Marine Biological Laboratory Library

Woods Hole, Massachusetts

Gift of F. R. Lillie estate - 1977

0

A MANUAL

OF

HUMAN PHYSIOLOGY.

A MANUAL OF

HUMAN PHYSIOLOGY,

INCLUDING

HISTOLOGY AND MICROSCOPICAL ANATOMY;

WITH SPECIAL REFERENCE TO THE REQUIREMENTS OF

PRACTICAL MEDICINE.

BY

DR. L. L A N D O I S,

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

TRANSLATED FROM THE FOURTH GERMAN EDITION.

WITH ADDITIONS BY

WILLIAM STIRLING, M.D., Sc.D.,

REGIUS PROFESSOR OF THE INSTITUTES OF MEDICINE OR PHYSIOLOGY IN THE UNIVERSITY OF ABERDEEN.

176 IT_,ljTJSTK,-A,TXOlTS.

VOL. I.

PHILADELPHIA:

P. BLAKISTON, SON, AND COMPANY,
1012 WALNUT STREET.

1885.
\All Rights Reserved.\

TO

SIR JOSEPH LISTER, BARONET,

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

PEOFESSOE OF CLINICAL SURGERY IN KING'S COLLEGE, LONDON, SURGEON-EXTRAORDINARY TO THE QCEEX;
FORMERLY REGIUS PROFESSOR OF CLINICAL SUHGEEY IN THE UNIVERSITY OF EDINBURGH.

IN ADMIRATION OF

%^t Pan oi jSmttJt*,

WHOSE BRILLIANT DISCOVERIES HAVE REVOLUTIONISED
MEDICAL PRACTICE, AND CONTRIBUTED INCALCULABLY TO THE

WELL-BEING OP MANKIND;
AND IN GRATITUDE TO

WHOSE NOBLE EARNESTNESS IN INCULCATING

THE SACREDNESS OF HUMAN LIFE
STIRRED THE HEARTS OF ALL WHO HEARD HIM :

cTbis Modi is rrspcttfulln Qcbitutcir
BY HIS FORMER PUPIL,

THE TRANSLATOR.

PKEFACE.

THE fact that Prof essor LANDOIS' " 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 commended the work will be found mainly to lie in its
eminent practicality; and it is this consideration which has induced

-/. it f

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 rdsum6 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 Avay, 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 lie used by the Practitioner, are carefully and fully
described ; and Histology, also, occupies a larger place than is usually
assigned to it in Text-books of Physiology.

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 be most ready to pardon any
shortcomings they may detect.

Viil PREFACE.

(2.) Very 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
acknowledge my indebtedness to many valuable Papers in the various
Medical Journals — British and Foreign — and also to the Histological
Treatises of Cadiat, Eanvier, and Klein; Quain's Anatomy, vol. n.,
ninth edition; Hermann's llandbucli der Physiologic; and the Text-
books on Physiology, by Rutherford, Foster, and Kirkes ; Gamgee's
Physiological Chemistry; Ewald's Digestion; and Roberta's Digestive
Ferments.

(3.) The Illustrations have been increased in number from 106
in the Fourth German Edition to 176 in the English version. These
additional Diagrams, with the sources whence derived, are distinguished
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 Public Library, for much valuable
assistance while the work was passing through the press.

The Second Part will, it is hoped, be issued early in 1885.

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.

GENERAL CONTENTS.

INTRODUCTION.

PAGE

The Scope of Physiology, and its Relation to the other Branches of Natural

Science, ............ xix

Matter, ............. xx

Forces, ............. xxii

Law of the Conservation of Energy, .... ... xxvii

Animals and Plants, ...... . xxviii

Vital Energy and Life, ...... ... xxxi

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, ..... 7

4. Effects of Reagents on the Blood-Corpuscles, ..... 7

5. Preparation of the Stroma — Making Blood "Lake-Coloured," . . 10

6. Form and Size of the Blood-Corpuscles of Different Animals, . . 11

7. Origin of the Red Blood-Corpuscles, . . . . . . . 12

8. Decay of the Red Blood-Corpuscles, . . . . . . . 16

9. The Colourless Corpuscles— Leucocytes, . . . . . . 17

10. Abnormal Changes of the Blood-Corpuscles, ...... 22

11. Chemical Constituents of the Red Blood-Corpxiscles, .... '_'.'{

12. Preparation of Haemoglobin Crystals, ....... 24

13. Quantitative Estimation of Haemoglobin, ...... 25

14. Use of the Spectroscope, ......... 27

15. Compounds of Haemoglobin — Methseinoglobin, ..... 29

16. Carbonic Oxide-Haemoglobin, . . . . . . . . 31

17. Poisoning by Carbonic Oxide, ........ 32

18. Decomposition of Haemoglobin, ........ 33

19. Hsemin and Blood Tests, 34

20. Hsematoidin, ........... 35

21. The Colourless Proteid of Haemoglobin, 36

22. Proteids of the Stroma, ... ... .36

23. The other Constituents of Red Blood-Corpuscles, .... 36

24. Chemical Composition of the Colourless Corpuscles, .... 37

25. Blood-Plasma, and its Relation to Serum, ...... 37

26. Preparation of Plasma, ......... 38

27. Fibrin — Coagulation of the Blood, ....... 39

28. General Phenomena of Coagulation, ....... 40

29. Cause of the Coagulation of the Blood, ....... 43

30. Source of the Fibrin- Factors, ........ 46

31. Relation of the Red Blood-Corpuscles to the Formation of Fibrin, . 47

X CONTENTS.

SECTION PAGE

32. Chemical Composition of the Plasma and Serum, .... 49

33. The Gases of the Blood, 51

34. Extraction of the Blood Gases, ........ 53

35. Quantitative Estimation of the Blood Gases, 55

36. The Blood Gases, ........... 55

37. Is ozone (03) present in Blood ? . . 57

38. Carbonic Acid and Nitrogen in Blood, ....... 58

39. Arterial and Venous Blood, ......... 59

40. Quantity of Blood, . . . ... 60

41. Variations from the Normal Conditions of the Blood, .... 61

II. PHYSIOLOGY OF THE CIRCULATION.

42. General View of the Circulation, 65

43. The Heart, 66

44. Arrangement of the Cardiac Muscular Fibres, ..... 67

45. Arrangement of the Ventricular Fibres, ...... 69

46. Pericardium, Endocardium, Valves, 71

47. Self-Steering Action of the Heart, 73

48. The Movements of the Heart, 76

49. Pathological Disturbances of Cardiac Action, ..... 79

50. The Apex-Beat — the Cardiogram, ....... SO

51. The Time occupied by the Cardiac Movements, ..... 85

52. Pathological Disturbance of the Cardiac Impulse, .... 89

53. The Heart-Sounds. 91

54. Variations of the Heart-Sounds, 95

55. The Duration of the Movements of the Heart, 96

56. Innervation of the Heart, 97

57. The Cardiac Nerves, ... 97

58. The Automatic Motor-Centres of the Heart, ...... 98

59. The Cardio-Pneumatic Movements, ....... 109

00. Influence of the Kespiratory Pressure on the Heart, . . . .111

THE CIRCULATION.

61. The Flow of Fluids through Tubes, 115

62. Propelling Force, Velocity of Current, Lateral Pressure, . . .115

63. Currents through Capillary Tubes, US

64. Movements of Fluids and Wave-Motion in Elastic Tubes, . . .118

65. Structure and Properties of the Blood- Vessels, 119

66. The Pulse— Historical, 127

67. Instruments for Investigating the Pulse, 128

68. The Pulse-Curve or Sphygmogram, 136

69. Dicrotic Pulse, 140

70. Characters of the Pulse, 141

71. Variations in the Strength, Tension, and Volume of the Pulse, . . 143

72. The Pulse-Curves of various Arteries, 144

73. Anacrotism, 146

74. Influence of the Respiratory Movements on the Pulse-Curve, . . 148

75. Influence of Pressure upon the Form of the Pulse-Wave, . . . 151

76. Rapidity of Transmission of Pulse- Waves, 152

77. Propagation of the Pulse-Wave in Elastic Tubes, .... 152

78. Velocity of the Pulse-Wave in Man, , 154

CONTENTS, XI

SECTION" PAGE

79. Further Pulsatile Phenomena ,156

80. Vibrations Communicated to the Body by the Action of the Heart, , 157

81. The Blood-Current, 159

82. Schemata of the Circulation, 161

83. Capacity of the Ventricles, ... . 161

84. Estimation of the Blood-Pressure, 162

85. Blood-Pressure in the Arteries, . .166

86. Blood-Pressure in the Capillaries, . . 173

87. Blood-Pressure in the Veins, . . . 175

88. Blood-Pressure in the Pulmonary Artery, . . ... 177

89. Measurement of the Velocity of the Blood-Stream, .... 179

90. Velocity of the Blood in Arteries, Capillaries, and Veins, . . . 182

91. Estimation of the Capacity of the Ventricles, . . . 184

92. The Duration of the Circulation, 184

93. Work of the Heart, 185

94. Blood-Current in the Smallest Vessels, ...... 186

95. Passage of the Blood-Corpuscles out of the Vessels— [Diapedesis], . 189

96. Movement of the Blood in the Veins, 190

97. Sounds or Bruits within Arteries, 192

98. Venous Murmurs, 193

99. The Venous Pulse— Phlebogram, . ... 194

100. Distribution of the Blood, 196

101. Plethysmography, ... 197

102. Transfusion of Blood, ... 199

THE BLOOD-GLANDS.

103. The Spleen — Thymus — Thyroid— Supra-Renal Capsules— Hypophysis

Cerebri — Coccygeal and Carotid Glands, ..... 203

104. Comparative, 215

105. Historical Retrospect, 215

III. PHYSIOLOGY OF RESPIRATION.

106. Structure of the Air-Passages and Lungs, , 217

107. Mechanism of Respiration, 226

108. Quantity of Gases Respired, 227

109. Number 'of Respirations, ......... 229

110. Time occupied by the Respiratory Movements, ..... 229

111. Pathological Variations of the Respiratory Movements, . . . 233

112. General View of the Respiratory Muscles, 234

113. Action of the Individual Respiratory Muscles, 235

114. Relative Size of the Chest, 240

115. Pathological Variations of the Percussion Sounds, .... 244

116. The Normal Respiratory Sounds, 245

117. Pathological Respiratory Sounds, 245

118. Pressure in the Air-Passages during Respiration, .... 247

119. Appendix to Respiration, ......... 248

120. Peculiarly Modified Respiratory Sounds, ...... 248

121. Quantitative Estimation of C02, O, and Watery Vapour, . . . 250

122. Methods of Investigation, 250

123. Composition and Properties of Atmospheric Air, 254

Xii CONTENTS.

SECTION ''AGE

124. Composition of Expired Air, . . . 254

125. Daily Quantity of Cases Exchanged, 256

126. Review of the Daily Gaseous Income and Expenditure, . . . 256

127. Conditions Influencing the Gaseous Exchanges, 256

128. Diffusion of Gases within the Lungs, ... . . 259

129. Exchange of Gases between the Blood and the Air, .... 260

130. Dissociation of Gases, 263

131. Cutaneous Respiration, ......... 264

132. Internal Respiration, . 265

133. Respiration in a Closed Space, ........ 267

134. Dyspnrea and Asphyxia, 268

135. Respiration of Foreign Gases, ........ 271

136. Accidental Impurities of the Air, . ...... 272

137. Ventilation of Rooms, .... .272

138. Formation of Mucus, 273

139. Action of the Atmospheric Pressure, 275

140. Comparative and Historical, . . 277

IV. PHYSIOLOGY OF DIGESTION.

141. The Mouth and its Glands, 279

142. The Salivary Glands, . 280

143. Histological Changes in the Salivary Glands, ..... 283

144. The Nerves of the Salivary Glands, 285

145. Action of Nerves on the Salivary Secretion, ..... 286

146. The Saliva of the Individual Glands, 291

147. The Mixed Saliva in the Mouth, 292

148. Physiological Action of Saliva, ........ '294

149. Tests for Sugar, 297

150. Quantitative Estimation of Sugar, 298

151. Mechanism of the Digestive Apparatus, ...... 298

152. Introduction of the Food, 298

153. The Movements of Mastication, 299

154. Structure and Development of the Teeth, ...... 300

155. Movements of the Tongue, ......... 304

156. Deglutition, 305

157. Movements of the Stomach, ........ 309

158. Vomiting, 310

159. Movements of the Intestine, . . . . . . .312

160. Excretion of Faecal Matter, 313

161. Influence of Nerves on the Intestine, 316

162. Structure of the Stomach, 321

163. The Gastric Juice, 325

164. Secretion of Gastric Juice, 326

165. Methods of obtaining Gastric Juice, ....... 330

166. Process of Gastric Digestion, ........ 331

167. Gases in the Stomach, 336

168. Structure of the Pancreas, 337

169. The Pancreatic Juice, 339

170. Digestive Action of the Pancreatic Juice, ...... 340

171. The Secretion of the Pancreatic Juice, ....... 340

172. Preparation of Peptonised Food, ..,,.... 345

CONTENTS. Xlii

SECTION PAGE

173. Structure of the Liver, 346

174. Chemical Composition of the Liver-Cells, 350

175. Diabetes Mellitus, or Glycosuria, ... . . 352

176. The Functions of the Liver, ... 354

177. Constituents of the Bile, ... 354

178. Secretion of Bile, 359

179. Excretion of Bile, ...... ... 361

180. Reabsorption of Bile, . .... .362

181. Functions of the Bile, . . 365

182. Fate of the Bile in the Intestine, 367

183. The IntestinalJuice, 368

184. Fermentation Processes in the Intestine, ...... 371

185. Processes in the Large Intestine, ... .... 377

186. Pathological Variations, .... . . 380

187. Comparative Physiology, ......... 383

188. Historical Retrospect, . 384

V. PHYSIOLOGY OF ABSORPTION.

189. The Organs of Absorption, , . ... 386

190. Structure of the Small and Large Intestines, 386

191. Absorption of the Digested Food, . . . .392

192. Absorptive Activity of the Wall of the Intestine, .... 395

193. Influence of the Nervous System, ....... 400

194. Feeding with "Nutrient Euemata," 400

195. Chyle-Vessels and Lymphatics, ........ 401

196. Origin of the Lymphatics, ......... 402

197. The Lymph-Glands, ; . 406

198. Properties of Chyle and Lymph, . 409

199. Quantity of Lymph and Chyle, . 412

200. Origin of Lymph, . ... 413

201. Movement of Chyle and Lymph, ....... 415

202. Absorption of Parenchymatous Effusions, ...... 418

203. Congestion of Lymph, Serous Effusions and (Edema, .... 419

204. Comparative Physiology, ....... . 420

205. Historical Retrospect, ... . ... 421

VI. PHYSIOLOGY OF ANIMAL HEAT.

206. Sources of Heat, 422

207. Homoiothermal and Poikilothertnal Animals, 426

208. Methods of Estimating Temperature — Thermometiy, .... 427

209. Temperature— Topography, ........ 430

210. Conditions Influencing the Temperature of Organs, .... 432

211. Estimation of the Amount of Heat — Calorimetry, .... 434

212. Thermal Conductivity of Animal Tissues, ...... 436

213. Variations of the Mean Temperature, . ..... 437

214. Regulation of the Temperature, . . ..... 441

215. Income and Expenditure of Heat, ....... 445

216. Variations in Heat Production, ........ 447

217. Relation of Heat Production to Bodily Work, 447

218. Accommodation for Different Temperatures, 448

XiV CONTENTS.

SECTION PAGE

219. Storage of Heat in the Body, . 450

220. Fever, .... . .... 450

221. Artificial Increase of the Temperature, . ... 452

222. Employment of Heat, ... . 453

223. Increase of Temperature post mortem, . . . . 453

224. Action of Cold on the Body, . . 454

225. Artificial Lowering of Temperatui'e, ... . 455

226. Employment of Cold, ... 456

227. Heat of Inflamed Parts, ... . .457

228. Historical and Comparative, • 457

VII. PHYSIOLOGY OF THE METABOLIC PHENOMENA

OF THE BODY.

229. General View of Food-Stuffs, . .458

230. Structure' and Secretion of the Mammary Glands, . . 461

231. Milk and its Preparations, ... . 464

232. Eggs, . 468

233. riesh and its Preparations, . ... 469

234. Vegetable Foods, . . . ... 471

235. Condiments— Tea and Alcohol, 473

PHENOMENA AND LAWS OF METABOLISM.

236. Equilibrium of the Metabolism, . 476

237. Metabolism during Hunger and Starvation, . . . 482

238. Metabolism during a purely Flesh Diet, ...... 485

239. A Diet of Fat or of Carbohydrates, . .... 486

240. Mixture of Flesh and Fat, . .... 486

241. Origin of Fat in the Body, . . 487

242. Corpulence, .... . . . 488

243. The Metabolism of the Tissues, . . 490

244. Regeneration of the Tissues, ........ 493

245. Transplantation of the Tissues, ........ 497

246. Increase in Size and Weight during Growth, ..... 497

GENERAL VIEW OF THE CHEMICAL CONSTITUENTS OF

THE ORGANISM.

247. Inorganic Constituents, . 499

248. Organic Constituents — Proteids, . . ..... 500

249. The Animal and Vegetable Proteids and their Properties, . . . 502

250. The Albuminoids, . . . 504

251. The Fats, . . . 508

252. The Carbohydrates, . 511

253. Historical Retrospect. . . ... . 514

LIST OF ILLUSTKATIONS.

FIGURE PAGE

1. Human coloured blood-corpuscles, .....

2. Malassez's apparatus for estimating the number of blood-corpuscle.s, . 4
*3. Gower's htemacytometer (Hawksley), .... 6

4. Eed blood-corpuscles showing various changes of shape,

5. Vaso-formative cells, .....

6. White blood-corpuscles, .... 18

7. Blood-plates and their derivatives, ....

8. Hreinoglobin crystals, ......

*9. Gower's haemoglobinometer (Hawksley), .... 26

10. Scheme of a spectroscope, ...... 28

11. Various spectra of haemoglobin, ..... 29

12. Hremin crystals, ........ 34

13. Haemin crystals prepared from traces of blood, ... 34

14. Haematoidin crystals, ....... 35

15. Scheme of Pfltiger's gas-pump, ...... 53

16. Scheme of the circulation, ...... 65

17. Muscular fibres from the heart, ..... 66

18. Muscular fibres in the left auricle, ... .68

19. Muscular fibres in the ventricles, ..... 70
*20. Lymphatic from the pericardium (Cadiat\ . . . . 71
*21. Section of the endocardium (Cadiat), . . . . .71
*22. Purkinje's fibres (Ranvier), .... 73

23. Cast of the ventricles of the human heart, .... 77

24. The closed semilunar valves, ...... 78

*25. Various cardiographs (Hermann), ..... 81

25a. Curves of the apex-beat, ...... 82

26. Changes of the heart during systole, ... 83

27. Curves from a rabbit's ventricle, ..... 86
*28. Marey's registering tambour (Hermann), .... 87

29. Curves obtained with a cardiac sound, .... 88

30. Curves from the cardiac impulse, ..... 90

31. Position of the heart in the chest (Luschka and Gairdner). . . 93
31a. Bipolar nerve-cells from a frog's heart, . . . .98

*32. Scheme of a frog-manometer (Stirling), ..... 102

*32a. Perfusion cannula (Kronecker and Stirling), , 102

*33. Roy's tonometer (Stirling), ... .103

*34. Luciani's groups of cardiac pulsations (Hermann), , . , 104

*35. Curves of a frog's heart at different temperatures (Hermann), . , J05

36. Cardio-pneumograph of Landois, , , , .110

xvi ILLUSTRATIONS.

FIGUKE PAGE

37. Apparatus for showing the effect of respiration, . . .113

38. Cylindrical vessel, . . . . . . .115

39. Cylindrical vessel •with manometers, ..... 116

40. Small artery with its various coats, . . . . .120

41. Capillaries injected with silver nitrate, . . . 122
*42. Longitudinal section of a vein at a valve (Cadiat), . . . 123

43. Poiseuille's pulse-measurer, ...... 128

44. Sphyguiometer of Herisson, . . . . 128

45. Scheme of Marey's sphj'gmogi-aph, . . . . .129
*46. Marey's improved sphygmograph (B. Bramwell), . . . 130
*47. Scheme of Marey's sphygmograph in working order (B. Bramwell), . 130
*48. Scheme of Marey's sphygmograph after increase of the pressure (B.

Bramwell), ... 130

*49. Dudgeon's sphygmograph (Dudgeon), . . . . 131

*50. Mode of applying Dudgeon's sphygmograph (Dudgeon), . . 131

*51. Sphygmogram (Dudgeon), ...... 132

52. Scheme of Brondgeest's pansphygmograph, .... 132

53. Scheme of Landois' angiograph, . . . . .133

54. Pulse-curves of the carotid, radial, and posterior tibial arteries, . 134

55. Landois' gas-sphygraoscope, ...... 135

56. Hremautographic curve, . . . . . . .136

*57. Sphygmogram of radial artery (Dudgeon), .... 137

58. Sphygmograms of various arteries, ..... 138

59. Pulsus dicrotus, P. caprizans, P. monocrotus. . . . .140

60. Pulsus alteruans, ....... 143

61. Curves of the posterior tibial and pedal arteries, . . • 145

62. Anacrotic pulse-curves, ....... 147

63. Influence of the respiration on the Sphygmogram, . . 148

64. Curves of the radial and carotid arteries during Miiller's and Val-

salva's experiments, .... 150

65. Pulsus paradoxus, ..... 150

66. Various radial cui-ves altered by pressure, .... 151

67. Apparatus for measuring the velocity of the pulse-wave in an elastic

tube, ....... 153

67«. Tracing obtained from 67, .... 154

68. Pulse tracings of the radial and carotid arteries, . . 155

69. Tracings from the posterior, tibial, and carotid arteries, 156

70. Apparatus for registering the molar motions of the body, 157

71. Vibration and heart ciirves, , 158

72. Ludwig and Fick's kymographs, . . • 163
*73. Ludwig's improved revolving cylinder (Hermann), . . 164
*74. Blood-pressure tracing of the carotid of a dog (Hermann), . . 165
*75. Fick's spring kymograph by Heriug (Hermann), . . 166
*76. Depressor curve (Stirling), ...... 168

77. Blood-pressure and respiration tracings taken simultaneously, . 169

78. Blood-pressure tracing during stimulation of the vagus (Stirling), . 173

79. f Apparatus of v. Kries for estimating the capillary pressure (C. ")••,-,
SO. \ Ludwig), ...... j

81. Volkmann's htemadromometer, ..... ISO

82. Ludwig and Dogiel's rheometer, .... ISO
S3. Vierordt's hrcmataehometer, .... . 181
84. Dromograph, . . . . . . . .182

*

ILLUSTRATIONS. XVil

PAGE

85. Diapedesis, . . . ; . . . .190

86. Various forms of venous pulse, ..... 195

87. Mosso's plethysmograph, ...... 198

*88. Trabeculaa of the spleen (Cadiat), 203

*S9. Adenoid tissue of spleen (Cadiat), ..... 203

*90. Malpighian corpuscle of the spleen (Cadiat), .... 205

*91. Tracing of a splenic curve (Roy), ..... 209

*92. Thymus gland (Cadiat), ....... 212

*93. Elements of the thymus gland (Cadiat), . . . .212

*94. Thyroid gland (Cadiat), 213

*95. Supra-renal capsule (Cadiat), ...... 214

*97. Human bronchus (Hamilton), ...... 219

*98. Air-vesicles injected with silver nitrate (Hamilton), . . 221

99. Scheme of the air- vesicles of lung, ..... 222
*100. Interlobular septa of lung (Hamilton), . . . .223

101. Scheme of Hutchinson's spirometer,' ..... 228

102. Marey's stethograph (M'Kendrick), ..... 230

103. Brondgeest's tambour and curve, ..... 230

104. Pneumatogram, ....... 231

105. Section through diaphragm (Hermann), .... 236

106. Action of intercostal muscles, ...... 237

107. Cyrtometer curve, ....... 241

108. Sibson's thoracometer, ....... 242

109. Topography of the lungs and heart, ..... 243

110. Andral and Gavarret's respiration apparatus, . . . 251

111. Scharling's apparatus, . . . . . . .251

112. Regnault and Reiset's apparatus, ..... 252

113. v. Pettenkofer's apparatus, ...... 253

114. Valentin and Bruuner's apparatus, ..... 255

115. Objects found in sputum, ...... 274

116. Histology of the salivary glands, ..... 281
*117. Human sub-maxillary gland (Heidenhain), .... 282

*118 )

*119 ( Sections of a serous gland (Heidenhain), . 284

*120. Diagram of a salivary gland (L. Brunton), . . . 289

121. Apparatus for estimation of sugar, ..... 298

122. Vertical section of a tooth, ...... 300

123. Dentine, ........ 300

124. Dentine and enamel, ....... 301

125. Dentine and crusta petrosa, .'.... 302

126. )

127. [Development of a tooth, . 302 and 303

128. )

129. Perinaeum and its muscles, ...... 314

130. Levator ani externus and internus, ..... 315

131. Auerbach's plexus (Cadiat), ...... 317

132. Meissner's plexus (Cadiat), ... . . 317

133. Surface section of gastric mucous membrane, .... 321

134. Fundus gland of the stomach, ...... 322

135. Pyloric gland and goblet-cells, ...... 323

136. Scheme of the gastric mucous membrane, .... 324

137. Pyloric mucous membrane (Hermann), .... 326

*

xviii ILLUSTRATIONS.

FIGURE PAGE

*13S. Pyloric glands during digestion (Hermann), .... 326

*139. Section of the tubes of the pancreas (Hermann), . . . 337

140. Changes of the pancreatic cells during activity, . . 338

141. Scheme of a liver lobule, . . % • • 347
*142. Human liver-cells (Cadiat), ...... 348

*143. Liver-cells during fasting (Hermann), ..... 348

144. Various appearances of the liver-cells, . 349

*145. Cholesterin (Aitken), ...... 358

*146. Lieberkuhn's gland (Hermann), . . • 369

147. Bacterium aceti and B. butyricus, ... • 373

148. Bacillus subtilis, . . . . . • .375
*149. Villi of small intestine injected (Cadiat), . . 387

150. Scheme of an intestinal villus, . . • 388

*151. Villi and Lieberkiihn's follicles (Cadiat), 389

*152. Section of a solitary follicle (Cadiat), .... 390

*153. Section of a Peyer's patch (Cadiat), ..... 391

*154. Section of Auerbach's plexus (Cadiat), .... 391

*155. Lieberkiihn's gland (Hermann), .• . . • 392

156. Endosmometer, ....... 393

157. Origin of lymphatics in the tendon of diaphragm, . . . 403
*158. Lymphatics of diaphragm silvered (Ranvier), . . . 403

159. Perivascular lymphatics, ... ... 405

160. Stomata from lymph-sac of frog, ..... 405

161. Section of two lymph-follicles, ..... 406
*162. Scheme of a lymphatic gland (Knott), .... 407

163. Part of a lymphatic gland ...... 408

*164. Section of central tendon of diaphragm (Brunton), . . . 416

*165. Section of fascia lata of a dog (Brunton), .... 416

166. Water calorimeter of Favre and Silbermann, .... 422

167. Walferdin's metastatic thermometer, ..... 427

168. Scheme of thermo-electric arrangements, .... 428

169. Kopp's apparatus for specific heat, . . . . . . 435

170. Daily variations of temperature, ..... 439
*171. Acini of the mammary gland of a sheep (Cadiat), . . . 462

172. Milk-glands during inaction and secretion, .... 462

*173. Section of a grain of wheat (Blyth), ..... 471

174. Yeast-cells growing, ....... 474

175. Composition of animal and vegetable foods, .... 479

176. Starch grains (Blyth), . . . . . 512

[The illustrations indicated by the word Hermann, are from Hermann's
Handbuch der Physiologie; by Cadiat, from Cadiat's Traite d'Anatomie Gen&rale;
by Ranvier, from Ranvier's Traite Technique d 'Histologie ; by Brunton, from The.
Practitioner; and by Hamilton, from, Hamilton's Pathology of Bronchitis.]

Introduction,

The Scope of Physiology and its Eelations to other
Branches of Natural Science,

PHYSIOLOGY 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 — ie., the so-called
Protistce of Hseckel, micro-organisms, and those elementary organisms
or cells which exist on the same level.

The object of Physiology is to establish these phenomena, to deter-
mine 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,
protistae, and elementary organisms).

I. Morphology.

The doctrine of the form of

organisms.

General
Morphology.

The doctrine of the
formed elemen-
tary constituents
of organisms.

(Histology)—

(a) Histology of

Plants,
(6) Histology of

Animals.

Special
Morphology.
The doctrine of
the parts and
organs of organ-
isms.

(Organology
Anatomy)—
(a) Phytotomy,
(6) Zootomy.

II. Physiology-

The doctrine of the vital pheno-
mena of organisms.

General
Physiology.

The doctrine of
vital phenomena
in general —
(a) Of Plants,
(6) Of Animals.

Special
Physiology.

The doctrine of
the activities of
the individual
organs —
(a) Of Plants,
(6) Of Animals.

XX

INTRODUCTION.

Morphological part of the
doctrine of develop-
ment, i.e., the doctrine
of form in its stages of
development —

(a) Genera],

(b) Special.

Physiological part of the
doctrine of develop-
ment, i.e., the doctrine
of the activity during
development —

(a) General,

(b) Special.

III. Embryology.

The doctrine of the generation and development of organisms.

ML History of the develop-
ment of single beings,
of the individual (.e.g. ,
of man) from the ovum

onwards (Ontogeny) :

(a) In Plants,

(b) In Animals.

2. History of the develop-
ment of a whole stock
of organisms from the
lowest forms of the
series upwards Phy-

logeny)—

(a) In Plants,

(b) In Animals.

v_ --

Morphology and Physiology are of equal rank in biological science,
and a previous acquaintance with Morphology is assumed as a 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, i.e., of substance which occupies space.

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

In ponderable materials, again, we distinguish their form, i.e., the
nature of their limiting surfaces ; further, their volume, i.e., the
amount of space which they occupy; and lastly, their aggregate condition,
i.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

INTRODUCTION. XXI

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 sec.) to our visual organs
(Tyndall).

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

Particles. — Supposing that ponderable matter were to be sub-
divided continuously into smaller and smaller portions, until we
reached 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 fluid,
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 sub-division, 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 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

XX11 INTRODUCTION.

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, i.e., 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.

1 . 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 9 '809 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 proportional
to the time, t, so that

V = 9t (1);

.INTRODUCTION. xxill

i.e., at the end of the 1st sec., V = g, 1 = g = 9'809M — the distance traversed —

s = f«2 (2);

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

V= V2<7« ......... (3).

The velocities are as the square roots of the distances traversed —

V2
Therefore, ~~= s ........... (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 —

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 = K S. 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, i.e., 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.

XXIV INTRODUCTION.

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

iu=.p, s, where p = ihe weight and ,s = the height,
p = m . g, is = the product of the mass (m), and the force of gravity (</), so that

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.

V = V "2gs (see above (3).

- = 2 my s.

m „„

6- V- = m g s.

m g s was the expression for the potential energy of the stone while

9??

it was still resting on the height; - V2 is the kinetic energy corre-

sponding 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 pen-
dulum 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 versa, 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 equilibrium, then in this system the sum of the kinetic

INTRODUCTION. XXV

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.e., the kinetic
energies diminish (Briicke).

The pendulum, which, after swinging from the highest point of its excursion,
approaches the vertical position, i.e., the position of equilibrium of a passive pen-
dulum, 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 diminish-
ing movement, and therefore of the kinetic energy.

3. Heat — Its 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 pro-
duced 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 juxtaposition ; 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 surrounding them on every side, i.e., until the heat of
the heated mass is " radiated" Heat is thus a vibratory movement of the
atoms.

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 amount 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 concussion,
produce as much heat as would raise the temperature of 1 gramme of
water 1°C. The "mechanical equivalent'' of the heat-unit is, there-
fore, 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

xxvi INTRODUCTION.

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
Eobert 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 ulti-
mately produce the light of the stars. At the present time, numerous cosmic bodies
collide in space, while innumerable small meteors (94,000-188,000 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 conver-
sion of potential energy into heat occurs, in a metallic spring, when it uncoils and
is so placed as to rub against a rough surface, producing heat by friction.

4. Chemical Affinity : Eolation 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 is 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 the chemical affinity by 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 gram, of H be burned
along with the requisite amount of O to form water, it yields 34,460
heat-units or calories; and 1 gram, carbon burned to carbonic acid
(carbon dioxide) yields 8,080 heat-units. Wherever, in chemical processes,
strong chemical affinities are satisfied, heat is set free — i.e., chemical affinity
is 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,

INTRODUCTION. XXV11

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
decomposition of the compound chemical body, is again represented 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 impres-
sion from without, the sum of all the forces acting within it is always the
same. The various fm-ms of energy can be transformed one into the other,
so that kinetic energy may be transformed into potential energy and vice versa,
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 follow-
ing modifications : —

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 constantly 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 u<orJc" = l gramme-metre,
and the "unit of heat" = 4:25-5 gramme-metres.

3. Potential Energy. — The organism contains many chemical com-
pounds which are characterised by the great complexity of their
constitution, by the imperfect saturation of their affinities, and hence,
by their great tendency 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 representing the potential

XXV111 INTRODUCTION.

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 currents (against considerable resist-
ance), 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 rela-
tively 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 transformed 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 spontaneously, 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,
p. 422).

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 it.

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 com-
bustion, simpler substances are formed from the more complex
compounds, whereby potential is converted into kinetic energy. It is
immaterial whether the combustion is rapid or slow ; the same amount

INTRODUCTION, XXIX

of the same chemical substances always produces the same amount of
kinetic energy, i.e., of heat.

A person when fasting, experiences after a certain time, the dis-
agreeable 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 re-
presentatives of food-stuffs — fats, carbohydrates, and proteids.

All these contain stores of potential energy, in virtue of their com-
plex chemical constitution.

The fats contain :- j Cn!^-£<°H) = ff* add9 } (§ 251).

( + C3H5(OH)3 = glycerine j

The carbohydrates contain : — C6H1005 . . . (§ 252).

f C. 51-5-54-5 '

H. 6-9- 7-3

The proteids contain per cent.:— •{ N. 1 5-2-17-0

I 0. 20-9-23-5

[ S. 0-3- 2-0 J

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, whereby chemically potential energy is transformed
into heat.

It is evident, that the products of this combustion must be bodies of
simpler constitution — 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 0, and possessing either no
potential energy, or only very little. These bodies are carbonic acid
(carbon dioxide), C02; water, H20; and as the chief representative of
the nitrogenous excreta, urea (CO(NH2)2), which has still a small
amount of potential energy, but which outside the body readily splits
into C02 and ammonia (NH3).

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

XXX INTRODUCTION.

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, C02, H20, NH3, and N,
of which carbonic acid, water, and ammonia (from urea), are also pro-
duced by the excreta of animals. Plants absorb the kinetic energy of
light from the suns 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 accompanied by the simultaneous
excretion of 0.

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 — e.g., the arum tribe. We must also remember that, during the forma-
tion of the solid parts of plants, when fluid juices are changed into solid masses,
heat is set free. In plants, under certain circumstances, 0 is absorbed, and C02
is excreted, but these processes are so trivial as compared with the typical condi-
tion in the vegetable kingdom, that they may be regarded as of small moment.

Plants, therefore, are organisms which, by a reduction process, trans-
form 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, i.e., of the whole of life.

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 in a 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 afterwards knocked down, then for this purpose we require — (1)

INTRODUCTION. XXXI

the motor power of the workman who lifts and carries the blocks ; (2)
a blow or other impulse from without 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 constructor 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 (StoffwecliseT) 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,
are actually what occur in the typical higher plants and animals.

But there is a large group of organisms which, throughout their
entire organisation, exhibit so low a degree of development, that by
some observers they are considered as undifferentiated " ground-forms."
They are regarded as neither plants nor animals, and are the most
simple forms of animated matter. Hseckel has called these organisms
Protista, as being the original and primitive forms.

We must assume that, corresponding with their simpler vital condi-
tions, their metabolism is also simpler, but on this point we still
require further observations.

Physiology of the Blood,

[THE blood is aptly described by Claude Bernard as an internal medium,
which acts as a " go-between " 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 new substances, but in its
passage through the tissues it gives up some of these new substances,
and receives in exchange certain effete and more or less useless sub-
stances which have to be got rid of. Its composition is thus highly
complex, containing, as it does, things both new and old. 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. Htill, with slight varia-
tions, there are certain general physical, histological, and chemical
properties which characterise blood as a ivhok.~]

1. Physical Properties of the Blood.

(1.) Colour. — The colour of blood varies from a 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 (Briicke).

In thin layers blood is opaqiie, 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. Blood behaves, therefore,
like an " opaque colour " (Kollett), 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 nitration. 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 two per cent, solution of sugar and filtered, the shrivelled corpuscles, now
robbed of part of their water, remain upon the filter.

PHYSICAL PROPERTIES OF THE BLOOD.

(2.) Reaction. — The reaction is alkaline, owing to the presence of
disodic phosphate, Na2,H,P04 (Maly). 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 decom-
position of their colouring-matter. A high temperature and the addi-
tion of an alkali favour the formation of the acid (N. Zuntz).

The alkalinity is less in persons suffering from anremia, cachectic conditions,
and chronic rheumatism (Lgpine). After the prolonged use of soda, the alkali
in the ash of blood is increased (Dubelir).

Methods. — Owing to the colour of the blood we cannot employ ordinary litmus
paper to test its reaction. One or other of the following methods may be used : —
(1.) Moisten a strip of glazed red litmus paper with solution of common salt, and
dip it quickly into the blood, or allow a drop of blood to fall on the paper, and
rapidly wipe it off before its colouring-matter has time to penetrate and tinge the
paper (Zuntz). (2.) Kiihne made a small cup of parchment paper which was
placed in water in a watch-glass. The colourless diffusate was afterwards tested
with litmus paper. (3.) Liebreich used thin plates of plaster-of- Paris of a per-
fectly neutral reaction. These are dried, and afterwards moistened with 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 remain at the surface.
The corpuscles are washed off with water, and the altered colour of the litmus-
stained slab is apparent. [(4.) 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 well-defined blue patch upon
a red or violet ground.]

The alkaline reaction of blood is diminished : («) By great muscular exertion,
owing to the formation of a large amount of acid in the muscles ; (ft) during
coagulation ; (y) in old blood, or blood dissolved by water from old blood-stains,
such blood being usually acid. Fresh cruor has a stronger alkaline reaction than
serum.

(3.) Odour. — Blood emits a peculiar odour (Halitm 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 com-
binations with alkalies, the characteristic odour becomes much more perceptible
(Barruel).

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

(5.) Specific Gravity. — The specific gravity is 1,055 (extreme limits
1,045—1,075); in women and young persons it is somewhat less.
The specific gravity of the blood-corpuscles is 1,105, that of the
plasma 1,027. Hence, the corpuscles tend to sink.

The specific gravity of the red blood-corpuscles is estimated by allowing the
corpuscles to subside to the bottom (which occurs most readily in the blood of
the horse) ; but it is more correctly estimated by placing the blood in a tall
cylindrical vessel, and setting the latter in the radiiis of the revolving
disc of a centrifugal apparatus, the base of the cylinder being directed out-
wards. The drinking of water and hunger diminish the specific gravity tern-

MICROSCOPIC EXAMINATION OF THE ELOOD. 3

porarily, 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
haemorrhage, and is less in badly-nourished individuals.

2. Microscopic Examination of the Blood.

[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 wnguinis.]

The RED blood-corpuscles were discovered in frog's blood by Swam-
merdam in 1658, and in human blood by Leeuwenhoek in 1673.

Characters of Human Blood — («.) Form. — The human red blood-
corpuscles 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 discs.

(5.) Size. — According to Welcker the diameter (a b) is 7'7 JJL* the
greatest thickness (c d} 1/9 /x (Fig. 1, C) [i.e., it is -^^ to ^^^ of
an inch in diameter, and about one-fourth of that in thickness].

The corpuscles are slightly diminished in size by septic fever, inanition, after the
subcutaneous injection of morphia, increased bodily temperature, and C02 ; while
they are increased by O, watery condition of the blood, cold, consumption of
alcohol, quinine, hydrocyanic acid, and acute anpemia (Manassei'n).

A B

L

A, Human coloured blood-corpuscles — 1, seen on the flat; 2, on edge; 3,
rouleau of coloured corpuscles slightly separated. B, Coloured amphibian
blood-corpuscles — 1, seen on the flat, and 2, on edge. C, Ideal transverse
section of a human coloured blood-corpuscle magnified 5,000 times linear ;
a b, diameter ; c d, thickness.

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

MICROSCOPIC EXAMINATION OF THE BLOOD.

If the total amount of blood in a man be taken at 4,400 cubic centimetres, the
corpuscles therein contained have a surface of 2,816 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
have a superficies of 81 square metres, equal to a square surface with a side of 13
paces (Welcker).

(c.) Weight. — The weight of a blood-corpuscle, according to Welcker,
is O'OOOOS milligrammes.

(?/.) Number. — According to Vierordt, the number exceeds 5,000,000
per cubic millimetre in the male, and 4,500,000 in the female; so that,
in 10 Ib.s. of blood, there are 25 billions of corpuscles.

The venous blood of the small cutaneous veins contains more red
corpuscles than arterial blood. As a general rule, 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 use of solid food increases their

B

If

Ibaa-Si) ' .
500-101 C

.L

^s

llong.-vo/um

1

Fig. 2.

Apparatus of Malassez for estimating the number of blood-corpuscles. A, the
mdangeur, or pipette, for mixing the blood with the artificial serum. /, tube
for sucking up these fluids. B, the artificial capillary tube, with an elastic
tube, /, attached for filling it. C, appearance of B under the microscope
when it is filled with blood. The squares are due to a piece of glass divided
into squares, which is put in the ocular of the microscope.

NUMBER OF BLOOD-CORPUSCLES. 5

number, copious draughts of water reduce it; during inanition the
number is relatively increased, because the blood plasma undergoes
decomposition sooner than the blood-corpuscles themselves (Buntzen).
The blood of the newly-born child contains a considerably larger number
of red corpuscles than the blood of the mother (Panum), while Hayem
found that the number diminished after the fourth day. In persons of
robust constitution the number is larger than in the weakly, and those
who live in the country have more than those who live in town.

(The pathological conditions which affect the number of corpuscles .
are given at p. 22).

a. Malasse^s Method of Estimating the number of Blood-Corpuscles.— The
pointed end of a glass pipette (Fig. 2, A), the mixer, is dipped into the blood, and
by sucking the elastic tube, /, blood is drawn into the tube 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 (S. G. 1,020) and 3 vols. of a solution
of equal parts of sodic sulphate and sodic chloride (S. G. 1,020). The process 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 sucked up to the mark, |, the strength of the mixture
is 1:200; if to the mark, 1, it is 1:100. A small drop of the mixture is
allowed to run into the artificial capillary tube (c c) (the first portions are not
used in order to obtain a uniform sample from the bulb of the pipette). The
mixture passes by capillarity into the capillary tube, which, when full, is emptied
by blowing through the thin caoutchouc tube, /", and then again rilled to §,
and the mixture sucked into the middle of the capillary tube. The capillary tube
is firmly fixed to a glass slide (B) with Canada balsam, and on it is inscribed the
following numbers :— »

Length. Volume.

600 yu . 89

500 M . . . . 107

400 M . . . . 134

i.e., a length of the capillary tube of GOO, 500, and 400 M contains -£a) 1|r, -5-^,
cubic millimetre.

In order to count the corpuscles, the same combination of lenses must always be
used. Select Hartnack's objective, No. 5 (Nachet, No. 2) ; the ocular contains a
piece of glass divided into 100 squares. The tube of the microscope must be so
made that it can be pulled out and in. A micrometer, divided into -^fa milli-
metre, is placed upon the stage of the microscope : 1 division, therefore, — 10 M
(p = i-,^ millimetre). The tube is now pulled out until the outer lines of the
divided ocular (tt, ii) exactly cover 600, 500, or 400 ;*. (500 M = k mm- i3 most
convenient). A mark is made on the tube of the microscope to indicate how far
it must be drawn out to accomplish this object, and, having been made, it indicates,
once for all, how far the tube must be drawn out to indicate exactly 500 M. The
capillary tube is then filled and placed on the stage, instead of the micrometer,
when a picture like C is obtained. The length of the capillary tube, from tt to i i,
is 500 ju. All the corpuscles observable between t t and i i are now counted.
Suppose 315 corpuscles to be counted between 1 1 and i i, the number, 315, is then
multiplied by 107 (which stands opposite 500 on B) and also by 100 (when the
mixture of blood and serum was 1 : 100), or by 200 as the case may be— i.e.,

NUMBER OF BLOOD-CORPUSCLES.

315 x 107 x 100 = 3,370,000 blood-corpuscles in 1 cubic millimetre. (After the
experiment the instruments must be carefully washed with distilled water. )

To estimate the colourless corpuscles only, mix the blood with 10
parts of 0'5 per cent, solution of acetic acid, which destroys all the red
corpuscles (Thoma).

Various forms of apparatus for the same purpose have been devised by Thoma,
Zeiss, Abbe", and Gowers.

[The following is a description of Gowers' instrument (Fig. 3): — "The
Hcemacytometer 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 millimetres, with India-rubber
tube for filling, &c. (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, -J- of a millimetre deep. The bottom
of this is divided into -^ 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,
S. G. 1,025, or the following — sodic sulphate, 104 grains; acetic acid, 1 drachm;
distilled water, 4 ozs.

Fig. 3.

Gowers' apparatus, made by Hawksley, London. 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, to which springs are fixed to secure
the cover glass. I). Vessel in which the solution is made. E, Spud for
mixing the blood and solution. F, Guarded spear-pointed needle.

" 995 cubic millimetres of the solution are placed in the mixing jar; 5 cubic
millimetres of blood are drawn into the capillary tube from a puncture in the

HISTOLOGY OP THE RED BLOOD-CORPUSCLES. 7

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 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. lu 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. "

Welcker attempted to ascertain the number of corpuscles by estimating the
colouring-power of the blood. His method was not exact, but other observers
have constructed apparatus for determining the amount of haemoglobin.

(«.) Ked blood-corpuscles are characterised by their great ELASTICITY,
FLEXIBILITY, and SOFTNESS. [The elastic property is shown by the
great extent to which red corpuscles still within the circulation may be
distorted, and yet resume their original form as soon as the pressure
is removed.]

3. Histology of the Human Red Blood-Corpuscles.

Wheu observed singly, blood-corpuscles have 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, trans-
parent, soft protoplasm — the stroma (Kollett) ; and (2.) of the red
pigment, or haemoglobin, which impregnates the stroma, much as
fluid passes into and is retained in the interstices of a bath-sponge.
Some observers (Bottcher, Eberhardt, Strieker), maintain that the
corpuscles contain a nucleus, but this is certainly a mistake.

4. Effects of Reagents.

(A.) Vital Phenomena. — Blood-corpuscles contained in shed blood—
or even in defibriiiated blood, when it is reintroduced into the circula-
tion— 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 extinguished. Mammalian blood may
be kept for four or live 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 (Laudois). Blood freshly shed from an artery,
frequently shows a transformation of the corpuscles into a peculiar
mulberry-shape. [This is the so-called crenation of the coloured cor-
puscles. It is produced by poisoning with Calabar bean (T. E. Fraser),
and also by the addition of a 2 per cent, solution of common salt]. The

HISTOLOGY OF THE RED BLOOD-CORPUSCLES.

blood of many persons crenates spontaneously — a condition ascribed
to an active contraction of the stroma (Klebs), but it is doubtful if
this is the cause. Max Schultze observed that the red corpuscles
of the embryo-chick undergo active contraction.

(B.) External Characters. — Many agents affect the external char-
acters of the corpuscles.

(a.) The Colour is changed by many gases. 0 makes blood scarlet,
want of 0 renders it dark bluish-red, CO makes it cherry-red, NO
violet-red. There is no difference between the shape of corpuscles in
arterial and venous blood, as was supposed by Harless. All reagents
(e.g., a concentrated solution of sodic sulphate), which cause great
shrinking of the coloured corpuscles, produce a very bright scarlet or
brick-red colour (Bartholinus, 1661). The red colour so produced
is quite different from the scarlet-red of arterial blood. Keagents
which render blood-corpuscles globular darken the blood, e.g., 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.]

(b.) Change of Position and Form. — 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 discs and the formation of a
sticky substance. [The cause of the arrangement of the red corpuscles into
rouleaux is by no means clear. They may be detached from each other by gently
touching the cover-glass, but the rouleaux may reform. Lister suggested that
the surfaces of the corpuscles were so altered that they became adhesive, and thus
cohered. Norris has made some ingenious experiments with corks weighted with
tacks or pins, so as to produce partial submersion of the cork discs. These discs
rapidly cohere, owing to capillarity, and form rouleaux. If the discs be com-
pletely 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.) The Changes of Form which, after blood is shed, the red corpuscles
undergo until they are gradually dissolved, are important. Some reagents
rapidly produce this series of events — e.g., the discharge of a Leyden jar
causes the corpuscles to crenate, so that their surfaces are beset with
large or small projections (Fig. 4, c, d, e, g, h); it also causes the corpuscles
to assume a spherical form (/,*), when they are smaller than normal.
The corpuscles so altered are sticky, and run together like drops of oil,

CHANGES IN THE FORM OF THE RED BLOOD-CORPUSCLES. 9

forming larger spheres. The prolonged action of the electrical spark
causes the haemoglobin to separate from the stroma (&), 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 decom-
posing blood, as well as after the action of many other reagents.

Fig. 4.

Red blood-corpuscles, showing various changes of shape — a, b, normal human red
corpuscles, with the central depression more or less in focus; c, d, e, mulberry
forms; g, h, crenated corpuscles; Tc, pale decolourised corpuscles; I, stroma;
/, a frog's blood-corpuscle, partly shrivelled, owing to the action of a strong
saline solution.

Action of Heat. — When blood is heated, on a warm stage, to 52°C.
the corpuscles begin to undergo 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 surround-
ing fluid, a proof that heat destroys the histological individuality of
the corpuscles (Max Schultze). If the heat be continued, the corpuscles
are ultimately dissolved.

Cytozoon or Wurmchen— Gaule's Experiment.— The following remarkable

observation made by Gaule deserves mention here : — A few drops of freshly-
shed frog's blood are mixed with 5 cc. of 0'6 per cent, solution of common salt,
and the mixture deh'brinated by shaking it along with a few cc. 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 "wiirmcJien," escapes with
a lively movement from many corpuscles, and ultimately dissolves. Similar
"cytozoa" 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
R,ay Lankester, who called the parasite Drepanidium ranartim.

If a finger moistened with blood be rapidly drawn across a warm
slip of glass, so that the fluid dries rapidly, very remarkable corpuscle-
shapes, showing their great ductility and softness, are observed under
the microscope.

10 LAKE-COLOURED BLOOD.

If blood be mixed with concentrated gum, and if concentrated salt solution be
added to it under the microscope, the corpuscles assume elongated forms
(Lindwurm). (Similar forms are obtained by mixing blood with an equal volume
of gelatine at 3G°C., allowing it to cool, and then making sections of the coagulated
mass (Rollett). The corpuscles may be broken up by pressing firmly on the
cover-glass. In all these experiments no trace of an envelope is observed.

5. Preparation of the Stroma— Making Blood

"Lake-Coloured."

There are many reagents which separate the haemoglobin from the
stroma. The hemoglobin dissolves in the serum ; the blood then
becomes transparent, as it contains its colouring matter in solution, and
hence it is called " lake-coloured " by Rollett. Lake-coloured blood is
dark-red. The aggregate condition of the hsemoglobin 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 (Landois). To obtain a large quantity
of the stroma, add ten volumes of a solution of common salt (1 vol.
concentrated solution, and 15 to 20 vols. of water) to one volume of
defibriuated blood, when the stromata are thrown down as a whitish
precipitate.

The following reagents cause a separation of the stroma from the haemo-
globin : —

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

(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).

(c.) Other Chemical Reagents. — 7. Water. 8. Conduction of vapour of
chloroform (Bottcher); ether (v. Wittich); amyls, small quantities of alcohol
(Rollett); thymol (Marchand); nitrobenzol, ethylic ether, aceton, petroleum
ether, etc. (L. Lewin). 9. Antimonuretted hydrogen, arseuiuretted hydrogen ;
carbon disulphide (Hiiuefeld, Hermann); boracic acid (2 per cent.), added to amphi-
bian blood, causes the red mass (which also encloses the nucleus when such is pre-
sent), the so-called zoold, to separate from the axoid. The zooid may shrink from
the periphery of the corpuscle, or it may even 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 adds dissolve the corpuscles; more
dilute solutions cause precipitates in the haemoglobin. This is easily seen with
carbolic 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
margin of a cover-glass, shows the process of solution going on under the micro-

FORM AND SIZE OF THE BLOOD-CORPUSCLES.

11

scope. At first the corpuscles become globular, and so appear smaller, but after-
wards they burst like soap-bubbles.

[Tannic Acid. — A freshly prepared solution of tannic acid has a remarkable
effect on the coloured blood-corpuscles of man and animals — causing a separa-
tion of the haemoglobin and the stroma. The usual effect is to produce one or
more granular buds of haemoglobin on the side of the corpuscles ; more rarely
the haemoglobin collects around the nucleus, if such be present (W. Roberts).]

[Ammonium or Potassium Sulpho-Cyanide removes the haemoglobin, and
reveals areticular structure — infra-nuclear plexus of fibrils (Stirling and Rannie).]

The quantity of gases contained in the blood-corpuscles exercises
an important influence on their solubility. The corpuscles of venous
blood, which contains much C02, are more easily dissolved than
those of arterial blood; while between both stands blood containing
CO (Laudois, Litterski). When the gases are completely removed
from the blood, it becomes lake-coloured.

6. Form and Size of the Blood- Corpuscles of
Different Animals.

All mammals (with the exception of the camel, llama, alpaca, and
their allies), and the cyclostomata amongst fishes — e.g., Petromyzon,
possess circular 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 (n - O'OOl Millimetre)

Of the Disc-shaped
Corpuscles.

Of the Elliptical Corpuscles.

Short Diameter.

Long Diameter.

Elephant, . 0'0094 Mm.
Man, . .0-0077,
Dog, . . 0-0073 ,
Rabbit, . 0'0069 ,
Cat, . . . 0-0065 ,
Sheep, . . 0-0050 ,
Goat, . . 0-0041 ,
Musk-deer, 0-0025 ,

Llama, 0 '0040 Mm.
Dove, 0-0065 ,,
Frog, 0-0157 „
Triton, 0'0195 „
Proteus, 0-035 ,,

The corpuscles of An
third larger than those of

0-0080 Mm.
0-0147 „
0-0223 ,,
0-0293 „
0-058 ,,

.pliiuma are nearly one-
Proteus (Riddel).

Amongst vertebrates, amphioxus has colourless blood — invertebrates 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 haemoglobin,
while the blood-corpuscles themselves are colourless.

[Elaborate measurements of the blood-corpuscles have been made in

12 ORIGIN OF THE RED BLOOD-CORPUSCLES.

this country by Gulliver, but the relative size may be best appreciated
by comparing the corpuscles from various vertebrates.]

Many invertebrates possess red, violet, brown, or green opalescent blood with
colourless corpuscles (amoeboid cells). In cephalopods, and some crabs, the blood
is blue, owing to the presence of a colouring-matter (Hcemo-cyanln) which, con-
tains copper, and combines with O (Bert, Kabuteau & Papillon, Fre"dericq, and
Krukeuberg). The large blood-corpuscles of many amphibia, e.g., amphiuma, are
visible to the naked eye. The blood-corpuscles of the frog contain, in addition to
a nucleus, a micleolus (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, alcohol; 2, water; Ranvier's "a!cool au tiers").'}
It is evident that the larger the blood-corpuscles are, the smaller must be the number
and total superficies of corpuscles in a given volume of blood. In birds, how-
ever, the number is relatively larger than in other classes of vertebrates, notwith-
standing the larger size of their corpuscles ; this, doubtless, has a relation to the
very energetic metabolism that takes place in birds (Malassez).

Amongst mammals, caruivora have more blood-corpuscles than herbivora.
Welcker has ascertained that goat's blood contains 9,720,000 corpuscles per cubic
millimetre; the llama's, 13,000,000; the bullfinch's, 3,600,000; the lizard's,
1,420,000; the frog's, 404,000; the proteus', 36,000. In liybernatinrj animals,
Vierordt found that the number of corpuscles diminished from 7,000,000 to
2,000,000 per cubic millimetre during hybernation.

7. Origin of the Red Blood-Corpuscles.

(A.) Origin of the Nucleated Red Corpuscles 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 or embyro, where they form the
" Hood-islands " of Pander. The mother-cells form an irregular net-
work 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 protoplasm, which represent the blood-corpuscles,
acquire a reddish hue, while the surrounding 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 may also
proliferate, and give rise to new corpuscles, which are washed away to
form blood-corpuscles.] At first the corpuscles are devoid of pigment,
nucleated, globular, larger and more irregular than the permanent
corpuscles, and they also exhibit amoeboid movements. They become

ORIGIN OF THE RED BLOOD-CORPUSCLES. 13

coloured, retain their nucleus, and are capable of undergoing multipli-
cation by division ; and, in fact, Remak observed all the stages of the
process of division. The process of division is best seen from the 3rd
— 5th day of incubation. Increase by division also takes place in the
larvre of the salamander, triton, and toad (Flemming, Peremeschko).

After the liver is developed, blood-corpuscles seem to be formed in it
(E. H. Weber, Kolliker). Protoplasmic, nucleated, colourless cells are
carried by the vena porta from the spleen into the liver, where they
take up pigment. Neumann found in the liver of the embryo proto-
plasmic cells containing red blood-corpuscles. 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 dis-
appears. 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 fetal life nucleated blood-
corpuscles are very rarely found. Of course, in animals with nucleated
blood-corpuscles, the nucleus of the embryonic blood-corpuscles remains.

(B.) Development of Blood-Vessels, Formation of Blood- Vessels and
Blood-Corpuscles during Post-embryonic Life. — Kolliker assumed
that, in the tail of the tadpole, capillaries are formed by the anasto-
moses 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. Von Golubew, on the other hand, opposes this view.
He assumes 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 ; their protoplasm
and contents disappearing, they become hollow and a branched
system of capillaries is formed in the tissues. Eanvier, be it remarked,
noticed the same mode of growth in the omentum of newly-born
kittens.

The latter observer has recently studied the development of blood-
vessels and blood-corpuscles in the omentum of young rabbits. These
animals, when a week old, have, in their omentum, little white or
milk spots (" taches laiteiises," Ranvier), in which lie " vaso-formative "
cells, i.e., highly refractive cells of variable shape, with long cylindrical
protoplasmic processes (Fig. 5). In its refractive power the protoplasm

14

ORIGIN OF THE RED BLOOD-CORPUSCLES.

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 sur-
rounded with proto-
plasm. These vaso-
formative cells give off
points
(a, a),

Fig. 5.

protoplasmic
and processes
some of which end
free, while others form

a network. Here and
Formation of red blood-corpuscles within "vaso-

formative cells," from the omentum of a rabbit there elongated COn-
seven days old. r, r, the formed corpuscles. K, K, nective tissue-corpus-
nucleiof the vaso-formative cell, a, a, processes cles lie Oil the branches,
which ultimately unite to form capillaries. &nd ultimately form

the adventitia of the blood-vessel.

The vaso-formative cells have many forms : they may be elongated
cylinders ending in points, or more round and oval, resembling
lymph cells, or they may be modified connective tissue-corpuscles, as
observed by Schafer in the subcutaneous tissue of young rats. These
cells are always the scat 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
form connections with the circulatory system by means of their pro-
cesses. It is probable that 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 1

[The observations of Schafer also prove the infra-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.]

Similar observations have been made by Neumann in the embryonic liver ; by
Wissotzky in the rabbit's amnion ; by Klein in the embryo chick ; and by Leboucq
and Hayem in various animals ; all of which go to show that at a certain early

ORIGIN OF THE RED BLOOD-CORPUSCLES. 15

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.

(C.) Later Formation of Red Blood-Corpuscles. — There is much
diversity of opinion as to how coloured blood-corpuscles are formed in
mammals at a later period. [They have been described as derived from
colourless corpuscles, one set of observers (including Kolliker) main-
taining that the nucleus of these corpuscles disappears, while the
peri-nuclear portion remains, becomes flattened and coloured, and
assumes the characters of the mammalian blood-corpuscles. On the
other hand, other observers (including Wharton Jones, Gulliver, Busk,
Huxley, and Balfour) are of opinion that the nucleus becomes pigmented,
and forms the future blood-corpuscle. It is still doubtful, however,
whether coloured corpuscles are developed in either of these ways.]
Neumann and Bizzozero described peculiar corpuscles occurring in the
red marrow of bone, which they maintain become developed into
coloured blood-corpuscles, undergoing a series of changes, and forming
a series of intermediate forms, which may be detected in the red
marrow. Bizzozero holds that it is the nucleus of the marrow-cell
which is coloured, while Neumann thinks it is the perinuclear part
which becomes coloured, and forms the blood-corpuscle. Schafer's
observations on the red marrow of the guinea-pig rather tend to con-
firm Neumann's view.

These transition cells are said by Erb to be more numerous after
severe haemorrhage, the number of them occurring in the blood
corresponding with the energy of the formative process. In dogs
and guinea-pigs which he had rendered an?emic, Bizzozero found in the
marrow and spleen nucleated red blood-corpuscles, which increased by
division.

According to Neumann, the bone-matron11 of adults contains all transi-
tion forms, from nucleated coloured corpuscles to true red blood-
corpuscles. After copious haemorrhage, these transition forms appear
in numbers in the blood-stream.

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 through-
out all the bones of the extremities (Neumann).

Rindfleisch also regards the connective substance of the red marrow and the
spleen as the mother-tissue of the red. blood-corpuscles, the connective substance
or the hfematogenous connective tissue either temporarily or permanently forming
red blood-corpuscles. Once the red corpuscles are formed, they easily enter the
blood-stream, as the capillaries and veins of the red marrow have either no walls

16 DECAY OF THE RED BLOOD-CORPUSCLES.

(Hoyer, Kollmann), or exceedingly thin perforated walls. Similar conditions
obtain, in the spleen.

Bizzozero and Torre found that after severe haemorrhage in birds, the marroio of
the bones contained globular, granular, nucleated cells, whose protoplasm was
coloured with haemoglobin, while between these and the oval biconvex nucleated
corpuscles of the bird, there were numerous transition stages. The spleen of the
bird seems to be of much less importance in the formation of blood-corpuscles
(Korn). All these observations prove that the red marrow of the bones is a great
manufactory for coloured blood-corpuscles.

v. R-eckliughausen observed the direct transformation of these intermediate
forms into blood-corpuscles in frog's blood, which was kept for several days in a
moist chamber. A. Schmidt and Semmer found large lymph cells in the blood,
filled with granules of ha?mogoblin, and they regard these as intermediate forms
between colourless and coloured corpuscles.

[Malassez, from an investigation of the red marrow of young kids,
finds that the cells of the red marrow and certain cells in the spleen
form rounded coloured projections or buds on their surface. These
get detached and form young blood-corpuscles, which soon become
disc-shaped; while the mother-cell itself continues to produce other
coloured corpuscles. Thus gemmation of the splenic and medullary cells
constitutes one great process in the manufacture of blood-corpuscles.
Hence it is apparent why diseases of bone in children lead to ansemia,
and soon bring about a cachectic condition.]

8. Decay of the Red Blood-Corpuscles.

The blood-corpuscles must positively 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
haemoglobin, and the blood of the hepatic vein contains fewer red
corpuscles than the blood of the portal vein.

The splenic pulp contains cells which seem to indicate that coloured
corpuscles are broken up within it. These are the so-called "blood-
corpuscle-containing cells." 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 white blood-corpuscles, and by the cells
of the spleen and the bone-marrow, and are stored up chiefly in the
spleen and 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.

THE COLOURLESS BLOOD-CORPUSCLES. 17

As the corpuscles grow older and become more rigid, they, as it were, are caught
by the amoeboid 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 pathological conditions, ferruginous substances
derived from the red blood-corpuscles are found in the spleen, in the marrow of
bone, and in the capillaries of the liver : — (1.) When the disintegration of blood-
corpuscles is increased, as in ana?mia (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, and in the tissue elements of other organs
(Quincke). When the amount of blood is greatly increased (in dogs), 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, the liver
cells, and the epithelium of the cortex of the kidney (Quincke). The iron reaction
in the two last situations occurs after the introduction of hemoglobin, or of salts
of iron into the blood (Glaeveck and v. Stark).

When we reflect how rapidly (relatively) large quantities of blood
are replaced after haemorrhage and after menstruation, it is evident
that there must be a brisk manufactory 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.

9. The Colourless Corpuscles (Leucocytes).

Blood, like many other tissues, contains a number of cells or cor-
puscles which reach it from without; the corpuscles vary somewhat
in form, and are called colourless or ivhitfi blood-corpuscles, or " leucocytes "
(Hewson, 1770). Similar corpuscles are found in lymph, adenoid
tissue, marrow of bone, as wandering cells or leucocytes, in connective
tissue, ami also between glandular and epithelial cells. They all con-
sist of more or less spherical masses of protoplasm, which is sticky,
highly refractile, soft, capable of movement, and devoid of an envelope
(Fig. 6). When they are quite fresh (A) it is difficult 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 proto-
plasm, and reveals the presence of the nuclei, of which the number
varies from one to four, although generally three are found. The
subsequent addition of magenta solution- stains the nuclei deeply.
Water makes the contents more turbid, and causes the cor-
puscles to swell up. One or more nucleoli may be present in the
nucleus. The corpuscles contain proteids, but they also contain fats,
lecithin, and salts (p. 37). The size of the corpuscles varies from four

2

18

THE COLOURLESS BLOOD-CORPUSCLES.

to thirteen //, and as a rule they are about

Fig. 6.

of an inch in diameter,
and in the smallest
the layer of the pro-
toplasm is extremely
thin. They all have
the property of ex-
hibiting amoeboid
movements which are
very apparent in the
larger corpuscles.

These movements AV ere
discovered by Wharton
Jones in the skate, and
by Davine in the cor-
puscles of man. Max
Schultze describes
three different forms
in human blood : —

(1.) The smallest,

White blood-corpuscles— A, Human, without the addi- •, f -, ,-,

„ , , , ,. . ,. round lorms, less man
tion of any reagent. 13, alter the addition ot i • i.

water, nuclei visible. C, after the action of acetic tne rec<- corpuscles, AVlth

acid. D, Frog's corpuscles showing changes of one to two nuclei, and

shape due to amceboid movement. E, Fibrils of a very small amount of
fibrin from coagulated blood. F, Fjlementary

granules. protoplasm ;

(2.) Round forms,
the same size as the coloured blood-corpuscles ;

(3.) The large amoeboid corpuscles, \vith much protoplasm and
distinctly evident movements.

[When a drop of human blood is examined under the microscope,
more especially after the coloured blood-corpuscles 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 corpuscles readily glide OArer 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. Cut off the tip
of the tail and express a drop of blood on to a slide, cover it with a
thin glass, and examine.

Neglecting the coloured corpuscles, search for the colourless, of which
there are three varieties : —

(1.) The Large Finely Granular Corpuscle, Avhich is about -^ of an

THE COLOURLESS BLOOD-CORPUSCLES. 19

inch ill diameter, irregular in outline, with fine processes or pseudo-
podia, projecting from its surface. It rapidly changes 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 proto-
plasm.

(2.) The Coarsely Granular Variety is less common than the first-
mentioned, but when detected its characters are distinct. The proto-
plasm contains, besides a nucleus, a large number of highly refractive
granules, and the corpuscle usually exhibits active amoeboid 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 amoeboid move-
ments.

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, and the nature of
which is unknown. Very large colourless corpuscles exist in the
axolotl's blood (Ranvier).

Action of Reagents. — («.) Water, when added slowly, causes the
colourless corpuscles to become globular, and the granules within them
to exhibit Brownian movements (Richardson, Strieker), (b.) Pigment*,
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 (horse's blood indicating the presence of
glycogen best), (e.) Dilute Alcohol causes the formation of clear blebs
on the surface of the corpuscles, and brings the nuclei clearly into view
(Eanvier, 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.]

The colourless corpuscles divide, and in this way reproduce them-
selves (Klein).

The Number of Colourless Blood-Corpuscles is very much less than
that of the red corpuscles, and is subject to considerable variations.

It is certain that the colourless corpuscles are very much fewer in

20 AMfEBOID MOVEMENTS OF THE COLOURLESS CORPUSCLES.

shed blood than in blood still within the circulation. Immediately
after blood is shed, an enormous number of white corpuscles disappear
(SQQ Formation of Fibrin, p. 47).

Al. Schmidt estimates the number that remain at XV of the whole originally
present in the circulating blood. The proportion is greater in children than in
adults (Bouchut and Dubrisay).

The following table gives the number in shed blood : —

NUMBER OF WHITE CORPUSCLES IN PROPORTION TO EED CORPUSCLES —

In Normal Conditions.

In Different Places.

In Different Conditions.

1 : 335 (Welcker).
1 : 357 (Moleschott).

Splenic Vein, 1 : 60
Splenic Artery, 1 : 2,260
Hepatic Vein, 1 : 170
Portal Vein, 1 : 740
Generally more numerous
in Veins than Arteries.

Increased by
Digestion, Loss of Blood,
Prolonged Suppuration,
Parturition, Leukaemia,
Quinine, Bitters.

Diminished by
Hunger, Bad Nourishment,

The old method of Welcker for estimating the number of colourless corpuscles is
unsatisfactory. The blood was defibrinated, placed in a tall vessel, and allowed to
subside, when a layer of colourless corpuscles was obtained immediately under
a layer of serum. [It is better to use the liEemocytometer (p. 6) as improved by
Gowers.]

The Amoeboid Movements of the white corpuscles (so-called because
they resemble the movements of amoeba) consist in an alternate con-
traction and relaxation of the protoplasm surrounding the nucleus.
Processes are given off from the surface, and are retracted again (like
the pseudopodia of amoeba).

There is an internal current in the protoplasm, and the nucleus has
also been observed to change its form (Lavdowsky). 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 their interior
(fat, pigment, foreign bodies). The particles adhere to the sticky
external surface, are carried into the interior by the internal currents
(Preyer), and may eventually be excreted, just as particles are
taken up by amceba and the effete particles excreted. [Max Schultze
observed that coloured particles were readily taken up by these
corpuscles.]

On a hot stage (35°-40°C.) the colourless corpuscles of mammals
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.
In cold-blooded animals (frogs) colourless corpuscles may be seen to crawl

THE BLOOD-PLATES.

21

out of small coagula, in a moist chamber, and move about in the
serum. Induction shocks cause them to withdraw their processes and
become spherical, and, if the shocks be not too severe, their movements
recommence. Strong shocks kill them. 0 is necessary for their
movements. 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 (Waller, Cohnheim).

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

Relation to Anililie 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 of amphibia, and
in the marrow of their bones. Human leucocytes exhibit a neutrophile reaction,
except in the case of those corpuscles that have large ovoid nuclei : the former
are said to be the early stage of the latter. The eosinophile corpuscles are greatly
increased in leukosmia. The basophile granules occur chiefly in connective tissue-
corpuscles and in the neighbourhood of epithelium — they are always greatly
increased where chronic inflammation occurs.

III. Special attention has recently been directed to a third element

Fig. 7.

' ' Blood-plates " and their derivatives, partly after Bizzozero and Laker. 1, Red
blood-corpuscles on the flat. 2, From the side. 3, Unchanged blood-plates.
4, A lymph-corpuscle, surrounded with blood-plates. 5, Blood-plates
variously altered. G, A lymph-corpuscle with two heaps of fused blood-
plates and threads of fibrin. 7, Group of blood-plates fused or run together.
8, A similar small heap of partially dissolved blood-plates with fibrils of fibrin.

22 CHANGES OF THE RED AND WHITE BLOOD-CORPUSCLES.

of the blood, the " llood-platcs " of Bizzozero ; pale, colourless, biconcave
discs of variable size (mean, 3 /uC). According to Hayem (who called
these structures H^EMATOBLASTS, supposing that they were an early
stage in the development of the red blood-corpuscles), they are forty
times as numerous as the leucocytes. These blood-plates may be
recognised in circulating blood, as in the mesentery of the guinea-pig.
They are precipitated in enormous numbers upon threads suspended in
fresh-shed blood (Bizzozero). They may be obtained from blood
flowing directly from a blood-vessel, on mixing it with 1 per cent,
solution of osmic acid or Hayem's fluid (mercury bichloride 0'5, sodium
carbonate 5, sodium chlorate 1, distilled water 200 — Laker). They
undergo a rapid change in shed blood (Fig. 7, 5), disintegrating,
forming small particles, and ultimately dissolving. When several occur
together they rapidly unite, form small groups (7), and collect into
masses resembling " stroma-fibrin " (p. 48). These masses may be
associated in coagulated blood with fibrils of fibrin.

Bizzozero believes that they yield the material for the formation of fibrin during
coagulation of the blood. It is not yet determined whether they are derived from
partially disintegrated leucocytes, or whether they are independent formations.
Along with the leucocytes they are concerned in the formation of fibrin (Hlava).
These structures were known to earlier observers (Max Sehultze, Puess, and
others) ; but their significance has been variously interpreted.

IV. Blood, especially after a microscopic preparation has been made
for a short time, is seen to contain ELEMENTARY GRANULES (Fig. 6, F),
[•/.('., 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 disintegration of these corpuscles, or
of the blood-plates. Others, again, are completely 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 fibrils or threads of FIBRIN (Fig.
G, E and G, S, G) 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.

[These granules and fibres are stained by magenta and iodine, but
not by carmine or picro-carmine (Ranvier).]

10. Abnormal Changes of the Red and White
Blood-Corpuscles.

(1.) All haemorrhages diminish the number of red corpuscles (at most one-
half), and so does menstruation. The loss is partly covered by the absorption of

CHANGES OF THE RED AND WHITE BLOOD-CORPUSCLES. 23

fluid from the tissues. Menstruation shows us that a moderate loss of red cor-
puscles is replaced within twenty-eight days. When a large amount of blood is
lost, 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 red corpuscles
diminishes, while the white corpuscles increase in number (Kiegel & Boeckmann).

(2.) Diminished production of new red corpuscles causes a decrease, since
blood-corpuscles are continually being used up. In chlorotic girls 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 rneso-blast. In
them the heart and the blood-vessels are small, and the absolute mimber of cor-
puscles may be diminished one-half, although the relative number may be retained,
while in the corpuscles themselves the haemoglobin is diminished almost one-third
(Duncan, Quincke) ; but it rises again after the administration of iron (Hayem).
The administration of iron increases the amount of haemoglobin in the blood
(Scherpf). The amount of iron in the blood maybe diminished one-half. [The
action of iron in anaemic persons has been known since the time of Sydenham.
Hayem also finds that in certain forms of anaemia 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 M to 6 M). There is, moreover, a
persistent alteration in the volume, colouring power, and consistence of the cor-
puscles, consequently a want of accord between the number of the corpuscles and
their colouring power — i.e., the amount of haemoglobin which they contain, as was
pointed out by Johaiui Duncan.] In so-called pernicious anwmia, in which the
continued 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 (microcytes), often being oval or tailed,
irregularly shaped, aud sometimes very pale ; while numerous cells containing
blood-corpuscles are found in the marrow of bone (Riess). Curiously enough in
this disease, although the red blood-corpuscles are diminished in number, some
may be larger and contain more hemoglobin than do normal corpuscles (Laache).
The number of coloured corpuscles is also diminished in chronic poisoning by lead
or miasmata, and also by the poison of syphilis.

(3.) Abnormal forms of the red corpuscles have been observe! after severe
bums (Lesser) ; the corpuscles 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 (Wertheim). 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 haeinatin are derived from
the granules arising from the disintegration of the blood-corpuscles, and these
particles float in the blood (Melancemia). They are partly absorbed by the colour-
less corpuscles, but they are also deposited in the spleen, liver, brain, and bone-
marrow (Arnstein). Sometimes the red corpuscles are abnormally soft, and
readily yield to pressure.

The white corpuscles are enormously increased in number in Leukaemia
(J. H. Bennett and Virchow) ; sometimes even to the extent of the red corpuscles.
In some cases the blood looks as if it were mixed with milk. The colourless cor-
puscles seem to be formed chiefly in bone-marrow (Neumann), but also in the
spleen and lymphatic glands.

11. Chemical Constituents of the Red
Blood-Corpuscles.

(1.) The colouring-matter or haemoglobin (Hb) (Hsemato-globulin,
Heemato-crystaUin) is the cause of the red colour of blood ; it also occurs

24

PREPARATION OF H/EMOGLOBIN CRYSTALS.

in muscle, and in traces in the fluid part of blood, but in this last case
only as the result of the solution of some red corpuscles. Its per-
centage composition is :— C 53'85, H 7'32, N 16-17, Fe 0'42, S 0'39,
0 21 '84 (dog). Its rational formula is unknown, but Preyer gives
the empirical formula C600, H960, N154, Fe, S3, 0179. Although it is a
colloid substance it crystallises (Hunefeld 1840, Beichert) in all classes
of vertebrates, according to the rhombic system, and chiefly in rhombic
plates or prisms ; in the guinea-pig in rhombic tetrahedra (v. Lang) ;
in the squirrel, however, it yields hexagonal plates. The varying
forms, perhaps, correspond to slight differences in the chemical com-
position 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.

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 have been
observed.

Haemoglobin crystals are doubli/
refractive and pleo-chromatic ; they
are bluish-red with transmitted light,
scarlet-red by reflected light. They
contain from 3 to 9 per cent, water
of crystallisation, and are soluble in
water, but more so in dilute alkalies.
They are insoluble in alcohol, ether,
chloroform, and fats. The solutions
are dichroic ; red in reflected light,

and green in transmitted light,

In the act of crystallisation' the. haemoglobin
seems to undergo some internal change.
Before it crystallises it does not diffuse like
a true colloid, and it also rapidly decomposes
hydric peroxide. If it be redissolved after
i f, crystallisation it diffuses, although only to

• i < '^_ i > • • • 1 1 1 • i ^ > i L>ii i • j 1 1 , L). It (nil 1*1 i i

, iii f ,1 a small extent, but it no longer decomposes

human blood ; c, from the cat ; , , . , f . , , .,

-. ,. , , . . nvdric peroxide, and is decolourised by it.

d, from the guinea-pig; e, /, , 1,., ••,••, -.1.- v

, f ^ -i A body like an acid is deposited from ha?mo-

hamster; f, squirrel. . J . 1*1

globm at the positive pole of a battery.

Fig. 8.
Haemoglobin crystals

12, Preparation of Haemoglobin Crystals.

Method Of Rollett.— Place defibrinated blood in a platinum capsule, allow
the capsule and the blood to freeze by setting them in a freezing-mixture, and

ESTIMATION OF H.KMOGLOBlN. L>5

then gradually to thaw ; pom- the lake-coloured blood into a plate, until it
forms a stratum not more than 1| in. in. in thickness, and allow it to evaporate
slowly in a cool place, when crystals will separate.

Method of Hoppe-Seyler.— Mix defibrinated blood with ten 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 (0°) alcohol, and allow the mixture
to stand in the cold for several days. The numerous crystals can be collected in
a filter and pressed between folds of blotting-paper.

Method of Gscheidlen.— Crystals several centimetres in length were obtained
by taking defibrinated blood which had been exposed for twenty-four hours to the
air, aud keeping 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 microscopic 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 aud guinea-pig, is rapidly
followed by the formation of crystals of haemoglobin. Very lai'ge crystals may
be obtained from the stomach of the leech several days after it has sucked blood.]

13. Quantitative Estimation of HsemogloMn*

(a.) From the Amount Of Iron- — As dry (100CC.) haemoglobin contains 0'42
per cent, of iron, the amount of iron may be calculated from the amount of
haemoglobin. If m represents the percentage amount of metallic iron, then the
percentage of haemoglobin in blood is

100m
: 0-42

The procedure is the following: — Calcine a weighed quantity of blood, and exhaust
the ash with HC1 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 haemoglobin
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, h&matinometer, the sides
are exactly one centimetre apart. Instead of using a standard solution of oxyhw-
moglobiii, a solution of picro-carminate of ammonia may be used (Rajewsky,
Malassez. ) ]

(c.) By the Spectroscope-— Preyer found that a O'S per cent, watery solution
(1 c.m. thick), allowed the red, the yellow, and the first strip of green to be seen
(Fig. 11, 1). Take the blood to be investigated (about O'S c.m.), and dilute it with
water until it shows exactly the same optical effects in the spectroscope. If A- is
the percentage of Hb, which allows green to pass through (O'S per cent.), b, the
volume of blood investigated (about 0'5 c.m.), -w, the necessary amount of water
added to dilute it, then x — the percentage of Hb in the blood to be investi-
gated—

k (w + 1)
I,

26

THE H/EMOGLOBINOMETER.

[ (d.) The Hsemoglobinometer of Gowers is used for the clinical estimation of
luemoglobin.]

" The tint of the dilution of a given volume of blood with distilled water is
taken as the index of the amount of haemoglobin. The distilled water rapidly
dissolves out all the haemoglobin, 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
haemoglobin 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 picrooariuiue 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 m.m. of blood, in 2 cubic centi-
metres of water (1 in 100).

The second tube (C) is graduated, 100 degrees = two centimetres (100 times
twenty cubic millimetres).

The twenty cubic millimetres of blood are measured by a capillary pipette (B)
(similar to, but larger than that used for the haemacytoineter). 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 drop
(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, and the amount of water which has
been added (i.e., the degree of dilution) indicates the amount of haemoglobin.

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 pei'centage propor-
tion of the haemoglobin
contained in it, compared
to the normal.

For instance, the 20
cubic millimetres of
blood from a patient
with anaemia gave the
standard tint at 30
degrees of dilution.
Hence it contained only
30 per cent, of the normal
quantity of haemoglobin.
By ascertaining with the
haemacytometer the cor-
puscular richness of the
blood, we are able to
compare the two. A
fraction, of which the
numerator is the per-

r.

Fig. 9.

A, pipette bottle for distilled water; B, capillary pipette; centage of haemoglobin,
C, graduated tube ; D, tube with standard dilution ; antl tbe denominator
F, lancet for pricking the finger. the Percentage of cor-

puscles, gives at once

the average value per corpuscle. Thus the blood mentioned above containing 30
pei- cent, of haemoglobin, contained GO per cent, of corpuscles ; hence the average

USE OF THE SPECTROSCOPE. 27

value of each corpuscle was %% or £ of the normal. Variations in the amount of
haemoglobin may be recorded on the same chart as that employed for the corpuscles.

In using the instrument, the tint may be estimated by holding the tubes between
the eye and the window, or by placing a piece of white paper behind the tubes ;
the former is perhaps the best. Care must be taken that the tubes are always
held in the line of light, not below it. In the latter case some light is reflected
from the suspended corpuscles from which the haemoglobin has been dissolved.
If the value of the corpuscles is small, then a perceptibly paler tint is seen when
the tubes are held below the line of illumination. If all the light is transmitted
directly through the tubes, the corpuscles do not interfere with the tint.

In using the instrument it will be found that, during 6 or 8 degrees of dilution,
it is difficult to distinguish a difference between the tint of the tubes. It is there-
fore necessary to note the degree at which the colour of the dilution ceases to be
deeper than the standard, and also that at which it is distinctly paler. The degree
midway between these two will represent the haemoglobin percentage.

The instrument is only expected to yield approximate results, accurate within
2 or 3 per cent. It has, however, been found of much iitility in clinical observa-
tion."]

The amount of haemoglobin in man is 12 to 15 per cent., in the
woman 12 to 14 per cent., during pregnancy 9 to 12 per cent.
(Preyer). According to Leichtenstern, Hb is in greatest amount in
the blood of the newly-born infant, but after ten weeks the excess
disappears. Between six months and five years, it becomes least in
amount, reaches its second highest maximum between twenty-one
and forty-five, and then sinks again. From 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.

Pathological- — A decrease is observable during recovery from febrile condi-
tions, and also during phthisis, cancer, ulcer of the stomach, cardiac disease,
chronic diseases, chlorosis, leuktemia, pernicious antemia, and during the rapid
mercurial treatment of syphilitic persons.

14. Use of the Spectroscope.

As the spectroscope is frequently used in the investigation of blood and other
substances of the body, it will be convenient to give a short description of the
instrument here (Fig. 10). It 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 l< ns,
C (called a collunator) 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, r - r. — (3. ) An astronomical telescope is directed to the spectrum,
r - v, 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 Blood in urine).

[The micro-spectroscope, e.g., that known as the '• Sorby-Browuiug " micro-
spectroscope is very useful when small quantities of a solution are to be examined.]

ABSORPTION AND FLAME SPECTRA.

[Every spectroscope ought to give two spectra, so that the position of any absorp-
tion baud 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 the fluid to be examined are made from short pieces of barometer-tubes
cemented to a plate of glass.]

B

Fig. 10.

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

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"

Flame Spectra. — If mineral substances be burned on a platinum-
wire in a non-luminous flame (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,
potassium a red and a violet line. These substances are found in
burning the ashes of almost all organs.

If sunlight be allowed to fall upon the slit, the spectrum shows
a large number of lines (Fraunhofer's lines) which occupy definite posi-
tions in the coloured spectrum. These lines are indicated by the
letters A, B, C, D, etc., a, b, c, etc. (Fig. 11).

COMPOUNDS OF HAEMOGLOBIN.

29

15, Compounds of Haemoglobin with 0; Oxytomoglobin,

and Mettomoglobin.

(1.) Oxyhasmoglobin (00Hb) behaves as a weak acid, and occurs to
the extent of 8678 to 94'30 per cent, in dry red human corpuscles
(Jiidell). It is formed very readily whenever Hb comes into
contact with 0 or atmospheric air. 1 gramme Hb unites with
1-6 to 1'8 cubic centimetres of 0 at 0° and 760 mm. Hg pressure.
Oxyhaemoglobin is a very loose chemical compound, and is slightly less
soluble than Hb ; its spectrum shows in the yellow and the green, two
dark absorption-bands (Hoppe-Seyler) whose length and breadth in a
0'18 per cent, solution are given in Fig. 11 (2).

Yellow.

Green.

Blue.

Red. Orange.

Illl ILIUIU I II.LI ILLI Ullllililllll

5o bo 70 80 oo 100 tio

A a B C

o =

Eaiiiofrlobin

0,8 7,

O =

Hemoglobin
0-18 7,

Ca rbonic

Oxide
Hamoglobin.

Reduced
Hamoglobin.

Hamatin in

Alcohol, with

Sulphuric

Acid.

Hamatin in

an Alkaline

Solution.

Reduced
Hamatin.

Various spectra of haemoglobin and its compounds.

30 REDUCTION OF HAEMOGLOBIN.

[The two absorption-bands lie between the lines D and E, the band
nearer D being more sharply defined and narrower than the second
band, which is wider and less clearly marked-off, and lies nearer E.]

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

Reduction of Oxyhsemoglobin. — It gives up its 0 very readily, how-
ever, even when means which set free absorbed gases are used. It is
reduced by the removal of the gases by the air-pump, by the conduction
through its solution of other gases (CO & NO), and by heating to the
boiling point. In the circulating blood its 0 is very rapidly given up
to the tissues, so that in suffocated animals only reduced hcemoglobin
is found in the arteries. Some constituents of the serum and sugar
use up 0. By adding to a solution of oxyhsemoglobin reducing sub-
stances— e.g., ammonium sulphide, ammoniated tartarate of zinc oxide
solution, iron filings, or Stokes's fluid [tartaric acid, iron proto-sulphate,
and excess of ammonia] — the two absorption bands of the spectrum dis-
appear, and reduced hemoglobin (gas-free) (Fig. 11, 4), with one absorp-
tion band is formed (Stokes, 18G4). [The single band which is obtained
from reduced haemoglobin lies between D and E, and its most deeply
shaded portion is opposite the interval between the two bands of oxy-
hsemoglobin. Its edges are less sharply defined. The colour of the
blood changes from a bright red to a brownish tint. Hoppe-Seyler
applies the term Haemoglobin to the reduced substance to distinguish it
from oxyhwmoglobin.]

The two bands are reproduced by shaking the reduced haemoglobin
with air, whereby O0Hb is again formed. Solutions of oxyhajmoglobin
are readily distinguished by their scarlet colour from the purplish tint
of reduced hemoglobin.

If a string be tied round the base of two fingers so as to interrupt the circulation,
the spectroscopic examination shows that the oxyhffimoglobin rapidly passes into
reduced Hb (Vierordt). Cold delays this reduction (Filehne).

The spectroscopic examination of small blood-stains is often of the utmost
forensic importance. A minimal drop is sufficient. Dissolve in a few drops of
distilled water, and place in a thin glass tube in front of the slit of the spectroscope.

(2.) Methsemoglobin (Hoppe-Seyler) contains more 0 than oxy-
hsemoglobin (Fig. 11, 5). Chemically it is fairly stable, contains 0, and
crystallises (Hiifner and J. Ott). It is obtained by acting upon a
solution of reduced or oxyhtemoglobin with oxidising reagents ; best,
however, by adding crystals of potassic ferridcyanide. It shows four
absorption bands like an acid solution of heematin, that between C and
D being the only one sharply defined.

If a trace of ammonia be added to such a solution, it gives an alkaline solution
of methsemoglobin, which shows two bands like oxyhajmoglobin, of which the first

CARBONIC OXIDE-HEMOGLOBIN. 31

one ia the broader, and extends more into the red. If ammonium sulphide be
added to the methaemoglobin solution, reduced Hb is formed (Jiiderholm). Methae-
raoglobin is produced in old brown blood-stains, in the crusts of bloody wounds, in
blood cysts — farther by the addition of minute traces of acid to blood, or by
heating blood with a trace of alkali. Sorby and Jaderholm regard it as a per-
oxidised haemoglobin, but this view is opposed by Hoppe-Seyler. It may also
be prepared by acting upon blood with potassic chlorate and nitrate, or nitrate of
amyl, which gives to blood a chocolate-brown colour (Saarbach, Gamgee).

16. Carbonic Oxide-Haemoglobin.

(3.) CO-Hsemoglobin is a more stable chemical compound than the
foregoing, and is produced at once when carbonic oxide is brought into
contact with pure Hb or 02Hb (Cl. Bernard, 1857). It has an
intensely florid or cherry-red colour, and gives two absorption-bands,
very like those of 02Hb, but they are slightly closer together and lie
more towards the violet (Fig. 11, 3). Reducing substances (which act
upon Hb00) do not affect these bands, i.e., they cannot convert the CO
compound into reduced Hb. Another good test to distinguish it from
Hb02 is the soda test. If a 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 Hb02 solution, it gives a dark-brown, greenish, greasy
mass (Hoppe-Seyler). Oxidising substances [solutions of potassic
permanganate (O025 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 HbO., pale yellow. After this
treatment both solutions show the absorption-bands of methaemoglobin.
If ammonium sulphide be added, Hb02 and CO-Hb are re-formed.

On account of its stability CO-Hb resists external influences and even putre-
faction for a long time (Hoppe-Seyler), 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 18 months previously by CO, and after
great putrefaction of the body had taken place.

If CO is breathed by man, or if air containing it be inspired, it
gradually displaces the 0, volume for volume, out of the Hb (L. Meyer),
and death soon occurs; 1,000 ccm inspired at once will kill a man.
A very small quantity in the air (^^"T^V o) suffices, in a relatively
short time, to form a large quantity of CO-Hb (Grehant). As
continued contact with other gases (such as the passing of 0 through
it for a very long time) gradually separates the CO from the Hb
(with the formation of 02Hb — Donders), it happens that, in very partial
poisoning with CO, the blood gradually gets rid of the latter. A
high degree of poisoning necessitates the transfusion of blood (p. 61).

[Gamgee and Zuntz also find that although the CO-Hb compound is very stable,
yet it may be reduced by passing air or neutral gases through, it for a lengthened
period ; it is also reduced when blood is boiled in the mercurial pump. ]

32 POISONING BY CARBONIC OXIDE.

17. Phenomena of Poisoning by Carbonic Oxide. Other
Compounds of Haemoglobin.

Carbonic oxide is formed during incomplete combustion of coal or coke, and
passes into the air of the room, provided there is not a free outlet for the
products of combustion. It occurs to the extent of 12-28 per cent, in ordinary
gas, which largely owes its poisonous properties to the presence of CO. If the 0
be gradually displaced from the blood by the respiration of air containing CO, life
can only be maintained as long as sufficient 0 can be obtained from the blood to
support the oxidations necessary for life. Death occurs befoi-e all the 0 is dis-
placed from the blood. CO has no effect when directly applied to muscle and
nerve. When it is inhaled, there is first 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 respiration,
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 110 dyspnoea, but sometimes 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. lu poisoning with the vapour of
charcoal, where CO and C02 both occur, there is a varying degree of coma ; pro-
nounced dyspnrea, muscular spasms which may last several minutes, gradual
paralysis and asphyxia, moniliform contractions and subsequent dilatation of the
blood-vessels, with congestion of various organs, occur, accompanied by a fall of the
blood-pressure (Klebs), 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 are catarrh of the respiratory organs and degeneration 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. The poisonous action of the vapours of combustion was known to
Aristotle.

(4.) Nitric Oxide -Haemoglobin (NO-Hb) — is formed when NO is
brought into contact with Hb (L. Hermann).

As NO has a great affinity for 0, red fumes of nitrogen peroxide (NOo) being
formed whenever 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 OjHb. It has a bluish-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 not abolished by the
action of reducing agents.

The three compounds of Hb, with 0, CO, and NO, are crystalline;
like Hb, they are isomorphous, and their solutions are not dichroic. One

DECOMPOSITION OF HEMOGLOBIN. 33

gramme Hb unites with 1 '33-1 '35 e.c.rn. of each of the gases at 0°
and 1 metre pressure (Preyer, L. Hermann).

(5.) Cyanogen, CNH (Hoppe-Seyler), and acetylene, C2H2 (Bistrow and
Liebreich), form easily decomposable compounds with Hb. The former occurs in
poisoning with hydrocyanic acid, and has a spectrum identical with that of 02Hb,
and, like 02Hb, it is reduced by special agents. [The existence of these com-
pounds is, however, highly doubtful (Gamgee).]

(6.) If C03 be passed through a solution of oxyhaemoglobin for a con-
siderable time, reduced Hb is first formed ; but if the process be
prolonged the HI) is decomposed, a precipitate of globulin is thrown
down, and an absorption-band, similar to that obtained when Hb is
decomposed with acids, is observed (see p. 33).

18. Decomposition of Haemoglobin.

In solution and in the dry state Hb gradually becomes decomposed, whereby
the iron -con tain ing pigment hsematin, along with certain bye-products, formic,
lactic, and butyric acids are formed.

Hcemoglobin, however, may be decomposed at once into — (1) a body
containing iron ha>matin, and — (2) a colourless proteid closely related to
globulin ; — by (a.) the addition of all acids, even by C02 in the presence
of plenty of water ; (b.) strong alkalies ; (c.) all reagents which coagulate
albumin, and by heat at 70°-80°C. ; (f/.) by ozone.

(A.) H.EMATIN (C68, H70, N8, Fe,, 010) forms about 4 per cent, of haemo-
globin (dog). It is insoluble in water, alcohol, and ether; soluble in
dilute alkalies and acids, and in acidulated ether and alcohol.

When Hb containing 0 is decomposed, haamatin is formed at once ; while Hb
free from 0 on being decomposed forms first a purplish-red body, HVEMOCHROMOGEN
(C34, H3C, N4, Fe 05), which contains less 0, and is a precursor of hrematin. In
the presence of 0 it becomes oxidised, and passes into hsematin. In solution it
gives the spectrum shown in Fig. 11, 7 (Hoppe-Seyler). Dilute acids in an
alkaline solution deprive hasmochromogen of its iron, and HJEMATO-POKPHYRIN, a
substance which remains stable in contact with air, is produced. It may also be
produced from hsematin by the action of acids, so that ha?matin is an oxidation
stage of hremochromogen.

(a) Hrpmatin in acid solution. — 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, a mahogany-brown fluid is obtained, containing h(f matin in acul
solution, which gives a spectrum with four absorption-bands in the yellow and
green (Fig. 11, 5).

(/3) If this solution be treated with excess of ammonia, Juemalin in alkaline solu-
tion is formed, which gives one absorption-band on the boundary line between red
and yellow (Fig. 11, 6).

(y) Reducing agents cause this band to disappear, and produce in the yellow
two broad bands, which are due to the presence of "reduced hcematin " (Fig.
H, 7).

(<5) When haemoglobin is extravasated into the subcutaneous tissue, it becomes
BO altered that ultimately hydrated oxide of iron appears in its place.

3

34 H^EMIN AND BLOOD TESTS.

19. Hsemin and Blood Tests.

In 1853 Teichmann prepared crystals from blood, which Hoppe-
Seyler showed to be chloride of hcematin or hydrochlorate of hsematin.
The presence of these crystals is nsed as a test for blood-stains or
blood in solution. These crystals of hremin (Fig. 12) are prepared by
adding a small crystal of common salt to dry blood on a glass slide,
and then an excess of glacial acetic acid ; the whole is gently heated
until bubbles of gas are given off. On allowing the preparation to
cool, the characteristic hremin crystals are obtained (Hrematin, + 2HC1).

Characters. — When well-formed, the crystals are small microscopic
rhombic plates, or rhombic 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 hremin are identical in all the different kinds
of blood that have been examined (Jahnke, Hogyes). They are doubli/
refractive and plco-cliromatic ; by transmitted light they are mahogany-
brown, and by reflected light bluish-black, glancing like steel. They
give a brown streak on porcelain.

(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. 13).

^ v V , v
~ ,* ^ *v V / *

_ \

Fig. 12. Fig. 13.

Hnemin Crystals of various forms. Hsemin Crystals prepared from

traces of blood.

(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

JLEMIN AND BLOOD TESTS. 35

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 .) (Struwe).

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

(4.) From very Dilute Solutions of Haemoglobin. — («.) Strmve's
Method — Add to the fluid, ammonia, tannic acid, and afterwards glacial
acetic acid, until it is acid; soon a black precipitate of tannate of
hrematin is thrown down. This is isolated, washed, dried, and treated
as in (1.), but instead of Nad a granule of ammonium chloride is added.

(b.) Guning and van Geuns recommend the addition of zinc acetate, •which gives
a reddish precipitate; this precipitate is to he treated as in (1.)

Hpemin crystals may sometimes be prepared from putrefying or
lake-coloured blood, but they are very small, and here 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 hsematiy forms a fluid, which in a thin layer is green ; in a
thick layer red (H. Rose).

Chemical Characters. — Hcemiii crystals have been prepared from all classes of
vertebrates and from the blood of the earth-worm.

They are insoluble in water, alcohol, ether, chloroform ; but HoSC^ dissolves
them, expelling the HC1, 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), pure hcematin is
obtained (Hoppe-Seyler) as 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 monochromatic and brown.

An alcoholic solution of ha?matin, when reduced by tin and hydro-
chloric acid, yields urdbilin (Hoppe-Seyler), (compare Bile).

20. Hsematoidin.

Virchow discovered this important derivative from haemoglobin. It
occurs in the body wherever blood stagnates outside the circulation, and
becomes decomposed — as when blood is extravasated into the tissues
— e.g., the brain — in solidified blood-plugs (thrombus) ; invariably in the
Graafian follicles. It contains no iron (C32, H36, N4, 06), and crystallises
in clinorhombic prisms (Fig. 14) of a
yellowish-brown colour. It is soluble in
warm alkalies, carbon disulphide, benzol, and
chloroform. Very probably it is identical with
one of the bile pigments — bili-rubin (Valen-
teiner). [When acted upon by impure nitric l[^
acid (Gmelin's reaction), it gives the same F- 14

play of colours as bile.] Hfematoidlii Crystals.

36 OTHER CONSTITUENTS OF RED CORPUSCLES.

In cases where a large amount of blood has undergone solution
within the blood-vessels (as by injecting foreign blood), hsematoidin
crystals have been found in the urine (v. Recklinghausen, Landois).

21. (B.) The Colourless Proteid of Haemoglobin.

It is closely related to globulin ; but, while the latter is precipitated
by all acids, even by CO.,, and re-dissolved on passing 0 through it,
the proteid of haemoglobin, on the other hand, is not dissolved after
precipitation on passing through it a stream of 0.

As crystals of haemoglobin can be decolourised under special circumstances, it
is probable that these owe their crystalline form to the proteid which they
contain. Landois placed crystals of haemoglobin along with alcohol in a dialyser,
putting ether acidulated with sulphuric acid outside, and thereby obtained
colourless crystals. [If frog's 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. II. Proteids of the Stroma.

Dry red human blood-corpuscles contain 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. Wittich). The
stroma tends to form masses which resemble fibrin (Landois).

L. Brunton found a body resembling mucin in the nuclei of red blood- corpuscles,
and Miescher detected nuclein.

23. The Other Constituents of Red Blood- Corpuscles.

III. LECITHIN (0-35-072 per cent.) in dry blood-corpuscles (Jiidell),
and also in brain, yelk, and seminal fluid.

It is regarded as a glycero-phosphate of neurin, in which, in the radical of
glycero-phosphoric acid, two atoms of H are replaced by two of the radical of
stearic acid. By gentle heat glycero-phosphoric acid is split up into glycerine and
phosphoric acid.

CHOLESTERIN (0*25 per cent.); — no FATS.

These substances are obtained by extracting stromata or blood itself 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 1,000— C. Schmidt).

V. SALTS (7-28 per 1,000, — C. Schmidt), chiefly compounds of

ANALYSIS OF BLOOD. 37

potash and phosphoric add; the phosphoric acid is derived only from
the burned lecithin ; while the greater part of the sulphuric acid in
the analysis is derived from the burning of the haemoglobin.

Analysis Of Blood.— 1:000 parts, by weight, of HORSE'S BLOOD contain : —

344'IS blood-corpuscles (containing about 128 per cent, of solids).
655'82 plasma (containing about 10 per cent, of solids).

1,000 parts, by weight, of MOIST BLOOD-CORPUSCLES contain: —

Solids, 367 '9 (pig); 400'1 (ox).
Water, 632 -1 „ 599 '9 „

The solids are: —

Pig. Ox.

Haemoglobin, . . . . 261' 280 '5

Albumin, 86 '1 107

Lecithin, Cholesterin, and other/ ,<,.„ „...

Organic Bodies, . . . \

Inorganic Salts, . . . . 8 "9 4'S

{POTASH, . . 5-543 0'747

Magnesia, . . O'lSS O'OIT

Chlorine, . . 1'504 1-635

PHOSPHORIC ACID, 2-067 0'703

Soda, ... 0 2-093 (Bunge).

24. Chemical Composition of the Colourless

Corpuscles.

Investigations have been made on pus cells, which closely resemble
colourless blood-corpuscles. They contain several proteids ; alkali albu-
ininate, a proteid which coagulates at 48°C., and another resembling
myosin, fibrino-plastin, and a coagulating ferment; nuclein in the
nuclei (Miescher); perhaps also glycogen (Salomon), lecithin, and
extractives.

100 parts, by weight, of dry PUS contain:—

Earthy Phosphates, . . 0'416
Sodic Phosphate, • . 0'606

Potash, . . . 0-201

Sodic Chloride, . . . 0'143

25. Blood-Plasma and its Relation to Serum.

The unaltered fluid in which the blood-corpuscles float is called plasma,
or liquor sangulnit. This fluid, however, after blood is withdrawn from the
vessels, rapidly undergoes a change, owing to the formation of a solid
fibrous substance, FIBRIN, which seems to be produced by the coming
together of three special substances, the so-called fibrin-factors. After this
occurs, the new fluid which remains no longer coagulates spontaneously
(it is plasma, minus the fibrin-factors), and is called scrum. Apart from

38 PREPARATION OF PLASMA.

the presence of the fibrin-factors, the chemical composition of plasma
and serum is the same.

[When blood coagulates, the following rearrangement of its elements takes
place : —

BLOOD.

Plasma. Corpuscles, \ re, :,

. j white.

A __

I I

feerum. Fibrin.

u-

I

Fibrin, Corpuscles, and some Serum (Blood Clot).]

The serum, however, still contains a portion of the fibrin-ferment,
and also some of the fibrino-plastin or fibrino-plastic substance.
Plasma is a clear, transparent, slightly thickish fluid, which, in most
animals (rabbit, 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: — Selecting the
blood of the horse (because it coagulates slowly, and its corpuscles sink
rapidly to the bottom), he receives it, as it flows from an artery, in a
tall narrow glass, placed in a freezing-mixture, and cooled to 0°. The
blood remains fluid, and, the coloured corpuscles subsiding in a few
hours, 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 of the horse 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 coagulates (owing to the formation of fibrin), and passes into
a trembling jelly. If, however, it be beaten with a glass-rod, the
fibrin is obtained as a white stringy mass, adhering to the rod. The
quantity of fibrin in a given volume of plasma is about 0'7 — 1 pel-
cent., although it varies much in different cases.

COAGULATION OF THE BLOOD. 39

(B.) With Admixture. — Blood flowing from an artery is caught in a
tall graduated measure containing -1-th of its volume of a concentrated
solution of sodic sulphate (Hewson) — or in a 25 per cent, solution of
maguesic sulphate (1 vol. to 4 vols. blood : Semmer) — or 1 vol. blood
with 2 vols. of a 4 per cent, solution of monophosphate of potash
(Masia). When the blood is mixed Avith 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. If the salts be
removed by dialysis, coagulation occurs; or it may be caused by the
addition of water (Joh. Miiller). 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 frog's blood Johannes
Miiller used a ^ per cent, solution of cane s,ugar, which permits the
corpuscles to be separated from the plasma by filtration. The plasma
mixed with the sugar coagulates in a short time.]

27. Fibrin— Coagulation of the Blood.

General Characters. — Fibrin is that substance which, becoming
solid in shed blood, in plasma and in lymph causes coagulation. In
these fluids, when left to themselves, fibrin is formed, consisting of
innumerable, excessively delicate, closely-packed, microscopic, doubly
refractive (Hermann) fibrils (Fig. 6, 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 (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 around the corpuscles, and a fairly solid, trembling,
jelly-like clot, which can be cut with a knife, is formed. During this
time the clot has expressed from its substance a fluid — the BLOOD-SERUM.
The clot takes the shape of the vessel in which the blood coagulates.
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 pliloyistica. Such blood contains more fibrin, and so coagulates
more slowly.

40 PHENOMENA OF COAGULATION.

The crusta is formed under other circumstances, but the cause of its formation
is not always clear — e.f/., with increased S.G. of the corpuscles, or diminished S.G.
of the plasma (as in hydrsemia 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 ; this, however, gradually
passes both as to size and colour into the normal dark-coloured clot. [Sometimes
the upper surface of the clot is concave or cupped. The older physicians used to
attribute great importance to this condition, and also to the occurrence of the
crusta phlogistica, or 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 " defilnnated Hood" [The
twigs and fibrin must be washed in a stream of water to remove
adhering corpuscles.]

Coagulation of Plasma. — Plasma shows phenomena exactly analogous,
save that there is no well-defined clot, owing to the absence of the
resisting corpuscles ; there is, however, always a soft, trembling jelly
formed, when plasma coagulates.

Properties of Fibrin. — Although the fibrin appears voluminous, it
only occurs to the extent of 0'2 per cent. (O'l to O3 per cent.) in the
blood. The amount varies considerably in two samples of the same
blood (Sig. Mayer). It is insoluble in water and ether; alcohol shrivels
it by extracting water; dilute hydrochloric acid (O'l per cent.) causes
it to swell up and become clear, and changes it into syntonin or acid-
albumin. When fresh, it has a grayish-yellow fibrous appearance, and
is elastic ; when dried, it is horny, transparent, brittle, and friable.

When fresh it dissolves in 6 to 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. If, however, to a solution of fibrin in
0'05 per cent, soda solution, there be added acids, or (the faintly alkaline) lactate,
formate, butyrate, acetate, or valerianate of ammonia or soda, coagulation occurs
(Deutschmanu). Hydric peroxide is rapidly decomposed by fibrin (The'nard).

According to H. Nasse, the first appearance of a coagulum occurs in man's
blood after 3 min. 45 sec., in woman's blood after 2 min. 20 sec. Age has no effect;
withdrawal of food accelerates coagulation (H. Vierordt).

28. General Phenomena of Coagulation.

I. Blood which is in direct contact with the living and unaltered
blood-vessels does not coagulate (Briicke, 1857). This important fact
was proved by Briicke, who filled the heart of a tortoise with blood which
had stood 1 5 minutes exposed to the air at 0°, and kept it in a moist
chamber. The blood was still fluid at the end of 5^ hours, while the

PHENOMENA OF COAGULATION. 41

heart itself still continued to beat. He observed that at 0° the blood
was uncoagulated in the contracting heart of a tortoise after eight days.
Blood inside a contracting frog's heart preserved under mercury does
not coagulate. If the wall of the vessel be altered by pathological pro-
cesses (e.g., if the intima becomes rough and uneven, or undergoes
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) (Virchow).

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. This influence of the wall of blood-vessels was, to some extent,
known to Thackrah (1819) and to Sir Astley Cooper.

II. Conditions which Hinder or Delay Coagulation. — (a.) The
addition of small quantities of alkalies and ammonia, or of con-
centrated 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 3^ vol. blood of the horse).

(&.) The precipitation of the fibrinoplastin by adding weak acids, or
by C02.

By the addition of acetic acid until the reaction is acid, the coagulation is com-
pletely arrested. A large amount of C02 delays it, and hence venous blood
coagulates more slowly than arterial. Hence, also, the blood of suffocated persona
remains fluid.

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

(d.) By cold at 0° coagulation may be delayed for one hour
(J. Davy.) 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 (Landois).

(e.) Blood of embryo-fowls does not coagulate before the 12th or 14th
day of incubation (Boll); that of the hepatic rein very slightly;
menstrual blood shows little tendency to coagulate when alkaline mucus
from the vagina is mixed with it. If it be rapidly discharged, it
coagulates in masses.

(/.) Blood rich in fibrin from inflamed parts coagulates slowly. In "bleeders "
(haemophilia), coagulation seems not to take place, owing to a want of the sub-
stances producing fibrin ; hence, in these cases, wounds of vessels are not plugged
with fibrin. Albertoni observed that if tryptic pancreas ferment (dissolved in
glycerine), be injected into the blood of an animal, blood does not coagulate.
Schmidt-Mulheim found that after the injection of pure peptone into the blood
(0'3 to 0'6 grammes per kilo.) of a dog, the blood lost its power of coagulating.
A substance is formed in the plasma, which prevents coagulation, but which is

42 PHENOMENA OF COAGULATION.

precipitated by C02. Lymph behaves similarly (Fano). After peptones are injected,
there is a great solution of leucocytes in the blood (v. Samson-Himmelstjerna).

III. Coagulation is Accelerated — (a.) By Contact with Foreign
Substances of all kinds ; hence, threads or needles introduced into
arteries are rapidly covered with fibrin. Even the introduction of
air-bubbles into the circulation accelerates it, and the pathologically
altered wall of a vessel acts like a foreign body. Blood shed from
an artery rapidly coagulates on the Avails of vessels, on the surfaces
exposed freely to air, and on the rods or twigs by which it is beat.
The passage through it of indifferent gases, such as N. and H., and
the addition of H20 have the same effect.

(b.) Heating from 39° to 55°C., rapidly facilitates coagulation
(Hewson).

(c.) Agitation of the blood, as shown by Hewson and Hunter.

IV. 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 a-half to one and a-half minute ; that of a pig, sheep,
rabbit, in a-half to one and a-half minute ; of a dog, one to three
minutes ; of a horse and ox, five to thirteen minutes ; of man, three
to four minutes ; solidification is completed in nine to eleven minutes,
but rather sooner in the case of women (Nasse) ]. The blood of
invertebrates, which is usually colourless, forms a soft whitish clot of
fibrin. Even in lymph and chyle, a small soft clot is formed.

V. When coagulation occurs, the aggregate condition of the fibrin-
factors is altered, so that heat must be set free (Valentin, 1884, Schiffer,
Lepine). The rise in the temperature may be ascertained with a very
delicate thermometer.

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. 2).

VII- Whether or not electricity is developed, is not positively proved. Hermann
supposes that the parts already coagulated are negative, while non-coagulated
parts are positive ; but this has not been clearly shown.

VIII. During coagulation there is a diminution of the 0 in the blood,
although a similar decrease also occurs in non-coagulated blood. Traces
of ammonia are also given oft', which Eichardson 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 follow-

CAUSES OF COAGULATION. 43

ing experiment of Lister : — He placed two ligatures on a vein con-
taining blood, moistening one-half of the outer surface of the vein
with ammonia, and leaving the other half intact. The blood coagu-
lated in the first half, and not in the other, owing to the properties of
the wall of the vein of the former being altered. Lister also proved
that blood will remain fluid for hours in a vein after it has been
freely exposed to the air, and even after it has been poured in a thin
stream from one vein to another.] Neither the decrease of 0 nor the
evolution of ammonia seems to have any causal connection with the
formation of fibrin.

29. Cause of the Coagulation of the Blood,

Alexander Schmidt stated that fibrin is formed by the coming-
together of two proteid substances which occur dissolved in the plasma
or liquor sanguinis, viz. : — (1.) Fibnnogen, i.e., the substance which yields
the chief mass of the fibrin, and (2.) Fibrinoplastic substance or fibrino-
plastin. In order to determine the coagulation a ferment seems to be
necessary, and this is supplied by (3.) the fibrin-ferment.

[The serous sacs of the body contain a fluid which in some respects closely
resembles lymph. The pericardium contains pericardia! fluid, which in some
animals coagulates spontaneously (e.g., in the rabbit, ox, horse, and sheep), if
the fluid be removed immediately after death. If this be not done till several
hours after death, the fluid does not coagulate spontaneously. The fluid of
the tunica vaginalis of the testis, again, sometimes accumulates 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,
to pleuritic fluid, or to hydrocele fluid, there be added clear blood-serum, then
coagulation takes place, i.e., two fluids— neither of which shows any tendency by
itself to coagulate — form a clot when they are mixed. He also found that if
"washed blood clot" (which consists of a mixture of fibrin and colourless cor-
puscles) be added to hydrocele fluid, coagulation occurred. Denis mixed unco-
agulated blood with a saturated solution of sodic sulphate, allowed the corpuscles
to subside, and decanted the clear fluid which was mixed with sodic chloride,
until a large amount of precipitate had been obtained. The precipitate, when
washed with a saturated solution of sodic chloride, he called plasmine. If plas-
mine be mixed with water, it coagiilates 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
and au insoluble proteid.]

[Researches Of A. Schmidt- — This observer rediscovered the chief facts
already known to Buchanan, viz., that some fluids which do not coagulate
spontaneously, clot when mixed with other fluids, which also show no tendency
to coagulate spontaneously, <:.fj., hydrocele fluid and blood-serum. He proceeded
to isolate from these fluids the bodies which are described as fibrinogen and
nbrinoplastin. The bodies so obtained were not pure, but Schmidt supposed that
the formation of fibrin was due to the interaction of these two proteids. The
reason why hydrocele fluid did not coagulate, he said, was that it contained
nbrinogeu aiid no fibrinoplaatin, while blood -serum contained the latter, but not

44 THE FIBRIN-FACTORS.

the former. Schmidt afterwards discovered that these two substances may be
present in a fluid, and yet that coagulation may not occur (e.g., occasionally 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 fibrin-ferment (Gamgee). ]

Properties of these Substances. — Fibrinogen and fibrinoplastin are

not distinguished from each other by well-marked chemical characters.
Still they differ as follows : —

(a.) Fibrinoplastin is more easily precipitated from its solutions than
ftbrinogen.

(I.) It is more readily redissolved when once it is precipitated.

(c.) It forms when precipitated a very light granular powder.

(d.) Fibrinogen adheres as a sticky deposit to the side of the vessel.
It coagulates at 56°C.

Both substances closely resemble globulin in their chemical composi-
tion (Kiihne called fibrinoplastin paraglobuliri), and in their reactions
they are not unlike myosin. Like all globulins, they require a trace of
common salt for their solution.

On account of their great similarity, both substances are not usually
prepared from blood-plasma. Fibrinogen is prepared from serous trans-
udations (pericardial, abdominal, or pleuritic fluid, or the fluid of
hydrocele), which contain no fibrinoplastin. Fibrinoplastin is most
readily prepared from serum, in which there is still plenty of fibrino-
plastin, but no fibrinogen.

Preparation of Fibrinoplastin. — (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 (b.) pass a stream of carbonic acid through
the diluted serum, which soon becomes turbid ; and after a time a
fine white powder, copious and granular, is precipitated (Schmidt,
18G2).

[(c.) The serum may be dialysed for a day ; at the end of this time the contents
of the dialyser have become turbid, and when a current of COo is passed through
them, a precipitate of fibrinoplastin is obtained. Schmidt's fibrinoplastin has
also been called SERUM-GLOBULIN (Hammarsten) or PARAGLOBULIN (Kiihue).]

Schmidt found that 100 c.c. of the serum of ox blood yielded 0'7 to O'S grins.;
horse serum, 0"3 to 0'56 grms. of dry fibrinoplastin. Fibrinoplastin occurs not
only in serum, but also in red blood-corpuscles, in the fluids of connective tissue,
and in the juices of the cornea.

[((/.) Method of Hammarsten. — All the fibrinoplastin in serum is
not precipitated either by adding acetic acid or by C02. 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 (Gamgee) ; it seems that in

THE FIBRIN-FACTORS. 45

the ox and horse serum-globulin is more abundant than serum-albumin,
while in the dog and rabbit the reverse obtains.]

Preparation of Fibrinogen. — This is best prepared from hydrocele
fluid, although it may also be obtained from the fluids of serous
cavities— e.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 C02, after the
paraglobulin is precipitated, (a.) Dilute hydrocele fluid with ten to
fifteen times its volume of water, and pass a stream of C02 through it ;
or (b.) carefully neutralise it by adding acetic acid, (c.) Add powdered
common salt to saturation to a serous transudation, when a sticky
glutinous (not very abundant) precipitate of fibrinogen is obtained.

[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 para-
globulin, which is not precipitated until the amount of salt exceeds
20 per cent. (Gamgee).]

Hammarsten found that it may be prepared from blood (of the
horse) by first precipitating all the serum-globulin or fibrinoplastin
with crystals of magnesium sulphate, and subsequent filtration, which
removes the corpuscles ; a clear salted plasma is thus obtained. If to
the filtrate a saturated solution of common salt be added, a turbid,
flaky, impure precipitate of fibrinogen is obtained. This may be dis-
solved in dilute common salt, and again precipitated by a saturated
solution of NaCl.

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 — e.g., caustic soda, and are precipitated from this solution by C02. 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.

Fibrinogen dissolved in a weak solution of common salt (1 to 5 per cent.) is
re-precipitated on adding water, so that it resembles fibrin. Its solution in
common salt coagulates at 52° to 55°C. (Hammarsten, Frede"ricq).

[Frederic^ finds that fibrinogen exists as such in the plasma, it coagulates at
56°C., and the plasma thereafter is uncoagulable (Gamgee).]

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

46 FORMATION OF FIBRIN.

water, and passes through the filter, while the coagulated albumin
remains behind (Schmidt).

In the preparation of fibrinoplastin, the ferment is carried down with it
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 SO°C.

[Gamgee'S Method.— Buchanan's "washed blood-clot" (p. 43) 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. ]

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

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).

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

According to Hammarsten, fibrin is formed when the ferment is
added to a solution of fibrinogen.

[Hattimarsten's Theory Of Coagulation.— Hamrnarsten's researches lead
him to believe that fibrinoplastiu 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 fibrin-ferment ; the latter, however, has not been
obtained in a pure 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 fibrinoplastin 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.]

30. Source of the Fibrin-Factors.

Al. Schmidt maintains that all the three substances out of which
fibrin is said to be formed, arise from the breaking 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

SOURCES OF THE FIBRIN-FACTORS. 47

retrogressive changes of the white corpuscles. Plasma contains
dissolved fibrinogen and serum-albumin. The circulating blood is
very rich in lymph or white cells, much richer, indeed, than was
formerly supposed (Schmidt, Landois). As soon as blood is shed from
an artery, enormous numbers of the colourless corpuscles are dissolved
(Mantegazza) — according to Alex. Schmidt 71'7 per cent, (horse).
First, the body of the cell disappears, and then the nucleus (Hlava).
The products of their dissolution are dissolved in the plasma, and one
of these products' is fibrinopltistin. At the same time the fibrin-ferment
is also produced, so that it would seem not to exist in the intact blood-
corpuscles. Fibrinoplastin and fibrin -ferment are also produced by
the " transition forms " of blood-corpuscles, i.e., those forms which are
intermediate between the red and the white corpuscles. They seem to
break up immediately after blood is shed. The blood-plates (p. 21),
are also probably sources of these substances.

In amphibians and birds, the red 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 also a constituent of the 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 union of the three
substances will ensue.

[It is worthy of remark to recall the conclusion arrived at by And.
Buchanan, viz., 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 horse's 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, Jakowicki and Birk, 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 is specially remarkable
that in septic fever the amount of ferment in blood may increase to such an extent
as to permit the occurrence of spontaneous coagulation (thrombosis), which may
even produce death (Arn. Kb'hler). In febrile cases generally, the amount of
ferment is somewhat more abundant (Edelberg and Birk). After the injection
of ichor into the blood an enormous number of colourless corpuscles are dissolved
(F. Hoffmann).

31. Relation of the Red Blood- Corpuscles to the

Formation of Fibrin.

That the red blood-corpuscles may participate in the production of
fibrin is proved by many experiments.

48 RED CORPUSCLES AND FIBRIN-FORMATION.

Hoppe-Seyler showed that the nucleated blood-corpuscles of birds,
when treated with water, give a copious precipitate which resembles
fibrin. Heynsius observed a similar result after the blood of fowls
had been acted upon by water and dilute solution of common salt, and
he also states that nearly 90 per cent, of the total fibrin may be
obtained from the washed blood-corpuscles of the horse, when the
corpuscles are gradually dissolved. Semmer discovered that he could
cause defibrinated frog's blood to coagulate by mixing it with 4 to 6 times
its volume of water. On adding 10 to 12 drops of a 0'2 per cent,
solution of soda to 1 c.c.m. of defibrinated frog's blood, Semmer and A.
Schmidt found that it became converted into a structureless glutinous
mass, in which neutralisation with acetic acid produced fibres of fibrin.
No fibrin was formed from serum. The same observers diluted 4 c.c.m.
of defibrinated frog's blood with 20 c.c.m. of water containing CO.,.
The haemoglobin was thereby dissolved in the water, while the colour-
less stromata fell to the bottom. When this deposit was mixed with a
solution of sodium hydrate, a similar glutinous mass was obtained,
which yielded fibrin on being neutralised with acetic acid. No such
result was obtained from haemoglobin.

In 1874, Landois observed under the microscope that the stromata
of the red blood- corpuscles of mammals passed into fibrin. If a drop
of defibrinated rabbit's blood be placed in serum of frog's blood, with-
out 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 new spherical
corpuscles are drawn out into threads. The corpuscles soon become
spherical, and those at the margin allow the haemoglobin to escape,
when the decolourisation progresses, from the margin inwards, until at
last there remains a mass 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 from 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-fibrin. Fibrin which is formed in the usual
way by the fibrin-factors he calls plasma-fibrin. The stroma-fibrin is
closely related chemically to stroma itself; and as yet the two kinds of
fibrin have not been sharply distinguished chemically. Substances which
rapidly dissolve red corpuscles cause extensive coagulation, e.g., injection
of bile or bile salts, or lake-coloured blood, into arteries (Naunyn and
Francken). After the injection of foreign blood the newly-injected
blood often breaks up in the blood-vessels of the recipient, while

COMPOSITION OF PLASMA AND SERUM, 49

the finer vessels are frequently found plugged with small thrombi
(see Transfusion, p. 61).

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, e.g., fluids secreted pathologically in serous
cavities ; for example, hydrocele fluid, which, as usually containing fibrinogen only,
does not coagulate spontaneously, coagulates on the addition of fibrinoplastin 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 the Plasma and

Serum.

I. Proteids occur to the amount of 8 to 1 0 per cent, in the plasma.
Only 0'2 per cent, of these go to form fibrin. When coagulation has
taken place, and after the separation of the fibrin, the plasma becomes
converted into serum. The S. G. of human serum is 1,027 to 1,029. It
contains several proteids. [According to Hammarsten, human serum
contains 9'2075 per cent, of solids, — of these, 3'103 = serum-globulin,
and 4'516 = serum-albumin, i.e., in the ratio of 1 : T511.]

(a.) Serum-Globulin (Th. Weyl) or Para-Globulin 2-4 p. c., was
formerly believed to occur in much smaller amount than it actually
does. Hammarsten found that if serum be diluted with two volumes
of water, and crystals of magnesium sulphate be added to saturation,
serum-globulin is precipitated, but not serum-albumin. In the serum
of the horse and ox serum-globulin is more abundant than serum-
albumin, while in the serum of the rabbit and dog the reverse is
the case. It is soluble in 10 per cent, solution of common salt, and
coagulates at 75°C.

[Serum-globulin was carefully described by Panum under the name of "Serum-
casein;" by Al. Schmidt, as " Fibrino-plastic substance;" and by Kiihne, as
"Para-globulin."]

As already mentioned, it may also be precipitated, in part, by diluting serum
with 10 to 15 vols. of water, and passing a stream of C02 through it (p. 44). If a
trace of acetic acid be added to serum after the separation of the serum-globulin,
Kiihne finds that a fine precipitate of what he calls soda-albuminate occurs. [It
is, however, highly doubtful if an alkali-albuminate does occur in the blood.
Hammarsten found that C02 does not precipitate all the serum-globulin, so that
it is improbable that Kiihne's soda-albuminate exists as a distinct substance
in serum.]

According to A. E. Burckhard, magnesium sulphate not only precipitates
serum-globulin, but also another proteid substance more closely resembling
albumin. During hunger the globulin increases and the albumin diminishes.

Serum-Albumin. — Its solutions begin to be turbid at 60°C.,
and coagulation occurs at 73°C., the fluid becoming slightly more

4

50 COMPOSITION OF PLASMA AND SERUM.

alkaline at the same time. The amount is about 3-4 p. c. (Fredmcq).
If sodium chloride be cautiously added to serum, the coagulating
temperature may be lowered to 50°C. It has a rotatory power of — 56°.
It is changed into syntonin or acid-albumin by the action of dilute
HC1, and by dilute alkalies into alkali-albuminate.

[Although serum-albumin is closely related to egg -albumin they differ :
(a.) as regards their action upon polarised light; (b. ) the precipitate produced by
adding HC1 or HN03 is readily soluble in 4 c.c.m. 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 (Stockvis).

Serum-albumiu has never been obtained free from salts, even when it is diatysed
for a very long time, as was maintained by Aronstein, whose results have not been
confirmed by Heynsius, Haas, Huizinga, Salkowski, and others.]

After all the para-globulin (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-albumin be filtered from the
fluid, and if the clear fluid be heated to over 60°C., FredeYicq found that it becomes
turbid from the precipitation of other proteids; the amount of these other bodies,
however, is small.

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). Rohrig showed that soluble soaps — i.e., alkaline
salts of the fatty acids — cannot exist in the blood. \Cholcsterin may
be considered along with the fats. It occurs in considerable amount
in nerve-tissues, and, like fats, is extracted by ether from the dry
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 (Hoppe-Seyler). Lecithin (and protagou) occur in
serum and also in the blood-corpuscles.]

III. Traces of Grape Sugar (O05 per cent.) occur normally in
blood and serum, and also a trace of glycogen.

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 (O'Ol to 0'085 per cent, in the

COMPOSITION OF PLASMA AND SERUM. 51

dog), hippurie acid, succinic acid, and uric acid (more abundant in gouty
conditions), hypoxanthin, all occur in very small amounts.

The plasma and serum contain a yellow pigment, or perhaps several
pigments. One of these is called cholepyrrhin (horse, calf), and is
identical with the bile pigment of the same name (Hammarsten).
[Rabbit's serum is colourless.] Thudichum regards the yellow pigment
as lutein ; Maly, as hydrobilirubin; and MacMunn as choletelin.

V. Sarcolactic Acid and Indican, also in small amount.

VI. Salts. — The amount of inorganic salts ('085 to '09 per cent.)
contained in the serum is slightly less than in the plasma, as a small
amount of lime and magnesic phosphate is removed by the fibrin
(Briicke). The most abundant salt is sodium chloride (0'5 per cent.),
and next to it sodium carbonate [which exists in the plasma, most
probably in the condition of sodium hydric carbonate (NaHC03).
There is a small amount of potassic chloride, and also sulphuric and
phosphoric acids, lime and magnesia. 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.]

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

Sodic Chloride. . 4'92 per 1000.

,, Sulphate, ..... 0'44 ' ,,

,, Carbonate, . . 0'21 ,,

,, Phosphate, . O'lo ,,

Calcic Phosphate, . ") A -„

TV r L/ l O . .

.Magnesic ,, . . . . )

VII. Water about 90 per cent.

33. The Gases of the Blood,

Absorption of Gases by Solid Bodies and by Fluids.

Absorption by Solid Bodies.— A considerable attraction exists between the
particles of solid porous bodies and gaseous substances, so that gases are attracted
and condensed •within the pores of solid bodies — i.e., the gases are absorbed.
Thus, one volume of boxwood charcoal (at 12°C. and ordinary barometric pressure)
absorbs 35 volumes C02 — 9'4 vol. 0 — 7 '5 vol. N — 1'75 vol. H. Heat is always
formed when gases are absorbed, and the amoiint 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 volume of gas. Whether the pressure
be great or small, the volume of the gas absorbed is equally great (W. Henry).
But according to Boyle and Mariotte's law (1679), 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

52 GASES OF THE BLOOD.

the same, but the quantify of gas (weight, density) is directly proportional to th?
pressure.. If the pressure — 0, the weight of the gas absorbed must also = 0.
As a necessary result of this, we see that (1.) fluid* can be freed of their absorbed
gases in a vacuum under an air-pump.

Coefficient Of absorption means the volume of a gas (at 0°C) which is absorbed
by a unit of volume of a liquid (at 760 mm. Hg) at a given temperature. The volume
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 from 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 COj in water diminishes with an
increasing temperature, while that for H in water remains unchanged between
0 and 20T.

Diffusion and Absorption of Gases.

Diffusion Of Gases. — Gases which do not enter into chemical combinations with
each other, mix with each other in quite a regular proportion. If, e.g., the necks
of two flasks be placed in communication by means of a glass or other tube, and if
the lower flask contain C02, and the upper one H, the gases mix quite indepen-
dently of their different specific gravities, both gases forming in each flask a perfectly
uniform mixture. This phenomenon is called the diffusion ofyases. If 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 rapidity through the pores, so that at the beginning of the experi-
ment a larger amount of gas is found 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 Bun sen, however, this is not quite correct.)

Different Gases forming 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 gas.

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 pressure
under which each gas would be, were it the only gas in the space. 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 m.m.
pressure, 1 volume of water absorbs 0 '02477 volume of air, consisting of 0'00862
volume 0, and 0 '01615 volume N. It contains, therefore, 34 per cent. 0, and
66 per cent. N. Therefore, water absorbs from the air a mixture of gases containing
a larger percentage of 0 than the air itself.

GASES OF THE BLOOD.

34. Extraction of the Blood Gases.

The extraction of the gases from the blood, and their collection for chemical
analysis, are carried out by means of the mercurial pump (C. Ludwig). Fig. 15
shows in a diagrammatic form the arrangement of Pnuger's gas-pump.

It consists of a RECEPTACLE FOR THE BLOOD, or "BLOOD-BULB" (A), a glass-
globe capable of containing 250 to 300 c.c.m., connected above and below with
tubes, each of which is provided with a stop-cock, « and b ; b is an ordinary stop-
cock, while a has through its long axis a perforation which opens at z, and is
so arranged that, according to the position of the handle, it leads up into the

Fig. 15.

Scheme of Pfkiger's gas-pump— A, blood-bulb ; a, stop-cock, with a longitudinal
perforation opening upwards ; a', the same opening downwards ; b and c,
stop-cocks ; B, froth-chamber ; d, e, f, stop-cocks ; G, drying-chambers,
containing sulphuric acid and pumice-stone ; D, tube, with manometer, y.

54: EXTRACTION OF THE BLOOD-GASES.

blood bulb (position x, a), or downwards through the lower tube (position
x', a'). This blood-bulb is first completely emptied of air (by means of a mercurial
air-pump), and then carefully weighed. One end (x') 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, x'. 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 pro-
vided with an ordinary stop-cock, c and d. The froth-chamber, as 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, provided below with a small glass-bulb, which is half filled with
sulphuric acid, while in its limbs are placed pieces of pumice-stone also moistened
with sulphuric acid. As the blood-gases pass through this apparatus (which may
be shut off by the stop-cocks, e and/) they are freed from their watery vapour by
the sulphuric acid, so that they pass quite dry through the stop-cock, /. The
short well -ground tube, D, is fixed to/ and to the former is attached the small
barometric tube 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 iv, 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 pulley with a rack and
pinion motion. If F be raised, E is filled ; if F be lowered, E is emptied. The
upper end of E divides into two tubes, g and A. of which (j is united to D. The
ascending tube, h- — gas-delivery tube — is very narrow, and is bent so that its
free end dips into a vessel containing mercury (u) — 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, I)
the chambers to be exhausted, and in the position, K, shuts off A, B, G, D, and
places the bulb, E, in communication with the gas-delivery tube, It, 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, i (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 i. Open the cocks, c and b, so that the blood-bulb, A, communi-
cates with the rest of the apparatus, and the blood-gases froth up in B, 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 0 undergoes a diminution if the blood be kept.
Of course, in making several analyses it is difficult to do this, and the best plan to
pursue in that case is to keep the receptacles containing the blood on ice.

Mayow (1670) observed that gases were given off from blood in vacua. Magnus
(1837) investigated the percentage composition of the blood-gases. The more
important recent investigations have been made by Lothar Meyer (1857), and by
the pupils of C. Ludwig and E. Pfliiger.

ESTIMATION OF THE BLOOD-GASES. 55

35. Quantitative Estimation of the Blood-Gases.

The gases obtained from blood consist of 0, C02 and N. Pfliiger
obtained (at 0°C. and 1 metre Hg pressure), 47'3 volumes per cent,
consisting of

O 16'9 per cent. - CO., 29 per cent. - N. 1'4 per cent.
As is shown in Fig. 15, the gases are obtained in an eudiometer,
i.e., in a narrow tube, J, 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 ??-).

(1.) Estimation Of the COs.— 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 it
moistened before it is introduced. The C02 unites with the potash to form
potassium carbonate. After it has been in for a considerable time (24 hours), it
is withdrawn iu a similar manner. The diminution in volume indicates the
amount of C02 absorbed.

(2.) Estimation Of the 0. — («•) Just as in estimating the COo. a ball of phos-
phorus on a platinum wire is introduced into the eudiometer (Bertholet); it
absorbs the 0 and forms phosphoric acid. Another plan is to employ a small
papier-mache ball saturated with pyrogalliQ acid in caustic potash, which rapidly
absorbs 0 (Liebig). After the ball is removed, the diminution in volume
indicates the quantity of 0.

(b.) The 0 is most easily and accurately estimated by exploding it in the
eudiometer (Volta and Bunsen). Introduce a sufficient quantity of H into
the eudiometer, and accurately ascertain its volume ; an electrical spark is
now passed between the wires, p and n, through the mixture of gases ; the 0 and H
unite to form water, which causes a diminution in the volume of the gases in the
eudiometer, of which ^ is due to the 0 used to form water (H20).

(c.) Estimation Of the N. — When the C02 and 0 are estimated by the above
method, the remainder is pure N.

36. The Blood Gases.

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 0, while, according to Hu'fner, it is saturated to the extent
of yi. 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.

The 0 in Blood occurs — (a.) simply absorbed in the plasma. This is
only a minimal amount, and does not exceed what distilled water
at the temperature of the body would take up at the partial pressure
of the 0 in the air of the lungs (Lothar Meyer). According to

56 THE BLOOD-GASES.

Fernet, serum takes up slightly more O than corresponds to the
pressure, and this is. perhaps, due to the trace of hemoglobin con-
tained in the plasma or the serum, and which is derived from the
solution of red corpuscles.

(b.) Almost the total 0 of the Hood is chemically united, and, therefore,
not subject to the law of absorption. It is loosely united to the
haemoglobin of the red corpuscles, with which it forms oxyhcemoglobin
(p. 29).

The absorption of this quantity of 0 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 0, when the atmospheric pressure is lowered
to 20 millimetres, Hg. (Worm Miiller) ; and, conversely, blood only takes up a
little more 0 when the pressure is increased to 6 atmospheres (Bert).

Physical Methods of obtaining 0 from Blood. — Notwithstanding
this chemical union between the Hb and 0, however, the total 0 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 torri-
cellian vacuum ; (b.) by boiling ; (c.) by the conduction of other gases
[H,N,CO or NO] through the blood, because the chemical union
of the oxyhsemoglobin is so loose that it is decomposed even by these
physical means.

Chemical Keagents. — Amongst chemical reagents the following re-
ducing substances — ammonium sulphide, sulphuretted hydrogen, alkaline
solutions of sub-salts, iron filings, &c., rob blood of its 0 (p. 30).

With regard to the taking up of 0, the total quantity of blood behaves
exactly like a solution of haemoglobin free from 0 (Preyer.) The
amount of iron in the blood (0'55 in 1,000 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
0 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 '3 6 grammes of iron in the blood can
fix chemically 1 grrn. 0; while, according to Hoppe-Seyler, the pro-
portion is 1 atom iron to 2 atoms 0.

When blood is kept long outside of the blood-vessels, the quantity of 0 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 within the
blood. By this decomposition in the blood (cadaveric phenomenon), reducing
substances are formed which consume the 0. All kinds of blood, however, do not
act with equal energy in consuming 0, e.g., venous blood from active muscles acts
most energetically, while that from the hepatic vein has very little effect. C02
appears in the blood in place of the 0, and the colour darkens. The amount of
C02 produced is sometimes greater than that of the O consumed.

THE BLOOD-GASES. 57

If blood (or a solution of oxyha?moglobin) be acted upon by adds (e.g., tartaric
acid) until it is strongly acid, O may be pumped out in considerably less amount,
while the formation of C02 is not increased. We must, therefore, assume that,
during the decomposition of the Hb caused by the acids (p. 33), a decomposition
product becomes more highly oxidised by the intense chemical union of the 0 at
the moment of its origin (Lothar Meyer, Zuntz, Strassburg). The same phe-
nomenon occurs when oxyhaMiioglobin is decomposed by boiling.

37. Is Ozone (08) 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 0 of the blood exists in the form of active O (08), or
ozone. Ozone, however, is contained neither in the blood itself
(Schonbein) nor in the blood-gases obtained from it. Nevertheless,
the red corpuscles (and Hb) have a distinct relation to ozone.

(1.) Tests for Ozone. — Hremoglobiu acts as a conveyer of ozone, i.e., it is able to
remove the active 0 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. (6.) Freshly-prepared tincture of guaiacum is also rendered blue
by ozone. If some tincture of guaiacum be added to turpentine there is no reaction,
but on adding a drop of blood a deep blue colour is immediately produced, i.e.,
blood takes the ozone from the turpentine and conveys it at once to the dissolved
guaiacum, which becomes blue (Schonbein, His). It is immaterial whether the
Hb contains 0 or not.

(2.) It has been asserted also that haemoglobin acts as an ozone-
producer, i.e., that it can convert the ordinary 0 of the air into ozone.
Hence the reason why red blood-corpuscles alone render guaiacum
blue. This reaction succeeds best when the guaiacum solution is
allowed to dry on blotting-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 experiment in which even red blood-
corpuscles containing carbonic oxide were found to cause the blue
colour (Kiiline and Scholz).

According to Pfliiger, however, these reactions only occur from
decomposition of the Hb, and as a result of this view the blood-
corpuscles cannot be regarded as producers of ozone.

Sulphuretted hydrogen is decomposed by blood (as by ozone itself) into sulphur
and water. Hydric peroxide is decomposed by blood into 0 and water [but this
reaction is prevented by the addition of a small amount of hydrocyanic acid
(Schonbein)]. Crystallised Hb does not do this, and H202 may be cautiously
injected into the blood-vessels of animals. This would show that unchanye.d Hb
does not produce ozone.

Various Forms Of Oxygen.— There are three forms of oxygen: (1.) The

58 CARBONIC ACID AND NITROGEN IN BLOOD.

ordinary oxygen (02) in the air. (2.) Active or nascent oxygen (0), which never
can occur iu 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 C02,
which ozone does not. It certainly plays an important part in the organism. (3.)
Ozone (Oz), which is formed by the decomposition of several molecules of ordinary
oxygen (02) into two atoms of 0, and the appropriation of each of these atoms by a
molecule of undecomposed oxygen. It is oxygen condensed to § of its volume.

38. Carbonic Acid and Nitrogen in Blood.

II. Carbonic Acid. — 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 ; e.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 amount of CO.,
in the lymph of asphyxia is less than that in the blood (Buehner,
Gaule).

The CO., in the entire mass 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 0 and heat.

(A.) The C02 in the Plasma. — The largest portion of the C02 belongs to
the- plasma (or serum) and it appears all to be in a state of chemical
combination. Serum takes up C00 quite independently of pressure,
hence it cannot be merely absorbed. A certain part of the C0.2 can be
removed from the serum (plasma) by the torricellian vacuum, while
another part is obtained only after the addition of an acid. [This is
called the "fixed" CO.,, while the former is known as the "loose"
CO,.]

The union of C02 in the serum may take place in the following
ways :—

(1.) C02 is united to the soda of the plasma in the form of " 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 role of an acid.)

(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
C02; Na2C03 + C02 + H20 = 2 NaHC03. This C02 may be pumped out,
as in the process the bicarbonate splits up again into the neutral
carbonate and CO.,.

CARBONIC ACID AND NITROGEN IN BLOOD. 59

Preyer has objected to this view on the ground that blood is alkaline in reaction,
whilst all solutions that contain C02 in a state of absorption, or loose chemical
combination, are always acid. Pflliger and Zuntz showed that blood, after being
completely saturated with C02, still remains alkaline.

As the bicarbonate only gives up its C02 very slowly in vacua, while blood gives
off its COo very energetically, perhaps the soda, united with an albuminous body,
combines with the CC>2 and forms a complex compound, from which the C02 is
rapidly given off in vacua.

(3.) A minimal portion of the C02 may be chemically united in the
plasma with neutral sodic phosphate (Fernet). One equivalent of this
salt can fix 1 equivalent of C02, so acid sodium phosphate and acid
sodium carbonate are formed, Na2HP04 + C02 + H20 = NaH2P04
+ NaH,C03 (Hermann). When the gases are removed the C02
escapes, and neutral sodic phosphate remains.

It is probable, however, that almost all 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
Sertoli).

(B.) The CO., in the Blood-Corpuscles. — The red corpuscles contain
CCX, in a 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
(Pfliiger, Zuntz). The red corpuscles may 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 C02, its power
of fixing the latter was increased, which is perhaps due to the forma-
tion of some substance (paraglobulin) more suited for fixing CO.,.
The colourless corpuscles also fix CO., after the manner of the serum-
constituents, and to the extent of to TV of the absorbing power of
serum (Setschenow).

III. Nitrogen exists in the blood to the extent of 14 to TG vol.
per cent., and it appears to be simply absorbed.

It is still doubtful whether a small part of the N exists chemically united in the
red corpuscles. Outside the body when blood is heated, and when there is a free
supply of 0 and warmth, it gives off very minute quantities of ammonia, which
are perhaps derived from the decomposition of some salt of ammonia as yet unknown
(Ktihne and Strauch).

39. 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 ; it also contains a rich supply of 0. Venous blood must

60 ARTERIAL AND VENOUS BLOOD.

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 retro-
gressive metabolism being more numerous, there is in venous blood a
larger amount of C00. It is evident also that the blood of certain
veins must have special characters, e.g., that of the portal and
hepatic veins.

The following are the most important points of difference between
arterial and venous blood :—

Arterial Blood contains —

more 0,
less C02,
more water,
more fibrin,
more extractives,

more sugar,

fewer blood-corpuscles,

less urea.

It is bright red and not

dichroic.

more salts. As a rule it is 1°C. warmer.

The bright red colour of arterial blood depends on the presence of
oxyhsemoglobin, whilst the dark colour of venous blood is due to its
smaller proportion of oxyhsemoglobin, and the quantity of reduced
luemoglobin which it contains. The dark change of colour is not to
be attributed to the larger quantity of C0.7 in venous blood (Marchand);
for if equal qualities of 0 be added to two portions of blood, and if
CO., be added to one of them, the colour is not changed (Pfliiger).

40. Quantity of Blood.

In the adult the quantity of blood is equal to jV Pai't °f the body-
weight (Bischoff), in newly-born children -^ (Welcker).

According to Schiicking, the amount of blood in a newly-born child depends to
some extent upon the time at which the umbilical cord is ligatured. The amount
= T± of the body-weight when the cord is tied at once, while if it is tied some-
what later it may be J. Immediate ligature of the cord may, therefore, deprive
a newly-born child of 100 grammes 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).

Various methods are adopted to ascertain the amount of blood, but
perhaps that of Welcker is the best.

The methods of Valentin (1838), and Ed. Weber (1850), are not now used, as
the results obtained are not sufficiently accurate.

Method 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, and in which small pebbles (or Hg) have been
placed in order to detibrinate the blood by shaking. Take a part of this deiibrin-
ated blood, and make it cherry-red in colour by passing through it a stream of CO

NORMAL QUANTITY OF BLOOD. 61

(because ordinary blood varies in colour according to the amount of 0 contained in
it — Gscheidlen, 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 until 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
part of the mixture is saturated with CO. A sample of this dilute blood is placed
in a vessel with parallel sides (1 c.m. thick), opposite the light (the so-called
hsematinometer), 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 aloue, we obtain the
amount of Hb present in them, which is not taken into calculation— Kuhne).

Quantity of Blood in Various Animals. — The quantity of blood in
the mouse = TV to TV; guinea-pig 1*-..- (^T to -oV) ', rabbit = ^
( l_ to ^V) ; dog = T'^ (tV to -L-) ; cat = ST.V ; birds = -^ to -V ;

\ 1 5 ;:-/" O 13X11 1 8 / 3 2103 10 13'

frog =r TV to ^j ; fishes = yj to JL of the body-weight (without the
contents of the stomach and intestines).

The specific gravity of the 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 haemorr-
hage the loss is at first replaced by a watery fluid, while the blood-
corpuscles are gradually regenerated (p. 63).

The estimation of the quantify 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, £ ; the
liver, £ : and other organs, ^ (Ranke).

41. Variations from the Normal Condition of

the Blood.

(A.) Increase of the Blood, or of its Individual Constituents.— (l.) An

increase in the entire mass of the blood, uniformly in all organs, constitutes
polyamia (or plethora), and in over-nourished individuals it may approach a patho-
logical 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, accompanied by congestion of the brain,
giving rise to vertigo, and congestion of the lungs, as shown by breathlessness.
After major amputations with little loss of blood a relative increase of blood has
been found (?) (plethora apocoptica).

Transfusion. — Poly^mia may be produced artificially by the injection of blood
of the same species. If the normal quantity of blood be increased 83 per cent.

62 TRANSFUSION OF BLOOD.

no abnormal condition occurs, because the blood-pressure is not permanently
raised. The excess of blood is accommodated in the greatly distended capillaries,
which may be stretched beyond their normal elasticity (Worm Miiller). 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 to two days the serum is used up, the
water is excreted chiefly by the urine, and the albumin is partly changed into
urea (Landois). 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 partly
(but not constantly) as bile pigments. Even after a month an increase of
coloured blood-corpuscles has been observed (Tschirjew). That the blood-cor-
puscles are broken up sloiuly in the economy is proved by the fact that the amount
of urea is much larger when the same quantity of blood is swallowed by the
animal, than when an equal amount is transfused (Tschirjew, Landois). In the
latter case there is a moderate increase of the urea lasting for days, a proof of
the slow decomposition of the red corpuscles. Pronounced over-filling of the
vessels causes loss of appetite, and a tendency to haemorrhage of the mucous
membranes.

(-•) PolySBlnia serosais that condition in which the amount of serum — i.e.,
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, pass-
ing 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 ; hremoglobinuria is
produced (Ponfick) ; and if there be general dissolution of the corpuscles, death
may occur (Landois).

PolySBmia 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.

(3.) Plethora poiycythaemica, Hypergloblllie.— An increase of the red cor-
puscles has been assumed to occur when customary regular haemorrhages are inter-
rupted— e.g. , menstruation, bleeding from the nose, &c. ; but the increase of corpuscles
has not been definitely proved. There is a proved case of temporary polycytha;mia —
viz., when similar blood is transfused, a part of the fluid is used up, while the
corpuscles remain unchanged for a considerable time. There is a remarkable increase
in the number of blood-corpuscles (to S'82 millions per cubic millimetre, p. 4) 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 of corpuscles is greater on the paralysed congested side (Penzoldt). After
diarrhoea, which diminishes the water of the blood, there is also an increase
(Brouardel). There is a temporary increase in the luzmatoblasts as a reparative
process after severe haemorrhage (p. 15), 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 hwmatoblasts ceases (Hayem).

(4.) 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 con-

ABNORMAL CONDITIONS OF THE BLOOD. (i,3

dition is produced by transfusing the serum of the same species, whereby, at the
same time, the urea is increased. Injection of egg-albumin produces albuminuria
(Stokes, Lehmann).

(B.) Diminution of the Quantity of Blood, or its Individual Consti-
tuents.— (1.) Oligaemia VCra, or diminution of the quantity of blood as a whole,
occurs whenever there is haemorrhage. 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 by renewed more rapidly in their case. Stout persons,
old people, and children do not bear the loss of blood well. The more rapidly
blood is lost, the more dangerous it is.

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 fteces, and lastly, general convulsions, are sure signs of death b;/
hcemorrhage. In the gravest cases restitution is only possible by means of trans-
fusion. 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 con-
tract 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 haemorrhage 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 (hydrcemia), and at last abnormally
poor in corpuscles (oligocytlicemia, hypocjlobulie). 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 (^.;/., for bile).

After moderate bleeding from an artery in animals, Buntzen observed that the
volume of the blood was restored in several hours; after more severe haemorrhage
in 24 to 48 hours. The red blood-corpuscles after a loss of blood equal to
I'l to 4 '4 per cent, of the body-weight, are restored only after 7 to 34 days.
The generation begins after 24 hours. During the period of regeneration the
number of the smallest blood-corpuscles (hsemato-blasts) is increased. Even in
man the duration of the period of regeneration depends upon the amount of blood
lost (Lyon). The amount of haemoglobin is diminished nearly in proportion to
the amount of the haemorrhage (Bizzozero and Salvioli).

Metabolism in Anasmia.— The condition of the metabolism within the bodies of
anasmic persons is important. The decomposition of proteids is increased (the
same is the case in hunger), hence the excretion of urea is increased (Bauer,
Jiirgensen). The decomposition of fats, on the contrary, is diminished, which
stands in relation with the diminution of C02 given off. Anaemic 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
01ig8Binia Sicca. This occurs in man after copious 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.

(3.) If the proteids in blood be abnormally diminished the condition is called
Oligsemia hypalbuminosa ; they may be diminished about one-half. They
are usually replaced by an excess of water in the blood. Loss of albumin from

64 ABNORMAL CONDITIONS OF THE BLOOD.

the blood is caused directly by albuminuria ('25 grammes of albumin may be given off
by the urine daily), persistent suppuration, great loss of milk, extensive cutaneous
ulceration, albuminous diarrhoea (dysentery). Frequent and copious haemorrhages,
however, by increasing the absorption of water into the vessels, at first produce
oligajmia hypalbuminosa.

Mellitaemia. — The su«ar in the blood is partly given off by the urine, and in
"diabetes mellitus " one kilo. ('2-2 Ibs.) may be given off daily, when the quantity
of urine may rise to 25 kilos. To replace this loss 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 albuminous 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 (Kunde, Heubel), and wounds heal
badly because of the abnormal condition of the blood. Absence of all carbo-
hydrates in the food causes a diminution of the sugar in the blood, but does not
cause it to disappear entirely. An excessive amount of inosite has been found in the
blood and urine, constituting mellituria inoslta (Vohl).

Lipseniia, or an Increase of the Fat in the Blood, occurs after every meal

rich in fat, 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 decomposition of albumin in the body (and therefore in very severe diseases),
the fat in the blood increases, and this also takes place after a liberal supply of
easily decomposable carbo-hydrates and much fat.

The Salts remain very persistently in the blood. The withdrawal of common
salt produces albuminuria, and, if all salts 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 softening 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 good sign when the chlorides begin to return to the
urine].

The amount Of fibrin is increased in inflammations of the lung and pleura;
hence, such blood forms a crusta pldo'j'istica (p. 39). 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 hpernorrhages, Signi. Mayer found an increase of fibrin. Blood rich
in fibrin is said to coagulate more tsloivly than when less fibrin is present — still
there are many exceptions.

For the abnormal changes of the red and white blood-corpuscles see p. 23.

Physiology of the Circulation,

42. General View of the Circulation.

THE blood within the vessels is in a state of
carried from the ventricles by the large
arteries (aorta and pulmonary) and their
branches to the system of capillary vessels,
from which again, it passes into the veins
that end in the atria of the auricles (W.
Harvey).

The cause of the circulation is the differ-
ence of pressure which exists between the
blood in the aorta and pulmonary artery on
the one hand, and the two venae cavse and
the four pulmonary veins on the other.
The blood, of course, moves continually 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 standstill. 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 vense
cavoa terminate in the right auricle.

('!.} 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 right auricle.

(3.) The portal circulation, which is some-
times spoken of as a special circulatory system,
although it represents only a second set of
capillaries (within the liver) introduced into

continual motion, being
K

L

J- 16-

of the c
right auricle ; A, right ven-
tricle ; l>, left auricle ; B,
left ventricle ; 1, pulmonary
artery ; 2, aorta with semi-
lunar valves ; I, area of pul-
monary circulation; K,area
of systemic circulation in
region supplying the supe-
i-ior vena cava, o; G, area
supplying the inferior vena
cava, u; d, d, intestine; m,
mesenteric artery; q, portal
vein; L, liver; /i, hepatic
vein.

the course of a venous
5

6G

MUSCULAR FIBRES OF THE HEART.

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. These last veins join the inferior vena cava.

Strictly speaking, however, there is no special portal circulation.
Similar arrangements occur in other animals in different places
— e.g., snakes have such a system in their supra-renal 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 mirabilc is formed, such as occurs in apes and the eden-
tata. Similar arrangements may exist on veins, giving rise to venous
retici mirabilia.

43. The Heart

Muscular Fibres of the Heart. — The musculature of the mammalian
heart consists of short (50 to 70 //, man), very fine, transversely striated
muscular fibres, which are actual uni-cellular elements (Eberth), devoid
of a sarcolemma (15 to 25 ^ broad), and usually divided at their
blunt ends, by which means they anastomose and form a net-
Avork. (Fig. 17, A, B.) The individual muscle-cells contain in their

A

C

Fio;. 17.

A, branched muscular fibres from the heart of a mammal ; B, transverse section of
the cardiac fibres ; b, connective tissue corpuscles ; c, capillaries ; C, muscular
fibres from the heart of a frog.

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, solu-
tion of nitric acid. The transverse strine are not very distinct, and
not unfrequently there is an appearance of longitudinal striation, pro-
duced by a number of very small granules arranged in rows within

ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. 67

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 (epicardiuvi)
is continuous with that of the endocardium by means of the peri-
mysium surrounding the bundles of muscular fibres.] The fine spaces
which exist between these bundles form narrow lacunse, 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 invohintary, not
being directly under the influence of the will, while they contract more slowly
than a voluntary muscle of the skeleton.]

[In the/ror/'s heart the muscular fibres are in shape elongated spindles, or fusi-
form, in this respect resembling the plain muscle-cells, but they are transversely
striped (Fig. 17, C). They are easily isolated by means of a 33 per cent, solution of
potash or dilute alcohol (Weissmann, Ranvier).]

44. Arrangement of the Cardiac Muscular Fibres,
and their Physiological Importance.

The study of the embryonic heart is the key to a proper understand-
ing of the complicated arrangement of the fibres in the adult heart.
The simple tubular heart of the embryo has an outer 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 these cavities undergo a sac-like
dilatation, and also become twisted in a spiral manner.

(1.) The Muscular Fibres of 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. 18, 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,

G8

ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES.

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-cartila-
ginous 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. 18, II). Similar fibres exist
around the four 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 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 the lungs that the walls of the smaller veins are
largely composed of striped muscle (Stieda).

v.p

Fig. 18.

I. Course of the muscular fibres on the left auricle — Observe the outer transverse
and inner longitudinal fibres, the circular fibres on the pulmonary veins (v, p)\
V, the left ventricle (John Reid). II. Arrangement of the striped muscular
fibres on the superior vena cava (Elischer) — o, opening of vena azygos ;
v, auricle.

Circular muscular fibres are found where the vena magna cordis
enters the heart, and in the valvula thelesii which guards it.

From a pliy 'siological point of view the following facts are to be noted
as a result of the anatomical arrangement :—

(l.)'The auricles contract independently of the ventricles. This is
seen when the heart is about to die ; then there may be several
auricular contractions for one ventricular, and at last only the auricles

ARRANGEMENT OF THE VENTRICULAR FIBRE.v 69

pulsate. The auricular portion of the right auricle heats longest ;
hence, it is called the " ultinrum moriens." Independent rhythmical
contractions of the vense cavje and pulmonary veins are often noticed
after the heart has ceased to beat (Haller, Nysten). [This beating-
can also be observed in those veins in a rabbit after the heart is cut
out of the body.]

(2.) The double arrangement of the fibres (transverse and longi-
tudinal) produces a simultaneous and uniform diminution of the
auricular cavity (such as occurs in most of the hollow viscera).

(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 into the auricle ; and by their presence
and action they prevent any large quantity of blood from passing back-
ward into the veins when the auricle contracts. [Xo 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 play 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 of the Ventricles. — The fibres in the thick
wall of the ventricles are arranged in several layers (Fig. 19, A) under the
pericardium. First, there is an outer longitudinal layer (A) which is in
the form of single bundles on the right ventricle, but forms a complete
layer on the left ventricle, Avhere it measures about one'-eighth of
the thickness of the ventricular Avail. 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 trabeculte carnese.
Between these two layers there lies the thickest layer, consisting of
more or less transversety-air&iiged bundles which may be broken up into
single layers more or less circularly disposed. The deep lympJitif/i-
vessels run between the layers, whilst the Uood-vessels lie within the
substance of the layers and are surrounded by the primitive bundles
of muscular fibres (Henle). 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 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

70

ARRANGEMENT OF THE VENTRICULAR FIBRES.

Fig. 19.

Course of the ventricular muscular fibres — A, On the anterior surface ; B, View
of the apex with the vortex (Henle); C, Scheme of the course of the
fibres within the ventricular wall ; D, Fibres passing into a papillary muscle
(C. Luclwig).

outer longitudinal fibres are so arranged as to cross the inner longi-
tudinal layer at an acute angle. The tranverse 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 at the so-called vortex (Wirbct) B, where they enter
the muscular substance, and, taking an upward and inward direction,
reach the papillary muscles, D (Lower) ; 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 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 representation of this view.]

A special layer of circular muscular fibres, which acts like a true
sphincter, surrounds the arterial opening of the left ventricle, and
seems to have a certain independence of action (Henle).

PERICARDIUM, ENDOCARDIUM, VALVES.

71

Only the general arrangement of the ventricular muscular fibres has been
indicated here (Lower, Gasp. Wolff, 1780-92). C. Ludwig (1849), and more
recently Pettigrew (1864) have made the subject a special study, and followed out
its complications. According to the last observer, 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 extenial 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 pericardia! space — which contains a small quantity of lymph — the
pericardial fluid. It has the structure of a serous membrane, i.e., it consists of
connective tissue mixed vn.ila.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. 20) and endocardium
and also in the deeper layers of the visceral pericardium next the heart, but stomata
have not been found leading from
the pericardial cavity into these
lymphatics, nor do these open-
ings exist on the parietal layer.
[Salvioli has shown that lym-
phatic spaces also lie between
the muscular bundles.] Around
the coronary arteries of the heart
exist deposits of fat and lymph-
vessels (Wedl), which lie in the
furrows and grooves in the sub-
serosa of the epicardium (visceral
layer).

The ENDOCARDIUM (accordingto
Luschka) does not represent the
intiina alone, but the entire wall
of a blood-vessel. Next the cavity
of the heart, it consists of a

.

single layer of polygonal, flat,

Fig. 20.

Lymphatic of the pericardium epithelium stained
with nitrate of silver.

nucleated endothclial cells. [Under this there is a nearly homogeneous hyaline
layer (fig. 21, 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 as-
suming the characters of a
fenestrated membrane. Be-
tween these fibres a small
quantity of connective tissue
exists, which is in larger
amount and more areolar in its
characters next the myocar- Fig. 21.

dium. Bundles of non-striped Section of the endocardium— a, hyaline layer ; //,
muscular fibres (few in the network of fine elastic fibres ; c, network of
auricles) are scattered and .stronger elastic fibres; d, myocardium with
arranged for the most part blood-vessels, which do not pass into the endo-
longitudmally between the cardium.

72 STRUCTURE OF THE VALVES.

clastic fibres. These seem evidently meant to resist the distension which is
.apt to occur when the heart contracts and great pressure is put upon the
endocardium. In all cases where high pressure is put upon walls composed of
soft parts, we always find muscular fibres present, and never elastic fibres alone.
No l>too<l-i;x.<i In occur in the endocardium (Langer).

The valves also belong to the endocardium — both the sr.mi-lunur
of the aorta and pulmonary artery, which prevent the blood from passing
back into the ventricles, and the tricuspid (right auriculo-ventricular)
and mitral (left auriculo-ventricular), which protect the auricles from
the same result. The lower vertebrata have valves in the orifices of
the vense cavee which prevent regurgitation into them; while in birds
and some mammals these valves exist in a rudimentary condition.

The VALVES are fixed by means of their base to resistant fibrous
rings, consisting of elastic and fibrous tissue. They are formed of
two layers— (1.) the fibrous, which is a direct continuation of the fibrous
rings, and (2.) a layer of clastic elements. The elastic layer of the
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.

Muscular Fibres in the Valves. — The auriculo-ventricular valves
also contain striped muscular fibres (Reid, Gussenbauer). 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 ; accord-
ing to Paladino, they raise the valves after they have been pressed
down by the blood-current. This observer also described some longi-
tudinal 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 chorda? tendinias also
contain striped muscle (Oehl), while a delicate muscular network
exists in the valvula thebesii and valvula eustachii.

Purkinje's Fibres. — This name is applied to an anastomosing system of
grayish 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. 22). 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

SELF-STEERING ACTION OF THE HEART.

73

in their development. 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 mus-
cular 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
lymphatics in the en-
docardium reaches to-
wards the middle of
the valves (Eberth and
Belajeff).

Weight Of the Heart. Purkinje's fibres isolated with dilute alcohol— c, cell ;
—According to W. Miiller /, striated substance ; n, nucleus— x 300.

the proportion between

the weight of the body and the heart in the child, and until the body reaches
40 kilos., is 5 grams, 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 grams, of heart-
substance ; at 100 kilos. 3 '5 grams. 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 9 oz. (1 oz. =29'2 grms.); female — Si oz. (Clen-
dinning as a mean of 400 observations). [According to Laennec the heart is about
the size of the closed fist of the individual]. Blosfield and Dieberg give 34G grms.
for the male, and 310 to 340 grms. for the female heart. The specific gravity of
the heart-muscle is 1'069 (Kapff).

47. Self-Steering Action of the Heart.

Coronary Vessels. — Many observations have been made to ascertain
whether the orifices of the coronary arteries are covered by the semi-
lunar valves during contraction of the left ventricle (Thebesius, 1739;
Briicke, 1854), or whether they are permanently open (Morgagni, 1723;
Hyrtl, 1855)— Fig. 23.

Anatomical Investigations The two coronary arteries whose

branches do not anastomose (Hyrtl, Henle ; but this is denied by
Krause and L. Langer), arise from the beginning of the aorta in the
region of the sinus of Valsalva. The position of origin varies — (1.)
either the origins lie within the sinus, or (2.) their openings are only
partially reached by the margins of the semi-lunar valves (which is
usually 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.

74 SELF-STEERING ACTION OF THE HEART.

The Self-Steering Action 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 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 ; (&.) on the con-
trary, 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 contrac-
tion. To this arrangement, Briicke gave the above name.

Arguments against B^ucke's View. — The following considei-ations militate
against this theory :—(!.) 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-pericardia! fatty tissue, in the
cardiac sulci, hence a dilatation of the ventricle through this agency is most
unlikely (Landois). (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 (Serafin), 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, Perls). (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 tilled 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, Eiidinger) 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 contraction of the muscle, and the blood
stream is accelerated. (9.) By the systolic filling of the aorta the arterial path is
elongated — this elastic distension 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 (Ceraclini). According to Sandborg and Worm Miiller, the semi-
lunar valves close just after the ventricles have begun to relax, which agrees with
the curve obtained from the cardiac impulse (Fig. 25a, A).

During the systole, the small arterial trunks lying next the ventricu-
lar 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

LIGATURE OF THE CORONARY ARTERIES. 75

heart. Where they pass into veins, several unite at once to form a thick 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 (Hyrtl and Henle) maintain that the
coronary arteries do not anastomose, but this is denied by Langer and Krause.
Many of the small lower vertebrates have no blood-vessels in their heart-muscle,
e.g., frog (Hyrtl).

Coronary Circulation. — The phenomena produced by partial oblitera-
tion or ligature of the coronary arteries are most important. In man
analogous conditions occur, as in atheroma or calcification of these
arteries.

Ligature of the Coronary Arteries. — See and others ligatured the
coronary arteries in a dog, and found that after 2 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 aortse and the ventricle, the heart's action is
soon weakened, owing to the sudden anaemia and to the retention of
the decomposition products of the metabolism in the heart-muscle (v.
Bezold, Erichsen). 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 contrac-
tions 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 suffi-
cient quantity, the left auricle becomes filled, whilst the right
ventricle, not being affected, pumps blood into the lungs. (Edema of
the lungs is produced by the high pressure in the pulmonary circula-
tion, which is propagated from the right heart through the pulmonary
vessels into the left auricle (Samuelson and Griinhagen).

According to Sig. Mayer, protracted dyspnoea 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 oedema during the death agony.

Cohnheim and v. Schulthess-Rechberg found after ligature of one of the large
branches of a coronary artery in a large dog, that at the end of a minute the

7fi THE MOVEMENTS OF THE HEART.

pulsations become discontinuous; several, as it were, do not occur. This inter-
mittence becomes more pronounced, the two sides of the heart do not contract
simultaneously (arltythmia), the heart beats more slowly, and the blood-pressure
falls. Suddenly, about 103 sees, after the ligature is applied, both ventricles cease
to beat, and there is the greatest fall of the blood-pressure. After 10 to 20 sees.,
twitching movements occur in the ventricles, while the auricles pulsate regularly,
and may continue to do so for many minutes, while the ventricles cease to beat
altogether after 50 sees. According to Lukjanow, there is a peristaltic condi-
tion which operates upwards and downwards, and occurs in the period between
the regular contraction and the twitching vibratory movement.

48. The Movements of the Heart.

Cardiac Revolution. — The movement of the heart is characterised by
an alternate contraction and relaxation of the cardiac 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 auricles, the contraction or systole of the ventricles, and the pause.
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 :—

EVENTS DURING A CARDIAC REVOLUTION.

(A.) The Blood Flows into the Auricles, and thus distends them and
the auricular appendages. This is caused by—

(1.) The pressure of the blood in the venae cavae (right side) and the
pulmonary veins (left side) being greater than the pressure in the
auricles.

(2.) The clastic traction of the lungs (§ 60) 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 (Haller, Nysten) 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

EVENTS DURING A CARDIAC CYCLE.

77

(3.) The blood is driven into the relaxed ventricles, which are con-
siderably distended thereby.

The contraction of the auricles is followed by

(a.) A slight stagnation of the blood in the large venous trunks, as
can be easily observed in a rabbit after division of the pectoral muscles
so as to expose the junction of the jugular Avith the subclavian vein.
There is no proper regurgitation of the blood, but only a partial
interruption of the inflow into the auricles, because, as already men-
tioned, the mouths of the veins are contracted, and because the
pressure in the superior vena cava and in the pulmonary veins soon
holds in equilibrium any reflux of blood; and lastly, because any reflux

Gypsum 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, position of
septum; F, left fibrous ring, with mitral valve closed; D, right fibrous ring,
with tricuspid closed ; A, aorta, with the left (Ci) and right (C) coronary
arteries ; S, siuus of valsalva ; P, pulmonary artery.

78 EVENTS DURING A CARDIAC CYCLE.

into the cardiac veins is prevented by valves. The movement of the
heart causes a regular pulsatile phenomenon in the blood of the vense
cavoe, which under abormal circumstances may produce a venous pulse
(see Venous pulse).

(&.) 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 force of the lungs.

The dilatation of the ventricles has been ascribed to the elasticity of the
muscular walls — the strongly contracted ventricular walls (like a compressed india-
rubber bag), in virtue of their elasticity, are supposed to return to their normal
resting form, and thereby to suck in or aspirate the blood under a negative pres-
sure. Such suction power on the part of the ventricle is, however, only effective
to a very slight extent.

(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 (Paladino).

(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 (Sand-
borg and Worm Miiller). It is impossible for the blood to push the
cusps backwards into the auricle, as the chordce tendinice hold fast their
margins and surfaces like a taut sail. The margins of the neighbouring

cusps are also kept in apposition by the
chordre tendinise from one papillary muscle
always passing to the adjoining edges of
two cusps (John Eeid). The extent to
which the ventricular wall is shortened is
compensated by the contraction of the
papillary muscle, and also of the large
muscular chordte, so that the cusps cannot
be pushed into the auricle.

24 ' When the valves are closed their surfaces

The closed semi-lunar are horizontal, so that even when the
valves of the pulmonary ventricles are contracted to their greatest
artery seen from below. extentj ft gmall amount of Uood remains,

which is not expelled (Sandborg and Worm Miiller).

PATHOLOGICAL DISTURBANCES OF CARDIAC ACTION. 79

(3.) Opening of the Semi-lunar Valves. — When the pressure within
the ventricle 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 firmly or directly applied to the wall of the
arteries (pulmonary and aorta), and thus the blood enters the arteries.

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 action. They surmised that that phase coincided with
the diastolic dilatation, for which they assumed a considerable power of aspiration.
Marey observed a similar condition and called it " vacuite postsystolique," but
thought that it coincided with the end of the systole; while Moens is of opinion that
this negative pressure within the ventricle obtains shortly lie/ore the. systole has
reached its height, i.e., just before the inner surface of the ventricles and the
valves, after the blood is expelled, are nearly in apposition. He explains this
aspiration as being due to the formation of an empty space in the ventricle caused
by the energetic expulsion of the blood through the aorta and pulmonary artery.

(D.) Pause. — As soon as the ventricular contraction ends, and the
ventricles begin to relax, the semi-lunar valves close. The diastole of
the ventricles is followed by the PAUSE. Under normal circumstances
the right and left halves of the heart always contract or relax uni-
formly and simultaneously.

49. Pathological Disturbances of Cardiac Action.

Cardiac Hypertrophy. — All RESISTANCES to the movement of the blood
through the various compartments 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 ; con-
sequently, 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 direction of the
blood-stream, these parts also subsequently undergo hypertrophy. If in addi-
tion 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 incompeteucy 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 in their course (Aneurisms) ; insufficiency of the aortic
valves, in which case the same pressure always obtain within the ventricle and in
the aorta ; and lastly, contraction of the kidneys, so that the excretion of water by
these organs is diminished. Even in mitral insufficiency compensatory hyper-
trophy 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.

80 III I] APEX-BEAT.

(2.) Hypertrophy of the Ivft auricle occurs in stenosis of the left auriculo-ven-
tricular orifice, or iu 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 riyht ventricle, occurs (a. ) when there is resistance to
the blood-stream through the pulmonary circuit. The resistance may be due to
(«.) obliteration of large vascular areas in consequence of destruction, shrinking or
compression of the lungs, and the disappearance of numerous capillaries in emphy-
sematous lungs. (jS.) Overfilling of the pulmonary circuit with blood in conse-
quence of stenosis of the left auriculo-ventricular orifice or mitral insufficiency —
consequent upon hypertrophy of the left auricle resulting from aortic insufficiency.
(b. ) Hypertrophy of the right ventricle will also occur 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 rirjlit auricle occurs in consequence of the last-named
condition, and also from stenosis of the tricuspid orifice, or insufficiency of the
tricuspid valve (rare). If several lesions occur simultaneously, the result is
complex.

Artificial Injury to the Valves. — 0. Rosenbach has made experiments on
the action of the heart when its valves are injured artificially. 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 for a 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 regurgitatiou of the blood into the heart. Hypertrophy then
occurs, but the compensation meanwhile must be obtained through the reserve
energy of the heart.

Impeded Diastole. — Among causes which hinder the diastole of the heart are —
copious effusions into the pericardium, or pressure of tumours upon the heart. The
systole is greatly interfered with when the heart is united to the pericardium and
to the connective tissue in the mediastinum. As a 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.

50. The Apex-Beat— The 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 fifth left intercostal
space, caused by the movement of the heart. [The apex-beat is felt in
the fifth left intercostal space, two inches below the nipple, and one
inch to its sternal side.] 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.

[Methods. — To obtain a curve of the apex-beat or a cardiogram, we may
use one or other of the following cardiographs (Fig. 25). Fig. 25, A, is the
first form used by Marey, and it consists of an oval wooden capsule applied in an

THE CARDIOGRAM.

81

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 t is a tube which may
be connected with a registering tambour (Fig. 28). B is an improved form of
the instrument, consisting essentially of a tambour, while attached to the mem-
brane is a button, p, to be applied over the apex-beat. The movements of the air
within the capsule are communicated by the tube, t, to a registering tambour. Fig.
25, C, is the pansphygmograph. of Brondgeest, which consists of a Marey's tam-
bour, in an iron horse-shoe frame, and adjustable by means of a screw, s. Burdon-
Sanderson's cardiograph is shown in D. The button, p, carried by the spring, e,
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. 25, E, shows a modified instrument on the same principle by Grunmach
and v. Knoll. In all these figures the t indicates the exit-tube communicating
with a registering tambour (Fig. 28). D and E may be used for other purposes,
e.y., for the pulse, so that they are polygraphs. See also Fig. 52.]

Fig. 25.

Various cardiographs — A, original form as used by Marey; B, improved form by
Marey; C, Pansphygmograph of Brondgeest; D, Cardiograph of Burdon-
Sandersou ; E, that of Grunmach and v. Knoll.

Fig. 25a, 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 sphygmo-
graph. In both the following points are to be noticed — a, &, corre-
sponds 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

82

THE CARDIOGRAM.

Fig. 25«.

Curves taken from the apex-beat — A, normal curve from mau ; B, from a dog;
C, vei y rapid curve from a dog ; D and E, normal curves from a mau, regis-
tered on a vibrating glass-plate where eacli indentation = O'OIGIS sees. In
all the curves, a, //, means contraction of the auricles ; b, c, ventricular
systole ; </, closure of the aortic valves ; e, closure of the pulmonary artery
valves; e,f, relaxation or diastole of the ventricle.

elevations are perhaps caused by the contractions of the ends of the
veins, the auricular appendices, and the atria themselves.

.Some observers ascribe the small elevations occurring before b to the rilling of
the ventricle during the diastole, whereby it is pressed against the intercostal
space (Maurer, Griitzner).

The portion, l>, c, 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 of the ventricle, and during it the first
sound of the heart occurs. Frequently, but erroneously, the cardiac
impulse has been ascribed to this contraction of the ventricle. It
however, is due to all those conditions which cause an elevation in the
region of the apex -beat.

CAUSE OF THE CARDIAC IMPULSE.

83

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 diastole a transversely-placed ellipse, while during contraction it
has a more circular figure. Thus, the long diameter of the ellipse is
diminished in the cat from 28 to 22*5 mm. (C. Ludwig) ; the small
diameter is increased (^ to -4-), while the base is brought nearer to
the chest- wall (Arnold, Ludwig) — Fig. 26, 1. This alone 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 movement which causes the impulse.

(2.) During relaxation, the ventricle lies with its apex obliquely
downwards, and with its long axis in an oblique direction — so that the
angles formed by the axis of the ventricles with the diameter of the
base are unequal — represents a regular cone, with its axis at right angles
to its base. Hence, the apex must be erected from below and behind,
forwards and upwards (Harvey — " cor sese erigere "), and when
hardened during systole presses itself into the intercostal space
(Ludwig)— Fig. '20, II.

Fig. 26.

I, Schematic horizontal section through the heart and lungs, and the thoracic
walls, to show the change of shape which the base of the heart undergoes
during contraction of the ventricle — 1, 2, transverse diameter of the ventricle
during diastole ; c, position of the thoracic wall during diastole ; a, b, trans-
verse diameter of the heart during systole, with e, the position of the anterior
thoracic wall during systole. II, Side-view of the heart — s, apex during
diastole ; p, the same during systole (C. Ludwig).

84 CAUSE OF THE CARDIAC IMPULSE.

(3.) The ventricle undergoes during systole a slight spiral twisting
on its 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 down-
wards, and to the left, and also run in part upon the posterior surface
of the ventricle. 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 (Harvey,
Kiirschner, Wilckens). This rotation is favoured by the slightly spiral
arrangement of the aorta and pulmonary artery (Koruitzer).

These are the most important causes, but minor causes are as
follows : —

(4.) The " reaction impulse " is that movement which the ventricles
are said to undergo (like an exploded gun or rocket) at the moment
when the blood is discharged into the aorta and pulmonary artery,
whereby the apex goes in the opposite direction — i.e., downwards and
slightly outwards (Alderson 1825, Gutbrod, Skoda, Hiffelsheim).
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 (Senac). As the heart is suspended from above by these
vessels, the apex is pressed slightly downwards and forwards towards
the intercostal space (?)

Guttmann and Jahn observed that the cardiac impulse disappeared after sudden
ligature of the aorta and pulmonary artery, while Chauveau and Eosensteiu
maintain that it persists.

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 be the case in (4) and (5), but that it
moves upwards and to the right — a result corroborated by v. Ziemssen,
which, however, is disputed by Losch.

It is to be remembered that as the apex is always applied to the chest- wall,
separated from it merely by the thin margin of the lung, it only presses
against the intercostal space during systole (Kiwisch).

After the apex of the curve, c, has been reached at the end of the

THE TIME OCCUPIED BY THE CARDIAC MOVEMENTS. 85

systole, the curve falls rapidly, as the ventricle rapidly becomes 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, which, occurring suddenly,
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 piilmonary
valves. The closure of the valves in these two vessels is not simul-
taneous, but is separated by an interval of 0'05 to 0'09 sec. The
aortic valves close sooner on account of the greater blood-pressure
there (Landois, 1876, Ott and Haas, Malbranc, Maurer, Griitzner,
Langendorff, v. Ziemssen, and Ter Gregorianz).

Complete diastolic relaxation of the ventricle occurs from c to / 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 con-
cerned in its production.

51. The Time Occupied by 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 experiment, of course all that is necessary is to measure the distance,
and so calculate the time occupied by any event (see Pulse).

(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.
25a, 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 healthy 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
sec., 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.

Pause and Contraction of Auricles.— The value of a b = pause + con-
traction 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 smaller 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 corresponding to the pause (indicated by a horizontal
line). In one case (heart-beats 55 per minute) the pause = 0'4 sec., the
auricular contraction = (H77 sec. In Fig. 25«, A, the time occupied by
the pause + the auricular contraction (74 beats per minute) = 0'5 sec.

80 TIME OCCUPIED BY THE VENTRICULAR SYSTOLE,

In D the a ft = 19 to 20 vibrations = 0'3 2 sec.; in E= 26 vibrations
= 0-42 sec.

Ventricular Systole. — The ventricular systole is calculated from the
beginning of the contraction, ft to e, 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 less — during slow action, greater. In E = 0-32 sec.; in D
= 0'29 sec. ; with 55 beats per minute Landois found it = 0*34, with a
very high rate of beating = 0'199 sec.

When the ventricle beats feebly, it contracts more slowly, as can be shown by
applying the registering apparatus to the heart of an animal just killed. In Fig.
27, from the ventricle of a rabbit just killed, the slow heart-beats, B, ai-e seen to
last longest.

Fig. 27.

Curves obtained from the ventricle of a rabbit, and written upon a vibrating plate
attached to a tuning-fork (vibration — 0 '01613 sec.) — A, tolerably] soon after
death ; B, from the dying ventricle.

In calculating the time occupied by the ventricular systole we must remember —
(1.) The time between the two sounds of the heart, i.e., from the beginning of the
first to the end of the second sound (fc to e). (2.) The time the Hood flows into the
aorta, which comes to an end at the depression between c and r? (in Fig. 25a, E).
Its commencement, however, does not coincide with b, as the aortic valves open
O'OSS (Landois) to 0'073 (Rive) sec. after the beginning of the ventricular systole.
Hence the aortic current lasts O'OS to 0'09 sec.

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 sec., and of this time 0'052
sec. are occupied in the propagation of the pulse-wave along the 30 cm. of artery
lying between the root of the aorta and the axilla. Thus the pulse-wave in the
aorta occurs 0'137 minus 0'052 = 0'OS5 sec. after the beginning of the first sound.

The current in the pulmonary artery is interrupted in the depression between
d and c. (3.) Lastly, the time occupied by the muscular contraction of the
ventricle, which begins at b, reaches its greatest extent at c, and is completely
relaxed at/. The apex of the curve, <:, may be higher or lower according to the
flexibility of the intercostal space, hence the position of c 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 e, i.e., 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

ENDOCARDIAL J'KKSM'KK.

valves are closed by the pressure from above, and the difference in
time may be 0'05 sec., or even double that time, in which case the
second sound appears double (compare p. 94). 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, e,f, during which the ventricle relaxes varies somewhat:
O'l sec. may be taken as a mean.

Accelerated Cardiac Action. — When the action of the heai-t is greatly
accelerated, the pause is considerably shortened in the first instance (Bonders),
and to a less extent the time of contraction 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. 25«, C (dog).

In registering the cardiac impulse, the apparatus is separated by a greater or
less extent 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
obtained may not coincide mathematically with the movements of the heart. It
is desirable that curves be obtained froai persons whose hearts are exposed, -i.e.,
in cases of ectopia cordis.

Gibson inscribed cardiograms from the heart of a man with cleft sternum.
The following were the results obtained: — Auricular contraction = O'l 15; ventri-
cular contraction (t>,d) = 0"2S ; difference between closure of valves (r/, r) = 0'09
ventricular diastole (<?,/) — O'll ; pa use = 0 '45 sec.

Endocardial Pressure. — In large mammals, such as the horse,
Chauveau and Marey determined
the duration of the events that
occur within the heart, and also
the endocardial pressure, by
means of a cardiac sound. Small
elastic bags attached to tubes
were introduced through the
jugular vein into the right auricle
and ventricle. Each of these
tubes was connected with a regis-
tering tambour (Fig. 28), and
simultaneous tracings of the varia-
tions of pressure within the cavi- Marey 's registering tambour, consisting of

Fi. 28.

ties of the heart were obtained
by causing the writing-points of
the levers of the tambours to
write upon a revolving cylinder.

a metallic capsule, T, with thin india-
rubber stretched over it, and bearing
an aluminium disc, which acts upon
the writing lever, H. By means of a
thick-walled caoutchouc tube, it may
be connected with any system con-
taining air, so as to record variations
of pressure.

Fig. 29, A, gives the result obtained
when the elastic bag was placed in
the right aiiricle, introduced through
the jugular vein and superior vena cava; B, when it was pushed through the
tricuspid valve into the right ventricle ; D, in the root of the aorta, pushed in

KNPOCARDTAL PRESSURE.

through the carotid ; 0, 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 ; «<?, closure of semi-lunar valves, sooner in C than B; P = pause.

Method. — The cardiac sound consists of a tube containing two separate air-
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 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 in
connection with it, is connected with a Marey's tambour, Fig. 28, 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 ampulla?, 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.

It has still to be determined whether the auricles and ventricles act
alternately, so that at the moment of the beginning of the ventricular

Eight Auricle.

Bight Ventricle.

Left Ventricle.

Aorta.

"Cardiac Impulse.

Fig. 29.
Curves obtained from the heart by the cardiac sound (Chauveau and Marey).

PATHOLOGICAL DISTURBANCES OF THE CARDIAC IMPULSE. 89

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, Bonders, Schiflf, and others, while Haller and
many 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 and Ter Gregorianz 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 (Fig. 29) the contraction of the ventricle is
represented as following that of the auricle.

52. Pathological Disturbances of the Cardiac

Impulse.

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 conversely the 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 (even to the third intercostal space), and also slightly to the left.
Thickening of the muscular walls and dilatation of the cavities (hypertrophy with
dilatation) of the left ventricle make that ventricle longer and broader, while the
increased cardiac impulse may be felt to the left of the mammary line, and
in the axillary line in the sixth, seventh, or even eighth intercostal space.
Hypertrophy, with dilatation of the right side, increases the breadth of the heart,
while the cardiac impulse is felt more to the right, even to the right of the
sternum, and at the same time it may be slightly beyond the left mammary
line. 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 parastemal line, the heart is increased in breadth, and
there is hypertrophy of the heart. A greatly increased cardiac impulse may
extend to several intercostal spaces.

The cardiac impulse is abnormally weakened during 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 after the influence of various stimuli (psychical, inflammatory, febrile,
toxic) which affect the cardiac ganglia. Great hypertrophy of the left ventricle

00

VARIATIONS OF TIFK rARITAC IMlTl.si:.

causes the heart to heave, so that a part of the left chest-wall may be raised and
also vibrate during systole.

A falling in of the anterior wall of the chest during cardiac systole occurs in the
third and fourth interspaces, not tmfrequently under normal circumstances,
sometimes during increased cardiac action, and in eccentric hypertrophy of the ven-
tricles. As the heart's apex is slightly displaced, and the ventricle becomes slightly
smaller during its systole, the empty space is rilled 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, a falling in 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.

Changes in the cardiac impulse are best ascertained by taking graphic repre-
sentations of the cardiac impulse, and studying the curves so obtained. This
method has been largely followed by many clinicians.

In all the following curves, <Y, />, means auricular contraction ; J>, c, ventricular

Fig. 30.

Various forms of curves obtained from the cardiac impulse — a, b, Contraction of
|^ auricles ? b, c, ventricular systole; d, closure of aortic, and 'e of pulmonary
valves ; e, f, 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 Baseclow's disease ; M, case of
so-called hemisystole.

THE HEART-SOUNDS. 01

contraction; d, closure of the aortic valves, and e of the pulmonary; c, /, the
time the ventricle is relaxed (Fig. 30.)

In curve P (much reduced), taken from a case of marked hypertrophy with,
dilatation, the ventricular contraction, 6 c, is usually very great, while the time
occupied by the contraction is not much increased. P and Q were obtained from
a man suffering from marked eccentric hypertrophy of the left ventricle, in con-
sequence of insufficiency of the aortic valves. Curve Q was taken intentionally
over the auriculo-ventricular groove, where a falling in 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 stenoxitt. The auricular contraction (a, b) lasts
only a short time ; the ventricular systole is obviously lengthened, and after a
short elevation (b, c) shows a series of fine indentations (c, e) caused by the blood
being pressed through the narrowed and roughened aorta.

Fig. F, from a case of insufficiency of the mitral valve, shows (a, b) 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 tension in
the arterial system. On the other hand, the shock from the accentuated pul-
monary sound (P) 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 mitral orifice (G) shows a long irregular notched
auricular contraction (a, b) caused by the blood being forced through an irregular
narrow orifice. The ventricular contraction (b, c) is feeble on account of its being
imperfectly tilled. The closures of the two valves, d and c, 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 a later contraction of its
valves (Geigel).

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
inorbus 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 con-
tract. 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, however, 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 (Skoda, v. Bamberger, Leyden) the mitral insufficiency leads to
overflowing of the right ventricle, 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, or by means of a

02 THE HEART-SOUND?!.

stethoscope (Laennec, 1819), we hear two characteristic sounds, the
so-called " heart-sounds." Harvey was acquainted with these sounds,
but they have been more carefully studied by clinicians since the time
of Laennec.

The first sound [long or systolic] is somewhat duller, longer, and
one-third or one-fourth deeper, than the second sound; it is less sharply
defined at first, and is isochronous with the systole of the ventricles (TurnerJ.
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
isochronous with the closure of the semi-lunar valves. There is a very
short interval between the first and second sounds, and between the
second and the next following first sound a distinctly longer interval.
This is the pause.

[The sounds emitted during each cardiac cycle have been compared
to the pronunciation of the syllables lubb, dtip. We may express the
course of events with reference to the sounds, thus: — lubb, dup, pause.]
Or the result may be expressed thus —

V V

Bu - fup. Bu - tup.

The causes of the first sound are due to two conditions. As^the
sound is heard 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
(Williams, 1835).

This sound is supported and increased by the sound produced by the
tension and vibration of the auriculo-ventricular valves and their
chordre tendiniae, at the moment of the ventricular systole (Rouanet,
Kiwisch, Bayer, Giese).

Wintrich, by means of proper resonators, has been able so to analyse
the first sound as to distinguish the clear, short, valvular part from the
deep, long, muscular sound.

The muscle-sound produced by transversely-striped muscle does not occur with a
simple contraction, but only when several contractions are superposed to produce
tetanus (see Muscle). 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 con-
traction.

Defective Heart-Sounds. — In certain conditions (typhus, fatty degeneration
of the heart) where the muscular substance of the heart is much weakened, the

THE HEART-SOUNDS.

93

Fig. 31.

The heart— its several parts arid 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 indi-
cated by very fine dotted lines. The area of propagation 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 puluionic
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
ventricle, where it touches the walls 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,
and traced in fine dotting on the sternum ; vi, the two innominate veins ;
rv, right ventricle ; Iv, left ventricle.

94. CAUSES OF THE HEART-SOUNDS.

lirst sound may be completely inaudible. In aortic insufficiency, in which, in con-
sequence of the reflux of blood from the aorta into the ventricle, the mitral valve
is gradually stretched, and sometimes even before the beginning of the ventricular
systole, the first sound may be absent. Both pathological cases show that for the
production of the iirst 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.

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 (Carswell and Rouanet, 1830). Perhaps it is augmented by the
sudden vibration of the fluid-particles in the large arterial trunks. As
already pointed out (p. 85), the aortic and pulmonary valves do not
close simultaneously. Usually, however, the difference in time is so
small that loth 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 the case, as occurs at the end of inspiration or
the beginning of expiration (v. Dusch).

[The second sound has all the characters of a valvular sound. That
the aortic valves are concerned in its production, is proved by intro-
ducing 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 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.]

Where the Sounds are Heard Loudest. — The sound produced by the
trinizpid ralce is heard loudest at the insertion of the fifth right rib into
the sternum, and from here somewhat inwards and obliquely upwards
along 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 con-
ducted 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 and where it comes nearest to
the surface, i.e., over the first right costal 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
in the second left intercostal space, somewhat to the left and external
to the margin of the sternum (Fig. 31).

\TARIATIONS Otf THE HEART-SOUNDS. 95

54. Variations of the Heart-Sounds.

An increase of the first sound of both ventricles indicates a more energetic con-
traction of the ventricular muscle and a simultaneously greater and more sudden
tension of the auriculo- ventricular valves. An increase of the second sound is a
sign of increased tension in the interior of the corresponding large arteries.
Hence, increase of the second (pulmonary) sound indicates overfilling and excessive
tension in the pulmonary circuit.

Feeble weak action of the heart, us 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 "impure." If a 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
"divided." The reduplication of the lirst sound is explained by the tension
of the tricuspid and that of the mitral valves not occurring simultaneously.
Sometimes a sound is produced by a hypertrophied auricle producing an audible
presystolic sound, i.e., a sound or " murmur,7' preceding the first sound. As the
aortic and pulmonary valves do not close quite simultaneously, a reduplicated
second sound is only an increase of a physiological condition (Landois). All con-
ditions 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 arise or accompany these — murmurs
or bruits, which, when combined, are always accompanied by disturbances of the
circulation. It is rare that tumours ur 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 or bruits 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, fremissement cataire).

In cases where dlastoltc 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 orifices (usually the left). Systolir murmurs do
not always necessitate a disturbance in the cardiac mechanism. They may
occur in the left side, owing to insufficiency of the mitral valve, stenosis of
the aorta, and in 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.

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, less
frequently at the mitral, and still less frequently at the aorta or the tricuspid
orifice. Anaemia, general mal-nutrition, acute febrile affections, are the causes of
these murmurs.

Murmurs 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.]

9G DURATION OF THE MOVEMENTS OF THE HEART.

55. Duration of the Movements of the Heart.

That the heart continues to beat for some time after it is cut out
of the body, was known to Cleanthes, a contemporary of Herophilus,
300 B.C. The movement lasts longer in cold-blooded animals (frog,
turtle, fish) — 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 1 1 minutes. 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, 2| days (Valentin). In
a human embryo (third month) the heart was found beating after
4 hours. In this condition stimulation causes an increase and accelera-
tion of the action. Afterwards, the ventricular contraction first becomes
weaker, and soon each auricular contraction is not followed by a
ventricular contraction, two or more of the former being succeeded by
only one of the latter. At the same time the ventricles contract more
slowly (Fig. 27), and soon stop altogether, while the auricles still con-
tinue 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 appendage continues to beat longest, as was
observed by Galen and Cardan us (1550). The term " ultimum
moriens " is applied to it. 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 (Harvey), more especially by heat ;
even under these circumstances, the auricles and their appendages are
the last parts to cease contracting. As a general rule, direct stimula-
tion, 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:
lesion of these vessels is followed by enfeebled action of the heart
(p. 75). Hammer found that in a man, whose left coronary artery was
plugged, the pulse fell from 80 to 8 beats per minute.

Action of Gases on the Heart.— During its activity the heart uses
0, and produces CO.,, so that it beats longest in pure 0 (12 hours)
(Castell), and not so long in N, — H (1 hour) — C02 (10 minutes), CO
(42 minutes) — Cl (2 minutes), or in a vacuum (20 to 30 minutes)
(Boyle, 1670; Fontana, Tiedemann, 1847), even when there is watery

THE CARDIAC NERVES. 97

vapour present to prevent evaporation. If the heart be re-introduced
into 0 it begins to beat again. [An excised heart suspended in
ordinary air beats three to four times as long as a heart which is
placed upon a glass-plate.] A heart which has ceased to contract
spontaneously may contract when an electrical stimulus is applied to
it, but it does not do so for a longer time than other muscles (Budge).

56, Innervation of the Heart.

[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 intracardiac ganglia. But the movements
of the heart are influenced by nervous impulses which reach it from
Avithout, so that there falls to be studied an intracardiac and an extra-
cardiac nervous mechanism.]

57. The Cardiac Nerves.

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 ganglia. 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 a ganglion). The following nerves may be
separately traced from the plexus —

(«.) The plexus coronarius dexter and sinister (Scarpa), which con-
tains the vaso-motor nerves for these vessels (physiological proof still
wanting) as well as the nerves (sensory?) proceeding from them (to
the pericardium ?)

(5.) Intra-cardiac Nerves and Ganglia. — The nerves lying in the
grooves of the heart and in its substance, containing numerous ganglia
(Remak), which 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
ganglia usually lie near the pericardium. In mammals the two largest

98

MOTOR CENTRES OF THE HEART.

ganglia lie near tho orifice of the superior vena cava — in birds the
largest ganglion (containing thousands of ganglionic cells) lies pos-
teriorly 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.
Nerves of the Frog's Heart. — In the frog there is a large ganglion
(EemaJc's) near the fibres of the vagus within the wall of the sinus
venosus. Branches of the vagus proceed from this ganglion along the an-
terior and posterior walls of the auricular septum, and each of these con-
tains a ganglion in the auriculo-ventricular groove, these aggregations
of ganglion cells constituting Bidder's ganglion. Fine branches proceed
from this ganglion, but they can be traced only for a short distance, so
that the greater part of the ventricle appears to be devoid of nerves.

According to Opeuchowsky, every part of the heart (frog, triton, tortoise) con-
tains nerve-fibres which are connected with every muscular fibre. In the auricles,
at the end of the non-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 endo-
cardium— 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 peri-
cardium contains (sensory) nerve-fibres. The following kinds of nerve-cells are found
— unipolar cells, the single processes of which afterwards divide ; bipolar cells (Fig.
31a), which in the frog possess a straight (n) and usually also a spiral process (o).

58. The Automatic Motor Centres of the Heart.

(1.) We must assume 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 are made to
move in rhythmical sequence from a principal
central point, an impulse being conducted
from this centre through the conducting paths
(Bonders). 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
Fig. 31a. electrical currents), all the. centres are thrown

Pyriforna ganglionic bi- into ti d spasm_iike action of the heart
polar nerve-cell from
the heart of a frog occurs. The dominating centre lies 'in the

ifstrafght processf S^ mrides, hence the regular progressive move-
spiral process. ment usually starts from them. If the excit-

MOTOR CENTRES OF THE HEART. 99

ability is diminished (e.g., by touching the septum with opium —
Ludwig, Hoffa), other centres seem to undertake this function, in
which case the movement may extend from the ventricles to the
auricles. 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.

(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.) The auricular centres seem to be more excitable than those of
the ventricle; hence, in a heart left to itself the auricles pulsate
longest.

(5.) 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 (Henry, 1832). The ventricle is always the part first to be
paralysed.

(6.) In order that the heart may continue to contract, it is necessary
that it be supplied with a fluid which in addition to 0 (Ludwig, Volk-
mann, Goltz) must contain the necessary nutritive materials. The most
perfect fluid, of course, is blood. Hence the heart ceases to beat
in an indifferent fluid (O'G p.c. 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-
Lilbumin — e.y., blood, serum, or lymph. Serum retains its nutritive properties
even after it has been subjected to diffusion (Martins and Kronecker). Milk and
whey (v. Ott), normal saline solution (O'G per cent. NaCl) mixed with blood,
albumin, or peptone, and 0'3 per cent, sodium carbonate (Kronecker, Merunowicz,
and Stienon), or a trace of caustic soda (Gaule), or a solution of the salts of
serum, are suitable.

(7.) 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 movements. But the ganglia are more
excitable than the heart-muscle itself, and they conduct the impulses

100 STANNIUS' EXPERIMENT.

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.

The chief experiments upon which the above statements are based
consist of two classes: — (1.) Where the heart is INCISED or DIVIDED;
and (2.) where it is STIMULATED DIRECTLY.

(I.) Experiments by CUTTING and LIGATURING the heart. These
experiments have been made chiefly upon the frog's heart. The
LIGATURE experiments are performed by tightening and then relaxing
a ligature placed around the heart, so that the physiological connection
is destroyed, while the anatomical or mechanical connections (con-
tinuity of the cardiac wall, intact condition of its cavities) still exist.
The most important of these experiments are —

(1.) Stannius' 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. If a second incision be
made at the auriculo-ventricular groove, as a rule the ventricle begins
at once to beat again, whilst the auricles remain in the condition of
diastolic rest. 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 (1852).

Explanations. — Various explanations of these experiments have been given : —
(a.) Remak's ganglion in the sinus vinosus 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 administration 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 (H. Munk), or by the action of a
constant current of moderate strength (Eckhard), 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 produced 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. (b.~) According to
another view, both Remak's (a.) and Bidder's ganglia (b.) are motor centres, but
in the auricles there is in addition an inhibitory ganglionic system (c.) (Bezold,
Traube). Under normal circumstances a + b is stronger than c, while c is stronger

LIGATURE AND SECTION OF THE HEART. 101

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, the auricles stand still owing to c,
while the ventricle beats owing to 6.

(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. Local stimulation of the ventricle causes a swrjh
contraction. If the incision be so made that the lower margin of the
auricular septum remains attached to the ventricle, the latter pulsates
(Rosenberger, 1850).

(3.) Section of the Heart. — Engelmann's recent experiments 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 strips still beat in a regularly
progressive, rhythmical manner, provided one strip is caused to con-
tract. The rapidity of the transmission is about 10 to 30 mm. per sec.
(Engelmann). Hence, it appears that the conducting paths for the
impulse causing the contraction 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 excite-
ment 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 auriculo-ventricular nervous apparatus. In fact, in the
mammalian heart the muscular fibres of the auricles are quite distinct from those
of the ventricle.]

(4.) It is usually stated that when the apex of a frog's heart is severed
from the rest of the heart, it no longer pulsates (Heidenhain, Goltz), but
such an apex, if stimulated mechanically, responds with a single con-
traction.

Action of Fluids on the Heart. — 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 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. Thus, a heart which is too feeble to
contract may be made to do so by supplying it with a fluid containing
proteids, when a latent intra-cardiac mechanism is brought into action,
the albuminous or other fluid merely supplying the pabulum for the
excitable elements.

102

ACTION OF FLUIDS ON THE HEART.

[Methods. — The action of fluids upon the excised frog's heart has been rendered
possible by the invention of the "frog-manometer" of Ludwig. The apparatus
has been improved by Ludwig's pupils, and already numerous important results
have been obtained. The apparatus, Fig. 32 consists of— (1.) a double-way
cannula, c, which is tied into the heart, li; (2. ) a manometer, m, connected with c,
and registering the movements of its mercury on a revolving cylinder, cyl ; (3.)
two Mariotte's flasks, a and b, which are connected with the other limb of the
cannula. Either a or b can be placed in communication with the interior of the
heart by means of the stop-cock, 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, c and <>' are electrodes, e is inserted into the fluid in d, e' is attached to
the german silver cannula which is shown in Fig. 32«.

Fig. 32.

Scheme of a frog-manometer — a, b,
Mariotte's flasks for the nutrient
fluids ; s, stop-cock ; c, cannula ;
m, manometer ; h, heart ; d, glass
cup for h ; e, c', electrodes ; cyl,
revolving cylinder.

d

Fig. 32a.

Double-way or perfu-
sion cannula (nat.
size) for a frog's
heart — c, for fixing
an electrode ; d, the
heart is tied over the
flanges, preventing
it from slipping out ;
e, section of d.

In the tonometer of Roy (Fig. 33) the ventricle, h, or the whole heart, is placed
in an air-tight chamber, o, filled with oil, or with oil and normal saline solution.
As before, a "perfusion" cannula is tied into the heart. A piston, p, works up
and down in a cylinder, and is adjusted by means of a thin flexible animal mem-
brane, such as is used by perfumers. Attached to the piston by means of a thread
is a writing lever, I, which records the variations of pressure within the
chamber, o. When the ventricle contracts, it becomes smaller, diminishes
the pressure within o, and hence the piston and lever rise ; conversely, when
the heart dilates, the lever and piston descend. Variations in the volume of
the ventricle may be registered, without in any way interfering with the flow
of fluids through it.

Two preparations of the frog's heart have been used — (1.) The "heart," in which
case the cannula is introduced into the heart through the sinus venosus, and a

ACTION OF FLUIDS ON THE HEART.'

103

ligature is tied over it around the auricle, or it may be the sinus venosus. Thus
the aiiriculo-ventricular ganglia and other nervous structures remain in the pre-
paration. This was the heart preparation employed by Luciani and Rossbach.
(2.) In the " henrt-apex " preparation the cannula is introduced as before, but the
ligature is^tied on it on the ventricle, several millimetres below the auriculo-

Fig. 33.

Roy's apparatus or tonometer for the heart — 7t, heart; o, air-tight chamber;

p, piston; I, writing lever.

ventricular groove, so that this preparation contains none of the auriculo- ventricu-
lar ganglia, and, according to the usual statement, this part of the heart is devoid
of nerve ganglia. This is the preparation which was used by Bowditch, Kronecker
and Stirling, Merunowicz, and others. 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 several minutes, while the
"heart-apex" does not contract spontaneously until after a much longer time
(10to90mins.).

If the " Heart- Apex " be filled with a O'G percent, solution of common salt,
the contractions are at first of greater extent, but they afterwards cease, and
the preparation passes into a condition of "apparent death;" 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). The "stille" or state of quiescence may last 90 mins. (Kronecker and
Merunowicz). If the 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 ventrical
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 to prevent blood passing out of the heart, and thus raising the
intracardial 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 spontaneous apex beats (Gaskell). If blood-serum, to which
a trace of delphinin is added, be transfused 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 (Schtschepotjew) and a mixture

104 ACTION OF FLUIDS ON THE HEART.

of atropine and muscarin have a similar action (v. Basch). These experiments
show that, provided no nervous apparatus exists within the heart-apex, the cause of
the varying contraction is to be sought for in the musculature of the heart
(Kronecker), and that the stimulus necessary for the systole of the heart's-
apex may arise within itself (Aubert). 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.

The "Heart" preparation in many respects behaves like the foregoing, i.e.,
it is exhausted after a time by the continued application of normal saline
solution (0'6 per cent. NaCl), while its activity may be restored by supplying it
with albuminous and other fluids (p. 99).]

[(5.) Luciani found that such a heart, when filled with pure serum,
produced groups of pulsations with a long diastolic pause between every
two groups (Fig. 34). The successive beats in each group assume a
"staircase" character (p. 107). These periodic groups undergo many

Fig. 34.

Four groups of pulsations with intervening pauses, as obtained by Luciani, with
their "staircase" character. The points on the abscissa were marked every
ten seconds.

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 haemoglobin
or normal saline solution (Kossbach) is used. They also occur when
the blood within the heart has become dark-coloured — i.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.) The same apparatus permits of the application of electrical stimuli
to either of the above-named preparations. 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.

ACTION OF HEAT ON THE HEART.

105

This is an important fact in connection with any theory of the cardiac
beat.]

(7.) If the bulbus aorta? (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 increase of the pressure within it increase
the number of pulsations (Engelmann).

(II.) 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 anil the
amplitude of the pulsations, as well as the duration of the systole and diastole and
the excitability of the heart.] Descartes (1614) observed that heat increased the
number of pulsations of an eel's heart. A. v. Humboldt found that when a frog's
heart was placed in lukewarm water, the number of beats increased from 12 to 40
per minute. 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

a

Fig. 35.
Fig. a, Contractions of a frog's heart at 19°C.; b£a,t 34°C.; c, at 3°C.

100 ACTION OF MECHANICAL AND ELECTRICAL STIMULI.

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. 35). The time occupied by any
single contraction at 20°C. is only about -^ of the time occupied by a contraction
occurring at 5"C. »

A heart which has been warmed is capable of reacting pretty rapidly to inter-
mittent stimuli, while a heart at a low temperature reacts only to stimuli occurring
at a considerable interval. If a frog be kept in a cold place its heart beats slowly
and does little work, but if the heart be supplied with the extract of a frog which
has been kept warm, it is rendered more capable of doing work (Gaule).

Cold. — When the temperature of the blood is diminished, the heart beats slower
(Kielmeyer, 1793). A frog's heart, placed between two watch-glasses and laid on
ice, beats very much slower (Ludwig, 1861). The pulsations of a frog's heart stop
when the heart is exposed to a temperature of 4°C. to 0° (E. Cyon). 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 in 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 demonstration 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 con-
tractions are readily made visible at a distance.]

[Gaskell fixes the heart by means of a clamp placed round the auriculo-ven-
tricular groove, while 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 contraction may be registered. This
method is applicable for studying the effect of the vagus and other nerves upon the
heart (Roy).]

(&.) Mechanical Stimuli. — Pressure applied externally to the heart 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 pressure 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. If the pressure within the
heart be increased, the heart-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 aud slower
(Heidenhain). A heart which has ceased to beat may, under certain circum-
stances, 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 Frail
Serafin (p. 74, 3), that the number of beats was doubled, when a constant uninter-
rupted 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 (Sigm. Mayer).

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 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

ACTION OF ELECTRICAL STIMULI ON THE HEART. 107

ventricle (Hildebrand). 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 musculature 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 isochronous with the stimuli, if electrical stimuli are used
(Bowditch). In this case the weakest stimuli (which are still active) behave like
the stronger stimuli— even with the weak stimulus the heart always gives the
strongest contraction possible. Hence this minimal electrical stimulus is as
effective as a "maximal" stimulus (Kronecker and Stirling).

V. Ziemssen found that he could not alter the heart-beats of the Imman heart (Frau
Serafin, p.74,3), 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 SO. When ISO shocks per minute
were applied the action of the heart assumed the characters of the pulsus alternans
(p. 143). Minimal stimuli were also found to act like maximal stimuli. The
normal pulse-rate of SO was reduced to 60 and 50, when the number of shocks was
reduced in the same ratio. The rhythm became at the same time somewhat
irregular. In these experiments a strong current is required, and v. Basch found
that the same was true for the frog's heart. Even in healthy persons, v. Ziemssen
ascertained that the energy and rhythm of the heart could be modified by passing
an electrical current through the uninjured chest-wall.

[Method. — The apparatus (Fig. 32.) is also well adapted for studying the effect
of electrical currents upon the heart. Bowditch, Kronecker and Stirling, and
other observers, used the " heart-apex," as it does not contract spontaneously
for some time after the ligature is applied. One electrode is attached to the
canuula, and the other is placed in the fluid in which the heart is bathed.]

[Opening induction shocks, if of sufficient strength, cause the heart to con-
tract, while weak stimuli have no effect; on the other hand, moderate stimuli,
when they do cause the heart to contract, always cause a maximal contrac-
tion, 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 contracts the
result is always a "maximal" contraction. Bowditch found, that the excit-
ability 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 are produced (Fig. 34. ) This staircase arrangement
occurs even when the strength of the stimulus is kept constant, so that the produc-
tion of one contraction facilitates the occurrence of the succeeding one. A staircase
arrangement of the pulsations is also seen in Luciani's groups (p. 104). The ques-
tion, whether a stimulus will cause a contraction, depends upon what
particular phase the heart is iu, 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.e. to say, they become what
are called "infallible." If stimuli are applied to the heart, at intervals which
are longer than the time the heart takes to execute its contraction, they are
effectual or "adequate," but if they are applied before the period of pulsation
comes to an end, then they are ineffectual (Kronecker). It is quite clear, there-

108 ACTION OF CHEMICAL STIMULI AND GASES ON THE HEART.

fore, that the relation of the strength of the stimulus, to the extent of the contrac-
tion of the cardiac muscle, is quite different from what occurs in a 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.]

(rf.) 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 (Budge), bile salts (Rohrig) diminish the heai't-beats (also
when they are absorbed into the blood as in jaundice) ; in very dilute solutions
both increase the heart-beats (Landois). A similar result is produced by acetic,
tartaric, citric (Bobrik), and phosphoric acids (Leyden). 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 1| to 2 per cent, passed
through the heart arrests it temporarily or completely. A dilute solution of
opium, strychnia, or alcohol applied to the endocardium, increases the heart-beats
(C. Ludwig) ; if concentrated they rapidly arrest its action. Chloral-hydrate
paralyses the heart (P. v. Rokitansky).

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 con-
taining 0 excites the heart (Castell), while the presence of much COo paralyses it,
and the presence of COo is more injurious than the want of 0. H and N have no
effect.]

Rossbach found on stimulating the ventricle of a frog's heart at a circumscribed
area, either mechanically, chemically, or electrically, during systole, that the
part so stimulated relaxes in partial diastole. The immediate direct after-effect
of this stimulation is. that the muscular fibres in the part irritated remain some-
what shrivelled. This part ceases to act, and has lost its vital functions. If the
stimulus is applied during diastole, the part irritated always relaxes sooner, and
its diastole lasts longer than does that of the parts which were not stimulated.
If weak stimuli are allowed to act for a long time upon any part of the ventricle
of a frog's heart, the part so stimulated always relaxes sooner than the non-stimu-
lated parts, and its diastole is also prolonged.

Cardiac Poisons are those substances whose action is characterised by special
effects upon the movements of the heart. Amongst these are the neutral salts of
potash. [Until 1863 it was believed that these salts were just as slightly active on
the heart as the soda salts, but Bernard and Grandeau showed that very small
doses of these salts produced death, the heart standing 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.

As early as 1691, Clayton and Moulin showed the poisonous action of potassium
sulphate, and alum, as compared with the non-poisonous action of sodium chloride,
which was demonstrated by Courten in 1679. Anliar (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 unfre-
quently accelerate it — e.g., digitalis, morphia, nicotin. Others, when given in
small doses, accelerate ita action, and in large doses slow it — veratria, aconitin,
camphor.

NATURE OF A CARDIAC CONTRACTION. 109

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
accelerator 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 stimulates permanently the inhibitory ganglia, so that the heart
stands still (Schmiedeberg and Koppe). As atropin and daturin paralyse these
ganglia, the stand-still 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 muscarin be
removed, and a solution of atropine applied to the heart, it will resume its contrac-
tions after a short time.] Physostigmin [Calabar bean] excites the energy of the
cardiac muscle to such an extent, that stimulation of the vagus no longer causes
the heart to stand still. lodine-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 it contracts. [According
to Gaskell, antiarin aud 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 very dilute alkali solution, while the action of a blood solution
containing muscarin closely resembles that of a dilute acid solution (§ 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. This 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 preparation (" rheo-
scopic limb") 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 con-
tracted diaphragm gives a similar result. The question as to 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.]

The peripheral or extra-cardiac nerves will be discussed in connec-
tion with the Nervous System.

59, The 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,

110

THE CARDIO-PNEUMATIC MOVEMENT.

air must be drawn into the chest when the heart contracts ; whenever
the heart relaxes, i.e., during diastole, air must be expelled through the
open glottis. But we must also take into account the degree to which
the larger intrathoracic 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 C02 and 0 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 meiocardie, and the
subsequent increase of volume when the heart is distended to its
maximum, auxocardie.]

Method. — The cai'do-pneumatic movements — i.e., the movement of the respira-
tory gases dependent on the movements of the heart and great vessels — may be
demonstrated in animals and man. 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 a gas-jet. It is clear that the
movements of the heart will affect the column of gas, and thus affect the flame.
Large animals previously curarised are best. 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 till 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 movements of the column of smoke within the tube are obvious.]

Fig. 36.

Landois' cardio-pueumograph, 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.

Cardio-Pneumograph. — Ceradini employed a special instrument, while
Landoia uses his cardio-pneumograph which consists of a tube (D), about one inch

INFLUENCE OF RESPIRATORY PRESSURE ON THE HEART. Ill

in diameter and six to eight inches iu length; the tube is bent at a right angle,
and communicates with a small metal capsule about the size of a saucer (T), over
which a membrane composed of collodion and castor 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 (K) is
placed on the side of the tube (D), which enables the experimenter to breathe
when necessary. The tube (D) is held in an air-tight manner between the lips,
the nostrils being closed, the glottis open, and respiration stopped. Fig. 36,
A, B, C, are curves obtained in this way. In them we observe—

(a) At the moment of the first sound (1.), the respiratory gases undergo a sharp
expiratory movement, because at the moment of the first part of the ventricular
systole the blood of the ventricle has not left the thorax, while venous blood is
streaming into the right auricle through the venaa cav*, and because the dilating
branches of the pulmonary artery compress the 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 by (a)
the muscular mass of the ventricle occupying slightly less bulk during the contrac-
tion, and (/3) owing to the thoracic cavity being slightly increased by the fifth
intercostal space being pushed forward by the cardiac impulse.

(b) Immediately after (1. ), there follows a strong inspiratory current of the respira-
tory 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 vente cavae.

(c) After the second sound (at 2.), indicated sometimes by a slight depression in
the apex of the curve, the arterial blood accumulates, and hence there is another
expiratory movement in the curve.

(d) The peripheral wave-movements of the blood from the thorax cause another
inspiratory movement of the gases.

(e) More blood flows into the chest through the veins, and the next heart-beat
occurs.

60. Influence of the Respiratory Pressure on the
Dilatation and Contraction of the Heart.

The variation ia 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 move-
ments of the heart, as was proved by Carson in 1820, and by Donders
in 185 4. Examine first the relations in different passive conditions of
the thorax, when the glottis is open.

The diastolic dilatation of the cavities of the heart (excluding 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
cavities of the heart ; the heart in diastole is small and contains a small

112 VALSALVA AND MULLEIl's EXPERIMENTS.

amount of blood. Hence the systole must also be small, which further
gives rise to a small pulse-beat.

(2.) On taking the greatest possible inspiration, 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. (Bonders).
This force may act so energetically as to interfere with the contraction
of the thin-walled atria and appendices, in consequence of which these
cavities do not completely empty themselves into the ventricles. The
heart is in a state of great distension in diastole, and is filled with
blood ; nevertheless, in consequence of the limited action of the auricles,
only small pulse-beats are observed. In several individuals Bonders
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. — Bonders), we have the condi-
tion most favourable to the action of the heart — sufficient diastolic
dilatation of the cavities of the heart, as well as unhindered emptying
of them during systole.

A very important factor, is the influence exerted upon the action of
the heart, by the voluntary increase or diminution of the intra-thoracic
'pressure.

(1.) Valsalva's Experiment. — 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 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.
Hence the lungs and the heart contain little blood. Hence also there
is a greater supply of blood in the systemic than in the pulmonary
circulation and the heart. The heart-sounds disappear, and the pulse
is absent (E. H. Weber, Bonders).

(2.) J. Miiller's Experiment. — Conversely, if after the deepest pos-
sible 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 in the direction of the lungs.
More blood flows into the right heart, and in proportion as the right
auricle and ventricle can overcome the traction outwards, the blood-

INFLUENCE OF THE RESPIRATION ON THE HEART.

113

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 — i.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
supply of blood (and lymph) through the vena? cavae, and favours the
occurrence of diastole. 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
arrangement of the valves of the heart causes the blood to move in a
definite direction through it.

a

II

Fte .37.

Apparatus for demonstrating the action of inspiration, II, and expiration, I, on
the heart and on the blood-stream — P, p, lungs ; H, h, heart ; L, /, closed
glottis ; M, m, manometers ; E, e, ingoing blood-stream, vein ; A, a, outgoing
blood-stream, artery ; D, diaphragm during expiration ; d, during inspiration.

8

114 INFLUENCE OF THE RESPIRATION ON THE HEART.

The elastic traction of the lungs aids the lesser circulation through the
lungs within the chest; 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 (Bonders).

The above apparatus (Fig. 37) 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 mem-
brane, D, the diaphragm ; P, j>, the lungs ; L, the trachea supplied with a stop-coclc
to represent the glottis ; H, the heart ; E, the venas cavaj ; A, the aorta. If the
glottis be dosed, and the expiratory phase imitated by pushing up D as in I, the
air in P, P is compressed, the heart, H, is compressed, the venous valve closes,
the arterial is opened, and the fluid is driven out through A. The manometer,
M, indicates the intrathoracic pressure. If the glottis be closed, and the
inspiratory phase imitated, as in II, p, p and li are dilated, the venous valve
opens, the arterial valve closes ; hence, venous blood flows from e 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 L and /, be open, the air in P, 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,

61. The Flow of Fluids through Tubes.

Toricelli's Theorem (1643) states that the velocity of efflux (c) 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 out-
flow. If h be the height of the propelling force, the
velocity of efflux is given by the formula —

v = V 2 \ g h (where ;/ =; 9 '8 metre).

The rapidity of outflow increases (as shown experi-
mentally) with increase in the height of the propelling
force, Ji. The former occurs in the ratio, 1, 2, 3, when 7t
increases in the ratio, 1, 4, 9 — i. e., the velocity of efflux
is as the square root of the height of the propelling
force. Hence, it follows that the velocity of efflux
depends upon the height of the liquid above the orifice
of outflow, and not upon the nature of the fluid.

Resistance. — Toricelli's theorem, however, is only
valid when all resistance to the outflow is absent ; but,
in fact, in every physical experiment such resistance
exists. Hence, the propelling force, h, has not only to
cause the ffflux 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 oiitflow of the fluid. So that

h = F + D.

Fig. 38.

Cylindrical vessel filled
with water — h, height
of the column of fluid ;
D, height of column of
fluid requii-ed to over-
come the resistance ;
and F, height of
column of fluid caus-
ing the efflux.

62. Propelling Force— Velocity of the Current,
and Lateral Pressure.

In the case of a fluid flowing through a tube, which it fills completely, we have
to consider the propelling force, /«, 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, /, of the

116

FLOW OF FLUIDS THROUGH TUBES.

tube ; and (b.) from the quantity of fluid, q, which flows through the tube in
the unit of time. So that v = q : I. Both values, q as well as /, can be accurately
measured. (The circumference of a round tube, whose diameter = d is 3'14.rf.

3-14

The sectional area (lumen of the tube) is l=~- . d".) 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.e., the height from which a body must fall in vacuo,

V

in order to attain tlie velocity, r, In this case F - j— (where y = the distance

if

traversed by a falling body in 1 sec. = 4'9 metre).

A cylindrical vessel rilled with water — a, I, outflow tube, along which are
placed at intervals vertical tubes, 1, 2, 3, to estimate the pressure.

(2.) The pressure, D (amount of resistance), is measured directly by placing
manometers at different parts of the tube (Fig. 39).
ropelling force at any part of the tube is

or,

(Bonders).

This is proved experimentally by taking a tall cylindrical vessel, A, of sufficient
size, which is kept filled with water at a constant level, h. The outflow
rigid tube, a, b, has in connection with it a number of tubes placed vertically
1, 2, 3, constituting a piezometer. At the end of the tube, b, there is an opening
with a short tube fixed in it, from which the water issues to a constant height,
provided the level of h is kept constant. The height to which it rises depends on
the height of the column of fluid causing the velocity, F. As the pressure in the
manometric tubes, B1, B2, B3, can be read off directly, the propelling force of the
water at the sections of the tubes, I, II, III, is—

h = ¥ + B1 ;-F + B'-;-F + B3.

At the end of the tube, b, where B4 = 0, A = F + 0, i.e., /* = 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 part where the fluid passes out of the cylinder into the tube towards the
end of the tube, b. The water in the pressure-cylinder, falling from the height, ft,
only rises as high as F at b. This diminution of the propelling power is due to the

ESTIMATION OF RESISTANCE. 117

presence of RESISTANCES, which oppose the current in the tube, i.e., part of the
energy is transformed into heat. As the propelling power at b is represented only
by F, while in the vessel it is h, the difference must be due to the sum of the
resistances, D ~ h - F ; hence it follows that h — F -f D (Donders).

Estimation of Resistance.

Estimation Of the Resistance. — When a Huid flows through a tube of
uniform calibre the propelling force, k, diminishes from point to point on account
of the uniformly acting resistance, hence the sum of the resistances 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 h = F + D). Experiment with the pressure-cylinder shows, that as a matter
of fact, the pressure towards the outflow end of the tube becomes gradually
diminished.

In 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 (Girard, Poiseuille). 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 with each other, the greater will be the resistance, and vice
versa. Hence, the sticky blood-current experiences greater resistance than water
or ether.

Heat diminishes the cohesion of the particles, hence it also diminishes the resistance
to the flow of a current. 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, therefore, i.e., the larger the number of
particles of fluid which are pulled asunder in the unit of time, the greater will he
the sum of the resistance. As already mentioned, the layer of fluid lying next the
tube, and moistening it, is at rest, hence the material which composes the tube
exerts no influence on the resistance.

Effect of Tubes of Unequal Calibre,

Unequal Diameter.— When the velocity of the current is uniform, the resis-
tance 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 experimentally.

In tubes of unequal calibre, at different parts of their course, the velocity of the
current varies — it is slower in the wide part of the tube and more rapid in the

118 CURRENTS THROUGH CAPILLARY TUBES.

narrow parts. As a general rule, in tubes of unequal diameter the velocity of
the current is inversely proportional to the diameter of the corresponding section
of the tube; i.e., 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 unequal 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, withiu 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 conversely 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). If a branch be opened
from a tube, the principal current is accelerated to a considerable extent, no
matter at what angle the branch may be given off.

63. Currents through 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 pro-
portional 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.

(3.) The product of the outflow (other things being equal) is as the fourth power
of the diameter.

(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. Movement of Fluids and Wave-Motion in

Elastic Tubes.

(1.) When an uninterrupted uniform current flows through an elastic tube, it
follows exactly the same laws as if the tube had rigid walls. If the propelling
power increases or diminishes, the elastic tubes become wider or narrower, and
they behave, as far as the movement of the fluid is concerned, as wider or narrower
rigid tubes.

MOVEMENT OF FLUIDS IN ELASTIC TUBES. 119

(2.) Wave-Motion. — If» however, more fluid be forced in jerks into an elastic
tube, i.e., interruptedly — 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 disappears. 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 translation 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 dis-
tinguish the movement of the current of the fluid, 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 continual movement, directed from the aorta to the capillaries
(movement of the current of blood) ; by means of the systole of the left ventricle
a quantity of fluid is suddenly pumped into the aorta, and causes a positive wave
(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. — It is of importance to contrast the movement
of fluids in rigid and in elastic tubes. If a certain 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 re-
sistance. In an elastic, tube, immediately after the forcing in of a certain
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 duration
of the outflow after the jerk has been completed. When fluid is pumped
periodically into rigid tubes, it causes a sharp abrupt outflow isochronous with
the inflow, and the outflow becomes continuous only when the inflow is
continuous and uninterrupted. In elastic tubes, an intermittent current under
the above conditions causes a continuous outflow which is increased with the
systole or contraction.

65. Structure and Properties of the Blood- Vessels.

In the body the large vessels carry the blood to and from the various
tissues and organs, while the thin-walled capillaries bring the blood into

120

STRUCTURE OF ARTERIES.

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 an exchange between the blood
and the fluids of the tissues. The fluid after it passes into the tissues
constitutes the lymph, and acts like a stream irrigating 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.]

The arteries consist of three coats
(Fig. 40). (1.) The Tunica intima,
or inner coat, consists of a layer of
(a) irregular, long, fusiform nucleated
squamous cells forming the exces-
sively thin transparent endothelium
(His, 1866), 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
hit/cr — 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
jg a structureless Or fibrous

d

Fig. 40.

Small artery to show the various

layers which compose its walls — . .

«, endothelium; b, internal elastic elasticmembranc— in artenesof medium

lamina; c, circular muscular fibres see it isafcnestrated membrane (Henle),

of the middle coat ;</, the connective while in the largest arteries there may

tissue outer coat (T. adventitia). , , , i , • i

be several layers 01 elastic laminae or

fenestrated elastic membrane mixed with connective tissue. [In some
arteries the elastic membrane is distinctly fibrous, the fibres being
chiefly arranged longitudinally. It may 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 curves are probably produced

STRUCTURE OF ARTERIES. 121

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 kncjitudinally between two elastic plates or lamina? (K.
Bardeleben). 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. It
is not probable that when they act by themselves they dilate the
vessel.

(2.) The Tunica media, or middle coat, contains much non-striped
muscle (c), which in the smallest arteries consist 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 laminoe are concentrically
arranged.

A few non-striped fibres lie scattered amongst these, and some of
them are arranged transversely, while a few have an oblique or longi-
tudinal 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 longi-
tudinal 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 umbilical arteries, which
are very muscular.

(3.) The Tunica adventitia, or outer coat, in the smallest arteries
consists of a structureless 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 ((/). In arteries of middle size, and in the largest arteries the
chief mass consists of bundles of fibrillar connective tissue containing
connective tissue corpuscles. The bundles cross each other in a variety
of directions, and fat cells often lie between them. Next the media
there are numerous fibrous or fenestrated elastic lamellae. In medium
sized and small arteries the elastic tissue next the media takes the
form of an independent elastic membrane (Henle's external elastic

122

STRUCTURE OF CAPILLARIES.

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, hypogas-
tric, and superior mesen-
teric arteries.

II. The Capillaries, while
retaining their diameter,
divide and reunite so as
to form net-works, whose
shape and arrangement
differ considerably in dif-
ferent tissues. The diame-
ter of the capillaries varies
considerably, but as a

Capillaries-The outlines of the endothelial cells general rllle> ifc is Sllch as
marked off from each other by the cement
which is blackened by the action of silver
nitrate. The nuclei of the cells are obvious.

Fig. 41.

to admit freely a single
row of blood-corpuscles.
In the retina and muscle
the diameter is 5 — 6 JUL, and in bone-marrow, liver, and choroid
10—20 /a. The tubes consist of a single layer of transparent, ex-
cessively thin nucleated endothelial cells joined to each other by their
margins (Hoyer, Auerbach, Eberth, Aeby, 1865).

[The nuclei contain a Avell-marked intra-nuclear plexus of fibrils,
like other nuclei.] The cells are more fusiform in the smaller capil-
laries 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.

Action of Silver Nitrate. —If a dilute solution (| per cent.) of
silver nitrate be injected into the blood-vessels, the cement substance
of the epithelium [and of the muscular fibres as well] is revealed by
the presence of the black " silver-lines" The blackened cement sub-
stance shows little specks and large black slits at different points.
It is not certain whether these are actual holes (J. Arnold) through
which colourless corpuscles may pass out of the vessels, or are merely
larger accumulations of the cement substance.

[Arnold called these small areas in the black silver lines when they were large
stomata, and when small stigmata. They are most numerous after venous
congestion, and after the disturbances which follow inflammation of a part
(Cohnheim, Winiwarter). They are not always present. The existence of cement
substance between the cells may also be inferred from the fact that indigo-

STRUCTURE OF VEINS.

123

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-medullated NERVES
terminate in small end-buds in relation with the capillary wall;
ganglia in connection with capillary nerves occur only in the region
of the sympathetic (Bremer and Waldeyer).

[If a capillary is examined in a perfectly 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.]

The small vessels next in size to the capillaries and continuous
with them have -a completely
structureless covering in addition
to the eudothelium.

III. The Veins are generally
distinguished from the arteries by
their lumen being under 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 longi-
tudinally 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. (1.) The inttma consists
of a layer of shorter and broader
endothelial cells, under which in
the smallest veins there is a
structureless elastic membrane,
sub-epithelial layer, which is fibrous
in veins somewhat larger in size,
but in all cases is thinner than in
the arteries. In large veins it
may assume the characters of a
fenestrated membrane, which is

Fig. 42.

Longitudinal section of a vein at the
level of a valve— a, hyaline layer of
the internal coat; b, elastic lamina;
c, groups of smooth muscular fibres
divided transversely; d, longitudinal
muscular fibres in the adventitia.

double in some parts of the

crural and iliac veins. Isolated muscular fibres exist in the intima

of the femoral and popliteal veins.

124 STRUCTURE OF VEINS.

(2.) The media of the larger veins consists of alternate layers of
elastic and muscular tissue united to each by a considerable amount of
connective tissue, but this coat is always thinner than in the corres-
ponding arteries. This coat diminishes in the following order in
the following vessels — popliteal, veins of the lower extremity, veins
of the upper extremity, superior mesenteric, other abdominal veins,
hepatic, pulmonary, and coronary veins. The following veins contain
no muscle — veins of bone, central nervous system, and its membranes,
retina, the superior cava, with the large trunks that open into it,
the upper part of the inferior cava. Of course, in these cases, 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 adventilia is thicker than that of the corresponding
arteries; it contains much connective tissue usually arranged longi-
tudinally, 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 net-
work exists on their convex surface, and both surfaces are covered
by endothelium. The valves contain many muscular fibres (Fig. 42).
[Ranvier has shown that the shape of the epithelial cells covering
the two surfaces of the valves differs. On the side over which the
blood passes, they are more elongated than on the cardiac side of
the valve, where the long axes of the cell 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 anasto-
moses 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 (Luschka).
This structure is richly supplied with sympathetic nerve-fibres, and is a
convoluted mass of ampullated or fusiform dilatations of the middle
sacral artery (Arnold), surrounded and permeated by non-striped
muscle (Eberth).

Vasa Vasorum. — [These are small vessels which nourish the coats of the
arteries and veins. They arise from one part of a vessel and enter the walls of

PHYSICAL PROPERTIES OF THE BLOOD-VESSELS. 125

the same vessel, or another 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, and the blood circulating in the arterial or venous wall is returned
by small veins.

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 plain muscular fibres, and the whole is lined
by a smooth layer of epithelium. One of the most important properties
is the CONTRACTILITY of the vascular wall, in virtue of which the
blood-vessel becomes contracted, so that the calibre of the vessel and,
therefore, the supply of blood to a part are 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 (J. Hunter) acting upon the muscular fibres.]

[Action of Alkalies and Acids on the Vascular System.— Gaskell finds

that very dilute alkalies and acids have a remarkable effect on the blood-vessels
and also upon the heart. A very dilute solution of lactic acid (1 part to 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 or 20,000 parts 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. Microscopic observations which con-
firmed these results, were also made on the blood-vessels of the mylohyoid muscle
of the frog. Dilute alkaline solutions act on the heart in the same way. After
a series of beats, the ventricle stops beating, the stand-still being in a state of con-
traction. Very dilute lactic acid causes the ventricle to stand still in the position
of complete relaxation. The action of the acid and alkali solutions are antagonistic
in their action on the ventricle. Gaskell attaches considerable importance to the
" tonic " and " atonic " conditions of the whole vascular system produced by very
dilute solutions of alkalies and acids respectively.]

That the capillaries undergo dilatation and contraction, owing to
variations in size of the protoplasmic elements of their walls, must be
admitted.

Strieker has described capillaries as "protoplasm in tubes," and observed that
they exhibited movements when stimulated in living animals. Golubew described
an active state of contraction of the capillary wall, but he regarded the nuclei as

126 PHYSICAL PROPERTIES OF THE BLOOD-VESSELS.

the parts which underwent change. 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.] Strieker's observations were made on the
capillaries of tadpoles. These phenomena became less marked as the animal
became older. Rouget observed the same result in the capillaries of new-born
mammals. As the capillaries are excessively thin and delicate, and as they are
soft structures, it is obvious that the form of the individual cells must depend to a
considerable extent upon the degree to which the vessels are tilled with blood. In
vessels which are distended with blood the eudothelial cells ai-e flattened, but when
the capillaries are collapsed, they project more or less into the lumen of the vessel
(Reuaut).

[It is a well-known fact 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 pres-
sure 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" (Roy and Graham Brown).]

Physical Properties. — Amongst the physical properties of the blood-
vessels, ELASTICITY is the most important ; their elasticity is small in
amount, i.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.

[The elasticity of the arteries is of the utmost importance in aiding the conversion
of the interrupted flow 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 intermittent.]

According to E. H. Weber, Volkmann, and Wertheim, the elongation of a blood-
vessel (and most moist tissues) 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 occurs during the last few moments occurs so
slowly and so gradually that it is well to observe the effect by means of a magni-
fying lens. Variations from the general law occur to this extent, that if a certain
weight is exceeded, less extension, and, it may be, permanent elongation of the
artery not unfrequently occur. K. Bardelebeu 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

THE PULSE. 127

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.

[Roy has made careful experiments 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 inclosed in a small vessel containing olive oil. The small vessel with
oil was arranged in the same way as in Fig. 33 for the heart. The variations of
the contents were recorded by means of a lever writing on a revolving cylinder.
The aorta and other large arteries were found to be most elastic and most distensible
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 clistensibility occurs with pressures imme-
diately 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 2UO mm. Hg., while that of the carotid was more than six times as great
at that pressure as 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 (Roy).]

Pathological. — Interference with the nutrition of an artery alters its elasticity
[and that in cases where no structural changes can be found]. Marasmus pre-
ceding death causes the arteries to become wider than normal (Roy). Age also
influences their elasticity — in some old people they become atheromatous and
even calcined. [The ratio of expansion of strips of the aortic wall to the weights
employed to stretch them, remains much the same from childhood up to a certain
age (Roy).]

Cohesion. — Blood-vessels are endowed with a very large amount of
cohesion, in virtue of which 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). A greater pressure is required to rupture a
vein than an artery with the same thickness of its wall.

66. The Pulse—Historical.

Although the movement of the pulse in the superficially placed arteries was
known to the ancients, still the pulse, as it was affected by disease, was more
studied by the older physicians than the normal pulse. Hippocrates (460 to 377
B.C.) speaks of the former as o-^uyuos, while Herophilus (300 B.C.) contrasted the
normal pulse (TraX/uos) with the pulse of disease (o-^uyjuos). He lays special stress
upon the relative time occupied by the dilatation and contraction of the arterial
tube, and compares these phenomena with the notes of music. He established the
fact that the rhythm of the pulse varies in the newly-born, in the adult, and in
the aged. Further, he distinguished the size, fulness, quickness, and. frequency of
the pulse. Erasistratus (f280 B.C.), a contemporary of Herophilus, made correct

128

INSTRUMENTS FOR INVESTIGATING THE PULSE.

observations on the pulse-wave. He points out that the pulse occurs sooner in
arteries near the heart than in those placed further away from it, because the pulse
proceeding from the heart passes towards the periphery. Erasistratus placed a
caunula in the course of an artery, and he found that the pulse could still be felt
on the distal side of this point. Archigenes gave the name dicrotic pulse to a
condition which he had observed in febrile conditions. Galen (131 to 202 A.D. )
gave more exact details as to the relations of the dilatation and contraction of the
arteries during the movement of the pulse, and supplied much information on the
pulse-rhythm, and the influence of temperament, age, sex, period of the year,
climate, sleep and waking, cold and warm baths, on its rate and other qualities.
Cusanus (15C5) was the first person to count the pulse-beats with the aid of a
watch.

67. Instruments for Investigating the Pulse.

The individual phases of the movement of the pulse could only be
accurately investigated by the application of instruments to the arteries.

(1.) Poiseilille's BOX Pulse-Measurer (1829).— An artery (Fig. 43, a, a) is
exposed and placed in an oblong box (K, K) rilled 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.

Fig. 43.

Poiseuille's pulse-measurer — a, a, exposed artery ; K, K, the
box consisting of two pieces ; b, vertical tube, with scale
attached.

Fig. 44.

Xphygmometer of
HeVisson and
Chelius.

(2.) He"risson's Tubular Sphygmometer consisted of a glass-tube whose

lower end was covered with an elastic membrane (Fig. 44). The tube was partly
rilled with Hg. The membrane was placed over the position of a pulsating artery,
so that its beat caused a movement in the Hg. Chelius used a similar instrument,

MAREY'S SPHYGMOGRAPH. 129

and he succeeded with this instrument in showing the existence of the double-
beat (dicrotism) in the normal pulse (1850).

(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 lever. Upon the artery rested a small pad, which
moved a complicated system of levers. At first he used a straw six 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. It consists of an elastic spring (Fig. 45, A)
fixed at one end, 2, 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, k, which is pressed upon by a weak spring, e, so that its teeth
dove-tail with similar teeth in the small wheel, t, from whose axis
there projects a long, light, wooden lever, v, running nearly parallel
with the elastic spring. This lever has 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.

*

V

J

P

JH

S

d^=. ^ . r^

u

Fig. 45.

Scheme of Marey's sphygmograph— A, spring with ivory pad, y, which rests on
the artery ; e, weak spring pressing k into t ; v, writing lever ; P, piece of
smoked glass or paper moved by clock-work, U ; H, screw to limit excursion
of A ; s, arrangement for fixing the instrument to the arm of the patient,

[Its more complete form, as in Fig. 46, 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 exact pressure exerted upon the
artery is indicated on the dial, M (Mahomed) ; (4.) the clock-work, H, which
moves the smoked paper, G, at a uniform rate ; (5.) a frame-work to which the
various parts of the instrument are attached, and by means of which the instru-
ment is fastened to the arm by the straps, K, K (Byrom Bramwell).

[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. 46). In
the newer form of instrument, 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. See that the clock-work is wound up, and apply the

9

130

MAREY'S SPHYGMOGRAPH.

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 (Fig. 46). Fix the slide holding the smoked
paper in position. The best paper to use is that with a very smooth surface
(albuminised or enamelled card) smoked over the flame of a turpentine lamp, or
over a piece of burning camphor. The writing-style is so arranged as to write
upon the smoked paper with the least possible friction. The most important part

Fig. 46.

Marey's improved sphygmograph as used when a tracing is taken — 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, screw for increasing the pressure ; M, dial indicating the amount of
pressure ; K. K, straps for fixing the instrument to the arm, and the arm to
the double-inclined plane or support (Byrom Bramwell).

of the process is to regulate the pressure exerted upon the 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 — c.y., photographic. In every
case scratch on the tracing with a needle the name, date, and amount of pressure
employed.]

Fig. 47.

A1

Fig. 48.

- 47. — Scheme showing the essential part of the instrument wlien in workincj
order — i.e., the turned up knife-edge, B", of the short lever in contact with
the writing lever, C. Every movement of the steel spring at A" — i.e., the
artery — will in this position be communicated to the writing lever.

[Fig. 48. — Scheme showing the essential parts of the instrument after increase of
the pressure. The knife-edge, B", is no longer in contact with the writing
lever, and the movements of the steel spring, A" — i.e., the artery — are no
longer communicated to it. In order to put the instrument into working
order, the knife-edge, B", must be raised to the position indicated by the
dotted lines. This is effected by means of the screw, D (Byrom Bramwell).]

DUDGEON S SPHYGMOGRAPH.

131

[(5.) Dudgeon's Sphygmograph. — This is a most convenient form of
sphygmograph. Fig. 49 shows its actual size.

Fig. 49.— Dudgeon's sphygmograph.

The instrument after being carefully adjusted 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.

Fig. 50. — Mode of applying Dudgeon's sphygmograph.

132

BRONDGEEST'S PANSPHYGMOGRAPH.

As in other instruments, 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. 51 is a sphygmogram taken
with this instrument from a
healthy individual. It represents
a perfect tracing — a. the vertical
upward, systolic or percussion
wave ; b, apex ; c, on the
descent ; d, first tidal or pre-
dicrotic wave; e, aortic notch ;
Fig. 51. — Sphygmogram — pressure 2 oz. /, dicrotic wave (Dudgeon).]

(6.) Marey's Tambours are also employed for registering the move-
ments of the pulse. They are used in the same way as the pansphygmograph
of Brondgeest. Fig. 52 shows their arrangement. Two pairs of metallic
cups (S, S and S', S', Upham's capsules) are pierced in the middle by

Z'

Fig. 52.

Scheme of Brondgeest's sphygmograph, on the principle of Upham and Marey's
tambours— 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.
This illustration also shows the principle of Marey's cardiograph.

thin metal tubes, whose free-ends are connected 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 p',
which are applied to the pulsating arteries, and the metal arcs, B and

LANDOIS ANGIOGRAPH.

133

B', retain them in position. On the other tambours are arranged the
writing levers, Z and 71. 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 used and is con-
venient. In Fig. 52 a double
arrangement is shown, where-
by one instrument, B, may
be placed over the heart, and
the other, B', on a distant
artery.

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, r, carrying a rod bearing a
pad, e, directed downwards,
which rests on the pulse.
The short arm carries a coun-
terpoise, d, so 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 /, which
is supported between two up-
rights, q, fixed to the opposite
end of the basal plate, G, G.
The writing-lever is equilibri-
ated by means of a light
weight. The writing-needle,
k, is fixed by a joint to e, and
it writes on the plate, /. The
first - mentioned lever, d, r,
carries a shallow plate, Q, just
above the pad, into which
weights may be put to weight
the pulse. In this instrument
the weight can be measured
and varied] the writing-lever moves vertically and not in a curve

134

CHARACTERS OF A PULSE-CURVE.

as iii Marey's apparatus, which greatly facilitates the measuring of
the curves. (Fig. 53.)

Other sphygmographs are used, botli in this country and abroad, including that
of Sommerbrodt, which is a complicated form of Marey's sphygmograph, and
those of Pond and Mach. In choosing a sphygmograph, that instrument is to be
preferred which yields a curve corresponding most closely with the variations of

the pressure within the artery, in
which the resistance of the instrument
is small, which gives the largest curve,
and in which the part in contact with
the artery is not greatly displaced
from its position of equilibrium
(Mach).

Characters of a Pulse-Curve. —
In every pulse-curve — SPHYGMO
GRAM 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 occur
constantly in the descent. Such
elevations occurring in the de-
scent are called catacrotic, and
those in the ascent, anacrotic
(Landois). 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 on which the tracing
is inscribed is moved at a uniform
rate by means of the clock-work,
then the height and length of the
curve are measured by means of an
ordinary rule. If we know the rate
at which the paper was moved, then
it is easy to calculate the duration of
any event in the curve. For exact
observation a low -power microscope
with a micrometer in the eye-piece
should be used,
fixing the tracings see p, 130.

Fig. 54.

Pulse-curves of the carotid, radial, and
posterial tibial arteries of a healthy
student, obtained by Landois' angio-
graph writing upon a plate attached
to a vibrating tuning-fork. Each
double vibration corresponds to
0-01613 sec.

For the method of smoking the paper and

LANDOIS' GAS-SPHYGMOSCOPE.

135

It is very convenient to write the curve upon 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. 54 was taken in this way from (A) the carotid, (B) the radial,
and (C) the posterior tibial arteries of a healthy student. The results

are : —

1-2,
1-3,

1-4,
1-5,

Carotid.

7
17

23-5
56

Radial.

7

16
22-5
39

Posterior
TibiaL

8
19
28
49

This method has also been used for the registration of other physiological
processes — e.g., contraction of muscle.

Landois Gas-SphyglUOSCOpe. — A superficially placed artery communicates its
movements to the overlying skin, and also to any freely movable body in contact
with the skin. In this instrument (Fig. 55) a thin layer of air over the pulsating
artery, a, is enclosed by means of a thin piece of metal, which ia so adjusted that
its concave side forms a tunnel of air over the artery. The narrow space between
the metallic wall, b, and the skin, a, is filled with ordinary gas, one end of the
metal shield being connected by means of a tube, y, with the gas-supply, while to
the other end there is attached by means of a short piece of caoutchouc, x, q, a
bent glass-tube, t, with a very small aperture which acts as a gas-burner. The
gas is allowed to flow through the apparatus at a low pressure, and is so regulated
that the flame, v, is only a few millimetres in height. The flame rises isochron-
ously with every pulse-beat, and the dicrotic beat in the normal pulse is quite
observable.

Fig. 55.

Landois' gas-sphygmoscope — a, skin over artery ; b, metal plate ; p, y, gas ;
x, q, caoutchouc tube attaching glass gas-burner, t to b.

Czermak photographed a beam of light set in motion by the movements of the
pulse.

Hsemautography. — 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

136

THE PULSE-CURVE.

of the blood-stream. A curve (Fig

Fig. 56.

Htemautographic curve of the pos-
terior tibial artery of a large dog
— P, primary pulse wave ; R,
dicrotic or recoil wave ; e, e,
elevations due to elasticity.

56), is obtained which corresponds very closely
with the pulse-tracing obtained from a normal
artery. In addition to the primary wave, P,
there is a distinct " recoil-elevation," or
dicrotic wave, R, and slight vibrations, c, e,
due to variations in the elasticity of the
arterial wall. The interest which attaches to
a curve obtained in this way is, that it shows
the movements to occur in the blood itself,
and these movements to be communicated
as waves to the arterial wall. By estimat-
ing the amount of blood in the various parts
of the ciirve we obtain a knowledge of the
amount of blood discharged by the divided
artery during the systole and diastole (i.e.,
the narrowing and dilatation) of the artery—
the ratio is 7:10. Thus in the unit of time,
during arterial dilatation rather more than
twice as much blood flows out as happens
during arterial contraction.

Microphone- — Fix a small piece of wax
over the radial artery, and to it attach a very
fine vertical wire which is brought into con-
tact with the charcoal of a microphone held
over the artery. The primary pulse wave
and dicrotic wave are distinctly heard in a
telephone brought into connection with the
microphone (Landois). All these methods
are well suited for demonstrating the pulse,
but for accuracy resort must be had to some
form of recording instrument.

68. The Pulse-Curve or Sphygmogram.

A sphygmogram consists of several curves, each one of which corre-
sponds with a beat of the heart. Each pulse-curve consists of (1.) the
ascending part which occurs during the dilatation (diastole) of the
artery; (2.) the apex, (P in Fig. 58 and b in Fig. 57); (3.) the de-
scending part, corresponding to the contraction (systole) of the artery.
The most noticeable peculiarity of the pulse-curve is the existence
of tico completely distinct elevations occurring in the descent. The more
distinct of the two occurs as a well-marked elevation about the
middle of the descent (R in Fig. 58 and / in Fig. 57); it is called the
DICROTIC WAVE, or with reference to its mode of origin, the " recoil
wave" The ascent, also called up-stroke or percussion stroke
(Mahomed), in a normal sphygmogram, is nearly vertical, while the
apex of the percussion stroke is usually pointed.

[In Fig. 57, each part of the curve between the base of one up-

ORIGIN AND CHARACTERS OF THE DICROTIC WAVE. 137

stroke and the base of the next up-stroke corresponds to a beat of the
heart, so that this figure
shows five heart-beats and
part of a sixth. The part,
a, b = the ascent, i, the
apex of the up-stroke, and
b to h, the descent, with a
curve, d, called the first

tidal or predicrotic wave, Sphygmogram of radial artery— pressure 2 oz.
e, an angle or notch, the
aortic notch, /, a second elevation, called the dicrotic wave, </, a slight
curve, sometimes called the second tidal wave. The descent is con-
tinued to h, where the ascent of the next heart-beat begins.]

I. Origin and Characters 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, in which this primary wav». 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 developes a new positive wave, which is pro-
pagated 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 wave of reflec-
tion 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.

138

CHARACTERS OF THE DICROTIC WAVE.

The following points regarding the dicrotic wave have been ascer-
tained experimentally : —

xn

XIII

Fig. 58.

I, II, III, Sphygrnogram of carotid artery ; IV, axillary ; V to IX, radial ;
X, dicrotic radial pulse ; XI, XII, crural ; XIII, posterior tibial ; XIV,
XV, pedal. In all the curves— P, indicates apex ; R, dicrotic wave ; e, e,
elevations due to elasticity; K, elevation caused by closure of the semi-lunar
valves of the aorta.

(1.) The dicrotic wave occurs later in the descending part of the

ORIGIN AND CHARACTERISTICS OF THE ELASTIC ELEVATIONS. 1 39

curve, the further the artery experimented upon is distant from the
heart (Landois, 1863). Compare the curves, Fig. 54, p. 134.

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 occurs 0'45 to 0'52 to 0'59 sec.
after the base of the curve. It varies with the height of the individual.

(2.) The dicrotic elevation in the descent is lower (Naumann), and
is less distinct (Landois), the further the artery is situated from the
heart. This is just what one would expect — viz., the longer the
distance which the wave has to travel the less distinct it must become.

(3). It is more pronounced in a pulse where the primary pulse-wave
is short and energetic (Marey, Landois). It is greatest relatively
when the systole of the heart is short and energetic.

(4.) It is greater the lower the tension or pressure of the blood
within the arteries (Marey, Landois), [and is best developed in a soft
pulse]. In Fig. 58, IX and X were obtained when the tension of the
arterial wall was low; V and VI, medium; and VII with high tension.

Conditions Influencing Arterial Tension.— It is diminished at the beginning
of inspiration, by haemorrhage, stoppage of the heart, heat, an elevated position of
parts of the body ; it is increased at the 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 (Knecht) ; further, by certain
poisons, as lead, amyl nitrite ; compression of other large arterial trunks, action of
cold and electricity on the small cutaneous vessels, and 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 conditions the arterial tension is greatly increased — [e.g., in Bright'a
disease, where the kidney is contracted ("granular"), and where the left ventricle
is hypertrophied].

In all these conditions increased arterial tension is indicated 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, with diminution of its thickness, and when ita
coefficient of elasticity diminishes.

II. Origin and Characteristics of the Elastic

Elevations.

Besides the dicrotic wave, a number of small less-marked elevations
occur in the course of the descent in a sphygmogram (Fig. 58, e, e).
These elevations are caused by the elastic tube being thrown into
vibrations by the rapid energetic pulse- wave, just as an elastic mem-
brane vibrates when it is suddenly stretched. The artery also executes

140 DICROTIC PULSE.

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 their 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 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 rive 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, a dicrotic pulse
may be felt, each pulse-beat, as it were, being composed of two beats (Fig. 58, X),

Fig. 59.
Pulsus dicrotus — P. caprizans ; P. monocrotus. '

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

CHARACTERS OF THE PULSE. 141

in a normal pulse. The sensible 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 a
diminished tension within the arterial system. A short systole and diminished
arterial blood-pressure are the most favourable conditions for causing a dicrotic
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 the 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 compressing 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 dis-
tended, and the heart-beat is shorter and more prompt (Riegel).

(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
(Landois). In Fig. 59, A, B, C, we observe the gradual passage of the normal
radial curve, A, into the dicrotic beat, B, C, where the dicrotic wave, r, appears
as an independent 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, i, between the
primary elevation, p, and the dicrotic elevation, r, the latter entirely dis-
appears, and the curves, H, assume what Landois calls the " monocrotic " type.

70. Characters of the Pulse.

1. Pulsus Frequens and Rarus.

Frequency. — According as a greater or less number of beats occurs in a given
time, e.g., per minute, the pulse is said to be frequent or rare. 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 (cle Haen), 17 (Hartog), and 14 (Cornil) ; but such
cases are rare, and are probably due to an affection of the cardiac nerves. The
frequency of the pulse is usually increased when the respirations are deeper, but
not more numerous, i.e., rapid shallow respirations do not affect the frequency of
the pulse, but deep respirations do (Knoll).

2. Pulsus Celer and Tardus.

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 pulse, the opposite condition gives rise to the p.
celer or quick 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.

142

CONDITIONS AFFECTING THE PULSE-RATE.

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 be higher
(90 to 100), in others lower (50), and such a fact must be borne in mind. The
following conditions influence it—

(a.) Age.

Newly Born,

1 Year,

2 Years,

3 „

4 „

5 „
10

Beats per
Minute.

130 to 140

120 to 130

105

100
97

94 to 90
about 90

10 to 15 Years,

15 to 20 ,,

20 to 25 ,,

25 to 50 „

60

SO

80 to 90

Beats per
Minute.

. 78

. 70

. 70

. 70

. 74

. 79

over 80

(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 formula?
of Volkmann and Kameaux —

Length of Body
in 10 Ctm.

80 to 90 .

90 to 100 .

100 to 110 .

110 to 120 .

120 to 130 .
130 to 140

Pulse
Calculated. Observed.

Length of Body
in 10 Ctm.

. 90

103

140 to 150 .

. 86

91

150 to 160 .

. 81

87

160 to 170 .

. 78

84

170 to 180 .

. 75

78

above ISO .

. 72

76

Pulse.
Calculated. Observed.

69
67
65
63
60

74
68
65
64
60

(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, and by
psychical disturbances. [Increased heat or fever (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.
no°

• 'O .....

99°

100° . . .

101°

102°

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 (Dogiel). Exposure to increased barometric
pressure diminishes the frequency.

The variation of the. pulse-rate during the day— 3 to 6 a.m. =61 beats ; 8 to 11 £
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 mid-
night =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.

Temp. F.

Pulse-Rate.

60

103°

. 110

70

104°

. 120

80

105°

. 130

90

106°

. 140

100

4. Variations in the Pulse-Rhythm.

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; at other times the beats become

VARIATIONS IN THE STRENGTH, TENSION, AND VOLUME OF THE PULSE. 143

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 (Traube). In the
P. bigeminus of Traube the beats occur in pairs, so that there is a longer pause

Fig. 60.
Pulsus alternans.

after every two beats. Traube found that lie could produce this form of pulse in
curarised dogs by stopping the artificial respiration for a long time. The P. frige-
minus and quadrigcminus 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 great 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 corclis.

71. Variations in the Strength, Tension, and
Volume of the Pulse.

The relative strength of the pulse (p. fortis and debilis), i.e., whether the pulse
is strong or ivealc, 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 npon the artery, may be used (Fig. 46). 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 puke.
[The ringer 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 requires 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, i.e., whether it is hard
or soft, it is important to observe whether the artery has this quality only during
the pulse- wave, i.e., 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

144 THE PULSE-CURVES OF VARIOUS ARTERIES.

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 incom-
petency of the 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. "]

Under similar conditions, the volume of the pulse is obvious from the size of
the sphygmogram, 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 hyper-
trophy of the left ventricle, a large amount of blood is forced into the aorta. A
small 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, or from disease of the mitral valve ; again,
where the ventricle contracts feebly, the pulse becomes small and thready.
Sometimes the pulse differs on the two sides, or it may be absent on one side.

Waldenburg constructed a "pulse-clock " to register the tension, the diameter
of the artery, and the volume of the pulse upon a dial. It does not give a graphic
tracing, the results being marked by the position of an indicator.

72. The Pulse-Curves of Various Arteries.

1. Carotid (Fig. 54, A.; Fig. 58, 1, II, III ; Fig. 64, C and C,).

The ascending part is very steep — the apex of the curve (Fig. 58, P)
is sharp and high. Below the apex there is a small notch — the
"AORTIC NOTCH" (Fig. 58, K) — which depends 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 (Fig.
58, II, e). Above the middle of the descending part of the curve is the
dicrotic elevation, E, produced by the reflection of a positive wave
from the already closed semi-lunar valves. The dicrotic wave is rela-
tively 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 wave — (Fig. 58, III, R), (Landois,
Moens). Here there is a true tricrotism, which is more easily obtained
from the carotid on account of the shortness of the arterial channel.

Moens describes the "aortic elevation" as occurring at the moment of the
closure of the aortic valves.

2. Axillary Artery (Fig. 58, 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

PULSE-CURVES OF VARIOUS ARTERIES. 145

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, e, e.

3. Radial Artery (Fig. 54, B; Fig. 58, V-X; Fig. 64, R and R,).

The line of ascent (Fig. 58) is tolerably high and sudden — some-
what in the form of a long/. The apex, P, is well marked. Below
this, if the tension be high, two elastic vibrations may occur (V, e, e), but
if it be low, only one (VI to IX, e). 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 distended (Fig. 58, VII, Rj); it is larger when the
tension is low (Fig. 56, IX, R), and is greatest of all when the
pulse is dicrotic (X, R). Two or three small elastic elevations occur
in the lowest part of the curve.

4. Femoral Artery (Fig. 58, XI, XII).

The ascent is steep and high — the apex of the curve is not unfre-
quently broad, and in it the closure of the aortic valves (K) is
indicated. The curve falls rapidly towards its lower third. The
dicrotic elevation, R, occurs late after the beginning of the curve, and
there are also small elastic elevations (e, e).

5. Pedal Artery (Fig. 58, XIV, XV), and Posterior Tibial
(Fig. 54, C, and Fig. 58, XIII).

In pulse-curves obtained from these arteries, there are well-marked
indications that the apparatus (heart) producing the waves is placed at

Fig. 61.

A, curve of posterior tibial, and B, pedal artery of a man. Curves written by the
angiograph upon a vibrating plate attached to a tuning-fork.

a considerable distance. The ascent is oblique and low — the dicotric
elevation occurs late. Two elastic vibrations (Fig. 58, XIV, e, e) occur

10

1 vibration is
= 0-01613 sec.

146 ANACROTISM.

in the descent, but they occur very close to the apex, while the elastic
vibrations at the lower part of the curve are feebly marked. In
Fig. 61, A is from the posterior tibial, and B from the pedal artery
of the same individual. When measured, they give the following

result : —

A B

1—2 . . .9-59

1—3 . . . 20 20

1—4 . . . 30-5 32

1-6 . . 61 62-5

73. Anacrotism.

As a general rule, the line of ascent of a pulse-curve has the form of an /, 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 sphyg-
mogram, usually occurs so rapidly that it is equal to one elastic vibration. The
elongated /-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 occasionally occur in the line of
ascent. Such a condition may occur normally (Fig. 56, VIII at 1 and 2 ; X at 1
and 2). When a series of closely-placed elastic vibrations occur in the upper 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. 62, a, a),
which, when it becomes so marked, may be characterised as pathological (Landois).
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, e.g., Fig. 62, 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 dilate 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 occurs in old people where the arteries tend to become
rigid, e.g., in atheroma. Cold also stimulates the arteries so that they become less
extensile. Within one hour after a tepid bath, the pulse assumes the anacrotic
form (Fig. 62, D)— (G. 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. 62, 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 compressed so that 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. 62, 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

ANACROTISM.

117

curve is anacrotic, and the dicrotic wave is diminished, while the elastic
elevations are increased.

I.

III.

Anacrotic pulse-curves— A, B, C, D, from the radial artery ; a, a, the anacrotic
notches; I., II., III., curves with anacrotic elevations— a in insufficiency of
the aortic valves.

(5.) A special form of anacrotisni 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. 62, I., was
obtained from the carotid of a man suffering from well-marked insufficiency of the
aortic valves, with considerable hypertrophy of the left ventricle and left auricle.
The ascent is steep, caused by the force of the contracted heart. In the apex of
the curve are two projections, A is the anacrotic auricular wave, and V is the
ventricular wave. Fig. 62, II. , is a curve obtained from the subclavian 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. 62
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

148 INFLUENCE OF RESPIRATORY MOVEMENTS ON PULSE-CURVE.

into the left ventricle when the venti'icle relaxes; (3) not unfrequently a pro-
jection 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 suffi-
ciently large surface to be reflected from. 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 the Respiratory Movements on

the Pulse-Curve.

The respiratory movements influence the pulse in two ways : — (1)
in a purely physical way, by diminishing the arterial pressure during
each inspiration and increasing it during expiration; (2) the respir-
atory movements are accompanied by stimulation of the vasomotor
centre, which produces variation of the blood-pressure.

(a.) Normal Respiration. — 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 sucked into the right auricle by
aspiration; 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 venae cavse — 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. 63 and Fig. 58, I., III., IV., in which J indicates the part of
the curve which occurred during inspiration, and E the expiratory por-
tion. The following are the points of difference: — (1.) The greater dis-
tension of the arteries during expiration causes all the parts of the

Fig. 63.

Influence of the respiration upon the sphygmogram, after Riegel— J, during in-
spiration; E, during expiration.

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.)

VALSALVA'S AND MULLER'S EXPERIMENTS. 149

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.

(6.) This purely mechanical effect of the respiratory movements is
modified by the simultaneous stimulation of the vasomotor centre
which accompanies these movements. 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 corresponding to the phases of the respiratory
movements (Klemensiewicz, Knoll, Schreiber, Lbwit). [There is, as it
were, a displacement of the blood-pressure curve relative to the respira-
tory curve.]

Forced Respiration. — With regard to the effect produced on the
pulse-curve by a powerful expiration and a foi'ced inspiration, observers
are by no means agreed.

Valsalva's Experiment. — Strong expiratory pressure is best produced
by closing the mouth and nose, and then making a great expiratory
effort ; at first there is increase of the blood-pressure and the formation
of pulse-waves resembling those which occur 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 (Riegel, Frank, and Sommerbrodt). 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 (compare Vol. ii.) Coughing, singing, and declaim-
ing, act like Valsalva's experiment, while the frequency of the pulse
is increased at the same time (Sommerbrodt). After 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 con-
dition being restored within a few minutes (Lenzmann).

Muller'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 char-
acteristic signs of diminished tension, viz., a higher and more distinct
dicrotic wave; then the tension can, by nervous influences, be in-
creased, just as in Fig. 64, where C and R are tracings taken from the

150 INFLUENCE OF RESPIRATORY MOVEMENTS ON PULSE-CURVE.

carotid and radial arteries respectively, during Miiller's experiment,
in which the dicrotic waves, r, r, indicate the diminished tension in the
vessels. In Cj and E19 taken from the same person during Valsalva's
experiment, the opposite condition occurs.

Fig. 64

C, curve from the carotid, and R, radial, during Miiller's experiment ; GX and Rj,
from the same vessels during Valsalva's experiment. Curves written on a
vibrating surface.

On expiring 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 from this apparatus of air under less pressure acts like
Miiller's experiment, i.e., 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 (Zuntz),
and the after-effect continues for some time. The pulse is more frequent both
during and after the experiment. Expiration in rarified air increases the blood-
pressure (Zuntz, Lenzmann). The effects which depend upon the action of the
nervous system do not occur to the same extent in all cases. Exposure to com-
pressed 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,

Fig. 65.
Pulsus paratloxus, after Kussmaul— E, expiration; J, inspiration.

Jacobsohn, Lazarus). Exposure to rarified air causes the opposite result, which is a
sign of diminished arterial tension.

INFLUENCE OP PRESSURE ON FORM OF PULSE-CURVE. 151

Pulsus FaradoXTlS. — Under pathological conditions, especially when there is
union of the heart or its large vessels with the surrounding parts, the pulse dur-
ing inspiration may be extremely small and changed, or may even be absent. This
condition has been called pulsus paradoxus (Griesinger, Kussmaul).

It depends upon a diminution of the arterial lumen during the inspiratory move-
ment. Even in health, it is possible by a change of the inspiratory movement to
produce the p. paradoxus (Riegel, Sommerbrodt).

75, Influence of Pressure upon the Form of 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 the individual parts thereof. In Fig. 66, a, b, c, d, e, are
radial curves ; a was taken with minimal pressure, b with 100, c 200, d 250, and e
450 grammes 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 curves 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 - 200 grammes) the dicrotic wave is best marked, the
whole curve is somewhat lower. (3) On increasing the weight, the size of the

200

250

450

A 100

B 170

C 220 D

Fig. 66.
Various forms of curves (radial) obtained by gradually increasing the pressure.

A

B

C

J O

gi

6

5;

1-a,

—

10

1-3, .

.. 18

I?"

16,

1-4,

. 25

234

23;

1-5, .

. 34

32

32

1-b, .

—

41

—

1-6, .

. 44

464

45

152 RAPIDITY OF TRANSMISSION OF PULSE- WAVES.

dicrotic wave again diminishes. (4) The fine elastic vibrations preceding the
dicrotic wave appear first when a weight of 220 to 300 grammes is used. (5) The
rapidity of the 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. 66, A, B, C, D, are curves obtained from the radial artery of a healthy
student. The pressure exerted upon the artery for A was 100; B, 170; C, 220;
and D, 240 grms. The time occupied by the various events was : —

D

1 vibration
= 0-01613

sec.

If 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 unfrequeiitly the pulse-curve assumes the form of a
dicrotic pulse, owing to the greater development 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 pi'oduction of a
dicrotic elevation. Fig. 58, X, is such a dicrotic curve obtained after considerable
pressure had been applied to the artery.

76. Rapidity of Transmission of Pulse-Waves,

The pulse-wave proceeds throughout 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 calculated the
rate of the pulse-wave as 9'240 metres [28^ feet] per sec. 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 resistant
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.

77. Propagation of the 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 '295 metres per sec.;

PROPAGATION OF PULSE-WAVES IN ELASTIC TUBES.

153

according to Bonders, 11-14 metres (34 - 43 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 dia-
meter, 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. (5) 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 propaga-
tion of waves inelastic 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).

Experiments With Caoutchouc Tubes. — For this purpose Landois employs
the following apparatus (Fig. 67):— A large tuning-fork, A (35 cmtr. long), carries
on one of its arms a glass-plate, P (25 cmtr. long, and 5 cmtr. broad), while the other
arm is weighted, G. The tuning-fork is fixed by an iron holder, T, to a movable
piece of wood which can be pushed along with the hand in a groove on a support
H, H. When the glass-plate is smoked, the curved needle of the angiograph
writes its movements upon it. The fork, when it vibrates, makes little teeth in
the curve, and the value of each vibration is estimated beforehand. Every com-
plete vibration in this instrument is equal to 0'01613 sec.

Velocity of the Waves in Elastic Tubes filled with Water or Mercury.

— Take a soft extensible elastic tube, A, 8 '80 metres long, 1 mm. thick, and

Fig. 67.

Instrument for measuring the velocity of the pulse-wave in an elastic tube con-
taining water or mercury— A, tuning-fork ; B, ampulla ; A, elastic tube ; P,
glass-plate smoked; Q, manometer; x, pad of lever of angiograph; writing-
style, D.

154 VELOCITY or THE PULSE-WAVE IN MAN.

7 mm. diameter. If 1 metre of the tube is weighted with 1 kilo, it elongates 68
cmtr. An ampulla, B, capable of containing 50 cmtr., is fixed to one end of the
tube, while to the other end of the ampulla is fixed a mercurial manometer, Q.

Fig. 67«.

Pulse-curve from an elastic tube registered upon a plate attached to a vibrating

tuning-fork.

The tube, A, is shut close to the ampulla every time the pressure is mea-
sured, in order to obviate the occurrence of oscillation in the mercury. A certain
portion of the tube, say 8 metres, is measured. The beginning, a, and end, b,
of this stretch of tubing are placed under the pad, x , of the angiograph. When
a positive wave is produced by compressing the ampulla, the writing-lever is raised
twice, the first time when the wave passes the first part of the tube, o, under the
pad, and the second time when the end part of the tube, b, is distended by the
wave. The curve obtained is shown in Fig. 67«, in which the two elevations,
1 and 2, are obvious. The time between the two may be ascertained by counting
the number of vibrations of the tuning-fork. The experiments gave the following
results : —

(A.) The velocity of the wave is 11 '809 metres per sec.

(B.) The intra-vascular pressure has a decided influence on the velocity: thus,
in the tube, A, with 18 cmtr. (Hg.) pressure, the velocity per metre = 0'093 sec.,
while with 21 cmtr. pressure (Hg.) = 0'095 sec. 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 (Marey
and Landois).

(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 whose height was 174 centi-
metres : — Difference between carotid and radial = 0*074 sec. (the distance being
taken as 62 centimetres); carotid and femoral = 0 '068 sec.; femoral (inguinal
region) and posterior tibial = 0'097 sec. (distance estimated at 91 centimetres).

The velocity of the pulse-wave in the arteries of the upper extre-
mities=:9-43 metres per sec., and in those of the lower extremity 9'40
metres per second. The velocity is greater in the less extensible arteries

VELOCITY or1 THE PULSE-WAVE IN MAN.

155

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 (Czermak).

E. H. Weber estimated the velocity at 9 '24 metres per sec.; Garrocl, 9 -10 '8
metres; Grashey, 8' 5 metres; Moens, 8" 3 metres, and with diminished pressure
during Valsalva's experiment (p. 112) 7'3 metres.

In animals, haemorrhage (Haller), slowing of the heart produced by stimulation
of the vagus (Moens), section of the spinal cord, deep morphia-narcosis, and dilata-
tion of blood-vessels by heat, produce slowing of the velocity, while stimulation of
the spinal cord accelerates it (Grimm ach).

The wave-length of the pulse-wave is obtained by multiplying the
duration of the inflow of blood into the aorta=0'OS to 0'09 sees.
(p. 86) by the velocity of the pulse-wave.

Method.— Place the knobs of two tambours (Fig. 52) 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. 52) so that their writing-levers are
directly over each other, and so arranged as to write simultaneously 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.] In Fig. 68, H is the curve obtained
from the heart, and C from the radial artery. The apparatus is improved by using
rigid tubes and filling them with water, in which all impulses are rapidly communi-
cated. 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 be connected by means
of a Y-tube with one writing-lever. In Fig. 68, 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

H

m

B

Fig. 68.

A, curve of radial artery on a vibrating surface (1 vib. =0'01613 sec.) ; P, apex
of curve ; e, e, elastic vibrations ; B,, dicrotic wave ; B, curve of same radial
taken along with the heart-beat ; v, H, P, contraction of the ventricle ; H,
curve of the heart-beat ; C, of the radial artery, taken simultaneously. The
arrows indicate the identical points in both curves. In B, v to p = 9 vibrations.

156

FURTHER PULSATILE PHENOMENA.

beginning of the ventricular contraction ; p, of the radial pulse. A is the curve of
the radial artery alone. From these curves, as well as from H and C, it is evident
that in this instance 9 vibrations occur between the beginning of the ventricular
contraction (in H at 22) until the beginning of the pulse in the radial artery (in C
at 13), so that 0' 15 sec. elapses between these two events (1 vibration = 0*01613 sec.).
In Fig. 69 the difference between the carotid and the posterior tibial pulse =
0-137 sec.

/^^^^^

"*» ^ww^/

Caret.

Fig. 69.

Curves of the carotid and posterior tibial taken simultaneously with Broudgeest's
pansphygmograph writing upon a vibrating plate, attached to a tuning-fork.
The arrows indicate the identical moment of time in each curve.

Pathological. — In cases of diminished extensibility of the arteries, e.g., in
atheroma (p. 127), 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 (Hamernjk).

79. Further 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), 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, Trb'ltsch).

2. Entoptical Pulse, — After violent exercise, an illumination corresponding to
each pulse-beat, occurs on a dark optical field. When the optical field is bright,
an analogous darkening occurs (Landois). The ophthalmoscope occasionally reveals
pulsation of the retinal arteries (Jiiger), which becomes marked in insufficiency of
the aortic valves (Quincke, 0. Becker, Helfreich).

3. Pulsatile Muscular Contraction. — The orbicularis palpebrarum muscle
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 in-
voluntarily 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

VIBRATIONS COMMUNICATED TO THE BODY BY THE HEART. 157

against the upper teeth, owing to the pulse-beat in the external maxillary artery
raising the lower jaw. The second elevation is clue 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 brain com-
municate 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 the beating in the epigastrium, as in
hypertrophy 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
coeliac axis.

Abnormal dilatations (aneurisms) of the arteries cause an abnormal pulsation,
while theyproducea slowing inthe 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 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 communicated to the Body by the

action of the Heart,

The beating of the heart and large arteries communicates vibrations to the body
as a whole, but the vibration is not simple but compound.

Gordon was the first to represent this pulsatory vibration graphically. If a

B

/LL

K

"1

n

Fig. 70.

II, Elastic support for registering the molar motions of the body — K, a wooden
box ; B, feet of patient ; p, cardiograph ; a, b, elastic tubing. I, III— Vibra-
tion curves of a healthy person. IV— Similar curve obtained from a patient
suffering from insufficiency of the aortic valves and great hypertrophy of the
heart.

158 VIBRATIONS COMMUNICATED TO THE BODY BY THE HEART.

person be placed in an erect attitude in the scale of a large balance, the index
oscillates, and its movements coincide with the heart's movements.

Fig. 70, I, shows a curve obtained by Gordon, written directly by the index of
the spring balance. The lowest part of the curve corresponds to the systole of the
ventricle.

Landois employed the following arrangement : — Take a long four-sided box, K,
open at the top, and arrange several coils, a, b, of stout caoutchouc tubing round
one end. A wooden board, B, smaller than the opening in the box, 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. Ill is a curve showing such vibrations, each heart-beat being followed
in this case by four oscillations. It corresponds to I. 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 (p. 71), placing one nob 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. 71, the rapidly-rising part is due to
the ventricular systole. It contains S vibrations (1 vib. =0'01G13 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 males a downward vibration,
i.e., 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 5 vibrations of the tuning-fork : during the last 3 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 imdergoes a
movement in a downward and outward direction — Gutbroclt's "reaction impulse."

Fig. 71.

The upper curve is the vibration-curve of a healthy person, and the lower one a

tracing of the apex beat.

In the upper curve analogous numbers are employed to indicate the vibrations
occurring simultaneously, viz., -28- 11 -10. The closure of the semi-lunar

THE BLOOD-CURRENT. 159

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.

In insufficiency of the aortic valves, as shown in Fig. 70, IV, the vibration com-
municated to the body is very considerable.

81. The Blood- Current.

The closed and much-branched vascular 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 the vessels may be emptied.

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). If, 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 venae cavse be suddenly ligatured in a living animal,
the blood continues to flow, 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 (E. H. Weber). Both in the systemic and pulmonary circulations
the point of highest 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 (E. H. Weber).

Bonders added another important fact — viz., that the action of the
heart not only causes the difference of pressure necessary to establish a
blood-current, but that it also raises the mean pressure within the vascular

160 THE BLOOD-CURRENT.

system. The terminations of the veins at the heart are wider and
more extensible than the arteries where they arise from the heart.
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 extensible as the veins. Thus the total
pressure must also increase.

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 pro-
pelling 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 compen-
sation 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 becomes the difference of pressure, 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 phenomena are due to the same fundamental cause. Every
pulse-beat causes a temporary rapid progressive 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. — These facts are capable of demonstration by means of very simple
physical experiments. [Tie a Higginson's syringe to a piece of an ordinary gas-
pipe. On forcing water through the tube by compressing 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. If a 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 resist-

CURRENT IN THE CAPILLARIES. 161

ance 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.

Current in the Capillaries. — In the capillary rebels 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 pulse is observed in the veins of the sub-
maxillary gland after stimulation of the chorda tympani nerve, which
contains the vascular or 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. [Koy and Graham Brown found that pulsatile pheno-
mena were produced in the capillaries, by increasing the extra-vascular
pressure (p. 173). 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, and is probably
produced by increased extra-vascular pressure,]

82. Schemata of the Circulation.

E. H. Weber constructed a scheme of the circulation. 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 [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

11

IB 2 ESTIMATION OF THE BLOOD-PRESSURE.

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 estimated in the following ways : —

(1.) Directly, by filling the dead ventricle with blood (Santorini, 1724; Legallois
and Collin). This method is unsatisfactory and inaccurate. (2.) All the vessels of
the relaxed heart are ligatured, the heart excised, and the contents of the cavities
estimated (Abegg, 1848). (3.) Volkmann estimated the capacity to be -^ of the
body- weight — i.e., for a man of 75 kilos. = 187 '5 grms.

84. Estimation of the Blood-Pressure.

(A.) In Animals : Method 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, i.e., how high the
blood rose in the tube. 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 nine 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 Hsemadynamometer of Poiseuille,— This observer (1828) 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 pulsation, and the extent of the oscillations was read off by means of a
scale attached to the bent tube. He called the instrument a hamadynamometer].

[(3. ) Vierordt used a tube five or six 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 solution prevented the coagulation of the blood.]

(4.) C. Ludwig's Kymograph.— C. Ludwig employed a U-shaped mano-
meter of the same kind, but he placed a light float (Fig. 72, d, s) upon
the surface of the mercury in the open limb of the tube. A
writing-style, /, 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. Volk-
mann 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 corresponding column of blood. Setschenow placed a stop-cock
in the lower bend, h, of the tube. If this be closed so as just to
permit a small aperture of communication 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-

LUDWIG'S KYMOGRAPH.

163

pressure tracing range. [Briefly, it is the average elevation of the
mercurial column.]

Fig. 72.
I, Scheme of C. Ludwig's kymograph ; II, Fick's spring-kymograph.

In a blood-pressure tracing, such as Fig. 74, each of the smaller waves corre-
sponds to a heart-beat, the ascent corresponding to the systole and the descent to the
diastole. The large undulations are due to the respiratory movements. It is clear
that the heart-beat is expressed as a simple rise and fall (Fig. 74), so that the curve
of the heart-beat obtained with a mercurial kymograph differs from a sphygmo-
graphic curve. 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. [The
theory of the mercurial manometer has been carefully worked out by Mach and
also by v. Kries.]

[Method. — Expose the carotid of a chloralised rabbit, and isolate a portion of
the vessel between two ligatures, or two spring clamps. With a pair of scissors
make an oblique slit into the artery, and into it insert a straight glass cannula,
directing the open 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 descending 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 several inches of mercury in the manometer, or until the
pressure is about equal to the estimated blood-pressure, and then clamp the tube

164

SPRING -KYMOGRAPH.

V

of the pressure-bottle where it joins the lead tube. By having this positive
pressure, the escape of blood from the artery into the solution of sodium carbonate
is to a large extent avoided. 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 move-
ments upon the recording sur-
face. The fluid within the
artery exerts pressure laterally
upon the sodium carbonate
solution, and this in turn trans-
mits it to the mercury.]

[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. 73).
Various arrangements are em-
ployed 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 cylin-
der revolves, it gradually winds
off the strip of paper, which is
kept applied to the revolving
surface by ivory friction wheels.
In Fick'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.]

[In order to measure the
height of the pressure, we
must know the position of the

Fig. 73.

Ludwig's improved form of revolving cylinder, S,
which is moved by the clock-work in the box,
A, 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 two wheels, ??, which can be raised
or lowered by the screw, L, thus altering the
position of n on D, so as to cause the
cylinder to rotate at different rates. The
cylinder itself can be raised by the handle, v.
On the left side of the figure is a mercurial
manometer. When the cylinder is used, it is
covered with smoked smooth paper.

abscissa or line of no pressure, and it may be recorded at the same time as the
blood-pressure or afterwards. ]

[In Fig. 74, 0 - x 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) constructed a " spring-kymo-
graph" on the principle of Bourdon's manometer (Fig. 72, II).

A hollow C-shaped metallic spring, F, is filled with alcohol. One end of the
hollow spring is closed, and t he 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 communication with the artery is opened, the pressure
rises, and the spring, of course, tends to straighten itself. To the closed end, b,

ESTIMATION OF THE BLOOD-PRESSURE IN MAN.

165

there is fixed a vertical rod attached to a series of levers, /<, 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 ia
not done with absolute accuracy.

Fig. 74.

Blood-pressure curve of the carotid of a dog obtained with a mercurial manometer.
0 - x = line 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.

[Bering improved Pick's instrument (Fig. 75). a, b, c, is the hollow spring filled
with alcohol, and communicating at a with the lead tube, d, passing to the cannula
in the artery. To c is attached a series of light wooden levers with a writing-
style, s. The lower part of 4 dips into a vessel, e, 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, h, by means of
the millhead opposite, y, to which all the parts of the apparatus are attached.]

(B.) In Man the blood-pressure may be estimated by means of a
properly graduated sphygmoyraph (p. 130). The pressure required to
abolish the movement of the lever indicates approximately the vascular
tension. Landois (Schobel) investigated the radial pulse in a healthy
student, and obtained a mean blood-pressure equal to 550 grammes.

(2.) By a manometric method v. Basch estimated the blood-prea-

166

BLOOD-PRESSURE IN THE ARTERIES.

sure. He placed a capsule containing fluid upon a pulsating artery, and
the capsule communicated with a mercurial manometer. As soon as
the pressure within the manometer slightly exceeded that within the

artery, the artery was
compressed so that a
sphygmograph placed
on a peripheral por-
tion of the vessel
ceased to beat. Both
arrangements, how-
ever, 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

Fig. 75.
Fick's Spring-manometer, as improved by Hering.

only 4 mm. Hg. v. Basch estimated the pressure in the radial artery
of a healthy man to be 135 - 165 millimetres of mercury.

In children the blood-pressure increases with age, height, and weight. In the
superficial temporal artery from 2-3 years, it is — 97 mm. ; from 12-13 years, 113
mm. Hg. (A. Eckert, c. § 100). The blood-pressure is raised immediately after
bodily movements ; it is higher when a person is in the horizontal position than
when sitting, and in sitting than in standing (Friedmann). After a cold as well
as after a warm bath (L. Lehrnann), the first effect is an increase of blood-
pressure and of the quantity of urine (Grefberg).

85. Blood-Pressure in the Arteries.

The following results have been obtained by experiment on systemic
arteries: —

(a.) 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 is = 140 - 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 -. —

BLOOD-PRESSURE IN THE ARTERIES. 167

* Carotid, Horse, 161 mm.
+ , ,, 122-214 mm.

,, Dog, 151 mm.

130- 190 mm. (Ludwig).

+ ,, Goat, 118-135 mm.

+ Aorta of frog, 22-29 mm.

+ Gill artery of Pike, 35-84 mm.

Brachial artery of man during an

operation, 110-120 mm. (Faivre).

Perhaps too low owing to the

injury.

+ ,, Rabbit, 90 mm.
+ „ Fowl, 88-171 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 consider-
ably 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.

(b.) Branching of the Blood-Vessels. — Within the large arteries the
blood-pressure diminishes relatively little as we pass towards the
periphery, because the difference of the resistance in the different
sections of large tubes is very small. As soon, however, 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 propelling energy of the blood is much weakened owing
to the resistance which it has to overcome (p. 118).

(c.) Amount of Blood. — The blood-pressure is increased with greater
fitting of the arteries, and vice versd ; it

Increases

1. With increased and accelerated

action of the heart;

2. In plethoric persons;

3. After increase of the quantity of

blood by direct transfusion, or
after a copious meal.

Decreases

1. During diminished and enfeebled

action of the heart;

2. In anaemic persons;

3. After haemorrhage or considerable ex-

cretions from the blood by sweat-
ing, the urine, severe diarrhoea.

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). Small and moderate
haemorrhages (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
Miiller). If a large amount of blood be withdrawn, it causes a great fall of the
blood-pressure (Hales, Magendie), and when haemorrhage 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 experiments, viz., that the blood-pressure cannot
be diminished directly by moderate blood-letting, and that the blood-pressure is
not necessarily high in plethoric persons.]

Capacity of the Vessels. — The arterial pressure rises when the
capacity of the arterial system is diminished, and conversely. The
plain circularly-disposed muscular fibres of the arteries are the chief

1G8

BLOOD-PRESSURE IN THE ARTERIES.

agents concerned in this process. When they relax, the arterial blood-
pressure falls, and when they contract, it rises. These actions of
muscular fibres are controlled and regulated by the action of the vaso-
motor nerves (vol. ii.)

(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 —
increasing or diminishing the atmospheric pressure on a part — the
paralysis or stimulation of certain vaso-motor areas (vol. ii.), all pro-
duce 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. If the central end of the superior cardiac nerve of a rabbit be
stimulated, 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. 76 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 latent period, there is
a steady fall of the blood-pressure. The nerve which causes this reflex

Fig. 76.

Kyniographic tracing showing the effect on the blood-pressure of stimulation of the central end of the
depressor nerve in the rabbit. Stimulation began at «, and ended at b ; o—x, the abscissa.

RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE CURVE. 169

dilatation of the abdominal blood-vessels, and consequent lowering of
the blood-pressure, is also called the depressor nerve.

(/.) Respiratory Undulations. — The arterial pressure also undergoes
regular variations or undulations owing to the respiratory movements.
These undulations are called respiratory undulations (Figs. 74 and
77). Stated broadly, during every strong inspiration the pressure
rises, and during expiration it falls (§ 74). This is not quite correct —
(see below). 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 diminu-
tion of the air in the lungs acting upon the aorta. Besides, the
inspiratory movements of the chest aspirate blood from the venae
cavse 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,
Avhich runs parallel with the respiratory movements. This stimulation
of the vaso-motor centre causes 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 (p. 171). In Fig. 77 are represented a
blood-pressure tracing and a curve of the movements of respiration
(thick line) taken simultaneously in a dog by C. Ludwig and Einbrodt.
The blood-pressure tracing was obtained from the carotid artery, while

Fig. 77.

Kyinographic blood-pressure tracing (upper, thin line), and respiration curve
(lower, thick line), taken simultaneously — ex, expiration ; in, inspiration ; c, c,
heart-beats. The large curves in the blood-pressure tracing are due to
respiration (Ludwig and Einbrodt).

the pressure within the thorax was measured by means of a manometer
placed in connection with one pleural cavity. In this curve, when
expiration begins (at ex), and as the expiratory-pressure rises, the blood-
pressure rises, while when inspiration begins (at in) both fall. The
blood-curve, however, begins to rise (at c) before expiration com-

170 RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE CURVE.

mences — i.e., during the last part of the act of inspiration. This
is due to the contraction of the arteries, caused by impulses sent
from the vaso-motor centre. It is also aided by the circum-
stance that during inspiration there is an increased inflow of
venous blood to the heart, so that when it contracts, more blood is
forced into the arteries. [The maxima and minima of the two 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, while in a
rabbit this difference of the pulse-rate is but slightly marked. The
smaller number of pulse-beats during the descent — i.e., during the
greater part of expiration — 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-rnotor centre in the medulla oblongata by
the impure blood. This causes contraction of the small arteries
throughout the body, which retards the out-flow 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

TRAUBE-HERING CURVES. 171

on the heart, or on any local peripheral nervous mechanism, or on the
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 undula-
tions 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 respi-
ration 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-Heriug curves. As in other
conditions, stimulation gives place to 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, i.e., 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.]

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.

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 diaphragm descends during inspiration, it
presses upon the abdominal contents, including the abdominal vessels,

172 VARIATIONS OF THE BLOOD-PRESSURE.

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 undulations,
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, pres-
sure upon the abdomen of the animal with the hand, causes the
blood-pressure to rise rapidly.]

(g.) 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. 77, c). The mass of blood forced into
the arteries with each ventricular systole causes a positive wave and an
increase of the pressure corresponding with it, which of course corre-
sponds 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
= TV (horse) and :V (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.

(A.) If the heart's action be arrested or interrupted by continued
stimulation of the vagus (Brunner, 1855), or by a high positive
respiratory-pressure (Einbrodt), the arterial blood-pressure falls enor-
mously, while it rises in the veins as the blood flows into them
from the arteries to equilibrate the difference of pressure in the two
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 — i.e., on account of the overfilling of the blood-
vessels, a slight pressure is exerted upon the walls, even when there
is no circulation (Brunner). [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. 78 shows the
effect on the blood-pressure, 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 shown by the rapid fall of the curve
from a].

For the effects of the nervous system upon the blood-pressure, see "Vase-motor
Centre" (vol. ii.)

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

BLOOD-PRESSURE IN THE CAPILLARIES, 173

v. Bascb, 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

Fig. 78.

Blood -pressure tracing taken with a mercurial kymograph from the carotid of a
rabbit ; o - x, abscissa ; vagus nerve stimulated between the vertical lines,
a and b.

after the injection of morphia (Kristeller). The blood-pressure falls in fever
(Wetzel), a fact also indicated in the sphygmogram (§ 69). In chlorosis and
phthisis the blood-pressure is low (Waldenburg).

86. Blood-Pressure in the Capillaries.

Methods. — Direct estimation of the capillary pressure is not possible on account
of the smallness of the capillary tubes. If a 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 necessary to over-
come the capillary pressure. N. v. Kries placed a small glass plate (Figs. 79, 80)
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 ascertained the hydrostatic pressure necessary to occlude
the vessels in transparent parts placed under the microscope, e.g., the web of a
frog's foot, tongue or mesentery of a frog, the tails of newts and small fishes. The
upper surface of the part to be investigated, e.g., the web of a frog's foot, is made just
to touch a thin glass plate. The under surface is in contact with a delicate trans-

174 CONDITIONS AFFECTING CAPILLARY PRESSURE.

parent membrane covering the upper end of a small brass cylinder, whose lower
end contains a piece of glass fitted air-tight into it. The interior of the brass
cylinder communicates by means of a tube with an arrangement for obtaining any
desired pressure, and the amount of the pressure is indicated by a manometer.
Air pressure is used, and this is obtained by compressing a caoutchouc bag between
two brass plates. The membrane to be investigated lies between two transparent

Fig. 79. Fig. 80.

Apparatus used by v. Kries for estimating the capillary pressure — a, the small
square of glass. In Fig. 79 the scale-pan for the weights is below, and in
Fig. 80, above.

media, an upper one of glass and a lower one of transparent membrane, on which
the pressure acts. Any change in the vessels is observable by means of the micro-
scope. These observers conclude from their experiments that the capillaries are
contractile, and that their contractility is, to all appearance, in constant action.
The regulation of the peripheral blood-stream is due not only to the cerebro-spinal
vaso-motor centres, but also to independent peripheral vaso-motor mechanisms,
which may be nervous in their nature, or are due to some direct action on the walls
of the vessels (p. 12fi).]

Conditions influencing Capillary Pressure. — The intra-capillary blood-
pressure in a given area increases — (1.) When the afferent small
arteries dilate. When they are dilated 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 the
veins may quadruple the pressure (v. Kries). (4.) By increasing the
pressure in the veins (e.g., by altering the position of a limb). A
diminution of the capillary pressure is caused by the opposite
conditions.

Changes in the diameter of the capillaries influence the internal pressure. We
have to consider the movements of the capillary wall itself (protoplasma-movements,
Strieker — p. 125), as well as the pressure, swelling, and consistence of the surround-

BLOOD-PRESSURE IN THE VEINS. 175

ing 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
(Bonders). The capillary pressure nmst 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, musb 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, sub-clavian,
jugular) a mean negative pressure of about - O'l mm. Hg. prevails (H.
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.
(Jacobson). [The pressure is said to be negative when it is less than
that of the atmosphere.]

Conditions Influencing the Venous Pressure. — (1.) All conditions
which diminish the difference of pressure between the arterial and
venous systems increase the venous pressure and vice versa.

(2.) General plethora of blood increases it ; anaemia 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 expira-
tion it is retarded. The effects are greater the deeper the respiratory
movements, 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— a fact which was known to Valsalva. The respiratory
movements do not affect the venous stream in the 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 ; while every
surgeon is well acquainted with the fact that air is particularly apt to be sucked
into the veins, especially in operations near the root of the neck. This is due to
the negative intra-thoracic pressure occurring during inspiration.]

(4.) Aspiration of the Heart. — Blood is sucked or aspirated into
the auricles when they dilate, so that there is a double aspiration-
one synchronous with inspiration, and the other, which is but
slight, synchronous with the heart-beat. There is a corresponding
retardation of the blood-stream in the venae cavae, caused by the
contraction of the auricle (see p. 77, a). The respiratory and cardiac

176 BLOOD-PRESSURE IN THE VEINS.

undulations are occasionally observable in the jugular vein of a healthy
person (§ 99).

[Braune showed that the femoral vein under Poupart's ligament collapsed when
the lower limb was rotated outwards! and backwards, but filled again when the
limb was restored to its former position. All the veins which open into the
femoral vein have valves, which permit blood to pass into the femoral vein, but
prevent its reflux. This mechanism acts to a slight degree as a kind of suction
and pressure apparatus when a person walks, and thus favours the onward move-
ment of the blood.]

(5.) Changes in the position of the limbs or of the body, for hydro-
static reasons, greatly alter the venous pressure. The veins of the
lower extremity bear the greatest pressure, while at the same time
they contain most muscle (K. Bardeleben, § 65). Hence, when
these muscles from any cause become insufficient, dilatations occur in
the veins, giving rise to the production of varicose veins.

[(6.) Movements of the Voluntary Muscles. — Veins which lie between
muscles are compressed when these muscles contract, and as valves
exist in the veins the flow of the 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 course of the superficial
veins can be distinctly traced on the surface of the limb.]

[(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 dis-
tribution 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 (Paschutin). 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 are 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.— The pressure and other conditions vary in
particular veins. Thus, if the portal vein be ligatured, there is congestion of the
capillaries and rootlets of the portal vein, and dilatation of all the blood-vessels in
the abdomen, and 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. As a consequence of sudden and complete ligature of this vein, the arterial

BLOOD-PRESSURE IN THE PULMONARY ARTERY. 177

blood-pressure gradually and rapidly falls, and the animal dies very quickly. If
the ligature be removed before the blood-pressure falls too much, the animal may
recover.

Ligature Of the Veins Of a Limb.— The effect of ligaturing or compressing all
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
oedema of the parts beyond the obstruction. Ligature of one vein does not always
produce osdema, but if several veins of a limb be ligatured, and the vaso-motor
nerves be divided at the same time, the rapid production of oedema is ensured.
In pathological cases the pressure of a tumour upon a large vein may produce
similar results.]

. Blood-Pressure in the Pulmonary Artery.

Methods. — (1.) Direct estimation of the blood-pressure in the pulmouary artery
by opening the chest was made by C. Ludwig and Beutner (1850). Artificial re-
spiration was kept up, and the manometer was placed iu connection 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 dis-
turbing element, viz., the removal of the elastic force of the lungs owing to the
opening of the chest, whereby the venous blood no longer flows normally into the
right heart, while the right heart itself is under the full pressure of the atmo-
sphere. The estimated pressure in the dog = 29 '6; in the cat = 17 '6; in the
rabbit, 12 mm. Hg.— i.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.) Chauveau and Faivre (1856) introduced a catheter through the jugular vein
into the right ventricle, and placed it in connection with a manometer (p. 87).

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, for there must be a relation between the pressure and the thickness of the
muscle in the two cases.

Beutner and Marey estimated the relation of the pulmonary artery
to the aortic presssure as 1 to 3 ; Goltz and Gaule as 2 to 5 ; Tick
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
(Beneke).

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 the large blood-vessels within the
chest are not exposed to the full pressure of the atmosphere, but only

12

178 BLOOD-PRESSURE IN THE PULMONARY ARTERY.

to the pressure which corresponds to the atmospheric pressure minus
the pressure exerted by the elastic traction of the lungs (§ 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 disten-
sible 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 (Funke and Latschenberger). 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 Jager). Hence also, more blood
flows through the lungs distended within the thorax than through
collapsed lungs. The dilatation 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 (v. Openchowski).

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 (Beutner). Even when
one pulmonary artery is plugged with an embolon of paraffin, the
pressure within the aortic system is not raised (Lichtheim). Thus,
when a large branch of the pulmonary artery becomes impervious, the
obstruction is rapidly compensated, and this is not due to the action of

BLOOD-PRESSURE IN THE PULMONARY ARTERY. 179

the nervous system. The vaso-raotor system has much less effect upon
the pulmonary blood-vessels than upon those of the systemic circulation
(Badoud, Hofmokl, Lichtheim). 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
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.] Morel found that
electrical and mechanical stimulation of the abdominal organs caused a
considerable rise of pressure in the pulmonary artery (dog).

During the act of great straining, the blood at first flows rapidly out of the pul-
monary veins and afterwards ceases to flow, because the inflow of blood into
the pulmonary vessels is interfered 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 C02 than when the air within them
is rich in O. He supposes that these 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 frequently 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).

[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 peripheral 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. Measurement of the Velocity of the Blood-Stream.

Methods. (1.) A. W. Volkmann's Haemadromometer.— A glass tube of the

shape of a hair-pin, GO - 130 ctm. long and 2 or 3 mm. broad, with a scale
etched on it, or attached to it, is fixed to a metallic basal plate, B, so that each limb
passes to a stop-cock with three channels. The basal plate is perforated along its
length, and carries at each end short cannulze, c, c, which are tied into the ends
of a divided artery. The whole apparatus is first filled with water [or, better,

180 MEASUREMENT OF THE VELOCITY OF THE BLOOD-STREAM.

with salt solution]. The stop-cocks are moved simultaneously, as they are

attached to a toothed wheel and have at first the position given in Fig. 81, I,

so that the blood simply flows through the hole in the v

basal piece, i.e., directly from one end of the artery to

the other. If at a given moment the stop-cock is

turned in the direction indicated in Fig. 81, 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.

Volkmann found the velocity to be in the
carotid (dog) = 205 — 357 mm. ; carotid (horse) =
306; maxillary (horse) = 232; metatarsal= 56
mm. per second. The method has very obvious

Fig. 81.

Volkmann's H^madromometer (B)— I, blood
flows from artery to artery ; II, blood
must pass through the glass tube of
B ; c, c, canuula; for the divided artery.

Y

Fig. 82.

Ludwig & Dogiel's Stro-
muhr or Rheometer —
X, Y, axis of rotation ;
A, B, glass bulbs ; h, k,
cannuloj inserted in the
divided artery; e,e\, ro-
tates on g, f; c, d, tubes.

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.

MEASUREMENT OF THE VELOCITY OF THE BLOOD-STREAM. 181

(2.) C. Ludwig and Dogicl (1867) devised a STROMUHR or RHEOMETER
for measuring the amount of blood which passed through an artery in a
given time (Fig. 82). It consists of two glass bulbs, A and B, of exactly
the same capacity. These bulbs communicate with each other, above,
their lower ends being fixed by means of the tubes, c and d, to the metal
disc, ee^ This disc rotates round the axis, X Y, so that, after a
complete revolution the tube, c, communicates with /, and d with g ; f
and g are provided with horizontally placed cannulre, h and k, which are
tied into the ends of the divided artery. The cannula, h, is fixed in
the central end, and k in the peripheral end of the artery (e.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 k into 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.

(3.) Vierordt's Hsematachometer

(1858) consists of a small metal box (Fig.
83) with parallel glass sides. To the
narrow sides of the box are fitted an
entrance, c, 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 Volk-
mann's apparatus, has only a historical
interest. ]

e

I

Fig. 83.

Vierordt's Hsematachometer — A, glass ;
e, entrance ; a, exit cannula ; p,
pendulum.

(4.) Chauveau and Lortet'S (DromOgraph) (I860) is constructed on the same
principle. A tube, A, B (Fig. 84) of sufficient diameter, with a side-tube fixed to
it, C, which can be placed in connection 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 pen-
dulum, a, I, with a long index, b, projects into the tube, i.e., into the blood-
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.

The curve of the velocity may be written off on a smoked glass,

182

VELOCITY OF THE BLOOD IN THE BLOOD-VESSELS.

moving parallel with the index b. The dromograph curve, III, shows
the primary elevation, P, and the dicrotic elevation, R.

Dromograph — A, B, tube inserted in artery; C, lateral tube connected with a
manometer; b, index moving in a caoutchouc membrane, a; G, handle. Ill,
curve obtained by dromograph.

90. Velocity of the Blood in Arteries, Capillaries,

and Veins,

(1.) Division of Vessels. — 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 from the aorta towards the
capillaries, so that the capillary area is 700 times greater than the
sectional area of the aorta (Vierordt). 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.

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 artery and aorta, notwithstanding
the very unequal blood-pressure in these two vessels.

VELOCITY OF THE BLOOD IN THE BLOOD-VESSELS. 183

(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 consider-
ably 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. (E.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. Hence the total sectional area of all the capillaries must be
500 times greater than that of the aorta.. Bonders found the velocity
of the stream in the small afferent arteries, to be 10 times faster than
in the capillaries. A pulsatory acceleration, more rapid during its first
phase, is observable in the small arteries, although these are not
themselves distended thereby.

Veins. — The current becomes accelerated in the veins, but in the
larger trunks it is 0'5 to 075 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 anaemic 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 commencement and at the end of that particular section
of a blood-vessel; it depends, therefore, on (1) the vis a tercjo (i.e., the
action of the heart), and (2) on the amount of the resistance at the
periphery (dilatation or contraction of the small vessels — C. Ludwig
and Dogiel).

(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, so that every ascent of the sphygmogram corre-
sponds to an acceleration, and every descent to a diminished velocity of
the blood-stream. The variations in the velocity caused by the heart-
beat are recorded in Fig. 84, obtained by Chauveau's dromograph from
the carotid of a horse. The velocity-curve corresponds with a sphyg-
mogram— P represents the primary elevation and B, the dicrotic wave.
This acceleration, as well as the pulse, disappears in the capillaries.
In large vessels, Vierordt found the increase of the velocity during
the systole to be greater by £ to -^ than the velocity during the
diastole.

(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

184 DURATION OF THE CIRCULATION.

on the contraction and dilatation of the heart and on the blood-stream (§ 60), it
is clear that respiration favours the. blood-stream, so does artificial respiration.
When artificial respiration is interrupted, the blood-stream becomes slower (Dogiel).
If the suspension of respiration lasts somewhat longer, the current is again acceler-
ated on account of the dyspnoeic stimulation of the vaso-motor centre (Heidenhain)
(see Vaso-motor centre, vol. ii.)

(9.) Conditions Affecting Velocity in the Veins. — Many circumstances
affect the velocity of the blood in the veins. (1) There are regular
variations in the large veins near the heart (Valsalva) due to the
respiration and the movements of the heart (§§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 position of a limb or of the body. The pump-like action
of the veins of the groin during walking 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. Estimation of the Capacity of the Ventricles.

Vierordt calculated the capacity of the left ventricle from the velo-
city of the blood-stream, and the amount of blood discharged per
second 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 centimetres (equal to
182 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 question as to how long the blood takes to make a complete
circuit through the course of the circulation was first answered by
Hering (1829) in the case of the horse. He injected a 2 per cent,
solution of potassium 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 cor-
responding vein of the opposite side a rotating disc, in which was
fixed a, number of cups at regular intervals. The first appearance of

WORK OF THE HEART. 185

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.
Dog, . . 167 ,,
Rabbit, . 7 '79 ,,

Hedgehog, 7 '61 seconds.
Cat, . . 6'69 „
Goose, . 10-86 „

Duck, . . 10 '64 seconds.
Buzzard, . 6 '73 ,,
Fowl, . . 5'17 „

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 — i.e., for man=23'2 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.

Conditions Influencing the Time. — The time is influenced by the
following factors : —

1. Long vascular channels (e.g., from the metatarsal vein of one foot to the
other foot) require a longer 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 (e.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, i.e., in man, 187'5 grams, x 27 = 5062 '5
grams. This is equal to T\r of the body-weight, in a person weighing 65 '8 kilos,
(compare § 49).

It is not to be forgotten that the salt used is to some extent poisonous (p. 108).

93. Work of the Heart,

Johann Alfons Bernoulli (1679) and Julius Robert Mayer estimated
the work done by the heart. The work of a motor is expressed in
kilogramme-metres — i.e., the number of kilos, which the motor can
raise in the unit of time to the height of 1 metre.

The left ventricle expels 0'188 kilo, of blood (Yolkmann) 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 (Bonders). [The
amount of blood expelled from each ventricle during the systole is
about 180 grms. (6 ozs.) It is forced out against a pressure of

186 BLOOD-CURRENT IN THE SMALLEST VESSELS.

250 mm. Hg. = 3'21 metres of blood.] The work of the heart at each
systole is O188 X 3*21 — 0'604 kilogramme-metres. If the number of
beats =75 per minute, then the work of the left ventricle in 24 hours
= (0-604 X 75 X GO x 24) = 65,230 kilogramme-metres. While the
" work" done by the right ventricle is about one-third that of the left, and
therefore =2 1,740 kilogramme-metres. Both ventricles do work equal
to 86,970 kilogramme-metres. A workman during eight hours produces
300,000 kilogramme-metres — i.e., about four times as much as the heart.
As the whole of the work of the heart is consumed in overcoming the
resistance within the circulation, or rather is converted into heat, the
body must be partly warmed thereby (425'5 gramme-meters are equal
to 1 heat-unit — i.e., 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 8,080 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 Smallest 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 circulation in this way in the
lung of a frog (1661).

The following parts have been employed : — the tails of tadpoles and small fishes ;
the web, tongue, mesentery, and lungs of curarised frogs (Cowper, 1704) ; the wing
of the bat, the third eyelid of the pigeon or fowl, the mesentery ; the vessels of the
liver of frogs and newts (Gruithuisen), of the pia mater of rabbits, of the skin on
the belly of the frog, of the mucous membrane of the inner surface of the human
lip (Hiiter's Cheiloangioscope, 1879) ; of the conjunctiva of the eyeball and eyelids.
All these may be examined by reflected light.

[EntOptical appearances of the circulation (Purkinje, 1825). 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 arrange-
ment of the capillaries, 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 /* - 2 /u, so that two 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.

CAPILLARY CIRCULATION. 187

4. They form numerous anastomoses, and give rise to net-works, whose form and
arrangement are largely determined by the arrangement of the tissue elements them-
selves. They form simple, loops in the skin, and polygonal net-works in the serous
membranes, and on the surface of many gland tubes ; they occur m the form of
elongated net- works, with short connecting branches in muscle and nerve, as well
as between the straight tubules of the kidney ; they converge 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.

[A good contrast as to the vascularity of two adjacent parts is seen in the gray
and white matter of the brain, the former being very vascular, the latter but slightly
so.] ^

[Direct termination Of Arteries in Veins. — Arteries sometimes terminate
directly in veins, without the intervention of capillaries, e.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 (Hoyer). 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).]

End- Arteries, — In connection with the termination of arteries in capillaries,
it is important to determine if the arterioles are " end or terminal arteries," i.e., 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 f is taken up
with the axial current, and the plasma layer occupies ~ on each side of it
(Fig. 85). A great many, but not all, of the colourless corpuscles run in
this layer. It is much less distinct in the capillaries. End. Wagner stated
that it is absent in the finest vessels of the lung and gills [although
Gunning was unable to confirm this statement.] The coloured corpuscles
move in the smallest capillaries in single file 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 unfrecaiently we see a red corpuscle becoming
bent where two vessels meet, but on all occasions it rapidly regains

188 CAPILLARY CIRCULATION.

its original form. This is a good proof of the elasticity of the
coloured corpuscles.

Colourless Corpuscles. — The motion of the colourless corpuscles is
quite different in character; they roll directly on the vascular icall,
moistened on their peripheral zone by the plasma in Poiseuille's space,
their other surface being in contact with the thread of coloured cor-
puscles in the centre of the stream. Schklarewsky 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 suspended 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 slower 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. 117).

[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 upper surface, and only a few on the loAver 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 slightly greater specific gravity than the blood-
plasma. Hamilton controverts 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

DIAPEDESIS. 189

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 those of 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 provided with muscular fibres, but also in the capillaries, which vary in
diameter, owing to the contraction of the cells composing their walls (p. 125).

The velocity of the blood is greater in the pulmonary than in the
systemic capillaries (Hales, 1727); hence, we must conclude that the
total sectional area of the pulmonary capillaries is less than that of all
the systemic capillaries.

95. Passage of the Blood-Corpuscles out of the

Vessels— Diapedesis.

Biapedesis. — 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 num-
bers (Fig. 85). 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 peri-vascular 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 between the endothelial cells (p. 122). This process 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 process,
whereby the corpuscle appears constricted in the centre (Fig. 85, c). (d.) The com-
plete passage of the corpuscle through the wall, and its farther motion in virtue of
its own amosboid movements. Hering observed that in large vessels with peri-
vascular lymph spaces, the corpuscles passed into these latter, 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, 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
intra-vascular 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).

190

MOVEMENT OF THE BLOOD IN THE VEINS.

This remarkable phenomenon was described by Waller in 1846. Cohnheim has

_W recently re-described it, and accord-

ing to him the out-wandering is a
sign of inflammation, and the
colourless corpuscles which accum-
ulate in the tissues are to be
regarded as true pus corpuscles,
which may undergo further in-
crease by division.

Stasis. — When a strong stim ulus
acts on a vascular part, hyper remic
redness and swelling occur. Micro-
scopic observation shows, that the
capillaries and the small vessels
are dilated and overfilled 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 con-
tinued, the retardation becomes considerable, the stream moves in jerks, then
follows a to and fro movement 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. [The vapour
of chloroform causes hypeneniia of the web (Lister).]

Fig. 85.

Small vessel of the mesentery of a frog, show-
ing the diapedesis of the colourless
corpuscles— «0, iv, vascular walls ; a, a,
Poiseuille's space ; r, r, red corpuscles ;
/, /, colourless corpuscles adhering to
the wall, and c, c, in various stages of
extrusion ; /, /, extruded corpuscles.

96. Movement of the Blood in the Veins.

As already mentioned, in the smallest veins coming from the
capillaries, the blood-stream is more rapid than in the capillaries them-
selves, 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 in different parts of its course. Amongst these are : —
(1) The relative laxness, great distensibility, and the ready compressibility
of the walls, even of the thickest veins. (2) The incomplete filling
of the veins, which does not amount to any considerable 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.

MOVEMENT OF THE BLOOD IN THE VEINS. 191

(4) The presence of numerous valves which permit the blood-stream to
move only in a centripetal direction (Fabricius ab Aquapendente).
They are absent from the smallest veins, and are most numerous in
those of middle size.

Law of the Position Of Valves. — The venous valves always have two
pouches, and are placed at definite intervals, which correspond to the 1, 2, 3, or
nth power of a certain "fundamental distance," which ig = 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 — e.g., in the
cutaneous veins. The pulsatile pressure of the arteries accompanying
the veins favours the venous current (Ozanam).

From a hydrostatic 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 hama-
dromometer and the stromuhr— § 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.

As we proceed from the small veins towards the venee cavse, 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 vente cavre 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. The velocity of the
blood-current in the veins is accelerated during inspiration — compare
§ 88 (De Jager).

[Active pulsation occurs in the veins of the wing of the bat (Schiff).]

192 SOUNDS WITHIN ARTERIES.

97. Sounds or Bruits within Arteries.

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. In four-fifths of all healthy men two sounds— corresponding 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."

Arterial Sounds or murmurs are readily produced by pressing upon
a strong artery — e.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 com-
pression. Thus arises the " pressure-stream " (P. Niemeyer), or the
"fluid vein" (" Veine fluide" of Chauveau.) The particles of the fluid
are thrown into rapid oscillation, and undergo vibratory movements,
and by their movement produce the sound within the peripheral
dilated portion of the tube. A sound is produced in the fluid by
pressure (Corrigan, Heynsius). The sounds are not caused by vibra-
tions 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 (Friedreich). This result is indicated in a
diminution or absence of the pulse-wave in the radial artery (Weil).

Arterial murmurs are favoured by — (1) Sufficient delicacy and
elasticity of the arterial walls (Th. Weber). (2) Diminished peri-
pheral resistance — e.g., an easy outflow of the fluid at the end of the
stream (Kiwisch). (3) Accelerated current in the vascular system
generally. (4) A considerable difference of the pressure in the
narrow and wide portions of the tube (Marey). (5) Large calibre of
the arteries.

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, within which murmurs are generally audible.
(b.) 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, (c.) A murmur corresponding to each pulse-beat is heard, especially where
two or more large arteries lie together ; hence, during pregnancy, we hear the uterine
•murmur, or placenlal bruit, or souffle 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 (Fisher, 1833). A
murmur due to the systole of the heart is often heard in the carotid (Jurasz). In such

VENOUS MURMURS. 193

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 (Traube, Weil) — i.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 soiiuds in the arteries are greatly
diminished.

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 first 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 (Duroziez, 1861). 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 (Landois)— compare
§ 73, Fig. 62, III. In atheroma a double sound may sometimes be heard (§ 73, 2).

98. Venous Murmurs.

1. 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 phe-
nomenon. If, however, pressure be exerted, and if, at the same time,
the person examined turns his head to the opposite side a similar
sound is heard in nearly all cases (Weil). The pathological bruit de
diable occurs especially in ansemic persons, in lead-poisoning, syphilitic
and scrofulous persons, sometimes in young persons, and less frequently
in elderly people. Sometimes a thrill 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 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 (scrofula), facial,
innominate and crural veins and superior cava.

13

194 THE VENOUS PULSE.

II. Regnrgitant Murmurs. — On making a sudden effort, a murmur may be
heard in the crural 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 (ex-
piratory 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 ventricular systole, a large volume of blood is propelled backwards into
the venas cavse. The venous valves are closed suddenly thereby and a sound pro-
duced. This occurs at the bulb or dilatation on the jugular vein (v. Bamberger),
and in the crural vein at the groin (N. Friedreicli), 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 tinder 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 phleboyram (Fig. 86). 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. 29, p. 88), is synchronous with al>; le, with the ven-
tricular systole, during which time the first sound occurs, whilst a, b is a
presystolic movement. The carotid pulse coincides nearly with the apex of the
cardiogi'am, i.e., almost simultaneously with the descending limb of the phlebogram
(Riegel).

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 up-
wards, 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.

The venous pulse resembles very closely the tracing of the cardiac
impulse (Landois). Compare Fig. 86, 1, with Fig. 25a, A, p. 82.

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. 8G, 9 and 10, are venous
pulses of a healthy person with insufficiency of the valves of the jugular
vein. In these curves, the part a, b, corresponds to the contraction of
the auricle. Occasionally this part consists of two elevations, corre-
sponding 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, isochronous with the systole of the right
ventricle, there is a positive wave in the jugular vein in Fig. 86, 9 and

THE VENOUS PULSE.

195

10. indicated by b, 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. 86, 9, at (T). 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 (Riegel, FranQois-
Franck).

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 (Helfrich).

Jugular Vein Pulse. — The venous pulse in the jugular vein is far better
marked in insufficiency of (he 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 (Friedreich).

Liver Pulse. — The ventricular systole is propagated into the valve-less

Fig. 8G.

Various forms of venous pulses, chiefly after Friedreich — 1-8 from insufficiency of
the tricuspid ; 9 and 10, pulse of the jugular vein of a healthy person. In all
the curves, a, b — contraction of the right auricle; b, c, of the right ventricle ;
d, closure of the aortic valves ; e, closure of the pulmonary valves ; e, f,
diastole of the right ventricle.

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.

196 DISTRIBUTION OF THE BLOOD.

Fig. 86, 2-8, are curves of the pulse in the common jugular vein (after Friedreich).
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, a, b = auricular contraction.
The auricle, when it contracts, excites a positive wave in the veins (Gendrin, 1843,
Marey, Friedreich). 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. 86, 9 and 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 sphygmo-
graph. As a general rule, at least one notch (4, 5, 6, e) follows the apex, due to
the prompt closure of the valves of the pulmonary artery. The closure of the
closely adjacent aortic valves may cause a small secondary wave near to c (as in 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, at first the carotid pulse becomes
smaller and the venous pulse larger; beyond a certain pressure, the latter ceases
(Riegel).

100, Distribution of the Blood.

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 warm.

In a rabbit, one-fourth of the total amount of the blood is found in
each of the following : — a, in the passive muscles ; b, in the liver ; c, in
the organs of the circulation (heart and great vessels) ; d, in all other
parts together (J. Eanke).

The amount of blood is influenced by — (1) The anatomical distribution (vascularity
or the reverse) of the vessels 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-dilatator nerves ; (c) on the condition
of the tissues themselves, e.g., the vessels of the intestine during absorption; by the
vessels of muscle during muscular contraction ; of vessels in inflamed parts.

PLETHYSMOGRAPHY. 197

Activity of an Organ. — 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 (J. Ranke).
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
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. Eanke).

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).

In the condition of increased activity, a more rapid renewal of the
blood seems to occur; after muscular exertion the duration of the cir-
culation diminishes (Vierordt).

3. — The development of the heart and large vessels determines a different dis-
tribution of the blood iu 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, 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 in the 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.

Plethysmograph. — In order to estimate and register the amount of
blood in a limb Mosso devised an instrument (Fig. 87), which he
termed a Plethysmograph. It is constructed on the same principle as
the less perfect apparatus of Chelius and Fick.

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 with the increased supply of arterial blood passing into it at each

198

PLETHYSMOGRAPHY.

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 resera-

Fig. 87.

Mosso 's Plethysmograph — G, glass-vessel for holding a limb; F, flask for varying
the water-pressure in G; T, recording apparatus.

bled the pulse-curve; it was even dicrotic. In Fig. 87 the movement of the
fluid is represented as conveyed to a Marey's tambour, T, similar to the recording
apparatus employed in Brondgeest's Pausphygmograph (p. 87).

From the curve obtained we learn that — (1.) The pulsatile variations
in the volume are similar to the pulse-curve. As 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). (2.) The respiratory undulations
correspond to similar variations in the blood-pressure tracing
(§ 85, /). Vigorous respiration and cessation of the respiration cause
a diminution of the volume. The limb swells during straining (v.
Basch) and coughing, and diminishes during sighing. (3.) Certain
periodic undulations occur, due to the regular periodic contractions
of the small arteries. (4.) Other undulations, due to various acci-
dental 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 (ex-
periment of Fr. Glisson, 1677); as the venous current is accelerated,
the musculature is also very slightly diminished in volume, even when
the ultra-muscular vessels are dilated. (6.) Mental exercise causes a
diminution in the volume of the limb, and so does sleep (Mosso).
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). Compression of the
afferent artery causes a decrease, and compression of the vein an
increase in the volume qf the limb (Mosso).

TRANSFUSION OF BLOOD, 199

102. Transfusion of Blood.

Transfusion is the introduction of blood from one animal into the
vascular system of another animal.

Historical. — The first indication of direct transfusion from blood-vessel to
blood-vessel dates from the time of Cardanus in 1556. After the discovery of the
circulation in England, J. Potter (1638) evolved the idea of transfusion of blood.
Numerous experiments were made on animals. New blood was transfused in
order to restore life in animals that had been bled. Boyle and Lower conducted
these and other experiments. The blood of the same species, as well as the blood
of other species, was employed. The first case of transfusion on man was per-
formed by Jean Denis in Paris (1667), lamb's blood being used. At the present
time, when transfusion is practised on man, only human blood is used.

(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 (Prevost and Dumas, 1821). The effect of various
reagents upon them has already been noticed (§ 4, A).

(&.) With regard to the GASES of the blood-corpuscles, oxygenated
(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 respira-
tory centre, causing dyspnoea, convulsions, and death.

(c.) The FIBRIN, or the substances' from which it is formed (§ 29),
do not seem to play any part in connection with the restorative
powers of the blood ; hence, defibrinated blood performs all the func-
tions of non-defibrinated blood within the body (Panum, Landois).

(d.*) The investigations of Worm Miiller shoAved that an excess of
83 per cent, of blood might be transfused into the vascular system
of an animal without producing any injurious effects. Hence it follows
that the vascular system has the power of accommodating large quan-
tities of blood within it. That the vascular system can accommodate
itself to a diminished amount of blood has been known for a long
time.

When Employed. — The transfusion of blood is used — (1.) in acute
ancemia (§41, I), e.g., after copious hemorrhage. New blood from the
same species of animal is introduced directly into the vessels, to supply
the place of the blood lost by the haemorrhage.

200 TRANSFUSION OF BLOOD.

(2.) In cases of poisoning, where the blood has been rendered use-
less 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 (Kiihne), and its effects on the body have already been
described (compare p. 32). The indication is also obtained for a
similar practice in poisoning with ether, chloral, chloroform, opium,
morphia, strychnine, cobra poison.

(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 propor-
tion of its other constituents. Amongst these conditions, may be cited
the pathological condition of uraemia, due, it may be, to the accumula-
tion of urea or the products of its decomposition Avithin the blood [or
to the retention of the potash and other urinary salts — Feltz and
Ritter] ; accumulation of the biliary constituents in the blood (Cholsemia),
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 (Landois).

Amongst conditions where the morphological constituents of the blood
are altered qualitatively or quantitatively are : hydra3inia (excessive
amount of water in the blood § 41, 1) ; oligocythsemia (abnormal dimi-
nution 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 suffer-
ing from leukaemia (compare p. 23).

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 (compare Fever).

Operation. — The operative procedure to be adopted in the process of trans-
fusion varies according as defibrinated or non-detibrinated blood is used. In order
to defibrinate blood, some blood is withdrawn from a vein of a healthy man in the
ordinary way, it is collected in an open vessel and whipped or beaten with a glass
rod until all 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 warm water)
and injected by means of a syringe into an artery opened for the purpose. A vein
(f.<j., basilic or great saphenous) may be selected for the transfusion, in which case
the blood is driven in, 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, Unger, Schafer).

Dangers. — It is most important not to permit the entrance of air into the circu-
lation, for if it be introduced in sufficient quantity, it may cause death. When air
enters the circulation it reaches 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.

TRANSFUSION OF BLOOD. 201

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.

Peritoneal Transfusion. — Recently, the injection of denbrinated blood into
the peritoneal cavity has been recommended. The blood so injected is absorbed
(Ponh'ck). Even after twenty minutes the number of blood-corpuscles in the
blood of the recipient (rabbit) is increased, and the number is greatest on the first
or second day (Bizzozero and Golgi). The operation, however, may cause death,
and one fatal case, owing to peritonitis, is recorded (Mosler). It is evident that
this method of transfusion is not applicable in cases where blood must be intro-
duced into the circulation as rapidly as possible (e.g., after severe haemorrhage 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. Some surgeons have transfused blood directly from the
carotid of a lamb into the human subject. It is 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). As a general
rule, the blood-serum of many mammals dissolves the blood-corpuscles of other
mammals (§ 5, 5).

Solution Of the Blood-CorpUSCleS.— The serum of clog's blood is a powerful
solvent, while that of the blood of the horse and rabbit dissolves corpuscles rela-
tively 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 rabbit's 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 defibriuated as well as in ordinary
blood. When the blood of a rabbit or lamb is injected into the blood-vessels of a
dog they 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 Hsemoglobin and Haemoglobinuria.— As a consequence of

the solution of the coloured corpuscles, the blood-plasma is reddened by the
liberated haemoglobin. 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 haemoglobin is excreted in the urine (haemo-
lobiuuria) in less amount in the intestine, the bronchi, and serous cavities
(Panum). Bloody urine has been observed in man after the injection of 100
grammes of lamb's blood. Even some of the recipient's own corpuscles may be
dissolved, as in the case where the recipient's blood-corpuscles are dissolved by
the serum of the transfused blood — e.g., transfusing dog's blood into man. In the
rabbit, whose corpuscles are readily dissolved, the transfusion of the blood-serum
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 (i.e., blood from a different
species) is transfused, 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 capillaries.
After a time they give up their haemoglobin, leaving the stroma, which yields a
sticky fibrin-like mass that may occlude fine vessels (p. 48).

(2.) The presence of a large quantity of dissolved haemoglobin may cause
extensive coagulation within the blood-vessels. The injection of dissolved haemo-
globin causes extensive coagulations (Naunyn and Francken).

The coagulation occurs usually in the venous system and in the large vessels,
and may cause death either suddenly or after a considerable time.

6

202 TRANSFUSION OF OTHER FLUIDS.

Dissolved haemoglobin seems greatly to increase the activity of the fibrin-ferment
(§ 30), perhaps by accelerating the decomposition of the colourless corpuscles.
Haemoglobin exposed to the air gradually loses this property; and the fibrin-
ferment, when in contact with haemoglobin, is either destroyed or rendered less
active (Sachssendahl).

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 expectoration. 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 peristalais, 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 (Ponfick). Owing to the occlusion
of numerous small muscular branches the muscles may become stiff, or coagulation
of their rnyosin may occur. Other symptoms, referable to the nervous system, the
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 transfusion of heterogeneous blood.
When many vessels are occluded, rupture of some small blood-vessels may take
place. This explains, the occurrence of slight yet persistent haemorrhages, which
occur on the free surfaces of the mucous and serous membranes, and in the paren-
chyma 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 SOLUTION (0'6 p.c. NaCl) aids the circulation in a purely
mechanical way (Goltz), and it even excites the circulation (Kronecker, Sander,
Ott). In severe anaemia this fluid cannot maintain life (Eulenburg and Landois).
The injection of PEPTONE, even in moderate amount, is dangerous to life, as it causes
paralysis of the vessels. The injection of MILK is accompanied with danger ;
fever occurs after the injection, and the milk globules cause the occlusion of many
vessels, producing subsequent degenerations. Fat may appear in the urine,
and there may be fatty infiltration of the urinary tubules. The urine contains
sugar and albumin, the liver cells often contain fatty granules, and the weight of
the body diminishes. If too large a quantity of milk be transfused, death occurs.
When unboiled milk is injected, numerous bacteria are developed in the blood
(Schiifer).

The Blood-Glands.

103. The Spleen.

Structure. — The spleen is covered by the peritoneum, except at the
hilus. Under this SEROUS covering there is a tough thick elastic
fibrous CAPSULE, which closely invests the organ and gives a covering
to the vessels which enter or leave it at the hilus, so that fibrous tissue
is carried into the organ along the course of the vessels. [The capsule
cannot be separated without tearing the splenic pulp.] Numerous
TRABECUL/E pass into the spleen from the deep surface of the capsule.
These trabeculas branch and anastomose so as to produce a net-work
or sustentacular tissue, which is continuous with the connective tissue,
prolonged inwards and surrounding the blood-vessels (Fig. 88). Thus,
the connective tissue in the spleen, as in other viscera, is continuous

Fig. 88.

Trabeculse of the spleen of a cat with the splenic pulp
washed out — a, trabecula ; b, vein.

Fig. 89.

Spleen of a cat injected
with gelatine, show-
ing the adenoid re-
ticulum.

throughout the organ. In this way an irregular dense net-work is
formed, comparable to the meshes of a bath-sponge. [This net-work 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 net-work
of rounded and flattened threads is obtained.]

The Capsule is composed of interlacing bundles of connective tissue

204 BLOOD-VESSELS OF THE SPLEEN.

mixed with numerous fine fibres of elastic tissue and some non-striped
muscular fibres.

Reticulum. — Within the meshes of the trabecular framework there is
dispersed a very delicate net-work (reticuluni) of adenoid tissue (Billroth),
which, with the other coloured elements that fill up the meshes, con-
stitute the splenic pulp (Fig. 89). The reticuluni is continuous with the
fibres of the trabeculse. [If a fine section of the spleen be " pencilled "
in water, so as to remove the cellular elements, the preparation presents
much the same characters as a section of a lymph-gland similarly
treated, viz., a very fine net-work of adenoid tissue, continuous with,
and surrounding the walls of, the blood-vessels. The spaces of this
tissue (His) 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
splits up into several branches before it enters the spleen, and it is accom-
panied in its course by the vein. Both vessels and their branches are
enclosed in a fibrous sheath, which becomes continuous with the trabeculas.
The smaller branches of the artery gradually lose this fibrous investment,
and each one ultimately divides into a group or pencil of arterioles (PENI-
CILLI) which do not anastomose with each other. [Thus each branch is
terminal — a condition which is of great importance in connection with
the pathology 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 about
the size of a small millet seed (^ to ^ inch in diameter) — the MAL-
PIGHIAN 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 — [7,000 in man
(Sappey)] — and are readily detected in the dark reddish pulp.
We must be careful not to mistake sections of the trabeculse for
them. These corpuscles consist of adenoid tissue, whose meshes
are loaded with lymph-corpuscles, and they present exactly the same
structure as the solitary follicles of the intestine (compare Lymphatic
Glands).

[They are just small lymphatic accumulations around the arteries—
per/arterial masses of adenoid tissue similar to those masses that occur
in a slightly different form in other organs, e.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

BLOOD-VESSELS OF THE SPLEEN.

205

lob-sided. They are not surrounded by any special envelope,
some animals the lymphatic
tissue is continued for some
distance along the small
arteries, so that to some ex-
tent it resembles a peri-
vascular sheath of adenoid
tissue (W. Miiller, Schweig-
ger-Seidel). In a well injec-
ted spleen, a few fine capillaries
may be found within these
corpuscles (Sanders). The
capillaries distributed in the
substance of the Malpighian
corpuscle (Fig. 90) form a
net-work, and ultimately pour
their blood into the spaces in
the pulp. According to Ilobin
and Legros, these vessels are
comparable to the vasa vaso-
rum of other blood-vessels.
According to Cadiat, the

In

Fig. 90.

Malpighian "corpuscle of the spleen of a cat
injected — a, artery around which the
corpuscle is placed ; b, meshes of the pulp
injected ; c, the artery of the corpuscle
ramifying in the lymphatic tissue composing
it. The clear space around the corpuscle is
the lymphatic sinus.

corpuscles are separated from the splenic pulp by a lymphatic sinus,
which is traversed by efferent capillaries passing to the pulp (Fig. 90).]
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 difficult to inject the blood-vessels of
the spleen. According to Stieda, W. Miiller, Peremeschko, and Klein,
the fine "capillary arteries" formed by the division of the small
arteries do not open directly into the capillary veins, but the connec-
tion 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. According to
Billroth and Kolliker, a closed blood-channel actually does exist
between the capillary arteries and the veins, consisting of dilated
spaces (similar to those of erectile 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

200 LYMPHATICS AN!) NERVES OF THE SPLEEN.

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 net-work of the pulp. From these passages the
venous radicles arise. At first, their walls are imperfect and cribri-
form, 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 anasto-
mose freely, but they soon become ensheathed, and accompany the
arteries in their course.]

Elements of the Pulp. — The morphological 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 amoeboid move-
ments.] (Compare § 8.)

[The Lymphatics undoubtedly arise within the spleen. The lym-
phatics which leave the spleen are not numerous (Kolliker). There
are two systems — a superficial, capsular, and trabecular system ; and a
peri-vascular set. The superficial lymphatics in the capsule are rather
more numerous. Some of them seem to communicate with the
lymphatics within the organ (Tomsa, Kolliker). In the horse's spleen,
they communicate with the lymphatics in the trabeculae, and with the
peri-vascular lymphatics. The exact mode of origin of the peri-vascular
system is unknown, but in part at least it begins in the spaces of
the adenoid tissue of the Malpighian corpuscles and peri-vascular
adenoid tissue, and runs along the arteries towards the hilus. There
seem to be no 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 trabecula?. [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 albu-
minous bodies exist in the spleen. Besides the ordinary constituents of the blood,
there exist : — leucin, tyrosin, xanthin, hypoxanthin ; also lactic, butyric acetic,
formic, succinic, and uric acids, and perhaps glycero-phosphoric acid (Salkowski) ;
Cholesterin, a glutin-like body, inosite, a pigment containing iron, and even free
iron oxide (Nasse). The ash is rich in phosphoric acid and iron — poor in chlorine
compounds. The splenic juice is alkaline in reaction ; the specific gravity of the

FUNCTIONS OF THE SPLEEN, 207

spleen = 1059 - 10G6. [The watery extract of the spleen contcains a proteid combined
with iron.]

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 follow-
ing— (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 lie removed from an animal
without the organism suffering any very obvious change (Galen). The
human spleen has been successfully removed by Koberle, Ptian,
Zacaralla (1849), and others. As a result (compensatory ?) the lym-
phatic 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 com-
pensatory 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 (Meinhard, Koch, and Wachsmuth). [Schindeler
found that animals after extirpation of the spleen became very
ravenous, but there was no other marked symptom.]

Schiff stated that after extirpation of the spleen, the pancreatic juice failed to
digest proteids. The evidence in support of this statement is unsatisfactory, and
Mosler affirms that this operation has no effect either on gastric or pancreatic diges-
tion. Heidenhain also found a similar negative result. The operation ought to
be performed on young auimals, as old animals often succumb to it.

(2.) According to Gerlach and Funke the spleen is a BLOOD-FORMING
GLAND. As already mentioned (p. 20) the blood of the splenic vein
contains far more colourless corpuscles than the blood of the splenic
artery. Many of these corpuscles undergo fatty degeneration, and
disappear in the blood-stream (Virchow). That colourless blood-cor-
puscles 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 hyperplasia of the spleen or leukaemia (Bennett, 1852,
Virchow). Bizzozero and Salvioli found that several days after severe
haemorrhage, the spleen became enlarged, and its parenchyma contained
numerous red nucleated hremato-blasts.

According to Schiff, extirpation of the spleen has no effect, either upon the
absolute or relative number of coloured or colourless corpuscles. [According to
the more accurate observations of Picard and Malassez, there is a temporary

208 FUNCTIONS OF THE SPLEEN.

diminution of the coloured blood-corpuscles and their haemoglobin, after extirpa-
tion of the spleen.]

(3.) Other observers (Kolliker 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 (p. 16)
as a proof of this. According to the observations of von Kusnetzow,
these structures are merely lymph-corpuscles, which, in virtue of their
amoeboid movements, have entangled coloured blood-corpuscles. [Such
corpuscles exhibit similar properties when placed upon a warm stage.]
Similar cells occur in extravasations of blood (Virchow). The coloured
blood-corpuscles within the lymph-cells gradually become disintegrated,
and give rise to the production of granules of hsematin and other
derivatives of haemoglobin. Hence, the spleen contains more iron than
corresponds to the amount of blood present in it. When we con-
sider that the spleen contains a large number of extractives derived
from the decomposition 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 of the spleen is said to undergo other changes, but the following
statements 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 haemoglobin crystallises more easily,
and there is a larger proportion of 0 during digestion.

[It would thus appear that the spleen has a very direct relation
to the blood ; that coloured blood-corpuscles undergo disintegration,
and that colourless corpuscles are manufactured within it.]

(4.) Contraction. — In virtue of the plain muscular fibres in its
capsule and trabecula?, the spleen undergoes variations in its volume
(Kolliker). Stimulation of the spleen (Rud. Wagner, 1849) or its
nerves, by cold, electricity, quinine, eucalyptus, ergot of rye, and other
" splenic reagents " (Mosler) 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 — i.e., at a time when the digestive
organs 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

CONTRACTION OF THE SPLEEN.

209

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 Koy, have studied various
conditions which affect the size of the spleen. Eoy's observations
are most important. He enclosed the spleen of a living animal (dog)
in a box with rigid walls, and filled with oil after the manner of the
plethysmograph (§ 101). Any variations in the size of the organ
caused a variation in the amount of oil within the box, and these
variations were recorded. This instrument Roy termed an " ONCO-
GRAPH" (oyx°e> volume). The blood-pressure was recorded at the
same time.

Koy finds that the circulation through the spleen is peculiar, and
that it 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 trabeculse. The spleen undergoes very regular rhyth-
mical contractions (systole) and dilatations (diastole). This alternation

-Spleen

Blood-pressure

Abscissa, of Blood-pressure- curve

2 sec? intervals

Fig. 91.

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 b, give the relative positions of the lever
point of the oncograph, and of the point of the recording style of the kymograph
respectively (Roy).

14

210 INFLUENCE OF NERVES ON THE SPLEEN.

of systole and diastole may last for hours, and the two events together
occupy about one minute (Fig. 91). Changes in the arterial blood-
pressure have comparatively little influence 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 move-
ments.]

Influence of Nerves. — Section of the splenic nerves causes an
increase in the size of the spleen ; and when the nerves at the hilum
are extirpated it swells and assumes a deep piirple colour. The nerves
have their centre in the medulla oblongata, and so far they are com-
parable to vaso-motor nerves. 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 are probably
joined by other fibres derived from ganglion cells lying opposite the
first to the fourth cervical vertebi-re, which cells also act on the spleen.
The fibres leave the cord in the dorsal region, enter the left splanchnic,
pass through the semi-lunar ganglion, and thus reach the splenic plexus
(Jaschkowitz.) 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 this last case the result
is brought about reflexly. Section or paralysis of these nerves causes
dilatation, and so does curara or continued narcosis (Bulgak). [Botkin
found that the application of the induced current to the skin over the
spleen, in a case of leukaemia, caused well-marked contraction of the
spleen in all its dimensions ; the spleen becoming firmer, and its surface
more irregular. The result lasted much longer than the duration of
the stimulus. The same occurred in a case of enlarged lymphatic
glands. After a time the organ began to enlarge. After every stimu-
lation 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 in-
creased its size, while 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 to a less degree.

INFLUENCE OF NERVES ON THE SPLEEN. 21 1

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 by afferent nerves, and sending out efferent
impulses.]

[Eoy confirmed most of these results, and found that stimulation of
(1) the central end of a sensory nerve, (2) of the peripheral ends of
both splanchnics, (3) of the peripheral ends of both vagi, caused
contraction of the spleen. But even after section of the splanchnics
and vagi, stimulation of a sensory nerve still caused contraction, so
that there must be some other channel as yet unknown. Boche-
fontaine 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 (Mosler) ; hence,
increased pressure in this vein (congestion of the portal vein, cessation of hsemor-
rhoidal and menstrual discharges) also causes its enlargement. With regard to the
action of "splenic reagents," siach as Quinine, on the contraction of the spleen,
Binz is of opinion that this drug retards the formation of the colourless blood-cor-
puscles, 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 dilata-
tion 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 earl}'
attracted the attention of physicians. The healthy spleen undergoes several varia-
tions 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, probably due to paralysis of its
nerves. It is greatly increased in intermittent fever or ague, and often during
the course of typhus. When it becomes abnormally enlarged, and remains so after
repeated attacks of ague, it is greatly hypertrophied and constitutes "ague cake."
In cases of splenic leukaemia 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 (p. 23).

II. The Thymus.

During fcetal life this gland is largely developed, and it increases during the first
two or three years of life, remaining stationary until the tenth or fourteenth year,
when it begins to atrophy and undergo fatty degeneration. [The degeneration
begins at the outer part of each lobule and progress inwards (His). ]

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 con-
nective tissue which contains blood-vessels, lymphatics, and a few nerves (Fig. 92).
The framework of connective tissue gives off septa which divide the gland into lobes,
these being further subdivided by finer septa into lobules, the lobules being separated

212

THE THYMUS.

by fine intra-lobular lamellrc of connective tissue into follicles (0'5-1'5 mm.).
These follicles make up the gland substance, and they are usually polygonal when
seen in a section. Each follicle consists of a cortical and a medullary part, and the
matrix or framework of both consists of a fine adenoid reticulum whose meshes
are filled with lymph-corpuscles " (Fig. 93, a).] 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. 93, I).

<Y

Fig. 92.

Section of the thymus gland of a cat, showing
one complete lobule with an outer cortical
part, a centre, 6, and parts of adjoining
lobules — «, lymphoid tissue; c, blood-
vessels injected ; tZ, connective tissue.

Fig. 93.

Elements of the thymus ( x 300) —
a, lymph-corpuscles ; b, con-
centric coi-puscle of Hassall.

They have also been compared to similar bodies which occur in the prostate.
They are most numerous when the gland undergoes its retrograde metamorphosis."]

Simon, His, and others described a convoluted blind canal, the " central canal,"
as occurring 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 tymph-CQr-
puscles are conveyed away from the gland.] Numerous blood-vessels are also dis-
tributed to the septa and follicles (Fig 92, 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 (v. Gorup-
Besanez).

[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 tymph-glands, the thymus remains as a permanently active
organ. That the thymus forms colourless corpuscles was first maintained by
Hewson, and confirmed by His and Jendrassik. Extirpation (Friedleben) gave few

THE THYROID. 213

positive results, but chemical investigation shows that the parenchyma contains a
large number of products indicating considerable metabolic activity. The volume
of the gland undergoes variations both in health and disease.]

III. The Thyroid.

Structure.— In a connective tissue net-work rich in cells there lie numerous
completely closed sacs (O04— O'l 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. 94). The sacs contain a transparent, viscid, albuminous
fluid. [Not unfrequently the
sacs contain many coloured c
blood-corpuscles (Baber). As
in other glands, there are
lobes and lobules.] Each sac
is surrounded by a plexus of
capillaries which do not pene-
trate the membrana propria.
There are also numerous
lymphatics. At an early
period the sacs dilate, their
cellular lining atrophies, and
their contents undergo colloid
degeneration. When the
gland vesicles are greatly
enlarged, "goitre" is pro-
duced.

The Chemical Composi-
tion of this gland has not
been much investigated. In
addition to the ordinary con-
stituents, leucin, xanthin,
sarkin, lactic, succinic, and
volatile fatty acids have been
found.

Functions. — Its functions are quite unknown. 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
[Exophthalmos], which seem to depend upon a simultaneous stimulation of the
accelerating nerve of the heart, and the sympathetic fibres for 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, associated
with idiocy and cretinism.

Fig. 94.

Section of the thyroid gland ( x 250) — or, small
closed vesicles lined by low columnar epithe-
lium ; 6, colloid masses distending the vesicles ;
c, connective tissue between the vesicles.

IV, The Supra-Renal Capsules.

Structure. — These organs are invested by a thin capsule which sends processes
into the interior 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. 953 b), the trabeculte form polygonal meshes which contain the

214

THE SUPRA-RENAL CAPSULES.

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 contain-
ing groups of cells of very irregular shape.
Numerous blood-vessels 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 mu Itipolar nerve-cells exist with-
in the gland.] — (Eberth, Creighton, v.
Brunn).

Chemical Composition.— The supra-

renals contain the constituents of connec-
tive-tissue and nerve-tissue; also leiicin,
hypoxanthin, benzoic, hippuric, andtauro-
cholic acids, taurin, inosit, fats, and a body
which becomes pigmented by oxidation.
Amongst inorganic substances potash and
phosphoric acid are most abundant.

The function of the supra-renal bodies
is quite unknown. It is noticeable, how-
ever, that in Addison's disease ("bronzed
skin ") which is perhaps primarily a
nervous affection, these glands have fre-
quently, 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. Brown-Se'quard thinks they may
be concerned in preventing the over-production of pigment in the blood.

Fig. 95.

Section of a human supra-renal capsule
— a, capsule ; b, gland cells of the
cortex arranged in columns ; c,
glandular net-work of the medulla ;
d, blood-vessels.

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 infimdibulum. The nervous elements are displaced
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 supra-renal capsule in its structure, while,

COMPARATIVE PHYSIOLOGY OF THE CIRCULATION. 215

according to other observers, in some animals it is more like the thyroid. Its
functions are entirely unknown.

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
(Luschka). Between these lie polyhedral granular cells arranged in net-works.
The carotid gland has a similar structure (p. 124). 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 as well as in the larva; of amphibians 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. From the latter there proceeds one vessel which gives off the pul-
monary 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
commencement of the aorta, the bulbus arteriosus, which is partly provided with
strong muscles. The reptiles 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 septum seems capable of
being closed. The crocodile has two quite separate ventricles. The lower vertebrates
have valves at the orifices of the vena; cava?, which are rudimentary in birds and
some mammals. All birds and mammals have two completely separate auricles
and two separate ventricles. In the halicore the apex of the ventricles is deeply
cleft. Some animals have accessory hearts, e. <j. , the eel in its caudal vein. They
are very probably lymph-hearts (Robin). The veins of the wing of the bat
pulsate (Schiff). The lowest vertebrate, amphioxus, has no heart, but only a
rhythmically -contracting vessel.

Amongst blood-glands the thymus and spleen occur throughout the vertebrata,
the latter being absent only in amphioxus and a few fishes.

Amongst invertebrata a dosed vascular system, with pulsatile movement,
occui-s here and there, e.g., amongst echinodermata (star-fishes, sea-urchins, holo-
thurians) 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 B.C. ), the heart, the

216 HISTORICAL RETROSPECT OF THE CIRCULATION.

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 i?.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.D.) — " When-
ever 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 (the 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 fifth 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 circula-
tion (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 chorda3
tendinias, the auricles, the closure of the semi-lunar valves. Aristotle was the first
to apply the terms aorta and venas cavse; the school of Erasistratus used the
term carotid, and indicated the functions of the venous valves. In Cicero a dis-
tinction 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
(t 79 A.D.) described the pulsating fontanelle in the child. Galen (131-203 A.D.) 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 demonstration 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 circulation. 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. Blancard (1676) proved the
existence of capillary passages by means of injections. William Cooper (1697)
proved that the same condition exists in warm-blooded animals, and Euysch 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). Job. Alfons Borelli (1608-1679) was the first to estimate the
amount of work done by the heart.

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
carbonic acid formed within the body. The most important organs
for this purpose are the lungs. There is an outer and an inner respira-
tion— 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 bodj''.

[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 (racemose ?) glands which separate C02 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 a number (16-20) of C-shaped incom-
plete 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. [In a transverse section of a large intra-pulmonary
bronchus, two, three, or more pieces of cartilage, each invested by its peri-
chondrium, may be found.] At the points of bifurcation of the bronchi, 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 resophagus, 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
nan-striped muscular fibres which pass trans versely between the cartilages behind,
and also in the intervals between the cartilages. [These pale reddish fibres con-

218 STRUCTURE OF THE TRACHEA.

stitute the trachealis muscle, and are attached to the inner surfaces of the cartilages
by means of elastic tendons at a little distance from their free-ends (Munniks, 1697).
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 sm-faces^Stirling).]
Some muscular fibres are arranged longitiidinally external to the transverse fibres
(Kramer). 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 con-
taining much adenoid-tissue with numerous lymph-corpuscles. It also contains
numerous elastic fibres, arranged chiefly in a longitudinal direction under the base-
ment 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 contaiuing the large blood-vessels, glands, 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 cells under them. [The superficial layer of cells is columnar and
ciliated (Fig. 97, b), while those lying under them present a variety of forms, and
below all is a layer of somewhat flattened 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 by De'bove. They are active germi-
nating cells, and play a most important part in connection with the regeneration
)of the epithelium, after the superficial layers have been shed, in such conditions as
bronchitis (v. Drasch, Hamilton). 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 (Hamilton), 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."]

Underneath the epithelial is the homogeneous basement membrane, through
which tine 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 pathological conditions, e.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. [The acini of some of these
glands lie outside the trachealis muscle. The acini are lined by cubical or
columnar secretory epithelium. In some animals (dog) these cells are clear, and
present the usual characters of a mucous-secreting gland ; in man, some of the cells
maybe clear, and others "granular," but the appearance of the cells depends
upon the physiological state of activity.] These glands secrete the mucus, which
entangles particles 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 aggregations of adenoid tissue occur (especially in the
cat) in the mucous coat, usually around the ducts of the glands. They are com-
parable 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 con-
taining 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 : —

STRUCTURE OF THE BRONCHI.

219

(1.) Stratified columnar ciliated epithelium.
(2.) A layer of flattened cells (Debove's membrane).
(3.) A clear homogeneous basement membrane.

(4.) A basis of areolar tissue, with adenoid tissue and blood-vessels, and out-
side 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.]

[The Bronchi.— In structure" the extra-pulmonary bronchi resemble the
trachea. As they pass into the lung they divide dichotomously very frequently, and
the branches do not anastomose. The subdivisions become finer and finer, the finest

Fig. 97.

Transverse section of part of a normal human bronchus ( x 450) — a, precipitated
mucus on the surface of the ciliated epithelium, b; b, ciliated columnar
epithelium ; c, deep germinal layer of cells (Debove's membrane) ; d, elastic
basement membrane ; e, elastic fibres divided transversely (inner fibrous
layer);/, bronchial muscle (non-striped); (/, outer fibrous layer with leuco-
cytes and pigment granules (black) deposited in it. The lower part of the
figure shows a mass of a denoid tissue.

branches being called terminal bronchi, or bronchioles, which open separately into
clusters of air-vesicles.]

220 STRUCTURE OF THE BRONCHI AND BRONCHIOLES.

[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.
97, f). 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, e,
disposed longitudinally, exist under the basement membrane, d. They are con-
tinuous with those of the trachea, and are continued onwards into the lung.
The mucous membrane of the larger intra-pulmonanj bronchi consists of the
following layers from within outwards : —

(1.) Stratified columnar ciliated epithelium (Fig. 97, b).
(2.) De"bove's membrane (Fig. 97, c).

(3.) Transparent homogeneous basement membrane (Fig. 97, d).
(4.) Areolar tissue with longitudinal elastic fibres (Fig. 97, e).
(5.) A continuous layer of non-striped muscular fibres disposed circularly
(bronchial muscle — Fig. 97, /).

Outside this is the sub-mucous coat, consisting of areolar tissue mixed with much
adenoid tissue (Fig. 97, g), sometimes arranged in the form of cords, the lymph-
follicular cords of Klein. 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. A branch of the pulmonary artery and 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
bronc/ii" (about O'5-l 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" (Kblliker), 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. 100, e) which are continuous on the one hand with the sub-pleural
connective-tissue, and on the other with the peri-bronchial connective-tissue.]

[It is evident that 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 iu the smaller bronchi, and

STRUCTURE OF THE AIR-CELLS.

221

on the other, with those in the walls of the air-cells, lie outside the muscular
fibres in the bronchioles 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-Ceils.— The form of the air-cells, which are 250/J- (rJT inch)
in diameter, may be more or less spherical, polygonal, or cup-shaped. They are
disposed around and in communication 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 corpuscles. This is sur-
rounded by numerous fine elastic fibres which give to the pulmonary parenchyma
its well-marked elastic characters (Fig. 99, e, e). These fibres often bifurcate,
and are arranged with reference to the alveolar wall. They are very resist-
ant, and in some cases of lung-disease may be recognised in the sputum.
A few non-striped mus-
cular fibres exist in the
delicate connective - tissue
between adjoining air- ves-
icles (Moleschott). These
muscular fibres sometimes
become greatly developed in
certain diseases (W. Stir-
ling). The air-cells are lined
by two kinds of cells — (1)

large,transparent,clearpoly- ^.._^±^$SrW^N//EL ^>4~- I
gonal (nucleated ?) squames
or placoids (22-45/u) lying
over and between the capil-
laries in the alveolar wall
(Fig. 98, a); (2) small irre-
gular "granular" nucleated
cells (7-15^) arranged singly
or in groups (two or three)
in the interstices between
the capillaries. They are
well seen in a cat's lung
(Fig. 98, (/). [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
(Klein). They open into the lymph-canalicular system of the alveolar wall (Klein),
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 par-
ticles of carbon derived from the air. ] In the alveolar walls is a very dense plexus of
fine capillaries (Fig. 99, c), which lie more towards the cavity of the air-vesicle
(Rainey), 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, thua
projecting sometimes into the one alveolus, sometimes into the other.

Fig. 98.

Air-vesicles from a kitten whose lungs were injected
with silver nitrate ( x 450) — a, outlines of fully-
developed squamous epithelium; 6, alveolar wall;
c, young epithelial cell losing its granular appear-
ance; d, aggregation of young epithelial cells
germinating.

222

THE BLOOD-VESSELS OF THE LUNG.

The Blood-vessels of the lung belong to two different systems : — (A) PUL-
MONARY 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. 99, 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 are joined in
their course by a few small bronchial veins (Zuckerkandl). 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

Fig. 99.

.Semi-schematic representation of the air vesicles of the lung — v, v, blood-vessels
at the margins of an alveolus ; e, c. its blood capillaries ; E, relation of the
squamous epithelium of an alveolus to the capillaries in its wall ; f, alveolar
epithelium shown alone ; f, e, elastic tissue of the lung.

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,

THE PLEUP.A AND THE LYMPHATICS OF THE LUNG.

223

to the walls of the large blood-vessels (vasa vasorum), the pulmonary pleura,
the bronchial walls, and the interlobular septa. The blood which issues from
their capillaries is returned— prer^y by the pulmonary veins — hence, any con-
siderable 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 veins of the smaller
bronchi (fourth order onwards) open into the pulmonary veins, and the anterior
bronchial also communicate with the pulmonary veins (Zuckerkandl).

[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 pari-
etal. The visceral pleura
covers the lung ; the pari-
etal portion lines the
wall of the chest, and the
two layers of the corre-
sponding pleura are con-
tinuous 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 mem-
brane, and consists of a
thin layer of fibrous tissue
covered by a layer of en-
dothelium. Under this
layer, or the pleura pro-
per, is a deep or sub -serous
layer of looser areolar
tissue, containing many
elastic fibres. This layer
of the pleura pulmonalis
of some animals, as the
guinea - pig, contains a
net-work of non- striped
muscular fibres (Klein).
Over the lung it is also
continuous with the in-
terlobular septa. The
interlobular septa (Fig.
100, e) consist of bands
of fibrous tissue separat-
ing adjoining lobules, 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 through-
out the lung, just as in other organs. The connection of the sub-pleura! fibrous
tissue with the connective-tissue within the substance of the lung, has most im-
portant 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

Fig. 100.

Normal human lung ( x 50 and reduced |) — a, small
bronchus; 6 6, branches of the pulmonary artery;
c, branch of the pulmonary vein; e, interlobular
septa, continuous with the deep layer of the
pleiira, p.

224 THE LYMPHATICS OF THE LUNG.

the volume of the lung, so that they are more flattened when the lung is distended,
as during inspiration (Klein). The pleura contains many lymphatics, which com-
municate by means of stomata with the pleural cavity.]

[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-canalchen.] [In the deep layer of the pleura, there is
a (a) sub-pleural plexus of lymphatics partly derived from the pleura, 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-broncliial 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 lymphatics (Klein)]. 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 lymphatics
(v. Wittich) ; or, according to Klein, they pass through actual holes or pores in the
cement (p. 221). [This pigmentation is well seen in coal-miners' lung or anthra-
cosis, where the particles of carbon pass into and are found in the lymphatics.
Sikorski and Kuttner showed that pigment reached the lymphatics in this way
during life. If pigment, China ink, or indigo carmine be introduced into a frog's
lung, it is found in the lymphatic system of the lung. Euppert, and also
Schottelius, 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. A. Schestopal used China ink and cinnabar suspended in f p.c. 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
(Wydwozoff ). According to 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-corpuscles rapidly pass into the lymphatics. [Nothnagel
found that, if blood was sucked into the lung of a rabbit, the blood-corpuscles were
found within the interstitial connective-tissue of the lung after 3^-5 minutes,
from which he concludes that the communications between the cavity of the air-
cells and the lymphatics must be very numerous.]

The superficial lymphatics of the pulmonary pleura communicate with the
pleural cavity by means of free openings or stomata (Klein), and the same is true
of the lymphatics of the parietal pleura, but these stomata are confined 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 (Grancher).

[The movements of the lung during respiration are most important factors in
moving the lymph onwards in the pulmonary lymphatics. The return 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 distribution of the bronchi, several sections of nerve-

PHYSICAL PROPERTIES OF THE LUNGS. 225

trunks being usually found in a section of a large bronchial tube. These 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 these ganglia are so large as to be macroscopic. 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 simple lung of the newt, there are also numerous nerve-cells disposed
along the course of the ultra-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 muscular 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, etc. The vagus is the motor-nerve for these fibres,
and according to Longet (1842), the "lung-tonus" during increased
tension depends upon these muscles. Stimulation of the lower end of
the vagus causes a slight contraction of the bronchial muscles, but the
movement is neither sudden nor considerable. It is highly doubtful if
bronchial (spasmodic) asthma depends upon contraction of these mus-
cular fibres due to stimulation of the vagus.

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 degeneration urea, oxalic acid,
and ammonia salts; and in diseases where decomposition takes place, leucin and
tyrosin.

[Physical Properties of the Lungs. — The lungs, in virtue of the large
amount of elastic tissue which they contain, are endowed with great elas-
ticity, so that when the chest is opened, they collapse. If a 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

15

226 MECHANISM OF RESPIRATION.

the child, the lungs float. Hence, this hydrostatic test is largely used in
medico-legal cases, as a test of the child 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.]

107. Mechanism of Respiration.

The mechanism of respiration consists in an alternate dilatation and
contraction of the chest. The dilatation is called inspiration, the con-
traction 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
the parietal pleura, it is clear, that the lungs must be distended with
every dilatation of the chest, and diminished by every contraction
thereof. These movements of the lungs, therefore, are entirely jwsswe,
and are dependent on the thoracic movements (Galen).

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, i.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 perforation 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.

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 Us original form, and again becomes functionally active.]

QUANTITY OF GASES RESPIRED.

227

Estimation Of Elastic Tension. — If a manometer be introduced through an
intercostal space into the pleura! cavity, in a 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. (Ponders).

If the glottis be closed and a deep inspiration taken, the air within
the lungs must become rarified, 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 expira-
tory 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 gradually. During
tranquil inspiration there is a slight negative pressure ; during expira-
tion 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
it is clear, that only a part
spiration and expiration,
depth of the respirations.

1

chest never give out all the air they contain,
of the air of the lungs is changed during in-
The volume of this air will depend upon the

COMPLEMENTAL
AIR,

110

TIDAL AIR,

20

RESERVE AIR,
100

RESIDUAL AIR,

100

^ I

ro

CO

o

cr
to

CO

»

s

O

»
K|

c

*a
o

Hutchinson (1846) distinguishes the following
points : —

(1.) Residual Air is the volume of air which
remains in the chest after the most complete expira-
tion. It is equal to 1,230-1,640 c.c. [100-130 cubic
inches.]

(2.) Eeserve or Supplemental Air is the volume

of air which can be expelled from the chest after a
normal quiet expiration. It is equal to 1,240-1,800
c.c. [100 cubic inches.]

(3.) Tidal Air is the volume of air which is
taken in and given out at each respiration. It is
equal to 500 cubic centimetres [20 cubic inches.]

(4.) Complemental Air is the volume of air
that can be forcibly inspired over and above what
is taken in at a normal respiration. It amounts to
about 1,500 c.c. [100-130 cubic inches.]

228

SPIROMETRY AND VITAL CAPACITY.

(5.) Vital Capacity is the term applied to the volume of air which
can be forcibly expelled from the chest after the deepest possible
inspiration. It is equal to 3,772 c.c. (or 230 cubic inches) for an
Englishman (Hutchinson), and 3,222 for a German (Haeser).

Hence, after every quiet inspiration, both lungs contain (1 + 2 + 3)
= 3,000-3,900 c.ctmr. [220 cubic inches] ; after a quiet expiration
(1 + 2) = 2,500-3,400 c.ctmr. [200 cubic inches.] So that about ^
to f of the air in the lungs is subject to renewal at each respiration.

Estimation of Vital Capacity. — The estimation of the vital capacity
was formerly thought to be of great consequence, 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 SPIROMETER of

_t Hutchinson. This instrument (Fig.

101), consists of a graduated
cylinder filled with water and in-
verted like a gasometer over water,
and balanced by means of a counter-
poise. Into this cylinder a tube
projects, and this tube is connected
with a mouth-piece. The person
to be experimented upon takes the
deepest possible inspiration, closes
his nostrils, and breathes forcibly
into the mouth-piece of the tube.
After doing so the tube is closed.
The cylinder is raised by the air
forced into it, and after the water
inside and outside the cylinder is
equalised, the height to which the
cylinder is raised indicates the
amount of air expired, or the vital

rig. 101.

Scheme of Hutchinson's Spirometer.

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 capacity : —

(1.) The height. — Every inch added to the height of persons between 5 and 6
feet, gives an increase of the vital capacity = 130 c.c. [8 cubic inches.]

(2.) The body -weight- — When the body-weight exceeds 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; there is an annual
decrease of 23'4 c. c. from this age 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 cir-
cumference of chest, and the same height in a man and a woman, the ratio is 10 : 7.

(5.) Position- — More air is respired in the erect than in the recumbent position.

(6.) Disease. — Abdominal and thoracic diseases dimmish it.

NUMBER OF RESPIRATIONS. 229

109. Number of Respirations.

In the adult, the number of respirations 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.) The age. — Quetelet found the mean number of respirations in 300
individuals to be : —

Tear. Respirations. \

0-1, 44 /

5, . . 26 f Average Number

15-20, 20 \ per

20-25, . . 18-7 Minute.

25-30, 16 \

30-50, . . 18-1 J

(3.) The state Of activity. — Gorham counted 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 the higher the surrounding temperature, but this result only
occurs when the actual temperature 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 respirations, but after a short time the impulse to respire overcomes the
voluntary impulse.

(7.) The gases Of the blood have a marked effect, and so has the heat of the
blood in fever.]

110. Time occupied by the Respiratory Movements.

The time occupied in the various phases of a respiration can only be
accurately ascertained by obtaining a curve or pneumatogram of the
respiratory movements.

Methods. — 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.
Eiegel (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 other on the unsound side.

(2.) An air-tambour, such as is used in Brondgeest's pansphygmograph (Fig. 103,
A) may be used. It consists of a brass vessel, a, shaped like a small saucer. The
mouth of the brass vessel is covered with a double layer of caoutchouc membrane,
b, 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 posi-
tion by means of the bands, d, d. The cavity of the tambour communicates by
means of a caotitchouc tube, s, with a recording tambour which inscribes its

230

VARIOUS FORMS OF STETIIOGRAPHS.

Fig. 102.
Marey's Stethograph.

B

Fig. 103.

A, Brondgeest's tambour for registering the respiratory movements— b, c, inner
and outer caoutchouc 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 on a vibrating plate (each vibration = O'OIGIS sec.).

MEASUREMENT OF THE TIME OP THE RESPIRATORY MOVEMENTS. 231

movements upon a revolving cylinder. Every dilatation of the chest compresses
the membrane, and thus the air within the tambour is also compressed.

(3.) A cannula or cesophageal sound may be introduced into that portion of the
oesophagus which lies in the chest, and a connection established with an Upham's
capsule— p. 132 (Rosenthal).

Marey's StethOgraph or Pneumograph. — [There are two forms of this instru-
ment, one modified by P. Bert and the more modern form (Fig. 102). A tambour (h)
is fixed at right angles to a thin elastic plate of steel (/). The aluminium disc on
the caoutchouc of the tambour is attached to an upright (b), whose end lies in con-
tact with a horizontal screw (#). Two arms (d, c) are attached to opposite sides of
the steel plate, and to them the belt (c) which fastens the instrument to the chest
is attached. When the chest expands these two arms are pulled asunder, the steel
plate is bent and the tambour is affected, and any movement of the tambour is
transmitted to a registering tambour by the air in the tube (a).]

In the case of animals placed on their backs, Snellen 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 regis-
tered its movements (PHREXOGRAPH).

Fig. 104.

Pneumatogram 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.

The curve (Fig. 103, B) was obtained by placing the tambour of a
Brondgeest's pansphygmograph upon the xiphoid process, and recording

232 TYPE OF RESPIRATION.

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 expira-
tion 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 ratio for an adult is as G to 7 ; in women, children, and old people,
6 to 8' or G to 9. Vierordt found the ratio to be 10 to 14'1 (to 24'1);
J. E. Ewald, 1 1 to 1 2. 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 (Eiegel). The very flat part of
the expiratory curve has been wrongly regarded as due to a pause.
Of course, we may make a voluntary 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 considerably shorter than the former.

During very deep and slow respiration, there is usually an 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 clue to vibrations communicated to the thoracic walls by vigorous
heart-beats (Fig. 104).

The " type" of respiration may be ascertained by taking curves from
various parts of the respiratory movements. Hutchiuson showed that
in the female, the thorax is dilated chiefly by raising the sternum and
the ribs (Eespiratio costalis), while in man it is caused chiefly by a
descent of the diaphragm (Respiratio diaphragmatica or abdorninalis).
In the former, there is the so-called " costal type" in the latter the
" abdominal or diaphragmatic type."

Forced Respiration. — 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, 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

VARIATIONS OF THE RESPIRATORY MOVEMENTS. 233

that the costal type occurs in children of both sexes, and they ascribe as a 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. [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.]

111. Pathological Variations of the Respiratory

Movements.

I. Changes in the mode Of movement. — In persons suffering from disease of
the respiratory organs, the dilatation of the chest may be diminished (to the
extent of 6 or 5 cmtr. ) 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, e.g., in nar-
rowing 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 horizontally outwards from 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. 104). _

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 DySpnCBa.

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); (6) narrowing of the respiratory passages; (c) diminution of the red
blood-corpuscles; (cl) disturbances of the respiratory mechanism (e.g., due to affec-
tions of the respiratory muscles or nerves, or painful affections of the chest-wall);
(e) impeded circulation through the lungs due to various forms of heart-disease.
(2) Heat-dyspncea. — The frequency of the respirations is increased in febrile con-
ditions. 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-dyspncea"). If the carotids be placed in warm tubes, so as to heat the
blood going to the medulla oblongata, the same phenomena are produced (A.
Fick. ) See also " Respiratory centre" (vol. ii.).

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, e.g., in certain affections of the brain and heart,
and in ura3mic poisoning. Respiratory pauses of one-half to three-quarters of a minute
alternate with a short period (A-f 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 dyspno?ic, 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 (Leube). Hein observed that consciousness was abolished during the pause,

234 THE MUSCLES of RESPIRATION.

and that it returned when respiration commenced. A few muscular contractions
may occur towards the end of the pause (rare).

With regard to the causes of this phenomenon there is some doubt. According to
Rosenbach, the anomalous nutrition of the brain causes certain intracranial centres,
especially the respiratory centre, to be less excitable and to be sooner exhausted,
and this condition reaches its maximum during the respiratory pause. During the
pause these centres recover, and they again become more active. As soon as they are
again exhausted, their activity ceases. Luciani also regards variations in the ex-
citability of the respiratory centre as the cause of the phenomenon, which
he compares with the periodic contraction of the heart (p. 104). He observed
this phenomenon after injury to the medulla oblongata above the respiratory
centre, and after apnoea produced in animals deeply narcotised with opium. It
also occurs in the last stages of asphyxia, during respiration in a closed space.
Mosso found a similar phenomenon normally in the hybernating dormouse
(Myoxus.)

Periodic Respiration Of Frogs. — 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 Cheyne-Stokes' phenomenon. In such 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 (vSiebert and LangendorfF). Muscarin and digitalm cause
periodic respiration in frogs [which is not due to the action of these drugs on the
heart.]

112. General View of the Respiratory Muscles.

(A.) Inspiration.

I. During Ordinary Inspiration are Active.

1. The diaphragm (Nervus phrenicus.)

2. The Mm. levatores costarum. longi et breves (Rami poster lores
Nn. dorsaltum).

3. The Mm. intercostales extern! et intercartilaginei (Nn. Inter-
cost ales}.

II. During Forced Respiration are Active.

(a.) Muscles of the Trunk.

1. The three Mm. scaleni (Rami musculares of the frtexus cervicalis et
Irachialis).

2. M. sternocleidomastoideus (Ram. externus N. accessorii).

3. M. trapezius (R. externus N. accessorii et Ram. musculares ple-xun
cervicalis).

4. M. pectoralis minor (Nn. thoracici anteriores).

5. M. serratus posticus superior (N. dorsalis scapulae).
G. Mm. rhomboidei (N. dorsalis scapulae).

THE MUSCLES OF FORCED RESPIRATION. 2 3" 5

7. Mm. extensores columnae vertebralis (Ram. posteriores nervorum
dorsalium).

[8. Mm. serratus anticus major (N". thoracicus longus). ? 1]

(b.) Muscles of the Larynx.

1. M. sternohyoideus (Ram. descendens hypoglossi).

2. M. sternothyreoideus (Ram. descendens hypoglossi).

3. M. crico-arytaenoideus posticus (N. laryngeus inferior vagi}.

4. M. thyreo-arytaenoideus (N. laryngeus inferior vagi).

(c.) Muscles of the Face.

1. M. dilatator narium anterior et posterior (N. facialis).

2. M. levator alae nasi (N. facialis'),

3. The dilators of the mouth and nares, during forced respiration,
["gasping for breath"] (N. facialis).

(d.) Muscles of the Pharynx.

1. M. levator veli palatini (N. facialis).

2. M. azygos uvulae (N. facialis).

3. According to Garland, the pharynx is always narrowed.

(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] (Nn. aldominis internis anteriores
e nerris intercostalibus, 8-12).

2. Mm. intercostales interni, so far as they lie between the osseous
ribs, and the Mm. infracostales (Nn. intercostales).

3. M. triangularis sterni (Nn. 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 vertebrae, and a sternal portion from
the back of the ensiform process.

236

THE ACTION OF THE DIAPHRAGM.

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 diaphragm contracts, both
arched portions become natter, 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. 105),

and during a forced inspiration,
the lowest lateral portions, which
during rest are in contact with
the chest-wall, become separated
from it. The middle of the cen-
tral tendon where the heart rests
(fixed by means of the pericardium
and inferior vena cava) takes no
share in this movement ; hence,
this part is highest in the thorax
during a forced inspiration.

Undoubtedly, the diaphragm is
the most powerful agent in in-
creasing the cavity of the chest.
Britcke, in fact, believes that in
addition to increasing the length
of the thoracic cavity from above
downwards, it also increases the
Sagittal section through the second rib transverse diameter of the lower
on the right side. This figure shows part Of the cliest. It presses upon

that when the arched muscular part , -, i -i • i • c i

,,, ,. , the abdominal viscera from above,

ot the diaphragm contracts, a wedge-
shaped space, with its apex clown- and strives to press these out-
wards, is formed around the circum- wards, thus tending to push out
ference of the lower part of the chest, the adjoining thoracic wall,
so that the chest is enlarged from

above downwards. If tne contents of the abdomen are

removed from a living animal, every

time the diaphragm contracts, the ribs are drawn inwards (Haller). 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.
The immense importance of the diaphragm as the great inspiratory muscle is
proved by the fact that, after both phrenic nerves (third and fourth cervica nerves)

Fig. 105.

THE ELEVATORS OF THE RIBS.

237

are divided, death occurs (Budge, Eulenkamp) . The phrenic nerve contains some
sensory fibres for the pleura, pericardium, and a portion of the diaphragm
(Schreiber, Henle, Schwalbe).

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 at any stage of its activity without
bringing into action any antagonistic muscles (Kronecker and Marckwald).

(2.) The Elevators Of the Bibs. — 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 axes 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 smaller below (88°) (A. W. Volkmann). 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
backwards, 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.

f

Fig. 106.
Scheme of the action of the intercostal muscles.

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

238 THE ACTION OF THE INTERCOSTAL MUSCLES.

raised, the intercostal spaces are widened, (b.) 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 inspiration,
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 inspiration, we may regard all those
muscles as elevators of the ribs, whose origin and insertion become
approximated. Everyone is agreed that the scaleni and levatores
costarum longi et breves, the scnatus 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 inspiratory 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 Ham-
berger (1727) as depressors of the ribs or expiratory muscles.

In Fig. 106, I, when the rods, a and b (which represent the ribs) are raised, the
intercostal space must be widened (e/> c d). On the opposite side of the figure,
it is evident that when the rods are raised, the line, rj h, is shortened (ik<gh,
direction of the external intercostals) — I m is lengthened (I in ~<.on, direction of
internal intercostals). Fig. 106, II, shows, that when the ribs are raised, the inter-
cartilaginei, indicated by g 7t, and the external intercostals, indicated by I 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.D.) regarded the externals as inspiratory, the internals as expiratory. Hamberger
(1727) accepted this proposition and considered the intercartilaginei also as inspira-
tory. Haller took both the external and internal intercostals as inspiratory, while
Vesalius (1540) regarded both as expiratory. Landerer observing that the upper
two or three intercostal spaces became narrower during 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 inter-
costals and intercartilaginei as active only during inspiration, the internal
intercostals only during expiration. [Martin and Hartwell exposed the internal
intercostals and observed whether they contracted 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

MECHANISM OF ORDINARY EXPIRATION. 239

action of these muscles is not to raise or depress the ribs, but rather that the
external intercostals and the intercartilaginei offer resistance to the inspiratory
dilatation of the intercostal spaces and to the simultaneously increased elastic ten-
sion of the lungs. Internal intercostals act during powerful expiratory efforts,
(e.g., coughing), and oppose the distension 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 (1 Serratus Anticus Major) can only act
as elevators of the ribs, when the shoulders are fixed, partly by the rhom-
boidei, and partly by fixing the shoulder- joint and supporting the arms,
as is done instinctively by persons suffering from breathlessness.

(3.) Muscles acting upon the Sternum, Clavicle and Vertebral Column.
— When the head is fixed by the muscles of the neck, the sternocleido-
mastoid can raise the manubrium sterni, and the sternal end of the
clavicle, so that the thorax is raised and thereby dilated. The scaleni
also aid in this 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
dilatation of the intercostal spaces which aid inspiration. During deep
respiration, this straightening of the vertebral column takes place in-
voluntarily.

(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 inspira-
tory movement. During inspiration the pharynx becomes narrower
(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 inspira-
tion. 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 inspira-
tory forces cease, the costal cartilages return to their normal position

240 MUSCLES OF FORCED EXPIRATION.

—i.e., the position 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 Aveight 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 interims and externus, trans-
versalis abdominis and levator ani] are always active during laboured
respiration. They act by diminishing 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 down-
wards ; and the Serratus posticus inferior depresses the four lowest
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 throwing backwards
of the head compensate for the protrusion of the anterior walls of the trunk.

114. Relative Dimensions of the Chest.

It is important, from a physician's point of view, to know the dimensions of the
thorax, and also the variations it undergoes at different parts. 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
(immediately under the arms) is 88 centimetres (34'3 inches), in
females 82 centimetres (32 inches); on the level of the ensiform process
82 centimetres (32 inches) and 78 centimetres (30*4 inches) respectively.
When the arms are placed horizontally, during the phase of moderate
expiration, the circumference immediately under the nipple and the
angles of the scapulae is equal to half the length of the body; in man

RELATIVE DIMENSIONS OF THE CHEST. 241

82, and during deep inspiration 89 centimetres. 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, 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 below is 25-26 centi-
metres (9-7-10-1 inches), in females 23-24 centimetres (8'9-9'2
inches) ; above the nipple it is 1 centimetre more. The antero-

Fig. 107.

Curve taken with the cyvtometer— Left side of the chest retracted in a girl twelve

years of age (Eichhorst).

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 man
during the deepest inspiration the chest on a level with the groove in
the heart was increased about ~- to -J-; while Sibson estimates the
increase at the level of the nipple to be TV

Thoraco-meter. — In order to obtain a knowledge of the degree of movement-
rising or falling — of the chest-wall during respiration, various instruments have
been invented. The thoraco-meter of Sibson (Fig. 108) 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

16

242

LIMITS OF THE LUNGS.

moves an index, whose excursions are indicated on a circle with a scale attached
to it.

The Cyrtometer of

Woillez is very useful. A
brass chain, composed of
movable links, is applied in
a definite direction to part
of the chest-wall, e.g., trans-
versely 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.
107).

Fig. IDS.
Sibson's Thoraco-meter.

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 bony plate (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 con-
dition of the subjacent lung-tissue. Wherever 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 are only partially filled with air, the sound is
" muffled."

Fig. 109, along with Fig. 31, indicate the relations of the lungs to
the anterior surface of the chest. The apices of the lungs reach 3-7
centimetres (l'l-2'7 inches) above the clavicles anteriorly, while
posteriorly they extend from the spines of the .scapulse 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 tipper border of the sixth rib,
and descends a little in the axillary line, to the upper margin of the
seventh rib. On the left side (apart from the position of the heart), the
lower limit reaches as far down anteriorly as the right. In Fig. 109
the line, a, t, I, shows the lowest limit of the passive lungs. Posteriorly,

LIMITS OF THE LUNGS.

243

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 to the eleventh rib — whereby the
diaphragm is separated from the thoracic ^wall (Fig. 105). During the
deepest expiration, the lower margins of the lungs are elevated almost
as much as they descend during inspiration. In Fig. 109, m, n, indicates
the margin of the right lung during deep inspiration ; h, I, during deep
expiration.

It is important to observe the relation of the margin of the left lung

Fig. 109.

Topography of the lungs and heart during inspiration and expiration (v. Dusch) —
h, I, upward limit of margin of lung during deepest expiration; m, n, lower
limit during deepest inspiration; I, t', t", triangular area where the heart is
uncovered by lung, dull percussion sound; d, d', d", muffled percussion
sound; i, i', anterior margin of left lung reaches this line during deep inspira-
tion, and during deep expiration it recedes as far as e, e'.

to the heart. In Fig. 109, 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. This area
is represented by the triangle, t, t', t", and percussion over it gives a
dull sound (superficial dulness).

In the area of the larger triangle, d, d', d", where the heart is

244 PATHOLOGICAL VARIATIONS OF THE PERCUSSION SOUNDS.

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 insertion
of the mediastinum, whereby the dull sound is limited to the smallest
triangle, t, i, i'. Conversely, during very complete expiration, the
margin of the lung recedes so far that the cardiac dulness embraces
the space, t, e, e.

115. Pathological Variations of the Percussion

Sounds.

The normal clear resonant percussion sound of the lungs becomes muffled when
infiltration takes place into the lungs, so as to dimmish the normal amount of air
within them, or when the lungs are compressed from without, e.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, 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 (Skoda) when it has a musical quality
resembling the timbre of a sound produced on a drum, 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 vomicse within the substance of the lung (the sound becomes deeper when the
mouth, or, better, the mouth and nose, 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 resembles 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 reflec-
tion of the sound-waves within the cavity are present.

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.

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 contains little or no air its sound is enfeebled (von
Baas).

Historical. — The actual discoverer of the art of percussion was Auenbrugger
(t!809). Piorry and Skoda developed the art and theory of percussion, while
Skoda originated and developed the physical theory (1839).

THE NORMAL RESPIRATORY SOUNDS. 245

116. The Normal Respiratory Sounds.

Normal Vesicular Sound. — 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 "vesicular" sound, which is audible only during
inspiration. It is a fine sighing or rustling sound. It is said to be
caused by the sudden dilatation of the air-vesicles (hence " vesicular")
during inspiration, 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 friction. As the air passes out
of the air-vesicles during expiration, it gives rise to a feeble sighing
sound of an indistinct soft character.

Bronchial Respiration. — Within the larger air-passages — larynx,
trachea, bronchi — during inspiration and expiration, there are loud
sounds like a sharp h or ch — the " bronchial" — the laryngeal, tracheal,
or " tubular" sound, or breathing. This sound is also heard between
the scapulce, at the level of the fourth dorsal vertebra (bifurcation of
trachea), and it occurs also during expiration, being slightly louder on
the right side, owing to the slightly greater calibre of the right
bronchus.

At all other parts 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. It is asserted that, when
lungs containing air are placed over the trachea, the tubular sound
there produced becomes vesicular. In this case, we must suppose
that the vesicular sound arises from the tubular breathing becoming
weakened, and being acoustically altered, by being conducted through
the lung alveoli (Baas, Penzoldt). A sighing sound is often produced
at the apertures of the nose and mouth during forced respiration.

117. Pathological Respiratory Sounds.

Historical. — Although several abnormal sounds in connection with diseases of
the respiratory organs were known to Hippocrates (succussion-sound, friction, and
several catarrhal sounds), still, Laennec was the discoverer of the method of
auscultation (1816), while Skoda greatly extended our knowledge of its facts.

(1.) Bronchial 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

246 PATHOLOGICAL RESPIRATORY SOUNDS.

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. It also occurs
in large cavities, with resistant walls near the surface of the lung, provided these
cavities communicate with a large bronchus.

(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 is produced; or when the
lung still 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.

(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, e.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 lung are not supplied with air continuously ; it
only reaches them periodically. In these cases a cog-wheel 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, (b. ) 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 hi small
spaces when the walls are separated from their fluid contents 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, (c.) When the mucous membrane of the
bronchi is greatly swollen, or is so covered with mucus that the air must force its
way through, deep sonorous ronchi (ronchi sonori) may occur in the large air-
passages, and clear shrill sibillant sounds (ronchi sibilantes) in the smaller ones.
When there is extensive bronchial catarrh, not unfrequently we feel the chest-
wall vibrating with the rale sounds (Bronchial fremitus).

(4. ) If fluid and air occur together in one pleural cavity in which the lung is
collapsed, on moving 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
succussiox sound of Hippocrates. Much more rarely, this sound is heard under
similar conditions in large pulmonary cavities.

(5.) When the two apposed surfaces of the pleura are inflamed, have become
soft, and are covered with exudation, they move over each other during
respiration, and 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.) When we speak or sing in a loud tone, the walls of the chest vibrate
(PECTORAL FREMITUS), because the vibration of the vocal cords is propagated
throughout the entire bronchial ramifications. The vibration is, of course,
greatest near the trachea and large bronchi. If there be much exudation or air in
the pleura, or great accumulation of mucus in the bronchi, the pectoral fremitus
is diminished or altogether absent.

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, which is called BRONCHO-
PHONY. If through effusion into the pleura or inflammatory processes in the lung-
tissue the bronchi are pressed flat, a peculiar bleating sound (JEGOPHONY) may be
heard.

PRESSURE IN THE AIR-PASSAGES DURING RESPIRATION. 247

118. Pressure in the Air-Passages During

Respiration.

Normal Respiration. — If a manometer be tied into the trachea of an
animal, so that the respiration goes on completely undisturbed, during
every inspiration there is a negative pressure ( — 3 mm. Hg.) and dur-
ing expiration a positive pressure (Bonders). Bonders placed the
U-shaped manometer tube in one nostril, closed his mouth, leaving
the other nostril open, and respired quietly. Buring every quiet
inspiration, the mercury showed a negative pressure of 1 mm., and
during expiration a positive pressure of 2-3 mm. (Hg.)

Forced Eespiration. — 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. (Bonders). The pressure of forced expiration therefore, is 30
mm. greater than the inspiratory pressure.

Resistance to Inspiration. — Notwithstanding this, we must not con-
clude that the expiratory muscles act more powerfully than the inspira-
tory; for during inspiration, a variety of resistances has 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 =r 6 mm. ; during the deepest in-
spirations =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 resistances, 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.

As the lungs within the chest, in virtue of their elasticity, con-
tinually 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. (Heynsius).
The analogous values for man have been estimated at 4*5 mm. Hg. and
3 mm. Hg., by Hutchinson.

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.

Effects 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 fcetus, pneumo-thorax does not occur (Bernstein).

248 NASAL BREATHING.

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 said rendered moist, and
thus irritation of the mucous membrane of the air-passages by the cold
air is prevented ; (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 epithelium 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. Ewald and
Koberts).

Pulmonary (Edema, or the exudation of lymph or serum into the pulmonary
alveoli, occurs: — (1) When there is very great resistance to the blood-stream in
the aorta or its branches, e.g., by ligaturing all the arteries going to the head
(Sig. Mayer), or the arch of the aorta, so that only one carotid remains pervious
(Welch). (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 (p. 75). These conditions produce at the same time anaemia
of the vaso-motor centre, which results in stimulation of that centre, and conse-
quent 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
oedema of the lungs.

120. Peculiarly 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 respiratory
mucous membrane ia violently ejected through the open mouth. It is produced

PECULIARLY MODIFIED RESPIRATORY MOVEMENTS. 249

voluntarily or reflexly; in the latter case, it can be controlled by the will only to
a limited extent.

[Causes. — A cough may be discharged rcjlexly from a large number of surfaces.
— (1) A draught of cold air striking the skin, especially of the upper part of the
body. (2) More frequently it is discharged from the respiratory mucous mem-
brane, especially of the larynx, the sensory branches of the vagus and the superior
laryngeal nerve being the afferent nerves. (3) Sometimes an offending body, such
as a pea 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 cough," especially in cases of indigestion, produced by
stimulation of the gastric branches of the vagus.]

(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 (Cassius
Felix, A.D. 97) [the afferent nerve is the optic]. This reflex act may be interfered
with to a certain extent, or even prevented, by stimulation of sensor y nerves,
firmly compressing the nose \vhere the nasal nerve issues. The continued use of
sternutatories, as in persons who take snuff, dulls the sensory nerves, so that they
no louger act when stimulated reflexly.

(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. It is 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 expirations with the glottis narrowed, relaxed facial and jaw
muscles, secretion of tears, often combined 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 vibrations 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 ouly be suppressed, to a
certain degree, by the will (by forcibly closing the mouth and stopping 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 character-
istic 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

250 CHEMISTKY OF RESPIRATION.

that a characteristic sound is emitted. Not unfrequently it is due to irritation of
the gastric mucous membrane, and sometimes it is a very troublesome symptom in
ursemic poisoning.]

Chemistry of Respiration,

121. Quantitative Estimation of Carbonic Acid,
Oxygen, and Watery Vapour.

1. Estimation Of CCb- — 1- The volume of C02 is estimated by means of the
anthracometer (Fig. 110, II) of Vierordt. The volume of gas is collected in a gradu-
ated tube, r r, provided with a bulb at one end (previously filled with water and
carefully calibrated, i.e., 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, n, completely filled with a solution of caustic potash;
the stop-cock is then opened, the potash solution is allowed to ascend into the
tube, which is moved about until all the C02 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 C02 which
is combined with the potash.

2. By weight. — A large quantity of the mixture of gases which has to be investi-
gated is made to pass through a Liebig's bulb filled with caustic potash. The
potash apparatus having been carefully weighed beforehand, the increase of weight
indicates the amount of C02 which has been taken up by the potash from the air
passed through it.

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 C02 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 C02 the
smaller will be the amount of oxalic acid used, and vice versa.

II- Estimation Of Oxygen. — According to volume — (re) By the union of the
O with potassium pyrogallate. The same procedure is adopted as for the estima-
tion of C02, only the flask, n, is filled with the pyrogallate solution instead of
potash, (b) By exposure in an eudiometer (see Blood gases, p. 55).

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 of water is directly indicated by the
increase of weight.

122. Methods of Investigation.

I. Collecting the Expired Air. — 1. The air expired may be collected in the cylinder
of the spirometer (§ 108) which is suspended in concentrated salt solution to
avoid the absorption of C02.

QUANTITATIVE ESTIMATION OF THE RESPIRED GASES.

251

The apparatus of Andral and Gavarret is thus used :— The operator breathed
several times into a capacious cylinder (Fig. 110). A mouth-piece (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 b). 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

Fig. 110.

I. Apparatus of Andral and Gavarret for collecting the expired air— C, large
cylinder to collect the air expired; P, weight to balance cylinder; a, b, two
Muller's valves; M, mouth-piece. II. Anthracometer of Vierordt.

Fig. 111.

Respiratory Apparatus of Scharling— d, bulb containing caustic potash to absorb
C03 from in-going air; A, box for man or animal experimented on; e and g,
tubes containing sulphuric acid to absorb watery vapour; /, potash bulb to
absorb C02 given off; C, vessel filled with water to aspirate air through the
foregoing system; h, stop-cock.

252

REGNAULT AND EEISET S APPARATUS.

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. Ill), which consists of a closed box, A, of sufficient size to contain a man.
It has two openings — an entrance opening, z, and an exit, 6. The latter is con-
nected with an aspirator, C, a large barrel filled with water. When the stop-cock,
h, is opened and the water flows out of the barrel, fresh air will rush in continu-
ously 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 com-
pletely deprived of C02, so that the person experimented on is supplied with air
free from (J02. The air passing out by the exit tube, b, has to pass first through
e, where it gives up its watery vapour to sulphuric acid, whereby the amount of
watery vapour is estimated by the increase of the weight of the apparatus, e.
Afterwards the air passes through a bulb, /, containing caustic potash, which
absorbs all the C02, while the tube, g, filled with sulphuric acid, absorbs any
watery vapour that may have come from f. The increase of weight of / and y
indicate the amount of COg. The total volume of air used is known from the
capacity of C.

(6.) Kegnault and Keiset'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 (Fig. 112) of a globe, K, in which is placed the dog to be experimented
on. Around this is placed a cylinder, cj y (provided with a thermometer, t) which
maybe used for calorimetric experiments. A tube, e, leads into the globe, R;
through this tube passes a known quantity of pure oxygen (Fig. 112, 0). To absorb

CaCli

112.

Scheme of the Respiration Apparatus of Eegnault and Reiset— R, globe for
animal ; g g, outer casing for R, provided with a thermometer, t; d and e,
exit tubes to movable potash bulbs, KOH and KoA; 0, in-going oxygen; C02,
vessel to absorb any carbonic acid; CaCl2, apparatus for estimating the
amount of 0 supplied; /, manometer.

v. PETTENKOFER'S RESPIRATION APPARATUS.

253

any trace of COo, a vessel containing potash (Fig. 112, CC>2) is placed 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 (Ca C12) provided with large flasks.
Two tubes, d and e, lead from R, and are united by caoutchouc tubes with the
potash bulbs (KOH, Ko/t), which can be raised or depressed alternately by means
of the beam, AY. In this way they aspirate alternately the air from R, and the
caustic potash absorbs the COg. The increase of weight of these flasks after the
experiment indicates the amount of C02 expired. The manometer, 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. 113). It
consists of a chamber, Z, with metallic walls, and provided with a door and a
window. At a is an opening for the admission of air, while a large double suction-
pump, P PJ (driven by means of a steam-engine) continually renews the air within
the chamber. The air passes into a vessel, b, filled writh 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 passing through it.

After the air is measured, it is emptied outwards by means of the pump, P Pj.
From the chief exit tube, x, of the chamber, provided with a small manometer, q, a
narrow laterally placed tube, n, passes, conducting a small secondary stream,

Fig. 113.

Respiration Apparatus of v. Pettenkofer — Z, chamber for person experimented on ;
x, exit tube with manometer, q; b, vessel with sulphuric acid; C, gas-meter;
PPi, pump; n, secondary current, with, k, bulb; MM1} suction apparatus;
u, gas-meter; N, stream for investigating air before it enters Z.

which is chemically investigated. This current passes through the suction-
apparatus, M M! (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 MMi, it goes through the

254 COMPOSITION AND PROPERTIES OF ATMOSPHERIC AIR.

tube, B, filled with baryta solution, which takes up the C02. The quantity of
air which passes through the accessory current, n, is measured by the small gas-
meter, u, 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 n.

The increase of CC>2 and Hg O in the accessory stream, n (I.e., more than in N),
indicates the amount of COj given off by the pressure in the chamber, Z.

123. Composition and Properties of Atmospheric Air.

1. DRY AIR contains : —

Gas. By Weight. By Volume.

O, . . 23-015 20-96

N, 76-985 79-02

C02, . . . 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. In connection with the moisture 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 (fy, the
relative moisture, i.e., the amount of watery vapour which a volume of
air contains with respect to its temperature.

Experience shows that people generally can breathe most comfortably in an
atmosphere which is not completely saturated with aqueous vapour according to its
temperature, but is only 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 disagree-
able 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, 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 midwinter, nevertheless the air in summer is relatively drier than the air in
winter.

3. The air EXPANDS BY HEAT. Rudberg found that 1,000 volumes
of air, at 0°, expanded to 1,365 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 C02 — in normal respiration = 4'38
vols. per cent. (3'3 to 5 -5 per cent.), so that it contains nearly 100
times more C02 than the atmospheric air.

2. It contains LESS O (4'782 vols. per cent, less) than the atmos-
pheric air, i.e., it contains only 16'033 vols. per cent, of 0.

COMPOSITION OF EXPIRED AIR.

255

3. Respiratory Quotient. — Hence, during respiration, more 0 is
taken into the body from the air than C02 is given off (Lavoisier) ; so
that the volume of the expired air is (TV - -g^) 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 0
absorbed to the C02 given off, is 4-38 : 4'782. This is expressed by
the " respiratory quotient"-

0 4-7S2

4. An excessively small quantity of N is added to the expired air
(Regnault and Reiset). Seegen found that all the N taken in with the
food did not reappear in the excreta (urine and faeces), 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 water from the
body. The percentage of watery vapour falls during rapid respiration
(Moleschott).

G. The expired air is WARMER (36'3°C), that is, very A

near the temperature of the body, and even although
the temperature of the surrounding atmosphere be very
variable, the temperature of the expired air still remains
nearly the same.

The Instrument (Fig. 114) was used by Valentin and Brunner
to determine the temperature of the expired air. It consists of a
glass tube, A, A, with a mouth-piece, B, and in it is a fine
thermometer, C. The operator breathes through the nose and
expires slowly through the mouth-piece into the tube.

Temperature of
the Air.

Temperature of the
Expired Air.

+ 29'S°C
+ 36-2-37
+ 38-1°
+ 38-5°

7

-6-3°C, ....
+ 17-19°,

+ 41°, ....

+ 44°, ....

. 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
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 (Regnault and Reiset) — 0'0204 grammes in
24 hours (Lossen) ; it is probably derived from the blood,
for blood exposed to the air evolves ammonia (Briicke).

9. Small quantities of H and CH4 are expired, both
being absorbed from the intestine. In herbivora, Reiset
found that 30 litres of CH4 were expired in 24 hours.

256

DAILY QUANTITY OF GASES EXCHANGED.

125. Daily Quantity of Gases Exchanged.

As under normal circumstances more 0 is absorbed than there is
CO given off (equal volumes of 0 and C02 contain equal quantities of
0), a part of the 0 must be used for other oxidation-processes in the
body. According to the extent of these latter processes, the ratio of
the 0 taken in to the C02 given out —

O906 normally) must vary.

The amount of C02 given off may be less than the " mean " above
stated. The quantity of C02 alone is not a reliable indication of the
entire exchange of gases during respiration ; we must estimate simul-
taneously the amount of 0 absorbed, and the C02 given off.

126, Review of Daily Gaseous Income and

Expenditure.

Income In 24 hours.

Oxygen—

744 grms. = 516'500c.cmtr. (Vierordt)

(At 0°C and mean barometric
pressure. )

Expenditure in 24 hours.
Carbonic Acid—

900 grms. = 455500 c.cmtr. (Vierordt).

36 grms. ]>er hour (Scharling).

32'S-33'4 grms. ,, (Liebermeister).

34 grms. . ,, . (Panum).

31-5-33 grms. ,, . (Ranke).

Water— 640 grms. . . (Valentin).

330 ,, . . (Vierordt).

127, Conditions Influencing the Gaseous Exchanges.

The formation of C02, in all probability, consists of two distinct
processes. First, compounds containing C02 seem to be formed in
the tissues which are oxidation products of substances containing carbon.
The second process consists in the separation of this C02, which, how-
ever, takes place without the absorption of O. Both processes do not
always occur simultaneously, and the one process may exceed the other
in extent (L. Hermann, Pfliiger).

According to Schmiedeberg, the oxidation in the tissues depends upon a
synthesis with the liberation of H20, the blood supplying the necessary 0.

The following affect these processes : —

1. Age. — Until the body is fully developed, the C02 given off increases,
but it diminishes as the bodily energies decay. Hence, in young persons
the 0 absorbed is relatively greater than the C02 given off ; at other
periods both values are pretty constant. Example : —

CONDITIONS INFLUENCING THE EXCRETION OF CO,.

257

Age — years.

In 24 hours.

CO, Gram, excreted.
= Carbon.

Absorbed Gram.

8

443 Gram. = 121 Carbon.

375 Grammes.

15

76G „ = 209 „

652

16

950 „ = 259

809 „

18-20

1003 „ = 274

854

20-24

1074 „ = 293

914

40-60

889 „ = 242

757

60-80

810 „ = 221 „

G89

The absolute amount of C02 given off is less in children than in adults;
but if the C02 given off be calculated with reference to body-weight,
then, weight for weight, a child gives off twice as much C02 as an adult.

2. Sex. — Males, from the eighth year onwards to old age, give off
about one-third more CO, than females (Andral and Gavarret). 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 C02 given off diminishes. Pregnancy increases the
amount, owing to causes which are easily understood.

3. The Constitution. — As a general rule, muscular, energetic persons
use more 0 and excrete more CO, than less active persons of the same
weight.

4. Alternation of Day and Night.— The C02 given off is diminished
during sleep about one-fourth (Scharling). This diminution is caused
by the constant heat of the surroundings (bed), darkness, absence of
muscular activity, and the non-taking of food (see 5, 6, 7, 9). It does
not seem that any 0 is stored up during sleep (S. Lewin). After
awaking in the morning, the respirations are more rapid and deeper,
and thus the amount of C02 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 enormously diminished, the respiratory exchange of gases
is carried out by diffusion and by the cardio-pneumatic movements
(p. 109). The C02 given off falls to TV, the 0 taken in to TV of what
they are in the waking condition (Valentin). Much less C02 is given
off than 0 taken in, so that the body-weight may increase through the
excess of 0.

5. Temperature of the Surroundings. — Cold-Hooded 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
(Spallanzani) — e.g., a frog with the temperature of the surroundings at

17

258 CONDITIONS INFLUENCING THE EXCRETION OF CO,.

39°C. excreted three times as much C02 as when the temperature was
6°C. (Moleschott).

Warm-Hooded animals behave somewhat differently when the temper-
ature of the surrounding medium is changed. When the temperature
of the animal is lowered thereby, there is a considerable decrease in the
amount of C02 given off, as in cold-blooded animals ; but if the temper-
ature of the animal be increased (also in fever), the C02 is increased
(C. Ludwig and Sanders-Ezn). Exactly the reverse obtains when the
temperature of the surroundings varies, and the bodily temperature
remains constant. As the cold of the surrounding medium increases,
the processes of oxidation within the body are increased through some
as yet unknown reflex mechanism ; the number and depth of the
respirations increase, whereby more 0 is taken in and more C02 is given
out (Lavoisier). A man in January uses 32'2 grammes 0 per hour; in
July only 31 '7 grammes. In animals, with the temperature of the
surroundings at 8°C., the C02 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 C02 given off diminish, while the pulse remains nearly constant
(Vierordt). On passing suddenly from a cold to a warm medium the
amount of C02 is considerably diminished ; and conversely, on passing
from a warm to a cold medium, the amount is considerably increased
(compare Regulation of Temperature').

6. Muscular exercise causes a considerable increase in the C02 given
out (Scharling), which may be three times greater during walking than
during rest (Ed. Smith). Ludwig and Sczelkow estimated the 0 taken
in and the C02 given off by a rabbit during rest, and when the muscles
of the hind limbs were tetanised. During tetanus the 0 and C02 were
increased considerably, but in tetanised animals more 0 was given
off in the C02 expired than was taken up simultaneously during respira-
tion. The passive animal absorbed nearly twice as much 0 as the
amount of C02 given off (compare Metabolism in Muscle).

7. Taking of food causes constantly a not inconsiderable increase in
the C02 given off, which depends upon the quantity taken, and the
increase generally occurs about an hour after the chief meal — dinner
(Vierordt). During inanition, the exchange of gases diminishes con-
siderably until death occurs (Letellier). At first the C02 given off
diminishes more quickly than the 0 is taken up. The quality of the food
influences the C0.2 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). Regnault and Eeiset found that a dog
gave off 79 per cent, of the 0 inspired after a flesh diet, and 91 per cent,
after a diet of starch. If easily oxidisable substances (glycerine or

CONDITIONS INFLUENCING THE EXCRETION OF CO.,.

259

lactate of soda), are injected into the blood, the 0 taken in, and the C02
given off, undergo a considerable increase (Ludwig and Scheremetjewsky).
Alcohols, tea, and ethereal oils, diminish the C02 (Prout, Vierordt).
[Ed. Smith 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 C02, or the oxidation-processes within the
body, these being regulated by the tissues themselves, by some mechanism
as yet unknown (Pfliiger). 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, cause 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.
per miii.

Vol. of Air.

Amount of per cent.
C02. COs.

Depth of
Resps.

Amount of per cent.
COi COi

12

cooo

258 c.cmtr. =4,3 %

500

21 c.cmtr. =4'3 %

24

12000

420 „ =3,5 „

1000

36 „ =3-6 „

48

24000

744 „ =3,1 „

1500

51 „ =3-4,,

96

48000

1000 — 9 Q
LOaA , , — — , J , ,

2000

64 „ =3-2,,

3000

72 „ =2-4 „

9. Exposure to a bright light causes an increase in the C02 given off in
frogs (Moleschott, 1855); in mammals and birds (Selmi and Piacentini); even in
frogs deprived of their lungs (Fubini); or in those whose spinal cord has been
divided high up (Chasanowitz). The consumption of O is increased at the same
time (Pfliiger and v. Platen). 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 (Moleschott and Fubini).

10. The experiments of Grehant on dogs, seem to show that intense inflamma-
tion of the bronchial mucous membrane influences the COo given off.

11. Amongst poisons, thebaia increases the C02 given off, while morphia,
codeia, narcein, narcotin, papaverin, diminish it (Fubiui).

128. Diffusion of Gases within the Lungs.

The air within the air-vesicles contains most C02 and least 0, 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 (Allan and Pepys). Hence, if the air expired be
collected in two portions, the first half (i.e., the air from the larger air-
passages), contains less C02 (3'7vols. per cent.) than the second half
(5*4 vols. per cent.). This difference in the percentage of gases gives

260 EXCHANGES OF GASES BETWEEN THE AIR AND THE BLOOD.

rise to a diffusion of the gases within the air-passages ; the C02 must
diffuse from the air-vesicles outwards, and the 0 from the atmosphere
and nostrils inwards (compare p. 52). This movement is aided by
the cardio-pneumatic movement (Landois, p. 109). 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 0 and C00 pass, on account of the difference of tension of
the gases.

129. Exchange of Gases between the Blood of the

Pulmonary Capillaries and the Air in

the Air- Vesicles.

This exchange of gases occurs almost exclusively through the agency
of chemical processes (independent of the diffusion of gases).

Method- — It is important to ascertain the tension of the 0 and C02 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 can 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 0 and C02 in
the venous blood of the pulmonary capillaries. The direct estima-
tion 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 tabular arrangement indicates the tension and per-
centage of O and C02 in arterial and venous blood, in the atmosphere,
and in the air of the alveoli : —

0-Tension in arterial blood =29 '6 mm.
Hg. (corresponding to a mixture con-
taining 3-9 vol. per cent, of 0).

II.

C02 -Tension in arterial blood = 21 mm.
Hg. (corresponding to 2 '8 vol. per
cent. )

III.

0-Tension in venous blood =22 mm. Hg,
(corresponding to 2 '9 vol. per cent.)

IV.

COa-Tension in venous blood =41 mm.
Hg. (corresponding to 5 '4 vol. per
cent.)

ABSORPTION OF OXYGEN IN THE LUNGS. 2G1

V.

0-Tension in the air of the alveoli of the
catheterised lung = 27 '44 mm. Hg.
(corresponding to 3 "6 vol. per cent.)

VI.

C02-Tension iu the air of the alveoli of
the catheterised lung = 27 mm. Hg.
(corresponding to 3 '56 vol. per cent.)

VII.

0-Tension in the atmosphere = 158 mm.
Hg. (corresponding to 20'S vol. per
cent.)

VIII.

C02-Tension in the atmosphere = 0 '38
mm. Hg. (corresponding to U '03-0 '05
vol. per cent.)

When we compare the tension of the 0 in the air (VII. = 158 mm.
Hg.) with the tension of the 0 in venous blood (III. — 22 mm. Hg., or
V. = 27'44 mm. Hg.), we might be inclined to assume that the passage
of the 0 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
C02 of the venous blood (IV. or VI.) diffused into the air-vesicles,
because the tension of the C02 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.

Absorption of 0. — With regard to the absorption of 0 from the air
in the alveoli into the venous blood of the lung capillaries, whereby
the blood is arterialised, it is proved that this is a chemical process. The
gas-free (reduced) haemoglobin takes up 0 to form oxyhaemoglobin (§ 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 0 is respired, the blood does not
take up more 0 than when atmospheric air is respired ; further, that
animals made to breathe in a limited closed space can absorb almost all
the 0 — even to traces — into their blood before suffocation occurs. Of
course if the absorption of 0 were due to diffusion, in the former case
more 0 would be absorbed, while in the latter case the absorption of 0
could not possibly occur to such an extent as it does.

The law of diffusion comes into play in connection with the absorp-
tion of 0 to this extent, viz., that the 0 diffuses from the air-cells of
the lung into the blood-plasma, where it reaches the blood-corpuscles
suspended in the plasma. The haemoglobin of the blood-corpuscles
forms at once a chemical compound (oxyhcemoglobin) with the 0.

Even in very rarified air, such as is met with in the upper regions of the
atmosphere during a balloon ascent, the absorption of 0 still remains independent
of the partial pressure (Loth. Mayer, Fernet). But a much longer time is required
for this process at the ordinary temperature of the body, so that in rarified air, the
absorption of 0 is greatly delayed, but it is not diminished. This is the cause of
death in Eeronauts who have ascended so high that the atmospheric pressure is
diminished to one-third (Setschenow).

Excretion of C02. — With regard to the excretion of CO., from the
blood, we must remember that the C02 in the blood exists in two con-

262 EXCRETION OF CARBONIC ACID BY THE LUNGS.

ditions. Part of the C02 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 C02 from the blood it
is difficult to determine whether the C(X, so removed, obeyed the law
of diffusion, or if it was expelled by chemical meaus.

Although it is convenient to represent the excretion of C02 from the
blood into the air-vesicles of the lung, as due to equilibration of the
tension of the C02 on opposite sides of the alveolar membrane, i.e., 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 C02. This is proved by the fact that the expulsion
of C02 from the blood takes place more readily when 0 is simultaneously
admitted (Ludwig and Holmgren).

The free supply of 0 not only favours the removal of the C02, which
is loosely combined, but it also favours the expulsion of that portion of
the C02 which is more firmly combined, and which can only be
expelled by the addition of acids to the blood (Ludwig, Schoffer and
Sczelkow). That the oxygenated blood-corpuscles (i.e., their oxyhsemo-
globin) are concerned in the removal of C02, is proved by the fact that
C02 is more easily removed from serum which contains oxygenated
blood-corpuscles than from serum charged with 0.

[The following scheme may serve to illustrate the extent to which
diffusion comes into play. The O must pass through the alveolar
membrane, A B — including the alveolar epithelium and the wall of the
capillaries — as well as the blood-plasma, to reach the hremoglobin of
the blood-corpuscles. Similarly, the C09 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

C02 0

Partial pressure of air in
alveoli of lun.

.

27 . . 27-44

1* I
_T B

Tension of gases in venous ) ^, oo

blood of lung. )

I C02 O

alveolar membrane; on the one side of it is represented the partial
pressure of the C02 and 0 in the air-vesicles; and on the other, the
partial pressure of the C09 and O in the venous blood entering the
lung. The arrows indicate the direction of diffusion.]

Theories. — Various theories have been proposed to account for the expulsion of
the C02 from its state of chemical combination in the blood due to the action of
the oxygenated blood-corpuscles, (a.) It is possible that the C02 in the blood-

DISSOCIATION OF GASES. 2G3

corpuscles (perhaps united with paraglobulin ? — Setschenow) is expelled by the O
taken up ; (6.) the acid reaction of the haemoglobin (Preyer) may act so as to expel
the C02 out of the corpuscles and the plasma ; (c.) by the absorption of O volatile
fatty acids may be formed from the hemoglobin (Hoppe-Seyler). These acids
may act so as to expel the C02.

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 a
process of dissociation.

130. Dissociation of Gases.

Many gases form true chemical compounds with other bodies (i.e.,
they combine according to their equivalents), when the contact of these
bodies is effected under conditions such that the partial pressure of
the gases is high. The chemical compound formed under these con-
ditions is broken up, whenever the partial pressure is diminished, or
when it reaches a certain minimum level, which varies with the nature
of the bodies forming the compound. Thus, by increasing and dimin-
ishing the partial pressure alternately, a chemical compound of the gas
may be formed and again broken up. This process is called Dissocia-
tion 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, C02 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
C02 and those containing 0 within the blood-stream behave in a similar
manner — viz., the salts of the plasma, which are combined with C02, and
the oxyhcemoglobin. If these compounds of 0 and C02 are placed under
conditions where the partial pressure of these gases is very low — i.e.,
in a medium containing a very small amount of these gases, the com-
pounds are dissociated — i.e., they give off C02 or 0. If after being
dissociated, they are placed under conditions where, owing to the large
amount of these gases, the partial pressure of 0 or of C02 is high,
these gases are taken up again, and enter into a condition of chemical
combination.

The haemoglobin of the blood in the pulmonary capillaries finds
plenty of 0 in the alveoli ; hence, it unites with the 0 owing to the
high partial pressure of the 0 in the lung, and so forms the compound
oxyhaemoglobin. On its course through the capillaries of the systemic

264 CUTANEOUS RESPIRATION.

circulation, the oxyhremoglobin of the blood comes into relation with
tissues poor in 0; the oxyhsemoglobin is dissociated, the 0 is supplied to
the tissues, and the blood freed from this 0, returns to the right heart,
and passes to the lungs, where it takes up new 0.

The blood whilst circulating meets with most C02 in the tissues;
the high partial pressure of the C02 in the tissues causes the CO, to
unite with certain constituents in the blood so as to form chemical
compounds, which carry the C02 from the tissues to the lungs. In
the air of the lungs,. however, the partial pressure of the C02 is very
low, dissociation of these chemical compounds occurs under the low
partial pressure, and the C02 passes into the air-cells of the lung, from
which it is expelled during expiration. It is evident that the giving
up of 0 from the blood to the tissues, and the absorption of C02 from
the tissues, go on side by side and take place simultaneously, while in
the lungs the reverse processes occur also simultaneously.

131. Cutaneous Respiration.

Methods. — If a man or an animal be placed in the chamber of a respiratory
apparatus (Scharling's, or v. Pettenkofer's), 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 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 ascer-
tained by enclosing it in an air-tight vessel (Rbhrig) similar to that used for the
arm in the plethysmograph (p. 198).

Loss by Skin. — A healthy man loses by the skin, in 24 hours, ^ of
his body- weight (Seguin), which is greater than the loss by the lungs,
in the ratio of 3 : 2 (Valentin, 1843). Only 10 grammes — 150 grains
(Scharling), or it may be 3'9 grammes — 60 grains (Aubert), of the
entire loss is due to the C02 given off by the skin. The remainder of
the excretion from the skin is due to water, containing a few salts in
solution. When the surrounding temperature is raised, the C02 is
increased (Gerlach), in fact it may be doubled (Aubert) ; violent
muscular exercise has the same effect.

0 Absorbed. — The 0 taken up by the skin is either equal to
(Regnault and Keiset), or slightly less than, the C02 given off. As the
C02 excreted by the skin is only ^\^ °f that excreted by the lungs,
while the 0 taken in = yl^ 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. — (See Artificial Diminution of Temperature.)

INTERNAL RESPIRATION. 265

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,

132. Internal Respiration.

Where C02 is Formed. — By the term " internal respiration" is under-
stood the exchange of gases between the capillaries of the systemic
circulation and the tissues of the various organs of the body. As the
organic constituents of the tissues, during their activity, undergo gradual
oxidation, and form, amongst other products, C02 : we may assume — (1.)
That the chief focus for the absorption of 0 and the formation of C(X
is to be sought for within the TISSUES themselves. That the 0 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 0 and gains C02, while blood containing 0, and kept warm out-
side the body, changes very slowly and incompletely. If portions of
fresh tissues be placed in defibrinated blood containing 0, then the 0
rapidly disappears (Hoppe-Seyler). 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
(Pfliiger and Oertmann). If the chief oxidations took place in the
blood and not in the tissues, then, during suffocation, when 0 is
excluded, the substances which use up 0, i.e., 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 (Pfliiger). It is difficult to say how the 0 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 C02. On this supposition, it is evident that the absorption
of 0 and the excretion of C02 need not occur to the same extent, so
that the amount of C02 given off at any period is not necessarily an
index of the amount of 0 absorbed during the same period.

[There are two views as to where the C02 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 bo
easily solved, but we can only arrive at a knowledge of this subject
indirectly, in the following ways] : —

COa in Cavities.— That the C02 is formed in the tissues is supported by the
fact, that the amount of C02 in the fluids of the cavities of the body is greater
than the C02 in the blood of the capillaries.

266 TENSION OF THE GASES IN CAVITIES AND LYMPH.

Pfluger and Strassburger found the tension of C02 to be, in

Mm,

Arterial blood, . 21 -28 Hg. tension.
Peritoneal cavity, 58 '5 ,, ,,
Acid urine, . 68*0 ,, ,,

Mm.

Bile, . . . 50'0 Hg. tension.
Hydrocele fluid, . 46'5 ,, ,,

The large amount of C02 in these fluids can only arise from the C02 of the
tissues passing into them.

Gases Of Lymph. — In the lymph of the ductus thoraciciis the tension of
C02 = 33'4 to 37 '2 mm. Hg., which is greater than in arterial blood, but consider-
ably less than in venous blood (41 '0 mm. Hg). This does not entitle us to
conclude that hi the tissues from which the lymph comes, only a small quantity of
C02 is formed, but rather that in the lymph there is less attraction for the COs
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 C02 is partly given back to the tissues, or that C02 is formed in the blood
itself. Further, the muscles, which are by far the largest producers of C02, con-
tain few lymphatics, nevertheless they supply much C02 to the blood.

The amount of free "non-fixed" C02 contained in the juices and tissues indi-
cates that the C02 passes from the tissues into the blood; still, Preyer believes that
in venous blood C02 undergoes chemical combination. The exchange of 0 and
C02 varies much in the different tissues. The muscles are the most important
organs, for in their active condition they excrete a large amount of C02, and use
up much O. The 0 is so rapidly used up by them that no free O can be pumped
out of muscular tissue (L. 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 C02 is more than compensated by the increased volume of blood
which passes through these organs.

(2.) In the BLOOD itself, as in all tissues, 0 is used up and C02 is
formed. This is proved by the following facts : — That blood with-
drawn from the body becomes poorer in 0 and richer in C02 ; that in
the blood of asphyxia, free from 0, and in the blood-corpuscles
(Afanassieff), there are slight traces of reducing agents, which become
oxidised on the addition of 0 (A. Schmidt). Still, this process is
comparatively insignificant 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 0 and produce C02 is
unquestionable, although it is so slight that the blood in its whole
arterial course undergoes no visible change.

Ludwig and his pupils have proved that C02 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 0 is used up and more C02 is formed than in unmixed blood similarly
transfused.

(3.) That the tissues of the living lungs use 0 and give off C02 is
probable. When C. Ludwig and Miiller passed arterial blood through
the blood-vessels of a lung deprived of air, the 0 was diminished and
the CO., increased.

RESPIRATION IN A CLOSED SPACE. 267

As the total amount of C02 and 0 found in the entire blood, at any
one time, is only 4 grammes, and as the daily excretion of C02 = 900
grammes, and the 0 absorbed daily = 744 grammes, it is clear that
exchange of gases must go on with great rapidity, that the 0 absorbed
must be used quickly, and the C02 must be excreted.

Still, it is a striking fact that oxidation-processes of such magnitude as, e.g.,
the union of C to form C02, occur at a relatively low temperature of the blood
and the tissues. It has been assumed 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 processes of oxida-
tion. Numerous organic substances, which are not altered by O alone, become
rapidly oxidised in the presence of free alkalies, e.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 (Gortip-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 the urine, but when they are administered as
alkaline compounds they are changed into carbonates.

133. Respiration in a Closed Space,

Respiration in a closed or confined space causes : — (1) a gradual
diminution of O ; (2) a simultaneous increase of C(X> ; (3) a diminu-
tion in the volume of the gases. If the space be of moderate dimensions,
the animal uses up almost all the 0 contained therein (Nysten), and
dies ultimately from spasms caused by the asphyxia. The 0 is absorbed,
therefore — independently of the laws of absorption — by chemical means.
The 0 in the blood is almost completely used up (Setschenow). In a
larger closed space, the C02 accumulates rapidly, before the diminution of
O is such as to affect the life of the animal. As C02 can only be ex-
creted from the blood when the tension of the C02 in the blood is greater
than the tension of C02 in the air, as soon as the C02 in the surrounding
air in the closed space becomes the same as in the blood, the C02 will
be retained in the blood, and finally C02 may pass back into the body.
This occurs in a large closed space, when the amount of 0 is still
sufficient to support life, so that death occurs under these circumstances
(in rabbits) through poisoning with C02, causing diminished excitability,
loss of consciousness, and lowering of temperature, but no spasms
(Worm Miiller). In pure 0, animals breathe in a normal way; the quantity
of 0 absorbed and the C02 excreted is quite independent of the percentage
of 0, so that the former occurs through chemical agency independent of
pressure. In closed spaces filled with 0, animals died by re-absorption
of the C02 excreted. Worm Miiller found that rabbits died after absorb-
ing C02 equal to half the volume of their body, although the air still
contained 50 per cent. 0. Animals can breathe quite quietly a mixture
of air containing 14'8 per cent. (20'9 per cent, normal); with 7 per cent.

268 DYSPNCEA AND ASPHYXIA,

they breathe with difficulty; with 4'5 per cent, there is marked dyspnoea ;
with 3 per cent. 0 there is tolerably rapid asphyxia (W. Miiller). The
air expired by man normally contains 14-18 per cent. 0. 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.

Dyspnoea occurs when the respired air i.s deficient in 0, as well as when it is
overcharged with C02, but the dyspnoea in the former case is prolonged and
severe; in the latter, the respiratory activity soon ceases. The want of 0 causes
a greater and more prolonged increase of the blood-pressure than is caused by
excess of C02. Lastly, the consumption of 0 in the body is less affected when the
O in the air is diminished than when there is excess of C02. If air containing a
diminished amount of 0 be respired, death is preceded by violent phenomena of
excitement and spasms, which are absent in cases of death by breathing air over-
charged with C02. In poisoning with COo. the excretion of COo, is greatly
diminished, while with diminution of 0, it is almost unchanged (C. Friedlander
and E. Herter).

Cl. Bernard found that, when an animal breathed in a closed space, it became
partially accustomed to the condition. On placing a bird under a bell-jar, it lived
several hours ; but if several hours before 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 0, give off just as much
C02 as in air containing 0, and they do this without any obvious disturbance
(Pfliiger, Aubert). Hence, it appears that the formation of COo is independent of
the absorption of O, and the C02 must be formed from the decomposition of other
compounds. Ultimately, however, complete motor paralysis occurs, whilst the
circulation remains undisturbed (Aubert).

134. Dyspnoea and Asphyxia.

[The causes of dyspnoea have already been referred to (§ 111), and
those of asphyxia are referred to in detail in vol. ii. under Nervous
Mechanism of Respiration. 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 hyperpnoea, or increased respiration,
dyspnoea or difficulty of breathing, to the final condition of suffocation
or asphyxia. The phenomena of asphyxia may be developed in an
animal by closing its trachea by means of a clamp, and in fact by any
means which prevent the entrance of air or blood into the lungs.

The phenomena of asphyxia are usually divided into several stages.
— 1. During the first stage there is hyperpnoea, the respirations being
deeper, more frequent, and laboured. The extraordinary muscles of
respiration — both those of inspiration and expiration — referred to in
§ 118, are called into action, the condition of dyspnoea being rapidly
produced, and the struggle for air becomes more and more severe.
During this time the oxygen of the blood is being used up, the blood

PHENOMENA OF ASPHYXIA. 2G9

itself is becoming more and more venous. This venous blood circulat-
ing in the medulla oblongata, and spinal cord stimulates the respiratory
centres, thus causing these violent respirations. This stage usually
lasts about a minute and gradually gives place 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
somewhat sudden. This condition is 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 inspirations feebler and of a gasping
character. As the venous blood circulates in the spinal cord it causes
n 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 open 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 continues 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 venae cavse, 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

270 THE CHANGES OP THE CIRCULATION DURING ASPHYXIA.

systemic veins. The blood itself is almost black, and is deprived of almost
all its oxygen, while its haemoglobin is nearly all in the condition of
reduced haemoglobin, while ordinary venous blood contains a considerable
amount of reduced and oxyhaemoglobin. The blood of an asphyxiated
animal practically contains none of the latter, and much of the former.

It is important to study the changes in the circulation in connection
with the outward 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 respi-
ration, and place a manometer in a systemic artery, e.g., 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.

If the blood-pressure be measured in a systemic artery, e.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 pulmonary artery not being influenced to the same extent
as other arteries, by the vaso-motor centre, or by its greater distensibility
(Lichtheim — compare § 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 contract, 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

RESPIRATION OF FOREIGN GASES. 271

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.]

[Recovery from the condition of asphyxia.— If the trachea of a dog be

closed suddenly and completely, the average duration of the respiratory move-
ments 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.

If a clog be drowned, the result is different. After complete submersion for 14
minutes, recovery did not take place. In the case of 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 live 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 Respiration. — The methods of performing artificial respira-
tion in persons apparently suffocated are fully given in rol. ii., under
Nervous Mechanism of Respiration.

135. Respiration of Foreign Gases.

No gas without a sufficient admixture of 0 can support life. Even with com-
pletely innocuous and indifferent gases, if no 0 be mixed with them, they cause
suffocation in 2 to 3 minutes.

I. Completely indifferent gases are N", H, CH4. The living blood of an

animal breathing these gases yields no 0 to them (Pfluger).

II. Poisonous gases-— («•) Those that displace O, and form a permanent
stable compound with the haemoglobin— (1.) CO (§ 16 and 17). (2.) CNH
(Hydrocyanic acid) displaces (?) O from haemoglobin, with which it forms a
more stable compound and kills exceedingly rapidly. It prevents O being changed
into ozone in the blood. Blood-corpuscles charged with hydrocyanic acid lose the
property of decomposing hydric peroxide into water and O (§ 17, 5).

(b.) Narcotic gases. — (1.) COo — v. Petteiikofer characterises air containing O
with •! p.c. C02 as "bad air ; " still, air in a room containing this amount of C02
produces a disagreeable feeling rather from the impurities mixed with it than from
the actual amount of COj itself. Air containing 1 p.c. C02 produces decided
discomfort, and with 10 p.c. it endangers life, while larger amounts cause death
with symptoms of coma. (2.) N2O (nitrous oxide) respired, mixed with ^volume
0, causes, after 1 to 2 minutes, a short temporary stage of excitement ("Laughing
gas" of H. Davy), which is succeeded by unconsciousness, and afterwards an
increased excretion of C02- (3.) Ozonised air causes similar effects (Binz).

272 ACCIDENTAL IMPURITIES IN THE AIR.

(c.) Reducing gases. — (1.) H2S (sulphuretted hydrogen) rapidly robs blood-
corpuscles of 0 : S and H20 being formed, and death occurs rapidly before the
gas can decompose the hemoglobin (Hoppe-Seyler).

(2.) PH3 — Phosphuretted hydrogen is oxidised in the blood to form phosphoric
acid and water with decomposition of the haemoglobin (Dybkowski, Koschlakoff,
and Popoff).

(3.) AsH3, arseniuretted hydrogen and SbH3, antimoniuretted hydrogen, act
like PH3, but in addition, the haemoglobin passes out of the stroma and appears in
the urine.

(4.) C2N2, cyanogen absorbs 0, and decomposes the blood (Rosenthal and
Laschkewitsch).

III. Irrespirable gases, i-e., 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.

Dust Particles. — 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. Some of them, however, reach the air-vesicles of the lung,
where they penetrate the epithelium, reach the interstitial lung-tissue and lym-
phatics and so pass with the lymph-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 tissues, but when there are large accumulations they give rise to lung
affections, which lead to disintegration of these organs. [In coal-miners, for
example, the luug-tissues along the track of the lymphatics 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.

There seems no doubt that the seeds of some contagious diseases may be inhaled.
Diphtheritic bacteria become localised in the pharynx and in the larynx —
glanders in the nose — measles in the bronchi — hay -monads in the nose. Many
seeds of disease pass into the mouth along with air, are swallowed, and undergo
development in the intestinal tract, as is probably the case in cholera and typhoid
fever.

137. 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 800 cubic feet, and every sick person 1000 cubic
feet of space. [The space allowed per individual varies greatly, but 1000 cubic
feet is a fair average. If the air in this space is to be kept sweet, so that the C02
does not exceed '06 p.c., 2000 cubic feet of air per hour must be supplied.] In
France only 42 cubic feet per head are allowed in barracks, 60 cubic feet in
hospitals. In Prussia in barracks 420-500 cubic feet are allowed for every
soldier, for hospital GOO -720; in England 600 cubic feet per head. When there
is overcrowding in a room the amount of COg increases, v. Pettenkofer found
the normal amount of C02 ( '04 to '05 per 1000) increased in comfortable rooms to

FORMATION OF MUCUS IN THE RESPIRATORY PASSAGES. 273

0'54^07 per 1000; in badly ventilated sick chambers = 2'4; in overcrowded
auditoriums, 3 '2 ; in pits = 4'9 ; in school-rooms, 7 '2 per 1000. Although it is not the
quantity of C02 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 C02
is taken as an index of the presence and amount of these other deleterious sub-
stances. The question as to whether the ventilation of a room or ward occupied
by persons is sufficient, is ascertained by estimating the amount of C02. A room
which does not give a disagreeable, somewhat stuffy, odour has less than 0'7 per
1000 of C02, while the ventilation is certainly insufficient if the C02 = 1 per 1000.

As the air contains only 0'0005 cubic meter C02 in 1 cubic meter of air, and as
an adult produces hourly 0 '0226 cubic meters C02, calculation shows that every
person requires 113 cubic meters of fresh air per hour, if the C02 is not to exceed
0'7 per 1000 : for 0'7 : 1000 = (0'0226 + x x O'OOOS) :x, i.e., x = 113.

In ordinary rooms, where every person is allowed the necessary 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 (Lindwurra).

138. Formation of Mucus in the Respiratory
Passages— Sputum.

The respiratory mucous membrane is covered normally with a thin
layer of mucus (Fig. 97). By its presence this substance 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 con-
gestion of the respiratory mucous membrane. Division of the nerves
on one side of the trachea (cat) causes redness of the tracheal mucous
membrane and increased secretion (Rossbach).

Effects of reagents on the mucous secretion.— 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 limits the secretion. The local application of alum,
silver nitrate, or tannic acid makes the mucous membrane dry, and the epithelium
is shed. The secretion is excited by apomorphin, emetin, pilocarpin, and
ipecacuanha, while it is limited by atropin and morphia (Rossbach).

Normal 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 respiratory mucous membrane, the sputum
is greatly increased in amount, and is often mixed with other character-
istic products. Microscopically, sputum contains : —

1. Epithelial cells — chiefly squames from the mouth and pharynx

18

274

THE SPUTUM.

(Fig. 115), more rarely alveolar epithelium and ciliated epithelium (7)
from the respiratory passages, The epithelial cells are often altered,
having undergone maceration or other changes. Thus some cells may
have lost their cilia (6).

The epithelium of the alveoli (2) is squamous epithelium, the cells being 2 to 4
times the breadth of a colourless blood-corpuscle. These cells occur 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
(Guttman, H. Schmidt, and Bizzozero). They often undergo fatty degeneration,
and theyjnay contain pigment granules (3); or, they may present the appearance
of what Buhl has called "mydin degenerated cells;" i.e., cells filled with clear
refractive drops of various sizes, some colourless, others coloured particles, the
latter having been absorbed (4). Mucin in the form of myelin drops (5)] is
always present in sputum.

2. Lymplwid cells (9) are to be regarded as 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.

Fig. 115.

Various objects found in sputum — 1, Detritus and particles of dust; 2, alveolar
epithelium with pigment ; 3, fatty and partly pigmented alveolar epithelium ;
4, alveolar epithelium containing myeliii-forms ; 5, free myelm-forms ; 6, 7,
ciliated epithelium, some changed, others 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 spirochteti; a,
fatty acid crystals and free fatty granules ; b, htematoidin ; c, Charcot's
crystals; d, Cholesterin.

ACTION OF THE ATMOSPHERIC PRESSURE. 275

The fluid substance of the sputum contains much mucus arising from
the mucous glands and goblet cells ; together with nuclein, and lecithin,
and the constituents of saliva according to the amount of the latter
mixed with the secretion. Albumin occurs only during inflammation of
the respiratory passages, and its amount increases with the degree of
inflammation. Urea has been found in cases of nephritis.

Pathological. — 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 — (a. ) Red blood-
corpuscles from rupture of a blood-vessel. (b.) 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 the other elements and leaves the elastic fibres untouched.] Their pre-
sence 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 (Fig. 115, a) in bundles of fine needles. They indicate great decomposition
of the stagnant secretion — colourless, sharp-pointed, octagonal, or rhombic plates
— (c) (Charcofs crystals) of unknown nature (perhaps tyrosin), Haematoidiu (b)
and cholesterin crystals (d) occur much more rarely. (/. ) Fungi and other lower
organisms frequently occur. The threads of leptothrix buccalis (12) ; Oiidiuui
albicans in the mouth of sucklings, rod-shaped bacilli and bacteria. In phthisis,
the tubercle-bacillus of Koch.

Abnormal coloration of the sputum — red from blood — when the blood remains
long in the king 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 disagree-
able 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 (Galileo). This pressure acts equally on all sides upon the body,
and occurs also in all internal cavities containing air, both those that are
constantly filled with air (the respiratory passages and the spaces in the
superior maxillary, frontal, and ethmoid bones), and those that are
temporarily in direct communication with the outer air (the digestive
tract and tympanum ). As the fluids of the body (blood, lymph, secre-
tions, parenchymatous juices) are practically incompressible, their volume
remains practically unchanged under the pressure ; but they will absorb
gases from the air corresponding to the prevailing pressure (i.e., the
partial pressure of the individual gases), and according to their tempera-
ture (compare § 33).

276 ACTION OP DIMINISHED ATMOSPHERIC PRESSURE.

The solids consist of elementary parts (cells and fibres), each of which
presents only a microscopic 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 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. In these cases, 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 (Brothers' Weber). Even when the colytoid cavity is perforated,
the limb 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 C02 remains the same (§ 127, 8).

A Great Diminution of the Atmospheric Pressure, such as occurs in

ballooning (highest ascent, 8,600 meters), or in ascending mountains, causes a series
of characteristic phenomena : — (1.) In consequence of the diminution of the pressure
upon the parts 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 haemorrhage 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 of 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, deeper, and
irregular. When the atmospheric pressure is diminished ^-^, the amount of 0
in the blood is diminished (Bert, Friinkel and Geppert), the COo is imperfectly re-
moved 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 C02 in arterial blood is lessened ; and the amount of N diminishes proportionally
with the decrease of the atmospheric pressure (Frankeland Gepert). 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 anremic ; hence, there is
diminished secretion of urine, muscular weakness, disturbances of digestion, dull-
ness 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 8,000 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 com-
plicated with anajmia of the internal organs. Al. v. Humboldt found that in those
who lived on the Andes, the thorax was capacious. At 6,000 to 8,000 feet above
sea-level, water contains only one-third of the absorbed gases, so that fishes cannot
live in it (Boussingault). Animals may be subjected to a farther diminution of the
atmospheric pressure, by being placed under the receiver of an air-pump. Birds

COMPARATIVE AND HISTORICAL. 277

die when the pressure is reduced to 120 mm. Hg. ; mammals at 40 mm. Hg. ; frogs
endure repeated evacuations of the receiver, whereby they are much dis-
tended, 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 by
Hoppe-Seyler to the evolution of Irabbles of gas in the blood; these bubbles stop
up the capillaries, and the circulation is arrested. Local diminution of the atmo
spheric pressure causes marked congestion and swelling of the part, as occurs
when a cupping-glass is used.

Great Increase of the Atmospheric Pressure.— The phenomena, which

are, for the most part, the reverse of the foregoing, have been observed in pneumatic
cabinets and in diving bells, where men may work even under 4^ atmospheres
pressure. The phenomena are : — (!.) Paleness and dryness of the external sur-
faces, collapse of the cutaneous veins, diminution of perspiration, and mucous
secretions. (2.) The tympanic membrane is pressed hvwards (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 diminution of the intestinal gases. Owing to the more rapid oxidations hi the
body, muscular movement is easier and more active. The 0 absorbed and the C02
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, sub-
jective feeling of warmth, pulse beats slower, and pulse-curve is lower (compare
p. 150). In animals subjected to excessively high atmospheric pressure, P. Bert
found, that the arterial blood contained 30 vols. per cent. 0 (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 respiration of air under a greater or less pressure.

140, Comparative and Historical.

Mammals have lungs similar to those of man. The lungs of hirds are spongy,
united to the chest-wall, and there are openings 011 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
(Aristotle). 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 amphibians (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

closed and the glottis opened. When young — until their metamorphosis f

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 0 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 (Erman, JSOS). Insects and centipedes
respire by " tracheae," 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 trachea? and tracheal sacs, crabs by gills. The
molluscs and cephalopods have gills, some gasteropoda have gills aud others lungs.

278 HISTORICAL.

Amongst the lower invertebrata some breathe by gills, others by means of a special
" water-vascular system," and others again by no special organs.

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.D.), 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 pueumothorax 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 (i* 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
(f 1644) detected C02. [Joseph Black (1757) discovered, by the following experi-
ment, that C02 or "fixed air" is given out during expiration: — take two jars of
lime water, breathe into one through a bent glass tube, and force ordinary air
through the other, when a white precipitate of calcium carbonate will be found to
occur in the former.] In 1774 Priestley discovered 0. Lavoisier detected N (1775),
and ascertained the composition of atmospheric air, and he regarded the formation
of COo and H20 of the breath as a result of a combustion within the lungs
themselves. J. Ingen-Houss (1730-1790) discovered the respiration of plants.
Vogel and others proved the existence of C02 in venous blood, and Hoffmann and
others that of 0 in arterial blood. The more complete conception of the exchange
of gases was, however, only possible after Magmis had extracted and analysed
the gases of arterial and venous blood (p. 55).

Physiology of Digestion.

141. The Mouth and its Glands.

THE inilCOUS membrane of the cavity of the mouth, which becomes continuous
with the skin at the red margin of the lips, has a number of sebaceous 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. Papillae — 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. 115, 8), which is thickest, as a rule, where the longest papillae occur.

All the glands of the mouth, including the salivary glands, may be
divided into different classes according to the nature of their secretions.

1. The serous or albuminous glands [true salivary], whose secretion
contains a certain amount of albumin, e.g., the human parotid.

2. The mucous glands, whose secretion in addition to some albumin,
contains the characteristic constituent mucin.

3. The mixed [or muco-salivary\ glands, some of the acini secreting
albumin and others mucin — e.g., the human maxillary gland (Heiden-
hain). The structure of these glands is referred to under the salivary
glands.

Numerous mUCOUS glands (labial, buccal, palatine, lingual, molar) 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 trans-
parent secretory cells whose nuclei are placed near the attached end of the cells.
The acini have a distinct membrana propria. (2.) The serous glands (Ebner's)
are acinous glands occurring in the region of the circumvallate papillae (and in
animals near the papillae foliatse). They are lined with turbid granular epithelium
with a central nucleus, and they secrete saliva (Henle). (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

280 THE SALIVARY GLANDS.

sub-mucosa, whilst the finer twigs penetrate into the papilla, where they form
either a capillary net- work or simple loops.

The larger lymphatics lie in the sub-mucosa, whilst the finer brandies
form a fine net-work placed in the mucosa. The lymph-follicles also belong
to the lymphatic system. 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),
and placed in the sub-mucosa. They consist of adenoid tissue loaded with lymph -
corpuscles. The outer part of the adenoid reticulum is compressed so as to 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 depres-
sion into which a mucous gland opens, which fills the small cj-ater with mucus.

The Tonsils have fundamentally the same structure. On their surface are
a number of depressions into which the ducts of small mucous glands opeu. Thefe
depressions are surrounded by groups (10-20) of lymph-follicles, and the whole
is environed by a capsule of connective tissue. After E. H. Weber discovered
lymphatics in the neighbourhood of the tonsils, Briicke referred these structures to
the lymphatic system. Large lymph-spaces, communicating with lymphatics, 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.
Stohr found that numerous leucocytes passed between the epithelium covering
the tonsils, and reached the mouth.

Nerves- — Numerous medullated nerve-fibres occur in the sub-mucosa, pass into
the mucosa and terminate partly in the individual papilla? in Krause's End-bulbs,
which are most abundant in the lips and soft palate, and not so numerous in the
cheeks and in the floor of the mouth. The nerves administer not only to common
sensation, but they also are the organs of transmission for tactile (heat and pres-
sure) impressions. It is highly probable, however, that some nerve-fibres end in
fine terminal fibrils, between the epithelial cells, such as occur in the cornea and
elsewhere .

142. The Salivary Glands.

Structure of the Duds. — The three pairs of salivary glands, sub-
maxillary, sub-lingual, and parotid, are compound tubular glands.
Fig. 116, A, shows a fine duct, terminating in the more or less flask-
shaped alveoli or acini. [Each gland consists of a number of lobes,
and each lobe in turn of a number of lobules, which, again, are
composed of acini. All these are held together by a framework of con-
nective tissue. The larger branches of the duct lie between the lobules,
and constitute the intcrlobular ducts, giving branches to each lobule which
they enter, constituting the intralobular ducts. These intralobular ducts
branch and finally terminate in connection with the alveoli, by means
of an intermediary or intercalary part. The larger interlobar and inter-
lobular 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 STRUCTURE OF THE SALIVARY GLANDS.

281

the large cells and the membrana propria. The intralobular ducts are
lined by a single layer of large cylindrical epithelium. As is shown in
Fig. 1 1 6, E, the nucleus occurs about the middle of the cell, while the
outer half, i.e., next the basement membrana of the cell, is finely striated
longitudinally, which is due to fibrilke; the inner half next the lumen is
granular. The intermediary part is narrow, and is lined with a single
layer of flattened cells, each with an elongated oval nucleus. There is
usually a narrow " neck," where the intralobular duct becomes continuous
with the intermediary part, and here the cells are polyhedral (Klein).

The acini, or alveoli, are the parts where the actual process of secretion
takes place. They vary somewhat in shape — some are tubular, others
branched, some are dilated and resemble a Florence flask, and several
of them usually open into one intermediary part of a duct. Each

rOr\

Fig. 116.

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; E, transverse section of an excretory duct lined with cylindrical
"rodded" epithelium; F, entrance of a non-medullated nerve-fibre into a
secretory cell.

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

282

THE STRUCTURE OF THE SALIVARY GLANDS.

alveoli in addition to this basket-shaped structure. Immediately out-
side this membrane is a lymph-space (Gianuzzi), and outside this again
the net-work of capillaries is distributed. [The extent to which this
lymph-space is filled with lymph determines the distance of the capil-
laries from the membrana propria. The interalveolar lymph-spaces
communicate 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. 117), are lined by a single
layer of " mucin cells " (Heidenhain) (Fig. 116, B, c), which are large
cells distended with mucin, or at least with a hypothetical sub-
stance, 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 over-
laps the fixed part of the
cell next to it. Owing
to the fact that the body
of each cell is infiltrated
with mucin, these cells do
not stain with carmine,
although the nucleus and
its immediately investing
protoplasm do. Another
kind of cell occurs in the
sub-maxillary gland of the
dog. It forms a half-
moon-shaped structure
(Gianuzzi) lying in direct
contact with the wall of
the acinus. Each " half-
moon " or " crescent " con-
sists of a number of small,
closely packed, angular,
strongly 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

Fig. 117.

Section of part of the human sub-maxillary
gland. On the left of the figure is a group
of serous alveoli, and on the right a group
of mucous alveoli.

HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 283

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 mem-
brana 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 condition spreads towards the inner part of the cell.]

[In the mixed or muco-salivary glands (Klein), (e.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. 117)].

143. Histological Changes during the Activity of

the Salivary Glands.

[The condition of physiological activity of the gland-cells is accom-
panied by changes in the histological characters of the secretory cells.]

[Serous Glands. — The changes in the secretory cells have been care-
fully studied in the parotid of the rabbit. The histological 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 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. 1 1 8)].

[During activity, if the gland be caused to secrete by stimulating
the sympathetic, all parts of the cells undergo a change (Figs. 118, 119)
(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).

284

HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS.

On studying the changes which occur in a living serous gland, Langley
found that, during rest, the substance of the cells of the parotid is per-
vaded by fine granules, which are so numerous as to obscure the nucleus,
while the outlines of the cells are indistinct. No lumen is visible in
the acini during activity, the granules disappear from the outer zone of
the cells, the cells themselves becoming more distinct and smaller. After

^S^^feS^fe

w»^-^§ssMi ijpr

4-14'iWH.SSlW *-- ?i>---^7^< ^.lE"!**.' «>J 'wife^*^ £»".-'

Fis. 118.

Fiir. 119.

Sections of a "serous" gland — the parotid of a rabbit, Fig. 118, at rest; Fig. 110,
after stimulation of the cervical sympathetic.

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 round 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 dis-
appearance taking place from without inwards. Similar changes occur
in the cells of the pancreas.]

[Mucous Glands. — 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. 116, B, c), surrounded with a small amount of
protoplasm, and placed near the basement membrane. The clear sub-
stance 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, refractive, and " mucous-cells," which occur in
the quiescent gland, and which do not 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 (Fig. 116, C), devoid of mucin. These cells

THE NERVES OF THE SALIVARY GLANDS, 285

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.

The change may be produced in two ways. Either it is due to the "mucous cells "
during secretion becoming broken up, so that they yield their mucin directly to the
saliva ; in saliva rich 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, Stohr); 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 their mucin. If we assume, with Heidenhain, that the mucous
cells break up, then these granular non-mucous cells must be regarded as new
formations produced by the proliferation and growth of the composite marginal cells,
i.e., 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 proto-
plasm 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 hiluni
of the gland, where they form a rich plexus provided with ganglia
between the lobules. [According to Klein, there are no ganglia in the
parotid gland.]

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 to (a.) the sub-maxillaiy
and the sub- lingual glands, derived from the plexus on the external
maxillary artery • (6.) to the parotid gland from the carotid plexus.

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. The branches to the parotid
reach it in a roundabout way. They arise from the tympanic branch
of the glosso-pharyngeal nerve (dog). The tympanic plexus sends
fibres to the small superficial petrosal nerve (Eckhard, Loeb, Heiden-
hain), and with it these fibres run to the anterior surface of the
pyramid in the temporal bone, and, after passing through the fora-
men lacerum anticum, reach 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 tem-
poral region under cover of the parotid, gives branches to this gland
(v. Wittich).

The sub-maxillary ganglion, which gives branches to the sub-

286 ACTION OF NERVES ON THE SECRETION OF SALIVA.

maxillary and sub-lingual glands, receives fibres from the tympanico-
lingual nerve, 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. Pfliiger states, with regard to the latter, that (a.)
medullated nerve-fibres penetrate the acini ; the sheath of Schwann
(gray sheath) 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"1 the nucleus of a secretory cell. [This,
however, is not proved] (Fig. 116, 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 describes 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.

[(d) The direct termination of nerve-fibres has been observed hi 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 (Ludwig and Rahn) causes a profuse secretion of a thin
watery saliva, which contains a very small amount of specific consti-
tuents (Eckhard). Simultaneously with the act of secretion, the blood-
vessels of the glands become dilated, 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 contains one-
third more 0 than the venous blood of the non-stimulated gland.
Notwithstanding this relatively high percentage of 0, the secreting
gland uses more O than the passive gland (§ 131, 1).

[If a cannula be placed in AVharton'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—

ACTION OF NERVES ON THE SECRETION OF SALIVA. 287

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. The increased
amount of secretion is not due simply to the increased blood supply.

II. Stimulation of the sympathetic nerve causes a scanty amount
of a very thick, sticky, mucous secretion (Eckhard), in which the
specific salivary constituents, mucin, and the salivary corpuscles are
very abundant. The specific gravity of the saliva is raised from 1,007
to 1,010. 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.

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 constituents, especially in the
organic elements, which are more affected than the inorganic (C. Ludwig and
Becher). After prolonged 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 stimula-
tion 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 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).

Relation to Blood Supply. — The secretion of saliva is not simply the
result of the amount of blood in the glands ; that there is a 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 con-
tinues for some time after the blood-vessels of the gland have been ligatured
(Ludwig, Czermack). [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 lymph-spaces of the gland
(Ludwig)].

(2.) Atropin and Daturiit extinguish the activity of the secretory fibres in the
chorda tympaui, but do not affect the vaso-dilator fibres (Heidenhain). The
same results occur after the injection of acids and alkalies into the excretory
duct (Gianuzzi).

288 ACTION OF NERVES ON THE SECRETION OF SALIVA,

(3.) 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 (Ludwig), or even in the carotid itself. The
pressure in Whartoii's duct may reach 200 mm. Hg.

(•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 in-
jecting acids or alkalies into the duct, which shows that the secretory activity of the
gland is independent of the circulation (Gianuzzi).

[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 rela-
tion 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. 120). 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.]

[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 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.]

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. This physiological
consideration goes hand in hand with the anatomical fact of the direct continuation
of nerve-fibres with the secretory cells. 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 (Bufalini).

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.

"Paralytic Secretion" of Saliva. — By this term is meant the continued
secretion of a thin watery saliva from the sub-maxillary gland, which
occurs 24 hours after the secretion of the cerebral nerves (chorda of the
seventh), i.e., those branches of them that go to this gland, whether the

REFLEX SECRETION OF SALIVA.

289

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. Perhaps it arises from the secretion, which
stagnates within the gland after section of the nerves, acting as a direct
stimulus to secretion (Heidenhain). Perhaps it may be explained as a
degeneration effect, comparable to the fibrillar contractions which occur
in a muscle after secretion of its motor nerve.

B. Sub-lingnal 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 Avhen the glosso-pharyngeal branch to the
parotid is simultaneously excited. This branch may be reached within
the tympanum in the tympanic plexus. A thick secretion containing much
organic matter is thereby obtained. 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 (Heidenhain).

Reflex Secretion of Saliva. — [If a cannula be placed in Wharton's
duct, e.g., in a dog, during fasting, no saliva will now out. If the mu-
cous membrane of the mouth be stimulated by a sapid substance placed
on the tongue, there is a copious flow of saliva. If the sympathetic
nerve be divided, secre-
tion still takes place when
the mouth is stimulated,
but if the chorda tympaui
be cut, secretion no longer
takes place. Hence, the
secretion is a reflex act ;
in this case, the lingual
is the afferent, and the
chorda the nerve-carry-
ing impulses from a
centre situated in the
medulla oblongata (Fig.
120).] In the intact body,
the secretion of saliva

Vsss

Diagram of a salivary gland.

occurs through a reflex stimulation of the nerves concerned, whereby
under normal circumstances 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 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,

19

290 REFLEX SECRETION OF SALIVA.

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 (Frerichs, Oehl). A rush of saliva into the mouth
usually precedes the act of vomiting (p. 310).

(5) The stimulation of distant sensory nerves, e.g., the central end of the sciatic
— certainly through a complicated reflex mechanism — causes a secretion of saliva
(Owsjannikow and Tschierjew). Perhaps the secretion of saliva, which sometimes
occurs during pregnancy, is caused in the same reflex manner.

Stimulation of the conjunctiva, e.g., by applying an irritating fluid
to the eye of carnivorous animals, causes a reflex secretion of saliva
(Aschanbrandt).

The reflex centre for the secretion of saliva lies in the medulla
oblongata, at the origin of the seventh and ninth cranial nerves (Eckhard,
Loeb). The centre for the sympathetic fibres is also placed here
(Griitzner and Chlapowski). This region is connected by nerve-fibres
with the cerebrum; hence, the thought of a savory morsel, some-
times 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 same effect. The reflex secretion of saliva
may be inhibited by stimulation of certain sensory nerves, e.g., by pulling
out a loop of the intestine (Pawlow). Stimulation of the cortex cerebri
of a dog, near the sulcus cruciatus, is often followed by secretion of
saliva (Eulenberg and Landois, Bochefontaine, Bubnoff, and Heideuhain).
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 (Mitscherlich). Directly after the section of all the
nerves, secretion stops, for a time at least.

Pathological Conditions and Poisons.— Certain affections, as inflammation
of the mouth, neuralgia, ulcers of the mucous membrane, 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 — imralyse
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 (Prevost). Pilocarpin acts on the chorda tympaui, 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 does, excites the secretory nerves, but in large doses
paralyses them (Heidenhain). Daturin, cicutin, and iodide of a;thylstrychnine,
paralyse the chorda.

THE PAROTID SALIVA. 291

Theory Of Salivary Secretion. — Heidenhain has recently formulated the
following theory regarding the secretion of saliva : — " During the passive or quies-
cent 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 secreting gland, there are
two processes occurring together, but independent of each other, and
regulated by two different classes of nerve-fibres ; secretory fibres cause
the act of secretion, while trophic fibres cause chemical processes within the
cells, partly resulting in the formation of the soluble constituents of the secre-
tion, and partly in growth of the protoplasm. According to the number of
both kinds of fibres present in a nerve passing to a gland, such nerve being
stimulated, the secretion takes place more rapidly (cerebral nerve) or more
slowly (sympathetic), while the secretion contains less or more solid constituents.
The cerebral nerves contain many secretory fibres and few trophic fibres, while
the sympathetic contains many 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 pro-
toplasm ; hence, the amount of organic constituents diminishes, and the micro-
scopic characters of the cells are altered. The microscopic characters of the cells
are altered also by the increase of the protoplasm, 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 proliferation of
the marginal cells. The energy which causes the current of fluid depends upon
the protoplasm of the gland-cells."

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.

146. The Saliva of the Individual Glands.

(a.) The Parotid Saliva is obtained by placing a fine cannula in
Steno's duct (Eckhard) ; it has an alkaline reaction, but during fasting,
the first few drops may be neutral or even acid on account of free
C02 (Oehl) — its specific gravity is 1,003 to 1,004. When allowed to
stand it becomes turbid, and deposits, in addition to albuminous
matter, calcium carbonate, which is present in the fresh saliva in the
form of bicarbonate.

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 con-
stitueuts ; 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 decom-
posing saliva in carious cavities between the teeth.

It contains small quantities (more abundant in the horse) of a
globulin-like body, and never seems to be without C N K S sulpho-
cyanide of potassium (or sodium — Treviranus, 1814), which, however,
is absent in the sheep and dog (Brettel).

The sulphocyanide gives a dark red colour (ferric sulphocyauide) with ferric
chloride. 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).

292 THE MIXED SALIVA IN THE MOUTH.

Mucin is absent, hence the parotid saliva is fluid, is not sticky,
and can readily be poured from one vessel into another. It contains
1*5-1 '6 per cent, of solids (Mitscherlich, van Setten) in man, of which
0'3-1P0 per cent, is inorganic.

Amongst the organic substances the most important are Ptyalin, a small
amount of urea (Gobley), and traces of a volatile acid (Caproic ?)

Of the inorganic constituents — the most abundant are potassium and sodium
chlorides ; then potassium, sodium, and calcium carbonates, some phosphates
and a trace of an alkaline sulphate.

(b.) The Sub -maxillary Saliva is obtained by placing a cannula in
Wharton's duct; it is alkaline, and may be strongly so. When allowed
to stand for a long 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 some-
what tenacious. Farther, it contains ptyalin, but in less amount than in
parotid saliva ; and, according to Oehl, only 0'0036 per cent, of potassium
sulphocyauide.

Chemical Composition.— Sub-maxillary saliva (dog) :
Water, .... 991-45 per 1,000,
Organic Matter, . . 2 -89 ,, ,,

( 4-50 NaCl and CaCl2.
Inorganic Matter, . . 5-6G< 1'IG CaCO3, Calcium and Magnesium

( phosphates.

Pfluger found that 100 cubic centimetres of the saliva contained 0'6 O— 64'7 C02
(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 C02, 1'21 N.

(c.) The Sub-lingual Saliva is obtained by placing a very fine cannula
in the ductus Rivinianus (Oehl), is strongly alkaline in reaction, very
sticky and cohesive, contains much mucin, numerous salivary corpuscles,
and some potassium sulphocyanide (Louget).

147, The Mixed Saliva in the Mouth.

The fluid in the mouth is a mixture of the secretions from the
salivary glands, and the secretions of the mucous glands of the mouth.

(1.) Physical Characters. — The mixed saliva of the mouth is a some-
what opalescent, tasteless, odourless, slightly glairy, fluid, with a specific
gravity of 1,004-1,009, and an alkaline reaction. The amount secreted
in 2-i hours— 200 to 1,500 grammes (7-70 oz.) ; according to Bidder
and Schmidt, however, 1,000 to 2,000 grammes. The solid con-
stituents = 5'8 per 1,000.

Composition. — The solids are: — Epithelium and mucus, 2'2 ; ptyalin and
albumin, 1/4 ; salts, 2'2 ; potassium sulphocyanide, 0'04per 1,000. The ash con-
tains chiefly potash, phosphoric acid, and chlorine (Hammerbacher).

Decomposition products of epithelium, salivary corpuscles, or the remains of food,

THE MIXED SALIVA IN THE MOUTH. 293

may render it acid temporarily, as after long fasting, and after much speaking
(Hoppe-Seyler). Even outside the body, saliva containing much epithelium
becomes acid before it putrifies (Gorup-Besanez). 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 (8-11 /z), and are nucleated pro-
toplasmic globular cells without an envelope. During their living
condition, the particles in their interior exhibit molecular or Broivnian
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 —
e.g., gamboge rubbed up in water, particles of carmine, charcoal, &c.]

(b.) Pavement epithelial cells from the mucous membrane of the mouth and
tongue ; they are very abundant in catarrh of the mouth (Fig. 115, 8).

(c.~) Living organisms, which live and thrive in the cavities of teeth nourished
by the remains of food. Amongst these are Lcptothrix buccalis (Fig. 115, 12)
and small bacteria-like organisms.

(3.) Chemical Properties — (a.) Organic Constituents. — Serum-albumin
is precipitated by heat and by the addition of alcohol. In saliva, mixed
with much water and shaken up with C02, a globulin-Wee body is
precipitated ; mucin occurs in small amount. Amongst the extractives,
the most important is ptyalin (Berzelius) ; fats and urea occur only in
traces. In twenty-four hours 130 milligrammes of potassium or sodium
sulphocyanide are secreted.

(b.) Inorganic Constituents. — Sodium and potassium chlorides, potas-
sium sulphate, alkaline and earthy phosphates, ferric phosphate.

Abnormal Constituents. — In diabetes mellitus, lactic acid, derived from a
further decomposition of grape-sugar, is found (Lehmann). It dissolves the
lime in the teeth, giving rise to diabetic dental caries. Frerichs found leucin, 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 suffering 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

294 PHYSIOLOGICAL ACTION OF SALIVA.

increase considerably. 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. The most important part played by saliva in digestion is its
diastatic or amylolytic action (Leuchs, 1831) — i.e., the transformation of
starch into dextrin and some form of sugar. This is due to the ptyalin
— a hydrolytic ferment or ensym — which acts in very minute quantity,
so that starch takes up water and becomes soluble, the ferment itself
undergoing no essential change in the process. [Ptyalin belongs to
the group of unorganised ferments. 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. It 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 maltose and dextrin (both soluble in water).
Several closely allied varieties of dextrin, distinguishable by their
colour reactions, seem to be produced (Briicke). Erytlirodextrin is
formed first ; it gives a red colour with iodine, then a reducing
dextrin — Achroodextrin, which gives no colour reaction with iodine.
The sugar formed by the action of ptyaline upon starch is maltose
(C12H22011-|-H20), which is distinguished from grape-sugar (C12H24012)
by containing one molecule less of water, which, however, it holds
as a molecule of water of hydration, as indicated in the formula given
above (Ad. Mayer). [Maltose also differs from grape-sugar in its
greater rotatory power on polarised light, and in its less power of
reducing cupric oxide.]

[Thus, it will be seen that between the original starch and the final
product, maltose, several intermediate bodies are formed. The starch

PHYSIOLOGICAL ACTION OF SALIVA. 295

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 erythrodextrin,
there being a simultaneous production of sugar; but ultimately no
colour is obtained on adding iodine — achroodextrin, which gives no
colour with iodine, and maltose being formed. The presence of the
maltose is easily determined by testing with Fehling's solution.

Brown and Heron suggest that the final result of the transformation
may be represented by the equation —

10 (C12H20010) + 8 H20 = 8 (C12H22On) + 2 (C12H20010)

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 Dystropodex-
trin). For the further changes that maltose undergoes in the intestine,
see Intestinal Juice, ii., 2.

[The formula of starch is usually expressed as C6H1005, but the researches
already mentioned, and those of Brown and Heron, make it probable that it is more
complex, which we may provisionally represent by n (C^HgoOjo).]

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.
It is easily isolated from the precipitate. The saliva is acidulated with phos-
phoric acid, and lime-water is added until the reaction becomes alkaline, when a
precipitate of basic calcium phosphate occurs, which carries the ptyaline along with
it. This precipitate is collected on a filter and washed with water, which dissolves
the ptyaline, 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 (Cohn-
heim).

(2.) V. W'MlcKs 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. The glycerine extracts the ptyalin. It is
precipitated by alcohol from the glycerine extract.

(3.) William Roberts recommends the following solutions for extracting ferments
from organs which contain them: — (1) A 3-4 p.c. solution of a mixture of two parts
of boracic acid and 1 part borax. (2) Water, with 12-15 p.c. of alcohol. (3) One
part chloroform to 200 of water.

Diastatic action Of Saliva.— («.) 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).

(&.) The action takes place more slowly in the cold than at the temperature of

296 FUNCTIONS OF SALIVA.

the body— its action is enfeebled at 55°C., and destroyed at 75°C. {Paschutin).
The most favourable temperature is 35°-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
Becond time (Paschutin).

(d.) Saliva acts best in a slightly alkaline medium, but it also acts in a neutral
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 (vou den Velden). In
both cases, however, dextrin is formed. Ptyalin is destroyed by hydrochloric
acid or digestion by pepsin (Chittenden and Griswold). 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 (01. Bernard).

(e.) The addition of common salt, ammonium chloride, or sodium sulphate (4 p.c.
solution), increases the activity of the ptyalin, and so do C02, acetate of
quinine, strychnia, morphia, curara, 0'025 p.c. sulphuric acid.

(/.) Much alcohol and caustic potash destroy the ptyalin; long exposure to the
air weakens its action. Salicylic acid and much atropin arrest the formation of
sugar.

(#.) Ptyalin acts very feebly 'and very gradually upon raw starch, only after
2-3 hours (Schiff); while upon boiled starch it acts rapidly. [Hence the necessity
for boiling thoroughly all starchy foods.]

(/(.) The various kinds of starch are changed more or less rapidly according to
the amount of cellulose which they contain; raw potato-starch after 2-3 hours,
raw maize-starch after 2-3 minutes (Hammarsten). Starch cellulose is dissolved
at 55°C. (Niigeli). When the starches are powdered and boiled, they are changed
with equal rapidity.

(£.) A mixture of the saliva from all the glands is more active than the saliva
from any single gland (Jakubowitsch), while mucin is inactive. Ptyalin differs
from diastase in so far that the latter first begins to act at + 66°C. Ptyalin
decomposes salicin into saligenin and grape-sugar (Frerichs and Stlidler), but it
has no action on cane-sugar and amygdalin.

II. Saliva dissolves those substances which are soluble in Avater ;
while the alkaline 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 aids the act of swallowing, the mucin being
given off unchanged in the fseces. 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 0.]

[V. It is necessary to the sense of taste to dissolve sapid substances,
and bring them in relation with the end-organs of the nerves of taste.]

The presence of a peptone-forming ferment has recently been detected in saliva
(Hiifner, Munk, Kuhne). This ferment is likewise said to occur in the saliva of the
horse, which can also convert cane-sugar into invert sugar, and slightly einul-
sionise fats (Ellenberger and v. Hofmeister). According to Hofmeister, the saliva
of the sheep has a digestive action on cellulose .

Saliva has no action on proteids, while on fats it produces a very
feeble emulsion,

TESTS FOR SUGAR. 297

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 redis-
solved 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 ; 2 CuO — 0 = Cu90.

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 afterwards 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 precipitate. The
reason for boiling the test itself is, that the solution is apt to decom-
pose 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.]

3. Bottger's Test.— Alkaline bismuth oxide solution (5 grammes each of basic
bismuth nitrate, and tartaric acid, 30 cubic centimetres water, and caustic soda
sufficient for neutralisation) is reduced to bismuth suboxide by sugar, with the
formation of a dark olive green and ultimately black precipitate.

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 colouration is obtained. 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 atmospheric air, the fluid again becomes blue.

In all cases where albumin is present it must be removed — in urine by acidula-
ting with acetic acid and boiling; in blood, by adding four times its volume of
alcohol and afterwards filtering, while the alcohol is expelled by heat.

298

VITANTITATIVE ESTIMATION OF SUGAR.

150. Quantitative Estimation of Sugar.

I. By Fermentation. — Into the glass vessel

^_ ^- (Fig- 121, «) a measured quantity (20 cmtr.)of

the fluid (sugar) is placed along with some yeast,
while b contains concentrated sulphuric acid.
The whole apparatus is now weighed. When
exposed to a sufficient temperature (10-40°C.),
the sugar splits into 2 molecules of alcohol and
2 of carbonic acid,

•••••MM*

Fig. 121.

Apparatus for the quantitative
estimation of sugar by fer-
mentation.

C6H1206 = 2 (C2H60) +2 (C0a),
Grape-sugar = 2 alcohol + 2 carbonic acid ;

and in addition there are formed traces
of glycerine and succinic acid. The COg
escapes from b, and as it passes through the

H2S04, C02 yields to the latter its water. The apparatus is weighed after two
days, when the reaction is ended, and the amoiiut of sugar is calculated from the
loss of weight in the 20 cmtr. of fluid. 100 parts of water-free sugar = 48 "89
parts COg, or 100 parts C02 correspond to 204'54 parts of sugar.

II. Titration. — By means of Fehling's solution, which consists of cupric sul-
phate, tartrate of potash and soda, caustic soda, and water. It 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 (see Urine, vol. ii.).

III. The amount may also be estimated by the polarisation apparatus (see Urine,
vol. ii.).

151. Mechanism of the Digestive Apparatus.

This embraces the following acts :—

1. The introduction of the food; the movements of mastication and
those of the tongue ; insalivation and the formation of the bolus of food.

2. Deglutition.

3. The movements of the stomach, of the small and large intestine.

4. The excretion of faecal 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 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
= 3-10 mm. Hg. (2) The fluid is Japped 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.

The solids when they consist of small particles are licked up with
the lips, aided by the movements of the tongue. In the case of large

THE MOVEMENTS OF MASTICATION. 299

masses, a part is bitten off with the incisor teeth, and is afterwards
brought under the action of the molar teeth by means of the lips,
cheeks, and tongue.

153. The Movements of Mastication.

The articulation of the jaw is provided with an interarticular cartilage (Vidius,
1567) — 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 upon the articular tubercle, whereby the meniscus
moves with it, and covers the articular surface.

The process of mastication consists of the following movements : —
(«..) The elevation of the jaw is accomplished 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.

(&.) 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 (Haller). The muscles act 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.

\Yhen the articular surface of the lower jaw passes forwards on to the tubercle,
the External Pterygoids actively aid in producing this (Berard).

(c.) Displacement of both or one articular surface forwards or backwards.
During rest, when the mouth is closed, the incisor teeth of the lower
jaw fall 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 External
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, when the individual movements of the lower
jaw are variously combined, 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

300

STRUCTURE OF THE TEETH.

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. At the
same 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 and the buccinator
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, and the muscles of the lips. The general centre for
the muscles of mastication lies in the medulla oblongata.

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 2-4 mm. Hg. (Metzger and Ponders).

154. Structure and Development of the Teeth.

A tooth is just a papilla of the mucous membrane of the gum, which has under-
gone 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 calcined 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 pctrosa or cement.

The dentine or ivory which surrounds the pulp cavity and the canal of the
fang (Fig. 122) is very firm, elastic, and brittle. Like the matrix of bone, dentine,

when treated in a certain
way, presents a fibrillar
structure (v. Ebner). It
is permeated by innumer-
able long, tortuous, wavy
tubes — ihedentinal tubules
(Leeuwenhoek, 1678)—
each of which communi-
cates with the pulp cavity
bymeansof a fine opening,
and passes more or less
horizontally outwards as
far as the outer layers of
•p. ,OQ the dentine. The tubules

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.

soft fibres, the "fibres of Tomes" (1840), which are merely greatly elongated and
branched processes of the odontoblasts of the pulp (Waldeyer, 1865).

Fig. 122.

Vertical section of a
tooth — p, pulp
cavity; d, dentine;
c, cement; s,enamel.

are bounded by an ex-
tremely resistant, thin,
cuticular membrane,
which strongly resists
the action of chemical
reagents. These tubules
are tilled completely by

STRUCTURE OF THE TEETH.

301

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. 124, c), whilst others pass into the " inter globular spaces," which are so
abundant in the outer part of the dentine (Czermak, 1850). These interglobular
spaces are small spaces bounded by curved surfaces. Certain curved lines
" Schreger's lines" (1800), 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 (Retzius, 1837).

The enamel, the hardest substance in the body (resembling apatite), covers
the crown of the teeth. It consists of hexagonal flattened prisms (Malpighi, 16S7)
arranged side by side like a palisade (Fig. 124, a and B). They are 3-5 ^ (T(FV7 inch)
broad, not quite uniform in thickness, curved slightly in different directions, and

Fig. 124.

Section of a tooth between the dentine and enamel— «, enamel; c, dentinal tubules;

B, enamel prisms highly magnified.

owing to inequalities of thickness, they exhibit transverse markings. They are
elongated, calcified, cylindrical, epithelial cells derived from the dental papilla.

Retzius described dark-brown lines running parallel with the outer boundary of
the enamel, due to the presence of pigment. The fully-formed enamel is nega-
tively doubly refractive and uniaxial, while the developing enamel is positively
doubly refractive (Hoppe-Seyler).

The cuticula or Nasmyth's membrane (1839) covers the free surface of the
enamel as a completely structureless membrane 1 - 2 fj. thick, but in quite young
teeth it exhibits an epithelial structure, and is derived from the outer epithelial
layer of the enamel-organ.

The cement (John Hunter, 177S) or crusta petrosa, is a thin layer of
bone covering the fang (Fig. 125, a). The bone lacunae communicate directly
with the dentinal tubules of the fang. Haversian canals and lamellaj are only
found where the layer of cement is thick, and the former may communicate
with the pulp-cavity (Salter). Very thin layers of cement may be devoid of
bone-corpuscles. Sharpey's fibres occur in the cement of the dog's tooth (Wal-
deyer) ; while in the horse's tooth single bone-corpuscles are enveloped by a
capsule (Gerber). 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 with a delicate capsule
of connective-tissue (C. Wedl).

302

CHEMISTRY OF A TOOTH.

a

Fig. 125.

Transverse section of the fang — a,
cement with bone-corpuscles ; b,
dentine with dentiiial tubules ; c,
boundary between both.

Chemistry Of a Tooth. — The teeth consist of a gelatine-yielding matrix infil-
trated with calcium phosphate and carbonate (like bone). — 1. The dentine con-
tains— organic matter, 27'70; calcium phosphate and carbonate, 72'06; magnesium
phosphate, 0'75, with traces of iron, fluorine, and sulphuric acid (Aeby, Hoppe-
Seyler).

2. The enamel contains an organic
proteid matrix allied to the substance
of epithelium. It contains 3 '60 organic
matter and 96 '00 of calcium phosphate
and carbonate, 1*05 magnesium phos-
phate, with traces of calcium fluoride
and an insoluble chlorine compound.

3. The cement is identical with
bone.

The pulp in a fully-grown tooth re-
presents the remainder of the dental
papilla around which the dentine was
deposited. It consists of a very vas-
cular indistinctly fibrillar connective-
tissue, laden with cells. The layers of
cells, resembling epithelium, which lie
in direct contact with the dentine are
called odontoblasts (Waldeyer, 1865),
i.e., those cells which build up the
dentine. These cells send off long
branched processes into the dentiiial 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 Trigerniuus) 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 periosteum, and consists of delicate connective-tissue with few
elastic fibres and many nerves.

The gums are devoid of mucous glands, are very vascular, and often pro-
vided with long vascular papillae 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 ridge (Fig. 126, 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 (6), 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.
127, c), so that the apex of tLe papilla comes to have
the enamel-organ resting upon it like a 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).

, Dental ridge ; b, enamel-
organ ; c, beginning of
the dentine-germ ; d, first
indication of the tooth -
sac.

DEVELOPMENT OF THE TEETH.

303

Those epithelial cells (Fig. 127, 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 occurs there (Figs. 127 and 128, k). During the process, fibres

Fig. 127.

a, Dental ridge; b, enamel -organ
with 1, outer epithelium; 2,
middle stellate layer ; 3, ena-
mel-prism cell layer ; c, den-
tine-germ with blood-vessels
and the long osteoblasts ou
the surface ; d, tooth - sac ;
e, secondary enamel-germ.

-Jt

Fig. 128.

a, Dental ridge ; b, enamel-organ ;
c, dentine-germ ; /, enamel ; g,
dentine ; h, interval between
enamel-organ and the position of
the tooth ; k, layer of odonto-
blasts.

or branches of these cells are left 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.

Dentition. — During the development of the first (temporary or milk) teeth a
special enamel-organ (Fig. 127, e) 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 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 amoeboid cells of the granulation tissue.
[Multinuclear giant-cells also erode the fangs of the teeth.]

Eruption Of the Teeth. — The followiug is the order in which the twenty milk-
teeth cut the gum — i.e., 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.]

304

MOVEMENTS OF THE TONGUE.

Molars.

Canines.

Incisors.

Canines.

Molars.

24 12

IS

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-
fifth 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 per-
manent teeth, except the wisdom-tooth, making forty-eight in all.

[Eruption of Permanent Teeth. — The age at which each tooth cuts the gum ia
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

— (Kirkes.)]

155. Movements of the Tongue.

The tongue being a muscular organ (Aretaeus, A.D. 81), 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 collects 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, whence it passes
into the oesophagus.

The muscular fibres of the tongue run in three directions — longi-
tudinally, from base to tip ; transversely, the fibres for the most part
proceeding outwards from the vertically placed septum linguae ; 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, to the styloid process, and the palate.

Microscopically, the fibres are transversely striated, with a delicate sarcolemma,
and very often they are divided where they are inserted Into the mucous membrane
(Leeuwenhoek). The muscular bundles cross each other in various directions,
and in the interspaces fat cells and glands occur.

On analysing the lingual movements, we may distinguish changes
in form and changes in position : —

DEGLUTITION. 305

(1.) Shortening and broadening by the longitudinal muscle, aided by
the hyo-glossus.

(2.) Elongation and narrowing, by the transversus linguse.

(3.) The dorsum rendered concave by the transversus and the
simultaneous action of the median vertical fibres.

(4.) Arching of the dorsum : — (a) transversely by contraction of the
lowest transverse bundles ; (&) longitudinally by the action of the lowest
longitudinal muscles.

(5.) Protrusion, by the genio-glossus, while at the same time the
tongue usually becomes narrower and longer (2).

(6.) Eetraction, by the hyo-glossus and stylo-glossus, and (1) usually
occurring at the same time.

(7.) Depression of the tongue into the floor of the mouth, by the hyo-
glossus. The floor of the mouth may be made deeper by simultaneously
depressing the hyoid bone.

(8.) Elevation of the tongue towards the gums : — (a) At the tip by
the anterior part of the longitudinal fibres ; (6) in the middle by eleva-
ting the entire hyoid bone by the mylo-hyoid (N. triyeminus) ; (c) at the
root by the stylo-glossus and palato-glossus, as well as indirectly by the
stylo-hyoid (N. facialis).

(9.) Lateral movements, whereby the tip of the tongue passes to the
right or the left ; these are caused by the contraction of the longitudinal
fibres of one side.

Motor Nerves.— The proper 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
outwards), and the tongue follows the direction of its action. The tongues of
animals which have been killed exhibit tibrillar contractions of the muscles, some-
times lasting for a whole day (Cardanus, 1550).

156. Deglutition.

The onward movements of the contents of the digestive canal 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
distinguish in order the following individual movements : —

(1.) The aperture of the mouth is closed by the orbicularis oris (N.

facialis).

20

306 DEGLUTITION.

(2.) The jaws are pressed against each other by the muscles of
mastication (N. 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.

(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
— Dzondi, 1831).

(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; N. facial is), and tension (Tensor veli palatini; X. frige-
minus, otic ganglion} of the soft palate (Bidder, 1838). 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 (Passavant), 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 cases where
the soft palate is defective, part of the food usually passes into the
nose.

(6.) The bolus is propelled onwards by the successive contractions
of the constrictors of the pharynx until it passes into the oesophagus.
At the same time the entrance to the glottis is closed, else the morsel
would pass into the larynx.

Falk and Kronecker assert, that by the rapid contraction of the transversely
striped muscles which diminish the aperture of the mouth, the bolus is projected
into the oesophagus, so that peristalsis of the pharynx and oesophagus only occurs
during forced deglutition.

If we make a series of efforts to swallow, one after the other, con-
traction of the oesophagus takes place only after the last attempt.
Kronecker and Meltzer found that stimulation of the glosso-pharyngeal
nerve inhibited the act of deglutition and the propagation of the move-
ment through the oesophagus. Section of both nerves causes tonic
epasm of the oesophagus and cardia.

NERVES CONCERNED IN DEGLUTITION. 307

The closure of the glottis is effected in the following manner: — («.) 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 approxi-
mated close to the hyoid bone (Berengar, 1521) by the thyro-hyoid.

(6.) When the larynx is raised so that it comes to lie below the over-
hanging root of the tongue, the epiglottis is pressed downwards over
the entrance to the glottis, and the bolus passes over it. In addition,
the epiglottis is pulled down by the special muscular fibres of the
reflector epiglottidis (Thiele) and aryepiglotticus.

Injury to the Epiglottis. — Intentional injury of the epiglottis in animals, or
its destruction in man may cause fluids to "go the wrong \vay,:' i.e., into the
glottis, whilst solid food can be swallowed without disturbance. In dogs, at any
rate, coloured fluids placed on the root of the tongue have been observed to pass
directly into the pharynx without coming into contact with, so as to tinge, the
upper surface of the epiglottis (Magendie, Schiff).

(c.) Lastly, the closure of the glottis by the constrictors of the
larynx also prevents the entrance of substances into the larnyx
(Czermak).

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.

Nerves. — 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 sensory nerves which, when
mechanically stimulated, excite the involuntary act of deglutition, are,
according to Schroeder van der Kolk, the palatine branches of the tri-
geminus (from the sphenopalatine ganglion) and the pharyngeal branches
of the vagus (Waller, Prevost). The centre for the nerves concerned
(for the striped muscles) lies in the superior olives of the medulla
oblongata. Swallowing can be carried out when a person is uncon-
scious, or after destruction of the cerebrum, cerebellum, and pons.
[Even in the deep coma of alcoholism, the tube of a stomach-pump
is readily carried into the stomach reflexly, provided the surgeon
passes it back into the pharynx to bring it within the action of the
constrictors of the pharynx.] The nerves of the pharynx are derived
from the pharyngeal plexus, which receives branches from the vagus,
glosso-pharyngeal, and sympathetic.

308 NERVES CONCERNED IN DEGLUTITION.

Within the esophagus, whose stratified epithelium is moistened with
the mucus derived from the mucous glands in its walls, the downward
movement is involuntary, and depends upon a complicated reflex
movement discharged from the centre for deglutition — there is a peri-
staltic movement of the outer longitudinal and inner circular non-
striped muscular fibres.

In the upper part of the oesophagus which contains striped muscular fibres, the
peristalsis takes place more quickly than in the lower part. The movements of
the oesophagus never occur independently, but are always the continuation of a
foregoing act of deglutition. If food be introduced into the oesophagus through a
hole in its wall, there it lies; and it is only carried downwards when a movement
to swallow is maole (Volkmann). The peristalsis extends along the whole length
of the oesophagus, even when it is ligatured or when a part of it is removed
(Mosso). If a olog be allowed to swallow a piece of flesh tieol to a string, so that
the flesh goes half-way down the oesophagus, and if the flesh be witholrawn, the
peristalsis still passes downwards (G. Ludwig anol Wild).

The motor nerve of the oesophagus is the vagus (not the accessory fibres) ; after it
is olivioled, the food lodges in the lower part of the oesophagus. 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 experi-
ment, or greatly diminished, as in Valsalva's experiment (p. 112), deglutition is
rendered more difficult.

Goltz observed, that the oesophagus and stomach (frog) became greatly more
excitable, i.e., the excitability of the ganglionic plexuses in their walls was
increased, when the brain and spinal corol or both vagi were destroyed. These
organs contracted energetically after slight stimulation, while frogs whose cen-
tral nervous system was intact, swallowed fluids simply by peristalsis. Females,
and sometimes men also, with marked weakening of the nervoiis system
(Hysteria), not unfrequently have similar spasmodic contractions of the cesophageal
region (globus hystcricus). After section of both vagi, Schiff observed spasmodic
contraction of the oesophagus.

[Structure of the (Esophagus. — The walls of the oesophagus are
composed of three coats — mucous, sub-mucous, and muscular.

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 its inner part, of dense fibrous tissue, which projects in
the form of papillre, into the stratified epithelium. At its outer part
is a continuous layer of non-striped muscle, the muscularis mucoscc.

The sub-mucous coat is thicker than the foregoing, and consists of
loose connective-tissue, with the acini of small compound tubular
mucous glands imbedded in it. The ducts pierce the muscularis
mucosse to open on the inner surface of the tube.

The muscular coat consists of an inner, thicker, circular, and an outer,
thinner, longitudinal layer of non-striped muscle. In man, the upper
third of the gullet consists of striped muscular fibres. Outside the
muscular coat is a layer of fibrous tissue with elastic fibres.

MOVEMENTS OF THE STOMACH. 309

As in the intestine, there are two plexuses of nerves with ganglia;
one in the sub-mucous coat and the other between the two muscular
coats. Blood-vessels and numerous lymphatics lie in the mucous and
sub-mucous coats.]

157. Movements of the Stomach.

When the stomach is empty, the great curvature is directed down-
wards and the lesser upwards ; but when the stomach 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 back-
wards.

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 oesophagus. 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 com-
plete layer, but at the pylorus they are well marked and constitute
the pyloric sphincter-muscle, or valve ; whilst at the cardia (inlet),
such a muscular ring is absent (Gianuzzi). The innermost oblique or
diagonal layer is incomplete.

The movements of the stomach are of two kinds : — (1.) The rotatory
or churning movements, whereby the parts of the wall of the stomach
lying in contact with the contents or ingesta glide to and fro with a
slow rubbing movement. Such movements seem to occur periodically,
every period lasting several minutes (Beaumont). By these move-
ments 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 portions of the contents of the stomach first dissolved
are forced into the duodenum. They begin after a quarter of an hour
(Busch), and recur until about five hours after a meal (Beaumont).
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 mus-
cular fibres, when they contract, especially when the pyloric end is
filled, may act so as to dilate the pylorus.

The strongly muscular walls of the stomach of grain-eating birds effect a tritura-
tion of the food. The mechauical force thereby exerted was often experimented

310 INFLUENCE OF NERVES ON THE STOMACH.

upon by the older physiologists, who found that glass balls and lead tubes, which
could be compressed only by a weight of 40 kilos. , were broken or compressed in the
stomach of a turkey.

Influence of Nerves on the Movements. — [The stomach is supplied by
the vagi and by the sympathetic, the right vagus being distributed to
the posterior surface, and the left to the anterior surface, of the
stomach.] The ganglionic plexus of nerve-fibres and nerve-cells (Auer-
bach's), which lies between the muscular coats of the stomach, must be
regarded as its proper motor centre, and to it motor impulses are con-
ducted 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 cardire), (v.
Openchowski). [If the vagi be divided in the neck, there is a short
temporary spasmodic contraction of the cardiac aperture. On stimulat-
ing 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.]

Stimulation of the cceliac plexus causes movements in the stomach of
ruminants (Eckhard), perhaps indirectly through the effect upon the
blood-vessels.

Local electrical stimulation of the surface of the stomach causes circular constric-
tions 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 (Calliburces). 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 haemorrhage into the mucous
membrane.

[It is no uncommon occurrence to find haemorrhage into the gastric mucous
membrane of rabbits, after they have been killed by a violent blow on the head.]

158. Vomiting.

Mechanism. — Vomiting is caused by contraction of the walls of the
stomach, whereby the pyloric sphincter is closed. It occurs most
easily 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, this vomiting occurs through con-
traction of the walls of the stomach without the spasmodic action of
the abdominal walls. When the vomiting is violent, the abdominal
muscles act energetically. [The act of vomiting is generally preceded

VOMITING. 311

by a feeling of nausea, and usually there is a rush of saliva into the
mouth, caused by a reflex stimulation of afferent fibres in the gastric
branches of the vagus, the efferent nerve 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 con-
tents, aud it is kept contracted ; 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 antiperistalsis, as can be seen in the stomach
when it is exposed (Galen). The cardia is opened by the longitudinal muscular
h'bres (Schiff) which pull towards the lower orifice of the oasophagus, 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 oasophagus,
which is caused thus:— The glottis is closed, inspiration occurs suddenly and
violently, whereby the tesophagus is distended by gases proceeding from the
stomach (Liittich). The larynx and hyoid bone by the combine'd action of the
geniohyoicl, sternohyoid, sternothyroid, and thyrohyoid muscles are forcibly pulled
forwards, so that the air passes from the pharynx downwards into the upper
section of the tesophagus (Landois). 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 outwards. During continued vomiting, anti-
peristalsis 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. The
capacity of the stomach of a new-born child is 35-43 cubic centimetres; after 14
days, 153-160 c.c.; at 2 years, 740 c.c.

Magendie was of opinion that the abdominal muscles alone were concerned in
vomiting, as he found that vomiting occurred when he replaced the stomach by a
bag. This was much too crude an experiment. But it only succeeds when the
lowest part of the cesophagus has been removed (Fantini, Schiff). The view of
Gianuzzi, that the abdominal muscles are the chief factor, because animals poisoned
with curara — in whom these muscles are paralysed, but not the walls of the
stomach — cannot vomit, is too wide a deduction.

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 over-
come 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 apncea.

The act of vomiting is most easily excited (chemically or mechani-
cally) by stimulation of the centripetal or afferent nerves of the mucous
membrane of the soft palate, pharynx, root of the tongue (glosso-

312 MOVEMENTS OF THE INTESTINE.

pharyngeal nerve), stomach, and further, by stimulation of the uterus
(pregnancy), intestine (inflammation of the abdomen), urinary apparatus
(passing a renal calculus), and also by direct stimulation of the vomiting
centre.

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. Vomiting is very common in diseases of the brain. Section of both vagi
prevents vomiting.

Emetics act (1) partly by mechanically or chemically stimulating the ends of
the centripetal (afferent) nerves of the mucous membrane. Tickling the fauces,
touching the surface of the exposed stomach (dog); and many chemical emetics —
e.g., cupric and zinc sulphate and other metallic salts — act in this way. (2) Other
substances cause vomiting when they are introduced into the blood (without being
first introduced into the stomach), and act directly upon the vomiting centre, e.y.,
apomorphm. (3) Lastly, there are some substances which act in both ways,
e.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. [According to Lauder Brunton, cupric sulphate acts even when
injected into the blood.]

Vomiting is analogous to the process of rumination in animals that chew the
cud. 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 pro-
ceeds from above downwards, thus propelling the contents before it.
Frequently after death, or when air acts freely upon the gut, we may
observe that 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 —
Engelmann).

Method of Observation.— Open the abdomen of an animal under a'6 p.c. saline
solution to prevent the exposure of the gut to air (Sanders, and Braam-Houckgeest).

The iko-colic valve (Bauhin's valve, 1579, known to Eondelet in
1554), as a rule, prevents the contents of the large intestine from pass-
ing backwards into the small intestine. The movements of the
stomach and intestine cease during sleep (Busch).

However, when nuid is slowly introduced into the rectum through a tube, it
may pass upwards into the intestine, and even go through the ileo-colic valve into
the small intestine.

EXCRETION OF F^CAL MATTER. 313

Muscarin excites very lively peristalsis of the intestines, which may be set aside
by atropin (Schmiecleberg and Koppe).

Pathological. — -When any condition excites an acute inflammation of the intes-
tinal 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 in darned part, the peristalsis recurs, and is 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.

Antiperistalsis — i.e., a- movement which sets in and travels in an upward
direction towards the stomach, does not occur normally. That such a condition
takes place has been inferred from the fact, that in cases where the intestine is
occluded (Ileus) faecal matter is vomited. The most recent experiments of
Nothnagel throw doubts upon this view, as he failed to observe antiperistalsis in
cases where the intestine was occluded artificially. The ftecal odour of the ejecta
may result from the prolonged retention of the material within the small intestine.

160. Excretion of Fsocal 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. The contents assume the characters of faeces, and become
" formed " in the lower part of the great intestine. The faeces 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 faeces have been expelled, the external
sphincter (Fig. 129, S, and Fig. 130) usually contracts vigorously, and
remains in this condition for some time. Afterwards it relaxes, when
the elasticity of the parts surrounding the anal opening, 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 faeces lie above the
rectum, they do not excite any conscious sensations, but the sensation
of requiring to go to stool occurs, when the faeces 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 ; in the rabbit, between the sixth and seventh, and in
the dog, at the fifth lumbar vertebra (Masius).

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 con-
traction, the sphincters relax again, and the anus may remain opeu for a time.
This occurs, because the voluntary impulses which proceed from the brain to cause
the contraction of the external sphincter are absent. Landois observed, that in

314

EXCRETION OF F/ECAL MATTER.

2
Fig. 129.

The Perinseum and its Muscles — 1, Anus ; 2, coccyx ; 3, tuberosity ; 4, sciatic
ligament ; 5, cotyloid cavity ; B, bulbo-caveruosus muscle ; Ts, superficial
transverse perineai muscle ; F, fascia of the deep transverse perineal muscle ;
J, ischio-cavernosus muscle ; M, obturator internus ; S, external anal sphinc-
ter ; L, levator ani ; P, pyriformis (Henle).

dogs with the posterior roots of their lower lumbar and sacral nerves divided,
the anus remained open, and not unfrequeutly a mass of feces 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 con-
traction of the sphincters.

The external sphincter can be contracted voluntarily from the cerebrum,
like any voluntary muscle, but the closure can only be effected up to a
certain degree. When the pressure from above is very great, the energetic-
peristalsis at last overcomes the strongest voluntary impulses. Stimula-
tion of the peduncles of the cerebrum and of the spinal cord below this
point, causes contraction of the external sphincter.

Defaecation. — The evacuation of the fseces, 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

DEF/ECATION.

315

faeces may not excite reflexly the sphincter-muscles, iu consequence of
mechanical stimulation of the sensory nerves of the rectum, there seems
to be an inhibitory centre for the reflex action of the sphincters, which is
set in action, owing, as it appears, to voluntary impulses. Its seat
is in the brain; Masius thinks it is in the optic thalami, from whence
fibres pass through the peduncles of the cerebrum to the lumbar
part of the spinal cord. When this inhibitory apparatus is in action,
the faecal mass passes through the anus, without causing it to close
reflexly.

The strong peristalsis which precedes defalcation can be aided, and to
a certain degree, excited by voluntary, short, movements of the external
sphincter and levator ani, whereby the plexus myentericus of the large
intestine is stimulated mechanically, thus causing lively peristaltic

Fig. 130.
Levator ani and Sphincter ani externus.

movements in the large intestine. The expulsion of the faeces is also
aided by the pressure of the abdominal muscles, and most efficiently
when a deep inspiration is taken, so as to fix the diaphragm, whereby
the abdominal cavity is diminished to the greatest extent. The soft

316 INFLUENCE OF NERVES ON THE INTESTINE.

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. 1 29, 1 30) 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 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 puts 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
faeces appear only to reach the lower end of the sigmoid flexure. As a
rule, from thence downwards, the rectum is normally devoid of fceces. It
seems that the strong circular fibres of the muscular coat, which Nelaton
has called sphincter ani tertius, when they are well developed, contract
and prevent the entrance of the fa3ces. When the tendency to the
evacuation of the rectum is very pressing, the anus may be closed more
firmly from without, by energetically rotating the thigh outwards, and
contracting the muscles of the gluteal region.

161. Influence of Nerves on the Intestinal

Movements.

Auerbach's Plexus. — The intestinal canal contains an automatic motor
centre within its walls — the plexus myenterieus of Auerlach — 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.

[Structure. — The plexus of Auerbach consists of non-medullated nerve-fibres
which form a dense plexus, groups of ganglion cells occurring at the nodes (Fig.
131). A similar plexus extends throughout the whole intestine between the
longitudinal and circular muscular coats from the oesophagus to the rectum.
Branches are given off to the muscular bundles. A similar, but not so rich a
plexus lies in the sub-mucous coat, Meissner's plexus, which gives branches to
supply the muscularis nmcosre, the smooth muscular fibres of the villi, and the
glands of the intestine (Fig. 132).]

1. If this centre is not affected by any stimulus, the movements of
the intestine cease — comparable to the condition of the medulla
oblongata in apnoea (Sig. Mayer and v. Basch). The same is true —
just as in the case of the respiration — during intra-uterine life, in con-
sequence of the foetal blood being well supplied with 0. This condition
may be termed aperistalsis. It also occurs during sleep, perhaps on
account of the greater amount of 0 in the blood during that state.

AUERBACH AND MEISSNER'S PLEXUSES.

317

Fig. 131.

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 pro-
ceeding from the ganglia, and the anastomosing fibres, lie between the
muscular bundles.

Fig. 132.

Plexus of Meissner— a, ganglia; b, anastomosing fibres; r, artery; d, vaso-motor

nerve-fibres accompanying c.

2. When blood containing the normal amount of blood-gases passes
throiigh the intestinal blood-vessels, the quiet peristaltic movements of

318 INFLUENCE OF BLOOD ON THE INTESTINE.

health occur (cuperistalsis) provided no other stimulus be applied to the
intestine.

3. All stimuli applied to the plexus myentericus increase the peri-
stalsis, which may become so very violent as to cause evacuation of
the contents of the large gut, and may even produce spasmodic con-
traction of the musculature, of the intestine. This condition may be
termed dysperistalsis, corresponding to dyspnoea. The condition of the
blood flowing through the intestinal vessels has a most important effect
on the peristaltic movements.

Condition of the Blood. — Dysperistalsis may be produced by (a) interrupting
the circulation of blood iu the intestines, no matter whether anasmia (as after
compressing the aorta — Schiff,) or venous hypertemia be produced. The stimu-
lating condition is the want of 0, i.e., the increase of COo. Very slight dis-
turbance in the intestinal blood-vessels, e.g. , venous congestion 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 foces
takes place when there is congestion, owing to the plugging of the intestinal
blood-vessels when blood from another species of animal is used for trans-
fusion (p. 202 — Landoia). The marked peristalsis which occurs on the approach
of death is undoubtedly due to the derangements of the circulation, and the con-
sequent alteration of the amount of gases in the blood of the intestine. The same
is true of the increased movements of the intestines which occur as a result of
psychical excitement, e.g., grief. The stimulus, in this case, passes from the
cerebrum through the medulla oblongata (vaso-motor centre) to the intestinal
nerves and causes anosmia of the intestine, (corresponding to the palor occurring
elsewhere). When the normal condition of the circulation is restored, the peri-
stalsis diminishes. (b) Direct stimulation of the intestine, conducted to the
plexus myentericus, causes dysperistalsis ; direct exposure of the intestines to the
air (stronger when C02 or Cl is present) — the 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 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,
and cease below 19°C. (Horwath).

4. The continued application of strong stimuli causes the dysperi-
stalsis 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 coagula-
tion within these vessels (Landois). Filling the blood-vessels with " indifferent "
fluids, after the peristalsis has been previously caused 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.

INFLUENCE OF NERVES ON THE INTESTINE. 319

5. The continued application of strong stimuli causes complete
paralysis of the intestine, such as occurs after violent peritonitis, or
inflammation of the musculature or mucous coat in man. In this con-
dition, 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 intes-
tine), 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 (Sigm. Mayer, and
von Basch) ; when the latter condition occurs, stimulation of the
splanchnic increases the peristalsis. If arterial blood be freely sup-
plied, the inhibitory action continues for some time (0. Nasse). Stimu-
lation 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. 0. ISTasse concludes from these experiments that the splanchnic
contains — (2) inhibitory fibres which are easily exhausted by a venous
condition of the blood, and also motor fibres which remain excitable for
a longer time, because after death, stimulation of the splanchnics always
causes peristalsis, just like stimulation of the vagus. (3) The splanch-
nic is also the vaso-motor nerve of all the intestinal blood-vessels, so that
it governs the largest vascular area in the body. When it is stimu-
lated, 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 anaemia 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) The splanchnic is the sensory
nerve of the intestine, and as such, under certain circumstances, it may
give rise to extremely painful sensations.

As stimulation of the splanchnic contracts th<T~blood-vessels, von Basch has
raised the question, 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 Engelinann and v. Brakel, the peristaltic movement is chiefly pro-
pagated by direct muscular conduction, as in the heart and ureter, without the
intervention of any nerve-fibres.

320 EFFECT OF DRUGS ON THE INTESTINE.

Effect of Drugs Amongst the reagents which act upon the intestinal move-
ments are :— (1) Such as diminish the excitability of the plexus myentericus, i.e.,
which lessen or even abolish intestinal peristalsis, e.g., belladonna. (2) Such as
stimulate the inhibitory fibres of the splanchnic, and in large doses paralyse them —
opium, morphia (Nothnagel) ; 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 (Schmiedeberg and Koppe). 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 evacua-
tions 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 (C. Schmidt, Moreau), 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 decompositions in the intestine.
The stools are thin and greenish from the admixture of bili-verdin. (6) Certain
saline purgatives — sodium sulphate, magnesium sulphate, cause fluid evacuations by
retaining the water in the intestine (Buchheim) ; and it is said, that if they be injected
into the blood-vessels of animals, the}' cause constipation (Aubert).

If a crystal of a potash salt be applied to the intestine, it causes a local con-
striction, accompanied by lively movement extending about 10 centimetres above
where the crystal was applied. Soda salts are not so powerful, and they seem to
act upon the nerves and not upon the musculature (Nothnagel, K. Bardeleben).

[Action Of Saline Cathartics.— From an extended investigation recently
made by Matthew Hay on the action of saline cathartics, it would appear certain
that 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 accumula-
tion of fluid within the canal, which, partly from ordinary dynamical laws, partly
from a gentle stimulation of the peristaltic movements excited by distension,
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. This absence of effect is due to a deficiency of
water in the blood, so that the blood cannot, throiigh the intestinal glands, yield
enough fluid to the salt in order to produce purgation. When a concentrated
solution of a salt is administered to an animal whose alimentary canal is known,
from a few hours' preliminary fasting, to be 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 concen-
tration without having reabsorbed fluid from the intestine. It apparently recoups
itself from the tissue-fluids. After a few days' abstention from water, the tissue-
fluids are so much diminished as not to be able any longer to recoup the blood, and
the blood itself gradually becomes concentrated; hence a concentrated saline
solution fails to excite any secretion when administered.

It is also interesting in connection with saline cathartics that 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. After the maximum of excretion of the acid has been reached, the salt
begins very slowly and gradually to disappear by absorption, which is checked
only by the occurrence of purgation. The salt does not purge when injected into
the blood, and excites no intestinal secretion; nor does it purge when injected
subciitaneously, 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.]

STRUCTURE OF THE STOMACH.

321

162. Structure of the Stomach,

Structure. — [The walls of the stomach consist of four coats, which
are from without inwards—

(1) The serous layer, from the peritoneum.

(2) The muscular layer, composed of three layers of non-striped

muscular fibres — (a), longitudinal; (b), circular; (r),
oblique (see p. 309).

(3) The sub-mucous layer, of loose connective-tissue, with the

larger blood-vessels, lymphatics, and nerves.

(4) The mucous layer.]

The well-developed mucous membrane of the stomach is thrown
into a series of folds or ruga', in the contracted condition of the
organ. With the aid of a hand-lens, it is seen to be beset with small
irregular depressions or pits (Vidius, 1567 — Fig. 133). Throughout
its entire extent it is covered by a single layer of moderately tall,
narrow cylindrical epithelium, which seems to consist of mucus-secret-
ing goblet cells (Fig. 135, d). The epithelium is sharply defined at
the cardia from the stratified epithelium of the oesophagus, and also at
the pylorus, from the true cylindrical epithelium with the striated disc in
the duodenum. [The cells in the passive condition seem to consist of
two zones, an outer clear part, next the lumen of the organ, consisting
of a substance (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 replacing 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 (F. E. Schultze).
Numerous tubular glands of two
distinct kinds are placed ver-
tically, like rows of test-tubes, in
the mucous membrane.

Fundus-glands. — On making a
vertical section of the cardiac
portion of the gastric mucous
membrane, and submitting it to
microscopic examination, it is seen to consist of a number of tubular glands

21
i

Fig. 133.

Surface section of the clog's gastric muc-
ous membrane, showing the crater-like
depressions or pits, it; a, the elevations
round ii.

322

FUNDUS-GLANDS OF THE STOMACH.

placed side by side. These are the fundus-glands (Heidenhain), otherwise
called peptic, or cardiac. Several gland-tubes, which are wider below,
usually open into the short duct (Fig. 136). Each gland consists of a
structureless membrana propria with anastomosing branched cells in
relation with it. The duct is lined by a layer of cells like those lining
the stomach, while the secretory part of the tubes is lined throughout
by a layer of granular, short, small, polyhedral, or columnar nucleated
cells. These cells border the very narrow lumen, and were called
chief or principal cells by Heideuhain; they are also known as central
cells (Fig. 134, II, a), or adelomorphous (aSrjXoc, 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 Heidenhai: , or the delomorphous cells of Eollett

Fig. 134.

I, Transverse section of a duct of a fundus-gland— a, membrana propria; b, mucus-
secreting goblet cells; c, adenoid interstitial substance. II, Transverse sec-
tion of a fundus-gland — a, chief cells; /;, parietal cells; r, adenoid-tissue
between the gland-tubes ; c, divided capillaries.

(Fig. 134, II, A). 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
distinguished 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 (Stohr).
Isolated cells are sometimes found under the epithelium of the surface
of the stomach (Heidenhain), and occasionally in individual pyloric
glands (Stohr). The fundus-glands are most numerous (about 5
millions, according to Sappey), and are of considerable size in the
funclus.

•2. The Pyloric Glands occur only in the region of the pylorus,

PYLORIC GLANDS OF THE STOMACH.

323

where the mucous membrane is more yellowish-white in colour

(Fig. 135, 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, extending

often to half the depth of

the mucous membrane.

The duct is lined by epi-

thelium 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. Ebstein regards

these cells as forming-

pepsin. It is to be remem-

bered that the appearance

of the cells differs ac-

cording to their state of

physiological activity

(Figs. 137 and 138). When

they are exhausted they

are smaller and more gran-

ular, owing to the denser

reticulation of their net-work ; at any rate, they are granular in pre-

parations hardened in alcohol (Fig. 138).]

Fig. 135.

A, Isolated pyloric gland ; (/, isolated goblet
cells.

MUCOSSB. — The glands are supported by very delicate connective-
tissue mixed with adenoid -tissue (Fig. 134). Below this are two layers, circular
and longitudinal, of non-striped muscle, the muscularis mucosce, and from<it fine
processes of smooth muscular fibres pass up between groups of the glands towards
the free epithelial surface of the gastric mucous membrane. These muscular
processes are said to be concerned in emptying the glands. [In the gastric mucous
membrane of the cat, there is a clear homogeneous layer which is stained red by
picrocanniue, and placed immediately internal to the muscularis mncoste. It is
pierced by the processes passing from the muscularis mueosse.]

Masses of adenoid-tissue occur in the mucous membrane, especially near the
pylorus, constituting lynqjh-follic/i <, which are comparable to the solitary glands
of the small intestine.

324

LYMPHATICS AND NERVES OF THE STOMACH.

The Lymphatics are numerous, aud begin close under the epithelium by
dilated extremities or loops (Fig. 136, d); they run vertically, and anastomose in the
mucosa between the gland-tubes, which they envelope in sinus-like spaces. They
join large trunks in the mucosa ; another plexus of large vessels exists in the sub-
mucosa (Loven).

[The Nerves. — A plexus of non-inedullated nerve-fibres and a few ganglion cells

Vertical section of the gastric mucous membrane — y y, pits on the surface ; p, neck
of fundus-glands opening into a duct, g; x, parietal, and y, chief cells; a, v, <•,
artery, vein, capillaries; (/, (/, lymphatics, emptying into a large trunk, e.
(Partly schematic).

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 net-work,
c c, which forms a narrow net-work under the epithelium, and between its meshes
the gland-ducts open (y). The veins gradually collect from this horizontal
capillary net-work and run towards the large veins of the sub-mucosa, v.

THE GASTRIC JUICE. 32")

163. The Gastric Juice.

Properties — The gastric juice is a tolerably clear colourless fluid,
with a strong acid reaction, sour taste, and peculiar characteristic odour;
it rotates the plane of polarised light to the left (Hoppc-Seyler). It is
not rendered turbid by boiling, and resists putrefaction for a long time.
Its specific gravity = 1002'5 (dog, 1005), and it contains only ^ p.c. of
solid constituents. The quantity of gastric juice 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
Griinewald (1853), in a similar case, as equal to 26'4 p.c. of the body-
weight; while Bidder and Schmidt (from corresponding observations on
dogs) estimated it as equal to 6i kilos, daily, corresponding to j1^ of the
body-weight. It contains :—

(1.) Pepsin (Th. Schwann, 1836), the characteristic nitrogenous
hydrolytic ferment or enzym, which dissolves proteids — 3 per 1000.

(2.) Hydrochloric Acid (Front, 1824), 0-2-0-3 (according to Eichet,
0-8-2-1) per 1000; (in the dog. 15 times more). This occurs free in the
gastric juice, as the latter always contains more free chlorine than
bases, to which it can be united (C. Schmidt). Lactic acid is usually
met with, but it arises from the fermentation of the carbohydrates of
the food.

[It has been for a long time disputed, whether the acidity of the gastric juice is
due to hydrochloric acid or to free lactic acid. The most reliable of recent methods
for determining this, point conclusively to hydrochloric acid as the cause of the
acidity (Richet and others).]

Tests — Free hydrochloric acid is detected by the following reactions: — 0'025
p.c. solution of methylviolet becomes blue; or, alkaline solution of tropseolin
becomes lilac; or, red Bordeaux wine is treated with amy lie alcohol until its colour
almost disappears — when, if dilute hydrochloric acid be added, a rose colour is
obtained.

(3.) The large amount of mucus Avhich covers the surface of the
mucous membrane is to be regarded as the secretion from the goblet
cells of the mucous membrane (p. 321). [The reaction of the mucus
covering the walls of the empty stomach is in many cases alkaline
(M. Hay).]

(4.) Mineral Salts (2 per 1000).

They are chiefly sodium and potassium chlorides, less calcic chloride (ammonium
chloride, also in animals), and the compounds of phosphoric acid with lime,
magnesium, and iron.

Amongst foreign substances, which may be introduced into the body, the follow-
ing appear in the gastric juice, HI, after the use of potassium iodide — potassium
sulpho-cyanide, ferric lactate, and sugar, and ammonium carbonate in uraaruia.

SKCRKTTON OF CIASTRIC JUICE.

164. Secretion of Gastric Juice.

After the discovery of the two kinds of glands in the stomach, and
after it was found that the fundus-glands contained two different forms
of cells, the question as to whether the different constituents of gastric
juice were formed by different histological elements came to be
investigated.

Changes of the Cells during Digestion. — During the course of
digestion, the cells of the fundus (and pyloric glands, dog) undergo

Fig. 137.

Section of the pyloric mucous mem-
brane (Ebstein).

Fig. 138.

Pyloric glands, showing changes
of the cells during digestion
(Ebstein).

important changes (Heidenhain, Ebstein). During hunger, the chief
cells are dear and large, the parietal investing cells are small, the
pyloric cells dear and of moderate size. During the first six hours of

CHANGES TN THE GLANDS DURING SECRETION. 327

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 9th 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. 137 and 138).

[Langley gives a different description of the appearances presented by these cells,
during different phases of secretory activity. 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 intra-cellular fibrillar net-work (Klein), 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 (Langley).
Speaking generally, during active secretion, the granules decrease in number and
size, the hyaline substance increases in amount, the net-work 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 con-
dition, 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. Dur-
ing digestion, the parietal cells increase in size, but do not become granular. In
all cells containing much pepsinogen, distinct granules are present, and the quan-
tity 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 (Langley). Compare Serous Glands, p. 284, 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 (Griitzner). The pyloric glands are
also said to secrete pepsin, but only to a small extent (Ebstein, Griitzner,
Klemensiewicz). Pepsin accumulates during the first stage of hunger,
and it is eliminated during digestion and also during prolonged hunger.
According to Ebstein, Griitzner, and Langley, pepsin as such, is not
present within the cells, but only a " mother-substance," a pepsinogen
substance (zymogeri), which occurs in the granules of the chief cells
(Langley). 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 ex-
tracted from the gastric mucous membrane by means of water free from
acids.

The pyloric glands sf.crele 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.

328 FORMATION OF HYDROCHLORIC ACID.

The animals experimented on died, at the latest, after six days. The secretion of
this part was thin, alkaline, and contained 2 p.c. of solids, including pepsin.

In the frog, the alkaline glands of the oesophagus contain only
chief cells which produce pepsin; while the stomach has glands which
secrete acid (and perhaps some pepsin), and are lined by parietal
cells (Partsch, v. Swiecicki). Amongst^fsAcs-, the carps have no fundus-
glands in the stomach (Luchau).

[The secreting portions of glands of the cardiac sac (crop) of the herring, are
lined by a single layer of polygonal cells (W. Stirling).]

The hydrochloric acid is formed, according to Heidenhain, by the
parietal cells. It occurs on the free surface of the gastric mucous mem-
brane as well as in the ducts of the gastric glands. The deep parts of
the glands are usually alkaline. Free HC1 is detected in human gastric
juice, within 45 minutes to 1-2 hours after a moderate meal (von den
Velden, and others), and 3-4 hours after a full meal (Eclinger); the
amount gradually increases during the process of digestion (Kretschy
and Uffelmann).

Cl. Bernard injected potassium ferrocyanide and afterwards lactate of iron into
the veins of a dog. After death, blue colouration occurred only in the upper, add
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.

With regard 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. Accord-
ing to Voit, the formation of acid ceases if chlorides be withheld from the
food. The active agent is lactic acid, which splits up sodium chloride
and forms free HC1 (Maly). The base set free is excreted by the urine,
rendering it at the same time less acid (Jones, Maly). The formation
of acid is arrested during hunger. According to H. Schulz, watery
solutions of alkaline and earthy chlorides are decomposed, even at a low
temperature, by C02, free hydrochloric acid being formed.

[A solution of sulphate of soda, not sufficiently strong to cause inflammatory
redness of the gastric mucous membrane, yet concentrated enough to excite
secretion, causes, when injected into the empty stomach, the pouring out of an
alkaline, not an acid secretion (Matthew Hay).]

Secretion. — When the stomach is empty, there is no secretion of
gastric juice ; this occurs only after appropriate (mechanical, thermal,
or chemical) stimulation. In the normal condition, it takes place imme-
diately on the introduction of food, but also of indigestible substances,

INFLUENCE OF NERVES ON THE SECRETION. 329

such as stones. The mucous membrane becomes red, and the circulation
more active, so that the venous blood becomes 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 (Rutherford).] The secretion is probably
caused reflexly, and the centre is perhaps 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 Avith 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 oesophagus
in man, produced by sAvallowing a caustic 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 secretion of
gastric juice. In this case, no saliA'a could be swalloAved to excite
secretion, so that it must have taken place through some nervous
channels. Even the sight or smell of food caused secretion. Emo-
tional states also are known to interfere Avith gastric digestion.]

Heidenhain isolated a part of the mucous membrane of the fundus
so as to form a blind-sac of it, and he found that mechanical stimula-
tion caused merely local secretion. If, hoAvever, at the same time,
absorption of digested matter also occurred, secretion took place over
larger surfaces.

The statement of Schiff, that active gastric juice is secreted only after absorption
of the so-called peptogenic substances (especially dextrin), is denied.

Action Of Alcohol. — Small doses of alcohol, introduced into the stomach,
increase the secretion of gastric juice; large doses arrest it. Artificial digestion
is not affected by 10 p.c. of alcohol, is retarded by 20 p. c., and is arrested
by stronger doses. Beer and wine hinder digestion, and in an undiluted form
they interfere with artificial digestion (Buchner).

The gastric juice, which passes into the duodenum after gastric
digestion is completed, is neutralised by the alkali of the intestinal
mucous membrane and the pancreatic juice. Part of the pepsin is
re-absorbed as such, and is found in traces in the urine and muscle-
juice (Briicke).

METHODS OF OBTAINING GASTRIC JUICE.

If the gastric juice be completely discharged externally through a gastric
fistula, the alkalinity of the intestine is so strong, that the urine becomes alkaline
(Maly).

The acid gastric juice of the iiew-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 (Simon, Biedert — see Milk). This occurs
more especially after the use of cow's milk.

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 with saliva, the sponges are best introduced through an
opening in the oesophagus (Manassei'n). Starving animals were forced to swallow
small stones, which excited the secretion of gastric juice. After a time, the
animals were killed, and the juice collected.

Dr. Beaumont (1825), au American physician, was the first to obtain human
gastric juice, from a Canadian named Alexis St. Martin, who was injured by a
gunshot wound, whereby a permanent gastric fistiila 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 (1843), and Bardeleben (1849) were thereby led to make
artificial gastric fistulas.

Gastric Fistula. — The anterior abdominal wall is opened by a medium 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. A silver cannula about an inch wide,
and with a flange, is introduced into the stomach, so that the flange lies in contact
with the gastric mucous membrane. The inner surface of the tube of the cauuula
is provided with a screw into which a similar cannula is screwed, and its flange
comes in contact with the abdominal wall. When the two are placed together
they have the form of J*, where a passes into b. [When the two parts of the
cannula are screwed together, the flanges keep the abdominal walls and gastric
walls in contact, until they become united organically.] As a rule, the tube is
kept corked. If the ducts of the salivary glands be tied, a perfectly uncompli-
cated 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.

Artificial Gastric Juice. — An important advance was made when Eberle
(1834) prepared "artificial gastric j nice," by extracting the pepsin from the gastric-
mucous membrane with dilute hydrochloric acid. A certain degree of concentra-
tion, however, is required (Schwann). Four litres of a watery solution of
O'S-1'0-1'7 of pure hydrochloric acid per 1000 (Briicke) are sufficient to extract
the chopped-up mucous membrane of the pig's stomach. Half a litre is infused
with the stomach and renewed every six hours. The collected fluid is afterwards
filtered (Hoppe-Seyler.) 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
HC1 from time to time (Schwann). The HC1 may be replaced by ten times its
volume of lactic acid (Lehmann) and also by nitric acid ; while oxalic, sulphuric,
phosphoric, acetic, formic, succinic, tartaric, and citric acid are much less active ;
butyric and salicylic acids are inactive.

ACTION ON TROTEIDS. 331

Von Wittich's Glycerine Method.— (a) Glycerine extracts pepsin in a very
pure form. The mucous membrane is rubbed up with 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 HC1, to form
an artificial digestive fluid. [The addition of a few drops of the glycerine extract
to dilute HC1, is sufficient for experiments on artificial digestion.]

(6.) Or the mucous membrane may be placed for 24 hours in alcohol, and after-
wards dried and extracted for 8 days with glycerine.

(f.) Wm. Roberts has used other agents for extracting enzyms (p. 295).

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 afterwards with pure water. The cholesterin-pulp is placed in ether to dis-
solve the cholesterin, and the ether is then removed. The small watery deposit
contains the pepsin in solution.

Properties. — Pepsin so prepared is a colloid substance ; it does not
react like albumin with the following tests, viz. : — it does not give the
xanthoprotein reaction (p. 333), 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
albumins. It is rendered inactive in an acid fluid by heating it to
55°-60°C. (Ad. Mayer).

166. Process of Gastric Digestion.

Chyme. — The finely divided mixture of food and gastric juice is
railed chyme. The gastric juice acts upon certain constituents of this
chyme.

L— Action on Proteids.

Pepsin and the dilute hydrochloric acid, at the temperature of the body,
transform proteids into a snlulle form, to which Lehmann (1850) gave
the name of " Peptone." During this change, they are first transformed
into a substance which has the characters of syntonin (Mulder).
Syntonin is an acid-albumin or albuminate; when neutralised by an
alkali [e.g., sodium carbonate], the albuminate is again precipitated.
An intermediate product is formed, a body which, as it were, stands
midway between albumin and peptone. This is called propeptone
(Schmidt-Miilheim), and is identical with Kiihne's hemialbuminose and
Meissner's parapeptone. It is not coagulated by heat, but is precipitated

332 ACTION ON T'ROTKIDS.

by concentrated solution of common salt. It is soluble in water in the
presence of weak acids and alkalies. It is precipitated by nitric acid
and adheres firmly to the Avails of the reagent glass; it dissolves in
nitric acid with the aid of heat, giving an intense yellow colour, and is
again precipitated in the cold (E. Salkowski). The compound of
nitric acid with propeptone is of the nature of a salt, and it is
deposited in the form of spheroids.

By the continued action of the gastric juice, the propeptone 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
hi/drolytic ferment pepsin, and the action takes place most readily at the
temperature of the body. Gelatin is changed into a gelatin-peptone.
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 pepsin can dissolve new quantities of
albumin. Still, it seems that some pepsin is used up in the process of
digestion (Griitzner). 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 propeptone and
directly peptonised, i.e., actually dissolved.

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 O20-0'6°C in 2-3 hours (v. Vintschgau and
Dietl).

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 hydratiou, viz., treatment with strong acids, (from fibrin, with 0 '2 HC1—
v. Wittich), caustic alkalies, putrefactive, and various other ferments and ozone
(Gorup-Besanez).

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 decom-
posing it into a body resembling syntonin.

Properties of Peptones:— (1) They are completely soluble in water.
(2) They diffuse very easily through membranes (Funke), and are
twelve times as diffusible as fluid albumin ; the fibrin-peptone is said

PROPERTIES OP PEPTONES. 333

to crystallise (Drechsel). (3) They filter quite easily through the
pores of animal membranes (Acker). (4) They are not precipitated by
boiling nitric acid, acetic acid and potassium ferrocyanide, weak alcohol,
or metaphosphoric acid. (5) They are precipitated from neutral or
feebly acid solutions by mercuric chloride, mercuric nitrate [Millon's
reagent], silver nitrate, basic lead acetate, potassio-mercuric iodide,
tannic acid, picric acid, bile acids, strong alcohol, phosphoro-wolframic
acid, and phosphoro-molybdic acid (Briicke). (6) With Millon's
reagent they react like proteids, and give a red colour, and with nitric
acid give the yellow xautho-protein reaction. (7) With caustic potash
or soda and a small quantity of cupric sulphate, they give a beautiful
purplish-red colour (Biuret-reaction). (8) They rotate the plane of
polarised light to the left.

The biuret-reaction is obtained with propeptone, as well as with a form of
albumin, which is formed during artificial digestion and is soluble in alcohol. It
is called Alkophyr by Brticke.

[Darby's fluid meat gives all the above reactions, and is very useful
for studying the tests for peptones.]

Preparation. — Pure peptones are prepared by taking fluid which contains
them and neutralising 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 (Hoppe-Seyler). 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.e., alkaloids obtained from dead
bodies.

Peptones are undoubtedly those modifications of albumin or proteids
which, after their absorption from the intestinal canal into the blood,
are destined to be used 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 (Plosz and Maly, Adamkiewicz).

The N-equilibrium in the metabolism of the body may be kept up
by administering I'll grammes of peptones, artificially prepared from
flesh, per kilo, of the body-weight (Catillon). After being absorbed
into the blood-stream, peptones are retransformed, first into propeptone,
and then into serum-albumin.

Conditions Affecting Gastric Digestion.— The presence 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 par-
ticles (Hoppe-Seyler). Boiling concentrated acids, alum, and tanuic acid, alkalinity
of the gastric juice (e.g., by the admixture of much saliva) abolish the action.
The salts of the heavy metals, which cause precipitates with pepsin, peptone,
and mucin, interfere with gastric digestion, and so do concentrated solutions of
alkaline salts, common salt, magnesium and sodium sulphates. Alcohol precipi-
tates the pepsin, but by the subsequent addition of water it is rodissolved, so that

334

ARTIFICIAL DIGESTION OF PROTEIDS.

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 riot 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 ; Avhile warm clothing, especially over the pit of
the stomach, aids it. Menstruation retards gastric 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.
Pepsin, 0-3 per cent.
Fibrin.

Water.
HC1, 0-2 per cent.
Fibrin.

Water.
Pepsin, 0'3 per cent.
HC1, 0-2 „
Fibrin.

Keep all in water-bath
at 38°C.

Unchanged.

Fibrin swells up, be-
comes clear, and is
changed into acid-
albumin or syntonin.

Fibrin ultimately
changed into
peptone.

The fibrin is obtained by beating blood, and afterwards washing and
boiling it to destroy any traces of pepsin. The fibrin may be coloured
with carmine, and from the rapidity with which the fibrin is dissolved
—i.e., the depth of the colour of the fluid — we may estimate the
digestive power of the gastric juice. Similar experiments may be
made with unboiled white of egg, mixed with nine volumes of water,
and filtered through muslin.]

[In all animals gastric digestion is essentially an add digestion, and
between the native proteid, fibrin, albumin, or any other form of
proteid, and the end-product peptone, there are many intermediate
substances and bye-products, whose properties and characters have still
to be investigated. If the peptones be decomposed, small quantities of
leucin and tyrosin are produced. W. Roberts obtained a bitter
substance during gastric 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 oft' (Mosso, Ad.

ACTION ON OTHER CONSTITUENTS OF FOODS. 335

Mayer). The free hydrochloric acid of the gastric juice is itself
sufficient to precipitate 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 juice — quite distinct from pepsin — the
milk-curdling ferment which, quite independently of the acid, pre-
cipitates the casein either in neutral or alkaline solutions. It is this
ferment or rennet which is used to coagulate casein in the making of
cheese. [Eennet is an infusion of the fourth stomach of the calf in
brine.]

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 proteicl
which constitutes cheese, and a body resembling peptone dissolved in the whey.
The addition of calcium chloride accelerated, while water retarded the coagu-
lation (Hammarsteu). — See Milk.

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 " (Hammarsten) also present, which
changes milk-sugar into lactic acid. Part of the milk-sugar is changed
in the stomach and intestine into grape-sugar.

Action on Carbohydrates. — Gastric juice does not act a.s a solvent of
starch, inulin, or gums. Cane-sugar is slowly changed into grape-sugar
(Bouchardat and Saudras, 1845, Lehmami). According to Ufielmann,
the gastric mucus, and according to Leube, the gastric acids are the chief
agents in this process. [Matthew Hay has failed to find any organic
ferment in the stomach capable of digesting sugar.] During the
digestion of true cartilage, there is formed a chondriu-peptone, and a
body which gives the sugar reaction with Trommer's test. Perfectly
pure elastiu yields an elastin-peptone, similar to albumin-peptone, and
hemi-elastin similar to hemi-albuminose (Horbaczewski).

Fats formerly were stated not to be acted on, but the recent re-
searches of Cash and Ogata show that a small part of the fats is broken
up into glycerine and fatty acids.

[We still require further observations on the gastric digestion of fats. Richet
observed in his case of fistula (p. 329), 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. W.
Roberts suggests that there may be some slight decomposition of neutral fats and
liberation of fatty acids. In this connection, it is important to remember that
fatty acids are liberated from neutral fats by bacteroid ferments (zymophytes).]

III. Action of Gastric Juice on the
various Tissues.

(1.) The gelatin-yieldiny substance (collagen) of all the connective-tissues (con-
nective-tissue, white fibro -cartilage, and the matrix of bone), as well as glutiii,

33G ACTION ON VARIOUS TISSUES.

are dissolved and peptonised by the gastric juice (Uffelmann). (2.) The structure-
less membranes (membranae proprice) of glands, sarcolemma, Schwann's sheath of
nerve-fibres, capsule of the lens, the elastic laminae of the cornea, the membranes
of fat cells are dissolved, but the true elastic (fenestrated) membranes and fibres
are not affected. (3.) The striped-muscular substance, 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, 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 haemoglobin decomposed into hosmatin and
a globulin-like substance; the latter is peptonised, while the former remains un-
changed, and is partly absorbed and transformed into bile-pigment. Fibrin is
easily dissolved to form propeptone and fibrin-peptone. (7.) Mucin, which is also
secreted by the goblet cells of the stomach, passes through the intestines un-
changed. (8.) Vegetable fats are not affected by the gastric juice; these cells
yield their protoplasmic contents to form peptones, while the cellulose of the cell-
wall, in the case of man at least, remains undigested. During putrefaction in the
intestine, some cellulose seems to be transformed into sugar.

Why the Stomach does not digest itself.— That the stomach can digest
living things is shown by the following facts: — The limb of a living frog was intro-
duced through a gastric fistula into the stomach of a dog (Cl. Bernard)— the ear of a
rabbit (Pavy) was also introduced — and both were partly digested. The margins of
a gastric ulcer and of gastric fistulae in man are attacked by the gastric juice. John
Hunter (1772) discussed the question as to why the stomach does not digest itself.
Not unfrequently 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 partially
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). Ligature
of the arteries to the stomach, according to Pavy, 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).

167. Gases in the Stomach.

The stomach always contains a certain quantity of gases, which are
derived partly from the gases swallowed with the saliva, partly
from gases which pass backwards from the duodenum, and partly from
air swallowed directly.

If the larynx and hyoid bone (p. 311) are suddenly and forcibly raised upwards
and forwards, there passes into the space behind the larynx a considerable amount
of air, which, on the latter regaining its position, is swallowed, owing to the
peristalsis of the oesophagus. We can feel the passage of such a mass of air as it
passes along the oesophagus. In this way a considerable volume of air may be
swallowed.

STRUCTURE OF THE PANCREAS.

337

The air in the stomach is constantly undergoing changes, whereby
its O is absorbed by the blood, and for 1 vol. of 0 absorbed 2 vols. of
C02 are returned to the stomach from the blood. Hence, the amount
of 0 in the stomach is very small, the CO., very considerable (Planer).

Gases in the Stomach — Vol. per cent. (Planer).

HUMAN SUBJECT AFTER VEGETABLE DIET.

DOG.

I.

n.

i

After Animal Diet.

ii.

After Legumes.

COa, . . 20-79
H, . . 6-71
N, . . 72-50
0, . .

33-83
27-58
38-22
0-37

25-2

68-7
6-1

32-9

66-3

0-8

1

A part of the C02 is set free by the acid of the stomach from the
saliva, which contains much CO., (p. 292). The N acts as an in-
different substance.

Abnormal development Of gases in persons suffering from gastric catarrh,
only occurs when the gastric contents are neutral in reaction ; during the butyric
acid fermentation H and COa are formed, while the acetic-acid and lactic -acid
fermentations do not cause the formation of gases. Marsh gas (CH4) has also
been found, but it must come from the intestine, as it can only be formed when no
O is present (Intestinal Oases).

168. Structure of the Pancreas.

The pancreas is built on the type of compound tubular or acino-
tubular glands, 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 flask -
shaped, and often convoluted. They consist of
a membrana propria, resembling that of the
salivary-glands, lined by a single layer of some-
what cylindrical cells, with a more or less
conical apex towards the very narrow lumen of
the acini. [As in the salivary glands, there
is a narrow intermediary part of the ducts
opening into the acini, and lined by flattened
epithelium]. The cells lining the acini consist
of two zones (Fig. 139) : —

(1.) The smaller parietal layer (outer) is transparent, homogeneous,
sometimes faintly striated, and readily stained with carmine and log-

22

Fig. 139.

Section of the tubes of
the pancreas in the
fresh condition.

338

STRUCTURE OF THE PANCREAS.

wood ; and (2.) the inner layer (Bernard's granular layer) is strongly
granular, and stains but slightly with carmine. It undoubtedly con-
tributes to the secretion by giving off material, the granules being
dissolved, and this zone becoming smaller (Heidenhain). The spherical

Fig. 140.

Changes of the pancreatic cells in various stages of activity — 1, During hunger ; 2,
in the first stage of digestion ; 3, in the second stage ; 4, during paralytic
secretion.

nucleus lies between the two zones. [The lumen of the acini is very
small, and, according to Langerhans, 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 continuous change in the appearance of
the cell-substance ; the granules of the inner zone dissolve in the
secretion ; the homogeneous substance of the outer zone is reversed
and transformed into granules, which pass towards the inner zone
(Heidenhain, Kiihne, and Lea).

Changes in the Cells during Digestion.— During the first stage (6-10

hours) the granular inner zone diminishes in size, the granules disappear, while
the striated outer zone increases in size (Fig. 140, 2). In the second stage (10-20
hours) the inner zone is greatly enlarged and granular, while the outer zone is
small (Fig. 140, 3). During hunger the outer zone again enlarges (Fig. 140, 1).
In a gland where paralytic secretion takes place, the gland is much diminished in
size, the cells are shrivelled (Fig. 140, 4) and greatly changed (Heidenhain).
According to Ogata, some cells actually disappear during secretion. When a
coloured injection is forced into the duct under a high pressure, fine intercellular
passages between the secreting cells are formed (Saviotti's canals), but they are
artificial products.

Duct. — The axially-placed excretory duct consists of an inner thick and an
outer loose wall of connective and elastic tissues, lined by a single layer of non-
striated columnar epithelium. Small mucous glands lie in the largest trunks.
The connective-tissue separates the gland into lobes and lobules. Non-medullated
nerves, with ganglia in their course, pass to the acini, but their mode of termina-
tion 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 lym-
phatic in their nature.] The lymphatics resemble those of the salivary glands.
The pancreas contains water, proteids, ferments, fats, and salts.

THE PANCREATIC JUICE. 339

[In making experiments upon the pancreatic secretion, it is important to remem-
ber, that the number of pancreatic ducts varies in different animals. In man
there is just one duct opening along with the common bile-duct at Vater's
ampulla, at the junction of the middle and lower thirds of the duodenum. The
rabbit has two ducts, the larger opening separately about 16 inches below the
entrance of the bile-duct. The dog and cat have each two ducts opening
separately.]

In a gland which has been exposed for some time, leucin, butalanin, tyrosin,
often xanthin and guanin are found ; lactic and fatty acids seem to be formed
from chemical decompositions taking place.

169. The Pancreatic Juice.

Method of obtaining the pancreatic juice. Regner de Graaf (1664) tied a
cannula in the pancreatic duct of a dog, and collected the juice in a small bag
placed in the abdomen. Other experimenters brought the tube through the abdo-
minal wall, and made a temporary n'stula, which after some days became inflamed
so that the cannula fell out. To make a permanent fistula, a duodenal n'stula
(like a gastric fistula) is made, and Wirsung's duct is catheretised with a fine tube ;
or the abdomen is opened (dog), and the pancreatic duct is pulled forward and
stitched to the abdominal wall, with which in certain cases it unites.

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 acts
far more energetically. This thick secretion, which is small in
amount, is the normal secretion. The copious watery secretion is per-
haps 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 secretion "
(p. 288). The quantity varies much, according as the fluid is thick
or thin.

During digestion, a large dog secretes 1-1 '5 grammes of a thick
secretion (01. Bernard). Bidder and Schmidt obtained in 24 hours
35-117 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, C02 is given off. It
contains albumin and alkali-albuminate ; like thin white of egg it is
sticky, somewhat viscid, flows with difficulty, and is coagulated by heat
into a white mass. In the cold, there separates a jelly-like albuminous
coagulum. Nitric, hydrochloric, and sulphuric acids cause a pre-
cipitate; while the precipitate caused by alcohol is redissolved by
water. 01. Bernard found in the pancreatic juice of a dog 8 '2 p.c. of

1,000 parts, . (like those of

blood-serum).

340 DIGESTIVE ACTION OF THE PANCREATIC JUICE.

organic substances, and O'S p.c. of ash. The juice (dog) analysed by
Carl Schmidt contained in 1000 parts: —

("Organic, . . 81 '84 f Common Salt, . . . 7 -36

Solids, 90-38 in ] Inorganic, . . 8 '54 Sodic Phosphate, . . 0'45

,, Sulphate, . . O'lO

Soda, 0-32

Lime, 0'22

Magnesia, . . . . 0'05

Potassic Sulphate, . 0'02

Ferric Oxide, . . . 0'02

The more rapid and more profuse the secretion, the poorer it is in
organic substances (Weinmann, Bernstein), 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 (Eadziejewski) and soaps are contained 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 juice 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.

The statement made by Schiff that the pancreas secretes only after the absorp-
tion of dextrin has not been confirmed. The secretory activity of the pancreas is
not dependent on the presence of the spleen.

170. Digestive Action of the Pancreatic Juice.

The presence of at least four hydrolytic ferments or enzymes makes
the pancreatic juice one of the most important digestive fluids in the
body.

I. The Diastatic Action (Valentin, 1844) is caused by a diastatic
ferment, amylopsin, a substance which seems to be identical with the
saliva ferment; but it acts much more energetically than the ptyalin
of saliva, on raiv starch as well as upon boiled starch; at the tempera-
ture 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 (Briicke's) into sugar.
Even cellulose is said to be dissolved (Schmulewitsch), and gum
changed into sugar by it (v. Voit).

According to v. Mering and Musculus, the starch (as in the case of the saliva
p. 294) is changed into maltose, a reducing-dextrin and grape-sugar; so also is
glycogen.

Amylopsin changes achroodextrin into maltose ; at 40°C. maltose is slowly

DIGESTIVE ACTION OF THE PANCREATIC .IL'K K. 341

changed into dextrose (Brown and Heron), but cane-sugar is not changed into
invertin.

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 (p. 296) 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"). The ferment is isolated by the same methods as obtain for the saliva-
ptyalin (p. 295); but the tryptic ferment is precipitated at the same time. The
addition of neutral salts (4 p.c. solution) e.g., potassium nitrate, common salt,
ammonium chloride, increases the diastatic action.

II. The Tryptic Action (Cl. Bernard, 1855), or the action on pro-
teids, depends upon the presence of a hydrolytic ferment which
Corvisart (1858) called pancreatin, and \V. Kiihne (1876) termed
trypsin. Trypsin acts upon proteids at the temperature of the body,
when the reaction is alkaline, and changes them first into a
globulin-like body, propeptone (p. 331), and then into a true peptone,
sometimes called tryptone. The proteids do not swell up before they
are changed into peptone. 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. Gelatin is
peptonised by it; but nuclein (Bokay) and haemoglobin withstand
solution (Hoppe-Seyler). Trypsin acts upon the connective-tissues
just like pepsin (§ 166, III.).

When the trypsin is allowed to act upon the peptone formed by its
own action, the peptone is partly changed into the amido-acid, leucin,
or amido-caproic acid (CGH13N00), and tyrosin (C9HUN03), which
belongs to the aromatic series (Kiihne). Hypoxanthin, xanthin (Salo-
mon) and asparaginic acid (C4H7N04), are also formed during the
digestion of fibrin and gluten, and so are glutaminic acid (C5H9N04),
amido-valerianic acid (C5HUN02). Gelatin is first changed into a
gelatin-peptone, and afterwards is decomposed into glycin and ammonia.

If the action of the pancreatic juice be still further prolonged, especi-
ally if the reaction be alkaline, a body with a strong, stinking, disagree-
able faecal odour, iiidol (C8H7N), volatile fatty acids, skatol (C9H9N), and
phenol (C6H60) are formed, while, at the same time, HCO.,H0SCH4
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 (Hiifner, Kiihne).

[If some fibrin be placed in pancreatic juice, or in a 1 per cent,
solution of sodium carbonate containing the ferment trypsin, peptones
are rapidly formed. When we compare gastric with pancreatic digestion,
we find that there are marked differences. The fibrin in pancreatic
digestion is eroded, or eaten away, and never swells up. The process

.'542 DIGESTIVE ACTION OF THE PANCREATIC JUICE.

takes place in an alkaline medium, and never in an acid one. In fact,
a 1 per cent, solution of sodium carbonate seems to play the same part
in assisting trypsin as a '2 per cent, solution of HC1 does for pepsin in
gastric digestion. In gastric digestion there is a by-product, syntonin,
formed in addition to the true peptones. In pancreatic digestion a
body resembling alkali-albumin, which passes into a globulin-like body,
and ultimately into a tryptic peptone, is formed. Of the peptones so
formed, one is called anti-peptone, and it is not further changed, but part
of the proteid is changed in a by-product, 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.

ANTI-PEPTONE HEMI-PEPTONE

yields yields

Normal Digestive
Products.

Undergoes Leucin,

no further Tyrosin,

change. Hypoxanthin,

Asparaginic Acid.

Putrefactive
Products.

Indol,

Skatol,

Phenol,

Volatile Fatty Acids,

HC02H(,S,

CH4N.

It seems that trypsin in pure water can act slowly upon fibrin to
produce peptone. Pepsin cannot do this Avithout the aid of an acid.]

When proteids are boiled for a long time with dilute H2SO.t, we obtain peptone,
then leucin and tyrosin (Kiihne) ; gelatin yields glycin. Hypoxan^hin 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 (Carica
papaya) possesses digestive properties (Roy, Wittmack), and the action is due to
an albuminous peptonising ferment, closely related to trypsin, and called caricin
or papai'n. The milky juice of the fig-tree has a similar action.

According to Gorup-Besauez, sprouting malt, vetch, hop, hemp during sprout-
ing, and the receptacle of the artichoke contain a peptonising ferment.

Leucin, tyrosin, glutaminic and asparaginic 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 fermentative actions that occur in the intestine
(Salomon).

Origin of Trypsin. — It is formed within the pancreas from a " mother-
substance" or zymogen (Heidenhain), which takes up oxygen. The

DIGESTIVE ACTION OF THE PANCREATIC JUICE. 343

zymogen is found in small amount, 6 to 10 hours after a meal, in the
inner zone of the secretory cells, but, after 1 6 hours, it is very abundant
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 (W. Kiihne). The addition of sodium chloride,
carbonate, and glycocholate, favours the activity of the tryptic ferment
(Heidenhain).

[The following facts show that zymogen (£^17, 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 pancreas which has been
kept for twenty-four hours, it will be found that an alkaline solution of
the former has practically no effect on fibrin, while the latter is power-
fully 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 (Heidenhain). 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.]

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 (Ewald, Mays).

III. The action on neutral fats is twofold: — (1) It acts upon fats
so as to form a, fine permanent emulsion (Eberle). (2) It causes fats to
take up a molecule of water and split into glycerine and fatty acids:—
Tristearin. Water. Glycerine. Stearic Acid.

(C57H11000) + 3(HS0) = (C3H803) + 3(C18H3602).

The latter result is due to the action of an easily decomposable fat-
splitting ferment (Cl. Bernard), also called steapsin. Lecithin is decom-
posed by it into glycero-phosphoric acid, neurin and fatty acids (Bokay).
After the decomposition is completed, the fatty acids are saponified
by the alkali of the pancreatic and intestinal juices.

Emulsification. — The most important change effected on fats in the small
intestine, is the production of an emulsion, or their sub-division into exceedingly
minute particles. This is necessary in order that the fats may be taken up by

344 SECRETION OF PANCREATIC JUICE.

the lacteals. If the fat to be emulsified contains a free fatty acid, i.e., if
it be slightly rancid, and if the fluid with which it is mixed be alkaline, emulsifi-
cation 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 p.c. solution of soda, instantly gives rise to an emulsion (Gad). The exces-
sively minute oil globules that compose the enmlsion 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 (G. Quincke). 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 (Briicke). Animal oils
emulsionise more readily than vegetable oils; castor oil does not emulsionise (Gad).

[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 pancreas of new-born children contains trypsin and the fat-decomposing
ferment, but not the diastatic one (Zweifel). A slight diastatic action is obtained
after two months, but the full effect is not obtained until after the first year
(Korowin).

IV. According to Kiihne and W. Roberts, the pancreas contains a
milk-curdling ferment, which may be extracted by means of con-
centrated solution of common salt.

171, The Secretion of the Pancreatic Juice.

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 in a reflex way 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 2-3 hours thereafter. The amount falls to-
wards the 5th or 7th hour, and rises again (owing to the entrance of the
chyme into the duodenum) towards the 9th and llth hour, gradually
falling towards the 17th-24th hour, until it ceases completely. When
more food is taken the same process is repeated. As a general rule,
when the secretion occurs rapidly it contains less solids than when it
takes place slowly.

Condition of Blood-vessels. — During secretion, the blood-vessels
behave like the blood-vessels of the salivary glands after stimulation of

PEPTONISED FOOD. 345

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 upon the secretion. The nerves arise from the
hepatic, splenic, and superior mesenteric plexuses, together with branches
from the vagus and sympathetic. The secretion is excited by stimula-
tion of the medulla oblongata (Heidenhain and Landau), as well as
by direct stimulation of the gland itself by induction shocks (Kuhne
and Lea). The secretion is suppressed by atropin, by producing vomit-
ing (Cl. Bernard), by stimulation of the central end of the vagus (C.
Ludwig and Bernstein), as well as by stimulation of other sensory
nerves — e.g., the crural and sciatic (Afanassiew and Pawlow). Extir-
pation of the nerves accompanying the blood-vessels prevents the
above-named stimuli from acting. Lender these circumstances a thin
"paralytic secretion " with feeble digestive powers is formed, but its
amount is not influenced by the taking of food (Bernstein).

Extirpation of the gland may be performed (Schiff), or the duct ligatured in
animals (Frerichs), 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 opera-
tion (Langendorff).

172. Preparation of Peptonised Food.

[Peptonised food may be given to patients whose digestion is feeble.
Dr. Wm. Roberts, of Manchester, uses various forms of this food. Food
may be peptonised 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 by-products
are formed. Hence, Dr. Roberts employs pancreatic digestion, which
yields a more palatable and agreeable product. As trypsin is destroyed
by gastric digestion, obviously it is useless to give extract of the pan-
creas 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 flavour does not
appear to be developed in the pancreatic digestion of vegetable proteids.

346 STRUCTURE OF THE LIVER.

Peptonised Milk-Gruel yielded Roberts the most satisfactory results,
as a complete and highly nutritious food for weak digestions. Make a
thick gruel from any farinaceous food, e.g., oatmeal, and while still hot
add to it an equal volume of cold milk, when the mixture will have a
temperature of 52°C. (125°F.). To each pint of this mixture, add two
or three tea-spoonfuls of liquor pancreaticus and 20 grains of bicarbonate
of soda. It is kept warm for two hours under a " cosey." It is then
boiled for a few minutes and strained. The bitterness of the digested
milk is almost completely covered by the sugar produced during the
process (Eoberts).

Peptonised soups and beef-tea have also been made and used with
success.]

173. Structure of the Liver.

The liver, the largest gland in the body, consists of innumerable
small lobules or acini, 1-2 millimetres (Jj -TV inch) in diameter.
These lobules are visible to the naked eye. All the lobules have the
same structure.

1. The Connective-tissue and 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 transverse fissure, where it
surrounds the portal 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 con-
nective-tissue, but small in amount, is also found within the lobules (Fleischl,
Kupffer). Leucocytes are sometimes found in the tissue of Glisson's capsule.

2. Blood-vessels. — («•) Branches of the Venous System. — If the vena porta be
traced from its entrance into the liver at the portal fissure, it will be found to
give 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 (Fig. 141, V. i). From these veins numerous
capillaries (e, 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
(cl, 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 neigh-
bouring cells. The capillai'ies converge towards the centre of each lobule, where
they join to form one large vein, the intralobular 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 (V. s). These in turn unite
to form wide veins, the origins of the hepatic veins, which open into the vena cava
inferior.

(b.) Branches of the Hepatic Artery. — The branches of the hepatic artery accom-
pany the branches of the portal vein and bile duct in the portal canals between
the lobiiles, and in their course they give off capillaries to supply the walls of the

STRUCTURE OF THE LIVER.

347

portal vein and larger bile ducts. The branches of the hepatic artery anastomose
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

V.i

Fig. 141.

I, Scheme of a liver lobule— V. i, V. i, interlobular veins (portal); V. c, central or
intra-lobular vein (hepatic) ; c, c, capillaries between both ; V. s, sublobular
vein ; V. v, vena vascularis; A, A. branches of the hepatic artery, giving branches,
r, r, to Glisson's capsule and the larger vessels, and ultimately forming the
vena? vasculares at i, i, opening into the intralobular capillaries ; y, branches
of the bile ducts ; x, x, intralobular bile capillaries between the liver-cells ;
it, d, position of the liver-cells between the meshes of the blood capillaries.
II, Isolated liver-cells — c, a blood capillary; a, fine bile capillary channel.

and terminate in the capillaries of the portal vein (i, i). Those capillaries, however,
which supply the walls of the portal vein and large bile ducts (r* r), terminate in
veins which end in the portal vein (V. v — Ferrein).

Several branches — capsular — pass to the surface of the liver, where they form a
wide-meshed plexus under the peritoneum. The blood is returned by veins which
open into branches of the portal vein.

[Pathologists draw a sharp distinction between different zones within a hepatic
lobule. Thus, the central area, capillaries, and cells are the zone of the hepatic vein,
which is specially liable to cyanotic changes; the area next the periphery of the
lobule is the portal vein zone, whose cells under certain circumstances are particu-
larly apt to undergo fatty degeneration; while there is an area lying midway
between the two foregoing — the hepatic artery zone — which is specially liable to
amyloid or waxy degeneration.]

348

STRUCTURE OF THE LIVER.

The Hepatic Cells (Fig. 141, II, a) are irregular polygonal cells of about
th of an inch (34-45^) in diameter (Fig. 142). The arrangement of the capil-
laries within a lobule determines the arrangement of the liver-cells. The liver-
cells form anastomosing columns which radiate from the centre to the periphery
of each lobule (Fig. 143). [The liver-cells are usually stated to be devoid of an
envelope, although Haycraft states that they possess one. They usually contain
a single nucleus with one or more nucleoli, but sometimes two nuclei occur. The
protoplasm and nucleus of each cell contains a plexus of fibrils just like other
epithelial cells. In some animals, globules of oil and pigment granules are found

Fig. 142.

Human liver-cells — the cell protoplasm con-
tains biliary colouring matter and oil-
globules b; d, has two nuclei.

Fig. 143.

Appearance of the liver-
cells after withholding
food for 36 hours.

in the cell protoplasm (Fig. 142).] Each cell is in relation with the wide-meshed
blood-capillaries (d, d), and also with the much narrower mesh-work of bile
ducts (I, x.)

It is important to observe that the appearance of the cells varies with the
period of digestion. During hunger, the liver cells are finely granular and very
cloudy (Fig. 143). About 13 hours after a full meal, especially of starchy food,
they contain coarse glancing masses of glycogen (Fig. 144, 2). The protoplasm
near the surface of the cell is condensed, and a fine net-work stretches towards the
centre of the cell, and in it is suspended the nucleus (Kupffer, Heidenhain). [The
net-work within the cells is best seen after solution of the glycogen.]

4. The bile ducts.— The finest bile capillaries or canaliculi arise from the
centre of the lobule, and indeed throughout the whole lobule, they form a regular
anastomosing net-work of very fine tubes or channels. Each cell is surrounded
by a polygonal — usually hexagonal — mesh (x, x). The bile capillaries always lie
in the middle of the surfaces between two adjoining cells (II, ft), where they form
actual intercellular passages (Hering). [According to some observers, they are
merely excessively narrow channels (1-2 mm. wide) in the cement-substance
between the cells, while according to others, they have a distinct delicate wall
(Fritsch). The bile capillary net-work is much closer and finer than the blood
capillary net-work.

[Thus, there are three net-works within each lobule — (1) a net-work of capil-
laries; (2) a net-work of hepatic cells; (3) a net-work of bile capillaries.]

Excessively minute intracellular passages are said to pass from the bile
capillaries into the interior of the liver-cells, where they communicate with certain
small cavities or vacuoles (Asp, Kupffer, Pfliiger)— (Fig. 144, 3). As the blood
capillaries run along the edges of the liver-cells, and the bile capillaries between
the opposed surfaces of adjacent cells, the two systems of canals within the

STRUCTURE OF THE LIVER. 349

lobule are kept separate. Some bile capillaries run along the edges of the
liver-cells in the human liver, especially during embryonic life (Zuckerkandl,
Toldt).

Towards the peripheral part of the lobule, the bile capillaries are larger, while
adjoining channels anastomose, and leave the lobule, when they become interlobular
ducts (#), 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 (Asp), possess a structureless 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, mixed with circularly
disposed smooth muscular fibres. 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 longi- 123
ttidinal and circular layers in the gall-bladder, 'Fjo-. 144.

whose mucous membrane is provided with numer- j; Liver-cell during fastin^;
ous folds and depressions. The epithelium lining o containing masses of gly-
the gall-bladder is cylindrical, with a distinct clear cogen ; 3, a liver-cell sur-
disc, and between these cells are goblet cells. Small rounded with bile-channels
branched tubular mucous glands occur in the large from which fine twio-s pro-
bile ducts and in the gall-bladder. ceed into the cell-substance
Vasa A berrantia are isolated bile ducts which where they end in vacuole-
occur on the surface of the liver, but have no rela- \{^e enlargements. From
tion to any system of liver lobules. They occur a rabbit's° liver injected
at the sharp margin of the liver, in the region of the with Berlin blue from the
inferior vena cava, of the gall-bladder, and of the bjie duct,
parts near the portal fissure. It seems that the

liver lobules to which they originally belonged have atrophied and disappeared
(Zuckerkandl and Toldt).

5. The Lymphatics begin as pericapfflary tubes around the capillaries within the
lobules (MacGillavry). They emerge from the lobule, and run within the walls of
the branches of the hepatic and portal veins, and afterwards surround the venous
trunks (Fleischl, A. Budge), thus forming the interlobular lymphatics. These
unite to form larger trunks, which leave the liver partly at the portal fissure,
partly along with the hepatic veins, and partly at different points on the surface
of the organ. There is a narrow superficial mesh-work of lymphatics under the
peritoneum — sub-peritoneal — which communicates with the thoracic lymphatics
through the triangular ligament and suspensorium, while on the under surface, they
communicate with the lymphatics of the interlobular connective tissue.

o'. 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 vase-motor in function, and,
according to Pfliiger, other nerve-fibres terminate directly in connection with
liver-cells, although this observation has still to be confirmed.

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 (Liver Cirrhosis). In such interlobular con-
nective tissue, newly-formed bile ducts are found (Cornil, Charcot, and others).

Liyature of the ductus cholcdochus, after a time, causes interstitial inflammation
of the liver. In rabbits and guinea-pigs, the liver parenchyma disappears, and its

350 CHEMICAL COMPOSITION OF THE LIVER-CELLS.

place is taken by newly-formed connective tissue and bile ducts (Charcot and
Gombault). In all these cases of interstitial inflammation, there is proliferation of
the epithelium of the bile ducts (Fok, Salvioli).

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 (Pl6sz). The
liver contains other albuminous bodies ; one coagulating at 45°C, another
at 70°C, and one which is slightly soluble in dilute acids and alkalies.
The cell nuclei contain nuclein (Plosz). The connective tissue yields
gelatin.

(2.) Glycogen or Animal Starch — 1-2-2-6 p.c. — is most closely
related to inulin, is soluble in water, but diffuses with difficulty, is a
true carbohydrate (Cl. Bernard and v. Hensen, 1857), and has the
formula G(C6 H10 05) + H00 (Kiilz and Borntrager). It is stored up
in the liver-cells (Bock and Hoffmann), in amorphous granules around
the nuclei, but it is not uniformly distributed in all parts of the liver
(v. Wittich). Like inulin, it gives a deep red colour with solution of
iodine in iodide of potassium. It is changed into dextrin and sugar
(p. 294) by diastatic ferments, and when boiled with dilute mineral
acids, it yields grape-sugar.

Preparation Of GlyCOgen. — Let a rabbit have a hearty meal, and kill it
three or four hours thereafter. The liver is removed immediately after death;
it is cut into fine pieces, plunged in boiliny water and boiled for some time
in order to obtain a watery extract of the liver-cells. [It is placed in boil-
ing water to destroy the ferment 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 as long as a precipitate occurs. The
albuminates or proteids are precipitated by the iodine compound in the presence of
free HC1. It is then filtered, 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 70-80 p.c. alcohol. The precipitate is
washed with 60 p.c. , and afterwards with 95 p.c. alcohol, then with ether, and
lastly, with absolute alcohol; it is dried over sulphuric acid and weighed (Brucke).

Conditions which influence its amount. — If large quantities of starch,
milk-, fruit-, or cane-sugar, or glycerine, but not mannite or glycol
(Luchsinger), or inosite (Kiilz), be added to the proteids of the food,
the amount of glycogen in the liver is very greatly increased (to 1 2
p.c. in the fowl), while a purely albuminous or purely fatty diet
diminishes it enormously. During hunger, it almost disappears (Pavy
and Tscherinoff). The injection of dissolved carbohydrates into a

CHEMICAL COMPOSITION OF THE LIVER-CELLS. 351

mesenteric vein of a starving rabbit causes the liver, previously free from
glycogen, to contain glycogen (Nauuyn).

During life, under normal conditions, the glycogen in the liver is
either not transformed into grape-sugar (Pavy, Eltter, Euleuberg), or,
what is more probable, only a very small amount of it is so changed.
The normal amount of sugar in blood is O'5-l per 1000, although the
blood of the hepatic vein contains somewhat more. A considerable
amount is transformed into sugar only when there is a decided de-
rangement of the hepatic circulation, and in these circumstances, the
blood of the hepatic vein contains more sugar. The glycogen under-
goes 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 ferment which effects this change can be obtained from the
extract of the liver-cells by the same means as are applicable for obtain-
ing 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 derangement (Hitter, Schiff). A
similar ferment is formed when red blood-corpuscles are dissolved
(Tiegel), and, as there is a destruction of red blood-corpuscles taking
place continually within the liver, this is one source from which the
ferment may be formed, whereby minute quantities of sugar would be
continually formed in the liver.

If glycogeu is injected into the blood, achroodextrin appears in the urine, and
also haemoglobin, as glycogen dissolves red blood-corpuscles (Bohm, Hoffmann).

Ligature of the bile duct causes decrease of the glycogen in the liver (v. Wittich);
it appears as if, after this operation, the liver loses the property of forming glycogen
from the materials supplied to it.

(3.) The following substances have also been found in the liver-cells: —
Fats in the form of highly refractive granules in the liver-cells, as well
as in the bile ducts; sometimes, when the food contains much fat (more
abundant in drunkards and the phthisical), olein, palmitin, stearin,
volatile fatty acids, and sarcolactic acid are found.

[Fatty granules are of common occurrence within the cells of the liver, and when
they do not occiir in too great amount, do not seem to interfere very greatly with
the functions of the liver-cells. These fatty granules are common in disease, con-
stituting fatty infiltration and degeneration, and in such cases the cells within a
lobule of the liver, next the portal vein, are usually most highly charged with the
fatty particles. Fatty particles occur if too much fatty food be taken, and they
are commonly found in the livers of stall-fed animals, and the well-known pdt£-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. ]

There are also found traces of cholesterin, minute quantities of urea, uric acid.

352 DIABETES MELLITUS.

[Leucin ( ? guanin), sarkin, xanthin, cystin, and tyrosin occur pathologically in
certain diseases where marked chemical decompositions occur.]

4. The inorganic substances found in the human liver are — potassium,
sodium, calcium, magnesium, iron, manganese, chlorine, and phosphoric,
sulphuric, carbonic, and silicic acids ; while copper, zinc, lead, mercury,
and arsenic, are accidentally deposited in the hepatic tissue.

175, Diabetes Mellitus, or Glycosuria.

The formation of large quantities of grape-sugar by the liver, and
its passage into the blood (p. 62), and from the blood into the urine,
are related to the above-mentioned normal conditions. Extirpation of
the liver in frogs (Moleschott), or destruction of the hepatic cells as
by fatty degeneration from poisoning Avith phosphorus or arsenic
(Salkowski) do not cause this condition. It occurs for several hours,
however, after the injury of a certain part — the centre for the hepatic
vaso-motor nerves — of the floor of the lower part of the fourth ventricle
(Cl. Bernard's piqure); also after section of the vaso-motor channels in
the spinal cord, from above down to 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 (Eckhard),
of the abdominal ganglia (Klebs, Munk), and often of the splanchnic
itself (Hensen, v. Graefe), produces diabetes. The paralysis of the
blood-vessels causes the liver to contain much blood, and the intra-
hepatic blood-stream is slowed. This 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, Aladoff). 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 hyperaemia, of the abdominal blood-vessels
thereby produced, renders the liver anaemic.

A number of poisons which paralyse the hepatic vaso-motor nerves produce
diabetes in a similar way — curara (when artificial respiration is not maintained),
chloroform, ether, chloral, amyl nitrite, carbon disulphide, morphia, mercuric

SOURCES OF GLYCOGEN. 353

chloride, and (?) CO. But congestion of the liver produced in other ways appears
to cause diabetes— e.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.
[Injection of a solution of a neutral salt into a ligatured loop of the small intestine
sometimes causes mellituria (M. Hay).]

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, Eckhard, Kiilz, Lobeck), and also after stimulation of the
central end of the depressor nerve (Filehne). Even section and subse-
quent stimulation of the central end of the sciatic nerve causes diabetes
(Schiff, Kiilz, Bohm and Hoffmann, Froning), and thus is explained
the occurrence of diabetes in people who suffer from sciatica.

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 exent 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 pro-
duced 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.

Theoretical. — In order to explain the more immediate cause of these pheno-
mena 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 (see above). 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.

(b.) If we assume that under normal conditions, 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 those 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
(v. Pettenkofer and Voit), and to have an increased formation of urea.

Sources of Glycogen.— The "mother-substance" of the glycogen of
the liver has been variously stated to be the carbo-hydrates of the food
(Pavy), fats (olive oil, Salomon), glycerine (van Been, Weiss), taurin
and glycin (the latter splitting into glycogen and urea — Heynsius and
Kiithe), the proteids (Cl. Bernard), and gelatin (Salomon). If it is
derived from the albumins, it must be formed from a non-nitrogenous
derivative thereof.

Effects of Food. — Eabbits 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, and exposure to cold diminishes its amount. Dextrin and

23

354 OCCURRENCE OF GLYCOGEN.

grape-sugar occur in the dead liver (Limpricht, Kiilz), but in addition,
some glycogen is found for a considerable time after death, in the liver
and in the muscles.

Other Situations. — Glycogen is by no means confined to the liver-cells; it
occurs during foetal life in all the tissues of the body of the embryo, also in young
animals (Kiihne), and in the placenta (Bernard). In the adult it occurs in the
testicle (Kiihue), in the muscles (MacDonnel, 0. Nasse), in numerous pathological
products, in inflamed lungs (Kiihne), and also in the corresponding tissues of the
lower animals. [It also occurs in the chorionic villi (Cl. Bernard), in colourless
blood-corpuscles, in fresh pus cells which still exhibit amoeboid movements, and in
fact in all developing animal cells, with amoeboid movement; it is a never-failing
constituent in cartilage, and in the muscles and liver of invertebrata, such as
the oyster (Hoppe-Seyler).]

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 severe cases towards death, not unfrequently a peculiar
comatose condition — diabetic coma — occurs, when the breath often has
the odour of acetone, which is also found in the urine (Fetters). But
neither acetone nor its precursor, aceto-acetic acid, nor rethyl-diacetic
acid, nor the unknown substance, in diabetic urine, which gives the
red colour with ferric chloride, is the cause of the coma (Frerichs and
Brieger). The urinary tubules often show the signs of coagulation-
necrosis, which is recognised by a clear swollen-up condition of the
dead cells (Ebstein). As yet there is no satisfactory explanation of
those rarer cases of " acetomemia" without diabetes (Kanlecti, Cantini,
v. Jacksch).

176. The Functions of the Liver.

[We have still much to learn regarding the functions of the liver, but
it has two distinct functions — one obvious, the other not. (1) The
liver secretes lile, which is formed by the hepatic cells, and leaves the
organ by the bile-ducts, to be poured by them into the duodenum.
(2) But 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 relation of the liver to the blood-corpuscles has already
been mentioned (pp. 13-17).]

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

CONSTITUENTS OF THE BILE. 355

neutral reaction. The specific gravity of human bile from the gall-
bladder = 1026-1032, while that from a fistula = 1010-101 1 (Jacobsen).
It contains: —

(1.) Mucus, which gives bile its sticky character, and not unfre-
quently makes it alkaline, 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. [Bile from the gall-bladder,
when poured from one vessel into another, shows the presence of mucin
in the form of thin threads connecting the fluids in the two vessels.
When such bile is treated with alcohol, it no longer exhibits this
property, but flows like a non-viscid watery fluid. The bile formed in
the ultimate bile-ducts does not seem to contain muciu or mucus, but
bile from the gall-bladder always does.]

(2.) The Bile Acids. — Glycocholic and taurocholic acids, so-called
conjugate acids, are united Avith soda (in traces with potash) to form
glycocholate and taurocholate of soda, which have a bitter taste. In
human bile (as well as in that of birds, many mammals, and amphibians),
taurocholic acid is most abundant; in other animals (pig, ox) glyco-
cholic acid is most abundant. These acicls rotate the plane of polarised
light to the right.

((/.) Glycocholic acid, C26H43N06 (first discovered and described as
cholic acid by Gmelin, and called, by Lehmann, glycocholic acid).
When boiled with caustic potash, or baryta Avater, or Avith dilute
mineral acids, it takes up H20 (Strecker, 1848), and splits into —

Glycin ( = Glycocoll = Gelatin Sugar = Amidoacetic acid) =C2H5N02.
+ Cholalic acid (also called Cholic acid) . . . =C24H4005.

= Glycocholic acid + Water . . =C2CH43NOG + H20.

(b.) Taurocholic acid, CoGH45]S[S07, Avhen similarly treated, takes
up Avater and splits into—

Taurin (= Amidonethyl-sulphuric acid) = C2
+ Cholalic acid .... =C

= Taurocholic acid + Water . . =C26H45NS07 + H20 (Strecker).

Preparation Of the Bile acids.— Bile is evaporated to ^ of its volume, rubbed
up into a paste with excess of animal charcoal, and dried at 100°C. The black
mass is extracted with absolute alcohol, which is filtered until it is clear. After a
part of the alcohol has been removed by distillation, the bile salts are precipitated
in a resinous form, and on the addition of excess of ether, there is formed immedi-
ately a crystalline mass of glancing needles (Platner's "crystallised 6-ife"). The
alkaline salts of the bile acids are freely soluble in water or alcohol, and insoluble in
ether. Neutral 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 H2S ; 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

3 5 6 THE BILE ACIDS.

basic lead acetate, a precipitate of lead taurocholate is formed, from which the
aoid may be obtained in the same way as described above (Strecker).

When human bile is similarly treated, instead of the "crystallised bile," a
resinous non-crystalline precipitate is obtained. Boiling with baryta water isolates
the cholalic acid from it, which is obtained from its barium salt by adding hydro-
chloric acid. When dissolved in ether, it occurs in the form of prismatic crystals
if petroleum-ether is added. The anthropocliolic and (CisH2804 — H. Bayer), so
obtained is not soluble in water, but readily so in alcohol, and rotates the ray of
polarised light to the left.

With regard to the decomposition products of the bile acids, glydn,
as such, does not occur in the body, but only in the bile in combination
with cholalic 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 (perhaps it is to be regarded as
benzoic acid, in which a complex of atoms similar to oleic acid is intro-
duced— Hoppe-Seyler). It occurs free only in the intestine, where it is
derived from the splitting up of taurocholic acid, and it passes in part
into the faeces. 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.

Cholalic acid is replaced in the bile of many animals by a nearly related acid,
e./j., in pig's bile, by hyo-cholalic acid (Strecker, Guudlach); in the bile of the
goose, cheno-cholalic acid is present (Marsson, Otto).

When cholalic acid is boiled with concentrated HC1, or dried at
200°C, it becomes an anhydride, thus:—

Cholalic acid . = C2.tH4005, produces

Choloidinic acid = C^H^C^-l-HoO, and this again yields

Dyslysin . . = C^HgcOg-HoO.

(Choloidiuic acid is, however, not improbably a mixture of cholalic acid and
dyslysin ; dyslysin, when fused with caustic potash, is changed into cholalate
of potash— Hoppe-Seyler). If anthropocholic acid be heated to 185°C, it gives up
1 molecule of water, and yields anthropochol-dyslysin (Bayer).

By oxidation cholalic acid yields a tribasic acid, as yet uninvestigated, and a
fair amount of oxalic acid, but no fatty acids (Cleve).

Pettenkofer's Test. — The bile acids, cholalic acids, and their anhy-
drides, when dissolved in water, yield on the addition of f concentrated
sulphuric acid (added in drops so as not to heat the fluid above 70°C),
and several drops of a 10 p.c. solution of cane-sugar, a reddish purple
transparent fluid, which shows two absorption-bands at E & F (Schenk).

[A very good method is to mix a few drops of the cane-sugar solu-
tion 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.]

According to Drechsel, it is better to add phosphoric acid, instead of sulphuric

THE F.ILE PIGMENTS. .°>:>7

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 beforehand, 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.

The origin of the bile acids takes place within the liver. After its
extirpation, there is no accumulation of biliary matters in the blood
(Joh. Miiller, Kunde, Moleschott).

How the formation of the nitrogenous bile acids is effected 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 the sulphur of albumin ; bile salts contains 4-4'6 p.c. of sulphur
(Voit), which may perhaps be derived from the stroma of the 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
(Stadler). When it remains for a considerable time in the gall-bladder,
or when alkaline bile is exposed to the air, the bilirubin absorbs 0 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.

(«.) Bilirubin (C3.,H36]Sr406) is, according to Stadler and Maly,
perhaps united with an alkali ; it crystallises in transparent fox-red
clinorhombic prisms. It is insoluble in water, soluble in chloroform, by
which substance it may be separated from biliverdin, which is in-
soluble in chloroform. It unites as a monobasic acid with alkalies, and
as such is soluble. It is identical with Virchow's hsematoidin
(p. 35).

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 haemoglobin is very probable, considering its
identity with hsematoidin. Very probably red blood-corpuscles are dissolved in
the liver, and their haemoglobin changed into bilirubin.

(b.) Biliverdin (Heintz), C32H36N408, is simply an oxidised derivative
of the former, from 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 considerable
amount in the placenta of the bitch. As yet it has not been retrans-
formed by reducing agents into bilirubin.

Tests for Bile Pigments. — Bilirubin and biliverdin may occur in
other fluids — e.g., the urine, and are detected by the Gmelin-Heintz'
reaction. When nitric acid containing some nitrous acid is added to the
licjuid containing these pigments, a play of colours is obtained, begin-
ning with green (biliverdin), blue, violet, red, ending with yellow.

358

C'HOLESTERIN.

[This reaction 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, bili-
Cyanin (Heynsius, Campbell), in acid solution blue, (in alkaline violet) is obtained,
which shows two ill-defined absorption-bands near D (Jaffe). Capranica advises
that the acid fluids be shaken with a mixture of chloroform and alcohol (1 : 1).
This mixture absorbs the pigment ; pour off the fluid and add bromine in alcohol
(^ p.c.), and the play of colour is obtained.

(d.) Bilifuscin occurs in small amount in decomposing bile and in gall-stones
= bilirubin + H2O.

(e.) Biliprasin (Stadler) also occurs = bilirubin + H2O + 0.
(/.) The yellow pigment, which results from the prolonged action
of the oxidising reagent, is the choletelin (C16H18N206) of Maly ; it is
amorphous, and soluble in water, alcohol, acids, and alkalies.

(g.} Hydro-bilirubin. — Bilirubin absorbs H + H20 (by putrefaction,
or by the treatment of alkaline watery solutions with the powerfully
reducing sodium amalgam), and becomes converted into Maly's hydro-
bilirubin (C32H14N407), 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 b, F. This substance, which, accord-
ing to Hammarsten, occurs in normal bile, is a constant colouring-
matter of faeces, and was called stercobilin by Vaulair and Masius, but
is identical with hydro-bilirubin (Maly). It is, however, probably
identical with the urinary pigment urobilin of Jaff6 (Stokvis, p. 35).
(4.) Cholesterin, C20H440 (H20) is an alcohol which rotates the

ray of polarised light to the
left, and whose constitution is
unknown; it occurs also in
blood, yelk, nervous matter, and
[gall-stones]. It forms trans-
parent rhombic plates, which
usually have a small oblong
piece cut out of one corner
(Fig. 145, a). It is insoluble in
water, soluble in hot alcohol, in
ether, and 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 con-
sist almost entirely of cholesterin, by
extracting them with hot alcohol after
they are pulverised. Crystals are
excreted after evaporation of the
alcohol, and they give a red colour

Crystals
laminated ;

Fig. 145.

of Cholesterin — a, regularly
b, irregularly laminated,

partially injured forms ; x 300 (Aitkeu
after Wedl).

THE SECRETION OF BILE. 359

with sulphuric acid (5 vol. to 1 vol. H20 — Moleschott), while they give a blue —
as cellulose does — with sulphuric acid and iodine. When dissolved in chloro-
form, 1 drop of concentrated sulphuric acid causes a deep red colour (H. Schiff).

(5.) Amongst the other organic constituents of bile are: — Lecithin
(p. 36), or its decomposition product, neurin (cholin), and glycero-
phosphoric acid (into which lecithin may be artificially transformed by
boiling with baryta); Pahnitin, Stearin,. Olein, as well as their soda
soaps ; Diastatic Ferment (Jacobson, v. Wittich) ; traces of Urea
(Picard) ; (in ox bile, acetic acid and propionic acid, united with
glycerine and metals, Dogiel).

[The proportion of diastatic ferment is not greater than in the tissues of the
body generally (M. Hay).]

(6.) Inorganic constituents of bile (0-6 to 1 p.c.): —

They are — sodium chloride, potassium, 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 (Kunkel); manganese and
silica. Freshly secreted bile contains in the dog more than 50 vol., and in the
rabbit 109 vol. per cent. C02 (Pfliiger, Boguljubow, Charles), partly united to
alkalies, partly absorbed, the latter, however, being almost completely absorbed
within the gall-bladder.

Thejnean composition of human bile is : —

Lecithin, . . 0-5 p.c.
Mucin, . . 1-3 „

Ash, 0-61

Water, . 82-90 p.c.

Bile Salts, 6-11 „

Fats and Soaps, . 2 „

Cholesterin, . . 0-4 „

Farther, unchanged fat probably always passes into the bile, but is
again absorbed therefrom (Virchow). The amount of S in dry dog's
bile = 2-8-3-1 p.c., the N = 7-10 p.c. (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.

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 (Heidenhain, Kayser). It is secreted
continually; it is partly 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 C02 in the bile (Pfliiger), indicate that
oxidations occur within the liver. The water of the bile is not merely

300 (CONDITIONS INFLUENCING THE SECRETION OF BILE.

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 24 hours (some bile passed into the
intestine); by Westphalen, at 453-566 grms.; [by Murchison, at 40
oz.]; Joh. Ranke, on a biliary-pulmonary fistula, at 652 cubic centi-
metres. The last observation gives 14 grms. (with 0'44 grms. solids)
per kilo, of man in 24 hours.

Analogous values for animals are — 1 kilo, clog, 32 grm. (1 '2 solids) — Kolliker,
H. Mu'ller; 1 kilo, rabbit, 137 grm. (2'5 solids)— Bidder and Schmidt; 1 kilo,
guinea-pig, 176 grms. (5'2 solids)— Bidder and Schmidt.

(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 simul-
taneous 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 correspond-
ing relative diminution of the solid constituents.

(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
(Heidenhain).

(ft.) Simultaneous ligature of the hepatic artery (diameter 5§ mm.) and the
portal vein (diameter 6 mm.) abolishes the secretion (Rohrig). 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 (Simon, Schiff, Schmulewitsch, Asp). According to Kotbmeier, Betz,
Cohnheim and Litten, 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 (Schmulewitsch and Asp). Complete ligature of the portal vein rapidly
causes death. [The blood-pressure falls rapidly and the blood accumulates in the
blood-vessels of the abdomen. In fact, the accumulation of the blood within the
abdomen takes place to so great an extent, that practically the animal is bled
into its own abdomen (p. 176).]

Neither the ligature of the hepatic artery by itself (Schiff, Betz), nor the
gradual obliteration of the portal vein by itself, causes the cessation of the
secretion, but it is diminished. That sudden ligature of the portal vein causes
cessation is explained by 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
organs makes the liver very anremic, 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).

BILIARY FISTUL.E. 361

(/. ) 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 muscles of the trunk — during vigorous exercise, diminishes the
secretion, while the transfusion of large quantities of blood increases it (Landois);
but if too high a pressure is caused in the portal vein, by introducing blood from
the carotid of another animal, it is diminished (Heidenhain).

({/•) The influence Of nerves. — All conditions which cause contraction of the
abdominal blood-vessels — e.g., stimulation of the ansa Vieussenii, of the inferior
cervical ganglion, of the hepatic nerves (Afanassiew) 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 stagnation or
congestion of the blood in the hepatic vessels (section of the splanchnic nerves,
diabetic puncture, § 175), section of the cervical spinal cord (Heidenhain). Par-
alysis (ligature) of the hepatic nerves causes at first an increase of the biliary
secretion (Afanassieff).

(/i.) 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 (Drosdoff), and blood-corpuscles, but Jess albumin, fibrin, hemoglobin,
fat, water, and salts.

(6.) The formation of bile is largely dependent upon the decomposi-
tion of coloured 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 Fistulas. — The mechanism of the biliary secretion is studied in animals
by means of biliary fistula?. 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 of the wound in the abdomen, and afterwards
introduced a cannula into the wound. As a rule all the bile is discharged externally ;
but to be quite certain that this is so, the common bile-duct ought to be tied between
two ligatures, and divided. After a 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. Regeneration of the divided bile-duct may occur in dogs.
v. Wittich observed a biliary fistula in man. [A temporary biliary fistula may also
be made. The abdomen is opened in the same way as described above. A long
bent glass cannula is introduced and tied into the common bile-duct, and the cystic
duct is ligatured or clamped. The tube is brought out through the wound in the
abdomen. Necessarily all the bile must be discharged by the tube].

179. Excretion of Bile.

[In connection with the excretion of bile, we must keep in view two
distinct mechanisms. (1) The bile-secreting mechanism dependent upon
the 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 (p. 360).]

362 EXCRETION OF BILE.

This occurs — (1.) Owing to the continual pressure of the newly-
formed bile within the interlobular bile-ducts forcing onward the bile
in the excretory ducts.

(2.) Owing to the interrupted periodic compression of the liver from
above, by the diaphragm, at every inspiration. Farther, every inspira-
tion assists the flow of blood in the hepatic veins, and every respiratory
increase of pressure within the abdomen favours the current in the
portal veiu.

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.) Owing to 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 (Heiden-
hain, J. Munk). 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 (Pfliiger), and reflex stimulation
of the spinal cord (Eohrig), diminish the excretion ; while extirpation
of the hepatic plexus (Pfliiger), and injury to the floor of the fourth
ventricle (Heidenhain) do not exert any disturbing influence.

(5.) A relatively small amount of resistance causes bile to stagnate
in the bile-ducts.

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
(Heidenhain, Friedlander, Barisch). 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.

180. Reabsorption of Bile.

Phenomena of Jaundice (Icterus; Cholsemia).

Absorption Jaundice. — When an impediment or resistance is offered to the
outflow of bile into the intestine — e.fj., 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 — Afanassiew)— reabsorption of bile from
the distended larger bile-ducts takes place into the lymphatics (not the blood-

PHENOMENA OF JAUNDICE. 3 60

vessels) cf the liver (Saunders, 1795); the bile acids pass into the lymphatics of the
liver. [The lymphatics can be seen at the portal fissure filled with a deep yellow-
coloured lymph]. The lymph passes into the thoracic duct, and so into the blood
(Fleischl, Kunkel, Kufferath). 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 neonatornm, as after ligature of the
umbilical cord, no more blood passes through the umbilical vein; farther, in the
icterus of hunger, as the portal vein is relatively empty, owing to the feeble absorp-
tion from the intestinal canal (Cl. Bernard, "\7oit, Naimyn).

II. Cholremia may also occur, owing to the excessive production of bile (hyper -
cholia), 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 yields 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 (Afanassiew). The transfusion of heterogeneous
blood by dissolving coloured blood-corpuscles acts in this direction (p. 201).
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 (Landois), by the injection of bile acids into the vessels (Frerichs),
and by other salts, by phosphoric acid, water (Herrmann), chloral, inhalation of
chloroform, and ether (Nothnagel, Bernstein); the injection of dissolved hsemo-
globin into the arteries (Kiihne), or into a loop of small intestine, acts in the same
way (Naunyn).

Icterus Neonatomm. — When, owing to compression of the placenta within
the uterus, too much blood is forced into the blood-vessels of the newly-born
infant, a part of the surplus blood during the first few days becomes dissolved,
whereby the haemoglobin passes into bilirubin, thus causing jaundice (Virchow,
Violet).

When the jaundice is caused by the absortion of bile already formed
in the liver, it is called hepatogenic or absorption-jaundice. The
following are the symptoms :—

Phenomena. — (1.) Bile pigments and bile acids pass into the tissues of the
body ; hence, the most pronounced external symptom is the yellowish tint or
jaundice. The skin and the sclerotic become deeply coloured yellow. In preg-
nancy the foetus is also tinged.

(2. ) Bile pigments and bile acids pass into the urine (not into the saliva, tears, or
mucus), and their presence is ascertained by the usual tests (§ 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 ( = haematoidin) crystals occur in the iirine.

(3.) The faeces are ilday coloured " (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 more than
60 p.c. of the fat taken with the food reappears in the faeces (v. Voit) ; they have
a very disagreeable odour, because bile normally greatly limits the putrefaction in
the intestine. The evacuation of the fa>ces occurs slowly, partly owing to the hard-
ness of the faeces, 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, e.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. The injection of bile salts into the heart, produces at first a tem-
porary acceleration of the pulse (Landois), and afterwards slowing (Rb'hrig). The

364 KKKKCTS OF DRUGS ON THE SECRETION OF BILE.

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 (Traube). 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 (Flint, K. Miiller),
is shown by the very general relaxation, sensation of fatigue, weakness and
drowsiness, lastly deep coma — sometimes there is sleeplessness, itchiness of the
skin, even mania, and spasms. Lciwit, after injecting bile into animals, observed
phenomena referable to stimulation of the respiratory, cardio-inhibitory, and vaso-
motor nerve-centres.

(6.) In very pronounced jaundice, there may be " yellow vision'" (Lucretius
Carus), owing to impregnation of the retiua and macula lutca with the bile pig-
ment.

(7.) The bile acids in the blood dissolve the red blood-corpuscles. The haemo-
globin is changed into new bile pigment, and the globulin-like body of the
haemoglobin may form urinary cylinders or casts in the urinary tubules
(Nothnagel), which are ultimately washed out of the tubules by the urine.

Passage Of substances into the Bile. — Various substances pass into the
bile, such substances being in the blood, viz., the metals (v. Sartoris, Mohnheim,
Orfila)— copper, lead, zinc, nickel, silver, bismuth (Wichert), arsenic, antimony,
iron ; these substances are also deposited in the hepatic tissues. Potassium iodide,
bromide, and sulphocyanide (Peiper), and turpentine also pass into the bile, and, to
a less degree, cane-sugar and grape-sugar (Mosler) ; sodium salicylate, and carbolic
acid (Peiper). If a large amount of water be injected into the blood, the bile
becomes albuminous (Mosler); mercuric and mercurous chlorides cause an increase
of the water of the bile (G. Scott). 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.

[Influence of Drugs on the Secretion of Bile.— Two methods are adopted,

one by means of permanent fistula?, and the other by establishing temporary
h'stulae. 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, as described at p. 361, the animal is curarised, artificial
respiration being kept up, while the drug is injected into the stomach or intestine.
Rohrig iised this method, which was improved by Rutherford and Vignal. Rb'hrig
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,
colchiciim, euonymin, iridin, sanguinarin, ipecacuan, colocynth, sodium phosphate,
phytolaccin, sodium benzoate, sodium salicylate, dilute nitrohydrochloric acid,
ammonium phosphate, mercuric chloride (corrosive sublimate), are all powerful, or
very considerable, hepatic stimulants. They found that some substances stimulate
the intestinal glands, but not the liver, e.g., magnesium sulphate, castor oil,
gamboge, ammonium chloride, manganese sulphate, calomel. Other substances
stimulate the liver as well as the intestinal glands, although not to the same extent,
e.g., scammony (powerful intestinal, feeble hepatic stimulant) ; colocynth excites
both powerfully; jalap, sodium sulphate, baptisin, act with considerable power
both on the liver and the intestinal glands. Calabar 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 purely intestinal stimulants, such as

FUNCTIONS OF THE BILfi. 3Go

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 by covering it with cotton wool, else the secretion of bile diminishes.

As yet, we cannot say definitely whether these substances stimulate the secretion
of bile, by exciting the mucous membrane of the duodenum or other part 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 pro-
bably, 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. ]

CholesteraBHlia. — Flint 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 ingredient of nervous-tissue, is excreted by the bile ; and if it be
retained in the blood, "cholesteramia," 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 of it is absorbed;

(3) part is excreted.]

(A.) Bile plays an important part in the absorption of fats :—

(1.) It emulsionises neutral fats (§ 170, III.), whereby the fatty granules
pass more readily through or between the cylindrical epithelium of
the small intestine into the lacteals. It does not decompose neutral
fats into glycerine and a fatty acid, as the pancreas does.

When, however, fatty acids are dissolved in the bile (Lenz) the bile salts are
decomposed, the bile acids being set free, while the soda of the decomposed bile salts
readily forms a soluble soap with the fatty acids. These soaps are soluble in the
bile, and increase considerably the emulsifying power of this fluid. Bile can
dissolve directly fatty acids to form an acid fluid, which has high emulsion ising
properties (Steiner).

(2.) As fluid fat flows more rapidly through capillary tubes when they
are moistened with bile, it is concluded that when the pores of the
absorbing 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 (v.
Wistinghausen).

It is clear, therefore, that the bile is of great importance in the preparation and
iu the absorption of fats. This is forcibly illustrated by experiments on animals,
in which the bile is entirely discharged externally through a fistula. Dogs, under
these conditions, absorbed at most 40 p.c. of the fat taken with the food (v. Voit).

30 G FUNCTIONS OF THE BILE.

The chyle of such animals is very poor in fat, is not white but transparent; the
faeces, however, contain much fat, and are oily. Such animals are voracious
(Nasse); 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.

(B.) Fresh bile contains a diastatic ferment which transforms starch
into sugar (Nasse, Jacobson, v. Wittich), and also glycogen into sugar
(Bufaliui).

(C.) Bile excites contractions of the muscular coats of the intestine, and
contributes thereby to absorption.

(1.) The bile acids act as a stimulus to the muscles of the v'tlli, which contract
from time to time, so that the contents of the lymph-spaces [origins of the
lacteals] are emptied towards the larger lymphatics, and the villi are thus in a
position to absorb more (Schiff). [The villi act like numerous small pumps, and
expel their contents, which are prevented from returning by the presence of valves
iu the larger lymphatics.]

(2.) The musculature of the intestine itself seems to be excited, perhaps through
the agency of the plexus myeutericus. 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 diarrhoea and
vomiting (Leyden, Schiileiu). As contraction of the intestine aids absorption,
bile is also necessary in this way for the absorption of the dissolved food stuffs.

(D.) The bile moistens the walls of the intestine, as it is copiously
excreted. It gives to the faeces 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 of the
bile aids the forward movement of the ingesta through the intestinal
canal. [Thus, in a certain sense, bile is a natural purgative]

(E.) The bile diminishes putrefactive decomposition of the intestinal
contents (Valentin). [Thus, it is an antiseptic.]

*

(F.) 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 as yet not peptonised, is also precipitated,
but it does not seem that peptone or propeptone are precipitated by the
mixture of the bile acids (Maly and Emich). The bile salts are decom-
posed by the acid of the gastric juice. When the mixture is rendered
alkaline by the pancreatic juice and the alkali derived from the decom-
position of the bile salts, the pancreatic juice acts energetically in this
alkaline medium (Moleschott).

When bile passes into the stomach, as in vomiting, the acid of the gastric juice
unites with the bases of the bile salts; so that sodium chloride and free bile acids
are formed, and the acid reaction is thereby somewhat diminished. The bile

FATE OF THE BILE IN THE INTESTINE. 3G7

acids are not effective for carrying on gastric digestion; the peptone is precipitated
by them; neutralisation also causes a precipitate of pepsin and mucin. As
soon, however, as the walls of the stomach secrete new acid, the pepsin is redis-
solvecl. The bile which passes into the stomach deranges gastric digestion, by
shrivelling the proteids, which can only be peptonised when they are swollen up.

182. Fate of the Bile in the Intestine.

Some of the biliary constituents are completely evacuated with the
faeces, while others are reabsorbed by the intestinal walls.

(1.) Mucin passes unchanged into the faeces.

(2.) The bile pigments are reduced, and are partly excreted with the
faeces as hydroUliruUn (§ 1 77, 3 0), and partly as the identical end-product
urolilin by the urine.

Hydrobilirubin is absent from MeCOnium, while bilirubin and biliverclin and
an unknown red oxidation product of it are present (Zweifel). Hence, no reduc-
tion —but rather oxidation — processes occur in the fcetal intestine (Hoppe-Seyler).

(3.) Cholesterin is given off with the faeces.

(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 quan-
tities pass from the blood into the urine. Only a very small amount
of glycocholic acid appears unchanged in the faeces. The taurocholic
acid, as far as it is not absorbed, is easily decomposed in the intestine,
by the putrefactive processes, into cholalic acid and taurin ; the former
of these is found in the faeces, but the taurin at least seems not to lie
constantly present.

As putrefactive decomposition does not occur in the fcetal intestine, unchanged
taurocholic acid i.s found in meconium (Zweifel). The anhydride stage of cholalic
acid (the artificially prepared choloidinic acid ?), dyslysin, is an artificial product,
and does not occur in the ffeces (Hoppe-Seyler).

(5.) The faeces contain mere traces of Lecithin (Wegscheider, Bokay).

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, carbo-
hydrates most beneficially replace the fats. If the digestive apparatus is other-
wise intact, the animals, on account of their voracity, may even increase in weight,
but the flesh and not the fat is increased.

The fact that bile is secreted during the foetal 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 C02 and H20. The glycin (with

368 THE INTESTINAL JUICE.

hippuric acid) forms urea, as the urea is increased after the injection of glycin
(Horsford, Schultzen, Nencki). The fate of taurin is unknown. When large
quantities are introduced into the human stomach, it reappears in the urine, as
tauro-carbonic acid, along with a small quantity of unchanged taurin. When
injected subcutaneously into a rabbit, nearly all of it reappears in the urine.

183. The Intestinal Juice,

The human intestine is ten times longer than the length of the body, as
measured from the vertex to the anus. It is longer comparatively than that of
the omnivora (Henning). Its minimum length is 507, its maximum 1,149 centi-
metres; its capacity is relatively greater in children (Beneke). In childhood the
absorptive elements, in adults the secreto-chemical processes, appear to be most
active (Baginsky).

The succus entericus is the digestive fluid secreted by the numerous
glands of the intestinal mucous membrane. The largest amount is
produced by Lieberklihn's glands, while in the duodenum, there is
added the scanty secretion of the small compound tubular Brunner's
glands.

Brunner's glands are small convoluted, branched, tubular glands, lying in
the sub-mucosa of the duodeuum. Their fine ducts run inwards, pierce the
mucous membrane, and open at the bases of the villi, The acini are lined by
cylindrical cells, like those lining the pyloric glands. In fact, Brunner's glands
are structurally and anatomically identical with the pyloric glands 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).

I. 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 albuminous
substances, consist of mucin and a ferment-substance of unknown consti-
tution. The watery extract of the glands causes: — (1) Solution of
proteids at the temperature of the body (Krolow). (2) It also has a
diastatic (?) action. It does not appear to act upon fats. [Brown and
Heron have shown that the secretion of Brunner's glands, more actively
than any other glands of the intestines, converts maltose into glucose.]

On account of the smallness of the objects, such experiments are only made
with great difficulty, and, therefore, there is a certain amount of uncertainty with
regard to the action of the secretion.

Lieberkullll 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; 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. 146). 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 Heidenhain).

CHARACTERS OF THE INTESTINAL JUICE.

369

II. The Secretion of Lieberkuhn's glands is, from the duodenum
onwards, the chief constituent of the intestinal juice.

Intestinal Fistula.— The intestinal juice is obtained by making a Thiry'a
fistula (1864). A loop of the intestine of a
dog is pulled forward, and a piece about
four 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. One end of this tube is closed, and
the other end is left open and stitched to the
abdominal wall. After the two ends of the
intestine, from which this piece was taken, have
been carefully brought together with sutures,
so as to establish the continuity of the intestinal
canal, animals still continue to live. The excised
piece of intestine yields a secretion which
is uncontaminated with any other digestive
secretion.

[Thiry's method is very unsatisfactory, as
judged from the action of the separated loop in
relation to medicaments, probably owing to
its mucous membrane becoming atrophied
from disuse, or injured by inflammation.
Meade Smith has lately used a better method,
in which he makes a small opening in the
intestine, through which he introduces two
small hollow and 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 gastric cannula (p. 330) inserted into
the fistula in the loop, the secretion can be
removed when desired.]

Fig. 146.

Lieberkuhn's Gland, from the
large intestine of a dog.

The intestinal juice of such fistulre 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 iZJ
centimetres yields 13 to 18 grammes of this juice in an hour (Thiry,
Masloff).

Characters. — The juice is light yellow, opalescent, thin, strongly
alkaline, specific gravity 1011, evolves C02 Avhen an acid is added;
it contains albumin and ferments ; mucin occurs in the juice of the
large intestine. Its composition is — proteids = 0'SO p.c.; other organic
substances = 07 3 p.c.; salts, 0'8S p.c.; amongst these — sodium car-
bonate, 0-32-0-34 p.c.; water, 97'59 p.c.

24

•"'70 ACTIONS OF THE INTESTINAL JUICE.

[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. — The digestive functions of the fluid of
the small intestine are:—

(1.) It has less diastatic action than either the saliva or the
pancreatic juice (Schiff, Buscli, Quincke, Garland), but it does not form
maltose; while the juice of the large intestine is said to possess this
property (Eichhorst). V. Wittich extracted the ferment with a
mixture of glycerine and water.

[The diastatic action of the small intestine is incomparably weaker than that of
the saliva, or pancreatic juice, and barely exceeds that of the tissues and fluids of
the bodies generally. A similarly weak diastatic action is possessed by the
secretion of the colon.]

(±) 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. Thus maltose seems to be
transformed into grape-sugar by the intestinal juice.

(3.) Fibrin is slowly (by the trypsin and pepsin — Kiihne) peptonised
(Thiry, Leube); less easily albumin (Masloff), fresh casein, flesh raw or
cooked, vegetable albumin (Kolliker, Schiff); probably gelatin also is
changed by a special ferment into a solution which does not gelatinise
(Eichhorst).

[The ferment for this purpose is mainly contained in Brunner's glands, and in
Peyer's patches (Brown and Heron).]

(4.) Fats are only partly emulsionised (SchifF), and afterwards
decomposed (Vella).

[M. Hay has never observed any emulsifying action. The apparent emulsification
in certain instances is due to shaking the alkaline juice with a rancid oil, containing
free fatty acids, when a certain quantity of a soap is at once formed.]

(f>.) According to Cl. Bernard, invertin occurs in intestinal juice (this
ferment can also be extracted from yeast), whereby cane-sugar
(C12H22On) takes up water ( + H20) and becomes converted into invert
sugar, which is a mixture of left rotating sugar (laevulose, CGH1200)
and of grape-sugar (dextrose, CGH120G). Heat seems to be absorbed
during the process (Leube). (See Carbohydrates for the various kinds
of sugar).

[Hoppe-Seyler lias suggested that this ferment is not a natural product of the
body, but is introduced from without with the food. Matthew Hay has recently
disproved this theory by, amongst other reasons, finding it to be invariably present
in the intestine of the fretus. It is found in every portion of the small intestine,
but not in the large intestine, nor in any other part of the body, and is much less
diffusible than diastase.]

FERMENTATION PROCESSES IN THE INTESTINE. 371

Fate Of the Ferments. — With regard to the digestive ferments, Langley is
of opinion that they are destroyed in the intestinal canal ; the diastatic ferment
of saliva is destroyed by the HC1 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
iuliuence of the acid fermentation in the large intestine.

The action Of the NerVOUS System 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 sympathetic abdominal ganglia causes the intestinal
canal to be filled with a watery fluid, and gives rise to diarrhoea (Budge). This
may be explained by the paralysis of the vaso-motor nerves, and also by the
section of large lymphatic vessels during the operation, whereby absorption is
interfered with and transudation is favoured.

Moreau's Experiment. — A .similar result is caused by extirpation of the nerves
which accompany the blood-vessels going to a loop of intestine (Moreau). [Moreau
placed four ligatures on a loop of intestine at equal distances from each other.
The ligatures were tied so that three loops of intestine were shut off. The nerves
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 — i.e., in those with the nerves
and blood-vessels intact — but the compartment whose nerves had been divided
contained a watery secretion.]

The secretion of the intestinal and gastric juices is diminished in man in certain
nervous affections (hysteria, hypochondriasis, and various cerebral diseases) ; while
in other conditions, these secretions are increased.

If an isolated intestinal fistula be made, and various drugs administered,
experiment shows that the mucous membrane excretes iodine, bromine, lithium,
sulphocyanides, but not potassium ferrocyanide, arsenious or boracic acid
(Quincke), or iron salts (Glaevecke).

In sucklings, not unfrequently a large amount of acid is formed when the fungi
in the intestine (Leube) split up milk-sugar or grape-sugar into lactic acid. Starch
changed into grape-sugar may undergo the same abnormal process ; hence, infants
ought not to be fed with starchy food.

184. Fermentation Processes in the Intestine.

Those processes, which are to be regarded as fermentations or putre-
factive processes, are quite different from those caused by the action of
distinct ferments (Frerichs, Hoppe-Seyler). The putrefactive changes
are connected with the presence of lower organisms, so-called fermenta-
tion or putrefaction producers (Nencki) ; and they may develop in
suitable media outside the body. The lower organisms which cause
the intestinal fermentation are swallowed with the food and the 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 fcetal period until birth,
this fermentation cannot occur ; hence, gases are never present in the
intestine of the newly-born (Breslau). 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

372

FUNGI AS EXCITERS OF FERMENTATION.

intestinal tract, and give rise to the formation of gases. The evolution
of intestinal gases goes hand-in-hand with the fermentations. Atmo-
spheric air is also swallowed, and an exchange of gases takes place in
the intestine, so that the composition of the intestinal gases depends
upon various conditions.

Kolbe and Kuge collected the gases from the anus of a man, and
found in 100 vols. : —

Food.

CO-2.

H.

cm

N.

HaS.

Milk, . . .
Flesh, . . .
Peas, . . .

16-8
12-4
21-0

43-3
2-1
4'0

0-9
27-5
55-9

38-3
57-8
18-9

Quantity not
estimated.

With regard to the formation of gas and the processes of fermenta-
tion we note—

1. Air bubbles are swallowed when food is taken. The 0 thereof
is rapidly absorbed by the walls of the intestinal tract, so that in the
lower part of the large intestine, even traces of 0 are absent. In
exchange, the blood-vessels in the intestinal wall give off C02 into the
intestine, so that a part of the C02 in the intestine is derived by
diffusion from the blood.

2. H and C02NH3 and CH4 are also formed from the intestinal
contents by fermentation, which takes place even in the small
intestine (Planer).

Fungi as Exciters Of Fermentation. — The chief agents in the production
of fermentations, putrefaction and other similar decompositions are undoubtedly the
group of the fungi called Scliizomycetes. They are small unicellular organisms of
various forms, globular (Micrococcus), short rods (Bacterium), long rods (Bacillus),
or spiral threads ( Vibrio, Spirillum, Spirochceta). The mode 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 micro-
scopic organisms take certain constituents from the "nutrient fluids" in which
they live, and use them partly for building up their own tissues and partly for their
own metabolism. In these processes, some of the siibstances 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 or envelope 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 constitiiting zooyloca. In some fungi, repro-
duction 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/u) highly refractive globules or spores are
developed (Fig. 148, 7). In some cases, as in the butyric acid fermentation, the rods

FERMENTATION OF THE CARBOHYDRATES.

373

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 sprung. The process of spore-production is illustrated in Fig. 147, 7, 8,
9, and in 1, 2, 3, 4 is 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 not killed by being boiled. Some fungi exhibit
their vital activities only in the presence of 0 (Aerobes), while others require the
exclusion of Q (Anaerobes, Pasteur). 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 odours, as during putrefaction (bromogenic); and those that when
introduced into the living tissues of other organisms produce pathological condition*,
and even death (pathogenic). All these different kinds occur in the human body.

D
1

5

s

6

I

0

/4

A

Fig. 147.

A, Bacterium actti in the form of — cocci (1); diplococci (2); short rods (3), and
jointed threads (4, 5). B, Bacillus butyricus — (1) isolated spores; (2, 3, 4)
germinating condition of the spores ; (5, 6) short and long rods ; (7, 8, 9)
formation of spores within a cellular fungus.

When we consider that numerous fungi are introduced into the intestinal
canal with the food and drink — that the temperature and other conditions within
this tube are specially favourable for their development; that there also they meet
with sufficient pabulum for their development and reproduction — we cannot
wonder that a rich crop of these organisms is met with in the intestine, and that
they produce these numerous decompositions.

I. Fermentation of the Carbo-hydrates. — (1.) Bacterium lacticum
(Cohn), (Ferment lactique, Pasteur) are biscuit-shaped cells, T5-3 fj. in
length, arranged in groups or isolated. They split up sugar into lactic

acid;

1 grape-sugar = C0H12Oe=: 2 (C3H603) = 2 milk-sugar.

Milk-sugar (C12H2204) may be split up by the same ferment causing it
to take up H20, and forming 2 molecules of grape-sugar, 2 (C0H120C),
which are again split into 4 molecules of lactic acid, 4 (C3HG03).

374 FERMENTATION OF THE FATS.

The fungi which occur everywhere in the atmosphere are the cause of the spon-
taneous acidification, and subsequent coagulation of milk. — See Mill:

(2.) Bacillus butyricus (B. amylobacter, Van Tieghem ; Clostridiutn
butyricum, Vibrion butyrique, Pasteur), which in the presence of starch
is often coloured blue by iodine, changes lactic acid into butyric acid,
together with CO., and H (Prazmowski).

C C4HS03=1 butyric acid.

2 (C3H603) lactic acid = I 2 (C02) — 2 carbonic acid.

4 H = 4 hydrogen.

This fungus (Fig. 147, B) is a true anaerobe, and grows only in the absence of 0.
The lactic acid fungus uses O very largely, and is, therefore, its natural precursor.
The butyric acid fermentation is the last change undergone by many carbo-
hydrates, especially of starch and inulin. It takes place constantly in the fseces.

(3.) A fungus, whose nature is not yet determined, causes alcohol to
be formed from carbohydrates (Fitz). 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 (p. 298, I).

(4.) Bacterium aceti (Fig. 147, A) converts alcohol into acetic acid outside the
body. Alcohol (C2H0O) + 0 = C2H4O ( Aldehyd) + H2O. Acetic acid (C2H402)
is formed from aldehyd by oxidation. According to Niigeli, the same fungus causes
the formation of a small amount of C02 and H20. 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 ffeces, must be derived from another source.
During putrefaction of the proteids with exclusion of air, acetic acid is produced
(Nencki).

(5.) Starch and cellulose are partly dissolved by the schizomycetes of
the intestine. If cellulose be mixed with cloacal-mucus (Hoppe-
Seyler), or with the contents of the intestine (Tappeiner), n molecules,
[n (C6H1005)], take up n molecules of water, + %(H20), and produce
three times n molecules C02, and three times n molecules of marsh-
gas 3 n (CH4).

(6.) Fungi, whose nature is unknown, can partly transform starch
(? and cellulose) into sugar, others excrete invert-in — e.g., the Leuko-
nostoc mesenteriodes, which develops in the juice of turnips. Invertin
changes cane-sugar into invert-sugar (§ 183, II, 5).

II. Fermentation of the Fats.— In certain putrefactive conditions,
organisms of an unknown nature can cause neutral fats to take
up water and split into glycerine and fatty acids. Glycerine — C3H5
(H0)3 — is a triatomic alcohol, and is capable of undergoing several
fermentations, according to the fungus which acts upon it. With a
neutral reaction, in addition to succinic acid, a number of fatty acids,
H and C02, are formed.

Fitz found under the influence of the liay-funyus (Bacillus subtilis, Fig. 148)
alcohol with caproic, butyric, and acetic acids ; in other cases butylic alcohol is
the chief product.

FERMENTATION OF THE PROTEIPS. 375

The fatty acids, especially as chalk soaps, form an excellent material
for fermentation. Calcium formiate mixed with cloacal-mucus fer-
ments and yields calcium carbonate, C02 and H ; calcium acetate,
under the same conditions, produces calcium carbonate, CO, and CH4.
Amongst the oxy-atids, we are acquainted with the fermentations of
lactic, glycerinic, malic, tartaric, and citric acids.

0 0 y

1 2 'J 4

Fig. 148.

Bacillus subtilis — 1, spore ; 2, 3, 4, germination of the spores ; 5, 6, short rods ;
7, jointed thread, with the formation of spores in each segment or cell; 8,
short rods, some of them containing spores ; 9, spores in single short rods ;
10, fungus with a cilium.

According to Fitz, lactic acid (in combination with chalk), produces propionic
and acetic acids, C02H2O. Other ferments cause the formation of valerianic
acid. Glycerinic acid, in addition to alcohol and succinic, yields chiefly acetic acid;
malic acid forms succinic and acetic acid. The other acids above enumerated
yield somewhat similar products.

III. Fermentation of the Proteids. — There do not seem to be
fungi of sufficient activity in the intestine to act upon undigested
proteids and their derivatives. Many schizomycetes, however, can pro-
duce a peptonising ferment.

We have already seen that pancreatic digestion (p. 341), acts upon
the proteids, forming, among other products, amido-acids, leucin, tyrosin,
and other bodies. Under normal conditions, this is the greatest decom-
position produced by the pancreatic juice. The putrefactive fermentation
of the large intestine (Hiiffner, Nencki) causes further and more profound
decompositions. Leucin (C6H13N"02) takes up two molecules of water
and yields valerianic acid (C5H1002), ammonia, CO., and 2(H2);
fjlydn behaves in a similar manner. Tyrosin (C9HUN03) is decom-
posed into indol (CgH7N), which is constantly present in the intes-
tine (Kiihne), C02H2ON (Nencki). If 0 be present, other decom-
positions take place. These putrefactive products are absent from
the intestinal canal of the foetus and the newly-born (Senator).
During the putrefactive decomposition of proteids, C02H2S, also H
and CH4, are formed; the same result is obtained by boiling them with

370 INDOL — SKATOL — PHENOL.

alkalies. Gelatin, under the same conditions, yields much leucin and
ammonia, C02, acetic, butyric, and valerianic acids, and glycin (Nencki).
Mucin and nuclein undergo no change. Artificial pancreatic digestion
experiments rapidly tend to undergo putrefaction.

The substance which causes the peculiar ftecal odour is produced by putrefaction,
but its nature is not known. It clings so firmly to inclol and skatol that these svib-
stances were formerly regarded as the odorous bodies, but when they are prepared
pure they are odourless (Bayer). The above-mentioned putrefactive processes,
which also occur in pancreas undergoing decomposition, may be interrupted by
antiseptics (salicylic acid). The putrefactive products of the pancreas give a red
colour or precipitate with chlorine water.

Indol. — Amongst the solid substances in the large intestine formed
only by putrefaction is inclol (CgH^N), a substance which is also formed
when proteids are heated with alkalies, or by overheating 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.

Jaffe" found much indican in the urine in strangulated hernia, and when the
small intestine was obstructed. Landois observed the same after the transfusion
of heterogeneous blood.

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 foxind that on feeding
rabbits with ortho-nitrophenyl-proprionic acid, much indican was present in the
urine.

Phenol (C6HC0) is formed by putrefaction in the intestine, and it
is also formed when fibrin and pancreatic juice putrefy outside the
body (Baumann), while Brieger found it constantly in the faeces. It
seems to be increased by the same circumstances that increase indol
(Salkowski), as an excess of indican in the urine is accompanied by
an increase of phenylsulphuric acid in that fluid.

Hydrocinnamic acid (phenylpropionic acid) may also be obtained from putre-
fying flesh and fibrin. It 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 (E. and H. Salkowski).

Skatol (C9H9N = methylindol) — (Brieger), is a constant human
fffical 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 sulphuric acid com-
pound. The excretin of human fseces, described by Marcet, is related
to cholesterin, but its history and constitution are unknown.

PROCESSES IN THE LARGE INTESTINE. 377

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 (Pasteur). When 0 is absent, reductions take place ;
oxy-acids are reduced to fatty acids, and HCH4 and H2S are formed;
while the H may produce further reductions. If 0 be present, the
nascent H separates the molecule of free ordinary oxygen ( = 02) into
two atoms of active oxygen ( = 0). Water is formed on the one hand,
while the second atom of 0 is a powerful oxidizing agent (Hoppe-
Seyler).

[It is not improbable that some substances, as sulphur, are in part rendered
soluble and absorbed by the action of the nascent hydrogen evolved by the
schizomycetes, forming a soluble hydrogen compound with the substance (Matthew
Hay).]

It is remarkable that the putrefactive processes, after the development of
phenol, indol, skatol, cresol, phenylpropionic and phenylacetic acids, are after-
wards limited, and after a certain concentration is reached they cease altogether.
The putrefactive process produces antiseptic substances which kill the micro-
organisms (Wernich), so that 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 feces.

185. Processes in the Large Intestine.

Within the large' intestine, the fermentative and putrefactive pro-
cesses are certainly more prominent than the digestive processes proper,
as only a very small amount of the intestinal juice is found in it
(Kiihne). The absorptive function of the large intestine is greater than
its secretory function, as 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 solution are not
the only substances absorbed, but under certain circumstances, un-
changed fluid egg-albumin (Voit and Bauer, Czerny and Latschen-
berger), milk and its proteids (Eichhorst), flesh- juice, solution of
gelatin, myosin with common salt, may also be absorbed. Experi-
ments with acid-albumin, syntonin, or blood-serum gave no result.
Toxic substances are absorbed more rapidly than from the stomach
(Savory). The fsecal matters are formed or rather shaped in the lower
part of the gut. The cajcum of many animals, e.g., rabbit, is of con-
siderable size, and in it fermentation seems to occur with considerable
energy, giving rise to an acid reaction. In man, the chief function of

378 CHARACTERS OF THE F/EOES.

the caecum is absorption, as is shown by the great number of lymphatics
in its walls. From the lower part of the small intestine and the caecum
onwards, the ingesta assume the faecal odour.

The amount of fasces is about 170 grms. (60-250 grms.) in 24
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
fasces are rendered lighter by the evolution of gases, and hence they
float on water.

The consistence of the faeces depends on the amount of water pre-
sent— it is usually about 75 per cent. The amount of water depends
partly on the food — pure flesh diet causes relatively dry faeces, while
substances rich in sugar yield faeces with a relatively large amount of
water. The quantity of water taken has no effect upon the amount of
water in the faeces. But the energy of the peristalsis has this effect,
that the more energetic it is, the more Avatery the faeces are, because
sufficient time is not allowed for absorption of the fluid from the
ingesta. Paralysis of the blood- and lymph-vessels, after section of the
nerves, leads to a watery condition of the faeces (p. 371).

The reaction is often acid in consequence of lactic acid being
developed from the carbo-hydrates 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.

The odour, which is stronger after a flesh diet than after a vegetable
diet, is caused by some faecal 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 faeces depends upon the amount of altered bile-
pigments mixed with them, whereby a bright yellow to a dark-brown
colour is obtained.

The colour of the food is also of importance. If much blood be present in the
food, the fa;ces are almost brownish-black from ha?matiu ; 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
pigment of claret tinges the fceces.]

The faeces 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, gum.

(2.) Portions of digestible substances, especially when these have
been taken in too large amount, or when they have not been sufficiently

COMPOSITION OF THE F.-ECES. 379

broken up by chewing. Portions of muscular fibres, ham, tendon,
cartilage, particles of fat, coagulated albumin — vegetable cells from
potatoes and vegetables, raw starch, &c.

All food yields a certain amount of residue— white bread, 3 '7 p.c.; rice, 4'1 p.c. ;
flesh, 4'7 p.c.; potatoes, 9'4p.c.; cabbage, 14'9p.c.; black bread, 15 p.c.; yellow
turnip, 20'7 p.c. (Rubner).

(3.) The decomposition products of the bile-pigments, which do not
now give the Gmelin-Heintz 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, bili-
verdin, glycocholic, and taurocholic acids occur in meconium (Zweifel,
Hoppe-Seyler).

(4.) Unchanged mucin and nuclein — the latter occasionally after a
diet of bread, together with cylindrical epithelium in a state of partial
solution, from the intestinal canal, and occasional drops of oil.
Cholesterin is very rare. The less the mucus is mixed with the faeces,
the lower the part of the intestine from which it was derived
(Nothnagel).

(5.) After a milk diet and also after a fatty diet, crystalline needles
of lime, combined with fatty acids, chalk-soaps, constantly occur, even
in sucklings (Wegscheider). Even unchanged masses of casein and
fat occur during the milk-cure. Compounds of ammonia, with the
acids mentioned at p. 375, the result of putrefaction, belong to the
faecal matters (Brieger).

(6.) Amongst inorganic residues, soluble salts rarely occur in the
faces 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, j^ellow coloured
lime salts, calcium carbonate, and magnesium phosphate are the chief,
form 70 p.c. 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.

The excretion of inorganic substances is sometimes so great, that
they form incrustations around other fsecal matters. Usually
ammoniaco-magnesic phosphate occurs in large crystals by itself, or it
may be mixed with magnesium phosphate.

(7.) A considerable portion of normal fsecal matter consists of
micrococci and microbactcria (Bacterium termo — Woodward, Noth-
nagel). Bacillus subtilis is not very plentiful, while yeast is seldom
absent (Frerichs, Nothnagel). In stools that contain much starch, the
bacillus amylobacter, which is tinged blue with iodine, occurs (p. 374),

•°>80 I'ATHOLOGICAL VARIATIONS OK DKiESTION.

and other small globular or rod-like fungi, which give a similar reaction
(Notlmagel, Uffelmann). Bienstock, who has devoted attention to the
microbes of the faeces, finds two kinds of bacteria in all faeces ; both
resemble B. subtilis (Fig. 148) very closely, but they are distinguished
from it by their mode of development. They do not cause any
fermentative action. There are several other forms found in the faecal
evacuations, under different circumstances.

The changes of the intestinal contents have been studied on persons with an
accidental intestinal fistula, or an artificial anus.

186. Pathological Variations.

A. The taking Of food may be interfered with by spasm of the muscles of
mastication (usually accompanied by general spasms), stricture of the oeso-
phagus, by cicatrices after swallowing caustic fluids (e.g., caustic potash, mineral
acids), or by the presence of a tumour, such as cancer. Inflammation of all kiucls
in the mouth or pharynx interferes with the taking of food. Impossibility of
swallowing occurs as part of the general phenomena in disease of the medulla
oblongata, in consequence 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 gloss-pharyngeal, vagus, and trigeminus. Stimulation or abnormal excitation
of these parts causes spasmodic swallowing, and the disagreeable feeling of a
constriction in the neck (globus hystericus).

B. The secretion Of Saliva is diminished during inflammation of the salivary
glands; occlusion 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 (p. 287). 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 diastatic action of the saliva
diminishes (Uffelmann). The secretion is increased, by stimulation of the buccal
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. Even
diseases of the stomach accompanied by vomiting, cause secretion of saliva. A
very thick tenacious sympathetic saliva occurs when there is violent 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 consequence of decomposition of the buccal epithelium, and in diabetes mellitu.s
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 anaesthesia 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 ; vomiting often occurs.

DIGESTION DURING FEVER AND ANEMIA. 38 1

Gastric digestion is delayed by violent bodily or mental exercise, and some-
times it is arrested altogether. Sudden mental excitement may have the same
effect. These effects 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). [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.]

Inflammatory or catarrhal affections of the stomach, as well as ulceration

and new formations, 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 sauces or alcohol. In the case of a dog suffering from chronic gastric catarrh,
Griitzner observed that the secretion took place continuously, 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 (0'4 p.c.) hydrochloric acid ought to be adminis-
tered. Small doses of common salt seem to aid digestion. [In cases of carcinoma
of the stomach, the acid reaction of the gastric juice is almost invariably absent.]

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 are useful (Hoppe-
Seyler), together with some hydrochloric acid. 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.

D. Digestion during Fever and Anaemia. — Beaumont found that in the

case of Alexis St. Martin, when fever occurred, a small amount of gastric juice
was secreted ; the mucous membrane was dry, red, and irritable. Dogs suffering
from septica?mic fever, or rendered anfemic by great loss of blood, secrete gastric juice
of feeble digestive power and containing little acid (Manassein). Hoppe-Seyler
investigated the gastric juice of a typhus patient, in which Von der Velden found
no free acid, and he found the same in gastric catarrh, fever, and 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 cir-
cumstances, 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).
He advises the administration of hydrochloric acid and pepsin, and when there
are symptoms of fermentation, small doses of salicylic acid. Uffelmann found 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 (Heiden-
hain) is disadvantageous for the secretion of the digestive fluids. 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
mucosoe (Leube).

Many salts when given in large amount disturb gastric digestion — e.g., the

382 CONSTIPATION AND DIARRHCEA.

sulphates. While the alkaloids, morphia, strychnia, digitalin, narcotiu, veratria
have a similar action ; quinine favours it (Wolberg). In some nervous individuals
a " peristaltic un-rest of the stomach," conjoined with a dyspeptic condition, occurs
(Kussmaul).

E. In acute diseases, the secretion of bile is affected ; it becomes less in amount
and more watery, i.e., it contains less specific constituents. If the liver undergoes
great structural change, the secretion may be arrested.

F. Gallstones. — When decomposition of the bile occurs, gallstones are formed
iu the gall-bladder or in the bile-ducts. Some are white, and consist almost entirely
of stratified layers of crystals of cholesterin. The brown forms consist of bilirubin-
lime and calcium carbonate, often mixed with iron, copper, and manganese. The
gallstones in the gall-bladder become facetted by rubbing against each other. The
nucleus of the white stones often consists of chalk and bile colouring matters,
together with nitrogenous residues, derived from shed epithelium, muciii, bile salts
and fats. Gallstones may occlude the bile-duct and cause cholsemia. When a
small stone becomes impacted iu a duct, it gives rise to excessive pain constituting
hepatic colic, and may even cause rupture of the bile-duct with its sharp edges.

G. 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 forces.

H. Constipation is a most important derangement of the digestive tract. It
may be caused by — 1. Conditions which obstruct the normal channel, e.g., con-
striction of the gut from stricture — in the large gut after dysentery, tumours,
rotation on its axis of a loop of intestine (volvulus), or invagiuation, occlusion
of a coil of gut in a heriiial sac, or by the pressure of tumours or exudations
from without, or congenital absence of the anus. 2. Too great dryness of
the contents, caused by too little water in the articles of diet, diminution
of the aniouut of the digestive secretions, e.i/., of bile in icterus; or in
consequence of much fluid being given oti" 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, 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 hypochondrias 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
fajcal masses in constipation are usually hard and dry, owing to the water being
absorbed ; hence they form large masses or xcybala 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, e.g. , opium, morphia; some diminish the secretion of
the intestinal mucous membrane, and cause constriction of the blood-vessels, as
taiinic acid, vegetables containing tannin, alum, chalk, lead acetate, silver nitrate,
bismuth nitrate.

I. Increased evacuation of the intestinal contents is usually accompanied by a
watery condition of the faeces, 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-

COMPARATIVE PHYSIOLOGY OF DIGESTION. 383

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 muciu, Charcot's crystals (Fig. 115, c) occur. In ulcera-
tioii of the intestine, leucocytes (pus) are present ^othnagel).

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 intestinal mucous membrane.
[Irritation over the abdomen, as from the subcutaneous injection of small quan-
tities of saline somtions, causes diarrhoea (M. Hay).]

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.

Trausudation 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 diarrlm-a
following upon a cold. Certain substances seem directly to excite the secretory
organs of the intestines or their nerves, such as the drastic purgatives (p. o64).
Pilocarpin injected into the blood causes great secretion (Maslotf).

During febrile conditions, the secretion of the intestinal glands seems to be
altered quantitatively and qualitatively, with simultaneous alteration of the
functional activity of the musculature and the organs of absorption, while the
excitability of the mucous membrane is increased (Uffelmann). It is 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.

187. 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 pinuipedia have a small parotid, which is
absent in the echidna. The dog and many caruivora have a special gland lying
in the orbit, the orbital or zyyomutic gland. In Birds the salivary glands open at
the angle of the mouth, in them 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 de-
veloped in molluscs, and the saliva of dolium galea contains more than 3 p.c. 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 stomach of ruminants is compound, and consists of four cavities.
The intestine is short in flesh-eating animals and long in herbivora. The caecum is
a very large and important digestive organ in herbivora, and in most rodents;
it is small in man, and absent in carnivora. The oesophagus 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
secretion — "pigeon's milk," which is used to feed the young (J. Hunter). The

384 HISTORICAL ACCOUNT OP DIGESTION.

stomach consists of a glandular proventriculus and a strong muscular stomach
which is covered with horny epithelium 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 usually 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 pylorica). There are usually longi-
tudinal folds in the intestinal mucous membrane, but in some fishes, e.g., the shark,
there is a spiral valve. [It is curious to find that the inversive (cane-sugar) fer-
ment is wanting in the herbivora, as the cow, horse, and sheep, but is present in
the carnivora, as the dog and cat. It is also met with in birds and reptiles, and
in many of the invertebrates, as the ordinary earth-worm (Matthew 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.

Digestion in Plants. — The observations on the albumin-digesting power of
some plants (Canby, 1869; Ch. Darwin, 1875) are extremely interesting. The
sundew or drosera has a series of tentacles on the surface of its leaves, and the
tentacles are provided with glands. As soon as 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 secretion, 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 con-
tains a pepsin-like ferment and formic acid. Similar phenomena are manifested
by the Venus flytrap (Dionrea), 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.

188. Historical.

Digestion in the Mouth — The Hippocratic school was acquainted with the
vessels of the teeth ; Aristotle ascribed an uninterrupted growth to these organs, and
he farther noticed that animals that were provided with horns, and had cloven
hoofs, had an imperfect set of teeth — the upper incisors were absent. It is curious
to note that in some cases where men have had an excessive formation of hairy
appendages, the incisor teeth have been found to be badly developed. The muscles
of mastication were known at an early period ; Vidius (t!567) described the tempero-
maxillary articulation with its meniscus. Ihe 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. Human saliva, without organisms, is
poisonous to birds (Gautier). The salivary glands have been known for a long
time. Galen (131-203 A.D.) was acquainted with Wharton's duct, and Aetius
(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. Spallanzaui (17SG) 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 ptyalm to the characteristic organic constituent of saliva, but
Leuchs (1S31) was the first to detect its diastatic action.

Gastric Digestion. — Digestion was formerly compared to boiling, whereby
solution was effected. According to Galen, only substances that have been dis-
solved passed through the pylorus into the intestine. He described the move-
ments of the stomach and the peristalsis of the intestines. Aelian gave names to

HISTORICAL. 385

the four stomachs of the ruminants. Vidius (t 1567) noticed the numerous small
apertures of the gastric glands. Van Helmont (t 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 fistulas upon animals.
Eberle (1834) prepared artificial gastric juice. Mialhe called albumin, when
altered by gastric digestion, albuminose; Lehmann, who investigated this sub-
stance 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. Hoffmaun (1642) demonstrated its duct (fowl), and
Wirsung described it in man. Regner cle Graaf (1664) collected the pancreatic
juice from a fistula, and Tiedmann and Gmelin found it to be alkaline, while
Leuret and Lassaigne found that it resembled saliva. Valentin discovered 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 excretion; according to Erasistratus
(304 B.C.), fine invisible channels conduct the bile from the liver into the gall-
bladder. Aretaeus 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 de la Boe 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 descrip-
tion of the hepatic blood-vessels (1834). Beale injected the lymphatics, and Gerlach
the finest bile-ducts. Schwann (1844) made the first biliary fistula; Demarcay
particularly referred to the combination of the bile acids with soda (1838); Strecker
discovered the soda compounds of both acids, and isolated them.

Corn. Celsus mentions nutrient enemata (3-5 A.D.) Fallopius (1561) described
the valvulte conm'ventes 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).

25

Physiology of Absorption,

189. The Organs of Absorption.

THE mucous membrane of the whole intestinal tract, as far as it is
covered by a single layer of columnar epithelium — i.e., from the
cardiac orifice of the stomach to the anus — is adapted for absorption.
The mouth and oesophagus, lined as they are by stratified squamous
epithelium, are much less adapted for this purpose. Still, poisoning is
caused by placing potassium cyanide in the mouth.

The channels of absorption in the intestinal tract are — (1) the
capillary Hood-vessels; and (2) the ladeals of the mucous membrane.
Almost the whole of the substances absorbed by the former pass into
the rootlets of the portal vein, and traverse the liver, while those
that enter the lacteals 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 — e.g., potassium iodide (in T\f— H hours),
grape-sugar, poisons, peptones, and in a still higher degree, alcoholic-
solutions of poisons are absorbed from the stomach.

The greatest area of absorption is undoubtedly the small intestine,
especially its upper half (Landois and L6pine).

190. Structure of the Small and Large Intestines.

[The wall of the small intestine consists of four coats ; which from
without inwards are named serous, muscular, sub-mucous, and mucous.

The serous coat has the same structure as the peritoneum — i.e., a thin basis of
librous tissue covered on its outer surface by endothelium.

The muscular COat consists of a thin outer longitudinal and an Inner thicker
circular layer of non-striped muscular fibres.

The SUb-mucoUS coat consists of loose connective-tissue containing large blood-
vessels and nerves, and it connects the muscular with the mucous coat.]

The muCOUS coat is the most internal coat, and its absorbing surface is largely
increased by the presence of the valvula? conniventes and villi. [The valvula;
conniventes are permanent folds of the mucous membrane of the small intes-
tine, 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

STRUCTURE OF THE SMALL INTESTINE.

387

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 disappear 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 be-
tween the valvulre conni-
ventes (Fig. 149). 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 r\ to -aV of an inch,
are most numerous and
largest in the upper part
of the intestine, duo-
denum, 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

Fig. 149.

Mucous membrane of the small intestine of the dog;
the lacteals are black and the blood-vessels lighter—
a, artery; b, lymphatic; c, plexus of capillaries in
the villi ; d, lacteal ; e, Lieberkiihn's glands.

contains within itself
representatives of all the
tissue elements of the
mucosa. The orifices of
the glands of Lieberkiihn open between the bases of villi (Fig, 151).

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 intranuclear plexus of fibrils. The ends of the epithelial
cells directed towards the gut are polygonal, and present the appearance of a
mosaic (Fig. 150, 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 strife. These stria? were supposed by Kolliker to represent pores for the
absorption 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 some observers (v. Thanhoffer), however, this clear disc is the
optical expression of a thinning of the cell membrane, 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 projects pseudo-
podia-like bundles of protoplasmic processes (Fig. 150, B). These processes are
supposed to be extended beyond the margin of the cell and again rapidly retracted,
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 entangles its food. [This view has
not been confirmed by a sufficient number of observers.] Between the epithelial
cells are the so-called goblet-cdls (Fig. 150, C). [Each goblet-cell is more~or less

388

STRUCTURE OF A VILLUS.

like a chalice, narrower above and below, and broad in the middle, with a tapering
fixed extremity. The outer part of each cell 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 net-work of fibrils, which pervades the cell protoplasm. The
protoplasm, containing a globular or triangular nucleus, is pushed into the lower part

B

o •« .••'a

Fig. 150.

.Scheme of an intestinal villus — A, Transverse section of part of a villus ; a,
columnar epithelium with, b, clear disc ; c, goblet-cell ; i, i, adenoid reti-
culum ; d, d, spaces within the same and containing leucocytes, e, e ; f, section
of the central lacteal ; B, scheme of a cell with processes supposed to be
projected from its interior ; C, columnar epithelium after the absorption of
fatty granules ; D, the columnar epithelium of a villus seen from above with
a goblet-cell in the centre.

of the cell. These goblet-cells are simply altered columnar epithelial cells, which
secrete mucus in their interior. They are more numerous under certain conditions.
Not unfrequently in sections of the mucous membrane 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. 150, D.]
The epithelial cells are shed in enormous numbers in cholera, and in poisoning
with arsenic and muscarin (Bo'hm).

[The epithelial cells covering the villus are placed upon a layer of squamous
epithelium (basement membrane) — the sub-epithelial membrane of Debove. This
basement membrane is said to be connected by processes with the so-called
branched cells of the adenoid tissue of the villus, while it also sends up processes
between the epithelial covering.]

The villus itself consists of a basis of adenoid tissue, containing in its centre one

STRUCTURE OF A VILLUS.

389

or more lacteals, closely invested with a few longitudinal smooth muscular fibres,
derived from the muscularis mucoste, 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 net-work of
inter-communicating channels containing stroma-cells or leucocytes (Fig. 150, A, e, e).
These leucocytes or lymph-corpuscles have been seen to contain fatty granules,
and they may, perhaps, play an important part in the absorption of fatty particles.

The lymphatic or lacteal lies in the axis of the villus (Fig. 149, d). By some
observers, the lacteal is regarded merely as a space 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
place the interior of the lacteal in direct communication with the spaces of the
adenoid tissue. It is very probable that white blood-corpuscles wander out
of the blood-vessels of the villi into the spaces of the adenoid tissue, where
they become loaded with fatty granules, and pass into the central lacteal.
Zuwarykin and Wiedersheim suppose that the leucocytes pass from the par-
enchyma of the villus towards the epithelial layer, and even between the
epithelial cells, from which they return towards the axis of the villus, laden
with substances which they have taken into their interior (p. 399).

A small artery placed eccentrically passes into each villus. 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 net-work placed superficially, immediately under the epithelium of the
surface. The blood is carried out of a villus by one or two veins (Fig. 149, a, c).

*- 01 " "

r-£fl.&i-j:

'&i H$j
miVi i i"W

< ^

<, 'l?c'
'-/.vir J

i \ p j .' i-ir -•*>'/

}>^. ,\^':^^

Ht^i, v ViWif'o '

l-^-

ife

S(HK\v

i ?:S-^''\VK^

ilp|lfil

:^4 S?1; ,t
'«»«

1 »

^::'^/

vttASM

m

Fig. 151.

Section of the mucous membrane of the small intestine, showing Lieberkiilm's
glands— a, with irregular epithelium; b, villi, cut short; c, muscularis mucosse;
d, sub-mucous tissue.

390

BRUNNER'S GLANDS AND SOLITARY FOLLICLES.

Non-striped muscular fibres are present in villi (Henle). Some are arranged
longitudinally from base to apex, immediately outside the central lacteal. When
they contract they tend to empty the lacteal (Briicke). A few muscular fibres are
placed more superficially, and run in a more transverse direction. [The muscular
fibres of the villi are direct prolongations of the muscularis mucosse].

Nerves pass into the villi from Meissner'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 partly in the muscular fibres and partly in the arteries
of the villi.

[On making a vertical section of the muCOUS membrane of the small intestine,
it is seen to consist of a net-work of adenoid tissue loaded with leucocytes. This
tissiie forms its basis, and in it are placed vertically side by side, like test-tubes in
a stand, immense numbers of simple tubular glands — the Crypts of Lieberkllhn
(Fig. 151). They open above at the bases of the villi, while their lower extremity
reaches almost to the muscularis mucosse. Each tube consists of a basement mem-
brane lined by a single layer of columnar epithelium, leaving a wide lumen, the
cells lining them being continuous with those that cover the mucous membrane.
Some goblet-cells are often found between the columnar epithelium. Immediately
below the bases of the follicles of Lieberkuhn is the muscularis mucoste, consisting of
two or three narrow layers of non-striped muscular fibres arranged circularly and
longitudinally. It is continuous with the muscularis mucosa? of the stomach, aud
extends throughout the whole intestine. It sends fibres upwards into the villi.]

[Brunner's glands are compound tubular glands lying in and confined to the
sub-mucous coat of the duodenum. Their ducts perforate the muscularis mucosse
to open on the surface. They seem to be the homologues of the pyloric glands of
the stomach (p. 308).]

[Solitary follicles are small round or oval white masses of adenoid tissue,
with their deeper parts embedded in the sub-mucosa, and their apices pro-
jecting into the mucosa of the intestine. They begin at the pyloric end of the

kVV^lllTC^ «t»S f. • ,«'i&'M$$Wfr\
l|Wj|fP5» ^^\'$^$£?&-' •• 7'v •

J^° 'Sir' '»' ^ >lix - -»*OT ^^ '»"'.'! rS^^a"^^ -

Section of a solitary follicle of the small intestine (human), showing — a, lymph-
follicle covered with epithelium (b) which has fallen from the villi, c ; d,
Lieberkiihn's follicle ; c, muscularis mucosse ; /, sub-mucous tissue.

STRUCTURE OF PEYER'S GLANDS.

391

stomach and are found throughout the whole intestine. They consist of small
masses of adenoid tissue loaded with leucocytes (Fig. 152). They are well supplied
with blood-vessels (p. 406), although no lymphatic vessels enter them. They are
surrounded by lymphatics, and, in fact, they may be said to hang into a lymph -
stream,]

Diagram of a vertical section of the mucous membrane of the small intestine of a
dog, showing the closed follicles, a a ; b, muscularis mucosag.

[Peyer's glands, or agminated glands, consist .of groups of lymph-follicles like
the foregoing (Fig. 153). 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 project between the epithelium. 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
or lacteals. They are most abundant in the lower part of the ileum. These
glands are specially affected in typhoid fever.]

Auerbach's plexus shown in section (human) — a, ganglionic cells ; b, nerve fibres ;
c, section of the circular muscular fibres ; d, longitudinal muscular fibres.

392

STRUCTURE OF THE LARGE INTESTINE.

Nerves Of the Intestine. — Thoughout the whole intestinal tract, there exists
the plexus myentericus of Auerbach (Fig. 154), lying between the longitudinal
and circular muscular coats. This plexus consists of non-medullated nerves with

groups of ganglionic cells at the nodes. Fibres
are given off by it to the muscular coats.

Connected by branches with the foregoing and
lying in the sub-mucosa, is the plexus ofMeissner,
which is much finer, the meshes being wider, the
nodes smaller, but also provided with ganglionic
cells. It supplies the muscular fibres and arteries
of the mucosa, including those of the villi. It
also supplies branches to Lieberkiihn's glands
(Drasch). — Compare Figs. 131 and 132.

[Structure of the Large Intestine.— It has
four coats like those of the small intestine. The
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 ribband-like longi-
tudinal bands in the caecum and colon. Inside
this coat are the circular fibres. The sub-
milCOSa is practically the same as that of the
small intestine. The niUCOSa is characterised
by negative characters. It has no villi and
no Peyer's patches, but otherwise it resembles
structurally the small intestine, consisting of a
basis of adenoid with the simple tubular glands
of Lieberkiikn (Fig. 155). These glands are very
numerous and somewhat longer than those of the
small intestine, and they always contain far
more goblet-cells. The cells lining them are
devoid of a clear disc. Solitary glands occur
throughout the entire length of the large intes-
tine. At the bases of Lieberkiihn's glands is
the muscularis mucosce. The blood-vessels and
nerves have a similar arrangement to those
the stomach.]

155.

Lieberkiihn's gland from
large intestine (dog).

the

in

191. Absorption of the Digested Food.

The physical forces concerned are endosmosis, diffusion, and filtration.

All the constituents of the food, with the exception of the fats, which in part
are changed into a fine emulsion, are brought into a state of solution by the digestive
processes. These 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 processes come into play —
endosmosis and diffusion as well as filtration.

I. Endosmosis and diffusion occur between two fluids which are capable of
forming an intimate mixture with each other, e.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 each other, but of different com-
positions, be separated from each other by means of a septum with physical pores,
(which occur even in a homogeneous membrane), an exchange of the constituents in

FORCES CONCERNED IN ABSORPTION.

303

the fluids occurs until both fluids have the same composition. This exchange of
fluids is termed endosmosis or diosmosis.

If we remember that within the intestinal tract, there are relatively concen-
trated solutions of those substances which have been brought into solution by
the digestive juices— peptone, sugar, soaps, and solutions of the salts — while
separated from these by the porous mucous membrane and the walls of the blood-
and lymph-capillaries is the blood, which contains relatively less of these sub-
stances, it is clear that an endosmotic current must set in towards the blood and
lymph-vessels.

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 composi-
tion. This process is called Diffusion.

Conditions Influencing Diffusion.— Graham's investigations showed that the
rapidity of diffusion is influenced by a variety of conditions: — (1) The nature of
the fluids themselves is of importance; acids diffuse most rapidly; the alkaline
salts more slowly; and most slowly, fluid albumin, gelatin, gum, dextrin. These
last do not crystallise, and perhaps do not form true solutions. (2) The more
concentrated the solutions, the greater the diffusion. (3) Heat accelerates, 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 diffuses o

more readily than the other, may be chemically separated by
diffusion.

The exchange of the fluid particles takes place independently
of the hydrostatic pressure. Fig. 156 represents an endosmo-
meter. A glass cylinder is 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 concen-
trated 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 salt solution pass into the
cylinder and mix with the water, F. These outgoing 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 — i.e., a
known weight of a soluble substance (in the 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 gram, alcohol 4'2 grams, water were exchanged; while for 1 gram. NaCl, 4'3

Fig. 156.
Endosmometer for

Diffusion.

394 ENDOSMOSIS AND FILTRATION.

grams, water passed into the endosmometer. The following numbers give the
endosmotic equivalent of

Acid Potassium Sulphate, . = 2 '3

Common Salt, . . . = 4'3

Sugar, ... 7'1

Sodium Sulphate, . . . = 1 1 '6

Magnesium Sulphate, . . = 1 1 '7

Potassium ,, . . = 12'0

Sulphuric Acid, . . . : 0'39

Potassium Hydrate, . . = 215'0

The amount of the substance which passes through the membrane into the water
of the cylinder is proportional to the concentration of the solution (Vierorclt). If
the water in the cylinder, therefore, be repeatedly renewed, the endosmosis takes
place more rapidly, and the process of equilibration 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 — thus, the rapidity of sugar, sodium sulphate, common salt, and
urea is in the ratio of 1: 1'l: 5: 9'5 (Eckhard, Hoffmann).

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 solutions of the substances (C. Ludwig and
Cloetta).

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 pig's bladder = 4*3, gives 6 '4 when
an ox bladder is used; 2'9 with a swimming bladder; and 20'2 with a collodion
membrane (Harzer).

Colloids. — There is a number of fluid substances which, on account of the great
size of their molecules, do not pass, or pass only with difficulty, through the pores
of a membrane impregnated 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 substances
Colloids, because when concentrated, they present a glue-like or gelatinous appear-
ance; farther, they do not crystallise, while those substances which diffuse readily
are crystalline, and are called Crystalloids. Crystallisable substances may be
separated from nou-crystallisable by this process, which Graham called Dialysis.
Mineral salts favour the passage of colloids through membranes (Baranetzky).

That Endosmosis takes place in the intestinal canal 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 the highly diffusible peptones, sugar, and soaps,
and within the blood-vessels are the colloids which are scarcely diffusible,
e.g., the proteids 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

ABSORPTION OF WATER AND SOLUBLE SALTS. 395

different membranes with varying rapidity. The nitration 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, e.cj. , colloid sub-
stances— 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 sub-
stances 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 nitration only from without inwards ; [and the
same is true to a much less extent with an ordinary filter paper — the smooth side
of the filter paper ought always to be placed next the fluid to be filtered]. There
is a similar difference with the gastric and intestinal mucous membrane.

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 musculature between these two points contracts
upon the fluid contents. (2) Filtration, under negative pressure, may be
caused by the mill (Briicke). When the villi contract energetically,
they empty their contents towards the blood- and lymph-vessels. The
lymph-vessels remain 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 pass
again into the relaxed condition, they again become filled with the
fluids of the intestinal contents.

192. Absorptive Activity of the Wall of the

Intestine.

The process of digestion produces from the food, partly solutions and
partly finely divided emulsions, whose fine particles are surrounded by
an albuminous envelope, the haptogen membrane [of Ascherson], where-
by these particles become more stable. Unchanged colloid substances
may also be present in the intestinal tract.

I. Absorption of Solutions. — 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 of the tube
take an active part in the process of absorption. The forces concerned
have not as yet been referred simply to physical and chemical
processes.

(1.) The Inorganic Substances. — Water and the soluble salts neces-
sary for nutrition are easily absorbed. When saline solutions pass by
endosmosis into the vessels, water must pass from 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 (Funke).

39G ABSORPTION OF SOLUBLE CARBOHYDRATES.

]f largo quantities of salts, with a high cndosmotic equivalent, are intro-
duced into the intestine, e.g., magnesium or sodium sulphate, these salts
retain the water necessary for their solution, and thus diarrhoea is
caused (Poiseuille, Buchheim). Conversely, when these substances are
injected into the blood a large quantity of water passes from the intes-
tine into the blood, so that constipation occurs, owing to dryness of the
intestinal contents (Aubert). [M. Hay concludes from his experi-
ments (p. 320), 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. Absorption is probably due to
filtration and diffusion, or processes of imbibition other than en-
dosmosis, 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.]

Numerous inorganic substances, which do not occur in the body, are absorbed by
endosmosis from the intestine, e.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 representative is grape-sugar, with a relatively high endosmotic
equivalent. Cane-sugar is changed by a special ferment into invert
sugar, which is a mixture of grape-sugar and Isevulose (p. 370).
Perhaps a very small proportion of the cellulose is changed into
grape-sugar. The 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 in-
creased (Naunyn). 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 substance (C. Schmidt and v. Becker), so that it may appear
in the urine, in which case, the blood must contain at least 0'6 per
cent, of sugar (Lehmann and Uhle). A small amount of cane-sugar
has also been found in the blood (Cl. Bernard, Hoppe-Seyler). The
sugar is used up in the bodily metabolism ; some of it is perhaps
oxidised in the muscles (Zimmer).

(3.) The peptones have a small endosmotic equivalent (Funke), a 2-9
per cent, solution = 7-10. 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 concen~

ABSORPTION OF PEPTONES AND PROTEIDS. 39?

tration of their solution in the intestine. They pass into the blood-
vessels (Schmidt-Mill heim). When animals are fed on peptones (with
the necessary fat or sugar), they serve to maintain the body-weight
(Maly, Plosz, and Gyorgyai). Only minute quantities of peptone have
as yet been found in the blood (Drosdorff ) ; hence, it is assumed, either
that they are rapidly converted into true albuminous bodies, or that in
part at least, they undergo further decompositions, with which we are
as yet unacquainted. As, however, they can compensate for the total
metabolism of the proteids within the body, we must assume that they
are converted into proteids.

Schmidt-Miilheim has recently found that, four hours after feeding a pig with
fibrin, a large quantity of crystalline propeptone (p. 331) can be obtained from
the blood. When 5 c.c. of a 20 per cent, solution of peptone in 0'6 per cent.
NaCl solution, for every kilo, of a dog, are injected into the blood, death is pro-
duced owing to paralysis of the blood-vessels (compare 28, II,/). Fano is of
opinion that the red blood-corpuscles take up the peptone, and subject it to further
changes.

(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 difficulty, and only in traces through
membranes. Nevertheless, it has been conclusively proved that un-
changed proteids can be absorbed (Briicke), e.g., casein, soluble myosin,
alkali-albuminate, albumin mixed with common salt, gelatin (Voit,
Bauer, Eichhorst). 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 (Eichhorst). Landois observed in the case of a young man who took the
whites of 14-20 eggs along with NaCl, that albumin was given off by the urine for
4-10 hours thereafter. The amount of albumin given off rose until the third day
and ceased on the fifth day. The more albumin that was 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. The
absorbed soaps have been found in 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

398 ABSORPTION OF FATTY PARTICLES.

amount of bile and pancreatic juice. The maximum per 1 kilo, (cat)
was O'G grms. of fat per hour.

It appears as if the soaps reunite with glycerine in the parenchyma
of the villi, to form neutral fats, as Perewoznikoff and Will found, after
injecting these two ingredients into the intestinal canal. C. A. 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.

Absorption Of Other Substances. — Of soluble substances which are intro-
duced into the intestinal 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 C02 and H2O, within the
body; tartaric, citric, inalic, and lactic acids; glycerine, inulin (Komanos); 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 ; hsematin 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, e.g., hydrocyanic acid after a few seconds; potassium cyanide
has been found in the chyle.

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 (v. Frey). 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
epithelium 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? (p. 387) in the clear band of the epithelium (Kolliker).
[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 8-10
per cent., while the fat disappears from the blood within thirty hours.

ABSORPTION OF FATTY PARTICLES. 399

With regard to the farces concerned in the absorption of fats,
v. Wistinghausen 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 explain the copious and rapid absorption
of fats. It appears probable, 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 observa-
tions of Briicke and v. Thanhoffer. This view is supported by the
observation of Griiiiliageu, 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 nitration 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 was
chiefly due to nitration, we would expect that there would most
probably be a direct relation between the amount of water and the 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 correct, the absorbing surface is thereby greatly diminished.]

[Schafer suggests 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 (p. 389)].

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.

Spina observed that the intestinal epithelium of the larva? of flies shortened
when they were stimulated with electricity, and absorbed fluid from the intestinal
canal. The cells of the villi of the frog also react to electrical stimulation.

The increase in the size of the cells occurs simultaneously with the contraction
of the intestine. Spina also supports the view that the cells, in virtue of their
activity, possess the property of absorbing fluid from the intestinal contents and
again giving it up. An exchange of fluids in the opposite direction never takes place.

The statements of former observers that particles of charcoal, pigments, and

400 INFLUENCE OF NERVES ON ABSORPTION.

even mammalian blood-corpuscles (in the frog) were absorbed by the epithelial
cells of the intestine, and passed into the blood, are erroneous. 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 — e.g., from intestinal catarrh —
cause sudden variations of absorption, and even the passage of fluids into the
intestine.

If absorption was 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-l 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.

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 (Budge), as well as after section of the mesenteric nerves
(Moreau), the intestinal contents become more fluid, and are increased
in amount. This may be partly due to diminished absorption, v.
ThanhofFer 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.

[Matthew Hay injected saline solutions directly into the exposed intestine. He
found that a 20 per cent, solution of sulphate of soda always excites a profuse
secretion, but that a 10 per cent, solution only does so, or rather, that it only
increases in bulk, when injected in sufficient quantity — a certain weight of salt
failing to increase the bulk of the fluid secretion when dissolved as a 10 per cent,
solution, but exciting a profuse secretion when forming a 20 per cent, solution. Se-
cretion, he has reason to believe, is active in both — perhaps, almost equally active —
but absorption is greatly impeded in the'case of the concentrated salt, by its injurious
action on the absorptive mechanism of the mucous membrane. Moreau has recently
maintained that, under such circumstances, there is actually no absorption, but
Hay has disproved this, by observing that strychnia injected into a loop of intestine,
containing the concentrated salt, still causes death, although after an interval three
times longer than when the loop contains a 10 per cent, solution of the salt.

Hay has also observed that the local effect of a ligature applied to the intestine
is to excite secretion from the mucous membrane in its immediate vicinity, and
therefore add to the bulk of the saline solution ; whereas the reflex effect of a
ligature, as exercised through the nervous system, is to diminish the quantity of
the secreted fluid in a remote portion of the intestine, probably by stimulating and
accelerating absorption. Division of the vagi does not affect the nature or the
quantity of the secretion].

194. Feeding with "Nutrient Enemata."

In cases where food cannot be taken by the mouth — e.g., in stricture of the
oesophagus, continued vomiting, &c., food is given per rectum (Celsus, 3-5 A.D.).
As the digestive 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

LACTEALS AND LYMPHATICS, 401

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 gradually introduced, it
may pass above the ileo-csecal 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, Adauikiewicz, in Germany, and Darby's fluid meat in
this country, are to be recommended. The amount of peptone required is I'll
grms. 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 injects into the rectum where the proteids
are peptonised and absorbed. 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.

Within the tissues of the body, and even in those tissues which do
not contain blood-vessels — e.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 sub-
clavian veins ; that on the left side is the thoracic duct, and that on
the right, the right lymphatic trunk.

Lymphatics. — 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 lymphatics represent the
nutrient channels, by which the fluid which 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 sali-
vary glands (Gianuzzi) and the testis, the lymph-spaces are the first
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 irrigation system, which supplies the tissues with
nutrient fluids, Avhile the lymphatic system may be regarded as a
drainage apparatus, which conducts away the fluids that have trans-
uded through the capillary walls. Some of the decomposition pro-
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

26

402 ORIGIN OF THE LYMPHATICS.

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 considerable 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 distinguishes them at once from the clear watery con-
tents of the true lymphatics. 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.

The mode of origin of the lymphatics varies within the different
tissues. The following modes are known :—

1. Origin in Spaces. — Within the connective-tissues (connective-tissue proper,
bouc), are numerous stellate, irregular, or branched, spaces which communicate with
each other by numerous tubular processes (Fig. 157, 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 protoplasmic cell. These spaces are the so-called "juice-canals "
or " saftcanalchen," and they represent the origin of the lymphatic vessels (v.
Reckliughausen). As they communicate with neighbouring spaces, the movement
of the lymph is provided for. The cells which lie in the spaces, and which were
formerly but erroneously regarded by Virchow as the origins of the lymphatics,
exhibit amoeboid 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, andare called "wandering cells," or "leucocytes;"
but the latter are merely lymph-corpuscles, or colourless blood-corpuscles which
have passed out of the blood-vessels into the origin of the lymphatics. These cells
exhibit amoeboid movements. These spaces communicate with the small tubular
lymphatics — the so-called lymph-capillaries (L). The spaces lie close together
where they pass into a lymph-capillary (a). The lymph-capillary, which is
usually of greater diameter than the blood capillary, generally lies in the middle

ORIGIN OF THE LYMPHATICS.

403

Fig. 157.

Origin of lymphatics — From the central tendon of the diaphragm of a rabbit
(semi-diagrammatic) ; a, the juice-canals,"? communicating at x with the
lymphatics; a, origin of the lymphatics by the confluence of several juice-
canals. The tissue has been stained with nitrate of silver.

Fig. 158.

Central tendon of the diaphragm of the rabbit stained with silver nitrate and
viewed from the pleural side — L, lymphatic with its sinuous endothelium;
c, cells of the connective-tissue brought into view by the silver nitrate.

404 ORIGIN OF THE LYMPHATICS.

of the space within the capillary arch (B). The finest lymphatics are lined by a
layer of delicate, nucleated endothelial cells (e,e), with characteristic sinuous
margins, whose characters are easily revealed by the action of silver nitrate
(Fig. 158, L). This .substance blackens the cement substance which holds the
endothelial cells together. Between the endothelial cells are small holes, or
xtomata, by means of which the lymph-capillaries communicate (at x) with the
juice canals.

It is assumed that the blood-vessels communicate with the juice
canals (J. Arnold, Thoma, Uskoff), and that fluid passes out of the
thin-walled capillaries through their stomata (p. 122) into these spaces.
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 for con-
jecture. We can imagine that by contracting 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 inunction — 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.]

After what has been said regarding the passage of colourless blood-
corpuscles through the stomata of the blood-capillaries, or through the
walls of the smaller blood-vessels (§ 95), the passage of cellular
elements from the blood-vessels into the origin of the lymphatics is to
be considered as a normal process (E. Hering). Granular colouring
matter passes from the blood into the protoplasmic body of the cells
within the lymph-spaces ; and only when the granular pigment is in
large amount, does it appear as a granular injection in the branches of
the juice-spaces (Uskoff).

(2.) The origin of lymphatics within villi — i.e., of the chyle vessel or lacteal—
lias been described at p. 389. The central lacteal communicates with the lacunar
interstitial spaces in the adenoid tissue of the villus, and this again with the
protoplasmic body of the epithelial cells. It is assumed that the lymph-corpuscles,
which lie in the meshes of the adenoid tissue, pass into the central lacteal (His),
while new cells are continually passing out of the blood-capillaries of the villi into
the tissue, where they perhaps undergo increase through division.

(3.) Origin of lymphatics in perivascular spaces (Fig. 159). — 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 (Roth). Fig. 159, 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

PERIVASCULAR SPACES AND STOMATA.

405

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 considerably in

A

Fig. 159.

Perivascular lymphatics — A, aorta
of tortoise ; B, artery from the
brain.

Fig. 160.

.Stomata from the great lymph-sac of a
frog — a, stoma open; b, half-closed;
c, closed.

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 facili-
tated. In the tortoise, the large blood-vessels are often surrounded with, peri-
vascular lymphatics. Fig. 159, A, gives a representation of the aorta sur-
rounded by a perivascular space (Gegenbaur) which is visible to the unaided eye.
In mammals, 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 glands, 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
(Fig. 160, a). — The investigations of v. Recklinghausen, Ludwig, Dybkowsky,
Schweigger-Seidel, Dogiel, and others have shown, that the old view of Mascagni,
that the serous cavities freely communicate with the lymphatics, is correct. The
investigation of the serous surfaces, most easily accomplished on the septum of
the great abdominal lymph-sac of the frog, by means of silver nitrate, reveals
the presence of relatively large free openings or stomata lying between the
endothelium. Each stoma is bounded by several cells, which have a granular
appearance, and are capable of undergoing 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 (b), or completely closed (c). These stomata
are the origin of the lymphatics. The serous cavities belong therefore to the
lymphatic system, and fluids placed in the serous cavities readily pass into the

406

LYMPH-FOLLICLES.

lymphatics. The cavities of th peritoneum, pleura, pericardium, tunica vaginalis
testis, arachnoid space, aqueous chambers of the eye (Schwalbe), and the
labyrinth of the ear, are true lymph-cavities, and the fluid they contain is to
be regarded as lymph.

(6.) Free open pores have been observed on some mucous membranes, which are
regarded as the origin of lymphatics, e.g., in the bronchi (Klein) — the nasal
mucous membrane (Hjalmar-Heiberg), in the trachea and larynx.

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. 158).]

197. The Lymph-Glands.

The so-called lymphatic glands belong to the lymph apparatus.
They are incorrectly termed glands, as they are much branched
lacunar labyrinthine spaces merely composed of adenoid tissue, and
intercalated in the course of the lymphatic vessels.

There are simple and compound lymph-glands.

(1.) The simple lymph-glands, 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. 161, A), i.e., of a very delicate net-work of fine reticular fibres with
nuclei at their points of intersection, and in the spaces of the mesh-work lie the
lymph and the lymph-corpuscles. Near the surface, the tissue is somewhat denser,
where it forms a capsule, 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

Fig. 161.

Two lymph-follicles — A, a small follicle highly magnified, showing the adenoid
reticulum ; B, a follicle less highly magnified, showing injected blood-vessels.

close net-work. 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 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 (Briicke) whose juices and lymph-corpuscles can pass into the nearest
lymphatic. The follicles are surrounded by a net-work of blood-vessels which

LYMPHATIC GLANDS.

407

sends loops of capillaries into their interior (Fig. 161, 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, 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 siibseqiiently (Ph. Stohr).

(2.) The compound lymph-glands — the so-called 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. 162, c), which con-
tains numerous non-striped muscular fibres (0. Heyf elder). From its inner surface,
numerous septa and trabeculaj (tr) pass into the interior of the gland, so that the
gland-substance is divided into a large number of compartments. These com-
partments 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 elongated
and irregular form. [On making a section of a lymph-gland we can readily dis-
tinguish the cortical from the medullary portion of the gland.] All the compart-
ments are of equal dignity, and they all communicate with each other by means
of openings, so that the septa bound a rich net- work of spaces within the gland,
which communicate on all sides with each other.

.z.

Fig. 162.

Diagrammatic section of a lymphatic gland — a, I, afferent ; e, I, efferent lymphatics ;
C, cortical substance; M, reticular cords of medulla; I, s, lymph-sinus; r,
capsule, with trabeculse, tr.

These spaces are traversed by the follicular threads (Fig. 163, /, /). These repre-
sent the contents of the spaces, but they are smaller than the spaces in which they
lie, and do not come into contact anywhere with the walls of the spaces. If we
imagine the spaces to be injected 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 (b) 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
(o, o) covered by the cells of the adenoid reticulum, in such a way as to leave
free communications through the narrow meshes.

408

LYMPHATIC GLAND.

Between the surface of the follieular 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 (v. Reckliughausen).

Fig. 163.

Part of a lymphatic gland— A, Vas afferens ; B, B, lymph-spaces within the gland;
a, a, septa or trabeculse seen on edge ; /,/, follieular strand from the medulla;
x, x, its adenoid reticulum ; b, its blood-vessels ; o, o, narrow meshed part
limiting the follieular strands from the lymph-space.

The vasa affcrentia (Fig. 1C2, a, 0, 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 (C) of the gland. The vasa e/erentia, 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, I). 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 effei'ent 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 (Briicke). The lymph-cor-
puscles lying within the follieular threads, pass through the narrow meshes (0)

PROPERTIES OF CHYLE AND LYMPH. 409

into the lymph-paths. The formation of lymph-corpuscles occurs either 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 capsule contracts energetically, it
must compress the gland like a sponge, and the direction in which the fluid moves
is regulated by the position and arrangement of the valves.

The researches of Teichmaun, His, Frey, Briicke, and v. Recklinghausen have
chiefly contributed to the elucidation of the morphological and physiological
relations of the lymph-glands.

In addition to the constituents of lymph, the following chemical substances
have been found in lymphatic glands : — Leucin (Frerichs and Stildeler) and
Xanthin.

198. Properties of Chyle and Lymph.

(1.) Both fluids are albuminous, colourless, clear juices, containing
lymph-corpuscles (§ 9), which are identical with the colourless blood-
corpuscles. In some places, e.g., in the lymphatics of the spleen, especially
in starving animals (Nasse), 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. They also pass out of the blood-vessels and wander into the
lymphatics, and as coloured blood-corpuscles have also been seen to pass
out of the blood-vessels (Strieker, J. Arnold), this explains the occa-
sional presence of these corpuscles in some lymphatics ; but when the
pressure within the veins is high near the orifice of the thoracic duct,
red blood-corpuscles may pass into the thoracic duct. In addition, the
chyle contains numerous fatty granules each surrounded with an
albuminous envelope. [Thus the chyle, in addition to the constituents
of the lymph, contains, especially during digestion, a very large amount
of fat in the form of the finely emulsion ised fat of the food, which
gives it its characteristic white or milky appearance. During hunger,
the fluid in the lacteals resembles ordinary lymph. The fine fat
granules constitute the so-called " molecular basis " of the chyle.]

Composition of Lymph. — The lymph consists of a plasma with lymph-
coi'puscles suspended in it. The corpuscles — for the most part investi-
gated in the form of pus-cells — consist of swollen-up proteid and soluble
paraglolulin, together with lecithin, cerebrin, cholesterin, and fat, while their
nuclei yield nuclein. Nuclein contains P, and is prepared by the
artificial digestion of pus, as it alone remains undigested ; it is soluble
in alkalies, and is precipitated from this solution by acids. It gives a
feeble xanthoproteic reaction. When subjected to the prolonged action
of alkalies and acids, it yields substances allied to albumin and
syntonin. Miescher found glycogen in the lymph-corpuscles of serous
fluids. The lymph-plasma contains the three fibrin-factors (§ 29),

410 COMPOSITION OF CHYLE.

derived very probably from the breaking up of lymph-corpuscles. 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-clot," which contains most of the lymph-corpuscles.
The exuded fluid or lymph-serum contains alkali-albuminate (precipitated
by acids), serum-albumin (coagulated by heat), a,nd.paraglobuUn — the two
latter occurring in the same proportion as in blood-serum; 37 per cent.
of the coagulable proteids is paraglobulin (Salvioli). Peptone has been
found in chyle (? and perhaps also in lymph) ; also urea (Wurtz), leucin
and sugar.

(2.) 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 difficulty 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 diges-
tion, on the contrary, diminishes when chyle mixes with lymph.
After a diet rich in fatty matters, the chyle contains innumerable fatty
granules (2-4 /m. in size). [This is the so-called "molecular basis"
of the chyle.] The amount of fibrin-factors increases with the
increase of lymph-corpuscles, as they are formed from the breaking-up
of the lymph-corpuscles. Groh6 found a diastatic ferment in chyle,
which was probably absorbed from the intestine, occasionally sugar, to
2 per cent. (Colin), and after much starchy food, lactates have been
found (Lehmann).

The Chyle of a person who was executed contained :—

Water, . . . 90 '5 per cent.
Solids, . . . 9 '5 ,,

Fibrin, . . . trace.

Albumin, . . . 7*1

Fats, . 0-9

Extractives, 1 '0

Salts, . 0-4

Cl. Schmidt found the following inorganic substances in 1000 parts of chyle
(horse): —

Sodic Chloride, .... . 5'84

Soda, 1'17

Potash 0-13

Sulphuric Acid, 0'05

Phosphoric ,, ...... 0'05

Calcic Phosphate, .... 0'20

Magnesic ,, 0*05

Iron, trace.

COMPOSITION OF LYMPH.

411

(3.) The Lymph obtained from the beginning of the lymphatic
system also 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 8,200 lymph-
corpuscles in 1 cubic centimetre of the lymph of a dog.

Hensen and Dahnhardt obtained pure lymph in considerable quantity
from a lymphatic fistula, in the leg of a man. It had an alkaline
reaction, and a saline taste. It had the following composition, which
may be compared with the composition of serous transudations : —

Pure Lymph
(Hensen & Dahnhardt).

Cerefcrospinal Fluid
(Hoppe-Seyler).

Pericardial Fluid
(v. Gorup-Besanez).

tVater, . . . 98 '63

98-74

95-51

Solids, . . .1-37

1-25

4-48

Fibrin, . . . O'll

...

0-08

ybumin, . . 0'14

0-16

2-46

\lkali-albuminate, . 0'09

...

...

Extractives, .

...

1-26

Jrea, Leucin, . 1*05

...

Salts, . . . 0-88

The cerebrospinal fluid,

JO vol. per cent, of ab-

and abdominal - lymph

sorbed C02, 50°/0 of which

contain a kind of sugar

:ould be pumped out, and

(without the property of

20% by the addition of an

rotating polarised light —

icid.

Hoppe-Seyler).

100 parts of the Ash of lymph contained the following substances:—

Sodium chloride,
Soda, • .
Potash, .
Lime,

Magnesia,

74-48

10-36

3-26

0'9S

0-27

Phosphoric acid,
Sulphuric acid,
Carbonic acid,
Iron oxide,

1-09
1-28
8-21
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 icater in the lymph rises and falls with that of the blood.
Dog's lymph contains much C02 — 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 0 and 1*2 vols. per cent. N (Ludwig,
Hammersten).

412 QUANTITY OF LYMPH AND CHYLE.

The observation that when lymph is collected from large vessels and. exposed to
the air it becomes red (Funke) is as yet unexplained ; but it is certainly not due to
the formation of coloured corpuscles from colourless ones, owing to contact with
the 0 of the air.

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 24 hours is equal to the amount of
the blood (Bidder and C. Schmidt), 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 24 hours from a lymphatic fistula in the arm of a woman,
by Gubler and Quevenne; 70 to 100 grms. were collected in 1^ 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 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 centi-
metres lymph from a fasting dog, Avhereby 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 versa. These con-
ditions are :—

(«. ) 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 versA (Ludwig, Tomsa). This however is doubtful, as has been shown by
Paschutin and Emminghaus. [In order to increase the amount of lymph depend-
ing upon pressure within the vessels, what must happen is increased pressure
within the capillaries and veins].

(b.) Ligature or obstruction of the efferent reins greatly increases the amount of
lymph which flows from the corresponding parts (Bidder, Emminghaus). It may
be doubled in amount (Weiss). Tight bandages cause a swelling of the parts ou
the peripheral side of the bandage, owing to a copious effusion of lymph into the
tissue (congestive oedema).

(c.) An increased supply of arterial blood acts in the same way, but to a less
degree. Paralysis of the vaso-motor nerves (Ludwig), or stimulation of vaso-
dilator fibres (Gianuzzi), 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 (W. Krause).

ORIGIN OF LYMPH. 413

(4.) When the total amount of the blood is increased, by the injec-
tion of blood, serum, or milk into the arteries, much fluid passes into
the tissues and increases the formation of lymph.

(5.) The formation of lymph still goes on for a 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 lymphatics
(Genersich). 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, e.g., connective-tissues, con-
tain more fluid after death than during life, whilst 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
(Lesser, Paschutin), and so is the amount of solids in the lymph. A
large amount of lymph collects in the lymph-sacs [especially the sub-
lingual] of frogs poisoned with curara, which is partly explained by
the fact that the lymph-hearts are paralysed by curara (Bidder). The
amount of lymph is also increased in inflamed parts (Lassar).

200. Origin of Lymph.

(1.) Origin of the Lymph-Plasma. — The lymph-plasma may be re-
garded as fluid which has been pressed through the walls of the blood-
vessels by the blood-pressure, i.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 fibrin-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 transuded 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 are in action, not only is the lymph poured out
more rapidly, but more lymph is formed. The tendons and fascia? of
the muscles of the skeleton which are provided with numerous small
stomata, absorb the lymph from the muscles. By the alternate contrac-
tion and relaxation of these fibrous structures, they act like suction-
pumps, whereby the lymphatics are alternately filled, and emptied, while

414 ORIGIN OF THE LYMPH-CORPUSCLES.

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, and Genersich).

(2.) The Origin of the Lymph-Corpuscles varies — 1. A very con-
siderable number of the lymph-corpuscles are derived from the lymphatic
glands; they are washed out of these glands into the vas eflerens
by the lymph-stream, hence, the lymph always contains more cor-
puscles 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. A second source is 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, the spleen. In these cases, the cells reach
the origin of the lymph-stream by their own amoeboid movements.
3. As lymph-corpuscles are returned to the blood-stream, Avhere they
appear as colourless blood-corpuscles, so they again pass out of the
Uood-capillaries into the tissues, partly owing to their amoeboid move-
ments (Cohnheim), and they are partly expelled by the blood-pressure
(Heriug). In rare cases, lymph-corpuscles wander from lymphatic
spaces back again into the blood-vessels (v. Recklinghausen).

Fine particles of cinnabar or milk-globules introduced into the blood soon pass
into the lymphatics, and the vaso-motor nerves do not affect the process. The
extrusion of particles is greater during venous congestion, just as with diapedesis
(p. 189), than when the circulation is undisturbed; inflammatory affections of the
vascular wall also favour their passage. The vessels of the portal system are
especially pervious (Riitiineyer).

(4.) By increase of the lymph-corpuscles by division, and also by
proliferation of the fixed connective-tissue corpuscles (His). This process
certainly occurs during inflammation of many organs. This has been
proved for the excised cornea kept in a moist chamber (v. Reckling-
hauseu, Hoffmann) ; the nuclei of the cornea-corpuscles proliferate also
(Strieker, Norris). That the connective-tissue corpuscles proliferate is
shown by the enormous production of lymph-corpuscles in acute in-
flammations (with the formation of pus) — e.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 lymphatics arise. The occurrence of the fibrin-factors in
the lymph — formed as they are from the breaking-up of lymph-
corpuscles — would seem to indicate this. In inflammation of con-
nective-tissue, in addition to the formation of numerous new lymph-

MOVEMENT OF CHYLE AND LYMPH. 415

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 dissolved 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 ladeals receive the first impulse towards the
movements of their contents — the chyle — from the contraction of the
muscular fibres of the mill (p. 390). When these contract and shorten, the
axial lacteal is compressed, and its contents forced in a centripetal direc-
tion towards the large lymphatic trunks. When the villi relax the
numerous valves prevent the return of the chyle into the villi.
(i) Within those lymphatics which take the form of peri-vascular
spaces, every time the contained Hood-vessel is dilated the surrounding
lymph will be pressed onwards, (c) In the case of the pleural
lymphatics with open mouths, every inspiratory movement acts like a
suction-pump upon the lymph (Dybkowsky), and the same is the case
with the openings (stomata) of the lymphatics on the abdominal side
of the diaphragm (Ludwig, Schweigger-Seidel). (d) In the case of
those vessels which begin by means of fine juice-canals, the movement
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 rootlets of the lymphatics.

[In some organs .peculiar pumping arrangements are brought into
action. As already mentioned, the abdominal surface of the central
tendon of the diaphragm is provided with stomata, or open communi-
cations between the peritoneal cavity and the lymphatics in the sub-
stance of the tendon, v. Eecklinghausen found that milk put upon
the peritoneal surface of the central tendon showed little eddies caused
by the milk-globules passing through the stomata and entering the
lymphatics. The central tendon consists of two layers of fibrous tissue
arranged in different directions. 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 (Fig. 164, Ji) through the stomata].

416

MOVEMENT OP THE LYMPH.

[Lttdwig'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 a ring, and hang it up with the head downwards;

Section of central tendon of diaphragm — The injected lymph spaces, h and h, are
black. At /the walls of the space are collapsed (Brunton, after Ludwig and
Schweigger-Seidel).

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.]

[The same kind of pumping mechanism exists over the costal pleura
(p. 224).]

[The fascia covering the muscles is another similar mechanism. The
fascia consists of two layers of fibrous tissue, with intervening
lymphatics (Fig. 165). When a muscle contracts, lymph is forced out

Fig. 165.

Injected lymph spaces from the fascia lata of the dog — The injected spaces are
black in the figure (Brunton, after Ludwig and Schweigger-Seidel).

from between the layers of the fascia, while when it relaxes, the
lymph from the 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.]

(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

MOVEMENT OF THE LYMPH. 417

the lymphatic wall passed in a centripetal direction. The numerous
valves prevent any reflux. The contraction of the surrounding muscles,
and every pressure upon the vessels and the tissues aid the current
(Ludwig, Noll). If the outflow of blood from the veins is interfered
with, lymph flows copiously from the corresponding tissues (Nasse,
Tomsa). [If a cannula be tied in a lymphatic of a dog, a few drops
of lymph flow out at long intervals. But if even passive movements
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, to a certain extent,
compensated by the non-striped muscle which exists in the capsule and
trabeculcB of the glands. When they contract, they force on the
lymph, Avhile 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
leukaemia.]

(4.) As the lymph-vessels gradually join and form larger vessels,
and finally form one trunk, the transverse section, or sectional area,
diminishes, so that the velocity of the current and the pressure are
increased. Nevertheless, the velocity is always small ; it varied from
230-300 millimetres per minute in the large lymphatic in the neck of
a horse (Weiss), a fact which enables us to conclude that the move-
ment must be very slow in the small vessels. The lateral pressure at
the same place, was 10-20 mm., and in the dog 5-10 mm. of a weak
solution of soda (Weiss, Noll), although it was found to be 12 mm.
Hg. in the thoracic duct of a horse (Weiss).

(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 also of
the lymph towards the heart, whereby the tension in the thoracic duct
may even become negative (Bidder). [The diastolic suction of the heart
by diminishing the pressure in the veins, also favours the inflow of
lymph into the thorax.]

(G.) Lymph -hearts exist in certain cold-blooded animals (Panizza, Job.
M tiller). The frog has two axillary hearts (above the shoulder near the vertebral
column), and two sacral hearts, one on each side of the coccyx near the anus.
They beat, but not synchronously, about GO times per minute, and contain 10 cubic
centimetres of lymph. They have transversely striped muscular iibres in their
walls, and are also provided with nerve ganglia (Waldeyer). The posterior pair
pump the lymph into the branch of the Vena iliaca communicans, and the anterior
pair into the Vena subscapularis. Their pulsation depends partly, but not

27

418 ABSORPTION OF PARENCHYMATOUS EFFUSIONS.

exclusively, upon the spinal cord, for if the cord be rapidly destroyed, they may
cease to pulsate (Volkmann), but not unfrequently they continue to pulsate after
removal of the cord (Valentin, Luchsinger). A second source of their pulsatile
movements is to be sought for in Waldeyer's ganglia. Stimulation of the skin,
intestine, or blood-heart influences them reflexly — partly accelerating and partly
retarding them. If the coccygeal nerve, which connects the sacral hearts to
the spinal cord, be divided, these effects do not occur (v. Wittich). Strychnia
accelerates their movements (Scherhej). Antiar paralyses the lymph-heart and
the blood-heart at the same time (Vintschgau), while curara paralyses the former
alone (Bidder).

In other amphibians, there are two lymph-hearts, in the ostrich and cassowary
and some swimming birds (Panizza), and in the embryo chick (A. Budge). They
occur in some fishes — e.g., near the caudal vein of the eel.

(7.) The nervoiis 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. Farther,
Kiihne observed that the cornea-corpuscles contracted when the corneal
nerves were stimulated. Goltz also observed that when a dilute solu-
tion of common salt was injected under the skin of a frog, it was
rapidly absorbed, but if the central nervous system was destroyed it
was not absorbed.

If inflammation be produced in the posterior extremities of a dog, and if the
sciatic nerve be divided on one side, oedema and a simultaneous increase of the
lymph-stream occur on that side (Jankowski).

Ligatvire 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 (Lautenbach).

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 (Magendie); 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 parenchymatous juices takes place (Emmert,
Henle, v. Dusch), 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 many drugs is now 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 mouth, and amygdalin be injected into the veins of an animal, hydro-

(EDEMA AND DROPSY. 419

cyanic 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 formation
of hydrocyanic acid, as the amygdalin is rapidly absorbed from the intestinal
canal. The amygdalin, a glucoside (CgoH^NOn), is acted upon by fresh
emulsin like a ferment ; it takes up 2 (H2 O) and yields hydrocyanic acid (C H N),
-f-oil of bitter almonds (C7H60), + sugar 2 (C6H1206) — (Cl. Bernard).

When serum is injected subcutaneously, it is rapidly absorbed; it is decomposed
within the blood-stream, and increases the amount of urea (p. 62, 2). Albuminous
solutions, oil, peptones and sugars are also absorbed (Eichhorst).

203. Congestion of Lymph and Serous Effusions.

(Edema and Dropsy.

[As aptly illustrated by Lauder Brunton, the lymph-spaces may be represented
by cisterns, each of which is provided with .supply pipes — the arteries and
capillaries; while there are two exit pipes — the veins and lymphatics. In health,
the balance between the inflow and outflow is such, that the spaces are merely
moistened with fluid. When a cannula is placed in a lymphatic vessel in a dog,
only a few drops of lymph flow out at long intervals. Emminghaus found that, if
the veins of the limb be ligatured, the lymph flows much more quickly. This is
in part due to the increased transudation of fluid from the small blood-vessels, but
as Brunton suggests, it may also be due to fluid passing away by the lymphatics
when it can 110 longer be carried away by the veins. We cannot say what is the
relative share of the veins and lymphatics, nor in the above experiment do we
know how much is due to increased transudation or diminished absorption.
When there is an undue accumulation of fluid in the lymph-spaces, we have the
condition termed dropsy.'}

If the efferent veins and lymphatics of an oi'gan be ligatured, or if resistance be
offered to the outflow of their contents, congestion and a copious transudation of
lymph into the tissues take place. These are most marked in the skin and sub-
cutaneous 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 (edema when the fluid is watery.

Under similar circumstances, lymph is effused into the serous cavities. 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 considerable percentage of albumin is neces-
sary. When the pressure within the serous cavity rises above that in the small
blood-vessels, water may pass into the blood. These sero-puruleiit effusions not
unfrequeutly undergo changes, and yield decomposition products, such as leucin,
tyrosin, xanthin, kreatin, kreatinin (?), uric acid (?), urea. Endothelium from the
serous cavity (Quiucke), sugar in pleuritic effusions (Eichhorst), and in cedemas
with little albumin (Rosenbach), 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 from pressure upon the lymphatics,
but also from inflammation and thrombosis of the lymphatics themselves, in which
cases not unf requently 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

420 CONDITIONS FAVOURING TRANSLATION.

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, in which case the effusion
usually contains little albumin, and few lymph-corpuscles, while the coloured-cor-
puscles 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 cedema. 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 weak-
ness of the vaso-motor nerves, slight obstruction is sufficient to produce cedema
(Lander Bronton).] When the leg veins are occluded with an injection of gypsum,
cedema occurs (Sotnischewsky). (2) Some unknown physical changes occur in
the protoplasm of the endothelium of the capillaries and blood-vessels, which
favour the transudation of albumin, haemoglobin, and even blood-corpuscles.
This occurs when abnormal substances accumulate iu the blood— e. p., dissolved
haemoglobin — 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 permea-
bility of the vascular wall (Cohuheim). Watery lymphatic effusions from watery-
blood — "cachectic cedema" — occur in feeble and badly nourished individuals.
[One of the commonest forms of dropsy is the slight cedema of the legs in
anamic persons, in whom the heart and lungs are healthy. Many factors are
involved — the watery condition of the blood, the condition of nutrition of the
capillaries, and probably a tendency to vaso-motor paresis (Brunton).]

[ (4) Ostroumoff found that stimulation of the lingual nerve not only causes the
blood-vessels of the tongue to dilate, but the corresponding side of the tongue
becomes cedematous. If a solution of dilute hydrochloric acid or quinine (p. 287)
be injected into the duct of the submaxillary 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
points to some action of atropin on the blood-vessels which has hitherto been
entirely overlooked.]

204. Comparative Physiology.

In the frog, large lymph-sacs, lined with endothelium, exist under the skin,
\vhilelarge lymph-sacs lie in relation with the vertebral column— one on each side

COMPARATIVE AND HISTORICAL. 421

—separated by a thin membrane, perforated with stomata, from the abdominal
cavity. This is the cystcrna li/mp/iatica magnet, of Panizza. Some amphibians and
many reptiles have large lymph-spaces under the skin, which occupy the whole of
the dorsal region of the body. All reptiles and the tailed amphibians have large
elongated reservoirs for lymph along the course of the aorta. The lymph apparatus
of the tortoise (Fig. 159) 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 oesophagus. 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 (p. 417).

In carnivora, the lymph-glands of the mesentery are united into one large com-
pact 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 Erasis-
tratus had seen the mesenteric glands, yet Aselli (1662) was the first who accur-
ately described the lacteals of the mesentery with their valves. Pecquet (1648)
discovered the receptaculum chyli ; Rudbeck and Thorn. 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) ; Sommering
observed the separation of fibrin when lymph coagulated; Reuss and Ernmert
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 observers noticed that the white colour of chyle was
due to the presence of small fatty granules.

Physiology of Animal Heat,

206. Sources of Heat.

Sources. — 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 the amount of energy liberated
(see Introduction).

The energy of the food-stuffs 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 liberated only
in the form of heat. As
a matter of fact, how-
ever, mechanical energy
g and electrical energy are
developed from the poten-
tial 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
instrument enables us to
transform the potential
energy of the food into
heat, and, at the same
time, to measure the num-
ber of heat-units pro-
duced.

Favre and Silbcrmann used a

water-calorimeter (Fig. 166).

The substance to be burned
is placed in a large cylindrical
combustion chamber (K), sus-
pended in a large cylindrical vessel (L) filled with water (w), so that the combustion
chamber is completely^surrouuded by the water. Three tubes open into the upper

Eig. 166.
Water calorimeter of Favre and Silbermann.

C ALORIMETR Y. 423

part of the chamber ; one of them (0) supplies the air which is necessary for combus-
tion, it reaches almost to the bottom of the chamber ; the second tube (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 see into the
interior of the chamber, and to observe the process of combustion at c. 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 (e, e) with many twists on it,
passes from the upper part of the chamber through the water, and finally opens at
fj. The gaseous products of combustion pass out through this tube, and in doing
so help to heat the water. The 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-conductor of heat, and
this again is placed in a large vessel filled with water (W). This is to prevent
any heat reaching the inner cylinder from without. A weighed quantity of the
substance (c) to be investigated, is placed in the combustion chamber. When
combustion 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 temperature 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 acting upon the inner ice. The heat 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 to 1 grm. of water at 0°C.

Just as in a calorimeter, although much more slowly, the food-stuffs
within our body are burned up, oxygen being supplied, and thus
potential energy is transformed into kinetic energy, which, in the case
of a person at rest — i.e., when the muscles are inactive, almost completely
appears in the form of heat (see Introduction).

Favre, Silbermann, Frankland, Rechenberg, B. Danilewsky, and others have
made calorimetric experiments on the heat produced by food. Thus, there are
produced by

1 grm. Albumin 4,998 heat-uuits f Completely dried and completely
1 ,, Ox-flesh 5,103 ,, t burned.

( When burned to urea (i.e., the heat-units

1 grm. Albumin 4,263 ,, J corresponding to the urea (1 grm. =2,206

1 ,, Ox-flesh 4,368 ,, '. calories) is deducted from those of the

albumin and flesh.

1 gramme of the following dry substances yields heat-units :—

Casein, .... 5,785

Potatoes, . . . 3,752

Milk, 5,093

Bread, . . . . 3,984

Rice, 3,813

Starch, .... 4,479

Yelk of egg, . . 6,460
Alcohol, . . . .8,958

Stearin, .... 9,036

Palmitin, . . . 8,883

Olein, .... 8,958

Glycerin, . . . 4,179

Leucin, .... 6,141

Creatin, . . . 4,118

Grape-sugar, . . 3,939

Cane-sugar, . . 4,173

Milk-sugar, . . 4,162

Vegetable fibrin, . 6,231

Glutin, . . . . 6,141

Legumin, . . . 5,573

Blood fibrin, . . 5,709

Peptone, . . . 4,914

Glutin, .... 5,493

Chondrin, . . . 4,909
Flesh extract

(Liebig), . . 3,206

424 CHEMICAL SOURCES OF HEAT.

When wo 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 many heat-units are formed in the body by
oxidation — i.e., provided the substance is completely oxidised.

Sources of Heat. — The individual sources of heat are to be found in
the following : —

(1.) In the transformation of the chemical constituents of the food,
endowed with a large amount of potential energy, into such substances
as have little or no energy.

The organic substances used as food consist of C, H, 0, N, so that there
takes place — (a) Combustion of C into C02, of H into H20, whereby heat
is produced; 1 grm. C burned to produce C02 yields 8,080 heat-units,
while 1 grm. H oxidised to H20 yields 34,460 heat-units. The 0 neces-
sary for these processes is absorbed during respiration, so that, to a cer-
tain extent at least, the amount of heat produced may be estimated from
the amount of 0 consumed. The same consumption of 0 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 0 consumed. The
cold-blooded animals, which consume little 0 have a low temperature ;
amongst warm-blooded animals, 1 kilo, of a living rabbit takes up
within an hour 0'914 grm. 0, and its body is heated to a mean of
38°C. 1 kilo, of a living fowl uses T186 grms. 0, and gives a mean
temperature of 43'9°C. (Eegnault and Reiset). 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 combustion of inorganic
substances in the body, such as the sulphur into sulphuric acid, the
phosphorus into phosphoric acid, is another, although very small, source
of heat.

(ft.) In addition to the processes of combustion or oxidation, all
those chemical processes in our body, by which the amount of the avail-
able 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 (Andrews). The nature of the base
determines the amount of heat prodiiced, while the nature of the acid is without
effect. Only in those cases where the acid, e.g., C02, is unable to set aside the
alkaline reaction, the amount of heat produced is less. The formation of com-
pounds of chlorine (e.g., in the stomach) produces heat.

PHYSICAL SOURCES OF HEAT. 425

(/3) When a neutral salt is changed into a basic one (Andrews). In the blood, the
sulphuric and phosphoric acids derived from the combustion of S and P are united
with the alkalies of the blood to form basic salts. The decomposition of the car-
bonates of the blood by lactic and phosphoric acids forms a double source of heat,
on the one hand, by the formation of a new salt, as well as by the liberation
of COo, which is partly absorbed by the blood.

(y) The combination of hemoglobin with 0 (§ 36).

In connection with those chemical processes, whereby the heat of
the body is produced, heat-absorbing intermediate compounds are
not unfrequently formed. Thus, in 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 transformation of tJie kinetic mechanical energy of internal
organs, when the work done is not transferred outside the body, pro-
duces heat. Thus the whole of the kinetic energy of the heart is
changed into heat, owing to the obstructions which are opposed to the
blood-stream. 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 trans-
ferred to surrounding bodies by the cardiac impulse and the superficial pulse-beats,
but this is infinitesimally 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 24 hours (§ 93), which is sufficient to raise the temperature of a
person of medium size, 2°C. In former times, Boerhave and others thought that
the heat of the body was chiefly due to the friction of the blood within the
vessels.

(/>) When, owing to muscular activity, the body produces work which
is transferred 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.

426 HOMOIOTHERMAL AND POIKILOTHERMAL ANIMALS.

(rf) Other processes are the formation of heat from the absorption of C02
(Henry), by the concentration of water as it passes through membranes (Regnault
and Pouillet), in imbibition (Matteucci, 1834), formation of solids— e.g., of chalk
in the bones. After death, and in some pathological processes during life, the
coagulation of blood (Valentin, Schiffer), 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 animals 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 in a 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 re-
mained ten minutes in an oven containing very dry hot air, and yet the tempera-
ture 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-electric needles), when the arm had been one hour in ice, 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 or rapidly supplied to the body, so as
to produce rapid variation of the temperature, life is endangered.

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, e.g., frogs (Rana Esculenta), which were placed in air and water
of varying temperatures. The frogs were fixed to an iron support, and
immersed up to the mouth. The temperature was measured by means
of a thermometer introduced through the mouth into the stomach.

THERMOMETRY.

427

In Water.

In

Temperature of the
Water.

Temperature of Frog's
Stomach.

Temperature of the
Air.

41'0°C.

38 0° C.

40-4° C.

35-2

34-3

35-8

30-0

29-6

27-4

23-0

22-6

198

20-6

20-7

16-4

11-5

12-9

14-7

5-9

8-0

6-2

2-8

5-3

5-9

Temperature of Frog's
Stomach.

31 -7° C.

24-2

19-7

15-6

14-6

10-2

7-6

8-6

Temperature of different Animals.— Birds— Gull, 37-8°; swallow, 44-03°.

Mammals — Dolphin, 35 '5°; mouse, 41 '1°. Reptiles — Snakes, 10°-12°, but higher
when incubating. Amphibians and fishes — 0'5°-3° above the temperature of the
surroundings. Arthropoda — 0'l0-5'8° 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°; echino-
derms, 0'40° ; medusa, 0'27° ; polyps, 0'21°C.

208. Methods of Estimating Temperature-

Thermometry.

Thermometry. — 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 (Galileo, 1603). — Sanctorius made the first ther-
mometric observations on man (1626). Celsius (1701-1744) divided his ther-
mometer into 100 parts, and each part was again divided into 10 parts, so
that roCC. could be easily read off. All thermometers which have been used for
a long time give too high readings (Bellani), hence they should be compared, from
time to time, with a normal thermometer. When taking the temperature, the
bulbs ought to be surrounded for 15 minutes, and during the last 5 minutes the
mercury column ought not to vary. A very sensitive thermometer will indicate
the temperature after 7 seconds if the urine-stream be directed upon its bulb
(Oertmann). Minimal and maximal thermometers are often of use to the
physician.

Walferdin's metastatic thermometer (Fig. 167) 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., it
is then suddenly cooled, and shaken at the same time, so that the thread of mercury
is thereby suddenly broken above 40°. The tube is so narrow that 1°C. is equal to
about 10 centimetres of the length of the tube, so that i^°C. is still 1 millimetre
in length. The scale is divided empirically, but the value of the divisions must be
compared with a normal thermometer.

Kroneclcer and Meyer used veiy small maximal "outflow thermometers :> (Dulong
and Petit), and caused them to pass through the intestinal canal, or through large Fig. 167.
blood-vessels. The mercury flows out of the short open tube, and of course more Walferdin's
flows out the higher the temperature. After these small bulbs have passed Metastatic
through the animal, a comparison is instituted with a normal thermometer to Thermo-
determine at what temperature the mercury reaches the free margin of the tube. meter.

428

THERMO-ELECTRIC MEASUREMENT OF HEAT.

in

Fig. 168.
Scheme of thermo-electric arrangements for estimating the temperature.

B. Thermo-electric Method. — This method enables us to determine the
temperature accurately and rapidly (Fig. 168, I). The thermo-electric galvanometer
of MeissnerF and | Meyer stein consists of a circular magnet (m), suspended by a
thread of silk (c), to which a small mirror (S) is attached. A large stationary
bar magnet (M) is placed near the magnet (m), so that the north poles (n 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 minimal action of M.

A thick copper -wire (b, b) is coiled several times round m (although in the Fig.
it 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 and German silver,
the two similar free elements being united by a wire (6j), 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

THERMO-ELECTRIC NEEDLES. 420

in the mirror. When the magnet, and with it the mirror, swing out of the mag-
netic 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 direc-
tion of the current in the conducting wire, then the north pole of the magnet goes
to the north (Ampere). The tangent of the angle 0, through which the freely
moveable 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

p

magnetic energy I), I.e., tang. 0 = fy If G is to remain the same, and the tang. <£ to

be as large as possible, 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 T) — Tm, so that D can be diminished 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 galvan-
ometer; (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 sus-
pended 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 a current of electricity in this
closed circuit, 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 arc 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 deter-
mine 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. — aa can be
determined by the thermometers. 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 1|o°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 intro-
duced 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

430 TEMPERATURE TOPOGRAPHY.

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 1C antimony-bismuth couples,
he could detect an increase of 40100°C. Schiffer prepared a simple thermopile
(IV) by soldering together alternately four pairs of wires of iron (/) and German
silver (a). These are placed 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 23 seconds, must exercise a very consider-
able 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: —

1. Temperature of the Skin. —

Middle of the sole of the foot, . 32-26°C. )

Near tendo achillis, . . 33-85 I J. Davy made these observations

Anterior surface of leg, . 33 '05 I directly after standing, while

Middle of calf, . . 33 '85 \ naked, with the temperature

Bend of knee, . . 35 "00 / of the room at 21 °C. Only the

Middle of upper arm, . . . 34'40 I under surface of the ther-
Inguinal fold, . . . 35'SO 1 mometer touched the skin.

Near cardiac impulse, . . 34 '40 J

In the closed axilla, 36'49 (mean of 505 individuals); — 36'5 to 37 '25 ( Wunderlich) ;

— 36'89°C (Liebermeister).

The temperature of the skin of the head is higher in the region of the forehead
and parietal region than in the occipital region; the left side is warmer than the
right (Maragliano). Dyspnoea increases the temperature of the skin (Heidenhain,
Friinkel).

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 begins 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. Temperature of the Cavities.—

Mouth under the tongue, . . . 37'19°C.

Rectum, ... 38 '01

Vagina, 38'30

(Uterine cavity somewhat warmer; cervical canal somewhat cooler.)
Urine, 37'03

The temperature falls in the stomach during digestion (p. 332).
Cold injections (11°C.) into the rectum rapidly lowe rthe 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: —

TEMPERATURE OF THE BLOOD AND TISSUES.

431

Blood of the right heart, .

left „
,, aorta,
,, hepatic veins,

,, superior vena cava,
,, inferior ,,

,, crural vein,

38-8

38 -6

38-7

39-7

36-78

38-11

37-20

Cl. Bernard.

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 of Malgaigne (1832), Berger, and
G. v. Liebig is disputed by others, who say that the left heart is slightly warmer
(Jacobson and Bernhardt) because the combustion processes are more active in
arterial blood, and heat is evolved during the formation of oxyhoemoglobin
(Gamgee). The blood in the veins is usually cooler than in the corresponding
arteries (Haller), 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 5 to
2°C. lower than the blood in the carotid (Colin); the crural vein f-l° cooler than in
the crural artery (Becquerel and Brechet). Superficial veins, more especially those
of the skin, give off much heat, and their blood is, therefore, somewhat cooler.
The ^oarmcst blood is that of the hepatic vein, 39-7°C. (Cl. Bernard), partly owing
to the great chemical changes which occur within the liver (p. 432), and partly
to its protected situation. By means of small outflow thermometers introduced
into the circulation, Kronecker and Meyer found the following temperatures in
three starving dogs:— Vena azygos, 37'7 (38'0) (39'0); right ventricle, 38 '3 (39-2)
(39'2); branch of the pulmonary artery, 38'4 (38'6) (40'2). At the same time, the
temperature in the stomach was 38 '6 (37 '3) (40 -0), and in the rectum, 39 -5 (39 '5)
(39*4); the maximum temperature in the last two dogs was 40'1 and 41 '2, hence
in the starving condition, the temperature of the stomach was less than the
tempei-ature of the blood in the pulmonary circulation.

4. Temperature of the Tissues. — The individual tissues are warmer:
(1) the greater the transformation of kinetic energy into heat3 i.e., the
greater the tissue metabolism; (2) the more blood they contain; (3)
and the more protected their situation. According to Heideuhaiu and
Korner, the cerebrum is the warmest organ in the body.

Berger measured the temperature of the tissues of a sheep, and found the
following:—

Subcutaneous tissue, . 37 "35

Brain, . . . 40 '25

Liver, . . . 41 -25

Lungs, . . . 4T40

While the temperature was in—
Rectum, . . . 40 '67
Eight heart, . 41 -60

Left heart, . 40 "90

Becquerel and Brechet found the temperature of the human subcutaneous tissue
to be 2'1°C. 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 temperature of the cornea partly depends on
that of the iris, and the more contracted the pupil is, it receives more heat from
the blood-vessels of the iris.

432 CONDITIONS INFLUENCING TEMPERATURE OF ORGANS.

210. Conditions influencing the Temperature

of Organs.

The temperature of the individual organs is by no means constant;
it is influenced by many conditions; amongst these are the following: —

(1.) The more heat that is produced independently within a part, the
higher is its temperature. As the amount of heat produced within a part
depends upon its metabolism, therefore, when the metabolism is in-
creased, 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 tempera-
ture of the venous blood flowing out of their veins. Ludwig found
that when he stimulated the chorda tympani, the secretion of the sub-
maxillary gland was l'5°C. warmer than the blood in the carotid, which
supplied the gland with blood. 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. 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, . 37'8°C. 1 After 4 days / Blood of right heart,
„ hepatic ,, .38*4 J starvation. \ 38 '8°.

(Hunger period.)

: 81 ! Begins of digestion.'

Temperature of portal vein, . 39 '7 ) Digestion most / Blood of right heart
,, hepatic, . 41 '3 \ active. \ during digestion, 39 -2°.

When a dog receives a moderate diet, the mean temperature in the stomach is
39°C., in the rectum, 39'5°C.; at the end of the first day of hunger, in the stomach,
387°, in the rectum, 39'3°; while after food, in both situations it is 40°.
Chemical or mechanical stimulation of the gastric mucous membrane, or even the
sight of food, has a similar action (Kronecker and Meyer).

(&) When the muscles contract they evolve heat (Bunsen, 1805).
Davy found that an active muscle became 0'7°C. warmer; while
Becquerel (1835), by means of a thermo-galvanometer, found that
human muscles, when kept contracted for five minutes, became 1°C.
warmer (see Physiology of Muscle).

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 H hours (Billroth). 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 tempera-

CONDITIONS INFLUENCING THE TEMPERATURE. 433

ture, one of the first points to ascertain is whether the circulation 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, I., 3). In the former
case, the temperature of the interior and rectum is increased; in the
latter, diminished.

That there are heat-regulating nerve-centres has not been definitely
proved; with regard to the influence of vaso-motor nerves see vol. ii.

(d) The temperature of the body rises during mental exertion. Davy
observed an increase of 0'3°C. after vigorous mental exertion.

Lombard observed that the temperature of the forehead rose 0'5°C. during
mental activity and emotional disturbances. The part of the forehead corre-
sponded to the posterior region of both upper frontal convolutions, to the anterior
central convolution, and (?) to the anterior part of the posterior central convolu-
tion. The temperature was higher on the left side.

(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 circulation. 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 iliac artery in a dog caused a fall of A°C. within 18 minutes; while the
removal of the ligature caused the temperature to rise rapidly to normal. Liga-
ture of the crural artery and vein in a dog causes a fall of several degrees (Landois).
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. Accelera-
tion 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 (Heidenhain). Hence it follows, that the greater the difference of the
temperature between peripheral and internal parts, the slower must be the
velocity of the circulation.

(3.) If the position of an organ be such, or if other conditions

28

434

ESTIMATION OF THE AMOUNT OF HEAT.

cause it to give off heat by conduction or radiation, then its tem-
perature falls.

A good example of this is the skin, which varies greatly in temperature accord-
ing to the temperature of the surrounding medium, whether it is covered or
uncovered, whether it is dry or moist with sweat (which abstracts heat when
it evaporates). When much cold food or drink 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 the Amount of Heat—

Calorimetry.

Calorimetry is the method of determining the amount of heat
possessed by any body, or what amount of heat it is capable of pro-
ducing. The unit of measurement is the "heat-unit," i.e., the amount
of heat (or potential energy) required to raise the temperature of 1
gramme of water, 1°C. (see Introduction).

Experiment has shown that equal quantities 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
temperature. 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 gramme) of a substance to a certain higher degree (e.g. ,
1°C.) is called "specific heat" (Wilkie, 1780). 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 (Crawford).

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 (waters 1) is:—

Human Blood = T02 (?)

Arterial „ = 1'031 (?)

Venous „ = 0'892 (?)

Cow's Milk = 0-992

Human Muscle = 0741

Ox = 0-787

Compact Bone = 0'3

Spongy ,, = 071

Fat-tissue = 0712

Striped Muscle = 0'825

Defibrinated Blood = 0'927

The specific heat of the human body, as a whole, is about that of
an equal volume of water.

Kopp has estimated the specific heat of solids and fluids by the following
method (Fig. 169) : — The solid to be investigated is broken in pieces about the size
of a pea, and 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. The test-tube con-
tarns 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

SPECIFIC HEAT OF THE BODY.

435

weight (1) of the empty glass, (2) after it is filled with the solid substance, (3)
after the fluid is added, so that we obtain the weight of the solid substance, m,
and that of the fluid,/. The test-tube and its contents are placed in a mercury
bath, BB, and this again in an oil lath, C C, and the whole is raised to a high
temperature. Into BB there is introduced a fine thermometer, T. When the
tube, A, has reached the necessary temperature (say 40°) it is rapidly placed in
the water of the accompanying calorimeter-box, D D. The water in this box,
which also contains a thermometer, D, is kept in motion until it has completely

BB

Fig. 169.
Kopp's apparatus for the estimation of specific heat.

absorbed all the heat given off by A. Let T represent the temperature to which
A and its contents were raised in the mercury bath, and Tj 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 a 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.

W = (*. m + w + <r. M) (T - T!).

The amount of heat, Wi, absorbed by the calorimeter is

W1=M (<!-0,

where M represents the amount of water in the calorimeter, and t the original
temperature of the water in the calorimeter, and tl the temperature to which it is
raised by placing A in it. If W and Wj are equal, then

Tke specific heat, s = M (*, -0 -

(T - TI)

m

If a fluid substance is placed in the test-tube, and its weight = m, and its
specific heat = s, the formula for the specific heat of the fluid to be investigated is

M

s =

-<)-w (T-T,)

m(T-Tj).

This is a subject which has been very slightly cultivated. J. Rosenthal in his
investigations used an ice-calorimeter (§ 206).

436 THERMAL CONDUCTIVITY OF THE TISSUES.

II. Calorimetry is more important for determining the ammint of
heat produced in a given time by the body as a whole, or by its in-
dividual parts.

Lavoisier and Laplace made the first calorimetric observations on animals in
1783, by means of an ice-calorimeter; a guinea-pig melted 13 ozs. of ice in 10
hours. Crawford, and afterwards Dulong and Despretz (1824), used Rumford's
water-calorimeter, which is similar to the one already described — viz., of Favre
and Silbermann. 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 GQ2 in the gases evolved is estimated chemically.

According to Despretz, a bitch forms 14,610 heat-units per hour —
i.e., 393,000 in 24 hours. Other things being equal, a man seven
times heavier than this would produce in 24 hours about 2,750,000
calories. Senator found that a dog weighing 6,330 grms. produced
15,370 calories, and excreted at the same time 3,67 grms. C(X. 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 6,000 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 24 hours.

212. Thermal Conductivity of Animal 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 impos-
sible. Investigations upon this subject, however, are few. Griess (1870)
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 interest-
ing to note how much better skin containing blood in its blood-vessels conducts
compared with bloodless skin. Hence little heat is given off from a bloodless
skin, while congested skin conducts and gives off much more heat.

VARIATIONS OF THE MEAN TEMPERATURE. 437

Like all other substances, the human body 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 (teudoii) is extended by
heat, while elastic tissue, the skin, like caoutchouc, are contracted (Lombard and
Walton).

213. Variations of the Mean Temperature.

(1.) General Climatic and Somatic Influences. — In the tropics, the
mean temperature of the body is about l°C. higher than in temperate
climates, where again it is several tenths of a degree warmer than in
cold climates (J. Davy) ; but this has recently been denied by Boileau
and Pinkerton. This 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 tempera-
ture 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
0'1-0'3°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, anaemic 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 H00, are C02 and urea, the amount
of heat formed must go pari pasu 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 (Lichtenfels and Frohlich).

Jiirgenseu 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 con-
stant for a considerable time, while during the last days it fell considerably.
Schmidt starved a cat— on the 15th day the temperature was 3S'6°; on the 16th,
38-3°; 17th, 37'64°; 18th, 35'S0; 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.) Influence of Age. — Age has a decided effect upon the tempera-
ture of the body. The extent of the general metabolism is in part an

438

VARIATIONS OF THE MEAN TEMPERATURE.

index of the heat of the body at different ages, but it is possible that
other unknown influences also are active.

Age.

Mean Temperature at
the Ordinary Ternp.

Normal Limits.

Where Measured.

Newly-born,

37'45°C.

37 -35-37 -55°C.

Rectum.

5-9 year,

37-72

37-87-37-62

Mouth and Rectum.

15-20 ,,

37-37

36-12-38-1

Axilla.

21-30 ,,

37-22

...

» »

25-30 „

36-91

>?

31-40 „

37-1

36-25-37-5

!>

41-50 ,,

36-87

...

) >

51-60 „

36-83

)>

80 „

37-46

...

Mouth.

Newly-born Animals exhibit peculiarities owing to the sudden
change in their conditions of existence. Immediately after birth, the
infant is O3° warmer than the vagina of the mother, viz., 37'86°. A
short time after birth, the temperature falls 0*9°, while 12-24 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 ;

Time.

Baren-
sprung.

J. Davy.

Hallmann.

Qierse.

Jurgensen.

Jiiger.

Morning, 5

36 '7

36-6

36-9

6

36-68

36-7

36-4

37-1

7

36-94*

36-63

36-98

36-7*

36-5*

37-5*

8

37-16*

36-80*

37-08*

36-8

36-7

37-4

9

36-89

36-9

36-8

37-5

10

37-26.

104 = 37-36

37-23

37-0

37-0

37-5

11

36-89

37-2

37-2

37-3

Mid-day, 12

36-87

37-3*

37-3*

37-5*

1

36-83

. .

37-21

37-13

37-3

37-3

37-4

2

37-05

37-50*

37-4

37-4

37-5

3

37-15*

...

37-43

37-4*

37-3*

37-5

4

37-17

37-4

37-3

37-5*

5

37-48

37-05*

54 = 37-31

37-43

37-5

37-5

37-5

6

• • •

6^ = 36-83

• • i

37-29

37-5

37-6

37-4

7

37-43

74 = 36-50*

37-31*

. . .

37-5*

37-6*

37-3

8

...

37-4

37-7

37-1*

9

37-02*

37-4

37-5

36-9

10

37-29

37-3

37-4

36-8

11

36-85

36-72

36-70

36-81

37-2

37-1

36-8

Night, 12

...

• . •

...

37-1

36-9

36-9

1

36-65

36-44

...

37-0

36-9

36-9

2

...

369

36-7

36-8

3

...

36-8

36-7

36-7

4

36-31

...

...

...

36-7

36-7

36-7

[* Indicates taking of food.]

VARIATIONS OF THE MEAN TEMPERATURE.

439

they become cold sooner, and hence ought to wear warm clothing to
keep up their temperature.

(4.) Periodical Daily Variations. — In the course of 24 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 5-8 p.m.), while it continues to fall during
tlie night (minimum 2-6 a.m.). The mean temperature occurs at the
third hour after breakfast (Lichtenfels and Frohlich).

According to Lichtenfels and Frohlich, the morning temperature rises 4-6
hours after breakfast until its first maximum, then it falls until dinner time ; and
it rises again within two hours, to a second maximum, falls again towards evening,
while supper does not appear to cause any obvious increase. The daily variation
of the temperature is given in Fig. 170, according to Liebermeister and Jiirgensen.
According to Bonnal, the minimum occurs between 12-3 a.m. (in winter 36'05,
in summer 36'45°r.\ the maximum between 2-4 p.m.

Morning.

Variations of the daily temperature in health during 24thours — L-
Liebermeister : J— , after Jiirgenseu.

As the variations occur when a person is starved — 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 daily variation in the frequency of the pulse (p. 142) often coincides with
variation of the temperature. Biirensprung found that the mid-day temperatm-e-
maximum slightly preceded the pulse-maximum.

If we sleep during the day, and do all our daily duties during
the night, the above described typical course of the temperature is
inverted (Krieger). 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
temperature is less than in the case of a person at rest (Liebermeister).

440 CONDITIONS AFFECTING THE MEAN 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 9-10 a.m. This is followed by a slow rise,
which reaches a high maximum after dinner ; it falls between 1-3 p.m.. and after
two to three hours reaches a minimum. It rises from 6-8 p.m., and falls again
towards morning. A rapid fall of the temperature in a peripheral part cor-
responds to a rise of temperature in internal parts (Rb'mer).

(5.) Many operations upon the body affect the temperature. After
luemorrliage, 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 -J- 2°C. Very long continued hae-
morrhage (dog) causes it to fall to 31° or 29°C. (Marshall Hall).

This is obviously due to the diminution of the processes of oxidation in the
aniemic body, 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 Arnmon).

The transfusion of a considerable quantity of blood raises the tem-
perature 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 (Albert and Strieker) (§ 102).

(6.) Many poisons diminish the temperature — e.g., chloroform (Schei-
nesson), and the anaesthetics, as also alcohol, digitalis, quinin, aconitin,
muscarin. These may act upon the blood so as to limit its oxidising
power, or they may render the tissues less liable to undergo molecular
transformations for the production of heat. In the case of the
anaesthetics, the latter effect perhaps occurs, and is due possibly to a
semi-coagulation of the nervous substance (?).

The temperature is increased by strychnin, nicotin, picrotoxin, veratrin (Hogyes),
laudanin (F. A. Falck). Curara (muscarin — Hogyes), laudanosin (F. A. Falck),
give an uncertain effect.

(7.) Various diseases have a decided effect upon the temperature.
Loewenhardt found that in insane persons, several weeks before
their death, the rectal temperature was 30°-31°C. ; Bechterew found
in dementica paralytica, before death 27'5°C. (rectum); the lowest
temperature observed, and life retained, in a drunk person was 24°C.
(lieinke, Nicolaysen). The temperature is increased in fever, and
the highest point reached just before death, and recorded by Wunder-
lich, was 44'65°C. (compare § 220).

REGULATION OF THE TEMPERATURE. 441

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 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."

214. Regulation of the Temperature.

As the bodily temperature of man and similar animals is nearly con-
stant, 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.

I. Regulatory arrangements governing the production of heat.—

Liebermeister estimates the amount of heat produced by a healthy man
at 1'S calories 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 (Hoppe-Seyler, Liebermeister).
This is accomplished chiefly in a reflex manner. The peripheral ends of
cutaneous nerves (by thermal stimulation), or the nerves of the intestine
and the digestive glands (by mechanical or chemical stimulation during
digestion or inanition) may be stimulated, whereby impressions are
conveyed to the heat-centre which sends out impulses through efferent
fibres to the depots 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. The following phenomena
indicate the existence of mechanisms regulating the production of
heat : —

(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 C0.7 excreted,
by increasing the production of heat (Lieberrneister, Gildermeister),
while the 0 consumed is also increased simultaneously; heating the
surrounding medium diminishes the CO., (compare Respiration, p. 257).

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 com-
pared with summer, so that the same relation obtains as in the case of a diminution
of the surrounding temperature of short duration.

442 KEGULATION OF THE TEMPERATURE.

C. Ludwig and Sanders-Ezn found, that in a rabbit there was a rapid increase in
the amount of C02 given off, when the surroundings were cooled from 38° to 6°-7°C. ,
while the excretion 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 0 and excreted
more C02.

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 C02 does not go hand in hand with the formation of C02, so that the
increased excretion of C02 in a cold bath is perhaps due to more complete expira-
tion, and Berthelot has proved that the formation of C02 is not a certain test of
the amount of heat produced. If mammals be placed in a warm bath, which is
2°-3° higher than their own temperature, the excretion of C02 and the consump-
tion of 0 are increased, owing to the stimulation of their metabolism (Pfliiger),
while the excretion of urea is also increased in animals (Naunyn) and in man
(Schleich).

(3.) Cold acting upon the skin causes involuntary muscular move-
ments (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 (Pfluger). After poisoning with curara, which paralyses voluntary
motion, this regulation of the heat falls to a minimum (Rb'hrig and Zuntz).

(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. In winter the amount
of ozone in the air is greater, and thus the oxidising power of the
inspired air is increased.

II. Regulatory mechanisms governing the excretion of heat. —
The mean amount of heat given off by the human skin in 24 hours,
by a man weighing 82 kilos, is 2,092-2,592 calories — i.e., 1-3G-1-60
per minute.

(1.) Increased temperature causes dilatation of the cutaneous vessels;
the skin becomes red and congested, soft, and with more fluids, so that
it 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.

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

REGULATION OF THE TEMPERATURE. 443

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 sub-cutaneous 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 (Winternitz). 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 Iwat 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 brought about
at the expense of the easily expelled blood.

Landois and Hauschild ligatured the arteries alone, or the arteries
and veins (dog) — e.g., the axillary artery and vein, the crurals, the
carotids and the jugular veins, and found that in a short time the
temperature rose several tenths of a degree.

By the systematic application of stimuli— e.g., cold baths, and washing with
cold water, the muscles of the skin and its blood-vessels may be caused to con-
tract, and become so vigorous and excitable, that when cold is suddenly applied
to the body or to a part of it the excretion of heat is energetically prevented, so
that cold baths and washing with cold water are, to a certain extent, "gym-
nastics of the cutaneous muscles," which, under the above circumstances, protect
the body from cold (Rosenthal, du Bois-Reymond).

(2.) Increased temperature causes increased heart-beats, while
diminished temperature diminishes the number of contractions of the
heart (p. 105). 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 — 27 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 (Walther). In very hot
air (over 100°C.) the pulse rose to over 160 per minute. The same is
true in fever (p. 142). Liebermeister gives the following numbers
with reference to the temperature in an adult: —

Pulse-beats, per min., 78 "6 — 91 "2— 99 -8 — 1 OS ~5 — 110 — 137 '5.
Temperature in C°., 37° — 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

444 CLOTHING.

body. Farther, a certain amount of watery vapour is given off with
each expiration, which must be evaporated, whereby heat is abstracted.
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
(p. 259, 8), whereby the increased respiration must act in producing an
amount of heat greater than normal. This excess is more than com-
pensated 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 (Lombard).

(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 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.

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.

Stimulation of the central end of a sensory nerve (sciatic) increases the surface
temperature and diminishes the internal temperature (Ostroumow, Mitropolsky).

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 pre-
vents it from giving off too much heat. Summer clothes weigh 3-4 kilo., and
winter ones, 6-7 kilo.

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, sheeps' wool,
cotton wool, flax, spun-silk, are given in order, from the worst to the best con-
ductors. (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 water as linen; hence, the latter gives it off in evaporation
more rapidly. Flannel next the skin, therefore, is not so easily moistened, nor
does it so rapidly become cold by evaporation; hence, it protects against the

INCOME AND EXPENDITURE OF HEAT. 445

action of cold. (5.) Ike 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, buckskin, linen,
silk, leather, waxcloth.

215. Income and Expenditure of Heat-
Balance of Heat.

As the temperature of the body is maintained within narrow limits,
the amount of heat taken in must balance the heat given off, i.e., 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 was given off, the body
would become very hot in a short time ; it would reach the boiling-
point in 36 hours, supposing the production of heat continued
uninterruptedly.

The following are the most important calculations on this subject :—

A. According to Helmholtz.

Helmholtz was the first to estimate numerically the amount of heat produced by
a man.

(1.) Heat-income.— («) A healthy adult, weighing 82 kilos.,
expires in 24 hours, 878 '4 grms. C02 (Scharling). The
combustion of the C therein into C02 produces . . 1,730,760 Cal.

(b) But he takes in more 0 than reappears in the C02 ; the
excess is used in oxidation-processes, e.g., for the forma-
tion of H20, by union with H, so that 13,615 grms. H
will be oxidised by the excess of 0, which gives . . 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 = 2,732,000 Cal.

2,732,000 calories are actually sufficient to raise the
temperature of an adult weighing 80-90 kilos., from 10° to
3S-39°C., i.e., to a normal temperature.

(2.) Heat-expenditure.— O) Heating the food

and drink, which have a mean temperature

0fl2°C 70,157 Cal. = 2 '6 per cent.

(b) Heating the air respired — 16,400 grin., with an

initial temperature of 20°C. . . 70,032 ,, = 2 '6 ,,

( When the temperature of the air is 0°, 140,064 Cal. = 5'2 per cent. )

(c) Evaporation of 656 grm. water by the lungs, 397,536 Cal. = 14'7 per cent.

(d) The remainder given off by radiation and

evaporation of water by the skin, (77 '5 per cent, to) = 80'1 per cent.

446 INCOME AND EXPENDITURE OF HEAT.

B. According to Dulong.

(1.) Heat-inCOme. — Dulong, and after him Boussingault, Liebig and Dumas,
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 = 8,040 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 C02 and the H into H20. But Dulong omitted the H in
the carbohydrates (e.g., grape-sugar = C6Hi20,j) as producing heat, because
the H is already combined 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 24 hours, 120 grm. proteids, 90 grm. fat, and 340 grm. starch
(carbohydrates). These contain:—

Grain. C. H.

Proteids, .... 120 contain 64,18 and 8,60

Fat, 90 70,20 ,, 10,26

Starch, .... 330 ,, 146,82 „ ...

281,20 and 18,86
The urine and faces contain still unconsumed, 29,8 ,, 6,3

Remainder to be burned, .... 251,4 and 12,56

As 1 grm. C = 8,040 heat-units and 1 grm. H = 34,460 heat-units, we have the
following calculation:—

251,4 x 8,040 = 2,031,312 (from combustion of C).
12,56x34,460= 432,818 ( „ „ H).

2,464,130 heat-units.

(2.) Heat-expenditure:—

Heat-units. Percent, of
the excreta.

1. 1,900 grm. are excreted daily by the urine and

fceces, and they are 25" warmer than the food, 47,500 1*8

2. 13,000 grm. air are heated (from 12° to 37°C.)

(heat-capacity of the air = 0'26), . . . 84,500 3'5

3. 330 grm. water are evaporated by the respiration

(1 grm. = 582 heat-units), .... 192,060 7'2

4. 660 grm. water are evaporated from the skin, 384,120 14'5

Total, 708,180

Remainder radiated and conducted from the skin, 1,791,810 72

Total amount of heat-units given off, . 2,500,000 100

C. Heat-income, according to Frankland.

Frankland burned the food directly in a calorimeter, and found that 1 grm. of
the following substances yielded: —

Albumin, 4,998 heat-units.

Grape-sugar, . . . .3,277 ,,
Ox fat, 9,069

VARIATIONS IN HEAT-PRODUCTION. 447

The albumin, however, is only oxidised to the stage of urea, hence the heat-
units of urea must be deducted from 4,998, which gives 4,263 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 following:—

With animal diet, ..... 2,779,524 heat-units.

„ food free from N, . . . 2,059,506

,, mixed diet, ..... 2,200,000
,, during hunger, . 2,012,816

216. Variations in Heat-production.

According to Helmholtz, an adult weighing 82 kilos, produces 2,732,000 calories
in 24 hours.

(1.) Influence of the body-weir/ht. — Accepting the above number, Immermann has
given the following formula for the heat-production in living tissues: —

(where W = 2, 732,000; P = 82 kilos. [W : ^/p= 144,75]; p=body-weight of the
person to be investigated, and w represents the heat-production which is required. )
It is highly desirable that W : /^p- (= m) was ascertained as a mean from a
large number of observations, then the heat production for any body-weight p
would be

w -= m z.

(2.) Aye 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 24 hours corre-
sponding with the temperature of the body (§ 2 1 3, 4).

(4.) The heat-production is greater in the waking condition, during physical and
mental exertion, and during digestion, than in the opposite conditions.

217. Relation of Heat-production to the
Work of the Body.

The potential energy supplied to the body may be transformed into
heal and potential energy (see Introduction). In the passive condition,
almost all the potential energy is changed into heat ; the workman, how-
ever, 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 10C.) = 425'5 gramme-metres.

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

448 RELATION OF HEAT-PRODUCTION TO WORK.

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
much less than in the first experiment, i.e., 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 experi-
ment the useful work is very nearly proportional to the decrease of the heat
(Him).

In good steam-engines only -=?-$> an(i m the very best £, of the potential energy
is changed into mechanical energy, while i£-J passes into heat.

Compare this with what happens within the body: — A man in a
2>assive condition forms from the potential energy of the food between
2|-2f million calories. The work done by a workman is reckoned at
200,000 kilogramme-metres.

If the organism were entirely 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 passive person ; much more is burned in his body, and hence,
the increased consumption is not only covered, but even over-com-
pensated. Hence, the workman is warmer than the passive person, owing
to the increased muscular activity (§ 210, 1, i). Take the following
example : — Him (1858) remained passive, and absorbed 30 grm. 0 per
hour in a calorimeter, and produced 155 calories. When in the calori-
meter he did work equal to 27,450 kilogramme-metres, which was
transferred beyond it; he absorbed 132 grm. 0, and produced only
251 calories.

In estimating the work done, we must include only the heat equivalent of the
work transferred beyond the body; lifting weights, pushing anything, throwing
a weight, and lifting the body, are examples. In ordinary walking, there is no loss
of heat (apart from overcoming the resistance of the air); when descending from a
height there may be increased warmth of the body.

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 f as heat, the body produces -i as
work and ^ 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 Degrees of

Temperature.

All substances which possess high conductivity for heat, when
brought into contact with the skin, appear to be very much colder or

ACCOMMODATION FOR VARYING TEMPERATURES. 449

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 1S°C., is moderately warm;
„ 25°-2S°C., hot;
above 28°, very hot.

Water,

at 18CC., is cold;
from 1S-29°C., cool;

,, 29-35'5°C., warm;

,, 37 '5 and above, hot.

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 air heated to 99'95-
127°C., and a temperature of 132°C. has been borne for ten minutes
(Tillett, 1763). The body-temperature rises only to 38'6-38'9°
(Fordyce, Blagden, 1774). This depends upon the air being a bad
conductor, and thus it gives less heat to the body than water would do.
Farther, 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. In a Turkish vapour bath
of 53° to 60°C., the rectal temperature rises to 40'7-41-6°C. (Barthels,
Jiirgensen, Krishaber). A person may work continuously in air at
31°C. which is almost saturated with moisture (Stapff).

If a person be placed in water at the temperature of the body, the
normal temperature rises 1°C. in 1 hour, and in H hours about 2°C.
(Liebermeister). A gradual increase of the temperature from 38'G to
40'2°C. causes the axillary temperature to rise to 39'0°C. within fifteen
minutes.

29

450 STORAGE OF HEAT IN THE BODY.

Rabbits placed in a warm box at 36°C. acquire a constant temperature of 42°C.,
and lose weight; but if the temperature of the box be raised to 40°, death occurs,
the body-temperature rising to 45°C. (J. Rosenthal).

219. Storage of Heat in the Body.

As the uniform temperature of the body, under normal circumstances,
is due to the reciprocal relation between the amount of heat 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 tem-
porarily contracted (Rb'hrig). (b) Any other circumstances prevent heat from
being given off by the skin (Winternitz). (c) When the vaso-motor centre is
excited, causing all the blood-vessels of the body — those of the skin included — to
contract. This seems to be the cause of the rise of temperature after transfusion
of blood (Landois), 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 contracted 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).
Landois found that ligature of both carotids, and the axillary and crural arteries,
caused a rise of 1°C. within two hours.

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 de-
composition of the tissues at this temperature ; while, if a slightly
lower temperature be kept up continuously, fatty degeneration of many
tissues occurs (Litten). If animals, which have been exposed artifici-
ally to a temperature of over 42°-44°C., be transferred to a cooler
atmosphere, their temperature becomes sub-normal (3G°C.) and may
remain so for several days.

220. Fever.

Fever consists in a greatly increased tissue, metabolism (especially in the muscles —
Finkler, Zuntz), with simultaneous increase of the temperature. Of course the
mechanism regulating the balance of formation and expenditure of heat is disturbed.

FEVER AND ITS PHENOMENA. 451

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.— (3S°-39°C., slight; from
39°-41°C. and upwards, 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 (Ant. de Haen,
1760). The congested red skin is a good conductor of heat, while the pale blood-
less skin conducts badly; hence, the former feels hot to the touch (v. Barensprung —
compare § 212).

(2.) The increased production Of heat (assumed by Lavoisier and Crawford)
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, and in 1852 v.
Barensprung 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 C02 = 70°-80° per cent. (Leyden and Frankel), while more
0 is consumed, although the respiratory quotient remains the same (Zuntz and
Lilienfeld). According to D. Finkler, the C02 excreted shows greater variations
than the 0 consumed. The excretion of urea is increased ^ to f . In dogs suffering
from septic fever, Naunyn observed that the urea began to increase before the temper-
ature rose, ' ' prefelrile rise. " Part of the urea, however, is sometimes retained
during the fever, and appears after the fever is over, " epicrilical excretion of
urea " (Naunyn). The uric acid is also increased ; the urine pigment (§ 19)
derived from the hemoglobin, may be increased 20 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 oxidation in a
warm medium is very much greater than in the cold (D. Finkler). The amount
of C02 in the blood is diminished, but not at once after the onset even of a very
severe fever (Goppert).

(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 14~2^ times. The sudden and considerable rise of
the temperature during this stage shows that the diminished excretion of heat is not
the onl}7 cause of the rise of the temperature, (b) During the hot Stage, the heat
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, 4°C. corresponds
to an increased production of heat of 6, 12, IS, 24 per cent, (c) In the sweating
Stage, the excretion of heat through the red moist skin and evaporation are
greatest, more than two to three tunes the normal (Leyden). 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

452 ARTIFICIAL INCREASE OF THE BODILY TEMPERATURE.

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 (§ 186, D) and intestinal
movements ; disturbances of the cerebral activities ; of secretion ; of muscular
activity; slower excretion — e.g., of potassium iodide through the uriiie (Bachrach,
Scholze). In severe fever, molecular degenerations of the tissues are very common.

For the condition of the blood-corpuscles in fever see p. 23, the vascular ten-
sion, § 69; the saliva, § 146.

Quinine, the most important febrifuge, causes a decrease of the temperature by
limiting the production of heat (Lewizky, Binz. Naunyn, Quincke, Arntz). Toxic
doses of the metallic salts act in the same way, while there is at the same time
diminished formation of C0% (Luchsinger).

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 somewhat for a very short time (Obernier),
but soon a decided increase occurs. The respirations and pulse are
increased, while the latter becomes irregular and weaker. The 0
absorbed and C0.2 given off are diminished after 6-8 hours (Litten),
and death occurs 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 49-50°C., in birds at 53°C., and in frogs at 40°C. If
mammals are suddenly placed in air at 100°C., death occurs (in 15-20
min.) very rapidly, and with the same phenomena, while the bodily
temperature rises 4-5°C. In rabbits, the body-weight diminishes
1 grm. per min. Birds bear a high temperature somewhat longer;
they die when their blood reaches 4S-50°C.

Even maw may remain for some time in air at 100-110-132°C.,
but in 10-15 minutes there is danger to life. The skin is burning to
the touch, is red, a copious secretion of sweat bursts forth, and the
cutaneous Veins are fuller and redder (Crawford). The pulse and
respirations are greatly accelerated. Violent headache, vertigo, feeble-
ness, stupefaction indicate great danger to life. The rectal temperature
is only 1-2°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'G°C. (Weikart). If the
artificial heating does not produce death, fatty infiltration and degenera-

USE OF HEAT— POST-MORTEM TEMPER ATURE. 453

tion of the liver, heart, kidneys, and muscles begin after 36-48 hours
(Litton).

Cold-blooded animals, if placed in hot air or warm water, soon have their
temperature raised G-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 algse, may live in water at 60°C.
(Hoppe-Seyler). Several bacteria withstand a boiliug temperature (Tyndall,
C'hamberland).

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 temperature,
partly because it retards reflexly the production of heat (Kernig), and partly be-
cause, owing to the dilatation of the cutaneous vessels and the stretching of the skin,
more heat is given off (Senator). 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 algid stage of
cholera, and in infants born prematurely. The general application of heat is
obtained by the use of warm baths, packing, vapour, insolation, and the copious
use of hot drinks. The local 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.

223, 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 temperature, 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. Thus, Wunderlich
measured the temperature 57 minutes after death in a case of tetanus, and found
ittobe45-375°C.

The causes are : —

(1.) A temporary increased 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 (v. Walther, Fick). All conditions
which cause rapid and intense coagulation of the muscles— e.g., spasms, favour a
post-mortem rise of temperature (see Physiology of Muscle) ; a rapid coagulation
of the blood has a similar result (p. 42).

(2.) Immediately after death, a series of chemical processes occur within the body,
whereby heat is produced. Valentin placed dead rabbits in a chamber, so that
no heat could be given off from the body, and he found that the internal tempera-
ture of the animal's body was increased. The processes which cause a rise of

454 ACTION OF COLD ON THE BODY.

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 post mortem (Quincke and Brieger).

(3. ) Another cause is the diminished excretion of heat jwst mortem. After the
circulation is abolished, within a few minutes little heat is given off from the
surface of the body, as rapid excretion implies that the cutaneous vessels must be
continually filled with warm blood.

224. Action of Cold on the Body.

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 (Lieber-
meister). The slight rise, when it occurs, is due to the stimulation of
the skin, causing reflexly a more rapid molecular transformation, and
therefore a greater production of heat (Liebermeister), while the
amount of heat given off is diminished owing to 'contraction of the
small cutaneous vessels and the skin (Jiirgensen, Senator, Speck). The
continuous and intense application of cold causes a decrease of the
temperature (Currie), 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"— Liebermeister); thus after an hour it was — 0'22°C. in the
rectum. There is a "secondary after-effect" which occurs after the first
after-effect is over, when the temperature rises (Jiirgensen). This
effect begins 5-8 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 35UC.,
and suddenly cooled, it shivers, and there may be temporary diarrhoea. 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 contain thrombi, and
in the neighbourhood of the veins are accumulations of leucocytes. In pregnant
animals, the ketus shows the same conditions (Lassar). Perhaps the greatly cooled
blood acts as an irritant causing inflammation (Rosentlial).

Action of Frost. — The continued application of a high degree of cold causes at
first contraction 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 0 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 —

ARTIFICIAL LOWERING OF THE TEMPERATURE. 455

ears, nose, toes, and fingers. The sensory nerves are paralysed, so that there is
numbness and 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 circulation, 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 parts freeze sooner. Too rapid movements of the frost-bitten
parts ought to be avoided. Rubbing with snow, and the very gradual application
of heat, produce the best results. Partial death of a part is not un frequently
produced by the prolonged action of cold.

225. Artificial Lowering of the Temperature

in Animals,

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 (A. Walther). 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
(Howarth), the secretion of urine stops, and the liver is congested.
The animal may remain for 12 hours in this condition, and when the
muscles and nerves 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 (Kichet and
Rondeau).

An animal cooled to 18°C., and left to itself, at the same temperature
of the surroundings, does not recover of itself, but if artificial respira-
tion be employed, the temperature rises 10°C. If this be combined
with the application of external warmth, the animals may recover com-
pletely, 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; while Howarth cooled young
animals 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; hence,
drunk men are more liable to die when exposed to cold.

456 IIYBERNATION AND USE OF COLD.

Artificial Cold-Blooded Condition. — Cl. Bernard made the important
observation, that the muscles of animals that had been cooled remained
irritable for a long time, both 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 0. An " artificial cold-blooded condition" i.e., a
condition in which warm-blooded animals have a lower temperature,
and retain muscular and nervous excitability (Cl. Bernard), 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 (Wegner).

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 8-10 per minute. The respiratory, urinary, and intestinal movements cease
completely, and the cardio -pneumatic movement alone (p. 110) sustains the slight
exchange of gases in the lungs. They cannot endure cooling to 0°C. ; they awake
before the temperature falls so low. 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 (Kiihne). The
germs and ova of lower animals, e.g., insects' eggs, survive continued frost; and
if the cold be moderate, it merely retards development. Bacteria survive a
temperature of— 87°C.; yeast, even— 100° C. (Frisch).

Varnishing the Skin causes a series of similar phenomena. The varnished
skin gives off a large amount of heat by radiation (Krieger), and sometimes the
cutaneous vessels are greatly dilated (Laschkewitsch). Hence the animals cool
rapidly and die, although the consumption of 0 is not diminished. If cooling be
prevented (Valentin, Schiff, Brunton) 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. Varnishing the human skin does not seem to be dangerous^
(Senator).

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 (v. Ziemssen), The addition of stimulating substances,

HISTORICAL AND COMPARATIVE. 457

e.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.

(b) Cold may be applied locally by means of ice in a bag, which causes contrac-
tion 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 sub-
stances (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, or the injection of cold fluids into the intestine acts locally,
and also produces 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 stronger dilatation and turgescence.

227. Heat of Inflamed Parts,

" Calor " or heat is reckoned one of the fundamental phenomena of inflamma-
tion, in addition to rubor (redness), tumor (swelling), and dolor (pain). But the
apparent increase in the heat of the inflamed parts is not above the temperature
of the blood. Simon, in I860, asserted that the arterial blood flowing to an
inflamed part was cooler than the part itself; but v. Blirensprung denies this, as
J. Hunter did, and so does Jacobson, Bernhardt, and Laudien. 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 acceleration of the blood-stream in the
inflamed part, and owing to the swelling (tumor) from the presence of good heat-
conducting fluids ; but the heat is not greater than the heat of the blood. It is
not proved that an increased amount of heat is produced, owiug to increased
molecular decompositions within an inflamed part.

228. Historical and Comparative.

According to Aristotle, the heart prepares 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, " flamula cordis "). The iatro-mechanical school (Boerhave, van Swieten)
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 fermenta-
tions that arose from the passage of the absorbed substances into the blood (van
Helmont, Sylvius, Ettmuller). 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, ami also under I [ybernation
(p. 456).

Physiology of the Metabolic Phenomena

of the Body.

BY the term metabolism are meant all 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 meta-
bolism forms a store of potential energy, which it can transform 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 accompanied, 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 pre-
paration of the effete products which have to be given out through the
excretory organs.

229. General View of the most Important
Substances used as Food.

Water.

When we remember that 5 8 '5 per cent, of the body consists of
water, that water is being continually given off by the urine and faeces,
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 — e.g., 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

WATER. 459

different forms as drink: — (1) Rain-water, which most closely resembles
distilled or chemically pure water, always contains minute quantities
of C09NH3, nitrous and nitric acids. (2) Spring-water usually con-
tains much mineral substance. It is formed from the deposition of watery
vapour or rain from the air, which permeates the soil containing much
C02; the CO, is dissolved by the water, and aids in dissolving the
alkalies, alkaline earths, and metals, which appear in solution as
bicarbonates — e.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) The running-water of rivers
usually contains much less mineral matter than spring-water. Spring-
water floating on the surface rapidly gives off its C02, whereby many
substances — e.g., lime — are thrown out of solution, and deposited as
insoluble precipitates.

Gases. — Spring-water contains little 0, but much CO.,, which latter
gives to it its fresh taste. Hence, vegetable organisms flourish in
spring-water, while animals requiring, as they do, much 0, are
but poorly represented in such water. Water flowing freely gives up
C02, and absorbs 0 from the air, and thus affords the necessary con-
ditions for the existence of fishes and other marine animals. Eiver-
water contains -^ - ^ of its volume of absorbed gases, which may be
expelled by boiling or freezing.

Drinking-water is chiefly obtained from springs. River-water, if
used for this purpose, must be filtered to get rid of mechanically
suspended impurities. For household purposes a charcoal filter may
be used, as the charcoal acts as a disinfectant. Alum has a remarkable
action ; if 0 '00 01 per cent, be added, 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° of hardness con-
tains 20 parts of lime (calcium oxide) combined with C02, sulphuric, or hydro-
chloric acids (the small amount of magnesia may be neglected). A good drinking
water ought not to exceed 20° of hardness. The hardness is determined by titrating
the water with a standard soap solution, the result being the formation of a
scum on the surface.

The hardness of unboiled water is called its total hardness, while that of boiled
water is called permanent hardness. Boiling drives off the COg, 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

460 SALTS AND OTHER SUBSTANCES IN WATER.

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 precipitates 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 2-3 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 niay be ascertained by acidulating 50 cubic centimetres of
the water with HC1 and adding ammonia in excess, and afterwards adding
ammonia oxalate ; the white 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 are which indicate the presence of sulphuric
acid, chlorine, lime, and magnesia, 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 2 to 3
drops of concentrated sulphuric acid, add several pieces of zinc together with a solu-
tion 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 2
drops of a watery solution of Brucinum sulphuricum, and afterwards several drops
of concentrated sulphuric acid ; a rose-red colouration indicates the presence of
nitric acid.

The presence of nitl'OUS acid is ascertained by the blue colouration 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 colouration when a trace of ammonia is present in water ; while
a large amount of these compounds 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 TS71
grms. potassium nitrate in 1 litre distilled water — 1 cubic centimetre contains 1
milligramme nitric acid ; (B) a dilute solution of indigo, which is prepared by rubbing
together 1 part of pulverised indigotin with 6 parts H2SO.j, and allowing the
deposit to subside, when the blue fluid is poured into 40 times its volume of dis-
tilled water and filtered. This fluid is diluted with distilled water until a layer,
12-15 mm. in thickness begins to be transparent.

To test the activity of B, place 1 cubic centimetre of A in 24 cubic centimetres
water, add 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.

MAMMARY GLANDS. 46 1

25 cubic centimetres of the water to be investigated are mixed with 50 cubic
centimetres of concentrated HoSO-i, 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 milli-
grammes nitric acid have been found in spring- water (Marx, Trommsdorff ).

Sulphuretted Hydrogen is recognised by its odour ; 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 wrater, 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, e.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 delected 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. The presence of micro-organisms may be determined microsco-
pically after evaporating a small quantity of the water on a glass-slide. (2) The
addition of potassio-gold chloride added 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 decolourised, 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 diarrhoea. 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, Structure and Secretion of the ^Mammary

Glands.

About 20 galactoferous ducts open singly upon the surface of the nipple. Eacli
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 terminations of the ducts communicate with the globular
glandular acini. Every gland acinus consists of a membrana propria, surrounded
externally with a net-work of branched connective-tissue corpuscles, and lined
internally with a somewhat flattened polyhedral layer of nucleated secretory cells (Fig.
171.) The size of the lumen of the acini depends upon the secretory activity of the
glands ; when it is large it is tilled with milk containing numerous refractive fatty
granules. The milk-ducts 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 membraua propria
continuous with that of the gland acini. The ducts are lined by cylindrical
epithelium.

402

STRUCTURE OF THE MAMMA.

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. Sometimes a nucleus
is observable within them, and rarely they
exhibit amoeboid movements (Fig. 172, c, d, c).
The regular secretion of milk begins after 3-4 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 the observations of Strieker,
Schwarz, Partsch and Heidenhain, 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.

Fig. 171.

Acini of the mammary gland
of a sheep during lactation—
a, membrana propria ; b,
secretory epithelium.

Changes during Secretion. — Partsch and
Heidenhain found that the secretory cells
in the passive non-secreting gland (Fig. 172, I) were flat, polyhedral,
and uni-nucleated, whilst the secreting cells (Fig. II) often con-

Fig. 172.

I — Inactive acinus of the mamma. II — During the secretion of milk ; a, b, milk-
globules ; c, d, ?, colostrum-corpuscles ; f, pale cells (bitch).

tained 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. Fatty
granules are formed in this part of the cell, and are afterwards ex-
truded. The decomposed portion of the cell is dissolved in the milk,
and the fatty granules become free as milk-globules. (Fig. 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 (/). Occasionally milk-globules
are found with traces of the cell-substance adhering to their surface (6).

Formation Of Milk. — Concerning the formation of the individual constituents

STRUCTURE OF THE MAMMA. 463

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 alcohol 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 — hi the rete Malpighii of the skin, and by large papilla?
in the cutis vera. Some of the papillae contain touch-corpuscles. Numerous non-
striped muscular fibres surround the milk-ducts hi 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
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 ; the gland acini are each surrounded by a net-
work of capillaries, which 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 II-IV-VI
iutercostals ; 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 surrounding the acini.

The comparative anatomy of the mamma. — The rodents, insectivora, and car-
nivora, have 10 to 12 teats, while some of them have only 4. The pachydermata and
ruminantia have 2-4 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, which open on a patch of skin devoid
of hair without any nipple. The young animals remain within the mother's pouch,
and the milk is expelled into their mouths by the action of a muscle — the com-
pressor mammas.

The development of the human mamma begins in both sexes during the third
month ; at the fourth and fifth months, a few simple tubular gland-ducts are
arranged radially around the position of the future nipple, which is devoid of hair.
In the new-born child the ducts are branched twice or thrice, and are provided
with dilated extremities, the future acini. Up to the 12th year in both sexes, the
ducts continue to divide dendritically, but without any proper acini being formed.

In the girl at puberty the ducts branch rapidly ; but the acini are formed only at
Hie periphery of the gland, while during pregnancy, acini are also formed in the
centre of the gland, while the connective-tissue at the same time becomes some-
what more opened out. At the climacteric period, or menopause, all the acini and
numerous fine milk-ducts 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 hi
the axilla, on the back, over the acromion process, or on the leg. A slight secre-
tion 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.
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 stim-

4G4 MILK AND ITS PREPARATIONS.

ulation 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 (Rohrig). 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 secre-
tion. 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 galactorrh(Ea is perhaps to be regarded as a paralytic secre-
tion analogous to the paralytic secretion of saliva. Heidenhain and Partsch 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 all the con-
stituents necessary for maintaining the life and growth of the body
are present. To every 10 parts of proteids there are 10 parts fat and
20 parts sugar. Eelatively more fat than albumin is absorbed from
the milk (Rubner) ; while a part of both is excreted in the faeces.

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 1026-1035 (Radenhausen). When it
stands for a time, numerous milk-globules, butter-globules, or cream,
collect on its surface, under which there is a watery bluish fluid.
Human milk is always alkaline, cow's milk may be alkaline, acid or
amphoteric ; while the milk of carnivora is always acid.

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 (Fig. 172, a, &,); 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-
globules which reflect the light ; the globules consist of a fat, or butter,
surrounded with a very thin envelope of casein. If acetic acid be
added to a microscopic preparation of milk, this caseous envelope
is dissolved, the fatty granules are liberated, and they run
together to form irregular masses. If cow's milk be shaken with
caustic potash, the casein envelopes are dissolved, and if ether be
added, the milk becomes clear and transparent, as the ether dissolves

FATS AND PLASMA OF MILK. 465

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 shaking with ether is
sufficient to extract the fats from human milk (Radenhausen). 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,
myristic, oleic, arachinic (butinic), capric, caprylic, caproic, and butyric acids,
with traces of acetic and formic acids (Heintz), and cholesterin (Schmidt-Miilheim).
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
becomes 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 raucid
odour.

The milk-plasma, obtained by filtration through clay filters or mem-
branes, is a clear, slightly opalescent fluid, and contains casein (§ 249,
III, 3), serum-albumin (p. 49), and to a less extent a body resembling
albumin (lactoprotein — Millon, Liebermann) ; galactin, albuminose, and
globulin; peptone (0'13 per cent.); nuclein, diastatic ferment (in
human milk — Bechamp). Milk-sugar (§ 252), a carbohydrate resemb-
ling dextrin (Eitthausen), (? lactic acid), lecithin, urea, extractives; —
sodic and potassic chlorides, alkaline phosphates, calcium and mag-
nesium sulphates, alkaline carbonates, traces of iron, fluorine, and
silica ; C02N, 0.

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.

When milk is filtered through fresh animal membranes (Hoppe-Seyler), or
through a clay filter, the casein does not pass through (Helmholtz, Zahn, Kehrer),
while burned pulverised clay and animal charcoal also attract the casein (Dupre
and Hermann).

The coagulation Of milk depends upon the coagulation of its casein. In milk,
casein is combined with calcium phosphate, which keeps it in solution; acids
which act on the calcium phosphate cause coagulation of the casein (acetic and tar-
taric acids in excess redissolve it). All acids do not coagulate human milk (Biedert).
It is coagulated by two or more drops of hydrochloric acid (O'l per 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 formation of lactic acid, which is

30

4G6 COMPOSITION OF MILK.

formed from the milk-sugar in the milk by the action of bacterium lacticum [which
is introduced from without (Pasteur, Cohii, Lister)]. It changes the neutral alka-
line phosphate into the acid phosphate, takes the casein from the calcium phosphate,
and precipitates the casein (p. 373). The ferment may be isolated by means of
alcohol.

Rennet, which contains a special ferment, 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 (Hammarsten, Koster), so
that the coagulation by rennet is a process quite distinct from the coagulation of
milk by the gastric and pancreatic juices. When the milk is coagulated 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-sugar, together with lactic acid.

Boiling (by killing all the lower organisms), sodium bicarbonate (T-JUTJ), ammonia,
salicylic acid (sinnr)? glycerine, and ethereal oil of mustard prevent the spon-
taneoiis coagulation. Fresh milk makes tincture of guaiacum blue, but boiled
milk does not do so (Schacht, C. Arnold). When milk is exposed to the air for a
long time, it gives off COg, and absorbs 0 ; the fats are increased (? owing to the
development of fungi in the milk), and so are the alcoholic and ethereal extracts,
from the decomposition of the casein (Hoppe-Seyler, Kemmerich). According to
Schmidt-Miilheim, some of the casein becomes converted into peptone, but this
occurs only in unboiled milk.

Composition. — 100 parts of milk contain—

Human. Cow. Goat, Ass.

Water, 87 '24— 90 '58 86 '23 86 "85 89 "01

Solids, 9-42—12-39 13'77 13'52 10'99

Casein, 2'91— 3'92 ) . .„„ «,.„, \ 3-23 2-53 \ ,.w

Albumin, f / 0-50 1-26 J

Butter, 2-67— 4-30 4'50 4'34 1'85

Milk-sugar, . . . 3'15— 6'09 4 '93 3'78 ) r ^,

Salts, 0'14— 0-28 U'6 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. — Pflllger and Setscheuow found in 100 vols. of milk 5 '01-7 '60 C02 ;
0-09-0-32 0; 0'70-1'41 N, according to volume. Only part of the C02 is expelled
by phosphoric acid.

Salts. — The potash salts (as in blood and muscle) are more abundant than the
soda compounds, while there is a considerable amount of calcium phosphate,
which is necessary for forming 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'S7; 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 more frequently 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 (Reiset, Heynsius, Forster, de Leon). Some substances are

TESTS FOR MILK. 467

diminished 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 8-1 Oth months, the sugar. The following are diminished: — From
10-24th months, casein; from 5-6th and 10-llth months, fat; during 1st month,
the sugar; from the 5th month, the salts.

[That cow's milk is influenced by the pasture and food is well-known. Turnip
as food give 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, while many substances given as medicines reappear in the milk, such as
dill, copaiba, conium, aniseed, garlic, potassium iodide, arsenic, mercury, opium,
rhubarb, or its active principle, and the cathartic principle of senna. 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 adulteration or cleansing ; by the milk absorbing
deleterous gases; by the secretion being altered in diseased animals.]

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 proteids (small amount of vegetable food), increase the
amount of milk and the casein, sugar, and fat in it ; a large amount of carbo-
hydrates (not fats) increases the amount of sugar.

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 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
(Biedert); its coagulated flocculi or curd are much coarser than the fine curd of
human milk, and they are only f dissolved by the digestive juices, while human milk
is completely dissolved. Cow's milk when boiled is less digestible than unboiled
(E. Jessen).

Milk ought not to be kept in zinc vessels owing to the formation of zinc
lactate.

Tests for Milk. — The amount of cream is estimated by placing the milk for
24 hours in a tall cylindrical glass graduated into a hundred parts; the cream
collects on the surface, ami ought to form from 10-24 vols. per cent. The
specific gravity (fresh cow's milk, 1,029-1,034; when creamed, 1,032-1,040) is
estimated with an araeometer or lactometer at 15°C. The sityar is estimated by
titration with Fehling's solution (p. 298), but in this case 1 cubic centimetre of
this solution corresponds to O'OOGT grm. of milk-sugar; or its amount may be
estimated with the polariscopic apparatus (vol. ii). The proteids are precipitated
and the fats extracted with ether. The fats in fresh milk form about 3 per cent.,
and in skimmed milk 1| per cent. The amount of water in relation to the milk-
globules is estimated by the lactoscope (the diaphanometer of Donne", modified by
Vogel and Hoppe-Seyler), which consists of a glass-vessel with plane parallel sides
placed 1 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, 70-85 centimetres water are
required.

Various substances pass into the milk ivhen they are administered to the mother—
many odoriferous vegetable bodies, e.g., anise, vermuth garlic, &c.; opium, indigo,
salicylic acid, iodine, iron, zinc, mercury, lead, bismuth, antimony. In osteo-
malacia the amount of lime in the milk is increased (Gusserow). Potassium iodide

468 EGGS.

diminishes the secretion of m ilk by affecting the secretory function (Stumpf).
Amongst abnormal COnstit ents are— hemoglobin, bile-pigments, ruucin,
blood-corpuscles, pus, fibriu. Numerous fungi and other low organisms develop
in evacuated milk, and the rare blue milk is due to the development of Bacterium
cyanogeneum (Fuchs, Neelsen). The blue colour is due to aniline blue derived
from casein (Erdmann). The milk-serum is blue, not the fungus. Blue milk is
unhealthy, and causes diarrhoea (Mosler). Red and yellow milk are produced by
a similar action of chromogenic fungi (p. 373). The former is produced by
Micrococcus prodigiosus, which is colourless. The colour seems to be due to
fuchsin. The yellow colour is produced by Bacterium ftynxantlmm (Ehrenberg),
and the colour is also due to an aniline substance (Schroter).

Preparations Of Milk. — (1.) Condensed mill: — SO grms. cane-sugar are added
to 1 litre of milk; the whole is evaporated to ^; and while hot sealed up in tin
cans (Lignac). 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. Koumiss and sour
milk are added to 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 2-3 per cent, of alcohol; while the
casein is at first precipitated, but is afterwards partly redissolved and changed
into acid-albumin and peptone (Dochmann).

(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 recalls the
digestive processes.

232. Eggs.

Eggs must also be regarded as a complete food, as the organism
of the young chick is developed from them. The yelk contains a
characteristic proteid body, Vitellin (§ 249), and an albuminate in the
envelopes of the yellow yelk spheres — Nudein, from the white yelk ;
fats in the yellow yelk (palmitin, olein), cholesterin, much lecithin;
and as its decomposition product, glycerin-phosphoric acid — grape-
sugar, pigments (lutein), and a body containing iron and related to
haemoglobin; lastly, salts qualitatively the same as in blood — quanti-
tatively as in the Hood-corpuscles — 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, quali-
tatively resembling those of blood, but quantitatively like those of
serum, and a trace of fluorine.

Kelatively more of the nitrogenous constituents than the fatty
constituents of eggs are absorbed (Rubner).

FLESH AND ITS PREPARATIONS.

469

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. The following results
refer to flesh freed as much as possible from these constituents.
The chief proteid constituent of the contractile muscular substance
is myosin (Kiihne); scrum-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 interfibrillar fat cells, and so are lecithin and
cholesterin from the nerves of the muscles; the gelatin is derived
from the connective-tissue of the perimysium, perineurium, and the
walls of blood-vessels and tendons. The red colour of the flesh is
due to the haemoglobin present in the sarcous substance (Kiihne,
Gscheidlen). Elastin 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 substance, the result of the retrogressive
metabolism of the sarcous substance, is kreatin (Chevreul — 0'25 per
cent., Perls) ; Ireatinin, the inconstant inosinic acid, then lactic, or rather
sarcolactic acid (see Muscle). Farther, taurin, sarkin, xanthin, uric acid, car-
nin, inosit (most abundant in the muscles of drunkards), dextrin (in horse
and rabbit, not constant — Sanson, Limpricht) ; grape-sugar (Meissner),
but it is very probably derived post mortem from glycogen (0'43 per
cent.), which occurs in considerable amount in foetal muscles (0.
Nasse) ; lastly, fatty acids. Amongst the salts, potash and phosphoric
acid compounds (Braconnot) are most abundant ; magnesium phosphate
exceeds calcium phosphate in amount.

In 1 00 parts FLESH there is, according to Schlossberger and v. Bibra—

Ox.

Calf.

Deer.

Pig.

Man.

Fowl.

Carp.

Frog.

Water,

77-50

78-20

74-63

78-30

74-45

77-30

79-78

80-43

Solids,

22-50

21-80

25-37

21-70

25-55

22-7

20-22

19-57

Soluble Albumin,
Colouring Matter,

J2-20

2-60

1-94

2-40

1-93

3-0 1

2-35

1-86

Glutin, .

1-30

1-60

0-50

0-80

2-07

1-2

1-98

2-48

Alcoholic Extract, .

1-50

1-40

4-75

1-70

3-71

1-4

3-47

3-46

Fats,

...

...

1-30

...

2-30

...

1-11

o-io

Insoluble Albumin,

Blood-vessels, &c.,

17-50

16-2

16-81

16-81

15-54

16-5

ill'31

11-67

470

COMPOSITION OF FLESH.

In 100 parts ASH there is—

Horse.

Ox.

Calf.

Pig.

Potash

39'40

35'94

3440

3779

v 1 f </

Soda,

4-86

...

2-35

4-02

Magnesia,

3-88

3-31

1-45

4-81

Chalk,

1-80

1-73

1-99

7-54

Potassium, ....

...

5-36

...

• . .

Sodium, .....

! 1-47 1

4-86

{ 10-59 }

0-40
0'62

Iron oxide, ....

i-o

0-98

I J
0-27

0-35

Phosphoric Acid, .

4674

34-36

4813

44-47

Sulphuric ,,

0-30

3-37

...

* . .

Silicic ,,

...

2-07

0-81

. . .

Carbonic ,,

...

8-02

...

...

Ammonia, ....

...

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 S'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, when sarcolactic acid is developed, and
the flesh becomes more tender and is more palatable. Some of the extractives
excite the nervous system, e.g., kreatin and kreatinin ; and others give to flesh its
characteristic agreeable taste (" osmasome "), but this is also partly due to the
different fats of the flesh, and is best developed when the flesh is cooked. The
extractives in 100 parts of flesh— in man and pigeon, 3 ; deer and duck, 4 ; swallow,
7 per cent.

Preparation, or 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 glycogeu 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 60-70°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 exit 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 coagulated and 3 '3

VEGETABLE FOODS,

471

remained dissolved in the soup. By boiling for a very long time, part of the
albumin may be redissolved (Mulder). 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
inosiuates and lactates which give to broth or beef-tea their stimulating qualities,
and a small amount of aromatic extractives. 3. 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. The flesh after the extraction
of the broth is still available 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.

[Mastermanu has shown that the chemical analysis of beef -tea is analogoiis to
that of urine, except that it contains less urea and uric acid. ]

234. Vegetable Foods.

The nitrogenous constituents of plants are not so easily absorbed as
animal food (Rubner). Carbohydrates, starch, and sugar are very
completely absorbed, and
inconsiderable
of cellulose

even a not

proportion

may be digested (Weislce,

Konig). The more fats

that are contained in the

vegetable food, the less

are the carbohydrates

digested and absorbed

(Rubner).

1 . The cereals are most
important vegetable foods ;
they contain proteids,
starch, salts, and water to
14 per cent. The nitro-
genous glutin is most abun-
dant under the husk
(Payen). The use of whole

meal containing the outer layers of the grain is highly nutritive, but
bread containing much bran is somewhat indigestible (Rubner).
[A section of a wheat grain with its layers of glutiu is shown in
Fig. 173.] Their composition is the following: —

Fig. 173.

Microscopic characters of wheat — x 200 ; a, cells
of the bran ; I, cells of thin cuticle ; c, glutin
cells ; d, starch cells ; B, wheat starch x 350.

472

PULSES, POTATOES, FRUITS.

100 PARTS OF THE DRV MEAL CONTAIN

100 PARTS OP ASH CONTAIN

OF

ALBUMIN.

STAECH.

RED
WHEAT.

WHITE
WHEAT.

Wheat, . .
Rye, . . .
Barley, . .
Maize,. . .

16-52 p.c.
11-92
17-70
13-65

56- 25 p.c.
60-91
38-31

77-74

27'87
15-75
1-93
9 '60

Potash, ....

Soda,

33-84

3-09
13-54

Lime,

Magnesia, . . .

Rice, . . .

7-40

86-21

1-36

Iron oxide, . . .

0-31

Buckwheat, .

6-8-10-5

65-05

49-36
0-15

Phosphoric Acid,

Silica, .....

49'21

(Will, Fresenius).

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.

In the preparation of bread, the meal is kneaded with water until dough is
formed, and to it is added salt and yeast (saccharomycetes cerevisiae). When
placed in a warm oven, the proteids of the meal begin to decompose and act as a
ferment upon the swollen np starch, which becomes in part changed into sugar.
The sugar is farther decomposed into C02 and alcohol, the C02 forms bubbles,
which make the bread spongy and porous. The alcohol is driven off by the baking
(200°), while much soluble dextrin is formed in the crust of the bread.

2. The Pulses contain much albumin, especially vegetable casein or legumin;
together with starch, lecithin, cholesterin, and 9-19 per cent, water.
Peas contain 28'02 proteids, and 38'81 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
prepared from them. On account of the large amount of proteids
which they contain they are admirably adapted as food for the
poorer classes.

3. Potatoes contain 70-81 per cent, water. In the fresh juicy cellular
tissue, which has an acid reaction, from the presence of phosphoric,
malic, and hydrochloric acids, there is 16-23 per cent, of starch, 2'5
soluble albumin, globulin (Zoller), 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 46'96 potash, 2'41
sodium chloride, 8- 11 potassium chloride, G'50 sulphuric acid derived
from burned proteids, 7 "17 silica.

4. 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 (C30H4S030), which can be pre-
pared artificially by boiling the very insoluble pectose of unripe fruits
and mulberries.

CONDIMENTS, TEA, COFFEE. 473

5. The Green Vegetables are specially 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.

235. Condiments— Coffee— Tea— Chocolate-
Alcoholic Drinks,

Some substances are used along with food, not so much on account of their
nutritive properties as on account of their stimulating effects and agreeable
qualities, which are exerted partly upon the organ of taste, and partly upon the
nervous system. These are called condiments.

Coffee, tea, and chocolate are prepared as infusions of these substances. Their
chief active ingredients are respectively cajfein, thein (C8H10N402 + H20), and
theobromln (CyHs^Oo), which are regarded as alkaloids of the vegetable
bases, and which have recently been prepared artificially from xanthin (E. Fischer).

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, atropiii, strychnin, cm-arm, nicotin, muscarin).

All these substances act on the nervous system; they quicken
thought, accelerate movement, and stir one to greater activity. In
these respects they resemble the stimulating extractives — kreatin and
kreatinin — of beef-tea. Coffee contains about ^ per cent of caffein,
part of which is only liberated by the act of roasting. Tea has G per
cent, of thein, whilst green tea contains 1 per cent, ethereal oil, and
black tea \ 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. The alcohol, when taken into the body, undergoes certain
changes and produces certain effects : — 1. It is oxidised chiefly into
C0.2 and H20, 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. Small doses diminish the

474

ACTION OF ALCOHOL.

decomposition of the proteids to the extent of 6-7 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, e.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 tlms 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.

Preparation. — Alcoholic drinks are prepared by the fermentation of various
carbohydrates, such as sugar derived from starch. The alcoholic fermentation, such
as occurs in the manufacture of beer, is caused by the development of the yeast
plant, Saccharomycetes cerevisire ; while in the fermentation of the grape (wine),
8. ellipsoideus is the species present. The yeast takes the substances necessary
for the maintenance of its organic processes directly from the mixture of the
sugar — viz. , carbohydrates, proteids, and salts, especially calcium and potassium
phosphates and magnesium sulphate. These substances undergo decomposition

1.

2.

3. 4.

Fig. 174.

1, Isolated yeast cells; 2, 3, yeast cells budding; 4, 5, so-called endogenous
formation of cells ; 6, sprouting and formation of buds.

within the cells of the yeast plant, which multiply during the process, and there
are produced alcohol and C02 (p. 298), together with glycerine (3"2-3'6 per cent.)

PREPARATION OF ALCOHOLIC DRINKS. 475

and succinic acid (0'6-0'7 per cent.). Yeast is either added intentionally or it
reaches the mixture 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 (Schwann,
Mitscherlich, Pasteur).

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 fer-
mentation thereby produced ; the mixture is distilled at 78'3°C. The fusel oil is
prevented from mixing with the alcohol by passing the vapour through heated
charcoal. The distillate contains 50-55 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 10-15°C., and the yeast
cells, which are floating about, drop into it and excite fermentation, which lasts
10-14 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 COo, 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 89-90 per cent, water, 7-8 per cent, alcohol,
together with sethylic, 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 fermeutation, red grapes yield white wine.

When wine is stored it develops a fine flavour or bouquet. The characteristic
vinous odour is due to (Knantldc ether. The salts of wine closely resemble the salts
of the blood.

In the preparation of beer the grain is moisten, 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 70-75°, the watery extract being the "wort."
Hops are added to the wort, and the whole is evaporated, when the proteids are
coagulated. Hops give beer its bitter taste, make it keep, while their tannic acid
precipitates any starch that may be present, and clarifies the wort. After being
boiled, it is cooled rapidly (12°C.); yeast is added, and fermentation goes on
rapidly and with considerable effervescence at 10°-14°. Beer contains 75-95 per
cent, water; alcohol, 2-5 percent, (porter and ale, to 8 per cent.); C02, 0'1-0'8
per cent.; sugar, 2-8 per cent.; gum, dextrin, 2-10 per cent.; the hops yield
traces of protein, fat, lactic acid, ammonia compounds, 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 phosphorus, magnesium phosphate 20, calcium
phosphate 2-6, salica 16'6 per cent. The formation of blood, muscle, and other
tissues from the consumption of beer is due to the phosphoric acid and potash,
while if too much be taken, the potash produces fatigue.

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. We may also include many substances of unknown
constitution which act upon the gustatory organs, e.g., substances in
the crust of bread and in meat which has been roasted.

Phenomena and laws of letabolism,

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. As long
as the body continues to grow, 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 (Crusius). Conversely, during senile decay, there
is an excess of expenditure from the body.

Methods. — The normal equilibrium of the metabolism of the body is investi-
gated—(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, 0, salts and water of the food, and the 0 inspired, must be equal to
the C, H, N, O, salts and water given off in the excreta (iirine, faeces, air expired,
water excreted). (2) The j)hysiological 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
convalescence 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. Their observations showed, that in the circulation of materials the C and
N were the most important. 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 C02 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 faeces (10 per
cent.). With regard to the N, nearly all the N taken in with the food is excreted
within 24 hours in the form of urea. A very small amount of nitrogenous matter
is excreted in the faeces, while the other nitrogenous urinary constituents (uric
acid, kreatin, &c.) represent about 2 per cent, of N. A trace of the N is given off
by the breath (p. 255), and a minute proportion in combination, in the epidermal
scales (50 milligrammes daily in the hair and nails) and in the sweat.

That nearly all the N taken in the food reappears in the urine and
fasces, as v. Voit showed for carnivora, and Henneberg, Stohman and
Grouven for herbivora, and v. Ranke for man, is contradicted partly by
old and partly by new observations (Barral, Boussingault, Bischoff,
Regnault and Reiset, Seegen and Nowak), which go to show that the

EQUILIBRIUM OF THE METABOLISM. 477

whole of the N cannot be recovered from these excretions, but on the
contrary there is a considerable deficit.

According to Seegen and Nowak, 1 kilo, weight of a living animal excretes of
gaseous N per hour, thus — rabbit, 4-5 milligrammes (according to Leo, only Ta5 of
this value); dog, 8 milligrammes ; fowls, pigeons, 7-9 milligrammes. According
to Leo, only 0 '55 per cent, of the albumin transformed within the body (assuming
15 per cent. N in albumin) is given off in the form of gaseous N.

The H leaves the body chiefly in the form of water— a part, however, is in
combination in other excreta; the 0 is chiefly excreted as C02 and water; a little
is given off in combination in other excreta; water is given off by evaporation from
the lungs and skin. As H is oxidised to form H20, more water is excreted than
is taken in. With regard to the salts, most of the readily soluble salts are given
off by the m*ine; less, especially potash salts and rather insoluble salts, in the
fteces, while others, e.g., common salt, 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 fteces (taurin) and in the epidermal tissues.

Every body has a minimum and a maximum limit with reference to
its 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 faeces. When
food is liberally supplied and the weight increases, of course the
minimum limit rises; hence, during the process of "feeding" or
" fattening," the income 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. Bischoff, v. Voit, v. Pettenkofer).

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 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 may undergo
decomposition sooner than the organised " organ albumin" which forms
an integral part of the tissues.

According to v. Voit only 1 per cent, of the organ albumin present in
the body, while 70 per cent, of the circulating albumin, is transformed
in 24 hours.

The excretion of N after taking food is not equal from hour to hour ; it rises
rapidly at first, reaches a maximum in 5-6 hours, and then gradually falls. The
same is the case with the excretion of S and P, only in these cases, after a flesh
diet, the maximum is reached at the fourth hour. After the addition of fat to a

478 REQUISITES FOR A PERFECT DIET.

flesh diet, the excretion of N and S is uniform from hour to hour (Feder and v.
Voit).

duality and Quantity of the Income in a Healthy Adult.

As far as his organisation is concerned, man belongs to the
omnivorous animals, i.e., those that can live upon a mixed diet.

Requisites. — Man requires for his existence and to maintain health
the following four groups of foods ; none of them must be absent from
the food for any length of time. Thej1- are : —

1. Water— for an adult in his food and drink, 2,700-2,800 grms.
daily (§ 229 and § 247, 1).

2. Inorganic Substances are an integral part of all tissues, and with-
out 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 (Weiske).
If an animal be deprived of salts, nutrition is interfered with ; food
deprived of its lime affects the formation of the bones ; deprival of
common salt causes albuminuria (247, A, III).

The alkaline salts serve to neutralise the sulphuric acid formed by
the oxidation of the sulphur of the proteids (E. Salkowski, Bunge,
Lunin).

Sodium acetate in large doses causes diuresis, and diminishes the transforma-
tion of nitrogenous substances in the body, and the same diminution is caused by
sodium sulphate and phosphate ; sodium carbonate (? Ott) increases the trans-
formation of nitrogenous substances (J. Mayer), diminishes the uric acid, and
increases the urea in the urine.

Only in times of famine is man driven to eat large quantities of inorganic sub-
stances, to extract the organic matter mixed therewith. A. v. Humboldt states, in
regard to the inhabitants of the Orinocco, that they eat a kind of earth which con-
tains innumerable infusoria.

3. At least one animal or vegetable albuminous body or proteid
(§ 248, § 250). The proteids are required to replace the used-up nitro-
genous tissues, e.g., for muscles. They contain 15 '4 to 16-5 per
cent. N.

Asparagin, in combination with gelatin, can replace albumin in the food
(Weiske), while asparagin alone limits the decomposition of albumin in herbivora
(Weiske, Zuntz, Bahlmann, Lehmann), but not in carnivora (J. Mtink).
Ammoniacal salts, glycocoll, sarkosin, and benzamid, increase the amount of albu-
min in the body.

4. At least one fat (§ 251), or a digestible carbohydrate (§ 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

COMPOSITION OF FOODS.

479

heat of the body (§ 20G). Fats and carbohydrates may replace
each other in the food, and in inverse proportion too, corresponding
to the amount of C which each contains. According to v. Voit, for
this purpose 175 parts of starch by iveight are equal to 100 parts of fat.

Animal Foods.

Explanation of the signs.

Water.

Proteids. Albuminoids. N-free org. bodies. Salts.

Beef.
Pork.
Fowl.
Fish.

Ezc.

L_

55

\

73

76

73,5

Cow's milk.
Human milk.

8fi

89

Vegetable Foods.

Explanation of the signs.

Water. Proteids Digestible Non-digestible Salts.

N-free organ bodies.

Wheaten-bread.

Peas.

Rice.

Potatoes.

White Turnip.

Cauliflower.

Beer.

I

1-4

75 ^5

~. i.-'lSiii1,

M\

90,5

90

90

0,2

iil

illil

0-5

1

0-5

Fig. 175.

480 AMOUNT AND QUALITY OF FOOD REQUIRED.

Proportion. — 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 nitro-
genous foods to 3£ or, at most, 4^- of the non-nitrogenous. 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.

1. Veal, . . 10 ... 1

2. Hare's flesh, . 10 ... 2

3. Beef, . . 10 ... 17

4. Lentils, . . 10 ... 21

5. Beans, . . 10 ... 22

6. Peas, . . 10 ... 23

7. Mutton, . . 10 ... 27

8. Pork, . . 10 ... 30

9. Cow's milk, . 10 ... 30

Nit. Non-Nit.

10. Human milk, 10 ... 37

11. Wheaten-flour, 10 ... 46

12. Oat-meal, . 10 ... 50

13. Rye-meal, . 10 ... 57

14. Barley-meal, 10 ... 57

15. White potatoes, 10 ... 86

16. Blue „ 10 ... 115

17. Rice, . . 10 ... 123

18. Buckwheat meal, 10 ... 130

An examination of this table shows that, in addition to human milk, wheat-
flour has the right proportion of nitrogenous to non-nitrogenoiis substances. A
man who tries to nourish himself on beef alone, commits as great a mistake as one
who would feed himself with 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
climes 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 (p. 442).

The graphic representation of the composition of Foods (Fig. 175),
taken from Fick, shows at once the relative proportions of the
food constituents and how they vary from the standard of 1
nitrogenous to 3-J— 4-g- non-nitrogenous.

The absolute amount of food stuffs required by an adult in 24
hours depends upon a variety of conditions. As the food represents
the chemical reservoir 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. As a general rule an adult requires daily
130 grammes proteids, 84 grammes fats, 404 grammes carbohydrates.

The following tables express the mean of numerous single observations : —

DAILY QUANTITY OF FOOD REQUIRED.
A HEALTHY ADULT REQUIRES IN 24 HOURS—

481

Food in Grammes.

At Kest

(Playfair).

Moderate
Work
(Moleschott).

Laborious Work —

(Playfair).

(v. Pettenkofer
and v. Voit )

Proteids,

70-87

130

155-92

137

Fats, ....

28-35

84

70-87

117

Carbohydrates (Sugar,

Starch, etc.), .

310-20

404

567-50

352

In an analogous example from Vierordt, the elementary substances in the food
are given (p. 446), and compared with the income and expenditure.

AN* ADULT DOING A MODERATE AMOUNT OF WORK TAKES IN : —

c.

H.

N.

0.

120 Grammes Albumin, containing,
90 ,, Fats „
330 „ Starch ,,

64-18
70-20
146-82

8-60
10-26
20-33

18-88

28-34
9-54
162-85

281-20

39-19

18-88

200-73

Add 744-11 grm. 0 from the air by respiration.
,, ~,S1S ,, HoO.

)> 32 ,, Inorganic compounds (Salts).

The whole is equal to 3i kilo., i.e., about ^ 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.

AN ADULT DOING MODERATE WORK GIVES OFF:—

Water.

C.

II.

N.

0.

By respiration,

330

24S-8

9

651-15

Transpiration,

660

2-0

. . •

7-2

Urine, .

1,700

9-8

3'3

15'8

11-1

Faeces,

128

20-0

3-0

3-0

12-0

2,818

281-2

6-3

18-8

681-45

Add to this (besides 2,818 grammes water as drink), 296 grammes water
formed in the body by the oxidation of H. These 296 grammes of water contain
32,89 grammes H, and 263,41 grammes O; 26 grammes of salts are given off in the
urine, and 6 by the faeces.

Effect of Age. — The investigations of the Munich School have shown,
that the following numbers represent the smallest amount of food
necessary for different ages : —

31

482

RELATIVE PROPORTION OP POODS REQUIRED DAILY.

Age.

Nitrogenous.

Fat.

Carbohydrates.

Child until 1 i years, .

20-36 grm.

30-45 grm.

60-90 grm.

,, from 6-15 years,

70-80 „

37-50 „

250-400 „

Mail (moderate work),

118 „

56

500 „

Woman ,,

92 „

44 „

400 „

Old man, , .

100 „

68 „

350 „

Old woman, .

SO „

50 „

260 „

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 : 31 to 1 : 41.

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. Moleschott finds that a person, in order to obtain the 130
grammes of proteids necessary, must use

Cheese,
Lentils,
Peas, .

388 grm.
491 „

582

Beef, . . 614 grm.
Eggs, . 968 „

Wheat bread, 1,444 ,,

Eice, .
Rye bread,
Potatoes,

2,562 grm.
2,875 „
10,000 „

provided he were to take only one of these substances as food; so that
it is perfectly obvious that if a workman were to live on potatoes alone,
in order to get the necessary amount of N, he would have to consume
an altogether preposterous amount of this kind of food.

To obtain the 448 grammes of carbohydrates, or the equivalent
amount of fat (100 : 175), necessary to support him, a man must eat

Bice, .

Wheat bread,
Lentils,

572 grm.
625 „
806 „

Peas, . .

Eggs,
Piye bread,

819 grm.
902 „
930 „

Cheese, ,
Potatoes, .
Beef,

2,011 grm.
2,039 „
2,261 „

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 the herbivora, the proportion of nitrogenous to non-nitrogenous
food necessary is 1 of the former to 8 or 9 parts of the latter.

237. Metabolism during Hunger and 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.

HUNGER AND STARVATION.

483

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 faeces, urine, and expired air. The N and C, of course, can only be
obtained from the decomposition of tissues containing them.

The following table from Bidder and Schmidt shows the amounts of the
different excreta in the case of a starved cat : —

Day.

Body-
weight.

"Water
taken.

Urine.

Urea.

Inorganic
substances
in Urine.

Dry

Faeces.

Expired
C.

Water in
Urine
andFeeces.

1.

2,464

98

7-9

1-3

1-2

13-9

91-4

0^

2,297

11-5

54

5-3

0-8

1-2

12-9

50-5

3.

2,210

45

4-2

0-7

1-1

13

42-9

4.

2,172

GS-2

45

3-8

07

1-1

12'3

43

5.

2,129

. . .

55

4-7

0-7

1-7

11-9

54-1

6.

2,024

...

44

4-3

0-6

0-6

11-6

41-1

7.

1,946

• . •

40

3-8

0-5

0-7

11

37-5

8.

1,873

. . .

42

3-9

0-6

1-1

10-6

40

9.

1,782

15-2

42

4

0-5

17

10-6

41-4

10.

1,717

...

35

3-3

0-4

1-3

10-5

34

11.

1,695

4

32

2-9

0-5

1-1

10-2

30-9

12.

1,634

22-5

30

2-7

0-4

1-1

10-3

29-6

13.

1,570

7-1

40

3-4

0-5

0-4

10-1

36-6

14.

1,518

3

41

3-4

0-5

0-3

9-7

38

15.

1,434

...

41

2-9

0-4

0-3

9-4

38-4

16.

1,389

48

3

0-4

0-2

8-8

45-5

17.

1,335

. . .

28

1-6

0-2

0-3

7-8

26 -G

18. f

1,267

13

0-7

0-1

0-3

6-1

12-9

-1,197

131-5

775

65-9

9-8

15-8

190-8

734-4

The cat lost 1,197 grm. in weight before it died, and this amount
is apportioned in the following way: 204'43 grm. ( = 17'01 per cent.);
loss of albumin, 132'75 grm. ( = 11-05 per cent.); loss of fat, 8G3-S2
grm., loss of water (=71 '91 per cent, of the total body-weight).

Amongst the general phenomena of inanition, it is found that
strong, well-nourished dogs die after 4 weeks, man after 21-24 days
(Moleschott) — (G melancholies who took water died after 41 days) ;
small mammals and birds, 9 days, and frogs 9 months. Vigorous
adults die when they lose T% of their body-weight, but young
individuals die much sooner than adults.

The symptoms of inanition are obvious: — The mouth is dry, the
walls of the alimentary canal become thin, and the digestive 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

484 LOSS OF WEIGHT DURING STARVATION.

and almost disappear. The blood contains less water and the plasma
less albumin, the gall-bladder is distended, which indicates a con-
tinuous 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 diminished excretion of urea is much greater than that of C00,
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 decomposition. The excretion
of CO., therefore falls more slowly than the total body-weight, so
that the unit-weight of the living animal from day to day may
even show an increased production of C00. The amount of 0
consumed, depends of course upon the oxidation of proteids (which
require less 0), and of fats (which require more 0).

According to D. Finkler, starving animals consume nearly as much 0 as well-
nourished animals, so that the energy of oxidation is scarcely altered during
inanition. Corresponding to this, the temperature of a starving animal is the
same as normal. The respiratory quotient (p. 255) falls from 0'9 to 0'7, and the
excretion of C02 diminishes more rapidly than the consumption of 0. It would
be wrong, however, to conclude, from the diminished condition of COo, that the
oxidation also was diminished, as the simultaneous consumption of 0 is the only
guide to the energy of the metabolism. As starving animals use up their own
flesh and fat, they form less C02 than well-nourished animals which oxidise carbo-
hydrates.

Loss of weight of Organs.— It is of importance to determine to
what extent the individual organs and tissues lose weight; some
undergo simple loss of weight, e.g., the bones, the fat undergoes very
considerable and rapid decomposition, while other organs, as the heart,
undergo little change, because they seem to be able to nourish
themselves from the transformation products of other tissues.

A starving cat, according to v. Voit, lost—

Per cent, of Per cent, of

the originally tho total loss of
present. body-weight.

1. Fat, . . 97 ... 2G-2

2. Spleen, . GG'7 ... O'G

3. Liver, . 537 ... 4 -8

4. Testicles, . 40 '0 ... O'l

5. Muscles, . 30'5 ... 42 -2

6. Blood, . 27-0 ... 3-7

7. Kidneys, . 25'9 ... O'G

8. Skin, . 20-6 ... 8-8

9. Intestine, . IS'O 2'0

Per cent, of Per cent, of
the originally the total loss of

present. body-weight.

10. Lungs, . 17'7 ... 0'3

11. Pancreas, 17'0 ... O'l

12. Bones, . 13'9 ... 5'4

13. Central Nervous

System, 3'2 ... O'l

14. Heart, . 2-6 ... Q-Q2

15. Total loss of
the rest of the

body, . 36-8 ... 5'0

METABOLISM DURING A FLESH DIET. 485

There is a very important difference according as the animals before
inanition have been fed freely on flesh and fat, 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 " drculatinrj " or
"storage-albumin" so that during hunger, it must decompose more
readily and to a greater extent than the "organ-albumin" which
forms an integral part of the tissues (p. 477). Further, in fat indi-
viduals, tho decomposition of fat is much greater than in slender
persons.

238, Metabolism during a purely Flesh Diet—
Albumin or Gelatin.

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. 480). A healthy person excretes 280 grammes of carbon, in the
form of CO.,, in the expired air and in the urine and fceces. If a man
is to obtain 280 grammes C from a flesh diet he must consume —
digest and assimilate — more than 2 kilos, of beef in 24 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 maintain 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 ^ to ^ 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 J- to *V 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 apparatus is
adapted solely for the digestion of vegetable food.

Exactly the same result occurs with other forms of proteids, as
with flesh. It 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

486 DIET OF PURE FAT OR CARBOHYDRATES.

albumin. The carnivora which can 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 (v. Bischoff, v.
Voit, v. Pettenkofer, Oerum).

Owing to the great solubility of gelatin, the value of gelatin as a food used
to be greatly discussed, and now again the addition of gelatin in the form of
calf s-foot jelly is recommended to invalids. When chondrin is given along with
flesh for a time, grape-sugar is found in the urine (Bodeker).

239. A Diet of Fat or of Carbohydrates.

If fat alone be given as a food, the animal lives but a short time.
The animal so fed secretes even less urea than when it is starving ;
so that the consumption of fat limits the decomposition of the animal's
own proteids. This depends upon the fact that, fat being an easily
oxidised body, 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, e.g., in the C02 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.

When carbohydrates alone are given, they must first be converted
by the act of digestion into sugar. The result of such feeding
coincides pretty nearly with the results of feeding with fat alone.
But the sugar is more easily burned or oxidised within the body
than the fat, and 17 parts of a 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 direct introduction of grape-sugar and cane-sugar into the blood does not
increase the amount of oxygen used, although the amount of COs formed is
increased (Wolfers).

240. Mixture of Flesh and Fat,

or of Flesh and Carbohydrates.

Since an amount of flesh equal to -^-g—^ 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 carbohydrates be added to
the diet, a quantity of flesh three or four times less is required. A
carbohydrate has a greater effect in diminishing the amount of urea

DIET OF MIXTURE OF FLESH AND FAT. 487

excreted, than a quantity of fat, which requires the same amount of 0
to oxidise it, as is required by the amount of carbohydrates con-
sumed. 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 Avith the
amount of flesh consumed. It is remarkable that more 0 is con-
sumed when a given amount of flesh is taken, than when the same
amount of flesh is taken with the addition of fat (v. Pettenkofer
and v. Voit).

It seems that instead of fat, the corresponding amount of fatty acids has the
same effect on the metabolism. 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 (J. Munk, Will). Glycerin does not
diminish the decomposition of albumin within the body (Lewin, Tschirwinsky,
J. Munk). According to Lebedeff and v. Voit, it diminishes the decomposition of
the fats, and is therefore a food.

241. Origin of Fat in the Body.

I. Part of the fat of the body is derived directly from the food, i.e.,
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).

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.

II. A second source of the fats is their formation from albuminous
bodies (Liebig and others).

In the case of the formation of fat from proteids, which may yield
11 per cent, of fat, these proteids split up into a non-nitrogenous and a
nitrogenous atomic compound. The former, during a diet containing
much albumin, when it is not completely oxidised into C00, and H00, is
the substance from which the fat is formed — the latter leaves the body
oxidised chiefly to the stage of urea (Hoppe-Seyler, Fiirstenberg, v.
Voit, v. Pettenkofer).

Examples. — That/cite are formed from proteids is shown by the following :— 1.
A cow which produces 1 Ib. of butter daily, does not take nearly this amount of

488 ORIGIN OF FAT IN THE BODY.

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 some 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 degeneration, e.g.,
of nerve and muscle, is due to a decomposition of proteids. 5. The transformation
of entire bodies, e.g., such as have lain for a long time surrounded with water, into
a mass consisting almost entirely of palmitic acid (the adipocere of Fourcroy), is
also a proof of the transformation of part of the proteids into fats. 6. Fungi are
also able to form fat from albumin during their growth (v. Naegeli, and 0. Low).

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 : — 1.
Fattening occurs with flesh and soaps ; it is most improbable that the soaps are
retransformed into neutral fats by taking up glycerin and giving up alkali
(Kiihne and Radziejewski). 2. If a lean dog be fed with flesh and palmitin-of
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 all the fat
arises in this way, aud that none of it is absorbed and redeposited.

III. According to v. Voit, no fat is formed in the body directly, e.g.,
by reduction from carbohydrates. As fattening occurs on a diet of pure
flesh with the addition of carbohydrates, we must assume 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 stored up as
such.

From experiments upon animals, however, Lawes, Lehmann, Heiden,
v. Wolff, think they are entitled to conclude that the carbohydrates
absorbed are directly concerned in the formation of fats, a view which is
supported by Henneberg, B. Schulze, Gilbert and Soxhlet. According
to Pasteur, glycerine (the basis of neutral fats) may be formed from
carbohydrates.

Formerly it was believed that bees could prepare wax from honey alone; this is
a mistake— an equivalent of albumin is required in addition— the necessary amount
is found in the raw honey itself.

242. Corpulence.

The addition of too much fat to the body is a pathological phenomenon which
is attended with disagreeable consequences. With regard to the caUSCS of
obesity, without doubt there is an inherited tendency (in 33-56 per cent, of the
cases — Bouchard, Chalmers) in many families — and in some breeds of cattle — to
lay up fat in the body, while other families may be richly supplied with fat, and
yet remain lean. The chief cause, however, is taking too much food, i.e. , 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 (p. 477).

CORPULENCE. 489

Conditions favouring Corpulence.— The following conditions favour the
occurrence of corpulence: — (1) A diet 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 (p. 487), the assumption
that fats and carbohydrates fatten, or when taken alone, act as fattening agents,
is completely without foundation. No one ever becomes fat without taking
plenty of albumin. (2) Diminished disintegration of materials within the body —
e.g. (a) diminished muscular activity (much sleep and little exercise); (b) abroga-
tion 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) ; (c) 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 deposition of fat in the
abdomen, limiting the action of the diaphragm (breathlessness of corpulent
people), whereby the combustion of the fatty matters, which become deposited in
the body, is limited ; (e) 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 conduction of heat (p. 444). Thus
corresponding to the relatively diminished production of heat, more fat may be
stored up; (/) 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 (p. 63) — women
with fewer red blood-corpuscles are usually fatter than men; (n) 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).

Well-nourished individuals are usually at first both muscular and endowed
with a fair amount of fatty tissue. When they begin to put on fat, the develop-
ment of the muscular system lags behind, partly because the increasing corpulence
leads to diminished activity of the muscular system, so that this system is
involved secondarily. Some lively corpulent people, nevertheless, retain their
muscular energy. When those conditions which favour corpulence are specially
active, corpulence may ultimately pass into a condition of great obesity.

Besides the inconvenience of the great size and weight of the body, corpulent
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.

In order to 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 diminution in the body-weight the amount of food ought to be
gradually and uniformly reduced (notwithstanding the appetite). This must be
done very gradually and not suddenly. 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 metabolism is apt to
occur. (2) The muscular activity ought to be greatly developed by doing plenty of
muscular work, or taking plenty of exercise, both physical and mental. (3) Favour
the evolution of heat by taking cold baths of considerable duration, and afterwards
rubbing the skin strongly so as to cause it to become red; farther, dress lightly;
and at night use light bed-clothing; tea and coffee are useful, as they excite the
circulation. (4) Use gentle laxatives; acid fruits, cider, alkaline carbonates
(Marienbad, Carlsbad, Vichy, Neuenahr, Ems, &c.). The copious drinking of
water is also serviceable, as it favours the metabolism.

Fatty Degeneration, — The process of fattening consists in the deposition of

490 METABOLISM OF THE TISSUES.

drops of fat within the fat-cells of the pauniculus and around the viscera, as well
as in the marrow of bone (but they 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 degeneration which
occurs in the form of fatty globules or granules in albuminous tissues — e.g., 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; wben a too small amount of 0 is supplied to the tissues, as occiirs in
cases of phosphorus poisoning (Bauer); in drunkards; after poisoning with arsenic
and other substances; and after some disturbances of the circulation and inner-
vation. Some organs are especially prone to undergo fatty degeneration during the
course of certain diseases.

243. The Metabolism of the Tissues,

The blood-stream is the chief medium whereby new material is
supplied to the tissues and the effete products removed 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, as
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 affection of the blood-vessels on which the
cornea depends for its nutrition]. Total compression or ligature
of all the blood-vessels, results in necrosis of the parts supplied by
the ligatured blood-vessels.

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. That such a current exists is proved by
injecting an indifferent, easily recognisable substance into the blood,
e.g., potassium ferrocyanide, when its presence may be detected in
the tissues, to which it has been carried by the out-going current.
The efferent stream carries away the decomposition products from
the various tissues, more especially urea, C02, H20 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,

METABOLISM OF THE TISSUES. 491

e.g., subcutaneously, when its presence may be detected in the urine
within 2 to 5 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. This occurs when certain poisons are injected sub-
cutaneously, when they pass rapidly into the blood and are carried
in great quantity to other tissues, e.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 two
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 swelling of the tissues may occur (oedema, p. 419.)

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.

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). When an 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 become 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
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 (p. 283), and those of mucous and pepsin-
forming glands (p. 327), 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 glandular
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 influence. The variations in the total metabolism
of the body are reflected in the excretion of CO., and urea, which
may be expressed graphically in the form, of a curve corresponding

492 METABOLISM OF THE TISSUES.

•with the activity of the organism ; this curve corresponds very closely
with the daily variations in the respirations, pulse, and temperature.

2. The composition or quality 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, e.g., in cholera, makes
the tissues dry, while if much water be absorbed into the blood, the
tissues become more succulent and even oedema may occur. When
much common salt is present in the blood and when the red blood-
corpuscles contain a diminished amount of 0, 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 of urea. Hence, exposure to a rarified atmosphere is
accompanied by increased excretion of urea (Frankel, Penzoldt, and
R. Fleischer). Certain abnormal conditions of the blood produce
remarkable results; blood charged with carbonic oxide cannot absorb
0 from the air, and does not remove CO., from the tissues (compare
p. 31). The presence of hydrocyanic acid in the blood (p. 33), is said
to interrupt at once the chemical oxidation processes in the blood
(Mialhe), so that rapid asphyxia, owing to cessation of the internal
respiration, occurs (Ed. Wagner). 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
(p. 63), but the absorption of substances — such as poisons or patho-
logical effusions (Kaup), from the tissues or intestines is delayed.
If the substances which pass from the tissues into the blood be
rapidly eliminated from it, absorption takes place more rapidly.

3. The blood-pressure is of importance in so far that, when it is
greatly increased, the tissues contain more fluid, while the blood
itself becomes more concentrated, to the extent of 3-5 per 1000
(Nasse). 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.

4. Increased temperature of the tissues favours the metabolism,
so that the excretion of C02 and the production of urea are increased
(§§ 220, 221); while diminution of the temperature has the opposite
result (§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

REGENERATION OF ORGANS AND TISSUES. 493

agency of vaso-motor nerves, whereby it influences the amount of blood
supplied, and also affects the blood-pressure. But ill addition to this,
and quite independently of the blood-vessels, it is probable that certain
special nerves — the so-called trophic nerves, influence the metabolism or
nutrition of the tissues (see Trophic Nerves). 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 (p. 287), and by
the metabolism during the contraction of bloodless muscles. Increased
respiration and apncea are not followed by increased oxidation (Pfliiger)
(compare p. 259).

244, Regeneration of Organs and Tissues.

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 (Spallanzani). The Planarians also show a great capability
of reproducing lost parts (Duges). 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 tins, 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
(Philippeaux).

In amphibians and reptiles, the regeneration of organs and tissues as a whole,
takes place after the type of the embryonic development (Fraisse, Giitte), and the
same is true as regards the histological processes which occur in the regenerated
tail and other parts of the body of the earth-worm (Bulow).

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 (compare § 7 and § 41), including the plasma, the
colourless and coloured corpuscles.

2. The epidermal appendages (see Skin, vol. £), and the epithelium of
the mucous membranes are reproduced by a proliferation of the cells of
the deeper layers of the epithelium, with simultaneous division of their
nuclei. Epithelial cells are reproduced 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,

494 REGENERATION OF TISSUES.

while the deepest layer of cells forms large multi-nucleated cells which
reproduce by division polygonal, flat nucleated cells (Klebs, Heller).
The nails grow from the root forwards ; those of the fingers in 4-5
months, and that of the great toe in about 1 2 months, although growth is
slower in the case of fracture of the bones. The matrix is co-extensive
with the lumdc, and if it be destroyed the nail is not reproduced
(see vol. ii.). The eyelashes are changed in 100 - 150 days
(Donders), 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
(Aristotle). 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 (vol. ii.) proves this ; the spermatozoa 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 epithe-
lium, while many cells are but indifferently formed and constitute mucous
corpuscles. The crystalline lens, which is just modified epithelium, is
reorganised just 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, 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 (Kunde, Koehnhorn). [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 frog.]

3. The blood-vessels undergo extensive regeneration, and they
are regenerated in the same way as they are formed (p. 13).
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 deriva-
tives 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 (Sigm. Mayer).

4. The contractile substance of muscle may undergo regeneration
after it has become partially degenerated. This takes place after amy-
loid or wax-like degeneration, such as occurs not unfrequently after
typhus and other severe fevers. This is chiefly accomplished by an

REGENERATION OF TISSUES. 495

increase of the muscle corpuscles. After being compressed, the mus-
cular nuclei disappear and at the same time the contractile contents
degenerate (Heidelberg). After several days, the sarcolemma contains
numerous nuclei which reproduce new muscular nuclei and the con-
tractile substance (Kraske, Erbkam). In fibres injured by a subcu-
taneous wound, Neumann found that, after 5-7 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 differen-
tiation 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 which are described in vol. u. 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 vol. ii.
There seems to be in peripheral nerves a continual disappearance of
fibres by fatty degeneration, accompanied by a consecutive formation of
new fibres (Sigm. Mayer). The regeneration of peripheral ganglionic
cells is unknown, v. Voit, however, observed that a pigeon, part of whose
brain was removed, had within five months reproduced a nervous mass
within the skull consisting 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 ana-
tomical and physiological regeneration to such an extent that voluntary
movements could be executed. 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 does not
occur.

6. If a portion of a secretory gland be removed, as a general rule, it
is not reproduced. But the bile-ducts (p. 350), and the pancreatic
duct may be reproduced (p. 345). According to Philippeaux and
Griffini, if part of the spleen be removed, it is reproduced (compare
p. 207). Tizzoni and Collucci observed the formation of new liver-
cells and bile-ducts after injury to the liver.

7. Amongst connective-tissues, cartilage, provided its perichondrium
be not injured, reproduces itself by division of its cartilage cells

496 REGENERATION OF BONE.

(Legrand, Ewetzky, Schklarewsky); 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 (Jakimowitsch).
If a piece of periosteum be transplanted to another region of the body,
it eventually gives rise to the formation 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 (P. Bruns, MacEwen).

In fracture of along 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 tirst 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 proliferation 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 becomes 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. When this begins to
be definitely ossified, the outer and inner callus begins to be absorbed, and ultimately
the intermediary callus has the same structure as the rest of the bone.

There are many interesting observations connected with the growth and meta-
bolism of bones. 1. The addition of a very small amount of phosphorus (Wagner)
or arsenious acid (Maas) to the food causes considerable 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
(v. Voit), but the bones become thinner, whereby all parts, even the organic basis of
the bone, undergo a uniform diminution (Chossat, A. Milne-Edwards). 3. Feeding
with madder makes the bones 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 (Siedamgrotzky and Hofmeister). 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. The normal de-
velopment of bone is described in vol. ii.

When a lost tissue is not replaced by the same kind of tissue, its
place is always taken by cicatricial connective-tissue.

TRANSPLANTATION OF TISSUES. 497

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 themselves, and many of them
undergo fatty degeneration, whilst others take up nutriment and become con-
verted into large uninucleated protoplasma-cells, from which giant-cells are
developed (Ziegler, Cohnheim). 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. The 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.

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.

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 adjoining parts.

Oilier found that, when periosteum was transplanted it grew and reproduced
bone in its new situation. Even blood and lymph may be transfused (Trans-
fusion— p. 199).

All 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. [While J. R. Wolfe has transplanted the conjunctiva of the
rabbit to the human eye]. Most tissues, however, do not admit of transplanta-
tion, 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
reaction ; they, in fact, behave like inert foreign matter.

246. Increase in Size and Weight during Growth,

The length of the body, which at birth is usually ~ 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 5-16 years the annual increase is
about 5| centimetres. In the twentieth year the increase is very slight. From
50 onwards the size of the body diminishes, owing to the intervertebral discs
becoming thinner, and the loss may be 6-7 centimetres about the eightieth year.
The weight of the body (-£$ of an adult) sinks during the first 5-7 days, owing to
the evacuation of the meconium and the small amount of food which ia taken at
first.

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

32

498

INCREASE IN SIZE AND WEIGHT.

reached about 40, while towards 60 a decrease begins, which «it 80 may amount
even to 6 kilo. The results of measurements, chiefly by Quetelet, are given in the
following table: —

Age.

Length (Cmtr.)

Weight (Kilo.)

Age.

Length (Cmtr.)

Weight (Kilo.)

Man.

Woman.

Man.

Woman.

Man.

Woman.

Man.

Woman.

0

49-6

48-3

3-20

2-91

15

155-9

147-5

46-41

41-30

1

696

69-0

10-00

9-30

16

161-0

150-0

53-39

44-44

o

79-6

78-0

12-00

11-40

17

167-0

154-4

57-40

49-08

3

86-0

85-0

13-21

12-45

18

170-0

156-2

61-26

53-10

4

93-2

91-0

15-07

14-18

19

170-6

63-32

• . ,

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

111-2

109-6

20-16

18-45

30

1722

157-9

68-90

55-14

8

117-0

113-9

22-26

19-82

40

171-3

155-5

68-81

56-65

9

122-7

120-0

24-09

22-44

50

167-4

153-6

67-45

58-45

10

128-2

124-8

26-12

24-24

60

163-9

151-6

65-50

56-73

11

1327

127-5

27-85

26-25

70

162-3

151-4

63-03

53-72

12

135-9

132-7

31-00

30-54

80

161-3

150-6

61-22

51-52

13

140-3

1386

35-32

34-65

90

• • •

57-83

49-34

14

148-7

144-7

40-50

38-10

(Chiefly from Quetelet).

Between the 12th and 15th years, the weight and size of the female are greater
than of the male. Growth is most active in the last months of fcetal life, and
afterwards from the 6th to 9th year, until the 13th to 16th. The full stature is
reached about 30, but not the greatest weight (Thoma).

General Yiew 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, S2-7 per
cent.; bones, 22 per cent.; teeth, 10 per cent.; while enamel contains the least,
0'2 per cent.

[ Water is of the utmost importance in the economy, and it is no paradox to say
that all organisms live in water, for though the entire animal may not live in
water, all its tissues are bathed by watery fluids, and the essential vital processes
occur in water (p. 458). A constant stream of water may be said to be passing
through organisms, a certain quantity of water is taken in with the food and
drink, which ultimately reaches the blood, while from the blood a constant loss is
taking place by the urine, the sweat and breath. The greater quantity of the water
in our bodies is derived from without, but it is probable that a small amount is
formed within our bodies by the action of free oxygen on certain organic sub-
stances. According to some observers, peroxide of hydrogen (B.202) is also
present in the body.]

II. Gases.— [Oxygen is absorbed from the air, and enters the blood, where it
forms a loose chemical compound, with the colouring matter or haemoglobin, while
a small amount exists in a free state, or is simply absorbed.] Hydrogen is found
in the alimentary canal. Nitrogen [like oxygen, is absorbed from the atmosphere
by the blood, in which it is dissolved, and from which it passes into other fluids
of the body. It is probable that a very small quantity is formed within the body.]

The presence of Marsh gas (CH4) (p. 255), ammonia (NH3), and sulphuretted
hydrogen (H2S) (p. 372) has been referred to already.

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 it 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. 502). In some cases it exists in
a state of combination with albuminous 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, the great part being excreted by
the urine. Boussingault showed that, the addition of a certain
amount of common salt to the daily food of cattle greatly improved
their condition.]

Calcium phosphate [ (Ca3P208) is the moat abundant salt in the body, ag it forms
more than one-half of our bonea, but it also occurs in dentine, enamel, and to a

500 SALTS, ACIDS, AND BASES IN THE BODY.

much less extent in the other solids and fluids of the body. Amongst secretions,
milk contains relatively the largest amount (2 '72) per cent. In milk it is neces-
sary for forming the calcareous matter of the bones of the infant. It gives bones
their hardness, solidity, 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 (PNa304), acid sodium phosphate, (PNa2H04), acid
potassium phosphate (PK.7H04). [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,
and also forms an important constituent of nerve-tissue.]

Sodium carbonate (Na2C03) and sodium bicarbonate (NaHC03) [exist in small
quantities in the food, and are chiefly 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 C02 from the tissues to the lungs.]

Sodium and jiotassium sulphates (NaS04, and K2S04) [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.]

[Potassium chloride (KC12) is pretty widely distributed, and it occurs specially
in muscle, coloured blood-corpuscles, and milk. Calcium fluoride (CaFlo) occurs
in small quantity in bones and teeth. Calcium carbonate (CaCOo) is associated
with calcium phosphate in bone, tooth, and in some fluids, but it occurs in rela-
tively much smaller amount. It is kept in solution by alkaline chlorides, or by the
presence of free carbonic acid.]

Ammonium chloride (NH4C1). — [Minute traces occur in the gastric juice and
the urine.]

Magnesium phosphate (Mg3P04) [occurs in the tissues and fluids of the body
along with calcium phosphate, but in very much smaller quantity.]

IV. Free Acids. — Hydrochloric acid (HC1) [occurs free in the gastric juice, but
in combination with the alkalies it is widely distributed as chlorides.] Sulphuric
acid (H2S04) [is said to occur free] in] the saliva of certain gasteropods, as Dolium
galea. In the body it forms sulphates, being chiefly in combination with soda and
potash.]

V. Bases- — Silicon as silicic acid (Si02) ; manganese, iron, the last forms an
integral constituent of the blood pigment ; copper (?), p. 352.

248. (B.) Organic Compounds,

I. THE ALBUMINOUS OR PROTEID SUBSTANCES.
1. Proteids and their Allies.

Proteids and their allies are composed of C, H, 0, N, and S, and are derived
from plants (see Introduction).
[According to Hoppe'Seyler their general percentage composition is

O. H. N. 0. S.

From . . . 20-9 6'9 15'2 51'5 0'3
to . „ . . 23-5 to 7'3 to 17-0 to 54'5 to 2'0.]

CHARACTERS OF THE PROTEIDS. 501

They exist in all animal fluids, and in nearly all the tissues. They occur partly
in the fluid form, although Briicke maintains that the molecule of albumin exists
in a condition midway between a state of imbibition 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. White of egg is the type. In the alimentary canal they are changed into
peptones. The chief products derived from their oxidation within the body are
CC^HjO, and especially urea, which contains nearly all the N of the proteids.

Constitution. — Their chemical constitution is quite unknown. The N seems
to exist in two distinct conditions, partly loosely combined, so as to yield am-
monia readily when they are decomposed, and partly in a more fixed condition.
According to Pfliiger, part of the N in living proteicl bodies exists in the form of
cyanogen. 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 of milk, this last view seems not improbable.

Characters. — Proteids, the anhydrides of peptones are colloids (p. 394), 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 and
others are insoluble in water ; they are insoluble in alcohol ; they rotate the ray of
polarised light to the left; in a flame, they give the odour of burned horn.
Various metallic salts and alcohol precipitate them from their solution, and 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.

Decompositions. — When acted upon in a suitable manner by acids and alkalies,
they give rise to the decomposition products — leucin (10-18 per cent.), tyrosin
(0-25-2 per cent.), asparaginic acid, glutamic acid, and also volatile fatty acids,
benzoic and hydrocyanic acids, and aldehydes of benzoic and fatty acids ; also,
indol (Hlasiwetz, Habermann). Similar products are formed during pancreatic
digestion (p. 342), and during putrefaction (p. 376).

Reactions. — They are coagulated by (1) nitric acid, and when boiled there-
with give a yellow, the xanthoproteic reaction; the addition of ammonia gives a
deep orange colour.

(2) Millon's reagent (nitrate of mercury with nitrous acid); when heated M'ith
this reagent above 60° C., they give a red, probably owing to the formation of
tyrosin. [If the proteids are present in large amount, a red precipitate occurs,
but if mere traces are present only the fluid becomes red.]

(3) The addition of a few drops of solution of cupric sulphate, and the subse-
quent addition of caustic potash or soda give a violet colour, which deepens on
boiling, [or the same colour may be obtained by adding a few drops of Fehling's
solution. ]

(4) They are precipitated by acetic acid and potassium ferrocyanide.

(5) When boiled with concentrated hydrochloric acid they give a violet-red
colour.

(6) Sulphuric acid containing molybdic acid gives a blue colour (Frb'hde).

(7) Their solution in acetic acid is coloured violet with concentrated sulphuric
acid, and shows 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 (E. Schultze).

[ (9) When boiled with acetic acid and an equal volume of a concentrated
solution of sodium sulphate, they are precipitated. This method is frequently
used for removing proteids from other liquids, as it does not interfere with the
presence of other substances.]

502 NATIVE ALBUMINS AND GLOBULINS.

249. The Animal Proteids and their Characters.

They have been divided into classes: —

Class I. — Native Albumins.

Native Albumins occur in a natural condition in the solids and fluids of the
body. They are soluble in water, and are not precipitated by alkaline carbonates,
NaCl, or by very dilute acids. Their solutions are coagulated by heat at 65°-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, whose cheinico-physical characters are given at p. 49,
and its physiological properties at § 41. Almost all its salts may be removed
from it by dialysis, when it no longer coagulates with heat (Schmidt). It is
coagulated by strong alcohol, and is easily dissolved in strong hydrochloric 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.

(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 (p. 397). When shaken with ether, it is precipitated.
These two reactions serve to distinguish it from (1). The specihc rotation is —
37-8°.

(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.
They are not precipitated by acetic acid, by acetic acid and potassium ferro-
cyanide, by mercuric chloride, or by saturation with magnesium sulphate. Con-
centrated sulphuric acid and acetic acid give a violet colour (Adamkiewicz).
According to Hammarsten, metalbumin is a mixture of paralbumin and other
proteid substances. On being boiled with dilute sulphuric acid they yield a
reducing substance (? sugar)).

Class II.— Globulins.

They are native proteids, which are insoluble in distilled water, but are soluble
in dilute saline solutions, 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 C02 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 of the foregoing are not
precipitated from their neutral solutions by saturation with sodium chloride.

(3.) Para-globulin or Serum-globulin (p. 44).

(4.) Fibrinogen (p. 45).

(5.) Myosin is the chief proteid in dead muscle. Its coagulation in muscle
post mortem constitutes rigor mortis. If muscle be repeatedly washed and after-
wards treated with a 10 per cent, solution of sodium 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 method of preparation, see Muscle.

(6.) Globin (Preyer), the proteid residue of haemoglobin.

ALBUMIN ATES AND OTHER PROTEIDS. 503

Class III. — Derived Albumins (Albuminates).

(1-) Acid- Albumin or Syntonin. — When proteids are dissolved in the stronger
acids, e.g., hydrochloric, they become changed into acid-albumins. They are
precipitated from solution by the addition of many salts (NaCl, Na2S04) or by
neutralisation with an alkali, e.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. 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) arid in the other with the acid.

(2.) Alkali- Albumin. — If egg- or serum-albumin be acted upon by dilute
alkalies, a solution of alkali-albumin is obtained. Strong caustic potash acts upon
white of egg and yields a thick jelly (Lieberkiihn). The solution is not precipitated
by heat, but is precipitated by the addition of an acid.

(3. ) Casein is the chief proteid in milk (p. 466). It is precipitated by acids and by
rennet at 40°C. In its characters it is closely related to alkali-albuminate, but,
according to 0. Nasse, it contains more N. It contains a large amount of phos-
phorus (O'SS per cent.). It may be precipitated from milk by diluting it with
several tunes 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 HC1 (O'l per cent.) and pepsin at the
temperature of the body, it gradually yields nuclein.

Class IV.— Fibrin.

For fibrin, see p. 39, and for the fibrin-factors, p. 43.

Class V. — Peptones.

For peptones and propeptones, see p. 331.

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 — Valenciennes and Fremy); also the indigestible Amyloid substance
(Virchow) 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, e.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
dissolved 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 com-
position and reaction they resemble animal proteids. Vegetable proteids have fre-
quently been obtained in a crystalline form (Radlkofer), e.g., from the seeds of
the gourd (Griibler) and various oleaginous seeds (Ritthausen).

504 VEGETABLE PROTEIDS.

1. Vegetable albumin is found dissolved in most juices of plants and closely
resembles animal albumin. If the dough of wheat be washed with water, and the
starch be allowed to subside, on boiling the supernatant fluid the vegetable
albumin is coagulated.

2. Glutin (vegetable fibrin) occurs in cereal grains, and its peculiar glutinous
or sticky characters, when mixed with water, enable it to form dough. From
wheat, which may contain as much as 17 per cent., it is prepared by washing away
all the starch from the dough with a stream of water. This is best effected by
washing the dough in a muslin bag or over a fine sieve. It is elastic, gray, insol-
uble in water and alcohol, and soluble in dilute acids (1 HC1 per 1000), and in
alkalies. Glutin is a complex substance. If it be boiled with water a sticky
varnish-like mass is obtained, yliadin (animal gelatin). If this substance is
treated with strong alcohol it dissolves, but a slimy body remains undissolved,
mucedin. If glutin be digested with alcohol, a brownish-yellow substance, glutin-
fibrin (Ritthausen) is extracted from it.

3. Vegetable Casein occurs specially in the leguminosae. It is slightly soluble
in water, but readily soluble in weak alkalies, and in solutions of basic calcic
phosphate. These solutions, like animal casein, are precipitated by acids or
rennet. The varieties of it are— (a) Legumin in peas, beans, lentils (Einhof, 1805);
it has an acid reaction, is insoluble in water, easily soluble in dilute alkalies, and
in very dilute HC1 or acetic acid; (6) the casein -like body occurring in hops and
almonds which closely resembles (a), and is called conglutin (Ritthausen). Vegetable
casein, like animal casern, is an alkali-albuminate, and is precipitated by the same
substances ; it is not precipitated by boiling. When long exposed to the air. its
solution coagulates with the formation of lactic acid.

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 contain S, but
the most of them have not been prepared free from ash. Their reactions and
decomposition products closely resemble those of the proteids ; some of them pro-
duce, in addition to leucin and tyrosin, glycin and alanin (amido-propionic acid).
They occur as organised constituents of the tissues and also in a fluid form. It is
unknown whether they are formed by oxidation from proteid bodies or by
synthesis.

1 . Mucill is the characteristic substance present in mucus. It contains no S.
That obtained from the sub-maxillary gland contains C. 52'31, H. 7'22, N. 11 '84,
O. 28'63 (Obolensky). 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 ferro-cyanide of
potassium, but HN03 and other mineral acids precipitate it (Scherer). It occurs
in saliva (p. 292), in bile, in mucous glands, secretions of mucous membranes, in
mucous tissue, in synovia, and in tendons (A. Rollet). Pathologically it occurs
not unfrequently in cysts ; in the animal kingdom, especially in snails and in the
skin of holothurians (Eichwald). It yields leucin and 7 per cent, of tyrosin when
it is decomposed by prolonged boiling with sulphuric pcid.

2. Nudein (Miescher— p. 409) C. 29, H. 49, N. 9, P. 3, 0. 22, is slightly
soluble in water, easily in ammonia, alkaline carbonates, strong HN03 ; 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 (p. 36), in
spermatozoids, yelk-spheres, liver, brain, and milk, yeast, fungi, and many seeds.
Its most remarkable characteristic is the large quautity of phosphorus it contains,
nearly 10 per cent. Hypoxauthin and guanin have been obtained as decomposition
products from it (Kossel).

THE ALBUMINOIDS.

505

3. Keratin occurs in all horny and epidermic tissues (epidermic scales, hairs,
nails, feathers)- C. 50'3-52'5 ; H. 6 '4-7 ; N. 16'2-17'7 ; O. 20'8-25 ; S. 07-5 per
cent., is soluble only in boiling caustic alkalies, but swells up in cold concentrated
acetic acid. When decomposed by HoS04 it yields 10 per cent, leucin and 3'6 per
cent, tyrosin.

4. Fibroin is soluble in strong alkalies and mineral acids, in ammonio-
sulphate of copper ; when boiled with H2S04 it yields 5 per cent, tyrosin, leucin,
and glycin. It is the chief constituent of the cocoons of insects and threads of
spiders.

5. Spongin, allied to fibroin, occurs in the bath-sponge, and yields as decom-
position products, leucin and glycin (St'adeler).

6. Elastill, the fundamental substance in elastic tissue, is soluble only
when boiled in concentrated caustic potash (C. 55-55 '6 ; H. 7'l-7'7 ; N. 16'1-17'7 ;
0. 19'2-21 '1 per cent. ) It yields 36-45 per cent, of leucin and £ per cent, of tyrosin.

7. Gelatin, 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-lS'S;
S. + 0, 23'5-25 ; (.S. O'G 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. By pro-
longed boiling and digestion it is converted into a peptone-like body (gelatin-
peptone), which does not gelatinise (p. 332). [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 leuksernic blood and in the juice of the spleen (p. 206). When decom-
posed with sulphuric acid it yields glycin, ammonia, leucin, but no tyrosin. It
gives insoluble precipitates with mercuric chloride and tannin.

8. Chondrin (Job. Mtiller) 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. It occurs also in the mantle of molluscs (C. 49 '5-50 %9; H. 6'6-7'l;
N. 14-4-14-9; S + 0. 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 contain 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 chondrin.
The following properties of gelatin and chondrin are to be noted: —

Reagent.

Gelatin.

Chondrin.

Acids, ....

Not precipitated, .

Precipitated by acetic

acid, dilute HC1 and

H2S04.

Tannic acid, mercuric

chloride,

Precipitated, .

Give slight opalescence.

Chlorine water, platinic

chloride,

Precipitated.

Alum, silver, iron, cop-

per, lead salts,

Precipitated, .

Precipitated copiously.

Potassic ferrocyanide and

acetic acid,

Not precipitated.

Alcohol,

Precipitated, precipitate

soluble in water.

Specific Rotation, .

-130°.

—213°.

506

HYDROLYTIC FERMENTS.

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-
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.

[Table showing the unorganised ferments present in the body, and their
actions: —

Fiuid or Tissues.

Saliva, .

Ferment.

1. Ptyalin, . . .
(See also p. 296.)

Actions.

Converts Starch chiefly into Maltose.

Gastric Juice,/

1. Pepsin, . . .

2. Milk-curdling,

3. Lactic Acid Ferment

4. Fat-splitting,

Converts Proteids into Peptones in an
Acid Medium, certain by-product;
being formed (p. 331).

Curdles Casein of Milk.

Splits up Milk-sugar into Lactic Acid.

Splits up Fats into Glycerin and
Fatty Acids.

Pancreatic
Juice, .

1. Diastatic or

Amylopsin, .

2. Trypsin, . . .

3. Emulsive,

4. Fat-splitting or

Steapsin,

5. Milk-curdling, .

Converts Starch chiefly into Maltose.

Changes Proteids into Peptones in
an Alkaline Medium, certain by-
products being formed (p. 341).

Emulsifies Fats.

Splits Fats into Glycerin and Fatty
Acids.

Curdles Casein of Milk.

Intestinal
Juice,

Blood, . .

Chyle, . .
Liver, . .
Milk, . . .
Most Tissues,

1. Diastatic,

2. Proteolytic, .

3. Invertin,

4. Milk-curdling,

!

Does not form Maltose, but Maltose is

changed into Glucose (p. 370).
Fibrin into Peptone (?).
Changes Cane- into Grape-Sugar.
(?in Small Intestine.)

> Diastatic Ferments.

Muscle,
Urine,

Pepsin.

Blood,

Fibrin-forming
Ferment.

(Modified from W. Roberts).]

ORGANISED AND UNORGANISED FERMENTS. 507

(a.) Sugar-forming or diastatic ferment occurs in saliva (p. 294), pancreatic juice
(p. 340), intestinal juice (p. 335), bile (p. 366), blood (p. 36), chyle (p. 410),
liver (p. 351), in human milk (p. 465). Invertin in intestinal juice (p. 370).—
(Cl. Bernard.)

Almost all dead tissues, organic fluids, and even proteicls, although only to a
slight degree, may act diastatically. Diastatic ferments are very generally distri-
buted in the vegetable kingdom.

(b.) Proteolytic or Ferments which act upon proteids. — Pepsin in gastric juice
and in muscle (p. 332), in vetches, myxomycetes (Krukenberg), trypsin in the
pancreatic juice (p. 341 ) , and a similar ferment in the intestinal juice (p. 370).

(c.) Fat-decomposing in pancreatic juice (p. 343) in the stomach (p. 335).

(d.) Milk-coagulating in the stomach (p. 335), pancreatic juice (p. 344), 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.

( 1 . ) The Unorganised ferments are those mentioned in the above 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
produced within the body, in many secretions, by the vital activity of the
protoplasm of cells. They are termed soluble because they are soluble iu water,
glycerine, and some other substances (p. 295), 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].

[(2.) The Organised or living ferments are represented by yeast (p. 474). 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 C02
and alcohol (p. 298), 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 fermentation. 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 compression 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.

All purely physiological processes in the body, except some in the intestinal
canal, depend upon unorganised ferments].

10. Haemoglobin, the colouring matter of blood, which, in addition to
C,H,0,N, andS, contains iron, may be taken with the albuminoids (p. 23).

508 GLUCOSIDES, AND ORGANIC ACIDS.

(3.) Glucosides containing Nitrogen.

In addition to chondrin, the following glucosides containing nitrogen, when sub-
jected to hydrolytic processes, may combine with water, and form sugar and other
substances: —

Cerebrin (see Nervous Syslem) = C57'H.i-loN2025 (Geoghegan).

Protagon occurs in nerves, and contains phosphorus.

CMtin, 2(C15H26N2Oio), is a glucoside containing nitrogen, and occurs in the
cutaneous coverings of arthropoda, and also in their intestine and trachea?; it is
soluble in concentrated acids, e.g. , hydrochloric or nitric acid, but insoluble in
other reagents. According to Sandwick, chitin is an amm-derivative of a carbo-
hydrate with the general formula n(Ci2H2oOio). The hyalin of worms is closely
related to chitin. (Solanin, amygdalin, p. 49, 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) hcematin (p. 33) and
hcematoidin (p. 33). (2) Bile-pigments (p. 357). (3) Urine-pigments (except
ludican). (4) Melanin, C. 44'2, H3, N. 9'9, 0. 42'6, 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).

II.— Organic Acids free from Nitrogen.

(1.) The fatty acids with the formula CnH2n-iO(OH) occur in the body
partly free and partly in combination. Free volatile fatty acids occur in decom-
posing 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 glycerine to form neutral
fats, from which the fatty acid is again set free by pancreatic digestion (p. 343).

(2.) The acids of the acrylic acid series, with the formula CnH2n-30(HO), are
represented in the body by one acid, oleic acid, which in combination with
glycerine yields the neutral fat olein.

251. Fats.

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 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. 507, c), they take up water and yield glycerine 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 glycerine and fatty acids; the fatty acid
unites with the alkali and forms a soap, while glycerine is set free. The soap-
solution dissolves fats.

FATS.

509

Glycerine is a tri-atomic alcohol, C3H5(OH)3) and unites with (1) the following
mono-basic fatty adds (those occurring in the body are printed in italics) : —

1. Formic

2. Acetic

3. Propionic

4. Butyric
[Isobutyric

5. Valerianic

6. Caproic

7. (Enanthylic

8. Caprylic

9. Pelargonic

acid,

))
»

J)

CH202

Corio Oo

C3Hg Oo
04 HS Oo
C4H8 02]
C5H1002

10. Capric acid, Ci0H2002

11. Laurostearic ,, Ci2H2402

12. Myristic ,, C!4H2802

13. Palmitic „ C16H3202
[Margaric ,, C17H3402,

is a mixture of 13 and 14.]

14. Stearic acid, C18H3C02

15. Arachinic ,, C2oH4o02

16. Hyiinic ,, C25H5002

17. Cerotinic ,, C27H5402

The acids form a homologous series with the formula CnH2n-iO(OH). With
every CH2 added their boiling point rises 19°. Those containing most carbon are
solid, and non-volatile; those containing less C (up to and including capric acid)
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 CH2 being removed, while C02 and H20 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, and in milk (p. 465).
Many of them are developed during the decomposition of albumin and gelatin.
Most of the above (except 15-17) occur in the contents of the large intestine
(p. 376).

(2.) Glycerine also unites with the mono-basic oleic acid, which also forms a series,
whose general formula is CnH2u-sO(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), Ci8H3402, is the only one found in the organism; united with glycerine, it
forms the fluid fat, olein (Gottlieb, 1846). 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 (L. Langer). Oleic acid also occurs united with
alkalies (in soaps), and (like some fatty acids) in the lecithins (p. 36). If lecithin
be acted on with barium hydrate, we obtain insoluble stearic, or oleic, or palmitic
acids and barium oleate, together with dissolved neurin 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 pahnitin + oleic acid radicle
(Diakonow).

The neutral fats, the glycerides of fatty acids, and of oleic acid, are triple
ethers of the tri-atomic alcohol glycerine.

With the neutral fats may be associated glycerin-phosphoric acid, an acid
glycerin-ether, formed by the union of glycerine and phosphoric acid, with the
giving off of a molecule of water (C3H9P06) ; it is a decomposition product of
lecithin (p. 36).

(3.) The gly colic acids — (acids of the lactic acid series) have the formula
CnH2ll_oO(OH)2. They are formed by oxidation from the fatty acid series by sub-
stituting OH (hydroxyl) for 1 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)2 ; in this form, however, it only
makes salts. Free carbonic acid or carbon dioxide is an anhydride of the same
= C02.

(b.) Glycolic Acid (oxy-acetic acid), C2H20 (OH)2, doea not occur free in the body.

510 ACIDS AND ALCOHOLS.

One of its compounds, glycin (glycocoll, amidoacetic acid, or gelatin-sugar), occurs
as a conjugate acid, viz., as glycocholic acid in the bile (p. 355), and as hippuric
acid in the urine. Glycin exists in complex combination in gelatin.

(c.) Lactic Acid (oxy-propionic acid), C3H40 (OH)2, occurs in the body in two
isomeric forms — 1. 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 inactive product of "lactic fermentation," which
occurs in gastric juice, in sour milk (sauerkraut, acid cucumber), and can be
obtained by fermentation from sugar (p. 373). 2. The isomer, ethylene-lactic acid,
occurs in the watery extract of muscles.

(d.) Leucic acid (oxy-caproic acid), CgH^Og, 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 (p. 342).
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,
CnH2n_402 (OH)2, are bi-basic acids, which are formed as completely oxidised
products by the oxidation of fatty acids and glycolic acid (H20 being removed);
and it is important to note their origin from substances rich in carbon, e.g., fats,
carbohydrates, and proteids.

(a.) Oxalic Acid, C202 (OH)2, arises from the oxidation of glycol, glycin,
cellulose, sugar, starch, glycerine, and many vegetable acids — it occurs in the
urine as calcium oxalate.

(b.) Succinic Acid, C4H402 (OH)2, has been found in small amount in animal
solids and fluids; spleen, liver, thymus, thyroid; in the fluids of echinococcus, of
hydrocephalus, and of 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 (p. 298).

(5.) CholallC Acids in the bile (p. 35G) and in the intestine (p. 367).

(6.) Aromatic Acids — Benzole acid (= phenyl-formic acid) occurs in urine
united with glycin, as hippuric acid (see Urine).

Ill— Alcohols.

Alcohols are those bodies which originate from carbohydrates, in which the
radicle hydroxyl (HO) is substituted for one or more atoms of H. They may be

TT "I

regarded as water, T \ 0, in which the half of the H is replaced by a CH com-

/~1 TT -V

pound. Thus, C2HG (ethyl-hydrogen) passes into 2 T| \ 0 (ethylic alcohol).

C TT 1
(a.) Cholesterin, 2G T? j-0, is a true men-atomic alcohol, and occurs in blood,

yelk, brain, bile (p. 358), and generally in vegetable cells.

I OH

(6.) Glycerine, C3H5 < OH, is a tri-atomic alcohol. It occurs in neutral fats

(OH

united with fatty acids and oleic acid ; it is formed by the splitting-up of
neutral fats during pancreatic digestion (p. 343), and during the alcoholic fermen-
tation (p. 298).

(c.) Phenol (= phenylic acid, carbolic acid, oxybenzol, p. 376).

(d.) BrenzTcatecliin ( = dioxybenzol).

(e.) 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 bodies 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.

CARBOHYDRATES. 511

252. The Carbohydrates.

These substances, which occur in plants and animals, have received their name,
because in addition to C (at least 6 atoms), they contain H and O, in the propor-
tion 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 constitution is concerned,
they may be regarded as fatty bodies, as hexatomic alcohols, in which 2H are
wanting.

They are divided into the following group: —

I. Division. Glucoses (C6H1206)— (i) 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 (p. 352). 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 decom-
posed by bases; it reduces many metallic oxides (p. 297). Fresh solutions have a
rotatory power of + 10G°. By fermentation with yeast, it splits up into alcohol and
C02 (p. 298) ; with decomposing proteids, it splits into two molecules of lactic
acid (p. 373) ; the lactic acid splits up under the same conditions in alkaline
solutions, into butyric acid, C02 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, or potassium, and it also forms a
crystalline compound with common salt.

(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
(p. 370), and occurs rarely as a pathological product in urine.

II. Division contains carbohydrates with the formula Ci2H22On, and which
may be regarded as anhydrides of the first division — (1) Milk-SUgar or lactose
occurs only in milk, crystallises in cakes (with one 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 (Koumis preparation, p. 468). For its quantita-
tive estimation, see Milk.

(2.) Maltose (Ci2H22On) + H20 (O'Sullivan) has one molecule of water less
than grape-sugar (Ci2H24012), is formed during the action of a diastatic ferment,
such as saliva upon starch (p. 294); is soluble in alcohol, right rotatory power =
150°, it is crystalline, while its reducing power is only two-thirds that of dextrose.

(3. Saccharose (cane-sugar) occurs in sugar-cane and some plants, it does
not reduce solutions 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) which ferments with difficulty and is left-rotatory (p. 370). When
oxidised with nitric acid, it passes into gl';cic acid and oxalic acid.)

51:

CARBOHYDRATES.

(4. MelitOSe, from Eucalyptus-manna; MelezitOSfi, from Larch-manna;
Trehalose (Mycose), from Ergot ; all right-rotatory, and do not reduce alkaline
cupric solutions.)

Ill- Division, contains carbohydrates with the formula, CeHjoOs, which may
be regarded as anhydrides of the second division.

1. GlyCOgen, with a rotatory power of 211° (Bohm and Hoffmann, Kiilz), does
not reduce cupric oxide. It occurs in the liver (p. 350), muscles, many embryonic
tissues, the embryonic area of the chick (Kitlz), in normal and pathological
epithelium (Schiele), and according to Pavy, in the spleen, pancreas, kidney, ovum,
brain and blood, together with a small amount of glucose. It also occurs in the
oyster and some of the molluscs (Bizio).

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, p. 472), by dilute acids, and in the body by the action
of ferments (p. 294). 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 ex-
centric nucleus (Fig. 176, B)
The diameter of starch grains
varies greatly with the plant
from which they are derived.
At 72°C. it swells up in water
and forms mucilage ; in the
cold, iodine colours it blue.
Starch grams always contain
more or less cellulose and a sub-
stance which is coloured red
with iodine (erythrogranulose)
(see p. 294). 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. )
(4. Gum occurs in vegetable juices (specially in acacia? and mimosse), is partly
soluble in water (arabin), partly swells up like mucin (bassorin). Alcohol pre-
cipitates it.)

(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 algas; is transformed into glucose by dilute sulphuric acid.)

(7. Paramylum occurs in the form of granules resembling starch, in the infus-
orian, Euglena viridis.)

(8. Cellulose occurs in the cell- walla of all plants (in the exo-skeleton of
arthropoda, and the skin of snakes) ; soluble only in ammonio-cupric oxide ; ren-
dered blue by sulphuric acid and iodine. Boiled with dilute sulphuric acid, it
yields dextrin and glucose. Concentrated nitric acid mixed with sulphuric acid
changes it (cotton) into mtro-cellulose (gun cotton) C6H7(N02)305, which dissolves
in a mixture of ether and alcohol and forms collodion.)

Fig. 176.

Section of a wheat grain — d, starch-corpuscles
within vegetable cells; B, starch-corpuscles
with concentric markings (See also Fig.
173).

DERIVATIVES OF AMMONIA AND THEIR COMPOUNDS.' 513

(9. Tuilicin is a substance resembling cellulose, and occurs in the integument of
the tunicata or ascidians.)

IV. Division contains the carbohydrates which do not ferment.

1. Inositd'haseo-mannit, muscle-sugar) occurs in muscle (Scherer), lung, liver,
spleen, kidney, brain of ox, human kidney; pathologically in urine and the fluid
of echinococcus. In the vegetable kingdom, in beans (leguminosse), and the juice
of the grape. It is an isomer of grape-sugar; optically it is inactive, crystallises
in warts with two molecules of water, in long monoclinic crystals ; it has a sweet
taste, is insoluble in water, does not give Trommer's reaction, is capable of under-
going only the sarcolactic acid fermentation. (Nearly allied are Sorbin from sorbic
acid — Scyllit from the intestines of the hag-fish and skate — and Eukabjn 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 tlieir metabolism.

(1.) AniineS) i.e., compound ammonias which can be obtained from ammonia
(NH3), or from ammonium-hydroxide (NH4 - OH), by replacing one or all the at' >ins
of H by groups of carbohydrates (alcohol radicals). The amine derived from
one molecule of ammonia is called monamine. We are only acquainted with

H ^ CH3)

H [• N Methylamine and Tri-Methylanrine CH3 - N,
CH3) CH3)

as decomposition products of cholin (neurin) and of kreatin. Neurin occurs in
lecithin in a very complex combination (see Lecithin under Fats, and also p. 36).

(2.) Amides, i.e., derivatives of acids, which have exchanged the hydroxyl
(HO) of the acids for NH2. Urea, CO(NH2)2, the biamid of C02, is the chief end-
product of the metabolism of the nitrogenous constituents of our bodies (see
Urine]. Carbonic acid containing water = CO(OH)2; in it both OH are replaced
by NH2— thus we get CO(NH2)2, urea.

(3-) Amido-acids, i.e., nitrogenous compounds (p. 341), which show partly the
character of an acid and partly that of a weak base, in which the atoms of H of
the acid radicle are replaced by NH2, or by the substituted ammonia groups.

(«•) Glycin — (p. 355), (or amido-acetic acid, glycocoll, gelatin-sugar is formed
by boiling gelatin with dilute sulphuric acid. It has a sweet taste (gelatin-sugar),
behaves as a weak acid, but also unites with acids as an arnine-base. It occurs as
glycin + benzoic acid = hippuric acid in urine ; and also as glycin + cholalic acid =
glyco-cholic acid in bile (p. 355). (b.) Leucin— (p. 341)*= amido-caproic acid,
(c.) Serin — (=? amido-lactic acid) obtained from silk-gelatin. (</.) Asparaglnic
acid — (amido-succinic acid) ; and (e.) Glutaminic acid obtained by the splitting
up of proteids (p. 342). Other amido-acids are — (/.) Cystin = amido-lactic acid in
which 0 is replaced by S (see Urine). (g.) Taurin— (p. 355), amido-ethyl-sul-
phuric acid occurs (except in certain glands) chiefly in combination with cholalic
acid, as taurocholic acid in bile. TyrOSin (parahydro-oxyphenyl-amido-propionic
acid), an amido-acid of unknown constitution, occurs along with leucin during
pancreatic digestion (p. 341), is a decomposition product of proteids, and occurs
plentifully in the urine in acute yellow atrophy of the liver.

To the amido-acids are related — (a.) Kreatin in muscle, brain, blood, urine,
regarded as methyl-uramido-acetic acid (C4H9N302). It has been prepared arti-
ficially. When boiled with baryta water, it takes up H20, and splits into urea ;
and (b.) Sarkosin (C3H7N02), 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 (C4HrN30). This strong
base can be rechanged by alkalies into kreatiu.

33

5 1 4 HISTORICAL.

(4) Ammonia Derivatives of Unknown Constitution.— Uric add,

allantoin (see - Urine) is formed by the oxidation of uric acid by means of
potassium permanganate; cyanuric acid in dog's urine; inosinic acid in muscle;
gunnin 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; hypoxanthin or sarkin occurs along with
xanthin in many organs and in urine. Kossel prepared hypoxanthin from nuclein
by projonged boiling of the latter. It may be obtained from fibrin by putrefac-
tion, by gastric and pancreatic digestion, and by dilute acids (Salomon, H. Krause,
Chittenden); xanthin is prepared by oxidation from hypoxanthin. It occurs very
rarely in the form of a urinary calculus. Paraxanthin in urine, and a similar body
carnln in flesh (§ 233).

Aromatic Substances.

1- MonatomiC phenols — (») Phenol (hydroxyl of benzol) in the intestine
(p. 376). Phenylsulphuric acid in urine. (6) Kresol in the form of orthokresol
and parokresol, united with sulphuric acid, occiir in urine. 2- Diatomic phenols
— (a) Benzkatechin united with sulphuric acid in urine. 3- Aromatic OXyacids
— (a) Hydroparacumaric acid; (b) Paraoxyplienylacetic acid in urine. 4. Indol
and skatol in the intestine (p. 376), conjoined with sulphuric acid in urine.

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 concoc-
tion, the heat so formed being distributed to all parts of the body by means of the
blood, while the respiration is regarded as an act whereby the body is cooled.
Galen accepted this view in a somewhat modified form ; according to him, the
metabolic processes maybe 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
decomposition-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.

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.