow, y; on the right of the orifice of the cava, and opposite the fold, is the Eustachian valve,
which, in conjunction with the tubercle of Lower (¢Z), directs the stream from the inferior
vena cava to the left into the left auricle, through the pervious foramen ovale, Compare the
fwtal circulation (p. 876). After birth, the valve of the foramen ovale closes that aperture,
while the ductus arteriosus also becomes impervious, so that the blood of the pulmonary artery
is forced to go through the pulmonary branches proceeding to the expanding lungs. Some-
times the foramen ovale remains pervious, giving rise to serious symptoms after a time, and
constituting morbus ceruleus,
Arteries. —With the formation of the branchial arches and clefts, the number of aortic arches
on each side becomes increased to 5 (fig. 676), which run above and below each branchial cleft,

Fig. 676.

The aortic arches. 1. The first position of the 1, 2, and 8 arches. 2. 5 aortic arches ; éa,
common aortic trunk ; ad, descending aorta. 3. Disappearance of the upper two arches on
each side—S, subclavian artery ; v, vertebral artery ; aa, axillary artery. 4. Transition
to the final stage—P, pulmonary artery ; 4, aorta; dB, ductus arteriosus (Botalli) ; 8,
right subclavian, united with the right common carotid, which divides into the internal
(Ci) and external carotid (Ce) ; az, axillary ; v, vertebral artery.

in a branchial arch, and then all reunite behind in a common descending trunk (2, ad) (Rathke).
These blood-vessels remain only in animals that breathe by gills. In man, the upper two
arches disappear completely (3). When the truncus arteriosus divides into the pulmonary
artery and the aorta (4, P, A), the lowest arch on the left side, with its origin, forms the
pulmonary artery (4), and it springs from the right side of the heart. Of these the eft lowest
arch forms the ductus arteriosus (dB), and from the commencement of the latter proceed the
pulmonary branches of the pulmonary artery. Of the remaining arches which are united with the
aorta, the left middle one (7.¢., the fourth left) forms the permanent aortic arch into which the
ductus arteriosus opens, while the right one (fourth) forms the subclavian artery; the third
arch forms on each side the origin of the carotids (Ci, Ce). The arteries of the first and second
circulations have been referred to already (p. 870). When the umbilical vesicle, with its
primary circulation, diminishes, only one omphalo-mesenteric artery is present, which gives
a branch to the intestine. At a later period, the omphalo-mesenteric arteries atrophy, while
the artery to the intestine—the superior mesenteric—becomes the largest of all, it being
originally derived from one of the omphalo-mesenteric arteries.

Veins of the Body.—The veins first formed in the body of the embryo itself ave the two
cardinal veins ; on each side an anterior (fig. 677, I, cs), and a posterior (ci), which proceed
towards the heart and unite on each side to form a large trunk, the duct of Cuvier (DC), which
passes into the venous part of the heart. The anterior cardinal veins give off the subclavian
veins (bb) and the common jugular veins, which divide into the external (Je) and internal

(Ji) j veins. In addition, there is a transverse anastomosing branch passing — |

from the left (where it divides) to the right, which joins their trunk lower down. In the

=

ae. Gy

DEVELOPMENT OF THE VEINS. 885

arrangement (II) this anastomosis (4s) becomes very large to form the left innominate vein,
while with the growth of the arms the subclavian veins increase (bb) ; and lastly, the calibre of
the jugular vein changes, the internal jugular (Ji) becoming very large, and the external jugular
(Je) smaller. In some animals, ¢.g., the dog and rabbit, the large embryonic size is retained.
The part of the left superior cardinal vein, from the anastomosis downwards to the left duct of
Cuvier, disappears. The posterior cardinal veins divide in the pelvis into the hypogastric
(I, %) and external iliac (f, f). The inferior cava at first is very small (I, Vc), divides at the
entrance to the pelvis, and on each side
goes into the point of division of the I. T.
cardinal veins. There is also a trans-
verse ascending anastomosis between the
right and left cardinal veins. For the
final arrangement, the cava inferior (II,
C7) dilates, and with it the hypogastric
and external iliac vein on each side. The
right cardinal vein remains very small
(Vena azygos, Az), and also the lower
part from the left one to the transverse
anastomosis. The latter itself also re-
mains very small (Vena hemiazygos, Hz).
On the other hand, the upper part above
the anastomosis to the duct of Cuvier
disappears. Lastly, the common large
venous trunk is so absorbed into the wall
of the auricle (V) that both vene cave
have each a separate orifice (p. 876).
The embryonic condition of the veins
persists in fishes.

Veins of the First and Second Circu-
lation, and Portal System.—The two
omphalo-mesenteric veins (om, 0m,) open
into the posterior or venous end of the
tubular heart (fig. 678, 1,.H). The right
vein, however, disappears very soon. As Fig. 677.
soon as the allantois is formed, the two J], First appearance of the veins of the embryo. IT,
umbilical veins join the truncus venosus “ Thejr transformations to form the final arrange-
(1, wu, u,). At first the omphalo-mesen- — enk.
teric veins are larger than the umbilical
veins ; at a later period this is reversed, and the right umbilical vein disappears. As soon as
veins are formed within the body proper of the embryo, the inferior cava also opens into the

H
RY L
om om,
U uy,

3 om,

Fig. 678.

Development of the veins and portal system. H, heart; R, Z, right and left side of the body;
om, right omphalo-mesenteric vein ; 07, left; wu, right umbilical vein ; 2, left; Cz, vena
cava inferior ; @, vene advehentes; 7, vene revehentes; D, intestine: m, mesenteric
vein ; 4, J, splenic vein ; 2, J, liver.

truncus venosus (2, Cz). Gradually, the umbilical vein (2, ,) becomes the chief trunk, while
the small omphalo-mesenteric (2, 0m) carries little blood.
Portal System,—The umbilical and omphalo-mesenteric veins pass in part dire tly under the

886 FORMATION OF THE INTESTINAL CANAL.

i © reach the heart. They send branches—carrying arterial blood—to the liver, and the
iatearieoe round these veoetla: These branches are the vene advehentes (2 and 3, a). . The
blood circulating through the liver from the venz advehentes is returned by other veins, the
venm revehentes (2 and 3, 7), which reunite at the blunt margin of the liver with the chief
trunk of the umbilical vein. The umbilical vein (8, %) and the omphalo-mesenteric vein
(3, om,) anastomose in the liver. When the intestine develops (3, D), the mesenteric
vein (mJ) opens into the omphalo-mesenteric vein, and the splenic vein as well (4, 2),
when the spleen is formed. At a later period, when the omphalo-mesenteric vein (4, om)
disappears, the vein from the intestine now becomes the common trunk of the pera
united vessels. It unites in the liver with the umbilical vein to form the trunk of the vena
porte. When, after birth, the umbilical vein disappears (4, w,), the mesenteric alone remains
as the portal vein. As the ductus venosus is obliterated, the portal vein must send its blood
through the liver, and thus the portal circulation is completed.

449, FORMATION OF THE INTESTINAL CANAL,—The primitive intestine, or gut,
consists of a straight tube proceeding from the head to the tail. ‘he vitelline duct is inserted
at that point, which at ateior period corresponds to the lower part of the ileum. At the 4th
week the tube makes a slight bend toward the umbilicus (fig. 679, I). As already mentioned,
the vitelline duct
is obliterated, re-
maining only fora |
time as a thread
attached to the in-
testine, being still
visible at the 3rd
month. Sometimes }
itremainsasashort 4
blind tube com-
municating with
the intestine. This
is the so-called
““true intestinal
diverticulum” ; oc-
casionally a cord
Fig. 679. Fig. 680. —the obliterated

Fig. 679.—Development of the intestine. », stomach; 0, insertion of the 0™Phalo-mesente-
vitelline duct ; ¢, small intestine ; c, colon; 7, rectum. Fig. 680.—For- 1° vesse]s—passes
mation of the lungs. A, Diverticula of the lungs as double sacs—xk, {rom it to the um-
mesoblastic layer ; 7, hypoblastic layer ; m, stomach; s, esophagus, B, Dilicus. In very
Further branching of the langs—t, trachea ; }, e, bronchi ; 7, projecting Tare cases, the duct

vesicles, may remain open
- , : as far as the um- |
bilicus, forming a congenital fistula of the ileum, or it may give rise to cystic formations (I. dl

Koth). Ina human feetus at the 4th week, His distinguished the cavity of the mouth, pharynx,
cesophagnus, stomach, duodenum, mesenterial intestine, and the hind-gut, with the cloaca. The
intestine then forms the jirst coil (fig. 679, II) by rotating on itself at the intestinal umbilicus,
so that the lower part of the intestine lying next the knee-like bend comes to lie above, while
the upper part lies below. From the lower part of this loop, there proceed the coils of the
small intestine (III, ¢), which gradually grow longer. From the upper limb of the loop,
which also elongates, the large intestine is formed ; first the descending colon, then by elonga-
tion the transverse colon, and lastly the ascending colon.

Glands.—By diverticula, or protrusions from the intestine, the various glands are formed.
The cells of the hypoblast ponerse and take part in the process, as they form the secretory
cells of the glands, while the mesoblastic part of the solanohie leure forms the membranes of
the glands, giving them their shape. The diverticula are as follows :—

1, The salivary glands, which grow out from the oral cavity at first as simple solid buds,
but afterwards become hollow and branched. [The salivary glands are deve oped from the
epiblast lining the mouth (stomodeum). ]

2. The lungs, which arise as two ‘separate hollow buds (fig. 680, A, 2), and ultimately have
only one common duct, are protrusions from the cesophagus. The upper part of the united
tracheal tube forms the larynx. The epiglottis and the thyroid cartilage originate from the
ns which forms the tongue (Ganghofner). The two hollow spheres grow and ramify like
branched tubular Y cep with hollow processes (B, f). In the first period of development, there
is no essential difference between the epithelium of the bronchi and that of the primitive air-
zonicues = (Sale) ar renand marerenel pagenles, however, are not developed in this way.

of the mesogastrium is) ; igin
ally item tia tikowes ga bf the 2nd month (His); the latter are org

DEVELOPMENT OF THE REPRODUCTIVE ORGANS. 887

' 3. The pancreas arises in the same way as the salivary glands, but is not visible at the 4th

week (His).

4. The liver begins very early, and appears as a diverticulum, with two hollow primitive hepatic

ducts, which branch and form
bile-ducts. At their periphery
they penetrate between the solid
masses of cells—the liver-cells—
which are derived from the hypo-
blast. At the 2nd month the
liver is a large organ, and secretes
at the 3rd month (§ 182).
5. In birds two small blind
sacs are formed from the hind-gut.
6. The foetal respiratory organ,
the allantois, is treated of speci-
“I (§ 444).
eritoneum and Mesentery. —
The inner surface of the celom,
or body-cavity, the surface of the
intestine, and its mesentery are
covered by a serous coat—the
peritoneum. At first the simple
intestine is contained in a fold,
or duplicature of the peritoneum ;
on the stomach, which is merely
at first a spindle-shaped dilata-
tion of the tube placed vertically,
it is called mesogastrium. After-
wards, the stomach turns on its
side, so that the left surface’ is
directed forwards and the right
backwards. Thus, the insertion
of the mesogastrium, which ori-
ginally was directed backwards (to

Ss
=

PD PS

“
aw

a et cote

SS
~,

BLE,

i

iT

Fig. 681.

Formation of the omentum. I and II.—j/g, gastro-hepatic
ligament ; m, great, , lesser curvature of the stomach ;
8, posterior, and 7, anterior fold or plate of the omentum ;
mc, mesocolon; c, colon. III.—Z, liver; ¢, small intes-
tine; 6, mesentery ; ~, pancreas; d, duodenum ; 7, rectum ;
NV, great omentum.

the vertebral column), is directed to the left ; the line of insertion forming the region of the

Fig. 682.

Development of the internal generative organs, I., Undifferentiated condition—D, reproductive
gland, lying on the tubules of the Wolffian body ; W, Wolffian duct; M, Miillerian duct ;
S, uro-genital sinus. - IJ., Transformations in the female—F, fimbria, with the hydatid,
hi; T, Fallopian tube ; U, uterus ; S, uro-genital sinus; O, ovary; P, parovariun. III.,
Transformations in the male—H, testis; E, epididymis, with the hydatid, h; a, vas
aberrans ; V, vas deferens; S, uro-genital sinus; w, male uterus. 4, d, hind-gut; a,
allantois ; uw, urachus ; K, cloaca. 5, M, rectum ; m, perineum; 8, position of the bladder;

_S, uro-genital sinus,

great curvature, which becomes still more curved, From the great curvature, the mesogastrium
becomes elongated like a pouch (fig, 681, I and II, s, 2), constituting the omental sac, which

888 _ DEVELOPMENT OF THE URINARY APPARATUS.

extends so far downwards as to pass over the transverse colon and the loops of the small intestine
(III, V). As the mesogastrium originally consists of two plates, of course the omentum must
consist of four plates. At the 4th month, the posterior surface of the omental sac unites with
the surface of the transverse colon (Joh. Miiller).

450. URINARY AND GENERATIVE ORGANS.—Urinary apparatus.—The first indica-
tion of this apparatus occurs in the chick at the 2nd day and in the rabbit at the 9th, as the
ducts of the primitive kidneys or Wolffian ducts (fig. 682, 1, W), which are formed from some
cells mapped off from the lateral plate above and to the side of the protovertebre, and extendin
from the fifth to the last vertebra. The ducts are solid at first, but soon become hollow, ‘an
from their cavities there extend laterally a series of small tubes, which in the chick communi-
cate freely with the peritoneal cavity (K@lliker), Into one end of each of these tubes grows a
tuft of blood-vessels forming a structure resembling the glomeruli of the kidney. The tubes
elongate, form convolutions, and increase in number. The upper end of the Wolffian duct is
closed at first, its lower end, which lies in a projecting fold—the plica urogenitalis of Waldeyer
—in the peritoneal cavity, opens into the uro-genital sinus. Close above the orifice of the
Wolffian duct appears the ureter as the duct of the kidney. The duct elongates, and branches
at its upper end. Each canal at its end is like a stalked caoutchouc sac ( Zoldt), and into it
there grow the already formed glomeruli. The duct of the kidney opens independently into
the uro-genital sinus, and forms the ureter. The part where the branching of the duct stops
forms the pelvis of the kidney, and the branches themselves the renal tubules. Toldt found
Malpighian corpuscles in the human kidney at the
2nd month, and Henle’s loops at the 4th. ‘The first
appearance of the urinary bladder is at the 4th week
(His), and is more distinct at the 2nd month, as
the dilated first part of the allantois (fig. 682). The
upper part of the allantois remains as the obliterated
urachus, in the middle vesicle ligament.

Internal Reproductive Organs.—In front of and
internal to the Wolffian bodies, there arises in the
mesoblast the elongated reproductive gland, germ-
ridge, or mass of germ-epithelium (fig. 682, I, D),
which in both sexes is originally alike (fig. 683, K, E),
In addition, there is formed a canal or duct parallel to
the Wolffian duct (W), which also opens into the
uro-genital sinus ; this is Miiller’s duct (M). The
elevation of the future reproductive gland is covered
originally by germ-epithelium (Waldeyer). The
upper end of the Miillerian duct opens free into the
abdominal cavity, while the lower ends of both ducts
unite for a distance. Some of the germinal cells
covering the surface of the future ovary enlarge to
form ova, and sink into the stroma to form ova em-
bedded in their Graafian follicles (§ 433) (fig. 683).
In the female, the Miillerian ducts form the Fal-
lopian tube (II, T), and the lower united ends the
uterus.

In the male, the germ-epithelium is not so tall.
According to Waldeyer, there are two kinds of tubes

iy Be

Fig. 683.
Section of mammalian ovary showing de-

:
a
—— Se

velopment of ova and their follicles.
Ei, Ripe ovum; 4G, follicular cells of
germinal epithelium ; g, blood-vessels ;
K, germinal vesicle and spot; KE,
germinal epithelium ; Zf, liquor folli-
culi; Mg, membrana granulosa ; Mp,
zona pellucida; PS, ingrowths from
germinal > rps ovarian tubes, by
means of which some of the nests retain
their connection with the epithelium ;
S, cavity which appears within the
Graafian follicle ; So, stroma of ovary ;
Tf, Theea folliculi or ovi-capsule; JU,
primative ova,

uterus or vesicula prostatica (III, ~)—the

Wolffian body unite at the 3rd month wit

bod of the testis), and become the coni y
epithelium (E) ; the remainder of the W

in the Wolffian bodies, and some of these penetrate
the position of the reproductive gland. These tubes,
which are connected with the Wolffian ducts, be-
come the seminiferous tubules (v. Wéittich), and the
Wolffian duct itself becomes the vas deferens, with
the vesicule seminales. According to some other
observers, however, tubes which become the semi-
niferous tubules, are developed within the reproduc-
tive gland itself, and these tubes lined with their
germ-epithelium ultimately form a connection with
the Wolffian ducts.

The Miillerian ducts, which are really the ducts
of the reproductive glands, disappear in man, all
except the lowest part, which becomes the male

homologue of the uterus. The upper tubules of the
h the reproductive gland (which has now become the
asculosi of the epididymis, which are lined by ciliated
olffian body disappears. Some detached tubules form

:

DEVELOPMENT OF THE OVARY AND TESTICLE, 889

the vasa aberrantia (a) of the testicle (Kobelt). The hydatid of Morgagni (/), at the head of
the epididymis, according to Luschka and others, is a part of the epididymis—Fleischl regards |
it as the rudiment of the male ovary. The organ of the Giraldés is part of the Wolffian body.
The Wolffian duct itself becomes the vas deferens (V) from which the vesicule seminales are
developed. The two Wolffian and two Miillerian ducts, as they enter the pelvis, unite to form
a common cord—the genital cord.

In the female, the tubes of the Wolffian bodies disappear, all except a few tubules, lined with
ciliated epithelium, constituting the parovarium, or organ of Rosenmiiller (fig. 646), and a part
analogous to the organ of Giraldés in the broad ligament of the uterus ( Waldeyer) (fig. 682,
P). The same is the case with the Wolffian ducts. In some animals (ruminants, pig, cat, and
fox) they remain permanently as the ducts of Gaertner.

The Miillerian duct is frayed out at its upper end to form the fimbrie of the Fallopian tube,
and it is often provided with a hydatid (41). That part of the uro-genital sinus into which the
four ducts open grows above into a hollow sphere, which forms the vagina (Rathke). Accord-
ing to Thiersch and Leuckart, however, the two Miillerian ducts unite at their lower ends to
form the united uterus (U) and vagina, while their free upper ends form the Fallopian tubes (T).
The Miillerian ducts at first open into the posterior part of the urinary bladder below the
ureters (uro-genital sinus, S), while ultimately this part of the bladder becomes so elongated
posteriorly that the vagina (the united Miillerian ducts) and the urethra are united below and
deeply within the vestibule of the vagina. At the 3rd to the 4th month, the uterus and
vagina are not separate from each other, but at the 5th to the 6th month the uterus is defined
from the vagina.

The testicles lie originally in the lumbar region of the abdominal cavity (fig. 684, V, ¢), and
are carried by a fold of the peritoneum—the mesorchium (m). From the hilum of the testicle
a cord, the gubernaculum testis, runs through the inguinal canal into the base of the scrotum.
At the same time a septum-like process is developed independently from the peritoneum to the
base of the scrotum (pv). The testicle passes through the inguinal canal into the scrotum, but
the mechanism and the cause of the descent are not accurately ascertained.—[Descent of testis,
§ 446. ]

The ovaries also descend somewhat. The round ligament of the uterus corresponds to the
gubernaculum testis. A process of the peritoneum passes in the female into the inguinal canal
as Nuck’s canal. It is rare to find the ovaries descending into the labia majora.

[The origin of the urinary and generative organs is undoubtedly associated with the develop-
ment of the Wolffian bodies. The researches of Semper and Balfour on elasmobranch fishes
show that the process is a very complex one. There is a mass of cells on each side of the verte-
bral column, which is divided into three parts, the first called the pronephros, or head-kidney
of Balfour and Sedgwick, the middle one, the mesonephros or Wolffian body, and the posterior
one or metanephros, which is formed after the other two, gives origin to the permanent kidney
in the amniota. The Miillerian duct is connected with the pronephros, the Wolffian duct with
the mesonephros, and the ureter with the metanephros. ]

[The following table, modified from Quain, shows the destiny of these structures :—

MULLERIAN Ducts (Ducts of the Pronephros).

Female. Male.
Fallopian tubes, Hydatid of Morgagni.
Hydatid. Male uterus.

Uterus and vagina.
WoOLFFIAN BopiEs (MESONEPHROS),.

Parovarium, . Vasa efferentia, Coni vasculosi.
Parodphoron. Organ of Giraldés, Vasa aberrantia.
Round ligament of the uterus. Gubernaculum testis.

WoLrFFiAn Ducts.
Chief tube of parovarium. Convoluted tube of epididymis.
Ducts of Gaertner. Vas deferens and vesicule seminales.

METANEPHROS.
Kidney. Ureter. ]

The external genitals are at first not distinguishable in the two sexes (fig. 684, J). At the
4th week, there is merely an orifice at the posterior extremity of the trunk, representing both the
anus and the opening of the urachus, and forming a cloaca (fig. 682, 4, K). In front of this an
elevation—the genital eminence—appears about the 6th week, and on each side of the orifice a
large cutaneous elevation (ZZ, w). At the end of the 2nd month, there is a groove on the under
surface of the genital eminence, leading back to the cloaca, and with distinct walls bounding it
(IJ, v). At the middle of the 8rd month, the cloacal opening is divided by the growth of the

890 DEVELOPMENT OF THE EXTERNAL GENITALS.

perineum, between the urachus (now become the urinary bladder) (fig. 682, 5, 6) and the

rectum (M). . ‘ ;
In the male, the genital eminence enlarges, its groove deepens from the opening of the
bladder onwards to the apex of the elevation at the 10th week. The two edges unite to enclose

: Fig. 683.
Development of the external genitals. J. and II. —Genital eminence ; 7, genital groove ; s,
coccyx ; w, cutaneous elevations. JV.—P, penis ; R, raphe penis; S, scrotum. III.—
c, clitoris ; 7, labia minora; Z, labia majora ; a, anus. V. and VJI.—Descent of the
testicle ; ¢, testis ; m, mesorchium ; pv, processus vaginalis of the peritoneum; Jf, ab-
dominal wall ; S, scrotum.

the groove which becomes the urethra. When this does not take place, hypospadias occurs.
At the 4th month the glans, and at the 6th the prepuce, are formed. The large cutaneous
folds meet in the middle line or raphe to form the scrotum.

In the female, the undifferentiated condition remains to a certain extent permanent. The
small genital eminence remains as the clitoris, the margins of its furrow become the nymphe,
the cutaneous elevations remain separate to form the labia majora, The uro-genital sinus

J Ve Ye

Fig. 685. Fig. 686. Fig. 687. Fig. 688.

Fig. 685.—R, rectum continuous with the allantois (ALL—bladder); M, duct of Miiller
(vagina) ; A, depression of skin below genital eminence, growing inwards to form the
vulva. Fig. 686.—The depression has become continuous with the rectum and allantois
to form the cloaca (CL). Fig. 687.—The cloaca is becoming divided into uro-genital
sinus (SU) and anus by the downward growth of the perineal septum. The ducts of Miiller
are united to form the vagina (V). Fig. 688.—Perineum completely formed.

remains short as the vestibule of the vagina, while in man, by the closing of the genital groove,
it has a long additional tube, the urethra. [The accompanying illustrations, after Schroeder,
show the changes of the external organs of generation in the female. In the early period (6th
week), the hind-gut (fig. 685, R), allantois (ALL), and the Miillerian ducts (M) communicate,
but not with the exterior. About the 10th week a depression or inflection of the skin takes
place, genital cleft, until it meets the hind-gut and allantois, whereby the cloaca (fig. 686, CL)
1s formed. _ The cloaca is then divided into an anterior part, the uro-genital sinus, into which
the Miillerian ducts open, and a posterior part, the anus. There is a downward growth of the
tissue between the hind-gut and the allantois to form the perineum (fig. 687). The uro-genital
sinus then contracts at its upper part to form the short urethra, its lower part remaining as the
— (fig. 688, SV), while the vagina has been formed by the union of the lower parts of
ae at ona ducts. The bladder (B) is the expanded lower end of the stalk of the
The causes of the difference of sex are by no means well known. Froma statistica i
of 80,000 cases, the influence of the aia sah the parents has been shown Oy Tofacker and

FORMATION OF THE CENTRAL NERVOUS SYSTEM. 8gI

Sadler. Ifthe husband is younger than the wife, there are as many boys as girls ; if both are
of the same age, there are 1029 boys to 1000 girls ; if the husband is older, 1057 boys to 1000
girls. In insects, food has a most important influence. Pfliiger’s investigations on frogs show
that all external conditions during development are without effect on the determination of the
sex, so that the latter would seem to be determined before impregnation.

451. FORMATION OF THE CENTRAL NERVOUS SYSTEM.—Fore-brain.—At each side
of the fore-brain, or anterior cerebral vesicle, which is covered externally by epiblast and in-
ternally by the ependyma, there
grows out a large stalked hollow h
vesicle, the rudiment of the cere- |
bral hemispheres. The relatively
wide opening in the stalk, or com-
munication, ultimately ‘becomes
very small, and is the foramen of
Monro. The middle part between
the two cerebral vesicles remains
small, and is the ’tween or inter-
brain with the 8rd ventricle inits sf
interior. It elongates at the second
month towards the base of the brain
as a funnel-shaped projection, to
form the tuber cinereum with the
infundibulum. The thalami optici,
projecting and enlarging from the |
sides of the 3rd ventricle, narrow 74
the foramen of Monro to a semi-
lunar slit. At the base of the brain

are formed, in the 2nd month, the NE XS Vou a S
corpora albicantia, at the 3rd the YO NG STRESS
chiasma; while within the 3rd ven- Bs a 47 f se » a

tricle the commissures are formed.
The hypophysis, belonging to the :
mid-brain, isa diverticulum of the Fig. 689.

nasal mucous membrane, extending Transverse section of the brain of an embryo sheep 2°7 cm.
through the base of the skull to- long; x 10. a, cartilage of orbito-sphenoid ; c, peduncu-
wards the hollow infundibulum, _ lar fibres ; ch, optic chiasm ; 7, median cerebral fissure ;
which grows to meet it (fig. 505, , cerebral hemispheres, with a convolution upon their
T). There is, as it were, a tend- inner wall, projecting into the lateral ventricle, 7; m,
ency to the union of the cavity of foramen of Monro; 0, optic nerve; p, pharynx; pi,
the fore-gut with the medullary lateral plexus; s, termination of the median fissure,
tube. In the amphioxus (Kowal- which forms the roof of the third ventricle ; sa, body
ewsky), goose (Gasser), and lizard of the anterior sphenoid ; sf, corpus striatum ; ¢, third
(Strahl) the medullary tube com- ventricle ; ¢h, anterior deep portion of the optic thalamus
municated originally with the hind- (Kélliker).

gut by the canalis myeloentericus.

The choroid plexus, which grows into the ventricles of the hemispheres through the foramen of
Monro, is a vascular development of the ependyma. At the 4th month, the conarium (pineal
gland) is formed, and at this time the corpora quadrigemina cover the hemispheres. The corpora
striata begin to be developed in the cerebral (lateral) ventricle at the 2nd month, while the cornu
ammonis is formed at the 4th month. [The external walls and floor of the primitively simple
central hemispheres become much thickened, the thickenings in the floor constitute the corpora
striata, which protrude into the lateral ventricles, their position being indicated on the
surface of the brain by the Sylvian fissure. As they extend backwards, they become con-
nected with the optic thalami (fig. 689, st, th). The corpora striata are connected together by
the anterior commissure. From the inner wall of each hemisphere, there grow into each
lateral ventricle two projections ; the upper one forms the hippocampus major or cornu
ammonis (fig. 689, 2), while the lower one becomes folded, remains thin, receives numerous
blood-vessels from the falx cerebri, and forms the choroid plexus (fig. 689, pl).] At the 3rd
month the Sylvian fissure is formed, and the basis of the island of Reil. The permanent
cerebral convolutions are formed from the 7th month onwards.

The mid-brain, or middle cerebral vesicle, is gradually covered over by the backward growth
of the hemispheres ; its cavity forms the edvietiah of Sylvius (fig. 690). Depressions appear
on the surface of the vesicle to divide it into four, the corpora quadrigemina, in birds into
two, the corpora bigemina (fig. 690, by), the longitudinal depression being formed at the 3rd,
and the transverse one at the 7th month. The cerebral peduncle is formed by a thickening
in the base of this vesicle.

892 | DEVELOPMENT OF THE SENSE ORGANS. ,

In the hind-brain are found the cerebellar hemispheres, which grow backwards to meet in
the middle line. The vermis is formed at the 7th month. The cerebellum covers in the part
of the medullary tube lying below it, which is not closed, as far as the calamus. The pons
arises in the floor of the hind-brain at the 8rd month. ;

The spindle-shaped narrow after-brain forms the medulla oblongata, with the opening of
the medullary tube in its upper part. ;

[The following table, from Quain, shows the destiny of each cerebral vesicle :—

Cerebral hemispheres, corpora striata,
corpus callosum, fornix, lateral

1. Prosencephalon, . . us |
| ventricles, olfactory bulb.

I. Anterior Primary (fore-brain)

|
| 2. Thalamencephalon, . a
|
\

Vesicle, Thalami optici, pineal gland, pitui-
: date : tary body, crura cerebri, aqueduct
(inter or ’tween brain) | of Sylvius, optic nerve.
i. | Corpora quadrigemina, cruri cerebri
II, Middle Primary ( 3. Mesencephalon, . . . aqueduct of Sylvius, optic nerve
Vesicle, ...-\{ (mid-brain) | (secondarily).
4. Epencephalon,. . . ~ { Cerebellum, pons, anterior part of
III. Posterior Primary | (hind-brain) | the fourth ventricle.
Vesicle, ... | 5. Metencephalon, . . . { Medulla oblongata, fourth ventricle,
: (after-brain) auditory nerve.

Spinal Cord.—-The spinal cord is developed from the medullary tube behind the medulla
oblongata, first the grey matter around the canal, while the white matter is added afterwards
; outside this. The ganglionic cells increase
Z dt che by division in amphibians (Lominsky). At
first the spinal cord reaches to the coccyx.
In the adult, the spinal cord reaches only
to the Ist or 2nd lumbar vertebre, so that
it does not elongate so much as the verte-
bre can. It is a question how far this want
of harmony in the development of these
two structures may lead to disturbances of
3. sensibility or paralysis of the lower limbs in
: ESN ae he a 7 children. The first muscles are formed in
gies A ta ee ¢ the back at the 2nd month; at the 4th
hey are red. The spinal ganglia
Fig. 690. month Faby wee Pp ta
are formed from a special strip of epiblastic
cells. They are seen at the 4th week, and
so are the anterior spinal roots and some of
the trunks of the spinal nerves, while the
posterior roots are still absent. At this
period the ganglia of the 5th, 7th, 8th, 9th,
and 10th nerves and part of their origins
are present, while the Ist, 2nd, 3rd, and
12th nerves and the sympathetic are not
yet far differentiated (His). The peripheral
nerves grow out from the ganglia of the

Diagram of an embryonic fowl’s brain. ac, an-
terior commissure; amv, anterior medullary
velum, and below it the aqueduct of Sylvius
and the cerebral peduncles ; ba, basilar artery ;
bg, corpora bigemina; cai, internal carotid
artery ; cbl, cerebellum ; ch*, ch4, choroid plexuses
of the third and fourth ventricles ; h, cerebral
hemispheres; inf, infundibulum; 7¢, lamina
terminalis; Zi, lateral ventricle; ob/, medulla
oblongata ; olf, olfactory lobe and nerve; ope,
ince pearls ; pny pres! aus Fy Fall owed Wt cord (first the motor and afterwards
ary body ; ps, pons Varolii; 7, floor of fourth ven- = p
tricle; st, ei striatum ; v*, third ventricle ; are eoneory etree), AN bea ee

v‘, fourth ventricle (Quain, after Mihalkovics). paige q Er peed (His). At first

452. THE SENSE ORGANS, —Eye.—The primary optic vesicle grows out from the fore-
brain towards the outer covering of the head or epiblast, and soon becomes folded in on itself
(4th week), so that the stalked aoe vesicle is shaped like an egg-cup (fig. 691, I). The cavity
in the interior of this cup is called the secondary optic vesicle. The inflected part becomes
the retina (IV, 7), while the posterior part becomes the choroidal epithelium (IV, p). The
stalk becomes the optic nerve. At the under surface of the depression there is a slit—the
choroidal fissure—which permits some of the mesoblast to gain access to the interior of the
eye. This slit forms the coloboma (II); it is prolonged backward on the stalk, and contains
the central artery of the retina. The margins of the coloboma afterwards unite completely
with each other, but in some rare conditions this does not take place, in which case we have to
deal with a coloboma of the choroid or retina, as the case may be. In the bird the embryonic
coloboma slit does not close up, but a vascular process of the mesoblast dips into it, and passes
into the eye to form the pecten (p. 796). The same is the case in fishes, where there is a large
vascular process of the meso- and epiblast forming the processus faleiformis (p. 796). ‘

The depression or inflection of the optic vesicle is due to the downgrowth into it of a

DEVELOPMENT OF THE SENSE ORGANS. . 893

thickening of the epiblast (I, L). It is hollow, and as it grows inwards ultimately becomes
ere and separated from the epiblast to form the crystalline lens, so that the lens is epi-
blastic in its origin, while the capsule of the lens is a cuticular structure formed from the epiblast.
That part of the epiblast which covers the vesicle in front of the lens ultimately becomes the
stratified epithelium of the cornea. The layer of pigment of the invaginated optic vesicle is
applied to the ciliary body, and the posterior surface of the iris, when the latter is formed.
The cornea is formed at the 6th week. The substance of the choroid, sclerotic, and cornea is
formed around the position of the eye from the mesoblast (7). The capsule of the lens is
at first completely surrounded by a vascular membrane—the membrana capsulo-pupillaris.
Afterwards, the lens passes more posteriorly into the eye—the anterior part of the capsulo-
pupillary membrane, however, remains in the anterior part of the eye, while towards it grows

Fig. 691.

Development of the eye. I., Inflexion of the sac of the lens (L) into the primary optic vesicle
(P)—e, epidermis ; m, mesoblast. II., The inflexion seen from below—z, optic nerve ; ¢,
the outer, 7, the inner layer of the inflected vesicle ; L, lens. III., Longitudinal section
of II. IV., Further development—e, corneal epithelium; ¢, cornea; m, membrana
capsulo-pupillaris ; L, lens ; a, central artery of the retina; s, sclerotic ; ch, choroid ; p,
pigment layer of the retina ; 7, retina. V., Persistent remains of the pupillary membrane.

the margin of the iris (7th week), so that the pupil is closed by this part of the vascular capsule,
membrana pupillaris. The blood-vessels of the iris are continuous with those of the pupillary
membrane ; those of the posterior capsule of the lens give off the hyaloid artery, a continuation
of the central artery of the retina ; its veins pass into those of the iris and choroid. The
vitreous humour at the 4th week is represented by a cellular mass between the lens and the

Fig. 692.

Early stages in the development of the vertebrate ear. A-D, Early stages in the chick (Reissner).
E, Transverse section uke the auditory pit of a 50 hours’ chick (J/arshall). F, Trans-

verse section through the hind-brain of a fotal sheep. acv, anterior cardinal (jugular)
vein ; am, amnion ; ao, aortic arch ; ce, cochlea ; rv, recessus (aqueductus) vestibuli ; 2,
vestibulum ; vc, vertical semicircular canal ; vit, auditory nerve.

retina. The pupillary membrane disappears at the 7th month. It may remain throughout
life (V).

Abe. of Smell.—On the under surface and lateral limit of the fore-brain, the epiblast forms
a groove or pit with thickened epithelium, which forms a depression towards the brain, but

894 BIRTH,
remains as a
— ciiewards sends its branches. For the formation of the nose, see p. 879, _

Organ of Hearing.—On both sides of the after-brain or posterior brain vesicle, above the
first visceral or hyoid arch, there is a depression or pit formed in the epiblast, which gradually
extends deeper towards the brain—this is the labyrinth pit or auditory sac, which soon becomes

sk-shaped (fig. 692, A, B).
aethe ook hich ae connected the cavity of the sac with the surface, persists as the
aqueductus vestibuli; and its blind swollen distal extremity as the saccus endolymphaticus,
or recessus vestibuli (Haddon, fig. 692, 7, v).] The pit is ultimately completely cut off from
the epiblast, just like the lens, and is now called the vesicle of the labyrinth or primary
auditory vesicle. Its related portion forms the utricle, from which, at the 2nd month, the
semicircular canals and the cochlea are developed (fig. 692, D). The union with the brain
occurs later, along with the development of the auditory nerve, The first visceral cleft remains
as an irregular passage from the Eustachian tube to the external auditory meatus. The outer
ear appears at the 7th week. ih.

Organ of Taste.—The gustatory papille are developed in the later period of intra-uterine life,
and several days before birth the taste-buds appear (#’r, Hermann).

453. BIRTH.—With the growth of the ovum, the uterus becomes more dis-
tended, its walls more muscular and more vascular, although the uterine walls are not
thicker at the end of pregnancy. Toward the end of gestation the cervical canal is
intact until labour begins, or at any rate it is but slightly opened up at its upper part.
After a period of 280 days of gestation, “labour” begins, whereby the contents of
the uterus are discharged. The labour pains occur rhythmically and periodically,
being separated from each other by intervals free from pain. Lach pain begins
gradually, reaches a maximum, and then slowly declines. With each pain the heat
of the uterus increases (§ 303), while the heart-beat of the foetus becomes slower and

feebler, which is due to stimulation of the vagus in the medulla oblongata (§ 369,

3).

{At the full time the membranes and placenta line the uterus. The membranes
consist, from within outwards, of amnion, chorion, decidua reflexa, and decidua
vera. The fundi of the uterine glands persist in the deep part of the decidua vera,
and thus form a spongy layer, the part above this being the compact layer in the
deep part of the placenta, e.g., near the uterine wall, we have also the fundi of the
uterine gland persisting in the decidua serotina. When the placenta and mem-
branes are expelled after birth, the line of separation takes place in the part of
the membranes and placenta where the fundi of the glands persist. After labour
is completely finished, the uterus is lined by the remains of the spongy layer of the
decidua vera and serotina, ¢.g., is lined by a layer which contains the fundi of the
uterine glands. The new mucous membrane is regenerated by the growth of the
epithelium and connective-tissue in this part. The membranes expelled are made
up of amnion, chorion, deciduz reflex, and the compact layer of the decidua vera. ]

The uterine movements during labour proceed in a peristaltic manner from the
Fallopian tube to the cervix, and occupy 20 to 30 seconds. In the curve registered
by these movements there is usually a more steep ascent than descent.

[Power in Ordinary Labour.—Sometimes the ovum is expelled whole, the membranes con-
taining the liquor amnii remaining unruptured. Poppel has pointed out that the force’ which
ruptures the bag of membranes is sufficient to complete delivery, so that, as Matthews Duncan
remarks, the strength of the membranes gives us a means of ascertaining the power of labour
in the easiest class of natural labours. Matthews Duncan, from experiments on the pressure
required to rupture the membranes, concludes that the great majority of labours are completed
by a propelling force not exceeding 40 lbs. i.

Polaillon estimates the pressure exerted by the uterus upon the foetus at each pain to be 154
kilos. [338°8 lbs.], so that, according to this caléulation, the uterus at each pain performs 8820
kilogrammetres of work (§ 301). [This estimate is certainly far too high. ]

ter-Birth.—After the foetus is expelled, the placenta remains behind; but it is soon
expelled by the contractions of the uterus. During the contraction of the uterus to expel the
placenta, a not inconsiderable amount of the placental blood is forced into the child (§ 40). [It
is more probable that the child aspirates the blood from the foetus portion of the placenta.
This can be seen in late ligature of the cord, The child may thus gain two ounces of blood.]

it or depression; this is the olfactory or nasal pit, to which the olfactory —

INFLUENCE OF NERVES ON THE UTERUS. 895

After a time the placenta, the membranes, and the decidua—constituting the after-birth—are
expelled.
nfluence of Nerves on the Uterus.—1. Stimulation of the hypogastric plexus causes con-
traction of the uterus. The fibres arise from the spinal cord, from the last dorsal, and upper
three or four lumbar nerves, run into the sympathetic, aud then reach the hypogastric plexus
(Frankenhdéuser), 2. Stimulation of the nervi erigentes, which are derived from the sacral
plexus, causes movement (v. Basch and Hofmann). 3. Stimulation of the lumbar and sacral
parts of the cord causes powerful movements (Spiegelberg). There is a centre for the act of
_ parturition in the lumbar region of the cord (§ 362, 6). The uterus, like the intestine, prob-
ably contains independent or parenchymatous nerve-centres (Kirner), which can be excited by
suspension of the respiration, and by anemia (by compressing the aorta, or rapid hemorrhage).
Decrease of the bodily temperature diminishes, while an increase of the temperature increases
the movement, which, however, ceases during high fever (Fromme). The experiments made by
Rein upon bitches show that, if all the nerves going to the uterus be divided, practically all the
functions connected with conception, pregnancy, and parturition can take place, even although
the uterus is separated from all its cerebro-spinal connections. Hence, we must look to the
presence of some automatic ganglia in the uterus itself. According to Dembo, there is a
centre in the anterior wall of the vagina of the rabbit. According to Jastreboff, the vagina of
the rabbit contracts rhythmically. ‘Sclerotic acid greatly excites the uterine contractions (v.
Swiecicki), so does anemia (Kronecker and Jastreboff). 4. The uterus contracts reflexly on
stimulating the central end of the sciatic nerve (v. Basch and Hofmann), the central end of the
branchial plexus (Schlesinger), and the nipple (Scanzoni). 5. The uterus is supplied by vaso-
motor nerves (hypogastric plexus), which come from the splanchnic; and also by vaso-dilator
Jibres, the latter through the nervi erigentes. The vaso-motor nerves are affected reflexly by
stimulation of the sciatic nerve (v. Basch and Hofmann),

[In the rabbit the vagina and uterine cornua exhibit regular movements of a ‘‘ peristaltic”
nature. These exist apart from any extraneous stimulus, and are probably a vital property of
the tissue. They can be demonstrated in animals a few weeks old, and have been recorded
continuously for many hours.» Frequently they are more vigorous six hours after than at the
beginning, showing that they are not due to the irritation of the operation necessary to demon-
strate them.

Their rate and extent vary. In young animals they are frequent (1 to 4 per minute), but
irregular in character. In nulliparous adults they are less frequent and somewhat more
regular. During pregnancy they increase greatly in extent, and their rate becomes 1 in 120 to
130 seconds. These characters are retained after pregnancy for many months at least. They
are diminished or abolished by chloroform narcosis, are scarcely affected by ether. Water at
100° to 120° F. produces a persistent contraction accompanied by blanching of the tissue.
Similar effects are produced by dilute acetic acid (Milne Murray).]

Lochia.— After birth the whole mucous membrane (decidua) is shed; its inner
surface, therefore, represents a large wounded surface, on which a new mucous
membrane is developed. The discharge given off after birth constitutes the lochia.

Involution of the Uterus.—After birth the thick muscular mass decreases in
size, some of its fibres undergoing fatty degeneration. Within the lumen of the
blood-vessels of the uterus itself, there begins in the interna of these vessels a pro-
liferation of the connective-tissue elements, whereby within a few months the blood-
vessels so affected become completely occluded. The smooth muscular fibres of
the middle coat of the arteries undergo fatty degeneration. The relatively large
vascular spaces in the region of the placenta are filled by blood-clots, which are
ultimately traversed by outgrowths of the connective-tissue of the vascular walls.

Milk-Fever.—After birth, there is a peculiar action on the vaso-motor system,
constituting milk-fever, while at the 2nd to 3rd day there is a more copious supply
of blood to the mammary nnd for the secretion of milk (§ 231), [After birth
the pulse becomes slow and remains so in a normal puerperium. The so-called
milk-fever is not found in cases where strict cleanliness is observed during the
labour and puerperium.] For the cause of the first respiration in the child, see
p- 666,

454, COMPARATIVE—HISTORICAL.—A sketch of the development of man must neces-
sarily have some reference to the general scheme of development in the Animal Kingdom.
The question as to how the numerous forms of animal life at present existing on the globe have
arisen has been answered in several ways. It has been asserted that each species has retained

its characters unchanged from the beginning, so that we speak of the “ constancy of species.”
This view, developed by Linneus, Cuvier, Agassiz, and others, is opposed by that supported

896 COMPARATIVE—HISTORICAL.

by Lamarck 1809, or the doctrine of the ‘‘ Unity of the Animal Kingdom,” corresponding to
the ancient view of Empedocles, that all species of animals were derived by variations: from a
few fundamental forms; that at first there were only a few lower forms from which the
numerous species were developed—a view supported by Geoffrey St Hilaire and Goethe. After
a long period this view was restated and elucidated in the most brilliant and most fruitful
manner by. Charles Darwin in his “‘ Origin of Species ” (1859) and other works, He.attempted
to show how modifications may be brought about by uniform and varying conditions acting for
along time. Amongst created beings each one struggles with its neigh our, so that there is a
real *‘ struggle for existence.” Many qualities, such as vigour, rapidity, colour, reproductive
activity, &c., are hereditary, so that in this way by ‘‘natural selection” there may be a
pace improvement, and therewith a gradual change of the species. In addition, organisms
can, within certain limits, accommodate themselves to their surroundings or environment. Thus
certain useful organs or parts may undergo development, while inactive or useless parts may
undergo retrogression, and form ‘‘ rudimentary organs. This process of ‘ natural selection,”
causing gradual changes in the form of organisms, finds its counterpart in - artificial selection
amongst plauts and animals. Breeders of animals, for example, by selecting the proper crosses,
can within a relatively short time produce very material alterations in the form and characters
of the animals which they breed, the changes being more pronounced than many of those
that separate well-defined species. But, just as with artificial selection, there is sometimes a
sudden ‘‘ reversion” to a former type, so in the development of species by natural selection
there is sometimes a condition of atavism, Obviously, a wide distribution of one species in
different climates must increase the liability to change, as very different conditions of environ-
ment come into play. Thus, the migration of organisms may gradually lead to a change of
species.

P Biological Law.—Without discussing the development of different organisms, we may refer
to the ‘‘ fundamental biological law” of Haeckel, viz., ‘‘ that the ontogeny is a short repetition
of the phylogeny,” [ontogeny being the history of the development of single beings, or of the
individual from the ovum onwards, while phylogeny is the history of the development of a
whole stock of organisms, from the lowest forms of the series upwards] (p. xxxv). When applied
to man, this law asserts that the individual stages in the course of the development of the
human embryo, ¢.g., its existence asa unicellular ovum, as a group of cells after complete
cleavage, as a blastodermic vesicle, as an organism without a body-cavity, &c.; that these
stages of development indicate or represent so many animal forms, through which the human
species in the course of untold ages has been gradually evolved. The individual stages which
the human race has passed in this process of evolution are rapidly rehearsed in its embryonic
development. This conception has not passed without challenge. In any case, the comparison
of the human development and its individual organs with the corresponding perfect organs of
lower vertebrates is of great importance. Thus, a mammal during the development of its
organs is originally possessed of the tubular heart, the branchial clefts, the undeveloped brain,
the cartilaginous chorda dorsalis, and many arrangements of the vascular system, &c), which
are permanent throughout the life of the lowest vertebrates. These incomplete stages are per-
fected in the ascending classes of vertebrates. Still, there are many difficulties to contend with
in establishing both the evolution hypothesis of Darwin and the biological law of Haeckel.

Historical.—Although the impetus to the study of the history of development has been most
stimulated in recent times, the ancient philosophers held distinct but very varied views on the
question of development. Passing over the views of Pythagoras (550 B.c.) and Anaxagoras
(500 3.c.), Empedocles (473 B.c.) taught that the embryo was nourished through the
umbilicus ; while he named the chorion and amnion. Hippocrates observed incubated e
from day to day, noticed that the allantois protruded through the umbilicus, and observed that
the chick escaped from the egg on the 20th day. He taught that a7 months’ foetus was viable,
and explained the possibility of superfcetation from the horns of the uterus. The writings of
Aristotle (born 384 B.c.) contain many references to development, and many of them are
already referred to in the text. He taught that the embryo receives its vascular supply
through the umbilical vessels, and that the placenta sucked the blood from the vascular uterus
like the rootlets of a tree absorbing moisture. He distinguished the polycotyledonary from the
diffuse placenta ;and he referred the former to animals without a complete row of teeth in both
jaws. In the incubated egg of the chick he distinguished the blood-vessels of the umbilical
vesicle, which carried food from the cavity of the latter, and also the allantois. He also
observed that the head of the chick lay on its right leg, and that the umbilical sac was ulti-
mately absorbed into the body. The formation of double monsters he ascribed to the union of
two germs or two embryos lying near each other. During generation the female produces the
matter, the male the principle which gives it form and motion. There are also numerous
references to reproduction in the lower animals, Erasistratus (304 B.c.) described the embryo
as arising by new formations in the ovum—Epigenesis,—while his contemporary, Herophilus,
found that the pregnant uterus was closed. He was aware of the glandular nature of the
prostate, and named the vesicule seminalis and the epididymus. en (131-203 A.D.) was
acquainted with the existence of the foramen ovale, and the course of the blood in the fetus |

HISTORICAL, 897

through it, and through the ductus arteriosus. He was also aware of the physiological relation
between the breast and the blood-vessels of the uterus, and he described how the uterus con-
tracted on pressure being applied to it. In the Talmud it is stated that an animal with its
uterus extirpated may live, that the pubes separates during birth, and there is a record of a case
of Ceesarian section, the child being saved. Sylvius described the value of the foramen ovale ;
Vesalius (1540) the ovarian follicles ; Eustachius (+1570) the ductus arteriosus (Botalli) and the
branches of the umbilical vein to the liver. Arantius investigated the duct which bears his
name, and he asserted that the umbilical arteries do not anastomose with the maternal vessels
in the placenta. In Libavius (1597) it is stated that the child may cry in wtero. Riolan (1618)
was aware of the existence of the corpus Highmorianum testis. Pavius (1657) investigated the
position of the testes in the lumbar region of the foetus. Harvey (1633) stated the funda-
mental axiom, ‘‘Omne vivum ex ovo.” Fabricius ab Aquapendente (1600) collected the materials
known for the history of the development of the chick. Regner de Graaf described more care-
fully the follicles which bear his name, and he found a mammalian ovum in the Fallopian tube

Swammerdam (+t 1685) discovered metamorphosis, and he dissected a butterfly from the
chrysalis before the Grand Duke of Tuscany. He described the cleavage of the frog’s egg.
Malpighi (+ 1694) gave a good description of the development of the chick with illustrations.
Hartsoecker (1730) asserted that the spermatozoa pass into the ovum. The first half of the
18th century was occupied with a discussion as to whether the ovum or the sperm was the more
important for the new formation (the Ovulists and Spermatists) ; and also as to whether the
foetus was formed or developed within the ovum (Epigenesis), or if it merely increased in
growth. The question of spontaneous generation has been frequently investigated since the
time of Needham in 1745.

New Epoch,—A new epoch began with Caspar Fried. Wolff (1759), who was the first to
teach that the embryo was formed from layers, and that the tissues were composed of smaller
parts (corresponding to the cells of the present period). He observed exactly the formation of
the intestine. William Hunter (1775) described the membranes of the pregnant uterus,
Scemmering (1799) described the formation of the external human configuration, and Oken and
Kieser that of the intestines.+ Oken and Goethe taught that the skull was composed of
vertebree. Tiedemann described the formation of the brain, and Meckel that of monsters.
The basis for the study of the development of an animal from the layers of the embryo was laid
by the researches of Pander (1817), Carl Ernst v. Baer (1828-1834), Remak, and many other
observers ; and Schwann was the first to trace the development of all the tissues from the ovum,
[Schleiden enunciated the cell-theory with reference to the minute structure of vegetable tissues,
while Schwann applied the theory to the structure of animal tissues. Amongst those whose
names are most prominent in connection with the evolution of this theory are Martin Barry,
von Mohl, Leydig, Remak, Goodsir, Virchow, Beale, Max Schultze, Briicke, and a host of recent
observers, | .

ok

APPENDIX A.

General Bibliography,

SYSTEMATIC WORKS AND TEXT-BOOKS.—A. v. Haller, Elementa physiologic corporis
humani, 1757-1766, 8 vols., Auctarium, 1780.—F. Magendie, Précis élémentaire de physiologie,
1816, 2nd ed., 1825.—Johannes Miiller, Handbuch der Physiologie des Menschen, 2nd ed.,
1858-1861 (translated by W. Baly).—Donders, Phys. d. Mensch., pt. i, Leip., 1856.—C.
Ludwig, Lehrbuch der Physiologie des Menschen, 2nd ed. , 1858-1861.—Otto e, Lehrbuch
der Physiologie, 7th ed., by A. Griinhagen, 1884.—G. Valentin, Lehrbuch der Physiologie,
1844 (translated by Brinton, 1853).—Moleschott, Phys. d. Nahrungsmittel, 2nd ed., Giessen,
1859.—F. A. Longet, Traité de physiologie, 2nd ed., 1860-1861.—Joh, Ranke, Grundziige der
Physiologie, 4th ed., 1881.—E. Briicke, Vorlesungen iiber Physiologie, 3rd ed., 1885.—L,
Hermann, Grundriss der Physiologie, 8th ed., 1885 (translated and enlarged by A. Gamgee,
2nd English ed., 1878).—W. Wundt, Lehrbuch der Physiologie, 4th ed., 1878, and Grundziige
d. physiol. Psycholog., 3rd ed., Leip., 1887.—M. Foster, Text-book of Physiology, 4th ed.,
1883.—H. Milne-Edwards, Lecons sur la physiologie et l’anatomie comparee, 14 vols., 1857-
1880.—G. Colin, Traité de Physiologie Go aa des animaux, Paris, 1871-1873.—Bernard,
Leg. de Pathol. expér., Paris, 1872.—Marshall, Phys. (Diagrams and Text), 1875,—Stricker,
Vorles. ii. allg. u. exp. Path., Wien, 1878. -Munk, Physiologie d. Menschen u. d. Saugethiere,
Berlin, 2nd ed., 1888.—Schmidt-Mulheim, Grundriss d. spec. Physiologie d. Haussiugethiere,
Leipzig, 1879.—Vierordt, Grundriss d. Physiologie d. Menschen, 5th ed., Tiibingen, 1857.—
Todd and Bowman’s Cyclopedia of Anat. and Phys.—Hermann, Expt. Toxicologie, 1874.—W.
Rutherford, A Text-book of Physiology, pt. i, Edinburgh, 1880.—W. B. Carpenter, Princip.
of Phys., 8th ed., edited by Power, London, 1876.—J. Beclard, Traité élém. de Phys., Paris,
1880.—Cohnheim, Vorlesungen ii. allgem. Pathologie, Berlin, 1880.—Huxley’s Elements,
1885.—H. Beaunis, Nouveaux éléments de Physiologie humaine, 2nd ed., 1881.—Flint, Text-
book, New York, 1876 ; and Phys. of Man, 1866-1873.—Kirkes, Handbook of Physiology,
11th ed., 1884.—Dalton, Text-book, 1882.—J. G. M‘Kendrick, Text-book of Physiology, Glas-
gow, 1888.—Samuel, Handb. d. allg. Path., Stutt., 1879.—The works of Herbert Spencer and
G. H. Lewes.—E. D. Mapother, Manual of Physiology, 3rd ed., rewritten by J. F. Knott,
Dublin, 1882.—A. Fick, Compendium d. Phys., 1882.—Steiner, Physiologie, 4th ed., Leipzig,
1888.—Nuel and Frédéricq, Elém. de Phys., Gand, 1883.—Preyer, Elemente der allgemeinen
Physiologie, 1883..—T. Lauder-Brunton, Pharmacology, Therapeutics, and Materia Medica,
1887.—H. Power, Elements of Physiol., London, 1884.—Wundt, Phys. méd., 1878.—Daniell,
Text-book of the Principles of Physics, 1884.—Fick, Med. Physik., 2nd ed., 1884.—M‘Gregor
Robertson, Physiological Physics, London, 1885.—Draper, Med. Physics, 1885.—Yeo, Manual
of Physiology, 2nd ed., London, 1887.—L. v. Thanhoffer, Grundziige d. vergl. Physiologie u.
Histologie, Stuttgart, 1885.—Ziegler, Text-book of Path. Anat. (trans. by D. Macalister),

1883-1884.—P. H. Pye-Smith, Syllabus of Lectures on Physiology, London, 1885.—Chapman, —

Treatise on Human Phys., Philad., 1887.—Klein, Micro-organisms and Disease, 1884. —Magnin
and Steinberg, Bacteria, 1884.—Woodhead and Hare, Mycology, 1885.—Crookshank, Bac-

teriology, 1886.—Davis, Text-book of Biol., London, 1888.—Vines, Physiology of Plants.— —

Albertoni and Stefani, Manuale di Fisiol. umana, 1888.—Ellenberger, Lehrb. d. vergleich.
yim u. Physiol. d. Hausthiere, Berlin, 1887.—Landois and Stirling, Text-book, 8rd ed.,

YEARLY REPORTS, BIBLIOGRAPHICAL WORKS.—1834-1837 : «‘ Jahresberichte iiber
die Fortschritte der Physiologie,” by Joh. Miiller, in his Archiv. —1838-1846 : by Th, L,

Bischoff, chenda,—1836-1843: in ‘‘Repertorium fiir Anatomie und Physiologie,” by G.

——

GENERAL BIBLIOGRAPHY. 899

Valentin, 8 vols.—1856-1871: in ‘‘ Zeitschrift fiir rationelle Medicin,” by G@. Meissner, and
continued since 1872 under the title—‘‘ Jahresberichte iiber die Fortschritte der Anatomie und
Physiologie,” by F. Hofmann, and G. Schwalbe, Leipzig. —1841-1865 : Jahresbericht iiber die
Fortschritte der gesammten Medicin, by Canstatt, continued by Virchow and Hirsch.—1822~
1849: Froriep’s Notizen, 101 vols. (References and Bibliography).—Centralblatt fiir die
medicinischen Wissenschaften, Berlin ; yearly since 1863.—Biologisches Centralblatt, Erlangen,
since 1881.—1817-1818: Isis, by Oken.-—Catalogue of Scientific Papers compiled and published
by the Royal Society of London, 1800-1873, 8 vols.—Engelmann, 1700-1846: Bibliotheca
historico-naturalis (Titles of Books on Comparative Physiology).—Jahrbuch der gesammten
Medicin, by Schmidt, since 1826.—Bibliotheca anatomica qua scripta ad anatomen et physio-
logiam facientia a rerum initus recensentur auctore Alberto von Haller, 2 vols. (important for
the older literature up to 1776).—Yearly Reports on Physiology, in Journal of Anat. and
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since its‘commencement in 1873.—Index. medicus.—Neurologisches Centralblatt.—Med. Biblio-
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HISTORICAL.—Kurt Sprengel, Versuch einer pragmatischen Geschichte der Arzneykunde,
3rd ed., 1821.—W. Hamilton, Hist. of Med. Surg. and Anat., 1831.—Bostock’s Syst. of Phys.,
3rd ed., 1836.—J. ©. Poggendorf, Geschichte der exacten Wissenschaft, 1863.—J. Goodsir,
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Konigs., 1854-1857,—H. Haeser, Lehrbuch der Geschichte der Medicin, Jena, 1875.—Julius
Sachs, Geschichte der Botanik seit 16. Jahrh. bis 1860 ; 1875.—Bouchut, Hist. de la méd.,
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ENCYCLOPAIDIAS.—R, Wagner, Handworterbuch der Physiologie, 4 vols., 1842-1853.—
R. B. Todd, The Cyclopedia of Anatomy and Physiology, 1836-1852.—Pierer and N.
Choulant, Anatomisch-physiologisches Realwérterbuch, 8 vols., 1816-1829.—L. Hermann,
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PRACTICAL WORK IN THE LABORATORY.—R. Gscheidlen, Physiologische Methodik,
1876 (not yet completed).—E, Cyon, Methodik der physiologischen Experimente u. Vivisek-
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Paris, 1879. Sanderson, Foster, Klein, and Brunton, Handbook for the Physiological Labora-
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of Pract. Hist., 1876.—Meade-Smith, Trans. of Hermann’s Toxicol.—J. Burdon-Sanderson,
Practical Exercises in Physiology, London, 1882.—Foster and Langley, Pract. Phys., London,
1884.—B. Stewart and Gee, Pract. Physics. —Vierordt, Anat. Physiol. u. Physik. Daten u.
Tabellen, Jena, 1888.—Miller-Pouillet, Lehrb. d. Physik., 8th ed., Braunschweig. —Wiillmer,
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for the Phys. Lab., 5th ed., 1888. —Straus-Durckheim, Anat. descrip. comp. du. chat, Paris,
1845.—W. Krause, Die Anatomie des Kaninchens, Leipzig, 2nd ed., 1883.—A. Ecker, Die
Anatomie des Frosches, 1864-1882, 2nd ed., pt. i., 1888.—Biolog. Memoirs, edited by Burdon-
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SPECIAL LABORATORY REPORTS.—Ludwig and his pupils, Arbeiten aus der physio-
logischen Anstalt zu Leipzig, since 1866.—Burdon-Sanderson and Schafer, Collected papers
from the Physiological Laboratory of University College, London, 1876-1885.—Gamgee,
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Beitr. z. Path. u. Phys., Berlin, 1871.—J. Czermak, Gesammelte Schriften, 1879.—Marey,
Physiologie expérimentale, Travaux du laboratoire, Paris, 1875.—L. Ranvier, Laboratoire
d’histologie du Collége de France, Paris, since 1875.—Lovén, Physiol. Mittheil., Stockholm,
1882-84.—W, Kuhne, Untersuchungen des physiologischen Instituts der Universitit Heidel-
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hys. Abhandl., Jena, 1877-.—Von Wittich, Mitth. a. d. Konigsb. Phys. Lab., 1878,—

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de Phys. dela Faculté de Méd., Paris, 1885, Studies from the Biol. Lab. of Owens College,
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JOURNALS, PERIODICALS.—Archiv fiir die Physiologie, by J. C. Reil and Autenrieth.
12 vols., Halle, 1796-1815. Continued as—Deutsches Archiv fiir die Physiologie, by J. F..
Meckel, 8 vols., Halle, 1815-1823. Continwed as—Archiv fiir Anatomie und Physiologie, by
J. F. Meckel, 6 vols., Leipzig, 1826-1832. Continwed as—Archiv fiir Anatomie und wissen-

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iche Medicin, by Johannes Miiller, 25 vols., Berlin, 1834-1858. Continued under the
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fiir Physiologie, by E. du Bois-Reymond, until 1877. Js continued as—Archiv fiir Anatomie
und Physiologie by W. His, W. Braune, and E, du Bois-Reymond,—<Archiv fiir die gesammte
Physiologie des Menschen und der Thiere, by E. F. W. Pfluger, Bonn, since 1868.—Aeitschrift
fur Biologie, edited from 1865 by Buhl, Pettenkofer, Voit, and Radlkofer ; from 1875 by the
first three, and since 1880 by Pettenkofer and Voit, presently by Voit and Kihne.—Journal de
Physiologie expérimentale et pathologique, by F. igendie, 11 vols., Paris, 1821-1831,—
Zeitschrift fiir die organische Sg Aa by C, F. Heusinger, 4 vols., Eisenach, 1827-1828, —
Zeitschrift fiir Physiologie, by F, Tiedemann and Treviranus, 5 vols., 1824-1833.—Journal de
l’anatomie et de la physiologie normales et pathologiques de "homme et des animaux, by Ch.
Robin and Pouchet, since 1864.—Archives de physiologie normale et pathologique, by Brown-
Sequard, Charcot, Vulpian, Paris, since 1868.—Journal of Anatomy and Physiology, edited by
Humphry, Turner, and M‘Kendrick, since 1867,—Journal of Physiology, edited by M, Foster,
since 1878.--Archives Italiennes de Biologie, by C. Emery and A, Mosso, since 1881.—Annales
des sciences naturelles, Paris, since 1824.—Archives de Zoologie expérimentale et générale by
Lacaze-Duthiers, Paris, since 1872.—Archives de Biologie, by Ed. van Beneden, and Ch. van
Bambeke, since 1880.—Physiolog. Centralblatt, by Exner and Gad, since 1887.—Zeitschrift
fiir wissenschaftliche Zoologie, by C, T. von Siebold and A. von Kolliker, Re He since 1849,
—Archiv fiir pathologische Anatomie und Physiologie und fiir klinische Medicin, by R.
Virchow, Berlin, since 1847,—Zeit. f. wissensch. Mikroscop., Behrens, Braunschweig.—Archiv
fiir Naturgeschichte, by Wiegmann ; continued by Erichson and Troschel, Berlin, since 1835.—
Untersuchungen zur Naturlehre des Menschen und der Thiere, by Jac. Moleschott, since 1857,
—Zeitschrift fiir rationelle Medicin, Henle, Pfeufer, and Meissner.—Sitzungsberichte der
Akademie der Wissenschaften (Math. Nat.-Wiss. Classe), Vienna.—Philosophical Trans-
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Society, Edinburgh.—Proceedings of the Royal Society, Edinburgh.—Quarterly Micro-
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Microscopical Society, London.—Comptes rendus, Paris.—Anatomisches Anzeiger.—Index
Medicus.—Cohn, Beitrige zur Physiologie der Pflanzen, Breslau, 1872.—The Philosophical
Magazine, Edinburgh, London, and Cambridge.— Boston Medical and Surgical Journal,—
Verhandlungen der physikal.-medicinischen Gesellschaft zu Wiirzburg.—Archives of Medicine,
edited by Beale, London, 1856.—Annals and Magazine of Natural History.—Annales
(Mémoires) Archives du Muséum d'histoire naturelle, Paris.—Jenaische Zeitschrift fiir
Naturwissenschaft.—Mémoires de ]’Academie des Sciences de ]’Institut de France, Paris.—
Morphologisches Jahrbuch, by C. Gegenbaur, since 1876.—Nova Acta Academie Leopoldino-
Carolinee.—Zoologischer Anzeiger, by V. Carus, since 1878.—Abhandlungen and Monats-
berichte der k. preussischen Akademie der Wissenschaft zu Berlin.—Archiv fur experimentelle
Pathologie und Pharmakologie, by Naunyn and Schreiber, Leipzig, since 1873.—Deutsches
Archiv fiir klin, Medicin, by v. Ziemssen and Zenker, Leipzig.—Journal de Pharmacie et de
Chimie, Paris.—Archiv fiir Psychiatrie und Nervenkrankheiten, by Gudden and others, Berlin,
since 1868.—Archiv fiir wissenschaftliche und praktische Thierheilkunde by Roloff, Berlin,
1874.—Archives générales de médecine, Paris. —Brain, since 1879, edited by de Watteville,—
Archives de Neurologie, by Charcot, Paris, 1875.—Zeit. f. Hygiene, by Koch and Fliigge,—
The various Medical Journals, including the Lancet and British Medical Journal, Edinburgh
Medical Journal, London Medical Record, New York Med. Record, Practitioner, Medical
Chronicle.—Arch. for Otology, N. Y.—Arch. for Ophthal., N. Y.—Internat, Jour. of Med.
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Anat. u. Physiol.—Asclepiad:—Nature.

HISTOLOGY. —Henle, Handbuch der systematischen Anatomie des Menschen, 8rd ed., 1866~
1883,—Rutherford, Outlines of Pract. Histol., 1876.—W. Krause, Allgemeine und Mikros-
kopische Anatomie, Hannover, 1876.—F. Leydig, Lehrbuch der Histologie des Menschen und
der Thiere, Hamm, 1857; and his Untersuchungen, 1883 ; and his Zell u. Gewebe, Bonn,
1885.—V. Mihalkovics, General grea (Hungarian), 1881.—L, Ranvier, Traité technique
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d. Anat. d. Sinnesorgane.—S, Stricker, Handbook of Histology (translated by the New Syden-
ham Society), 1871-1873.—Archiv fiir mikroskopische Anatomie, Bonn; edited formerly by
Max Schultze, and presently by Waldeyer and La Valette.—Quarterly Microscopical Journal,
London.—Monthly a Mere ge Journal, London.—Journal of the Royal Microscopical Society,
London.—Schwann, Mikrosk, Untersuch., 1838 (translated by the Sydenham Society, 1847),
W. Kuhne, Das Protoplasma, Leipzig, 1864.Max Schultze, Das Protoplasma, Leipzig, 1863.—
R. Virchow, Die Cellular Pathologie (translated by Chance), 1860.—L, Beale, The Structure of
the Elemen Tissues, London, 1881.—A, Kolliker, A Manual of Human Microscopic
Anatomy, London, 1860; and his Icones Histolog., Leip., 1864.—J. Goodsir, Anatomical and
Pathological Observations, edited by W. Turner, Edinburgh, —Quain’s Anatomy, 9thed., edited

GENERAL BIBLIOGRAPHY, gor

by A, Thomson, Schafer, and Thane, London, 1882.—Rindfleisch, A Manual of Pathological
Anatomy (translated by R, Baxter), London, 1873.—C. Toldt, Lehrbuch der Gewebelehre,
Stuttgart, 3rd ed., 1888.—E. Klein and E. Noble-Smith, Atlas of Histology, London, 1872.—
H, Frey, Handbuch der Histologie und Histochemie des Menschen, Leipzig, 1876, Grundziige,
1885, and Das Mikroskop., 8th ed., 1886.—Fol, Lehr. d. vergleich. mikros. Anatomie, Leip., 1885.
—Behrens, Tabellen z. Gebrauch b. mik. Arbeiten, Braunschweig, 1887.—Fearnley, Pract.
Histol., 1887.—Brass, Kurzes Lehrb. d. Histol., Leip., 1888.—Beale, How to Work with the
Micros., Lond., 1880.—W. Stirling, Histological Memoranda, Aberdeen, 1880.—E. A. Schafer,
Practical Histol., 1877 ; and Essentials of Histol., 1887.—W. Stirling, Text-book of Practical
Histology, London, 1881.—Heitzmann, Microsc. Morphology, 1882.—Purser, Man. of Hist.,
Dublin.—E, Klein, Elements of Hist., London, 1883.—W. Flemming, Zellsubst. u. Zelltheil.,
Leipzig, 1882. —Cadiat, Traite d’anat. gén., Paris, 1879.—Bizzozero, Hand. d. klin. Mikroskop.,
Erlang., 2nd ed., 1888.—Carnoy, Gilson and Denys, Biol. Cellul., Louvain, 1884-88,-—
Friedlander, Mik. Technik., 3rd ed., Berlin, 1888. —Gierke, Farberei z. mik. Zwecken., Braun.,
1885.—Frommann, Unters. u. thier. u. pflanz. Zellen, Jena, 1884.—Wiedersheim, Lehrb. d.
vergl. Anat., Jena, 1888.—S. L. Schenk, Grundriss der Histologie d. Menschen, Vienna, 1885.
—Orth, Cursus d. norm. Histol., 4th ed., 1886.—-S. Mayer, Histolog. Taschenbuch, Prag., 1887.
—Stohr, Lehrb. d. Histol., Jena, 1888.—Lee and Henneguy, Traité de meth. de ]’Anat., Paris,
1888.

PHYSIOLOGICAL CHEMISTRY.—Hoppe-Seyler, Physiologische Chemie, Berlin, 1877-
1879.—Lehmann, Lehrb.:d. phys. Chem., 3rd ed., Leipzig, 1853; and Handbuch, 1859.—J.
Konig, Chemie der menschlichen Nahrung und Genussmittel, 2nd ed., Berlin, 1883.—Leo.
Liebermann, Grundziige der Chemie des Menschen, Stuttgart, 1880.—Robin and Verdeil,
Traité de chim. anat. et phys. (with Atlas), Paris, 1853.—J. Moleschott, Physiologie der
Nahrungsmittel, 2nd ed., Giessen, 1859.—E. Smith, Foods, 1873.—A. Wynter Blyth, Foods,
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1851-54), with Atlas of O. Funke’s plates.—Kingzett, Animal Chem., 1878,.—Thudichum,
Ann. of Chem. Med., 1879.—A. Gamgee, Physiological Chemistry of the Animal Body, vol. i.,
1880. — Hoppe-Seyler, Medicinische-Chemische Untersuchungen, Berlin.—Zeitschrift fiir
physiologische Chemie, by Hoppe-Seyler, Strassburg, since 1877.—Watts’ Dictionary of
Chemistry, second supplement, London, 1875.—Ralfe, Clinical Chemistry, London, 1889; and
Clinical Chem., 1883,—Wurtz, Traité de chim. biol., Paris, 1880.—T. C. Charles, Physiological
and Pathological Chemistry, London, 1884.—Parkes’ Hygiene, 7th ed.—Flugge, Lehrb. d.
hygien. Untersuchung., Leip., 1881.—Maly’s Jahresb. ii. Thierchemie since 1870.—Landolt, Das
opt. Drehungsvermog. org. Subst. Braun., 1879.—Articles in Hermann’s Handbuch d. Physi-
ologie, 1879-1884, and the various Text-books on Organic Chemistry. —Roscoe and Schorlemmer,
(Organic) Chem., 1884.—Nowak, Lehrbuch d. Hygiene, Wien.—Beilstein, Handb. d. org.
Chem., Hamb. and Leip., 2nd ed., 1885.—Ladenburg, Handb. d. Chemie, Breslau, 1883.—
Rosenthal, Vorles. ii. dffent. u. priv. Gesundheitspflege, Erlangen, 1887.—Kossel, Leitfaden f.
med.-chem, Curse, 2nd ed., Berlin, 1888.

COMPARISON OF METRICAL WITH COMMON MEASURES,

go2
=
APPENDIX B.
COMPARISON OF THE METRICAL WITH THE COMMON MEASURES.
By Dr WARREN DE 1A RUE.
: MEASURES OF LENGTH.
In English Feet In English Yards
In English Inches. | =12 Inches. =3 Feet.

Millimetre 0:03937 0°0032809 0°0010936
Centimetre 0°39371 0:0328090 0°0109363
Decimetre 3°93708 0°3280899 01093633
Metre 39°37079 | 8°2808992 1°0936331
Decametre 393°70790 82°8089920 10°9363310
Hectometre . 3937°07900 | 328°0899200 109°3633100
Kilometre 39370°79000 3280°8992000 1093°6331000
Myriometre . 393707 °90000 32808°9920000 10936°3310000

1 Inch =2°539954 Centimetres, | 1 Foot = 30479449 Decimetres. ] 1 Yard=0°91438348 Metre.

MEASURES OF CAPACITY.
In Cubic Feet =1,728 In Pints =34°65923

In Cubic Inches. Cubic Inches. Cubic Inches.
Millilitre or cubic centimetre 0°061027 0°0000353 0-001761
Centilitre or 10 cubie centimetres 0°610271 0°0003532 0°017608
Decilitre or 100 cubic centimetres 6°102705 0°0035317 0°176077
Litre or Cubic decimetre 61°027052 0°0353166 1°760773

Decalitre or centistere 610°270515 0°3531658 17°607734
Hectolitre or decistere 6102°705152 3°5316581 176°077341
Kilolitre or stere, or cubic metre. 61027°051519 35°3165807 1760°773414

Myriolitre or decastere - : 610270°515194 353°1658074 17607°734140 ©

1 Cubie Inch = 16°3861759 Cubic Centimetres. 1 Cubic Foot =28°3153119 Cubic Decimetres.
The UNIT OF VOLUME is 1 Cubic Centimetre.

MEASURES OF WEIGHT,

> TOR In Troy Ounces In Avoirdupois Lbs.
Tn Eogtiab Grains: =480 Grains. =7,000 Grains.
Milligramme 0°015432 0°000032 0°0000022
Centigramme 0°154323 0°000322 00000220
Decigramme 1°543235 0°003215 0°0002205
Gramme 15°432349 0032151 0°0022046
Decagramme 154°323488 0°321507 0°0220462
Hectogramme 1543°234880 3°215073 0°2204621
Kilogramme . 15432°348800 $2°150727 2°2046213
Myriogramme 154323 °488000 321°507267 22°0462126

The UNIT OF MASS in the metrical system is 1 Gramme, which is the mass or weight of 1 Cubic Centimetre
(1 c.c.) of water at 4° C., 7.¢., at its temperature of maximum density.

CORRESPONDING DEGREES IN THE FAHRENHEIT AND CENTIGRADE SCALES,

Fahr. Cent. | Fahr. Cent. | Fahr. Cent Cent. Fahr.| Cent. Fahr. | Cent. Fahr

500° ---260"-0 140°... 60°00] 40°... 4°4 100° ...212°: ae | Po oe
gerne Cy aie Jal C0 Re 7 oa sane be | 98° Bea Nr 60 ood | st ee yh
400° .. . 204°°4 | 130° 54°°4 32° 0°-0 96° ... 204°°8 56° ... 182°°8 8 | 16° .., 60°°S
350°... 176°°7 | 125° §1°7 30° ...— 1° 1 94°"... 2019 54°... 1993 2 | 14°: 2» STS
300°... 148°°9 | 120° 48°°9 25°... 3°°9 92° ,.. 197°°6 52° ... 125°°6 12° ... 53°°6
212° ...100°° 115° 46°°1 20° ...— 6°°7 90° ...194°° 50° ...122°: 10° .... $06
210° .. 98°°9'| 110° 43°°3 15° 9°°4 88° ... 190°°4 48° ... 118°°4 &° 1. 46°
205° 96°"1 105° 40°°5 10° ...—12°°2 86° 186°°8 46° ... 114°°8 6° 42°°8

200° ... 93°°3 | 100°... 37°8 | 5° ...—15°0 84°... 183°2 |] 44°. 111°2 | 4° es 89%
95° : 90° 5 95 35°°0 Oc ...—17°°8 82° 179°°6 42° ... 107°°6 2 400 36°C
190° see 87"°8 90° 32 2 —— 5° ooo —20°°S ts eee 6°:0 40° -..104°°0 0° ore 32°°0
185° : 85°°0 5° 29°°4 | —10° ...—23°°3 48. css Ada 38° ... 100°°4 | — 2°... 28°°4

180° : 82°-2 80° ... 26°°7 | —15° ...—26°'1 76° ... 168°°8 36°... 96°°B | — 4° oe 24°
175° 79° "4 75° 23°°9 | —20° ...—28°°9 74 eve LOD 2 34° 2... 9 98°03 | — 0s wee

170) on. TET | 70" on 211 | —25° ...—81°7 72°... 161°6 | 32°... 89°6 | — 8°... 17°6
165°... 739 | 65°... 18°38 | —30° ...—34°4 70° ...158°°0 | 30° ... 86°0 | —10°... 14°°0
160° eee 711 60°... 15° | —35° ...—37°-2 68° ... 154°°4 28° ... 82°4 | —12°... 10°°4
155° ... 68°"3 55°... 12°°R | —40° ...—40°°0 66° .,. 150°°8 26°... 786 Pealt’... Cee

aes eee 65 5 DO: ‘sos 10°°0 —45° ...—42°8 64° ... 147°°2 24° 00 C2 1 IO oo. Se
45 ste 62° 8 “** 7 br —50° aee me :} 62° oe 143°°6 22° eee 71°°6 —18° oe —0°"4
—20 one —4°0

To turn C° into F°, multiply by 9, divide by 5, and add 32°,

To turn F° into Cc’, deduct 32, multiply by 5, and divide by 9.

Abdominal muscles in respira-

tion, 173.

Abdominal reflex, 641.
Abducens, 599.
Aberration, chromatic, 757.
m spherical, 757.
Abiogenesis, 841.
Absolute blindness, 702.
Absorption by fluids, 39.
a _ by solids, 39.
Absorption of —

Carbohydrates, 298.

Colouring matter, 299.

Digested food, 295.

Effusions, 312.

Fat soaps, 299.

Forces of, 295.

Grape-sugar, 298.

Influence of nerves on, 301. °

Inorganic substances, 297.

Nutrient enemata, 301.

Organs of, 290.

Oxygen, 188, 191.

Peptones, 298.

Small particles, 300.

Solutions, 297.

Sugars, 298.

Unchanged proteids, 299.
Absorption spectra, 21,
Accelerans nerve, 669.

a in frog, 671.
Accommodation of eye, 749.

‘3 defective, 755.
Sy force of, 755.
a line of, 753.

a nerves of, 753.
a phosphene, 763.
5 range of, 756.
ens spot, 763.

~ time for, 752.
Accord, 811.
Acetic acid, 381.

Aceton, 405, 415.
Acetylene, 25.
Achromatin, 841.
Achromatopsy, 778.
Achroodextrin, 218.
Acid-albumin, 377.
Acid-hematin, 25

Acids, free, 374.

Acoustic nerve, 603.

» tetanus, 550,
Acquired movements, 708.
Acrylic acid series, 381
Action currents, 554,
Active insufficiency, 502.
Addison’s disease, 156, 446.

Adelomorphous cells, 241. ‘

Adenin, 385,
Adenoid tissue, 304.

INDEX.

Adipocere, 365.
Adventitia, 95.
ZZgophony, 181.
Aérobes, 280.
Asthesiometer, 831.
sthesodic substance, 645.
Afferent nerves, 583
After-birth, 894.
After-images, 779.
After-sensation, 732.
Ageusia, 826.
Agoraphobia, 606.
Agrammatism, 711.
Agraphia, 711. _
Ague, 153.

Air, changes in respiration, 187.

,, collection of, 184
composition of, 186.

,, diffusion of, 190.

», expired, 187.

», impurities in, 200.

5, quantity exchanged, 188.
Air-cells, 161.
Albumimeter, 410.
Albuminoids, 378.
Albumin of egg, 853.
Albumins, 374.
Albuminuria, 408.
Albumoses, animal, 377.
a vegetable, 377.
Alcohol, 352.
Alcohols, 382.
Alcoholic drinks, 353.
Alcool au tiers, 10.
Aleurone grains, 377.
Alexia, 713
Alkali-albumin, 377.
Alkali-hematin, 26.
Alkaline fermentation, 408,
Alkaloids, 353.
Allantoin, 355, 403,
Allantois, 871.
Allochiria, 838.
Allorhythmia, 107.
Alloxan, 400.
Almén’s test, 412.
Alternate hemiplegia, 655.

- paralysis, 655, 719.

serbia of generations,

a

Amaurosis, 587.

Amblyopia, 587.

American crow-bar case, 681.
Amido-acids, 384.
Amido-acetic acid, 267, 384.
peer tag. Phe acid, 255,
Amimia, P

Amines, 384.

Ammoniemia, 430.

Amnesia, 711. |

Amnion, 871,
Amniota, 872.
Amniotic fluid, 872.
Ameceboid movement, 15, 451.
Ampére’s rule, 543,
Amphiarthroses, 499,
Ampho-peptone, 248.
Amphoric breathing, 180.
Amygdalin, 312.
Amyloid substance, 377.
Amylopsin, 254.
Amylum, 383.
Anabiosis, 841.
Anacrotism, 109.
Anemia, 17, 48.

i metabolism in,

- pernicious, 17.
Anzrobes, 280.
Anesthesia dolorosa, 838.
Anesthetic leprosy, 582.
Anesthetics, 839.
Anabolic nerves, 583,
Anabolism, 341.
Anakusis, 604.
Analgesia, 647.
Analgia, 839.
Anamunia, 872.
Anarthria, 710.
Anasarea, 313.
Anelectrotonus, 566.
Aneurism, 114, 115.
Angiograph, 100.
Angiometer, 108.
Angioneuroses, 678.
Anidrosis, 448.
Animals, characters of, xlii.

| Animal foods, 343.

» Magnetism, 686.
Anions, 545.
Anisotropous substance, 45d.
Ankle clonus, 6438.
Anode, 545.
Anosmia, 584. ;
Antagonistic muscles,’ 502.
Anthracometer, 184
Anthracosis, 164.
Anti-albumin, 248.
Antiar, 312.
Anti-emetics, 233.
Antihydrotics, 446,
Antipeptone, 248.
Antiperistalsis, 233.
Anti-pyretics, 336.
Anti-sialics, 215.
Aortic valves, 54.
ss insufficiency of,
110.

Aperistalsis, 237.
Apex-beat, 61, 69.
Aphakia, 740.

904 INDEX.
Aphasia, 710. Atresia ani, 871. Bile, composition of, 270,
Aghenia, 522. Atrophy, 504. » crystallised, 267.
Apnoea, 663. - soos — face, 598. », ducts, ated ae
Appunn’s apparatus, 815. d in, 475. 39 99 gature of, 262.
ipeaaieeda. 838. . in eye, 588, 760. »» effects of on, 273.
queous humour, 720. Attention, time for, 685. » excretion of, 271.
Arachnoid mater, 726. Audible tone, lowest, 813. »5 fate of, 275.
Archiblastic cells, 868. Auditory after-sensations, 820. », functions of, 274. }
Area opaca, 864. » area, 703. »» gases of, 269. _ |
» pellucida, 864. : 5 aure, 704. »» passage of drugs into, 272.
,, vasculosa, 870. » centre, 703. 55 Pigments, 268.
Argyll Robertson pupil, 760. », delusions, 604. »» pressure, 272. a
Arhythmia cordis, 57. ¢ meatus, 799. 5, reabsorption of, 272.
Aristotle’s experiment, 833. 5 nerve, 797. 3, secretion of, 270.
Aromatic acids, 382. », ossicles, 801. »» spectrum of, 269.
$s oxyacids, 385. » paths, 704, 3, test-for, 267, 268.
Arrector pili muscle, 441. +» perceptions, 811. Biliary fistula, 271.
Arterial tension, 105. », sac, 894, Bilicyanin, 269.
Arteries, 93. Auerbach’s plexus, 237, 294. Bilifuscin, 269.
,, blood-pressure in, 122. | Augmentor nerves, 671. Biliprasin, 269.
, central, 689. Auricles of heart, 50, 52, 57. Bilirubin, 268. .
¥ development of, 884. », development of, 883. Biliverdin, 268.
», emptiness of, 672. Auscultation of heart, 75. Binocular vision, 787.
, rhythmical contrac- ff of lungs, 179. Biological law, 896.

tion of, 675. Automatic excitement, 625. Biology, xxxv.

», sounds in, 140. Autonomy, 686, Biot’s respiration, 172. {
» structure of, 93. Auxocardia, 86. Birth, 894.

», tension in, 122. Avidity, 245. Biuret reaction, 376.

,, termination in veins, | Axis of vision, 769. Blastoderm, 851, 862.

137. : Blastomere, 862.
Arteriogram, 101. Bacillus, 49, 279. Blastosphere, 862.
Arthroidal joints, 499. we acidi lactici, 280. Blepharospasm, 603.
Articular cartilage, 498. Pe anthracis, 49. Blind spot, 768.

Articulation nerve-corpuscles, Af butyricus, 280. Blood, 1.
829. BS subtilis, 281. », abnormal, 46.
Artificial cold-blooded condi- x tubercle and others, » analysis, 29,
tion, 339. 200. » arterial, 45.
Artificial eye, 748. Bacterium, 49, 279, 284. ;, carbon dioxide in, 44,
», digestion, 250. nf aceti, 280. », clot, 29,
5 gastric juice, 247. “ coli, 285. » coagulation, 31.
a pancreatic juice, 255, As foetidum, 449. » colour, 1
» respiration, 198. 5 lactis, 284. », colouring matter, 18,
- Marshall Hall’s me- ee synxanthum, 348. »» composition of, 20
thod, 199. Ball and socket joints, 499. », defibrinated, 29.
3 Sylvester’s method, | Bantingism, 366. », distribution of, 144.
199, Baresthesiometer, 834. », electrical condition of,
» _ selection, 896, Basal development, 891. 579.
Aspartic acid, 256, 385. », ganglia, 650, 715. »» extractives, 39,
Asphyxia, 196, 663. . Basedow’s disease, 155, 678. » fats in, 38
:s artificial respiration | Bases, 374. », fibrin in, 17, 30,
in, 198. Basilar membrane, 810, +> gases in, 39.
” recovery from, 198. Bass-deafness, 813. » granules of, 17.
Aspirates, 542. Batteries, galvanic, 545. », Islands, 10, 870.

Aspiration of heart, 129.
% thoracic, 129.
a ventricles, 58.

“e Bunsen’s, 545,
aA Daniell’s, 545,
z Grennet’s, 546.

;, lake-coloured, 8.
», loss of, 48.
»» Iicroseopic examina-

Assimilation, 341, . 3 Grove’s, 545. tion, 3.
Associated movement, 760, 787. A Lechlanché’s, 546, » nitrogen in, 45.
Astatic needles, 544. vs Smee’s, 546, », odour, 2
Asteatosis, 449, Beats, 818. »» organisms in, 49,
Asthma nervosum, 614. » isolated, 818. »» oxygen in, 42

¥s Ae ip 614, 5, suecessive, 818. » Oozone-in, 43.
Astigmatism, 757. Bed-sores, 542. »» Plasma, 29.

a correction of, 758. | Beef-tea, 350. »» Plates, 16.

99 test for, 758. Beer, 354, »» portal vein, 45.
Atavism, 896. Bell’s law, 617. » proteids of, 37.
Ataxaphasia, 911. », deductions from, 619, » quantity, 45.

Ataxia, 619, 700, 709, Bell’s paralysis, 602. »» Yeaction, 1.

Ataxic tabes, 647. Benzoic acid, 402. »» salts in, 39.
‘Atnoeghee’ 82, 199, 208 ae srpecment ay »» serum, 29. a.
¢ pressure, 203. idder’s ion, 78. specific gravi os
diminution of, 204. | Bile, 267° : 1: aoe oe lah

a4 increase of, 2b4, »» acids, 267,

Blood, transfusion of, 46.
», Variations in, 46.
»» venous, 45
» water in, 39.
7 channels, intercellular,

Blood-corpuscles—stroma, 6.
5, abnormal changes, 17.
», action of reagents on, 6,

>
» amceboid movements,
15

», change of form, 7.
», chemical composition,

», circulation, 137.
3, colour, 6
» colourless, 13.
55 conservation of, 8.
3,5 crenation, 6.
» decay, 12.
5, diapedesis, 15, 139.
» effect of drugs, 15.
» effect of reagents, 6.
49: LOL, 3...
35 Gower’s method, 5.
» histology of, 6.
5, human, red, 3.
Ee 9» white, 13, 29.
» intracellular origin, 11.
>» Malassez’s method, 4.,
», nucleated, 17.
+> number, 4, 17,
», of newt, 13.
3 Origin, 10,
», parasites of, 18.
5, pathological changes, 17.
», proteids of, 28
», rouleaux of, 6.
» Size, 3, 9, 17.
», staining of, 7.
» stroma, 6.
» transfusion of, 46.
» weight, 3.
white, 13.
Blood- current, 137,

2 an capillaries, 137.

», velocity of, 134.
Blood-gases, 39.

» estimation of, O, COs,

and ;

»5 extraction, 40.

»» gas-pumps for, 40.

» . quantity, 42.
Blood-glands, 148.
Blood-islands, 10, 870.
Blood-plasma, 29,
Blood-pressure, 119.

» arterial, 122.

~ capillary, 128.

» estimation of, 119.

Ga ak pulmonary artery, 130.

3, in veins, 128
» relation to pulse, 127.
variations of, 122, 127.
Blood-vessels, 92.
», action of drugs on, 95.
s, cohesion of, 97.
>, elasticity of, 96.
», lymphatics, 95.
» 5, pathology of, 97.
3, properties of, 95, 96.
a structure of, 92.

INDEX,

Blue pus, 449.

5, sweat, 449,
Body, vibrations of, 116.
Body-wall, formation of, 870.

Bone, chemical composition of,
882

», - callus of, 371.
», development of, 881.
», effect of madder on, 371.
», fracture of, 371
»» growth of, 882.
», histogenesis of, 881.
red marrow, 12,
Bones, mechanism of, 498,
Bottger’s test, 220.
Boutons terminals, 829.
Bowman’s tubes, 735.
ss glands, 821.
Box pulse-measurer, 97.
Bradyphasia, 711.
Brain, 649.
5, arteries of, 728.
», blood- vessels of; 727.
», general scheme ‘of, 649.
», impulses, course of, 633.
» in invertebrata, 730.
»> membranes of, 726.
»» motor centres of, 691.
»» movements of, 727.
», of dog, 693.
»» pressure on, 729.

», protective apparatus of,
726.

»» psychical functions of,
681.

», pulse in, 115.
Fe Dates tracts of, 653,
70

», topography of, 706, 714.
weight of,
Branchial arches, 871.
- clefts, 871, 880.
Brandy, 354,
Bread, 351.
Brenner’s formula, 603.
Broca’s convolution, 710.
Bromidrosis, 449.
Bronchial breathing, 179, 180.
fremitus, 180.
Bronchiole, 161.
Bronchophony, 181.
Bronchus extra-pulmonary, 166.
a intra-pulmonary, 161.
- small, 161.
Bronzed skin, 156.
Brownian movement, 217,
Bruit, 140.

» de diable, 141.
Brunner’s glands, 276, 293.
Buchanan’s experiments, 33.
Bulbar paralysis, 661.

Bulbus arteriosus, 883.
Butter, 346.
Butyric acid, 280, 381,

Cachexia, 154,

Caffein, 353.

Calabar hean on eye, 588.

Calcic phosphate, 373.

Calculi, biliary, 269, 287.
», Salivary, 216, 285.
5, urinary, 419.

Callus, 371.

905

Calorimeter, 315.
Canal of cochlea, 808.
» hyaloid, 741.
», Nuck, 889.
5, of spinal cord, 626.
, of Stilling, 741.
ss Petit, 740. .
» Schlemm, 735.
semicircular, 808.
Canalis cochlearis, 808.
s, Yreuniens, 808.
Capillaries, 93.

+5 action of _ silver
nitrate on, 94.

ys blood - current in,
137.

3 circulation, 138.

s contractility of, 96.
a development of, 11.

‘5 form and arrange-
ment of, 137.

3 pressure in, 128.

Ps stigmata of, 94.

ee velocity of blood in,
135

Capillary electrometer, 554.
Capsule, external, 717.
re Glisson’s, 259.
»» internal, 716.
of Tenon, 741.
Carbohydrates, 382.
. fermentation of,
280.

Carbolic acid urine, 404.
Carbon dioxide, conditions af-
fecting, 188
ap estimation of, 183.
<5 excretion of, 188, 192.
a in air, 186.
ee in blood, 44.
» in expired air, 187.
where formed, 194.
Carbonic oxide- hemoglobin, 24.
re oxide, 24,
Ag poisoning by, 24.
Cardiac cycle, 57.
» dulness, 76.
» ganglia, 76.
», hypertrophy, 69.
>» impulse, 61, 69.
5 movements, 66.
y» murmurs, 74.

» nerves, 76. ?
» nutritive fluids, 779.
»» Plexus, 76.

», poisons, 85.
»,» Yrevolution, 57.
sounds, 71.

Cardinal points, 747..
Cardiogram, 61.
Cardiograph, 61.
Cardio-inhibitory centre, 125,

» nerves, 667.
Cardio-pneumatic movement, 86.
Caricin, 256.
Carnin, 349.
Carotid gland, 77, 157.
Cartilage, .498, 871.
Casein, 346, 377.
Catacrotic pulse, 102.
Cataphoric action, 548.
Cataract, 740,

906

Cathartics, 239.
Cathelectrotonus, 565.
Cathode, 545.
Caudate nucleus, 715.
Cavernous formations, 95.
Cells, division of, 841.
Cellulose, 218.
Cement, 225.
action of silver nitrate
on, 95.

é substance, 95.
Centre, accelerans, 669.

»» ano-spinal, 644.

»» auditory, 7

. eardio-inhibitory, 667.

», Cilio-spinal, 643.

., closure of eyelids, 659.

», coughing, 660,

dilator of pupil, 643,
660.

ejaculation, 644.

erection, 644, 858.

., for coughing, 660.
for defecation, 644.
for mastication

sucking, 660.

,, for saliva, 660.

», gustatory, 713.

;» heat regulating, 680.

;; micturition, 644.

.. olfactory, 713.

»» parturition, 644.
pupil, 660.
respiratory, 661.

+» sensory, 701.

+ sneezing, 660.
spasm, 680,
speech, 710.

,, swallowing, 660.

» sweat, 644, 680.
vaso-dilator, 644, 678.

+s Vaso-motor, 644, 672.

+» Vesico- spinal, 644.

» Visual, 713.
vomiting, 660.

Centre of gravity, 505.
Centrifugal nerves, 581.
Centripetal nerves, 583.
Centro-acinar cells, 252.
Cereals, 351,
Cerebellum, 723.
Action of electrici
Connections of, 652,
Function of, 724.
Pathology of, 725.
Removal of, 724.
Structure of, 728.
Cerebral arteries, 689 728.

” epilepsy, 695, 709

», fissures, dog, 693,"

= inspiratory centre, 662,

»» motor centres, 706,

ss sensory centres, 713.
vesicles, 865.

Cerebrin, 380, 531.
Cerebro-spinal fluid, 307.
Cerebrum, 649.
Pe blood-vessels of, 688,
689, 727.

and

on, 725.

e eenane of, 689.

Se epilepsy of, 6 95.
pe excision of centres,
700.

INDEX.

Cerebrum, Flourens’ doctrine,
682

,, functions of, 681.

9 Goltz’s theory of,
705.

af imperfect develop-
ment of, 682

- lobes of, 689.
aa motor regions of,
694.

movements of, 727
removal of, 682.
sensory centres, 701.
ie structure of, 656.

‘3 sulci and gyri of, 689.
ee centres of,

weight of, 649.
Cerumen, 445,
Cervical sympathetic, section of,
623.

Chalazx, 852.
Charcot’s crystals, 203.
rf disease, 582.
Cheese, 348.
Chemical affinity, xl.
Chess-board phenomenon, 792.
Chest, dimensions of, 176.
Cheyne: -Stokes’ phenomenon,
id
Chiasma, 585.
Chitin, 380.
Chloasma, 446.
Chloral, 674.
Chlorophane, 740.
Chlorosis, 17.
Chocolate, 353.
Cholemia, 272.
Cholalic acid, 267, 382,
Cholesterzmia, 274.
Cholesterin, 28, 269, 275, 532.
Choletelin, 269.
Cholin, 531.
Choloidinic acid, 268,
Choluria, 413.
Chondrin, 379.
Chondrogen, 379.
Chorda dorsalis, 867.
Chorda tympani, 600, 678,
Chord tendiniz, 59.
Chorion leve, 874.
»» frondosum, 874.
1» __ primitive, 873.
Choroid, 735.
Choroidal fissure, 892.
Christison’s formula, 393.

Chromatic aberration, 757.

Chromatin, 842.
Chromatophores, 450,
Chromatopsia, 587.
Chromidrosis, 449.

| Chromophanes, 740.

Chrono
Chyle,
»» movement of, 310.
», vessels, 301.
Chylous urine, 418.
ter i 85
icatric 1.
Cilia, 451.
»,» conditions for movement,
452

9 effect of reagents on, 452,

oeert, 481,

oa functions. ni ee {
ganglion,

me = 451.

force of, 452.

3) ”

Cilio-spinal region, 643.
Circle of Willis, 728. |
Circulating albumin, 356.
Circulation, capillary, 137.

— duration of, 136.

5, foetal, 875,
ae portal, 50.

>» muscle, 750,
»» nerves, 591, 7
Ciliated epithelium, 451. |

c pulmonary, 50.
fs schemata of, 118. ©
Pea second, 870.

systemic, 50.
Circumpolarisation, 221.
Circumvallate papille, 824.
Claustrum, ate
Cleft sternum, 71.

3 late, 880.
ee Taxwell’s

Clevage of yelk, 862.
», lines of, 863.
ae partial, 866.
Climacteric, 854.
Clitoris, 890.
we continued contraction,

Closing shock, 549.
Clothing, Sat:
Coagulable fluids, 37.
Coagulated proteids, 377.

experiment,

Coagulation experiments, 35,

Coagulation of blood, 30, 31, 33.
ys theories of, 33, _34,

36.

Cocaine, 760.

Pet aar se 77, 157.

Cochlea, 8

Cocoa, 353.

Coecitas verbalis, 703.

Cceelom, 868.

Coffee, 353.
Cold-blooded animals, 318.
Cold on the body, 337

» uses of, 339.
Cold-spots 836.
Collagen, 379.
Colloids, 296,
Coloboma, 892.
Colostrum, 347.
Colour associations, 820.
Colour-blindness, th

ba *
Colour sensation, 774...

», Hering’s theo ory, 776.
holtz

” Te theory,

Coloured Semi same

Colourless co

Colour top, =: ei

Colours, complementary, 774,
» con |
> geome I table, 775.
i mice, 7 mixing, 775. :
» Simple, 774... | A

Columella, 820. .

Columns of the cord, 626.
Coma, diabetic, 266.
Comedo, 449.

Common sensation, 838.
Comparative—

Absorption, 314.

Circulation, 157.

Digestion, 288.

Hearing, 820

Heat, 340

Kidney and urine, 437.

Metabolism, 385.

Motor organs, 508.

Nerve centres, 730.

N oor and electrophysiology,

7.
Peripheral nerves, 624.
Reproduction and develop-
ment, 895

Respiration, 205.

Sight, 795.

Skin, 449.

Smell, 823.

Taste, 826.

Voice and Speech, 523.
Compensation, 554.
Complemental air, 166.
Complementary colours, 774.
Compound eye, 795
Concretions, 284.

Condensed milk, 348.
Condiments, 352.
eee in the cord, 633,

Conductivity, 573.
Conglutin, 378.
Congo red, 243.
Conjugate deviation, 588, 708.
Conjugation, 842.
Connective-tissue spaces, 302.
Consonance, 818
Consonants, 521.
Constant current, action of, 482.
Constant elements—

Bunsen’s, 545.

Daniell’s, 545.

Grennet, 546.

Grove’s, 545.

Leclanché’s, 546.

Smee’s, 546.
Constipation, 287.
Contraction, cardiac, 86.
fibrillar, 476.
initial, 487.
muscular (see Myo-

gram).
of blood-vessels, 95.
remainder, 480.
rhythmical, 474.
secondary, 558, 559.
without metals, 556.
Contracture, 480.
Contrast, 780.

F colours, 774, 780.
Convergent lens, action of, 743.
Cornea, 733.

Coronary vessels, 55.
art of ligature of,

650,

”

Co
652, 720.
Corpulence, 366.

quadrigemina,

INDEX,

Corpus callosum, 715.

»» luteum, 856.

»» spongiosum, 887.

3, Striatum, 650, 715.
Corresponding points, 787.
Cortical blindness, .702.
Corti’s organ, 808.
Cotyledons, 877.

Coughing, 182.

ts centre for, 660.
Cracked pot sound, 179.
Cramp, 840...
Cranial flexures, 865.

9» -nerves, 584.
Cranioscopy, 682.
Creamometer, 347.
Cremasteric reflex, 641.
Crepitation, 180.

Crescents of Gianuzzi, 209.
Crista acustica, 809.
Crossed reflexes, 638.
Crura cerebri, 718.

Crusta, 718.

1» petrosa, 225.

$s Pees: 30.
Crying, 183.

Crystallin, 376, 740.
Crystalline lens, 740.
spheres, 795.

Crystallised bile, 267.
Crystalloids, 297.
Cubic space, 200.
Curara, action of, 471, 474, 674.
Cutaneous respiration, 198.

“a trophic

581

Cuticular membrane, 225.
Cyanogen, 25.
Cylindrical lenses, 757
Cynuric acid, 403.
Cyrtometer, 177.
Cysticercus, 843.

Cystin, 416.

Cytozoon, 7.

Daltonism, 778.
Damping apparatus, 801.
Darby’s fluid meat, 249.
Death of a nerve, 541.
Débove’s membrane, 161.
Decidua reflexa, 873.
»» Serotina, 873.
» vera, 873.
Decubitus acutus, 582, 722.
Decussation of pyramids, 657,
Defzcation, 233.
centre for, 644.
Degeneration, fatty, 366, 539.
traumatic, 539.
Deglutition, 227.
nerves of, 229.
Deiter’s cells, 810.
Delomorphous cells, 241.
Demarcation current, 554.
Demodex folliculorum, 445.
Denis’s. plasmine, 33.
Dentine, 224.
Dentition, 226:
Depressor fibres, 610, 613, 674.
% nerve, 124, 610.
Deutero-albumose, 248,
Development,

affections,

chronology of,

907

Dextrin, 383.
Dextrose, 383.
Diabetes mellitus, 264.
Diabetic.coma, 266.
Dialysis, 297.
Diapedesis, 139.
Diaphanometer, 348.
Diaphoretics, 446.
Diaphragm, 173.
Diarrhea, 288.
ee action, 218, 254, 278,

Diastole, 57.
Dichroism, 18.
Dicrotic pulse, 106.
9» wave, 103.
Diet, adequate, 359.
effect of age on, 360.
», effect of work on, 360.
» flesh, 362.
», flesh and fat, 364.
of carbohydrates, 363.
» quality of, 356.
quantity, 356.
Difference theory, 563.
Differential rheotom, 560.
tones, 819,
Diffusion, 295.
circles, 749.
of gases, 39.
Digestion during fever, 286.
in plants, 289
Digestion, 206.
5 artificial, 250, 255.
Digestive apparatus, 221.
gee of pupil, centre for,

39

Dilator pupille, 759.
Dilemma, 685.
Dioptric, 757.

observations, 742.
Diphthongia, 523.
Diphthongs, 521.
Diplacusis, 813.
Diplopia, 588, 787.
Direct vision, 769.
Direction, 819.
Discharging forces, 470.
Discus proligerus, 850.
Disdiaclasts, 462.
Dissociation, 193.
Dissonance, 818.
Distance, estimation of, 793.
false estimate of, 793.

i smallest appreciable,
833.

99

Diuretics, 422.

Division of cells, 841.

el conduction in nerve,
3

Double contact, feeling of, 831.
Double images, "neglect of, 789.
Dreams, 685.
Drepanidium, 7.
Dromograph, 133.
Dropsy, 312.
Duct of Cuvier, 884.
», Gaertner, 889.
Ductus arteriosus, 876,
», venosus, 876.
Dura mater, 726.
Dust particles, 200.
Dys-albumose, 248

908

Dyschromatopsy, 778.
Dyslysin, 268.

sy 171, 196, 663.

Ear, 797.

,, conduction in, 798.

»» development of, 894.

,, external, 799.

», fatigue of, 820.

,, fineness of, 813.

,, labyrinth of, 893,

», meatus of, 799.

., ossicles of, 801.

+, speculum, 800.

», tympanum of, 799.
Earthy phosphates, 406.
Eccentric hypertrophy, 60.
Echo speech, 686.
Ectoderm, 863.

Ectopia cordis, 67.
Efferent nerves, 581.
Effusions, 312.
Egg albumin, 376, 411.
Eggs, 349.
Ejaculation, centre for, 644.
Elastic after-affect, 96, 492.
» elevations, 105.
,, tension, 130.
», tubes, 92.
Elasticity of blood-vessels, 96.
‘3 lens, 750.
5 lungs, 165.
ae muscle, 491.
Elastin, 379.
Electrical charge of body, 579.
fi fishes, 579.
re nerves, 573.
organs, 580.

Electrical currents of muscle,

554, 557.

“ eye, 561.

a glands, 561.

és heart, 558.

ce mucous membranes,
561.

Fat nerve, 554, 557.

oe plants, 565.

skin, 561.

sare therapeutical uses,

0/4.

Electrodes, non-polarisable, 547.
is other forms, 574,

Electrolysis, 545.

Electrometer, 554.

Electro-motive force, 541.

Electro-physiology, 541.

Electro-therapeutics, 574.

Electrotonus, 561.

ea currents in, 561.
% in conductors, 562..
BS in inhibitory
nerves, 567,
9 in motor nerves,
% in muscle, 567.
sd in sensory nerves,
Eleidin, 438.
mi. eee granules of blood,
Embryo formation of, 869,
Emetics, 232.

INDEX,

Emmetropic eye, 750, 753.
Emotions, expression of, 523.
Emulsification, 256.
Emulsin, 312.
eae a
Emydi ‘
Enamel, 225.
Enamel-organ, 225.
Enchylema, 842.
End-arteries, 148.

», bulbs, 828.

,, organs, 581,

», Plate, 458.
Endocardial pressure, 67.

' Endocardium, 54.

Endoderm, 863.

_Endolymph, 808.

Endomysium, 453,

_Endoneurium, 530.

Endosmometer, 296.
Endosmosis, 295.
Endosmotic equivalent, 296.
Enemata, 301.

Energy, conservation of, xli.

5, potential, xli.
Eneuresis nocturna, 437.
Entoptical phenomena, 762.

os pulse, 763.
Entotical perceptions, 820.
Enzym, 379.

Epiblast, 863.

Epicardium, 51.

Epidermal appendages, 369.
Epididymis, 845.

Epidural space, 727.
Epigenesis, 869.

Epiglottis, 229.

. injury to, 229,

Epilepsy, 680, 695.
Epineurium, 529.
Epiphysis cerebri, 722.
Epithelium, ciliated, 159, 451.
Eponychium, 440
Equator, 561.
Equilibrium, 603, 647, 682.
Erectile tissue, 857.
Erection, centre for, 857.

3 of penis, 857.
Erect vision, 749.
Errhines, 183.
Erythrochlorophy, 778.
Erythro-dextrin, 218.

» -granulose, 383.
Esbach’s method, 410.
Eserine, 761.

Ether, xxxvi.
Eudiometer, 40.
Eukalyn, 384.
Euperistalsis, 237.
Eupneea, 663.

Eustachian catheter, 806,

os tube, :

omer ad action of poisons

on, 646.
Excitable points of a nerve, 541.
Excito-motor nerves, 583.
Excretin, 282.
Excretion of fecal matter, 233.
Exophthalmos, 783, .
Expectorants, 202.
Experimentum mirabile, 686.
Expiration, 169.
Expiratory muscles, 173.

Extra-current, 549.

Explosives, 521.
Extensor tetanus, 637.
External capsule, 717.

» genitals, 890.

Extrapolar region, 565.
Extremities, development of,

871.
Exudation, 313.
Eye, 733.
3» accommodation of, 749.
», artificial, 748.
», astigmatism, 758.
‘<i sca aberration of,
757.
55 compound, 793.
», development of, 892.
- res of electrical currents.
763.
+, emmetropic, 750. .
», entoptical phenomena, 762. ,
», epiphysial, 796.
» excised, 761.
5, fundus of, 766.
», hypermetropic, 754.
,, illumination of, 764.
»» movements of, 782.
»» muscles a
»» myopic, °
»» pineal, 796.
»» presbyopic, 755.
5» protective organs of, 793.
», refractive power of, 753.
», structure of, 733.
Eyeballs, axis of, 783.
s» | movements of, 785.
»» muscles of, 785.
»» planes of, 783.
5» positions of, 784.
53 protrusion of, 783.
» retraction of, 783.
ss simultaneous move-
ments of, 780.
Eye-currents, 561.
Eyelids, 793.

Facial nerve, 599.

Fecal matter, 283.

o excretion of, 233.

Fainting, 61.

Fallopian tubes, 853,

Fall-rhetom, 563.

Falsetto voice, 578.

Faradic current, 549.

Faradisation in paralysis, 577.

Far point, 753. ;

Fascia, lymphatics of, 310.

Fatigue of muscle, 495. 4

» stuffs, 496. |

Fats, 381. ~
»» decomposition of, 256.
»» metabolism of, 363.

»» origin of, 364, .
Fat-splitting ferment, 256.
Fatty acids, 381.

5». degeneration, 366.

Febri , 336.
Fechner’s law, 732.
Fehling’s solution, 220, 414.
Fermentation, 354.
” in intestine, 279. aus
” test, 221, P » "
Ferments, 380, Te

Ferments, fate of, 279.
a organised, 380.
unorganised, 379.
Fertilisation of ovum, 860.
Fever, 335
» after transfusion, 147.
Fibres of Tomes, 224.
Fibrillar contraction, 476.
Fibrin, 17, 30, 31.
Fibrin-factors, 35.
Fibrin-ferment, 35.
Fibrinogen, 34, 376.
Fibrinoplastin, 34.
Fibroin, 378.
Field of vision, 749.
contest of, 791.
Filaria sanguinis, 418.
Filiform papille, 824.
Filtration, 297.

First Se ial discharge of,
66.

», effects of, on thorax, 182.

Fish extract, 356.
Fission, 841.
Fistula, biliary, 271.

» gastric, 247.

- intestinal, 277

Ke pancreatic, 253.

ae pyloric, 245.

es Thiry’ By 20

Vella’s, 277.

Flame spectra, 21.
Flavour, 823.
Fleischl’s ery contraction,

a hemometer, 20.
Flesh, 349.
Flight, 509.

Floor-space, 201.

Flourens’ doctrine, 682.

Fluid vein, 140.

Fluids, flow of, 89.’

», introduction of, 222.

Fluorescence, is

of eye, 749.
Fluorescin, 742,
Focal distance, 743.

», line, 752

» point, 744.

Feetal circulation, 875.

‘ membranes, 873.
Follicles, solitary, 293.
Fontana’s markings, 532.
Fontanelle, pulse in, 115,
Foods, isodynamic, 316.

» plastic, 356.

», quantity, 356, 358,

+ se salah 356.

» utilisation of, 350.

», vegetable, 350.
Foramen ovale, 876.

es of Magendie, 726.
Force of accommodation, 755,
Forced movements, 721,
Forces, xxxvii.

Fore-gut, 869.

Formatio reticularis, 658,
Formative cells, 865,
Fovea cardica, 869.

», centralis, 739, 769.
Fractional heat coagulation, 38.
Free acid, formation of, 245.
Fremitus, 180.

INDEX,

Friction sounds, 180.
Frog current, 557.
Fromann’s lines, 529.
Fruits, 352
Fundamental note, 814.
Fundus glands, 241.
Fungi, 279.

Fungiform papille, 824.

Gaertner, ducts of, 889.
Galactorrhcea, 345.
Galactose, 383,
Gallop, 508.
Gall stones, 287.
Galton’s whistle, 812.
Galvanic battery, 545.
= excitability, 578.
Galvano-cautery, 579.
Galvanometer, 544.
reflecting, 547.
Galvano- -puncture, 579,
ss tonus, 536.
Gamgee’s method, 35.
Ganglionic arteries, 689,
Gangrene, 583,
Gargling, 183.
Gaseous exchanges, 188.
Gases, absorption of, 39.
». diffusion of, 39.
5, extraction of, 40,
s> in blood, 39.
»» in lymph, 195.
>» in stomach, 252.
3, indifferent, 200.
»» irrespirable, 200,
»» poisonous, 199.
respired, 188.
Gaskell’s clamp, 80.
Gas-pump, 41.
Gasserian ganglion, 591.
Gas-sphygmoscope, 101.
Gastric digestion, 247.
» conditions affecting, 250,
» fistula, 247
,, pathological variations,
286.

Gastric giddiness, 606.
Gastric juice, 241.
,, action of drugs on, 246.
;, action on tissues, 251.
», actions of, 247,
artificial, 2.
Gaule’s ex eriment, (5
Gelatin, 251, 379.
Gelatin v. albumin, 362.
Gemmation, 842.
Genital cord, 889,
»» corpuscles, 829.
» eminence, 889
Genu valgum, 503.

»» varum, 503.
Geometrical colour-table, 775.
Gerlach’s theory, 629.
Germ-epithelium, 849, 868,
Germinal area, 863

59 membrane, 863.
Germinating cells, 304.
Germs, 200.
Gestation, period of, 878,
Giddiness, 601, 605.
Ginglymus, 498,
Giraldés, organ of, 889.
Girdle sensation, 648,

go9

Gizzard, 231,
Glance, 791.
Glands, albuminous, 206.
», Bowman’s, 821.
7 Brunner’s, 276, 293.
» buccal, 206.
» carotid, 77, 157.

5, ceruminous, 445,

» changes in, 209.

», coccygeal, 77, 157.

»» Ebner’s, 206.
;», fundus, 241.
>», Harderian, 796.
», . lachrymal, 794.

», Lieberkiihn’s, 277, 293.

» lingual, 206.

»> lymph, 304.

»» Mammary, 343.

5 Meibomian, 793.

- mixed, 209.

59 Moll’s, 443.

FS mucous, 206.
BA Nuhn’s, 206.

»» parotid, 214,

» peptic, 241.

3» Peyer’s, 294.

» pyloric, 241.

» salivary, 206.
55 sebaceous, 442.
re serous, 206.

» solitary, 293.

», sublingual, 214.
», submaxillary, 209.
», sweat, 442
» uterine, 853.
Weber’s, 206.
Glaucoma, 594,
Gliadin, 378.
Glisson’s capsule, 259.
Globin, 377.
Globulins, 376.
Globuloses, 248.
Glomerulus, 387.
Glosso- ged be Sr nerve, 606.
Glossoplegia, 615
Glossy skin, 582,
Glottis, 512.
Glucose, 264, 383, 413.

$6 tests for, 220, 414.
Glucosides, 380.

Glutamic acid, 385.
Gluteal reflex, 641.
Gluten, 378.
Glycerin, 381, 382.

4 method, 219.
Glycerin i phosphoric acid, 382.
Glycin, 3
Glycocholic acid, 267.
Glycogen, 262, 383.

Glycolic acid, "382.

Glycosuria, 264, 413.

Gmelin- Heintz’ cota 269.

Goblet cells, 291.

Goitre, 154.

Goll’s column, 633.

Goltz’s a7 tie experiments,
» ecroaking © experiment,

>, embrace experiment,

638.

” Sa rhe experiments,

gio

Gorham’s pupil photometer,
761.

Gout, 48.

Graafian follicle, 849, _

Gracilis experiment, 574.
Grandry’s corpuscles, 829.
Granules; elementary, 17.
Granulose, 218.

Grape-sugar, 383, 413.
absorption of, 298.
estimation of, 221.
injection of, 264.
in urine, 413.

a tests for, 220.

sis, 414.
Gravitation, xxxvii.
Great auricular nerve, 675.
Green-blindness, 778.
Green vegetables, 352.
Growth, 372.
Guanidin, 482.
Guanin, 439, 453.
Guarana, 353.
Gubernaculum testis, 889.
Gum, 384,
Gustatory centre, 704, 713.

7A fibres, 600

55 region, 823.

a sensations, 825.
Gymnastics, 503.
Gymnotus, 580.

Gyri, 649.

Hay’s reaction, 268, 413.
Hemacytometer, 5.
Hemadynamometer, 119.
Hematin, 25, 26.
Hematoblasts, 17.
Hematohidrosis, 449.
Hematoidin, 27.
Hzematoma aurium, 583,
linea Hk 97 ae 26.
Hematuria, 411.
Hemautography, 101.
Hemin and its tests, 26, 412.
Hemochromogen, 26.
Hemocyanin, 38.
Hemocytolysis, 7.
Hzmocytometer, 5.
Hzmocytotrypsis, 7.
Hemodromometer, 133.
Hzemodynamometer, 119.
Hemoglobin, 18.

ss amount of, 20.

“ analysis, 18.

Fr carbonic oxide, 24.

- compounds of, 22.

” crystals, 18

> = of,

estimation of, 19.
re nitric oxide, 25.
” pathological, 21.

”» preparation, 19.
” proteids of, 28.
+ reduced, 23.

49 spectrum, 22,
Hemoglobinometer, 19.
Hemoglobinuria, 411.
Seamer te 20,

smophilia, 32,
Hemorrhage, death by, 48.

volumetric analy-

INDEX.

Hemorrhage, effect on, 672.
Hemorrhagic diathesis, 32.
Hemotachometer, 133.
Haidinger’s brushes, 764.
Hair, 440.

», cells, 810.

;, follicle, 441.
Halisterisis, 503.
Hallucinations, 732.
Hammarsten, 34.
Hammarsten on blood, 34.
Harderian gland, 796.
Hare-lip, 879.

Harmony, 818.
Harrison’s groove, 171.
Hassall’s corpuscles, 154.
Hawking, 183.
Hay’s test, 268.
Head-fold, 869.
Head-gut, 869.
Hearing, 797.
Heart, 51.
», accelerated action, 67.
», action of fluids on, 81.
», action of gases, 85.
5 penen of poisons on, 83,

‘5 apex, 82.

», apex beat, 61. :

a ereene of fibres,
1B

5, aspiration of, 129.

»» auricular systole, 57.

», automatic centres, 78.

5, automatic regulation, 55.
», blood-vessels of, 56.

»» changes in shape, 65.

» chord tendiniz, 59.

», cutting experiments, 69.
», development of, 869, 882.
», diastole, 57.

a eee of movements,

» endocardium, 54.

», examination of, 75.
oy ROR By- 87

» ganglia of, 76.

», hypertrophy of, 60.
>» impulse of, 61.

»> innervation of, 76.
»» movements of, 57.
s» muscular fibres, 53.
>» myocardium, 51.

»» nerves, 76,

», nhutritive fluids, 79.
», palpitation of, 60.
5» pause of, 59, 66.

»> pericardium, 54.

», Purkinje’s fibres, 55.
»» regulation of, 55.

s, section of, 80.

», sounds of, 71.

», Staircase beats of, 81, 84.
»>. systole, 57.

» valves of, 54.

» » weight, 55.

work of, 136,

XXxXix.
», balance of, 331.

», calorimeter, 324,
»» centres, 329, 705.
», conductivity, 325.
s» dyspnoea, 171, 664.

Heat, employment of 337.
K; : delimithon of bo4
:, excretion of, 330.

»» income and expenditure, zs
* $82. ne

» in inflamed p
»» in muscle, 493.
»» latent, 315.
»» production, 317.
» regulating centre, 329.
»» relation to work, 333.
», sources of, 315,
>> Specific, 324,
», stiffening, 468.
», storage of, 334.
-5, units, xl, 316.
7 a in production,

Helicotrema, 808.
Heller’s test, 202, 409.

os blood-test, 412.
Helmholtz’s modification, 549. -
Hemeralopia, 587.
Hemialbumin, 248.
Hemialbumose, 247.
Hemianesthesia, 714.
Hemianopsia, 586.

Hemicrania, 678.
Hemiopia, 586.
Hemipeptone, 248.
Hemiplegia, 707
Hemisystole, 71.
Henle’s loop, 387.
», Sheath, 530.
Hen’s egg, 851.
Hensen’s experiments, 818,
Hepatic cells, 260.
"a chemical composition
of, 262.

a zones, 260.
Hepatogenic icterus, 273.
Herbst’s corpuscles, 829. _
Hermann’s theory of tissue

currents, 563.

Herpes, 582.
Hetero-albumose, 248.

», °xanthin, 401.
Heterologous stimuli, 731.
Hewson’s experiments, 33,
Hiccough, 183.

Hippocampus, 687.
Hippuric acid, 402.
Hippus, 588.
Histo-hematin, 156.
Historical—
Absorption, 314, .

Circulation, 158.

Digestion, 289.

Hearing, 820. —

Heat, 340.

Kidney and urine, 437.

Metabolism, 3865. a.

moe and electro-physiology,

, 839..

re 205. 270%

;
7
|
:
4

Historical—

Voice and speech, 523,
Hoarseness, 523.
Holoblastic ova, 851.
Homoiothermal animals, 318.
Homologous stimuli, 731.
Horopter, 788
Hot- “spots, 836.
Howship’s lacune, 882.
Humour, aqueous, 720.
Hunger and oe 360.
Hyaloid canal, 741
Hybernation, 339.
Hybrids, 860
Hydatids, 844.
Hydremia, 48.
Hydramnion, 871.
Hydrobilirubin, 269.
Hydrocele, 34.
Hydrocephalus, 728.
Hydrochinon, 404.
Hydrochloric acid, 243.
Hydrocyanic acid, 25.
Hydrogen in body, 373.
Hydrolytic fepinenta: 379.
Hydronephrosis, : 436.
Hydrostatic test, 165,
Hydroxylbenzol, 404.
Hyo-cholalic acid, 267.
Hypakusis, 604,
Hypalgia, 839.
Hyperesthesia, 646.
Hyperakusis, 604.
Hyperalgia, 604.
Hyperdicrotism, 106.
Hypergeusia, 826.
Hyperglobulie, 47.
Hyperidrosis, 448.
Hyperkinesia, 646.
Hypermetropia, 754.
Hyperoptic, 754.
Hyperosmia, 584.
Hyperpselaphesia, 838.
Hypertrophy of heart, 60, 70.

of muscle, 504,
Hypnotism, 686.
Hypoblast, 863.
Hypogeusia, 826.
Hypoglossal nerve, 615.
Hypophysis cerebri, 156, 722
Hypopselaphesia, 838,
Hyposmia, 584.
Hypospadias, 890.
Hypoxanthin, 385.

Iehthidin, 377.
Icterus, 273.

Identical points, 787.
Tleo-colic valve, 233.
Tleus, 233.

Hlumination of eye, 764.
Illusion, 732

Images, formation of, 747.
Imbibition currents, 564.
Impregnation, 861.
Impulse, cardiac, 61. .

Impulses in brain, course of,
653.

Inanition, 360.
Incisures, 528.
Income, 358.

Indican, 404.
Indifferent point, 554.

INDEX,

Indigo blue, 404.
Indigo-carmine test, 414.
Indigogen, 404,

Indirect vision, 769.

Indol, 255, 282.

Induction, 549.

Inductorium, 551.

Inferior maxillary nerve, 595.
Inhibition, nature of, 640
Inhibition of reflexes, 639.
Inhibitory action of brain, 706.

o nerves, 583.
eS for heart, 667.
a for intestine, 238.

5 for respiration, 665.
Inion, 714.
Initial contraction, 487.
Inosinic acid, 385.

Inosit, 384,
Insectivorous plants, 289.
Inspiration, 169.

- centre for, 662.
me muscles of, 172.
» ordinary, 172,

Intelligence, degree of, 684.
Intercellular blood-channels, 95.
Intercentral nerves, 583.
Intercostal muscles, 174.
Interference, 818.
Interglobular spaces, 225.
Interlobular vein, 259.
Internal capsule, 716.

», Yeproductive organs,

8.
- 4, ‘respiration, 159, 194.

Intestinal fistula, 277

a gases, 279.

a juice, 278.

> » actions of, 278.

paresis, 238.

Intestine, 33.

5s eae circulation,

56 development of, 886.
re effect of drugs on,
239.

s fermentation
cesses in, 279

> large, 283, 294.

ro movements of, 233.

35 small, 290.
Intralabyrinthine pressure, 810.
Intralobular vein, 259
Intraocular pressure, 594, 742,

pro-

Intrathoracic pressure, 181.
Intravascular hemorrhage, 676.
Inulin, 384
Inunction, 449.
Invertin, 281.
Invert sugar, 281.
Inverted image, 747.
Tons, 545
Iris, 736.
», action of poisons on, 760.
3, blood-vessels of, 737
,, functions of, 758.
»> movements of, 759.
», muscles of, 759.
nerves of, 759.
Irradiation, 780.
of pain, 648, 839.
Isehuria, 436.

OII
Island of Reil, 690.

| Isodynamic foods, 316.

Isolated beats, 818.
Isometrical act, 487.
Isotropous, 476.

Jacksonian epilepsy, 695, 709.
J acobson’ s organ, 822,
Jaeger’s types, 755
Jaundice, 272.
Jaw-jerk, 643.
Joints, 498.
» arthrodial, 499.
», ball and socket, 499.
» ginglymus, 498.
», mechanism of, 498.
3 Migid, 499;
screw-hinge, 499.
Juice canals, 302.

Karyokinesis, 842.
Karyomiton, 842.
Karyoplasma, 842.
Katabolic metabolism, 341.
nerves, 583.
Katalepsy, 686.
Kations, 545,
Keratin, 378.
Keratitis, 602.
Keys—
Capillary contact, 553.
Friction, 552.
Plug, 552.
Kidney, 386.
ss blood of, 426.
», chemistry of, 426.
Ye conditions affecting,
427.
»» reabsorption in, 424,
is structure of, 386.
volume of, 428,
Kinzesodic substance, 645,
Kinetic energy, 315.
» theory, 604.
Klang, 811
Knee phenomenon, 643.
3 “jerk, 643
», reflex, 643.
Keenig’s monometric
815,
Koumiss, 348,
Krause’s end- bulbs, 828.
Kreatin, 385.
Kreatinin, 385, 401.
oP properties, 401.
x quantity, 401.
Sh test, 401.
Kresol, 385.
Kryptophanie acid, 405.
Kiihne’s artificial eye, 74.
a oabartineite 556, 573.
»» pancreas powder, 256.
Kymograph, 119.
os Fick’s, 121.
me Hering’s, 121.
Ludwig’s, 119.
Kyphosis, 503.

Labials, 522,

Labour, power of, 894.
Labyrinth, 806.
Lachrymal apparatus, 98,

flames,

‘Lacteals, ‘290, 302,

gi2

Lactic acid, 243, 346, 382.
ferment, 251.

Lactometer, 347.

Lactoprotein, 346.

Lactosco , 348.

Lactose

Levulose, 81, 383.

Lagophthalmus, 588.

Lambert’s method, 774.

Laminz dorsales, 865.

Lamina spiralis, 808.

Language, 711.

Lanoline, 445.

Lanugo, 442.

pa ieee 222.

Lardacein, 377.

Large intestine, 283, 294.
= absorption in,

283.
Laryngoscope, 515.

Larynx, cartilages of, 510.
during respiration, 517.
experiments on, 518.
illumination of, 515.
mucous membrane of,

514.
muscles of, 511.
view of, 516.
vocal cords, 510.
Latent heat, 315.

- period, 480.
Lateral plates, 868.
Laughing, 183.
Law of conservation of energy,
xli.

,» contraction, 568.

;, isolated conduction, 573.

»> peripheral ‘aac A 830.

», specific energy, /

Leaping, 507.

Lecithin, 28, 381, 531.
Legumin, 351.

Lens, chemistry of, 740.

»» crystalline, 740.

», development of, 893,
Lenticular nucleus, 716.
Leptothrix epidermalis, 449,

” buccalis, 217,
Leucic acid, 382,

Leucin, 255.

Leucocytes, 13.
Leucoderma, 582.
Leucomaines, 249,
Leukemia, 18

Levers, 501.

Lichenin, 384,

Lieben’s test, 405.
Lieberktihn’s glands, 277,

“ jelly, 377.
Liebermann’s reaction, 376.
Liebig’s extract, 350.

Life, xli.

Limbie lobe, 704.

Limb plexus, 620.

Liminal intensity, 731.

Line of accommodation, 753,

Ling’s system, 503.

Lingual nerve, 596.

Lipaemia, 47,

Liquor sa: is, 29.

Listing’s reduced eye, 747,
Pop a: 784.

Liver,

+B]

9?

INDEX.

Liver, irr of drugs on cells,

», chemical composition,
262.

cirrhosis of, 262.

development of, 887.

» fat in, 264

», functions of, 266.

5» glycogen in, 263,

,» influence on metabolism,
271.

»» pathology of, 262.

»> pulse in, 143.

»» regeneration of, 262.

structure of, 258,

| Lobes of brain, 689.

Locality, sense of, 830.
ss illusions of, 833.

Lochia, 895.
Locomotor ataxia, 647.
Lordosis, 503.
Loss by skin, 194.
Loss of weight, 361.
Lowe’s ring, 7
Lungs, 159.

», chemical composition of,

» development of, 886,
» @lastic tension of, 87,
»» @Xamination of, 177
x excision of, 165.
», limits of, 177.
»» physical properties, 165.
, structure of, 161
tonus, 165.
Lunule, 440.
Lutein, 856.
Luxus consumption, 356.
Lymph, 306.
»» movement of, 310.
» gases of, 195, 308.
Lymphatics, 301.
” of eye, 741.
origin of, 301.
Lymph- -corpuscles, 305.
» origin and decay of, 309.
Lymph-follicles, 304.
» glands, 304.
» hearts, 311.

Macropia, 588.
Macula lutea, 739.
Macule acustice, 809.
Madder, feeding with, 371.
Magnetisation, 549.
Magneto-induction, 550.
Major chord, 812.
Malapterurus, 579.
Malt, 354.
Maltose, 218, 383.
Mammary glands, 343.

= changes in, 343.

of development of, 344.

structure of, 343,

Manometer, 119,

s frog, 82.

Pe maximum, 59.

minimum, 59.

Manometric flames, B15,
Marey’s tambour, 67.
Ma 438.

argarin,
Marginal convolutions, 690.

Mariotte’s smperhalaal 768,
Massage, 503.
Mastication, 223.
a _ muscles of, 223,
sf nerves of, 223,
Mate, 353.

Matter, xxxvi.
Maturation of ovum, 861.
Meat soup,
Meckel’s cartilage, 880,
- ganglion, 595,

Meconium, 275,
Medulla oblongata, 655.

Functions of, 359,

Grey matter of, 657.

Reflex centres in, 659.

Structure of, 655.
Medullary groove, 864.

re tube, 865.

Meibomian glands, 793.
Meiocardia, 56.
Meissner’s plexus, 230, 236, 294,
Melanemia, 18
Melanin, 381.
Melitose, 383.
Mellitzemia, 47.
Mellituria, 47.
Membrana barn menstrualis,

» flaccida, 800.

si reticularis, 810. .

ae reuniens, 870.

Ea secundaria, 806.

ay tectoria, 810.
tympani, 799.

Membranes of brain, 726,
Meniére’s disease, 605,
Menopause, 854,
Menstruation, 854.
Mercurial balance, 834.
Merkel’s cells, 829.
Meroblastic ova, 851.
Mesentery, development of, 887,
Mesoblast, 864.
Mesonephros, 889.
Metabolic equilibrium, 355.
a acter 341.

Mowholign: 341.

‘ in anzemia, 48.

ne on_fiesh and other

diets, 362.
Metakresol, 404.
Metalbumin, 376.
Metallic tinkling, 180.
Metalloscopy, 839.
Metamorphosis, 843.
Metanephros, 889.
Meteorism, 238.
Methzemoglobin
Methylamine, a
Meynert’s a systems,

oe theory, 684.
Micrococci, 41,
Micrococcus ure, 408,
Microcytes, 17. |
Micropyle, 850.
Microscope, 137.
Micro-organisms,
Micro- pe; 21.
Micturition, 434.

centre for, 644. _
Migration of ovum, 860.

|

Milk, 345.
», action of drugs on, 347,
» coagulation of, 346,
3, colostrum, 343.
»5 composition of, 344,
» curdling ferment, 243,
346.
5, digestion of, 250,
»» fever, 345, 895.
3» globules of, 345,
>» peptonised, 258,
»> plasma, 345.
5» preparations of, 348.
5, substitutes for, 347.
», sugar, 346.
tests for, 347.
Millon’s reagent, 375,
Mimetic spasm, 603.
Mimicry, 523.
Minor chord, 812.
Mitosis, 842.
Mixed colours, 774.
Modiolus, 808.
Molecular basis of chyle, 306.
Molecules, xxxvi
Molisch’s test, 222,
Monoplegia, 709.
Monospasm, 710.
Moore’s test, 220.
Moreau’s experiment, 278.
Mormyrus,
Morphology, xxxv.
Morula, 862.
Motion, illusions of, 780,
Motor areas, 706.
Motor centres, dog, 691, 695.
» excision of, 699
»» in man, 698.
» in monkey, 696.
>, nerves, 581.
» paths, 653.
» points on the surface,

575.
Mouth, 206.

», glands of, 206.
Mouvements de manége, 721,
Movements of the eye, 782,

a acquired, 700.

Ss forced, 721.

inco- -ordinated, 619,

Mucedin, 378.
Mucigen, 291.
Mucin, 267, 378.
si membrane currents,
Mucous tissue, 741.
Mucus, effect of drugs on, 201.

» formation of, 201, 267.
Mulberry mass, 862.

Mulder’s test, 220.
Miiller’s ducts, 888.
5 rae 88, 112.
59 fibres, 7
valve, 184. |
Multiplicator, 543.
Murexide test, 400.
Murmurs, cardiac, 74,
venous, 141.
Muscze volitantes, 762.
Muscarin, 669,
Muscle, 453.
» action of two stimuli
on, 484,

INDEX.

Muscle, action of veratrin, 483.

Pr]
3?
9?

active changes in, 475.
arrangement of, 500.
atrophic proliferation

blood-vessels of, 457.

cardiac, 51, 460.

changes during con-
traction, 475.

chemical composition,
462,

current, 547.

curve of, 479.
degenerations of, 504,
development of, 640.
effect of acids on, 469.
effect of cold on, 469.

effect of distilled water

on, 469.
effect of exercise on,

effect of heat on, 468.
elasticity of, 491.
electric currents of, 554.
excitability of, 470.
extractives of, 465,
fatigue of, 495.
ferments, 463.
fibrillee, 455.
formation of heat in,
493.
gases in, 464.
glycogen in, 463, 465,
hypertrophy of, 504.
involuntary, 453.
lymphatics of, 458.
metabolism of, 464.
myosin of, 463.
nerves of, 458.
nutrition of, 503.
of heart, 51, 460.
perimysium of, 453.
a characters,

plasma of, 463.

plate, 870.

polarised light on, 462.

reaction, 462

recovery of, 497.

red and pale, 460.

relation to tendons,
457.

ae ia contraction,
4

rigor mortis of, 466.
rods, 456.
sensibility, 459, 493.
serum of, 463.
smooth, 453, 460.
sound of, 495.
spectrum of, 460.
staircase of, 485.
stimuli of, 473.
structure of
453.
tetanus, 485.
tonus, 493, 644,
uses of, 500.
volume of, 475.
voluntary, 453.
work of, 489,

striped,

Muscle- current, 554.

theories, 562.

913

Muscular contraction (see
Myogram), rate of, 487.
Muscular energy, 466.
* exercise, 189.
‘s sense, 839,
a work, 465.

ae. » laws of, 489.
Mutes, 521.

Mydriasis, 588. |
Mydriatics, 760.
Myelin forms, 527,
Myocardium, 51.
Myogram, 479.
effect of constant
current on, 482.
fe effect of fatigue on,

482,

Pr effect of poisons on,
482.

ig effect of veratrin on,
483.

sn effect of weights on,
482.
Pr era of studying,

os stages of, 479,
Myograph, Helmholtz’ BAe
be pendulum, 477,
3 Pfliiger’s, 478.
- simple, 478.
spring, 478.
Myohzmatin, 381, 460.
Myopia, 754.
Myoryctes Weismanni, 462,
Myosin, 376, 463.
» ferment, 463.
Myosis, 588.
Myotics, 761.
Myxcedema, 155, 582.

Nails, 440.
Narcotics, 839.
Nasal breathing, 182.
», timbre, 521
Nasmyth’s membrane, 225,
Native albumins, 376.
Natural selection, 896,
Near point, 753.
Neef’s hammer, 551.
Negative accommodation, 749.

os after-images, 780.

. pressure, 297.

a variation, 557, 559,
Nephrozymose, 405.
Nerve-cells, 525, 530,

» bipolar, 530.
», multipolar, 530, 628.
», of cerebrum, 687.
», Purkinje’s, 723.
», With a spiral fibre, 530,
Nerve centres, general func-
tions, 625.
Nerve-current, 554,
Nerve-fibres, 525.
5, action of nitrate of silver
on, 529,
», Chemical properties of,
531

» Classification of, 581.
», death of, 541

_ 5, degeneration of, 537.
», development of, 530.
» division of, 529.

3M

914

Nerve-fibres, effect of a constant |
current on, 5
», @lectrical current of,
554.
electrical stimuli, 535.
»» excitability of, 533.
% fatigue of, 537.
incisures of, 528.
mechanical properties of,
532

medullated, 525.
metabolism of, 532.

5» nutrition of, 538.

. Ranvier’s nodes, 52S.
reaction of, 532.
recovery of, 537.
regeneration of, 537, 540.

,, Sheaths of, 529.

». stimuli of, 533.

>> structure of, 525.
suture of, 540.
terminations of, 827.
to glands, 212.
traumatic degeneration
of, 539.
_ trophic centres of, 539.
y unequal excitability of,
536.

» union of, 540.
-% unipolar stimulation, 537.
Nerve-impulse, rate of, 570.

method of measuring,
57 via

Pe modifying conditions,
57 70.

Nerve-motion, 573.
Nerve-inuscle preparation, 555.
Nerves, 581.

se afferent, 583.

- anabolic, 583.

3 centrifugal, 581.

a centripetal, 583.

a cranial, 584.

= electrical, 573.

.» intercentral, 583.

»» katabolic, 583.

+» . motor, 581.

», secretory, 581.

5, sensory, 583.

d: special sense, 583.

» spinal, 615.

», trophic, 581.
union of, 540.
vaso- -dilator, 678.

+» vaso-motor, 672.

visceral, 583.
Nerve- -stretching, 533.
Nervi nervorum, 530.
Nervous system, 725.

ae evelopment of, 891.
Nervus abducens, 599

» accelerans, 669.

s, accessorius, 611.

>» acusticus, 603.

»» depressor, 610.

a — 644, 679, 859.
mer 599.

9 emt mre he “Hy 606.
# penn rece dit 587.
a ee. 584.
” pee
pathicus, 620

INDEX.

Nervus trigeminus, 590.
trochlearis 5 , 589.
vagus,
Neubauer’s test, 220.
Neuralgia, 598, 631.
Neural tube, 865.
Neurasthenia gastrica, 286.

3?

| Neurin, 531

Neuro- epithelium, 738.
Neuro-keratin, 528.

_ Neuro-muscular cells, 473.
New-born on digestion of,

Ps sabe 107.
i size, 372.
temperature, 326.
urine of, 393.
weight, 372.
Nictitating Pienhian 796.
Nitrites, 24.

», on pulse, 105.
so a in air, 186.

- n blood, 44.

3 if body, 873.

* given off, 355.
Noeud vital, 661.
Noises, 811.
Nose, development of, 879.

», structure, 821.

Notochord, 867.
Nuclear spindle, 861.
Nuclein, 378.
Nucleus of Pander, 852.
Number-forms, 820.
Nussbaum’s experiments, 423.
Nutrient enemata, 310.
Nyctalopia, 587.
Nystagmus, 605, 721.

Oatmeal, 351.
Octave, 812.
Oculomotorius, 587.
Odontoblasts, 224.
(Edema, 313.
“5 cachectic, 313.
pulmonary, 182.
(Esophagus, 229, 2 0.
Ohm’s law, 542.
Oleic acid, 381.
Oligzemia, 48.
Olivary body, 656.
Olfactory centre, 704, 713.
os nerve, 584.
me sensations, 822.
pic acacia duct, 869.

,, Vessels 870.

Onamato

Oncograph, 1 1, 98,
Oncometer, 428,
Ontogeny, 896.

Opening shock, 549.
Ophthalmia te paralytica,

” intermittens, ne
8 etic,
O phthalmie po brs ap 591.
Ophthalaibtnebr, 748,
Ophthalmoscope, 764.
Optic nerve, , 768,
s; radiation, 585,
», thalamus, 716.
» tract,
» vesicle, 866.

Optical cardinal point, 745,

Optogram, 773.

Optometer, 755.

Ordinates,’ 121.

Organic albumin, 356.

» | compounds, 374.

reflexes, 643.

Ortho-kresol, 404,

Orthopnoea, ‘171.

Orthoscope, 767.

Osmasome, 350.

Ossein, 379.

oe system, formation of,

Osteoblasts, 882.
Osteoclasts, 882.
Osteomalacia, 503.
Otic ganglion, 597.
Ovarian tubes, 850.
Ovary, 849.
Overcrowding, 201.
Ovulation, 855.

theories of, 856.

Ovum, 849,
development of, 850.

» discharge of, 855.

» fertilisation ‘of, 860.

ss impregnation of, 861.

»» Maturation of, 861.

» migration of, 860.

structure of, 849.
Oxalic acid, 382, 401,
series, 382.

Oxaluria, 401.
Oxaluric acid, 401.
Oxy-acids, 405,
Oxyakoia, 603.
Oxygen in blood, 42.

3, estimation of, 42, 184.

» forms of, 44.

», in body, 373.
Oxyhzmoglobin, 22.
Ozone in blood, 43.

Pacchionian bodies, 727.
Pacini’s corpuscles, 828.
Pain, "4

;, irradiation of, 839.

points, 830.

Painful i impressions, condustien

of, 647.
Palmitic ‘acid, 381.
Palpitation, 60.
Pancreas, 252.
changes in, 253.
development of, 887.
» fistula of, 253.
* juice of, 54, |
$3 paralytic secretion,

ai powder, 256.
salt, 257.
Pancreatiy secretion, 253.
- actions of, 254.

x artificial juice, 255.
vs ae of nerves on,

‘ — of poisons on,.
i . composition, * —
extracts :

Panophthalmia, 59°, i
Pansphygmograph, 61. ‘one

Papain, 256.

Papilla foliata, 825.

Papille of tongue, 824.

Parablastic cells, 868,

Paradoxical contraction, 562.

Paraglobulin, 37.

Parakresol, 385, 404. -

Paralbumin, 376.

Paralgia, 839.

Paralytic sat aaa of saliva,
1

pancreatic juice, 258.
Paeanigians: 384,
Para-peptone, 247.
Paraphasia, 711.
Paraxanthin, 385, 401.
Parelectronomy, 563,
Paridrosis, 449.
Parodphoron, 889.
Parotid gland, 207, 214.
Parovarium, 889.
Parthenogenesis, 844.
Partial pressure, 40.

» reflexes, 636.
Particles, xxxvi.

Parturition, centre for, 644.
Passive insufficiency, 502.
Patellar reflex, 642.

Pavy’s test, 220.

Pecten, 796, 892.

Pectoral fremitus, 181. .
Pedunculi cerebri, 718.
Penis, erection of, 857.
Pepsin, 242

Pepsinogen, 244.

Peptic glands, 241.

» Changes in, 244.
Peptogenic substances, 246.
Peptone, 247, 249.

re absorption of, 298.
», forming ferment, 242.
», injection of, 32, 299,
“e metabolism of, 363.
as tests for, 249.
Peptonised foods, 258.
Peptonuria, 410,
Percussion of heart, 76.
an lungs, 178.
se sounds, 178.
ss wave, 102.
a ame ulcer of the foot,

Pericardium, 54.

fluid of, 307.
Perilymph, 808.
Perimeter, se and Forster,

, M‘Hardy’s, 770.
ey Priestley Smith’s,
772

Perimetric chart, 770.
Perimetry, 769.
Perimysium, 51, 453.
Perineurium, 29,
Periodontal membrane, 225.
Peristaltic movement, 233.

* 4 of blood on,

*3 action of nerves on,
238

Peritoneum, development of,
887

Perivascular spaces, 688,

INDEX,

Pernicious anemia, 17.
Pettenkofer’s test, 268.

3 apparatus, 185.
Peyer’s glands, 294.
Pfliiger’s law, 567.

ie law of reflexes, 637.
Phagocytes, 15.
Phakoscope, 752.
Phinakistoscope, 780.
Phases, displacement of, 814.
Phenol, 282, 404.
Phenylsulphonic acid, 404.
Phlebogram, 142.
Phloro-glucin-vanilin, 243.
Phonation, 513
Phonograph, 815.
Phonometry, 179.
Phosphenes, 763.
Phosphoric acid, 406.
Photo-hematachometer, 133.
Photophobia, 603
Photopsia, 587.
Phrenograph, 169,
Phrenology, 682.
Phylogeny, 896.
Physostigmin, 761.
Phytalbumose, 377.
Phytomycetes, 417.

Pia mater, 626.
Picric acid test, 410.
Picro-saccharimeter, 415.
Pigment cells, 452.
Pineal eye, 722.
» gland, 722.
Pitch, 811.
Pituitary body, 712.
Placenta, 874.
Placental bruit, 141.
Plantar reflex, 642.
Plants, characters of, xlii.
», digestion by, 289.
», electrical currents
565.
Plasma cells, 726. °

», of blood, 29, 37.

»» of invertebrates, 38.

5, of lymph, 307

>», of milk, 345.

of muscle, 462.
Plasmine, 33.
Plethora, 47.
Plethysmography, 144.
Pleura, 163.
Pleuro-peritoneal cavity, 868.
Pleximeter, 177.
Pneumatic cabinet, 112.
Pneumatogram, 170.
Pneumatometer, 182.
Pneumograph, 86, 169.
or ae after section of vagi,

in,

Pneumothorax, 166,
Poikilothermal animals, 318.
Poiseuille’s space, 137,
Poisons, heart, 85.
Polar globules, 861.
Polarisation, galvanic, 545.

a internal, 548.
Polarising after-curr ents, 562.
Politzer’s ear-bag, 806
Polyzemia, 46.

¥ apocoptica, 46.

= aquosa, 47

915

Polyzmia hyperalbuminosa, 47.
», polycythemica, 47.
~ serosa, 47.
Polyopia monocularis, 758,
Pons Varolii, 719.
Porret’s phenomenon, 548.
Portal canals, 259.
» circulation, 50,
a aye development of,
5. ‘

3, vein in liver, 259.
Positive accommodation, 749.
after-images, 779.
Potash salts, 373.
oo sulphocyanide, 216,

Potatoes, 351.
Presbyopia, 754.
Pressor fibres, 674.
Pressure, arterial, 122.
‘ atmospheric, 203.
a intra-labyrinthine,
810

5» Of blood, 119.

»» phosphenes, 763.

iy points, 830, 833.

»» respiratory, 181.

sense of, 833.

Presystolic sound, 74.
Prickle cells, 438.
Primitive anus, 871.

aorta, 869.

- chorion, 863, 873.

a circulation, 870.

as groove, 863.

a kidneys, 888.

A mouth, 871.

streak, 863.
Primordial cranium, 878.
5 ova, 850.

Principal focus, 743.
Proctodzeum, 865
Proglottis, 843.
gs ea muscular atrophy,
3)
Pronephros, 889.
Pronucleus, male, 861.
Ss female, 861.

Propepsin, 244.
Propeptone, 247,
Protagon, 380.
Proteids, 374.

- coagulated, 377.

PF eee digestion of,

Pe fermentation of, 281.
a metabolism of, 362.
ae pancreatic digestion
of, 255. |
AA reactions of, 375.
vegetable, 377.

Proteolytic ferments, 379.
Proteoses, 248
Protistz, xxxv, xliv.
Proto-albumose, 248.
Protovertebra, 868.
Pagnge: hypertrophic paralysis,

Pseudo-motor action, 601, 603.
Pseudoscope, 791.
Pseudo-stomata, 162.
Psychical activities, 681.

i‘ blindness, 702.

916

Psychical deafness, 703.

- processes, time of, 684.
Psycho-physical law, 731.
Ptomaines, 249.

Ptosis, 588.

Ptyalin, 219.

Ptyalism, 215.

Puberty, 853.

Pulmonary artery, pressure in,
7 830.

< vessels, 162.

Pulmonary cedema, 182.
Pulp of tooth, 225.

,, of spleen, 148.
Pulse, 97.
anacrotic, 109.
capillary, 118.
catacrotic, 102.
characters of, 102.
conditions affecting, 107.
curve, 101.
dicrotic, 106.
, entoptical, 115.
hyperdicrotic, 106.
in animals, 107.
in jugular vein, 142.
in liver, 143.
influence of pressure on,

1

on, 110.

gating, 97.

s+; monocrotic, 106.
of various arteries, 108.
»» paradoxical, 112.
as pathological, Pe:
, rate, 107, 127.
»> recurrent, 110.
tracing, 102.
trigeminal, 108.
variations in, 108.
venous, 142,

» wave, 113,
Pulses, 351.
Pulsus alternans, 108.
bigeminus, 108.
caprizans, 106.

ss dicrotus, 106.

5 intercurrens, 108.

ss myurus, 108.
Pum ving mechanisms, 310.
Pupil 792

+» action of poisons on, 760.
Argyll Robertson, 660.
functions of, 758.
movements of, 759.

+» photometer, 761.

>, size of, 761.
Pupilometer, 761.
Purgatives, 239.
Purkinje, cells of, 723.
fibres of, 55, 460.
figure, 762.

i. Sanson’s images, 751.
Pus-corpuscles, 139.
Putrefaction, pancreatic, 255.
Putrefactive processes, 283.
Pyloric glands, 241.

99 changes in, 244,
” fistula, 246.
Pyramidal cells, 687.

%? ?

99

9

9?
>?

|

|
|
|

influence of respiration
|

: : ail
instruments for investi- |

INDEX.

Sag em tracts, degenerat on
of, 708.

Pyrokatechin, 382, 405.

Pyuria, 416.

Quality of a note, 811, 813.
Quantity of blood, 45.
of food, 357.
of gases, 188.

2?

99

Rales, dry, 180.

ss moist, 180.
Rami communicantes, 620.
Range of accommodation, 756.
Ranvier’s nodes, 528.
Raynaud’s disease, 583.
Reaction impulse, 63.
Reaction of degeneration, 578.
Reaction time, 573, 685, ~
Recoil wave, 103.
Rectum, 238.
Recurrent pulse, 110.

ze sensibility, 617.

Red-blindness, 778.
Reduced eye of Listing, 747.
Reducing agents, 43.
Reductions in intestine, 283.
Reflex acts, examples of, 636.

»» inhibition of, 639.

sy.) dawol, 63s;

+; movements, 636.
Reflex movements, theory of,

641.
nerves, 583.
organic, 643.
spasms, 636.
tactile, 647.
time, 639.

», tonus, 645.
Reflexes, crossed, 638.
deep, 642.
spinal, 635.

PP organic, 643.
Refracted ray, 744.
Refractive indices, 744.
Regeneration of tissues, 369,

i of nerve, 540.
Regio olfactoria, 821.

» Tespiratoria, 821.
Regnault’s apparatus, 184.
Reissner’s membrane, 808.
roa proportions of diet,

3?
”

Remak’s ganglion, 77.

Renal plexus, 427.

Rennet, 251, 346.
Reproduction, forms of, 841.
Requisites in a proper diet, 357.
Reserve air, 166.

Residual air, 166.

Resistance, 89.

Resonance organs, 510.
Resonants, 522.

Resonators, 817.

Resorcin, 404.

Respiration, 159.

amphorie, 180.
artificial, 198,
Biot’s, 172.
bronchial, 180.
centre for, 661.
chemistry of, 183,
cog-wheel, 180.

Respiration, cutaneous, 193.

39

4

foreign gases, 199.
at closed space,

in animals, 168.
internal, 194. ~
mechanism of, 165.
muscles of, 172.
nasal, 182,
muiaber of, eyes
pathological, ‘
periodic, 172.
pressure during,
181.

pressure on heart,
86

sounds of, 179.

time of, 168.

type, ;

variations of, 167.

vesicular, 179.

apparatus, 159.

Andral and Gavar-
ret, 184.

centre, 661.

mechanism of, 165.

v. Pettenkofer, 185.

quotient, 186. .

Regnault and Rei-
set, 185.

Scharling, 185.

7. undulations, 124.

Restiform bodies, 655. ~

Rete mirabile, 51.

Retina, 737.

activity in vision, 768.

blood-vessels of, 739.

capillaries, movements
in, 763.

chemistry of, 740.

epithelium of, 737.

pe ae cones of, 738,

Respiratory

stimulation of, 779.
structure of, 737.
visual purple of, 739.
Bn formation, of

a size of, 748.
Retinoscopy, 767.
Reversion, 896.
Rheocord, 542.
Rheometer, 132.
Rheophores, 575,
Rheoscopic limb, 556.
Rheostat, 543.
Rheotom, 560.
Rhinoscopy, 517.
Rhodophane, 740.
Rhodopsin, 739.
Ribs, 174.

Ricket’s, 503,
Rigor mortis, 466.
Ritter’s opening — 567.

Me

Retinal

Rumination, 288.
Running, 505.

Saccharomycetes, 354.
Saccharose, 383.
Saccule, 808.
Saftcanadlchen, 302.
Saline cathartics, 239.

Saliva, action of nerves on, 212.
», action of poisons on, 213.

», action on starch, 218.
» chorda, 212

5, composition of, 217.
»: facial, 212.

», functions of, 216.

99 mixed, 217.

» new-born child, 218,

», paralytic secretion, 214.

»» parotid, 216.

», pathological, 285.

»» ptyalin, 216, 219.

», reflex secretion of, 214.

» sublingual, 217.

»» submaxillary, 216.

» sympathetic, 212.

», theory of secretion, 216.
Salivary corpuscles, 217.
Salivary glands, 207.

3 changes in, 209.

Pe development of, 886.

fe extirpation of, 215. *
Pe nerves of, 211.
Salts, 373.
Sanson-Purkinje’s images, 751.
Saponification, 256.

Sarcina ventriculi, 287.
Sarcoglia, 459.
Sarcolactic acid, 463.
Sarcolemma, 455.
Sarcolytes, 640.
Sarcoplasts, 640.
Sarcous elements, 455.
Sarkin, 401.
Sarkosin, 385.
Saviotti’s canals, 253.
Scheiner’s experiment, 753.
Schiff’s test, 400.
Schizomycetes, 49, 279.
Schmidt’s researches, 34.
Schreger’s lines, 225.
Schwann’s sheath, 528.
Sclerotic, 735.
Scoliosis, 503.
Scotoma, 772.
Screw-hinge joint, 499.
Scrotum, formation of, 890.
Scurvy, 48.
Scyllit, 384.
Sebaceous glands, 442.

a secretion, 444.
Seborrhoea, 449.
Secondary circulation, 870.

of contraction, 558.
~ decompositions, 545,
oe degeneration, 633.

x tetanus, 559.
Secretion currents, 561.
Secretory nerves, 581.
Sectional area, 134.
Segmentation sphere, 862.
Self-stimulation of muscle, 556.
Semen, composition of, 846.

» ejaculation of, 859.

INDEX.

Semen, reception of, 859.
Semicircular canals, 604, 808.
Sensation, 731.
Sense organs, 731.

», development of, 892.
Sensory areas, 701.

» crossway, 654, 718.

5, paths, 644.

5 sensations, 830.
Serin, 385.
Serous cavities, 303.

Serum of blood, 30.
Serum-albumin, 37, 376.
Serum-globulin, 37, 376.
Setschenow’s centres, 639.
Sex, difference of, 890.
Shadows, lens, 762.

Pr coloured, 782.
Sharpey’s fibres, 882.
Short-sightedness, 754.
Shunt, 548.

Sialogogues, 215.
Sighing, 183.
Silver lines, 94.
Simple colours, 778.
Simultaneous contrast, 780.
Sinuses, 95.
Sitting, 505.
Size, 372.
» estimation of, 791.
»> increase in, 372.
», false estimate of, 793.
Skatol, 255, 282, 405.
Skin, absorption by, 449.
» chorium of, 437.
», currents of, 557.
» epidermis, 437.
», functions of, 444.
», galvanic conduction of,
», glands of, 442.
», historical, 450.
», pigments, 446.
», protective covering, 443.
5 ev ea organ, 193,
444,

;, structure of, 437.
», varnishing the, 444.
Skin currents, 561

Sleep, 685.
Small intestine, 290.
‘5 absorption by,
297.
= structure of,
290.
Smegma, 445.

Smell, sense of, 821.
Sneezing, 183.
Snellen’s types, 754.
Sniffing, 822.
Snoring, 183.
Sodic chloride, 373.

» salts, 373.
Solitary follicles, 293, 295.
Somatopleure, 868
Somnambulism, 684.
Sorbin, 384. -
Sound, 798.

5 ~ cardiac, 67.

», conduction to ear, 798,

807

direction of, 819.
- 5, distance of, 819.

917

Sound, perception of, 819.

», reflection of, 798.
Sounds, cardiac, 71.

» cracked pot, 180.

» respiratory, 179.

», tympanitic, 179.

» vesicular, 179.
Spasm centre, 680.
Spasmus nictitans, 603.
Specific energy, 731, 773.
Spectacles, 756.
Spectra, absorption, 21.

», flame, 21.

», ocular, 764.
Spectroscope, 21.
Spectrum mucro-lacrimale, 762.

re of bile, 269.

. of blood, 22.
_ of muscle, 460.
Speech, 519.

;, centre for, 710.

3, pathological variations,

522

Spermatin, 846.
Spermatozoa, 846.
Spermatoblasts, 847.
Spheno-palatine ganglion, 595.
Spherical aberration, 757.
Sphincters, 502.
Sphincter ani, 233.
oe pupille, 736.
bs urethree, 433.

Sphygmogram, 102.
Sphygmograph, 97.

3 Dudgeon’s, 99.

‘3 Ludwig’s, 99.

5 Marey’s, 98.
Sphygmometer, 97.
Sphygmomanometer, 122.
Sphygmoscope, 101.
Sphygmotonometer, 97.
Spina bifida, 727, 870.
Spinal accessory nerve, 614.
Spinal cord, 626.

» action of blood
poisons on, 646.
blood-vessels of, 632.

centres, 643.
conducting paths in, 633.
conducting system of,
633, 646.

degeneration of, 636.
development of, 892.
», excitability of, 645.
Flechsig’s systems, 633.
,, functions of, 632.

», ganglion, 616.
',, Gerlach’s theory, 629.

5, nerves, 615. |

», meuroglia of, 631.
nutritive centres in, 635.
» reflexes, 635.
regeneration of, 681.
», secondary degeneration

of, 636. ie

>» segment of, 7
as stetetare of, 626.

5, time of development, 635.
‘s bo Fa section of,

4

and

29

a9 unilateral section of, 649.
;, Vaso-motor centres in,
676.

918

Spinal cord, Woroschiloff’s ob-
servations, 627.
Spinal nerves, 615.
,» anterior roots of, 619.
»» posterior roots of, 620.
Spiral joints, 499.
Spirillum, 49, 279.
Spirocheta, 49, 279.
Spirometer, 167. -
Splanchnic nerve, 238.
Splanchnopleure, 868.
Spleen, 148.
», action of drugs on, 153.
;, chemical composition,
150.
», contraction of, 151.
», extirpation of, 150.
,, functions of, 150.
- influence of nerves on,
152.

» | oncograph, 151.

», regeneration of, 150.

., structure, 148.

», tumours of, 153.
Spongin, 379.
Spontaneous generation, 841.
Spores, 281.

Spring kymograph, 121. |
Spring myograph, 479.
Springing, 505.

Sputum, abnormal, 201.

re normal, 200
Squint, 588.

Staircase, 485.
Stammering, 523.
Standing, 504.

Stannius’s experiment, 79.
Stapedius, 804.

Starch, 383.

Starvation, 360,

Stasis, 139.

Statical theory of Goltz, 604.
Stationary vibrations, 799.
Steapsin, 256.

Stenopaic spectacles, 757.
Stenosis, 70.

Stenson’s experiment, 468.
Stercobilin, 269, 284,
Stercorin, 284.
Stereoscope, 791.
Stereoscopic vision, 789.
Sternutatories, 183.
Stethograph, 169.
Stigmata, 94.

Stilling, canal of, 741.
Stimuli, 470.

a adequate, 731.

», heterologous, 731.

a homologous, 731.

es muscular, 473,
Stoffwechsel, xliv.
Stomach, 239,

0 cancer of, 286.

ue catarrh of, 286.

as changes in glands, 244.

> gases in, 252.

o. glands of, 241,

* movements of, 230,

* structure of, 239,
Stomata, 139, 303.

Stra: , 437.

Strassb ’s test, 413.

Striz medullares, 717.

Strobie dises, 780.

Stroboscopic discs, 780.
Stroma-fibrin and plasma-fibrin,

37.
Stromuhr, 132.
Struggle for existence, 896.
Struma, 678.
Strychnin, action of, 637.
Stuttering, 523. . -
Subarachnoid space, 726.

Ss fluid, 726.
Subdural space, 726.
Subjective sensations, 732.
Sublingual gland, 214.
Submaxillary ganglion, 598.

~ atropin on, 213.
as gland, 209
‘5 saliva, 216.
Substantia gelatinosa, 628.
Successive beats, 818.
es contrast, 782.
: light-induction, 782.
Succinic acid, 405.
Succus entericus, 278.

», action of drugs on, 278.
Suction, 222.

Sudorifics, 446.
Sugars, 382.

» estimation of, 161.

», tests for, 220.
Sulphindigotate of soda, 423.
paca of stimuli, 485,

i.
Summational tones, 819.
Superfecundation, 860.
Superficial reflexes, 641.
Superfcetation, 860.
Superior maxillary nerve, 594.
Supplemental air, 166
Supra-renal capsules, 156.

Surditas verbalis, 713.
Sutures, 499.
erator fluids, 668.

Sweat, 445.
», chemical composition,
45,

conditions influencing
secretion, 446,
» excretion of substances
by, :
»» glands, 443.
insensible, 445,
5» nerves, 447.
LY ae variations
of, 448.

447, 680.
| os spinal, 680.
' Swimming, 509.

Sympathetic ganglion, 621.
i nerve, 620,
a section of, 623, 675.
a stimulation of, 624,

Symphyses, 499.
Synchondroses, 499,
Syncope, 61.

Synergetic muscles, 502.
Synovia, 498.

Syntonin, 247, 377.
Systole, cardiac, 51.

?
Sweat centre,

Tabes, 647.
Taches cerebrales, 678.
Tactile areas, 714.
»» corpuscles, 829.
» sensations, 829.

»» sensations, conduction
of, 646.
Tenia, 843.
Tail-fold, 869.
Talipes caleaneus, 503.

» equinus, 503,

»» varus, 503.
Tambour, Marey’s, 99,
Tapetum, 767.

Tapping experiment, 668.

Taste, centre for, 704. J

organ of, 823.

» testing, 826.
Taste-bulbs, 825.
Taurin, 385.
Taurocholic acid, 247.
Tea, 353.

5, effects of, 220,
Tears, 794.
Tegmentum, 718.
Peleetetcec es: 791.
Telolemma, 499.
Temperature of animals, 319.

99

as accommodation
for, 334. |

re artificial increase
of, 336. ag

7 estimation of, 319.

P febrile, 335.

es how influenced,

re lowering of, 338.

$3 post-mortem, 337.

3 regulation of, 328.

. topography of, 321.

a5 variations of, 325.
Temperature-sense, 836.
- illusions of,
838.
Tendon, 457.
», nerves of, 462, 829.
»» reflexes, 642.
Tensor choroidez, 750.

»» _ tympani, .
PTS he, ed 137.
Testicle, descent of, 889,
Testis, 844.
Tetanomotor, 534,
Tetanus, 485, 486, 536.

% secon , 039.
Tetonetenuent
Theobromin, 353.
Thermal centre, 329.
- nerves, 329. ,
Thermo-electric methods, 320.
a needles, 321.

Thermogenesis, 317,
Thermometer, 319,

” c

9 and

= metastatic, 320.

- outflow, 320.
Thermometry, 319.
Thirs .

i

Thoracometer, 176.

Thrombosis, 33.
Thymus, 153.

i development of, 880.
Thyroid, 154.

» development of, 880.
Tidal air, 166.
5, wave, 102.
Timbre, 519, 521, 811.
Time in psychical processes, 684.
Time-sense, 813.
Tinnitus, 606.
Tissue-formers, 356.

99 metabolism of,
367.

‘3 regeneration of,
369.

Tizzoni’s reaction, 264.
Tobin’s tubes, 201.
Tomes, fibres of, 224.
Tone-inductorium, 487.
Tones, 814.

Tongue, glands of, 206.

5 movements of, 227.

Sa nerves of, 227.

th taste-bulbs of, 825.
Tonometer, 82.

Tonsils, 207.
Tonus, 644.
Tooth, 223.

», action of drugs on, 226.

;; chemistry of, 225. -

», development of, 225.*

» eruption of, 226.

» permanent, 226.

». pulp of, 224.

», structure of, 223.

» temporary, 226.
Topography, cerebral, 706, 714.
Toricelli’s theorem, 89.
Torpedo, 579.

Torticollis, 615.
Touch corpuscles, 827.
Touch, sense of, 827.
_ Trachea, 159.
Transfusion, 145.

%s of blood, 145.

fh of other fluids, 148.
Transitional epithelium, 432.
Transplantation of tissues, 371.
Transudations, 313.
Trapezius, spasm of, 615.
Traube-Hering curves, 126.
Traumatic degeneration of

nerves, 539.

Trehalose, 383.
Trichina, 843.
Trigeminus, 590.

35 ganglia of, 591, 595,

97, 598.

a5 inferior maxillary
branch, 595.

“3 neuralgia of, 598.

‘i sr ame branch,

‘e paralysis of, 599.

sf pathological, 598.
section of, 593, 599.
Pei superior maxillary
branch, 594.

ai trophic functions

of, 593.
Triple phosphate, 408.
Ritamnts, 608”

INDEX.

Trochlearis, 589.
Trommer’s test, 221.
Tropxolin, 242.
Trophic centres, 539.
», fibres, 539.

_y, nerves, 539, 582.
Trophoneuroses, 582.
Trotting, 508.

Trypsin, 255.
Trypsinogen, 255.
Tryptone, 254.
Tube casts, 417.
Tubes, capillary, 91.
» division of, 91.
» elastic, 92.
a eee of fluids in,
» Yigid, 92.
Tumultus sermonis, 711.
Tunicin, 384
Turacin, 381.
Tiirck’s method, 641.
Twins, 860.
Twitch, 479.
Tympanic membrane, 799.
a artificial, 801.
Tyrosin, 255, 385, 416.

Ulcer of foot, perforating, 583.
Umbilical arteries, 872.

Fe cord, 875.
x veins, 872.
, - vesicle, 869.

Unipolar induction, 550.
Eas stimulation, 537.
Upper tones, 814.
Urachus, 888.
Uremia, 430.
Urates, 399.
Urea, 395.
», antecedents of, 396.
», compounds of, 397.
», decomposition of, 395.
,, effect of exercise on, 396.
>, ferment, 408.
», formation of, 396, 425.
» nitrate of, 397.
5, occurrence of, 396.
», oxalate of, 397.
,, pathological, 396.
», phosphate of, 397.
>» preparation of, 397.
5, properties of, 395.
» qualitative estimation of,
397.
» quantitative estimation
of, 397.
» quantity of, 395.
relation of, to muscular
work, 396
Ureameter, 397.
Ureter, ligature of, 424.
»» pressure in, 412.
>> structure and functions
. of, 431.
Uric acid, 399.
», diathesis, 431.
,, formation of, 426.
3, occurrence, 399.
55 properties of, 399.
», qualitative estimation, 400.
$9 ones estimation of,

919

Uric acid, quantity, 399.
», solubility, 399.
», tests for, 400.
Urinary bladder, 433.
‘-y, calculi, 419.
», closure of, 433.
s, deposits, 416.
3, development of, 873.
Bs organs, 386.

»» pressure in, 436.
Urine, 392.
»» accumulation of, 434.

5, aceton in, 415.

», acid fermentation, 408.

> acidity, 394.

s, albumin in, 408.

5, alkaline fermentation,
408.

», alkaloids in, 431.

» amount of solids, 393.

», bile in, 413.

», blood in, 411.

», calculi, 419.

», Changes of in bladder,
436,

»» characters of, 392.

»» colour, 393.

» colouring matters of, 4038.

5, consistence, 394

>, ceystin in, 416.

», deposits in, 416.

», dextrin in, 415.

» effect of blood-pressure
on, :

» egg-albumin in, 411.

5, electrical condition o
579.

» excretion of pigments by,
oe) ;

», fermentations of, 407.

», ferments in, 405.

5, fluorescence, 393.

», fungi in, 417.

», gases in, 407.

», globulin in, 410.

>> hemi-albumose, 411.

», incontinence of, 437.

», influence of nerves on,
427.

», inorganic constituents,
405.

»» inosit in, 415.

», leucin in, 416.

», milk-sugar in, 415.

»» movement of, 432.

>> mucin in, 393, 411.

» mucus in, 393, 411.

5», organisms in, 417..

»» passage of substances
into, 426.

>> peptone in, 410.

»» Phosphoric acid in, 406.

55 oe ha characters of,

» pigments of, 403.

»» propeptone in, 410.

» quantity, 392.

», reaction, 394.

», retention of, 436.

» secretion of, 420.

», Silicie acid in, 407.

3, sodic chloride in, 405.
», solids of, 393.

920

Urine, specific gravity, 392.
9 27 eras changes in,

f in, 413.

ss, ccs acid in, 406.
s. ro of, 394.
test for albumin in, 409.
tube casts in, 417.
tyrosin in, 416,
Urinometer, 393.
Urobilin, 26, 403.
Urochrome, "403.
Uroerythrin, 403.
Uro-genital sinus, 890.
Uromelanin, 403.
Urorubin, 403.
Urostealith, 419.
Uterine milk, 875.
Uterus, 853.
development of, 890,

», involution of, 895.

» nerves of, 895.
Utricle, 808,
Uvea, 735.

2

Vagotomy, 665.

Vagus, 606.

cardiac branches, 611.

depressor nerve of, 124,

610.

;, effect of section, 611.

»» on heart, 126.

»» pathological, 613.

oe after section,
61

??

., Yretlex effects of, 613.
», stimulation of, 127, 668.
», unequal excitability of,
613.
Valleix’s points douloureux,
839.
Valsalva’s experiment, 88, 111.
Valve, illeo-colic, 233.
»» pyloric, 230.
Valves of heart, 54.
» disease of, 70.
»» injury to, 60
» Of veins, 94.
», sounds of, 142.
Valvulz conniventes, 290.
Varicose fibres, 526.
Varix, 129.
Varnishing the skin, 339.
Vas deferens, 845.
Vasa vasorum, 95,
Vascular system, development
of, 882.
Vaso-dilator centre, 678,
nerves, 678,
Vaso-formative cells, 11.
Vaso-motor centre, 672.

- destruction of, 673,
a nerves,
ie spinal, 676,

vow -motor nerves, course of,
Vater’s corpuscles, 828.
Vegetable albumin, 377.

ms casein, 377.

+ foods, 350.

PRINTED BY NEILL AND COMPANY, EDINBURGH,

INDEX, §

Vegetable, oe 352,
proteids, 377.
Veins, ~
29 rdinal, 884.

9
9

9
9?
bP]

a pe of, 884,
at a of blood in,
1

murmurs in, 141,
pressure in, 1

pulse in, 142.

structure of, 94.

tonus of, 673.

valves in, 94, 140.
valvular sounds in, 142.
varicose, 129.

velocity of blood in, 139.

Vella’s fistula, 277.

Velocity of blood-stream, 90.
Venous blood, 45
Ventilation, 200.

Ventricles, 53, 66.

Veratrin, 48

Vern

aspiration of, 58.

ee brain, 726.

Ge capacity of, 118, 135.
a fibres of, 53

<4 impulse of, 62.

a negative pressure in,

systole of, 59, 66.
ix caseosa, 445.

Vertebrze, mobility of, 504.
Vertebral column, 870.
Vertigo, 605.

Vestibular sacs, 808.
Vibrations of body, 116.
Vibratives, 522.

Vibrio, 49.

Villus, intestinal, 291.

9
2?
?
9

absorption by, 300.

chorionic, 873.

contractility of, 292.
lacental, 874.

Violet-blindness, 778.
Visceral arches, 871.

>)

clefts, 871.

Vision, binocular, 787.

9

stereoscopic, 789.

Visual angle, 748.

9

apparatus, 731.
centre, 702, 713.
purple, 739, 773.

Vital capacity, 166,
Vitellin, 376.

Vitelline duct, 869.
Vitreous humour, 740.
Vocal cords, 509.

”

conditions influencing the,
518,

Voice, 509.

>?
9°
9

falsetto, 518.
in animals, 523,
sore Ea variations

physics of, 510,
pitch of, 510,
production of, 519,
range of, 419,

Volume pulse, 145,
Feluinpicth method, 398,

Vomiting, 23
és pooh for, 232, 660,
Vowels, 520.
»» analysis of, 520, 814.
» artificial, 815.
» formation of, 520.
a ier apparatus for,

Wagner's corpuscles, 827.
Waking, .

Walking, 505.

a law of degeneration,

Wandering cells, 303. .
Warm-blooded animals, 318,
Washed blood-clot, 33.
Water, 341, 373.
99 absorbed by skin, 449,
»,» absorption of, 297.
ss a by ‘akin, 194,

», exhaled from lungs, 188,

>» hardness of, 342,

», impurities, 342.

», in urine, 392.

vapour of, in air, 187.
Wave- -pulse, 102.
»» propagation of, 111,

Wave-motion, 92.
Wave- movements, 798.
Waves, in elastic tubes, 113.
Weber’s a 493.

Weigert’ 8 method, 529,
Weight, 372.

Weyl’s test, 401.
Wharton’s jelly, 875.
Whispering, 5

White of egg, 375.
Wine, 354.

Wolffian bodies, 888.

“ ducts, 888.
Word-blindness, 711.
Word-deafness, 704, 711.
Work, 489

» Unit of, xxxviii.

Xanthin, 401.
Xanthokyanopy, 778.
Xanthoplane’ 7 740,
Xanthoproteic reaction, 375
Xerosis, 594,

Yawning, 183.

Yeast, 380.

Yelk, 852.

5, Cleavage of, 862.
, 869.

Yellow-sp t, 764.
Young-Helmholtz theory, 776.

Zero-temperature, 836. \
Zimmermann, igo 7. of, 17.
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A textbook

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