WO1PT.Y

BIOLOGY

USRARY

G

TEXT-BOOK OF PHYSIOLOGY.

NUNQUAM ALIUD NATURA, ALIUD SAl'IENTIA DIGIT.

CONTRIBUTORS.

J. S. EDKINS, M.B., Lecturer on Practical Physiology in St. Barthol-
omew's Hospital Medical School, London.

ARTHUR GAMGEE, M.D., F.R.S., Emeritus Professor of Physiology
in Owens College, Manchester.

W. H. GASKELL, M.D., LL.D., F.R.S., Lecturer on Physiology in the
University of Cambridge.

FRANCIS GOTCH, B.Sc., F.R.S., Waynflete Professor of Physiology
in the University of Oxford.

ALBERT A. GRAY, M.D., University of Glasgow.

W. D. HALLIBURTON, M.D., F.R.S., Professor of Physiology in King's
College, London.

J. BERRY HAYCRAFT, D.Sc., M.D., Professor of Physiology in
University College, Cardiff.

LEONARD HILL, M.B., Lecturer on Physiology in the London Hospital
Medical School, London.

F. GOWLAND HOPKINS, B.Sc., M.B., Demonstrator of Chemical
Physiology in Guy's Hospital Medical School, London.

J. N. LANGLEY, D.Sc., F.R.S., Lecturer on Physiology in the University
of Cambridge.

J. G. M'KENDRICK, M.D., LL.D., F.R.S., Professor of Physiology in
the University of Glasgow.

B. MOORE, M.A., Assistant Professor of Physiology in University

College, London.

D. NOEL PATON, M.D., Lecturer on Physiology in the School of

Medicine, Edinburgh.

M. S. PEMBREY, M.D., Lecturer on Physiology in Charing Cross
Hospital Medical School, London.

E. WAYMOUTH REID, M.B., Professor of Physiology in University

College, Dundee.

W. H. R. RIVERS, M.D., Lecturer on Physiological Psychology in the
University of Cambridge and in University College, London.

J. BURDON SANDERSON, M.D., D.C.L., F.R.S., Regius Professor
of Medicine in the University of Oxford.

E. A. SCHAFER, LL.D., F.R.S., Jodrell Professor of Physiology in
University College, London.

C. S. SHERRINGTON, M.D., F.R.S., Holt Professor of Physiology in

University College, Liverpool.

E. H. STARLING, M.D., Joint-Lecturer on Physiology in Guy's
Hospital Medical School, London.

TEXT-BOOK

OP

PHYSIOLOGY

EDITED BY

E. A. SCHAFER, LL.D., F.R.S.,

JODRELL PROFESSOR OP PHYSIOLOGY, UNIVERSITY COLLEGE, LONDON.

VOLUME FIRST.

EDINBURGH & LONDON:
YOUNG J. PENTLAND.

1898.

BIOLOGY

LIBRARY

G

EDINBURGH : PRINTED FOR YOUNG .1. PENTLAND, 11 TEVIOT PLACE, AND
.38 WEST SMITIIFIELD, LONDON, B.C., BY MORRISON AND GIBB LIMITED.

(All rights reserved.)

PREFACE.

THE want of a text-book in the English language to which students
could turn for information beyond that contained in the ordinary
manuals has long been felt by teachers of physiology in this country.
The most extensive of the existing text-books do not aim at giving
the full and precise information nor the references to original
authorities which are required by the advanced student. It has
hitherto been necessary for those who seek such information to consult
original articles — an operation which frequently involves a familiar
acquaintance with foreign languages and an expenditure of time rarely
at the disposal of the student. The present work is not intended
altogether to supersede this consultation of original papers, but will,
it is hoped, reduce the need of it to more reasonable limits, and will,
moreover, by the references to literature which throughout form an
important feature of each article, facilitate such study where it is still
necessary.

A book of this character, from the enormous amount of literary
labour which is involved in its production, and from the progressive
character of the science with which it deals, could hardly be undertaken
by one person. The editor has been fortunate enough to secure the
co-operation of many of the leading physiologists in this country, each
of whom deals with some branch of the subject to which he has given
special attention. Accordingly the reader will find in each article, in
addition to information as to the present state of knowledge as com-
plete as it has been possible to make it, many original observations
upon the matter to which it relates.

The subjects of generation and reproduction have been omitted in
this text-book, because, although strictly speaking appertaining to
physiology, they are studied almost entirely by morphological methods,
and are more conveniently treated in connection with morphology. It
has therefore been decided that it would be better not to swell the bulk
of these volumes, which have already grown beyond the limits originally
intended, by the introduction of subjects such as these, which possess
an enormous recent literature, and are exhaustively dealt with in
special works accessible to every student. The same remark will apply
to the general physiology of the cell, a branch of biology which has

547786

x PREFACE.

of late attained so great an extent and importance as to necessitate
text-books devoted to itself alone, and which it is usual to study rather
as an introduction to, than as a part of, animal physiology.

Of the two volumes of which it is intended this book shall consist,
the articles in the first volume deal mainly with the chemical constitu-
tion and the chemical processes of the animal body, and with those
physical and chemical phenomena which are connected with the pro-
duction and elaboration of the secretions and other fluids of the
body. The articles in the second volume include the mechanics of the
circulation and respiration, and of special muscular movements ; the
general physiology of muscle and nerve ; the special senses ; and the
functions of the central nervous system.*

It is nearly twenty years since the publication in six volumes of the
important " Handbuch der Physiologic," under the editorship of Pro-
fessor L. Hermann. The articles in that book, as in this, were under-
taken by physiologists who were specially conversant with the particular
branches of the science with which they severally dealt ; and since most
of the articles in it are prefaced by short historical introductions,
and interspersed with abundant references to the literature of the
subject, the whole work constitutes a storehouse of information,
which has proved of great value to teachers and investigators. But
the size of the work, and the fact that it is written in the German
language, have limited its utility to students in this country ; moreover,
in the course of the twenty years that have elapsed since its appearance,
rapid progress has been made in every branch of physiology, so that
several of the articles in it have been long out of date. Nevertheless
its publication served both to lay a firm foundation for the exposition of
the science in its modern aspect, and also to clear the ground for all
future publications of a similar character. It has thus been a marked
advantage, in preparing many of the articles for the present book, to have
had the work of Hermann and his coadjutors to refer to ; and although
due acknowledgment is made both of this and of other sources of infor-
mation in the articles themselves, it has seemed right specially to
mention the " Handbuch " in this preface.

UNIVERSITY COLLEGE, LONDON,
February 1898.

CONTENTS OF VOLUME FIRST.

THE CHEMICAL CONSTITUENTS OF THE BODY
AND FOOD.

BY W. D. HALLIBURTON.

The Carbohydrates— The Fats— Lecithin— Cholesterin— The Proteids— Decom-
position Products of Proteids — -Synthesis of Proteids — Theories of Proteid
Constitution — General Properties' and Reactions of Proteids — Classification
of Proteids — Vegetable Proteids — Poisonous Proteids — Compound Proteids
—The Albuminoids — Inorganic Compounds ..... Page 1

THE CHEMISTEY OF THE TISSUES AND ORGANS.
BY W. D. HALLIBURTON.

Cells and Protoplasm — Liver — Spleen — Thymus — Thyroid — Suprarenals — Pancreas
— Kidneys — Testis — Muscle— Skeletal Tissues — Nervous Tissues — The Eye —
Milk . . . . . . page 80

THE BLOOD.
BY E. A. SCHAFER.

General Properties — Amount — Colour — Specific Gravity— Reaction— Coagulation —
Relative Amounts of Plasma and Corpuscles — Number of Corpuscles — General
Composition of Blood — Composition of Blood Corpuscles — Composition of
Plasma — Proteids of Plasma — Theories of Coagulation — Causes of Coagulation
— Lymph and Allied Fluids page 141

HEMOGLOBIN: ITS COMPOUNDS AND THE PRINCIPAL
PRODUCTS OF ITS DECOMPOSITION;

BY ARTHUR GAMGEE.

Distribution in the Animal Kingdom — Relations to other Constituents of Red
Corpuscles (Arterin and Phlebin) — Oxyhaemoglobin— Methods of Obtaining
— Composition of — Crystalline Form — Action of Reagents on — Spectrum —
Spectrophotometry — Photographic Spectrum — Haemoglobin — Preparation of —
Colour and Spectrum — Compounds with Gases — Derivatives and Products of
Decomposition ........... page 185

xii CONTENTS.

A GENEEAL ACCOUNT OF THE PEOCESSES OF DIFFUSION,
OSMOSIS, AND FILTEATION.

BY E. WAYMOUTH KEID.
Diffusion — Osmosis — Filtration ........ page 261

THE PEODUCTION AND ABSORPTION OF LYMPH.

BY ERNEST H. STARLING.

The Production of Lymph — The Physical Forces concerned in the Movement of
Lymph — The Absorption of Lymph from the Connective Tissues — On the
Functions of the Lymph in the Nutrition of the Tissues . . . page 285

•

CHEMISTEY OF THE DIGESTIVE PEOCESSES.
BY B. MOORE.

Digestive Ferments — Chemical Composition of Digestive Juices — Saliva—Gastric
Juice — Pancreatic Juice — Intestinal Juice — Bile — Digestion of Carbohydrates
— Digestion of Proteids — Absorption of Carbohydrates and Proteids —
Digestion and Absorption of Fats — Bacterial Digestion — Composition of
Faeces page 312

THE SALIVAEY GLANDS.
BY J. N. LANGLEY.

Anatomical Characters — Histological Characters — Origin and Course of Nerves —
Changes during Secretion — Reflex Secretion— The Dyspnceic Secretion —
Stimulation of the Cranial Nerve — Stimulation of the Sympathetic Nerve —
The Augmented Secretion— Effect of Protracted Stimulation on the Amount
and Percentage Composition of Saliva — Relation of the Rate of Secretion to
the Percentage Composition of Saliva — Some General Characters of Saliva-
Substances secreted in Saliva — Effects of the Cranial and Sympathetic Nerves
upon the Blood Flow — Mutual Effects of the Cranial and Sympathetic Nerves
upon Secretion — Effect of Variations in the Amount and Quality of the Blood
supplied to a Gland — Relation of Secretion to the Flow of Lymph — The
Secretory Pressure — Reflex Inhibition of Saliva — The Action of Alkaloids —
Formation of Heat— Electrical Changes —Section of Glandular Nerves— The
Paralytic Secretion — Secretion due to Reflex Action of Peripheral Ganglia
— Direct Irritability of Gland Cells — Extirpation of the Glands — Injection
into the Blood of Saliva and of Gland Extracts — General Considerations —
Theories of the Mode of Action of Secretory Nerves . . . page 475

MECHANISM OF SECEETION OF GASTEIC, PANCEEATIC,
AND, INTESTINAL JUICES.

BY J. S. EDKINS.

Histological Appearances accompanying Secretory Conditions of Stomach — Functions
of the Cells and Regions of the Stomach — Methods of obtaining Gastric Juice —
Influence of the Nervous System on Gastric Secretion — Conditions which
provoke Secretion — Formation of the Ferments of Gastric Juice — Formation
of Renniii — Variations in Gastric Juice during Digestion — Histological Appear-
ances of the Secretory Conditions of the Pancreas — Influence of the Nervous
System upon Pancreatic Secretion — Conditions which provoke the Flow of
Pancreatic Juice— Ferments of the Pancreatic Juice and their Antecedents —
Variations in Pancreatic Juice during Digestion — Evidence of Secretion in the
Intestine page 531

CONTENTS. xiii

MECHANISM OF BILE SECRETION.
BY D. NOEL PATON.

Mode of Formation of Bile Constituents — Water — Inorganic Salts — Nueleo-
Proteid — Bile Acids — Bile Pigments — Cholesterin — Lecithin, etc. — Influence
of Various Factors on the Secretion of Bile — Flow of Blood — Food —
Pressure of other Organs — Nerves — Chemical Substances — General Con-
clusions ............ page 55^

THE CHEMISTEY OF THE URINE.
BY F. GOWLAND HOPKINS.

Hippuric Acid ; Amido- Acids — Proteids — The Aromatic Substances — The-
Carbohydrates — Glycuroiiic Acid and its Conjugated Compounds — Oxalic Acid
— Acids and Oxyacids of the Fatty Series —Colour of the Urine and the
Chemistry of its Pigments : The Preformed Pigments of Normal Urine ;
Chromogenic Substances ; The Pigmentation of Pathological Urine — The In-
organic Constituents — General Characteristics of the Organic Urinary Com-
pounds— Comparative Chemistry of the Urine .... page 570

THE MECHANISM OF THE SECRETION OF URINE.
BY ERNEST H. STARLING.

Theories of Urinary Secretion — Theory of Bowman — Theory of Ludwig — Secretion
of Water — Methods — The Concentration of the Urine — Heidenhain's Criticism
of the Theory of Ludwig — Experiments of Nussbaum — Experiments of Ribbert
— Experiments of Bradford — The Influence of the Nervous System on the
Secretion of Urine page 639-

THE MECHANISM OF THE SECRETION OF MILK.
BY E. A. SCHAFER.

General Considerations— Influence of the Nervous System — Action of Pilocarpine-
and Atropine — Influence of Diet — Place of Formation of the Organic Con-
stituents— Manner in which the Secreted Materials pass out of the Cells —
Mechanism of the Discharge of Milk • page 662.

SECRETION AND ABSORPTION BY THE SKIN.
BY E. WAYMOUTH REID.

Chemical Nature of Skin Secretions— The Secretion of Sweat— ElectroiMotive-
Phenomena in Skin Glands— Absorption by the Skin of Man— Of Lower
Mammals— Of the Frog . page 669-

xiv CONTENTS.

CHEMISTRY OF RESPIRATION.

BY M. S. PEMBREY.

Historical — Respiratory Changes in Air — Methods — Conditions affecting Respiratory
Exchange — Cold - Blooded Animals — Fishes — Warm - Blooded Animals — In-
fluence of External Temperature — Of Muscular Activity— Of Food — Of
Size of Animal — Of Time of Day — Of Age — Respiration by Skin
in Amphibia — In Mammals — Effects of Varnishing Skin — Respiration in
Alimentary Canal — Respiration of Foetus — Of Embryo — The Respiration of
Different Gases — The Respiration of Vitiated Air — Asphyxia — Exchange of
Gases between Blood and Air — Frequency of Respiration in Man — In Animals
— Changes in Composition of Air — Effect of Respiration on Blood— Gases of
Blood — Methods — Arterial and Venous Blood — Condition of Gases in Blood —
Causes of Gaseous Exchange between 3^ood and Air — Exchange of Gases
between Blood and Tissues — Causes of such Exchange . . . page 692

ANIMAL HEAT.

BY M. S. PEMBREY.

Thermometry — Warm and Cold Blooded Animals — Temperature of Man and other
Warm-Blooded Animals — Hibernation — Influence of Various Conditions upon
Temperature — Time of Day — Age — Muscular Work — Mental Work — Food —
Sleep — Seasons — Race — Menstruation and Pregnancy — Individual Peculiarities
— Temperature of Surroundings — Extreme Heat and Cold — Baths — Drugs —
Temperature of Different Parts of Body — Of Arterial and Venous Blood — Of
the Skin — Regulation of Temperature — Heat Production — Historical — Relation
to Chemical Changes — Specific Heat of Body — Seats of Heat Production —
Measurement of Heat Production— Calorimetry — Respiratory Exchange as
Measure of Heat Production — Heat Production in Cold-Blooded Animals
— Regulation of Heat Loss — Influence of Size of Body — Influence of Nervous
System — Development of Power of Regulation — Temperature of Body after
Death . . . page 785

METABOLISM.
BY E. A. SCHAFER.

Introductory — Balance of Nutrition — Composition of Foodstuff's — Heat Value of
Foodstuffs — Necessary Amount of Proteid — Special Constituents of Diet —
Their Effect on Metabolism — Gelatin — Carbohydrates — Fats — Inorganic Sub-
stances— Metabolism in Inanition — With purely Proteid Diet — Relative Meta-
bolic Activity of Tissues — Nitrogenous Metabolism — In Muscle — In the Liver
— Effect of Muscular Activity on Proteid Metabolism — Metabolism of Carbo-
hydrates— Glycogen Formation — Phloridzin Diabetes — Glycogenesis— Puncture
Diabetes — Influence of Pancreas on Carbohydrate Metabolism — Metabolism of
Pat — Source and Formation of Fat — Action of Liver on Metabolism of
Fat .... page 868

THE INFLUENCE OF THE DUCTLESS GLANDS UPON
METABOLISM— INTERNAL SECRETIONS.

BY E. A. SCHAFER.

Introductory— The Thyroid Gland— The Pituitary Body— The Suprarenal Bodies
— Influence of the Spleen on Metabolism ...... page 937

INDEX OF SUBJECTS page 963

INDEX OF AUTHORS page 999

LIST OF ILLUSTRATIONS.

I. PLATES.

PLATES

I., ii. — Spectra of haemoglobin, its compounds and derivatives (modified from

Preyer, " Die Blutkrystalle ").

in. — Spectra of various colouring matters (from MacMunn, " The Spectroscope
in Medicine ").

1. Solar spectrum, with Frauenhofer's lines and millimetre scale.

2. Fresh human bile.

3. Alcoholic extract of human bile.

4. Diluted solution of human bile treated with hydrochloric acid.

5. Bile treated with nitric acid, and the precipitate dissolved in boiling

absolute alcohol.

6. Pig's bile.

7. Ox or sheep bile.

8. Ox or sheep bile treated with nitric acid, and the precipitate dissolved

in boiling alcohol.

9. Ox bile treated with hydrochloric acid, and the precipitate dissolved in

boiling alcohol.

10. Guinea-pig's bile.

11. Rabbit's bile.

12. Mouse's bile.

13. Crow's bile.

14. Pettenkofer's test on human bile salts.

15. „ „ pig's bile salts.

16. Band of urobilin in normal human urine.

17. Bands in urine of rheumatic fever ; the urine treated with nitric acid.

18. „ ,, „ with albuminuria ; the urine treated with nitric acid.

19. Urine of same case treated with caustic potash.

20. Bands of hsematin from ovarian cyst.

21. The same treated with a reducing agent.

22. Spectrum of 02, after twenty-four hours.

23. „ ,, lutein, from peritoneal fluid.

24. „ „ ,, from serum of dog's blood.

LIST OF ILL USTRA TIONS.

II. FIGURES IN TEXT.

FIG. PAQK

1. Crystals of phenylglucosazone ...... 8

2. „ „ phenylmaltosazone . . . . . .11

3. Lactose crystals (Frey) . . . . . . .12

4. Crystals of phenyllactosazone . . . . . .13

5. Inosite crystals (Frey) . . . . . . .17

6. Cholesterin crystals (Frey) ....... 23

7. Leucine crystals (Kiihne) ....... 28

8. Tyrosine crystals (Frey) ... ... 28

9. Crystals of egg albumin ....... 44

10. Proteid crystals from human urine (Bramwell and Noel Paton) . . 45

11. Crystallised vitellin of the oat kernel (®sborne) . . . .53

12. Charcot's crystals ........ 94

13. Creatine crystals (Kiiline) . . . . . . .100

14. Creatinine crystals (Kiihne) ....... 100

15. Creatine-zinc chloride crystals (Kiihne) ..... 101

16. Spherical compound of mercury and creatine (G. S. Johnson) . . 102

17. Compounds of xanthine and hypoxanthine, by means of which these sub-

stances may be isolated and identified (Kiihne) . . . .103

18. Zinc sarcolactate (Kiihne) . . . . . . .107

19. Calcium sarcolactate (Kiihne) ...... 107

20. Absorption spectra of retinal pigments (Kiihne) .... 123

21. Oliver's apparatus for estimating the number of blood corpuscles . .149

22. „ hacmoglobinometer . . . . . . .151

23. The hsematinometer . . . . . . . .211

24. The haematoscope . . . . . . . .211

25. Graphic representation of the spectrum of oxyhaemoglobin and hemo-

globin (Eollett) . . . . . . . .212

26. Double slit employed in Vierordt's method of spectrophotometry . 216

27. Glass troughs for containing the liquids to be examined by the methods

of spectrophotometry (Kriiss) . . . . . .217

28. Trough mounted on stand, as used in spectrophotometry (Kriiss) . .217

29. Section of glass trough (Kriiss) ..... 217

30. Spectrophotometer with absorption trough and lamp . . .218

31. Hiifner's spectrophotometer . . . . . . .221

32. Schematic representation of the path followed by the rays of light before

entering the slit of the collimator of Hiifner's spectrophotometer
(Kriiss) ......... 222

33. The photographic spectrum of haemoglobin and oxy haemoglobin . .227

34. Graphic representation of the spectra of oxyhieinoglobliii and haemoglobin

(Rollett) . . . .:'-'" 233

35. The photographic spectrum of oxyhsemoglobin and of CO-haemoglobm . 240

36. ,, ,, ,, oxyhaernoglobiii and methsemoglobin . 247

37. „ ,, „ hsemin ..... 254

38. ,, ,, ,, oxygenised hiumochromogen and of hamio-
chromogen ........ 256

39. The photographic spectrum of haematoporphyrin .... 259

40. Diagram to show the dilution of the blood produced in dogs by the

injection of dextrose (Leathes) ...... 294

41. Diagram to show the influence of the intravenous injection of dextrose

on the blood pressure in the abdominal viscera . . . 294

42. Diagram to show the effect of injecting dextrose after a previous

bleeding ......... 295

LIST OF ILL USTRA TIONS. xvii

FIG. PAGE

43. Diagram to show effects of the injection of a lymphagogue of the first

class on the blood pressures in the abdominal organs . . . 297

44. Diagram to indicate variations in pepsin after food (Griitzner) . . 544

45. Chart showing acidity of gastric juice after feeding with mixed

food ...... . 545

46. Chart of the course of secretion of pancreatic juice . . . 553

47. Chart of the percentage composition of the flow of pancreatic juice . 553

48. Showing influence of various foodstuff's upon the secretion of bile . 566

49. Urea nitrate and oxalate crystals . . . . . .582

50. Uric acid crystals ........ 587

51. „ .589

52. Ammonium and sodium urate ...... 591

53. Creatinin and hippuric acid ...... 600

54. Leucine and tyrosine . . . . . . 602

55. Cystine ......... 603

56. Calcium oxalate . . . . . . . .615

57. Chart of spectra of urinary pigments ..... 624

58. Stellar phosphates ; triple phosphates ..... 633

59. Roy's oncometer ........ 641

60. Diagrammatic section through Roy's oncometer .... 642

61. Roy's oncograph ........ 643

62. Regnault and Reiset's respiration apparatus .... 694

63. Voit's respiration apparatus . . . . . . 696

64. The respiration apparatus in the Physiological Laboratory, Oxford . 697

65. Haldane's respiration apparatus ...... 697

66. Lb'wy's „ „ ...... 698

67. Frederick's curve of daily variation in the absorption of oxygen . .721

68. Hutchinson's spirometer ....... 752

69. Pfliiger's blood-pump . . . . . .758

70. Leonard Hill's blood-pump ....... 759

71. Pfliiger's lung catheter ....... 774

72. Curves of dissociation of oxyhsemoglobin , 775

73. Pfliiger's aerotonometer ....... 776

74. Frederick's „ . . . . . . .777

75. Bohr's hsemataerometer ....... 777

76. Chart showing daily variation in temperature observed by Ringer and

Stewart ......... 800

77. Chart showing daily variations in temperature observed by Ogle,

Clifford Allbutt, Casey and Rattray, and Crombie . . .800

78. Chart showing daily variation in temperature observed by Jtirgensen and

Liebermeister ........ 800

79. Curve of daily variation in the temperature of the urine . . . 801

80. Chart showing daily variations in temperature observed during U. Mosso's

experiments . ....... 802

81. Diagram of ice calorimeter ..... . 844

82. Diagram of Dulong's water calorimeter ..... 845

83. Diagram of air calorimeter (Haldane, Hale White, and Washbourn) . 845

84. Monkey deprived of thyroid (Horsley) ..... 941

85. Effect upon the blood pressure in the dog of the intravenous injection

of decoction of thyroid ..... . 944

86. Tracing showing effect of pituitary extract upon heart-beats and blood-

pressure in the dog ....... 947

87. Tracing showing effect of suprarenal extract upon muscle contraction in

the frog ......... 951

xviii LIST OF ILL USTRA TIONS.

FIG. PAGE

88. Tracing showing effect of suprarenal extract upon heart-beats and blood-

pressure in the dog ; one vagus only cut .... 952

89. The same with both vagi cut ...... 953

90. Tracing showing effect of suprarenal extract upon heart, limbs, spleen,

and blood-pressure, after section of cord and vagi . . . 954

91. Tracing showing effect of suprarenal extract upon blood-pressure and

limb-volume ........ 956

92. A, Ergograph tracing of a person suffering from Addison's disease. B,

Tracing made from the same person after six weeks' treatment with
suprarenal extract (Langlois) ...... 958

TEXT-BOOK OF PHYSIOLOGY.

TEXT-BOOK OF PHYSIOLOGY.

THE CHEMICAL CONSTITUENTS OF THE BODY

AND FOOD.

By W. D. HALLIBURTON.

CONTENTS :— The Carbohydrates, p. 2 — The Fats, p. 17— Lecithin, p. 21— Choles-
terin, p. 22 — The Proteids, p. 24 — Decomposition Products of Proteids, p. 28 —
Synthesis of Proteids, p. 35 — Theories of Proteid Constitution, p. 38 — General
Properties and Reactions of Proteids, p. 39 — Classification of Proteids, p. 49 —
Vegetable Proteids, p. 51 — Poisonous Proteids, p. 55 — Compound Proteids, p. 61
—The Albuminoids, p. 69 — Inorganic Compounds, p. 76.

THE chemical constituents of the body are very numerous, and the
majority of them are compounds of complicated structure. In the
following article I propose to treat of these compounds, first in classes,
and then individually, and in a subsequent chapter to discuss the various
tissues and organs in their chemico-physiological aspects.

In order to classify the chemical constituents of the body, one might
proceed upon a purely chemical basis, beginning with the simplest and ending
with the most complex compounds ; or a purely physiological basis might be
adopted, in which the compounds would be described in the order of their im-
portance in the vital processes of the organism. But a compromise between these
two exclusive methods is found to be that which is of most practical usefulness.

We may, in the first place, divide the compounds found in the body
into those of inorganic, or mineral nature ; and those which are termed
organic, or carbon compounds.

The inorganic compounds present are water ; various acids, such as
the hydrochloric acid of the gastric juice ; and numerous salts, such as
calcium phosphate in bone, and sodium chloride in blood, urine, etc.

The organic compounds are more numerous, and these we may
conveniently group as follows : —

( Proteids, e.g. albumin, myosin.
NITROGENOUS . J Albuminoids, e.g. gelatin, keratin.

[Simpler nitrogenous substances, e.g. lecithin, creatine.

[Fats.
NON-NITROGENOUS ^ Carbohydrates, e.g. sugar, starch.

[Simpler organic substances, e.g. alcohols, lactic acid.
VOL. i. — i

2 CHEMICAL CONSTITUENTS OF BODY AND FOOD,

The most useful classification of the more complex organic com-
pounds is the time-honoured one, into proteids, carbohydrates, and
fats. Taking this as our starting-point, we shall find that the other
substances present may be described either in subsidiary classes to
these, or as decomposition products of the more complex substances.

The elements found in these compounds are carbon, hydrogen,
nitrogen, oxygen, sulphur, phosphorus, chlorine, iodine, fluorine, silicon,
sodium, potassium, calcium, magnesium, lithium, iron, and occasionally
manganese, copper, and lead.

It will be on the whole most convenient to study the organic
compounds first, in the following order : —

1. Carbohydrates ;

2. Fats, with which we shall stucfy the lecithins and cholesterins ;

3. Proteids and albuminoids.

In following out this plan we shall discuss some of the chemical
constituents of the food as well as those of the body.

THE CARBOHYDRATES.

The carbohydrates are found chiefly in vegetable tissues, and many
of them form important foods. Some, however, are found in or formed
by the animal organism, such as glycogen or animal starch, dextrose, and
lactose or milk-sugar. The carbohydrates may be conveniently but
loosely defined as compounds of carbon, hydrogen, and oxygen, the
two last-named elements being in the proportion in which they
occur in water. But this definition, if pushed, would include several
substances like inosite, acetic acid, and lactic acid, which are not
carbohydrates.

The work of Fischer,1 Tollens,2 and many other chemists has,
moreover, shown that carbohydrates are not, as their name would
imply, simply compounds of carbon with water, but their constitutional
formula has been in many cases thoroughly worked out, and their
composition shown to be much more complex. This work has culminated
in the synthetical production of many of the sugars.

From the chemical standpoint, the sugars (which are the simplest
of the carbohydrates) may be divided into two classes —

1. Those which, when digested with dilute acids, do not yield any
other sugar or sugars ; this class includes the glucoses ; and

2. Those which, when so treated, do yield some other sugar or sugars ;
this class includes the members of the cane-sugar group.

Further, the sugars are designated according to the number of
carbon atoms they contain ; thus we have trioses (e.g. glycerose), tetroses
(e.g. erythrose), pentoses (e.g. arabinose, xylose, rhamnose), hexoses (e.g.
glucose, mannose), heptoses, octoses, and nonoses, according as they
contain, three, four, five, six, seven, eight, and nine atoms of carbon
respectively in their molecules.

The great majority of these sugars possess, however, but little

1 See especially E. Fischer, Ber. d. deutsch. diem. Gesellsch., Berlin, Bd. xxiii. S. 2114.

2 Tollens. " Kurzes Hftudbuch dor Kohlenhydrate," BresTau.

THE CARBOHYDRATES. 3

physiological interest, and their chemical relationships and reactions
will be found described in works on chemistry.1

Those which are of physiological importance are the hexoses and
their derivatives. Nearly all the carbohydrates with which we have
to deal in the animal body contain either six carbon atoms, or some
multiple of six. The same is true of those which are used as food. The
remainder are either synthetical products of the chemical laboratory, or
more or less rare products of the vegetable world.

But to this rule there is one exception ; the pentoses do possess some
physiological importance. When Hammarsten 2 was investigating the nucleo-
proteid material he separated from the pancreas, he found that by boiling it
with dilute mineral acid he obtained a reducing substance. This formation
of a reducing sugar-like substance from nuclein is not unique, as Kossel 3 and
his pupils have obtained a similar product from yeast-nuclein. The sugar,
however, does not ferment with yeast, but, like the pentoses, gives a red
coloration with phloroglucinol and hydrochloric acid, and by distillation with
hydrochloric acid yields furfuraldehyde. An osazone is obtainable from it
in the form of fine rosettes of crystals, melting at 158° to 160° C., and these
appear to be identical with those prepared from pentoses by E. Salkowski
and M. Jastrowitz.4

The physiological action of pentoses was investigated by W. Ebstein.5
When xylose or arabinose, dissolved in water or coffee, are taken with the
food, they rapidly appear in the urine ; they are not assimilated. The use of
fruits, such as pears, that contain pentosanes, the mother substances of pentoses,
may lead to the appearance of the latter substances in the urine. It is
of course important not to confound such a temporary condition with diabetes.

Max Cremer 6 has investigated the physiological action of some of the rare
sugars, especially their influence on the formation of glycogen. He found that
in rabbits mannose increases the hepatic glycogen, and that, though the
pentoses readily pass into the urine, a small quantity is assimilated as glycogen.
Lindeman and May 7 have confirmed Cremer's results.

Salkowski8 has investigated a large number of diabetic urines, but was
unable to find pentose in any of them. Nevertheless, he found pentose in
various other morbid conditions in the urine, in which their presence could
not be attributed to diet. He suggests that in these cases they originate in
the body from such nucleo-proteids as Hammarsten found in the pancreas, the
processes of oxidation being lessened so that they were not broken up into
simpler materials.

We can now proceed to the study of the carbohydrates concerning
which we have more accurate physiological knowledge ; and these may
be classified into the following three groups : —

1 See article f: Sugars," Watts's "Dictionary of Chemistry," London, 1894, vol. iv.

2 Ztschr.f. pliysiol. Chem., Strassburg, Bd. xix. S. 19.

3 Kossel and Neumann, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxvii. S. 2215.

4 Centralbl. f. d. med. Wissensch., Berlin, 1892. Nos. 19 and 32. Blumenthal (Berl. Urn.
Wchnschr., 1897, Bd. xxxiv. S. 245) has obtained pentoses from numerous other nucleo-
proteids.

5 Virchows Archiv, Bde. cxxix. S. 401 ; cxxxii. S. 368 ; cxxxiv. S. 361.

6 Ztschr.f. BioL, Miinchen, Bd. xxix. S. 484.

7 Chem. Ccntr.-BL, Leipzig, 1896, Bd. i. S. 932.

8 Berl. klin. Wchnschr., Bd. xxxii. S. 364. See also Kiilz and Vogel (Ztschr.f. BioL,
Miinchen, 1895, Bd. xxxii. S. 185). These observers found pentoses in only four out of
sixty-four cases of human diabetes. But they are generally found in the severe forms of
diabetes produced in dogs by the extirpation of the pancreas or by administration of
phlorid/in.

4 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

1. Monosaccliarides (C6H1206). — The most important members of this
group are :

Dextrose.
Levulose.

Galactose.
Mannose.

2. Disaccharides (C12H22On). — The most important members of this
group are :

Cane Sugar,
Lactose.

Maltose.
Isomaltose.

3. Polysaccliarides (C6H1006)n. — The most important members of this
group are :

Starch. | Cellulose.

Glycogen.
Dextrins.

Tunicin.
Gums.

Inulth.

The monosaccharides. — When an alcohol is oxidised, the first
stage in oxidation is the formation of an aldehyde, or a ketone ; if
oxidation of the aldehyde is continued, an acid is formed.

When more complicated alcohols are oxidised, similar products result.
The monosaccharides are the first oxidation products of the hexatomic
alcohols (CH2.OH— (CH.OH)4— CH2OH).

Of the hexatomic alcohols, three are known, namely sorbite, mannite,
and dulcite.

Dextrose is the aldehyde of sorbite.1
Mannose „ ,, mannite.

Galactose „ „ dulcite.

Levulose „ ketone of mannite.

Sugars of the monosaccharide group may thus be either aldehydes,
when they are called aldoses ; or ketones, when they are called ketoses.

Dextrose, mannose, and galactose are aldoses, and have the structure
represented by the following formula :—

CH2.OH— (CHOH)4— CHO

They differ from one another in their stereochemical formulae.
Levulose is a ketose, and has the structure represented by —

CH2.OH— (CH.OH.)3— CO— CH.2— OH

The difference between the aldoses and ketoses is shown by oxidation,
levulose, like all ketoses, yielding acids which are poorer in carbon.

If chlorine or bromine water is used as the oxidising agent, the
aldoses (dextrose, mannose, and galactose) give isomeric monobasic acids
of the formula —

CH2.OH— (CH.OH)4— COOH ;

and then, by further oxidation by means of nitric acid, yield dibasic
acids of the formula —

COOH— (CH.OH)4— COOH
Both sets of acids are stereo-isomerides.

Monobasic acid. Dibasic acid.

From Dextrose . . Gluconic acid Saccharic acid.

„ Mannose . . Mannonic acid Manosaccharic acid.

„ Galactose . . Galactonic acid Mucic acid.

1 JVleunier, Compt. rend. Acad. d. sc.. Paris, tome cxi. p. 49 ; Vincent and Delachanal,
Hid., p. 51.

THE MONOSACCHARIDES 5

Glycuronic acid. — If saccharic acid is heated five or six hours in the
water bath, it is changed into saccharo-lactonic acid, C6H807. If this is
reduced by means of sodium amalgam, one obtains ylycuronic acid ; * this
substance is of considerable interest because it is sometimes found in the
body, and when it passes into the urine is apt to be mistaken for sugar,
many of the tests for which it gives.

Its composition is —

COOH— (CH.OH)4— CHO = C6H1007

It is soluble in water and alcohol, is dextro-rotatory, reduces alkaline
solutions of metallic salts, and yields saccharic acid on oxidation with
bromine. It does not undergo the alcoholic fermentation. Though
related in its composition so nearly to the carbohydrates, it yields with
urea decomposition products which are aromatic, such as orthonitro-
benzyl alcohol (Jaffe).2 It occurs in the urine in the form of the
potassium salt (C6H907K) after the administration of chloral and
butylchloral,3 nitrobenzol,4 orthonitrotoluol,5 camphor,6 etc. It also
occurs in the urine after chloroform narcosis, and in the paralytic
secretion that takes place on section of the renal nerves.7 Occasion-
ally it is found without any apparent cause, as a result of disordered
metabolism.

Levulose on oxidation always yields acids containing less carbon
atoms than itself, namely, trioxybutyric (CH2OH(CH.OH)2COOH),
formic (H.COOH), and glycollic (CH2.OH.COOH) acids. But different
acids are yielded by different methods of oxidation; thus chlorine or
bromine and silver oxide oxidise levulose to glycollic acid ; 8 nitric acid
yields oxalic, tartaric, glycollic, acetic, and other acids.9

Synthesis of sugars. — The first step towards the synthesis of the sugars
was made by Butlerow.10 He obtained a sugar-like substance by adding lime
water to a solution of dioxymethylene ; this he termed metliylenitan,
and gave its formula as C7H1406. Loew n next obtained a condensation
product of formaldehyde (CH20) by means of lime water ; to this substance
he attributed the formula (C6H120(.), and called it formose.

Neither methylenitan nor formose ferment with yeast. Fischer12
investigated these substances, and found that they were mixtures of two
sugars, one of which is formose (C6H1206), and another a-acrose13 (C6H1206),
both of which yield crystalline osazones.

From the osazone which is yielded by a-acrose the sugar can be again

1 H. Thicvfelder, Ztschr. f.phi/sioL Chem. , Strassburg, 1887, Bd. xi. S. 388; 1891, Bd. xv.
S. 71 ; Ber. d. dentsch. chem. G-esellsch. , Berlin, 1886, Bd. xix. S. 3148; E. Fischer and
0. Piloty, ibid., 1891, Bd. xxiv. S. 521.

Ztschr. f. pliysiol. Chem., Strassburg, Bd. ii. S. 47.

Musculus and v. Mering, Arch. f. d. gcs. Phijsiol., Bonn, Bd. xx. S. 64.

v. Mering, Centralbl. f. d. med. Wissensch., Berlin, 1875, No. 55.

Jaffe, loc. cit.

Schmiedeberg and Meyer, Ztschr. f. pliysiol. Chem., Strassburg, Bd. iii. S. 422.

Aahdown, Brit. Med. Journ., London, 1890, vol. i. p. 171.

8 Hlasiwetz and Habermann, Ann. d. Chem., Leipzig, Bd. civ. ; Kiliani, ibid., Bd.
civ. S. 175.

9 Kiliani, ibid., S. 162 ; Hornemann. Journ. f. prakt. Chem., Leipzig, Bd. Ixxxix. S. 283.

10 Ann. d. Chem., Leipzig, Bd. cxx. S. 295 *; Compt. rend. Acad. d. sc., Paris, tome Hi.
p. 145.

11 Journ. f. prakt. Chem., Leipzig, Bd. xxxiii. S. 321.

12 .Ber. d^deutsch. chem. Gesellsch., Berlin, Bd. xix. S. 2133.

13 Acrose is a sugar obtained by Fischer, ibid., Bd. xx. S. 1093 and 2566, by acting on
acrolein bromide with bases (2C3H4OBr., + (2Ba(OH)., = C6H1206 +2BaBr., ; two isomeric
sugars, «- and /3-acrose are thus produced. "

6 CHEMICAL CONSTITUENTS OF BOD Y AND FOOD.

obtained by reduction through the intermediate osone (see p. 9). The sugar
obtained is identical with levulose or fructose, except that it is optically inactive.
If this inactive levulose (i-levulose) is submitted to the action of yeast, the
levorotatory constituent (cMevulose) ferments, and the residue is dextro-
rotatory. This is Z-levulose,1 but it is not the natural sugar. The natural
sugar was formed in the following way : — a-acrose was reduced to the corre-
sponding alcohol, a-acrite, which is identical with i-mannite ; from this the
sugar 2-mannose was obtained, which was fermented, and Z-mannose alone
remained. By further oxidation i-mannose yields ^-mannonic acid. By
fractional crystallisation of the morphine or strychnine salt of this acid, it can
be separated into its two active (d and Z) constituents, and from these the
corresponding sugars (mannoses) are obtained by reduction, and these by
means of the ozones into the corresponding levuloses, the fZ-levulose being
the levorotatory natural sugar.

In order to get dextrose, the d- and 7-mannonic acids are heated with
quinoline ; this partly decomposes these acids, yielding d- and /-gluconic acids,
and by reduction of these acids the sugars cZ-glucose (or dextrose) and /-glucose
are obtained.

Of the numerous sugars in the monosaccharide group, dextrose,
levulose, and galactose possess special physiological interest.

Dextrose is found widely distributed in nature in grapes, and many
other fruits ; also in seeds and roots, and in honey. It is generally
mixed with levulose. In the animal body it is the final result of the
digestion of starch, and occurs in small quantities in the blood and
lymph ; traces only occur in normal urine. The quantity both in the
blood and urine is increased in diabetes. It crystallises either in fine
needles, free from water of crystallisation, or with 1 molecule of water of
crystallisation in small plates ; these melt at 100° and lose their water
at 110° C. The water-free crystals melt at 146° and at 170° C. lose
water, the residue being glucosane (C6H1005). By higher temperatures
it is converted into caramel.

Dextrose is readily soluble in water ; the solution is not so sweet as
one of cane-sugar; it is dextrorotatory. The specific rotation2 varies
with temperature and concentration, but at 20° C. averages + 520-6.
A freshly -made solution may have nearly double this rotatory power,
but on standing for some time, or on heating the solution, the rotation
becomes normal. Dextrose is slightly soluble in cold, very soluble in
hot alcohol. It is insoluble in ether.

Levulose is found with dextrose in the vegetable kingdom, and in
honey. It is formed by the hydrolytic splitting of cane-sugar and other
carbohydrates, but is obtainable with special ease from inulin. It is
occasionally found in diabetic urine.3 In many cases of diabetes it may
be used with impunity in the food.

1 The I, i, and d are prefixes primarily attached to isomeric sugars, to indicate their action
on polarised light, which is due to the presence and position of an asymmetric carbon atom.
The terms were introduced by Fischer to denote this character, but they have been extended
to comprise derivatives of the original sugar, which derivatives may have the opposite
rotatory power, as is seen in the above example, where a d sugar is levo- and an I sugar is
dextrorotatory.

2 The specific rotation (a)D of any substance is the amount of rotation in degrees of a
circle of the plane of polarised light, produced by 1 grm. of the substance dissolved in
1 c.c. of liquid, examined in a tube 1 decimetre long. It is measured for yellow (sodium)
light.

3 Leo (Virchoio's Archiv, 1887, Bd. cvii. S. 108) has found as an occasional constituent
of diabetic urine, a levorotatory sugar which is not levulose. Its reducing power is small,

REACTIONS OF THE MONOSACCHARIDES. 7

Its crystals, which are difficult to obtain, are partly water-free
(C6H1200) and partly contain water of crystallisation (2C6H1206.H20).
Levulose is different in chemical constitution from the other sugars we
have studied in this group. It, however, gives the same general tests ;
but its specific rotatory power has not been satisfactorily determined.

Galactose is obtained by the hydrolytic decomposition of lactose or
milk-sugar, and from many other carbohydrates, especially gums and
mucilages. It is obtained by the decomposition of a glucoside occurring
in the brain called cerebrin.1 It crystallises in needles or plates, which
melt at 168° C. It is somewhat more difficult of solution in water than
dextrose, and more strongly dextrorotatory.

Mannose or seminose is another monosaccharide which is of scientific
interest, as it is the aldehyde of the alcohol (mannite) of which levulose is the
corresponding ketone.

It does not occur free in nature. It is obtained from mannite by
oxidation,2 and also by the action of dilute sulphuric acid on the so-called
reserve cellulose.3

Reactions of the monosaccharid.es. — (a) Fermentation. — They are
directly fermentable by yeast into alcohol and carbonic acid (CGH1206
= 2C2H5.OIH-2C02) ; and by the Bacterium lactis into lactic acid (C6H1206
= 2CH3 — CH.OH. — GOOH). But this property of fermentation is only
possessed by those which occur in nature.

(&) Reducing power. — Being aldehydes or ketones, they are easily
oxidisable, and reduce metallic oxides in alkaline media.

They cause a deposition of metallic silver in an ammoniacal silver solution
containing some caustic soda ; and of metallic bismuth from basic bismuth
nitrate suspended in soda (Bottcher's test) • and of the red cuprous oxide (Cu20),
or of the yellow cuprous hydrate Cu(OH2), from an alkaline solution of cupric
oxide, as in Trommer's and Fehling's tests.4

(c) When heated in the dry state, before they char, they yield a
brownish product called caramel. A similar substance is formed by
boiling with alkalies (Moore's test).5 In the brown substance formed,
among other bodies is levulinic acid, CH3 — CO — CH2 — CH2 — COOH.

its rotatory power weak («D - 26) ; it forms an osazone. Neubauer and Vogel
(" Anleitung zur qualitativen mid quantitativen Analyse desHarns," 1890) suggest the name
"laiose " for it.

1 Thierfclder, Ztschr. f. physiol. Glum., Strassburg, Bd. xiv. S. 209; Brown and
Morris, Proc. Glum. Soc., London, 1889, p. 167.

2 Fischer and Hirschberger, Ber. d. deutsch. chem. Gesellsch., Berlin, Bde. xxi. S. 1805 ;
xxii. S. 1155 and 3218. 3 Reiss, ibid., Bd. xxii. S. 909 and 3218.

4 In Allihn's method (Journ. f. prakt. Chem., Leipzig, Bd. xxii. S. 55) of estimating
the reducing power of a sugar, the cuprous oxide obtained by Fehling's method is collected
and weighed as metallic copper. Pfliiger (Arch. f. d. ges. Physiol., Bonn, 1877, Bd. Ixvi. )
recommends that the cuprous oxide should be dried at 120° and weighed. O'Sullivan and
Stern (Journ. Chem. Soc., London, 1896, p. 1691), who have recently prepared dextrose
from several sources, have found that 1 gr. of CuO is reduced by 0'4535 gr. of dextrose
(1 gr. Cu20 = 0*5045 gr. dextrose). On the relation between reducing power and specific
rotation see a series of papers by H. T. Brown, G. H. Harris, and J. H. Millar (Proc.
Chem. Soc., London, 1896, pp. 241-244). If the reducing power of dextrose is taken as
100, that of levulose is 92 to 94 (ibid., 1897, p. 4).

5F. Framm (Arch. f. d. gcs. Physiol., Bonn, 1896, Bd. Ixiv. S. 575) has found that
Moore's test is accompanied by the formation of products of oxidation, namely aldehyde
and formic acid.

8

CHEMICAL CONSTITUENTS OF BODY AND FOOD.

(cl) Phenylhydrazine test. — This is carried out in the following
way:—

To 5 c.c. of a solution of sugar (which should not he stronger than 0*5 per
cent.) 1 decigramme of phenylhydrazine hydrochloride and 2 decigrammes of
sodium acetate are added, and the mixture heated on the water hath for
half an hour. On cooling, if not "before, a crystalline or amorphous pre-
cipitate separates out. If amorphous it may he dissolved in hot alcohol,
the mixture diluted with water, and boiled to expel the alcohol, whereupon

FIG. 1— Crystals of phenylglucosazone.

the compound or osazone separates out in yellow crystals. It is important
that there should he an excess of phenylhydrazine.

Dextrose gives a precipitate of phenylglucosazone (C^H^N^),
which crystallises in yellow needles (melting-point 205° C.). Levnlose
and mannose yield osazones identical with this.

Galactose yields a very similar osazone (phenylgalactoeazone). It
differs from phenylglucosazone by melting at 190-193° C., and in being
optically inactive when dissolved in glacial acetic acid.

The chemistry of the reaction is represented in the following
equations : —

THE DISACCHARIDES.

1. CH2OH[CH(OH)]3CH(OH)COH + H2

(dextro.se) (pfienylhydrazine)

CH,OH[CH(OH)]..CH(OH)CH

II +H20

N-NH(C,H6)

(hydrazone) (water)

2. CH2OHrCH(OH)]oCH(OH)CH

|| +C6H5.NH-NH

(hydrazone) (phenylhydrazine)

CHoOH[CH(OH)]3C— CH

|| || +H2 +H20

C6H5.NH-N N— NH.C6H6

(osazone) (hydrogen) (water)

The hydrogen seen in the second equation is not really set free, but
it is used to split up a further molecule of phenylhydrazine into aniline and
ammonia (NH2— NH.C6H- + H2 = NH2C6H5 + NH3).

In order to obtain the sugar from the osazone again, it is first
treated with fuming hydrochloric acid.1 This gives rise to phenylhy-
drazine and a so-called osone. An osone is a substance which, besides
the ketone group, contains an aldehyde group as well : CH2OH — (CH.OH)3
-CO— COH.

By means of zinc and acetic acid the osone is easily reduced to sugar.

Glucosamine. — A derivative of glucose which is of some physiological
interest is amido-glucose or glucosamine, C6H11Of).NH2. This is obtained on
the decomposition of chitin and chondroitin. By treatment with nitrous acid
it passes into dextrose —

C6HU05.NH2 + NOOH *= C6H1206 + N2 + H20

Glucosamine can also be obtained by treating phenylglucosazone directly with
reducing agents —

C6H1004. (K2H.C6H5)2 + H,0 + Hs = CcHn05.NH2 +

(phenylglucosazone) (glucosamine)

NH2— NH.CQH6 + NH?C6H6

(phenylhydrazine) (aniline)

This shows us another way of regenerating the sugars from their osazones.2
Further particulars about glucosamine will be found in connection with chitin
and cartilage.

The disaccharides. — A disaccharide is a condensation product of
two molecules of the simple sugars or monosaccharides, the change being
attended with the loss of a molecule of water : —

C6H1206 + C6H1206 - C12H22On + H20
Thus—

Cane-sugar is derivable from dextrose and levulose ;
Milk-sugar, or lactose, from dextrose and galactose ;
Maltose, from dextrose and dextrose.

The general properties of these sugars are like those of the monosac-

1 E. Fischer, Ber. d. deutsch. cliem. Gesellsch,, Berlin, 1888, Bd. xxi. S. 2631; 1889,
Bd. xxii. S. 87 ; 1890, Bd. xxiii. S. 2118.

2 E. Fischer, ibid., Berlin, Bd. xix. S. 1920 ; Fischer and J. Tafel, ibid., Bd.
xx. S. 2569.

io CHEMICAL CONSTITUENTS OF BODY AND FOOD.

charides ; their solubilities are similar ; they are optically active,
crystallisable, diffusible, and sweet. Heated dry, they give rise to
caramel. Further, they (with the exception of cane-sugar) reduce
alkaline solutions of metallic oxides like Fehliag'e solution, and (again
with the exception of cane-sugar) form crystalline osazones.

By hydrolysing agencies they take up water, and split into the simple
sugars of which they are made up. Thus —

Cane-sugar + water = dextrose + levulose.
Maltose + water = dextrose + dextrose.
Lactose + water — dextrose + galactose.

Among the agents capable of producing this decomposition the
inverting ferment of the small intestiiae must be particularly mentioned.
The term inversion arose from the fact that, if cane-sugar is the sub-
stance acted on, the previously dextrorotatory solution becomes levo-
rotatory, because the levorotatory power of the levulose is greater than
the dextrorotatory power of the dextrose formed. The term inversion
has, however, been extended to include the similar decompositions of
lactose and maltose. The reverse action by which the monosaccharides
are united to form disaccharides is called reversion.

Cane-sugar is generally distributed throughout the vegetable
kingdom in the juices of plants and fruits, especially the sugar-cane,
beetroot, mallow, and sugar-maple. As a food it is of high value. After
abundant ingestion of cane-sugar, traces may be found in the blood and
urine ; but the greater part undergoes inversion in the alimentary
canal.

It is readily soluble in water (100 parts of saturated solution contain
67 of sugar),1 but soluble with difficulty in alcohol. It forms large,
colourless monoclinic crystals. It is strongly dextrorotatory, and
the amount of rotation does not vary so much with concentration
and temperature as do most of the other sugars. The average value
of (<*)„= +66-5.

Cane-sugar does not give many of the sugar tests ; thus, it does not
give Moore's test ; with Trommer's test, it gives a blue solution, but no
reduction occurs on heating. It does not react with phenylhydrazine,
and it is not directly fermentable by yeast ; the yeast, however, secretes
an inverting ferment, and after inversion the glucoses formed are con-
verted into alcohol and "carbonic acid.

By boiling with concentrated hydrochloric acid a deep red solution
is formed. Dextrose, maltose, and lactose do not give this reaction.

Maltose is one of the end products of the action of malt diastase on
starch. It is also the chief sugar formed from starch by the diastatic
ferments contained in the saliva and pancreatic juice. It is an inter-
mediate product in the action of sulphuric acid on starch. It crystallises
with one molecule of water of crystallisation in fine white needles. It
is easily soluble in water and in alcohol ; insoluble in ether. It is
dextrorotatory; but its rotatory power decreases with concentration
(relatively) and with rise of temperature.

For a 20 per cent, solution at 15° C. (a)D = + 139°-3. The amount
of rotation is about 18° less for a freshly prepared solution than for one
which has stood for some hours.2

1 Scheibler, see Tollen's "Handbuch."

2 Brown, Morris, and Millar (Proc. C'hem. Soc., London, 1896, p. 244) give («)D= +138°.

THE DISACCHARIDES.

ii

Maltose reduces copper, bismuth, and other metallic salts in alkaline
solutions, but its reducing power as measured by Fehling's solution is
about one-third less than that of dextrose.1 It does not reduce Barfoed's
reagent2 as dextrose does. It ferments readily with yeast. With
phenylhydrazine, phenylmaltosazone is formed (C24H32N409) ; this crystal-
lises in yellow needles much broader than those yielded by dextrose or
lactose; it melts at 206° C. Unlike phenylglucosazone, it dissolves
in seventy-five parts of boiling water, and is still more soluble in hot
alcohol (Fig. 2).

FIG. 2. — Crystals of phenylmaltosazone.

Isomaltose 3 is a sugar formed at the same time as maltose by the
action of either diastase, ptyalin, or amylopsin 4 on starch. It is also an

1 Tenc.c. of Fehling solution corresponds to 0-05 grms. of dextrose, levulose, orgalactose,
and to 0*07196 of maltose.

2 13*3 grms. of cupric acetate are dissolved in 200 c.c. of water; to . this solution,
6 c.c. of acetic acid containing 38 per cent, of glacial acetic acid are added (Barfoed,
"Organic Analysis," p. 254).

3 Originally described by Fischer, Ber. d. deutsch. diem. Gcsellsch., Berlin, Bd. xxiii.
S. 3687. Fischer's observations, which have been called in question by some chemists, have
been veiy generally confirmed. In his most recent paper on the subject, ibid., 1896, Bd.
xxvii. S. 3024, he shows that isomaltose is not directly fermentable by yeast, and so may be
separated from maltose. Its osazone is soluble in four parts of hot water, while that from
maltose requires seventy-five parts.

4 Klilz and Vogel, Ztschr.f. BioL, Miinchen, Bd. xxxi.

12 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

intermediate product in the formation of dextrose by mineral acids from
starch. An amylolytic ferment in blood serum, capable of forming
dextrose from starch, acts similarly.1 A small quantity occurs in
normal urine.2 It is readily soluble in water, is very sweet, and
ferments slowly with yeast. Its general characters are like those of
maltose, but its osazone forms fine yellow needles which melt at 150° C.
Lactose or milk-sugar occurs only in milk, and occasionally in the
first days of lactation in the urine in small quantities.3

It crystallises in rhombic prisms, which contain one molecule of water
of crystallisation (Fig. 3). It is soluble in six
parts of cold, and two and a half parts of hot
water; it is therefore less soluble than the
other sugar's. It has only a faint sweet
taste. Aqueous solutions are dextro-rotatory
/ A * («)D = + 59°-3 (Hesse)4 and +52°-5 for the

V £2 fy hydrate at 20° C. (Schmoger).5 Its reducing

_ power as tested by Fehling's solution is

j) ~~J intermediate between that of dextrose and

L - / maltose.6 Lactose is very resistant to the

FIG. 3.— Lactose crystals.— After inverting ferment of yeast, and so undergoes
lrey' the alcoholic fermentation very slowly. It

is, however, rapidly inverted by the Kephir fungus, and of all the
sugars is that most readily affected by the B. ladis; the lactic acid
fermentation occurs in two stages, as follow : —

>A<?

1222n 2 36,

(lactose) (lactic acid)

(lactic acid) (butyric acid)

With phenylhydrazine, lactose yields phenyl-lactosazone, which readily
crystallises in needles (Fig 4). It is soluble in eighty to ninety parts
of boiling water. Its melting point is 200° 0.

Among the rarer disaccharides must be mentioned trelialose (from certain
fungi), and meleliose, a saccharose which with cMructose (levulose) is obtained
from raffinose. Raffinose 7 is an interesting sugar found in Eucalyptus manna,
cotton seeds, and barley. It is a trisaccharide, consisting of a combination
of dextrose, levulose, and galactose.

The polysaccharid.es. — To this group belong a large number of
carbohydrates of high molecular weight, and with the formula (C6H1005)n.
Their molecular weights differ a good deal, but have not yet been
determined directly by chemical methods.8 They are not crystalline,
are indiffusible, and, as a rule, insoluble in cold water. In hot water
they partially dissolve, forming opalescent solutions. Like the proteids,

1 Rohmann, CentralU. f. d. med. Wissenscli., Berlin, 1893, S. 849.

2 Lemaire, Ztsclir. /. pliysiol. Chem., Strassburg, 1896, Bd. xxi. S. 442.

3 The most recent observations on lactose in the urine of women after childbirth are by
Lemaire, Ztschr.f.physiol. Chem., Strassburg, 1896, Bd. xxi. S. 442. Pavy, Lancet, London,
1897, vol. i. p. 1075. See also Hofmeister, Ztschr.f. physiol. Chem. , Strassburg, Bd. i. S. 101.

4 Ann. d. Chem., Leipzig, 1875, Bd. clxxvi. S. 98.

5 Ber. d. deutsch. chem. Gesellsch., Berlin, 1880, Bd. xiii. S. 1922.

6 Ten c.c. of Fehling's solution = 0 '06334 lactose ; see footnote 1, p. 11.

7 Loiseau, Compt. rend. Acad. d. sc., Paris, 1876, tome Ixxxii. p. 1058 ; Ber. d. deutsch.
chem. Gesellsch., Berlin, Bd. ix. S. 7-32; Scheibler, ibid., 1886, Bd. xix. S. 2868.

8 By Raoult's method of determining the lowering of the freezing point in very dilute
solutions, Brown and Morris (Journ. Chem. Soc., London, 1888, p. 610), have provisionally

THE POL YSA CCHARIDES. 1 3

they are precipitated from their solutions by saturation with certain
neutral salts, such as ammonium sulphate.1

FIG. 4.— Crystals of phenyl-lactosazone.

By hydrolysis they are finally split up into simple sugars ; various
dextrins and disaccharides being intermediate products. The dextrins
are of various kinds, and are differently named by different observers.
The reaction cannot be represented by equations with certainty as long
as the molecular weights of the members of the group are unknown.

Brown and Morris suggest the following series, indicating the successive
steps of the hydrolysis, in the case of starch under the influence of diastatic
ferments : —

(C6H1005)n + H20 T (C6H1005)n_2 + C12H22On

(starch) (dextrin) (maltose)

(CcH1005),,-2 + H20 = (C6Hlo05)n_4 + C12H22On

(dextrin) (dextrin) (maltose)

(C,;H1005)n-4 + H20 = (C6H1005)n_6 + C12H22On

(dextrin)

(dextrin)

(maltose)

assigned to dextrin and soluble starch the formulae (C6H1005)12 and (C6H1005)30 re-
spectively. The same method applied to starch, though not so satisfactorily, points to a
molecular weight of between 20,000 and 30,000 ; that is, about three times greater than that
of soluble starch. Sabanejeff, Cham. Ccntr.-BL, Leipzig, 1891, S. 10 ; Journ. Russian Chem.
Soc., vol. xxi. p. 515, by the same method assigns to glycogen the formula (C6H1005)10.

1 Pohl, Ztschr. f. physiol. Chem., Strassbtirg, Bd. xiv. S. 151 ; Young, " Proc. Physiol.
Soc.," Feb. 13, 1897, in Journ. Physiol. , Cambridge and London, vol. xxi.

14 CHEMICAL CONSTITUENTS OF BODY AND FOOD.
and so on, until at last we get to

(C6H1005)4 + H20 = (C6H1005)2 + C12H220U

(dextrin) (dextrin) (maltose)

and finally

(C,.,H1005).2 + H20 = C12H,2On

(dextrin) (maltose)

The principal sub-groups of the polysaccharides are the starch
group, the gum group, and the cellulose group. The starch group
includes starch, inulin, lichenin, and glycogen. The gum group includes
the dextrins, the plant gums and mucilages, and animal gum. The
cellulose group includes cellulose, the hemicelluloses, and tunicin.

Starch is one of the most widely* distributed carbohydrates in the
vegetable kingdom. It occurs in nature in granules, which consist of
two principal substances, starch-granulose and starch-cellulose ; of these
the former only is dissolved by the digestive juices. Erythrogranulose,
which gives a red colour with iodine, is present in small quantities
(Briicke).

Starch is insoluble in cold water, in alcohol, and in ether. With
hot water it swells, forming an opalescent solution or starch paste.
This, if concentrated, gelatinises on cooling. On hydrolysis it forms
first soluble starch (also called amylodextrin or amidulin), then other
dextrins, and finally maltose and dextrose.

The most characteristic reaction of starch is the blue compound it
forms with iodine.1 It does not give Trommer's test or Moore's
test, nor does it ferment with yeast. The specific rotatory power 2
of soluble starch for concentrations of 2*5 to 4-5 per cent, at 15°'5 C.,

Inulin is found in the roots of many composites. It is usually
prepared from dahlias. It is the only polysaccharide which can be
obtained in a crystallised form, namely, as sphere-crystals which
polarise light. It is readily soluble in warm water ; by cooling the
solution it is precipitated. By hydrolysis its final product is levulose.3

Lichenin is a polysaccharide occurring in Iceland moss, and certain
algae. It is insoluble in cold water, soluble in hot water, gives a yellow
colour with iodine, is converted into glucose by hot dilute mineral acids,
but is not affected by saliva or pancreatic juice.4

Glycogen. — This is a small but constant constituent of protoplasm,
and of animal tissues generally. It is found in white blood corpuscles,5
and in pus,6 occasionally in diabetic urine,7 but is specially abundant in

1 E. Zander finds that the iodine reaction given by polysaccharides and by chitin varies
considerably with the solvent used (Arch. f. d. ges. PhysioL, Bonn, 1897, Bd. Ixvi.
S. 545).

3 Brown, Morris, and Millar, loc. cit.

3 Kulz, "Beitr. z. Path, des Diabetes," Marburg, 1894, S. 130. ; Worm-Miiller, Arch.
f. d. ges. PhysioL, Bonn, 1884, Bd. xxxiv. S. 576 ; 1885, Bd. xxxvi. S. 172 ; F. Hofmeister,
'Arch. f. exper. Path. u. PharmaJcoL, Leipzig, 1889, Bd. xxv. S. 240. On " Inulin as a

Precursor of Glycogen," see Miura, Ztschr. f. Biol., Miinchen, Bd. xxxii. ; he obtained
very inconstant results.

4 Nilson, Upsala Ldkaref. Forh., vol. xxviii., quoted by Hammarsten, in "Physiol.
Chem.," 3rd German edition, S. 67.

5 Salomon, Deutsche med. Wchnschr., Leipzig, 1877, Nos. 8 and 35 ; CentralU. f.
PhysioL, Leipzig, Bd. vi. S. 512 ; Huppert, Centralbl. f. PhysioL, Leipzig. Bd. vi
S. 394.

6 Salomon, loc. cit.

7 Leube, Virchow's Archiv, Bd. cxiii. S. 391.

THE POL YSA CCHARIDES. 1 5

liver and muscle,1 in embryonic tissues generally,2 and in the bodies of
molluscs.3 It has been described in pathological growths,4 and in
the vegetable kingdom in many fungi5 (truffles, mucor, yeast,
niyxomycetes).

It may be dissolved out with boiling water (Briicke),6 2 per cent,
potash (Klilz),7 or by trichloracetic acid,8 from the tissues in which it
occurs. The extraction with this acid is, however, incomplete, and the
product is impure.9 Huizinga 10 recommends that glycogen should be
extracted from the liver by a mixture of equal parts of saturated
solution of mercuric chloride, and Esbach's reagent (10 grms. of picric
and 20 of citric acid in a litre of water). From this solution,
which is proteid free, glycogen is precipitable by alcohol.

The pure material is a white tasteless powder, soluble in water, forming
a strongly opalescent solution. It is insoluble in alcohol and in ether.
It is strongly dextrorotatory ; n (a)D = + 196°'63. With Trommer's test
it gives a blue solution, but no reduction occurs on boiling.

With iodine it gives a port-wine red colour, which easily distin-
guishes it from starch. Its precipitability by basic lead acetate dis-
tinguishes it from dextrin.

Prolonged boiling with water or boiling with dilute mineral acids
converts it into sugar. The diastatic ferments act similarly.

Max Cremer 12 investigated the action of dilute acids on glycogen ; he
found glucose and isomaltose (identified by their osazones), but no maltose.
Kiilz and Yogel 13 investigated the action of diastatic ferments ; parotid saliva
produced isomaltose and maltose in the proportion of 1 to 2 from liver-glycogeri,
and isomaltose with small amounts of maltose and dextrose from nmscle-
glycogen ; pancreatic juice and malt diastase produced practically the same
result. The ferment in the liver which acts on glycogen produces dextrose.

The physiological relationships of glycogen will be treated elsewhere.
There is much controversy on the subject of the origin and fate of glycogen.
There is, however, little doubt that it is chiefly a storage product from the
carbohydrates of the food,14 and that after death it is transformed into dextrose ;
the principal controversies of recent years have centred round the question
whether glycogen normally leaves the liver in the hepatic blood as sugar (as

1 Claude Bernard, Compt. rend. Acad. d. sc., Paris, 1857, tome xliv. pp. 578 and 1325 ;
xlviii. pp. 77, 683, 763 and 784; Hensen, Virchow's Archiv, 1857, Bd. xi. S. 395; O.
Nasse, Arch. f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 97.

2 Claude Bernard, " Physiologie expei-.," 1855, tome i. p. 241; iv. p. 44; Salomon,
Centralbl. f. d. med. Wissensch., Berlin, 1874, S. 738 ; Moriggia, ibid., 1875, S. 186 ; v.
Wittich, Hermann's " Handbuch," 1883.

3 Bizio, Ztschr. f. Chem., Leipzig, 1866, S. 222 ; Bernard, " Lecons sur les phe'nomenes
de la vie," 1879, tome ii. ; Krukenberg, " Vergl. physiol. Studien," 1880, Bd. ii. S. 52.

4 Kiihne, Virckows Archiv, Bd. xxxii. S. 536 ; Sotnitschewski, Ztschr. f. physiol.
Chem., Strassburg, 1880, Bd. iv. S. 220.

5 Kiihne, "Lehrbuch der physiol. Chem.," 1868, S. 334; Reinke and Rodewald,
"Studien ueber das Protoplasma, " Berlin, 1881, S. 34, 54, and 169; Errera, Bull. Acad.
roy. de med. de Bcly., Bruxelles, Bd. iv. S. 451.

6 Sitznngsb. d. k. AJcad. d. Wissensch., Wien, 1871, Bd. Ixiii. S. 214.

7 Ztschr. f. BioL, Miincheu, 1886, Bd. iv. S. 191.

8 Friinkel, Arch. f. d. ges. Physiol., Bonn, Bde. lii. S. 125 ; Iv. S. 378.

9 Weidenbaum, ibid., Bde. liv. S. 319 ; Iv. S. 380.

10 Arch.f. d. ges. PhysioL, Bonn, Bd. Ixi.

11 Huppert, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 137.

12 Ztschr. f. BioL, Miinchen, 1894, Bd. xxxi. S. 181. 13 Ibid., S. 108.

14 According to Voit and his pupils (Ztschr. f. BioL, Miinchen, Bd. xxviii. S. 245), the
liver forms glycogen only from dextrose and levulose, or from those carbohydrates which
are converted into these sugars before they reach the liver.

1 6 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Bernard originally taught), or is employed in the synthesis of fat and proteid
(as Pavy holds).

Dextrin is the name given to a number of intermediate substances
formed during the hydrolysis of starch ; the principal varieties are
erythrodextrin, which gives a red colour with iodine; achroodextrin, which
does not ; and maltodextrin, which has a lower molecular weight than
these.1 The dextrins are dextrorotatory (maltodextrin has an (a)D = +
174° -5). They are soluble in water, and insoluble in alcohol and ether.
They give a blue solution with Trommer's test, but no reduction occurs
on boiling.

Animal gum was discovered by Landwehr,2 and resembles achroodextrin
and glycogen in some of its propertie^. It is a decomposition product of
mucin. When boiled with dilute sulphuric acid it yields a reducing but
unfermentable sugar. Animal gum, like the vegetable gums, gives gelatinous
precipitates with copper and iron salts.

Animal dextran is a gummy material, secreted by the Schizoneura
lamiginosa, a gall-producing louse that attacks elms.3

Vegetable gums and mucilages include such substances as gum arabic,
wood gum, etc., which are of subordinate physiological interest.

Cellulose is the name given to a number of carbohydrates which form
the chief constituent of vegetable cell walls. In old cells, where it
becomes very insoluble, it is called lignin. The celluloses are insoluble
in cold and hot water, in alcohol, ether, and dilute acids and alkalies.
A specific reagent for dissolving them is Schweitzer's reagent (a solution
of cupric hydrate in ammonia).

With iodine and concentrated sulphuric acid they are turned blue ;
with nitric acid they yield nitroso-compounds of an explosive nature.
Prolonged treatment with strong mineral acids leads to the formation of
sugars ; in some cases glucose, in others mannose, is formed. Schulze's
inannoso-cellulose,4 found in coffee and other seeds, is not a hemicellu-
lose (see next paragraph). The celluloses are not acted upon by the
digestive ferments proper ; but they may be broken up in the intestine
by bacteria into carbonic acid and methane.

Hemicelluloses are those varieties of cellulose which differ from the others
by yielding monosaccharides by treatment with dilute mineral acids. The
hemicellulose of yellow lupins yields galactose and arabinose ; that of rye and
wheat, arabinose and xylose; that of certain nuts, mannose.5

Tunicin is animal cellulose. It is the chief constituent of the test or outer
investment of the turiicates.6

Cellulose has also been found in the animal kingdom in the skin of the
silkworm,7 and in the zoocytium of Oplirydium versatile.^

Inosite. — Inosite is a substance found in muscle and other animal
tissues, and in many vegetables also. Its crystalline form is shown

1 Recent papers on dextrin will be found in Ber. d. deutsch. chem. Gesellsch., Berlin.
Bde. xxiii. S. 3060 ; xxvi. S. 2930 (by Scheibler and Mittelmeier), and Bd. xxvi. 8.
2533 (by Leubner and Doll).

2 Ztschr.f. physiol. Chem., Strassburg, Bd. viii. S. 119, 124.

3 Lieberraann, Arch. f. d. yes. Physiol. , Bonn, Bd. xl. S. 454.

4 Ztschr. f. physiol. Chem., Strassburg, Bd. xvi.

5 See Schulze, loc. cit. ; and Reiss, Ber. d. deutsch. chem. Gcsellsch., Berlin, Bd. xxii.

6 Schafer, Ann. d. Chem., Leipzig, Bd. ccx. S. 312; Berthelot, Ann. dechim., Paris,
Se"r. 3, tome Ivi. p. 153.

7 De Lucca, Compt. rend. Acad. d. sc.t Paris, tome lii. p. 102 ; Ivii. p. 43.

8 Halliburton, Quart. Journ. Micr. Sc., London, July 1885.

THE FATS.

in Fig. 5. For many years it was regarded as a carbohydrate, though an

exceptional one. It is sweet to the taste, but it gives none of the

characteristic reactions of sugar. As the chemical constitution of the

sugars was revealed, it became more and more evident that inosite is

not a sugar. Its constitution was

worked out by Maquenne1 from a

study of its nitro-substitution and

other products. It belongs to the

substances which have a closed

carbon chain, and its graphic formula

may be written thus : —

CHOH

CHOH

CHOH

FIG. 5. — Inosite crystals. — After Frey.

THE FATS.

Fat is found in most of the animal tissues. The following table from
Gorup-Besanez gives the percentage in the organs and fluids of the body: —

Sweat . . . 0-001

Vitreous humour . 0-002

Saliva . . . 0'02

Lymph . . . ' 0'05

Synovia . . O'OG

Liquor amnii . O'OG

Chyle ... 0-2

Mucus . . . 0'3

Blood . . . 0-4

Bile . . . 1-4

Milk 4-3

Cartilage
Bone .

Crystalline lens
Liver .
Muscles
Hair .
Brain .

Egg • •
Nerves

Adipose tissue
Marrow

1-3
1*4

2-0

2-4

3-3

4-2

8-0

11-6

22-1

82-7

96-0

The fats are usually extracted from the finely divided tissue by
means of ether in a Soxhlet's apparatus, but in the case of many organs
the extraction is incomplete. Dormeyer therefore recommends that
the tissue should be subjected to artificial gastric digestion before the
extraction with ether ; 2 when this was done, flesh was found to yield an
additional 0-75 per cent, of fat.

The fats are compounds of fatty acids with glycerin, and are termed
glycerides or glyceric ethers. The fatty acids form a series of acids derived
from the monatomic alcohols by oxidation; thus —

From methyl alcohol (CH3HO) formic acid (H.COOH) is obtained.

From ethyl alcohol (C2H5HO) acetic acid (CH3COOH) is obtained, and so on.

1 Compt. rend. Acad.. d. sc., Paris, 1887, tome civ. pp. 225, 297, 1719, 1853. For colour
reactions of inosite, see Scherer, Ann. d. Ohem., Leipzig, 1852, Bd. Ixxxi. S. 375 ; Gaulois,
Ztschr. f. anal. Chem., Wiesbaden, 1865, Bd. iv. S. 264 ; Seidel, Bcr. d. deutsch. chcm.
Gesellsch., Berlin, 1887, Bd. xx. S. 320.

* Arch. f. d. ges. PhysioL, Bonn, 1895, Bd. Ixi. S. 341 ; 1896, Bd. Ixv. S. 90; F. N.
Schulze (ibid., Bd. Ixv. S. 299 ; 1897, Ixxii. S. 145) has used the same method for the
extraction of the fat of blood, and numerous organs.
VOL. I. — 2

i8 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Or, in general terms —

From the alcohol with formula CI1H2n+1.HO the acid with formula
Cn_1H2ll_1.CO.OH is obtained. The sixteenth term of this series has the
formula C15H31.CO.OH, and is called palmitic acid; the eighteenth has the
formula C1TH35.CO.OH, and is called stearic acid. Each acid, as will be seen,
consists of a radicle, Cn_1H2ll jCO, united to hydroxyl (HO).

Oleic acid, however, is not a member of this series, but belongs to a some-
what similar series of acids known as the acrylic series,1 of which the general
formula is Cn_1H.,n_3COOH. It is the eighteenth term of the series, and
its formula is C17H33.CO.OH.

Glycerin or glycerol is a triatornic alcohol, C3H5(OH)3 — i.e. three atoms of
hydroxyl united to a radicle glyceryl (C3H5).

The hydrogen in the hydroxyl atoms is replaceable by other organic radicles.
As an example, take the radicle of acetc acid, called aoetyl (CH3.CO). The
following formulae represent the derivatives that can be obtained by replacing
one, two, or all three hydroxyl hydrogen atoms in this way : —

(OH
C3H J OH

[OH

(glycerin)

(OH (OH (O.CH3.CO

iJOH CgHJo.CH3.CO C3HJO.CH3.CO

[O.CH,.CO [O.CH3.CO [O.CH8.CO

(monoacetin) (diacetin) (triacetin)

The contents of the fat cells of adipose tissue in man are fluid during
life, the normal body temperature being higher than the melting point
of the mixture of fats found there ; but this is not the case in all
(even warm-blooded) animals, for beef fat melts at about 45° C., and
mutton fat at a still higher temperature. Human fat consists of
the three glycerides — palmitin, stearin, and olein. They differ in
chemical composition, melting point, and solubilities. Olein melts at
-5° C., palmitin at 45° C., and stearin at 53° to 66° C. It is thus olein
which holds the other two dissolved at the body temperature. All are
soluble in hot alcohol, ether, and chloroform, but insoluble in water.

The proportion in which these fats are mixed differs in different
animals ; in cold-blooded animals olein is much more abundant than in
warm-blooded animals. Human fat contains from 67 to 80 per cent,
of olein. Mixed with these neutral fats, there is generally a small
amount of free fatty acids.

Fats are also found in the vegetable kingdom, especially in seeds and
fruits, but in many cases in the roots also.

Stearin, palmitin, and olein ought more properly to be called tristearin,
tripalmitin, and triolein respectively. Each consists of glycerin, in which the
three atoms of hydrogen in the hydroxyls are replaced by radicles of the fatty
acid. This is represented in the following formulse : —

Acid.

Radicle.

Fat.

Palmitic acid C16
Stearic acid . C17
Oleic acid . C17

H31.COOH
H35.COOH
H33.COOH

Palmityl C15H31.CO
Stearyl . C17H35.CO
Oleyl . C17H33.CO

Palmitin
Stearin .
Olein .

C3H3(OC15H31
C3H5(OC17H35
C3H5(OC17H33

C0)3
C0)3
C0)3

1 Acrylic acid itself (C3H403) is obtained by the oxidation of acrolein (C8H40), the
ddehyde of allyl alcohol.

THE FATS. 19

Under the influence of superheated steam, mineral acids, and in the
body by means of certain ferments (for instance, the fat-splitting
ferment of the pancreatic juice), a fat combines with water and splits
into glycerin and the fatty acid. The following equation represents
what occurs in a fat, taking tripalmitin as an example : —

C3H5(O.C1.,H31CO)3H-3H20 = C3H5(OH)3+3C15H31CO.OH

(palmitin — a fat) (glycerin) (palmitic acid — a

fatty acid)

Saponification. — In the process of saponification much the same sort
of reaction occurs, the final products being glycerin and a compound of
the base with the fatty acid, which is called a soap.

Suppose, for instance, that potassium hydrate is used, we get —

C3H5(O.C15H31CO)3+3KHO - C3H5(OH)3+3C15H31CO.OK

(palmitin — a fat) (glycerin) (potassium palm itate

— a soap)

To separate the neutral fats from one another, they have always to be
saponified; this can be accomplished by potassium hydrate, or still
better by sodium alcoholate (Kossel, Obermuller, and Kriiger).1 On
evaporation of the alcohol, the soaps are dissolved in water, and pre-
cipitated by sugar of lead ; the lead compound of oleic acid is soluble in
ether ; the remaining soaps are treated with soda on the water bath,
dried, dissolved in alcohol, and separated by fractional precipitation with
barium acetate or barium chloride.

In the decomposition of fat, propionic, acetic, and formic acids may
be found, which are absent from the fat in the fresh condition. This
occurs when the fat becomes rancid, and is also produced by putre-
factive organisms in the alimentary canal. The process is one of
oxidation, and the way in which lowrer terms of the series are produced
may be illustrated by the following equations : —

C3Hoqa+03= C2H402+C02+H20.

(propionic acid) (acetic acid)

C2HA+03=:CH202+C02+H20.

(acetic acid) (formic acid)

2CH202+02:=2C02+2H20.

(formic acid)

Emulsification. — Another change that fats undergo in the body is very
different from saponification. It is a physical rather than a chemical
change ; the fat is broken up into very small globules, such as is seen in
the natural emulsion — milk.

The fats of milk resemble in a general way those of adipose tissue,
but there is a considerable admixture of glycerides lower in the series
(see "Milk").

The fats of marrow are also like those of adipose tissue. As will be
noticed in the table on p. 17, bone marrow is the tissue which is richest
of all in fat.

Eylert2 described a new fatty acid in the marrow of ox-bone which he
called medullic acid, but this was shown by Mohr3 to be only stearic acid.

1 Numerous papers in vols. xiv., xv., and xvi. of Ztschr. f. pliysiol. Chem., Strassburg.

2 Frtljschr.f. prdkt. PharmakoL, Bd. ix. S. 330.

3 Ztschr. /. physiol. Chcm., Strassburg, 1890, Bd. xiv. S. 390.

20 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Mohr gives the proportion of the acids in marrow fat as — palmitic acid, 22 ;
stearic acid, 10; and oleic acid, 63 per cent.

Among the exceptional forms of fat are the following : —

Spermaceti, obtained from the sperm whale. This fat sets into a solid,
white crystalline mass, melting at from 30° to 50° C. Its chief constituent
is the palmitate of cetyl alcohol, or ethal (C1CH33OH). This alcohol is the
one from which palmitic acid is derived in the same way as acetic acid
is derived from ethyl alcohol. Spermaceti contains also small quanti-
ties of compounds of lauristic, myristic, and stearic acids, with the
radicles of the alcohols lethal (C12H25OH), methal (C14H29OH), and
stethal (C18H37OH).

Beeswax contains three chief constituents : —

(1) Myricin; this is its principal^ constituent ; it is the palmitate of
myricyl alcohol (C30HC1OH) ; (2) Cerotic acid (C27H5402) ; and (3) Cerolein,
which is probably a mixture of several substances.

Chinese wax is chiefly the cerotic acid compound of cerotyl alcohol
(C27H,,OH).i

Adipocere is the name given to a waxy substance which replaces the
muscular tissue in corpses buried in damp soil, or which have been
allowed to remain in water some time after death. It consists chiefly
of the calcium soaps of palmitic and stearic acids, and in some cases of
acid ammonium soaps also.2 Hoppe-Seyler 3 considered that the change
is the result of a ferment action.

LIPOCHROMES, LECITHIN, CHOLESTERIN.

Lipochromes. — This name is given to the pigments which occur in
fat and fatty tissues. They are mostly yellow or yellowish red. They
include the pigment of the blood serum (serum lutein) and of the corpus
luteum ; the chromophanes or coloured oil globules of the retinal cones ;
the yellowish pigment in butter, adipose tissue, and egg-yolk ; tetronery-
thrin, a reddish pigment, found in many invertebrates; and several
vegetable pigments, such as carrotin, which is found in carrots and
tomatoes. The lipochromes have been separated by their various
solubilities after saponification ; they give various colour reactions, such
as a greenish-blue colour with iodine and sulphuric acid, and a green
colour with nitric acid; they show absorption-bands towards the
violet end of the spectrum, and especially in the region of the F line.

Nothing is known about their chemical constitution ; carrotin, which
has been examined more fully than the others, has been assigned the
formula C18H240 by Husemann, and C26H38 by Arnaud.4

1 On these rarer forms of fat and wax, see Liebermann, Ber. d. deutsch. chem. Gesellsch. ,
Berlin, 1885, Bd. xviii. S. 1975.

2 Quain, Med.-Chir. Trans., London, 1850, p. 141 ; Virchow, Vcrliandl. d. phys.-med.
Gesellsch. in Wurzburg, Bd. iii. ; Wetherill, Journ. f. praH. Chem., Leipzig, Bd. Ixviii. S.
26 ; K. B. Lehmann, Centralbl. f. Agric. Chem,., Leipzig, 1889, S. 66.

3 "Physiol. Chem.," Strassburg, S. 119. According to some authors, its formation is
brought about by micro-organisms (Jacobsthal, Arch. f. d. ges. Physiol., Bonn, 1893, Bd.
liv. S. 499.

4 The principal papers on lipochromes are the following :— On lutein— Thudichum,
Centralbl. f. d. med. Wissensch., Berlin, 1869, Bd. vii. S. 1. On colour reactions of
luteins — Thudichum, loc. cit. ; Piccolo and Lieben. Gior. de sc. nat. ed. ccon., Palermo,
vol. ii. p. 258 ; Caprarnica, Arch. /. Physiol., Leipzig, 1877, S. 283.; Schwalbe,
"Handb. d. ges. Augenheilkunde," Leipzig/ 187 4, Bd. i. S. 414. On chromophanes
— Kiihne and Ayres, Journ. Physiol., Cambridge and London, _ 1878, vol. i.
p. 109 ; Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, Bd. i. Heft 4. On

LECITHIN. 21

Lecithin is a complex fat of wide distribution. It is a constant
constituent of protoplasm, and is found both in the animal and
vegetable1 world. In the animal tissues, it is found principally in
the brain and nervous tissues, where it is probably a decomposition
product of a more complex substance originally called protagon by
Liebreich '2 (see section on " Chemistry of Nervous Tissues ") ; in yolk
of egg;3 and in blood corpuscles.4 Lecithin is found in all organs
composed of cells, and also in certain secretions, namely, semen, bile,
and milk.

Lecithin is a yellowish white, waxy, hygroscopic solid, soluble in
ether and in alcohol ; it swells and forms a kind of emulsion with
water. When ignited it burns and leaves a residue of metaphosphoric
acid. Its most important compounds are those of its hydrochloride
with platinum chloride (C44H90NP09Cl)2+PtCl2, and with cadmium
chloride which has a corresponding formula.5

Montgomery 6 showed that when water, glycerin, and other reagents
were added on a microscopic slide to impure lecithin (or protagon, as he
termed it), prepared from egg-yolk, snake-like forms shoot out, bending
and curling and even simulating nerve fibres or nerve cells. On
cooling a solution of lecithin in alcohol, it separates out in crystal-
line clumps. On decomposition by alkalis, it yields glycero-phosphoric
acid, a fatty acid, and an alkaloid choline.

Choline is an ammonium base, and has the following constitution: —

f(CH3)3 ]

N CH,— CH,OH [ = C5H15N02

IOH J

It is therefore trimethyl-oxyethyl-ammonium hydroxide; its name
is derived from the fact that it was first separated from the lecithin of
the bile. Its synthesis was accomplished by Wurtz7 from ethylene

tetronerythrin — Wiirm, Ztschr. f. wissensch. Zool., Leipzig, 1871, Bd. xxxi. S. 535 ;
Merejkowski, Compt. rend. Acad. d. sc., Paris, 1881, tome xciii. p. 1029 ; MacMunn, Proc.
Birmingham Phil. Soc., vol. iii. p. 351 ; Proc. Roy. Soc. London, 1883, No. 226, p. 17 ;
Halliburton, Journ. Physiol., Cambridge and London, 1884, vol. vi. p. 324 ; Krukenberg,
Centralbl. f. d. med. Wissensch., Berlin, 1879, Bd. ix. S. 705. On serum lutein—
Krukenberg, Sitzungsb. d. Jenaisch. Gescllsch.f. Med. u. Naturu:, 1885; Halliburton, Journ.
Physiol., Cambridge and London, 1885, vol. vii. p. 324. On saponification of lipochromes
— Kiihue, loc. cit. ; Maly, Afonatih. d. Chem., Wien, 1881, Bd. ii. S. 351 ; Bein, Ber. d.
deutscli. chem. Gcscllsch., Berlin, 1890, Bd. xxiii. S. 204. On carrotin — Husemann, Ann. d.
chem., Leipzig, Bd. cxvii. S. 200 ; Arnaud, Compt. rend. Acad. d. sc., Paris, tome cii.
p. 119; civ. 1293. New biggin, "On Crustacean Pigments," Journ. Physiol., Cambridge
and London, 1897, vol. xxi. p. 237.

1 On the subject of lecithin and choline in vegetable oils, etc., see Heckel and
Schlagdenhauft'en, Compt. rend. Acad. d. sc., Paris, tome ciii. p. 188 ; Jacobson, Ztschr. f.
physiol. Chem., Strassburg, Bd. xxiii. S. 33 ; Schulze, ibid., Bde. xi. S. 365 ; xii. S. 441 ;
xvii. S. 204 ; J. Stoklasa, Ber. d. deutsch. chem. Gesellsch., Berlin, 1896, Bd. xxix. S. 2761.

2 Ann. d. Chem., Leipzig, Bd. cxxxiv. S. 29.

3 Gobley, Journ. de pharm. et chim., Paris, tomes xi., xii.. xvii., xviii. ; Parke,
Hoppe-Seyler's "Med. Chem. Untersuch.," Berlin, Heft 2. S. 213 ;'Hoppe-Seyler, ibid., S.
215 ; Diaconow, ibid., S. 221 ; Centralbl. f. d. med. Wissensch., Berlin, 1868, S. 2.

4 Gobley, Journ. de pharm. et chim., Paris, tome xxi. p. 250; Hermann, Arch,
f. Anat. u. Physiol., Leipzig, 1866, S. 33; Hoppe-Seyler, "Med. Chem. Untersuch.," Berlin,
Heft 1, S. 140 ; Jiidell, ibid., Heft 3, S. 386.

5 The formation of these compounds enables one to prepare lecithin in a pure form, the
metal being subsequently got rid of by sulphuretted hydrogen.

(i "On the Formation of So-called Cells," London, 1867.

7 Ann. d. Chem., Leipzig, 1868, Supplement, Bd, vi. S, 116 and 197 ; see also Bayer,
ibid., Bd. cxl. S, 306,

22 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

oxide (C2H40), trimethylamine N(CH3)3, and water. It was at one time
thought to be identical with the base neurine, which Liebreich separated
from nervous tissues, and the two are closely related; empirically
choline (C6H15lSr02) is neurine (C5H13lSrO), plus water. In constitution
neurine is trimethylvinylammonium hydroxide.

Glycero-plwsplwric acid is glycerin, in which one of the hydroxyl
hydrogens is replaced by phosphoric acid, less hydroxyl ; thus —

HO OH

C3H5HO (H2P03)HO C3H5OH

HO 0— P03H2

(glycerin) (phosphoric acid) (glycero-phosphoric acid)

If the other two hydroxyl hydrogens are replaced by the radicle of
stearic acid, we obtain

OH9.0— CrH35CO

CH".O— c17H35co

which is distearyl-glycero-phosphoric acid. This is then united to
choline (less hydroxyl), and we obtain lecithin, or distearyl lecithin, as
it should be more properly termed ; for other lecithins exist in which
palmityl, oleyl, or other fatty acid radicles take the place of stearyl.

The exact manner of the union of the acid with choline is a matter of
controversy, for up to the present lecithin has not been prepared synthetically.
Hundeshagen l prepared artificially a choline salt of distearyl-glycero-phosphoric
acid, which is isorneric with lecithin, but which possesses none of its
characteristic properties.

The constitution of lecithin is not therefore that of a salt in which choline
plays a part of the base, as Diaconow 2 first suggested, but more probably it
is an ether-like combination, the choline radicle being united to the acid by
means of the oxygen of the hydroxyl; the formula for distearyl-lecithin
would therefore be (Strecker) 3 —

CH2.0— C17IL5CO

/"ITT S~\ /"^ TT f~^t \

OH . U Uj^llorV^^

CIIo.O— PO— O.C2H4)

| (CHo)A N
OH HOU )

The following equation represents the decomposition of lecithin, such
as occurs on boiling it with alkaline solutions : —

044H90NP09+3H20 - 2C1?H3flp2H-C3HflPOfl+C6H16N02

(lecithin) (stearic acid) (glycero- (choline)

phosphoric acid)

Lecith-albumins. — See p. 69.

Cholesterin. — Cholesterin is contained in small quantities in all proto-
plasmic structures ; it is also found in blood corpuscles and in bile. It is a
large constituent of sebum and similar oily secretions of the skin. In
nervous tissues it is an especially abundant constituent of the white sub-
stance of the medullary sheath. It may be prepared by making a hot

1 Journ.f. praJct. Chem., Leipzig, 1883, Bd. xxviii. S. 219 ; see also E. Gilson, Ztschr. /.
physiol. Chem., Strassburg, Bd. xii. S. 585.

2 Ccntralbl.f. d. med. Wissensch., Berlin, 1868.

3 Ann. d, Chem., Leip/ig, 1868, Bd. cxlviii. S. 77.

CHOLESTERIN. 23

alcoholic extract of the brain or spinal cord; on cooling, the cholesterin, to-
gether with protagon and cerebrin, separates out. From this mixture the
cholesterin is dissolved out with ether, and the ether distilled off'. To
get rid of traces of lecithin it is heated for an hour with alcoholic potash ;
this decomposes the lecithin, and the residue obtained by evaporating to
dryness is dissolved in a mixture of alcohol and ether ; from this solution,
cholesterin crystallises out as its solvents evaporate off.

Cholesterin is readily obtained from gall stones by simply extracting
them with boiling alcohol, and treating with alcoholic potash to free it
from extraneous matter.

Like the fats, cholesterin is insoluble in water, but freely soluble
in hot or cold ether, glycerine, benzol, hot alcohol, and chloro-
form. From anhydrous ether or chloro-
form it separates in the form of needles,
containing no water of crystallisation ;
from alcohol, or ether containing water,
it separates in the form of rhombic,
bright tables, which contain a mole-
cule of water of crystallisation, and
are easily identified by the microscope
(Fig. 6).

Dry cholesterin melts at 145°, distils in
vacuo at 360° C. ; its specific rotatory power
is (a)D = - 31°'6. It may be recognised by FIG.
the following colour tests : —

).— Cholesterin crystals. —
After Frey.

1. With iodine and concentrated sulphuric acid the crystals give a
play of red, green, and blue.

2. Salkowski's reaction.1 — The cholesterin is dissolved in chloroform
and an equal volume of concentrated sulphuric acid added ; the solution
becomes first red and then purplish, while the sulphuric acid is dark red
with a green fluorescence. On pouring off the chloroformic solution, it
becomes green and finally yellow.

3. Licbermann- Bur chard' s reaction.2 — This is a very delicate test, and
is stated to be capable of detecting one part of cholesterin in 20,000 of
solvent. The cholesterin is dissolved in 2 c.c. of chloroform, and ten
drops of acetic anhydride are added, and then concentrated sulphuric
acid drop by drop. The mixture becomes first red, then blue, and
finally green.

Cholesterin is a monatomic alcohol, the formula of which has been
given as C26H43OH and C27H45OH. The second formula was first
ascribed to the substance by Eeinitzer,3 and it is probably the correct
one, as it has been confirmed by the careful work of Obermiiller.4 These
observers have prepared a large number of compounds and derivatives
of cholesterin, but its constitution still remains unknown.

The subject is complicated by the circumstance that there are several
isomeric cholesterins.

1 Arch. f. d. ges. PhysioL, Bonn. Bd. vi.

2 Liebermann, Ber. d. deutsch. chem. Gescllsch., Berlin, Bd. xviii. S. 1804; Burchard,
" Beitrage zur Kenntniss der Cholesterine," Rostock, 1889.

3 Reinitzer, Monatsh. f. Chem., Wien, 1888, Bd. ix. s. 421.

4 Arch. f. PhysioL, Leipzig, 1889; Ztschr. f. pJnjsiol. Chem., Strasstmrg, 1889, Bde.
xv. S. 37 ; xvi. S* 143, 152.

24 CHEMICAL CONSTITUENTS OE BODY AND FOOD.

It forms, like glycerine, compounds often called esters, with fatty acids ;
and these compounds, which are found in the fatty secretions of the skin,
especially in the fat of sheep's wool (lanoline), are very resistant to bacterial
action ; as a protection to the skin lanoline is therefore admirable.

In lanoline there are two cholesterins at least; one is levorotatory, the
other (isocholesterin) is dextrorotatory. Isocholesterin was first described
by Schultze,1 and does not give Salkowski's reaction.

Cholesterins of various kinds are present in vegetable tissues.2

The cholesterin of the blood is in combination with oleic and palmitic
acids.3

In man the cholesterin of the bile passes away in the fseces as koprosterin
(C.2TH4S0) ; in the horse as hippokoprosterin (C27H540 or C27H560) ; in the dog
it is unchanged.4

THE PROTEIDS.5

The proteids are the most important substances present in animal
and vegetable organisms ; none of the phenomena of life occur without
their presence ; they are constant decomposition products of, and therefore
probable constituents of, protoplasm.

" They are highly complex and, for the most part, uncrystallisable
compounds of carbon, hydrogen, oxygen, nitrogen, and sulphur,6 occurring
in a solid, viscous condition, or in solution in nearly all the solids and
liquids of the organism. The different members of the group present
differences in physical, and to a certain extent even in chemical
properties. They all possess, however, certain common chemical reactions,
and are united by a close genetic relationship " (Gaingee).7

The following table from Gorup-Besanez 8 exhibits the percentage of
proteids contained in the liquids and solids of the body : —

Cerebro-spinal fluid . 0'09

Aqueous humour . . 0*14

Liquor amnii . . 0*70

Intestinal juice . . 0'95

Pericardial fluid . . 2 -36

Lymph . . . 2*46

Pancreatic juice . . 3-33

Synovia . . . 3 '91

Chyle . 4-09

Blood . . 8-56

Spinal cord . . 7*49

Brain . . . S'G3

Liver . . . 11 -64

Thy mus . . 12 '29

Muscle . . 16-18
Tunica media of arteries 27*33

Milk .... 3-94 Crystalline lens . 3S'30

1 J3er. d. deutsch. chem. Gesellsch., Berlin, Bd. vi. ; Journ. f. prakt. Chcm., Leipzig,
N.F., Bd. xxv. S. 458; Ztschr. f, physiol. Chem., Strassburg, Bd. xiv. S. 522. On
isocholesterin in remix caseosa see Rappel, ibid., Bd. xxi. S. 122.

2 Beneke, Jahresb. ii. d. Leistung d. ges. Med., Berlin, 1862 ; Hesse, Ami. d.

Chem., Leipzig, Bd. cxcii. S. 177; Bd. ccx., S. 283; Reinke and Rodewald, ibid., Bd.
ccvii. S. 232; Schulzc and Barbieri, Journ. f. prakt. Chem., Leipzig, N.F., Bd. xxv. S.
159, 458; Heckel and Schlagdenhauffen, Compt. rend. Acad. d. sc., Paris, 1886, tome cii.
p. 1317 ; Arnaud, ibid., p. 1319. See also Jacobson's paper on " Vegetable Oils," Ztschr.

f. physiol. Chem., Strassburg, Bd. xiii. S. 32.

3 K. Hiirthle, Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 331.

4 St. Bondzynski and V. Hunmicki, Ztschr. f. physiol. Chcm., Strassburg, 1896, Bd.
xxii. S. 396.

5 In the preparation of this section I have derived special assistance from the articles
"Eiweisskorper," in Beilstein's " Handbuch der org. Chemic," and in Ladenburg's
" Handworterbueh d. Chemie," 1885, Bd. iii. S. 534 (article by E. Drechsel) ; and from
an article by T. G. Brodie in Science Progress, London, 1895, vol. iv. p. 62.

6 In some cases phosphorus also is present.

7 "Physiological Chemistry," London, vol. i. p. 4.

8 "LehrbucV'S. 128.

COMPOSITION OF THE PROTEIDS. 25

The proteid constituents of the animal body are derived from
vegetables either directly, or indirectly through the body of another
animal. Synthetic processes do occur in the animal body,1 but to a
much greater extent in vegetables ; here the proteids are built up from
simpler compounds, derived ultimately from the soil and atmosphere.
In animals, the proteids are converted during digestion into hydrated
products, called peptones ; these are re-converted into proteids,
similar, in a general sense, to those originally ingested, and these are
assimilated to become part of the living organism. In time, they
become subjected to katabolic processes, and give rise to carbonic acid,
sulphuric acid, water, and certain not fully oxidised products (urea, uric
acid, etc.) which contain the nitrogen of the original proteid.

Composition of the proteids. — Various proteids differ a good deal
in elementary composition, as is seen by the following percentages : —

From From

Hoppe-Seyler.2 Dveclisel.3

C 51-5 to 54-5 50-0 to 55-0

H ... 6-9 „ 7-3 6-8 „ 7-3

N 15-2 „ 17-0 15-4,, 18-2

0 .... 20-9 „ 23-5 22-8 „ 24-1

S . . . . 0-3 „ 2-0 0-4 „ 5-0

In addition to the above constituents, many proteids or proteid-like
substances contain small quantities of phosphorus; and practically all
proteids leave on ignition a variable amount of ash. In the case of egg-
albumin the chief substances in the ash are chlorides of potassium and
sodium, and smaller quantities of phosphoric, sulphuric, and carbonic
acids, in combination with sodium, potassium, calcium, magnesium, and
iron. There may also be a trace of silica.4 The ash of serum pro-
teids contains an excess of sodium chloride, and that of muscle proteids
a preponderance of potassium and phosphoric acid.

Whether these mineral substances are integral constituents of the proteid
molecule, or closely adherent impurities, is a matter of doubt; the latter
supposition is the more probable, as there are certain methods of obtaining
proteids practically free from ash. The best of these is Harnack's,5 in which
lie precipitates the proteid as a copper albuminate ; this is dissolved in sodium
hydrate, and the proteid is precipitated from this solution by hydrochloric acid.
The so-called ash-free albumin obtained earlier by Aronstein and Schmidt6 by
means of dialysis, was shown by later observers (Heynsius, Winogradoff) to be
poor in ash, but not free from ash, and, moreover, that its incoagulability by
heat and other characteristic properties were due to the use of alkali in its
preparation. Nevertheless, Harnack's ash-free albumin is also not coagulable
by heat, and more closely resembles acid albumin in its properties than any
other known proteid.7

1 A very suggestive article by Pfliiger on this subject will be found in Arch. f. d. ges.
Physiol., Bonn, Bd. xlii. S. 144.

2 "Handlmch d. physiol. path. chem. Anal.," 1885, 5th edition, S. 258.

3 Loc. cit. Kuhne and Chittenden's analyses of peptones, which they give with reserve,
lie considerably outside these limits, Ztschr. /. BioL, Miinchen, 1886, Bd. xxii. S. 452.

4 Gmelin, "Hanclb. d. org. Chem.," Bd. viii. S. 285.

5 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxii. S. 3046 ; Bd. xxiii. S. 3745 ; Bd. xxv.
S. 204.

6 Arch. f. d. gcs. Physiol., Bonn, 1875, S. 1.

7 Werigo, ibid., Bd. xlviii. S. 127. Harnack denies that his material is acid-albumin,
in spite of the acid used in its precipitation.

26 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Globin prepared from haemoglobin is stated to be free from ash. It is
perhaps hardly correct to say that the ash is an impurity, because it is
extremely probable that in their native condition the actual proteid molecules
are combined more or less loosely with inorganic substances.

The process of incinerating has its drawbacks in determining the amount
of ash in a proteid ; for in the heating, some of the sulphur of the proteid, and
when phosphorus is present the phosphorus also, will be oxidised and form
sulphuric and phosphoric acids respectively. H. Schulz l has recently shown
that sulphates are formed in tissues as a result of drying them at 110° C. ; this
would occur to a greater extent still at the temperature necessary for ignition.

The sulphur in proteids is in the body normally burnt off as
sulphuric acid, which leaves the body in the urine as sulphates. The
ethereal hydrogen sulphates of the*urine originate in the intestine, as a
result of putrefactive changes in proteids,2 and when putrefaction is
hindered by the administration of large doses of iodoform in dogs, these
products do not appear in the urine.3 Krliger 4 has shown that a part
of the sulphur in proteids is present in a condition of stable combination,
a part loosely combined ; the latter is removed by boiling with alkalis,
the former is not ; the proportions of the two differ in different proteids.
Among tbe primary decomposition products of proteid, thio-acids, of
which thioglycollic acid is probably the most abundant, are obtained.5

From the elementary analyses which have been made of proteids, various
observers have attempted to construct an empirical formula for certain typical
proteids, egg-albumin being the one usually selected. Thus Lieberkiihn
assigned to albumin the formula C72H112N18022S ; Loew Q gives the same
formula ; Harnack 7 gives C204H322N52b66S2 ; Schiitzenberger,8 C240H392N6B075
S3 ; and there have been others. The great divergence between these numbers
requires no comment.

Equally conflicting results have been obtained in attempts to ascertain the
molecular weight of albumin. Lieberkiihn, in 1852, attempted to establish it
by analysing the copper compound of egg-albumin ; more recently, Harnack
has done similar work. But very little importance can be attached to
such work at present, for Chittenden and Whitehouse9 find there is no
definite copper albuminate, but that there are several in the mixture ; and
equally variable results are obtained with other metals both with egg albumin
and myosin.

Such researches lead to the same conclusion as dialysis, namely, that
the molecules of proteid are extremely large, but leave us quite in the
dark as to their exact magnitude.10 It is possible that in the future the

1 Arch.f. d. ges. Physiol., Bonn, 1894, Bd. Ivi. S. 203. See also Halliburton and Brodie,
Journ. Physiol., Cambridge and London, 1894-95, vol. xvii. p. 154.

2 Baumann, Ztschr. f. physioL Chem., Strassburg, Bd. x. S. 123.

3 Morax, ibid., S. 318. See also more recently Nuttall and Thierfelder on "Animal
Life without Bacteria in the Alimentary Canal," ibid., vol. xxi. p. 109 ; xxii. p. 62. In tins
paper it is shown that healthy animal life is possible without micro-organisms in the
alimentary canal.

4 Arch.f. d. yes. PhysioL, Bonn, 1888, Bd. xliii. S. 244.

5 F. Suter, Ztschr. f. physiol. Chem., Strassburg, 1895, Bd. xx. S. 564 ; E. Baumann,
ibid., S. 583, and VirchoivsArchiv, 1894, Bd. cxxxviii. S. 560 ; E. Salkowski, ibid., S. 562.

6 Loew and Bokorny, "Die chemische Kraftquelle im lebenden Protoplasma, " Munich,
1882.

7 Ztschr. f. physiol. Chem., Strassburg, Bd. v. S. 207.

8 Bull. Soc. chim., Paris, Ser. 5, tomes xxiii. and xxiv. See also Schmiedeberg, Arch. f.
exper. Path. u. PharmakoL, Leipzig, 1897, Bd. xxxix. S. 1.

9 Stud. Lab. Physiol. Chem., New Haven, vol. ii. p. 95.

10 The large size of the proteid molecule can be very strikingly demonstrated by the fact

COMPOSITION OF THE PROTEIDS. 27

result will be achieved, when proteids obtainable in a crystalline form
have been thoroughly investigated.

Vegetable proteids have been prepared in a crystalline form1 in
combination with magnesia; Drechsel2 found in one preparation 14 per
cent, of magnesia (MgO) ; in another, prepared by an improved method,
143 per cent. From this the molecular weight x may be calculated as
follows : —

a; _ 100 -143. 975.
40 143

From the similar examination of the sodium compound the mole-
cular weight of albumin was found to be 1496. Other vegetable pro-
teids examined by Griibler3 also gave high but variable molecular
weights.

Haemoglobin belongs to the proteid compounds capable of crystallisa-
tion; Zinoffsky4 prepared haemoglobin crystals from the blood of the
horse in a very pure state, and the formula calculated for haemoglobin
from his elementary analyses would be —

If a molecule of haematin, C32H32N404Fe, is subtracted, the formula for
proteid left is —

241

Jaquet's5 formula for pure haemoglobin of dog's blood would give the
proteid molecule a formula —

C726-"-117i-N194S3O214

So that here again there are great discrepancies.

Such a summary of the principal analyses made, is quite sufficient to
give point to Drechsel's conclusion, that while divergences of analysis
exist, even though they are due to extremely small errors, it is futile
to attempt to measure accurately the size of the proteid molecule.
Drechsel points out that in so large a molecule an analytical error of
O'Ol per cent, would have the same importance as one of 01 per cent, in
ordinary analyses.

It should be added, in conclusion, that some few investigators have
used the cryoscopic method in attempting the solution of this problem ;
the molecular weight of egg-albumin by this method is 14,000
(Sabanejeff),6 of albumoses 1200-2100, and of antipepton much less
(Paal).7

Equally inconclusive, though much more interesting, have been the
attempts to discover the rational formula for the proteid molecule. The

that proteids in solution will not pass through a membrane of gelatin or silicic acid, when
filtered under pressure. The products of proteolysis (proteoses and peptones) will,
however, pass such a membrane ; the smaller size of their molecules has also been demon-
strated by the cryoscopic method. Crystalloids pass through such membranes at the same
rate as water, and can thus be easily separated from colloids in a solution containing both
(C. J. Martin, Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 364).

1 The subject of vegetable and crystalline proteids will be treated at length in a later
section of this chapter.

'2 Journ. /. prdkt. Chem., Leipzig, 1879, N.F., Bd. xix. S. 331.

3 Ibid., 1881, Bd. xxiii. S. 97.

4 Ztschr. f. physiol. Chem., Strassburg, 1885, Bd. x. S. 16. 5 Inaug. Diss., Basel, 1889.

6 Ber. d. deutsch. chem. Ge*dlach., Berlin, 1891, Bd. xxiv. Ref. 558.

7 Ibid. , 1894, Bd. xxvii. S. 1827. For Siegfried's work on the identity of antipeptone
with a simple compound, which he has called carnic acid, see under " Chemistry of Muscle,"
p. 103.

28 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

FIG. 7. — Leucine crystals. — After Kiihne.

usual method which a chemist follows in attempting to unravel the
constitution of any substance, is first to discover the way in which it decom-
poses (analysis), and then to build up the original material once more from
the simple compounds so obtained (synthesis). In the case of the proteids
there have been many observations on the analytical side, but synthesis
has not yet been successful. We will first consider the results of
analysis, next the attempts at synthesis, and finally state some of the
theories founded on these observations.

The decomposition products of proteids. — The experiments which

have been performed fall into two
main groups: the first, designed with
a view to determine the series of
changes a proteid undergoes in its
passage through the body ; the second,
with the object of investigating the
chemical substances obtained as
cleavage products by artificial means
in the laboratory. In the first group
the progress which has been made
is slight, great and obvious difficulties
being encountered at nearly every
step ; the end products, carbonic
anhydride, water, urea, uric acid,
ammonia, etc., are known, but the
intermediate substances, resulting
from metabolic changes within the
cells and tissues, are still in the
region of conjecture.

In the alimentary canal itself there are, however, changes which are

within the grasp of the investi-
gator, and the proteoses, al-
buminates, and peptones there
formed will be treated under
the head of " Digestion." Here,
too, under the prolonged action
of the pancreatic juice, simpler
nitrogenous substances, such
as leucine, tyrosine, aspartic
acid, and ammonia, are formed
in small quantities. Leucine
(C0H13N20) is empirically
amido-caproic acid, but of the
numerous possible isomerides
which could be included under
that name, leucine has
been shown to be a-amido-
isobutylacetic acid, (CH3)9CH.
CH2 CH2 (NH2) COOH. ^The
leucine obtained on pancreatic
digestion is dextrorotatory.
Levorotatory and optically in-

FIG, 8. -Tyrosine crystals.— After Frey. active varieties of leucine exist,

and some of them have been

THE DECOMPOSITION PRODUCTS OF PROTEIDS, 29

prepared synthetically.1 Tyrosine (C(JH11N03) is oxyphenyl amidopropionic
acid, HO.C0H4.C2H3(NH2).COOH. This substance has also been made
synthetically.2 The crystalline forms of these two substances are seen in
the accompanying figures (Figs. 7 and 8). Aspartic or asparaginic acid 3
(C4H7N04) is amido-succinic acid, C2H3(NH2)(COOH)2. That ammonia
is produced in prolonged pancreatic digestion, under conditions preclud-
ing the possibility of putrefaction, was shown by Stadelmann.4

To this list must be added lysine, lysatinine, arginine5 (see p.
33), glutaminic acid, and proteinchromogen,6 a substance of un-
certain nature which gives a reddish -violet product with chlorine or
bromine water.

Within the intestine many changes occur which are due to bacterial
action. The products which have just been enumerated arise first,
and then by different changes other substances are formed; of these
the following may be mentioned : — indol, skatol, skatol-carbonic acid,
oxyphenylpropionic acid, phenylpropionic, and phenylacetic acids,
parakresol, and phenol, and simpler bodies like carbonic anhydride,
water, ammonia, hydrogen, and sulphuretted hydrogen, arnido-fatty acids,
and fatty acids themselves.7 The most interesting point to note here
is the large number of derivatives containing the benzene nucleus. The
indol group has never been obtained from the proteid molecule by any
other method than that of bacterial decomposition.8

We can now pass to the second category of investigations, namely,
those carried out in vitro.

The first action produced by most reagents, especially if they bring
about hydrolysis, is the formation of proteoses and peptones ; these are
then broken up into more simple substances. The subject may be most
conveniently treated of under the heads of the different methods employed.

1. Treatment with alkalis. — Mulder 9 treated albumin with caustic
potash, and obtained the substance which we now call alkali-albumin ;
this material is free from most of the sulphur present in the original
proteid, namely, that which is present in loose combination ; the firmly
combined sulphur, however, remains undisturbed.10

Mulder thought that by this method he had obtained the base of
all albuminous material, and called it "protein"; he described many

1 For recent literature on lencine, see Sclmlze and Likiernik, Ztschr. f. physiol. Chem.
Strassbtirg, Bd. xviii. ; Gmelin, ibid., Bd. xviii. ; Hiifner, "Synthesis of Leucine," Journ. f.
praJct. Chem., Leipzig, N. F., Bd. i. ; E. Schulze, Barbieri and Bosshard, Ztschr. f. physiol.
Chem., Strassburg, Bde. ix. and x. ; Cohn, ibid., Bd. xx.

2 Erlenmeyer and Lipp, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xv. S. 1544.

3 For chemistry and preparation, see Hlasiwetz and Habermann, Ann. d. Chem.,
Leipzig, Bd. clxix. S. 160 ; E. Schulze, Ztschr. f. physiol. Chem., Strassburg, Bd. ix.

4 Ztschr. f. Biol., Mimchen, 1888, Bd. xxiv. S. 261. See also Hirschler, Ztschr. f.
physiol. Chem., Strassburg, Bd. x. S. 302.

5 Hedin, Arch. f. Physiol., Leipzig, 1891, S. 273.

6 Stadelmann, Ztschr. f. Biol., Mimchen, Bd. xxvi. S. 491. Neumeister suggests the
name tryptophan for this substance, ibid., S. 324 ; Nencki, Ber. d. deutsch. chem. Gesellsch.,
Berlin, Bd. xxviii. S. 560.

7 Salkowski, ibid., Bd. xii. S. 648; Tappeiner, Ztschr. f. Biol., Mimchen, Bd. xxii.
S. 236.

8 For recent- work on the mycological processes in the intestines, see V. D. Harris,
Journ. Path, and Bacteriol., Edin. and London, 1895, vol. iii. p. 310. On the putrefaction
of pure proteids see 0. Emmerling (Ber. d. deutsch. chem. Gesellsch., Berlin, 1896, Bd. xxix.
S. 2721) ; in addition to the substances enumerated above he tinds betaine.

9 Journ. f. prakt. Chem., Leipzig, Bd. xvi. S. 129; Bd. xvii. S. 312; Ann. d. Chem.,
Leipzig, Bd. xxxi. S. 129.

10 Kriiger, Arch. f. d. ges. Physiol., Bonn, Bd. xliii. S. 244.

30 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

compounds of this substance, but, as Liebig1 was the first to show,
this work was full of fallacies, and the only remnant of it is the survival
of the word proteid.

Pavy2 has used caustic potash in his researches on proteids, and
shown that the action of the alkali is to split off a substance of an amylose
nature which, on further treatment with mineral acids, yields a reducing
but non-fermentable sugar, C6H1206, which gives a crystalline osazone
with phenylhydrazine. Pavy, however, himself points out that he is
not the first to obtain this result. Schiitzenberger 3 many years ago
obtained from proteid a dextrin-like substance by the prolonged use
of baryta water, which, after treatment with sulphuric acid, reduces
Fehling's solution, and " appears to be glucose, or an analogous substance."
From his own and Schiitzenberger 's work, he draws the conclusion that
proteid matter has the constitution of a glucoside. These experiments
will be again referred to under the gluco-proteids.

0. Nasse 4 discovered that by boiling proteids with a strong solution
of barium hydrate some of their nitrogen was disengaged as ammonia,
but this only accounted for a small percentage of the total nitrogen.
He concluded that the nitrogen which is readily liberated is in the form
of an amide, that some is combined similarly to that of creatine, but that
the major part which is unaffected by this treatment is in the form of
an amido-acid.

Schiitzenberger 5 has elaborated the baryta method. He obtained dif-
ferent results by varying the conditions of temperature and pressure, of
the time of treatment, and of the amount of barium hydrate employed. In
his earlier researches he employed coagulated egg-white, which had been
thoroughly washed with water, alcohol, and ether ; weighed amounts of
it were treated with from two to six times their weight of crystallised
barium hydrate and with water, the whole being heated in a closed iron
vessel to temperatures ranging from 100° to 250° C., and for periods of
time varying from 8 to 120 hours. He found that nitrogen to the extent
of about one per cent, of the total weight of albumin is given off as
ammonia at atmospheric pressure, by boiling for half an hour ; a second
one per cent, comes off slowly by continued boiling for 120 hours (this
result is, however, more easily obtained by treating with three parts of
barium hydrate at 120° C. for six to eight hours) ; a third one per cent, is
given off by treating with two parts of barium hydrate at 150° C., and a
fourth one per cent, by heating with excess of barium hydrate at 260° C.

He next found that accompanying these four stages there were
different cleavage products obtained. First, some insoluble barium salts,
namely, oxalate, carbonate, phosphate, and sulphate. On calculating
the quantities of oxalate and carbonate formed, he arrived at the
interesting result that they were present in proportions to support the
hypothesis that, with the ammonia set free, they had existed in the pro-
teid molecule as a urea and oxamide radicle. The barium carbonate
and oxalate, moreover, were formed at different stages of ammonia

1 Ann. d. Chem., Leipzig, Bd. Ixii. S. 132.

2 "Physiology of the Carbohydrates," London, 1894, p. 28; Proc. Roy. Soc.
London, 1893, vol. liv. p. 53 ; Eep. Brit. Ass. Adv. Sc., London, 1896.

3 Bull. Soc. chim., Paris, 1875, Se*r. 5, tome xxiii. p. 161.

4 Chem. Centr.-BL Leipzig, 1873, S. 137; Arch. f. d. ges. Physiol., Bonn, Bde. vi. S.
589 ; vii. S. 139 ; viii. s. 381.

5 Ann. dechim., Paris, Se"r. 5, tome xvi. p. 289 ; Compt. rend. Acad. d. sc., Paris, tomeci.
p. 1267 ; cii. p. 289 ; cvi. p. 1407 ; cxii. p. 189 ; Bull. Soc. chim., Paris, Ser. 5, tome xxiv.

THE DECOMPOSITION PRODUCTS OF PROTEIDS. 31

elimination, in such a way that the first amount of ammonia might be
considered to come from one of the amide radicles of the oxamide, while
the second corresponded to the urea, and the third to the remaining
nitrogen of the oxarnide, then present as oxamic acid.

After precipitating the barium with carbonic anhydride and sulphuric
acid, he obtained, by distillation in a partial vacuum, a small quantity of
acetic acid, traces of formic acid, and an essential volatile oil which he
indentified as pyrrol contaminated with smaller quantities of methyl-
pyrrol and ethyl-pyrrol. The remainder, which did not volatilise
nor sublime at a low temperature, he termed rfeidu fixe. By con-
trasting the composition of this with that of the original albumin,
and taking into account the substances already enumerated, he found
that the essential action of the barium hydrate was that of
hydrolysis. By repeated crystallisations from water, alcohol, and
ether, he separated the constituents of his rdsidu fixe and found
they were amido-acids of two classes, which we may term A and B.

A. These comprised over 80 per cent, of the total weight ; in them
the proportion N:0 = 1:2. They consisted of —

1. Amido-acids of the series CnH2n+1N02.

These he called Icucines. They included alanine (0 = 3) in small
quantities, propalanine or amidobutyric acid (0 = 4), butalanine or
amidovaleric acid (C = 5), both in considerable amount, and leucine or
amidocaproic acid (C = 6), in very large quantities. Glycocine or amido-
acetic acid (0 = 2) was not found.

2. Amido-acids of the series CnH2n_1N20.

These are amido-acids of the acrylic series, and were called leuceines.
Here, too, the term which was most abundant is that in which 0 = 6, but
bodies corresponding to C = 4 or 5 were also found.

3. Amido-acids of the series CnH2nN204, or some multiple of this.
To these substances he gave the name of gluco-proteins, on account
of their sweet taste. The most abundant of these were those in which
C = 9 or 7, or some multiple of these numbers ; but others in which
0 — 8, 10, and 11 were also isolated.

B. These comprised about 16 per cent, of the total weight; in them
the proportion N:0 = 1:3, or 1:4, or 2:5. In this class were found—

1. Tyrosine ; the amount of this was about 3'5 per cent.

2. Tyroleucine, C7HnN02, in about the same quantity.

3. Very small quantities of glutaminic acid, C5H9N04. This is an
optically inactive amido-derivative of one of the pyrotartaric acids
(glutaric).

Of these substances, Schiitzenberger found varying quantities,
according to the degree to which the hydrolytic decomposition had been
carried out. The more thorough the hydrolysation, the more leucines
and leuceines were found ; but in earlier stages gluco-proteins were
in excess.

With other proteids he obtained corresponding results. Gelatin
gave the same substances, with the addition of amido-acetic acid or
glycocine ; 20 to 25 per cent, of this substance was obtained.

He concluded that the albumin molecule, under the action of barium
hydrate, loses ammonia, carbonic anhydride, acetic and oxalic acid, and,
becoming hydrated, forms in the first instance gluco-proteins, mainly
those in which 0=9, or some multiple of this, and that on further action
these are changed into leucines and leuceines.

32 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

2. Treatment with acids. — Prolonged heating of proteids with dilute
acids results in their hydration and the formation of proteoses and
peptone.1 Strong acids produce the same effect at the ordinary tempera-
ture in the course of a few days.2 This method has the disadvantage
that strongly coloured materials make their appearance, and to avoid
this Hlasiwetz and Habermann 3 introduced the important modification
of heating with strong hydrochloric acid and stannous chloride, by which
pale yellow solutions were obtained without a trace of charring. A
certain amount of reduction occurred during the operations, leading to
the formation of stannic chloride. These methods yielded the following
substances : —

(1) Ammonia ; (2) an amido-acid of the acetic series, namely, leucine ;
(3) two amido-acids of the acrylic series, namely, asparaginic acid
(C4H7N04, amido-succinic acid), and •glutaminic acid (C5H9N04, amido-
pyrotartaric acid), both in considerable amount ; (4) tyrosine or
oxyphenylalanine.

Ritthausen 4 was the first to separate glutaminic acid and asparaginic acids
from proteids. He and Kreusler suggested that glutaminic acid was a typical
product of vegetable proteid ; but Hlasiwetz and Habermann 5 obtained it from
casein, albumin, and other animal proteids. The glutaminic acid they isolated
was levorotatory, while that obtained by Schiitzenberger was only found in
small quantities and was optically inactive. By boiling the active form with
barium hydrate, however, it is converted into the inactive form, and further,
the inactive form if allowed to ferment under the action of the mould
Penicillium glaucum, is transformed into the optically active modification.6

Employing the same method, Horbaczewski 7 obtained leucine, glutaminic acid,
and glycocine from gelatin, but no asparaginic acid or tyrosine. Hofmeister,8
however, obtained small quantities of asparaginic acid.

From elastin were obtained ammonia, leucine, tyrosine, glycocine, butalanine
(C5H11N02, amido-valeric acid), but no glutaminic or asparaginic acids.9

From reticulin (a substance separated from reticular tissue) were obtained
ammonia, sulphuretted hydrogen, and amido-valeric acid, but no tyrosine or
glutaminic acid (Siegfried).

By the employment of the same method, Drechsel10 has discovered two
new substances, which are of special interest. He began by studying
the quantities of nitrogenous bodies which other observers had obtained ;
and if he assumed that only one-half of these had been isolated there
still remained about 30 per cent, of the nitrogen of the proteid to be
accounted for. He pointed out also that Schiitzenberger obtained
carbonic anhydride by his method, and that Hlasiwetz and Habermann
did not by theirs. He argued from this that there should be some other

1 Neumeister, Ztschr. f. Biol., Miinchen, Bd. xxiii. S. 381.

2 See Brodie, Science Progress, London, 1895, vol. iv. p. 67.

3 Ann. d. Chem., Leipzig, 1873, Bd. clxix. S. 150. In a paper published previous to
this by the same observers (ibid., Bd. clix. S. 304), they sought unsuccessfully to establish a
definite relationship between proteids and carbohydrates.

4 Journ. f. prakt. Chem., Leipzig, Bde. xcix. S. 454 ; cvii. S. 218.

5 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1872, Bd. ix. S. 114.

6 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xvii. S. 388. Similar changes in the
optical varieties of leucine and other substances are similarly produced.

7 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1880, Abth. 2, Bd. Ixxx. S. 101.

8 Ztschr. f. physiol. Chem., Strassburg, Bd. ii. S. 299.

9 Horbaczewski, Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1886, Abth. 2, Bd. xcii.
S. 657.

10 "Der Abbau d. Eiweissstoffe, " Arch. f. Physiol., Leipzig, 1891, S. 248.

THE DECOMPOSITION PRODUCTS OF PROTEIDS. 33

substance produced by the latter method, which should yield carbonic
anhydride on treatment with an alkali. As he considered it probable
that this substance might be basic, he endeavoured to isolate it as a
precipitate by means of phosphotungstic acid, a reagent which is of
great value as a precipitant of basic or alkaloidal bodies. By this means
he succeeded in isolating not one but two bases, which he named lysine
and lysatinine.

Lysine has the formula C6H14N202, and is homologous with Jaffe's 1
ornithin (C5H12N202, probably diamidovalerianic acid). Lysine is pro-
bably diamidocaproic acid. On heating it to 120°— 130° with barium
hydrate, barium carbonate is formed. It will therefore account for some
of Schiitzenberger's carbonic anhydride.

Lysatine or lysatinine, the second base, is even more interesting.
Its formula is either C0H13N302 or C6HUN30, and is a homologue of
either creatine (C4H9N302) or creatinine (C4H7N30), according as the first
or second formula is taken.

It can be obtained pure as a double salt of its nitrate with silver
nitrate, and this when boiled with barium hydrate for twenty-five
minutes yields urea ; this is a decomposition exactly analogous to that of
creatinine under the same circumstances. From 10 grms. of the
double salt Drechsel obtained about 1 grm. of urea ; which is a large
quantity when one considers that under the conditions urea is quickly
broken up into ammonia and carbonic anhydride.

This is the first time that urea has been obtained from proteid in laboratory
experiments. Many years ago, Bechamp 2 stated that he had obtained urea
from egg-white by the oxidising action of potassium permanganate. Lossen 3
found that the substance Bechamp took for urea was guanidine, which
probably came from small quantities of xanthine, present in the egg-white as
an impurity, or, as Drechsel4 points out, from lysatinine. DrechsePs method,
it is important to notice, is one of hydration ; not, like Bechamp's, one of
oxidation.5

It should be added that Drechsel's work was carried out in the first
instance with casein, but his pupils have discovered lysine and lysatinine
among the cleavage products of other proteids and proteid-like substances,6
and further that the same substances are formed during pancreatic digestion.7

Hedin 8 has more recently arrived at the conclusion that lysatinine is not
a chemical individual, but a mixture of lysine with another base called
arginine. Arginine (C6HUN402) was originally separated from vegetable
tissues by Schulze and Steiger,9 and subsequently it was found by Hedin10

1 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. x. S. 1925.
-Ann. d. Chem., Leipzig, 1856, Bd. 100, S. 247.

vesti^

1871, N.F., Bd. iii. S. 289 ; Tappeiner,

rend. Acad. d. sc., Paris, tome Ixxiii. p. 1219 ; all of whom except Bitter failed to confirm

Bechamp's results.

4 Loc. cit.

5 On the formation of nrea by oxidation from many organic substances, see F. Hofmeister,
Arch.f. exper. Path. u. PharmakoL, Leipzig, 1897, Bd. xxxvii. S. 426.

6 Fischer (from gelatin), Inaug. Diss., Leipzig, 1890; Arch.f. Anat. u. Physiol., Leipzig,
1891, S. 205. Siegfried- (from conglutin), Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxiv.
S. 418 ; (from reticulin), " Ueber d. chem. Eigenschaften des retic. Gewebes," Habilitation-
schrift, Leipzig, 1892. Siegfried also obtained from conglutin a sweet substance
(CgHT GN204), corresponding to one of Schiitzenberger's gluco-proteins.

7 Hedin, loc. cit. 8 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 297.

9 Ibid., Bd. xi. S. 43 ; Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxiv. S. 2707 ; 1896,
Bd. xxix. S. 352.

10 Ztschr. f. physiol. Chem., Strassburg, Bd. xx. S. 186 ; xxi. S. 155 ; xxii. S.I 91.

VOL. I. 3

34 CHEMICAL CONSTITUENTS OF BOD Y AND FOOD.

to be a constant decomposition product of proteids and albuminoids. It
yields urea on treatment of its silver salt with barium hydrate.

Other recently published work on the decomposition of proteids by
hydrochloric acid is by K. Cohn.1 He used concentrated acid, and no
stannous chloride. From 1000 parts of casein he recovered 916'75 of
products ; these consisted of fatty acids, 34*25 • tyrosine, 35 ; leucine, 321 ; an
oily product containing an acid, C7H18N308, 180; pyridine derivatives, 3'65 ;
other substances, including cystin, cystein, thiolactic acid, and Drechsel's bases,
the remainder.

3. Treatment with oxidising agents. — Treatment of proteids with
nitric acid yields, first, an insoluble yellow substance of uncertain
composition, called xanthoproteic acid ; this dissolves gradually, and
finally paraoxybenzoic acid (probabiy from the oxidation of tyrosine),2
oxalic, fumaric, and saccharic acids are formed.

Oxidation by manganese dioxide or potassium bichromate, with
sulphuric acid, has yielded — (1) Fatty acids, from formic up to caprylic
(C8H1C02), and their aldehydes ; (2) nitrates of acetic, propionic, valeric,
butyric, and hydrocyanic acids ; (3) benzoic acid and benzoic aldehyde.
Oxidation with chlorine water has yielded, among other products, fumaric
acid, oxalic acid, and chlorazol. Oxidation with bromine water at high
temperatures in a sealed tube has yielded carbonic anhydride, oxalic
acid, ammonia, bromanil (C6Br402), bromoform (CHBr3), monobrom-
benzoic acid, mono- and dibromacetic acids, tribromamidobenzoic acid
(CGHBr3(NH)COOH), asparaginic and malaminic acids, leucine and
leucimide (CcHnNO). No tyrosine was obtained.3

4. Treatment % action of heat. — Dry distillation leads to the forma-
tion of a complex oily material, called "Dippel's oil," which contains
a large number of substances; among these are hydrocarbons of the
fatty series, ammonium salts of fatty acids, nitrates and ketones of the
same series, carbonic anhydride, ammonia, amines of fatty acid radicles,
hydrocarbons and amines of the benzene series, aniline and its
homologues, phenol and its homologues, members of the pyridine
group of bases, namely, pyridine (C6Hf)N5), picoline (CCH7N), lutidine
(C7H9N), and collidine (C8HUN), and lastly, pyrrol.

Some of the substances last mentioned will also be found in our list of the
animal alkaloids (p. 59) ; here we have direct proof that proteid substances
have within them, or are capable of forming by intramolecular rearrangement,
basic bodies of this nature. The pyridine bases have, moreover, been shown
to take a part in the formation of the vegetable alkaloids, piperidine,
cinchonine, etc.

It is extremely probable that proteids contain within their molecule
a radicle of the closed ring series, but even if they do not, there still
remains the possibility that by the action of heat, substances with
open carbon chains may be transformed into those with closed rings.
The following example is selected by Brodie 4 :—

1 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 153.

2 Baumann, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xii. S. 1453.

3 Hlasiwetz and Habermann, Ann. d. Chem., Leipzig, 1871, Bd. clix. S. 304. Blennard,
Compt. rend. Acad. d. sc., Paris, tome xc. p. 612; xcii. p. 458. This latter observer also
obtained glnco-proteins.

4 Loc. cit.

THE ATTEMPTED SYNTHESIS OF PROTEIDS.

At 190° dry glutaminic acid is converted into pyroglutaminic
and at a higher temperature this, in turn, is converted into pyrrol.1

35
acid,

COOH

COOH

. CH:CH

CH2 CH.NH,

(

/
}II2— CH

yNH

/

ptr POOTT

^)NH

/
CH:CH

(glutaminic acid)

(

)Ho— CO

(pyrrol)

(pyroglutaminic acid)

The attempted synthesis of proteids. — Since Wohler in 1828
succeeded in making urea artificially from its elements, the strides
that organic chemistry has made have been prodigious. Complex
substances, previously made only in the living laboratory of plants
and animals, are now manufactured daily in the test tubes and retorts
of the chemist. The substances of most importance to vital processes,
the carbohydrates and the proteids, have been among the last to yield
before this advance, but we have seen how sugar has given way to
Fischer ; and there are signs that the last conquest of organic chemistry,
the synthesis of proteids, cannot be far distant. I propose to sketch one
or two of the principal attempts that have been made in the manu-
facture of albuminous from simpler substances.

Scliutzenbergers experiments. — We have already seen that the pro-
ducts of decomposition of a proteid are extremely numerous, but briefly
they fall into two principal groups, the fatty compounds (generally con-
taining an amidogen radicle) and the aromatic compounds or derivatives
of benzene. To Schiitzenberger 2 belongs the credit of an attempt to
build up from some of the compounds he had shown could be obtained
from albumin, something like the original proteid.

In order to effect the synthesis of proteid material, he considered it
necessary to combine a molecule of a leucine (i.e. an amido-fatty acid)
with a molecule of a leuceine (an amido-acid of the acrylic series), with
elimination of water, and then to combine this complex group with one
or more molecules of urea and oxamide, also with the elimination of
water. We have already seen that the method he had adopted for the
breaking up of proteids — heating with alkali — leads to hydrolysis ; so in
any attempt at synthesis he recognised as a sine qua non the necessity
of some method of dehydration.

The provisional formula he gives is the following : —

H2C204+2 NH3+3CmH2m+1N02+3 CnH2n_1N02
with elimination of eight molecules of water. This would give

the percentage composition calculated from the formula agrees closely
with that of albumin.

1 Bernhoimer, JBer. d. deutscli. chcm. Gesellsch., Berlin, Bd. xv. S. 1222.

2 Compt. rend. Acad. d. sc., Paris, tome cvi. p. 1407 ; cxii. p. 198.

36 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Accordingly, amido-compounds, leucines (CmH2m+1NO.,), and leuceines
(CnH2n_iNOo), were mixed with about 10 per cent, of urea, and finely
powdered. The mixture was dried at 110° C., intimately mixed with 1/5
times its weight of phosphoric anhydride, and heated in an oil bath. At
120° C. there is no change; at 125° dehydration takes place rapidly, and
the mixture becomes pasty, but solidifies to a compact solid mass without any
darkening. This is dissolved in water, the solution mixed with excess of
alcohol, and the pasty precipitate so produced washed with alcohol and
re-dissolved in water. Phosphoric acid is removed by baryta, and the filtered
liquid when concentrated yields an amorphous product soluble in water, but
precipitated in a curdy form on the addition of alcohol.

Aqueous solutions of this product are precipitable by most of the other preci-
pitants of proteids ; it gives the biuret and the xanthoproteic reactions. When
burnt it gives the characteristic odour oi burning nitrogenous animal matter.

The product he obtained does not give all the proteid reactions ;
it is, for instance, not precipitable by acetic acid and ferrocyanide of
potassium ; and the evidence as to its proteid nature is otherwise hardly
conclusive, because the colour tests for proteids are given by many of
the decomposition products of albuminous matter. The partial success
obtained will, however, point the way for future attempts, and so far
as it goes, is in favour of Schiitzenberger's ureide theory of proteid
constitution. Complete success could hardly have been anticipated
from such an experiment, because no means were taken to ensure the
presence of sulphur, an element present in all proteids. Moreover,
in the synthesis, no aromatic substance was introduced; this, how-
ever, is not absolutely necessary, as the formation of aromatic from
fatty compounds by heat is a familiar chemical change (see p. 34).

Grrimaux's experiments. — Some years previous to Schiitzenberger's
work, Grimaux l had obtained, by somewhat simpler processes, substances
which even more resembled proteids in their reactions than Schiitzen-
berger's. He was engaged in studying the properties of certain sub-
stances, inorganic and organic, which he termed " colloides" and of those
which he prepared the three which especially bear on the present
question are the following : —

(a) Colloide amidobenzoique. — This is made by heating, to 125° C.,
meta-arnidobenzoic acid in a sealed tube, with one and a half times its
weight of phosphorus pentachloricle, for ninety minutes. The product is
a white friable powder ; this is washed repeatedly with boiling water to
remove all phosphoric acid. The remaining substance Grimaux supposes
to be an intramolecular anhydride, formed by the union of several mole-
cules of meta-amidobenzoic acid, with the elimination of water. When
ammonia is added, it dissolves slowly in the cold, but rapidly on heating.
The solution obtained is evaporated in vacuo, at a low temperature, and
the resulting solid is a transparent jelly which dries into translucent,
yellowish plates, which in their physical properties resemble dried
serum albumin.

(&) A colloid which is similarly prepared, except that the temperature
in the sealed tube is allowed to rise to 135C 0.

(c) Colloide aspartique. — This is made by the action of a current of
gaseous ammonia on solid aspartic anhydride, heated to 170° C. The

1 Compt. rend. Acad. d. sc., Paris, tome xciii. p. 771 ; xcvii. pp. 231, 1336, 1434, 1485,
1540, 1578 ; Rev. sclent., Paris, April 18, 1886 ; this article gives a summary of the other
papers.

THE ATTEMPTED SYNTHESIS OF PROTEIDS. 37

product is washed with water, and after evaporation in vacuo yields a
substance similar in appearance to the colloid (a).

In all three cases, heavy molecules were formed ; and in all, the
result was a colloidal substance, exhibiting many of the properties of
proteids. In the case of the first two colloids, there was present not
only the amidogen, but also the aromatic radicle. Although the result
is not albumin, the resemblance between the physical properties and
chemical reactions of proteids and of these synthesised colloids is
remarkably close. Pickering l has fully confirmed Grimaux's results, and
has added new facts illustrating the points of similarity between them
and proteids.

The chief of these are as follows : —

1. All give the xanthoproteic reaction.

2. With copper sulphate and caustic potash, a gives a blue-violet ;
b, nil ; c, a typical violet coloration, like that given by albumin.

3. Their solutions do not coagulate on heating in the absence of salt ;
if, however, a trace of a soluble barium, strontium, or calcium salt is
present, opalescence occurs at 56°, and coagulation at 75° C.

4. The colloids are removed from solution (rising to the surface of
the fluid) by saturation with magnesium sulphate, sodium chloride or
ammonium sulphate. Here they especially resemble the class of
proteids called globulins.

5. Another resemblance to globulins is seen in their behaviour to a
stream of carbonic anhydride, which, in the presence of salts, causes
precipitation. The passage of a current of air through the mixture
redissolves the precipitate.

6. The colloid 1) is not digested by pepsin-hydrochloric acid ; a is
slightly digested ; c is easily digested, and the solution gives the typical
peptone colour, pink, on the addition of copper sulphate and caustic
potash.

7. Any one of the three colloids, when intravenously injected into
animals (rabbits, cats, dogs, rats, guinea-pigs) causes extensive intra-
vascular coagulation. In a typical experiment death is due to respiratory
failure. In this property of the proteid-like colloids, which was dis-
covered by Pickering, they closely resemble the nucleo-proteids (see
p. 67). The resemblance to the action of the nucleo-proteids extends
even to minor points ; for instance, neither cause intra vascular clotting
in albino rabbits ; "2 and in dogs very minute doses indeed, cause a slowing
of the rate of coagulation (Wooldridge's negative phase).

The artificial colloids do not resemble nucleo-proteids in promoting
the formation of fibrin in solutions of fibrinogen.

If nucleo-proteids and these colloids both produce the same effect in
the same way, their physiological activity is probably connected with
the presence of some radicle common to both. The colloidal condi-
tion will not explain the action, since most colloids do not act thus.

1 Pickering, J. W., Journ. PhysioL, Cambridge and London, vol. xiv. p. 347 ; xviii.
p. 54 ; Pickering and Halliburton, ibid., vol. xviii. p. 285. More recently Pickering has
succeeded in making several new proteid-like colloids (Proc. Roy. Soc. London, 1896,
vol. Ix. p. 337).

2 This point has been worked out by Pickering also in the case of the Arctic hare.
During the albino stage of the animal, neither nucleo-proteids nor synthesised colloids cause
intravascular coagulation, but during their pigmented stage intravascular coagulation is
produced in the usual way. The change in the external appearance of the animal is thus
associated with other changes in its constitution (Journ. PhysioL, Cambridge and London,
1896, vol. xx. p. 310).

3$ CHEMICAL CONSTITUENTS OF BOD Y AND FOOD.

The active radicle cannot be one which contains phosphorus, since the
synthesized colloids are free from that element. It may possibly be the
amido-fatty radicle in a high state of condensation.

Lilienfeld and Wolkowicz,1 by the condensation of amido-acid compounds,
have obtained substances which resemble proteoses in their reactions.

Theories of proteid constitution — The views of Schiitzenberger
on this subject will have been gathered from the preceding section.
There now remain to be mentioned some other theories on the subject,
which are in part deductions from the work of others, and partake
more of the nature of speculation than of hypotheses that have been
tested by experiment.

Pflugers theory. — The distinction between non-living proteids and
living protoplasm was noted as early as 1821 by Kudolphi,2 who
wrote : " The components of the dead and living body do not exist under
the same chemical conditions." A few years later the distinction
between living and non-living proteids was emphasised by John
Fletcher.3 PHiiger's theory 4 was, however, the first intelligible one to
explain such differences. The non-living proteids, such as are contained
in white of egg, are stable and indifferent to neutral oxygen ; but when
such proteids are assimilated — that is, become part of a living cell — the
molecules live by breathing oxygen. The assimilation of a proteid is
probably due to the formation of ether-like combinations between
the molecules of living proteid and the isomeric molecules of the food
proteid, water being eliminated ; this process of polymerisation produces
large and heavy but still simple molecules ; and during its occurrence
the nitrogen of the non-living proteid leaves the hydrogen with which it
is combined in the form of amidogen (NH2), and enters into combination
with carbon to form the much more unstable substance cyanogen (CN).
We thus find uric acid, creatine, guanine, etc., as products of proteid
metabolism, while none *of such cyanogen-containing molecules are
obtainable from non-living proteid.

Pfliiger's theory was put forward in 1876; but in the light of .Drechsel's
later work, the part involving exchange of nitrogen between cyanogen and
amidogen is rendered unlikely, and with that the whole theory must probably fall.

Loews theory. — The researches of Loew and Bokorny 5 have taken
the same direction as those of Pfliiger, in that they are attempts to
explain the distinction between living and dead protoplasm. Living
protoplasm or proteid (in the cells of various alg?e) has the property of
reducing silver from a weak alkaline solution of silver nitrate ; dead
proteid has no such effect; animal protoplasm is so quickly killed by
silver nitrate, that it does not give the reaction. The conclusion
formed is, that something of the nature of an aldehyde occurs in living
protoplasm. Formic aldehyde is probably formed in plants by the union
of carbon and water ; if this is united to ammonia, aspartic aldehyde is
formed, thus : —

1 Arch.f. Anat. u. Physiol., Leipzig, 1894, Physiol. Abth. S. 383 and 555.

2 " Grundriss der Physiologic," 1821.

3 "''Rudiments of Physiology," Edinburgh, 1837.

4 Arch.f. d. ges. FhysioL, Bonn, Bd. x. S. 251.

5 " Die chem. Kraftquelle im lebenden Protoplasma," Munich, 1882. Loew's most
recent views on this subject will be found in a recently published pamphlet, " The Energy
of Living Protoplasm," London, 1896.

GENERAL PROPERTIES AND REACTIONS OF PROTEIDS. 39
4CHOH+NH3 = NH2.CH.COH+2H20

CH2.COH

By polymerisation of aspartic aldehyde we have —

fNH2.CH.COH]

M | \ = C12H17N304+2H,0

[ CH2COHJ

and by further polymerisation in the presence of a sulphur compound
and hydrogen we get

6C12H17N304+H2S+6H2 = C72H112N18S022+2H20

which represents the composition of ordinary albumin. If such an
aldehyde does exist in " living proteid " its instability is explicable,
because molecular movements would be constantly occurring in the
aldehyde group.

The theory is ingenious, but an obvious objection to it is that it assumes
the empirical formula above given for albumin to be the correct one. The
theory has been adversely criticised by Baumann 1 who points out that alde-
hydes are not the only substances that reduce alkaline solutions of silver
nitrate, but that many organic substances, such as pyrogallol, resorcin, hydro-
chinon, pyrocatechuic acid, alloxan, and morphine do so also. It is stated,
moreover, by Kretzschmar 2 and Griffiths,3 that both living and dead proto-
plasm give the reaction.

Lathams theory* — This is to some extent a combination of the two
just described. Latham considers living proteid to be composed to a
chain of cyanalcohols or cyanhydrins, as they are often called, united to
a benzene nucleus.

A cyanalcohol is a substance obtained by the union of an aldehyde
with hydrocyanic acid ; for instance —

CH3.COH+HCN=CH3.CH(CN)OH

(ethaldehyde) (hydro- (cyanethylic alcohol)
cyanic acid)

Other alcohols are formed from other aldehydes, and these are all
united to one another and to benzene to form a proteid.

Latham shows that the various products of the disintegration of
albumin can also be obtained by the condensation and intramolecular
changes that these cyanalcohols, which are exceedingly unstable
substances, undergo. Instability and proneness to undergo intra-
molecular changes are two properties common to " living proteids " and
to cyanalcohols.

General properties and reactions of proteids. — Solubilities.—
All proteids are insoluble in alcohol and ether. Some are soluble in
water, others insoluble. Many of the latter are soluble in weak saline
solutions. Some are insoluble, others soluble in concentrated saline
solutions. It is on these varying solubilities that proteids are classified.

All proteids are soluble with the aid of heat in concentrated mineral
acids, in glacial acetic acid, and in caustic alkalis. Such treatment, how-

1 Arch.f. d. ges. Physiol, Bonn, 3882, Bd. xxix. S. 400.

2 Centralbl.f. agric. C/icm., Leipzig, 1882, p. 830.

3 Chem. News, London, vol. xlviii. p. 179.

4 Brit. Med. Journ., London, 1886, vol. i. p. 629; Lancet, London, 1888, vol. ii. p. 751.

40 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

ever, decomposes as well as dissolves the proteid. Proteids are also soluble
in gastric and pancreatic juices, but here again they undergo a change,
being converted into the hydrated varieties of proteid known as proteoses
and peptones. Solutions of the proteids are precipitated by a large
number of reagents, but the proteoses and peptones furnish many ex-
ceptions to this statement.

The principal precipitants of proteids are : —

1. Strong mineral acids, especially nitric, metaphosphoric, and
phosphotungstic acids.

2. Acetic acid with potassium ferrocyanide.

3. Acetic or oxalic acid, with excess of certain neutral salts, such
as sodium sulphate, sodium chloride, or magnesium sulphate.

4. Salts of the heavy metals ; bf^ic lead acetate, mercuric chloride,
silver nitrate, copper sulphate, ferric chloride or acetate, potassio-
mercuric iodide, sodium tungstate, etc. The precipitates consist of
the proteid in combination with variable amounts of the metal, in
the form of albuminates. On the removal of the metal by a stream
of sulphuretted hydrogen, the proteid is recoverable in an unchanged
form.

5. Tannin ; or tannin and sodium chloride together.

6. Saturation with ammonium sulphate or sodiomagnesium sulphate,
or potassium acetate or carbonate. These precipitates are soluble on
diluting the solution of salt in which they are suspended.

7. Picric acid.

8. Salicylsulphonic acid.

9. Trichloracetic acid.

10. Alcohol, except in the presence of free alkali, when the proteids
are slightly soluble in hot alcohol.

The precipitate given by the proteoses is in many cases (as with
nitric, trichloracetic, and salicylsulphonic acid, or with acetic acid and
potassium ferrocyanide) soluble on heating, but re-appears when the
solution cools. The greater number of the reagents mentioned do
not precipitate peptone. It is precipitated completely by alcohol,
tannin, and potassio-mercuric iodide, and incompletely by phospho-
tungstic and phosphomolybdic acids.

The following are the methods used to remove all proteid from a
solution : —

1. Br Here's method1 consists in the alternate addition of hydrochloric acid
and potassio-mercuric iodide.

2. Gii'gensohn's method 2 consists in the addition of sodium chloride and
tannin.

3. Devoto's method? — This consists in boiling an acidulated solution
of the proteid with excess of ammonium sulphate crystals ; all proteids are
precipitated by this means except peptone. Proteoses, if present, are
precipitated but not coagulated, and can be extracted from the precipitate
by water.

4. By trichloracetic acid. — This method consists in adding to the solution an
equal volume of a 10 per cent, solution of trichloracetic acid, boiling and filtering
hot. The filtrate contains the proteoses and peptone, if these are present, and
the precipitate contains the other proteids. This is by far the most rapid and

1 Sitzungsb. d. k. AJcad. d. Wissenscli., Wien, 1871.

2 N. Repert.f. Pharm., Miinchen, Bd. xxii. S. 557.

3 Zttchr. f. physiol. Chcm., Strassburg, Bd. xv.

GENERAL PROPERTIES AND REACTIONS OF PROTEIDS. 41

simple method of separating the two classes of proteids.1 If boiling is omitted,
the proteoses are in part precipitated also (C. J. Martin).

5. The alcohol method. — -The solution is rendered faintly acid with acetic acid,
and several times its volume of absolute alcohol are added. After twenty-four
hours it is boiled and filtered ; the filtrate is proteid-free.2 The action of alcohol
on proteids is peculiar ; it precipitates proteids in the cold ; and the precipitate,
if washed free from alcohol, is found to be readily soluble in suitable reagents
such as saline solution. But if the precipitate is left in contact with the alcohol
for days or weeks, the solubility of the precipitate is lost ; the precipitate has
been converted into a coagulum. This loss of solubility, however, does not
occur with proteoses and peptone, and thus this is another very good though
tedious method of separating native proteids from products of proteolysis.3

6. Salicylsulphonic-acid method. — This is recommended by Me William.4
The reagent precipitates albumins and globulins ; on heating, the precipitate is
coagulated. The same reagent precipitates proteoses ; on heating, the precipitate
dissolves, and re-appears on cooling. The reagent does not precipitate
peptones.

7. By boiiinij. — In some cases the proteids are precipitated or more properly
coagulated by boiling after faintly acidulating the solution. This is the case
with the albumins and globulins, and with the proteids which are usually
found in morbid urines. For the separation of native proteids from proteoses
and peptones, the method is not to be recommended, because boiling with even
dilute acids leads to the formation of small quantities of these products of
proteolysis. The use of this method has thus produced many mistakes ; it led
Struve, Schmidt-Miilheim, and others, to the conclusion that a peptone-like
substance exists in milk and in blood ; and more recently Chabrie,5 by the use of
the same method, has described a new proteose-like constituent of blood
serum, to which he has given the name "albumone." Chabrie's mistake has
been amply demonstrated by R. Brunner.6 It should be added that Devoto's
method is not wholly free from the same objection.7

For quantitative purposes the precipitate produced by these several
methods may be collected, washed, dried, and weighed, then incinerated,
and the ash deducted. Other methods that have been devised are
densimetric methods, in which, after removal of the proteid, the loss of
specific gravity is multiplied by a constant factor,8 and methods in which,
by Kjeldahl's process, a nitrogen estimation is made in the precipitate
produced by some precipitant. Sebelien9 recommends tannin for this
purpose.

Precipitation l>y neutral salts (German, Aussalzung). — There are a
number of organic substances which can be precipitated from their

1 Obermayer, Med. Jahrb., Wien, 1888, S. 375—381 ; Starling, Journ. PhysioL,
Cambridge and London, vol. xiv. p. 131 ; C. J. Martin, ibid., vol. xv. p. 375 ; Halliburton
and Brodie, ibid., vol. xvii. p. 169 ; Halliburton and Colls, Journ. Path, and Bacterial.,
Edin. and London, 1895, vol. iii. p. 295.

2 Hoppe-Seyler, "Handbuch," S. 312 ; Schmidt, Arch. f. d. ges. PhysioL, Bonn, Bd.
xi. S. 10 ; Hoffman, Virchows Archiv, 1879, November, S. 255.

3 S. Martin, Goulstonian Lectures, Brit. Med. Journ., London, 1892, vol. i. ; Gourlay,
Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 32.

4 Brit. Med. Journ., London, 1891, vol. i. p. 837 ; 1892, i. p. 115. The reaction was
previously described by Roch, Pharm. Centr.-BL, Leipzig, 1889, S. 549.

5 Coii^t. rend. Acad. d. sc., Paris, tome cxiii. p. 557.

6 Inaug. Diss., Bern, 1894.

7 M. Matthes, Berl. klin. Wchnschr., Bd. xxxi. S. 351 ; Halliburton and Colls,
loc. cit.

8 Bornhardt, Ztschr. f. anal. C/iem. , Wiesbaden, 1870, S. 149 ; 1877, S. 124 : Huppert
and Zahor, Ztschr. f. physiol. Chcm., Strassburg, Bd. xii. S. 467, 484.

9 Ibid., Bd. xiii. S. 135 ; Konig and Kisch, Ztschr. /. anal. Chem., Wiesbaden, Bd.
xxvii. S. 191.

42 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

aqueous solutions, by the addition of certain neutral salts in large
quantities ; in some cases complete saturation is necessary. In some in-
stances, as in the precipitation of urates by ammonium chloride,1 or
ammonium sulphate,2 the formation of an insoluble compound with the
base of the salt used will explain the phenomenon. In other cases,
especially in the case of colloidal substances, the water-attracting power
of the salt is more probably the explanation.3 The solutions used
should not be too concentrated, or the thick precipitate obtained is
difficult of filtration.

The phenomenon is not confined to substances of a colloidal nature ;
thus, picric acid is precipitable by this means ; so are soaps, especially
potassium soaps by sodium chloride. But it is in connection with non-
diffusible substances,4 and especially with proteids, that the method is
most used.

Proteids differ from one another a good deal in the readiness by
which they are precipitated in this way. Ammonium sulphate added to
saturation, precipitates all proteids except peptones 5 and certain forms
of deuteroalbumose.6 Half saturation with the same salt is sufficient to
precipitate globulins,7 acid and alkali albumin and caseinogen. Speaking
generally, the globulins and nucleo-proteids are more readily precipitable
by neutral salts than the albumins. Thus, globulins are precipitated by
magnesium sulphate and sodium chloride, whereas albumins are not, and
some globulins, like fibrinogen, are precipitated by half-saturation with
sodium chloride. If the operations are carried out at the temperature
of the air, the precipitated proteids are not coagulated, but are
soluble in suitable liquids ; and they then again show their characteristic
properties.8

Heat coagulation. — The albumins, globulins, and some nucleo-proteids
are coagulated at different temperatures, by heating their solutions.
The temperature varies with the reaction of the solution,9 the quantity
and nature of the salts present10 (minute quantities of calcium salts
favour heat coagulation as they do ferment coagulation),11 and
under certain circumstances, especially in an alkaline solution, with its
concentration.12

1 F. G. Hopkins, Journ. Path, and Bacterial., Edinburgh and London, 1893, vol. i. p.
451.

2 A. Edmunds, Journ. Physiol., Cambridge and London, 1894-5, vol. xvii. p. 451.

3 0. Nasse, Arch. f. d. ges. Physiol., Bonn, Bd. xli. S. 504; F. Hofmeister and S.
Lewith, Arch. f. exper. Path. u. PharmaJcoL, Leipzig, 1888, Bd. xx. S. 247; xxv.
S. 1.

4 On the precipitation of colloid carbohydrates by salts, see Pohl, Ztschr. f. physiol.
C/iem., Strassburg, Bd. xiv. S. 151 ; R. A. Young, "Proc. Physiol. Soc.," 1896-97, p. xvi. in
Journ. Physiol., Cambridge and London, 1897, vol. xxi.

5 Wenz, Ztschr.f. BioL, Miinchen, Bd. xxii. S. 1.

6 Kiihne, ibid., Bd. xxiv. S. 1 and 308 ; Chittenden, Journ. Physiol., Cambridge and
London, vol. xvii. p. 48.

7 Kauder, Arch. f. cxper. Path. u. PharmaJcoL, Leipzig, Bd. xx. S. 411.

8 On the precipitation of proteids by numerous salts, see Denis, " Memoire sur le
sang," p. 39 ; Schafer, Journ. Physiol., Cambridge and London, vol. iii. p. 181 ;
Halliburton, ibid., vol. v. p. 177; vii. p. 321; Hammarsten, Arch. f. d. ges. Physiol.,
Bonn, 1878, Bd. xvii. S. 424.

9 Traces of acid lower, of alkali raise, the temperature of coagulation ; more than
traces convert the proteid into acid or alkali-albumin respectively, and these substances do
not coagulate by heat.— Halliburton, Journ. Physiol., Cambridge and London, vol.
v. p. 165.

10 Limbourg, Ztscbr. f. physiol. Chem., Strassburg, Bd. xiii. S. 450.

11 Ringer and Sainsbury, Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 170.

12 Haycraft, Brit. Med. Journ., London, 1890, vol. i. p. 167.

GENERAL PROPERTIES AND RE A CTIONS OF PROTEIDS. 43

The temperature of heat coagulation of some of the principal proteids
may be approximately stated as follows : —

ALBUMINS.

Egg albumin . . . 73° C.

Serum albumin (a) . . 73 c

(0) . .

. (y) • •

Muscle albumin . . 73C

Lact-albumin . 77C

• • 84

GLOBULINS.

Cell globulin . . 48°-50° C.

Fibrinogen . . . 56° ,,

Serum globulin . . 75° „

Myosinogen . . . 56° „

Vitellin . . . . 75° „

Crystallin ... 73° „

Hsemocyanin . . . 68° „

With regard to the separation of proteids by the use of the method
of fractional heat-coagulation, the opinion has been expressed by Hay craft
that the results obtained are not trustworthy. It is probable, nevertheless,
that the method is trustworthy, since the proteids so separated can be shown
to possess other differences.1

Mechanical precipitation of proteids. — By mechanical means, such as
shaking with sand, or even pouring from one test tube to another, a solution
of egg-white deposits threads of insoluble proteid, reminding one of fibrin
filaments, which also they resemble in their difficulty of solubility. By
prolonged shaking, 96 per cent, of the proteid present may be
deposited. Other proteids behave similarly, but as a rule less markedly,
namely, egg globulin, vitellin, the proteids of blood plasma, myosinogen,
potato proteid, plant vitellin, alkali albumin, and some specimens of
caseinogen (Eamsden).2

Indiffusibility. — The proteids belong to the class of substances called
colloids by Thomas Graham; that is, they pass with difficulty or not
at all through animal membranes, or vegetable parchment, the substance
usually employed in the construction of dialysers. Proteids may thus be
separated from diffusible (crystalloid) substances, like sugar and salts.
If a mixture of albumin and globulin, dissolved in a saline medium as
in blood serum, is placed in a dialyser, with distilled water outside, the
salts and extractives pass through the membrane into the water, and
water passes in ; the proteids remain within ; the albumin in solution, but
the globulin, which is insoluble in water containing no salts, precipitated.

The term colloid does not necessarily imply that the indiffusible
substances are not capable of crystallisation; for many of the pro-
teids have now been crystallised; this is particularly the case with
the vegetable proteids (p. 52), with haemoglobin (p. 61), with egg
albumin, and with serum albumin. F. Hofmeister3 was the first to
crystallise egg albumin ; a solution of egg white is mixed with an equal
volume of saturated solution of ammonium sulphate, and the globulin so

1 The following are the principal papers on this question : — Halliburton on "Proteids
of Serum," Journ. Physiol., Cambridge and London, vol. v. p. 159; xi. 456; Corin and
Berard, "Egg White," Bull. Acad. roy. dc nUd. de Belg., Brnxelles, 1888, tome xv. p. 4 ;
Colin and Ansiaux, ibid., 1891, tome xxi. p. 3 ; Haycraft and Duggan, Brit. Mcd. Journ.,
London, 1890, vol. i. p. 167 ; Proc. Roy. Soc. Edin., 1889, p. 351 ; Centralbl.f. Physiol.,
Leipzig, Bd. iv. S. 1 ; Fredericq, ibid., Bd. iii. S. 601 ; Chittenden and Osborne on "Corn-
Proteids," Am. Chem. Journ., Baltimore, vol. xiii. pp. 7 and 8 ; xiv. p. 1 ; Hewlett,
Journ. Physiol. , Cambridge and London, 1892, vol. xiii. p. 512 ; Ramsden, Proc. Physiol.
Soc., London, 1892, p. 23; A. di Frassineto, Sperimentale, Firenze, 1895, tome xlix. All
the above except Haycraft and Ramsden defend the method.

2 Arch. f. Physiol., Leipzig, 1894, S. 517.

3 Ztschr. f. physiol. Chem., Strassburg, Bd. xiv. S. 165; 1892, xvi. S. 187; see also
Gabriel, ibid., 1891, Bd. xv. S. 456.

44 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

precipitated is filtered off. The filtrate is allowed to stand at the
temperature of the air, and as it gets concentrated minute spheroidal
globules of varying size, and finally minute needles, either aggregated or
separate, make their appearance (Fig. 9). On examining these crystals,
they are found to consist of egg albumin, with a variable (but usually
small) admixture of ammonium sulphate. Serum albumin has similarly
been obtained by G-iirber and Michel,1 in a crystalline form, from the
blood serum of horses and rabbits. More recently still, caseinogen has
been crystallised. When a solution of this substance is mixed with

FIG 9.— Crystals of egg albumin.

ammoniacal magnesia mixture, it proceeds after some days to deposit
sphreroliths, and ultimately aggregations of needle-like crystals. They
contain 45 per cent, of ash, and 14'98 per cent, of nitrogen. Nuclein
also yields a crystalline deposit with ammoniacal magnesia mixture
(v. Moraczewski).2

Byrom Bramwell and Noel Paton 3 have described a case of albuni-

1 Sitzungsb. d. phys.-med. GeseUsch. zu Wurzburg, 1894. Michel (ibid., No. 3, B<K
xxix.; Centralbl.f. d.' med. Wissensch., Berlin, 1896, S. 152) gives full details of the method
employed. The crystals are hexagonal prisms with the following percentage composi-
tion :— C, 53-1 ; H. 7-1 ; N, 15'9 ; S, 1'9 ; 0, 22'0 ; ash, only 0'22. They coagulate at
51° -53° C. («)D= -61°.

2 Ztsclir. f. physiol. Chem., Strasshurg, Bd. xxi. S. 71.

3 Hep. Lab. Roy. Coll. Phys., Edinburgh, 1892, vol. iv. p. 47.

GENERAL PROPERTIES AND REACTIONS OF PROTEIDS, 45

inuria, in which the urine on standing deposited the proteid matter jri a
crystalline form (see Fig. 10). They considered it to be of the nature of
a globulin. Huppert l has questioned this conclusion, and thinks it pro-
bable that the proteid was heteroalbumose.

It is not, therefore, upon the non-crystalline character of proteid, but
upon the enormous size of the proteid molecules, whether crystalline
or non-crystalline, that the difficulty of diffusion depends. It thus
becomes interesting to inquire into the diffusibility of the proteids of
lower molecular weight, namely, the proteoses and peptones. Peptones
are diffusible ; this has long been known ; they are highly diffusible
compared to albumin, but of low diffusibility as compared with salt.

FIG. 10.— Proteid crystals from human urine.— After Byrom Bramwell and Noel Paton.

The diffusibility of the proteoses has long been inferred, but it is only
quite recently that it has been accurately made out that they are inter-
mediate in this character between peptones and albumins. The work
in this direction was done independently by Kuhne 2 and Chittenden,3
and both arrived at the same results. A curious fact found was, that
deuteroproteose (generally regarded as intermediate between the other
proteoses and peptones) is less diffusible than protoproteose. But this

1 Ztschr.f. physioL Chcm., Strassbnrg, 1896, Bd. xxii. S. 500.

2 Ztschr.f. Biol., Miinchen, Bd. xxix. S. 1.

3 Journ.'Physiol., Cambridge and London, vol. xiv. p. 483.

46 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

is quite in accordance with Sabanejeff's l cryoscopic determination of the
molecular weights of these substances ; he gives the molecular weight
of protoproteose as 2467 to 2640, of deuteroproteose as 3200, and of
peptone as 400 or less. The diffusion power of the different sub-
stances investigated by Kulme was as follows : — Heteroproteose is
the least diffusible of the proteoses; in neutral saline solutions it is
precipitated as the salt passes out, and none goes through the dialyser ;
dissolved in ammonia it loses 5 -2 2 per cent. Deuteroproteose comes
next (loss, 241 per cent.) ; then protoproteose (loss, 28*3 per cent.) ;
while peptone loses 51 to 51 '8 per cent. Each experiment lasted
twenty -four hours.

Action on polarised light. — All the proteids are levorotatory. The
specific rotatory power of some of jthe principal members of the group
is as follows : —

Proteids.

Observer.

Value of (a)p.

( Hoppe-Seyler 2

104-1 3

-56°

( Starke J
! Hoppe-Seyler

- 68°
-35° -5

Lact-albumin ......
Serum globulin

Haas4, Starke
Sebelien 5
Haas
Herrman 6

-38° '08
-36c-37°
-59° -75
-43°

Haas

- 6 2° -2

Syntonin (prepared from myosin) .
Casein (dissolved in MgS04 solution) .

Hoppe-Seyler
Hoppe-Seyler
Kiihne and Chittenden7

-72°
-80°
- 70°-80°

Colour reactions. — These are numerous, and doubtless depend for their
occurrence on the various radicles which, as we have seen, are probably
present in the proteid molecules. Many of them are given by certain of
the decomposition products of the proteids ; and by a careful comparison
of these simpler substances, conclusions have been reached concerning the
particular groups in the proteid molecule to which each reaction is due.

The majority of the colour tests are due to the presence of the
aromatic radicle ; it will, therefore, be well to preface the description of
the reactions themselves by a classification of the aromatic substances
derived from proteids by putrefaction. Salkowski 8 arranges them into
three groups ; whether all these groups exist pre-f ormed in the proteid
molecule, or are derived, as Maly considered, from only one aromatic
group, matters but little in the question under investigation. The
groups are as follows :—

First group — The phenol group. — This includes tyrosine, the aromatic
hydroxy acids, phenol, and cresol.

Second group — The phenyl group. — This includes phenylacetic and
phenylpropionic acids.

1 Ber. d. deutsdi. chem. Gesellsch., Berlin, Bd. xxvi. S. 385.

2 Ztschr.f. Chem., Leipzig, 1864, S. 737.

3 Jahresb. ii. d. Fortschr. d. Thier-Clicm., Wiesbaden, Bd. xi. S. 17.

4 Arch. f. d. ges. PhysioL, Bonn, Bd. xii. S. 378; Chem. Centr.-BL, Leipzig, 1876,
S. 295, 811, 824.

5 Jahrcsl. it. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xv. S. 184.

6 Ztschr.f. physiol. Chem., Strassburg, Bd. xi. S. 508.

7 Ztschr.f. Biol, Miinchen, Bd. xx. S. 51.

8 Ztschr.f. physiol. Chem., Strassburg, Bd. xii. S. 215.

GENERAL PROPERTIES AND REACTIONS OF PROTEIDS. 47

Third group — The indol group, of which indol, skatol, and skatol-
carbonic acid are the most important members.

We can now proceed to the consideration of the proteid colour
reactions.

1. The xanthoprotcic reaction. — This is characterised by the yellow
colour given by boiling with nitric acid, turned orange by ammonia.
0. Loew x considered that the yellow material was a mixture of oxynitro-,
trinitro-, and hexanitro-albumin ; but these substances are very doubtful
as chemical individuals. Salkowski found the reaction to be given by all
the members of his first and third groups of aromatic substances.
Pickering2 found that salicylic acid, and salicylsulphonic acid, cholesterin,
cholalic acid, and taurocholic acid also give the test. A large number
of other organic substances which were tested did not give the same
result. It was noticed that bodies with a benzene nucleus with one
hydrogen replaced by hydroxyl, give the xanthoproteic reaction, whereas
substances which contain a benzene nucleus without the hydroxyl, as
phenylacetic and benzoic acids, do not.

Millon's reaction. — A brick-red coloration occurs when proteid matter
is boiled with Millon's reagent (a mixture of the nitrates of mercury
with excess of nitric acid) ; the reaction was thought by Kiihne 3 to
be due to tyrosine. Salkowski also took this view, as the reaction is
given by the substances in his first group, the most prominent member
of which is tyrosine. Those in the second and third groups do not give
the test. Nasse,4 however, demonstrated that Millon's reaction is due
to benzene derivatives, in which one hydrogen atom has been replaced
by hydroxyl (hydroxybenzene nucleus) and not to tyrosine. That
Nasse's view is correct is shown by the following considerations : —
Kiihne and Chittenden 5 have found that certain anti-products of diges-
tion, which yield neither leucine nor tyrosine on further digestion, or on
decomposition with sulphuric acid, do not give the reaction. Schiitzen-
berger 6 found that tyrosine is absent from the putrefaction products of
gelatin. Now, Salkowski stated that gelatin does not react with Millon's
reagent. But Chittenden and Solley7 have found that the products of
gelatin digestion give a characteristic reaction, and Pickering that pure
gelatin and gelatinoses give it in a marked manner ; thus confirming the
statement made by Millon 8 in his original memoir. Gelatin, therefore,
owes this property to something which is not tyrosine, but which, like
tyrosine, contains a hydroxybenzene nucleus.

Adamkiewicz reaction? — If glacial acetic acid in excess and then
concentrated sulphuric acid are added to proteid, a violet colour with
feeble fluorescence is produced. The test is by no means a oertain one,
and is given by proteoses and peptones in concentrated solutions only.
It is not given by gelatin (Hammarsten).

This test is only given by the aromatic substances of Salkowski's
third (indol) group. The strong reagents added are likely to produce

1 Journ. f. pralct. Chem., Leipzig, N.F., Bd. iii. S. 180.

2 Journ. Physiol., Cambridge and London, 1893, vol. xiv. p. 372.

3 Ztschr. f. d. ges. Naturw., Halle, Bd. xxix. S. 506 ; Virchow's Archiv, Bd. xxxix. S. 130.

4 Chem. Ccntr.-BL, Leipzig, 1879, Bd. x.

5 Ztschr. f. Biol., Miinchen, Bd. xxii. S. 423.

6 Article in Wurtz' "Diet, de chim.," 1886, Suppl. 1 A, p. 58.

7 Journ. Physiol., Cambridge and London, vol. xii. p. 23.

8 Qompt. rend. Acad. d. sc., Paris, tome xxviii. p. 40.

9 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. viii. S. 761. See also Wurster, Chem.
Ztg., Cothen, Bd. xi. S. 187.

48 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

considerable change in the proteid molecule; inclol and skatol can
hardly be considered to be simple cleavage products of the proteid
molecule (see p. 29).

Liebermanns test1 is performed by precipitating the proteid by
alcohol, and then heating the washed precipitate with strong hydrochloric
acid. The result is a violet-blue colour. The reaction is not given by pure
peptone.2 It is also not given by any of the aromatic putrefactive products
of proteid, nor by a large number of other cleavage products of proteid
which Pickering worked with. Its cause is therefore at present unknown.

Krassers reaction? — Alloxan in solution stains proteid matter a
brilliant red. It reacts in the same way with asparagin, aspartic acid,
and tyrosine. The reaction is probably connected with the presence
of amido groups.

Piotrowski's reaction^ — If a few drops of dilute copper sulphate
solution are added, and then excess of strong solution of caustic soda
and potash, a violet solution is the result. If ammonia is used instead,
a blue solution is formed.

In the case of the proteoses and peptones, the result is a rose -red solu-
tion with potash5 and a reddish violet with ammonia. As the same colour
is given by the decomposition product of urea called biuret,6 the test
is often called the biuret reaction (2CON2H4 - NH3 = C202N3H5). Biuret
yields, on decomposition, compounds which contain cyanogen ; for instance,
by heat it is split into ammonia and cyanuric acid, (CN)3H303. Biuret,
cyanuric acid, xanthine, hypoxanthine, sarcosine, hydrocyanic acid, all give
similar reactions to the proteids. Gne/da 7 considered it probable that the
biuret reaction was due to a cyanogen radicle, and that the cyanogen in
albumin and peptone is differently combined, corresponding to the similar
differences in cyanuric and hydrocyanic acid respectively. Pickering,8
however, concludes, that the radicle in question is not ON but CONH.

The related metals, nickel (Gnezda) and cobalt (Pickering) give correspond-
ing colour reactions, which may be summarised in the following table : —

Copper Sul-

Copper Sul-

Nickel Sul-

Nickel Sul-

Cobalt Sul-

Cobalt Sul-

Proteid.

phate and

phate and

phate 111 id

phate and

phate and

phate and

Ammonia.

Potash.

Ammonia.

Potash.

Ammonia.

Potash.

Native proteids^

(albu min s, |
globulins, and 1-
nucleo - pro- |

Blue

Violet

Nil

Yellow

Nil

Heliotrope-
purple

teids) J

Products of pro-"|

teolysis (pro- (
teosesandpep- |

Violet

Rose -red

Yellow

Orange

Nil

Red-brown

tones) J

Pickering found that when a cobalt salt has entered into the proteid

1 Jahresb. it. d. Fortschr. d. Thier-Chcm., Wiesbaden, Bd. xvii. S. 8 ; Chem. Centr.-BL,
Leipzig, 1887, Nos. 18 and 25.

Le Nobel, Jahresb. it. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xvii. S. 3.

Monalsh. d. Chem., Wien, Bd. vii. S. 673.

Sitzungsb. d. Ic. AJcad. d. Wisscnsch., Wien, Bd. xxiv. S. 335.

Brucke, Monatsh. d. Chem., Wien, Bd. iv.

Wiedemann, Ann. d. Phys. u. Chem., Leipzig, Bd. Ixxiv. S. 67.

7 Proc. Roy. Soc. London, 1889, vol. xlvii. p. 202.

8 Journ. Physiol., Cambridge and London, 1893, vol. xiv, p. 347.

CLASSIFICATION OF PROTEIDS. 49

molecule, it can be easily displaced by a nickel salt, and then in turn by a
copper salt, each yielding its characteristic colour reaction. He examined
these and other reactions in connection with various albuminoids as well ; the
addition of cobalt sulphate and potash to gelatin he found to produce a play
of colours in the order of those of the spectrum, commencing with violet.

Drechsel l has drawn attention to an old observation of Krukenberg's, that
at the boiling temperature there is in the so-called biuret reaction a reduction
of the cupric to cuprous oxide ; the latter, however, remains in solution.
Drechsel shows that the reduction also occurs at the ordinary temperature.
C. J. Martin2 is also of opinion that the biuret reaction is a reduction.
He rinds that alkali albumin dissolves cuprous oxide and forms a pink solution,
never violet or purple ; these latter colours, when the test is ordinarily performed
with copper sulphate, are due to admixture with cupric hydrate, held in solu-
tion by the proteid and not reduced. The most powerful reducing proteids are
proteoses and peptone, hence the pink biuret reaction ; whereas the native
proteids have a smaller reducing power, and the pink colour is mixed with the
blue cupric hydrate, and so the colour obtained is a violet.

From the preceding study of the properties and reactions of the
proteids, it will be gathered that since many other substances give the
same tests, a proteid can only be identified by employing a large
number of its reactions. Winternitz 3 recommends a combination of a
precipitant and colour reactions. The precipitant he has chiefly used
in cases of albuminuria is acetic acid and potassium ferrocyanicle. The
precipitate so obtained gives the colour reactions well. This is also the
case with the precipitate produced by several other reagents, among
which may be mentioned salicylsulphonic acid,4 and the halogens.5

CLASSIFICATION OF PROTEIDS.

It will be seen from the preceding description of the proteids, that
I have used the term proteids throughout as an equivalent for albuminous
substances (German, Eiweisskorper) ; certain other substances (such as
haemoglobin, mucin, nucleo-proteids) named proteids, by Hammarsten,
Neumeister, and other continental writers, will be treated separately
as compound proteids.

The proteids may be divided into those of animal and those of
vegetable origin. There does not appear to be any essential difference
between these two classes, and each can be subdivided in the same
manner into sub-groups, but the distinction is a convenient one in practice.

Animal proteids. — Class 1. Albumins. — These are proteids which
are soluble in water, in dilute saline solutions, and in saturated solutions
of sodium chloride and magnesium sulphate. They are, however, pre-
cipitated by saturating their solutions with ammonium sulphate. Their
solutions are coagulated by heat, usually at 70°-73° C. Serum albumin,
egg albumin, lact-albumin are examples.

Class 2. Globulins. — These are proteids which are insoluble in water,
soluble in dilute saline solutions, and insoluble in saturated solutions of
sodium chloride, magnesium sulphate, and in half -saturated solution of

1 Ztschr. f. physiol. Ohem., Strassburg, 1895, Bd. xxi. S. 68.

2 Private communication to author.

3 Ztschr. f. physiol. Chem., Strassburg, Bd. xv. S. 187; xvi. S. 439.

4 Pickering, loc. cit., p. 377.

5 F. G. Hopkins, Proc. Physiol. Soc., June 12, 1897.
VOL. I. — 4

50 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

ammonium sulphate. Their solutions are coagulated by heat, the
temperature of heat coagulation varying considerably. Fibrinogen,
serum globulin, globin, paramyosinogen, and myosinogen, crystallin,
vitellin,1 egg globulin are examples.

The differences in solubility of these two important classes of native
proteids may be stated in tabular form as follows :—

Reagent.

Albumin.

Globulin.

Water • .

Soluble

Insoluble

Dilute saline solution .....

Soluble

Saturated solution of magnesium sulphate or
sodium chloride .......

Insoluble

Half-saturated solution of ammonium sulphate

Saturated solution of ammonium sulphate

Insoluble

) J

Class 3. Albiiminates. — These are proteids derived from either
albumins or globulins by the action of weak acids or alkalis. The term
has been extended to include metallic compounds of the proteids, but
restricting it here to acid albumin or syntonin, and alkali albumin, the
class may be defined as consisting of proteids which are insoluble in
water, and in neutral solutions containing no salt. They are soluble in
acid or alkaline solutions, and in weak saline solutions. They are
precipitated by neutralisation, and resemble globulins in their behaviour
to neutral salts. Their solutions are not coagulated by heat.

A less soluble variety of these proteids, called Lieberkiihn's jelly,
is formed by adding strong acid or alkali respectively to undiluted
white of egg.

Caseinogen, formerly regarded as a member of this group, will be
studied with nucleo-proteids and with milk.

After egg albumin is treated with formaldehyde it remains soluble
in water, but is not coagulable on heating.2

Class 4. Products of proteolysis ; proteases and peptones. — These will
be studied in detail in connection with digestion. They can, however,
be formed by other hydrolysing agencies than digestive juices, such as
treatment with mineral acids, or superheated steam.3 The term proteose
for the intermediate products of hydration is a convenient general name,
which includes not only albumoses, but also vitelloses, globuloses, caseoses,
myosinoses, and the like.

Class 5. Coagulated protcids. — This class includes the proteids in
which coagulation has been produced by heat, and those in which coagu-
lation has been induced by ferment action, such as fibrin, myosin, casein,
and anti-all Himid, an insoluble by-product formed in gastric digestion.

Since the individual members of these groups have either been
described in preceding sections, or will be discussed elsewhere under
other heads, such as blood, milk, etc., they need not be further considered
in this place.

1 Vitellin, unlike other globulins, is not precipitated by sodium chloride. Some regard
it as a nucleo-proteid. It will be more fully discussed later.

2 Blum, Ztschr. f. physiol. Ohem., Strassburg, 1896, Bd. xxii. S. 127; Berl. klin.
Wchnschr., 1897, Bd. xxxiii. S. 1043.

3 On " Atmid-albumoses " (that is, those formed by superheated steam) see Neumeister,
Ztschr. f. JBioL, Mimchen, Bd. xxvi. S. 57 ; Chittenden and Meara, Journ. Physiol. ,
Cambridge and London, 1894, vol. xv. p. 501.

VEGETABLE PROTEIDS. 51

Vegetable proteids. — The amount of proteid matter in plants,
especially in those which are full grown, is less than in animals. It occurs
dissolved in their juices, or in their protoplasm, or deposited in the form
of granules called aleuron grains. Plant proteids have frequently been
obtained in a crystalline form. They may be divided into the same
classes as the animal proteids.

Class 1. Albumins. — Small quantities of true albumin have been
described by S. Martin x in the juice of the papaw fruit, and by Green 2
in the latex of several caoutchouc-yielding plants of the natural orders
Apocynese and Sapotacese.

Class 2. Globulins. — These are by far the most abundant natural
proteids present in plants. This view, which was taken by Hoppe-
Seyler,3 is contrary to that of Kitthausen,4 who regarded vegetable
proteids as consisting chiefly of legumin and allied substances.5

Class 3. Albuminatcs. — Acid and alkali albumin are formed readily
from vegetable proteids, especially from plant myosin. Legumin or
vegetable casein was used synonymously with vegetable proteid by some
of the earlier investigators,6 but it is now usually regarded as alkali
albumin, formed artificially in the extraction of the globulins by alkali.
The name conglutin was introduced by Kitthausen7 for the more
glutinous product obtained from almonds and lupins.

Class 4. Proteases and peptones. — Proteoses have been described in
latex, in papaw juice, and flours of different kinds. True peptones are
not found in the circulating juices of plants. Probably the circulating
proteids in plant life are proteoses, hemialbumoses (Vines), though amido-
acids (leucine, tyrosine, asparagine, adenine, etc.) 8 also occur. These
substances are formed by proteolytic ferments during germination. The
best known of these ferments, papain, has been investigated by Wurtz,
Martin, and others. Such ferments, as well as malting ferments, which
convert the insoluble starch of the seed into the soluble sugar, are probably
almost ubiquitous.9 In carnivorous plants, another ferment is met with
of a somewhat different character.

Class 5. Coagulated protvids. — Vegetable albumin and globulin, like
those of animal origin, are converted at a high temperature into an
insoluble heat coagulum.

With regard to the value of vegetable proteids as food, it may be stated that
as a rule they are not nearly so readily digested as animal proteids. Prausnitz 10

1 Journ. PhysioL, Cambridge and London, vol. vi. p. 336.

- Proc. Roy. Soc. London, vol. xl. p. 28.
3 "Physiol Chem.," S. 75.

* Ztschr. f. Chem., Leipzig, Ser. 2, Bd. iv. S, 528, 541; vi. 126; Journ. f. praJct. Chem.,
Leipzig, Bd. ciii. S. 65, 78, ]93, 273.

5 Ritthansen defends his view in Chem. Centr.-BL, Leipzig, 1877, S. 567, 578.

6 Einhof, Neue allg. Journ. d. Chem., v. A. Gehlen, 1805, Bd. vi. S. 126, 548. Dumas
and Caliours, Liebig, and others also examined this substance.

7 Ibid., Ser. 2, Bd. xxvi. S. 440.

8 E. Schulze and E. Kisser, Landw. Versuchs Stat., Berlin, Bd. xxxvi. S. 1 ; E. Schulze,
numerous papers in Ztschr. f. physiol. Chem., Strassburg. See especially Bd. xii. S. 405.

9 Gorup-Besanez, Ber. d. deutsch. chem. Gescllsch., Berlin, 1874, S. 1478 ; Krauch,
Journ. Chem. Soc., London, 1878, Abst. p. 996 ; Green, Proc. Roy. Soc. London, vol.
xli. p. 466; Thiselton Dyer's Presidential Address, Sect. D, Brit. Assoc., 1888; Hansen,
Bot. Ztg., 1886, S. 137; Ellenberger and Hofmeister, CentralU. f. auric. Chem., Leipzig,
1888, S. 319. The subject of enzymes and reserve materials in plants, however, is now
a very large one, and it will be found discussed, with bibliography, in a series of articles by
J. Reynolds Green, in Science Progress, London, vol. i. p. 342 ; ii. p. 109 ; iii. pp. 68, 376 ;
v. p. 60.

10 Ztschr. f. BioL, Miinchen, Bd. xxiv. S. 227.

52 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

experimented with beans; he found the faeces contained as much as 30'3 of the
nitrogen of the beans in an undigested condition. Beans thus compare
unfavourably with lentils and bread, but even here there is a considerable
undigested residue. The investigations of Rutgers l point to the fact that this
is due rather to the admixture of vegetable proteids with cellulose and other
indigestible materials than to any peculiarity in the proteids themselves.

The foregoing brief account of the vegetable proteids may be amplified by
further consideration of some of the points raised : —

Researches on crystallised vegetable proteids. — In 1855, Hartig2 pointed out
the existence of crystallised proteid matter in seeds. Four years later, Maschke3
obtained hexagonal plates of proteid matter by extracting Brazil nuts with
water at 40°-50° C., and evaporating the filtered extract at 40°. Nageli4 de-
signated such crystals as crystalloids. 4Veyl5 identified the crystals as vitellin.
Sachsse,6 by Maschke 's method, and also by precipitating the aqueous extract
by a stream of carbonic anhydride, obtained several preparations of proteid from
Brazil nut which he analysed. The precipitate consisted of small discs,
not crystals. Schmiedeberg 7 obtained crystalline products from the car-
bonic anhydride precipitate by digesting it with magnesia solution at 35° C., and
evaporating at the same temperature. Drechsel 8 obtained hexagonal crystals,
by submitting the solution containing Schmiedeberg's magnesia compound to
dialysis against alcohol, and also by the slow evaporation of a warm sodium
chloride solution of the proteid.9 At Drechsel's suggestion, Griibler 10 applied
this method with some modifications to the proteids of squash seed, from which
he obtained octahedral crystals ; he obtained lime as well as magnesia crystalline
compounds. Bitthausen,11 by similar methods, obtained octahedra and rhombic
dodecahedra from expressed hemp cake, castor-oil seeds, and seeds of Sesamum
indicum. Molisch12 has separated by the use of ammonium sulphate a
crystalline proteid (phycocyanin) from the alga, Oscillaria leptotriclia.
Vines 13 found that the natural crystalloids, embedded in the ground
substance of the aleuron grains, were hexagonal rhombohedra in some plants,
and regular tetrahedra in others.

Some of the details of Vines' work are as follows : —

The aleuron grains of the peony contain an albumose and vegetable
myosin ; of the castor-oil plant, an albumose, a myosin, and vitellin ; of blue
lupin, chiefly crystalloid vitellin. He classified aleuron grains into —

1. Those soluble in water, albumose.

2. Those soluble in 10 per cent, sodium chloride solution —

(a) Without crystalloids, soluble in saturated sodium chloride solution,
vitellin.

(b) With crystalloids, insoluble in saturated sodium chloride solution, myosin.

3. Those partially soluble in 10 per cent, sodium chloride solution. Some of
these are crystalloid, some insoluble, some soluble in saturated salt solution.

Vitellin is the principal constituent of egg yolk, and occurs there in the
form of seniicrystalline sphaerules, corresponding to the crystalloid aleuron
grains of plants. The proteids described by Valenciennes and Fremy u in the

1 Ztsc.hr, f. BioL, Miinchen, Bd. xxiv. S. 251. 2 Bot. Ztg., 1855, S. 881.

8 Journ. f. prali. Chem. , Leipzig, Bd. Ixxiv. S. 436.

4 Bot. Mitth., Miinchen, 1863, Bd. i.

5 Arch. f. d. ges. Pliysiol., Bonn, Bd. xii. S. 635 ; Zlschr. f. pliysiol. Chem., Strassburg,
Bd. i. S. 72.

6 "Die Farbstoffe, Kohlenhydrate mid Proteinsubstanz, " Leipzig, 1877, S. 315.

7 Ztschr. f. pliysiol. Chem., Strassburg, Bd. i. S. 205.

8 Journ. f. praU. Chem., Leipzig, Bd. xix. S. 331.

9 See Grubler, ibid., Bd. xxiii. S. 100. 10 Ibid., Bd. xxiii. S. 97.

11 Ibid., Bd. xxiii. S. 481. 12 Bot. Ztg., 1895, Bd. i. S. 131.

13 Proc. Roy. Soc. London, vol. xxviii. p. 218 ; xxx. p. 387 ; xxxi. p. 62.

14 Ann. dechim., Paris, Ser. 3. tome 1. p. 129 ; Ann. d. Chem., Leipzig, Bd. cxxvii. S. 188.

VEGETABLE PROTEIDS.

53

yolks of fishes' eggs, and termed by them ichthin, ichthulin, and emydin, are
regarded by Hoppe-Seyler as doubtful chemical units, and are probably mixtures
of vitellin with nuclein and lecithin. Whether vitellin contains phosphorus in
its molecule or not is a moot point. Some regard it as a nucleo-proteid rather
than a globulin ; others look upon the phosphorus generally found in it as
belonging to either nuclein or lecithin, adherent to it as an impurity. The
same question arises in connection with phytovitellin (vegetable vitellin).
Kecent analyses by Osborne l show that it contains no phosphorus, though
Sachsse, one of the earlier workers, described the presence of this element.

Proteids of flours. — Sidney Martin 2 found the principal proteids in wheat
flour to be (1) a vegetable myosin, and (2) a soluble proteose, which he
called phytalbumose.

Gluten is a mixture of two substances —

(a) Gluten fibrin, which is insoluble in alcohol, and formed from the
myosin ; and

(b) A proteose insoluble in water, formed from the phytalbumose. This

FIG. 11.— Crystallised vitelliu of the oat kernel. —After Osborne.

insoluble proteose is, however, soluble in strong alcohol, and gives the sticky
consistency to gluten ; it corresponds to the two substances called gliadin and
mucediii by Ritthausen.3

The existence of proteids soluble in strong, though probably not in abso-
lute, alcohol, is a remarkable occurrence, and is not unique in vegetable
physiology.

Martin considered that gluten does not pre-exist in wheat-flour, but is
formed on the addition of water by a ferment action. This is supported by
the fact that washing flour with water at a low temperature (2° C.) does not
lead to the formation of gluten. The ferment, however, has not been
separated, and Johannsen4 has advanced certain facts that tell against the
ferment theory and in favour of the pre-existence of gluten in the flour.

1 Am. Cliem. Journ., Baltimore, vol. xiv. No. 8.

2 Brit. Med. Journ., London, 1886, vol. ii. p. 104.

3 Journ. f.praU. Chcm., Leipzig, Bel. Ixxiv. S. 193, 384. For other observations on
gluten, see Bouehanlat, Compt. rend. Acad. d. sc., Paris, tome xiv. p. 962 ; Tarldei, Gior.
fisica di Hn/gnatdli, vol. xii. p. 860 ; Gunsberg, Journ. f. prakt. Chem., Leipzig, Bd.
Ixxxv. S. 213.

4 Ann. agronomiqucs, Paris, tome xiv. p. 420.

54 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Osborne l investigated the proteids of the oat and analysed three primary
oat proteids, one soluble in alcohol, the second a globulin, and the third a
proteid soluble in alkali only. From these, secondary proteids are obtained
by mixing the ground oats with water ; he regards the change as one pro-
duced by ferment activity.

In conjunction with Chittenden,2 he worked out in a similar way the
proteids of maize, and found there two globulins, one or more albumins, and a
proteid soluble in alcohol. These differ in solubilities, coagulating points, and
elementary composition ; one of the globulins is a vitellin, the other a myosin.
A small amount of proteose also present was regarded as artificially produced
in the processes of analysis. The proteid soluble in alcohol is called zein ;
and it, like the globulins, is converted into an insoluble modification on ad-
mixture of the flour with water.

The proteids of flax seed 3 he foiled to be chiefly globulin, with smaller
quantities of albumin, proteose, and peptone.

In wheat Osborne and Voorhees 4 describe five proteids : —

1. Gliadin; a proteid soluble in alcohol, and like gelatin in some of its
other properties.

2. Glutenin ; a proteid soluble only in alkalis.

3. Edestin ; a globulin of the vitellin class.

4. Leucosin ; an albumin, which Martin described as a myosin.

5. Proteoses.

They do not agree with Martin's ferment theory of gluten formation.
O'Brien 5 has arrived at a similar conclusion ; he regards gluten formation as
due to hydra tion, though not produced by a ferment. The proteids in the
flour he describes as globulins of the myosin and vitellin type, and a
proteose which he regards as the mother substance of gluten.

Other vegetable proteids investigated by Osborne are those of the kidney
bean 6 (two globulins called phaseolin and phaselin, and proteose) ; of the
cotton seed (almost altogether proteose, with small amounts of edestin and
insoluble proteid) ; of rye (gliadin, leucosin, edestin, and proteose) ; and of
barley7 (leucosin, proteose, edestin, and hordein, an insoluble protoid,
corresponding to Kitthausen's mucedin). He also investigated the chemical
nature of diastase, and considers it is closely related to the albumin he has
named leucosin.

Researches on proteolytic ferments in plants. — Those in the papaw plant
and in pine-apple juice are the best known, or most fully worked out.

Papain was the name given by Wurtz to the proteolytic ferment in the
juice of the papaw plant.8 The close similarity of its action to that of
trypsin was shown by S. Martin.9 The proteids in the juice are a globulin
very like serum globulin, small quantities of an albumin, and proteoses of
two kinds, with one of which the ferment appears to be closely associated
(Martin).10

Bromelin.— This is the proteolytic ferment in pine-apple juice. Its
existence was first noted by Marcano of Venezuela. It is made use of
extensively in South America for the preparation of artificially digested

1 Am. Chem. Journ., Baltimore, vol. xiv. No. 3.

2 Ibid., vol. xiii. Nos. 7, 8, and 9 ; vol. xiv. No. 1. 3 Ibid., vol. xiv. No. 8.

4 Ibid., vol. xv. No. 6; "Seventeenth Ann. Rep. Connecticut Agric. Expt. Station,"
Newhaven, 1893.

5 Ann. Botany, Oxford, 1895, vol. ix. pp. 171, 503.

6 Journ. Am. Chem. Soc., N. Y., 1894, vol. xvi. p. 633.

7 Ibid., 1895, vol. xvii. p. 539. See also Osborne and Campbell on proteids of potato
on conglutin and vitellin, on legnmin and other proteids of the pea and vetch, ibid., 1896
vol. xviii. No. 7.

8 Compt. rend. Acad. d. sc., Paris, 1879, p. 425 ; 1880, p. 1379.

9 Journ. Physiol., Cambridge and London, vol. v. p. 213.
10 Ibid., vol. vi. p. 336.

PROTEIDS AS POISONS. 55

foods.1 Its action has been studied by Chittenden2 and his pupils. It is a
ferment of intense activity, and acts well in neutral, acid, and alkaline
solutions, especially at 60° C. The ferment itself is associated or identical
with a proteose-like substance in the juice. The products of its action
(proteoses and peptone) are like those of other proteolytic ferments.

I have alluded to these two ferments because they have formed the basis
of very thorough investigations, not because they are in any way exceptional
occurrences in the vegetable kingdom; as already stated, such ferments
probably play an important part in all plants, by converting the insoluble
proteid of the seed into the soluble nitrogenous substances of the sap.3

PROTEIDS AS POISONS.

The line between food and poison is easily crossed. When, a few
years ago, the idea was first mooted that proteicls may act as poisons, it
was received with incredulity in many quarters ; but there can now be
no doubt that it is a fact.4

The best known of the vegetable proteid poisons are : —

1. Those contained in the seeds of jequirity (Abrus precatorius).
Warden and Waddell 5 named the poisonous substance abrin. S. Martin 6
separated the two proteicls — a globulin and a proteose — of which it is
composed. The material is used as a drug to produce conjunctivitis.

2. The proteid associated with or identical with papain (S. Martin).

3. Ricin, the poisonous proteid in castor-oil beans.7

4. Lupino-toxin from Lupinus luteus.8

The most important of the animal proteid poisons are —

1. Snake poison.

2. Proteicls in the serum of certain fishes (conger eel, mursena, etc.).9

3. Proteid poisons found in certain spiders,10 and in the stinging
apparatus of many insects.

4. Ordinary peptones and proteoses ; 0'3 gr. of commercial peptone
per kilog. of body weight is in clogs usually fatal, when injected into
the blood.

5. Nucleo - proteicls. — These were called tissue fibrinogens by
Wooldridge, and cause intravascular clotting when injected into the
blood (see " Coagulation of Blood ").

6. Poisonous proteicls produced by bacterial action. This subject
has recently received much attention, and opens up the whole subject
of toxins and antitoxins. To go into this matter thoroughly would

1 Bull. Pharm., Detroit, 1891, vol. v. p. 77.

2 Trans. Connect. Acad. Arts and *'c., New Haven, 1891, vol. viii. ; Journ. PhysioL, Cam-
bridge and London, vol. xv. p. 249.

3 See further Green's papers already quoted ; also J. R. Green, " On the presence of
vegetable trypsin in the fruit of Cucumis utilis and other plants," Ann. agronomiqucs,
Paris, tomexix. p. 508 ; Neumeister, Ztschr. f. BioL, Mimchen, Bd. xxx. Another recent
paper on the subject (J. Hjort, Oentralbl. /. Physiol., Leipzig, 1896, Bd. x. S. 192) shows
that there are similar ferments in fungi.

4 Nencki's opinion that poisonous proteids are more labile than other proteids can
hardly be considered an explanation of this fact (" Ueber die labile Eiweissstoffe, " Wchnschr.
f. Pharm., 1891, No. 29).

5 "Non-Bacillar Nature of Abrus Poison," Calcutta, 1884.

6 Brit. Med. Journ., London, 1889, vol. ii. p. 184.

7 Stillmark, Pharm. (Jcntr.-ltt., Leipzig, 1890, Bd. xxx. S. 650.
* Schmidt's Jahrb., Leipzig, 1888, Bd. cciv. S. 10.

9 Mosso, Jahrcsb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xviii. S. 92.
10 Robert, Sitzungsb. d. Dorpatcr naturforsch. Gcsellsch., 1888 ; Centralbl. /. d. ined.
Wisscnsch., Berlin, 1888, S. 514.

56 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

lead us too far into pathological regions. The exact nature of the
toxalbumoses and their antitoxins is by no means settled, but has
already been followed by important practical results in the way of
treatment.

Snake poison. — The first group of proteid poisons in the foregoing
list will furnish us with a typical example of the class, and it appears
probable that, as the nature of the poison has been more thoroughly
worked out in this than in most of the other cases, this will also form
an important field of research in furnishing the key to the question of
the nature of antitoxins; for protective inoculation has here been
followed with considerable success (Calmette,1 Eraser 2 ).

The first investigation into the chemistry of snake poison of any
importance was by Prince Lucien Buonaparte, on the poison of an adder,
in 1843.3 He found that the activity of the poison was associated with
the portion precipitable by alcohol ; and he gave the name wperi/fw to
this precipitate.

About 1860, Weir Mitchell4 turned his attention to the subject, and
he was the first to recognise that the toxic principle of the venom is
albuminous in nature. He termed it crotalin in the case of the rattle-
snake. From that time till 1886 (in conjunction with Reichert) he
continued his work, and confirmed his general conclusion in the case
of the North American snakes. About 1871 the Indian snakes received
their share of attention, and the names of Sir Joseph Fayrer5 and
Lander Brunton6 are associated with valuable researches concerning
the venom of the cobra, krait, and Indian viper. These observers dealt,
however, with the object mainly from the point of view of the physio-
logical action of the venom.

In 1883 Wall,7 in 1886 Wolfenden,8 and in 1892 Kanthack,9
published important contributions to our knowledge of cobra poison,
the improved methods of chemical physiology enabling them not only
to identify the poison as a proteid, but to show that the variety of
proteid present is principally proteose. Two observers have described
poisons other than proteid in snake venom, viz. Gautier,10 who regarded
the venomous principle as alkaloidal ; and Wynter Blyth,11 who gave the
name cobric acid to a crystalline substance which he separated from
cobra venom, and which he asserted to be highly poisonous. Recent
work has failed to substantiate these results, and such alkaloids as are
present (and they are generally absent) are non-poisonous ones.

In their researches on the venom of the Australian black snake, C.
J. Martin and M'Gr. Smith12 determined positively the nature of the

1 "Le Venin des Serpents," Paris, 1896.

2 Brit. Med. Journ., London, 1895, vol. i. p. 1309. The name given to the antitoxin
contained in the serum of immunised animals is antivenine.

3 See Sir J. Fayrer, Proc. Med. Soc. London, 1884.

4 N. Am. Med.-CMr. Rev., vol. v. p. 269 ; Med. News, Philadelphia, 1883 ; "Researches
upon the Venoms of Poisonous Serpents," Smithsonian Contributions to Knowledge, 1886.

5 Rep. on san. improvement* in India, London, 1873, 1874.

6 Pep. on san. measures in India, London, 1874 ; Proc. Roy. Soc. London, 1872-3,
1873-4, 1875 and 1878; Sir J. Fayrer, "Thanatophidia of India," London, 1872, and
numerous papers by same author in Edin. Med. Journ., -And Indian Med. Gaz., Calcutta,
between 1868 and 1874.

7 " Indian Snake Poisons, their Nature and Effects."

8 Journ. Physiol., Cambridge and London, vol. vii. pp. 327, 357, 365.

9 Ibid., vol. xiii. p. 372. 10 Bull. Acad. de mcd., Paris, 1881.

11 Analyst, London, 1876, vol. i.

12 Proc. Roy. Soc. New South Wales, Sydney, July 3, Aug. 3, 1892; Journ. Physiol.,
Cambridge and London, 1893, vol. xv. p. 380.

SNAKE POISON. 57

venom. By appropriate experiments they excluded micro-organisms,
ferments, alkaloids, ptomaines, and crystalline acids.1 They next showed
that there are three proteids in the secretion ; one, an albumin, is not
irulent ; but the other two, which are proteoses (proto- and hetero-pro-
teose), are extremely poisonous. Their action is the same as that of the
venom itself. They, like the venom, can be momentarily boiled without
impairing their activity, but prolonged boiling for days destroys their
virulence.

The action of the poison is local and general. The most marked
local effect is oedema ; the general symptoms in non-lethal doses consist
of twitching and convulsions. A fatal dose kills within a few seconds
or minutes. There is also a peculiar effect on the blood. More than a
century ago, the Abbe Fontana 2 noticed that the blood of animals
killed by viper bite remained fluid. Brainard,3 writing more than forty
years ago, states that when death occurs immediately, in animals bitten by
rattlesnakes, the blood is found at the post-mortem examination to be
clotted ; but if some time elapses before the animal succumbs, the blood
remains fluid in the vessels. The continued fluidity of the blood has
since then been noted by numerous observers in the case of various
snakes. These observations are explained by C. J. Martin's researches.
He found that different doses produce different results. Immediately after
the introduction of the venom, the coagulability of the blood increases,
and this increase in the case of moderate or large doses (more than
O'OOOl grm. per kilog. of body weight) culminates in intravascular
clotting of greater or less extent. The injection of smaller doses
produces a transient phase of increased coagulability, but after two
minutes this is succeeded by a negative phase ; the blood when drawn
either fails to clot at all, or does so only after the lapse of several hours.
The thrombosis occurs more readily in venous than arterial blood, and is
frequently confined to the portal area. These results show a great
resemblance between the action of the venom and that of nucleo-proteid.
The effect of diminished coagulability is not unexpected, seeing that the
principal substance in the venom is proteose, but the minuteness of the
dose necessary is very striking and distinctive. The smallness of the dose
suggests that the injected material does not itself contribute to fibrin-
formation. It probably acts by producing disintegration of the cells of
the endothelium of the blood vessels, or, according to Martin's later
observations, of the red corpuscles ; in either case the result would be
liberation of nucleo-proteid material.

With regard to the question of how these poisonous proteoses are
formed, Martin puts forward the following hypothesis: the cells of
the venom gland exercise a hydrolysing agency on the albumins supplied
them by the blood, the results of which influence are the poisonous
proteoses found in the venom. A difference between the process and
digestion by pepsin, or by anthrax bacilli, is that the hydratioii stops
short at the proteose stage, and is not continued so as to form peptone,
or simpler nitrogenous materials, like leucine, tyrosine, or alkaloids.
Gland epithelium is certainly capable of exercising such a hydrolysing
influence; the conversion of glycogen into sugar in the liver cells is
one of the best known examples.

1 A questionable trace of organic acid found did not possess toxic properties.

2 Fontana, "Poisons," Trans, by J. Skinner, London, 1787.

3 Rep. Smithson. Inst., Washington, 1854.

58 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

The following table, somewhat altered from Sidney Martin,1 illustrates
the analogy between various hydrolysing processes, proteid being in all cases
the material acted on.

PRIMARY AGENTS.

FERMENT.

PRODUCTS.

Albuminous.

Nitrogenous but not
Albuminous.

1. Epithelial cell of gastric

Pepsin.

Proteoses, peptone.

Brieger's pepto-

gjand

toxin ; a very

doubtful basic

substance.

2. Epithelial cell of pancreas

Trypsin.

Proteoses, peptone.

Leucine, tyrosine,

lysine, arginine,

-

aspartic acid,

ammonia.

3. Bacillus anthracis

None yet

Proteoses, peptone.

Leucine, tyrosine,

found.

and an anthrax

alkaloid.

4. B. diphtherias

Ferment not
named.

Proteoses.

Organic acid of
doubtful nature.

5. Epithelial cell of snake's

None yet

Proteoses.

Trace of organic

venom-gland

found.

acid.

Calmette 2 has worked out a table of the relative toxicity of venoms, as
Roux and Yaillarcl have done for tetanus toxins, based on the ratio of
lethal dose weight, subcutaneously injected, to body weight. He found the
toxic value to be represented by the following numbers : —

Cobra . . 4,000,000

Hoplocephalus curtus 3,450,000

Pseudechis 800,000

Pelias berus 250,000

Martin places the toxic power of the two Australian venoms at —

Hoplocephalus 4,000,000

Pseudecis 2,000,000

This is a very high virulence ; put in another way, it means that 0*00025
gr. of the one, and 0*0005 gr. of the other poison is sufficient to kill a rabbit
weighing a kilogramme. The virulence of snake poison much exceeds that of
most of the poisonous proteids of zymotic diseases, though it is about the
same as the diphtheria toxin of Roux and Yersin.3 The following table also
gives the toxic value of anthrax toxin,4 and toxopeptone5 from cholera
cultures calculated in the same way : —

Diphtheria toxin . . " 4,000,000 (about)

Anthrax albumoses ..... 80

Toxo-peptone . 3,000

ANIMAL ALKALOIDS.

Ptomaines and leucomaines.— The word ptomaine was originally
employed to designate those putrefactive products of animal substances which
give the reactions of vegetable alkaloids, and which are more
poisonous. The similar substances formed by
from lecithin or proteids,6 are called leucomaines.

1 Published in Brit. Med. Journ., London, March 1892.

2 Ann. de I'Inst. Pasteur, Paris, 1894, tome viii.

3 Quoted by Sims Woodhead, "Bacteria and their Products," p. 307.

4 Sidney Martin, Rep. Med. Off. Local Gov. Bd., London, 1890-91.

5 Petri, quoted by Vaughan and Novy, "Ptomaines and Leucomaines," p. 109.

6 A discussion of the chemistry of the origin of alkaloids from proteids will be found
in a paper by Latham, Lancet, London, 1888, vol. ii. p. 751.

or less
metabolic activity, either

PTOMAINES AND LEUCOMA1NES. 59

The importance of the animal alkaloids was first brought into prominence
in courts of law ; the defence urged in certain notorious trials for murder, was
that the alkaloid alleged to have been administered to the victim, or found in
his stomach, really arose as the result of putrefactive changes occurring after
death. It has, moreover, been demonstrated that alkaloids existing in
different forms of putrefying food, produce poisonous symptoms. Sausages
made with bad meat, certain forms of stale milk and cheese,1 mussels and
other shell fish,2 at certain seasons of the year, produce serious symptoms
in those who partake of them.

It has further been supposed that, in many cases of disease, the poison
formed by bacteria in the body, and which produces the symptoms of the
disease, is of an alkaloidal nature. The probability that cholera is caused by
an alkaloid was first pointed out by Lander Brunton,3 from the similarity of
the symptoms to those produced by muscarine poisoning. Two alkaloids at
least have, in fact, been discovered in cholera, and in cultures of Koch's
comma bacillus, and have been named cadaverine and putrescine, but they
cannot be the actual poisons in cholera, because they are not markedly
toxic. The same two alkaloids are found in the urine and faeces in
totally different pathological conditions, namely, cystinuria,4 and pernicious
anaemia.5

Alkaloids in animal tissues were first described by Dupre and Bence
Jones;0 the substance they separated they called "animal quinoidine";
about the same time, Marquardt7 obtained an alkaloid from a corpse, and
named it "septicine." Schmidt8 and Panum9 obtained a substance they
named sepsine from septic fluids, and they considered that it was the cause of
septicaemia. Later, prominent workers at the subject have been, Selmi,10
Gautier,11 and Brieger;12 to Brieger we owe the best methods of obtaining
these substances in a state of purity. Brieger separated some alkaloids with
such powerfully toxic properties, that he named them toxins ; these include
typhotoxine (from cases of typhoid fever), and tetanine 13 (from cases of
tetanus).

All poisons produced by bacteria are, however, not necessarily ptomaines.
In fact, many of the toxins and antitoxins have been shown to owe their
power, at one time ascribed to ptomaines, to the tox-albumoses or poisonous
proteids (see "Proteids as Poisons," p. 55).

A few details concerning the principal animal alkaloids may be added.

Parvoline (C9H13N). — This was first separated from the putrid flesh of the
mackerel and horse. It is an oily base, but its chloroaurate and chloro-
platinate are crystalline (Gautier).14

Hydrocollidine (C8H13N, boiling point 210° C.), and

Cottuline (C8HnN) have been obtained from flesh, from putrid ox pancreas,
and from gelatin. Nencki considers collidine to be isophenylethylamine,

These three bases are all highly toxic.

1 Vaughan separated an alkaloid, which he named tyrotoxicon, from certain forms of
bad cheese, Ztschr. f. phi/siol. C'hem., Strassburg, Bd. x. S. 146.
- Mytilotoxin is the alkaloid separated from mussels by Brieger.

3 Rep. Brit. Ass. Adv. Sc., London, 1873.

4 Baumann and Udranszky, Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 562.

5 Hunter, Lancet, London, 1888, vol. ii. p. 654.

e Proc. Hoy. Soc. London, vol. xv. p. 73 ; Ztschr. f. Chem. 1866, S. 348.

7 Schuchardt in Maschka's " Handb. f. ger. Med.," Bd. ii. S. 60.

8 Inaug. Diss., Dorpat, 1869.

9 Virchoiv's Archiv, Bde. xxvii., xxviii., and xxix.

10 Jicr. d. deutsch. chem. Gesellseh., Berlin, Bd. xi. 8. 808.

11 Numerous papers; see especially Bull. Soc. chim., Paris, tome xi. p. 6.

12 Brieger, "Die Ptomaine," 1885, part i. ; 1885, part ii. ; 1886, part iii.

13 Brieger, Bed. kliu. Wclinschr., 1888, No. 17. 14 Loc. cit.

60 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Neuridine (C5H14N2) is a constant product of putrefaction of proteids. It
is broken up by sodium hydrate into dimethylamine and trimethylamine
(Brieger). Isomeric with this, though differing from it in the solubility of its
salts, is saprine.

Cadaverine, a third isomeride, belongs to the diamine group, and in consti-
tution is pentamethylenediamine (Ladenberg).1

Putrescine (C4H12N2) is also a diamine, being tetramethylenediamine. It
usually accompanies cadaverine, but as a rule makes its appearance later.-'

All the above are free from oxygen ; the remainder are oxygenated.

Neurine (C5H13NO) and choline (C5H15N02) are constant products of
cadaveric putrefaction, and their constitution has been described on p. 21.
They are toxic, and derive additional interest from their close relationship to
muscarine (C5H13N02), the alkaloid of the poisonous mushroom, Agaricus
muscarius? Muscarine was discovered by Schmiedeberg and Koppe.4
Schmiedeberg and Harnack 5 obtained it also by oxidising choline with nitric
acid. Brieger found it in putrid fish, and it occurs in several vegetables.6

The natural alkaloid is probably not identical, but isomeric with that
prepared by the oxidation of choline ; 7 more recently an alkaloid, with all the
properties of the muscarine of plants, has been prepared artificially from rnono-
chloracetal and trimethylamine.8 The constitutional formula of muscarine

•JQ

(CH3)3

CH2-C^

OH

and it is the aldehyde of the non-toxic betaine (trimethylglycocine).9

Choline, neurine, and muscarine are all toxic ; and are antagonistic to
atropine, so far as relates to their action on the heart and glandular system.10

Gadinine (C7H16X02) is a less toxic alkaloid, which is mixed with the
muscarine obtained by Brieger from putrefying cod-fish.

Mytilotoxine (C)3H15N02) is the active agent in mussel poisoning.

Typlwtoxine (C7H1VN02) is obtained from cultures of the typhoid bacillus,
and was regarded by Brieger as the chemical poison in typhoid fever.

Tetanine (C13H22]S~204) is, or was supposed to be, the toxin in cases of
tetanus (Brieger).

Gautier completes his list of animal alkaloids by including a number of
substances of the* uric acid group (adenine, guanine, xanthine, hypoxanthine,
etc.), and of the creatinine group (creatinine itself, and certain sub-
stances separated from muscle, which are termed xanthocreatinine, C5H10N40,

1 Ber. d. deutseh. chem. GeseUsch., Berlin, Bd. xix. S. 2585.

2 Brieger, Berl. klin. Wchnschr., 1887, No. 44 ; Boeklisch, Ber. d. deutseh. chem.
GeseUsch., Berlin, Bd. xx. S. 1441 ; Baumann and Udranszky, ibid., Bd. xxi. S. 2938 ;
Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 562; Brieger and Stadthacen, Virchow's
Archiv, Bd. cxv. Heft 3.

3 The Agaricus muscarius also contains a considerable amount of a non-toxic alkaloid,
amanitine, Nemneister, "Physiol. Chem.,"Pd. i. S. 71. 4 " Das Muscarin," Leipzig, 1869.

5 Arch.f. exper. Path. u. PharmaJcoL, Leipzig, 1876, Bd. vi. S. 101.

6 Such as Beta vulgaris, and the seeds of vetches and cotton. E. Schulze, Ztschr. f.
physiol. Chem., Strassburg, 1891, Bd. xv. S. 140; and 1892, Bd. xvi. S. 205.

c? Boehm, Arch. f. exper. Path. u. PharmaJcoL, Leipzig, 1885, Bd. xix. S. 87.

8 Berlinerblau, Ber. d. deutseh. chem. GeseUsch., Berlin, 1884, Bd. xvii. S. 1139.

9 Found in Beta vulgaris; betaine has been also synthetically prepared from mono-
chloracetic acid and trimethylamine : —

f(CHs)a

CHoCl.COOH + N(CH3)3 + H00 = N \ CH0— COOH + HC1.

tOH"

10 The fall of blood pressure produced by choline and neurine is of cardiac origin
(Mott and Halliburton, " Proc. Physiol. Soc.," Feb. 1897, p. xviii., in Journ. Physiol.,
Cambridge and London, vol. xxi.).

COMPOUND PROTEIDS. 61

crusocreatinine, C5H8N40, and amphicreatinine, C(JH19Nr04).
maines are regarded by Gautier, Bouchard, Pouchet, and others,

These leuco-
, as feebly toxic

products of metabolism, from which the organism is normally freed by excretion,
or by destructive oxidation; it has been suggested that their retention in
the body may be the cause of certain obscure pathological conditions. The
poisonous properties of normal urine are regarded by some as due to
alkaloids of this nature, while others (Stadthagen) look upon the inorganic,
especially the potassium, salts of urine, as the toxic agents.1

COMPOUND PROTEIDS.

The compound proteids are compounds of albuminous substances
with other materials, which are as a rule also of a complex nature.
They may be divided into the following groups : —

1. Respiratory ^ pigments. - - The most important of these are
haemoglobin and its compounds, chlorocruorin2 (found in the blood
of certain worms), and hcemocyanin3 (found in the blood of many
molluscs and Crustacea). Haemoglobin and chlorocruorin are compounds
of proteids, with an iron-containing pigment. ILemocyanin contains
copper in its molecule. Turacin, the red pigment in the feathers of
certain birds (plantain-eaters), also contains copper, and though not
respiratory in function, should probably be included in the same group
of substances.4 Hemoglobin with its derivatives and allies will be
considered in a separate article.

2. Grluco - proteids. — Compounds of proteids with members of the
carbohydrate group. This class includes mucins, mucoids, hyalogens
and phospho-gluco-proteids.

3. Nudein. — Compounds of proteid with phosphoric acid, or with
nucleic acid.

4. Nudeo-proteids. — Compounds of proteid with nuclein.

5. Lecitli-albumins. — Compounds of proteid with lecithin.
We may consider the last four groups in detail.

The gluco - proteids. — The gluco -proteids are mostly free from
phosphorus (mucins, mucoids, and hyalogens), but some contain phos-
phorus (phospho-gluco-proteids).

Mucins. — The mucins are colloid, viscous substances of acid nature,
soluble in alkalis, but precipitable from such solution by acetic acid.
On boiling with dilute mineral acid they yield a substance which
reduces Eehling's solution. They are found in the secretion of mucous
glands, including the mucous salivary glands, and of slimy animals like

1 For the principal papers on alkaloidal substances in urine, see Baumann and
Udranszky, Ztschr. /. physiol. Chem., Strassburg, Bd. xiii. S. 562 ; Stadthagen and Brieger,
Virchow'* Archiv, Bd. cxv.; Stadthagen, Ztschr. f. Tclin. Mad., Berlin, 1889, Bd. xv. Hefte
5 and 6 ; Pouchet, Compt. rend. Acad. d. sc., Pt,ris, tome xcviii. p. 1360 ; Bouchard, ibid.,
tome cii. pp. 669, 727, 1127 ; Griffiths, ibid., tomes cxiii., cxiv., and cxv. ; Gantier, Bull.
Acad. dc med., Paris, 1886, tome xix. A very complete bibliography will be found in
Huppert-Neubauer's "Analyse des Harns," 9th edition, p. 241.

- Quatrefages, see Gamgee, "Physiological Chemistry," vol. i. p. 131; Krukenberg,
"Vergl. physiol. Studien," 2te Reihe. Abth. 1, S. 87; Lankester, Journ. Anat. and
Physiol., London, vol. ii. p. 114 ; vol. iii. p. 119. ; MacMunn, Quart. Journ. Micr. Sc.,
London, Oct. 1885.

3 Fredericq, Bull. Acad. roy. de mid. de Belg., Bruxelles, 1878, Se"r. 2, tome xlvi. Xo.
11 ; Halliburton, Journ. Physiol., Cambridge and London, vol. vi. p. 300. In the latter
paper numerous references to other writers will be found.

4 A. H. Church, Proc. Roy. Soc. London, 1869, vol. xvii. p. 436 ; Phil. Trans., London,
1869, vol. clix. p. 627 ; 1892, vol. clxxxiii. p. 511 ; A. Gamgee, Proc. Roy. Soc. London,
1896, vol. lix. p. 339.

62 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

snails.1 A mucinogen is found in the investment around frogs' eggs ; 2
it is also the most important constituent of the intercellular or ground
substance of connective tissues, and has been especially investigated
in the jelly-like connective tissues (vitreous humour,3 Whartonian
jelly 4 ), and in tendon.5

Elementary analysis of different mucins has given different results, as will
be seen from the following table : —

SNAIL MUCIN.

TENDON MUCIN.

SUHMAXII.LARY MlJCIN.

Haminarsten.6

Loebiscli.7

Chittenden.8

llamuiar.steu.9

Oboltmsky.io

c .

50-32

48-3

• 48-26

48-84

52-31

H .

6-84

6-44

G-49

6-80

7-22

N .

13-65

1175 11-51 12-32

11-84

S .

1-75

0-81

2-31

0-84

0 .

27-44

32-70

31-43

31-20

28-63

The mucins thus contain less carbon, and considerably less nitrogen,
than proteids.

Decomposition products of mucin. — By the action of superheated
steam, a carbohydrate is split oil' from mucin, which was CM lied animal
gum by Landwehr.11 He assigns to it the formula (C(JH]0Oft). By
the action of dilute mineral acids this is converted into a reducing but
non-fermentable sugar or giunmose (CGH1;iOG). The gum-like substance
obtained from submaxillary mucin contains nitrogen.12 The sugar
obtained from tendon mucin by Chittenden yielded an osazone molting
at 160°, and resembled that obtained from pentoses. F. Miiller13has
investigated the mucin of sputum. He found it yielded as much as
25 to 32 per cent, of a reducing substance ; this is not a pentose, but is
probably glucosaniine.

1 Eichwald, Ann. d. Chcm., Leipzig, 13d. cxxxiv.

2 Giaeosa, Ztschr. f. physiol. Chcm., Strassburg, 13d. vii. S. 40; Hammarsten, Ar<-/i. /'.
d. gcs. Physiol., Bonn, Bd. xxxvi. ; Wolfenden, Journ. Physiol., Cambridge and London,
vol. v. p. 91.

3 R. A. Young, Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 325 ; C. Th.
Morner, Ztschr. f. physiol. Chcm., Strassburg. 1893, Bd. xviii. S. 245. References to previous
literature will be found in these papers. Young arrived at the conclusion that the principal
substance in vitreous humour is mucinogen, not mucin.

4 Jernstrom, . Jahresb. u. d. Fortschr. d. Thier-Chcm., Wiesbaden, 1889, Bd. x. S. 34.
Young, loc. cit., separated two mucins from the Whartonian jelly, one soluble, the other
insoluble in excess of acetic acid.

aRollett, S'ttsungsb. d. k. Akad. d. Wissciisch., Wien, Bd. xxxix. S. 308, Strieker's
"Handbuch," 13d. i. S. 72. Loebisch, Ztschr. f. physiol. Chcm., Strassburg, Bd. x. S. 40 ;
Chittenden and Gies, Journ. Expcr. Mcd., Baltimore, 1896, vol. i. p. 188.

6 Arch. f. d. gcs. Physiol., Bonn, Bd. xxxvi. 7 Loc. cit.

8 Loc. cit. The high percentage of sulphur found is attributed by Chittenden to proteid
impurities.

9 Ztschr. f. physiol. Chcm., Strassburg, Bd. xii.

10 Arch. f. d. gcs. Physiol., Bonn, Bd. iv. S. 336. Probably Obolensky's preparation
was not so pure as Hammarsten 's.

11 Ztschr. f. physiol. Chcm., Strassburg, 1881, Bd. viii. S. 124, 199 ; Arch. f. d. <jcs.
Physiol., Bonn, Bde. xxxix. and xl.

12 Hammarsten, " Physiol. Chem.," 3rd German edition, p. 39.

13 Centralbl.f. Physiol., Leipzig, 1896, Bd. x. S. 480; Sitzungsb. d. Gcscllsch. z. Eeford.
d. gcs. Naturw. zu Marburg, 1896, No. 6.

THE GLUCO-PROTEIDS. 63

By the action of dilute mineral acids on mucin, this reducing sub-
stance, whatever its exact nature is, is also obtained, together with syntonin
and proteose-like materials, from the proteid part of the mucin molecule.
Strong acids lead to the formation of leucine, tyrosine, and levulinic acid
(Landwehr). Strong alkalis lead to the formation of similar products ;
but weak alkalis, like lime water, have no effect on tendon mucin, though
they readily break up submaxillary mucin (Loebisch). There is a good
deal of difference among the mucins in their solubilities in acid and
alkaline solutions. Obolensky obtained pyrocatechin by boiling sub-
maxillary mucin with caustic soda ; but I have not succeeded in getting
it from connective tissue mucin.1

The putrefactive products of mucin are similar to those obtained
from proteids.

Mucoids or mucinoids. — These are mucin-like substances, which differ
from the true mucins either in being non-precipitable from alkaline solu-
tions by acetic acid, or in being readily soluble in excess of acetic acid. The
designation was originally given to this class by Hammarsten, and includes
the following substances :—

1 . The mucin from vitreous humour.

2. The mucin from cartilage — cliondro-inucoid (see " Cartilage ").

3. The mucin from cornea — cornea-mucoid.2

4. Pseudo-mucin ; the colloid-like substance often found in ovarian fluids,
and previously known as paralbumin and metalbumin.3

5. A similar mucoid, sometimes found in ascitic fluid.4

6. Ovomucoid, a mucoid found in white of egg. This was first studied
by Neumeister,5 who called it pseudo-peptone, then by Salkowski,6 and finally
by C. T. Morner,7 who identified it as a mucoid.

7. Paramucin, a substance found sometimes in ovarian cysts, differing
from pseudomucin in reducing Fehling's solution without previous treatment
with acids (K. Mitjukoff).8 Leathes,9 who has worked at this substance under
Drechsel's supervision, finds that the reducing substance yields no osazone ;
that on decomposition it yields sulphuric acid, and thus resembles chondro-
mucoid; and on treatment with hydrochloric acid it gives off carbonic anhydride.
Its nature is still uncertain.

Hyaloyens. — The term hyalin was originally applied to the principal
constituent of the wall of hydatid cysts.10 Krukenberg11 extended the
name to allied substances obtainable from other animal structures. In the
natural state these substances are insoluble, and are termed hyalogens; by the
action of alkalis or superheated water they are converted into the soluble
hyalins. Neossidin is the hyalin obtained from neossin,12 the chief con-
stituent of the edible bird's nest. Chondrosidin and chondrosin are the hyalin
and hyalogen respectively obtained from the sponge, Gliondrosia reniformis,

1 See also Young, loc. cit.

2 C. T. Morner, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 213.

8 Hammarsten, "Lehrbuch d. physiol. Chem.," 3rd Gorman edition, S. 366. See also
Hammarsten, Jahresb. it. d. Fortschr. d. Thier-Chein.t Wiesbaden, Bd. xi. S. 11 ; Land-
wehr, Ztschr. f. physi ol. Chcvi., Strassburg, Bd. vii. S. 118.

4 Hammarsten, ibid., 1891, Bd. xv. S. 202.

5 Ztschr. f. Biol., Miinchen, Bd. xxvii. S. 309.

6 CentralU.f. d. med. Wissensch., Berlin, 1893, Nos. 31 and 43.

7 Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 525.

8 Inaug. Diss., Berlin, 1895.

9 Communication to Physiological Society, London, Oct. 17, 1896 (not published).

10 Lilcke, Virchow's Archiv, Bd. xix. S. 189.

11 Ztschr. f. BioL, Miinchen, Bd. xxii. S. 261.

1:2 The word "neossin" is Mulder's, Butt, des sc. phys. in Ncdwlandc, 1838, S. 172;
Green, Journ. Physiol., Cambridge and London, vol. vi. p. 40, pointed out the resemblance
of the nest substance to mucin.

64 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

spirographidin and spirographin from the skeletal tissues of the worm Spiro-
graphis. Krukenberg obtained a hyalogeri also from the tubes of Onupliis
tubicola, another from the membrane of Descemet and lens capsule (membranin,
C. T. Morner),1 and another from hyaline cartilage (now called chondroitin-
sulphuric acid, see " Cartilage "). These substances are all, like the mucins and
mucoids, decomposed by acids with the formation of a reducing substance.
They differ from the mucins in some of their solubilities, but it is doubtful
whether they should be classed apart from the mucoids.

Phospho-yluco-proteids. — These substances not only yield a reducing
carbohydrate or carbohydrate-like body, like the mucins and mucoids, but on
gastric digestion they leave a residue of pseudo-nuclein, a substance which,
like nuclein, contains phosphorus. Pseudo-nuclein does not, however, yield
bodies of the xanthine group, on further decomposition, as do true nucleins.
Among these substances are the following :—

(a) IchthuHn, a substance separated from the eggs of the carp by Walter,8
and at first supposed to be identical with vitellin.

(b) Helico-proteid, secreted by the glands of the snail (Helix poinatia), and
separated by Hammarsten.3 By the action of alkalis a levorotatory carbohydrate
(animal sinistrin) is split off ; a dextrorotatory reducing sugar is obtained by the
use of dilute mineral acids.

(c) The principal constituent of the cells of the pancreas is a complex
nucleo-proteid which Hammarsten4 considers to be identical with trypsin ;
by boiling this, it is split into coagulated proteid and a phospho-gluco-proteid.
The sugar which this substance gives, on treatment with dilute acids, is
probably a pentose (see p. 3).

Kossel and his pupils have also obtained reducing sugar-like substances
from yeast nuclein.

In concluding the subject of the gluco-proteids, it may again be mentioned
that Pavy regards all the common proteids (casein excepted) as having a
glucoside constitution (see p. 30). Whether this be so or not, the fact insisted
upon by Pavy that a carbohydrate may be obtained by hydrolytic decompo-
sition of proteids has been confirmed by other observers. Thus K. Morner
obtained from serum globulin a reducing substance on treatment with
hydrochloric acid, which, like Pavy's, is optically inactive ; but failed to get
such a substance from purified myosin, vitellin, crystallin, serum albumin, and
egg albumin. He got it from fibrin, but considered that it was due to carbo-
hydrate in entangled blood corpuscles.5 I myself was at one time of opinion
that Pavy's results, which were principally obtained with egg-white, were due
to the admixture of the pure albumin with a mucoid (ovomucoid, which
exists to the extent of 10 per cent, in egg-white) ; but I learn from Dr. Pavy
that his method of preparing coagulated egg-white would exclude any large
admixture of this kind. Pavy's work, moreover, has been recently confirmed
by N. Krawkow.6 He found egg-white difficult to obtain free from ovomucoid,
but the purest products he obtained always yielded a reducing substance,
which gave a crystalline osazone (melting at 183° to 185° C. ; Pavy gives
189° C.). This reducing substance he regards as a carbohydrate, though he
does not commit himself as to its identity. He, however, never found pen-
toses, nor did he find that the gastric digestion of egg albumin yielded any
carbohydrate. The same carbohydrate was obtained from acid albumin,
alkali albumin, albumose, peptone, fibrin, serum albumin, serum globulin,
and lact-albumin. Casein, vitellin, gelatin, and nucleo-proteid from peas
gave a negative result. Albumin from peas yielded an osazone rather

1 Ztsclir.f. physiol. Chem., Strassburg, Bd. xviii. S. 213. 2 Ibid. Bd. xv.

3 Arch.f. d. ges. Physiol., Bonn, Bd. xxxvi.

4 Ztschr. f. physiol. Chem., Strassburg, Bd. xix. S. 19.

5 CentralU.f. Physiol., Leipzig, Bd. vii. S. 581.

6 Arch.f. d. ges. Physiol., Bonn, 1896, Bd. Ixv. S. 281.

THE NUCLEINS. 65

different in its characters from the one just described. H. Weydemann1 has
also confirmed Pavy's work; he considers that the material in the proteid
that yields the reducing substance is identical with Landwehr's animal gum.

The nucleins. — Lander Brunton2 described the nuclei of the red
corpuscles of birds as consisting of a mucin-like substance. Plosz,3
however, found that, though the material in question resembled mucin
in its solubility in alkalis, and precipitability by acids, it was not mucin,
as it contains a high percentage of phosphorus. About the same time
Miescher 4 separated a similar phosphorus-rich substance from the nuclei
of pus corpuscles ; the pus was subjected to gastric digestion, and the
nuclein alone remained undissolvecl. Later, Miescher 5 prepared a similar
substance from the spermatozoa of different animals, and from egg-yolk ;
Hoppe-Seyler,6 Kossel,7 and Loew8 from yeast, Plosz9 from the liver,
Jaksch 10 and Geoghegan11 from brain, Lubavin 12 from cows' milk, and
Worm-Miiller 13 from egg-yolk.

It was soon surmised that nuclein is not a single substance, because
the different nucleins vary in their solubilities, and even in their compo-
sition. Miescher's nuclein from spermatozoa, for instance, contained no
sulphur. Of recent years our knowledge of the nucleins has been con-
siderably advanced by Kossel,14 Liebermann, and others.

It has long been known that metaphosphoric acid is a precipitant
of albumin. Liebermann 15 examined this precipitate and found that it
gave many of the reactions of nuclein. He therefore came to the con-
clusion that nuclein is simply a compound of albumin with phosphoric
acid. Malfatti 16 carried this idea still further, for he found that, by
fractional precipitation with different amounts of phosphoric acid, he
was able to obtain a chain of nucleins with different amounts of
phosphorus in each, and with varying solubilities, corresponding closely
with those obtainable from nuclei.

Pohl,17 however, very soon showed that Liebermann's precipitate
differs from true nuclein (i.e. the nuclein from nuclei) in the fact that
substances of the xanthine group are not obtainable from it on
decomposition, and Kossel18 has contested Liebermann's and Malfatti's
views chiefly on the same grounds.

Kossel divides the nucleins into two groups. The first is that of
the true nucleins. These are obtainable from nuclei ; they yield on
decomposition the xanthine bases — hypoxanthine, aclenine, and other sub-
stances of the same group. The second class of nucleins may be called
pseudo-nucleins, and include those obtainable from milk, egg-yolk,

1 Inaug. Diss., Marburg. 1896 ; Centralbl. f. Physiol., Leipzig, 1897, Bd. x. S. 749.

3 Journ. Anat. and Physiol., London, 2nd series, vol. iii. p. 91.

3 Hoppe-Seyler, "Mod! Ohem. Untersuch. , " 1871, Heft 4, S. 460. 4 Ibid., S. 441.

5 Verhandl. d. naturf. Gesellsch. in Basel, 1874, Heft i.

G "Med. Chem. Untersuch.," Bd. iv. S. 500.

7 Ztschr. f. physiol. Chem., Strassburg, Bde. iii. and iv.

8 Arch.f. d. gcs. Physiol. , Bonn, 1880, Bd. xxii. 9 Ibid., Bd. vii.

10 Ibid., Bd. xiii. u Ztschr. f. physiol. Chem., Strassburg, Bd. i.

12 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. x. S. 2237.

13 Arch.f. d. ges. Physiol., Bonn, 1873, Bd. viii. S. 190.

14 Zlschr.f. physiol. Chem., Strassburg. Numerous papers from Bd. viii. to present time.

15 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxi. S. 598.

16 Ber. d. naturw.-med. Ver. in Innsbruck, 1891-92, Bd. xx. ; Ztschr. f. physiol. Chem.,
Strassburg, Bd. xvi. S. 69 ; xvii. S. 8.

37 Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 292.

18 Verhandl. d. physiol. Gesellsch., Berlin, Oct. 21, 1892 (in Arch. f. Physiol., Leipzig,
1892).

VOL. I. — 5

66 CHEMICAL CONSTITUENTS OE BODY AND FOOD.

and Lieberiiiann's artificial imclein. Altinann1 showed that the
nitrogenous bases just alluded to originate from a complex organic acid,
which he termed nucleic acid, and that the true nucleins differ from one
another in the relative quantities of proteid and nucleic acid which they
contain. Nucleic acid is free from sulphur, and is in fact identical with
Miescher's imclein from spermatozoa. Miescher's formula for this
sulphur -free material was C29H49N9P3022. Kossel's is C30H32N9P3017.
More recent investigations by Miescher,2 which were not published
until quite recently (after his death), by Schmiedeberg, led him to adopt
the formula C40H54N14017(P206)2 for nucleic acid. He further considered
that in the spermatozoa, this acid is united to protamine. An exami-
nation of a preparation of nucleic acid, made from yeast by Altmann,
showed that here the formula was C40H50Ni6O22(l\Of>)2 (see further
under " Spermatozoa "). Nucleic a^id does not give the proteid reactions.
The relative amount of nucleic acid in different nucleins can be roughly
determined by micro-chemical reactions with aniline dyes, nucleic acid
having a great affinity for basic dyes like methyl-green.3

Hoppe-Seyler's classification of nucleins is the following : —

1. Nucleins like those found in spermatozoa, which contain no proteid,
but consist only of nucleic acid.

2. The true nucleins, those found in cell nuclei. They yield proteid,
xanthine or alloxuric bases (hypoxanthine, xanthine, guanine, adenine),
and phosphoric acid. Those richest in nucleic acid occur in the chro-
matic fibres of the nucleus ; poorer in nucleic acid are the nucleins which
occur in the nucleoli (e.g. pyrenin), and which constitute the chief bulk
of the substance called plastin by histologists ; these are comparatively
insoluble in alkalis. They form numerous links in a chain which passes
insensibly into the group of the nucleo-proteids.

3. The para-nucleins (or pseudo-nucleins) ; these are the nucleins
obtainable from nucleo-proteids (caseinogen, vitellin, cell nucleo-proteids).
They yield (like Liebermann's artificial nuclein) no nitrogenous bases,
but only proteid and phosphoric acid on boiling with water or dilute
acid. The nucleo-proteids of cell protoplasm can only be provisionally
included in this group; they contain so little nuclein, that even if
xanthine bases were obtained from these (and the point does riot seem
to have been thoroughly investigated yet) the small yield might escape
detection. The nucleo-proteid from muscle yields some of these bases
(see " Chemistry of Muscle ").

There are at least four nucleic acids. They are compounds of an acid with
various bases, such as adenine, hypoxanthine, guanine, and xanthine. They
differ in the amount and character of the bases, and in the acid with
which these bases are combined. That from the thymus is called adenylic
acid (from the fact that its chief base is adenine). This, when heated with
sulphuric acid, yields a crystalline substance called thyxnin4 (G6H6N2O2),
cytosine, ammonia, levulinic acid, formic acid, and phosphoric acid. The
yield of cytosine, a new crystalline base (C21H30N][604 + 5H20) amounts to
about 2 per cent, of the nucleic acid employed. The presence of levul-
inic acid among the products of decomposition is significant, and shows
that adenylic acid contains a carbohydrate group. This agrees with previous

1 Arch.f. PhysioL, Leipzig, 1889, S. 524. See also Kossel, ibid., 1891.
zArch.f. exper. Path. u. PhannakoL, Leipzig, 1896, Bd. xxxvii. S. 100.

3 For a criticism of these microchemical methods, see Heine, Ztschr. f. physiol. C/iem.,
Strassburg, Bd. xxi. S. 494.

4 Kossel and Neumann, Ber. d. deutscJi. chem. Gesellsch.. Berlin, Bd. xxvi. S. 2753.

THE NUCLEO-PROTEIDS. 67

researches of Kossel, who obtained a carbohydrate from the nucleic acid of
yeast.1

Kossel and Neumann 2 have further shown that adenylic acid yields also
a new acid called thymic acid, precipitable as a barium salt (C16H^N3P2012Ba).
The acid is readily soluble in cold water, and differs from nucleic acid in not
being precipitated by mineral acids.3

Kesearches such as these show how complicated the subject is, and
how much yet remains to be discovered, especially regarding the nuclein
acids. The nuclein bases are comparatively simple, and the principal
ones may be arranged in two groups : —

Adenine has the formula C5H5N5; on heating it with sulphuric acid,
Nil is replaced by 0, and hypoxanthine is formed : —

C5H4N4.NH + H20 = C0H4N40 + NH3

(adenine) (water) (hypoxanthine) (ammonia)

Both substances contain a radicle, C5H4N4, which Kossel terms adenyl ;
adenine is its imide, hypoxanthine its oxide. The following equation
shows a similar relationship between guanine and .xanthine : —

C5H4N4O.NH + H20 = C5H4N402 + NH3

(guanine) (water) (xanthine) (ammonia)

On comparing the formulae of hypoxanthine and xanthine with uric
acid (C5H4N403), we see their close relationship. Leaving aside other
possible ways in which uric acid is undoubtedly formed in the organism,
we have here a way in which uric acid may arise by oxidation
from the nuclein bases, and thus ultimately from the nuclei of cells.4
The name " alloxuric bases " for these substances was suggested by
Kriiger and Wulff.5 They are often spoken of as the " xanthine bases."

The nucleo-proteids. — These are compounds of nuclein with pro-
teids. The amount of proteid matter is large, and the substances in
question give the reactions of proteids, and in their solubilities approach
very nearly to the globulins. On gastric digestion the nuclein they con-
tain is left as an insoluble residue, but on pancreatic digestion a good
deal of the nuclein is dissolved, and presumably, when this occurs in the
body, is absorbed.6

Hammarsten divides the nucleo-proteids into two classes ; the first, to
which he restricts that name, yields true nuclein on gastric digestion ;
the other class he calls nucleo-albumins ; these yield pseudo-nuclein on
gastric digestion, and include caseinogen and vitellin. In addition to
these, there are the phospho-gluco-proteids, which have already been
described (p. 64).

Nucleo-proteids, using the term in the widest sense, are obtain-

1 Kossel and Neumann, JBer. d. deutscli. chem. Gesellsch., Berlin, Bd. xxvii. S. 2215.

2 Ztschr. f. pliysiol. Chem., Strassburg, Bd. xxii. S. 74.

a It was later obtained from spermatozoa nuclein (Kossel, ibid., p. 188). Milroy (ibid.,
1896, Bd. xxii. S. 307) states that the precipitate formed on adding nucleic acid to a solu-
tion of albumin resembles true nuclein in its characters ; whereas the precipitate produced
by thymic acid is somewhat similar to para-nuclein or pseudo-nuclein.

4 This subject has been specially taken up by Horbaczewski (Sitzungsb. d. k. Akad. d.
Wissensch,, Wien, Bd. c.), who has pointed out the close relationship between uric acid
formation and leucocytosis. Diet increases uric acid formation by leading to an increase
of leucocytes, or possibly, as some recent investigators think, the increase is chiefly due
to the nuclein in the food (Weintrand, Chem. Centr.-BL, Leipzig, 1895, Bd. ii. S. 54,
234, 310). See also Umber, Ztschr. f. klin. Med., Berlin, 1896, Bd. xxix. S. 174 ; Camerer,
Ztschr. f. BioL, Miinchen, 1896, Bd. xxxiii. S. 139.

5 Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xx. S. 176. .

6 Popoff, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 533 ; Gumlich, ibid., S. 508.

68 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

able from the nuclei and protoplasm of cells. They appear to be the
most abundant of the proteid materials obtainable from cells. Nucleo-
histon is the name of one of these separated from the thymus by Kossel
and Lilienfeld.1 The latter gives its percentage composition as
C, 4846; H, 7 ; N, 16-86; P, 3-025; S/0'7; 0, 23'95. The high
percentage of phosphorus given here has never been obtained by me,
from the numerous nucleo-proteids I have prepared and examined from
the thymus and other organs. Details of these will be given under the
heads of the various organs in question. In my own analyses, the
amount of phosphorus rarely has exceeded 1 per cent.

Nucleo-liiston appears to be identical with the tissue fibrinogen of
Wooldridge, but this included a variable amount of lecithin. Other
forms of the same substance have bsen called cytoglobin and preglobin by
A. Schmidt.2 Wooldridge prepared his tissue nbrinogens from cellular
structures, such as thymus and testis. The gland is finely minced and
extracted with water for twenty-four hours. Weak acetic acid is then added
to the decanted extract, and after some hours the precipitated nucleo-proteid
falls to the bottom of the vessel. This is the method used by Lilienfeld in
the manufacture of nucleo-histon. Another method, which I have largely
used, is to grind up the finely minced organ with about an equal volume of
sodium chloride in a mortar. The resulting viscous mass (originally called
hyaline substance by Eovida) is poured into excess of distilled water. The
nucleo-proteid rises in strings to the surface of the water, where it may be
skimmed off.

Prepared by either method, the nucleo-proteid may be dissolved in 1 per
cent, sodium carbonate solution. This solution injected intravascularly in
small doses in dogs produces a hindering of the coagulation of the blood
(Wooldridge's negative phase). In larger doses it produces intravascular
coagulation.3

The lecithin found associated with Wooldridge's tissue nbrinogens is
variable in quantity, and does not appear to be organically united to them.
After its removal the nucleo-proteids continue to exercise their most distinctive
physiological characteristic, in producing intravascular clotting.4

In connection with nucleins and nucleo-proteids, it should be men-
tioned that many of them contain iron, and, according to Bunge,5 con-
stitute in foods the normal supply of iron to the body ; in this sense he
has called them hsematogens. The composition of haernatogen from egg-
yolk he gives in percentages, which may be compared with the com-
position of nuclein from yeast, as follows : —

Haematogen. Nuclein from Yeast.

. C ... 42-11 40-81

H . . . 6-08 5-38

N 14-73 15-98

0 ... 31-05 31-26

S 0-55 0-38

P 5-19 6-19

Fe 0-29

1 Ztschr. f. pliysiol. Chem.. Strassburg, Bde. xviii. and xx.

2 " Weitere Beitr. z. Blutlehre," Wiesbaden, 1895.

3 Details with reference to the influence of nucleo-proteids on blood coagulation are
given in the article dealing with that subject.

4 Halliburton and Brodie, Journ. Physiol., Cambridge and London, 1894, vol.
xvii. p. 135.

5 Ztschr. f. physiol. Chem., Strassburg, 1884, Bd. ix. S. 49.

THE ALBUMINOIDS. 69

If the iron is, as it appears to be, in organic union, the nucleins that
contain it must be among the most complex of known organic compounds,
consisting of seven elements.

The exact method in which the iron is combined is however, like the
constitution of nuclein, still unknown.

Zaleski l has succeeded in separating from the liver one of these iron-con-
taining nucleins, which he terms liepatin. The subject has been largely worked
by microchemical methods for the detection of iron ; and the terms " firmly
combined" and "loosely combined" iron are often used, according as the com-
pounds which contain that element give the reactions with difficulty or ease.
Macallum 2 finds that the chromatin of nuclei contains iron ; he regards
it as the mother substance of haemoglobin, both in embryological develop-
ment and during nutrition in extra-uterine life. He finds similar haematogens
in plants, as did also Bunge.

Lecith - albumins. — Liebermann3 has given the name lecith-albu-
mins to certain compounds of lecithin and proteid which he obtained from
the kidney, gastric mucous membrane, lungs, spleen, and liver. The
lecithin is not removable from these compounds by simple extraction
with alcohol and ether. These, however, can hardly be considered to
be immediate constituents of the cells, as they are obtained after sub-
jecting them to a very severe process, namely, artificial gastric digestion.
They yield no phosphoric acid and no xanthine bases on decomposition.
According to their discoverer, they play an important part (in virtue of
the acidity which they possess in common with nuclein compounds) in
the separation of the hydrochloric acid of the gastric juice, and in decom-
posing the alkaline salts of the blood plasma, so as to yield the acid
salts of the urine. Much more extended investigations are needed,
however, before important functions like these can be safely attributed
to them.

We have already seen that vitellin is a proteid which by some is
regarded as a globulin, by others as a nucleo-proteid. Hoppe-Seyler 4 was
inclined to regard the phosphorus found in it as due to a combination
with lecithin, whereas Hammarsten looks upon some forms of vitellin as
phospho-gluco-proteids. No doubt, vitellin is a name which covers a
number of different substances; the substance Hoppe-Seyler worked
with contained as much as 25 per cent, of lecithin. In those cases
where the phosphorus is present as a nuclein, the nuclein obtained by
gastric digestion is of the pseudo-nuclem variety.

THE ALBUMINOIDS.

The albuminoids form a heterogeneous group of substances allied to
the proteids, but differing from them by certain marked characteristics.
As a rule, they are found in skeletal and epidermal structures, and
usually they are remarkable for their resistance to reagents. They

1 Ztschr. f. physiol. Chem., Strassburg, Bd. x. S. 453 ; xiv. S. 274 ; Chem. Centr.-BL,
Leipzig, 1888, S. 759. See also Quincke, Deutsches Arch. f. klin. Med., Leipzig, Bd. xxv.
S. 567 ; xxvii. S. 202 ; xxxiii. S. 23 ; Peters, ibid., Bd. xxxii. S. 182.

'2 Macallum's most recent papers are in Journ. Physiol. , Cambridge and London, 1894,
vol. xvi. p. 268 ; Proc. Roy. Soc. London, 1895, vol. Ivii. p. 261 ; 1. 277 ; Quart. Journ.
Mic/r. Sc., London, 1896, vol. xxxviii. p. 175 ; Rep. Brit. Assoc. Adv. Sc., London, 1896.

3 Arch.f. d. ges. Physiol., Bonn, Bde. 1. and liv.
"Med. chem, Untersuch.," 1868; Ztscltr. f. physiol. Chem., Strassburg, Bd, xiii. S,

70 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

include keratin, elastin, collagen, gelatin, reticulin, amyloid substance,
and a group of materials called skeletins.

Collagen. — Collagen is the mother substance of gelatin. It is the
material of which the white fibres of connective tissue are made, and is
the principal constituent of which the organic substratum of bone is
composed; it is there called ossein. In cartilage the material 'called
chondrigen is collagen mixed with the mucinoid materials of the carti-
laginous matrix. Collagen has also been obtained from the flesh of
cephalopods.1

By boiling with water, especially if it is faintly acidified, collagen is
converted into gelatin ; and gelatin is reconverted into collagen by
heating it to 130° C. Hence collagen is regarded as the anhydride of
gelatin (Hofmeister) ; 2 the reaction* may be represented by the equation—

CK.HU.N.A.-H, o = c10.2H110N31o28

(gelatin) (collagen)

The above formulae, however, cannot be regarded as more than provisional,
for we are as ignorant of the molecular constitution of the albuminoids
as of the proteids. Schiitzenberger attributes the formula C70H124]Sr34029
to gelatin, and regards the sulphur described by other investigators as
due to admixture with proteid impurities. Hainmarsten,8 on the other
hand, regards the sulphur, of which there is 0*6 per cent., as an integral
part of collagen and gelatin.

Collagen is insoluble in water, alcohol, salt solutions, and dilute acids,
and alkalis. It swells with dilute acids. Its decomposition products
are the same as those of gelatin.

Gelatin. — Gelatin is a colourless, amorphous, and translucent sub-
stance ; it swells but does not dissolve in cold water ; it readily dissolves
in hot water, and on cooling the solution, if its concentration is greater
than 1 per cent., it sets into a jelly. It contains a considerable amount
of ash, the removal of which lessens its power of gelatinising.4

Gelatin is precipitated by saturating its solution with neutral salts,
like magnesium sulphate and ammonium sulphate.5 This is also true for
gelatin which has been altered by the action of hot water so as to be no
longer or only partially gelatinisable.

Gelatin is not precipitated by acetic acid, nor by acetic acid and ferro-
cyanide of potassium, nor by most of the heavy metallic salts that precipi-
tate proteids. It gives a violet colour with copper sulphate and caustic
potash ; it gives Millon's reaction, but only a faint xanthoproteic reaction.6

It is precipitated by mercuric chloride, and also, as in the process of
tanning, by tannic acid. Gelatin is levorotatory.7

Derivatives of gelatin. — The prolonged action (twenty-four hours) of
boiling water, or the shorter action of water heated above the boiling
point, destroys the gelatinising power of gelatin. Gelatin, in fact, under-
goes hydrolysis, being converted into the so-called gelatin peptones.
Similar substances are formed during digestion. Hofmeister distinguished

1 Hoppe-Seyler, "Physiol. Clieni.," S. 97.

2 Ztschr. f. physiol. Chem., Strassburg, Bd. ii. S. 315.

3 " Physiol. Chem.," 3rd German edition, S. 46. Analyses of gelatin were made in addi-
tion to those quoted above by Mulder, Ann. d. Chem., Leipzig, Bd. xlv. ; Fremy, Jahresb.
d. Chem., 1854 ; and Paal, Ber. d. deutsch. diem. Gescllsch., Berlin, Bd. x'xv. S. 1208.

4 Nasse and Kriiger, Jahresb. n. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xix. S. 29.

5 Nasse, Arch. f. d. ges. Physiol., Bonn, Bd. xli. S. 504.

6 Salkowski, Ztschr. f. physiol. Chem., Strassburg. Bd. xii. S. 215 ; Berl. Tclin. Wchnschr.,
1885, No. 2.

7 Hoppe-Seyler gives («)p= - 130°at 30°C, Nasseand Kriiger give («)p= - 136°t<s - 167 '5°,

THE ALBUMINOIDS. 71

two of these substances, which he named semiglutin and hemicollin.
Chittenden and Solley l distinguish between proto- and deuterogelatose,
and true gelatin-peptone. Paal2 has obtained similar substances by the
use of hydrochloric acid. By the use of Eaoult's method, he gives the
molecular weight of gelatin as 878 to 960, and of gelatin-peptone as 352.

Strong reagents like sulphuric acid, on putrefaction, decompose
gelatin with the formation of glycocine,3 leucine, various fatty acids,
glutaminic acid, carbon dioxide and ammonia. The absence of tyrosine
should be noted. Schiitzenberger,4 who has worked with gelatin by the
same methods as he used with proteids, considers that gelatin, like
proteid, is a compound of urea with certain amido-acids.

The importance of gelatin as a proteid-sparing food, though it will
not replace proteid entirely in a diet, will be considered under " Nutrition."

Chondrin is the name given to the impure gelatin obtained from
cartilage (which see).

Elastin. — Elastin is a material yielded by the yellow fibres of con-
nective tissue. It offers great resistance to reagents, and may be pre-
pared from the ligamentum nuchse by extracting the finely divided
tissue successively with reagents in which it is insoluble, and in which
adherent fatty, collagenous, and proteid matters dissolve (boiling water,
1 per cent, potassium hydroxide, 5 per cent, hydrochloric acid, alcohol
and ether). By this means a substance free from sulphur is obtained.
Chittenden and Hart,5 in some of their preparations, omitted the
extraction with potash, and in these a small percentage of sulphur (0*3)
was obtained ; this may be due to proteid impurities, or it may be loosely
combined in the elastin molecule. Schwartz 6 has also prepared a sulphur-
containing elastin from the aorta.

The following table shows the results of elementary analyses in per-

M tiller. 7

Tilanus.8

Horbaczewski.9

Chittenden
and Hart.

Schwartz.

c .

55-09-557

54-9-55-65

54-32

54-24

53-95

H .

7-11-7-67

7-25-7-41

6-99

7-27

7-03

N .

15-71-16-52

17-52-17-74

16-75

16-7

16-67

0 .

20-7-21-15

19-5-20-33

21-94

21-69

21-97

s .

.

0-3

0-38

Derivatives of elastin. — Elastin is gradually and slowly dissolved by

1 Journ. PhysioL, Cambridge and London, vol. xii. p. 25.

2 Ber. d. deutsch. chem. Gescllsch., Berlin, Bd. xxv.

3 On the preparation and estimation of glycocine from gelatin, see C. S. Fischer, Ztsdw.
/. physiol. Chem., Strassburg, Bd. xix. S. 164; and Gonnermann, Arch. f. d. ges.

PhysioL, Bonn, Bd. lix. S. 42.

4 Compt. rend. Acad. d. sc., Paris, tome cii. p. 1296. See also Buclmer and Curtius,
Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xix. S. 850.

3 Ztschr. f. BioL, Miinchen, Bd. xxv. S. 368 ; Stud. Lab. PhysioL Chem., New Haven,
vol. iii. p. 19.

(i Ztsdir. f. physiol. Chem., Strassburg, Bd. xviii.

7 Ztschr. f. rat. Med., Leipzig, Dritte Reihe, Bd. x. pt. 2.

8 Gorup-Besanez, "PhysioL Chem.," Aurl. 3, S. 148.

9 Ztschr. f. pliysiol. Chem., Strassburg, Bil. vi. S. 330.

72 CHEMICAL CONSTITUENTS OF BOD Y AND FOOD.

pepsin or trypsin.1 Horbaczewski named the two products of digestion he
obtained, hemielastin and elastin-peptone. Chittendeii and Hart, using
Kiihne's methods and nomenclature, have shown that hemielastin is
protoelastose, and elastin-peptone is deuteroelastose.

On more complete decomposition elastin yields products very like those
obtained from proteids, except that glycocine is obtained, but no aspartic
or glutamic acid, and very little tyrosine.2 Lysatinine but no lysine was
obtained.3 By fusing with potash, indol, skatol, phenol, benzene, but no
methylmercaptan, were yielded (Schwartz).

Reticidin. — The fibres of reticular tissue, though histologically not
distinguishable from those of areolar tissue, were first stated to be
chemically different from them by Mall.4 He asserted that no gelatin
was obtainable from them, a statement corrected by R. A. Young,5
and subsequently by Siegfried.6 Siegfried, however, confirmed Mail's
idea that the fibres contained something special, and separated from
them a material he called reticulin. Eeticulin has the following per-
centage composition :—C, 52-88 ; H, 6*97 ; N, 15-63; S, 1-88; P, 0'34;
ash, 2*27. By decomposition it yields sulphuretted hydrogen, ammonia,
lysine, lysatinine, and amidovaleriaiiic acid, but no tyrosine and no glu-
taminic acid. It gives the proteid reactions with the exception of Millon's.

Siegfried prepared reticulin from the mucous membrane of the
intestine by digestion with trypsin and alkali. The residue was washed
and extracted with ether, again subjected to tryptic digestion, and
extracted with alcohol and ether ; the collagen was removed by hot water.

If glutaminic acid is absent, as Siegfried states, from the decomposi-
tion products of reticulin, and it is certainly very abundant in the
decomposition products of collagen and gelatin, there is distinct evidence
that reticulin is a new material.

We are therefore confronted with the difficulty, that the fibres of
reticular tissue are anatomically continuous with and histologically
identical with the white fibres of connective tissue, and yet they con-
tain chemically this new material. The answer to the problem is pro-
bably that reticulin is not specially characteristic of reticular fibres,
but is present in all white connective tissue fibres.

Keratin. — Keratin is the horny material of which the horny layer of
the epidermis, hair, wool, nails, hoofs, horns, feathers, etc., are composed.

It is prepared by successively boiling the tissue with ether, alcohol,
water, and dilute acid ; the insoluble residue is keratin. A variety of
keratin called neurokeratin is found in neuroglia, and has also been
described in the medullary sheath of nerve fibres ; though here no doubt
some of the histological appearances described maybe artificially pro-
duced by reagents. It resembles keratin in its general properties, but
is less easily soluble in boiling solutions of caustic potash.7

1 Ktihne and Ewald, "Die Verdauung als histol. Metbode," Verliandl. d. naturh.-med.
Ver. zu Heidelberg, 1877, N. F., Bd. i. S. 451; Etzinger, Ztschr. f. Biol., Miinchen, Bd. x.
S. 84 ; Horbaczewski, loc. cit. ; Morochewetz, Jahr&sb. il. d. Fortsclir. d. Thier-Chem., Wies-
baden, 1886, S. 271 ; Chittenden and Hart, loc. cit.

2 Drechsel, Ladenburg's " Handworterbuch, " Bd. hi.; see also Horbaczewski, Monatsh.
d. Chem., Wien, Bd. vi.

3 See, however, Hediri's recent work referred to on p. 33 of tbis article.

4 Anat. Anz., Jena, 1888, Bd. iii. No. 14; Abhandl. d. math.-phys. Cl. d. k. sacks.
Gesellsch. d. Wissensch., 1887, Bd. xiv. No. 3 ; xvii. No. 14.

5 Journ. Physiol., Cambridge and London, vol. xiii. p. 332.

6 " Habilitationschrift," Leipzig, 1892.

7 Ewald and Kiihne, Verliandl. d. naturh.-med. Ver. zn Heidelberg, N. F., Bd. i.
Heft 5 ; Kiihne and Chittenden, Ztschr. f. Eiol., Miinchen, Bd. xxvi. S. 291.

THE ALBUMINOIDS.

73

The following are some elementary analyses that have been made of
keratin from different sources : —

TISSUE .

ANALYST

From Hair.
V. Laar.i

Nail.
Mulder.2

Neurokeratin.
Kuhne.3

Horn.
Horbaczewski.4

c .

50-60

51-00

56-1-58-4

50-86

H .

6-36

6-94

7-2-8-0

6-94

N .

17-14

17-51

11-5-14-3

0 .

20-85

21-75

s

5-00

2-80

1-6-2-2

3-30

The main feature in the above analyses is the high percentage of
sulphur,5 which is in part in loose combination, and can be removed by
alkalis or even by boiling water.

An albuminoid obtainable from tracheal cartilage by C. T. Mb'rner,0
and further investigated by Hedenius,7 is included by Hammarsten 8
among the keratins, or as a substance intermediate between keratin and
coagulated proteid. It contains only 1 per cent, of sulphur. Keratin
gives the proteid reactions.

Derivatives of keratin. — Keratin is not digestible by either gastric
or pancreatic juice. By heating with water to 150°-200° C. it dissolves,
forming a turbid solution. It dissolves more readily in alkalis ; the
solution contains alkaline sulphides, and substances of the proteose class,
called keratinoses by Krukenberg.9

The decomposition products of keratin obtained by the use of acids
are like those of the proteids, and include leucine, a good deal of tyrosine
(1-5 per cent.), aspartic acid,10 glutaminic acid,11 ammonia, and sul-
phuretted hydrogen, lysine,12 lysatinine,12 and a sulphur-containing sub-
stance 12 which forms a compound with hydrochloric acid, with the
formula C14H38N4012SC14. Drechsel 13 considers that some of the oxygen
of the keratin is united to sulphur, and a part to amido-acid radicles.

The close chemical relationship of keratin to proteid coincides with
what is known as to its formation within the protoplasm of cells, for
instance in the epidermis. The eleidin granules of the stratum granulosum
probably represent an intermediate stage in the transformation.

1 Ann. d. Ghem., Leipzig, Bd. xlv.
" Versuch. einer allgem. physiol. Chem.," Braunschweig, 1844-51.

3 Kiiline and Chittenden, loc. cit.

4 See Drechsel, Ladenbnrg's "Handworterbuch," Bd. iii. Other analyses of horn have
been made by Tilanus, Hoppe-Seyler's "Physiol. Chem.," S. 90 ; Liiulvall, Jahresb. u. d.
Fortschr. d. Thier-Chem., Wiesbaden, 1881.

5 A large number of estimations of sulphur in keratins from different sources will be
found in a paper by Mohr, Ztschr. f. physiol. Chem., Strassburg, 1895, Bd. xx. S.-403.
The percentage varies from 2'6 to 5'3. During (ibid., 1896, Bd. xxii. S. 281) obtained very
similar results.

6 Jahresb. il. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xviii. S. 217.

7 Skandin. Arch. f. Physiol., Leipzig, Bd. iii.

8 "Physiol. Chem.," 3rd German edition. S. 44.

9 Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Naturu:, 1886.

10 Kreusler, Journ. f. prakt. Chem., Leipzig, Bd. cvii.

11 Horbaczewski, Sitzungsb. d. k. Akad. d. Wissensch., Wien, Bd. Ixxx.

13 Hedin, Jahresb. il. d.' Fortschr. d. Thier-Chem., W7iesbaden, 1893, Bd. xxii.
13 Loc. cit.

74 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

Amyloid Substance. — This material, also called lardacein, occurs in
disease in the form of degeneration, called waxy, albuminoid, amyloid, or
lardaceous. It principally affects small blood vessels, but it may involve
the tissue elements of organs. The degeneration occurs specially in
cases of chronic pus formation, and is frequently a sequela of syphilis.
The name amyloid was given to it, because the substance is coloured
brownish red by iodine, and was supposed by Virchow to be of
carbohydrate nature. Friedrich and Kekule1 were the first to show
that it is nitrogenous, and gave as its percentage composition, 0, 53*6 ;
H, 7 ; N, 15 ; O, 244. It also contains 1*3 per cent, of sulphur.2
On decomposition it yields leucine, tyrosine, and the other products
usually obtained from albuminous matter, but no sugar or other
reducing substance. By boiling with alkali a chitin-like residue is left.3
It is slowly soluble in gastric juice.4

Skeletins. — This term is applied by Krukenberg6 to a number of
nitrogenous substances found in the skeletal tissues of invertebrates.
They are characterised by great insolubility, and are probably all
amido-derivatives of carbohydrates. Under the term are included
chitin, conchiolin, spongin, cornein, fibroin, and sericin.

Chitin. — This substance forms the chief constituent of the ectodermal
skeletal tissues of invertebrate animals, especially of arthropods.6 In
Crustacea it is often impregnated with calcareous matter, and in the
odontophore of molluscs with silica. According to Krawkow,7 it is in
union with a proteid-like substance. Gibson,8 Winterstein,9 and
Escombe10 have found chitin instead of cellulose in several fungi.

It is prepared from the wing-cases of beetles by boiling them with
caustic soda. The chitin remains insoluble ; it may be dissolved in cold
concentrated hydrochloric acid, and precipitated unchanged from this
solution by the addition of water. It is colourless, amorphous, insoluble
in water, alcohol, ether, acetic acid, dilute mineral acids, and concen-
trated solutions of the alkalis. It is soluble in concentrated mineral acids.

The formula and constitution of chitin are differently given by
different observers. Ledderhose n gave it the formula C1;VH26N2010.
Berthelot 12 stated that it yields a fermentable sugar on boiling with
sulphuric acid. Sundwik 13 gave it the formula C(i0H100N8038 + ?iH20
(n varying from 1 to 4), and considered it to be an amine derivative of
a carbohydrate with the formula (C12H20010)n. Krawkow 14 considers

I Virchow's Archiv, Bd. xvi. S. 58. 2 Kithne and Rudneff, ibid., BJ. xxxiii.

3 Krawkow, Centralbl. f. d. med. Wissensch., Berlin, 1892. The resemblance to chitin is
supported only by its behaviour to staining agents like iodine. There is no true chemical
resemblance between the two substances. Amyloid substance, for. instance, yields no gluco-
samine (Colin, Ztschr. f. pliysiol. Chem.. Strassburg, 1896, Bd. xxii. S. 153).

4 Kostiurin, Wien. med. Jahrb., 1886, S. 181. See also Tschermak, Ztschr. f. pliysiol.
Chem., Strassburg, 1895? Bd. xx. S. 343.

6 Ztschr. f. Biol., Miinchen, Bd. xxii. S. 241; " Grundziige einer vergl. Physiol. d.
thier. Gertistsubstanz," Heidelberg, 1885.

6 Gamgee ("Physiol. Chem.." vol. i. p. 299) gives a list of the situations where chitin
has been described or inferred to exist. To these must be added the pen of cuttle-fishes
(Krukenberg, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xviii. S. 989) ; and the cartilages
and other mesoblastic structures of the sepia and king crab (Halliburton, Proe. Roy. Soc.
London, vol. xxxviii. p. 75).

7 Ztschr. f. Biol., Miinchen, Bd. xxix. 8 Compt. rend. Acad. d. sc., Paris, tome oxx.
9 Ber. d. deutsch. chem. Gesellsch., Berlin, 1894 and 1895.

10 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 288.

II Ibid., Bd. ii. S. 213 ; iv. S. 139.

12 Compt. rend. Acad. d. sc., Paris, tome xlvii. p. 227.

13 Ztschr. f. physiol. Chem., Strassburg, Bd. v. 14 Loc. cit.

SKELETINS. 75

that there are a number of chitins, amine derivatives of different
carbohydrates (dextrose, glycogen, dextrin, etc.) ; they give different
colour reactions with iodine.1 Ledderhose 2 was the first to show that
the reducing substance obtained by the action of mineral acids in
chitin is not sugar but glucosamine (see p. 9). The equation re-
presenting its decomposition he gives as follows : —

2C15H20N2010 + 6H20 = 4C6H13NO5+ 3C2H402

(chitin) (water) (glucosamine) (acetic acid)

Glucosamine is an amido-derivative of glucose ; it forms crystalline
salts, of which the hydrochloride is readily prepared by boiling chitin
with hydrochloric acid ; this is soluble in water, and is dextrorotatory
(«)Dr=:-f700-G. The base is prepared by the action of baryta on the
sulphate. It is crystalline and not fermentable with yeast.

Schmiedeberg 3 looks upon chitin as an acetyl derivate of glucosamine,
and as he has also obtained the latter substance from the chondroitin-
sulphuric acid of cartilage, he regards it as indicating a connection
between the skeletal tissues of vertebrate and invertebrate animals.

By heating chitin with ten times its weight of caustic alkali at 180°,
Hoppe-Seyler and Araki4 obtained a substance which possesses the
original form of the pieces of chitin, but differs from chitin in being
very soluble in dilute acids such as acetic acid ; from such solutions it is
precipitable by alkalis. This substance is called chitosan, and its forma-
tion from chitin. is shown in the following equation : —

C18H30N2012+ 2H2O =CUH26N2010+2C2H402

(chitin) (water) (chitosan) (acetic acid)

Chitosan in dilute acetic acid is levorotatory ; («)D= - 17°'7 to 17°*9.
By heating it with acetic acid in sealed tubes to 135°, a substance
very like chitin is regenerated ; it, however, contains three, whereas
true chitin only contains two acetyl groups.

By boiling with concentrated hydrochloric acid, chitosan yields
hydrochloride of glucosamine, formic and acetic acids.

Neurocliitin. — In Crustacea, chitin has been said to take the, place of neuro-
keratin as a support to the nerve fibres.5

Concliiolin (C30H48N9On) forms the organic basis of the shells of mussels
and snails. On decomposition it yields leucine, perhaps glycociiie, but no
tyrosine or reducing substance. It does not give the xanthoproteic, Millon's,
nor the Adamkiewicz reactions. The byssus of molluscs is similar. The
cementing substance between the eggs of various molluscs contains a substance
more like keratin. Cornein, from corals (C80H44]Sr9033), differs from conchiolin
by giving a red colour with Millon's test ; on decomposition it yields leucine
and a crystalline material called cornicrystallin.

Spojigin, the organic basis of the common sponge, yields as decomposition
products, leucine and glycocine (Stadeler), but no tyrosine.6 It does not give
the colour reactions just mentioned ; it resembles conchiolin by yielding

1 E. Zander (Arch. f. d. ges. PhysioL, Bonn, 1897, Bd. Ixvi. S. 545) also finds that
chitin gives a colour with iodine very like that given by glycogen.

2 Ztschr.f. physiol. Chem., Strassburg, Bd. ii. S. 213 ; iv. S. 137.

3 Arch. f. exper. Path. u. PharmakoL, Leipzig, Bd. xxviii.

4 Bar. d. deutsch. chem. Gesellsch., Berlin, 1894, Bd. xxvii. S. 3329 ; 1895, Bd. xxviii. S.
82 ; Zfschr. f. phijsiol. Chem., Strassburg, 1895, Bd. xx. S. 498.

5 Griffiths, Compt. rend. Acad. d. sc., Paris, tome cxv,

<; Zalocostas (ibid., tome cvii. p. 252), however, obtained tyrosine, butalanine, and
glucalanine (C0H18N804).

76 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

peptone-like materials on digestion, which differ from true peptones and
proteoses by not giving the colour reactions in question.

Fibroin is the substance of which spiders' webs are composed. It
is insoluble except in concentrated mineral acids and alkalis. It yields on
decomposition glycocine, leucine, and tyrosine, and gives the proteid colour
reactions. This substance and sericin, a similar material (which, however,
gives no glycocine on decomposition), are found together in silk.1 Hammarsten '2
gives the following table of percentage compositions : —

C

H

N

S

0

Conchiolin .
Spongin

50-92
46-5

48-75

6-88
6-3
6-35

17-86
16-2
16-4

0-31
0-5

24-34
27-5

Krukenberg.3
Crookewitt.4
Possell.5

Cornein
Fibroin

48-96
48-23

5-9
6-27

16-84
18-31

...

28<33
27-19

Krukenberg.
Cramer.6

JJ

Sericin

48-3
44-32

6-5
6-18

19-20
18-30

26-0
30-2

Vignon.7
Cramer.

INORGANIC COMPOUNDS.

Water forms about 5 8 -5 per cent, of the weight of the body ;
in infants it is 664 per cent. An adult takes in food 2,500 c.c. of
water daily, and excretes rather more, as some is formed in the body
by the oxidation of hydrogen.

Hydrogen peroxide is stated by "Wiirster 8 to be given off in various
situations ; he uses tetramethyl-paraphenylenediamine papers to detect
it.

Hydrogen sulphide occurs in small quantities as the result of putre-
factive changes in the alimentary canal.

Ammonia is also formed in putrefactive processes, and in pancreatic
digestion. A small quantity occurs in fresh urine, and increases when
the urine putrefies.

Hydrochloric acid occurs in gastric juice.

Carlonic acid occurs in the blood, lymph, and secretions.

The acids found in the body are, however, usually in combination as
salts.

Salts. — The chief salts found are the chlorides of sodium and potassium,
the sulphates of the same metals, phosphates of sodium, potassium,
calcium, and magnesium, carbonates of sodium and calcium. Bone,
dentine, and enamel are chiefly rich in calcium salts, especially the
phosphate. Other solid tissues are especially rich in potassium salts.
In the fluids (milk excepted) the most abundant salt is sodium chloride.

A fuller consideration of the various saline constituents will be taken with
the individual tissues and secretions. The following general tables may be,
however, quoted here ; 9 the figures give percentage quantities of mineral
matters in the ash : —

1 Weyl, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxi. S. 1407, 1529.

2 " Physiol. Chem.." 3rd German edition, S. 49.

3 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xvii.

4 Ann. d. Chem., Leipzig, Bd. xlviii. 5 Ibid., Bd. xlv.
0 Journ. f. prakt. Chem., Leipzig, Bd. xcvi.

7 Compl. rend. Acad. d. sc., Paris, tome cxv.

8 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xix. S. 3195 ; xx. S. 263, 1033.

9 From Beaunis, " Physiologic humaine."

INORGANIC COMPOUNDS,

77

TISSUE .
ANALYST

Bone.
Heintz.

Calf-musclos.
Staffel.

Brain.
Breed.

Liver.
Oidtmann

Lungs.
C. Schmidt.

Spleen.
Oidtmann.

Sodium chloride .

10-59

474

13-0

Soda .

2-35

10-69

14-51

19-5

44-33

Potash

34-40

34-42

25-23

1-3

9'60

Lime .

37-58

1-99

0-72

3-61

1-9

7-48

Magnesia . . 1'22

1-45

1-23

0-20

1-9

0-49

Ferric oxide

274

3-2

7-28

Chlorine

2-58

0'54

Fluorine

1-66

Phosphoric acid .

53-31

48-13

48-17

5018

48:5

27- 10

Sulphuric acid .

...

0-75

0-92

1-4

2-54

Carbonic acid

5:47

Silicic acid .

...

0-81

0-12

6 '-27

017

FLUID .

Blood.

Serum.

Blood-
clot.

Lymph.

Urine.

Milk.

Bile.

Excre-
ments.

ANALYST

Verdeil.

Weber.

Weber.

Dahn-
hardt.

Porter.

Wilden-
stein.

Rose.

Porter.

Sodium chloride

58-81

72-88

17'36

74-48

67-26

1073

27-70

4-33

Potassium , ,

29-87

...

26-33

Soda .

415

12-93

3-55

10-35

l"-33

36:73

5 '-07

Potash

11-97

2-95

22-36

3-25

13-64

21-44

4-80

610

Lime .

1-76

2-28

2-58

0-97

1-15

18-78

1-43

26-40

Magnesia .

1-12

0-27

0-53

0-26

1-34

0-87

0-53

10-54

Ferric oxide

8-37

0-26

10-43

0-05

o-io

0-23

2-50

Phosphoric acid .

10-23

1-73

10-64

1-09

11-21

19-00

10-45

36-03

Sulphuric acid .

1-67

210

0-09

2-64

6-39

Carbonic acid

1-19

4-40

217

» 8-20

11-26

...

Silicic acid .

0-20

0-42

0'42

4-06

0-36

313

Sodium and potassium salts. — Probably 200 grins, may be taken
as an average amount of sodium chloride (common salt) in the adult
human body. It is a most important food, and about 16 grms. are
daily excreted in the urine,1 and smaller amounts in the sweat and
faeces. If potassium chloride be substituted in the food for the sodium
salt, disturbances arise from deficiency of the latter. The tissues, how-
ever, retain common salt very tenaciously, so that during a dietary
devoid of salt it disappears slowly from the urine.

During its passage through the body, it facilitates the absorption of
proteid food, and increases tissue metabolism. The following table 2 gives
the probable relative amounts of sodium and potassium chlorides in
parts per thousand : —

Blood

Blood corpuscles

Plasma

Lymph

Chyle

Pancreatic juice
(from perman-
ent fistula)

NaCl

KC1

NaCl

KC1

2-70

2-05

Pancreatic juice

3-67

(from tempo-

5-54

0-35

rary fistula)

7-35

0-02

5-67

Gastric juice

1-45

0-55

5-84

Bile

5-33

0-28

Milk .

0-87

2-13

Urine

11-00

4-50

2-50 0-93

Bunge found that the soda salts are more abundant in embryonic

1 Vierordt's " Daten u. Tabellen," 1893, Aufl. 2, S. 122.

2 From M'Kendrick's "Text-book of Physiology, " Glasgow, 1888, vol. i. p. 39.

78 CHEMICAL CONSTITUENTS OF BODY AND FOOD.

and early life than in adult life. This is illustrated by the following
table : —

Na20 K20 1 Na,0 K20

Babbit's embryo . 2'183 2 '605

Babbit 14 days old 1-630 2'967

Kitten 1 day „ 2'666 2-691

Cat 19 davs 2'285 2'790

Cat 29 days old 2-292 2'684
Dog 4 „ „ 2-589 2-G67
Adult mouse . 1-700 3-280

This fact is probably due to the larger amount of cartilage (rich in
soda salts) and the smaller amount of muscle (rich in potash salts) in
early life as compared with the adult condition.1

Various phosphates of sodium and potassium are found in the blood,
lymph, urine, and other secretions.

Sodium carbonate and bicarbonate occur in the food, and originate
in the body from the salts of vegetable acids (tartaric, citric, etc.).

Sodium and potassium sulphate exist in smaller quantities in the
body. Only minute quantities of these salts are introduced with the
food; they are chiefly formed by the oxidation of proteids and other
organic substances containing sulphur.

Ammonium salts. — Minute traces of ammonium chloride are found in
the urine. The urine of reptiles and birds is largely composed of
ammonium urate. Small quantities of this salt, and also of ammonio-
magnesic phosphate, are found in human urine. Ammonium carbonate
is formed from urea in decomposing urine.

Calcium salts. — About three-quarters of the total mineral solids in
the body consist of calcium phosphate, Ca.,(l)04)., ; this is because of the
great preponderance of this salt in bone. Other calcium salts occurring
in bone, dentine, and enamel are the carbonate, sulphate, and fluoride.
Calcium phosphate, urate, and oxalate, are found in the urine. Most
tissues contain small quantities of the phosphate and carbonate. Egg
shells, the shells of Crustacea, coral, and otoliths consist chiefly of
carbonate of lime.2

Magnesium salts. — Magnesium phosphate (Mg3(P04)2) occurs in the
tissues along with the calcium phosphates (Ca3(P04)2 and CaH4(P04)2)
but in smaller amount. It occurs also in the urine. Ammonio-magnesium
or triple phosphate (NH4MgP04+6H20) is also often found in decom-
posing urine. Magnesium palmitate and stearate are found in the faeces.

Iron is an important constituent of the blood pigment. The blood
of an adult contains 3 grms. of iron. Small quantities are found in
other liquids of the body (chyle, lymph, bile, milk, urine, gastric juice) ;
it is also contained in the black pigment of the skin and hair, and of
melanotic sarcomata. A small quantity of ferric sulphide is found in
the faeces, and small quantities of iron are found in both liver and
spleen.3 It is present in the tissues in organic combination with nuclein
(see p. 68).

Copper is found in two proximate principles, hsemocyanin, the blue pig-
ment of the blood of many invertebrates (crustacea, cuttle-fishes, scorpions,
etc.), and in the pigment, turacin, of birds' feathers. Small quantities of this
metal, and also of aluminium, manganese and lead, may occur accidentally in

1 Bunge, Ztschr. f. physiol. Cftem., Strassburg, Bd. xiii. S. 399.

2 On excretion and absorption of lime see Rey, Chem. Centr.-EL, Leipzig, 1895, Bd. ii.
S. 55, 837.

8 For data concerning the amount of iron in foods, see Stockman, Journ. Physiol.,
Cambridge and London, 1895, vol. xviii. p. 484 ; 1897, vol. xxi. p. 55. An ordinary
daily diet contains 9-10 mgrms. of iron.

INORGANIC COMPOUNDS. 79

other parts, being taken in with the food,1 and not excreted at once with the
faeces, but deposited in some tissue or organ. Drugs and poisons (mercury,
arsenic) may be similarly deposited.

Silica. — A minute quantity of silica exists in the blood, urine, bones,
hair, and other parts.

Phosphates. — The amount of phosphoric acid given in analyses of
the ash of animal structures is not always correct, since a certain
quantity is obtained during the process of incineration, from the decom-
position of organic compounds, which, like lecithin, contain phosphorus.

The phosphoric acid which occurs in mineral compounds in the body
is derived in part directly from the food, and in part from the metabolism
of lecithin and nuclein. It unites with soda, potash, lime, and magnesia
to form the various phosphates already alluded to. An adult man
eliminates by the kidneys 2 '5 to 3 '5 grins, of phosphoric acid daily.
Carnivora eliminate phosphates chiefly by the kidneys, herbivora chiefly
with the faeces.

Carbonates. — The presence of carbonates in the ash of animal matters
is partly derived from the decomposition of organic compounds.
Alkaline carbonates and bicarbonates are, however, found in blood,
urine, lymph, saliva, etc.

Sulphates. — These also may be partly formed during the process of
incineration, from proteids and other organic compounds containing
sulphur. The sulphuric acid in the urine is in part combined as ordinary
sulphates, in part as ethereal sulphates. It is derived to a small extent
from the food, but chiefly from the metabolism of proteids, the amounts
of sulphuric acid and urea in the urine running parallel.

1 Karl B. Lehmann (Arch. f. Hyg., Miinclien u. Leipzig, Bd. xxiv. S. 1, 18, 72)
states that in an ordinary diet we take 20 mgrms. of copper daily, and if preserves are much
used, it may rise to over 300 mgrms. per diem ; more than 120 mgrms. appears to be harmful.

THE CHEMISTRY OF THE TISSUES AND ORGANS.
By W. D. MALLIBUHTON.

CONTENTS. — Cells and Protoplasm, p. 80 ; Liver, p. 85 ; Spleen, p. 87 ; Thyinus,
p. 88 ; Thyroid, p. 88 ; Suprarenals, p. 90 ; Pancreas, p. 92 ; Kidneys, p.
92 ; Testis, p. 92 ; Muscle, p. 95 ; Skeletal Tissues, p. Ill ; Nervous Tissues,
p. 115 ; The Eye, p. 121 ; Milk, p. 125.

THE preceding article contains an account of the principal proximate
principles occurring in the body and in food.

In the present article I propose to present the subject from another
standpoint, and to discuss the chemical composition of the various
animal tissues and organs. This will in great measure be complemented
to what has been already done, and will give the opportunity of describ-
ing some substances which have only been treated incidentally in the
foregoing chapter.

In describing the chemistry of the organs, I shall endeavour to avoid
discussions as to their metabolic functions, and shall omit all considera-
tion of their secretions, since these are treated elsewhere in this work ;
an exception, however, will be made in the case of milk.

Protoplasm and cells. — The chemical structure of living substance
is still beyond our knowledge. All that chemists are able to do is to
examine the disintegration products of the substance which they un-
avoidably kill by the use of reagents.

Some authors speak of living substance as if it were merely proteid
in composition, and have adopted the phrase " living proteid " (see p. 38).
But it is doubtful if the use of such a term is justifiable, for proto-
plasm even in its simplest condition invariably contains, or yields on
disintegration, substances other than proteid, though proteids and
compound proteids like nucleo-proteid are by far the most abundant of
these disintegration products. Among the other solid substances con-
stantly present in protoplasm are lecithin, cholesterin, and inorganic
salts (especially phosphates and chlorides of calcium, sodium, and
potassium); and frequently fat and carbohydrate material, such as
glycogen, are also to be found. Water occurs to the extent of 75 per
cent, or more. Whether these substances are all present in the free
state, or, as is much more probable, are linked together in intimate
union, to form the complex protoplasmic molecule, it is at present
impossible to say with certainty. Living cells are alkaline ; after death
they become acid.

The simplest form of protoplasm known is that found in the
plasmodium of the myxomycetous fungus, ufflthalium septicum. It has

PROTOPLASM AND CELLS. 81

been analysed by Eeinke 1 and Krukenberg,2 and their observations con-
firm what has just been stated.

The nucleus of cells, the study of which began with the work of
Brunton, Plosz, and Miescher, has of recent years been very thoroughly
worked at by Hoppe-Seyler, Kossel, and numerous other physiological
chemists ; the result will be gathered from the section in the preceding
chapter on nuclein, and, as will be there seen, there are yet many gaps
in our knowledge which require to be filled up.

The proteids obtained from the cell protoplasm have been examined
in simple cells such as those of lymphoid tissue, and in the more special-
ised cells of secreting organs, such as the liver, kidneys, testis, and so forth.
The main result is the same in all, though there are minor differences
between individual cases.

The proteid contained in greatest abundance is nucleo-proteid ; small
quantities of globulin usually coagulating at the low temperature of
50* C. or even lower, and minute traces of an albumin are also found.

The nucleo-proteids from different cells differ in the amount of
nuclein (as evidenced by the percentage of phosphorus) they contain.3

The nucleo-proteid from the thymus contains 0*8 per cent, of phosphorus.

kidney „ 0'37

liver „ 1-45

brain „ 0'5

red marrow ,, 1'6

red corpuscles ,, 0*68

Schmidt's fibrin ferment „ 1'25

In my early work 4 on the proteids of cell protoplasm, I selected the
cells of lymphatic glands, because one can obtain from these structures
an abundant supply of comparatively simple cells ; later, I found that
the cells of thymus 5 gave similar results. At first I described the pro-
teids obtained as four in number, namely nucleo-proteid, cell globulin- a,
cell globulin-/?, and cell albumin. The nucleo-proteid can be obtained
either by Wooldridge's acetic acid method or by the sodium chloride
process (p. 68).

The material obtained by both methods is the same, though they
differ in their physical condition ; that obtained by the sodium chloride
process being more viscous than that by Wooldridge's method. That
they are the same is shown by the facts that both give the same re-
actions, which closely resemble those of globulins ; both contain
practically the same amount of phosphorus, and both produce intra-
vascular coagulation.6

The term cell globulin was originally introduced by me as a con-
venient designation for the proteids which are coagulable by heat in
sodium sulphate extracts of the cells. The nucleo-proteid just men-
tioned is viscid when extracted by sodium chloride and magnesium
sulphate, but an extract with sodium sulphate solution does not exhibit

1 "Studien ueber das Protoplasma," Berlin, 1881.

2 Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, 1882, Bd. ii. S. 273.

3 Halliburton, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 306.

4 Proe. Roy. Soc. London, 1888, vol. xliv. p. 255; Journ. Physiol., Cambridge and
London, 1888, vol. ix. p. 229. 5 Ibid., vol. xviii. p. 306.

6 Halliburton and Brodie, ibid., 1894, vol. xvii. p. 135.
VOL. I. — 6

82 THE CHEMISTRY OF THE TISSUES AND ORGANS.

viscidity, and it was the absence of this character which led me to the
erroneous conclusion that no nucleo-proteid had gone into solution.

The sodium sulphate extract contains two proteids, one which co-
agulates at 4S°-50° C., the other at 75° C. The first, which I called cell
globulin-a, is really a globulin ; it yields no nuclein on gastric digestion ; l
but the second, which I called cell globulin-j6, though like a globulin in its
solubilities, is really the same nucleo-proteid which by treatment with
other salts is rendered viscid.2 That this substance is related to, if not
identical with, the fibrin ferment or its zymogen (Pekelharing) has been
rendered probable by the researches of Pekelharing and myself.

The albumin is only present in minute quantities ; its properties are
like those of serum albumin, and it may partly arise from blood or
lymph imperfectly washed away fr«in the cells.

Proteases and peptone, when present, are the result of post-mortem
changes, or of manipulations during the processes employed in separating
the other proteids.

Myosin is absent.

Lilienfeld3 has carried out a similar research on the chemistry of
cells which he obtained from the thymus, by the usual means of pressure
and the centrifuge. He found a proteid corresponding to cell globulin-a
coagulating at 48° C., and another corresponding to cell albumin
coagulating at 73-75° C. The nucleo-proteid which he obtained by my
sodium chloride process contained C, 53*46 ; H, 7 '64 ; N, 15 '5 7, and P,
0*433 per cent. The alcoholic extract of the cells contained protagon,
amido-valeric acid, inosite, and monopotassium phosphate.

By Wooldridge's method he obtained the nucleo-proteid he has
called " nucleo-histon " (see p. 68), and he considers that this, in part at
any rate, is derived from the nuclei. Its percentage composition is C,
48-46; H, 7'0 ; N, 16-86 ; P, 3-025 ; and S, 0701. The action of artificial
gastric juice, or of 0'8 per cent, hydrochloric acid, on this, is to separate
the nuclein from the proteid, which goes into solution as peptone. The
nuclein contains 4*991 per cent., and the nucleic acid prepared from
this 9-94 per cent., of phosphorus.

In the following table he gives the quantitative composition of
leucocytes : —

Water . 88-51

Solids 11-49

One hundred parts of the solids contain—

Total phosphorus 3 -01

Total nitrogen 15*03

Proteid 176

Nuclein 6878

Histon (i.e. proteid part of the nucleo-proteid) . 8-67

Lecithin 7*51

Fat 4*02

Cholesterin 4*40

Glycogen 0*80

1 Halliburton, Journ. Physiol., Cambridge and London, 1892, vol. xiii. p. 806.

2 Ibid., 1895, vol. xviii. p. 312. Pekelharing showed this also to be the case.

3 Ztschr.f. physiol. €%em., Strassburg, Bd, xviii. S. 473.

PROTOPLASM AND CELLS. 83

The high percentage of phosphorus in the nucleo-proteicl obtained by this
method is certainly not in accord with the observations of Brodie and myself.

We are justified in concluding from this work that the colourless
corpuscles of the blood which originate from lymphoid structures have a
similar composition. It is, however, impossible to investigate the actual
colourless blood corpuscles by inacrochemical methods. Microchemically
they can be shown sometimes to contain fat and glycogen.1

Pus cells are colourless corpuscles, which show a considerable amount
of fatty degeneration and are generally dead ; these have been the subject
of several researches. The nuclei consist of nuclein, which is historically
interesting, because this was the first preparation made by the method of
gastric digestion (Miescher).2

The protoplasm consists of proteids chiefly, but it also yields ex-
tractives and inorganic salts. Hoppe-Seyler's analysis of two samples of
dried pus cells give the following percentage results : —

I. II.

Proteids . . . 13-762 )

Nuclein . . . 34'257 V 68'585 67-369

Insoluble substances . 20 '566 )

Lecithin { / 7 '564

Fats J ' \ 7-500

Cholesterin . . . 7'400 7'283

Cerebrin . . . 5-199) ift-984.

Extractives . . . 4-433)

Inorganic constituents in one hundred parts of dried pus corpuscles —

NaCl . . . 0-435 P04 . . . 0-916

Ca3(P04)2 . . 0-205 Na . . . 0-068

Mg3(P04)2 . . 0-113 K . traces.

Fe,(P04)2 . 0-106

Proteids of pus. — Boedecker3 asserted that pus occasionally contains
gelatin and choridrin in addition to proteids, and a crystalline acid he
termed chlorrhodinic acid, but Miescher was unable to confirm these
results ; Miescher was also unable to find any myosin, a substance pre-
viously supposed to exist in the cell protoplasm.

My own observations coincide with those of Miescher on this point,
and also show that the most abundant proteid is nucleo-proteid. In
fact, the proteids obtained from pus are practically the same as those from
the thymus and other lymphoid structures.

Fibrin ferment was prepared from pus by Kauschenbach.4 Consider-
able quantities of proteoses and peptone are generally found in pus, and
are doubtless produced during the retrogressive metamorphosis of the
corpuscles. The original statement that pus contains peptone was made
by Eichwald 5 and Hofmeister.6 Though the method they employed
was not perfectly trustworthy, S. Martin 7 showed that they were right
in their conclusions. He placed pus under alcohol for many weeks,

1 Schafer, "Course of Practical Histology," London, 1876, p. 39.

2 Hoppe-Seyler's " Med. Chem. Untersuch.," 1871, Heft 4, S. 497.
* Ztschr.f. rat. Med., Leipzig, N.F., Bd. vi.

4 Inaug. Diss., Dorpat, 1883 ; Jahresb. ii. d. Fortsclir. d. TMer-Chcm. ,Wi&fo*fato Bd.
xiii. S. 134.

5 Verhandl. d. phys-med. Gesellscli. KU Wurzburg, 1864, S. 335.

6 Ztsclir. f. physiol. Chem., Strassburg, 1864, Bd. ii. S. '295.

7 Jh'it. Med. Journ.. London, 1890, voL ii. p. 234.

84 THE CHEMISTR Y OF THE TISSUES AND ORGANS.

and then dried it and extracted it with water. Proteoses and peptone
went into solution, the other proteids having been coagulated. It is pro-
bable that some of the symptoms which accompany the suppurative pro-
cess is produced by the entrance of these substances into the circulation.1

There is little to add concerning the other constituents of pus cells.
The large increase of fat, lecithin, and cholesterin confirms the fact of
fatty degeneration, evident to the microscope ; free fatty acids may even
be found in old pus, forming crystalline deposits.

Glycogen can often be demonstrated in pus corpuscles micro-
chemically by the use of iodine ; 2 Salomon 3 separated it from the cells
in appreciable quantities.

Pigments (pyocyanin, pyoxanthose) are frequently found in pus, and
are produced by chromogenic bacteria (Fordos, Liicke, Fitz, Kunz,
Babes).4

The proteids of red marrow cells. — In the lymphatic glands and
thymus the cells are non-eosinophile ; in the red marrow the cells are
mostly eosinophile. Sherrington 5 showed that the eosinophile granules
give microchemically the reaction for phosphorus, introduced by Lilienf eld
and Monti ; 6 the cells themselves were investigated macrochemically by
J. R Forrest.7 The marrow used was obtained from the interior of
rabbits' femora and horses' ribs.

His results were very like those obtained from other cellular
structures. Two proteids only were obtainable in any quantity, these
were a cell globulin, coagulating at 47°-50°, and a nucleo-proteid. The
latter contains a high percentage of phosphorus,8 namely, 1/6. Haemo-
globin is present in small quantities, and proteose and peptone are absent.

Epithelium. — Our knowledge of the tissues included under the
heading epithelium is principally histological. There is no reason to
suppose that the proteid constituents of the protoplasm and nucleus are
in any way different from that found in cells generally.

Mucin is formed in many situations, both in the cells of mucous
glands and in goblet cells. It is also the principal constituent of the
cementing material between the cells.

Mucus is the name given to the secretion which owes its sliminess to
mucin. Mucus also contains epithelial cells, more or less disintegrated, and a
few leucocytes. It has an alkaline reaction, and contains a certain small pro-
portion of proteids, extractives, and salts, similar to those of the blood. In
some cases, the mucinoid material in secretions is really a nucleo-proteid.
Thus, in the bile of some animals like the ox, there is very little true mucin,
but the viscidity is almost entirely due to nucleo-proteid ; 9 in human bile, on
the other hand, the viscid material is mucin, very little nucleo-proteid being

1 Ott and Collmar, Journ. PhysioL, Cambridge and London, vol. viii. p. 218 ; Krebl
and Matthes, Deutxches Arch. f. klin. Med., Leipzig, 1896, Bd. liv. S. 501 ; Arch. f. exper.
Path. u. PharmaTcol., Leipzig, 1896, Bd. xxxvi. S. 437.

2 Ranvier, Programed., Paris, 1877, p. 422.

3 Deutsche, med. Wchnschr., Leipzig, 1877, No. 35.

4 Compt. rend. Acad. d. sc., Paris, 1860, tome li. p. 215; Arch. f. klin. Chir.,
Berlin, 1862, Bd. iii. S. 125 ; Quart. Journ. Mic.r. Sc., London, Jan. 1880, p. 106 ;
Monatsh. d. Chem., Wien, Bd. ix. S. 361 ; Compt. rend. Soc. de biol., Paris, 1889,
p. 438.

5 Proc. Roy. Soc. London, 1894, Bd. Iv. p. 161.

6 Ztschr.f. physiol. Chem., Strassburg, 1893, Bd. xvii. S. 410.

7 Journ. PhysioL, Cambridge and London, 1894, vol. xvii. p. 174.

8 Halliburton, ibid., 1895, vol. xviii. p. 307.

» Paijkull, Ztschr. f. physiol. Chem., Strassburg, Bd. xii. S. 196.

GLANDULAR ORGANS. £5

present.1 The mucus of urine has also been stated to be nucleo-proteid in
nature.2 K. A. H. Morner3 investigated healthy human urine ; each experiment
necessitated the use of 80-90 litres. He found proteid or proteid-like materials
partly in suspension in the ordinary mucous cloud or nubecula, and partly in
solution. From the nubecula he separated a specific member of the mucin
group, which he calls urine mucoid. This probably originates from the mucous
membrane of the urinary passages. It contains C 49 '4, N 12 '74, and
S 2*3 per cent. ; and in its general properties agrees with ovo-mucoid pretty
closely (see p. 63). The soluble proteid in urine, which is present in the
merest traces, is chiefly serum albumin, but some is precipitable by acetic
acid, and this part consists of a nucleo-proteid; precipitated with it was
found a small quantity of chondroitin sulphuric acid (see " Cartilage " ).

The mucin of the respiratory passages has been investigated by F. Miiller.4
He finds it is true mucin, not nucleo-proteid. It yields from 25 to 32 per cent,
of reducing substance. This is a nitrogenous derivative of a hexose, and is
probably glucosamine.

Keratin and the skeletins are epithelial products which have already been
described (p. 72). The enamel of teeth, although epithelial in origin, will
be taken with the skeletal tissues. The epithelium of secreting glands will
be studied with those glands and their secretions.

GLANDULAK ORGANS.

The liver. — The fresh liver is alkaline in reaction, but after death
soon becomes acid from the development of sarcolactic acid.

The number of organic substances in the liver is very numerous.
There are proteids and nuclein from the hepatic cells; there are
substances like glycogen, sugar, and fat, stored up within the cells, or
produced from stored-up substances. Gelatin and mucin are obtainable
from the connective tissue framework. There are also extractives like
xanthine, hypoxanthine, and uric acid; lastly, a small proportion of
inorganic constituents.

The proportion of water is about 75 per cent. v. Bibra5 gives the
following numbers : —

Water . . 76 '17 per cent.
Insoluble tissues 9-44 „
Proteids . 2 '40

Gelatin . . 3'37 per cent.
Extractives . 2 -40 „
Fats 2-50 „

Proteids of the liver cells. — These were first investigated by P. Plosz.6
He found that, accompanying the onset of acidity after death, the
liver became harder and less transparent; he therefore compared the
condition to the rigor mortis of muscle, and sought for myosin by the
methods Kiihne had introduced for separating muscle plasma. He did
not, however, find any myosin. He extracted the proteids by means of
saline solutions of various strengths, and found—

(1) A proteid coagulating at 45° C., wholly soluble in gastric digestion ;
(2) a nucleo-proteid, coagulating at 70° C., yielding an insoluble residue of

1 Hanmiarsten, Km. Ges. der Wiss., Upsala, 1893 (Separat-abzug) ; Baginsky anrl Somer-
feld, Verhandl. d. pliysiol. Gesellsch., Berlin, 1894-5, Nos 13, 14, 15 in Arch. f. PhysioL,
Leipzig, 1895, S. 362.

aL6nnherg, Upsala Lakarcf. Fork., vol. xxv. ; K. Morner, Hygiea, Stockholm, 1892,
vol. lii; Obennayer, CentralbL f. Uin. Med., Bonn, Bd. xii.

* Skandin. Arch. f. PhysioL, Leipzig, 1895, S. 332.

4 Sitzungsb. d. Gesellsch. z. Beford. d. ges. Naturw. zu Marburg, 1896, No. 6.

5 v. Bibra, "Chemische Fragments ueber die Leber," 1849.

6 Arch.f. d. ges. PhysioL, Bonn, Bd. vii. S. 371.

86 THE CHEMISTRY OF THE TISSUES AND ORGANS.

nuclein on gastric digestion ; (3) a globulin coagulating at 75° C. ; and
(4) alkali albumin.

A good many years later,1 I repeated these experiments ; and, like
Plosz, failed to find myosin. Myosin appears to be a specific constituent
of muscle, and has not been found anywhere else. The hardening that
occurs in the liver after death, and which is very slight, is possibly due
to the solidification of the fat in the cells ; though it is also quite possible,
as Plosz suggests, that if coagulation does occur in the cells with the
formation of a myosin-like clot, this takes place so rapidly that our
present methods do not enable us to separate its precursor from the cells.

The proteids I obtained by the use of saline solutions were four in
number : —

1. A globulin (cell-globulin) coagulating at 45°-50° C.

2. A nucleo-proteid which coagulates at about 60° C., and is identical
with that obtainable by Wooldridge's acetic acid method from the cells.
It contains 145 per cent, of phosphorus. It does not become viscous on
admixture with neutral salts, and the sodium chloride method of
preparing nucleo-proteids is not applicable to it. It produces intra-
vascular coagulation.

3. A globulin coagulating at 70° C.

4. An albumin in mere traces, which coagulates at about the same
temperature.

Other organic constituents of the liver cells. — Urea, uric acid (especially
in birds), xanthine, and hypoxanthine, are found in the liver ; 2 leucine
and tyrosine are found in cases of acute yellow atrophy, and in
phosphorus poisoning.3 Various other substances have been described
as occasional constituents.4

A substance called jecorin, containing phosphorus (C106H186N6SP3046),
was separated from the liver by Drechsel.5 In its properties it some-
what resembles lecithin ; it, however, reduces Fehliiig's solution, which
lecithin does not. According to Baldi,6 it occurs in many other organs —
spleen, muscle, brain, etc.

The question of the iron-containing nucleins of the liver (Zaleski's
hepatin, Schmiedeberg's ferratin,7 etc.) is alluded to on p. 69. The
iron in the liver is increased in diseases, like pernicious ami-mia, which
lead to increased destruction of red blood corpuscles ; it is normally
greater in young (especially new-born) animals than in older ones.
Animals appear to enter the world with a store of iron in the liver, and
to a less degree in the spleen, which lasts them until they are able to
take foods other than milk, which is poor in iron.8

1 Journ. Physiol., Cambridge and London, 1892, vol. xiii. p. 806.

a Scherer, Ann. d. Chem., Leipzig, Bd. cvii. S. 314 ; Cloetta, ibid., 13d. xcvii. S. 289.

3 Sotnitschewsky, Ztschr. f. physiol. Chem., Strassburg, Bd. iii. S. 391; see also
Rohmann, Berl. klin. Wchnschr., 1888, S. 43 and 44.

4 Guanine, inosite, scyllite (Frerichs and Stiideler, Mitth. d. Zurich, naiur. Gesellsch.
1858) ; cystine (Hoppe-Seyler, "Physiol. Chem.," S. 718) ; sarcolactic acid, probably formed
after death.

5 Journ. /. prakt. Chem., Leipzig, Bd. xxxiii. S. 435.

6 Arch.f. Physiol. , Leipzig, 1887, Suppl., S. 100.

7 For recent work in ferratin and iron in the liver, and absorption of iron compounds
as food, see F. Vay, Ztschr. f. physiol. Chem., Strassburg, Bd. xx. S. 377 ; Weltering,
ibid., Bd. xxi. S. 186 ; Hall, Arch.f. Physiol., Leipzig, 1896, S. 49, 142; Cloetta,
Arch. /. exper. Path. u. PharmakoL, Leipzig, 1896, Bd. xxxiii. S. 6 ; Hochhaus and
Qnincke, ibid., S. 152 ; Quincke, ibid., S. 182.

8 Meyer and Pern on, Ztschr. f. Biol., Miinchen, Bd. xxvii. S. 439; Lapicque, Compt.
rend. Soc. de biol., Paris, tome xli. p. 435.

THE SPLEEN. 87

Inorganic constituents of the liver. — Oidtmami1 found I'l per cent, of
inorganic material in the liver, of which potassium phosphate, as in
many other organs, is the most abundant. His numbers per cent, are : —

Potash . . . 25-17

Soda . . . 14-17

Lime . . . 3*62

Magnesia . . 0*19

Iron oxide 2 -75

Phosphoric acid . 43 '3 7
Sulphuric acid . 0'9

Silicic acid . . 0'27

Chlorine . . 2 -5

Manganese, lead, copper traces.

F. Kriiger and Lenz 2 found that the liver cells of the calf contain about
70 per cent, more calcium than in the ox. During the foetal period there are
two maxima and two minima in the amount of calcium, which varies inversely
with that of iron. In the liver cells of adult men, Kriiger and his assistants3
found 2*38 of sulphur, 1*28 of phosphorus, and 0*77 of iron per cent. In new-
born children the three numbers are respectively 5*56, 1*54, and 0*314.

The spleen. — The percentage of water in the adult human
spleen varies from 694 to 77'5, the solids, from 31 -6 to 22-5, of which
oO'l to 21*6 consist of organic, and from I'l to 0'9 of inorganic, matters.4

During life the spleen is alkaline. Acidity sets in after death, due
to the formation of sarcolactic acid.5

The organic constituents of the spleen are proteids and haemoglobin,
xanthine,6 hypoxanthine, uric acid/glycogen,8 inosite,9 scyllite,10 cerebrin,11
cholesterin, lecithin, and jecorin.12 Various fatty acids (formic, acetic,
butyric) described by Scherer 13 are, no doubt, derived during the process
of distillation from the proteids. Leucine and tyrosine, which are
absent from the fresh organ, are often found as a result of putrefactive
changes (Hoppe-Seyler). The inorganic constituents are very like those
found in the liver, except that sodium are more abundant than
potassium salts.14

The proteids of the spleen. — G our lay 15 found that the proteids which
can be extracted from fresh spleen resemble those found in lymphoid
structures ; the most important of these are a cell globulin coagulating
at 49°-50° C., and a nucleo-proteid coagulating at 57-60° C. Bottazzi16
confirms these observations in the main. The nucleo-proteid can be pre-
pared either by Wooldridge's or the sodium chloride method, and, like that
obtained from other cellular organs, produces intravascular coagulation.

1 "Die anorg. Bestandtheile der Leber," Linnich, 1858.

2 Ztschr.f. Biol, Miinchen, 1895, Bd. xxxi. S. 392. 3 Ibid., S. 400.

4 Oidtmann, loc. cit.

5 Hirschler, ZtscJir. f. physiol. Chem., Strassburg, Bd. xi. S. 41.

6 Scherer, Ann. d. Ohem.., Leipzig, Bel. cvii. S. 314 ; Stadeler, ibid., Bd. cxvi. S. 102 ;
Neubauer, Ztschr. f. anal. Chem., Wiesbaden, Bd. vi. S. 33 ; Gorup-Besanez, Ann. d.
Chem., Leipzig, Bd. xcviii. S. 1 ; Cloetta, ibid., Bd. xcix. S. 289.

7 Scherer, Gorup-Besanez, Cloetta.

8 Hoppe-Seyler, " Med. Chem. Untersuch.," Bd. iv. S. 495; Abeles, Centralbl. f. d.
med. Wissensch., Berlin, 1876, No. 5.

9 Cloetta, Scherer.

10 Frerichs and Stadeler, Mitth. d. Zurich, natur. Gesellsch., 1855.

11 Hoppe-Seyler. 12 Baldi, Arch. f. Physiol. , Leipzig, Suppl., 1887, S. 100.

13 Verha-ndl. d. phys.-med. Gesellsch. zu Wilrzburg, Bd. ii. S. 323.

14 Oidtmann gives the following percentages:— Soda, 35-45; phosphoric acid, 18-30;
sulphuric acid, 1-5-2 '5; potash, 9-17; oxide of iron, 7-16; silica, 0'2-0'7 ; lime, 7;
chlorine, 0'5-1'3 ; manganese, copper, lead, traces. For a comparison of the percentage of
sulphur and phosphorus in the hepatic and splenic cells at different ages, see F. Kriiger,
Ztschr.f. BioL, Miinchen, 1895, Bd. xxxi. S. 400.

15 Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 23.

16 Ann. di chim. e difarm., 1895, vol. xxi.

THE CHEMISTRY OF THE TISSUES AND ORGANS.

Another point in connection with the spleen relates to the question
whether or not proteoses or peptones are obtainable from it ; this is im-
portant, because Sidney Martin l has found that the proteoses of diseases
(diphtheria, tetanus, etc.) accumulate in the spleen, v. Jaksch 2 states
that normal spleen contains " peptone " ; but the careful work of Gourlay,
in which he used Devoto's ammonium sulphate method and the alcohol
method failed to detect any.

Lymphatic glands. — The capsule yields gelatin and mucin like
connective tissue structures generally. The reticular tissue yields
reticulin (see p. 72) and gelatin (see p. 70). The chemistry of the cells
has been already described (p. 81).

In a lymphatic gland, about two-thirds are water, the remainder
solids. The tissue is alkaline cluing life, and turns acid, clue to the
development of sarcolactic acid, after death.3

Thymus. — This is also principally lymphoid tissue, and the above
remarks apply equally well to it. Nothing special is known of the
chemistry of the concentric corpuscles. The presence of extractives
like xanthine and hypoxanthine has been noted by Scherer, Gorup-
Besanez, Frerichs, Stadeler, etc., whose writings have been already
referred to. Schindler 4 has estimated the " nuclein or alloxuric bases "
(see p. 67) obtainable from the thymus of the calf, with the following
results : —

Percentage in

Adenine.

Hypoxanthine.

Guanine.

Xanthine.

Fresh tissue

0-179

0-0023

0-0075

0-038

Dry tissue

1-919

0-218

0-071

0-360

The high percentage of adenine is noteworthy. Like the other
organs already described, the reaction, alkaline during life, becomes
rapidly acid after death. The acid is sarcolactic acid.5

The thyroid. — This organ is also alkaline during life, but becomes
acid after death ; this is due to sarcolactic acid (Moscatelli).

Various extractives (fatty acids, xanthine, hypoxanthine, etc.) have
been found in it by Gorup-Besanez, Scherer, Frerichs. and Stadeler.
Inosite has been found by Frankell6 and by Tambach.7 The main
constituents of the thyroid, however, are proteids, and a proteid-like
substance from the colloid material in the acini.

Oidtmann found in the adult thyroid, 82'24 water, 17'66 organic and
O'l inorganic material per cent. In an infant's thyroid the numbers
were 77*21, 22'35, and 044 respectively.

The importance of the chemistry of the thyroid arises from the fact that
the administration of thyroid extracts has been attended with curative
results in cases where the thyroid is absent, or no longer forms the
internal secretion which is believed to be necessary for the nutrition of
the nervous system.

1 Goulstonian Lectures, Brit. Mcd. Joum., London, March 1892.

2 Ztschr.f. physiol. Chem., Strassburg, 1892, Bd. xvi. S. 243.

3 Hirschler, Ibid., Bd. xi. S. 41.

4 Ibid., Bd. xiii. S. 438.

5 Moscatelli, ibid., Bd. xii. S. 416.

6 Wicn. Tried. BL, 1895, No. 48 ; 1896, Nos. 13, 14, 15.
1 Pharm. Centr.-BL, Leipzig, 1896, Bd. iv. S. 119.

THE THYROID. 89

Various attempts have been made to discover the active principle in
the thyroid which is responsible for its curative properties. Notkin1
attributes the activity of the gland to its proteid constituents, especially
to the one called thyrcoproteid by Bubnow,2 which acts after the
manner of an enzyme.

Gourlay 3 made a thorough investigation of the proteids obtainable
from the organ. His conclusions were as follows : —

1. The only proteid that can be obtained in any quantity from the
thyroid is a nucleo-proteid.4 This may be prepared by either the acetic
acid or sodium chloride method, and when intravascularly injected
causes thrombosis.

2. This is derived, at any rate partly, from the colloid matter in the
acini; it yields no sugar on treatment with dilute mineral acid, and
is therefore not a mucin or mucoid. Moreover, the microchemical
method of Lilienfeld and Monti shows that it contains phosphorus.
The absence of mucin is confirmed by Frankel and by Hutchison.

3. Small quantities of albumin are also obtainable.

A year later Frankel 5 separated from the gland a crystalline
material, with the formula CgH^NgOg, which he called thyr co-antitoxin,
though the experimental and clinical evidence quoted hardly seem to
justify the name.

Eoos and Baumann 6 have discovered an iodine-containing material,
which occurs chiefly in combination with the proteid of the organ, but
partly free. It is remarkable in being insoluble in 10 per cent, hydro-
chloric acid, a reagent which dissolves all the other substances present.
It was previously known that the active substance was very stable.
Thyroid feeding is followed by as good results as injection of thyroid
extracts ; the active substance therefore resists the action of digestive
ferments. The substance was named by its discoverers thyro-iodin, or
iodo-thyrin ; it contains 9'3 per cent, of iodine, and 0*56 per cent, of phos-
phorus. It is not probably a derivation of nuclein, but its constitution is
not yet known. The amount of iodine per gramme of the organ in human
adults varies from 0'3 to 0'9.

Whether this substance is really the important proximate principle in
thyroid extracts and by inference in the normal internal secretion of the
organ, must still be left to the future. For, though Eoos and Baumann
state that it acts in every way like thyroid extracts, Gottlieb 7 has been
unable to confirm the statement, though possibly, as Auerbach 8 suggests,
this is to be attributed to his having used preparations very poor in iodine.
Weak points in the theory appear to be the absence of the substance
in the thyroids of children, and in some animals like dogs unless they
are put on a particular diet (dog biscuits). Small quantities of iodine
are found also in the thymus.

1 Wien. med. Wchnschr., 1895, Nos. 19 and 20 ; Virchow's Archiv, 1896, Bd. cxliv.
S. 224. The ferment theory was also urged by White and Davies, Brit. Mcd. Journ., London,
1892, vol. ii. p. 966.

2 Ztschr.f. physiol. Chem., Strassburg, Bd. viii. S. 1.

3 Journ. Physiol. , Cambridge and London, 1894, vol. xvi. p. 23.

4 Morkotun (Vrach, St. Petersburg, 1895, No. 37) gives the composition of this
nucleo-proteid as— C, 51 '46 ; N, 15 '56 ; P, 0'32 ; H, 6 '94 ; S, 1'5 ; 0, 24 '22 per cent.

5 Wien. med. BL, 1895, No. 48 ; 1896, Nos. 13, 14, and 15.

6 Ztschr. f. physiol. Chem., Strassburg, Bd. xxi. S. 19, 319, 481 ; xxii. S. 1, 18.

7 Deutsche med. Wchnschr., Leipzig, Bd. xxii. S. 235,

8 Centralbl. /. Physiol., Leipzig, 1896, Bd. x. S. 133. For various other references
to clinical work on this question, see ibid., No. 6. For the influence of iodo-thyrin on
metabolism, see F. Voit, Ztschr.f. Biol , Miinchen, 1897, Bd. xxxv. S. 116.

9o THE CHEMISTRY OF THE TISSUES AND ORGANS.

This discovery of a compound containing iodine in the animal body
is a very remarkable one, but is not unique. Almost simultaneously with
Baumann's announcement, Drechsel l published a research on the horny
skeleton of Gorgonia cavolinii. Here he found iodine in organic com-
bination, and on decomposition the skeleton yielded a crystalline amido-
acid (iodo-gorgonic acid) of uncertain constitution, and with the formula
C^gNIO^. Drechsel has also found iodine in the hair of a syphilitic
patient, taking iodide of potassium. With reference to the thyroid, lie
suggests the very reasonable hypothesis that this organ produces more
than one active substance, and that the different substances have
different actions. He has confirmed the existence both of Baumann's
iodo-thyrin and of Frankel's thyreo-antitoxin, and has further separ-
ated out a second crystalline base. Hutchison,2 however, finds that
the proteid-free extracts which contain these bases are physiologically
inactive. He finds that the activity is connected with the iodine-con-
taining colloid substance. He distinguishes between the colloid of the
acini and the nucleo-proteid of the epithelium lining them. The former
is the active constituent, and is by gastric digestion decomposed into
two parts. One part is proteid ; it contains a little iodine, and has
feeble physiological powers. The other part is not proteid, and not
nuclein. It is more active, and contains the greater part of the iodine
and all the phosphorus of the original colloid.

The suprarenal body. — In this gland, in addition to proteids and
the usual extractives and salts (among which potassium phosphate is
the most abundant), various other substances have been described, such
as hippuric and taurocholic acid,3 benzoic acid, taurine,4 and inosite.5

The chemistry of the suprarenal is of especial interest because of the
work of Schafer and Oliver6 on the action of extracts obtained from
it. It is now generally believed that the function of the gland is
secretory, and that the fatal effects of its removal in animals, or
disease in man ( A< Id i son's disease), is due to the removal of an internal
secretion, and not to auto-intoxication from the non-removal of waste
products.7 The active principle is obtained from extracts of the
medulla of the healthy gland ; it is absent in advanced cases of Addi-
son's disease.

The earlier observers8 were inclined to attribute the toxic
results of suprarenal injections to neurine. This is not so. Neurine

1 Ztschr. f. Biol., Miinchen, 1896, Bd. xxxiii. S. 83; CentrcdU. f. Physiol., Leipzig,
Bd. ix. S. 704.

2 Brit. Med. Journ., London, 1896, vol. i. p. 722; 1897, vol. i. p. 4; Journ. Physiol.,
Cambridge and London, 1896, vol. xx. p. 474.

3 Cloez and Vulpian, Compt. rend. Acad. d. sc., Paris, 1857, tome ii. p. 10 ; Gaz. med.
de Paris, 1858, No. 24.

4 Seligsohn, Diss. , Berlin, 1858; Holm, Journ. f. prakt. Chem., Leipzig, Bd. c. S. 150.
Stadelmann could not confirm these statements, Ztschr. f. physiol. Chcm., Strassburg, Bd.
xviii. Possibly these substances are absorbed from the neighbouring gall bladder and
kidney.

5 Klilz, Sitzungsb. d. Gesellsch. z. Befdrd. d. ges. Naturw. zu Marburg, 1876, No. 4.

6 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 230. Some speculations
as to the function of the cortex by Auld will be found, Brit. Med. Journ., London, July
4, 1896 ; Manasse, Virclww's Archiv, Bd. cxxxv. S. 263.

7 The discovery of ruemochromogen in the medulla of the organ by MacMunn (Proc. Roy.
Soc. London, Bd/xxxix. S. 248) appeared to favour the removal hypothesis.

8 Pellacani, Arch, per le sc. vied., Torino, 1874, vol. iii. ; Foa, ibid., 1884, vol. viii. ;
Marino-Zucco, Chem. Centr.-BL, Leipzig, 1888; Untersuch. s. Naturl. d. Mensch. u. d.
Thier, Bd. xiv. ; Arch. ital. de biol., Turin, vol. x.

THE SUPRARENAL BODY.

can be obtained from the gland, it is true, but the symptoms
of neurine poisoning are different. The active principle has not
yet been satisfactorily identified, although its solubilities and many
of its reactions have been worked out by Moore,1 who at first thought
it identical with a powerfully reducing substance found only in the
medulla of the gland, and first described by Vulpian.2 The solubilities
of this reducing substance are nearly identical with those of the active
physiological principle. It gives a dark green or blue colour with
ferric chloride, passing through purple to a dark red on the addition of
ammonia or sodium carbonate. With chlorine, bromine, or iodine water,
peroxide of hydrogen, or alkalis in the presence of oxygen, it gives a
rose-red colour, discharged by sulphide of hydrogen or ammonium sul-
phide. It is insoluble in alcohol, ether, or benzene; it is soluble in
water, alcohol plus water, and dilute acids. It dialyses freely through
vegetable parchment. It is not a proteid, nor a carbohydrate, nor a
fat, nor is it affected by gastric digestion.

Manasse,3 who investigated the composition of the organ without
any special reference to the question of its physiological action, or the
work of Schafer and his colleagues, states that a reducing substance
is present, similar in many of its properties to jecorin (see p. 86). It
is, however, not jecorin ; the two substances are alike in some of their
solubilities, but the material from the suprarenal does not reduce
Fehling's solution until after prolonged boiling with sulphuric acid ;
the sugar formed appears to be dextrose. Moore has, however, been un-
able to obtain from the suprarenal any substance that reduces Fehling's
solution. If one, moreover, compares the percentage composition of
Manasse's material with jecorin, the difference is seen to be striking, as
in the following table : —

JECORIN.

SUBSTANCE FROM
SUPRARENALS.

Drechsel.

Baldi.

Manasse.

c

51-32-51-64

46-88-46-89

41-43

H

8-11- 8-25

7-81- 8-09

7-16

N

2-86

4-36- 4-88

0-3

s

1-42-1-47

2-14- 2-70

1-8

P

2-2 -37

2-29- 2-75

4-44

Na

2-72

5-72

0 .

30-10

...

S. Frankel 4 has also made an attempt to identify the active substance,
but with no better success than Moore ; according to him, the material
obtained by Manasse is inactive. Nabarro 5 has investigated the pro-
teid s of the organ and found them similar to those of other glandular
structures, namely, cell globulin and nucleo-proteid. They appear to be
physiologically inactive. In his later work Moore 6 criticises Frankel's

1 " Proc. Physiol. Soc.," London, March 1894 (Journ. Physiol., Cambridge and London,
vol. xvi. ]t. i) ; ibid., March 1895 (Journ. Physiol., Cambridge and London, vol. xvii. p.
ix.) ; Journ. PhysioL, Cambridge and London, vol. xvii. p. 230.

2 Compt. rend. Acad. d. sc., Paris, tomes xliii. and xlv.

3 Ztschr.f. physiol. Chem., Strassburg, 1895, Bd. xx. S. 478.

4 Wien. mcd. Bl., 1896, Nos. 14, 15, and 16.

5 " Proc. Physiol. Soc.," London, 1895, Journ. Physiol., Cambridge and London, vol. xvii.
(i Journ. Physiol., Cambridge and London, 1897, vol. xxi. p. 382.

92 THE CHEMISTRY OF THE TISSUES AND ORGANS.

methods and results. He finds that absolute alcohol, which Frunkel
used for extracting the active substance from the gland, only dissolves
it in traces ; and that the prolonged action of alcohol, especially
if heat is employed, renders the material physiologically inactive,
though it still continues to give the colour reactions enumerated
above. He is inclined to consider the substance to be a derivative
of piperidine, not of pyrocatechin, as Frankel supposes. Piperidine
certainly produces a marked rise of blood pressure, like suprarenal
extract.1

Pancreas. — This organ is alkaline during life, and rapidly becomes
acid after death. The solids are like those usually obtained from cellular
organs, namely, proteids (for the phospho-gluco-proteid separated from
the gland by Hammarsten, see p. «64) ; extractives (guanine,2 xanthine,
hypoxanthine, leucine,3 tyrosine, uric acid, lactic acid, inosite), and a
small proportion of inorganic salts.

Salivary glands. — The subinaxillary gland yields proteids, of which
the most abundant is a nucleo-proteid ; 4 the cells also contain mucinogen,
which passes as mucin into the saliva. The parotid cells contain no
mucin. A small amount of mucin is, with gelatin, obtainable from the
investing connective tissue.

The kidneys. — During life the reaction of renal tissue is alkaline ;
after death it rapidly becomes acid, especially the medulla.5

Gottwalt6 gives the following table relating to the percentage
composition of kidney tissue freed from blood : —

Proteids 1M85 to 12*217 per cent.

Gelatin 0-996 „ 1'849

Mucin ...... Traces.

The following extractives have been obtained by various observers : —
xanthine, hypoxanthine, creatine, taurine, leucine, cystin, urea, uric acid,
glycogen, and inosite.

The kidney also contains a small proportion of inorganic salts (01
to 07, Oidtmann).

The proteids of kidney tissue.1 — These are very like the proteids of
other glands, and consist of cell globulin, coagulable by heat at 52° C.,
and a nucleo-proteid. This is far the more abundant ; it coagulates at
63° C. ; it may be prepared by either the acetic acid or sodium chloride
method. It contains 0*37 per cent, of phosphorus, and produces, like
other nucleo-proteids, intravascular coagulation.

The lungs. — The chemical constituents of these organs call for no
special notice.8

The testis. — Chemically, the testis is mainly composed of proteids,

1 This was shown independently by Tunnicliffe, Cenlralbl. f. PhysioL, Leipzig, 1897,
Bd. x. S. 777.

2 Scherer, Ann. d. Chem., Leipzig, Bd. cxii. S. 276.

3 Virchow, Frerichs, and Stadeler, see Hoppe-Seyler, "PhysioL Chem.," S. 260. These
substances are present in the fresh organ, and are not, as in -the spleen, the result of putre-
faction.

4 Hammarsten, Ztschr. f. pliysiol. Chem., Strassburg. Bd. xii. S. 163.

5 Halliburton, Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 806.
Liebermann states that the normal reaction of kidney tissue is acid, Arch. f. d. ges. PhysioL,
Bonn, Bd. 1. S. 55.

6 Ztschr. f. pliysiol. Chem., Strassburg, Bd. iv. S. 431.

7 Halliburton, loc. cit.

8 " On Lecithin in Lungs and Sputum," see Zoja, Gazz. med. di Torino, 1894,
vol. xlv.

THE TESTIS. 93

or substances allied to proteids ; of the latter, nuclein and nucleo-
proteids are the most abundant.

As in other cases, the fresh gland is alkaline ; l the acidity noted by
Treskin 2 was probably the result of post-mortem changes. The extract-
ives which have been found are leucine and tyrosine (these are probably
post-mortem products); lecithin, cholesterin, and fat (Treskin); creatine ; 3
inosite ; 4 adenine, xanthine, hypoxanthine, guanine, 5 and other derivat-
ives of nuclein.6

The salts present are chiefly chlorides of sodium and potassium
(Treskin).

Semen. — The chief chemical constituent of the spermatozoa is nuclein
(Miescher, see p. 66). Miescher also prepared a base which he called
protamine, and to which Piccard7 ascribed the formula C16H32N904.
Another organic substance, akin to a proteid, and containing 4 per cent.
of sulphur, was also described by Miescher.

Kossel8 has examined the protamine from the testis of salmon and stur-
geons ; he calls it salmine or sturine, according to its origin. He prepared
from it various crystalline salts, and a new base, C6H9N309, he terms
histidine. 9

Among other substances he prepared from fishes' spermatozoa, was thymin,
the substance he had previously got from the nucleic acid of the thymus
(see p. 66).

Lecithin, next to nuclein and proteids, is the chief organic substance
in spermatozoa.10 Cholesterin and fat are also fairly abundant. Miescher
gives the following percentage for the salmon's spermatozoa : —

Nuclein . . 46 '68 per cent. | Lecithin . .7*47 per cent.
Protamine . 26'76 ,, | Cholesterin . 2'24 ,,

Proteids . . 10'32 „ | Fat . . . 4'53 „

Miescher continued to work at this subject (salmon's spermatozoa)
throughout his life. He, however, never published much beyond his
early papers. After his death, Schmiedeberg published an article n
compiled from his numerous notes. This paper relates to the quantitat-
ive composition of the spermatozoa, and gives analyses of the principal
substances obtained from them, especially nuclein and protamine. He
considers these are in chemical union, thus :

(nucleic acid) (protamine)

The heads of the spermatozoa contain 6073 per cent, of nucleic acid
and 1978 per cent, of protamine. The tails (which are soluble in

1 Sertoli, Gazz. med.-vet., Milano, 1872, Anno ii.

2 Arch.f. d. ges. Physiol., Bonn, Bd. v. S. 122.

3 Schottin, see Hoppe-Seyler, " Physiol. Chem.," S. 773.

4 Schottin, Kiilz, Sitzungsb. d. Gesdlsch. z. Beford. d. ges. Naturw. zu Marburg, 1876,
No. 4.

5 Schindler, Ztsckr. f. physiol. Chem., Strassburg, Bd. xiii. S. 438.

6 Kossel, ibid., 1896, Bd. xxii. S. 172, 188 ; HediD, ibid., S. 191.

7 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. vii. S. 1714.

8 Loc. cit.

9 Hedin (loc. cit. ) believes histidine is identical with a base he had previously obtained
iu his work on the decomposition products of proteids.

10 Diaconovv ; see Hoppe-Seyler's "Med. Chem. Untersuch.," Bd. ii. S. 221 ; Hi. S. 405.

11 Arch.f. expcr. Path. u. PharmaJcol., Leipzig, 1896, Bd. xxxvii. S. 100.

94 THE CHEMISTR Y OF THE TISSUES AND ORGANS.

saline solutions) contain, proteicl, 41 -9; lecithin, 3173; fat and choles-
terin, 2 6 -2 7 per cent. In young spermatozoa some interest attaches
to the presence of a proteose which is regarded as the mother
substance of protainine. Proteose and protamine both give the biuret
reaction.

Charcot's crystals. — These can be obtained from semen on evaporation.1
They are frequently found in sputum, in the blood, and in other situa-
tions, in leucocythaemia. Schreiner 2 considered that they consist of the
phosphate of a base he called spermine, C2H5N. Ladenburg and Abel 3

FIG. 12. — Charcot's crystals.

thought they were identical with ethylenimine, which can be prepared
artificially from ethylenediamine-hydrochloride. This identity, however,
is denied by Majert and A. Schmidt 4 and by Poehl.5 Poehl gives the
formula C5H14N2 to the base. He states that it is a normal constituent of
the testis, ovary, and blood, and that, used as a drug, it has a tonic effect.
Ovary. — The connective tissue element is large, and yields chiefly
gelatin and mucin. Proteids and nuclem are derived from the ova and

1 Bottger, VircJiow's Archiv, Bd. xxxii. S. 525.

2 Ann. d. Chem., Leipzig, Bd. cxciv. S. 68.

3 Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxi. S. 758.

4 Com.pt. rend. Acad. d. sc., Paris, tome cxv.
* Berl. Min. Wchnschr., 1893, No. 36.

MUSCLE.

95

other cells present. The corpora lutea are coloured by lutein. This is a
lipochrome (see p. 20). Tlmdichum l was the first to point out that it
is distinct from ha?matoidin, which is also generally present.

The constituents of eggs are described with the various proteids,
etc., of which they are made up.

MUSCLE.

Skeletal muscle. — A muscle contains, besides the muscular fibres,
supporting connective tissue with fat. Each fibre consists of two parts,
the sheath or sarcolemma, and the contractile substance which it
encloses. The sarcolemma resembles elastin very closely in its
solubilities.2

The contractile substance is of soft consistency, and contains a large
percentage of proteids, and smaller quantities of various extractives and
salts. By the use of a press a juice can be squeezed out of perfectly
fresh muscles, which is called the muscle plasma. Like blood plasma,
this coagulates, and the proteid clot is called myosin; this occurring
within the body after death is the cause of rigor mortis.

Living muscle is alkaline ; but after extreme activity, and after
death, the reaction becomes acid ; this is due in part to the development
of sarcolactic acid.

The percentage of water in muscle varies in different animals : 3 —

Man . 72 to 74 per cent.

Ox . .77

Pig. . 78

Cat. . 75
Fox. 74

Birds

70 to 76 per cent.

80

82

Amphibians 76
Fishes . 79 „
Crab . 85
Pecten 79 „ 80

In young animals, and during inanition, the percentage of water is
greater.

Human muscle has the following average percentage composition : —

Water 73 -5 per cent.

Solids 26-5 „

Proteids, including sarcolemma, proteids of con-
nective tissue, vessels, and pigments . . 18*02 „

Gelatin 1*99 „

Fat 2-27

Extractives (creatine, lactic acid, glycogen, etc.) 0*22
Inorganic salts . . . . . .3*12

This may be compared with the muscle of a mollusc (Pecten) :

Water .

Solids .

Proteids .

Glycogen .

Glycocine

Ethereal extractives .

Inorganic salts .

1 CentralU.f. d. med. Wissensch., Berlin, 1869. Bd. vii. S. 1.

2 Ewald, Ztschr.f. Biol., Mtinchen, Bd. xxvi. 8. 1.

79-60 to 80-25 percent.
20-40 „ 19-75
15-68 „ 15-04

1-98

0-39

0-24

1-22

2-43
0-71
0-33
1-26

Schlossberger, " Chem. der Gewebe," Leipzig and Heidelberg, ]856, S. 169; Gornp
Besanez, " Lehrbuch," 1878, S. 676; Hoppe-Seyler, "Physiol. Chem.," S. 636.
4 Chitteuden, Ann. d. Chem., Leipzig, Bd. clxxviii. S. 266.

96 THE CHEMISTRY OF THE TISSUES AND ORGANS.

Muscle considered as meat is the most concentrated and most easily
assimilable of the animal nitrogenous foods. It forms our chief source
of nitrogen. In 100 parts of nitrogen from beef, 774 come from proteid
insoluble in water, 10'08 from soluble proteid, and 12'52 from extract-
ives.1 In addition to the proteids, extractives, and salts contained in
muscle, the flesh used as food contains a certain variable percentage of
fat, even though all visible adipose tissue is cleaned off. In estimating
the amount of fat, Dormeyer2 recommends that the meat should be
subjected to artificial digestion before extraction with ether ; ilesh then
yields an additional 075 per cent, of fat.

The following table 3 gives the chief substances in some of the principal
meats used as food : —

Constituents.

Ox.

Calf.

Pig.

Horse.

Fowl.

Pike.

Water

767

75'6

72-6

74-3

70-8

79-3

Solids

23-3

24-4

27-4

25'7

29-2

20-7

Proteids and gelatin

20-0

19-4

19-9

21-6

227

18-3

Fat ......

T5

2-9

6-2

2-5

4-1

07

Carbohydrate ....

0-6

0-8

0-6

0-6

1-3

0-9

Salts

1-2

1-3

1-1

1-0

1-1

0-8

The flesh of young animals is richer in gelatin than that of old ones;
thus 1000 parts of beef yield 6, of veal 50, parts of gelatin (Liebig).

Meat contains four times the amount of proteid present in an equal
weight of milk.

The process of cooking meat (after it has been kept to allow rigor
mortis to pass off) renders the investing connective tissues looser,
separates the muscular fibres, and destroys parasitic growths. The
muscular fibres themselves, especially if boiled, are rendered more
difficult of digestion.

The muscle plasma and the muscle serum. — Kiihne 4 was the first to
obtain muscle plasma; he used frogs' muscle. The fresh blood-free
muscle is frozen and subjected to strong pressure, the expressed fluid
(muscle plasma) is filtered ; it is found to be syrupy in consistence, and
faintly alkaline. As the temperature of the plasma rises to that of the
air, it clots, and the myosin, so formed, contracts to a slight extent,
squeezing out muscle serum. Kiihne found this latter fluid to contain—

(1) A proteid coagulating at 45° C. ; (2) an alkali albumin ; 5 (3) a
small quantity of albumin ; (4) extractives and salts.

A good many years later, I was successful in repeating these ex-
periments with mammalian muscle,6 and showed, moreover, that not only

1 Salkowski, Centralbl. f. d. med. Wissensch., Berlin, 1894.

2 Arch.f. d. ges. Physiol., Bonn, 1895, Bd. Ixi. S. 341 ; 1896, Bd. Ixv. S. 90; Schulze,
ibid., S. 299 ; 1897, Bu. Ixxii. S. 145.

3 Munk's "Physiologic," Ann. 4, S. 280.

4 " Lehrbuch d. physiol. Chem.," S. 272 ; "Untersuch. it. das Protoplasma," Leipzig,
1864.

5 The natural alkali albumins described by older workers are no doubt all globulins.

6 Halliburton, Journ. Physiol., Cambridge and London, vol. viii. pp. 133-202.

SKELETAL MUSCLE. 97

does cold prevent the coagulation of muscle plasma, but, as in the case of
blood plasma, admixture with solutions of neutral salts has the same
effect. Addition of water to the salted muscle plasma brings about
coagulation (an acid reaction making its appearance simultaneously),
especially at 40° C., and still more rapidly if solution of " myosin
ferment " is added. The myosin ferment was prepared from muscle
in the same way as fibrin ferment from blood serum.

Saline extracts of muscle which has undergone rigor mortis, resemble
salted muscle plasma very closely ; after dilution they undergo coagula-
tion; this may be a re-coagulation of the redissolved myosin, for the
acidity of the saline extract is increased by re-coagulation. Some
observers, however, regard this phenomenon not as a true re-coagulation,
but as a simple precipitation of the myosin by dilution with water.

Myosin may be most readily extracted from muscle by means of
ammonium chloride solution, and may be precipitated in a gelatinous
form by dialysing away the salt.1 Elementary analysis2 gives the
following results : -C, 5279; H, 712; N, 16'86 ; S, 1-26; 0, 22*97.

Eecent research has shown that calcium salts are essential for the
effective coagulation of milk and blood. The facts are not so positive
in the case of muscle, but there is some evidence pointing to the
existence of an analogy in the three cases.3

By fractional heat coagulation, and by their varying solubilities in
different salts, I was able to separate four different proteids iii the
muscle plasma.

(1) A globulin precipitable by heat at 47° C. This is analogous to
the cell globulin found in most protoplasmic structures. It is termed
musculin by Hammarsten. I gave it the name paramyosinogen.

(2) A globulin precipitated by heat at 56° C. This is the proteid
which is especially acted on by the myosin ferment, and is converted
into myosin. I termed it myosinogen: both it and paramyosinogen
contribute to the muscle clot.

(3) A third globulin precipitated at 63° C. (myoglobulin) is con-
tained in the muscle serum.

(4) Small quantities of an albumin (myoalbumiri), similar in its
properties to serum albumin, are also present.

In addition to this, in the case of red muscles, there is haemoglobin ;
and if the muscle has been kept warm, and acidity developed, small
quantities of proteoses and peptone, which are formed by a process of
self-digestion. Briicke showed, many years ago, that muscle contains
small quantities of pepsin, doubtless absorbed from the gastric mucous
membrane ; this becomes active on the onset of acidity. The action of
such a ferment within the body will perhaps explain the phenomenon
called the disappearance of rigor mortis'., it is unnecessary to suppose
that this is always due to putrefactive organisms,4 since rigor often dis-
appears before putrefaction sets in. Perfectly fresh muscle contains no
proteose or peptone.5

Whitfield also investigated the question whether myosin or its precursors are

1 Kiihne and Chittenderi, Ztschr. f. Biol., Miinchen, Bd. xxv. S. 358.

2 Chittenden, ibid. See also Stud. Lab. Plujsiol. Chem., New Haven, 1889, vol. iii.
p. 116.

3 Locke, Journ. Physiol., Cambridge and London, vol. xvii. p. 293 ; other references will
be found in this paper.

4 Cossar Ewart, Proc. Physiol. Soc., London, 1887, p. xxv.

5 Whitfield, Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 487.

VOL. I. — 7

98 THE CHEMISTRY OF THE TISSUES AND ORGANS.

of the nature of nucleo-proteids. He found that they are not. He was indeed
able to obtain no nucleo-proteid at all from muscle. Pekelharing 1 has taken
up the latter question, and by an improved method discovered that muscular
tissue does contain a small amount of nucleo-proteid. He points out that on
gastric digestion small quantities of nuclein are soluble, if the amount of
hydrochloric acid present exceeds O'l per cent. Whitfield used water as an ex-
tracting agent for any possible nucleo-proteid. Pekelharing points out that the
water will soon become acid from sarcolactic acid, and uses dilute (0*15 per cent.)
sodium carbonate solution instead. From such an extract the nucleo-proteid
can be precipitated by acetic acid. From 543 grms. of flesh he obtained 2 grms.
of nucleo-proteid. This substance produces intravascular clotting, and contains
0*7 of phosphorus. The nuclein split off from it contains 3*5 per cent, of
phosphorus, and on decomposition yields alloxuric bases, especially xanthine
and guanine. Hypoxanthine and adenine were not found. Kossel 2 also failed
to get adenine from muscle.

An important research on muscle plasma and its proteids has lately
been published by v. Ftirth.3 He obtained the plasma from blood-free
muscles by extracting them with physiological saline solution. This
extract coagulates spontaneously, and the clotted proteid formed he calls
myogen fibrin or myosin fibrin. The proteids in the muscle plasma he re-
duces to three, namely, paramyosinogen, 17 to 22 per cent, of the total pro-
teid ; myosinogen or myogen, 77 to 83 per cent., and traces of an albumin.4

My work is confirmed in its main point, namely, that there are two
proteids in the muscle plasma, paramyosinogen and myosinogen, which
enter into the formation of the muscle clot ; the action of a specific
ferment to bring about this change was not specially investigated. The
principal new fact made out is, that paramyosinogen passes into the
condition of myosin fibrin directly ; whilst in the passage of myosinogen
into the state of myogen fibrin, there' is an intermediate soluble stage
coagulable by heat, at the remarkably low temperature t)f 40° C.5

Paramyosinogen is described as a typical globulin, and is regarded as
identical with Kiihne's myosin which he obtained by dropping muscle plasma
into water. Myosinogen is described as differing from a globulin in some
particulars, and is spoken of as a proteid sui generis. Myoglobulin is not
regarded as a separate proteid, but as part of the myosinogen which has
escaped coagulation. The phenomenon regarded by Chittenden and myself as
re-coagulation of myosin is considered to be a simple re-precipitation of globulin.
Whitfield's work on the absence of peptones and proteoses is confirmed.

The muscle plasma from fishes' and crabs' muscle contains another proteid,
called myo-proteid. It gives the usual proteid reactions, and is readily digested
by gastric juice ; though precipitated by a removal of the salts by dialysis, it
is not coagulable by heat. It is precipitable by acetic acid, but is neither a
mucin nor a nucleo-proteid.

In his second paper, v. Furth treats of (1) the properties (solubilities,

1 Ztschr.f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 245.

2 Ibid., 1886, Bd. x. S. 248.

3 Arch. f. exper. Path. u. Pharmakol., Leipzig, 1895, Bd. xxxvi. S. 231; also ibid.,
1896, Bd. xxxvii. S. 389.

4 J. H. Milroy (Arch. f. Hyg., Miinchen u. Leipzig, 1896, Bd. xxv. S. 154) has also made
quantitative estimations of the various muscle proteids coagulable at different temperatures.

5 If the reader refers to my memoir on "Muscle Plasma," he will find, on p. 186, that I
accidentally noted this fact, though I failed to appreciate its meaning. In frogs' muscle
plasma there is a considerable amount of this soluble myogen fibrin in a "preformed"
condition (v. Furth). The separation of the muscle proteids by fractional heat coagulation
fits in exactly with Brodie and Richardson's work on heat rigor ; as the temperature of a
muscle is raised, successive shortenings occur at the coagulation temperature of each
proteid (Proc. Roy. Soc. London, 1897, vol. Ixi. p. 77).

SKELETAL MUSCLE. 99

effect of numerous reagents, etc.) of myosinogen and paramyosinogen; (2) the
influence of blood serum in hindering the coagulation of the muscle plasma ;
and (3) the action of various chemical substances on living muscle.

Involuntary muscle. — Our chemical knowledge of involuntary muscle
is of a fragmentary nature. Like voluntary muscle, the heart becomes
rapidly rigid after death, and simultaneously acid,1 from the formation of
sarcolactic acid. Both paramyosinogen and myosinogen are present in
the muscle cells of the heart, and myosin is the result of coagulation.
In the stomach and uterus, rigor has been observed, but in other forms
of plain muscle it is difficult to recognise. A proteid coagulating at
56° C., has been obtained from all kinds of unstriped muscle. In a
muscular tumour of the uterus, Kossel 2 found the one coagulating at
45° C. (paramyosinogen) to be absent.

The reaction of unstriped muscle is normally alkaline.3 Lehmann 4
found small quantities of lactic acid in the muscular substance of the
stomach after death. There is, however, no marked change in the
reaction after death, as in striated muscle. Du Bois-Eeymond 5 observed
in the stomach and intestines of birds that after death the muscular
walls were still alkaline.

Myohcematin. — Though haemoglobin is the pigment of the red
muscles, MacMunn6 considers that the specific pigment of ordinary
muscle is myohamiatin, one of the most widely distributed of the colour-
ing matters which he has described under the name liistoluematins. The
histohsematins have only been observed by the spectroscope ; they have
not been separated out by chemical processes. They often occur in
animals that possess no haemoglobin. As they undergo changes in their
absorption bands, by oxygenation and reduction, it is believed that they
are respiratory in function. The spectrum of these substances is some-
what like that of haemochromogen ; and Levy, working under Hoppe-
Seyler,7 has gone so far as to say that myohaematin is hsemochromogen
produced by the methods used to render the muscle transparent. The
resemblance is not absolute, but is specially close in what MacMunn calls
modified niyohaematin. This is produced by artificial gastric digestion ;
or it can be obtained in the following way: — The muscle is chopped finely
and covered with ether for some days. A yellow lipochrome derived from
the fat between the muscular fibres8 passes into solution, and below this
floats a red juice, which on filtration gives the spectrum in question.

Until myohaematin. and the other histohaeniatins are examined
by methods other than spectroscopic, it is impossible to pronounce
positively on the point of dispute between MacMunn and Levy. The
fact that in the last experiment described, the muscles, even if they are
full of blood, yield no longer any haemoglobin, points to haemoglobin
as the source of the myohaematin ; whether this substance can be pro-
duced in the muscles intra mtam must be left to the future to decide.9

The extractives of muscle. — These are — (a) Nitrogenous, namely,

Boruttau, Ztschr. f. physiol. Chem., Strasslmrg, Bd. xviii. S. 513.

2 Quoted by Hoppe-Seyler, "Physiol. Chem.," S. 669.
Kiih

3 Bernstein (Kiihne's "Lehrbuch," S. 332) found the actively contracting muscles of
Anodon acid. 4 "Lehrbuch," Bd. iii. S. 73.

5 Monatsb. d. k. preuss. Akad. d. Wissensch. zu Berlin, 1859, S. 312.
G Phil. Trans., London, 1886 ; Journ. PhysioL, Cambridge and London, vol. vii.

7 Ztschr.f. physiol. Chem. , Strassburg , Bd. xiii. MacMunn's reply is in the same vol. , S. 497.

8 Halliburton, Journ. PhysioL, Cambridge and London, vol. vii. p. 325.

9 K. Mb'rner (Nord. med. Ark., Stockholm, Festband, 1897) states that muscle pigment is
hemoglobin which spectroscopically shows slight differences from that obtained from blood.

ioo THE CHEMISTR Y OF THE TISSUES AND ORGANS.

FIG. 13.— Creatine crystals.— After Kiiline.

creatine, creatinine, xanthine, hypoxanthine, carnine, carnic acid, uric
acid, urea, taurine, and inosinic acid. (&) Non-nitrogenous, namely, fats,
glycogen, inosite, dextrose, and lactic acids.

Creatine and creatinine. — Creatine can be crystallised out by

evaporating aqueous extracts
of meat from which proteids
and salts have been previously
removed ; 011 heating it with
mineral acids it is converted
into creatinine. The relation-
ship of these two substances
is shown by the following
equation : —
C4H9N A— H20 - C4HTN30

(creatine) (creatinine)

According to Yoit,1 the
quantity of creatine in the
voluntary muscles varies from
0-2 to 0-3 per cent. This
increases during starvation.2

Involuntary (cardiac and plain) contains less than voluntary muscle.8
The compound with zinc chloride which creatinine forms (Fig. 15) has

been generally used for isolating it from urine, and other places where it

occurs. .My own experience with

j$£±,'\ r^SBfc this method has shown that for

quantitative purposes it is most
uncertain ; and this no doubt ac-
counts for the different results
obtained by different observers.
Thus Neubauer denies the exist-
ence of creatinine in muscle
altogether ; Voit, Sarokin,4 and
Monari5 say that it increases
during muscular activity, while
Nawrocki6 states that it does
not. Much more certain results
are obtained by the use of G. S.
Johnson's method, in which he
precipitates the creatinine as a
compound of mercury.7 This
method, which has received the

FIG. 14. — Creatinine crystals. — After Kiihne.

powerful recommendation of Hoppe-Seyler,8 may be used to identify
creatinine when it is present in very small quantities, as in the blood.9
The microscopic appearance of the precipitate is shown in Fig. 16. By

1 ZUchr.f. BioL, Miinchen, Bd. iv. S. 77.

2 Demant, Ztsclir. f. physiol. Chem., Strassbnrg, Bd. iii. S. 387.

3 Voit, loc. cit. ; Lehmann, " Lehrbuch," Bd. iii. S. 73.

4 Virchow's Archiv, Bd. xxvii. 5 Gazz. chim. ital., vol. xvii. p. 36'7.

6 Centralbl.f. d. med. Wisscnsch., Berlin, 1865, S. 417.

7 Proc. Roy. Soc. London, vol. xlii. p. 365 ; xlii. p. 493 ; 1. p. 28. Johnson
here points out that there are several isomeric varieties of creatinine, differing in reducing
power, etc. In his process he is careful to employ no heat; otherwise the creatinine is
transformed into a non-reducing variety, or even may be changed into creatine.

"Handbuch. d. physiol. clieni. Analyse," 1893, 7th edition, S. 142.
9 Colls, Journ. Physiol. , Cambridge and London, 1896, vol. xx. p. 107.

THE EXTRACTIVES OF MUSCLE.

101

this means Johnson showed that creatinine (a different creatinine from
urinary creatinine) is more abundant in muscle than creatine, which
is usually almost entirely absent. This unexpected result has been
confirmed by Kemmerich.1 Creatinine is readily changed into creatine
by the action of putrefactive micro-organisms.

Xanthocreatinine (C5H10N40), crusocreatinine (C5H8N40), ampliicrea-
tine (C0H19N704), and pseudoxantJiine (C4H5N50) are leucomaines stated
by Gautier 2 to be present in small quantities.

Xanthine, hypoxanthine, and uric acid are found in small quantities
only; the numbers given are as follows: — xanthine, O0026 per cent.;3
hypoxanthine, 0'022-0'026 ;4 uric acid, traces.5 Uric acid is more
abundant in the muscles of reptiles (alligators). The crystalline forms
of some of the compounds of xanthine
and hypoxanthine are given in Fig. 17.

Car nine is a crystalline base
(CTH8N40;!+H20), originally found by
Weidel6 in large quantities (1 per
cent.) in American meat extracts, but
since found in the flesh of many
animals.7 It is probably closely re-
lated to the members of the uric acid
group just mentioned.

Urea. — It is generally stated that
muscle contains little or no urea.
This statement is chiefly due to the
fact that it was until recently a
matter of difficulty to separate
urea, when only present in small
quantities, from other nitrogenous bases. In some animals, however,
the muscular tissue contains a fairly large amount of urea. This is
the case with the muscles of arthropods.8 Stadeler and Frerichs9
were the first to discover that the organs, including the muscles,
of Selachian fishes are rich in urea. This was confirmed in the case
of Selachian embryos by Krukenberg,10 and more recently in the
adult animals by Schroder.11 In two varieties of dog-fish, the
mean percentage of urea in the blood was 2*61, in muscle 1/95, and
in liver 1-36. Schrceder explains this by the fact that the kidneys are
sluggish in these animals. By a new method, Schondorff12 has been
able to satisfactorily establish the existence of a small quantity of
urea in the muscles of mammals; Kaufmann13 gives the percentage

1 Kemmerich, Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xviii. S. 409.

2 Jahresb. u. d. Fortsc.hr. d. Thier-Chem., Wiesbaden, Bd. xxii. S. 335.

3 Scherer, Ann. d. Chem., Leipzig, Bd. cvii. S. 314.
JNeubatier, Ztschr. f. anal. Chem., Wiesbaden, Bd. vi. S. 33.

5 Meissner, Ztschr. f. rat. Med., Leipzig, Bd. xxxi. p. 144.

6 Ann. d. Chem., Leipzig, Bd. clviii. S. 353.

7 Krukenberg and Wagner, Sitzungsb. d. phys.-mcd. Gfesellsch. zu IVurzburg, 1883, No. 4.
See also Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xi. S. 340.

8 Krukenberg, -'(Inter such. a. d. physiol. Inst. d. Univ. Heidelberg, 1881, Bd. iv. S. 33 ;
"Vergleich. pliysiol. Vortrage," 1886J S. 313.

9 Journ. f. prakt. Cham., Leipzig, 1858, Bd. Ixxiii. S. 48 ; ibid., Bd. Ixxvi. S. 58.

10 "Vergleich. pliysiol. Vortrage,'" 1886, S. 314.

11 Ztschr. f. physiol. Chem., Strassburg, 1890, Bd. xiv. S. 576 ; Krukenberg, Centralbl.
f. d. med. Wissensch.. Berlin, 1887. No. *25.

12 Arch.f. d. ges. Physiol. ,Bonn , 1 895, Bd. Ixii. S. 332. For tbe method employed, see ibid. , S. 1«

13 Arch, dc physiol. norm,, ctpath., Paris, Se"r. 5, tome vi.

FIG. 15. — Creatine-zinc chloride crystals.
— After Klihne.

102 THE CHEMISTRY OF THE TISSUES AND ORGANS.

as 0'027 to 0'07. On the other hand, it must be stated that such
an experienced chemist as Nencki1 is still unable to discover any
urea in muscle.

Taurine is found in the muscles of horses, fishes, and molluscs. In
fishes Limpricht2 found T06 per cent.

G-lycocine is found to the extent of O39 to 0'71 per cent, in the non-
striated muscles of molluscs.3

Protic acid is an acid of doubtful nature, described by Limpricht in
fishes' muscles.

Inosinic acid (C10H14N4On) was first described by Liebig, and

f3 *%S

°c

ft

,%

\

^ 5

>0~

<5«r &'
^oooct^v

tl

0

1 H£

^ ^f)

*r

f-3

o®

FIG. 16. — Spherical compound of mercury and creatine. —
After G. S. Johnson.

estimated (0'005 to 0'02 per cent.) by Creite.4 According to Frankel,5
it is closely related to carnic acid, to be immediately described.

Lecithin and its decomposition products are present in small
quantities, and are probably derived from the nerves supplying the
muscle.6 Small quantities of cholesterin are found as well.

Carnic acid (Meischsdure) is the name given by Siegfried 7 to a con-
stituent of muscle, the discovery of which is of great importance. He
first prepared it from muscle extracts by means of ferric chloride ; the
compound so obtained is called carnifcrrin ; this contains phosphorus as

1 Nencki and Kowaski, Arch. f. exper. Path. n. PharmaJcol., Leipzig, 1895, Bd. xxxvi.
S. 395.

2 Ann. d. C%em., Leipzig, Bd. cxxvii. S. 185 ; cxxxiii. S. 300.

3 Chittenden, ibid., Bd. clxxviii. S. 266.

* Ztsclir.f. rat. Med., Leipzig, Bd. xxxvi. S. 195.

5 " Zur Kenntniss der Zerfallproducte des Eiweisses," Wien, 1896.

6 Hoppe-Seyler, "Physiol. Chem.," S. 647.

7 JBer. d. deutsch. chem. Gesellsch., Berlin, 1894, Bd. xxvii. S. 2762 ; Ztsclir. f. physiol.
Chem., Strassbnrg, Bd. xxi. S. 360.

THE EXTRACTIVES OF MUSCLE.

103

well as iron. By means of baryta water, carnic acid (C10H15N305) was
separated out from it. In muscle, this acid is combined with phosphorus
as phospho-carnic acid. Carnic acid itself is identical with antipeptone.
This discovery itself shows that our views concerning the hemi- and
anti-products of digestive proteolysis will need revision. Carnic acid
is a comparatively simple substance, of low molecular weight, and of
acid reaction. It is free from sulphur, and gives most of the proteid

FIG. 17. — Compounds of xanthine and hypoxanthine, by means of which these substances
may be isolated and identified. — After Kiihne.

a. Hypoxanthine silver nitrate, C5H4N4O.AgN03.

b. Hypoxanthine nitrate, C5H4N40. HN03.

c. Hypoxanthine hydrochloride, C-H4N40. HC1.

d. Xanthine silver nitrate, C5H4N4'00 AgN03.

e. Xanthine nitrate, C5H4N402. HN03.

/. Xanthine hydrochloride, CSH4N402HC1.

tests ; it does not give Millon's reaction. This discovery will no doubt
form an important clue in the problem of proteid constitution. This
announcement of Siegfried's has been fully confirmed by Balke,1
who has prepared many compounds and derivatives (oxycarnic acid,
C30H41N9015; oxylic acid, C18H28N408; and various crystalline metallic
salts of these acids), and has devised a method for its estimation.2 It

1 Ztschr. /. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 248.

2 Balke and Ide, ibid., Bd. xxi. S. 380.

io4 THE CHEMISTRY OF THE TISSUES AND ORGANS.

has been further confirmed by Frankel,1 who finds that pure amplio-
peptone is also sulphur-free.

Phosphocarnic acid has a complicated molecule ; it yields on
decomposition carnic acid, carbonic anhydride, succinic acid, sarcolactic
acid, and a strongly reducing carbohydrate. Siegfried compares it to
nuclein; but nucleins yield proteid on decomposition; phosphocarnic
acid yields carnic acid (antipeptoiie) instead; he suggests the term
nucleon for it. The percentage of this substance in human muscle is
0'1-0'2. In new-born children the muscles contain less (0 to 0'06 per
cent.2

A phosphocarnic acid is also found in milk, but differs from that in
muscle by yielding fermentation lactic acid instead of sarcolactic acid
on decomposition.3

Kriiger* has found that on hydrolysis and simultaneous oxidation by
means of ferric chloride, phosphocarnic acid gives off carbonic anhydride ;
no other substance in muscle extracts does this. He therefore looks
upon it as the material in muscle which during muscular activity gives
off carbonic anhydride without using up oxygen. This is a conclusion
that requires serious consideration and renewed research before it can
be accepted, but it is another indication of the importance of Siegfried's
work.

We now pass to the non-nitrogenous extractives : —

Glycogcn. — This substance may be extracted from muscle by hot
water5; or by dilute potash6; the latter reagent HVrc.ts a, much more,
thorough extraction. Cramer,7 using Kiilz's method, found that different
groups of muscles contain varying amounts of glycogen, but that corre-
sponding muscles of the two sides of the body contain the same amount.
In the heart, glycogen is unequally distributed in the different regions
(Cramer). The average percentage of glycogen in fresh heart muscle
is, however, about the same as in voluntary muscle, though it dis-
appears after death (being converted into sugar as in the liver) more
rapidly than in skeletal muscle.8 Glycogen also occurs in other
involuntary muscles.9

The glycogen in muscle during life varies in quantity. The following
are the principal causes of variation : —

1. Starvation. — The muscle glycogen disappears during inanition, but
much more slowly than the hepatic glycogen.10 Luchsinger11 stated
that the glycogen of the heart muscle disappears still less quickly, but
Aldehoff (using Kiilz's method) could not confirm this.

1 Loc. cii.

2 M. Miiller, Ztschr. f. physiol. Chem., Strassburg, 1897, Bd. xxii. S. 561.

:; K. Wittmaack (ibid., S. 567) gives the percentage of nucleon in human milk as 0'124 ;
in cows' milk, 0'056, and in goats' milk, O'll. Blumenthal (Vircliow's Archiv, Bd. cxlvi.
S. 65) gives the percentage in cows' milk as 0'05.

4 Ztschr. f. physiol. Chem., Strassburg, 1896. Bd. xxii. S. 95.

5 Briicke, Sitzungsb. d. k. Akad. d. Wissensch., Wicn, 1871, Bd. Ixiii. Abtli. 2, S. 214 ;
Nasse, Arch. f. d. ges. Physiol., Bonn, Bd. ii. S. 97.

6 Abeles, Med. Jahrb., Wien, 1877, S. 551 : Ktilz, Ztschr. f. Bid., Mlinchcn, Bd. xxii.
S. 161. See also Schmelz, ibid., Bd. xxv. S. 180.

7 Ibid., Bd. xxiv. S. 67.

8 Boruttau, Ztschr. f. physiol Chem., Strassburg, Bd. xviii. S. 513.

9 In the stomach, Briicke, loc. cit. ; in the plain muscles of gastropods, Chittenden,
Ann. d. Chem., Leipzig, Bd. clxxviii. S. 266 ; Bizio, Atti. r. 1st. Veneto di sc., lett. et arti,
1866, Se>. 3, tome i.

10 Weiss, Sitzungsb. d. k. Akad. d. Wisscnsch., Wien, Bd. Ixiv. ; Aldehoff, Ztschr. f.
J3ioL, Miinchen, Bd. xxv. S. 137.

11 Dissertation, Zurich, 1875.

THE EXTRACTIVES OF MUSCLE.

I05

2. Work. — During work the glycogen disappears, being perhaps
transformed into sugar and the products of its combustion, of which
lactic acid may be an intermediate one1 (Weiss, Manchc, Monari).
This loss of glycogen is shown by numerous analyses, of which the
following from Manche will serve as a type : —

Percentage of Glycogen in
Limb at rest.

Percentage of Glycogen in
opposite Limb, which was made
to contract for 23-65 minutes.

Percentage loss of Glycogen
in Tetanised Limb.

1

0-1277

0-114

12-76

2

0-2287

0-1942

15-09

3

0-2267

0-1917

15-44

3. Removal of liver. — Minkowski,2 Laves,3 and Schmelz 4 find that
after removal of the liver the muscle glycogen rapidly diminishes. Some
observers,5 however, consider that the muscles have a glycogenic
function apart from that of the liver.

4. Cutting the nerve of a muscle causes an accumulation of glycogen
in the muscle so paralysed.6

5. Cutting the tendon of a muscle produces the same effect.7

6. Ligature of the artery of a muscle leads to a decrease in its
glycogen, especially if cedema follows the operation, the accumulated
lymph leading to saccharification (Chandelon, Manche).

Sugar. — During life the sugar in muscle is at a minimum ; it
increases after death as the glycogen disappears. The sugar is not
maltose, as Nasse 8 supposed, but dextrose, as Meissner 9 suggested ; the
work of Panormoff lo with the phenylhydrazine reaction has placed this
beyond doubt. Small quantities of dextrin are found as an intermediate
product.11

Inosite. — The occurrence of this substance in voluntary muscle
has been noted by Scherer 12 and Limpricht ; in unstriated muscle by
Lehmann ; and in heart muscle, where it is more abundant than in
skeletal muscle, by Boruttau.13

Fat. — This is always obtained from muscle, though whether any
occurs in the true muscular substance apart from the entangled
adipose tissue, it is difficult to say. Dormeyer 14 finds that after muscle
has been subjected to preliminary gastric digestion, ether extracts 8'5

1 Weiss, loc. cit. ; Manchu, Ztschr. f. BioL, Miinchen, Bd. xxv. S. 163 ; Monari, Chem.
Centr.-Ll., Leipzig, 1889, Bd. ii. S. 372.

^ Arch, f. cxper. Path. u. PharmakoL, Leipzig, Bd. xxiii. S. 139.

3 Inaug. Diss., Konigsberg, 1886.

4 Ztschr. f. Biol., Miinchen, Bd. xxv. S. 180.

5 Prausnitz. Ibid., Bd. xxvi. S. 377 ; Schmelz, loc. cit.

6 Chandelon, Arch. f. d. ges. Physiol., Bonn, Bd. xiii. S. 626 ; Manchd, loc. cit.

7 E. Krauss, Virchow's Archiv, Bd. cxiii. S. 315.

8 "Zur. Anat. u. Physiol. der quergestreiften Muskel," Leipzig, 1882.

9 Nadir, v. d. k. Gcscllsch. d. Wisscnsch. u. d. Gearg-Aug.-Unii\,Gottinsen, 1861, S. 206 :
1862, S. 157.

10 Ztschr. f. physiol. Chem., Strasslmrg, Bd. xvii.

11 Nasse, loc. cit. ; Limpricht, loc. cit.

™ Ann. d. Chem., Leipzig, Bd. Ixxvii. S. 322.

13 Ztschr. f. physiol. Chem., Strasslmrg, Bd. xviii. S. 513.

14 Arch.f. d. gcs. Physiol., Bonn, 1896, Bd. Ixv. S. 90.

io6 THE CHEMISTRY OF THE TISSUES AND ORGANS.

per cent, more of the total fat obtainable ; without such preliminary
digestion, extraction with ether is useless for quantitative purposes. E.
Bogdanow x believes that the fat which is thus soluble in ether with
difficulty is a real constituent of the muscle plasma, and states that it is
richer in volatile fatty acids than that from the surrounding connective
tissues. For " Adipocere," see p. 20.

Lactic acids. — Among the oxypropionic acids with the empirical
formula C3H603, one called hydracrylic acid, or ethylene lactic acid, CH2
(OH).CH2.COOH, is not found in the body. Small quantities of this
material were formerly described 2 as occurring in muscle extracts, but
this is not the case ; the acid mistaken for it was acetyl-lactic acid
H3CH(C2H302)COOH.3

The remaining lactic acids^ are stereochemical isomerides of
ethylidene lactic acid. They are three in number, and differ in optical
activity, and in the solubility, optical activity, and amount of crystallisa-
tion water in their zinc, calcium, and lithium salts.4

Their formula is CH3.CH(OH).COOH. The differences between
them are due, according to the theory of Bel and Van't Hoff, and as the
expression stereochemical implies, to the space relationships of the atoms.

The three isomerides are —

(a) The optically inactive acid. This is the ordinary fermentation
lactic acid, which occurs in milk when it turns sour ; it has been found
in small quantities in muscle,5 in the grey matter of the brain,6 and in
some cases of diabetic urine. Its most characteristic salts are —

Zinc lactate Zn(C3H503)2 4- 3H.20 ; soluble in fifty-three parts of water
at 15° ; in six parts at 100° C. ; almost insoluble in alcohol.

Calcium lactate, Ca(C3H503)2-h5H20 ; soluble in 9 '5 of cold, and in
all proportions in boiling water. Insoluble in cold alcohol.

(&) Dextrorotatory lactic acid. — This is paralactic, or sarcolactic
acid. This is the lactic acid par excellence of muscle.7 It is found in
the blood,8 particularly after muscular activity.9 It is found in the
urine after muscular activity,10 during diminution of oxidation processes,11
in phosphorus poisoning, and after extirpation of the liver.12 It is found
as noted when we considered them, in many organs and tissues after
death. Its best known salts are —

Zinc sarcolactate, Zn(C3H503)2 + 2H20. Soluble in 17 '5 parts of water at
15° C., and in 96'4 parts of boiling 98 per cent, alcohol.

lArch.f. d. ges. Physiol., Bonn, Bd. Ixv. S. 81.

2 Wislicenus, Ann. d. Chem. Leipzig, 1873, Bd. clxvii. S. 302.

3 Siegfried, Ber. d. deutsch. cliem. Gesellsch., Berlin, 1889, S. 2711.

4 On lithium lactates, see Hoppe-Seyler and Araki, Ztschr. f. physiol. Chem., Strassburg,
1895, Bd. xx. S. 365.

5 Heintz, Ann. d. Chem., Leipzig, 1871, Bd. clvii. S. 314.

6 Gschleidlen, Arch. f. d. ges. Physiol., Bonn, 1873-4, Bd. viii. S. 71.

7 Liebig, Ann. d. Chem., Leipzig, 1847, Bd. Ixii. S. 326 ; Wislicenus, ibid., S. 302.

8 Gaglio, Arch. f. Physiol., Leipzig, 1886, S. 400; Irisawa, Ztschr. f. physiol. Chem.,
Strassburg, Bel. xvii. S. 340.

9 Spiro, Ztschr. f. physiol. Chem., Strassburg, 1877, Bd. i. S. Ill : v. Frey, Arch. /.
Physiol., Leipzig, 1885, S. 557.

10 Colasanti and Moscatelli, Jahresb. it. d. Fortschr. d. Thicr-Chem., Wiesbaden, 1887,
S. 212 ; Marcus, Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxix. S. 425.

11 Araki, Ztschr. f. physiol. Chem., Strassburg, Bde. xv., xvi., xvii., and xix.

12 Minkowski, Centralbl.f. d. med. Wissensch., Berlin, 1885, No. 2 ; Arch.f. exper. Path.
u. Pharmakol., Leipzig, 1886, Bd. xxi. S. 40 ; Marcuse, loc. cit.; Nebelthan, Ztschr. f. Biol.,
Mimchen, 1889, Bd. xxv. S. 123.

THE EXTRACTIVES OF MUSCLE,

107

Calcium sarcolactate, Ca(C3H503)2 + 4 or 4J H20. Soluble in 12*4 parts
of cold water and in all proportions of boiling water or alcohol.
These salts are levorotatory, though the free acid is dextrorotatory.

This is produced by the fermentation

1

(c) Levorotatory lactic acid,
of cane-sugar by means of a
special kind of bacillus,1 and
is also found in cultures of
Gaffky's typhoid bacillus in
a solution of sugar and pep-
tone.2 Very little is known
about it yet.

In all cases where three
isomerides exist, as in the
present case — one optically
inactive, one levorotatory,
and the third dextroro-
tatory— it should be under-
stood that strictly speaking
there are only two isomer-
ides, one dextro- the other
levorotatory, the third or
inactive variety being a com-
pound of the other two.
This was first shown by

Pasteur 3 in connection with raceinic acid, which is optically inactive.
By appropriate methods of crystallisation it can be separated into two
varieties of tartaric acid, one dextrorotatory, the other levorotatory.

Another method of separating
an optically inactive material into
its optically active components,
has been alluded to on p. 32, in
connection with glutaminic acid
and leucine. It consists in allow-
ing moulds, like Penicillium
ylaucum, to grow in a solution of
the inactive compound ; one only

FIG. 18. — Zinc sarcolactate. — After Klihue.

«|f jt
| *

Hi

V!

of its active components is des-
troyed by the mould, and the
other remains untouched. In the
case of optically inactive lactic
acid, the question has been
attacked by the method of

Crystallisation of various of its FIG. 19.— Calcium sarcolactate.— After Kiihne.

compounds, particularly of those

with strychnine, and also of zinc ammonium lactate.4

The mode of formation of lactic acid in muscles has been the subject
of numerous researches. That the acid is sarcolactic acid has been

1 Schardinger, Monatsh. f. Chem., Wien, Bd. xi.

2 Blaclistein, Arch, de sc. lioL, St. Petersbourg, tome i. p. 199.

3 Ann. de. chim., Paris, Ser. 2, tome xxiv. p. 442 ; xxviii. p. 56 ; Compt. rend. Acad.
d. sc., Paris, tome xxxvi. p. 26; xxxvii. p. 162; Ann. d. Phys. u. Chem., Leipzig, Bd.
Ixxx. S. 127 ; xc. S. 498, 504.

4 Purdie and Walker, Trans. Chem. Soc. London, 1892, p. 754 ; 1893, p. 1143.

io8 THE CHEMISTRY OF THE TISSUES AND ORGANS.

stated by Berzelius,1 Du Bois-Reymond,2 Kiilme,3 and Heidenhain.4 It
may be readily detected in an ethereal extract by Uffelmann's reaction.5
Lactic acid is formed, not only after death, but also on activity
during life : it is doubtless one of the acid products the accumulation
of which produces fatigue? though the possibilities of basic products
being also produced and causing fatigue by their influence on the
central nervous system should not be overlooked.7

A number of recent researches have, however, thrown doubt on the ques-
tion whether any free lactic acid is actually formed under these circumstances.
In determining this question, it is very important to know the indicator
employed in the investigation ; but even with the same indicator the results
obtained by different workers are sometimes discordant. One of the best
indicator? for detecting weak acids i»phenolphtalein.

Moleschott and Battistini8 found a rise of acidity during rigor, while
Blome9 did not. Warren10 finds in fatigue that the acidity is increased,
but that the number of acid molecules is diminished. This is explained by
supposing that in resting muscle the anhydride, and in contracting muscle
the free acid, is present, which latter combines with twice as much base as
the anhydride.

Gleiss n agrees with the generally accepted view, that the acidity of contract-
ing muscle is due to lactic acid, and finds that the slowly contracting red
muscles of the rabbit, or the very slowly contracting muscles of the tortoise,
become acid less rapidly than ordinary voluntary muscles.

Weyl and Seitler l'2 were the first to point out that the increase of acidity
may be at least in part due to acid potassium phosphate, produced from the
alkaline phosphate by the development of new phosphoric acid from organic
compounds, like lecithin and nuclein. Irisawa13 takes a similar view in
reference to the acidity of dead organs like the liver and pancreas. The
most careful work in this direction, however, is that of Rohmann.14 He used
lacmoid and turmeric as indicators, and found that fresh muscle is alkaline to
lacmoid, and neutral or weakly acid to turmeric. During tetanus and rigor,
the alkalinity to lacmoid decreases, and the acidity to turmeric increases. He
attributes the acid reaction to monopotassium phosphate (KH2P04), and
the alkaline reaction to dipotassium phosphate (K2HP04), and to sodium
bicarbonate. If lactic acid is formed, none is free. He admits that ether
will extract lactic acid from muscle, but it will do so from alkaline muscle,
and is produced by monopotassium phosphate turning it out of combination
during the process of extraction.

With regard to the origin of lactic acid, 0. Nasse believes it comes
from the glycogen. This is the simplest view of the matter to take,
and it is supported by some work of Ekunina.15 Many facts, however,
do not fit in with this explanation ; and the view very generally held

1 "Lehrbucli d. Chem.," vol. vi. p. 557.

2 "Gesammelte Abhandl. zur allgemein. Muskel mid Nerven Physik," Leipzig, 1877.

3 "Untersuch. ii. das Protoplasma," Leipzig, 1864.

4 " Mechanische Leistung," Leipzig, 1864, S. 143.

5 A dilute solution of ferric chloride and carbolic acid, which is violet, is turned yellow
by a trace (1 in 10,000) of lactic acid (Ztschr. f. klin. Med., Berlin, Bd. viii. S. 392).

(i Ranke, "Tetanus." Leipzig, 1865, p. 350.

7 A. Mosso, Trans. Internat. Med. Cong., Berlin, 1890.

8 Arch. ital. de. biol., Turin, vol. viii. p. 90.

9 Arch. /. cxper. Path. u. PharmakoL, Leipzig, 1890, Bd. xxviii. S. 113. Blome's
results have been much criticised by Rohmann ; Arch. f. d. yes. Physiol., Bonn, 1892, Bd.
1. S. 84, ibid.. 1893, Bd. Iv. S. 589.

10 Arch.f. 'd. ges. Physiol., Bonn, Bel. xxiv. S. 391. n Ibid., Bd. xli. S. 69.

12 Ztschr. f. physiol. Chem., Strassburg, Bd. vi. S. 557. 13 Ibid., Bd. xvii. S. 340.

14 Loc. cit. 15 Journ.f. prakt. Chem., Leipzig, N.F., Bd. xx.

INORGANIC CONSTITUENTS OF MUSCLE. 109

is that the acid arises from the decomposition of complex molecules,
of which proteid forms a part. It is quite possible that the lactic acid
may originate in both ways.

The idea that the acid has a proteid origin was mooted by Kiihne 1
in some of his earliest observations. He showed that not only is the
acid formed during rigor mortis, but also during the heat-coagulation of
myosin. Bohm 2 supported the proteid origin of lactic acid, and his view
was endorsed by Hoppe-Seyler.3 Some of my own experiments showing
the development of acid during the coagulation of pure myosin,4 and
Latham's theoretical views5 on the constitution of the proteid mole-
cule, tend in the same direction. Araki6 found that diminution of
oxidation in the body, such as is produced by the inhalation of carbonic
oxide, leads to the appearance of lactic acid (and sometimes albumin
and sugar) in the urine. This is accompanied by increase in proteid
katabolism ; and this again, as Hammarsten 7 points out, is in favour of
the same view.

Inorganic constituents of muscle. — The total ash is from 1 to 1'5
per cent. In it may be noted the predominance of potash among the
oases, and of phosphoric acid among the acids. The following analyses
are by Bunge : 8 —

In parts per 1000.

I. II.

K20 . . . 4-654 4-160

Na.,0 . . . 0-770 0-811

CaO ... 0-086 0-072

MgO . . . 0-412 0-381
Fe203 . . . 0-057

P905 . . . 4-644 4-58

Cl ... 0-672 0-70

S03 . . ... 0-10

More recent work on this question is by J. Katz.9 The flesh of a
large number of animals was investigated. The following figures give the
minimum and maximum in 1000 parts of fresh flesh' — :K, 2 '4 to 4'6; JN"a, 0'3
to 1-5; Fe, 0'04 to 0-25; Ca, 0'02 to 0'39; Mg, 0-18 to 0'37 : P (from
phosphates), 1-22 to 2-04 • (from lecithin), 0'13 to 0'48 ; (from nuclein), 0'09 to
0-32 ; CI, 0-32 to 0-8.

Chemical changes accompanying the contraction of muscle —

The physiology of muscular contraction, the influence of muscular
work in metabolism, the gases of muscle, and other problems, will be
studied in other portions of this work. It may not be inappropriate here,
however, to conclude this section by stating briefly the main facts,
having a chemical bearing, relating to changes accompanying muscular
contraction. The changes are in kind similar to those which occur in

1 ArcJi.f. Anat. u. PhysioL, Leipzig, 1859, S. 795 ; " Myologische Untersuch.," Leipzig,
1860, p. 184.

2 Arch. f. d. ges. PhysioL, Bonn, Bd. xxiii. S. 44. In a later paper (ibid., 1890, Bd. xlvi.
S. 265) Bohm reaffirms his position in reference to some criticisms of Werther (ibid., S. 53).

3 "Physiol. Chem.," S. 666, 667.

4 Journ. PhysioL, Cambridge and London, 1887, vol. viii. p. 154. These results, how-
ever, are criticised by v. Flirth.

5 Brit. Med. Journ., London, 1886, vol. i. p. 630.

6 Loc. cit. (Note 11, p. 106).

7 "PhysioL Chem," 3rd German edition, S. 332.

8 Ztsclir. f. pliysiol. Chem., Strassburg, Bd. ix. S. 60.

9 Arch.f. d. yes. PhysioL, Bonn, 1896, Bd. Ixiii. S. 1-85.

no THE CHEMISTRY OF THE TISSUES AND ORGANS.

muscles during so-called rest; there is an exaggeration of the normal
" chemical tone " of the tissue, and an explosive liberation of energy.

1. Change in reaction. — The muscle becomes acid ; this is generally
believed to be due to the production of sarcolactic acid. The views
of Bohmann and others in relation to this question (see p. 108) deserve,
however, careful consideration.

2. Changes in the proteid. — There is no marked and immediate
increase of urea in muscular activity, though recent work tends to show
that proteid katabolism is increased, and that the increase in urea
leaves the body the next day or the day after. The main work,
however, appears to fall on the non-nitrogenous part of the muscle, as
evidenced by the immediate and large increase in the amount of
carbonic anhydride that leaves the muscle. Hermann's theory of
muscular contraction assumes that* the change is similar in kind to that
which occurs on death, though less in degree. On death, he assumes
that the hypothetical molecule he terms inogen l is split into carbonic
anhydride, sarcolactic acid, and myosin. But anything like the
formation of a clot of myosin has never been observed in living con-
tracting muscle.

3. Changes in the extractives. — During tetanus the extractives
soluble in water decrease, and those soluble in alcohol increase.2
This appears to be chiefly explicable by the disappearance of glycogen,
and appearance of sugar and lactic acid.

4. Changes in the gases. — Hermann's theory just referred to was
largely the outcome of his failure to discover oxygen among the gases
of muscle. The oxygen used in the formation of carbonic anhydride
must therefore be held in complex union within the muscle. On
contraction, as on the occurrence of rigor mortis, the amount of
carbonic anhydride given off is increased. The amount of oxygen
absorbed from the blood is also raised, but not in proportion ; hence the
fraction -^^^^«i riges. (See more Mly ,. Eespiration >y

5. Production of reducing substances. — Eesting muscle oxidises
pyrogallic acid ; tetanised muscle does not. A solution of nitrites
passed through contracting muscle is changed into one of nitrates, and
the colour of solutions of indigo sulphate is altered in the same
way as by reducing agents.3 A. Schmidt4 arrived at the same
conclusion from the examination of the venous blood of tetanised
muscle, but what the reducing substances are that are produced is
quite unknown.

Electrical organs. — From the torpedo organ, Weyl5 extracted,
probably from the mucous fluid between the plates, a " torpedo mucin."
This, however, yields no reducing sugar. A small quantity of gelatin
and a globulin (coagulated by heat at 55°- 60°) were also obtained.6
The tissue, like muscle, becomes acid and less transparent after

1 The nearest approach to Hermann's theoretical substance, inogen, is Siegfried's phospho-
carnic acid (see p. 103).

2 Helmholtz, Arch. f. Anat. u. PhysioL, Leipzig, 1845, S. 72; Ranke, "Tetanus,"
Leipzig, 1865; Heidenhain, Arch. f. d. ges. PhysioL, Bonn, Bd. iii. S. 574.

» Griitzner, ibid., Bd. vii. S. 255 ; Gscheidlen, ibid., Bd. viii. S. 506.

4 Sitzungsb. d. Tc. Alcad. d. Wissensch., Wien, Bd. xx.

5 Ztschr. f. physiol. Chem., Strassburg, Bd. vi. S. 525.

6 Kriikenberg was unable to obtain myosin ("Weitere Untersuch. zur vergleich.
Muskelchem." Vergleich. physiol. Studien, 2 Reihe, Abth. 1, S. 143-7).

THE SKELETAL TISSUES.

ITI

death.1 Weyl 2 found the percentage of water in the muscles of
torpedo to be 7 7 '5 ; in the electrical organ, 89. He was also able to
separate a number of organic substances from the organ, similar to
those occurring in muscle and nerve, such as creatine, xanthine,
lecithin, fat, cholesterin, fatty acids, and inosite. Frerichs and
Stadeler found urea. In another research, Weyl 3 found that excitation
of the organ produced an increased formation of phosphoric acid in it.

THE SKELETAL TISSUES.

Most of the chemical substances occurring in the connective tissues
(collagen, elastin, mucin, fat) have been already described (see pp. 69-72).
There are still a few to be discussed, which will be most conveniently
done under the heads — Bone, Tooth, Cartilage, and Notochord.

Bone. — Bone differs from most other tissues in its high percentage of
mineral matter. It contains 46*7 per cent, of water,4 of which Aeby 5
considers 11 or 12 are in a state of loose chemical combination,
analogous to water of crystallisation.

The composition of undried bone without separation of marrow or
blood is given by Hoppe-Seyler thus : —

Water, 50 '00 per cent.
Fat, 15-75 „

Ossein, 11 '40 per cent.
Bone earth, 21 '85 ,,

Zalesky's analyses of dried macerated bone are as follows : —

Human Bone.

Bone of Ox.

Bone of Guinea-Pig.

Organic constituents .

34-56

32-02

34-70

Inorganic ,,

65-44

67-98

65-30

Fossil bones analysed by Fremy6 show a smaller percentage of
organic matter.

The organic constituents of bone are ossein or collagen, small quantities
of elastin from the lining of the lacunae and canaliculi,7 proteids, and
nuclein from the cells, and a small quantity of fat even after the removal
of all the marrow. The absence of mucin in compact bone is noteworthy,
showing that the ground substance is entirely replaced by calcareous
matter.8 Marrow, however, yields mucin.9 The inorganic constituents
of bone are calcium phosphate, calcium carbonate, calcium chloride,
calcium fluoride, magnesium phosphate, and small quantities of sulphates
and other chlorides.

1 Boll, Arch. f. Anat. u. PhysioL, Leipzig, 1893, S. 99 ; Du Bois-Reymond found
that the electrical organ of Malapterurus also becomes acid on activity.

2 Monatsb. d. Jc. ATcad. d. Wissensch., Berlin, April 1881.

3 Arch. f. Anat. u, PhysioL, Leipzig, 1884, PhysioL AUh., S. 316.

4 Lukjanow, Ztsdir. f. physiol. Chem., Strassburg, Bd. xiii. S. 339.

5 Centralbl.f. d. med. Wissensch., Berlin, 1871, No. 14.

6 Ann. de chim., Paris, Ser. 3, tome xliii. p. 47.

7 This substance is not keratin, as Brosicke supposed. See H. E. Smith, Ztschr. f.
Biol. , Mlinchen, Bd. xix. S. 469.

8 R. A. Young, Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 803.
9Rustiksky, Centralbl. f. d. med. Wissensch., Berlin, 1872, S. 562.

ii2 THE CHEMISTR Y OF THE TISSUES AND ORGANS.

From a large number of analyses, Hoppe-Seyler gives the following
figures representing percentages of the total ash : —

Ca. P04. CO,. Fl. Mg. Cl.

38-49 54-46 6-24 1-28 0-44 0-19

From his own numbers, Zalesky has calculated the probable composition
of the mineral constituents of bone as follows : —

Calcium phosphate . . . 83 '889

„ carbonate . . . 13 -03 2
Calcium in combination with fluorine,

chlorine, etc. .... 0*350

Fluorine 0-229

Chlorine . . ^ . . . 0-183

Hoppe-kSeyler considered that the characteristic inorganic ingredient of
bone, dentine, and enamel is one analogous to apatite. Apatite has the
formula Ca10Fl2(P04)G, or Ca10Cl.2(P04)6. Very small quantities of these
substances, however, occur in bone ; the chief compound is one in which C0.j
takes the place of the F12 or C12, namely, Ca10C03(P04)G. See, however,
Gabriel's researches below.

Tooth. — The calcareous tissues of tooth are dentine, enamel, and
crusta petrosa. The last named is bone ; dentine is chemically similar
to bone. Enamel, though epithelial in origin, may be conveniently
taken here.

Dentine. — This consists of water 10 per cent., and solids 90 per cent.
The solids are organic and inorganic. The organic solids are less
abundant than in bone. They consist of collagen and elastin ; the latter
form the lining of the dentinal tubules. From Aeby's analyses, Hoppe-
Seyler gives the following table : —

Ca1()C03(P04)6 . . . 72-06 per cent.
MgH(P04). . . . 0-75 „

Organic substances . . 27*70 ,,

Enamel. — This is the hardest tissue in the body. Hoppe-Seyler 's
quantitative analyses give the following mean result : —

Ca10C03(P04)(. . . . 96-00 per cent.
MgHPO4 . . . .1-05
Organic substances . . 3 '60 ,,

Various other investigators give numbers varying from 2 to 10 per
cent, of organic matter. This they estimate by loss on ignition. Tomes,1
however, has recently shown that this loss is chiefly if not wholly due
to water. On attempting to estimate the organic matter directly,
none was found, or a quantity too small to be weighed.

Gabriel 2 has recently worked at the question of the constitution of
the mineral matter of bones and teeth. Some of his conclusions do
not accord with the older work of Hoppe-Seyler. He finds that the
constituents are water, lime, magnesia, potash, soda, phosphoric acid,
carbonic anhydride, chlorine, and fluorine. The quantities of lime
and phosphoric acid, which are the most abundant constituents, vary

1 Journ. PhysioL, Cambridge and London, 1896, vol. xix. p. 217 ; Trans. Odont. Soc.
Gr. Brit., London, 1896. p. 114.

2 Ztschr. f. physiol. Chem., Strassburg, Bd. xviii, S, 257,

CARTILAGE. 113

but little, and are proportional to each other ; the amounts of magnesia
and carbonic anhydride are also proportional the one to the other.
The amount of potash is greater than that of soda. The amount of
chlorine is very small, and is greater in the teeth (0*21 per cent.) than
in bone. Fluorine is a minimal constituent of both 1 ; as a rule, not
more than 0*05 per cent, is present.

Water is present in two forms ; one part passing off at 300°-350° C.
is similar to water of crystallisation ; the other part is only expelled by
fusion with silicic acid, and is an expression of the basicity of the
phosphate, and is called water of constitution or acidic water.

The composition of the ash finds its simplest expression in the
formula, Ca3(P04)2+Ca5HP3013+Aq, in which 2 to 3 per cent, of
the lime is replaced by magnesia, potash, and soda, and 4 to 6 per cent,
of the phosphoric acid by carbonic anhydride, chlorine, and fluorine.
The limit of variation is, however, small, and the differences between
bone ash and tooth ash are not greater than those between the ash of
different bones.

The notochord. — Steinberg2 found that neither gelatin nor chondrin
is obtainable from the notochord, and Neumann3 that the cells stain
with iodine as though they contained glycogen. Kossel 4 obtained a con-
siderable supply of material from large lampreys, and found that it
contains 95-96 per cent, of water ; this contrasts strongly with cartilage,
and corresponds with what one finds in other embryonic tissues. The
amount of ash is O85 per cent. The amount of glycogen constitutes
from 12 to 15 per cent, of the solids present; the high percentage of
this substance is another feature common to embryonic structures.
There is not much more than a trace of proteid matter soluble in water.
Gelatin, collagen, and mucin are all absent ; the bulk of the solid matter
is an insoluble proteid easily digested by artificial gastric juice ; it yields
no sugar on treatment with mineral acids.

Cartilage. — The following analyses by Hoppe-Seyler exhibit the
relative proportions of the chemical constituents of human hyaline
cartilage. In 1000 parts —

Costal Cartilage. Articular Cartilage.

Water 676*6 735'9

Solids 323-3 264-1

Organic solids . . 301'3 248'7

Inorganic solids . . 22'0 15 '4

Potassium sulphate (in a hundred parts of ash) . 26 '66
Sodium sulphate „ „ . 44 '81

Sodium chloride ,, ,, .6*11

Sodium phosphate ,, „ . 8*42

Calcium phosphate ,, „ 7 '88

Magnesium phosphate „ ,, . 4*55

The organic solids consist in small part of those in the cells,
which are of the usual proteid nature, together with small quantities
of fat and glycogen, demonstrable by micro-chemical means; but the

1 For recent estimations of fluorine in bone and teeth by Carnot's method (Compt. rend.
Acad. d. sc., Paris, tome cxiv. p. 750), see Gabriel, Ztschr. f. anal. Chem., Wiesbaden,
Bd. xxxi. S. 522 ; and Waampelmeyer, ibid., Bd. xxxii. S. 550.

*Arch.f. PhysioL, Leipzig, 1881, S. 105.

3 Arch. f. mikr. Anat., Bonn, Bd. xiv. S. 54.

4 Ztschr. f. physiol. Chem., Strassburg, Bd. xv. S. 331.

VOL. I. — 8

1 14 THE CHEMISTR Y OF THE TISSUES AND ORGANS.

great bulk of the organic solids is derived from the matrix of the
cartilage.

In fibrocartilage, the hyaline matrix is pervaded either by white
fibres (white fibrocartilage), or by yellow fibres (yellow or elastic fibro-
cartilage).

In contrast with true bone, the analysis (by Fremy) of the calcified
cartilage of the ray may be here given : —

Ash per cent. . . . 30*00
Calcium phosphate . .27*7

Calcium carbonate . . 4'3
Magnesium phosphate, traces.

The matrix of hyaline cartilage. — The organic basis of the matrix was
formerly described as choinlriijcn ; ^nd just as gelatin is obtained from
collagen on boiling, so chondrin is obtained by boiling chondrigen.
Chondrin, like gelatin, gelatinises on cooling a solution of it made with
warm water, but in many of its reactions it differs from gelatin.

Elementary analyses of chondrin, however, showed very great dis-
crepancies, and Morochowetz 1 arrived at the conclusion that chondrin is
not a chemical unit but a mixture of gelatin and mucin. This conclusion
has been more recently amplified by C. T. Morner,2 who worked under
the superintendence of Hammarsten.

The matrix contains four substances — (1) collagen, (2) an albuminoid,
(3) chondromucoid, and (4) chondroi tin-sulphuric acid. Of these con-
stituents the last two, with perhaps a little collagen, lie around the cells,
forming what Morner calls chondrin balls; they correspond to the mucin
of Morochowetz, or hyalogen of Krukenberg, and are coloured blue by
methyl-violet. They lie in the meshes of a network composed of collagen
and inucoid, which is stainable by tropseolin.

These four constituents may be separated as follows. The mucoid
and chondroitin-sulphuric acid are dissolved out with 0'2 to 0*5 per
cent, solution of potash ; the collagen is dissolved out by hot water, being
converted into gelatin in the process; the albuminoid remains undissolved.

(1) The collagen differs from ordinary collagen in only containing
164 per cent, of nitrogen.

(2) The albuminoid, which is found only in late adult life, is a proteid-
like substance of an insoluble nature. It contains loosely combined
sulphur. It differs from elastin in its high percentage of sulphur (see p. 73).

(3) Chondromucoid. — This substance has the following percentage
composition :— C, 47'3 ; H, 642; N, 12-58; S, 242; 0, 31-28 (Morner).
The sulphur is loosely combined. Chondromucoid gives the ordinary
proteid reactions. On decomposition, it yields the usual decomposition
products of proteids, with chondroitin-sulphuric acid in addition; this
latter substance is, on further decomposition, broken up into sulphuric
acid and a reducing substance. Schmiedeberg 3 regards chondromucoid
as a union of proteid with chondroitin-sulphuric acid.

(4) Chondroitin-sulphuric acid. — This substance was called chondroitic
acid by Bodeker 4 and Krukenberg 5 (who classed it among his hyalins,

1 Verliandl. d. natur'h.-mcd. Ver. zu Heidelberg, Part 5, Bd. i.

2 Ztschr. f. pliysiol. Chem., Strassburg, Bd. xii. S. 396; Skandin. Arch. f. PhysioL,
Leipzig, Bd. i. S. 210.

3 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1891, Bd. xxviii. S. 355.

4 Ann. d. Chem., Leipzig, 1861, Bd. cxvii. S. 111.

5 Ztschr. f. BioL, Munchen, Bd. xx. S. 307.

NERVOUS TISSUES.

see p. 64). It was first prepared in a pure condition by Morner, and
its constitution made out by that observer and by Schrniedeberg. It is
partly found as such in the cartilaginous matrix, but most originates
from the decomposition of chondromucoid.

Morner found that the sulphur in it was all in the form of ethereal
hydrogen sulphate ; hence the name chondroitin-sulphuric acid. It is
almost, but not quite, characteristic of cartilage. Morner l separated it
from twenty different varieties of cartilage, from cartilaginous tumours,
and also from the tunica intiina of the aorta,2 but from no other tissue
or organ of the body.3

Schmiedeberg ascribes to it the formula C18H27NS017. On decom-
position, the first products are sulphuric acid, and a nitrogenous sub-
stance chondroitin.

C18H27NS017+H20 - H2SOf+C J

(chondroitin-sul- (water) (sulphuric (chondroitin)
phuricacid) acid)

Chondroitin is a gummy material, and a monobasic acid. On
hydration it yields acetic acid, and a new nitrogenous body called
chondrosin.

C18H2TNOH+3H.20 - C2H402+C12H21NOn

(chondroitin) (water) (acetic acid) (chondrosin)

Chondrosin is also gummy, and a monobasic acid. It reduces
Fehling's solution even more strongly than dextrose; it is dextro-
rotatory, and is the reducing substance which so many previous chemists
have obtained in an impure form from cartilage. On further decomposi-
tion it yields glycuronic acid (see p. 5) and glucosamine (see pp. 9 and 75).

NERVOUS TISSUES.

General composition. — The amount of water varies. It is present
in larger amount in the grey than in the white matter, in early
than in adult life, in the brain than in the spinal cord, in the spinal
cord than in nerves. These facts are illustrated by the following
table 4 :—

PORTION OF NERVOUS
SYSTEM.

PERCENTAGES OF WATER.

In Foetus
(W.).

Age, 20-30
(W.).

Age, 70-90
(W.).

(B.)

(P-)

(M.)

(B.)

Grey matter of brain)
White ,, i

87-92 |

83
69

84

72

85
70

81)

68/

«{

86
70

Spinal cord

73-76

68

Nerves .

...

64-72

57

...

1 Ztschr. f. physiol. Chem., Strassburg, 1895, Bd. xx. S. 357.

2 Upsala Lakarsf. Forh. , Bd. xxix.

3 Oddi (Arch. f. exper. Path. u. PharmahoL, Leipzig, Bd. xxxiii.) states he has obtained
it from livers which had undergone amyloid degeneration.

4 In the above table, ( W.) refers to Weisbach (Hofmann's "Lehrbuchd. Zoochemie," Wien
1876, S. 121); (B.) to Bernhart (Gamgee's "Physiol. Chem.," vol. i. p. 446); (P.) to
Petrowsky (Arch. f. d. gcs. Physiol., Bonn, Bd. vii.' S. 367) ; (M.) to Moleschott (Charles,
"Physiol. Chem.," p. 335); and (R.) to de Regibus (Jahresb. it. d. Fortschr. d. Thier-
Chem., Wiesbaden, Bd. xiv. S. 346).

n6 THE CHEMISTRY OF THE TISSUES AND ORGANS.

Solids. — The solids may be divided into the following classes : —

(a) Proteids. — These comprise a very considerable percentage of the
solids, especially in the grey matter (over 50 per cent.).

(b) Neurokeratin and nuclein.

(c) Phosphorised constituents ; especially protagon and lecithin.

(d) Cerebrins. — Nitrogenous substances of unknown constitution.

(e) Cholesterin. — Especially abundant in white matter.

(/) Extractives. — Creatine,1 xanthine,2 hypoxanthine,2 inosite,3 lactic
acid,3 leucine,3 uric acid,3 and urea.

(g) Gelatin and Fat. — From the adherent connective tissue.

(A) Inorganic salts. — The total mineral matter varies according to
different writers from 01 to 1 per cent.

Geoghegan 4 gives the following figures in parts per thousand of
brain : —

Total ash

Potassium

Sodium

Magnesium

Calcium

2-9 to 7-1

Chlorine .

0-6 „ 1-7

P04 .

0-4 „ 1-1

CO,

0-0 „ 0-07

S04

0-005 „ 0-02

Fe(P04)2

0-4
0-9
0-2
0-1
0-01

to 1-2
„ 2-0
„ 0-7
,, 0-2
„ 0-09

The grey matter is stated by Schlossberger to be richer in total ash
than the white, but poorer in phosphates ; Petrowsky, on the other hand,
found more phosphates in grey than in white matter.

The following table gives some typical quantitative analyses which
have been made of the proportion in which the principal solids occur in
different nervous structures : —

Portion of Nervous
System.

Proteids.

Lecithin.

Cholestarin

and Fat.

Cerebrins.

Neuro-
keratin.

Other

Organic

Matters.

Salts.

Grey matter of ox
brain 5

55-37

17-24

18-68

0-53

"~67-T^

1-45

White matter of
ox brain 5

Spinal cord 6

Human sciatic
nerve 7

24-72
23-8
36-8

9-90

51-91

9-55

3-34

>

0-57
1-1

75-1

4-0

32-57

12-22

11-30

3-07

The quantitative work 1 8 have done on this question may be sum-

1 Miiller, Ann. d. Chem., Leipzig, Bd. ciii. S. 141 ; Stadeler, Journ. f.prakt. Chem.,
Leipzig, Bd. Ixxii. S. 256.

2 Stadeler, Ann. d. Chem., Leipzig, Bd. cxvi. S. 102; Scherer, ibid., Bd. cvii.
S. 314.

3 Miiller, loc. cit. ; see also Strecker, Ann. d. Chem., Leipzig, Bd. cv. S. 316.

4 Ztschr. f. physiol. Chem., Strassburg, Bd. i. S. 330.

5 Petrowsky, toe. cit.

6 Moleschott, loc. cit.

7 Josephine Chevalier, Ztschr. f. physiol. Clicm., Strassburg, Bd. x. S. 97.

8 Halliburton, Journ. Physiol., Cambridge and London, 1893, vol. xv. p. 90.

PROTEIDS OF NERVOUS TISSUES.

117

marised in the following table of mean analyses. The organs were from
adult human beings, dogs, cats, and monkeys : —

Water.

Solids.

Percentage
of Proteids
in Solids.

Grey matter of cerebrum .

83-467

16-533

51

White „ „ .

69-912

30-088

33

Cerebellum ....

79-809

20-191

42

Spinal cord as a whole

71-641

28-359

31

Cervical cord ....

72-529

27-471

31

Dorsal cord ....

69-755

30-245

28

Lumbar cord ....

72-639

27-631

33

Sciatic nerves ....

61-316

38-684

29

This table illustrates the fact that the amount of grey matter, of
water, and the percentage of proteid in the solids, vary directly the one
with the other. This is very well seen in the different regions of the
spinal cord. The percentage of proteid in the white matter of the
brain is a little higher than in the spinal cord; this exception is
perhaps to be explained by the high percentage of neurokeratin l in
white matter, which, according to the methods used, would be included
with the proteids.

Reaction of nervous tissues. — Heidenhain 2 and Gscheidlen 3 state that
the normal reaction of the axis cylinder is alkaline ; on death or on
long-continued activity the reaction becomes acid. They further state
that the grey matter is acid even during life. 0. Langendorff4 found
the reaction of the central nervous system alkaline during life ; the
alkalinity rapidly diminishes after death, or on stoppage of the circula-
tion. S. Moleschott and Battistini 5 found both central and peripheral
portions of the nervous system acid, especially the grey matter ; this was
increased by activity.

In my own work I found in animals that the fresh tissues were
invariably alkaline, but they became, rapidly acid, especially the grey
matter. In the human brains I received from the post-mortem room the
reaction of the grey matter was always, of the white matter often, acid.
This I put down to changes after death, for at least twenty-four hours
had always elapsed since death.

The acidity is due to lactic acid ; but, according to Miiller and
Gscheidlen, it is not sarcolactic acid but the fermentation lactic acid
(optically inactive ethylidene -lactic acid). Miiller also obtained traces
of formic acid.

Proteids of nervous tissues. — The large quantity of these, especi-

1 The percentage of neurokeratin is in grey matter, 0'3 : in white matter, 2 '2 to 2 '9 ; and
in nerve, 0'3 to 0'6 (Kiihne and Chittenden, Ztschr.f. BioL, Munchen, Bd. xxvi. S. 291).

2 CentralU.f. d. med. Wissensch., Berlin, 1868, S. 833.

3 Arch.f. d. ges. Physiol. Bonn, Bd. viii. S. 171.

4 NeuroL CentralbL, Leipzig, 1885, No. 14; Centralbl. f. d. mcd. Wissensch., Berlin,
1886, No. 25.

5 Arch. ital. de biol, Turin, vol. viii. p. 90 ; Chem. Centr.-BL, Leipzig, 1887, S. 1224.

n8 THE CHEMISTRY OF THE TISSUES AND ORGANS.

ally in the grey matter, has been already alluded to. Petrowsky, in
the investigation just mentioned, describes a globulin somewhat
resembling myosin, and an albumin especially abundant in grey matter
which is coagulated at a temperature of 75° C. Baumstark,1 in a more
recent research, speaks of the chief proteid matter in nervous tissue as
resembling casein ; this is so, for it is a nucleo-proteid. My own con-
clusions 2 on the subject are as follows : —

The proteids present are three in number. The first is a globulin,
coagulated by heat at 47° C., and analogous to the cell globulin deriv-
able from nearly all cellular tissues. The second and most abundant is
nucleo-proteid. In a saline extract of nervous tissues it is mixed with
the other proteids ; attempts to prepare it by the sodium-chloride
method failed. It may, however, be "prepared in large quantities by
precipitating an aqueous extract of brain by weak acetic acid ("VVool-
dridge's method). The supply obtainable from white matter is small. It
is coagulated at 56°-60° C. ; it contains O5 per cent, of phosphorus, and
gives the general reactions of nucleo-proteids, production of intra vascular
coagulation included. The third proteid is a globulin, coagulated by
heat at 70°-75° C., and analogous to a similar globulin separable from
liver cells (see p. 86). Peptone, proteose, myosin, and albumin are not
obtainable.

Protagon. — In the year 1865, Liebreich3 separated from the brain
a material he called protagon ; he further found that, when decomposed
by baryta water, it yielded two acids — stearic acid and glycero-phosphoric
acid — and a base choline.

Hoppe-Seyler, and Diaconow 4 working under Hoppe-Seyler's direc-
tion, denied the existence of this substance, and considered that it was a
mere mechanical mixture of lecithin with a nitrogenous non-phosphor-
ised substance called cerebrin. Diaconow's analyses were, however, far
from convincing.

The subject was taken up in this country by Garngee and
Blankenhorn,5 who showed that protagon is a perfectly definite
crystalline substance of constant elementary composition. They also
showed that even prolonged treatment with alcohol and ether will not
extract lecithin from protagon, as alleged by Diaconow. When protagon
is digested with alkalis it yields cerebrin or cerebrins, and the decom-
position products of lecithin. This work has been confirmed by
Baumstark,6 Euppel,7 and Kossel and Freytag.8

Protagon is prepared as follows : — The brain is digested with alcohol
at 45° C. ; the extract is filtered warm, and cooled to 0° C. It then
deposits a white precipitate of protagon mixed with cholesterin, which
is dissolved out by means of ether. The protagon is dried, redissolved
in warm alcohol, and crystallises out on cooling. The empirical formula,
calculated from their analytical results, is given as C160H308N5P035 by
Gamgee and Blankenhorn.

1 Ztsclir. f. physiol. Chem., Strassburg, Bd. ix. S. 145.

- Journ. ' Physiol., Cambridge and London, 1893, vol. xv. p. 100.

3 Ann. d. Chem., Leipzig, Bd. cxxxiv. S. 29.

4 Centralbl.f. d. med. Wissensch., Berlin, 1868, S. 97.

5 Journ. Physiol., Cambridge and London, vol. ii. p. 113; Gamgee's "Physiol. Chem.,"
vol. i. p. 427.

6 Ztsclir. f. pliysiol. Chem., Strassburg, Bd. ix. S. 329.

7 Ztschr.f. Biol., Miincheu, Bd. xxxi. S. 86.

8 Ztschr. f. physiol. Chem., Strassburg, Bd. xvii. S. 431,

THE CEREBRINS OR CEREBROSIDES. 119

The percentage composition is seen in the following table :—

ELEMENTS.

LlEBRElCH.

GAMGEK AND
BLANKENHORN.

BAUMSTARK.

KOSSEL.

RUPPEL.

CALCULATED

FROM

FORMULA.

Ox.

Human.

C

6674 66-39

66-48

66-25

66-29

66-51

66-45

II

1174

10-69

11-12

11-13

10-75

10-88

10-66

N

2-80

2-39

2-35

3-25

2-32

2-55

2"42

P

1-23

1-068

1-02

0-97

1-13

1-138

1-07

S

...

...

0-51

0-096

...

0

...

19-462

18-701

19-40

An elaborate research by Thudichum l led him to the conclusion that
there are three groups of phosphorised substances in the brain, which he
termed kephalines (very soluble in ether), myelines (less soluble in
ether), and lecithins (characterised by their extreme instability). In
each of these ill-defined groups several members with their empirical
formulas are described. Thudichum's work has been so far confirmed
by that of Kossel, in that he has shown that protagon is not a single
substance, but that there is more than one protagon. They yield either
one or two or perhaps three derivatives (cerebrosides), called cere-
brin, kerasin or honiocerebrin, and encephalin ; and, further, probably
several lecithins are obtainable from the different protagons. The
constitution of lecithin is discussed on p. 22, and there it will be seen
that the existence of several lecithins (i.e. containing different fatty acid
radicles) is mooted. The protagons, according to Kossel, resemble each
other in the following points : —

1. They contain carbon, hydrogen, nitrogen, oxygen, and phosphorus.
Elementary analysis gives practically the same results as those obtained
by other observers. But the existence of sulphur in some varieties of
protagon is a new point.

2. By oxidation with nitric acid they yield higher fatty acids (palmitic
and stearic).

8. By the action of boiling sulphuric or hydrochloric acid a reducing
carbohydrate is formed.

4. By the action of alkalis they yield cerebrosides (formerly called
cerebrins).

5. The cerebrosides are the source of the reducing carbohydrate
mentioned above.

6. The carbohydrate formed is galactose.

7. Other decomposition products of the cerebrosides are ammonia, and
a complex material which on fusion with potash yields higher fatty acids.

The cerebrins or cerebrosides. — These substances, the glucoside
constitution of which lias just been alluded to, form a group of ill-
defined, nitrogenous substances, existing especially in the white sub-
stance of nervous tissue, and also in the yolk of egg, pus corpuscles,
and spleen cells.2

1 Rep. Med. Off. Privy Council, London, 1874, p.

2 Hoppe-Scyler, "Ph'ysiol. Chem.," S. 720, 788.

113 et seq.

120 THE CHEMISTRY OF THE TISSUES AND ORGANS,

Miiller l obtained cerebrin by rubbing brain up with baryta water,
so as to form a milky fluid ; this is boiled, and the resulting coagulmn
extracted with boiling alcohol ; on cooling, the alcoholic solution deposits
cerebrin and cholesterm. The latter is removed by ether, and the former
is purified by repeated crystallisation from boiling alcohol. According to
Miiller, its formula is C17H33N03; according to Parcus,2 C80H100N2015.
Parcus also obtained two other similar substances (homocerebrin and
encephalin) with different formulae. Adopting a slightly different modus
operandi, Geoghegan3 obtained a substance with the formula C37H110N2025.
Thudichum4 separated three cerebrins, which he named cerebrin
(C34H6GN208), phrenosine5 (C34H07N08), and kerasine (C4CH91N09).
Gamgee 6 found that, while protagon cannot be separated by the simple
action of solvents into lecithin and cefebrin, yet such non-phosphorised
substances do exist by its side in the brain, and one which he called
pseudo-cerebrin (C44H92N08) can be obtained from protagon by the
action of caustic baryta.

The fact that the cerebrins are glucosides was known to Liebreich,7
Diaconow, Otto,8 Geoghegan,9 and Thudichum,10 but it was only within
quite recent years that the sugar was identified as galactose, almost
simultaneously in this country and in Germany.11

The most recent work on the subject is that by Kossel and Freytag,12
who adopt the very appropriate name of cerebrosides for these bodies.
They find that these substances are constituents of the medullary
sheaths rather than of the axis cylinders. They have especially worked
at two, which they obtained by the decomposition of protagon crystals,
namely, cerebrin and kerasin. The analyses of these agree very well
with those previously published by Thudichum, Parcus, and others.
Their molecular weight was investigated by Beckmann's boiling method,
and by the examination of their barium and bromine compounds. By
treatment with nitric acid they yield not only galactose but also a
fatty acid recognised as neurostearic acid by Thudichum, and correctly
analysed but not identified by Miiller. It is, in fact, stearic acid, three
molecules of which are formed from cerebrin for every two atoms of
nitrogen. From all these considerations, the formula given to cere-
brin is C70H140N2013, and to kerasin (the homocerebrin of Parcus),
C70H1>38N2012.

Similar substances occur in other parts of the body ; thus two
separated from pus are named pyosin, C57H110N2015, or C^R^NgO^
and pyog&twn, C63H128N2019. These bodies and similar ones separated
from testicular cells are components of the cell protoplasm, not of the
nucleus (Kossel and Freytag).

1 Ann. d. Chem., Leipzig, Bd. ciii. S. 131 ; cv. S. 361.

2 Journ. f. praTct. Chem., Leipzig, Ed. cxxxii. S. 310.

3 Ztschr. /. pJiysiol. Chem., Strassburg, Bd. iii. S. 332.

4 Loc. cit.

5 For recent papers on phrenosine, see Thudichum, Journ. f. prakt. Chem., Leipzig,
Bd. liii. S. 49 ; Kossel, ibid., 1896, Bd. liv. S. 215.

(! Loc. cit.

"' Virchow's Archiv, Bd. xxxix. S. 183.

8 Ibid., Bd. xli. S. 272.

9 Geoghegan stated that the reducing substance had the formula CooH4505 ; he termed
it cetylid ; cetylid was no doubt a mixture of galactose and fatty acids.

10 Journ. f. prakt. Chem., Leipzig, Bd. xxv. S. 23.

11 Thierf elder, Ztschr. f. pJiysiol. Chem., Strassburg, Bd. xiv. S. 209 ; Brown and
Morris, Proc. Chem. Soc. London, 1889, p. 167.

12 Zttchr. f. physiol. Chem., Strassburg, Bd. xvii. S. 431.

THE EYE. 121

THE EYE.

The cornea. — A thousand parts of corneal tissue contain 242 of
solids, of which 204 consist of collagen, 28 of other organic matters, and
10 of ash.1

The erroneous idea that the cornea, like cartilage, contains a specific
substance called chondrin (Mliller), was first combated by Morochowetz,2
who showed that chondrin here as elsewhere is a mixture of gelatin and
a mucinoid material. This latter substance is named by C. T. Morner,3
cornea-mucoid ; its percentage composition is C, 50*16 ; H, 6*97 ; N,
1279 ; S, 2'07 ; 0, 28-01. It resembles other mucoids very closely in
its properties (see p. 63). The gelatin obtained from the collagen
resembles that found elsewhere. The same mucoid and collagen are
present in the sclerotic.

Descemet's membrane is resistant to reagents. Morner terms its
chief constituent menibranin. It belongs to the mucoid group. The lens
capsule has a similar chemical structure.

The choroid and iris are principally of chemical interest from con-
taining the black pigment which is identical with or nearly related to
that in the pigment layer of the retina.

The retina. — Calm4 gives the following table of the quantitative
composition of the retinre of geese :—

Water 86 to 89 per cent.

Solids 14,, 11 " „

Proteids (globulin coagulating at 50° C.,

albumin and mucin (?) ) . . . 4,6

Gelatin 13

Cholesterin 0'3

Lecithin I'O

Fat . : . . . . . . 0-05

Salts . 07

17
0-8
2-9
0-5
1-2

The pigments of the retina. — The black pigment of the retinal
epithelium is called fuscin. In some animals the epithelium is free from
pigment in part ; this constitutes the tapetum lucidum. In some fish this
contains crystals of guanine ; in the ox and sheep it does not.5

Fuscin is one of the group of black pigments, termed melanins. It
was investigated by Berzelius, and by Heintz, who found it contained a
small quantity of iron, by Scherer, who found no iron, and also by Eosow
and Sieber. The percentage composition obtained by the various
observers shows great discrepancies, and this, taken into account with their
methods of preparing the pigment, renders it probable they were dealing
with impure substances. The failure to find iron was due to the fact
that hydrochloric acid was employed at one stage of the operations,
and this dissolves out nine-tenths of the iron.6

1 His, quoted by Ganigee, "Physiological Chemistry," vol. i. p. 451.

2 Verhandl. d. naturh.-med. Ver. zu Heidelberg \ pt. 5, Bd. i.

3 Ztsclir. f. physiol. Chem., Strassburg, Bd. xviii. S. 213.

4 Hoppe-Seyler, "Physiol. Chem.," S. 699.

5 Kiihne and Sewall, Verhandl. d. naturh.-med. Ver. zu Heidelberf}, N. F., Bd. ii.
Heft 5.

6 K. A. H. Morner, Ztschr. f. physiol. Chem., Strassburg, Bd. xi. S. 66. The pigment
in the skin of negroes, and in melanotic sarcomata, is closely allied to fuscin. It appears
to contain iron. In melanotic sarcomata, Berdez and Nencki named the pigment phyma-
torusin ; in those of horses, hippomelanin. The subject of melanin in the urine has been

122 THE CHEMISTRY OF THE TISSUES AND ORGANS.

May's method l of preparing f uscin is to boil retime in alcohol, then in
ether, lastly in water. The residue is then subjected to try p tic digestion.
Three things remain undigested ; of these iiuclein is got rid of by tritura-
tion with alkali; the second, neurokeratin, must be picked out with
forceps ; the third is the pigment.

Fuscin is slowly bleached in the air ; it dissolves by boiling it a long
time with concentrated sulphuric acid, or caustic alkalis.

There is a considerable doubt, as in the case of other melanins,
such as those in the skin, whether or not it is derived from
haemoglobin.2 Krlikenberg considers it is more closely related to
the lipochromes. It is, however, undoubtedly nitrogenous. It is
certainly not a member of the group of pigments occurring in
plants named humous substances by* Hoppe-Seyler,3 since on fusing
with alkali it yields no pyrocatechin or protocatechnic acid.4 The
chief interest of fuscin is not, however, chemical but physiological.
Such problems as its varying distribution under the influence of light
and its relationship to the visual purple of the rods will be treated
under " Vision."

Visual purple or rlwdopsin. — AV<i possess very little chemical
knowledge of visual purple. Klihne found it to be soluble in certain
reagents such as solutions of bile salts, that in the process of bleaching it
passes through a yellow stage, that the bleaching occurs at different
rates at different temperatures and in different coloured lights, and
that spectroscopically it cuts out a very considerable portion of the
spectrum. It is destroyed by alcohol, ether, chloroform, ^ and strong
alkalis and acids, but not by most oxidising agents. It is perhaps
related to the lipochromes. The green, yellow, and red pigments
(chromophanes) of the oil droplets in the cones of birds are undoubtedly
lipochromes (see p. 20).

The aqueous humour is lymph.5 In parts per 1000 it contains:
water, 986'87 ; solids, 1313 ; proteids; 1-22 ; extractives, 4*21 ; inorganic
salts, 770 ; sodium chloride, 6'89.6 It does not clot spontaneously, but
does so on addition of serum. The proteids in it are fibrinogen, serum
globulin, and serum albumin.7 Kiilme8 found a reducing substance
among the extractives. This is not sugar. Urea and sarcolactic acid
are also present in small quantities.1'

The vitreous humour. — The membranes of the vitreous humour

worked at especially by v. Jaksch. The following are references to the principal papers
on the subject :— Miirner, loc. cit., also ibid., Bel. xii. S. 229; Nencki, Arch. f. cs'per.
Path. u. PharmaM., Leipzig, Bd. xxiv. S. 17, 27 ; Chem. Centr.-BL, Leipzig, 1888,
S. 587; Brandl and Pfeitfer, Ztsclir. f. Biol., Mitnchen, Bd. xxvi. S. 348; v. Jaksch,
Ztschr. f. pkysiol. Chem., Strassbnrg. Bd. xiii. ; Abel and Davis, Journ. Exper. Med..
Baltimore, 1896, No. 3, vol. i. ; Schmiedeberg, Arch. f. cxpcr. Path. u. Pharmakol. ,
Leipzig, 1897, Bd. xxxix. S. 1.

1 Untersuch. a. d. pliysiol. Inst. d. Univ. Heidelberg, Bd. ii. S. 324.

2 Delepine has even suggested that, in the case of the skin pigment, haemoglobin is derived
from it (Proc. PhysioL Soc., London, Dec. 13, 1890, p. xxvii.). Abel and Davies (loc. cit.}
have recently studied the pigment of the negro's skin. The granules contain inorganic
matter as well as pigment. The latter contains the merest trace of iron. They conclude
that it originates not from haemoglobin, but from the proteids of the tissue juice.

3 Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 66.

4 Hirschfeld, ibid., Bd. xiii. S. 407.

5 Chavvas, Arch. f. d. ges. PhysioL, Bonn, Bil. xvi. S. 143.

0 Lohmeyer. See Gorup-Besanez, "Lehrbuch," 4th edition, 1878, S. 401.

7 Friend and Halliburton, Rep. Brit. Ass. Adi\ Sc., London, 1889, p. 130.

8 Arch. f. d. ges. PhysioL, Bonn, Bd. xii. S. 200.

9 Griinhagen, ibid., Bd. xliii. S. 377 ; Pautz, Ztschr. f. Biol., Miinchen, Bd. xxxi.

THE LENS.

123

yield gelatin. Its chief constituent is inucin, or mucinogen (Young),
called mucoici by C. T. Morner. According to the latter, this inucoid con-
tains 12-27 nitrogen, and 1*19 sulphur, per cent. There are also small
quantities of proteid. References to the papers of Young and Morner,
the most recent workers on this subject, will be found on p. 62.

The lens. — The following are the results of Laptschinsky's 1
analyses : —

Water .
Solids .
Proteids
Lecithin

63-50 per cent.
36-50 „
34-93 „
0-23

Cholesterin 2

Fats

Salts

0-22 per cent.
0-29 „

0-82

FIG. 20. — Absorption spectra of retinal pigments. — 1, of visual purple ; 2, of visual yellow ;
3, of xanthophane in ether ; 4, of rhodophane in turpentine ; 5, of chlorophane in
ether. This diagram inatic way of representing absorption spectra indicates the thick-
ness of the absorption-bands in solutions of different strengths ; the top of each
spectrum shows the thickness of the bands in a dilute solution ; as the concentra-
tion of the solution increases, the bauds become wider, as in the lower part of each
diagram. — After Kiihne.

The proteid matter is thus very abundant ; it is chiefly a globulin, to
which Berzelius gave the name of crystallin. It has also been the
subject of researches by Hoppe-Seyler, Laptschinsky, Kiihne, and C. T.
Morner.3 According to the last-named investigator, about 52 per cent.
of the proteid matter of the lens is insoluble in water and saline
solutions. The insoluble proteid residue is an albuminoid, and it is

1 Arch.f. (I. cjes. PhysioL, Bonn, Bd. xiii. S. 631.

2 The cholesterin increases greatly in cataract (Calm, Hoppe-Seyler's " Phvsiol. Chem.,"
S. 692).

3 Ztschr. f. physiol. Chem., Strasslmrg. Bd. xviii. S. 61.

124 THE CHEMISTRY OF THE TISSUES AND ORGANS.

most abundant in the inner denser portions of the lens. It yields
no nuclein on gastric digestion; the small amount of phosphorus it
contains is due to inorganic phosphates. The soluble proteids of the
lens are also not nuclein compounds. About one per cent, of the
soluble proteid is albumin; the rest is globulin. The globulin is
precipitated by saturation with magnesium sulphate, but not with
sodium chloride ; in this it resembles vitellin. The globulin consists
of two proteids, a-crystallin and /S-crystallin.

a-Crystallin is completely precipitable by saturation with magnesium
sulphate or with sodium sulphate at 30° C., by the addition of one and a
half times its volume of saturated ammonium sulphate solution, by a
stream of carbonic anhydride, and by very dilute acetic or hydrochloric
acids. It coagulates at 72° C. It contains : N, 16-68 ; S, O56 ; C, 52*83 ;
and H, 6'94 per cent. («)D = -46°-9.

|3— Crystallin differs from this in its coagulation temperature (64° C.)
and specific rotatory power (a)D=-43°. It contains 17 '04 nitrogen and
1'27 sulphur per cent.

a-Crystallin is more abundant in the outer, /3-crystallin in the inner,
portions of the lens ; the albumin is equally distributed. The. lens
contains no keratin. The proportion between the four proteids in the
lens as a whole is as follows : —

Total Proteids.

Soluble Proteids.

In Fresh Lens.

Albuminoid .

4S'0 per cent.

17'0 per cent.

a-Crystallin .

19-5 „

37 per cent.

6-8 „

^-Crystallin .

32-0 ,,

62

11-0

Albumin

0-5 „

1 ,,

0-2

THE MAMMARY GLANDS.

The chemical constituents of the mammary gland have not been
much studied. The principal proteid constituent of the cells is nucleo-
proteid, which swells with dilute alkali, and yields, by boiling with
mineral acid, a reducing substance. That a reducing substance (sugar)
can be obtained from the gland was first noted by Bert,1 and confirmed
by Landwehr,2 who considered its mother substance to be animal-gum ;
it is considered by Thierf elder 3 to be the mother-substance of lactose.
It is possible that the nucleo-proteid just mentioned may be the precursor
of caseinogen. The lactalbumin of milk is not identical with serum
albumin, so that its presence in milk cannot be explained by a simple
transudation from the blood.

The extractives of the mammary gland contain not unimportant
quantities of hypoxanthine ; 4 they have not been further investigated.

1 Gaz. hebd. de med., Paris, 1879, No. 2 ; Compt. rend. Acad. d. sc., Paris, tome xcviii.

2 Arch. f. d. ges. PhysioL, Bonn, Bd. xl. S. 21. Tbierfelder had previously (ibid., Bd.
xxxii. S. 6i9) recognised that the substance is not glycogen.

3 Loc. cit.

4 Hanimarsten, "PhysioL Chem.," S. 378.

MILK. 125

MILK.

General properties and composition. — Milk consists of fluid (milk
plasma) in which are suspended innumerable minute globules of fat.1 It
is therefore an emulsion, and its white colour is produced, as in other
emulsions, by reflection from the surface of the numerous globules.
The specific gravity of cow's and of human milk is about the same,
namely, 1028 to 10342 It is increased by the removal of the lightest
constituent, the cream. Among the milk globules are smaller particles
of proteid matter (caseinogen or nuclein ?).3

The statement is still often made that each fat globule in milk is
surrounded by a thin membrane of caseinogen — the so-called haptogen
membrane,4 and it was considered that it was the rupture of these
membranes during the process of churning that enabled the fat globules
to run together to form butter. The evidence on which this idea has
rested is of a threefold nature : —

1. If the milk is filtered through a cell of porous earthenware, the
filtrate is free, not only from fat, but also from caseinogen.

2. The mass of milk globules, after having been well washed within
the filter, gives the reactions for caseinogen.5

3. If ether is added to the milk, without previous addition of
caustic potash or acetic acid (these were supposed to dissolve or
break up the proteid envelope), the fat is dissolved out with great
difficulty.

But it is now generally held with Quincke,6 who made experiments
with oil and mucilage, that each fat globule by molecular attraction
is surrounded by a more closely adherent layer of caseinogen solution
(or rather milk plasma), and not by a membrane. How then can
one explain the three facts just adduced in favour of the membrane
theory ?

1. If milk is filtered through porous earthenware, it is naturally free
from caseinogen ; blood serum filtered in the same way is proteid free.
The molecules of proteid are too big to go through the pores of the filter ;
there is no necessity, therefore, to suppose that the caseinogen is in a
solid condition in the milk.

2. For the same reason, no amount of washing would wash the
caseinogen through, and so naturally the milk globules would give the
reactions of the proteid with which they are contaminated. Further,
Hoppe-Seyler 7 has shown that cream yields the same percentage of
casein as the layers of milk below it.

3. The addition of reagents such as acetic acid (and rennet) enables
the fat to pass into solution more easily, not because they are solvents
of proteid, for they are not, but because they alter the relations
between the surface tensions of fat globules and milk plasma, and so

1 For the measurement and examination of the fat globules, see Fleischmann, " Das
Molkereiwesen," Braunschweig, 1876-9, S. 206; F. W. Woll, "Wisconsin Exper. Stat.
Agric. So.," 1892, vol. vi.

2 For observations on the specific gravity of human milk, see Monti, Arch. f. Kinderh.,
Stuttgart, Bd. xiii.

3 Kehrer, Arch. f. Gyimck., Berlin, Bd. ii. S. 1 ; D. F. Harris, Proc. Roy. Soc. Edin.,
1896, p. 72.

4 Ascherson, Arch. f. Anat. u. PhysioZ., Leipzig, 1840, S. 53.

5 Radenhausen and Danilewsky, Forsch. a. d. Geb. d. Vichhaltimg, Bremen, 1880, Heft 9.
(i Arch.f. d. (jes. PhysioL, Bonn, 1879, Bd. xix. S. 129.

7 "Physiol. Chem.,"S. 728.

126 THE CHEMISTRY OF THE TISSUES AND ORGANS.

enable the ether to attack the fat more easily. Moreover, Hoppe-Seyler
states that it is not so difficult to remove the fat simply with ether ;
the fluid still remains cloudy, it is true, but solutions of caseinogen
are always opalescent, and this is increased by the presence in the
milk of particles of proteid or proteid-like substances, as described by
Kehrer.

The reaction of milk. — Milk readily turns sour from the fermentation
of lactose and formation of lactic acid. In carnivora fresh milk has an
acid reaction, but in most animals it gives either an alkaline or, more
frequently, an amphoteric reaction; the acid phosphates in the milk
turn neutral litmus red, and the alkaline phosphates turn it blue. The
proportion between these salts varies very considerably in different
animals, in the same animal at different stages of lactation, and even
between the first and last portions of the same milking (Thorner,1
Sebelien,2 Courant 3).

Courant estimated the alkaline constituent by titration with
decinormal sulphuric acid, with blue lackmoid as indicator, and the acid
constituent with decinormal soda with phenolphthalehi as indicator.
He found as a mean for the first and last portions of the milking of
twenty cows, that the alkalinity of 100 c.c. of the milk was equal to
41 c.c., and the acidity equal to 19'5 c.c. of the respective solutions
used. In human milk the proportional alkalinity is higher ; the average
of the numbers was 10'8 and 3*6 c.c. respectively.

Constituents of milk. — These are water, three proteids (caseinogen,
lactalbumin, lacto-globulin), two carbohydrates (lactose, animal gum?),
fats, extractives (traces of urea, creatine, creatinine, hypoxanthine,
lecithin, cholesterin, citric acid 4), salts and gases. Most of these de-
mand separate discussion.

Effect of boiling milk. — When milk is heated to, or near to, the
boiling point, a scum forms on the surface ; on the removal of this skin
it is rapidly renewed, and this can be repeated over and over again.
This is probably in part produced by the coagulation of the lact-
albumin ; this carries to the surface some caseinogen and fat.5 Contact
with air appears to be the chief influence in causing the solidification
which results in the formation of the scum ; evaporation is rapid from
the surface exposed to the atmosphere, and thus partial drying occurs
there.

The boiling of milk before it is used as a food is advantageous in
two ways — (1) all micro-organisms are destroyed; (2) the gastric juice, in
virtue of its rennet, causes a flocculent and not a bulky precipitate.
These quite outweigh any slight diminution of digestibility alleged to
occur.6 The reason that boiled milk curdles with rennet with greater
difficulty than fresh milk appears to be that, by boiling, a part of the
dissolved calcium salt is precipitated as tricalcium phosphate.

As milk turns sour, it is possible to get a bulky heat coagulum by
boiling.7

1 Chan. Ztg., Cbthen, Bd. xvi. S. 1469. 2 Ibid., S. 597.

3 Inaug. Diss., Bonn, 1891 ; and Arch. f. d. ges. Physiol., Bonn, 13d. 1.

4 Soldner, Landw. Versuchs. Stat., Berlin, Bd. xxxv.

5 See D. F. Harris, Joiirn. Anal, and Physiol., London, 1894, vol. xxix. p. 188.

6 Raudnitz, ZtsrJir.f. physiol. Chcm., Strassburg, Bd. xiv. S. 1.

7 Recent work on this question will be found in a paper by Cazeneuve and Haddon,
Compt. rend. Acad. d. sc., Paris, 1895, tome cxx. p. 1272. See also influence of boiling on
the proteids of cows' milk, Centralbl.f. d. mcd. Wissensch., Berlin, Bd. xxxiv. S. 145.

HUMAN MILK.

127

Under the influence of extracts of the pancreas, the caseinogen,
before it is clotted by the milk-curdling ferment of the gland, passes
through a stage in which it coagulates by heat. This was termed
the " metacasein " reaction by its discoverer, Sir William Eoberts.1 It
does not appear to be due to the simultaneous development of acid
produced by the fat-splitting ferment of the pancreas, but rather to
the action of trypsin. Edkins2 showed that Klihne's purified trypsin
also produces " metacasein " in an early stage of its action, though it
does not produce coagulation of milk.

The composition of milk varies in different animals; human milk
and cows' milk are those which have been most investigated. There
are also variations due to constitution, state of nutrition, and age.

Human milk. — The mammary glands of new-born animals of both
sexes often secrete a small quantity of milk for a few days. It is
popularly termed " witches milk!' It is alkaline.3 Analyses by Schloss-
berger and Hauff,4 Gubler and Quevenne,5 and Genser,8 show that the
milk of new-born children contains from 1'05 to 2'8 proteicl, O82 to
146 fat, 0'9 to 64 sugar, and 0'8 salts per cent.

Colostrum. — This liquid is yellower and more alkaline than fully-
formed milk. It contains colostrum corpuscles, rather more solids than
milk, and coagulates on heating. It contains little or no caseinogen,
but a mixture of lacto-globulin and lactalbumin.7 The globulin is only
present in traces in fully-formed milk. The following analyses are by
Clemm,8 with the exception of the last, which is by Tidy.9

Constituents.

Four Weeks before
Delivery.

Seventeen
Days before
Delivery.

Nine Days
before
Delivery.

Twenty-
four Hours
after
Delivery.

Two Days
after'
Delivery.

'•

n.

Water

94-52

85-2

85-17

85-85

84-38

86-79

84-08

Solids .

5-48

14-8

14-83

14-15

15-62

13-21

15-92

Casein

2-18s

Albumin and

2-88

6-9

748

8-07

...

3-23

globulin

J

Fat .

0-71

4-1

3-02

2-35

4-86

5-78

Lactose

1-73

3-9

4-37

3-64

...

6-10

6-51

Salts .

044

044

045

0-54

0-51

...

0-34

1 Proc. Roy. Soc. London, 1879, 1891.

" Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 203.

3 Witches' milk obtained from foals by Ammoii (Jahrcsb. u. d. Fortschr. d. Thier-Chem.,
"Wiesbaden, 1876, S. 118) was acid, but this was probably due to fermentation having set in.

4 Ann. d. Chem., Leipzig, Bd. xcvi. S. 68.

5 Gaz. med. de Paris, 1856, p. 15.

6 Jahrb.f. Kindcrh., Leipzig, N. F., Bd. ix. S. 60.

7 J. Sebelien, Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 135.

8 Wagner's " Haudworterbuch d. Physiol,." Bd. ii. S. 464.

9 Lond. Hosp. Rep., 1867-8, p. 77. See also Woodward (Journ, Exper. Med., Baltimore,
1897, vol. ii. p. 217), for recent analyses of human colostrum. Colostrum corpuscles are
not constantly present.

i28 THE CHEMISTRY OF THE TISSUES AND ORGANS.

Normal human milk. — The following table gives some of the
principal analyses that have been published : —

Water.

Case-
inogen.

Albu-
min.

Fat.

Sugar.

Salts.

Remarks.

Observers.

88-58
90-58

0

2

69
91

3-53
3-34

4-3
3-15

0-17
0-19

9 days after delivery.

12 „ „ „ ;

\ Clemm.

86-27

2-95

5-37

5-13

0-22

Tidy.

86-3)

T2-6

5-8

0-23 }

to L

1-68 to 3-15

\to

to

to I

Biel.1

88 -8 J

\5-4

6-6

0-34 j

1-28

0-34

2-56

5-6

Tolmatscheff.2

89 '-1

1-79

3-3

5-4

0-42

Gerber.3

87-24

1-9

4-3

5-9

0-28

Christemi.4

89-29
89-06

1-6
1-72

3-2
2-9

5-8
6-0

0-16
0-2

W«iien 20-30years old
,, 30-40

{ Pfeiffer.5

8779

2-53

3-9

5-5

0-25

Mendus de Leon.6

...j

1-8
to

0-7
to I

Makris.7

(^

4-8

1-7

97-6

1-52

3-28

6-50

0-27

Soldner & Camerer.8

88-5

1-2 0-5

3-3

6-0

0-2

...

Lehmami & Hem pel.9

The most constant feature in these analyses is the relatively low
percentage of proteids and high percentage of sugar.

Among other constituents of human milk are, 0*32 per cent, of
cholesterin (Tolmatscheff), O05 of citric acid,10 and 078 n of unknown
extractives; the last are more abundant in the colostrum, and less
abundant in cows' milk (Soldner and Camerer).

Variations in the composition of the milk occur with the stages of lactation,12
in the milk from the two breasts and between the first and last portions of
the milking,13 with the complexion 14 (Vernois and Becquerel — questioned
by Tolmatscheff), with the age of the individual (Pfeiffer), and with menstrua-
tion (Vernois and Becquerel). The nature and quality of the food have a
considerable influence on the quality of the milk.15

The salts of human milk are thus given by Bunge 16 in parts per 1000.—

K90

CaO
MgO

A.

0-780
0-232
0-328
0-064

B.

0-703
0-257
0-343
0-065

Fe903

A.

0-004
0-473
0-438

B.

0-006
0-469
0-445

1 Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1874, S. 168.

2 "Med. Chem. Untersuch.," Bd. ii. S. 272.

3 Bull. soc. chim., Paris, tome xxiii. 4 Diss., Erlangen, 1877.

5 Jahrb.f. Kinderh., Leipzig, Bd. xx. 6 Diss., Heidelberg, 1881.

7 Diss., Strassburg, 1876. 8 Ztschr.f. EioL, Mlinchen, 1896, Bd. xxxiii. S. 43.

9 Arch.f. d. ges. Physiol., Bonn, Bd. Ivi. S. 558.

10 The presence of citric acid has also been noticed by Scheibe, Landw. Versuchs. Stat.,
Berlin, Bd. xxxix.

11 J. Munk (Virchow's Archiv, Bd. cxxxiv. S. 501) gives the proportion of extractive
nitrogen to total nitrogen as 1:11 in human and 1:16 in cows' milk.

12 Pfeiffer, loc. cit. ; Vernois and Becquerel, Compt. rend. A cad. d. sc., Paris, tome xxxvi.
p. 188.

13 Sourdat, ibid.> tome Ixxi. ; Brummer, Arch.f. d. ges. Physiol., Bonn, Bd. vii.

14 1'Heritier, "Traite de chim. pathol.," Paris, 1842.

15 Decaisne, Gaz. med. de Paris, 1871, p. 317. These are very interesting observations
made during the siege of Paris. Other work on the influence of food on milk is that by
Szubotin, Centralbl. f. d. med. Wissensch., Berlin, 1866, S. 337, and by Commaille, quoted
by Konig, "Chem. d. menschl. Nahrungs. u. Genussmittel, " Bd. ii. S. 235. The question
of the influence of diseases and drugs will be found discussed in works on Therapeutics
and Pathology. 16 Ztsclir. f. JSioL, Mimchen, Bd. x.

CO WS> MILK.

129

The gases of human milk. — In five experiments, 100 c.c. of milk
yielded 1/07 to 1*44 c.c. of oxygen, 2*35 to 2-87 c.c. of carbonic anhydride,
and 3-37 and 3*81 c.c. of nitrogen. The method of collecting the milk
could riot have obviated admixture with small quantities of air ; hence,
no doubt, the higher percentage of oxygen and nitrogen than previous
observers have found in the milk of lower animals.1

Cows' milk. — Colostrum. — This has a high specific gravity (1046-
1080). Its fat has a higher melting point than that of normal milk,
being poorer in the lower • fatty acids.2 It contains more lecithin,
cholesterin, and proteid coagulable by heat than normal milk.3 The
following are some analyses that have been made : —

Fleischmann.4

Konig.5

Vaudin.e
Just after delivery.

Vaudin.6
Five days after
delivery.

Water

78-7

74-7

77-6-72-7

85-63

Solids

21-3

25-3

22-4-27-4

14-37

Casein
Albumin ai d globulin

7-3

7'5

4'04"\
13-6 /

14-9-20-1

4-35

Fat .

4-0

3-6

2-42-6-3

5-18

Lactose

1-5

27

1-02-2-86

4-07

Salts .

1-0

1-6

1-1-1-2

0-16

Normal cows' milk. — The following are averages of numerous
analyses, in the first column of those collected by Gorup-Besanez,7 in the
second, by Hoppe-Seyler.8

I. II.

Water .... 84'28 85-86

Solids .... 15-72 15-18

Caseinogen . . . 3 -5 7 3-4

Albumin . . . 0'75 0'3-0'5

Fat .... 6-47 4

Lactose .... 4 -34 4 -5-5
Salts ..... 0-63

Hammarsten9 gives the following tables (from Konig) of normal
milk and the averages of various preparations from milk as follows : —

Milk.

Skimmed Milk.

Cream.

Butter Milk.

Whey.

Water

87-17

90-66

65-51

90-27

93-24

Solids

12-83

9-34

34-49

9-73

6-76

Caseinogen
Albumin

3-02)
0-53J

3-11

3-61

4-06

0-85

Fat .

3-69

0-74

26-75

0-93

0-23

Sugar.

4-88

4-75

3-52

3-73

4-7

Salts .

0-71

0-74

0-61

0-67

0-65

Lactic acid

...

...

0-34

0-33

Tatlock10 gives the average composition of skimmed milk as follows — (1)

1 E. Kiilz, Ztschr.f. Biol., Miinchen, 1895, Bd. xxxii. S. 180.

2Nilson, Jahresb.'ii. d. Fortschr. d. Thier-Chem,, Wiesbaden, Bd. xvii. S. 169.

3 Ibid., Bd. xviii. S. 102.

4 "Das Molkereivvesen," S. 39. 5 "Chem. d. Mensch. Nahrungsmittel. "

6 Journ. de pharm. et chim., Paris, 1894, Ser. 5, tome xxx. p. 337.

7 " Lehrbuch," 1878, S. 424. 8 " Physiol. Chem."
"Physiol. Chem.," 3rd German edition, S. 388, 390.

10 "Produce of the Dairy," Glasgow, 1888. Numerous milk analyses will be found in
this book.

VOL. I. — 9

1 30 THE CHEMISTRY OF THE TISSUES AND ORGANS.

By repose and skimming — fat, 1; proteid, 3*44; lactose, 5*1; ash, 0*75;
water, 89'67. (2) By separator — fat, 0*2 ; proteids, 3'4; lactose, 5'01 ; ash,
0-75 ; and water, 90'64.

The presence of citric acid in milk was first shown by Soxhlet. Yaudin l
considers that this is not from the food, but produced in the mammary gland.

The variations in the milk with feeding, species of animal, time of day,
etc., are described by Struckmann and Bodeker,2 Fleischmann,3 Tatlock,3
Eoihne and Fleischer,4 and others.

Salts of cows' milk. — Soldner 5 gives the following percentages : —

K0

CaO ........

MgO .......

P205 (after correction for pseudo-nuclein)
Cl .......

0-172
0-051
0-198
0-020
0'182
0-098

Of the total phosphoric acid, from 36 to 56 per cent., and of the lime from
53 to 72 per cent., is not simply dissolved in the fluid, but is united more or
less firmly to the caseinogen. The excess of bases over mineral acids is united
to organic acids, such as citric. Bunge found 0-00035 per cent, of iron.

The gases of cows' milk have been analysed by Setchenow6 and Pfiiiger.7
There are small quantities of oxygen and nitrogen, and from 5 to 10 per
cent, of carbonic anhydride.

In comparing the composition of cows' milk with that of human milk,
the main difference consists in the high percentage of proteids, fats, and
salts, and the low percentage of sugar in cows' milk as compared with
human milk. Qualitative differences will be noted under the headings
" Proteids " and " Fats."

The milk of other animals. — Some of the principal analyses are
collected into the following table : —

Reference

Animal.

Water.

Caseinogen.

Albumin.

Fat.

Lactose.

Salts.

to Notes

below.

Dog .

75-4

9-91

9-57

3-19

0-73

8

Cat .

81'6

9

•08

3-33

4-91

0-58

8

Goat .

86-91

3

•69

4-09

4-45

0-86

9

Goat .

86-75

3-64

5-35

3-60

0-66

10

Sheep

83-5

5-74

6-14

3-96

0-66

11

Sheep

82-84

4

'7

4-8

3-4-6

0-6

12

1 Journ. de pharm. et chim., Paris, tome xxx, p. 464.

2 Ann. d. Chem., Leipzig, Bd. xcvii. S. 150. 3 LOG. cit.
4 Landw. Versuchs. Stat., Berlin, Bd. xii. S. 405. 5 Loc. cit.

6 Ztschr. f. rat. Med,, Bd. x. S. 285.

7 Arch.f. d. ges. Physiol., Bonn, Bd. ii. S. 166.

8 Taken from Konig's analyses. The milk is acid, rich in proteids and calcium. The
lactose is increased by starchy, and lessened though not abolished by a flesh diet (Benscli,
Ann. d. Chem., Leipzig, Bd. Ixi. S. 221 ; Poggiale, Gaz. med. de Paris, Ser. 3,
tome x. p. 259). See also Simon, "Die Frauenmilch," Berlin, 1838; Dumas, Compt.
rend. Acad. d. sc., Paris, tome xxi. p. 707 ; Kemmerich, Centralbl. f. d. med. IVissenscli.,
Berlin, 1866, No. 30 ; Szubotin, ibid., No. 22.

y Taken from Konig.

10 From Pizzi's analyses (Staz. Sper. Agrar., 1894, Bd. xxvi. S. 615 ; Abstract in Journ.
Chem. Soc., London,- 1896, vol. ii. p. 120). Goats' milk differs from cows' milk in smell
and taste, and in containing more insoluble volatile fatty acids. In reindeer's milk these
acids are less abundant (Solberg, Centralbl. f. agric. Chem., Leipzig, 1896, S. 15).

11 From Konig.

12 From Vernois and Becquerel, Union med., Paris, 1867, p. 78.

THE MILK OF OTHER ANIMALS.
The milk of other animals — continued.

13*

Animal.

Water.

Caseinogen.

Albumin.

Fat.

Lactose.

Salts.

Reference
to Notes
below.

Sheep

80-42

4

44

9-66

4-4

1-1

1

Mare

90-06

1

89

1-09

6-65

0-31

2

j ?

90

1-8

0-3

1-3

5-5

0-3

3

92-5

1-3

0-3

0-6

4-7

0-3

4

it ' •

91-0

1

05

1-3

57

0-3

5

Ass .

90-0

2

1

1-3

6-3

0-3

6

Ass .

90-5

1

7

1-4

6'40

7

Ass .

89-0

3

5

1-8

5-0

0-5

8

Pig • • •

82-37

6-09

6-4

4-04

1-06

9

Pig • • •

83-0

7

0

7-0

2.0

1-05

10

Pig . - -

81-8

5

3

6-0

6-0

0-08

10

Mule.

89-3

2-6

1-9

6-03

0-53

11

Hippopotamus .
Camel

90-0
86-3

3

7

4-5
2-9

5V8

o-i

0-6

12
13

Elephant .

67-85

3-09

1-95

8-84

0-65

14

Dolphin .

48-67

>

,

43-76

0-46

15

Buffalo .

82-20

4

13

7'95

4-75

0-97

16

Rabbit

69-50

15

54

10-4

1-95

2-56

17

Salts of dogs and mares milk. — These may be compared in the
following table of Bunge's 18 with those we have already studied : —

HUMAN.

DOG.

n

M\RE

I.

II.

I.

II.

K00

0-78

0-71

1-41

1-68

1-76

1-04

Na20

0-23

0-26

0-80

0-69

1-11

0-14

CaO

0-33

0-34

4-53

4-28

1-59

1-23

MgO . . . . ' .

0-06

0-06

0-19

0-21

0-21

0-12

Fe00,

0-003

0-006

0-02

o-oi

0-003

0-015

P205

0-47

0-47

4-93

4-67

1-97

1-31

Cl

0-43

0-44

1-62

1-8

1-69

0-31

Total ash per 1000 .

2-22

2-18

13-15

12-96

7-97

4-17

1 From Pizzi. Sheep's milk contains a high percentage of fat.

2 From Konig.

3 From Biel, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1864, S. 17L

4 From Soxhlet, ibid., 1878, S. 152.

5 From Weiske and Schrodt, ibid., 1878, S. 151. The caseinogen of mares' milk is more
like that of human than of cows' milk. This is the milk originally used in the preparation
of koumiss and similar fermented liquors in Russia.

6 From Konig.

7 From Gubler and Quevenne, Gmelin's "Handbuch," Bd. viii. S. 267.

8 From Vernois and Becquerel. Asses' milk is much used by invalids.

9 From Konig.

10 From Leutner, in Gorup-Besanez, "Lehrbuch," S. 424.

11 From Aubert and Colby, Chem. News, London, vol. Ixviii. p. 168.

12 From Chem. Centr.-BL, Leipzig, 1871, S. 149.

13 From Dragendorf, ibid., 1867, S. 78. See also Vernois and Becquerel for analyses of
camels' milk.

14 From Konig.

15 From Frankland, Chem. News, London, 1890, vol. Ixi. Note the enormous percentage
of fat.

16 From Pizzi. For buffaloes' milk, see also Pappel and Richmond, Journ. Chem. Soc.,
London, 1894, p. 754.

17 From Pizzi.

18 Diss., Dorpat., 1874 ; Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 399.

132 THE CHEMISTRY OF THE TISSUES AND ORGANS.

The chief acid present throughout is phosphoric acid ; the chief base
in human rnilk is potash ; but this in most other mammals is second to
lime ; in dogs' milk the lime is especially high.

In connection with the iron in the milk it is to be noticed, that
although the other mineral constituents of the milk are present in the
proportion in which they are contained in the foetal tissues, the quantity
of iron in milk is less.

One hundred parts by weight of ash contain —

In New-born Dog. In Dogs' Milk.

K90 . . 11-42 . . 14-98

Na20 . . 10-64 . . 8-80

CaO . . 29-52 . . 27*24

MgO . . 1-82 . . 1-54

Ee2(X . . 0-72 . . 0-12

P205° . . 39-42 . . 34-22

Cl . 8-35 . . 16-90

The slightly different proportion in soda and potash is easily ex-
plained by the fact that in the young animal the potash-rich muscle is
increasing, and the soda-rich cartilage is diminishing. The high per-
centage of chlorine in the milk is also explicable, on the hypothesis that
the chlorides serve not only to build up tissues, but also largely as
solvents in removing waste products. But the percentage of iron
in the milk is only one-sixth of that in the foetal tissues. The foetus
obtains its supply of iron before birth through the placenta, and stores
it in the liver (see p. 86). As the young animal grows, a kilogram of
body weight contains less and less iron.

Iron appears to pass to the offspring through the placenta rather
than by the milk, because of the difficulties of absorbing iron by the
alimentary canal, and the danger that heematogenous (i.e. nuclein)
compounds may there become the prey of bacteria. Bunge further
regards it as probable that the large amount of iron which passes to the
foetus is not all derived from the mother's food during the relatively
short period of pregnancy, but that a storage of iron occurs in the
maternal organs even before the first conception ; and this may explain
the occurrence of chlorosis at the age of puberty.

The carbohydrates of milk. — The most important carbohydrate
in milk is lactose, or milk-sugar, the properties of which are described
on page 12. . It is found in varying quantities in the milk of all
animals ; the only exception to this rule hitherto noted is that of
the Egyptian buffalo (JBos bubalus), where it is replaced by another
sugar christened tewfikose 1 by Pappel and Richmond ; 2 it yields dex-
trose only on hydrolysis.

Though lactose is not fermented by yeast, yet it undergoes the
alcoholic fermentation under the influence of other schizomycetes, as
in the preparation of koumiss and kephir.

Ritthausen 3 found in milk another carbohydrate which is soluble in water,
and is not crystallisable ; its reducing power is low, and increased after boiling

1 After the Khedive of Egypt.

2 Journ. Chem. Soc., London, 1894, p. 754.

3 Journ. f. prakt. Chem., Leipzig, N. F., Bd. xv.

THE FA TS OF MILK 133

with acid. Landwehr1 identified it as animal gum, Be"champ2 as dextrin.
J. Herz 3 found granules in milk, which behave towards iodine like starch ;
he called them "animal amyloid."

The fats of milk. — Milk fat has a specific gravity of from 949
to 996.4 It consists of palmitin, stearin, and olein, with small quantities
of triglycerides of butyric, caproic, caprylic, capric, myristic, and arachic
acids in addition.5 It also contains small quantities of lecithin, choles-
terin, and a yellow lipochrome.

The amount of fat in cream varies from 14 to 44 per cent. In butter,
besides fat, there are small quantities of caseinogen and lactose. The
fats of cows' butter consist of 68 per cent, of palmitin and stearin, 30
per cent, of olein, and 2 per cent, of the specific butter fats.6 Their
melting point is 31° to 34° C. The volatile fatty acids in cows' milk, accord-
ing, to Duclaux,7 amount to 7 per cent., of which 3 '7 to 51 is butyric, and
2'0 to 3'3 is caproic acid. Some analysts give still higher percentages.

By exposure to the air butter becomes rancid ; this is partly due to
the production of lower fatty acids from the higher fats (see p. 19),
partly to the formation of acrolein from glycerine, and partly, and
according to Hagemann chiefly, to the formation of lactic acid from the
entangled lactose.

The composition of butter is very variable. Thus, in Finland butter,
Koefoed8 found two fatty acids of the acrylic series in addition to oleic
acid; 100 parts of the fatty acid contained 66 of these acids, 28 of
palmitic, 22 of myristic, 8 of lauric, 1-5 of butyric, 2 of caproic, 2 of capric,
and 0*5 of caprylic acid. According to Wanklyn,9 there is no true palmitic
acid in butter ; the acid is aldepalmitic acid (C16H3002).

The fats of human milk are somewhat different from those of cows'
milk. They have been the subject of two recent researches — one by
Kuppel,10 the other by Laves.11

Their melting point is 34° C., and solidifying point 20°'2 C. Their
specific gravity at 15° C. is 966. The fatty acids found are butyric,
caproic, capric, myristic, palmitic, stearic, and oleic acids, all combined
with glycerine. The presence of formic acid 12 is also inferred from its
reducing action, but not by any further tests. Human milk is poor in
volatile acids (Kuppel).

Laves confirms this work, and gives some quantitative results. The
fat contains 14 per cent, of volatile acids, 1-9 of acids soluble in water,
and 49 -4 (a very high percentage) of unsaturated acids. The volatile

1 Arch.f. d. ges. Physiol., Bonn, Bde. xxxix. and xl.

2 Bull. Soc. cMm., Paris, Ser. 3, tome vi.

3 Chem. Zig., Cothen, Bd. xvi. S. 1594.

4 Bohr, Jahresb. it. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. x. S. 182.

5 Grunzweig, Ann. d. Chem., Leipzig, Bd. clxii. S. 215; E. Wein, Diss., Erlangen,
1876; Chevreul, " Recherches sur le corps gras," Paris, 1823; Lerch, Ann. d. Chem.,
Leipzig, Bd. xjix. S. 212 ; Heintz, ibid., Bd. Ixxxviii. S. 300.

6 Bromeis, ibid., 1842, Bd. xlii. S. 46.

7 Compt. rend. Acad. d. sc., Paris, tome civ.

8 Overs, o. d. k. Danske Vidensk. Selsk. Fork., Kjobenhavn, 1891.

9 Chem. Neivs, London, vol. Ixiil.

10 Ztschr.f. JBiol., Munchen, Bd. xxxi. S. 1.

11 Ztschr.f. physiol. Chem., Strassburg, Bd. xix. S. 369.

12 Duclaux (loc. cit.) found formic acid in cows' butter which had been exposed to
sunlight.

i34 THE CHEMISTRY OF THE TISSUES AND ORGANS.

acids contain equal quantities of caproic, capiylic, and capric acids, and
the merest traces of butyric acid. The principal acids present, as is
usual in animal fat, are palmitic, stearic, and oleic acids, and one or
more acids of lower molecular weight, including myristic acid. The
melting point of the mixture of acids is 37° to 39°, and of the fat itself
30° to 31° C.

The proteids of milk. — The proteids which occur in milk are
three in number. The most abundant and most important of these is
caseinogen. It is this proteid which is acted upon by rennet, and
converted into casein or cheese.1 The other two proteids are only
present in small quantities; they are called lactoglobulin and lact-
albumin. Proteoses and peptone were described in milk by many of
the older workers. This was due tt> the use of faulty methods of
analysis (see p. 41).2

Coagulation of milk. — When milk is allowed to stand at the
ordinary temperature exposed to the air, the chief change it undergoes
is the lactic acid fermentation. The acid formed precipitates a part of
the caseinogen, but this is a different thing from the conversion of
caseinogen into casein. Sometimes, however, certain aerobic bacterial
growths act like rennet in causing a true curd. Certain of the higher
plants (Ficus, etc.) also curdle milk.

The agency by which the clot is most readily formed is that of
rennet. This is a ferment secreted by the stomach, and is usually obtained
from the stomach of sucking animals, like the calf. The pancreatic
juice also has a curdling action on milk (see p. 137), and extracts of
many tissues (such as testis, liver, lung, muscle) have a feeble action of
the same nature.3

Hammarsten4 and, later, Friedberg5 showed conclusively that the
active principle of rennet is not pepsin ; that it requires for its efficient
action the presence of calcium salts, of which the phosphate is the one
which is mostly present in the milk, and that it will act in a weakly
acid, neutral, or alkaline solution. It acts most readily at 40° C., and
is destroyed at 70° C. The ferment itself in the rennet extracts is
termed chymosin by Friedberg, and rennin by Foster.6

When rennet is added to cows' milk the result is a coherent clot or
curd, which expresses a clear yellowish fluid, the whey. The curd
contains the fat entangled with the casein ; the whey contains the other
proteids, sugar, and salts of the milk. In human milk the curd is
usually composed of smaller flocculi, and a similar flocculent coagulation
can be produced in cows' milk by previously boiling it, or by diluting it.
Lime water, soda water, or barley water are generally used as diluents
for this purpose.

The coagulation of milk is somewhat analogous to that of blood,
and the analogy is accentuated by the fact that in both cases calcium

1 The utility of this nomenclature is at once apparent when casein and caseinogen are
contrasted with fibrin and fibrinogen, myosin and myosinogen, even although the analogy
is not complete in details. Hammarsten, however, prefers to call the proteid in milk,
casein ; while the coagulated proteid he terms, after Schulze and Rose (Landw.
Versuchs. Stat., Berlin, Bd. xxxi.), paracasein.

2 For a critical article on the estimation of the various proteids in milk, see Schlossmann,
Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 197.

3 Edmunds, Journ. Physiol, Cambridge and London, 1896, vol. xix. p. 465r
4Jahresb. il. d. Fortschr. d. Thier-Chem., Wiesbaden, 1874, S. 135..

5 Journ. Am. Chem. Soc., N. Y., 1888, p. 15.

6 "Text-book," 5th edition, p. 519.

THE PROTEIDS OF MILK. 135

salts appear necessary, and that coagulation can be delayed or prevented
by decalcifying the fluid. This is most readily done by adding a small
quantity of a soluble oxalate.1 Peptone has, as with blood, a retarding
effect on coagulation.2

Green 3 has suggested that there is a definite relationship between
the ferment and the calcium salt, resembling that which exists between
pepsin and hydrochloric acid. Hammarsten 4 and, later, Einger 5 showed
what this relationship is. The formation of casein from caseinogen is, in
fact, a double process : the first action is that of the ferment which
converts the caseinogen into what we may call " soluble casein " ; the
second action is that of the calcium salt which precipitates the casein
as curd, which is probably caseate of lime. This may be shown by
taking a solution of caseinogen and adding rennet ; if the mixture is
warmed to 40° C., no visible change occurs ; but nevertheless soluble
casein, and not caseinogen, is now present. If the mixture is now boiled
to destroy the ferment, cooled, and a drop of 2 per cent, calcium chloride
added, the formation of a curd takes place.6

Casein and caseinogen differ in several of their properties. The
curd of caseinogen precipitated by acetic acid is not nearly so coherent
as the curd of casein produced by rennet. The precipitability of
caseinogen by acid is not prevented by the addition of an oxalate,
and there is 13 per cent, more calcium phosphate used up in rennet
coagulation than in acid precipitation.7

The action of rennin upon caseinogen is not a simple conversion of
that proteid into one of a more insoluble kind ; but just as the fibrin
ferment splits the molecule of fibrinogen into an insoluble proteid, fibrin,
and a soluble globulin which passes into the serum, so rennin splits
the caseinogen molecule into two parts : one part is the curd or casein ;
the other is a soluble proteid which passes into the whey, and is termed
" whey proteid " by Hammarsten. This is the equivalent of the lacto-
protein of other investigators. Some of these state it is like a proteose
or peptone. It is certainly not coagulated by heat ; it is precipitable by
saturating with magnesium sulphate ; rennet has no further action on
it. It does not, however, give the pink biuret reaction.8 It contains
C., 50-3 ; and N., 13'2 per cent.9

Caseinogen. — This proteid may be precipitated from milk by the
addition of acids like acetic, or by saturation with salts like sodium
chloride and magnesium sulphate, or by half-saturation with ammonium
sulphate. In all cases the fat of the milk is entangled with the
precipitate. Caseinogen may be most readily prepared free from fat
by first half-saturating the milk with ammonium sulphate ; the precipi-
tate is collected, well washed with half-saturated solution of the same

1 Arthur and Pages, Arch, de physiol. norm, et path., Paris, Ser. 5, tome ii. ; Compt.
rend. Soc. de biol., Paris, tome xliii. The addition of oxalates does not absolutely decalcify
blood or milk ; the calcium in close combination with the proteid remains unprecipitated.
See Schafer (Proc. Physiol. Soc., 1895, p. xviii) ; Hammarsten (Ztschr. f. j)hysiol. Chem.,
Strassburg, 1896, Bd. xxii. S. 333), and also the article in this book on Blood.

2 Edmunds, loc. cit. 3 Journ. Physiol., Cambridge and London, vol. viii. p. 371.

4 •' Zur Kenntniss des Kaseins," Nova Acta Reg. Soc. Sclent., Upsala, 1877. Festschrift.

5 Journ. Physiol., Cambridge and London, vol. xi. p. 464.

6 Here the analogy of casein and fibrin breaks down. In blood coagulation the cal-
cium salts assist in the genesis of the fibrin ferment rather than in the formation of
fibrin from fibrinogen (Hammarsten, loc. cit.}

7 D. F. Harris, Journ. Anat. and Physiol., London, 1894, vol. xxix. p. 188.

8 Halliburton, Journ. Physiol., Cambridge and London, vol. xi. p. 462.

9 Koster, Jahresb. ii. d. Fortschr. d. Thier-Chem., Bd. xi. S. 14.

136 THE CHEMISTRY OF THE TISSUES AND ORGANS.

salt, and then distilled water is added. This, in virtue of the salt adhering
to the precipitate, dissolves out the caseinogen, and carries it through
the filter, the greater part of the fat being left behind. From this
solution the caseinogen is precipitated by acetic acid ; it is collected,
thoroughly washed, and dissolved in dilute alkali like lime water, and
purified by repeated precipitation with acid and re-solution in alkali.

Einger's method of obtaining caseinogen is a slight modification of
that of Hammarsten : he precipitates caseinogen with acetic acid, collects
and washes the precipitate, and grinds it up in a mortar with calcium
carbonate ; the mixture is thrown into excess of distilled water ; the fat
rises to the top; the chalk falls to the bottom, and the intermediate
opalescent fluid is a solution of caseinogen. The separation into the
three layers may be hastened by the n«e of the centrifuge.

In both cases, the caseinogen, if it has been thoroughly washed from
soluble calcium salts, will not clot with rennet ; the lime water in the one
case and the calcium carbonate in the other not being sufficient to
cause the separation of the curd : this, however, occurs immediately on
the addition of a soluble salt of lime like the phosphate or chloride.

Solutions of caseinogen are not coagulated by heat. By prolonged
heating they become opalescent ; this often disappears on cooling. In
some cases a scum forms on the surface, as in milk.

Caseinogen is not a globulin ; still less is it an alkali albumin : it is
a nucleo -albumin.

Analyses by Chittenden l gave the following result — C, 53*3 ; H, 7'07 ;
N, 15-91; S, 0-82; 0, 22'04. The amount of phosphorus was not
estimated. Danilewsky 2 considered it to be a mixture of two proteids,
but this, as Hammarsten 3 showed, was due to faulty methods of prepara-
tion. Chittenden made a study of the caseoses and proteoses obtainable
from it by digestion.4 Sebelien,5 who also prepared casein peptone,
states it is optically inactive — a most exceptional occurrence among pro-
teids. The most interesting fact about its digestion by gastric juice,
however, is, that it yields a precipitate of nuclein, or rather of pseudo-
nuclein 6 (see pp. 65, 66).

The amount of and varieties of calcium phosphate in union with
caseinogen and casein has been investigated by Soxhlet and Soldner7
and by Courant.8 Soldner describes two calcium compounds of
caseinogen, containing respectively T55 and 2*36 per cent, of CaO ; these
are called dicalcium casein and tricalcium casein. Moraczewski 9 finds
that the yield of pseudo-nuclein varies from 1*3 to 21*1 per cent,
of the caseinogen employed; he finds that the amount of phos-
phorus in the pseudo-nuclein varies from O'SS to 6-86 per cent. The
whole phosphorus of the casein is not in the nuclein ; the quantity
in the nuclein is given as from 6 to 60 per cent, of the whole. This has
been confirmed by Salkowski and Hahn.10 These observers also find that

1 Stud. Lab. Physiol. Chem., New Haven, vol. ii. p. 156 ; iii. p. 66.

2 Ztschr. f. pJiysiol. Chem., Strassburg, Bd. vii. S. 433.
* Ibid., Bd. vii. S. 227.

4 On peptonised milk see also Horton-Smith, Journ. Physiol., Cambridge and London,
1891, vol. xii. p. 42.

5 Centralbl.f. agric. Chem., Leipzig, 1889, S. 717.

6 Moraczewski, Ztschr. f. physiol. Chem., Strassburg, Bd. xx.

7 Loc. cit. 8 Loc. cit.
9 Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xx. S. 28.

10 Arc.h.f. d. ges. Physiol., Bonn, Bd. lix.

THE PROTEIDS OF MILK. 137

the pseudo-nuclein is partly soluble in gastric juice ; l it is by far the
most soluble of the nucleins,2 though the majority are partly soluble
after pancreatic digestion.3

Casein. — This name should be restricted to the proteid formed by
the action of renhin, or of ferments that act like rennin. As a general
rule, it is more insoluble than caseinogen ; it is, however, readily soluble
in dilute alkalis such as lime water. From these solutions it is readily
precipitable by traces of calcium chloride ; and also by sodium chloride
(Hammarsten.). The precipitate with calcium chloride increases on
heating, but, like many calcium compounds, partially redissolves on
cooling (Kinger).

The main distinction between casein and caseinogen is, however,
that which was first insisted on by Hammarsten, namely, that caseinogen
can be curdled by rennet, casein cannot. Some recent work by D. F.
Harris 4 and Peters 5 appeared to cast doubt upon this essential distinction,
and to suggest the possibility of recoagulation of casein, analogous to
that of myosin. The fallacies into which these observers were drawn
have been pointed out independently by Edmunds,6 Hammarsten,7 and
E. Benjamin.8 Peters, for instance, used a preparation of rennet, rich in
sodium chloride and calcium salts ; the precipitate he obtained by adding
this to a solution of casein was due to these salts, not to the ferment.

Pancreatic casein. — An interesting variety of casein is that formed
by the action of pancreatic juice on milk, which has been recently
investigated by Brodie and myself.9

Kiihne10 was the first to point out that extracts made from the
pancreas of the dog cause milk to coagulate ; this action was described
in some detail by Sir William Eoberts.11 Various conditions which
influence the clotting were observed by Edkins,12 and the occurrence of
the action in pancreatic extracts from a number of animals determined by
Harris and Gow.13

Our attention was drawn to the subject by a sentence in Prof.
Gamgee's " Physiological Chemistry," u in which he points out that it does
not necessarily follow that because extracts of the organ have a clotting-
action, the pancreatic juice possesses it also.

We accordingly performed experiments with the actual pancreatic
secretion, obtained from temporary fistulse in dogs, and our conclusions
are summarised as follows : —

1. The pancreatic juice obtained from temporary pancreatic fistulse,
from dogs, produces a change in the caseinogen of milk.

1 The nutritive value of casein is given by Marcuse (Arch. f. d. ges. PhysioL, Bonn, Bd.
Ixii. S. 223) as equal to that of meat proteids.

2 E. Salkowski ( Virchow's Archiv, Bd. cxliv.) states that caseinogen, if not coagulated in
the process of preparation, is completely digested by gastric juice, if a sufficient volume of
the latter is employed, e.g. 500 parts of gastric juice to 1 of caseinogen.

3Sebelien, Ztschr. f. physiol. Ohem., Strassburg, Bd. xx. ; Popoff, ibid., Bd. xviii. ;
Gumlich, ibid., Bd. xviii. ; Weintrand, Terhandl. d. physiol. Gfesellsch., Arch. f. physiol.,
Berlin, 1895; Clara Willdenow, Inaug. Diss., Bern, 1893; W. Sandmeyer, Ztschr. /.
physiol. Ohem., Strassburg, 1895, Bd. xxi. S. 87. 4 Loc. cit.

5 Preisschrifc, Rostock, 1894. 6 Loc. cit.

7 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 103.

8 Virchow's Archiv, 1896, Bd. cxlv. S. 30.

9 Journ. PhysioL, Cambridge and London, 1896, vol. xx. S. 97.

10 Verhandl. d. naturh.-med. Ver. zu Heidelberg, N. F., Bd. iii. S. 3.

11 Proc. Roy. Soc. London, 1879 and 1881.

12 Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 193.

13 Ibid., 1892, vol. xiii. p. 469. 14 Vol. ii. p. 446.

138 THE CHEMISTRY OF THE TISSUES AND ORGANS.

2. This action differs from the action of rennet in the following
particulars : —

(a) The precipitate of casein occurs in the warm bath (35°-40° C.)
in the form of a finely granular precipitate, the milk to the naked eye
undergoing no change in its fluidity. On cooling this to the temperature
of the air, it sets into a coherent curd which contracts to only a small
extent, and is again broken up into fine granules by warming to 35° C.,
the milk to the naked eye becoming again fluid. This may be repeated
a great number of times.

(b) This phenomenon is not prevented, but only slightly hindered, by
such an addition of potassium oxalate as completely inhibits the activity
of rennet.

3. The experiments performed witTi extracts of the gland lead to
similar results, which may be masked if the action of the tryptic ferment
is very energetic.

4. The precipitate produced may be provisionally termed pancreatic
casein. By the action of rennet it can be converted into true casein.
Its solubilities, as summarised in the following table, are partly like
those of caseinogen, partly like those of casein. It is probably some-
thing intermediate between the two.

(a) Caseinogen.

(/>) Casein.

(c) Pancreatic Casein.

(«)Inwater + CaC03

Soluble.

Insoluble.

Insoluble.

(b) In lime water .

Soluble ; precipitable
with difficulty by

Soluble ; precipitable
with ease by CaCl2 ;

Soluble ; precipitable
with ease by CaCl2 ;

CaCl2.

precipitate pro-

precipitate pro-

duced by trace of

duced by trace of

CaCl2at40°, soluble

CaCl2 at 40°, not

on cooling.

soluble on cooling.

(c) The precipitate
produced by add-

Soluble in 5 per cent.
NaCl.

Insoluble in 5 per
cent. NaCl.

Slightly soluble in 5
per cent. NaCl.

ing CaCl2 to (b)

(d) Lime water solu-

Converted into casein

So readily precipitable

Behaves like casein-

tion.

by trace of phos-

by trace of calcium

ogen.

phoric acid and

salts that the action

rennet.

of rennet could not

be properly tested.

(e) In 0*5 sodium
bicarbonate solu-

Soluble ; precipitablc
with ease by CaCl2 ;

Soluble ; precipitable
with difficulty by

Soluble ; precipitable
with ease by CaCl2 ;

tion.

precipitate pro-

CaCl2.

Sirecipitate pro-

duced by trace of

need by trace of

CaCl2 at 40°, dis-

CaCLat 40° C., not

solves on cooling.

soluble on cooling.

The casein and caseinogen of human milk. — The facts described up
to the present point are derived from experiments on cows' milk.
There are very important differences between this and the principal
proteid of human milk. A large number of investigators x have noted
such differences as a more finely subdivided and more easily digestible
clot formed by rennet, but the difference between the two proteids goes
deeper than that. Human caseinogen is more difficult to precipitate by
acids (arid is easily soluble in excess) and by salts; it often will not

1 Bredert and Schroter, Centralbl. f. agric. Chem., Leipzig, 1888; Biedert, " Untersuch.
it. d. chem. Unterschiede der Menschen und Kuhmilch," Stuttgart, 1884 ; Langgaard,
Virchow's Archiv, Bd. Ixv. ; Makris, Inaug. Diss., Strassburg, 1876.

THE PROTEIDS OF MILK. 139

clot with rennet at all ; when it does so, the clot is a fiocculent
precipitate, which frequently redissolves rapidly in excess of gastric
juice. According to Szontagh,1 human caseinogen yields no pseudo-nuclein
on gastric digestion; this was confirmed by Wroblewski,2 who found
also that human caseinogen has the following percentage composition —
C, 52-24; H, 7'31 ; N, 14-9; P, 0-68; S, 1117; 0, 23'66. This, it will
be seen, is different from the composition of the caseinogen of cows' milk.
Human caseinogen contains phosphorus, but not in the form of pseudo-
nuclein, as in cows' milk.

Wroblewski finds that human milk contains small quantities of lact-albnmin,
and of another proteid very rich in sulphur (4*7 per cent.) and poor in carbon
(45 '01 per cent.). Lehmann and Hempel3 find that the caseinogen of cows'
milk contains 7 '2 per cent, of ash; this consists of CaO, 49*5; MgO, 2'4;
Po05, 47 '0 ; and S03 1 '06 per cent. The elementary composition of the
proteid is given as C, 50'86 ; H, 672 ; N, 14'63 ; P, 0-81 ; S, 0'72 ; ash, 6-47
per cent. The caseinogen of woman's milk contains more sulphur, 1*09, and
less ash, 3*2 per cent. Some of the differences between the two caseinogens
are doubtless dependent on the amount and nature of the ash with which they
are associated.

The occurrence of nucleon (phospho-carmc acid) in milk has already been
mentioned on p. 104. Siegfried 4 states that the nucleon accounts for 41 -5 per
cent, of the phosphorus in human milk, but for only 6 per cent, of that in
cows' milk. Practically all the phosphorus in human milk is in organic com-
bination (nucleon and caseinogen).

Lad-albumin. — After the precipitation of caseinogen and lacto-
globulin by half-saturation with ammonium sulphate, lact-albumium re-
mains in solution. It can be incompletely precipitated from this solution
by saturation with sodium sulphate. It is completely precipitated with
the other proteids when milk is saturated with ammonium sulphate. It
coagulates between 70° and 80° C. ; in cows' milk at 77° C. It is not
separable, like serum albumin and egg albumin, into several proteids by
fractional heat coagulation. It, moreover, is coagulated by heat very
slowly; the solution must be kept some hours at 77° C., before it is
completely precipitated. Its specific rotatory power5 «D= -36°, i.e. less
than that of serum albumin ; it has the following percentage composi-
tion: C, 5219; H, 718; N, 15-77; S, 1-73; 0, 23-13. The high
percentage of sulphur is another distinction between it and serum
albumin.

Lactoglobulin. — A trace of globulin is obtained from cows' milk by
saturating it with magnesium sulphate, after the removal of the
caseinogen by saturation with sodium chloride (Sebelien). Its
characters are like those of serum globulin. The amount of globulin in
colostrum is considerable, but in fully-formed milk it is present in so small
an amount that for a long time I was unable to confirm Sebelien's state-
ment. Hewlett,6 however, who worked with me, confirmed its presence.

1 Ungar. Arch. f. Med., Wiesbaden, Bd. i. S. 192 ; Jahresb. il. d. Fortschr. d. Thier-
C/iem., Wiesbaden, Bd. xxii. S. 168.

2 Inaug. Diss., Bern, 1894. See also Moraczewski, Ztschr. f. physiol. Chem., Strassburg,
1894, Bd. xx. S. 28.

3 Arch.f. d. ges. Physiol., Bonn, Bd. Ivi. S. 558.

4 Ztschr. f. physiol. Chem., Strassburg, 1897, Bd. xxii. S. 575.

5 Sebelien, Jahresb. il. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xv. S. 184.

6 Journ. Physiol., Cambridge and London, 1892, vol. xiii. p. 7!>8. See also Arthus, Arch,
de physiol. norm, etpath., Paris, 1893, p. 673,

140 THE CHEMISTRY OF THE TISSUES AND ORGANS.

Kemmerich l stated that casein (i.e. caseinogen) is formed at the cost of
the albumin of milk after secretion. He estimated the caseinogen by pre-
cipitating it with dilute acetic acid, the precipitate being subsequently freed
from fat by ether, dried and weighed. He estimated the albumin by weighing
the heat coagulum after separating out the acetic acid precipitate, and he found
that, after the milk is allowed to stand some hours at the body temperature,
the caseinogen increases in quantity, and the albumin diminishes. Diihnhardt 2
claimed to have separated out from the cells of the mammary gland a ferment
soluble in glycerine which hastens this process.3

These experiments are quoted with approval by Heidenhain,4 but do not
seem to have been followed up recently by the more precise methods of
modern milk analysis. The differences noted by Kemmerich are usually small,
and might be well within the limits of experimental error.5 They date from a
time when lact-albumin was considered to be identical with serum-albumin,
and when caseinogen was looked upon as nothing more than alkali-albumin.
Among other statements made by Kemmerich is the one that lact-albumin is
converted into casein by boiling — an assertion which is quite sufficient to show
the somewhat crude notions prevalent at the time concerning the proteids of
milk. The dominant idea of these workers appears to be to account for the
milk-proteids as simple derivatives of the blood proteids.

In the foregoing account of milk, no description of analytical processes has
been given. For the numerous methods which may be used in this highly
technical branch of analytical chemistry, the. reader is referred to text-books
on that science.

1 Arch.f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 401.
* Ibid., 1870, Bd. iii. S. 586.

3 J. C. Lehmann considered that caseinogen is formed from albumin by weak alkali
(CentralbL f. d. med. Wissensch., Berlin, 1864, S. 530).

4 Hermann's "Handbuch," 1883, Bd. v. S. 395.

5 That this explanation is probably correct, is shown by some experiments of Schmidt-
Mulheim (Arch.f. d. ges. PhysioL, Bonn, 1882, Bd. xxviii. S. 243) and Thierfelder (ibid.,
1883, Bd. xxxii. S. 619), who, by using the same methods, found a slight diminution of the
casein after milk had stood some hours at the body temperature. Schmidt-Mulheirn sup-
posed that on standing some of the casein is converted into peptone.

THE BLOOD.
By E. A. SCHAFER.

CONTENTS : — General Properties, p. 141 — Amount, p. 141 — Colour, p. 142 — Specific
Gravity, p. 143 — Reaction, p. 144 — Coagulation, p. 145 — Relative Amounts of
Plasma and Corpuscles, p. 147 — Number of Corpuscles, p. 149 — General Com-
position of Blood, p. 153 — Composition of Blood Corpuscles, p. 155 — Composi-
tion of Plasma, p. 156 — Proteids of Plasma, p. 161— Theories of Coagulation,
p. 168 — Causes of Coagulation, p. 178 — Lymph and allied Fluids, p. 181.

THE blood is a red fluid of alkaline reaction ; in man its specific gravity
is about 1*060. It has an odour which is different in different species
of animals, and is brought out by the addition of sulphuric acid. It
sets more or less rapidly into a solid clot or coagulum after death, or on
removal from the living blood vessels. It consists of a clear, yellowish
liquid, the plasma or liquor sanguinis, and of microscopic particles or
corpuscles of two kinds : the one kind, less numerous, termed the white,
or colourless, or lymph corpuscles (leucocytes) ; the other kind, by far
the most numerous, the red, or coloured corpuscles (erythrocytes),
which give the blood its characteristic tint. In addition to these, a
variable number of much finer discoid colourless particles (elemen-
tary particles, blood-platelets) are apparent in a microscopic preparation
of drawn blood.

Amount. — The amount of blood in the body was determined in the
following manner by Welcker : l — A measured sample of blood is drawn,
and, after being defibrinated, portions of it are diluted to different degrees
to serve as samples of comparison. The rest of the blood is then collected
and defibrinated, and the vessels are washed out with salt solution until
the washings are colourless : they are all added to the defibrinated blood,
which is now diluted with water until it corresponds in tint with one of
the above samples, the dilution of which is accurately known. The total
quantity of blood in the vessels can then be calculated. In order to
obtain every trace of blood, Welcker further minced up the whole
animal and extracted the tissues with water, adding this to the mass
of blood. Some haemoglobin would thereby, however, be yielded by the
muscles (Kiihne).

The amount has also been determined during life by the method
of Grehant and Quinquaud,2 who allowed an animal to inspire a

1 Ztschr. f. rat. Med., 1858, Ser. 3, Bd. iv. S. 147. Welcker's method is improved
by combining the haemoglobin with carbonic oxide gas (Gescheidlen).

2 Compt. rend. Acad. d. sc., Paris, 1882, tome xciv. p. 1450 ; Journ. de Vanai. et
physioL etc., Paris, 1882, No. 6, p. 564.

142 THE BLOOD.

measured amount of carbonic oxide (mixed with oxygen) ; then drew
off a measured quantity of blood, and determined the amount of carbonic
oxide this contained ; the amount in the whole of the blood in the body
would be in the same proportion, and the quantity of blood could thus
be calculated. The result arrived at by these two methods is that the
blood is equal to one-eleventh to one-fourteenth of the body weight
(about 5 1 kilos, in a man of 70 kilos.).

Colour : laking of blood. — The colour of the blood varies in different
parts of the vascular system. The differences are dependent upon the
amount of oxygen in combination with the haemoglobin. The colour
also becomes altered by any reagent or circumstance which tends to
cause the haemoglobin to pass out fr^m the corpuscles into the circum-
jacent fluid. When this is brought about, the blood loses its opaque
appearance and becomes transparent and of a laky tint. Such " laky "
blood is readily produced by the addition of distilled water, and also by
water holding neutral salts in solution up to a certain percentage ; which
percentage varies for different salts, and also, with the same salts, for the
blood of different animals. A solution containing just such a percentage
of salt as suffices to keep the corpuscles unaltered in form, and without
removal of any of their haemoglobin, is " isotonic " ; l solutions below and
above such strength are respectively " hypisotonic " and " hyperisotonic." 2
For human blood, a solution of common salt is isotonic with a percentage of
0'9 ; for defibrinated ox blood, with 0'6, and about the same for frog's blood.
Very slight differences of external condition will tend to alter the per-
meability of the blood corpuscles both for haemoglobin and for other
substances. A minute diminution in the alkalinity, such as is produced
by the addition of 0'003 per cent. HC1, so alters the permeability as to
cause proteid to pass from the corpuscles into the serum, and chlorides or
phosphates to pass into the corpuscles from the serum ; a minute increase
of alkalinity has the opposite effect. The passing of oxygen and carbonic
acid respectively through blood produces like physical changes, and it has
been suggested that these changes may come into operation in connection
with the metabolic exchanges in the capillaries.3 These osmotic effects
alter the total volume of the corpuscles as compared with the plasma ;
the proportional alterations are determined by centrifugalising blood,
and then measuring the respective amounts of subsided corpuscles and
superjacent plasma.4 Laky blood is produced not only by water and
dilute solutions of neutral salts, but also by many other reagents or con-
ditions, such as crushing of the corpuscles, freezing and thawing the
blood, and also by the action of acids, of alkalies, of bile salts, of ether and
chloroform, of heat and electricity.5 In all cases the permeability of
the envelope of the red corpuscle (see p. 154) becomes altered either by
mechanical means or by the solution of one or more of its constituents,

1 Having the same osmotic pressure (de Yries, Ztschr. f. physikal. Chem., Leipzig, 1888,
Bd. ii. S. 415).

2 Hamburger, Arch. f. PhysioL, Leipzig, 1886, S. 476 ; Ztschr. f. Biol., Miinclien, 1890,
Bd. xxvi. S. 414.

3 Hamburger, Ztschr. f. Biol., Mitnchen, 1892, Bd. xxviii. S. 405; Arch. /. PhysioL,
Leipzig, 1892, S. 513 ; 1893, Suppl. Heft, S. 153 ; and Verhandel. d. k. AJcad. v. Wetensh.
te Amsterdam, 1897, S. 368.

4 Koeppe, Arch.f. PhysioL, Leipzig, 1895, S. 154 ; Hedin, Skandin. Arch.f. PhysioL,
Leipzig, 1895, Bd. v. S. 207 and 238.

° For literature of this, see Rollett in Hermann's "Handbuch der Physiologic," Bd. iv.
S. 14.

SPECIFIC GRAVITY. 143

and the haemoglobin is thereby permitted to diffuse into the circumjacent
fluid.

Specific gravity. — The specific gravity of the blood varies in health
within small limits, namely, for men, 1057 to 1066 ; for women, 1054 to
106 1.1 According to Lloyd Jones,2 it is lower than this in women, averaging
1051*5 between the ages of 35 and 45, whereas in men of the same age it
averages 1058*5. It falls a little when much fluid is injected, and is raised
a little by profuse perspiration, but the changes thus produced are very
small.3 It is slightly less in children than in adults, but it is higher in
the foetus than in the mother ; and it is highest in the child at term, in
which it is 1066, the specific gravity of the maternal blood being then
only about 1050.4 The diurnal variations are normally so small as to be
almost negligeable. Passive congestion of the part from which the speci-
men examined is taken increases the specific gravity, whereas active con-
gestion lowers it. It varies also according to the part, of the body from
which it is taken, such variation being probably due to accidental admix-
ture with lymph. Thus Lloyd Jones found a difference of as much as
three or four per 1000 between blood from the finger (lower) and blood
from the skin over the shin (higher). Of the animals examined, it has
been found higher in birds than mammals, and to vary somewhat in these
animals in different species. The variations in age and sex are closely
related to variations in the amount of haemoglobin. Saline solution
(NaCl, 075 per cent.) injected in quantity into the blood only depresses
the specific gravity for a short time. The specific gravity of blood from
a vein is practically the same as that from the corresponding artery, if
care be taken to avoid venous congestion.5

The specific gravity of the blood falls after the removal of blood,
doubtless from absorption of the specifically lighter lymph from the
tissues. It subsequently (in about six hours) not only returns to
normal, but even rises above normal ; after about twelve hours it has
permanently recovered its normal specific gravity.6

Almost any operation performed upon an animal, especially one
involving exposure or irritation of a serous membrane, will produce an
increased percentage of corpuscles (polycythaemia), or a corresponding
diminution of plasma. This is due, not to increased formation of cor-
puscles, but to exudation of plasma in the inflamed or irritated part.7

1 Haramersclilag, Ztschr. f. Uin. Med., Berlin, 1892, Bd. xx. S. 444. The results of
other workers will be found in this paper. For the older literature, see Kollett, op. cit., S.
134. The numbers given by Peiper (CentralU. f. Uin. Med., Bonn, 1891, Bd. xii. S. 217)
are 1*055 as the average for men, and 1 '053 for women.

2 Journ. Physiol., Cambridge and London, 1888, vol. viii. p. 1.

3 Schmaltz, Arch. f. Uin. Med., Berlin, 1891, Bd. xlvii. S. 145; Grawitz, Ztschr. f.
Uin. Med., Berlin, Bd. xxi. S. 459, and Bd. xxii. S. 411.

4 Lloyd Jones, op. cit.

5 Cohnheim and Zuntz, Arch. f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 303.
For the effects of varying conditions of health and disease upon the specific gravity
of the blood consult Lloyd Jones, Journ. Physiol., Cambridge and London, 1891, vol. xii.
p. 299, where a large number of observations are accumulated. Lloyd Jones worked by
Roy's method, Scholkoff (Diss., Bern, 1892), working by a different method (pycnometer),
has obtained very similar results. Both observers agree in the important fact that the
specific gravity varies as a rule pari passu with the richness in haemoglobin. For the
specific gravity in different animals, and for variations experimentally induced, see Sher-
rington and Copeman, Journ. Physiol., Cambridge and London, 1893, vol. xiv. p. 52.

6 Ziegelroth, Virchows Archiv, 1895, Bd. clxi. S. 395.

7 See on this subject, Lowit, "Studien z. Phys. u. Path. d. Blutes," Jena, 1892; W.
Hunter, Journ. Physiol., Cambridge and London, 1890, vol. xi. S. 115; Sherrington and
Copeman, Joe. cit. ; Sherrington, Proc. Roy. Soc. London, 1893, vol. Iv. p. 161.

144 THE BLOOD.

The methods which have been used for determining the specific gravity of
the blood are — (1) that of directly weighing a sample (pycnometer), and (2)
Roy's method. The latter is by far the readiest, and, for small quantities of
blood, the more accurate. It consists in transferring minute drops of blood to
glycerine and water, mixed in varying proportions, and forming a graduated
series of liquids of different and known specific gravities, and in observing in
which mixture the drop tends neither to rise nor to fall. The method has been
modified by the use of benzene and chloroform mixtures instead of glycerine and
water, and also by placing the drop of blood in such a mixture, and adding benzene
or chloroform, as the case may be, until the drop remains exactly suspended,
tending neither to rise nor fall ; the specific gravity of the mixture is then
taken (Hammerschlag). It may be doubted, however, whether these modifica-
tions are more readily applied, or more accurate than Roy's method.

Reaction. — The alkaline reaction of the blood is easily recognised, in
spite of its red colour, by applying a drop of blood to the surface of a piece
of glazed litmus paper, and after half a minute wiping away the blood
with a piece of clean linen, wetted with distilled water or with neutral
salt solution. The part of the paper which was covered by the blood
will show a blue patch.1 A comparison may be made between different
samples of blood, by using a series of litmus papers which have been
reddened by standard acid of different strengths.2 For estimating the
amount of its alkalinity the blood is mixed in small measured quantity
with a solution of sulphate of soda, containing a definite amount of
tartaric acid,3 titrated against sodium hydroxide, and the mixture found
which is exactly neutral to glazed litmus paper. Tested by this method,4
the alkalinity of human blood is found to be equal to about O200
grms. of sodium hydroxide per 100 c.c. blood.5 There appears to be
a diurnal variation, the alkalinity being lowest in the morning, and
gradually rising in the afternoon, becoming less again in the evening. It
rises during digestion.6 It is diminished by muscular work, especially
with a diet containing little or no proteid.7 On the other hand, with a
diet rich in proteids, it undergoes very little alteration. In accordance
with this-, it is found that carnivora resist an artificial diminution of the
normal blood alkalinity (such as would be caused by giving dilute mineral

1 Schafer, Journ. PhysioL, Cambridge and London, 1881, vol. iii. p. 292.

2 Haycraft and Williamson, Proc. Roy. Soc. Edin., 1888, vol. xv. p. 396. For fallacies
in the clinical application of this method, see Hutchison, Lancet, London, 1896, vol. i.
p. 616.

3 Lassar, Arch. f. d. ges. PhysioL, Bonn, 1874, Bd. ix. S. 44; Drouin (These, Paris,
1892) used oxalic acid.

4 The principle of the method is due to Zuntz, who, however, used phosphoric acid
(CentralbL f. d. med. Wissensch., Berlin, 1867, S. 801) ; but the details were greatly
improved by Landois ("Real-Encyklopadie," Aufl. 2, Bd. iii., article "Blut"). For other
methods of estimating the alkalinity, see v. Limbeck, Wi&n. med. BL, 1895, S. 295 ; and
Schutz-Sehultzerstein, CentralbL f. d. med. Wissensch., Berlin, 1894, Bd. xxxii. S. 801.
According to Mayer (Arch.f. exper. Path. u. Pharmakol., Leipzig, 1883, Bd. xvii. S. 304),
all titration methods are unreliable with blood, but his conclusions have not been accepted
by most physiologists.

5 Freudb'erg, Virchow's Archiv, 1891, Bd. cxxv. S. 566, gives an average alkalinity in
health of 0 '200 to 0'240 gmi. NaHO per cent. Jeffries (Boston Med. and S. Journ., 1889)
obtained about 0*200 as the average, and Drouin about 0'206. v. Jaksch. (Ztschr.f. Jclin.
Med., Berlin, 1888, Bd. xiii. S. 353) found the alkalinity of normal human blood as high
as 0'260 to 0'300.; Loewy (Arch. f. d. ges. PhysioL, Bonn, 1894, Bd. Iviiii. S. 498), working
with "laked" blood, found its alkalinity =0 '449 grms. NaHO ; and Berend (Ztschr.f.
Heilk., Berlin, 1896, S. 351) obtained an alkalinity from "laked" blood of 0'450 to 0'500.

6 Peiper, Virchow's Archiv, 1889, Bd. cxvi. S. 337.

7 Cohnstein, Virchow's Archiv, 1892, Bd. cxxx. S. 332. See also Geppert u. Zuntz,
Arch.f. d. ges. PhysioL, Bonn, 1888, Bd. xlii. S. 233, and Peiper, loc. cit.

COAGULATION. 145

acids by the mouth), whereas herbivora show no such resistance.1 The
result appears to be due to the fact that ammonia becomes split off from
the superabundant proteid in place of urea, and serves to unite with
and neutralise the excess of acid.

Kraus found the alkalinity to be diminished by laking the blood, i.e. the
blood to become more acid after the corpuscles are broken up, but Loewy and
others have found it to be very high under these conditions ; alkaline substances
in the corpuscles coming also into estimation.2 It is diminished after with-
drawal, and during the process of coagulation (Zuntz) ; 3 when this is completed,
it is about "04 grm. NaHO less. The alkalinity is also diminished in fever and
in many diseases. In diabetic coma 4 and in the cold stage of cholera 5 an
acid reaction has even been detected. The diminution of alkalinity is accom-
panied by a diminished amount of carbonic acid in the blood.

The alkalinity is usually stated to be due to carbonate and phosphate
of soda. This may be true for the alkalinity of the plasma, but it is
insufficient to account for that of the corpuscles as well, and in them is
probably largely due to the presence of organic substances of weak basic
nature. Thus it was found by Zuntz and Lehmann,6 that whereas a
sample of calcined blood showed an alkalinity equivalent to 0'240, and
the estimation of the alkalinity of the same blood by the amount of
carbonic acid it would combine with gave an alkalinity equal to 0*276,
the estimation by titration of the same blood after laking gave a result
as high as 0-832. Saturation of blood with carbonic acid causes the
corpuscles to become less and the serum more alkaline.7

Although the blood is alkaline in reaction to litmus, it contains salts
(hydrodisodic phosphate and sodic bicarbonate) which are theoretically
acid,8 having the power both of fixing bases and of turning other acids
out of combination (Kollett). In this sense the " acidity " as well as the
" alkalinity " of the blood can be spoken of. According to Kraus 9 it is
normally equivalent in venous blood to from 0*162 to 0'232 grm. NaHO per
100 grms. blood ; being increased in conditions of fever to 0-272 grm., and
in diabetic coma to 0*347 grm.

Coagulation. — The blood begins to coagulate three .or four
minutes after it is drawn, and the process is completed in seven
or eight minutes.10 The process is hastened by warmth, by agita-

1 Walter, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1877, Bd. vii. S. 148.

3 Kraus, Ztschr. f. Heilk., 1890, Bd. x. S. 106 ; Arch. f. exper. Path. u. Pharmakol.,
Leipzig, 1889, Bd. xxvi. S. 186 ; Winternitz, Ztschr. f. physiol. Chem., Strassburg, 1891,
Bd. xv. S. 505 ; Loewy, Arch. f. d. ges. Physiol., Bonn, 1894, Bd. viii. S. 462; also Loewy
and Zuntz, ibid., S. 511, and Lehmann, ibid., S. 428. See note on p. 144.

3 See also Loewy and Zuntz, Arch. f. d. ges. Physiol. , Bonn, 1894, Bd. Iviii. S. 507.

4 Minkowski, Arch. f. exper. Path. u. Pharmakol., Leipzig, Bd. xix. S. 209; Mitth.
a. d. med. Klin. z. Konigsberg, Leipzig, 1888, S. 174.

5 C. Schmidt, "Charakt. d. epid. Cholera," Leipzig, 1850 ; Straus, Roux, Thuiller et
Nocard, Compt. rend. Hoc. d. biol., Paris, 1883, S. 569.

6 Arch.f. Physiol., Leipzig, 1893, S. 556.

7 Zuntz in Hermann's "Handbuch," 1880, Bd. iv. Th. 2, S. 77.

8 Maly, Sitzungsb. d. k. Akad. d. Wissensch., Wieu, 1878, Bd. Ixxvi. Abth. 2, S. 21 ;
and ibid., 1882, Bd. Ixxxv. Abth. 3, S. 314.

9 Op. cit.

10 Hevvson, "Properties of the Blood," 1772. In "Works," edited by G. Gulliver for
the Sydenham Society, p. 24. Blood from the hepatic veins coagulates rather more
slowly than blood from other parts of the vascular system. Paulesco (Arch. d. physiol.
norm, et path., Paris, 1897, p. 21) states that blood from the portal vein from animals in full
digestion of proteid food may take as long as fifty minutes to coagulate, but otherwise there
is little difference in blood from different vessels. For a method of accurately estimating
the time of commencing coagulation, see Brodie, Journ. Physiol., Cambridge and London,
1897, vol. xxi. p. 403.
VOL. I. 10

146 THE BLOOD.

tion, by contact with foreign matter, by moderate dilution with water,
by addition of calcium salts, and by fibrin ferment and nucleo-proteids.
It is delayed by cold, by dilution with solutions of neutral salts
or of sugar, by intravenous injection of albumose, and of various
other organic substances, such as diastatic ferments ; also by prevention
of contact with foreign matter, as by drawing it into oil. It is also
prevented if the soluble lime salts are precipitated by soluble oxalates,
by fluorides, or by soap. A temperature of 56° C. prevents coagulation
by precipitating the fibrinogen upon which the coagulation depends.
It remains fluid for an indefinite time within the living blood vessels,
even in a portion of vessel which has been isolated by ligatures. But if
the inner surface of any blood vessel is injured, the blood tends to
deposit a coagulum upon the injured part. And if a foreign substance
is introduced into a blood vessel a clot forms upon it.

It also coagulates within the vessels of a living animal if a solution
of nucleo-proteids is injected in a certain amount into the veins (Wool-
dridge) ; l but if the amount injected is too small to cause coagulation, the
opposite effect is obtained, the coagulability being temporarily destroyed
(negative phase, Wooldridge). These effects are not peculiar to nucleo-
proteids, but have been shown to be also produced by intravenous injection
of artificially prepared " colloids " 2 (see p. 37), and by snake-venom.3

If the coagulation is prevented by any of the above means, the cor-
puscles, which are heavier than the plasma, tend to fall to the bottom of
the vessel, and to leave the upper layers of plasma clear. At the junction
between the mass of subsided red corpuscles and the plasma is a " buffy "
layer containing most of the white corpuscles. The subsidence may be
accelerated by centrifugalising the blood. If cold be used to delay the
coagulation, or if the blood be contained in a ligatured vein, carefully
removed from an animal immediately after death, and suspended in a glass
vessel, pure plasma may be drawn off from the upper layer completely free
from red corpuscles, but usually containing a few leucocytes. The experi-
ment is best performed with horse's blood, the corpuscles being relatively
heavier in this as compared with that of other animals. This plasma
clots on "being placed in a glass vessel at the temperature of the air, but
much more slowly than a sample of the original blood, and the more
slowly the fewer the blood platelets and leucocytes it contains. If a
sample be taken from the buffy layer — containing, therefore, many leuco-
cytes and many blood platelets — the clotting is speedy and firm. If
bird's blood is rapidly and repeatedly centrif ugalised, plasma is obtainable
almost entirely free from corpuscles, and no clotting occurs in it for
days on standing in a glass vessel.4 It appears, therefore, that the
coagulation is independent of the red corpuscles, and is dependent
upon the plasma and white corpuscles, and perhaps also upon the
blood platelets. It is also dependent upon the presence of calcium
salts. The exact relations which these factors bear to one another in
the phenomenon of coagulation will be discussed later in considering the
properties of fibrinogen.

The delay of coagulation produced by neutral salts is best obtained

1 Proc. Hoy. Soc. London, 1886, vol. xviii. p. 186 ; Arch. f. PhysioL, Leipzig, 1886,
S. 397.

2 Pickering, Journ. PhysioL, Cambridge and London, 1895, vol. xvii. (Proc. PhysioL
Soc., p. v); and Halliburton and Pickering, ibid., 1895, vol. xviii. p. 285.

3 C. J. Martin, Journ. and Proc. Eoy. Soc. New South Wales, Sydney, 1895.

4 Delezenne, Compt. rend. Soc. de. bioL, Paris, 1896, p. 782.

RELATIVE AMOUNT OF PLASMA AND CORPUSCLES. 147

by allowing the blood as it flows from a cut artery to mix with an equal
volume of saturated solution of sulphate of soda or with a 10 per cent,
solution of sodium chloride, or with one-third its bulk of a saturated
solution of sulphate of magnesia. The plasma obtained after subsidence
of the corpuscles is in these cases diluted with the salt solution (salted
plasma), and may remain indefinitely uncoagulated. But, on diluting it
with a sufficient amount of water, coagulation will usually occur. The
delay produced by albumoses (commercial " peptone " is generally used)
is obtained by injecting these, in the proportion of 0'3 grm. per kilog. of
body weight into the circulating blood of a dog or cat.1 The effect is
not got in the rabbit.2 Malt diastase and emulsin in somewhat larger
quantity have a similar effect.3 The blood of such a " peptonised "
animal does not clot on being drawn, but it coagulates on passing
carbonic anhydride through it, or on diluting it with water. Extract of
leech-heads,4 which contains an albumose,5 and also extract of crayfish
muscle (Heidenhain), act similarly in preventing coagulation, but in smaller
doses. Leech extract does not, however, act exactly in the same manner as
albumose, for the latter does not arrest coagulation if added in moderate
quantity to drawn blood, whereas leech extract does arrest it (Haycraft).

To hinder coagulation by removal of lime salts, the blood is mixed as it
flows from the vessels with a small amount of solution of sodium oxalate ;
1 part of the salt to 1000 parts of blood is sufficient.6 The corpuscles
usually subside very readily in oxalated blood, and a clear plasma, nearly
but not quite free from soluble lime salts, is easily got from it, coagulating
quickly on the addition of chloride of calcium. It is not, however, the
case that, as Arthus has asserted, oxalated blood or plasma always
remains indefinitely uncoagulated without the addition of lime salts,
for on allowing it to stand a few days a clot is frequently found in it.7

All the above methods yield plasma, either pure or in a somewhat
modified condition. To obtain the blood corpuscles free from plasma it
is necessary, after drawing off the superjacent fluid from them, to mix
them with a further quantity of the salt solution used to prevent
coagulation (e.g. 10 per cent. NaCl), and again to centrifugalise. Or
the blood may be mixed as soon as drawn with a sufficient quantity of
isotonic salt solution to delay its coagulation, and centrifugalised. By
repeating the process several times the corpuscles may be got free from
plasma, and may thus be analysed separately from the liquor sanguinis.
But it is by no means certain that they have not undergone some altera-
tion in composition by diffusion. Hitherto no means has been devised
for meeting this objection.

Relative amount of plasma and corpuscles. — The relative amounts
of plasma or serum and corpuscles can therefore only be found approxi-
mately by weighing the corpuscles obtained by this method from a
given amount of blood. Indirectly, it has been arrived at for defibrin-
ated blood by Hoppe-Seyler, by determining the percentage amount of

1 Schmidt-Mulheim, Arch. f. PhysioL, Leipzig, 1880, S. 33.
2Fano, ibid., 1881, S. 276.

3 Salvioli, Arch, per le sc. med., Torino, 1888, vol. xii. p. 245.

4 Haycraft, Proc. Roy. Soc. London, 1884, vol. xxxvi. p. 478. Haycraft showed that luech
extract acts by destroying fibrin ferment.

5 Dickinson, Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 566.

6 Arthus et Pages, Arch, dephysiol. norm, etpath., Paris, 1890, p. 739.

7 This is certainly so with the plasma obtained from oxalated dog's blood and sheep's
blood (Schafer, Proc. PhysioL Soc., Journ. PhysioL, Cambridge and London, 1895, vol.
xvii. p. xx).

148 THE BLOOD.

proteids in the serum, and of proteids and haemoglobin in the subsided
corpuscles, and in the whole blood respectively ; and, calculating from
the results obtained, the amount of plasma and of corpuscles respectively
in 100 grms.1 An earlier method consisted in determining the amount
of fibrin in a given quantity of the whole blood, and of the plasma
respectively, and from this calculating the percentage amount of plasma
in the sample of blood.2 Bunge determined the proportions in a similar
manner by estimating the sodium in a sample of blood, and also in
plasma of the same blood. This method is only applicable to certain
animals (horse, pig) which have no sodium in their blood corpuscles.

The following example of the application of these methods is given by
Bunge :3 —

(A) By Hoppe-Seyler's method :-—

In 100 grms. of defibrinated pig's blood were found —

>?/ -10.00 > mean : 18 '90 grms. proteids + haemoglobin.

In the blood corpuscles of 100 grms. of the same blood —

(a) 15-04)

(b) 15-13 > mean: 15-07 grms. proteids + haemoglobin.
(e) 15-05)

In the serum of 100 grms. of blood were —

18-90-15-0 7 = 3 -8 3 grms. proteids.
In 100 grms. of serum —

(b\ 6-79 [mean: 6'77 proteids.

From this the amount of serum in 100 grms. of the defibrinated blood
may be computed —

6-77 : 3-83 : : 100 : 56-5.

Therefore 100 grms. blood contained 56*5 parts serum and 43 '5 corpuscles.
(J5) By estimation of sodium —

In 100 grms. of the whole blood of the same pig was found —

$ 0-2409 } mean : °'2406 grms' Na'°'
In 100 grms. of serum —

(6) 0:4260 } mean : °'4272 Srms- NaA
0-4272 : 0-2406 : : 100 : 56'3.

Therefore, by this method, 100 grms. blood contained 5 6 -3 parts serum
and 43*7 corpuscles — a result which agrees closely with that obtained by Hoppe-
Seyler's method.

Similarly, in horse's blood, Bunge found by Hoppe-Seyler's method 46 '5 per
cent, serum, and 53 -5 corpuscles, and by the sodium method 46 -9 serum and
53'1 corpuscles.

A rapid approximate determination may be made by Blix's method
(haematocrit).4 The blood is mixed with a definite amount of 2J
per cent, potassium bichromate, and centrifugalised. The corpuscles
rapidly accumulate at the bottom in an almost solid mass, and their

1 " Handb. d. physiol. chem. Analyse," Aufl. 2, Berlin, 1865.

2 Hoppe, Virchow's Archiv, 1857, Bd. xii. S. 483.

3 "Physiol. and Pathol. Chemistry," trans, by Wooldridge, 1890, pp. 243, 244.

4 Hedin, Skandin. Arch. f. Physiol., Leipzig, 1890, Bd. ii. S. 134. Gaertner, Berl. med.
Wchnschr., 1892, No. 36, p. 890.

THE NUMBER OF CORPUSCLES.

149

collective volume can be directly read off.1 The estimation can be made
with a small quantity of blood, and is therefore capable of being used for
clinical purposes. The average percentage of corpuscles in human
blood, as obtained by
these several methods,
is about 48, or very
nearly one-half of the
entire amount of blood.
In the horse it is 53
per cent., in the pig
43'5 per cent., in the
dog 35'7 per cent.,
and in the ox 32 per
cent. Hedin obtained
in himself an average
percentage total cor-
puscular volume of 51,
the greatest differences
in his own blood being
54-4 and 48 per cent. ;
but the average for a
large number of adult
males was 48 and of
females 4 3 '3. In chil-
dren of 6 to 13 years
the amount was 45 per
cent.

Number of corpus-
cles.— The number of
red corpuscles in a
cubic millimetre of
blood was determined
by Vierordt and Wel-
cker to be about
5,000,000 in adult
men. There are rather
fewer in women (about
4,500,000). Vierordt's
method consisted in
diluting the blood with
a known amount of
fluid which would pre-
serve the corpuscles,
and counting the number in a measured amount of the mixture. The same
method is still in use, but its application has been greatly simplified in the

1 An indirect method, based on the principle of centrifugalising blood with varying
amounts of salt solution, and determining the organic nitrogen in the supernatant fluid, has
been introduced by M. andL. Bleibtreu (Arch. f. d. ges. Physiol., Bonn, 1891, Bd. li. S. 151),
who claim to be able to estimate by its aid, not only the total corpuscular volume, but even
the average volume and weight of a single blood corpuscle. The method has, however,
been sharply criticised. (Hamburger, Centralbl. f. Physiol., Leipzig, 1893, Bd. vii. S. 161;
and Virchows Archiv, 1895, Bd. cxli. S. 230 ; Eyckmann, Arch. f. d. ges. Physiol., Bonn,
1895, Bd. Ix. S. 340 ; and Hedin, ibid., S. 360). See further, on the same subject, Lange,
ibid.t 1892, Bd. lii. S. 427, and Bleibtreu, ibid.t Bd. Ix. S. 405.

— SO)

FIG. 21. — Oliver's apparatus for estimating the number of
blood corpuscles, a, measuring pipette ; b, dropper to
contain Hayem's fluid ; c, mixing tube graduated in
percentages ; d, mode of making the observation. (This
must be done in a dark room. ) a, b, and c are natural size.

ISO THE BLOOD.

blood-counting apparatus (haemacytometer) of Gowers and of Thoma.1
The hsematocrit can also be employed, since it has been determined (by
exact enumeration.) that each volume per cent, shown by that instrument
represents 97,000 corpuscles. A still readier mode of rapidly estimat-
ing the number of red corpuscles in a sample of blood is that of G.
Oliver.2 Oliver takes a small measured quantity of blood and mixes it
in a graduated glass tube with Hayem's fluid,3 until the flame of a candle
placed at a certain distance behind becomes apparent through the mix-
ture. With 5,000,000 corpuscles per cent, the mixture will now be
found to fill the tube to a certain point. This point is taken as the
normal (or 100 per cent.), and above or below it the tube is graduated
in percentages. The fine flutings which are produced in drawing out
the tube enable the point at which the flame first becomes visible to be
determined with great accuracy, for they cause it to appear as a trans-
verse luminous line, and it is in this factor that Oliver's application of the
method is superior to previous attempts that have been made to apply it.
The following results have been obtained by Oliver and others : —
There is a diurnal variation in the percentage of corpuscles, which
falls somewhat during the daytime and rises at night. This variation
amounts to between 4 and 5 per cent, of the normal number. Food
usually produces a fall in the number of red corpuscles, independent of
the amount of water taken with the meals. The posture of a limb has
a considerable influence on the number of corpuscles obtained from it
by a prick, probably in keeping with alterations in the intracapillary
pressure, which governs the production of lymph. Muscular exercise,
whether active or passive (voluntary movements, electrical stimulation,
massage, passive movement of limbs), causes an increase in the per-
centage of the corpuscles, which is sometimes very marked.4 This may
also be due to a difference in the production and flow of lymph in
the part. The number is increased in the case of residents in high
altitudes (to as much as 8,000,000 ! per c.mm.).5 This appears to be
due, partly to increased evaporation from the general surface, and loss
of water from the blood; partly to increased arterial tension, which
increases the amount of lymph formed ; probably not to increased
formation of red corpuscles.6 It is also increased in certain diseased
conditions (e.g. gout), but more commonly it is diminished in disease.

1 Lancet, London, 1877, vol. ii. p. 797 ; Virchow's Archiv, 1882, Bd. Ixxxvii. S. 201. The
older literature is given by Rollett in Hermann's "Handbuch," 1880, Bd. iv. Th. 1, S. 27-31.

2 G. Oliver, Croonian Lectures, Lancet, London, 1896, vol. i.

3 Distilled water, 200 c.c. ; sulphate soda, 5 grms. ; common salt, 1 grm. ; corrosive
sublimate, 0'5 grm. See Hayem ("Du Sang," Paris, 1889), where will be found an
extended series of observations upon the microscopical characters of the blood.

4 Noted also by Malassez, Compt. rend. Soc. d. bioL, Paris, stance du 31 Oct. 1874, Gaz.
med. de Paris, 1874, p. 573. For numerous other observations by this author consult "De
la numeration des globules rouges du sang," Paris, 1873, and papers in Arch, de physiol.
norm, etpath., Paris, 1874, et seq.

5 Viault, Compt. rend. Acad. d. sc., Paris, 1890, tome cxi. p. 917 ; and 1891, tome cxii.
p. 295. Oliver (Croonian Lectures. Lancet, London, 1896, vol. i. p. 1782) gives a useful
epitome of what is known at present on this subject, together with many original observa-
tions.

6Grawitz, Berl. Jclin. Wchnschr., 1895, S. 713 and 740. Cf. also A. Fick, Arch. f. d.
ges. Physiol., Bonn, 1895, Bd. Ix. S. 589. Grawitz points out that at altitudes below
16,000 feet there is no need for a compensatory increase in number of red corpuscles, since
the experiments of Frankel and Geppert have shown that in dogs subjected to an atmo-
spheric pressure, equal to that at this altitude, there is just as much oxygen taken up by
the blood as at the ordinary pressure. Miintz found relatively more iron in the blood
of rabbits and sheep from near the top of the Pic du Midi than in others living in the

THE AMOUNT OF HAEMOGLOBIN.

Stierlin1 found individual variations in healthy men, amounting
to 1,650,000, and in healthy women to 2,230,000 per c.mm. E. Schiff2
obtained more than 5,500,000 per c.mm. in new - born children : as
development progresses, the number
gradually sinks to about 5,000,000.

There is normally no difference
between the number of corpuscles in
corresponding arteries and veins, pro-
vided there exists no congestion of
the part due to venous obstruction.
In such a case the exudation of
lymph from the capillaries increases
the number of corpuscles per cent.
in the blood of the vein. Capillary
blood is poorer in corpuscles than
that of the trunks, but the proportion
varies with their width and the rate
of the blood stream.3

Equally important for clinical pur-
poses, with the determination of the
number of red blood corpuscles as com-
pared with the normal, is the estima-
tion of the amount of haemoglobin,

a-

receiving the blood

FIG. 22. — Oliver's haemoglobinometer. e, glass cell for receiving the blood from the
pipette : the dilution is effected within the cell itself, a, standard graduations
made of tinted glass. To avoid multiplying these unduly they are furnished in tens
per cent., the intermediate divisions of the scale being obtained by superposing tinted
glass riders in a graduated series from 1 to 9. (These riders are not represented in
the figure). The apparatus is shown of the natural size.

and the consequent determination of the proportionate amount of hemo-
globin per blood corpuscle. This may be expressed as a quotient thus : —

percentage amount of haemoglobin 100 -, -,

—r. — - = — - = 1 or normal

percentage number ot corpuscles 100

at least theoretically : practically it is found to vary in health from

plains (Gompt. rend. Acad. d. sc., Paris, 1891, tome cxii. p. 298). Weiss, who kept rabbits
at high altitudes for about four weeks, and compared them with control animals at lower levels,
found an increase of corpuscles to the extent of 12 to 24 per cent., but no absolute increase of
haemoglobin in the whole body (Ztschr. f.pliysiol. Chem., Strassburg, 1897, Bd. xxii. S. 526).

1 Deutsches Arch. f. Tclin. Med., Leipzig, 1889, Bd. xlv., S. 75 and 256.

2 Ztschr. f. Heilk., 1890, Bd. xi.

3 Cohnstein and Zunt/, Arch. f. d. ges. PhysioL, Bonn, Bd. xlii. S. 303.

152 THE BLOOD.

0'95 to 1-05 in men, and from '9 to 1 in women.1 This "blood
quotient " has been also termed " the worth " of a corpuscle.2

The more exact methods for the determination of the amount of haemo-
globin in blood are dealt with elsewhere (see article on Haemoglobin). For
clinical purposes a comparison with a standard colour of the colour of the
blood diluted to a known amount is found to give sufficiently accurate results.
The chief methods used have been — (1) That of Gowers,3 who employs picro-
carmine gelatin as a standard ; (2) that of F. Hoppe-Seyler,4 who combines
the haemoglobin with carbonic oxide, and compares it with a standard solution
of CO haemoglobin ; and (3) that of v. Fleischl, who used a wedge of tinted
glass as a comparison. The method of v. Fleischl is by far the most con-
venient. It has been greatly improved by Oliver, who has adapted to it
the principle of Lovibond's tintometer.5 rfThus modified it takes the form of
a series of tinted glasses, one of which represents accurately the colour of a
measured amount of normal blood diluted with water and placed in a flat
glass cell of a certain size, whilst the others represent percentages of haemo-
globin below and above the normal (Fig. 22). The blood is measured in a
pipette similar to that shown in Fig. 21, a.6

The number of white corpuscles in a cubic millimetre of blood is
usually stated as 10,000, but it varies greatly even in health. By far
the larger proportion (70 to 90 per cent.) are of the finely granular
oxyphil variety.7 Of the rest less than 5 per cent, are coarsely granular
oxyphil cells, while the remainder, except a few which are hyaline,
contain basophil grannies.

Injection of many substances (peptones, nuclein, leech extract) into
the vessels causes an immediate and marked diminution in the number
of the leucocytes, chiefly affecting the finely granular kind (leucocytopenic
phase, Lowit) ;8 it is followed by an increase in their number (leucocytotic
phase). Acute local inflammation causes similar changes, but the
diminution in the number of leucocytes also largely affects the coarsely
granular cells, whereas the after increase is mainly in the finely
granular. Hankin noticed that the blood clots more readily when the
coarsely granular cell is scanty; this may explain the more ready
clotting of blood in inflammatory conditions.

The blood possesses, in the presence of free oxygen, a certain power of
producing oxidation in readily oxidisable substances, which may be added to
it, such as salicylaldehyde.9 This property it shares with some of the
tissues (spleen, liver, lung, thyroid, kidney, thymus), while other tissues
show no such tendency (muscle, brain, pancreas). The oxidation power is
greater in young subjects than in the adult.10 On the other hand, the blood
contains a substance or substances ("reducing substances" of Pfliiger) which
greedily appropriate any free oxygen which may be present in the plasma,

1 Oliver, loc. cit., p. 1705.

2 Garrod, Med.-Chir. Trans., London, vol. Ixxv. p. 191.

3 Lancet, London, 1878, vol. ii. p. 822.

4 Ztschr. f. physiol. Chem., Strassburg, Bd. xvi. S. 505. See also G. Hoppe-Seyler,
ibid., 1896, Bd. xxi. S. 461, and Winternitz, ibid., S. 468.

5 Lovibond, "Measurement of Light and Colour Sensations."

6 For more complete details of the method see Oliver, loc. cit., pp. 1699-1703.

7 Sherrington, Proc. Roy. Soc. London, 1894, vol. Iv. ; Kanthack and Hardy, Journ.
Physiol. , Cambridge and London, 1894, vol. xvii. p. 81. The earlier literature is given by
Sherrington.

8 "Studien z. Phys. u. Path. d. Brutes," Jena, 1892.

9 Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vii. S. 115 ; Centralbl. f.
d.med. Wissensch., Berlin, 1892, Bd. xxx. S. 489.

10 Abelous and Biarnes, Arch, de physiol. norm, etpath., Paris, 1895, pp. 195 and 239.

GENERAL COMPOSITION. 153

and are even capable of abstracting the oxygen which is combined with
haemoglobin, so that arterial blood rapidly becomes converted into venous
blood, when it is not exposed to the access of fresh oxygen. It is not known
upon what substance or substances these properties depend, but it is prob-
able that it is a function of the protoplasm of cells, and, in the case of the
blood, it may be due to the protoplasm of the white corpuscles.

General composition. — The general composition of blood and the
relative distribution of its constituents in the corpuscles and plasma
respectively is illustrated in the accompanying tables from C. Schmidt l
and Bunge. 2

Venous Blood of a Man, cet. 25, sp. gr. 1*0599 (C. Schmidt).
In 1000 grms. blood corpuscles (sp. gr. 1*0886) —

Water . . . . . .. 681*63

Substances not vaporising at 120° C. 318'37

Haemoglobin and other proteid substances . . 311*09

Inorganic substances —

Chlorine .... 1*750

Sulphuric acid . . . .0*061

Phosphoric acid . . . . 1*355

Potassium . . . .3*091

Sodium .... 0*470

Phosph. lime .... 0*094

Phosphate magnesia . . . 0*060

Oxygen. .... 0*401

Total of inorganic constituents (exclusive of iron) 7*282

In 1000 grms. plasma (sp. gr. 1*0312)—

Water . . . . . . .901*51

Substances not vaporising at 120° C. 98*49

Fibrin . . . . . . 8*06

Other proteids and organic substances . . , 81*92
Inorganic substances —

Chlorine . . . 3*536
Sulphuric acid . . . .0*129

Phosphoric acid .... 0*145

Potassium . . . . 0*314

Sodium ..... 3*410

Phosphate lime .... 0*298

Phosphate magnesia . . . 0.218

Oxygen . . . . . ' 0*455

Total of inorganic constituents 8*505

In this estimation the phosphoric acid is probably too high, being
increased in the process of calcining by the phosphorus in the lecithin.
Sertoli,3 by eliminating this error, obtained only 0'025 grin, phosphoric
acid per 1000 grms. ox serum, equivalent to only 0'005 per cent, hydro-
disodic phosphate (Na2HP04).

It is clear from the following table that there are considerable
differences in the composition of the whole blood and of its parts in

1 "Charakter. der epid. Cholera," Leipzig, 1850.

2 Ztschr. f. BioL, Miinchcn, 1876, Bd. xii. S. 191; and "Physiol. and Pathol.
Chemistry," trans, by Wooldridge, 1890, p. 245.

3 Sertoli in Hoppe-Seylers Med. Chem. Untersuch.. Berlin, 1868, S. 352. See also
Miroczkowski, Centralbl. f. d. med. Wissensch., Berlin, 1878, S. 353, who obtained in calf
serum, O'OIS ; in sheep serum, 0.0092 and 0'0064 ; and in dog serum, 0*0083 parts
NaaHP04 per 100 serum.

THE BLOOD.

different species of animals. In most animals the blood corpuscles have
a relatively large proportion of potash salts and phosphates, whereas
the preponderating salt in the serum is sodium chloride. In the bullock,
however, this salt also occurs in large amount in the corpuscles.

Defibrincded Blood of Pig, Horse, and Bullock (Bunge).

IN 1000 GRMS. CORPUSCLES.

IN 1000 GRMS. SERUM.

Pig.

Horse.

Bullock.

Pig.

Horse.

Bullock.

Water ....
Solids

632-1
367-9

60S.-9
391-1

599-9

400-1

919-6
80-4

896-6
103-4

913-3
86-7

Proteids, including haemoglobin
Other organic substances

347-1
12-0

387-8
7-5

67-7

5

73-2
5-6

Inorganic substances

8-9

4-8

7-7

7-9

K.O

5-543

4-92

0-747

0-273

0-27

0-254

Na,0

2-092

4-272

4-43

4-351

CaO

0-136

0-126

MgO

0-158

0-017

0-038

0-045

Fe203

0-011

01

1-504

1-93

1-635

3-611

3-75

3-717

P206

2-067

...

0-703

0-188

0-266

In the pig's blood analysed, there were, in 1000 parts, 436 '8 corpuscles, and
563-2 serum.

In the horse's blood analysed, there were, in 1000 parts, 531*5 corpuscles,
and 468 -5 serum.

In the bullock's blood analysed, there were, in 1000 parts, 318'7 corpuscles,
and 681 '3 serum.

A. Schmidt, in conjunction with his pupils,1 got the following results
from analyses of human blood obtained by venesection.

Percentage
Amount.

Specific
Gravity.

Amount of
Dry Residue
in 100
Grms.

Amount of Na, K, and 01, in
100 grms. (Warnach).

Na.

K.

01.

Serum

52-120

1028-3

9-709

0-344

0-02

0-353

Corpuscles . . .

47-880

...

35-458

0-282

0-307

Total blood

10607

21-971

0-185

0182 | 0-259

Gases of the blood. — Arterial blood of the dog contains from 15 to
25 vols. per cent, oxygen (at 0° C. and 760 mm. pressure), 25 to 40 car-
bonic anhydride, and about 1P8 vols. per cent, nitrogen. Venous blood
of the same animal contains from 5 to 15 vols. per cent, oxygen, 38 to
52 carbonic anhydride, and also about 1'8 vols. per cent, nitrogen.2 The
proportions of these gases and the manner in which they are combined
with constituents of the corpuscles and plasma is discussed elsewhere.3

1 Arronet, Diss., Dorpat, 1887 ; Warnach, Diss., Dorpat, 1888.

2 Schoffer, Sitzungsb. d. Tc. Akad. d. Wissensch., Wien, 1860, Bd. xli. S. 589 ;
Sczelkow, ibid., 1862, Bd. xlv. S. 171 ; Pfliiger, Arch. /. d. ges. Physiol., Bonn, 1868, Bd.
i. S. 275.

3 See " Chemistry of Respiration."

COMPOSITION OF RED CORPUSCLES.

155

The red corpuscles. — These consist of a delicate external envelope
enclosing coloured fluid contents.1 In all vertebrates below mammals
they contain a nucleus, the chief chemical constituent of which is
nuclein (see p. 65).

The organic matter in one hundred parts of dried red corpuscles
consists of : 2 —

HUMAN BLOOD.

DOG'S BLOOD.

GOOSE'S BLOOD.

II.

I.

Proteids and
nuclein .

12'24

5-10

12-55

36-11

Haemoglobin

86-79

94-30

86-50

62-65

Lecithin

0-72

0-35

0-59

0-46

Cholesterin

0-25

0-25

0-36

0.48

Goose's blood was taken as an instance of one in which nucleated
red corpuscles are present ; the higher percentage of proteids apparent
in this is due to the included nuclein.

The mineral constituents of the red corpuscles vary greatly in
relative quantity in different species of animals. Thus potassium con-
stitutes 40-89 per cent, of the total ash of human red corpuscles, and
sodium only 971, whereas in the dog the percentage of potassium is
6-07, and of sodium 3617 (0. Schmidt).

The remarkable excess of potassium over sodium salts is the opposite to
their relative proportion in plasma.

The chief organic constituent of the corpuscles, haemoglobin, will be
considered in a separate article. The other organic constituents consist
of nucleo-proteid, lecithin, and cholesterin.

The nucleo-proteid of the red corpuscle. — Wooldridge's 3 method for
obtaining the nucleo-proteid consists in centrifugalising defibrinated
blood repeatedly with a 1 per cent, sodium chloride solution until all
the serum is washed away. The red corpuscles are then laked by
the addition of water, and the mixture is shaken with a little ether,
to assist the solution; the white corpuscles are allowed to settle,
or removed by the centrifuge. To the clear but highly coloured
decanted fluid a little 1 per cent, solution of acid sodium sulphate is
added. This causes a considerable precipitate of nucleo-proteid, which
is chiefly derived from the red corpuscles, but a small part of which
may come from the white corpuscles and blood platelets.

The material thus obtained was shown by Kiihne,4 who used a rather
different method of separating it, to possess fibrino-plastic properties. It
was further examined by Halliburton and Friend,5 who found that it was

1 Schiifer in Quain's "Anatomy," 10th edition. 1893, vol. i. pt. 2, p. 210.

2 Hoppe-Seyler and Jiidell, Med. Ohem. Untersuch., Berlin, 1866, Heft 3. Manasse,
Ztschr. /. physiol. Chem., Strassburg, Bd. xiv. S. 452, gives the following percentages —
Lecithin, 1-687; Cholesterin, 0*151.

3 Arch. f. Physiol., Leipzig, 1881, S. 387.

4 "Lehrbuch," S. 193.

5 Journ. Physiol., Cambridge and London, 1886, vol. x. p. 532.

156 THE BLOOD.

identical in properties with what had been called by Halliburton cell
globulin-/3 (see p. 82). When cell globnlin-j3 was discovered to be a
nucleo-proteid, this also was found to be of the same nature.1 It can
also be prepared from the red corpuscles by Wooldridge's acetic-acid
method, or, provided the corpuscles are well caked together by the action
of an efficient centrifuge, by the sodium-chloride method of Halliburton.
In these experiments the colourless corpuscles may be got rid of by a
previous injection of commercial peptone.

In cats the percentage of phosphorus in the corpuscular nucleo-proteid
is 0*68. It produces in tra vascular coagulation when a solution in 1 per
cent, sodium carbonate is injected intravenously (Halliburton).

The lecithin and cholesterin. — L^ Hermann 2 and Hoppe-Seyler 3
described the phosphorus-containing organic constituent of the cor-
puscle as protagon, a substance got in large quantities from medullated
nerves, but subsequently it was recognised by Hoppe-Seyler 4 to be in
reality lecithin, which is a decomposition product of protagon (see p. 83).
Both lecithin and cholesterin are extracted from the corpuscles by ether,
and are therefore either free or, at most, in very loose combination
with the nucleo-proteid.

The chemical composition of the white corpuscles has been
already dealt with (p. 83).

The blood platelets. — In spite of the large amount of research from
the histological standpoint which has been carried out in relation to the
blood platelets (Blutpldttchen of Bizzozero), very little is known about
their function or their chemical composition. According to Lowit,5
they consist chiefly of a globulin, and play an important part in
fibrin formation. As the result of microchemical work, Lilienfeld6
considers that they consist of nucleo-proteid.

Lowit states that they are not to be seen in the circulating blood,7
and regards them as being produced partly from the white corpuscles,
partly from globulins of the plasma, after withdrawal of the blood.
They can, however, be seen within capillary blood vessels which have just
been removed from animals, and in which the blood is still fluid.8
Mosen failed to find them in lymph.9

Their number in the blood has been variously estimated at from
180,000 to over 600,000 per c.mm.10

BLOOD PLASMA.

The methods of obtaining plasma from blood, by preventing coagula-
tion and allowing the corpuscles to subside, have already been given.
Obtained thus from a suspended vein or from a cooled vessel, plasma

1 Halliburton, Journ. PhysioL, Cambridge and London, 1895, vol. xviii. p. 306.

2 Arch.f. Anat. u. PhysioL, Leipzig, 1866, S. 33.

3 Mcd. Chem. Untcrsuch., Berlin, Heft 1, S. 140.

4 Jbid., Heft3.

5 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1888, Bd. xxiv. S. 188.

6 Arch.f. PhysioL, Leipzig, 1892, S. 115.

7 Virchow's Archiv, 1889, Bd. cxvii. S. 545 ; and "Studien z. Phys. u. Path. d. Blutes
u. d. Lymphe," Jena, 1892.

8 Osier, Proc. Roy. Soc. London, 1874, No. 183. This observation I can entirely confirm.
^Arch.f. PhysioL, Leipzig, 1893, S. 352. See also Druebin, 1892, ibid., Suppl., S.

211.

10 See on this subject, Muir, Journ. Anat. and PhysioL, London, 1891, vol. xxi. ; also
Brodie and Russell, Journ. PhysioL, 1897, vol. xxi. p. 390, who give reasons for regarding
the higher number as more correct. Probably, however, the number varies greatly.

INORGANIC SUBSTANCES. 157

is a clear yellowish liquid of alkaline reaction and sp. gr. about 1027-1031.
It contains about 90 per cent, of water, holding various organic and
inorganic substances in solution. With the exception of certain proteids,
the constituents of plasma are identical with those of serum, in which
they are more readily studied.

Inorganic substances. — Plasma consists to about 90 per cent, of
water. The inorganic salts occur to the amount of about 0'8 per cent.
The principal is chloride of sodium. This can be crystallised out from
plasma after inspissation. According to the analyses of C. Schmidt, it
is present to the extent of 0'55 per cent. Carbonate of soda is probably
the next most abundant salt, although its exact amount cannot be stated.
It is to this salt that plasma mainly owes its alkalinity and its power of
absorbing carbonic acid. Although it is not possible to state definitely
in what manner the acids and bases of the plasma are distributed, it
appears probable that, besides these two salts, chloride of potassium,
sulphate of potassium, phosphate of calcium, phosphate of sodium, and
phosphate of magnesium, and probably chloride of calcium, occur l in
small amounts. Traces of a fluoride have also been found.2

Gases. — The gases of plasma have not been satisfactorily investi-
gated. They are probably not very different from those of serum,
which in the dog consist of from 43 to 57 vols. of carbonic anhydride,
2 -2 5 of nitrogen, and 0*25 of oxygen.3 The oxygen and nitrogen are
probably simply dissolved in the plasma, but the carbonic anhydride
is present in far too great an amount for this to be the case, since
not more than 2 or 3 vols. per cent, of this gas could be dissolved. The
remaining amount must therefore be in chemical combination. This can
only be with soda, as carbonate and bicarbonate ; for other bases are
present in too small amount in plasma to be taken into serious considera-
tion. This statement is also true for alkaline phosphates, although in
the corpuscles, in which they are present in considerable quantity, they
may play an important part in fixing C02 (Bunge), as shown by the
following equation : —

Na2HP04 + H3C03 - H2P04 + NaHC03.

Some of the CO2 may be combined with proteid,4 but this can only be
very little. As a matter of fact, Bunge calculates that, after allowing
for the amount of soda required to saturate the only strong mineral acid
of the plasma (hydrochloric), there is enough left to fix 63 vols. per cent,
of C02 as carbonate, and an equal additional amount as bicarbonate,
which is far more than the amount of C02 actually present.5

Organic constituents of blood plasma. — The organic constituents
of plasma may be divided into proteids and non-proteids, and the latter
into nitrogenous and non-nitrogenous.

Non-nitrogenous organic substances found in plasma. — These
consist of carbohydrates and fats; and, in addition, there are present
small quantities of a lipochrome, of cholesterin, and probably of sarco-
lactic acid.

Carbohydrates of plasma.— Three carbohydrates have been described

1 Pribram, Abhandl. d. math.-phys. CL d. Tc. Sachs. Gesellsch. d. Wissensch., Math. -phys.
Klasse, 1871, Bd. xxiii. S. 279 ; and in Arb. a. d, physiol. Aiist. zu Leipzig, 1871, p. 63.

2 Tamtnann, Ztschr. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 325.

3 Bunge, op. cit., S. 286.

4 Sertoli, Hoppe- Seyler s Mcd. Chem. Untersuch., Berlin, 1868, Heft 3, S. 350,

5 Op. cit., S. 286.

158 THE BLOOD.

in plasma, namely — (1) glycogen ; (2) an animal gum ; (3) dextrose or
grape sugar.

1. Glycogen. — There seems to be no doubt that traces of glycogen can
be obtained from fresh blood. Some is said to occur free in plasma, but
if so it is probably derived from intermixed or disintegrated leucocytes,
which can be shown by histochemical reaction to contain it.1 Kaufmann
finds the amount of glycogen in blood to be greatly increased (from 0*025
to 0*59 per litre) by removal of the pancreas.2

2. Animal gum. — Freund 3 has obtained from blood a carbohydrate
substance, resembling that described by Landwehr under the above name.
It has the formula (C6H1005)n, and is converted by boiling with dilute
mineral acids into a substance (sugar) which reduces Fehling's solution,
but is not fermentable, nor is it rotatory for polarised light. Four litres of
ox blood yielded 0'82 grms. of the gum, giving a percentage amount of 0*02.

3. Dextrose. — This is a constant constituent of plasma, whatever the
nature of the diet, and even in starving animals.4 It occurs in man to
the amount of about 012 per cent, of the blood, in the dog from Oil
to 015 per cent, (or a little over 1 per 1000).5 It is present in
nearly equal amount in blood from all parts, except in the blood of the
portal vein, during digestion of carbohydrate-containing foods, where
it is markedly increased. In the blood of the hepatic veins, in the
intervals of digestion, the amount was stated by Bernard to be some-
what greater than in the portal vein, or in the blood of the general cir-
culation ; but this difference has not been found by Pavy and most other
observers, although the statement has of late been reaffirmed by Seegen.6

Bernard 7 obtained a larger amount of sugar from arterial than from
venous blood, and Seegen has in some instances obtained a similar
result. Chauveau,8 and Chauveau and Kaufmann,9 have also published
analyses, which seem to show a disappearance of sugar after passing
the capillaries. But the differences observed have not been constant,
and are in any case so small as to lie within the range of experimental
error. As the result of eleven experiments, Pavy finds the sugar in
arterial blood to exceed that in venous by only 0*003 parts per 1000 ;
and he concludes that no appreciable difference exists between the two.10

1 E. A. Schafer, "A Course of Practical Histology," London, 1876, p. 39; Salomon,
Deutsche med. Wchnschr., Leipzig, 1877, S. 92 and 421 ; Arch. f. Physiol., Leipzig, 1878 ;
Oentralbl.f. Physiol., Leipzig u. Wien, 1892, Bd. vi. S. 512 ; Ehiiich, Ztschr.f. klin. Med.,
Berlin, 1883, Bd. vi. S. 40 ; Gabritschewsky, Arch. f. exper. Path. u. Pharmakol., Leipzig,
1891, Bd. xxviii. S. 272; Huppert, Centralbl. f.' Physiol, Leipzig u. Wien, 1892, No.
14, S. 394 (Huppert found more in dog's blood than in the blood of herbivora) ; Hoppe-
Seyler, Ztschr.f. physiol. Chem., Strassburg, 1894, Bd. xviii. S. 144.

2 Compt. rend. Acad. d. sc., Paris, 1895, tome cxx. p. 567.

3 Centralbl. f. Physiol., Leipzig u. Wien, 1892, Bd. vi. S. 345.

4 01. Bernard, Arch. g6n. de med., Paris, 1848, tome xviii. p. 303; Pavy, Phil. Trans.,
London, 1860 ; v. Mering, Arch. f. Physiol., Leipzig, 1877, S. 379 ; Otto, Arch. f. d. ges.
PhysioJ.. Bonn, 1885, Bd. xxxv. S. 467; Pickardt, Ztschr. f. physiol. Chem.. Strassburg,
Bd. xvii'. S. 217; Miura, Ztschr.f. Biol., Miinchen, Bd. xxxii. S. 255.

5 Pavy, "Physiology of the Carbohydrates," 1894, p. 161.

6 Arch. f. d. ges. Physiol., Bonn, 1884, Bd. xxxiv. S. 388, and 1885, Bd. xxxvii. S.
348; CentralU. f. Physiol., Leipzig u. Wien, 1893, No. 12; " Zuckerbildung im Thier-
korper," 1890.

7 Compt. rend. Acad. d. sc., Paris, tome Ixxxiii. p. 373, and "Leconssurle Diabete," 1877.

8 Ibid., 1856, tome xliii. p. 1008.

9 Ibid., 1886, tome ciii. p. 974.

10 Pavy, Proc. Roy. Sac. London, 1877, vol. xxvi. p. 346 ; "On Certain Points connected
with Diabetes," London, 1878 ; "Physiology of the Carbohydrates," pp. 170-171. This
is also apparently admitted by Seegen ("La Glycogenie Animale," Paris, 1890, p. 100),
although his theory of the production of energy requires that there should be a diminution
in the amount of sugar in venous blood.

NON-NITROGENOUS SUBSTANCES IN PLASMA. 159

Apart from these somewhat doubtful differences in blood from different
parts, the amount in the blood remains almost constant, whatever the char-
acter of the food, and even during starvation. The amount is somewhat in-
creased as the result of haemorrhage, a result due either to accession of lymph
(which contains a larger proportion of sugar than does blood), or to the
operation, through the agency of the nervous system, causing an increased
production of sugar from the liver -glycogen. If the amount of dextrose in
the blood be artificially increased to more than aboutO'25per cent, the excess
passes off by the urine. The amount is increased in diabetes, whether this be
the result of the sugar puncture, of removal of pancreas, or of disease,1
but even under these circumstances does not rise above 048 per cent.

Fats. — These are present in plasma in small but variable quantity
(0-2 to 0*5 or even 1 per cent.)2 being most abundant after a meal
containing much fat. The plasma or serum may then be milky from
admixture with the fat-containing chyle. They are composed of the
usual glycerides of fatty acids (palmitin, stearin, and olein). A small
amount, 0'05-O1 per cent., is in the form of soap.3 It has been stated4
that there is a greater amount of fat (ether extract) in arterial than in
venous blood, but this result is shown by Eohmann and Miihsam 5 to
have been probably due to an error brought about by venous congestion,
which affects the proportion of all the solids of blood as compared with
the water. The fatty acids appear also to be partly in combination with
cholesterin, forming cholesterin-esters, of which two have been separated
by Hlirthle 6 in a crystalline form, namely, the olein and palmitin com-
pounds, to the extent in horse serum of 0'08 and 0'06 per cent, respec-
tively. Hiirthle further found that in the dog they were increased
during inanition. The amount of cholesterin in serum or plasma is
stated by Hoppe-Seyler to be about O05 gr. per 100 c.c. blood,7 and is
probably mainly in the form of the fatty acid combinations just referred
to, and not, as was formerly supposed, in the free condition (Hiirthle).

Lipochrome. — The yellow-colouring matter of serum is a lipochrome
soluble in amylic and also in ethylic alcohol, but insoluble in turpentine.
Its absorption spectrum shows two ill-defined bands,8 one at the F and
the other between the F and G Frauenhofer lines (Plate IIL, Fig.
24). It resembles the lutein of Kiihne.

Lactic acid. — The presence of sarcolactic acid as a regular con-
stituent of normal blood plasma has been affirmed (0'017-0-054 per cent,
in dogs).9 Salomon could only find it in blood from the dead body, not
in that drawn during life,10 but Irisawa confirms its existence in fresh
blood (dog), and states that it is present to some extent in the cor-
puscles as well as in the plasma.11 It is increased in blood which has

1 Pavy, "On Certain Points connected with Diabetes"; Seegen, Wien. med. Wchnschr.,
1886, S. 1561 and 1595.

2 Rohrig, Abhandl. d. mouth. -phys. Gl. d. k. Sachs. Gesellsch. d. Wissensch., 1874^ S. 1,
and Arb. a. d. physiol. Anst. zu Leipzig.

3 Hoppe-Seyler, Ztschr. f. physiol. Chem., Strassburg, Bd. viii. S. 503.

4 Bornstein, Diss.. Breslau, 1887.

5 Arch. f. d. ges. Physiol., Bonn, 1889, Bd. xlvi. S. 383.

6 Ztschr. f. physiol. Chem.. Strassburg, 1893, Bd. xxi. S. 331.

7 Med. Chem. Untersuch./EerliTi, 1866, S. 145.

8 Kr\\kenbeTg,Sitziingsb.d.Jenaisch. Gesellsch. f.Med.u.Natunv., 1885, Suppl. Bd.xix.S.25.

9 Gaglio (with Drechsel), Arch. f. Phijsiol., Leipzig, 1886, S. 400; Spiro, Ztschr. f.
physiol. Chem., Strassburg, 1887, Bd. i. S. 110 ; Berlinerblau (witli Nencki), Arch. f.
exper. Path. u. Pharmakol., Leipzig, 1887, Bd. xxiii. S. 333.

10 Firchow's Archiv, 1888, Bd. cxiii. S. 356.

31 Ztschr. f. physiol. Chem., Strassburg, 1893, Bd. xvii. S. 340.

160 THE BLOOD.

been perfused through the still living kidneys or lungs, or through the
muscles of the lower limb, especially if inosit or glycogen or dextrose
be added to the blood used for perfusion (Gaglio, Berlinerblau). It is
also increased by intravenous injection of dextrose in blood circulating
normally through the body. It appears to enter into combination with
sodium hydrate, driving out CO^1

Non-proteid nitrogenous constituents of plasma. — The most im-
portant of these are urea2 (0'02-0'05 per cent.), kreatin, kreatinine,3
and uric acid,4 and occasionally hippuric acid.5 Xanthine and hypo-
xanthine are stated to be also present.6 Grehant and Quinquand found
the amount of urea in blood drawn from the splenic, portal, and hepatic
veins to be slightly greater than in that taken from the carotid.7
Lecithin occurs in small amount in. plasma.8 According to Marino-
Zucco, neurine and glycero-phosphoric acid are also present in traces in
the free state. There has also been described as a constant constituent,
jecorin9 — a substance which reduces Fehling's solution, but is soluble
in ether and is not fermentable. It is stated to occur in considerably
larger amount in venous than in arterial blood.10

Ferments. — Three ferments have been described as occurring in blood,
namely —

1. A diastatic ferment, producing the conversion of amyloids to sugar.

2. A glycolytic ferment, producing the disappearance of sugar.

3. A fat-splitting ferment (lipase).11

4. A fibrin ferment (thrombin), or its precursor (prothrombin), pro-
ducing the formation of fibrin from fibrinogen. The last will be con-
sidered in connection with coagulation.

Diastatic action. — A ferment action, converting starch into dextrin
and maltose, and ultimately into dextrose, has been obtained with
blood and lymph by Eohmann 12 and Bial,13 and also by Hamburger,14 by

1 Vaughan Harley, Arch. f. Physiol., Leipzig, 1894, S. 451.

2 Simon, Arch. f. Anat. u. Physiol. t Leipzig, 1841, S. 454 ; I. Munk, Arch. f. d. ges.
Physiol., Bonn, 1875, Bd. xi. S. 105; Schroder, Arch. f. exper. Path. u. Pharmakol.,
Leipzig, 1882, Bd. xv. S. 364 ; and 1885, Bd. xix. S. 373. Picard (Jpurn. de I'anat. et
physiol. etc., Paris, 1881, p. 530) found the percentage of urea rather higher than this in
the dog (0-09 to 0-13).

3 Yerdeil and Marcet found both kreatin and kreatinine (Journ. de pharm. et chim.,
Paris, 1851, tome xx. p. 89) ; Voit (Ztschr. f. Biol., Miinchen, 1868, S. 93) could find no
kreatinine ; but Colls (Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 107)
obtained a small but definite quantity.

4 Scherer and Strecker, quoted by Hoppe-Seyler ("Physiol. Chem."); Garrod, Med.-
Chir. Trans., London, 1848, vol. xxxv. p. 83, and 1854, vol. xxxvii. p. 49. See also
"Nature and Treatment of Gout," 1861 ; Abeles, Med. Jahrb., Wien, 1887, S. 479. On
the other hand, v. Jaksch (Ztschr. f. Heilk., 1890, Bd. xi. S. 415) could find no uric
acid in the blood of healthy individuals (nine cases).

5 Verdeiland Goldfuss, Compt. rend. Soc. debiol., Paris, 1850, tomeii. p. 79. Meissnerand
Shepard (" Untersuch. ii. d. Ensteh. d. Hippurs.," Hannover, 1866) were unable to find it.

6 Halliburton, "Chem. Physiol.," p. 251.

7 Journ. de I'anat. et physiol. etc., Paris, 1884, p. 317.

8 Hoppe-Seyler, Med. Chem. Untersuch., Berlin, 1869, S. 551.

9 Baldi, Arch. f. Physiol., Leipzig, 1887, Suppl. Heft, S. 100; Henriques, Ztschr. f.
physiol. Chem., Strassburg, Bd. xxiii. S. 244.

10 Jacobsen, Centralbl. f. Physiol., Leipzig u. Wien, 1892, S. 368.

11 Hanriot, Compt. rend. Soc. de biol., Paris, 1896, p. 925.

12 Arch.f. d. ges. Physiol., Bonn, 1892, Bd. lii. S. 157.

13 Ibid., 1892, Bd. lii. S. 137; and Bd. liii. S. 156; Rohmann and Bial, Arch. f.
d. ges. Physiol., Bonn, 1893, Bd. liv. S. 72 ; Bd. Iv. S. 469. According to Le'pine and
Barral (Compt. rend. Acad. d. sc., Paris, 1893, tome cxiii., pp. 118, 729, 1014, and cxv.
p. 304) sugar may be formed in blood on standing, at the expense of added peptone, as
well as starch or glycogen ; but this was not confirmed by Bial.

ulbid., 1895, Bd. Ix. S. 543.

PROTEIDS OF PLASMA. 161

mixing blood or serum with starch or glycogen solution, and keeping it
at body -temperature. Kohmann has shown that the diastatic change may
occur in lymph within the vessels as well as in vitro. Cavazzani
obtained most effect in blood taken from the portal vein.1 Tscherevkoff
finds that the diastatic ferment is precipitated by excess of alcohol, and
that its action is not destroyed by long standing under alcohol, nor by
sodium oxalate.2

Glycolytic action. — It was noticed by Bernard3 that the sugar of
blood diminished on standing in vitro, Pavy found that both the normal
sugar and added sugar diminishes in blood on standing.4 In any case,
and without standing, it is difficult to recover the full amount from
blood or serum, apparently owing to the fact that, in coagulating the
proteids with a view to their removal, a part of the sugar is mechanically
carried down or retained by them ; 5 this fact may lead to very con-
siderable experimental errors.6 Allowing, however, for such errors, it
appears clear that there is some actual loss of sugar on standing both
in blood 7 and in lymph or chyle.8 According to Seegen, the glycolytic
action is active in the presence of chloroform, and is destroyed by a
temperature of more than 54° C., in these respects resembling an enzyme.
Lepine states that it is absent or diminished in activity in diabetes,9
whether the result of disease or operation (removal of pancreas), and
that a very active glycolysis occurs in perfusing blood through various
organs (kidney, lower limbs).10 Arthus, on the other hand, denies the
pre-existence of a glycolytic ferment in blood. He finds no glycolysis
in oxalated blood, and thinks it probable that the ferment is formed
from leucocytes during coagulation.11 Kraus finds that the glycolysis
which occurs in blood on standing is accompanied by a splitting off of
C02, and is probably due therefore to oxidation.12

Proteids of plasma. — The proteids of plasma are —

1. One or more closely allied albumins (serum albumins).

2. Two globulins, termed respectively serum globulin and fibrinogen.

3. A nucleo-proteid or nucleo-proteids.

Blood contains normally neither albumose nor peptones.13 All the
proteids are completely precipitated by saturating plasma with ammo-

1 Arch, per le sc. med., Torino, 1893, vol. xvii. p. 105.

2 Arch, de physiol. norm, et path., Paris, 1895, p. 628.

3 Compt. rend. Acad. d. sc., Paris, 1876, p. 1406.

* Proc. Roy. Soc. London, 1877, vol. xxvi. p. 346; and 1879, vol. xxvii. p. 520. See
also "Physiol. of Carbohydrates," pp. 171-179.

5 Riihrnann, Centralbl. f. PhysioL, Liepzig u. Wien, 1890, No. 1 ; V. Harley, Journ.
Physiol., Cambridge and London, 189i, vol. xii. p. 391 ; Pavy, Brit. Med. Journ., London,
1896, vol. i. p. 453.

6 Schenck, Arch. f. d. ges. PhysioL, Bonn, 1890, Bd. xlvi. S. 607 ; 1891, Bd. xlvii.
S. 621. For a method whereby such errors may be largely avoided see E. Waymouth
Reid, Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 316.

7 Rohmann, loc. cit. ; Harley, loc. cit. ; Seegen, Wien. klin. Wchnschr., 1892, Nos. 14
and 15.

8 Lupine, Compt. rend. Acad. d. sc., Paris, 1890, tome ex. p. 742; Le'pine and Barral,
ibid., 1890, tome ex. p. 134; ibid., 1891, tome cxii. pp. 411, 604, 1185, 1414; and
tome cxiii. p. 118.

9 Lepine antl Metroz, ibid., 1893, tome cxvii. p. 154.

10 Lepine and Barral, loc. cit.

11 Arch, de physiol. norm, et path., Paris, 1892, p. 337 ; Compt. rend. Acad. d. sc.,
Paris, 1892, tome cxiv. p. 605.

12 Ztschr. f. klin. Med., Berlin, 1892, Bd. xxi. S. 315. See also Rohmann and Spitzer,
Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxviii. ; and Spitzer, Arch. f. d. ges. PhysioL,
Bonn, 1895, Bd. lx.

13 Halliburton and Colls, Journ. Path, and BacterioL, Edin. and London, 1895, p. 295.

VOL. I. II

162

THE BLOOD.

nium sulphate. The globulins and nucleo-proteids are completely pre-
cipitated by half-saturation with ammonium sulphate, or by complete
saturation with magnesium sulphate ; whilst fibrinogen is precipitated
by half -saturating plasma with chloride of sodium (probably some nucleo-
proteid is carried down with it). Upon these differences of solubility in
solutions of neutral salts the separation of the blood-proteids one from
another depends.

The proportion of globulin to albumin & ~ is known as the " proteid

albumin

quotient " ; it varies in different animals and in the same species of animal
under different conditions.1 For the same individual it is almost constant in
the blood serum, lymph, and serous transudations, although the absolute
amount of proteid in these may vary greatly.2

The annexed table 3 shows the total and relative amounts of the proteids
in the serum of different animals. The numbers are taken from different
sources ; the first four from Hammarsten.4

They are obtained — (a) the total proteids, by weighing the alcohol
precipitate; (b) the globulin, by separating off the magnesium sulphate
precipitate, re-dissolving this and weighing its alcohol precipitate: (c) the
albumins, by taking the difference between these two results. (6) includes,
besides serum globulin, a globulin formed from fibrinogen in coagulation, and
also the nucleo-proteids of plasma, but both of these are in very small amount.

(a) Total Proteids
per Cent.

(6) Globulins
per Cent.

(c) Albumins
per Cent.

Man .

7-62

3-10

4-52

Horse

7-25

4-56

2.69

Ox .

7'50

4-17

3-33

Rabbit

6-22

1-79

4-43

Pigeon

5-01

1-32

3-69

Hen .

4-14

2-90

1-24

Tortoise

476

2-82

1-94

Lizard

5-16

3-33

1-83

Terrapin

5-35

4-66

0-69

Snake

5-32

4-95

0-37

Frog .

2-54

2-18

0-36

Toad.

3-22

1-82

1-40

Newt

374

3-31

0-43

Eel .

673

5-28

1-45

Dog-fish

1-62

1-17

0-45

The most noteworthy feature shown in these figures is the relatively
small amount of albumins present in the serum of cold-blooded animals
as compared with the globulins. It has been stated that the albumins
proportionately diminish in starved animals,5 but other investigators
have failed to confirm this conclusion.6

1 Compare Frassineto, Arch. ital. de biol., Turin, 1895, vol. xxiv. p. 457 ; Paulesco,
Arch, de physiol. norm, et path., Paris, 1897, p. 21 ; W. Engel, Arch. f. Hyg., Miinchen
u. Leipzig (4), Bd. xxviii. S. 334.

2 Salvioli, Arch. f. Physiol., Leipzig, 1881, S. 269 ; Hoffmann, Arch. f. exper. Path. u.
Pharmakol. , Leipzig, 1882, Bd. xvi. S. 133.

3 Halliburton, Journ. Physiol., Cambridge and London, 1878, vol. vii. p. 321.

4 Arch.f. d. ges. Physiol., Bonn, 1878, Bd. xvii. S. 413.

5 Tiegel, ibid., 1880, Bd. xxiii. S. 278 ; Bnrckhardt, Arch.f. exper. Path. u. Pharmakol. ,
Leipzig, 1883, Bd. xvi. S. 322.

6 Salvioli, Arch. f. Physiol., Leipzig, 1881, S. 269 ; Ho well, John Hopkins Univ.
Stud. Mol. lab., Baltimore, vol. iii. p. 49; Rubbrecht, Trav. du lab. de L. Fredericq
tome v. p. 121.

PROTEIDS OF PLASMA. 163

Albumins of Hood plasma. — The albumins of plasma are also found
in the serum after coagulation of blood, and hence they^ have been
termed serum albumins. They remain in plasma or serum after half-
saturating it with ammonium sulphate, i.e. by mixing it with an equal
amount of saturated ammonium sulphate solution, or after entirely
saturating it with magnesium sulphate.

The precipitated globulins and nucleo-proteid are removed by filtra-
tion, and the filtrate dialysed to remove the salts. The solution which
remains contains only the albumins ; they can be precipitated from it by
saturation with ammonium sulphate or by sodio-magnesium sulphate.
According to Giirber, they can be obtained in a crystalline form by
adding ammonium sulphate just sufficient to produce precipitation and
allowing the fluid to stand exposed to the air.1

The material obtained in these ways constitutes what has usually
been called serum albumin (serine), but, as Halliburton has shown,2 it is
really a mixture of three separate albumins, which he has termed
respectively a, ft, y. These differ from one another in their temperature
of heat coagulation ; a-albumin coagulates at 72°— 75° C. ; /3-albumin at
77°-78° C. ; and -/-albumin at 83°-86° C. In the plasma of horse, ox,
and sheep blood, a-albumin is absent, but the other two are present ; in
man, and all other mammals and birds investigated by Halliburton, all
three were present ; but in reptiles, amphibia, and fishes investigated,
a-albumin was usually the only one found.3

The crystals of serum albumin which were obtained by Giirber from the
serum of horse's blood were hexagonal prisms with one pyramidal end,
and were doubly refracting ; some of them were as much as 1 cm. long.
Their elementary composition was C, 53'1 ; H, 7'1 ; N, 15'9 / S, 1-9,
0'22 ; and ash, O22 per cent. Dissolved in water and the excess of
ammonium sulphate removed by dialysis, the solution had a heat coagulation
temperature of 51° to 53°, and a specific rotation for yellow light of -6 10.4

The globulins of blood plasma. — The globulins of blood plasma con-
sist of serum globulin and fibrinogen. Serum globulin (paraglobulin,
Kiihne ; fibrino-plastic substance, A. Schmidt) has a heat coagulation
temperature of 75° C., which is almost constant in all animals in
which it has been examined. The amount to which it is contained
in plasma is represented by the figures in the second column of the
table on p. 162. It will be seen from this, that in man it constitutes about
three parts per cent, of the total serum. It is precipitated from serum by
half-saturation with ammonium sulphate,5 and also by complete saturation
with magnesium sulphate, sodium chloride, and some other neutral salts
which do not precipitate the albumins ; also, but less completely, by dilut-
ing the serum with water (fifteen times) and passing C02 through it, or by

1 Sitzungsb. d. phys.-med. Gesellsch. zu Wilrzburg, 1894, S. 143.

2 Journ. PkysioL, Cambridge and London, vol. v. p. 152.

3 In the slider terrapin (Howell, John Hopkins Univ. Stud. biol. lab., Baltimore, vol.
iii. p. 49) the albumin present is apparently of the 0 variety, coagulating at 77° to 80°,
and in the eel and dog-fish this variety was also found by Halliburton (Journ. PhysioL,
Cambridge and London, vol. vii. p. 320).

4 Michel (with Giirber), Verhandl. d. phys.-med. Gesellsch. zu Wiirzlmrg, 1895, N". F.,
Bd. xxix. No. 3.

5 Kauder (Arch. f. exper. Path. u. Pharmakol., Leipzig, 1886, Bd. xx. S. 411) found
that solutions of ammonium sulphate stronger than 24 per cent, completely precipitated
serum globulin ; above 33 '5 per cent, some of the serum albumin also comes down. A
half-saturated solution contains about 26 per cent.

1 64 THE BLOOD.

diluting with water and neutralising it with dilute acetic acid (in excess
of which it easily dissolves). Like other globulins, it requires the
presence of a certain amount of salts, or weak alkali, to be dissolved in
water ; it is therefore precipitated by dialysis or by sufficient dilution
of its solutions in salts or in serum, even without the addition of an
acid.

Fibrinogen. — This is the substance to which the plasma of the blood
especially owes its property of so-called spontaneous coagulability ; which
led to the term " coagulable lymph " being applied to it by older writers.1
It is precipitated from plasma along with serum globulin, by saturation
with magnesium sulphate or sodium chloride; the precipitation of
mixed globulins so obtained (the plasmine of Denis) forms a coagulable
liquid, on dissolving it in a more dilute Solution of salt. Fibrinogen is
entirely precipitated from plasma, or any other fluid containing it, by
half-saturation with sodium chloride ; 2 it can be re-dissolved in water
with the aid of the salt adhering to it, reprecipitated by half-saturation,
and so on until it is obtained in a condition which may be regarded as
approaching purity. But in contact with the salt solution it gradually
loses its solubility, and every time that it is precipitated less of the
precipitate redissolves on adding water ; the material which forms and
which remains undissolved in the dilute solution of salt resembles
fibrin in many physical and chemical characters, but is not similarly
rapidly swollen by dilute acids ; it may be termed par a- fibrinogen or
pseudo-fibrin. Fibrinogen dissolves also in dilute alkali, even in the
absence of neutral salts ; its alkaline solutions are clear, but its solutions
in neutral salt solutions are opalescent. It is precipitated from the
solution in weak alkali by careful neutralisation with acetic acid, and from
solutions in neutral salt solutions by slightly acidulating with the same
acid, but it is readily soluble in excess of the acid. The temperature of
heat coagulation of fibrinogen in salt solution is between 52° and 55° ; 3
but the whole of the dissolved proteid is not thrown down at this
temperature ; a small amount remains in solution, and is not coagulated
until the temperature of 65° C. is attained. According to Haminarsten,4
this is due to the splitting of the fibrinogen, under the influence of
heat, into coagulated fibrinogen and a globulin, which is coagulated at
the higher temperature. If fibrinogen which has been obtained from
blood plasma by the above method of half-saturation with NaCl, and
purified by repeated re-solution and re-precipitation with acetic acid, be
dissolved in water rendered faintly alkaline by NaHO, . it gives a
coagulum-like precipitate (if sufficiently concentrated) a short time after
the addition of a lime salt. The coagulum resembles fibrin in many
respects, but, according to Hammarsten, it is not true fibrin, but a
combination of fibrinogen with lime.5

1 Houlston, Diss. Med. Inaug., " de Inflammatione," pp. 11, 12, 14, Lugd. But., 17C7.
See Hewson's Works, Introduction, p. xxxvii, edited by G. Gulliver, London, printed for
the Sydenham Society, 1846.

2 Hammarsten, Arch. f. d. ges. Physiol., Bonn, 1879, Bd. xix. S. 563.

3 Hammarsten, ibid., 1880, Bd. xxii. S. 431.

4 Ibid., 1879, Bd. xix. S. 563.

5 Hammarsten. Ztschr.f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 333. It is
unnecessary to add any ferment or nucleo-proteid to the solution to produce the result, but
there is no doubt that nucleo-proteid may be present along with the fibrinogen. It was
shown by Lilienfeld (Ztschr. f. physiol. Chem., Strassburg, 1895, Bd. xx. S. 89) that
fibrinogen prepared by Hammarsten's method contains nuclein ; from this he inferred that
it is a nucleo-proteid, and not a globulin. But the amount of nuclein present is not sufficient

PRO TEWS OF PLASMA. 1 65

As just stated, fibrinogen is precipitated from plasma, and from
its solutions in neutral salt solution, or dilute alkalies, by the addition of
dilute acetic acid, even in slight excess. This precipitate has been
termed " thrombosin " by Lilienfeld,1 who regards it as due to a splitting
of the fibrinogen under the influence of the acid into this substance and
an albumose, but it has not been shown that it possesses any properties
differing from fibrinogen.2

From what has been stated, it will be seen that it is improbable that the
material which is obtained from plasma, under the name of fibrinogen, is a
simple substance. It is probably either a mixture, or a loose combination, of
at least three substances, namely —

1. Fibrinogen proper, coagulating at 56° C.

2. The globulin described by Hammarsten, and termed fibrino-glolulin,
coagulating at 65° C.

3. A nucleo-proteid.

The nucleo-proteid of plasma. — Beyond the fact of its presence, and
that it appears to be one of the essential factors in the formation of
fibrin, very little is known regarding the nucleo-proteid of blood plasma.
It is doubtful if it exists in the plasma of circulating blood; it is
thought by many that in this it is confined to the white corpuscles and
blood platelets — a very little being also present in the red corpuscles —
and that it is shed out by these as soon as the blood is drawn. The
reasons for this belief are —

1. White blood corpuscles and similar cells (lymph cells, thymus
cells, etc.) always contain a considerable amount of nucleo-proteid.

2. In plasma obtained by subsidence of the corpuscles there is most
nucleo-proteid in the lower layers, which contain most leucocytes ; and
least in the upper, which contain very few.

3. Fluids which collect in the serous cavities of the body (peri-
cardial fluid, hydrocele fluid, ascitic fluid) frequently contain no
leucocytes. When this is the case they are also devoid of nucleo-
proteid and of the property of spontaneous coagulability, although they
contain fibrinogen.

The nucleo-proteid is precipitated from oxalate plasma, by allowing
it to stand for twenty-four hours at 0° C. The addition of acetic acid
in slight excess also throws it down, but not in a pure form, for fibrin-
ogen is carried down along with it. Its solutions are coagulated at 65° C. ;
at a temperature of 60° C., in presence of free alkali, it is split into
nuclein and a proteid. This is stated by Pekelharing to be a proteose,3
but its proteose character is denied by Martin.4 Halliburton and Brodie
could also find no proteose in blood after the injection of nucleo-
albumin.5 In the presence of soluble salts of lime, it forms a

to justify this inference, and its presence is probably due to the fact that some or all of
the nucleo-proteid present in the plasma is precipitated along with the fibrinogen, and
clings to it in the subsequent processes of purification (Schafer, Proc. PhysioL Soc., Journ.
PhysioL, Cambridge and London, 1895, p. xviii). See later, p. 172.

1 Loc. cit.

2 Schafer, Proc. Pliysiol. Soc., Journ. PhysioL, Cambridge and London, 1895, vol. xvii.
p. xx ; Hammarsten, Ztschr. f. physiol. Chctn., Strassburg, Bd. xxii. S. 384; Cramer, ibid.,
1897, Bd. xxiii. S. 74. According to Hammarsten, this coagulum, like that produced in a solu-
tion of the original fibrinogen, is not fibrin, but a fibrin-like combination of lime and fibrin-
ogen. To me, however, it has often appeared difficult to distinguish from fibrin.

"Pekelharing, "Untersuch. ii. d. Fibrin-Ferment," Amsterdam, 1892.

4 Journ. PhysioL, Cambridge and London, 1894, vol. xv. p. 375.

5 Ibid., 1894-5, vol. xvii. p. 159.

166 THE BLOOD.

substance which possesses the property of converting fibrinogen into
fibrin, and is, according to Pekelharing, a combination of the nucleo-
proteid with lime, and identical with the fibrin ferment of A. Schmidt.
The fibrin ferment is sometimes spoken of as "thrombin," and the
nucleo-proteid material in the plasma from which it is produced is then
termed " prothrombin."

Wooldridge1 found that, on subjecting peptone plasma to cold, he
obtained a finely granular deposit, which had the property of producing
clotting in fibrinogenous fluids, which are not themselves spontaneously
coagulable, and of accelerating the process of clotting in coagulable fluids.
To the material thus obtained, and which he described as having, under
the microscope, an appearance similar to masses of blood platelets, he
gave the name " A-fibrinogen," because *he found that on adding it to
peptone plasma it produced fibrin, and that the amount of coagulation
was more or less proportional to the amount of A-fibrinogen added. It
is not fibrinogen as the term is ordinarily used, but is probably either a
micleo-proteid, or a mixture of nucleo-proteid with globulin. A similar
deposit occurs, as already stated, in oxalate plasma, on standing in the
cold. A precipitate containing the same substance is also produced by
adding magnesium sulphate solution in considerable amount to blood, and
in both plasma and serum of certain animals on acidulation with acetic
acid, but in both cases it is liable to be mixed with serum globulin.
It also occasionally occurs in serum, on standing, even without the
application of cold. Halliburton has suggested that the deposit in
peptone plasma may be a part of the proteoses, which were injected into
the blood, for he found that solutions of albumose were liable to give a
similar deposit on cooling by means of ice, but there is not enough proteose
present in peptone plasma to account for such deposit, and the fact that it
occurs under other conditions in plasma also negatives this supposition.
These experiments of Wooldridge, and the behaviour of the body termed
by him A-fibrinogen, will be again referred to in a subsequent section.

Fibrin. — Fibrin is the chief substance formed from fibrinogen in the
coagulation of blood plasma, and it is also produced in the coagulation of
lymph and other fibrinogen-containing fluids. It is usually got by whipping
blood as it flows from the blood vessels with a bundle of wires or glass
rods before it has had time to coagulate into a solid mass. The coagulum
then forms upon the wires or rods, and can be washed free from adherent
red corpuscles by putting it under a stream of water for a few hours.
But to obtain pure fibrin it is necessary first to prepare fibrinogen from
blood plasma by precipitation with NaCl (half -saturated), to purify this
by re-solution and re-precipitation, and finally to cause the coagulation of
the fibrinogen solution by fibrin ferment. The clot thus obtained, which
must be thoroughly washed, is composed of nearly pure fibrin.

When obtained by whipping blood, fibrin is a white stringy substance
when wet, drying to a glue-like mass. The threads of which it is com-
posed, and which, as may be seen in a microscopic preparation of blood,
interlace with one another and form a network of the finest possible
filaments, entangling the blood corpuscles in its meshes, have a strong
tendency to retract or shorten when formed ; this is the reason why a
clot shrinks and expresses serum from its interior. Fibrin is slowly
soluble in 5 to 10 per cent, solutions of certain salts, such as sodium
chloride, sodium sulphate, potassium nitrate, magnesium sulphate, and

1 Wright, Lancet, London, 1892, vol. i. pp. 457, 535.

PROTEIDS OF PLASMA. 167

ammonium sulphate, and also in iodides and fluorides, and in solutions
of urea.1 It is also very slowly dissolved to some extent by normal salt
solution ; the solution is in all cases assisted by moderate warmth. Fibrin
obtained from venous blood is slightly more soluble in salt solutions than
that yielded by arterial blood. The proteid material which is found dis-
solved after solution of fibrin in the above salts is composed of two
globulins,2 having heat coagulation temperatures of 55° and 75° respec-
tively. The latter, according to Halliburton, is reduced to 60°-65° in
sodium chloride solutions, being 73°-75° in magnesium sulphate solutions
only. Albumoses are also present in the fluid (Limbourg, Dastre). This
solution of fibrin in neutral salts occurs in the entire absence of putre-
factive decomposition (Green, Dastre). Fibrin swells in dilute acid (such
as 0*2 per cent. HC1) into a clear jelly, which very slowly undergoes
solution with the formation of acid albumin and proteoses. Stronger acids
and, with the aid of heat, weak acids, effect the conversion more readily.
The addition of pepsin to the acids employed greatly accelerates the con-
version, the fibrin first splitting into two globulins, one coagulating at 56°
and the other at 75°, and then becoming transformed into acid-albumin, pro-
teoses, and peptones.3 Trypsin in alkaline solutions has a similar action.4
Blood yields from *2 to '4 per cent, of its weight of dry fibrin. Ham-
marsten 5 gives the following as the elementary composition of fibrin : —

C . . 52-68
H . . 6-83

N 16-91

S . . MO

0 22-48

It is, however, never free from ash, and the ash invariably contains
lime,6 but not more than other proteids,7 nor does it contain more
lime than the fibrinogen from which it is formed. Thus in one
experiment Hammarsten found that a sample of fibrin, obtained by
the action of ferment prepared from oxalated serum, upon fibrinogen
prepared by precipitation from oxalated plasma by acetic acid, yielded
exactly the same amount of lime as a sample of the fibrinogen itself,
namely, 0*055 per cent. This fact completely disposes of the theories of
coagulation which assume that fibrin is merely a combination of
fibrinogen with lime, such as those of Freund, Arthus, Pekelharing, and
Lilienfeld. Fibrin obtained by whipping blood leaves a considerable
phosphorus-containing residue (nuclein) after subjection to peptic
digestion ; this is probably largely derived from the nucleo-proteids of the
entangled leucocytes. But even fibrin obtained from solution of purified
fibrinogen in dilute salt solution yields a certain amount of such residue.8
It is possible that this may be an accidental impurity, but, on the other
hand, it may be an integral constituent of the fibrin.

1 Dastre, Arch, de physiol. norm, et path., Paris, 1895, p. 408 ; Compt. rend. Acad. d.
sc., Paris, 1895, tome cxx. p. 589. See also on the solubility of fibrin in neutral salts,
Holzmaun, Arch, f, Physiol. , Leipzig, 1884, S. 210; and Arthus, " Coag. des liquides
organiques." Paris, 1894, pp. 105 et seq.

2 Green, Journ. Physiol., Cambridge and London, 1887, vol. viii. p. 372.

3 Hasebro'ck, Ztschr. f. physiol. Chem., Strassburg, Bd. xi. S. 348.

4 A. Herrmann, ibid., Bd. xi. S. 508. The other literature on this subject will be
found in Halliburton, "Text-Book of Physiol. and Path. Chemistry."

5 Arch.f. d. ges. Physiol., Bonn, Bd. xxii. S. 484.

6 Frederikse, Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xix. S. 143.

7 Hammarsten, ibid., Bd. xxii. S. 392.

8 Sehafer, Proc. Physiol. Soc., Journ. Physiol., Cambridge and London, 1895, vol.
xvii. p. xx.

168 THE BLOOD.

THEORIES OF COAGULATION.

That the coagulation of the blood is due to the formation of an
insoluble substance (fibrin) in the plasma, was proved by Hewson,1 who
showed that a coagulable plasma can be obtained by skimming, after
allowing the corpuscles to subside, in blood the coagulation of which
is delayed in any way, as by cold, by neutral salts, or by its retention
within a living vein. The old theories which ascribed the coagulation to
the cooling of the blood, to its coming to rest, to the running together
of the corpuscles into rouleaux, were all effectually disproved by the
same careful observer. Hewson also showed that ribrinogen (" coagul-
able lymph ") is precipitable and removable from plasma by a tempera-
ture of a little over 50° C.2 Many*of Hewson's observations upon
coagulation were forgotten, and the facts rediscovered by subsequent
observers, but their accuracy was such that until comparatively modern
times no addition of any permanent value to the knowledge of the
subject was made. The most important of such additions (which was
also overlooked for many years)3 was the observation of Andrew
Buchanan, that a substance could be extracted by water and solutions of
salt from lymphatic glands, from blood clot (especially the buffy coat),
and from various tissues, which had the property of producing the
coagulation of serous fluids, not themselves spontaneously coagulable,
such as hydrocele and pericardial fluid ; such action being comparable
to that of a ferment. But it is only quite recently that the active sub-
stance extracted by Buchanan has been examined, and found to belong
to the class of bodies known as nucleo-proteids.

Schmidt's theory. — A theory of coagulation, which was long accepted,
was that of Alexander Schmidt. Schmidt noticed that fluids which
contained fibrinogen but were not spontaneously coagulable, such
as pericardial or hydrocele fluid, coagulated on the addition of serum.
He ascribed the fibrin formation which resulted to the action (fibrino-
plastic action) of the globulin in the serum upon the fibrinogen of the
pericardial fluid. Since, however, the same globulin is already present
in abundance in pericardial and hydrocele fluid, it became clear that
this explanation of the action of serum was insufficient. It was, how-
ever, shown by Schmidt that a substance is extracted by water from the
alcohol precipitate of blood or serum, which possesses the property of
causing coagulation in these fibrinogenous liquids, or of causing coagula-
tion in plasma, the coagulation of which has been prevented by the
addition of neutral salts. To this substance the name of fibrin ferment
was applied, on account of its action resembling in general that of the
unorganised ferments or enzymes. Thus it was found to have its
activity accelerated by warmth, and destroyed by a high tempera-
ture (65° C.), and also to be capable of producing the coagulation of a
relatively large amount of fibrinogen. It was still held by Schmidt that
the globulin of serum takes an important share in the formation of fibrin.

Hammarsten's earlier researches. — Hamniarsten showed that serum

1 Op. dt.

2 For the history of this see Schiifer, Journ. PhysioL, Cambridge and London, 1880,
vol. iii. p. 185.

3 Cf. Gamgee, "PhysioL Chemistry," 1880, vol. i., where will also be found an excellent
account of the earlier history of the subject of blood coagulation. See also Arthus, " Coag.
des liquides organiques," Paris, 1894, for a good epitome of the history of the subject up
to that date.

THEORIES OF COAGULATION. 169

globulin does not take part in forming fibrin. By precipitating fibiin-
ogen by half-saturating plasma with sodium chloride, he obtained it
free from serum globulin, and found that its solution in dilute salt
solution was coagulated by the addition of Schmidt's extract — the so-
called fibrin ferment — alone. Hammarsten proved that coagulation
consists in a conversion of fibrinogen into fibrin ; the change being
accompanied by a splitting of the fibrinogen, and not by a combination
of it with the serum globulin, as was supposed by Schmidt.

Influence of lime salts. — Theories of Freund and of Arthus and Pages.
—The more recent researches since these of Hammarsten have been
in the direction of elucidating the true nature of the substances
contained in Schmidt's extract. Green l found the extract to contain
sulphate of lime, and that if lime were removed from plasma by
dialysis its coagulability became lost, but was restored by the addition
of sulphate of lime. Einger and Sainsbury 2 showed that other salts of
lime, such as calcium chloride, might replace the sulphate, and that the
calcium might be replaced by barium and by strontium, although the
salts of these metals are not so efficacious as the corresponding salts
of calcium.

Freund 3 also drew special attention to the important part played by
lime salts in promoting the formation of fibrin. He supposed the
original cause of the deposition of fibrin in fibrinogenous liquids to be
the formation of insoluble tribasic phosphate of lime, by the interaction
of soluble phosphates (which he supposed to be shed out from the
corpuscles whenever they come in contact with and adhere to foreign
surfaces) with soluble lime salts contained in the plasma; the lime
phosphate combining at the moment of formation with fibrinogen, and
forming fibrin, and no other agency in the shape of a special ferment
being necessary. This inference has not, however, been confirmed by
subsequent observers. Freund supposed neutral salts, peptone, etc., to
act in preventing coagulation, by keeping phosphate of lime in solution,
and the walls of the blood vessels to act in preventing coagulation
because the corpuscles do not adhere to them. Freund based his theory,
partly upon the fact that if blood is drawn from an artery through a
tube smeared with oil or vaseline into a vessel similarly prepared, the
blood remains fluid for a long time, presumably because the adhesion of
the corpuscles to the walls does not occur. Similar experiments with
blood kept surrounded by paraffin or oil were performed by Hay craft
with like result.4

Arthus and Pages 5 mixed blood as it flowed from the vessels with a
small quantity of a soluble oxalate6 (O'07-O'l parts per 100 of blood)
sufficient to precipitate the lime salts dissolved in the plasma. They
found that blood thus treated did not coagulate, however long it might
be kept,7 but that coagulability of its plasma is immediately restored on
again adding a soluble lime salt, such as calcium chloride. They

1 Journ. Physiol., Cambridge and London, 1887, vol. viii. p. 354.

2 Ibid., 1890, vol. xi. p. 369. 3 Mcd. Jahrb., Wein, 1888, S. 259.

4 Journ. Anat. and Physiol., London, 1888, p. 172 ; Haycraft and Carlier, ibid., p. 582.

5 Arch, dephysiol. norm, et path., Paris, 1890, p. 739 ; Arthus, These de Paris, 1892.

6 Solutions of soap (0'5 parts per 100 of blood) or of soluble fluorides (0'2 parts per ]00
of blood) act similarly to those of oxalate.

7 Hammarsten makes a similar statement for horse's blood, but it is certainly not
correct for all kinds of blood. Oxalate plasma, obtained from dog's or sheep's blood, does
undergo coagulation on standing ; coagulability is therefore not abolished by precipita-
tion of the lime by oxalate, but merely deferred. We shall return to this point immediately.

170 THE BLOOD

inferred that the presence of a soluble salt of lime is necessary to the
formation of fibrin, which, according to them, is produced by a combina-
tion, under the influence of fibrin ferment, of a part of the fibrinogen
with lime, the remainder of the fibrinogen — which is assumed to split
into two parts — forming a globulin coagulating at 64° C. (Hammarsten's
fibrino-globulin).1

Whilst it would appear from these researches that soluble lime salts are
necessary to the formation of fibrin,2 it has been shown by Home that the
presence of a slight excess of these salts and also those of barium and strontium
will hinder or, in great amount, entirely prevent its formation ; their action
being far more marked in this respect than that of other neutral salts, which
require to be mixed in much greater amount with blood to prevent its co-
agulation.3 The reason for this is probably to be found in the fact that fibrin
is soluble to some extent in neutral salts of a certain strength (including salts
of calcium, barium, and strontium).

Influence of nucleo-proteid. — Theory of Pekelharing. — Halliburton4 and
Pekelharing 5 both obtained from Schmidt's extract a body giving proteid
reactions, and resembling in many particulars the globulins, to which
class of proteids they at first regarded it as belonging.6 They showed
that the ferment action of Schmidt's extract is intimately dependent
upon the presence of this substance, which could also, as Halliburton
showed, be obtained from lymphatic glands. Halliburton termed it
cell globulin ; subsequently both observers recognised the fact that the
substance in question was not a true globulin but a nucleo-proteid.7
According to Pekelharing, it possesses the property of combining with
lime, which it does not yield to distilled water by dialysis, nor is the
combination broken up by soluble oxalates, although these, if present
from the first, may prevent the original combination. The albumose in
commercial peptone also prevents such combination, the albumose itself
combining with the lime salts present ; 8 if these are in excess, " peptone "
does not prevent coagulation from taking place. The lime combination
of nucleo-proteid is, according to Pekelharing, the body which has been
known as fibrin ferment (thrombin). It can be formed not only from
the nucleo-proteids contained in plasma or serum, but also from nucleo-
proteids in the cells of the thymus, testicle, and other glands, by

1 Artlms and Pages found that strontium can replace lime in this reaction, but that
barium and magnesium cannot. Ringer and Sainsbury have, however, shown that barium
may take the place of lime in promoting coagulation, although it is less powerful (Journ.
PhysioL, Cambridge and London, 1890, vol. xi. p. 369). They also found that the salts of
sodium and potassium act antagonistically to those of lime, barium, and strontium.

2 A. Schmidt, even in his last communication upon the subject ("Weitere Beitr. z.
Blutlehre," Wiesbaden, 1895), denied altogether that lime salts have any specific action
or differed from other neutral salts, and considered that the addition of a soluble oxalate to
blood acts either by preventing the formation of fibrin ferment or by hindering the action
of ferment, if present, on fibrinogen. Cf., however, Arthus, Arch, de physiol. norm, ct
path., Paris, 1896, and Hammarsten, loc. cit.

3 Journ. PhysioL, Cambridge and London, 1896, vol. xix. p. 356. Wright also noticed
the fact that considerable excess of calcium added to oxalate blood prevents coagulation,
Journ. Path, and Bacterial., Edin. and London, 1893, vol. i. p. 434.

4 Proc. Roy. Soc. London, 1888, vol. xliv. p. 255.

5 Festschr. Rudolf Virchow, Berlin, 1891, S. 435.

c Lilienfeld has recently repeated this error, Ztschr. f. physiol. Chem., Strassburg,
Bd. xx.

7 Pekelharing, "Untersuch. ii. d. Fibrin- ferment," Amsterdam, 1892; Halliburton,
Journ. Phijsiol., Cambridge and London, 1895, vol. xviii. p. 312.

8 Pekelharing. Cf., however, C. J. Martin, "Venom of Australian Black Snake,"
pp. 36-40, Journ. and Proc. Roy. Soc. New South Wales, Sydney, July 3, 1895.

THEORIES OF CO A G ULA TION. 1 7 1

digesting these with calcium chloride, the excess of calcium salt being
afterwards dialysed off. Pekelharing supposes that the ferment action
consists in the transference of lime from its nucleo-proteid combination
to fibrinogen, the lime-compound of this being the insoluble fibrin,1 and
that if there is more lime salt in the solution the nucleo-proteid can
recombine with lime, and thus become reconstituted as an agent for the
conversion of fibrinogen into fibrin. As already pointed out (p. 166),
however, it is not possible to accept this theory in view of the analyses
of fibrin and fibrinogen given by Hammarsten. Pekelharing has himself
shown that even in the entire absence of free lime salts, or in the
presence of soluble oxalates, the transformation of fibrinogen into fibrin
may be produced, provided that the ferment is present.2 This has also
been shown to be the case by A. Schmidt 3 and by myself,4 and more
recently in a series of carefully conducted experiments by Hammarsten.
Hammarsten precipitated fibrinogen by oxalated solution of salt, and,
after purifying it by repeated re-solution and re-precipitation, added to
its solution a fibrin ferment obtained from oxalated serum, and obtained
as the result a typical fibrin.5

Exception has been taken to the inference drawn by Pekelharing that
Schmidt's ferment is a compound of nucleo-proteid and lime, on the ground
that the ferment contained in Schmidt's extract differs from nucleo-proteids
in the effect of alcohol upon its solubility in water, and in the fact that
nucleo-proteids cause coagulation in intravascular plasma, which Schmidt's
extract does not, whereas the latter causes coagulation in extravascular (salted)
plasma, and nucleo-proteids do not.6 The ^ differences may, however, depend,
in part at least, upon the relative amounts of nucleo-proteid and lime. Thus
in Schmidt's extract the amount of nucleo-proteid is small and the amount of
lime large ; in extracts of thymus and the like the amount of nucleo-proteid
is large and the amount of lime small. In part also they depend upon other
circumstances, such as the influence of the magnesium sulphate of the salted
plasma in antagonising the effect of lime.7

The origin of the nucleo-proteid of plasma and serum is probably the white
corpuscles. It would appear that many of the latter disintegrate after removal
of blood from the body. Giirber 8 found that in coagulated blood the number
of white corpuscles was reduced to one-half, the difference being chiefly in the
number of polynuclear cells. This disappearance has not, however, been
found by all observers, and is not fully admitted. Nevertheless, without
actually disintegrating, the white corpuscles may shed out or secrete nucleo-
proteid into the plasma. This may occur normally in mere traces, but on with-

1 Centralbl.f. Physiol., Leipzig u. Wien, 1895, No. 3.

2 It would appear that a soluble oxalate does not throw down all the lime from a proteid-
containing fluid, and that a trace of lime is still held in solution so that an oxalate plasma
is not lime-free, as was supposed by Artlras and Pages. This is well illustrated by an
observation by Ringer upon the frog's heart, who finds that a normal saline solution,
to which a little CaCl2 has been added, will exhibit the physiological effect of lime,
even after the addition to the fluid of a slight excess of a soluble oxalate. It may be
inferred from this that a trace of lime may be held in solution even in a fluid destitute of
proteid.

3 " Weitere Beitr. z. Blutlehre," Wiesbaden, 1895.

4 Proc. Physiol. Soc., Journ. Physiol., Cambridge and London, 1895, vol. xvii.
p. xviii.

5 Ztschr. f. physiol. Chem., Strassburg, Bd. xxii.

6 Hnlliburton and Brodie, Journ. Physiol.. Cambridge and London, 1894, vol. xvii. p. 143.

7 Pekelharing, Centralll f. Physiol.', Leipzig u. Wien, 1895, Bd. ix. S. 102. Halliburton
in a recent paper (Journ. Physiol., Cambridge and London, 1895, vol. xviii.) comes to a
similar conclusion, namely, that Schmidt's fibrin ferment is a weak solution of nucleo-
proteid. It produces Wooldridge's negative phase when intravenously injected.

8 Sitzungsb. d. phys.-med. Gesellsch. zu Wilrzburg, 1892, No. 6.

172 THE BLOOD.

drawal from the body in larger amount. It is noteworthy in this connection
that certain forms of lymph, such as the aqueous humour, which contain no
cells, contain also no nucleo-proteid, and are only coagulable on the addition of
nucleo-proteid.

Theory of Lilienfeld. — Lilienfeld,1 like Arthus and Pekelharing, con-
siders that fibrin is formed by a combination of fibrinogen with lime, any
soluble lime salt being equally effectual to produce the combination.
Lilienfeld differs, however, from them in denying the necessity for the
intervention of a ferment in the ordinary sense of the word. He considers
that what the nucleo-proteid effects is not the combination of nbrinogen
with lime, but a transformation or splitting of the nbrinogen into a sub-
stance which he terms " thrombosin," Slid a globulin ; the throuibosin then
combines with lime, if any be present, to form fibrin. The nucleo-proteid
only acts, according to Lilienfeld, by reason of the acid qualities of the
nucleic acid it contains. Any other weak acid, e.g. acetic, will answer
equally well. Thus, if a solution of nbrinogen in NaCl (prepared
according to Hammarsten's method) is precipitated by acetic acid, the
precipitate (thrombosin), if dissolved in weak sodium carbonate, instantly
forms a coagulum (fibrin), on the addition of calcium chloride. The
formation of the thrombosin by the action of an acid upon fibrinogen
is, according to Lilienfeld, a precursor to the production of fibrin, and
is analogous to the change in caseinogen by the action of rennin, which
will occur in the absence of lime salts, although the latter are necessary
for the formation of the casein clot (see p. 135).

I have elsewhere shown '2 that this theory is untenable ; for a solution
of fibrinogen in dilute salt solution, prepared by Hammarsten's method,
will, if sufficiently strong, coagulate, on the addition of calcium chloride,
equally well with a solution of the acetic acid precipitate — the so-called
thrombosin — although somewhat less rapidly.3 The difference in rapidity
depends, no doubt, upon the fact that sodium chloride in a certain
amount retards the formation of the clot, or even may prevent it
altogether. This, as Hammarsten has pointed out, is the reason why
Lilienfeld obtained no coagulum on the addition of calcium chloride
to his fibrinogen solution, although he got a coagulum with his
so-called thrombosin solution, for the former was dissolved by aid
of sodium chloride, and the latter by dilute alkali. As already
stated,4 Hammarsten holds that in neither case is the coagulum pro-
duced a true fibrin, but in both cases it is a fibrin-like combination
of fibrinogen with lime. The influence of nucleo-proteid is, however,
not eliminated,5 for, as has been already insisted on, fibrinogen pre-
pared by Hammarsten's method always contains some nucleo-proteid.
This is clear both from my own experiments and from the analyses
of Lilienfeld, who indeed — but as it would appear without sufficient
cause — supposes fibrinogen itself to be a nucleo-proteid. The amount
of nuclein or phosphorus which can be obtained from it certainly does
not warrant the assumption ; nevertheless there is always a distinct

1 Ztschr. f. physiol. Chem., Strasslmrg, 1895, Bd. xx.

2 Proc. Physiol. Soc., Journ. Physiol. , Cambridge and London, 1895, vol. xvii.
p. xviii.

3 Cf. Cramer, Ztschr. f. physiol. Chem., Strassburg, 1897, Bd. xxiii. S. 74, who has
fully confirmed the conclusion that the so-called " thrombosin " is merely fibrinogen.

4 See note 5, p. 165.

5 Cf. Wistinghausen, Diss., Dorpat, 1894.

THEORIES OF COAGULATION. 173

residue after gastric digestion of its solution, showing that it at least,
as above stated, contains some nucleo-proteid. Probably this is an
accidental contamination.

Production of intravascular coagulation of Hood and of uncoagulable
blood. — It was discovered by Edelberg1 that intravenous injection of
Schmidt's fibrin ferment may produce thrombosis in the vense cavae,
the right side of the heart, and the pulmonary arteries. Foa and
Pellacani2 showed that the same will occur with extracts of various
organs. The same fact was independently noticed by Wooldridge,3
who found that a substance or substances obtainable from saline extract
of lymphatic glands, thymus, testicle, and other glandular organs, tend to
produce, when injected rapidly in sufficient amount into the veins of
animals, instant coagulation of the blood whilst still within the blood
vessels. On the other hand, if injected more slowly, or in insufficient
amount to produce intravascular coagulation, the coagulability of the
blood in vitro becomes abolished ; this condition was termed by Wool-
dridge the " negative phase." When the negative phase is once obtained,
a very large dose of the material fails to produce intravascular clotting.4
Wooldridge gave the name " tissue fibrinogens " to the substances thus
extracted, and more extended knowledge has led to the general recog-
nition of the fact that they belong to the class of nucleo-albumins or
nucleo-proteids. The coagulation when it occurs is found, first, in the
portal venous system ; then in the general venous system, and pulmonary
arteries and in the right side of the heart ; and finally, when the effect
is most pronounced, in the general arterial system ; but rarely in the
pulmonary veins. Its occurrence is assisted by an excess of C02 in the
blood.5 Albino rabbits and the Norway hare in its albino condition are
immune to these effects (Pickering).

It has been supposed by Lilienfeld ° that this action of the nucleo-
proteid in causing coagulation is due to the nuclein or nucleic acid
which it contains, and that, when the negative phase is obtained, this
result is due to the action of the proteid part of the molecule of
nucleo-proteid in preventing coagulation. This hypothesis is rendered
improbable by the observations of Halliburton and Pickering,7 who
found that intravascular coagulation can be readily obtained in rabbits
by intravenous injection of artificial colloids (containing no nucleic
acid).8 These colloids likewise yield the negative phase (retardation of
coagulation), if injected in quantity insufficient to produce coagulation ;
and, as with solution of nucleo-proteids, they are without action upon
albino rabbits. Nevertheless, like solutions of nucleo-proteid, they
hasten the coagulation of the blood of other animals, if mixed with it
in vitro. These observers also found that the retarding influence of

1 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1880, Bd. xii. S. 283.

2 Riv. din. di. Bologna, 1880, p. 241.

3 Proc. Roy. Soc. London, 1886. See also ''Die Gerinnung des Blutes," Leipzig, 1891.

4 Wooldridge, Arch. f. PhysioL, Leipzig, 1888.

5 Wright, Journ. PhysioL, Cambridge and London, vol. xii. 6 Loc cit.

7 Journ. PhysioL, Cambridge and London, 1895, vol. xviii. pp. 54 and 285 ; Pickering,
Proc. Roy. Soc. London, 1896, vol. Ix. p. 337.

8 The artificial colloids investigated were prepared by Grimaux's methods (Compt. rend.
Soc. de bioL, Paris, 1881, tome xciii. p. 771 ; 1884, xcviii. pp. 105, 1434, and 1578).
Their chemical properties and mode of preparation have already been described by Professor
Halliburton in a previous article (p. 36). It is possible that they may act, not directly,
but by setting free nucleo-proteid from the white corpuscles. Their solutions do not,
however, cause disintegration either of the red or white corpuscles, nor any apparent
change in the epithelium of the vessels.

174 THE BLOOD.

intravascular injections of soap, peptone, and potassium oxalate on the
coagulation of blood is antagonised by previous intravascular injection of
the colloid. The action of the colloids in promoting coagulation is
assisted, like that of nucleo-proteid, by accumulation of C02 in the
blood. The same effects are produced by snake venom,1 which contains
no nucleo-proteid, and the active principles of which consist of albumoses.
This produces, although in far more minute doses, effects which are in
every way comparable with those produced by Wboldridge's " tissue
fibrinogen." In doses of O00001 to O00002 grm. per kilog. body weight,
the venom of the Australian black snake (Pseudechis porphyriaca) causes
the blood, after a brief interval of increased coagulability (positive
phase), to lose its tendency to clot (negative phase), and much larger
doses of the poison will now not restore its coagulability. On the other
hand, moderate and large doses (more than O'OOOl grm. per kilog.)
produce instantaneous clotting within the vessels. But any blood
which has not undergone the intravascular coagulation is found to be
incoagulable in vitro, and in this point also there is an exact resemblance
to the phenomena produced by nucleo-proteids and by artificial colloids.

Solutions of certain other chemical substances, such as ether, tannic
acid, arsenic,2 glycerin, toluylenediamin,3 are also found when injected
into the circulation to produce thrombosis. But, to produce the effect,
these all require doses large enough to cause disintegration of the
blood corpuscles, thereby setting free the nucleo-proteids which the
corpuscles contain, so that their action is probably a secondary one. It
is possible that snake venom may also operate in this way,4 since it does
produce to a certain extent such disintegration, but the rapidity of the
production of the intravascular clotting, and the small amount of such
disintegration which normally occurs, render such an explanation
improbable.

Peptone plasma. — Researches of Wooldridge. — Other substances, such
as commercial peptone, the action of which is due to the albumoses which
it contains, and leech extract, produce a diminution or loss of coagulability
when injected into the blood vessels, without, in any dose, tending to cause
intravascular coagulation. The incoagulable blood or plasma obtained
by their employment resembles very closely that obtained in the negative
phase, produced by Wooldridge's tissue fibrinogen, by colloids and by
snake venom. Peptone plasma can be made to coagulate by

1. Addition of lymph cells.

2. Addition of nucleo-proteids.

3. Addition of calcium chloride.

4. Dilution with water, or 0'5 per cent, salt solution.

5. A stream of C02.

6. Neutralisation with acetic acid.

But if an excess of the reagents employed to prevent coagulation
(or to produce the negative phase), whether peptones or slowly

1 C. J. Martin, Journ. PhysioL, Cambridge and London, 1893, vol. xv. p. 380 ; and
Journ. and Proc. Hoy. Soc. New South Wales, Sydney, July 3, 1895. These papers contain
full references to the previous literature of the subject.

2 The administration of arsenic and phosphorus by the mouth diminishes the coagulability
of the blood (of. Gley and Pachon, Arch, de physioL norm, et path., Paris, 1896, p. 716).

3 Silbermann, Virchow's Archiv, 1889, Bd. cxvii. S. 288.

4 C. J. Martin, op. cit., Journ. and Proc. Roy. Soc. New South Wales, Sydney, pp. 45-47
of reprint.

THEORIES OF CO A G ULA TION. 1 7 5

administered nucleo-proteids or snake venom be employed, then these
additions do not produce coagulation.1 In view of the fact that
calcium chloride will not, under these circumstances, produce coagula-
tion, the hypothesis of Freund and Pekelharing, that " peptones "
deprive blood of its coagulability by combining with its calcium salts,
loses probability.

Peptone injected intravenously rapidly disappears from the blood.2 The
action of peptone differs from that of leech extract, in that a second dose,
given soon after the action of the first dose has passed off, fails to produce an
effect on coagulability. Moreover, the blood of a " peptonised " dog confers
immunity from the action of peptone, if injected intravenously into a second
animal.3

The properties of peptone plasma, and the effects of leucocytes and
their saline extracts upon the coagulability of blood, were carefully
studied by Wooldridge. This observer found, as already stated, that if
peptone plasma be kept for a time at 0° a precipitate forms, which takes
the form, under the microscope, of minute discoid particles, almost exactly
similar to blood platelets. The substance thus precipitated was termed
" A-fibrinogen " by Wooldridge, while he named the substance precipit-
able by half -saturation with NaCl " B-fibrinogen " ; this is the same
thing as fibrinogen as ordinarily understood. After the removal of the
A-fibrinogen, the coagulability of peptone plasma by C02 and other
conditions is greatly diminished or altogether lost, but is restored on
dissolving the A-fibrinogen again with the aid of warmth.

Wooldridge's A-fibrinogen is also obtainable, as Wright has shown, by
cooling oxalate plasma, and it is probably composed mainly, if not entirely,
of nucleo-proteid. It has been shown by Hammarsten that if by prolonged
cooling and filtration it is removed as much as possible from oxalated plasma,
the plasma will not coagulate on the addition of sufficient lime salts to more
than balance the excess of oxalic acid, but that, if the precipitate be collected
and treated with lime salts, it furnishes, on subsequently removing the
lime by oxalate, a powerful thrombin or fibrin ferment. Hammarsten
accordingly terms the substance in question, which is precipitated by cold
from plasma, prothrombin, and considers that it can only be converted into
thrombin by the action upon it of lime salts. Pekelharing regards the
precipitate in question as composed of nucleo-proteid, and considers that the
lime acts by combining with it to form fibrin ferment.

The addition of lymph cells (washed with 0'6 per cent. NaCl solution)
to peptone plasma causes its coagulation outside the body, and also acceler-
ates the coagulation of ordinary blood in vitro, whereas the intravenous
injection of salt solution holding these washed lymph cells in suspension
produces an incoagulable condition (negative phase) of blood, which
does not then coagulate, even on withdrawal. But on addition of some
of this fluid, holding cells in suspension, to such blood after withdrawal,
coagulation is rapidly produced. The loss of coagulability of peptone
plasma is not due, as was supposed by A. Schmidt, to the disappearance
and disintegration of leucocytes, for, as Wooldridge showed, the addition

1 C. J. Martin, op. cit., pp. 35-40. According to Dastre and Floresco, the chief cause of
the lack of coagulation in peptone plasma is its high alkalinity (Arch, de jihysiol. norm, et
path., Paris, 1897, p. 216).

2 Schmidt-Mulheim, loc. cit.

3 Contejean, Arch, dephysiol. norm, etpath., Paris, 1895.

176 THE BLOOD.

of leucocytes to the circulating blood does not increase its coagulability,
but the contrary; and, moreover, peptone plasma contains many
leucocytes.1 These several facts were explained by Wooldridge by
the supposition that coagulation is produced or prevented in the
absence of leucocytes by the action of one substance in the plasma upon
another, or in the presence of leucocytes by the action of a substance
within the plasma upon these cells, or material yielded by them ; the
kind of interaction being different under different circumstances, and
producing, respectively, the phase of incoagulability or coagulation
(negative or positive phase) according to such circumstances. All such
substances, which by their interaction tended to produce fibrin, were
termed by Wooldridge " fibrinogens " ; but the progress of research has
since rendered it probable that WooMridge's " A-fibrinogen " obtained
from plasma, his " serum fibrinogen " obtained from dog's serum, and
the " tissue fibrinogens," which he obtained from various organs, all
owe their action to the nucleo-proteid which they contain. Translating,
then, the phraseology employed by Wooldridge, the alterations in
blood plasma, which come under the various conditions above noticed, are
due to the interaction of nucleo-proteids and fibrinogen. And it would
appear that, when in the interaction the nucleo-proteids are present in
relatively small amount, the negative phase is the result; when in
large amount, the positive phase. Also that, when added to the
circulating blood, leucocytes yield but little of their nucleo-proteid to
plasma, and hence a negative phase is the result : but, 011 the other
hand, when added to plasma in vitro, a larger amount is yielded, and
coagulation results. A remarkable observation, and one very difficult to
explain, is the fact that, if the negative phase is once established by the
intravascular injection of a small amount of nucleo-proteid, artificial
colloid, or snake venom, a large excess of the same will then not only
fail to produce the positive phase, but will even strengthen the negative
phase. It is, therefore, only the initial change which is influenced by
the relative amounts of interacting material ; and, when once this change
is established, it does not again become modified.

Wright's experiments. — Wooldridge further found that under some cir-
cumstances the amount of fibrin produced was dependent upon the amount
of tissue fibrinogen or A-fibrinogen (nucleo-proteid) added to plasma. He
therefore came to the conclusion, since the extent of action was not in all
cases independent of the amount of these substances, that the action could
not be looked upon as that of a ferment, although under some cir-
cumstances the extent of action did appear to be independent of the
amount of these substances. Wooldridge offered no explanation of the
different effects obtained with large and small doses respectively, his
work upon the subject having been cut short by his untimely death.
It has, however, been continued on the same lines by Wright,2 who,
whilst confirming most of Wooldridge's observations, has added
materially to our knowledge of the conditions under which " tissue
fibrinogen " or nucleo-proteids produce the negative and positive phase
of coagulability. Wright states that the extracts of glands containing

1 Wright found, however, that the number of leucocytes in peptone blood was extremely
reduced, much move so than is the case in oxalate or magnesium-sulphate blood, and that
it contains a correspondingly larger amount of nucleo-albumins, Proc. Roy. Soc. London,
10th Feb. 1893.

2 Proc. Roy. Irish Acad., Dublin, 1891, 3rd series, vol. ii. p. 117.

THEORIES OF COAGULATION. 177

these substances readily yield, under the influence of certain reagents
and conditions, a body or bodies giving albumose reactions ; and he finds
that such a body is also present in the blood after their injection, and
rapidly appears in the urine.1 Wright considers it probable, therefore,
that the contrary effects of large and rapid, or small and gradual,
administration of these extracts is due in the one case to the immediate
action of the nucleo-proteids in effecting the conversion of the fibrinogen
into fibrin before there has been time for the formation of albumose ;
and in the other case, where there has been time for such formation, to
the action of the albumose thus formed in preventing coagulation (as
in the case of directly injecting albumose into the blood vessels). If
any albumose is formed, the action of this would, by delaying coagula-
tion, give time for the formation of more, when a second dose of
nucleo-proteids is injected. Hence, a dose of nucleo-proteid, which would,
if administered rapidly, produce instantaneous coagulation throughout
the vascular system, may, if administered gradually, tend altogether to
prevent coagulation. But, as Halliburton points out, the explanation of
the action of "peptone" in producing a negative form of coagulation
may be that it liberates small quantities of nucleo-proteid, rather than
that it removes calcium ; and if this is so, the explanation offered by
Wright (and Pekelharing) of the action of nucleo-proteids falls to the
ground. Moreover, it cannot be accepted as proven that a " peptone "
moiety is split oft' from nucleo-proteid. " Peptone " (i.e. " albumose")-
blood is characterised by extreme diminution of the amount of C02
which it contains,2 and by diminished alkalinity,3 and the reason for
the uncoagulability of such blood is apparently connected with its
deficiency in C02 tension,4 since it coagulates on passing a stream of
C02 throughout it. For the occurrence of intra vascular coagulation,
after injection of nucleo-proteid and similarly acting substances, is
largely influenced by the amount of C02 in the blood, and it is due to
its richness in C02 that the blood coagulates under these circumstances,
first in the systematic veins, and of these most readily in the portal
venous system.5

From what has been before said as to the influence of lime, it will be
understood that the lime-salts of the plasma play an essential part in the
interaction between the nucleo-proteid and the fibrinogen. This parti-
cipation of lime in the reaction had not yet been recognised when
Wooldriclge's researches were made, but is freely admitted by Wright,
whose views upon the subject of the combined action of nucleo-proteid
and lime in producing coagulation seem to be in close agreement with
those of Pekelharing (see p. 171). It is, however, still by no means
clear why in " peptone " plasma, where all the necessary factors for the
formation of fibrin are present, coagulation, nevertheless, does not occur,

1 This lias been also shown independently by Pekelharing ("Untersuch. u. d. Fibrin-
ferment," Amsterdam, 1892), who offers a similar explanation of the phenomenon of
negative and positive coagulation. Halliburton and Pickering, on the other hand, con-
sider that, in the case of colloids, the negative phase cannot be regarded as a subsidiary
phenomenon, due to disintegration of the material intravenously injected, but is rather a
result characteristic of the action of small doses, and is comparable to the inhibitory action
of small doses of certain drugs, which act contrary to the action of larger doses (such as the
physiological immunity produced by small doses of alexines).

2 Lahousse, Arch. f. PhysioL, Leipzig, 1889, S. 77.

3 Salvioli, Arch. ital. de Uol., Turin, 1892, vol. xvii. p. 155.

4 Wright, loc. cit., andJourn. Path. andBaderiol., Edin. and London, 1893, vol. i. p. 434.

5 Wright, Journ. PhysioL, Cambridge and London, 1891, vol. xii.

VOL. I. — 12

1 78 THE BLOOD.

although it speedily occurs on further addition of lime or on passing
C02. Wright l assumes that the nucleo-proteid acting as a weak acid
has ousted C00 from the bases of the plasma, and that the action of C02
is to set the nucleo-proteid free again. But this would not account for
the effect of addition of calcium chloride. It may, on the other hand, be
that the lime which is present in the plasma is unable to act upon the
nucleo-proteid also present, owing to the former having entered into some
combination from which it is set free by C02. It must be admitted
that the subject is still, in spite of much research, enveloped largely in
obscurity.

Influence of the liver and lungs upon blood coagulability. — It was shown by
Pawlow 2 that if blood be allowed to emulate through the heart and lungs
only, and be cut off from the rest of the body, it gradually loses its
coagulability, and the same observation was made independently by Jewell
Martin.3 Bohr4 obtained a similar result, on preventing the blood from
reaching the portal circulation by occluding the thoracic aorta. The blood
lost its coagulability in a quarter of an hour, nor was it restored for twenty-four
hours after readmission to the abdominal viscera. This was in the dog. In a
rabbit, ligature of the coeliac axis and mesenteric arteries produced a similar
but rather less pronounced effect. Delezemie has shown that artificial
perfusion of " peptone-blood " through the liver restores its coagulability, but
that other organs do not produce the same result.5

Gley and Pachon 6 find, in confirmation of Contejean,7 that every cause
which diminishes or suppresses the functional activity of the liver diminishes
or suspends the anti-coagulating action of " peptone." They thus explain the
experiments of Contejean, who noticed that after extirpation of the coeliac
ganglia the action of " peptone " is not obtained.8

H6don and Delezenne 9 also found that after the establishment of an Eck's
fistula (communication between portal vein and vena cava) in the dog, and the
subsequent removal of the liver, injection of " peptone," although it produces
a great fall of blood pressure, no longer removes the coagulability of the blood.
These experiments appear to show that the liver lias a special function in
connection with the maintenance of the coagulability of the blood, and that in
passing through the lungs an effect of an opposite character is produced, but
in what way exactly these organs exert their influence has not as yet been
ascertained.

Blood or plasma can be temporarily made uncoagulable in the living vessels
by removing the fibrin. Dastre found that, if a large quantity of blood be
drawn from an animal, and this be whipped and filtered and returned to the
blood vessels, and the process repeated two or three times, all the fibrin can
be temporarily removed ; and it is only gradually that the blood resumes its
coagulability, which is not completely restored until the lapse of some
hours.

Conclusions regarding the causes of coagulation. — At least three
factors appear necessary to effect the formation of fibrin, namely,

1 Journ. Path, and Bacterial., Edin. and London, 1893, vol. i. p. 434.

2 Arch. f. PhysioL, Leipzig, 1887, S. 458.

3 Quoted by Gad, VerhandL d. Berl. phys. Gesellsch., Arch. f. PhysioL, Leipzig, 1887,
S. 584.

4 CentralU.f. PhysioL, Leipzig u. Wien, 1888, S. 261.

5 Compt. rend. Acad. d. sc., Paris, 11 Mai, 1896, p. 1072.

6 Arch, dephysiol. norm, etpath., Paris, 1895, p. 711. 7 Ibid. p. 245.

8 Ibid., 1896, p. 159.

9 Compt. rend. Soc. de. MoL, Paris, 1896, p. 633.

THE CAUSE OF THE COAGULATION OF BLOOD. 179

fibrinogen, nucleo - proteid (prothrombin), and lime, and it would
appear probable from Pekelharing's researches that the two latter act
in combination, and in fact represent the body which was termed by
Schmidt the fibrin ferment (thrombin). The reason why in the healthy
living vessels the blood does not coagulate, is, in all probability, that the
nucleo-proteid and lime have not entered into the necessary combina-
tion or interaction which enables them to act as a ferment upon the
fibrinogen.1

Of the three factors above mentioned, it is certain that fibrinogen and
lime are both present in the plasma of circulating blood, and the problem
therefore resolves itself into the question whether nucleo-proteid is
present or not, or whether, if present, it is in a different condition from
that necessary to promote fibrin formation. We may consider the latter
question first, and in doing so it will be convenient to assume, as
the experiments of Pekelharing seem to have proved, that the fibrin
ferment of Schmidt is a product of the interaction of nucleo-proteid with
lime. This conclusion of Pekelharing's has, in fact, been confirmed by
the researches of Hammarsten, who has shown that the nucleo-proteid
(or prothrombin) which is obtainable from plasma is inactive as a ferment,
except in the presence of or after it has been exposed to the action of
soluble lime salts. It is not, however, equally clear that the fibrin
ferment is a compound of the prothrombin with lime, as Pekelharing
supposed it to be.

Is fibrin ferment present in the plasma of circulating blood ? As is
well known, Schmidt's fibrin ferment is ordinarily obtained from clotted
blood or from serum, and the ferment-like substance used by A.
Buchanan was also obtained by him from blood clot, and especially
from buffy coat, i.e. the portion containing most white corpuscles.
Schmidt found that if blood were drawn from the vessels direct into
alcohol, no ferment could be obtained from it.2 He came, therefore, to
the conclusion that the blood does not coagulate in the living vessels
owing to the absence of fibrin ferment, and that this is only formed or
set free when the blood is drawn. Since fibrin ferment could be obtained
in greatest abundance from the layer of the clot where leucocytes are
most abundant, and from other tissues and organs rich in similar cells, it
appeared probable that it is derived in drawn blood from the white
corpuscles, and, as Schmidt believed, from their disintegration. Such
disintegration of leucocytes was in fact described by Schmidt in drawn
blood, but the observation has not been generally confirmed. It is not,
however, necessary to suppose disintegration of the corpuscles, for they
may shed out the ferment without actually undergoing disintegration.
Now, conditions which render the blood incoagulable, such as injections
of " peptones," of snake venom, and nucleo-proteids in small amount,
greatly diminish the number of leucocytes in the blood. This they do,
however, not by causing the solution and disintegration of the corpuscles,

1 Hammarsten, Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. We may dismiss
the hypothesis of Astley Cooper (Thackrah, " An Essay on the Cause of the Coagulation
of the Blood," Med.-CMr. Rev., London, 1807, p. 191), which was revived by Briicke,
(Srit. and For. Med.-Chir. Rev., London, 1857, and Virchow's Archiv, 1857, Bd. xii.), that
the living vascular walls exercise by their presence a restraining action upon coagulation,
as having been sufficiently disproved by Lister ("On the Coagulation of the Blood,"
Proc. Roy. Soc. London, 1863).

2 Subsequent researches conducted in his laboratory have shown that a very small
amount is obtainable even under these conditions.

i8o THE BLOOD.

as supposed by Lowit l and by Wright,2 but by causing their accumula-
tion within the tissues (? capillary blood vessels). For a very short
time after their almost complete disappearance from the blood they
begin gradually to reappear, and in one experiment C. J. Martin found
that the full number had reappeared within as short a time as fifteen
minutes.3 Moreover, if such disintegration, really took place one would
expect the coagulability of the blood to be visibly increased, from the
setting free of their nucleo-proteids, whereas it is actually diminished
or abolished. Nevertheless, those substances, such as snake venom,
nucleo-proteids, and colloids, which in larger doses produce intravas-
cular coagulation, may in part act by causing disintegration, if not of
leucocytes at least of red corpuscles which also contain nucleo-proteids.
That this occurs to some extent is shown by the fact that the serum is
usually tinged by haemoglobin. And even without actual disintegration
the permeability of the corpuscles may become altered, and nucleo-
proteid shed out.

But there is another tissue upon which the reagent in question may
act, namely, the epithelial cells of the blood vessels. These are in all
probability composed of living protoplasm, and the reagents may either
cause them to shed out nucleo-proteid and so produce fibrin ferment,
or, by deleteriously affecting them, may cause them to react upon the
leucocytes which are passing along in contact with their inner surface,
and effect a discharge of nucleo-proteid from these cells. That snake
venom affects the blood vessels deleteriously is shown by the capillary
haemorrhages which are so frequently seen after poisoning by it, and
by the rapid effect it produces on the blood circulating in the mesentery,
if a little be applied to the surface of that membrane.4 The same does
not, however, obtain with artificial colloids, nor with nucleo-proteids ;
although, with partial blocking of the portal vein, after injection of a
small dose, capillary haemorrhages have been found to occur in the liver.5

The evidence which we have had before us points to the following
conclusions regarding coagulation : —

1. That the coagulation of blood, i.e. the transformation of fibrinogen
into fibrin, requires for its consummation the interaction of a nucleo-
proteid (prothrombin) and soluble lime salts, and the consequent produc-
tion of a ferment (thrombin).

2. That either nucleo-proteid is not present in appreciable amount
in the plasma of circulating blood, or that the interaction in question is
prevented from occurring within the blood vessels by some means at
present not understood.

3. That the nucleo-proteid (prothrombin) appears and the interaction
occurs, as soon as the blood is drawn and is allowed to come into contact
with a foreign surface, the source of the nucleo-proteid being in all
probability mainly the leucocytes (and blood-platelets ?).

4. That, under certain circumstances and conditions, either the
nucleo-proteid does not appear in the plasma of drawn blood, or it
appears, but the interaction between it and the lime salts is prevented
or delayed.

1 "Stud. z. Physiol. u. Path. d. Blutea," Jena, 1892.

2 Proc. Roy. Soc. London, 1893. vol. Hi.

3 Loc. cit.

4 Weir Mitchell and Reichert, " Researches upon the Venoms of Poisonous Serpents,"
Smithson. Contrib. Knowl., Washington, vol. xxvi.

5 Wooldridge, Trans. Path. Soc. London, 1888, p. 421.

CONCLUSIONS REGARDING COAGULATION. 181

5. That the nucleo-proteid (prothrombin) appears in the plasma of
circulating blood under certain conditions, being in all probability shed
out from the white corpuscles and blood platelets, or in some cases even
from the red corpuscles ; and that when shed out under these conditions
from the corpuscles, or when artificially injected into the vessels, it
tends at once to interact with the lime salts of the plasma and to
form fibrin ferment (thrombin), intravascular coagulation being the
result.

6. That, under other conditions, either the shedding out of nucleo-
proteid from the corpuscles, or its interaction with the lime salts of the
plasma, may be altogether prevented and the blood rendered incoagulable,
unless nucleo-proteid be artificially added, or unless a modification of
the conditions is introduced which will permit of the interaction of
the nucleo-proteid with lime to form ferment.

7. That the nucleo-proteid (prothrombin) is incompetent, in the
entire absence of lime salts, to promote the transformation of
fibrinogen into fibrin; but, as a result of its interaction with lime
salts, it becomes transformed into a ferment (thrombin), which,
under suitable conditions of temperature and the like, produces
fibrin.

8. That either the place of nucleo-proteid in coagulation may
be taken by certain albumoses, such as those found in snake venom,
and by certain artificial colloidal substances, such as those prepared
by Grimaux, or that such substances may act by setting free nucleo-
proteid from the leucocytes and other elements in the blood, or
from the cells of the blood vessels, and thus indirectly promote
coagulation.

If the former supposition is the correct one, in all probability these three
substances (nucleo-proteid, snake venom, albumose, and colloid of Grimaux)
contain the same active molecular group.1

LYMPH, CHYLE, SEROUS FLUIDS, CEREBRO-SPINAL FLUID, SYNOVIA.

Lymph, which is obtainable from the lymphatic vessels of the limbs,
from the thoracic duct, and from the lacteals in the intervals of absorp-
tion of digestive products, or from the serous cavities — although only
occurring normally in sufficient amount for purposes of analysis and
experiment in the pericardial cavity — resembles generally in the char-
acter of its constituents, but not in their relative amount, the plasma of
the blood. Nor are the proportions of its constituents so constant as are
those of blood plasma, for there is reason to believe that the lymph from
different organs presents very considerable differences in their relative
amounts.

Lymph has generally been obtained for analysis from accidental
lymphatic fistulas in man, from experimental fistulae in large animals,
such as the horse, or from the thoracic duct of fasting animals (dog).
The amount flowing along the thoracic duct is about 64 c.c. per kilog.
body weight per diem.2

1 Halliburton and Pickering, op. cit.

2 R. Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1891, Bd. xlix. S. 216 ; Noel Paton,
Journ. PhysioL, Cambridge and London, 1890, vol. xl. p. 109.

1 8 2 L YMPH AND ALLIED FL UIDS.

The following analysis is given by J. Munk and Kosenstein from a
case of fistula of the thoracic duct in man : l —

In 100 parts lymph —

Total solids . . . 3 '7-5 "5

Proteids .... 3 -4-4-1
Substances soluble in ether . 0*04 6-0' 13
Sugar . . . .0-1

Salts .... 0-8-0-9

Nacl . . 0-55-0-58

Na2C03 • • 0-24

Hensen and Danhardt 2 found the following inorganic constituents : —

In 100 parts lymph —

NaCl . . . 0-614

. . . 0-057

K9O . . . 0-049

CaO . . . 0-013

MgO I rp

-n°r\ f • • Iraces

Fe203 /

C02 . . . 0-0815

p°A I . . - 0-033

r2U5 )

They obtained only O'l per cent, of fibrin (as compared with 0*4 per
cent, in blood plasma). This is perhaps the reason why the intravenous
injection of peptone in small amount or at a slow rate may, as noticed
by L. E. Shore,3 prevent the clotting of the lymph but not that of the
blood. The experiments of Spiro and Ellinger4 seem, however, to
indicate that, under the influence of peptone, an anti-coagulating
substance is formed in lymph, and from this passes into the blood.
The other proteids are also present in much less amount, but the relative
proportion of albumin to globulin is almost exactly maintained. As
already stated (p. 162), the present proteid quotient is fairly constant in
the same individual, both for blood serum, lymph serum, and serous
effusions.5 Lymph generally contains more urea than does the blood of
the same individual. Thus in a dog Wurtz found —

In the blood, 0-009 parts per cent, of urea.
In the lymph, O'OIG „

The amount of sugar in lymph is about the same as in blood plasma,
although, if dextrose be injected into the blood vessels, it soon appears in
greater proportion in the lymph than in the blood.6 Lymph contains
a distinct amount of glycogen, but this substance is wholly contained in
the corpuscles, and none exists in the plasma.7

The aqueous humour is a form of lymph, and contains the same pro-
teid substances as lymph, namely, fibrinogen, serum globulin, serum
albumin, and similar extractives and salts.8 It contains no corpuscles,

1 Arch. f. Physiol., Leipzig, 1890, S. 376 ; Virchow-s Archiv, 1891, Bd. cxxiii. S. 230
(contains a historical account of other cases).

2 Firchow's Archiv, 1866, Bd. xxxvii.

3 Journ. Physiol., Cambridge and London, 1890, vol. xl. p. 561.

4 Ztschr.f. phyyiol. Chem., Strassburg, 1897, Bd. xxiii. S. 121.

5 Salvioli, Arch. f. Physiol., Leipzig, 1881, S. 269; Hofmann, Arch. f. exper. Path.
u. Pharmakol., Leipzig, 1882, Bd. xvi. S. 135.

6 The reasons for this will be considered in the article on "Lymph Production."

7 Dastre, Compt. rend. Acad. d. sc., Paris, 1895, tome cxx.

8 Halliburton and Friend, Rep. Brit. Ass. Adv. Sc., London, 1889.

CHYLE — CEREBRO-SPINAL FLUID. 183

and does not clot spontaneously, but only on addition of fibrin ferment,
such as is contained in serum. Traces of urea are present but no sugar,
although a slight reduction of Fehling's solution is sometimes obtainable.
This is probably due to paralactic acid.1

The following analysis of aqueous humour is by Lohmeyer : 2 —

In 1000 parts —

Water .... 986 -87

Proteids . . . . 1*22

Extractives . . . . 4 '21

NaCl . . . . 6-89

Other salts . . . . 0'81

Pericardial fluid is a form of lymph which is found in small
quantity within the sac of the pericardium. Peritoneal and pleural
fluids, and the fluid of the tunica vaginalis, are not normally present in
sufficient quantity to be collected and analysed. Pericardial fluid
contains rather less proteid than ordinary lymph (2'28-2'55 per cent.).3

Pericardial fluid, as obtained from the horse or ox, is a yellowish
fluid, resembling serum in appearance and in its general composition,
but it contains fibrinogen.4 It usually has no leucocytes, nor is it
spontaneously coagulable, but it coagulates on the addition of ferment or
of nucleo -proteid.

Chyle has nearly the same composition as lymph, but it contains
more solid matter, the increase being chiefly in fats, but also in proteids.
The following table from Hoppe-Seyler gives its general composition in
the dog and a comparison with the serum of the same animal.

Chyle of Serum of

Dog. same Dog.

Water .... 90*67 93'60
Fibrin .... O'll

Albumin and globulin . . 2-10 4 -5 2

Fat, lecithin, cholesterin . 6'48 0'68

Other organic substances . 0'23 0'29

Salts .... 0-79 0-87

The ether extract of chyle was found by Hoppe-Seyler to contain,
per cent. : —

Cholesterin . . . 14 "09

Lecithin . . . . 8 '8 4

Fats ..... 77-07

There is also, according to Hoppe-Seyler, a small amount of soap in
chyle. The amount of urea and of sugar is about the same as in lymph.

The cerebro-spinal fluid, although resembling lymph in its appear-
ance, and probably in being formed by transudation from the blood
vessels, differs from lymph chemically in certain important details.
Although cerebro-spinal fluid is not obtainable normally in sufficient
amount for analysis, the fluid of a meningocele appears to be nothing
but an accumulation of the normal fluid, and has been frequently
analysed, and the fluid of hydrocephalus has also been used for this
purpose. Cerebro-spinal fluid as thus obtained is a clear, colourless

1 Kuhn, Arch.f. d. ges. PhysioL, Bonn, 1888, Bd. xi. S. 200 ; Griinhagen, ibid., S. 377.

2 Gorup-Besanez, "Lehrbuch," 1878, S. 401.

3 Hoppe-Seyler, " Physiol. Chem.," 3881, S. 605.

4 For analyses of pericardial fluid from the horse, and also for the analysis of various
dropsical fluids which tend to accumulate in the serous cavities of man, see Halliburton,
"Chem. PhysioL," pp. 338 and 339, and Brit. Med. Journ., London, 1S90.

184 LYMPH AND ALLIED FLUIDS.

liquid of specific gravity about 1007-8, and of a faintly alkaline reaction.
It contains only about 1 per cent, of solids, chiefly inorganic salts, of
which the greater part is sodium chloride, the other salts being potas-
sium chloride, phosphates of lime and magnesia, and traces of iron and
sulphates.1 There is, as a rule, not more than 1 part per 1000 of
proteids. These consist almost entirely of proteoses ; chiefly in the form
of protoalbumose, which is precipitable by saturation with sodium
chloride or magnesium sulphate. There is also a very small amount of
serum globulin, but no serum albumin or fibrinogen, nor is there any
nucleo-proteid or fibrin ferment. Karely peptone occurs.

In addition to proteids and traces of nitrogenous extractives, there is
present in cerebro -spinal fluid a non-nitrogenous substance peculiar to it,
which has the property of reducing copper salts when heated with them
in an alkaline solution. This was thought by Claude Bernard to be
sugar. The substance, however, is not sugar, being non-fermentable,
non-rotatory, and incapable of combining with phenylhydrazln to form
a crystalline compound. According to Halliburton, it is pyrocatechin,
and has the formula C6H4(OH)2, being probably one of the decomposi-
tion products of proteids ; it occurs in traces in the urine. In tapped
cases of hydrocephalus and meningocele the amount of this substance
increases after the first tapping.2

The presence of proteoses, and occasionally of peptones, in the cerebro-spinal
fluid, although these substances do not occur in blood or lymph, is of interest
in connection with the theory of Gaskell, which supposes the central nervous
system of vertebrates to have become developed in connection with a dorsal
alimentary canal, such as is found in arthropods.3 No digestive ferment
(pepsin, trypsin) has, however, been detected in cerebro-spinal fluid.

Synovia differs from lymph in containing a larger amount of solids
and also a mucin-like substance. Mucin, according to Landwehr,4 yields
a reducing sugar on boiling with mineral acids, but, according to Ham-
marsten,5 this mucin-like substance of synovia does not yield such
reducing sugar, and is of the nature of nucleo -albumin (containing 5 per
cent, of phosphorus).6 But the mucin-like material obtained by
Salkowski7 from synovia neither yielded phosphorus nor did it give
any reducing sugar.

Salkowski gives the following as the composition of the synovia
analysed by him :—

In 100 grms. — Water . . . .93*084

„ Mucin-like substance . . 0'375)rlQQ

Other proteids . . . 4*824 / °

Fat .... -282

„ Lecithin .... 0*017

„ Cholesterin . . . 0*569 8

„ Inorganic salts . . . 0*849 (Nacl 0'772)

1 Yvon, quoted by Halliburton.

2 For further details consult Halliburton, " Chem. Physiol.," p. 355 ; also "Report
of Spina Bifida Committee," Trans. Clin. Soc,. London, vol. xviii. ; and Journ. Physiol. ,
Cambridge and London, vol. x. p. 232, where the previous literature will be found.

s Address to the Section of Physiology, Rep. Brit. Ass. Adv. Sc., London, 1896.

4 Arch.f. d. ges. Physiol., Bonn, Bd. xxxix. S. 193.

5 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xii. S. 484.

6 For analysis of synovia by different observers, see Halliburton, "Chem. Physiol.,"
p. 351.

7 Virchow's Archiv, Bd. cxxxi. S. 304.

8 This is unquestionably abnormally high. The fluid was from a case of chronic coxitis.

HEMOGLOBIN : ITS COMPOUNDS AND THE
PRINCIPAL PRODUCTS OF ITS DECOMPOSITION.

By ARTHUR GAMGEE.

CONTENTS. — Distribution in the Animal Kingdom, p. 186 — Relations to other Con-
stituents of Red Corpuscles, p. 188— Arterin? and Phlebin? p, 190— Oxyhse-
moglobin, p. 193 — Methods of obtaining, p. 194 — Composition of, p. 197—
Crystalline form, p. 203 — Action of Reagents on, p. 207 — Spectrum, p. 208 —
Spectrophotometry, p. 213 — Photographic spectrum, p. 225 — Haemoglobin, p.
229 — Preparation of, p. 232 — Colour and Spectrum, p. 233 — Compounds with
Gases, p. 237 — Derivatives and Products of Decomposition, p. 243.

BY the term haemoglobin l is designated the highly complex, iron-con-
taining, crystalline colouring matter, which forms the most important
constituent of the coloured corpuscles of the blood,2 and in virtue of
which they perform their function as the oxygen-carriers of the
organism. This body possesses the remarkable property of linking
to itself a molecule of oxygen, so as to form an easily dissociated
compound, which is termed oxyhsemoglobin, to distinguish it specifically
from the colouring matter which has parted with its dissociable
oxygen ; for the latter some retain the name haemoglobin, though
it is commonly, and by English writers usually, distinguished by
the term reduced haemoglobin.

Both oxyhsemoglobin and reduced hemoglobin invariably (Hlifner)
exist side by side in varying proportions in the living blood; the
former being most abundant in arterial, the latter in venous, blood.
In the present chapter the term haemoglobin will be generally employed
when speaking of the blood-colouring matter, without specific reference
to its relation to oxygen ; the term reduced hemoglobin being invariably
employed when reference is made to the colouring matter, deprived of
its dissociable, or, as we may term it, in consideration of the part which
it plays in the organism, its respiratory oxygen.

Should we speak of "haemoglobin" or "the heemoglobins," of
" oxy haemoglobin '' or "the oxyhsemoglobins ? "— In a subsequent
section, it will be shown that the blood-colouring matter is by no
means absolutely identical in all animals, but that it exhibits con-
siderable variations in certain physical characters, and in chemical

1 Hoppe-Seyler, to whom we owe a great part of our knowledge of the blood-colouring
matter, first suggested this term. "Urn Verwechselungen zu vermeiden nenne ich das
Blutfarbstoff ' Hsemoglobulin oder Haemoglobin,' " Virchows Archiv. 1864, Bd. xxix. S.
223.

2 Haemoglobin constitutes about 40 '4 per cent, of the weight of the moist corpuscles,
and about 95 '5 per cent, of all the organic substances contained in them.

186 HAEMOGLOBIN.

composition, according to the species of animal from which it has
been derived. Based upon these facts, or perhaps in order to emphasise
them, it is now customary with German writers, following the example
of Hoppe-Seyler, to speak, not of " oxyhsemoglobin," but of " the
oxyhgemoglobins," of " the haemoglobins " and not of " haBmoglobin."
This appears to me to be an unnecessary and misleading attempt to
attain accuracy in scientific terminology, at the expense of true and
philosophical conceptions. As will be shown in the sequel, the
proportion in which iron, the characteristic element in the blood-
colouring matter, occurs, is absolutely the same in many animals, the
weight of the molecule being probably identical in these cases. There
is further abundant evidence in favour of the view that the typical
nucleus, upon which the optical and physiological properties of haemo-
globin depend, is absolutely identical in all animals. The grounds
for this assertion will be given in the sequel, when it will be shown
that the opinion advanced of recent years, as to the existence of
several haemoglobins, not only varying in composition, but possessed
of different powers of combining with oxygen, rests upon undoubted
fallacies.

DISTRIBUTION OF HEMOGLOBIN THROUGHOUT THE ANIMAL KINGDOM.

After the discovery by Hoppe-Seyler l of the characteristic spectrum of
haemoglobin had enabled him definitely to prove that this substance is the
true blood-colouring matter, Kiihne 2 showed that the same body is the cause
of the red colour of the voluntary muscles of vertebrates. Hunefeld3 and
Rollett * had shown that the blood of the earth-worm and of Chironmous
yielded crystals identical with the blood crystals obtained from other animals ;
and Kay Lankester 5 and Nawrocki 6 simultaneously established the fact that
these crystals consisted of haemoglobin, by examining their spectroscopic
characters.

In a series of researches, which extended from 1867 to 1872, Lankester
investigated the distribution of haemoglobin throughout the animal kingdom,
and comparatively few facts have since been added to those which he
published in 1872.7

The following are among the principal facts hitherto ascertained in rela-
tion to the distribution of haemoglobin.8

Haemoglobin occurs : —

1. In special corpuscles—

(a) In the blood of all vertebrates, excepting Leptoceplialus and Amphioxus.

1 Felix Hoppe in Tubingen, "Ueber das Arerhalten des Blutfarbstoffes im Spectrum
des Sonnenlichtes," Vircliows Archiv, 1862, 13d. xxiii. S. 446-449 ; "Ueber die chenii-
sclien 11. optischen Eigenschaften des BlutfarbstolFs, " Virchow's Archiv, 1864, Bd. xxix.
S. 233-245.

2 "Ueber den Farbstoff der Muskeln," Virchow's Archiv, 1865, Bd. xxxiii. S. 79;
Kiihne, " Lehrbuch d. phys. Chemie," 1868, S. 288.

3 " Das Bint der Regenwiirmer, " Journ. f. prakt. Chem., Leipzig, 1839, Bd. xvi. S. 152.

4 " Ziir Kenntniss der Verbreitungdes Hfematins," Sitzungsb. d, k. Akad. d. IVissensch. ,
Wien, 1861, Bd. xliv. S. 615-630.

5 " Observations with the Spectroscope," Journ. Anat. and Physiol., London, 1867,
S. 114.

6 "Optische Eigenschaften des Blutfarbstoffs, " Centralbl. /. d. mcd. Wissensch., Berlin,
1867, S. 196.

7 "A Contribution to the Knowledge of Haemoglobin," Proc. Roy. Soc. London, 1872,
vol. xxi. pp. 70-81.

8 The student is advised to read the interesting chapter, entitled "The Blood of
Invertebrate Animals," in Halliburton's Text-Book, see pp. 316-330.

HAEMOGLOBIN IN THE ANIMAL KINGDOM. 187

(In Ampliioxus Lankester failed to obtain spectroscopic evidence of the pre-
sence of haemoglobin, though Wilhelm Miiller of Jena had described the
corpuscles of this vertebrate as of a pale red colour.) :

(b) In the perivisceral fluid of some species of the vermian genera,
Glycera, Capitilla, and Phoronis :

(c) In the lamellibranchiate molluscs Solen and Area.

2. Diffused in a vascular or ambient liquid —

(a) In the peculiar vascular system of the chsetopodous annelids, very
generally, but with apparently arbitrary exceptions :

(b) In the vascular system (which represents a reduced perivisceral cavity)
of certain leeches (Nephelis, Hirudo), but not of all :

(c) In the vascular system of certain turbellarians, as in Polia sanguirubra :

(d) In a special vascular system (distinct from the general blood system)
of a marine parasitic crustacean (undescribed), observed by Professor Edouard
van Beneden :

(e) In the general blood system of the larva of the dipterous insect
Chironomus ; and in Musca domestica : l

(/) In the general blood system of the pulmonate mollusc Planorbis. Mr.
H. C. Sorby expressed the opinion that probably the colouring matter found in
the blood of Planorbis is not identical with haemoglobin. I have shown, how-
ever, that the position of the absorption-bands of the colouring matter of the
blood of Planorbis coincides exactly with that of the haemoglobin bands : 2

(g) In the general blood system of the crustaceans Daplinia and
Cheiroceplialus (Lankester) ; also in Apus and Cypris.3

3. Diffused in the substance of muscular tissue —

(a) In the voluntary muscles generally of Mammalia, and probably of
birds, and in some muscles of reptiles :

(b) In the muscles of the dorsal fin of the fish Hippocampus, being
generally absent from the voluntary muscular tissue of fish :

(c) In the muscular tissue of the heart of Vertebrata generally :

(d) In the unstriped muscular tissue of the rectum of man, being absent
from the unstriped muscular tissue of the alimentary canal generally :

(e) In the muscles of the pharynx and odontophore of the gastropodous
molluscs (observed in Lymnceus, Paludina, Littorina, Patella, Chiton,
Aplysia), and of the pharyngeal gizzard of Aplysia, being entirely absent from
the rest of the muscular and other tissues and the blood of these molluscs :

(/) In the muscular tissue of the pharyngeal tube of Aphrodite aculeata
(Lankester), being absent from the rest of the muscular tissue, and from the
blood in this animal, and absent from the muscular tissue generally in all
other annelids, as far as yet examined.

4. Diffused in the substance of nervous tissue —

(a) In the chain of nerve ganglia of Aphrodite aculeata (Lankester). In
this annelid the chain of nerve ganglia possesses a bright crimson colour. The
colour is most intense in the supra-oesophageal ganglion, which has as intense
a colour as a drop of fresh human blood. The colour impregnates the nerve
itself, and is not contained in a liquid bathing the tissue :

(b) An exactly similar observation has been made by Hubrecht, who found
haemoglobin in the red-coloured cerebral ganglia of certain Nemertine worms,
which possess no coloured blood corpuscles.4

1 MacMunn, "Animal Chromatology," Proc. Birmingham Phil. Soc., vol. iii. p.
130 (quoted at second-hand).

2 Gamgee, ' 'A Text-Book of the Physiological Chemistry of the Animal Body," vol. i. p. 131.

3 Regnard et Blanchard, " Kote sur la presence de I'he'moglobine dans le sang des
crustace's branchiopodes," Compt. rend. Soc. de biol., Paris, 1883, pp. 197-200.

4 A. A. W. Hubrecht, " Untersuch. ueber Nemertinen aus dem Golf von Neapel,"
Niederland. Arch. f. Zoologie, 1876, Heft 3, Abstract in Jahresb. u. d. Fortschr. d. Tliier-
Chem., Wiesbaden, Bd. vi. S. 92.

i88 HEMOGLOBIN.

THE PROBABLE EELATIONS OF THE BLOOD-COLOURING MATTER TO
THE OTHER CONSTITUENTS OF THE COLOURED CORPUSCLES.

Without encroaching upon the domain of histology, reference must
be made to the two principal views which have been advanced in
reference to the structure of the coloured corpuscles.

According to the first,1 which dates from the time of Bidloo,2 Wells,3
and Hewson,4 and which was strongly advocated by Schwann, the
coloured corpuscles of the blood are vesicular bodies, possessing an
external envelope enclosing fluid contents.

This view has been revived and strongly insisted upon by Scluifer,5
who briefly describes the structure of the red corpuscle in the following
sentence : — " Each red corpuscle is formed of two parts, a coloured and
a colourless, the former being a solution of haemoglobin ; the latter, the
so-called stroma, which is in by far the smaller quantity, being composed
of various substances, chief among these being lecithin and cholesterin,
together with a small amount of cell globulin." 6

According to the second view, which, in its present form, we owe to
Eollett 7 and Brlicke,8 and which for many years found general favour, the
coloured blood corpuscle is not considered as vesicular, but as a viscous
solid mass composed of a colourless, highly elastic framework, the stroma
(Rollett) denser at the periphery than at the centre, in the interstices
or trabeculse of which haemoglobin and the other constituents of the
corpuscles are contained.

Without attempting to decide which of these views, if either, is the
correct one, it is expedient to consider some questions bearing upon
them, and towards the solution of which we possess important facts.

Making for the moment the assumption which, as will be shown in
the sequel, is denied by Hoppe-Seyler, that oxyhamioglobin exists as
such in the coloured blood corpuscles, the question arises, in what
physical state does it occur? Is it simply dissolved in the liquid
contents of the corpuscles, or is it dissolved in virtue of its being in com-
bination with other constituents ? Is it in a solid condition ? and if so,
is there any evidence as to whether its structure is crystalline or
amorphous ?

That the colour of the blood does not depend upon a simple aqueous
solution of haemoglobin, is evident when we consider that the blood
corpuscles are among the soft parts of the body which contain the least
water ; 9 and that not only is the water which the coloured corpuscles
contain altogether insufficient to hold the haemoglobin in solution, but in
some animals, the haemoglobin of which is more sparingly soluble than

1 A reference to and discussion of the earlier literature relating to this view will be
found in Gamgee's "Physiological Chemistry," vol. i. p. 72.

2 " Anatomia humani corporis, 1685," quoted by Milne-Edwards, "Lecons, etc.,"
tome i. p. 66.

"On the Colour of the Blood," Phil. Trans., London, 1797, p. 429.

4 Hewson's Works, Syd. Soc.

5 "Quain's Anatomy," 1891, vol. i. pt. 2, p. 210.

6 Halliburton and Friend ; since shown to be a nucleo-proteid. — EDITOR.

7 Sitzungsb. d. k. Akad. d. Wisscnsch., Wien, 1862, Bd. xlvi. Abth. 2, S. 73.

8 Briicke applied the term Oekoid to the stroma, ibid., Wien, 1867, Bd. Ivi. Abth. 2,
S. 79.

9 According to Bunge, "Zur quantitative!! Analyse des Blutes," Ztschr. f. BioL,
Munchen, 1876, Bd. xii. S. 191, the blood corpuscles contain 367 parts of solids, and 63'3
parts of water ; muscular tissue contains about 25 per cent, of solids, and 75 per cent, of
water ; nerves contain about 22 per cent, of solids, and 78 per cent, of water.

CONDITION OF HEMOGLOBIN IN CORPUSCLES. 189

is generally the case, the whole of the water contained in the blood would
not suffice to dissolve the haemoglobin stored up in the coloured
corpuscles.

That the haemoglobin is not contained in the blood corpuscles in the
form of infinitely minute crystals, is proved by examining the corpuscles
between crossed Mcols, when they are found not to be doubly refract-
ing ; whilst crystals of haemoglobin, even when reduced to a state of most
minute subdivision, are so.1

Furthermore, no crystalline or granular structure can be discovered
when the coloured corpuscles are examined with the highest powers of
the microscope.

The assumption was made by Preyer,2 that haemoglobin exists in the
corpuscles in combination with potassium, alkaline solutions possessing the
property of dissolving much larger quantities of haemoglobin than pure water,
and potassium being the most abundant of the mineral constituents of the
coloured corpuscles of man, though by no means of all animals.3 But, as a
matter of fact, the coloured blood corpuscles do not behave as if they contained
free haemoglobin in a solid condition, or in solution, or a solution of an alkaline
compound of haemoglobin. Only one proof of this statement need be given in
this place, others being adduced when discussing the remarkable, and, as it
appears to me, untenable proposition of Hoppe-Seyler, that the blood-colouring
matter, as it exists in the living corpuscles, differs remarkably in properties from
haemoglobin, so that it should be distinguished by a separate name or names.
The one proof to which reference is made is furnished by the fact that the
colouring matter of the red corpuscles is not extracted from them by the plasma,
or serum, or by fairly concentrated solution of neutral salts, as would be the
case if they contained free haemoglobin, or an alkaline compound of that
substance.4 To explain the fact that haemoglobin is retained by the corpuscles,
Hoppe-Seyler advanced the plausible hypothesis, that it exists in them in
combination with some constituent of the stroma, and he expressed the opinion
that this constituent is lecithin. There are absolutely no grounds for the
latter assumption ; and it has indeed yet to be proved that the phosphorus-con-
taining principle of the stroma of the coloured corpuscles is lecithin and not
protagon, as had been very positively asserted by Hermann.5

Without attempting to speculate beyond the facts which we possess,
it may, however, be assumed that haemoglobin exists in the blood
corpuscles in the form of a compound with a yet unknown constituent
of the corpuscle. This compound, the existence of which we are forced
to assume, is characterised by remarkable instability, for it is decomposed,
setting free the haemoglobin, which then passes into solution — (1) when
the blood plasma or serum, in which the corpuscles are suspended, is
diluted ; (2) when certain substances act upon the corpuscles (ether,
chloroform, salts of the bile acids, certain products of putrefaction) ;
(3) by the action of heat ; by alternate freezing and thawing ; by induction
shocks, etc.

1 W. Preyer, "Die Blutkrystalle," Jena, 1871, S. 28.

2 Ibid., S. 30-33.

3 G. Bunge, " Zur quantitati ven Analyse des Blutes, " Ztschr. f. BioL, Miincheu, 1876,
Bd. xii. S. 191.

4 This is no real proof that haemoglobin is not in solution ; it is merely a statement of
the fact that it is indiffusible through the unaltered envelope of the corpuscle. It is,
moreover, capable of proof that the contents of the red corpuscles are completely fluid
during life. Cf. p. 193, lines 9 to 12. — EDITOR.

5 Arch.f. Anat. w. PhysioL, Leipzig, 1866, S. 33.

190 HAEMOGLOBIN,

Hypothesis of Hoppe-Seyler, that the coloured substance of the
corpuscles possesses properties which differ from those of hsemo-
globin— Arterin (?), and Phlebin (?). — It has been shown that we are
forced to assume the existence in the coloured corpuscles of a very unstable
compound of haemoglobin. Hoppe-Seyler, as far back as 1877,1 expressed the
opinion that whilst the compound or compounds of haemoglobin existing in the
blood corpuscles absorb the rays of the spectrum precisely as solutions of
haemoglobin, in other respects very remarkable differences can be detected,
certain of these differences being, in his opinion, of great physiological
importance.

Subsequently,2 Hoppe-Seyler, returning to this subject, endeavoured to
prove by a variety of arguments that such are the differences between the
properties of the colouring matter as it exists in the coloured corpuscles and
pure haemoglobin, that we cannot logically assert that they are identical. He
examined in detail the differences in behaviour which had been observed by
himself and by others, between the blood-colouring matter as it exists in the
corpuscles and solutions of pure oxy- or reduced haemoglobin. He referred to
the undoubted fact that the colouring matter, as it exists in the coloured
corpuscles, is not dissolved out by serum, liquor sanguinis, or saline solutions,
of a certain strength. It does not, he alleged, crystallise, nor readily yield
its dissociable oxygen when heated in vacua • it readily decomposes peroxide
of hydrogen (H202), setting free ordinary inactive oxygen, and is not oxidised
during the process ; a solution of potassium ferricyanide does not for a long
time attack the blood corpuscles, or convert their colouring matter into
methsemoglobin.

On the other hand, a solution of oxyhaemoglobin (or, as Hoppe-Seyler
preferred to express it, of the oxyhcemoglobins, so as to recall the fact of the
minor differences presented by the haemoglobin of different species of animals)
is soluble in serum or in blood plasma, or in solutions of the neutral salts ;
it crystallises with greater or less facility, according to the animal whence
the blood is obtained. When thoroughly pure, it has scarcely any power
of decomposing H209, but under the influence of this body it is readily
oxidised.

Solutions of crystallised oxyhaemoglobin, Hoppe-Seyler maintained, give
up their dissociable oxygen with difficulty and incompletely, when heated
in vacuo. When blood is saturated with CO, this gas can subsequently be
entirely removed, by passing a stream of hydrogen gas through it for some
hours, or by long-continued boiling in vacuo. On the other hand, when a
solution of oxyhaemoglobin is saturated with CO, and the solution is heated
in vacuo, the poisonous gas is, Hoppe-Seyler stated, given off with great
difficulty and incompletely.

Lastly, highly dilute solutions of potassium ferricyanide readily convert the
oxyhaemoglobins into methaemoglobin.

The evidence by which Hoppe-Seyler endeavoured to prove that the
properties of the blood-colouring matter, as it exists in the corpuscles, differ so
greatly from those of haemoglobin, that we cannot with truth say that this
body exists in them, is, on every single point, of so unsatisfactory a character
as not to stand a moment's investigation, and would lead us to reject his
hypothesis, even if we had not been placed in possession of some remarkable
facts bearing on this subject, which have been ascertained by the method of
spectrophotometry. The non-crystallisation of the colouring matter as it
exists in the coloured corpuscles might, were it really true, well be explained
by the fact that haemoglobin does not exist in a free state, but is combined

1 " Physiologische Chemie," Berlin, 1877, Th. 1, S. 381.

2 "Beitrage zur Kenntniss des Blutfarbstoffes," Ztschr. f. physiol, Chem., Strassburg,
1889, Bd. xii'i. S. 477.

"ARTERIN" (?) AND "PHLEBIN" (?). 191

with another constituent of the corpuscle ; but the statement itself, as made
by Hoppe-Seyler, is incorrect. Although the fact has been denied by some
writers, there can be no question whatever, on the evidence of so eminent
an observer as Klihne,1 as well as of Funke,2 Brisegger and Bruch,3 Bottcher,
Kolliker, L. Beale,4 Owsjannikow,5 Eichardson,6 and Klebs, that what Preyer
terms " intraglobular crystallisation" can and does occur, i.e. a single crystal
forms in the interior of a coloured blood corpuscle. The process is most easily
followed in the blood corpuscles of certain fishes,7 though it has also been
observed in those of the dog (Kiihne) and of the rat.8 The most remarkable
fact with regard to intraglobular crystallisation is, that when water is added
to a preparation exhibiting it, the crystal at once disappears, and the cor-
puscles resume their original appearance.7

Again, at first sight, the difference in behaviour of the blood corpuscles
and of haemoglobin towards peroxide of hydrogen appears thoroughly in
favour of Hoppe-Seyler's hypothesis. It was, however, shown by Bergengruen,
who first discovered the facts in reference to H202, that the decomposing
action exerted by the blood corpuscles on H202 depends upon their stroma.
Solutions of perfectly pure crystals of oxyhaemoglobin have no action what-
ever on peroxide of hydrogen, whilst the stroma of the coloured blood
corpuscles exerts an intense action.8 All forms of protoplasm (splenic
cells, colourless corpuscles, yeast cells), decompose H202, though the stroma
of the coloured corpuscles acts most powerfully. The fact of the decom-
posing action being exerted by the stroma, and the stroma only, explains
why the blood corpuscles are not oxidised whilst oxyhaemoglobin is so, the
colouring matter in the corpuscles not coming in contact with the unde-
composed H202.

The greater readiness, as compared with pure haemoglobin, with which,
according to Hoppe-Seyler, the blood corpuscles give up either the oxygen or
the carbonic oxide which may be combined with their colouring matter (if the
facts were true, which we are not prepared to admit), would be much more
probably due to a katalytic action, exerted by some other constituent of the
corpuscle, than to any radical difference between the colouring matter of the
corpuscles and haemoglobin.

The one point of difference between the colouring matter of the corpuscles
and oxyhaemoglobin, which at first sight appears most difficult to explain, is
the action of solution of potassium f erricyanide. As von Mering 9 showed, if
fresh defibrinated blood be mixed with solutions containing 2J, 5, and 10 per
cent, of the ferricyanide, the mixture assumes a scarlet colour, and even after
twenty-four hours contains the blood-colouring matter unaltered. On adding,
however, the same solution of the ferricyanide, in the same proportions, to
solutions of pure oxyhaemoglobin, they assume almost instantaneously the
colour, and exhibit the spectrum of methaemoglobin.

1 W. Kiihne, Virchow's Archiv, Bd. xxxiv. S. 423.

2 "Ueber Blutkrystallisation," Ztschr. f. rat. Med., 1852, N.F., Bd. i. S. 288-292.

3 " Blutkrystalle, und organisclie Krystalle ueberhaupt" (15th Sept. and 15th Oct.
1852), Verhandl. d. naturf. Gesellsch. in Basel, 1854-1857, Bd. i. S. 173-185.

4 "Observations upon the Nature of the Red Blood Corpuscles." Quart. Journ. Micr.
Sc., London, 1864, pp. 32-43.

5 " Zur Histologie der Blutkorperchem," Bull. Acad. d. sc. de St. Pttersbourg, vol. viii.
pp. 561-572 (describes intraglobular crystallisation in Osmerus eperlanus).

6 "Structure of the Red Blood Corpuscles," Philadelphia, 1870 (describes intraglobular
crystallisation in Menobranclws).

7 Kiihne, see W. Preyer, "Die Blutkrystalle," Jena, 1871, S. 2 and 3. See also Funke's
"Atlas of Physiological Chemistry" (London, printed for the Cavendish Society, 1853),
Plate x. fig. 5. and the description at p. 17 of the " Description of the Plates."

8 Paul Bergengruen, "Ueber die "Wechselwirkung zwischen Wasserstoffsuperoxyd und
verschiedenen^Protoplasniaformen," Inaug. Diss., Dorpat, 1888.

9 "Ueber die Wirkung des ferricyan. Kalium auf Blut," Ztschr. f. physiol. Chem.,
Strassburg, 1883, Bd. viii. S. 186, 189.

192 HAEMOGLOBIN.

The extraordinary difference in the result predisposes one at first to
conclude that it must be due to a radical difference betwen the colouring
matter of the corpuscles and oxyhaemoglobin, such as Hoppe-Seyler believed to
exist. If, however, instead of the solutions mentioned above, solutions ten
times more dilute (containing 0*25, 0*5 and 1 per cent.) be mixed with
defibrinated blood in the same proportions as before, the mixture assumes
instantly the colour, and exhibits the spectrum of methsemoglobin. In this
case the dilute solution extracts, in the first instance, the blood-colouring
matter from the corpuscle, and then the ferricyanide acts upon the solution,
exactly as it does when brought in contact with a solution of crystals of
oxyhaernoglobin. The fact that the strong solution of potassium ferricyanide
does not act upon the colouring matter of the blood corpuscles, is due to its
incapacity to reach, in the first instance, the oxyhaemoglobin of the corpuscles.
In this case also, it appears that the difference (supposed) between the colour-
ing matter, as it exists in the intact blood corpuscles and solutions of haemo-
globin, is only an apparent one.

Though closely connected with the subject which has been discussed in
this section, the views of Bohr1 (who believes that he has succeeded in
establishing, in addition to the already known oxyhaemoglobin, the existence of
at least three additional compounds of oxygen with haemoglobin, all possessing
the spectrum of oxyhaemoglobin, but differing in elementary composition and
in their capacity to combine with oxygen), will be referred to under the heading
of "Oxyhaemoglobin." There can be no question, however, that these views
have been completely disproved by Hiifner,2 the supposed individual oxyhaemo-
globins of Bohr being mechanical mixtures of pure oxyhaemoglobin with
products of its decomposition, — the necessary results of the methods of pre-
paration followed by the Scandinavian observer.

We have shown that even admitting, for the sake of argument, the
correctness of all Hoppe-Seyler's statements, these when carefully analysed
afford no evidence whatever in support of his bold hypothesis. Whilst such
is the case, the splendid investigations of Hiifner 2 have conclusively proved
that, in respect of its power of combining with oxygen, the blood-colouring
matter, as it exists in the coloured blood corpuscles, behaves precisely as a
solution of pure haemoglobin of the same concentration. Further, by the
method of spectrophotometry, Hiifner has shown, as could be done by no
other method, that the colouring matter of the blood is one— haemoglobin —
and that in every specimen of living blood, this colouring matter exists, partly
as oxyhaemoglobin and partly as reduced haemoglobin.

The discussion which has preceded will have prepared the reader for the
conclusion, which appears to be the only one which can legitimately be based
upon the facts in our possession — to wit, that whilst oxyhaemoglobin and
reduced haemoglobin exist in the coloured blood corpuscles in the form of
loose or unstable combinations with some other constituent of the corpuscle,
evidence is altogether wanting in support of Hoppe-Seyler's contention that
the blood- colouring matter, as it exists in the corpuscles, possesses properties
so different from those of oxyhaemoglobin and of reduced haemoglobin, as to
warrant its being looked upon as a distinct substance, to be distinguished by
a different name. Hoppe-Seyler suggested,3 indeed, that the colouring matter
of arterial blood should be called Arterin, to distinguish it from oxyhaemo-
globin, whilst that contained in venous blood should be named PMebin, to

1 " Ueber die Verbindungen des Hamoglobins mit Sauerstoff," " Ueber die specifische
Sauerstoffmenge des Blutes und die Bedeutimg derselbeii fur den respiratorischen Stoff-
wechsel," Centralbl.f. PhysioL, Leipzig u. Wien, 1890, Bd. iv. S. 242, 254.

2 In this place it is only necessary to refer to one of Hiifner's papers. See G. Hiifner,
"Neue Versuche zur Bestimrnung der Sauerstoff capacitat des Blutfarbstoffs, " Arch. f.
PhysioL, Leipzig, 1894, S. 130, 176. Refer particularly to pp. 130, 134, 175, 176.

3 Ztschr. f. physlol. Chem., Strassburg, 1889, Bd. xiii. S. 495.

OXYH^EMOGLOBIN. 193

distinguish it from reduced haemoglobin ! The only distinction which Hoppe-
Seyler found to exist between " arterin " and " phlebin " consisted in the alleged
greater ease with which the hypothetical constituent of arterial blood yielded
its dissociable oxygen, when boiled in vacuo, as compared with the hypo-
thetical constituent of venous blood. To establish this alleged difference
between arterial and venous blood would require a body of experimental facts,
such as does not exist. Even were the difference shown to be a real one, it
would in no way support the hypothesis of a radical difference between the
colouring matter of arterial and venous blood. But the investigations of
Hiifner, which have proved with mathematical accuracy that the colouring
matter of the blood behaves, both in so far as its optical characters and
its relations to oxygen are concerned, precisely as a solution of haemoglobin,
and is the only coloured constituent of the corpuscles, complete the demonstra-
tion of the erroneous nature of the hypothesis advanced by Hoppe-Seyler
on this subject.

OXYELEMOGLOBIN.

METHODS OF PREPARATION.

Introductory remarks. — It has already been stated that the blood-
colouring matter of different species of animals is not, in all particulars,
absolutely identical. Although behaving in the same manner in refer-
ence to the gases with which it can combine to form more or less
easily dissociated compounds, and whilst possessing identical powers of
absorbing the rays of the spectrum, the haemoglobin of different animals
exhibits differences (1) in crystalline form, (2) in solubility, (3) in the
quantity of water of crystallisation, (4) in percentage composition.
These differences will be carefully examined in the sequel, but attention
is drawn to them in this place, in relation to another point of difference,
namely, the variation in the facility of separating haemoglobin in a
crystalline form. From the blood of certain animals, crystals of haemo-
globin can most readily be prepared, whilst in other cases the task
is one of very considerable difficulty. Among the conditions which
influence the result, the degree of solubility of the blood-colouring
matter is the chief. Thus the blood of the rat, the guinea-pig, and
the squirrel, which contains the least soluble haemoglobin, yields crystals
with great facility ; whilst the blood of man, and that of the domestic
herbivorous animals, which possess haemoglobin of remarkable solu-
bility, yields crystals with extraordinary difficulty. It is impossible
to state with accuracy the relative facility of crystallisation of the
haemoglobin of different animals, but the following statements are pro-
bably correct. The blood of the rat, the guinea-pig, and the squirrel
crystallises most readily ; next comes the blood of the cat, the dog, and
the horse ; the blood of man and the pig follow, whilst that of the
rabbit, the sheep, the ox, and the frog crystallise with the greatest
difficulty.

The principle upon which the majority of the methods for the
separation -of haemoglobin in a crystalline form are based is the
following : — To effect the solution of the haemoglobin of the coloured
corpuscles in the serum, or in water, added to the previously separated
corpuscles ; and thereafter, by the addition of alcohol, or of ether, or
by the agency of cold, or of both cold and alcohol or ether conjointly,
sometimes aided by the process of evaporation, to cause the haemoglobin,
VOL. i.— 13

i94 HAEMOGLOBIN.

which is sparingly soluble in dilute alcohol, especially at low tempera-
tures, to crystallise. In the case of animals, the haemoglobin of whose
blood is very sparingly soluble, the addition of alcohol or ether is often
dispensed with. We shall, in the first place,' describe those methods
which readily furnish haemoglobin crystals for the purposes of micro-
scopical research, and then the methods which are employed for the
preparation and purification of large quantities of haemoglobin.

Methods employed in preparing small quantities of haemoglobin
for microscopic examination. — 1. Funkes method.1 — From the blood of
those animals whose blood crystallises readily, but especially in the
case of the rat, oxyhsemoglobin can be obtained for microscopic exami-
nation in three or four minutes, by receiving a drop of blood on a
glass slide, adding a drop of distilled water, mixing the two liquids
by means of a needle, and spreading the mixture over the central part
of the slide. When the edges of the liquid commence to dry, cover
with a microscopic covering glass. Crystals of haemoglobin form at
once.

2. Rollett's method? — A platinum capsule is placed in a freezing
mixture, and freshly defibrinated blood is poured into it, so as to convert
it into a lump of red ice. After being in the freezing mixture for half
an hour the blood is allowed to thaw gradually, and the contents of the
capsule are poured into a glass vessel of such dimensions that the
bottom is covered by the lake-coloured blood to a depth of 15 mm. ;
the glass vessel is then set aside in a cool place. In a short time,
the blood of rats, of guinea-pigs, and of squirrels, treated by this method,
furnishes well-formed crystals.

' 3. Grscheidlens method.3 — Defibrinated blood, 'which has been exposed
to the air for a period of twenty-four hours, is sealed in narrow glass
tubes (vaccine tubes answer well), and these tubes are then placed in
the incubator and kept a temperature of about 37° 0. for some days.
On opening the tubes and emptying their contents into a watch glass or
on a glass slide, and allowing some time for evaporation to take place,
crystals of extraordinary size are obtained.

4. Max Schultzes method* — Defibrinated blood is heated (on a warm
stage, in the case of a microscopic preparation) to a temperature of 60° F.,
when the corpuscles dissolve and the blood becomes lake-coloured ; it
is then allowed slowly to cool and to evaporate. This method may be
employed with large quantities of blood, and Preyer 5 found that by no
other method did he obtain as fine and as large crystals from horse's
blood.

In addition to the four methods which have been above described as
most conveniently yielding crystals of oxyhaemoglobin, when these are
desired on a small scale, there are many others which have been employed,
and which occasionally give good results.

Thus Ilollett 6 found that when induction shocks were passed through
blood, it became lake-coloured and yielded crystals of haemoglobin, and

1 Ztschr.f. rat. Med., 1851, S. 185.

2 "Versuclie und Beobachtungen am Blute," Sitzungsb. d. Jc. ATcad. d. Wissensch..
Wien, 1863, Bd. xlvi. S. 77.

3 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xvi. S. 421.

4 " Ein heitzbarer Objecttisch und seine Verwendung bei Untersuchungen des Blutes,"
Arch.f. mikr. Anat., Bonn, 1865, Bd. i. S. 31.

5 "Die Blutkrystalle," S. 23.

6 Sitzungsb. d. Jc. Akad. d. Wissensch., Wien, 1852, Bd. xlvi. S. 75.

PREPARATION OF OXYHsEMOGLOBIN. 195

A. Schmidt 1 made the same observation in reference to the blood near
the positive pole, when this liquid is subjected to the action of a
constant current.

Without undergoing any other treatment, the blood of asphyxiated
animals often crystallises. Blood which has been deprived of its gases,
by boiling in vacuo, often crystallises. Indeed, by this method, Preyer 2
succeeded in the very difficult task of crystallising sheep's blood.

Methods of preparing considerable quantities of oxyheemo-
globin. — Certain of the methods already recommended for the prepara-
tion of haemoglobin, when small quantities only are needed for the
purposes of microscopic investigation, might be employed in the pre-
paration of larger quantities. Other processes, however, are to be
preferred, and of these some which are specially to be recommended
are given below. Of these processes, the first, or Hiifner's modification
of it, should, by preference, be employed, especially if a preparation, as
free as possible from products of decomposition, be desired.3

Hoppc-Seylcrs method.^ — Defibrinated blood is mixed with ten times
its volume of a solution of sodium chloride5 (made by diluting one
volume of a saturated solution of NaCl with nine volumes of water),
and the mixture is poured into shallow basins, which are set aside in a
cool place, so as to allow the greater part of the blood corpuscles to
settle.6 The supernatant liquid is decanted, and the magma of corpuscles,
mixed with a small quantity of water, is poured into a stoppered
separating funnel. The contents of this funnel are treated with an
equal volume of ether. After repeated, but not too violent, agitation,
the deep red aqueous solution is separated from the supernatant ether,
and filtered as quickly as possible. The clear red filtrate cooled to 0° C.
is then mixed with one-fourth of its volume of absolute alcohol, likewise
cooled to 0° C. The mixture is then maintained for a couple of days
(and, if crystallisation has not occurred, even longer), at a temperature of
— 5° C. to — 10° C. In a period varying between twenty-four and
forty-eight hours crystallisation has usually occurred, and, unless the
solution of haemoglobin was too dilute, the whole of the liquid has set into
a mass of crystals. The crystals are now collected on a filter (the process
of filtration being carried on at as low a temperature as possible, in any
case below 0° C.) and washed several times with a previously cooled
mixture, composed of one volume of absolute alcohol and four volumes
of distilled water. The filter with its contents is now placed between
sheets of filtering paper, and as much as possible of the adhering mother-
liquor is removed by gentle pressure. The oxyhsemoglobin thus

1 "Zuv Krystallisation des Blutes," Virchow's Archiv, 1864, Bd. xxix. S. 29.

2 "Die Blutkrystalle," S. 19 and 20.

3 The blood of the dog, and especially of the horse, are to be preferred for the preparation
of large quantities of oxyhiemoglobin. As the success of the various operations depends
upon their being conducted at a low temperature, the preparation of haemoglobin for purposes
of research should only be attempted in the depth of winter.

4 " Beitrage zur Kenntniss des Blutes des Menschen und der Wirbelthiere," Med.
Chem. Untersuch., Berlin, 1866, S. 170, 180-185; "Handbuch d. physiologisch. cheni.
Analyse," Berlin, 1893, Aufl. 6, S. 274.

5 In the preparation of haemoglobin from the blood of birds, amphibia, and fish, sodium
sulphate is to be employed in the place of sodium chloride. In the case of mammalian
blood, it presents no advantages over sodium chloride.

6 Instead of allowing the corpuscles to separate, as described, it is preferable to employ a
centrifugal machine. The separation of the corpuscles from the mixture of serum and salt,
solution is not only very much more rapid, but also much more complete, and therefore the
obtaining of pure oxyluiemoglobm is facilitated.

196 HEMOGLOBIN.

obtained may now be purified by being recrystallised. With this object
the moist crystals are removed by means of a spatula from the filter,
and placed in a fiask or beaker, and about three times their volume
of distilled water is added. The mixture is heated to 55° C., the solu-
tion filtered ; the filtrate is cooled to 0° C., and to every four volumes
one volume of absolute alcohol, cooled to 0° C., is added. The mixture
is then cooled to - 5° C. or - 10° C.

When the oxyhsemoglobin separates again, this process of crystallisa-
tion may be repeated five or even six times, providing the temperature
at which the various operations are conducted be a very low one. The
recrystallised haemoglobin obtained by these processes may be employed
to make standard solutions of the body, or it may be dried. It is very
questionable, however, whether the refcrystallising of oxyhaemoglobin is
advisable, for reasons to be stated below, it being probably better to purify
the crystals by repeated washings with ice-cold water. Hoppe-Seyler
states that oxyhsemoglobin can only be dried, without decomposition, in
vacuo, at a temperature under 0° C. If dried at a higher temperature it
assumes a dark colour, and ceases to be entirely soluble in distilled water.

Zinoffsky,1 who worked with oxyhaemoglobin prepared from the
blood of the horse, found that, when spread out in very thin layers, it
could be dried in vacuo in eight hours, without undergoing decomposi-
tion, at a temperature of 10° C. to 20° C. He found that the oxy-
hsemoglobin thus prepared was entirely soluble in distilled water, and
that the solution was not precipitated by lead acetate ; proving that no
methaemoglobin had been formed.

Haemoglobin which has been dried in vacuo, over sulphuric acid or
phosphoric anhydride, at a temperature of 0° C., may be heated to 110° C.
or 115° C., without undergoing any decomposition.

Modifications of Hoppe-Seylers method. — (a) Among numerous modi-
fications may be mentioned one employed by Hlifner,2 and which may
with advantage be adopted in laboratories provided with centrifugal
machines. The blood is not treated with salt solution, but the corpuscles
are separated by the action of the centrifuge alone. Crystals thus
obtained are treated with ice-cold water, separated by the centrifuge,
and this process repeated several times, finally, the crystals are dried
on porous plates made of cellulose, or solutions are made of the yet
moist crystals, and the percentage of haemoglobin in them determined.

(&) The defibrinated blood of the dog is mixed with its own volume
of distilled water, and the diluted fluid is treated with one-fourth its
volume of alcohol. The mixture is kept for twenty-four hours, at a
temperature which must be lower than 0° C. The crystals which
separate are dissolved in about three times their bulk of distilled water,
at a temperature of 30° C., and the solution being cooled to 0° C., a
fourth of its volume of absolute alcohol at 0° C. is added. The fluid
should be kept in a freezing mixture at a temperature of - 10° C. to
- 20° C. for twenty-four hours. The whole fluid then becomes con-
verted into a magma of crystals. The process of recrystallisation may
be several times repeated.

1 "Ueber die Grosse des Hamoglobin-moleciils," Ztschr. /. physiol. Chem., Strassburg,
1886, Bd. x. S. 15-34. See "Darstellung des Hamoglobins, ' S. 18-24.

2 " Beitrag zur Lehre von Blutfarbstoffe, " Beitr. z. Physiol. C. Ludioig s. s. 70 Gelurtst.
etc., Leipzig, 1887, S. 74-81; and "Neue Versuche, u.s.w.," Arch. f. Physiol., Leipzig,
1894, S. 134-136.

PURIFICATION OF HEMOGLOBIN. 197

(c) Defibrinated blood is treated with about one-sixteenth its
volume of ether (say 31 c.c. of ether to 500 c.c. blood), and the mixture
shaken for some minutes. It is then set aside in a cool place. After a
period, varying from twenty-four hours to three days, the liquid has
been converted into a thick magma of crystals. These may be separated
by placing in tubes and using the centrifugal apparatus. The cakes of
crystals are treated with a mixture of one part of absolute alcohol and
four parts of distilled water, and again centrifugalised. By repeating
this process the crystals are ultimately obtained free from serum
albumin. The crystals may be dissolved in water and recrystallised, as
described in Hoppe-Seyler's method.

In addition to the methods described, many others have been
suggested, and to these only a passing reference need be made.

Thus Kiihiie devised a method based upon the fact that the stroma
of the coloured corpuscles is dissolved by the addition of a watery
solution of crystallised bile (a mixture of sodium glycocholate and
taurocholate).1 Hiifner2 and his pupil Otto employed a 1 per cent,
alcoholic solution of chinoline, or a watery solution of the hydrochlorate
of the same base, to prepare oxyhaemoglobin from pig's blood, though
Otto afterwards found2 that, by taking special precautions, Hoppe-Seyler's
method is available, even in the case of pig's blood, and indeed preferable
to all others.

Remarks on the purification of haemoglobin. — It has, until lately,
been assumed that in the preparation of pure oxyhsemoglobin the body should
be recrystallised as frequently as possible, with the object of getting rid of all
traces of adherent albuminous and saline impurities derived from the plasma
or serum. Since spectrophotometry has supplied us with a method of deter-
mining, with an accuracy previously unattainable, the purity of a colouring
matter, it has been found that although oxyhaemoglobin which has been
recrystallised, when examined in the ordinary manner, exhibits a spectrum
which appears identical with that of the colouring matter which has been only
once crystallised, its spectrophotometric constants have changed; in other
words, when oxyhaemoglobin is recrystallised it undergoes a change, possibly
only affecting its physical, but more probably affecting its chemical constitution
also. The knowledge of these facts has caused Hiifner in his recent researches
to employ haemoglobin which has not been recrystallised.

If precautions are taken in the first instance to separate (by the most perfect
nitration, followed by prolonged centrifugalising) all formed elements and acci-
dental solid impurities from the solution of blood corpuscles which is to be
crystallised, and if the crystalline mass of oxyhsemoglobin obtained be repeatedly,
say five or six times, treated with ice-cold water, the resulting solution being
each time separated from the undissolved crystals by very rapid and very
prolonged centrifugalising, the portion of the original crystals still left undis-
solved will be found, on chemical, microscopical, and spectrophotometric
investigation, to furnish evidence of being a pure substance.

The new method is more easily and much more expeditiously carried out
than the old.

Elementary composition of oxyhsemoglobin dried at 11O°-115° C.

—Before describing either the physical or chemical properties of the

1 CentralU.f. d. med. Wissenscli., Berlin, S. 833.

2 The account of Hu'fner's discovery of this method is contained in a paper by his pupil,
F. Otto, "Ueber das Oxyhamoglobin des Schweines," Ztschr.f. physio!. Chem., Strassburg,
1882-83, Bd. vii. S. 57.

198

HEMOGLOBIN.

blood-colouring matter, it is advisable to consider its elementary com-
position, and to ascertain how the results of chemical analysis bear on
the question as to haemoglobin being a definite chemical individual, its
composition being invariable.

Haemoglobin is a compound of carbon, hydrogen, nitrogen, sulphur,
iron, and oxygen. The crystals of haemoglobin contain water of crystal-
lisation, which varies considerably in amount in the haemoglobin of
different animals. When ignited, pure haemoglobin obtained from
mammalian blood yields an ash composed entirely of ferric oxide ; the
haemoglobin of birds and fishes, and probably of all animals with
nucleated corpuscles, yields on ignition an ash which, in addition to
Fe203, contains phosphoric anhydride (l^Oj), derived in all probability
from nuclein contained in the corpuscles.1

The earlier analyses of oxyhaemoglobin made by C. Schmidt2 and
by Hoppe-Seyler 3 exhibited results which appeared to indicate that
crystallised oxyhsemoglobin is a body of constant composition. From
the analyses of these two observers, and his own determinations of the
iron and sulphur in crystallised oxyhaemoglobin, Preyer deduced the
following as the mean percentage composition of oxyhaemoglobin : —

In 100 Parts.

C
H
N

Fe

S

o

54-00
7-25

16-25
0-42
0-63

21-45

100-00

On the assumption, which a large number of facts have since shown
to be almost certainly correct, that the molecule of haemoglobin contains

one atom of iron, Preyer assigned to it the empirical formula Cc
N154FeS30170, the molecular weight being 13,332.

Jl <

Analysis of Oxyliwrnoglobin dried at a temperature above 100° C.5 (Hoppe-Seyler).

Oxyhsemoglobin of

Water of Crystallisa-
tion in the Crystals
which had been
dried in vacuo.

C.

H.

N.

0.

S.

Fe.

P203.

Dog .

3-4 per cent.

53-85

7-32

16-17

21-84

0-39

0-43

Goose .

7 „ „

54-26

7-10

16-21

20-69

0-54

0-43

0-77

Guinea-pig .

6 ,, ,,

54-12

7-36

16-78

20-68

0-58

0-48

...

Squirrel

9 „ „

54-09

7-39

16-09

21-44

0-40

0-59

...

1 Y. Inoko, " Einige Bemerkungen ueber phosphorhaltige Blutfarbstoffe," Ztschr. /.
physiol. Chem., Strassburg, 1894, Bd. xviii. S. 57.

2 " Analyse der Blutkrystalle," in Bottcher's monograph, "Ueber Blutkrystalle,"
Dorpat, 1862.

3 "Beitrage zur Kenntniss des Blutes des Menschen mid der Wirbelthiere ; Zusammen-
setzung der Farbstoffkrystalle des Meerschweinchen- und des Hunde-blutcs," Mcd. Chem,
Untersuch., Berlin, 1868, S. 186 et seq.

ELEMENTARY COMPOSITION OF OXYHAMOGLOBIN. 199

The subsequent researches of Hoppe-Seyler soon demonstrated,
however, that the blood crystals obtained from the blood of different
animals did not possess an identical composition, though the differences
brought out by Hoppe-Seyler's analyses were not very great. His
results are shown in the table on p. 198.1

The very numerous analyses of oxyhaemoglobin of different animals,
made in recent years by Kossel,2 Otto,3 Zinoffsky,4 Hiifner,5 Jaquet,6
and others exhibit, however, such extraordinary discrepancies in the
results of ultimate organic analysis as to preclude a precise answer
being given to such simple questions as the following : —

Is haemoglobin a body, having a constant composition in animals
of the same species ?

Does the haemoglobin of different animals vary in chemical com-
position, and if so, within what limits ?

Results of the more recent Analyses of Oxyhcemoglolin (1878-1890).

' Oxyhsemoglobin of

C.

H.

N.

s.

Fe.

O.

P205.

Dog .

53-85

7-32

16-17

0-39

0-43

21-84

Hoppe-Seyler.7

53-91

6-62

15-98

0-540

0-333

22-62

...

Jaquet.8

.

54-57

7-22

16-38

0-568

0-336

20-93

Jaquet.9

Horse

54-87

6-97

17-31

0-650

0-47

19-73

Kossel.10

54-76

7-03

17-28

0-67

0-45

19-81

Otto.11

54-40

7-07

17-40

0-66

0-45

19-74

Bucheler.12

51-15

6-76

17-94

0-39

0-335

23-43

Zinoffsky.13

CK !

54-66

7-25

1770

0-447

0'400

19-54

Hiifner.14

...

0-336

Hiifner.15

Pig '. '. '.

54:17

7-38

16:23

0-660

0-430

21-360

Otto.16

54-71

7-38

17-43

0-479

0-399

19-602

Hufner.17

Hen! '. '.

52-47

7-19

16-45

0-857

0-335

22-500

0-197

Jaquet.18

1 Med. Chem. Vntersuch., Berlin, 1868, Heft 3, S. 370.

2 The results of the analyses made by Dr. Kossel were published in a paper by Hoppe-
Seyler, entitled "Weitere Mittheilungen ueber die Eigenschaften des Blutfarbstotfs — Das
Oxyhamoglobin des Pferdeblutes, " Ztschr. /. physiol. Chem., Strassburg, 1878-79, Bd. ii.
S. 149-155.

a "Ueber das Oxyhamoglobin des Schweines," ibid., 1882-83, Bd. vii. S. 57-68.

4 "Ueber die Grbsse des Hamoglobinmoleculs," ibid., 1886, Bd. x. S. 16-34.

5 "Ueber das Oxyhamoglobin des Pferdes," Ztschr. f. physiol. Chem., Strassburg,
1883-84, Bd. viii. S. 358-365; "Beitrage zur Lehre voni Blutfarbstoffe," in Beitr. s.
Physiol. O. Ludwifj 2. s. Geburtst. etc., Leipzig, 18,87, S. 74-81; "Neue Yersuche zur
Bestimmung des SauerstofFscapacitat des Blutfarbstoffs," Arch. f. Physiol., Leipzig, 1894,
S. 130-176. See especially S. 174-176.

6 " Elementaranalyse des Hundeblut-Hamoglobins," Ztschr. f. physiol. Chem., Strass-
burg, 1888, Bd. xii. S. 285-288 ; Beitrage zur Kenntniss des Blutfarbstoffes," ibid.,
1890, Bd. xiv. S. 289-296.

7 This analysis, which is adduced for purposes of comparison, does not fall within the
dates given above, having been published in 1868.

8 Ztschr. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 285.

9 Ibid., 1890, Bd. xiv. S. 289.

10 Ibid., 187S-79, Bd. ii. S. 149. Refer to Note 2.

11 Arch. f. d. ges. Physiol., Bonn, 1884, Bd. xxxi. S. 240.

12 Hiifner, Ztschr. f. physiol. Chem., Strassburg, 1883-84, Bd. viii. S. 358. This paper
contains the results of Biicheler's researches, which have been carried out under Hiifner's
direction, and had appeared as a Tubingen Dissertation in 1883.

13 Ibid., Strassburg, 1886, Bd. x. S. 16.

14 Beitr. z. Physiol. C. Ludwig z. s. Geburtst. etc., Leipzig, 1887, S. 74.

15 Arch. f. Physiol., Leipzig, 1894, S. 174.

10 Ztschr. f. physiol. Chem., Strassburg, 1882-83, Bd. vii. S. 57.

17 Beitr. z. Physiol. C. Ludwig z. s. Geburtst. etc., Leipzig, 1887, S. 74.

18 Ztschr. f. physiol. Chem., Strassburg, Bd. xiv. S. 289.

200 HEMOGLOBIN.

Were we to- admit the accuracy of the work of all the observers,
whose results are exhibited on the table on p. 199, we should be forced
to the conclusion that haemoglobin is a body which does not only vary
considerably in composition in different animals, but does not possess a
constant composition even in different individuals of the same species.
Thus, whilst Kossel found the percentage of carbon in the oxyhaemoglobin
of the horse to be 54'87, and the mean of a large number of analyses
by Kossel, Otto, and Biicheler gave 54*68, Zinoffsky, as a result of his
analyses (only two in number, so far as the carbon and hydrogen are
concerned !), found the percentage of carbon in the haemoglobin of the
horse to be 51/15 (!!). A body in which the carbon differs by 8*72 per
cent, in different specimens cannot, it wijl be argued, be a chemical indivi-
dual. But to draw this conclusion in reference to haemoglobin from the
facts in our possession would certainly be an error. The discrepancies
between the results of the analyses of the haemoglobin of the same
animals are doubtless due to differences in the purity of the substance
analysed, and to errors of analysis. The preparation of perfectly pure
oxyhaemoglobin, entirely free from contamination with other con-
stituents of the blood corpuscles and from products of decomposition, is
much more difficult than has, until very recently, been supposed. In
the attempt to purify the substance by crystallising it as frequently as
practicable, nearly all observers have in all probability decomposed it,
and have afterwards analysed a mixture of oxyhaemoglobin and products
of its decomposition. How far this is the source of the above discrep-
ancies must now, in the light of recent spectrophotometric work, be
carefully enquired into. Moreover, assuming that perfectly pure crystal-
lised oxyhaemoglobin is at the disposal of the analyst, the task of drying
without decomposing it is one of peculiar difficulty, concerning the
method of execution of which the chemists who have carried out the
researches under discussion have been by no means agreed. Thus, whilst
some (following Hoppe-Seyler's directions) have dried the oxyhaemoglobin
intended for analysis, in the first instance in vacuo at 0° C., and only
afterwards at higher temperatures, others (Zinoffsky, Hiifner, Jaquet)
have dried the substance in vacuo at ordinary temperatures (15° to
18° C.), and subsequently at 110° to 115° C.

It is conceivable, nay probable, that some of the differences in the results
of different observers may have depended upon the above-mentioned differ-
ence in the treatment of the substance analysed. But, unquestionably, some
of the best marked differences must depend upon differences in the
method of analysis employed (e.g. where one observer determines the N in
oxyhsemoglobin by Will and Varrentrapp's method, whilst another employs
Dumas' method), and upon accidental errors of analysis, which can easily be
rendered obvious, by making a considerable number of analyses.

For instance, it appears to me that the percentage of carbon given by
Zinoffsky,1 as representing the proportion of this element in the hsemoglobin
of the horse, must be due to imperfect combustion. Whilst this observer
carried out the determinations of iron and sulphur in the haemoglobin of the
horse in the most elaborate and perfect manner, making many analyses of
each of three separately prepared specimens of crystallised haemoglobin, he
rested satisfied with only two determinations of carbon and hydrogen, and
two determinations of nitrogen (the latter by the method of Will and

1 "Ueber die Grosse des Hamoglobinmoleciils," Ztschr. f. physiol, CJiem., Strassburg
1886, Bd. x.

ELEMENTAR Y COMPOSITION OF OXYH^MOGLOBIN. 201

Varrentrapp), though the results which he obtained differed in a remarkable
manner from all those of previous observers. It is clear that whilst very great
value must be attached to the determination of the iron and sulphur contained in
haemoglobin, made by Zinoffsky, his conclusions as to the percentage of carbon
and hydrogen must be rejected, as being based upon an insufficient number
of analyses, and as being in all probability incorrect. This opinion is supported
by the remarkable discrepancy between his results and those of other observers
— a discrepancy which cannot be accounted for by differences in purity of the
bodies analysed.

While it is almost inconceivable, and against the weight of evidence, that
haemoglobin derived from animals of the same species should not have a
constant composition, the differences in centesimal composition which certainly
do exist between the haemoglobin of certain animals and that of others
cannot surprise us when we reflect that haemoglobin does exhibit marked
physical differences in different animals — that it exhibits variations in
crystalline form, in the amount of water of crystallisation, and in solubility.

The study of the general results of the ultimate analyses of oxy-
haemoglobin made of recent years forces us assuredly to the conclusion
that new and still more precise investigations are needed before we can
lay claim even to so limited a knowledge as that of its precise centesimal
composition. Nevertheless, it would be wrong to leave the study of
the more recent researches without drawing attention to certain of the
numerical results obtained, which are more deserving of confidence
than others.

The most characteristic and the most important of the elements
which enter into the composition of haemoglobin is its iron. Iron is
the typical element in a molecular group which exists and possesses
identical chemical and physical properties in all the varieties of
haemoglobin with which we are acquainted. Besides furnishing us
with data by which the molecular weight of haemoglobin may be
calculated, the amount of iron appears to bear a definite relation to
the quantity of the dissociable oxygen and carbonic oxide which
haemoglobin combines with. For these reasons, an extremely accurate
determination of the iron in haemoglobin, carried out with all the
precision which the present state of science permits of, has been a great
desideratum. Such determinations have been carried out by Zinoffsky,
Jaquet, and Hiifner (see p. 199).

Haemoglobin of

Fe per cent.

Authority.

Dog
Horse
Ox .

0-336
0-335
0-336

Jaquet.
Zinoffsky.
Hiifner.

Hen

0-336

Jaquet.

These observers have determined the proportion of iron in the
oxyhaemoglobin of the dog, the horse, the ox, the pig, and the hen.
They have shown : First, that the amount of iron in the blood-colouring
matter of these animals is decidedly smaller than had been assumed
on the basis of the older analyses. Secondly, that in the animals
mentioned the percentage of iron in the haemoglobin is identical, so
that we may conclude that in these very different animals, in spite of

202 HAEMOGLOBIN.

the discrepancies between the results of the ultimate organic analyses
yet made, the oxyhaemoglobin possesses the same molecular weight.
The concordance between the more recent determinations of the iron
of oxyhaemoglobin is well shown in the table given on the previous
page.

On the assumption that one molecule of haemoglobin contains one
atom of iron, the molecular weight of the haemoglobin of the dog, horse,
ox, and hen would be 16,669, and this result is borne out, as will be
afterwards shown, by the volume of oxygen or of carbonic oxide which
enters into combination with the blood-colouring matter.

In addition to the estimation of the iron in haemoglobin, that of
the sulphur has been carried out with remarkable care by Hlifner,1
Zinoffsky, and Jaquet; and their results, whilst establishing that the
centesimal composition of the blood-colouring matter of all animals is
not identical, show that in haemoglobin the sulphur stands to the iron
in definite relations.

Thus Zinoffsky's analyses appear to establish that in the haemoglobin
of the horse the sulphur is to the iron in the relation of two atoms of
the former to one of the latter element, and Hiifner has shown that
exactly the same relation obtains in the case of the haemoglobin of the
ox and the pig. On the other hand, Jaquet 's analyses of the haemo-
globin of the dog indicate that in it three atoms of sulphur correspond
to one atom of iron. When, in a subsequent section, we shall examine
the products of decomposition of haemoglobin, we shall show that, under
the influence of acids and alkalies, the blood-colouring matter breaks
up into an iron-containing body (of which the composition and the
properties vary, according to the presence or absence of oxygen during
the decomposition) and into an albuminous body or bodies. The
sulphur of haemoglobin belongs to the albuminous part of the molecule,
and the difference in the relation of S to Fe, brought out by the
researches of Hiifner, Zinoffsky, and Jaquet indicates that the albuminous
moiety of the haemoglobin molecule varies in different animals, and that
among the points of difference is the difference in the proportion of
sulphur. This point will be certainly cleared up by future researches
specially directed to its elucidation; it may be remarked, however,
that the proportion of sulphur in different albuminous bodies does
exhibit great variations.

It appears to me, moreover, that we must not lose sight of the possi-
bility (even when there is no evidence afforded by ultimate organic
analysis -of there being a difference in the percentage composition of the
albuminous part of the haemoglobin moiety), and indeed probability, that
haemoglobins varying in certain physical properties may he formed by the
linking of the iron- containing molecule to various polymeric combinations of
the same albuminous molecule.

Although it is highly probable that the molecular weight of the
haemoglobin of the dog and of the ox (16,669), as determined by the
iron determinations of Jaquet and Hiifner, and by determinations by
Hiifner of the volumes of O and CO with which haemoglobin combines,
has been ascertained with correctness, or nearly so, the discrepancies in
the results of the determinations of 0, H, and N, made by different
observers, are too great to warrant our placing confidence in the
empirical formulae which have been assigned to haemoglobin. Of these

1 " Bestimmung d. Sauerstoffscapacitat d. Blutfarbstoffs, " S. 76.

CRYSTALLINE FORM OF HEMOGLOBIN. 203

empirical formulae, that calculated by Jaquet for the haemoglobin of the
dog is probably the nearest the truth, namely —

Why should haemoglobin possess so enormously high a molecular
weight ? The question suggested itself to the acute mind of Bunge, who
has furnished us with one reason which is eminently suggestive : " The
enormous size of the haemoglobin molecule," says this writer, " finds a
teleological explanation, if we consider that iron is eight times as heavy
as water. A compound of iron, which would float easily along with the
blood current through the vessels, could only be secured by the iron
being taken up by so large an organic molecule." 2

When discussing the compounds and products of decomposition of
oxyhaeinoglobin and haemoglobin, we shall have again to revert to and
further examine certain of the facts which have found a place in this
section.

The crystalline form, the amount of water of crystallisation, the
solubility, and the diffusibility of oxyhsemoglobin. — Although, as has
already been stated, the oxyhaemoglobin of different animals varies con-
siderably in the facility with which it crystallises, we now know that the
haemoglobin of all animals, without exception, may, by suitable treat-
ment, be obtained in the crystalline form.3 Great differences exist in
the solubility of the blood-colouring matter obtained from different
animals, and, as might have been anticipated, the- blood of these
animals whose haemoglobin is least soluble (as the rat, the guinea-pig,
and the squirrel) yields crystals of oxyhaemoglobin most readily ; whilst
the converse is also true, i.e. the oxyhaemoglobin of man, of the rabbit,
the sheep, and the ox, all of which are exceedingly soluble, yield crystals
with considerable difficulty. It was, indeed, long supposed to be impos-
sible to obtain large quantities of oxyhaemoglobin from the blood of
certain of these animals.

• As a rule, crystals of oxyhaemoglobin are of such a size that their
form, and even their crystalline nature, cannot be made out by the
naked eye. The blood of certain animals, however, as the dog, and
particularly the horse, yields under favourable circumstances rhombic
prisms of macroscopic size. From horse's blood Hoppe-Seyler frequently
obtained prisms over 5 mm. in length and 4 mm. in thickness. The
colour of crystals of oxyhaemoglobin appears different, according to
their size or the number aggregated together.4 Thus the finest needles
or prisms of oxyhaemoglobin, when seen singly under the microscope,
appear almost colourless, or possess the yellowish tint characteristic of
the coloured corpuscles. On the other hand, large crystals, or consider-

1 From the results of Hiifner's analyses of the haemoglobin of the ox, but substituting
his most recent determinations (1894) of the iron for the older ones, published in 1887, I
have calculated for the haemoglobin of this animal the formula —

C759H1208N210S2Fe0204

2 G. Bunge, "Text-Book of Physiological and Pathological Chemistry." Translated by
L. G. Wooldridge : London, 1890, p. 24.

3 It was Dr. Otto Funke who first asserted, as the result of his own researches, " that
all blood is capable of crystallisation, whatever animal or organ it may be taken from."-
" Explanation of the Plates" of his "Atlas of Physiological Chemistry," p. 15 (see p. 205,
note 1).

4 F. Hoppe-Seyler, "Das Oxyhamoglobin des Pferdeblutes," Ztsclir. f. physiol, Chcm.,
Strassburg, 1878-79, Bd, ii, S, 149.

204 HAEMOGLOBIN.

able aggregations of the smaller crystals, exhibit, like aggregations of
Mood corpuscles, the red colour characteristic of the blood.

We shall now examine successively the most important facts con-
nected with the (1) form, (2) quantity of water of crystallisation,
(3) solubility, presented by crystallised oxyhsemoglobin, (4) diffusibility.

1. Form. — (a) The blood of man and of the immense majority of
animals yields oxyheemoglobin which crystallises in rhombic prisms or
needles belonging to the rhombic system.

(&) The oxyhtemoglobin of the guinea-pig presents crystals which
were described by Lehinann as regular octohedra. They were, however,
shown by the eminent crystallographer v. Lang1 to be tetrahedra
belonging to the rhombic system.

The blood of certain birds,2 and occasionally apparently of the
rat 3, 4, 5, yields crystals of the same form.

(c) The oxyhremoglobin of the squirrel crystallises normally in the
form of six-sided plates belonging, as proved by v. Lang, to the hexagonal
system. These crystals had been first described by Lehmann and Kunde.
The blood of the hamster (Cricetus vulgaris) contains oxyhaemoglobin
which crystallises, as Lehmann showed, in rhombohedra and six-sided
plates belonging to the hexagonal system. Halliburton,6 who has studied
the crystallography of oxyhaemoglobin with great care, has made the
interesting observation that " after recrystallising squirrel's hc^moglobin
several times the hexagonal constitution of the crystals is broken down,
and the crystals obtained are either rhombic prisms or a mixture of
these with rhombic tetrahedra."

Rollett,7 taking for granted that oxyhsemoglobin, from whatever source
obtained, possessed the same chemical composition, argued, from the fact of
its crystallising generally in the rhombic, but in the case of the squirrel in the
hexagonal system, that oxyhaemoglobin should be looked upon as dimorphous.

Halliburton, however, with perfect correctness, hesitates to admit this
view, which could only be held if we were certain that the haemoglobins whose
crystals belong to different systems possess identical composition, and suggests
that perhaps the difference in the crystalline form, as well as the difference in
solubility of the haemoglobins which crystallise differently, depends upon
varying quantities of water of crystallisation — that, in fact, the haemoglobins
which crystallise in different systems represent "different hydrates of oxy-
haemoglobin." 8 This may be the case, though it appears to me that the cause
of the difference lies deeper.

It has been previously stated — and the grounds for the statement will be
given in a subsequent section — that, notwithstanding the perplexingly dis-
cordant results of the analyses of oxyhaemoglobin, there is, in the haemoglobin
of all animals, absolute identity of the essential iron-containing nucleus, i.e.

1 In a paper by A. Rollett, entitled "Versuche u. Beobachtungen am Blut, nebst
krystallographisch. u. optisch. Mittheilmigen ueber die Blutkrystalle von v. Lang,"
Sitzungsb. d. k. Akad. d. Wissenseh., Wien, 1862, Bd. xlvi. S. 66-98.

" Halliburton, "Text Book of Chemical Physiology," London, 1891, S. 270.

3, 4 Kunde, Lehmann, see Preyer, "Die Blutkrystalle, " S. 38.

5 Hoppe-Seyler, "Ueber die Krystallformen der Blutkrystalle," Med. Ohem. Untersuch. ,
Berlin, 1868, S. 195.

6 "Preliminary Communication on the Haemoglobin Crystals of Rodents," Journ.
PhysioL, Cambridge and London, 1886, vol. vii. p. 2 ; Quart. Journ. Micr. Sc., London,
vol. xxviii. p. 181.

7 LOG tit.

8 Halliburton, "Text Book of Chemical Physiology," section on the "Crystallography of
Oxyhfiemoglobin," pp. 270-274. The student is recommended to read this interesting and
suggestive section.

THE WATER OF CRYSTALLISATION,

205

of that moiety of the molecule on which its colour and its physiological func-
tion depends. At the same time, there is such a difference in the ratio of
S : Fe in the haemoglobin of certain animals as renders it highly probable, or
rather certain, that, in the haemoglobin of different animal groups, the albu-
minous moiety of the complex molecule differs. Such being the case, it is not
surprising that certain of the physical characters of haemoglobin, such as
crystalline form and solubility, should exhibit variations.1 Nor can we lose
sight of the possibility, to which I have already drawn attention, that the
differences in the haemoglobins of certain animals may be due to their being
formed by the linking of the iron-containing molecule with different polymers
of the same albuminous group. The existence of haemoglobins varying some-
what in their percentage of iron renders this view highly probable.

2. Quantity of water of crystallisation. — Remarkable difficulties
encounter the observer in his attempts to determine the amount of
water of crystallisation of oxyha^moglobin, and considerable discrepancies
are to be noticed in the results obtained by different processes.

In order to make the determination, pure oxyh&moglobin is dried
in vacuo at 0° C., and after ceasing to lose weight under these conditions
it is heated to a temperature of 115° C.

The following are some of the principal and most reliable results
obtained : —

Water of

Oxyhsemoglobin.

Crystallisation

Authority.

per cent.

Dog.
Horse

3-4
3-94

Hoppe-Seyler.
Hiifner.

Pig ...

5-9

Otto.

Guinea-pig

6

Hoppe-Seyler.

Squirrel .

9

Hoppe-Seyler.

According to Bohr,2 the water of crystallisation of oxy haemoglobin may
vary in amount between 1*2 and 6 '3 per cent., but these results, like others
obtained by the same author, and to which reference has been made (see p.
192), are explicable by the fact that his preparations of haemoglobin did not
represent the pure substance, and contained products of decomposition.

Without taking Bohr's results into consideration, there can be no
doubt that crystals of oxyhremoglobin of different animals exhibit
differences in the amount of water of crystallisation. Assuming the
above results to be correct, the highly soluble oxyhgemoglobiii of the
pig, which crystallises in rhombic prisms, possesses the same amount of
water of crystallisation as the very sparingly soluble oxyhamioglobin of
the guinea-pig, separating in the form of tetrahedra.

3. Solubility. — The difficulties which encounter the observer in

1 The reader is referred to an admirable account of all the researches on the Crystal-
lography of Haemoglobin, up to the date of its publication (1871), to the chapter entitled
" Krystallformen des Blutroths," in Preyer's work, "Die Blutkry stalle. " Very fine
coloured engravings of the haemoglobin crystals of various animals — amongst others, of
man, the guinea-pig, and the squirrel — are to be seen in Funke's "Atlas of Physiological
Chemistry," being a Supplement to Lehmann's "Physiological Chemistry,' London,
printed for the Cavendish Society, 1853. See plate x. and pp. 15-17 of the appended
letterpress.

2 "Exp. Untersuchungen it. die Sauerstoffaufnahme des Blutfarbstoffes, " Copenhagen,
1885.

206 HEMOGLOBIN.

determining the water of crystallisation of the blood-colouring matter
are surpassed by those attending the estimation of its solubility. It is
doubtless in some measure due to the difficulty, almost the impossibility,
of eliminating every trace of certain of the reagents (especially the
alcohol), employed in the preparation of the body, that any attempts
to determine with precision the solubility of oxyhsemoglobin have
failed. The chief cause of the discrepancies between the observations
of different observers is, however, probably that they were unaware
of the physical, and perhaps also chemical, changes which haemoglobin
undergoes in the process of recrystallisation.

The oxyhaamoglobin of all birds, of the ox, of the pig, and of man
is distinguished by its great solubility, the relative solubility increasing
in the above order. Next in order of solubility comes the haemoglobin
of the horse, dog, squirrel, guinea-pig, and rat, the latter being certainly
the least soluble.

According to C. Schmidt, 100 grms. of water at 18° C. dissolve 15 '59 grms.
of the crystallised oxyhsemoglobin of the dog. From the fact that the oxy-
hsemoglobin analysed by C. Schmidt when ignited yielded on an average 0'91
per cent, of P205, we are in a position to state that the body he experimented
with was very impure, and consequently that his estimate of its solubility in
water possesses no value. Hoppe-Seyler found that 100 c.c. of water at
5° C. dissolved 2 grms. of the dry oxyhsemoglobin of the dog.

Lehmann found that one part of the dry crystallised oxyhsemoglobin of
the guinea-pig required 597 parts of water to dissolve it, but the temperature
at which the determination was made is not stated ; l moreover, it is more
than doubtful whether the substance experimented with was pure.

The present state of our knowledge permits us, therefore, to state
that the oxyheemoglobin of different animals differs in no property so
remarkably as in its solubility in water. It appears, further, that oxy-
haemoglobin — which, according to the more recent researches, contains
the same percentage of iron (that of the horse, ox, dog, and pig), and
therefore presumably possesses the same molecular weight, and which,
further, crystallises in the same manner — exhibits marked differences in
solubility. As the oxyhaemoglobins of the horse and of the dog seem,
in so far as the water of crystallisation is concerned, to be identical,
and as the researches of Hiifner and his school have proved the identity
of the iron-containing part of the molecule in the haemoglobin from the
most different animals, we are, it appears to me, driven to the con-
clusion that the difference in solubility must le due to differences in
the albuminous residue in the haemoglobin molecule.

Solubility in liquids other than water. — Oxyhaemoglobin is soluble in
highly diluted solutions of ammonia, and the other caustic alkalies, and
their carbonates. These solutions resist decomposition much longer
than aqueous solutions of haemoglobin.2 Kiihne states that a highly
dilute ammoniacal solution of oxyhamioglobin will remain in great part
unchanged for several weeks at ordinary temperatures. Stronger
solutions of the caustic alkalies or their carbonates induce decom-

1 W. Preyer, "Die Blutkrystalle, " S. 55.

2 Based upon these facts is the method, introduced by Hiifner, of diluting blood or
solutions of oxyhsemoglobin with solutions containing O'l per cent, of NaOH. Such
solutions are much more transparent than purely aqueous solutions, and are therefore
most valuable for the purposes of spectroscopic researches.

ACTION OF REAGENTS ON OXYH^EMOGLOBIN. 207

position of ox y hemoglobin with a rapidity which depends upon their
concentration.

Oxyhaemoglobin is soluble in highly diluted alcohol, the solutions
resisting putrefaction much longer than aqueous solutions. By contact
with even highly dilute alcohol, crystals of oxyhsemoglobin become much
more sparingly soluble in water. Oxyhaemoglobin is insoluble in absolute
alcohol. When crystallised oxyhaenioglobin is treated with a large excess
of absolute alcohol, it is under favourable circumstances converted into an
insoluble crystalline modification, to which Nencki and Sieber have
given the name of parahcemoglobin.1 This body cannot be looked upon
as a chemical individual. Oxyhaemoglobin is insoluble in chloroform,
benzol, and carbon disulphide.

4. Diffusibility. — Oxy haemoglobin offers a remarkable example of a
soluble crystalline body, which, judged by its power to pass through a
septum of parchment paper, must be declared to be absolutely non-
diffusible. This character depends upon the enormous size of its
molecule.

Comparison of the action of certain reagents on solutions of
oxyheemoglobin and on solutions of albuminous bodies. — It has
already been incidentally stated that in haemoglobin an iron-containing
body is linked to an albuminous body or bodies, and reference has been
made to the fact that, under the action of various agents, oxyhaemoglobin
breaks up into the iron-containing hsematin, and into albuminous bodies.
Although the decomposition of haemoglobin and its products will be con-
sidered in some detail in a future section, it is convenient in this place
to refer to this point, and to state that when oxyhaemoglobin is decom-
posed so as to yield hsematin and albuminous substances, the former
amounts approximately to 4 per cent, and the latter to 96 per cent, of
the original hemoglobin.

Such being the case, it is of particular interest to contrast the
action of certain reagents on solutions of albuminous bodies, and on
solutions of oxyhaemoglobin.

Solutions of oxyhaemoglobin differ remarkably from solutions of
albuminous bodies in their behaviour towards a large number of
reagents.

As Klilme pointed out long ago,2 all those tests for albumin which
do not immediately bring about a decomposition of oxyhaemoglobin,
furnish a negative result when applied to aqueous solutions of this
body. Cupric and ferrous sulphates, mercuric chloride, silver nitrate,
neutral and basic acetates of lead, all of which precipitate albuminous
solutions, occasion (so long as the body remains undecomposed) no pre-
cipitate— not even cloudiness — when added to solution of oxyhaemo-
globin. So soon, however, as the red colour of oxyhaemoglobin has
disappeared under the action of any one of the above salts, and the
brown colour due to haematin has appeared (a result which they all
sooner or later bring about), the characteristic albuminous precipitates
appear.

1 M. Nencki und N. Sieber, " Untersuch. ueber die Blutfarbstoff, " Ber. d. deutsch.
chem. Gesdhcli., Berlin, 1885, Bd. xviii. S. 392 ; M. Nencki und B. Lachowitz, "Ueber das
Parahiimoglobin," Hid., Bd. xviii. S. 2126. The reader is referred for a criticism of Nencki
and Sieber's researches on parahtemoglobin, to a paper by Hoppe-Seyler, entitled "Ueber
Blutfarbstoffe und ibre Zersetzungsproducte, " Ztschr. f, physiol. Chem., Strassburg, 1886,
Bd. x. S. 531.

2 "Lehrbuch der physiolog. Chemie," Leipzig, 1866, S. 207.

208 HAEMOGLOBIN.

Other reagents which bring about an instant decomposition of
oxyhsemoglobin, and, consequently, instantly set free the albuminous
matter, exhibit also, as might have been anticipated, the characteristic
albumin reactions, i.e. behave towards a solution of haemoglobin as if
it were a solution of a native albumin. This remark applies to acetic
acid and potassium ferrocyanide, to mercuric nitrate, to the concentrated
mineral acids — reagents, all of which precipitate a solution of oxyhasino-
globin as they do solutions containing albuminous bodies.

When subjected to the action of heat, solutions of oxyhsemoglobin
coagulate like solutions of the native albumins; but, doubtless, before
the temperature of coagulation (64° to 68°'5 C.) is reached, the complex
haemoglobin molecule has already been decomposed — a supposition
which is suggested by the following^observation : l — If to an aqueous
solution of crystallised oxyhaemoglobin of the dog a small quantity
of sodium carbonate be added, on applying heat no coagulation occurs,
even though the temperature be raised to 100° C. When, however, the
temperature reaches 54° C., the colour of the solution instantly changes to
deep brown, and spectroscopic examination indicates that the spectrum
of oxyhsemoglobin has been replaced by that of alkaline hsematin.

THE ABSORPTION OF LIGHT BY OXYH^MOGLOBIN.

(a) The visible spectrum.— Historical notes.— The researches of
Brewster and Herschel had shown that absorption-bands occur in the
spectrum of light which has been passed through certain coloured gases,
vapours, and coloured solutions, and the so-called absorption spectra of indigo
and chlorophyll had been described before the time when Hoppe 2 made the
discovery of the beautiful absorption spectrum of blood, distinguished by
two very characteristic absorption-bands, situated in the Tegion which inter-
venes between the lines of Frauenhofer, D and E.

This discovery at once enabled Hoppe to affirm that haematin, which had
up to that time been generally looked upon as the true blood-colouring matter,
does not exist as such in the blood corpuscles, but that it is a product of the
decomposition of the colouring matter ; that the latter, to which he afterwards
gave the name of hemoglobin, and which he recognised as forming the so-called
blood crystals described by Kunde, Lehmann, and Funke, is the cause of the
absorption-bands which lie had discovered in the spectrum of diluted blood,
and that this colouring matter, under the influence of heat, acids, and various
other chemical agents, splits up into hsematin and an albuminous substance or
substances.

There can be no question that, although Hoppe, in a certain measure,
appreciated the immense value of the knowledge which he had gained by his
study of the optical properties of the blood, the full light which it was
destined to shed on the function of the blood- colouring matter was only
recognised when Professor Stokes, two years later, published his paper " On
the Reduction and Oxidation of the Colouring Matter of the Blood."8 The
new facts acquired by the combination of chemical and optical methods in
this research, and which at once shed a flood of light on phenomena which
had until then been shrouded in darkness, enlisted as workers in this field

1 Preyer, "Die Blutkrystalle," S. 61.

2 Hoppe only assumed the name of Hoppe-Seyler in 1864. The paper containing
his first observations on the spectrum of the blood bore the following title :• — Professor
Hoppe in Tubingen, "Ueber das Verhalten des Blutfarbstoffes ini Spectrum des
Sonnenlichtes," Virchow's Arcliiv, 1862, Bd. xxiii. S. 446-449.

3 Proc. Roy. Soc. London, 1864, vol. xiii. p. 357.

VISIBLE SPECTRUM OF OXYH^MOGLOBIN. 209

many persons of distinction in all countries, amongst the first and most
successful of whom were W. Preyer1 in Germany, and Sorby and Ray
Lankester in England. Amongst all, however, who by their work have
contributed to the spectroscopic investigation of the blood, two appear to
me to stand out pre-eminently — these are Vierordt and Hiifner. By the dis-
covery of the first practical method of determining the extinction-coefficient
of coloured liquids, and his elaboration of a general method for the
quantitative analysis of colouring matters, a method capable of surprising
refinement and accuracy, and which is based upon the relation which exists
between the extinction-coefficient and concentration, Vierordt has placed
both the sciences of physics and physiology under a lasting obligation.2
To Hiifner belongs the merit of having developed and perfected the
methods of spectrophotometry, but especially of employing it so as to obtain
results of paramount importance to physiology, and which would have been
unattainable without its aid. Not only has he, by his own long-continued
researches, and those of his pupils, determined the spectrophotometric con-
stants of haemoglobin and its compounds with oxygen and carbonic oxide,
but he has by spectrophotometry succeeded in determining the absolute
and relative amounts of reduced and oxyhaemoglobiii existing side by side
in the blood. He has further shown that, as we now know the volume of
oxygen which can combine with 1 grm. of haemoglobin, by determining the
amount of haemoglobin and of oxyhsemoglobin coexisting in any specimen of
blood, we possess data enabling us to calculate the volume of the dissociable
or respiratory oxygen of the blood, without having recourse to direct deter-
minations by means of the mercurial pump and gas analysis.

Further, by the method of spectrophotometry, combined with the results
of chemical investigation, Hiifner has furnished us with the proof that, in
spite of the differences in many physical characters, and even in centesimal
composition presented by the blood-colouring matter of different animals, the
coloured iron-containing group existing in haemoglobin, upon which its essen-
tial physiological functions depend, is identical in all.3

General description of the visible spectrum of oxyhsemoglobin.
— Instruments required. — For the study of the visible, as distinguished from
the photographic spectrum of the blood, or of oxyhaemoglobin, the spectro-
scopes which are in common use in physical and chemical laboratories may be
employed, providing the dispersion of their prisms be not too great. A
spectroscope of the ordinary Bunsen type, provided with a single good flint-
glass prism, is infinitely to be preferred for the study of absorption spectra to
an instrument with two prisms, for, with the greater dispersion, absorption-
bands appear much less clearly defined than with the smaller. Direct vision
spectroscopes of the Browning or Hofmann patterns, or microspectroscopes,
i.e. direct vision spectroscopes adapted to the eyepiece of the compound
microscope, may be employed ; and the second class of these instruments
renders great services in the investigation of minute quantities of colouring
matters — as, for instance, in the examination of the optical characters of
the colouring matters of the tissues.

It is advisable, indeed for the purposes of original research indispensable,
that the spectroscope employed should furnish means of determining accur-

1 Preyer's monograph, entitled "Die Blutkrystalle, " which appeared in Jena in 1871,
still continues indispensable to the physiological chemist. It is replete with original
observations of "great value, and establishes that Preyer had no unimportant share in the
development of our knowledge of the blood-colouring matter.

2 Karl Vierordt, "Die Anwendung des Spektral-apparates zur Photometric der Absorp-
tionsspektren und zur quantitative!! chemischen Analyse," Tubingen, 1873; "Die
quantitative Spektralanalyse in ihrer Anwendung auf Physiologic, Physik, Chemie, und
Technologic," Tubingen, 1876.

3 As the chief of Hiifner's papers have been already quoted, or will be referred to sub-
sequently in detail, their dates and titles are not given in this place.

VOL. I. — 14

210 HEMOGLOBIN.

ately the position of any line or the boundaries of any absorption-band
observed in the spectrum, it being usual to express the position in terms of
the wave length of the light corresponding to it. With this object the
spectrum of sunlight is observed, and the position of the principal lines of
Frauenhofer is determined in reference to the divisions of the photographic
scale, or, in the case of the finer spectroscopes and spectrometers, in reference
to the divisions of the graduated circle of the instrument. From the results
of these observations a curve is readily plotted, enabling the experimenter at
any time to convert the readings of the arbitrary scale of his instrument into
wave lengths.1

For all exact spectroscopic work the eyepiece of the spectroscope should
be provided with cross-threads ; and, when employed in the investigation of
absorption spectra, if possible with the arrangement employed in spectro-
photometry, which enables the observer* to limit, by a variable slit in the
eyepiece, any particular spectral region and to shut out of the field of view
the remainder of the spectrum.

As a source of light, for some investigations the light of the sun reflected
from the mirror of a heliostat driven by clock-work is desirable ; for general
purposes the light of the sun, reflected from a white surface, may be employed.
Artificial sources of illumination possess the great advantage of being available
at all times, and susceptible of considerable constancy. A gas lamp, furnished
with the Auer incandescent burner, is the best of all lamps for the examina-
tion of absorption spectra.

In examining the absorption-spectra of liquids, it is convenient to employ
cells or troughs with perfectly parallel glass or quartz sides, which are a
definite width apart. Such vessels are made according to the model of
Hoppe-Seyler, and sold under the name of hcematinometers (Fig. 23), the
internal surface of the parallel glass plates being exactly 1 cm. apart, and the
little trough being so arranged as to be readily taken to pieces for cleaning.
The small troughs employed in spectrophotometry, and which are usually
constructed with great care, are well adapted to the general purposes of the
spectroscopist.

Instead of a vessel of which the sides are at a constant and known dis-
tance apart, it is convenient for many purposes to employ the so-called
hcematoscope, or licemoscope, of Hermann,2 as shown in the accompanying
woodcut (see Fig. 24). F is a glass plate, forming the anterior wall of the
tube D, which is supported on the stand A. C is a metallic tube, sliding in
and out of the tube D, and closed anteriorly by a glass plate parallel to F. E
is a funnel communicating with the interior of D F B. By sliding the piston
C in and out of the tube I), the capacity of the vessel I) F B and the
depth of a stratum of liquid contained between the two glass plates, may be
modified at will within wide limits.

The depth of the stratum is read off by the aid of a millimetre scale,
engraved on the sliding tube C.

As the absorption of light passing through a coloured liquid depends
upon the number of absorbing molecules in its path, by doubling the thick-
ness of the stratum of a coloured liquid examined, we obtain the same result
as by examining a solution of double concentration. With such a contrivance
as the hsematoscope, we are, within certain limits, able therefore to obtain the
same result with a solution of constant concentration as with a large number
of solutions of which the concentration varies in known proportions.

1 In a work intended for the advanced student of physiology, it appears superfluous to
enter into such details concerning the construction of the spectroscope, or the method of
working with it, as can be learned in all courses of practical physics, or may be found in
any elementary treatise devoted to this branch of science.

2 " Notizen fur Vorlesungs und andere Versuche," Arch. f. d. ges. Physiol., Bonn,
Bd. iv. S. 209.

VISIBLE SPECTRUM OF OXYH^EMOGLOBIN.

21 I

The spectrum as seen with solutions of varying concentration. —

When well-arterialised defibriiiated blood (containing on an average
from 12 to 14 per cent, of oxyhsemoglobin) is diluted with nine times
its volume of distilled water, and a stratum 1 cm. thick is brought before
the slit of the spectroscope, it will be found that the whole of the
spectrum is absorbed, with the exception of the red end, or rather of
those rays having a wave length greater than about 600 millionths of
a millimetre (X 600).

If, now, the blood solution be gradually diluted, a point is reached
at which the spectrum is (proceeding from the red end) clear up to D
(\ 598), and a strip of green is visible between I and F (x 518'3-X 486'1).
Between D and b the absorption is intense (see Plate I., Spectrum 4),
and beyond F no trace of light appears. On diluting still further, that

FIG. 23. — The hseinatinometer.

FIG. 24. — The lisematoscope.

which appeared as a single wide absorption-band between D and b, and
afterwards as the solution was progressively diluted between D and E,
is seen to resolve itself into two distinct absorption-bands, separated by
a green interspace ; the violet end of the spectrum is still powerfully
absorbed (Plate I., Spectrum 3).

Of the two absorption-bands just referred to, the one next to D is
narrower than its fellow ; it has more sharply denned borders, and to the
eye appears more intense ; its centre corresponds to X 579, and we may
conveniently distinguish it as the absorption-band a in the spectrum of
oxyheemoglobin.

The second of these absorption-bands, i.e. the one next to E, which
we shall designate the band /3, is broader, has less sharply-defined edges,
and its centre corresponds approximately to X 553*8. Between the two
bands is a green interspace.

On diluting the solution more and more largely, and continuing to
examine a stratum 1 cm. thick, the absorption of the violet end becomes

212

HAEMOGLOBIN.

less and less, and the whole spectrum as far as G- appears beautifully
clear, except where the two absorption-bands are situated (Plate I.,
Spectrum 2). If dilution be pushed still further, these disappear ; before
they vanish they appear as faint shadows across the limited region which
they occupy. The band a is said to disappear last. I find, however, that
whenever I can detect a I am able to detect a faint shadow in the
position of X 540-X 550. When the bands are just perceptible, there is
no obvious absorption of either the red or the violet end of the spectrum.
The two absorption-bands of oxyhaemoglobin are seen in greatest
perfection when a stratum 1 cm. thick of a solution containing 1 part
per 1000 of oxyhaemoglobin is examined; this corresponds to a solution
made by diluting from 1-2-14 parts of blood to 100. They are still
perceptible when the solution contains *L part oxyhtemoglobin in 100,000
parts of water (1 grm. in 10 litres).

OXYILEMOGLOBIN.

ABC

ABC D

FIG. 25. — Graphic representation of the spectrum of oxyhaemoglobin and
htemoglobin. The numbers on the right are percentages. — After
Kollett.

The above figure illustrates a method of representing graphically
the variations in the spectrum of the blood-colouring matter, correspond-
ing to all concentrations (a stratum of 1 c.c. being examined).1

In these diagrams the position of the principal Frauenhofer lines
is shown ; the numbers on the right indicate percentages of the blood-
colouring matter. The shaded part of the diagram indicates absorp-
tion of light. By drawing lines parallel to the abscissae we at once
observe the character of the absorption spectrum which corresponds
to the concentration indicated at the right-hand side of each diagram.
Thus, by inspection of the left-hand diagram, we learn that solutions of
oxyhaemoglobin, containing more than 0*65 per cent., exhibit a single
broad absorption-band in the visible spectrum, owing to the fact that
the two absorption-bands « and /3 have run together, and that the
green interspace between ~b and F is shown only by solutions of less
concentration than from O8 to 0*9 per cent. When the absorption of
this part of the spectrum is complete, only orange and red remain
unabsorbed.

By placing the solution of oxyhaemoglobin in a wedge-shaped cell,

1 A. Rollett, "PhysioloeiedesBlutes," Hermann's "Handbuch," Leipzig, 1880, Bd. iv.
Th. 1, S. 48.

THEOR Y 6- METHODS OF SPECTRO PHOTO ME TRY. 213

the slit being perpendicular to the edge of the wedge, the accuracy of
the diagram can be realised objectively, each section of the slit forming
a spectrum corresponding with a given thickness of stratum, which
increases in a continuous manner from the edge towards the base of the
wedge. This method of examination was first employed by J. H. Glad-
stone.1

The theory and methods of spectrophotometry.— The spectro-
photometric constants of oxyhsemoglobin — (a) The theory. — Inte-
resting and attractive though it undoubtedly is, the examination of an
absorption-spectrum, or the comparison of allied absorption-spectra, by
the unaided sense of sight, may be singularly deceptive.

The impression which the unaided eye enables us to form of the
boundaries, the breadth, the intensity of an absorption-band, or of the
extent and depth of a less defined general absorption, is often very
fallacious. When, for instance, the absorption of a definite region of the
spectrum commences and ceases abruptly, the band appears to the eye
more intense than when the absorption commences and ceases more
gradually.2 The most striking illustration of the truth of these remarks
is indeed furnished by the two oxyhaemoglobin bands. The first, less
refrangible band («), has always been described as much more intense
than the second, which is broader and less sharply defined, and un-
questionably this is the impression which we form by ordinary methods
of examination. Vierordt 3 has, however, shown that, in opposition to
the visual impression, a greater percentage of light is absorbed in the
spectral region which corresponds to the second band than in that
corresponding to the first band. Measuring, spectrophotometrically, the
percentage of light remaining unabsorbed, after traversing a stratum 1 cm.
broad of a solution containing 1 per cent, of defibrinated mammalian
blood, he found that in the region of the first, apparently more intense
band, 87 per cent, of the light was absorbed and 13 per cent, trans-
mitted ; whilst in the region of the second, apparently less intense band,
90 per cent, of the light was absorbed, and only 10 per cent, transmitted.

This result at once suggests the necessity of a method of determin-
ing quantitatively the amount of light absorbed by any medium whose
absorption-spectrum forms the subject of investigation, instead of trusting
to our unaided sense of sight. When, however, we are made acquainted
with the remarkable and far-reaching conclusions which can be legiti-
mately drawn from an accurate determination of the percentage of light
of a definite wave length, absorbed by colouring matters existing in
solution, the beauty and the importance of the method of spectrophoto-
metry become apparent. Until Yierordt's discovery, those coloured
bodies whose visible spectrum presented no definite absorption-bands,
were held to be beyond the scope of spectroscopic research. Now, how-
ever, we know that a photometric study of the spectrum affords us not
only the means of identifying them, but supplies us with a method
for the quantitative analysis of colouring matters, surpassing all others
in accuracy, and permitting, in certain cases, of the accurate determination
of data not to be ascertained in any other way.

1 J. H. Gladstone, "On the Use of the Prism in Qualitative Analysis," Journ. Chem.
Soc., London, 1858, vol. x. p. 79.

2 A. Rollett, "PhysiologiedesBlutes," Hermann's "Handbuch," Leipzig, 1880, Bd. iv.
Th. 1, S. 50.

3 "Die Anwendung des Spektral-apparates zur Photometric der Absorptionsspektren,"
Tubingen, 1873.

2i4 HEMOGLOBIN.

1. Relation between the concentration of a solution and the percentage
of light absorbed by it. — Before investigating the theory of the methods
of spectrophotometry, to be subsequently described, it is essential to
examine (1) the relation which exists between the power of light
absorption exerted by a coloured liquid of constant composition and the
thickness of the layer traversed ; (2) to study the influence of concen-
tration on the absorption of light by a stratum of a liquid holding a
colouring matter in solution.

It was shown by Lambert that if light of intensity /, by transmission
through one layer of an absorbing medium of thickness 1, has its in-

tensity reduced to 7- =. - by transmission through d such layers, the

T?/ 7Z/

final intensity of the light, which we Shall represent by /', will be re-
duced to — , i.e. I' = —. Beer showed that Lambert's law holds good,

not only for transparent solid media, but also for liquids, i.e. that the
amount of light absorbed by a solution of a given colouring matter of con-
stant concentration is dependent upon the thickness of the stratum?- This
law is only true, however, in respect to monochromatic light.

We must now examine the influence of the concentration of a liquid
containing a colouring matter in solution upon the percentage of light
which it absorbs and transmits, when the stratum examined remains of a
constant width, 1. It has been experimentally proved that the absorp-
tion exerted by a stratum of a coloured solution of known width is
equal to that exerted by a stratum twice as thick of a solution of half
the concentration ; i.e. the absorption which light undergoes in passing
through a stratum of coloured liquid of unit thickness increases propor-
tionally to the concentration.

2. Definition of the " extinction-coefficient." — In their photo-chemical
researches, studying the comparative absorption of light by different
gases, Bunsen and Roscoe'2 introduced the conception of, and defined,
the so-called extinction-coefficient. They ascertained the relative thick-
nesses of the strata of various media required to reduce the intensity
of light passed through them to one-tenth of its initial value, and defined
the extinction-coefficient as the reciprocal of the number expressing the
width of the stratum of a given medium., required to reduce the intensity of
light passed through it to one-tenth its initial value.

For any given coloured medium, e.g. a solution of a colouring matter
of a definite strength, there must be a definite thickness of layer which
we shall call d, capable of reducing the intensity of light to one-tenth

its original value. The reciprocal of d is -v, and if by e we represent
the extinction-coefficient,

As will be shown in the sequel, the method of spectrophotometry
discovered by Vierordt rests upon the determination of this constant g,
for particular, very limited, regions of the spectrum. The practical diffi-
culties of varying the thickness of the stratum of a coloured liquid, until

1 When the thicknesses of various strata increase in arithmetical, the intensities of
the light decrease in geometrical, ratio.

2 Ann. d. Chem., Leipzig, 1857, Bd. ci. S. 238.

THEORY 6- METHODS OF SPECTRO PHOTO ME TRY. 215

the intensity of the light remaining unabsorbed is reduced precisely to
one-tenth, would be extremely great. Fortunately, the coefficient of
extinction can be determined in a manner presenting far smaller practical
difficulties and admitting of great accuracy.

If, instead of varying the thickness of the stratum of the coloured
solution until the initial intensity of the light entering it is reduced to
one-tenth its value, we invariably examine in our photometric investi-
gations a stratum of unit width (say 1 cm.), or a stratum of known
width, and possess the means of estimating the proportion of light which
remains unabsorbed, we possess data enabling us to calculate the ex-
tinction-coefficient.

It was previously shown that /' == — and that g = -3, and when x = d,
T — yV Then log I' = — x log n, and d log n = l .\s = log n = — - ;

so that, if the thickness of the stratum traversed by the light be known,
and the intensity of the unabsorbed light /' ascertained, the coefficient
e can be calculated. But if x be of the constant value 1 (say 1 cm.),
then B = — log /'; that is to say, the extinction-coefficient is equal to the
negative logarithm of the unabsorbed light. Let us suppose that by pass-
ing through a stratum of coloured solution 1 cm. wide, the intensity of
light has been reduced to two-thirds its original value, then

2
6 = — log 9 = log 3 — log 2

J = 0176091

3. Definition of the term " absorption relation!' — It has already been
stated (see previous page) that the more concentrated a coloured liquid,
the greater its absorbing power, the smaller, therefore, is the width of
the stratum required to reduce the intensity of the light passed through
it to one-tenth of its initial value. As the extinction-coefficient is, by
definition, the reciprocal of the thickness of the stratum required to
bring about this result, it follows that the greater the concentration of
the solution, the greater will be the extinction-coefficient ; in other words,
the extinction-coefficient g and the concentration c are proportional.
Let c and cf represent the concentration of two coloured solutions, of
which the extinction-coefficients are g and g' respectively, then

c c
and - = — = A

z z

i.e. the relation of the concentration of a coloured solution to its extinction-
coefficient is a constant, represented ly A, and termed the "Absorption-
relation " (Absorptionsverhciltniss, Vierordt). Upon the determination of
this constant rests Vierordt's method of quantitative spectrophotometric
analysis. If we have, in the case of a solution of a particular body,
determined by analysis its concentration c, and then with the spectro-
photometer determined its extinction-coefficient for a particular spectral
region, and thus obtained the value of A, we • can find out how much
of the same substance is contained in a solution of unknown strength
(c') by merely determining g', according to the equation ;

c' = As,

216

HAEMOGLOBIN.

It is usual to determine the value of the constant A of any coloured
body under examination for, at least, two spectral regions. The reasons
for this practice will appear in the sequel.

(b) The actual methods of spectrophotometry. --The elementary theo-
retical discussion of the theory of spectrophotometry which has preceded has
shown that, as developed by Yierordt, it resolves itself into the determination
of the extinction-coefficient and of the absorption relation of coloured bodies,
and that the optical investigation is concerned with, and confined to, the
determination of the value of e. We have now to consider the two principal
methods by which this determination can be effected.

Vierordt's method. — For the determination of the extinction-coefficient
according to the original method of Yierordt, any good spectroscope of the
type introduced by Bunsen for laboratory purposes may be employed, provided
certain modifications and additions are made. The most essential of these
modifications consists in replacing the usual single slit of the collimator by a
double slit, i.e. by a slit composed of two independent halves — an upper one
and a lower one — each of which is controlled by a micrometer screw provided
with a divided circle or drum, so that the width of each half of the slit may
be ascertained by direct reading (see Fig. 26). In so-called symmetrical slits,

FIG. 26. — Double slit employed in Vierordt's method of spectrophoto-
metry, as adjusted to their spectrophotometers by the Brothers
Kriiss of Hamburg.

both edges of the slit move symmetrically. When the two halves of such a
slit are of the saine width, if the illumination be uniform, the observer, on
looking through the telescope of the spectroscope, observes two superposed
spectra of equal brightness. If one slit be narrower than the other, the
illumination of the corresponding spectrum will be diminished in proportion.

The second modification which has to be made in the ordinary spectro-
scope consists in substituting for the usual eyepiece, one which is provided
with a slit for isolating any desired region of the spectrum, the remainder of the
spectrum being concealed from view. In Yierordt's original instrument this slit
was formed by two lateral shutters, moving in the focal plane of the eyepiece,
which could be approximated to any desired extent. This simple contrivance
has been perfected by Hiifner, and adapted to his beautiful spectrophotometer.
A very ingeniously contrived and readily adjusted slit has been devised by the
Brothers Kriiss of Hamburg, and adapted to the spectrophotometers made by

METHODS OF SPECTROPHOTOMETR Y.

217

their firm. Whatever the precise form of the slit in the eyepiece, it must
permit of the isolation of a perfectly denned spectral region, and of the precise
determination of the limits of that region, these being expressed in wave
lengths.1 For all coloured solutions there are regions in which the absorption
of light is peculiarly distinctive, and which are specially favourable to the
determination of the coefficient of extinction. In the case of oxyhaemoglobin,
Hiifner has in his most recent researches selected a part of the region
between the two absorption-bands (A. 550-A. 540) and a part of the region
lying within the second band (A 542'5-A 531 -5).

There remains to be described an absolutely essential accessory to the
spectroscope, without which it would be impossible to determine the spectro-
photometric constants. This is a specially contrived glass trough, for holding
the solutions to be investigated, the anterior and posterior walls of which
are formed by two perfectly parallel glass plates. Two forms of this trough
are shown in Fig. 27, whilst Fig. 28 exhibits a trough mounted on its

FIG. 27. — Glass troughs for containing the liquids
to be examined by the methods of spectro-
photometry. — After Kriiss.

FIG. 28. — Trough mounted on stand,
as used in spectrophotometry. —
After Kriiss.

stand, the stand permitting of the trough being easily and gradually

lowered or raised, and of its being accurately levelled.

The inner surfaces of the parallel glass plates of the

little trough are exactly 11 mm. apart. A glass

cube (called after the person who suggested its use,

der Schuh'sche Glaskurper) exactly 10 mm. broad,

and half the height of the interior of the trough,

rests on the floor of the latter, so that the anterior

and posterior surface of the cube shall be parallel

with the glass plates of the trough (Fig. 29). When

the coefficient of extinction of a coloured liquid is

to be determined, such a trough is filled with it.

When light passes through the lower half of the

trough, it must traverse a stratum of coloured liquid

1 mm. in thickness, whilst light passing through

the upper half traverses a stratum 11 mm. thick.

FIG. 29.— Section of glass
trough with the Schuh-
'sche Glaskorpcr, a, in situ
(schematic). — After Kriiss.

In the latter case, the light is subjected to the absorbing action of a layer of

1 The reader who wishes to understand the details which are necessary for practical
work in spectrophotometry is advised to read in the first instance a useful, indeed almost

218

HAEMOGLOBIN.

coloured liquid 1 cm. broader than that which is contained in the lower half
of the trough, and this is for spectrophotometric purposes exactly equivalent
to interposing a stratum 1 cm. broad in the path of the light impinging on one
(the upper) half of the slit, and no coloured liquid in the path of the light
reaching the other half.

Spectrophotometric measurements are invariably made by the aid of artificial
light. Hitherto, oil or petroleum lamps have been used for this purpose, but
lately Hufner has adopted a gas lamp fitted with an Auer incandescent burner.

We are now in a position to complete our explanation of Yierordt's
method. We shall assume that a spectrophotometer, such as has been
described, is at the disposal of the observer. The lamp is lighted and the
height of the flame adjusted, so as to equally illuminate the two halves of the
double slit ; this is seen to be the case when with equal widths of the slits
two superposed spectra of exactly equffl brightness are seen. The two
halves of the slit are then opened to the extent which is thought advisable ;
we shall, for convenience of description, suppose that they have been opened
to the extent represented by the index on the two divided circles of the
micrometer screws, pointing to the division 100. The observer then arranges
the slit in the eyepiece, so as to isolate and measure precisely the region of
the spectrum for which he desires to determine the coefficient of extinction.
In the case of haemoglobin, of oxyhsemoglobin, and of CO-hsemoglobin, he will
select for his observations one of the two regions which have been shown by
Hiifner to be specially favourable to the determination, and in which he has
determined the constants which he distinguishes as A0 and A'0 respectively.

FIG. 30. — A spectrophotometer with absorption trough and lamp as
arranged for spectrophotometric determinations by Vierordt's
method.

This operation having been effected, he will again observe whether the two
limited spectral areas appear to be of precisely equal brightness. If this is
the case, the trough containing the coloured liquid is brought in front of the
double slit, and the height of the former is carefully adjusted, so that the
upper border of the glass cube appears as a line exactly coinciding with the
separation between the upper and the lower spectral strips.

indispensable, book by Dr. Gerhard Kriiss and Dr. Hugo Kriiss, entitled " Kolorimetric
und quantitative Spektralanalyse, etc.," Hamburg u. Leipzig, 1891. Though specially
written for those who intend to work with Hiifner's instrument, an accurate though very
succinct account of spectrophotometry is contained in a pamphlet entitled " Anleitung
zum Gebrauche des Hiifner'schen Spectrophotometers, etc.," von Eugen Albreclit, Univer-
sitats-Mechaniker in Tiibingen : Tubingen, 1892. Subsequently, all Hiifner's papers on
spectrophotometry should be studied.

METHODS OF SPECTROPHOTOMETR Y. 219

We shall suppose this result to have been attained, and next direct our atten-
tion to the relative illumination of the two spectral areas under examination.
It will be at once seen that the interposition of the absorption-cell has brought
about a great difference in this respect. The upper spectrum is seen to be
much less bright than the lower, the difference depending upon the amount
of colouring matter in solution. Unless the concentration be excessive, we can
restore the equality of illumination of the two superposed spectral areas by
narrowing the lower slit. This is done with great care until we are convinced
that the luminous intensity is the same in both, or that we have secured the
greatest attainable equality (see, below, the discussion of the objections to
Yierordt's method). We have then merely to read the division on the
divided circle of the micrometer screw of the lower half of the slit. Supposing
we find that the width of the lower slit is represented by division 20, whilst
the width of the upper slit remains at 100, then the former number represents
the percentage of unabsorbed light. We have seen that the extinction-
coefficient e can be determined by the formula —

€= -log /', where /'

represents the unabsorbed light. By a table of logarithms, or more quickly by
special tables, we find that in our case —

€=- logT^ = log 100 -log 20
6 = 0-69897

As has been shown, having determined e, we may, if we know the precise
proportion of colouring matter contained in the coloured solution, calculate the
value of A ; or supposing that the substance is one of which the value of A
has been determined, and that we are unacquainted with its concentration, we
can ascertain the latter by the formula c = A€.

Although Vierordt's method of determining the extinction-coefficient
possesses historical interest, and its study is the natural introduction to that
of the more perfect methods which have been suggested by it, it is open to
serious objections, to the principal of which reference may here be made.

However wide one slit may be, and however much the other may be
narrowed, it is, in the case of solutions of high colorific intensity, most difficult,
or impossible, to obtain by these means alone equality in the illumination
of the spectra ; and accordingly Vierordt frequently had recourse to the use of
smoke-tinted glass plates (Rauchglciser) of previously determined absorptive
power, these being interposed in the path of the light which had not traversed
the coloured solution. There are unquestionably theoretical and practical
objections to this mode of proceeding. The principal objection to Yierordt's
method is, however, a fundamental one, namely, that no absolute comparison
is possible between spectra obtained with slits varying considerably in width.
The more the slit of a spectroscope is widened, not only does the amount of
light admitted increase and the spectrum become brighter, but the more and
more impure does it become, i.e. the greater the admixture of light of different
wave lengths in any region of the spectrum. But the accurate determination
of the coefficient e is only possible with monochromatic light. It has been
sought to diminish the error due to the cause just referred to by substituting
for the original double slit of Yierordt one of which both edges move symmet-
rically, so that the centre of the slit remains in a constant position. Although,
doubtless, the error is reduced in this way, it is not entirely corrected.

Although Yierordt's method of determining the value of the co-efficient e
will probably fall in future into disuse, his great merit of having been the
first to work out a method of spectrophotometry admitting of considerable
accuracy, and of having discovered and established its applicability to the
quantitative analysis of colouring matters, will always endure.

Hiifner's method. — This method, which has been made more and more

220 HEMOGLOBIN.

efficient by the long-continued labours of its author, differs from Yierordt's in
the mode by which the equalisation of the intensity of two beams of light is
brought about, the difference in mode requiring a spectrophotometer which
differs in important respects from the instrument already described.

In Hufner's spectrophotometer there is a single slit, the ividth of which,
after it has been once adjusted, is never varied.

The light which reaches one-half of this slit has been polarised by a small
JSTichol's prism (the polariser), whilst that which reaches the other half (which
in the determination of the value of e passes through the thicker stratum of
coloured liquid) is unpolarised. When these two beams of light fall upon the
refracting prism of the spectroscope, they are refracted and furnish two super-
posed spectra, of which that corresponding to the polarised beam is naturally
much less intense than the other. Before making any observations of e, the
two spectra must be equalised, this bein<* done by interposing a wedge of
smoke-tinted glass in the path of the unpolarised beam. Equality of both
spectra having been obtained, if a coloured medium be placed in the path of
the unpolarised beam, its spectrum will be correspondingly reduced. Equality
is, however, restored by rotating a second Xichol's prism (the analyser) which
is in the path of the beams issuing from the refracting prism, and the rotation
of which diminishes the intensity of the polarised beam alone. When equality
in the illumination of both spectra has been restored, the angle (</>), through
which the analysing Nichol has been rotated, is measured in two opposed
quadrants of a divided circle provided with a vernier, and from the value of
<£ that of /' is calculated.

If the original intensity of the light = 1, and the intensity of the un-
absorbed light which has traversed the coloured medium be represented by
/', then

/' = cos2<£ ;

If the layer of coloured liquid investigated be always = 1 (e.g. 1 cm.), then

as e = — log /',
e — — log cos2<£

The following example will illustrate the mode of procedure and the steps
of the calculation in an actual experiment for the determination of the ex-
tinction-coefficient of blood, carried out with Hiifner's spectrophotometer : —

1 c.c. of defibrinated blood of the ox was diluted to 160 c.c. with a O'l
per cent, aqueous solution of Na(OH). The absorption-trough was filled with
some of the perfectly clear red liquid thus obtained. The spectral region (r),
for which e was determined, was one of the two in which Hufner has, in his
most recent experiments, determined the constant A of oxyh?emoglobin (i.e.
a portion of the region between the bands a and /3 of oxy haemoglobin).

r=A557'5~A568-7

(Mean of ten measurements) <f> = 61° -8 7
Converting the decimal

fractions of a degree into

seconds <£ =61°52'

It has been stated that with Hiifner's spectrophotometer

/' = COS2c£

and e — - log cos2<£

In the above experiment

e= - log cos261°52'
"«-2 Iogcos61052'
" = -2 (0-67350-1)
" = -1-34700 + 2
" = 0-653

HUFNEKS SPECTROPHOTOMETER. 221

Hiifner's spectrophotometer is an instrument of so much importance to the
physiologist who intends to work at spectrophotometry, that a short descrip-
tion of the arrangements of its several parts appears desirable.

The instrument as a whole, as well as the stand carrying the absorption-
trough and the lamp, are shown in Fig. 31.

FIG. 31. — Hiifner's spectrophotometer, as made by Albrecht.

The spectrophotometer, the stand for the trough, and the lamp, rest upon
the optical bench which forms the base for the whole. The position of the
spectrophotometer is constant ; the trough-stand and the lamp move along a
slide, and can be placed at any required distance. During the actual experi-
ment, the anterior edge of the trough is in close contact with the anterior part
of the collimator. The lamp (which in the models recently and at present
constructed is a gas lamp provided with an Auer incandescent burner) is
for actual work placed at a distance of 24 to 25 cms. from the distal end of the
collimator. The lamp is fitted with a positive lens the focus of which is
made to correspond with the brightest part of the flame, so that perfectly
parallel rays fall upon the absorption- trough. The latter is in all respects
similar to the one used in Yierordt's method.

Turning our attention to the spectrophotometer, see Fig. 31, it is seen to be
composed of a three-footed stand, furnished with levelling screws, the stand
supporting the platform on which is fixed the dispersing prism, which is
enclosed in a metallic case. To the right is seen the collimator and to the left
the telescope.

1. The collimator. — This is furnished with a single slit formed by the
edges of two slides moving transversely, each of which possesses its own
micrometer screw, furnished with an accurately divided drum. This arrange-
ment enables a slit of a precisely known width to be obtained, and the slit can
be widened or narrowed symmetrically, — so that its centre remains constant.

Unlike ordinary spectroscopes, Hiifner's spectrophotometer has, fixed to the

222

HEMOGLOBIN.

front of the slit, a metallic box enclosing the following optical parts. (In order
to facilitate our description, these are shown in the following diagram, Fig. 32,

FIG. 32. — Schematic representation of the path followed by the rays of
light before entering the slit of the collimator of Hiifner's spectro-
photometer. — After Kriiss.

which indicates also the path of the rays passing through the glass trough
containing the coloured solution.)

Placed centrally, in the position shown in the diagram, is an oblique parallel-
epiped of flint glass, with two of its diagonally-opposed angles in a line with
the optic axis of the collimator. This admirable optical contrivance (which
is known in Germany after the optician who devised it as " der Albrecht'sche
Glaswiirfel oder Glaskorper") refracts light falling on its two anterior faces
so as to alter its direction, as shown in the diagram, and as will be after-
wards referred to. Placed anteriorly to the lower half of Albrecht's body
is the small Nichol's prism d. Corresponding to the upper part of the glass
body is a composite glass plate e, with perfectly parallel sides. This plate is
formed by cementing together two glass wedges, of which one is of clear glass
and the other of smoke-tinted glass, and can be moved from side to side by
means of a special arrangement. According to the position of this plate it
will absorb more or less light. The purposes of these various parts are
sufficiently obvious from the diagram ; aa represents the absorption-trough for
containing the coloured liquid to be spectrophotometrically investigated. In
the lower half of the trough is seen the Schulz's cube (b) ; r and r1 represent
two parallel beams of light falling on the anterior surface of the trough. The
lower beam (r) traverses in its path the Nichol prism (d), and is polarised ;
falling then on the adjacent surface of the parallelepiped, it is deviated so
as to fall upon the upper half of the slit. The upper beam may or may not
meet in its path the composite plate c previously referred to, and to which
reference will again be made. This beam is so deviated as to fall upon the
lower half of the slit. After traversing the structures just described, two
beams of light fall upon the slit — a polarised beam on the upper half and a
non-polarised beam on the lower.

2. The telescope. — A very ingenious arrangement, which is indicated by
a separate drawing in the centre of Fig. 31, permits of the precise
position of the telescope in reference to the prism being determined, and
consequently of the most accurate determination of the position of any line
in the spectrum. The reader is referred for details to Professor Hiifner's
original description. At the distal end of the telescope is the object glass,
next to it is a Mchol's prism, the rotation of which is measured 011 a graduated
circle by the help of a vernier. In the focal plane of the eyepiece is a
modification of Yierordt's eyepiece slit, permitting of any determined spectral
region being exactly isolated. For further details as to the construction and
adjustment of the spectrophotometer, the reader is referred to the original

SPECTROPHOTOMETRIC CONSTANTS. 223

sources of information. It is absolutely essential to work with Hiifner's
spectrophotometer in a perfectly darkened room.

Before commencing photometric measurements, the observer will ascertain
whether the analysing Mchol is in the position in which it allows the polarised
beam to pass unabsorbed. He will then fill the absorption-trough, and isolate
and measure the spectral region for which the extinction-coefficient is to
be determined.

On now looking through the eyepiece two spectral strips will be seen,
separated by a sharp horizontal line ; these spectral strips will be of unequal
brightness ; the upper, being a portion of the spectrum of the polarised
beam, will be much less luminous than the lower. The composite glass
plate in front of the slit of the collimator is now moved inwards in the
direction of the beam of the unpolarised light, so as to diminish its intensity,
until the upper and the lower spectral strips appear of precisely the same
brightness.

The trough containing the coloured liquid under investigation is now
brought into position, the upper surface of the glass cube in the trough being
placed about 1 mm. below the plane passing through two horizontal angles of
Albrecht's glass body. On now examining the spectra, it is at once seen that
the lower of the two is darker than the upper. The analysing Nichol is then
carefully rotated until equality in the intensity of the two spectral strips is
attained ; the angle through which the prism has been moved is then deter-
mined ; several, say five, sets of readings being made in two opposite quadrants
of the large divided circle. The mean of these readings gives the value

Of C/).1

The spectrophotometric constants of oxyhsemoglobin. — It was

previously stated that it is usual to determine the photometric constants
of colouring matters in two spectral regions, those regions being chosen
in which the variations in the absorption of light are most rapidly affected
by variations in the concentration of the colouring matter.

The reasons for determining in the first instance at least two values
for A (which we shall distinguish as A and A'), and subsequently, each
time that a determination is made, ascertaining the value of e in the
same two regions (the two extinction-coefficients being distinguished
as e and e', or in the case of oxyhaemoglobin as e0 and e0') are the
following: — (1) If we know the value of A and A' for any body, we are
able to make two independent estimations when determining the
concentration of a solution of the same body of unknown strength, the
one estimate acting as a check on the other. (2) The knowledge of the
value of A and A', for each of two colouring matters co -existing in
solution, is a necessary condition to being able to determine spectro-
photometrically the amount of each constituent when occurring together.
(3) In the case of oxyhsemoglobin, haemoglobin, and CO-haemoglobin, the

quotient - is absolutely characteristic of each substance, and affords a

valuable check on the purity of the colouring matter in solution and on
the accuracy of the analysis.

Hiifner's most recent determinations2 of the spectrophotometric
constants of oxyhaainoglobin, made with his perfected spectrophotometer,
have led to the results shown below. The two values of A are, as has

1 Hiifner's spectrophotometer is constructed by, and can be obtained from, the original
maker, Herr Eugen Albrecht, Universitats-Mechaniker in Tubingen.

2Hiifner, "Photometrische Constanten des Oxyhamoglobins,"^rc7t./. PhysioL, Leipzig,
1894, PhysioL Abth., S. 134 et seq.

224

HEMOGLOBIN.

been previously stated, in the case of oxyhaemoglobin, distinguished by
the symbols AQ and A\ ; the first has been determined for the spectral
region which lies between the two bands a and /3 of oxyhsemoglobin,
and is limited by \ 554 and x 565 ; the second has been determined for
the spectral region which corresponds to the darkest part of the second
(j8) band of oxyhaemoglobin, and extends from /. 531'5-X 542-5.

SpectropJwtometric Constants of Oxyhcemoglobin 1 (Hufner).

Limits of Spectral Region in which
f0 and e'0 were determined.

Absorption relation A0 and A'0 corre-
sponding to the two regions.

(72 of e ) X 554-X 565

A0 0-002070

(E of e' ) X531'5-X542'5

A\ 0'001312

From the above constants we are able, as has been shown (see p. 215),
to determine the percentage of haemoglobin in the blood with surprising
accuracy. The further use of these constants will be referred to in
explaining the mode of determining the relative amounts of haemoglobin
and oxyhaemoglobin coexisting in any sample of blood.

We have now to consider in some detail the light which spectro-
photometry has shed on certain questions which possess great interest
to the physiologist, and which have up to a certain point been already
discussed in this article.

Hufner and his pupil v. Noorden long ago noticed that the quotient

A ' '

— L, which is the same as — -, was remarkably constant, not only in

-"•0 ^0

the blood of animals of the same species, but in all, however widely
separated in the animal scale.2 Subsequent researches by Hufner and
his pupils, carried out with a much more perfect spectrophotoineter
than the one employed by v. Noorden and himself, more than confirm
the earlier results in so far as the constancy of the quotient is
concerned.

If the defibrinated blood of any animal, diluted with 150—160 parts
of 01 solution of NaOH, or a solution in the same dilute NaOH of
crystals of oxyhsemoglobin of approximately equivalent concentration,
be thoroughly oxygenated by shaking with air and the values of SQ and

zQ be determined, it will be found that the quotient — will vary very

2<>

slightly from 1'580. In very few determinations, out of a large number,
was it as low as 1'578. So soon, however, as the blood commences to
undergo any change, as, e.g., a partial conversion into methsemoglobin,
the coefficient is lowered.

lrrhe values of A0 and A\ given above differ materially from those which had been
assigned to them previously by Hufner and his pupil v. Noorden as a result of researches
carried out with Hiifner's earlier and much less perfect spectrophotometer, and employing
haemoglobin which had been frequently recrystallised.

2 v. Noorden's observations included the blood of man, the dog, the cat, the rat, the
guinea-pig, and the owl. " Beitrage zur quantitativen Spektralanalyse, in besondere zu
derjenigen des Blutes" (aus d. Lab. d. Prof. Hufner in Tubingen), Ztschr.f.physiol. Chem.,
Strassburg, 1880, Bd. iv. S. 9-35.

THE PHOTOGRAPHIC SPECTRUM. 225

From the extraordinary constancy of this quotient some interesting
conclusions may be legitimately drawn. (1) The constancy of the
quotient in all animals affords presumptive evidence, amounting to
absolute proof, that the iron-containing molecular group existing in
haemoglobin, upon which its colour, its light-absorbing power, and its
capacity to combine with 0, CO, and NO depend, is identical in
all animals. The truth of this hypothesis is borne out by many
weighty facts, e.g. the identity in chemical composition (as revealed
by analysis) of the iron-containing products of the decomposition
of haemoglobin, whatever its source ; the constancy in the propor-
tion of 0 and CO which can combine with 1 grm. of haemoglobin
of different animals. (2) The constancy of the quotient (whether
solution of crystallised haemoglobin, or an alkaline solution made by
diluting defibrinated blood with O'l per cent. vol. of Na(OH), or a
liquid holding intact blood corpuscles in suspension, be investigated),
shuts out the possibility of more than one colouring matter existing
in the blood. It renders absolutely untenable the views of Bohr,
who has assumed the existence of several haemoglobins, possessed
of different powers of combining with oxygen ; and utterly disproves
Hoppe-Seyler's hypothesis that the colouring matter of the corpuscles
is distinct from haemoglobin so as to deserve a special designation of
arterin or phlebin, as the case may be.

(&) The photographic spectrum. — In the year 1878 the late
Professor J. L. Soret, of Geneva, in his first memoir on the absorption
of the ultra-violet rays of the spectrum by diverse organic substances,1
announced the fact that diluted blood, when examined with the aid
of a spectroscope provided with a fluorescent eyepiece, presented in
the extreme violet, between Frauenhofer's lines G and H, an absorp-
tion-band which appeared to him to be slightly shifted towards the
less refrangible end of the spectrum, when the blood solution was
saturated with carbonic oxide. Soret subsequently2 confirmed the
accuracy of the above facts, employing the photographic method in
his experiments, though he published none of his photographs. Since
the date of the publication of Soret's short notes on this subject,
d'Arsonval 3 has independently, and without referring to Soret's observa-
tions, described anew the extreme violet absorption-band of the blood-
colouring matter, but without adding to the facts discovered by the
Swiss observer.

The complete absence of all reference to Soret's scanty but
interesting and suggestive observations, in text -books and treatises
on physiology and physiological chemistry; and the fact, which my
own observations soon elicited, that the absorption-band of Soret is
even more distinctive of the blood-colouring matter than the absorp-
tion-bands in the visible spectrum which have hitherto engrossed the
attention of observers, led me to study this absorption-band in more
detail in haemoglobin, its compounds and principal derivatives.4 I

1 J. L. Soret, " Recherches sur 1'absorption des rayons ultra- violets par diverses
substances," Arch. d. sc. phys. et nat., Geneve, 1878, pp. 322, 359.

2 Soret, ibid., 1883, pp. 194, 195, 204.

3 A. d'Arsonval, Arch, dephysiol. norm, etpath., Paris, 1890, Ser. 5, tomeii. pp. 340-346.

4 A. Gamgee, "On the Absorption of the Extreme Violet and Ultra- Violet Rays of the
Solar Spectrum by Haemoglobin, its Compounds, and certain of its Derivatives,"
Proc. Roy. Soc. London, 1896, vol. lix. p. 276.

VOL. I. — 15

226 HEMOGLOBIN

propose that the band in the extreme violet should henceforward be
distinguished as the band y, or the band of Soret, in the spectrum of
oxyhsemoglobin.

Methods of demonstrating the land of Soret. — The limits of visibility
of the solar spectrum correspond, as usually stated, with the H group of
lines; here lies the arbitrary boundary which separates the extreme
violet from the ultra-violet properly so called — that region which
we can only see by interposing fluorescent media in the path of the
rays (e.g. a fluorescent eyepiece), or by allowing the spectrum to fall
on a fluorescent surface — the region which is best studied by the aid of
photography.

Although Soret's band lies at the limit, but yet within the boundaries,
of the visible spectrum, it is impossible to see it with the ordinary
spectroscope, i.e., unless this be provided with special devices. It has
already been stated that it can be seen with any spectroscope, if we
substitute a fluorescent for the ordinary eyepiece ; a cell containing
a dilute solution of sesculin must, however, be substituted for and
placed in the position of the uranium glass plate of the eyepiece,
uranium glass fluorescing most feebly in the light of the spectral region
where the absorption-band under discussion is situated. It was, indeed,
with the aid of his fluorescent eyepiece that Soret first discovered this
band, though d'Arsonval asserts that it is impossible to see it in this
way. Observations with the fluorescent eyepiece are, however, difficult
and require experience. Still more difficult and unsatisfactory is the
method, also suggested by Soret, and lately published as an original
suggestion by d'Arsonval, of rendering this band visible by interposing a
blue glass between the eye and the spectroscope. If the light be very
intense the band is just perceptible to a person who is already
acquainted with its position and characters through other methods of
observation.

In order to demonstrate Soret's band and the absorption-bands in
the ultra-violet of derivatives of the blood-colouring matter, I projected
the spectrum of sunlight or of the positive pole of the electric arc on to
a fluorescent screen, similar to those which have since come into
common use in observations made with the X or Eontgen rays,
i.e. a screen made by coating a white surface, such as cardboard, with
barium platinocyanide.

In order to render absorption - bands of coloured liquids in the
extreme violet and ultra-violet beautifully visible by this method, it is
essential, however, to open the slit which intervenes between the
source of light, and the collimating lens very widely. In the highly
luminous spectra thus obtained, though none of the spectral lines
are visible, except perhaps H and K appearing blurred and indistinct,
absorption-bands appear with remarkable distinctness and sharpness.
The method is valuable, not only for purposes of demonstration, but
for making preliminary observations prior to having recourse to
photography. By its help I ascertained with correctness the position
and characters of the extreme violet and ultra-violet absorption-bands
of the acid compounds of hasmatin, of methaemoglobin, of hsemato-
porphyrin, and of turacin. In no case where this method yielded
negative results, was the presence of a band afterwards demonstrated
by photography.

As few physiological laboratories possess a perfectly darkened optical

THE PHOTOGRAPHIC SPECTRUM. 227

room provided with a heliostat for projecting a beam of sunlight into it,
the following simple arrangement,1 which requires merely an electric
arc lamp and an ordinary laboratory spectroscope of the Bunsen type,
may be adopted.2 The telescope of the spectroscope is removed, and
a beam from the + pole of the arc is allowed to fall on the slit of the
collimator. The spectrum is focussed on a fluorescent screen, then the
slit is opened very widely. If the spectrum be a continuous one
(which is the case if it be that of the positive pole of the electric
arc), the coloured solution is then interposed in the path of the beam
falling on the slit.

The position and limits of Soret's land. — Defibrinated arterialised
blood, diluted with from 400 to 600 volumes of distilled water, or still
better with a similar amount of 0*1 per cent, solution of sodium hydrate,

G h HK L M N

FIG. 33. — The photographic spectrum of haemoglobin and oxyhsemoglobin.

furnishes solutions (containing about 1 part of oxyhsemoglobin in 3000
and 1 part in 5000 respectively) of a concentration suited for
photographic investigations of the spectrum. With solutions of this
strength (a stratum 1 cm. thick being placed in the path of the beam
falling upon the slit of the collimator) Soret's band can be studied
to perfection, though it can be well seen with solutions much more
concentrated and much more dilute. The appearance and position of
Soret's band in the spectrum of oxyhaemoglobin are shown in Fig. 33
along with that of reduced haemoglobin.

Within fairly wide limits of concentration (the stratum examined
being invariably 1 cm. wide), the limits and characters of Soret's band

1 I employed this simple arrangement in demonstrating these bands in the violet and
ultra-violet to members of the Internat. Physiological Congress, Bern Meeting, September
1895.

'-' Direct vision spectroscopes cannot be used, the absorption of the ultra-violet rays being
very great in these instruments.

228 HAEMOGLOBIN.

remain very constant, the increase in the amount of oxyhaemoglobin
influencing more the intensity of the band than its width. In the case
of solutions containing approximately the proportion of oxyh?emoglobin
above mentioned (i.e. from 0*20 to 0-33 parts in 1000), the spectral
region between F and G is absolutely unshaded. Soret's band is then
seen, extending from X 404— X 434 ; i.e. it occupies the greater part of the
spectral region intervening between G and H ; the edges, however,
uniformly shade away as far as these lines.

By examining a series of photographs of spectra obtained by inter-
posing solutions of oxyhsemoglobin of very different concentrations, I
have determined that the mean ray absorbed does not, as Soret thought,
coincide with h (x 410*1), but is decidedly on the red side of that line,
corresponding to X 414.

When the concentration of the solution of oxyhsemoglobin increases,
the width of the band very slowly increases. Its less refrangible border
never passes beyond G ; as the solution becomes highly concentrated,
the band widens perceptibly, and it does so in the direction of the ultra-
violet. With a solution made by diluting 1 volume of blood to the volume
of 250 (water or O'l per cent, solution of Na(OH) being employed as the
diluent), the absorption-band, though much more intense than with the
more dilute solutions, retains almost the same boundaries, its shadowy
borders approaching, but not passing beyond, G and H. With a
solution containing 1 part of blood in 100, the appearances differ
remarkably from those previously referred to. The solution is
transparent for light from F to nearly G ; it transmits light with
difficulty from L to N" (x 38l*9-X 35.0*01) ; the remainder of the ultra-
violet is completely absorbed. A solution containing 5 per cent, of
defibrinated blood (or about 6*5 parts of oxyhsemoglobin in 1000 parts)
absorbs the whole of the violet and ultra-violet regions of the spectrum,
with the exception of a region between F and G, but nearer the former
(X 460-X 490).

It remains to be considered with how dilute a solution of oxy-
hsemoglobin a photographic record of Soret's band can be obtained.
Examining a stratum 10 mm. broad I have obtained definite results,
when the solution contained somewhat, but not much, less than 1 part
of oxyhsemoglobin in 10,000.

No colouring matter yet investigated exhibits the intense absorption-
band between G and H which is characteristic of haemoglobin and its
compounds. Several substances (carmine, picro-carmine, and the colouring
matter of alkanet root) exhibit absorption-bands in the visible part of
the spectrum which bear a superficial resemblance to those of oxy-
hsemoglobin. The spectrum of none of these colouring matters exhibits,
however, any absorption in the extreme violet or the adjacent ultra-
violet.

The researches which I have conducted have shown that the band of
Soret depends on the iron-containing group existing in the haemoglobin
molecule, yet not upon its iron. The variations in character and position
which this band exhibits in the various compounds and derivatives of
haemoglobin will be referred to under each.

HEMOGLOBIN (REDUCED HEMOGLOBIN}. 229

HEMOGLOBIN (EEDUCED HEMOGLOBIN).
SYNONYM, "PURPLE CRUORIN."

Historical note. — Fully two years had passed since the date of Hoppe's
publication (1862) of his observations on the spectrum of blood, before it was
shown that the oxygen which enters into combination with haemoglobin has
a fundamental influence on its spectrum. It was on the 16th of June 1864
that Professor Stokes 1 communicated to the Royal Society the interesting
observation that when diluted blood is treated with certain reducing agents,
the colour of the liquid and its spectrum undergo remarkable changes ; the
former loses its bright red appearance, becoming darker in tint, whilst the
absorption-bands a and /3 are replaced by a single band which we may
designate the band y, which appears less deeply shaded and with less denned
edges, and which extends from D nearly to E. If, now, the solution which
exhibits this spectrum be shaken with air or oxygen, the single band at
once gives place to the two original bands, whilst the liquid reacquires
more or less of its primitive florid-red colour. The process of reduction
and oxidation may be repeated many times in succession.

From his experiments, Stokes concluded that "the colouring matter of blood,
like indigo, is capable of existing in two states of oxidation, distinguishable by a
difference of colour and a fundamental difference in the action on the spectrum.
It may be made to pass from the more to the less oxidised state by the action of
suitable reducing agents, and recovers its oxygen by absorption from the air." 2

The researches of Magnus, Lothar Meyer, and Claude Bernard had shown
that the blood holds in solution an amount of oxygen greatly in excess of that
which could exist in a state of simple solution, but that this oxygen exists in a
condition which permits of its being extracted from the blood by boiling in a
Toricellian vacuum, as well as by the action of carbonic oxide. Hoppe-Seyler,
having succeeded in crystallising oxyhsemoglobin, and, by means of its optical
properties, having identified it with the colouring matter as it exists in the living
blood, was able to show that a solution of crystallised oxyhsemoglobin behaves
towards reducing solutions in the same manner as diluted blood; that, like blood,
it yields oxygen when boiled in vacuo, and that the blood-colouring matter thus
deprived in vacuo of its loosely combined or respiratory oxygen manifests the
absorption-band which had been described by Stokes as the result of reduction.

The further steps in the growth of our knowledge of reduced haemoglobin
will be more conveniently referred to in discussing the chief facts with which
we are acquainted relative to this remarkable body.

Methods of effecting the reduction of oxyhsemoglobin to reduced
haemoglobin. — In nearly all experiments on the reduction of oxyhsemo-
globin, diluted blood may be substituted for a solution of the pure blood-
colouring matter, it having been shown by the spectrophotometric and
chemical researches of Hiifner that, both in respect of their power of
absorbing light and of the influence of reducing agencies upon them, the
two solutions possess identical properties. Instead, however, of employ-
ing pure distilled water as a diluent, it is advisable to use, according to
Hiifner 's plan, a 01 per cent, solution of sodium hydrate. A diluted
solution of blood prepared in this way is free from all turbidity, and
therefore more transparent than a pure aqueous solution, and undergoes
putrefactive alterations more slowly.

1 l( On the Reduction and Oxidation of the Colouring Matter of the Blood," Proc. Roy.
Soc. London, 1864, vol. xiii. pp. 353-364 ; London, Edinburgh, and Dublin Phil. Mag.,
London, 1864, vol. xxviii. pp. 391-400.

2 Stokes, op. cit., p. 357, par. 8.

23o HAEMOGLOBIN.

1. By the action of reagents exerting a reducing action.—
It is an essential condition which all reagents to be employed in the
reduction of oxyhsemoglobin to haemoglobin must fulfil, that they do not
act destructively on these substances, as is the case with acids and salts
possessed of an acid reaction.

Ordinary solutions of ferrous sulphate or stannous chloride cannot,
for instance, be employed, as they instantly lead to a decomposition
of the blood-colouring matter. The first and still the most generally
employed reducing agents, the use of which dates back to the researches
of Stokes on the blood-colouring matter, are ferrous and stannous salts
and the alkaline sulphides. Utilising the well-known property of citric
and tartaric acids to prevent the precipitation of the salts of iron and
tin by ammonia and the alkaline hydrates, Stokes indicated easy
methods of preparing active solutions of ferrous and stannous salts for
the study of the reduction of oxyhgemoglobin.

(a) Alkaline solutions of ferrous salts (Stokes' reagent). — To a solution
of a ferrous salt (usually ferrous sulphate or ferrous ammonium sulphate)
(Fe(NH4)2(S04)2.6H201), citric or tartaric acids or one of their alkaline
salts is added, and then ammonia, until the reaction is alkaline. A light
green solution is thus obtained, which rapidly darkens in the presence of
air by the absorption of atmospheric oxygen. Such a solution, which,
must be freshly prepared, exerts a powerful and exceedingly rapid
reducing action on oxyhsemoglobin, even in the cold. Alkaline ferrous
solutions possess the disadvantage, in proportion as they absorb oxygen
and become oxidised, of becoming coloured, and absorbing the more
refrangible rays of the spectrum, interfering, therefore, with the accurate
study of the specific absorption due to the colouring matter.

(b) Alkaline solutions of stannous salts. — These are made as described
under a, by substituting a stannous (usually SnCL2) for a ferrous salt.
As they do not become coloured on salt being oxidised, these solutions
do not interfere with the accurate study of the absorption of the violet
rays. Like the analogous ferrous solutions, those containing tin rapidly
reduce haemoglobin even in the cold.

(c) Solutions of the alkaline sulphides. — Solutions of these salts
(ammonium sulphide being almost invariably employed) effect the
reduction of oxyhaemoglobin, but much more slowly than is the case
with a and ft, and their action is greatly accelerated by heat. Solutions
of ammonium sulphide for this purpose should be freshly prepared, and
be protected from the action of atmospheric oxygen and light, which
bring about chemical changes, and cause them to assume a yellow colour
and to absorb the violet end of the solar spectrum.

Solutions of the crystalline sodium monosulphide (Na2S) cannot be
employed with advantage as reducing agents for oxyhsemoglobin, as, according
to my experiments, they lead at once to the formation of sulphomethsemo-
globin, so that the pure spectrum of reduced haemoglobin cannot be observed.

(/) Agitation with finely -divided iron,1 or with metallic iron reduced
by hydrogen — the so-called officinal ferrum rcdactum.2

1 Rollett, "Versuche ueber thatsachliche und vermeintliclie Beziehungen d. Blutsauer-
stoffes," Sitzungsb. d. k. Alcad. d. Wissensch., Wien, 1866, Bel. lii. Abth. 2, S. 246 et seq.

2 Ludwig und Schmidt, "Das Verhalten der Gase welche mit dem Blut durch den
reizbaren Saugethiermuskel stromen," Sitzungsb. d. k. Sachs. Gesellsch., Leipzig, 1868, Bd.
xx. S. 12-72.

HAEMOGLOBIN (REDUCED HAEMOGLOBIN). 231

(g) Solution of sodium hydrosulpliite (NaHS03). — By the action of metallic
zinc on a solution of sodium sulphate, in the absence of oxygen, a solution of
intense reducing power is retained. Such a solution, which instantly decolor-
ises indigo and litmus, reduces oxy haemoglobin.1

Methods of determining the percentage of haemoglobin have been based on
this reaction,2 3 though they have been abandoned as unreliable.4

(li) Solution of hydrazin and its salts. — It was pointed out by Curtius 5 that
a solution of a salt of hydrazin reduces solutions of oxy haemoglobin with great
rapidity ; and Hiifner 6 afterwards employed an aqueous solution of hydrazin
hydrate to effect the reduction of concentrated solutions of oxyhaemoglobin,
the advantages of this reducing agent being that the only products of its
decomposition are nitrogen and water, as shown in the following equation : —

H2N— NH2.H20 + 02 = Na + 3H20.

(hydrazin hydrate)

2. By taking advantage of the reducing action exerted by pro-
ducts of putrefaction. — The solutions of oxyhaemoglobin, or of diluted
blood, is set aside in sealed tubes, when, especially at temperatures ap-
proaching 40° C., reduction rapidly occurs. It is worthy of remark that,
whilst oxyhsemoglobin or its solutions very rapidly undergo change at
temperatures above 0° C., such is not the case with reduced haemoglobin,
which may be kept for many years in sealed tubes in the presence of
putrefactive bacteria and the products of their activity. On opening the
tubes and agitating with air, oxyhsemoglobin is at once formed, and under
favourable conditions may be crystallised.

3. By taking advantage of the conditions which favour the
"dissociation" of the compound of O2 with haemoglobin. — (a) By
boiling in a "Toricellian" or barometric vacuum; (&) by subjecting
diluted blood or a solution of oxyhaemoglobin to the action of a
long-continued stream of a neutral gas, such as hydrogen, nitrogen, or
nitrous acid.

4. By temporarily arresting the circulation through a suffi-
ciently transparent part of the animal body. — It was first pointed
out by Vierordt,7 that the spectrum of oxyhaemoglobin can be satisfac-
torily demonstrated by bringing two fingers (preferably the fourth and
fifth) close together and passing a beam of sunlight through the com-
paratively thin layer of tissues at the boundaries of the adjacent fingers.
He further pointed out that, on placing caoutchouc rings at the base of
the first phalanges, after an interval varying between 40 and 300
seconds (?), the two bands of oxyhaemoglobin became replaced by the
single band indicative of reduced haemoglobin.8

1 Schiitzenberger and Risler, " Recherches sur le pouvoir oxydant du sang," Compt. rend.
Acad. d. sc., Paris, 1873, tome Ixxvi. pp. 440-442, and pp. 1214-1216.

2 Rollett, loc. cit.

3 Ludwig and Schmidt, loc. cit.

4 Qninquaud, "Sur un precede de dosage de I'he'moglobine dans le sang," Compt. rend.
Acad. d. sc., Paris, 1877, tome Ixxvi. p. 1489.

5 Journ. f. prakt. Chem., Leipzig, 1889, Bd. xxxix. S. 27.

6 " Bestimmung d. Sauerstoffscapacitat d. Blutfarbstoffs, " S. 156.

7 "Das Hamoglobinspectrum am lebenden Menschen," Ztschr. f. Biol., Mitnchen, 1876,
Bd. xi. S. 188 ; and "Die Sauerstoffzehrung der lebenden Gewebe," ibid., 1878, Bd. xiv.
S. 422.

8 Refer to the following papers by A. Henocque, " fitude spectroscopique du sang a la
surface sous-ungueale du pouce," Compt. fend. Soc. de biol., Paris, Ser. 8, tome i. p. 671 ;
and also "Notes complernentaires," ibid., p. 700. According to this author, the average
time of reduction, when the circulation through the thumb is arrested, varies between fifty-
five and sixty- five seconds.

232 HEMOGLOBIN.

Preparation of crystallised hsemoglobin (reduced haemoglobin).—

It was shown almost simultaneously and independently by Kiihne1 and
by Rollett 2 that highly concentrated solutions of pure oxyhremoglobin
may, after reduction, be made to crystallise, and that the crystals of
reduced haemoglobin, though differing in colour and spectroscopic char-
acters from the oxygen compound, are essentially identical with it in
crystalline form. Kiihne explained that the difficulty which is en-
countered, when attempting to crystallise reduced hsemoglobin, depends
upon its very great solubility.

Hoppe-Seyler was unable to crystallise reduced haemoglobin ; 3 and Hiifner4
in 1880 published a note, in which he announced that he had succeeded in
obtaining crystals of reduced haemoglobin^though he neither then nor after-
wards referred to the much more complete account published by Kiihne fifteen
years earlier.

In order to obtain crystals of reduced haemoglobin for microscopic
examination, a pure and highly concentrated solution of oxyhoemoglobin
in very dilute ammonia is placed in a gas chamber, and a stream of
chemically pure and thoroughly dried hydrogen is passed over it ; as the
solution evaporates crystals separate.5

Nencki and Sieber have obtained large quantities of crystals of
reduced haemoglobin by reducing concentrated solutions of pure oxyhse-
moglobin of the horse through the agency of putrefactive bacteria, then
adding a sufficient quantity of 25 per cent, alcohol and exposing to cold.
The method which I employed more than twenty years ago, and which
appears to me to offer some advantages, is to place a magna of pure
oxyhaemoglobin crystals with a small quantity of the mother liquor
from which they have separated in a glass tube, so as nearly to fill the
latter, and then to seal it. The tube is heated for some days in an
incubator at about 35° C., and is then set aside in a cool place. After
some weeks of exposure to a winter temperature, the tube is found to
contain large quantities of crystallised and perfectly reduced haemo-
globin.

No one has hitherto attempted to recrystallise reduced haemoglobin,
though, with the conveniences at present at the disposal of the scientific
chemist, the process would present little difficulty.

Characters of the crystals of reduced hsemoglobin. — In form
they are, as has been said, essentially identical with those of the
oxygen compound, and like these are doubly refracting. Hiifner
often obtained crystals 1 mm. long ; and Nencki and Sieber, working
with horses' blood, obtained crystals, mostly in the form of hexagonal
plates, 2 or 3 mm. in diameter. They are pleochromatic, appearing
of a dark red colour in some lights, and exhibiting a bluish or purple
tinge in others.

1 " Das Vorkommen und die Ausscheidung des Hamoglobins aus dem Blute," Virdiow's
Archiv, 1865, Bd. xxxiv. S. 423-436.

2 Loc. cif.

3 Med. Chem. Untersuch., Berlin, S. 373.

4 "Ueber krystallische Hamoglobin," Ztschr. f. physiol. Chem., Strassburg, 1880,
S. 383. It is singular that Nencki and Sieber, in an interesting and really valuable
paper, should in 1887 have published again, as a new discovery, the obtaining of crystals
of reduced haemoglobin, though they subsequently disclaimed all priority (see M. Nencki
and N. Sieber, "Venose Hamoglobinkrystalle," Ber. d. deutsch. chem. Gfesellsch., Berlin,
1886, Bd. xix. S. 128 and 410).

5 Ktihne, op. cit.

COLOUR OF REDUCED HEMOGLOBIN.

233

When the blood crystals of horses' blood are prepared in closed
vessels, it happens very frequently that large quantities of hexagonal
tables of a dark red colour are found mixed with the well-known ordinary
prisms. If a drop of the liquid in which the crystals are suspended be
examined with the microscope, without a cover-glass, the hexagonal plates
are observed rapidly to liquefy, and simultaneously bundles of fine,
bright-red prismatic needles appear. Nencki long ago showed that the
dark red hexagonal tables are crystals of reduced haemoglobin, whilst
the scarlet prisms are those of oxyhaemoglobin. Horses' blood appears
peculiarly apt to give crystals of the reduced blood-colouring matter.
In the preparation of the haemoglobin of the horses' blood by ordinary
methods, i.e. without special precautions in reference to the access of
air, both forms of crystals are usually obtained.1

THE ABSORPTION OF LIGHT BY SOLUTIONS OF EEDUCED HEMOGLOBIN.

Colour of solutions : dichroism. — In thick layers, or in thin layers
if concentrated, solutions of reduced haemoglobin present a dark cherry-
red colour, whilst very dilute solutions exhibit a green tint.

H.-EMOGLOBIN.

ABC

FIG. 34. — Graphic representation of the spectrum of — (] ) oxyheemoglobin
and (2) haemoglobin. The numbers at the right-hand side of each
diagram indicate percentages. — After Rollett.

This dichroism is also characteristic of the blood of asphyxiated
animals, and was first observed by Brticke. It is specially to be noted
that, whilst solutions of reduced haemoglobin are dichroic, solutions of the
02- CO- and NQ-compounds of haemoglobin exhibit no trace of dichroism.

Cause of the differences observed in the colour of blood contrasted
with that of solutions of haemoglobin. — The much brighter colour pre-
sented by blood, as contrasted with corresponding solutions of the blood-
colouring matter, depends upon the presence of the blood corpuscles.
Were we to conceive, as Eollett argues, the blood corpuscles suspended
in the liquor sanguinis or in serum, and retaining all their physical
properties save their colour, then, as a result of the repeated total reflec-
tions, due to the differences in the refractive indices of the corpuscles
and the fluid in which they float, blood would appear as white as milk.

1 Hiifner, op. cit., Arch. f. PhysioL, Leipzig, 1894, S. 150.

234

HEMOGLOBIN.

But these total reflections do go on in the case of the actual coloured
corpuscles in a precisely similar manner to that which would occur in
the hypothetical case just discussed ; and the light reflected by them
is conditioned by, and corresponds to, the absorption of the spectral
colours exerted by the haemoglobin and the oxyhaemoglobin respectively.

The visible spectrum of reduced haemoglobin. — It has already
been stated that, when a solution of oxyhaemoglobin is reduced, the
two absorption-bands a and |3 disappear and are replaced by a single
one (7) situated between D and E, which is less deeply shaded and
possesses less sharply-defined edges (see Plate I., Spectrum 5). This
summary description must now be supplemented.

The right-hand diagram on p. 233 exhibits fairly accurately the
absorption of light by solutions of reduced haemoglobin of varying con-
centrations. The single absorption-band (7), though occupying in solutions
of from 0*2 to O4 per cent, and 1 cm. in thickness, the greater part of
the space between Frauenhofer's lines D and E, has its centre or darkest
region rather nearer D than E. According to my own measurements,
the darkest part of the band corresponds approximately to A. 550.

It is to be noted that solutions of reduced haemoglobin have a much
greater absorptive power for the rays between A and B, and a smaller
absorptive power for those between F and G-, than corresponding solu-
tions of oxyhaemoglobin.

THE SPECTROPHOTOMETHIC CONSTANTS OF EEDUCED HAEMOGLOBIN.

In his most recent researches, Hlifner has determined the spectro-
photometric constants of haemoglobin for the same spectral regions as
were selected by him, in the same researches, for the determination of
the constants of oxyhaemoglobin.

In the case of reduced haemoglobin the respective extinction-co-
efficients are distinguished as sr and s'r, and the corresponding absorp-
tion relations as Ar and A'r.

The following are the results of Hiifner's determination i1—

Ar

A'r

(\ 554-A 556)

(X 531 -5-A 542-5)

0-001354

0-001778

The quotient — is a constant of special importance; it is 07617.

2r

The value of the quotient - has also been determined by Hiifner ; 1 it
is 0-6541.

The determination of the amount of oxy- and reduced haemo-
globin 'when both are present. — Yierordt pointed out that the absorption

1 G. Hiifner, "Neue Versuche zur Bestimmung der Sauerstoffcapacitat des Blutfarb-
stoffs," Arch.f. PhysioL, Leipzig, 1894, S. 140.

SPECTROPHOTOMETRIC DATA. 235

of light (as determined by the extinction-coefficient) in a definite spectral
region, exerted by a mixture of two or more colouring matters, is the sum of
the extinction-coefficients of each of its coloured constituents; and that in
the case of a solution containing two colouring matters, if we are acquainted
with the optical constants of each in two and the same spectral regions, we are
able by the spectrophotometer to determine the relative and absolute amount
of each constituent. In a similar manner we should, according to theory,
be able to determine the amounts of three or of x colouring matters coexisting
in a solution, if we were acquainted with the value of A in three and the same,
or in x and the same spectral regions. The immense importance of a method
which permits of the accurate determination of oxy- and reduced haemoglobin
in blood, and which furnishes us with essential data for calculating the
amount of oxygen present in combination with haemoglobin, makes it
necessary that we should explain the nature of the very simple calculations
which enable us, from the determination of the extinction-coefficients in two
spectral regions, to effect a determination which, so far as I know, cannot
be carried out with any pretence to scientific accuracy, or even with any claim
to be presumably correct, by any other process whatsoever.

We shall assume that, by following methods which we shall not attempt
to describe, but for which the reader is referred to Hiifner's original papers,
blood has been diluted with O'l per cent, of aqueous solution of NaOH,
under conditions which preclude the possibility of contact with oxygen, and
that in the diluted blood solution the extinction-coefficients have been deter-
mined in the first and in the second regions selected by Hiifner. These
extinction- coefficients of a mixture of two colouring matters, we shall represent
by E and E.'

Let Ar be the absorption relation of (reduced) haemoglobin in the first

region (A 554 - A 556).
A'r that of the same body in the second spectral region (A 531*5 -

A 542-5).
A0 the absorption relation of oxyhsemoglobin in the first spectral

region.
A'0 that of the same body in the second spectral region.

Then the percentage of (reduced) haemoglobin, which we may designate x, will
be found by the equation —

x__ArA'r(E'A'0-EA0)

A 0 Ar — A0 A r

and the percentage of oxyhaemoglobin by the following equation —

_A0A'0(EAr-E'A'r)

y A' A 44'

j± 0Ar — <a.0 A r

Having thus determined by spectrophotometry the amount of oxyhaemoglobin
by weight existing in a known volume, say 100 c.c. of blood, we can ascertain
the volume of the respiratory oxygen measured at 0° C. and 760 mm. pressure
(which could, but probably with less accuracy, be likewise determined with the
aid of the mercurial pump and subsequent analyses of the gases boiled out of the
blood) by multiplying each gramme of oxyhsemoglobin found by 1-338 (or 1'34).
In this manner Hiifner, having determined the relative and absolute amounts of
haemoglobin and oxyhaemoglobin in the blood, drawn simultaneously from the
main artery and vein of a limb, ascertained the amount of oxygen in each.
There is a strong presumption that determinations of oxygen made in this manner
are nearer the truth than those which the more complex and laborious methods
by means of the mercurial pump and gas analysis are capable of giving. In the
process of raising the blood to a temperature of at least 40° C. in the exhausted

236 HEMOGLOBIN.

chamber connected with the mercurial pump, some of the oxygen must be used
up in oxidising the readily oxidisable substances existing in the blood, and
especially in venous blood, and an error will be thereby introduced unequally
affecting different samples of blood, — an error which is influenced by the
duration and extent to which the heat is applied to the blood and the rapidity
with which the aqueous vapour and gases evolved by the blood are removed.

The photographic spectrum of reduced haemoglobin. — When
the molecule of dissociable oxygen is removed from oxyhaemoglobin,
either by the action of reducing agents, or by boiling in vacuo, the
absorption-band in the extreme violet is remarkably displaced towards
the less refrangible end of the spectrum, the centre of absorption-
corresponding to X 426-0. The difference in the position of Soret's
band in the oxy- and in reduced haernoglobin is shown in the photo-
type (Fig. 33). VvHien we reflect that the addition of a molecule of
oxygen to the enormous molecule of haemoglobin cannot affect in an
appreciable manner the mass of the molecule, we must conclude that
the displacement of the absorption-band towards the ultra-violet end
when hemoglobin combines with oxygen (all other conditions remaining
the same), indicates that this combination leads to a notable acceleration
of the motion of the intramolecular group of carbon atoms upon which
the extreme violet absorption-band depends.

The amount of oxygen with which haemoglobin combines to
form oxy haemoglobin. — It is believed, on various grounds, that one
molecule of haemoglobin combines with one molecule of oxygen to form
the compound which we know as oxyhaemoglobin.

The most recent determinations made by Hlifner have shown that
1 grm. of reduced haemoglobin of the ox can link to itself T338 c.c. of
oxygen or carbonic oxide (measured at 0° C. and 760 mm. pressure).
The molecular weight of the haemoglobin of the ox (calculated from
Hiifner's most recent estimations of the iron which this body contains)
= 16669. The volume of oxygen absorbed by reduced haemoglobin,
calculated from this molecular weight, should be 1*34 c.c., so that the
result of experiment agrees in a surprising manner with theory.

Differences in chemical reactions between solutions of reduced
and oxyhaemoglobin. — 1. Solutions of reduced haemoglobin when boiled
in vacuo, or subjected to the action of CO, unlike solutions of oxyhaemo-
globin, yield no oxygen.

2. They are not decomposed even by long contact with trypsin, which
readily splits up oxyhaemoglobin into hsematin and the products of
trypsin proteolysis.

3. They are unaffected by H2S, which, when acting for a sufficient
length of time upon oxyhaemoglobin, converts it into sulpho-methaemo-
globin.

4. Nitrites, potassium ferricyanide, and permanganate, and many
other oxidising and reducing agents, exert no action on reduced haemo-
globin, whilst they convert oxyhaemoglobin into methaemoglobin.

5. When treated with alcoholic or watery solutions of acids or
alkalies, in the complete absence of free oxygen, haemoglobin yields
purple-red solutions or precipitates. The haemoglobin is, under these
circumstances, split up into an iron-containing coloured body — Jicemo-
chromogen — and into an albuminous body or bodies. Oxyhaemoglobin,
under the same conditions, splits up into an iron-containing body—
Ticematin — and albuminous products.

COMPOUNDS OF HEMOGLOBIN WITH GASES. 237

Non-existence of the so-called " pseudo-haemoglobin."— After
treating blood with reducing agents until the two bands of oxyhaemoglobin
were no longer visible, Siegfried1 found that there yet remained oxygen
removable by boiling in a barometric vacuum. He therefore concluded that,
in addition to oxyhsemoglobin, there existed another oxygen compound of
haemoglobin, and that this is characterised by the same absorption spectrum as
reduced haemoglobin. To this hypothetical body he gave the name of pseudo-
luemogloljin. Its existence has been absolutely disproved by Hiifner.2 The
mistake into which Siegfried fell illustrates the danger of drawing conclusions
from qualitative spectroscopic observations. Hiifner has shown that without
spectrophotometric determinations it is impossible to know whether a solution
of blood or of haemoglobin is completely reduced. The only reliable criterion
is to be obtained by determining the values of er and e'r so as to ascertain the

quotient — which should = 0'76 17.

er

Blood which has been proved to be completely reduced in this manner,
yields no trace of oxygen when boiled in a mercurial pump.

THE COMPOUNDS OF HEMOGLOBIN WITH CARBONIC OXIDE AND NITRIC
OXIDE, AND THEIR RELATION TO OXYHSEMOGLOBIN.

Introductory remarks. — In a previous part of this article, I have
referred to oxyhsemoglobin as an easily dissociated compound, formed
by the linking of one molecule of oxygen to a molecule of the highly
complex, iron-containing, crystalline colouring matter, "haemoglobin,"
and I have subsequently shown that this conception has received con-
firmation through the fine researches of Hiifner on the molecular
weight of haemoglobin and on the volume of oxygen with which it
can combine. In the present section, reference must be made to ad-
ditional facts which, besides possessing an interest of their own, throw
fresh light on the nature of oxyhsemoglobin, and, in a measure, on the
function subserved by it, although this subject will be more fully dis-
cussed under the heading of " Respiration."

It had been noticed independently by Claude Bernard 3 and by Hoppe,4
that blood which had been treated with carbonic oxide, or the blood of
men and animals asphyxiated by charcoal fumes, presents an intensely bright
arterial colour, but that, unlike arterial blood, it does not in a few hours change
to a venous hue, but retains its vermilion tint for long periods of time. The
idea forced itself on the minds of both Claude Bernard and Hoppe, that through
the action of CO the power which the coloured corpuscles possess of acting as
oxygen-carriers had in some way been interfered with. Claude Bernard has,
however, the merit of being the first to show that, when brought in contact
with the blood, CO is absorbed and displaces oxygen ; and he afterwards based
upon these facts a method for the quantitative determination of the oxygen of
the blood.

At the same time as, and independently of, Bernard, Lothar Meyer5

1 "Ueber Hamoglobin/'^rc/i. /. Physiol., Leipzig, 1890, Phys. Abtli., S. 385.

2 " Bestimmung der Sauerstoffcapacitiit des Blutfarbstoffs," ibid., 1894, Phys. Abth.,
S. 140 and 175.

3 " Lemons sur les effets des substances toxiques et me'dicamenteuses," Paris, 1857,
p. 158 ; also " Proprie'te's des liq. de 1'organisme," Paris, 1859, tome i, p. 355.

4 "Ueber die Einwirkung des Kohlenoxydgases auf das Hamatoglobulin, " Virchow's
Archiv, 1857, Bd. xi. S. 288.

5 "Die Gase des Blutes," Gottingen, 1857; and Ztschr. f. rat. Med., 1858, S. 256;
"De sanguine oxydo carbonico infecto," Diss. Inaug., Vratislavice, 1858.

238 HEMOGLOBIN.

showed — (1) that the absorption of oxygen and carbonic oxide by blood does
not proceed according to Dal ton and Henry's law — a proof, amongst many
others, that these gases are chemically combined with some constituent of
the blood and not held in a state of simple solution ; (2) that blood which
has been deprived of its gases by boiling in vacuo, combines with the same
volume of carbonic oxide as of oxygen — in other words, that when carbonic
oxide replaces the oxygen of the blood, one molecule of the former takes the
place of one molecule of the latter (i.e. CO replaces 02). Lothar Meyer
further showed that hsematin could not be the body with which 02 and CO
entered into combination, and expressed the surmise that it might prove
to be the same as constituted the red blood crystals described by Lehmann.1
The truth of the surmise was soon proved beyond the possibility of doubt,
it being shown that the O2- and CO-compounds of the blood-colouring matter
are isomorphous, that they are characterised by a similarity in their power of
absorbing light, but that the CO-compound is distinguished by not being
decomposed by reducing agents (Hoppe-Seyler).

Hermann 2 subsequently showed that just as CO possesses the power
of displacing the oxygen of oxyhaemoglobin, nitric oxide (NO) in its
turn is capable of displacing CO, one molecule of the former replacing
one molecule of the latter, the NO-compound being, like the CO-com-
pound, absolutely irreducible.

The three compounds of haemoglobin were shown to be isomorphous,
to be characterised by a highly florid colour, only slightly differing in
tint one from the other; their visible spectrum was found to be distin-
guished by two absorption-bands between D and E, at first sight appear-
ing identical in the three cases, though careful measurement revealed a
very slight shifting of the bands towards the more refrangible end of the
spectrum in the case of the CO -compound.

They were all three found to be free from pleochromatism —
a character in which they differ strikingly from reduced haemo-
globin. Whilst the CO - compound is much more stable than the
02-compound, the NO-compound is again more stable than the CO-
compound.

It was at first believed that the CO-compound, unlike oxyhaemo-
globin, could not be dissociated. I was the first to show that by the
long-continued passage of neutral gases through solutions of CO-hsemo-
globin, the CO is gradually driven out, and reduced haemoglobin is
obtained.3 Donders,4 to whom the discovery of the fact is always
ascribed, drew attention to it in a highly interesting theoretical paper.
Zuntz 5 immediately afterwards showed, in contradiction of Nawrocki,6
that blood saturated with carbonic oxide, when boiled in vacuo, gives up
its carbonic oxide and that it manifests the absorption-band of reduced

1 " Consideranti enim quaj his in rebus din versatus Lehmann de rubris illis sanguinis
crystallis nuper publicavit, plus quam verisimile videbitur, hac cum substantia et oxygenium
et oxydum carbonicum conjunctionem chymicam posse mire"; Lothar Meyer, "De
sanguine oxydo carbonico infecto," p. 12.

2 " Ueber die Wirkungen des Stickstoffoxydgases auf das Brut," Arch. f. Physiol.,
Leipzig, 1865, S. 469.

3 A. Gamgee, "On Poisoning by Carbonic Oxide Gas, and by Charcoal Fumes,"
Journ. Anat. andPhysiol., London, 1867, vol. i. pp. 339-346.

4 Donders, " Der Chemismtis der Athmung, ein Dissociations-process," Arch. f. d. ges.
PkysioL, Bonn, 1872, Bd. v. S. 20-26.

5 " 1st Kohlenoxydhamoglobin eine feste Verbindung ? " Arch. f. d. ges. Physiol.,
Bonn, 1872, Bd. v. S. 584-588.

6 " De Claudii Bernard! methodo oxygenii copiam in sanguine determinandi," Inang.
Diss., Vratislaviw, 1863.

CARBONIC OXIDE HEMOGLOBIN.

239

haemoglobin, and Podolinski 1 succeeded in dissociating blood saturated
with nitric oxide, by passing a stream of hydrogen through it for an
hour and a half; at the end of which time the blood presented the
absorption-band of reduced haemoglobin.

Having passed in review the chief facts which exhibit the relation-
ship existing between the different compounds of haemoglobin, and which
illustrate the nature of the combination of haemoglobin with gases, some
of the characters and properties of CO-haemoglobin and NO -haemoglobin,
but particularly of the former, must be systematically though briefly
described.

CARBONIC OXIDE HAEMOGLOBIN (CO-HAEMOGLOBIN).

Mode of preparation. — A current of pure carbon monoxide is passed
through a saturated solution of oxyhsemoglobin. The solution acquires a
carmine-like tint in contrast to the scarlet colour of oxyhsemoglobin. This
solution is then cooled to 0° C., and, after being treated with one-fourth of
its volume of alcohol previously cooled to 0° C., is set aside at a tempera-
ture which must not rise above 0° C., but which should be as low as possible.
After some hours or days, the CO-compound, which is more sparingly soluble
than Og-hsemoglobin, separates in crystals, of which the forms are identical
with those of that body.

The absorption of light by CO-hsemoglobin. — (a) The visible
spectrum. —Solutions of this body possess more of a bluish-red tint
than the 02-compound. If solutions of equal concentration of the
oxygen and carbonic-oxide compounds be compared, it will be found, on
spectroscopic examination, that the CO-compound absorbs the blue rays
of the spectrum to a less degree than oxyhaemoglobin.

Between D and E are seen two absorption-bands which, unless very
closely studied, appear absolutely identical with those of oxyhaemo-
globin (see Plate I., Spectrum 6). On careful measurement, however, it
is seen that both the bands are very slightly shifted in the direction
of E; that is to say, towards the violet end. This is best seen by
noticing the interval between D and the adjacent border of the first
absorption-band ; in the case of the CO-compound this interval is broader
than in that of the 02-compound.

The spectrophotometric constants of CO-hsemoglobin. — These
constants were re-determined by Hiifner in 1894, at the same time as
those of oxy- and reduced haemoglobin, and for the same spectral
regions, with the results exhibited below.2 The coefficients of extinction
in the case of CO -haemoglobin are designated for the region X 554-?, 565,
ec, and for the region x 531-5— X 542'5 e'c, whilst the corresponding
absorptive relations are designated Ac and A'c.

Ac

*.

A 554-X 565

A 531-5-X 542-5

0-001383

0-001263

1 " Ueber die Austreibbarkeit des CO- und NO- aus dem Blute," Arch.f. d. ges. Physiol.,
Bonn, 1872, Bd. vi. S. 553-555.

2 Hiifner, op. cit., S. 141 and 142.

24o HEMOGLOBIN.

(b) The photographic spectrum of CO-heemoglobin.— In Fig. 35
are shown reproductions of the photographic spectrum of this com-
pound, contrasted with that of the oxygen compound. The band of
Soret is just as well marked in the one as in the other, but in the
case of the CO-hsemoglobin there is a decided shifting of the band
in the extreme violet towards the red, which is somewhat curious,
considering that the bands in the visible spectrum are, though to a
much less extent, shifted in the opposite direction. I have shown that
there is absolute identity in the position of the absorption-band in the
extreme violet, in the case of the CO- and NO- compounds of haemoglobin.1

The principal characteristic reactions of CO-hsemoglobin.
1. When treated with Stokes' reagent, solutions of ammonium sulphide,
and the like, no change whatever occurs, either in the colour or the
spectrum of blood saturated with carbonic oxide, or in solutions of
pure CO-hsemoglobm.

G HK L M N 0

FIG. 35. — The photographic spectrum of oxyhsemoglobin and of CO-hsemoglobin.

2. The blood of men or animals asphyxiated by carbonic oxide, or
by a gas containing it (charcoal fumes, coal gas), if pretty fully saturated,
possesses and retains for a long time a florid arterial colour, and when
diluted is found to be partially or completely irreducible. Hoppe-
Seyler found that if such blood is sealed in glass tubes, it may retain for
some years its characteristic spectroscopic properties, and even admit
of CO being boiled out, with the aid of the mercurial pump, and
identified by chemical analysis.

3. The addition of a concentrated solution of sodium hydrate (density
1*3) to blood, saturated with CO in the proportion of about two parts
of the former to one of the latter, causes the blood to assume a fine
scarlet colour, and to deposit a cinnabar-red precipitate. The same
coloration and precipitate is produced with solutions of pure CO-
hsemoglobin. According to Hoppe-Seyler, the precipitate is composed
of CO-hsemoglobin, rapidly passing into CO-hoemochromogen. When
normal blood is treated in the same way with sodium hydrate, it is

1 Gamgee, Proc. Roy. Soc. London, 1896, vol. lix. p. 276.

NITRIC OXIDE HAEMOGLOBIN. 241

converted into a black shining mass, which when spread in thin layers
over porcelain appears of a greenish-brown colour.

4. Aqueous neutral solutions of pure CO-haemoglobin, when heated
to boiling point, furnish a bright red precipitate, composed of coagulated
albuminous substances and CO-haemochromogen (Hoppe-Seyler).

5. Solutions of carbonic oxide haemoglobin, treated with NO in the
absence of oxygen, are at once decomposed, and liberate CO (Hiifner).

NITRIC OXIDE HEMOGLOBIN (NO-HEMOGLOBIN).

Mode of preparation. — So great is the affinity of nitric oxide for oxygen,
that, when it comes in contact with it, deep red fumes of nitrogen peroxide, N0.2,
is formed. When this gas comes in contact with water, the decomposition
indicated in the following equation occurs : —

But as all free acids decompose the colouring matter of the blood, before
causing nitric oxide to act upon blood certain precautions must be taken ;
for even if atmospheric oxygen be eliminated and nitric oxide caused to act
upon oxyhaemoglobin, nitrous oxide would be formed at the expense of the
oxygen of that body ; and next, by the action of water, nitric acid, which
would immediately decompose the haemoglobin.

Two methods of proceeding are open to us — (a) To add to the solution of
oxy haemoglobin which is to be subjected to the action of nitric oxide, sufficient
alkali to neutralise the nitric acid which will be formed. Such a solution
must be placed in a flask, permitting of the whole of the air above the solution
being driven out and replaced by a neutral gas, before allowing access to the
nitric oxide. After the latter has exerted its action, care must be taken again
to pass a neutral gas through the apparatus and solution, so as to remove all
traces of free nitric oxide.

(b) The solution of oxyhaemoglobin is subjected to the long-continued
action of carbonic oxide, so as to form CO-haemoglobin and to expel nil traces
of dissolved oxygen. Otherwise, the process is constructed as described
under (a). This process would be certainly preferred, if it were desired to
crystallise the NO-compound.

Physical and chemical characters. — Blood saturated with nitric oxide
possesses almost as florid a colour as CO -blood, though Hermann says
that it does not present the slight bluish shade of the latter. It exhibits
no dichroism. Solutions of NO -haemoglobin, or diluted NO-blood,
exhibit a visible spectrum in which, as I have convinced myself, the
bands occupy precisely the position of the two oxyhsemoglobin bands.
In the photographic spectrum, however, the band in the extreme violet
exhibits absolute coincidence with that of CO -haemoglobin.

NO-haemoglobin can be crystallised, and, as Hermann showed, the
crystals are identical with those of oxyhaemoglobin and CO-haemoglobin.

ALLEGED (BUT PROBLEMATICAL) COMPOUNDS OF HEMOGLOBIN

WITH GASES.

1. With hydrocyanic acid.— The most discrepant statements have
been made in reference to the very simple question — whether hydrocyanic
acid added to, or passed through, blood affects the characters of its absorption-
spectrum. In spite of these, it may be definitely stated that, at ordinary
temperatures, and when acting for moderate periods, hydrocyanic acid leads
VOL. i. — 1 6

242 HEMOGLOBIN.

to no change in the physical characters of the blood, of which the spectrum
remains unchanged, and of which the property of being reduced by suitable
agents remains unaffected.

Upon what appears to me to be altogether insufficient evidence, Hoppe-
Seyler,1 however, came to the conclusion that hydrocyanic acid forms an easily
decomposed compound with haemoglobin. If hydrocyanic acid be added to
a solution of oxyhaemoglobin, on crystallising out the latter it retains some of
the acid. These crystals may be repeatedly crystallised, and when dried in
vacuo over sulphuric acid they are found to contain hydrocyanic acid. The
supposed compound of hydrocyanic acid with oxyhaemoglobin presents an
absorption-spectrum absolutely identical with that of oxyhaemoglobin, and is
reduced just as easily by such agents as ammonium sulphide or Stokes's re-
agent. On the other hand, blood to which hydrocyanic acid has been added
shows the bands of oxyhaemoglobin for a much longer time than normal blood.

It appears to me that no proof whatever has been advanced of the
existence of a chemical compound of oxyhaemoglobin with HCN.

That some hydrocyanic acid should adhere to haemoglobin, as it crystallises
out of the mother liquor which contains the acid, is quite in accordance with
a number of experiences of a similar kind, and can by itself afford no evidence
of an actual compound existing. The resistance of blood to which hydro-
cyanic acid has been added, to decomposition, when confined in a sealed or
closed vessel, can, on the other hand, be easily explained by the unquestion-
able arrest or slowing of the process of putrefaction in the presence of hydro-
cyanic acid. It is, undoubtedly, the products of putrefaction which are the
causes of the apparently spontaneous reduction of the oxyhaemoglobin of blood
confined in a receptacle to which air has no access ; so that an agent which
does inhibit putrefaction — as hydrocyanic acid unquestionably and admittedly
does — and, at the same time, does not, at ordinary temperatures, decompose
oxyhaemoglobin, would be expected to act as hydrocyanic acid has been found
to do in furthering the persistence of the oxyhaemoglobin bands.

What I have just stated in reference to the probable non-existence of a
compound of HCN with oxyhaemoglobin, does not imply my disbelief in the
existence of an interesting compound of hydrocyanic acid with methaemo-
globin, described by Robert, which will be discussed after the latter body
has been described.

2. With cyanogen.— Kay Lankester'2 believed that cyanogen formed a
compound with haemoglobin, probably analogous to the CO- and NO-com-
pounds, and characterised by an absorption-band, resembling that of, but
obviously not due to, reduced haemoglobin. Many discordant statements have
been published on this matter. It appears that by the prolonged action of
cyanogen, as by the prolonged action of HCN, there is produced Kobert's
cyanogenmethaemoglobin (see p. 248).

3. With acetylene (C2H2). — Bistrow and Liebreich 3 surmised that acety-
lene forms a very unstable compound with haemoglobin, easily reducible by
sulphide of ammonium and similar agents. On the evidence at present at our
disposal, the existence of this compound must be considered as more than
problematical.

4. With carbon dioxide. — According to Bohr, haemoglobin forms a series
of compounds with carbon dioxide, which possess spectra identical with those
of reduced haemoglobin. He states, further, that if a solution of haemoglobin
be brought in contact with a mixture of oxygen and carbon dioxide, the

1 " Cyanwasserstoffheemoglobinverbindungen," Med.-chem. Untcrsuch., Berlin, 1868, S.
206-208.

2 " Ueber den Einfluss des Cyangases auf Hamoglobin nach spectroscopischen Beobach-
tungen," Arch. f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 491-493.

8 " Ueber die Wirkung des Acetylens auf das Blut," Ber. d. deutsch. chem. Gesellsch.,
Berlin, 1868, Bd. i. S. 220.

PRODUCTS OF DECOMPOSITION. 243

amount of either of these gases which is absorbed is independent of the
other.

A careful study of the whole of Bohr's researches on this subject, as well
as those on the various hypothetical compounds of haemoglobin with oxygen,
has convinced me that his work is pervaded by fallacies, which spring in part
from erroneous methods of work, in part from a non-appreciation of physical
principles of which the exactitude is beyond dispute ; the discussion of Bohr's
statements in a text-book would be, under these circumstances, altogether out
of the question.

THE IMMEDIATE DERIVATIVES AND PRODUCTS OF DECOM-
POSITION OF OXYH^MOGLOBIN AND REDUCED HAEMO-
GLOBIN.

Introductory observations. — It has already been stated, that when
the blood-colouring matter is subjected to the action of strong alkalies
and of acids, or even of salts possessing an acid reaction, or to the
action of heat, of alcohol, and of many other chemical agents, it under-
goes a decomposition of which the chief products are an albuminous
substance or substances, and a colouring matter which contains the whole
of the iron originally present in the oxyhsemoglobin or haemoglobin
decomposed.

Under ordinary circumstances, when oxyheeinoglobin is decomposed in
the presence of air, the coloured product of decomposition is the body
we know as licematin, the amount of which produced corresponds theo-
retically to 3*8 per cent, of the oxyhsemoglobin. Traces of organic
acids are said to result from the decomposition, the main product of
which is, however, composed of the albuminous residue of the blood-
colouring matter (vide infra). If, however, instead of decomposing
oxyhciemoglobin, we employ reduced haemoglobin and carry out the
process in the complete absence of oxygen, we obtain, not hsematin, but
a body of which some of the optical characters were first described
by Stokes, and which he named reduced hcematin, to indicate that it
may be obtained by the action of reducing agents on hseinatm. Instead
of employing this term, it is better to adopt that of hamiochromogen,
introduced by Hoppe-Seyler, to whom we owe nearly all the knowledge
we possess with regard to it. According to Hoppe-Seyler, hsemochro-
mogen constitutes the coloured radicle of the blood-colouring matter,
upon which its essential optical properties and its property of com-
bining with oxygen, carbonic oxide, and nitric oxide depend.

Under the influence of carbonic acid, and very dilute acids acting
for comparatively short periods of time, oxyhsemoglobin, long before the
complete splitting up into hsematin, undergoes a change which is doubt-
less of the nature of a decomposition ; this change is identical with that
which is also brought about by a variety of oxidising agents, typically
by ozone, nitrites, and potassium ferricyanide ; to the body which
results, the name of methsemoglobin has been given. It will be con-
sidered first amongst the decomposition products of oxyhsemoglobin.
We shall show it to be a substance which is formed in the living body,
under the influence of certain poisonous agents, and is occasionally
found in old blood extravasations; it possesses the power of forming
molecular compounds with certain bodies, such as nitrites, hydrocyanic
acid, and cyanogen.

244 HEMOGLOBIN.

THE ALBUMINOUS EESIDUE OF THE BLOOD-COLOURING MATTER.

An unfortunate error has become popular, and has, indeed, been
propagated by a large number of text-books, namely, that when oxy-
haernoglobin is decomposed, it splits up into haematin and a definite
albuminous matter belonging to the group of globulins, and designated
globin. There is absolutely no ground for such a statement. The term
globin was, it is true, assigned by Preyer to an albuminous substance,
which he obtained as a product of the spontaneous decomposition of
solutions of oxyhaemoglobin, but this body did not possess the character-
istic properties of the globulins, and there is no ground for considering
it as representing the albuminous body which, by linking to itself a
coloured iron-containing radicle, forms crystalline haemoglobin.

Our knowledge on this matter is indeed of the most unsatisfactory
character. We know, and have shown (see p. 207), that solutions of oxy-
haemoglobin in the presence of many of the reagents for albumin (so long
as these do not decompose the blood-colouring matter) behave quite differ-
ently from solutions of the native albumins, globulins, etc. Thus copper
sulphate, mercuric chloride, silver nitrate, and the acetates of lead do
not produce even a cloudiness when added to solutions of pure haemo-
globin, so long as this remains undecomposed. It has long been recog-
nised, too, that Lehmann's hypothesis, that the blood-colouring matter
was composed of colourless crystals tinted by a red pigment, was false ;
but as to the true nature of the albuminous residue, we have very little
knowledge, though the facts in our possession almost force us to the
conclusion that it is not identical in all animals, as shown by the
difference in the percentage of sulphur in the haemoglobin of the horse
and the dog.

The reagents which we employ to decompose the blood-colouring
matter yield us derivatives of the albuminous residue, not the body
itself ; we obtain acid albumin as a result of treatment with acids, alkaline
albuminates as a result of treatment with alkalies. The most interest-
ing observations on the albuminous products of the decomposition of oxy-
haemoglobin were published by Kiihne1 thirty years ago. He showed that
when C02 is passed through solutions of pure oxyhaemoglobin a flocculent
precipitate is thrown down, which does not possess, as had been errone-
ously asserted by A. Schmidt, fibrinoplastic properties, and which does
not behave as a globulin. According to Kiihne, this precipitate possesses
so peculiar an appearance under the microscope that it cannot be mis-
taken for any other substance. It forms long colourless fibres which
are so like fibres of connective tissue that they might be taken for them.
This substance differs fundamentally from globulin ; it is, for example,
insoluble in water containing oxygen in solution.

METH^EMOGLOBIN.

Hoppe-Seyler was the first 2 to observe that solutions of oxyhaemo-
globin exposed to the air, or filter papers saturated with such solutions,
often assume a brown colour. Under these circumstances, the solution

1 "Lehrbuch," 1866, S. 206, 207.

2 Centralbl. f. d. med. Wissenscli. , Berlin, 1864, No. 53. See also Med.-chem. Unter-
snch., Berlin, S. 378, mid " Die Zusammensetzung des Methamoglobin, imd seine Umwand-
limg zu Oxyhamoglobin," Ztsclir. /. physiol. Chem., Strassburg, 1878, Bd. ii. S. 150, 155.

METH.ZMOGLOBIN. 245

is found to have become acid and to exhibit a spectrum in which, in
addition to the two bands of oxyhsemoglobin, one is seen in the red,
occupying much the position of the band of acid hematin.

Hoppe-Seyler applied the name of inethsemoglobin to the very
indefinite and problematical body whose solutions possessed the above
characters, and held it to be a product of the partial reduction of
oxyh?emoglobin, derived from it by the removal of a portion of the
dissociable oxygen of that compound.

I myself, soon after, investigated the changes brought about in the
properties of oxyhsemoglobin under the influence of nitrites, and in a
memoir,1 of which the experimental facts have, so far as they have yet
been controlled, been confirmed in every particular, pointed out the
remarkable phenomena which attended the conversion of oxyhsemoglobin
into methaemoglobin, though I committed the error of believing that the
changes described by me were due to the combination of nitrites with
oxyhsemoglobin, and not to an action which was afterwards shown to be
possessed by a large number of both oxidising and reducing substances.
I showed that blood which had been acted upon by nitrites, in addition
to marked and definite changes in colour and spectrum, had almost
entirely lost its power of absorbing oxygen from the atmosphere ; that,
under the influence of nitrites, the oxygen of oxyhgemoglobin is not
removed, but passes into a condition in which it is no longer removable
by boiling in vacuo or by the action of carbonic oxide. The action
of reducing agents reveals, however, as I showed, that the molecule
of loose oxygen of oxyhremoglobin is still present in blood which
has been acted upon by nitrites, for, in the absence of all traces
of oxygen, reducing agents first of all and instantaneously liberate
oxyhaemoglobin, which is only afterwards reduced. I pointed out that
the chocolate-coloured nitrite blood can be crystallised, the colouring
matter being isomorphous with haemoglobin and its compounds, and
that the crystals contain the nitrite which has brought about the
change, though I showed that the composition of these molecular com-
pounds of oxyhsemoglobin is not a constant one. After innumerable
contradictions, it has been proved, though without a word of acknow-
ledgment, mainly by the researches of Hiifner and his pupils, that my
account of the changes which characterise the formation of methaBmo-
globin was, in every particular, exact, whilst the comparatively recent
statement, by Kobert, of the existence of combinations of hydrocyanic
acid and cyanides with methsemoglobin is an illustration of the class
of compounds of oxyhaemoglobin which I was the first to discover and
describe, and of which doubtless a large number will be obtained.

Mode of preparation. — A large number of inorganic and organic bodies,
acting upon solutions of oxy haemoglobin, convert it into methsemoglobin.
The chief of these are potassium ferricyanide — which, on account of the
rapidity of its action, is to be preferred to all others — nitrites, chlorates,
potassium permanganate, nitrobenzol, pyrogallol, pyrocatechin, acetanilid, etc.

In order to study the spectroscopic characters of methsemoglobin, a
solution of diluted blood is treated with a few drops of a strong solution
of potassium ferricyanide, when the change in colour and spectrum is seen to
occur almost instantly. To prepare the crystalline colouring matter, 2 or
3 c.c. of a saturated solution of potassium ferricyanide or of a nitrite is

1 A. Gamgee, "On the Action of Nitrites on Blood," Phil. Trans., London, 1868, vol.
clviii. pp. 589-626.

246 HAEMOGLOBIN.

added to a litre of saturated aqueous solution of crystals of oxylisemoglobin,
and after the conversion into methaemoglobin lias occurred, about 25 per cent,
of alcohol added. The mixture is then exposed to a temperature below 0° C.
I succeeded in recrystallising methsemoglobin prepared by the action of
potassium nitrite and of ethyl and amyl nitrites on oxyhseinoglobin.

Chemical and physical characters. — Crystals of methsemoglobin are
more sparingly soluble than those of oxyhaemoglobin, and the colorific
intensity of their solutions is less.

It is to be noted that, whilst solutions of reduced and oxyhaemoglobin
are not precipitated by either neutral or basic lead acetates, these
reagents added cautiously, with careful avoidance of an excess, precipi-
tate methcemoglobin, hcematin, and hcemytoporphyrin, and may be em-
ployed for the separation and detection of traces of oxy haemoglobin
when mixed with and concealed by any of the above-mentioned bodies.

Solutions of methaemoglobin, when of a neutral or a slightly acid
reaction, possess a chocolate-brown colour. When the solution is
rendered alkaline, its colour changes to red without a tinge of the
chocolate-brown.

The acid solution is found to present a spectrum in which the oxy-
heemoglobin bands a and /3 are very weak or even not visible, whilst an
absorption-band is seen in the red between C and 1), and nearer the
former. This band occupies nearly, though by no means exactly, the
position of a similar band in the spectrum of acid haematin (see Plate
II., Spectrum 5).

On now rendering the solution alkaline by means of ammonia, the
band in the red disappears, and is replaced by a faint absorption-band
immediately on the red side of D. By changing the reaction of the
solution, the alterations in its colour and spectrum may be repeated
indefinitely (Garngee).

If a solution of methaemoglobin be placed in a deep test tube, in
front of a spectroscope, and arrangements be made for allowing a stream
of solution of ammonium sulphide to flow to the bottom of the
liquid, it can be readily shown that at the very moment of the
contact of the reducing and the methsemoglobin solution, the spec-
trum of oxyhaemoglobin appears ; to be subsequently and much more
slowly replaced by that of reduced haemoglobin, which in its turn,
when shaken with air, yields oxyhaemoglobin.

A study of the photographic spectrum of methaemoglobin has led
me to results of great interest. The conversion of oxyhaemoglobin into
inethaemoglobin is attended by a shifting of the band of Soret from the
extreme violet to the ultra-violet properly so called (Fig. 36). The most
persistent part of the band in very dilute solutions, coincides, indeed,
with the H and K bands, but the band extends more and more into the
ultra-violet, as the concentration of the solution increases. The position
and characters of this band in the case of methsemoglobin absolutely
corresponds with those of the acid compounds of haematin, and not
with those presented by haemoglobin and its compounds, or by
haemochromogen (see Fig. 38).

This spectroscopic character certainly seems to lend weight to the
evidence of other kinds, which indicates that methaemoglobin is a first
product of the decomposition of the oxyhaemoglobin molecule, and that
this is a decomposition which leads to the separation of a compound of
haematin, and not of haemochromogen. Hoppe-Seyler, indeed, expressed

METHSEMOGLOBIN. 247

the opinion that the colouring matter in methsemoglobin is in the same
state as in hsematin, the iron being, as he thought, in the condition of a
ferric compound, whilst in oxyhsemoglobin and in hsemochromogen he
believed it to exist in a ferrous state, though the grounds for these very
definite statements are certainly wanting.

The researches of Hiifner on the oxygen of methsemoglobin.

—I had shown that the action of methsemoglobin, as produced by the action
of nitrites, could not be attended by a profound alteration in the constitution
of oxy haemoglobin, seeing that the addition of certain reagents at once caused
all the effects of the action to disappear, and revealed the continued existence
of oxidised haemoglobin. Nitrites (for these we should now read all agents
capable of transforming oxyhaBmoglobin into methsemoglobin) had, by my
experiments, been shown to resemble in no way those agents which thrust
oxygen out of the blood ; on the other hand, I had shown that the action of

G HK L M N 0

FIG. 36. — The photographic spectrum of oxyhsemoglobin and methsemoglobin.

nitrites resulted in ihe locking up of the oxygen of the blood, so as to render
it irremovable by carbonic oxide, or by a vacuum. But although I had dis-
covered that methaemoglobin, when treated with reducing agents, at once
liberates oxyhaBmoglobin, I had not been able to show that when the latter
substance is converted into the former the whole of its oxygen is locked up
without loss, and may be subsequently liberated. This was reserved for
Hiifner.

When nitric oxide acts upon a solution of rnethaemoglobin, the brown
colour is changed to bright red, the spectrum of the red solution being
identical with that of NO-hsemoglobin. Eeflecting on this experiment, Hiifner
thought that perhaps NO possesses the power of becoming oxidised to N02,
at the expense of the oxygen locked up in methsemoglobin (i.e. oxygen of
the original oxyhsemoglobin which had passed into a more stable combination).

As such might be the case, it occurred to Hiifner to determine the volume
of N02 produced (for this would bear a definite relation to the 0 abstracted
from methsemoglobin), by causing the nitrous acid (HN02), which would
be produced by the action of the water of the blood on N02, to decompose
urea, the N liberated being a measure of the oxygen derived from niethaenio-

248 HAEMOGLOBIN.

globin. The ingenious conception of Hiifner will be rendered evident by the
three following equations : —

(1) 6X0 + 2(Hb-09) = 4NO, + 2(Hb-NO).

(2) 4(N02) + 2(H26) = 2(N02H) + 2(N03H).

(3) 2(N02H) + CH4N20 = 3(H20) + 2C02 + 2(N2).

From these equations it results that each molecule of nitrogen liberated
will correspond to a molecule of oxygen which had become fixed in methsemo-
globin.

Whether the more firmly combined oxygen of methsemoglobin were capable
of oxidising nitric oxide or not, the oxygen of oxyhsemoglobin would certainly
be able to do so, and Hiifner proceeded to oompare the amount of N liberated
in the above reaction by solutions of exactly corresponding concentration of
oxyhsemoglobin and of alkaline methsemoglobin. The results left no room for
doubt, and led to the conclusion that when oxyhsemoglobin is converted into
methsemoglobin, the whole of its oxygen passes into a state of more intimate
combination, so that it can no longer be removed either by CO nor by a
vacuum, but is yet available to oxidise such bodies as N02.

The compounds of metheemoglobin with nitrites. — I showed, as
has already been stated, that when a solution of pure oxyhsemoglobin is
treated with a solution of a nitrite, so as to produce the change in colour
and spectrum which we now know to be characteristic of methsemoglobin,
the blood-colouring matter crystallised out of the solution is found to con-
tain the nitrite, though the proportion in which the latter combines with
the hsemoglobin is not constant. The discordance in results did not appear
to me surprising, and that " as in the case of other combinations of a molecular
kind, such as the union of salts with their water of crystallisation, of bases
with sugar, of albumin with metallic oxides, of iodine with the compound
ammonias, the amount of the simpler body added to the more complex should
vary within wide limits." I further speculated on the probability of a large
number of similar combinations to that of oxyhsemoglobin with nitrites
existing.

The compounds of methsemoglobin with HCN and cyanides.—
It has long been noticed that hypostatic marks on the bodies of men and
animals poisoned by prussic acid or metallic cyanides, as well as the mucous
membrane of the stomach, present a striking bright red colour. Kobert1
surmised ..that this coloration might be due to combination of methsemo-
globin with HCN or metallic cyanides, a hypothesis of which he thinks
he has obtained confirmation from his experiments. Kobert found that on
adding solutions of HCN of extreme dilution to a 1 or 2 per cent, solution
of methsemoglobin, these assume a beautiful bright red colour, whilst the
absorption band or bands of methsemoglobin have disappeared, and are
replaced by a single broad absorption-band between D and E, occupying about
the position of the band of reduced hsemoglobin. This band cannot, however,
be made to disappear by the action of oxygen.

According to Kobert, this band is not affected by the addition of ammonium
sulphide. He believes the body which is produced by the action of HCN on
methsemoglobin to be a compound of the two bodies, and he ascribes to it the
name " cyanogenmethsemoglobin," and represents it for brevity by the symbol
CNH'MetHb. He further lays claim to have discovered for the first time
similar compounds with nitrites (! !). But Kobert's view of the nature of the
action of HCN on methsemoglobin has not been universally accepted. The
absorption-spectrum which he has described as characteristic of his new
compound is identical with that described by Preyer as resulting from the

1 " Ueber Cyanmethamoglobin und den Nachweis der Blausaure," Stuttgart, 1891.

SULPHO-METH^EMOGLOBIN (?). 249

action of HCN on oxy haemoglobin, and by Nawrocki and Lankester as pro-
duced when KCN acts upon blood, especially with the aid of gentle heat, and
which has generally been held to be a compound of cyanogen and hsematin
(cyanhsematin).

Szigeti l maintains that Kobert's cyanogenmethsemoglobin is in reality
cyanhaematin, the first step in the action of HCJST being to split up the
methsemoglobin molecule into hsematin and an albuminous substance. I do
not, however, take this view, and, in spite of the evidence which Kobert has
adduced being in many respects incomplete, I am inclined to think that the
view which he has advanced is correct. In the first place, the certain existence
of compounds of the nitrites with methaemoglobin affords presumptive
evidence of the strongest kind that similar compounds with such bodies
as cyanogen, hydrocyanic acid, and cyanides exist ; in the second, the almost-
instantaneous action of solutions of hydrocyanic acid of phenomenal dilu-
tion renders it highly improbable that the action of hydrocyanic acid on
methaemoglobin is one in which decomposition into haematin is a preliminary
stage.

There can be no question that HCN acting in the cold, and, for a short
time upon, blood or on solutions of oxyhsemoglobin, produces no change in the
spectrum, and it is against all experience and analogy from the action of other
dilute acids on either oxyhaemoglobin or metheemoglobin to conclude that
solutions of HCN of extraordinary dilution should be able — and almost instan-
taneously— to split up the oxyorthomethsemoglobin molecule. Kobert has
found that a solution containing 0*000003 grin, of HCN is able to produce the
characteristic change in 1 c.c. of a 1 per cent, solution of methsemoglobin.
He has further shown that his assumed cyanogenmethaemoglobin contains
HCN which can be recovered from it without loss by distilling with sulphuric
acid.

CO-methsemoglobin. — According to Weyl and v. Anrep,'2 this com-
pound is produced when aqueous solutions of iodine and potassium iodide,
or solutions of potassium permanganate, continue to act upon a solution of
CO-hsemoglobin for several days. This body is said to retain the red colour
of CO-hsemoglobin, and to present the same absorption-bands in its spectrum.
I fail to understand the grounds for believing in its existence.

Sulpho - methsemoglobin. — This hypothetical body was believed by
Hoppe-Seyler3 to be the cause of the green coloration observed on the
surface of putrefying organs.

Sulphuretted hydrogen has no action on reduced haemoglobin. When
acting in small quantities on neutral solutions of pure oxyhsemoglobin, it
reduces these. If, simultaneously, a stream of sulphuretted hydrogen and
oxygen be passed through blood or neutral solutions of pure oxyhaemoglobin,
the solution assumes a green colour in thin, and a red colour in thick layers,
and becomes turbid. These solutions are characterised by the presence of two
absorption-bands in the red, one on the red side of, but quite close to, C ; the
other is about midway between C and D, the two bands being united together
by a shadow.

It appears to me that there is not the slightest ground for believing
that the phenomena above described are due to a definite body, — "sulpho-

1 " Ueber Cyanliamatin," Vrtljschr. f. gerichlt. u. off. Mcd., Berlin, Supp. Bd. vi.
S. 9-35. I only know this paper from the abstract by Andreasch in Jahresb. u. d. Fortschr.
d. Thicr-Chem. , Wiesbaden, 1883, Bd. xxiii. S. 620.

2 "Ueber Kohlenoxyd-Hamocrlobin," 1. Oxydation von CO-Hb zu Meth-Hb, Arch.f.
Physiol., Leipzig, 1880, S. 227-240.

3 CentralU. f. d. med. Wis&ensch., Berlin, 1868, No. 28; "Ueber die Einwirkung
des Schwefelwasserstoffs auf d. Blutfarbstoff," Med.-chem. Untersuch., Berlin, S. 651 ;
Araki, " Schwefelmethsemoglobin ," Ztschr. f. physiol. Chem., Strassbnrg, 1890, Bd. xi. S.
412-416.

250 HAEMOGLOBIN.

methsemoglobin " ; they are almost certainly caused by a mixture of de-
composition products of oxy haemoglobin, brought about by the action of H2S
upon it.

H^MATIN (C34H35N4Fe05, Hoppe-Seyler) ; (C32H30N4Fe03, Nencki

and Sieber).

As has been already stated, hsematin is the colouring matter
which results from the decomposition of oxyhsemoglobin by acids and
alkalies. In acid and alkaline solutions the body is characterised by
certain spectroscopic appearances, and especially by yielding, under
suitable conditions, when treated with reducing agents, a body possessing
the optical characters, when examine?!, with the spectroscope, which
were originally described by Stokes as those of " reduced hcematin" now
known as " JicemocJiromogen " (Hoppe-Seyler).

Mode of preparation. — As we are now in possession of an easy and in
all respects admirable method of preparing, in a state of great purity, the
crystalline hydrochlorate of haematin or " httanin " (see p. 252), the latter
body should invariably be employed in the preparation of pure haematin.

Pure crystallised hsemin (prepared by Schalfijew's process) is dissolved
in a highly dilute solution of potassium hydrate, and the alkaline solution
is precipitated by means of dilute hydrochloric acid. The rlocculent-
brown precipitate is washed with hot distilled water until the washings
give no turbidity with silver nitrate. The hsematin thus precipitated is
first dried at the temperature of 100°, and then at 115°, or even higher.

Physical and chemical properties. — Hsematin has not hitherto been
crystallised. In the condition of utmost purity it possesses a bluish-black
colour, and a very pronounced metallic lustre. When finely powdered it
appears as a dark brown powder, which is distinctly pleochromatic.

It is insoluble in water, alcohol, ether, and chloroform, but slightly
soluble in glacial acetic acid ; also in acidulated alcohol, but absolutely
insoluble in aqueous solutions of acids. It is very readily soluble in all,
even highly dilute, alkaline solutions.

Hsematin forms a crystalline compound with hydrochloric acid
(hsematin hydrochloride, or hsemin), which, because of its importance,
will be separately described, and also others with hydrochloric and
hydrobromic acids.1

It combines with potassium and sodium, as well as with calcium,
barium, and other metals. The calcium and barium compounds are
obtained by precipitating ammoniacal solutions of hsematin by means
of solutions of calcium or barium chloride, but they have not been yet
obtained in a state of purity, and have not been analysed.

Hsematin may be strongly heated to 180° C. without undergoing
decomposition. When heated further it is carbonised without previously
melting or taking fire, and liberates hydrocyanic acid, leaving a
residue of pure oxide of iron, which amounts to 12'6 per cent, of
the hsematin incinerated.

When boiled with concentrated potassium hydrate, hsematin under-
goes no perceptible change ; when fused with caustic potash, it is very
slowly decomposed, and evolves ammonia. It is only attacked by

1 M. C. Husson, Compt. rend. Acad. d. sc., Paris, tome Ixxxi. p. 477 ; Ar. D. Harris,
Journ. Physiol., Cambridge and London, 1885, vol. v. p. 209; D. Axenfield, Centralbl.
f. d. med. Wissensch., Berlin, 1885, No. 47.

H^MATIN. 251

concentrated hydrochloric acid, at a temperature above 150° 0. Con-
centrated sulphuric acid dissolves it, without any gas being evolved,
giving rise to a dark red solution, from which water precipitates the
substance known as " hsematoporphyrin " (see p. 258), which, as it
contains no iron, has been sometimes spoken of as iron-free hsematin.
This body is soluble in alkaline solutions, and both its acids and
alkaline solutions exhibit very characteristic absorption-spectra.

Alkaline solutions of hsematin in thick layers, when examined by
transmitted light, appear red, whilst thin layers appear of an olive-
green colour. Acid solutions, whatever the thickness of the stratum
examined, always appear of a brown colour.

When the spectrum of light transmitted through alkaline and acid
solutions of hgematin is examined by the photographic as well as by the
direct method, it is seen that the last rays of the spectrum to be
absorbed are the red rays up to B ; that the solutions are characterised
by a denned absorption-band between C and D, which is shifted towards
D in the case of the alkaline, towards C in the case of the acid solutions ;
that alkaline solutions, even when extremely diluted, effect a general
absorption of the whole ultra-violet, violet, etc., rays ; that acid solutions,
even when very highly diluted, whilst not exerting a general absorption
of the ultra-violet, exhibit an absorption-band at the junction of the
extreme violet and the ultra-violet, properly so called.

The absorption-bands in the visible spectrum of both alkaline and
acid solutions of hsematin are shown in Plate II., Spectra 2, 4, and 6.
The alkaline solutions exhibit one absorption-band between C and D, of
which the more refrangible border adjoins D, whilst acid solutions exhibit
an absorption-band also between C and D, of which the less refrangible
border adjoins C, though the position of the band is somewhat in-
fluenced by the particular acid which has been employed. Attention
is directed to the fact that the band between C and D in the spectrum
of methsemoglobin differs in position from the band in the spectrum
of acid as well as from that of alkaline haematin. Whilst the absorption-
band of the former is close to C and that of the latter close to D, the
band of methsemoglobin, in acid solutions, is separated by a marked
interval Loth from C and I), though it is closer to the former than to
the latter.

Alkaline solutions of hsematin in the presence of certain foreign
matters, when treated with reducing agents, exhiLit a spectrum which
is apparently identical with that which will Le described under " Hsemo-
chromogen," and which was first described by Stokes as the spectrum of
reduced hcematin. The band in the red disappears, and two characteristic
bands appear in the green (Plate II., Spectrum 3). On now shaking
the reduced liquid with air, the two bands first referred to disappear,
and are replaced by the original hsematin band.

This experiment would appear to show that hsematin is but oxidised hsemo-
chromogen, a conclusion which is false, and which is an illustration of the
mistakes into which observers may be led who conclude as to the identity of
two colouring matters from the identity of prominent absorption-bands in their
spectra.

A strong proof that oxidised hsemochromogen is not identical with hsematin.
is derived from my own observations on the absorption of the extreme violet and
ultra-violet. Whilst hsematin possesses even in solutions of great dilution the
power of absorbing the whole of the ultra-violet, the violet and even the blue

252 HEMOGLOBIN.

rays of the solar spectrum, oxidised hseniochromogen is, in solutions of much
greater concentration, remarkably transparent for the ultra-violet.

Hoppe-Seyler made the observation that perfectly pure solutions of hsematin
are quite unaffected by reducing agents, but that the addition of certain foreign
matters (e.g. albumin) renders reduction possible. I can, from my own re-
peated observations, emphatically confirm this fact.

It has been stated above that diluted blood and solutions of oxyhgemoglobin
treated with acids exhibit a band in the red between C and D (of which the
centre is approximately situated at A 640), though it varies somewhat with the
nature of the acid which has effected the decomposition. If, however, blood
be treated with glacial acetic acid, and the mixture at once shaken with ether,
the latter subsequently separates, holding so much of an acid compound of
hfematin in solution as to possess a deep red colour. This ethereal solution,
in addition to the characteristic band of acid hasmatin, exhibits three other
bands whose positions and relative intensities are indicated in Plate II.,
Spectrum 6.

Hsematin hydro chloride (syn. hsemin). — When a minute drop of
blood on a glass slide is mixed with a drop or two of glacial acetic
acid, and the mixture is boiled over a tiny name, and then allowed
to evaporate, the residue is found on microscopic examination to
contain innumerable reddish-brown prismatic crystals, which were
formerly constantly referred to as Teichmann's l crystals (after their
discoverer). Such crystals may be obtained from any old blood stain
on cloth, linen, wood, metal, etc. The stained tissue or the scrapings
of the stain are heated, as above, with glacial acetic acid. It is neces-
sary, however, in the case of stains which may have been subjected
to the action of water, to add a minute crystal of sodium chloride
to the glacial acetic acid before boiling. Hoppe-Seyler2 subsequently
discovered methods of obtaining Teichmann's crystals in quantities,
which enabled him to examine their physical properties with some
degree of completeness and to analyse them, and he was able to show
that haeniin is a compound of heematin and hydrochloric acid, to which,
as a result of his more recent researches, he ascribed the empirical
formula C34H35N4Fe06HCL Nencki and Sieber,3 on the other hand,
assigned to hsemin the formula C32H30N4Fe03HCl, corresponding to the
formula C32H30N4Fe03, which they assign to hsematin.

Method of preparing licemin in bulk. — A method for preparing liaemin in
bulk was, as has been said, first devised by Hoppe-Seyler, and other methods
were described by Nencki and Sieber. These methods demand the ex-
penditure of much time, labour, and patience ; and none of them, as I know
from my own abundant personal experience, yield a product which can
compare in the absolute uniformity of its crystallisation and the complete
absence of all amorphous matter with the one described by Schalfijew, which
is as follows : —

One volume of defibrinated and strained blood is added to four volumes of
glacial acetic acid, previously heated to 80° C. As soon as the temperature has
fallen to 55°-60°, the liquid is again heated to 80° C. On cooling, crystals at
once separate, and can be seen floating in the liquid, presenting a charac-

1 Ztschr.f. rat. Med., 1853, Bd. iii. S. 375, and Bd. viii. S. 141.

2 Virchow's Archiv, 1864, Bd. xxix. S. 597-600; "Das Hamin," Med.-cliem. Unter-
such., Berlin, S. 379-385.

3 Arch.f. exper. Path. u. PharmaJcoL, Leipzig, 1884, Bd. xviii. S. 401 ; 1886, Bd. xxi.
S. 325 ; 1888, Bd. xxiv. S. 430.

H^EMATIN HYDROCHLORIDE. 253

teristic silky lustre and a dark blue colour. The crystals are allowed to settle
for at least twelve hours, and the clear dark brown mother-liquid is syphoned
off. The blue sediment, if care was taken to avoid the presence of any
blood clots in the defibrinated blood used in the preparation, is found on
microscopic examination to be entirely composed of crystals of haemin. It
is repeatedly washed by decantation with water; then thrown on a filter,
and, after renewed washing with distilled water, it is subjected to long-con-
tinued washing with spirit and ultimately with absolute alcohol. This washing
with alcohol must be continued so long as the alcohol assumes a brown colour,
and is a very long process. The blue mass remaining on the filter is ultimately
washed with ether and alcohol, and in the first instance is allowed to dry by
exposure to the air, and afterwards by heating to 115° C.1

It was stated by Schalfijew that by his process 5 grms. of pure hsemin can
be obtained from 1 litre of defibrinated blood. This yield, which would be
approximately equivalent to the theoretical yield, on the assumption that the
blood contains in the mean 1 2 per cent, of haemoglobin, is from my own experi-
ence never realised, 1 litre of blood yielding on the average 3 '5 grms. of
pure haemin.

Physical and chemical properties. — Whilst presenting in mass a blue
colour, and exhibiting, when floating in a liquid, a silky lustre, on micro-
scopic examination hsemin crystals appear dark brown elongated rhombic
plates and prisms belonging to the triclinic system. They are arranged
singly or in groups. They are sfcrongly doubly-refracting. They are
quite insoluble in water, alcohol, ether, or chloroform.

When pure uniformly crystallised hsemin is boiled in pure glacial
acetic acid, the latter dissolves an appreciable quantity, assuming a dark
brownish-red colour. From this solution the hsemin is in great part de-
posited, on cooling, in perfect crystals, without any admixture with
amorphous substances. I find, however, that if the process of re-crystal-
lisation be repeated, the substance deposited on cooling consists of
haemin crystals mixed with some amorphous colouring matter.

Haemin is very easily soluble in highly dilute solutions of the caustic
alkalies and their carbonates ; from these solutions hsematin is pre-
cipitated on the addition of an acid. If nitric acid be used as the
precipitant, the chlorine which had originally been combined with the
haematin, and which is now present in the filtrate as an alkaline
chloride, can be precipitated by silver nitrate.

When hsemin crystals are heated, they remain unchanged up to
about 200° C. ; more strongly heated, they glow and leave an ash com-
posed of pure iron oxide. When pure lisemin is intimately mixed, as by
pounding, with pure concentrated sulphuric acid, hydrochloric acid is
liberated.

Nencki and Sieber, who employed amyl alcohol in the preparation of
haemin, found that when prepared in this way the crystals contained amyl
alcohol, and that their composition corresponded to the formula (Co9HonN,
Fe03.HCl)4C5H9.OH.

The existence of a definite compound of haemin and amyl alcohol is,
however, doubted by Hoppe-Seyler.2

1 M. Schalfijew. I have not seen the original paper in the Journ. russlc. fiz.-cMm.
Obsh., St. Petersburg, 1885, S. 30-37. See abstracts in Ber. d. deutsch. chem. Gesellsch.,
Berlin, 1885, Bd. xviii. (Referat Bd.), S. 232-233 ; also in Jahresb. u. d. Fortschr. d. Thier-
Chem., Wiesbaden, 1885, Bd. xv. S. 138.

'-' " Ueber Blutfarbstoffe und ihre Zersetzungsproducte, " Ztschr. f. physiol. Chem.,
Strassburg, 1882, Bd. x. S. 331.

254 HEMOGLOBIN.

The compounds of hsematin with acids, e.g. hsematin-hydrochloride,
present, even in solutions of great dilution (1 : 25,000-1 : 50,000), an
intense absorption - band, which encroaches more and more on the
ultra-violet, as the strength of the solution increases. In a solution con-
taining one part of crystallised hgematin. hydrochloride in 20,000 parts
of glacial acetic acid, the band extends between h and M, the most
intense absorption between h and L. The less refrangible border of this
band is sharply defined, whilst the more refrangible border is less
definite. As the solution is diluted the band becomes narrower,
through less and less of the ultra-violet being absorbed. In highly dilute
solutions the band which is still intense absorbs both H and K.1

The acid compounds of hsematin exhibit, therefore, an absorption-
band, which is exactly on the boundary of the idtra- violet proper, and
which extends further and further into the ultra-violet as the con-
centration of the solution increases.

G HK L M NO

FIG. 37. — The photographic spectrum of luemin.

HJEMOCHROMOGEN (SYN. " KEDUCED H^MATIN ").

It has already been explained that Hoppe-Seyler employed the
name hsemochromogen to denote the very remarkable body which he
was the first to study with care, and which results from the decomposi-
tion of reduced haemoglobin, in the absence of all oxygen, by acids, and
especially by alkalies, and of which the solutions present absorption-
bands in the visible spectrum, which are identical with those of the
reduced haematin of Stokes.

The latter name had been applied by Stokes to the chemical
substance assumed to be the cause of the characteristic absorption-
spectra which are exhibited by solutions of the blood-colouring matter,
and likewise by impure solutions of hsematin when subjected to the
action of reducing agents. It now remains to describe the methods of
preparing solutions of hsemochromogen, the body itself and its properties
(so far as these are known to us), its combinations, and especially to
refer to the views which Hoppe-Seyler advanced and held, in reference
1 Gamgee, Proc, Hoy. Soc. London, 1896, vol. lix. p. 276.

HAEMOCHROMOGEN. 255

to the relations of haemochromogen to haemoglobin, and the part which
it plays in relation to the optical properties of, and the chemical affinities
for gases manifested by, the complex molecule of haemoglobin.

Methods of preparing solutions containing hcemochromogen by the direct
decomposition of hcemoglobin. — Without referring to a more complicated
and in some respects more satisfactory method of decomposing haemo-
globin in the absence of oxygen,1 the following very simple method,
which, like the first, we owe to Hoppe-Seyler,2 will be described.

A solution of oxyhaemoglobin is placed in a glass tube, and then a
smaller glass tube containing a solution of sodium or potassium hydrate,
or, if desired, of tartaric or phosphoric acid, is introduced into the larger
tube, the open end of which is then drawn out and sealed in the blow-
pipe name. The apparatus thus prepared is then subjected to gentle
heat, taking care not to incline the tubes so as to cause their contents
to mix.

The oxyhaemoglobin contained in the larger, outer tube first becomes
reduced, and thereafter the oxygen contained in the air of the tube is
absorbed by the haemoglobin. When many days have elapsed, and the
whole of the haemoglobin is again reduced, the tubes are inverted and
their contents mixed, when the formation of haemochromogen may be
followed by the changes in colour and in the spectrum, which the
colouring matter undergoes.

Physical and chemical properties. — When acted upon by dilute solu-
tions of the caustic alkalies, haemochromogen gives rise to a beautiful
cherry-red solution, which, when sufficiently diluted, exhibits two
absorption-bands apparently identical with those of Stokes' reduced
haematin, which have already been referred to.

The visible spectrum of solutions of haemochromogen in alkaline
solutions is distinguished from all others by the extraordinary intensity
and sharpness of the absorption-band nearest to D. The second ab-
sorption-band, which is very much less intense, has less sharply-defined
borders. The solution, even when concentrated, absorbs very little of
the red.

The following are measurements of the position of the absorption-
bands in the visible spectrum by Hoppe-Seyler and myself : —

Gamgee's measurements3 (1878) X 567-547 A 532-518

Hoppe-Seyler's „ 4 (1889) X 565-547 X 527-514

My study of the photographic spectrum of haemochromogen has led
to the following results : 5 — Solutions, even of very great dilution, exhibit
an absorption-band between h and g. This band has the same position
as the band of CO-haemoglobin, but is much more intense. With one
part of haemochromogen in 25,000 parts of water, a stratum 10 mm. thick
being examined, an intense absorption-band occupies the region between
X410'0 and X430'0. From the examination of solutions of various strengths
it results that the mean ray absorbed corresponds to about A 420 '0.

By heating to 110° C. a solution of haemochromogen mixed with
a sufficiently concentrated solution of sodium hydrate, haemochromogen

1 Hoppe-Seyler, Med.-chem. Untersuch., Berlin, S. 540 and 541 ; and Gamgee's
"Physiological Chemistry," vol. i. pp. 118 and 119.

2 "Physiol. Chem.," 1878, S. 390.

3 "Physiological Chemistry," 1880, vol. i. p. 111.

* Ztsctir.f. pliysiol. Chem., Strassburg, 1889, Bd. xiii. S. 496.
5 Gamgee, Proc, Roy. Soc. London, 1896, vol. lix. p. 276.

256

HAEMOGLOBIN.

separates as a violet-grey powdery precipitate, which dissolves again in
the liquid from which it had separated, as soon as this cools. It is quite
erroneous to state, as is asserted in all text-books,1 that Hoppe-Seyler
succeeded in separating hsemochromogen in a crystalline condition. He
only succeeded (at most) in obtaining crystals of the CO-compound,
and concluded that haemochromogen itself must be a crystalline body, but
he never even asserted that he had actually obtained the crystals, and a
promise made in 1889 2 to describe the assumed crystalline haemo-
chromogen, though implying that he had already obtained the body in
this condition, was never fulfilled. Moreover, in the last systematic
account of haemochromogen which he published in 1893, Hoppe-Seyler3
does not refer to its being crystalline, but, on the contrary, speaks of it
(as he had done in 1889) as separating in the form of a violet-grey
powdery precipitate.

G H K L M N 0

* **, w

111

"I

FIG. 38. — The photographic spectrum of oxygenized hsemochromogen and of
haemochromogen.

Acids, even when very dilute, lead in the first instance to the forma-
tion of hsemochromogen from reduced haemoglobin, in the absence of
oxygen ; they, however, decompose a part of the haemochromogen with
great rapidity, removing its iron and giving rise to haematoporphyrin.
This explains, according to Jaderholm,4 the complex (four-banded) nature
of the spectrum of haemochroinogen, as at first described by Hoppe-
Seyler,5 when prepared by the action of acids on haemoglobin.

1 Hammarsten, " Lehrbuch d. phys. Chem.," Dritte Auflage, 1895, S. 122 ; Neumeister,
"Lehrbuch der physiol. Chem., etc.," 1895, Bd. ii. S. 154 ; Halliburton, "A Text-Book
of Phys. Chemistry," 1891, p. 290; Sheridan Lea, "The Chemical Basis of the Animal
Body," Appendix to Foster's "Physiology," 1892, p. 232.

2 Hoppe-Seyler, Ztschr. f. physiol. Chem., Strassburg, 1889, Bd. xiii. S. 495.

3 Hoppe-Seyler und Thierfelder, "Handbuch d. phys. u. path. Chem. Analyse,"
Berlin, 1893, S. 214, 215 (" Hamochromogen ").

4 See Abstract by Hammarsten in Jahresb. it. d. Fortschr. d. Thier-Chem., Wiesbaden,
1874, Bd. iv. S. 102.

5 Med. -chem. Untersuch., Berlin, S. 542. In his later descriptions of the spectrum of
acid solutions of hsemochromogen no mention is made of four bands.

HMMOCHROMQGMN. 257

When subjected to the action of such reducing agents as tin and
hydrochloric acid, hsemochromogen gives rise to coloured products, which
are obviously nearly related to, though not identical with, such bodies as
the so-called urobilins.

It was stated that when blood saturated with CO, or a concentrated
solution of CO-haemoglobm, is treated with a concentrated solution of
sodium hydrate, a bright red precipitate separates. Jaderholm stated
that this precipitate consisted of a compound of CO with hsematin, and
could be prepared directly by the action of the gas on a solution of
reduced haematin ; he further asserted that the visible absorption-
spectrum of the CO-haematin closely resembled that of CO-haemoglobin,
the bands occupying the same position ; though he described them as
being less intense in the haematin compound, and as differing from the
CO-haemoglobm compound in the fact that the two bands « and 13
exhibit equal intensities.

By causing an alkaline hydrate to act upon CO -haemoglobin in the
absence of oxygen (method with double tubes previously described), and
heating to 100° C., Hoppe-Seyler separated the body which Jader-
holm had described as CO-haematin, but which appears really to be
CO-haemochromogen. Like haemoehromogen itself, its CO -compound,
which has been deposited at 100° C., dissolves again when
the liquid from which it separates cools. The CO-compound of
haemochromogen is described by Hoppe-Seyler as a crystalline body,
though none of its physical characters have been subjected to even a
superficial examination. The visible spectrum of its solution is, accord-
ing to Hoppe-Seyler, absolutely undistinguishable from that of CO-
hsemoglobin.

The most interesting and weighty observation made by Hoppe-
Seyler on this subject was, however, that concerning the volume of CO
which combines with haemochromogen to form its CO -combination. He
found that the same volume of CO combines with haemochromogen. as
would be required to convert an equivalent weight of reduced haemo-
globin into the CO-compound. This unquestionably interesting ob-
servation, taken in connection with the fact that crystals form under
certain circumstances in solutions which contain CO-haemochromogen
(there is no absolute proof that the crystals represent this substance),
led Hoppe-Seyler to form certain hypotheses of extraordinary boldness,
for which the experimental bases are as yet altogether wanting, but
which have been accepted with misplaced confidence ; these hypotheses
he looked upon as legitimate conclusions from his own experiments, and
formulated as follows : —

" We are justified in concluding that in crystallised CO-hsemoglobin,
as well as in the colouring matter of the blood corpuscles, there is
present a particular group of atoms which combines with and retains
carbonic oxide, which is characterised by the special manner in which it
absorbs light, and which, after separation from the albuminous residues,
passes unchanged into CO-haemochromogen.

" Without possibility of doubt, this group of atoms is identical with
the one which, in the arterial blood-colouring matter,1 and in crystallised
oxyhaemoglobin, holds two atoms of oxygen in combination, in the place
of a molecule of CO.

" The oxyhaemoglobins, the haemoglobins, and the CO-hsemoglobins, as

1 Reference is here made to the hypothetical "arterin."
VOL. I. — 17

25$ HEMOGLOBIN.

well as the colouring matters of the red-blood corpuscles, all contain
hsemochromogen, and this body can be obtained from them all by a
process of simple decomposition, even in the crystalline condition, and
almost in theoretical proportions." l

In other words, Hoppe-Seyler announced that, from his experiments
it might be concluded that hremochromogen represented an iron-con-
taining coloured radical, which, by linking itself to an albuminous residue
or albuminous residues, forms haemoglobin, and that hsemochromogen in
the latter body combining with a molecule of oxygen forms oxyhsemo-
globin ; with a molecule of carbonic oxide, carbonic-oxide haemoglobin,
etc. — these substances containing oxyhsemochromogen and CO-hsemo-
chromogen respectively.

Not only are the facts wanting whiah would be needed in order to
prove this hypothesis, but there are many others which appear to me
to indicate that whilst, when once formed, hsemochromogen, as indeed
hsematin, includes the specific atomic group upon which the character-
istic optical and physico-physiological properties of the blood-colouring
matter depend, probably hsemochromogen does not exist preformed in
haemoglobin and its compounds. I trust shortly to throw more light
on this question.

Linossier2 described compounds of hsematin and reduced hsematin with
nitric oxide as well as with carbonic oxide. On repeating his experiments,
I convinced myself that (as had been shown by Jaderholm and by Hoppe-
Seyler in the case of CO) JSTO exerts no action on hsematin, but appears to form
a compound with hsemochromogen, which is possessed, as Linossier describes,
of a fine red colour, and exhibits two absorption-bands between D and E,
similar to those of oxyhsemoglobin. This NO-hflemochromogen awaits a careful
examination.

Hoppe-Seyler has speculated in reference to the condition in which the
iron exists in hsemochromogen and hsematin respectively, and has emitted the
opinion that the iron in haemochromogen is present in a ferrous and in hsematin
in a ferric condition, but the grounds for an opinion do not actually exist.3

HJ^MATOPORPHYRIN.

Methods of preparation. — When either hsematin or hsemin is
thoroughly mixed with concentrated sulphuric acid, it dissolves, and
by filtering through asbestos a clear and beautiful purple-red solution
is obtained. When this solution is poured into a large quantity of
water, the greater part of the dissolved colouring matter is precipitated
in the form of a brown flocculent precipitate, the quantity of which
increases if alkalies be added so as to neutralise the acid. This colour-
ing matter is impure hsematoporphyrin. In this operation the acid
separates the whole of the iron from the hsematin, and it is found in
solution in the state of a ferrous salt. In the process of decomposition
of hsematin by sulphuric acid there is no evolution of hydrogen gas.

From hsematin and hsemin hsematoporphyrin can also be obtained—
(1) by the action of strong HC1 in sealed tubes heated to 130° C.

1 Hoppe-Seyler, Ztschr. f. physiol. Chem., Strassburg, Bd. xiii. S. 492 and 493.

2 " Sur une combinaison de i'he'matine avec le bioxyde d'azote," Compt. rend. Acad. d.
sc., Paris, tome civ. p. 1296.

3 For tbe discussion of the question, see Hoppe-Seyler, Med.-ckem. Untcrsuch. , Berlin,
S. 546-559.

H^MATOPORPHYRIN. 259

(Hoppe-Seyler) ; (2) by the action of acetic acid saturated with HBr,
aided by heat (Nencki and Sieber).

Hsemochromogen is, in the absence of oxygen, converted even by the
weakest acids into hajmatoporphyrin, the iron being found in the
solution as the ferrous salt of the acid employed. Although occurring
more slowly, the decomposition of CO-haemochroinogen by acids also
yields htematoporphyrin.

According to Hoppe-Seyler, the composition of hsematoporphyrin is
represented by the formula C34H3,JN40(..

According to Nencki and Sieber, who have made the most complete
investigation of this body, it has the composition C16H18N203, and they
explain its origin from hsematin by the following equation, in which
they adopt their own as distinguished from Hoppe-Seyler 's formula for
hsematin —

C32H30N4Fe03+3H20 = 2(C16H18N208+Fe)

(htematin)

According to Nencki and Sieber, hsematoporphyrin is isomeric with
bilirubin.

G h HKLM NO

FIG. 39. — The photographic spectrum of hsematoporphyrin.

Physical and chemical properties. — Hsematoporphyrin forms beauti-
ful crystalline compounds with Na and with HCL

It is insoluble in pure distilled water, slightly soluble in dilute acids,
more soluble in strong acids, and readily soluble in alkaline solutions,
weak and strong. It is also readily soluble in acid and alkaline alcohol.

Solutions of hsematoporphyrin in acidulated alcohol have a beautiful
purple colour, and assume a bluish violet tint when the solution is made
very strongly acid. Alkaline solutions are of a fine red, but in the
presence of a great excess of alkali exhibit a violet tint. Solutions of
haematoporphyrin, even if extraordinarily dilute, exhibit a magnificent
red fluorescence, which strangely enough is not referred to in text-books,
though it seems to me to be their most remarkable characteristic.

An alcoholic solution of haematoporphyrin, acidulated with hydro-

26o HAEMOGLOBIN.

chloric or sulphuric acids, exhibits in the visible spectrum two absorption-
bands, of which one, which is the narrower and the weaker, is situated
between C and D and immediately adjoins D. The second, which is
much more intense, more sharply denned and broader, lies nearly mid-
way between D and E ; but nearer the former than the latter.

Alkaline solutions exhibit in the visible spectrum four absorption-
bands, to wit, a weak band midway between C and D, an equally
weak band between D and E, but nearer to the former, a more strongly
marked band nearer to E, and lastly a fourth band, darkest of all, which
occupies four-fifths of the interval between B and F.

The spectra of acid and alkaline haematoporphyrin are exhibited in
Fig. 57.

A study of the photographic spectrum of hajmatoporphyrin has
given me the following results : l — Acid solutions of hamiatoporphyrin,
so dilute as to appear colourless (though presenting, if examined in a
dark room by means of a beam of sunlight reflected from the mirror of
the heliostat, the marked red fluorescence previously referred to), exhibit
an intense absorption-band between h and H. If the solution be
slightly more concentrated, K is absorbed, and with increasing con-
centration of the solution the absorption of the ultra-violet extends
more and more.

Alkaline solutions of hamiatoporphyrin absorb the same spectral
region, but the intensity of the absorption is greater.

Haematoporphyrin, as MacMunn has shown, occurs as a colouring matter
in the integument of some invertebrates and in the egg-shells of certain
birds.2 In small quantities it occurs in the normal urine (Arch. Garrod),
and in larger quantities in certain toxic conditions, especially in one of the
forms of chronic sulphonal poisoning.

H^MATOIDIN.

This name was applied by Virchow to a substance which occurs in
the form of orange-coloured microscopic crystals (rhombic plates) in old
extravasations of blood, as in apoplectic clots, and which is certainly de-
rived from haemoglobin. These crystals are, according to most observers,
identical in form with those of bilirubin, and when treated with fuming
nitric acid exhibit the same colour reaction (Gmelin's reaction).
Hiematoidin, like bilirubin, exhibits no definite absorption-band in its
spectrum, but effects a general absorption of the ultra-violet, violet, and
blue rays of the spectrum. Opinions were long divided on the question
of the identity or non-identity of hsematoidin and bilirubin, but they
are now generally regarded as identical.

Certain other substances (of which the chemical history is very imperfect),
which can be directly obtained by the action of reagents 011 the blood-colour-
ing matter, and certain pigments occurring in the organism, and which, on
grounds more or less satisfactory, have been held to be derived from it like-
wise, will be considered in the account of the chemistry of the urine as well
as in that of the chemical processes occurring within the alimentary canal.

1 Proc. Roy. Soc. London, 1896, vol. lix. p. 279.

2 MacMunn, Journ. PhysioL, Cambridge and London, 1885, vol. vii. p. 240; vol.
viii. p. 384.

A GENERAL ACCOUNT OF THE PROCESSES OF
DIFFUSION, OSMOSIS, AND FILTRATION.

BY E. WAYMOUTH EEID.
CONTENTS : —Diffusion, p. 261 — Osmosis, p. 264 — Filtration, p. 280.

DIFFUSION.

BY current hypothesis the molecules of a liquid are considered to be in
constant motion, so that if two liquids, miscible without chemical inter-
action, are placed in contact, a mutual interpenetration, without the
action of any external force, takes place ; or, in other words, a diffusion
of the molecules of one among those of the other, and vice versa, occurs,
the process tending to continue until in the final state a homogeneous
mixture of the two exists. In physiological problems we deal with the
diffusion of substances in dilute aqueous solution, and it must at once
be noted that the condition of the molecules of a substance in dilute
aqueous solution is probably different in the case of different substances,
and by no means necessarily the same as that of the undissolved
substance ; that, in fact, the solvent and dissolved substance in many
cases interact, with a resultant alteration of physico-chemical pro-
perties.

In the case of substances acting as electrolytes in aqueous solution,
it is believed that dissociation into the ions takes place to a greater or
less extent of the total number of molecules, according to the degree of
dilution.1 There will thus be at lower degrees of dilution a mixture of
molecules, active as regards electrolytic conduction and chemical action,
and inactive molecules, the latter tending to become active by ionic
dissociation as dilution is increased, so that at infinite dilution only
active molecules exist in the solution. The coefficient of activity will be
the number expressing the ratio of active molecules to the total of
active plus inactive, and is unity at infinite dilution. The electrical
conductivity of a solution of an electrolyte is dependent on the velocity
of migration of its ions,2 so that the ratio of the molecular conductivity 3
of a solution of an electrolyte at given dilution, to the limiting value

1 Arrhenius, Bijhang. till k. Svens. Vet.-Akad., Stockholm, 1884, Bd. viii., Nos.
13 and 14 ; Ztschr. f. physikal. Chem., Leipzig, 1887, Bd. i. S. 631.

2 Kohlrausch, Ann. d. Phys. u. Chem., Leipzig, 1879, Bd. vi. S. 1, 145 ; 1885, Bd. xxvi.
S. 161.

3 The molecular conductivity is the ratio of the conductivity to the molecular concen-
tration of the solution, the latter being the ratio of grammes per litre to the molecular
weight in grammes.

262 DIFFUSION, OSMOSIS, AND FILTRATION.

which this approaches on increasing dilution, is a measure of the
coefficient of activity of the solution. According to this view, then, a
very dilute solution of sodium chloride consists of positively -charged
sodium and negatively-charged chlorine ions moving amongst the water
molecules, but unable to part company by virtue of their charges of
opposite sign, and only separable by the application of energy from
without (electrolysis). Other substances which do not conduct elec-
tricity in aqueous solution are believed to be in a simpler state of
solution, the molecules moving among those of the solvent not being
known to be in a different condition to those of the undissolved sub-
stance, but simply capable of freer motion.

It is further probable that in the case of certain non-electrolytes in
solution, instead of single molecules wf deal with aggregates of mole-
cules, and such substances are said to be in colloidal solution (x&XXa,
glue). As instances of organic substances the aqueous solutions of
which are colloidal, may be mentioned albumin, gum-arabic, starch,
haemoglobin.1

It must at once appear likely that the ease with which the
" molecules " of different substances can move among those of the
solvent in a solution is different in the case of different substances, i.e.
that the power of diffusibility must be very variable.

Graham z gives the following table : —

Equal weights had diffused to the same extent in the following times : —

Hydrochloric acid . 1
Sodium chloride . 2 '3 3
Cane-sugar 7

Magnesium sulphate . 7
Albumin . . .49
Caramel 98

Substances in solution tend to diffuse from places of higher to those
of lower concentration, and in the law of Tick 3 it is stated that the
quantity of dissolved substance so diffusing is proportional to the rate
of fall in concentration.

Thus, if a is the quantity of substance passing section q of a diffusion
cylinder in time z, when at x the concentration in the section is c, and at
x ~h dx is c + dc ; then —

do

where & is a constant peculiar to the substance and known as the
coefficient of diffusion.

From the law of Fick, Stefan4 calculated for a special case the
following formula : —

/kz

a = cq*/ -

(T

1 Picton and Linder (Journ. Chem. Soc., London, 1892, vol. Ixi. p. 148; 1895, vol.
Ixvii. p. 63) have prepared solutions of arsenious sulphide of various " grades." Thus one
may have (a) aggregates visible by microscope ; (/S) no visible aggregates, but the substance
not diffusible ; (y) the substance .diffusible but not filterable ; (2) the substance both
diffusible and filterable, but the aggregates still large enough to scatter light. They
consider that in matter in solution one can pass by grades from obvious suspension, to
colloidal solution, to non -electrolytic crystallised solution, and so to the first grade of
electrolytic solution.

2 Phil. Trans., London, 1861, vol. cli. p. 183.

3 Ann. d. Phys. u. Chem., Leipzig, 1855, Bd. xciv. S. 59.

4 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1879, Bd. Ixxix. S. 161.

DIFFUSION. 263

where a is the amount of substance, passing in time z, through section q,
from an infinitely long cylinder of solution of concentration c, into
another such cylinder of pure solvent.

This formula was experimentally verified by Voigtlander l with
cylinders of agar jelly, in which diffusion occurs as easily as in water.2
He further investigated the temperature coefficient (a) for k, and found
that it is not a linear function of the temperature, as stated by Weber,3
but stands in the following relation 4 : —

In the case of an electrolyte in solution, the diffusion must be con-
sidered as that of the ions into which it is dissociated on passing into
solution. The velocity of the separated ions may be very different, but
since in solution by virtue of their opposite charges they cannot part,
the more rapidly moving ion must be retarded by the more slowly
moving, and the more slowly moving accelerated by its more active
fellow. The diffusion of an electrolyte may also be accelerated by
the presence in the liquid into which it is diffusing, of ions charged
oppositely to those forming the more active partner in the diffusing
substance. Thus hydrochloric acid diffuses faster into a solution of
sodium chloride than into water.5 As a rule, those electrolytes which
are the best conductors, are the most diffusible in solution.6 The pre-
sence of a substance that is not an electrolyte in the fluid into which
diffusion is taking place may slow the diffusion of an electrolyte.
Thus sodium chloride diffuses more slowly into sugar solution than
into water, and the presence of ethyl alcohol also retards its diffusion.7
In the case of non-electrolytes in solution, diffusion must concern the
" molecules " of the dissolved substance, and the " aggregates " of colloids
will find their way with greater difficulty than the " molecules " of
crystalloids.

No definite rule can be stated as regards the effect of concentration
of the solution upon the rapidity of diffusion of the dissolved substance.
With sodium chloride the coefficient of diffusion is practically unaltered
by change in concentration of the solution. In the case of magnesium
sulphate the coefficient falls with the concentration of solution, while
with hydrochloric, nitric, and sulphuric acids the coefficient rises with
the concentration.8

The simultaneous diffusion of two salts, studied first by Graham, has
been since more completely investigated by Marignac.9 In general the
rapidity of diffusion of the more diffusible of a pair of salts diffusing
simultaneously is found to be increased, that of the less diffusible
diminished.

In the following table the diffusions of five pairs of salts, separately
and simultaneously, are contrasted.

1 Ztschr. f. physical. Chem., Leipzig, 1889, Bd. iii. S. 316.

2 Graham, Ann. d. Chem., Leipzig, 1862, Bd. cxxi. S. 5, 29.

3 Ann. d. Phys. u. Chem., Leipzig, 1879, Bd. vii. S. 536.

4 For the values of a, which vary slightly with different substances, see Voigtlander's
original paper, loc. cit.

5 Arrhenius, Ztschr. f. physical. Chem., Leipzig, 1892, Bd. x. S. 51.

6 Long, Ann. d. Phys. u. Chem., Leipzig, 1880, Bd. ix. S. 613 ; Lenz, Mem. Acad. imp.
d. sc. de St. Petersbourg, 1882, tome vii. p. 30.

7 Arrhenius, loc. cit.

8 Schetter, Ztschr. f. physikal. Chem., Leipzig, 1888, Bd. ii. S. 390.

9 Ann. de chim., Paris, 1874, Se"r. 5, tome ii. p. 546.

264 DIFFUSION, OSMOSIS, AND FILTRATION.

T is the ratio of the diffusion coefficients of the two salts, with
separate diffusions.

T is the ratio with simultaneous diffusions.

R, the ratio of the amounts diffused of the same salt in separate
and in simultaneous diffusion, i.e. the alteration of the coefficient of
diffusion produced by the presence of the other salt.

Separate.

Simultaneous.

T.

r'.

T' : T.

R.

/NaCl .

•5833

•6054

1

1

1-038

\Na2S04

•3770

•2497

•590

•352

•596

•662

( KC1

•8560

•9276

1

1

.

1-083

\BaCla .

•8433

•4424

•5£e

•401

•701

•814

fNaCl .

•7142

•7883

1

1

...

1-019

IBaCl, .

•5673

•5225

•757

•668

•882

•921

/K2S04.

•4745

•4378

1

1

•901

\MgS04

•2028

•1684

•382

•345

•903

•830

f Na2S04

•3757

•3420

1

1

•910

\MgS04

•2097

•1823

•523

•502

•960

•869

As a rule, as seen in R, the more diffusible salt is accelerated, the
less diffusible delayed. In the two last pairs both members are delayed,
but the less diffusible more markedly.

In the body it is rare to find the conditions present for a free
diffusion between the constituents of two solutions ; a membrane,
whether composed of cells or the surface layer of the protoplasm of
a cell, as a rule intervenes, and obviously the permeability of the
membrane affects the result. If pig's bladder separates methyl alcohol
and ether, the methyl alcohol diffuses into the ether, but if a caoutchouc
membrane separates the two liquids, the ether diffuses into the alcohol.1

OSMOSIS.

The term osmosis is applied to diffusion taking place between two
liquids separated by a membrane.

The simplest case of this is that in which a solution of a substance
is separated from the pure solvent by a membrane permeable by the
solvent but impermeable by the dissolved substance. Such membranes
were first prepared by Traube,2 in the form of colloidal precipitates,
such as tannate of gelatin and ferrocyanide of copper, but Pfeffer3
was the first to thoroughly study the process of osmosis under such
conditions. The name " semipermeable " has been given to such mem-
branes, but it must be noted at once that this expression is seldom
strictly accurate and must always be used relatively to some particular
substance. Tamman4 has pointed out that such membranes are by
no means the " molecule sieves " that Traube imagined,5 and in experi-
mental work the membrane must be chosen to suit the substance, or
vice versd. Copper ferrocyanide forms one of the best of such mem-
branes, and is nearly impermeable to cane sugar.

1 Raoult, Ztschr. f. physical. Chem., Leipzig, 1885, Bd. xvii. S. 735.

2 Arch.f. Anat. u. Physiol., Leipzig, 1867, S. 87 and 129.

3 "Osmotische Untersuch.," Leipzig, 1877.

4 Ztschr. f. physikal. Chem., Leipzig, 1892, Bd. x. S. 255.

5 See also Walden, ibid., 1892, Bd. x. S. 699.

OSMOSIS.

265

In practice such membranes are formed in the interstices of an
indifferent supporting structure, such as the pores of a porous battery
pot (preferably previously soaked in gelatin), by placing one of the mem-
branogens inside the pot, which is then lowered into a solution of the
other, so that the precipitate is formed within the structure of the
earthenware where the two solutions come into contact. It is only by
such an artifice that the membrane can be sufficiently supported to
enable it to withstand the high pressure produced by the osmosis under
the conditions.1

If, now, a battery pot with such a membrane in its pores be filled
with a solution of sugar in water, hermetically sealed, and placed in
a vessel of water, the water molecules will diffuse in either direction
through the membrane, which is permeable to them ; the sugar molecules,
on the other hand, cannot pass out, for to them the membrane is imper-
meable. As a result of the presence of the sugar on the inner side of
the membrane, in unit time, more water enters the pot than passes out,
and the pressure rises until it is sufficient to bring about the condition
of equality in the number of water molecules entering and leaving the pot.

This pressure is called the osmotic pressure of the solution of sugar,
under the conditions of concentration and temperature. That this
pressure is comparable to that of a gas was first clearly pointed out
by van 't Hoff.2

Thus the osmotic pressure of a dilute solution at constant tem-
perature is proportional to its concentration (i.e. density of a gas in
the law of Boyle). This is illustrated by the following table from
Pfeffer:3—

Cane Sugar Solutions at 13°'5 C. to 16°-1 C.

Concentration of

Osmotic Pressure

Osmotic Pressure

Solution.

in Mm. of Hg.

Concentration.

1 per cent.
2

535
1016

535
508

274 „

1518

554

4

2082

521

6

3075

513

Again, at constant concentration of a dilute solution, the osmotic
pressure is proportional to the absolute temperature (law of Charles).
Thus, again, taking Pfeffer's data —

1 per Cent. Cane Sugar Solution.

Temperature.

Observed Pressure.

Calculated Pressure.

Mm. Hg.

Mm. Hg.

(1)

32°

544

14°'15

510

512

(2)

36°

567

15°'5

520-5

529

1 For details of manufacture see Adie, Journ. Chem. Soc., London, 1891, vol. lix. p. 344.

2 Arch, netrl. d. sc. exactes, etc., 1885, Bd. xx. S. 239; Ztschr. f. physikal. Chem.
Leipzig, 1887, Bd. i. S. 479.

* Loc. cit., p. 85.

266

DIFFUSION, OSMOSIS, AND FILTRATION.

The experiments of Soret,1 again, show that in a solution, as in a gas,
the warmest part is the most dilute. Soret introduced a solution into
a long vertical tube and maintained a difference of temperature at the
two ends, the upper end being warmer than the lower. At the end
of several weeks the concentration of the solution at the warm end of
the tube was found to be lowered. Thus, with solution of copper
sulphate, the concentration at the end of the tube at 20° C. was 17'332
per cent., while that at the end maintained at 80° C. was 14'03 per cent.,
instead of 14*3 per cent, as calculated by Charles' law. And, again, with
concentration of 29'867 per cent, at the 20° C. end, a concentration of
23'871 per cent, was found at the end warmed to 80° C. instead of 24'8
per cent, as calculated.

Thus " the osmotic pressure of a dissolved substance is exactly the
same as the gas pressure, measured by the manometer, which one would
observe if he could remove the solvent, and leave the dissolved substance
as a gas filling the same volume." 2 The hypothesis of Avogadro then
is, according to van 't Hoff, not merely capable of extension by the law
of Henry to solutions of gases, but to solutions of matter which is not
gaseous under ordinary circumstances, and it may be stated that
equal volumes of gases or dilute solutions at the same gas or osmotic
pressure, and at the same temperature, contain equal numbers of
molecules.

A marked concordance is seen in the table below, between the
observed osmotic pressures for sugar solution taken from Pfeffer 3 and
those calculated on the hypothesis of Avogadro and the law of Charles.

One per cent, sugar solution contains 1 grm. of sugar in 100-6 c.c. of
solution. At the same temperature and pressure, -gf^ of a grm. of hydrogen
contains by hypothesis the same number of molecules (C12H22On = 342).

Taking the weight of a litre of hydrogen, at 0° C. and one atmosphere
pressure, as '08956 grm., and the above concentration as '0581 grm. per litre,
the gas pressure at 0° C., at the volume 100*6 c.c., is '649 atmosphere, and at
the temperature t= "649 (1 + -003670.

Temperature.

Observed Osmotic
Pressures.4

Calculated Gas
Pressures
•649(1+ -003670.

G°-8 C.

•664

•665

13°7 C.

•691

•681

14°-2 C.

•671

•682

15°-5 C.

•684

•686

22° C.

•721

•701

32° C.

•716

•725

36° C.

•746

•735

The law of Dalton may also be applied, with certain restrictions, to
the osmotic pressure of solutions, the total pressure of a mixture of
substances being equal to the sum of the partial osmotic pressures of
the several components.

1 Arch. d. sc. pliys. et nat., Geneve, S^r. 3, tome ii. p. 48 ; Ann. de chim., Paris, Se'r. 5,
tome xxii. p. 293.

9 Nernst's "Theoretical Chemistry," 1895, Palmer's trans., p. 148.

3 Loc. cit. 4 Pfeffer, loc. cit., p. 85.

OSMOSIS.

The following instances are taken from Pfeffer : l —
Copper Ferrocyanide Membrane.

267

CONCENTRATION.

RISE OF FLUID IN MEASURING TUBE
IN MM. PER HOUR.

Experiment I.
Temp. 17° -1 C.

Experiment II.
Temp. 15° -8 C.

1 per cent, saltpetre .

Mm.

6-08

Mm.

5'4

15 ,, gum-arabic

2-06

1-8

1 ,, saltpetre-f 15 per cent,
gum-arabic

7-90

7-0

1 per cent, saltpetre .

6-06

5'3

Parchment Paper Membrane.

CONCENTRATION.

1 "5 per cent, calcium chloride

2 ,, gum-arabic

1*5 ,, calcium chloride + 2
per cent, gum-arabic

RISE OF FLUID IN MEASURING TUBE
IN MM. PER HOUR.

Experiment I.

1-2
1T4

Experiment II.

10-3

1-3

11-3

Temperature in both experiments, 17°*4 C.

In cases, however, where the two constituents of the solution have
a common ion, each salt diminishes the dissociation of the other, so that
the pressure of the mixture is less than the sum of the pressures of the
two components.2

Thus for a double salt —

A.

B.

Osmotic
Pressure.

Sum of
Components.

Osmotic
Pressure.

Sum of
Components.

¥V(NHJ2S04

1-264 At.

1-295

...

*VA12(SOJ3 .

1-265 ,,

1-22

...

AKaS04. . . .

1-29 ,,

1-40

...

A(NH4)aAla(S04)424Aq

^K2Al2(SOJ424Aq

2-37 ,,

2-39 ,,

2-53
2-56

1-98
1-96

2-515
2-62

1 Pfeffer, loc. cit., p. 68.

2 From Adie, Journ. Ohem. Soc., London. 1891, vol. lix. p. 344.

268 DIFFUSION, OSMOSIS, AND FILTRATION.

It is, however, by no means the fact that, in the case of all sub-
stances in aqueous solution, agreement exists between the observed
osmotic pressure and that directly calculated on the above hypothesis
alone. In many cases the pressures observed in solution are far higher
than those calculated from the concentration in gramme-molecules per
unit volume. Thus the osmotic pressure of a 1 per cent, aqueous solu-
tion of common salt at 0° C., by calculation on the above data, should
be 3*79 atmospheres, but actual measurement shows it to be over 7
atmospheres.

This phenomenon, common to all solutions of electrolytes, is
accounted for on the hypothesis of Arrhenius,1 that the dissociated ions
of an electrolyte in solution are capable of exerting pressure as well as
the undissociated molecules. The osmotic pressure of solutions of
electrolytes is then raised above the simple molecular value by the
coefficient expressing the extent to which the molecules are dissociated
in passing into solution (dissociation coefficient).

This coefficient gives the ratio of the observed osmotic pressure of a
solution to the pressure calculated on the assumption that no dissocia-
tion of molecules occurs in passing into solution. It may be deter-
mined for a substance at a particular dilution most accurately, by
measurement of the electrical conductivity of the solution.

If m is the number of inactive molecules in the solution, and n the
number of active, and k the number of ions into which a molecule can

be dissociated, then the dissociation coefficient i = — — :— —

m-rn

Since the " activity co-efficient " a = — ^ — is measurable by the

m + n

ratio of the molecular conductivity of the solution to the limiting value
it approaches by increased dilution, & = !+(/;- 1)« can be obtained
by measurement of conductivity of solution, i can obviously also be
obtained from measurements of osmotic pressure.

This coefficient will necessarily be of very different value for
different classes of electrolytes, since the possible number of ions is
variable. Thus sodium chloride has 2, potassium sulphate 3,
potassium ferrocyanide 5 ions.

Hence as a formula may be given—

P = 22-35 (1 + -003670- * atmospheres,

m

where 22-35 atmospheres is the pressure exerted by the gramme-
molecule of gas in volume of 1 litre at 0° C1., c the number of grammes
of the substance per litre, m its molecular weight, and i its dissociation
coefficient at the concentration c.

As regards the practical estimation of the osmotic pressure of a
solution, the direct measurement by a semipermeable membrane is not
only tedious, and limited to cases where the dissolved substance has no
chemical action on the film, but seldom practicable, on account of the
difficulty in constructing membranes, to which the term may be strictly
applied. Obviously, unless the membrane is really impermeable to the
dissolved substance, the values on account of the " leakage " of dissolved
substance must be below the real amount.

1 Ztschr.f. physikal. Chem., Leipzig, 1887, Bd. i. S. 631.

OSMOSIS. 269

Blagden l discovered the fact that the freezing-point of a solution is
lower than that of the solvent, and that the lowering of freezing-point
is proportional to the concentration of the solution. Kudorff,2 Coppet,3
and Kaoult 4 have since more thoroughly investigated the matter. If,
therefore, we know the lowering of the freezing-point of water, produced by
the addition of a gramme-molecule to the litre (1°'89 C.), and the osmotic
(or gas) pressure at 0° C. corresponding to this (22*35 atmospheres), it is
merely a matter of simple proportion to calculate the pressure at 0° C.
corresponding to any given lowering of freezing-point, and from that to
obtain the pressure at any other temperature by the law of Charles.

Many pieces of apparatus have been devised for measuring the
lowering of the freezing-point, but that of Beckmann 5 is in most
general use. Unfortunately, the method does not yield concordant
results in the hands of different observers (when aqueous solutions
are used) within about 005° C., which corresponds to an osmotic pressure
of about 50 mm. of mercury at the temperature of the body (37° C.), and
is hence of little value for the correct estimation of small differences of
osmotic pressure in the aqueous solutions to which the physiologist
confines his attention. t;

An optical method has been used by Tamilian.7 If a drop of
solution of potassium ferrocyanide is allowed to fall into a solution
of copper sulphate, a so-called " Traube cell " is formed, the ferrocyanide
solution within which is separated from the copper sulphate solution
outside by a precipitation membrane of copper ferrocyanide, through
which osmotic interchange can take place.

If the internal solution be of higher osmotic pressure than the
external, water passes from the copper solution outside into the
cell, and the copper solution immediately round about the cell, being
raised in concentration, tends to sink. In the reverse case, by dilution
of the layer round the cell, an upward current is started. There are
thus produced differences in the refractive index of the layer of solution
against the outside of the cell, in contrast to the rest of the copper
solution. These are easily detected by the Topler Schlierenapparat.8
If the ferrocyanide solution have the same osmotic pressure as the
copper solution, no schlieren will be produced, and there will be no
change in refraction. Now, since the total osmotic pressure is the sum
of the partial pressures, a third substance, not reacting with the
membranogens, may be added to the solution of one of them, and the
concentration of the other, isosmotic with the mixture, determined by the
method. Since the osmotic pressure of the solution of the mem-
branogens, to which the third substance was added, is directly
measurable, it is obvious that the partial pressure of the added
substance can be measured.

1 Phil. Trans., London, 1788, vol. Ixxviii. p. 277.

2 Ann. d. Phys. u. Chem., Leipzig, 1861, Bd. cxiv. S. 63 ; 1862, Bd. cxvi. S. 55 ; 1871,
Bd. cxlv. S. 599.

s Ann. de chim., Paris, 1871, Ser. 4, tome xxiii. p. 366 ; 1872, tome, xxv. p. 502 ; 1872,
tome xxvi. p. 98.

4 Ibid., Paris, 1884, Se'r. 6, tome ii. p. 66; Compt. rend. Acad. d. sc., Paris, 1882,
tome xcv. p. 1030.

5 Ztschr. f. physical. Chem., Leipzig, 1888, Bd. ii. S. 638.

" Loomis, Ann. d. Phys. u. Chem., Leipzig, 1894, Bd. Ii. S. 500; Jones, Ztschr. f.
nkal. Chem., Leipzig, 1893, Bd. xi. S. 110 ; Raoult, ibid., 1892, Bd. ix. S. 343.
7 Ztschr. f. physikal. Chem., Leipzig, 1888, Bd. ii. S. 415.
8 Ann. d. Phys. u. Chem., Leipzig," 1867, Bd. cxxxi. S. 33.

270 DIFFUSION, OSMOSIS, AND FILTRATION.

Physiological methods of estimating osmotic pressure have also been
devised. The method of de Vries l is based upon the plasmolysis of the
protoplasts of vegetable cells. The cells filled with coloured sap from
the middle nervure of the leaf of Tradescantia discolor are useful
for the purpose, sections of this part being allowed to soak for three to
five hours in the solutions whose osmotic pressures are to be determined.
If the cells are plasmolysed, i.e. if the protoplasts are found on
examination to have shrunk from the cell walls, the osmotic pressure
of the solution producing this effect is above that of the cell sap, for
water has passed from the latter to the former, as evidenced by the
diminution in volume. By investigating a series of solutions with
sections from the same leaf, it is of course possible to find two of
slightly differing concentration of the •substance under investigation,
one of which just causes plasmolysis, while the other (weaker) does
not. A solution of concentration equal to the mean of these two is
said to be isotonic with the cell sap.

De Vries, on preparing a number of solutions of different substances,
all isotonic with the same batch of cells, and expressing their
concentrations in gramme-molecules to the litre, found that it required
a lower gramme -molecular concentration of some substances than of
others to obtain isotony. The term " water extracting power "
( Wasseranzieliungsvermogen) was used to express this peculiarity which
is obviously related to what has above been termed dissociation.
Taking O'l grin, molecule to the litre of saltpetre as a standard, and
giving it a magnitude of 3, the relative value (as regards plasmolysis
of vegetable cells) of a molecule of a number of substances was
expressed in terms of that of a molecule of saltpetre, and the numbers
expressing this ratio called isotonic coefficients of the substances.

Thus, to barium chloride (BaCL, + 2Aq = 244) is given the
isotonic coefficient 4, which means that f'244 parts by weight of
barium chloride in aqueous solution exert the same plasmolysing
action as 101(KN03= 101) parts by weight of saltpetre i.e. a T83
per cent, solution of crystallised barium chloride is isotonic by the
method, with a I'Ol per cent, solution of potassium nitrate.

Since cane sugar on this system is given the value of 2 for its
isotonic coefficient, and since, being a non-electrolyte, it is not
dissociated in solution, it is merely necessary to divide the isotonic
coefficients of de Vries by 2, in order to obtain ordinary dissociation
coefficients.

It is obvious that the substances in solution must exert no
deleterious action on the protoplast of the cell, and must, moreover,
be quite unable to diffuse through it, if the method is to be exact.

Here, again, we are met with the difficulty, that the protoplast is
not a strictly semipermeable membrane. It must let certain substances
pass, otherwise the cell sap could not have any other constituent than
water ; and it is only because the permeability to certain substances is
so far below that to water, that it is possible to obtain fairly approximate
measures of osmotic pressure by this method. With other substances
the permeability is so great that the values are far too low.

Thus with sodium chloride, by this method, the dissociation coefficient
is reckoned as 1*5 (de Vries' isotonic coefficient 3), but by lowering of

1Jahrb f. wis*. Botanik, 1884, Bd. xiv. S. 427; Ztschr. f. physikal. Chcm., Leipzig,
1888, Bd. ii'. S. 415.

OSMOSIS. 271

freezing-point method, it is found to be higher (about 1'89). Other
indices of " isotony " than the plasmolysis of the vegetable cell have
been used by physiologists.

Hamburger1 has used red blood corpuscles. If these are placed
in solutions of substances which do not penetrate, and which do not
act chemically upon them, an index of the entrance of water into
the substance of the corpuscle is presented by the setting free of
haemoglobin, which is recognisable in the solution. In a solution of lower
osmotic pressure than the corpuscle-contents (hypoisotonic solution),
water enters the corpuscles and the solution is reddened. In a solution
of higher osmotic, pressure than the contents (hyperisotonic solution),
water is extracted from the corpuscles, they shrivel and sink, and the
solution retains its original colour. Two limiting solutions are thus
obtainable, and the mean concentration of the two is taken as that
isosmotic with the contents of the corpuscle.

The method has very considerable limits in practice, for not only
is it obviously restricted to colourless solutions, but it can also only
give results approaching the truth, in cases where the substance in
solution does not penetrate ; and, as indicated by Gryns,2 who has
criticised the method very severely, the red corpuscles are penetrable
by a very large number of substances.3

Another blood corpuscle method is that of the haematokrit.4 Here
the gauge of entrance or exit of water from the corpuscles is the volume
they occupy, in a graduated capillary tube, after having been centrifu-
galised with the solution. The volume of the corpuscles is dependent
on the osmotic pressure of the solution in which they are placed (provided
the dissolved substance does not penetrate), and if equal volumes of the
same blood specimen, contemporaneously centrif ugalised in two solutions
of different substances, give the same volume of corpuscles, those solutions
have the same osmotic pressure. By centrifugalising a given volume
of a blood sample in a series of solutions of a substance not penetrating
corpuscles (cane sugar), of different and known osmotic pressure, in
separate tubes, at the same time as an equal volume of the same blood
treated with the solution of the substance to be investigated, a final
comparison of the length of the " threads " of corpuscles in the tubes
gives a gauge of the osmotic pressure of the solution.

By centrifugalising blood in a pipette, previously oiled (cedar oil)
to prevent clotting, measuring the length of the " thread," and
comparing with the same, blood treated with sugar solutions of known
osmotic pressure, the pressure of the plasma is determinable and is
found to vary, rising after meals, and especially after the ingestion
of solutions of salt (Koeppe).

A bacterial method even has been used by Wladimiroff,5 who has

1 Arch. f. Anat. u. Physiol., Leipzig, 1886, Phys. Abth., S. 476; 1887. S. 31 ;
Ztschr. f. physical. Chem., Leipzig, 1890, Bd. vi. S. 319.

2 Arch.f. d. ges. Physiol., Bonn, 1896, Bd. Ixiii. S. 86.

3 Hamburger himself (Ztschr. f. physical Chem., Leipzig, 1890, Bd. vi. S. 319)
maintained that permeability did not affect his method, since, by a "vital act"
(" Lebenserscheinung"), S. 331, the corpuscles give up to the solution from their juice
an amount of some other substance exactly equivalent to that which penetrates from
without, so that the total osmotic pressure of the juice is unaltered !

4Hedin, Slcandm. Arch. f. Physiol., Leipzig, 1890 ; Gaertner, Berl. klin. Wchnschr.,
1892, Bd. xxix. S. 36 ; Koeppe, Arch. f. Physiol., Leipzig, 1895, S. 154 ; Arch. /. d. ges.
Physiol., Bonn, 1896, Bd. Ixii. S. 567 ; Miinchen. med. Wchnschr., 1893. No. 24.

5 Ztschr. f. physikal. Chem., Leipzig, 1891, Bd. vii. S. 529.

272 DIFFUSION, OSMOSIS, AND FILTRATION.

maintained that cessation of motion of bacteria placed in solutions
indicates that the solution is isosmotic with the cell sap, in cases
where poisonous action can be excluded.

The above physiological methods of measuring osmotic pressure are
of considerable interest, but, as already stated, their application is
decidedly limited ; and though, as will appear below, often of indirect
value, as giving information bearing on the permeability of cells and
membranes, they are not to be classed with the more accurate methods
of experimental physics.

In the case of colloid solutions, it is not necessary to use pre-
cipitation membranes for the direct measurement of osmotic pressure,
for such material as vegetable parchment is, as a rule, impermeable to
colloids, and it moreover presents ceftain advantages in particular
cases, namely, those in which the colloidal substance is contaminated
by salts (e.g. albuminous solutions), since the salts can pass out, and
the determination is freer from the error of inclusion of the partial
pressure of these, unavoidable by a direct measurement by a copper
ferrocyanide membrane, or an indirect determination by lowering of
freezing-point.

It is known that solutions of colloids of considerable concentration
exert very low osmotic pressure, though their exact measurement is
difficult. Picton and Linder,1 in a direct measurement (by a copper
ferrocyanide membrane) of the pressure of a 4 per cent, solution
of colloidal arsenious sulphide, obtained a pressure of only 17 mm. of
water. Sabanejew 2 states that the lowering of freezing-point by silicic
acid is so small as to be within the limits of the method. With
albuminous solutions the difficulty of contaminating salts is almost
insuperable, and since the molecular weight of albumin is not known,
calculation is excluded.

Sabanejew 3 investigated the lowering of freezing-point of water by
solution of egg albumin, and quotes a lowering of '02° C. for a 15*6 per
cent, solution, and -042° C. for a 30*35 per cent, solution, but since the
specimens held *4 to '66 per cent, of ash, the numbers are of 110 value.
Tamman4 gives the difference in lowering of freezing-point of horses'
serum, produced by coagulation of the proteids by heat and removing
them, as only "006° C., which is in the region of the error of the method.5
Dreser6 and Koeppe7 also state that the removal of proteid from
albuminous solutions does not affect the osmotic pressure, while
Ludeking8 maintains that the boiling point of 40 per cent, solution
of gelatin is 100° C.9 It is therefore uncertain whether proteids in

1 Journ. Chem. Soc., London. 1895, vol. Ixvii. p. 63.

2 Ber. d. deutsch. chem. Gesettsch., Berlin, 1890, Bd. xxiii. S. 87.
3 Ibid., 1891, Bd. xxiv. S. 558.

4 Ztschr. f. physikal. Chem., Leipzig, 1896, Bd. xx. S. 180.

5 Starling, on the other hand, quotes two experiments to prove that the osmotic
pressure of the proteids of serum can be directly measured. It is stated to be from 30 to
40 mm. of Hg. Journ. PhysioL, Cambridge and London, 1895, vol. xix. p. 323. Cf. also
next article, p. 308.

6 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1892, Bd. xxix. S. 314.

7 Arch. f. d. ges. PhysioL, Bonn, 1896, Bd. Ixii. S. 571 (footnote).
8 Ann. d. Phys. u. Chem., Leipzig, 1888, Bd. xxxv. S. 552.

9 A lowering of vapour pressure (raising of boiling point) is produced by solution
of a substance in a solvent, and the lowering of vapour pressure, like that of the
freezing-point, is proportional to the concentration. Wiillner, Ann. d. Phys. u. Chem.,
Leipzig, 1858, Bd. ciii. S. 529 ; 1858, Bd. cv. S. 85 ; 1860, Bd. ex. S. 564 ; Tamman,
Ann. d. Phys. u. Chem., Leipzig, 1888, Bd. xxxiv. S. 299.

OSMOSIS. 273

colloidal solution exert an osmotic pressure capable of measurement
by our present methods.

From the above account of osmotic pressure, it is evident that,
since it is present in high or low degree in all true solutions, as a result
of the kinetic energy of the dissolved molecules, the phenomena of
diffusion are most satisfactorily accounted for as directly dependent
on the osmotic pressure exerted by the diffusing substance.1 Substances
diffuse from places of higher to those of lower partial pressure, and
the differences in rapidity of diffusion of different substances, though
present in concentrations exerting the same osmotic pressure, must be
accounted for by differences in the resistance met in their passage
among the molecules of the solvent.

When we now turn to the consideration of the interchange of the
constituents of solutions through animal membranes, we at once find
that, since these membranes are never strictly semipermeable, and are
frequently very permeable for dissolved substances, the phenomena are
neither those of pure osmose nor pure diffusion, but a complex of
the two, in which the relative permeability of the membrane to solvent
and dissolved substance is of paramount importance, but, unfortunately,
a variable factor with different membranes.2 All the earlier work upon
osmosis was carried out with membranes not fulfilling the condition of
semipermeability, so that a double stream of solvent into solution
(endosmose) and dissolved substance into solvent (exosmose) was con-
sidered as a necessary feature of the process until Traube's discovery of
precipitation membranes.

The first osmose experiment was probably that of the Abbe Nollet,3
in which it was observed that a bladder tied over a vessel of spirits of
wine became distended, or even burst, when vessel and membrane were
under water. Parrot4 again called attention to the fact, which
had been forgotten, and ascribed the process to " affinity of the first
order," which causes all miscible fluids to " wander " into one another.
Fischer5 in Germany and Dutrochet6 in France again rediscovered
the prime fact, and commenced its systematic study. Certainly the
main stimulus to subsequent study of the phenomena was given
by the work of Dutrochet.7 Dutrochet's endosmometer was a funnel
closed by membrane and provided with a long stem. The body
of the funnel was filled with the solution, and the whole immersed
in water. The height to which the fluid rose in the stem was the
gauge of the osmotic action of the solution. Dutrochet recognised
that the concentration of the solution and the temperature affected
the results.

Vierordt 8 improved upon the arrangement used by Dutrochet, by
setting the membrane vertical and the stem horizontal, so that filtration
error was avoided, and also concluded that the stream of water into the

1 Nernst, Ztschr. f. physikal. Chem., Leipzig, 1888, Bd. ii. S. 611.

2 In this connection see a paper by Lazarus Barlow, Journ. PhysioL, Cambridge and
London, 1895, vol. xix. p. 140.

3 " Histoire de 1'Academie royale des sciences," 1748, p. 101.

4 Ann. d. Phys. u. Chem., Leipzig, 1815, Bd. li. S. 318.

5 Ibid., 1822, Bd. Ixxii. S. 300.

6 Ann. de chim., Paris, 1827, tome xxxv. p. 393 ; "Agent imme'diat du mouvement
vital," Paris, 1826.

7 See also " Me"moires pour servir a I'histoire anatomique et physiologique des vegetaux
et des animaux," Bruxelles, 1837.

8 Ann. d. Phys. u. Chem., Leipzig, 1848, Bd. Ixxiii. S. 519.

VOL. I.— 18

274 DIFFUSION, OSMOSIS, AND FILTRATION.

funnel was proportional to the difference of concentration of the solu-
tions on either side of the membrane.

Jolly1 specially studied the ratio between the amount of water
passing into the solution and the amount of dissolved substance passing
out, using salts with pig's bladder as membrane. This ratio he termed
the endosmotic equivalent of the salt, and maintained that it is constant
for the same membrane, concentration of the salt solution, and tem-
perature. For some years after this the whole attention of those interested
in the matter of osmosis was directed to a fuller study of this ratio in
the case of different substances.2

As a result of these researches, it was seen that even with the same
membrane it was only within slight changes of concentration of the
solution that constancy of the endosm<ftic equivalent was obtainable, a
result in accordance with expectation, seeing that the physical nature of
an animal membrane must necessarily undergo change with the amount
of water imbibed, a quantity variable with the concentration of the solu-
tions in which it is in contact. With a strictly semipermeable membrane,
the endosmotic equivalent is evidently infinite, while the more permeable
the membrane to dissolved substance the lower will be the equivalent.
Thus, according to Harzer,3 the endosmotic equivalent for sodium chloride
is with fish-swim-bladder, 2 '9 ; ox-pericardium, 4'0 ; ox-bladder, 6 '4.

It must therefore be admitted that, in spite of the great labour that
has been expended on the determination of endosmotic equivalents of
different substances with different membranes, the results obtained are
of little value to the practical physiologist, who deals with membranes
in the living body, whose physical characters are by no means necessarily
those of the structures used in such experiments. The only value that can
be attached to these determinations is an orienting one, as to the diffusi-
bility of the substances into water, through dead animal membranes,
under the conditions of the experiments.

Before we can attempt to answer the question, How is the process of
diffusion modified when in an osmose experiment an animal membrane
is placed between solution and solvent ? it is obviously necessary to
know the physical structure of the membrane. Of this we must admit
great ignorance. To Briicke4 we owe a theory of "pore diffusion."
Assuming capillary pores in the membrane, it maintains that, by
attraction, a layer of pure water lines these, while an axis of salt solu-
tion, whose concentration falls from axis to mantle of the cylindrical
pore, lies centrally. The highest concentration in the axis must be that
of the salt solution in the experiment, and along the axis ordinary
hydrodiffusion takes place, water entering the salt solution and salt
entering the water. Along the mantle, however, only water can pass
into the salt solution, so that the stream of water exceeds that of salt.
If the pores are very narrow, it is conceivable that there is no central
core of salt solution, in fact the membrane becomes semipermeable.

1 Ztschr. f. rat. Med., 1849, Bd. vii. p. 83 ; Ann. d. Phys. u. Chem., Leipzig, 1849,
Bd. Ixxviii. S. 261.

2 Fick, Untersuch. z. Naturl d. Mensch. u. d. Thiere, 1857, Bd. iii. S. 294 ; W. Schmidt,
Ann. d. Phys. u. Chem., Leipzig, 1857, Bd. cii. S. 122 ; Beitr. z. Anat. u. Physiol.
(Eckhard), Giessen, 1855, Bd. i. S. 97 ; 1860, Bd. ii. S. 1, 31, 147 ; Hoffmann, ibid.,
1860, Bd. ii. S. 59.

3 Arch. f. physiol. Heilk., Stuttgart, 1856, Bd. xv. S. 194.

4 " De diffusione humorum per septa mortua et viva," Berlin, 1842 ; Ann. d. Phys. u.
Chem., Leipzig, 1843, Bd. Iviii. S. 77.

OSMOSIS. 275

The attraction of the substance of the membrane for water, at any
rate, may then be a factor in the case. Ludwig x demonstrated, indeed,
that the concentration of the solution imbibed by an animal membrane
may be lower than that of the solution in which it is soaked.

Fick 2 distinguished between two possibilities for diffusion through an
animal membrane — a " pore diffusion " in Brlicke's sense, and a
diffusion occurring through the spaces between the molecular aggregates
of which the membrane may be considered to be built. The latter idea
is somewhat of the nature of that formed of the diffusion of a gas
through a film of liquid in which it is soluble, or is perhaps better
illustrated in the experiment of L'Hermite,3 in which, when water
separates chloroform from ether in a tube, the chloroform increases at
the expense of the ether. Tick's " homogeneous " membranes were
made of collodion ; but his results show that such a membrane is not
unalterable, since the amount of salt passing through increases with
time, and it is difficult to escape the conclusion that in many cases
some interaction of chemical nature takes place between the membrane
and the substances to which it is permeable.4

The property possessed by certain substances of imbibing certain liquids
(apart from capillary action), must be borne in mind in all considerations of the
essential nature of the processes involved in the passage of fluids through
membranes. This property can only be ascribed to some " affinity " between
the molecules of the imbibing substance and that imbibed; thus gelatin
swells in water but not in ether, while the reverse is true of caoutchouc. The
retention of a gas, or a colouring matter by charcoal, of water by the silica
of the opal, or that of pepsin by fibrin, are instances of the class of phenomena
to which attention is here called, and to which the name of adsorption is often
applied. When a homogeneous substance imbibes a solution, compounds of
the imbibed with the imbibing substance may be formed, which may have a
greater affinity for the solvent than the original imbibing substance, but at the
same time the osmotic pressure of the solution tends to retard the imbibition
of the solvent; hence, with a given pair of substances, the amount of the
solution of one taken up by the other will reach a maximum at a certain con-
centration, a maximum, however, which may be well above that for imbibition
of the pure solvent.

The "affinity" of the imbibing substance for the solvent and dissolved
substance imbibed may be of very different order, for gelatin takes up a more
concentrated solution of methyl- violet than that in the dye-bath ; while, on the
other hand, a ferrocyanide of copper membrane will take up water while almost
absolutely indifferent to dissolved cane sugar.

Such "affinities" are not purely mechanical, since they vary with the
chemical nature of the substances, and yet are not of the nature of chemical
affinity in the usual sense of the term, since the "compounds" do not obey the
laws of constant and multiple proportion. Ostwald has introduced the term
mechanical affinity to meet the case.

In the complex known as protoplasm there may be imbibing substances of
different nature, permeated by a solution of substances whose chemical nature
may, directly and indirectly, affect the imbibition of a solution brought in
contact with the mass ; and, furthermore, undissolved particles may themselves

lZtschr.f. rat. Med., 1849, Bd. viii. S. 1; Ann. d. Phys. u. Chem., Leipzig, Bd.
Ixxviii. S. 307.

2 Untersuch. z. Naturl. d. Mensch. u. d. Thieve, 1857, Bd. iii. S. 294.

3 Ann. de chim., Paris, 1854. S^r. 3, tome xliii. p. 420.

4 Tcamman, Ztschr. f. physikal. Chem., Leipzig, 1892, Bd. x. S. 255 ; Walden, ibid.,S. 699.

276 DIFFUSION, OSMOSIS, AND FILTRATION.

exert surface action, so that the possibilities for purely physical absorption are
quite unknown, and so-called vital elective action may be the result of specific
adsorptive affinity. Hofmeister * has shown that gelatin has an " elective " action,
for common salt, the concentration of the solution imbibed exceeding that of
the surrounding solution ; and, further, that the combination of sodic chloride
with the gelatin favours the uptake of water. Again, gelatin takes up more
water from '5 to 2 per cent, solution of ethyl-alcohol in water than from pure
water.

With salts that undergo electrolytic dissociation in solution, permeability
must be a function of ions. Thus, according to Ostwald,2 copper ferrocyanide
is permeable to potassium chloride, because both chlorine and potassium ions can
pass ; it is impermeable to barium chloride, because the barium ion is stopped ; and
impermeable to potassium sulphate, because the sulphuric acid ion cannot pass ;
and, under ordinary circumstances, on account of opposite electrical charges, if
one ion is stopped, so must be the other. There are, however, conditions
under which an ion, stopped on account of the impermeability of the membrane
to its fellow in a salt, may pass the membrane.

If the negative ion of a salt is prevented from passing through the
membrane, only because it is impermeable to its positive fellow, the addition of
another salt, whose positive ion can pass the membrane, will allow the negative
ion of the first salt to pass in company with it. Or a salt whose negative ion
can pass the membrane may be placed on the opposite side, the two negatives
exchanging with their positive fellows across the membrane, and equal numbers
of the two negative ions passing in opposite directions in a given time. This is
of interest to the physiologist, since it opens a possible physical explanation of
the fact that a cell may hold back a substance under certain conditions, while
under others, when surrounded by a differently constituted fluid, the same
substance may be given up.

Koeppe3 has attempted to apply this to the formation of hydrochloric acid
in the stomach from sodium chloride, maintaining that the stomach wall is
impermeable to chlorine ions, but that the sodium ions are exchanged for
hydrogen ions from the blood. That free hydrogen ions are present in the
alkaline blood is, however, hardly possible.

Whether permeability be a function of physical or chemical nature, it
is obvious that in the case of a living membrane the complex to which
the term " physiological condition " is applied must affect the property,
so that one and the same membrane in the body may, under different
circumstances, be more or less permeable by the same substance.

The simplest living membrane with which experiments can be made
is probably the differentiated outer layer of the protoplast of the vege-
table cell (PlasmaJiaut). There is no doubt that the permeability of this
membrane for different chemical substances is very variable. It is pene-
trated by some dye-stuffs but not by others, very impermeable to
many simple salts, though easily permeable by certain complex organic
substances.4 Since this membrane is in its living condition so
slightly permeable to salts, the osmotic pressure within vegetable cells is
high (3 to 4 atmospheres). This special relative impermeability to salts
is obviously regulated in some manner by the " physiological condition "
of the membrane. Jansen 5 found that the cell sap of the alga, Cliceto-

1 Arch. f. cxper. Path. u. PharmakoL, Leipzig, 1891, Bd. xxviii. S. 210.
8 Ztschr. f. physical. Chem., Leipzig, 1890, Bd. vi. S. 71.
sArch.f. d. ges. PhysioL, Bonn, 1896, Bd. Ixii. S. 567.

4 Pfeffer, Abhandl. d. math.-phys. Cl. d. k. sacks. Gesellsch. d. Wissenscli., 1890, Bd.
xvi. S. 149.

5 Verhandl. d. Jc. Akad. v. Wetensch., Amsterdam, 1888, vol. iv. p. 345.

OSMOSIS. 277

morpJia, growing in sea water, is practically isosmotic with that of
Spirogyra, growing in fresh water, though the osmotic pressure of sea
water is some 240 times that of fresh. Thus the osmotic pressure of the
cell sap of Chcetomorpha is far below that of the water in which it lives,
while that of the sap of Spirogyra is far above that of fresh water.

One can investigate the permeability of the living protoplast by the
plasmolytic method already alluded to above. The cell is plasmolysed
with a solution of some substance indifferent to the protoplasm and known
not to penetrate (sugar). A solution of the substance to be tested is now
prepared of the same osmotic pressure as the solution of indifferent
substance which just causes plasmolysis. If the solution so prepared has
exactly the same effect as the standard, it cannot pass through the proto-
plast, for, if it did, there would no longer be equality of osmotic pressure
on the two sides thereof. If the substance to be tested is only slightly
soluble in water, or is poisonous to the protoplasm, a small amount of it
is added to the standard indifferent solution, and the effect of the
addition on the plasmolysis noted. If it does not pass the membrane,
then, by virtue of the higher osmotic pressure due to its addition, the
mixture will produce more plasmolysis than did the standard solution,
and the effect will be lasting. If no effect results from the addition, it
must pass quickly through the membrane ; if a passing effect, with
subsequent recovery, it must pass slowly.

In this way Overton1 has investigated the permeability of the
protoplast by a number of chemical substances, and finds that salts
much dissociated in solution hardly pass the membrane, while many
complex organic bodies rapidly penetrate, and that the presence of
certain radicles in these markedly affects the result.

In animal cells investigations are rather limited (by the fact that
there is no plasmolysis) to shrinkage and swelling and escape of
haemoglobin (in red corpuscles), as indices of permeability, under
conditions of variation of osmotic pressure of surrounding solutions.
More, therefore, is known about the permeability of the red corpuscle
than any other cell. A table of substances is given by Gryns,2 and we
here confine ourselves to stating that red corpuscles are permeable
to urea,3 glycerin, ethyl- and methyl-alcohol, and most ammonium salts
(not to sulphate, phosphate, and thiocyanate), impermeable to sugars,
sodium and potassium salts, barium and calcium chlorides, glycin and
asparagin.

Thus, as regards action on red blood corpuscles, dilution of an isosmotic
sodic chloride solution with urea solution produces the same effect as
dilution with water, because the urea diffuses at once into the interior of
the corpuscle, while, on the other hand, addition of sugar at once causes
contraction of the cell.

Obviously, therefore, a so-called " hyperisotonic " solution does not
necessarily extract water from a cell, and absorption of water from such
a solution by the blood may be a purely physical action, if the substance
in solution can permeate the wall separating it from the blood. Again,
a drug, by making the wall of a cell less permeable by virtue of its
chemical action on the protoplasm, may markedly affect the "water
extracting power " of a salt solution. Possibly the fact that some salts

1 Ztschr. f. physical. Chem., Leipzig, 1897, Bd. xxii. S. 189.

2 Loc. cit., p. 102.

3 See also Schondorff, Arch. /. d. cjes. PhysioL, Bonn, 1896, Bd. Ixiii. S. 192.

278

DIFFUSION, OSMOSIS, AND FILTRATION.

in the intestine purge (sodic sulphate), while others do not (sodic
chloride), may in the end find its explanation in a permeability of the
membrane by the latter, but not by the former. A universal
" physiological salt solution," then, if by such a term is meant a salt
solution in which tissues neither lose nor take up water, and the dis-
solved substance of which does not enter the cells, is not a possibility ;
each tissue must in fact have its own "normal solution,"1 and this may
possibly be in some cases a solution of some other substance than a
salt.

The effective osmotic pressure, therefore, exerted against membranes
such as those in the body which are, as a rule, partially permeable to
dissolved substances, is far below that measured by a semipermeable
membrane, and freezing-point determinations of osmotic pressures
(determinations which give a gauge of the full osmotic pressure as it
would be exerted against a semipermeable membrane), are of but
orienting value to the physiologist, except in cases where the per-
meability of the membrane to the substance in solution is known.

The following table from Pfeffer 2 is illustrative of the diminution in
the estimate of the full osmotic pressure caused by substituting a
permeable membrane (bladder or parchment paper) for copper ferrocy-
anide, and it is evident that the effect is far more marked in the case of
the crystalloids (saltpetre and sugar) than in that of the colloid (gum).

Six per cent. Solution of

Parchment Paper.

Bladder.

Copper Ferrocyanide.

Gum arable .

17-9

13-2

25-9

Cane sugar

29-0

14-5

2877

Saltpetre

20'4

8-9

700-0
(not directly estimated.)

The pressures are in cms. of mercury.

The conditions, then, for the interchange of water and the con-
stituents of solutions through membranes in the body, are evidently
exceedingly complex, and it is at present practically impossible to assess
the value of all the factors. Broadly stated, the following factors are
concerned : —

1. The quantitative composition of the solutions separated by the
membrane, and consequently the partial osmotic pressure exerted by the
several constituents.

2. The coefficients of diffusion of the various constituents.

3. The permeability of the membrane in its physiological condition
to the constituents.

4. The circumstances affecting the relative concentrations of a
constituent on the two sides of the membrane with time, e.g. circulation
and stirring.

5. The hydrostatic pressure on the two sides of the membrane.

6. The temperature.

The partial osmotic pressure of the constituents of a solution is
obtainable from a quantitative analysis, if the molecular weight and

1 Koeppe, Arcli.f. d. ges. PhysioL, Bonn, 1897, Bd. Ixv. S. 492.

2 "Osmotische Untersuch.," Leipzig, 1877, S. 73.

OSMOSIS. 279

dissociation coefficient (in case of electrolytes) is known. If the
molecular weight is not known, as in the case of proteids, the substance
must be removed from the solution, and the difference in the total
osmotic pressure so produced estimated.

The coefficients of diffusion must be obtained under the special
conditions (e.g. diffusion into serum, etc.).

The permeability of the membrane to dissolved substances, one of
the most important factors, and one generally not capable of accurate
estimation, will not only affect the passage of water and dissolved sub-
stances across the membrane by osmotic action, but also the hydrostatic
pressure necessary to cause nitration.

We shall here content ourselves with considering a simple but usual
case of absorption of a solution by blood, namely, one in which the
osmotic pressure of the solution is lower than that of the blood, and the
membrane separating the two permeable to the substance in solution,
and to one at least of the constituents of the blood, but impermeable to
others. For convenience the dissolved substance is called x, and that
constituent of the blood to which the membrane is permeable, y. The
blood, by virtue of its superior osmotic pressure, tends to take up water
from the solution, arid at the same time x diffuses through the membrane
into the blood, and y into the solution. If the blood be first supposed
to be stationary, a time is arrived at when the partial pressure of x and
y is the same on either side of the membrane ; in other words, this
solution of x and y is now the " solvent " in an osmotic experiment, and
the substances in the blood to which the membrane is impermeable are
the " dissolved substances." The whole of x, of y, and the water of the
original solution, must therefore in the end be absorbed.1 If the blood,
however, is circulated, the conditions for absorption are at once improved,
for the diffusion of x into the blood is favoured by the fact that its
partial pressure in the blood is kept low by renewed supplies of blood,
by the stirring action of the corpuscles preventing the formation of
" wall layers," and by the fact that cells in other parts of the body are
enabled to take up the substance as it is brought round. It is also
evident from the above that if, as a rare case, the solution had a higher
osmotic pressure than the blood, provided only the membrane separating
the two is permeable to the dissolved substance, and impermeable to
some constituents of the blood, when once the solution has taken up
enough water from the blood, and lost enough of its dissolved substance
to the blood, to lower its osmotic pressure to that of the blood, the
process described above is gone through, and it is in the end all
absorbed.

For such absorption to be carried out completely, it is evident that
the osmotic pressure of those constituents of the blood to which the
membrane and capillary wall are not permeable, must exceed the
pressure necessary to cause filtration across the same structures, for if
the available osmotic pressure on the inner side of the capillary wall is
less than the difference between the hydrostatic pressure on the two
sides of the membrane, filtration must occur, and the solution can never
be totally absorbed.

The assumption is here made that the resistance to the passage of
fluid across the membrane is the same in both directions. It must be

1 For this explanation to hold good, the substances in the blood to which the membrane
is impermeable must be in true solution; and capable therefore of exerting osmotic pressure.

28o DIFFUSION, OSMOSIS, AND FILTRATION.

noted, however, that animal membranes are known in which the
resistance to the passage of fluid is quite different in opposite directions.
The most familiar example is the shell membrane of the egg, which
permits nitration far more easily from within outwards than in the
reverse direction,1 and the same is true of the skin of the frog.2

FILTRATION.

By nitration is meant the passage of fluid through a membrane, as a
result of a difference of hydrostatic pressure on the two sides. To filter
water from a solution across a membrane into another solution, the
difference between the hydrostatic pressures on the two sides must
exceed the difference between the osmose pressures of the solutions, in
the case where the higher osmotic and hydrostatic pressures are on the
same side. If a porous pot bearing a semipermeable membrane is
filled with a solution and immersed in the pure solvent, the pressure
necessary to produce filtration of the solvent from the solution is one
just exceeding the full osmotic pressure of the solution ; but where we
deal with permeable membranes, as those in the body, the necessary
pressure is far less, because the difference of osmotic pressure on the
two sides of the membrane is reduced by the diffusion of some of the
dissolved substance.

Experiments on filtration through animal membranes appear to have
given very contradictory results, which seems to be due to the fact that
not only does continued pressure upon such membranes vary their
permeability, but a certain amount of " recovery " takes place in the
intervals between use ; hence the conditions of the membranes have been
by no means uniform in the experiments of different observers.

If the passage of fluid through an animal membrane is by more or
less tortuous paths, and if the walls of these are more or less elastic, it
is obvious, not only that by continued pressure must the resistance to
filtration rise, but that on removal of the pressure a slow " recovery " will
take place. Deformation of the membrane, if simply tied over a tube,
must also, unless it is properly supported, tend to distort channels and
so increase resistance to filtration. To these sources of difference in the
experiments must be added, previous drying of the membrane or not,
the condition of imbibition of the fibrous tissue, and temperature
variations. All these sources of differences are, moreover, accentuated
by the fact that most of the experiments have been made with thick
membranes, such as pericardium, bladder, intestine, and ureter.

Nearly all who have studied filtration have found that at constant
pressure the amount of the filtrate falls off with time,3 but, as pointed
out by Tigerstedt and Santesson,4 this falling off is far more rapid in the
earlier hours of an experiment than later, so that it is advisable in all
such experiments on filtration to expose the membrane to pressure for

1 Meckel quoted by Ranke, " Physiologie des Menschen," 1872, S. 122.

2 Cima, Mem. d. Accad. di Torino, 1853, vol. xiii. ; Reid, Journ. PhysioL, Cambridge
and London, 1890, vol. xi. p. 312.

3 Liebig, " Untersuch. ii. einige Ursachen der Saftebewegungim thierischen Organismus, "
Braunschweig, 1848, S. 7 ; Beitr. z. Anat. u. PhysioL (Eckhard), Giessen, 1858, Bd. i. S.
95 ; Runeberg, Arch. d. Heilk., Leipzig, 1876, Bd. xviii. S. 58 ; Gottwalt, Ztsclir. f. physiol.
Chem., Strassburg, 1880, Bd. iv. S. 423 ; v. Regeczy, Arch. f. d. ges. PhysioL, Bonn, 1883
Bd. xxx. S. 544.

* Bijhang. till k. Svens. Vet.-Akad., Stockholm, 1886, Bd. xi., No. 2.

FILTRATION.

281

many hours before the observations are conducted, and the stage of
relatively constant rapidity of filtration (a uniform rate is never actually
attained) is reached quicker at higher than at lower pressure. This
phenomenon is not due to any stopping of pores by particles suspended
in the fluids, since it is not noted when filtration is effected through
unglazed porcelain, and is probably simply a result of compression of
tortuous channels.

The quantity of filtrate rises with the pressure, but in lower ratio.

Thus, in an experiment by Tigerstedt and Santesson l of filtration of
distilled water through goldbeater's skin (serosa of ox-gut), which had
previously been exposed for 95 hours to a pressure of 80 cms. of water,

Pressure.

Filtrate per Minute
Observed.

Filtrate per Minute if
proportional to Pressure.

20 cm.

•046 grin.

•046 grm.

40 ,,

•081 „

•092 „

60 „

•no „

•138 „

80 „

•148 „

•184 „

The experiments of Wilibald Schmidt2 showed a contrary result,
i.e. that the filtration rapidity increased at a higher ratio than the
pressure (possibly due to using dried membranes, the pores of which
were opened during experiment), as also did those of v. Kegeczy.3

A period of rest, interpolated between two filtration experiments at
the same pressure, is found to often cause an increase of the permeability
of the membrane above the value it possessed at the time of dis-
continuing the first experiment (Eckhard, Euneberg, Tigerstedt and
Santesson).

Thus Tigerstedt and Santesson,4 in a filtration of distilled water
through gold-beater's skin at 40 cm. pressure, observed a filtrate of
•490 grm. per minute, but after a resting period of 530' the filtrate at
the same pressure was -577 grm. per minute. But whether or not this
phenomenon is observed, is probably due to whether or not the elastic
limits of the fibres have been passed, " recovery " not being possible if
the membrane has been excessively stretched. The interpolation of a
period of filtration at lower pressure of course produces the same effect.5

The rapidity of filtration rises with the temperature,6 and, according
to Schmidt, the temperature coefficient is nearly that of Poiseuille, for
the flow of fluids in capillary tubes.

The nature of the solution to be filtered must obviously affect
both the rapidity of filtration, from differences in viscosity, and also
the quantitative composition of the filtrate in relation to that of the
original solution.

The following experiment from Tigerstedt and Santesson 7 may be
quoted in evidence of the first point : —

1 Loc. ciL. p. 31.

2 Ann. d. Phys. u. Chem,, Leipzig, 1856, Bd. xcix. S. 337 ; 1861, Bd. cxiv. S. 337.

3 Loc. cit. 4 Loc. cit. , p. 30. 5 Runeberg, loc. cit.

6 Schmidt, loc. cit. ; Eckhard, loc. cit. ; Lowy, Ztschr. f. physiol. Chem., Strassburg,
1885, Bd. ix. S. 537.

7 Loc. cit., p. 42.

282

DIFFUSION, OSMOSIS, AND FILTRATION.

1. Egg albumin — 4'14 per cent, proteids ; pressure, 32'5 cm.; goldbeater's skin.

(Filtrate per minute in grms. , '820, '051, '008, '003, '002, '002.)

2. Ox serum — 4 '5 per cent, proteids ; pressure, 30 '5 to 34 cm. ; goldbeater's skin.

(Filtrate per minute in grms., 2'586, 1-594, TOGO, -812.)

In neither case had the membrane been previously stretched.

According to Gottwalt,1 the serum albumin of blood serum niters
through a ureter more easily than the globulin. Martin 2 has shown
that homogeneous membranes of gelatin and gelatinous silicic acid form
filters impermeable to solutions of many colloids, but as permeable
to certain crystalloids as to water.

The relation of the concentration of the filtrate to that of the
original solution is perhaps the most important point to the physiolo-
gist in the matter of filtration through* animal membranes. There is
general agreement that in the filtration of crystalloids the concentration
of the filtrate is very nearly that of the original solution, and this
appears to obtain at very various filtration pressures.3 There is also
general agreement that in filtration of colloids the concentration of the
filtrate is always less than that of the original solution.4 But as regards
the effect of pressure on the concentration of a colloid filtrate, the
results of different observers are not in accordance. Kuneberg5 has
maintained that the concentration of the filtrate is higher at lower
than at higher pressures, and the following table, taken from his later
paper,6 is illustrative : —

Fresh Sheep7 s Intestine — Ascitic Fluid (circulated) holding
3 '7 2 per cent, of Proteids.

Time.

Pressure in Cm.
of Fluid.

Filtrate per hour
in Grms.

Per Cent. Albumin
in Filtrate.

8 P.M. to 8.15 A.M.
8.15 A.M. to 2.15 P.M. .
2.15P.M. to 8.15 P.M. .

1 r I

T84
1-85
1-97

2-34
1-86
1-60

8.50 P.M. to 8.50 A.M. .
8.50 A.M. to 3.0 P.M.

} » {

1-29
1-52

2-02
2-12

4.0 P.M. to 7.30 P.M.
7.30 P.M. to 9.30 A.M. .

} » {

7-30
3-60

1-44
1-26

10.15 A.M. to 2.15 P.M. .
2-15 P.M. to 6.15 P.M. .

} » {

2-89
3-56

2-42
2-60

7.0 P.M. to 9.30 P.M.
9.30 P.M. to 8.15 A.M. .

} » {

6'70
6-21

1-84
1-68

1 Loc. cit. 2 Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 364.

3 Schmidt, urea, sodic chloride, and potassium nitrate, Ann. d. Phys. u. Chem.,
Leipzig, 1861, Bd. cxiv. S. 391.

4 Schmidt, loc. cit., gum and albumin through ox -pericardium ; Hoppe-Seyler, Virchow's
Archiv, 1856, Bd. ix. S. 245, blood-gerum through ureter ; Eurieberg, loc. cit., gut,
ureter, and pleural membrane, with serum, ascitic, and pleuritic fluids ; Gottwalt, loc. cit.,
egg albumin, hydrocele fluid, serum, and parovarian cyst fluid through ureter.

5 Loc. cit. " 6 Ztschr.f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 508.

FILTRATION.

283

On the other hand, the older experiments of Schmidt l with gum
and albumin gave quite opposite results ; thus (p. 364 of 1861 paper) —

Albumin through Ox Pericardium.

Concentration of Original
Solution per Cent.

Pressure.

Per Cent. Albumin in Filtrate.

Per Cent. Albumin in Original
Solution.

,a

(220 mm.
120 mm.

•7037
•6638

3-5

{220 mm.
120 mm.

•7050

•7742

And the experiments of Gottwalt2 and v. Kegeczy 3 are in agreement
with those of Schmidt.

According to Lowy,4 who filtered serum and egg albumin solutions
through pig's bladder at constant pressure, rise of temperature affects
the quantity of the organic solids filtering more than the inorganic, and
such slight temperature changes as from 37°'5 to 410-5 C. have a distinct
effect.

It is therefore evident that our knowledge of the phenomena of filtra-
tion through animal membranes is at present very restricted, and it is
of course impossible to directly apply the results of the above observers
to filtrations in the living body. No experiments, perhaps, have more
clearly pointed out the difference between a dead and living filter than
those of Tigerstedt and Santesson 5 with the frog's lung. A fresh frog's
lung, filled with -6 per cent, sodic chloride solution, will stand a pressure
of some 13 or 14 mm. of mercury without filtering for many hours ;
heating in water at 54° C., or treatment with weak acetic acid, frog's bile,
weak sodic hydrate, or distilled water, at once, however (presumably by
killing the cells), allows filtration. Leber,6 moreover, showed that the
fresh cornea, provided the epithelium of the membrane of Descemet is
intact, will stand a pressure of 200 mm. of mercury, but at once
allows filtration to occur when the epithelium is removed, the tissue
of the cornea itself allowing fluid to pass.

It must be confessed that experiments on living membranes (and
these alone) can give any information of real value ; and, furthermore, it
must be remembered that filtrations in the body are, as a rule, accom-
panied by osmotic phenomena, since filtration must nearly always occur
from one solution into another, and not into air, as in most experiments.

In concluding this article, a word must be said with regard to the
theory that in some cases the cells of a part take some active part in
moving solutions across membranes. So little is known of cell mechanics,
that if such a process does take place we have certainly no conception
of its modus operandi, and it is at least probable that a process con-
sidered to-day as a " vital action " may in the future become capable
of a simpler explanation. Certainly, if the same solution is placed on

1 Loc. cit. 2 Loc. cit. 3 Loc. cit. 4 Loc. cit.

6 Arch.f. Ophth., Leipzig, 1873, Bd. xix. Abth. 2, S. 125.

Loc. cit.

284 DIFFUSION, OSMOSIS, AND FILTRATION.

either side of a living membrane, and a current is found to pass from
one side to the other, when the possibilities of nitration and electro-
osmose are excluded, we have no physical explanation. Thus Heiden-
hain x has demonstrated that serum is absorbed by the intestine. The
pressure in the gut in relation to that in the capillaries, it is true, was
not measured, and the serum was not the animal's own serum, yet these
objections are not of great force, especially the former, since an excess
of pressure in the intestine would probably cause collapse of the capil-
laries or venules.2 It is absurd to maintain that the motion of the
blood in the capillaries aspirates the serum through the epithelium,
because the rate of the blood stream is too slow to have any appreciable
effect in this direction, and weak salt solution is moved across exsected
and still living gut with equality of pressure on the two sides and no
stream.3

This class of absorption experiment appears to be the only one in
which it is justifiable to speak of " vital action," for differences in the
ratios of " diffusion " of two substances into serum outside the body,
and in the cavities thereof, are, per se, no proof of such action, since, as
has been already indicated, the physical permeability of membranes
differs much to one and the same substance ; and again, the fact that a
drug affects the rate of absorption of a substance, after exclusion of the
action of that drug (if any) on the circulation, is as well (and as little)
explained by stating that the permeability of the membrane is altered
by its combination with the drug, as by stating that the activity of the
cells is affected.

In spite of the magnificent labours of Dutrochet, Graham, Pfeffer,
van 't Hoff, and Arrhenius, the enigma of the physical chemistry of
protoplasm in many cases still puts a limit to the physiologist's concep-
tion of the mode of motion of fluids through the membranes and cells
of the body.

1 Arch. f. d. yes. PhysioL, Bonn, 1894, Bd. Ivi. S. 570.

2 The author has repeated Heidenhain's experiment, using the animal's own serum, and
measuring the pressure in the gut, and in a mesenteric vein throughout. Active absorption
occurs, of the water, of the organic, and of the inorganic solids of the serum, when the
pressure in the gut is far below that in a mesenteric vein, and when all the lacteals leaving
the loop have been ligatured.

3 Reid, Brit. Med. Journ., London, May 28, 1892.

THE PRODUCTION AND ABSORPTION OF LYMPH.

By ERNEST H. STARLING.

CONTENTS. — Tlie Production of Lymph, p. 285 — The Physical Forces concerned in
the Movement of Lymph, p. 299 — The Absorption of Lymph from the Con-
nective Tissues, p. 302 — On the Functions of the Lymph in the Nutrition of
the Tissues, p. 310.

THE PRODUCTION OF LYMPH.

THE spleen is the only part of the body where the blood comes in actual
contact with the living cells of the tissue. In all other parts of the
body the blood flows in capillaries with definite walls consisting of a
single layer of cells, and is thus separated from the tissue elements by
these walls and by a varying thickness of tissue. All the interstices of
the tissues are filled with a fluid, lymph,1 which thus acts as an inter-
mediary between blood and tissues. The tissue spaces, which are filled
with lymph, are always found in association with connective tissue.
They have an incomplete lining of endothelial cells, and are connected
with definite channels, lymphatics, by which any excess of fluid in the
part is drained off. The lymphatics all run towards the chest, where
those from the lower limbs as well as from the viscera join to form
a large vessel, the receptaculum chyli, which is continued into the
chest as the thoracic duct. This runs on the left side of the oeso-
phagus, to open into the large veins at the junction of the left internal
jugular with the subclavian vein. A small vessel on the right side
drains the lymph from the right upper extremity and side of the
chest.

Lymph may be collected for examination by placing a cannula in
one of the main lymphatics of a limb, and inducing a flow by move-
ments of kneading and massage, from the lymphatic duct of the neck, or
from the thoracic duct. Since, moreover, the serous cavities of the pleura,
peritoneum, pericardium, and tunica vaginalis are in free communication
with the lymphatic system, any fluid which is normally found in them
may be looked upon as lymph. The various analyses of lymph that
have been made, show that its composition may vary considerably
according to the locality from which it is derived and the circumstances
under which it is obtained. Certain general characteristics are, how-
ever, common to all specimens of lymph. It is always slightly alkaline,
and clots spontaneously at a variable time after it has left the vessels,

1 Adler and Meltzer (Journ. Exper. Med., Baltimore, 1896, vol. i. No. 3) draw a sharp
distinction between the interstitial fluid of the tissue spaces, and the lymph obtained from
the lymphatics which drain these spaces.

2 86 PROD UCTION AND ABSORPTION OF L YMPH.

forming a colourless clot of fibrin. It contains from 2 to 8 parts
per 100 of solids, of which about 1 per cent, consists of inorganic
salts, while the rest is made up chiefly of proteids. The proteids are
similar to those of the blood plasma ; and it seems that the process of
clotting is identical in the two fluids. The salts vary very little in
different samples of lymph, and are generally described as being present
in exactly the same proportions as in the blood plasma from which the
analysed specimen of lymph was derived. Hamburger has recently
called attention to the existence of minute differences of composition in
the salts of the two fluids, and this difference may be credibly ascribed
to chemical changes effected in the lymph by the tissues over which it
has flowed. All specimens of lymph contain leucocytes, chiefly of the
small uninuclear variety ; these are foun4 in greater numbers after the
lymph has passed through a lymphatic gland. Further information re-
garding the composition of lymph will be found in the article on lymph
and serous exudations (p. 181).

The similarity in composition between liquor sanguinis and lymph
suggests that the latter may be regarded as part of the plasma which
exudes through the capillary wall, bathes all the tissue elements, and is
collected by the lymphatics into the thoracic duct to be returned again
to the blood.

Forces involved in lymph production.— Older theories.— As to
the forces involved in its production and the use of this fluid in the
functions of the body, the most various views have been held. Asellius,1
who discovered the lacteals in 1622, thought that these ducts
carried the foodstuffs from the intestines to the liver to be there
elaborated into blood. In order to explain the filling of the lacteals
from the intestines, Asellius invoked the aid of the complicated
mechanism which had already been imagined by Avicenna to account
for the filling of the mesenteric veins. He explained the passage of
chyle to the liver as due partly to the intestinal movements and partly
to the suction-action of the blood vessels and of the liver itself. The
chief factor however was, according to him, the suction-action exerted
by the open mouths of the lacteals themselves, and he compares the
latter to leeches, which suck blood from any surface to which they are
applied. This theory was overthrown by Pecquet 2 by the discovery of
the connection of the lacteals with the thoracic duct and through this
with the venous system. The general lymphatics were discovered
by Eudbeck 3 and Bartholin 4 almost simultaneously. In these authors
we meet with the first conception of lymph apart from absorbed
foodstuffs ; moreover, Bartholin, assuming that this lymph is formed
from the blood, discusses the possible ways by which the fluid could
get from blood vessels to lymphatics. He thinks it possible that
there may be a direct communication between lymphatics and blood
vessels, but is more inclined to the view that the communication is
indirect by means of the parenchyma of the organs. Failing to remark
what Rudbeck had already noticed, namely, that the lymph had a salt
taste, and like blood clotted spontaneously, he describes the lymph as
pure water, and imagines that from the blood vessels there is a

1 " De lactibus sive lacteis venis," Basel, 1628.

2 "Experimenta nova anatomica," Paris, 1654.

3 "Nova exercitatio anatomica, etc." 1653.

4 " Vasa lymph atica nuper in animantibus inventa," Hafniae, 1653.

THEORY OF L UD WIG. 287

transudation of water carrying solids in solution, the solids being taken
up by the tissues, and the pure water which is left over returned by
the lymphatics to the blood. We get here the first conception of the
irrigation theory of tissue nutrition which has played so great a part in
the speculations of later physiologists.

With Hunter l and Monro 9> we find a return to the older theory, that
lymph was produced by a process of suction. This indefinite conception,
however, allowed a considerable degree of individual licence as to the
details of the process, and important authors, such as Hunter and
Mascagni,3 recognised the possibility of a simple transudation or filtra-
tion through the blood-vessel walls. This latter view, however, did not
meet with general recognition, physiologists preferring to believe
in the existence of the exhalant arteries which no one had yet seen
or was ever going to see. Thus we find Bichat 4 definitely asserting
the existence of " vasa exhalantia." Speaking of connective tissues, he
writes : " Chaque cellule du tissue cellulaire est un reservoir inter-
mediare aux exhalants, qui s'y terminent, et aux. absorbants qui en
naissent." The absorption through the supposed open mouths of the
lymphatic and lacteal vessels was attributed by most authorities of this
time to capillary attraction, while the onward flow of the fluid in the
lymphatics could, according to Cruickshank, only be explained as due
to the vital activity of living cells or tissues. Haller describes the
movement of the chyle from the intestines in exactly the same manner.
Particularly ingenious is Hewson's 5 explanation of the absorption and
movement of chyle in theTacteals. He shows that during life the blood
vessels of the villi and in the papillae of the skin and mucous mem-
brane, by their turgescence, keep the orifices of the lacteals or the similar
openings of the lymphatics patent, so that these are now capable of
attracting like capillary tubes made of hard substances. The further
movement of the chyle and lymph he ascribes to the peristaltic con-
traction of muscular fibres in the walls of the lacteals or lymphatics.

Views very similar to these were held by some of the most dis-
tinguished of subsequent physiologists, such as Prochaska, Fohmann,
Burdach and Henle. In opposition to this mechanical theory of lymph
formation, Johannes Miiller,6 having regard to the apparent power of
choice possessed by the lacteals, some substances being absorbed while
others were left, was inclined to ascribe at any rate the act of absorption
to the vital activities of the Living cells of the body.

On the discovery of endosmosis by Dutrochet,7 many physiologists
believed that at last the riddle of absorption and secretion of lymph was
solved, and from this time onwards we find an invocation, generally
more or less vague, of osmotic action to explain the phenomena of
absorption and secretion.

Theory of Ludwig.— The beginning of the new era in the history
of the physiology of lymph formation is marked by the important
paper of Ludwig and Noll.8 In consequence of experiments on

1 Works, edited by Palmer, London, 1835, vol. iv. p. 299.

2 ' De venis lymphaticis valvulosis," 1757.

Vasorum lymphaticorum corporis human! historia et iconographia," 1787.
Anatomie ge"ne"rale," 1812.

A Description of the Lymphatic System, etc.," Collected Works, Syd. 8oc., 1846.
Elements of Physiology," Baly's trans., 1838, vol. i. p. 248.

7 Previous article, p. 273. See also "Cyclopaedia of Anat. and Phys.," art. " Endosmose."

8 Ztschr.f. rat. Mod., 1850, Bd. ix. S. 52.

288 PROD UCTION AND ABSORPTION OF L YMPH.

blood pressure, carried out by the aid of the mercurial manometer of
Ludwig, these authors concluded that the chief factor in the forma-
tion of lymph was the pressure of the blood in the capillaries, and
that in fact the lymph was essentially only the fluid part of blood
which had filtered through the vessel wall into the surrounding
tissues. On arriving in the tissues, this lymph or blood filtrate was
still under a certain pressure, derived from the blood pressure, and
it was this pressure which occasioned the movement of the lymph
into and along the lymphatics. Ludwig concluded that the flow and
composition of the lymph must be explained not only by filtration
of the fluid parts of the blood, but also by processes of osmosis taking
place between the tissue juices and the blood. He summarises his theory
in the following words : — " The blood whjph is contained in the vessels must
always tend to equalise its pressure and its chemical constitution with
those of the extravascular fluids, which are only separated from it by the
porous blood-vessel walls. If, for example, the quantity of blood in the
vessels has increased, the mean blood pressure is also increased, and at
once a portion of the blood is driven out into the tissues by a mere
process of filtration. The same result is brought about when the con-
stitution of the blood is altered by the absorption of food or by increased
excretion by the kidneys, blood, or skin, or when the composition of the
tissue fluids is altered in consequence of increased metabolic changes
taking place in the tissues. In the latter case, the changes brought
about in the lymph are effected by processes of diffusion." Since it is a
condition of the maintenance of life that these chemical changes in the
tissues should go on, and that the waste products should be continually
excreted by the kidneys, lungs, and skin, there must be at the same
time constant changes in the amount and composition of the lymph
produced.1

The testing of this, the mechanical theory of lymph formation and
the lineal descendant of the theory propounded two hundred years
previously by Bartholin, has been the object of all subsequent investiga-
tions dealing with this question. Although we cannot claim to have
arrived at a final decision on the matter, I shall endeavour to show in
the following pages that the two processes — filtration and diffusion-
described by Ludwig, will probably account for the lymph flow and
composition in all the cases which have been sufficiently investigated.

It was shown many years ago by Magendie and others, that chemical
differences between blood and lymph provoked a transference of the
substance that was in excess from one side of the vessel wall to the
other. Thus, if colouring matters, salts, or sugar be injected into the
blood, they are very shortly afterwards found in the lymph in various
parts of the body. If, on the other hand, these substances be injected
into the tissue spaces or into the pleural or peritoneal cavities, their
existence can very soon be detected in the blood, whence they make
their way into the urine. Other instances of the extreme rapidity with
which osmotic interchanges take place between the blood and lymph
will be mentioned later on in dealing with the action of lymphagogues.
Since these interchanges take place after the introduction of abnormal
as well as normal substances into the body, we must assume the general
applicability of the results, and look upon processes of diffusion or
osmosis as one of the factors in regulating the composition of the lymph.

1 "Lelirbuch der Physiologic," 1861, Aufl. 2, Bd. ii. S. 562.

THEOR Y OF HEIDENHAIN. 2S9

Not so successful were Ludwig's attempts to demonstrate a direct
relationship between blood pressure and lymph formation. According
to Ludwig's hypothesis, the amount of lymph produced in any given
part must be proportionate to the difference between the pressure in
the capillaries and the pressure in the extra vascular spaces. In most of
Ludwig's earlier experiments on the subject this condition was found to
hold good. On leading defibrinated blood through a limb, the lymph
production in the limb was found proportional to the pressure at which
the blood was led through it. In the testis Tomsa1 showed that ligature
of the pampiniforin plexus caused a large increase in the lymph from
this organ. Paschutin 2 and Emininghaus 3 found that, in the arm and
leg, extensive ligature of the veins led to an increased lymph production.
In all these cases, therefore, an augmented flow of lymph was obtained
by raising the capillary pressure of the part. On the other hand, the
two last-named observers were unable to prove any constant alteration
of lymph production incident on vasomotor changes. Thus, in one
experiment, Paschutin divided the brachial plexus of a dog and then
stimulated the cut spinal cord, so that there was constriction of all the
arteries of the body with the exception of those of the fore-limb under
observation. Even this rise of pressure had no effect on the lymph flow
from the fore-limb. A little later, Eogowicz,4 working in Heidenhain's
laboratory, repeated Emininghaus' experiments on the hind-limb with
slight alterations, and found almost invariably a slight increase in the
lymph after section of the sciatic nerve or in consequence of active vaso-
dilatation. He proved, moreover, that the vaso-dilatation of the tongue
produced by excitation of the lingual nerve was followed by an increased
lymph production in the tongue, which might at times amount to an
actual unilateral oedema of this organ.

Theory of Heidenhain. — In dealing with the laws affecting
lymph production, we are hampered by the fact that, from the limbs
of an animal at rest, there is, under normal conditions, no lymph flow
at all, so that, when we wish to study the effects of our various
procedures on the lymph production in the limb, we have artificially
to bring about a lymph flow by kneading and massaging the limb.
This fact introduces at once an arbitrary element into the observa-
tion, and Heidenhain suggested, therefore, that the best mode of
investigating the truth of the filtration hypothesis would be to
experiment on the lymph flow from the thoracic duct. This physio-
logist carried out a long research on the various conditions under
which the lymph flow from the thoracic duct might be increased
or diminished,5 and came to the conclusion that the results of his
experiments were irreconcilable with the filtration doctrine, and that we
must assume that the cells forming the walls of the capillaries take an
active part in lymph formation, i.e. that lymph must be looked upon as
a secretion rather than as a transudation. A very similar conclusion had
been previously arrived at by Tigerstedt,6 mainly on theoretical grounds.

Heidenhain's arguments may be shortly summarised as follows : —

1. Obstr action of the thoracic aorta causes a general fall of arterial

!>. d. k. Akad. d. Wissensch., Wien, 1862, Bd. xlvi. S. 185.
2 Arb. a. d. physiol. Anst. zu Leipzig, 1873. 3 Ibid., 1873.

4 Arch. f. d. ges. Physiol. , Bonn, 1885, Bd. xxxvi. S. 252.

5 Ibid., 1891, Bd. xlix. S. 209.

6 Mitth. a. d. physiol. Inst. zu Stockholm, 1886.
VOL. I. — 19

290 PROD UCTION AND ABSORPTION OF L YMPH.

blood pressure below the obstruction. In spite of this fact, the lymph
flow from the thoracic duct may in some cases be unaltered and even
slightly increased.

2. Obstruction of the inferior vena cava above the diaphragm causes
a general fall of blood pressure, and the intestines become apparently
anaemic. The lymph flow from the thoracic duct is largely increased, and
the lymph undergoes chemical changes, becoming more concentrated
than it was before the obstruction. This lymph, according to Heiden-
hain, comes from the intestines, whereas, on obstruction of the portal
vein, these organs yield an increased flow of a lymph which is less
concentrated than normal and contains red blood corpuscles.

3. Heidenhain describes two classes of bodies, which on injection
into the circulation increase the lymph Jlow from the thoracic duct.

The first class comprises bodies such as commercial peptone, watery
extract of dried leeches or of crayfish. These increase the lymph and
make it more concentrated. They usually cause a lowering of arterial
blood pressure, although by careful injection this may be avoided.

The second class includes crystalloids such as sodium chloride, sugar,
etc. Injection of concentrated solutions of these bodies into the circula-
tion evokes an increased flow of lymph which is less concentrated than
before. Some time after the injection, it is found that the lymph
contains a greater percentage amount of injected substance than does
the blood plasma. There may be a slight rise in the arterial pressure,
but this rise is in no way proportionate to the augmentation in the
lymph flow.

Since, therefore, the lymph flow may be increased without any
corresponding elevation in the blood pressure, and since the amount of
injected substance in the lymph may rise above that in the blood plasma,
Heidenhain concludes that the processes of filtration and diffusion are
incapable of accounting for the changes observed in the amount and
composition of the lymph ; although he does not deny that, under certain
pathological conditions, such as heart disease and cirrhosis of the liver,
dropsy or ascites may be and probably is conditioned by the increased
intracapillary pressure acting in many cases on a capillary wall already
weakened and abnormal in consequence of amemic and diseased states
of the blood.

Comparison of the theories of Ludwig and Heidenhain. — A
renewed examination1 of Heidenhain's experiments, combined with a
more thorough investigation of their conditions, has persuaded me that,
so far from overthrowing the filtration hypothesis, they furnish the
strongest arguments which have yet been adduced in its favour. I may
therefore give some account of these experiments, and show how they
support Ludwig's contention with regard to the production of lymph.

Sources of the lymph investigated. — In dealing with the lymph flow
from the thoracic duct, it is essential to know from what parts of the
body this lymph is derived, especially since, as is well known, the
lymphatics from all parts of the body, with the exception of the
right upper extremity and right side of the neck, converge to pour
their contents into this duct. In placing a cannula in the duct,
in order to collect and measure the lymph, the ducts from the left
side of the neck and left upper extremity are ligatured. From the

1 Bayliss and Starling, Journ. PhysioL, Cambridge and London, vol. xvi. p. 159 ; Star-
ling, ibid. vol. xvi. p. 224, and vol. xvii. p. 30.

THEORIES OF LUDWIG AND HEIDENHAIN. 291

hind-limbs we know that, in an animal at rest on the table, there is no
lymph now at all. Hence the sources of the lymph are confined to the
trunk. We can, moreover, exclude the thorax and its contents, since
ligature of the thoracic duct just above the diaphragm absolutely stops
the lymph now. Therefore, when dealing with the lymph now from the
thoracic duct, we deal only with the lymph coming from the abdominal
viscera. As I shall show presently, the abdominal viscera, so far as their
lymph is concerned, may be divided into two groups — (1) the viscera
drained by the portal vein, and (2) the liver.

Influence of venous obstruction. — In testing the filtration hypothesis
on the lymph flow, we have to investigate whether the flow is always
proportional to the difference between the intra- and extracapillary
pressures. We may regard the extracapillary pressure as not varying
to any large extent, so that we have to see what effect is produced
on the lymph by variations in the intracapillary pressure in the
intestines and the liver. The simplest experiments on the subject
are those in which some large vessel is obstructed. Speaking generally,
we may say that obstruction of a large vein raises the pressure in
the capillaries immediately behind it, whereas obstruction of an
artery will diminish the pressure immediately in front of it. If,
for instance, we ligature the portal vein, the arterial pressure is very
little affected, while the pressure in the vein behind the ligature
rises enormously. In consequence of this, there is a large rise of
pressure in the capillaries of the intestines and spleen, so that the
spleen swells and the intestines become black from venous congestion,
haemorrhages being produced into their mucous membrane. The effect
of this ligature on the lymph flow from the thoracic duct is to increase
it four or five times. The lymph also becomes bloody and its total
solids are diminished. The diminution in solids is due solely to a
diminution in proteids, the salts remaining the same as before ; so that
we have here an increased capillary pressure, causing an increased trans-
udation of lymph containing a diminished percentage of proteid — a result
which is also obtained when proteids are filtered with pressure through
dead animal membranes. The presence of red blood corpuscles in the
lymph is not a necessary consequence of a rise of pressure in the
portal vein. If a less excessive rise of pressure be produced by
ligaturing the vein, not at its entry into the liver but just below the
pancreatico- duodenal vein, thus leaving a circuitous route for the blood
to the liver through the anastomoses of this branch, an increased flow
of lymph is produced, containing less proteids than normal lymph,
but which may be quite free from red blood corpuscles.

Still more striking is the effect produced by Heidenhain's experi-
ment of obstructing the vena cava just above the diaphragm (i.e.
between the opening of the hepatic veins and the heart). The lymph
is increased from ten to twenty fold, and it is found that the lymph
obtained after the obstruction is free from red blood corpuscles and is
more concentrated than normal lymph. Thus, in one experiment of
this description, the lymph flow rose from 3 c.c. in the ten minutes
preceding the obstruction to 25 c.c. in the ten minutes after the vein was
occluded. At the same time the percentage of solids in the lymph rose
from 4*8 per cent, before, to 6 '6 per cent, after the obstruction.

What is the cause of this increased lymph flow and why is it more
concentrated ? To answer these questions we must find out first, the

292 PRODUCTION AND ABSORPTION OF L YMPH.

source of the lymph, and secondly, the condition of the capillary
pressure in the organ or organs from which the lymph is derived. We
can determine the source of the lymph by a process of exclusion.
Tying the kidney vessels and lymphatics has no effect on the usual
consequences of obstructing the inferior vena cava. On the other
hand, if we ligature the lymphatics in the portal fissure which carry
off the liver lymph, we find that a subsequent obstruction has no effect
on the lymph flow, or indeed, may slightly diminish it. We must
conclude that the excess of lymph production consequent upon the
obstruction is entirely derived from the liver, and not, as Heidenhain
thought, from the intestines. The change in concentration is easily ex-
plained if we assume that, just as intestinal lymph is more concentrated
(i.e. richer in proteids) than the lyn^ph from the limbs, so the liver
lymph is more concentrated than intestinal lymph, or than the mixed
lymph obtained from the thoracic duct.

In order to answer the question as to the cause of this increased
production of lymph in the liver, we must investigate the changes in
the circulation brought about by the obstruction. On obstructing the
inferior vena cava and recording the blood pressure in the chief vessels
of the abdomen, we notice that the pressure in the aorta drops almost
at once to a third of its previous height, whereas there is a very
considerable rise of pressure both in the portal vein and inferior cava.
It is probable that the effect of the rise of portal pressure on the
intestinal capillaries is more than counterbalanced by the severe drop
in arterial pressure, so that there is a fall of pressure in the intestinal
capillaries. This conclusion is borne out by the fact that, if the
abdomen be open, the obstruction of the inferior vena cava is seen to be
at once followed by blanching of the intestines, as Heidenhain pointed
out. On the other hand, the effect of the simultaneous rise of pressures
in the portal vein and vena cava must be to increase the pressure in
the capillaries of the liver to three or four times the normal amount.
We have then, as the results of this experiment, no rise of pressure in
the portal area and no increase of lymph flow from the portal area, a
large rise of pressure in the hepatic capillaries and a very large
increase of lymph flow from the liver.

Influence of aortic obstruction. — Another experiment, on which
much stress has been laid by Heidenhain, is the one in which
the descending aorta is obstructed in the thorax. The obstruction
of this vessel is easily effected by passing an indiarubber balloon,
tied on the end of a catheter, down the right carotid artery into
the aorta just beyond the arch. The results of this obstruction on
the lymph flow are somewhat variable. In most cases the lymph is
diminished to one-half or one-third its previous amount; in a few
cases the lymph is unaltered in quantity or even slightly increased.
In all experiments the amount of proteids in the lymph is increased.
Now, if we investigate the state of the circulation under these con-
ditions, we find that obstruction of the thoracic aorta causes a very
considerable fall of pressure in the aorta below the obstruction and
a corresponding fall in the portal vein, whereas the pressure in the
inferior vena cava is unaltered or in some cases even slightly increased.
We must conclude, therefore, that in the intestinal capillaries the
pressure has fallen considerably below its normal limits, while in the
hepatic capillaries the pressure is very little altered or may even be

THEORIES OF L UD WIG AND HEIDENHAIN. 293

somewhat increased. Hence the only region of the body below the
point of obstruction where the capillary pressure is not much diminished
is the liver. Now we find that the liver is also the sole source of the
lymph obtained under these circumstances. If the hepatic lymphatics
be ligatured, and the thoracic aorta be then obstructed, the now of
lymph from the thoracic duct is absolutely stopped.

These three experiments show, therefore, that the lymph production
in the organs of the abdomen is directly proportional to the capillary
pressure in these organs, and not independent of them, as was imagined
by Heidenhain.

Hydrcemia and hydrcemic plethora. — In another series of experi-
ments we find, as was predicted by Ludwig (cf. p. 288), that a marked
increase in the lymph flow is produced by a general rise of capillary pres-
sure in all the organs of the abdomen. Such a general rise of capillary
pressure may be brought about by the injection of large quantities
of normal saline fluid into the circulation, thus causing a condition of
hydrcemic plethora. Under such circumstances the lymph may be in-
creased from fifty to one hundred times in amount, and may in some
cases run from the cannula in the duct in a steady stream. Now, in
hydraemic plethora there are two changes in the circulation which might
possibly be responsible for the increased production of lymph — first,
the change in the composition of the blood, and secondly, the increased
pressure in the capillaries of the abdominal viscera. We can decide
which of these two factors is responsible for the increased lymph flow
by a very simple experiment. Previously to injecting 300 c.c. of normal
saline, we bleed the dog to 300 c.c., so that after the injection the total
amount of circulating fluid is the same as at the beginning of the
experiment. In this way we entirely avoid any rise of capillary
pressure, while we have diluted the blood to an even greater extent
than in the experiments in which hydrsemic plethora was produced.
The effect of such a simple hydrsemia is to increase the lymph flow
from 3 c.c. in ten minutes to 4 or 6 c.c. in ten minutes ; whereas, if
hydraemic plethora were produced, the lymph would be increased from
3 c.c. to 30, 50, or 100 c.c. in ten minutes. It is evident, therefore, that
in the production of this increased lymph flow the all-important factor is
the rise of capillary pressure ; although the slight increase in the lymph
flow observed as the result of simple hydrsemia shows that, as might be
expected, a watery plasma gives rise to a transudation of lymph more
easily than does the normal more concentrated plasma.

Heidenhain s second class of lymphagogues. — In a precisely similar
manner we may explain the mode of action of the substances which
were described by Heidenhain as the second class of lymphagogues.
These include bodies such as salt, sugar, potassium iodide, etc. The
injection of a strong solution of dextrose (30 grms. in 30 c.c. water) into
the veins of an animal causes a considerable increase in the lymph flow
from the thoracic duct. The lymph at the same time becomes more
watery than at the commencement of the experiment. Heidenhain
ascribes this effect to a specific excitation of the secretory activities of
the endothelial cells. The effect, however, can be explained in a much
more simple fashion. All these solutions have an osmotic pressure
which is considerably higher than that of normal blood plasma. A
solution of dextrose that should be isotonic with the blood plasma would
contain from 5 to 6 per cent, of this body. When we inject a solution

2 94 PROD UCTION AND ABSORPTION OF L YMPH.

%Hb

55

I

\

65
70
75
80

III

II

.

X

IV

V

X

^

^

>

\

85

^

'^

^

\

*s

,, s

^

in

DO

in

X-

X

:';*

—

- — ,

100

/>''

' ,'

1

3 5 A :

' IO' 15' 2O' 25' 3O' 35' 4O' 4

r/ 5

FIG. 40. — Diagram to show the dilution of the
blood (i. e. hydrcemic plethora) produced in
dogs (Experiments 1, 2, 3, 4) by the injec-

containing from 50 to 75 per cent, of dextrose, it will attract fluid from

the tissues until its percentage
is reduced to 5 or 6 per cent. ;
that is to say, 45 c.c. of fluid
containing 30 grms. of dextrose
will attract water from the tissues
until its total volume is increased
to 500 c.c. Of course this esti-
mate is merely a rough approxi-
mation at the truth, since before
the sugar has had time to attract
all this fluid, a considerable
Amount of it will already have
left the vessels by diffusion. As
a matter of fact, however, we find

w. , 4 „ that injection of a strong solu-

tion of 5 grms. dextrose per kilo, body- ti f clextrose is followed in a
weight. The ordinates represent the . ., ,,

volume of the blood (compared with the few minutes by a considerabl

normal) as indicated by percentage of dilution of the blood, caused by
hemoglobin. The abscissa represent inter- increase in its volume. In

vals of five minutes. The line AAn marks . e , ,

the time at which the injection was finished some experiments of von Brasol,1

in each experiment. The dotted lines to the volume of the circulating
the left of AAj indicate the theoretical diln- blood wag thug uicreased to twice
tion effected by the volume of fluid injected. 1 , , . . ,

-After J. B. Leathes. or three times its previous

amount; and these observations

have been fully confirmed in a series of careful experiments made by
J. B. Leathes 2 (Fig. 40).
As we should expect, 60
this increase in the vol-
ume of the circulating
blood is attended by a
large rise of capillary
pressure in the abdomi-
nal viscera (Fig 41), and
we have here again to
decide whether it is this
rise of capillary pressure,
or the change in the
chemical composition of
the blood, that determines
the increased lymph flow.
This question can be
solved by using the same
method that we adopted
when dealing with the
production of the in-
creased lymph flow in
hydrsemic plethora. We
can entirely obviate the
rise of capillary pressure

01 6 !b 20 so 40 5o so minutes

Inj. of 40 grams dextrose

FIG. 41. — To show influence of the intravenous injection
of dextrose on the blood pressure in the abdominal
viscera, and on the lymph flow from the thoracic duct.
The upper dotted line = pressure in portal vein. The
lower clotted line = pressure in inferior vena cava.
The thick continuous line = pressure in aorta. The
thin continuous line = lymph flow. The ordinates
represent venous pressure in centimetres of water,
arterial pressure in centimetres Hg, and lymph flow
in cubic centimetres per ten minutes.

if we bleed first to 300 c.c. and then inject a concentrated solution

1 Arch.f. PhysioL, Leipzig, 1884, S. 211.

2 Journ. PhysioL, Cambridge and London, 1895, vol. xix. p. 1.

THEORIES OF LUDWIG AND HE1DENHAIN.

295

containing 18 grms. of dextrose (Fig. 42). In this case the fluid that
is dragged by the sugar from the tissues into the blood vessels only
just suffices to make up for the previous loss of blood. No hydreemic
plethora is produced ; there is no rise of capillary pressure, and there
is no increase in lymph flow, although an abnormally large amount
of dextrose is present in the circulation.

The fact that the immediate agent in the production of the increased
lymph flow is the hydrae-
mic plethora which suc-
ceeds the injection, explains
the point noticed by Heid-
enhain, that the efficacy
of these substances is di-

— 1 — r^

\

32

*-

^^

*^-

3£*

•^

.

•

3 5 IO 20 3O 4O 5O 6

'led to Inj. 18 grams dextrose

0 minute

FIG. 42. — To show absence of effect of injecting dextrose
after a previous bleeding. The description of the
curves in Fig. 41 also applies to this figure.

rectly proportional to their

attraction for water ( Was-

seranziehungsvermogen), i.e.

to the osmotic pressure of the solution injected, and is therefore a

function of their molecular weights. A similar relation was noticed

by von Limbeck 1 to hold for the diuretic action of these bodies, which

may therefore also be possibly determined directly by the hydrsemic

plethora.

The advocates of the secretory hypothesis have laid great stress on
the fact that if we analyse the lymph and the blood at different periods
after the injection of sugar, we find that the amount of this substance in
the blood steadily diminishes (even when the kidneys are cut out of the
circulation), while the sugar in the lymph gradually rises to a maximum
and then diminishes parallel with but above that in the plasma. This
was found to hold good for sugar by Heidenhain,2 for potassium iodide
by Ascher,3 and for commercial peptone by myself.4 We are not, how-
ever, justified in concluding from these facts that the sugar, etc., have
been turned out from the blood vessels against pressure, so to speak.
As Cohnstein 5 has pointed out, the lymph flowing at any given moment
from the thoracic duct does not represent the transudation from the
blood at that moment, but is derived from the lymph that has been
formed some time previously. If we had a solution of sugar in gradually
diminishing strength flowing into a lymphatic trunk of the leg, it is evident
that this fluid would mix with the lymph in the other lymphatics, through
which it flowed on its way to the thoracic duct. Later, the solution of
sugar would have displaced practically all the lymph from these channels,
and would flow through the thoracic duct almost undiluted. It would
take, however, some considerable time to flow from the leg to the
thoracic duct, so that the outflow from the duct would represent, not the
fluid which was being injected into the leg at that moment, but the
stronger solution which had been flowing in some time previously. If
one compared, therefore, the percentage of sugar in the fluid flowing
from the duct and in the fluid flowing into the leg lymphatic at different
times after the beginning of the injection, we should obtain a curve
exactly similar to those obtained by Heidenhain after the injection of
sugar into the circulation, and regarded by him as undeniable evidence

1 Arch. f. exper. Path. u. Pharmakol., Leipzig, 1888, Bd. xxv. S. 69.

2 Loc. cit. 3 Ztschr.f. BioL, Miinchen, 1893, Bd. xxix. S. 247.

4 Starling, Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 131.

5 Arch.f. d. ges. PhysioL, Bonn, Bd. lix. S. 350.

296 PRODUCTION AND ABSORPTION OF L YMPH.

of secretory activity. We may conclude, therefore, -that the increased
flow of lymph caused by injection of the second class of lymphagogues
is entirely due to the rise of capillary pressure thereby induced, and is in
no wise conditioned by a stimulation of the secretory activities of the
endothelial cells.

The permeability of the capillary wall. — The dependence of lymph
formation on capillary pressure is not the only important relationship
brought to light by these experiments. The amount and composition of
the transudation through a membrane depend not only on the pressure
at which the transudation is effected, but also on the nature of the mem-
brane. According to the permeability of the membrane, so the amount
and composition in proteids of the transuding fluid will vary. After
obstruction of the inferior vena cava, the pressure in the intestinal capil-
laries, although it probably sinks below *ts normal height, is yet as high
as that in the hepatic capillaries. Nevertheless, we get a very small
amount of transudation through the intestinal capillaries, and a very large
amount through the hepatic capillaries. Hence the permeability of the
liver capillaries must be very much more marked than that of the intestinal
capillaries. In the same way we may compare the permeability of the
intestinal capillaries with those of the limb capillaries. Normally from
the limb there is no flow of lymph at all, whereas a probably equal
pressure in the intestinal capillaries suffices to give rise to a steady flow
of lymph. If we ligature all the veins of the leg, a lymph flow may be
set up, but such a flow is incomparably smaller than that produced on
ligature of the portal vein. We can therefore arrange the capillaries of
the body in a descending order of permeability, the liver capillaries being
the most permeable and the limb capillaries the least permeable. I have
already mentioned how, on filtering solutions of proteid through various
membranes, the percentage of proteids in the filtrate increases with the
permeability of the membrane. As we have seen, exactly the same
thing holds good for the capillaries in the body. The lymph in the
limbs, the filtrate through the impermeable limb capillaries, contains
only from 2 to 3 per cent, proteids ; that from the intestines contains
from 4 to 6 per cent, proteids ; while that from the permeable capillaries
of the liver contains from 6 to 8 per cent, proteids — in fact, almost as
much as the blood plasma itself. It is conceivable that we might alter
the amount of lymph in any organ by changing, not the intracapillary pres-
sure, but the filtering membrane, i.e. the endothelial wall of the capillaries.
Such a change can be brought about in the body by various means.
Thus the permeability of the limb capillaries is considerably increased as
the effect of any local injury, such as that caused by plunging the limbs
into water at 56 C. for a few minutes. Cohnheim 1 pointed out that if a
cannula be placed in one of the lymphatics of the foot, and the foot be
then scalded in this manner, in a few minutes the lymph begins to flow
spontaneously from the cannula. The lymph which is thus produced is
much richer in proteids than is lymph from a normal limb. Moreover,
as Jankowski 2 showed, the amount of lymph flowing from the foot can
now be varied within wide limits by altering the pressure in the capil-
laries, either by ligature of the vein or artery, injection of salt solution,
or production of vasomotor paralysis. By this scalding, in fact, we may
reduce the limb capillaries to the condition of liver capillaries.

1 Virclww's Archiv, 1877, Bd. Ixix. S. 516.

2 Ibid., 1883, Bd. xciii. S. 259.

THEORIES OF LUDWIG AND HEIDENHAIN.

297

Heidenhairis first class of lymphagogues. — We are now in a position to
discuss the mode of action of the animal poisons included in the first
class of lymphagogues. On injecting a decoction of crayfish, leeches, or
mussels into the blood, the lymph flowing from the thoracic duct is
increased in amount, and becomes much more concentrated than before.
In both blood and lymph coagulability is lessened or abolished; the
blood becomes more concentrated from a loss of plasma, while the
plasma itself is less concentrated than before the injection. The blood
pressure, though generally lowered, may be unaltered if the injection be
carefully carried out ; the heart-beat is always quickened. Heidenhain
concludes that these bodies exert a specific influence on the endothelial
cells, causing them to secrete an increased amount of lymph more con-
centrated than the blood plasma.

There can be no doubt that the greater concentration of the lymph
obtained under these circumstances is due to the fact that it is chiefly
derived from the liver, since the effect of these lymphagogues on the
lymph flow may be almost abolished, if the portal lymphatics be liga-
tured previous to the injection. On investigating the changes in
capillary pressure consequent on the injection, I have found that they
are not sufficient to account for the increased lymph production. It is
true that injection of one of these bodies is invariably followed by a con-
siderable rise of pressure in the portal vein, associated with general
vascular dilatation. But this rise of pressure is comparatively transitory
(Fig. 43), lasting only fifteen to forty minutes, whereas the increased lymph
flow lasts from forty
minutes to two
hours after the in-
jection. Moreover,
this rise of pressure
in the portal vein
would have more
influence in in-
creasing the capil-
lary pressure in the
intestines than in
the liver. Taking
these facts into con-
sideration, we must
conclude that the

Inj. of mussel extract

FIG. 43. — To show effects of the injection of a lymphagogue of
the first class on the blood pressures in the abdominal
organs, and also on the lymph flow. (For explanation of
curves see Fig. 41.)

increased lymph flow observed after injection of lymphagosrues of the
first class cannot be accounted for by a rise of capillary pressure. It
is open to us to conclude that these bodies act in Heidenhain's sense
on the endothelial cells of the capillaries, exciting them to an active
secretion. It must be remembered, however, that all these bodies are
active poisons. We should expect them, therefore, to diminish rather
than to excite the physiological activity of the endothelial cells. We
have already seen that the effect of a slight injury to or diminished
nutrition of the capillary wall is to increase its permeability. I would
explain the action of these bodies, therefore, as dependent on injury to
the capillary wall, and a consequent enhanced permeability, so that a
pressure which is very little above the normal capillary pressure is able
to cause a greatly increased transudation of fluid.

I have already mentioned that these bodies chiefly affect the capil-

298 PROD UCTION AND ABSORPTION OF LYMPH.

laries of the liver. Their action, however, is not absolutely confined to
that organ. I have experimental evidence that there is a certain
degree of increased permeability of the intestinal capillaries after the
injection of these lymphagogues, an increased permeability which is
brought into evidence only after raising to a certain extent the pressure
in these capillaries. The first class of lymphagogues also affects the
capillaries of the skin. In a number of the experiments in which these
bodies have been injected, we may observe a rapid development of an
urticarial eruption on the skin, and it is a matter of common knowledge
that the ingestion of the animals from which these bodies are derived
(mussels, crayfish, lobster) is often followed in man by an eruption
of urticaria which may or may not be accompanied by other symptoms
of poisoning.

Another substance which seems to act directly on the capillary wall
is curari. This body, however, differs from the class of lymphagogues
under discussion, in the fact that its chief action is on the vessels of the
limbs. The effect of curari in increasing the lymph production in the
limbs was noticed long ago by Paschutin working in Ludwig's labora-
tory. Its direct action on the endothelial wall of the capillaries can be
easily demonstrated in the living frog's web. It may be seen that, after
the injection of curari, the capillary walls become apparently more
sticky, so that the capillaries become filled with a number of leucocytes
adhering to their walls.

Conclusions. — Thus a renewed investigation of the facts discovered
by Heidenhain has shown that they are not irreconcilable with the
filtration hypothesis, but rather serve to support it. At the same
time they prove the extreme importance of the factor upon which
so much stress was laid by Cohnheim, namely, the nature of the
filtering membrane. In fact, we may say that the formation of lymph
and its composition apart from the changes brought about by diffusion
and osmosis between it and the tissues it bathes, depend entirely on
two factors —

1. The permeability of the vessel wall.

2. The intracapillary blood pressure.

So far as our experimental data go, we have no sufficient evi-
dence to conclude that the endothelial cells of the capillary walls
take any active part in the formation of lymph. It seems rather
that the vital activities of these cells are devoted entirely to maintain-
ing their integrity as a filtering membrane, differing in permeability
according to the region of the body in which they may be situated.
Any injury, whether from within or without, leads to a failure of
this their one function, and therefore to an increased permeability,
with the production of an increased flow of a more concentrated
lymph.

We have no evidence that the nervous system has any influence on
the production of lymph in any part, except an indirect one by altering
the capillary pressures in the part through the intermediation of vaso-
constrictor or dilator fibres. This action is better marked in situations
where the capillaries are normally very permeable or where the per-
meability has been increased by local injury to the vessels, or by the
circulation of poisons in the blood stream.1

1 Cf. Cohnheim u. Lassar, Virchours Archiv, 1878, Bd. Ixxii. S. 132 ; and Jankow-
ski, ibid., Bd. xciii. S. 259.

FORCES CONCERNED IN MO VEMENT OF L YMPH. 299

THE PHYSICAL FORCES CONCERNED IN THE MOVEMENT OF LYMPH.

We may now consider briefly the forces which bring about the flow
of the lymph and chyle from the origin of the lymphatics towards the
termination of the thoracic duct in the subclavian vein.

In the living animal the lymphatics, like the blood vessels, are in a
condition of moderate distension. The lateral pressure in the lymphatic
duct of the neck was measured in 1849 by Ludwig and Noll.1 In the
dog they found that this pressure varied from 8 to 18 mm. sodium car-
bonate solution. A little later, Weiss 2 measured the pressure in the
same vessel in the dog and horse. In the dog he found that it varied
from 5 to 20 mm., and in the horse from 10 to 20 mm. soda solution.
The latter observer also estimated the velocity of the lymph flow in the
cervical lymphatic by means of Volkmann's hsemodromometer. He
found that the average velocity was about 4 mm. in the second, a
velocity which is exceedingly small as compared with the velocity of
blood in arteries or veins of the same calibre, and is only a few times
greater than the velocity in the capillaries. Since there is a constant
flow of lymph from the periphery to the thoracic duct, it is evident that,
as we trace the lymphatics towards their radicles, the pressure of the
lymph must increase. This increased pressure in the peripheral parts
of the lymphatic system is shown by the fact, to which Eudbeck 3 first
called attention, that if a lymphatic be emptied by pressure, it always
fills from the periphery, and if a ligature be placed round it, the vessel
swells upon the peripheral, and shrinks on the central side of the
ligature.

We see then that the first and chief factor in the onward flow
of lymph is the pressure under which this is formed in the radicles
of the lymphatics and in the tissue spaces. As the blood flows through
the capillaries at a given pressure, a certain proportion of its fluid con-
stituents filteis through the vessel wall, forming a transudation which
is still under a certain amount of pressure, and it is this remaining
pressure which causes the onward flow of the lymph. Hence the
ultimate cause of the lymph flow must be looked for in the energy of
the heart's contraction.

When this hypothesis was first put forward by Ludwig and Noll (in
opposition to the suction theories mentioned previously), it was objected
to by Donders 4 on anatomical grounds. At that time it was thought
that the lymphatics formed a closed system of capillaries, ramifying in
the tissues ; and Donders pointed out that if the pressure in the tissue
juices were higher than that of the contents of the lymphatic capillaries,
the effect would be, not a flow from spaces into capillaries, but a collapse
of the latter with obliteration of their lumen. Further anatomical
investigations have shown us, however, that, in the first place, the
lymphatics are probably not a closed system of tubes, but are in com-
munication with the tissue spaces (Eecklinghausen,5 Ludwig); and
secondly, that the walls of the lymphatics, at any rate in certain situa-
tions, are 'so connected by strands of elastic fibres with the surrounding

1 Loc. cit.

2 " Experimentelle Untersuch. ueber die Lymphstrom, " Diss., Dorpat, 1860 (quoted by
Gruenhagen, Bd. i. S. 282).

3 LOG. cit. 4 Ztsclir.f. rat. Med., 1853, N. F., Bd. iv. S. 238.
5 Strieker's "Histology," Syd. Soc. Trans., 1869, vol. i. p. 297.

3oo PROD UCTION AND ABSORPTION OF L YMPH.

connective tissue, that a rise of tension in the meshes of the latter will
only drag the walls of the lymphatics further apart, and thus increase
rather than diminish their lumen.1

Although the blood pressure is therefore the primary mechanical
factor in the movement of lymph, there are several other factors which,
though subsidiary, are of considerable importance. In the first place, the
flow of lymph through the thoracic duct is much aided by the respira-
tory movements. In all experiments on the subject of lymph formation,
it is necessary to maintain the animal in as quiet a condition as possible,
since any disturbance of the respiratory movements causes a variation
in the lymph flow from the thoracic duct. With every inspiration, in
consequence of the descent of the diaphragm, there is a rise of pressure
in the abdominal cavity, and a fall of pressure in the thorax. Hence
we get an emptying of the lymphatics of the abdomen, including the
receptaculum chyli, and a distension of the duct in the thoracic
cavity. With each expiration the thoracic duct tends to collapse
to a certain degree and so empties itself into the veins, a backward
flow of lymph being prevented by the valves in the duct. If a
manometer be connected by a T-tube with the thoracic duct, it is
found that there is a rise of pressure during expiration and a fall
during inspiration, so that during the latter period the pressure may
become negative.

Respiration has also an indirect influence on the lymph flow. With
each inspiration the negative pressure in the thorax is increased, so that
a negative pressure is also produced in the intrathoracic venous trunks,
which must cause a suction of lymph through the thoracic duct into the
subclavian vein. That the blood pressure in the subclavian vein at
the opening of the thoracic duct is of importance for the flow of lymph,
is shown by the fact that, if the pressure here is raised in any way, as by
ligature of the vein, the flow of lymph is entirely stopped, and there
may be a reflux of blood from the vein into the duct.

The work of Ludwig and his pupils has revealed to us the existence
of certain anatomical arrangements for furthering the flow of lymph.
Thus, in all tendons and aponeuroses of the body, we find a double
system of lymphatics, consisting of a deep network of capillaries with
meshes elongated in the direction of the fibrous bundles, and lying
directly on the muscular fibres ; and a superficial network with polygonal
meshes lying in the peritendinous connective tissue.2 Both networks
are in connection by means of small vertical branches, and contain no
valves. It is found that the slightest pressure or stretching of the
aponeuroses causes a flow of lymph from the deep into the superficial
meshwork, and from here into larger lymphatic vessels, which pass
through the substance of the muscles to join the large lymphatic
trunks. A very similar arrangement of lymphatics has been described
by Ludwig and Schweigger-Seidel,3 in the central tendon of the
diaphragm. These may be injected by introducing some coloured fluid
into the abdominal cavity of a freshly-killed animal, and then carrying
out artificial respiratory movements.

The physiological proof of these deductions from anatomical obser-
vations was furnished by Genersich,4 who showed that the lymph flow

1 Gaskell, Arb. a. d. physiol. Anst. zu Leipzig, 1876.

2 "Die Lymphgefasse der Fascien und Selinen," Leipzig, 1872.

3 Arb. a. d. physiol. Anst. zu Leipzig, 1866. 4 Ibid., 1870.

FOR CES CONCERNED IN MO VEMENT OF L YMFH. 30 1

could be largely increased by passive flexion and extension of the limbs.
We must therefore look upon the entire muscular system as one of
the chief sources of the energy for maintaining the lymphatic circula-
tion, especially as the presence of valves in the lymphatics converts
every muscular contraction which may press on the vessels into a
driving force.

We have finally to consider the effect of changes in the calibre of
the lymphatics themselves on the onward flow of lymph. In the frog
(and in other amphibia, and also in Sauropsida) the lymph circulation
is maintained by special contractile cavities called lymph hearts, situated
in pairs, an anterior pair beneath the scapulae, and a posterior pair in
the ileo-coccygeal space.

The chief points with regard to the normal anatomy and physiology of the
batrachian lymph hearts have been summed up as follows, by J. Priestley : l —

1. The hearts are muscular sacs, the fibres of which branch and freely
anastomose and are transversely striated. Their walls are penetrated by
medullated and non-medullated nerve fibres, and small nerve ganglia are
situated in the neighbourhood of the hearts, but no ganglion cells
have as yet been recognised amidst the muscular fibres. They collect the
lymph from more or less extensive lymphatic regions, and force it past valves
into large veins, the anterior pair of hearts into branches of the jugular, the
posterior pair into branches of the ischiatic vein. They are supplied by
nerves from the spinal cord, the anterior pair by the second, the posterior pair
by the tenth spinal nerve.

2. The hearts exhibit throughout life a pulsation with a mean rate of
sixty to seventy a minute. It is, however, not continuously regular, being
interrupted by pauses, and by periods of great acceleration. The pauses some-
times follow movements on the part of the animal, but often they cannot be
set down to any definite cause. After such pauses the pulsations begin as
twitches before falling into beats of normal fulness. The periods of acceleration
also seem to be determined, for the most part, by movements of the animal.

3. The hearts are governed by cerebro-spinal centres — motor and inhibitory.
The motor centres are situated in the spinal cord, those for the anterior pair
opposite the third, and those for the posterior pair opposite the sixth
vertebra. They transmit their impulses down the appropriate spinal nerves
of their own side of the body ; and each is independent of the rest. They
originate the normal rhythm of the hearts ; and their action, whatever its exact
nature, is automatic, or not due directly to afferent stimuli ; hence no change
in the lymph current traversing the hearts can alter their rhythm. The
inhibitory centre is situated in the encephalon, in the optic lobes; it is
constantly in action.

4. These centres are in connection with afferent nerves. Strong stimuli,
applied to the blood heart or to the abdominal viscera, lead to inhibition of the
heart beats, if the upper centre is intact ; while strong sensory stimuli applied
to the skin may inhibit the lymph hearts whether the upper centre is
present or not.

5. But though governed by the above centres, the lymph hearts seem
capable of an irregular pulsation when separated from them. Such pulsation
consists of flickers and indefinite confused twitchings for the most part,
which, when the heart is vigorous, harmonise occasionally to full beats. The
nature of these movements is still doubtful. The most that can be said about
them is that they are probably not solely muscular, since curari abolishes them.

1 Journ. PhysioL, Cambridge and London, 1879, vol. i. p. 1. Cf. also the account by v.
Wittich in Hermann's " Handbuch," Bd. v. (2) S. 325, where full references to the liter-
ature of the subject are given.

302 PROD UCTION AND ABSORPTION OF L YMPH.

No such mechanism exists in the mammalia. Heller and Colin
have observed rhythmic contractions of the lacteals in the mesentery,
but only in the herbivora. In the case of the chyle vessels, Briicke l has
shown that the onward flow of lymph is helped by the rhythmic con-
tractions of the muscular fibres of the intestinal villi, which empty the
central cavity of the villus into the underlying network of lymphatics.

Since the walls of most lymphatic vessels and of the thoracic duct
are provided with unstriated muscular fibres, we should expect these
vessels to be constricted, in consequence of direct stimulation, and such
constrictions have been observed in executed criminals. It has been
shown more recently that' an active contraction or dilatation of the
lymphatics can be brought about by electrical stimulation of certain
nerves. Thus Paul Bert and Laffont '2 noticed contraction of the
lacteals on stimulation of the mesenteric nerves, and a dilatation of the
same vessels on exciting the splanchnics. Gley and Camus3 have
lately repeated these experiments more carefully, and have obtained
graphic evidence of a dilatation of the cisterna lymphatica on stimula-
tion of the splanchnic nerve. This dilatation of the cisterna probably
explains the temporary stoppage in the lymph flow from the thoracic
duct which I described as the immediate effect of splanchnic stimulation.

It is probable, however, that the active contractility of the walls of
the lymphatics is of very little importance for the flow of lymph
through them. The only factors which are of importance are mechanical,
and are —

1. The pressure under which the lymph is poured into the tissue
spaces. This in its turn is dependent on the differences of pressure
between the intra- and extracapillary fluids, as well as on the per-
meability of the vessel walls.

2. All the muscular contractions of the body, and especially those
by which the respiratory movements are carried out.

THE ABSORPTION OF LYMPH FROM THE CONNECTIVE TISSUES.

Relative importance of blood vessels and lymphatics. —Before
the discovery of the lacteals by Asellius, anatomists ascribed the office
of absorption generally to the veins. From this time until the begin-
ning of the present century, no subject was more hotly disputed than
the question of the relative importance of the veins and of lymphatics
in the processes of absorption.

It was generally conceded that the lacteals performed practically
the whole work of absorbing the products of digestion from the intes-
tines ; but the views as to the functions of the other lymphatics of the
body were many and various. Thus, when Nuck4 first made his
experiments, in which he thought he injected these lymphatics from the
arteries, he concluded that they had no other use than as correspondent
veins, to return the lymph from such arteries as were too small to admit
the red blood corpuscles. As anatomical and clinical knowledge increased,
it was gradually recognised that the general lymphatics of the body had
a function similar to that of the lacteals in the intestines, and like them

1 "Ueber die Chylusgefasse und Fortbewegung des Chylus," Wien, 1853.

2 CompL rend. Acad. d. sc., Paris, March 13, 1872.

3 "Recherches dans les causes de la circulation lymph atique," Diss., Paris, 1894.

4 " Adenographia curiosa, " Leidse, 1691.

ABSORPTION FROM CONNECTIVE TISSUES. 303

were able to absorb fluids as well as solids in fine suspension or solution.
A number of reasons for this conclusion are given by Johannes Miiller,
and I may quote some of these as an example of the arguments by
which older anatomists, such as Hunter and Hewson, had come to hold
this opinion. In the first place, the lymphatics often become painful,
red streaks appear in their course, and the neighbouring lymphatic
glands become swollen after the application by friction of irritating
matters to the skin. Mascagni asserted that, in animals which died
from pulmonary or abdominal haemorrhage, the lymphatics of the pleura
and peritoneum were filled with blood (Miiller discredits this assertion as
" extravagant "). Mascagni and Soemmering observed bile in the
lymphatics coming from the liver, in cases where the bile ducts were
obstructed. Tiedemann and G-melin,1 after tying the ductus choledo-
chus in dogs, found the lymphatics of the liver filled with a fluid of a deep
yellow colour. The lymphatic glands through which these lymphatics
passed were yellow, and the yellow fluid taken from the thoracic duct con-
tained biliary constituents. The effect of this and similar evidence on the
minds of the anatomists in Hunter's time was rather curious. Since
nature had provided a system — the lymphatics — on purpose to serve
the office of absorption, it was considered in the highest degree
improbable that this office would also be carried out by the veins, and
William and John Hunter, as the result of experiments on absorption
from the intestines, concluded that the veins take no part in absorption.
To this view of exclusive power of absorption possessed by the
lymphatics, it was objected that animals exist which possess neither
lacteals nor lymphatics. It was therefore regarded as a brilliant victory
for the hypothesis, when Hewson demonstrated the existence of lacteal
and lymphatic vessels in birds, reptiles, and fishes.

Subsequent researches, especially by Magendie,2 have shown, how-
ever, that absorption from all parts of the body can be effected by
blood vessels as well as by lymphatics. Magendie's researches have
been continued and extended of late years by Ascher 3 in the case of
the connective tissues of the lower limbs, by Tubby and myself 4 in the
case of the pleural and peritoneal cavities. We found, for example,
that, after injecting methylene-blue or indigo -car mine into the pleura,
the dye-stuff appeared in the urine within five minutes, whereas the
lymph presented no trace of blue for another twenty minutes, or even
two hours. It is evident that in this case the dye must have been
taken up by the blood vessels and not by the lymphatics, and that
this vascular absorption takes place with extreme rapidity. In a later
series of experiments, Leathes 5 has shown that, after introduction of
various salt solutions into the serous cavities, an interchange of con-
stituents takes place directly between the blood and the injected fluid,
so that the latter in a very short time becomes isotonic with the blood
plasma. Now, in this mode of absorption by the blood vessels the so-
called absorption really consists in an interchange between blood and
extravascular fluids — an interchange apparently dependent entirely
upon processes of diffusion between these two fluids. So long as any

1 Quoted by Muller (Baly's translation, vol. i. p. 242).

2 Precis elementaire de physiologic," Paris, 1836.

* Ztschr.f. Bid., Miinchen, 1893, Bd. xxix. S. 247.

4 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 140.

5 Ibid., 1895, vol. xviii. p. 106.

3o4 PROD UCTION AND ABSORPTION OF L YMPH.

difference in composition exists between intra- and extra vascular fluids,
so long will diffusion currents be set up tending to equalise this
difference.

Absorption of isotonic fluids. — These experiments, therefore, have
no direct bearing on the absorption of lymph, i.e. the normal tissue
juices. In this case the fluid to be absorbed resembles in almost all
particulars the blood plasma, and possesses the same osmotic pressure
as the latter, so that it would seem that there are no forces of diffusion
or osmosis tending to absorption. Mliller1 concludes from similar
considerations that " the removal of collections of fluid must be effected
in many cases by means of the lymphatics, independently of imbibi-
tion into the capillaries." The mechanism of this lymphatic absorption
has been already studied. We have aow to inquire whether at any
time fluids, such as those normally present in the tissues and isotonic
with the blood, can be taken up by the blood vessels.

We may arrange the experiments which have been made to decide
this point under three headings —

1. In the first set, observations were made on the absorption of
isotonic salt solutions and blood serum from the pleural and peritoneal
cavities. (Mow,2 working under Heidenhain's direction, found that
such fluids were absorbed rapidly from the peritoneal cavities of living
animals, while the lymph flow from a cannula placed in the thoracic
duct showed no (or only slight) increase, in no way comparable to
the amount of fluid absorbed. He concluded, therefore, that the
absorption was effected by the blood vessels and was dependent on
the vital activity of the cells lining the serous cavities or of the
endothelial cells of the capillaries. Hamburger and Leathes con-
firmed these results, but showed that they could not depend on any
vital activity of the endothelial cells, since absorption took place with
equal rapidity even when poisonous solutions of sodium fluoride were
employed.

The great objection to these experiments is that they do not prove
conclusively absorption by the blood vessels. It is still possible that the
fluids may have been taken up by the subserous lymphatic network -and
had not reached the thoracic duct during the experiment. This is an
objection raised by Cohnstein,3 who concludes from very similar experi-
ments that these fluids are carried away solely by the lymphatics. It
might be thought that this question could be easily decided by observing
whether fluids were still absorbed from the serous cavities after ligature
of both lymphatic ducts. I have made a number of experiments of this
description, but have failed to get decisive results. It is true that, after
ligature of both thoracic ducts as well as of the right innominate vein,
isotonic salt solutions were taken up fairly quickly from the serous
cavities. In none of these cases, however, could I be certain that the
lymph was absolutely shut off from the blood. As a rule I injected
on three succeeding days several hundred c.c. saline solution into the
peritoneal cavity, the last injection containing carmine granules in
suspension. On killing the dog two days after the last injection, the
peritoneal cavity was generally found to be empty, and carmine granules
could be traced along the glands of the anterior mediastinum, showing
that, in spite of the ligature of both lymphatic ducts, there had been a

1 Loc. cit. 2 Arck.f. d. ges. PhysioL, Bonn, 1894, Bd. lix. S. 170.

3 Centralbl.f. PhysioL, Leipzig u. Wien, 1895, Bd. ix.

ABSORPTION OF ISOTONIC FL UIDS. 305

passage of lymph upwards and through the chest. We must therefore
look to other methods to decide this question.

2. There is a whole series of experiments made by other observers
which I think prove conclusively the power of the blood vessels to take
up fluid from the tissue spaces. If an animal be bled several times, it
will be found that the blood obtained in the later bleedings is more
watery than that obtained at the beginning of the experiment. Now
this diminution of total solids in the blood seems to be due chiefly to a
dilution of the serum ; the serum contains less solids than before, and is
increased in volume relatively to the blood corpuscles. I may here
quote some observations which show this point.1

Dog 11 '4 kilos. — Solids of serum = 7 '72 per cent. Dog then bled to
220 c.c. Thirty minutes later, solids of serum = 7*14 per cent.

In another experiment the solids of the serum were at first 6*98 per cent. ;
after bleeding to 200 c.c. = 6*57 per cent.; after further bleeding to 100 c.c.
= 6*37 per cent.

In a smaller dog (6 '5 kilos.), withdrawal of 150 c.c. blood reduced the
solids of the serum from 7*77 per cent, to 6*47 per cent.

It must be noticed that this attempt to regulate the amount of the
circulating blood by bringing it up to its normal volume is carried out
with great rapidity, so that it is, even while an animal is being bled,
found that the later portions of blood are more dilute than the earlier
portions. That the fluid which is added to the blood in these cases is
derived from the tissues or tissue spaces, is shown by Lazarus-Barlow's 2
experiments. This dilution of the blood takes place even when the
thoracic duct is tied or when the lymph is conducted away by placing a
cannula in the duct, so that it cannot be due, as was formerly thought,
to an increased lymph flow into the blood.

3. In order to be absolutely certain of the power of the blood
vessels to take up isotonic solutions and dropsical fluids from the
tissue spaces, I carried out a series of experiments,3 in which I led
defibrinated blood through the blood vessels of amputated limbs. In
each case I had a double set of transfusion apparatus, and sent one-half
of the blood many times through a limb which had been rendered
dropsical by the injection of isotonic salt solution, while simultaneously
fluid was flowing at the same pressure through the other limb, which was
not dropsical, and thus served as a control. In each case the blood was
analysed and its haemoglobin estimated before the experiment, and from
both limbs after the experiment. It was invariably found that, whereas
the blood which had passed from twelve to twenty-five times through
the sound limb had become rather more concentrated, the blood which
had passed through the oedematous limb had taken up fluid from this
limb. I may here quote one of these experiments as an example : —

Total Percentage

Solids. of Oxy haemoglobin.

1. Blood before experiment . . 2 1*2 per cent. 100

2. After twenty passages through

noimal leg .... 21 '4 „ „ 103

3. After twenty passages through

oedematous leg .... 20*5 „ ,, 95'5

1 Tscherewkow, Arch. f. d. ges. Physiol., Bonn, 1895, Bd. Ixii. S. 304.

2 Journ. Physiol. , Cambridge and London, vol. xvi. p. 13.

3 Ibid., 1895, vol. xix. p. 312.
VOL. I. — 20

306 PROD UCTION AND ABSORPTION OF L YMPH.

From a consideration of these facts we must conclude that lymph
and saline solutions, isotonic with the blood, may be taken up by the
blood circulating through the capillaries, and that this process may
occur comparatively rapidly.

Effect of intracapillary pressure. — We have already seen how
any excess of intracapillary pressure, such as accompanies plethora,
causes an increased transudation from the capillaries, so that the
volume of circulating fluid is diminished. Now we see that, on any
diminution of capillary pressure taking place, as after bleeding, the
fluid in the tissue spaces goes back into the vessels to make up for
the volume of circulating fluid lost. This wonderful balance between
capillary pressure and lymph production or absorption is, I think,
well illustrated by Lazarus Barlow's observations. This author has
shown that the slight plethora produced by wrapping up a limb in
Esmarch's bandage causes an appreciable increase in the transudation in
other parts of the body, so that the specific gravity of the tissues of the
upper limb for instance falls, while the specific gravity of the blood
rises. The reverse is the case when circulation is restored to a limb
which has been kept ansemic for an hour or two. Here considerable
hypersemia of the affected limb is produced, and corresponding anaemia of
other parts of the body. We find, then, that absorption as well as trans-
udation through the capillary wall is determined by the intracapillary
pressure. When the pressure rises transudation is increased, when the
pressure falls absorption is increased. We have seen that the depend-
ence of transudation on capillary pressure is susceptible of a fairly simple
mechanical explanation. We have now to discuss the mechanism of the
absorption process.

Mechanism of absorption. — Filtration. — Is absorption effected by
the active intervention of the endothelial cells, or are there physical
factors at work which will serve to explain it ? An explanation of
absorption, which will strike anyone who investigates this problem, is
that it may take place in the same manner as lymph is produced,
i.e. by a process analogous to filtration. A series of mechanical
experiments by Klemensiewicz l would seem at first sight to show
that such a backward filtration is impossible. Klemensiewicz points
out that, if fluid be passing at a given pressure through a permeable
tube contained within a rigid tube, transudation will occur until the
pressure of the transuded fluid is equal to that of the fluid flowing
through. At a certain point in the experiment the pressure of the
transuded fluid will exceed the pressure at the outflow end of the
tube. The tube will collapse and the flow through it will be stopped.
He imagines that the same sequence of events occurs in the living
body in the presence of a considerable transudation. Arteries, capil-
laries, and veins are bathed in the transuded fluid. The fluid which
leaves the capillaries will, if a free outflow for it be absent, after
a time attain a pressure near that ruling in the capillaries and higher
than the venous pressure. The veins will therefore collapse, venous
obstruction will be produced, and the capillary pressure and trans-
udation will be higher than ever, so that we have a vicious circle
of events tending continually to increase the oedema of that part.
Now Klemensiewicz' objections are true only under one condition — i.e.
that the venous tubes should run freely through the lymphatic spaces of

1 Sitzungsb. d. k. ATcad. d. Wissenscli., Wien, 1881. Bd. Ixxxiv.; 1886, Bd. xciv.

MECHANISM OF ABSORPTION. 307

the tissues. If, however, we consider a system in which the inner
tube is connected at various points in its circumference to the outer
tube by strands of fibres, it is apparent that a rise of pressure in the
space surrounding the inner tube will only serve to extend this tube
still further. No collapse will take place, but a back filtration will be
possible. If we cut sections of injected connective tissues, we find
that the capillaries are bound to surrounding parts by radiating fibres
which might possibly prevent their collapse under high extravascular
pressure. In the larger veins, on the other hand, the arrangement of
the fibres of the adventitia is circular and not radial, so that a high
extravascular pressure would apparently cause collapse of the veins.
From these anatomical facts one would conclude that a backward filtra-
tion is possible, provided that the extravascular pressure be raised in the
region of the capillaries. If, however, the pressure be freely propagated
through the tissues so as to affect the larger veins draining them, we
shall have collapse of the veins and increased oedema. Here, as in so
many other cases, we cannot get a decisive answer to our physiological
questions by purely anatomical investigation, but must have recourse to
physiological experiment.

The question that we have immediately to decide is, whether an
increased tissue tension augments or leaves unaltered the flow of blood
through the tissues, or whether it causes venous collapse and so
diminishes the flow. In the former case a back filtration would be
possible, and in the latter case impossible. I have investigated this
point in various regions of the body, e.g. the connective tissues of the
leg, the tongue as a type of muscular tissue, and the submaxillary gland
as a type of glandular tissue. In all these cases I have found that a rise
of tissue tension above the pressure in the veins causes collapse of these
veins, a rise of capillary pressure, and a diminished flow of blood through
the part. In these regions of the body, therefore, absorption of lymph
by a backward filtration is impossible.

Imbibition.— Hamburger,1 finding that serum and isotonic fluids are
absorbed from the peritoneal cavities of animals that have been dead some
hours, concludes that the life of the endothelial cell can have nothing to do
with the process, and ascribes the absorption to processes of capillary and
molecular imbibition, so that the absorption of fluids would be analogous
to the taking up of fluids and gases by animal charcoal. Though these
factors probably co-operate to a certain extent in the distribution of the
fluid through the tissues surrounding the serous cavities, it is evident
that they would be much more pronounced in dying and disintegrating
tissues, and could with difficulty explain the taking up of fluids by the
blood vessels. They would certainly not explain the wonderful balance
which exists between the intracapillary pressure and the amount of
fluid transuded from or absorbed by the blood vessels. What, then, is
the explanation of this absorption ?

Osmosis.— The explanation is, I believe, to be found in a property
on which much stress was laid by the older physiologists, and which
they termed the high endosmotic equivalent of albumin. It must
be remembered that the older physiologists used animal membranes
in their experiments on osmotic interchanges. These membranes permit
the passage of water and salts, but hinder the passage of coagulable
proteid. The application of semipermeable membranes to the measure-

1 ArcJi.f. PhysioL, Leipzig, 1895, S. 281.

3o8 PROD UCTION AND ABSORPTION OF L YMPH.

ment of osmotic pressure has shown that the osmotic pressures of salts
and other crystalloids are enormously higher than those of colloids
such as albumin, and it has therefore been supposed that the osmotic
pressure of the proteids in the serum, being so insignificant, must be of
no account in physiological processes. The reverse is, however, the
case. Whereas the enormous pressures of the salts and crystalloids in
the various fluids of the body are of very little importance for most
physiological functions, the comparatively insignificant osmotic pressure
of the albumins is of great importance — and for this reason. It has
been shown that bodies in solution behave in most respects like gases.
Now, there can be no difference in pressure between two gases in a vessel
which are not separated or are only divided by a screen freely permeable
to both gases. In the same way, if we hap^e two solutions of crystallised
substances separated by a membrane which offers free passage to the
water and the salts on either side, there can be no enduring difference of
the osmotic pressure on the two sides, especially if a free agitation of
the fluids on both sides is kept up. The pressures on the two sides will
be speedily equalised, and then any flow of fluid from one side to the
other will cease. Now, the capillaries in the living body represent such
a membrane. Leathes l has shown that, within five minutes after the
injection of sugar or salt into the blood vessels, their osmotic pressures in
the blood and lymph have become equal. Supposing, however, that we
have on one side of this membrane a substance to which the membrane
is impermeable, this substance will exert an osmotic pressure and will
attract water from the other side of the membrane with a force propor-
tional to its osmotic pressure. This attraction of fluid must go on until
all the fluid has passed through the membrane to the side where the
indiffusible substance is.

Now the capillaries of the limbs are almost impermeable to proteids.
In consequence of this impermeability, the fluid which is transuded
from the capillaries under pressure contains very little proteid. From
what I have just said, it follows that the proteids left in solution within
the capillaries must exert a certain osmotic attraction on the salt
solution outside the capillaries. It is easy to measure the value of this
attractive force. If we place blood serum in a small thistle funnel, over
the open end of which is stretched a layer of peritoneal membrane
soaked in gelatine, and immerse the inverted funnel into salt solution
which is isotonic or even hypertonic as compared with the serum,
within the next two days fluid will pass into the funnel and will rise in
its capillary stem to a considerable height. I have found that the
osmotic pressure of the non-diffusible portions of blood serum, measured
in this way, may amount to about 30 mm. Hg. The importance of
this fact is obvious. Although the osmotic pressure of albumin is so
insignificant, it possesses an order of magnitude comparable to that of
the capillary pressures; and whereas capillary pressure determines
transudation, the osmotic pressure of the proteids of the serum
determines absorption. Moreover, the osmotic attraction of the serum
for the extravascular fluid will be proportional to the force expended in
the production of this extravascular fluid, so that at any given time
there must be a balance between the hydrostatic pressure of the blood in
the capillaries and the osmotic attraction of the blood for the surround-
ing fluids. With increased capillary pressure we shall have increased

] Journ. PhysioL, Cambridge and London, 1895, vol. xix. p. 1.

OSMOSIS. 309

transudation, until we get equilibrium established at a somewhat higher
point, when there is a more dilute fluid in the tissue spaces, and there-
fore a higher absorbing force to balance the increased capillary pressure.
With diminished capillary pressure there will be an osmotic absorption
of salt solution from the extravascular fluid until this becomes richer in
proteids, and the difference between its osmotic pressure and that of the
intravascular plasma is equal to the diminished capillary pressure.1

Here, then, we have the balance of forces necessary to explain the
accurate regulation of the quantity of circulating blood according to the
conditions under which the animal may be placed, and it seems
unnecessary to invoke the aid of vital activity to explain the process.
Certain corollaries of this mode of explanation agree well with observed
facts of experiment. Thus the more impermeable the capillary the
smaller will be the amount of proteid exuded with the lymph. A
higher capillary pressure will therefore be needed in its production, and
there will be an equally high force tending to its reabsorption. A rise of
capillary pressure will only increase the amount of lymph in the
extravascular spaces to a certain extent, but will at the same time cause
this lymph to be more dilute, so that there will be a corresponding rise
in the force tending towards absorption. In consequence of this
sequence of events, considerable alterations of capillary pressure may
be produced in impermeable capillaries, such as those in the limbs,
without causing any appreciable increase in the lymph overflow from the
limbs. On the other hand, where the capillaries are very permeable,
very little pressure will be required to cause a transudation, since no
work is done in the concentration of a proteid solution, and we find as a
matter of fact, that capillaries where the pressure is lowest — i.e. in
the liver — are also those which are the most permeable. Here, too,
the absorbing force will be insignificant, since there is very little
difference in the percentage of albumin between liver blood and liver
lymph.

Moreover, since the pressure on the venous side of the capillaries is
considerably less than that on the arterial side, there will be a continual
exudation of a very dilute lymph from the arterial capillaries, and a
re-absorption of water and salts from this lymph in the venous
capillaries. The lymph, therefore, will assume a composition such that
the osmotic pressure of its proteids approximates the mean capillary
pressure in the part where it is formed.

This osmotic difference between blood plasma and tissue fluid will
not serve to explain the absorption of proteids by the blood vessels nor the
absorption of serum from the serous cavities. It is difficult, however, if
not impossible, to prove that serum or proteid is absorbed by the blood
vessels. In some of my transfusion experiments I have rendered a limb
cedematous by means of serum, and in these cases have obtained no
evidence at all of absorption by the blood vessels. There is no doubt
that serum may be absorbed from the pleural and peritoneal cavities,
but the absorption of these fluids is very much slower than the absorp-
tion of salt solutions, and is, in fact, so slow that the whole of it can in
most cases be effected by the lymphatic channels. A slow absorption of
serum from tissue spaces by means of the blood vessels is also physically
possible. As the cells of the tissues feed on the proteids of the fluid,

1 For a fuller discussion of this point, cf. Science Progress, London, 1896, vol. v.
p. 151.

3io PRODUCTION AND ABSORPTION OF L YMPH.

the serum will tend to become gradually weaker, so that the watery
and saline constituents corresponding to the proteid used up can then
be absorbed by the blood vessels in the way I have indicated.

The physical process which I have described above as causing the
absorption of lymph by the blood vessels must be in action at all times
in the body, and must therefore be a predominant factor in the process of
absorption. I have not been able to absolutely exclude the absorption
of proteids by the blood vessels, but, in the absence of direct experi-
mental evidence that such an absorption does occur, the physical factors
I have described in this chapter suffice to explain the phenomena of
absorption observed both under normal and under pathological conditions.

ON THE FUNCTIONS OF THE LYMI% IN THE NUTRITION OF

THE TISSUES.

The fact that the tissue cells are bathed by lymph and are
separated by this fluid and by the capillary wall from the blood,
shows that in all interchanges between blood and tissues the lymph
must act as the medium of communication.

I have already mentioned the irrigation theory of Bartholin, accord-
ing to which the nutrition of the tissues was carried out by a taking up
of solids from the lymph as it left the blood vessels, so that only pure
water (or water and salts — Eudbeck) was left over to be carried away
by the lymphatics.

The observations of the Ludwig school on the lymph flow from the
limbs, showed clearly, however, that the nutrition of the tissues could
be normally carried out without any lymph flow at all. The muscles
of a resting limb are taking up nourishment as well as oxygen from the
blood, and giving off their waste products, carbonic acid and ammonia,
although not a drop of lymph may flow from a cannula placed in a
lymphatic trunk of the limb. It is evident, therefore, that to a large
extent, at any rate, the giving up of nourishment by blood to tissues and
the taking up of the waste products of the latter through the inter-
mediation of the lymph, is carried out in the same way as are the gaseous
interchanges — i.e. by a process of diffusion.

I have already mentioned the experiments which demonstrate the
extreme rapidity with which diffusion takes place between the blood and
the lymph, so that, as Leathes points out, the time taken for the
equalisation of the constitution of the two fluids after introduction of
some diffusible substance into the blood is " inappreciable." There can
be no doubt that such changes are of great importance for the normal
metabolism of the tissues. Thus there has been considerable discussion
of late years concerning the supply of lime to the cells of the mammary
gland. Heidenhain pointed out that if the lime were supplied to the cells
by filtration, the whole flow from the thoracic duct would be inadequate
for the purpose. His conclusion that the lymph with its constituents is
therefore a secretion is, however, unnecessary. As the gland cell uses
up or turns out lime into the ducts of the gland, it will take up lime
from the adjoining lymph, thus lowering the partial osmotic tension of
the lime in its neighbourhood. There will be, therefore, a passage of
lime from blood to lymph by a process of diffusion, to supply the
deficiency. No flow of lymph at all is necessary to furnish the amount
of lime required by the gland cell.

FUNCTIONS OF THE L YMPff. 3 1 1

The case is rather different when we come to consider the supply of
proteid food to the tissues. The diffusibility of the large molecular
serum proteids is so small that it may be disregarded, even in the
living body with its wonderfully perfect arrangement for allowing the
free contact of fluids without intermingling. Hence the only way by
which the tissues can obtain their supply of proteid is from the proteid
which has filtered through the vessel wall in the lymph. So far as the
proteid supply to the tissues is concerned, therefore, I believe that the
irrigation theory is correct, unless, indeed, we attribute to the vascular
epithelium the power of actively taking up proteid and transferring it
from one side of the vessel wall to the other in proportion to the needs
of the tissues.

Even under the former hypothesis, however, we could not, from the
amount of lymph draining away from a part, draw any conclusions as to
the amount of proteid which has been supplied to the part. As I
have above shown, the composition of the lymph is determined by the
permeability of the wall and the mean capillary pressure. If the com-
position of the lymph be altered after transudation, in consequence of
an active using up of the proteids of the tissue cells, the effective
osmotic difference between blood and lymph will be increased, and the
watery and saline constituents of the lymph will be reabsorbed until the
original constitution of the lymph is restored.

We may conclude, therefore, in default of definite evidence to the
contrary, that while the interchange between tissues and blood, so far as
diffusible substances are concerned, is effected by diffusion through the
medium of the lymph, the proteid supply to the cells is dependent on
the amount of proteid transuding with the lymph.

Perhaps it is on this account — i.e., increased proteid supply to the
cells — that chronic inflammation or hypersemia of any part is apt to lead
to its hypertrophy. Growing tissues, as well as those in a state of repair,
have delicate vessels, which probably supply a lymph much richer in
proteids than is supplied to adult tissues.

CHEMISTRY OF THE DIGESTIVE PEOCESSES.

BY B. MOORE.

CONTENTS : — Digestive Ferments, p. 312 — Chemical Composition of Digestive Juices,
p. 342 — Saliva, p. 342 — Gastric Juice, p. 349 — Pancreatic Juice, p. 366 — Intes-
tinal Juice, p. 368 — Bile, p. 369 — Digestion of Carbohydrates, p. 392 — Digestion
of Proteids, p. 428 — Absorption of Carbohydrates and Proteids, p. 430 —
Digestion and Absorption of Fats, p. 443 — Bacterial Digestion, p. 463— Com-
position of Fa3ces, p. 472.

THE DIGESTIVE FERMENTS, OR ENZYMES.

Organised and unorganised ferments. — Fermentation is invariably
brought about, directly or indirectly, by cell life, either vegetable or
animal. When the action is direct, and the chemical changes involved
in the process occur only in the presence of the cell, the latter is
spoken of as an organised ferment. When the action is indirect, and
the changes are the result of the presence of a soluble material secreted
by the cell acting apart from the cell, this soluble substance is termed
an unorganised ferment, soluble ferment, or enzyme.1

The action of an organised ferment is intimately connected with the
life of the cell, and is instantly stopped by anything which either kills
the cell or temporarily arrests its activity; while that of a soluble
ferment is not a vital process, but one which is purely physical or
chemical in its nature. As a consequence, an organised ferment is
destroyed, and its specific action stopped, by any protoplasmic poison,2
while an unorganised ferment, provided it is not precipitated, is un-
affected by such reagents.

All the differences in the mode of action of organised and un-
organised ferments arise from this close connection of the organised
ferment with the cell. Thus, an organised ferment, provided there is a
supply of nitrogenous food at its disposal, can grow and multiply in a
medium in which it is sown, while an unorganised ferment can never so
increase in quantity ; from this it follows that the rapidity of action of
an unorganised ferment depends (within limits) on the initial quantity
added, but in the case of an organised ferment the initial amount soon
becomes a matter of no moment.

Organised ferments are unicellular organisms (microfungi), while the

1 This term was first used by Kiihne, Verhandl. d. naturJi.-med. Ver. zu Heidelberg,
1879, N. F., Bd. i. S. 236.

2 Such as any of those substances commonly known as antiseptics.

ATTEMPTS TO ISOLATE PURE ENZYMES. 313

unorganised ferments are typically found in the secretions of specialised
cells of the higher plants and animals, and take an important part in
the chemical changes involved in their nutrition.

There is probably at bottom very little difference in the manner of action
of cellular ferments and enzymes. From the cell substances of several
bacteria, extracts have been obtained possessing the same fermentative action
as the living bacteria ; this indicates that in such bacteria, substances are
present in the cell which act like ordinary unorganised ferments, but normally
remain during the life of the cell within its substance, and perform their
fermentative functions there.

A good example of such an isolation of an unorganised from an organised
ferment, is afforded by that series of brilliant researches into the nature of
the action of the micro-organism, torula ureas, upon urine, which began with
the observation that the change into ammonium carbonate was not stopped by
the presence of carbolic acid in sufficient amount to paralyse the growth of
the micro-organism,1 and ended in the extraction from the bacteria of
a soluble ferment, which converted urea into ammonia and carbonic acid, even
in the presence of chloroform, which effectually stops all bacterial action.2

In a similar manner, a soluble ferment, capable of inverting cane sugar,
can be extracted from yeast cells after they have been killed by the action of
alcohol or ether,3 and from certain putrefactive bacteria unorganised ferments
have been obtained, possessing an action on proteids analogous to that of the
proteolytic ferment of the pancreatic juice. Such intracellular soluble ferments
have not been shown to exist in by far the greater number of organised ferments,
but if they do so exist the only remaining difference between organised and
unorganised ferments is that in the former the substance formed by the cell
remains in the cell substance, and does its work there, the products of its
action being poured forth as a kind of secretion or excretion, while in the
latter the ferment becomes separated from the cell in a secretion, and carries
out its work apart from the cell.

Most of the chemical changes involved in the digestion of the food
are brought about by the presence in the digestive secretions of soluble
ferments. So that digestion might be described as the physical and chemical
alteration of the foodstuffs, into forms letter fitted for absorption, ~by the
action of certain soluble ferments, the digestive enzymes.

Attempts to isolate pure enzymes. — Many attempts have been
made to isolate chemically pure enzymes, but the task is very difficult,
and it is highly probable that no one has yet succeeded in obtaining a
pure product.

There are two great difficulties in the way : first, our ignorance of a
specific precipitant for any of the enzymes ; and, secondly, the extremely
small quantities in which they are present in the secretions. On account
of the first, the enzyme cannot be thrown out of solution unaccompanied
by other substances; on account of the second, it is not present in
workable quantity, and is rapidly lost in any lengthened process of
chemical manipulation. When to these disadvantages are added the
non-diffusibility of the enzymes, which shuts out a means of separating
them from the traces of proteid which always accompany them, and
their sensitiveness to reaction and temperature, some idea is obtained of
the difficulties which the problem of isolation presents.

1 Hoppe-Seyler, Med.-chem. Untersuch., Berlin, 1871, Heft 4, S. 570.

a Sheridan Lea, Journ. PhysioL, Cambridge and London, 1885, vol. vi. p. 136.

3 Hoppe-Seyler, Ber. d. dcutsch. chem. Gesellsch., Berlin, 1871, S. 810.

314 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

Method of mechanical precipitation. — When an indifferent precipitate
is produced in a solution containing an enzyme, this is often carried
out of solution with the precipitate, probably in a condition of mechanical
adhesion. This observation was made by Briicke, who utilised the
property to free pepsin as far as possible from other substances. The
method has been extended to the preparation of purified forms of other
enzymes, and, as applied by Briicke * to pepsin, may be quoted as an
example of a general method. It is as follows : —

The mucous membrane of a pig's stomach is submitted to partial self-
digestion, in water acidulated with phosphoric acid ; the products of this
first digestion are rejected, being too rich in products of digestion, and not
containing much pepsin, which clings in^reat part to the mucous membrane.
The residue of the mucous membrane is again digested in water made acid
with phosphoric acid, and after some days is filtered from insoluble residue,
and just neutralised by the addition of lime water. The insoluble calcium
phosphate so precipitated carries down with it all the pepsin ; it is collected on
a filter paper, just dissolved by cautious addition of very dilute hydrochloric
acid, filtered off, and once more precipitated by the addition of just sufficient
lime water. This double precipitation is to free the pepsin of proteid, which
also has the property of being mechanically carried down, though more feebly
than pepsin. To this somewhat purified solution of pepsin a solution of
cholesterin in four parts of alcohol and one part of ether is added. On this
solution mixing with the water the cholesterin becomes insoluble, and is thrown
out of solution in a finely divided condition, carrying the pepsin mechanically
adhering to it just as it did to the calcium phosphate. The mixture is well
shaken up, and then filtered ; the precipitate is washed first with water, then
with water acidulated with acetic acid, and finally with water alone. It is
next, without drying, shaken up with ether, free of alcohol, but saturated
with water. The ether extracts the cholesterin, while the pepsin remains in
the watery layer beneath ; the extraction is repeated with fresh portions of
ether until all the cholesterin has been removed, and finally the watery
solution containing the pepsin is filtered. In this manner a solution is
obtained, which actively peptonises, but contains so little proteid as not to give
many of the proteid reactions.

Method of auto-digestion. — Kiihne and Chittenden2 have combined
auto-digestion with precipitation by ammonium sulphate as a means of
preparing purified solutions of pepsin and trypsin. The following is an
outline of their methods : —

For the preparation of pepsin the mucous membrane of a pig's stomach is
taken, and allowed to undergo auto-digestion for several days, until peptonisa-
tion has far advanced, and but comparatively little albumose is left. The
solution, after filtration from undigested debris of nuclein, etc., is next satu-
rated with ammonium sulphate. The pepsin is thus completely thrown out
of solution along with the albumoses ; this precipitate is dissolved again, after
pressing in filter paper, in dilute hydrochloric acid, and allowed to go on
finishing the digestion of the albumoses for some days.

The process is repeated as often as is necessary to remove the albumose,
and finally the pepsin, after being dissolved by addition of water, is freed from

1 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1862, Bd. xliii. S. 601 ; " Vorlesungen ii.
Physiologic," Wien, 1885, S. 308. See also v. Heltzl, Jahresb. it. d. Fortschr. d. ges. Med.,
Erlangen, 1864, Bd. i. S. 138.

2 Ztschr. f. Biol., Miinchen, 1886, Bd. xxii. S. 428. Such a method of auto-digestion
can obviously only be employed in the case of proteoly tic enzymes.

PREPARA TION OF DIGESTIVE EXTRA CTS. 3 1 5

ammonium sulphate by dialysis, and may be precipitated by alcohol, filtered
off and dried as quickly as possible.

The preparation of a purified trypsin solution is carried out by
Klirme's 1 method much on the same lines : —

The pancreas first has all its fat removed by extraction with alcohol
followed by ether, after which process it forms Kuhne's "pancreas powder."
This is digested with five times its volume of 0*1 per cent, salicylic acid for
about four hours. The residue is next digested with 0'25 per cent, sodium
carbonate solution for a further period of twelve hours, and the solution is
separated from the undissolved part. The two extracts are now mixed, the
mixture made up with carbonate of sodium solution to a strength of 0'25 to a
0'5 per cent, carbonate, and allowed to digest at 40° C. for a week, thymol being
added to prevent putrefaction (0'5 per cent.). During this time the albumoses
become converted into peptones, and on saturating the cold solution, made
very faintly acid with acetic acid, with ammonium sulphate, trypsin is
precipitated, accompanied by traces only of unconverted albumoses. The pre-
cipitate so obtained is sufficiently pure for all digestion experiments. It
contains so little accompanying albumose, that, from 10 grms. of pancreas
powder, merely a thin yellowish slime is obtained on the filter paper, yet this,
when taken up by 100 c.c. of 0'25 per cent, sodium carbonate solution, forms
a strong digestive fluid. This gives an idea of the extreme power of the
digestive ferments, and shows at the same time in what mere traces they
must be present in the glands. This product may be still further purified by
partially precipitating the solution obtained from it with excess of alcohol,
dissolving in water, separating by dialysis the bulk of the ammonium sulphate
also precipitated by the alcohol, removing the last traces of ammonium sulphate
by barium carbonate, and finally precipitating as a snow-white amorphous
substance by excess of alcohol.

This pure product gives all the proteid reactions (unlike Briicke's
pepsin), but in spite of all the elaborate and painstaking processes used
in its preparation, there is no evidence that it does not still contain
traces of proteid along with trypsin; the other conclusion of course
would be that trypsin is itself a proteid.

Preparation of digestive extracts. — When the object is simply to
test or demonstrate the action of the enzymes, and the admixture of
products of digestion formed from the gland tissue is a matter of no
moment, much simpler methods of preparation may be employed than
those above described.

1. In many such cases a simple extraction of the gland with water may
be used, if the action is to be tested immediately.

2. A general method of obtaining digestive extracts is that first recom-
mended by v. Wittich,2 which consists in preparing a glycerin extract. Such
an extract has the advantage of efficiency and stability. It contains a good
deal of proteid, and cannot be used where the products of digestion are to be
exactly studied, but for general laboratory work glycerin extracts are most
convenient preparations. They are easily made, and may be preserved for
years. As the glycerin only slowly extracts the enzymes, the same tissue will
continue for a long time to yield fresh extracts, if fresh glycerin be added.

A glycerin extract should not be made with a quite fresh gland, but with

1 Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, 1878, Bd. i. S. 222 ; Verhandl. d.
naturh.-med. Ver. zu Heidelberg, 1886, N. F., Bd. iii. S. 463. See also ibid., 1876, N. F.,
Bd. i. S. 195.

2 Arch.f. d. ges. Physiol., Bonn, 1869, Bd. ii. S. 193; 1870, Bd. iii. S. 339.

316 CHEMISTRY OF THE DIGESTIVE PROCESSES.

a gland which has been minced up and allowed to stand for a few hours (it
may be in nearly all cases made faintly acid with very dilute acetic acid to set
free the zymogen as enzyme). Such a minced-up gland is rubbed up in a
mortar with some clean sand, taken up with glycerin, shaken up with more
glycerin (10-20 parts to 1 part of gland), and allowed to stand so until
required ; the process of extraction is very slow, and requires from seven to
fourteen days. In the case of gastric mucous membrane, 1 part per 1000 of
hydrochloric acid may be added to the glycerin.

There are many modifications of the process. v. Wittich recommends
digesting the minced gland (or mucous membrane) twenty-four hours in alcohol,
drying after this in the air, sifting the powder through gauze to remove
coarser fragments of tissue, and extracting with glycerin. It is often recom-
mended to filter the extract after seven to fourteen days, but this is unnecessary,
as the tissue neither decomposes nor becomes digested in the glycerin, and
the extract improves on keeping in contact with the tissue. The enzyme
accompanied by proteid may be precipitated from a glycerin extract by the
addition of absolute alcohol, and so a purer extract be obtained.

Chemical nature of enzymes. — The failure of all attempts to isolate
pure enzymes necessarily deprives us of the possession of any certain
knowledge of the chemical nature of these substances. Analyses of the
purer preparations of the enzymes give figures approximating to those
obtained with the various proteids ; but whether or not this is due to
admixture with proteid it is at present impossible to say. The behaviour
of Briicke's " pure " pepsin solution goes against the supposition that this
enzyme is a proteid. This solution did not give the proteid reactions,
and was not precipitated by any of the proteid precipitants, save neutral
and basic lead acetates and platinic chloride. These results are confirmed
by Sundberg,1 who succeeded in preparing a still more proteid-free solu-
tion, which did not even react to these reagents, and was only precipi-
tated as a slight, pure white, nocculent precipitate, on adding five to six
times its volume of absolute alcohol and allowing to stand, and yet was
exceedingly active in digesting fibrin. The amount of this precipitate
was much too small for analysis, and it could only be shown that it was
nitrogenous, and contained a certain amount of ash. This is not quite
conclusive against the proteid nature of the active substance, since, as
Sundberg argues, the physiological test by digestion may be much more
delicate than any of the purely chemical tests. Still, the fact that it
was totally unaffected by tannic acid and precipitated by alcohol has
some weight against the substance being proteid in nature ; since tannic
acid will show 1 part of ordinary proteid in 100,000,2 and alcohol is by
no means so delicate a proteid test. It is most probable, then, that
pepsin is not a proteid ; and it will subsequently be seen in the descrip-
tion of the other enzymes that most of these have been obtained in
forms which do not yield all the proteid reactions.

The enzymes are soluble in water, from which they are precipitable
by saturation with ammonium sulphate or by adding excess of alcohol.3
Most of them are unalterable, or very slowly alterable in contact with
alcohol, but pepsin is an exception, being attacked and rendered inactive
if left long in contact. The enzymes are commonly said to be soluble

1 ZtscJir. f. physiol. Chem., Strassburg, 1885, Bd. ix. S. 319. See also under " Ptyalin."

2 Hofmeister, ' Ztschr. /. physiol. Chem., Strassburg, 1878-9, Bd. ii. S. 292.

3 These may only be particular cases of their general mechanical precipitation, whenever
a precipitate is caused.

MODE OF A CTION OF ENZ YMES. 3 1 7

in glycerin, but it has not been shown that the dried enzymes are
soluble in anhydrous glycerin; on the contrary, Kiihne1 states that
pure trypsin is not soluble in strong glycerin ; and it is well known
that, after precipitation by alcohol from glycerin extracts, the enzymes
are afterwards much less soluble in glycerin.2

An elevated temperature rapidly destroys all enzymes when in
solution, and it is of some importance that the temperature at which
they are rapidly destroyed, although it varies considerably with the
reaction of the solution, lies just a little below the range at which the
bulk of the proteids coagulate. In the dried condition the enzymes are
much more resistant to increased temperature, and can be heated to over
100° C. for some time without losing their digestive properties on cooling
and dissolving in water.

The digestive action of the enzymes is not stopped by the presence
of disinfectants, such as thymol, chloroform, or salicylic acid, in quantity
sufficient to stop completely the action of organised ferments, particu-
larly that of the putrefactive bacteria.3 This fact has been turned to
account practically in conducting prolonged digestion experiments,
especially when the digestive action must be allowed to proceed in
alkaline solution.

Mode of action of enzymes. — The manner in which ferments bring
about the changes characteristic of them is very puzzling. The enzymes
are altogether unaffected by the changes which they occasion, and, pro-
vided the products of the action are not allowed to become concen-
trated in solution, the ferment can work on indefinitely, and a finite
amount of ferment can convert an infinite amount of material. The
ferment may become by dilution, or unavoidable loss in manipulation,
so weak that finally its action becomes inappreciable ; but before this
happens it can be shown that it has converted a mass of material so
many times greater than its own, that the idea that it undergoes any
permanent alteration in the reaction which it induces must be abandoned.
Thus, according to Hammarsten,4 one part of rennin will curdle 400,000
to 800,000 parts of milk ; while Petit 5 prepared a pepsin powder which
in seven hours dissolved 500,000 times its weight of fibrin.

There are numberless examples of chemical reactions, in which only
well-known and much simpler compounds take a part, of a substance
inducing a chemical reaction without itself becoming altered thereby.
Such a substance is called a catalytic agent, and the reaction a catalysis
or catalytic reaction. Ferment actions are such catalytic reactions, but
when we say that ferments act catalytically the problem of how they
act is not by any means solved ; we have merely found a name for it.

In some cases, in which the presence of a substance is essential to a
certain reaction, although this substance is not finally altered thereby,
there is evidence that it is altered intermediately and rechanged again
back to its initial condition during the reaction.

Such a case is to be found in the action of sulphuric acid in the con-
tinuous etherification process for producing ether from alcohol. It can
be shown that the sulphuric acid first combines with part of the alcohol

1 Verhandl. d. naturh.-med. Vcr. zu Heidelberg, 1876, N. F., Bd. i. S. 196.

2 v. Wittich, Arch.f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 193.

3 Klihne, Verhtmdl. d. naturh.-med. Ver. zu Heidelberg, 1876, N. F., Bd. i. S. 190.

4 Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1877, Bd, vii. S. 166.

5 Journ. de tMrap., Paris, 1880.

3r8 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

molecule, forming a substance which can be isolated, and is known as
ethylsulphovinic acid ; and that this compound then reacts with another
molecule of alcohol, forming ether and regenerating the sulphuric acid
molecule, which is then free to repeat the process, and can be made to
do so indefinitely.

This action may be represented thus : —

(1) C2H5.O.H + : j S04 = H.O.H + CA SO4

(alcohol, sulphuric acid) (water, ethylsulphovinic

acid)

(2) C A S04 + C2H5.OH = I S04 + ^ 0

(ethylsulpho- (alcohol) • (sulphuric (ether)

vinic acid) acid)

Another good example of such an interaction is that of the alternate
formation of a higher oxide of nitrogen (N203) from a lower (NO), and
then the regeneration of the lower oxide, which is said to occur in the
formation of English sulphuric acid; the oxygen taken up in each
cycle going to form, with sulphur dioxide and water, sulphuric acid;
while, as a net result, the nitric oxide remains unchanged, and may take
action again and again until it is dissipated by diffusion or otherwise.1

Such a part the enzyme may take in a ferment action ; a molecule
of it may unite with a molecule of the substance undergoing digestion.
Thus an unstable compound may be formed; the elements of a water
molecule may combine with those of the fermentable substance, forming
a new substance ; while the ferment is regenerated to undergo another
cycle. Of all this, however, there is no experimental evidence ; there
is only the analogy, and analogies are sometimes misleading.

Besides these reactions, there are others in which the action of the
catalytic agent is, almost undoubtedly, merely a physical one ; that is to
say, in which the catalytic agent does not combine with the catalysed
substance, and then become regenerated. Such an action, for example,
is that of a trace of iodine in converting amorphous into red
phosphorus. Here the amount of iodine required is too excessively
small to suppose that it combines with phosphorus in one form and
yields it up in the other. The supposition is more probable that the
iodine finds the phosphorus in an unstable state, and in some fashion
enables it to do that which it already has a tendency to do, namely, swing
into stability. Such a reaction, only still more physical in character,
is found in the case of exceedingly unstable compounds (such as
detonating substances), where mere mechanical percussion, most probably
by producing molecular vibration, causes a chemical reaction to take
place with great rapidity. It is very likely that in many cases,
especially those in which the catalytic agent is merely required to
be present in traces, that there is no intermediate substance formed,
and that the catalytic agent acts in a physical manner, inducing a
compound already unstable to pass into a more stable condition. It
is not even necessary that the substance should be unstable in the
usual sense of the word, but only that the new products should be

1 A similar oxygen-carrier, of oxygen to be used in tissue metabolism, is found in
haemoglobin, which may be looked upon as a catalytic agent, taking up oxygen, parting
with it to bring about a reaction, the details of which we do not know, and so becoming
regenerated and coining out of the total process unchanged.

NATURE OF THE CHEMICAL CHANGE. 319

more stable ; or, in other words, that there should be energy set free in
the process of change.

In ferment action, the chemical energy of the resulting products
is always less than that of the substances from which they were formed ;
this is shown by the heats of combustion of the end products amounting
to less than those of the initial products.

The action of ferments is hence in all respects analogous to that of
catalytic agents ; there is a passage from a less stable to a more stable
condition, which is brought about by an agent which is not itself altered
in the process.

The two principal hypotheses are then — (1) That the enzyme
combines with the substance on which it is acting, and that the unstable
compound so formed decomposes, yielding the new substance and
regenerating the enzyme ; (2) that the enzyme is in a state of molecular
movement, which induces a molecular movement in the fermentable
substance, or increases such a movement when already present, so that
the molecule breaks up, over-swings, or over-vibrates as it were, into a
more stable condition, so giving rise to new substances.

Nature of the chemical change. — Somewhat more is known of the
nature of the chemical changes induced by the ferments than of the
mode in which they bring about such changes. It is probable that in
all cases ferment action is accompanied by hydrolysis, i.e. the taking
up of the elements of water.1 This is known with certainty to be the
case in all actions of diastatic and inverting ferments, and is very pro-
bably true also for proteolytic ferments. This subject will be considered
more in detail in treating of the specific action of the various enzymes
on the different classes of foodstuffs ; reference will only be made here
to the general arguments which go to show that such a process of
hydrolysis is a universal accompaniment of ferment action.

1. In many cases the composition of the products of the fermentation
compared with that of the initial substance shows directly a taking up
of water. In those in which this is not so, carbonic anhydride is usually
one of the constituents, and if this be considered as united with the
elements of a water molecule to form carbonic acid, as it probably is
when formed in the reaction, water is taken up here also. In all cases,
however, whether the products of the reaction directly show the taking
up of water or not, the presence of water is essential to the reaction,
for no ferment is known which will act otherwise than in the presence
of water.

2. Again, the action of any of the ferments may be closely imitated
by- the action on the several fermentable or digestible materials of
dilute acids or alkalies, and these are recognised throughout the domain
of organic chemistry as the most powerful hydrolytic agents known.

3. It has been shown that in the case of coagulation by fibrin ferment
an increase of weight of dried material takes place, probably due to the
elements of water being taken up in the process. This was demonstrated
by taking two equal portions of plasma, allowing one to clot and not the
other, and then drying both under similar conditions, when the clotted
sample was found to weigh a half per cent, more than the other.2

1 Hoppe-Seyler, Arch. f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 1 ; ISTencki, Journ.
f.prakt. Chem., Leipzig, 1879, Bd. xvii. S. 105.

2 Observation by A. Schmidt, communicated by G. Tamman, Ztschr. f. physiol. Chem.,
Strassburg, 1892, Bd. xvi. S. 271.

320 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

Rate of zymolysis l or enzymic action.— The rate at which diges-
tion goes on in any digestive fluid varies chiefly with the following
conditions, namely — (1) The temperature, (2) the reaction, (3) the con-
centration of the products of digestion, (4) the concentration of the
digestive enzyme, (5) the condition of the material to be digested.

Temperature. — The digestive enzymes are very sensitive to changes
in temperature ; they all act most energetically at or slightly above the
body temperature. The point of greatest activity is called the optimum
point ; as the temperature varies, either above or below this point, the
rapidity of action of the enzyme slackens ; and, as the interval apart from
the optimum point is increased, a point is finally reached at which the
action of the enzyme is no longer appreciable. Any temperature
markedly above that of optimum action slowly destroys the enzyme,
and this destructive action in all cases becomes very rapid at tempera-
tures varying (between 50° and 65° C.) with the particular ferment, the
reaction of the fluid in which it is so heated, and the degree of its dilu-
tion.2 On the other hand, low temperatures, though they slow and
finally stop ferment action, do not destroy the ferment ; this recovers its
activity completely when the temperature is again raised, even though
the temperature has been kept at — 5° C. for several hours.3

Reaction. — The variation in chemical reaction of the fluid in which
they act has a similar effect on enzymes to that of variation in tempera-
ture. For each of the digestive enzymes there is a particular reaction,
and degree of that reaction, at which it acts with maximum power. A
departure from this degree of acidity or alkalinity causes a more or less
rapid diminution in the speed with which the enzyme acts, and a
sufficient amount of departure from the optimum reaction causes the
destruction of the enzyme. Some of the enzymes act in solutions of
either acid, neutral, or alkaline reaction, provided always that the
reaction does not stray too widely from that at which they act best ;
examples of such are ptyalin and trypsin. Others only act with one
specific reaction, and are rapidly destroyed if the reaction changes from
this. Examples of these are pepsin, only active in acid solution, and
rapidly destroyed by a trace of alkalinity ; and the fat-splitting ferment
of the pancreas, active only in alkaline or neutral solutions, and rapidly
destroyed by acid.

Accumulation of dissolved products of action. — Accumulation of the
products of the action of an enzyme in the solution acts unfavourably
upon its continued action, slowing and finally altogether checking it.4
This action may be to some extent prevented by removing the products
formed by dialysis, or diluting them by the addition of water. In the
latter case, however, the ferment is also diluted, and in the former, since
the products of digestion in most cases have no very high diffusive
power, the removal is very slow and incomplete.

Eemoval of the digestive products by dialysis has, in addition, the
disadvantage that the digestive solution is diluted by the osmosis, due to

1 This term is that proposed by Sheridan Lea, Journ. PhysioL, Cambridge and London,
1890, vol. xi. p. 254.

2 v. Wittich, Arch.f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 193 ; 1870, Bd. iii. S. 339.

3 Bidder u. Schmidt, "Die Verdauungssafte, etc."

4 Briicke, Sitzungsb. d. k. Alcad. d. Wissensch., Wien, 1862, Bd. xliii. S. 601 ;
"Vorlesungen," Wien, 1885, Bd. i. S. 312; Cohnheim, Virchow's Archiv, 1863, Bd.
xxviii. S. 241 ; Ktihne, " Lehrbuch der physiol. Chern.," 1866, S. 39, 51, 52 ; Sheridan Lea,
Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 226.

RA TE OF ENZYMIC A CTION. 3 2 1

the osmotic pressure of the dissolved products. This water may, of
course, be removed by subsequent evaporation at a low temperature, to
avoid injuring the ferment, and again dialysing; but practically the
diffusive power of the usual products of digestion is so low as to render
a process of alternate dialysis and evaporation a tedious and almost im-
possible method of freeing the solution completely of the products of
digestion. This action of the accumulated products of digestion renders
all digestive experiments carried out in glass essentially different from
those which go on within the alimentary canal, where the products of
digestion are removed as fast as they are formed. Not only must the
natural process run more quickly, but there is no reason for assuming
that it will even run qualitatively along the same lines. To take as an
example the tryptic digestion of proteids. There are formed, as we shall
see later, as end products, certain ainido-acids, and a substance known as
antipeptone, but long before these products are finally reached, soluble
bodies are formed which can be shown to be capable of absorption and
assimilation by the epithelial cells lining the intestine.

Digestion experiments in vitro teach us the effects of digestion alone,
sundered from its constant companion in the natural process — absorption ;
and no perfect method has hitherto been devised whereby the effects of
these two processes working in conjunction can be demonstrated. In
the animal body the pure effect of digestion and absorption cannot be
observed by studying the chemical composition of the intestinal contents
and that of the contents of the channels of absorption, because the pro-
ducts of digestion are not merely absorbed by the lining cells, but are
profoundly modified by them in the process. Nor can the combined
effect of digestion and absorption be studied in perfection by any known
method of digestion and dialysis, because no artificial dialyser bears any
but a very remote resemblance to the living intestine. A dialyser of
parchment paper not only removes diffusible substances with infinite
slowness compared with the intestinal epithelium,1 but it also acts on
purely physical laws, diffusion taking place at rates directly proportional
to the diffusion coefficients of the substances involved ; while the living
epithelium takes up with great avidity soluble substances which do not
diffuse at all, and absolutely refuses passage to other very diffusible sub-
stances, such as soluble salts of iron. That is to say, absorption by the
cell is selective, being governed, indeed, by fixed and definite laws, pro-
bably purely physical and chemical at bottom, but profoundly modified
by the action of living protoplasm.2

The effects of removal of products of digestion by dialysis has been studied
by Sheridan Lea,3 in the case of starch digestion by ptyalin, and proteid
digestion by trypsin. The rapidity of dialysis was increased by mechanically
raising and lowering the dialysing tube, and the rate of digestion and nature
of products formed were compared with those in an exactly similar experiment
arranged in a glass vessel. It was found (1) that the speed of digestion was
in all cases increased, and (2) that before the process came to a standstill
much more conversion took place than it was possible to attain to in glass,
although complete conversion never took place in either case ; these differences
were in every case more marked when concentrated solutions of the material
to be digested were used, showing that the slower digestion and earlier stoppage

1 Heidenhain, Arch. f. d. gcs. PhysioL, Bonn, 1888, Suppl. Heft, Bd. xliii. S. 60.

2 For a further consideration of this subject, see " Proteid Absorption," p. 430.

3 Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 226.

VOL. I. — 21

322 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

in glass was due to accumulation in the solution of digested products. Similar
experiments on the digestion of various forms of proteid, by pepsin and hydro-
chloric acid, dialysing into hydrochloric acid of equal concentration, have been
made by Chittenden and Amerman,1 who found that removal of the products
of digestion did not essentially favour peptonisation or alter the relative
amount of albumose and peptone formed.

Concentration of enzyme. — The rapidity with which zymolysis takes
place naturally varies with the concentration of the enzyme in the
solution, as well as with the concentration of the material to be digested,
when this is soluble. Eoberts found in the case of conversion of starch
by the diastatic enzyme of the pancreas, that the amount of standard
starch mucilage which can be converte<J in a given time and at a given
temperature varies directly as the quantity of active solution employed.

Schiitz 2 found in the digestion of proteid by pepsin, that when the
solutions employed were sufficiently dilute, the amount of conversion
was proportional to the square roots of the quantities of pepsin present.
Any such rule can only hold within certain limits of concentration, a
maximum being reached beyond which further concentration of the
enzyme has no effect.

Methods of estimating the relative activity of digestive solu-
tions.—As none of the enzymes have been isolated in a pure condition,
it follows that there is no means of estimating the absolute amount of an
enzyme in solution. This is practically never a matter of any moment,
but a problem which often presents itself in practical work on digestion
is that of estimating the relative activities of two digestive extracts.

The activity of a diastatic enzyme can be most accurately estimated
by determining the amount of sugar (maltose) formed under given con-
ditions in a given time by a given volume of the solution, acting on a
measured volume of a standard solution of starch mucilage ; this, however,
is a tedious and troublesome process, and for most purposes a sufficiently
accurate process is that of observing when the starch has all disappeared,
as shown by the failure of the iodine reaction.

Such a method has been introduced by Roberts.3 He varies the amount
of the diastatic solution added until the " achromic point " is reached within a
period lying between the limits of four and six minutes. This achromic point
is that point at which the starch solution ceases to give a yellow tinge with
iodine, when accordingly the solution contains only achroodextrins and maltose.
Roberts defines the diastatic value of a solution (denoted by the symbol D)
by the volume in cubic centimetres of a standard starch mucilage which can
be converted to the achromic point by 1 c.c. of that solution, acting during five
minutes at a temperature of 40° C.

The standard solution of starch mucilage must be prepared fresh ; it is
made by stirring up 5 grms. of pure potato starch with 30 c.c. of water, and
pouring slowly into nearly 470 c.c. of water, which is kept boiling. The
mixture is stirred and boiled for a few seconds, and finally accurately made up
to 500 c.c., thus giving a standard solution (1 per cent.) of starch.

The solution of iodine used is made by diluting 1 part of the liq. iodi of
the Pharm. Brit, with 200 parts of water.

In making a determination, one proceeds as follows : — Ten c.c. of the
standard starch mucilage are diluted with distilled water to 100 c.c. and

1 Journ. Physiol., Cambridge and London, 1893, vol. xiv. p. 483.

2 Ztschr. f. physiol. Chem., Strassburg, 1885, Bd. ix. S. 577.

3 Diastasimetry, In "Digestion and Diet," London, 1891, p. 68.

RE LA TIVE A CTIVITY OF DIGESTIVE SOL UTIONS. 3 2 3

warmed to 40° C. ; a known volume of the diastatic solution to be tested is
next added, say 1 c.c., noting the time; drops of the solution are then tested
from time to time, say at intervals of ten seconds, with drops of iodine on a
porcelain slab until no yellow tinge is produced, and the interval of time
which has elapsed is noted. By altering the amount of diastatic solution
added, as a result of preliminary experiment, this time must be arranged to lie
between four and six minutes ; if the time is shorter than four minutes, an
error of a few seconds in determining the time of conversion makes too large a
percentage error, or if it be much longer than six minutes the transition is too
gradual at the end for the eye to accurately catch the achromic point. If v
be the volume in cubic centimetres of diastatic solution added, n the time to
reach the achromic point in minutes, and D the diastatic value of the solution

10 5

as above denned — then, D = — x —

v n

This value of D gives a measure of the activity of a given diastatic solution,
in terms of a standard which can be easily reproduced at any time to measure
the activity of another diastatic solution, and so comparable results may be
obtained.

Various methods are in use for determining the relative activity of
proteolytic solutions.

The earliest method is that first introduced by Bidder and Schmidt, and
used in various modifications by other experimenters. It consists in deter-
mining the weight of proteid dissolved in equal times, by equal volumes of the
digestive liquids added to equal volumes of a proper digestive medium. The
method is oftenest used for relative determinations of pepsin, when the
medium used is hydrochloric acid solution of 1 or 2 per mille, but it may also
be used for trypsin, when J per cent, sodium carbonate can be used as a
medium. The digestive solutions are placed in a bath at 40° C., and when
they have acquired the temperature of the bath, equal weighed portions of
equally finely subdivided hard-boiled white of egg (obtained by passing through
gauze netting) are added to each, and digestion allowed to proceed for the same
period in each case, say twenty-four hours ; the liquids are then filtered, and the
residues left undigested are washed, dried, and weighed ; a third equal quantity
of the white of egg used is also dried and weighed without previous digestion ;
and from the figures so obtained the amounts of dissolved white of egg are
deduced, and these are taken as representing the comparative peptonising
values of the two samples.

Bruckes l method. — This method consists essentially in diluting the
two proteolytic solutions to be compared with the same medium (1 per
mille HC1) in two series, and then picking out those two members in
each series which are most nearly equal ; from the relative dilution of
these two the comparative activity of the two original solutions easily
follows.

Vessels. Pepsin Solution of Acidity, "Water of Acidity,

1 per Mille. 1 per Mille.

1 . . 16 0

2 . . 8 8

3 . . 4 12

4 . . 2 14

5 . . 1 15

6 . . 0-5 15-5

7 . . 0-25 15-75

1 " Vorlesungen ueber Physiologie, " Wien, 1885, Aufl. 4, Bd. i. S. 311.

324 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

Hydrochloric acid is added to the two pepsin solutions, until the acidity
represents 1 grin, of hydrochloric acid per litre. These are then diluted in a
series of vessels with hydrochloric acid (1 per mille) according to the foregoing
scheme ; the figures represent volumes, say cubic centimetres.

A corresponding series of dilutions of the second solution is also prepared,
and in the vessels of both series a shred of fibrin l is digested for a given time.
At the end of the time, correspondingly advanced specimens are picked out in
the two series, especial attention being paid to the more dilute samples, which
give the truer indications, and the comparative power of the two solutions
easily follows. For example, if No. 3 in one series corresponds to No. 5 in the
other, the latter is four times as powerful as the former ; a closer approximation
can then evidently be obtained by a second experiment.

Grunhagen's'2 method. — Fibrin is swoUen out by placing it for some hours
in dilute hydrochloric acid. Equal weighed portions of this swollen fibrin are
placed in similar niters. Over each portion an equal volume, say 1 c.c., of the
various digestive solutions to be compared are poured. Soon the fibrin begins
to dissolve and drop from the funnels, dissolving in the dilute acid which had
previously swollen it. From the measured amounts dropping in equal times
from the different funnels, or by counting the rate of the drops, the compar-
ative activities of the various solutions can be determined. This method
evidently cannot be used for trypsin.

Griitzner's3 method. — Also cannot be used for trypsin, but is one of the best
methods for pepsin. It is a colorimetric method, and consists in measuring
the velocity with which the solution under examination dissolves fibrin stained
uniformly with carmine, by means of the depth of tint imparted to the solution
by the finely divided particles of carmine, which are set free in the solution at
a rate proportional to that of solution of the fibrin.

The method is best carried out by comparing the depth of the tints
produced at observed time intervals with those of a number of standard solu-
tions of carmine. The methods employed in preparing the stained fibrin and
these standard tints are as follows : — The fibrin is first well washed in a stream
of running water accompanied by kneading,4 and then placed for twenty-four
hours in a bath of weakly ammoniacal 0*25 per cent, carmine solution,5 the
volume of staining fluid being large compared with that of the mass of fibrin
to be stained, and the latter being pulled into small pieces, so as to ensure
thorough and uniform staining. After staining for twenty-four hours, the
fibrin is removed from the staining bath and washed well in a stream of
running water until it ceases to colour it. Before using for a digestion experi-
ment, the coloured fibrin in small pieces is immersed in about five times its
volume of 0*2 per cent, hydrochloric acid for thirty to sixty minutes ; this
swells it up to a clot-like mass, and it is used in this condition, pieces of
approximately equal size being placed in equal volumes of the various digest-
ive fluids to be compared, contained in equal-sized test tubes.

The scale of comparison tints may be prepared by adding, in varying pro-
portion, a glycerin solution containing one-tenth per cent, of carmine, to water
in test tubes of equal size; thus, to 19*9 c.c. of water are added O'l c.c. of
one-tenth per cent, glycerin-carmine solution; to 19'8 c.c. of water, 0*2 c.c. of
the same glycerin-carmine solution ; and so on, finishing with a solution

1 Approximately of equal size ; a slight difference has no appreciable effect.

2 Arch. f. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 203. For a method of adopting this to
experiment at body temperature, see Griitzner and Ebstein, ibid., 1874, Bd. viii. S. 122.

3 Ibid., 1874, Bd. viii. S. 452 ; "Neue Untersuch. li. Bildungu. Ausscheid. des Pepsins,"
Habilitationsschrift, Breslau, 1875.

4 It may advantageously be left in water over night to remove accompanying hemo-
globin.

5 Prepared by dissolving 1 grm. of carmine in a small volume of dilute ammonia and
making up to 400 c.c. with water ; the solution should only very faintly smell of ammonia,
and if necessary must be left exposed to the air until the odour of ammonia almost disappears.

RELA TIVE A CTIVITY OF DIGESTIVE SOL UTIONS. 325

of 19 c.c. of water and 1 c.c. of glycerin-carmine solution. In this manner
ten standard tints are obtained, the values of which correspond to the numbers
1 to 10; these are mounted in a stand against a uniform white background,
and are used to compare with the results of digestion, after equal intervals
of time. For example, if after thirty minutes' digestion the tint of one test
tube corresponds most closely to that of Standard 2, while that of another
corresponds to Standard 6, the latter is three times as powerful a digestive
solution as the former. The digestive solutions should be so diluted that they
act somewhat slowly, because after a time a maximum tint obtains, and then
the weaker digestive fluid catches up on the other ; the farther apart from
this maximum the measurements are taken the better. Also, if a close approxi-
mation to the comparative amounts of pepsin in two solutions is required,
after a preliminary experiment the stronger of the two must be diluted
experimentally until its 'action is equal to that of the other, then the pro-
portion of dilution gives the proportionate strength in pepsin of the two
solutions. This determination may be most speedily attained by making a
simultaneous series of dilutions of the stronger solution, and comparing the
strength of their action with that of the other solution or a series made
from it.

Two tubes of equal speed of action are picked out, and from their dilutions
the comparative richness in pepsin of the original fluid easily follows. Griitzner's
method may also be employed without a scale of standard tints, by stopping
digestion after an equal period, and then diluting the stronger solution until
its tint becomes equal to that of the weaker, or by carrying out two series
in aliquot dilution of the two solutions to be compared, and picking out
equally advanced members of the two series. In case the comparison is made
with solutions of unequal power, it must be remembered that what is measured
is the comparative digestive power and not the comparative strength of the
solutions in pepsin, because the two are not proportional;1 in all 'cases it is
preferable, for accuracy, to prepare solutions from the originals of equal power,
and from the amount of dilutions of these to deduce the comparative strength
in pepsin of the originals, as indicated above.

Mette's method.2 — This method is stated by Samojloff to yield exact
results. It consists in filling fine glass tubes of 1 to 2 mm. in diameter with
fluid white of egg, then coagulating by heat, and cutting off pieces of equal
length. These are placed in the digestive solutions at body temperature, and,
after the lapse of a certain interval, the length of white of egg digested off is
measured, which gives a measure for the comparative activities of the two
fluids.

Griitzner 3 has also introduced methods for comparing the diastatic
and fat-splitting powers of pancreatic extracts.

That for diastatic action closely resembles Griinhagen's method for proteo-
lytic action. Equal volumes of 3-4 per cent, starch paste are placed on similar
filters, through which they do not filter until dissolved; to each filter 0'2 to
0'3 c.c. of the extracts to be compared are next added, when solution of the
starch takes place at a rate proportional to the amount of enzyme present,
and a comparison of the amounts filtering through in a given time supplies
a measure for the activities of the extracts.

The method of comparing the fat-splitting powers of different extracts
consists in allowing the extracts to act on an emulsion in presence of litmus,
and noticing the time and amount to which the latter is turned red by the
acid developed. The emulsion recommended is made by mixing 10 parts of

1 See Schiitz's law, p. 322.

2 Samojloff, Arch, de sc. IrioL, St. Petersbourg, 1893, tome ii. p. 707.

3 Arch.f. d. ges. PhysioL, Bonn, 1876, Bd. xii. S. 293, 303.

326

CHEMISTRY OF THE DIGESTIVE PROCESSES.

oil of almonds, 5 parts of gum-arabic, and 35 parts of water. A solution
of litmus is prepared of such concentration and reaction that it shows a violet
colour when placed in test tubes about a centimetre in diameter in front
of white paper; in each test tube 10 c.c. of this dilute litmus solution are
placed • to each five drops of emulsion are added ; then equal volumes of each
of the pancreatic extracts to be compared. From the times in which an equal
amount of red develops in the litmus in each case, the richness of the extracts
in fat- splitting ferment may be determined. Or a series of determinations
for each extract, using a varying quantity of it, may be made, and the
members of each series compared.

The condition of the material to be digested has also a profound
effect upon the rapidity. The factors of most moment are —

1. Whether the material is fluid or solid.

2. Whether it has previously been heated (cooked) or not. In the
case of starch, previous heating and formation of a starch paste shortens
the process in the ratio of hours to minutes ; in the case of proteids,
previous heat coagulation slows the after process of digestion.

3. Materials which must first be dissolved, and must therefore be
attacked from the outside, are digested more quickly when in a finely
subdivided condition.

Classification of Enzymes.

Class of Enzyme.

Name of Enzyme.

Digestive Fluid in
which found.

Concise Description of
Specific Action.

Diastatic . . <

1. Ptyalin
2. Amylopsin

Saliva
Pancreatic juice

Convert amyloses
(starches and glyco-
gen) into dextrins,
maltose, and isomal-
tose, accompanied by
a trace of glucose.

Proteolytic . . -

1. Pepsin
2. Trypsin

Gastric juice
Pancreatic juice

Converts proteids into
albumoses and pep-
tones.

Converts proteids into
albumoses, peptones,
and amido-acids.

Fat-splitting or
steatolytic

Steapsin or
pialyn

Pancreatic juice

Splits up neutral fats
into fatty acids and
glycerin.

Coagulating
\

1. Rennin

2. An unnamed
ferment occur-
ring in pan-
creatic juice,
which also
coagulates
milk

Gastric juice

Coagulates milk, con-
verting caseinogen in
presence of calcium
salts into casein.

SPECIFIC ACTION OF ENZYMES. 327

Specific action of enzymes. — The different enzymes are specific in
their action ; that is to say, each enzyme only acts on one class of
material and acts on it in a determinate manner, producing certain
specific substances as the result of that action. The table on p. 326 is
a classification of the digestive enzymes according to their specific action.

Description of the digestive enzymes.— The digestive enzymes
may be here most conveniently treated of according to their occurrence
in the various digestive secretions, because of the description of the mode
of their separation, where more than one is found in the same digestive
fluid. Their action on the different classes of foodstuffs and the products
formed thereby will be considered afterwards.

Ptyalin.— In the saliva of many animals, and especially in the herbivora,
a diastatic enzyme is found, to which, soon after the discovery that saliva
possessed such an action,1 the name ptyalin was applied. In fishes
and in cetacea no salivary glands are present,2 and in some other
animals the salivary secretion possesses no diastatic action ; for example,
the saliva of the dog has no diastatic action, and the same statement is
made for the typical carnivora in general.3 In man, the secretion of both
the parotid and submaxillary glands has a diastatic action. At birth the
ferment is only found in the parotid ; it makes its first appearance in
the submaxillary two months later.4 In the horse the secretion leaves
the parotid with the diastatic ferment still in the condition of a
zymogen, from which the enzyme is set free by treatment with alcohol
or by contact with unfiltered air.5

Ptyalin was first separated from saliva in an impure form by
Mialhe,6 by precipitating filtered saliva with excess of absolute alcohol.
A scanty flocculent proteid precipitate is so obtained, which carries
down the ptyalin mechanically. Mialhe showed that this precipitate,
which was insoluble in strong alcohol, but partly soluble in water or
weak alcohol, possessed when dissolved the diastatic power of the
original saliva. From its supposed identity with the diastase of malt,
he called it diastase animal ou salivaire, and used the term ptyalin as a
synonym. It is now known that ptyalin and malt diastase, though
alike in their action upon starch, are not identical. This is shown best
by the difference in the reaction of the two enzymes to changes in
temperature. According to Roberts,7 saliva possesses a maximum
action between the temperatures of 30° and 45° C., and, according to
Kjeldahl,8 the optimum temperature is 46° C., while the enzyme is rapidly
destroyed by a temperature lying between 65° and 70° C.9 On the

1 Leuclis, Arch. f. d. ges. NaturL, Niirnberg, 1831 ; Schwann, Ann. d. Phys. u. Chem.,
Leipzig, 1836, Bd. xxxviii. S. 358.

2 According to Krukenberg ("Grundzlige einer vergleich. Physiol. der Verdauung,"
1882, S. 67), in some fishes the secretion of the mucous glands of the mouth possesses a
diastatic action; the same is true of the mucous secretion of the frog's mouth.

3 Griitzner, Arch. f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 285; Bunge, "Lehrbuch
der physiol. Chem.," Leipzig, 1894, Aufl. 3, S. 140; Neumeister, "Lehrbuch der
physiol. Chem., etc.," Jena, 1893, Th. 1, S. 122.

4 Zweifel, " Untersuch. ueber den Verdauungsapparat. der Neugeborenen," Berlin,
1874. See also Schiffer, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1872, Bd.
ii. S. 205 ; Korowin, ibid., 1873, Bd. iii. S. 158 ; Bayer, ibid., 1876, Bd. vi. S. 172.

5 Goldschmidt, Ztschr. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 273.
I Compt. rend. Acad. d. sc., Paris, 1845, tome xx. pp. 654, 1483.

7 " Digestion and Diet," London, 1891, p. 79.

8 Abstract in Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1879, Bd. ix. S. 381.

9 Roberts, loc. cit. ; Kiihue states that saliva loses its activity at a temperature of
60° C. ("Physiol. Chem.,"S. 21).

328 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

other hand, the optimum temperature for malt diastase lies at 50° to
56° C. ; l the activity does not greatly diminish until 60° C. is passed, and
then rapidly decreases and disappears, the ferment being destroyed by a
temperature of 80° C. Malt diastase is also much more sensitive to the
presence of salicylic acid than is ptyalin, being stopped by the presence
of 0-05 per cent., while ptyalin is first affected by 01 per cent., and not
completely stopped until a strength of 1 per cent, is reached.2

There is unfortunately no such certainty as to the identity or non-
identity of ptyalin and amylopsin (the diastatic ferment of the pancreas),
which is also called ptyalin by some authors.3 By others, the two
enzymes are accounted different, because (a) the pancreatic action is more
intense and complete, and (b) there are certain differences in the
products formed by the action of tlfe two enzymes.4 It is, however,
questionable whether these effects may not be entirely produced by
differences in concentration in the two cases of one and the same
ferment. In their behaviour to change of temperature and reaction the
two enzymes are identical ; the rate of conversion of starch into other
substances depends on the concentration of the enzymes in the solution ;
and with regard to differences in the products formed, it is not denied
that in prolonged salivary digestion a small quantity of dextrose is
formed, it is only claimed that larger quantities of dextrose are
formed in a shorter time 5 by the action of the diastatic enzyme of the
pancreas ; this again is a difference in degree and not in kind, and may
well be due to a difference in concentration of enzyme.

Cohnheim 6 obtained ptyalin in a purer form, that is, more free from
admixed proteids, by a method closely resembling that of Brlicke for
pepsin, and consisting essentially in producing a precipitate of tricalcic
phosphate in the saliva by the addition of phosphoric acid followed by
milk of lime ; this precipitates mechanically ptyalin and proteid, the
ptyalin dissolves more easily than the proteid on afterwards washing
the precipitate with distilled water, and may in this way be separated.

The solution so obtained was actively diastatic, but yet gave none of
the usual proteid reactions, was not coagulated on boiling, gave no
reactions with nitric acid, mercuric chloride, tannin, iodine, or acetic acid
and potassium ferrocyanide. The ptyalin precipitated from it was not
a pure substance, but contained chlorides and phosphates of sodium and
calcium.

Excess of alcohol caused a flocky precipitate of phosphates, and an
amorphous granular substance coloured yellow by iodine. Dried at a low
temperature, this precipitate furnished a white powder, only slightly
soluble in water, which retained its diastatic action for months.

A very active material may also be obtained by v. Wittich's method

1 Chittenden and Martin, Stud. Lab. Physiol. Chem., New Haven, 1885, vol. i. p. 117 ;
abstract in Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1885, Bd. xv. S. 263;
Lintner and Eckhard, Journ. f. prakt. Chem., Leipzig, 1891, N. F., Bd. xli. S. 91 ; Stutzer
and Isbert, Ztschr. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 72.

2 Jul. Miiller, Journ. f. prakt. Chem., Leipzig, 1875, N. F., Bd. x. S. 45.

3 Neumeister, " Lehrbuch der physiol. Chem.," Jena, 1893, Th. 1, S. 147.

4 See Sheridan Lea, " Chemical Basis of the Animal Body," London, 1892, p. 57.

5 Lea, however, found no dextrose, but only maltose, in his experiments quoted on p. 394.
See also Brown and Heron, Proc. Roy. Soc. London, 1880, No. 204, p. 393 ; Musculus and
Gruber, Ztschr. f. physiol. Chem., Strassburg, 1878-9, Bd. ii. S. 177; Musculus and v.
Mering, ibid., S. 403 ; v. Mering, ibid., 1881, Bd. v. S. 185.

6 Virchow's Archiv. 1863, Bd. xxviii. S. 241. Compare Sundberg's statement as to
similar precipitation of pepsin by alcohol and not by tannic acid, p. 316.

PTYALIN. 329

of extracting the salivary glands with glycerin, precipitating the
glycerin extract with excess of alcohol, washing with strong alcohol,
and then extracting with water.

Effects of reaction. — A knowledge of the effects of change of
reaction on the amylolytic activity of ptyalin, apart from its intrinsic
interest, possesses considerable importance from the bearing it has on
the natural process of digestion of starch, and for this reason probably
the subject has attracted the attention of a great number of workers.1
Ptyalin is secreted in an alkaline fluid, the saliva, and after a few
seconds admixture with the food passes with it into the stomach ; here
its alkaline reaction is lessened by the gastric secretion, and finally
replaced by an acid reaction. The amount of starch changed by the
ptyalin will depend on the effect of this gradual diminution in alkalinity
on its activity, and if the activity is decreased thereby, on the rate at
which progress is made towards an acid reaction.

It was formerly supposed that ptyalin was only active in a fluid
of alkaline reaction, that it was in consequence only active during
the few seconds of mastication, while the food remained in the
mouth, and was instantly destroyed on coming in contact with
gastric juice. More recent observations have, however, shown that
the importance of saliva as a digestive fluid is much underrated by
such a view.

The diastatic action of ptyalin attains a maximum when the reaction
of the fluid containing it is neutral, or even faintly acid, provided the
acidity is due to acid combined with proteid. Even mere traces oifree
acid, however, lessen and rapidly destroy its activity. Sodium carbonate
added to neutralised saliva decreases its activity, and in greater
quantity arrests it; here, again, proteids present in solution play a
protecting part, and by combining with the alkali prevent its injurious
action on the ferment. A solution of ptyalin free of proteid would
therefore probably act best in a neutral fluid, and would be quickly
destroyed by either an acid or alkaline reaction, due to acid or alkali
uncombined with proteid.2

The diastatic action of the saliva, therefore, continues in the stomach
during and after a meal until (1) the alkali of the saliva has been
neutralised, (2) the proteid present in solution has been satisfied, and
(3) a trace of free hydrochloric acid remains in excess. According

1 Jacubowitsch, Lehmann's " Zoochemie," in Gmelin's " Handbuch der Chem.,"
Heidelberg, 1858, Bd. viii. S. 22 ; Paschutin, Arch. f. Anat. u. Physiol., Leipzig, 1871,
S. 366 ; Hammarsten, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i.
S. 35; Briicke, Sitzungsb. d. Tc. Akad. d. Wissensch., Wien, 1872, Abth. 3; Watson,
Trans. Chem. Soc., London, 1879, p. 539 ; Chittenden and Grisvvold, Am. Chem. Journ.,
Baltimore, 1881, vol. iii. p. 305 ; Falk, Jahresb. U. d. Fortschr. d. Thicr-Chem., Wiesbaden,
1881, Bd. xi. S. 444 ; Langley, Journ. Physiol., Cambridge and London, 1880-2, vol. iii.
p. 246 ; NyleX Jahresb. ii. d. Fortschr. d. Thicr-Chem., Wiesbaden, 1882, Bd. xii. S.
241 ; Chittenden and Ely, Am. Chem. Journ., Baltimore, 1882, vol. iv. ; Journ. Physiol.,
Cambridge and London, 1882. vol. iii. p. 327 ; Detmar, Ztschr. f. physioL Chem.,
Strassburg, 1882, Bd. vii. S. 1 ; Langley and Eves, Journ. PhysioL, Cambridge and
London, 1883, vol. iv. p. 18 ; Chittenden and Smith, Chem. News, London, 1885, vol.
liii. ; Stud. Lab. PhysioL Chem., New Haven, 1885, vol. i. p. 1 ; John, CentralbL f. klin.
Med., Bonn, Bd. xii.; Schlesinger, Virchoiv's Archiv, 1891, Bd. cxxv. S. 146 ; Schierbach,
Skandin. Arch. f. PhysioL, Leipzig, 1892, Bd. iii. S. 344; Ebstein u. Schulze, Virchwfs
Archiv, 1893, Bd. cxxxiv. S. 475.

2 It is generally held that ptyalin acts best in neutral solution or with a faint acid
reaction, due to acid combined with proteid ; but there are slight differences of opinion as to
where the exact optimum point lies, for which the original papers should be consulted,
especially those by Langley and by Chittenden and their co-workers.

330 CHEMISTRY OF THE DIGESTIVE PROCESSES.

to the observations of van d. Yelden1 there is no free hydrochloric acid
found in the stomach until, on an average, three-quarters of an hour
after a carbohydrate meal. During this time the diastatic action of the
saliva must continue, and probably during most of the interval more
intensely than it would with its natural reaction. In this stage gastric
juice removed by the pump possesses a diastatic action on starch, but
later, when free acid is present, even when saliva is added to it, has no
such power. After all the proteid present in solution in the stomach
has been combined with the acid first secreted in the gastric juice,
and still more acid is secreted which remains free, the ptyalin not only
becomes inert, but is rapidly destroyed, and does not come into action
again after the acid of the gastric juice is neutralised in the small
intestine.2

Free organic acids also act destructively on ptyalin ; the concentration
of acid required is greater than in the case of hydrochloric acid, and
varies with the particular acid as well as with the concentration of the
ferment in the solution. Different neutral metallic salts possess different
actions ; some diminish the activity, such as mercuric chloride, which
even in a concentration of 0'005 per cent, is sufficient to stop all action ;
others increase it when present in small quantity, such as magnesium
sulphate up to 0'025 per cent., but have an opposite effect in greater
concentration.3 Carbolic acid does not produce much effect, digestion
with 5 per cent, solution for some hours being required to destroy the
ferment.4

Pepsin. — Pepsin is very widely distributed in the animal kingdom ;
it is found in the gastric juice of all vertebrates, with the possible excep-
tion of some fishes.5 In the frog it is found chiefly in the oesophagus.6
In the crayfish a yellowish-brown fluid is found in the mouth, of strong
acid reaction, which digests fibrin readily.7 And in many insects an acid
proteolytic secretion has been observed. Similar acid proteolytic secre-
tions are also known in the vegetable kingdom, such as those which may
be obtained by stimulating the leaves of insectivorous plants.8 Whether
these acid proteolytic ferments of the invertebrates and plants are
identical with pepsin is not known with certainty, but they are very
similar in their action.

Pepsin is found in the stomach of the herbivora at birth, and in
some other animals, including man ; in others, it first appears two or
three weeks after birth, as in the dog and cat.9

The different regions of the stomach do not, on extraction, yield

1 Ztschr. f. physiol. Chem., Strassburg, 1879, Bd. iii. S. 205.

2 See Langley, Journ. Physiol., Cambridge and London, 1882, vol. iii. p. 246 ; Nyle"n,
Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1882, Bd. xii. S. 241 ; and other
authorities quoted above. Opposite results were obtained by Cohnheim, Virchow's Archiv,
1863, Bd. xxviii. S. 248 ; Schiff, " Lecons sur la digestion," tome i. p. 162 ; and Dufresne,
Compt. rend. Acad. d. sc., Paris, 1879, tome Ixxxix. p. 1070.

3 Nasse, Arch. f. d. ges. Physiol., Bonn, 1875, Bd. xi. S. 138 ; Chittenden and Painter,
Stud. Lab. Physiol. Chem., New Haven, 1885, vol. i. p. 52.

4 Plugge, Arch.f. d. ges. Physiol., Bonn, 1872, Bd. v. S. 550.

5 Hamniarsten, " Lehrbuch der Physiol. Chem.," Wiesbaden, 1895, Ann. 3, S. 234.

6 Swiecicki, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1876, Bd. vi. S. 172.

7 Hoppe-Seyler, ibid., S. 170.

8 Darwin. "Insectivorous Plants" ; Goebeb and Loew, Chem. Centr.-BL, Leipzig, 1893,
Bd. ii. S. 1065.

9 Moriggia, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1876, Bd. xi. S. 455 ;
Hamniarsten, Beitr. z. Anat. u. Physiol. als Fcstgabe C. Ludwig, Leipzig, 1874, S. 110 ;
Zweifel, "Ueber d. Verdauungsapparat der Neugeborenen," Berlin, 1874.

PEPSIN. 331

equal amounts of pepsin: the pyloric end always contains much less
than the fundus or the cardiac end, but is never quite devoid of pepsin.
It was formerly held by some observers that the pepsin found in the
pyloric end was due to infiltration by the secretion from the glands of
the remainder of the stomach, but the secretion obtained from pyloric
fistulse contains pepsin which can only be secreted by the glands of this
region of the stomach.1

Effects of temperature. — Pepsin in neutral solution is destroyed by a
temperature of 55° C. ; in a solution containing two parts per thousand
of hydrochloric acid it is not destroyed at this temperature, but is
destroyed in five minutes at a temperature of 65° C. By the addition
of peptones or certain salts it is so protected that it is only destroyed
in an equal time by a temperature of 60° C.2 According to v. Wittich,3
the maximum rapidity of action is found between 35° and 50° C., and
the rapidity of destruction by elevated temperature (as in the case of
ptyalin) is dependent on the amount of dilution of the ferment, and the
duration of the high temperature. The more dilute the pepsin solution
the more quickly it is destroyed, and the lower the limit of temperature
necessary. Pepsin is still faintly active at 0° C.4

Effects of reaction. — Pepsin is only active in acid solution ; the most
effective acid is hydrochloric acid, but other acids are also capable of
setting it in action in varying degree. The most energetic of the other
acids are nitric, lactic, and phosphoric, followed at some distance by
sulphuric, acetic, oxalic, and tartaric acids. The most effective acids
seem also to be those which most easily swell up fibrin. Acid sodium
phosphate does not confer activity on pepsin.5

The amount of acidity required for optimum activity varies greatly
with the form of proteid to be digested; thus Briicke6 gives for
fresh fibrin '08 per cent., but for heat-coagulated fibrin '12 to *16 per
cent.

Supposed compound of pepsin and hydrochloric acid. — The hypothesis
has been put forward, that the pepsin and hydrochloric acid in gastric
juice are united to form a loose compound " pepsin - hydrochloric
acid."

There is no clear evidence in favour of the existence of such a
compound. It is said to be precipitated from gastric juice by the
soluble salts of lead and mercury, and to be re-obtainable unaltered
from the precipitate by decomposing with sulphuretted hydrogen. But
it is certain that both the acid and pepsin would be thrown down by
such salts, and there is no reason to suppose that they are not thrown
down separately instead of as a compound, and recovered together again
on decomposing the mixed precipitate. A second argument, that the
supposed compound acid can be decomposed by strong acids or alkalies,
and that the pepsin so separated does not again become active on the

1 See Ebstein and Griitzner, Jahresb. it. d. Fortschr. d. Thier-Chem., Wiesbaden, 1872,
Bd. ii. S. 210 ; 1873, Bd. iii. S. 169 ; 1874, Bd. iv. S. 236 ; Klemensiewicz, ibid., 1875,
Bd. v. S. 162; Heidenhain, ibid., 1878, Bd. viii. S. 245 ; King, ibid., 1894, Bd. xxiv.
S. 334; Akermann, Skandin. Arch. f. Physiol., Leipzig, 1895, Bd. v. S. 134.

2 Biernacki, Ztschr. f. BioL, Miinchen, 1892, Bd. xxviii. S. 49.

3 Arch.f. d. ges. Physiol., Bonn, 1869, Bd. ii. S. 193 ; 1870, Bd. iii. S. 339.

4 Flaum, Ztschr. f. BioL, Miinchen, 1892, Bd. xxviii. S. 453.

5 Maly, Hermann's " Handbuch," Bd. v. (2) S. 73.

6 Sitzungsb. d. k. Akad. cl. Wissensch., Wien, 1859, Bd. xxxvii. S. 131 ; Hammarsten
gives for fibrin 0'8 to 1 ; for myosin, casein, and vegetable proteid, 1 ; for hard-boiled proteid,
2-5 parts per litre. — " Lehrbuch," Aufl. 3, S. 238.

332 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

addition of hydrochloric acid, because the compound is not re-formed,
meets a simple answer in the statement that the pepsin is permanently
destroyed by the strong acid or alkali used. A strong argument against
any such compound is that the concentrations of different acids causing
equal activity in pepsin are not proportional to the chemical equivalents
of the acids, as might be expected if the acids entered into chemical
combination with the pepsin.1

Pepsin is very rapidly destroyed by solutions of alkalies or alkaline
salts.2 The principal conditions which influence the rate of destruction
of pepsin by sodium carbonate are — the strength of the solution of the
alkaline salt, the time during which it is allowed to act, the temperature
of the mixture, and the amount of proteid present. The mere act of
neutralising an acid pepsin solution may destroy a considerable part of
the pepsin. When equal volumes of a fluid containing pepsin and of a
1 per cent, solution of sodium carbonate are well mixed, the greater part
of the pepsin is destroyed in fifteen seconds ; in a neutralised acid
extract of the gastric mucous membrane of a cat, the amount thus
destroyed may be JJ of the whole. Even very dilute sodium carbonate
(•005 per cent.) will cause an appreciable destruction of pepsin in one
or two hours at the body temperature, provided proteids are present
in small amount only.

Proteids lessen the rate of destruction of pepsin, probably by
combining with the alkali or alkaline salts, for the greater the amount
of sodium carbonate present the greater must be the amount of proteid
to lessen appreciably the destruction. In the presence of -5 per cent,
sodium carbonate, less than -25 per cent, of peptone has very little effect,
and even 2*5 per cent, of peptone does not prevent the greater part of the
pepsin from being destroyed. Thus, in the presence of 2'5 per cent,
peptone, seven-eighths of the pepsin in an extract of a cat's gastric
mucous membrane may be destroyed at 17° C. by -5 per cent, sodium
carbonate in sixty seconds. Pepsin prepared from a frog is less rapidly
destroyed than pepsin prepared from a mammal. Carbonic acid destroys
pepsin also, but less rapidly than it destroys pepsinogen.3

Solutions of salts of the heavy metals weaken or entirely remove the
activity of pepsin solutions, according to the amount added. This effect
is probably due to the enzyme being mechanically carried down in the
usual fashion by the precipitate formed between heavy metal and pro-
teid. The neutral salts of the alkalies and alkaline earths, when added
(even in small quantity) to solutions of pepsin, decrease the activity.
Thus Al. Schmidt 4 found that salt-free proteid dissolved in a few seconds
in salt-free pepsin solution, but on the addition of 0'5-0'G per cent, of
sodium chloride the time of solution was increased three to ten times.
Hydrobromic and hydriodic acids in large doses, and to a still greater
extent their potassium salts, delay peptic digestion. Sulphurous acid stops
peptic digestion, but arsenious and hydrocyanic acids, except in large
amounts, have little effect. Carbolic acid in small quantities has also
little effect, but acts injuriously in greater concentration. Salicylic acid

1 Davidson n. Dietrich, Arch. f. Anat. u. PhysioL, Leipzig, 1860, S. 688 ; Putzeys,
Jahresb. it. d. Fortschr. d. Thier-Chem., Wiesbaden,' 1877, Bd. vii. S. 279; Halm, Virchow's
Archiv, 1894, Bd. cxxxvii. S. 597.

a Langley, Journ. Physiol., Cambridge and London, 1882, vol. iii. pp. 253, 283 ;
Langley and Edkins, ibid., 1886, vol. vii. p. 371.

3 Quoted from Langley and Edkins, loc. cit.

4 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1876, Bd. vi. S. 23.

PEPSIN.

333

was formerly credited with a powerful checking action, but, as shown
by Kiihne,1 while powerful in preventing the growth of bacteria, this
acid has no appreciable action, especially in small quantity, on the un-
organised ferments. Pepsin is much more rapidly destroyed by standing
under strong alcohol than are the other enzymes.

Anything which prevents swelling of the proteid by the acid retards
the progress of peptic digestion. Briicke 2 states that fibrin tied tightly
round with a thread, so that it cannot be so easily swollen by the acid,
is digested much more slowly. Adding a sufficient amount of neutral
salt also slows the digestion, probably from a similar cause, the salt
preventing the imbibition of acid by the fibrin. The comparative slow-
ness of digestion of heat-coagulated proteid, such as coagulated white of
egg, may also be due to a like cause, for such a form of proteid does not
swell up with acid. Finally, stronger acid than the optimum strength
does not cause so much swelling, and this may in part be the reason of
the slowing due to this cause.

Variation in rapidity with form of proteid. — The time of digestion
by pepsin varies enormously with the nature and condition of the pro-
teid to be digested ; coagulated white of egg requires almost as many
hours as unboiled fibrin does minutes. The comparative rate of pepton-
isation of coagulated and non-coagulated white of egg has been much
investigated, and with varying results. According to Waurinski,3 these
variations are due to want of uniformity in the concentration of acid
employed as a digesting medium ; with more dilute acid the coagulated
proteid is much more quickly digested, but the reverse is true when acid
of greater concentration is used.

The comparative speed of peptic digestion of different kinds of pro-
teid has, because of its practical bearing, been made the subject of much
investigation.4

Casein is the most easily digested of all forms of proteid. Fibrin is
much more quickly digested than coagulated egg-white, though, according
to its state of aggregation and time of boiling, the latter shows a con-
siderable variation. In general, proteids of animal origin are more
easily digested than those of vegetables, and of the latter legumin is
most easily, glutin most difficultly, digestible.5 Jessen 6 observed that
muscle fibre is more rapidly dissolved when raw than when coagulated
by boiling or roasting, and that boiled milk is digested more slowly than
unboiled. Beef appears to be both more easily dissolved and peptonised
than fish.7

The conclusion ought not, however, to be too hastily drawn that
those forms of proteid which are most easily dissolved by gastric juice
are therefore best and most nutritious; gastric juice is not the only
proteolytic fluid which acts on the food. If the food has been properly

1 Verhandl. cL naturh.-med. Ver. zu Heidelberg, 1876. 1ST. F., Bd. i. S. 90.

2 " Voiiesungen," Wien, 1887, Aufl. 4, Th. 1, S. 312.

3 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1873, Bd. iii. S. 175.

4 Besides those quoted below, see Stutzer, Ztschr. f. physiol. Chem., Strassburg, 1885,
Bd. ix. S. 212 ; 1886, Bd. x. S. 153 ; 1887, Bd. xi. S. 207 ; 1888, Bd. xii. S. 72 ; Pfeiffer,
ibid., 1887, Bd. xi. S. 1; Wolff, Landwirthsch. Jahrb., 1890, Bd. xix. S. 795; Hahn,
Vircliows Archiv, 1894, Bd. cxxxvii. S. 597.

5 Maly, in Hermann's " Handbuch," Bd. v. (2) S. 79.

6 Ztschr. f. Biol., Miinchen, 1883, Bd. xix. S. 129. See also Bergeat, ibid., 1888, Bd.
xxiv. S. 1391

7 Chittenden and Cummins, Am. Chem. Journ., Baltimore, 1884, vol. vi. No. 5 ;
Popoff, Ztschr. f. physiol. Chem., Strassburg, 1890, Bd. xxiv. S. 524.

334 CHEMISTR Y OF THE DIGESTIVE PROCESSES,

masticated, it is not necessary that it should be dissolved before leaving
the stomach. It does not follow that the foods which are more rapidly
dissolved are also more rapidly peptonised, nor, indeed, that those which
are more rapidly peptonised are also more thoroughly utilised by the
organism.1

Rennin.2 — The presence of a milk-curdling principle in the stomach
of the calf has been known for ages, but it is only within recent times
that it has been shown that this action is due to the presence of a
soluble ferment or enzyme.

This enzyme is present in neutral aqueous infusions of the mucous
membrane of the stomach of the calf and sheep, but in the case of other
mammalia, of birds and of fishes, the zymogen is more stable, and the
active enzyme itself is only set free ori^ treating a neutral infusion with
acid.3

The presence of rennin in the stomachs of birds and fishes is very
remarkable, and points to some wider function of the enzyme, at present
unknown to us, since it cannot be supposed that in such animals the
ferment plays any part in connection with the clotting of milk. Many
plant juices also contain enzymes which coagulate milk, such as the latter
of the fig tree,4 and of Carica pepaya, and the flowers of many cynaria.
Milk 5 is also coagulated by bacterial action with the development of
an acid reaction due to lactic acid (in the souring of milk). A curdy
precipitate somewhat resembling a clot is caused by the addition of acids
to milk, which led to the erroneous analogy being drawn, that the
coagulation of milk by rennet was also an acid action, due to lactic acid
set free from the lactose of the milk by ferment action.

The following is a summary of the proofs that milk coagulation is not an
acid action, but due to a specific enzyme (rennin), which acts on a proteid
(caseinogen) of the milk : — 1. When a neutral solution of rennin (rennet) is
added to alkaline milk, and the mixture is kept at 38°-40° C., complete
coagulation occurs in 4-10 minutes, and in the process the reaction remains
unchanged. 2. Solutions of caseinogen prepared from milk and free from
lactose coagulate in presence of calcium salts, on the addition of rennin.
3. Purified solutions of rennin have no action whatever on lactose.6

Eennin is always present under normal conditions in human gastric
juice, both at birth and in the adult.7 The distribution of the enzyme
and its zymogen in the gastric mucous membrane is similar to that of

1 See "Absorption of Proteids," p. 441.

2 The name is due to Sheridan Lea ; that of chymosin has been proposed by Deschamp.

3 Hammarsten, " Lehrbuch d. physiol. Chem.,'" Wiesbaden. 1895, Aufl. 3, S. 241.

4 This also contains a proteolytic ferment, active in either alkaline, neutral, or acid
reaction (Baginsky, Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vii. S. 209 ; Arch. f.
Anat. u. Physiol. , Leipzig, 1883, S. 276).

5 For the chemistry of milk, see p. 125.

6 These proofs are due to : Heintz, Journ. f. praJct. Chem., Leipzig, 1872, N. F., Bd. vi.
S. 374 ; Hammarsten, Jahresb. il. d. Fortsclir. d. Thier-Chem., Wiesbaden, 1872, Bd. ii.
S. 118 ; 1874, Bd. iv. S. 135 ; 1887, Bd. vii. S. 158 ; "Zur Kenntniss des Caseins und der
Wirkungdes Labfermentes, " Upsala, 1877 ; Al. Schmidt, Jahresb. il. d. Fortsclir. d. Thier-
Chem., Wiesbaden, 1874, Bd. iv. S. 154. From the fact that rennet when impure acts on
lactose, but not after purification, Hammarsten supposed that gastric juice contained a
third enzyme, which acted on lactose, forming lactic acid, but this has not been sub-
stantiated.

7 Zweifel, Cenlralbl. f. d. med. Wissensch., Berlin, 1874, Bd. xii. S. 939 ; Hammarsten,
Beitr. 2. Anat. u. Physiol. als Festgabe C. Ludwig, Leipzig, 1874 ; Schumberg, Virchow's
Archiv, 1884, Bd. xcvii. S. 260 ; Boas, Centralbl.f. d. med. Wissensch., Berlin, 1887, Bd.
xxv. S. 417.

SEPARA TION OF PEPSIN AND RENNIN. 335

pepsin ; that is, the pyloric part furnishes very weak extracts compared
with those yielded by the fundus.1

Solutions of rennin, commonly called rennets, may be prepared by
extracting the mucous membrane of the stomach in various ways, of
which the following is a summary : —

1. Extraction of the mucous membrane of the stomach of the calf for some
days with glycerin. Purer solutions may be afterwards obtained by precipi-
tating the glycerin extract with excess of alcohol, filtering, and treating the
precipitate with water.

2. Digesting the mucous membrane of the stomach for twenty-four hours
at atmospheric temperature with water containing 1 to 2 parts per mille of
hydrochloric acid, filtering, and neutralising.

3. Extracting with a saturated aqueous solution of salicylic acid, precipi-
tating by excess of alcohol, and extracting the precipitate with water.

4. The best extractive for making permanent preparations is solution of
sodium chloride of from 5 to 15 per cent, concentration, putrefaction being
prevented by the addition of alcohol, thymol, or some such innocuous pre-
servative.

Effects of temperature. — Eennin is quickly destroyed in neutral solu-
tion by a temperature of 70° C., in acid solution by a temperature of
63° C. The temperature of maximum activity lies at 38 to 40° C. It
also acts, though more slowly, at atmospheric temperatures.

Action of acids and alkalies. — Eennin is rapidly destroyed by caustic
alkalies ; even O025 per cent, of caustic soda suffices, at atmospheric
temperature in twenty-four hours, to completely destroy a very active
solution. The amount of ferment so destroyed varies as usual with the
duration of the action, the temperature, and the concentration of the
destructive agent. In their behaviour towards alkaline carbonates
rennin and its zymogen closely resemble pepsin and pepsinogen ; rennin
being quickly destroyed by 0'5 to 1/0 per cent, of sodium carbonate
(Na2C03), while its zymogen is much less readily affected thereby.2

Eennin is destroyed by standing under alcohol, but this change occurs
more slowly than the corresponding one in the case of pepsin.

Separation of pepsin and rennin. — For the preparation of a pepsin
solution free from rennin, a gastric extract containing both enzymes is
submitted to digestion in 0-3 per cent, hydrochloric acid for forty-eight
hours at 38° to 40° C. ; the rennin is completely destroyed. Hammarsten 3
utilises Briicke's principle of mechanical precipitation, for the preparation
of a rennin solution free from pepsin, in the following method. An acid
infusion of the gastric mucous membrane is neutralised with magnesium
carbonate, and enough neutral acetate of lead is added to completely
precipitate all the pepsin accompanied by a portion of the rennin.4 The
nitrate is further precipitated by more lead acetate aided by ammonia,
and the precipitate is separated and decomposed by very dilute sulphuric
acid, so yielding a solution of rennin almost free from proteid. This
solution is then further purified by mechanical precipitation with
cholesterin.

The final product so obtained produced no effect on a flock of fibrin

1 Hammarsten, loc. cit.

2 Langley, Journ. PhysioL, Cambridge and London, 1880-2, vol. iii. p. 287; Boas, Ztschr.
f. Jelin. Med., Berlin, 1888, Bd. xiv. S. 249.

3 Loc. cit. 4 As tested by the inability of the nitrate to digest fibrin.

336 CHEM1STR Y OF THE DIGESTIVE PROCESSES.

in twenty-four hours, but caused coagulation of fresh milk of neutral
reaction in one to three minutes.

Such a solution of purified rennin behaves essentially differently in
its reactions from a proteid solution. It is not coagulated by heat,
does not give the xanthoproteic reaction, and is not precipitated by
alcohol, tannin, iodine, or neutral acetate of lead ; it is, however, pre-
cipitated by basic acetate of lead.

THE PANCREATIC ENZYMES.

The pancreatic juice of all vertebrates in which it has been tested 1
contains three distinct enzymes, each of which acts on a different class
of the three great divisions of foodstuffs.2 In the invertebrates generally,
the place of the pancreas is taken by the so-called liver, hepato-pancreas,
or digestive gland. This usually contains enzymes, capable collectively
of attacking all three classes of foodstuffs, and with varying reaction ;
so that this organ may be considered as taking the place of the combined
digestive glands of the vertebrates.3

The different enzymes of the pancreas do not appear equally early in
life ; the pancreatic diastase, amylopsin, is not found at birth, but first
appears a month or more afterwards.4 The proteolytic ferment, trypsin,
is found during the last third of foetal life.5 No similar information is
on record regarding the fat-splitting ferment, steapsin.

The relative amounts of the different enzymes in pancreatic juice
vary considerably. In passing from a flesh to a bread-and-milk diet, the
proteolytic activity is said to diminish while the diastatic activity in-
creases, and vice versa in passing from a carbohydrate to a proteid
diet.6

In addition to the methods of extraction already described under
general methods, the pancreatic enzymes may be obtained in solution by
various other methods, of which the following is a summary : —

1. By extracting with water saturated with chloroform; such an extract
keeps well and is very efficient.7

2. By extracting with water containing 3 to 4 per cent, of a mixture of
2 parts of boracic acid and 1 part of borax.8

3. By placing the fresh gland, finely minced, in a saturated solution of
sodium chloride. This gives a strong solution of the proteolytic and diastatic
enzymes.9

4. By extracting the fresh pancreas, freed from fat and finely minced,
with about four times its weight of 25 per cent, alcohol for four or five days;
succeeded by filtration, which may be assisted by a trace of acetic acid.10

1 For a detailed account of the action of pancreatic extracts in different animals, see
Harris and Gow, Journ. PhysioL, Cambridge and London. 1892, vol. xiii. p. 469.

2 A milk curdling enzyme is also present ; see Milk, p. 127.

3 Krukenberg, " Grundziige einer vergleichenden Physiologic der Verdauung," Heidel-
berg, 1882.

4 Korowin, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1873, Bd. iii ; Zweifel,
"Untersuch. ueber den Yerdauungsapparat der Neugeborenen," Berlin, 1874.

5 Albertoni, Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1878, Bd. viii. S. 254.

6 Vassiliew, Arch, de sc. biol., St. Petersbourg, 1893, vol. ii. p. 219 ; Jahresb. it. d.
Fortschr. d. Thier-Chem., Wiesbaden, 1893, Bd. xxiii. S. 219.

7 Roberts, "Lumleian Lectures," 1880 ; "Digestion and Diet," London, 1891, p. 18.

8 Roberts, loc. cit.

9 Roberts, loc. cit. Also recommended by Harris and Gow, Journ. PhysioL, Cambridge
and London, 1892, vol. xiii. p. 469.

10 Roberts, loc. cit.

THE PANCREA TIC ENZYMES. 337

5. A very active proteolytic extract may be obtained by extracting with
water containing O'Ol to O05 per cent, of ammonia. The filtered extract gives
a precipitate with acetic acid which digests proteid very energetically, and can
be further purified.1

In preparing pancreatic extracts, it should be remembered that the
gland does not at all periods contain the same amount of the ferments,
or rather their zymogens, but that the amount fluctuates within wide
limits according to the period after a meal. The pancreas of an animal
in which digestion is not going on will yield little or no ferments ; the
best time is from four to seven hours after a meal. An inactive prepara-
tion may often be cured by making the extract faintly acid with acetic
acid some time before using ; this sets free ferment which may be present
as zymogen in the extract.

Trypsin.2— The proteolytic enzyme of the pancreatic juice in the
purest form in which Kiihne obtained it, gave all the proteid reactions,
thus differing from all the other purer forms of enzyme hitherto described.
Kiihne's product is decomposed on boiling, yielding 20 per cent, of
albumin and 80 per cent, of peptone ; it is soluble in water, but insoluble
in anhydrous alcohol or glycerin. The insolubility of the purified dry
product in anhydrous glycerin accords with v. Wittich's 3 observations,
that both enzymes can be extracted from the fresh gland by glycerin ;
but if the gland mass be previously thoroughly dried by extraction with
alcohol, glycerin only takes out the diastatic enzyme, the proteolytic
one being left behind.

Influence of temperature. — The activity of trypsin increases, accord-
ing to Eoberts,4 with rising temperature until 60° C. is reached, and
then rapidly falls, all action ceasing between 75° C. and 80° C. ;
Biernacki5 states that purified trypsin in 0'25 to 0*5 per cent, sodium
carbonate solution is destroyed in five minutes by a temperature of
50° C., and in neutral solution by a temperature of 45° C. The presence
of albumoses or of certain ammonium salts protects against the action
of elevated temperature in alkaline solution.

Influence of reaction. — Kiihne 6 made the observation that the activity
of trypsin was permanently destroyed by digesting its solutions with
pepjsin and hydrochloric acid, and attributed the greater share in this
action to the pepsin. Boas7 afterwards showed that the destruction
might be due to acid action alone, by demonstrating that addition of
hydrochloric acid to the filtered intestinal contents causes a precipitate
containing nearly all the ferments. This precipitate, on standing for a
few hours under the acid, became inert, but, when quickly separated and
redissolved in sodium carbonate, showed both diastatic and proteolytic
action. The matter has recently been again tested by Melzer,8 who

1 Hammarsten, " Lehrbuch, " Wiesbaden, 1895, Aufl. 3, S. 265.

2 So named by Kiihne, Verhandl. d. naturh.-med. Ver. zu Heidelberg, 1876, N. F.,
Bd. i. S. 190. Danilewski (Virchoiv's Archiv, 1862, Bd. xxv. S. 279) had previously to this
obtained a product which failed to give many of the usual proteid reactions.

3 Arch. f. d. ges. Physiol., Bonn, 1869, Bd. ii. S. 198 ; Hiifner (Jahresb. ii. d. Fortschr.
d. Thier-Chem., Wiesbaden, 1872, Bd. ii. S. 360) failed to obtain a similar result, probably
through using glycerin containing water.

4 Proc. Roy. Soc. London, 1881, vol. xxxii. p. 158.

5 Ztschr.f. BioL, Miinchen, 1891, Bd. xxviii. S. 51.

6 Verhandl. d. naturh.-med. Ver. zu Heidelberg, 1876, N. F., Bd. i. S. 193.

7 Ztschr.f. klin. Med., Berlin, 1890, Bd. xvii. S. 170.

8 Inaug. Diss., Erlangen, 1894 ; Melzer's figures show that most of the destruction is due
to acid alone.

VOL. I. — 22

338 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

finds that hydrochloric acid alone does destroy trypsin, but not so
rapidly as when pepsin is also present.

All possible opinions have been held by various observers as to the
reaction with which trypsin acts, and acts best ; * it is now generally
accepted that it can act either in an alkaline, neutral, or very faintly
acid solution, but that the optimum reaction is that given by about 1
per cent, sodium carbonate (Na2Co3).2

Active proteolysis by trypsin cannot take place in presence of an
acid reaction, except the acid be combined with proteid. If the proteid
be completely saturated with acid, the rate is greatly slackened even
when there is no free acid in the solution; and if much proteid be
present, the ferment action may be abolished even before this stage is
reached.3

Heidenhain 4 states that the concentration of sodium carbonate
necessary to ensure maximum activity varies with the richness in
ferment of the solution experimented upon ; the richer in ferment, the
lower the percentage of sodium carbonate necessary for maximum
action.

Other alkaline carbonates are much less effective than sodium
carbonate in increasing the activity of trypsin. The action is also said
to be assisted, but to a still less degree, by other salts of the alkalies.5

Organic acids have not nearly so destructive an action as hydro-
chloric acids, arsenious acid has no hindering effect, and salicylic acid
only when in saturated solution.6

The nature of the proteid submitted to digestion by trypsin has
also a profound effect upon the rapidity of the process. Fresh unboiled
fibrin is so quickly dissolved that it cannot be used as a comparative
test for trypsin, and fibrin which has been boiled, or discs of hard-boiled
white of egg, must be substituted for it.

Amylopsin.— An active amylolytic extract of pancreas can best be
prepared by following Eoberts' method of extracting with dilute alcohol.

Pancreatic juice is much more intensely diastatic than saliva, but
it cannot be determined, until some method for isolating the diastases
has been discovered, whether this is due to a difference in the amylolytic
ferments present or to a mere difference in concentration. It is certain,
however, that salivary, pancreatic, and malt diastases are practically
identical in the qualitative character of their action on starch. Eoberts

1 See Corvisart, "Collection de me'moires sur une function peu comme du pancreas, la
digestion des aliments azotes," Paris, 1857-8, p. 41 ; Meissner, Ztsclir. /. rat. Med., 1859,
3 Reihe, Bd. vii. S. 17 ; Kiihne, Verhandl. d. naturh.-med. Ver. zu Heidelberg, N. F.,
Bd. i. S. 190 ; Danilewski, Virchow's Archiv, 1862, Bd. xxv. S. 291 ; May, Untersuch. a. d.
physiol. Inst. d. Univ. Heidelberg, 1880, Bd. iii. S. 378 ; Lindberger, Jahrcsb. u. d. Fortschr.
d. Thier-Chem., Wiesbaden, 1883, Bd. xiii. S. 280 ; Ewald, Ztschr. f. Uin. Med., Berlin,
1880, Bd. i. S. 615 ; Langley, Journ. Physiol., Cambridge and London, 1880-2, vol. iii.
p. 262.

2 Weiss, Virchows Archiv, 1876, Bd. Ixviii. S. 413 ; Melzer, Inaug. Diss., Erlangen,
1894. According to the latter author, a digestion which is complete in two and a half
hours with 1 per cent. Na2C03 is incomplete in twenty-four hours with either 3 per cent.
Na2Co3 or O'OIO per cent, of HC1.

3 Chittenden and Cummins, Stud. Lab. Physiol. Chem., New Haven, 1885, vol. i. p. 100.

4 Hermann's "Handbuch," Bd. v. (1), S. 187.

6 Podolinski, " Beitr. z. Kenntniss des pankreatische Eiweissfermentes, " Breslau, 1876,
S. 43. See also Chittenden and Cummins, loc. cit., who found that borax and potassium
cyanide augment, while salts of mercury and iron decrease, the activity.

(! Lindberger, Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1883, Bd. xiii.
S. 280 ; Schafer u. Bohm, ibid., 1872, Bd. ii. S. 363 ; Kiihne, Verhandl. d. naturh.-med.
Ver. zu Heidelberg, N. F., Bd. i. S. 190.

THE PANCREA TIC ENZ YMES. 339

states that pancreatic diastase is capable of converting 40,000 times
its weight of starch into maltose and dextrin ; Kroger, that 1 grm. of
pancreatic juice, containing 0'021 grm. of dry solid, of which in turn
only a small fraction could be amylopsin, digested in half an hour 4'67
grins, of starch.

Influence of temperature. — The rate of conversion increases with
rising temperature from 0° C. to 30° C.; from 30° C. to 45° C. the rate
is at a maximum and practically constant. Above 45° C. the action
becomes slower with rising temperature, and ceases between 60° C. and
70° C., the ferment being here destroyed.1

Influence of reaction. — Pancreatic diastase closely resembles salivary
diastase in its behaviour to change in reaction of the medium in which
it is dissolved. It seems to act best when neutralised or in presence
of minute traces of acid ; but a limit of acidity is soon reached beyond
which the rapidity of action rapidly diminishes, and the enzyme itself
is quickly destroyed.2 The optimum activity, according to Melzer's
measurements, coincides with the presence of O'Ol per cent, of hydro-
chloric acid.

Pialyn.— Very little is known of the fat-splitting enzyme, pialyn, of
the pancreatic juice. That the action is due to an enzyme is shown
by the following experimental observations : — (a) The action is de-
stroyed when the pancreatic juice or active pancreatic extracts are
boiled ; (&) it takes place in presence of antiseptics, and hence cannot
be due to bacteria.3

The enzyme is much less stable than either of the other two
associated with it in pancreatic juice. It is especially susceptible to
the action of acids, being quickly destroyed by all except the higher
fatty acids, so that great care to avoid acidity of solution must be
exercised in the preparation of it from the pancreas. Paschutin4
recommends for its extraction a dilute solution of sodium carbonate
and bicarbonate in water, and Griitzner 5 that it should be extracted
from the perfectly fresh pancreas with a solution containing 90 c.c. of
glycerin to 10 c.c. of 1 per cent, sodium carbonate, ten times the weight
of gland to be extracted being taken of this fluid. However extracted,
it must l)e taken from a fresh gland and not from one which has stood over
a day, as in the case of the other two enzymes, for thereby an acid reaction
would be developed, and as a consequence the fat-splitting enzyme would
be destroyed.

The rapidity of action of the enzyme is at first increased by rising
temperature. It acts almost twice as fast at 38° C. as at 18° C., but it
is destroyed by boiling ; the temperature of destruction is not accurately
known.

It acts more slowly in the presence of 0'25 per cent, of sodium
carbonate than in neutral solution.

Its activity is greatly increased by the presence of bile, still more
by a mixture of bile and hydrochloric acid ; this increase in activity is
due to the bile salts or bile acids, which have a similar effect. The
rapidity of action of the enzyme is usually much underrated, and it

1 Roberts, " Digestion and Diet," London, 1891, p. 74 ; Proc. Roy. Soc. London, 1881,
vol. xxxii. p. 145.

- Melzer, Inaug. Diss., Erlangen, 1894.

3 Nencki, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1886, Bd. xx. S. 367.

4 Arch.f. Anat. u. PhysioL, Leipzig, 1873, S. 386.

5 Arch. f. d. ges. PhysioL, Bonn, 1876, Bd. xii. S. 302.

340 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

is probable that it is capable of splitting up all the fat of a full meal
in the ordinary time of digestion within the body.1

Pialyn acts on other esters than the neutral fats causing a similar
saponification.2

Separation of the pancreatic enzymes.— There has, strictly speak-
ing, been no complete isolation of the pancreatic enzymes obtained by
the various workers on the subject. Partial success has been so far
obtained, in that methods have been invented which yield solutions
much richer in one of the two principal enzymes than in the other.

Danilewski 3 was the first to tackle this difficult task, under the direction
of Kiihne. He found that, after shaking up a watery infusion of the
pancreas of the dog with excess of magnesia, and filtering, there remained an
infusion which possessed only a proteolytic and diastatic action.

This solution was mixed up with one (fUarter of its volume of thick collodion
solution (in alcohol and ether), and thoroughly shaken. The collodion is
thrown out of solution as a pasty mass, which mechanically carries with it
the proteolytic ferment, while the diastatic ferment remains in solution.
The collodion is removed, washed, and dissolved in a mixture of alcohol and
ether. This solution is allowed to stand for some days, when the proteolytic
ferment with a little proteid falls to the bottom as a yellow sediment. This
sediment, when dissolved again in water, digests fibrin in alkaline or neutral,
not in acid solution. The filtrate from the collodion, which contains the
diastatic enzyme, is evaporated down in vacua, and filtered from anything
which precipitates out. The filtrate is precipitated by excess of absolute
alcohol, extracted by a mixture of 2 parts water to 1 part alcohol, and
dried in vacuo. The solution so obtained rapidly converted starch into
sugar, and only possessed a very feeble action on fibrin. Lossnitzer 4 has
repeated these experiments, and only partially confirms them. Neither of
the two products obtained by Danilewski gave the xanthoproteic, or Millon's
reactions.

Cohnheim 5 obtained the diastatic enzyme from an infusion of pancreas, by
a method identical with that by which he obtained ptyalin.6 This substance
possessed no proteolytic action, did not give the proteid reactions, but acted
very energetically on starch.

v. Wittich 7 made use of the insolubility of trypsin in dry glycerin to
obtain an extract rich in diastatic ferment and free from proteolytic action.
The pancreas is dehydrated in strong alcohol, and further allowed to stand
under absolute alcohol for some time ; the tissue is then dried and extracted
with dry glycerin ; the extract after filtration is precipitated by excess of
alcohol, and the precipitate is again extracted with dry glycerin. In this
manner v. Wittich obtained an extract which did not act on fibrin and had
an intense action on starch. Hiifner got an extract, on repeating the process,
which also contained trypsin ; but as Kiihne states that trypsin is not soluble
in glycerin, Hiifner's results may be due to water in the glycerin em-
ployed.

Paschutin8 attempted to separate the pancreatic enzymes by using as

1 All these observations on the rapidity of action of this enzyme, and its variations,
have been made by Rachford, Journ. Physiol., Cambridge and London, 1891, vol. xii.
p. 72.

2 Berthelot, Ann. d. chim., Paris, 1854, tome xli. p. 272 ; Nencki, Arch. f. exper. Path,
u. PharmaTcoL, Leipzig, 1886, Bd. xx. S. 367 ; Baas, Ztschr. f. physiol. Chcm., Strassburg,
1890, Bd. xiv. S. 416.

3 Firchow's Archiv, 1862, Bd. xxv. S. 279.

4 Arch. d. Hcillc., Leipzig, 1864, Bd. v. S. 556.

5 Firchow's Archiv, 1863, Bd. xxviii. S. 241. 6 See p. 328.

7 Arch.f. d. ges. Physiol., Bonn, 1869, Bd. ii. S. 198.

8 Arch.f. Anat. u. Physiol., Leipzig, 1873, S. 382.

THE INTESTINAL ENZYMES. 341

extractives concentrated solutions of different salts. He found that some salt
solutions extracted all three ferments, while others especially extracted one
ferment accompanied by traces of the others. Thus sodium chloride, sodium
sulphate, and potassium chlorate extracted all three ferments indifferently;
sodium bicarbonate, with a little of the normal carbonate added, extracted best
the fat-splitting ferment ; the proteolytic ferment was taken up best by
potassium iodide, arsenite, or sulphite ; and the diastatic ferment by
potassium arsenate alone or with the addition of ammonia.

Dastre l has recently described methods for approximately separating the
proteolytic and diastatic enzymes of the pancreas.

1. If the pancreas of an animal killed during digestion be cut into large
pieces, and these then digested for 15-20 minutes at 40° C., in normal saline
(*7 per cent.), the filtrate is found to possess a strong diastatic action, but
scarcely any proteolytic action. If, after this first extraction, the pieces are
finely minced and extracted anew with normal saline (1 per cent, of sodium
fluoride being added to prevent putrefaction), an extract is obtained rich
in proteolytic ferment, but containing scarcely any diastase.

2. On extracting a fresh gland with alcohol of increasing strength, after-
wards with ether, and drying over sulphuric acid, a powder is obtained
which yields, on extraction with saline, a fluid which is almost inert towards
starch, but is actively proteolytic.

3. An extract made from the pancreas of an animal which has not been fed
for some days, contains proteolytic ferment but has scarcely any diastatic action.

THE INTESTINAL ENZYMES.

Practically nothing is known of the enzymes of the small intestine
save their action on foodstuffs; none of them have been obtained in
even approximately pure condition, and the fact that there are enzymes
rests on the observations — (1) that the action is destroyed by boiling,
and (2) that it takes place under antiseptic conditions. Until the
importance of this latter condition was demonstrated by the work of
Ktihne on pancreatic digestion, there was much difference of opinion
as to whether the succus entericus contained a proteolytic enzyme
or not ; some observers had observed digestion of proteids by this
fluid, and others had been unable to do so. At length it was shown
by Masloff 2 and by Wenz 3 that when precautions are taken to
prevent bacterial growth, the succus entericus or extracts of the
intestinal mucous membranes have no action on proteids or on
albumoses.

With regard to the action of succus entericus on carbohydrates, the
more recent work on the subject all goes to show that starch is con-
verted into maltose, maltose into dextrose, and cane-sugar into dextrose
and Isevulose, both by the succus entericus and by extracts of the
intestinal mucous membrane.

The succus entericus contains no enzyme which acts on neutral fats.
The power of emulsifying fats, which was occasionally observed by the
earlier workers on the subject, was doubtless due to the alkalinity of the

1 Compt. rend. Soc. de bioL, Paris, 1893, tome xlv. p. 648 ; Arch. dephysiol. norm, etpath.,
Paris, 1893, tome xxv. p. 774.

2 Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, 1882, Bd. ii. S. 920. Masloff
found very slight action of the juice when acidified, probably due to infiltrated pepsin.

3 Ztschr. f. BioL, Miinchen, 1886, Bd. xxii. S. 1. This result is confirmed by the
observations of Tubby and Manning on human succus entericus, Guy's Hosp. Rep., London,
1891, vol. xlviii. p. 277.

342 CHEM1STR Y OF THE DIGESTIVE PROCESSES.

fluid, aided by the presence of free fatty acid in the fat used for the
experiments.1

Paschutin 2 attempted by two different methods to separate the
diastatic and inverting ferments : —

1. An infusion of the intestinal mucous membrane was made by rubbing
it up with water and powdered glass, and filtering. When this infusion was
mixed with a solution of collodion, the precipitated collodion brought down
most of the inverting enzyme, and most of the diastatic enzyme was left in
solution, but only a partial separation could be effected in this manner.

2. The mucous coat of a piece of intestine was freed from the other coats,
and then water was filtered through this, under pressure. The fluid which
filtered through acted energetically on starch, but had no action or only a
very feeble one on cane-sugar.

THE CHEMICAL COMPOSITION OF THE DIGESTIVE
SECRETIONS.

SALIVA.

The saliva is a mixture in varying proportions of the secretions
of the different salivary glands. As these secretions differ from
one another considerably in chemical composition, it will be well
to consider first the physical and chemical nature of each of them
in turn, and afterwards that of the fluid which results from their
admixture.

Submaxillary saliva.— Submaxillary saliva may be obtained by in-
serting a fine cannula into the opening of Wharton's duct. In some
individuals Wharton's duct carries to the mouth the secretion of the
Submaxillary gland only, in others the duct of Bartholin leads into
Wharton's duct, when the latter conducts the mixed secretion of the
Submaxillary and sublingual glands to the month. The tongue should
be raised, but not too high, the cannula carefully inserted and gently
pushed into the duct for about an inch. By this procedure the end of
the cannula is thrust past the opening of the duct of the sublingual
gland, in case both glands share a common duct, and so the obtaining of
Submaxillary saliva only is ensured.3

Human snbmaxillary saliva is a clear, watery, mobile fluid, which
becomes viscid on standing in contact with air, and deposits flocculi.
It is always alkaline in reaction. On boiling, it becomes cloudy, and
the cloudiness is increased by the addition of acid. Its specific gravity
varies between 1'0026 and 1*0033, and is lessened by hunger. The
amount of total solids lies between 0'36 and 0'46 per cent., and is not
much influenced by food. According to Eckhard, it contains no
sulphocyanates, while Oehl and Sertoli4 state that it contains them,
but in less amount than the secretion of the parotid. Colorimetric

1 See, however, Schiff, Arch, de physiol. norm, ct path., Paris, 1892, tome xxiv. p. 679.
Schiff here repeats his earlier statements, that succus entericus acts both on proteids and
neutral fats. Prege (Arch. f. d. ges. PhysioL, Bonn, 1896, Bd. Ixi. S. 359) has recently
obtained succus entericus from a Vella fistula in the sheep, and determined that it has no
action on proteids or neutral fats.

2 Arch. f. Anat. u. PhysioL, Leipzig, 1871, S. 305.

3 Eckhard, Jahresb. it. d. Fortschr. d. ges. Med., Erlangen, 1862, Bd. i. S. 126 ; cited
from Maly, Hermann's " Handbuch," Bd. v. (2), S. 17.

4 Oehl, Jahresb. u. d. Fortschr. d. ges. Med., Erlangen, 1865, Bd. i. S. 120 ; Sertoli,
ibid., 124.

SUBLINGUAL SALIVA. 343

measurements gave for the submaxillary saliva 0*004 per cent., for
the parotid 0*03 per cent., of this substance, reckoned as potassium
sulphocyanate. It contains ptyalin, as shown by its powerful diastatic
action on starch.

The submaxillary saliva in the dog contains much more mucin than in
man, and is in consequence much more viscid. It is alkaline in reaction, 100
grins, requiring for neutralisation 0*135 to 0'144 grms. of sulphuric acid,
reckoned as S03. On standing in contact with air, calcium carbonate is
thrown down as a flocculent precipitate, which was previously held in solution
by the dissolved carbon-dioxide as bicarbonate. The same result is brought
about more rapidly by heating. It contains, at most, only traces of proteid
or of sulphocyanate. Its specific gravity is 1*0026 to 1*004.

The quantitative composition of the saliva obtained on stimulation of
the submaxillary gland varies according to the nerve stimulated. The
saliva obtained on stimulation of the sympathetic (sympathetic saliva)
is scanty in quantity, and contains much mucin, which gives it a viscid
consistency. Chorda saliva, on the other hand, is plentiful in quantity,
contains less mucin, and is hence a thin watery fluid. The chorda saliva
has a specific gravity of 1*0049 to 1*0056, and contains 1*2 to 1-4 per
cent, of total solids; sympathetic saliva has a specific gravity of 1/0075
to 1-018, and contains 1*6 to 2*8 per cent, of total solids.1

Parotid saliva.— Human parotid saliva may be obtained by intro-
ducing a fine cannnla into Stenson's duct.2

It is a thin, mobile fluid, usually clear, sometimes somewhat turbid,
and contains no formed element save epithelial cells. It is alkaline in
reaction, but the first few drops secreted may be neutral or acid,
especially in a state of hunger ; in all cases the alkalinity is less than
that of submaxillary saliva.3 Its specific gravity seems to be very
variable (Mitscherlich, 1*006 to 1*008 ; Oehl, 1*010 to 1*012 with scanty
secretion, 1*0035 to 1*0039 with plentiful secretion; Hoppe-Seyler,
1*0061 to 1*0088); the amount of total solids lies between 5 and 16
parts per thousand. It contains traces of proteids, but is free from
mucin ; it also contains ptyalin and sulphocyanate.

The parotid saliva of some animals, such as the dog and horse, is very
rich in calcium bicarbonate, and often deposits crystals of calcium
carbonate on standing.4 Stimulation of Jacobson's nerve in the dog
produces a flow of saliva from the parotid, poor in organic constituents.
If, before this is done, the cervical sympathetic be stimulated, which
alone produces no effect, on now stimulating the nerve of Jacobson
a flow of saliva is obtained which is much richer in organic con-
stituents.5

Sublingual saliva.— Oehl attempted to obtain human sublingual
saliva by a similar method to that described in the case of the other two
glands ; he was only able to obtain a very small quantity, insufficient for

1 Eckhard, JBeitr. z. Anat. u. Physiol. (Eckhard), Giessen, 1860, Bd. ii. For further
details regarding the influence of nerves on the composition of saliva, see article on
" Mechanism of Salivary Secretion."

2 Eckhard, loc. cit.; Oehl, Jahresb. u. d. Fortschr. d. ges. Med., Erlangen, 1865, Bd. i.
S. 120. See also Brim ton in Sanderson's "Handbook of the Physiol. Laboratory," p. 467.

3 See Astaschewsky, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1878, Bd. viii.
S. 234 ; Fubini, ibid. , S. 235.

4 Lehmann, "Physiol. Chem.," Bd. ii. S. 13.

5 Heidenhain, Arch. f. d. ges. Physiol., Bonn, 1878, Bd. xvii. S. 28 ; also in Hermann's
"Handbucb," Bd. v. (1), S. 55.

344 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

quantitative analysis, but made out that it was a clear slimy fluid of
stronger alkaline reaction than submaxillary saliva, and containing
mucin, diastatic ferment, and sulphocyariide.

The sublingual saliva of the dog is a viscous, scarcely fluid mass ; it contains
salivary corpuscles, but is otherwise quite clear and transparent, is alkaline in
reaction, and contains 2*75 per cent, of total solids.1 Werther2 has analysed
the sublingual saliva of the dog, and finds that its great viscidity is not due
to any excess of organic constituents ; he attributes it to the reaction which he
found to be neutral or barely alkaline. The proportion of inorganic salts is
much larger than in parotid or submaxillary saliva.

Secretion of the raucous glands of the mouth.— This has not
been obtained in man. In the dog it»has been obtained by ligaturing
the ducts of all the salivary glands, or by extirpating the salivary
glands. The amount secreted is exceedingly small ; it is a thick ropy
mucus of alkaline reaction, full of fragments of epithelial and mucous
cells, and containing about 1 per cent, of total solids.3

The mixed saliva.— Mixed saliva may easily be obtained from the
mouth by depressing the head . and everting the lower lip ; or by
depressing the head, keeping the mouth widely open, and avoiding
all attempts to swallow. It is a clear, viscid, and very slightly
opalescent fluid, which froths easily. It is normally alkaline in
reaction; when it is acid this reaction is commonly due to fer-
mentation of particles of food in the mouth. The alkalinity is least
when fasting, as in the morning before breakfast, and reaches its
maximum with the height of secretion during, or immediately after
eating. According to Chittenden and Ely,4 the alkalinity is equiva-
lent to that of a solution containing 0*08 per cent, of sodium carbonate
(Na2Co3).

The quantitative composition of mixed saliva is very variable, as
might be expected from the difference in composition of the secretions
which form it, and the varying proportion in which these must be pre-
sent in different samples. The amount of total solids in human saliva
varies normally between 5 and 10 parts per 1000 ; the specific gravity
between 1'002 and 1'OOS.

Organic constituents. — The organic matter is partially in suspension,
and partially in solution. The suspended matter consists of squamous
cells detached from the epithelium of the mouth, and of the sali-
vary corpuscles, which are leucocytes altered by the action of the
saliva, and containing granules which exhibit in fresh saliva active
Brownian movements. The dissolved organic matter consists of
mucin, ptyalin, and traces of proteids ; the amount of the latter is
so small that it cannot be quantitatively estimated. Saliva is also
said to contain normally minute traces of urea; but the amount
is so small that such a statement cannot be made with certainty.
In pathological conditions the amount of urea present may, however,
become very appreciable. Leucine and lactic acid are found under

1 Heidenhain, Stud. d. physiol. Inst. zu Breslau, Leipzig, Heft 4.

2 Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxviii. S. 293. See also Langley and
Fletcher, Phil. Trans., London, 1887, vol. clxxx. p. 109.

3 Bidder and Schmidt, "Die Verdauungssafte," Mitau und Leipzig, 1852, S. 5.

4 Am. Chem. Journ., Baltimore, 1883, p. 329. See also Werther, Arch. f. d. ges. Physiol.,
Bonn, 1886, Bd. xxxviii. S. 293.

SULPHOCYANATE OF SALIVA. 345

pathological conditions, but are not normal constituents. Grape-sugar
and bile pigments are never found even in the severest cases of diabetes
or icterus.1

Inorganic constituents. — These consist of salts of the alkalies (chiefly
sodium) and alkaline earths ; principally as chlorides, but also as
phosphates and carbonates.2 Calcium carbonate often separates from
saliva, as a thin surface film, or as a cloudiness in the fluid on standing ;
this is due to the escape of carbon-dioxide by which the calcium was
held in solution as bicarbonate. A precipitation of the calcium of the
saliva, partially as carbonate and partially as phosphate, in the ducts of
the salivary glands, often gives rise to salivary concretions ; and a similar
deposit, mixed with phosphate and traces of silica, forms the tartar
of teeth.

Sulphocyanate of saliva. — Treviranus,3 as early as 1814, observed
that when a dilute solution of ferric chloride is added to saliva a reddish
coloration is obtained. This was even before sulphocyanic acid was
known chemically, and Tiedemann and Gmelin4 afterwards proved that
the effect was due to the presence of a sulphocyanate.

The amount of sulphocyanate is not large. Oehl states it as equivalent to
0 '000 16-0 '0084 per cent., estimated as potassium sulphocyanate, and Munk
as equivalent to O'Ol per cent, sulphocyanic acid, or 0'014 per cent, of
sodium sulphocyanate.5 The presence of a sulphocyanate in saliva may be
demonstrated qualitatively in several ways — (1) A very greatly diluted and
slightly acidulated solution of ferric chloride is added drop by drop to saliva,
when a reddish coloration is obtained, if sulphocyanate is present in normal
quantity; the colour disappears on adding mercuric chloride. This test is
difficult to obtain. (2) A filter paper is dipped in a weak solution of ferric
chloride, containing a trace of hydrochloric acid, and then allowed to dry, when
it should have only a faint amber colour. On such test paper a drop of saliva
produces a reddish stain.6 (3) Filter paper is impregnated with tincture of
guaiacum, and then drawn through a solution of 0'05 per cent, copper sulphate.
On such paper, saliva containing sulphocyanate causes a blue stain.7 (4) Saliva
is treated with iodic acid, when iodine is set free ; this in turn is treated with
starch paste, when the blue compound of starch and iodine appears. This is
said to be an exceedingly delicate reaction, showing a most minute trace of
sulphocyanate, and not being produced by saliva free from sulphocyanate,8 but
iodic acid is an exceedingly unstable compound, and the latter statement is
questionable.

Sulphocyanate is often absent in human saliva. Some authors state that
it is found in dog's saliva, others that it is not ; the explanation may be that
its presence in dog's saliva is also not constant. It is said to be absent in the
saliva of the horse, ox, sheep, goat, and pig.9 Leared 10 found that sulpho-

1 See Maly, Hermann's "Handbueh," Bd. v. (2), S. 8.

2 The older analysts were accustomed to proportion the bases and acids, on the
supposition that as much as possible of the so-called strongest acid was combined with the
strongest base. We now know that the acids and bases are distributed according to definite
laws, and no longer speak of so much chloride, for example, as existing in a complex
mixture, but state separately so much sodium and so much chlorine, etc.

3 " Biologie," 1814, Bd. iv. S. 330.

4 "Die Verdauung nach Versuchen," Bd. i. S. 8.

5 See Maly, Hermann's "Handbueh," Bd. v. (2), S. 10, 14.

6 Gscheidlen, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden. 1874, Bd. iv. S. 91.

7 Bottger, ibid., 1872, Bd. ii. S. 204.

8 Solera, ibid., 1877, Bd. vii. S. 256 ; 1878, Bd. viii. S. 235.

9 Ellenberger and Hofmeister, " Vergleich. Phys. d. Haustiere," Berlin, 1890, S.
495.

10 Proc. Roy. Soc. London, 1870, vol. xviii. p. 16.

346 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

cyanate was present in the blood and urine as well as in the saliva.
Gscheidlen l and Munk 2 have also found it in urine.

An exalted importance has been given to the sulphocyanate in saliva,
from its supposed origin from proteid, and from its assumed value as an
indicator of the rate of proteid metabolism. Sulphocyanic acid has a
similar constitution to cyanic acid, an atom of sulphur merely replacing an
atom of oxygen, and the ammonium salt of sulphocyanic acid undergoes a
similar decomposition to that of cyanic acid, yielding sulpho-urea instead
of urea, thus : —

Oxygen compounds— CK OH ; CN".O.NH4 ; CO.(NH2)2
(cyanic acid) (ammonium (urea)

cyauate)

Sulphur compounds— CKSH ; • CKS.NH4 ; CS.(NH2)2
(sulphocyanic (ammonium (sulpho-urea)
acid) sulphocyanate)

From this relationship, from the presence of sulphur in its molecule, and
from its presence in the urine, and in traces in the blood, it is probable that
the sulphocyanate of the saliva is a product of proteid metabolism. Fenwick 3
has investigated the variation in the sulphocyanate of the saliva, especially in
relation to the variations in the nutrition of the body under pathological
conditions. He states that the amount of sulphocyanate bears a relationship
to the amount of sulphur (as taurocholates) in the bile, and that when the
bile is diverted from the alimentary canal the sulphocyanate of the saliva
disappears. That it would be dangerous to take the amount of sulphocyanate
as any gauge of the amount of proteid metabolism, is shown by its complete
absence in many species of animals, and in many individuals where it is
normally present in a species ; this does not make any the less probable
the statement that in those individuals in which sulphocyanate is present its
quantity should vary with the activity of proteid metabolism.

Saliva also contains traces of nitrites,4 which may be demonstrated by
diluting saliva with five times its volume of water, making acid with sul-
phuric acid and adding a solution of metadiamido-benzol, when an intense
yellow colour is produced. In this way Griess estimated colorimetrically
the amount of nitrite in saliva at 1-10 mgrms. per litre. Minute traces of
ammonia may also be shown to be present in saliva by the addition of Nessler's
reagent.5

Gases of the saliva. — The saliva holds considerable volumes of gas in
solution or in chemical combination. In human parotid saliva, Kiilz 6 found
in 100 vols. of saliva, of oxygen, 1'46 vols.; of nitrogen, 2*8 vols.; and of
carbon-dioxide 66 '7 vols., of which latter 62 vols. were in chemical
combination. In submaxillary saliva of the dog, obtained by stimulating
the chorda tympani, Pfliiger7 found 0'5-0'S vols. of oxygen, O'9-l'O vols.
of nitrogen, and 64*73-85 '13 vols. of carbon-dioxide, most of the latter
being chemically combined. These figures are interesting, both because of the
large amount of carbon-dioxide present, and the fact that the oxygen exceeds
the amount dissolved by blood plasma.

1 Arch.f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 401.

2 Firchow's Archiv, 1877, Bd. Ixix. S. 354.

3 Fenwick, "The Saliva as a Test for Functional Disorders of the Liver," London, 1889.

4 Schonbein, Journ. f. prakt. Chem., Leipzig, Bd. Ixxxvi. S. 151 ; Schaer, Ztschr.f. BioL,
Mlinchen, Bd. vi. S. 467 ; Griess, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. ii. S. 624.

5 Maly, Hermann's "Handbuch," Bd. v. (2), S. 8. See also W. Sticker, Mimchen.
med. Wchnschr., 1896, Bd. xliii. Nos. 42-43.

6 Ztschr. f. BioL, Mimchen, 1887, Bd. xxiii. S. 321.

7 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 686.

ANALYSES OF SALIVA.

347

Tables of Analyses of Saliva.
TABLE I.

SUBMAXILLARY SALIVA.

GASES.

I.

II.

Water .

991-45

996-04

994-4

991-14

K2S04 0-209 I

5-

CO 2 free 19 -3

22-5

i

C00 com-

Total Solids .

8-55

3-96

5-6

8-86

KC1 0-940

~

bined 29-9

42-5

(a) Organic .

2-89

1-51

1-75

3-53

Na 01 1-546

5

Nitrogen 07

0-8

(b) Inorganic

5-66

2-45

3-85

5-33

Na2C03 0-902

a.

1. Soluble

4-50

3-59

5-27

CaC03 0-150

|

Oxygen 0 "4

0-6

2. Insoluble

1-16

0-26

0-06

Ca3(POJ2 0-113

4

F

Analyses I. and II. are of dog's saliva, by Bidder and Schmidt.1 Analysis
III. is by Herter.2 Analysis IV. is of cow's saliva.3 The ash analysis is by
Herter.4 The gas analyses are of dog's saliva by Pfliiger.5

TABLE II.
PAROTID SALIVA.

I.

II.

III.

IV.

V.

VI.

VII.

Water

985-4-983-7

993-16

995-3

991-5-993-8

990-00

9907

869-0

Total Solids

14-6-16-3

6-84

47

8-47-6-1

10-0

9-3

11-0

(a) Organic

9-0

3-44

1-4

1-53

2-06-6-0

0'44

1-0

(b) Inorganic .

5-3

3-40

3-3

6-93

4"8-873

8-82

10-0

1. Soluble .

2-1

6-25

872

10-0

2. Insoluble

1-2

0-68

o-io

Traces

This table has been compiled from Maly.6 I. and II. are analyses of
human parotid saliva, by Mitscherlich and Hoppe-Seyler respectively. The
former states the amount of the sulphocyanate in his sample at 0'3 per thousand.
III. and IV. are of dog's parotid saliva, by Jacubowitsch and Herter respect-
ively ; that given as soluble is set down by them as CaC03. V. is of horse's

parotid saliva by Lehmann.
respectively, by Lassaigne.

VI. and VII. of the cow's and ram's parotid saliva

TABLE III.

SUBMAXILLARY, PAROTID, AND SUBLINGUAL SALIVA.

Submaxillary Saliva.

Parotid Saliva.

Sublingual Saliva.

I.

II.

III.

IV.

I.

II.

III.

I.

II.

III.

IV.

Water .
Total Solids
(a) Organic
(b) Inorganic
1. Soluble
2. Insoluble
Alkalinity —
(asNa2C03) .
Chlorides —
(as NaCl)

987-7
12-3

5:6

1-6
3-35

9887
11-3
6-6
47
4-3
0-42

17
1-5

983-2
16-8
10-2
6-6
5-8
0-73

1-1
3-29

987-4
12-5
6-2
6-4
6-0
0-42

991-4

8-6

5:6

1-9

2-39

992-6
7-4
0-6
6-8
6-4
0-45

17

0-78

992-6
8-1
4-0
4-1
3-6
0-54

17

0-85

978-8
21-2

11 :0

984-7
15-3
1-9
13-4
127
0-68

986-3
137
4-3
9-4
9-0
0-44

957-2
12-8
3-4
9-4
9-3
0-17

7-06

10-8

8-14

1 Maly, Hermann's "Handbuch," Bd. v. (2), S. 19.

2 Hoppe-Seyler, " Physiol. Chem.," Bd. ii. S. 191.

3 Lassaigne, cited by Maly, loc. cit. 4 Loc. cit. 5 Maly, loc. cit.

6 Hermann's "Handbuch," Bd. v. (2), S. 16, 17; Hoppe-Seyler, "Physiol. Chem.,"
Bd. ii. S. 198, 199.

348

CHEMISTRY OF THE DIGESTIVE PROCESSES.

This table shows the results obtained by Werther 1 in four experiments on
dogs, in which all three kinds of saliva were collected and analysed. The results
have been placed in a similar form to that of the other tables, for ease of com-
parison. It should be observed that the sublingual saliva was barely alkaline
in all four experiments, while the submaxillary saliva was only so in one
experiment; that the sublingual saliva contains in spite of its viscidity no
more organic matter than the others, while it does contain much more
chlorides. Human sublingual saliva has never been obtained in sufficient
quantity for analysis.

TABLE IV.

BUCCAL Mucus.

Water

Total solids

Organic matter —

(a) Soluble in alcohol ,

(b) Insoluble in alcohol ....
Inorganic salts —

Chiefly chloride and phosphate of sodium

From Bidder and Schmidt, quoted by Maly.2

990-02

1-67
2-18

6-13

TABLE V.
MIXED SALIVA.

I.

II.

III.

IV.

v.

VI.

VII.

Water ....

992-9

995-1

994-1

988-3

994-7

994-2

989-6

Total solids

7-1

4-84

5-9

117

5-3

5-8

10-3

Suspended solids (epithe

lium, mucus, etc.) .

1-4

1-62

2-13

2-2

Soluble organic matter

3-8

1-34

1-42

3-27

1-4

3-58

Potassium sulphocyanide

0-06

o-io

0-04

Inorganic salts .

1-9

1-82

2-19

1-03

2-2

6-79

ASH OF MIXED SALIVA.

Human.

Dog.

Total solids (in 1000 parts

of saliva)

1*82

6-79

Phosphoric acid .
Soda ....

0-51\
0-43J

0-82

Lime ....

Magnesia

0'03\

o-oij

0'15

Alkaline chlorides

0-84

5-82

Analyses I. to VI. are of human saliva by Berzelius, Jacubowitsch, Frerichs,
Tiedemann and Gmelin, Herter, and Hammerbacher respectively. Analysis
VII. is of dog's saliva by Schmidt. The table is taken from Maly,8 except
Analysis VI., which is from Hammerbacher.4 The analyses of ash are by
Jacubowitsch.5 In 1000 parts of the ash of mixed human saliva, Hammer-
bacher6 found 457-2 of K90, 95'9 of Na20, 50-11 of Fe203, 1-55 of MgO,
63-8 of S03, 188-48 of P20,T, and 183-5 of chlorine.

1 Arch.f. d. ges. PhysioL, Bonn, 1886, Bd. xxxviii. S. 293.

2 Hermann's " Handbuch, " Bd. v. (2), S. 20.

4 Ztschr. f. physioL Chem. , Strassburg, Bd. v.

5 Maly, loc. cii.

3 Ibid. Bd. v. (2), S. 14.

GASTRIC JUICE. 349

GASTRIC JUICE.

Human gastric juice mixed with water or food may be obtained
for clinical purposes by the use of a gastric sound or the stomach pump,
but pure gastric juice cannot be obtained in this way, because when the
stomach is empty the secretion of gastric juice stops, and can only
be initiated by the drinking of water or the taking of food.1

Notwithstanding the considerable number of cases of gastric fistula
in man already enumerated, the details as to the quantitative chemical
composition and physical characteristics of that fluid are very meagre.
Only one set of complete analyses of the fluid has been carried out by
Schmidt, and these, along with certain incomplete analyses by other
observers of the total solids and amount of acid, are all the quantitative
data we possess.

In a case of human gastric fistula, observed by C. Schmidt,2
the fluid obtained was clear as water, less acid than dog's gastric juice,
and had a specific gravity of 1 -0022-1 -0024. It scarcely became clouded
on heating, and left on evaporation a brownish-yellow deliquescent acid
residue, which on incinerating left a colourless, neutral, or faintly alkaline
ash, containing no carbonates. On distilling the liquid, only water
came over, until the fluid attained the consistency of oil, then traces of
hydrochloric acid, which became stronger as the process was continued.

In a case observed by Eichet, in which the oesophagus had been
occluded by strong alkali, and the gastric fistula was the result of an
operation, the gastric juice was also colourless, had a faint smell, and
varied greatly in acidity.

Pure gastric juice has also recently been obtained by Fremont 3 from
a fistula in the isolated stomach of the dog. Gastric juice so obtained
is a limpid, clear, colourless, inodorous, very acid, and powerfully peptic
fluid, capable of digesting its own weight of coagulated albumin. The
dog in question weighed 12 kilos., and yielded 800 grms. of gastric
juice daily. If the secretion takes place at the same rate in the human
subject, a man weighing 60 kilos. (132 Ibs.) should secrete 4 litres
of gastric juice daily.

Pure gastric juice may be collected from a Pawlow fistula 4 twelve to
fifteen hours after a true meal, by giving the animal a fictitious meal.
The food which is eaten does not reach the stomach, but drops from
an cesophageal fistula. The process of feeding induces reflexly an
abundant secretion of gastric juice, which can be collected in a pure
condition. A dog will go on feeding voraciously in this manner for
hours, and in the course of an hour 200-300 c.c. of gastric juice may be
collected. The animal is said to be unaffected in health by a collection
of an hour per diem.

1 This method is of more service clinically than physiologically as a mode of obtaining
gastric juice in cases of dyspepsia, in order to determine the amount of acidity, and whether
this is due to a normal amount of hydrochloric acid or to excess of organic acids, the pro-
duct of bacterial action. See Leube, Sitzungsb. d. phys.-med. Soc. zu Erlangen, 1871.
Heft 3; Kiilz, Deutsche Ztschr. f. praTct. Med., Leipzig, 1875, No. 27; C. A. Ewald,
" Klinik der Verdauungskrankheiten," 1890, Bd. i. S. 87; Gamgee, "Physiological
Chemistry," vol. ii. pp. 163-178.

2 The case was that of a healthy woman with a chronic fistula, yielding gastric juice
freely without apparent effect on the health of the patient.

3 Demonstrated by Herzen, International Congress, Bern, 1895.

4 Pawlow and Schoumow-Simanowsky, Centralll. f. PhysioL, Leipzig u. "VVien, 1889,
Bd. iii. S. 113. See article on "Mechanism of Gastric Secretion."

35°

CHEMISTRY OF THE DIGESTIVE PROCESSES.

Konowaloff l collected over 10 litres, as above described, and sub-
jected the fluid to chemical examination. It was a clear, colourless,
odourless fluid, which could be kept indefinitely without undergoing
decomposition. When diluted with its own volume of water, it becomes
somewhat cloudy ; with four volumes of water, a permanent opalescence
resulted, which on further dilution eventually disappeared. On neutral-
ising with alkali, a flocky precipitate appeared, redissolving in the slightest
excess. Cooling the juice to 10-11° C. caused a finely granular precipit-
ate to appear, which dissolved again on warming. Its specific gravity
averaged 1*00478 ; total solids, 0*478 per cent. ; acidity, equivalent to
0*544 per cent, of hydrochloric acid. When the acid gastric juice is so
removed the reaction of the urine becomes alkaline2 (0*96-1*31 per cent,
of Na20).

Freshly secreted gastric juice is «aid to contain traces of proteid,3
which, on standing, is converted into albumoses and peptones ; these, with
traces of mucin, and the two enzymes, pepsin and rennin, are the only
organic constituents.

The inorganic salts consist chiefly of chlorides (with traces of phos-
phates) of sodium, potassium, and calcium, and traces of magnesium
and iron.

The total amount of solids in gastric juice is very small, seldom
amounting to more than 2 per cent., and often being much less. Excess
of alcohol causes a flocky precipitate containing all the organic matter.

Alkalies and alkaline carbonates added to gastric juice cause a
cloudiness or a flocky precipitate of tricalcic phosphate, with traces
of phosphates of iron and magnesium, and some organic matter. The
precipitation of tricalcic phosphate by ammonia shows that calcium is
present as acid phosphate in gastric juice.

Quantitative Composition of Gastric Juice.

i.

II.

III.

IV.

Human.

Dog.

Dog.

Sheep.

Water .

994-40

973-06

971*17

986-14

Total solids

5*60

26-94

28-83

13-86

Organic matter

3-19

17-13

17*34

4-05

HC1 .

0-20?

3-34

2-34

1-23

CaCl2 .

0-06

0-26

1-66

0-11

NaCl .

1*46

2-50

3-15

4-37

KC1 .

0-55

1-12

1-07

1-52

NH4C1

Ca3(POJ2)
Mg3(POJ2
FeP04

0*125 J

0-47
1-73
0-23
0-08

0-54
2-29
0-32

0-12

0-47
1-18
0-57
0-33

The analyses are by C. Schmidt, quoted from Maly, Hermann's "Handbucli," Bd. v. (2)
S. 70 ; Ann. d. Chem., Leipzig, 1854, Bd. xcii. S. 42 ; and " Verdauungssafte," S. 44.

Analysis I. is of human gastric juice, obtained from Schmidt's case of
gastric fistula already quoted • it is evident that this gastric juice contained

1 Inaug. Diss., St. Petersburg, 1893; Jahresb. it. d. Fortschr. d. Thier-Chem., Wies-
baden, 1893, Bd. xxiii. S. 289.

2 Schoumow-Simanowsky, Arch, de sc. bioL, St. Petersbourg, 1893, vol. ii. p. 462.

3 Hammarsten, "Lehrbuch der physiol. Chem.," Wiesbaden, 1895, Aufl. 3, S. 233.

THE ACID OF THE GASTRIC JUICE. 351

much saliva, as the total solids and amount of acid are much less than those
usually found. Analyses II. and III. are of dog's saliva. Analysis II. gives
the mean of ten determinations, in the case of a dog in which all the salivary
ducts had been ligatured. Analysis III. gives the mean of three, in the case of
a dog with normal salivary glands. Analysis IV. is that of the gastric juice
of a sheep.

The acid of the gastric juice. — The acid of the gastric juice
has probably given rise to more discussion than any other subject in
physiological chemistry. The principal points for consideration are —
(a) the nature of the acid ; (&) the seat of formation and the mode of
origin of the acid ; (c) the function of the acid.

The nature of the acid. — Before discussing this question in detail,
it may be well to state clearly the present state of opinion on the
subject.

It has been demonstrated that hydrochloric acid is the principal acid
of the gastric juice, and that in the purer samples free from food it is
always present, and is almost exclusively the only acid present ; while in
gastric juice mixed with food, especially with carbohydrate food, it may
be, and often undoubtedly is, accompanied by lactic acid. C. Schmidt,
from a large number of painstaking and laborious analyses, concluded
that the pure gastric juice of carnivora, obtained after a fast of eighteen
to twenty hours, contains only hydrochloric acid, and no trace of lactic or
acetic acids ; while the gastric juice of herbivora contains, besides hydro-
chloric acid, small quantities of lactic acid, but this is even then probably
from remnants of carbohydrate food.1

Prout,2 in 1824, first showed that gastric juice contains free hydro-
chloric acid by the following method : —

The contents of a stomach were mixed up with water, and, after the
mixture had settled, the clear part was removed by decantation. This
was divided into three equal portions, a, &, and c.

(a) The first portion was evaporated to dryness, incinerated, and the
total amount of chlorine in the ash determined by weighing, as silver
chloride.

(&) The second portion was first made alkaline by the addition of
potash, then evaporated to dryness, incinerated, and the total chlorine
determined as before.

(c) In the third portion, the total acidity was determined by titration
against standard alkali, and reckoned as hydrochloric acid.

In portion (a) all the free acid is driven off as well as any which may
be combined with volatile or decomposable bases (such as ammonium
chloride) ; in portion (&) all the chlorine remains, that which was either
free or combined with ammonia becoming converted into non-volatile
potassium chloride ; therefore the difference of (&) and (a) gives the free
hydrochloric acid, plus any volatile chlorides which may be present. In
(c) all the acid is estimated as hydrochloric acid, and by subtracting
this from the difference of (I) and (a) the amount present as volatile
chlorides is obtained.

Prout also showed that when gastric juice is distilled, towards the

1 The stomach of the herbivora retains food for a ranch longer period than that of
carnivora. Traces of food are usually found in the stomach of the sheep even thirty-six
hours after a meal. See Cl. Bernard, "Lemons de physiol. expe*r." 1856, tome ii. p.
389.

2 Phil. Trans., London, 1824, part i. p. 45.

352 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

end of the process hydrochloric acid passes over. In addition, he tried
to obtain lactic acid from gastric juice, but with negative results.

The remarkable results so obtained by Prout were confirmed by
Children1 in England, by Braconnot2 in France, and by Dunglison
and Emmet,3 with gastric juice obtained from Beaumont's case of
fistula.

When the period at which they were carried out is considered, it
must be admitted that these experiments of Prout were most ingenious,
and he well deserves the honour of being the first to awaken the minds
of men to the conception that the animal organism was capable of
producing such a substance as hydrochloric acid.4 Physiological chemists,
however, were chary in believing that the gentler forces of the animal
organism were capable of producing such a substance as hydrochloric
acid, which they were unable to obtttin experimentally except by the
use of potent inorganic reagents. Accordingly, objections flowed in
against Prout's work.

Claude Bernard and Barreswil 5 showed that when sodium chloride
was added to a solution of lactic acid, and the mixture distilled, hydro-
chloric acid appeared in the distillate towards the end of the process
when the mixture was beginning to grow solid. They concluded that the
free acid of the gastric juice was lactic acid. Lehmann 6 ascribed the
free hydrochloric acid of Prout's distillation experiment to the action of
the lactic acid, concentrated by evaporation, on the calcium chloride also
present in gastric juice. Many other observers were also -agreed that
the free acid in gastric juice was lactic acid.7 Blondlot 8 about this time
enunciated the hypothesis that the acidity of the gastric juice was due
in part to acid calcium phosphate, and evolved a theory, closely
resembling a much more recent one by Maly, as to the origin of the
acid by the formation of this substance, accompanied by traces of hydro-
chloric and phosphoric acids in the stomach wall, from the sodium
chloride and calcium phosphate of the blood.9 In presence of hydro-
chloric acid it is now known that part of any calcium phosphate present
would be resolved into acid phosphates, but the amount of calcium
phosphate present in gastric juice is altogether insufficient to account for
any appreciable part of its acidity.

While the subject was still in this vexed condition, Bidder and
Schmidt's 10 classical work on digestion appeared, containing the results
of Schmidt's experiments, to which reference has already been made. As

1 Annals of Philosophy, July 1824.

2 Ann. de chim., Paris, 1835, tome lix. p. 348.

3 Published with Beaumont's results, 1834.

4 As is often the case in great discoveries, Prout seems not to have been much in time
ahead of his fellows. Tiedemann and Gmelin state in the preface to their classical work,
"Die Verdauung nach Versuchen," 1826 (while admitting Prout's priority), that independ-
ently they had found hydrochloric acid in distilling various gastric fluids, and a month
later first saw Prout's publication. However, Prout was clearly ahead of them, both in the
distillation method, and in its ingenious confirmation by analytical results, as described in
the text.

5 Compt. rend. Acad. d. sc., Paris, 1844-5 ; "Legons de physiol. exper. applique" a la
me"d.," 1856, tome ii. p. 397.

6 Ber. d. Sachs. Gesellsch. d. Wissensch., Leipzig, 1847.

7 Pelouse, Compt. rend. Acad. d. sc., Paris, tome xix. p. 1227; Thomson, Lcmd.
Edin. and Dub. Phil. Mag., London, 1845.

8 "Traite analytique de la digestion," 1843; Jahresb. ii. d. Fortschr. d. ges. Med.,
Erlangen, 1851, Bd. i. S. 97 ; 1858, Bd. i. S. 37.

9 See p. 361.

10 "Die Verdauungssafte und der Stoffwechsel," Mitau u. Leipzig, 1852, S. 44.

THE ACID OF THE GASTRIC JUICE. 353

the result of eighteen concordant analyses, Schmidt found that gastric
juice always contained more hydrochloric acid than was sufficient to
neutralise all the bases present, and that the excess of hydrochloric acid
was alone sufficient to account for the entire acidity of the gastric juice.
Schmidt's course of procedure was as follows : —

The total chlorides in a weighed quantity (100 grms.) of gastric juice
were precipitated and weighed as silver chloride in the usual fashion, by
adding a drop or two of nitric acid followed by slight excess of silver nitrate
solution. From the nitrate the excess of silver nitrate was removed by addi-
tion of pure hydrochloric acid, as silver chloride ; and the filtrate, containing
all the bases of the gastric juice, was evaporated to dry ness, ignited, and the
amount of each separate base in the ash determined by appropriate methods.
In many cases the percentage of ammonia present was also determined in a
different portion as ammonio-platinic chloride.

The amount of hydrochloric acid present, combined and uncombined, was
found from the weight of the first silver chloride precipitate ; the weight of
chlorine necessary to combine with the weight of each base present was next
calculated, on the assumption that all of each base was actually present as
chloride ; and by adding all these weights of chlorine the amount of chlorine
(and hence hydrochloric acid) necessary to satisfy all the bases was determined.
This was found to be considerably less than the total chlorine present ; in fact,
the difference in the two amounts represented very accurately the total acidity
reckoned as hydrochloric acid.

The argument underlying Schmidt's experiments cannot be gainsaid,
and as the experimental part of his work was confirmed by other
observers,1 there remained no choice but to accept the presence of
hydrochloric acid in the stomach as proven. This view accordingly
gained ground after the publication of his results, and is now universally
accepted.

Although Schmidt's experiments demonstrate that there is an excess
of hydrochloric acid in gastric juice, uncombined with inorganic bases, they
do not show that this excess of acid is entirely uncombined. It is
certain that if the excess of acid is in chemical combination with any-
thing, the compound so formed is a very unstable one ; this is shown by
the ease with which the acid combines with fixed alkalies, and by the
persistence of the acid reaction in spite of the combination. Still there
are clear grounds for believing that the hydrochloric acid is in most
cases combined loosely with some other body, most probably albumose
or peptone, which are always present in traces in gastric juice. These
reasons are as follows : —

1. Organic acids do not dissolve calcium oxalate, but a solution of
hydrochloric acid in water, containing one part of acid in a thousand
parts of water, does dissolve this compound. Now gastric juice does not
dissolve calcium oxalate, from which Bernard and Barreswil 2 argued that the
acidity of gastric juice is not due to hydrochloric acid. This difference in
action on calcium oxalate of (a) a solution of hydrochloric acid in water, and
(b) gastric juice, is, however, probably due to the presence of albumoses and
peptones, which form a loose combination with the acid, of sufficient stability
to prevent it from acting on calcium oxalate.

1 Cb. Richet, " Le sue gastrique chez 1'homrae et les animanx," Paris, 1878, p. 32;
Maly, Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 227.

2 01. Bernard, "Lecons de pliysiol. exper.," 1856, tome ii. p. 395.

VOL. I.— 23

354 CHEM1STR Y OF THE DIGESTIVE PROCESSES.

2. Laborde l compared the inverting power of gastric juice on cane-sugar
with that of a solution of pure hydrochloric acid in water, of equal acidity to
the gastric juice, and under similar conditions. He found that the hydro-
chloric acid inverted much more rapidly than the gastric juice, which
possessed much the same inverting power as a solution of lactic acid of equal
concentration. He also found that gastric juice converted starch into grape-
sugar and dextrin much more slowly than a solution of hydrochloric acid
under similar conditions. On the other hand, Szabo 2 found that peptones do
indeed interfere with the action of dilute hydrochloric acid on starch ; but,
contrary to Laborde, found that the action of gastric juice on starch lies in
intensity much closer to that of hydrochloric than to that of lactic acid.

3. In treating of the digestive enzymes, it has been seen that these are
much less injured by hydrochloric acid, in presence of albumoses and peptones,
than by free hydrochloric acid alone, which shows that hydrochloric acid in
presence of albumoses and peptones berfkves as if it entered into combina-
tion with them.

4. Berthelot and Jungfleisch 3 showed that, when a substance which is
soluble in each of two solvents, which are not completely soluble in each
other, is shaken up with a quantity of both solvents, it divides itself between
the two solvents so that the ratio of its concentrations in each is constant, and
does not vary with the proportion of the two solvents used, nor the amount of
soluble material used. This constant ratio they called the coefficient de
partage, which may be rendered in English "coefficient of distribution."4
For example, if succinic acid be well shaken up with water and ether, the
concentration of succinic acid in the watery layer will always be about six
times as great as in the ethereal layer, no matter, within wide limits,5 what
have been the quantities of ether, water, and succinic acid used; the co-
efficient of distribution is here six. Mineral acids are much more soluble in
water compared with ether than are organic acids ; accordingly the co-
efficients of distribution of the mineral acids for these two solvents are
much larger than those of the organic acids.

Richet 6 made use of this property to test whether pure gastric juice con-
tains only hydrochloric acid, or hydrochloric acid plus organic acids. He
found that the coefficient of distribution was 137*1. To a portion of the
same gastric juice he next added barium lactate, and found that the co-
efficient was reduced to 9*9, that of lactic acid is 8*8 to ll'O. This experiment
shows that the acid first present was a mineral acid, which afterwards dis-
placed nearly all the lactic acid from combination, so that in the second case
the acidity was mainly due to lactic acid. Richet further added sodium
acetate (a) to a solution of hydrochloric acid in water ; (b) to gastric juice of
equal acidity, and found that in the first case the coefficient was reduced to
1*7 (practically that of acetic acid, 1*4), while in the second case the co-
efficient was only reduced to 5 to 5 '8. Richet supposes that this difference is
due to the hydrochloric acid in the gastric juice being combined feebly with
some other substance.- When sodium acetate is added to hydrochloric acid
alone, the base will be shared between the two acids in proportion to their
mutual avidities for it, which are in the ratio of 1 to '03. That is to say, about

1 Gaz. med. de Paris, 1874, Nos. 32-34, pp. 399, 411, 422.

2 Ztsclir. f. pliysiol. Chem., Strassburg, 1877, Bd. i. S. 140.

3 Ann. de chim., Paris, 1872, Ser. 4, tome xxvi. p. 396. For a complete account of
this subject, see Ostwald, " Lelirbucli der allgemeinen Cliem.," Leipzig, 1891, Aufi. 2,
Bd. i. S. 809.

4 This term has been proposed by Gamgee, "Physiological Chemistry," vol. ii. p. 97,
as well as "coefficient of repartition. "

5 The quantities of solvent must be so chosen, compared with the quantity of soluble
substance, that the solutions are not too concentrated.

6 "Le sue gastriqne chez 1'homme et les animaux, ses proprietes chemiques et physio-
logiques," Paris, 1878, p. 37.

THE ACID OF THE GASTRIC JUICE. 355

97 per cent, of the base will be combined with the hydrochloric acid, and
3 per cent, with the acetic acid ; or, otherwise, 3 per cent, of the hydrochloric
acid will be free and 97 per cent, of the acetic acid, supposing that equivalent
quantities of the two acids are present.1 Such a mixture would possess only
a slightly higher coefficient of distribution than acetic acid. But if the
sodium acetate be added to hydrochloric acid, already feebly combined with
something else, the power of the acid to combine with the sodium will be
diminished, on account of the tendency to remain combined with this sub-
stance, and the amount of hydrochloric acid uncombined with sodium will be
increased ; this will remain to a greater extent in the watery layer, and on
shaking with ether the coefficient of distribution will be much greater than
that of acetic acid.

Richet found traces of leucine in the gastric mucous membrane^ and be-
lieves, mainly on this ground, that the hydrochloric acid of the gastric juice
is in combination with leucine. But there is no good reason for going so far
afield to seek a partner for the hydrochloric acid; any substance in combination
with the acid would produce such an effect as Richet obtained, and it is far
more probable that the hydrochloric acid is in combination with the albumoses
of the gastric juice than with leucine, especially as leucine has not been found
in gastric juice, and hydrochlorate of leucine does not act as an acid to pepsin,
as shown by the inability of a mixture of the two to digest proteids.2

This account of Eichet's work has been placed here on account of the bear-
ing of the latter part of it on the question of the combination of the hydro-
chloric acid, but the first part of it is also of great value in showing that pure
gastric juice is practically free from organic acid.

Organic acids present during carbohydrate digestion. — Although organic
acids are entirely absent in pure gastric juice, or at most are only present
in traces, this is by no means the case during digestion, especially of food
rich in carbohydrates.

The food passing into the stomach during a meal is alkaline in
reaction, by reason of the saliva with which it is abundantly mixed ; and
in addition, during and after a meal a considerable quantity of saliva is
swallowed by itself. As Beaumont 3 and others have shown, there is no
secretion of acid gastric juice when the stomach is empty, and although
active secretion begins with the arrival of the first portions of food in
the stomach, some time must elapse before the alkaline reaction of the
masses of food and saliva is neutralised by the acid of the gastric juice,
and a reaction due to free hydrochloric acid established, after saturation
of the soluble proteid of the food. This interval is exceedingly difficult
to estimate, the delicate colour reactions for free hydrochloric acid being so
deceptive in a heterogeneous fluid like the contents of a stomach ;
van de Velden 4 states that it varies from half an hour to two hours,
and is on an average three-quarters of an hour. During this time con-
version of starch by ptyalin goes on,5 and in addition bacterial action
begins with the production, from the carbohydrate part of the food, of
lactic acid,6 accompanied by traces of butyric and acetic acids.

1 J. Thomsen, " Thermochemische Untersuchungen," Ann. d. Phys. u. Chem., Leipzig,
1869-1871, Bde. cxxxviii.-cxliii.

2 See Gamgee, "Physiological Chemistry," vol. ii. pp. 97-99.

3 See article on " Mechanism of Gastric Secretion."'

* Ztschr.f. physiol. Chem., Strassburg, 1878, Bd. ii. S. 205.

fi See under " Ptyalin," p. 329.

6 According to Maly, the greater part of the lactic acid is the ordinary lactic acid of
fermentation, but this is accompanied by a smaller quantity of sarcolactic acid, which may
occasionally be much increased in amount, Ber. d. deutsch. chem. Gesellsch., Berlin, 1874,
S. 156 ; Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 227.

356 CHEM1STR Y OF THE DIGESTIVE PROCESSES.

It was long believed that this action was due to the growth of the
Bacillus acidi lactici on sugar only, either that of the food or that produced
by the action of ptyalin on the starch of the food. Briicke * has shown,
however, that starch can be also changed into lactic acid without con-
version by ptyalin, by demonstrating that soluble starch, erythrodextrin
and lactic acid, are found in the stomach of the dog after a meal contain-
ing boiled starch. Now the saliva of the dog contains 110 ptyalin, so that
these products must be formed directly from starch. Traces of sugar
are also found, and Briicke supposes that sugar is first formed by the
action of the bacterium but immediately becomes converted into lactic acid
by its further action. A similar change in starch paste takes place on
standing in the air.

Goldschmidt 2 divides gastric digestion in the horse into four stages,
which are, however, not sharply markea off, but merge into one another.
(1) No proteolysis, acid reaction due to lactic acid. (2) Proteolysis
and amylolysis proceed together, both lactic and hydrochloric acids
present. (3) Stoppage of amylolysis in the middle part of the stomach,
in this portion only hydrochloric acid, elsewhere lactic acid. (4) Stop-
page of amylolysis everywhere ; hydrochloric acid only present in all
parts of the stomach. Ewald and Boas3 describe a similar state of
affairs in the healthy human stomach under normal conditions after
a carbohydrate meal. In the first stage (from ten to thirty minutes after
the meal) lactic acid alone is present ; in the second, lactic and hydro-
chloric acids are present together, but the former rapidly disappears so
soon as any free hydrochloric acid is present ; and in the third stage,
hydrochloric acid alone is present. This disappearance of the lactic acid
is very interesting, as showing that it is rapidly absorbed in the
stomach.

Other inorganic acids free in pure gastric juice besides hydrochloric
acid. — It must not be assumed, from the usual mode of stating the
results of quantitative analysis of gastric juice,4 that hydrochloric acid is
the only inorganic acid present in the gastric juice. All the phosphoric
acid is not united, in the gastric juice, to calcium, magnesium, and iron
to complete saturation, as usually set forth in such analytical results ;
nor are all the bases saturated by the hydrochloric acid, and only that
amount of hydrochloric acid free, which is left over after so saturating
them.5 Suppose a solution in water of neutral chlorides is taken, say
such a solution as the gastric juice would be, minus its free hydrochloric
acid and its phosphates, and to this phosphoric acid is added. As soon

1 Briicke, Sitzungsb. d. k. AJcad. d. Wissensch. , Wien, 1872, Bd. Ixv. Abth. 3, S. 126 ;
" Vorlesungen," Wien, 1885, Aufl. 4, Bd. i. S. 321. See also W. de Bary, Arch. f. exper.
Path. u. PharmakoL, Leipzig, 1886, Bd. xx. S. 243.

2 Ztschr. f. physioL Chem., Strassburg, 1886, Bd. x. S. 361. See also Ellenberger and
Hofmeister, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1885, Bd. xv. S. 284, 301 ;
1886, Bd. xvi. S. 260, 261.

3 Virchow's Archiv, 1885, Bd. ci. S. 325 ; 1886, Bd. civ. S. 271 ; Ewald, " Kliiiik der
Verdauungskrankheiten," 1890, Bd. i. S. 83.

4 See p. 350.

5 This was merely an assumption made by Schmidt, in order to conclusively show that
gastric juice contained an excess of hydrochloric acid above even this quantity. Fortunately,
the excess of hydrochloric acid was sufficient to allow Schmidt to give this form of proof ;
but if the quantity of phosphates had been greater, or the excess of hydrochloric acid less,
Schmidt's process might easily have yielded a negative result, and yet the gastric juice
have contained free hydrochloric acid ; indeed, the massed equivalent in chlorine of the total
bases might have been greater than the total quantity of chlorine present, and still there
might have been free hydrochloric acid present.

THE ACID OF THE GASTRIC JUICE. 357

as the phosphoric acid passes into solution, it no longer remains present
as free phosphoric acid, to the amount to which it has been added, but
reacts with the other salts present in solution, displacing a definite
amount of each metal from combination with chlorine, thus setting free
hydrochloric acicl and forming phosphates, so that there comes to be in
solution free hydrochloric acid and free phosphoric acid, combined
phosphoric acid, and combined hydrochloric acid (that is, chlorides and
phosphates). When a polybasic acid, such as phosphoric acid, is present
in solution, the matter is somewhat further complicated by there being
certain steps between free acid and combined acid, namely, acid salts ;
these also are represented in the distribution of bases among the acids,
so that there are in solution free acids, acid salts, and neutral salts. In
pure gastric juice, then, the acidity is in chief due to hydrochloric acid,
but also in part to acid phosphates and phosphoric acid, and the amount
of each of these free is perfectly determinate, and depends upon the
amount of each base and each acid present. For one fixed distribution
only can there be chemical equilibrium in the solution ; the introduction
of any salt, acid, or base into the solution will alter this equilibrium, and
a new distribution to suit the new conditions will occur, giving rise
again to equilibrium.

The facts stated above follow directly from Thomson's1 "avidity
law." Thomsen arrived at this law by comparing the amount of heat
set free when an equivalent weight of a base unites with a mixture of
equivalent weights of two different acids, with the amount set free when
it combines with each acid separately.2 The law is that no acid in solu-
tion is combined with the bases present, to the complete exclusion of
other acids, however weak (as it is popularly expressed), which may be
simultaneously present in the solution ; but the acids share the bases,
according to their different avidities. Thomsen worked out a number of
avidity coefficients. Those of the organic acids are much smaller than
those of the inorganic acids. Thus, taking the avidity coefficient of
hydrochloric acid as unity, that of oxalic acid is '25, tartaric acid "05,
acetic acid "03. These coefficients mean, for example, that if one
equivalent each of sodic hydrate, of hydrochloric acid, and of oxalic acid,
be mixed in solution together, four-fifths of the base is combined with
the hydrochloric acid and one-fifth with the oxalic acid, and con-
sequently one-fifth of the hydrochloric acid is free and four-fifths of the
oxalic acid.

Maly 3 has also shown qualitatively, by a method of diffusion, that
this displacement of a strong acid (i.e. acid with a large avidity co-
efficient) by a weak acid (acid with a small acidity coefficient) takes

1 " Thermochemische Untersuchungen," Ann. a. Phys. u. Chem., Leipzig, 1869-71,
Bde. cxxxviii.-cxliii.

'2 Let a be the amount of heat in heat units developed when, say, one equivalent of
NaOH in grammes combines with one equivalent of HC1, and b that when it combines
with an equivalent of HN03, c that when it partially combines with a mixture of one
equivalent of HC1 and one equivalent of HN03, also let x be the fraction which combines
with HC1. Then, since a is the amount of heat set free when a whole equivalent of
NaOH unites with HC1, a x will be that set free when the fraction x combines ; similarly
b (I -x) will he the amount set free by the combination of the fraction (1 -x} with HN03;
the sum of these two must equal c, the amount of heat actually observed ; therefore a x +
b (1 -x) = c, from which x and l-x can be determined. Their ratio is the measure of the
avidity of the two acids for combining with the base.

2 Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 250; Sitzungsb. d. k. Akad. d.
Wissenscli., Wien, 1874, Bd. Ixix. Abth. 3, S. 251 ; Ztschr. f. yflnjKiol. Chcm., Strassburg,
1877, Bd. i. S. 174.

358 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

place in solution. He dissolved sodium chloride and lactic acid together
in water, placed the solution in the bottom of a cylindrical vessel, and
then carefully poured a layer of distilled water on the top. After some
days, part of the upper layer was removed and analysed ; it was found to
contain more than sufficient chlorine to balance all the sodium present ;
that is to say, it contained free hydrochloric acid. Similar results were
obtained with a mixture of monosodium phosphate, and other acid salts,
in common solution with sodium chloride.

These results of Thomsen and Maly will be again referred to in
discussing the mode of origin of hydrochloric acid. They are introduced
here to show that any weaker acids in gastric juice along with the
hydrochloric acid must in part be uncombined. Any organic acids
present during digestion will also be inj^art free and in part combined,
and as these have very small avidities compared with hydrochloric acid,
they will be almost completely free. This has a bearing of some import-
ance. Any organic acids formed in the stomach by bacterial action on
carbohydrates will be found as free acids, and will not reduce the amount
of free hydrochloric acid,1 but salts of organic acids entering the stomach
with the food will reduce the amount of acidity due to free hydrochloric,
because, from the organic salts, free acids will be formed, by hydrochloric
acid combining with their bases.

Source of the hydrochloric acid. — The only possible source of chlorine
lies in the chlorides of the food, and from this either directly, or indirectly
through the blood, the hydrochloric acid must necessarily have its origin.
That the chlorides present in the blood plasma are the source of the acid,
has been experimentally proved by Voit 2 and Cahn.3

Following a method first used by Yoit, Cahn fed dogs exclusively
on meat which had previously had all its salts extracted by boiling it
repeatedly with distilled water. An animal fed in this manner continues
to excrete a diminishing quantity of chlorides in the urine for a period
varying from two to five days. After this only traces of chlorides are
found in the urine, but the tissues and blood still cling on to their
necessary minimum quantity of chlorides, digestion goes on, and the
animal lives. At this period, if the contents of the stomach are washed
out with distilled water, the secretion is found to contain free acid and
to possess digestive power. If now the animal's reserve stock of chlorine
be still further reduced by administering diuretics, such as potassium
nitrate, which cause some additional chlorides to be excreted ; or if free
hydrochloric acid be repeatedly removed by pumping out the contents of
the stomach with the aid of distilled water, a condition is finally reached
in which the stomach secretes a completely neutral fluid, which is
altogether inactive so long as it is neutral, but quickly digests fibrin if
1 part per 1000 of hydrochloric acid be added to it. When this
stage is reached the animal rapidly fails ; but if a small quantity of
sodium chloride be now given to it, it rapidly recovers, and soon becomes
in every respect normal.

This experiment also shows that the secretion of pepsin is independ-
ent of that of acid, and that in the absence of hydrochloric acid no

1 In fact will slightly increase it by combining to a certain extent with the bases of the
chlorides.

2 Sitzungsb. d. Jc.-bayer. ATcad. d. Wissensch. zu Miinchen, 1869, Bd. ii. S. 483. See
also M. Gruber, Bcitr. z. Pliysiol. C. Ludiuig z. s. Geburtst., Leipzig, 1887.

3 Ztschr. f. physiol Chem., Strassburg, 1886, Bd. x. S. 522.

THE ACID OF THE GASTRIC JUICE. 359

lactic acid or other organic acid is formed, which disproves the theory
that lactic acid is first formed and then decomposes sodium chloride, so
forming free hydrochloric acid.1

It may here be pointed out that experiments have been made by
Nencki and Schoumova-Simanowsky 2 to ascertain the possibility of
replacing the chlorine by other halogens, so as to form hydrobromic or
hydriodic acids. These experiments were performed on dogs operated
on by Pawlow's method,3 and the animals were fed with food in which
sodium chloride was as far as possible absent. Some had added to their
food sodium bromide, others sodium iodide. The administration of
sodium bromide resulted in the animals becoming so ill after a wTeek or
so that the experiments had to cease. The gastric juice was secreted as
before, but the hydrochloric acid was largely replaced by hydrobromic
acid. In the case of those dogs to which sodium iodide was administered,
though less general disturbance resulted from the administration than
was the case with sodium bromide, yet the amount of hydriodic acid
replacing hydrochloric acid was very small.

Reciprocity between the secretion of hydrochloric acid and the reaction
of the urine. — That the hydrochloric acid of the gastric juice is formed
from the chlorides of the blood plasma, is likewise shown by Maly's 4
observation that at the same period after a meal at which the secretion
of gastric juice is at a maximum, the acidity of the urine is at a minimum,
and may be replaced by an alkaline reaction. One function of the kidneys
is to preserve unaltered in degree the alkalinity of the blood. If now
neutral salts, such as sodium chloride, be removed from the blood, split
up in some manner by the agency of the gastric gland cell into hydro-
chloric acid and sodic hydrate, of which the hydrochloric acid is sent
towards the stomach cavity, while the alkali is expedited in the opposite
direction back to the blood stream, it follows that the alkalinity of the
blood will be increased. Hence, to preserve equilibrium, the kidneys
must excrete a less proportion of acid salts, or, if the rate of increasing
alkalinity of the blood demands it, must separate an alkaline fluid from
the blood. This is experimentally found to be the case. Under ordinary
circumstances, the kidneys preserve the constant value of the alkalinity
of the blood, by excreting phosphates of the alkalies so proportioned that
the reaction is acid, but during active digestion, 2 to 4 hours after a full
meal such as dinner, the relative amounts of bases and phosphoric acid
are so altered that the reaction becomes neutral or faintly alkaline, or, as
it is often commonly but not very exactly expressed, in the first case
monosodic phosphate (NaH2P04) is secreted with acid reaction ; in the
second, disodic phosphate Na2HP04 with alkaline reaction.5

Theories as to the mode of origin of the hydrochloric acid. — Many
ingenious theories have been proposed to account for the specific function
of the gland cells of the stomach, of splitting up such a stable substance

1 See p. 352.

2 Arch. f. exper. Path. u. PhartnakoL, Leipzig, 1894, Bd. xxxiv. S. 313.

3 See article on " Mechanism of Gastric Secretion."

4 Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 232. See also Quincke, JaJircsb. ii. d.
Fortschr. d. Thier-Chcm., Wiesbaden, 1874, Bd. iv. S. 241 ; Stein, ibid., 1876, Bd. vi.
S. 161.

5 The reaction will really vary according to the relative amounts of base and acid
present. Monosodic phosphate alone dissolved in water has an acid reaction, disodic
phosphate similarly has an alkaline reaction, and mixtures in varying proportions can
have acid, neutral, or alkaline reaction. In a complex mixture such as urine, no one can
say to what the reaction is due, but only that there is an excess of alkali or acid.

360 CHEMISTRY OF THE DIGESTIVE PROCESSES.

as sodium chloride, of forming such a strong acid as hydrochloric acid is
in the face of the alkalinity of the blood, and of determining an alkaline
stream towards the blood and an acid stream towards the lumen of the
gland.

The oldest theory was, that the process was an electrolytic one.
Blondlot1 supposed that by electric agency sodium chloride in the
stomach wall was broken up into sodic hydrate and hydrochloric acid
(in the language of to-day, hydrolysed, NaCl + H20 = NaHO -f HC1).
The free acid then, for the most part, acted on the calcium phosphate
of the blood, forming acid phosphate and a trace of phosphoric acid,
while a trace of hydrochloric acid also remained free. To such a mixture
of acid substances (mainly acid calcium phosphate) he ascribed the
acidity of gastric juice. He electrolysed tricalcic phosphate, suspended
in a solution of sodium chloride, aiicf claimed to have obtained such
products as his theory demands. Briicke 2 considered that the energy
required came from transformation of nervous energy, modified to this
purpose, and, admitting that the details are not explicable, compared the
effect to others called forth by nerve impulses, such as the electric effects
in the electric end-organ of some fishes. He also considered the secretion
of acid more analogous to electrolysis than to any other known process.
Lussana 3 supposed that in the glands of the stomach a decomposition of
the salts of the plasma took place, and that the preponderating part of
the free acid of the gastric juice was hydrochloric, simply because by far
the greater part of the salts of the plasma are chlorides. He tried to
test his theory by intravenous injection of salts not present in quantity
in blood plasma, such as sulphates and phosphates. He did not,
however, obtain the corresponding acids in the gastric juice, except
in the case of borax and tartar emetic, after injection of which traces
of boric and tartaric acids respectively were found in the gastric juice.

Buchheim4 suggested that the chlorides of the plasma combined
with the proteid, so that the metal combined with one proteid molecule
and the acid radicle with another ; the latter combination being absorbed
by the acid-secreting cells and broken up there into proteid and acid.

These older theories can at best be only regarded as mere specu-
lations ; there is absolutely no experimental proof of them. Nor can
we lay claim at the present day to a complete knowledge of the
process of secretion of hydrochloric acid. Only thus far the progress
of physical chemistry, and a more exact knowledge of the laws of
solutions, has brought us, that we no longer need look upon the
production of hydrochloric acid by the animal organism as a chemical
wonder. The secretion of hydrochloric acid is still a mystery as great
as the secretion of pepsin or any other product of cell activity, but
no greater.

To the chemist, before the therinochemical work of Thomsen, and
the diffusion experiments of Maly already described,5 and when he was
acquainted with no other means of setting free hydrochloric acid from
its salts than the electric current or displacement by a . stronger acid
such as sulphuric acid, the occurrence of hydrochloric acid in the gastric

1 " Traite analytique de la digestion," Nancy et Paris, 1843 ; Jahresb. u. d. Fortschr.
d. ges. Med., Eiiangen, 1851, Bd. i. S. 97 ; 1858, Bd. i. S. 37. See also Ralfe, Lancet,
London, 1874, vol. ii. p. 29.

2 "Vorlesungen," Wicn, 1885, Aufl. 4, Th. 1, S. 307.

3 Jdkrcsb. u. d. Fortschr. d. ges. Med., Erlangen, 1862, Bd. i. S. 110.

4 Arch.f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 332. 5 See p. 357.

THE ACID OF THE GASTRIC JUICE. 361

juice was an unsolvable riddle. But when Thomsen had shown that
the weakest acid is in some measure capable of displacing the strongest
from its salts, and Maly that by a simple process of diffusion this strong
acid may be afterwards separated, the subject assumed a different aspect.
It was no longer necessary for the cell to be endowed with some force
of sufficient intensity, to directly break up such stable substances as the
alkaline chlorides. All that was necessary was that the cell should be
able from the organic material at its disposal to form an organic acid,
and afterwards to rapidly excrete the small fraction of hydrochloric
acid formed by the interaction between this organic acid and the neutral
chlorides, so that a fresh quantity of hydrochloric acid may be formed
by the mass action of the remainder of the organic acid on the remainder
of the chlorides. The organic salts so formed can then decompose by
cell activity into organic acid and base again, and the base be returned to
the blood stream. Since gastric juice is not accompanied by an organic
acid, this must be retained in the cell and induce a continuous cyclic
change. It is thus possible, with the aid of the new facts of physical
chemistry, to see that the process of secretion of hydrochloric acid can
be reduced to the same level as that of the secretion of any organic
material.

This, however, is but a small portion of the entire problem. As Bunge
says: "In the appearance of the free hydrochloric acid lies nothing puzzling.
Puzzling only is the power of the epithelial cell to send the hydrochloric acid
freed from the sodium chloride streaming always in one direction towards the
lumen of the gland, and the sodium carbonate l simultaneously formed always
back in the opposite direction towards the lymph and blood channels. But
such a puzzle we meet everywhere in the living tissue. Every cell possesses
the power to dispose of material in a suitable manner, attracting or repelling
it and sending it streaming in different directions." J

Malys theory. — Maly has attempted to build on a purely physical
basis a theory of the formation of hydrochloric acid from the chlorides of
the blood, of which the following are the outlines : 3 —

l>There are no theoretically alkaline salts in the blood. Blood
plasma owes its alkalinity to two theoretically acid salts, di-sodic
phosphate (Na2HP04), and sodium bicarbonate (NaHC03); besides
these two acid salts plasma contains excess of carbonic acid.

2. Disodic phosphate in presence of calcium chloride forms some
free hydrochloric acid, thus:— 3CaCl9+2Na2HP04=Ca3(P04)2+4NaCl+
2HC1.4

Chiefly from the facts above stated, Maly supposes that by the
interaction of these theoretically acid salts of the plasma, on the chlorides
present with them in solution, traces of hydrochloric acid are formed ;
these traces of hydrochloric acid are rapidly removed, on account of the
high diffusibility of hydrochloric acid,5 by the gland-cells which act as a

1 Bunge is considering the hydrochloric acid as set free by the action of carbonic acid.

2 Somewhat freely translated from Bunge, " Lehrbuch der physiol. Chemie," Leipzig,
1894, Ann. 3, S. 148.

3 Abstracted, from Maly, Hermann's "Handbuch," Bd. v. (2), S. 66.

4 R. Pribram, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i. S. 107 ;
Gerlach, ibid., 1873, Bd. iii. S. 109.

5 Graham has shown that the free acids diffuse more rapidly than their salts ; HC1
diffusing thirty-four times as rapidly as NaCl. Graham was also the first to show that, by
diffusion of acid potassium sulphate, sulphuric acid was obtained in the dialysate, while
normal sulphate remained behind.

362 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

perfect diffusion l apparatus ; on the removal of the hydrochloric acid,
fresh acid is formed by further mass action on the chlorides. The
kidneys or sweat glands probably do not so secrete hydrochloric acid,
because they are not such perfect diffusion arrangements as the gastric
glands, and cannot bring about such a molecular separation as the latter.

Objections to Malys theory. — 1. Modern work has shown that the
alkaline reaction of theoretically acid salts is probably due to a hydro-
lysis taking place on solution. Thus on dissolving sodium bicarbonate
there are formed sodic hydrate and carbonic acid (NaHCO, + H20— NaOH
+ H2C03) ; and the sodic hydrate being a powerful base, and the car-
bonic acid a weak acid, one equivalent of the base more than balances
two of the acid, and the reaction is alkaline. On the other hand, when
acid potassium sulphate is dissolved, there is one equivalent in solution
of a strong base, and two equivalents of a strong acid, and the reaction
is acid. Such an hydrolysis of phosphates of the alkalies also takes
place. Trisodic phosphate yields an equivalent of base to one of acid,
and the reaction is intensely alkaline ; disodic phosphate yields only two
equivalents of base to three of acid, but the reaction is still alkaline ;
while monosodic phosphate yields but one equivalent of base to three of
acid, and at last the reaction is acid. A mixture of mono- and disodic
phosphates in proper proportion would be neutral. In fact, after these
salts are dissolved, they no longer exist as such, but there are present in
solution bases and acids in certain concentrations, and the reaction of the
solution will depend on which of these acts most strongly on the in-
dicator. Now the hydrolysing effect on the neutral salts, chlorides, etc,
(if such are also present in solution), of these so-called acid salts must
closely resemble their effect on the indicator.

Whether there will be a tendency to formation of hydrochloric acid
or not from sodium chloride, will be determined by whether the attraction
of the acids (phosphoric and carbonic) for the base is greater or less
than the attraction of the bases for the hydrochloric acid. The reaction
of the solution of phosphates and carbonates in the plasma is alkaline,
which shows that the latter is the case, and that, therefore, there will be
no hydrochloric acid formed.

2. The continuous formation of hydrochloric acid by a reaction
between disodic phosphate and calcium chloride is impossible, because it
necessitates the formation of insoluble tricalcic phosphate, and as the
supply of calcium chloride is small, must soon stop.

3. Even if it be admitted that there are traces of hydrochloric acid
in the blood, there is no reason, if the process be purely one of diffusion,
why it should not go on continuously. This it does not do, but ceases
when digestion is not going on, and when digestion begins is secreted in
such amount that no mere physical diffusion could bring it through the
epithelial cells fast enough ; not to speak of separating it from a fluid
in which it is supposed to be present in traces only.2

1 By a perfect diffusion apparatus (vollkommener Diffusions-apparat] Maly seems to
mean here semipermeable membrane ; that is, an arrangement permeable to the hydrochloric
acid and not to the other dissolved substances.

2 Gastric juice contains at least 2 parts per 1000 of hydrochloric acid ; the amount of
hydrochloric acid formed by mass action in a solution of 6 parts per 1000 of sodium
chloride, and a still smaller quantity of monosodium phosphates, no one has ever attempted
to measure, but it must be many thousand times less than this ; so that not only must the
hydrochloric acid diffuse with a tremendous velocity, but it must get infinitely more con-
centrated in the process of diffusion, which, under purely physical conditions, so far as
we know them, is an utter impossibility.

THE ACID OF THE GASTRIC JUICE, 363

These facts indicate that the formation of hydrochloric acid is a
process going on in the cell, that the acid is a cell secretion, and not a
diftusate from the blood plasma.

Gamgees modification of Malys theory. — Gamgee,1 while retaining
the supposition that the hydrochloric acid is formed by the action of
the alkaline phosphates on the chlorides, removes the seat of action from
the blood to the parietal cells. He supposes that these cells possess a
peculiar selective absorption for the phosphates of sodium, both alkaline
and acid, and for chlorides, and that within the cell there occur the
same reactions between these substances as occur in vitro when they
coexist in solution. One of the products of the reaction will then be
hydrochloric acid, which, in virtue of its high power of diffusion, will
pass, as soon as formed, into the secretion of the gland. This supposition
is certainly a step in the right direction, in so far as it brings the seat
of action to the cell — a much more probable place than the blood — but,
on the other hand, it assumes a good deal, without overcoming many of
the objections to Maly's theory. Thus, selective absorption, of both
alkaline and acid phosphates (probably di- and mono-sodium phosphates)
is assumed. Unless these are also assumed to be absorbed in such pro-
portions that the reaction of the cell contents becomes acid, no formation
of hydrochloric acid will take place, for, under merely physical conditions,
no such formation can be demonstrated in vitro.

Unless, again, the substances selectively absorbed are kept out of
action in some equally obscure manner by cell activity, there is no
reason why the secretion of acid should not be continuous ; and if absorp-
tion of phosphates and chlorides only begins at the commencement of
digestion, it is not easy to see how the traces of hydrochloric acid,
formed by such interactions, can keep pace with the demand then made
for hydrochloric acid.

Lastly, there is no experimental evidence that there is any such
selective absorption of phosphates and chlorides by the parietal cells.
And if a purely physical theory is to be abandoned, and a specific functional
activity of the cell invoked, there remains no reason for adhering to
theories which have been evolved on a purely physical basis.

It is easier, and more in accordance with our notions regarding the
secretion of other substances, to suppose that the hydrochloric acid
is formed by cell activity in some metabolic process, from the chlorides
and organic matters at its disposal. There are an infinite variety of
such processes capable of taking place, under the varying conditions of
cell life. It is true we do not know the details of these, nor why such
processes take place under certain given conditions ; nevertheless we
see the end-results, and there is no reason why hydrochloric acid should
not also be the end-product of such a cell metabolism rather than the
product of a kind of specialised diffusion.2

1 " Physiological Chemistry," 1893, vol. ii. p. 113.

2 Hammarsten, " Lehrbuch der physiol. Chem.," Wiesbaden, 1895, Aufl. 3, S. 242.
See also Heidenhain, Hermann's Handbuch," Bd. v. (1), S. 151. One such possible process
is the formation in the cell of an organic acid which does not diffuse away, but is retained
in the cell and' exercises a continuous action on the chlorides, forming hydrochloric acid
which the cell actively excretes. Another possibility would be the formation during
rest of an organic chlorine-containing substance, while the base combined with carbonic
acid passed into the blood, and the subsequent breaking up during activity of this
chlorine-compound yielding hydrochloric acid. There are indeed many courses which such
a cell-metabolism might take yielding hydrochloric acid as an end-result. See also Bunge,
''Lehrbuch der physiol. Chemie," Leipzig, 1894, Aufl. 3, S. 149.

364 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

Function of the hydrochloric acid. — One obvious purpose of the
hydrochloric acid of the gastric juice is to confer activity on the pepsin
accompanying it, which is only active in an acid medium. But, as
Bunge l points out, the establishment of an acid reaction is not necessary
for proteid digestion. In the pancreatic juice another proteolytic
ferment, trypsiii, is found, which acts most powerfully on proteids in an
alkaline medium. A much more important function of the hydrochloric
acid lies, according to Bunge, in its powerful action as a disinfectant
and germicide, in destroying bacteria introduced with the food. In this
manner the formation of decomposition products, and the disturbance
thereby produced in the normal course of digestion, is prevented, and
also in many cases the animal is preserved from the attacks of patho-
genic bacteria by the destruction of these or their spores.

Modern research has, in fact, led tf> the remarkable result, that the
average amount of hydrochloric acid found in the gastric juice just about
coincides with that which is found experimentally to be required to stop
the growth of most fermentative organisms and many pathogenic
bacteria.2

Spallanzani 3 first called attention to the powerful preservative action
of gastric juice, and not only showed that gastric juice prevented
putrefaction, but that it stopped putrefaction which had already com-
menced. This he showed by feeding dogs on pieces of flesh which had
commenced to putrefy. After a short interval of gastric digestion the
flesh lost all putrefactive odour.

The action of the gastric juice on the bacilli of tubercle and splenic fever
has been investigated by Falk,4 and by Frank.5 Falk found that the bacillus
of splenic fever (B. anthracis) is easily destroyed by gastric juice, but that
its spores escape destruction, and that the tubercle bacillus is unaffected by
gastric juice. Frank completely confirms these results, and both observers
are agreed that the gastric juice is incapable of making any very effectual
resistance to infection of the organism by these pathogenic bacteria. The
comma bacillus of cholera, however, is readily destroyed by gastric juice or
dilute hydrochloric acid.6 Cholera cannot be communicated by the mouth in
healthy animals ; but, after washing out the stomach with alkaline solutions,
symptoms resembling those of cholera follow introduction of a pure culture of
the cholera bacillus, as is also the case when this is introduced into the
intestine.

The acetic and lactic fermentations are stopped by mere traces of free
hydrochloric acid, while acid combined with proteid is ineffectual. According
to Cohn, this action is due to the free acid decomposing the alkaline phosphates,
which are necessary for the growth of the bacteria.7

Qualitative tests for free hydrochloric acid in gastric juice. — The
many colour tests for detecting the presence of free hydrochloric acid
in gastric juice, in contradistinction to organic acids, are all more or

1 "Lehrbuch der physiol. Chemie," 1894, Aufl. 3, S. 141-145.

a Sieber, Journ. f. prakt. Chem., Leipzig, 1880, Bd. xix. S. 433 ; Miquel, CenlralU. f.
(dig. Gsndlitspjlg., Bonn, 1884, Bd. ii. S. 403. See also Ziemke, Inaug. Diss., Halle, 1893 ;
Hester, Ztschr.f. klin. Med., Berlin, 1894, Bd. xxiv. S. 441 ; Schmitz, Ztscltr. f. physiol.
Chem., Strassburg, 1894, Bd. xix. S. 401.

3 " Experiences sur la digestion," Traduit par Senebier, Geneva, 1784.

4 Virchoufs Archiv, 1883, Bd. xciii. S. 177.

5 Deutsche mcd. Wchnschr., Leipzig, 1884, No. 20, S. 309.

6 Nicati and Lietsch, Rev. sclent., Paris, 1884, p. 658 ; Compt. rend. Acad. d. sc., Paris,
1884, tomexcix. S. 928; Koch, Deutsche med. Wchnschr., Leipzig, 1884, No. 45, S. 725.

7 Ztschr. f. physiol. Chem., Strassburg, 1890, Bd. xiv. S. 75.

THE ACID OF THE GASTRIC JUICE. 365

less influenced by the presence of proteid or peptone, and cannot be
much depended on for proving the entire absence of hydrochloric acid.
The quantity of organic acid required to give the reaction in each case is
much in excess of that present in the stomach, so that if the test gives a
positive result this may usually be relied upon.

The best of these reagents are the following : — (a) Gunnery's reagent,1
which consists of 2 parts of phloroglucinol, 1 part of vanillin, and 30 parts of
absolute alcohol. A few drops of this reagent and a few drops of filtered
gastric juice are evaporated to dryness together, when, if free hydrochloric
acid be present, a carmine-red mirror or carmine-red crystals are obtained.
The test is unaffected by organic acids, but does hot succeed in the presence of
proteids or leucine ; it is said to detect 1 part of free acid in 20,000. (b) The
tropceolin test. — Drops of a saturated solution of tropaeolin in methylated spirit
are allowed to evaporate on porcelain ; to the stain so left a drop of the solu-
tion to be tested is applied, and the drop is evaporated at 40° C. In the
presence of hydrochloric acid the result is a violet stain. The test has about
the same delicacy as Gunzberg's, and is subject to the same objections.
(c) Reoch's test 2 consists of a mixture of citrate of iron and quinine, and of
potassium sulphocyanide. This is coloured red by a trace of a mineral acid,
but not by dilute solutions of organic acid. Szabo 3 has modified this test into
a quick, colorimetric quantitative method. He finds the Reoch test a satis-
factory one, unaffected by chlorides, peptones, or the usual amount of lactic
acid present in gastric juice. (d} Congo-red is strongly recommended by
Gamgee,4 either in aqueous solution, or as test paper made by saturating filter
paper with it, and then drying. Traces of hydrochloric acid turn it an intense
blue, while organic acids give a violet tint.

Gentian-blue, methylaniline-violet, malachite-green, and benzo-purpurin
are other reagents which have been recommended as colour tests for traces of
free mineral acids.

Quantitative estimation of the free hydrochloric acid of the gastric juice. —
Mb'rn&r and Sjoqvist's method^ — This method consists essentially in con-
verting all the acids present into barium salts by shaking up with barium
carbonate, drying, incinerating, and extracting thoroughly with warm water.
In the process of incinerating, the barium salts of the organic acids which may
have been present are destroyed and barium carbonate is reformed ; the barium
chloride formed from the hydrochloric acid alone dissolves afterwards, and
gives, by estimating the barium, a measure of the amount of hydrochloric acid
present. Using litmus as an indicator, 10 c.c. of the gastric juice is neutralised
with finely-powdered barium carbonate in a platinum evaporating dish. The
mixture is dried on the water bath, the residue incinerated, the ash powdered,
extracted with as little warm water as possible, and finally filtered. The
filtrate should measure about 50 c.c. To this filtrate an equal volume of
absolute alcohol is added, and then three or four drops of a solution containing
10 per cent, each of sodium acetate and acetic acid. Into this solution a
standard solution of potassium bichromate, containing 8 '5 grins, per litre, is
run from a burette until all the barium is precipitated. The alcohol added
aids the precipitation, and the acetate solution prevents the precipitation of
calcium salts or the formation of any free hydrochloric acid. " Tetra

1 Chem. Centr.-Bl., Leipzig, 1887, S. 1560.

2 Jonrn. Anat. and Physiol., London, 1874, vol. viii. p. -274.

3 Ztsclir. f. physiol. Chem., Strassburg, 1877, Bd. i. S. 152.

4 "Physiological Chemistry," London, 1893, vol. ii. p. 94, where a full account of
these colour tests may be found.

5 Ztsclir. f. physiol. Chem., Strassburg, 1889, Bd. xiii. S. 1. See also Sjoq vis t, SJcandin.
Arch. f. Physiol., Leipzig, 1895, Bd. v. S. 277, where a full history of this subject is given,
and a bibliography of over 150 memoirs on the subject.

366 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

paper " l is used as an indicator ; this turns a deep blue when the end of the
reaction is reached.

Leo's methods — In this method two determinations are made. — First, of
the total acidity by titrating 10 c.c. of the gastric juice, after the addition of
5 c.c. of a concentrated solution of calcium chloride, with decinonnal sodic
hydrate solution, using litmus as an indicator. Secondly, the amount of
acidity due to acid phosphates is similarly determined in a fresh portion of the
gastric juice, after removing the acidity due to free acid by shaking up with
finely-powdered calcium carbonate. The difference gives the amount of acidity
due to free acid.

Toepfer's method3 consists in titrating 5-10 c.c. of the gastric juice against
decinormal caustic soda with different indicators — (a) with phenolphthalein,
(b) with alizarin, (c) with dimethylamido-azobenzol. The first titration
gives the total acidity (consisting of free ^hydrochloric acid, hydrochloric acid
combined with proteid, and organic acids) ; the second gives free hydrochloric
acid, plus organic acids ; the third, free hydrochloric acid only. Thus three
equations are given for the determination of three unknown quantities. The
method had been tested by Mohr with favourable results, and has the advan-
tage of rapidity.

Qualitative tests for lactic acid. — 1. Uffelmann's4 test consists of an
amethyst blue-coloured solution made by adding a trace of ferric chloride to a
1 per cent, solution of carbolic acid. A trace of lactic acid added to this
causes it to turn yellow ; hydrochloric acid only decolorises it, and must be
present in relatively large quantity to do so. The test is most safely applied
by filtering the contents of the stomach, extracting the filtrate with ether, dis-
tilling off the ether, extracting the residue with water, and adding this to a
small quantity of the reagent. The test shows with 1 part of lactic acid in
10,000. 2. A very dilute solution of ferric chloride, possessing only a trace of
colour, is much deepened in colour on the addition of a mere trace of lactic
acid.

PANCREATIC JUICE.

Normal pancreatic juice is difficult to obtain in quantity, on account
of the inflammatory changes occurring in the gland, in consequence of the
operation of inserting a cannula into the duct.5 The fluid obtained from
a fistula of the pancreatic duct in an animal is quite different, according
to whether it is collected soon after the operation, during the first two
or three hours, or after the lapse of a day or two. The fluid secreted
during the first few hours is rich in solids, and is secreted very slowly ;
that flowing from a permanent fistula is poor in solids, and is much more
copious. The temporary secretion probably resembles the natural pan-
creatic juice much more closely than the permanent secretion.

1 Paper impregnated with paraphenylendiamine. For modifications of this method
see Fawitsky, Virchoirfs Archiv, 1891, Bd. cxxiii. S. 292; von Jaksch, "Klin. Diagnostik
innerer Krankheiten, " 1892, Ann. 3 ; Boas, CentralbL f. Jclin. Med., Bonn, 1891, Bd. xii.
S. 33 ; Kossler, Ztschr. f. physiol. Chcm., Strassburg, 1893, Bd. xvii. S. 91.

2 CentralbL f. d. mecl. Wissensch., Berlin, 1889, Bd. xxvii. S. 481.

3 Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xix. S. 104; Mohr, ibid., S. 647.

4 Ztschr. f. klin. Med., Berlin, 1884, Bd. viii. S. 392.

5 The first to make a pancreatic fistula was de Graaf, 1664. For modern methods see
Cl. Bernard, "Le9ons de physiologic experimental, " Paris, 1856, tome ii. p. 180 ; Bern-
stein, Arb. a. d. physiol. Anst. zu Leipzig, 1869 ; Heidenhain, Hermann's " Handbuch,"
Bd. v. (1), S. 177; Piachford, Journ. Physiol., Cambridge and London, vol. xii. p. 80;
Vassiliew, Arch. d. sc. biol., St. Petersbourg, 1893, tome ii. p. 219; Fodera, Untersuch.
z. Naturl. d. Mensch. u. d. Thiere, 1896, Bd. xvi. S. 79 ; Lewin, Arch. j. d. ges.
Physiol., Bonn, 1896, Bd. Ixiii. For further details see article on "Mechanism of Pan-
creatic Secretion."

PANCREA TIC JUICE.

367

A temporary fistula should be made two or three hours after a meal,
and the fluid collected during the next two or three hours. The greater
number of such fistulse have been made on dogs. The fluid obtained is
clear like water, but of a slimy, syrupy consistency ; it becomes still
more viscid as it cools, and undergoes at 0° C. a true coagulation, separat-
ing into a gelatinous and a fluid portion. Its specific gravity is about
1*030. It contains in suspension white corpuscles, which exhibit sluggish
amoeboid movements. It is alkaline in reaction, the alkalinity being
equal to 0*2-0 -4 per cent, of NaHO, but the first few drops secreted may
be acid. The alkalinity is commonly said to be due to carbonates
and phosphates of sodium. The fluid is rich in proteid, froths on
shaking, and on heating to 75° C. coagulates to a solid white mass.
If kept warm for some time, its proteids become peptonised by the
trypsin present with them. On dropping into water a precipitate is
formed, which is soluble in dilute saline or acids. Alcohol gives
an abundant flocculent precipitate, mostly soluble in water, and con-
sisting of the proteid and enzymes. Leucine is present in traces,
but not tyrosine. Similar secretions have been obtained from many
other animals ; the pancreatic juice of herbivora (rabbit, ox, and sheep)
contains much less proteid than that of carnivora, but is in other
respects similar.

The permanent secretion sets in at a variable period, from a
few hours to some days after the operation. It is very similar
to the temporary secretion, except in containing much less organic
matter, and in having in consequence a much lower specific gravity,
1-010-1-011.

Quantitative chemical composition. — The following table gives the
results of analyses of both temporary and permanent secretions of dog's
pancreatic juice by C. Schmidt : l —

1. ANALYSES OF TEMPORARY SECRETION, OBTAINED
DIRECTLY AFTER THE OPERATION.

2. ANALYSES OF SECRETION, OBTAINED
FROM PERMANENT FISTULA.

a.

b.

a.

1.

c.

Water ....
Total solids .
Organic matter .
Ash .

900-8
99-2
90-4

8-8

884-4
115-6

976-8
23-2,
16-4
6-8

979-9
20-1
12-4
7 '5

984-6
15-4
9-2
6-1

3. COMPOSITION OF THE ASH (IN PARTS PER 1000 PARTS OF PANCREATIC JCICE).

(a) From Temporary
Secretion.

(6) From Permanent
Secretion.

Soda (Na20) ....
Sodium chloride
Potassium chloride .
Earthy phosphates with traces of iron
Trisodic phosphate (Na3P04) .
Lime (CaO) and Magnesia (MgO)

0'58
7-35
0-02
0-53

0-32

3-31
2-50
0-93
0-08

o-oi
o-oi

Quoted fromMaly, Hermann's "Handbuch," Bd. v. (2), S. 189.

368 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

These results show that, even in the same form of fistula, the amount of
total solids and of organic matter is a very variable quantity. This is also
shown by the results obtained by others. In the clog, Bernard found the
total solids in temporary secretion, 86 to 100 per 1000; Tiedemann and
Gmelin, 87 per 1000; Skrebitzki, 23 to 56 per 1000; in the sheep, Tiede-
mann and Gmelin, 36 to 52 per 1000; in the horse, Hoppe-Seyler, 8*88
organic, 8'59 inorganic, per 1000; in the rabbit, Heidenhain, 17'6 per 1000;
in the sheep, Heidenhain, 14 '3 to 36 '9 per 1000.

Very few analyses of human pancreatic juice have been made, and
it has never been obtained under quite normal conditions. Herter1
obtained pancreatic juice, containing all three ferments, from an enlarged
duct, due to carcinoma of the duodenum, which contained per 1000 parts,
24' 1 parts of total solids, 17 '9 parts of organic matter, 6 '2 parts of ash.
Zawadski 2 has more recently published an account of human pancreatic
juice, obtained from a pancreatic fistula, remaining after removal of a
pancreatic tumour. This sample resembled in composition those ob-
tained from temporary fistulre in animals, much more closely than
Herter 's sample ; it possessed a powerful digestive action, and probably
was an almost normal secretion. It contained, per 1000 parts, 135'9 of
total solids, 92 parts of proteids, 34 parts of inorganic matter, the
remainder being organic matter soluble in alcohol.

Rate of secretion. — The figures given by various observers for the
total quantity of pancreatic juice secreted in twenty-four hours vary
greatly, and it is impossible to state an average quantity with any
approach to accuracy. Figures obtained from observations on permanent
fistulse greatly exceed those obtained from temporary fistulse. Bidder and
Schmidt place the yield in the dog, at the rate of temporary secretion, at
2 '5 grins, per kilo, of body weight per diem. At this rate a man of 70
kilos. (154 Ibs.) would secrete 175 grins, of pancreatic juice per diem.

Succus ENTERICUS.

The secretion of the small intestine may be obtained in animals,
unmixed with the other digestive secretions, by one of two forms of fistula.

The first form of fistula was introduced by Thiry,3 and is made by
cutting across the intestine at two places, 10 to 30 cms. apart, without
interfering with the blood supply, restoring the continuity of the
intestine, stitching up one end of the isolated piece, and uniting the
other to the wound in the abdominal wall. The second form clue to
Vella,4 is a modification in which both ends of the isolated piece of gut
are left open and stitched to the abdominal wall one above the other.5

Thiry describes the succus entericus as a limpid, opalescent, light
yellow-coloured fluid, strongly alkaline in reaction, and possessing a
specific gravity of 1010.

It contains proteid and mucin, and much carbonate, as shown
by effervescence with dilute acids. According to Eohmann,6 in the dog,

1 Ztschr. f. physiol. Chem., Strassburg, 1880, Bd. iv. S. 160.

2 Centralbl.f. Physiol. , Leipzig u. Wien, 1891, Bd. v. S. 179.

3 Sitzungsb. d. Jc. Akad. d. Wisscnsch., Wien, 1864, Bd. 1. Abth. 1, S. 77.

4 Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1888, Bd. xiii. S. 40. For details as
to establishing such fistulse, see Gamgee, "Physiological Chemistry," vol. ii. pp. 406-408.

5 For a full description of the methods of collecting intestinal juice, see article on
" Mechanism of Intestinal Secretion."

6 Arch.f. d. ges. Physiol., Bonn, 1887, Bd. xli. S. 424.

COMPOSITION OF BILE. 369

the secretion of the upper part of the small intestine is scanty in
quantity, slimy and clot-like, while in the lower part the secretion is
much more fluid, and contains small clot-like masses. It contains
4-5 parts per 1000 each of sodium chloride and sodium carbonate.1
Pregl 2 has recently obtained succus enter icus from a Vella fistula in the
sheep, and estimated its alkalinity as equivalent to 0454 per cent, of
Na2C03. The specific gravity of the fluid averaged 1-014. It contained
proteid, and coagulated on standing. Thiry found in the dog, 2 -2 to 2 '8 of
total solids, 07 to 1-2 of proteid, 07 to 0-9 of ash, per cent.; Leube, 0'8 to 27
per cent, of proteid; Quincke, 1/34 to 145 per cent, of total solids;
Frerichs, 2*27 per cent, of total solids; Gumilewski, 1-5 per cent, of
total solids.

Tubby and Manning 3 obtained pure human succus entericus from a
piece of intestine, 3J in. in length, situated about 8 in. from the
ileo-caecal. valve, for a period of some months; the daily yield from this
length of gut averaged 27 c.c. (19 to 35). As a mean of thirty determina-
tions, the specific gravity was found to be 1-0069 (1-0016 to 1-0162). The
fluid was generally opalescent, and often had a brownish tint ; it con-
tained a few leucocytes and columnar cells, and was free from bacteria.
It was invariably alkaline in reaction, and gave off carbonic acid gas on
treatment with acids. It gave all the proteid reactions, and did not
reduce Fehling's solution or alter the colour of iodine solution. It con-
tained lactates, as shown by darkening a dilute solution of ferric chloride,
and giving Uffelmann's test. It also contained much mucin.

BILE.

Action on foodstuffs.— Bile differs from the other digestive secre-
tions in not possessing a marked chemical action on any of the organic
foodstuffs. Bile alone is said to exert a diastatic action on starch,4 but
this is very slight and inconstant, and seems to be merely due to a slight
absorption of diastatic enzymes ; 5 on the other foodstuffs it has no
chemical action whatever. Bile also increases the rate of action of
pancreatic diastase ; but the bile salts alone have a similar effect, so that
this accelerating action is not due to a diastatic enzyme.6

It has been shown that the presence of bile in the intestine
has a favourable influence on the absorption of fat, and that when
it is excluded, although the absorption of fat is not stopped, it be-
comes very defective, and the same amount -of fat cannot be taken
up as when bile is present. This will be considered later under Fat
Absorption.

Chemical composition.— In its physical characteristics and chemical
composition the bile is a variable mixture, not only in different classes of
animals, but in the same individual. As secreted by the liver cells, and
until it reaches the gall bladder, it is a clear limpid fluid, with a low

1 Gumilewski, Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxix. S. 565.

2 Ibid., 1896, Bd. Ixi. S. 359. .

3 Guy's Hosp. Rep., London, 1891, vol. xlviii. p. 277.

4Ewald, "Klinikd. Verdauungskrankheiten," 1890, Bd. i. S. 150.

5 According to Kaufmann (Compt. rend. Soc. de. bioL, Paris, 1890, tome xli. p. 600),
the ferment occurs in the bile of the ox, pig, and sheep, in traces in that of the cat, and
never in dog's bile. Ellenberg and Hofmeister (Arch. f. wissensch. u. prakt. TMerh.,
Berlin, 1885, Bd. xi. S. 381, 393) found a diastatic ferment in horse, ox, and sheep bile, and
occasionally in that of the dog and pig. In all cases, traces only of ferment are present.

6 Martin and Williams, Proc. Roy. Soc. London, 1889, vol. xlv. p. 358.

VOL. I. — 24

370

CHEMISTRY OF THE DIGESTIVE PROCESSES.

percentage of total solids and a correspondingly low specific gravity
(1010). In the gall bladder absorption of water takes place,1 and a
mucin-like substance secreted by the epithelium of the gall bladder is
added to it, so that it becomes viscid in consistency, the percentage of
total solids is much increased, and the specific gravity rises (1030 to 1040).

According to the time it stands in the gall bladder, these changes
become more or less advanced, which accounts for much of the variation
observed in the quantitative composition of different specimens of bile.

The following table of analyses of dogs' bile, (a) from the gall bladder
and (b) freshly secreted from a fistula, illustrates this difference : 2 —

IN A HUNDRED PARTS BY WEIGHT OF

(a) Bile from Gall Bladder.

(6) Freshly secreted Bile from
a Fistula.

I.

n.

'•

II.

Mucin .....

0-454

0-245

0-053

0-170

Alkaline taurocholates

11-959

12-602

3-460

3-402

Cholesterin ....

0-449

0-133

0-074

0-049

Lecithin .....

2-692

0-930

0-118

0-121

Fats

2-841

0-083

0-335

0-239

Soaps

3-155

0-104

0-127

0-110

Organic matter insoluble in\
alcohol J

0-973

0-274

0-442

0-543

Bile is an alkaline fluid containing on an average 0*2 per 1000 each of
sodium carbonate and alkaline sodium phosphate. It has an intensely
bitter taste, leaving a sweetish after-taste in the case of human or ox
bile, but not in that of rabbit's or pig's bile. The bile of the ox and
some other animals has a faint characteristic odour resembling musk,
especially after warming. The colour is very variable : in carnivora it
is usually golden-yellow ; in herbivora a grass -green ; but these colours
are not constant, and vary with the amount of oxidation of the bile
pigments ; the two chief colours are often mixed with brown, giving
intermediate shades of yellowish and greenish brown. Human bile,
when observed in a healthy condition and immediately after death, is
often green, occasionally golden-yellow in colour.

Bile contains no coagulable proteid, and remains clear on boiling ; it
can also be diluted with water without any turbidity arising. In human
bile true mucin is present,3 but the substance which gives viscidity to ox

1 Accompanied by a selective absorption of inorganic constituents, so that the percentage
of chlorides in gall bladder bile is even less than that in liver bile (Hammarsten, loc. cit.,
sub. 15).

2 Hoppe-Seyler, " Lehrbuch der Physiol. Chem.," Berlin, 1881, S. 302. See also
Hammarsten, Nova Acta. Reg. Soc. Sc. Upsala, 1893, .Ser. 3, vol. xvi. ; Jahresb. u. d.
Fortschr. d. Thier-Chem. , Wiesbaden, 1893, Bd. xxiii. S. 331.

3 Hammarsten, Nova Acta Reg. Soc. Sc. Upsala, 1893, Ser. 3, vol. xvi. ; Jahresb. ii. d.
Fortschr. d. Thier-Chem., Wiesbaden, 1893, Bd. xxiii. S. 333.

SPECIFIC CONSTITUENTS OF BILE.

371

bile has been shown not to be mucin but a nucleo-albumin. Other
substances present in bile are — (1) the alkaline salts of certain organic
acids known as the bile acids ; (2) the bile pigments ; (3) traces of
lecithin, cholesterin, soaps, and fats ; (4) mineral salts.

Both the total and relative amount of each of these several con-
stituents or group of constituents is very variable, as is shown by the
following table of analyses of human bile made by different observers.
The numbers indicate parts by weight contained in 1000 parts by
weight of bile : l —

FRESH BILE FROM GALL BLADDER.

BILE FROM FISTULA.

Frerichs.2

v. Gorup-Besanez.3

Jacob-
son.*

Yeo and
Herroun.s

Copeman
and
Winston.e

Mayo
Robson."

NSel Paton and
Balfour.8

Water

860-0

859-2

822-7

898-1

977-4

98716

985-77

981-98

988-08

98479

Total solids

140-0

140-8

177-3

101-9

22-6

12-84

14-23

18-02

11-92

15-27

Sodium gly-

\

cocholate
Sodium taur-

V102-2

91-4

107-9

56-5

10-1 •!

1-65
0-55

i 6-28

J 7-51
\ 0-09

3-56
0-49

1 3-49

ocholate

J

Cholesterin
Lecithin

1-6

2-6

- 47-3

30-9

0-56
0-05

10-38

0-99

r 0-45

0-53

10-75

Fats .

3-2

9-2

J

1

0-12

0-09

}• 1-50

Soaps .

J

, 0-97

0-15

Mucin pig-

^|

ment, epi-
thelium,

I 26-6

29-8

22-1

14-5

2-3

1-48

1-72

1-30

1

{4-61

etc.

J

V 7-09

Inorganic
salts

6-5

7-7

10 '8

6-3

8-5

8-41

4-51

7-58

)

. 6-41

The samples of bile from the gall bladder, analysed by Frerichs and by v.
Gorup-Besanez, were obtained immediately after death from healthy subjects,
the others were from biliary fistulas of long standing.

Specific Constituents of Bile.

Nucleo-proteid of bile. — Landwehr 9 first drew attention to the fact
that the percentage composition of the mucin of bile was different from
that of other mucins, and that no reducing sugar was formed on heating
it with a mineral acid, but attempted to explain this by assuming that

1 Extracted partially from Bunge, "Lelirbuch. der physiol. und pathol. Chemie,"
Leipzig, 1894, S. 192 ; and partially from Noel Paton and Balfour, Rep. Lab. Roy. Coll.
Phys., Edin., 1891, vol. iii. p. 191.

2 Hannover. Ann. f. d. ges. ffeilk., 1845, N.F. Bd. v. S. 42.

3 Prager. Frtljschr. f. praJct. Pharmakol., 1851, Bd. iii. S. 86.

4 Ber. d. deutsch. chem. Gesellsch., Berlin, 1873, Bd. vi. S. 1026.

5 Journ. Physiol., Cambridge and London, 1884, vol. v. p. 116.

6 Ibid., 1889, vol. x. p. 213. .

7 Proc. Roy. Soc. London, 1890, vol. xlvii. p. 499.

8 Loc. cit.

9 Ztschr.f. physiol. Chem., Strassburg, 1881, Bd. v. S. 371.

372 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

a glycogen-like substance was present in the other inucins, which, on
boiling with a mineral acid, formed a reducing sugar ; this substance he
supposed to be absent in bile mucin, and hence no reducing sugar was
formed on heating it with a dilute mineral acid.

Paijkull1 afterwards proved that the mucin-like substance which
gives bile its viscidity really belongs to the nucleo-proteids. If bile be
precipitated with dilute acetic acid, the presence of the bile salts
prevents the precipitate from redissolving in excess, and so causes it to
simulate a mucin ; but if the bile salts are removed by dialysing, or by
precipitating the substance with alcohol, centrifugalising and quickly
redissolving in water, the precipitate readily redissolves in excess of
acetic acid, and in this respect resembles a nucleo-proteid and not a
mucin. Also, when the substance is precipitated by, and just redissolved
in, dilute hydrochloric acid, and theft subjected to peptic digestion, a
substance is precipitated, which by its percentage of phosphorus can be
recognised as similar to the nuclein yielded under like conditions by"
nucleo-proteids. These facts, together with the much higher percentage
of nitrogen (14 to 16 per cent.) than mucin which it contains, and its
failing to yield a reducing sugar on boiling with dilute mineral acids,
show the substance to be a nucleo-proteid and not a mucin. The quantity
of this substance present in bile is very variable but always small,
amounting in ox bile to about one per thousand.2

The bile salts.— There are found in bile the salts of a number of
organic acids of complicated structure, which are closely allied to one
another ; these salts are collectively called the bile salts. They are not
found in health in appreciable quantity elsewhere than in the bile, and
usually occur as sodium salts, except in the bile of some sea fishes, in
which they are present as potassium salts.

Since bile is so easily obtainable in quantity, it is not surprising that
it should early have attracted the notice of the physiological chemist.
Thenard, in 1809, working with ox bile, was the first to obtain any
scientific knowledge of the bile acids. He distinguished two com-
ponents in bile, one precipitated by acetate of lead, which he called
bile resin, and a soluble part, which he named picromel He seems
. to have roughly separated in an impure condition those two most
commonly occurring bile acids, which we know to-day as glycocholic and
taurocholic acid, by a method not widely differing from that most used
at the present time. He precipitated bile with neutral and basic acetates
of lead, and then extracted the precipitate with nitric acid ; the insoluble
part left behind, his resin of bile, was impure glycocholic acid. The filtrate
he reprecipitated with excess of acetate of lead, collected the precipitate,
and decomposed it by a current of sulphuretted hydrogen, thus obtaining
his picromel, which must have corresponded to impure taurocholic acid.

In 1826, Gmelin published a memoir 3 in which is described a large
number of bile constituents; amongst them, one corresponding to
glycocholic acid, which he obtained in a crystalline form ; and another
substance, taurine, of which he was the discoverer, although he wrongly
supposed that it existed ready formed in the bile. The next important
advance was made by Demarcay,4 who obtained a substance (Choleinsaure)
which yielded, on heating with acids, taurine and a resinous substance,

1 Ztschr.f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 196. 2 Paijkull, loc. tit.

3 " Die Verdauung nach Versuchen."

4 Ann. d. Chem., Leipzig, 1838, Bd. xxvii. S. 270.

THE BILE SALTS. 373

and, on treatment with alkalies, ammonia and a non-nitrogenous acid,
corresponding to what to-day is called cholalic acid.

In 1844, Plattner1 succeeded in obtaining the bile salts in a
crystalline form, and so laid a sure foundation for all succeeding work on
the isolation and study of the bile acids. He also showed, by boiling
this crystalline product with acid, that taurin is a decomposition product
and does not exist as such in bile. Bedtenbacher 2 previously to this had
shown that this body contains sulphur, and established its formula as
C2H7NS03. Plattner3 afterwards discovered a simpler method of
obtaining the mixed bile salts in crystalline form. He concentrated the
bile without decolorising, and then added an excess of alcohol, warmed,
and after some time filtered and added ether, till a brown sticky
precipitate began to fall ; this was allowed to settle, and the clear fluid
decanted off, cooled, and treated with more ether from time to time.
The bile salts alone being the only constituents which are soluble in
water and alcohol, and insoluble in ether, are slowly thrown out of
solution ; and on standing for some days or weeks in the cold, under the
alcoholic ethereal mother-liquid, form themselves into ball-shaped masses,
or starlike clusters of fine needles, which increase in size on standing.
This crystalline mass is known as' " Plattner s crystallised bile." The
crystals are dried between filter-paper, washed with alcohol, containing 1
in 10 of ether, purified by recrystallisation, and dried over sulphuric acid.

This discovery of Plattner 's paved the way for the classical researches
of Strecker, to whom we owe the greater part of any exact knowledge we
have of the bile acids. Strecker 4 first showed that " Plattner s crystallised
Hie " consists of a mixture of the sodium salts of two acids, which are so
related to each other that they yield, on boiling with acids, a common
non-nitrogenous constituent, cholalic acid, and a nitrogenous constituent,
which in both cases is an amido-acid. One of these amido-acids is
glycocoll or amidoacetic-acid, the other taurine or amidoethylsulphonic-
acid. Of the two bile acids the one which yields glycocoll and cholalic
acid is called glycocholic acid, while the other, which yields taurine and
cholalic acid, is named taurocholic acid.

Cholic or cholalic acid is not, however, the only basis of the different
varieties of bile acids ; other acids closely allied to it in percentage com-
position, but quite distinct from it, have been isolated. In ox bile about
a third part of the cholalic acid is replaced by an acid called choleic
acid.5 In human bile an acid called f ellic acid 6 has been described as
occurring along with cholalic and choleic acids ; and modified cholalic
acids are present in the hyoglycocholic acid of pig's bile and the cheno-
taurocholic acid of goose bile. None of these substitutes of cholalic
acid occur free in bile, but always combined with glycocoll or taurine
to form modified glycocholic or taurocholic acids ; they are all soluble
with difficulty in water and ether, and easily soluble in alcohol.7

lAnn. d. Chem., Leipzig, 1844, Bd. li. S. 105. 2 Ibid., 1846, Bd. Ivii. S. 170.

3 Journ. f. pralct. Chem., Leipzig, 1847, Bd. xi. S. 129.

4 Ann. d. Chem., Leipzig, 1848, Bd. Ixv. S. 1 ; 1848, Bd. Ixvii. S. 1 ; 1849, Bd. Ixx.
S. 149.

5 Latschinoff, Ber. d. deutsch. chcm. Gesellsch., Berlin, 1885, Bd. xviii. S. 3039 ; 1886,
Bd. xix. S. 1140 ; 1887, Bd. xx. S. 1043.

6 Fellinsdure of Schotten, Ztschr.f.physiol. Chem., Strassburg, 1887, Bd. xi. S. 268. See
also Lassar-Cohn, Ber. d. deutsch. chem. Gesellsch., Berlin, 1894, Bd. xxvii. S. 1339.

7 Hammarsten's "Lelirbuch," 1895, S. 198. He describes a third variety of bile acid,
found in shark's bile, which is rich in sulphur, and from which boiling with hydrochloric
acid splits off sulphuric acid.

374 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

The alkaline salts of the bile acids are soluble in water and alcohol,
but insoluble in ether, and these solubilities form the basis of Plattner's
method of separating them from the other biliary constituents. This
is best done by mixing the bile with freshly-heated animal charcoal,
evaporating to complete dryness, and then extracting with absolute
alcohol, which takes up the bile salts along with cholesterin and traces
of lecithin, fats, and soaps ; but, on addition of excess of ether, only the
bile salts are thrown out of solution.

The relative amount of each of the bile acids present in bile varies
within wide limits. In the bile of carnivora, glycocholate of sodium is
present in very small quantity ; for example, the bile salts of dog's bile
consist exclusively of taurocholate of sodium,1 while in most herbivora
the glycocholate is usually present in^greater quantity than the tauro-
cholate ; to this rule the goat and sheep are said to be exceptions.

In human bile most of the cholalic acid is combined with glycocoll,
occasionally the whole of it.2 Hammarsten's 3 analysis of the mixed bile
salts of healthy human bile gave 13*1 per cent, taurocholic acid, 86'9
per cent, glycocholic acid. Since glycocholic acid is sulphur-free, and
the percentage in taurocholic acid is known, the relative amount of the
two acids may be determined from the percentage of sulphur in a
preparation of Plattners crystallised Hie, obtained from any given sample
of bile.

The isolation of each of the bile acids from a mixture of their
salts is usually a lengthy and difficult process, especially in the case of
taurocholic acid, which can only with great difficulty be freed from
glycocholic acid, so that taurocholic acid is usually prepared from dog's
bile, while glycocholic acid is prepared from ox bile.

Both free acids behave like their sodium salts in being soluble in
alcohol and insoluble in ether, but differ in that taurocholic acid is easily
soluble in water, while glycocholic acid is soluble with great difficulty.
On this property is based the simplest method of obtaining pure
glycocholic acid, that of Hiifner;4 unfortunately, the presence of
taurocholic acid confers solubility on the glycocholic acid, so that the
method often fails when too much taurocholate is present in the sample
of bile experimented upon.

The method consists in adding to fresh ox bile a few drops of hydrochloric
acid, and filtering from the precipitated pseudo-mucin. To 100 c.c. of this
filtrate 5 c.c. of concentrated hydrochloric acid and 30 c.c. of ether are added.
The hydrochloric acid sets free both bile acids, and the glycocholic acid is
precipitated in crystalline form (unless too much taurocholic acid be present),
either immediately, or on standing some hours in the cold. The ether added
aids in the production of this crystalline precipitate, which is next washed
with acidulated water saturated with ether, and finally recrystallised from
boiling water.

Marshall5 tested Hiifner's method with 543 samples of ox bile, and
obtained a precipitation in 121 cases. A similar method was employed by
Strecker,6 using a watery solution of crystallised bile instead of fresh bile.

1 Strecker, Ann. d. Chem., Leipzig, 1849, Bd. Ixx. S. 178; Hoppe-Seyler, Journ. f.
praU. Chem., Leipzig, 1863, Bd. Ixxxix. S. 283.

2 Jacobson, Ber. d. deutsch. chem. Gesdlsch., Berlin, 1873, Bd. vi. S. 1028.

3 Schmidt's Jahrb. , Leipzig, 1879, Bd. clxxxi. S. 5.

4 Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1874, Bd. iv. S. 301.

5 Ztschr. f. physiol. Chem., Strassburg, 1887, Bd. xi. S. 233.

6 Ann. d. Chem., Leipzig, 1848, Bd. Ixv. S. 1.

THE BILE A CIDS. 3 7 5

The different solubilities of the lead salts of the two acids provides
another means of separating glycocholic acid; the separation of pure
taurocholic acid from the mixture by this method is more difficult.

Glycocholate of lead is thrown out of solution on the addition of neutral
acetate of lead to a solution of a mixture of the bile salts ; the remainder of
the glycocholate and all the taurocholate are thrown down on the addition of
ammonia or of basic acetate of lead to the nitrate.

Fresh ox bile is treated with alcohol to precipitate the pseudo-mucin.
The alcohol is evaporated off, and neutral acetate of lead added as long as a
precipitate forms ; this precipitate is collected and decomposed by warming
with a solution of sodium carbonate, whereby sodium glycocholate is formed ;
the mixture is next evaporated to dryness, and extracted with alcohol, in which
the sodium glycocholate dissolves. This alcoholic solution is filtered, the
filtrate is evaporated to dryness, and the residue is dissolved in water. The
watery solution of sodium glycocholate so obtained is decolorised with animal
charcoal, and the glycocholic acid thrown out of solution by adding a mineral
acid. Finally, it can be recrystallised, either from boiling water, or by the
addition of ether to its alcoholic solution. Taurocholic acid can be obtained
from the filtrate from neutral acetate of lead, by fractional precipitation with
basic acetate of lead, as the remaining glycocholate unprecipitated by the
neutral acetate is precipitated by the portion of basic acetate first added.1
Basic acetate of lead is stirred into the filtrate from the neutral acetate, until
the precipitate commences to gather into a sticky mass, when the addition is
discontinued, and the solution decanted off from the precipitate. More basic
acetate solution is now added, and throws down a plastic mass, consisting of
fairly pure taurocholate of lead. This precipitate is dissolved in boiling
alcohol, filtered warm into water, and the resulting reprecipitated mass, after
being purified by kneading, is dried, dissolved in a small quantity of alcohol,
decomposed with sulphuretted hydrogen, filtered from lead sulphide, and
dried at first in the air, afterwards in a vacuum over sulphuric acid.

Taurocholic acid is, however, best prepared from dog's bile, as
described by Parke.2

The bile is evaporated down, extracted with alcohol, decolorised with
animal charcoal, evaporated to dryness, dissolved in absolute alcohol, and
treated with excess of ether. After some time the crystalline precipitate of
sodium taurocholate so obtained is dissolved in water, and the solutions
precipitated with acetate of lead and ammonia. The precipitate is collected,
washed, suspended in alcohol, or dissolved therein by boiling, and decomposed
by sulphuretted hydrogen. The filtrate from sulphide of lead is evaporated
to a small volume, and mixed with excess of ether, when the taurocholic acid
is precipitated as a syrup, in which, after some time, small crystals appear.
These are in the form of fine needles which deliquesce in the air.

Glycoclwlic acid (C26H43N06) is a monobasic acid, crystallising in
long fine needles, which fell together into a light, voluminous mass
when first formed from a solution, and on drying form a loose, snowy
white mass with a silky glance. These crystals melt at 100° C., losing
water in so doing and forming glycocholonic acid ; they are very
sparingly soluble in cold water (1 in 300), somewhat more soluble in
boiling water (1 in 120), and so can easily be recrystallised from hot
water ; they are easily soluble in alcohol and in acetic acid, but soluble
in ether with great difficulty. Glycocholic acid and its salts in solution

1 Lieberkiilm, Jahresb. ii. d. Fortschr. d. ges. Med., Erlangen, 1852, Bd. i. S. 113.

2 Hoppe-Seyler's Mcd.-cliem. Untersuch.. Berlin, S. 160.

376 CHEMISTRY OF THE DIGESTIVE PROCESSES.

rotate the plane of polarised light to the right ; in alcoholic solution the
specific rotatory power for the acid is +20°'0, for the sodium salt 4-250-?
(Hoppe-Seyler). The salts of the alkalies and alkaline earths are
soluble both in water and in alcohol, those of the heavy metals are
mostly much more insoluble in water, so that addition of salts of such
metals as lead, copper, iron, or silver, causes precipitation of the corre-
sponding glycocholates. The lead salt is soluble in rectified spirit, from
which it is precipitated on the addition of water. The acid and its
salts possess a peculiar taste, sweetish at first, but afterwards intensely
bitter.

Taurocholic acid (C26H45NS07), also a monobasic acid, is crystallisable
with difficulty, forming fine deliquescent needles. It is very easily soluble
in water, and also possesses the powqy of carrying glycocholic acid into
solution when that acid is simultaneously present. It is exceedingly
soluble in alcohol, but insoluble in ether. In solution it possesses a
bitter-sweet taste, which is shared by its alkaline salts. The salts are
generally easily soluble in water, and a solution of an alkaline tauro-
cholate, unlike that of a glycocholate, is not precipitated by the usual
salts of the heavy metals, such as copper sulphate, silver nitrate, or
neutral lead acetate ; basic lead acetate does, however, precipitate it, and
the compound so formed is soluble in boiling alcohol.

Taurocholic acid is not nearly so stable a compound as glycocholic
acid, it decomposes on boiling in aqueous solution, or in evaporating to
dryness ; hence the dry pure acid has never been prepared or analysed,
and its formula has been deduced from analogy with glycocholic acid,
and from analyses of its more stable salts. Its solutions rotate the
plane of polarisation to the right, like glycocholic acid. The specific
rotation of the alcoholic solution of the sodium salt is +24° '5. Potassium
taurocholate occurs in the bile of many fishes ; it possesses the peculiar
property of being completely thrown out of solution in water by the
addition of solution of caustic potash, and so may be prepared by adding
this reagent to an aqueous solution of an alkaline taurocholate.
Analyses of this salt by Strecker1 established its formula as
C26H44KNS07, and analyses of the sodium salt gave a corresponding
result, from which it follows that the formula of taurocholic acid
itself is C26H45NS07.

Hyoylycoclwlic acid is an acid found in pig's bile,2 which yields on decom-
position glycocoll, like ordinary glycocholic acid, but an acid differing in
composition and behaviour from ordinary cholalic acid (C24H4005), and
called hyocholalic acid (C25H4004). This acid differs from cholalic acid in not
being so easily crystallisable, and in having a difficultly soluble barium salt.
Severin John 3 states that pig's bile contains, as principal bile salts, the sodium
salts of two different hyoglycocholic acids, each of which yields on decomposi-
tion glycocoll and a hyocholalic acid (a and /?). The two hyoglycocholic acids
are distinguished by the different solubilities of their sodium salts in neutral
salt solutions. The /3-salt is present in much greater quantity; but the
distinguishing character of pig's bile, that it is precipitated by saturation with
various neutral salts, is not due to the {3- but to the a-hyoglycocholic acid.

1 Loc. cit.

2 Strecker and Grundelacli, Ann. d. Chem., Leipzig, 1847-9, Bd. Ixii. S. 205 ; Bd. Ixx.
S. 179.

3 Ztschr. f. physiol. Chem., Strassburg, 1887-9, Bd. xi. S. 417; Bd. xii. S. 512;
Bd. xiii. S. 205.

THE BILE ACIDS. 377

The two hyocholalic acids show analogous differences to the two hyoglycocholic
acids. The formula of a-hyoglycocholic acid is C27H43N05, that of fi-hyo-
glycocholic acid is C26H43N05.

Tauroclienocholic acid,1 the principal bile acid of goose bile, has the
formula C29H49NSQ6, has not been crystallised, and is soluble in water and
alcohol. From this acid Heintz and Wislicenus 2 prepared chenocholic acid
(C27H4404) ; this is itself crystallisable with difficulty, but yields a barium salt,
which is insoluble in water and can easily be obtained in a crystalline form.

Pettenkofers test for bile acids? — When bile is gently warmed with
concentrated sulphuric acid and cane-sugar, a beautiful purple or
purplish-red colour develops, becoming deeper on standing. The colour
is due to an interaction between the bile salts, or cholalic acid, and a
substance called furfurol or furfuraldehyde developed by the action of
the strong, sulphuric acid on the cane-sugar;4 hence the test may
be more satisfactorily carried out where only traces of bile salts are
suspected, by using a solution of furfurol (1 per 1000) instead of cane-
sugar.

To carry out the test in the ordinary manner, add to a drop or two of the
bile, or fluid suspected of containing bile acids, a drop of strong sulphuric
acid, taking care that any great rise in temperature does not occur ; spread the
mixture out in a thin film in a porcelain capsule, and either add a drop of a
10 per cent, solution or a small crystal of cane-sugar ; if the violet colour does
not appear at once, warm very gently. To carry out the test with furfurol, one
drop of a solution of furfurol (1 per 1000) is added to 1 c.c. of an alcoholic
solution of bile salts, and 1 c.c. of concentrated sulphuric acid is added
cautiously to this, so as not to overheat. In this manner -J^-^-Q of a milligramme
of cholalic acid may be detected.5

The test with sugar may be easily spoiled by overheating or when
too much sugar is used, which favours carbonisation. The presence of
sulphurous acids or nitrous fumes in the sulphuric acid is also unfavour-
able to the reaction. Strong phosphoric acid may be used instead of
sulphuric acid.

Many other substances give a similar reaction. Pettenkofer himself
was aware that proteids gave a similar colour, though much less easily.
By subsequent observers 6 a large number of substances giving colour re-
actions with furfurol have been described ; amongst these many phenols
and aromatic bases are included, some of which are also found in
the urine, v. Udranszky7 gives a list of over forty substances which
give colour reactions with furfurol, but none except a-naphthol show
the reaction with the same delicacy as the bile salts. That the
coloured substance so produced is not in all cases the same, is shown
by the fact that some possess no absorption spectrum, and that the
spectra of the others differ from one another. In this way the
spectrum of the colour given by the bile salts may be distinguished

1 Marsson, Arch. d. Pharm., Bd. Ivii. S. 138.

2 Ann. d. 'Ptiys. u. Chem., Leipzig, 1859, Bd. cviii. S. 547.

3 Ann. d. Chem., Leipzig, 1844, Bd. Hi. S. 90.

4 Mylius, Ztschr. f. physiol. Chem., Strassburg, 1887, Bd. xi. S. 492.

5 v. Udrdnszky, ibid., 1888, Bd. xii. S. 355.

6 Baeyer, Ber. d. deutsch. chem. Gesellsch., Berlin, 1872, Bd. v. S. 26; Stenhouse,
Ann. d. Chem., Leipzig, 1870, Bd. clvi. S. 197 ; Schiff, ibid., Bd. cci. S. 355.

7 Loc. cit. Drechsel, Journ. f. praH. Chem., Leipzig, Bd. xxvii. S. 424.

378 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

from the others by two bands, one between the solar lines D and E
near to E, the other at F.1

The bile salts produce great slowing of the heart's beat, which may be used
as a physiological test for them in confirmation of Pettenkofer's reaction. In
a curarised frog the heart is exposed, the pericardium removed, and the action
of the vagus paralysed by atropine ; on now adding a drop of a solution of a
bile salt, the rhythm of the heart is greatly slowed.2

Cleavage products of the bile acids. — All the bile acids, under the
action of hydrating agents, split up into two components, of which one
is always either glycocoll or taurin, and the other a non-nitrogenous
monobasic acid which may be cholalic acid or one of several allied acids.

Glycocoll and taurin are nitrogenous bodies, belonging to that class
of substances called amido-acids, i.e. organic acids, in which one or more
hydrogen atoms are replaced by the group amidogen (NH2). Both these
amido-acids are probably formed by the breaking up of proteids, or
their allies the albuminoids.

The process of hydration can be carried out directly from bile, by heating
with hydrochloric acid, in a flask attached to a reversed condenser. Taurin
and hydrochlorate of glycocoll are formed, and the free cholalic acids, which
slowly lose water and pass into the form of their anhydrides (the dyslysins,
p. 382) ; these being insoluble are precipitated. As soon as the reaction is
completed, as shown by the failure of Pettenkofer's test, the flask is allowed
to cool and the dyslysins filtered off. The filtrate, which contains the
amido-acids, is strongly concentrated, and, while still warm, decanted from the
sodium chloride which has crystallised out. It is next evaporated to com-
plete dry ness and treated with absolute alcohol, which takes up the glycocoll
hydrochlorate and leaves the taurin behind. The residue is dissolved in as
small a quantity as possible of warm water, and filtered while warm ; to
this filtrate a little alcohol is added, and, on slowly cooling, crystals of taurin
are formed.

The. alcohol is evaporated from the alcoholic extract containing the glycocoll
hydrochlorate, and water is added ; to the watery solution, hydrate of lead is
added, when insoluble lead chloride and a soluble lead compound of glycocoll
are formed. The latter is separated in solution by filtration ; into the solution
a stream of sulphuretted hydrogen is passed, the lead sulphide is filtered off,
and the filtrate is concentrated, until, on cooling, free glycocoll crystallises out.

The free cholalic acids3 can be recovered from the dyslysins formed in
the first step of the above process. The dyslysins are removed from the
filter, and boiled with dilute alkali, when they take up water, and, combining
with some of the alkali, are converted into soluble alkaline cholalates. On
acidifying with hydrochloric acid, and evaporating to dry ness, the cholalic
acids can be extracted with a small quantity of hot alcohol, from which they
crystallise on cooling, or on the addition of excess of ether.

Glycocoll, glycocine, or glycine, is ami'do-acetic acid (NH2.CH2.COOH).
Besides occurring combined with cholalic acid, as glycocholic acid in the
bile, it is found in the urine of certain animals and occasionally in man,
combined with benzoic acid, to form hippuric acid, and is formed as an
end hydration product from gelatine and similar substances.

1 Koschlakoff and Bogomoloff, CentralbL f. d. mcd. Wissensch., Berlin, 1868, Bd. vi.
S. 529. In this paper four bands are described. Bogomoloff, ibid., 1869, Bd. vii. S. 529 ;
Schenck, Jahresb. u. d. Fortsckr. d. Thier-Chcm., Wiesbaden, 1872, Bd. ii. S. 232.

2 Mackay, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1885, Bd. xix. S. 279.

3 The term "cholalic acids" is used to signify cholalic acid and its allies.

CLEA VAGE PRODUCTS OF THE BILE ACIDS. 379

It crystallises in colourless rhombohedra, or in four-sided prisms, which have
a sweet taste and dissolve easily in cold water (1 in 4 '3) ; in alcohol and ether
they are insoluble. Glycocoll, like other amido-acids, can act chemically, either
as a base or an acid in forming compounds with acids and bases respectively.
As a type of these combinations with bases, the copper compound may be
taken. When freshly precipitated cupric hydrate is added to a warm con-
centrated solution of glycocoll, it dissolves to form a deep blue solution, which
is not reduced on boiling ; on cooling this solution, or on adding alcohol and
allowing to stand, fine dark blue needles crystallise out of the composition
(ra2.CH2.C02)2Cu,H20. Glycocoll has been obtained synthetically by the
action of ammonia on monochloracetic acid thus : —

NH3 + CH2.C1— COOH = CH2.(NH2)— COOH + HC1.

Taurine is amido-isethionic acid, also called amido-oxyethylsulphonic
acid (NH^CgH^SOaOH).1 It occurs in the body, apart from the bile, only
in minute and inconstant traces ; it has been stated to occur in the lungs
and kidneys of oxen, in some of the organs of cold-blooded animals, and
in inconstant traces, probably due to the decomposition of taurocholates,
in the intestine. The presence of sulphur in its molecule shows it to be
formed from proteids in the body; but the intermediate steps in its
formation are unknown.

Taurine is very easily crystallised, and forms large colourless prismatic
prisms with a glassy glance,2 without any taste, and gritty between the teeth,
neutral in reaction and very stable, not being altered by a temperature of
240 °C. ; heated above this temperature they melt and decompose in so doing.
It is much less soluble in cold water than glycocoll, but still easily soluble
(1 in 15*5), and still more so in hot water; in alcohol and ether it is insoluble.
It is soluble in concentrated sulphuric and nitric acids without decomposition,
and the latter acid may even be boiled off, leaving it unaffected ; neither is it
affected by boiling with aqua regia. To alkalies also it is much more stable
than glycocoll ; it is not affected by weak alkalies, and only by continued
boiling in strong alkaline solution is slowly broken up into ammonia, acetic,
and sulphurous acids ; so that it is one of the most stable of the organic
compounds found in the body. Taurine is also a much more neutral substance
in its chemical behaviour than glycocoll j it does not combine at all with acids,
and its affinity for bases is very feeble. An amorphous mercury compound is
however obtained by boiling a solution of taurine with freshly-precipitated
mercuric oxide.3

The constitution of taurine is shown by its synthesis from chlorethyl-
sulphonic acid by the action of ammonia.4

/C^Cl /C2H4NH2

SO/ + 2NH3 = SO/ + NH4C1

This synthesis, as well as the fact that taurine is not saponified by
dilute alkalies, shows that taurine is not an ester but a sulphonic
derivative ; that is, that the sulphur atom is united directly to carbon,
and not indirectly by oxygen. Taurine may also be obtained by heating

1 The amido-oxyethyl radicle is directly united to sulphur in the molecule.

2 Gmelin, " Ver darning uach Versuchen," S. 60.

3 Lang, Jahresb. u. d. Fortschr. d. Thicr-Chem., Wiesbaden, 1876, Bd. vi. S. 74.

4 Kolbe. Ann. d. Chem., Leipzig, 1862, Bd. cxxii. S. 33.

380 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

the ammonium salt of oxyethylsulphonic acid to 230° C., when a
molecular rearrangement takes place, thus :

/C2H4.OH ,C2

SO/ = SO/

XONH4 X)H

Cholalic acid is the usual partner with glycocoll or taurine in the
formation of the bile acids ; it is also found in the intestinal contents,
and sometimes, in cases of jaundice, in the urine. One method of
obtaining it has already been incidentally mentioned, but it is better
prepared by the following method : 1 —

Ox bile is boiled for about twenty-four hours with the fifth part of its
volume of 30 per cent, caustic soda solutjpn, the water being replaced as it is
removed by evaporation. The solution is then saturated with carbon-dioxide
gas, and evaporated almost to dryness. The residue is extracted with 96 per
cent, alcohol, and the extract, diluted so that it does not contain above 20
per cent, of alcohol, is completely precipitated with a solution of barium chloride.
The precipitate, which consists of impure barium choleate, is filtered off, and
cholalic acid is precipitated from the filtrate by the addition of hydrochloric acid.
The acid slowly becomes crystalline on standing, when it is separated and puri-
fied by repeated recrystallisation from alcohol. Cholalic acid occurs in many
crystalline forms.2 Anhydrous crystals forming flat- ended 4- to 6-sided prisms,
may be obtained by dissolving the amorphous form of the acid, produced by
drying one of the other crystalline forms, in ether and allowing the solution
to crystallise out.

From strong alcohol the acid crystallises, on the addition of a very little
water, in octohedra and tetrahedra, belonging to the orthorhombic system, and
containing two and a half molecules of water of crystallisation ; from dilute alcohol
it crystallises in fine shining flat needles or plates, containing only one molecule
of water of crystallisation.3 It also crystallises in large rhombic tetrahedra, or
octohedra containing one molecule of alcohol. Pure anhydrous cholalic acid
melts at 194° to 195° to a colourless liquid; and on heating above this temperature,
loses water and is converted into its anhydride or dyslysin ; on further heating,
it loses more water and yields a viscid yellow or yellow-brown oil with a
green fluorescence ; this is another anhydride, with the composition C48H660;5.

All forms of the acid are sparingly soluble in water and ether, and easily
soluble in alcohol. The solutions possess the bitter-sweet taste of bile. The
alkaline salts are crystalline and soluble in water, but precipitated by strong
solutions of alkalies or their carbonates. The barium salt is much more
soluble in cold water (1-30) than the corresponding salts of the allied acids
described below. Cholalic acid and its soluble salts turn the plane of polarisa-
tion to the right.4 Methyl and ethyl ethers of cholalic acid have been
obtained.

The formula of cholalic acid was first established by Strecker5 as
C24H4005, and this formula, after some dissent,6 is now generally
accepted. With regard to its constitution, in spite of a vast amount of
labour on the subject, we are still only possessed of very fragmentary
and uncertain information. It is certainly a monobasic acid, and must

1 Mylius, Ztschr. f. physiol. Chem., Strassbnrg, 1888, Bd. xii. S. 262.

2 See Maly, Hermann's " Handbuch," Bd. v. (2), S. 136.

3 Schotten, Ztschr. f. physiol. Chem., Strassburg, 1886-7, Bd. x. S. 175; xi. S. 268.

4 Hoppe-Seyler, Journ. f. prakt. Chem., Leipzig, 1863, Bd. Ixxxix. S. 265; E. Vahlan,
Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 253.

5 Loc. cit.

6 Latschinoff, Bar. d. deutsch. chem. Gesellsch., Berlin, 1887, Bd. xx. S. 1968.

CLEA VAGE PRODUCTS OF THE BILE ACIDS. 381

therefore contain one carboxyl group (COOH), and according to Mylius 1
it also contains one secondary (CHOH) and two primary alcohol
groups (CH2OH).

The evidence for this is derived from its behaviour on cautious
oxidation. It first yields, when oxidised, monobasic dehydrocholalic acid
(C24H34O5),2 and on further oxidation tribasic bilic, or bilianic acid
(C24H3408).3 These changes may be expressed by supposing that, in
the formation of dehydrocholalic acid, the two primary alcohol groups
form aldehyde groups (H — C = 0), and the secondary group, a ketone
group (C = 0), and that in the further formation of bilianic acid the two
aldehyde groups pass into (acid or) carboxyl groups, so producing a
tribasic acid ; while besides, in the rest of the molecule, an additional
ketone group is formed, as shown by the following formulae : —

Cholalic acid, C20H31(CHOH)(CH2OH).2(COOH), on oxidation forms,
in place of one secondary alcohol group (CHOH) and two primary
alcohol groups (CH2OH), one ketone group (CO) and two aldehyde
groups (COH), thus yielding dehydrocholalic acid, C20H31(CO)(COH)2
(COOH), in which, on further oxidation, an additional ketone group is
formed, and the aldehyde groups change into carboxyl groups (COOH),
thus yielding the tribasic acid, bilianic (or bilic) acid, C19H31(CO.)2(COOH)3.

Scarcely anything is known of the arrangement of the atoms in the
hydrocarbon part of the molecule. Mylius4 has obtained a reaction
between cholalic acid and iodine, in solution, with the formation of a
blue compound, which is crystallisable and becomes easily dissociated in
the same manner as iodide of starch. For example, in solution, it
becomes decolorised on heating.

This substance is probably an addition product of cholalic acid and
iodine, and so points out that the hydrocarbon radicle of the acid is not
fully saturated ; beyond this, however, we know nothing of its composition.

Desoxycliolalic acid is a reduction compound obtained by Mylius 5 of
the formula C24H4004.

Choleic acid 6 was first found in the preparation of cholalic acid from ox
bile, and separated from it by means of the more sparing solubility of its barium
salt. According to Lassar- Colin, it also occurs in human bile, and its formula
is C24H4004. Latschinoff,7 its discoverer, ascribed to it the formula C25H4204.
From Lassar-Cohn's 8 formula it appears to be isomeric, or perhaps identical,
with desoxycholalic acid.

Fellic acid 9 (C23H4004) is an acid which has been obtained from human
bile ; it is crystalline, insoluble in water, and forms insoluble barium and
magnesium salts.

The acids formed by the cleavage of the peculiar bile acids found in the bile
of the pig and goose have been already mentioned in treating of these acids.

1 Ber. d. deutsch. chcm. GeseUsch., Berlin, 1886, Bd. xix. S. 369, 2000.

2 Hammarsten, ibid., 1881, Bd. xiv. S. 71 (Dehydrocholsaure] ; Lassar-Cohn, ibid., 1892,
Bd. xxv. S. 805 ; Ztschr. f. physiol. Chem., Strassburg, 1892, Bd. xvi. S. 488.

3 Cleve, Bull. Soc. chim., Paris, tome xxxv.

4 Ztschr. /. physiol. Chem., Strassburg, 1887, Bd. xi. S. 306 ; Ber. d. deutsch. chem.
GeseUsch., Berlin, 1887, Bd. xx. S. 683.

5 Loc. cU.

6 Cholcinsdure of Latschinoff, Ber. d. deutsch. chem. GeseUsch., Berlin, 1885, Bd. xviii.
S. 3039.

7 Loc. cit.

8 Ber. d. deutsch. chem. GeseUsch., Berlin, 1894, Bd. xxvii. S. 1339.

9 Fellinsaure of Schotten, Ztschr. /. physiol. Chcm.. Strassburg, 1887, Bd. xi. S. 268. See
also Lassar-Cohn, ibid., 1894, Bd. xix. S. 563.

382 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

The acids formed as cleavage products from human bile are cholalic,
choleic, and fellic acids.

Cholalic acid and its allies, on boiling with acids, on heating in the
dry state, or by putrefaction, lose water, and become converted into
anhydrides, or, as they are called, dyslysins. The dyslysin corresponding
to cholalic acid has the formula C24H3G03 ; it is found in faeces ; is a white
amorphous substance, insoluble in water and alcohol, soluble in ether
and melting at 140° C. Another compound, choloidinic acid, is formed,
as an intermediate stage, of the formula C24H3804. On boiling with
alkalies, dyslysin takes up water, and is reconverted into cholalic acid.

The bile pigments and their derivatives. — The variations in the
colour of bile early attracted attention, and Gmelin,1 in 1826, first
obtained proof of a relationship between these colours, and described
the test which still bears his name. *He was aware that the play of
colours was due to a process of oxidation, and made an experiment to
illustrate this by acidifying bile with hydrochloric acid, and enclosing
it in a tube from which the air was shut oft" by a mercury trap. Under
these circumstances no change in colour took place; but on exposing
the acidified bile to the air, a green colour slowly developed. He also
accurately described the play of colours obtained on oxidising with
nitric acid.

Berzelius 2 precipitated biliverdin from ox bile with barium chloride,
purified it to some extent, and described its properties, but he fell into
the error of supposing that it was identical with chlorophyll.3

Heintz,4 preventing oxidation by exclusion of air, extracted from
gallstones a brown amorphous pigment, which he named biliphain.
He analysed it, and converted it by dissolving in sodium carbonate, and
leading oxygen through the solution into a green pigment, biliverdin.
His biliphain corresponded to the bilirubin of the present day, and his
experiment shows well the connection between the two pigments.

Valentiner,5 in 1859, was the first to obtain bilirubin in a crystalline
form, by dissolving in chloroform, from which, on evaporation of the
solvent, it crystallises in microscopic crystals. From this discovery
onwards, research 011 the bile pigments took a more exact form, as
methods for the isolation of the pigments were discovered and perfected.6

Although a considerable number of more or less well-characterised
bile pigments have been described, only two are found under normal
conditions in the bile, these are bilirubin and biliverdin ; the others are
obtained by artificial means from these, are found under pathological
conditions only in the body, or are formed after death. The colour of
the bile is a compound of the colour of these two pigments, and varies
with the varying ratio of their amounts through all shades between

1 Tiedemann and Gmelin, " Verdauung nach Versuchen," 1826.

2 "Chemie," S. 281.

3 The spectra of phylloporphyrin and hsematoporphyrin and their derivatives are almost
identical, and in other respects the substances closely resemble each other, so that there is
undoubtedly a relationship between them (Sclmnck and Marchlawski, Proc. Roy. Soc.
London, Jan. 1896). Now, phylloporphyrin is a derivative of chlorophyll, and hfemato-
porphyrin is isomeric with bilirubin, so that there may be some remote connection between
biliverdin and chlorophyll.

4 Jahresb. u. d. Fortschr. d. ges. Med., Erlangen, 1851, Bd. ii. S. 59; Ann. d. Phys.
u. Chem., Leipzig, 1851, Bd. Ixxxiv. S. 106.

5 Jahresb. ii. d. Fortschr. d. ges. Med., Erlangen, 1859, Bd. ii. S. 87.

6 Briicke, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, Bd. vi. S. 173 ; Stadeler,
Vrtljschr. d. naturf. Gesellsch. in Zurich, 1863, Bd. viii. S. 1 ; Ann. d. Chem., Leipzig
1864. Bd. cxxxii. S. 323.

BILE PIGMENTS AND THEIR DERIVATIVES. 383

reddish-brown and grass-green. To the variation in relative amount of
these two pigments is also due the difference in colour between fresh
and stale bile. When bile stands in the gall bladder, its pigments
become reduced, the biliverdin is converted into bilirubin, and the
colour becomes yellow or brown. Fresh human bile has also a green
colour, but that observed in the post-mortem or dissecting-room is
always brown, because of this process of reduction. These two normally
occurring bile pigments are related to each other in a manner analogous
to haemoglobin and oxyhsemoglobin ; bilirubin (C10H18N203) on oxidation
passes into biliverdin (C16H18N204).

Haycraft and Scofield 1 observed in the gall bladder itself reduction
going on, as shown by the fact that, while the bile in the middle of the
gall bladder was green, the thicker bile mixed with mucus near the
bladder wall was orange-brown, and the mucous membrane itself of a
brown colour. To this slow reduction Haycraft and Scofield ascribe
also the presence of bilirubin and not biliverdin in the gallstones of
oxen, although the latter is the chief pigment found in ox bile. Putre-
faction readily brings about the same reduction in the bile pigments.
Bile with the bilirubin tint predominant does not turn green from
oxidation of this pigment to biliverdin, when it is exposed to the air,
unless it be made strongly alkaline with caustic alkali. In this increased
readiness to take up oxygen in alkaline solution, bilirubin resembles a
large number of other organic substances, such as pyrogallol and pyro-
catechin. Haycraft and Scofield were also able to induce these changes
by the action of nascent oxygen and of ozone. Working with a battery of
four or five Grove cells, and leading from platinum electrodes into brown-
coloured bile (in a beaker or on filter paper), they found that the oxygen
developed at the anode caused in a few minutes a change in colour of
the bile, through green and blue into violet, followed by bleaching. On
reversing the poles, so that reduction instead of oxidation took place at
this spot, an inverse change in colour back to brown was observed.

Bilirubin and biliverdin have chemically the character of weak acids,
as is shown by the ease with which they unite with bases to form salt-
like bodies. Such compounds with alkalies are soluble in water, but
with alkaline earths are insoluble; as, for example, the compound of
bilirubin with calcium, which makes up the bulk of red gall stones, and
forms a convenient source for the preparation of the pigment. Neither
pigment has a spectrum showing absorption bands, but in each there is
continuous absorption at the blue end of the spectrum.

Bilirubin has borne in the history of the bile pigments many names,
such as cholepyrrhin,biliphain,cholephain, and bilifulvin; but, fortunately,
all these names have now disappeared, and the properties of the sub-
stances described under them by different observers, so far as they have
been substantiated, have been aggregated under one name and to one
substance, bilirubin, the red colouring matter of bile. Bilirubin is a con-
stant constituent of bile, and is found besides as a calcium compound in
red gall stones. It is also present in traces in the serum of some animals.
Hammarsten 2 found it in the serum of the horse. By precipitating
the serum globulin with acetic acid, the pigment is thrown down with
the globulin, and on drying the precipitate and extracting with chloro-
form, bilirubin is dissolved out. It seems, however, to be absent in

1 Ztschr.f. physiol. Chem., Strassburg, 1889, Bd. xiv. S. 173.

2 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1878, Bd. viii. S. 129.

384 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

human serum and that of the ox. Most important, from the point of
view of the origin of the bile pigments, is the discovery that the
microscopic crystals often found in old blood clots and extravasations,
and described by Virchow 1 as hceinatoidin, are usually bilirubin ; this
shows that the bile pigments are probably products of disintegration of
haemoglobin. Here it is needful to guard against mistaking lutein for
bilirubin. The two substances may be distinguished by their solubilities.
Both are soluble in chloroform, but bilirubin is thrown out of solution
on the addition of an alkali (from the formation of a compound with the
alkali insoluble in chloroform), while lutein is not so precipitated.
Bilirubin is also found, in cases of jaundice, in the urine and in the
tissues.

Bilirubin is best prepared from the gallstones of the ox, which are very
common and easily procurable. The gallstones are washed, dried, powdered,
and then extracted in turn with ether, boiling alcohol, and boiling water, to
remove cholesterin (which is, however, rarely present in appreciable quantity
in ox gallstones) and bile acids. The residue is treated with dilute hydro-
chloric acid, to set free the bilirubin from its calcium combination, washed
with water and alcohol, and finally extracted with boiling chloroform, in which
the bilirubin dissolves.

The chloroform is distilled from the extract, and the impure bilirubin is
freed from an accompanying substance, bilifuscin, by digesting with absolute
alcohol, in which this substance dissolves, and is then redissolved in chloro-
form. It is purified further by throwing out of concentrated solution in
chloroform, by the addition of absolute alcohol, redissolving and reprecipitating
repeatedly. It is lastly dissolved in as little as possible of boiling chloroform,
from which it crystallises on cooling.

In amorphous condition, as when precipitated by alcohol and dried,
bilirubin is an orange-coloured powder ; when crystalline, it is of a dark red
or reddish-brown colour, resembling chromic acid. The crystals are rhombic
plates with rounded-off angles ; they are more easily soluble in chloroform
than in any other solvent ; somewhat soluble in carbon bisulphide and amyl
alcohol ; nearly insoluble in ether, alcohol, turpentine, benzol, and glacial acetic
acid. Bilirubin is soluble easily in alkalies and their carbonates, combining
with them to form salts. Calcium chloride, added to these solutions, pre-
cipitates the calcium compound (C16Hl7]Sr203)2Ca as a rust-coloured precipitate.
Treated with sodium amalgam, bilirubin yields hydrobilirubin ; on oxidation
it passes into biliverdin and more highly oxygenated compounds. Several
formulae have been proposed for bilirubin ; 2 the most generally accepted is
that of Maly (C16H18ISr203). Bilirubin is oxidised in alkaline solution in the
air to biliverdin in the same manner as bile, which owes this reaction to the
bilirubin it contains.

Ehrlich's test.3 — Ehrlich describes a colour test for bilirubin, which is not
given by biliverdin. To a solution of bilirubin in chloroform an equal volume
of a watery solution of diazobenzolsulphonic acid is added, and just enough
alcohol to cause the two fluids to mix, when the fluid turns a beautiful red
colour ; on adding, drop by drop, concentrated hydrochloric acid, the colour of

1 Virchow' 's Archiv, 1847, Bd. i. S. 379, 407. See also Robin, Compt. rend. Acad. d. sc.,
Paris, 1855, tome xli. p. 506 ; Jaffa", Virclioufs Archiv, 1862, Bd. xxiii. S. 192 ; E. Salkowski,
Hoppe-Seylers Med.-chem. Untersuch., Berlin, 1868, S. 436.

2 Stadeler, Ann. d. Chem., Leipzig, 1864, Bd. cxxxii. S. 323 ; Thudichum, Journ. f.
prakt. Chem., Leipzig, 1868, Bd. civ. S. 401 ; Maly, ibid., Bd. civ. S. 28 ; Maly, Ann. d.
Chem., Leipzig, 1876, Bd. clxxxi. S. 106 : Nencki u. Sieber, JBer. d. deutsch. chem. Gesellsch.,
Berlin, 1884, Bd. xvii. S. 2275.

3 Centralbl. f. Tclin. Med., Bonn, 1883, Bd. iv. S. 722; Krukenberg, "Chem. Unter-
such.," 1886, S. 77.

BILE PIGMENTS AND THEIR DERIVATIVES. 385

the solution changes through violet into blue ; if a layer of potassium hydrate
solution is now introduced beneath the blue solution, there develops an
(alkaline) bluish-green zone underneath, separated from the blue solution above
by a red band where the reaction is neutral.

Biliverdin is present in all green-coloured biles, and may be obtained from
them, by adding a solution of barium chloride, as a dark green precipitate,
which may be washed with water and alcohol, and decomposed by dilute hydro-
chloric acid, when the biliverdin remains as a flocky precipitate ; this is freed
from fats by washing with ether, and is then dissolved in alcohol ; on evaporat-
ing the alcohol, the biliverdin is left behind as a dark green scale. Biliverdin
can best be prepared pure from an alkaline solution of bilirubin. This is
allowed to oxidise by exposing to the air in a shallow dish, until it turns a
brownish-green colour ; the solution is then precipitated with hydrochloric
acid, which sets free insoluble biliverdin from the soluble compound with the
alkali ; the precipitate is washed with water till free from hydrochloric acid,
dissolved in alcohol, and reprecipitated by the addition of water. This
precipitate is washed with chloroform to remove traces of bilirubin, and pure
biliverdin remains behind, being insoluble in chloroform. It forms a very
dark green amorphous powder, insoluble in water, ether, chloroform, carbon
bisulphide, or benzol ; but soluble with a fine green colour in alcohol, glacial
acetic acid, or concentrated sulphuric acid. According to MacMunn,1 there is
a green pigment in ox bile which differs from that prepared as above, in being
soluble in chloroform. Biliverdin does not easily crystallise ; it is said to be
occasionally obtainable, by evaporating a solution in glacial acetic acid, in
rhombic plates with rounded angles. With alkalies, biliverdin forms soluble
compounds, giving brownish-green solutions, from which biliverdin falls as a
flocky precipitate on the addition of acids. Calcium, barium, and lead salts
form insoluble compounds with biliverdin ; these are thrown down as dark
green precipitates on addition of solutions of the corresponding salts to an
alkaline solution of biliverdin. By nascent hydrogen, biliverdin^is converted
through bilirubin into hydrobilirubin. Different formulae are given by different
authors for biliverdin. Stadeler 2 calculated it as C16H20N205, from analyses
by Heintz. Heintz himself 3 gives C16H1S]N"205. This formula assumes that
in passing from bilirubin to biliverdin, the molecule takes up water as well as
oxygen (C10H18N"203 + H20 + 0 = C16H20N205), but the accuracy of this is
denied by Maly,4 both from analysis and the amount of increase in weight
observed in passing from bilirubin into biliverdin. He gives the formula of
biliverdin as C16H1SN204, and this result is confirmed by Thudichum,5 except
that the latter halves the formula, giving C8H9N02.

G-melins test for 'bile pigments. — This very distinctive test for the bile
pigments has already been mentioned. It depends upon the remarkable
changes in colour accompanying the oxidation of bilirubin. In such
oxidation the other normal bile pigment, biliverdin, is first produced ;
and this in turn, by further oxidation, is converted into a blue pigment,
bilicyanin; after this follows, according to some, a purple pigment
(bilipurpurin) before the final stage of oxidation to a yellow compound,
choletelin. The production in series of these artificial products of
oxidation is what constitutes Gmelin's test.

If either a solution of bilirubin or some diluted bile be carefully

1 Journ. Physiol., Cambridge and London, 1885, vol. vi. p. 25.

2 Ann. d. Chem., Leipzig, 1864, Bd. cxxxii. S. 323.

3 Jahresb. il. d. Fortschr. d. ges. Med., Erlangen, 1851, Bd. ii. S. 59; Ann. d. Phys.
u. Chem., Leipzig, 1851, Bd. Ixxxiv. S. 106.

4 Jahresb. il. d. Fortschr. d. Thier-Chem., Wiesbaden, 1874, Bd. iv. S. 302 ; and Her-
mann's "Handbuch," Bd. v. (2), S. 159.

5 Journ. /. prakt. Chem., Leipzig, 1868, Bd. civ. S. 220.

VOL. I. — 25

386 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

poured on the surface of fuming nitric acid in a test tube, so as not
to mix the two liquids, a series of coloured zones appears in the
lower part of the column of bile above the acid ; next to the acid is the
most oxidized product (choletelin), represented by a yellow-red zone ;
above this is a purer red, passing into a purple, which is replaced by a
blue zone (bilicyanin) ; and, lastly, there is a very broad green zone,
corresponding to the least oxidized product (biliverdin). The test may
also be made by spreading out the bile in a thin film over the inside
of a porcelain capsule and placing a drop of fuming nitric acid in the
centre of this film, when a series of colours develop in the above order
around the drop ; or perhaps, most conveniently of all, according to
Eosenbach's modification, by moistening a piece of filter paper in the
suspected fluid, and placing a drop of fuming nitric acid in the
centre.

Huppert's test. — Huppert's test consists in precipitating calcium
bilirubinate, by the addition of milk of lime, or calcium chloride and
ammonia, to a solution of an alkaline bilirubinate (or alkaline bile) ;
after washing with water, the precipitate is boiled for some minutes
with alcohol acidified with sulphuric acid, when, in presence of bile
pigments, the solution develops an emerald-green or blue -green colour.

Bilicyanin is the name given to the substance present at that stage of
oxidation of bilirubin by artificial means, such as fuming nitric acid, when
the solution has a blue colour. The stage is a very transient one, and, though
many have worked at the subject, no one has yet succeeded in isolating the
substance to which the blue colour is due. It is probably an unstable
oxidation product, intermediate between biliverdin and choletelin. A blue
solution, which keeps for some hours, may be obtained by adding to a solution
of bilirubin in chloroform a little nitric acid, and shaking till a violet tint
first appears. Rectified spirit is then quickly added ; this very much slows the
completion of the oxidation, so that the blue colour is preserved for some
time. If an ammoniacal solution of bilirubin be mixed with strong fuming
nitric acid, a little at a time, and excess of acid removed each time by addition
of ammonia, a dark flocky precipitate is obtained, from which biliverdin can
be removed by alcohol, leaving behind a deep dark blue powder.1 Heynsius
and Campbell 2 have found that certain gall stones in man, after extraction
with alcohol and ether, yield to dilute acids a violet-brown pigment, which
they identified as bilicyanin spectroscopically.

Jaffe3 first observed that the blue stage of the oxidation process
gave an absorption spectrum ; in strong solution, it shows a wide band
beginning to the red side of D, and ending between D and E ; on dilution
this band resolves itself into two dimmer bands (« and /3). As oxida-
tion proceeds, a third band (7) appears between I and F, whilst the two
first mentioned gradually become fainter and disappear. This third
band does not belong to the blue stage (bilicyanin), but to the substance
formed in the final stage of the oxidation (choletelin). The violet
colour obtained before the final permanent reddish brown is probably
due to an admixture of the latter colour with blue.

Bilifuscin is a substance separated in the preparation of bilirubin from
gall stones ; very little is known of its properties or chemical relationships.

1 Jaffe, Centralbl. f. d. med. Wissensch., Berlin, 1868, Bd. vi., S. 241 ; Journ. /.
prakt. Chem., Leipzig, 1868, Bd. civ. S. 401.

2 Arch.f. d. ges. PhysioL, Bonn, 1871, Bd. iv. S. 537. 3 Loc. cit.

BILE PIGMENTS AND THEIR DERIVATIVES. 387

In the presence of bilirubin it is soluble in chloroform, although diffi-
cultly soluble in this solvent alone ; hence, after treatment with chloroform in
preparing bilirubin, both substances come into solution. When the chloroform
solution is concentrated, and excess of alcohol added, the bilirubin is pre-
cipitated, while the bilifuscin remains soluble, and is found in the alcoholic
filtrate along with some cholesterin and higher fatty acids. After removal of
the alcohol by evaporation, the residue is treated with ether, which dissolves
out these impurities, and chloroform, which removes any traces of bilirubin
left behind. The almost black, dark brown residue so obtained, was termed
bilifuscin by Sta'deler ; l who made incomplete analyses of it, from which he
deduced the formula C1GH20N204 (?). When quite pure, bilifuscin does not
give Gmelin's reaction ; 2 it is found in very old post-mortem bile 3 as well as
in gallstones, but not in fresh bile. Bilifuscin has only been obtained in an
amorphous form ; it is soluble in alcohol and in alkalies ; almost insoluble in
water, ether, and chloroform ; its relationship to bilirubin is unknown. The
biliprasin of Sta'deler4 is probably only a mixture of bilifuscin and biliverdin.
Bilihumin is a name used by the same observer to designate a black mass
taken up by strong solution of ammonia, from the residue of gallstones
which have been thoroughly exhausted with chloroform, alcohol, and ether;
it does not give Gmelin's reaction.

Hydrobilirubin (C32H40N407), a reduction product of bilirubin, is an
important substance, from the connection it makes between the bile
pigments, those of the urine and the products of disintegration of
haemoglobin.

Maly 5 first obtained it by the action of nascent hydrogen (from sodium
amalgam) on an alkaline solution of bilirubin ; biliverdin similarly treated
also yields it, being first converted into bilirubin. At the end of the reaction
the light brown coloured fluid is decanted from the mercury, and acidified
with hydrochloric acid. On the addition of the acid the solution becomes
much darker in colour, and abundant dark brown flocks of hydrobilirubin
separate out; these are separated from the solution, dissolved in ammonia,
reprecipitated with hydrochloric acid, and washed with water. After so
washing away all the salts the pigment becomes less soluble in water. After
drying it forms a dark reddish-brown powder, easily soluble in alcohol, or a
mixture of alcohol and ether ; not so soluble in ether alone. These solutions
have, when concentrated a reddish brown, when dilute a rose colour.
Chloroform dissolves it to form a yellowish-red solution. In alkalies it
dissolves to a pale yellow solution, becoming red on the addition of an acid.
Maly ascribes the yellow colour to a compound with the alkali, the red to
the free substance.

Hydrobilirubin in solution has an absorption spectrum, showing a
dark band between I and F. On addition of ammonia this band fades
out, but reappears a little to the left on the addition of a trace of zinc
chloride to the solution. This solution containing zinc chloride and
ammonia has a rose colour and a green fluorescence. Hydrobilirubin
once formed does not readily give Gmelin's test ; that is to say, it is not
easily oxidisable again to bilirubin or biliverdin.

Maly recognised his new substance as identical with a urinary

1 Vrtljschr. d. naturf. Gesellsch. in Zurich, 1863, Bd. viii.

2 Briicke, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1860, Bd. vi. S. 173.

3 Simony, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1876, Bd. vi. S. 75.

4 Loc. cit.

5 Jahresb. u. d. Fortschr. d Thier-Chem., Wiesbaden, 1872, Bd. ii. S. 232.

388 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

pigment, already described under the name of urobilin, and discovered
by Jaffe l under pathological conditions in the urine. Immediately
before Maly's discovery, Hoppe-Seyler 2 had described a brownish-red
substance, which he obtained by the action of zinc and hydrochloric
acid (i.e. nascent hydrogen), on haematin ; this, he afterwards stated to
be impure hydrobilirubin.3 When one considers that bilirubin is poured
into the intestine with the bile, and that it is here subjected to reducing
influences, as is shown by the frequent presence of hydrogen in the
intestinal gases, it is natural to suppose that a considerable conversion
of bilirubin into hydrobilirubin goes on in the intestine. The pigments
of the faeces, which must arise mainly from the bile pigments, do not
give Gmelin's reaction; extraction of the faeces with dilute spirit,
evaporating and extracting the residue with strong spirit, yields a
solution which shows the spectrum ?»f hydrobilirubin.4 This pigment
of the faeces had been already described as stercobilin by Vanlair and
Masius.5 Jaffe6 considered it as identical with his urobilin. Maly
gives the above theory of its formation in the intestine from bilirubin,
and looks upon all three, as well as Hoppe-Seyler's compound from
haamatin, as one substance, namely, hydrobilirubin.7

It is generally accepted that these substances are closely related, if
not identical, and their relationship is of the utmost importance in con-
necting the pigments of the bile with the waste products of haemoglobin.8

Choletelin. — Besides this important reduction derivative of bilirubin,
we also owe to Maly9 the discovery of choletelin, the final substance
obtained in its oxidation by nitric acid.

At the end of the reaction a yellow colour is obtained, not widely
different from that of the bilirubin from which the reaction started;
when this condition is reached, all the intermediate products have been
converted by oxidation into one substance.

Choletelin is best prepared, according to Maly,10 by leading a stream of
nitrous fumes (prepared by acting on arsenious acid with nitric acid) through
bilirubin suspended in alcohol. The fluid passes through the colours of
Gmelin's reaction, and finally a clear, pale, yellowish-red solution is left ; this
is thrown into water, when choletelin separates out in rust-coloured flocks,
which form, when dried, a brown powder. Choletelin is amorphous and
probably represented by the formula C1GH18N206; it is soluble in alcohol,
ether, chloroform, and acetic acid. It is also soluble in alkalies, and
precipitated from such solution by acids. In acid solution it shows a dim
absorption band lying between b and F, and corresponding to the band y
observed by Jaffe in solutions of bilicyanin. In neutral alcoholic solution this
band disappears.

1 Virchow's Archiv, 1869, Bd. xlvii. S. 405-418.

2 Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i. S. 80 ; Med.-chem.
Untersuch., Berlin, 1871, S. 536.

3 Ber. d. deutsch. chem. Gesellsch., Berlin, 1874, Bd. vii. S. 1065.

4 Maly, Hermann's "Handbuch," Bd. v. (2), S. 162.

5 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1871, Bd. i. S. 229.

6 Arch.f. d. ges. PhysioL, Bonn, 1871, Bd. iv. S. 537.

7 Hermann's "Handbuch," Bd. v. (2), S. 162.

8 See MacMunn, Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 71 ; Eichhok,
Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 326 ; Garrod and Hopkins,
Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 113 ; Garvoch, ibid., 1897, vol.
xxi. p. 190.

9 Sitzungsb. d. k. Alcad. d. Wissensch., Wien, 1868, Bd. Ivii. Abth. 2, S. 107 ; 1869.
Bd. lix. Abth. 2, S. 602.

10 Hermann's "Handbuch " Bd. v. (2), S. 165.

BILE PIGMENTS AND THEIR DERIVATIVES. 389

The halogens react energetically with bilirubin, forming substitution
products. When bromine acts on bilirubin, a series of changes in colour
take place, exactly counterfeiting those observed in Gmelin's reaction.
The reactions are, however, quite different ; and the process is not, as one
might naturally have expected, an oxidation, but a substitution of
bromine for hydrogen1 (2C16H18N203+3Br2 = C32H33Br3N4O6+3HBr).2

The reaction is best shown by adding a dilute solution of bromine in
chloroform, cautiously, to a solution of bilirubin, also in chloroform. The solu-
tion changes through green, blue, and red into yellow, as the bromine is added,
and may be stopped and examined at any stage. If chloroform free from
alcohol be used, a tribromo derivative separates out of solution. Decanted
from chloroform, dissolved in alcohol, and reprecipitated by adding water, this
compound is obtained as a dark blue powder, soluble in alcohol, in ether, or
in chloroform containing alcohol ; but insoluble in pure chloroform, or in
water. Alkalies split it up, yielding biliverdin.

Nothing is known of the chemical constitution of the bile pigments,
and very little of the intermediate stages in their production from
haemoglobin. Their connection with haemoglobin rests on — (1) The
identity of haematoidin produced in old blood clots with bilirubin. (2)
The identity of Hoppe-Seyler's reduction product obtained from haematin,
and thus indirectly from haemoglobin, with Maly's hydrobilirubin.

(3) The absence of bile pigments in such animals as have no haemoglobin.3

(4) The fact that anything causing increased destruction of red blood
corpuscles, or the intravenous injection of haemoglobin, causes an increased
secretion of bile pigments.4 (5) Haematoporphyrin is isomeric with
bilirubin, shows with nitric acid colour changes somewhat resembling
Gmelin's reaction, and yields on reduction with nascent hydrogen a
substance closely resembling and probably isomeric with hydrobilirubin.
According to Nencki and Sieber,5 bilirubin is formed in the liver by the
haemoglobin first splitting up into haematin and proteid. The haematin
thus formed then takes up water, loses its iron, which is retained in
combination in the liver, and so forms bilirubin, thus —

C32H32N404Fe-f 2H20— Fe = C32H36N406; or 2(C16H18N203)

(hsematin) (bilirubin)

Direct experiments on the formation of bile pigments from haemo-
globin apart from the liver have been carried out by Latschenberger.6
If the corpuscles and serum of horse blood be separately injected sub-
cutaneously at different parts in the horse, and after the lapse of about
twelve days the animal be killed, and the parts where the injections have
been made are examined, it is found that while, at the part where the

1 Thudichum, Journ. Chem. Soc., London, 1875, vol. xxviii. p. 389 ; Maly, Sitzungsb. d.
k. Akad. d. Wissensch., Wien, Bd. Ixxii. Abth. 2.

2 Maly, Hermann's "Handbuch," Bd. v. (2), S. 167.

3 Hoppe-Seyler, Arch. f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 399. See, however,
Krukenberg, CentralU. f. d. med. Wissensch., Berlin. 1883, No. 44, S. 785.

4 Frerichs, Arch. f. Anat. u. PhysioL, Leipzig, 1856, S. 59 ; W. Kiihne, Virchow'sArchiv,
1858, Bd. xiv. 8. 310 ; Nothnagel, BerL klin. Wchnschr., 1866, vol. vi. S. 31 ; Tarchanoff,
Arch. f. d. ges'. PhysioL, Bonn, 1874, Bd. ix. S. 329 ; Minkowski and Bassorin, Arch. f.
exper. Path. u. Pharmakol., Leipzig, 1887, Bd. xxiii. S. 145.

5 Ber. d. deutsch. chem. Gesdlsch., Berlin, 1884, Bd. xvii. S. 2275 ; Monatsh. f. Chem.,
Wien, 1888, Bd. ix. S. 115 ; Arch. f. exper. Path. u. Pharmakol., Leipzig, 1888, Bd. xxiv.
S. 430.

6 Monatsh. f. Chem., Wien, 1888, Bd. ix. S. 52; Sitzungsb. d. k. Akad. d. Wissensch.,
Wien, 1888, Bd. xcvii. Abth. 2b, S. 15.

390 CHEMISTR Y OF THE DIGESTIVE PROCESSES,

serum has been injected the tissues present a normal appearance and
contain no bile pigments, on the other hand, round the spot where the
corpuscles have been injected, the tissues contain, besides fluid blood, a
substance in flakes, varying in colour from dark orange to bright yellow,
composed of small spherical masses about a quarter of the size of red
corpuscles, which give Gmelin's reaction very readily. The same result
may be obtained on injecting crystallised haemoglobin, suspended in
water; here granular masses of a greenish-yellow colour are obtained,
which also give Gmelin's reaction.

Spectra of bile. — A considerable amount of continuous absorption at
both ends of the spectrum is found on examining the bile of any animal,
but in some animals the bile also shows well-marked absorption bands.1

Cholohtematin. — The most characteristic of these band-spectra is that
exhibited by ox or sheep bile which has stood for some time in contact with
air. This spectrum, according to MacMunn,2 " presents in a deep layer three
bands, in a thinner one four bands, and in a still thinner a fifth band at F is
visible." The spectrum is well seen in an alcoholic solution of evaporated ox
bile. Of the four well-marked bands, two lie close to the D line, on either side
of it ; a third lies in the red, immediately to the right of the C line ; and the
fourth covers the E and b lines. No pure material has yet been isolated,
so that it is not even known whether the spectrum is due to one or several
substances. MacMunn3 has obtained an amorphous residue of a dark sap-
green colour, containing abundantly material which gives the spectrum, by
treating ox bile with absolute alcohol and acetic acid, alternately dissolving in
chloroform and ether, and washing the chloroform solution with water. This
material has been named cholohsematin by MacMunn, from its occurrence in
bile and its supposed origin from hsematin.

The spectrum is not exhibited by fresh ox or sheep bile,4 but is first
developed on standing in contact with air, probably from a chromogen present
in the fresh bile. The bands near D first appear, to be followed much later by
the other two ; the appearance of the spectrum is not a result of putrefaction.5

MacMunn6 obtained a spectrum closely resembling that of ha3matoporphyrin
by the action of sodium amalgam on cholohaematin, prepared as above indicated,
from which he argues that the latter is a derivative of hsematin.

The fresh bile of the mouse shows a well-marked band at F, corresponding
to the urobilin band ; and more or less distinct bands in the same position in
the bile of other animals indicate, according to MacMunn, traces of urobilin
in these fluids. Characteristic absorption-band spectra are also found in the
bile of the guinea-pig, pig, rabbit, and crow. Human bile shows no bands, but
an alcoholic extract exhibits a well-marked band at D ; these, as well as the
spectra of Gmelin's and Pettenkofer's reactions, are shown in Plate III. at
the end of this volume.

Other constituents of bile.— Besides the bile salts and bile pig-
ments, which are normally found only in the bile, other constituents are
present which are also found in other parts of the body; these are
cholesterin, fats, soaps, and lecithin, besides minute traces of urea and
of the diastatic ferment already mentioned.

1 Bogomoloff, CentralU.f. d. med. Wissensch., Berlin, 1869, vol. vii. S. 530.

2 "The Spectroscope in Medicine," London, 1880, p. 158.

3 Journ. Physiol., Cambridge and London, 1885, vol. vi. p. 24.

4 Bogomoloff, loc. cit.; Heynsius and Campbell, Arch. f. d. ges. PhysioL, Bonn, 1871,
Bd. iv. S. 540.

5 Gamgee, "Physiological Chemistry," London, 1893, voL ii. p. 333; see also Hoppe-
Seyler, loc. cit.

6 Loc. cit., p. 27.

REABSORPTION OF BILE SALTS. 391

Cholesterin. — The amount of cholesterin in bile is very variable,
ranging from 0'5 to 5 per cent. Cholesterin is insoluble in water or
dilute saline solution, and is dissolved in bile by the agency of the bile
salts, in solutions of which it is easily soluble. When the amount of bile
salts is insufficient to hold it in solution, it slowly passes out of solution
in a concretionary form around any particle of foreign matter present in
the bile, or around an existing concretion forming in this manner a
variety of gall stone.

According to Hoppe-Seyler, cholesterin is a cleavage product,
constantly formed in the metabolic changes of the living cell ; and for
this reason it is that cholesterin is invariably found as a chemical
constituent of both animal and vegetable cells. Cholesterin does not
easily undergo decomposition in the animal organism when once formed,
and is principally excreted in the higher animals in the bile. It is
found in increased quantity in tissue which is undergoing pathological
change ; this may, perhaps, be due to increased inability on the part of
the cells in their vitiated condition to break up the stable cholesterin.
Cholesterin is found in largest quantity as a constituent of the myelin
of nerve fibres and in the blood corpuscles. It is probably formed most
in the metabolism of nerve tissue,, taken up by the liver cells from the
blood, and passed as an excretion into the bile ducts.

Cholesterin is purely an excretion, and is not reabsorbed, but passes
out of the body with the faeces. This is also the fate of the bile
pigments, which are gradually reduced to hydrobilirubin (stercobilin)
in their passage along the intestine. This substance may easily be
extracted from the fseces by absolute alcohol, after making acid with
sulphuric acid. The bile pigments have a poisonous action when
injected 'into a vein, which indicates that if they are reabsorbed at all
they must be changed in the process.1

Lecithin. — The amount of lecithin present in bile is much greater
than in any of the other secretions. All the lecithin, and any direct
products of its decomposition to be removed from the body, are carried
off' in the bile. As lecithin, as well as cholesterin, is one of the con-
stituents of nerve tissue, the liver, by means of the bile, may be looked
upon as the great channel for the removal of the products of nervous
metabolism. Lecithin is also held in solution by the bile salts.

Reabsorption of bile salts — Their functions in the organism. —
The bile salts differ from the other biliary constituents in that they are
not purely an excretion. They are to a large extent reabsorbed, and
undergo a circulation in the body, with the probable function of acting
as carriers for the otherwise insoluble cholesterin in the bile. Such an
absorption of bile salts has been shown to take place in different ways,
which are, briefly, as follows : —

1. Bile salts taken by the mouth, cause an increased flow of bile ;
indeed, from recent observations by various experimenters,2 it seems that
the bile salts are the only substances which truly act as cholalogues.
This action can only be due to their absorption followed by an increased
elimination of them by the liver.

2. The bile of the dog contains only taurocholates. If impaired

1 De Bruin, Centralbl. f. klin. Med., Bonn, 1890, Bd. xi. S. 491.

'2 Baldi, Arch. ital. de biol., Turin, 1883, tome iii. p. 395; Paschkis, Schmidt's Jahrb.,
Leipzig, 1885, Bd. ccvi. S. 19 ; Nissen, Centralbl. f. d. med. Wissensch., Berlin, 1890, Bd.
xxviii.1 S. 948.

392 CHEMISTRY OF THE DIGESTIVE PROCESSES.

cholalic acid be given by the mouth, the amount of bile is increased, but
still only taurocholates are found in the bile ; but Weiss l found, after
giving sodium glycocholate for three days (5-9 grins, per diem), that
the bile in the gall bladder at death contained glycocholates, amounting
to 25-30 per cent, of the total bile salts present.

3. No connection exists between the amount of proteid metabolism
and the amount of cholates produced, such as would be found if the
cholates were a channel for the excretion of the nitrogen and sulphur of
proteid decomposition products.2

4. Tappeiner 3 identified bile salts in chyle obtained from the
thoracic duct in the dog.

5. Bidder and Schmidt 4 only found cholalic acid in traces in the faeces.
A review of all these facts shows that the bile salts are not an

excretion, but perform a circulation in the body. Besides the function
of dissolving the cholesterin to be excreted, the bile salts are also
credited with the effect produced by bile in aiding the absorption of
fats.5 Again, bile salts dissolve insoluble soaps of the alkaline earths.
This may be shown by precipitating a soluble soap with calcium or
magnesium sulphate, and then adding a solution of bile salts and gently
warming when the precipitate dissolves.6 Maly and Emich state that
taurocholic acid completely precipitates native proteids, but not album-
oses or peptones.7 This in part explains the precipitation observed when
a solution in which peptic digestion is going on (or gastric chyme) is
mixed with bile; but part of the precipitate is doubtless mucin from
the bile itself. The subject has been investigated by Hammarsten,8
who found that syntonin was completely, peptone only partially, pre-
cipitated from an acid solution in which peptic digestion of hard-boiled
white of egg had been carried out, by the addition of bile from which
the mucin had been removed by alcohol. Hammarsten supposes that
the purpose of this precipitation of the semi-digested proteid, which
must occur in natural digestion when the gastric chyme comes in
contact with the bile, is that it may, by adhering to the intestinal wall,
be longer subjected to intestinal digestion than it would be if it remained
in solution.

1 Centralbl.f. d. med. WissenscJi., Berlin, 1885, Bd. xxiii. S. 121. Similar results have
been obtained by Prevost and Binet, Compt. rend. Acad. d. sc., Paris, 1888, tome cvi. p.
1690 ; Winteler, Inaug. Diss., Dorpat, 1892.

2 Kunkel, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 344 ; Spiro, Arch. f. Anat.
u. PhysioL, Leipzig^ 1880, Supp. Bd. S. 50.

3 Sitzungsb. d. Jo. Akad. d. Wissensch., Wien, 1878, Bd. Ixxvii. Abth. 3.

4 " Die Verdauungssiifte," S. 217. 5 Vide " Fat Absorption," p. 454.

6 Neumeister, " Lehrbuch d. physiol. Chem.," Jena, 1893.

7 Monatsh.f. Chem., Wien, 1883, Bd. iv. S. 89 ; 1885, Bd. vi. S. 95.

8 Jahresb. it. d. Fortschr. d. ges. Med., Erlangen, 1870, Bd. 1, S. 106. See also
Chittenden and Cummins, Am. Chem. Journ., Baltimore. 1885, vol. vii. p. 36 ; Jahresb.
ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1885, Bd. xv. S. 319.

DIGESTION OF CARBOHYDRA TES. 393

DIGESTION OF CARBOHYDKATES.

The digestion of carbohydrates is brought about by the action of two
distinct classes of enzymes, namely — 1. Those which act on starches,
producing sugars and dextrins : these are called amylolytic or diastatic
ferments. 2. Those which act on various saccharoses, producing glu-
coses : these are called inverting ferments.

The two chief amylolytic ferments found in the digestive juices are
ptyalin and amylopsin. The action of these ferments on starch may be
demonstrated by adding to starch paste, either saliva or pancreatic juice,
or a watery infusion of salivary or pancreatic gland. The paste very
soon becomes quite fluid, and if the fluid be tested chemically for starch,
it will be found that this substance is rapidly disappearing, and that a
reducing material is being formed in continuously increasing amount in
the solution. This testing may be done by removing a drop of the
solution at intervals, and mixing it with a drop of a solution of iodine.
At first the deep blue colour given by starch is obtained ; this is replaced
after a time by a violet, this again by a red colour, and finally no
coloration at all is obtained. If at each of these stages portions of the
solution be tested with Fehling's solution, it will be found that it has
acquired reducing power, and that the amount of reduction increases
with the length of time during which the action goes on.

The diastase of malt is very similar in its action to both these
ferments, but is not identical with either of them, as is shown by the
fact that while ptyalin and amylopsin act best at body temperature, the
optimum temperature for the action of malt diastase is about 55° C.

Products of digestion of starch. — Whether the ferments are
identical or not, their action, according to all observers, is the same. It
was shown by Leube,1 in 1831, that saliva dissolves starch-paste and
forms sugar, and the same was shown for pancreatic juice by Bouchardat
and Sandras,2 in 1845. It was for many years believed that the
action of these ferments was closely analogous to that of mineral
acids, and that the sugar produced was grape-sugar. Dextrin was
supposed to be the first stage in the process of saccharification, and
from the dextrin it was thought that grape-sugar was afterwards
formed. Musculus 3 was the first to show that all the starch was not
so converted into sugar, but that saccharification only proceeded until
the solution gave no longer a colour reaction with iodine; on adding
fresh starch-paste, the reaction recommenced and proceeded as before,
until again all colour reaction with iodine had vanished, when, as
before, the reaction slackened and stopped, although there remained
plenty of dextrin in the solution.

According to the earlier work of Musculus, the quantitative relationship in
which the sugar and dextrin stand at the end of the reaction is, one part of
sugar to two of dextrin; his later papers gave the reaction as stationary,
when approximately equal quantities of sugar and dextrin are present in the
solution.4

1 Arch.f. d. ges. NaturL, Niirnberg, 1831.

2 Compt. rend. Acad. d. sc., Paris, 1845, tome xx. p. 1085.

3 Journ. depharm. et chim., Paris, 1860, Ser. 3, tome xxxvii. p. 419.

4 Payen, Chem. Centr.-BL, Leipzig, 1865, S. 845; Schwarzer, ibid., 1870, S. 295;
Schulze u. Marker, ibid., 1872, S. 823.

394 CHEMISTRY OF THE DIGESTIVE PROCESSES.

Still later, Sheridan Lea,1 working with much more dilute solutions than
were usually employed by other experimenters (0'4 to 4 per cent.), found as
much as 85 per cent, of the starch converted into sugar ; and by more closely
approximating the conditions of experiment to those of natural digestion, by
carrying out the experiment in a dialyser instead of in a glass vessel, obtained
a still greater reduction in the percentage of dextrin formed (7 to 8 per cent.).
He is therefore of the opinion that in the alimentary canal starch is
completely converted into sugar before absorption. The increase in sugar
formation, due to removal of the products of digestion, was more marked in
working with strong than in working with dilute solutions ; this also goes to
show that it is the accumulation of maltose in the solution which slackens and
stops the reaction. All chemical reactions involving hydration, such as saponi-
fieation of esters, become stationary at a determinate point when a lixed
proportion of hydration has taken pla§e ; and this point is rigorously de-
termined by the concentration in the solution of the various factors in the
reaction. If the substance or substances formed in the reaction be continuously
removed from the solution, or changed in nature as they are formed, the
reaction proceeds to completion ; but if the products of the reaction remain in
solution unchanged, at a perfectly fixed point, dependent on the concentration
in solution of each of the reacting substances, equilibrium is established, and
no further change in the composition of the solution takes place.

On the other hand, Musculus and Gruber 2 claim to have isolated a dextrin
after acting on starch paste with diastase for five days, by precipitating the
dextrin with alcohol ; on this dextrin, diastase, even in the absence of the sugar ^
has no further action.

In 1872, O'Sullivan 3 rediscovered the sugar described by Dubrunfaut 4
as formed by the action of malt extract on starch paste, isolated it,
investigated its properties, and named it maltose. When it was so shown
that the sugar formed by the action of malt diastase is not grape-sugar,
attention was directed naturally to the sugars similarly formed by the
action of the digestive enzymes of the saliva and pancreatic juice.
Nasse5 stated that the sugar formed by the action of saliva is not
dextrose, but another sugar of different reducing power, to which he
gave the name of ptyalose, which, however, was not maltose, as its
reducing power was doubled on boiling with acids, while that of maltose
was only increased by one -half. Soon after, v. Mering and Musculus 6
conclusively showed that the sugar really formed both by ptyalin and
amylopsin is identical with O'Sullivan's maltose, and these results have
been abundantly confirmed by subsequent observers. This result they
established by the amount of increase of reducing power and reduction
of rotating power, following boiling with a dilute mineral acid, as well as
by the observation of birotation in the solution after boiling, which
could only be due to the formation of grape-sugar. Such an analysis is
rendered easy by the widely different specific rotatory powers and
reducing powers of the two sugars (see table, p. 396).

The action of malt diastase, ptyalin, or amylopsin on starch paste
takes place in several stages, corresponding to which more or less

1 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 226.

2 Ztschr.f. physiol. Chem., Strasslmrg, 1878, Bd. ii. S. 187.

3 Journ. Chem. Soc., London, 1872, vol. xxv. p. 579.

4 Ann. de chim. etphys., Paris, 1847, tome xxi. p. 178.

5 Arch. f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 477 ; see also Seegen, Centralbl. f. d.
med. PTissensch., Berlin, 1876, 8. 851.

6 Zischr. f. physiol. Chem., Strassbnrg, 1877, Bd. i. S. 395 ; 1878, Bd. ii. S. 403. See
also Brown and Heron, Proc. Roy. 8oc. London, 1880,- vol. xxx. p. 393.

PROD UCTS OF DIGESTION OF STARCH. 395

well-differentiated substances have been described. The first step in
the action is, according to all observers,1 the formation of soluble starch
(amigdulin, amidulin, arnidogen, or amylodextrin). This substance is
rapidly formed, usually in one or two minutes ; it gives the same blue
reaction with iodine as raw starch or starch paste, and is precipitated by
tannic acid, by which it is distinguished from the dextrins formed in the
subsequent stages.

In the second stage, this' soluble starch is decomposed into a sub-
stance giving a red colour with iodine and maltose. The substance
giving the red colour now gets the name given by Briicke of erythro-
dextrin; it corresponds to Nasse's dextrin, Griessmayer's dextrin-1
and Bondonneau's dextrin-a.

In the third stage, this erythrodextrin is split up into a dextrin (or
several dextrins), giving no coloration with iodine, and hence called
achroodextrin, and a further quantity of maltose. Finally, according to
some, a part of this achroodextrin breaks up, yielding more maltose,
and a variety of achroodextrin, altogether unaffected by diastatic
ferments, which with the maltose split off at different stages from the
intermediate products, forms the final product of the reaction, no matter
how long prolonged.

These successive changes may be represented as in the following

scheme : —

Starch

Soluble Starch.

I

Erythrodextrin Maltose

I

Achroodextrin Maltose

All observers are agreed as to the existence of soluble starch, and
practically all as to that of erythrodextrin, although Musculus and Meyer 2
state that, on carefully mixing dextrin stained with iodine, with soluble
starch stained with iodine, they obtained the colour of erythrodextrin, and
conclude that Avhat has been called erythrodextrin is probably such a mixed
colour. This result has not been confirmed by other observers ; still it
should be borne in mind that a pure substance has not yet been isolated, and
that at present erythrodextrin is only a name given to a substance supposed
to exist, because of a red colour which is obtained at a certain stage in the
digestion of starch by diastatic enzymes. The material which is found later
in the process, which is not a sugar and gives no coloration with iodine, has
been called achroodextrin, but it has none of the constant properties of a
pure simple substance, and is probably a mixture of several substances
(achroodextrins), though as yet none of these have been properly isolated.

Musculus and Gruber,3 working on starch solutions with dilute acids and
with diastase, differentiated, according to varying conditions of temperature,
amount of diastase added, and length of time of action of the ferment, three
achroodextrins (a, (3, and y), possessing, according to these observers, different

1 Nasse, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 474 ; Griessmayer, Chem.
Centr.-BL, Leipzig, 1871, S. 636; Briicke, " Vorlesungen," and Sitzungsb. d. k. Akad. d.
Wissensch., Wien, 1872, Abtli. 3; Bondonnean, Compt. rend. Acad. d. Se., Paris, 1875,
tome Ixxxi. pp. 972, 1210; Musculus, Ztschr. f.physiol. Chem., Strassburg, 1878, Bd. ii.
S. 177.

2 Ztschr. f. physiol. Chem., Strassburg, 1880, Bd. iv. S. 451.

3 Ibid., 1878, Bd. ii. S. 177.

396

CHEMISTRY OF THE DIGESTIVE PROCESSES.

specific rotatory powers and reduction coefficients ; but they scarcely give
adequate proofs that they are describing pure substances.1 They found that
even after twelve months a portion of the dextrin remained unconverted into
maltose, and the substance so remaining was unfermentable by yeast. This
substance is y-achroodextrin, and is formed together with some maltose by the
splitting up of /3-achrob'dextrin, which in its turn is formed by a similar
decomposition of a-achroodextrin.

The following is a summary of their results : —

Sp. Rotatory Power.

Relative reducing
Power for Fehling's
Solution.

Reaction with
Iodine.

Soluble starch .

218 .

6

Reddish blue.

Erythrodextrin

Red.

«-Achroodextrin

210°

12

No coloration.

£ ,,

190°

12

f j

y

150°

28

J}

Maltose .

150°

66

Grape-sugar

50°

100

5)

The digestion of starch by diastatic enzymes consists of a breaking
up, through several more or less well-defined stages, by a process of
gradual hydrolysis, of a very complex molecule into a much simpler one,
and might be represented schematically by the following general
equation, which cannot be made more definite, because we are un-
acquainted with the molecular weights of starch and dextrin, only
knowing that they are very large —

Starch Maltose

(C6H.1005)n + (H20)m = ™(CI2H220U,H20) + »

Dextrin

That is, starch and water, in presence of a suitable ferment, yield
maltose and different dextrins, but we are ignorant of the value of
n, in, and p.

Attempts to carry too far the analogy between the action of
dilute mineral acids and that of the diastatic ferments on starch,
led, as already stated, to an error, which persisted for several years,
as to the products of the latter action. Nevertheless, a close analogy
does exist between the two processes ; both are essentially hydration
processes; and in both the same stages may be observed. They
only differ in two respects, first, that the dilute acid at boiling tem-
perature acts much more rapidly; secondly, that it proceeds a
stage further, and very rapidly converts the maltose formed into grape-
sugar.

These successive changes may be best observed by boiling with very
dilute acid ('2 per cent, or less). Soluble starch is first formed, giving, on
neutralisation, a blue with iodine ; next, is an intermediate stage, in which a
violet is obtained followed by a stage giving a red colour (erythrodextrin) ;
and finally a stage is reached at which a coloration is no longer obtained

1 According to Brown and Morris (see Trans. Chem. Soc., London, 1885, p. 527 ; 1889,
p. 462), the chemical and physical properties of these different achroodextrins might be
given by a variable mixture of one achroodextrin possessing no reducing power with mal-
tose. They admit the existence besides achroodextrin, of maltodextrin (Herzfeld). a body
intermediate between achroodextrin and maltose, but more nearly allied to the latter.

PRODUCTS OF DIGESTION OF STARCH. 397

(achroodextrin). If, when this stage is reached, the solution is rapidly
cooled and neutralised, a little maltose can be separated from accompany-
ing dextrose, showing that maltose is here also formed, but is con-
verted rapidly into grape-sugar.

Although maltose is the chief sugar formed in the action of both
ptyalin and amylopsin upon starch, yet a trace of grape-sugar is also
formed.1 The quantity of grape-sugar formed is in both cases small, but
is greater in the case of the pancreatic ferment. It has recently been
discovered that in both salivary and pancreatic digestion, besides
maltose and small quantities of grape-sugar, another sugar, isomaltose,2
is formed, in considerable quantity. The relative quantity of the three
sugars varies with the quantity of ferment present, and the duration of
the experiment. A weak ferment and short time of action favour the
formation of isomaltose; by much ferment and prolonged action large
quantities of maltose are produced, accompanied by traces of dextrose.3
It is stated that traces of an inverting ferment are present, both in the
salivary and pancreatic glands, especially the latter ; and it is possible
that the traces of dextrose formed may be due to the action of these on
the maltose and isomaltose first formed.

The action of the amylolytic enzymes on glycogen is precisely similar
to their action on starch ; dextrin, maltose, and isomaltose being formed
in very much the same proportions.4

The production of maltose by the diastatic ferments is not the end
of the digestion of amyloses; there is evidence that maltose never
reaches the systemic circulation. If it be injected intravenously it is soon
discoverable in the urine ; 5 this shows that in digestion it is inverted,
either before it is absorbed, or after absorption and before reaching the
systemic circulation.

This further process of hydrolysis may be to some extent carried out,
so far at least as concerns that portion of maltose arising from
salivary digestion, by the hydrochloric acid of the gastric secretion, but it
is mainly brought about by an inverting ferment, discovered by Brown
and Heron in the mucous membrane of the small intestine, and also in
the succus entericus.6

The succus entericus (as well as the intestinal mucous membrane and
glycerin or water extracts of it) possesses only a feeble diastatic action

1 Musculus and Gruber, Ztsclir. f. physioL Chem., Strassburg, 1878, Bd. ii. S. 177 ;
Musculus and von Mering, ibid., 1878, Bd. ii. S. 403 ; von Mering, ibid., 1881, Bd. v. S.
185 ; Brown and Heron, Ann. d. Glum., Leipzig, 1879, Bd. cxcix. S. 165 ; 1880. Bd. cciv. S.
228 ; Proc. Roy. Soc. London, 1880, p. 393.

2 Kiilz u. Vogel, Ztschr. f. Biol., Miinchen, 1894, Bd. xxxi. S. 108. The existence of
isomaltose is, however, denied by Brown and Morris (Trans. Chem. Soc., London, 1895, vol.
Ixvii. p. 737), who state that it is a mixture of maltose and dextrins.

3 Journ. PhysioL, Cambridge and London, vol. xv.; Abelous, Compt. rend. Soc. de biol.,
Paris, 1891.

4 Hensen, Verhandl. d. phys.-med. Gesellsch. zu Wurzburg, 1856, Bd. vii. S. 219 ;
Virchow's Archiv, 1857, Bd. xi. S. 395 ; Claude Bernard, Gaz. med. de Paris, 1857, No. 13 ;
J. Seegen, Oentralbl. f. d. med. Wissensch., Berlin, 1876, S. 849; Arch.f.'d. ges. PhysioL,
Bonn, 1879, Bd. xix. S. 106 ; Kitlz u. Vogel, Ztschr. f. Biol., Miinchen, 1894, Bd. xxxi.
S. 108.

5 Bimmemunn, Arch. f. d. ges. PhysioL, Bonn, 1879, Bd. xx. S. 201; Philips,
Jahresb. ii. d. Fortschr. d. Thier-Chem.. Wiesbaden, 1881, Bd. xi. S. 60 ; Dastre et Bour-
quelot, Compt. rend. Acad. d. sc., Paris, 1884, tome xcviii. p. 1604; Bourquelot, Journ. de
t'anat. et physioL, etc., Paris, 1886, tome xxii. p. 161.

6 Brown and Heron, Proc. Roy. Soc. London, 1880, p. 393; Ann. d. Chem., Leipzig,
1880, Bd. cciv. S. 228; Vella, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1881, Bd.
xiii. S. 40; Bourquelot, Compt. rend. Acad. d. sc., Paris, 1883, tome xcvii. p. 1000.

398 CHEMISTRY OF THE DIGESTIVE PROCESSES.

on starch,1 but has a remarkable power in converting maltose into
grape-sugar. Brown and Heron surmised from this that maltose
would be found to be a non-assimilable substance ; unknown to them,
Bimmermann had already shown this to be the case, and many subse-
quent observers have confirmed the result.

Digestion of cane-sugar. — Cane-sugar resembles maltose in not
being directly assimilable from the blood ; after intravenous injection it
is excreted by the kidneys. In the course of digestion it is either com-
pletely inverted while in the alimentary canal, or may in part be so
changed in its passage through the absorbing cells of the mucous
membrane.

Some cane-sugar is inverted in the stomach, probably by the action
of the hydrochloric acid there present.2 Lehmann 3 repeatedly found, in
the stomach and duodenum of rabbits ied on beetroot, invert-sugar only.
Seegen found that, after feeding dogs on cane-sugar, the stomach always
contained a small amount of a reducing sugar along with a great deal of
unchanged cane-sugar ; and that the small intestine contained no sugar.
He argues from this, that all the cane-sugar is inverted in the stomach,
the invert-sugar being there absorbed as fast as it is produced.
It is probable, however, from the work of other observers, that a con-
siderable part of the inversion takes place in the small intestine by the
action of the intestinal juice, and it may be also by the direct action
of the cells of the intestinal mucous membrane.

Watery infusions of the mucous membrane from any part of the
small intestine are capable of inverting cane-sugar,4 and the same
power is possessed by the intestinal contents in animals which have
been killed during active digestion.5 The intestinal juice obtained by
Vella 6 from fistulae almost instantly inverted cane-sugar, and a strong
inverting action of pure succus entericus has been observed by many
others.

The inversion of the saccharoses by the intestinal juice is brought
about by enzymic action, but very little is known of the enzyme
or enzymes involved. It was supposed by Hoppe-Seyler and Thier-
f elder7 that the inversion might be due to bacterial action or to
inverting enzymes taken in with the carbohydrate food, but the former

1 A diastatic action on starch was found by Schiff, Jahresb. u. d. Fortschr. d. ges. Med.,
Erlangen, 1867, Bd. i. S. 155 ; Eichhorst, Jahresb. u. d. Fortschr. d. Thier-Chem.,
Wiesbaden, 1871, Bd. i. S. 198 ; Paschutin, ibid., S. 304 ; Ewald, Virchow's Archiv, 1879,
Bd. Ixxv. S. 409 ; Garland and Masloff, Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg,
1878, Bd. ii. S. 290 ; Brown and Heron, loc. cit. ; Dana, Med. News, Phila., 1882, vol. xli.
p. 59. ; Hamburger, Arch. f. d. cjes. PhysioL, Bonn, 1895, Bd. Ix. S. 560; Mendel, ibid.,
1896, Bd. Ixiii. S. 425. On the other hand, its existence is denied by Thiry and by Leube,
Jahresb. u. d. Fortschr. d. ges. Med., Erlangen, 1868, Bd. i. S. 97. It must be remembered
that the diastatic action is admittedly a slight one by most of those observers who confirm
it, and that most organs and tissues possess a slight diastatic action, so that it is difficult to
be certain that the intestinal mucous membrane specifically secretes a diastatic ferment.

2 It is certain, from purely chemical experiments, that the acid is capable of producing such
an effect, and no inverting enzyme has ever been shown to exist in the gastric secretion.

3"Lehrbuch der physiol. Chem.," Aufl. 2. Bd. iii. S. 255; v. Becker, Ztechr. f.
unssensch. Zoologle, Bd. v. S. 123 ; J. Seegen, Arch. f. d. ges. Physiol., Bonn, 1887, Bd. xl.
S. 41.

4 Paschutin, Arch. f. Anat. u. Physiol, Leipzig. 1871, S. 306.

5 Claude Bernard. "Le9ous sur la diabete et la glycogenese auimale," Paris, 1877,
257-261.

6 Untcrsuch. z. Naturl. d. Mensch. u. d. Thiere, 1889, Bd. xiii. S. 62 ; see also
Bastianelli, ibid., 1886, Bd. xiv. S. 146.

7 "Handbuch der. path. u. physiol. chem. Analyse," 1893, Aufl. 6, S. 298. See also
Pautz and Yogel, Ztschr. /. BioL, Miinchen, 1895, Bd. xxxii. S. 304.

DIGESTION OF PROTEIDS. 399

supposition is negatived by the rapidity of the action, and its progress
in presence of antiseptics ; and both by the recent observations of
Miura,1 which show that the mucous membrane of the intestine of
newly-born animals, under antiseptic conditions, causes inversion. No
inversion was obtained with the mucous membrane of the stomach or
large intestine.

Brown and Heron2 have shown that the dried mucous membrane
of the small intestine is much more powerful, both in its diastatic action
on starch and in its inverting action on cane-sugar and maltose, than
are infusions of the same material. Starch also disappears from an
intestinal fistula (Thiry) much more rapidly than it is possible for the
succus entericus,3 judging from other experiments, to convert it into
sugar. These facts point to a possibility that the epithelial cells of
the intestinal mucous membrane may possess the power of absorbing
starches and saccharoses, and submitting them to diastatic and inverting
processes, in passing them on to the lymph spaces of the villi ; that, in
fact, cellular digestion of absorbed carbohydrates may take place in the
epithelial cells after absorption.

The secretion of the small intestine is generally stated to be
inactive towards lactose, so that the inversion of this sugar probably
occurs after its absorption by the columnar cells.4

Human succus entericus has been investigated by Ewald,5 by Demant,6
and by Tubby and Manning ; 7 they all agree as to its diastatic action on starch
and inverting action on cane-sugar. Tubby and Manning also tested its action
on maltose, and found that this was converted into dextrose. The ferment or
inverting material adhered to mucus whenever a precipitation of this took
place in the fluid, so that the mucus was more effective than the clear
fluid.8

DIGESTION OF PROTEIDS.

The digestion of proteids is a much more complex process than that of
either the fats or carbohydrates, and one of which our knowledge is still
less exact. In the digestion of carbohydrates we are absolutely certain
that we have to do with a hydrolytic process, and that from a body
of absolutely fixed percentage composition, though often of unknown
molecular weight, there is produced in digestion a substance of known
formula, and to a certain extent of known structure. In proteid digestion,
while it is probable that a very similar action is taking place, we have
no such certainty. The digestive process begins with material, the
different proteids, which varies considerably in percentage composition.

1 Ztschr.f. Biol., Miinchen, 1895, Bd. xxxii: S. 266.

2 Proc. Roy. Soc. London, 1880, vol. xxx. p. 399. See also Shore and Tebb, Journ.
Physiol., Cambridge and London, 1892, vol. xiii. (Proc. Physiol. Soc.), and M. C. Tebb, ibid.
vol. xv. p. 421.

3 Rohmanii, Arch. f. d. ges. Physiol., Bonn, 1887. Bd. xli. S. 424.

4 Meyer, "Die Lehre von den chemischen Fermenten," 1882 ; Dastre, Arch, de physiol.
norm, etpath., Paris, 1890, tome xxii. p. 103 ; C. Voit and Lusk, Ztschr.f. JBioL, Miinchen,
1891, Bd. xxviii. S. 275 ; Mendel, Arch. /. d. ges. Physiol., Bonn, 1896, Bd. Ixiii. S. 425.
See, however, Pautz and Vogel, Ztschr.f. Biol., Miinchen, 1895, Bd. xxxii. S. 304 ; Rohmann
u. Lappe, Ber. d. deutsch. chem. Gesellsch., Berlin, 1895, Bd. xxviii. S. 2506.

5 Virchow's Archiv, 1879, Bd. Ixxv. S. 409. 6 Ibid., S. 490.

7 Guy's Hosp. Rep., London, 1891, vol. xlviii. p. 271 ; Centralbl. f. d. mcd. Wissensch.,
Berlin, 1892, S. 945.

8 Paschutin (loc. cit.) found that the inverting enzyme was mechanically precipitated
along with collodion.

4oo CHEMISTR Y OF THE DIGESTIVE PROCESSES.

From this variable material products showing minute variations are
produced, of which we only know that they are more soluble than the
mother substance, less easily thrown out of solution by various precipit-
ants, and to a certain slight extent are capable of diffusing through
membranes.

Here our knowledge at present stops. In spite of most laborious
researches on the subject by a host of observers, we know no more of
the structure of any save the final decomposition products of proteid
digestion than we do of the proteids themselves. Certain products have
been isolated at various intervals in the progress of digestion of proteids,
which show that the process gives rise to several intermediate bodies,
ever increasing in solubility towards precipitants as they are formed
nearer the end of the process ; and it may be — it is a probable inference
from analogy — that these substances *re simpler than the proteids from
which they originate, but as yet the simplest of them is too complex
for our fragmentary knowledge to give any indication of its structure.
Nor is there any knowledge of the relationship of these several stages of
proteid digestion to one another.

It is very probable that the process of proteid digestion, like all the
other digestive processes, is one of continuous absorption of the elements of
water or hydrolysis.

This is shown by the following observations : — (1) One of the commonest
agents employed in organic chemistry for the purpose of hydrolysing a
substance is boiling with a dilute mineral acid, or subjecting in closed
vessels to the action of superheated steam. On submitting proteids to the
prolonged action of these reagents, products closely resembling or identical
with those produced by the action of the proteolytic enzymes are obtained.
(2) A small but decided increase in weight has been observed in the formation
of peptone from proteid.1 (3) Peptones can be converted artificially back
into proteids by the use of reagents which are essentially dehydrating in
their action. If fibrin- peptone be heated for an hour with acetic anhydride,
the excess of anydride distilled off along with acetic acid formed in the pro-
cess, and the residue treated with hot water, the greater part of it dissolves.
When this solution is dialysed, there remains behind in the dialyser a solution
which coagulates on boiling, and is precipitable by nitric acid or potassium
ferrocyanide. Also, peptone heated for some time to 140° C. yields a substance
which on solution in water shows more of the properties of a native albumin
than of a peptone.2

Other theories regarding the digestion of proteids are — (1) That the proteids
are polymers of the peptones, and that the process of digestion is a process of
depolymerisation,3 (2) that proteids and peptones are simply different isomeric
forms of the same substance, and (3) the micellar theory,4 according to which
the proteids are composed of micelli, which are a kind of second order of
molecule much more complex in structure. On peptonisation, the proteid first
breaks up into its constituent micelli, then the micelli fall into molecules, in
the chemical sense of the word, and these molecules are the peptone molecules.

1 A. Danilewski, CentralU. f. d. med. Wissensch., Berlin, 1880, No. 42, S. 769.

2 Hemiinger, Compt. rend. A cad. d. sc., Paris, 1878, tome Ixxxvi. p. 1464; Hofmeister,
Ztsclir. f. physiol. Chem., Strassburg, 1878, Bd. ii. S. 206 ; Neumeister, Ztschr. f. Biol.,
Miinchen, 1887, Bd. xxiii. S. 394.

8 Maly, Arch. f. d. ges. Physiol., Bonn, 1874, Bd. ix. S. 585; ibid., 1879, Bd. xx.
S. 315 ; Herth, Ztschr. f. physiol. Chem., Strassburg, Bd. i. S. 277 ; Monatsh. f. Chem.,
Wien, Bd. v. ; Poehl, Ber. d. deutsch. diem. Gescllsch., Berlin, 1881, S. 1355; 1883, S.
1152 ; Loew, Arch. f. d. ges. Physiol., Bonn, 1883, Bd. xxxi. S. 393.

4 Griessmayer, Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xiv. S. 26.

PEPTIC DIGESTION OF PROTEIDS. 401

Ultimate chemical analysis shows that the composition of the peptones
and albumoses is practically the same as that of the proteids from which they
are formed ; in some cases the proteids show a somewhat higher percentage of
carbon and lower of hydrogen and oxygen than the proteids of their digestion,
in others the reverse, but in no cases any very considerable variation. So
that, if the process of peptonisation is one of hydrolysis, the peptone molecule
must be out of all proportion greater than that of the molecule of water.
Nevertheless the hydrolytic theory is the one most generally received, and
against this unfavourable argument from analytical results must be set the
other experiments already quoted.

The main differences between the proteids and peptones of physio-
logical importance are the physical ones, that the latter are much more
soluble, and are diffusible, though with difficulty, through membranes.
It is indeed purely by physical means that we at present differentiate
proteids and peptones and the intermediate products between them,
and not by any well-marked chemical differences shown by them. The
different proteids, albumoses, and peptones are classified and marked
off from one another almost entirely by the behaviour of their solutions
towards solutions of neutral salts of different strength, according to
whether these dissolve or precipitate them. It is questionable whether
it is justifiable on such a slender basis to assume, as is commonly done
that these precipitates correspond to pure compounds. It ought to be
remembered that these names at present only apply to certain precipi-
tates, and that it is not at all known whether these represent distinct
chemical substances, nor indeed what they do represent. Still less right
have we to assume from mere proteid .analyses that the products of
digestion of different proteids yield substances distinctive of them and
worthy of distinctive names.

The two proteolytic enzymes, pepsin and trypsin, closely resemble
each other in their action on proteids, a series of very similar products
being in each case evolved, which, generally speaking, become more
soluble and probably simpler in constitution as the end of the process is
approached. Still there is sufficient difference to warrant a separate
consideration of the two processes.

PEPTIC DIGESTION OF PROTEIDS.

The stomach was recognised even by the ancients as a digestive
organ, and its action attributed in many cases to the " animal heat "
assisted by mechanical force. Digestion seems to have been first con-
sidered as a similar process to fermentation by van Helmont, and this
view was also maintained by Sylvius.

Reaumur1 seems to have been the first to experiment on gastric
digestion. He carried out his successful experiments on a tame buzzard,
which, like some other birds of prey, regurgitates after a time the more
indigestible portions of its food. He administered various kinds of
food, enclosed in small metallic tubes closed at one end and covered by
muslin at the other, so as to prevent any mechanical action of the
gizzard and yet allow the gastric juice to act ; he found that meat was
digested in the course of some hours, and in a shorter period was digested
partially on the outside while the interior still remained untouched.
Reaumur also obtained gastric juice by enclosing pieces of sponge in

1 "Hist. Acad. roy. d. sc. de Paris," 1752, pp. 266, 461.
VOL. I. — 26

402 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

such tubes, but could not get it to act outside the body. Similar ex-
periments were carried out by Stevens 1 of Edinburgh, who availed him-
self of the services of a juggler possessing a trick of swallowing stones
and regurgitating them. This man he gave to swallow some hollow
silver balls which were perforated with holes ; the balls were screwed
together in two halves and could be filled with meat. He found that
the meat was rapidly dissolved and disappeared. To Stevens also belongs
the credit of being the first to observe digestion outside the body. He
obtained gastric juice from a dog's stomach, and found that when a piece
of meat was subjected to its action in a warm place it became dissolved
in about eight hours.

Soon afterwards Spallanzani confirmed these experiments, and
showed conclusively that, under favourable conditions, the juice acted
outside the body, and also that it haft a marked action in preventing
putrefaction.

Between 1825 and 1833 Beaumont published his classical observa-
tions on Alexis St. Martin. In 1834, Eberle 2 discovered a method of
preparing an artificial gastric juice, which possessed all the digestive
properties of the normal secretion, by acting on the gastric mucous
membrane with dilute hydrochloric acid. Schwann3 in 1836 gave the
name pepsin to the active principle to which he supposed the gastric
juice owed its activity.

Products of peptic digestion.— The first exact investigations into
the nature of the products of gastric digestion are those of Meissner 4
and his pupils. After digestion in acid solution and filtration, a pre-
cipitate was obtained on nearly neutralising, to which the name of
parapeptone was given.

There is a considerable difference of opinion among various authors as to
what this parapeptone of Meissner is represented by in our more modern nomen-
clature. By some it is stated to have been syntonin. If Meissner had used a
strongly peptic digestive medium, filtered and neutralised, just after the bulk
of the proteid was dissolved, he would undoubtedly have obtained syntonin or
acid albumin ; but from his description it is evident that he was dealing
with a substance afterwards discovered by Kiihne, and renamed antialbumate.
This substance seems by its behaviour to be indeed a close ally of acid
albumin, and is obtained most readily by a more prolonged action of dilute
acids at 40° C. than is necessary to form acid albumin. It is also formed to
a small extent in a weak peptic digestive medium, probably from a similar
cause. Like acid (or alkali) albumin, it is insoluble in water, but easily
soluble in even very dilute acids or alkalies ; but it differs from acid albumin
in that when once formed it is not attacked by any pepsin in acid solution
by which acid albumin is actively peptonised. It is, however, convertible into
peptone (antipeptone) by the action of pancreatic juice, no leucine or tyrosine
being simultaneously formed. Meissner was undoubtedly using very weak
solutions of pepsin, and the action he obtained approximated to the prolonged
action of weak acids alone at 40° C. The action of the pepsin present was
too weak to catch, as it were, all the acid albumin on its way into antialbumate
and peptonise it ; and when once any antialbumate was formed, it could not then
be attacked and peptonised. Meissner's product was thus almost purely anti-

" De alhnentornm concoctione," Edin., 1777.

2 "Physiol. d. Verdauung nach Versuch.," AViirzburg, 1834.

3 Arch.f. Anat., Physiol. u. wissensch. Med., 1836, S. 90.

4 Ztschr. /. rat. Med., 1859-1862, Dritte Reihe, Bd. vii. S. 1 ; viii. S. 280 ; x. S. 1 ;
xii. S. 46 ; xiv. S. 303. Reviewed in Biol. CentralbL, Erlangen, 1884, Bd. iv. S.
407.

PROD UCTS OF PEPTIC DIGESTION. 403

albumate. If he had used a slightly stronger solution for a somewhat shorter
time, he would have obtained a mixture which would have been partially
peptonised and partially remained unchanged when subjected to the action
afterwards of strong fresh pepsin and acid ; if he had used a strongly peptic
solution for a much shorter time, the result would have been purely acid
albumin and no antialbumate whatever; giving with fresh pepsin, or more
prolonged action, complete peptonisation.

On the addition of acid to the almost neutral faintly acid solution, a
further precipitate formed, which Meissner regarded as a different sub-
stance, and called metapeptone. It was insoluble in very dilute acids (O'l
per cent.), soluble in stronger acids. A third residue obtained in the diges-
tion of casein or fibrin he called dyspeptone ; this was insoluble in dilute
acids (2 per cent. HC1), but soluble in dilute alkalies and in stronger
acids. This substance was probably a mixture of nucleins, with the sub-
stance subsequently described by Klihne as antialbumid.1

After the removal of these neutralisation products, various other
substances were still left in solution ; these Meissner classed together
as peptones, distinguishing —

a-peptone, precipitable by concentrated nitric acid, as well as by potassium
ferrocyanide and dilute acetic acid.

/?-peptoiie, not precipitated by nitric acid, but by potassium ferrocyanide
and strong acetic acid.

y-peptone, not precipitated either by nitric acid or by potassium ferro-
cyanide and acetic acid.

Of these three substances only y-peptone corresponds to the present-day
definition of a peptone • the others were probably different albumoses.

A valuable side-light was thrown on the digestion products of
proteids by Schiitzenberger's 2 researches on the prolonged action of
acids and alkalies at high temperatures on these substances. It has
already been indicated that peptonisation is the result obtained,
followed finally by a splitting up into amido-acids.

Superheated steam possesses a similar peptonising action on proteids, and
yields by prolonged action the usual amido-acids.3 According to Neumeister,4
the intermediate substances produced are, however, somewhat different, the
substance first formed lies intermediate between the coagulable proteids and
the albumoses. It is not coagulated by boiling, but in its behaviour towards the
usual precipitants behaves like a coagulable proteid ; this substance is termed
atmidalbumin. By further hydration it yields a true albumose, which, however,
differs somewhat in its properties from any of the albumoses naturally formed
in digestion, and has been named atmidalbumose. Both atmidalbumin and
atmidalbumose are precipitated by dilute acids, and are converted by boiling
with dilute sulphuric acid into deutero-albumose. Similar products are pro-
duced by the action of the vegetable digestive ferment papoyotin or papain,
and are in the end, by the prolonged action of this ferment, converted into
amido-acids.5

1 See p. 406.

2 Bull. Soc. chim., Paris, 1875, tome xxiii. pp. 161, 193, 216, 242, 385, 433 ; xxiv. pp.
2, 145 ; Jahr&b. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1875, Bd. v. S. 299.
Schutzenberger's researches are referred to at length in the article on the ' ' Chemical Con-
stituents of the Body," pp. 30-32 of this volume.

3 Lubavin, Hoppc-Seyler's Med.-chem. Untersucli. , Berlin, 1871, S. 480; Krukenberg,
Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Naturw., 1886.

4 Ztschr. f. Blol. Miinchen, 1890,, Bd. xxvi. S. 57.

5 Sidney Martin, Journ. Physiol., Cambridge and London, 1885, vol. vi. p. 336.

4o4 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

Meissner's views as to the decomposition of proteids on digestion
did not at first obtain much credence. The formation of a substance
precipitated by neutralisation, and incapable of further conversion ly
pepsin and an acid in the course of normal digestion, was denied, and
with right, by Briicke and others.

Briicke l stated that there was no such decomposition of the pro-
teid molecule as Meissner indicated, but that fibrin is first dissolved
and afterwards converted in great part into acid albumin, accom-
panied even at first by peptone in small quantity. If neutralisation
takes place at this stage, a heavy precipitation is the result, and there
remains in solution a small quantity of coagulable proteid (formed by
the solution of the fibrin and not yet converted into acid albumin by
the acid) mixed with albumoses and peptone. If, however, peptic
digestion be allowed to proceed to completion, no precipitation occurs
on neutralising, and the solution contains only albumoses and peptones.
This shows that Meissner's parapeptone, as well as Kiihne's antialbumate
and antialbumid, which will be described later,2 are not formed to any
extent in active peptic digestion, but are merely products of prolonged
action of dilute acid.

In order to study the products formed in peptic digestion, it is necessary
to proceed with a digestive fluid which has been purified from products of
digestion, due to self-digestion or otherwise, by one of the methods already
described,3 or else to take advantage of a peculiar property possessed by
fibrin, and in a lesser degree by some other forms of proteid, of absorbing
pepsin from solution.4

Any digestive fluid containing pepsin (such as that obtained by auto-
digestion of pig's gastric mucous membrane in dilute hydrochloric acid) is
carefully neutralised, using powdered chalk for the purpose, so as to avoid all
danger of alkalinity, by which the pepsin would be rapidly destroyed.5 After
neutralising and filtering, the fluid is shaken up with flakes of fibrin for
some time ; this is best done by blowing a stream of air through the mixture,
placed in a tall vessel, by means of a Bunsen filter pump. In about an hour
the fibrin becomes impregnated with pepsin, which, however, cannot attack it
in the neutral fluid. So firmly adherent is the enzyme to the fibrin, that the
latter may be freely washed without parting from it. If this fibrin be now
placed in dilute hydrochloric acid ('2 per cent.) at 40° .C., it is quickly dis-
solved and digested. Instead of neutralising the impure digestive fluid, it
may be saturated with sodium chloride, which stops the digestive action of the
pepsin ; on now agitating thoroughly for about an hour, the fibrin is saturated
with pepsin, after which it may be washed as before. This peculiar power of
absorbing pepsin is shown in a varying degree by all solid forms of proteid.
Fibrin possesses it most markedly, muscle fibre and casein also show it well,
but coagulated proteids show it comparatively much more feebly.6

Fibrin, or other solid proteid, on digestion, swells up, dissolves, and
is converted into syntonin or acid albumin. The same result is obtained

1 Sitzungsb. d. Jc. Akad. d. Wissensch. , Wien, 1859, Bd. xxxvii. S. 131 ; 1861, Bd. xliii.
S. 601.

2 See pp. 406-409. 3 See p. 402.

4 Von Wittich, Arch. /. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 443 ; K. Mann, "TJeber
die Absorption der proteolytischen Enzyme durch die Eiweisskorper," Inaug. Diss.,
Wtirzburg, 1892, S. 23.

5 Langley, Journ. PhysioL, Cambridge and London, 1882, vol. iii. p. 253.

6 Wurtz, Compt. rend. Acad. d. sc., Paris, 188i, tome xciii. p. 1104; A. Fick,
Sitzungsb. d. pTiys.-med. Gesellsch. zu Wurzburg, 1889, S. 23 ; K. Mann, Inaug. Diss.,
Wtirzburg, 1892.

CLEA VA GE THEOR Y OF PROTEID DIGESTION. 405

with acid alone, but incomparably more slowly. The acid and ferment
seem to mutually assist each other. Pepsin alone is inactive, the acid
alone acts with extreme slowness, but in the presence of the acid the
ferment speedily dissolves the proteid, which is then rapidly attacked by
the acid and converted into acid albumin.

When the proteid undergoing digestion is fresh fibrin which has not been
previously subjected to heat coagulation, a body possessing the properties of
a globulin is found in the solution in the first stage of digestion, before or
just when complete solution has taken place ; a similar body is also said to be
formed in small quantity as a first product of digestion of other forms of
proteid.1 In a recent paper it is stated by Arthus and Huber2 that this
globulin is simply dissolved fibrin. These authors found such a body co-
agulating at 56° C. on digesting unboiled fibrin ; but boiled fibrin yielded no
such product. They also determined that " Witte's Peptone " dissolved un-
boiled fibrin, at 40° C., giving a solution which coagulated on heating at
56°, 68°, and 75° C.

The acid albumin is next attacked by the pepsin and further
altered, giving rise to a number of substances called albumoses, proteases,
or propeptones, and these in turn are slowly and incompletely con-
verted into peptones. Here the action of pepsin ceases.

Cleavage theory of proteid digestion.— The cleavage theory of
proteid digestion was first enunciated by Klihne in 1877.3 He describes
the digestion of albumins by trypsin as taking place in two stages : in
the first stage the albumin is changed into peptone (amphopeptone) ;
in the second stage, one-half of this peptone (hemipeptone) is further
changed, while the other half (antipeptone) remains unaltered. Peptic
digestion is not essentially different from the first stage of tryptic, and
while it is not possible to obtain two bodies from pepsin peptone, still it
is probable that this substance is a mixture of two bodies, antipeptone
and hemipeptone, as is also the case after the first stage of tryptic
digestion.

Unable to isolate two bodies from the end products of peptic
digestion, one of which should remain unchanged when subjected to
tryptic digestion, while the other broke up under like treatment into
leucine and tyrosine, Kiihne surmised that the cleavage might take
place earlier in the process of peptic digestion, and that more success
might attend an attempt to separate the precursors of anti- and hemi-
peptone, namely, the corresponding albumoses, by interrupting peptic
digestion at an early stage, and experimenting upon the products then
in solution. By interrupting peptic digestion at an early stage, two
substances were obtained : one was a neutralisation precipitate, which, on
tryptic digestion, afterwards yielded only antipeptone, and was hence
named antialbumose ; the other, obtained from the filtrate, was de-
composed by trypsin, with formation of leucine and tryosine, and was
hence named hemialbumose.* Kiihne 5 also reinvestigated the action of
acids, renaming Schiitzenberger's hemiprotein anticdbumid, and a body

1 Brticke, Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1859, Bd. xxxvii. S. 182 ; Otto,
Ztschr. f. physiol. Chem., Strassburg, 1883, Bd. viii. S. 129; Hasebroek, ibid., 1887, Bd.
xi. S. 348 ; A. Herrmann, ibid., 1887, Bd. xi. S. 508 ; Neumeister, Ztschr. /. £iol.,
Munchen, 1890, Bd. xxvii. S. 310.

2 Arch, de physiol. norm, ct path., Paris, 1893, tome xxv. p. 447.

3 Vcrhandl. d, naturh.-med. Ver. zu Heidelberg, 1877, K F., Bd. i. S. 236.

4 Vide infra. 5 Loc. cit.

406 CHEMISTR V OF THE DIGESTIVE PROCESSES.

closely resembling Meissner's parapeptone antialbumate ; considering
them anti bodies, from the fact that the}7 do not yield leucine and
tyrosine on tryptic digestion, but are, though with difficulty (especially
in the case of antialburnid), converted into antipeptone.

Klihne gave the following graphic representations of the cleavage of
proteids by acids and by digestion : —

Scheme of Proteid Cleavage ~by Acids.
ALBUMIN.

Antigroup. Hemigroup.

Autialbumid.

Antialbumate. ^

Antialbnmose. Heniialbumose.

Antipeptone. Heraipeptone.

Scheme of Digestive Cleavage of Proteids.

ALBUMIN

(ALBUMINATE).

|

I !

r Autialbumose. Heniialbumose.

Peptic J | . |

Digestion A I.I I I Tryptic

^. Autipeptone. Antipeptone. Hemipeptone. Hemipeptone. ^Digestion.

Leucine. Tyrosine. Leucine. Tyrosine.

Kiihne, in conjunction with Chittenden,1 subsequently investigated
more minutely the intermediate products in peptic digestion, and those
formed by the action of dilute acids. The following is an account of
the substances obtained and their mode of preparation : —

Antiallumid. — This substance was prepared as follows : — The white of fifty
eggs, freed from membrane and much diluted, was made feebly acid with
sulphuric acid and coagulated by boiling. The coagulum was suspended in
1300 c.c. of water containing 7 c.c. of sulphuric acid and heated to 100° C. ; after
ten hours it appeared little altered and was filtered off. The filtrate gave on
neutralisation a precipitate principally composed of acid albumin. After
removal of the first acid, the albumin which had remained undissolved was
heated with 3 litres of J per cent, sulphuric acid to 100° C. for nineteen hours,
then collected on a filter and completely washed.

The albumid thus obtained was insoluble both in dilute and concentrated
acetic acid, and in hydrochloric acid of 1'4 per mille and stronger, but easily
soluble in dilute caustic soda solution and in dilute alkaline carbonates, from
which it was precipitated by concentrated sodium chloride. Purified by diges-
tion with gastric extract, and 4 per mille hydrochloric acid for six hours at
40° C., it remained undissolved, but changed in appearance, becoming clotlike.
The clot was washed with water, dissolved in 1 per cent, solution of sodium
carbonate, filtered, reprecipitated with sulphuric acid, and washed again. It
now dissolved in 2 per mille hydrochloric acid, and in this solution was digested
with good peptic extract for eighteen hours. It was unchanged, and reappeared,
in equal amount to the eye, on neutralisation of the solution.
1 Ztsehr.f. Biol., Mlinchen, 1883, Bd. xix. S. 159.

CLEA VAGE THEOR Y OF PROTEID DIGESTION. 407

Now washed with water until no reaction for chlorides was obtained, and
afterwards treated with alcohol and ether, it formed a powder of slightly
yellowish colour. A part of this purified antialbumid was dissolved in sodium
carbonate solution of '5 per cent., and treated with a dialysed and very active
trypsin solution at 37°-38° C. After thirty minutes the mixture began to be
turbid, and in two hours solidified to a clot. By breaking up the clot and
filtering, the fluid part was separated from the clot; it was made scarcely
turbid by neutralisation, and yielded by further digestion no new precipitate, but
contained a fair amount of peptone.

The separated clot was soluble in hydrochloric acid of 2 per mille, but as
insoluble in sulphuric acid of 4 per mille as the original precipitate. It was
completely precipitated from solution in 1 per cent, sodium carbonate solution
by concentrated sodium chloride solution. From this it seems that in the
coagulation of albumid in trypsin no change takes place other that its becom-
ing more insoluble in sodium carbonate solution. The action of trypsin in
more alkaline solution was next tried; after the first precipitation of the
albumid it was dissolved in '75 per cent, sodium carbonate solution, digested
with dialysed tryptic fluid, neutralised and filtered. The clotlike albumid was
dissolved in 5 per cent, sodium carbonate solution, and by repeated digestion
with dialysed tryptic fluid, the greater portion was converted into antipeptone.
The final residue from this much accentuated tryptic digestion was completely
insoluble even in 5 per cent, sodium carbonate solution, but dissolved in 1 per
cent, caustic soda. Precipitated by neutralising with hydrochloric acid,
washed, redissolved in sodium carbonate, and treated with trypsin anew, it was
again completely thrown out as a clotlike coagulation. No leucine or tyrosine
was present in the tryptic filtrates.

How widely this account differs from the statement which occurs in
most text-books, that antialbumid is not attacked by pepsin, but is
converted into antipeptone by trypsin, may easily be seen. In a fluid of
equal alkalinity to that found in the body, antialbumid is no more
digested by trypsin than it is by pepsin and hydrochloric acid. Now
it has been shown that trypsin is most active in a sodium carbonate
solution of about 1 per cent.,1 and considerably less active in one of 5
per cent. ; why then does trypsin in 5 per cent, solution do that which it
is unable to do in 1 per cent, solution ? Obviously because the 5 per
cent, solution dissolves the clot of antialbumid, while the 1 per cent,
solution does not. In the former case a weaker trypsin acts on anti-
albumid in solution ; in the latter, a stronger trypsin on antialbumid as
an insoluble precipitate.

Be this as it may, antialbumid is only with great difficulty and
incompletely peptonised by trypsin. In all its properties, from its mode
of formation onward, the substance appears to be merely a very insoluble
form of acid albumin.

Antialbumose. — By a fractionated peptic digestion, Kuhne and
Chittenden2 obtained a substance which they termed antialbumose.
The preparation of this substance from white of egg is as follows : —

The white of fifty eggs was freed from membrane, diluted and coagulated
by boiling after acidifying with acetic acid. The coagulated proteid was
digested in two litres of 4 per mille hydrochloric acid and one litre of dialysed
gastric extract for one and a half hours at 40° C., it was then allowed to cool
to the temperature of the room and filtered from the undissolved part, the
process of filtration occupying two days. The undissolved residue was again
treated with fresh gastric extract until it was all dissolved, which occupied
1 See p. 338. 2 Loc. cit., p. 171.

4o8 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

fifteen hours. After filtration the fluid was neutralised, and the neutralisation
precipitate separated. This precipitate was digested anew for forty-eight
hours with 150 c.c. of strong gastric extract, after which it was re-obtained on
neutralisation not sensibly diminished in amount. Dissolved in '75 per cent,
sodium carbonate, and mixed with powerful dialysed pancreatic extract, it gave
no clot (see " Antialbumid ") when kept for forty-eight hours at 40° C., and
neutralisation precipitated only a part, the rest being converted into peptone.
This last neutralisation precipitate showed the properties of antialbumid ;
dissolved in sodium carbonate solution of 1*8 per cent., it was clear at first, but
began to cloud in one to two hours, and in twenty-four hours about half had
set into a thick clot which could not be peptonised completely by either peptic
or tryptic digestion. The various pancreatic solutions separated from the
neutralisation precipitates contained only peptone, and were free from leucine
and tyrosine. The antipeptone here obtained contained 30 per cent, of ash.

Of these three anti-compounds it is only claimed that one, anti-
albumose, is a product of natural digestion ; the other two, antialbumid
and antialbumate, are admittedly products of acid action or of acid and
very weak peptic solution, which amounts to the same thing, — and the
fact that they cannot be converted into peptones by the prolonged and
repeated action of pepsin and hydrochloric acid proves that they are not
natural products of strong peptic digestion in which no such inconvertible
residue is formed. Antialbumose is commonly stated to be convertible
by prolonged peptic digestion into peptone ; but, as may be seen from
the above description, it is not materially altered by forty-eight hours'
digestion with a strong extract of gastric mucous membrane, and even
with trypsin a considerable portion is left unaltered, betraying all the
properties of antialbumid. Antialbumose possesses all the chemical
properties of an acid albumin and none of those of the albumose class, so
that its name is a misnomer ; no such substance as an antialbumose has
actually been isolated. Antialbumid, antialbumate, and antialbumose,
to place them in the order of their solubility and facility for under-
going decomposition, are three substances all of which are remarkably
resistant to both peptic and tryptic digestion, and belong more to the class
of acid albumins than to any other. It is now generally recognised that
acid albumin is a generic and not a specific term, and it is to be hoped
that room will soon be found for these three bodies in this class, and the
terminology of digestion left a little less complicated than it is at present.
It may be asked, Why was antialbumose, if it is not a natural product
of peptic digestion, obtained in the above experiment ? The authors
themselves remark on the close resemblance between their product
and Meissner's parapeptone. The latter is produced either by the action
of dilute acid or of a very weak pepsin solution in the presence of acid.
Now for two days, while filtering at atmospheric temperature, after the
first hour and a half of digestion, the substance was under exactly the
proper conditions for the production of parapeptone. Finally, no product
so resistant to both pepsin and trypsin, as this substance is shown to be
by the above description, is formed during uninterrupted digestion.

Another method for preparing "antialbumose" — Kiihne and Chittenden1
also prepared antialbumose from fibrin by a somewhat similar course of
procedure, except that there was here no two days' delay in filtering, since the
fibrin was more quickly dissolved. There is, however, an objection no less
fatal, as will be pointed out after a description of the process.

1 LOG. cil.

CLEA VA GE THEOR Y OF PROTEID DIGESTION. 409

Five hundred grms. of unboiled fibrin, squeezed as dry as possible with the
hand, were placed at room temperature for twenty-four hours in 5 litres of 0'2
per cent, hydrochloric acid ; the mixture was then heated to 37° C., and
100 c.c. of gastric extract added. Solution took place inside an hour, after
which the fluid was filtered through a hair sieve, digestion stopped by neutral-
isation, and the neutralisation precipitate filtered off. This precipitate is stated
to be essentially antialbumose. It was long washed with water, and did not
then dissolve easily in 0'2 per cent, hydrochloric acid, so was heated for some
hours at 40° C. This acid solution was treated with an equal volume of strong
gastric extract in 0*2 per cent, hydrochloric acid for forty-eight hours, again a
heavy neutralisation precipitate was obtained. This precipitate, after washing
with water thoroughly till no biuret peptone reaction was given, was treated
with sodium carbonate solution of 2*5 per cent., in ichich it ivas not easily soluble,
and the solution was not clear until it had been digested for forty-eight hours at
48° C. with trypsin. Even then, on neutralising, a precipitate behaving like
antialbumid was obtained. Kedissolved in 2 '5 per cent, sodium carbonate solu-
tion, and redigested with trypsin, it was again precipitated in clotlike flakes,
and was only very slowly and partially converted by repeated tryptic digestion.

Here, again, there is no guarantee, after heating the first neutralisation
precipitate for some hours with 0'2 per cent, hydrochloric acid in order
to dissolve it, that a natural digestion product remains to be dealt with
in the subsequent processes. In addition, the obstinate resistance of the
substance to both peptic and tryptic digestion proclaims it a product of
experimental procedure, and not a true stage in natural or uninterrupted
digestion.

Hemialbumose. — Kiihne and Chittenden1 also obtained a precipitate, to
which they gave the name of hemialbumose ; this was obtained from the pro-
ducts of fractional peptic digestion in the filtrate after the removal of the
so-called antialbumose by neutralisation. This filtrate was concentrated to one-
fourth of its volume, acidified with acetic acid, boiled and filtered from a scanty
coagulum, again concentrated and precipitated by the addition of excess of
alcohol. In this precipitate by alcohol, the authors recognised, besides peptones,
two forms of albumose, soluble and insoluble hemialbumose. The precipitate
was rubbed up with cold water, until the wash water no longer gave the biuret
reaction. A part of the albumose (soluble hemialbumose) went into solution,
accompanied by all the peptone, a part remained insoluble (insoluble hemi-
albumose). The latter substance was not pure, but contained a proteid substance
insoluble in 2 per cent, acetic acid and in sulphuric acid of 0'4 per cent., and
with difficulty soluble in dilute caustic soda solution. The " insoluble hemialbu-
mose " was separated from this by treating with boiling water. From solution
in boiling water a part of the "insoluble hemialbumose" was precipitated as
the solution cooled. This was separated ; the remainder was precipitated from
the cold solution and added to it. The " soluble hemialbumose " was obtained,
free from its admixture with peptone in the cold water extract, by Salkowski's
method of boiling with excess of sodium chloride and dilute acetic acid so as
to form a saturated solution, washing the precipitate with saturated sodium
chloride solution, dissolving in water and dialysing until the dialysate gave
no reaction for chlorides with silver nitrate.

These hemialbumoses on tryptic digestion yielded leucine and tyrosine
abundantly, but could not be completely broken up by such digestion,
a variable amount of peptone being always left, no matter how prolonged
the digestion, which could only (on the cleavage theory) be antipeptone,
and so pointed to impurities in the form of anti-compounds in these

1 Loc. cit.

4io CHEMISTR Y OF THE DIGESTIVE PROCESSES.

hemialbumoses (or otherwise to the non-existence of cleavage at the
albumose stage into hemi and anti groups). Nor, when these hemi-
albumoses were subjected to more prolonged digestion yielding hemi-
peptone (?), could this substance be completely broken up by prolonged
tryptic digestion.

Kiihne l also described as hemialbumose a substance occasionally found in
the urine of patients suffering from osteomalacia, and first discovered by
Eence Jones. Much has been made of the importance of this albumose by
the supporters of the cleavage theory, but there is no more evidence that it is
a pure hemialbumose than there is in the case of the substances described
above ; that is to say, it has not been shown to be completely broken up by
tryptic digestion, and this is the crux of the whole question. The fact that it
yields leucine and tyrosine proves nothing. It has not been experimentally
shown that no peptone is left after the prolonged action of trypsin upon it.

Separation of the various albumoses from the " hemialbumose " pre-
cipitate.— Stimulated by a desire to obtain a pure hemialbumose which
should be capable of complete decomposition past the peptone stage by
trypsin, and encouraged in the belief that hemialbumose was a mixture,
as well by the known existence of two physically different forms (the
soluble and insoluble described above) as by certain inconstancies in its
behaviour towards sodium chloride, Kiihne and Chittenden 2 set to work
again upon the subject, and although they did not quite achieve their
object, produced a research which, whether the cleavage theory stands
or falls, must, from the experimental point of view, always remain of the
highest value, containing as it does the first basis for a classification of
the albumoses, the first light cast upon the relationship of this class
of proteids.

From the hemialbumose described in their previous paper, they were
able to separate, by the action of sodium chloride under various
conditions, four substances with the following properties : —

1. Protoalbumose. — Precipitated by saturation with sodium chloride,
soluble in cold and hot water.

2. Heteroalbumose. — Also precipitated by saturation with sodium
chloride, but insoluble in cold and in boiling water ; soluble in dilute and
in moderately concentrated saline solution.

3. Dysalbumose. — The same as heteroalbumose, but insoluble in
saline solution. This solution was recognised to be merely a more
insoluble modification of heteroalbumose ; each of the two substances is
easily convertible into the other. Dysalbumose corresponds to the
" insoluble albumose " of the earlier paper.

4. Deuteroalbumose is not precipitated by saturation with sodium
chloride alone, but is precipitated by saturation with sodium chloride in
the presence of acetic acid, and is soluble in water.

These various albumoses were subjected to tryptic digestion, and it
was found that none was a pure hemialbumose, — all yielded more or less
unconvertible peptone accompanied by leucine and tyrosine. A bigger
yield of amido-acids was obtained from protoalbumose and deutero-
albumose than from heteroalbumose ; indeed, the latter showed itself to
be more an anti- than a hemi- body, while protoalbumose yielded very
little peptone and an abundance of amido-acids. After this evidence

1 Ztschr.f. BioL, Miinclien, 1883, Bd. xix. S. 209.

2 Ibid., 1884, Bd. xx. S. 11.

CLEA VA GE THEOR Y OF PROTEID DIGESTION. 4 1 1

the term hemialbumose, as applied to the substance, or rather mixture
of substances, described above, ought to have speedily disappeared;
unfortunately it has not yet done so.

Soon after this a valuable aid to the study of the albumoses was
found in the discovery of Wenz,1 that saturation with ammonium
sulphate precipitated all albumoses from solution, while the peptones
remained dissolved. Heynsius2 first noticed the powerful action of
ammonium sulphate as a proteid precipitant, but fell into error in
thinking that it precipitated peptones as well. More careful experiments
by Wenz, in Kiihne's laboratory, showed that it did not precipitate
peptones, and so it was instituted as a means of separating albumoses
and peptones. The statement, however, that saturation with ammonium
sulphate totally precipitates albumoses and leaves peptones dissolved,
can only be made with a certain reservation. Certain proteid sub-
stances remain unprecipitated by saturation with ammonium sulphate,
and these may conventionally be labelled peptones; but it has been
shown3 that, in order to precipitate completely bodies which had
been known as albumoses before the introduction of ammonium sul-
phate, it is necessary to help the ammonium sulphate by saturating in
dilute solution and with varying reaction. If these bodies had not
been classed with the albumoses before Wenz's discovery, they would
probably now be peptones ; so conventional and artificial as this is the
proteid classification with which at present we are forced to be content.
In little or nothing except unimportant physical differences are the
albumoses and peptones distinct. If ammonium sulphate did not exist, it
would be difficult to say how to draw a sharp line between them : 4 both
classes of bodies give the same reaction to the biuret test, and both are
diffusible, though the albumoses more slowly so than the peptones.5

Separation of albumoses and peptones. — The following is the method
recommended by Klihne 6 for separating albumoses from peptones : —

The fluid containing the products of digestion is freed from albuminates
and coagulable proteids in the usual manner, and then, when sufficiently diluted
and of nearly neutral reaction, is saturated while boiling with ammonium
sulphate, and separated on cooling from the excess of salt and precipitated
albumose. The solution is again heated, and after it commences to boil it is
made strongly alkaline by the addition of ammonia and ammonium carbonate,
then again saturated with ammonium sulphate, and once more allowed to cool,
when a second precipitation of albumose and excess of salt takes place. A
third time heated, until the smell of ammonia disappears, it is once more
saturated while warm and made decidedly acid in reaction by the addition of
acetic acid, when, on cooling, a third and last precipitation of albumose takes
place, and the filtered fluid is supposed to contain nothing proteid except
peptone ; amphopeptone if the original fluid was the result of gastric digestion.
The albumoses can be obtained by dialysis and concentration from the united
precipitates.

1Ztschr.f. Biol, Miinchen, 1886, Bd. xxii. S. 1.

2 Arch.}, d. ges. PhysioL, Bonn, 1884, Bd. xxxiv. S. 330.

8Kiihne, Ztschr. f. Biol., Miinchen, 1893, Bd. xxix.

4 For a discussion of this point see Pekelharing. Arch. f. d. ges. PhysioL, Bonn, 1880,
Bd. xxii. S. 185 ; 1881, Bd. xxvi. S. 515 ; Internal. Beitr. z. u-isscnsch. Med. Fcstschr. R.
Virchow . . ., Berlin; Ztsclir. f. Biol., Miinchen, 1891, Bd. xxviii. S. 567; Neumeister,
ibid., S. 361 ; Kiihne, ibid., S. 571.

5 See Kiihne, Ztschr. f. Biol., Miinchen, 1892, Bd. xxix. S. 20; Chittenden and
Amerman, Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 483.

GLoc. cit.

4 1 2 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

The amphopeptone is obtained from the filtrate after removal of the
ammonium sulphate by complicated methods, consisting essentially in the
removal of ammonium sulphate as far as possible by concentration ; solution
of the amphopeptone in weak alcohol; removal of as much ammonium
sulphate from the weak alcohol as possible by a freezing mixture ; removal of
the alcohol by distillation ; removal of the last portions of ammonium sulphate
by boiling with barium carbonate ; removal of the last traces of barium salts by
cautious addition of dilute sulphuric acid ; and finally, precipitation of the
amphopeptone by excess of absolute alcohol.

Neumeisters method for separating the albumoses of peptic, digestion.
— The method of Kiihne and Chittenden for the separation of the
various albumoses has been perfected by Neuineister,1 who has in
addition proved that these bodies are not formed synchronously in the
process of digestion, or other form of 'hydrolysis, but that there are two
stages in the process. In the first stage proto- and /^eroalbumoses are
formed, which are called for this reason primary albumoses ; in the second
stage each of these primary albumoses gives rise to a deuteroalbumose,
and these deuteroalbumoses are hence called secondary albumqses.

Since heteroalbumose is completely and protoalbumose only partially
precipitated by saturation with sodium chloride in neutral solution,
while deuteroalbumose is not precipitated at all, it is easy, from a
mixture of all three albumoses, to obtain a solution containing only
heteroalbumose and protoalbumose ; and on dialysis of this solution
heteroalbumose, being insoluble in water, is precipitated alone, leaving
in solution only pure protoalbumose. In this way pure proto- and
heteroalbumoses can be obtained, but the preparation of pure deutero-
albumose is not quite so easy. In the filtrate from saturation with
sodium chloride there is not only deuteroalbumose but the unprecipitated
residue of the protoalbumose, and on adding acetic acid this is thrown
out along with the deuteroalbumose. However, a loophole is left in the
fact that just as saturation in neutral solution does not precipitate all
the protoalbumose, so saturation in acid solution does not precipitate all
the deuteroalbumose. Neuineister took advantage of this, sacrificed
the first portion of deuteroalbumose thrown out by the acetic acid,
accompanied by the last portions of protoalbumose, and then precipitated
the fraction of deuteroalbumose left alone in solution by saturation with
ammonium sulphate.

Kiihne and Chittenden had already got round this difficulty of isolating
deuteroalbumose by treating a dried mixture of the albumoses, such as is found
in Witte's peptone, with neutral and saturated solution of sodium chloride.
Here the deuteroalbumose only passes into solution. Although the proto-
albumose would only be partially thrown out of solution by saturating with
sodium chloride, yet it has not the power when dry to pass into solution
in such a solvent. Witte's peptone is, however, a variable mixture, and
Neumeister, working with other samples, was unable to reobtain Kiihne and
Chittenden's result ; it may be that they were working with a sample
containing little or no protoalbumose.

Neumeister effects the separation as follows : —

The faintly acid solution is saturated with ammonium sulphate, and so
separated from peptones. The precipitate is dissolved by the addition of
water, separated from the excess of the salt by dialysis, and then the neutral

1Ztschr.f. Biol., Miinchen, 1887, Bd. xxiii. S. 381 ; ibid., 1888, Bd. xxiv. S. 267 ; ibid.,
1890, Bd. xxvi. S. 324.

CLEA VAGE THEOR Y OF PROTEID DIGESTION. 413

solution is precipitated by saturation with sodium chloride, so throwing out
all the heteroalbumose and part of the protoalbumose which are separated
by dialysis. In the nitrate from saturation with sodium chlori'de in neutral
solution are the remainder of the protoalbumose and the whole of the deutero-
albumose ; to this, acetic acid solution, which has been saturated with sodium
chloride, is added, till a small portion filtered through a dry filter paper no
longer gives a precipitate with copper sulphate solution.1 The mixed pre-
cipitate of proto- and eZe^eroalbumoses is now filtered off, and deuteroalbumose
is isolated from the filtrate by neutralising, dialysing off the sodium chloride,
and precipitating by saturating with ammonium sulphate, or by adding excess
of alcohol.

This method of separating the albumoses may be shown schematically
thus : —

MIXED ALBUMOSES
(saturated with sodium chloride in neutral solution) give

Heteroalbumose and Protoalbumose Protoalbumose and Deuteroalbumose

(Precipitate). (Filtrate).

On dialysis, the solution of these two On adding acetic acid in saturated sodium
gives chloride, this solution gives

Heteroalbumose Protoalbumose Protoalbumose and Deuteroalbumose

(Precipitate). (Solution). Deuteroalbumose (dialysed and pre-

(not further treated) cipitated by alcohol)
(Precipitate). (Filtrate).

Neumeister also tested the action of hydrolysing agents on pure proto- and
/ieferoalbumoses prepared as has just been described. He showed that boiling
for three-quarters of an hour with 5 per cent, sulphuric acid was sufficient
to convert protoalbumose into deuteroalbumose accompanied by some peptone.
This was shown by the absence of turbidity on dialysis after neutralising
(absence of heteroalbumose), by saturation in neutral solution with sodium
chloride causing no precipitate (absence of protoalbumose), and by precipitation
occurring on making the saturated solution in sodium chloride acid with acetic
acid (presence of deuteroalbumose). In a similar fashion the conversion of
heteroalbumose into deuteroalbumose, by boiling with acid, was demonstrated ;
here a considerable formation of antialbumid was observed during the process.
On peptic digestion proto- and T^eroalbumose each yielded a deuteroalbumose,
but they behaved differently towards trypsin. In the case of heteroalbumose,
a specific point could easily be determined, in the course of digestion with
trypsin in 0'2 per cent, sodium carbonate solution, when, in the presence of a
considerable quantity of peptone, only deuteroalbumose was present ; on the
other hand, deuteroalbumose could not be obtained in large quantity by the
action of trypsin on protoalbumose ; the products obtained were chiefly amido-
acids accompanied by a little peptone, this being probably due to the ease
with which the deuteroalbumose formed from protoalbumose undergoes decom-
position.

Neumeister confirms the results obtained by Kiihne and Chittenden, that
heteroalbumose is principally an antialbumose, but has some hemialbumose
mixed with it, while the composition of protoalbumose is the exact reverse,
it being essentially a hemialbumose, always accompanied, however, by some
antialbumose. The yield of unalterable peptone was, however, so small in
some experiments as to induce Neumeister to believe that perfectly pure proto-
albumose would contain only hemi groups, or, in other words, be completely
convertible by tryptic digestion into amido-acids. The deuteroalbumose

1 This is a much more delicate test for protoalbumose (given by 1 in 5000) than acetic
acid and saturated sodium chloride solution (1 in 2000).

414

CHEMISTRY OF THE DIGESTIVE PROCESSES.

formed from protoalbumose and that from heteroalbumose are distinct bodies,
being distinguished by the fact that the deutero-compound formed from
protoalbumose is to some extent soluble in saturated solution of ammonium
sulphate.1

Starting with fibrin, and forming albumoses from it both by the
action of acids and by peptic digestion, Neumeister also showed that in
order of time proto- and Ae&roalbumoses first appeared, to be followed
later in the process by efewforoalbumose.

Fibrin was boiled for three-quarters of an hour with 1 per cent,
sulphuric acid, after which the fluid was neutralised, and the neutralisa-
tion precipitate removed. In the filtrate both proto- and heteroalbu-
moses were found, but not a trace of cleuteroalbumose ; the latter first
appeared after some hours' boiling, and by a continuance of the process
increased at the expense of the pr<5to- and hetero-compounds so as to be
present finally in preponderating quantity.

In accordance with these experiments, Nemneister2 considers that
the peptic digestion of proteids takes place as represented in the follow-
ing scheme, in which the preponderance of any group is shown by a
dark line, while its presence in small quantity is signified by a light
line : —

Proteid Molecule,

consisting of
Hemigroups Autigroups

Protoalbumose
(Amphoalbumose)

Deuteroalbumose
(Amplioalbumose)

Amphopeptone

Heteroalbumose Antialbumid

(Ainphoalbumose)

mlbt

Deuteroalbumose Deuteroalbumose
(Ainphoalbumose) (Antialbumose)

Amphopeptone Antipeptone

TRYPTIC DIGESTION OF PROTEIDS.

The proteolytic action of the pancreatic juice has not been known
for nearly so long a period as that of the gastric juice ; it was first
clearly proclaimed by Corvisart8 in 1857, although this author refers to
an earlier statement, by Purkinje and Pappenheim in 1836, that extracts
of pancreas possess a dissolving action on proteids.

Claude Bernard 4 knew that pancreatic juice in the presence of bile
had the power of dissolving proteids, but stated that when alone it
had no such action, unless the proteid matter had previously been sub-
jected to the action of bile. This error was removed by Corvisart, who
clearly proved that pancreatic juice alone at the temperature of the

1 Ztschr.f. Biol., Miiiichen, 1888, Bd. xxiv. S. 267.

2 Ibid., Miinchen, 1887, Bd. xxiii. S. 381. See also Neumeister, " Lehrbuch der
physiologischen Chemie," Jena, where Neumeister concludes: — "The expression
hemipeptone has, according to this representation, only a theoretical meaning, and the
term hemialbumose corresponds to older notions and ought to be allowed gradually to
disappear from the text-books."

3 ' ' Collection de memoires sur line fonction peu connue du pancreas, la digestion des
aliments azotes," Paris, 1857.

4 "Lecons de physiologic experimental e," 1856, tome ii. p. 440.

CLEAVAGE THEORY OF PROTEID DIGESTION. 415

body has a powerful digestive action on proteids in fluids of either
alkaline, acid or neutral reaction. In addition, he showed that infusions
of the fresh gland possess a similar action, that the active material
is precipitated by excess of alcohol and is dissolved again on the
addition of water to the precipitate, and that the activity of extracts
of the gland depends on the time after a meal at which the animal
is killed, being most active when a gland is extracted that has been
obtained from an animal killed six to nine hours after a full meal.
Corvisart also showed that the proteids are not merely dissolved, but
converted into substances possessing the same general characters as
those formed in peptic digestion.

These important results were denied at first by some observers, who
failed for some reason to obtain them on repeating Corvisart's experi-
ments, but were in the end abundantly confirmed by the researches of
Meissner,1 Danilewsky,2 and Kiihne,3 and are now universally accepted.

Klihne4 not only confirmed the results of Corvisart, but made an
important advance, by showing that pancreatic juice owes its action to
an enzyme, to which he gave the name of trypsin. He next showed
that, although trypsin is precipitated by excess of salicylic acid, smaller
quantities of that substance do not stop the action of the enzyme,
while they do, as shown by Kolbe, stop the growth of organisms,
especially those concerned in putrefaction. Until this was ascertained,
digestion experiments with pancreatic juice were complicated by the
putrefactive changes by which digestion was accompanied, for, while
trypsin acts in a neutral, and even in a faintly acid medium, its action
is stopped and the ferment gradually destroyed in a medium sufficiently
acid to stop the growth of bacteria by virtue of its acidity alone, so that
no one had been able to carry out prolonged experiments on pancreatic
digestion without the accompaniment of putrefaction. For this reason
it was unknown whether certain substances which appear towards the
end of the digestion were really due to the action of the enzyme or
were products of the putrefaction. Klihne was the first to carry out
antiseptic digestion, and to show that these substances are really formed
by the agency of the trypsin; he also perfected a method of freeing
solutions of the enzyme from the products of proteid digestion, resulting
either from the self-digestion of the gland in the preparation of the
extracts or otherwise, thus clearing the way for a study of the various
products formed by the action of trypsin on proteids.

Instead of preparing a purified solution of trypsin, which is a
rather troublesome process, the power possessed by fibrin of absorbing
the ferment, as described in the case of peptic digestion, may be
utilised here also ; but if the digestion of coagulated proteids is to be
observed, a purified solution of trypsin must be first prepared.5

The first action of trypsin seems to be a simple solution of the
proteid which is undergoing digestion. This effect is most easily observed
if fibrin is the proteid undergoing digestion, when the coagulable proteid
present in the solution, just before the fibrin is completely dissolved, has

1 Ztsclir.f. rat. Med., 1859, Dritte Reihe, Bd. vii. S. 1.

2 Virchow's Archiv, 1862, Bd. xxv. S. 279.

3 Ibid., 1867, Bd. xxxix. S. 130.

4 Verhandl. d. naturh.-med. Ver. zu Heidelberg, 1877, N. F., Bd. i. S. 233.

5 See Neumeister, " Lehrbuch der physiologischen Chemie," Jena, 1893, S. 198;
K. Mann, "Ueber die Absorption der proteolytischen Enzyme durch die Eiweisskorper,"
Diss., Wiirzburg, 1892, S. 23.

416 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

the properties of a globulin, but in the case of serum albumin no such
formation of a globulin takes place.1 If the proteid employed has
previously been coagulated, no formation of a coagulable proteid is
observed, the first product being apparently deuteroalbumose.2

The appearances presented by proteid undergoing solution by the
action of pepsin and of trypsin respectively, are characteristically
different. In the case of pepsin and hydrochloric acid, the proteid
swells up, becomes transparent or translucent, and gradually dissolves ;
while, by the action of trypsin in alkaline solutions, the proteid does not
swell up or become clearer, but is attacked and eroded from the outside.

After being dissolved, the proteid is further attacked by the trypsin
and decomposed into various products, the final result being a certain
amount of peptone which is not further acted on, accompanied by
various nitrogenous bodies, of which those occurring in largest quantity
are two amido-acids, leucine and tyrosine.

The primary albumoses of peptic digestion are not found among the
intermediate products of tryptic digestion. No matter at what stage
digestion is interrupted, no trace of either proto- or heteroalbumose is
found ; the only albumose present is deuteroalbumose.3

ISTeumeister suggests that this may be due to the protoalbumose being
broken up as rapidly as it is formed into amido-acids, while the heteroalbumose
is immediately converted into deuteroalbumose. Be this as it may, the
experimental fact is, that neither protoalbumose nor heteroalbumose are
found at any stage of tryptic digestion.

According to Neumeister, the deuteroalbumose present is an anti-compound
not yielding any amido-acids when subjected to the further action of trypsin.4

Peptone is formed much more rapidly in tryptic than in peptic
digestion, the preliminary stages being apparently rushed through ; while
in peptic digestion scarcely any peptone is formed before complete
conversion into albumoses has taken place, and complete peptonisation
never occurs.

The most essential difference between the digestive action of trypsin
and that of pepsin lies in the discovery of Kiihne, that the action of
the former enzyme does not cease with the formation of peptone, but
that approximately one-half of the proteid, or of the peptone formed
from it, is converted into a number of cystalline substances of much
simpler composition.

Not only does this take place in the direct tryptic digestion of proteids,
but if peptone formed by peptic digestion be submitted to tryptic
digestion, about one-half of it is decomposed in the above fashion. This
experiment led Kiihne to the cleavage theory, and to naming, on the
basis of this theory, the peptone of peptic digestion, fcmjpAopeptone ; the
peptone remaining after the completion of tryptic digestion, and which
is no longer affected by renewed digestion, ew^ipeptone; and that
hypothetical substance which is supposed to form one moiety of the
amphopeptone, and be broken up by the action of the trypsin,

1 Neumeister, Ztschr. f. Biol., Munchen, 1887, Bd. xxiii. S. 398 ; ibid., 1890, Bd. xxvii.
S. 311 ; Herrmann, Ztsclir. f. physiol. Chem., Strassburg, 1887, Bd. xi. S. 521.

2 When trypsin acts in an alkaline medium, alkali albumin is first formed ; but this is a
very transient stage, the alkali albumin being quickly changed into deuteroalbumose.

3 Otto, Ztschr. f. physiol. Chem., Strassburg, 1883, Bd. viii. S. 129; Neumeister,
Ztschr. f. Biol., Munchen, 1887, Bd. xxiii. S. 398.

4 Ztschr. f. BioL, Munchen, 1887, Bd. xxiii. S. 381.

CLEA VAGE THEOR Y OF PROTEID DIGESTION. 417

. It will be seen from this that the term hemipeptone is
a term for something which has a separate existence only in theory.
There has as yet been no method either devised or fallen upon by
accident of separating these two substances which are supposed by the
cleavage theory to be present, mixed in equal proportions, in ampho-
peptone. This is somewhat remarkable, in view of the number of years
the theory has now been in vogue, and the large amount of experimental
work that has been carried out in connection with it, and ought to be
looked upon as an indication, either that amphopeptone is not really
a mixture of antipeptone with a hypothetical hemipeptone, but a
substance capable of breaking up under the action of trypsin into a new
peptone (antipeptone) and a number of amido -compounds ; or that anti-
and hemipeptones are not separately present in amphopeptone, but that
this peptone breaks up upon the further action of trypsin into antipeptone
and hemipeptone, and that this hypothetical hemipeptone is next acted
upon and broken into simpler bodies, finally yielding leucine, tyrosine,
and the other companions of antipeptone found in complete tryptic
digestion.

The decomposition of proteids by trypsin is represented by
Neumeister l according to the following schema : —

Proteid.

Deuteroalbumose
Amphopeptone

Antipeptone Hemipeptone

I I I I

Leucine Tyrosine Aspartic Acid Tryptophan, etc.

According to the same author, several deuteroalbumoses are formed, in the
course of tryptic digestion, yielding corresponding amphopeptones. He also
states that all the albumoses, up to the present known, whether formed in
peptic or tryptic digestion, are amphoalbumoses, — that is to say, yield both
antipeptone and amido-acids on complete tryptic digestion. The ratio between
the amounts of antipeptone and of amido-acids is a very variable one ;
heteroalbumose, for example, yielding much antipeptone and little amido-acid,
while protoalbumose breaks up into much amido-acid and very little anti-
peptone. Those who hold the cleavage theory explain this by saying that
heteroalbumose is to a large extent an anti-substance, and protoalbumose
almost purely a hemi-substance ; but the experimental facts may be met
equally well by the statement, that heteroalbumose is an albumose of such a
chemical nature that it breaks up under the action of trypsin so as to yield a
large percentage of peptone unalterable by further action of trypsin, accom-
panied by a small amount of amido-acids; protoalbumose is an albumose
different in nature from heteroalbumose, and yielding, on further tryptic
digestion, very little peptone (antipeptone) and a large amount of the amido-
acids. There is no more proof that either heteroalbumose or protoalbumose is
such a mixture of albumoses as the cleavage theory demands, than there is
that amphopeptone is such a mixture of the corresponding peptones.

All the observed facts of peptic and tryptic digestion may be simply
represented by the following schema, without any reference to the

1 "Lehrbuch der physiologischen Chemie," Jena, 1893, Th. 1, S. 200.
VOL. I. — 27

418 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

cleavage or any other theory, save in the names of such of the substances
as have been named on a theoretical basis : —

PEPTIC DIGESTION. TRYPTIC DIGESTION.

Proteid. Proteid.

Acid Albumin Alkali Albumin

_J I

| | Deuteroalbumose

Protoalbumose Heteroalbumose [

\ / Antipeptone, amido-acids, etc.

Deuteroalbumose
Amphopeptone.

In the above account of the internTediate products formed between
proteid and peptone, an attempt has been made to point out how far
each important experimental result is in agreement with, or lends support
to, the cleavage theory of proteid digestion. Most of the results have
been obtained by supporters of that theory, but these results fall far
short of proving the truth of the theory, and may be explained without
reference to anti- and hemi-bodies. The main points may here be
summarised : —

1. Certain substances have been obtained by the action of dilute acids on
proteids, which do not yield amido-acids when subjected to prolonged tryptic
digestion; these substances have been on this account looked upon as pure
anti-compounds. But there is no evidence that such substances are formed
naturally in either peptic or tryptic digestion : there is evidence against it in
the extreme difficulty with which they are attacked either by pepsin or
trypsin. Neither are these substances in their chemical behaviour albumoses,
so that the term antialbumose, as applied to any of them, is a misnomer.

2. The substance originally obtained from a fractionated peptic digestion,
and named hemialbumose, was afterwards shown by its discoverers to be a
mixture of three bodies, — protoalbumose, heteroalbumose, and deuteroalbumose,
— and none of these three discrete bodies was found to be either a pure hemi-
albumose or pure antialbumose, so that, if the cleavage theory is to be main-
tained, we must be content to believe that each of these three is a mixture
in varying proportions of anti- and hemi-groups, and admit the existence of
antiprotoalbumose and hemiprotoalbumose, of antiheteroalbimiose and hemi-
heteroalbumose, of antideuteroalbumose and hemideuteroalbumose, without
any experimental evidence whatever. Again, the cleavage theory takes no
account of the fact that proto- and /z-eferoalbumose are formed prior to the
deuteroalbumose.

3. Amphopeptone is supposed to be a mixture in about equal proportions
of antipeptone and hemipeptone ; but these two bodies have never been isolated
from it. Antipeptone can only be obtained from amphopeptone by the action
of trypsin, and hemipeptone has never been obtained at all.

4. There is no doubt that some forms of proteids, or altered proteids, are
more easily decomposed by trypsin, yielding amido-acids, than are others ; but
this does not prove that such bodies are variable mixtures of a fraction which
is not decomposable at all with one which is completely decomposable. When
from an ampho-body there have been isolated two fractions, one a pure anti-
body that is completely unalterable by trypsin, the other a pure nemi-body
that is completely decomposable into amido-acids by trypsin, then it will be
time to believe in ampho-, anti-, and hemi-bodies. At present neither from
amphopeptone, protoalbumose, heteroalbumose, or deuteroalbumose has there

CLEA VAGE THEOR Y OF PROTEID DIGESTION. 419

been such a separation, even partially, achieved, although these are admitted
to be ampho-bodies by the supporters of the theory.

But if the cleavage theory be not accepted, what explanation is there
for the fact that different albumoses yield varying accounts of amido-
acids, which suffer varying amounts of decomposition, under the action
of trypsin ?

The different proteids, and the products derived from them, differ so
little in chemical composition (and this is especially true for the various
albumoses), that the difference in their nature is probably due to a differ-
ence in atomic grouping. Is it not probable, then, that some of these
groups are much more susceptible of decomposition than others ; that
those albumoses which yield much amido-acid contain more groups in
their molecules which are decomposable by trypsin ; that those which
yield much antipeptone contain less of these decomposable groups ; and
that in all cases that substance (or substances) which we call antipeptone
is the remainder after all those groups which are attackable by trypsin
have been removed in the form of amido-acids ?

It will be seen that this substitutes, for two molecules, one easily
attackable, the other wholly unattackable by trypsin, one molecule ; of
which a portion, variable in the case of each albumose, is attacked by the
trypsin and a residue left, in which there are no groups that the trypsin
is able to attack ; such a substitution relieves one from belief in a large
number of substances of which the existence has never been proven.

Again, if a cleavage of the proteid molecule takes place, at the begin-
ning of the digestive process, into anti- and hemi-groups, of which the
anti-groups, after passing through the albumose stage, become finally
converted into antipeptone, while the hemi-groups, after passing through
both albumose and peptone stage, become finally converted into amido-
acids, one would expect, in an interrupted tryptic digestion, to find
these intermediate hemi-products mixed with the intermediate anti-
products; to find substances, corresponding to those found in peptic
digestion, which would become on more complete tryptic digestion
partially, at least, broken up into amido-acids. No such compounds or
mixtures are, however, actually found ; no hemi-compound is ever found
at any stage of tryptic digestion. As already stated, proto- and hetero-
albuniose are never formed, only deuteroalbumose.

Neither is there any evidence of the formation of such a substance
as amphopeptone in tryptic digestion, only antipeptone is formed. In
short, there is no evidence whatever in tryptic digestion of two parallel
series of anti- and hemi-bodies proceeding pari passu into anti- and hemi-
peptones, of which the latter becomes decomposed into amido-acids. If
any hemi-bodies are formed, they are at once broken down into amido-
acids, without passing through the preliminary stages of hemialbumose
and hemipeptone ; at any rate, there is no experimental evidence of such
a passage. Also, when protoalbumose is obtained as a product of
fractional peptic digestion, and submitted to the action of trypsin, it is
directly broken up into amido-acids, no deuteroalbumose or hemipeptone
being discoverable as intermediate products. Similarly, heteroalbumose
is in part converted into amido-acids, and in part into aw^-deuteroalbu-
niose, which passes later into antipeptone without any formation of
/lera-i-deuteroalbumose or amphopeptone.1

1 Neumeister, Ztschr. f. BioL, Miinchen, 1887, Bd. xxiii. S. 381.

420 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

This is all easily accounted for on the supposition that a variable
fraction of the proteid molecule is easily attacked and broken off into
amido-acids by trypsin, but it is very difficult to explain on the sup-
position that the proteid molecule, early in the process of decomposition,
breaks up into two halves, of which one changes through the stages of
hemialbumose and hemipeptone into amido-acids, while the other,
passing through antialbumose, halts at antipeptone.

Description of the products formed in the pancreatic digestion
of proteids. — The products of tryptic digestion may be isolated most
easily by experimenting with fibrin, either by impregnating it with the
ferment, washing, and allowing it to digest in dilute sodium carbonate
solution, or by digesting with a purified pancreatic extract. The pro-
ducts present at different stages may be studied by removing at intervals
a portion of the digest, stopping the digestive process, by boiling and
then investigating the nature of the dissolved substances.

Coagulable proteid. — If the test portion be removed before complete solution,
or just on complete solution of the fibrin, it will be found to contain coagulahle
proteid ; on neutralising, part of this, being a globulin in character, is thrown
out of solution, and the remainder on making faintly acid and boiling.1

The deuteroalbumose of pancreatic digestion. — If, after removal of the
coagulated proteid by filtration, the solution be now concentrated, deuteroalbu-
mose can be precipitated from it by sodium chloride and acetic acid, and shown,
by subjection to further action of trypsin, to be purely an anti-compound, or,
in other words, to contain nothing in its molecule decomposable by the action
of trypsin into amido-acids. This anti-deuteroalbumose, as already stated, is
the only albumose found in tryptic digestion, and it is only found in the earlier
stages. Another portion of the digest may be acidified, and the albumose
thrown out of solution by saturation with ammonium sulphate, after which the
presence of peptone in the filtrate may be shown, after dilution or dialysis, by
the usual tests.

After some days of tryptic digestion, the digest contains no coagulable
proteid or albumose, but only antipeptone, and the simpler products formed
by more complete demolition of part of the proteid molecule (or of the hypo-
thetical hemi-moiety), such as the amido-acids.

The peptone of tryptic digestion or antipeptone. — The peptone or peptones
formed by the action of trypsin on proteids can best be obtained from a
pancreatic digest which has been allowed to proceed to completion by
repeated digestion during several days with trypsin and dilute sodium carbo-
nate solution. This solution is concentrated to a small volume and filtered
from the tyrosine, which separates out on cooling. The filtrate is saturated
with ammonium sulphate, with the precautions described under peptic diges-
tion,2 and the ammonium sulphate is similarly removed. The antipeptone may
now be precipitated by the addition of phosphoinolybdic acid, the precipitate
decomposed by baryta water, and excess of barium removed by cautious
addition of dilute sulphuric acid. Finally, the solution is concentrated to a
syrup on a water bath, and dried in vacua over sulphuric acid.3

Antipeptone agrees very closely in composition and properties with a
monobasic organic acid (Fleischsaure) recently isolated by Siegfried 4 from
muscle extract, of the composition and molecular weight represented by the

1 See pp. 405, 415. 2 See p. 411.

3 Kiihne, Ztschr. f. BioL, Munchen, 1893, Bd. xxx. S. 1.

4 Ber. d. Tc. sacks. Gesdlsch. d. Wissensch., Math.-phys. Cl., 1893, S. 485; Arch. f.
Anat. u. PhysioL, Leipzig. 1894, S. 401 ; Ztschr. f. physiol. Chem., Strassburg, 1896, Bd.
xxi. S. 360. See also C. W. Rockwood. Arch. f. Anat. u. PhysioL, Leipzig, 1895, S. 1 ;
Balke u. H. S. Ide, Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 380.

AMIDO-ACIDS FORMED IN TRYPTIC DIGESTION. 42 1

formula C10H15N305. This substance gives a similar biuret reaction to that
given by antipeptone ; like it also, it does not give Millon's reaction, is very
hygroscopic, and, on decomposition with hydrochloric acid, forms lysine and
lysatinine, but not tyrosine. It has also been obtained directly from the pro-
ducts of advanced tryptic digestion ; it has been found in milk, and in traces
in the urine. It is easily soluble in water ; sparingly in cold, more so in hot
alcohol, from which it crystallises in microscopic crystals. It is also soluble in
carbolic acid and glacial acetic acid, but is decomposed by these solvents,
especially at a high temperature. It combines with hydrochloric acid and with
phosphoric acid (Phosphorneischsaure). The compound with phosphoric acid
is the form in which it naturally occurs in the organism. Sjoqvist 1 has
recently estimated the molecular weight of antipeptone by cryoscopic determina-
tion at 250 ; this agrees very closely with the molecular weight similarly
determined by Siegfried for his new acid, and increases the probability that
the two substances are identical.

When a proteid is subjected to tryptic digestion, a portion is decomposed
beyond the stage of albumose or peptone, and there are formed several nitro-
genous bodies of much simpler constitution ; of these, some are amido-acids
and some organic bases. Of these substances, two amido-acids, leucine or amido-
caproic acid, and tyrosine or para-oxyphenylamido-propionic acid, are present in
much larger quantity than the others, which only occur in traces. These others
are aspartic acid or amido-succinic acid, glutamic acid or amido-pyrotartaric
acid, butalanine or amido-valerianic acid ; and of bases, ammonia, lysine, and
lysatinine. Besides these substances of known composition, there is another
substance of unknown composition formed, to which the name of tryptophan
has been given, although it has never been isolated, and is only known through
certain peculiar colour reactions which it gives.

The amido-acids formed in tryptic digestion.2 — Leucine, — Leucine
is an amidocaproic acid ((CH?)2CH.CH2.CH(:NTH2).COOH), and is always formed
in any profound decomposition of proteid, such as boiling with dilute acids or
alkalies, fusing with alkalies, in tryptic digestion, or in putrefaction. It has
been found in nearly all the tissues in the body, and there has been much
discussion as to whether it is a normal constituent here, or is formed as a
post-mortem product. Certainly it is rapidly increased in amount, because of
proteid decomposition, after death, but the evidence is strong for its normal
presence in more or less pronounced traces in most of the organs in the fresh
condition. It is, besides, a very common constituent of tissue in many
pathological conditions, and also occurs in the vegetable world.

Yirchow showed that both leucine and tyrosine are found normally in the
pancreas after death, and Kiihne afterwards showed that its amount here was
much increased by auto-digestion of the gland tissue post-mortem.

Leucine was first discovered by Proust in 1818 in putrefying cheese, and
named by him cheese oxide (Kase-oxyd). It was also obtained by Braconnet
by decomposing animal matter with sulphuric acid.3

Leucine may be prepared in many ways : by tryptic digestion of proteid s,
by boiling various forms of proteid with dilute acids or alkalies, with stannous
chloride and hydrochloric acid, with bromine water in sealed tubes, or by
fusing with caustic alkalies. A common method is that of boiling horn
shavings with dilute sulphuric acid for many hours ; but any form of proteid
will yield it when so treated, such as meat, cheese, fibrin, wool, feathers,
elastic tissue.

Leucine has been obtained artificially by Limpricht,4 by acting on isoval-

1 Skandin. Arch. f. Physiol., Leipzig, 1896, Bd. v. S. 277.

2 For a very full account of these bodies, see Gamgee, " Physiological Chemistry of the
Animal Body," vol. ii. p. 231.

3 Maly, Hermann's "Handbuch," Bd. v. (2), S. 207.

4 Ann. de chim., Paris, 1854, tome xciv. p. 243.

422 CHEMISTS. Y OF THE DIGESTIVE PROCESSES.

eraldehyde with hydrocyanic and hydrochloric acids. Isovaleraldehyde
(C4H9COH) is prepared, according to the general method, by oxidising amyl
alcohol with potassium bichromate and sulphuric acid ; purified by forming the
sodium bisulphite compound, decomposing this and collecting the distillate;
this is shaken with ammonia, when isovaleraldehyde-ammonia is thrown down
in crystalline form. These crystals are washed with water, and then boiled
with a mixture of strong hydrocyanic and dilute hydrochloric acids, when
a reaction takes place yielding a body of the composition C18H33N5, which
breaks up into leucine and ammonia.

Ci8H33N5 + 6H20 = 3(C6H13M)2)+2 NH3.
(leucine)

Leucine has also been obtained artificially by Hiifner,1 by heating mono-
bromocaproic acid with saturated ammonia under pressure to 120°-130° C.
during four or five hours.

C5H10BrCOOH + jtfH3 - C5H10(NH2)COOH + HBr.

Constitution of leucine. — That leucine is an amidocaproic acid is shown
both by these methods of artificial preparation and by the following
reactions : —

1. Heated under pressure to 140°-150° C., with strong hydriodic acid, it
yields caproic acid, iodide of ammonium, and iodine.

C5H10(NH2)COOH + 3 HI - C5HnCOOH + NH4I + 12

(leucine) (caproic acid)

2. Heated alone, rapidly over its melting-point (170° C.), to 180°-200° C.,
it yields amylamine and carbon-dioxide.

C5H10(NH2)COOH = C5HUNH3 + C02

3. When acted upon by nitrous acid, it breaks up in the usual manner of
amido-acids, all the nitrogen being evolved as such, and oxycaproic or leucic
acid being simultaneously formed.

C5H10(NH2)COOH + HM)2 = C5H10(OH)COOH + H20 + N2

(leucine) (leucic or oxycaproic acid)

These reactions show that leucine is an amidocaproic acid, but there are
several isomeric amidocaproic acids.2 It was thought until quite recently
that leucine was the amido-acid of normal caproic acid, but it has been recently
shown to be amido-isobutylacetic acid.3 The difference in the structure of these
two compounds would be represented according to the usual convention by the
two following graphic f orniulse : —

Normal a-amido-
caproic acid

CH3

CH2

CH2 Isobutyl-(a) amidoacetic

CH2 acid, or leucine

CH—

COOH

CHQ CH:

CH
CH,

COOH

Pure leucine crystallises in the form of thin white transparent plates,
forming in mass a snow-white powder, which feel greasy and are not wetted

1 Chem. Centr.-BL, Leipzig, 1869, ' S. 159; Journ. f. prakt. Chem., Leipzig, 1870,
Bd. i. S. 6.

2 According to R. Colin, not one but several leucines are formed in pancreatic digestion ;
these are probably the isomeric amidocaproic-acids, Ztschr. f. physiol. Chem., Strassbnrg,
1894, Bd. xx. S. 203.

3 Schulze and Likiernik, Bcr. d. detitsch. chem. Gesellsch., Berlin, 1891, Bd. xxiv. S. 669 ;
B. Gmelin, Inaug. Diss., Tubingen, 1892.

AMIDO-ACIDS FORMED IN TRYPTIC DIGESTION. 423

by water, so that they float on its surface, although their specific gravity is
about 1 '3 ; but usually leucine is found to separate from solutions containing
it in characteristic globules of microscopic size, often exhibiting a radial
striation, or a marking off into concentric alternately dark and light bands.
In this latter impure form it is easily soluble in water, and fairly so in
alcohol ; the pure product is less soluble, its solubility is variously stated from
1 in 29 to 1 in 47 parts of water at room temperature. This difference is
usually ascribed to the presence of different isomeric modifications in varying
proportions.

Heated slowly to 170° C., leucine melts and commences to sublime in loose
woolly flocks, resembling those formed when zinc is burnt to zinc oxide ; these
present the appearance microscopically of thin plates grouped into rosettes.
Leucine is very feebly soluble in strong alcohol (about 1 in 1000 in 98 per cent,
alcohol), and is insoluble in ether.

The artificial leucine obtained as described above is inactive ; so is that
obtained by the action of barium hydrate on proteids at high temperatures
(150°-160° C.). Leucine from the tissues is dextrorotatory, but also becomes
inactive when heated to 150° C. with baryta water. When Penicillium
glaucum is sown in inactive leucine, the organism lives on the dextrorotatory
variety, and laevorotatory leucine is left behind. These two are physical isomers
of each other ; their specific rotatory powers are (a)-D= + 17*3 for the right-
handed, and (a)-D= - 17 '5 for the left-handed.1

Tests for leucine. — Leucine may be recognised —

1. By its crystalline form in the above-described spherules, forming from
solution, and yielding a woolly sublimate which shows rosettes of platelets
under the microscope. If it be heated rapidly so as to raise the temperature
much above 170°, in subliming it the odour of amylamine is obtained.

2. By dissolving in boiling water and adding boiling solution of cupric
acetate, when a deep blue coloured crystalline compound appears.

3. By Scherer's test, which consists in adding a drop of nitric acid and
slowly evaporating on platinum foil, when a nearly colourless residue is left.
If this be wetted with sodium hydrate and gently heated, it forms into an oily
globule which rolls about on the foil.

Tyrosine. — Tyrosine, or _para-oxyphenyl-a-amidopropionic acid (C6H4(OH)
CH2CH(NH2)COOH), is the almost constant companion of leucine in the
decomposition of proteids. Unlike leucine, tyrosine is never found as a con-
stituent of fresh tissues ; its supposed presence in fresh pancreas has been
shown to be due to self-digestion of the gland,2 and it is not found in other
fresh tissues, but is a constant constituent of those in which proteid decom-
position has set in. It occurs very plentifully in old cheese, from which it
was first obtained by Liebig by fusing with caustic potash.

Tyrosine may be obtained in general by the same methods as leucine, but
it is not formed in the decomposition of gelatin nor of antipeptone.

Constitution of tyrosine. — The constitution of tyrosine has been established
mainly by the work of .von Earth,3 who first showed that tyrosine yielded on
fusing with caustic potash £>a?*a-oxybenzoic acid, an isomer of salicylic acid.
Previously to this, tyrosine had been looked upon as a derivative of salicylic
acid, but from this von Barth concluded it must be ethylamido-^a?-a-oxybenzoic
acid (C2H5.NH.C(;H3.OH.COOH). If this formula were correct, on treating
with hydriodic acid, ethylamine (C2H5.NH2) ought to be obtained, but Hiifner
showed that ammonia instead was split off. Von Barth next found that the

1 Schulze and Boshard, Ztschr. f. physiol. Chem., Strassburg, 1885, Bd. ix. S. 63 ; 1886,
Bd. x. S. 134.

2 Radsdejewski, Virchow's Archiv, 1866, Bd. xxxvi. S. 1; Ktihne, Untersuch. a. d.
physiol. In'st. d. Univ. Heidelberg, Bd. i. S. 317.

3 Ann. d. Chem., Leipzig,, Bd. cli. S. 100. See also Erlenmeyer u. Lipp, Ber. d. deutsch.
diem. Gescllsch., Berlin, 1882, Bd. xv. S. 1544.

424 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

2 group in his reaction was not replaced by hydrogen but by hydroxyl,
and so finally arrived at the formula C6H4.OH.C2H3(NH2)COOH, which is
in agreement with all the experimental facts, and is now universally accepted.

When fairly pure, tyrosine crystallises in long slender needles, which occur
both singly and in double sheaves or in rosettes. If impure, however, it very
often separates in balls or nodules closely resembling those of leucine,
recrystallising from warm water in the crystalline form above described ; if
the solution containing the crystals be filtered, these felt themselves together
on the surface of the paper to a thin, snow-white, paper-like mass. Tyrosine
is much more insoluble in water than leucine (1 in 1900 of cold water), more
so (1 in 150) in boiling water and in dilute and concentrated mineral acids,
and also in alkaline solutions (ammonia, alkalies and their carbonates, and the
alkaline earths). Tyrosine exhibits the usual facility of amido-acids for
forming compounds, both with bases and acids ; the copper compound is
sparingly soluble in water, and is formed in dark blue needles on the addition
of freshly precipitated cupric hydrate to a boiling solution of tyrosine, and
allowing to cool.

Tyrosine, unlike leucine, cannot be sublimed without decomposition, and on
dry distillation yields carbon-dioxide and a base of the composition C8HnNO.

Tests for tyrosine. — Tyrosine may be identified by the following tests : —

1. Its crystalline form.

2. Scherer's test, which consists in evaporating a portion with strong nitric
acid in a platinum dish, leaving a transparent deep yellow residue, which
turns red on moistening with caustic soda solution, and then a blackish brown
on again evaporating.

3. Piria's test. — A drop or two of strong sulphuric acid is added to the
tyrosine in a watch-glass ; after half-an-hour, during which tyrosine sulphuric
acid forms, the acid is diluted with water, and neutralised by the addition of
calcium carbonate. The solution is filtered from the calcium sulphate so
formed, and a drop of neutral ferric chloride solution added, when a deep
violet colour appears, similar to that given by salicylic acid.

4. R. Hoffmanris test. — This is really identical with the Millon test for
proteids, and in cases where there is no group present in the proteid molecule
capable of yielding tyrosine, the test with Millon's reagent does not succeed,
e.g., in the case of gelatin and of antipeptone. The test may be carried out
directly in the case of tyrosine itself, by boiling a solution containing this with
Millon's reagent, when the solution passes through pink into deep crimson.

Separation of leucine and tyrosine. — Leucine and tyrosine may very easily
be separated when in solution together by means of their very different
solubilities. To separate them after pancreatic digestion, it is best to allow
digestion to proceed for several days ; at the end of this time there is no
coagulable proteid, or albumose, except in traces, left in the solution. This is
neutralised and evaporated down, when the tyrosine, on account of its sparing
solubility in water, is thrown out in crystalline masses, while the more soluble
leucine nearly all remains in solution ; on cooling, more of the tyrosine separates
out, and when the solution is cold it is filtered off, extracted with hot alcohol
to remove traces of leucine, and purified by recrystallisation from hot water,
or by dissolving in weak ammonia and precipitating by neutralisation.

The filtrate containing the leucine and peptone is still further evaporated
until it becomes syrupy ; it is then extracted with boiling alcohol, which takes
up only the water and leucine. On evaporating off the alcohol, leucine is thrown
out of the concentrated solution, and may be purified by sublimation or by
repeated recrystallisation from alcohol. More tyrosine may be obtained from
the residue left by the boiling alcohol.

Or the solution, after completion of digestion and careful neutralisation,
may at once be evaporated to a thin syrup and set aside for twenty-four hours,

AMIDO-ACIDS FORMED IN TR YPTIC DIGESTION, 425

during which time most of both the leucine and tyrosine crystallises out. After
separation of the crystals, the filtrate may be once more reduced in bulk by
evaporation and a second crop of crystals obtained as before.

To the syrupy mother-liquor now remaining absolute alcohol is added, until
precipitation of the peptone commences, when the addition of alcohol is
stopped and the precipitate of peptone redissolved by gently warming. The
solution is now set aside to cool and crystallise as before. The united crops of
crystals of mixed leucine and tyrosine are boiled with alcohol, which dissolves
the leucine and but little of the tyrosine. On concentrating this alcoholic extract,
leucine crystallises out and may be purified by recrystallisation from alcohol.
From the residue insoluble in alcohol the tyrosine is obtained by dissolving in
weak ammonia water and neutralising.

The yield, both of leucine and tyrosine, obtained from different materials
varies greatly, but in all cases the former is always formed in much larger
quantity. The following table l gives the percentage yield of the substances
obtained in some cases ; the figures indicate parts per 100 : —

Source.

Leucine.

Tyrosine.

Observers and Method.

Gelatine .

1-5-2 (a]

None (a)

(a) Nencki, boiling with dilute

sulphuric acid.

Ligamentum nuclue

36-45 (b)

0-25 (6)

(b) Erlenmeyera,ndiSchdffer, boil-

ing for some hours 1 pint of

material, 2 pints sulphuric

acid, 3 pints water.

Fibrin

14-0 (6)

2-0 (6)-3'3 (e}

(c) Hlasiwetz and Habermann,

heating with bromine un-

der pressure.

Muscle .

18-0 (b}

1 -0 (6)

(d} Stddeler, heating with sul-

phuric acid.

Horn

10-0 (6)

3-6 (ZO-4-0 (d)

(e) Schutzenberger, heating with

baryta water for four to six

days, at 160°-200° C.

Egg albumin .
Plant albumin

22-6 (c)
1 7 '3 (c)

1-0 (6)-2-0 (e)

2-0 (e)

Casein

19-1 (c)

4-1 (e)

Fibrin

7-9 (/)

3-3 (/)

(/) Kuhne, digestion of boiled

fibrin.

Aspartic acid, or amido-succinic acid [C2H3.(NH2).(COOH)2], does not
occur in any of the animal tissues or secretions, but is formed in small
quantity in all those decompositions of proteids and their allies already described
as furnishing leucine and tyrosine.2 It was first identified among the products
of pancreatic digestion of fibrin by Radziejewski and Salkowski,3 and von
Knieriem afterwards showed that it is also formed in the pancreatic digestion
of plant glutin.

It may also be obtained by decomposing asparagin (amido-succinamic acid)
by an alkali or acid, thus : —

CH2— COOH

CH(NH2)— CO(NH2) + HC1 + H20
(asparagin or amido-succinamic acid).

CH2— COOH

CH(NH2)— COOH

(aspartic acid or amido-succinic acid).

* Compiled from Maly, Hermann's "Handbucli," Bd. v. (2), S. 209 et seg.

2 Ritthausen and Kreuster, Journ. /. prakt. Chem., Leipzig, 1871, Bd. iii. S. 314 ;
Hlasiwetz and Habermann, Ann. d. Chem., Leipzig, 1871, Bd. clix. S. 304.

3 Radziejewski and E. Salkowski, Ber. d. deutsch. chern. Gesellsch., Berlin, 1874, Bd. vii.
S. 1050 ; Ann. d. Chem., Leipzig, 1873, Bd. clxix. S. 150 ; W. v. Knieriem, Ztsehr. f. BioL,
Miinchen, 1875, Bd. xi. S. 198. From 100 pts. of dry egg albumin Hlasiwetz aud
Habermann obtained 23 '8 pts. of aspartic acid by the action of bromine in sealed tubes,

426 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

Aspartic acid is soluble with difficulty in cold water, easily soluble in. boiling
water, and insoluble in alcohol. It crystallises in rhombic prisms ; its solutions
are optically active, and curiously when in acid solution it is dextrorotatory,
but laevorotatory when in alkaline solution. It forms a crystalline compound
with copper, which may be used for purifying it. After leucine and tyrosine
have crystallised out from the products of a proteid decomposition, they
are separated from the mother-liquors, and these are further concentrated
and treated with a small quantity of alcohol, when after a time a new
crust of crystals forms. These are dissolved in water, the solution is
boiled with freshly precipitated cupric hydrate and filtered ; in the filtrate,
on cooling, crystals are deposited of the copper salt of aspartic acid just
mentioned. These crystals are dissolved in hydrochloric acid, the copper
is thrown out by a stream of sulphuretted hydrogen, and the copper
sulphide filtered oft'; in the filtrate, ^crystals of aspartic acid separate
out.

Glutamic acid is amido-pyrotartaric acid [C3H5.(NH2).(COOH).2], and is
homologous with aspartic acid, being the next higher member in the series,
It occurs in minute quantities in the artificial decomposition of proteids, but
has not yet been shown to be formed in the decomposition brought about by
pancreatic digestion. It has been obtained by Kitthausen and Kreuster,1 in
the decomposition of vegetable proteid by dilute sulphuric acid ; from casein
when decomposed by stannous chloride and hydrochloric acid, by Hlasiwetz
and Habermann; 2 and from reticulin, by Siegfried.3

It may be obtained by saturating its ice-cold solution with hydrochloric
acid gas, and then keeping in a freezing mixture until the compound with
hydrochloric acid (C5H9NO4 + HC1) separates out in crystals, which are
sparingly soluble in saturated hydrochloric acid, but easily soluble in water.
Next, these crystals are dissolved in warm water, and the boiling solution
is treated with freshly precipitated moist silver oxide, which removes the
hydrochloric acid by forming silver chloride ; the filtrate is freed of silver
by a stream of sulphuretted hydrogen, and concentrated. On standing, glutainic
acid separates in crystals which form rhombic tetrahedra or octahedra,
sparingly soluble in cold, readily soluble in hot water, but insoluble in
alcohol or ether. Solutions of the acid are dextrorotatory (a)D.= +31*1,
and it shows the same phenomena with regard to rotation as are described
for leucine.4

Organic bases formed in tryptic digestion. — Lysine and lysatine
or lysatinine. — Two organic bases, lysine and lysatine or lysatinine, have been
recently isolated from the products of artificial decomposition of proteids, by
means of a modification of the method of Hlasiwetz and Habermann, in which
metallic zinc was added in addition to stannous chloride and hydrochloric acid,
and means taken to exclude oxygen during the operation. These substances
were first isolated from casein by Drechsel,5 and afterwards extensively studied
by himself and others.6 They have since been found among the products of
tryptic digestion.7

Lysine and lysatine are both precipitated by a hot saturated solution of
phosphotungstic acid, which does not precipitate the amido-acids, and so
furnishes a means of separating the two from the other products of a proteid

1 Journ.f. prakt. Chem., Leipzig, 1871, Bd. iii. S. 314.

2 Ann. d. Chem., Leipzig, 1873, Bd. clxix. S. 150.

3 ;<Habilitationsschrif't," Leipzig, 1892. 4 See p. 423.

5 Arch. f. Physiol., Leipzig, 1891, S. 254; Ber. d. deutsch. diem. Gesellsch., Berlin,
1890, Bd. xxiii. S. 3096.

6 E. Fischer, Arch. f. Physiol., Leipzig, 1891, S. 265 ; Max Siegfried, Ber. d. deutsch.
diem. Gesellsch., Berlin, 1891, Bd. xxiv. S. 418 ; Arch. f. Physiol., 1891, S. 270; S. G.
Hedin, ibid., 1891, S. 273 ; Drechsel and Kriiger, Ber. d. deutsch. chcm. Gesellsch., Berlin,
1892, Bd. xxv. S. 2454.

7 Hedin, Arch. f. Anat. u. Physiol., Leipzig, 1891, S. 273.

CHROMOGEN OF PANCREA TIC DIGESTION. 42 7

decomposition. Lysine forms a platinochloride (CGH14IsT202, H2PtCl6 +
C2H5OH) which is insoluble in 50 per cent, alcohol, in which the corre-
sponding lysatine salt is soluble, and by this means the two bases may be
separated ; or they may be separated by means of the difference in solubility
of their silver salts.1

Lysine, C6H141ST20.,, in composition corresponds to a diamido-caproic acid
(Cf)H9(NH2)2COOH) ; its solutions are dextrorotatory, but, like leucine and
glutamic acid, become inactive when heated with baryta water to 150° C. The
salts of lysine are crystalline, but the base itself has not been obtained in a
crystalline form.

Lysatme or lysatinine yields a crystalline silver salt of the composition
C6H1SN3O2, HNO.j + AgN03, from which the formula of the base follows as
CGH18N300, except, as is supposed probable, the silver salt contains a molecule
of water of crystallisation, in which case the formula of the base would be
C(5H11jST30. With the former formula it would be homologous with creatine,
with the latter homologous with creatinine, and would be most properly
called lysatine or lysatinine accordingly.

Creatine is C4HS)N"302 and creatinine is C4H7N30. The new base may be
either lysatine with the formula C0H13N302, or lysatinine with the formula
G6HnN80 ; in either case being the second higher number in a homologous
series, that is differing in formula by (CH2)2.

Another similarity to creatine invests this organic base with its most
important physiological interest. Creatine when boiled with baryta water
splits up into sarcosin (or methyl-glycocoll) and urea ; similarly treated,
lysatine also yields urea. Drechsel treated the lysatine obtained from
10 grms. of the silver salt above referred to with excess of baryta water,
and obtained 1 grm. of urea nitrate, from which he isolated and identified
the urea. This is all the more interesting from the fact that creatine,
although it occurs in the body under such circumstances as leave little
doubt that it is formed as a decomposition product of proteids, has riot
yet been obtained artificially as a direct product of proteid decomposition.
Lysatine has not only been so obtained, but also as a product of pancreatic
digestion, and urea having been obtained from this, has consequently been
obtained as a product of proteid decomposition.

Hedin 2 obtained from 3 kilos, of moist fibrin, 28 grms. of pure platino-
chloride of lysine, and enough of the silver salt of lysatinine to establish
its identity.

Ammonia is found as a constant product in the artificial decomposition of
proteids, as might be inferred from what has been stated concerning lysatine,
and its formation has also been shown in pancreatic digestion. Hirschler 3
has shown that in the entire absence of putrefaction, in so short a period as
four hours, small quantities of ammonia appear in the pancreatic digestion of
fibrin ; this result has been confirmed by Stadelmann.4

The chromogen of pancreatic digestion.— As early as 1831 it was
observed, by Tiedemann and Gmelin,5 that the pancreatic juice of the dog takes
on a rose-red colour when mixed with chlorine water. Claude Bernard next
showed that no such reaction is obtained with fresh pancreatic juice, but first
appears after the juice has been kept for some time without putrefaction setting
in ; if putrefaction takes place, the reaction is also not obtained. The product
giving this colour reaction is now definitely recognised as a product of pancreatic
digestion, and not a constituent of pancreatic juice. For it the name trypto-

1 For details of these processes see Gamgee, "Physiological Chemistry," London, 1893,
vol. ii. p. 255.

-Arch.f. Anat. u. PhysioL, Leipzig, 1891, S. 273.

s Ztschr. f. physiol. Chcm., Strassburg, 1880, Bd. x. S. 302.

4 Ztschr. f. BioL, Mimclien, 1888, Bd. xxiv. S. 261.

5 " Die Verdauung nach Versuchen," Heidelberg, 1831.

428 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

phan has been suggested by Neumeister,1 from the point of view that
it may be made to serve as an indicator of when tryptic digestion has
reached a certain stage and amido-acids are beginning to be formed,- since
it first appears in the more advanced stages of proteid decomposition simul-
taneously with the amido-acids. Tryptophan has never been isolated, and is
only known by its colour reactions. When not very dilute, the rose-red colour
is replaced by violet, and Kiihne has shown that the colour is given by
bromine water as well as by chlorine water. According to Krukenberg,3
the colour is not due to oxidation by the chlorine or bromine, but to the
formation of an addition compound ; he also states that tryptophan is
slightly soluble in alcohol, ether, and chloroform. Hemala 4 has shown that
the coloured material is easily soluble in amyl alcohol. Here chlorine and not
bromine water must be used as a test, for the latter itself imparts colour to
amyl alcohol. When much peptone or Bother impurity is present with it in
solution, it falls, after some time, as a precipitate ; this on shaking up with
alcohol gives a fine violet solution showing an absorption band at the
D line. According to Krukenberg, a strong coloration is given even by
traces of the chromogen ; he also has shown that tryptophan is diffusible.

In its reaction with bromine and chlorine water, tryptophan closely
resembles the chromogen of the suprarenal gland ; the two chromogens are
also alike in being diffusible and in their powerful tinctorial action, but here
resemblance ceases. The chromogen of suprarenals is very easily destroyed by
alkalies, could not be formed in pancreatic digestion, and is quite insoluble in
dry alcohol, ether, or chloroform.

Kiihne has shown that tryptophan is a constant product in all proteid
decomposition, but that it is rapidly destroyed and disappears ; it is also
rapidly destroyed by putrefactive changes.

When pancreatic digestion is accompanied by putrefaction, many other
substances are formed besides those above described. These will be considered
in connection with bacterial digestion in the intestine.

DIGESTION OF VAKIOUS BODIES ALLIED TO THE PKOTEIDS.

Those substances, such as the mucins and nucleo-proteids, which
consist of a proteid molecule united to some organic radicle (and called
Prote'ide by Hoppe-Seyler), first undergo a cleavage into proteid and the
body involved with it ; the proteid is then digested in the usual fashion,
while the other substance very often suffers no change. In this manner
haemoglobin is decomposed by peptic digestion into a proteid commonly
supposed to be a globulin, which becomes converted through albumose
into peptone, and hrematin. which remains unchanged. Nucleo-proteids
and nucleo-albumins 5 yield on similar treatment an insoluble residue
of nuclein, or of pseudo-nuclem or paranuclein respectively, and the
proteid part of the molecule is peptonised. In the tryptic digestion of
fibrin some of the xanthin bases (or nuclein bases) have been found ;
these arise from the breaking up of nuclear-nuclein (Kernnudein)
present as a constituent of admixed nucleo-proteid, derived from the
nuclei of white blood corpuscles. The nuclein breaks up into nucleic

1 Ztsclir.f. Biol., Miinchcn, 1890, Bd, xxvii. S. 309.

2 The name proteiiiochromogen has been given to this chromogen by Stadelmann,
ibid., 1890, Bd. xxvi. S. 491.

3 Krukenberg, Virchow's Archiv, 1885, Bd. ci. S. 555; Verhandl. d. phys.-med.
Gesellsch. zu Wiirzburg, 1884, S. 179.

4 Loc. cit. See also Neumeister, Ztsclir.f. Biol., Miinchen, 1890, Bd. xxvi. S. 332.

5 Nucleo-proteids yield on decomposition a true nuclein, containing nucleic bases,
nucleo-albumins a pseudo-nuclem or paranuclein, which does not contain such bases.

DIGESTION OF BODIES ALLIED TO PROTEIDS. 429

acids and proteid, and the nucleic acids in their turn into nuclein bases
and phosphoric acid. These changes take place very slowly in tryptic
digestion. On digestion with pepsin and hydrochloric acid, the glyco-
proteids are decomposed, yielding a carbohydrate substance which
reduces Fehling's solution and a proteid which as before is peptonised.
This decomposition only takes place slowly, and is probably due in
great part to the feeble hydrolytic action of the hydrochloric acid.

The caseinogen of milk is first coagulated by the action of the rennin
of the gastric juice, and afterwards the insoluble casein formed in this
process is digested.

Casein is broken up in the process of gastric digestion into a proteid
and pseudo-nuclein, of which the former is changed into peptone, while
the latter is thrown out as an insoluble precipitate.

This precipitate corresponds to the dyspeptone of Meissner, and has been
the subject of a considerable amount of investigation. Lubavin 1 found that
it contained inorganic phosphorus, and that it is a mixture of which one part is
soluble in dilute sodic carbonate (Na2C03), while the other is insoluble. The
soluble part contains 4 '6 per cent, of phosphorus, and is probably identical
with Hoppe-Seyler's nuclein. Chittenden 2 and others state that dyspeptone does
not contain much phosphorus, and that this is probably present as calcium
phosphate, dyspeptone being therefore not a nuclein but a mixture of calcium
phosphate with a hydration product of casein. C. Wildenow 3 does not hold
with this view, having obtained dyspeptone which contained only O13
per cent, of calcium, and 3'85-4'66 per cent, of phosphorus, but agrees with
Lubavin that the precipitate is a nuclein. E. Salkowski 4 supports this con-
clusion ; he also announces that on prolonged digestion the precipitate
redissolves to a clear solution, part of the phosphorus being split off as
phosphoric acid, and part remaining in organic combination (probably as
paranucleic acid). Such a solution can be brought about, according to
Salkowski, by a strong peptic solution within forty-eight hours.

The albuminoids as a class are fairly resistant to the action of
digestive agents ; when they are broken up, they yield products closely
resembling those furnished by the decomposition of the true proteids.

Collagen is said to be converted into its hydrate gelatin more
rapidly by the action of pepsin and hydrochloric acid than it would be
by the acid alone ; the gelatin thus formed is then acted upon by the
pepsin and hydrochloric acid, and rapidly loses its characteristic property
of gelatinising on cooling.5 This physical change is the visible sign of a
chemical one, by which the gelatin is converted into a substance called
protogelatose ; this is again changed, yielding deuterogelatose ; and finally
gelatin peptone is formed.6 These substances resemble the corresponding
compounds of proteid digestion, the gelatin peptone being distinguished
from the other two products by its indifference to the saturation of its
solutions with neutral salts and by its diffusibility. Protogelatose is
thrown out of solution by saturation of its acidified solution with sodium

1 Med. -chem. Untersuch., Berlin, 1871, S. 463.

2 Stud. Lab. Physiol. Chem., New Haven, 1890, vol. iii. p. 66.

3 Inaug. Diss., Bern, 1893.

4 Centralbl.f. d. med. Wissensch., Berlin, 1893, Nos, 23, 28; Arch. f. d. ges. Physiol. ,
Bonn, 1896, Bd. Ixiii. S. 401.

3 J. de Bary, Ztschr. f. physiol. Chem., Strassburg, 1896, S. 75 ; Etzinger, Ztschr. f.
Biol., Miinchen, Bd. x. S. 84 ; Uffelmann, Deutsches Arch. f. klin. Med., Leipzig, Bd. xx.
S. 535.

6 Chittenden and Solley, Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 23.

430 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

chloride, while deuterogelatose is only precipitated by saturation with
ammonium sulphate. Protogelatose is also precipitated by platinic
chloride, while deuterogelatose is not so precipitated.

Collagen is not attacked by pancreatic juice unless it has been
previously boiled with water, or swollen by the action of dilute acids, as
it normally would be by the gastric juice.1 This result is confirmed by
the observation of Ludwig and Ogata, that after removal of the stomach
proteid was still digested, but connective tissue was not attacked. After
such preliminary treatment collagen is easily converted into gelatin,
and the after course of events closely resembles that described for
peptic digestion. There is first formed protogelatose, then deutero-
gelatose, and finally gelatin peptone, which is not converted by any
further action of trypsin into amido-acids.2 Trypsin acts so easily on
gelatin, and deprives it so readily of its power of gelatinising, that this
has been recommended by Fermi as a test for trypsin.3

The decomposition products of gelatin have been long known, though not
with the exactitude above described. Gmelin showed that it was decom-
posed by superheated steam at 140° C., and Hofmeister 4 obtained, after boil-
ing with water in 1 per cent, solution for thirty hours, two cleavage products
which he termed semiglutin and semicollin ; these are probably identical with
proto- and deuterogelatose.

Elastin is also dissolved by pepsin and hydrochloric acid,5 though
with more difficulty than collagen. The products of the peptic digestion
of elastin were studied by Horbaczewski,6 who described two products
which he called hemielastin and elastin peptone. The same subject has
been investigated more recently by Chittenden and Hart,7 who have
shown that two substances are formed in the peptic digestion of elastin,
but that both these substances are albumoses, since they are both pre-
cipitated by saturation of their solutions with ammonium sulphate ; to
these substances they gave the names of protoelastose and deutero-
elastose. The former is precipitated on saturation of its solution with
sodium chloride, while the latter is only precipitated on the addition of
acetic acid. Elastin is also directly attacked by trypsin and dissolved,
forming in turn proto- and deuteroelastoses as in peptic digestion, but
neither in peptic or tryptic digestion is there any peptone formed.8

1 Ewald and Kiihne, Verhandl. d. naturh.-med. Ver. zu Heidelberg, 1877, N. F.,
Bd. i. S. 451.

2 Chittenden and Solley, loc. cit.

3 Arch. f. Hyg., Miinchen u. Leipzig, 1891, Bd. xii.

4 Ztschr. f. physiol. Of/em., Strassburg, 1878, Bd. ii. S. 299.

5 Etzinger, Ztschr. f. BioL, Miinchen, Bd. x. S. 84.

6 Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 330.

7 Ztschr. /. BioL, Miinchen, 1889, Bd. xv. S. 368.

8 Chittenden and Hart, loc. cit.

ABSORPTION OF CARBOHYDRATES AND PROTEIDS. 431

THE ABSORPTION OF CARBOHYDRATES AND PROTEIDS.

It was for many years believed that the absorption of the products of
digestion from the alimentary canal was governed by exactly the same
physical laws as determine the passage of a solution and its dissolved
constituents through an inert membrane, but the accumulation of
experimental evidence has rendered such a belief no longer tenable.
It is now known that the cells which line the alimentary canal take an
active part, not only in absorbing the materials prepared for them by
the action of the digestive secretions, but in modifying these products
in various ways during the process.

Before the laws of diffusion of solutions were known, the process of
absorption by the columnar cells of the intestine was compared by Tiedemann
and Gmelin (1820) l to that of gland secretion. After the establishment of the
laws of diffusion, attempts were made to apply them in explanation of absorp-
tion, as well as of other similar processes in the body. Such physical views
persisted for a long time, until it was shown by conclusive experiments that
absorption^ like these other processes, does not obey the laws of physical
diffusion, but is selective in its character and governed in some subtle way
by the activity of the cells involved. Our modern view is thus, as is often
the case, a recurrence to an older theory ; the only difference being that we
have a somewhat broader experimental basis on which to build it.

The cells of a secreting gland take up certain materials from the lymph in
which they are bathed, and from these, in some manner, elaborate certain
products which are passed into the gland lumen as a secretion. Similarly, the
absorbing cells of the intestine take up certain products of digestion from
the intestinal contents by which they are bathed, and build up from these
certain materials which pass into the lymph. So that absorption may be
regarded as a kind of reversed secretion.

In both cases the process is a selective one, the constituents of the gland
secretion are definite in their nature, in many cases specific, and are probably
formed from definite constituents of the lymph taken up by the secreting cell
to the exclusion of others. In like fashion, certain materials only are taken
up by the epithelial absorbing cell, and from these definite products are
formed to be passed into the lymph.

That absorption is a selective process and not one of purely physical
diffusion, is shown by the following observations : —

1. Certain colloids (e.g. alkali albumin) disappear from the intestine
at a fairly rapid rate, even in the complete absence of digestive
enzymes.2

2. The rate of absorption from the intestine of various dissolved
substances is not proportional to their diffusion-coefficients. Sodium
sulphate is much more diffusible than grape-sugar, but when a solution
containing 0-5 per cent, of each of these is injected into the intestine,
the sugar disappears much more rapidly, and only traces of it remain
at a time when the greater part of the sodium sulphate is still left
behind.3

3. The rapidity of absorption is much greater than can be accounted

1 Quoted by Heidenhain, Arch. /. d. ges. PhysioL, Bonn, 1888, Supp. Heft, Bd.
xliii. S. 69.

2 See form of absorption of proteids, p. 436.

3 Rohmann, Arch. f. d. ges. PhysioL, Bonn, 1887, Bd. xli. S. 411.

432 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

for, on the basis of physical diffusion from the intestinal contents to the
lymph.1

4. If the dissolved products of digestion are carried through by
diffusion, it must be passively in a diffusion stream due to salt diffusion,
their own diffusive powers being too feeble to suppose they are carried
by these. Now, not only would such a stream be too slow, but, in such
a case, the amount of fluid which must be absorbed by the epithelial
cells would be enormous. There is at the height of proteid digestion,
even in an animal with such digestive powers as the pig, rarely more
than 2 per cent, of albumoses and peptones together in solution in the
intestine, and usually much less. If it be supposed that this is passively
and not selectively absorbed, then to carry 100 grms. of digested proteid
out of the intestine, 5 litres of water at least, and probably a great
deal more, would be required. During the digestion of starch, only
traces of sugar are found at any given time in the intestine, and
generally it may be stated that absorption takes place from very dilute
solution. There is no reason to believe that such enormous quantities
of fluid are thrown into the intestine during digestion, to be afterwards
absorbed from it, and hence it must be concluded that^ dissolved
substances are not passively absorbed by their solutions passing
unchanged into the epithelial cell.

Seat of absorption.— Absorption of some substances begins in the
stomach,2 but the main part takes place in the intestine. Water is
practically not absorbed at all in the stomach,3 while alcohol is readily
taken up. The absorption of chloral hydrate and of sugar by the
stomach is increased by the presence of alcohol.

Gastric absorption is said to be increased by greater concentration of
the substance to be absorbed, while the reverse holds for intestinal
absorption. A solution of grape-sugar is most rapidly absorbed from
the intestine when its concentration lies at 0'5 per cent. ; as the
concentration increases from this the rate of absorption diminishes;
while the rate of absorption in the stomach increases up to a concen-
tration of 20 per cent.4 According to v. Mering, all forms of sugar are
absorbed in the stomach to a greater or less extent. The products of pro-
teid digestion are also probably absorbed to a slight extent in the stomach.5

Channels of absorption.— The new materials formed by the action
of the intestinal epithelial cells on the absorbed products of digestion,
pass out of these cells into the lymphoid tissue of the villus underlying
them. The modified carbohydrates and proteids pass in solution into
the lymph which bathes the tissue, and in soluble form are absorbed
from this lymph by the capillary vessels of the villus, thus passing
directly into the portal circulation, while the fats leave the epithelial
cells as fat globules, and are carried as such past the capillary network
of the villus, to enter the lacteal situated in the axis of the villus.6

1 Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1888, Supp. Heft, Bd. xliii. S. 70.

2 See Busch, Firchow's Archiv, 1858, Bd. xiv. S. 171 ; Tappeiner, Ztschr. f. JBioL,
Miinchen, 1880, Bd. xvi. S. 497 ; v. Anrep, Arch. f. Anat. u. PhysioL, Leipzig, 1881,
S. 504 ; Meade-Smith, ibid., Leipzig, 1884, S. 481 ; v. Mering, Ferhandl. d. Cong. f.
innere M< ed. , Wiesbaden, 1893; CcntralU. f. PhysioL, Leipzig u. Wien, 1893, Bd. viii.
S. 533.

3 Edkins, Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 445 ; v. Mering,
loc. cit.; Gley and Rondeau, Compt. rend. Soc. de. biol., Paris, 1893, p. 516.

4Brandl, Ztschr. f. Biol., Miinchen, 1892, Bd. xxix. S. 277.

5 See F. Hofmeister, Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 69.

6 See " Digestion and Absorption of Fats," p. 457.

ABSORPTION OF CARBOHYDRATES AND PROTEIDS. 433

There are thus two channels of absorption leading to the systemic
blood stream. One by the capillaries of the villus, passing through the
liver ; the other by the lacteals, vid the abdominal lymphatics, to the
thoracic duct leading directly to the subclavian vein.

Absorption of water. — It has been shown by Heidenhain l that by
far the greater share of the water absorbed from the small intestine
is taken up by the capillaries of the villus and not by the lacteals.
When large quantities of dilute saline solution (0-3 per cent.) are injected
into the small intestine, the rate of lymph flow in the thoracic duct
is not markedly increased, unless so much salt solution is injected at one
time that the intestine becomes forcibly distended. Zawilsky2 also
found that even during active fat absorption there was no great increase
in the amount of lymph flowing from the thoracic duct; the lymph
became charged with an exceedingly fine emulsion of fat, but was not
largely increased in quantity.

The considerable absorption of water which commences in the lower
end of the ileum, and goes on throughout the entire length of the large
intestine, causing the thin chyme of the upper part of the small intestine
to become semi-solid, and finally to assume the consistency of the faeces,
is also carried out by the agency of capillary blood vessels, so that
practically all the water absorbed from the intestine is taken up by the
blood stream. The blood is not diluted to a corresponding extent in the
process ; in fact, even with the absorption of an excessive amount of
water, as in Heidenhain's experiments above quoted, the composition of
the blood is little altered. The absorbed water in such a case of
excessive absorption passes at first into the lymph which bathes the
tissues, to be afterwards brought out and gradually eliminated by the
kidneys as the excess in the blood diminishes.

Absorption of soluble constituents.8 — All those substances which leave
the epithelial cell in solution, are also carried away from the lymph
spaces of the villus by the capillaries.4 This has been shown chiefly by
observations made during active absorption of these several constituents,
on the rate of flow in the thoracic duct, the constitution of the lymph so
flowing, and the effects of ligature of the duct or diversion of the stream
to the exterior. Direct analyses of the blood of the portal vein, as com-
pared with the systemic blood, do not yield trustworthy results ; partly
because of the difficulty of making very exact determinations in such a
complex fluid as blood serum ; still more because of the very small change
in composition which is sufficient to account for the carriage of a great
weight of absorbed substance, by reason of the copious flow which takes
place through the capillaries, especially when active digestion is in
progress.

If a cannula be inserted into the upper end of the thoracic duct, and
the rate of flow of the lymph stream measured, as well as the amount of
proteid contained therein, neither of these is found materially to alter,
whether the animal (dog) be fasting, or active proteid digestion be going

1Arc-h.f. d. ges. Physiol., Bonn, 1888, Supp. Heft, Bd. xliii. S. 53; 1894, Bd. Ivi.
S. 579.

2 Arb. a. d. physiol. Anst. zu Leipzig, 1876, Bd. xi. S. 161.

3 For the Absorption of fats and fatty acids, see p. 443.

4 It is often stated that all the dissolved intestinal contents are so absorbed, but if, as
is probable, fats are absorbed in soluble form, such a statement is obviously incorrect. Only
those constituents which remain soluble, after the action of the absorbing cells, pass into
the capillaries.

VOL. I. — 28

434 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

on. This could obviously not be the case if any appreciable part of the
proteid were absorbed by the lacteals.

Again, if the thoracic duct be ligatured, and an hour after the opera-
tion the animal (dog) be given a rich meal of proteid food, absorption
goes on in a normal manner. If the animal be killed after the lapse of
about forty-eight hours, it will be found that all the proteid has been
absorbed, while a corresponding amount of nitrogen has been eliminated
in the urine.1

A similar proof has been given for carbohydrate absorption by the
blood vessels. In this case the animal is fed with carbohydrate food
instead of proteid ; and the amount of sugar in the lymph which flows
from a fistula of the thoracic duct is estimated. The percentage of sugar
lies between O6 and 1*6 per thousand^ and does not vary in the least
with the state of digestion, this being the usual percentage of sugar
found in lymph or blood serum.2

A direct proof has also been given of the absorption of sugar by the
capillaries, as it has been shown that on injection of sugar into the
intestine the percentage of sugar in the portal vein may rise as high
as 4 per 1000, while in a fasting condition the amount of sugar
contained in the blood of either portal or hepatic veins does not essentially
differ from that in the blood of the remainder of the circulation.2

It may be taken, then, that, under normal conditions, all the soluble
constituents which leave the epithelial cell are taken up by the capillaries.
But when excessive absorption is taking place, as when large quantities
of sugar in concentrated solution are injected into the intestine, this is
not the case. Here the work of absorption becomes too great for the
capillaries, a part of the dissolved foodstuff passes the region of their
action and is absorbed by the lacteals, probably in a passive fashion.

Conditions of absorption of carbohydrates. — There is no doubt
that a considerable share of the carbohydrate food is taken up from
the intestine by the absorbing cells as simple sugars (mainly as dex-
trose and leevulose), otherwise the reason of the ferment actions which
have been previously described would be difficult to see. But we
possess no experimental evidence to show that all the carbohydrate
is absorbed in such a form. Indeed, it is probable that the absorbing
cells are capable of taking up not only saccharoses, but even colloidal
carbohydrates, such as dextrin and starch, and converting these into
simple sugars before turning them into the blood stream.

We have already seen, in discussing the digestion of starch and
glycogen, that it is impossible, in experiments carried out in vitro, to
further convert all the dextrin formed into maltose or other form of
sugar. Sheridan Lea's 3 experiments show, indeed, that the rapidity of
diastatic action is much increased by dialysis, and the quantity of dextrin
left unchanged into maltose largely diminished. Lea argues from this
result that, under the more favourable conditions for removal of digestion
products existing in natural digestion, the conversion of dextrin into
maltose may become complete. Contrary to this view, there is the
experience of Musculus and G-ruber,4 that the unchanged dextrin remain-
ing after a prolonged digestion of starch, with a diastatic ferment, is not

1 Schmidt-Mlilheim, Arch. f. Anat. u. P/tysioL, Leipzig, 1877, S. 549.

2 Von Mering, ibid., 1877, S. 379.

" Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 226 ; see also pp. 321 and 394.
4 Ztsc/tr. /. physiol. Chem., Strassburg, 1878, Bd. ii. S. 177.

ABSORPTION OF CARBOHYDRATES. 435

convertible into maltose by a fresh addition of diastatic ferment after
complete removal of the maltose produced by the first digestion. So
that the failure of the ferment to convert the last portion of dextrin into
maltose cannot be wholly due to the stoppage of its action by the presence
of excess of maltose.

There is 110 very evident reason why soluble materials like the dex-
trins should not be absorbed as such by the epithelial cells. The argument
that dextrin is not directly assimilable, because, when injected subcutane-
ously or intravenously, it is eliminated by the kidneys, is not valid against
its absorption as dextrin by the epithelial cell. For there is no reason to
suppose that the cell must turn it into the lymph in exactly the same
form in which it takes it up from the intestine ; the chances are, in fact,
all against such a supposition. It may be taken as probable, then, that
the digestive enzymes of the alimentary canal are incapable of con-
verting all the starch of the food into maltose, and hence into dextrose,
and that a portion is absorbed as dextrin, and changed into something
else before reaching the blood stream.

What has been said above concerning dextrin applies also to the
double sugars. The intestinal juice, as we have seen, contains enzymes
capable of converting maltose and cane-sugar into simple sugars, and it is
probable that such a change does take place to a very large extent. Still
it cannot be concluded that the double sugars undergo complete conversion
before absorption. Lactose appears not to be acted upon by any of the
digestive enzymes, and so far as it escapes lactic acid fermentation this
double sugar must be absorbed by the epithelial cell unchanged. Again,
Brown and Heron l found that the dried mucous membrane acted much
more energetically on maltose than did any extract of it, which tends to
show that this action takes place in part within the cell.

Eohmann 2 has also shown that not only sugar, but even starch solution
disappears from a Thiry-Vella fistula with considerable rapidity ; and as
the succus entericus possesses only an exceedingly feeble diastatic action
on starch, it seems that here the starch must be directly taken up by the
intestinal cell. Such a view is also supported by the fact that, after
removal of the pancreas, the secretion of which must produce the greater
part of the diastatic action which goes on within the intestine, one-half
to three-fourths of the starch of the food is still utilised.3 Under normal
conditions, however, the diastatic conversion by the pancreatic juice is so
rapid, that it is very improbable than any appreciable portion of starch is
absorbed as such.

Form in which carbohydrates reach the Hood stream. — During active
carbohydrate absorption, traces of carbohydrates, resembling dextrin, are
said to be present in the blood of the portal vein,4 but it is probable that
very little carbohydrate leaves the epithelial cells other than dextrose
or laevulose. These two sugars are capable of direct assimilation after
subcutaneous injection, and of forming glycogen in the liver, but no such
direct assimilation takes place in the case of cane-sugar or maltose.

1 Loc. cit. 2 Arch.f. d. ges. Physiol., Bonn, 1887, Bd. xli. S. 411.

3 Minkowski" and Abelmann (Inaug. Diss., Dorpat, 1890; Centralbl. f. Physiol.,
Leipzig u. Wien, 1891, Bd. iv. S. 522) found, after complete extirpation of the pancreas,
an absorption of 57-71 per cent, of starch ; the brothers Cavazzanni (Centralbl. f. Physiol.,
Leipzig u. Wien, 1893, Bd. vii. S. 217), under like circumstances an absorption of 47 per
cent.

4 Otto, Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1888, Bd. xvii. S. 138 ;
v. Mering, Arch.f. Anat. u. Physiol., Leipzig, 1877, S. 413.

436 CHEMISTRY OF THE DIGESTIVE PROCESSES.

Ingestion of large quantities of solution of sugar leads to the appear-
ance of sugar in the urine (alimentary glycosuria), due to the assimilation
of the sugar not keeping pace with its absorption.1 Absorption itself
is also disturbed by the appearance of diarrhoea. But when carbohydrate
is introduced into the alimentary canal, in the form of starch, immense
quantities can be rapidly and completely absorbed without any glycosuria
or other disturbance ensuing.

Thus Kiibner 2 found that a man consuming a daily ration of 508-670
grins, of carbohydrate contained in wheaten bread, left unabsorbed only
0'8-2'6 per cent. ; of the carbohydrate of peas (357-588 grins.) 3'6-7'0 per
cent, was unabsorbed; and of potatoes (718 grins.) 7'6 percent. This
complete absorption and utilisation of carbohydrate, when taken in the
form of starch, is probably due to the ra^te of assimilation and storage as
glycogen in the liver, being able to keep pace with that of absorption
from the intestine.

Conditions of absorption of proteids. — The power possessed by
the intestinal cells of absorbing various forms of proteid affords one
of the best illustrations that this process is not one of mere
physical diffusion. The products found towards the end of a proteid
digestion in vitro are distinguished from the .proteids from which they
originate by being slightly diffusible. To this fact great importance
was at one time attributed, because it was thought that only proteids
in a diffusible form were capable of absorption, and hence that peptonisa-
tion was in all cases a necessary preliminary. It is now generally
admitted that many forms of native proteid are capable of entering the
epithelial cells without previous change by digestion or otherwise ; and
in those cases in which a proteid is incapable of direct absorption a much
less profound change than peptonisation is sufficient to render it so,
namely, conversion into acid or alkali albumin. Such an absorption of
soluble proteid, other than albumose or peptone, takes place not only in
the small intestine, but in the large intestine, and even in the rectum.

Voit and Bauer 3 cleared a loop of small intestine of its contents as
completely as possible by stroking, and separated it from the rest of the
gut by double ligatures at each end. Various forms of proteid, in solu-
tions of known amount and strength, were then injected into this loop ;
the intestine was replaced, and its contents examined on killing the
animal (cat or dog) some hours later. It was found that variable amounts
of these proteids had disappeared; thus, in one to four hours, 16-33 per
cent, of white of egg had disappeared, and of syntonin from ox muscle
28-95 per cent. It might be supposed that the portion of proteid ab-
sorbed had been peptonised by traces of proteolytic enzyme which might
be present in the intestine ; but in the unabsorbed proteid remaining at
the end of the experiment, no albumose or peptone was found. Voit and
Bauer also injected solutions of white of egg and sodium chloride into the
rectum of man and animals in a fasting condition, and found a marked
increase (6 to 8 grms. in 24 hours) in the amount of nitrogen eliminated
by the kidneys ; in fact, an equilibrium of nitrogenous metabolism may
even be maintained in this way. It has been shown by Eichhorst,4 who
confirms these results, that no appreciable amount of peptonisation takes

1 C. Voit, Ztschr. f. £iol., Miinchen, 1891, Bd. xxviii. S. 245.

2 Ibid., Bd. xix. S. 45.

3 Ibid., Bd. v. S. 562.

4 Arch.f. d. ges. PhysioL, Bonn, 1871, Bd. iv. S. 570.

ABSORPTION OF PROTEIDS. 437

place in the large intestine. Finally, the objection that the action is due
to traces of enzymes, has been disposed of by the observations of Czerny
and Latschenberger,1 in a case of a fistula situated in the sigmoid flexure.
The rectum was thoroughly washed out from the fistula, yet from 60—70
per cent, of the injected proteid disappeared in 23—29 hours.

Assimilable and non-assimilable proteids. — Some forms of proteid, such
as alkali albumin, prepared from white of egg, and acid albumin, prepared
from muscle, myosin, fibrin, or white of egg, are directly assimilable ; that
is to say, when injected into the blood stream they are not removed again
by the kidneys ; others, such as unchanged white of egg, caseinogen, and
glutin, are, when injected, at once excreted in the urine. The latter forms
must therefore, under normal conditions, be changed during absorption,
before passing into the blood ; but when excess of white of egg is present
in the intestine, absorption oversteps the rate at which this change can
take place, and a portion of the egg albumin reaches the circulation
unchanged. Under these circumstances, this portion is promptly re-
moved by the kidneys, and an " alimentary albuminuria " is the result,
just as an excessive amount of sugar in the intestine produces " alimentary
glycosuria."

Relative amounts of proteids absorbed in different forms. — It is
evident, then, that absorption can take place, either in the form of
albumose or peptone, of alkali or acid albumin, or even occasionally
in that of native proteid ; and the question arises, to what extent does
absorption take place under natural conditions in each of these different
forms ? Such a question is exceedingly difficult to answer by experiment.
It is impossible to do so exactly by observation of the amount of each
form of proteid present in the intestinal contents during proteid absorp-
tion, because the absorption is selective, and a substance present only in
traces may be passing out of the intestine more rapidly as it is con-
tinuously formed than another which is present in much larger quantity.

A rough estimate of the relative amounts of proteid absorbed as
albumose and peptone, and that absorbed in other forms, may be obtained
from analyses of the intestinal contents during proteid digestion. Thus,
Schmidt-Miilheim 2 examined the contents of the stomach and intestine
at varying periods during digestion of flesh in dogs ; he found that the
amount of proteid in solution, both in the stomach and intestine, was
small at any given time, but that the amount present as albumose and peptone
was always somewhat greater than that present in other forms. When it is
remembered that albumose and peptone are absorbed more rapidly than
other proteids, this points to the greater part of the proteid being absorbed
as albumose arid peptone.

It is not known with certainty to what extent amido -acids are formed
from proteids, in the natural course of intestinal digestion. The experi-
mental evidence on the subject is somewhat conflicting, but the majority
of observers are of the opinion that but little proteid is absorbed as leucine
and tyrosine, being nearly all absorbed as albumose or peptone, or even
at a still earlier stage.

The only positive evidence as to the formation of leucine and tyrosine
in natural digestion, rests on the amounts found in the intestinal contents

1 Virckow's Archiv, 1874, Bd. lix. S. 174 ; see also Ewald, Ztschr. f. Tclin. Med., Berlin,
1887, Bd. xii. S. 407 ; Huber, DeutscJics Arch. f. Jclin. Meet.., Leipzig. 1891, Bd. xlvii.
S. 495.

2 Arch. f. Anat. u. PhysioL, Leipzig, 1879, S. 39.

438 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

during proteid digestion. Such evidence can only give a reliable
estimate of the amount formed relatively to other proteid products,
when the rate of absorption from the intestine of these various products
is known.

Kolliker and Miiller l found only microscopic traces of leucine and
tyrosine in the upper part of the small intestine of carnivorous animals,
and none in the lower part. Kiihne 2 subjected fibrin to tryptic digestion
in a tied-off loop of intestine, into which the pancreatic duct entered,
and subjected the residue to analysis after four hours. Leucine and
tyrosine were found among the products, but the yield was small, and,
moreover, the conditions in such an experiment are not quite comparable
to those of natural digestion. Indeed, Kiihne himself thinks it probable
that the greater part of the " peptone " being rapidly absorbed escapes
such a decomposition.

Schmidt-Miilheim 3 states that, in proteid digestion in the carnivora, leucine
and tyrosine are either not formed at all, or else in such small quantities that
their absorption is of no physiological importance as a means of removing from
the alimentary canal any appreciable amount of nitrogen derived from the
proteid foodstuffs.

On the other hand, Sheridan Lea 4 obtained from the intestinal contents of
a dog, six hours after a plentiful meal of lean flesh, what must be regarded as a
considerable amount of amido-acids to be found there at any given time (par-
ticularly when it is remembered that the amount of intestinal contents in the
dog at any given moment, even during active proteid digestion, is very scanty),
namely, 1 grm. of pure leucine, and '3 grm. of tyrosine. These figures equal the
total amounts obtainable of these products from 10 grms. of dried proteid, and
if it be assumed that leucine and tyrosine are absorbed with a rapidity equal to
that with which albumoses are taken up, indicate that a considerable percentage
of proteid was being converted into amido-acids, and absorbed as such.

The relative amount of proteid decomposed in the intestine into amido-
acids, as well as that absorbed in the various other forms, probably varies within
wide limits with the state of nutrition of the animal and the amount of proteid
food. It is possible, as Foster 5 states, that such a degradation of proteid in
the intestine may serve as a safety-valve to the economy, diverting from the
tissues the burden of an often unnecessarily large proteid metabolism. The
waste of energy to the animal economy caused by the disintegration of proteid
into amido-acids in the intestine is often advanced as an argument against the
occurrence of this process to any marked extent. Certainly the potential
chemical energy of the proteid is lost to the economy, as far as the performance
of some forms of physiological work is concerned, but it should not be forgotten
that the total amount of energy abstracted by the animal from its food is
measured by the chemical form in which it enters and that in which it leaves
the body, and a given portion of proteid entering the body and then leaving it
as urea, water, and carbon dioxide, will give up to the body exactly the same
store of energy, no matter what may he the intermediate steps by which it is
reduced from one form to the other. In one case the energy is set free in
the tissues, in the other in the intestine. In the second case, the heat
set free by chemical decomposition is communicated to the intestine and
carried off by the circulating blood, to keep up the temperature of the body,
thus sparing reserve chemical energy which would otherwise have to be used
for this purpose.

1 VerliandL d. pliys.-med. Gesellscli. zu Wurzburg, 1856. Bd. vi. S. 499.

2 Virchow's Archiv, 1867, Bd. xxxix. S. 130. ;! Loc. tit.

4 Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 255.

5 "Text- Book of Physiology," 1889, 5th edition, part ii. p. 476.

ABSORPTION OF PROTEIDS. 439

Changes in albumose and peptone during absorption.1 — Although
there is no doubt that a considerable, if not the greater part of
the proteid of the food is absorbed as albumose or peptone, these
bodies are never found in appreciable amount in the blood. Schmidt-
Mlilheim 2 stated that the maximum amount in serum is 0*028 per cent.;
but recent experiments by Neumeister3 have given an altogether
negative result, and, according to this observer, albumoses are not present
at all in blood, even in traces.

Injected directly into the blood, albumoses and peptone are treated
by the organism as foreign bodies ; they are not assimilable proteids, but
are promptly excreted by the kidneys, unless injected in large quantities,4
and in a short time practically all the peptone and albumose injected is
found in the urine, while not a trace is to be found in the blood.5
That albumose and peptone are foreign substances in the blood stream,
is shown not only by this rapid elimination, but by the fact that they
possess, besides, marked toxic properties, and cause the death of the
animal when injected in larger doses, producing an immense and rapid
fall in arterial blood pressure ; in addition, they so alter the nature
of the blood that on drawing it from the vessels it no longer coagulates,
or does so very slowly. These results, taken in conjunction with the
fact that normal urine never contains albumoses, even in traces, prove
that the albumoses and peptones absorbed from the alimentary canal
never reach the general circulation as such, but are somewhere on their
route converted into other substances which can harmlessly enter the
circulation. Positive experiments on the subject not only confirm this
indirect proof, but clearly indicate that the change takes place in the
lining epithelial cells.

Seat of the modification of albumose and peptone during absorption. —
It might be supposed that the albumose and peptone disappeared as
such in the liver ; this is not, however, the case. Schmidt-Mulheim 6
found that the portal vein during proteid digestion contained no greater a
percentage of these bodies than the arterial blood, and Neumeister7 found
that the portal vein, while absorption of peptone was going on, did not
contain a trace of this material. Neumeister also circulated defibrinated
blood, to which peptone had been added through a liver immediately

1 In many of the papers referred to in this section, "peptone" is used to signify what
would to-day be called a mixture of albumose and peptone ; this has usually been trans-
lated by albumose and peptone, or by albumose.

2 Arch.f. Anat. u. PhysioL, Leipzig, 1880, S. 33. See also Hofmeister, Arch. f. exper.
Path. u. PharmakoL, Leipzig, 1885, Bd. xix. S. 17.

3 Ztschr. f. BioL, Miinchen, 1888, Bd. xxiv. S. 277. Neumeister caught the blood
from the carotid in ammonium oxalate to prevent clotting ; laked by shaking with ether ;
removed ether ; saturated with ammonium sulphate ; filtered ; reduced filtrate by evapor-
ating to a small bulk, filtering from time to time from crops of crystals ; and tested in final
filtrate for albumoses by the biuret test with negative results. Control experiments showed
that even a trace of albumose added to the blood intentionally could be easily identified.

4 When large amounts are injected, the fall in arterial blood pressure is so great that
secretion of urine is arrested. Even in such a case the albumose does not remain in the
blood, but passes into the lymph (Shore, Journ. PhysioL, Cambridge and London, 1890,
vol. xi. p. 549).

5 Ploz and Gyergyai, Arch.f. d. ges. PhysioL, Bonn, 1875, Bd. x. S. 536 ; Hofmeister,
Ztschr. f. pliysiol. Chem., Strassburg, 1881, Bd. v. S. 131 ; Schmidt-Mitlheim, Arch. f.
Anat. u. PhysioL, Leipzig, 1880, S. 33 ; Fano, ibid., 1881, S. 281 ; Shore, Journ. PhysioL,
Cambridge and London, 1890, vol. xi. p. 528. A similar effect folloAVS subcutaneous
injection (Hofmeister, loc. cit.}.

6 Arch. f. Anat. u. PhysioL, Leipzig, 1880, S. 33.

7 SUzungsb. d. phys.-med. Gesellsch. zu IViirzburg, 1889, S. 65; Ztschr. f. BioL,
Miinchen, 1888, Bd. vi. S. 287.

440 CHEMISTR Y OF THE DIGESTIVE PROCESSES,

after its removal from the body, and proved that the peptone remained
unchanged. Also, when a small quantity of peptone or albumose was
slowly injected into a mesenteric vein, this was not assimilated, but
appeared afterwards in the urine, showing that it had not been altered
by the liver. Shore x circulated peptone not only through the liver, but
through the spleen also, by injecting into a splenic artery, and arrived at
similar results ; practically, all the peptone appeared again in the urine
unchanged.

These results show that the albumose and peptone do not even enter
the portal circulation as such ; the only remaining place where they can
undergo modification is in the wall of the intestine itself, and the
following experiments show that this is the seat of change.

Ludwig and Salvioli 2 separated a loop of intestine in the dog with
the attached portion of mesentery, and rfijected a gramme of albumose and
peptone in 10 per cent, solution, ligaturing the piece of intestine at both
ends. The piece of isolated intestine was maintained alive by circulating
through it warm defibrinated blood diluted with normal saline, by means
of a cannula inserted into that branch of the mesenteric artery which
had supplied the loop (anastomosing arterial branches being excluded by
ligatures), the blood, after circulating, flowing away by the corresponding
branch of the mesenteric vein. After four hours of perfusion in this manner,
the piece of intestine and the defibrinated blood having been all the time
maintained at the body temperature, the remaining contents of the intes-
tine and the circulating fluid were examined for albumose. The intestine
contained about half a gramme of coagulable proteid, and only traces of
albumose, while the defibrinated blood contained no albumose whatever.
Therefore the albumose must have disappeared in the intestinal wall.

Hofmeister3 investigated the organs of dogs killed during proteid
digestion as to their content of albumose, and found it present in the
mucosa (only) of the stomach and intestine, as well as in small quantities
in the blood, and in four out of ten cases in the spleen ; in the other
organs it was entirely absent. He also showed experimentally that this
albumose underwent a rapid change.

A fresh stomach was divided into two symmetrical halves, or a piece of
small intestine longitudinally into two similar pieces.

The surface of the mucous membrane was washed clean with saline, then
one of the two pieces in each case was thrown immediately into boiling water,
while the other was similarly treated after being first kept for some time in a
moist chamber at 40° C. More peptone was always found in the first piece
than in the second, and when the second piece had been kept for a sufficient
time (1 to 2 hours) at body temperature, previous to placing in boiling water, it
was found to contain no albumose whatever. In another experiment, while
one piece was thrown, as before, immediately into boiling water, the second was
thrown for some minutes into water at 60° C., and then kept as before at 40°
C. for two hours ; the result now obtained was that both pieces contained an
equal amount of albumose. Since most enzymes would not be affected by such
a preliminary treatment, while living cells would be destroyed, this indicates
that the cells of the mucosa do not owe their activity to contained enzymes.

1 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 559 ; Verhandl. d. X.
internal, med. Cong., Berlin, 1891, Bd. ii. Abth. 2, S. 31.

2 Arch.f. Anat. u. Physiol., Leipzig, 1880, Supp. Band, S. 112.

3 Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 51 ; Arch. f. exper. Path. u.
PharmakoL, Leipzig, 1885, Bd. xix. S. 8.

ABSORPTION OF PROTEID S. 44 1

Neumeister l states that albumoses and peptones dissolved in
whipped blood can be changed by • mere contact with pieces of living
intestine, the rapidity of change being increased when a slow stream of
air is driven through the mixture, so as to bring the pieces of intestine
into rapid contact with different portions of the blood and albumose.

Hof meister 2 observed a considerable increase in the number of
leucocytes in the intestinal wall during digestion of proteids, and argued
from this that these took a considerable share in proteid absorption and
in the conversion of albumoses and peptones in the adenoid tissue of
the intestinal wrall, and in the mesenteric lymphatics. There is little
experimental ground for belief in such a theory. In the first place,
proteid is not absorbed to any appreciable extent by the lymphatics ;
secondly, albumoses are not changed, as Hofmeister 3 himself has shown,
in the blood, which contains plenty of leucocytes ; thirdly, Heidenhain 4
has shown that the amount of leucocytes in the wall of the intestine
(and the amount of active mitosis in these) is too small to render them
adequate for such a purpose. Finally, Shore5 has shown that, after
slow injection of a small amount of peptone (*049 grms.) into a lym-
phatic of the hind-limb in a dog, this can be detected again in the course
of twenty minutes in the chyle flowing from a fistula of the thoracic
duct, showing that it has traversed the lymphatic system unchanged.

All these experiments go to prove that albumoses and peptones are
modified during their passage through the epithelial cells by the action
of living protoplasm. What substances are formed from them is not
known by direct experiment, but it is highly probable that the process
is one of conversion backwards into coagulable proteid. It is known
that coagulable proteid can be artificially obtained from peptone and
albumose,6 and that albumose and some forms of peptone used as foods
can replace coagulable proteid in maintaining nitrogenous equilibrium.
It is difficult to see how such a result can be attained otherwise than by
a formation of coagulable proteid from albumose and peptone.

The percentage of any proteid foodstuff, which is absorbed from the
alimentary canal, may be deduced fairly accurately from a comparison
of the amount of nitrogen in the food with that of the urine and fasces
when such a food is taken into the system.

Experiment shows that the various forms of proteid are utilised by
the organism in widely varying degrees. It does not necessarily follow
that a food of which the nitrogenous part is only partially absorbed is
on that account to be despised as an adjunct to other classes of
nitrogenous food ; vegetable proteid is absorbed much more imperfectly
than that from animal sources; but vegetable food, amongst other
things, is valuable for the consistency and bulk it gives to the food,

1<(Lehrbuch der physiol. Chem.," Jena, 1893, Th. 1, S. 251; Ztschr. f. £ioL,
Miinchen. 1890, Bel. xxvii. S. 324.

2 Arch. f. exper. Path. u. PharmakoL, 1885, Bd. xix. S. 32; 1886, Bd. xx. S. 291 ;
1887, Bd. xxii. S. 306. See also Pohl, ibid., 1888, Bd. xxv. S. 31 ; Heidenhain, Arch. f.
d. ges. Physiol., Bonn, 1888, Supp. Heft., Bd. xliii. S. 72.

3 Hofmeister (loc. cit., Bd. xix.) is of the opinion that the portion of "peptone" which
he believes enters the blood unchanged is converted in the tissue, "peptone" being found
during digestion in the arteries but not in the veins. The presence of any albumose or
peptone, even in the arteries, is, according to more recent observers, however, very doubt-

4 Loc. cit.

5 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 553.

6 See p. 400.

442 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

and for the mechanical stimulation its presence gives to the intestinal
movements.

The small amount of vegetable proteid absorbed, compared with that
of animal proteid, is in part clue to the envelope of indigestible cellulose
by which it is surrounded, in part to the shorter stay in the intestine
due to its action in causing increased peristalsis, and in part to its own
less digestible character.

The percentage of various kinds of plant proteid absorbed also varies
considerably ; thus the proteids of some leguminous plants and cereals are
absorbed nearly as perfectly as those of animal origin, while in most
others (potato, lentil) it is much less complete (22 to 48 per cent. less).
The percentage of the nitrogen of meat or egg appearing again in
the fseces in man, only amounts to 2'5 to 2'8 per cent., that of milk to
6 to 12 per cent.

Considerable tracts of the alimentary canal can be removed or
thrown out of action without causing the death of the animal or even
causing serious impairment in absorption.

The stomach was first removed by Czerny l in dogs ; one animal
was preserved alive after such an operation for five years ; in the course
of two months after the operation it recovered to quite a normal con-
dition, and ate, digested, and absorbed all kinds of food. It was finally
killed for examination by Ludwig and Ogata, and the dissection
showed that only a very small portion of the cardiac end of the stomach
remained.

Ludwig and Ogata 2 further investigated the course of digestion and
absorption when gastric digestion is excluded, by another method. They
made a fistula beyond the pylorus and inserted into the beginning of the
duodenum a small thin rubber ball, attached to a rubber tube, by means
of which it could be distended with water under pressure, so as to
occlude the intestine from the stomach. In this way gastric juice could
be prevented from entering the duodenum, and by feeding from the
fistula the effect of intestinal digestion alone be studied. The food was
usually completely digested and absorbed, and the faeces presented a
normal appearance. Eaw meat was digested much more efficiently than
boiled, connective tissue was not so completely digested as in normal
dogs, but nevertheless two injections of meat per diem sufficed to keep
the animal in equilibrium.

The stomach has also recently been removed in dogs by F. de Fillipi,3
who found no disturbance in metabolism and no increase in intestinal
putrefaction in spite of the absence of hydrochloric acid.

The same experimenter also removed in a bitch 1/9 metres of the
small intestine (almost the entire length), and found no metabolic
disturbance, except that the absorption of fat was diminished ; the animal
lived, and afterwards brought up a litter of pups in this condition.
The author suggests that the large intestine here vicariously took on the
absorptive functions of the small intestine.

Complete or partial extirpation of the pancreas, or ligature of its
duct, causes more or less disturbance of proteid digestion and absorption,
but not so much as might be expected, in view of the most important
proteolytic function of the secretion of this gland.

1 " Beitrage z. operativen Chirurgie," Stuttgart, 1878, S. 141.

2 Arch.f. Anat. u. PhysioL, Leipzig, 1883, S. 89.

3 Deutsche med. Wchnschr., Leipzig, 1894, No. 40, S. 780.

DIGESTION AND ABSORPTION OF FA TS. 443

Minkowski and Abelmann1 found, after complete removal of the
gland in dogs, that on an average 44 per cent, of proteid was absorbed ;
after partial removal, 54 per cent. The amount of absorption was much
increased on giving raw pancreas with the food. Sandineyer 2 obtained
similar results. On removal of all but one-fifth to one-fourth of the gland
(the portion remaining behind not being in communication with the
intestine), 60 to 70 per cent, of proteid was still absorbed, and, on adding
a supply of finely-minced pancreas to the food, the absorption of proteid
became almost normal.

DIGESTION AND ABSORPTION OF FATS.

The pancreatic juice is the only digestive secretion which contains an
enzyme possessing a chemical action on the neutral fats.3 This action
consists in splitting the fats into fatty acids and glycerin,4 and may
be demonstrated in one of the following ways : —

1. A neutral fat is first obtained, e.g., by thoroughly shaking olive
oil with sodium carbonate solution and ether, pipetting off the ethereal
layer, filtering if necessary, and finally allowing the ether to evaporate,
when a neutral fat is left behind. This is mixed either with fresh
pancreatic juice, or an extract of the fresh gland prepared as already
described, and the mixture, after being coloured blue by the addition
of litmus, is placed in a bath at 37° to 40° C. The alkaline reaction is
seen gradually to change into an acid one.

2. Instead of adding litmus, after the mixture of neutral oil and
pancreatic juice, or extract, has digested for some time (half to two hours),
sodium carbonate solution is added (which converts the free fatty acids
formed into soaps), and the unattacked fat is removed by repeated
extraction with ether. The residue is next treated with dilute
sulphuric acid, setting free again the fatty acids, which are extracted
with fresh ether, and recovered after its removal by evaporation.

3. The formation of free fatty acid may be also qualitatively shown,
by removing water from the fresh, finely-divided gland, with 90 per cent,
alcohol, drying it with filter paper, and then covering it with a neutral
ethereal solution of butter, obtained by shaking up milk or cream with
ether and a solution of caustic soda. When this material is kept for a
short time at 37° to 40° C., a distinct odour of butyric acid appears ; and if
the mixture has been previously rendered blue by litmus, this turns red.

Form in which fats are absorbed from the intestine. — There has
been much discussion as to the extent to which the decomposition
of the fats by the pancreatic enzyme, as above described, takes place
in the intestine ; and also as to the subsequent fate in the intestine
of the fatty acids formed therein. According to the views held on

1 " Ueber die Ausnutzung der Nahrungsstoffe nach Pancreasextirpation," Inaug. Diss.,
Dorpat, 1890 ; Jahresb. ii. d. Forlschr. d. Thier-Chem,, Wiesbaden, 1890, Bd. xx. S. 45.
-Ztschr.f. Biol, Miinchen, 1895, Bd. xxxi. S. 35.

3 Fats are said to undergo a certain amount of decomposition into fatty acids in the
stomach (Marcet, Proc. Roy. Soc. London, 1858, vol. ix. p. 306 ; Cash, Arch. f. Anat. u.
Physiol., Leipzig, 1880, S. 323) ; the cause of this decomposition is unknown, but it is
probably bacterial during the first stage of gastric digestion.

4 Bernard, Compt. rend. Acad. d. sc., Paris, tome xxviii. ; Arch. gen. de med., Paris,
1849; "Mcmoire sur le pancreas," Paris, 1856; "Lecons de physiologic expe'rimentale,"
tome ii. p. 256. For the chemical equations representing such a decomposition, see
Chemistry of the Fats, p. 1 9.

444 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

these subjects by different experimenters, various theories have been
propounded as to the form in which fats leave the intestine. These
theories may be divided into two classes — (a) Those in which it is held
that the fats are absorbed in participate form, as emulsified fats or
fatty acids ; (b) those in which it is held that the fats are absorbed in
solution as fatty acids or as soaps.

Emulsification. — All fat or oil which has not been specially
neutralised contains a slight amount of free fatty acid. On long
standing in contact with air, the amount of this fatty acid is increased,
probably by bacterial action; when this proceeds beyond a certain
limit, the fat is said to become rancid.

If such a rancid oil, or fat melted by gently warming, be briskly
shaken up with a solution of an alkaline carbonate (e.g. a 0'25 per cent,
solution of sodium carbonate), it becomes suspended permanently in the
alkaline solution in the form of very minute particles or globules,
and so forms what is known as a permanent emulsion. But if the
rancid oil be previously carefully neutralised (e.g. by mechanically
shaking for some hours with a saturated solution of barium hydrate
at 95° C., and then pipetting off),1 no amount of shaking with a solution
of an alkaline carbonate afterwards will cause it to yield a permanent
emulsion; the fluid on standing will quickly settle into two distinct
layers. Neither can a lasting emulsion be obtained by shaking up a
rancid oil or fat with distilled or acid water ; some free fatty acid and
some alkali must be simultaneously present. In other words, the
necessary conditions for the formation of a soap must be satisfied.2

Emulsifying action of alkaline salts and bile. — Attention was first
drawn to the action of alkaline salts in promoting emulsion by Marcet 3
in 1857 ; this author investigated the effect of both disodic phosphate
and of bile on fatty acids and on neutral fats ; his results have not
obtained, even in English text-books, the attention they deserve, and
seem in part to have become forgotten. The results with bile and
fatty acids have an important bearing on more recent researches, to be
subsequently described, and for this reason are here quoted at length.

Disodic phosphate, " when mixed with pure stearic and margaric acids
prepared from sheep's fat, and heated, produced a perfect emulsion, resembling
milk ; on cooling, a substance solidified, consisting of fatty acids with more or
less soda, soap, and a small quantity of phosphate of soda; therefore the
formation of the emulsion had been attended with that of a small proportion
of soap. When neutral fats were heated, suspended in a solution of phosphate
of soda, no emulsion occurred ; the fats fused, and, on cooling, solidified under
the form of a hard cake ; the warm mixture, although strongly shaken, was
not converted into an emulsion, but the minutely divided globules of fat rose
to the surface, uniting with each other, and solidified on cooling; the fluid
remained perfectly clear.

"The next subject for inquiry was to determine whether bile exerts
a similar action on fatty acids and neutral fats. On heating and agitating
gently a mixture of fresh sheep's bile and fatty acid (margaric, stearic, and

1 Rachford, Journ. PhysioL, Cambridge and London, 1891, vol. xii. p. 73.

2 Only formation of "artificial emulsions," if the expression may be used, from rancid
oils is referred to here ; it will be seen later that a pancreatic emulsion can be formed and
persist in presence of an acid reaction due to fatty acids.

3 Compt. rend. Soc. de liol., Paris, 1857, p. 191 : Proc. Roy. Soc. London, 1858, vol. ix.
p. 306 ; Med. Times and Gaz., London, 1858, N. S., vol. xvii. p. 209. The extracts are
taken from the last quoted Journal.

DIGESTION AND ABSORPTION OF FA TS. 445

oleic acids), prepared from sheep's fat, as soon as the latter had begun fusing it
disappeared, and. finally the whole of the fatty acid 'was dissolved \ on standing,
however, it was observed that a very few extremely minute globules of fat rose to
the surface. As soon as the mixture had been allowed to become colder than the
temperature of fusion of the fatty acids, it assumed a turbid appearance
throughout, which gradually increased, the fluid becoming white and milky,
slightly coloured by the bile ; finally, if the fat present was in sufficient
proportion, the whole mass was converted into a semifluid paste, possessed of
a light green colour, and adhering so strongly to the sides of the vessel that it
could be turned upside down without letting out its contents.

" On diluting this remarkable emulsion with water, its consistency only
was altered, becoming thinner, but no decomposition occurred ; on heating
the diluted mass, the emulsion was dissolved ; it disappeared, but no globules
of fat could be seen floating on the surface beyond the few minute specks
previously mentioned. Besides this physical action of bile on fatty acids, the
phenomenon was accompanied by a chemical decomposition; for the bile,
which was neutral or slightly alkaline before the experiment, had become
strongly acid after being treated with the fatty acid.

"An experiment was now instituted to determine whether a similar
phenomenon takes place when bile and neutral fats are mixed together.
Indeed, it was hitherto generally admitted that bile had no action on neutral
fats. The results of my observations confirm this view, for in no case could I
succeed in obtaining an emulsion and chemical decomposition, by heating bile
with pure sheep's fat or with oil, having a neutral reaction ; on agitating the
hot mixture the globules of fat were broken up, but on standing they rose to
the surface, the bile being unaltered in its appearance and reaction. Conse-
quently, bile exerts no action on neutral fats."

Since these experiments of Marcet, many observers have busied
themselves with the nature and mode of formation of emulsions.1

Briicke found that the presence of a certain amount of free fatty acid
was sufficient to emulsify the remaining neutral fat, and stated that the
provision of a sufficient amount of free fatty acid to emulsify the rest
was probably the chief function of the fat-splitting property of the pan-
creatic juice. He obtained emulsion of fats containing fatty acids with
diluted egg albumin, with bile, and especially with solutions of sodium
carbonate and of borax. Gad discovered spontaneous emulsion, and
carried out exact experiments 011 the most favourable conditions for the
formation of emulsions. A spontaneous emulsion means the formation
of a permanent emulsion without any mechanical assistance by shaking ;
such as occurs when a drop of oil containing a sufficient percentage of
free fatty acid (5-7 per cent.) is placed on an alkaline solution of suit-
able strength (J per cent, sodium carbonate).

The following are the main conditions which influence the formation
of spontaneous emulsions, according to Gad : —

1. The power of different fats to form emulsions by contact with the
same fluid depends (a) on the amount of free fatty acid in the fat, (b) on
the solubility of the soaps formed from these fatty acids, (c) on the
viscosity of the fat.

2. The power of the same fat to form emulsions in contact with

1 Kiihne, " Physiol. Chem.," 1866, S. 129 ; Briicke, Sitzungsb. d. k. Akad. d. Wisscnseh,.,
Wien, 1870, Bd. Ixi. Abth. 2, S. 362 ; J. Steiner, Arch.f. Anat. u. Physiol., Leipzig, 1874,
S. 286 ; J. Gad, ibid., 1878, S. 181 ; G. Quincke, Arch.f. d. ges. Physiol., Bonn, 1879, Bd.
xix. S. 129 ; v. Frey, Arch.f. Anat. u. Physiol., Leipzig, 1881, S. 382 ; Rachford, Journ.
Physiol., Cambridge and London, 1891, vol. xii. p. 72.

446 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

different fluids depends (a) on the degree of alkalinity of the fluid, (b) on
their chemical composition, in so far as this influences the solubility of
the soaps formed.

3. The maximum of quantity and quality of emulsion formed coin-
cides with those conditions under which no formation of a membrane
can be demonstrated.1

There has been much discussion as to the factors at work in the formation
and conservation of emulsions. Briicke was of the opinion that it was the
dissolved soap which conferred on the solution the power of holding the
globules apart, after they had been mechanically formed in it. Gad supposed
that the breaking up of the globules into smaller ones was due to a want of
correspondence of the rate of solution and diffusion of the soap formed into
the outer solution with the rate of diffusion of fatty acids towards the sur-
face of the globule. In case fatty acid diffuses from the inner part of the fat
globule towards the common surface of oil globule and solution more quickly
than it can be dissolved by the solution, a film or membrane of soap will form
around the globule. This film will not form at all parts of the globule equally,
and this will give rise to amoeba-like movements (due to differences in surface
tension).2 Gad also supposes that the ultimate microscopic globules are sur-
rounded by soap films which keep them from coalescing.

Quincke attributes the formation of the emulsion to the differences in sur-
face tension produced by the formation of a soap solution round the globule ;
and he also assumes the existence of films of soap (solid or in solution) around
the ultimate oil globules in the emulsion, which have the property of keeping
the globules from coalescing.

There is no doubt that soap formation is an accompaniment to the forma-
tion of an emulsion of rancid oil in an alkaline solution, and it is easy to see
how the formation of such a soap film, at accidentally varying rapidity, at
different points on the surface of a globule of oil, will cause variations in
surface tension at these points, and so cause the oil globule following the soap
film which covers it, to be drawn out into various shapes and split up. Such
surface tension phenomena may be observed when two liquids which mix,
such as alcohol and water, are brought together. More mixing takes place at
one point than another ; as a consequence, the mutual surface tension is less at
one point than another, and those rapid, streaming movements are produced
which may always be observed when alcohol and water are mixed. Similarly,
when a small piece of a substance like camphor is placed on water, rapid
shooting movements take place, due to an accidentally unequal solution of the
substance at different points in the circumference, and consequently varying
surface tension, as a result of which the piece of camphor is rapidly moved
about from place to place. In an exactly similar manner a globule of rancid
oil will be pulled about, altered in shape, and broken up in an alkaline solu-
tion, from accidental variations in the strength of soap solution at different
points on its surface, causing variations in surface tension and corresponding
movements.

It is much more difficult to see how any permanent film of insoluble soap
can be formed round the ultimate globules, or even a film of soap solution of
different concentration from the rest of the menstruum in which the globules
float. From Gad's conclusions, it should be observed that in the cases where
emulsion takes place best and most quickly, no such soap film can be observed,
so that this soap film cannot be experimentally demonstrated ; it is merely a
theoretical thing, devised from the supposed necessity of having something to
keep the globules from coalescing. A proteid membrane surrounding the fat
globules in milk was supposed to have a similar office, but microscopically or
1 Vide infra. 2 The words in parenthesis are added.

DIGESTION AND ABSORPTION OF FA TS. 447

otherwise no such membrane can be demonstrated, and its existence is very
doubtful.1

A cloud is an emulsion, an emulsion of water particles in air, and no one
has ever supposed that the water particles are surrounded by membranes which
keep them apart. The prevention of coalescence is the result of the action of
several factors, of which our knowledge is not yet perfect. 1. One such
factor is the magnitude of the suspended drops ; the bigger the drops the more
rapidly they will come together, and fall (or rise) out of solution.2 The more
mechanical agitation an emulsion is given, the longer it will persist under
otherwise unfavourable circumstances. 2. Another factor is the viscosity of
the menstruum ; the greater this is the more slowly will the finely-divided
globules be able to move through the fluid, under the influence of differences
in specific gravity or mutual attraction, so as to pass out of solution or
coalesce. 3. Another factor is the comparative specific gravities of the fat
and menstruum. 4. Still another is the mutual surface tension between
globule and menstruum ; the greater this is, the greater will be the tend-
ency to diminution of surface, and hence to coalescence. On the other
hand, if the mutual surface tension were zero, the two fluids would mix in all
proportions.

It has been objected, by those who believe in the existence of a film around
the fat globules, to the contention that the altered nature of the menstruum is
sufficient to account for the permanency of the emulsions obtained with fats
and alkaline solutions, that a permanent emulsion cannot be obtained by
shaking up neutral fat with a soap solution. But the conditions in the two
cases are essentially different. Neutral fats and fatty acids mix together in a
rancid fat or oil in all proportions. When such a mixture is submitted to the
action of alkali, the soap formation takes place where the fatty acids are, that
is, intimately mixed with the neutral fat. So that soap is formed everywhere
at the surface of the mass, and, dissolving, carries away (in the surface tension
diffusion streams above described) the intimately admixed fat from the main
mass in a very finely subdivided condition. If the proper conditions exist in
the solution, these minute fat particles will not coalesce again. Such a result
is brought about by the viscosity and reduction in surface tension which the
solution acquires by means of the dissolved soap. On the other hand, when
neutral fat is shaken up with soap solution, no such disintegrating agency
comes into action, and the only thing to replace it is the mechanical subdivision
due to shaking. As v. Frey points out, the smaller the diameter of the fat
globules, the greater is the mechanical force necessary to subdivide them ; and
it is probable that by no amount of agitation can so fine a subdivision be
reached as is naturally attained by the formation of the soap amongst the fat.
By very prolonged and vigorous agitation, v. Frey has obtained "mechanical
emulsions " of very considerable stability, even with neutral fats and water.
The very fine subdivision of the fat, and the increased viscosity of the men-
struum occasioned by the dissolved soap, are hence quite sufficient to explain
the permanency of emulsions of rancid oils and fats in alkaline solution.

Formation of emulsions in the intestine. — The formation of an
emulsion of fats in the intestine was already known to Eberle3 in 1834,
but was first brought into prominence by the classic researches of
Claude Bernard.4 Bernard was unacquainted with our modern theories
of the formation of emulsion, and did not associate this process with

1 See v. Frey, Arch. f. Anat. u. Physiol., Leipzig, 1881, S. 382 ; Soxhlet, Landwirthsch.
Versnchsslat., 1876, Bd. xix.

2 See v. Frey, loc. cit. 3 "Physiologic d. Verdauung," Wiirzburg, 1834.

4 Compt. rend. Acad. d. sc., Paris, 1849, tome xxviii. p. 249 ; Arch. gtn. de med., Paris,
1849, Se"r. 4, tome xix. p. 60 ; "Me"moire sur le pancreas," Paris, 1856.

448 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

the production of fatty acid by pancreatic juice, although he was the
discoverer of this saponifying action. He states that, when neutral oil
is shaken up with pancreatic juice, an instantaneous emulsion takes
place; and, secondly, when neutral oil is submitted to the prolonged
action of pancreatic juice, fatty acids are developed. Bernard con-
sidered the formation of emulsion in the intestine as a more important
process than saponification, due to a ferment action, and speaks of a
"ferment emulsif" It is now certainly known that fatty acids are
always formed in the intestine after the ingestion of fat, but an emulsive
ferment is no longer believed in. The rapidity of fresh pancreatic juice
in forming fatty acid is remarkable; thus Eachford,1 in very favour-
able cases, found that a sufficient amount of fatty acid to form a spon-
taneous emulsion (5 '5 per cent.) is formed in presence of bile and'
hydrochloric acid at room temperature in two minutes. This very
rapid action explains the error into which Bernard fell.2

Pancreatic juice obtained from a permanent fistula has less emulsive
power than that from a temporary fistula ; it is also poorer in proteid, and,
according to Kiihne,3 the emulsive power does not depend upon the alkali,
for faintly acid juice is capable of producing emulsion. Minkowski is of the
opinion that it is chiefly to the proteid that emulsion is due, basing his
opinion on the observation, made by Abelmann 4 in his laboratory, that after
excision of the pancreas no fat except that of milk is absorbed ; unless minced
pancreatic tissue be taken with the food, when other fats are also absorbed.
These observations have been confirmed by Sandmeyer.5

Some observers 6 hold that emulsification does not occur at all inside the
intestine, and others 7 state that a considerable amount of emulsification takes
place, but that the granules of fat in the emulsion are not nearly so small as
those found in the chyle.

Cash8 found, in four experiments on dogs, that there was no emulsion
in the intestine during active fat absorption. Moore and Kockwood,9 in six
out of sixteen experiments, obtained a similar result, but in the other ten
experiments found emulsions in the intestine, containing fat globules of
various dimensions, some of considerable size, but many exceedingly minute.
These results indicate that in the dog at least, fats can be broken up and
absorbed without undergoing previous emulsification. Still it should be
borne in mind that these two different conditions of the intestine in the
dog during fat absorption may be phases of the same process. The contents
of the stomach are not discharged continuously into the duodenum, but from
time to time the pyloric sphincter is relaxed, and a portion of the contents
of the stomach ejected. It may well be that the condition of no emulsion is

1 Journ. PhysioL, Cambridge and Loiidon, 1891, vol. xii. p. 92.

2 The statement that the fat-splitting action of the pancreatic enzyme is very slow, and
hence that probably only a small percentage of fat is so decomposed in the intestine
(see Bunge, "Lehrbuch," Atifl. 3, S. 175), undoubtedly arises from most observers using
not pancreatic juice but pancreatic extracts, in which the easily decomposable fat-splitting
enzyme was only present in traces. Rachford's results with pancreatic juice clearly indicate
that the pancreatic secretion is capable within the time of digestion of a fatty meal of
decomposing all the fat into fatty acids and glycerin.

3 "Lehrbuch d. physiol. Chem.," 1868, S. 122.

4 Inaug. Diss., Dorpat, 1890.

5 Ztschr.f. BioL, Miinclien, 1895, Bd. xxxi. S. 40.

6 Cash, Arch.f. Anat. u. Physiol, Leipzig, 1880, S. 323; Altmann and Krehl, ibid.,
1889, Anat, Abth., Stipp. Bd. S. 86 ; 1890, Anat. Abth., S. 97.

7 Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1888, Supp. Heft, Bd. xliii. S. 88,
Other recent observers who describe an emulsion in the intestine are, Lebedeff, Arch. f.
Anat. u. PhysioL, Leipzig, 1883, S. 504 ; Lewin, Arch. f. d. ges. PhysioL, Bonn, 1896, Bd.
Ixiii. S. ISO.

8 Loc. cit. 9 Journ. PhysioL, Cambridge and London, 1897, vol. xxi. p. 74.

EMULSION THEORIES OF FA T ABSORPTION. 449

that existing immediately after such a discharge from the stomach, while the
emulsion condition is a later stage.

In whatever form fats may be absorbed from the intestine, it is certain
that previous emulsincation must greatly assist the digestive fluids, by
exposing an infinitely greater surface to their action. It is also certain that
in a great many cases, if not in all, previous emulsincation does take
place.

Emulsion theories of fat absorption. — It was for a long time a
popular theory that only a small fraction of fat is split up in the intes-
tine into fatty acid and glycerin; and that by means of the small
amount of acid so formed, aided by that present in the fat as it leaves
the stomach, the remainder of the fat is converted into a fine emul-
sion which passes as such into the villi, and reaches the central lacteal.1
Such a statement may be found in most text-books, but the progress of
recent work has had a tendency to cast grave doubts on its truth, and
to show that, at least as a general statement, it is erroneous. The theory
does not rest on any direct observation of the amount of fat which
leaves the intestine as emulsified fat, compared with that which leaves
it in other forms, such as soap, glycerin, and emulsified fatty acids,
— such a direct observation, in the present state of our knowledge, is
impossible, — but on indirect evidence, which is briefly as follows : —

1. The presence of a very small percentage of fatty acid is all that
is necessary in presence of an alkaline solution to perfectly emulsify
neutral fat.

2. This small amount of free fatty acid can readily be furnished by
the action of the pancreatic enzyme even on neutral fats, and to aid this
action all fats contain already some fatty acid mixed with them. The
alkaline juices poured into the intestine are capable of supplying the
alkali necessary for emulsification.

3. When an animal is killed during active fat digestion, the lacteals
invariably contain a white milky emulsion, consisting mainly of neutral
fats with a small percentage of alkaline soaps.

Therefore the most natural conclusion is that a fine emulsion is
formed in the intestine which passes in some manner into the lacteal.
The greater part of the fat is only physically, not chemically,
altered in digestion, and passes through the whole process as a neutral
fat.

The weak point in the emulsion theory of absorption always was,
how the fat globules got into the interior of the villus and made their
way to the lacteal. Although the fat granules in an emulsion are of
microscopic dimensions, they are still large compared to the dissolved
molecules of serum or egg albumin which are unable to pass into or out
of the intestine through the epithelial cells. If fat granules pass into
the epithelial cells at all, it must therefore be by means of a
special kind of absorption in bulk by these cells, and not by a process
even of selective diffusion from solution. Such an absorption by bulk is
easily carried out by a cell of which the protoplasm is capable of free
contraction, such as the amoeba, or leucocyte, but it is difficult to conceive
how it can take place with a fixed cell, such as those which line the
intestine. Impressed, perhaps, with the necessity of some such proto-
plasmic movement, some observers have looked earnestly for proto-

1 This theory was first stated by Briioke, Sitznngsb. d. k. Akad. d. JFissensch., Wien,
1870, Bd. Ixi. Abth. 2, S. 362.
VOL. I. — 29

450 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

plasmic processes from the epithelial cells, and one or two l fancied they
had discovered such appearances, but their observations have not been
confirmed, and are undoubtedly erroneous. If the epithelial cells of the
intestine possessed the power of absorbing in bulk fat granules, there
is no obvious reason why other food particles, such as granules of
starch or proteid, should not be similarly absorbed, but no such
absorption has ever been observed, nor are they capable of absorbing
finely subdivided granules of coloured matter, such as carmine.

The mucous membrane of the intestine contains an immense
number of lymph corpuscles.2 These are found not only in the lymph-
oid nodules, which occur so abundantly as solitary glands and Peyer's
patches, but in the intestinal villi, even between the epithelial cells, where
they may approach quite close to the fr^e surface, and abundantly in the
adenoid tissue underlying them. Now, such lymph corpuscles are capable
of enveloping and so absorbing fat granules, and have been credited with
an important function in the removal of fat from the intestine by so
doing. It was stated by Zawarykin 3 that when fat absorption is going
on, fat granules are to be found only in these lymphoid cells and not in
the cells of the columnar epithelium. This statement is undoubtedly
erroneous, for it is easy, from an animal killed after a meal rich in fats,
to obtain sections showing the columnar cells filled with fat globules.

" During active fat absorption, especially if the amount of fat in the
chyme is relatively large, the columnar epithelial cells become filled
with globules of fatty matter. These globules are of variable size, and
may occur in all parts of the cell, but they are generally largest in the
part between the nucleus and the thickened border, and are often quite
small near the attached end of the cell." 4

It is evident, then, that the greater part of the fat, if not the whole
of it, must be absorbed by the epithelial cells from the intestine. It
is also very improbable that these cells take up the fat in the form of
an emulsion. As has already been stated, the structure of the cell is
unsuitable for such a function, and, in addition, fat granules have never
been observed in the broad striated border. This almost amounts to a
demonstration that the fat passes through the border of the cell in some
soluble form, and is afterwards thrown down in a particulate form, as the
result of a process of cell metabolism.

Emulsion theories of fat absorption are therefore being gradually
replaced by theories of absorption in solution. These theories must
next be discussed, but before doing so reference may be made to another
emulsion theory of fat absorption introduced by Munk.

Theory of I. Munk. — Munk5 showed that fatty acids can be
emulsified under exactly the same conditions as rancid fats, and further
that these fatty acids are capable of absorption, and can completely take
the place in the animal economy of neutral fats, being in great measure

1 v. Thanhoffer, Arch. f. d. ges. PhysioL, Bonn, 1874, Bd. viii. S. 391 ; Fortuuatow,
ibid., 1877, Bd. xiv. S. 285.

2 These wandering cells ( Wanderzelleri) were first described as occurring in the epithelium
by Eberth (Wurzb. med. Ztschr., 1864, S. 23); Arnstein (Virchwfs Archiv, 1867, Bd.
xxxix. S. 537) first mentioned the presence of fat granules in them.

sArch.f. d. ges. PhysioL, Bonn. 1883, Bd. xxxi. S. 231.

4 Schafer, Internal. Monatschr. f. Anat. u. HistoL, Leipzig, 1885, Bd. ii. S. 6.

5 VerJiandl. d. BerL med. Gesellsch., March 1879 ; Arch. f. Anat. u. PhysioL, Leipzig,
1879, S. 371 ; Virchows Archiv, 1880, Bd. Ixxx. S. 10; ibid., 1884, Bd. xcv. S. 409; Ztschr.
f.physiol. Chem., Strassburg, 1885, Bd. ix. S. 568; Arch. /. Anat. u. PhysioL, Leipzig,
1890, Supp. Bd., S. 138. See also v. Walther, ibid., 1890, S. 329.

SOL UTION THEORIES OF FA T ABSORPTION. 45 1

converted into fats somewhere on their way from the intestine to the
thoracic duct. He is hence of the opinion that in the normal course of
digestion a considerable but indeterminate amount of fat may be
absorbed in the form of emulsified fatty acids.

Munk's experimental results as to the absorption and synthesis
during the process of absorption of the fatty acids, are of the highest
importance ; but it in no wise follows from them that the fatty acids
are absorbed in the form of an emulsion. Such a theory is subject to
the same objections as have above been urged against the older theory
of absorption as emulsified fats. The fatty acids are probably taken
up from the intestine by the epithelial cells in some soluble form, and
synthesised to neutral fats in these cells.

Solution theories of fat absorption. — Theory of absorption as
soaps. — One of the most important theories of fat absorption in soluble
form is, that the neutral fats are split up by the action of the pancreatic
enzyme into fatty acids and glycerin, that the fatty acids unite with a
part of the alkali of the intestinal secretions to form alkaline soaps
which are soluble in water, and that the alkaline soaps and glycerin
are absorbed in solution by the epithelial cells, and there synthesised
back to neutral fats. This theory is supported by a good deal of
experimental evidence. Eadziejewski1 showed that alkaline soaps were
absorbed ; Perewoznikoff,2 that a mixture of alkaline soap and glycerin
was absorbed and synthesised to neutral fat. The lacteals had the usual
milky appearance seen after a fatty meal; microscopic preparations,
stained with osmic acid and with alkanna, showed in the tissue of the
villi, and in the epithelial cells, fat globules of varying size. Will,3 work-
ing under Griinhagen's direction, confirmed these results by histological
observations on the frog; further, he showed that the presence of
glycerin was unnecessary. Will made two kinds of experiments. In
one he fed the frogs, which had previously been deprived of food,
with the materials to be tested ; in the other, he injected the materials
into the living but cut out intestine, and then examined teased speci-
mens stained with osmic acid. In both series the same results were
obtained, on feeding with a mixture of pure palmitic acid and glycerin,
or of potassium palmitate and glycerin; at the end of twenty-four
hours an examination of the villi showed a formation of fat, by the
presence everywhere of large distinct fat globules. Injection of palmitic
acid alone into the intestine also led to the appearance of fat globules
in the epithelium,4 but these were not nearly so numerous as in the
cases in which the palmitic acid was mixed with glycerin. As
Salkowski and Munk had shown that fatty acids can be emulsified
under certain conditions,5 Will proceeds to show that this could not be
the case in his experiments, and that the fat globules blackening with
osmic acid in the epithelial cells are not free fatty acid. The free fatty
acids only become emulsified when melted, and as pure palmitic acid

1 Virchow's Archiv, 1868, Bd. xliii. S. 271 ; 1872, Bd. Ivi. S. 211.

2 Centralbl.f. d. med. Wissensch., Berlin, 1876, S. 851.

3 Arch. f. d. ges. PhysioL, Bonn, 1879, Bd. xx. S. 255. See also v. Krehl, Arch. f.
Anat. u. PhysioL, Leipzig, 1890, Anat. Abth., S. 97.

4 In thus showing the formation of fat from fatty acid alone, Will anticipated I. Munk,
but to Munk belongs the merit of clearly showing from the chemical standpoint that the
organism, probably the epithelial cells, can furnish the glycerin radicle for the synthesis
of neutral fats from the fatty acids.

5 Sitzungsb. d. Berl. physiol. Gesellsch., March 1879 ; Virchow's Archiv, 1880, Bd. Ixxx.
This was a re-discovery of a fact known to Marcet many years previously, see p. 444.

452 CHEMISTRY OF THE DIGESTIVE PROCESSES.

only melts at 62° C., such a thing could not occur in the frog's intestine.
Moreover, a microscopic examination of the intestinal contents at the
end of an experiment showed only amorphous masses of fatty acid and no
emulsified globules. Will concludes that the fatty acid must be absorbed
as a soap and not as an emulsion.

That the mucous membrane of the small intestine is capable of
taking part in such a synthetical process, is shown by experiments of
Ewald,1 who dried the mucous membrane of a dog's intestine, which had
been killed in a condition of hunger, at a low temperature after the
method introduced by Brown and Heron,2 and showed that this was
capable of inducing the formation of neutral fat, from a mixture in
proper proportions of soap and glycerin.

This experiment shows that, provided glycerin and soap are formed
in the intestine, there is an agency provided for synthesising them
back into neutral fats. Let us next consider what the probabilities are
that such a complete decomposition, into fatty acids and glycerin
followed by solution of the fatty acids as alkaline soaps, takes place in
the intestine.

The idea that only a small fraction of the fats is decomposed in
the alimentary canal into fatty acids and glycerin, has arisen from
repetition of the emulsion theory only, and not from any experimental
observation of lack of intensity of action of the fat-splitting ferment.
Hoppe-Seyler3 found that most of the fatty matter in both small and
large intestine was composed of stearic and palmitic acids accompanied
by very little neutral fat, and concludes that the decomposition into the
fatty acids and glycerin is much greater than is usually supposed.
Eachford4 states that pancreatic juice must act very rapidly on fats,
under the favourable conditions found in the duodenum, and is capable,
unless checked or retarded in some manner, of splitting all the fats of
the food into fatty acids and glycerin in the time required for intestinal
digestion.

It may be concluded, then, that there is sufficient fat-splitting power
provided in the intestine for the complete conversion of the fats into
fatty acids ; and it has been already pointed out that, on feeding with
fatty acids or with soaps, these are absorbed, and converted into fats in
the process. It only remains to consider, in connection with the soap
theory, whether, in the natural process of fat digestion and absorption,
it is probable that the fatty acids so set free combine with alkalies to
form soaps, or whether they are absorbed in some other soluble form.

It has been objected to the theory of absorption in the form of
soaps, that the reaction of the small intestine in the dog during fat
absorption is not alkaline, but acid ; that soaps cannot persist in
presence of an acid reaction, and hence that fats cannot be absorbed
as soaps.

Cash5 investigated the reaction of the intestine in three experiments on
dogs, in which the animals were fed on a mixture of starch and fat, and in
three similar experiments in which the animals were fed on fat alone. He

1 Arch. f. Anat. u. PhysioL, Leipzig, 1883, Supp. Bd., "Festschrift f. du Bois-Rey-
mond," S. 302, Vorlaufige Mittheilnng.

2 Proc. Roy. Soc. London, 1880, p. 393.

3 Virchwfs Archiv, 1863, Bd. xxvi. S. 534, Anmerkung.

4 Journ. PhysioL, Cambridge and London, 1891, vol. xii. p. 92.

5 Arch. f. Anat. u. PhysioL, Leipzig, 1880, S. 323.

SOL UTION THEORIES OF FA T ABSORPTION. 45 3

found the reaction of the intestinal contents to be acid all the way from pylorus
to caecum.

Vaughan Harley1 tested the reaction of the upper and lower halves of
the small intestine, and of the large intestine, in three dogs which had been
fed on milk, and found that the reaction was acid in all three portions.

Moore and Kockwood2 have recently studied the reaction of the intestine
in the dog during fat absorption to different indicators, chosen with a view
to determining, not only the reaction, but also the character of the acids or
bases causing that reaction. The indicators used were litmus solution, methyl-
orange, and phenolphthalein. The reaction to litmus of the upper part of the
small intestine was found to be acid, changing to alkaline at a somewhat
variable point, situate two-thirds to three-fourths of the way from pylorus to
caecum. The contents of the large intestine are commonly acid to litmus,
while the reaction of the contents of the caecum lies intermediate between
that of the contents of the ileum and that of the contents of the large in-
testine, and may be either faintly alkaline or faintly acid.

The reaction at the pylorus, and for some distance below, may be nearly
neutral or even faintly akaline to litmus ; as the distance below the pylorus is
increased, the reaction always becomes more strongly acid at first, then less
acid again, and finally faintly alkaline at the limit described above. On
testing with the other two indicators, it was found that the reaction was
invariably alkaline all the way to methyl-orange, and acid all the way to
phenolphthalcin.

These results seem at first sight confusing and contradictor}', yet a
consideration of the properties of the indicators used, not only renders them
intelligible, but gives an indication as to the nature of the substances to
which the contents of the intestine during fat absorption owe their reactions.
An organic indicator only reacts to an acid which is stronger than the acid
which it itself contains in its molecule ; to a weaker acid it is stable, and
hence shows no acid reaction; and in case the weaker acid is present as a
salt, it decomposes that salt and reacts to the base with which it was com-
bined, giving an alkaline reaction. Now, methyl-orange is a very stable,
phenolphthalein a very unstable, indicator, while litmus lies intermediate be-
tween these two. Methyl-orange reacts sharply to the inorganic acids, less so
to the stronger organic acids such as acetic acid, and not at all to carbonic acid
and the weaker organic acids, including stearic, palmitic, and oleic acids. With
alkaline salts of these weaker acids (carbonates, bicarbonates, and the soaps)
it gives an alkaline reaction. Phenolphthalein reacts to traces of the weakest
organic acids, and to carbonic acid ; to normal sodium carbonate it is alkaline ;
to sodium bicarbonate, neutral ; with excess of carbonic acid, acid. Litmus
reacts to even weak organic acids, but the reaction is feeble, and a considerable
excess is necessary to give a clear reaction ; to carbonates and bicarbonates of
the alkalies, it is alkaline.

These considerations make it evident that the acid reaction of the
upper part of the small intestine to litmus during fat absorption is due
to weak organic acids, probably to dissolved acids set free from fats ; 3
while the alkaline reaction to methyl-orange can only be due to weak
organic acids combined with alkalies, i.e. in all probability to dissolved
soaps.

Since the acid reaction of the intestine during fat absorption is due
to weak organic acids, the contention that soaps cannot be present falls
to the ground. For the soaps would not be decomposed by these acids.

An objection, and apparently at first sight a very serious one, to

1 Journ. Physiol.y Cambridge and London, 1895, vol. xviii. p. 2.

2 Ibid., 1897, vol. xxi. p. 58. 3 Vide infra.

454 OHEMISTR Y OF THE DIGESTIVE PROCESSES.

absorption in the form of soaps, is that urged by I. Munk, namely, the
enormous quantity of alkali which would be required for such a purpose.
Munk 1 reckons that to so combine with the fatty acids of 200 grms. of
fat, about 40 grms. of sodium carbonate (Na2C03) would be required.
Now a dog of 25 kilos, can easily digest from 200 to 350 grms. of fat
in twenty-four hours.2 Supposing only 200 grins, are digested, and that
all this is absorbed as soaps and glycerin, about 40 grms. of sodium
carbonate will be required for the purpose ; now the total blood only
contains, in such an animal, alkali equivalent to 6 grms. of Na2C03 ; if
the other fluids of the body be supposed to contain an amount of alkali
equivalent to another 6 grms. of sodium carbonate, the total alkalinity is
equivalent to that of 12 grms. of sodium carbonate.3 Therefore, to
suffice for the absorption of the fatty acids as soaps, from three to four
times the total alkali of the body must pass out in the intestinal
secretions, and be reabsorbed with the fatty acids, during twenty -four
hours. This is obviously impossible ; therefore the fats are not absorbed
as soaps and glycerin.

This objection of Munk loses, however, most of its weight, when
the probable processes taking place, in case fats are absorbed as soaps
and glycerin, and synthesised again to neutral fats in the epithelial
cells, are carefully considered. In the synthesis of fat from soap and
glycerin within the cell, alkali is again set free in exactly equal amount
to that in which it was used up in the intestine, and this alkali must be
got rid of by the cell in some manner. Why should it not be sent back
again into the intestine, and act as a carrier to a fresh quantity of fatty
acid as soap into the cell ? In such a fashion a very small amount of
alkali would suffice to explain the carriage of all the 200 grms. of fat as
dissolved soap and dissolved glycerin into the epithelial cells.

It might possibly be further objected that soaps are only present in
small quantity in the intestinal contents. But this applies also to
alkali albumin, propeptones, peptones, and sugars ; in fact, to all the
products of the digestion of both proteids and carbohydrates. If soaps
are normally absorbed by the epithelial cells, it is probable that these
cells possess a selective capacity for soap absorption, as they do for many
other products of digestion, and hence that the soaps are absorbed as
they are formed, and never allowed to accumulate in appreciable
quantity in the intestine.

There is, then, no proof that soaps cannot be formed in the intestine,
nor is there any impossibility or improbability in the way of all the fats
being first decomposed into fatty acids, then converted into soluble
soaps and absorbed as such.

Theory of absorption as dissolved fatty acids. — Another theory is, that
the fats are absorbed in the form of dissolved fatty acids.

The fatty acids of the fats are practically insoluble in water, but are
soluble to a certain extent in bile, the solubility increasing with rising temper-
ature. Strecker4 stated, in 1848, that taurocholic acid possesses the property
of dissolving fat, fatty acids, and cholesterin in considerable quantity. This
fact is mentioned by Strecker in connection with the difficulties attending the

1 Virchows Archiv, 1880, Bd. Ixxx. S. 11 ; 1884, Bd. xcv. S. 408.

2 Pettenkofer and Voit, Ztschr. f. BioL, Miinchen, 1873, Bd. ix. S. 30.

3 These figures must only be taken as argumentative data, overstepping the truth, and
not as truly indicating the total alkalinity.

4 Ann. d. Chem., Leipzig, 1848, Bd. Ixv. S. 29.

SOL UTION THEORIES OP FA T ABSORPTION. 45 5

preparation of taurocholic acid in a pure condition from bile. He did not
pursue the subject further on its own account, and his statement is in part
erroneous, for the neutral fats scarcely dissolve at all in bile. In 1858, Marcet1
published the results already described, showing the great solubility of the
fatty acids in bile when heated above their melting points. LatschinofF2
described a variable compound, or rather mixture, formed by taurocholic acid
with a mixture of stearic and palmitic acids, which possesses certain crystallo-
graphic properties, but no definite chemical composition.

Altmann,3 mainly on histological grounds, concluded that fats are
not absorbed as an emulsion, but in some soluble form.

Krehl,4 under Altmann's direction, obtained sections of the intestine,
stained by osmic acid, from animals killed at varying times after feeding
on fat (olive oil and cream). These preparations showed a gradual
increase in the size of the globules with the advancement of the period
of digestion. Also, it was observed that in the earlier stages the
small fat globules showed a clear centre, surrounded by a dark ring.
From these appearances it was judged that the formation of the fat
granules was a gradual one from solution, and not from drops of fat
emulsion. In considering the soluble form in which the fats are
absorbed, Altmann rejects the idea that they are absorbed as soaps,
chiefly on the ground that the reaction in the small intestine of the dog
is acid, so that it cannot contain dissolved soaps ; 5 yet from such a por-
tion of intestine, with an acid reaction and containing a clear fluid, the
charged lacteals are often to be seen conveying away absorbed fat.
Altmann cites the statements as to the solubility of the fatty acids in
bile already mentioned,6 and adds an experiment of his own, in which he
shows that a considerable, but not too great, quantity of a solution of com-
mercial glycerin soap, and then excess of hydrochloric acid, may be added
to a solution of sodium glycocholate or taurocholate without producing
any precipitation of either fatty or bile acid. From these data, and the
observation of Munk that the fatty material found in the dog's intestine
during fat digestion may contain as much as 12 per cent, of free fatty
acids, Altmann argues that the free fatty acids are dissolved in the
intestine by the bile acids. As the fatty acids so dissolved are absorbed,
fresh amounts of the neutral fats are decomposed, and the free fatty
acids so formed pass into solution to replace those removed by absorp-
tion. So that there is a cyclic process involving the decomposition of fats,
solution of fatty acids in the bile acids present, absorption of these fatty
acids by the intestinal cell, and regeneration of neutral fat within the
cell, accompanied by the appearance of fat granules.

Altmann did not quantitatively determine the amount of solubility of
fatty acids in bile acids, bile, or intestinal fluid. The solubility in bile varies
greatly with temperature, as is shown by Marcet's experiments.7 At the
temperature of the body the solubility is much less than at the temperature of
fusion of the fatty acids, but is still considerable ; while at ordinary atmo-
spheric temperature (14° to 15° C.) the solubility is very slight.8

The solubilities of the fatty acids, and mixtures of these at or near the

1 See p. 444.

- Ber. d. deutsch. chem. Gescllsch., Berlin, 1880, Bd. xiii. S. 1911.

*Arch.f. Aiiat. u. PhysioL, Leipzig, 1889, Anat. Abth., Supp. Bd. S. 86.

4 Ibid., 1890, Anat. Abth., S. 97.

5 This objection is discussed under the soap-absorption theory. See p. 453.

6 Except those of Marcet. 7 See p. 444.

8 Moore and Rockwood, Journ. PhysioL, Cambridge and London, 1897, vol. xxi. p. 58.

456 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

temperature of the body, have recently been determined by Moore and Eock-
wood,1 in the bile of the ox, pig, and dog, and in the mixed bile salts of ox
bile, with the following results : —

1. Pure palmitic and stearic acids are practically insoluble in ox bile at a
temperature of 38° to 40° C., while oleic acid is easily soluble at this tempera-
ture to the extent of 4 per cent.

2. Of the mixed fatty acids of lard, beef -suet, and mutton-suet, respectively,
lard acids are most soluble, mutton-suet acids least soluble, while beef-suet
acids are intermediate. Thus in ox bile the solubilities are — lard fatty acids,
3 '5 per cent.; beef-suet fatty acids, 2*5 per cent.; mutton-suet fatty acids, 2
per cent.

3. The solubility of the fatty acids in bile is only in part due to the bile
salts. A strong solution (9 per cent.) of the bile salts of ox bile dissolves all
three mixtures of fatty acids both more feebly and more slowly than bile itself.
Mere removal of the " pseudo-mucin " frolh bile greatly diminishes its solvent
action on fatty acids.

The same experimenters have shown that the filtered contents of the dog's
intestine, removed during fat absorption, are capable, in some samples, of
digesting and dissolving at body temperature to a clear solution as much as
4 per cent, of neutral fats. On cooling, the dissolved fatty material was
thrown out of solution as fatty acids. This experiment shows that, in the dog
at least,2 fats can be dissolved and absorbed in solution as fatty acids.

The solubilities of the mixed fatty acids in bile, stated above, are quite
sufficient to account for the absorption of all the fats of the food in the form
of dissolved fatty acids, since they exceed the concentrations in which the
products of carbohydrate and proteid digestion are met with in the intestine.
But this alone is not sufficient evidence to prove that in the normal course of
events all the fat is absorbed in such form.

The acids of the fats give an acid reaction with litmus. The bile used in
the experiments arranged to determine the solubilities was at first strongly
alkaline to litmus, but after it had dissolved the fatty acids it became markedly
acid to that indicator. It follows, that a fluid with an alkaline reaction to
litmus cannot hold in solution any free fatty acids. Now, in the intestine of
the white rat, during active fat absorption, the reaction is commonly strongly
alkaline to litmus, all the way from pylorus to caecum, and is never acid to that
indicator for a greater distance than 6 in. from the pylorus.3

Further, even in the case of the dog, and in that part of the intestine where
the reaction is acid to litmus, there are probably soaps as well as fatty acids in
solution. This is shown by the behaviour towards litmus and methyl-orange
of the contents of this part of the intestine. The acid reaction towards litmus
is shown by the alkaline reaction to methyl-orange to be due to very weak
organic acids ; at the same time, the alkaline reaction to methyl-orange also
shows that there is an excess of bases present (above the amount necessary to
combine with the strong acids), which is combined with very weak acids.
The most probable conclusion, as such a state of affairs is met with during the
digestion of an almost purely fatty meal (beef-suet), is that these weak acids are
the acids of the fats (oleic, palmitic, and stearic) in combination as soaps.
Hence, in that part of the small intestine of the dog where the reaction is acid
to litmus, fat absorption is probably going on, partly in the form of dissolved
fatty acids and partly in the form of dissolved soaps ; in the part where the
reaction is alkaline to litmus, wholly in the form of dissolved soaps.

In those animals, such as herbivora, in which the reaction of the intestinal
contents is strongly alkaline, it is probable that all the fat is absorbed as soaps.

1 Loc. cit.

2 Similar results were not obtained with filtered intestinal contents obtained from the
rabbit or pig.

3 Moore and Roekwood, loc. cit.

PASSAGE OF THE FAT TO THE LACTEALS. 457

If a rabbit be killed some hours after a meal of oats, a certain amount of fat is
shown to be in process of absorption by the whiteness of the lacteals, but the
reaction of the contents of the small intestine is always markedly alkaline.

It is probable, then, that in all animals a great part of the fat is
absorbed dissolved in the form of soaps ; but in some animals a part
is also absorbed as dissolved fatty acids, while in others the entire
quantity leaves the intestine in the form of soaps.

These various theories as to the form in which fats enter the epithelial
cell, may be summarised as follows : —

Emulsion theories. — 1. A small percentage of the fat is split up into
fatty acids and glycerin, the fatty acids unite with the alkaline basis of the
mixed secretions present in the intestine, and the rest of the fat is thereby
converted into an emulsion, which is absorbed by the columnar cells.

2. A considerable part of the fat is split up into fatty acids and glycerin,
and absorbed as emulsified fatty acids and glycerin, which are synthesised
to neutral fats by the columnar cells.

Solution theories. — 1. All the fat is split up into fatty acids and glycerin ;
the fatty acids combine with alkaline bases to form soluble soaps ; these and
the dissolved glycerin are absorbed in solution, and synthesised to neutral
fats in the columnar cells.

2. All the fat is split up into fatty acids and glycerin ; the fatty acids
are dissolved as such by the intestinal fluid (the bile being that constituent
which gives this solvent property to the fluid), these dissolved fractions of the
fat are absorbed by the columnar cells, and by these are synthesised again to
neutral fats.

3. The processes indicated under solution theories 2 and 3 probably
mutually replace each other to a variable extent in some animals, but in
others absorption takes place entirely in the form of soaps.

Passage of the fat from the epithelial cells to the lacteals.—
In whatever form the fat passes into the columnar cells, it is certain
that it is here converted again into fat. During active fat absorption
these cells become gorged with fat globules of varying dimensions. It
is agreed by all observers that this fat passes from the epithelium to
the lacteals in the form of an emulsion, but there is some difference of
opinion as to the fashion in which it is conveyed.

It has already been stated that the tissue of the villi, especially
during active fat absorption, contains immense numbers of leucocytes.
These are found not only in the subepithelial tissue, but between the
epithelial cells. The number in this position is greatly increased during
absorption, and at this time lymphoid cells occur also in the lacteals,
but "are found more numerously in the lacteals of the villi than in
those which are more deeply seated, and, most numerously of all, near
the blind end of the lacteal. That they pass into this vessel from
the surrounding lymphoid tissue is certain, for a lymphoid cell may
often be seen, fixed by the reagent employed for hardening the tissue,
in the act of passing through the wall of the lacteal." 1 After a meal
containing fat, these lymphoid corpuscles contain granules, which stain
black with osmic acid ; many of these are soluble in ether, so that they
are unquestionably composed of fat.

1 Schafer, Internal. Monatschr. f. Anat. u. HistoL, Leipzig, 1885, Bd. ii. S. 6. The
greater part of the description of the carriage of fat by leucocytes, between epithelium and
lacteal, given in the text, is abstracted from this source.

458 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

These appearances led Schafer1 to express the view that the
lymphoid corpuscles have an important function in taking up the fat
from the epithelial cells, and carrying it towards and into the lacteal,
where they set the fat free by disintegrating. No fat particles are, as a
rule, found between the epithelium and the central lacteal, save such as
are embedded in lymphoid corpuscles. Nor is there any channel of
communication between the epithelial cell and the lacteal, as was
formerly supposed, by which the fat globules might be carried into the
lacteal. The epithelial cells never penetrate the basement membrane,
nor are they continued into the cells of the retiform tissue beneath.
Wiemar 2 admits the presence, during fat absorption, of fat granules in
the leucocytes, but from the small amount of fat so found, compared
with that in the epithelial cells, considers that the leucocytes can only
be of secondary importance. In this connection it should be noted that
Schafer 3 has pointed out that the relative amount of fat granules in
leucocytes and epithelial cells varies with the activity of absorption.
" When the absorptive activity is feeble, or when the amount of fat in
the chyme is relatively small, there may be little or no fat in the
columnar epithelial cells, although the amoeboid cells between them may
be gorged with fat granules. In frogs fed with lard in the spring,
fatty globules are still abundant in the columnar epithelial cells on the
eighth day after the feeding, whereas, in frogs similarly fed in November,
the greater part of the fat was discharged per anum, by the third day,
very little being absorbed, and what was being taken up during that
time was only to be found in the amoeboid cells, none at all being
present in the epithelial cells themselves." This seerns to indicate that,
when the rate of absorption is slow, the amoeboid cells are able to keep
pace with it, but when the supply is too abundant for this, the columnar
cells act as temporary storehouses, and become filled with granules,
which are afterwards carried off by the amoeboid cells.

Heidenhain4 ascribes only a secondary importance to the leuco-
cytes. He gives as grounds for this opinion — (1) That in newly-born
puppies, which have already sucked, and in which milk absorption is
going on, there are scarcely any leucocytes present in the epithelium, so
that there is no constant connection between fat absorption and the
presence of leucocytes. (2) Leucocytes containing granules, which stain
black with osmic acid, are to be found in the crypts of Lieberklihn, into
which fat cannot enter from the intestine. (3) The material which is
stained black with osmic acid is chiefly something else than fat, since
it stains with acid-fuchshi, and cannot be washed out of adhesively
mounted sections by ether or xylol.5 Heidenhain6 admits, however,
that in the guinea-pig fat is undoubtedly present in considerable
quantity in the amoeboid cells during fat absorption.

Heidenhain 7 still adheres to the emulsion theory of absorption, but

1 Quain's "Anatomy," 8th edition, 1876, vol. ii. p. 363; "Pract. Histology," 1876,
p. 194 ; Internat. Monatschr. f. Anat, u. HistoL, Leipzig, 1885, Bd. ii. S. 6 ; Arch. f. d.
yes. Physiol., Bonn, 1884, Bd. xxxiii. S. 513. Schafer's observations were chiefly made
upon the frog and rat.

2 Ibid., Bd. xxxiii. S. 532.

3 Internat. Monatschr. f. Anat. u. HistoL, Leipzig, 1885, Bd. ii. S. 6.

4 Arch f. d. ges. Physiol., Bonn, 1888, Bd. xliii. Supp. Heft, S. 82.

5 It should, however, be pointed out, that after prolonged treatment with osmic acid,
fats tend to become insoluble in these fluids.

6 Arch.f. d. ges. Physiol. , Bonn, 1888, Bd. xliii., Supp. Heft, S. 103, figs. 39 and 40, plate iv.

7 Ibid., S. 88.

ABSORPTION OF FATS, 459

offers no explanation of the mode in which the fat granules get into
the epithelial cells; he considers that the bile must essentially assist
in the process, partially by aiding the emulsification of the fats, and
partially by making the surface of the epithelium capable of being
wetted by the fats, which naturally facilitates the absorption. He
is further of opinion that the fat globules are passed on out of
the columnar epithelial cells by means of the contractions of the
cell protoplasm ; and that these on their further path to the lacteal,
apart from the small part eaten up by the leucocytes, pass in a
free condition through the intercellular spaces, and are first broken up
into the very fine granules characteristic of chyle when passing into
the lacteal.

The effects of absence of the pancreatic juice or bile on the
absorption of fats. — The results on record as to the absorption of fat,
when the action of the pancreatic juice is removed by excision of the
pancreas, ligature of the pancreatic ducts, or establishment of a pan-
creatic fistula, vary considerably ; although there is a concurrence of
opinion amongst recent observers l that the absorption of fat is
hindered to a greater or lesser extent by the absence of the secretion.
Minkowski 2 and Abelmann 3 found that no fat, except that of milk, was
absorbed after complete removal of the pancreas, and this was only
absorbed to the extent of 28 to 53 per cent. ; the failure of absorption
was not due to absence of fatty acids, for 80 per cent, of the ether
extract of the fseces was found to be free fatty acid.

Minkowski believes that the absorption of the milk fat is due to this emul-
sion being able to withstand an acid reaction, but the absorption of other fats,
when pancreas is given with the fat, points rather to some specific function
of the pancreatic juice, for this pancreatic tissue could not materially alter the
reaction of the intestine ; besides, fat absorption takes place normally from
the dog's intestine in presence of an acid reaction. Sandmeyer4 found in
dogs in which the pancreas had been partially extirpated, that the amount of
fat absorption was very variable ; occasionally no fat at all was absorbed,
and at other times, with the same animal, 30 and even 78 per cent, of the fat
was absorbed.

Teichmann 5 found by microscopic examination that fat absorption in the
rabbit was not influenced to any marked extent by ligature of the pancreatic
duct. Fr. Miiller 6 observed a considerable amount of fat absorption in a patient
with a pancreatic fistula. Vaughan Harley 7 extirpated the pancreas completely
in dogs, killed the animals a varying number of hours after feeding on milk,

1 On the other hand, Cohn (Bull. Acad. de med., Paris, 1856) found that the absorp-
tion of fat was not affected when the pancreatic juice was allowed to escape from a fistula.
Cash (Arcli.f. Anat. u. Physiol., Leipzig, 1880, S. 323) ligatured both pancreatic ducts in the
dog, and found that fat was still absorbed. Schiff (Jahresb. u. d. Fortschr. d. Thier-
Cliem., Wiesbaden, 1872, Bd. ii. S. 222) shut out the pancreatic secretion by injecting
paraffin into the duct, and found that fat to the amount of 120 to 150 grms. per diem was
still absorbed.

2 Von Mering and MinkoAvski, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1890, Bd.
xxvi. S. 371.

3 Inaug. Diss., Dorpat, 1890 ; Minkowski, Berl. klin. Wchtischr., 1890, S. 333.

4 Ztschr.f. BioL, Mtinchen, 1895, Bd. xxxi. S. 12. See also Rosenberg, Arch. f. Anat.
u. Physiol. , Leipzig, 1896, Physiol. Abth., S. 535.

5 " Mikroskop. Beitr. z. Lehre von der Fettresorption," Diss., Breslau, 1891.

6 Ztschr.f. Tclin. Med., Berlin, 1887, Bd. xii. S. 45. Defective fat absorption, however,
undoubtedly accompanies disease of the pancreas, or occlusion of its duct in most cases ; see
Bright, Mcd.-Chir. Trans., London, 1832; Ziehl, Deutsche med. Wchnschr., Leipzig, 1883,
S. 538 ; le Nobel, Deutschcs Arch. f. klin. Med., Leipzig, 1888, Bd. xliii. S. 285.

7 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 1.

460 CHEMISTRY OF THE DIGESTIVE PROCESSES.

and estimated the amount of fatty material in the stomach and intestine. The
amount so found was usually slightly in excess of that given in the food, the
surplus being probably due to intestinal secretion or excretion. Lewiii,1 as a
result of microscopic examination of sections of the intestine, concludes that fat
absorption does not take place in a normal manner if bile or pancreatic juice, or
both, are kept from entering the intestine. He also found under such circum-
stances that the lacteals did not present the usual milky appearance which
accompanies fat absorption.

The effect of a biliary fistula on fat absorption seems to be identical
with that of a pancreatic fistula ; exactly the same kinds of results have
been recorded in the two cases. All observers are agreed that so much
fat cannot be absorbed in presence of a biliary fistula as when bile has
access to the intestine, but, while some find fat absorption practically
arrested, others have observed that a considerable, nearly normal, amount
of fat can still be disposed of. As in the case of absence of the pan-
creatic secretion, most of the unabsorbed fat is found in the freces as
fatty acid.2

Rohmann 3 also found that sodium soaps were not absorbed, but were
converted into free fatty acids, and appeared as such in the faeces. Bidder
and Schmidt 4 state that normal dogs can digest as much as seven times the
quantity of fat which can be disposed of by dogs with fistula of the gall bladder,
and that, while during fat absorption in a normal dog the lacteals are filled with
milky chyle, they are, under similar conditions in a dog with a biliary fistula,
filled with a yellow or slightly opalescent fluid.

C. Voit5 estimates the average loss of fat at 22 "2 to 34'7 per cent.; Munk,6
at 33-1 per cent. ; Rohmann,7 at 48'5 to 58'4 per cent. ; Xoiil Paton,8 at 34-58
per cent. ; Dastre,9 at 57 '65 per cent. Munk 10 found that the absorption of fats
of high melting point (mutton) suffered more than that of fats of low melting
point (hog's lard) ; of the former but 35 '5 per cent, was utilised, of the latter
67 per cent. He also found that the free fatty acids in the absence of bile were
absorbed equally well, in fact slightly better, than the corresponding neutral
fats. Dastre n ligatured the ductus choledochus, and made a fistula between
the gall bladder and small intestine much lower down (60-150 cm.) ; he
observed, after a meal of fat, that the lacteals were only injected with milky
chyle below the artificial point of entry of the bile. ' As Dastre himself
remarks, the result is more elegant than decisive. It is only qualitative in
character, and does not show quantitatively the share taken by pancreatic
juice and bile in fat absorption. Hedon and Yille 12 established first a biliary
fistula, and afterwards removed nearly all the pancreas, leaving just enough of
the tail to preserve the animal alive, and destroying all communication with
the intestine. In this manner both bile and pancreatic juice were kept out of the
intestine, and under such conditions the digestion and absorption of fat was

1 Arch.f. d. ges. Physiol., Bonn, 1896, Bd. Ixiii. S. 171. Lewin removed the influence of
both secretions by making a Thiry-Vella fistula of that part of the duodenum into which
the ducts open.

2 Rohmann, Arch. f. d. ges. PhysioL, Bonn, 1882. Bd. xxix. S. 509 ; I. Munk, VirchovSs
Archiv, 1890, Bd. cxxii. S. 313 ; Hedon and Ville, Compt. rend. Soc. de UoL, Paris, 1892,
tome xliv. p. 309. See, however, Dastre, Arch, de physiol. norm, et path., Paris, 1891,
tome xxiii. p. 186.

3 Loc. cit., S. 532. 4 <: Die Verdainmgssafte, " etc.
"Beitr. z. Biologic," Julildumsschriftf. v. Bischoff, Stuttgart, 1882.

6 Virchow's Archiv, 1890, Bd. cxxii. S. 302. 7 LOG. cit.

8 Rep. Lab. Roy. Coll. Phys., Edin., 1891, vol. iii. p. 214. The case was one of a com-
plete biliary fistula in a woman.

9 Loc. cit. 10 Loc. cit., S. 324, 325. n LOG, cit. 12 LOG. cit.

A BSORPTION OF FA TS. 461

studied. It was found that food passed very rapidly through the alimentary
canal without much modification, scarcely any fat was absorbed, but it was
nearly all converted into fatty acid.

These varied results may be summed up as showing that both the
pancreatic juice and the bile are powerful aids in the digestion and
absorption of fats, but neither is absolutely indispensable.

The view to be taken of the part played by bile and pancreatic juice
in fat absorption must naturally vary with the view held as to the form
in which fat is absorbed.

1. It may be urged that, in the absence of pancreatic juice, a sufficient
supply of fatty acid is not set free for emulsification of the remainder.
Since bile (or bile salts) very much hastens the fat-splitting action of
pancreatic juice,1 the absence of bile would have a very similar effect to
that of pancreatic juice itself. A serious objection to this explanation
lies in the fact that in defective absorption, due to the absence of either
bile or pancreatic juice, nearly all the unabsorbed fat is found in the
faeces as free fatty acid.

It might be claimed that this fat-splitting, probably by bacterial
action, takes place much lower down in the intestine, at a less favourable
position for absorption, and that a considerable part of the intestine is
traversed before a sufficient amount of fatty acid is formed. But in the
faeces as much as 80 per cent, of the total fat is as free fatty acid, while
only about 5 per cent, is required for spontaneous emulsion ; besides, the
fat of the food contains nearly sufficient fatty acid to begin with, so that
this contention has little weight.

2. Another view which has been held is, that in the absence of either
bile or pancreatic juice the intestinal reaction is acid, so that no emul-
sion can take place, and hence the fat cannot be absorbed. It is not,
however, claimed that such an acid reaction is due to free hydrochloric
acid, since the remaining alkaline secretions are still more than sufficient
to neutralise this, and active fat absorption has often been observed in
presence of an acid reaction due to organic acids.

3. It has been supposed that the absence of the proteid of the
pancreatic juice has an unfavourable effect on the formation of an
emulsion (Minkowski).

4. A theory advanced by v. Wistinghausen 2 was that the bile aided
fat absorption by mechanically wetting the epithelial cells with a fluid
which rendered the passage of the fat easier. He claimed that oil
stood higher in capillary tubes wetted with bile than in similar tubes
wetted with water, and that oils or melted fats passed more rapidly
through a membrane wetted with bile than through one wetted
with water. These results have not, however, been confirmed by other
observers.3

5. It has also been supposed that the bile directly stimulates
(chemically) the epithelial cells of the intestine to increased fat absorp-
tion, and that in the absence of the bile this stimulus is absent. Under
these conditions the epithelial cells either do not absorb fat as an emul-

1 Rachford, Journ. Physiol., Cambridge and London, 1891, vol. xii. p. 87.

2 Translation in Arch. f. Anat. u. Physiol. , Leipzig, 1873, S. 137, by J. Steiner. See
also Schiff, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1857, Bd. ii. S. 345; Heiden-
hain, Arch. f. d. ges. Physiol.. Bonn, 1888, Bd. xliii. Supp. Heft, S. 91.

s Groper, Arch. f. Anat. u. Physiol., Leipzig, 1889, S. 505.

462 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

sion at all, or only absorb it at a greatly diminished rate.1 There is no
experimental evidence in support of this theory, and a great objection to
it is that bile is constantly present in the intestine, and is not poured
out in association with the presence of fat ; such are not the proper
conditions for a stimulus, which ought, if it is to be effective, to be inter-
mittent, and only be called into action when required.

6. All the previous views rest on the assumption that the fats are
absorbed in the form of an emulsion. If, on the other hand, the fats are
absorbed in soluble forms as fatty acids or soaps and glycerin, the most
obvious explanation of the action of bile and pancreatic juice in assisting
absorption is, that these secretions increase the solubility of the fatty
acids or soaps.

In the absence of bile or pancreatic juice, the fatty acids are not so
soluble in the intestinal fluid, and so tfie absorption is defective, and the
insoluble fatty acids appear in the faeces. In support of this the fact
may be recalled that the bile salts possess the power of dissolving the
insoluble soaps of the alkaline earths.2

Channels of absorption of the fats. — There is no doubt that the
lacteals are the main channel by which the fats are carried away from
the intestine, but it is by no means so clear that all the fat goes by this
route. The amount of fat absorbed from the intestine after a fatty meal
can easily be determined by weighing the amount of fat ingested, and that
remaining in the alimentary canal when digestion is nearly complete, and
taking the difference, which must be the amount absorbed. The amount
of fat poured into the blood by the thoracic duct during the same period
can also be determined, by inserting a cannula into the duct and collecting
the chyle, from which the fat is afterwards extracted and then weighed.
The amount thus carried by the thoracic duct during the period of active
absorption is always much less than the total quantity absorbed ; it lias
never been found to amount to more than 60 per cent., and is usually
much less than this.3 The fate of the balance of the fat is unknown ; the
first suggestion occurring to the mind, that it travels by the alternate
path of the portal circulation, has not been found to fit the experimental
facts. The portal vein during fat digestion does indeed contain an
abnormal amount of finely emulsified fat, but so does all the blood of the
body, and the presence of the fat is due to the admixture with the blood
of the chyle carried by the thoracic duct. On diverting from the blood
this supply of fat, by means of a cannula inserted into the thoracic duct,
Zawilski found scarcely any fat in the blood during fat absorption.
Neither is there any difference during fat absorption in the percentages
of fat present in portal and carotid blood.4 It would seem from this
that almost all the fat is carried by the lacteals, but that part is
removed somewhere in the lymphatic system between the lacteals and
the opening of the thoracic duct ; it may be in the lymphatic glands,5
but the subject requires further investigation.

1 Rohmann, Arch. f. d. ges. Physiol., Bonn, Bd. xxix. S. 509 ; Minkowski, BerL med.
Wchnschr., 1890, No. 15, S. 333 ; Lewin, Arch. f. d. ges. Physiol. , Bonn, 1896, Bd. Ixiii.
S. 186.

2 See p. 392.

3 Zawilski, Arb. a. d. physiol. Anst. zu Leipzig, 1867, Bd. xi. S. 147 ; "\Valther, Arch,
f. Anat. u. PhysioL, Leipzig, 1890, S. 329; Frank, ibid., 1892, S. 497 ; Munk u. Rosen-
'stein, Virchow's Archiv, Bd. cxxiii. S. 484.

4 Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1888, Bd. xliii., Supp. Heft, S. 95.

5 See M. Foster, "Text-book of Physiology, " pt. ii. p. 513.

BACTERIAL DIGESTION. 463

After a full meal of fat, absorption, in the case of the dog, goes on
for about thirty hours. At the height of absorption, the chyle in the
thoracic duct may contain as much as 15 per cent, of fat. Twenty-one
hours after a meal of 150 grms. of fat, Zawilski * still found in the stomach
974 grms., in the intestine 6 '24 grms. ; in thirty hours all but traces
have disappeared from both stomach and intestine. Throughout this
period of digestion, according to the same observer, the amount of fat in
the intestine at any time remains practically constant (6'24 to 9'9 grms.),
from which it would seem that the rate at which the fat is allowed to
pass the pylorus is regulated by the amount of fat already present in the
intestine.

None of the soap which may be formed during fat digestion and
absorption probably ever enters the general circulation as such, but is
reconverted into neutral fat beforehand; as Munk2 has shown, soaps
of the alkalies intravenously injected produce poisonous effects, closely
resembling those obtained on injection of albumoses.

As might be expected from their similar chemical constitution, the
lecithins are decomposed in the same manner as the fats by the steapsin
of the pancreatic juice, the products of the reaction being glycero-
phosphoric acid, neurin, and fatty acids. These products are probably
absorbed, as is shown by their absence in the fseces after the administra-
tion of lecithin by the mouth ; as well as by the increase of phosphates
in the urine after feeding on foods, such as yolk of egg, rich in lecithin.3

BACTERIAL DIGESTION.

The food in the alimentary canal is acted upon, not only by the
digestive secretions and their enzymes, but to a greater or less extent by
certain bacteria which are never entirely absent, although the amount of
their action varies greatly, under healthy conditions, with the nature of the
food and the class of animal. Under abnormal conditions the growth of
these organisms may be greatly increased, and nutrition be seriously
impaired, by their turning to their own uses the products of normal
digestion, and leaving only for the service of the animal, degradation-
products, inadequate or wholly unsuited for the purposes of its meta-
bolism. Along with this increased growth of the bacteria normally
present in the stomach, conditions may become so changed as to favour
the growth of other bacteria, often pathogenic in character, which find
under normal conditions no favourable soil for their growth in the
intestinal contents, and thus various forms of disease may be introduced.
We have here, however, only to deal with the changes induced by
bacteria under a normal condition of the alimentary canal.

In dealing with the function of the free hydrochloric acid of the
gastric juice, it has already been stated that this completely stops all
bacterial action,4 so that it is only in the first stage of gastric secretion,
before the acidity has become marked, that any bacterial changes can occur.

Proteids are not attacked during this first short stage (twenty to
forty minutes) of gastric digestion, but carbohydrates undergo to a

1 Loc. (At. 2 Arch.f. Anat. u. PhysioL, Leipzig, 1890, Snpp. Bd., S. 116.

3 A. Bokay, Ztschr. /. physiol. Chem., Strassburg, 1877, Bd. i. S. 157; see also Hase-
broek, ibid., 1888, Bd. xii. S. 148,

4 See p. 364.

464 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

slight extent lactic fermentation.1 A certain amount of decomposition
of neutral fats also occurs during gastric digestion, yielding fatty acids,
but it is not certainly known whether this is due to bacterial action or
not.2

Intestinal bacterial digestion— Reaction of the intestine.— There
is considerable difference of opinion both as to the amount of decom-
position of foodstuffs due to bacterial action which goes on in the
intestine, and as to the importance of such a decomposition as a normal
factor in digestion.

The extent of bacterial action can evidently be more accurately
gauged by the amount of bacterial decomposition products formed than
by the presence in the intestine of bacteria, which may not there be in
a very active condition.

Judged by this standard, the amount of proteid decomposition due
to bacteria which takes place in the small intestine is excessively small,
while a considerable amount takes place in the caecum and large intes-
tine generally. When carbohydrates and proteids are present in the
same solution along with various bacteria capable of attacking them,
the carbohydrates are first attacked, the action being accompanied by
the formation of certain organic acids ; at a later stage the proteids are
attacked and decomposed. This has been shown by Maly,3 who took
mucous membrane of the stomach, placed it in a solution of cane-sugar,
and kept the mixture at body temperature for several days. The lactic
acid formed by the decomposition of the sugar was neutralised from
time to time, and it was found that the process continued without a
trace of putrefaction appearing, until all the sugar had been converted
into lactate ; then first appeared, often somewhat suddenly, an intense
putrefactive odour, and the proteids began to be decomposed.

It is probable from this that, in the body, bacterial action on carbo-
hydrates precedes that on proteids ; and it has been supposed by some
that such an action commences with considerable intensity in the
duodenum, and persists throughout the entire length of the small
intestine, so involving bacterial decomposition of a large share of the
carbohydrate food.

This opinion rests chiefly on the observation that the acid reaction
of the chyme in the stomach, due to hydrochloric acid, becomes replaced
by an acid reaction, due to organic acids, in the small intestine. These
organic acids are supposed to be set free by the action of certain bacteria,
found in the small intestine, upon the carbohydrate food.

Such a result has been obtained by Macfadyen, JN"encki, and Sieber,4 from
observations made on a case of anus prceternaturalis in man, in which the
fistula occurred quite at the lower end of the ileum. The intestinal contents
arising from a mixed diet, consisting principally of animal food, had as they
flowed from the fistula an acid reaction, equivalent to that of a solution of
1 per mille of acetic acid; this reaction was principally due to acetic acid,

1 In this process hydrogen gas is set free along Avith lactic and traces of other acids ;
under abnormal conditions the amount of gas may be greatly increased. See E. Wissel,
Ztschr. f. physiol. Ckem., Strassburg, 1895, Bd. xxi. S. 234, where the literature of this
subject up to that date is given.

2 Marcet, Proc. Roy. Soc. London, 1858, vol. ix. p. 306 ; Cash, Arch. f. Anat. u.
Physiol., Leipzig, 1880, S. 323.

3 Hermann's "Handbuch," Bd. v. (2), S. 239.

4 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1891, Bd. xxviii. S. 311, reprinted in Journ.
Anat. and Physiol., London, 1891, vol. xxv. p. 390. See also C. A. Ewald, Virchow 's Archiv ',
1879, Bd. Ixxv. S. 409 ; and Jakowski, Arch. d. sc. biol., St. Pe"tersbourg, 1892, tome i, p. 539.

ACTION OF INTESTINAL BACTERIA ON PROTEIDS. 465

accompanied by traces of fermentation and paralactic acid, volatile fatty acids,
succinic acid, and bile acids. Hydrochloric acid was not present. The
mixture had very little odour ; occasionally the slight odour it had was faintly
putrefactive, resembling indol, but usually it was more like that of volatile
fatty acids. These authors state that it is the organic acids present in the
small intestine which limit the bacterial decomposition of carbohydrates, and
prevent the putrefaction of proteids.

On the other hand, Moore and Kockwood l state that the reaction of the
intestine in various classes of animals (dog, cat, white rat, guinea-pig, and
rabbit) is not normally acid throughout its entire length, and that the
alkalinity increases in passing down the intestine.

The presence of fat in the food causes in carnivora an acid reaction, which
persists until the lower third of the intestine is reached. This acid reaction is
due to very weak organic acid, most probably to the acids of the fats dissolved
by the agency of the bile.2 The alkalinity is much greater in herbivora than
in carnivora, although herbivora consume much more carbohydrate food than
carnivora. Also, in carnivora, the alkalinity is markedly increased by carbo-
hydrate food • this would not be the case if any considerable bacterial
decomposition of carbohydrates took place in the small intestine, but the
alkalinity would diminish from increased formation of organic acids. It is
therefore probable that in these animals any extensive bacterial decomposition
of carbohydrates that may occur, like that of proteids, takes place in the
large intestine, and by analogy the same is probably the case in the human
intestine.

Considerable importance has been attached to the normal action of bacteria
in the intestine, and it has even been supposed that the presence of bacteria
is essential to life. Such a view has recently been shown to be erroneous by
an elaborate and painstaking research carried out by Nuttall and Thierfelder,3
who obtained ripe foetal guinea-pigs, by means of a Csesarean section, carried
out under strict antiseptic precautions. They introduced the animals immedi-
ately into an aseptic chamber, through which a current of filtered air was
aspirated, and fed them hourly on sterilised milk day and night for over eight
days.

The animals lived and throve, and increased as much in weight as healthy
normal animals, subjected to a similar diet for the purpose of controlling the
results. Microscopic examination at the end of the experiment showed that
the alimentary canal contained no bacteria of any kind, nor could cultures of
any kind be obtained from it. The same authors, in a subsequent paper,
describe the extension of their research to vegetable food ; this was also digested
in the absence of bacteria. Under such conditions cellulose was not attacked ;
hence they consider that the chief function of this material is to give bulk and
a proper consistency to the food, so as to suit the conditions of herbivorous
digestion.

Action of the intestinal bacteria on proteids.— The changes brought
about in the intestine are very similar and probably identical with those
which occur when proteids undergo putrefaction in the air, with this
important exception, that those putrefactive bacteria which produce the
class of poisonous nitrogenous (alkaloidal) bases known as ptomaines do
not grow under normal conditions in the intestine. This may be due to
the intestinal contents not furnishing a suitable medium for their growth,
or to the time of putrefaction in the intestine not being sufficiently
prolonged. Ptomaines, and especially poisonous ones, are formed only in

1 Journ. PhysioL, Cambridge and London, 1897, vol. xxi. p. 373.

2 See " Digestion and Absorption of Fats," p. 454.

3 Ztschr. /. physiol. Chem., Strassburg, 1895, Bd. xxi. S. 109; 1896, Bd. xxii. S. 62.

VOL. I. — 30

466 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

the later stages of putrefaction. It has also been suggested that the
cause may be the absence of oxygen from the intestine, the ptomaine-
forming bacteria being aerobic. That the bacteria which produce
ptomaines are present in the intestine, is shown by the fact that cultures
producing ptomaines may be obtained by sowing from the intestinal
contents into suitable media.1 At any rate, ptomaines even in traces are
not to be found in the intestinal contents ; and it is fairly certain that
they are not produced there, as most of them, absorbed even in minute
doses, are capable of producing profound toxic effects.

The first stages in the action of bacteria on proteids are very similar
to those induced by trypsin ; they can also be brought about by enzymes
extracted from the bacteria,2 but, according to Kiihiie,3 are not due to
trypsin, which is never formed in bacterial putrefaction.

The first action is the solution of the proteid, if this is not already
dissolved. Solution takes place much more slowly than in the case of
the digestive enzymes, the complete solution of fresh fibrin thoroughly
infected with intestinal bacteria in faintly alkaline solution being a
process of some days' duration.4 Albumoses, peptones, and the other
products of tryptic digestion are next formed, but the amount of these
present at any time is never great, since they are gradually broken up
as they are formed into more advanced degradation products. In the
presence of albumoses or peptones, the native proteids are very faintly
attacked by the bacteria, until these have first been disposed of.
Neumeister 5 has shown that, when peptone is added to putrefying blood
or proteid, its quantity is not increased by the continuance of the putre-
factive process, but rather diminished until it finally disappears.

The proteid molecule probably contains a large number of both
fatty and aromatic radicles, but all those belonging to the aromatic
group yield, under the action of trypsin, only one substance, namely,
tyrosine. The same is true of all artificial modes of decomposition which
do not act too intensely on the primary products of decomposition.6
But with the decomposition produced by bacteria, the case is different,
and several aromatic compounds are formed.

These are in part produced by further action on tyrosine, formed in
an earlier stage, and in part spring from a specific action of the bacteria
on the proteid, without the intervention of tyrosine. Only some of these
products of bacterial decomposition have been hitherto found in the
intestinal canal ; the others are either, under the different conditions, not
formed there, or are so rapidly absorbed and altered that they cannot
be detected in the intestinal contents.

The chief aromatic compounds derived from the bacterial decomposi-
tion of proteids are : — (a) Tyrosine, and its derivatives, paraoxyphenyl-
propionic acid (hydroparacuinaric acid), and paraoxyphenylacetic acid,
as well as phenylpropionic and phenylacetic acids,7 of which the fore-
going are the oxy- or hydroxy-acids, also parakresol and phenol.

1 Brieger, Deutsche med. Wchnsclir., Leipzig, 1887, S. 469; Baumann u. Udransky,
Ztschr.f. physiol. Chem., Strassburg, 1889, Bd. xiii. S. 579.

2 See p. 313.

3 Untersuch. a. d. physiol. Inst. zu Heidelberg, 1878, Bd. i. S. 291.

4 Bienstoek, Ztschr. f. Jclin. Med., Berlin, 1884, Bd. viii. S. 1.

5 Ztschr.f. Biol, Mimchen, 1890, Bd. xxvii. S. 335; " Lehrbtich, " Th. 1, S. 207.

6 Klihne obtained indol by the fusion of proteid with caustic alkali, Ber. d. deutsch.
chem. Gesellsch., Berlin, 1875, Bd. viii. S. 206.

7 See E. Salkowski, Ztschr.f. physiol. Chem., Strassburg, 1885, Bd. ix. S. 491.

ACTION OF INTESTINAL BACTERIA ON PROTEIDS. 467

(&) Substances formed directly and not from tyrosine — indol, skatol, and
skatolcarbonic acid.

Of these substances, Zuinft 1 found indol, skatol, phenol, and para-
kresol in the large intestine of man, but skatolcarbonic acid was absent ;
this latter acid has not yet been detected in the intestine. According
to E. Salkowski, it is excreted unchanged in the urine, and he states that
he has detected it in normal urine.2

These several substances may now be considered seriatim.

Derivatives of tyrosine formed in putrefaction? — Hydroparacumaric acid,
or paraoxyphenylpropionic acid (HO.C0H4.C2H4.COOH) crystallises from
water in anhydrous monoclinic crystals, melting at 125°-128° C., soluble
in water, alcohol, and ether. It gives a transient blue coloration with ferric
chloride, and a red coloration or red precipitate when boiled with Millon's
reagent. It is the oxy-acid of phenylpropionic acid, which lias also been
found among the putrefaction-products of proteids. Phenylpropionic acid
crystallises in slender needles, melting at 47°-48° C. (B-Pt. 280° C.). As
follows from its constitution, its solutions do not give Millon's reaction.

Paraoxyphenylacetic, acid (HO.C6H4.CH2.COOH) crystallises from water
in prismatic crystals, melting at 148° C., and soluble in water, alcohol, and
ether. With ferric chloride it gives a faint violet coloration, changing to
a dirty grey -green. It also gives Millon's reaction. Phenylacetic acid
crystallises in scales, which melt at 76° '5 C.

Phenol and parakresol 4 are also formed in the bacterial decomposition of
tyrosine ; they are absorbed from the alimentary canal, and after conversion
into ethereal sulphates are excreted in the urine. The amount of these
ethereal sulphates in the urine gives a measure of the amount of bacterial
decomposition going on in the intestine.5

Tyrosine and its derivatives are very closely related to one another. In
the derivation of these compounds, according to Baumann,6 tyrosine (paraoxy-
phenyl-a-amidopropionic acid) undergoes reduction, ammonia being split off,
and hydroparacumaric acid (paraoxyphenylpropionic acid) formed. This
compound, by a series of oxidations, accompanied by a splitting off of carbon-
dioxide, yields paraoxyphenylacetic acid and parakresol. Parakresol is said
to similarly yield phenol.

These changes are illustrated by the following equations : —

/OH (p) /OH (p)

CGH/ + H2 = CCH/

XCIl,CH(^rH,).COOH XCH2.CH2.COOH

(paraoxyphenyl-a-amidopropionic (paraoxyphenylpropionic acid

acid or tyrosine) or hydroparacumaric acid)

/OH (p) /OH (p)

2G6H4< + 30o = 2C6H4<

XCH2.CH.2.COOH XCH2.COOH

(paraoxyphenylpropionic acid) (paraoxyphenylacetic acid)

1 Arch. d. sc. biol., St. Petersbourg, 1892, vol. i. p. 497.

2 Ztsckr. f. physiol. Ohem., Strassburg, 1885, Bd. ix. S. 32.

3 See Baumann. Ztschr.f. physiol. Ckem., Strassburg, 1877-1880, Bd. i. S. 60 ; iv. S. 304 ;
Ber. d. deutsch. diem. Gesellsch., Berlin, 1879, Bd. xii. S. 1450; 1880, Bd. xiii. S. 279;
Baumann and Brieger, Ztschr.f. physiol. Ckem., Strassburg, 1879, Bd. iii. S. 149; E.
and H. Salkowski, Ber. d. deutsch. chem. Gesellsch., Berlin, 1879, Bd. xii. S. 648; E.
Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1878-9, Bd. ii. S. 420 ; Weyl, ibid.,
1877-9, Bd. i. S. 339 ; iii. S. 312.

4 For a description of the physical and chemical properties of these bodies, see
Gamgee, " Physiological Chemistry of the Animal Body," 1893, vol. ii. p. 434.

5 Baumann, Ztschr. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 123.

6 Ber. d. deutsch. chem. Gesellsch., Berlin, 1879, Bd. xii. S. 1450.

468 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

/OH (p) /OH (p)

C6H/ = C6H/ + C02

CH2.COOH

(paraoxyphenylacetic (parakresol)

acid)

/OH (p) OH

2C6H4<^ + 30, = 2C6H/ + 2C02 + 2H20

V-/-tLo XI

(parakresol) (phenol)

By a process of reduction, the oxy-acids probably yield the phenylpropionic
and phenylacetic acids which have been found, thus : —

/OH (p)

G6H / + 2H = C6H5. CH2.COOH + H20

XCH2.COOH

(paraoxyphenylacetic (phenylacetic

acid) acid)

Aromatic bodies found in putrefaction not formed from tyrosine. — Indol,
skatol, and skatolcarbonic acid are not formed by bacterial action on tyrosine,
and their mode of formation is not very clearly known. According to
Baumann,1 they are not primary products of bacterial action on the proteid
molecule, but are formed in the decomposition of an intermediate body, which
is soluble in a mixture of alcohol and ether. E. and H. Salkowski 2 support
this conclusion. Nothing further is known of this intermediate substance,
except that it is not peptone. Neumeister 3 considers it possible that these
substances may be synthetically built up by the bacteria from simpler aromatic
compounds. Indol and skatol are formed from this mother substance in
varying proportion, probably due to the action of different bacteria, but these
have never been isolated.

Indol, skatol, and skatolcarbonic acid belong to the indigo group of aromatic
compounds. Indol on oxidation yields indoxyl, and on further oxidation,
this yields indigo blue. By an inverse process of reduction from indigo blue,
indol can be obtained.4 To indol and skatol the faeces owe to a great extent
their peculiar unpleasant odour.

Indolf CfHX /CH, crystallises from water in small scales (M. P.,

52° C., B. P., 245° - 246° C.). It is fairly soluble in hot, less so in cold water,
and is easily soluble in alcohol, ether, chloroform, benzol, and petroleum ether.
It distils over with steam ; this property may be used to separate it from
other putrefaction products.6 In long-continued putrefaction, indol gradually
disappears ; according to Salkowski, this is due to evaporation.

Indol may be recognised by the following tests : —

1. A wooden match moistened with strong hydrochloric acid and then
dipped into an alcoholic solution of iridol turns a cherry-red colour.

1 Ber. d. deutsch. chem. Gesellsch., Berlin, 1880, Bd. xiii. S. 284.

2 Ztschr. f. pliysiol. Chem., Strassburg, 1884, Bd. viii. S. 454 ; see also Nencki and Bovet,
Monatsh.f. Chem., Wien, 1889, Bd. x. S. 506.

3 "Lehrbuch. d. physiol. Chem.," Jena, 1893, Th. 1, S. 209.

4 Nencki, Ber. d. deutsch. chem. Gesellsch., Berlin, 1875, Bd. viii. S. 722 ; Baumann,
u. Brieger, Ztschr. f. physiol. Chem., Strassburg, 1879, Bd. iii. S. 254.

5 Baeyer, Ann. d. Chem., Leipzig, Bd. cxl. S. 295 ; Supp. Bd. vii. S. 56.

6 For method of isolation from these, see Gamgee, "Physiological Chemistry, etc.," vol. ii.
p. 421 ; orE. and H. Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1884, Bd. viii. S. 417.

ACTION OF INTESTINAL BACTERIA ON PROTEIDS. 469

2. An aqueous solution of indol treated with fuming nitric acid turns a
bright red colour, and on standing a red precipitate is formed.

3. When sodium nitroprusside is added to a very dilute solution of indol,
and afterwards caustic soda, the mixture turns a deep violet-blue, passing into
a pure blue on making faintly acid with acetic acid, and disappearing with
excess of acid (Legal's reaction).1

/xn.

Skatol,2 C6Hy />CH, is methyl-indol ; it crystallises in similar form

to indol (M. P., 95° C., B. P., 265° - 266° C.). It also possesses much the
same solubilities as indol, and is volatile with steam. Passed through a red-
hot tube, it decomposes and yields indol.

It is distinguished, in addition to its physical properties, by the following
tests : —

1. Instead of a red precipitate, as in the case of indol, it gives a milky
turbidity when treated with fuming nitric acid.

2. In Legal's test (vide supra) it gives an intense yellow, turning violet
with acid.

3. It dissolves in concentrated hydrochloric acid, giving a highly coloured
solution.

Both indol and skatol, dissolved in benzol in concentrated solution, give,
with a saturated solution of picric acid in benzol, a crop of fine red crystals.
When the compound of indol and picric acid is treated with caustic soda, and
distilled, the indol is decomposed ; under similar conditions the skatol picric
acid compound yields skatol which is not decomposed.

/ NH\

Skatol carbonic acid,3 CflH4<^ /C'COOH, crystallises in scales (M. P.,

NT1 PIT S/

NU.UH3'

164° C.), sparingly soluble in water, easily soluble in alcohol and ether. Heated
above its melting point, it breaks up into skatol and carbon-dioxide.
It may be identified by the following tests : —

1. Its aqueous solution, treated with pure nitric acid and afterwards with
potassium nitrite solution, turns a cherry -red colour, and deposits a red pre-
cipitate, which is dissolved by acetic ether.

2. Its aqueous solution, treated with an equal volume of hydrochloric acid
(sp. gr. 1'2), and afterwards with dilute bleaching powder solution, gradually
turns a purple-red colour, and, after long standing, deposits a purple-red
precipitate, easily soluble in alcohol.

3. A very dilute solution (1 in 10,000 of water), treated with a few drops
of hydrochloric acid, then with a few drops of a very dilute solution of ferric
chloride, and heated, gives an intense violet colour. More concentrated solution
gives an intense cherry-red colour.

The aromatic compounds resulting from bacterial decomposition in the
intestine are to a considerable extent absorbed. Tyrosine absorbed as such
disappears ; it is decomposed and completely oxidised in the tissues without
the formation of urea. The non-nitrogenous substances resulting from its de-
composition by bacteria (as well as indol and skatol) are not completely
oxidised, but are excreted in modified form in the urine, combined chiefly
with sulphuric acid, as ethereal sulphates, but also in part with glycocoll and
glycuronic acid. In this way the poisonous properties of the phenols and
similar compounds are removed, for the ethereal sulphates formed are very

1 Breslau. arztl. Ztschr., 1893.

2 Brieger, Ber. d. deutseh. chem. Gesellsch., Berlin, 1877, Bd. x. S. 1028.

3 E. and H. Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1885, Bd. ix. S. 8.

470 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

stable compounds, which are excreted unchanged ; thus phenol and kresol are
eliminated as potassium salts of phenylsulphuric acid and kresolsulphuric

/OC6H5 /OCGH4-CH3

acid respectively, SO./ , S02<\ •

XOK XOK

Indol and skatol are to a considerable extent excreted with the faeces.
The portion which is absorbed is first oxidised, yielding indoxyl and skatoxyl,
and these are then united to form sulphates with potassium-hydrogen sulphate,
thus : —

/CH.X /C-OEL /O(OS(Xj.K)

CflH/ CR CflH/ CH C6H

(indol) (indoxyl) 9 (potassium indoxylsulplmric acid)

The aromatic oxy-acids in part are found in the urine as simple salts,
and in part combined with sulphuric acid. The simple aromatic acids (phenyl-
acetic and phenylpropionic acids) are chiefly found united with glycocoll.
The phenylpropionic acid is first changed into benzoic acid, and then unites with
glycocoll to form hippuric acid (benzoylglycocoll, C6H5.CONH.CH2.COOH).
The phenylacetic acid unites directly with glycocoll to form phenaceturic
acid (C?H5.CH2.CO— NH.CH2.COOH).

Besides these substances belonging to the aromatic series, there are formed,
during the putrefactive decomposition of proteids, a number of substances
belonging to the fatty series. The chief of these are leucine, the ammonium
salts of a number of volatile fatty acids (caproic, valerianic, and butyric),
methane, hydrogen, sulphuretted hydrogen, and methylmercaptan (CH3.SH).

Action of the intestinal bacteria on carbohydrates.— The carbo-
hydrates suffer much more bacterial decomposition in the intestine
than do the proteids. Not only are the sugars formed in digestion
attacked, but starch is directly attacked by some bacteria,1 and
cellulose, so far as it is decomposed, owes its changes to bacterial action.
The products formed in such bacterial actions on the carbohydrates
are simpler in their composition than those produced during putrefaction ;
they consist chiefly of ethyl alcohol, lactic (active and inactive), butyric,
and succinic acids, accompanied by carbon-dioxide and hydrogen.

Nencki, Macfadyen, and Sieber2 isolated seven different intestinal
bacilli, of which five acted only on carbohydrates (dextrose), and the
other two mainly on proteids.

Cellulose is altogether unattacked by any of the digestive juices in
vitro ; nevertheless it disappears to a very considerable extent in natural
digestion. Experiments on herbivora show that 60 to 70 per cent, of
the cellulose disappears,3 and even shavings and paper mixed with hay
and given to sheep only partially reappear in the faeces. Experiments
on man show that, according to the condition and form of the cellulose,
amounts varying from 4 to 60 per cent, are digested.4

Of the manner in which this cellulose is broken up or dissolved we
know nothing with certainty. Bunge 5 supposes that the epithelial cells

1 Wortman, Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 293 ; Lander Brunt on
and Macfadyen, Proc. Roy. Soc. London, 1889, vol. xlvi. p. 542.

2 Arch.f. exper. Path. u. PharmaJcol., Leipzig, 1891, Bd. xxviii. S. 311. Reprinted in
Journ. Anat. and Physiol., London, 1891, vol. xxv. p. 390.

3 Haubner, Ztschr. f. Landwirthschaft, 1885, S. 177.

4 Weiske, Ztschr. f. Biol., Miinchen, 1870, Bd. vi. S. 456 ; v. Knieriem, ibid., 1885,
Bd. xxi. S. 67.

5 " Lehrbuch der physiol. n. path. Chem.," 1894, S. 174.

A CTION OF INTESTINAL BA CTERIA ON FA TS. 471

of the intestine possess the function, by means of a ferment, of dissolving
the cellulose ; this may be so, but no such ferment has ever been shown
to exist. Bunge supports his suggestion by analogy with the action
of some unicellular organisms on cellulose.1

Exposed to the action of certain organisms, cellulose undergoes
fermentation with the setting free of marsh gas (CH4), and the forma-
tion of acetic and butyric acids ; how much of the altered cellulose goes
in this way in the digestive process is unknown. Tappeiner2 tested
the action of the intestinal bacilli on cotton-wool, by soaking this in a
1 per cent, solution of bouillon and inoculating with the bacilli. Fer-
mentation with development of gas commenced, and there were formed
in the solution free fatty acids (up to and including valerianic acid),
while the cotton-wool nearly all dissolved. The gases set free were
marsh gas and carbon-dioxide. The nature of the products varies with
the organism acting on the cellulose ; thus Hoppe-Seyler 3 obtained the
same gases accompanied by a dextrin-like substance, by the action of
pond bacteria on cellulose in the form of filter paper, but did not observe
the formation of any fatty acids.

Experiments on the artificial digestion of cellulose in the form of
new hay were made by Hofrneister,4 who showed that the intestinal
juices of the horse were capable of dissolving nearly 80 per cent, of this
material. No formation of sugar but some fermentation and develop-
ment of gas were observed.

The most important uses of cellulose lie, however, not in its value
as a nutrient foodstuff, but in giving bulk and looseness to the food and
in mechanically inducing peristalsis by irritation of the intestine.5 For
this reason cellulose becomes an absolute necessity for animals with a
long intestine, such as the herbivora. Eabbits fed on food free from
cellulose rapidly die from intestinal inflammation ; but if the same food
be mixed with such an inert substance as horn shavings, nutrition goes
on quite normally, and the animals continue in perfect health, although
the horn shavings remain entirely unaltered.6 The carnivora with their
short intestine require no such aid to peristalsis ; but in animals in an
intermediate position, such as man, bulky or cellulose-containing food,
while not indispensable, is from a dietetic point of view exceedingly
desirable.

Action of the intestinal bacteria on fats. — Under a normal con-
dition of the intestine, it is probable that very little decomposition of
the fats by bacteria takes place, but under abnormal conditions, such
as the absence of the bile or pancreatic juice, they are almost completely
decomposed into fatty acids, which pass out unabsorbed along with the
faeces. The first action of bacteria on fats consists in setting free the
corresponding fatty acids ; these are afterwards partially broken down
into mixtures of fatty acids lower in the series.7

Lecithins undergo a similar decomposition by bacteria under anae-
robic conditions ; they at first are split up into glycerophosphoric acid,
fatty acids, and choline. Afterwards, the choline is decomposed with

1 E.g., Vampyrella ; Cienkowski, Arch. f. mikr. AnaL, Bonn, 1865, Bd. i. S. 203.
3 Ztsclir. f. Biol, Mlinchen, 1884, Bd. xx. S. 52 ; ibid., 1888, Bd. xxiv. S. 105.

3 Ztsclir. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 401.

4 Arcli.f. wissensch. u. prakt. Thicrh., Berlin, 1885, Bd. xi. S. 46.

5 Bunge, "Physiological and Pathological Chemistry," 1894, p. 75.

6 v. Knieriem, Ztsdir. f. Biol., Miinchen, 1885, Bd. xxi. S. 67.

7 Groger, Ztsclir. f. ang. Chem., Berlin, 1889, S. 62.

472 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

formation of carbon-dioxide, methane, and ammonia ; but if air is present,
neurin and muscarin are also formed in the process.1

COMPOSITION OF FAECES.

Amount and consistency. — The consistency of the contents of the
small intestine in the upper two -thirds to three -fourths of its length
is fairly uniform, the amount of water absorbed in this part being
approximately balanced by that added in the digestive fluids. But
in the lower part of the small intestine the amount of water absorbed
begins to exceed that secreted ; the intestinal contents become
thicker, and the thin fluid, with lumps of solid, undigested, or
partially digested food of various kincls floating in it, which is usually
found in the higher part of the intestine, is replaced by a pasty
or semi-solid mass. As this mass passes along the large intestine the
process of absorption continues with increased intensity, and a large
amount of water, together with anything it holds in solution of service
to the economy, is removed. The residue, a complex mixture of various
useless or unused material, usually acquires the consistency of a soft
solid before the completion of the process, and is finally ejected from the
rectum. The consistency of the faeces, as well as the amount excreted
per diem, varies within wide limits, with the character of the food
and the duration of its passage through the intestine. Even in the
rectum the process of absorption goes on, and faeces retained here become
dry and hard. The faeces passed on a vegetable diet, or on a diet con-
taining a liberal allowance of vegetables, are both much softer (i.e.
contain more water) and much greater in total quantity of dry solids
than those on a meat diet alone. The increase in the quantity of solids
is due to the vegetable food containing a much higher percentage of
undigestible tissue. The softer consistency arises from the stimulation of
the mucous membrane by the undigested remnants of the vegetable
tissue, causing increased peristalsis, so hastening the transit through the
intestine, and shortening the period of absorption. This stimulating
action of vegetable food adds greatly to its value in a mixed diet. In
consequence of the absence of this stimulus, the period of defaecation
is greatly prolonged on a purely flesh diet, and may only take place
at intervals of several days. The amount of faeces daily excreted by
man on a mixed diet averages, according to Voit,2 120 to 150 grms.,
containing 30-37 grms. of dried solids ; on a vegetarian diet, the
average amount obtained was 333 grms., containing 75 grms. of dry
material.

Colour. — The colour of the faeces varies greatly, being mainly influ-
enced by the nature of the food. On a diet of meat, the colour is dark
brown to pitch black, due to haematin and to ferrous sulphide, formed
by the action on haemoglobin-derivatives, of sulphuretted hydrogen
generated by bacteria in the intestine. Administration of iron or
bismuth salts produces a similar effect. A liberal allowance of bread,
especially of the coarser varieties, in the food, gives rise to light yellow-
coloured faeces. Fat, when eaten in greater quantity than the animal
requires, is excreted with the faeces chiefly as fatty acids and soaps, and

1 Hasebrock, Ztsclir. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 148.
*Ztschr.f. Biol., Mlinchen, 1889, Bd. xxv. S. 264.

COMPOSITION OFFICES. 473

causes the faeces to have a yellowish or clay-coloured appearance.
Such fatty stools also result when imperfect fat absorption is caused by
stoppage of the bile duct. The derivatives of bile pigments also con-
tribute to the colour of the faeces,1 and part of the brown colour of
normal faeces arises from these, although it is probably due in greater
measure to haematin. Administration of calomel, by arresting bacterial
decomposition, prevents the reduction of the bile pigment, which then
appears in the faeces as biliverdin, and produces a green colour. The
similar colour of meconium shows that bacteria are absent in the foetal
intestine. Green-coloured faeces are also excreted for some time after
birth, until the normal bacteria of the intestine gradually acquire
possession, when the biliverdin is reduced and the faeces assume a brown
colour.

Reaction. — The reaction of the faeces is also variable. According to
Hammarsten,2 they may often be alkaline on the surface, from contact
with the intestinal mucous membrane, while acid within the mass.
Gamgee 3 states that the faeces in man are normally alkaline, and very
exceptionally present an acid reaction. Wegscheider 4 found the faeces
normally acid in infants.

Composition. — The faeces are an exceedingly complex mixture, con-
taining substances of various origin and constitution, soluble and
insoluble, derived from the food, the bile, and the detritus of the in-
testinal surface.5 The number of these components is so large, and the
amounts in which they are present so variable, that tables of quantitative
composition possess little value.

The undissolved substances consist of fragments of undigested food,
such as pieces of vegetables, muscle fibres, connective tissue, elastic
fibres, and small masses of casein and fat. The amount of these is
largely increased when the supply of food taken in is more than
sufficient to satisfy the demands of the body. A microscopic examina-
tion further shows epithelial cells derived from the intestine, starch
granules, fat globules, and occasionally crystals of magnesium and
calcium phosphates, and of ammonia-magnesium phosphate. Besides
these, there is present the indigestible residue of various foodstuffs,
such as iiucleins from nucleo-proteids, keratin from epidermal struc-
tures, and haematin from haemoglobin.

The mineral salts present vary with the food, but consist chiefly of
the phosphates of the alkaline earths, with small quantities of silica and
phosphate of iron.

The other constituents include mucin, derived from the various
secretions, mainly from the mucous membrane of the intestine ; indol,
skatol, volatile fatty acids, ammonia, sulphuretted hydrogen, and methane,

1 There is some difference of opinion on this point. Gamgee ( ' ' Physiological Chemistry of
the Animal Body," vol. ii. p. 458) states that the brown colour of normal faeces is due to
hydrobilirubin ; Hammarsten ("Lehrbnch der physiol. Chemie," Ann. 3, S. 283), that the
decomposition products of the bile pigments have little influence on the normal colour of
the faeces.

" Lehrbuch der physiol. Chemie," Aufl. 3, S. 284.

3 "Physiological Chemistry of the Animal Body," vol. ii. p. 457.

4 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1876, Bd. vi. S. 482.

5 The mucous membrane of the intestine and its secretion furnish a considerable quota
to the faeces ; this is shown by an experiment due to Hermann (Arch. f. d. ges. Physiol.,
Bonn, 1890, Bd. xlvi. S. 93), who separated a loop of intestine, cleared it of contents, sewed
its two ends together so that it formed a ring, restored the continuity of the remainder of
the intestine, and closed the wound. In a few days it was found, on killing the animal,
that this loop was filled with a mass resembling faeces in appearance.

474 CHEMISTR Y OF THE DIGESTIVE PROCESSES.

which are formed in bacterial decomposition ; 1 and the products yielded
by the bile, stercobilin, cholesterin, and traces of bile acids.2

Stercobilin* is a reduction compound of the bile pigments formed
in their passage along the intestine, and is probably identical with
urobilin and hydrobilirubin. Normally, all the bile pigment is reduced
to this substance, but bilirubin has been observed in the faeces under
pathological conditions.

Excretine is a crystalline body, described by Marcet 4 as occurring
only in human fasces. It is very soluble in boiling alcohol, and may be
mechanically thrown down from an alcoholic extract of the fasces by
adding milk of lime. The precipitate is washed with water, dried and
extracted with a mixture of alcohol and ether. On concentration of the
solution by evaporation, impure exqfetine crystallises out. This is
dissolved in hot alcohol, decolorised by animal charcoal, and obtained
pure on r eery stal lisa tion in acicular four-sided prisms, melting at 92°-
96° C. It is insoluble in water, hot or cold ; sparingly soluble in cold,
readily in hot alcohol ; very soluble in ether ; and the solutions are
neutral in reaction. Its quantitative composition gives the formula
C78H156S02. Hinterberger 5 states that, by repeated crystallisation, it may
be obtained free from sulphur, and then has the empirical formula
C20H300 ; with bromine this yields a substitution compound, C20H34Br20.

Excretoleic acid is a body described by Marcet,6 who obtained it on
cooling a hot alcoholic solution of human fasces. On exhausting with
ether, a green ethereal solution is obtained, which, on evaporation, leaves
an oily residue of a dark green colour and acid reaction, melting at
25°-26° C.

Meconium is the name given to the contents of the large intestine in
the foetus, which are expelled at, or after, birth. It is a dark brownish-
green mass of acid reaction. It contains 20 to 30 per cent, of dried
solids, which consist of mucin, bile pigments (biliverdin and bilirubin),
bile acids, cholesterin, fats, fatty acids, calcium and magnesium phos-
phates and sulphates.

In addition it contains a substance giving two absorption bands, one
to the red side of the D line, and the other, broader and darker, between
the D and E lines.

1 The odour of the fneces arises from these bodies. - See p. 391.

3 Vanlair and Masius, CcntralU. f. d. med. JVissensch. , Berlin, 1871, No. 24, S. 369;
see also under "Bile," p. 388.

4 Med. Times and Gaz., London, 1858, 1ST. S., vol. xvii. p. 156.

5 Ann. d. Chem., Leipzig, 1873, Bd. clxvi. S. 213. 6 Loc. tit.

THE SALIVAEY GLANDS.1

By J. K LANGLEY.

CONTENTS : — Anatomical Characters, p. 475— Histological Characters, p. 477 — Origin
and Course of Nerves, p. 479 — Changes during Secretion, p. 485 — Reflex Secre-
tion, p. 489 — The Dyspnoeic Secretion, p. 493 — Stimulation of the Cranial
Nerve, p. 493 — Stimulation of the Sympathetic Nerve ; the Augmented Secre-
tion, p. 494 — Effect of Protracted Stimulation on the Amount and Percentage
Composition of Saliva, p. 498 — Relation of the Rate of Secretion to the Per-
centage Composition of Saliva, p. 499 — Some General Characters of Saliva, p. 501
— Substances secreted in Saliva, p. 503— Effects of the Cranial and Sympathetic
Nerves upon the Blood Flow, p. 504 — Mutual Effects of the Cranial and Sym-
pathetic Nerves upon Secretion, p. 506 — Effect of Variations in the Amount
and Quality of the Blood supplied to a Gland, p. 508 — Relation of Secretion to
the Flow of Lymph, p. 510 — The Secretory Pressure, p. 511 — Reflex Inhibition
of Saliva, p. 512 — The Action of Alkaloids, p. 512 — Formation of Heat, p. 516
—Electrical Changes, p. 517 — Section of Glandular Nerves ; the Paralytic
Secretion, p. 519 — Secretion due to Reflex Action of Peripheral Ganglia, p. 523
— Direct Irritability of Gland-Cells, p. 524 — Extirpation of the Glands ; injec-
tion into the Blood of Saliva and of Gland Extracts, p. 524 — General Con-
siderations ; theories of the Mode of Action of Secretory Nerves, p. 525.

SOME ANATOMICAL CHARACTERS OF THE SALIVARY GLANDS.

IN the dog and cat, the sublingual gland enlarges at its end, and
loses its flattened form ; the enlarged end is closely attached to the sub-
maxillary gland, and is enclosed in the firm capsule of this gland, so that
at first sight it appears to form part of it.

The ducts from the lobules of the submaxillary gland unite, either
in the connective tissue which stretches from the hilus of the gland, or
in the hilus itself. The gland duct — the duct of Wharton — runs from
the hilus to its opening underneath the tongue, without receiving, except
in rare cases, any further accession.

The sublingual gland in about its anterior two-thirds consists of
flattened lobules, the ducts of which enter the main duct on its course

1 Physiological investigations on the salivary glands have, for the most part, been
carried out on the larger glands, namely, the submaxillary, the parotid, and the sublingual.
But such conclusions as we may be able to form with regard to these, we may apply with
little change to the numerous smaller glands which pour their secretion into the mouth
and pharynx, and, indeed, to the lachrymal glands and glands of the nasal mucous mem-
brane also. Both in histological and physiological characters the lachrymal gland
resembles an albuminous salivary gland. It receives cranial secretory fibres by way of the
lachrymal branch of the fifth nerve ; the origin of these fibres from the medulla has not
been investigated. It receives sympathetic fibres by way of the cervical sympathetic and
the blood vessels of the gland. Secretion can be produced reflexly by stimulating most,
if not all, sensory nerves.

The animals on which investigations have been made are chiefly the dog, cat, and rabbit,
the horse, ox, and sheep.

476 THE SALIVAR Y GLANDS.

past them. Thus the gland has no proper hilus. The duct runs parallel
to and a little laterally of Wharton's duct.

The main blood supply, both to the submaxillary and the sublingual
gland, is derived from a branch given off by the external maxillary
artery. The submaxillary division of this branch runs to the hilus of
the gland, and there divides. The submaxillary gland receives also one
or two small branches from the great (or posterior) auricular artery,
where this curls round the digastric muscle.

The veins of the submaxillary gland are variable in position, and
somewhat variable in number. There are generally two ; they run a
short course, about half a centimetre, and then one enters the internal,
and the other the external, maxillary vein, a little before these unite to
form the external jugular vein.

In the dog and cat there is a fairly large gland situated in the orbit,
and hence called the orbital gland. Its duct opens near the second
upper molar tooth. The orbital gland corresponds to the large buccal
gland, which in some animals is called the superior molar.

In the rabbit, the only point we need mention is that the parotid
gland consists of two larger and thicker portions, a medial and a lateral,
connected by a thin central portion. By appropriate arrangement, the
thin central portion can be observed under a microscope, and the appear-
ance of the gland cells in life, and the variations of the blood flow in
varying conditions, can be observed.

Occasionally in the dog, and more constantly in some other animals,
for instance the guinea-pig, a small gland, called by Klein l the inferior
admaxillary, pours its secretion into the duct of the parotid. It
may be regarded as a separated lobule of the parotid gland, although
its secretory cells are mucous, instead of being albuminous, thus
differing from the parotid secretory cells in general (cf. below, p. 478).

In a considerable number of animals, a small mucous gland is
attached to the outer anterior end of the submaxillary gland. This
was described by Klein in the guinea-pig, and called by him the superior
admaxillary. The duct of this gland, according to Eanvier, runs parallel
to and on the outer side of Wharton's duct, but does not join it. He
calls it the retrolingual gland.

Ranvier 2 considers that the customary use of the term sublingual gland is
in many cases erroneous. The sublingual, lie defines as a gland which has a
number of separate ducts — the ducts of Rivini. But, besides the sublingual,
another gland occurs, which he calls the retrolingual gland. This is charac-
terised by having a single duct — the duct of Bartholin — running parallel to
Wharton's duct. An animal may have both sublingual and retrolingual, as
the guinea-pig, rat, and hedgehog ; or the retrolingual may be absent, as in
man, horse, sheep, and rabbit ; or, again, the sublingual may be absent, as in
the dog and cat. Thus Ranvier considers the gland usually called the sub-
lingual in the dog and cat to be the retrolingual.

In different classes of mammals, the relative development of the
salivary glands varies. Thus in the horse the parotid is four to five times
the weight of the submaxillary gland, in the sheep and ox the weights
are not very different, in the dog the submaxillary gland is slightly
heavier than the parotid.

1 Quart. Journ. Micr. Sc., London, 1881, p. 114.

2 " Etude anatomique des glands," Arch, de physiol. norm, etpath., Paris, 1886.

HISTOLOGICAL CHARACTERS.
The following table is taken from Colin : l —

477

Weight in Grammes of — •»

Parotid.

Submaxillary.

Sublingual.

Horse ....

400

86

23

Ox

283

298

43

Sheep ....

43

36

4

SOME HISTOLOGICAL CHARACTERS OF THE SALIVARY GLANDS.

It would be outside the scope of this account to give a detailed
description of the ducts, ductules, terminal tubes, lymphatics, and other
histological features of the several glands. But some of the histological
features have so intimate a relation to physiological observations, that it
is not advisable to pass them by without notice.

The narrow ductule, proceeding from a duct, commonly divides, and
each secondary ductule widens more or less suddenly into a tube of
secreting cells ; each tube gives off curved branches, and these also may
give off similar branches ; thus, a clump of tubes is formed around the
primary ductule. The terminal tubes are usually called alveoli, and their
cells alveolar cells.

The alveolar cells may be classified according to the chemical nature
of the substances they secrete. A step in this direction was taken by
Heidenhain, who divided the cells into mucous cells which secrete mucin,
and albuminous cells which secrete some form of proteid. There is good
evidence that the typical albuminous cell does not secrete any mucin,
and there is some evidence that the typical mucous cell does not secrete
any proteid, and on this basis it is apt to be assumed that all the alveolar
cells secrete either mucin only, or proteid only. It should, however, be
remembered that this is an assumption ; it is possible that some alveolar
cells secrete both mucin. and proteid.

In any one salivary gland all the alveolar cells may be mucous or
all may be albuminous, or some of them may be mucous and some
albuminous. Further, in different glands, the relative number of the
two kinds of cells varies in nearly all possible proportions. The
nomenclature in use takes notice of the broad distinctions only. Glands
which consist almost entirely of albuminous cells are called albuminous
glands, those which consist chiefly of mucous cells are called mucous
glands. The glands of intermediate structure are commonly placed
in the class of mucous glands, unless the proportion of mucous to
albuminous cells is very small.

The term "mixed gland" was introduced for certain special cases; for example,
the submaxillary gland of the guinea-pig, in which one or more lobules were
said to be mucous and the rest to be albuminous. But in the guinea-pig, and
possibly in the other cases, the mucous lobule appears to be a separate gland
(cf. above, p. 476). It would probably be more convenient to use the term
" mixed," for a gland in which the mucous and albuminous cells are present
in approximately equal proportions. And we might have the following scale,
passing from entirely albuminous to entirely mucous : — albuminous glands,
1 "Traite" de pliysiol. compare'e des animaux," 3rd edition, 1886, tome i.

478 THE SALIVAR Y GLANDS,

muco-albuminous glands, mixed glands, albumino-mucous glands, demilune
glands, mucous glands.

The demilune cells, there can be little doubt, are albuminous
secretory cells.1 If we compare a series of submaxillary glands, passing
from albuminous to mucous, we find that the albuminous cells become
more and more confined to the ends of the terminal tubes, and the fewer
there are the more compressed they become by the mucous cells, a
feature, however, which is more marked in hardened than in fresh
glands. And when the gland secretes, the demilune cells show obvious
signs of secretory activity. The small discrete granules in them
diminish in number, and in some animals form an inner granular zone ;
in alcohol-hardened glands, the demilune cells stain more deeply with
carmine, and the nuclei and nucleoli tre more conspicuous. The cells
diminish in size after prolonged activity of the gland. In the earlier
stages of secretion they appear to be larger, but this is probably due to
a diminution in the size of the mucous cells, and so of the whole tube,
whereby the demilune cells are less flattened.

A comparison of the large salivary glands in different mammals
shows that the parotid has least variation in structure, and the sub-
maxillary gland the most.

The parotid gland, as a rule, contains albuminous cells only ; but
in the dog there are commonly, if not always, a few mucous cells,
or mucous alveoli present. And there may be in the dog a small
mucous lobule, pouring its secretion into the duct a short distance from
the main gland.

The submaxillary glands are entirely albuminous in rodents. In
primates, the majority of the cells are albuminous, but some are mucous.
In solipedes and ruminants, the glands are "mixed," but most of the
cells are mucous. In carnivora the great majority of the alveolar cells
are mucous, but some are albuminous, and there are fewer albuminous
cells in the submaxillary gland of the dog than in that of the cat;
thus in a microscopical preparation of the gland of a dog, the albuminous
cells are almost entirely in the form of demilunes, whilst in a similar
preparation of the gland of a cat, a considerable number of albuminous
alveoli are seen. In the mole, large portions of the submaxillary gland
do not even contain demilunes, and in these portions none but typical
mucous cells occur.

The sublingual gland in all animals contains a greater or less
proportion of mucous cells, and it is in consequence generally called
a mucous gland. But as it always contains albuminous cells also
it belongs properly to the class of mixed glands. The sublingual gland
has certain characters which distinguish it from the submaxillary gland.
It is more obviously tubular, the lumina are often large, the cells in a
section of a hardened specimen are more columnar, and a considerable
number of -them consist, in their ordinary resting state, of proteid
material in the outer third, half, or even two-thirds, and of mucous
material in the remaining portion next the lumen.

The orbital gland 2 of the dog is mucous, the mucous cells are large and
contain very little proteid substance, the demilunes are much flattened. The

1 Langley, Trans. Internal. Med. Cong., 1880 ; Proc. Roy. Soc. London, vol. xi. p.
364 ; and this view has been taken by most subsequent observers.

2 Cf. Lavdowsky, Arch. f. mikr. AnaL, Bonn, 1877, Bd. xiii. p. 288.

ORIGIN AND COURSE OF NERVES.

479

adniaxillary glands (Klein) have been found, so far as they have been
investigated, to be mucous glands.

One or two points with regard to the structure of the alveolar cells,
which bear- upon questions we have to consider later, we may also
mention.

In all salivary alveolar cells there are found, though with very
different degrees of distinctness, more or less spherical granules, destined
in an altered or unaltered condition to become part of the secretion.
Whether the cell substance, in which the granules are embedded, has
or has not a definite structure, we cannot decide with certainty; this
cell substance may be what we speak of as granular structureless
protoplasm ; or it may consist of two parts, — a protoplasmic part form-
ing externally a boundary layer, except perhaps towards the lumen,
and internally a delicate network ; and another part between the net-
work and the granules, which in some cells may be of an albuminous
and in others of a mucous nature.

Every gland has its own distinctive histological features, implying a
distinctive chemical character in the substance it secretes. In addition,
secreting cells of obviously different nature often occur in the same gland.
Thus, in the submaxillary gland of the rat, there is an ordinary albuminous
portion, and running through this are tubes, in bold curves, consisting of cells
with large granules, which sometimes leave an outer clear zone. And in the
submaxillary gland of the rabbit, the first cells of the alveoli, and the terminal
ductules, have in the fresh state conspicuous granules, differing widely from
the faint granules of the rest of the cells in the alveoli.

OKIGIN AND COURSE OF THE NERVES TO THE SALIVARY GLANDS.

All the salivary glands are supplied with nerve-fibres from two
sources. They receive nerve-fibres, on the one hand, from the medulla
oblongata, by way of some cranial nerve ; and, on the other hand, from
the spinal cord, by way of the cervical sympathetic.

The cranial nerve contains many, the sympathetic nerve comparat-
ively few, secretory fibres. The cranial nerve contains vaso-dilator,
and the sympathetic nerve contains vaso-constrictor fibres for the small
arteries of the glands. There is, at present, no evidence worth con-
sidering that the cranial nerves have vaso-constrictor fibres for the
glands, or that the sympathetic nerve has vaso-dilator fibres for them.

The chorda tympani. and the nerve-cells with which it is
connected. — The submaxillary, the sublingual glands, and the glands
of the tongue, receive secretory and vaso-dilator fibres from the chorda
tympani. The chorda tympani arises from the seventh nerve ; it leaves
this in the Fallopian canal, runs across the tympanum, and joins the
lingual branch of the third division of the fifth nerve. The nerve thus
formed may be called the chordo-lingual ; it extends roughly up to the
dorsal edge of the sublingual gland ; here nearly all the fibres for the
submaxillary gland, and about half of those for the sublingual gland,
leave the lingual fibres, generally in four or five delicate strands, lying
close together. These strands, with the tissue around them, are easily
dissected out as a single bundle, and the bundle of nerve strands is
called the chorda tympani, although it is a part only of the chorda
tympani proper. The chorda tympani curves backwards towards the

480 THE SALIVAR Y GLANDS.

gland ducts, and accompanies them into the glands. Other fine
filaments, coming from the chorda tympani proper, are given off from
both sides of the lingual, as it runs • forward over the sublingual
gland ; most of these end in this gland, but a few fibres, varying in
number in different animals, run back and supply the submaxillary
gland. Finally, a few fibres, from the chorda tympani proper, con-
tinue their course in the lingual, and supply the glands and blood
vessels in the area of distribution of the lingual nerve in the tongue.

On the course of the nerve filaments to the glands are a number
of small and often microscopic ganglia. In the smaller filaments these
begin a very short distance from the lingual nerve, and then occur at
intervals as far as the terminations of the ducts. Fibres from the
filaments and ganglia intermingle, ami form a plexus ; this plexus, at
first, overlies the sublingual gland, but, further on, surrounds and
accompanies the ducts, chiefly those of the sublingual gland. The
larger part of the chorda tympani passes by this plexus, and runs
direct to a ganglion in the hilus of the submaxillary gland ; where the
duct begins to divide, this ganglion gives off strands, which form
another plexus, surrounding and accompanying the divisions of Whar-
ton's duct.

Some of the ganglia in the plexus over the sublingual gland are
relatively large ; thus in the dog there is, as a rule, a ganglion, which
may be seen with the eye, in the angle between the lingual and
the chorda tympani. This was called, by Bernard, the submaxillary
ganglion ; as we shall see presently, it is more appropriate to call it
the sublingual ganglion. Another, and a larger ganglion, is that
spoken of above, as present in the submaxillary gland. As this belongs
chiefly, if not entirely, to the submaxillary gland, we may call it the
submaxillary ganglion. But it must be remembered that the nerve-
cells which occur on the course of the chorda tympani fibres, either to
the sublingual or to the submaxillary gland, are not collected together
in a single ganglion, but occur scattered at intervals on the nerve-
plexus into which the fibres run.

The nerve-cells are on the course, both of the secretory and of the
vaso-dilator fibres of the chorda tympani. This may be shown by
stimulating the chorda tympani, centrally of the nerve-cells, and
peripherally of them, before and after injecting nicotine into a vein.1
The experiment is best made in a cat. Normally, stimulation of the
chorda tympani, in any part of its course, causes a flow of saliva, and an
increased blood flow from the gland vein. After injecting a small dose
of nicotine into a vein (cf. p. 515), stimulation of the chorda tympani in
the tympanic cavity, or of the chordo-lingual nerve, has no effect. But
a rapid secretion, and a greatly increased blood flow from the gland vein
— in fact, the usual effects of stimulating the chorda tympani — are
readily obtained by stimulating the nerve plexus in the hilus of the
gland. Since no nerve except the chorda tympani is able to produce
these effects, we may safely conclude that, in stimulating the nerve-
plexus in the hilus of the gland, it is the peripheral chorda tympani
fibres which cause the secretion and increased blood flow. The amount
of nicotine given does not prevent — nor, so far as we know, affect — the
passage of a nervous impulse along a nerve-fibre, and, in consequence,
we conclude that the nerve-cells are on the course of the chorda

1 Langley, Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 123.

THE CHORDA TYMPANI AND NERVE-CELLS. 481

tympani fibres, and that nicotine either acts on the connection of the
nerve-fibres with the nerve-cells, so that a nervous impulse cannot pass
from one to the other, or acts on and paralyses the cells. The former is
the more likely, and, in accordance with what is known generally
regarding the 'relations of different nerve units, we may suppose that
the nerve-fibres divide into fibrils, which terminate on the nerve-cells,
and that these terminations are paralysed by nicotine.

I have only spoken, so far, of the effect, after nicotine injection, of
stimulating the chordo-lingual and the plexus in the hilus of the gland.
If the stimulus be applied between these two places, the effect varies in
different cases, and varies also in different animals. Broadly speaking,
as- the electrodes are passed along the chorda tympani and nerve-
plexus, towards the hilus, a point will be found where the stimulus
causes a slight secretion ; as the electrodes are passed more peripherally,
the secretion increases, but it is rarely considerable, until the hilus of
the gland is reached. This means that a few of the nerve-cells,
outside the submaxillary gland, send their axis-cylinder processes to
the gland. It may be mentioned that the relative number of these
is greater in the rabbit than in the cat, and greater in the cat than
in the dog.

Similar conclusions as to the relation of the fibres of the chorda
tympani to the peripheral nerve-cells may be deduced from the experi-
ments in which the chorda timpani has been cut, and time allowed for
its fibres to degenerate. I shall deal later with these experiments
(p. 519); and it will be sufficient to give here the chief result which
bears on the question before us. When the chorda tympani, or the
chordo-lingual nerve, is cut in a dog or cat, and the peripheral cut end,
after about four days, is stimulated, no effect is produced ; but if a little
pilocarpine be injected, a fairly copious secretion is obtained, and the
blood flow through the gland is increased. Although it is not agreed on
all sides that pilocarpine produces a secretion by stimulating the nerve-
endings in the glands, this is probably the case, and if it be so, the
experiment shows that the chorda tympani fibres have degenerated up
to the peripheral nerve-cells, whilst the fibres given off by the nerve-
cells are still intact.

The position of the nerve-cells on the course of the chorda tympani
fibres to the sublingual gland can similarly be determined. If a
sufficient dose of nicotine be given to a dog, stimulation of the chordo-
lingual nerve has no effect ; stimulation of the ganglionic nerve-plexus,
lying in the angle between the chorda tympani and the lingual nerve,
causes constantly some secretion from the sublingual gland, but none, as
a rule, from the submaxillary gland. The ganglion, called by Bernard
the " submaxillary " ganglion, is the chief ganglion of this plexus ; it
follows, from what has just been said, that, at least in the dog, this
ganglion sends fibres to the sublingual gland, but commonly sends no
fibres to the submaxillary gland. It is, then, more accurate to speak of
it as the sublingual ganglion.

It is well known that there are small groups of nerve-cells in the tongue
itself ; these, for the most part, are probably on the course of the chorda
tympani fibres to the glands, and to the small arteries of the tongue, but there
is no experimental evidence on the point.

The fibres of the chorda tympani pass through the geniculate
VOL. i. — 31

482 THE SALIVAR Y GLANDS.

ganglion, but it is probable on general grounds that they are not con-
nected with the nerve-cells of this ganglion.

The nerve-strands which leave the chordo-lingual and the lingual
nerve to run to the sublingual and submaxillary plexuses consist in
very large part of small fibres, about 2 //, to o'o /j, in diameter,1 but a few
larger up to 8 or 10 ^ are also present. In the plexuses the number of
medullated fibres decreases, and the number of iion-medullated fibres
increases in passing towards the periphery. The axis-cylinder pro-
cesses, then, of most, if not of all, the peripheral nerve-cells are non-
medullated fibres.

The large nerve-fibres may occasionally be seen to divide. They are
probably sensory fibres for the gland arising from the fifth nerve. Some
of the small fibres may also be sensory.

Cranial nerve-fibres to the parotid and orbital glands.— The
course of the secretory and vaso-dilator fibres to the parotid gland varies
in different animals.

In the dog they arise from the ninth nerve ; they run — as Jacobson's
nerve — across the tympanic cavity over the promontorium forming part
of the tympanic plexus. From the tympanic cavity they proceed to the
small superficial petrosal and otic ganglion, and thence to the auriculo-
temporal branch of the fifth nerve, and so to the parotid gland.

In the sheep and ox the origin of the secretory fibres from the
medulla is not known. They run in the buccal branch of the fifth nerve,
instead of in the auriculo-temporal, leave this at the anterior end of the
masseter muscle, and run backwards to the parotid gland along the
duct.2

There are no experimental investigations on the place of connection
with nerve-cells of the cranial fibres to the parotid gland, but it has
been supposed that this connection occurs in the otic ganglion. No
ganglion cells have been described in the parotid gland itself.

The secretory fibres for the orbital gland of the dog run in the
buccinator branch 3 of the fifth nerve, and this is all that is known of
their course.

Historical.— The history of the discovery of the course taken by the
cranial secretory fibres 4 may be briefly summarised as follows : —

In 1851, Ludwig discovered in the dog secretory fibres for the sub-
maxillary gland in the lingual branch of the fifth nerve. Eahn (and Ludwig)
obtained in the rabbit secretion from the parotid, and sometimes from the sub-
maxillary gland, on stimulating certain cranial nerve roots, after removing the
brain. They found the effective nerve-roots to be those of the seventh and of
the fifth, but their experiments do not show satisfactorily that the secretory
fibres leave the medulla by way of these nerve roots.

Bernard showed that the secretory fibres of the submaxillary glands came
from the chorda tympani and so from the facial nerve. That the chorda
tympani had some connection with the flow of saliva from the submaxillary

1 Of. Heidenhain, Arch. f. Anat. u. PhysioL, Leipzig, 1883, Supp. Bd., S. 158 ;
Gaskell, Journ. PhysioL, Cambridge and London, 1886, p. 29.

2 Moussu, Arch, de physiol. norm, ctpalh., Paris, 1880, p. 68. (Cf. this paper also for
secretory nerves of horse and pig.) Eckhard, Centralbl. f. PhysioL, Leipzig u. Wien,
1893.

3 For the method of dissection for experimental purposes, see Heidenhain, Hermann's
"Handbuch der Physiol.," Bd. v. Th. 1, S. 38.

4 Ludwig, Ztschr. f. rat. Med., 1851, N. F., Bd.i. S. 255 ; Rahn, ibid., S. 285; Schiff,
Arch. f. physiol. Heilk., Stuttgart. 1851, Bd. x. S. 581 ; Bernard, "Lecons sur la physiol. et la

THE S YMPA THETIC NER VE-FIBRES. 483

gland was suggested before Ludwig's discovery of secretory nerves, and was
definitely stated by Schiff in 1851.

The course of the nerve-fibres to the parotid gland was also investigated by
Bernard. He obtained secretion in the dog by stimulating the auriculo-
temporal branch of the fifth nerve, and a cessation of reflex secretion by ex-
tirpation of the otic ganglion. He considered that the secretory fibres came
from the small superficial petrosal nerve, and that the superficial petrosals
and the chorda tympani arose from the nervus intermedius of Wrisberg.
Abolition of the reflex secretion in the rabbit was observed by Schiff on simple
section of the small superficial petrosal. Loeb found that section of the
tympanic branch of the glosso-pharyngeal nerve (i.e. of Jacobson's nerve), or of
the roots of this nerve in the skull, also abolished the reflex secretion, so that
the secretory fibres of the small superficial petrosal come from the ninth and
not from the facial. And Heidenhain obtained copious secretion on stimulat-
ing Jacobson's nerve.

If the secretory fibres of the parotid really arise from the ninth nerve, the
majority of the early observations form a singular record of inadequate experi-
ments and hasty deductions.

The sympathetic nerve-fibres and the nerve-cells with which
they are connected. — -All the salivary glands receive nerve-fibres from
the cervical sympathetic. The fibres run from the middle or from the
lower part of the superior cervical ganglion to the external carotid
artery, and accompany its branches. On the arteries they form a plexus
having two main longitudinal strands. The nerve-plexus, though chiefly
of noii-medullated fibres, contains some medullated fibres. In the artery
to the submaxillary gland of the dog, there are twenty to thirty
medullated fibres, a few of these being 5 ,0. to 7 //» in diameter, the rest
2 (L to 3*5 p\ the fibres run past the submaxillary ganglion in the hilus,
without being, so far as can be seen, connected with it.

The sympathetic fibres both secretory and vasomotor, for the sub-
maxillary gland of the dog and cat, arise chiefly from the second thoracic
nerve, to a less extent from the third, fourth, and to a slight and vary-
ing extent from the 'first and fifth thoracic nerves.1

Langendorff2 found that four months after hemisection of the
spinal cord in the upper cervical region, the cervical sympathetic pre-
sented its normal appearance. We may conclude, then, that the
glandular nerve-fibres do not descend from a secretory centre in the
medulla, and simply make their exit by the upper thoracic nerve roots.

And there are several grounds for believing that the efferent sym-
pathetic nerve-fibres issuing from a particular nerve root are the axis-
cylinder processes of nerve-cells situated in the corresponding segment
of the spinal cord.

pathol. dti systeme nerveux," 1858, tome ii. ; Schiff, "Lehrbuch. d. Mtiskel. u. Nerven-
physiologie, " 1858-1859, S. 393; Czermak, Sitzungsb. d. k. Akad. d. Wissensch.,Wien,
1860, Bd. xxxix. S. 526 ; Beitr. z. Anat. u. PhysioL (EcTchard), Giessen, 1860, Bd. ii. S.
214 ; 1863, Bd. iii. S. 49 ; Navrocki, Stud. d. physiol. Inst. zu Breslau, Leipzig, 1865,
Heft 4, S. 123 ; Loeb, Beitr. z, Anat. u. Physiol. (Hckhard), Giessen, 1869, Bd. v. S. 1 ;
Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xvii. S. 15; Bernard, "Lecons de
physiol. operatoire," 1879.

1 Langley, Phil. Trans., London, 1892, vol. clxxxiii. p. 104.

-Arch. f. d. ges. Physiol., Bonn, 1894, Bd. Iviii. S. 165. Strictly speaking, the
experiment only shows that the great majority of the nerve fibres of the cervical
sympathetic have their trophic centre in the spinal cord below the hemisection. If even
a considerable number of fibres had degenerated, they would have been absorbed in the
time allowed, and would have left no recognisable trace.

484 THE SALIVAR Y GLANDS.

The sympathetic nerve-fibres are connected with nerve-cells in the
superior cervical ganglion. If the cervical sympathetic be cut, the end
towards the ganglion gives, in about four days, no effect on stimulation,
but stimulation of the ganglion itself or of the fibres beyond it causes
secretion and pallor of the gland (p. 522). On microscopical examination,
the nerve-fibres are found to be degenerated, as far as the ganglion
but not beyond it. Injection of nicotine causes for a time, varying with
the dose, effects like those caused by degeneration of the nerve.1 In
the cat even 5 mgrms. of nicotine may be sufficient to paralyse the cervical
sympathetic for a time, but very large amounts, e.g. 500 mgrms., do not
paralyse the nerves beyond the ganglion. From this and from other
facts we deduce that the sympathetic fibres are not connected with any
sympathetic nerve- cells peripherally gf the superior cervical ganglion ;
and there are reasons for believing that they are not connected with
any nerve-cells between the ganglion and the spinal cord. In the dog
the cervical sympathetic is much less readily paralysed by nicotine.

Secretion of saliva produced by stimulation of the medulla
oblongata. — Bernard 2 found that puncture of the fourth ventricle in
the dog causes secretion from all the salivary glands, and if the puncture
be a little above the spot, injury of which produces diabetes, the secre-
tion may be confined to the submaxillary gland, and from this gland may
be abundant. Loeb3 showed that puncture of the medulla caused a greater
secretion from the submaxillary or the parotid gland, according as the
puncture was in the region of the nucleus of the ninth or of the seventh
nerve respectively. With puncture on one side, the effect on the sub-
maxillary gland of the opposite side was much greater than on the
parotid of the opposite side. Griitzner and Chtapowski 4 observed that
stimulation of the medulla oblongata caused abundant secretion if the
chorda tympani was intact, a slight secretion if it was cut, but none
after section of both the chorda and the sympathetic.

Secretion of saliva produced by stimulation of the cerebral cortex.
— It is not clear that the cortex of the cerebral hemispheres is connected
with secretion — or indeed with any visceral phenomenon — in the way
in which it is connected with the various body movements.

Stimulation of the motor area, taking the matter broadly, causes
secretion from the salivary glands, more readily than does stimulation of
any other part of the cortex. So far as the experiments go, the region
which causes maximum secretion from the submaxillary gland causes
also maximum secretion from the parotid. Apparently the secretion
ceases on cutting the cranial secretory nerve.

The experiments in which the portions of the cortex which cause
secretion have been mapped out were made on dogs under curari.
Those who have experimented on undrugged animals find that stimula-
tion of the facial area causes no secretion so long as the resulting move-
ment is confined to the facial muscles, and Eckhard5 states that the
secretion of saliva from the submaxillary glands only begins when the
stimulus is continued long enough, or is made strong enough, to induce

1 Langley and Dickinson, Proc. Roy. Soc. London, 1889, vol. xlvi. p. 425 ; Langley,
Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 131.

2 " Le9ons de physiol. expe"rimentale," 1856, Bd. ii.

3 Op. cit., supra.

4 Arch. f. d. ges. PhysioL, Bonn, 1873, Bd. vii. S. 522.

5 Neurol. Centralbl., Leipzig, 1889, p. 65. Of. also Beitr. z. Anat. u. Physiol.
(Eckhard), Giessen, 1876, Bd. vii S. 199.

CHANGES DURING SECRETION. 485

general convulsions; he considers that the saliva obtained in the
curarised animal is due to an irradiation of nervous impulses, and not to
a localised cortical stimulation.

Kiilz l obtained no secretion from the submaxillary gland in unansesthet-
ised dogs on stimulating the facial area, unless there was general tetanus, a
condition in which Braun 2 had already observed a flow of saliva from the
mouth. Lepine and Bochef ontaine 3 obtained secretion in curarised dogs by
stimulating the anterior portion of the cortex, including the facial area. The
secretion was more abundant on the side stimulated. Bochefontaine,4 shortly
after, gave a more detailed account of the parts of the cortex from which
secretion could be induced ; secretion was obtained by stimulating spots on the
posterior part of the brain, and also by stimulating parts of the dura mater.
The experiments show little or nothing as regards the question whether there
are special areas in the cortex connected with the secretion.

Bechterew and Mislawsky 5 found, also on curarised dogs, that the region
which caused secretion when stimulated with weak currents was more limited
than that described by Bochefontaine. Stimulation of the anterior Sylvian and
anterior composite convolutions caused secretion from both the submaxillary
and parotid glands. Stimulation of the anterior limb of the sigmoid gyrus,
and of the anterior extremities of the coronal and anterior ecto-Sylvian con-
volutions, caused secretion from the submaxillary gland only. With stronger
currents, secretion was sometimes obtained from the more posterior portions of
the cortex. They found, unlike Lepine and Bochefontaine, no effect on
stimulating the orbital convolution.

CHANGES IN SALIVARY GLANDS DURING SECRETION.

The changes which occur in salivary glands during secretion are
progressive, and there is no sufficient reason for believing that the
changes which occur in the cells at the end of a day's active secretion
differ in kind from those which occur in the first ten minutes.

The evidence is, it seems to me, decisively against the view that
during salivary secretion there is a breaking down of the mucous or of
other gland cells.6 If saliva at any stage of secretion is allowed to run
into alcohol, mercuric chloride, or other hardening reagent, disinte-
grating cells are not seen in the sediment as it forms, nor nuclei beyond
those which arise from the separated cells of Wharton's duct and from
leucocytes. And in the gland itself there is at no stage any sign of
active cell division ; the nuclei undergoing mitotic division are as rare
as they are in the resting gland.7

Two fundamental changes undoubtedly take place in the gland cells
during secretion.

There is, first, an excretion of a greater or less amount of the sub-
stance which has been previously formed in the cells ; 8 this substance,

lCentralbl.f. d. med. Wissensch., Berlin, 1875, S. 419.

2 Beitr. z. Anat. u. Physiol. (Eckhard\ Giessen, 1876, Bd. vii. S. 136.

3 Gaz. med. de Paris, 1875, p. 332.

4 Arch, de physiol. norm, etpath., Paris, 1876, p. 161.

5 Neurol. VentralbL, Leipzig, 1888, p. 553.

6 It must be mentioned, however, that Heidenhain in his treatise (Hermann's
"Handbuch," 1890, Bd. v.) maintains the view originally advanced by him, that mucous
cells disintegrate to form part of the secretion.

7 Langley, Proc. Roy. Soc. London, 1886, vol. xli. p. 362 ; Bizzozero, Vircliow's Archiv,
1887, Bd. ex. S. 181.

8 Heidenhain, Arch. f. d. ges. Physiol. , Bonn, 1878, Bd. xvii. S. 43; Hermann's
"Handbuch," 1883 ; Lavdowsky, Arch. f. mikr. Anat., Bonn, 1877, Bd. xiii. S. 335.

486 THE SALIVARY GLANDS.

as it is formed, is for the most part, at any rate, stored up in the cells in
the form of granules.1

Secondly, there is a taking up of proteid material by the cells.2 This
occurs more or less exclusively in the outer part of the cells, and is the
chief cause of the formation of an outer non-granular zone.1 The taking
up of fresh proteid substance is usually spoken of as a growth of proto-
plasm ; we may use the expression as a matter of convenience, bearing
in mind that a large portion of the fresh proteid substance may be
simply deposited in interstices or larger spaces of the protoplasm.

It is probable also that, during the whole period of secretion, there is
a conversion of the newly taken up proteid into the material for
secretion, or, in other words, the protoplasm is continuously disappearing
and giving rise to granules.

The loss of granules, together \vith the growth of protoplasm, causes
the gland to become less white and less opaque to the eye.

The nucleus, as was first shown by Heidenhain, is more obvious, and the
nucleolus more conspicuous, in sections of the active gland than in those of the
resting gland. The shrunken state of the nucleus in the resting gland appears
to be due to the action of the hardening agent, for in teased glands, when the
nucleus is visible, without serious alteration in the normal form of the cell, it
is seen to be spherical. Nevertheless it is probable that there is some increase
in the organic substance of the nucleus during prolonged secretion.

During rest 3 the protoplasm decreases and the granules increase, and
it would not be unnatural to suppose that no other changes take place in
the cells but those associated with the conversion of protoplasm into a
substance ripe for excretion. The point is one of great importance for
the proper understanding of the secretory processes. Is there or is
there riot during rest any interchange between the cells and the lymph,
beyond that of the taking up of oxygen and the giving off of carbonic
acid ? There is no experimental evidence to show whether the amount of
oxygen taken up by the gland cells is so much in excess of the carbonic
acid given off, that an increase in the weight of the gland takes place ;
but this is on general grounds probable enough, to prevent us from
attributing offhand any increase in weight which may occur in a gland
during rest to its cells having taken from the lymph proteid or substance
other than oxygen.

We may take first the evidence that glands increase in weight
during rest. Obviously this is proved, if it can be proved that there is
a decrease in weight during secretion.

Heidenhain stimulated the chorda tympani on one side in a dog, and,
after obtaining a considerable amount of saliva, killed the animal by
bleeding it, separated the glands on the two sides from their capsules,
and as far as possible from connective tissue, and then weighed them.
He found that the active gland weighed less than the resting gland.

1 Langley, Journ. PhysioL, Cambridge and London, vol. ii. p. 261 ; Internal. Monatsclir.
f. Anat. u. HistoL, 1884, vol. i. p. 69 ; Proc. Roy. Soc. London, 1886, vol. xi. p. 362.

2 Heidenhain, Arch. f. d, gas. PhysioL, Bonn, 1878, Bd. xvii. S. 43 ; Hermann's
"Handbuch," 1883 ; Lavdowsky, Arch. f. mikr. Anat., Bonn, 1877, Bd. xiii. S. 335.

3 It is perhaps hardly worth while to defend the use of the word "resting" for a gland
which for some time has secreted but little, and the use of the word "active " for a #land
which for some time has been secreting more or less copiously. The words lead to no
ambiguity, and the objections to them appear to me purely pedantic. "Active" and
"resting," applied to any living tissue, are essentially relative terms ; it can hardly be
doubted that there is greater chemical change when secretion is going on than when it is not.

CHANGES DURING SECRETION.

487

Three experiments were made ; the chorda tympani was stimulated on
the left side.

Amount of Saliva
obtained.

Weight of Active
Gland.

Weight of Resting
Gland.

Experiment 1 . .

55 c.c.

5 '04 grnis.

5*06 grms.

2 . .

75 c.c.

5-42 „

6-86 ,,

3 . .

220 c.c.

5-91 „

6-36 ,,

Iii these experiments the left gland was the one that was caused to
secrete, and there is some reason to think that the left gland is normally
heavier than the right, for Bidder found this to be the case in eleven
cases, and Heidenhain in two.1 Pawlow,2 however, noticed no appre-
ciable difference in the amount of nitrogen contained by ten right
and by ten left subniaxillary glands of the dog. But so long as it is not
shown that the right gland may be normally heavier than the left, we
may fairly conclude that there is a loss of weight by the gland during
secretion and a gain of weight during rest.

The question may be approached from another side. Microscopical
examination shows decisively that during secretion the gland cells
become smaller ; they must then, taken together, decrease in weight
unless the percentage of solids in them increases. But, according to
Heidenhain, the percentage does not increase during secretion ; on the
contrary, it decreases. Thus, in one experiment upon a dog, in which
about 220 c.c. of saliva were obtained by stimulating the chorda tympani,
the percentage of solids in the resting gland was 2 8 '3 per cent., and in
the stimulated gland it was only 21 '3 per cent., so that there were 7 per
cent, less solids on the stimulated side.

This, it must be remembered, applies to the gland as a whole. In con-
cluding that there is a decrease in the percentage of solids in the actual gland
cells, we assume that the percentage composition of the glands on the two sides
is approximately the same, that there is no appreciable difference in the amount
of blood and lymph upon the two sides, and that the connective tissues in the
gland are too small in amount or too constant in composition to affect the result ;
these assumptions, however, appear to be justifiable.

The other experiments made by Heidenhain 3 were as follows : —

1. The left chorda tympani was stimulated and 75 c.c. of saliva obtained.
The right subniaxillary gland contained 23 per cent, of solids, the left gland
18 '6 per cent. — a decrease of 4 '4 per cent.

2. The left chorda tympani was stimulated and 55 c.c. of saliva obtained.
The right subniaxillary gland contained 24 per cent, of solids, the left gland
21 '5 per cent. — a decrease of 3 '5 per cent.

Heidenhain found a slight decrease also in the percentage of solids on
stimulating the cervical sympathetic.4 The time of stimulation is given, but
not the amount of saliva obtained.

1 Op. tit., p. 57.

2 Centralbl. f. PhysioL, Leipzig u. Wien, 1888, S. 137.

3 Stud. d. physiol. Inst. zu Brcslau, Leipzig, 1868, Heft 4, S. 55.

4 Op. tit., p. '66.

488 THE SALIVARY GLANDS.

1. Sympathetic stimulated for two and a half hours. The resting gland
had 25 per cent, of solids, the stimulated gland 23 '6 per cent.

2. Sympathetic stimulated for five and a half hours. The resting gland
had 25 per cent, of solids, the stimulated gland 24*4 per cent.

We may conclude, then, that during secretion the gland cells
decrease in weight, and therefore that they increase in weight during
rest. The increase in rest might be due, as we have said, to a taking up
of oxygen. But the observations of Pawlow,1 if they are well founded,
show that, whether an increase in weight due to oxygen combinations
occurs or not, there is during rest a not inconsiderable increase in the
nitrogen of the glands, and this can hardly be due to anything else than
an absorption of proteids. Pawlow estimated by Kjeldahl's method the
amount of nitrogen in the resting submaxillary gland of the dog on the
one hand, and in the stimulated gland and in the saliva secreted by it
on the other hand. He obtained saliva by stimulating the central end of
the sciatic for one and a half to five hours. In ten (right) stimulated
glands he found 1*872 grms. nitrogen. In the ten (left) non-stimulated
glands he found 2*18 grms. of nitrogen. Assuming, then, that the glands
had the same amount of nitrogen to start with, the stimulated
glands had lost during secretion about \ of their nitrogen -holding
substance. In the saliva secreted he found 0416 grms. of nitrogen,
so that presumably the glands had taken up during secretion about
01 grm. of nitrogen ; this is about ^r °f the total amount. The
numerical results are not such as we should expect from the micro-
scopical appearances of the gland cells, and it is desirable that the
experiments should be repeated.

The general characters of the cells of the lobular ducts suggest that
they are not simply the lining cells of a conducting tube, but are rather
active constituents of the gland, concerned either with adding to the
saliva as it passes by them, or with subtracting from it. There is not,
however, any clear evidence on the matter. It is true that when a con-
siderable amount of methylene-blue is injected into the blood, and the
glands are excited to secrete, small deep blue particles may be found in
the duct cells as in the alveolar cells, but methylene-blue is so readily
taken up by many tissues that little trust can be placed on this as show-
ing a secretory function. The cells of the lobular ducts contain small
granules in their outer portion,2 and, according to Mislawsky and
Smirnow,3 these granules decrease during secretion, but it does not
appear to me certain that the changes described by these authors are not
due to conditions other than secretory activity. Merkel 4 observed that
the cells with striated epithelium, i.e. most of the lobular duct cells of
the submaxillary and parotid glands, stained a deep brown when treated
with pyrogallic acid in the presence of oxygen. He considered that the
stain was due to the presence of calcium salts in the cells. This
naturally suggested that the lobular ducts with striated epithelium might
secrete calcium salts. But Werther 5 has shown that the percentage of
calcium salts in the sublingual saliva of the dog is rather greater than in

1 Centralbl.f. PhysioL, Leipzig u. Wien, 1888, S. 137.

2 Langley, Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 433. When the
granules of the duct cells swell up and become indistinct, the substance between them takes
on the characteristic striated appearance seen in hardened specimens.

3 Arch. f. Anat. u. PhysioL, Leipzig, 1896, Physiol. Abth., S. 93.

4 "Die Speichelrohren," Leipzig, 1883.

5 Arch.f. d. yes. PhysioL, Bonn, 1886, Bd. xxxviii. S. 293.

REFLEX SECRETION OF SALIVA. 489

submaxillary saliva. And it happens that the ducts with striated
epithelium are very scanty in the sublingual gland, whilst they are
numerous in the submaxillary gland.

EEFLEX SECRETION OF SALIVA IN NORMAL AND IN OTHER
CONDITIONS.

In man, more complete observations have been made on the flow
of saliva from the parotid than on that from the submaxillary gland,
since the duct of the parotid is sometimes accidentally injured, so that
the establishment of a parotid fistula becomes necessary. But some of
the conditions of flow from either gland may be readily observed, when
a cannula is simply placed in the opening of the duct of the gland into
the mouth.

In the dog, sheep, horse, and other animals, sometimes a permanent
fistula, and sometimes a temporary fistula, of one or more of the glands
is established. The observations have been made with and without the
administration of anaesthetics.

Ordinarily, between meals, the large salivary glands — except the
parotid glands of ruminants — do not secrete. But as the mucous
membrane of the mouth is constantly kept moist, saliva must constantly
be formed by the smaller glands of the mucous membrane. In some
animals the amount of this secretion is very considerable ; thus in the
horse, during abstinence, 100 to 150 c.c. of saliva are, according to Colin,1
formed in an hour. Probably during sleep the amount diminishes.
There is little doubt that this secretion is produced reflexly by conditions
affecting the mucous membrane of the mouth, and a slight increase in
the strength of the stimuli probably sets in action the larger glands also.

In ruminants there are some peculiarities. The parotid gland se-
cretes continuously (Colin,1 Eckhard 2). The secretion is most abundant
during feeding, rather less during rumination, and one-eighth to one-
fourth the rumination rate during rest.1 During rest, the submaxillary
glands secrete little or not at all, and it is a remarkable fact that
rumination does not, as a rule, cause any secretion from these glands,
although it increases the secretion from the parotid gland, and although
feeding causes a secretion from all the glands.

Colin found in ruminants a slight continuous secretion from the sub-
maxillary and sublingual glands during rest. Ellenberger and Hofmeister3
found none, but they noticed that there was occasionally a slight secretion
from the submaxillary gland during rumination, and a more copious secretion
during the act of drinking. According to these observers, there are occasional
short pauses in the parotid secretion during rest.

In ruminants, further, it has been said 4 that the secretion from the parotid
gland continues after section of all the nerves running to it. In the ox,
Moussu (1890) found that section of the buccal nerves diminished greatly,
but did not quite stop, the parotid secretion. Eckhard (1893) states that
section of these nerves does not affect the parotid secretion in the sheep ; he
found about 1J c.c. to be secreted in ten minutes, whether the nerves were
cut or no. The matter requires further investigation.

1 Op. cit. 2 ztschr.f. rat. Med., 1867, Bd. xxix. S. 74.

3 Arch.f. Anat. u. Physiol., Leipzig, 1887, Physiol. Abth., Supp. Bd. S. 138.

4 Centralbl. f. Physiol., Leipzig u. Wien, 1893, S. 365. Cf. Schwann, Beitr. s. Anat.
u. Physiol. (Eckhard}, Giessen, Bd. vii. S. 170.

490 THE SALIVARY GLANDS.

In man during hunger, the sight, smell, or idea of food is sufficient
to cause a secretion of saliva from all the salivary glands ; and
chewing insoluble substances has a similar, though apparently a less
effect.1

Secretion in this way is said not to occur in lower animals. Thus
Schiff2 found in a dog with a parotid fistula, that no flow of parotid
saliva was caused by the sight or smell of the meat the animal was
endeavouring to obtain ; when it was induced to bite a piece of wood,
the meat still being in sight, there was slight secretion from the
submaxillary gland but none from the parotid, but on placing sapid
substances in the mouth there was at once a rapid secretion. And Colin
states that, after a parotid fistula has been established in a horse, and
when the animal is in a state of hunger, there is no secretion from the
parotid when the animal is offered, but not allowed to take, corn, nor
when it masticates oakum, although mastication of corn readily causes
a secretion.

Sapid substances taken into the mouth cause more or less secretion
from all the salivary glands. In man all substances are effective, and
drinking, wine for example, is sufficient.3 Acid placed on the tongue is
apparently the most effective stimulant among the sapid substances, but
there are not sufficient observations in man as to the amount of saliva
produced by other substances, to allow a satisfactory opinion to be formed
as to the relative effectiveness of salt, sweet, and bitter 1 todies. Masti-
cation considerably increases the flow of saliva, probably by bringing
the particles into better and more frequent contact with the mucous
membrane.

Chloroform and ether when inhaled cause secretion, by stimulating
the gustatory nerve endings, and possibly also the other nerve-endings in
the mucous membranes; if given by the trachea, they do not cause
secretion. Alcohol, ether, or chloroform, when mixed with water and
held in the mouth, cause a fairly free secretion of saliva.

In carnivora, so far as the experiments go, acids (vinegar, tartaric
acid) cause the most abundant secretion ; salts, either neutral or alka-
line, a less secretion, but still a fairly copious one ; bitter substances a
much less secretion, and sugar little or even none. With sapid sub-
stances in the mouth the secretion is increased by mastication.

Thus Bernard,4 in one experiment on a dog, in which eannulae were placed
in the ducts of all three glands, obtained a copious secretion from vinegar, less
from sodium carbonate, still less from colocynth, and none from sugar or from
water. The relative elfect on the several glands was practically the same with
all the substances.

Schirf5 obtained some secretion from the parotid fistula of a dog by
placing sugar on the base of the tongue, but none by placing it on the tip.

According to Colin,6 weak acids, salts, or aromatic substances placed on
the buccal mucous membrane give rise to no appreciable secretion from the
parotid of the horse during abstinence, and do not sensibly increase the con-

1 Colin and Prompt, 1874 (see Colin, "Traite de physiol. comparee," etc., 3rd edition,
p. 1), in the case of a girl with a parotid fistula, noticed that chewing a piece of ribbon
caused a secretion of only one drop of saliva in two minutes.

2 " Lemons sur la physiologic de la digestion," 1867.

3 Colin and Prompt (1874), case of parotid fistula (cf. supra}.

4 "Lemons dc physiol. exper.," 1856, tome ii. p. 82.

5 " Le9ons sur la physiol. de la digestion,'' 1867, tome i. p. 186.
«0p. cit., p. 653.

REFLEX SECRETION OF SALIVA. 491

tinuous parotid secretion of ruminants ; but do nevertheless cause a secretion
from the submaxillary and sublingual glands. His statements, however, are not
quite consistent, and we may suppose that the difference is only one of degree.

In herbivora, mastication is performed alternately on the two sides,
the periods being usually one quarter to half an hour. In the horse, and
probably in other herbivorous animals, the secretion from the parotid is
much greater on the masticating than on the non-masticating side. In
the horse two to three times as much saliva is usually secreted on the
masticating as on the opposite side, but the ratio may be either greater
or less than this (Bernard, Colin). It seems reasonable to suppose that
this is due to the better contact of food with the mucous membrane of
that side of the mouth. According to Colin, however, there is no such
difference in the secretion of the submaxillary and sublingual glands.

The amount of saliva secreted varies with the nature of the food.
In man the data are not sufficient to form an estimate of any value,
either of the relative amount of saliva secreted from the several glands,
or of the total amount secreted in twenty-four hours. It is generally
supposed that the total amount exceeds a litre a day.1

Bernard 2 found that in the clog, when saliva was obtained reflexly,
the submaxillary gland secreted about twice as much as the parotid, and
about ten times as much as the sublingual. And these are approxi-
mately the relative amounts obtained by injecting pilocarpine. The
amounts secreted are roughly in proportion to the respective weights of
the glands.

In herbivora the volume of saliva secreted by the submaxillary and
sublingual glands does not correspond with their respective weights.
According to Colin, the parotid gland of the horse secretes fifteen to
twenty times the volume of saliva secreted by the submaxillary gland,
but is only about four times its weight. And in the ox the parotid
secretes four to five times as much saliva as the submaxillary gland,
though it is slightly less in weight (cf. Table, p. 477).

Colin estimates that in the horse the total quantity of saliva secreted
in a day is about 40 litres.

The total quantity of saliva may be estimated in two ways — (1) By com-
paring the weights of a certain amount of food before and after mastication
and swallowing, the food after mastication being collected from an ossophageal
fistula ; and (2) by noting in different experiments the quantity secreted by
each gland during a given period of feeding. Colin found, by the first method,
that a horse secreted 5000 to 6000 grins, of saliva in an hour, when fed with
hay, one-half of this when fed with grass, and one-third more than this when
fed with oats.

During digestion, according to Colin, the submaxillary gland of one side
secretes 25 to 30 c.c. of saliva in fifteen minutes; the parotid secretes 500 to
1000 (about) in fifteen minutes, if mastication takes place on this side.3

In the ox he estimates that during three hours' mastication, and five
hours' rumination, about 40 litres of saliva are secreted, and that 16 litres are
secreted during the sixteen hours of rest.

Electrical excitation of the central end of the lingual or of the glosso-
pharyngeal causes secretion from all the salivary glands. The secretion

1 Some data are given by Tuczek, Ztschr. f. BioL, Miinchen, 1876, Bd. xii. S. 534.

" Lecons de physiol. exper.," 1856, tome ii. p. 82.
3 For other observations on this point, cf. Elleaberger and Hofmeister, op. cit., supra.

492 THE SALIVAR Y GLANDS.

is less copious than that obtained by placing acids in the mouth, and it
is more copious on the side stimulated than on the opposite side.

A special relation has also been said to exist between the state of
the mucous membrane of the stomach and the secretion of saliva. Thus
it has been said that a secretion of saliva is induced by the contact of
various substances with the gastric mucous membrane.1 This, however,
is not satisfactorily proved. Braun 2 observed a dog, in which a gastric
fistula had been established, and a cannula placed in Wharton's duct.
No secretion of saliva was caused by introducing into the stomach,
flesh, acetic acid, ether, nor by irritating the mucous membrane with a
sponge.

Stimulation of the central end of the vagus has rather variable
results on the submaxillary secretion, of the dog. It usually causes
secretion after a long latent period, and the secretion may continue for
some time after the cessation of the stimulus. Oehl 3 obtained secretion
although the stimulation caused no vomiting or arrest of respiration ; the
secretion occurred from both glands, but was greater on the side stimu-
lated. Buff, as a rule, only obtained secretion when there was some
body movement.

Bernard noticed that a flow of saliva may be obtained by stimulating
the sciatic 4 and various other sensory nerves ; it may, indeed, be obtained
by stimulating any sensory nerve in the body. This reflex secretion is
abolished by deep anaesthesia ; whether it ceases coincidently with the
production of anaesthesia is, however, uncertain. According to Buff,5
the secretion does not occur in uncurarised animals, unless the stimulus
produces also a reflex body movement.

The gustatory reflex secretion is caused wholly by impulses passing
down the cranial secretory nerves. But a secretion may, in certain
circumstances, be caused by impulses passing along the sympathetic
nerve ; for example, when the central end of a sensory nerve is stimu-
lated, the secretion, so far as is known, is always accompanied by a con-
striction of the blood vessels of the gland.

In man, cases sometimes occur in which there is a permanent absence
of secretion from the large salivary glands, and from the glands of the
mucous membrane of the mouth. Such cases are rarer in men than in
women. In women the loss of secretory power usually comes on after
middle life, and may be the result of an emotional shock. For some
time pilocarpine will still cause a secretion of saliva (Hadden), but
eventually it causes none, though it still causes sweating.6 The
absence of secretion is no doubt due to a derangement of the reflex
nervous mechanism, so that impulses passing up the afferent nerves no
longer give rise to efferent impulses. The lack of normal functional
activity probably causes a gradual atrophy of the glands, and a diminu-
tion of irritability of the nervous and glandular structures, so that
eventually pilocarpine — or the amount of it which can be given safely—
no longer produces a flow of saliva.

1 For an account of papers on the reflex secretion of saliva, cf. Buff, Beitr. z. Anat. u.
PhysioL (Eckhard), Giessen, 1888, Bd. xii. S. 3.
* Ibid., 1876, Bd. vii. S. 44.

3 Compt. rend. Acad. d. sc., Paris, 1864, tome ix. p. 336. Secretion on stimulation of
the central end of the vagus was first observed by Bernard, 1859.

4 Cf. also Owsjannikow and Tschiriew, Melanges biol. Acad. imp. d. sc. de St.-Peters-
bourg, 1872, tome viii. p. 651.

5 Op. cit. 6 Hutchinson, cf. Hadden, Brain, London, 1889, vol. xi. p. 484.

THE DYSPNCEIC SECRETION. 493

THE DYSPNCEIC SECRETION.

At a certain stage of dyspnoea the saliva Hows with considerable
rapidity from all the salivary glands. The time at which it begins and
its amount are dependent upon the degree of anaesthesia. In anaesthesia,
the secretion does not usuajly begin until the stage of expiratory convul-
sions. With a large excess of anaesthetics, the animal may be killed by
asphyxia without any secretion occurring, or with only a trifling amount.
When a copious secretion occurs it is due to impulses passing down the
cerebral nerve fibres, but some secretion may be obtained after section
of these nerve fibres. In such case there is also contraction of the
glandular arteries. Whether dyspnoea is capable of producing a secre-
tion after section of the cerebral nerve and excision of the superior
cervical ganglion, has not been sufficiently investigated.

STIMULATION OF THE CRANIAL NERVE SUPPLYING A SALIVARY

GLAND.

On some general features of the secretion.— A flow of saliva can
be obtained from any of the salivary glands by electrical, mechanical, or
chemical stimulation of the cranial secretory nerves. It need hardly be
said that the interrupted current is the most effective form of stimulus.
A very weak interrupted current, which cannot be felt on the tongue, is
sufficient to cause a secretion. Within certain limits the rate of flow of
the saliva increases with the strength of the stimuli, but strong currents
rapidly injure the nerve at the point of stimulation. Even with
moderate currents a very slight shifting of the electrodes on the nerve
usually causes a marked increase in the rate of secretion, a fact which it
is important to bear in mind in collecting for analysis different samples
of saliva, secreted under different conditions.

The flow of saliva with a moderate strength of current is very rapid ;
thus the submaxillary gland in the dog may secrete in five minutes an
amount of saliva weighing as much as the whole gland.

The nerve can be stimulated electrically for half an hour to an hour,
and probably with proper precautions very much longer, without the
flow of saliva ceasing. Pilocarpine in successive doses (cf. p. 513) will
cause a secretion for, so far as we know, an indefinite time.

In protracted electrical stimulation the maximum amount of saliva
is obtained by stimulating for short periods, with short intervals of rest ;
the stimulation being stopped each time as the secretion becomes slow.
In this way in ten to twelve hours about 250 c.c. of saliva can be
obtained from the submaxillary gland of the dog, and a half to two-
thirds of this amount from the parotid. The rate of flow gradually
diminishes during the progress of the experiment. With a given
strength of current, the maximum rate of secretion is produced with a
rate of interruption of about forty a second.1

According to Wedensky, rapid shocks, such as 100 to 250 a second, cause a
change in the nerve-endings, so that they soon cease to transmit nervous
impulses. His most striking experiment is the following : — Two pairs of
electrodes are placed on the chorda tympani, shocks of moderate rate are
passed through the lower, and of rapid rate through the upper ; the secretion
1 Wedensky, Compt. rend. Acad. d. sc., Paris, 1892.

494 THE SALIVAR Y GLANDS.

soon becomes slow or stops altogether, but, on cutting off the rapid shocks
from the upper electrodes, the stimuli at the lower electrodes become again
effective, and the secretion starts once more. The results are similar to those
he obtains with motor nerves to skeletal muscle.

The real latent period of the gland cells cannot be accurately deter-
mined by any direct method, and in consequence it is customary to speak
of the interval between the moment of stimulating the nerve, and the
moment at which the movement of saliva occurs in the duct, as the
latent period. When the cranial nerve is stimulated with a weak
current, there is an obvious interval — usually two to four seconds —
between the moment of application of the stimulus and the appear-
ance of saliva in the cannula, and this is the case although the
secretion when it occurs is not scant^. When stronger currents are
used, and the secretion is copious, the latent period is much dimin-
ished. On the other hand, when the • secretion is scanty, the latent
period is very much prolonged, whatever the strength of current ; thus,
after a small dose of atropine, it may be half a minute or even more.

The percentage of organic substance in saliva obtained from differ-
ent salivary glands varies considerably ; in each, as we shall see, it
varies in different circumstances, and in each it may be small (O2
to 0*5 per cent.). But, other things being equal, the submaxillary
saliva has usually a higher percentage of organic substance than
either the sublingual or the parotid saliva.

There is a curious difference in the percentage of salts found in
different salivas. In the clog the maximum percentage of salts in the
parotid saliva is about 0'6S, in that of the submaxillary gland about
0'77, and in that of the sublingual gland about I'O.1 In the rabbit
the parotid saliva has a maximum percentage of about 0'85.2

After action of a strong stimulus.— Strong stimulation of the
cranial nerve alters the gland it supplies in such a way, that the
saliva secreted shortly afterwards lias a higher percentage of solids
than it otherwise would have had.3 Thus, in the experiment quoted
on p. 501, the first weak stimulation of the chorda, tympani caused
secretion of a saliva containing 0'52 per cent, of organic substance,
whilst, after a strong stimulation, a second weak one caused a secre-
tion having a percentage of 1/07 of organic substance.

This, however, only holds when successive small quantities of
saliva are collected; with larger quantities, as 10 c.c. to 12 c.c.,
no such after action is observed (Werther).

STIMULATION OF THE SYMPATHETIC NERVE SUPPLYING A
SALIVARY GLAND.

Ludwig4 (in 1856) discovered the secretory power of the sym-
pathetic; he obtained a secretion from the submaxillary gland of
the dog, by stimulating both the cervical sympathetic and the nerve
filaments on the gland artery.

1 Werther, Arch. f. d. ges. PhysioL, Bonn, 1886, Bd. xxxviii. S. 293 ; Langley and
Fletcher, Phil. Trans., London, 1889, vol. clxxx. p. 109.

2 Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xvii. S. 40.

3 Heidenhain, op. cit., 1878,

4 Quoted by Czermak, Sitzunysb. d. k. AJcad. d. JVissensch. , Wien, 1857, Bd. xxv. S. 3 ;
Czermak also obtained secretion on stimulating the cervical sympathetic.

STIMULA TION OF THE S YMPA THE TIC NER VE. 495

Eckhard 1 noticed tliat the saliva secreted by the submaxillary
gland, on stimulation of the sympathetic, was more viscid and con-
tained a higher percentage of solids than that obtained by stimulat-
ing the chordo-lingual.

Neither from the submaxillary, the sublingual, nor the parotid
gland of any animal does the sympathetic produce a secretion which
approaches in amount that which is produced by the cranial nerve.
Unless the gland has been secreting under the influence of the cranial
nerve, before stimulation of the sympathetic (cf. p. 496), this stimula-
tion causes secretion of a few drops only, and it may be much less.
Thus, in the dog, stimulation of the sympathetic for a minute will
ordinarily produce two or three drops from the submaxillary gland, and
perhaps half a drop from the sublingual.

In most of the earlier experiments upon the parotid gland of the
dog, either no secretion was obtained by repeated stimulation of the
sympathetic, or a total amount not exceeding a few drops. This is,
however, only a more marked instance of the slow secretion which the
sympathetic, after the first few stimuli, causes in the submaxillary and
sublingual glands of the same animal. If the parotid gland, after
sympathetic stimulation, during which no secretion or a trace only has
been obtained, be hardened, and sections be cut, the lurnina, ductules,
and duct will be found distended with secretion.

The maximum total amount of saliva is obtained by stimulating the
sympathetic for short periods, with short intervals of rest. Stimulated
in this way — say, during every other half -minute — the sympathetic will
give from the submaxillary gland of the dog ^Otri to ^th of the
quantity of saliva that would be obtained by similar stimulation of the
chorda tyinpani.

With protracted stimulation the secretion may continue slowly for several
minutes, but sooner or later it stops. Koughly speaking, and within rather
narrow limits, the amount of saliva obtained is inversely proportional to the
duration of the previous stimulus and directly proportional to the length of
the preceding period of rest. After repeated stimulation of the sympathetic,
there may be no visible secretion for half a minute to a minute after the
beginning of the stimulation, and occasionally the slight secretion which
occurs only begins after the stimulation has ceased.

Heidenhain, stimulating for a quarter of an hour during each half-hour,
obtained a secretion from each stimulation for eleven successive hours, i.e.. as
long as the experiment lasted.

In different glands, and in the same gland in different animals, the
freedom of secretion of sympathetic saliva compared with that produced
by the cranial nerve, and the percentage of organic substance in the
saliva, varies considerably. I have already mentioned that the
sympathetic causes some secretion from the submaxillary gland, and
often none from the parotid. Eelatively, rather more sympathetic
secretion is obtained from the glands of the cat and rabbit than from
those of the dog. The sympathetic saliva from the submaxillary gland
of the dog contains 1 to 3 per cent, of organic substance, that from the

1 Adrian and Eckhar J, Beitr. z. Anat. u. Physiol. (Eckhard), Giessen, 1860, Bd. ii. S. 83.
Bernard, Journ. de I'anat. et physioL, etc., Paris, 1858, tome ii. (1) p. 657, stated that
sympathetic saliva was much more viscid than chorda saliva. The sympathetic secretion
in the sheep and rabbit was noticed by v. Wittich, Virchow's Archiv, 1866, Bd. xxxvii. S. 93.

496

THE SALIVAR Y GLANDS.

parotid of a rabbit 3 to 6 per cent. In the cat the percentage of
organic substance in sympathetic saliva from the submaxillary gland is
small (about O5 per cent.), and less than that in the chorda saliva.

The percentage of salts in sympathetic saliva does not exceed the
percentage of the salts in saliva produced by stimulating the cranial

nerve.

The analyses of the parotid saliva in the rabbit have been made by
Heidenhain.1 I extract the following from one experiment : —

Parotid Gland — Rabbit.

Time of collect-
ing Saliva.

Amount of

• Saliva.

Percentage
of Organic
Substance.

Percentage of
Salts.

Saliva from stimulating both

sympathetics . . . ! 38 min.

2-6 c.c.

4-93

0-54

Pilooarpine saliva from one

gland ....

18 „

4-2 „

0-65

0-81

The sympathetic saliva in the cat 2 is, as I have said, usually less viscid
than chorda saliva. But it is possible that a strong or prolonged stimulation
of the sympathetic might give rise to a saliva with a higher percentage of
solids than the chorda saliva. I append an analysis of sympathetic and chorda
saliva in the cat, obtained by moderately strong interrupted currents.

Percentage
of Organic
Substance.

Percentage
of Salts.

Percentage
of Solids.

Chorda saliva .

0-87

0-34

1-21

Sympathetic saliva .

0-43

0-28

070

The sympathetic secretion in the cat is very much like the " augmented "
secretion of the gland of the dog (cf. infra), in that it starts quickly,
quickly becomes slow, and is watery. It differs in the rapidity of recovery
from the effect of immediately preceding sympathetic stimulation. The
maximum amount of secretion is obtained by stimulating fifteen seconds out
of every thirty, or even for shorter periods.

In certain circumstances the sympathetic may produce a brief rapid
secretion from any or all of the salivary glands. That is the case when
it is stimulated shortly after stimulation of the cranial nerve. There is
a rush of saliva, quickly following the sympathetic stimulation, reaching
its maximum in a few seconds, and, after about seven to ten seconds,
rapidly declining. A very brief stimulation of the cranial nerve is
sufficient to increase in this way the amount of saliva obtained from
the sympathetic. And thus, if the cranial nerve and the sympathetic
nerve be stimulated alternately, a not inconsiderable quantity of

1 Arch.f. d.ges. PhysioL, Bonn, 1878, Bd. xvii. S. 38.

2 Langley, Journ. PhysioL, Cambridge and London, 1878, vol. i. p.
p. 92.

1885, vol. vi.

STIMULA TION OF THE S YMPA THE TIC NER VE, 497

sympathetic saliva may be obtained. It is convenient to have some
name for this unusually rapid sympathetic secretion, and I have called
it the augmented secretion)-

In the dog, the saliva of the augmented secretion is, in its physical
characters and apparently in its percentage composition, intermediate
between sympathetic saliva and that obtained by stimulating the
cranial nerve.

The augmented sympathetic saliva from the submaxillary gland of
the dog is three to ten times as abundant as ordinary sympathetic,
saliva. In fifteen seconds about \ c.c. is usually secreted, but there
may be as much at J c.c. The amount of the augmented secretion from
the parotid is one-third to one-half that of the submaxillary gland.

The augmenting effect of stimulating the cranial nerve disappears
in time, although the sympathetic is not stimulated in the interval.
In the submaxillary gland of the dog the greater part of the effect dis-
appears in ten to fifteen minutes. In the parotid, it has usually com-
pletely disappeared in ten minutes. The rate of disappearance does not
seem to be affected by the injection of atropine.

Mere vascular dilation does not cause an augmented secretion, for
if atropine be given in sufficient quantity, to paralyse completely the
cranial secretory nerves, stimulation of the cranial nerve, which still
gives largely increased blood flow, does not increase to any considerable
extent the sympathetic saliva obtained subsequently.

When the sympathetic nerve is stimulated two or three times in
succession for rather short periods, say of thirty seconds, the augmenting
effect of a preceding cranial nerve stimulation does not necessarily cease
with the first stimulation, but is visible, though to a much less degree, in
the second, and it may be in later stimulations. In the case of the dog's
parotid the third stimulation usually gives no secretion at all.

The following extracts from the notes of experiments will illustrate the
statements made above with regard to the augmented secretion : —

Submaxillary Gland — Dog — Stimulation of the Sympathetic after moderate
Stimulation of the Chorda Tympani.

Saliva secreted in mm. during

successive 30 sees., 35^ mm.

= •25 c.c li 1J 1 1 53^ 20 1 20 4 2 1

Nerve stimulated . . . Sy. Cli. Sy.

In the second sympathetic stimulation the flow of saliva was 16 mm.
during the first fifteen seconds, and 4 mm. during the second fifteen seconds.

Submaxillary Gland — Dog — Stimulation of the Sympathetic after brief
Stimulation of the Chorda Tympani.

Saliva flow every

30 sees, in mm. 0510 15 1000 Hi

Nerve stimulated Ch. Sy. Sy.

(for 2 to 3 sees.)

Longer stimulation of the chorda tympani has little effect upon the
maximum rate of flow of the augmented secretion, but it leads apparently to a
less rapid fall after the maximum is attained.

1 Journ. Physiol., Cambridge and London, 1889, vol. x. p. 291.
VOL. I. — 32

498

THE SALIVARY GLANDS.

Parotid Gland — Dog — Stimulation of the Sympathetic after Stimulation
of Jacobson's Nerve.

Saliva flow every
30 sees, in mm.
Nerve stimulated

35
J.

14 1 3

000

Sy.

76

minutes

0 0 32 0

J.

Sy.Sy. J.

10

Sy.

A brief rapid increase in the flow of saliva is obtained by stimulating
the sympathetic during the action of pilocarpine and other alkaloids
which cause a continuous free flow of saliva. After the first rapid rise
the secretion becomes slower, and in the parotid gland of the dog stops
altogether ; in the submaxillary gland the secretion slowly continues.

Parotid Gland — Dog — Pilocarpine Injected.
Rise of saliva 6 6 35 7 3 0 0

stim. symp.

EFFECT OF PKOTRACTED STIMULATION ON THE AMOUNT AND
PERCENTAGE COMPOSITION OF SALIVA.

During protracted stimulation, as was shown by Becker and Ludwig,1
the percentage of solids in the saliva diminishes. They found a marked
diminution in the percentage of organic substance ; and generally, but
not always, some diminution in the percentage of salts. The most striking
experiment given by them is the following. The chorda tympani was
stimulated, and successive portions of the saliva were analysed : —

Amount
of Saliva

Percentage of
Organic

Percentage
of

Percentage
of

Collected.

Substance.

Salts.

Solids.

1st portion ....

10-6

1-19

079

1'98

2nd „ ....

13-2

1-26

0-63

1-89

3rd ,,

14'4

0-62

0-54

1-16

4th

13-9

0-27

0-48

075

The decrease in the percentage of salts is probably connected, as
Heidenhain has pointed out, with the slower rate of secretion of saliva
in the later portions collected.

Heidenhain 2 showed that the percentage of solids sinks during pro-
tracted secretion, not only in chorda saliva,3 but also in sympathetic
submaxillary saliva. In the following experiment the sympathetic was
stimulated at short intervals during five and a half hours ; the first and
the last portions of saliva collected were analysed : —

Time of
Collection.

Amount
Collected.

Percentage
of Solids.

First portion .

80 minutes

0-68 grm.

373

Last ,,

88 „

0-89 „

1-49

1 Ztschr.f. rat. Med., 1851, N. F., Bd. i. S. 278.

2 Stud. d. physiol. Inst. zu Breslau, Leipzig, 1868, S. 65.

3 We have to refer so frequently to the saliva obtained from the submaxillary gland —
(1) by stimulating the chorda tympani, (2) by stimulating the sympathetic, (3) by
injecting pilocarpine — that we are driven to adopt the terms, chorda saliva, sympathetic
saliva, and pilocarpine saliva, for the saliva obtained respectively in these circumstances.

RELATION OF RATE TO PERCENTAGE COMPOSITION. 499

He l showed, further, that in parotid saliva, obtained by stimulating
Jacobson's nerve, there is similarly a decrease in the percentage of solids
as the secretion goes on, and, no doubt, it is a general rule for all
salivary glands.

KELATION OF THE KATE OF SECRETION TO THE PERCENTAGE
COMPOSITION OF SALIVA.

Heidenhain2 investigated the relations existing between the rate of
secretion and the percentage composition of saliva. He showed that an
increase in the rate of secretion was accompanied by an increase in the
percentage of salts, and this whether the gland had secreted for a long
time or for a short time.

An example of this is given in the following experiment, in which the
chorda tympani was stimulated with currents of varying strength, and a few
c.c. of saliva collected in each case. The samples of saliva are arranged in the
table in the order of their rate of secretion : —

Order of sample

Mean rate of secretion

per min. in c.c. .
Percentage of salts .

•15
•34

•18
•29

•19
•25

•22
•32

1-6
•37

2-0

•58

2-2

•44

2-5
•57

3'2

•58

It will be noticed that the percentage of salts does not quite go hand
in hand with the rate of secretion. But it is almost impossible to keep
the rate of secretion constant during the time of collecting a sample of
saliva, and to this the divergences may, in the main, be attributed.

A closer relation between the rate of flow and the percentage of saliva was
observed by Werther,3 and by Langley and Fletcher.4 Heidenhain found the
percentage of salts to have an upper limit, with increased rate of secretion.
This he gave as *5 to '6 per cent., though in one case '66 per cent, was found.
Becher and Ludwig had earlier found in one case '78 per cent. Werther, and
Langley and Fletcher found the maximum percentage to be *77. From the
observations of the latter, it appears that the faster the rate of secretion, the
less increase there is in the percentage of salts for a given increase in rate of
secretion. This is indicated in the following table : —

Rate of Secretion per
Minute in c.c.

Percentage of Salts.

Increase in Percentage
of Salts, correspond-
ing to an Increase of
O'l c.c. per Minute
in the Rate of Secretion.

•400
•500

•472^1
•512/

•04

•760

•599

•033

•900

•616

•012

1-333

•628

•003

1 Heidenhain, Arch. f. d. gcs. PhysioL, Bonn, 1878, Bd. xvii. S. 23. During eleven
hours' stimulation the percentage of solids sank from 0'88 per cent, to 0'49 per cent.

2 Ibid., Bd. xvii. p. 1. Earlier observations on the same lines were given by him in
1868 in his " Studien."

3 Arch. f. d. ges. PhysioL, Bonn, 1886, Bd. xxxviii. S. 293.

4 Phil. Trans., London, 1889, p. 109.

5°°

THE SALIVAR Y GLANDS.

The experiments on the parotid gland given by Heidenhain show a
general but not a very close relation between the rate of secretion and the
percentage of salts in the saliva.

Sodium chloride forms the larger part of the salts in saliva. The
percentage both of this and of sodium carbonate varies directly with the
rate of secretion.1 The salts insoluble in water, the chief of which is
calcium carbonate, do not seem to follow this rule, or at any rate only
partially, for, whilst there is sometimes an increase in the percentage
of insoluble salts, with increased rate of secretion, this is by no means
always the case;1 they appear to decrease in amount during the
progress of the secretion, as if in part they arose from a store in the
gland itself.

The following experiment from Werther will illustrate the variations in
the percentage of different salts. The saliva was obtained from a dog by
stimulating the chorda tympani : —

Amount
of Saliva
obtained
in c.c.

Rate of
Secretion
per Minute
in c.c.

Percentage
of
Organic
Substances.

Percentage
of
Salts.

Percentage
of
Insoluble
Salts.

Percentage
of
NaCl.

Percentage
of
Na2C03.

1

17-6

0-176

0-30

0-35

0-019

0-29

0-042 '

2

14-2

0-890

1-12

0-43

0-060

0-30

0-067

3

16-2

0-216

0-12

0-21

0-015

0-13

0-029

4

16-2

1-082

0-64

0-42

0-030

0-27

0-046

The relation thus determined between the percentage of salts and
the rate of secretion, holds for chorda saliva and for pilocarpine saliva 2
secreted under normal conditions. But it is not a universal rule. Thus,
sympathetic saliva has a much higher percentage of salts than corre-
sponds to its rate of secretion, if chorda saliva be taken as a standard of
comparison. And the rule does not hold for chorda or pilocarpine saliva,
when the blood flow through the gland is much diminished, or when
the character of the blood is much altered. On this I shall say more
presently.

Heidenhain also showed that in a fresh gland an increase in the rate
of secretion is accompanied by an increase in the percentage of organic
substance in the saliva. In the experiment given below, for example,
an increase in the rate of flow of the submaxillary saliva of the dog,
from 0'14 c.c. to 0'87 c.c. in one minute, was accompanied by an increase
from O52 to 1/54 in the percentage of organic substance. But when
a certain amount of the stored-up substance of the gland cells has been
secreted, an increase in rate of secretion no longer leads to an increase
in the percentage of organic substance in the saliva secreted in a
given time.

The closeness of the relation between percentage of organic sub-
stance and rate of secretion from a fresh gland seems to me to have
been much exaggerated. No doubt there is a relation of the kind, but,
in actual experiments, it is frequently overridden by other factors.
1 Werther, op. cit. 2 Langlcy and Fletcher, op. cit., supra.

SOME GENERAL CHARACTERS OF SALIVA.

Interval
between each
Period of Col-
lection and the
one before it.

Amount of
Saliva in c.c.

Rate of Secre-
tion in c.c. per
Minute.

Percentage
of
Organic
Substance.

Percentage
of
Salts.

Total
Percentage
of
Solids.

3-5

0-14

0-52

0-22

074

2 minutes

3-5

0-87

1-54

O'o6

2-10

3$ „

3-0 0-66

1-63

0-45

2-08

20 „

2-8

0-11

1-07

0-36

1-44

2 „

3-0

TOO

0-91

0-49

1-41

2

3-0

0-50

0'76

0-39

1-16

13

2'5

0-13

0-48

0-30

0-78

3

3-1

077

0-51

0-38

0-90

1

2-8

0-31

0-42

0-36

0-79

SOME GENERAL CHARACTERS OF SALIVA, AND ITS MICROSCOPIC
CONSTITUENTS.

The viscidity of saliva, secreted by mucous glands, is generally in
proportion to the percentage of mucin which it contains. This, of
course, would not be the case, if the amount of alkaline salt in the
saliva increased in much larger proportion than the amount of mucin,
for, with a given quantity of mucin, the viscidity of the fluid varies with
the amount of the solvent.

Saliva, from albuminous or from mixed glands, may be either watery
or thick, irrespective, within certain limits, of the percentage of organic
substance present. Sublingual saliva and parotid saliva of the dog,
when they have a high percentage of organic substance, have a tendency
to turn into a jelly-like mass, and this may further separate into a clot
and clear fluid.

In very watery saliva, freshly secreted, which has not been allowed
to stand in the ducts, and which is examined without delay, nothing is
to be seen under the microscope.

When saliva is allowed to stand a short time in the ducts, car-
bonic acid is given off from it, and, in consequence, calcium carbonate
is precipitated ; the precipitate renders the saliva cloudy, and under
the microscope appears as very fine particles, or groups of particles.
On irrigating such a specimen with dilute mineral acid, the particles
are dissolved. The saliva also may contain leucocytes, and will certainly
do so if it has been allowed to stay long in the gland ducts. In ordinary
experimental conditions, leucocytes collect in the connective tissue of
the glands, and migrate, at times in large numbers, into the ducts. The
leucocytes at first show amoeboid movement ; later, they swell, become
vacuolated, and form the bodies which have been called salivary cor-
puscles. The saliva may also contain some cells from the ducts
which have been separated or injured by insertion of the cannula,
some isolated nuclei, either of duct cells or of leucocytes, and. occasionally
a few small fat globules.

502 THE SALIVARY GLANDS.

In viscid saliva of the submaxillary gland of the dog, spheres or
clumps of secreted substance are present. The number and the
character of these vary broadly with the viscidity of the freshly-secreted
saliva, and are, so far as I have seen, independent of the way in which
the secretion is brought about. As sympathetic saliva is usually much
more viscid than chorda saliva, it usually contains these constituents in
much larger number.1

The spheres vary in appearance. In the more viscid specimens of
saliva they are pale, have a very faint outline, and appear homogeneous
(pale spheres). As a rule they are 2 to 4 ^ in diameter, but
larger and smaller ones occur. In the less viscid specimens of saliva
some spheres like these are also found, but most are more watery-
looking and are still paler (very pale spheres) ; they vary much in size,
but on an average are larger ; they are apparently the swollen forms of
the ordinary pale spheres. There are also, especially in more watery
saliva, spheres which differ from the preceding in having a fairly sharp
outline (vacuolar spheres). In the more viscid forms of saliva, clumps
occur as well as the pale spheres, and they are more numerous the more
viscid the saliva.

In saliva freshly secreted and freshly examined, the spheres and
clumps may easily escape notice, even though they be present in
hundreds in the field of the microscope. On standing they become
more distinct, and they become obvious at the periphery of the drop,
when they are still barely visible in the centre. In sufficiently viscid
saliva the spheres and clumps are much distorted at the edge of the
drop, and in still more viscid saliva most of them are drawn out into
elongated masses.

Acetic acid, *5 per cent, up to nearly glacial, makes the spheres and
clumps very refractive and rather oily-looking. Glacial acetic acid
causes them to swell up and become pale, and the clumps usually
become vacuolated. Sodium hydrate causes them to swell up and
disappear.

When saliva containing spheres and clumps is allowed to stand,
these bodies slowly settle, forming, as they do so, masses often of
considerable size. The addition of an equal volume of 5 to 20 per cent,
sodium chloride allows them to sink much more rapidly ; they make
a white, slightly adherent, but not viscid layer at the bottom of the
vessel.

On irrigating viscid saliva under a cover-slip, the fluid added mixes but
slowly with the saliva, so that, instead of irrigating, it is sometimes better to
mix a small drop of saliva with a small drop of the reagent, and to place a
cover-slip on the mixture. Water causes the spheres and clumps to disappear,
but up to a certain point they can again be made visible by acetic acid ; 1 per
cent. NaCl or Na2C03 makes the outlines of the bodies more distinct ; 1 per cent,
osmic acid causes them to swell up and take a faint brown tint. Methylene-
blue dissolved in Na2C03, 1 per cent, stains them, but as a rule not very quickly.
Picrocarmine, safranin, and other reagents stain them slowly. When saliva
is mixed with one to two volumes of dilute neutral or alkaline salts, dilute or

1 Eckhard, Ztschr. f. rat. Med., 1866, Bd. xxviii. S. 120. found the sympathetic saliva
from the parotid gland of the horse to be whitish and to contain fine particles. Scliiff,
"Le9ons sur la digestion," p. 293, found the same with the first drops of saliva secreted
reflexly after a pause. The characters described were no doubt due to a precipitation of
calcium salts in the saliva contained within the ducts.

SUBSTANCES SECRETED IN SALIVA. 503

strong acids, the spheres and clumps gradually disappear. In strong solutions
of neutral salts (e.g. 20 per cent, sodium chloride), they may be kept for months
at any rate. Strong alcohol and mercuric chloride cause them to shrink and
make them* irregularly granular. Flemming's fluid turns many of them into
vacuolated spheres) with sharp outline and a few distinct small granules. No
mucous cells are seen in saliva after treatment with any of these reagents.

In the submaxillary saliva of the cat, vacuolar and pale spheres are found,
but not the larger clumps.

Microscopical constituents in saliva have been described by Eckhard,
Kiihne, and Heidenhain. The account I have given above differs in several
points from theirs.

The most obvious view to take of these microscopical constituents
of saliva is, I think, that some of the mucous granules are turned bodily
out of the alveolar cells,1 the fluid passing through the cells being
insufficient to dissolve them; and that by swelling up or massing
together they make the various forms of spheres and clumps which are
seen. But although the mucous granules behave with some reagents
very much as do the small spheres of saliva, and have in some states
very much the same appearance, their behaviour with acetic acid is
strikingly different. The mucous granules, on treatment with dilute
acetic acid, swell up and burst like bubbles ; 2 the spheres in saliva, as we
have seen, become refractive and obvious. Although it is possible that
this difference may depend on differences in the surrounding fluids, it is
sufficient to prevent more than a provisional acceptance of the view
that the spheres of saliva are simply undissolved mucous granules.

SUBSTANCES WHICH ARE on WHICH MAY BE SECRETED IN SALIVA.S

In saliva obtained from mucous glands, the chief organic constituent
is naturally mucin. Little is known with certainty of the varieties of
mucin which exist. In mucous saliva, whilst most of the mucin is
precipitated by acetic acid as a stringy lump, there is not infrequently
a portion which is precipitated in fine particles, these making the fluid
cloudy. A small quantity of proteid is also present, probably belonging
to the class of globulins.

In saliva obtained from albuminous glands the proteid constituents
are globulin (or a body allied to globulin), alkali albuminate, and a
small amount of serum albumin.4

In typical mucous saliva, diastatic ferment is either absent, or
present in mere traces ; in saliva from albuminous glands, the amount
of diastatic ferment is variable and independent of the percentage of
proteid, but in the saliva of any one gland the diastatic action increases
with the percentage of proteid present.

The salts are, so far as is known, the same in mucous and in
albuminous saliva, although their percentage amount varies considerably
in the saliva obtained from different glands. The bases found are
sodium, potassium, calcium, and magnesium ; the acids are hydrochloric
acid, carbonic acid, phosphoric acid, and sulphuric acid. Sodium
chloride is by far the largest constituent ; after this comes usually

1 Langley, Proc. Eoy. Soc. London, 1886, vol. xi. p. 202.

2 Langley, Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 433.

3 See also article on " Composition of Saliva," p. 342.

4 Kiihne, " Lehrbuch. d. Physiol.," 1866.

504 THE SALIVAR Y GLANDS.

sodium carbonate ; calcium carbonate and calcium phosphate are kept
in solution by the excess of carbonic acid, and precipitated as the gas
escapes.

Saliva yields to a vacuum about twenty vols. per cent, of carbonic
acid, and small quantities of oxygen and nitrogen ; 1 the carbonic acid,
however, is all or nearly all combined with sodium carbonate to form
sodium bicarbonate.

In the saliva of man, potassium sulphocyanate is normally present.2

The alkalinity of saliva depends upon the presence of sodium
carbonate. In man and in the dog the percentage of this salt varies
from 0*08 to 019 per cent.

In disease,2 traces of other substances have been found in the saliva
of man, for example, urea and leucine. »In diabetes, lactic acid has been
found in the saliva; the presence of sugar has been denied by most
observers, but affirmed by some. In jaundice, saliva does not usually
contain either bile acids or bile pigments, but in some instances traces
are said to occur. In cases of poisoning with salts of mercury, lead, and
some other metals, small quantities of the salts may be present in
saliva ; it is stated, however, that the salts of arsenic are not secreted by
the salivary glands.

An investigation into the character of the substances which can and
which cannot be secreted by the salivary glands, would undoubtedly
lead to interesting and valuable information. It is possible that, with
bodies not acted on chemically, the size of the molecule is the determin-
ing factor. A beginning of such inquiry, though not from this point of
view, was made by Bernard.3 He experimented on the secretion from
the submaxillary and parotid glands of the dog, and on the parotid
glands of the horse. He found that potassium iodide was very readily
secreted, whilst neither sugar,4 ferrocyanide of potassium, nor lactate of
iron was secreted by the salivary glands, though they were all secreted
by the kidney. Iodide of iron, on the other hand, passed into the saliva.

When lithium citrate is injected into the blood, the spectrum of
lithium can be detected in the first drops of saliva secreted.5 And
methylene-blue also passes into the saliva, but it does not appear to do
so constantly. Sulphindigotate of soda, which is so readily secreted by
the liver and kidney, is not secreted by the salivary glands;6 after
injecting large amounts into the blood, a small quantity may be found
in the saliva, but there is no reason to believe that this is due to any
cause other than diffusion.

EFFECTS OF THE CRANIAL AND SYMPATHETIC NERVES ON THE
BLOOD FLOW.

The fundamental fact that the cranial nerve contains vaso-dilator
fibres and the sympathetic vaso-constrictor fibres, has been already
mentioned. If any salivary gland be exposed, it will be seen to flush on

1 Pflttger, Arch.f. d. gcs. Physiol., Bonn, 1868, Bd. i. S. 686.

2 Gamgee, "Physiological Chemistry," vol. ii.. from whom much of this paragraph
is taken.

;; " Lefons de physiol. expe'rimentale," 1856, Bd. ii.

4 On injecting a large quantity of dextrose into the blood, I have found sugar in the
saliva, and in qiiantity which is, 1 think, much too large to be accounted for by diffusion.

5 Langley and Fletcher, Phil. Trans.', London, 1889, vol. clxxx. p. 149.

6 Eckhard, Beitr. z. Physiol. C. Ludwiy, z. s. 70, Geburtst., Leipzig, 1887, S. 13.

EFFECTS OF NER VES ON THE BLOOD FLO W. 505

stimulating the cranial nerve, and to become pale on stimulating the
sympathetic,

The more detailed examination 1 of the blood flow through the gland
has been made almost exclusively on the submaxillary gland of the dog.
The blood flowing ordinarily from the vein is dark ; on stimulating the
chorda tympani, the blood flow increases rapidly for ten to twenty
seconds, and then slowly decreases to normal ; the blood itself becomes
arterial in colour. The degree of the increase naturally varies, the flow
may be five times as fast as the normal. In favourable cases the vein
pulsates, and when it is cut the blood issues in jets, somewhat as from
a small artery. Bernard gives the normal blood flow through the gland
as about 5 c.c. in a minute ; and this has been approximately the rate of
flow in my own experiments, in which anaesthetics were given. Von Frey
found — presumably in very large dogs — the rate of blood flow through
the gland to be much greater, about 12 c.c. in a minute. In v. Frey's
experiments, stimulation of the chorda for ten seconds caused the rate
of blood flow to be 3 to 7 c.c. in five seconds ; the effect rapidly decreased
on repeated stimulation ; the flow was diminished by curari.

There are no complete observations on the changes in the gases of the
blood as it passes through glands in rest and in activity, but some data are
given by Bernard.2

According to Bidder,3 the maximal blood pressure in the vein,
as the result of stimulation of the chorda tympani, is 37 mm. of
mercury.

On stimulating the sympathetic the blood becomes darker, and flows
more and more slowly, the maximal effect being obtained in twenty to
thirty seconds.

It is doubtful whether the sympathetic completely stops the blood flow
in the normal submaxillary gland ; it does so at times in an experiment, but
this may be due to clotting occurring when the blood becomes slow. In the
parotid the effect of the nerve appears to be greater.

The latent period of both chorda and sympathetic varies from a
barely perceptible time to several seconds ; it depends upon the strength
of the stimulus, the number of previous stimulations, and other con-
ditions; but, generally speaking, the latent period is longer with the
chorda than with the sympathetic.

Both nerves have a rather long after-action. The maximal effect
remains for ten to fifteen seconds, and the original rate of blood' flow
only recurs a minute or so after the end of the stimulation. The dura-
tion of the after-action depends, up to a certain limit, upon the duration
of the stimulus ; and it appears to be greater with the chorda tympani
than with the sympathetic. These points, however, have not received
much attention.

When both nerves are stimulated simultaneously with maximal
currents, tlie sympathetic gets the upper hand during the stimulation,

1 Bernard, Journ. de Vanat. et physiol., etc., Paris, 1858, tome i. pp. 233, 649 (reprints
from Compt. rend. Acad. d. sc., Paris, of the same year) ; "Le9ons sur les proprieties physiol.,
etc.," 1859; v. Frey, Arb. a. d. physiol. Anst. zu Leipzig, 1877, Bd. xi. S. 89; Langley,
Journ. Physiol. , Cambridge and London, 1889, vol. x. p. 316.

2 Cf. "La chaleur animale," 1876, p. 179.

3 Arch. f. Anat. u. Physiol., Leipzig, 1866, S. 339.

506 THE SALIVAR Y GLANDS.

and anaemia of the gland is produced as if the sympathetic alone were
being stimulated. Von Frey, using brief stimuli — usually lasting about
ten seconds — observed that the after-action was that of the chorda
tympani, and in some cases the increase of blood flow after the stimula-
tion appeared to be as great as if the chorda alone had been stimu-
lated.

When, however, the sympathetic is stimulated with weak currents,
and the chorda tympani with strong currents, there is, within certain
limits, an algebraical summation of effects. And the constriction pro-
duced by a weak stimulation of the sympathetic may be more or less
annulled by a strong stimulation of the chorda.

MUTUAL EFFECTS OF THE CRANIAL AND SYMPATHETIC NERVES
UPON SECRETION.

We have already mentioned, under the head of the augmented
secretion (p. 496), the effect on the sympathetic saliva of a previous
brief stimulation of the cerebral nerve.

When the chorda tympani and the sympathetic nerve in the cat
are stimulated simultaneously with minimal currents of not too long
duration, the amount of saliva obtained is greater than that which is
obtained from either nerve alone.1 In the dog the same effect may also
be seen ; at any rate, if the gland is in a state to allow the sympathetic
to produce an augmented secretion.

As the currents are increased in strength, the amount of the saliva
obtained by simultaneous stimulation becomes rapidly less and less in
excess of that obtained by stimulating the chorda alone. And with a
very moderate strength of sympathetic stimulation, the amount of saliva
obtained by simultaneous stimulation falls below, and it may be very
considerably below, that which is afforded by stimulation of the chorda
by itself. The secretion is rapid for five or ten seconds, and then
speedily becomes slow. The retarding effect of the sympathetic we may
reasonably attribute to the diminution in the blood supply to the
gland which it brings about.

In the parotid gland of the cat similar effects are seen on excitation
of the sympathetic and of Jacobson's nerve. The sympathetic nerve in
the dog has a very marked retarding action upon the flow of saliva pro-
duced by Jacobson's nerve from the parotid gland, and it may stop the
flow altogether (cf. also p. 498).

Prolonged stimulation of the sympathetic reduces the irritability of
the gland, so that, on subsequent stimulation of the chorda tympani, the
saliva only appears after a long latent period, and but gradually acquires
its normal rate of flow.

Czermak 2 was the first to call attention to the retarding action of the
sympathetic upon the chorda secretion. He stated that in the dog, the
sympathetic stopped the chorda secretion, and produced a condition of the
gland of such nature that it did not for some time respond to stimulation of
the chorda tympani. He referred the action to inhibitory fibres, which he
believed to be present in the sympathetic. Eckhard3 considered that the

1 Langley, Journ. PhyxioL, Cambridge and London, 1878, vol. i. p. 102.

2 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1857, Bd. xxv. S. 3.

3 Beitr. z. Anat. u. Pliysiol. (Eckhard}, Giessen, 1860, Bd. ii. S. 95.

CRANIAL A AW S YMPA THETIC NER VES. 507

retarding effect of the sympathetic was due to the secretion produced by it
being very thick and viscid, and in consequence blocking up the ducts.
Heidenhain l attributed the action of the sympathetic to the lack of oxygen
caused by the diminished blood supply.

The effects on the percentage composition of chorda saliva, caused by
first obtaining a considerable quantity of sympathetic saliva, and vice
versdj were noted by Heidenhain.2 He found that protracted stimulation
of either nerve diminishes the percentage of organic substance in the
secretion subsequently obtained by stimulating the other nerve.

(a) Thus stimulation of sympathetic for two hours — 0*65 grm. of saliva
secreted, containing 5 '9 per cent, solids.

The chorda tympani was then stimulated for two hours.
Stimulation of sympathetic for about one and a quarter hours — 0*54 grm.
saliva, containing 24 per cent, of solids.

(b) Stimulation of the sympathetic for six hours reduced the percentage of
the chorda saliva from 2*4 to I'D.

Since the organic substance in the saliva comes in the main at any
rate — entirely, so far as we know — from the substance stored up in the
gland-cells, the facts given by Heidenhain show that the secretion
obtained from the two nerves arises in part at least from the same gland-
cells.

On microscopic examination of the submaxillary gland of the dog,
after several hours' excitation, either of the chorda tympani or of the
sympathetic, the alveoli are found to be changed to a very unequal degree, a
few having still the ordinary resting characters. This renders it probable that
the secreting fibres are not equally distributed to all the alveoli.

Since the sympathetic saliva contains a higher percentage of organic
substance than chorda saliva, we should expect that simultaneous stimu-
lation of the sympathetic and of the chorda tympani would give a saliva
containing a less percentage of organic substance than sympathetic
saliva, and a greater percentage than chorda saliva; and this is the
case.

Heidenhain has shown that the chorda saliva which is obtained
shortly after stimulating the sympathetic has a higher percentage of
organic substance than that obtained before such stimulation. The
saliva, however, soon becomes normal, usually after 2 to 3 c.c. have
been secreted. The after-effect of sympathetic stimulation is com-
parable to the after-action caused by strong stimulation of the chorda
tympani, of which we have already spoken (p. 505).

We have dealt chiefly with the submaxillary gland, but the mutual
relations of the cranial and sympathetic nerves are essentially the same
in other salivary glands, including the parotid of the dog, in which the
sympathetic nerve by itself commonly gives no flow of saliva.

The following results, taken from experiments by Heidenhain, will serve
to illustrate some points regarding the saliva secreted by the parotid gland
when both the sympathetic and Jacobson's nerve are stimulated.

1 Hermann's "Handbuch," Bd. v. S. 46.

2 Stud. d. physiol. Inst. zu Brcslau, Leipzig, 1868, S. 71.

508

THE SALIVAR Y GLANDS.
EXPERIMENT 1. — The Parotid Gland of the Dog.1

Saliva obtained by Stimulating —

Duration of
Stimuli.

Amount of Saliva
collected.

Percentage of

Organic
Substance.

Percentage of
Salts.

Jacobson's nerve

18 min.

3*11 grins.

0-76

0-26

Jacobson's nerve and the

sympathetic

30 miu.

3-63 grms.

1-41

0-32

EXPERIMENT 2. — The Parotid Gland of the Rabbit?

In this experiment pilocarpine was ifijected, and a sample of the saliva
collected. The cervical sympathetic was then stimulated ; during the stimula-
1 tion the secretion became slower until it stopped ; on its cessation the stimula-
tion was also stopped. After a short time the flow began again ; when about
three drops had been secreted the sympathetic was again stimulated, and so
on, till a second sample of saliva was collected.

Saliva obtained from

Rate of Secre-
tion per Minute.

Percentage of
Organic

Substance.

Percentage of
Salts.

Pilocarpine .

0-22c.c.

0-39

0-85

Pilocarpine and sympa-
thetic stimulation

0'062 c.c.

3-62

0-75

EFFECT OF VARIATIONS IN THE AMOUNT AND QUALITY OF THE BLOOD
SUPPLIED TO A GLAND, UPON THE AMOUNT AND PERCENTAGE
COMPOSITION OF THE SALIVA SECRETED.

In order to form a satisfactory theory of the action of secretory
nerves, it is of the greatest importance to know how far variations in
the amount and character of the blood flowing through the gland affect
the amount and character of the saliva. Our information on this point
is unfortunately still vague in many respects.

Certain broad facts can be readily observed by compressing the
carotid artery on one side, after tying the carotid artery on the other
side, and the subclavian arteries on both. The gland-veins are cut, so
that the amount of blood flowing through the gland can be roughly
determined; aiid the chorda tympani is stimulated during different
degrees of compression of the carotid.

When the carotid is compressed to a moderate extent, the chorda on
stimulation will not cause so much increase in the blood flow through
the gland as it otherwise would, but it will nevertheless cause a con-
siderable increase, and the blood will issue from the vein of an arterial
colour. In such case, according to Heidenhain,3 the amount of saliva
obtained by a given stimulus will be of normal amount.

1 Heidenhain, Arch. f. d. ges. Physiol., Bonn, 1878. Bd. xvii. S. 31.

2 Heidenhain, op. cit., S. 40.

3 Heidenhain (Stud. d. pliysiol. Inst. zu Breslau, Leip/ig, S. 98) appears to refer to an
increase of blood flow above that occurring with partially compressed carotid, and not to an
increase above the normal blood flow.

EFFECT OF VARIATIONS IN THE BLOOD SUPPLY. 509

At a certain further stage of compression of the carotid, stimulation
of the chorda will still cause an increase of blood flow from the gland,
but the blood issuing from it, instead of being of an arterial colour, will
be of a venous colour. In this case Heidenhain finds that the amount
of saliva obtained by a given stimulus will be less than normal.

When the artery is so far compressed that little blood flows through
the gland, and the chorda causes no increase in it, there is naturally a
great decrease in the amount of saliva obtained by a given stimulus.
If the stimulus last about a minute only, the decrease is in fact nearly
as great as if the blood supply be entirely cut off. On allowing the
blood to flow again through the gland, the chorda saliva does not at
once attain its normal amount. Brief closure of the artery causes more
or less protracted diminution in the efficiency of the chorda; it may be
noted that the vaso-dilator effect of the chorda recovers more quickly
than its secretory effect.

The following example, taken from Heidenhain,1 may be given to illustrate
some of the points mentioned above : — Dog, arteries to head tied, except left
carotid. Wharton's duct connected with a tube graduated in millimetres.
Gland-vein opened. The chorda tympani was stimulated for one minute, and
the rise in millimetres of the saliva in the tube was noted each five seconds.

Saliva flow. -0, 20, 70, 50, 55, 45, 36, 30, 27, 29, 30, 28 = 410.

The artery was then clamped for five minutes ; during the last minute the
chorda was stimulated, the blood flow from the vein was very slight.

Saliva flow.— 0, 0, 21, 32, 33, 17, 14, 8, 6, 7, 2, 2 = 142.'

The carotid was left undamped for eight minutes, then clamped for one
minute, during which the chorda was stimulated.

Saliva flow.— 0, 0, 0, 2, 4, 6, 5, 5, 5, 4, 5, 4 = 40.

The carotid was undamped, but the stimulus kept up for two minutes.
The blood flow from the vein was moderately increased. The saliva rose
69 and 51 mm.

The carotid remaining undamped, the chorda was stimulated during the
third minute. It caused a rise of saliva of 203 mm.

The effect of diminished blood supply upon the percentage composition
of saliva has not been very fully investigated. But Eckhard 2 states that
ligature of the veins of the submaxillary gland does not cause chorda
saliva to alter its character and become like sympathetic saliva. And,
according to Heidenhain,3 diminution of the blood supply by compression
of the carotid does not cause an appreciable increase in the percentage of
solids in saliva.

Heidenhain's experiments undoubtedly show that, in certain circum-
stances, a diminution of the blood supply to the gland has no considerable
influence upon the percentage of organic substance in the saliva, obtained
by stimulating the cranial nerve. But this does not seem to me to hold
in all circumstances, for, in some observations on the submaxillary
gland of the dog, made by Fletcher and myself,4 bleeding the animal,
whilst decreasing the rate of the secretion of saliva produced by
pilocarpine, largely increased the percentage of organic substance in the
saliva.

1 St'ud. d. physiol. Inst. zu Breslau, Leipzig, S. 93.

2 Beitr. z. Anat. u. Physiol. (Eckhard), Giessen, 1860, Bd. ii. S. 212.

3 Arch./, d. gcs. Physiol., Bonn, 1878, Bd. xvii. S. 33, 43.

4 Phil. Trans., London, 1889, vol. clxxx. p. 131.

5 T o THE SALIVAR Y GLANDS.

There are no experiments which show definitely what is the effect on
the percentage composition oj5 saliva of a decrease of blood supply due
to simple constriction of the vessels. When the cranial nerve is
stimulated during compression of the carotid artery, the blood flowing
through the gland flows through dilated vessels. When the diminution
in blood supply is brought about by stimulating a vaso-constrictor
nerve, the blood flowing through the gland flows through constricted
vessels. It is probable that, in the former case, fluid passes more
readily through the vessel walls; hence, with the same amount of
organic substance secreted in the two cases, one saliva might have a
low and the other a high percentage of organic substance.

Changes in the amount and character of the saliva l may, however,
be produced by variations in the character of the blood. The injection
of a considerable quantity of dilute salt solution, such as 0-2 per cent., leads
to a considerable increase in the rate of secretion of saliva, whether this
is set up by stimulating the chorda tympani or by injecting small
quantities of pilocarpine. Up to a certain point the percentage of
salts increases in the normal manner ; beyond this the percentage ceases
to increase and may fall. An increase in rate may also be produced by in-
jecting into the blood 100 c.c. to 250 c.c. of stronger solution (as 2 per cent.)
of sodium chloride or sodium carbonate. Probably this amount leads to
the passage of water from the tissues, and so increases the volume of the
blood. The injection may cause an increase in the percentage of salts.
Injection of strong salt solution into the blood, in quantity sufficient to
increase the percentage of sodium chloride in the serum, was found by
Novi2 to increase the percentage of the salt in submaxillary saliva;
though never up to that in the serum. When a certain amount of strong
salt solution (20 per cent.) is injected, the gland becomes cedematous,
and neither placing acids on the tongue (Novi), nor stimulating the
chorda tympani, nor injecting pilocarpine (Langley and Fletcher), will
cause a secretion.

KELATION OF SECRETION TO THE FLOW OF LYMPH.

We know very little with regard to the flow of lymph from the
glands in various conditions. The lymph vessels leave the submaxillary
gland at the hilus. If the lymph could be collected and analysed, it
would give information very much needed with regard to the secretory
activity. Heidenhain,3 who has paid some attention to the subject,
appears only to have noticed whether oedema of the gland was produced
or not, but it is manifest that if the lymph vessels were large there
might be very great increase in the lymph flow without oedema.

Heidenhain 4 considers that there is no increase in lymph flow from
the gland during stimulation of the chorda, either before or after giving
atropine. Supposing, then, that atropine does not act on the vessel wall,
so as to hinder the passage of fluid through it, it would follow that fluid
passes from the vessels in increasing amount, as an increasing amount
of saliva is secreted by the gland. In other words, it would follow that
there is in rest a certain slight constant formation of lymph, and that,

1 Cf. Langley and Fletcher, op. tit.

2 Arch.f. Anat. u. PhysioL, Leipzig, 1888, Physio! . Abth., S. 403.
sArch.f. d. ges. PhysioL, Bonn, 1874, Bd. ix. S. 346.

4 Hermann's "Handbueh," 1880, Bd. i. Th. 1, S. 73.

THE SECRETOR Y PRESSURE. 5 1 1

when the gland secretes, an additional amount is formed exactly equal
to that of the fluid in the saliva secreted, — a conclusion which it is not
easy to accept.

In two conditions oedema of the gland is obtained : First, when
dilute acid (O5 per cent. HC1) or an alkaline salt (5 per cent. Na2CO3)
is injected into the gland duct.1 In this case, oedema is slowly pro-
duced; rapidly, however, if the chorda tympani be stimulated, though
no secretion follows. There can be little hesitation in attributing this
to the injury inflicted on the walls of the small vessels ; for damage of
the vessels, as we know, largely increases the amount of the lymph
formed in any given condition. Secondly, when there is a considerable
resistance to the flow of saliva from the duct. On continued stimulation
of the chorda in such cases, the lobules become separated by a mucous
fluid, and there is great oedema. At first this fluid consists simply of
filtered saliva ; later, probably, lymph is added, partly in consequence of
a direct injury to the vessels, and partly, as suggested by Heidenhain, in
consequence of pressure on the vein.

THE SECRETORY PRESSURE.

Ludwig 2 was the first to show, by experiment on the submaxillary
gland of the dog, that the secretory pressure may overpass considerably
the blood pressure. Thus in one case he obtained a pressure of 190 mm.
of mercury from the saliva caused to flow by stimulating the chordo-
lingual nerve, although the blood pressure in the carotid artery was only
112 mm. of mercury. Since that time considerably higher pressures
have been obtained from chorda saliva ; the maximum pressure observ-
able in any one species is, broadly speaking, the greater, the larger the
individual.

On connecting Wharton's duct with a mercurial manometer, and
stimulating the chorda tympani, the pressure rises at first rapidly, then
more and more slowly ; when the maximum pressure is attained, a
cessation of the stimulus is followed by a fall of pressure, due to filtra-
tion taking place between the cells of the ducts and of the alveoli.
When the observation is at all frequently repeated, the lobules of the
gland become separated by mucous fluid, the pressure attained becomes
less, and the irritability of the gland greatly decreases.

In the parotid gland of the dog, the observed secretory pressure is
less than in the submaxillary gland, usually being 100 to 130 mm. of
mercury, but the difference is probably due to the limpidity of the
parotid saliva, which allows a more rapid filtration.

The pressure of the sympathetic secretion may also exceed that
of arterial blood. In experimenting with a mercurial manometer, the
pressure should be raised artificially to about 150 mm. of mercury
during the first stimulation of the sympathetic, the connection of the
manometer with Wharton's duct clamped for about thirty seconds,
and then undamped and the sympathetic again stimulated. Heiden-
hain,3 in an experiment on the submaxillary gland of a dog, found
that the sympathetic saliva was secreted at a pressure of 150 to 160
mm., whilst the pressure of the chorda saliva was 250 to 270 mm.

1 Giamizzi, Ber. d. k. sacks. Gesellsch. d. Wissensch., 1865.

2 Ztschr.f. rat. Med., 1851, N. F., Bd. i. S. 271.

3 Stud. d. physiol. Inst. zu Breslau, Leipzig, S. 69.

5 1 2 THE SALIVAR Y GLANDS.

It may, however, be doubted whether there is such a difference in the
maximum pressure. In the observations I have made on the point,
stimulating alternately the chorda tympani and the sympathetic, the
sympathetic has given a perceptible though slight and brief rise of
pressure at approximately the maximum pressure obtainable from the
chorda tympani.

EEFLEX INHIBITION OF THE SALIVARY SECRETION.

During the progress of secretion, a certain decrease in the rate of
flow, or even a cessation, may be caused by stimulation of afferent
nerves. Such an effect might be due — to select the most probable
causes — either to an inhibition of the» central secretory centre, or to a
constriction of the blood vessels of the gland. The experiments have
not, however, been directed to an accurate determination of the method
of production of reflex inhibition. .

Pawlow l states that the slow secretion induced by partial dyspnoea,
or by curari, is decreased or temporarily stopped by stimulation of the
sciatic for one or two minutes with a particular strength of current, or
by exposure of the abdominal viscera. The experiments given can
hardly be considered to be conclusive, and Buff2 finds that, quite apart
from stimulation, the secretion occurring in the conditions of Pawlow's
experiments is not itself constant in rate.

ACTION OF ALKALOIDS UPON THE SALIVARY GLANDS.

There are obviously a number of ways in which a substance intro-
duced into the blood might cause a secretion of saliva. It might
stimulate the peripheral endings of sensory nerves and produce a reflex
secretion ; it might stimulate some part of the central nervous system,
the connections of the visceral nerve-fibres with the local nerve-cells,
the nerve-cells directly, the nerve-endings in the gland, or finally the
gland-cells directly. Of several of these modes of action we have no
certain example. We shall confine our attention to those alkaloids,
the effects of which have most served as a basis of physiological
deduction.3

Atropine. — Atropine arrests the normal secretion from the glands
of the mouth, nose, and pharnyx, so that the whole mucous membrane
becomes dry. The arrest is due -to a paralysis of the cranial secretory
nerves, the strongest stimulation of them no longer causing a secretion.4
In the dog, 10 to 15 mgrms. of atropine, when injected into a vein, pro-
duce the paralysis; in the cat, 3 to 5 mgrms. are sufficient. Considerably
smaller doses than these reduce to very small limits the secretory power
of the nerves ; hence, in determining the minimal amount of atropine
required to produce paralysis, it is advisable to stimulate the nerve for
a minute or more, and to repeat this after a few minutes' interval.

The sympathetic nerve is either not paralysed at all, or only by a

1 Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xvi. S. 272 (experiments made on the sub-
maxillary gland of the dog).

2 Beitr. z. Anat. u. Physiol. (EcMard), Giessen, 1888, Bd. xii. S. 3.

3 A few only of the original papers dealing with this subject can be given here ; fuller
references will be found in treatises on pharmacology.

4 Keuchel, "Das Atropin mid die Hemmungsnerven," Dorpat, 1868; Heidenhain,
Arch.f. d. ges. Physiol., Bonn, 1872, Bd. v. S. 309.

PILOCARPINE AND MUSCARINE. 513

comparatively large close of atropine.1 In the dog more than 100
mgrms. may be injected into a vein, and still secretion will be obtained
from the submaxillary gland by stimulating the cervical sympathetic.
In the cat this nerve ceases to cause a secretion after about 30 mgrms.
of atropine have been given.2

The point of action of atropine is the termination of the nerve-fibres
around the gland-cells. There are several facts which show this. We
may mention the following : — In the case of the submaxillary gland,
when a dose of atropine has been given just sufficient to paralyse the
chorda tympani, 110 secretion is obtained by stimulating peripherally of
the (true) submaxillary ganglion; i.e., the postganglionic nerve-fibres
cause no secretion. Atropine applied directly to nerve-fibres — whether
preganglionic or postganglionic — in their course towards a tissue, does
not paralyse them. The paralysis produced by it must then be either
one of nerve-endings or of gland-cells. But in the case we are consider-
ing the gland-cells are not paralysed, since they are at once set secreting
by stimulating the cervical sympathetic. Hence we conclude that
atropine acts upon and paralyses the nerve-endings of the postganglionic
secretory fibres of the chorda tympani. And we may conclude, further,
that in other cases in which atropine paralyses secretory nerves, it has
this effect in consequence of an action upon the nerve-endings in the
gland.

The exact method of action of atropine we can only guess at ; we might
suppose, either that it annuls the conductivity of the nerve-endings, or that
it causes a retraction of the terminal filaments, in the manner suggested by
Duval and others for the processes of nerve-cells in general, so that nervous
impulses can no longer pass from the nerve-endings to the gland-cells.

Atropine does not paralyse the vaso-dilator fibres which accompany
the cranial secretory nerves. This was first shown by Heidenhain 3 in
the case of the chorda tympani of the dog. It is true that, when large
doses of atropine are given, both vaso-dilator and vaso-constrictor glandular
nerves produce less effect than normal, but there is nothing to show that
this action is in any way specific.

Pilocarpine and muscarine.— Both pilocarpine and muscarine pro-
duce copious and prolonged secretion, when given in very small quantity ;
for example, when 1 or 2 mgrms. are injected into the blood.4 The
secretion when it slackens is increased by a further dose of the alkaloid,
so that the flow of saliva can be kept up for a very long time, apparently
indefinitely. A large dose is not required in order to produce the
maximum rate of flow, its effect is rather to increase the duration of the
flow. The saliva obtained is like that produced by stimulating the
cerebral nerve, and the secretion is accompanied by a great dilation of
the vessels of the gland.

The secretion to which these alkaloids give rise from the submaxillary
gland is unaffected by section of the chorda tympani, or by extirpation
of the superior cervical ganglion ; it occurs after the connections of the
chorda tympani with the local nerve-cells have been paralysed by

1 Heidenhain, op. cit.

2 Langley, Journ. Physiol., Cambridge, 1878, vol. i. p. 98.

3 Op. cit., supra.

4 The chief features of the action of muscarine were described, "Das Muscarin," Leipzig,
by Schmiedeberg u. Koppe in 1869.

VOL. i.— 33

5 14 THE SALIVAR Y GLANDS.

nicotine, and also after degeneration of the chorda tympani itself (cf.
p. 519). The alkaloids therefore stimulate some peripheral structure.
And as in the case of atropine, so with pilocarpine and muscarine, it is
hardly open to doubt that the nerve-endings of the postganglionic fibres
are the points of attack. The nerve-endings of the sympathetic nerve-
fibres, on the other hand, are not stimulated by pilocarpine or by
muscarine.

Stimulation of the chorda tympani during the pilocarpine secretion l
produces in most circumstances an increase in the rate of flow, but when
the secretion is as rapid, or nearly as rapid, as the alkaloid is capable
of producing, the chorda has little or no effect. Further, after large
doses of pilocarpine have been given, the chorda has also little or no
effect ; in the latter case, the apparent paralysing action may be due
to the presence of more than one alkaloid in what passes for pilo-
carpine.

Stimulation of the sympathetic during the pilocarpine secretion
causes a primary increase in rate, like that of the augmented secretion ;
after this there is a slowing, and if the stimulation be strong, there may
be a complete cessation of the flow. The slowing effect is less in the
submaxillary gland of the cat than in that of the dog, and less in the
submaxillary of the dog than in the parotid of the dog.

The effect of the sympathetic in the last two cases is seen in the following
extract from an experiment : 2 —

DOG. — Pilocarpine Nitrate injected — Rise of Saliva in Tubes connected with the
Ducts of the Submaxillary and Parotid Glands, taken every thirty seconds,
in millimetres.

Submaxillary . 25 54 9 3 2 1 0 0 0 1 3 11 19 29 32 32
Parotid .5920000000000122

stim. sympathetic

The mutual antagonism3 of atropine and pilocarpine (or mus-
carine).— If atropine, in quantity just sufficient to paralyse the chorda
tympani, be injected into a vein of an animal, subsequent injection of
pilocarpine or muscarine may or may not cause secretion. In many
cases, as the amount of the alkaloid given is increased, death ensues,
whilst the secretory nerves are still paralysed by atropine.

There are two methods by which the antagonistic action of two
poisons on the salivary glands may be observed more satisfactorily
than by injecting them both into the general circulation. The one is
to inject the weaker poison in such a way that it passes through the
vessels of the gland without entering the general circulation. The
other method is to inject a small quantity of a rather strong solution
of the weaker poison into the gland duct. In either case, the stronger
poison is injected into the general circulation.

1 Langley, Journ. Anat. and Physiol., London, 1876, vol. xi. p. 173 ; Journ. Physiol.,
Cambridge and London, 1878, vol. i. p. 339 ; Gley, Arch, de physiol. norm, et path., Paris,
1889, p. 151.

2 Langley, Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 826.

3 For the action of physostigmine and its antagonistic action on atropine, cf. Heidenhain,
Arch. f. d. ges. Physiol., Bonn, 1872, Bd. v. S. 309, and 1874, Bd. ix. S. 335. For the
mutual antagonism of poisons in general, and especially as regards muscarine and atropine,
cf. PreVost, Arch, de physiol. norm, etpath., Paris, 1877, p. 801.

NICOTINE. 515

I have tried both methods 1 in observations on the effects of
pilocarpine and atropine upon the submaxillary gland of the cat and
dog. The latter method is much simpler, and seems to me better. An
experiment, briefly stated, is as follows. A paralysing dose of atropine
is injected into a body vein. A cannula filled with a 2 to 4 per cent,
solution of pilocarpine nitrate is tied into Wharton's duct, and 01 to 0*25
per cent, of the solution driven into the gland. This causes a secretion
of saliva and great increase of blood flow, lasting several minutes, but
steadily lessening in rate. During the flow of saliva the chorda
tympani becomes again irritable, and may remain so for a short time
after pilocarpine has ceased to produce a secretion. As the pilocarpine
is carried out of the gland by the secretion, by the blood, and by the
lymph, the atropine continually flowing to the gland in the blood again
acquires the upper hand, and the nerve-endings become again paralysed.
With renewed injection of pilocarpine there is renewed transient secre-
tion and renewed transient irritability of the chorda tympani. And
the paralysis and recovery may be repeated many times in an hour.
It is, however, to be noticed, that if more than the minimal dose of
atropine be given, more than one injection of pilocarpine may be required.

Although pilocarpine can instantaneously restore some degree of activity to
the chorda tympani which has been paralysed by atropine, yet the activity is
always considerably less than normal.

In the cat, when the cervical sympathetic has been paralysed by atropine,
its activity can be restored by injecting pilocarpine into the duct, although
pilocarpine does not stimulate the secretory nerve endings of the sympathetic.

Nicotine. — Nicotine causes a brief flow of saliva, followed by a
temporary paralysis of the cranial and sympathetic fibres 2 up to their
connections with the peripheral ganglia.3 We have already described the
main features of this paralysis in connection with the chorda tympani,
and in connection with the sympathetic (p. 480). In all the mammals
which have been experimented on, small doses of nicotine readily pro-
duce excitatory effects, but the amount required to paralyse the secretory
and vasomotor preganglionic fibres varies widely in different cases.
Moreover, the minimal amount required to produce paralysis is not
precisely the same for fibres of different origin, or for fibres of similar
origin but different function. In the rabbit and cat the differences are
not great, the amount required varying from about 5 to about 10 mgrms.
In these animals about 10 mgrms. of nicotine injected into the blood
will cause a paralysis of preganglionic fibres lasting about fifteen
minutes. In the dog, 30 to 40 mgrms. have a similar effect on the chorda
tympani, in so far that, usually, stimulation of the chorda for about twenty
seconds causes no secretion ; but in some cases, at any rate, and even
after larger doses, more protracted stimulation of the chorda induces
gradually an active and protracted secretion,4 continuing for some time
after the cessation of the stimulus. And very large doses may be
given to a dog without paralysing completely the cervical sympathetic.

1 Journ. Anat. and PhysioL, London, 1876, vol. xi. p. 173 ; Journ. PhysioL, Cam-
bridge and London, 1878, vol. i. p. 339 ; 1880, vol. iii. p. 2. For method of injecting into
the gland arteries, cf. Heidenhain, op. cit., 1874.

" Heidenhain, Arch. f. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 316.

3 Langley and Dickinson, Proc. Roy. Soc. London, 1889, vol. xvi. p. 423 ; Langley,
Journ. PfiysioL, Cambridge and London, 1890, vol. xi. p. 123.

4 Repeated doses have a tendency to cause in the dog a continuous secretion.

5 1 6 THE SALIVAR Y GLANDS.

On the hypothesis that nicotine causes a contraction of the terminal
fibrils of the chorda tympani, we might suppose that protracted stimulation
leads to a slow gradual extension of the terminal fibrils, so that nervous
impulses passing down the chorda tympani can again set up impulses in the
peripheral nerve-cells.

FORMATION OF HEAT IN THE SUBMAXILLAKY GLAND.

The rapid flow of saliva caused by stimulating the chorda tympani
suggested, not unnaturally, that a considerable formation of heat must
take place in the submaxillary gland. Ludwig and Spiess,1 using thermo-
electric junctions, and Ludwig,2 using thermometers specially designed,
brought experimental proof that in the dog this was in fact the case.

Ludwig and Spiess placed one junction in the carotid artery,
arranged as in the method of determining lateral blood pressure, so
that the actual junction was, they said, in the full blood stream. The
other junction was placed in a cannula connected with Wharton's
duct, and apparently on the same side as that of the carotid taken.
With a moderate rate of secretion they found the saliva to be about
1° C. warmer than the blood in the carotid.

Ludwig placed one thermometer in the carotid near its origin, and
another in the course of a cannula connected with Wharton's duct of the
opposite side. He states that there was in no case clotting in the
carotid, but there does not seem to have been a flow of blood around the
bulb of the thermometer. The room was kept at a temperature not
less than 24° C. The saliva was found to be constantly of a higher
temperature than the blood. The extent of this varied in different
experiments, and, generally speaking, was greater the faster the secretion.
The maximum difference found was 1°'6 C., the temperature of the saliva
in this case being 41°'2 C., the rate of secretion 0-5 c.c. in 5'5 seconds.
Ludwig gives also three experiments upon the respective temperatures of
the blood in the carotid artery, of the blood issuing from the gland vein,
and of the saliva. As a rule, the temperature of the venous blood wras
below that of the carotid blood, but occasionally it was slightly greater
than that of carotid blood or of saliva. For example, in one case the
temperature of the blood in the carotid was 39°1 C., that of the saliva
39°'3 C., and that of the venous blood 390>4 C.

The proof of an appreciable formation of heat during secretion
appeared complete when Heidenhain 3 observed by the thermo-electric
method that the temperature of the gland was often higher than that
of the carotid blood, the difference in favour of the gland being still
greater on stimulation of the sympathetic; and when Morat,4 by the
same method, obtained a rise of temperature in the submaxillary gland
of the dog, on stimulating the sympathetic both after bleeding the
animal to death and during temporary ligature of the carotid, sub-
clavian, and vertebral arteries.

Bernard 5 plunged one thermo-electric junction needle in each gland, and
found that stimulation of the chorda tympani caused a rise of temperature, and

1 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1857, Bd. xxv. S. 584 ; reprinted in
Ztschr.f. rat. Med., 1858, N. F., Bd. ii. S. 361.

2 Wien. med. Wchnschr., I860, S. 433 and 449.

s Stud. d. physiol. Inst. zu Breslau, Leipzig, 1868, Heft 4, S. 110.

4 Arch, de physiol. norm, et path., Paris, 1893, p. 285.

5 "La chaleur auiraale," Paris, 1876, p. 325.

ELECTRICAL CHANGES IN THE GLANDS. 517

stimulation of the sympathetic caused a fall of temperature in the gland of the
same side. He concluded that calorific nerve-fibres are present in the chorda
tympani, and frigorific nerve-fibres in the sympathetic ; but there is nothing
in the account to show that the results were not due simply to a variation in
the blood supply.

These results till recently passed unquestioned. But Bayliss and
Hill,1 on testing them, both by the thermo-electric and the thermometric
methods, never found the chorda saliva to be warmer than the arterial
blood. Their experiments differed in some points of method from
Ludwig's. On one of these they consider the difference in result de-
pends. The thermo-electric junction or the thermometer was pushed up
the femoral artery into the aorta, so that it was exposed to the full
current of blood. Bayliss and Hill consider that in Ludwig's experiment
the temperature observed was less than the real temperature of arterial
blood, so that, on stimulating the chorda tympani, the saliva secreted,
though of a higher temperature than that recorded for the blood, was
not of a higher temperature than that of the blood actually supplied to
the gland.2 And they came to the conclusion that no formation of heat
in the submaxillary gland can be determined directly by any known
method of measuring variations in temperature.

Supposing for a moment that this conclusion is correct, it does not
of course mean that no heat is formed in the gland during secretion, but
simply that the heat — undoubtedly set free by the chemical changes — is
insufficient to cause an appreciable rise of temperature in the considerable
mass made up of the saliva, the gland, and the blood flowing through the
gland. But the main question can hardly be regarded as settled. For
the tissues in the neighbourhood of the gland artery and of the duct are
— at any rate, after placing a cannula in the duct and preparing the
chorda tympani — at a lower temperature than the aortic blood. So that
both the blood to the gland and the saliva secreted tend to become
cooled. And thus it would be possible for the recorded temperature of
the saliva to be less than that of aortic blood, although the temperature
of the saliva secreted were higher than that of the blood supplied to the
gland.

ELECTRICAL CHANGES IN THE SALIVARY GLANDS.

The electrical currents of the salivary glands of the dog and cat
have been made the subject of observation by Bayliss and Bradford,3 and
by Bradford.4 In such experiments, one non-polarisable electrode is
placed upon the outer convex surface of the gland, and the other upon
the gland close to the hilus. It is convenient to use Hermann's nomen-
clature for the currents which may be observed. When the outer
surface of the gland is positive to the hilus, so that the direction of the
current in the galvanometer circuit is towards the hilus, and in the

1 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 351.

- It may be mentioned that the blood temperatures recorded by Bayliss and Hill are in
nearly all cases less than those recorded by Ludwig, but no definite conclusion can be
drawn from this.

3 Proc. Roy. Soc. London, 1886, No. 243, p. 203 ; Internal. Journ. Anat. and HistoL,
1887, vol. iv. The ingoing current of the skin of the frog was discovered by du Bois Rey-
mond in 1857. He attributed it to the glands present in the skin (cf. " Untersuch. u.
thierische Elektricitat," I860. Bd. ii.

4 Journ. PhysioL, Cambridge and London, 1887, vol. viii. p. 86.

5 1 8 THE SALIVAR Y GLANDS.

gland itself from the gland-cells to the surrounding tissue — the current
is an ingoing current. When the outer surface of the gland is negative
to the hilus, so that the direction of the current in the galvanometer
circuit is from the hilus to the outer surface, and in the gland itself
from the gland-cells towards the duct, the current is outgoing. The
outgoing current, then, is one in the direction of the flow of the saliva
secreted.

The current of rest may be either outgoing or ingoing. It is
usually outgoing in the submaxillary gland of the dog, and usually ingoing
in the submaxillary gland of the cat. The causes of the difference of
direction have not been determined.

Any stimulation of nerves which causes a rapid now of saliva will
cause a strong outgoing current. Wheif the flow of saliva is slight, the
current, as a rule, is either diphasic, first outgoing and then ingoing, or
ingoing only. Thus in the submaxillary or parotid gland of the dog,
stimulation of the cranial nerve causes an outgoing current, and stimula-
tion of the sympathetic, provided the secretion be slight, causes an
ingoing current. The ingoing current begins less quickly and is less
strong than the outgoing current.

In the submaxillary gland of the dog, the current of rest is said to vary
from 1-500 to 1-10 of a volt. The outgoing current, caused by stimulating the
chorda tympani, begins about 0*37 seconds after the beginning of the stimu-
lation, and before saliva appears in the duct ; it reaches its maximum before
the maximum rate of secretion is attained. It may undergo temporary
diminution or reversal, indicating the development of an ingoing current.
The ingoing current, caused by stimulating the sympathetic, begins two to
three seconds after the beginning of the stimulation, and only slowly attains
its maximum.

In the submaxillary gland of the cat, stimulation, either of the chorda or
of the sympathetic, causes, in most cases, first an outgoing and then an ingoing
current.

Atropine annuls the effect of nerve stimulation, except perhaps in
the case of the sympathetic of the dog ; here the ingoing current pro-
duced by stimulation is much reduced, but it is not clear that it is com-
pletely abolished even by 100 mgrms. of atropine. Atropine annuls the
outgoing current of stimulation before the ingoing. The amount of
atropine required to abolish the outgoing current of stimulation is approxi-
mately that required to render the flow of saliva very slight. The
amount of atropine required to abolish the ingoing current of stimulation
is approximately that required to paralyse completely the secretory
activity of the nerve stimulated (cf. p. 512).

Bradford attributes the ingoing current to "changes in the gland
cells, leading to the elaboration of the organic constituents of the saliva,"
these being caused by the action of Heidenhain's trophic fibres, and
thinks that the outgoing current is probably due " either to the passage
of the fluid part of the secretion through the walls of the alveoli, or to
the changes in the gland structures, that follow the excitation of a
secretory nerve and precede the gland flow."

Most of the facts could be accounted for by supposing that the outgoing
current is due to physical causes, namely, due to the passage of fluid through the
gland-cells ; and that the ingoing current is due to chemical causes, namely, the
metabolic changes in the gland-cells, but the questions involved are too com-

SECTION OP GLAND ULAR NER VES. \ 519

plex to allow a definite conclusion to be arrived at. In any adequate discussion
of the matter, the facts regarding the production of electric currents in other
parts of the body, and especially in the skin and mucous membrane, would
have to be taken into account. One or two points only we can mention here.
In the skin and mucous membranes of the frog and other animals investigated,
there is generally an ingoing electric current, which is increased ,by weak
stimulation. Hermann l considers both currents to be due to an " apobiotic "
change in the protoplasm. By " apobiotic " is meant any change which
diminishes the vital energy of a part of the protoplasm, compared with the
rest ; such as is produced by stimulation, the act of dying, the change of proto-
plasm to mucin or to keratin, and so forth. Parts undergoing apobiotic
change are negative to the rest of the protoplasm. Thus, in a mucous cell,
the inner mucous portion of the cell becomes negative to the outer proto-
plasmic part, and a current is then set up, which passes in the galvanometer
from capsule to hilus, and in the gland from mucous to protoplasmic portion,
i.e. there is an ingoing current. As to the outgoing current, Hermann is
inclined to consider it as a simple diminution (negative variation) of the
normal ingoing or secretory current ; whilst Biedermann advocates the view
that the outgoing current is due to anabolic (assimilatory) processes in the
gland-cells.

SECTION OF GLANDULAR NERVES. THE PARALYTIC SECRETION.

Claude Bernard 2 was the first to make observations upon the effect
of section of glandular nerves. He found that section of the chorda
tympani in the dog caused the submaxillary gland in two or three days
to enter into a state of slow continuous secretion. The slow flow of
saliva continued for five to six weeks, and then stopped. During this
time the gland itself diminished more and more in size.

Since the secretion is the result of the section of nerve-fibres, it has
been called the " paralytic secretion." Claude Bernard attributed the
secretion to the complete removal of nervous impulses. Thus the flow
of saliva did not begin for two or three days, because the terminations
of the chorda tympani in the gland required two or three days to
degenerate completely. It stopped in five to six weeks, because then,
he thought, the chorda fibres had regenerated.

The question was taken up a few years later by Heidenhain.3 In
order to exclude the possibility of the paralytic secretion being caused
by irritation of the duct or gland, he cut the chorda tympani in the
tympanic cavity. The secretion occurred in the same way as when the
nerve was cut peripherally of the ganglion, then called the submaxillary
ganglion (cf. above, p. 481). It began in twenty-four hours at least,
i.e. considerably earlier than the time given by Bernard. It was watery,
and contained very little mucin ; it contained many leucocytes (amoe-
boide Korperchen), and was in consequence somewhat cloudy. The
secretion was at first very slow, but gradually increased in rapidity, so
that in about a week a large drop might be secreted every twenty
minutes. After three weeks it diminished markedly. The gland itself,
as its size diminished, became of a yellowish tint, and waxy appearance.

The time taken by the peripheral ends of the cut chorda tympani

1 Arch. f. d. ges. PhysioL, Bonn, 1894, Bd. Iviii. S. 246. References to much of the
earlier work will be found in this paper.

2 Journ. de I'anat. etphysiol., etc., Paris, 1864, tome i. p. 507.

:! Stud. d. physiol. Inst. zu Breslau, Leipzig, 1868, Heft 4, p. 73.

520 THE SALIVAR Y GLANDS.

fibres to degenerate is not quite accurately known, Heidenhain states
that in the dog, stimulation of the chorda causes a secretion three to four
days after its section, and implies that later than this the nerve has no
effect.1 In an experiment on the cat, 1 2 obtained a copious secretion by
stimulating the cut end of the chorda three days after section ; a secre-
tion too copious, it seemed to me, to be attributed to the nerve-cells
which sometimes occur in the region stimulated. But Bradford,3 three
days after section of the chordo-lingual nerve near the pterygoid muscle,
obtained no secretion from stimulation of the nerve up to the point
where the chorda tympani leaves the lingual. In the dog he found no
effect five days after section, but no experiment was made at an earlier
date. It appears, then, that the time required for a loss of irritability
of the cut chorda tympani in the cat and dog lies somewhere between
three and five days.

Notwithstanding the early loss of irritability of the chorda tympani
after section, stimulation of its nerve-strands near the gland will in the
cat still cause secretion. In this way I obtained a fairly rapid secretion
thirteen days after section of the nerve, and a slight secretion in another
experiment forty-two days after section of the nerve. And Bradford
obtained secretion from the chorda tympani in the cat up to eleven days
after section of the chordo-lingual. In his experiments he sometimes
obtained a secretion by stimulating the chorda immediately after it had
left the lingual nerve, but sometimes only when the electrodes were
shifted farther towards the gland. In the dog, five or more days after
section, he obtained no secretion by stimulating the chorda in any part
of its course.

Vulpian 4 noticed in the dog, that a fortnight after section of the
chorda tympani, injection of extract of jaborandi into a vein gave rise to
a secretion, though less than normal. Extirpation of the superior
cervical ganglion at the time of section did not affect the result. In
the cat, I found that thirteen days after section of the chorda, venous
injection of a few mgrms. of pilocarpine caused a copious secretion,
and that forty-two days after section of the nerve, pilocarpine still caused
a secretion, though distinctly less than on the opposite side.

These experiments, taken together with those already given on the
action of nicotine (cf. p. 515), and with our general knowledge of the
relation of visceral nerve-fibres to nerve-cells, show that, on section of
the chorda tympani, its nerve-fibres degenerate in three to five days up
to the peripheral nerve-cells. The nerve-cells are placed chiefly in the
gland itself — more so in the dog than in the cat. And there can lie
little doubt that the variations observed as the result of stimulating the
peripheral portions of the chorda depend in the main upon variations in
the position of the peripheral ganglia. In some animals, postganglionic
fibres are stimulated when the electrodes are placed on the strands
outside the gland ; in other animals, this only occurs when the electrodes
are placed in the hilus. As the gland diminishes in size it naturally
gives a less copious secretion under the influence of pilocarpine.

1 Heidenhain (Hermann's "Handbuch," 1880, Bd. vi. S. 88) states that, although there
was secretion, there was no increased flow of blood.

2 Journ. PhysioL, Cambridge and London, 1885, vol. vi. p. 71.

3 Ibid., 1888, vol. ix. p. 304.

4 Compt. rend. Acad. d. sc., Paris, 1878, tome Ixxxvii. p. 350. Before this, Provost had
stated that muscarine causes secretion after degeneration of the chorda tympani ; cf. Arch,
de physiol. norm, etpath., Paris, 1874, p. 719, note.

THE PARALYTIC SECRETION. 521

The peripheral nerve-cells1 in connection with the gland may be
spoken of as a local nerve-centre. This local centre is capable of
exciting the gland-cells to activity long after the chorda tympani, which
normally conveys impulses to it from the central nerve-centre, has
degenerated.

Heidenhain suggested that the paralytic secretion might be due to a
stimulation of the gland-cells by the decomposition products of the
stagnating saliva. He observed that if the duct were clamped for about
a day, a slow secretion of watery saliva ensued. The cases, however, are
hardly comparable, inasmuch as, whilst the duct is closed, secretion is
formed which partly distends the alveoli and partly is forced out of the
ducts and lumina, and bathes all the tissues of the gland.

A final explanation can hardly yet be given, but some observations
made on the cat lead me to think that the secretion is the result of
nervous stimuli. In the cat the paralytic secretion is much diminished
and even stopped by excess of chloroform and by apnoea ; and is
increased markedly by dyspnoea ; the dyspnoeic flow takes place more
readily than on the opposite side, and, so far as can be judged, more
readily than in a normal gland. These results indicate that the
paralytic secretion is due chiefly, at any rate, to a slight continuous
excitation of the local nerve mechanism.

Heidenhain found that the paralytic secretion also occurred in the dog,
when the superior cervical ganglion was excised at the time of section of
the chorda. In this case the secretion is due wholly to local changes.
In the early stage of secretion in the cat, three days after section of the
chorda alone, I noticed that section of the cervical sympathetic very
much diminished or even stopped both the paralytic secretion and the
dyspnoeic secretion, although, in the later stages, section of the cervical
sympathetic had little or no effect. Probably, then, if the sympathetic
is intact, the secretion which occurs in the first few days after section of
the chorda is largely due to impulses travelling down the sympathetic
from the central nervous system.

The loss of weight which occurs in the submaxillary and the sub-
lingual glands, after section of the chorda tympani, amounts in a few
weeks to one-third to one-half of the original weight of the glands.
Bradford has shown that section of Jacobson's nerve causes a similar
loss of weight in the parotid gland2 of the cat. Whether complete
atrophy takes place, and if so what time it requires, there is no evidence
to show.

In the submaxillary gland, and no doubt in the others also, the loss
of weight is due to a loss of cell substance by the individual cells. And
this loss is simply an instance of the gradual atrophy which occurs in
tissues in the absence of functional activity. The persistent slight
activity, of which the paralytic secretion is the sign, is quite insufficient
to replace the normal exercise' of function.

In the dog, according to Heidenhain, the paralytic gland contains a
number of alveoli, presenting the appearance of the alveoli of an active
gland. In my experiments, both on the dog and cat, the gland-cells were
undoubtedly in the resting state. In the cat the saliva obtained by

1 Six weeks after section of the chorda in the cat, when the submaxillary gland had lost
one-third to one-half of its weight, the nerve-cells in the alcohol-hardened gland presented
no certain difference from the nerve-cells of the gland of the opposite side.

- Bradford did not observe a paralytic secretion from the parotid.

5 2 2 THE SALIVAR Y GLANDS.

stimulating the postganglionic chorda fibres, and by injecting pilo-
carpine, was distinctly viscid, and more viscid than normal. The alveoli
mentioned by Heidenhain were, I am inclined to think, the demilunes
which a decrease in the size of the mucous cells inevitably brings into
prominence, notwithstanding an actual decrease in the size of the
individual demilune cells.

Stimulation of the cervical sympathetic, during the progress of the
paralytic secretion, has practically its normal action both in the dog and
the cat. In the dog, it gives, when- stimulated after a sufficient interval
of rest, a brief quick now of watery saliva, corresponding with the
augmented secretion, and after this a slow slight secretion even thicker
than usual. If the stimulus be prolonged, there is a long pause in the
paralytic secretion, due partly to anaemia of the gland, and partly to the
resistance offered to the now by the thick saliva in the lumina and
ducts. In the cat, the sympathetic produces secretion in the usual way
and of the usual kind ; and unless the stimulation be too prolonged, the
paralytic secretion slowly creeps on in the intervals between the several
stimulations.

Heidenhain noticed in the dog that section of the chorda tympani on
one side caused a slight continuous secretion from the submaxillary
gland of the opposite side. The occurrence of such a secretion I con-
firmed in the cat. It is convenient to have a name for this secretion,
and I have called it the antiparalytic, or, more briefly, the antilytic
secretion. In my experiments the antilytic secretion was stopped by
apncea and by excess of chloroform. Dyspnoea caused a secretion
apparently greater than normal, though less than on the paralytic side.
No certain antilytic secretion was observed either thirteen or forty-two
days after section of the chorda. In its early stage, three days after
section of the opposite chorda, it was diminished by cutting the chorda
of the same side, and abolished by cutting the sympathetic also. So far,
then, as regards the cat, there is some ground for thinking that the anti-
lytic secretion is transitory and due to impulses set up in the central
nervous system.

Section of the chorda tympani probably leads to slow changes in the nerve-
cells of the secretory centre which are connected with the chorda fibres ;
these changes might make the central nerve-cells more irritable, so that they
passed into a condition of continuous slight activity, thus producing the anti-
lytic secretion. Or the antilytic secretion might, as suggested by Bradford, be
simply a reflex from the tissues injured during the section of the chorda.

According to Heidenhain, the antilytic secretion in the dog continues after
section of both chorda tympani and sympathetic nerves. As it is difficult to
see why the local mechanism should be so easily thrown out of gear, it is best
to wait for further observations on the matter.

Little is known as to the time taken for the chorda tympani fibres to
regenerate. In a puppy, I obtained, three months after section of the chorda
tympani, a secretion much as usual, on stimulating either the nerve which had
been cut or the chordo-lingual, so that presumably regeneration is fairly com-
plete in three months.

Section of the cervical sympathetic x has no observable permanent effect
upon the gland, and it causes no paralytic secretion. The blood vessels
for a time dilate, but this soon passes off. The nerve soon loses its

1 Cf. Langley, op. cit,., and Bradford, op. cit.

REFLEX ACTION OF PERIPHERAL GANGLIA. 523

irritability ; in the cat, according to Bradford, it gives no secretion three
days after section.

Stimulation of the ganglion will still cause secretion and pallor of
the gland for several weeks after section of the nerve, and possibly
indefinitely.

Excision of the superior cervical ganglion has also no certain effect
upon the salivary glands, and does not give rise to a secretion. In the
rabbit I could see no decrease in the size of the submaxillary glands,
or alteration in their histological appearance, nine, sixteen, and twenty-
three days respectively after removal of the ganglion, nor in a case in
which the ganglion had been removed five years previously by Dr. Pye-
Smith. The chorda tympani still causes secretion and flushing of the
gland, though the flushing is apparently less than normal. Bradford
removed the superior cervical ganglion in the cat. He found no atrophy
of the gland up to seven weeks after the operation ; indeed, in his cases
both the submaxillary and the parotid glands were somewhat heavier
on the operated than on the sound side. Eemoval of the ganglion
causes the sympathetic filaments on the gland artery to degenerate, the
loss of irritability being fairly rapid ; thus, three days after the operation,
Bradford obtained no secretion on stimulating these nerve-filaments.

SECRETION DUE TO A REFLEX ACTION OF PERIPHERAL GANGLIA.

We may reject the view of Bernard,1 that a secretion can be
obtained from the submaxillary gland of the dog, by means of nervous
impulses passing from the mucous membrane of the tongue by the
lingual nerve to the " submaxillary " ganglion, and thence to the gland.
The direct proof alleged in favour of this view was that occasionally,
after section of the chordo-lingual, direct stimulation of the tongue, or
the application of ether, caused a slight secretion. As no anaesthetics
were given, it is quite possible that a slight flow from the duct might be
caused by reflex movements. The result was not obtained by Eckhard,
Bidder, and others ; and until it can be obtained with some constancy,
and after administering at any rate a moderate amount of anaesthetics, it
may properly be disregarded.

The indirect proof alleged is that after section of the chordo-lingual,
stimulation of the lingual on its course to the tongue (the nerve being
cut and the central end stimulated) causes a secretion from the sub-
maxillary gland. This, in fact, is commonly the case. The amount of
the secretion, broadly speaking, increases the nearer the electrodes are to
the chorda tympani. It is often barely more than perceptible. The
fact observed by Bernard, that three to five days after section of the
chordo-lingual, a secretion could no longer be obtained, seems sufficient,
with our present knowledge of the central nervous system, to show that
the lingual secretion cannot be reflex in the ordinary sense.

There can be little doubt that Schiff 's 2 explanation is in the main
correct, namely, that some secretory fibres for the submaxillary gland,
instead of running to it direct by the chorda tympani, accompany the
lingual for a short distance and then run back to the gland. Schiff

1 Journ. de I'anat. et physiol., etc., Paris, 1864, tome i. p. 507. For some further
account of the earlier papers, see Foster's "Text-book of Physiology," 1879, 3rd edition, p.

2 "Lesons sur la physiol. de la digestion," 1867, tome i. p. 284.

524 THE SALIVAR Y GLANDS.

seems to have thought that these recurrent fibres ran in a single bundle
a considerable distance down the lingual, for he says that when the
lingual nerve is cut about 2 cm. beyond the point where the chorda
tympani leaves it, and time is allowed for degeneration, no secretion is
obtained by stimulating the central end : a negative result which was
not obtained by Wertheimer.1 Wertheirner's positive result then may
be taken as showing that the recurrent fibres leave the lingual at more
than one spot.

But it is nevertheless possible that on stimulating the central end of
the lingual a secretion should be obtained which is not produced by
recurrent fibres, and which is due to nervous impulses passing through
local nerve-cells. The nerve-cells on the course of the chorda tympani
are, as we have seen, scattered ; if tie chorda tympani fibres branch
before running to these cells, stimulation of one of the branches would
probably cause a nervous impulse to pass to the more central branches
and to the cells connected with them. This would be a reflex through
efferent fibres of the kind described in some other peripheral ganglia.2
Such action with the actual anatomical arrangements is more likely to be
obtained from the sublingual than from the submaxillary gland. It
would, of course, be annulled by degeneration of the chorda tympani.

DIRECT IRRITABILITY OF GLAND-CELLS.

It is natural to suppose that stimulation of the gland-cells by
electrical, chemical, or mechanical stimuli should be capable of causing a
secretion. There is, however, no direct evidence that this is the case.
After atropine has been given, no secretion has been obtained ; but it
must be mentioned that, even when the nerve-endings in the sub-
maxillary gland are in a full state of irritability, it is difficult to obtain
secretion from it by electrical or other stimuli applied to its outer sur-
face, and which do not affect the internal bundles of nerves.3

EXTIRPATION OF SALIVARY GLANDS, INJECTION OF SALIVA INTO

THE BLOOD.

The extirpation of all the salivary glands is, of course, impossible ;
but the large salivary glands, i.e. those which secrete by far the greater
portion of the saliva, can be cut out. This has been done by Fehr.4
He states that in the dog he removed not only the parotid, submaxillary,
and sublingual glands on both sides, but also the orbital glands. The
operation had no appreciable effect on nutrition ; and the only difference
in the behaviour of the animal was that it drank more water. A
similar result was observed by Schafer and Moore.5 They removed
from a dog the parotid, the submaxillary, and the larger part of the sub-
lingual glands. There \vas no disturbance of nitrogenous metabolism,
and neither sugar nor albumin appeared in the urine. Carbohydrates

1 Arch, de physiol. norm, et path., Paris, 1890, p. 519.

2 Langley and Anderson, Journ. Physiol. , Cambridge and London, 1894, vol. xvi.
p. 410.

" Bernard ("Lecons sur la proprieties physiologiques," etc., 1859, tome ii.) found, by

stimulating the gland directly, that pain was caused.
4 Henle and Meissner's Jah\

Jahresb., in Ztschr. f. rat. Med., 1862, p. 255.
5 " Proc. Physiol. Soc.," 1896 p. xiii., Journ. Physiol., Cambridge and London,
vol. xix.

GENERAL CONSIDERATIONS. 525

were well digested, and the animal throve on a diet of bread and
milk.

The salivary glands, then, in the domestic dog, appear to be rather
a convenience than a necessity, and there is no evidence that they have
any " internal secretion " ; carbonic acid passes from the gland-cells to
the blood, but there is no indication that any other substance does so.

Saliva injected into the blood is much less harmful than might be
expected. Bernard,1 indeed, injected considerable quantities into a vein
of a dog to which no anaesthetics had been given, and did not observe a
result of any kind. Extracts of the salivary glands injected into the
blood cause a temporary fall of blood pressure,2 but so many substances
in solution do this that the action cannot be regarded as specific.

GENERAL CONSIDERATIONS ; THEORIES AS TO THE MODE OF ACTION
OF SECRETORY NERVES.S

The facts which show that secretory nerve-fibres exist in the cranial
nerves are so well known, that it is not necessary to consider them in
detail. It is sufficient here to recall the fundamental facts, that secre-
tion may in each salivary gland take place at a pressure higher than
that of the blood supplied to the gland, and that nerve-fibres end in
connection with the gland-cells.4.

In the case of the sympathetic, the comparatively slight amount
and the transitory nature of the secretion, render the question less clear.
It was in fact suggested,5 early in the history of sympathetic saliva,
that the cervical sympathetic nerve causes a secretion solely in con-
sequence of the pressure exercised on the gland-cells by the contraction
of the blood vessels, brought about by stimulation of the nerve. Such a
view offers a plausible explanation of many of the facts relating to the
secretory action of the sympathetic, such as the normal small quantity
of the secretion in the dog, the increased quantity after the cranial nerve
has been stimulated, the rapidity with which the maximum rate of the
" augmented " saliva is attained, the normal absence of reflex secretion
by way of the sympathetic when sapid substances are placed on the
tongue, and the absence of effect of atropine and pilocarpine upon the
secretory function of the sympathetic.

But a closer inquiry shows, nevertheless, that this view is untenable.
On the general theory it may be noted, that the constriction of the small
arteries of the gland in all probability decreases the pressure on the
gland-cells instead of increasing it. On the experimental side, we may
mention three points.

1. The constriction of the blood vessels has at times no relation to

1 "Le9ons de physiol. expe*r.," 1856, p. 141.

2 Schafer and Oliver, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 277.

3 For a general historical account of the views which have been held with regard to
secretion, I may refer the reader to Prof. Gamgee's Address to the Biological Section of the
British Association in 1882, and to Prof. Heidenhain's Introductory Account in Hermann's
"Handbuch," 1880, Bd. v. Th. 1, S. 1-13.

4 Cf. Fusari et. Panasci, Arch. ital. de biol., Turin, 1891, tome xiv. ; G. Eetzius,
Biol. Untcrsuch., Stockholm, 1892, N. F., Bde. iii., iv. ; Korolkow, Anat. Anz.,
Jena, 1892, Bd. vii. S. 580; A. Dogiel, Arch. f. mikr., Anat. Bonn, 1893, Bd. xlii. ;
Berkeley, Johns Hopkins Hosp. fiep., Baltimore, 1894, vol. v. ; C. Arnstein, Anat. Anz.,
Jena, 1895, Bd. x. S. 410; G. C. Huber, Journ. Exper. Med., Baltimore, 1896, vol. i.
p. 281.

5 Griinhagen. Ztschr. f. rat. Med., 1868, Bd. xxxiii. S, 258.

526 THE SALIVAR Y GLANDS.

the flow of saliva. Thus, on stimulating the cervical sympathetic in the
dog, it may happen that the secretion does not begin until the pallor of the
gland and the reduction of blood flow are about maximal ; the slow flow
of saliva may then continue without change in the blood flow, and may
even continue after the end of the stimulation, when the blood vessels
are dilated. In the cat, contraction of blood vessels without any flow
of saliva can be easily observed by stimulating the sympathetic after
about 30 mgrms. of atropine have been injected into the blood.

2. The quantity of saliva obtained by squeezing the gland is less
than that obtained by stimulating the sympathetic. This is most
readily observed in the submaxillary gland of the cat, in which about
ten times as much saliva is usually obtained by stimulating the sympa-
thetic as by squeezing the gland.

3. The total amount of saliva obtained by stimulating the sympathetic
is, in some cases, too great for it to be obtained by simple expression of
fluid from the gland. This is perhaps most striking in the case of the
augmented secretion of the submaxillary gland of the dog. In favour-
able circumstances, \ to J c.c. of saliva may be obtained by a single
continuous stimulation, and with a diminution in the size of the gland
not appreciably greater than would be accounted for by the diminution
in the amount of blood in it.

Some of these observations, it will be observed, negative also the
possibility that the sympathetic saliva can be due to pressure exercised
by contractile tissue other than blood vessels around the alveoli.

We conclude, then, that both the cranial and the sympathetic nerves
contain fibres which end in connection with the gland-cells, and which
are capable of causing changes in the cells leading to secretion; and
we pass on to consider whether the secretory nerve-fibres are of more
than one kind. There are two possibilities to take into account : — first,
whether there are fibres inhibiting the secretion as well as fibres excit-
ing the secretion ; and, secondly, whether there are fibres causing
chemical changes in the gland distinct from those which cause the flow
of fluid.

The former possibility we may treat briefly. Until it is shown that
the decrease in the blood flow through the gland which the sympathetic
causes is insufficient to account for the decrease in the flow of saliva
which the sympathetic at times produces, this hypothesis of inhibitory
fibres does not need serious attention.

The second possibility we must consider more at length. The
theory of the existence of two kinds of nerve-fibres in secretory nerves
is due to Heidenhain.1

According to this theory, the secretory fibres proper cause certain
unknown changes in the cells leading to the passage of fluid through
them. The trophic fibres cause chemical changes in the cells leading,
on the one hand, to the growth of protoplasm, and, on the other, to the
conversion of the stored-up secretory material into a more soluble form.
Further, according to this theory, the proportion of these two kinds of
nerve-fibres is different in cranial and sympathetic nerves. The cranial
nerve contains more secretory than trophic fibres. The sympathetic
nerve contains more trophic than secretory fibres.

The trophic fibres, it will be observed, have two functions, not
necessarily connected with one another. The evidence that they cause

1 Heidenhain, Hermann's "Handbuch," 1880, Bd. v. (1) p. 78.

GENERAL CONSIDERATIONS. 527

a growth of protoplasm is derived from the microscopical examination
of the various glands, after stimulating the sympathetic. Thus,
according to Heidenhaiii — to take the most striking example adduced
by him — if the cervical sympathetic be stimulated in the dog for several
hours, there is no secretion from the parotid gland, but the gland-cells
show a great increase in carmine-staining material, i.e. a considerable
growth of protoplasm.

I have not been able to convince myself that any considerable
changes of this nature take place. On stimulating the sympathetic the
thick secretion usually stops up the ducts, and if any further secretion
takes place it can only pass out into the lymph spaces. After
stimulating the sympathetic for five to seven hours, I do not find any
marked increase in the staining power of the cells ; and the fresh gland
either shows no outer non-granular zone at all, or a very small one.

The evidence that a separate class of trophic nerve-fibres exists,
which converts stored-up material into a more soluble form, rests on
certain facts, which we will discuss as far as possible separately. In the
first place, there are the facts adduced to prove that soluble substance is
formed during secretion, and which do not touch the question whether
the formation is due to a special nerve-fibre or not.

1. It was shown by Heidenhain that the percentage of organic
substance in saliva, secreted under the influence of the cranial nerve,
increases with the rate of secretion. On this fact Heidenhain argued
somewhat as follows : If the solvent power of the fluid passing through
the cells remains constant, and the solubility of the stored-up substance
in the cell also remains constant, the amount of the stored-up substance
dissolved by the fluid in its passage through the cell will decrease as the
rate of its passage increases. For, below saturation point, the amount
dissolved must decrease the less the time the solvent is in contact with
the solvend. But, in fact, the slower the passage of the solvent the less
it dissolves ; hence, with increasing rate of flow, there must be either an
increase in the solvent power of the fluid, or an increase in the solubility
of the stored-up substance. Heidenhain considered that in mucous
saliva, at any rate, the only substance which could increase the solvent
power of the fluid was sodium carbonate. And this salt, he found, did
not increase, as saliva was secreted more rapidly. In consequence,
he concluded that the substance in the cell must become more soluble.
An increase in solubility of part of the stored-up substance was then a
result of stimulating nerve-fibres.

But it is by no means clear that the rapidly-secreted fluid is not a
better solvent than the fluid secreted slowly. Werther, working in
Heidenhain's laboratory, found in fact that the percentage of sodium
carbonate in the submaxillary saliva of the dog does increase, though
but slightly, with the rate of secretion of saliva. And, in addition, it
cannot be regarded as certain that sodium chloride and other neutral
salts do not aid in the solution of the substances stored up in the cells.
The evidence, indeed, seems to me to be on the other side. And, as we
have seen, when saliva is secreted more rapidly, there is an increase in
the percentage of salts as well as in that of organic substances. Finally,
the statement that the faster the fluid passes through the cell, the less
substance it will dissolve, depends on the assumption that in slowly-
secreted and in rapidly-secreted saliva, the fluid has an equal oppor-
tunity of dissolving the stored-up material. This is not necessarily the

528 THE SALIVAR Y GLANDS,

case; the more rapidly-flowing fluid might pass more freely into the
intracellular spaces, and come into more intimate contact with the
mucous or other stored-up material of the cell.

2. Better evidence of the formation of soluble substances in gland-
cells, under the action of nerve stimulation, is afforded by the after-action
of strong nerve stimulation. If, between two weak stimulations of a
cranial nerve, a strong stimulation of the same nerve or a stimulation
of the sympathetic nerve be introduced, the second weak nerve
stimulation gives rise to saliva containing a higher percentage of organic
substance than that produced by the first similar stimulation. The
fact may be taken as showing that the strong stimulation, introduced
between the two weak ones, has converted slightly soluble into more
soluble material, which has only partTally been carried out of the cell.
But this is not the only possible explanation. We can imagine that the
stronger the stimulus the more the fluid passing through the cell will
be brought into contact with the stored-up substance, with the result
that more of this substance will absorb water and pass a stage on the
way to solution than would otherwise be the case. And consequently,
for some time after a strong stimulus, any fluid passing through the
cell would find substance already on the way to solution or already
dissolved, without any alteration in its chemical composition.

The experimental evidence, then, of the formation of a soluble
substance during secretion is not satisfactory. And, in fact, it is
doubtful whether the glands contain any stored-up organic substance
in a " comparatively insoluble " state. The granules of the glands are
seen to enter readily into solution — micellar or other — when a crushed
piece of the gland is irrigated with dilute alkaline salt solution. The
mucin or mucins of saliva have not been shown to be different from the
rnucin or mucins contained in the salivary glands. The mucous material
of the glands is often spoken of as mucigen, following the analogy of
trypsinogen and pepsiiiogen ; but it is well to remember that there is
nothing to show that trypsinogen and pepsiiiogen are less soluble in
dilute saline solution than trypsin and pepsin ; and further, that there is
some evidence that the cesophageal glands of the frog secrete pepsinogen
as such, and not as pepsin.

Supposing, however, it were shown that nerve stimulation causes an
increase in solubility of secretory material, it would still remain to show
that this change is caused by a special class of nerve-fibres ; and to this
part of the theory we may now pass.

It was thought that direct proof of the separate existence of trophic
fibres was afforded by the results on the parotid gland of stimulating
the sympathetic in the dog. Stimulation of the sympathetic caused no
flow of saliva, but caused nevertheless histological changes in the
gland-cells, and a great increase in the percentage composition of the
saliva obtained in other ways. Here was apparently an instance of
nerve-fibres producing the changes demanded of the trophic fibres, by
hypothesis, and producing no others.

But we have seen (p. 498) that the sympathetic is capable, in
favourable circumstances, of causing a flow of saliva from the parotid
gland of the dog. Since, then, secretory fibres are present in the
sympathetic strand supplying the parotid, the action of the nerve in
this particular instance cannot, without further examination, be taken to
show the existence of an additional class of nerve-fibres.

GENERAL CONSIDERATIONS. 529

We come, then, to a comparison of the relative effects of the cranial and
sympathetic nerves as the final part of the evidence for the existence of
two classes of nerve-fibres. It is said that the difference in the percentage
composition of sympathetic saliva, and of that produced by stimulating
the cranial nerve, can only be satisfactorily explained by supposing that
secretory and trophic fibres are present in both, and that the number
of trophic fibres relatively to the secretory is greater in the sympathetic
than in the cranial nerves.

This conclusion seems to me to be legitimate and unavoidable, if a
diminution in the blood supply to the glands brought about by vaso-
constrictor nerves does not markedly increase the percentage of organic
substance in the saliva secreted. But this, so far, has not been shown
to be the case (cf. p. 508). The question can hardly be settled until
means are found of stimulating the sympathetic vaso-constrictor fibres
of the salivary glands without stimulating the sympathetic secretory
fibres.

We find, then, that the hypothesis of a separate class of trophic
fibres, although affording a convenient explanation of a certain number
of facts, can hardly be considered proved at any point. It presents also
certain difficulties of its own which we need not insist on here.

On the whole, I think the most probable view is, that only one
kind of nerve-fibre runs to the gland-cells, and that this causes all the
changes in the gland-cells which are capable of being caused by nerve
stimulation. These changes include the taking up proteid material
from the lymph, some katabolic action — shown by the setting free of
carbonic acid — and changes leading to the passage of water and salts
through the cell. It is not improbable that the nervous impulses hasten
the conversion of absorbed proteid to secretory substances, and it is
perhaps possible that they increase the solubility of the secretory sub-
stance already formed. The effect of the secretory fibres, as regards
the amount and percentage composition of the saliva obtained, would
naturally vary with the strength of the stimulus, the condition of the
gland at the time, the quality and quantity of the blood flowing through
the gland.

The exact processes which take place in gland-cells and which lead
to secretion is at present outside the range of our knowledge. The high
secretory pressure naturally suggests osmosis as the cause of the passage
of water and of salts. And, about five and twenty years ago, the view
that secretion is due to the formation in the cells of a substance of high
endosmotic pressure was put forward by Hering and others. Much
more is known now of the phenomena of osmosis than was known then ;
but the nature of the process is still so obscure, that to attempt to
explain secretion on the lines of osmosis is to venture on little better
than conjecture.

It may, however, be worth while to state briefly some points regarding the
relation, or possible relation, of osmosis to secretion.

We will consider, first, what facts of secretion we could in some sort
account for, on the theory that osmotic pressure is of the same nature as
gaseous pressure, and assuming that osmosis does take place in the gland- cells.

The facts which it seems most feasible to offer an explanation of are, the
occurrence of secretion when the cells are stimulated and not at other times,
the increase in the rate of flow during stimulation, the increase in the per-
centage of salts in saliva with increase in the rate of flow.
VOL. i.— 34

530 THE SALIVAR Y GLANDS.

We may speak of the alveolar cells as forming a membrane, and call the
part towards the lymph the outer layer of it, and the part towards the lumina
of the gland the inner layer. In the inner layer are spaces containing soluble
organic substance.

The explanation of the above-mentioned facts on the osmotic theory might
be as follows : — The membrane is impermeable in the unstimulated state ; on
stimulation, a rearrangement of its molecules takes place, so that, of immedi-
ately adjoining portions, parts are permeable to water and parts are permeable
to salts also, whilst parts remain impermeable. On increasing the strength of
the stimulation, a larger and larger area of the membrane becomes permeable,
and of this a proportionately larger and larger part becomes permeable to
salts.

The increase in the percentage of organic substance in saliva, which accom-
panies increased rate of flow, might be due simply to the greater percentage
of salts causing an increase in the solvent power of the fluid, or to a larger
proportion of the fluid passing into the spaces of the inner layer.

Proteid molecules do not pass through the gland-cells, but they enter it,
and are deposited, forming the outer non-granular zone ; the process is spoken
of as the growth of protoplasm. We have reason to believe that the rate of
growth of the protoplasm increases more than the rate of flow of fluid as the
stimuli pass from weak to strong.

To account for this on the osmotic theory, it must be supposed that only
the outermost portion of the membrane becomes permeable to proteids, so that
the proteid molecules are blocked in their passage, and further that the ratio
of permeability to proteids and to water is greater with strong than with weak
stimuli. The theory becomes further complicated, if we have to apply it also
to a taking up of proteid during rest (cf. p. 486), when there is no passage of
fluid ; for in this case the inner part of the membrane at least must be im-
permeable to water, whilst the outer part is permeable to proteids.

So far we have assumed that the conditions of the solutions on the two
sides of the membrane are such as would lead to an osmotic flow through it,
directed from its outer to its inner surface. But this is precisely the point it
is difficult to be clear about. There is no obvious reason why the fluid in
contact with surfaces of the membrane bounding the spaces should be very
different from the fluid issuing from the inner surface of the membrane. But
the saliva contains commonly less organic substance and less salts than the
lymph. Why then should fluid pass from the lymph to the saliva 1 It can
only be said that it is perhaps possible that a passage both of water and salts
might take place if the organic substance in the spaces formed some combina-
tion with water and salts, of which at present we have not sufficient evidence.

The hypothesis which I have stated above seems capable of being put
to the test of experiment, and of being either proved or disproved. Failing
it, we are, I think, driven to suppose — apart from the hypothesis of special
vital activity — that the outer layer of the cell forms a loose chemical combina-
tion with various substances of the lymph, and that these are passed on from
molecule to molecule and disassociated at the inner surface. A process of this
kind forms the basis of the chemical theory of osmosis. And it seems to me
not improbable that such a process occurs in gland-cells, but it is extremely
difficult to see how to bring any experimental evidence to bear directly on the
question. The investigation appears to demand, as a preliminary, an intimate
knowledge of the chemical nature of the membrane. The membrane consists
of protoplasm. And there are few problems in physiology which appear more
remote from solution than that of the chemical nature of living substance.

MECHANISM OF SECKETION OF GASTRIC,
PANCREATIC, AND INTESTINAL JUICES.

By J. S. EDKINS.

CONTENTS. — Histological Appearances of tlie Secretory Conditions of the Stomach,
p. 531 — Functions of the Cells and Regions of the Stomach, p. 532 — Methods
of obtaining Gastric Juice, p. 536 — Influence of the Nervous System on Gastric
Secretion, p. 537 — Conditions which provoke Secretion, p. 540 — Formation of
the Ferments of Gastric Juice, p. 542 — Formation of Rennin, p. 543 — Variations
in Gastric Juice during Digestion, p. 544 — Histological Appearances of the
Secretory Conditions of the Pancreas, p. 546 — Influence of the Nervous System
upon Pancreatic Secretion, p. 547 — Conditions which provoke the Flow of
Pancreatic Juice, p. 551 — Ferments of the Pancreatic Juice and their Ante-
cedents, p. 551 — Variations in Pancreatic Juice during Digestion, p. 553 —
Evidence of Secretion in the Intestine, p. 554.

THE MECHANISM OF GASTRIC SECRETION.

The histological appearances of the different secretory con-
ditions of the stomach, and the relation of the secretory granules
to the enzyme.— Though the existence of specific granules in secretory
glands had previously been pointed out in connection with the pancreas
and some salivary glands, it was not till 1879 that their existence was
also observed in the secreting cells of the gastric mucous membrane by
Langley and Sewall,1 who showed that the chief or central cells are, in
the resting condition, crowded with conspicuous granules, and that
during digestion the granules in these cells diminish. As far as the
ovoid or border cells are concerned, granules are to be seen in these, but
they are much smaller in size, though quite discrete.

After digestion the cells take on different appearances, which consist
mainly in the decrease of the number of granules. This decrease may
be manifested in two different ways. In the first case, and the more
typical, the outer border of the cell alone may show the lack of granules,
the luminal border retaining them, unless in an extreme condition of
exhaustion. In the second case, there may be a uniform decrease of
granules throughout the cell, accompanied by a diminution in size
of the cell, but unaccompanied by any formation of zones. These two
forms of decrease may occur in different parts of the gastric mucous
membrane of the same animal. Thus in the greater curvature of the
stomach in both the rabbit and guinea-pig there is a formation of zones,
in the cells of the fundus such a division is not seen.

1 "Changes in Pepsin -forming Glands," Journ. PhysioL, Cambridge and London, 1879,
vol. ii.

532 MECHANISM OF SECRETION OF GASTRIC JUICE.

At the pyloric end of the dog's stomach in the resting or exhausted
state, an appearance is seen which consists of small and obscure granules
somewhat radially arranged, an appearance which bears a slight resem-
blance to that seen in the ducts of salivary glands in the fresh condition.
A very marked difference exists, however, between the pyloric cells and
the cardiac cells, and there seems little doubt that considerable histo-
logical distinction obtains. Nevertheless, attempts have been made by
Ebsteiii l and others to prove the identity of the chief cells of the cardiac
end with the lining cells of the body of the pyloric glands. It may be
stated that Langley and Sewall found no difference in the pyloric cells
whether the glands were in a resting or active condition, and other later
observations also show a marked uniformity of appearance in the cells
whatever the secretory condition be.

It may then be regarded as established that a diminution in the
amount of granules characterises the chief cells as digestion advances.
It has, moreover, been shown by Griitzner 2 and others, that as digestion
advances the fundus glands contain less ferment than in hunger. It is
therefore justifiable to conclude that the granules are in some way
connected with the ferment. In addition to this, we have the fact that
more pepsin can be obtained from the cells of the fundus in the rabbit
than from the greater curvature, and it is in the fundus that the cells
are conspicuously granular. We have, however, to consider that, though
the chief cells will yield pepsin, yet they do not actually contain pepsin.
If the granules then are connected with pepsin, it must be in some
antecedent form. The probable explanation of this is that the granules
of the chief cells consist wholly or in part of pepsinogen, the precursor
of pepsin.

The functions of the different forms of cells and of the different
regions of the stomach.— Heidenhaiii originated the view that the
chief cells were connected with the formation of pepsin, and the border
cells with the formation of the acid of the gastric juice. The arguments
upon which these conclusions are based are not direct, but though really
inferential they appear to be supported by such evidence that but little
doubt can be placed upon their accuracy.

The reasons for regarding the chief cells as connected with the
formation of pepsin have been dwelt upon in the previous section. But
is there evidence to disconnect the border cells from this same function ?
The most direct evidence we have is that, in the rabbit, the greater
curvature contains more border cells than any other portion of the
stomach ; the pyloric glands of the smaller curvature contain at most an
occasional border cell here and there, yet the amount of pepsin produced
by the two gland forms is scarcely different. The obvious conclusion is
that the border cells do not form the ferment. On the other hand, it is
noticed that the pyloric secretion is distinctly alkaline if separated from
the rest of the stomach ; this is affirmed by Klemensiewicz,3 Heidenhain,4
and, later, Ackermann.5 Apparently, therefore, such cells as are present

1 Arch. f. mikr. Anat., Bonn, 1870, Bd. vi.

"Untersuch. ueber d. Bildung u. Aussch. des Pepsins," Breslau, 1875.
3"Ueberden Succus pyloricus," Sitzungsb. d. k. Akad. d. Wissenxch., Wien, 1875,
Bd. Ixxi.

"Ueber die Pepsinbildung in den Pylorusdriisen," Arch. f. d. ges. PhysioL, Bonn,
1878, Bd. xviii.

5 " Experirnentelle Beitrage zur Kenntniss des Pylorussecretes beim Hunde," Skandin.
Arch.f. Physiol., Leipzig, 1894, Bd. v.

FUNCTIONS OF DIFFERENT FORMS OF CELLS. 533

in the pyloric region do not contribute to the formation of acid.
In the frog the source of the ferment is an alkaline juice fur-
nished by the oesophageal glands, whilst the cells in the stomach bear
resemblance to the border cells of the mammal, and here alone the
acid of the juice is secreted. The deeper parts of the cardiac glands,
where there are fewer border cells, do not give an acid reaction, the
acid reaction being evident only at the mouths and upper parts of the
glands.

Claude Bernard1 attempted to mark out the place where the free
hydrochloric acid first appeared, by injecting intravenously a solution of
ferric lactate followed by a solution of potassium ferrocyanide (these two
compounds react with the production of Prussian blue only in the
presence of a mineral acid). After the lapse of three quarters of an
hour the animal was killed and the tissues examined. A blue pre-
cipitate was only observed on the surface of the mucous membrane
of the stomach, especially in the neighbourhood of the lesser cur-
vature, but no trace of blue in the glands. This experiment might,
at first sight, be taken as indicating that the hydrochloric acid is first
set free on the stomach itself, and is not formed in the cells of the
gastric glands. Such a conclusion would be unwarranted. What the
experiment does teach is that there is no accumulation of acid in the
cells, but that the acid as rapidly as it is formed is thrown out of the
cells as a secretion.

Briicke2 tried to solve the same problem by exposing the stomach of
an animal in which digestion was actively going on, and carefully
removing all but the mucous coat ; both in the pigeon and in the rabbit
the reaction of the exposed mucous layer to litmus paper was found to
be faintly alkaline or very faintly acid, practically neutral, but on
testing the inner surface of the mucous membrane it was, as usual,
intensely acid. This again is an experiment which, had it given a
positive result, would have shown conclusively that the acid was
secreted by the gland-cells ; but, giving as it did a doubtful or negative
result, it teaches little, and by no means proves the statement that
the acid is not formed in the glands but in the stomach. In cutting
into the stomach wall in this manner, sources of alkali are tapped
in the small blood vessels and lymph spaces which are capable of
supplying more than sufficient alkali to neutralise any acid in the
gland lumina.

Briicke himself was not satisfied with this experiment, and attacked
the problem by another method, which gave him results from which he
concluded that the acid is really formed in the glands, and not in the
stomach cavity. In birds, the gastric glands are compound glands
forming flask-shaped bodies large enough to be easily seen without
magnification. These compound glands possess also a flask -shaped
cavity communicating with the stomach cavity by a comparatively
narrow duct. Into this central cavity of the gland the secretion passes.
Briicke took the secreting stomach of a fowl which had been killed
during digestion, washed it out with magnesia suspended in water to
neutralise the free acid on the surface of the mucous membrane, and
sought out one of the above-described glands filled with secretion.

1 "Lecons snr les proprieties physiol.," Paris, 1859, vol. ii.

" Sitzungsb. d. Jc. Akad. d. JVissensch., "VVien, 1859, Bd. xxxvii. ; " Vorlesungen,"
Aufl. 4, Bd. i. S. 306.

534 MECHANISM OF SECRETION OF GASTRIC JUICE.

This he cut across, and tested the reaction of the fluid in its cavity. He
found it as strongly acid as the secretion inside the stomach cavity.
This experiment may be taken to show that the acid is secreted in the
glands, but is continually being carried away by the stream of secretion.
It might be objected against this experiment, that the fluid in the cavity
of the compound gland is in communication with the stomach cavity
and is acid by reason of admixture, but the communicating duct is too
small to make this probable ; moreover, there must be a continual
stream flowing during secretion in the opposite direction from gland
cavity to stomach cavity. That the gland cavity is not passively filled
with secretion from the general stomach cavity, is also shown by the
fact that some of these glands are swollen out with secretion while
others are empty. It may be taken, thfen, that the gastric juice is acid
as secreted by the gland-cells, and does not first become acid in the
stomach.

Such observations as have been made in order to ascertain whether
the border cells yield an acid reaction have not been successful.
Though the mass of evidence is very greatly in favour of the view that
the border cells are the origin of the acid of the juice, there are not
wanting those who deny it entirely. Contejean 1 observed, as had
previously been shown by Langley,2 that the stomach cells of the frog,
although they secrete acid, also secrete pepsin. But a more remarkable
statement is that the pylorus cells secrete an acid juice. This is so
much at variance with the results of the majority of investigations, that
it cannot be accepted as correct. If it were true, a conclusive proof
would be furnished against the view that the border cells originate the
acid.

As regards the functions of the different regions of the stomach, it
may be stated that the fundus and the greater curvature form in most
animals pepsin, hydrochloric acid, and other constituents of the gastric
juice. But considerable discussion has taken place as to the functional
importance of the pyloric region. That an extract can be made from
the pyloric region containing pepsin is generally agreed, but such an
extract, in comparison with one prepared from the rest of the stomach,
has very small digestive value. Langley,2 in one experiment on the
mucous membrane of the mole, found that if the digestive power of
the pyloric region be taken as 1, that of the fundus would be 73.
What then is the source of the pepsin that can be obtained from
the pyloric mucous membrane ? Is it pepsin formed by the gland
cells in the pyloric region, or is it absorbed pepsin that has
passed with the absorbed food into the mucous membrane of this
region ?

Wassmann 3 and v. Wittich 4 have held that the pepsin was merely
infiltrated pepsin, and Wassmann stated that it was removable by
repeated washing with water. On the other hand, Ebstein and
Griitzner5 found that washing the mucous membrane of the pylorus
causes but a very slow loss of pepsin. If, then, the cells of the mucous

1 "Contribution a 1'etude de la physiologic de 1'estomac," CentralbL f. PhysioL,
Leipzig u. Wien, 1892.

2 Proc. Roy. Soc. London, 1881, No. 212.

3 " De digestione nonnulla," Berolini, 1839.

4 "Ueber die Pepsinwirknng der Pylorusdriiscn," Arch. f. d. gcs. Physiol., Bonn, 1873,
Bd. vii.

5 "Ueber den Ort der Pepsinbildung in Magen," ibid., 1872, Bd. vi.

FUNCTIONS OF DIFFERENT FORMS OF CELLS. 535

membrane absorb and fix pepsin, the)7 fix it in a somewhat stable
combination. Such absorption would be comparable to that which, as
v. Wittich pointed out, fibrin exerts when placed in a glycerin solution
of pepsin, the fibrin rapidly absorbing the pepsin so as finally to render
the glycerin solution inert. The pepsin so absorbed can only be
recovered by treatment with hydrochloric acid and not by extraction
with water. Finally, Klemensiewicz l and, later, Heidenhain2 have
isolated portions of the pyloric mucous membrane, and observed the
secretion thereby obtained. But in Klemensiewicz's experiments the
secretion was so mixed with abnormal fluids, such as pus, that the
observations cannot be regarded as 'an index of the normal state of its
composition. In Heidenhain's observations this difficulty was avoided
by the adoption of antiseptic precautions. He obtained a secretion
alkaline in reaction, viscous in character, rich in pepsin and rennet
ferment. With hydrochloric acid O'l per cent, it digested fibrin very
energetically, and caused milk to clot in about a quarter of an hour.
Both Klemensiewicz and Heidenhain insist on the strong proteolytic
powers of the secretion ; the former even states that it digests fibrin as
rapidly as the juice from the mucous membrane of the fundus. There
is then a certain amount of disparity between the results of extracting
the mucous membrane with various fluids, and testing the proteolytic
powers of the extracts and those obtained by observing the peptic
strength of the juice secreted by an isolated portion of the pyloric
region of the stomach. We must therefore ask which furnishes us with
the best criterion of the normal activity of the pyloric mucous
membrane ? By extracting with hydrochloric acid a large proportion of
the pepsin present in the mucous membrane can ultimately be removed.
But Klug 3 finds that, in order to obtain all the pepsin from the pyloric
mucous membrane, it is necessary to make at least three successive
extracts with hydrochloric acid, each one of the duration of twenty-four
hours. The first extract shows little or no peptic activity; the second and
third, marked activity. He ascribes the change of activity to the pro-
bability that the large amount of proteid present prevents the acid from
separating the pepsin from its proteid compounds. But this difference
is not found with the fundus, and it is somewhat difficult to understand
why it should be more easy to extract the pepsin by acid from the
fundus glands than the pyloric. We may regard it therefore as
probably true that repeated extracts furnish us with a considerable
amount of the pepsin obtainable. On the other hand, it may be asked
how far the juices secreted into artificially isolated portions of pyloric
mucous membrane are to be regarded as normal ? It seems that in
Heidenhain's case there was an absence of inflammatory conditions.
But it must be noticed that the operation performed involved very
considerable interference with the nerve supply to that portion of the
mucous membrane. The mucous membrane was probably, therefore, to
some degree in an abnormal condition. Nevertheless, the fact that
proteolytic powers were shown could not be explained by reason of
such an abnormal state ; they must probably be indicative of normal
secretion. It seems impossible that any "infiltrated" pepsin could
produce the enduring effect in the secretion noticed by Heidenhain, and

1 Op. tit. - Op. cit.

3 " (jutcrsuch. aus dem Gebiete der Magenverdauung, " Ungar. Arch. f. Jfed,,
Wiesbaden, 1894, Bd. iii.

536 MECHANISM OF SECRETION OF GASTRIC JUICE.

it may be regarded as established that the pyloric glands do secrete
pepsin.

The results of experiments that have been made to ascertain
whether pepsin or pepsinogen is contained in saline extracts of the
pyloric mucous membrane, lead to the conclusion that pepsinogen
may be present. The fact that the amount of pepsin obtainable from
the pyloric mucous membrane is increased rather than diminished l as
digestion advances is susceptible of one of two explanations. It may
be that during digestion the intracellular formation is more rapid than
the secretion, and thus an absolute increase in the pepsin contents of
the cells occurs. Or it may be that in course of absorption of certain
products of digestion by the pyloric mucous membrane, a certain
amount of pepsin becomes " infiltratec? " in the membrane. At any
rate, there is something fundamentally different in this respect between
the secretion of pepsin at the pyloric end of the stomach and in
the fundus glands, for in the latter the amount of pepsin decreases
as digestion advances, whilst in the former there is an increase. Nor
is there any evident change in the histological appearance of the pyloric
cells corresponding to a secretory process. It is probable, as Langley
has suggested, that the precursor of pepsin (" mesostate," as it may con-
veniently be called) is not so highly specialised as in the fundus glands ;
or there may be a series of mesostates, the more highly developed
splitting off the enzyme earlier than the more lowly. The observations
of King, which are confirmatory of the much older observations of
Briicke, that a series of hydrochloric acid extracts will continue to show
proteolytic powers, suggests that there are several mesostates of
different grades coexistent in the cell. It is, moreover, possible that
only in the most highly specialised mesostates does the condition of
secretory granules obtain. From all this it appears probable that the
formation of pepsin is a subsidiary function of the pyloric mucous
membrane, and that it yet remains to be discovered whether the cells
of the pyloric glands possess other more important functions.

The methods of obtaining gastric juice.— The older observers
obtained samples of gastric juice by causing animals to swallow hollow
perforated balls, containing pieces of sponge. In this way Keaumur,2
Stevens,3 and Spallanzani 4 obtained a fluid which caused meat to
become digested, and which was marked by antiseptic properties.
Tiedemann and Gmelin 5 made fasting animals swallow pebbles, which,
acting as mechanical irritants, permitted a certain quantity of gastric
juice to be secreted, and this was obtained by killing the animals shortly
afterwards.

Beaumont had under observation in 1822 a man who had a gun-shot
wound in the left side. There resulted from this a permanent fistula
into the stomach. A valve, formed of the mucous membrane, became
established over the opening, and on depressing this, introducing a
tube, and turning the man on his left side, a flow of gastric juice was
obtained.

1 See Griitzner's chart (Fig. 44), in the section on the variations in composition of gastric
juice during digestion.

2 " Sur la digestion/' Hist. Acad. roy. d. sc. de (Paris], 1752.

3 "De alimentorum concoctione," Ed'in., 1877.

4 "Experiences sur la digestion de I'homme et de diffe'rentes especes d'aniraaux,"
Geneve, 1783.

5 "Die Verdauung nach Versuchen," 1826.

I NFL UENCE OF NER VO US S YSTEM. 5 3 7

Since this time many other cases of gastric fistula in the human subject
have been under observation.1 In 1842, Bassow2 and Blondlot simultaneously
introduced the method of obtaining gastric juice by an artificial fistula in an
animal, and this method was further developed by Heidenhain,3 who introduced
antiseptic precautions into the operation.

Heidenhain also succeeded in so developing Klemensiewicz's method of
isolating one portion of the stomach from the rest, that it was possible to keep
the animals under protracted observation in this condition. In making the
incisions for the operation, Heidenhain interfered as little as possible with
the more important blood vessels, but he apparently produced some disturb-
ance as far as the connections of the main nerves of the stomach were
concerned.

Pawlow's 4 method of isolating by operation a portion of the stomach,
retained the advantages of that of Heidenhain, while keeping unimpaired
the nerve distribution to the isolated portion.

The influence of the nervous system on gastric secretion.—

The stomach is supplied with two sets of nerve-fibres, cerebro-spinal
and sympathetic. The vagi constitute the cerebro-spinal set, and branches
from the solar plexus the sympathetic. The fibres of the vagi are almost
entirely noii-medullated in their course over the stomach. Plexuses
formed by these nerves lie between the muscular and in the submucous
coats. The nerve-fibres are distributed to the muscular tissue, to the
blood vessels, and to the mucous membrane, and filaments have been
traced to terminal arborisations between and in close contact with the
cells of the gastric glands.5

Many have attempted to obtain indications of the nature of the
impulses passing along these nerves by artificial stimulation.

Kutherford6 cut the vagi during digestion, and found that the mucous
membrane became paler. If the peripheral ends were stimulated, no
regular effect resulted ; if the central ends were stimulated, the mucous
membrane became redder. After division of both vagi, apparently
normal gastric juice was still secreted. Rutherford also found that
normal secretion occurred after division of the splanchnics. The effect
on the blood supply of stimulation of the central end of the vagus was,
presumably, brought about by impulses passing to the medulla oblongata,
inhibiting the action of the vasomotor centre there, and resulting in

1 The following is a list of the principal observations on gastric fistulte in man : —
Helm, "Zwei Krankengeschichten," Wien, 1803; Briicke's " Vorlesungen, " Bd. i. S.
300; Beaumont (1825-33), "Experiments and Observations on the Gastric Juice and the
Physiology of Digestion," reprinted from the Plattsburgh edition, with notes by Andrew
Combe, M.D., Edinburgh, 1838 ; W. Robertson, 1851 ; C. Schmidt, Diss., Dorpat, 1851 ;
Ann. d. Chem., 1854, Bd. xcii. ; Kretschy, Jahresb. ii. d. Fortechr. d. Thier-Chcm.,
Wiesbaden, 1876, Bd. vi. S. 173 ; Uffelmann, ibid., 1877, Bd. vii. S. 273 ; Richet, " Le sue
gastrique," Paris, 1878.

2 The following is a list of the more important observations on gastric fistulte in
animals :— Bassow, Bull. Soc. imp. d. nat. de Moscou, 1842, tome xvi. ; Blondlot, "Traits'
aualytique de la digestion," Nancy et Paris, 1843; Bardeleben, Arch. f. physiol. Heilk.,
Stuttgart, 1849, Bd. viii. ; Bidder u. Schmidt, "Die Verdauungssafte," Leipzig, 1852;
Holmgren, Jahresb. ii. d. Leistwig. . . . d. ges. Med., Berlin, I860, Bd. i. ; Schiff, " Le9ons
sur la physiologic de la digestion," Paris and Berlin, 1867, Bd. i. S. 15 ; Klemensiewicz,
Sitzungsb. d. Jc. AJcad. d. Wissensch., Wien, 1875, Bd. Ixxi.; Panum, Jahresb. ii. d.
Fortschr. d. Thier-Chem., Wiesbaden, 1878, Bd. viii. S. 193; Heidenhain, Arch. f. d. ges.
Physiol., Bonn, 1878, Bd. xviii. S. 169 ; 1878, Bd. xix. S. 148 ; Hermann's "Handbuch,"
Leipzig, 1881, Bd. v. S. 107.

* " Anlegung von Magenftsteln," Hermann's "Handbuch," Leipzig, 1881, Bd. v. Th. 1.

4 The details of this method are described by Chischin, Inaug. Diss., St. Petersburg, 1894.

5 Kytinanov. Internal. M onatschr. /. Anat. u. Physiol., Leipzig, 1896, vol. xiii. p. 402

6 Trans. Roy. Soc. Edin., 1870, vol. xxvi.

538 MECHANISM OF SECRETION OF GASTRIC JUICE.

efferent impulses, dilator in character, passing along the sympathetic to
the mucous membrane.

That impulses passing along the vagi influence the movement of the
stomach, and possibly by that means to some extent the secretion, has
been shown by several observers.

Goltz 1 exposed the stomach and oesophagus of two curarised frogs,
and, after suspending them, dropped into their mouths salt solution. One,
however, had had the brain and spinal cord destroyed. After a time it
was found that in the complete animal the stomach and oesophagus were
widely distended, whilst in the pithed frog they were empty. The latter
result occurred equally well if the vagi only were cut. Stimulation of
the vagi peripherally caused only slight contractions. The explanation
given by Goltz of this result is thafr the stomach walls presumably
contain a local mechanism which, under the conditions in which the
animals were, would have undergone stimulation. The result of this
would have been peristaltic contraction, causing the fluid to be passed on
into the intestine. But ordinarily this is controlled by efferent impulses
passing from higher centres along the vagi. If the controlling influence
is destroyed, there results an exaggerated action of these centres. Goltz
was disposed to regard this local mechanism as of a ganglionic nature.

In connection with this question, it may be stated that Openchowski 2 has
described the existence of special nerve-plexuses with ganglionic cells, both at
the cardia and at the pylorus. He considers that the opening and closing of
these passages are to be referred to the direct influence of these ganglia, though
these again are under the control of the central nervous system. Openchowski
describes a centre for the contraction of the cardia situated in the posterior
corpora quadrigemina, and connected with the stomach mainly by the vagi. A
centre for the opening of the cardiac orifice lies in the basal ganglia, and
communicates with the stomach by means of the vagus. There are also
subsidiary centres in the spinal cord influencing dilatation of the cardiac
orifice. In the same regions are centres influencing movements of the pylorus
and the intermediate walls of the stomach. Openchowski emphasises the
antagonism between the movements of the cardia and the pylorus ; such nervous
impulses as proceed down the vagus and dilate the cardiac orifice simultaneously
close the pylorus.

As regards the more direct influence of impulses proceeding along
the vagi upon secretion in the stomach, for a long time the greatest
uncertainty prevailed, and it was held that in general such impulses did
not directly affect secretion, but merely indirectly, through promoting
movements of the stomach walls. Heidenhain 3 has suggested that, as
mechanical irritation produced secretion from the digestive glands in the
plant Drosera, so the direct irritation of food in the stomach might
stimulate the gastric epithelium. There has existed for a long time,
however, indirect evidence of a flow of gastric juice resulting from
psychical conditions. Bidder and Schmidt 4 noticed, as early as 1852, that
the sight of food in a gastrostomised dog resulted in an abnormal flow of
gastric juice. To obviate any possibility of swallowed saliva causing
this result, which saliva it was known could be secreted as the con-

1 " Studien liber die Bewegung von Speiserohre mid Magen d. Frosche," Arch. f. d.
ges. Physiol., Bonn, 1872, Bd. vi.

2 "Ueber die nervosen Vorrichtungen des Magens," Centralbl. f. Physiol., Leipzig u.
Wien, 1889, Bd. iii.

3 Hermann's "Handbuch/' Leipzig, 1881, Bd. v. Th. 1.

4 " Die Verdauungssafte mid der Stoffwechsel," Leipzig, 1852.

INFL UENCE OF NER VO US S YSTEM. 539

sequence of psychical conditions, oesophageal fistulse were made, and the
saliva was prevented from passing into the stomach.

In Kichet's l observations on a human subject, who, by swallowing a
caustic alkali, had rendered the oesophagus impassable, and in whom con-
sequently it had become necessary to make an opening into the stomach,
it was observed that chewing savoury food, none of which passed into
the stomach, produced a copious flow of gastric juice. It was not
possible in these cases to absolutely assert that this resulted from
nervous influence acting directly on the secreting epithelium, for move-
ments of the stomach may have brought about the flow, but the quan-
tity secreted suggested a direct nervous influence. That there is such
a direct nervous influence has been conclusively proved by Pawlow,2
in conjunction with Schoumow-Simanowsky. Their experiments were
made on dogs which had had a portion of the stomach isolated in the
manner already described, care being taken that the nervous connections
were intact. In addition, the oesophagus was separated, the cut ends
being attached to openings in the neck, so that swallowed food passed
out at one opening, and, through the other, food which it was desired
should enter the stomach could be passed in. It was possible, therefore,
to bring the animal under the influence of food in three ways. In the
first place, it might be shown food, but the food would not be actually
introduced into the stomach. This constituted the so-called " psychical
feeding." 3 Secondly, the animal might be fed by the mouth, but none
of the food allowed to enter the stomach, since it would make its exit
at the oesophageal opening. This was described as "pseudo-feeding"
(Scheinfiitterung). Thirdly, by the introduction of food into the lower
division of the oesophagus, true feeding was carried on. The results
varied according to the method adopted. The latent period, or period
elapsing after administration before secretion commences, is in the dog
about seven minutes. This does not vary much whether it be a case of
psychical, pseudo-, or true feeding. The latter course of secretion shows,
however, considerable variations. This was the first point established
by Pawlow.

He next attempted to discover the paths of the nervous impulses
bringing about these changes. Section of the splanchnics did not
affect the results, but after severing both vagi the reflex secretion
was absent. With one vagus cut (the right), the animal was found to
respond in the usual way. Later the left vagus was divided without
anaesthesia. The animals live for a few days in this condition, but
during this time no reflex secretion occurs. From this it was concluded
that the impulses constituting the efferent portion of the reflex act pass
along the vagi. But more positive results in this connection were
obtained by Pawlow by stimulating the peripheral ends of the cut vagi.
If, some twenty-four hours after the second section, the cut end be stimu-
lated,— and it is better to do this by applying induction shocks at the
rate of one per second, rather than by using the rapidly interrupted

' Le sue gastrique chez 1'honmie et les animaux," Paris, 1878.

" Die Innervation tier Magendriisen beim Hunde," Arch. f. PhysioL, Leipzig, 1895.
3 Though the exhibition of food to the dog, which had been operated on in the manner
described above, evoked a flow of gastric juice, if, from previous experience, the dog was led
to understand that the food would not actually be given, the secretion very soon stopped.
It may be mentioned that Heidenhain did not regularly obtain a floAv as the result of
showing the animal food, and this suggests that his method involved interference with the
nervous tracts.

540 MECHANISM OF SECRETION OF GASTRIC JUICE.

current, — there results a flow of gastric juice. A certain interval occurs
before the secretion is manifest, which is to be referred to changes
actually taking place in the epithelium of the stomach. The character
of the secretion varies according to the stage of the digestive act and the
nature of the food. This will be again referred to in a later section.

It must be mentioned that some observers have not had the same success
in showing the secretory importance of the vagus nerve. That certain differ-
ences are perceptible in consequence of its excitation, they admit, but they
refer the variations rather to the altered power of muscular contraction
possessed by the stomach. Thus Leubuscher and Schafer1 experimented
both upon rabbits and dogs, performing the operations according to Pawlow's
method. They frequently used a control animal for precision in estimating
the change. As far as variations in the amount of hydrochloric acid were
concerned, they came to the conclusion that there was no constant difference.
The stomach they found invariably relaxed, and the food introduced within
was, after a prolonged interval, found to be arranged in two zones, one against
the walls of the stomach, which was well digested and contained hydrochloric
acid in normal amount, that occupying the centre of the viscus being poor in
acid and rapidly becoming decomposed. As far as stimulation of the peripheral
stump of the vagus was concerned, they did not obtain constant results, but
they appear to have adopted the rapidly interrupted current rather than the
induction shocks at prolonged intervals used by Pawlow. That the food was
not perfectly mixed, is obvious from their experiments. This will probably
explain the decomposition occurring ; this change was noticed also by Pawlow to
come on a few days after section of both vagi. It is, however, to be noted that
they were unable to confirm the passage of secretory impulses along the vagus.

There exists one observation upon the human being from which it seems
that stimulation of the vagus may cause a flow of gastric juice. Regnard and
Loye 2 stimulated the vagus in a decapitated criminal some forty-five minutes
after death. Numerous drops of gastric juice appeared over the surface of the
stomach. This may also, however, have been the result of movements of the
stomach, which they observed at the same time to occur.

The conditions under which local stimulation provokes secre-
tion.— As already stated, it has been held by many that simple
mechanical irritation of the mucous membrane will directly produce a
flow of gastric juice. Beaumont 3 showed that mechanical irritation of
the mucous membrane caused increased vascularity and the appearance
of small drops of gastric juice, and he further pointed out that the effect
is confined to the irritated locality, and that the amount of juice secreted
is small in quantity. Tiedemann and Gmelin,4 Heidenhain,5 and
others also state that the secretion is limited. Pawlow6 states that
the amount secreted is practically nothing, when indigestible substances
such as pebbles are placed in the stomach. It may therefore be
regarded as probably true that any secretion produced by simple
mechanical irritation is extremely small, and the existence of this slight
secretion in no way suggests that the normal secretion can be looked
upon as the result, to any great extent, of such stimulation. On the
other hand, stimulation by food, even if solid, is much more effectual.

1 ' ' Ueber die Beziehungen des Nervus Vagus zur $alzsaure-secretion des Magenschleim-
haut," CentralU. f. inner e Med., Leipzig, 1894, Bd. xv.

2 "Recherches faites a Amiens sur les restes d'un supplicie," Compt. rend. Soc. de biol.,
Paris, 1887.

3 Op. cit. 4 Op. cit. 5 Arcli.f. d. ges. PhysioL, Bonn, 1879, Bd. xix.
6 Address at St, Petersburg. Reported in Brit. Med. Journ., London, 1895,

INFLUENCE OF LOCAL STIMULATION. 541

Heidenhain found that following a latent period of some fifteen minutes
after placing food in the organ, the stomach commenced to secrete gastric
juice. This delay beyond the interval observed in Pawlow's experiments
was presumably due to a certain amount of injury to the nervous
connections. If indigestible substances were swallowed, the secretion
was much longer delayed. The conclusion which Heidenhain arrived
at was that certain products of digestion when absorbed stimulate the
flow of gastric juice. The question then arises, What are these products
of digestion, and by what paths are they absorbed ? Are the completely
digested foodstuffs (that is to say, completely digested as far as gastric
digestion is concerned) passed on to the intestine and there absorbed,
or are they directly absorbed in the stomach ?

As regards the change undergone by different proteids when subject
to gastric digestion, there is reason to believe that the stage reached
in the stomach is not a final one, some further change taking place
in the duodenum, and that the amount of peptone formed in the
stomach may not be large, the proteose stage being, to a great
extent, the final stage of gastric digestion. If this is so, and if
the secretion from the gastric mucous membrane is influenced by
absorbed peptones, it must be influenced by peptones absorbed in
the small intestine. On the other hand, we are unable to state
definitely to what extent the intermediate results of the digestion
of proteids are absorbed in the stomach. As regards the carbohydrate
foodstuffs, v. Mering1 has shown that sugars are absorbed by the
stomach. If it is absorbed digestive products that provoke the
secretion, is it a specific product or products that cause this to occur, or
is it a common characteristic of all ? Chischin 2 has attempted to
answer this question. He finds that feeding a dog (which has had
a portion of its stomach isolated after the manner of Pawlow) with
different varieties of food, results in very different characters being
shown by the secreted juice during the course of digestion, and he
hence infers that there must be some specific stimulus or stimuli
influencing the secretion. The different substances were administered
in such a manner as to avoid the " psychical " influence on the secretion.
The administration of distilled water, gastric juice, or simple hydro-
chloric acid, caused but little change. Egg-albumin, sugar and starch
solution, were tested with the same negative results. The administra-
tion of peptone, however, resulted in a pronounced secretion. Chischin
considers that peptone was not only able to cause the gastric mucous
membrane to become active, but also to sustain it in activity. If egg-
albumin be administered so as to evoke the psychical influence, a well-
marked and sustained secretion resulted. Chischin accordingly explains
the usual process of secretion as occurring in the following manner : — At
the time of taking food the first flow of gastric juice is determined by
the reflex psychical influences involved in taking food. The digested
proteids are able later to evoke a secretion, at a time presumably
when the psychical influence begins to wane.

According to these experiments, then, we may assume that small
quantities of peptone may be normally formed in the stomach, and,

1 "Ueber die Function des Magens," Verhandl. d. Cong. f. innere Med., Wiesbaden,
1893.

2 Inaug. Diss., St. Petersburg, 1894. Reported in Jahrcsb. ii. d. Fortschr. d. Thier-
Chem., Wiesbaden, Bd. xxv.

542 MECHANISM OF SECRETION OF GASTRIC JUICE.

becoming absorbed there, in some way influence the epithelium so that
secretion results. The exact course of this absorption is a matter of
some difficulty as far as the secretory epithelium is concerned, but it is
yet more difficult to comprehend how peptone absorbed and changed in
the intestinal wall should influence secretion in the stomach. If, as
Schiff l long ago suggested, the absorption of these products should assist
in building up the precursor of pepsin, we could more easily see the
importance of these products passing to the secreting cells. Schiff,
however, emphasised dextrin as being pre-eminently a " peptogenous "
substance. Chischin finds that it does not evoke secretion.

The conditions of formation of the ferments of the gastric juice.
— (a) The conditions of the formation of pepsin. — As previously men-
tioned, Briicke2 had noticed that th« pepsin present in the gastric
mucous membrane was not yielded entirely to one extraction, and
Ebstein and Grutzner 3 pointed out that the peptic activity depended
considerably upon the manner in which an extract was prepared. An
extract made by treating the gastric mucous membrane with hydro-
chloric acid was much more powerful than one obtained by subjecting
the mucous membrane to the action of glycerin. That which was not
extracted by glycerin, Ebstein and Grutzner regarded as a compound
of pepsin with the proteid matter of the cells, this compound yielding
pepsin on subjection to the influence of acid, or to the action of sodium
chloride. Schiff4 had also remarked, that if a dilute acid be added to
the stomach and left for some weeks, the extract becomes gradually
richer in peptic activity. Schiff accounted for this by assuming the
existence of a precursor of pepsin in the cells of the mucous membrane,
which gradually became converted into pepsin by the acid. This he
called propepsin. In both cases the observers were dealing undoubtedly
with some substance which yielded pepsin, and to this substance the
name pepsinogen has since been applied. Ebstein's and Griitzner's
test for the existence of this substance was the fact that it was not
dissolved by glycerin as was pepsin, and yet would yield pepsin on
treatment with acid. But it was soon found that there were difficulties
in differentiating pepsin from its precursor in this manner. Von Wittich 5
pointed out that when fibrin is placed in a glycerin extract of pepsin,
the fibrin absorbs the pepsin, and will only yield it again to fresh treat-
ment with acid. Ebstein and Grutzner 6 further showed that even
coagulated egg-albumin would do this. Thence it followed that the
proteids of the gastric mucous membrane might fix the pepsin, and that
a glycerin extract of the mucous membrane might be an extract of such
pepsin as was not fixed by the proteids. It was necessary, therefore, to
find some more definite test of the presence of pepsinogen. This was
supplied by Langley,7 who found that sodium carbonate had a power-
fully destructive effect on pepsin, but a much less marked action on
certain extracts of the mucous membrane from which pepsin could be
derived. These extracts, therefore, were held to contain the zymogen.
He also inferred that the gastric glands contained the ferment in the
zymogen state, as they did not contain any appreciable amount of

1 "Leconssur la physiologic de la digestion," 1867, tome ii.
- " Yorlesungen," 1874.

3 Arch.f. d. ges. Physiol, Bonn, 1874, Bd. viii. 4 Ibid., 1877.

5 Ibid., 1872, Bd. v.; 1873, Bd. vii. <; Op. cif.

~ "The Histology of the Mammalian Gastric Glands, and the Relation of the Pepsin
to the Granules of the Chief Cells," Journ. Physiol., Cambridge and London, 1882, vol. iii.

FORMATION OF FERMENTS OF GASTRIC JUICE. 543

pepsin, but would yield the same under appropriate treatment. The
differentiation of the one from the other was further advanced by
Langley and Edkins.1 They confirmed the observation, that alkalies
and alkaline salts rapidly destroy pepsin. The conditions influencing
the rate of destruction by sodium carbonate were found to be the
strength of the solution of the alkaline salt, the time during which it is
allowed to act, the temperature of the mixture, and finally the amount
of proteids present. By mere neutralisation of an acid solution of
pepsin, a considerable amount might be destroyed. If equal volumes of
an extract of pepsin and of a 1 per cent, solution of sodium carbonate
were mixed, in fifteen seconds as much as 97 per cent, of the pepsin
might be destroyed. The greater the amount of proteid present, the
greater the amount of sodium carbonate necessary to cause destruction.
The difference between pepsin and pepsinogen in their behaviour with
different reagents is merely one of degree. Pepsinogen is destroyed
also by alkalies, but the destruction is so slow as compared with that of
pepsin, that this reaction furnishes a useful method of distinguishing
the one from the other. Since the aqueous extract of the gastric
mucous membrane of a fasting animal loses but very little peptic
power on brief treatment with 1 per cent, sodium carbonate, it follows
that pepsinogen, but little or no pepsin, is present in the gastric glands
in hunger. Schiff stated that "propepsin" was slowly converted into
true pepsin. Langley and Edkins found that the conversion of
pepsinogen into pepsin is one of great rapidity. All the pepsinogen
present in an aqueous extract of a cat's gastric mucous membrane
may be converted into pepsin by treatment with 1 per cent, hydro-
chloric acid in sixty seconds. With reference to the point as to
whether pepsin is present in the gland cells during digestion, no definite
result was arrived at. Pepsin can be obtained from the gastric
mucous membrane of an animal in digestion, but not invariably, and
such as is found may have been produced by the acid in the lumen of
the tubes affecting the pepsinogen in the contiguous chief cells. In the
oesophagus of the frog, where no acid is secreted, but only ferment,
injection of commercial peptone causes no accumulation of pepsin in
the gland cells. Carbonic acid destroys pepsinogen more rapidly than
pepsin ; but if only a small quantity of peptone is present, there is
practically no destruction. Finally, it is observed that both pepsin and
pepsinogen are rapidly destroyed on heating to a temperature of 55°—
57° C.

(b) The conditions of formation ofrennin (rennet-ferment). — -An enzyme
which has the property of causing milk or the separated caseinogen
to undergo coagulation, is found in the stomachs of almost all animals.
As regards the secretion of rennin, there is an important resemblance
to that of pepsin, inasmuch as, in the case of the former, there is a
precursor of the actual ferment existent in the glands of the stomach
which has the power, under the influence of acid, of producing the
active enzyme. It was in the case of the rennin that it first was
shown that -many of the ferments of the alimentary canal have a
zymogen stage. Hammarsten,2 in 1872, pointed out that the gastric
glands of many animals contain reimet-zyniogen, but do not contain
rennet-ferment. The zymogens of pepsin and trypsin were not

1 "Pepsin and Pepsinogen," Journ. Pkysiol., Cambridge and London, 1886, vol. vii.
- Jahresb. ii. d. Fortschr. d. Thicr-Chem., Wiesbaden, 1872.

544 MECHANISM OF SECRETION OF GASTRIC JUICE,

described till some years later. Langley l showed that the method of
separating pepsin from pepsinogen was applicable also to the remiin,
since rennet-ferment was destroyed by sodium carbonate, whilst rennet-
zyinogen is affected much less powerfully. Hammarsten has also shown
that the amount of rennet-ferment that can be extracted from the
cardiac end of the stomach is proportionally much greater than that
obtainable from the pyloric mucous membrane. Griitzner 2 has shown
that in the gastric glands of the dog, the rennet-ferment diminishes in
amount during digestion, and that the amount of diminution runs
parallel to that of pepsin. It seems that where pepsin is greatest in
quantity, there also is rennet-ferment most abundant, and it seems
probable that the granules of the chief cells contain the zymogens both
of rennet-ferment and pepsin. We cannot say whether the granules are of
one kind or whether there are separate forms of granules for the separate
ferments. But though in general the zymogen of the rennet-ferment,
and not the actual ferment, is existent in the gastric cells, yet in
some cases, e.g. the calf and sheep, the zymogen is presumably in a

2 4

8 10 12 14 16 18 20 22 24 26 28 30 32

34

FIG. 44. — The figures at the abscissa on the base line refer to the
number of hours elapsed since the last meal. The length of the
ordinates indicates the amount of pepsin yielded at any time. F is
the record of variation in the fundus mucous membrane, P of
variation in the pyloric mucous membrane. — After Griitzner.

much less stable condition, for a watery extract of the stomach of
these animals yields rennet-ferment in large quantities. As regards
the differentiation of the rennet-ferment from the proteolytic, they can
be separated from one another by chemical means, although we have
no morphological signs of their distinction. Hammarsten's method of
separating the two ferments chemically depends upon the fact that
the gradual addition of lead acetate precipitates the pepsin sooner than
the remiin.3

The variations in the amount and composition of gastric juice
during the course of digestion. — The amount of pepsin that can be
extracted from the mucous membrane has been estimated by Griitzner.4
He compared concurrently that obtained from the fundus with that
yielded by the pyloric region. In the above chart (Fig. 44), which shows
the chief variation during the lapse of some hours after a meal, the most

1 "On the Destruction of the Ferments of the Alimentary Canal," Journ. PhysioL,
Cambridge and London, 1882, vol. iii.

2 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xvi.

3 The conditions of formation of the hydrochloric acid of the gastric juice are treated
of in a preceding article (see pp. 351 et seq.).

4 Arch.f. d. ges. PhysioL, Bonn, 1879, Bd. xx.

VARIATIONS IN GASTRIC JUICE DURING DIGESTION. 545

striking feature is the absence of coincidence between the pepsin con-
tents of the pyloric and the fundus region of the stomach.

In general, it may be pointed out that the maximal yield of pepsin
from the pyloric region is at the same interval after ingestion of food as
marks the minimal yield of pepsin from the fundus.

A great number of observations have been directed to estimating the
acidity of the contents of the stomach at different intervals after a meal
has been taken. Gastric juice commences to be secreted almost as soon
as suitable food enters the stomach. For a time the acid juice merely
neutralises the alkalinity of the food and saliva, and the hydrochloric
acid combines with various food substances, so that free hydrochloric
acid does not occur till after an appreciable interval. Von den Velden l
states that free hydrochloric acid
cannot be detected until three-
quarters of an hour after a meal
is taken. Kichet 2 states that in
the human stomach the acidity
gradually increases during diges-
tion, and that it is apparently
independent of the quantity of
fluid taken. Towards the end
of digestion he finds that the
total acidity of the stomach con- I '1
tents may be further increased,
but this is to be referred to the
production of organic acids by
the decomposition of the food.
He also points out that the feebler
the activity of the juice, the
greater the amount of organic
acid liberated. Chischin's 3 observations give precise details of the course
of digestion with different foods. The annexed diagram (Fig. 45) shows
the course of the production of hydrochloric acid in an isolated portion
of the fundus, when the animal was fed with mixed food, comprising
milk, meat, and bread. The animal did not undergo the "psychical"
stimulation of the food, or the maximal percentage of hydrochloric acid
would probably have been in the first hour, instead of in the second or
third. If meat alone be given to such an animal under similar conditions,
the maximal acidity occurs in the first hour. With mixed food the digest-
ive power averages 3 '5 mm. (Mette's method of estimation by columns
of coagulated egg-white) ; 4 with simply meat food, about 4 mm. With
bread alone as food, the duration of secretion was found to be more
protracted, but the digestive strength was much greater, varying between
5 -2 2 mm. and 7 '5 6 mm. The digestive power was very marked in the
first hour, increased further in the second hour, and remained high both
in the third and fourth hours. With milk, the course of secretion is
much more irregular. The digestive power is moderately high at first,
but sinks, after the first hour, about one-half. It remains at this
strength for the third and fourth hours, but in the fifth hour increases
again to the original strength, and may, in the sixth hour, even go

" Zur Lelire von der Wirkung des Mundspeiohels im Magen," Ztschr. f. physiol.
Chem., Strassburg, 1879, vol. iii.

2 Op. Git. 3 Op. cit. 4 For Mette's method, see p. 325.

VOL. i.— 35

1 2345

Time in hours after food is taken

FIG. 45. — Chart showing acidity of gastric
juice after feeding with mixed food (300
c.c. milk, 50 grins, meat, and 50 grins,
white bread). The animal was not sub-
jected to the "psychical stimulation" of
the food.

546 MECHANISM OF SECRETION OF PANCREATIC JUICE.

beyond this. In another series of experiments the animals were fed
with peptone (Chapoteaux). This, according to Chischin, was equivalent
to reviewing the later stages of digestion, from the time when peptone
began to be formed in any quantity in the stomach. The noticeable
point about the results in these last cases is, that there is presented a
great contrast to feeding with such a primary proteid as egg-albumin.
With peptone, the juice becomes secreted in large quantities at once,
its acidity is high, and its digestive power well marked.

It is obvious, therefore, that the nature of the food has an important
influence on the course and nature of the secretion. This has been
drawn attention to by Khigine,1 who classes the different foods
mentioned above in different orders. He has also pointed out that the
amount of juice secreted is not necessarily proportional to its acidity
or its digestive power. These, again, are not necessarily proportional
to each other, as is shown in the case of bread as food, when a low
acidity in the secreted juice is shown, but a high degree of peptic
power ; whereas with milk a high degree of acidity is shown, but a much
lower degree of digestive power. Finally, the duration of the digestive
process is out of all relation to the strength of the secreted juice. It is
impossible, then, to draw up any regular scheme of the course of digestion,
except so far as specific foods are concerned, observations based upon the
course of digestion of foods mixed in arbitrary proportions being of but
little value.

THE MECHANISM OF PANCREATIC SECRETION.

The histological appearances of the different secretory condi-
tions of the pancreas. — The pancreas consists of secretory alveoli,
between which are here and there seen masses of cells of a different
character, and having no connection with the proper secretory channels
of the gland. These masses of cells are presumably not connected with
the ordinary processes of the secretion of a digestive juice, and the follow-
ing account will therefore be confined to the typical secretory alveoli.

If a small portion of the pancreas of an animal be examined in the
living state, it will be found to consist of many secretory alveoli, and
these secretory alveoli of cells contain numbers of discrete granules.
It is generally found that whatever digestive stage the animal is in, there
exists an outer zone in the alveolus free from granules. This is not,
however, invariably the case. Ordinary stains, such as hrematoxylin
and carmine, are found to colour this outer zone more deeply than the
rest. This is in conformity with the usual rule, that such stains do not
deeply colour the secretory granules of cells, or the substance formed by
their breaking down. If the cells are macerated for a few days in
neutral ammonium chromate, a radial fibrillation is revealed2 in this
outer zone. The addition of water to the fresh gland causes the
granules to disappear, and dilute alkalies produce this result even more
rapidly. Acids, either mineral or organic, cause the distinction between
the two zones to be lost, the whole cell becoming clear. By hardening
the gland in solutions of osmic acid, or in the vapour of osmic acid, the
granules may be preserved.

1 " Etudes sur 1'excitabilite' secretoire specifique de la muqueuse du canal digestif"
Arch, de, sc. bioL, St. Petersbourg, 1895, vol. iii. p. 5.

2 Heidenhain, Hermann's "Handbuch," Bd. v. Abth. 4.

METHODS OF OBTAINING PANCREATIC JUICE. 547

Although, in the resting condition of the gland, an outer border free
from granules is evident, this is still more manifest in the exhausted
condition. The granules may then be so reduced in number as to form
small aggregations at the luminal borders only of the cells.

As is the case in the stomach, there is reason to believe that the
granules are concerned with the specific secretion of the gland, the
amount of granules determining the activity of an extract.

The above described changes in the cells were first observed in the
living pancreas of the rabbit by Klihne and Sheridan Lea.1

Methods of obtaining pancreatic juice. — The methods that have been
adopted to procure a supply of pancreatic juice involve one of the following
procedures — (a) Fixing a cannnla into the duct of Wirsung ; (ft) opening the
duct and connecting it with the body wall; (c) cutting out a piece of the
intestine in which the pancreatic duct opens, and fixing this to the body
wall.

C. Bernard 2 adopted the first method, fixing a silver cannula into the duct.
Heidenhain 3 introduced antiseptic precautions into the operation. He made
an incision in the linea alba midway between the xiphoid process and the
umbilicus. The duodenum was drawn out through the opening and the duct
carefully sought for. This being found, into it was tied a glass cannula
of about 6-18 cms. in length. Around the intestine were placed two
temporary ligatures, keeping the gut closely applied to the body wall. The
opening was found to gradually close, allowing simply the cannula to pass
through. The second method was adopted by Ludwig with Weinmann,4 and
Bernstein.5 They found and opened the duct and inserted a piece of lead wire,
on the one hand, towards the papilla pancreatica in the duodenum, the other
end passing up to the gland substance. This wire did not fill the lumen, and
thus the flow was still permitted. The third method, which is due to Heidenhain
and adopted for permanent fistulse, consists in resecting the small portion of the
intestine which contains the papilla pancreatica, and joining the ends of the
main gut above and below. The piece of intestine is slit up, the mesenteric
surface is attached to the body wall, and thus the juice can be obtained.
Pawlow varied this method by not resecting the whole tube of the intestine.
He cut out a quadrangular piece, including the pancreatic papilla, and ligatured
this into the body wall.

By these different methods natural pancreatic juice may be obtained.
After a time the juice becomes somewhat altered; it retains, however, its
ferment activity in a marked manner throughout.

The influence of the nervous system upon pancreatic secretion.
— Our knowledge has lately been considerably extended in respect of
the precise influence of nervous impulses upon pancreatic secretion.
The following statements summarise our chief knowledge up to the
most recent researches upon the subject.6

1. After division of the nerves, proceeding to the gland, secretion is set
up and apparently increases. This was affirmed by Bernstein.7

2. Secretion can be set up by stimulation of the medulla oblongata,
or, if already in progress, can be increased.8

3. The medulla oblongata must not be regarded as exclusively the

1 Verhandl. d. naturh.-med. Ver. zu Heidelberg, N.F., Bd. i.

2 " Memoire sur le pancreas et sur le role du sue pancre"atique," Compt. rend. Acad. d. sc.
Paris, 1856.

3 Hermann's " Handbuch," Bd. v. 4 Ztschr. f. rat. Med., Bd. iii.

5 Ber. d. k. sacks. Gesellsch. d. Wissensch., Leipzig, 1869.

6 Cf. Heidenhain, Hermann's "Handbuch," Bd. v. Abth. 4. 7 Op. cit.
8 Heidenhain, Arch. f. d. ges. Physiol., Bonn, 1875.

548 MECHANISM OF SECRETION OF PANCREATIC JUICE.

centre for pancreatic secretion, as, after its separation from the cervical
spinal cord, the secretory process can continue, although with diminished
intensity.

4. The nerves proceeding to the pancreas do not seem to have the
same direct influence upon the secretion that the nerves to the salivary
glands possess.

5. Stimulation of the central end of the divided vagus, according to
Bernstein,1 or of sensory nerves in general (e.g. cutaneous), according to
Afanassiew and Pawlow,2 may inhibit the secretion, provided the pan-
creatic nerves are intact. This, Heidenhain regards as due to vascular
changes.

Pawlow3 found that the administration of atropine stopped the
secretion frequently, but not in all animals (e.g. in dogs but not in
rabbits), and Heidenhain observed that the administration of pilocarpine
caused a sluggish secretion of a concentrated juice.

The later experiments of Pawlow and the St. Petersburg school have
greatly amplified our knowledge of the nervous influence. In Pawlow's
further researches he observed the effects of nerve stimulation upon dogs
prepared for experiment in two different ways. In the first case the
dog had a permanent pancreatic fistula prepared, one vagus in the neck
was also divided. The stimulation of the peripheral stump of the vagus
was performed some five days after the section, at a time when certain
fibres in the vagus had degenerated. In the second case the vagus was
cut through in the neck, and after three or four days the animal was
prepared for experiment by the performance of tracheotomy, section of
the spinal cord just below the medulla oblongata, and the preparation of
a fresh pancreatic fistula. In both these cases stimulation of the peri-
pheral end of the vagus causes secretion from the pancreas. Moreover,
stimulation of the intact vagus also produces this result, and even if
neither vagus is divided a more or less pronounced secretion ensues.
Certain differences are observable, however, between the general effects in
the two cases. In the first case more secretion was produced, this being
comparatively watery in character and greatest in amount at the
commencement of stimulation. These differences are probably accounted
for by the general low blood pressure in the second case. The pressure
of the secretion was found by Pawlow to be lower than the corresponding
blood pressure, and it was noted that vagus stimulation in one case still
caused a secretion, although the blood pressure was reduced by bleeding
practically to nil. Frequently the secretion would end with the lowering
of the blood pressure, but nevertheless the one experiment is sufficient
to establish the independence of the secretion of the blood pressure.
The action of atropine is to cause a marked influence on the effects
of nerve stimulation, though complete cessation of the secretion is not
produced. Reflex effects can be produced on the secretion, which do nob
correspond to the effects upon the blood vessels. Stimulation of the
central stump of the lingual or of the vagus nerve will produce such reflex
effects. If, at the commencement of the experiment, either 110 secretion
or a slight secretion occurs, with the first stimulation of sensory nerves
either a commencement or an increase of the secretion results. After
the stimulation ceases this lessens. If after the first stimulation the

1 Ber. d. k. sacks. Gesellsch. d. JFissensch., Leipzig, 1869.
'2 ArcTi.f. d. yes. Physiol., Bonn, 1878, Bd. xvi.
zArch.f. Physiol., Leipzig, 1893, Supp. Bd.

INFLUENCE OF NERVES ON PANCREATIC SECRETION. 549

secretion is still fairly marked, a further stimulation will result in
inhibition of the secretion, which inhibition ends with the stimulation
provoking it. The spontaneous secretion that is sometimes observed
before the experiment begins, is stopped by cutting both vagi, and is
therefore due to impulses proceeding from the upper portion of the
cervical spinal cord or the medulla oblongata. Pawlow also points out
the importance of the circulation in general for the secretion. A brief
stoppage of the blood stream caused a cessation of the flow, and an
anaemic condition of the gland resulting from reflex nervous influence
caused a similar cessation. The latent period relapsing before the
secretion resulting from stimulation becomes obvious, is, according to
Pawlow, two to three minutes, but later observers such as Mette1 and
Kudrewetzky 2 regard it as somewhat longer, namely, from four to six
minutes. Mette in addition found that, though previous observers
(Lewaschew, Heidenhain) had stated that the proteolytic ferment failed
in the pancreatic juice of dogs which had fasted five or six days, yet it
was continuously obtainable by stimulation of the vagus. Gottlieb 3
confirms the old observation, that stimulation of the divided vagus at the
central end causes inhibition of the secretion, and he refers this result to
general spasm of the abdominal blood vessels. Another contribution to
the study of the inhibitory influences on the pancreatic secretion has
recently been made by Popielski.4 It had been previously noticed by
Mette and Kudrewetzky that the secretion caused by stimulating one
vagus could frequently be stopped by stimulating the other vagus.
Hence it was inferred that antagonistic fibres passed in these nerves.
Stimulation of such fibres may bring about sometimes a lengthened
latent period, sometimes total inhibition of the flow. Mette regarded
this as due to the existence of vaso-constrictor fibres, Kudrewetzky
to the presence of specific fibres inhibiting the secretion. Popielski
endeavoured to elucidate this point. He found that a secretion evoked
by peripheral stimulation of the vagus could later, by a repetition of
the stimulation of the same nerve, be interrupted. The interruption
started some seven seconds after the stimulation commenced, and
lasted about the same interval beyond the cessation of stimulation.
This inhibition also follows from stimulation of the other vagus, as
previously observed, and is best shown when the exciting current
is not too strong. The branch of the vagus which lies behind the
oesophagus in the thoracic cavity is that concerned with changes in
the secretory activity of the pancreas. Dolinski5 had previously
observed that the introduction of acids into the duodenum produces
a flow of pancreatic juice (see next section). Popielski made use of
this fact to see how far the secretion thus excited could be inhibited
by nerve stimulation. He found that a secretion so produced
was inhibited with perfect regularity by stimulation of the vagus.
Stimulation of the vagus, after secretion evoked by pilocarpine, pro-
duced the same result. Popielski points out that there are three
ways in which inhibition of the flow of pancreatic juice can be brought
about —

1. By stimulation of vaso-constrictor fibres.

1 Arch.f. Physio!., Leipzig, 1894, Supp. Bd. 2 Ibid., 1894.

3 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1895, Bd. xxxiii.

4 CentralU.f. PhysioL, Leipzig u. Wien, 1896, Bd. x.

5 Arch, de ac. bioL, St., P^tersbourg, 1895, vol. iii.

550 MECHANISM OF SECRETION OF PANCREATIC JUICE.

2. By constriction of the lumen of the duct, resulting from contrac-
tion of its smooth muscle.

3. By action of special nerve-fibres inhibiting secretion.

The first hypothesis is improbable, since stimulation of the splanchnics
does not cause the same cessation ; and, moreover, there is reason to doubt
the existence of vaso-constrictor fibres in the vagus.1

The second hypothesis will not hold, when it is considered that
physostigmine produces duct constriction, but at the same time increases
the secretion.

Before examining in detail the third supposition, Popielski endeavoured
to see how far special secretory fibres can be anatomically isolated. If
the larger branches of the vagi lying on the stomach, or those branches
which pass towards the liver, be dividedfstimulation of the vagus has the
same influence upon pancreatic secretion. The impulses pass therefore
along some of the finer nerve branches running in the subserous coat
towards the pyloric region of the stomach. If the duodenum be cut
through near the pylorus, stimulation of the vagus has no effect. If
the duodenum be cut across lower down, the vagus effect is apparent.
Stimulation of the lower cut edge of the duodenum in the first case
provokes secretion, and if the main mass of nerves passing with the vein
into the gland be stimulated (especially those lying at the upper side of
the vein), a secretion is evoked without marked latent period, and
uniform in character. This secretion is inhibited by the simultaneous
stimulation of the vagus in the thoracic cavity. The inhibition comes
about, then, either by impulses passing along nerve-fibres to the gland-
cells, or affecting some nerve-centre. Popielski finds that if the vagi
and sympathetic nerves be cut, a reflex secretion is still evoked by
placing hydrochloric acid in the duodenum. The reflex centre, he thinks,
then, must be in the abdominal cavity. He considers it probable that
such a centre exists in the region of the pylorus, since, if the duodenum
be cut through near the pylorus, the introduction of hydrochloric acid is
then without effect. If the pylorus be separated with the duodenum,
hydrochloric acid will then, however, have the usual effect of causing
pancreatic secretion. Popielski considers, however, that such a reflex
centre is not furnished by the semilunar ganglion.

If these observations are correct, we can assume the existence of
secretory and inhibitory nerve-fibres, both running in the vagi, and it
seems probable, from the differences of latent period which result from
stimulation in different regions, that the inhibitory impulses passing
along the vagus do not act directly on the cells of the gland, but on
some centre which has a controlling influence on the process of secretion.
Popielski's reasons for regarding the semilunar ganglion as probably not
furnishing such a centre, seem insufficient. The fact that Bernard found
an increased secretion after extirpating this, can be explained, on the
analogy of the salivary gland, as a paralytic secretion. There is some
evidence that the inferior mesenteric ganglion may also act as a centre
for reflex action, and if so, it seems less improbable that a similar reflex
centre for the pancreatic secretory processes may be referred to the
semilunar ganglion. Should such a centre exist, it is undoubtedly
subject to influences proceeding from the higher centres by means of the
vagi.

Though there is difficulty in admitting the existence of a controlling

1 Francois-Franck.

EFFECT OF LOCAL STIMULATION. 551

centre for the pancreatic secretion in the semilunar ganglion, there is
even greater difficulty in associating such a centre with any other
neighbouring structure, or in admitting that, as Popielski considers, it
may be placed in the walls of the pylorus.

The conditions under which local stimulation provokes the
flow of pancreatic juice. — As stated in the last section, a secretion
of the pancreatic juice, dependent upon integrity of the nerve connec-
tions, can be brought about by the action of certain substances upon the
mucous membrane of the stomach or duodenum. Thus it was long ago
noticed that injection of ether into the stomach will cause a flow of
pancreatic juice, the juice having characters corresponding to the par-
ticular stage of digestion in which the flow is brought about.1 More
recently, other substances have been found to similarly affect the secre-
tion. If mineral acid, or even organic acids such as acetic and lactic,
be brought into contact with the duodenal mucous membrane, a secre-
tion will result. Since alkaline substances have not the same effect,
Dolinski2 considers that the acid products of gastric digestion bring
about their own neutralisation by inducing a flow of alkaline pancreatic
juice when they enter the small intestine. Dolinski also found that
fat excited reflexly a pancreatic secretion, and that alcohol was also
effective in this direction, but only to a moderate degree. Gottlieb3
agrees that reflexly induced secretion starts generally by stimulation of
the duodenal mucous membrane. Becker 4 studied the effect upon the
secretion of the introduction into the stomach of . distilled water and
of various salts. The salts employed were various alkaline salts,
Carlsbad salts, sodium chloride, and " Essentouck " mineral water.
Becker found that distilled water exalted the secretion, whilst salts,
especially alkaline salts, diminished it, both in amount and in proteo-
lytic power. Sodium chloride in smaller doses was indifferent, in
larger doses it behaved as the alkaline salts. The better the
absorption the more marked the secretion. Water containing car-
bonic acid is more easily absorbed than simple distilled water, and,
correspondingly, the former excites a more plentiful secretion than the
latter.

We see, then, that the ordinary progress of the food can account for
the secretion normally appearing ; further, that the acid contents of the
stomach, when passed into the duodenum, may cause a powerful secretion,
and that alkaline salts in the stomach diminish the secretion.

The ferments of the pancreatic juice and their antecedents. —
Extracts made from the pancreas of many animals, and the pancreatic
juice obtained by the establishment of fistulae, possess the power of
changing different foodstuffs. Heidenhain5 showed in 1875 that there
could be obtained from the pancreas a substance from which the proteo-
lytic ferment could be derived, but which did not actually possess
proteolytic activity. This substance he called " zymogen," but since we
are acquainted with substances having similar relations to other enzymes,
it is better to retain the name zymogen for the whole class, and to refer
each individual precursor by a name associated with the particular
ferment. We thus speak of the particular zymogen of the proteolytic
enzyme of the pancreas as trypsinogen.

1 Kiihne, "Lehrbtich der physiol. Cliem." 2 Op. cit. 3 Op. cit.

4 Arch, de sc. UoL, St. P<§tersbourg, 1893, vol. ii.

5 Arch.f. d. f/es. Physiol. , Bonn, 1875, Bd. x.

552 MECHANISM OF SECRETION OF PANCREATIC JUICE.

Heidenhain established definite characters distinguishing trypsinogen
from the actual enzyme, and showed that in some respects their behaviour
was similar. The chief relations of the zymogen to the ferment are as
follows : —

1. Trypsinogen is soluble in glycerin. Some glycerin extracts of
pancreas have no ferment activity, since the ferment is in the condition
of zymogen, but if such glycerin extracts, dissolved in 1 per cent,
sodium hydrate, be diluted with distilled but not boiled water (this
being largely devoid of dissolved air), especially if digested for a time
at 40° 0., it will become active.

2. If an inactive glycerin extract of fresh pancreas be dissolved in
sodium carbonate, 1 to 2 per cent., the passing through it of oxygen
will cause the same to become active.

3. Platinum black will, according to Podolinski,1 also render the
inert extract proteolytic.

4. The converse of the change brought about by the influence of
oxygen may also occur, for, through the deprivation of oxygen, activity
becomes lost.

5. If fresh pancreas be mixed with the same weight of 1 per cent,
acetic acid for ten minutes, and then placed in glycerin, a very active
extract will be obtained. The acetic acid converts the trypsinogen into
trypsin. According to Kiihne,2 trypsin is also formed from the zymogen
by warming with alcohol.

The amount of trypsin that can be obtained from an extract varies
with the histological condition of the gland. When the luminal zone
is of considerable width, a greater amount of proteolytic activity is
shown than when it is much reduced. We are justified in associating
the ferment with the granules seen in the cells.

Sodium carbonate may be regarded as an adjuvant to the action of
trypsin. Kiihne 3 showed that it worked best in solutions of the strength
of 1 per cent. Edkins4 proved that sodium chloride has a beneficial
influence on the digestion of fibrin by pancreatic extracts, and it may be
noted that a large amount of the sodium carbonate associated with the
pancreatic secretion must be converted into sodium chloride in the
duodenum. Ewald5 states that digestion of fibrin at the instance of
trypsin can proceed in the presence of 0*3 per cent, of hydrochloric acid,
but, on the other hand, the prolonged action of dilute acids has been
shown by Langley 6 to be destructive of trypsin. If a glycerin extract
of pancreas be warmed for two and a half hours in 0'05 per cent, hydro-
chloric acid, its proteolytic powers are appreciably curtailed. The
diastatic ferment has not had the same study bestowed upon it as the
proteolytic. It contrasts with this latter in that there is no further
enhancement of its activity by treatment with such reagents as convert
trypsinogen into trypsin. Liversedge7 made observations in 1874,
which suggested the existence of a diastatic zymogen, but the possi-
bility of micro-organic change influencing his experiments was, as
pointed out by Gamgee,8 not eliminated. According to his observations,

1 Breslau, 1876.

2 Verhandl. d. naturh.-med. Ver. zu ffeidelberg, 1876, N". F., Bd. i.

3 Ibid., Bd. i. 4 Journ. PhysioL, Cambridge and London, 1891 Bd. xii.

5 Ztschr.f. Uin. Med., Berlin, Bd. i.

6 Journ. PhysioL, Cambridge and London, vol. iii.

7 Journ. of Anat. and PhysioL, London, 1874, vol. viii.

8 "Physiological Chemistry," vol. ii. p. 207,

VARIA TIONS IN PANCREA TIC JUICE.

553

/•(3
/•2

/•;

t'O
•9
<G

•r

•6

6 7 8

13 )+ 15 /G S7 J8 /<?

the zymogen is not soluble in water, thus contrasting markedly with
other zymogens. We must regard the existence of a precursor in
this case as doubtful, though it is undeniably possible that in the
living cell an ante-
cedent state of the
ferment exists, adapted
to storage of the fer-
ment ; in that case the
mere destruction of the
cell might involve the
breaking dowrn of this
hypothetical zymogen,
on account of the pre-
cursor of the diastatic
ferment being less
stable than that of the
proteolytic.

There is also no
evidence of any zymo-
gen of the fat-decom- FIG. 46. — Chart of the course of secretion of pancreatic juice.
T^nQinrr favTYiomf -rn'oKn-i The abscissae correspond to hours ; the ordinates corre-

LllsDJ..L.LcL IUlliJ.t5J.lU, I) IcllY 11. 1 , rt • . .«. -r-r . -I •, .

•n^ n -> i i spond to c.c. of jttice. — After Heidenhain.

Finally, it has been

found that extracts of pancreas and the pancreatic juice itself1 have

the power of inducing a clot in milk, probably by the agency of some

specific enzyme in the juice.

The variations in the composition and amount of pancreatic

juice during digestion. — From the earlier experiments of Bern-
stein,2 and those of
Heidenhain,3 it ap-
pears that the flow
of pancreatic juice
has somewhat the
following course : —
Before a meal
is over there com-
mences a secretion,
which reaches a
maximum not later
than the third hour.
Then the secretion
sinks to about the
sixth or seventh
hour, and yet again
increases to the
ninth or eleventh ;
thence it sinks gra-
dually to about the

* o L

6<O 1

frtSfl

•? f) 1

f-c5 1 •

4 O\\ —

f

^^-

,-—•

<3 <5 I

l\

c3 O II

/

>s

/

0 K\\

I/

\

/

/

s

^

/

^

--V

^«.

^

/• 0

L

/ 2 3 f 5 6 73 9 SO tl /£ 13 14 15 16 1 7

FIG. 47. — Chart of the percentage composition of the flow of
pancreatic juice. The abscissae correspond to hours ; the
ordinates to percentage of solids. — After Heidenhain.

eighteenth and twentieth. The quality of the juice varies inversely as
the quantity. When one rises the other falls. The accompanying
diagrams (Figs. 46 and 47) illustrate these variations.

1 Halliburton and Brodie, Journ. Physiol., Cambridge and London, 1896, vol. xx.

2 Op. cit.

3 Hermann's " Handbuch," Bd. v.

554 MECHANISM OF SECRETION OF INTESTINAL JUICE.

It has been pointed out by Mette that during normal digestion there is a
certain independence between the secretion of ferment and the secretion of water.
Observations have also been made by Wassilieff 1 on the influence of food in
causing changes in the activity of the juice. He found that the maximum of
secretion was in the first two hours, with meat diet in the first hour, and
milk diet in the second hour. By changing the diet from meat to bread and
milk, the proteolytic action of the juice diminished, whilst the diastatic action
remained unaltered. On the other hand, when changing from bread and
milk to meat, these were reversed. It is therefore to be noted that the
relative quantity of both ferments is variable and dependent upon the food.
The effects produced by other substances upon the flow of pancreatic juice
have already been mentioned (p. 551).

•
THE MECHANISM OF SECRETION OF Succus ENTERICUS.

The histological evidence of secretion in the intestine. — The
evidence of secretion from the histological standpoint is, in the case of
the mucous membrane of the intestine, very incomplete. Paneth'2 pointed
out that the cells at the base of the crypts of Lieberkulm frequently
contain definite granules. These cells were also studied by Nicolas,3
who noticed different phases in the condition of the cells ; thus, after
secretory activity, he found them either free from or containing but
few granules.

Hardy and Wesbrook 4 found that in fasting animals the granules
were large and numerous, in well-fed animals comparatively few, and
smaller than in the fasting state.

Bizzozero 5 regards the granules as mucigen granules. Schaffer 6
has also called attention to the fact that the cells containing them
are goblet - shaped. From the manner in which they stain, their
shape, and the fact that they are scattered in the crypt of Lieberkiihn,
it seems probable that they are to be looked upon as mucus-secreting
cells.

The cells covering the villi have been described by Nicolas 7 as con-
taining granules which do not stain, or at the best very slightly, with
safranin (unlike those just referred to). He states, however, that these
granules give rise to some secretion. Examined in the fresh state,
the cells do not show the existence of typical secretory granules.

Brunner's glands, from their structure, suggest the formation of
a mucous secretion,8 but it has been stated by Krolow 9 that an extract
of the glands will digest fibrin in acid solution, and they bear
considerable resemblance, histologically, to the pyloric glands of the
stomach.

The experimental evidence of secretion of succus entericus. —
Two methods have been adopted for obtaining evidence as to the
nature of succus entericus. The first consists in isolating, by operation,
a piece of the intestine, and observing the nature of the liquid which

1 Arch, de sc. biol., St. Petersbourg, 1893, vol. ii.

2 Arch.f. mikr. Anat., Bonn, 1888, Bd. xxxi.

" Internal. Monatschr. f. Anat. u. Physiol., Leipzig, 1891, Bd. viii.

4 Journ. Physiol., Cambridge and London, 1895, vol. xviii.

5 Anat. Anz., Jena, 1888, Bd. iii. ; Atti d. r. AcacL d. sc. di Torino, 1888-9.

6 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1891, Abth. 3, Bd. c.

7 Op. cit.

8 Kuczynski, Internal. Monatschr. f. Anat. u. Physiol., Leipzig, 1890, Bd. vii.

9 Berl. klin. Wchnschr., 1870, No. 1.

EXPERIMENTAL E VIDENCE. 555

collects in the interior ; the second, in making extracts of the intestinal
mucous membrane and investigating the digestive properties of such an
extract.

A method of permanently isolating a portion of the intestine was
first devised by Thiry.1 The abdomen of an animal having been opened,
a piece of intestine was cut away from its continuity with the main gut
without dividing the mesentery. The two ends of the main gut were
then brought together and ligatured, so that union of the cut surfaces was
brought about, the continuity of the intestine being thus re-established.
The isolated portion of the gut was then closed by a ligature at its lower
end, while the upper end was sewn into the incision in the abdominal
wall, a blind sac being thus formed. Vella 2 modified this procedure by
inserting the lower end of the isolated gut also into the abdominal wall ;
thus affording two openings for the separated intestine. This operation,
performed with due antiseptic precautions, is of constant service at the
present day, and is generally described as the establishment of a
" Thiry-Vella " fistula.

Older observers, such as Bidder and Schmidt,3 had ligatured off from
the general tract short lengths of the intestine, and, after replacing them
in the abdominal cavity for some hours, had examined the accumulated
liquid.

The chief facts that have been brought to light by these methods
are as follows : — In the absence of any stimulus, little or no secretion
has been obtained, as a rule. Thiry,4 with mechanical or electrical
stimulation, obtained a thin yellowish alkaline secretion, albuminous in
character. After food had been taken, although no previous secretion
was manifest, some fluid began to form. According to Eohmann,5 the
introduction of starch, sugar, or peptone provokes intestinal secretion.
The administration of pilocarpine results, according to Masloff,6 in
secretion. Gamgee,7 however, found that it was possible to produce
considerable increase of other secretions by the administration of
pilocarpine without affecting the succus entericus to any extent. This
result lie attributed to the fact that probably different regions of the
intestine reacted with different vigour to pilocarpine, the lower portion
of the intestine secreting a greater quantity than the upper.8

With respect to the existence of nervous influences on the secretion,
Thiry found no result to come about from stimulation of the vagi.
Budge 9 and Lainansky 10 obtained increase of secretion after extirpation
of the cosliac and mesenteric plexuses, but Adrian n did not succeed in
obtaining this increase. Brunton and Pye-Smith 12 found, in confirmation
of an observation of Moreau,13 that if all nervous connections be severed

1 " Eine neue Methode den Diinndarm zu isolieren," Sitzungsb. d. Jc. Akad. d. Wissensch.,
Wien, 1864, Bd. i.

2 Untersuch. z. Naturl. d. Menscli. u. d. Thiere, 1881, Bd. xiii.

3 "Die Verdauungssafte und der Stoffweehsel," Leipzig, 1852. 4 Op. cit.

5 Arch.f. d. ges. Physiol., Bonn, 1887, Bd. ii.

6 Untersuch. a. (/. physiol. Inst. d. Univ. Heidelberg, 1882, Bd. ii.

7 "Physiological Chemistry," London, 1893, vol. ii.

8 That pilocarpine provokes an intense secretory charge in the crypts of Lieberktihn of the
large intestine, is manifest from the experiments of Heidenhain (Hermann's "Handbuch,"
Bd. v.).

9 Verhandl. d. k. Jc. Leopold-Carol Acad. d. Naturforscher., 1860, Bd. xix.

10 Ztschr.f. rat. Med., 1866.

11 Beitr. z. Anat. u. Physiol. (Eekhard}, Giessen, 1863, Bd. iii.

12 Sep. Brit. Ass. Adv. Sc., London, 1874, 1875, 1876.

13 Compt. rend. Acad. d. sc., Paris, 1363, Bd. Ixvi.

556 ME CHAN ISM OF SE CRE TION OF INTESTINAL JUICE.

between higher centres and the mucous membrane by dividing the
intestinal nerves, an accumulation of fluid takes place. Brnnton and
Pye-Smith also found that if the inferior ganglia of the solar plexus and
their continuation along the superior mesenteric artery are left in con-
nection with the gut, this accumulation does not take place.

L. Hermann l initiated a somewhat different method of investigating
the secretion. A loop of intestine was separated from the main gut, and
its ends joined so as to form a confluent ring. This was replaced in the
intestine, and its contents examined after some weeks. These contents
were found to consist of solid material, and it was presumed that this
represented the inspissated juice. Blitstein and Ehrenthal 2 continued
these experiments, and came to the conclusion that the solid mass found
had its origin in two sources; the fir si? being the intestinal fluid, and the
second detached intestinal epithelial cells. They noticed micro-organisms
also to be present. Fr. Voit,3 who simply sewed up the ends of an iso-
lated loop, found, after the lapse of three weeks, a yellowish-grey mass, in
which he recognised no epithelium, and which he regarded as simply
inspissated juice. The nature of the fluid excreted in the Thiry-Vella
loop has been frequently examined. It is of a yellowish colour, and
contains albumin, and also a rather large amount of sodium carbonate.
It possesses certain ferment-powers, though with regard to these there
is considerable divergence of statement. Thiry4 found it to dissolve
fibrin, but not to affect other proteids. Masloff5 found it to act feebly
on starch, but not on proteids.

Funke 6 stated that starch injected into isolated loops is not con-
verted into sugar. Later observers,7 experimenting by the above
methods, agree that starch is converted into sugar, and llohman's
experiments suggest a greater diastatic activity in the upper part of the
intestine than the lower. This observer also finds, as Paschutin8 had
previously pointed out from experiments with extracts, that the
intestinal juice has the power of inverting cane-sugar. It is to be noted
that this is, even markedly, the case, as Gamgee 9 points out, in animals
which would have no opportunity, from the nature of their food, of
utilising the enzyme causing such a change. Observations made recently
by Pregl 10 on a Thiry-Vella fistula established in a lamb, have somewhat
completed the knowledge that has accrued from this method of research.
He found that the secretion was continuous, but it increased the first hour
after food, and this went on to about the third hour. From a length of
intestine of 72 cm. he obtained about 5 grms. of intestinal juice per hour;
this rate of secretion diminished to the fifth hour, when it reached 3 grms.
per hour, and remained at this rate for many hours after. He refers to
the prolapse which occurs at first, and with which other observers have
found difficulty, and points out that this is evidence of a catarrhal condi-
tion, which itself would account for a certain amount of flow, although he
failed to notice any difference between the juice reinforced by catarrhal

1 Arch./, d. ges. Physiol. t Bonn, 1889, Bd. xlvi.

2 Ibid., 1891, Bd. xlviii. :! Ztsclir. f. Bid., Munclien, 1893, Bd, xxix.

4 Op. cit. 5 Op. tit. (! "Lehrbuch."

7 Gumilewski, Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxix. ; Rohmann, op. cit. ;
Dobroslawin, " Beitr. z. Physiol. d. Darmsiiftes," Untersuch. a. d. Inst. f. Physiol. u>
Histol. in Graz, Leipzig, 1870 ; Lannois ct Lepine, Arch, de physiol. norm, et path.,
Paris, 1883.

8 Arch. f. Anat. u. Physiol., Leipzig, 1871. 9 Op. cit.
10 Arch.f. d. ges. Physiol., Bonn, 1896, Bd. Ixi.

EXPERIMENTA L E VIDENCE. 5 5 7

exudation and the simple juice. Pilocarpine, he found, did not cause
increased secretion, nor did electrical stimulation. He describes the
juice as consisting of a yellow fluid, in which are suspended flocculi,
staining deeply with eosin, and mainly mucous in nature. The alkalinity
is marked. Albumin and globulin are present, and what he regarded as
probably albumose. He also found a small amount of urea. The secre-
tion had no action upon proteids. From starch paste was formed after
twenty-four hours a fermentable sugar. This action was shown more
powerfully in the earlier than the later months after the operation.
Eaw starch was not affected. He found that dextrose (not maltose) was
formed both from starch and glycogen. No fat-splitting action was
manifest, but the juice easily emulsified fat. The loop experimented
upon was found to be situated about three times as far from the stomach
as from the large intestine. Pregl calculates that the whole intestine
would secrete nearly 3 litres in twenty -four hours.

It is difficult to say to what extent we are justified, from experiments
performed on isolated loops, in forming conclusions regarding the nature of
normal succus entericus. The first question that suggests itself is, How far
is the fluid secreted a catarrhal production 1 As above stated, Pregl has
pointed out that the mere prolapse of the gut causes a catarrhal increase above
what he regards as the ordinary flow. The facility with which micro-organisms
could enter would tend to increase any pathological condition. The presence
of albumose in a fluid which does not digest proteid, and also of urea, suggests
a pathological condition. Many of the ferment powers attributed to the
juice might be due simply to desquamated epithelium from the walls of
the loop.

Klecki l has criticised in the same way the experiments of L. Hermann,
Blitstein and Ehrenthal, and Voit, dwelling on the abnormal conditions of the
loop, and the small number of experiments upon which their conclusions are
based. He himself finds that when few micro-organisms are allowed to remain
in the gut, much less solid substance is finally found, and states that a large
amount of contents is found in Hermann's rings only when the intestinal wall
shows pathological changes, or if complete disinfection of the loop has not
been carried out.

It would seem, therefore, that we must hesitate before accepting all the
conclusions that have been drawn from the employment of the methods of
isolated loops and Thiry-Vella fistulse, bearing in mind that the juice so
obtained is probably seldom entirely uninfluenced by the abnormal condition
induced by the operation. Many, however, regard it as probable that the
crypts of Lieberkiihn, through their lining epithelium, yield a secretion
which is of assistance in dissolving the products of digestion by other juices,
even if it has no very well-marked digestive properties itself.

We may finally proceed to consider how far extracts made from
the intestinal wall are characterised by the possession of specific
properties.

In the first place, we must bear in mind that the intestinal mucous
membrane has primarily, without doubt, an absorbing function. We
have also reason to believe that the digested food in its passage through
the epithelial cells may undergo considerable changes. Consequently, on
making extracts of these epithelial cells, we may be separating substances
which are never secreted into the lumen of the intestine, but which
merely exercise influence on the absorbed food as it passes through the

1 Wien. Jclin. Wchnsclir., 1894, Bd. vii.

558 MECHANISM OF SECRETION OF INTESTINAL JUICE.

cells. It is, therefore, not justifiable to assume that the secreted
juice has the same action as an extract of the intestinal mucous
membrane.

That extracts of the intestinal mucous membrane have marked
physiological properties, there is little doubt. It is comparatively easy
to make such extracts free from micro-organisms, and it is generally
agreed that these extracts have a considerable power of inverting cane-
sugar and of changing starch, in an intense degree, into dextrose,
probably through the stage of maltose.

MECHANISM OF BILE SECRETION.
By D. NOEL PATON.

CONTENTS. — Mode of Formation of Bile Constituents, p. 559 — Water, p. 559 —
Inorganic Salts, p. 560— Nucleo-Proteid, p. 561— Bile Acids, p. 562— Bile Pig-
ments, p. 563 — Cholesteriu, p. 564 — Lecithin, etc., p. 564 — Influence of various
Factors on the Secretion of Bile, p. 564 — Flow of Blood, p. 565 — Food, p. 565
— Pressure of other Organs, p. 567 — Nerves, p. 567 — Chemical Substances, p.
567 — General Conclusions, p. 569.

IN considering the mechanism of bile secretion, it must be remembered
that the formation of bile is only one of many functions performed by
the liver.

Placed as it is upon the course of the portal vein, the great channel
of absorption of material from the alimentary canal, the liver regulates
the supply of carbohydrates to the body by storing the surplus sugar
absorbed in the form of glycogen. It also gets rid of any excess of
nitrogen absorbed, by converting it into the innocuous and easily
eliminated urea. In addition to performing these functions, the liver
acts as one of the great storehouses of iron in the body, and in many
animals it is also a situation in which surplus fats are accumulated.

When these numerous functions are considered, the small amount of
bile formed per diem by so large an organ is the less surprising. In man
about 800 or 900 grms. of bile, with about 14 or 15 grms. of solids, are
daily secreted from the liver, an organ which weighs about 1600 grms.

In studying how bile is formed in the liver, it is necessary to
remember that, besides the great mass of liver cells, there are in-
numerable bile passages lined by a living epithelium. In most animals
a saccular diverticulum, the gall bladder, is developed upon these
passages. In this and in the passages the surplus bile accumulates.
How far the liver cells, and how far the cells lining the ducts, act in
producing the various constituents of bile, must be subsequently con-
sidered.

The bile is a fluid containing many different substances in solution
(see article, " Chemistry of Bile " ), arid an investigation of the mechanism
of bile secretion necessitates a consideration of the mode of production
of each of these.

MODE OF FORMATION OF BILE CONSTITUENTS.

Water. — The water of the bile is in part secreted from the walls
of the bile passages, for it has been found that when the cystic duct
is occluded, and the fundus of the gall bladder opened, a small amount

5<5°

MECHANISM OF BILE SECRETION.

of fluid, about 70 c.c. per diem, is continually secreted from the walls of
the gall bladder.1 How far this fluid is a physiological secretion, and
how far it is due to pathological conditions, is difficult to decide.

That water is secreted by the liver cells, as well as by the cells of
the ducts, is proved by the way in which pigments,2 which are secreted
by the liver cells alone, are washed down into the bile passages.

The elimination of the water of the bile is a process of secretion,
and not of transudation. Heidenhain's observations on the relative
pressures in the bile passages and in the blood vessels passing to the
liver,3 given in the following table, demonstrate very clearly that, though
the pressure of secretion of bile is low, it is nevertheless considerably
higher than the blood pressure in the portal vein.

No.

Bile Pressure.

Pressure in Vena Mesenterica
Superior.

1

220 mm. carbonate of soda sol.

90

mm. carbonate of soda sol.

2

175 ,,

67

11 11

3

204 '„

90

i'. 11

4

no „

50

11

5

180 „

65

11 11

The absorption of water from the alimentary canal seems under
certain conditions to increase the secretion of water by the liver.

Eohrig,4 Bidder and Schmidt,5 and Zalesky,6 noticed that the intro-
duction of water into the stomach and intestine of dogs with biliary
fistulas increased the flow of bile. Eosenberg 7 found that if the intestine
had previously been cleared oub by a glycerin enema, the introduction
of 500 c.c. of water into the intestine increased the flow of bile. In a
case of complete biliary fistula in a woman,8 the amount of the bile
secretion was greater upon the days on which a large quantity of fluid
was taken, and this increase was in the water of the bile, not in the
solids.

Inorganic salts. — The analyses of the bile of the dog given by
Hoppe-Seyler,9 show that in bile taken from the gall bladder the salts
constitute about 5 per cent, of the solids, while in freshly secreted bile
they amount to about 13 or 14 per cent. The freshly secreted bile
alone need be considered in discussing the mode of formation of these
salts. A comparison of the salts of the bile with the salts of the blood
plasma indicates that the percentage amount of salts is smaller in bile
than in blood, and that, while chloride of sodium is the most abundant in

1 Birch and Spong, Journ. PhysioL, Cambridge and London, vol. viii. p. 378 ; Mayo
Robson, Proc. Roy. Soc. London, 1890, vol. xlvii. p. 499.

- Wertlieimer, Arch, dephysioL norm, etpath., Paris, 1891, p. 724.
3 Hermann's "Handbnch," Bd. v. S. 269.

* Med. Jahrb., Wien, 1873, Bd. ii.

5 " Die Verdauungssafte," 1852, S. 166.

6 Hermann and Schwalbe, Jaliresb. ii. d. Fortschr. d. Anat. u. PhysioL, Leipzig, 1877,
S. 219.

7 Arch./, d. ges. PhysioL, Bonn, 1890, Bd. xlvi. S. 361.

8 Noel Paton and Balfour, Rep. Lai. Roy. Coll. Phys., Edin., 1891, vol. iii. p. 191.

9 "PhysioL Chem.," S. 302.

FORMATION OF BILE CONSTITUENTS. 561

both, in bile the proportion of this salt is not nearly so high as in
plasma. This may possibly be explained by the withdrawal of hydro-
chloric acid in the stomach, leaving the soda to be combined with the
organic acids of the bile.

A study of the excretion of chlorine in the bile has been made by
Dagnini in Albertoni's laboratory.1 He finds that in dogs with a
permanent fistula the percentage of chlorine varies little, and that it
is only slightly raised by the administration of chloride of sodium, or
of potassium. Chlorides, as is well known, are chiefly excreted by
the kidney.

Giovanni Pirri 2 has studied the secretion of sodium and potassium,
and finds that, while the amount of sodium excreted per diem is very
constant in spite of variations in diet, and in spite of the administration
of chloride of sodium, the excretion of potassium varies within wide
limits, and is increased by giving sodium and potassium chloride in the
food. The sodium is in great measure combined with the organic
acids of the bile, and hence these results do not throw light upon the
excretion of sodium in inorganic compounds.

On the secretion of lime salts, work has been done under Naunyn's
direction by Jankau. He shows that the amount of lime in bile is very
small, and that it is not increased by the administration of lime salts.3
From the fact that lime salts are present in the secretions from mucous
membranes, Naunyn suggests that the lime of the bile may be formed in
the bile passages.

The very small quantity of iron which exists in the bile (less than
1 mgr. per diem in the dog)4 may be derived from the iron stored in the
liver cells, or may be formed from the disintegration of the epithelial
lining of the passages. Evidence on the subject is wanting.

How far the other inorganic salts are secreted by the liver cells,
and how far by the cells lining the bile passages, cannot be considered
as established. There is clear evidence to show that they are, in part
at any rate, formed in the latter situation. In a series of analyses of
bile, collected from a woman with a complete biliary fistula, it was found
that during attacks of fever the true biliary constituents, the organic
salts and pigments, were markedly diminished, while the proportion of
inorganic salts remained unaltered, between 07 and 0'8 per cent.5

Birch and Spong's analysis of the fluid from the gall bladder showed
the presence of 0-826 per cent, of inorganic salts, of which the chief was
chloride of sodium. Mayo Eobson found 0'84 per cent, of inorganic
matter. Analysis of freshly secreted human bile gives about the same
proportion of salts.6 Hence, since the amount of salts is the same in
the small amount of fluid secreted from the bile passages, and in the
total amount of bile poured out from bile passages and liver cells
together, about the same proportion of salts must exist in the secretion
from each.

Nucleo-proteid. — The mucus-like nucleo-proteid of bile is formed in
the bile passages and gall bladder. The amount in bile is small, about
0'2 per cent.

1 Mem. r. Accad. d. sc. d. 1st. di Bologna, 1893, Ser. 5, vol. i. p. 3.
* Ibid., 1893.

3 Naunyn, "Cholelithiasis," translated by A. E. Garrod, New. Syd. Soc., p. 15.

4 Ansel m, Arb. d. pharmakol. Inst. zu Dorpat, Stuttgart, 1892, Bd. vii.
3 Rep. Lab. Roy. Coll. Phys., Edin., vol. iv. p. 44.

0 Hoppe-Seyler, " Physiol. Chem.," S. 302.
VOL. I. — 36

562

MECHANISM OF BILE SECRETION.

In cases of occluded gall bladder this mucm-like substance has been
found to be the chief organic solid of the secretion.1

Mayo Robsoris Analysis.

Organic matter, chiefly muciri . . . '672 per cent.

Chlorides equal to NaCl . . . . '573 ,,

Sodium carbonate ..... '220 „
Other salts containing phosphates, potassium

salts, etc . -071 „

The fact that the amount of this substance does not vary with the
true bile constituents either at different periods of the day,2 or in febrile
conditions,3 indicates very clearly that it is not formed by the liver
cells.

Salts of the bile acids. — These are entirely produced in the liver
cells. In Birch and Spong's case, and in the case examined by Mayo
Eobson, they were entirely absent from the secretion of the gall
bladder.

That they are actually formed by the liver cells, and not merely ex-
tracted from the blood, was demonstrated by Minkowski and Naunyn.4
These observers found that, while bile salts are normally absent from the
blood, they appear when the bile duct is ligatured. If, however, the
liver be excluded from the circulation, there is no accumulation of bile
salts in the blood.

The source of the cholalic acid moiety of the glycocholic and
taurocholic acids is unknown. The source of the glycine and taurine is
to be sought ultimately in the proteids of the body and of the food,
since these alone can yield the nitrogen and sulphur. Both are amido-
acids of the fatty acid series.

Nencki, Pawlow and Zaleski,5 have shown that the surplus proteid
of the diet is largely broken down into ammonia compounds in the wall
of the intestine, and these compounds pass to the liver. Yon Schroder 6
demonstrated that ammonia compounds are readily converted to urea by
the liver. Hence by far the greater quantity of nitrogen in excess of
that required must undergo this transformation, and it is not to be
expected that an additional quantity of proteids in the food will lead to
a markedly increased formation of bile acids. Spiro,7 by feeding animals
with biliary fistulse upon various kinds of food, found that a proteid diet
increased the nitrogen and sulphur excreted in the bile, but not in
proportion to the amount of proteid taken.

The following figures illustrate Spiro's results : —

Food.

Sulphur of Bile
in Grms.

Nitrogen of Bile
in Grms.

Fasting ....
125 grins, flesh .

•059
•089

•195
•292

500 „ ...

•155

•398

949 ,, ...

•173

•604

I

1 Hoppe-Seyler, " Physiol. Chem.," S. 302.

2 Eep. Lab. Roy. Coll. Phys., Edinburgh, vol. iii. p. 204.

3 Ibid. p. 212. 4 Arch.f. exper. Path. u. PharmakoL, Leipzig, Bd. xxi. S. 7.
5 Ibid., Bd. xxxvi. S. 26.

G Ztsehr. f. physlol. Chem., Strassburg, Bd. ii. S. 234.
7 Arch.f. Physiol., Leipzig, 1880, Supp. Bd. S. 50.

BILE ACIDS AND PIGMENTS. 563

Kunkel,1 from similar experiments on dogs, concluded that a definite
part of the sulphur taken in the diet is excreted in the bile, but the
increase in biliary sulphur occurs two or three days after the ingestion,
and not upon the same day, as is the case with the sulphur of the urine.
Of the sulphur of the food, from 8 to 30 per cent, is excreted in taurine.

In man on an ordinary diet, about 33 grins, of urea with 15 grms. of
nitrogen are daily formed, while only about 10 grms. of bile acids with
about 0'3 grms. of nitrogen are excreted. The increased ingestion of
proteids leads to a proportionate increased excretion of urea, and any
increase in the bile acids is necessarily so small that it may readily
be overlooked. Similarly, any increased decomposition of the proteids
of the tissues leads to a proportionately increased excretion of the
nitrogen in the form of urea, and any increase in the bile acids which
may occur must be very trifling.

Whether the bile acids which are absorbed from the intestine can
be again excreted by the liver cells, has been investigated by injecting
into the blood of animals a bile salt differing from that which is normally
present. In dogs the taurocholate of soda is the normal salt of the
bile. After injecting glycocholate of soda, Prevost and Binet,2 and
Weiss a found it in the dog's bile. Socoloff,4 on the other hand, failed
to detect it after it had been injected. Huppert 5 observed that the
injection of glycocholic acid increases the amount of bile acids in the
bile. The experiments of Eosenberg6 show that the administration of
bile salts causes an increased secretion of bile with a marked increase
in the solids. They appear to be the only substances which produce
this result, and since the bile salts are the most abundant solids of bile,
it seems fairly certain that they are absorbed, and re-excreted from the
blood by the liver.

Bile pigments. — The pigments must be produced in the liver cells,
since the secretion from the bile passages is entirely destitute of colour-
ing matter.7 They are formed from the haematin moiety of the haemo-
globin molecule. The injection of free haemoglobin into the blood,8 or
the setting free of haemoglobin by solution of the red corpuscles,9 rapidly
leads to a great increase of the bilirubin of the bile. Minkowski and
Naunyn, by experiments upon birds,10 have confirmed these observations.
They further found that if the liver is excluded from the circulation
the formation of bilirubin does not take place. They thus showed that
bilirubin is actually produced in the liver cells. The iron-containing
part of the haematin molecule appears to be split off and retained in
these cells, giving rise to the accumulation of iron in the liver, which
follows the disintegration of red corpuscles.11

Not only do the liver cells manufacture bilirubin, but when this or
any other bile pigment is present in the blood they take it up and eliminate

1 Arch.f. d. ges. PhysioL, Bonn, Bd. xiv. S. 344.

2 Compt. rend. Acad. d. sc., Paris, 1888, tome cvi. p. 1690.

3 Bull. Soc. imp. d. nat. de Moscou, 1884.

4 Arch.f. d. ges. PhysioL, Bonn, 1875, Bd. xi. S. 166.

5 Arch. d. Heilk., Leipzig, 1869, Bd. v.

6 Arch.f. d. ges. PhysioL, Bonn, 1890, Bd. xlvi. S. 334.

7 Birch and Spong, Journ. PhysioL, Cambridge and London, vol. viii. p. 378 ; Mayo
Robson, Proc. Roy. Soc. London, 1890, vol. xlvii. p. 499.

8 Stiidelmann, Arch.f. exper. Path. u. PharmakoL, Leipzig, 1890, Bd. xvii. S. 93.

9 Afanassiew, Ztschr. f. klin. Mcd., Berlin, Bd. vi. Heft 4.

10 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1886, Bd. xxi. S. 1,

11 Hunter, Lancet, London, 1892, p. 1262.

564 MECHANISM OF BILE SECRETION.

it. This was definitely proved by Wertheimer,1 who injected into the
circulation of dogs the bile of the ox and sheep. The bile of these
animals contains a pigment, cholohsematin, which gives a characteristic
spectrum, and the appearance of this spectrum in the bile of the dog
showed that cholohsematin had been taken up and excreted.

Cholesterin.— Whether cholesterin is formed in the liver cells, or in
the cells lining the bile passages, or in both, is not definitely known.
In the two cases of fistula of the gall bladder already referred to, the
presence or absence of cholesterin is not noted.2

That the cholesterin is formed somewhere within the liver, and not
merely excreted by it, is shown by an experiment by Jankau, performed
in Naunyn's laboratory.3 He injected cholesterin into dogs, and also
gave it in their food, and ascertained ^hat it had been absorbed ; but he
failed to find any increase of cholesterin in the liver tissue, or in the
bile. The analyses of the liver and bile made by Kausch 4 in the same
laboratory show no relationship between the amount of cholesterin in
the gland, and in its secretion. Thomas,3 who also worked in Naunyn's
laboratory, found that there is no relationship between the amount of
cholesterin excreted and the kind of food taken. When the dog under
observation suffered from catarrh of the biliary passages, there was a
marked increase in the cholesterin of the bile.

From these experiments, and from the fact that cholesterin is always
found where cells are disintegrating, Naunyn strongly supports the view
that cholesterin is produced, not in the liver cells, but from the cells of
the passages, and that it is a product of the disintegration of their
protoplasm.

Lecithin and other compounds of the fatty acids.— The occur-
rence of these bodies in the secretion from the gall bladder has not
been observed. On the other hand, lecithin and fat are constant and
abundant constituents of liver cells. Liver tissue contains about 2 -3 5
per cent, of lecithin, and about 3 or 4 per cent, of fat.5 Thomas found 6
that, while cholesterin was unaltered in amount by the administration
of various diets, the amount of fat in the bile depended largely upon
the amount of fat taken in the food ; and since the fats of the food are
frequently stored in the liver cells, it is probable that the fatty acid
compounds in the bile are derived from this source.

INFLUENCE OF VARIOUS FACTORS UPON THE SECRETION.

The investigation of the influence of varying conditions upon bile
secretion is a matter of extreme difficulty, for the bile may accumulate
in the gall bladder and passages to be expelled from the liver some time
after secretion.

The flow of bile is governed by —

1. The rate of secretion.

2. The activity of the muscular walls of the passages.

3. The pressure upon the liver of adjacent organs.

1 Arch, de physiol. norm, etpatli., Paris, 1891, p. 724.

2 In the colourless fluid from a case of hydrops cystidis fellese, I found a considerable
quantity of cholesterin.

3 ''Cholelithiasis," translated by A. E. Garrod, New Syd. Sac., 1896.

4 Diss., Strassburg, 1891.

5 Noel Paton, Journ. Physiol., Cambridge and London, 1896, vol. xix. p. 213.

6 Loc. cit.

INFLUENCE OF VARIOUS FACTORS. 565

Further, the liver being placed upon the efferent vessel of the
alimentary canal, must have its vascular condition altered by every
modification in that of the gastro-intestinal tract, and it is impossible to
eliminate this element while studying the action of any agency on bile
secretion.

Influence of the hepatic circulation upon bile secretion.-—
The circulation in the liver may be profoundly altered without actual
stoppage of bile secretion. Thus it has been shown, in cases where, by
the method devised by Ore, the portal blood has been directed into the
inferior vena cava, that bile is still secreted by the liver ; l while
Wertheimer2 has confirmed the results of older investigators, that
ligature of the hepatic artery does not immediately stop the secretion,
although ultimately necrosis of liver tissue supervenes and leads to
abolition of function.

But while these marked disturbances do not at once stop secretion,
there is evidence that its rate depends upon the vascular supply.
Thus Heidenhain has shown3 that in dogs, section of the splanchnic
nerves, which causes a dilatation of the portal vessels, produces a
marked increase in the now of bile. If, however, this local dilatation
is accompanied by a general dilatation, such as is produced by section of
the spinal cord in the neck, a fall in the secretion occurs. Munk,4 on
the other hand, has shown that stimulation of the splanchnic nerves,
which produces constriction of the vessels, leads to a diminution in
the rate of bile secretion.

How far this influence of alteration in the blood supply is due to
variation in pressure, and how far to alteration in the rate of blood flow
through the liver, has not been directly investigated. But the observa-
tion of Eohrig,5 that constriction of the Vena cava inferior, which raises
the pressure in the liver while decreasing the rate of blood flow,
diminishes bile secretion, seems to indicate that the rate of flow is of
more importance than the mere intravascular pressure. In this con-
nection the relationship of the pressure of secretion to blood pressure
(p. 560) must be borne in mind.

Effects of food. — Starvation, according to Bidder and Schmidt,
causes a diminution in the amount of bile secretion, and a corresponding
fall in the amount of solids.6 Their experiments are unsatisfactory, in
so far that cats were taken at various stages of starvation up to 240
hours after food, a temporary fistula made, and the bile secretion
determined for a short period only. The most recent contribution
to our knowledge of this subject was made by Lukjanow,7 who
determined the changes in the various solids of the bile in guinea-pigs
kept without food or water. He concludes that both the secretion of
water and of solids diminishes throughout the period of fasting.

From the investigations on the relationship of bile secretion to
the flow of blood through the liver, it is obvious that the dilatation
of the abdominal vessels, which occurs in digestion, will of itself
cause an increased secretion of bile. Such an increased flow has

1 Arch. d. sc. bioL, St. Petersbourg, 1892, vol. ii.

2 Arch, de physiol. norm, etpath., Paris, 1892, p. 577.

3 Hermann's "Handbuch," Bd. v. S. 266.

4 Arch. f. d. ges. Physiol. , Bonn, 1874, Bd. viii. S. 151.

5 Med. Jahrb., Wien, 1873, Bd. ii.

6 Bidder and Schmidt, " Die Verdauungssafte. "

7 Ztschr.f. physiol. Chem., Strassburg, 1892, Bd. xvi. S. 87.

566

MECHANISM OF BILE SECRETION.

cells, is not made

o

manifest

been observed by various investigators. The most careful observations
on the influence of food in bile secretion are those recorded by Hoppe-
Seyler.1 The experiments were made on a dog with a permanent
biliary fistula, and they show that within an hour after food the flow of
bile is slightly and temporarily increased. It is very probable that
this initial increase is simply due to reflex stimulation of the gall bladder
and bile passages, expelling the bile already secreted. Four or five
hours after a meal the flow is enormously increased, the amount of
bile solids rising with the amount of bile. The extent of this accelerated
flow indicates that it is actually an increased secretion. How far it
is due to the increased vascularity of the abdominal viscera, and
how far to the stimulating action of absorbed material on the liver

by the -experiments. About nine or ten
hours after a meal there is a secondary
increase, not so marked as the first, but
lasting for two or three hours, and accom-
panied by a still more marked rise in the
excretion of solids. The cause of this is
unknown.

As to the special influence of the
various constituents of the food, our know-
ledge is somewhat defective. The re-
searches of Eosenberg2 and of Barbera,3
on dogs with a permanent fistula, show an
increase in the secretion of bile and of the
bile solids after proteid food. The latter
observer states that carbohydrates have
also a certain effect in increasing the secre-
tion of bile, but that their effect is very
small indeed. Both observers find that
the administration of fats very markedly
increases the bile flow ; but while in Eosen-
1 tore's experiments the flow of bile under
the influence of fats was greater than with
proteids, in Barbera's the increase was most
marked on a diet of flesh.

The accompanying chart (Fig. 48) gives
a summary of Barbera's observations.

In another paper Barbera 4 shows that
the excretion of bile after a meal of pro-
teids or carbohydrates runs parallel with
that after a meal of fats the bile secretion

grams

I

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*
#

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*

#

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*

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**

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>V

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•X-

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6' £

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. Water Carbohydrates

Fats Mixed Diet

##** Proteids

FIG. 48. — Showing influence of
various food stuffs upon the
secretion of bile.

the secretion of urea, but

increases out of proportion to the urea.

The slight increase in the secretion following the administration of
carbohydrates is probably due to the vascular dilatation. The more
marked increase after fats may be related to their more prolonged
digestion, and the correspondingly greater and more sustained dilatation
of vessels. The increase after proteids is in part due to the same cause,
but may also be due to the increased functional activity of the liver,

1 "Physiol. Chem.," S. 308.

2 Arch. f. d. ges. Physiol. , Bonn, 1890, Bd. xlvi. S. 243.

3 Bull. d. sc. med. di Bologna, 1894, Ser. 7, vol. v.

4 " Rapporto tra la eleminazione dell urea e della bile."

INFLUENCE OF VARIOUS FACTORS. 567

which has to deal with nitrogen in excess of the requirements of the
body.

After every kind of food the absorption of bile salts and their action
on the liver must be taken into account as a factor in increasing the
now of bile (see p. 563).

Influence of pressure of surrounding structures. — The liver,
being situated just below the diaphragm and above the abdominal
viscera, is subject to marked variations in pressure. It has already
been pointed out that a considerable quantity of bile may collect in
the bile passages. By pressure from adjacent organs, this may be
squeezed out. The facts that section of one vagus reduces the bile flow
only when the frequency of respiration is diminished,1 and that section
of the vagus just above the diaphragm, which has no influence on -the
rate of respiration, leaves the bile secretion unaltered, and that stimula-
tion has also no effect, seem to indicate that the flow of bile is acceler-
ated by respiratory movements.

The very marked rise in the amount of bile poured out between four
and eight A.M. in a case of biliary fistula,2 just at the time when the
patient wakened and commenced to move about, further supports the
view that pressure on the liver may cause an increased flow of bile.

Direct influence of nerves upon bile secretion. — It has already
been pointed out that the secretion of bile may be indirectly modified
by the influence of nerves upon the blood vessels. The flow of bile may
also be increased through the stimulation of the nerves to the muscular
coat of the bile ducts and gall bladder. Eeflex stimulation through
these nerves probably accounts for the first gush of bile after food is
taken. There is, however, no evidence that stimulation of nerves can
directly increase or diminish the actual secretion of bile — any change
in the flow being fully explained by indirect action. The facts that
the injection of pilocarpine, which so markedly increases the flow of
saliva and of pancreatic juice, has no influence on bile secretion,3 and
that atropine has no action in arresting the secretion,4 seem to oppose
the idea that there is any direct nervous influence upon the process.

Influence of various chemical substances on bile secretion.—
Certain substances, when introduced into the portal blood, either directly
or through the alimentary canal, cause an increase in the secretion of bile.

Tarchanoff 5 found that when haemoglobin is injected into the blood-
vessels the bilirubin of the bile is increased in amount. Stadelman 6 and
Afanassiew 7 afterwards demonstrated that such drugs as toluylenediamin
and arseniuretted hydrogen, which cause the solution of haemoglobin
from the blood corpuscles, produce not only an increase in the bilirubin
of bile, but also an increased flow of bile, and that this polycholia seems
to be proportionate to the destruction of haemoglobin. It is therefore
clear that the passage of free haemoglobin to the liver acts as a stimulant,
and may produce an increased flow of bile ; and hence all substances
which bring about an escape of the blood colouring-matter tend to
increase the secretion of bile.

1 Hermann's "Handbuch," S. 270.

- Rep. Lai). Roy. Coll. Phyx., Edinburgh, vol. iii. p. 200.

3 Paschkis, Med. Jdhrb., Wien, 1884, S. 169.

4 Rutherford, "Action of Drugs on the Secretion of Bile," Edinburgh, 1880, p. 96.

5 Arcli.f. d, ges. PhysioL, Bonn, 1874, Bd. ix.

0 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1883, Bd. xcviii. S. 460.
7 VircJiows Archiv, 1884, Bd. xcviii. S. 460.

568

MECHANISM OF BILE SECRETION.

Among these substances are the salts of the bile acids, and all in-
vestigators find that the administration of these causes an enormous
increase in bile secretion. But while such pure haemolytics as toluy-
lenediamin and arseniuretted hydrogen cause only a transitory increase
in the secretion, and produce a very concentrated, bile, the bile salts not
only markedly increase the solids, but also the water secreted. The
following record of one of Eosenberg's 1 experiments shows this effect : —

Time in Hours.

Amount of Bile.

Per Cent, of
Water.

Per Cent, of
Solids.

At 8.30-9.30 A.M. .

47673 9

94-4

5-6

10 grs. bile with 1*16 grs. solids given at 9.30

,, 9.30-10.30 ,, .

6-9095

95-3

4-7

,, 10.30-11.30 „ .

12-9783

93-9

6-1

,, 11.30 A.M.-12.30 P.M. .

3-6582

90-8

9-2

,, 12.30-1.30 P.M. .

2-3897

88-9

11-1

Again, Stadelman's work shows that, while the ordinary hsemolytics
do not increase the secretion of bile salts, the administration of the
bile salts leads to a marked increase in their percentage amount in the
bile. Paschkis' experiments 2 indicate that, while glycine and taurine
have little action as cholagogues, cholalic acid is exceedingly active. It
would thus seem that these substances act not only in virtue of their
hsemolytic action, but by reason of a special stimulating influence upon
the liver cells.

Salicylate of soda, which also has a hsemolytic action, greatly
increases the flow of bile. But while the bile salts cause an increase
in the solids, this substance produces a very marked dilution of the
bile (Rutherford,8 Lewaschew,4 and Eosenberg 5).

One of Eosenberg's experiments is here given to show this effect.

Time in Hours.

Bile Secreted.

Per Cent, of
Water.

Per Cent, of
Solids.

At 8-9 A.M. .

1-2944

80-6

19-3

r, 9 „ '

1
2 '0 grs. salicylate of soc

a given

„ 9-10 „ .

6-2885

90-7

9-3

,, 10-11,,

4-2914

92-3

7'7

„ 11 A.M.-12 noon

4-5218

92-1

7-9

,, 12 noon-1 P.M. .

4-6437

91-8

8-2

1 Loc. cit. 2 Loc. cit.

3 "Action of Drugs on the Secretion of Bile," Edinburgh, 1880, p. 118.

4 Ztschr.f. klin. Med., Berlin, 1884, Bd. viii. S. 67.

5 Arch.f. d. ges. PhysioL, Bonn, 1890, Bd. xlvi. S. 355.

GENERAL CONCLUSIONS. 569

Rutherford, Vignal, and Dodds have experimented with a very-
large number of drugs, which were injected, dissolved in bile, into the
duodenum.1 The action of certain of these drugs has been re-investi-
gated by Paschkis 2 and by Lewaschew,3 whose results do not in all cases
confirm those of the previous observers. It is, however, unnecessary to
consider them in detail. Naunyn4 sums up the matter by saying,
"Many substances, when taken into the stomach, and more surely
still when introduced into the duodenum (Rutherford), appear to pro-
duce under certain conditions a slight increase of the biliary secretion.
But the influence of these substances upon the secretion of bile is
uncertain, and never a potent one."

GENERAL CONCLUSIONS.

From a study of the mechanism of bile secretion, it is manifest that
in its bile-producing function the liver differs from most other glands,
since its activity is not under the direct control of the nervous system,
but is modified by the ebb and flow of the blood stream, and by the
influence of various chemical substances, such as the salts of the bile
acids.

The relationship of bile secretion to the other functions of the liver
is in many points still obscure. That the disintegration of haemoglobin
and the formation of bile pigments are closely connected, is definitely
known (p. 563). That these two functions are connected with the
production of urea, is shown by the fact that the administration of haemo-
lytic agents, such as toluylenediainin, pyrogallic acid, etc., which increase
the formation of bilirubin, cause a proportionate increase in the dis-
integration of red blood corpuscles, and in the excretion of urea.5

How far the formation of the amido-acids of the bile salts is con-
nected with the disintegration of proteids, cannot be considered as
settled, but the evidence adduced on p. 562 suggests that such a
relationship exists. If this be the case, the formation of biliary con-
stituents must be connected with .the manufacture of glycogen and
glucose from proteids. The formation of bile seems independent of the
mere accumulation of carbohydrates in the liver.

The various compounds of fatty acids in the bile are probably
derived from the fatty acid compounds stored in the liver (p. 564).
The nucleo-proteid, the mucin, and the cholesteriri are probably to be
regarded, not as true biliary constituents, but as products of the bile
passages. As to the relationship of the inorganic salts of the bile
with the other hepatic functions, nothing is known.

1 Rutherford, loc. cit. 2 Loc. cit. 3 Loc. cit.

"Cholelithiasis," translated by A. E. Garrod, New Syd. Soc., p. 172.
5 Noel Paton, Brit. Med. Journ., London, 1886, vol. ii. p. 207.

THE CHEMISTEY OF THE URINE.

BY F. GOWLAND HOPKINS.

-

CONTENTS : — Introductory — Quantitative Composition of Urine, p. 572 — Variations
in its Amount and Specific Gravity, p. 573 — Its Chemical Reaction, p. 574 —
The Nitrogenous Constituents : (a) Total Nitrogen, p. 580 ; (b) Urea, p. 581 ;
(c) Ammonia, p. 585 ; (d) Uric Acid, p. 586 ; (e) Xanthin Bases, p. 596 ; (/)
Creatinin, p. 598 ; (g) Hippuric Acid, p. 600 ; (h) Amido- Acids, p. 602 — Pro-
teids, p. 603— The Aromatic Substances, p. 605— The Carbohydrates, p. 607—
Glycuronic Acid and its Conjugated Compounds, p. 613 — Oxalic Acid, p. 614 —
Acids and Oxyacids of the Fatty Series, p. 615 — Colour of the Urine and the
Chemistry of its Pigments, p. 616: (a) The Preformed Pigments of Normal
Urine, p." 618 ; (b) Chromogenic Substances, p. 626 ; (c) The Pigmentation of
Pathological Urine, p. 628 — The Inorganic Constituents, p. 630 — General
Characteristics of the Organic Urinary Compounds, p. 635 — Comparative
Chemistry of the Urine, p. 637.

General considerations. — The chemical study of the urine gains its
chief importance from the light which it throws upon the processes of
metabolism. It is concerned mainly with a consideration of the nature
and amount of the various metabolic end-products, normal or patho-
logical, which converge into and appear together in the highly complex
excretion of the kidneys.

The great importance of this point of view has led to perhaps undue
neglect of a second aspect of the subject — the consideration of the
renal excretion as a complex whole ; as a chemical fluid with individual
characters of its own ; characters which are not to be foretold from a
knowledge of the nature and amount of each constituent considered
separately, but require for their explanation the further consideration of
the mutual effects of the constituents one upon another, as they exist
side by side in solution.

This study of the properties of the urine as a whole must be pursued
if we are to understand with exactness the nature of the processes which
go on in the kidney, and if we wish to interpret aright the ultimate
behaviour of any given type of urine while in the urinary passages, or
after it has left the body.

But while the first-mentioned line of study requires in the main the
services only of analysis — the earliest and best understood of the weapons
of chemistry — the second depends upon our more recently won, and as
yet very incomplete, knowledge of chemical statics, and of the conditions
of equilibrium in salt solutions.

All the chief proximate constituents of normal urine exhibit either
basic or acid characters. Indifferent or " neutral " substances are norm-
ally either absent, or present in minimal amount. The bases and acids
present necessarily enter into more or less stable combinations, and it

GENERAL CONSIDERATIONS. 571

follows that the urine is essentially a solution of salts ; its chemical and
physical properties being those of a complex saline mixture.

The chief bases are potassium, sodium, and ammonium ; calcium and
magnesium ; urea, creatinin, and the xanthin bases. The chief acids are
hydrochloric and sulphuric ; phosphoric and carbonic ; uric ; oxalic ; with
hippuric and certain other aromatic acids. To the acid group belong also
undoubtedly the pigments.

The particular combinations formed in the urine by these various
acids and bases depend primarily on their relative masses and avidities ;
the ultimate equilibrium of the fluid depending, secondarily, on the
mutual influences, in solution, of the salts which potentially tend to form
as a result of the two factors just mentioned. It should be understood
that our present knowledge does not carry us far towards a calculation
of this complex equilibrium in any particular case. When we have
determined by analysis the proportions of the various bases and acids
present, we may, for convenience, group them into various supposititious
combinations one with another, and speak of the urine as containing so
much sodium chloride, so much " earthy phosphates," and the like ; but
such groupings can, with our present knowledge, be for the most part
approximate only ; and, if insisted upon too closely, may be misleading.

If the chemistry of urine had to be read merely as a final chapter in
the history of metabolism, the actual condition of the acids and bases
present would be of little importance to the physiologist or to the
pathologist. The nature and amount of these constituents having been
determined, each would be considered in connection with the organ or
tissue the metabolism of which is responsible for its appearance in the
urine, and the chemistry of the latter would be of no further import.

But the case, as we have said, is otherwise. The two conditions of
chemical equilibrium represented respectively by the expressions —

(1) CaS04 + 2(NaH2P04) [three molecules]

(2) Na2S04 + Ca(H2P04)2 [two molecules]

involve each of them the same amount of the bases and acids concerned ;
but the presence of the first combination in the urine might involve a
renal activity quantitatively as well as qualitatively different from that
which would be indicated by the presence of the latter. Further, a
knowledge merely of the percentage of uric acid in a given specimen
of urine will by no means give us final information as to the power of
the fluid to retain this constituent in solution. One individual may
excrete a large percentage, and yet have no tendency to suffer from
uric acid gravel ; another may not be free from this, though he habitually
excrete a lower percentage. To explain this we must understand the
influence of other urinary constituents on the solubility of uric acid ; in
other words, we must study the properties of the urine as a whole.

Enough has been said to show7 that we are not to remain content
with analytical figures alone. The future study of the urine will con-
cern itself also with the application of facts derived from that domain of
chemistry which deals with the distribution of chemical forces in com-
plex mixtures. At present we have but little available knowledge of
this kind, and many urinary phenomena are consequently but imperfectly
understood. We may instance, however, a generalisation made from the
experimental and mathematical investigation of the mutual influence of
salts in solution, which is capable of immediate application to our subject.

572

THE CHEMISTR Y OF THE URINE.

If two salts contain an electrical ion in common (or without great inac-
curacy we may say, a base or acid in common), each decreases the solubility
of the other, whereas salts which contain no base or acid in common
may mutually increase each the other's solubility. Thus the presence of
sodium chloride in solution will diminish the solubility of sodium urate,1
and ammonium chloride that of ammonium urate ; but the presence of
either of these chlorides will increase the solubility of (say) calcium
phosphate. These laws will be found to have important application in
the explanation of certain urinary phenomena.

In addition to products which arise from metabolism in the tissues,
the urine contains substances which are derived more directly from the
ingesta. These comprise a large proportion of the normal inorganic
constituents, which are always found ir*the diet in excess of the needs
of the organism ; and they may consist also of substances accidental or
accessory to the diet, or again of drugs, or of substances experimentally
introduced into the body.

Some of these, while taking no share in metabolism proper, may
form " conjugated " or synthetic compounds with certain intermediate
products of metabolism, and so modify excretion. Thus glycin and
glycuronic acid are substances capable of easy oxidation in the body,
and are therefore not properly terminal products of metabolism ; but
they are protected from oxidation and are eliminated as synthetic
compounds with certain aromatic substances, whenever the latter are
absorbed in sufficient quantity from the bowel.

QUANTITATIVE COMPOSITION OF THE URINE.

The figures which follow are from the well-known table given by
Parkes, representing the normal twenty-four hours' excretion of the chief
urinary constituents : —

Percentage
Composition
of Solids.

Absolute Weight
of Solids in Grms.

Weight per
1000 of
Body-Weight.

Urea, CH4N20

45-75

33-18

0-5000

Creatinine, C4HrN30
Uric acid, C5H4N403

1-25
075

0-91
0-55

0-0140
0-0084

Hippuric acid, C0H9N03

0-55

0'40

0-0060

Pigment and other organic substances

13-79

10-00

0-1510

Sulphuric acid, S03 .

2-77

2-01

0-0305

Phosphoric acid, P205

4-36

3-16

0-0480

Calcium .

0-35

0-26

0-0004

Magnesium

0-28

0-21

0-0003

Potassium

3-45

2-50

0-0420

Sodium

15-29

11-09

0-1661

Chlorine .

10-35

7-50

0-1260

Ammonia ......

1-06

0-77

0-0130

100-00

72-54

1-1057

In the following analyses, derived from Bunge, all the figures were
obtained from the same individual. They represent the twenty-four
hours' excretion of a young man ; in the one case, upon a diet con-
sisting entirely of beef with a little salt and spring water; in the

1 As was shown experimentally by Sir William Roberts, before the general principle
enunciated above had been developed by Nernst.

URINE AND ITS SPECIFIC GRAVITY.

573

other case, upon a diet of bread with a little butter, again with water
as a beverage : —

Meat Diet.

Bread Diet.

Total measure of urine in twenty-four hours

1672 c.c.

1920 C.C.

Urea

67*2 grms.

20-6 grms.

Creatinine

2-163

0-961

Uric acid .

1-398

0-253

Sulphuric acid (total

4-674

1-265

Phosphoric acid

3-437

1-658

Lime

0-328

0-339

Magnesia

0-294

0-139

Potash

3-308

1-314

Soda

3-991

3-923

Chlorine

3-817

4-996

These analyses are interesting as showing the effect of two widely
differing forms of diet ; but they must not be taken as typical of the
relative effect of animal and vegetable diet in any absolute sense. As
regards such factors, for instance, as the relative proportion between
urea and uric acid, we shall find that, even when one or other of the
two types of diet (animal or vegetable) is adhered to, great differences
may be seen as the effect of variation in the specific composition of
either. Indeed, no great importance must be attached to the details of
collective quantitative analyses of the urine, except where the diet itself
has been simultaneously analysed. While abundant observations of this
kind have been published, relating to particular constituents of the
urine, no collective analyses appear to have been made upon the same
specimen of urine after a diet of known quantity and composition.

The following figures, which give the mean of many determinations
made by Yvon and Berlioz, show the differences in the excretion of
certain constituents by males and females respectively : —

MALE.

FEMALE.

Per Litre.

Per Diem.

Per Litre.

Per Diem.

Specific gravity

1-0225

1-0215

Volume .

1360 c.c.

1100 c.c.

Urea

21-5 grms.

26'5 grms.

19'0 grms.

20-5 grms.

Uric acid

0-5 ,,

0-6 „

0-55 ,,

0-57 „

Phosphoric acid

2-5 „

3-4 ,,

2-4 „

2-6 „

THE QUANTITY OF URINE AND ITS SPECIFIC GRAVITY.

A human adult excretes from 1200 to 1700 c.c. of urine in the
twenty -four hours, or about 1 c.c. per kilo, of body weight per hour.
During sleep the amount is less than at other times. The specific
gravity commonly varies from 1015 to 1025, and is, in general, inversely
as the quantity excreted.

574 THE CHEMISTRY OF THE URINE.

Both factors, however, may vary through much wider limits than
those given, without any departure from conditions of health. The
chief causes which lead to increase of quantity and diminution of density
are increased consumption of liquid and diminished activity of the sweat-
glands. With abstention from liquids, or increased activity of the skin,
the amount necessarily falls, and the density is raised.

Increase in the quantity may follow, not alone from a heightened
quantity of water in the blood, but from any influence, normal or
pathological, which increases the blood now through the kidneys.

Pathologically the quantity is increased in diabetes mellitus and
insipidus, in certain stages of chronic nephritis, and in some neurotic
conditions ; it is decreased in the early stages of acute nephritis, in the
congestive condition of cardiac disease, find when large quantities of fluid
are lost by the bowel, as in cholera. The specific gravity is increased in
diabetes, and diminished in chronic nephritis.

The specific gravity is roughly an indication of the amount of the
urinary solids. It cannot indicate the amount with exactness, as the
substances in solution are of various physical properties, and are not all
capable of increasing the density in like proportions. Thus, while a 10 per
cent, solution of common salt has (at 15°) a specific gravity of about 1073,
a 10 per cent, solution of urea indicates only 1028.1 An increase in the
urinary salines would therefore have a much greater effect in raising the
specific gravity than a like increase in the urea. A knowledge of the actual
weight of solids present seldom becomes of much importance. It may be
obtained with sufficient accuracy by multiplying the last two figures of the
sp. gr. by 2-2 ; the result indicating the total solid matter in grammes per
litre. Thus a specimen of sp. gr. 1020 contains about 44 grms. per litre of
substances in solution.

CHEMICAL BEACTION.

Acids and bases are so proportioned in human urine that the mixed
excretion of twenty-four hours generally reacts acid to litmus paper. It
may sometimes exhibit the so-called amphoteric reaction — a phenomenon
to be later discussed — but under strictly normal circumstances the
accumulated excretion of the day is never alkaline to litmus. On the
other hand, during limited periods of the daily cycle, it may sometimes,
though not commonly, become alkaline.

Litmus is reddened both by acids and by acid salts ; but there are
other coloured indicators which behave differently in the presence of
free acids and acid salts respectively. When such are applied to urine,
they show unequivocally that the former are never present, and we are
thus forced to the conclusion that urine owes its acidity to acid salts.
It will be shown immediately that we may conclude with some certainty
that the reaction is due, as a matter of fact, to the presence of acid
phosphates.

The nitrogen, carbon, phosphorus, and sulphur of food-stuffs are all
capable of oxidation to acid anhydrides, and the last three elements are
in fact oxidised to this acidic form in the body. The chief product of
the oxidation of carbon, carbon dioxide, may play a not unimportant
role in the equilibrium of urinary acids and bases, and the existence of
oxidised carbon in the molecules of certain organic compounds in the
1 A. H. Allen, "Chemistry of Urine," 1895, p. 12.

CHEMICAL REACTION. 575

urine confers upon them a definite acidic character. The acid oxides of
phosphorus and sulphur, which are the chief end-products of the meta-
bolism of these two elements, are eliminated almost entirely through
the kidneys. Eighty per cent, of the total sulphur ingested, and nearly
all the phosphorus, are eventually found in the urine as sulphuric and
phosphoric acids respectively. That these acids are eliminated as salts,
and not in the free state, depends in the main upon the fact that bases
are continually being ingested in the food in a form available for the
neutralisation of acids. The bases of the food are not all in the state
of stable neutral salts. Even animal food contains basic phosphates,
together with organic (proteid) combinations of the alkalies and
alkaline earths, and small quantities of alkaline carbonates; while
vegetable food contains, in addition, salts of the vegetable acids, which
in the body are converted into carbonates by oxidation. By the
ingestion of these unstable compounds of various bases, the organism
is saved from the necessity of eliminating free mineral acids. When
the supply of available bases is for any reason insufficient, a further
protective mechanism comes into action, metabolism being so modified
that a greater proportion of the nitrogen than usual is eliminated in
the strongly basic form of ammonia. All these factors are normally so
proportioned that, as we have seen, the urine, while containing no free
acid, is acid from acid salts.

Phosphoric acid (H3P04) as a tribasic acid forms three orders of salts.
Those in which two out of the three hydrogen atoms of the acid molecule
are intact, are known as acid or superphosphates. They are soluble salts, and
react acid to litmus. The second type, in which two hydrogen atoms are
replaced by a base (monohydrogen phosphates), and the third, in which all
the hydrogen is replaced (normal phosphates), are alkaline to litmus. While
all varieties of the phosphates of sodium, potassium, and ammonium are freely
dissolved by water, of the alkaline earth metals only the superphosphates
are at all freely soluble. The monohydrogen and normal phosphates of
calcium, magnesium, and, we may add, of barium, are scarcely taken up by
water.

If to a weak solution of, say, sodium - dihydrogen - phosphate
(NaH2P04) calcium chloride or barium chloride be added, no pre-
cipitation occurs ; the corresponding salts of these latter metals being
comparatively soluble. On the other hand, from a solution of di-
sodium-monohydrogen-phosphate (Na2HP04) nearly all of the phos-
phoric acid is precipitated on the addition of a calcium or barium
salt, in the form of the corresponding monohydrogen phosphate of the
alkaline earth. In any mixed solution of di- and mono-hydrogen
phosphates, the amount of phosphoric acid which is left unprecipitated
by, say, barium chloride, is a measure of the proportion of the di-
hydrogen phosphate originally present. Now, if we apply this test to
urine of average acidity, we find that about 60 per cent, of the total
phosphoric acid remains in solution after the addition of the barium
chloride. We are justified in concluding, therefore, that acid di-
hydrogen phosphates are present in about this proportion ; a fact in itself
sufficient to account for the acid reaction of the nuid towards litmus. The
composition of the barium precipitate from an acid urine proves that the
remaining phosphoric acid is mainly in the form of monohydrogen salts.

If, now, we suppose the excretion to receive an increased quantity

576 THE CHEMISTRY OF THE URINE.

of the acid products of metabolism — what will be the effect on the dis-
tribution of bases ? It has been shown experimentally, that if to a
mixed solution of mono- and di-hydrogen phosphates, a mineral acid
(such as sulphuric acid) be added, in quantity not greater than is
equivalent to the bases present in the monohydrogen form, no free acid
is afterwards found in solution; but there will be an increase in the
dihydrogen phosphates at the expense of the monohydrogen phosphates
in proportion to the amount of acid added. Not only is this true of
sulphuric acid ; it has been shown that all the weaker acids or acid salts
which are liable to reach the urine from the circulation (e.g. hippuric
acid or acid oxalates) are able, when added to a solution of the mixed
phosphates, to remove base from the monohydrogen form, and so to
produce almost an equivalent increase»in the acid phosphates. So long,
therefore, as both these types of phosphate exist side by side (and they
are always found together in acid urine), we can assume that the
acidity of the fluid is due to the acid phosphate, and practically to that
alone. The simultaneous existence of the monohydrogen form will
be seen to be a guarantee of this, as it will have to disappear by inter-
change of bases, before any other urinary constituent can begin to exert
its own proper acidity to any appreciable extent.

When the urine reacts alkaline to litmus, the alkalinity may under
different circumstances be due (1) to excess of basic phosphates, (2) to
carbonates of the fixed alkalies, or (3) to ammonium carbonate.

Determination of the acidity.1 — It is, as we have seen, not difficult
to assign the acidity of the urine to its proper cause ; but when we
endeavour to discover a method by which to estimate the degree of
acidity, and especially a mode in which to express its value numeric-
ally, we meet with considerable difficulties.

In the case of a fluid the acidity of which is due to a strong acid,
capable of forming stable salts with the alkalies, the ordinary methods
of acidirnetry yield a determinate result, and the estimation of acidity
is one of the simplest operations in chemistry. We have but to note
the amount of a standardised solution of alkali which is sufficient
exactly to neutralise the acid present, and the point of neutralisation is
given sharply and exactly by the colour change which occurs in the
presence of one of many available indicators. In urine, owing to the
unstable phosphate equilibrium, and the presence of other salts which
influence the result, the process is much less determinate. To litmus,
as already stated, a dihydrogen phosphate, e.g. NaH2P04, is acid, while
Na2HP04 and Na3P04 are alkaline ; but no mixture of these salts can
be found which is, strictly speaking, neutral to litmus paper.

If we start with a urine acid to litmus and gradually add alkali,
we at last reach a point when the fluid shows a paradoxical behaviour.
It makes red litmus paper tend to blue, and blue paper tend to red,
inducing in fact a somewhat violet colour in both. It reacts at once
acid and alkaline. This occurs when the monohydrogen phosphates,
which during the addition of alkali are gradually increased at the
expense of the dihydrogen salts, have come to bear a certain proportion
to the latter.

Many urines exhibit this so-called amphoteric reaction without the

1 I have discussed this subject at what may seem disproportionate length, but the pro-
blem involved illustrates well the complexity of chemical conditions in the urine ; and
much has been written upon it of late on what I venture to believe are erroneous lines.

DETERMINA TION OF THE A CIDITY. 5 7 7

addition of extraneous alkali. The reaction usually betokens that the
monohydrogen salts exist in larger proportion than the dihydrogen, but it
prevails through a considerable range of variations in this proportion ;
its exact limits depending in part upon the delicacy of the litmus paper
used. Throughout the range of the amphoteric reaction a solution of
litmus, actually mixed with the fluid, retains a violet or neutral colour
practically unchanged.

Heintz attempted to explain this amphoteric reaction as follows. The
red colouring matter of litmus acts as a dibasic acid, forming with bases,
either unsaturated salts which are violet, or saturated salts which are blue.
From the saturated salt the dihydrogen phosphates may extract half the base,
leaving the unsaturated violet salt. The monohydrogen phosphates, on the
other hand, may yield to the red acid substance sufficient base to form also
the violet compound. In an amphoteric mixture the affinities are so balanced
that this violet compound can alone exist. When, however, the acid phos-
phate is present in sufficient excess, it removes all the base and leaves the red
free acid ; with a large excess of the more basic phosphate, on the other hand,
the litmus acid obtains its full complement of base and forms its blue salt.

With other indicators we can obtain a colour change at a more
definite point during the process of alkalisation of an acid urine, and to
the use of these we shall shortly return. But it should be made clear
that only in the interaction between a " strong " acid and a " strong "
base is the colour change, with an indicator, synchronous (or approxi-
mately synchronous) with the final replacement of all the acidic hydrogen
atoms by the base. From this special case we have come to attach a
definite value to the expression "degree of acidity," which is not
found when we are dealing with such a substance as phosphoric acid.
The " acidity " is here a quantity varying with the indicator used. The
coloured indicator is itself an unstable compound which, in the play of
acid and basic affinities, suffers a definite change when a certain point
of equilibrium is reached. This point will depend upon the relative
stability of the indicator and of the phosphates with which it is in con-
tact, and may or may not occur simultaneously with the removal of
all replaceable hydrogen from the latter.

The " degree of acidity " of a certain quantity of acid phosphate, in
solution by itself, will be greater than that of an equal quantity mixed
with a proportion of the more basic phosphates ; and this is true, no
matter what the indicator used. During the process of neutralisation
by the standard alkali, the proportion of the more basic phosphates is
gradually increased until the tendency of these to affect the indicator
in one direction eventually balances the action of the acid phosphate
in the opposite direction. This "neutral" point will evidently be
reached the sooner, if some basic salt was originally present before
titration was commenced.

Such considerations as these have led to a proposal to estimate the
acidity of urine, not by simple titration, but by actually determining the
proportion between the acid phosphates and the more basic phosphates
present. For this purpose, Lieblein,1 after a careful study of the matter,
has recommended the process of Freund, which is an application of the
barium precipitation method referred to above. The total phosphoric acid

1 Ztschr. /. physiol. Chem., Strassburg, 1895, Bd. xx. S. 52-88. In this paper a criti-
cism of other methods will be found.
VOL. I.— 37

578 THE CHEMISTRY OF THE URINE.

is first determined in the original urine ; that existing as monohydrogen
phosphates is then removed by precipitation with barium chloride, and
that present as acid phosphates is finally determined in the filtrate.1

But how exactly are we to express the urinary acidity in terms of
the results so obtained ?

Some recent writers have denoted the acidity by the figure express-
ing simply the ratio of acid phosphates to total phosphates.2 If the
P205 in the former be (say) 54 per cent, of the total P205, the relative
acidity of the urine is to be called 54 ; if in another case it is only 27
per cent., the acidity is to be considered as half that in the first case.

Such a procedure seems to be wholly misleading. If of two
specimens of urine one contains twice as much acid phosphate as the
other, but at the same time twice the amount of the monohydrogen salt,
the acidity, expressed in the above manner, will be the same in each case.

Such urines will certainly not behave as if of equal acidity, nor will
they indicate the same acid production within the body.

We may here illustrate what we mean by the expression " behave as if of
equal acidity." One of the most important results of a high grade of acidity
is a tendency for the urine to deposit its uric acid in the free condition. In a
later section, dealing with the urates (q.v.\ the mechanism of this separation
will be discussed. We shall find that one essential step in the process con-
sists in the conversion of certain less acid urates (biurates) into more acid
urates (quadriurates).

Now it is the acid phosphates which bring this change about, by removing
base from the first form of urate, themselves becoming, of course, converted
pari passu into more basic phosphates. But the latter, as they increase in
quantity, tend to yield back the base to the quadriurates, so that a point is
possible when the whole system will be in equilibrium. The less acid the
urine, the sooner is this point reached. A little consideration will show that
the " degree of acidity," from this point of view (and it is an important aspect),
will be a function both of the absolute amount of the acid phosphates, and of
the ratio they bear to the total phosphates. But we are hardly in a position
to express the acidity quantitatively in terms of these two factors, because we
do not know precisely at what stage the urates and phosphates are in equi-
librium. It is probable, in fact, that the point of equilibrium is different for
each of the diverse changes which may occur in the urine, as a result of its
acidity, just as it is different for the colour change in diverse indicators. No
more striking instance of the relativity of the phenomena involved could be
given than a fact we shall discuss under the head of the pigments. Urinary
hsematoporphyrin is always found in the so-called alkaline form ; and if we
add to any normal urine either neutral or acid haematoporphyrin, we find
that it immediately assumes the alkaline form. Equilibrium in this case is
only attained when base has been transferred to the pigment from the acid
phosphate. If, then, heematoporphyrin had happened to be our only available
" indicator," we should have said that urine was normally an alkaline fluid !

The whole source of the difficulty we have been discussing is found
in the fact that the terms " degree of acidity " or " degree of alkalinity "
are unscientific, though convenient, modes of expression. With increase
of knowledge, they will be replaced by expressions denoting the actual

1 For the principles of this determination, see p. 633. An error of some 3 per cent, lias
to be allowed for, due to a conversion of monohydrogen into dihydrogen phosphate in the
process of precipitation.

2 Of. Hausmann, Ztschr. f klin. Med., Berlin, 1896, Bd. xxx. S. 350.

VARIA TIONS IN A CIDITY. 5 79

chemical energy of the system of mixed salts. The degree of acidity of
the urine (or any analogous fluid) is in fact not an absolute quantity,
but is wholly relative to the means which we employ to measure it.
But by always employing the same means, be it noted, we may obtain
relative results which are strictly comparable, and as an outcome of this
somewhat difficult discussion, it may be suggested that we shall do well
in the present state of our knowledge to continue to employ a simple
titration method, by which we obtain comparable, if only relative,
measurements. But we must employ an indicator which gives a more
definite point of colour change than does litmus, and we must retain
the same indicator for any one series of experiments ; moreover, the
nature of the indicator used must always be stated in stating the
results. Phenolphthalein, and perhaps cochineal, will serve our pur-
pose. If acid urine be gradually neutralised in the presence of the
former of these, which is colourless when acid, a pink tinge is developed
at a certain stage in the process, and we are justified in speaking of a
specimen of urine which requires more alkali to produce this change
as " more acid " than one which requires less.

What lias been said in this section will have left a wrong impression if it
be thought that such measurements are of no value. My endeavour has been
to show that we have at present no means of expressing the acidity of the
urine as an absolute quantity independent of the particular means adopted for
measuring it. But, having chosen a method of estimation, and being careful
always to use the same method, we may accurately follow the variations of
urinary acidity, and obtain results with important bearings.

Variations in acidity. — The degree of acidity as determined by
titration is, as we have seen, in the main, a resultant of two opposing
factors ; on the one hand, acid production in metabolism ; on the other,
the ingestion of unsaturated or unstable basic compounds, supplemented
by the production of ammonia within the body. To these, however, a
third factor must be added — the elimination of acids or bases respect-
ively by other than renal channels.

The separation of the acid gastric juice and the consequent libera-
tion of bases in the blood is associated with increased excretion of the
latter in the urine. On the other hand, the flow of alkaline secretions
— bile, pancreatic juice, etc. — diminishes the urinary bases.

From these considerations, the reasons for the variations in acidity
commonly met with become clear. The acidity increases with increased
proteid metabolism, with exercise, and with the consumption of food,
when this contains a small proportion of bases — in particular, with flesh
food. It diminishes when the food taken contains abundant bases. The
compounds of organic acids with the alkaline metals, which are so
plentiful in vegetable food, become oxidised in the body to carbonates,
and the excretion of bases thence derived tends to alkalise the urine.
From this follows the familiar fact that the urine of herbivorous
animals is alkaline, and that human urine may become alkaline (though
seldom continuously so) when a vegetarian diet is maintained.

The effect of the secretion of gastric juice is to produce what is called
the alkaline tide. During the period of full gastric digestion the urine
may become less acid, and may even (though this is rare) become alka-
line to litmus. The occurrence of this phenomenon was first noted by
Bence Jones.

580 THE CHEMISTRY OF THE URINE.

It must not be supposed, however, that the post-prandial alkaline
tide is a universal phenomenon. It will be easily seen that the effect
of digestion upon the bases and acids of the blood must be somewhat
complex. The flow of alkaline saliva precedes, and that of bile and pan-
creatic juice rapidly follows, the gastric secretion ; and these, by removing
bases, tend to neutralise the effect of the removal of acid via the
stomach. From this cause, and from the increased proteid metabolism
induced by the food, it not infrequently happens that the urinary acidity
is from the first raised, instead of lowered, after a meal.

According to Quincke, a periodic variation of acidity may occur dur-
ing the day, independently of food ingestion,1 and in my experience this
is a more constant phenomenon.

Gruber found that the urine may Become alkaline after a large con-
sumption of sodium chloride, and Eiidel 2 has recently stated that the
pure diuresis produced by such substances is in itself capable of inducing
this result. This may be true, under the somewhat extreme conditions
of experiment, but when the urinary constants are followed under
natural conditions from hour to hour, it is not found that the quantity
of urine passed during a given period has any regular influence on the
total acidity of the same period.3

Pathologically, a tendency to alkalinity is said to be found in most con-
ditions of debility, and especially in some types of anaemia ; probably from
diminished secretion of gastric juice, and from diminished general metabolism.
A process quite distinct from this occurs when, under the influence of
organisms (especially the Micrococcus urece), the urea and uric acid of the
urine are hydrolised into ammonium carbonate. In cystitis this may occur
in the bladder, and the urine is voided alkaline with ammonia.

The acidity is especially high in scorbutic urine, and is increased to a greater
or less degree in some forms of dyspepsia, in diabetes, leukaemia, and in per-
nicious anaemia.

THE NITROGENOUS COMPOUNDS.

(a) Total nitrogen. — The urinary nitrogen amounts, on an average,
to 15 grms. in the twenty-four hours. This comprises by far the greater
part of the nitrogenous loss to the body ; less than 1 grm. being eliminated
through the intestinal secretions and all other channels combined.

Pathologically, the amount may be greatly increased ; 20 to 25 grms.
per diem is frequently observed in fever, and in severe forms of diabetes
50 grms. and upwards may be daily eliminated. On the other hand, a
marked diminution of the amount is seen in the condition of contracted
or granular kidney.

Under normal conditions, the urinary nitrogen is distributed in
various compounds in the following proportions : About 86 per cent, of
the whole is found in the form of urea ; about 3 per cent, as ammonia,
3 per cent, as creatinin, 2 per cent, as uric acid and the allied xanthin
bases ; while the remaining 6 per cent, is present, in varying proportions,
in hippuric acid, in indol and skatol, in the urinary nucleo -albumin,
in the pigments, and in minute quantities of other constitutents.

The total nitrogen is estimated by one of the many modifications of
Kjeldahl's process, which is founded on the fact that organic substances,

1 Ztschr.f. Min. Med., Berlin, 1884, Bd. vii. Suppl. 22.

2 Arch.f. exper. Path. u. Pharmakol., Leipzig, 1892, Bd. xxx. S. 41.

3 Cf. Hausmann, Ztschr. f. klin. Med., Berlin, 1896, Bd. xxx. S. 362.

UREA, 581

when heated with concentrated sulphuric acid, become oxidised, and all the
nitrogen (except such as may be originally present in combination with
oxygen) is converted into ammonia. The resulting ammonia is liberated
by the addition of caustic alkali, and distilled into a measured quantity of
standard acid ; its amount being finally determined by titration. Kjeldahl's
method gives admirable results with urine, and may be applied to 5 c.c. of
the fluid.

(b) Urea— CO(NH2)2. — The presence of urea in the urine was first
demonstrated by Eouelle in 1773. It is the chief end-product of nitro-
genous metabolism in all mammals, in amphibia, and in fishes. In 1828
it was obtained artifically by Wohler, by heating the isomeric substance
ammonium cyanate (NH4.CNO).

The chemical constitution of urea is that of an amide of carbonic
acid (carbamide).

Properties. — Urea crystallises in colourless needles or rhombic prisms,
containing no water of crystallisation, and melting at about 130° C. It
is freely soluble in alcohol, and still more so in water ; in pure ether or
chloroform it is insoluble. Urea, like other amides of acids, is neutral
to litmus ; but, owing to the presence of two ammonia residues in its
molecule, it exhibits weak basic properties, and forms loose molecular
compounds, analogous to salts, two of which are of practical im-
portance.

Urea nitrate = CO(NH2)2.N02.OH. — This compound crystallises out
when excess of pure nitric acid is added to a not too weak solution of
urea ; excess of the acid assists its separation, as it is less soluble in
nitric acid than in water ; crystallisation is accelerated by shaking and
cooling the mixture. The fundamental form of the crystals is a rhombic
table, of which the more acute angles measure 82° ; but, by truncation
of the angles, six-sided tablets are commonly formed, and these are apt
to adhere together and overlap like tiles on a roof (Fig. 49). When
rapidly heated, the crystals deflagrate. At 140° they decompose into
nitrous oxide, carbon dioxide, and ammonium nitrate.

Urea oxalate = CO(NH2)2.(COOH)2 — is formed in an analogous
manner by mixing solutions of urea and oxalic acid ; like the nitrate,
this salt is less soluble in excess of the acid. Its crystals belong funda-
mentally to the same type as those of the preceding compound, but are
apt to appear as thick short rhombic prisms (Fig. 49).

A crystalline combination of urea with phosphoric acid is also known, and
others with various organic and inorganic acids.

Crystalline compounds are also formed with certain neutral salts; that
with sodium chloride is said occasionally to form when urine is concentrated
on the water bath. The compound with palladium chloride is very insoluble.
A molecular combination with basic mercury nitrate is quite insoluble in water,
and is of historic interest, as its formation is the basis of the classical method
of urea estimation suggested by Liebig in 1853 (vide infra).

When fused and gently heated after fusion, urea yields biuret and
cyanuric acid. Two reactions occur as follows : —

2NH2.CO.NH2 - NH2.CO.NH.CO.NH2 + H3N ; and
(biuret)

3NH2.CO.NH2 - C3N3(OH)3 + 3(H3N)

(cyanuric acid)

582

THE CHEMISTR Y OF THE URINE.

Its relations to ammonium carbonate and carbamate are very im-
portant from a physiological standpoint.

CO

+H0

C0

+ H0 - CO;

(urea)

(ammonium carbamate)

(ammonium carbonate)

The two molecules of water necessary to form carbonate of ammonia
are very readily taken up. Even at a temperature of 60° C., an aqueous
solution of urea slowly develops ammonia (Leube1); while a boiling
solution decomposes with considerable rapidity. Heated with water

FIG. 49. — Upper half, urea nitrate crystals. Lower half, urea oxalate
crystals.

under pressure, at 180°, the conversion into ammonium carbonate is
quickly complete. A solution of pure urea may be evaporated at tem-
peratures from 60° to 75°, without serious loss, but in the urine it is less
stable. Quite appreciable proportions of its nitrogen are lost as ammonia
when urine is evaporated, even at low temperatures. In the presence
of free acids and bases, the hydrolysis occurs with still greater readiness,
the ammonium carbonate formed being further decomposed by the
reagent. Thus, on boiling urea solutions with acids, carbonic acid is
given off; on boiling them with alkalies, free ammonia is evolved.

The hydrolysis is also induced by micro-organisms, as in the
ammoniacal fermentation of urine. The Micrococcus urece is the best
known of these ; but other organisms are found in decomposing urine
1 Virchow's Arckiv, 1885, Bd. c. S. 552.

UREA. 583

which can produce the same result. On the other hand, urine may
develop many organisms which have no such power.1 So long as the
bacteria which induce the change are alive, the enzyme is closely
associated with the living cell, and a filtered urine is ferment free
(Sheridan Lea). But when the cells are dead, a ferment may be
extracted from them which hydrolyses pure urea solutions.

While urea is thus easily converted into ammonium carbonate, the
intermediate substance ammonium carbamate (formed by the action of
dry C02 upon NH3), if heated to 135°, or treated with alternating electric
currents, splits up into urea and water. The hepatic cells have the
power of dehydrolising ammonium carbonate itself to form urea. Nitrous
acid and the hypobromites oxidise urea according to the following
equations : —

(1) CO(NH9)2+2NOOH=C02+2N2+3H90
(2)

Separation of urea. — To prepare pure urea from urine, advantage may
be taken of the insolubility of the nitrate. The urine is concentrated to a
small bulk, and pure nitric acid is added in excess ; the mixture being kept
thoroughly cool during the addition of acid. The crystals are strained off by
pouring through muslin, and freed from excess of acid by pressing between
thick filtering paper. They are mixed with excess of barium carbonate,
sufficient alcohol is added to form a paste, and the mixture dried on the water
bath. On extracting the dried residue with absolute alcohol, a fairly pure
solution of urea is obtained, from which crystals separate on evaporation.

I find that fine crystals may be prepared by the following simpler method.
Half a litre of urine is evaporated to a thick syrupy consistence, and the
residue is exhausted with hot absolute alcohol. The spirit is filtered and
taken to dryness ; and the residue extracted on the water bath with successive
quantities of pure acetone, which should be filtered while hot. The mixed
acetone extracts are evaporated nearly, but not quite, to dryness. On cooling,
fine white crystals of urea separate, any pigment present remaining in solution
in the small quantity of the solvent which is allowed to remain. The crystals
may be washed with cold acetone.

Tests. — For the detection of urea, the formation of the characteristic
crystals of the nitrate or oxalate (and especially of the former) is of
practical value. On the small scale the process of crystallisation may
be watched under the microscope ; a drop of the suspected fluid, after
concentration if necessary, and another of nitric acid, being allowed to
run together on a glass slide.

The formation of biuret is an excellent test for urea, if the crystals
are first obtained in moderate quantity and fairly pure. After heating
them, as described above, the residue is dissolved in water, excess of
caustic alkali is added, and one or two drops of a dilute copper sulphate
solution. A pink colour is produced like that given by peptones under
like circumstances (" biuret reaction ").

Estimation of urea. — No method is known by which urea can be separated,
as such, from the urine in a quantitative manner. The ease with which it is
hydrolised isr a fundamental difficulty in the way of such quantitative isolation.
We can, however, find precipitants for the other nitrogenous constituents, and
a determination of the remaining nitrogen after the removal of these gives the
best available measure of the urea.

1 For information on this subject, vide Leube and Graser, Virchoufs Archir, loc. cit.; and
Warrington, Journ. Chem. Soc.. London, 1888, vol. i. p. 727.

584 THE CHEMISTRY OF THE URINE.

The most satisfactory of the methods based upon this principle is that of
Morner and Sjb'quist.1 To carry out this process, 5 c.c. of the urine is treated
with an equal volume of a saturated solution of barium chloride containing
5 per cent, of caustic baryta ; 100 c.c. of an alcohol-ether mixture (2-1) is
added, and the whole allowed to stand for twenty-four hours in a closed flask.
After filtering from the precipitate the solution is evaporated at low tem-
peratures (below 60°), and a determination of nitrogen made, by Kjeldahl's
method, in the residue. By the precipitation thus described all nitrogenous
substances are removed except urea and ammonia, while the last is got rid of
during the evaporation of the filtrate. The percentage of nitrogen found
multiplied by 2 '143 will give the percentage of urea,

When less accuracy is required, the well-known process of Knop2 and
Hiifner is now universally employed. This depends on the decomposition of
urea by the action of hypobromites ; th« nitrogen which is evolved being
measured in a graduated tube, and the urea calculated from the amount thus
found. The equation for this reaction is given above (p. 583). The solution
of sodium hypobromite employed contains excess of caustic alkali, so that
the carbon dioxide which is formed simultaneously with the free nitrogen,
is retained in solution as carbonate of sodium. Only some 92 or 93 per
cent, of the total nitrogen present as urea is obtained in this process, the
remainder being converted into cyanates. On the other hand, the uric acid,
creatinin, and other nitrogenous substances present yield a proportion of their
nitrogen, so that part of this error is counterbalanced. Many varying in-
fluences affect the result, however ; diabetic urine, for instance, is said to
yield a greater proportion of its total nitrogen, owing to the effect of the
sugar present. It should, in fact, be clearly understood that the hypobromite
process, while of great convenience and of sufficient accuracy for clinical and
many other purposes, does not give a scientific measure of the urea. The
calculation of its results is best made by taking each 37'1 c.c. of nitrogen
measured at ordinary temperatures as equivalent to one decigramme of urea.3

The titration method of Liebig referred to on p. 581 is now of little more
than historical importance, though it was used in all the older work upon
metabolism. It depended in principle on the fact that urea, under carefully
defined conditions, forms a definite insoluble compound with basic mercuric
nitrate. A standard solution of nitrate of mercury was added to the urine
until the whole of the urea was precipitated in this form, the end-point being
marked when a drop of the urine gave a yellow colour with sodium carbonate
(indicating excess of mercury). The modifications necessary for accuracy have
been carefully worked out by Pfliiger and others ; in its perfected form, however,
the process becomes one for the estimation of the total nitrogen of the urine
rather than for the urea only, and for this purpose it is entirely superseded by
Kjeldahl's method (supra, p. 580).

The variations in the quantity of urea present in the urine are
dealt with in the article on metabolism, where their cause is dis-
cussed. The average quantity excreted by a healthy adult man under
normal circumstances is about 30 grms. per diem ; that is to say, the
urine will contain about 2 per cent. Its absolute amount is necessarily
increased by all causes which stimulate nitrogenous metabolism, but the
proportion which the urea bears to the other nitrogenous constituents is
an independent variable (vide infra).

1 Skandin. Arch. f. Physiol., Leipzig, 1891, Bd. ii. S. 438; Jahresb. u. d. Fortschr.
d. Thier-Chem., Wiesbaden, Bd. xxi. S. 168; cf. also Bodtker, Ztschr. f. pliysiol. Chem.,
Strassburg, 1893, Bd. xvii. S. 146.

2 The original description by Knop will be found in Chem. Cenlr.-BL, Leipzig, 1860,
S. 244. Details of various modern modifications are found in most practical handbooks.

3 Cf. A. H. Allen, "Chemistry of Urine," p. 148.

AMMONIA. 585

According to Tschlenoff,1 if the urea excretion after a meal rich in
proteids be estimated from hour to hour, it will be found to exhibit two
maxima: The first occurs at the third or fourth hours, and the second at
the sixth or seventh. These he considers to indicate the absorption of
peptones from the stomach and intestine respectively. If peptones be
given instead of ordinary proteids, the maximum is reached by the second
hour. Mares,2 on the other hand, found that after an isolated meal the
maximum of urea excretion was not reached till the ninth hour.
Kobler 3 has found that simple diuresis under normal circumstances is
not accompanied by increased excretion of urea.

(c) Ammonia. — The urine of man and of carnivorous animals
invariably contains small quantities of ammonium salts. They may
be absent, however, from that of herbivora. The quantity in human
urine is about 0'7 grm. NH3 per diem ; the variations in health extend-
ing from about 0'3 to 1*2 grms.4

The ingestion of ammonium carbonate, or of organic ammonium
compounds susceptible of oxidation in the body, does not increase the
excretion of ammonia, for the nitrogen of such compounds is excreted
wholly as urea. If, however, stable salts of ammonium, such as the
chloride, are given, they appear (in the case of carnivora, at any rate) as
such in the urine.

Apart from such direct ingestion of stable ammonium salts, the
excretion of ammonia depends almost entirely upon that question of
adjustment between acid production in metabolism and the supply of
bases in the food which was discussed in the section devoted to the
acidity of the urine (q.v.). Ammonia formation is the physiological
remedy for deficiency of bases.

When acid production is excessive (a condition especially seen in
certain forms of diabetes), or when mineral acids are given by the
mouth, the urinary ammonia increases at the expense of the urea.
When the bases are in excess, whether from the nature of the food or
from the administration of alkalies, the ammonia disappears, and a corre-
sponding amount of urea is excreted in its place. From this it follows
that little or no ammonia is found in the urine of herbivora ; and that,
in man, flesh food raises the quantity, and vegetable food diminishes it.5

From the abundance of bases in their food, it is very difficult, by any
means, to increase the urinary ammonia of herbivora. If, for example,
abundant ammonium chloride be given to a rabbit, together with a normal
supply of vegetable food, its urinary ammonia is but little increased.6 By
double decomposition with sodium carbonate in the tissues, ammonium car-
bonate and sodium chloride are formed, and the former is excreted as urea.

It would seem that the organisation of the herbivora does not permit of
a supply of ammonia to neutralise acids when given in excess. Thus, most
herbivorous animals are said to be much more susceptible to poisoning by
acids than are the carnivora.

1 Abstract in Centralbl. f. Physiol., Leipzig u. Wien, 1896; cf. also Veragutt, Journ.
Physiol., Cambridge and London, 1897, vol. xxi. p. 112.

2Jahresb. u. d. Leistung. . . . d. ges. Med., Berlin, 1887, Bd. i. S. 145.

3 Wien. Tclin. Wchnschr., 1891, Nos. 19, 20.

4 Neubauer, Journ. f. prakt. Chem., Leipzig, 1852, Bd. Ixiv. S. 177. These figures are
confirmed by numerous later observers.

5 Salkowski and Munk, Virchow's Archiv, 1877, Bd. Ixxi. S. 500 ; also Gumlich,
Ztschr.f. physiol. Chem., Strassburg, 1893, Bd. xvi. S. 19.

6 E. Salkowski, Ztschr. f. physiol. Chem., Strassburg, 1877, Bd. i. S. 26.

586 THE CHEMISTR Y OF THE URINE.

To demonstrate the presence of the small quantities of ammonia in
human urine is not easy, owing to the ready production of the base
by hydrolysis of urea, which must, obviously, lead to error. We must
employ a method analogous to that used for its estimation.

Estimation of ammonia (Schlosing's method). — Twenty-five c.c. of urine are
placed in a basin with vertical sides, and about 20 c.c. of milk of lime are
added. A glass triangle is placed over the basin, and, upon it, another small
vessel containing 20 c.c. of one-fifth normal sulphuric acid. These stand
upon a glass slab, and are covered with a bell-shaped glass cover, fitting air-
tight on the slab. The ammonia is liberated by the lime, without any
decomposition of other nitrogenous constituents, and, in the course of three
days, the whole is absorbed by the sulphuric acid, the degree of neutralisation
being afterwards estimated by titratioft. If dilute hydrochloric acid be
used instead of sulphuric, it may, after the experiment, be evaporated to
dryness on the water bath, and the residue taken up with a small quantity of
water. Platinic chloride added to this solution will demonstrate the presence
of ammonia, by giving a yellow crystalline precipitate of ammonio-platinic
chloride.

Pathologically, the urinary ammonia may be increased, not only after the
manner we have discussed, by abnormal acid production (as in diabetes and
fevers), but also by conditions which reduce the proper activity of the
hepatic cells, whereby the dehydrolysis of ammonium carbonate into urea is
less complete than normally.

(d) Uric acid. — Uric acid was first separated from human urine by
Scheele, in 1776. It is present in the urine of most mammals, though
from that of the dog and cat it has been shown to be frequently absent.
In man the daily output in the urine varies considerably (from 0'2 grm.
to 14 grm.), the average amount being 0'8 grin.

Chemical constitution. — Rightly to appreciate the physiology no less
than the chemistry of uric acid, its close relationship to urea should be
clearly understood. It yields the latter easily by a combined process of
oxidation and hydrolysis. It belongs, in fact, to the class of substances
known as diureides, in which the residue of two urea molecules are
united to a carbon - containing nucleus. In the case of uric acid this
nucleus contains a chain of three carbon atoms.

The constitutional formula first suggested by Medicus —

— C—
I II /CO

CO C— NHX

[—CO

has now received ample confirmation from the synthetic production of
the acid by Horbaczewski,1 and by Behrend and Eoosen.2

The ureides are, in general, produced by the condensation of hydroxy-
acids with urea. The hypothetical acid, which would yield uric acid
by such simple condensation, would be a trihydroxyacrylic acid; but
this has never been prepared.

Lactic acid also contains a three-carbon chain in its molecule, and,
because of the important physiological relationships of this acid, it is of
special interest to find that uric acid can be synthesised by linking urea

lMonatsh.f. Chem., Wien, 1887, Bd. viii. S. 201, 584.
2 Ber. d. deutsch. chem. Gesellsch., 1888, Bd. xxi. S. 999.

URIC ACID.

587

residues on to a nucleus derived from lactic acid. This Horbaczewski
succeeded in doing by heating urea with trichorlactamide : —

CC1.3CH.OH.CO.NH24-2(NH2)2CO=C5H4N403 + NH4C1 + 2HC1+H20

The simple changes involved in this reaction will be more clearly seen on
examination of the following graphic scheme : —

HNH

CO

HNH

(urea)

Cl

C1.C.C1

I

CH(OH)
CONH2

(trichlorlactamide)

HNH,
HNH

(urea)

)CO

The groups printed in thick type unite to form uric acid ; the atoms repre-
sented in thinner type split off to form respectively a molecule of ammonium
chloride, two molecules of hydrochloric acid, and one of water.

Uric acid is formed also when glycine is heated with urea (Hor-
baczewski), but the molecular changes involved are not so simple
as those shown above, and the yield is not so good. In Behrend and
Eoosen's synthesis the nucleus is primarily derived from acet-acetic
ether, and the urea residues are linked on separately at two different
stages in the synthetic process.

Properties. — Pure uric acid forms a white powder, which is made up
of small rhombic crystals, of more or less prismatic or tabular type. Its
crystalline forms become very diverse in the presence of impurities,
and when it separates from the urine, the crystals, which are then always
coloured, take shapes which depend to a large extent upon the nature of
the pigment associated with them1 (Figs. 50 and 51).

In cold water it is very in-
soluble, only dissolving to the ex-
tent of about 1 part in 15,000.
A litre of boiling water takes
up about half a gramme. Ether
and alcohol do not dissolve it. It
dissolves in oil of vitriol without
decomposition, and from the solu-
tion a crystalline sulphate separates
on freezing the mixture. By this
process pure uric acid may be
obtained from contaminated speci-
mens, the sulphate being resolved
into its constituents when treated
with water.

It acts as a somewhat weak
dibasic acid, but forms three orders
of salts.

1. The neutral urates, M'2U, have an intense caustic taste and are
very unstable. They are decomposed by carbonates and even by the
carbonic acid of the air. As they are only produced in the presence of
caustic alkalies, and cannot exist in the presence of carbonates, it is un-

1 A. E. Garrod.

FIG. 50. — Uric acid.

588 THE CHEMISTR Y OF THE URINE.

likely that they can, under any circumstances, occur as physiological
products.1

2. The acid urates or biurates, M'HIJ, are the most stable of the com-
pounds of uric acid. They are prepared by dissolving the acid at boiling
heat in weak solutions of the alkaline carbonates, from which they
separate, after cooling, in stellar crystals. These and the foregoing salts
were first studied by Bensch and Allan.2 The acid urates are less
soluble than the neutral salts.

3. The quadriurates, H2U,M'HU. — These hyperacid salts, for the ex-
istence and importance of which we have now satisfactory evidence, were
first described by Scherer,3 and (independently) by Bence Jones,4 but
they have since been more carefully studied by Sir Wm. Eoberts.5
They are best prepared by boiling uric acid with dilute solutions of
acetate of potassium, and from solutions so obtained a quadriurate
separates, as an amorphous precipitate, or in crystalline spheres.6 They
are very unstable, and when treated with water they split up into
biurates and free uric acid. Owing to this instability it is impossible to
determine directly their solubility in water ; but they are probably less
soluble than the preceding order of salts, as a strong solution of a
biurate, when treated with acid-sodium phosphate, gives an abundant
precipitate of a quadriurate. From analogy we might expect the three
orders of salts, as described, to be in a descending series as regards
solubility.

Condition of uric acid in the urine : its spontaneous separation. —
Coloured indicators which are sensitive to free uric acid give no
indication of its presence, as such, in freshly-passed urine. Again, the
quantity of uric acid present is generally greatly in excess of what
would dissolve in a volume of water equal to that of the urine. The
presence of neutral salts, and also, according to Eiidel,7 of urea, enhances
this solubility, but not to a degree necessary for the retention of all the
urinary uric acid in solution. We are led to expect, therefore, that it is
present not as free acid but as a more soluble compound. Neverthe-
less, most urines will, on cooling and prolonged standing, deposit a
certain (and sometimes a large) proportion of their uric acid in a free
condition.

We have to explain, therefore, the nature of the original solution and
the cause of the subsequent separation. The view generally held till
recently, and still current with some authorities, is that the acid exists as
biurates ; and that these are slowly decomposed, with liberation of the
free acid, by the action of the acid phosphates, according to the following
simple reaction: —

MHU + MH2P04 = H2U + M2HP04

From acid urines, however, the uric acid is frequently deposited, in
the first place, not as free acid, but in the form of urates, forming a
precipitate which has long been known as the " lateritious deposit."

A careful study of the chemistry of this deposit has led Sir William
Roberts to conclude that the above equation does not rightly, or at least

1 Roberts. 2 Ann. d. Chem., Leipzig, 1848, Bd. Ixv. S. 181.

3 Neubauer ii. Vogel, "Analyse des Harns," 9th edition, S. 192.

4 Journ. Chem. Soc., London, 1862, vol. xv. p. 8.

5 " Croonian Lectures," 1892. 6 Ibid.
7 Arch.f. exper. Path. u. PharmaJcoL, Leipzig, 1892, Bd. xxx. S. 469.

URIC ACID.

589

does not completely express the chemical mechanism of uric-acid solution
and precipitation.1

The urate deposit is amorphous, but on treatment with water it is
found to decompose, part of its uric acid being set free in crystalline
form and part going into solution (Fig. 51). But this is a property which
was stated above to be specially characteristic of the quadriurates, and
closer examination shows that the greater part of an amorphous urate
deposit does, in point of fact, consist of those hyperacid salts, and not
of ordinary biurates.

Eoberts' view is that the quadriurate is the only physiological type
of uric acid salt, whether in blood or in urine.

FIG. 51. — Uric acid. — In the lower half of the figure the crystals are
shown as they separate when a quadriurate deposit is decomposed
with water.

In the normal acid urine, immediately after its secretion, all the uric
acid is in this form. But in aqueous solution the quadriurates are neces-
sarily in a state of unstable equilibrium, and tend at once to decompose
according to the equation —

(1) MHU,H2U = MHU + H2U;

half the uric acid being precipitated and the other half remaining in
solution as biurates. But the latter are in the presence of acid phos-
phates, and this fact again involves a condition of unstable equilibrium;
the following change occurring —

(2)

1 Roberts, loc. cit.

590 THE CHEMISTR Y OF THE URINE.

In fact, quadriurates are thus re-formed, and become subject to the
same influences as before. "These alternating reactions — breaking up
of quadriurates by water into biurates and free uric acid, and recomposi-
tion of quadriurates by double decomposition of biurates with mono-
metallic phosphate — go on progressively, until all the uric acid may be
set free."

The quadriurates, therefore, are of great importance in the chemistry of
urinary uric acid, and beyond all doubt form an intermediate step in the
liberation of the free acid itself. The evidence that they are the form in
which the acid is actually excreted seems to be less conclusive. It is clear
that the alternating reactions just discussed would go on, whether the salts
which leave the renal tubules are quadriurates or biurates. In the latter case,
the interaction with the phosphates would be the first stage of the process,
and the decomposition of the resulting quadriurates the second. Equations
(1) and (2), above, would occur in reversed order, and the alternation would
then continue as before. The fact that the solid excretion of birds and snakes
consists of quadriurates,1 may be held to support the view that these salts
are the excretory form in man, as also the observation that certain urate con-
cretions found in the kidneys of new-born children approximate in composition
to the quadriurates.2 But it may be fairly argued that when, as in the
human adult, the mechanism of excretion has become more perfectly suited
to the elimination of a liquid urine, the uric acid will tend to assume the
more soluble form, and all the evidence points to the fact that this form is
the biurate. I have frequently observed that when ammonium urate separates
from a clear acid urine, as an effect of adding neutral ammonium chloride in
excess (vide infra), it is wholly in the form of a biurate. While it is not
inconceivable that a migration of bases occurs under these circumstances, it
is far more likely that the fact points to the pre- existence of biurates in the
urine.

Again, it will be found that many concentrated specimens of urine, when
first passed and while perfectly clear, will, on slight acidification with acetic
acid or with a mineral acid, give an immediate precipitate of quadriurates,
while the same specimen may require hours before any urate deposit separates
spontaneously. The explanation of this would seem to be that the urine
originally contained the more soluble biurates, and that these are changed
immediately upon artificial acidification, or more slowly by interaction with
phosphates, into less soluble quadriurates.

But whatever may be the primary form of the urates present, it is
in any case important to recall the facts discussed on p. 578. The
reaction between urates and phosphates is a reversible one ; with acid-
phosphates, biurates yield quadriurates ; with basic (monohydrogen)
phosphates, quadriurates yield biurates. With a certain proportion-
ate mixture of the two types of phosphate the uric acid salts will be
therefore in equilibrium.

In many urines this equilibrium between the phosphates and urates
is established, and the determining reactions described above, therefore,
cease before all the uric acid is liberated. In others, where the
proportion of monohydrogen phosphate is at the outside large, the
equilibrium occurs early, and little or no free uric acid separates. Only
when the original excess of acid phosphate over basic phosphate reaches
an adequate value is the whole of the uric acid set free. In other

1 Roberts, loc. cit.

2 Flensburg, Jahresb. u. d. Fortschr. d. TMer-Chem., Wiesbaden, 1894, Bd. xxiii.
S. 581.

URIC ACID. 591

words, the chief factor which determines the precipitation of uric acid
is the degree of acidity of the urine. Eoberts has found that two other
agencies exert an influence over this precipitation — the pigmentation
of the urine, and its comparative richness or poverty in salines. Other
things being equal, a specimen which is poor in pigments on the one
hand, or in neutral salts on the other, will exhibit a special tendency
to deposit its uric acid in crystals. But while the question of acidity
affects that stage of the process which consists in the change from
bin rates to quadriurates, the pigmentation and percentage of salts
affect rather the change from quadriurate to free acid. The urinary
pigments and the neutral salts inhibit the decomposition of quadri-
urates by water.

• * f ,

FIG. 52. — Upper half, ammonium urate. Lower half, sodium urate.

Upon standing, some specimens of urine deposit urates, not as amorphous
quadriurates, but as crystalline biurates. Ammonium urate is frequently to be
seen in the deposit from alkaline urine in the form of roughly dumb-bell-shaped
masses; and in concentrated specimens sodium urate forms the so-called thorn-
apple crystals (Fig. 52).

Isolation of uric acid from the urine. — If the urine be acidified with
hydrochloric acid, much of its uric acid separates in pigmented crystals,
which tend to adhere to the sides of the vessel. These can be easily
identified by the microscope. But for the purpose of applying the
characteristic tests, a supply of uric acid may be more conveniently and
quickly obtained by adding crystals of ammonium chloride to the
urine till near saturation, and then a few drops of strong ammonia.
The precipitate which falls is at once filtered off, washed from the filter
with a little hot water, and warmed with a few drops of hydrochloric

592 THE CHEMISTRY OF THE URINE.

acid. After cooling, the crystals of uric acid which fall may be washed
by decantation.

Tests and reactions — (a) The murexide test. — If a small quantity of
uric acid be placed upon a watch glass, a little strong nitric acid, or a
few drops of bromine water added, and the whole taken to dryness upon
the water-bath, an orange-red residue is obtained which, if touched with
a drop of ammonia, yields a fine purple colour. If a minute quantity of
sodic -hydrate solution be subsequently added, the purple colour changes
to blue ; while, on warming the alkaline solution, all colour is discharged.
The water-bath should always be used for evaporation in applying this test,
and if the watch glass be allowed to remain on the bath for a considerable
time, after evaporation is complete, a red colour will develop without
further treatment, and the residue will dissolve to a purple solution in
distilled water. This is the most delicate method of applying the test.

The residue left by the action of the nitric acid or bromine water consists
of various oxidation products of uric acid, amongst which is alloxantin
(C5HCN408 or C8H4N406.H20). This substance yields, with ammonia,
ammonium purpurate, which is the purple product of the test.

(&) If uric acid be dissolved in a little caustic soda, a few drops of
Fehling's solution added, and the solution boiled, a yellowish precipitate
of cuprous oxide is obtained (cf. p. 608).

(c) An alkaline solution of uric acid gives, on the addition of a few
drops of a solution of phospliomolyldic acid, a dark blue precipitate with
a metallic lustre, which under the microscope is seen to consist of small
six-sided prisms.1

Estimation. — The methods now used for the estimation of uric acid depend
either upon the insolubility of its silver compound in ammoniacal solutions, or
upon the depression in solubility which ammonium urate undergoes in the
presence of other ammonium salts. Of the silver processes the Salkowski- 2
Ludwig 3 method is the most accurate. In this the phosphates of the urine are
first precipitated by the addition of an ammoniacal solution of magnesium
chloride, containing ammonium chloride (magnesia mixture). Without filter-
ing off the phosphates, a solution of ammoniacal silver nitrate is next added,
which gives a further precipitate of silver-magnesium urate. After standing,
the mixed precipitates are filtered off, washed, and treated with a solution of
potassium-hydrogen sulphide, which decomposes the silver compound, forming
silver sulphide and potassium urate. The black precipitate of the former is
filtered off, and the uric acid liberated in the filtrate by the addition of hydro-
chloric acid. It is finally separated by filtration and weighed.

The writer 4 has modified the previous methods employed for the separation
of uric acid as ammonium urate in such a way that the precipitation is absol-
utely complete, and the results are as accurate as those of the foregoing method,
while much more easy to obtain.5 The urine (100 c.c.) is saturated with
chloride of ammonium, and allowed to stand for two hours, when the resulting
ammonium urate precipitate is filtered off, washed from the filter with hot
water, and the uric acid liberated by warming with hydrochloric acid.
After standing it is filtered off, washed, and weighed.

1 Offer, Centralbl.f. Physiol., Leipzig u. Wien, 1894, Bd. viii. S. 801.

2 Arch. f. d. ges. Physiol., Bonn, 1872, Bd. v. S. 210.

3 Zlschr.f. anal. Chem., Wiesbaden, 1885. Bd. xxiv. S. 637.

4 Hopkins, Journ. Path, and Bacterial., Edin. and London, 1893, vol. i. p. 450.

5 Cf. v Jaksch, " Klinische Diagnostik," 1896, 4th edition, S. 428, 431; Ritter,
Ztsc.hr. f. physiol. Chem., Strasburg, 1895, Bd. xxi. S. 288 ; Luff, Goulstonian Lectures,
1897, Lect. i.

URIC ACID. $9$

Variations in the amount. — (a) The relation to urea; the effects
of diet. — Variations in the quantity of uric acid have been considered
from two different points of view. By some, these variations have
been expressed always in relation to the quantity of urea excreted
simultaneously. Such observers have felt that an increase or decrease
in uric acid, which merely accompanies a corresponding change in the
general nitrogenous metabolism, is of less physiological significance than
a variation which occurs independently of (or out of proportion to) the
latter ; and since the urea excretion is a measure of this general
metabolism, the uric has been, by such writers, referred to the urea
output as a standard. Other and more recent authorities, seeing the
origin of uric acid in an entirely distinct series of events within the
body, and observing that the urea : uric acid ratio has no stable
value, have recommended the entire neglect of this relation, prefer-
ring to express the uric acid output always in terms of its absolute
amount.

An attempt has been made to show that urea and uric acid are
always produced in the body, so as to bear a constant and definite ratio
to each other, and that any alterations in this ratio indicate either a
retention of uric acid on the one hand, or a sweeping out of previously
retained acid on the other.1 That this position cannot be maintained in
its entirety is quite certain. Consideration of the effect of varying diet
alone gives sufficient evidence against it. If the two analyses by Bunge,
given in an early section of this article, be examined, we see that upon a
diet of bread, not only is the absolute amount of uric acid less than upon
a diet of beef, but also that the relation to urea is also strikingly less.
On bread the ratio is 1 to 81, on beef it is 1 to 48. Similar results are
obtained, as the writer has found, if the experiments are continued for
many days. If the two substances were always produced in constant ratio
we should have to conclude that a bread diet produces a continuous
storing up of uric acid in the body ; and for this conclusion there is
certainly no evidence.

Again, if we consider the effect of varying the quantity of the
ingested food — its composition being maintained uniform — we find that
on the whole the uric-acid excretion is less affected by such variations
than is the urea, so that we change the value of the ratio merely by
altering the amount of food taken.

It is therefore impossible to look upon the ratio which uric acid
bears to urea as an independent physiological constant, or to conclude
that even wide variations in its value are necessarily pathological.

But some authorities go further than to say that the uric acid
output is more stable than that of the urea, claiming, indeed, that it is
quite unaffected by the absorption of the ordinary proteids of diet — the
albumins and globulins with their derivatives. If this be a fact, and
the production of the acid is independent of variations in these main
nitrogenous constituents of food, we ought certainly, in studying the
quantity in the urine, to neglect its ratio to urea altogether. This ratio
will then be little more, under ordinary circumstances, than an expression
for the urea variations, measured from the more stable uric acid output,
so to speak, as a base line ; while, if we are studying the effect of special
factors upon uric acid production, reference to the urea will be un-
necessary and misleading.

1 Haig, "Uric Acid in Disease."
VOL. I. — 38

594 THE CHEMISTRY OF THE URINE.

Salkowski, in 1889,1 was among the first to give prominence to this
view, but the experiments upon which he then based his opinion were not
wholly calculated to decide as to what is the effect, if any, of the ingestion
of ordinary proteids. They were in the main those of Hirschfeld,2 but
the experiments of this investigator were directed to a broader question
than that of uric acid excretion, and the diet for the purposes of his
research was made entirely abnormal, so that definite conclusions on the
point we are discussing cannot be fairly drawn from them. In the experi-
ments of Horbaczewski and Camerer,3 undertaken with the object of ascer-
taining the effect of glycerin, carbohydrates, and fat, respectively, on uric
acid excretion, there were certain "normal periods," in which a standard
mixed diet was taken alone. The fact that the diet was carefully maintained
at a uniform level makes these very careful experiments more or less unavailable
for our purpose. Nevertheless, during <ftie of these control periods, which
lasted for many days, the urea excreted fluctuated somewhat widely, pre-
sumably from varying degrees of proteid absorption. Of this period the
author says : " The uric acid eliminated went hand in hand writh the nitrogen
excretion. In general, the more the total nitrogen present the more the uric
acid found."

There are but few experiments recorded which bear properly on our
problem, fundamental though it be : that is to say, experiments where the
uric acid and urea (or total nitrogen) have been estimated from day to day
by reliable processes ; while the quantity, but not the quality, of the proteids
ingested has been made to vary widely. Schiiltze 4 found the uric acid rise
with increase of flesh diet. Hester and Smith5 found it raised when the
ingestion of proteids was increased, though it was somewhat less affected than
the urea. I myself have repeatedly observed a rise to follow an increase in
the diet where the composition of this has been carefully maintained constant.

But these observations are open to one criticism. Whatever the effect of
globulins or albumins, there appears to be no doubt that ingestion of
nucleo-proteids increases the excretion of uric acid ; calves' thymus, with its
abundant nuclein, has been largely used to test this point. Umber6 and
Weintraud7 have found that with thymus the excretion of uric acid may
amount to double that of the same individual upon ordinary proteid (muscle)
diet of equal nitrogenous value.

Is, then, the smaller increase found when ordinary proteid diet is taken,
merely due to any nuclein present and not to the absorption of the ordinary
proteids? We shall be able to add the last word to this discussion
immediately.

If the effect of an isolated meal of ordinary mixed diet be studied, it
is found that an increase in the excretion of uric acid occurs very rapidly
after the food is taken. According to Mares 8 the maximum hourly excretion
occurs at the fifth hour after the meal ; four hours before the urea reaches
its maximum. This observer held, therefore, that it was not derived directly
from the ingested proteid, but from cellular activity during digestion.
Horbaczewski confirmed this result, and believed that it was due to a digestive
leucocytosis (vide article, "Metabolism"), with its consequent liberation of
nucleins in the body. But Camerer9 has recently found that this rise of

1 Virchow's Archiv, 1889, Bd. cxvii. S. 572 ; comments on a paper by Spilker.

2 Ibid., Bd. cxiv. S. 301.

8 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1886, Bd. xcviii. Abth. 3, S. 301.

4 Arch.f. d. ges. PhysioL, Bonn, 1889, Bd. xv. S. 427.

5 New York Med. Journ., 1892, p. 38.

6 Ztschr.f. klin. Med., Berlin, 1896, Bd. xxix. S. 174.

7 Berl. klin. Wchnschr., 1895, S. 407.

8 CentralU.f. d. med. Wissensch., Berlin, 1888, S. 2.

9 Ztschr. f. BioL, Miinchen, 1896, Bd. xxxiii. S. 136; also Weintraud, Chem. Centr.-
£1., Leipzig, 1895, Bd. ii. S. 234.

URIC ACID. 595

uric acid after a meal is by no means marked, unless the food taken contains
nuclein. On a diet composed, for instance, of egg albumin, the rise was very
small, while during the digestion of non-nitrogenous diet the output of uric
acid was even diminished. Camerer holds, therefore, that digestive leuco-
cytosis cannot be the cause of post-prandial increase, but only the actual
ingestion of nucleins, and his results would suggest that we must answer the
question in the previous paragraph in the affirmative, and recognise that
the excretion of uric acid is not increased by the ingestion of ordinary
proteids.

If this be confirmed, we must for the future attach no importance to the
urea : uric add ratio ; and when we wish to eliminate mere dietetic effects
from our study of other specific variations in the urinary uric acid (when, for
instance, we are endeavouring to ascertain if retention is occurring in disease,
or whether a certain drug is promoting elimination), we must do this by
controlling the ingestion of nucleins during the experiments.

It should be understood, however, that in spite of much labour spent
upon the problem, our knowledge of the relation of urinary uric acid to
diet is scarcely yet upon a firm foundation, and contradictory statements
will be found in the literature. Future investigators may have to face
yet another difficulty, if it be true, as Weintraud l affirms, that a true
excretion of uric acid may occur through the walls of the intestine.

One fact is abundantly certain — that great individual differences
exist in uric acid excretion. In spite of all that has been said above, it
is found that, with the ordinary regularity of habits and diet customary
in civilised life, the uric acid output (when the whole twenty-four hours'
excretion is dealt with), and even its relation to urea, will remain fairly
constant in any given individual ; whereas, when different individuals
are compared, much greater differences are seen. Before we can say
with certainty what constitutes a pathological or exceptional condition
in any case, we must know the normal behaviour of the particular
organisation in question (Salkowski).

The ratio borne to urea may vary in different healthy individuals
from 1 : 25 to 1 : 50 ; the proportion most commonly found being from
about 1 : 35 or 1 : 40.

(b) Variations apart from diet. — It is a well-established fact that
in newly -born children the uric acid excretion bears a high proportion
to the body weight, and also to the other nitrogenous constituents of
the urine. In the first few days of life 7'8 per cent, of the urinary
nitrogen may be in the form of uric acid.2

The absolute amount is increased by excessive exercise and
diminished by rest. With regard to drugs, the action of alkalies is
still disputed. It is possible that an isolated dose may temporarily
accelerate excretion ; but, according to Spilker and Salkowski,3 continued
administration diminishes it. There is certainly no foundation for the
statements of Haig, that the excretion of uric acid varies inversely as
the acidity of the urine.4 Salicylates undoubtedly increase the amount
in the urine. Pilocarpine produces an increase, possibly from the
leucocytosis which follows its use. Pathologically, there is increase in

1 Ohem. Centr.-BL, Leipzig, 1895, Bd. ii. S. 310.

2 Hofmeier, Vircliow's Archiv, 1882, Bd. Ixxxix. S. 493.

3 Ibid., 1889, Bd. cxvii. S. 570.

4 Of. Herringliam and Davies, also Herringh&m and Groves, Journ. PhysioL, Cambridge
and London, 1891, vol. xii. pp. 475 and 478.

596 THE CHEMISTR Y OF THE URINE.

conditions of leukaemia, and this may be said to be the only well-
established fact as to the effect of disease on uric acid excretion. In
gout, although the urate deposits form so prominent a factor, the question
of the amount excreted in the urine is still unsettled. In this country,
at any rate, many cases occur in which, as originally observed by Sir A.
Garrod, the excretion during the chronic condition is greatly diminished,
whereas, in relation to the acute attack, increased elimination may
occur.1 Pyrexia alone does not produce any marked increase ; but
in certain specific fevers with a definite crisis, a large temporary
increase may occur, depending, according to Horbaczewski, upon the
associated leucocytosis.

Uric acid is one of the commonest constituents of urinary calculi.

(e) The xanthin bases. — Several "members of this chemical group
are found in urine, in variable but always small amount. Xanthin
itself was discovered by Marcet in 1819 as a constituent of a urinary
calculus, and its presence in urine was first demonstrated by Strecker in
1857. In addition to xanthin, the following members of the group
may be present — heteroxanthin, paraxanthin, hypoxanthin (sarkin),
guanin, adenin, and carnin.

All these substances are closely related to each other and to uric
acid ; and the chemical group to which they belong also contains
certain important vegetable bases.

The relation of xanthin to uric acid is best understood by a com-
parison of the structural formulae ; our knowledge of the constitution of
the base being due to E. Fischer.

— C— NIL NH— C = Ev

I II >co i i )co

CO C— NH/ CO C— NH/

II II

NH— CO NH— CH

(uric acid) (xanthin)

Xanthin contains one atom less oxygen than uric acid, while hypo-
xanthin contains one less than xanthin.

C5H4N403 C6H4N402 C6H4N40

(uric acid) (xanthin) (hypoxanthin)

In the laboratory means have not been found to pass from one of
these three compounds to another by oxidation or reduction ; but in the
body the steps. involving oxidation can certainly occur.

Heteroxanthin and paraxanthin are homologues of xanthin, the
former being its methyl- and the latter its dimethyl-derivative ;
paraxanthin is therefore an isomer of the vegetable bases, theobromin
and theophyllin.

Gfuanin in an imido-xanthin ; that is to say, it is xanthin with an
oyygen atom replaced by an NH group ; and adenin bears the same
relation to hypoxanthin.

C5H4N40.0 C6H4N4O.NH C5H4N4.0 C5H4N4.NH

(xanthin) (guanin) (hypoxanthin) (adenin)

Uric acid and the xanthin bases are grouped together by recent

1 Cf. Fawcett, Guy's Hasp. Rep., London, 1895 ; Luff, Goulstonian Lectures, Lect. i.

THE XANTHIN BASES. 597

German writers l under the term, " alloxuric substances," a name meant
to show their relation on the one hand to alloxan,2 and on the other to
urea ; the bases themselves may be designated the " alloxuric bases."

The amount of the xanthin bases in the urine has been generally
understated until lately ; they amount collectively to something like
one-tenth of the uric acid present ; that is to say, an average of 0*1 to 0'07
grm. of the combined bases is excreted per diem (Camerer, Salkowski).
Of xanthin itself some O02 to O03 grm. is found, upon a mixed
diet.

General properties. — That the xanthin compounds, unlike uric acid,
are basic in character, is probably due to the fact that the CO group is
absent from the central carbon chain. (Cf. graphic formulae above.)

Their basicity is, however, very feeble, and many of their compounds
with acids are decomposed by water — just as is the " sulphate " of uric
acid ; while, on the other hand, they are all capable of forming metallic
derivatives and compounds with other bases. They contrast sharply
with uric acid in their easy solubility in mineral acids. In ammonia
they are also soluble (with the exception of guanin). Xanthin itself
dissolves to a very slight extent in water, but the other bases are more
soluble.

They are precipitated from urine — (1) By the addition of phospho-
tungstic or phosphomolybdic acids in acid solution ; (2) by silver nitrate
in ammoniacal solution ; and (3) by copper salts ; especially in the
presence of thiosulphates. When precipitated by any of these methods,
they are accompanied out of solution by uric acid (vide infra).

Isolation and estimation. — It is beyond the scope of this article to describe
in detail the separation of the xanthin bases individually. Very large quanti-
ties of urine (100 litres and upwards) are required for the purpose. If the
precipitate obtained by adding ammonia, and afterwards ammoniacal nitrate
of silver solution, be decomposed by sulphuretted hydrogen, and the filtrate
from the silver sulphide acidified with hydrochloric acid, concentrated, and
allowed to stand, the uric acid crystallises out. This being filtered off, the
liquid is again made alkaline with ammonia and the bases again precipitated
with silver nitrate. The varying solubility of the silver compounds so
obtained in nitric acid permits of a preliminary fractionation of the bases ;
and, when liberated from combination with silver, their diverse solubilities in
water and other media yield methods for their final separation from each
other.

If urine (100 c.c.) be heated to boiling, and precipitated with a mixed
solution of copper sulphate and sodium thiosulphate, some chloride of barium
being afterwards added, a precipitate is obtained which contains all the uric
acid and xanthin bases, but no other nitrogenous constituent (Kriiger and
Wulff). By estimating the nitrogen in this precipitate by means of Kjeldahl's
process, we obtain a measure of what may be called the " alloxuric nitrogen,"
an important urinary constant. If a separate estimation of the uric acid be
made, the nitrogen proper to this may be deducted from the "alloxuric
nitrogen," and we obtain a value for the "nitrogen of the bases." Such a

1 Kriiger and Wulff, Ztschr. f. physiol. Ohem., Strassburg, 1896, Bd. xx. S. 176.

rNH-co^

2 Alloxan-! CO CO r is an oxidation product of uric acid. The xanthin bases and uric

INH-CO>!

acid will all be seen to contain the urea residue and the three-carbon chain, which together
comprise the so-called " alloxan ring."

598 THE CHEMISTRY OF THE URINE.

procedure is our most convenient method for following the variations in the
excretion of the xanthin group.1

Tests. — Xanthin and its two homologues, and also carnin, but not the
other bases, give Weidel's reaction. This is almost identical with the
murexide test described for uric acid, but chlorine water is used instead
of nitric acid. The bases resist oxidation with nitric acid much more
fully than does uric acid, but, in the presence of a small quantity of a
chloride, xanthin will give the ordinary murexide reaction. Very
characteristic of xanthin and hypoxanthin are the crystalline precipi-
tates which they yield with silver nitrate in the presence of nitric
acid.

Variations in the amount of the urinary xanthin bases closely follow
those of uric acid, and for the most part depend upon the same
influences. The bases, however, are apt to vary even more widely.
According to Camerer 2 they are greatly increased by certain forms of
vegetable food ; thus, in one experiment, on a flesh diet the nitrogen
present as these bases was only 01 per cent, of the total nitrogen ;
while, when green vegetables formed the chief ingredient of the food, it
was 0'6 per cent. They are increased by diet rich in nucleins,3 and
pathologically their amount is greatly raised in some forms of leukaemia.

(f) Creatinin. — This base is chemically distinct from the alloxuric
compounds, in that its molecule contains neither the alloxan ring nor
the urea residues which are characteristic of these. Nevertheless, on
hydrolysis, it easily yields urea and an amido-acid (methylglycine). It
is the anhydride of creatin, which is itself methylglycocyamin.

X, /NH

C(NH)</ C(NH)<

\N(CH3)-CH2-COOH \N(CH3)-CH2-CO

(creatin) (creatinin)

Whether creatin itself is ever a urinary constituent is somewhat
uncertain. It has been stated to occur when the urine is excreted in
alkaline condition,4 but the quantity is, in any case, very small. So
easily are the two substances converted the one into the other, that care
is requisite in the isolation of either. When creatin stands in acid solu-
tion, it tends to change into its anhydride, while creatinin in alkaline
solution suffers the inverse change.

G. S. Johnson5 has found, however, that urinary creatinin is not
identical, but isomeric, with that obtained artificially from creatin (e.g.
by the action of acids), and distinct from the creatinin found in small
quantity in muscles.

The creatinin of urine was first isolated by Liebig. It is present on
an average to the extent of about I/O grm. in the excretion of twenty-
four hours, when a mixed diet is taken.

Properties. — In its compounds creatinin exhibits well-marked basic
tendencies, and it can liberate ammonia from ammonium salts on boil-
ing ; but, according to Salkowski, solutions of the pure substance react

1 For details see Kriiger and Wulff, loc. cit. supra.

2 Ztschr.f. Biol., Miinchen, 1891, Bd. xxviii. S. 72.

3 Weintraud, loc. cit.

4 Hoffemaiin, Virchaw's Archiv, 1869, Bd. xlviii. S. 358.

5 Proc. Roy. Soc. London, 1892, vol. 1. p. 287.

CREATININ. 599

neutral to litmus. The crystalline form of the base varies with the
method of preparation (Johnson). As ordinarily obtained, it exists as
colourless monoclinic prisms, which are often imperfectly formed, and
appear of whetstone shape (Fig. 53). It dissolves in about twelve parts
of cold water, but requires a hundred parts of alcohol to dissolve it at
ordinary temperatures. In ether it is almost insoluble. Creatinin
reduces alkaline copper solutions (cf. p. 608). It forms characteristic
crystalline salts with the mineral acids, aqueous solutions of which react
acid to litmus. With certain salts of the heavy metals it forms crystal-
line molecular compounds, two of which are of practical importance.

Creatinin zinc-chloride — (C4H7N3O)2ZnCl2 — separates as a precipi-
tate, consisting of stellate clusters of acicular crystals, when a concen-
trated neutral solution of chloride of zinc is added to an aqueous or
alcoholic solution of the base. The compound is soluble in hot water,
in mineral acids, and in alkalies; but insoluble in alcohol, and very
slightly soluble in cold water.

Creatinin mercuric-chloride, a complex compound of the formula
4(C4H7N3O.HCLHgO),3HgCl2. This is precipitated in colourless, glassy,
spherular masses, when sodium acetate and mercuric chloride are added to
creatinin solutions. The base is also precipitated, even from very dilute
solutions, by the addition of phosphotungstic, phosphomolybdic, or picric
acids.

Isolation and estimation. — Neubauer separated creatinin from the urine by
means of its combination with zinc chloride, this salt being added to an
alcoholic extract of the evaporated urine. A more convenient method is to
treat the urine direct with a little sodium acetate, and then with one-fourth
its volume of saturated mercuric-chloride solution. The precipitate which
first falls is at once filtered off; it contains uric acid and other constituents,
but not creatinin. The filtrate from this rapidly begins to deposit the mer-
cury compound described above, and in forty-eight hours precipitation is com-
plete (G. S. Johnson). The base itself is prepared by decomposing this
precipitate with sulphuretted hydrogen, and by treating the creatinin-hydro-
chloride, so obtained, with hydrate of lead.1 To determine the quantity, the
mercury precipitate may itself be weighed, and the percentage of creatinin
calculated from this.2

Tests. — If a solution of creatinin be treated with a small quantity of
very dilute sodium nitroprusside solution, and subsequently with weak
caustic alkali, a rich, ruby-red colour is produced, which afterwards
changes to yellow ( Weyl's reaction). If acetic acid be now added in
excess, and heat applied, the solution becomes green, and then blue,
and finally a precipitate of Prussian blue is formed. Acetone (p. 616)
gives an analogous reaction, but behaves differently after the addition of
the acetic acid. Many specimens of urine will give Weyl's test direct.

Jaffes test is an application of the fact that creatinin gives, with
picric acid and caustic alkali, an intense red colour, even in the cold.

The variations in the urinary creatinin generally follow very closely
those of the urea, but there can be no doubt that its quantity depends
largely on the amount of creatin taken with the food. Its physiological
relations are discussed elsewhere. Pathologically, it is increased in most
febrile conditions, and in diabetes. It has been stated to diminish in

1 In this process all the operations are carried out in the cold ; by this means the true
urinary creatinin is obtained. Heat produces isomeric change.

2 Cf., however, Allen, "Chemistry of Urine," pp. 156 and 159.

6oo

THE CHEMISTR Y OF THE URINE.

progressive muscular atrophy, and in pseudo-hypertrophic paralysis.
According to Senator, no increase is produced by the paroxysms of
tetanus — a fact which is of interest as bearing on the relation of
muscular activity to the urinary creatinin.

(g) Hippuric acid. — Hippuric acid is benzamido-acetic acid, or
benzoylglycin, C6H5.CO.NH.CH2.COOH ; in other words, it is a con-
densation product of benzoic and amido-acetic acids, in the formation
of which the hydroxyl group of the former is eliminated as water,
with an atom of hydrogen from the amido group of the latter. But

FIG. 53. — A. Creatinin ; B. Hippuric acid.

the simplest artificial synthesis is obtained when monochlor-acetic acid
is heated with benzamide.

CCH5CO.NH2+CH2C1.COOH = (C6H6.CO)NH.CH2.COOH+HC1

In most mammals the synthesis by dehydrolysis occurs in the kidney ;
hippuric acid appearing in the urine, whenever benzoic acid, or pre-
cursors of benzoic acid, are taken by the mouth. The excretion of
hippuric acid is, indeed, mainly dependent upon the relative richness of
the diet in such precursors of benzoic acid.

It is not necessary that benzoic acid should itself be ingested. A
benzene derivative containing a single "side-chain" is nearly always
oxidised in the body to benzoic acid. Such substances, therefore, as

toluene, C6H5.CH3; cinnamic acid, CJL.CH.OH.COOH

or

phenyl-

propionic acid, CCH5.CH2.CH2.COOH, all give rise to an excretion of
hippuric acid when they are taken by the mouth. Aromatic compounds
of this type are abundantly present in some forms of vegetable food, as

HIPPURIC A CID. 60 1

in many fruits and in the cortical parts of most plants. Vegetable food
greatly increases, therefore, the excretion of hippuric acid.

But the vegetable aromatic compounds are not the sole source of the
urinary hippuric acid. In the decomposition of proteids, which occurs
in the bowel, aromatic residues split off. Precursors of benzoic acid
(mainly, perhaps, phenylpropionic acid) are thus formed, and after
oxidation they appear in the urine as hippuric acid. The metabolism
of the tissue proteids themselves, moreover, may yield precursors of the
same kind, so that even in starvation hippuric acid does not wholly dis-
appear from the urine.

This dual origin (from aromatic precursors in the diet chiefly, but
likewise from proteid metabolism) is found also in the case of the other
aromatic constituents of the urine (p. 605).

Upon a mixed diet the excretion of hippuric acid in human urine
amounts to about 07 grms. per diem ; upon a diet rich in fruits it may
be raised to three or four times this. In herbivora the quantity is much
larger ; the urine of cattle, for instance, often contains as much as
2 per cent., though, as might be expected, that of sucking calves only
contains small amounts.

Properties. — It forms four-sided prismatic crystals ending in two or
four facets, and often grouped in clumps (Fig. 53), of which the melting
point is about 187°. It is but slightly soluble in cold water or alcohol ;
but both these solvents dissolve it easily when hot. It is soluble in
acetic ether, but not so in most other organic liquids. If heated to 240°
it decomposes, benzoic acid subliming out and a reddish residue being left
behind. When first heated at this temperature a hay-like odour is given
off, which is succeeded by that of prussic acid. When boiled with strong
hydrochloric acid it splits up into its components, benzoic and amido-
acetic acids. The growth of the Micrococcus urece can bring about this
decomposition, so that stale specimens of urine often contain benzoic in
place of hippuric acid. Taken to dryness with nitric acid, it yields an
odour of nitrobenzene.

Solutions of hippuric acid react acid to litmus, and even when very
dilute they impart a violet colour to congo-red. By the use of the latter
indicator Briicke proved the absence of the free acid from the urine. It
is present always as salts. It forms salts with bases, but does not
combine with acids. Its iron compound is insoluble in hot water, and
may be employed in separating the acid from its solutions.

Isolation and estimation. — The method of Bunge and Schmiedeberg a
consists in making an alcoholic extract of the urinary solids, evaporating off
the spirit, dissolving the residue in water, and, after acidifying with hydro-
chloric acid, shaking up repeatedly with successive quantities of acetic-ether.
On evaporating the latter, impure crystals of the acid are obtained, the
impurities being removed by treatment with petroleum-ether, in which
hippuric acid is insoluble.

Tests. — The substance is recognised by its crystalline form, by its
melting point, by its behaviour on heating, and by the formation of its
insoluble iron compound when neutral ferric chloride is added to its
solutions.

In addition to hippuric acid, minute quantities of its homologue
phenaceturic acid (phenylacetylglycin), C6H5.CH2CO— NH.CH2.COOH,
1 Arch. f. exper. Path. u. Pharmakol., Leipzig, Bd. vi. S. 235.

602

THE CHEMISTRY OF THE URINE.

are occasionally found in human urine. Its origin and significance are
analogous to those of the more abundant substance.

When benzoic acid or its precursors are administered to birds, they
are excreted as ornithuric acid, which is an analogous conjugated com-
pound of benzoic acid with diamidovalerianic acid.

(h) Amido- acids.— These, in simple unconjugated form, are seldom
found in normal urine. Under certain pathological conditions leucine
and tyrosine appear in considerable quantities. The elimination of these
substances is especially associated with conditions in which a rapid
destruction of the hepatic tissue has occurred ; thus they are found in
acute yellow atrophy of the liver, and, to a less extent, in phosphorus-
poisoning.

When these amido-acids are given by the mouth in moderate
quantity, and under conditions of normal health, their nitrogen is
excreted wholly in the form of urea. If, however, tyrosine be adminis-
tered in very large amounts, it may be excreted in part as tyrosine-
hydantoin, in which it exists as a conjugate compound with urea ; 1 and
at the same time other aromatic constituents of the urine are increased
in quantity by derivation from its aromatic nucleus. Only when the
normal hepatic functions are in abeyance does the unaltered amido-acid
itself appear.2

When present in urine, leucine and tyrosine are usually found
together. If in large quantity, they may, though very rarely, form
a deposit; at other times they may be seen under the microscope
when a drop of the urine is evaporated.

In general, however, they must be
separated by special means. The
leucine may be dissolved, by means of
hot alcohol, from the residue obtained
by evaporating the urine, and when
the alcoholic extract cools it separates
as a greasy mass, which under the
microscope will be seen to consist of
minute spheroids with concentric mark-
ings interrupting a radiated structure.
To demonstrate the presence of tyrosine,
the urine is first precipitated with
basic acetate of lead, the filtrate from
the lead precipitate treated with sul-
phuretted hydrogen and again filtered.
On thorough concentration and cool-
ing of the lead-free filtrate, the tyrosine

separates out in characteristic acicular prisms, which are mostly combined

into sheaves or stars (Fig. 54).

FIG. 54. — Leucine and Tyrosine.

Cystine 3 is another amido-acid, but it is at the same time a sulphur-
containing substance, differing in its metabolic significance from leucine
and tyrosine.

1 Jaffe, Ztschr.f. physioL Chem., Strassburg, 1883, Bd. vii. S. 306.

2 According to the recent observations of Ulrich, lencine and tyrosine are always to be
found in normal urine, though in small quantity, Centralbl. f. PhysioL, Leipzig n. "Wien,
1897, Bd. xi. S. 12.

3 Of. Baumann, Ztschr. f. physioL Chem., Strassburg, 1884. Bd. viii. S. 299 ; also
Brensinger, ibid., 1892, Bd. xvi. S. 552.

PROTEIDS.

603

It is a sulphur derivative of an amidolactic-acid, and has the
formula :

CH3 CH3

NH2— C— S— S— C— NH2
COOH COOH

It may appear in small quantity in certain diseases, but is generally
a product of peculiar disordered metabolism, which is found to be char-
acteristic of certain families. Members of such families may excrete
habitually from O5 to 1 grin, daily. It sometimes separates as a crystal-
line deposit from the urine, and occasionally forms calculi in the urinary
tract.

Physiologically it is of interest, in that cystine or substances allied to
it are probably the precursors of certain of the normal sulphur compounds
of the urine (p. 632).1

Its crystals are very characteristic, being usually in the form of
hexagonal plates (Fig. 55); more rarely it appears in rhombohedral
form. Urine which contains it will, if heated with caustic potash and
plumbic acetate, give a black precipitate of lead sulphide.

PROTEIDS.

Normal urine contains but traces of substances belonging or allied
to the proteid group. But minute quantities of a nucleo-proteid derived
from the cells of the urinary passages
are seldom or never absent. In the
majority of cases the amount of this
is so small that it is difficult directly
to demonstrate its presence. The
flocculent cloud which generally
separates on standing, even from the
clearest urine, by no means always
contains any isolated proteid, but may
consist entirely of intact epithelium
cells. But the nucleo-proteid may
be detected by suitable tests in the
precipitate which falls when large
quantities of normal urine are mixed
with alcohol.

The nucleo-proteid may, on the
other hand, so far increase in con-
ditions of apparent health, that the urine will react to Heller's test
(vide infra). Thus Flensburg2 found, on examining the urine of 1252
healthy persons, that 97 of these gave a reaction with nitric acid, which
could be shown to be due to a nucleo-proteid.

In such cases, and in others where the increase is greater and due to
inflammatory changes in the urinary tract, the nucleo-proteid may be
precipitated by the addition to the urine of acetic acid in the cold;
especially if the fluid be first diluted to eliminate the solvent action of

1 Goldmann and Baumann, ibid., 1888, Bd. xii. S. 254.

2 Skandin. Arch. f. PhysioL, Leipzig, 1893, Bd. iv. S. 410.

FIG. 55.— Cystine.

604 THE CHEMISTR Y OF THE URINE.

the salts present, or, better still, if the salts be first reduced by dialysis.
In some pathological conditions, and especially in cystitis, the amount may
be so greatly increased that it separates as a viscid gelatinous precipitate.
The mucoid appearance of the urinary nucleo-proteid led to its being long
looked upon as mucin ; but it does not yield a reducing substance on
hydrolysis, while, on the other hand, it is rich in phosphorus. Nevertheless,
recent researches made upon large quantities of urine indicate that the
precipitate given by acetic acid contains small quantities of ordinary
mucin, or a phosphorus-free mucoid, as well as the nucleo-proteid.1

Apart from increase due to inflammatory conditions of the excretory
tract, nucleo-proteid is said to be increased when the blood is excep-
tionally rich in leucocytes (leukaemia).2

The question as to whether or not normal urine contains serum albumin
or serum globulin offers a problem of the same order as that of physio-
logical glycosuria, fully discussed on p. 608. The matter is, however, of
less importance physiologically than is the latter question, as, although the
evidence to hand points to the fact that if sufficient urine is employed these
proteids may nearly always be separated in minimal traces, it by no means
follows that they form part of the true excretion, for they may arise
rather, like the nucleo-albumin, from the surface of the urinary tract.

As to the cases when, in apparent health, there is such an increase of
these proteids that their presence may be shown by the direct applica-
tion of ordinary tests, we are met with the difficulty of having to define
what is meant by " normal " urine. Such quantities may be present,
for instance, after exceptionally severe exercise, as in the urine of soldiers
after prolonged marching (Leube, Chateauburg) ; but it is not certain
that the excretory mechanism is here working physiologically.

When, as the effect of disease, the renal epithelium has undergone degenerat-
ive changes, the presence of albumin in the urine is a common phenomenon ;
one of the most familiar in pathology. Albuminuria may arise, too, from such
alterations in the constitution of the blood as upset its normal relations to the
renal cells ; this may be observed in anaemia, and as the effect of specific
poisons. Again, it may follow disturbances of blood pressure in the renal
vessels, even though these be unassociated with obvious changes in the
excretory epithelium. Lastly, the albumin due to addition from the excretory
tract, after the urine has left the kidneys, may pathologically reach a consider-
able proportion.

Under pathological conditions, also, the urine may come to contain
albumoses and peptones. On the one hand, a so-called enterogenous peptonuria
or albumosuria may occur, when, from degenerative changes in the gastro-
intestinal walls (e.g. in carcinoma ventriculi or the ulcerative stage of enterica),
the diffusible proteids reach the blood stream and thereupon are immediately
eliminated by the kidneys. On the other hand, these substances may reach
the blood stream from abscesses or other purulent collections where the tissue
proteids have been hydrolysed by the growth of organisms. Whatever their
origin (and it is sometimes not so clear as in the above groups of cases), the
proteoses and peptones no sooner reach the blood than they are found in the
urine. The older methods of investigation did not clearly distinguish between
peptones and albumoses in the urine • evidence is now accumulating to show
that the latter are by far the more common.

1 Cf. Malfatti, Wien. klin. Wchnschr., 1891, S. 433; also Morner, Skandin. Arch.
/. PhysioL, Leipzig, 1895, S. 437.

2 According to recent observations, the nucleo-proteid of urine is in some cases to be
identified with Lilienfeld's " nucleohiston. "

AROMATIC SUBSTANCES. 605

A very large number of tests for the presence of albumin and globulin in
the urine have been described. We can here refer to two only.

Heller's test. — A small quantity of strong nitric acid is placed in a test
tube, and the urine is allowed to flow gently down the side of the tube so that
it floats upon the surface of the acid without mixing with it. If coagulable
proteids are present, a dense white ring forms at the junction of the liquids.
As little as '002 per cent, of albumin may be thus detected. The urinary
nucleo-albumm may react to this test if in sufficient quantity, but the ring
formed is less dense, and more apt to be formed at some little distance from the
acid.

Ferrocyanide test. — -A-solution of potassic ferrocyanide is first added to the
urine, and the mixture made acid with acetic acid, when the albumin and
globulin are precipitated as a flocculent cloud. If the salt be added before the
acid, nucleo-proteid is not precipitated.

To separate serum globulin from albumin, the urine is, after neutralisation,
saturated with magnesium sulphate, which precipitates the former. The
precipitate may contain certain of the salts of the urine, and heteroalbumose
if present. The proportion of globulin to albumin may vary greatly, and may
be quite different from that present in the blood.

To detect peptones, the urine is saturated with sulphate of ammonium, and,
after standing, filtered ; the biuret test may now be applied to the filtrate, a
large excess of caustic alkali being used. The ammonium sulphate precipitate
contains (in addition to ammonium urate) all other proteids present and also
the urinary mucin. If this precipitate be allowed to stand under alcohol for
some days, the proteoses are obtained in solution when it is extracted with
water. The presence of urates must be borne in mind when the ammonium-
sulphate precipitate is being dealt with, as these yield a coloration with certain
proteid tests ; and again, may lead to error if ordinary mucin is to be identified
by its yield of a reducing body on boiling with acids, for uric acid itself
reduces copper solutions.

AROMATIC SUBSTANCES.

In addition to hippiiric acid, which, owing to its importance as a
nitrogenous constituent, we have treated specially, the urine contains
other substances belonging to the aromatic group ; that is to say,
substances the molecular structure of which contains the benzene
nucleus. Under normal circumstances each one of these is present in
very small amount, but collectively they are of importance. For our
knowledge of their chemistry in the urine we are largely indebted to
the initiative work of Baumann.

Like hippuric acid (q.v.), they are derived in part from the aromatic
constituents of the food, and they are all increased by a vegetable diet ;
but also, like hippuric acid, they partly arise from the breakdown of
proteids. In their derivation from the latter it is possible that tyrosine
in the bowel is an intermediate stage, as many of them are greatly
increased when that substance is given by the mouth.1 We cannot deal
with these substances in great detail, but the characteristic types
of compounds in which the aromatic nucleus is found in the urine
should be noted. They comprise, mainly, simple hydroxyl- substitution
products of benzene, and carboxyacids related to these. We shall also
consider in this section urinary indol and skatol, which are nitrogenous
aromatic compounds. Most of the substances to be dealt with are

1 Brieger, Ztschr. f. physiol. Chem., Strassburg, 1878, Bd. ii. S. 256 ; Wolkow imd
Baumami, ibid, 1891,' Bd. xv. S. 228.

606 THE CHEMISTRY OF THE URINE

excreted as conjugated sulphates (see p. 631), but the carboxyacids are
only in part so excreted. Inosit, which belongs to this group chemically,
has somewhat different physiological relationships to the other aro-
rnatics of urine.

Phenol (CeHs.OH) and kresol (CH3.C6H4. OH).— Traces of carbolic
acid are present in urine physiologically, but the " phenol " of the normal
fluid consists, as a matter of fact, mainly of the homologous kresol ; and,
of the isoineric forms of the latter, parakresol is the commonest. The
properties of this substance, however, closely resemble those of phenol
itself. The amount of phenol and kresol taken together may be upon a
mixed diet no more than some 30 mgrms. per diem. If the urine
be acidified and distilled, the distillate made alkaline, concentrated, and,
after concentration, neutralised, on the addition of bromine a whitish pre-
cipitate will appear, due mainly to the formation of the tribromphenols.

Pyrocatechin (orthodihydroxybenzene) and hydrochinon (para-
dihydroxybenzene) C6H4(OH)2. — Of these two isomeric substances
the former is a constant constituent of human urine in small
quantity; the latter is found probably only under exceptional cir-
cumstances. The former is easily removed from the acidified urine
by shaking with ether ; but its subsequent purification involves a
lengthy procedure.1 It is a white crystalline volatile solid, easily
soluble in water. It gives a dark green coloration with ferric chloride,
which, on the addition of ammonia, becomes violet and afterwards
cherry-red.

Inosit. — This substance, from its sweet taste, was originally classed
with the sugars, and was known as " muscle sugar." It strictly belongs,
however, to the group of substances we are considering, as it is by com-
position hexahydroxybenzene (CH.OH)6. It appears in normal urine
with considerable frequency when polyuria is induced by diuretics or by
copious drinking. On the other hand, its appearance is not entirely
dependent upon the flushing of the tissues which such polyuria might
denote, as extreme polyuria is at other times not associated with
inosituria. It may occur in diabetes. Galloise found it in five out of
thirty cases.

It may be separated from the urine by precipitation with acetate of
lead. The precipitate is decomposed with hydrogen sulphide, the fluid
concentrated, and finally precipitated by admixture with a large bulk of
alcohol. The alcohol precipitate is dissolved in water, the solution
mixed with an equal bulk of spirit and poured into ether, which pre-
cipitates the inosit almost pure.

The substance forms crystals not unlike those of cholesterin. It is
optically inactive and does not ferment. It is said to yield sarcolactic
acid by the action of bacteria.

Of the aromatic carboxyacids the following have been identified
in human urine: — ParaJiydroxyplienyl-acetic acid OH.C6H4 — CH2.COOH;
parahydroxyplienyl-propionic acid OH.C6H4 — C2H4.COOH ; dihydroxy-
phenyl-acetic acid (OH)2 — CH2.COOH (the homogentisic acid of
Wolkow and Baumami) ; 2 and trihydroxyphenyl-propionic acid
(OH)3C6H2.C2H4.COOH (the uroleucic acid of Kirk).

In the urine of herbivora other analogous compounds have been

1 Of. Halliburton, "Chemical Physiology and Pathology," 1891, p. 745.

2 Loc. cit., 1891, Bd. xv. S. 241. This is that isomeric acid which is related to hydro-
chinon.

CARBOHYDRATES AND RELATED SUBSTANCES. 607

detected, and Tcynurenic acid, a related substance, is an important consti-
tuent of dog's urine.1

Pathologically, the substances just described may become of considerable
importance. In carbolic acid poisoning many of them are excreted in greatly
increased amount; pyrocatechin and hydrochinon may be present in large
quantity, and then give rise, by their oxidation, to the peculiar coloration seen
in carboluria. In certain diseases other members of the group are increased,
and give rise to the phenomena of alcaptonuria. In this state the urine
develops, on standing, a dark colour, like that seen in carboluria ; and
Boedecker in 1861 isolated a substance which he termed alkapton, to the
oxidation of which he held the colour due. Alkapton was shown by Marshall
and Kirk to be impure uroleucic acid (vide supra). This latter substance,
however, is not wholly responsible for the coloration phenomenon. Wolkow
and Baumann 2 have recently shown that in a case investigated by them the
" alkaptonuria " was almost wholly due to the presence of homogeiitisic acid
(supra). Pyrocatechin is doubtless sometimes the cause.3 Most hydroxy-
derivatives of benzene in alkaline solution develop a dark coloration on
exposure to the air 4 (cf . p. 630).

The quantity of phenol and kresol in the urine is increased in extreme
constipation, in obstruction of the lower bowel, in peritonitis, and in pyaemia
(cf. indoxyl, infra, and p. 631).

Indoxyl and skatoxyl. — These, although nitrogenous compounds,
are closely related to the substances just treated, and may fitly be
considered here.

Indoxyl (C?H4.NH.CH.C.OH).— The so-called urinary indican is
indoxylsnlphuric acid. In normal urine on a mixed diet, the quantity
present is only from 5 to 20 mgrins. In herbivora the quantity
is much larger. It is absent from the urine of new-born children
(Senator). Indoxyl is derived from, oxidation in the body of the indol
absorbed from the bowel, and its amount is increased, like that of the
urinary phenols, by all causes which lead to increased bacterial decom-
position of proteids, in the intestine or elsewhere ; and by circumstances
which favour the absorption of the indol when formed (intestinal
obstruction, etc.). Skatoxyl (C9H8NOH) is derived from skatol (methyl-
indol), and accompanies indoxyl into the urine by parallel paths and
from kindred causes. Like indoxyl, it is present as a conjugated
sulphate.

By oxidation indoxyl forms indigo-blue and indigo-red, while skatoxyl
similarly yields red pigments. The consequent colour phenomena
which arise in the urine are discussed under the head of the pigments.

CARBOHYDRATES AND BELATED SUBSTANCES.

Normal urine contains small quantities of certain carbohydrates.
Under ordinary circumstances the physiological limit extends only to
a minute quantity of any one of these substances ; but, in the urine of
women during lactation, milk-sugar may occur in very considerable
amount, without departure from what must be considered physiological
conditions.

1 For phenaceturic acid, see under hippuric acid. 2 Loc. cit.

3 Cf. v. Jaksch, "Kliuische Diagnostik," 4th edition, 1896, p. 415.

4 The behaviour of the alkaline solution of pyrogallic acid used in photography will
be an example familiar to many.

608 THE CHEMISTR Y OF THE URINE.

The general chemistry of the carbohydrates is elsewhere discussed.
We shall deal only with their relation to the urine : —

(a) Dextrose. — The question as to whether or not small amounts of
grape-sugar are excreted in the urine during normal health has been
much debated. It is needless to confuse the issue by an attempt to
define what is meant by " normal " urine. We may ask rather, Does
the urine of the average individual, living an ordinary life, upon ordi-
nary diet, generally contain sugar ? There can be little doubt, in the
light of our present knowledge, that this question must be answered in
the affirmative.

Briicke l was the first (in 1858) to state that sugar is normally present in
human urine, and Bence Jones2 was a^ early supporter of the view. For
some years, however, the question was treated as an open one, and in 1871,
Seegen, after careful study of the matter, decided that means were not then
to hand by which its presence could be proved with certainty. Pavy,3 in
1878, affirmed that it was certainly a normal constituent, and has always
maintained this position. Since then other observers (in England especially
Sir G. Johnson and G. Stillingfleet Johnson4) have stoutly maintained the
contrary. The chief criticism of the earlier methods of demonstration which
gave positive results was that, while they depended upon reduction tests, they
did not eliminate the influence of other reducing substances. The creatinin,
uric acid, hippuric acid, and other aromatic constituents of the urine, all tend
to reduce salts of the heavy metals in alkaline solution. It is admitted by all
observers that normal urine exercises a reducing power on copper solutions,
which, if due to glucose, would indicate the presence of about O'l to 0*3 per
cent, of this substance. But it is equally admitted by all that a large part of
this reduction is due to the other substances mentioned above. The question
which has been at issue is as to whether any part of the reducing power is due
to sugar.

It is evident that we cannot rely alone upon reduction tests applied to
the original urine. The more accurate knowledge that we now posesss with
regard to the question has been obtained by three lines of investigation : —
(1) By the application of direct tests which are unaffected by substances
other than sugar; (2) by the use of methods which involve a preliminary
removal of interfering substances; and (3) by the employment of means
whereby the sugar itself is separated from the urine unmixed with the con-
stituents which lead to error.

1. The plienylhydrazine test of Fischer and v. Jakscli has given positive
results in the hands of several observers when applied directly to normal urine.5
The yellow crystals of phenylglucosazone may certainly be obtained from
urine containing as little as O'l per cent, of sugar (v. Jakscli). In my own
experience great care is generally necessary to secure unequivocal results in the
case of normal urine. As a crucial test, it suffers the disadvantage of yielding
crystals with the glycuronic acid compounds ; the amount of crystals obtain-
able from normal urine direct being in general too small for discriminating
tests to be applied to them. After the sugar has been previously isolated, the
reaction with phenylhydrazine is, however, of the utmost value as a confirma-
tory test (vide infra}.

A colour reaction may be observed in normal urine, which, is held by some
to be conclusive of the presence of sugar. This is the furfural reaction. A

1 Sitzungsb. d. Jc. Akad. d. Wissensch., Wien, 1858, Bd. xxix. S. 346.

2 Journ. Chem. Soc. , London, vol. xiv. p. 22.

3 Guy's Hosp. Rep., London, vol. x'xi. p. 413.

4 See articles and correspondence in the Lancet, London, during July and August 1894.

5 Cf. E. Roos, Ztschr.f. physiol. Chem., Strassburg, 1891, Bd. xv. S. 523; A. H. Allen,
" Chemistry of the Urine," 1895, p. 89.

DEXTROSE. 609

small quantity of /?-naphthol dissolved in chloroform is added, and then some
strong sulphuric acid. The latter, by acting upon the traces of sugar present,
produces furfurol, which, with the /3-naphthol, gives a violet or carmine-red
coloration.1 This test is also affected by the presence of glycuronic acid.

2. By treating the urine with mercuric acetate, creatinin and the various
non-saccharine reducing substances are precipitated. G. S. Johnson has main-
tained that in the nitrate obtained after treating a normal urine in this way,
no sugar reaction can be observed. A. H. Allen has, however, obtained posi-
tive results.2

3. By far the most satisfactory evidence is obtained by methods
capable of isolating any sugar that may be present. Moritz, by treating
5 to 6 litres of the urine of healthy men with lead salts and ammonia,
and by decomposing the precipitate so obtained with sulphuretted
hydrogen (Briicke's method), was able to isolate a substance which gave
all the reactions of grape-sugar. It was fermentable with yeast, yielded
phenylglucosazone crystals, was dextrorotatory, and reduced alkaline
copper and bismuth solutions.3 Pavy, by a similar method, long ago
obtained a fermentable reducing body from normal urine, and he has
since extended his earlier results by showing that the substance yields
phenylglucosazone.4

When solutions of carbohydrates are treated with benzoylchloride,
they yield a precipitate of insoluble compounds (esters) with benzoic
acid. Glycuronic acid gives no precipitate. Baumann has applied this
fact to the separation of urinary carbohydrates ; and, in the hands of
Wedenski 5 and Baisch,6 the method has yielded very convincing results.
The last observer decomposed the benzoic esters he obtained from
normal urine, with alcoholic soda, and isolated, inter alia, a sugar which
gave, with phenylhydrazine, an osazone melting at the right temperature
for that of glucose. The product gave also all the other reactions of
dextrose. The quantity found varied from 0'08 to 0*18 grms. in the
twenty-four hours.

The evidence we have detailed leaves little room for doubt that
grape-sugar is a constituent of normal urine, and we may take the
figures just quoted from Baisch as the most accurate estimate we possess
of its amount. Pavy and v. Udransky found larger quantities, and
Seegen considerably less, but their methods are perhaps more open to
question from the quantitative point of view.7

Alimentary glycosuria. — It is certain that many healthy individuals, after
a meal rich in sugar, and especially after the consumption of an excessive
amount of sugar in solution — as in sweet wines and the like — excrete tem-
porarily quantities of sugar greatly in excess of the small normal constant we
have just discussed. The explanation of this is probably to be found in the
observation of Ginsberg,8 that when large quantities of sugar are present

1 Molisch, CentralbLf. d. med. Wissensch., Berlin, 1888, Nos. 34 and 49. Also Luther,
Chem. Centr.-BL, Leipzig, 1891, Bd. ii. S. 90 j v. Udransky, Ztschr.f.physiol. Chem., Strass-
burg, 1888, Bd. xii. S. 380.

'2 Loc. tit., p. 19.

3 Deutsches Arch. f. klin. Med., Leipzig, 1890, Bd. xlvi. S. 252. A complete review of
the earlier literature will he found in this paper.

4 "Physiology of the Carbohydrates," 1894, p. 180 et seq.

5 Ztschr. f. physiol. Chem., Strasshurg, 1889, Bd. xiii. S. 122.

6 Ibid., 1894, Bd. xviii. S. 193 ; 1895, xix. S. 348 ; xx. S. 249.

7 For a criticism of Briicke's lead-precipitation method, see Colls, Journ. Physiol., Cam-
bridge and London, 1896, vol. xx. p. 109.

8 Arch.f. d. ges. Physiol., Bonn, 1889, Bd. xliv. S. 306.

VOL. I.— 39

6 io THE CHEMISTRY OF THE URINE.

in the bowel, some may be absorbed, not by the ordinary path of the capil-
laries and portal vessels, but by way of the lacteals and thoracic duct, thus
escaping the influence of the liver. The percentage of sugar in the blood is
thereby increased, and the excess is excreted by the kidneys. A distinction
between such cases and those in which diabetes exists, is seen in the fact that
the "alimentary glycosuria " is not produced by starchy foods, however large
the quantity taken, but only by excess of ready-formed sugar in the diet.1
According to Moritz, dextrose, laevulose, cane-sugar, and probably milk-sugar,
may all appear unaltered in the urine when severally taken by the mouth in
considerable quantity (e.g. 200 grins.). Such alimentary effects last from
three to six hours.2

Pathological glycosuria.- — The great increase of dextrose in the urine
of diabetes is a familiar phenomenon. Its excretion may range in this disease
from quite small quantities up to 500 or 600 grms. per diem. The morning
urine is apt to contain least sugar ; that passed three or four hours after a
meal generally contains most.

In other diseased conditions, quite apart from diabetes, a special tendency
has been observed to the occurrence of an alimentary glycosuria ; gout,
exophthalmic goitre, and certain nervous diseases may be instanced. An
increase of reducing substances, almost certainly consisting at least in part of
dextrose, is said to be found in the urine of some pysemic conditions. As the
effect of certain drugs and toxic substances, such as chloral, chloral amide,
morphine, hydrocyanic acid, turpentine, and carbon monoxide, the urine
commonly reduces copper solutions ; but in most of these cases the reduction
is due to conjugated compounds of glycuronic acid, and not to dextrose
(vide p. 613).

The detection and estimation of dextrose, which, as we have seen, have
proved difficult problems in the case of the minute amount normally present
in urine, become easy when the increased amount excreted in disease is to be
dealt with. The methods used depend upon the reducing power which the
sugar exerts upon metallic salts, or upon certain coloured organic substances,
and these may be checked by the fermentation of the suspected urine by
means of yeast, by the indications of the phenylhydrazine test, and again by
the use of the polariscope. Of reduction tests a great number have been
proposed; we shall here refer to two only. The well-known Fehling's test
consists of a solution of copper sulphate of definite strength, mixed with caustic
alkali and alkaline tartrates (Rochelle salt). The presence of the last pre-
vents the precipitation of cupric oxide when the solution is boiled by itself,
but allows the precipitation of yellow or cuprous oxide when reduction has
occurred from the action of the sugar. The reduction may be observed,
after boiling the liquid, if the urine contain not less than 0*2 per cent, of
dextrose. If less than about 0*5 per cent, be present, no precipitation occurs
until after cooling, when the liquid becomes opaque, and of a greenish colour.
With larger amounts a definite precipitate of a yellow or red colour is seen,
immediately after heating the test with a small proportion of the urine.
Nylander's solution has some advantages over Fehling's, in that it is much less
affected by creatinin, urates, and reducing bodies other than sugar (vide supra).
It is a modification of the bismuth test, originally suggested by Bottcher, and
is prepared with the same reagents as Fehling's solution, but with the sub-
stitution of basic nitrate of bismuth for the copper sulphate. On boiling this
solution with urine containing sugar, the liquid turns black. The reaction is
easily seen if O'l per cent, or upwards of dextrose is present.

Both solutions are reduced by lactose and by glycuronic acid; but the
former of these substances can only be present under special circumstances

1 Of. Neumeister, " Lehrbuch der physiol. Chem.," Th. 2, S. 306.

2 Moritz, Centralbl.f. klin. Mod., Bonn, Bd. xii. No. 28.

L^E VUL OSE — LA CTOSE. 6 1 1

(infra), while the latter is never present in the urine in amounts large
enough to lead to confusion with glycosuria in the pathological sense;
except when quite special substances have been taken by the mouth. But
in order to make the identification of glucose more certain, we may confirm
the results of a reduction test by means of yeast fermentation. Lactose and
glycuronic acid do not ferment. The urine should be placed in a test-tube
so as completely to fill it, and the tube inverted over a basin containing a
further quantity of the urine. After ascertaining that no air is present, a
small piece of pressed yeast is passed under the inverted tube, and the latter
secured in position with a clamp. The tube is then allowed to stand at a
temperature of 25° to 30° C. In twelve hours, if dextrose be present in
quantity, a notable amount of carbon dioxide will have collected in the upper
part of the tube. The fermentation test is very conclusive, but it is not easily
obtained when less than 0*5 per cent, dextrose is present. With phenyl-
hydrazine, however, as already stated, urines containing as little as O'l per
cent, will yield easily recognisable crystals of phenylglucosazone. The fact
that Isevulose also ferments with yeast, and yields an identical glucosazone, is
of little importance in practice ; this sugar is rarely present (infra), and except
under special circumstances it is unnecessary to distinguish it from dextrose.

For the estimation of dextrose, modifications of the various tests just
described are employed. We may ascertain, for instance, how much of a
given specimen of urine is required to precipitate all the copper from a
measured quantity of standardised Fehling solution. Or, with greater con-
venience, we may employ the modified copper test known as Pavy's solution.
This contains a large excess of ammonia, in addition to the ordinary constitu-
ents of Fehling's test. In ammoniacal solution cupric salts are blue, but
cuprous salts are colourless. By noting, therefore, the amount of the urine
(diluted, if necessary, to a known bulk) which is necessary to decolorise a
given quantity of the standard Pavy's test, we obtain a measure of its reducing
power, and so of the dextrose present. Again, we can adapt the fermentation
test to quantitative purposes, by measuring the C02 produced from a definite
quantity of the urine, or by ascertaining the diminution in the specific gravity
of the fluid which follows the destruction of the sugar by the yeast. Lastly,
we may employ the polarimeter, which indicates the percentage of dextrose by
the number of degrees through which a polarised ray is turned to the right
on passing through a layer of urine of determinate depth. A drawback to
the use of this instrument, when applied to the urine, arises from the fact
that other substances may be present which are optically active.1

(b) Laevulose. — The occurrence of laevulose in normal urine has not
been observed ; but in certain cases of glycosuria it is said to be present.
Kulz2 separated from the urine of a diabetic a laevorotatory sugar,
which possessed all the properties of ordinary laevulose, except that,
unlike the latter, it was precipitated by basic acetate of lead. When
laevulose is given by the mouth in diabetes, it can be utilised in
metabolism more readily than dextrose, and within certain limits of
administration it is not excreted in the urine. Beyond these limits,
however, it is eliminated partly unaltered and partly as dextrose.3

(c) Lactose. — That a reducing substance is apt to appear in the urine
of women during the period of lactation, was first observed by Heller as
far back as 1849 ; and F. Hofmeister,4 in 1877, showed definitely that

1 Details of all these processes will be found in practical handbooks.

2 Ztschr.f. BioL, Miinchen, 1890, Bd. ix. S. 228. References to the earlier literature
will be found in this paper.

3 Cf. Haycraft, Ztschr. f. physiol. Chem., Strassburg, Bd. xix. S. 137 ; Hale White,
Guy's Hosp. Rep., London, 1893, p. 133.

14 Ztschr. /. physiol. Chem., Strassburg, 1877, Bd. i. S. 104.

612 THE CHEMISTRY OF THE URINE.

this was milk-sugar. Only lately, however, has it been recognised that
laetosuria is an almost constant phenomenon during lactation. Even
when the conditions are altogether favourable and normal, it is seldom
that the sugar is not present in the urine at some portion of the period.
When any interruption to the natural removal of the milk occurs, the
amount may be very considerable.

The phenomenon is easily understood when it is remembered that
the lactose excreted into the blood from the mammary gland does not
come under the normal influence of the liver. Eecent researches,
indeed, indicate that milk-sugar cannot in any case act as a precursor
of glycogen, until it has been inverted. When lactose is taken by the
mouth, this inversion occurs before or during absorption from the bowel.

The complete identification of lactose in the urine is difficult, unless it be
first isolated by processes too lengthy to be described here. But if the urine
exhibit the following characters, the presence of lactose is established almost
without the possibility of doubt. It should reduce copper and bismuth solu-
tion ; but, with the fermentation test, it should give negative results for the
first twenty-four hours of the experiment, and it should give no definite crystal-
line precipitate with the phenylhydrazine test when this is directly applied.1
On the other hand, after boiling with 5 per cent, sulphuric acid for a short time,
the urine should, if first neutralised with ammonia, give the phenylhydrazine
test readily; crystals of dextrosazone should be thus obtained, and, with
proper precautions, galactosazone crystals may be also distinguished. Although
the lactose is converted by the mineral acid into dextrose and galactose, a
fermentation is not always to be obtained after treatment, as the large amount
of sulphate, which is present after neutralising the acid, interferes with the
growth of the yeast. If the reducing power of the urine be estimated, this
should be found increased after boiling with mineral acid, but unaffected by
boiling with citric acid.

(d) Pentoses — Xylose, arabinose (C5H10Ofi). — Ebstein,2 Salkowski,3 and
others have observed the presence of 5 -carbon sugars in the urine.
They are generally, when present, derived from the food, and then pro-
bably arise from certain fruits, especially cherries and plums, which
contain either pentoses or a precursor of these sugars, the so-called
" fruit gum." The pentoses are apparently assimilable with difficulty.
Under exceptional circumstances, it seems possible that they may
arise in the organism, as the result of disordered metabolism. It has
been found that a certain proteid, derived from the pancreas, yields
pentoses when boiled with acids, and some such substance may be the
source of pentosuria.

The pentoses give a red coloration when treated with strong hydrochloric
acid in the presence of phloroglucin (Tollens' reaction). Glycuronic acid,
however, behaves similarly. They reduce copper solutions, and yield an
osazone after somewhat prolonged warming with phenylhydrazine, but they
do not ferment.

(e) Isomaltose. — When the mixture of carbohydrates obtained from
normal urine by precipitation with benzoylchloride is fermented with
yeast, so that all the dextrose present is destroyed, there remain small

1 Lactosazone does not crystallise readily, except from pure solutions of the sugar.

2 Firchow's Archiv, 1892, Bd. cxxix. S* 40] ; cxxxii. S; 368.

3 Centralbl. f. d, med. Wissenscli., Berlin, 1893, S. 193; Berl. klin. Wclmschr.,
1895, No, 17.

ANIMAL GUM—GL YCURONIC ACID. 613

quantities of a sugar, which, though not fermentable, gives a well-
crystallised osazone, and reduces Fehling's solution. According to the
researches of Baisch,1 the properties of this substance agree with those
of " isomaltose."

(f) Animal gum. — The third and remaining carbohydrate which
separates from normal urine when this is treated with benzoylchloride,
is a dextrin-like substance, in all probability identical with "animal
gum." This was first isolated from urine by Landwehr,2 who took
advantage for this purpose of the insolubility of its copper compound.
Its presence has been confirmed both by Wedenski and Baisch, who
employed the benzoylchloride method.

The substance does not reduce metallic salts, but, on the other hand,
on boiling with mineral acids, it yields a derivative which will reduce
Fehling's and Nylander's reagents freely. Simultaneously it yields
(like many other carbohydrates and certain of the aromatic constituents
of the urine) with acids a brown flocculent precipitate of the " humous
substances " of v. Udransky.3 It is due to the presence of this substance
that the reducing power of most urines is increased after boiling with
mineral acids.

(g) G-lycuronic acid. — The chemical relationship of this acid to the
glucoses is seen by a comparison of their respective formulas : —

CH2HO(CH.OH)4CHO COOH.(CH.OH)4CHO

(glucose) (glycuronic acid)

It is derived from these sugars by oxidation of the primary alcohol
group, CH2.OH, to the carboxyl group, COOH. It is at once, therefore,
an aldehyde and an acid. As an aldehyde, it reduces copper solutions.

It should be understood that glycuronic acid is never a constituent
of normal urine in appreciable amount, nor does it appear as the result
of pathological processes in the ordinary sense. Its presence almost
always depends upon the ingestion of special substances, which are for
the most part foreign to ordinary foodstuffs ; and, when excreted, it is
" conjugated " with these, or with derivatives of these.

It is apparently an intermediate product in the metabolism of
carbohydrates, which, normally, becomes fully oxidised in the body ;
but which, when conjugated with the exceptional substances referred to,
escapes oxidation, and appears in the urine, just as the easily oxidisable
glycin is protected by conjugation with benzoic acid and appears as
hippuric acid.

Some of the substances which form these conjugated compounds
with glycuronic acid, are those which ordinarily form conjugated or
ethereal sulphates (cf. pp. 606 and 631), especially the aromatic hydroxy-
compounds. Phenol- indoxyl- and skatoxyl-glycuronic acids and many
analogues have been described in the urine. But apparently the sulphate
conjugation is the more constant process, and it is only when the above
substances are present in very large amount that their glycuronic con-
jugates appear in addition to their sulphuric acid compounds, — in
general, only when they, or their precursors, are given abundantly by
the mouth for the purposes of experiment.

Of more practical importance are those conjugated compounds of

1 Baisch, Ztschr. f, physioL OJiem., Strassburg, Bd. xx. S. 249.

2 Centralbl.f. d. med. Wissensch., Berlin, 1885, S. 369.

3 Ztschr. f. physioL Chem., Strassburg, 1888, Bd. xii. S. 33.

6 14 THE CHEMISTRY OF THE URINE.

glycuronic acid with members of the fatty group of alcohols, which are
excreted after the use of certain common drugs. Thus, when chloral
hydrate is being taken, trichlorethylglycuronic acid (urochloralic acid) l
is often found in the urine, and analogous compounds arise after the
administration of butylchloral hydrate and chloroform.

All these compounds are leevorotatory, though glycuronic acid itself
is dextrorotatory ; many of them, urochloralic acid for instance, reduce
bismuth and copper solutions freely, and their presence may therefore
lead to error in testing for sugar ; but they are not fermentable. They
split up with varying degrees of ease into glycuronic acid and the
conjugated substance, either by boiling with mineral acids, or when
heated with water in sealed tubes ; »ome (e.g. phenolglycuronic acid)
decompose when boiled with water alone.

Glycuronic acid itself is a syrupy substance, soluble in water and
alcohol ; but when its aqueous solutions are boiled or evaporated, it
loses water, and forms a crystalline anhydride which is insoluble in
alcohol.

To separate the urinary glycuronic compounds, a large quantity of urine is
precipitated with acetate of lead, and the precipitate decomposed with
sulphuretted hydrogen. After filtering, barium hydrate is added to the
solution. The sulphates and phosphates thus precipitated are filtered off, and
alcohol added to the filtrate, whereupon the barium salts of the conjugated
glycuronic acids crystallise out.2

OTHER ORGANIC COMPOUNDS.

Oxalic acid. — Small quantities of oxalic acid (COOH)2 are present
in all specimens of urine, about 50 mgrms. being the average for the
day's excretion. Much of this may arise directly from preformed
oxalates ingested with the food, as all vegetable food contains traces of
these salts, and direct experiment has shown that they are susceptible
of but very incomplete oxidation in the body.3 But oxalic acid does
not disappear from the urine when pure flesh-food is taken, nor even
during starvation;4 it would thus seem certain that it can arise
from proteid metabolism. It is, in certain cases, very largely increased
in amount, from causes which are not clearly understood. Some
authorities hold that these cases of " oxaluria " depend always upon
excess of preformed oxalates in the diet ; but no one who has observed
the marked tendency to increased oxalate excretion in diabetes, or the
way in which, in some cases of glycosuria, a temporary decrease in the
sugar may be associated with an increase of oxalates, can doubt that it
may arise also from incomplete oxidation of carbohydrates.

Oxalate of calcium frequently separates from the urine to form a
crystalline deposit. It mostly takes the form of the so-called
" envelope crystals," but may appear as dumb-bells, and is often seen as
clear o voids (Fig. 56). It is responsible for the formation of a variety of
urinary calculus.

1 This was the first of these substances to be described, vide Musculus and v. Mering,
Ber. d. deutsch. chem. Gesellsch., Berlin, 1875, Bd. viii. S. 662.

2 Of. Ashdown, Brit. Med. Journ., London, 1890, vol. i. p. 169.

8Gaglio, Arch. /. exper. Path. u. PIiarmaJcoL , Leipzig, 1887, Bd. xxii. S. 246.
4Marfori, Jahresb. it. d. Fortschr. d. Thier-Chem., Wiesbaden, 1892, S. 72.

ACIDS AND HYDROXYAC1DS.

615

To demonstrate the presence of oxalic acid, and to estimate its amount, a
litre of urine should be treated with calcium chloride and ammonia, and
afterwards made acid with acetic acid. After twenty-four hours' standing,
the crystalline precipitate, which contains uric acid crystals mixed with
calcium oxalate, is filtered off and treated with dilute hydrochloric acid. The
oxalate dissolves, and is reprecipitated, after filtering off the uric acid, by the
addition of ammonia. At a dull red heat it is converted into calcium
carbonate, and may be weighed as such.

FIG. 56. — Calcium oxalate.

Acids and hydroxyacids of the fatty series, with derived
substances. — Normal urine contains minute quantities of the volatile
fatty acids, especially acetic, but also formic, propionic, and butyric
acids.1 They do not, as a rule, amount collectively to more than some
50 mgrms. in the day's excretion, and they arise doubtless from the
bacterial decomposition of carbohydrates and proteids in the lower
bowel. Fatty acids of low atomic weight, such as the above, are less
easily oxidised in the organism than are those of greater complexity.2

The amount is considerable in the urine of herbivora, and in man it is
increased by many diseases, especially by such as lead to increased decomposi-
tion in the bowel, or to prolonged constipation.

When a specimen of urine undergoes ammoniacal fermentation, the
volatile acids are increased at the expense of the carbohydrates it contains.3

These acids are obtained from the urine by distillation with phosphoric

^Cf. v. Jaksch, Ztschr. f. physiol. Chem., Strassburg, 1886, Bd. x. S. 536. The
earlier literature is here summarised.

2C. Schotten, ibid., 1883, Bd. vii. S. 375.
3Salkowski, ibid., 1889, Bd. xiii. S. 264.

616 THE CHEMISTRY OP THE URINE.

acid. They are found in the distillate so obtained, together with traces of
hydrochloric and benzoic acids, phenol, and acetone.

Sarcolactic acid is not a normal component of human urine, but it appears
in many diseased or abnormal conditions of the body, of which it may be said
generally that they involve either a suspension of normal hepatic functions or
interference with the proper oxidative processes of the body.1 It was first
observed in the urine of phosphorus poisoning, and of acute yellow hepatic
atrophy,2 and may be always demonstrated in these conditions. It is found
also after slow asphyxia ; in poisoning by carbon monoxide, in prolonged
anaemia, and shortly before death in very many diseases. That it may appear
after prolonged and severe exercise, is doubtless explained by the fact that
oxidation in the body has not kept pace with the increased production of
lactates in the muscles.3

The three closely related substances, (3-hydroxybutyric acid, acetacetic
acid (diacetic), and acetone rise to importance only in diabetes, but small
quantities of the last may be found in normal urine, and all may be increased
in disease apart from glycosuria. The following equations show the relation
which obtains between them : 4 —

CH3CH(OH).CH2.COOH + 0 - CH8.CO— CH2.COOH + H20

(/3-hydroxybutyric acid) (diacetic acid)

CH3.CO— CH2.COOH - CH3.CO.CH3 + C02

(diacetic acid) (acetone)

The first only appears in the urine in conjunction with the others, but
either of the two latter may be found alone. Large amounts of all three may
be found in diabetes ; of the hydroxy-acid many grammes may be passed in
the day.

The presence of diacetic acid may be demonstrated by making the urine
acid with sulphuric acid, and shaking with ether ; the latter, which extracts
the substance, is then transferred to another vessel, and is shaken with a weak
aqueous solution of ferric chloride, which, if acetacetic acid was present in the
urine, becomes of deep burgundy wine colour.

In testing for the hydroxy butyric acid, advantage is taken of the fact that
it yields a volatile derivative, a crotonic acid, on distilling with sulphuric acid.
This substance crystallises out from the distillate of the urine, and may be
identified by its melting point (72° C.). The urinary hydroxy butyric acid is
laevorotatory.

Acetone is identified in a urinary distillate by first adding a few drops of a
solution of sodium nitroprusside, and then caustic alkali, whereupon, in the
presence of acetone, a fine cherry-red colour is produced. Acetic acid subse-
quently added in excess changes the colour to purple (Legal's test).

THE COLOUR OF URINE AND THE CHEMISTRY OF THE PIGMENTS.

It is a familiar fact that, under physiological conditions, the urine
may be almost colourless, or may exhibit tints varying from a pale
straw yellow, through deep orange, to reddish brown. In its commonest
condition it is yellow. Pathologically, the colour may undergo variations
wider than those seen in health.

1 Cf. Araki, Ztschr. f. physiol. Chem., Strassburg, 1895, Bd. xix. S. 422, with reference
to previous papers by this author.

2Schultzenu. Riess, Chem. Centr.-BL, Leipzig, 1869, S. 681.

3 Colasanti and Moscatelli, Arch. f. exper. Path. u. PharmdkoL, Leipzig, 1890, Bd.
xxvii. S. 158.

4 Cf. Miukowski, ibid., 1893, Bd. xxxi. S. 183.

THE COL 0 UR OF URINE. 6 1 7

An effort has been made to refer the varying degree of pigmentation
to a standard colour scale, so that the condition of a given specimen, as
regards colour, might be quantitatively expressed. But much difficulty
intervenes, in that variations may be due, not alone to differing amounts
of a single colouring matter, but to independent and quite irregular
variations in at least three or four. The endeavour to attain to quanti-
tative precision has on this account proved unsuccessful in practice.1
We may content ourselves with speaking of physiological urine as pale,
normal, or high-coloured respectively, and assist the description by
comparison with other substances of familiar appearance (" straw-
coloured," " sherry-coloured," etc.).

Pale urine is usually of low density, and contains a small proportion
of solid matter. It results from all causes which promote a copious
flow of fluid from the kidneys, such as free ingestion of liquids, a check
to the cutaneous transpiration (as from the effect of cold), and emotional
excitement.

High-coloured urine is generally of high density, and is excreted
when the transpiration from the skin is more than usually free, or
under conditions of high metabolic activity. After a full meal the
urine is often at once copious and of full colour.

In general the amount of pigment rises with an increase in the con-
stituents excreted by the renal epithelium, and not with the glomerular
excretives. The depth of colour may be affected by the reaction of the
urine ; other things being equal, an acid urine will show a darker tint
than one that is alkaline.

Examined directly by means of the spectroscope, fresh normal urine
is found nearly always to show no definite absorption-band ; a diffuse
absorption of the more refrangible rays being alone evident.

But by the aid of the spectropliotometer 2 we may measure the amount of
light absorption in any region of the spectrum apart from the presence of
actual bands. When light passes through urine, the amount of absorption
increases progressively from the mid-red to the violet.

Suppose the absolute absorption at any two points in this region of
spectrum be measured ; say in the neighbourhood of the Fraunhofer lines, E
and F respectively. If in any one specimen of normal urine the absorption
near F is found to be twice as great as that near E, then if the urine contained
but one pigment, this same ratio would be found in any other specimen. The
absorption at F would in all cases be double that at E. For, clearly, the
dilution of an individual pigment would decrease the absolute absorption
throughout the spectrum, but would leave the relative absorption at any two
points unaffected; similarly, concentration would increase the absolute, but
would nowhere affect the relative, absorption. But different specimens of
normal urine do not agree in this way. One urine may show more relative
absorption (say) in the mid-green, another more in the blue. This can only be
due to the fact that more than one pigment is concerned.3 Although it yields
no definite bands, the spectroscopic properties of fresh normal yellow urine
thus indicate some complexity in its pigmentation ; but the same experimental
evidence indicates nevertheless that no more than one pigment is usually
present in a relatively large amount.

1 By the use, however, of Lovibond's tintometer, the colour of urine under varying
circumstances may be very exactly imitated, and expressed in terms of a scale.

2 See this textbook, article "Hsemoglobin," p. 213.

3 This argument only holds for colouring matters which do .not undergo dissociation in
solution.

6i8 THE CHEMISTRY OF THE URINE.

The pigments of the urine have long received attention and have
been the subject of many laborious researches ; but, owing to the great
difficulties they present to the investigator, our knowledge of the
chemistry of most of them has remained indefinite. These difficulties
arise from various causes. Pigment metabolism appears to be always
of a highly conservative nature. The colouring matters found in the
epidermal structures of animals, serving for ornament, protection, or
other purposes, are almost always present in strikingly small quantity ;
and those which are purely excretory leave the body in equally small
proportionate amount.

The highly developed optical activity of these substances, which has
led us to group them together in a special class as " pigments," at the
same time gives to them a prominence in various phenomena, dispro-
portionate to the actual quantity in which they are present. The
urinary pigments are (at least, under normal conditions) quite minute
in amount, and this fact is the primary difficulty in the path of chemical
investigation. As Bunge has written, many endeavours have resulted
merely in applying Greek and Latin names to substances which have
been obtained in quantity too small for proper investigation.

The extremely delicate indications of the spectroscope have been of
the greatest assistance in overcoming this fundamental difficulty, and
our knowledge of pigments has been much extended by its use. But
evidence so gained has to be checked and assisted by other methods. A
complex spectrum may indicate a mixture of substances ; but it may,
with equal probability, be due to one alone. A mixture, on the con-
trary, may show but a single absorption-band, for the reason that of the
pigments present one alone extinguishes light in a specific region.

It is therefore easy, by a mere qualitative use of the spectroscope,
to mistake a mixture for a chemical individual. On the other hand,
very slight variations in the physical condition of a pigment, or a
minute change in its molecular constitution, may produce a great
effect upon its spectrum, and, unless we are aware of these conditions,
we may be led to see wide differences where chemically there is little or
none.

When, again, endeavours are made to isolate pigments by chemical
means, the great instability which they exhibit as a class is apt to lead
to error. So often has this danger been overlooked, that we are
compelled to attach no importance, beyond what accrues from historic
interest, to much of the work which has been done on this problem.

It is of prime importance, when we endeavour to obtain these
unstable substances in their integrity, that the use of highly active
reagents should be avoided.

We shall deal only with the pigments of which we have comparat-
ively accurate knowledge ; but it may be safely asserted that the four
substances now to be described form the basis of urinary chromatology.
These are urochrome, urobilin, uroerythrin, and hwmatoporpJiyrin. Other
pigments exist, and some have doubtless yet to be recognised, but they
are exceptional, or take but very small share in the coloration of the
urine.

Preformed pigments of normal urine— (a) The essential yellow
pigment, urochrome. — In 1864,Thudichum gave the name of urochrome
to preparations obtained from normal urine by complicated processes of
extraction. Thudichum's products undoubtedly contained a large pro-

PREFORMED PIGMENTS OF NORMAL URINE. 619

portion of the substance we are now to describe, but they were mixed
with urobilin and with decomposition products.

To A. E. Garrod l we owe a process for the extraction of the essential
yellow colouring matter, which is beyond reproach in its avoidance of
destructive reagents. It yields a product entitled to be considered, with
a large degree of probability, as a chemical individual.

Following Garrod, we shall describe this pigment under the name of
uroclirome — a name eminently fitted for a substance which is the prime
cause of the familiar colour of urine, but in the use of which we must
avoid historical confusion.

Between the uro chrome of Garrod and that described thirty years
earlier there is the difference between presumptive chemical individual-
ity and almost certain admixture. It should be stated, however, that
Thudichum still holds the pigment described by him to be a definite
substance, and has recently investigated certain of its reactions, which he
believes indicate for it the combined characters of an alcohol and a base.

Separation of urochrome (Garrod). — The urine is saturated with crystals
of ammonium sulphate, and, after standing, is filtered (vide infra, " Separation of
Urobilin"). The filtrate, which is still almost as highly coloured as the original
urine, is shaken with alcohol. The latter solvent separates rapidly from the
saline mixture, and is seen to withdraw a large proportion of the colouring
matter. Repeated extraction removes practically all. The alcoholic solution
is diluted with a large bulk of water, and the mixture again saturated with
ammonium sulphate \ by this procedure the alcohol is again made to separate
from the water, carrying the pigment with it, and a satisfactory washing of
the original extract is secured. This second alcoholic solution is now made
just alkaline with ammonia, and evaporated to dryness ; the residue is
extracted once or twice with acetic ether, which removes certain impurities,
and is again dissolved in strong alcohol. Somewhat prolonged digestion is
necessary at this stage, as the solubility in alcohol is decreased when the
pigment has once been taken to dryness. Finally, the alcohol is concentrated
till it has a deep orange colour, and is poured into at least an equal volume of
ether, when an amorphous brown precipitate falls, consisting of the greater
portion of the pigment present, in almost pure condition. The precipitate
may be filtered off, dried on the paper, and washed with a little chloroform
and absolute alcohol.2

Properties. — The substance so prepared is a hygroscopic, brown,
amorphous substance, easily soluble in water, much less soluble in
alcohol ; only slightly soluble in acetic ether, amyl alcohol, or acetone ;
and insoluble in chloroform, ether, and benzene. Its solutions show no
definite spectroscopic absorption-bands, even after the addition of acids.
Zinc chloride and ammonia produce no fluorescence. Alkalies give the
solution a brownish tint, acids a reddish brown. The pigment forms
insoluble compounds with the heavy metals, and is precipitated by
phosphotungstic and phosphomolybdic acids. With strong nitric acid
it undergoes a colour change resembling the xantho-proteic reaction.

Urochrome we have seen to be a pigment which can be removed
from the urine without the use of strong reagents, and in the removal
of which the fluid loses nearly all its colour. At the same time, its aqueous

1 Proc. Roy. Soc. London, 1894, vol. Iv. p. 394.

2 See also Kramm, Deutsche med. Wclmschr., Leipzig, 1896, Bd. xxii. S. 25 arid 42. This
author separates the pigment by an entirely different method. He confirms Garrod's
original account of its properties.

620 THE CHEMISTRY OF THE URINE.

solutions have a tint like that of urine itself, and, like normal urine,
show no absorption-bands. There can be no doubt, therefore, that it is
the essential cause of normal urinary coloration.

Physiological relations, — Until quite recently, we had no knowledge
of the chemical relationship, or of the metabolic precursors of this im-
portant physiological pigment. But Biva x and Chiodera 2 have obtained,
by the action of potassium permanganate upon solutions of urobiliii,
a substance which they believe to be identical with urochrome. A. E.
Garrod3 has added still more conclusive evidence for the existence
of a simple relation between this pigment and urobilin, by observing
that alcoholic solutions of pure urochrome, when treated with aldehyde
(which we may believe acts as a milct reducing agent), yields a pigment
showing the spectrum and all the more characteristic properties of
urobilin. The establishment of this relation is most important in
bringing our knowledge of physiological pigments into line, since, as
will be shown immediately, the derivation of urobilin from blood and
bile pigments is clearly established. We can now ascribe a similar
origin to the fundamental colouring matter of urine.

(b) Urobilin. — In 1868, Jaffe,4 as an outcome of a spectroscopic
study of the urine, discovered a pigment with well-characterised pro-
perties, to which he gave the name of urobilin.

This pigment is perhaps scarcely entitled to be classified among
the preformed pigments of normal urine, for it is present as a rule in
minimal amount and almost always in the form of a chromogen. But on
rare occasions the free pigment is found in the fresh urine of normal
individuals, and, moreover, the importance of urobilin in other respects
makes it necessary to give it a prominent place in this section. It was
the first physiological urinary pigment of which we had accurate know-
ledge from the point of view of genesis and metabolic history. Its
increase in disease is a familiar phenomenon. These facts and its well-
marked spectroscopic characters have made it predominant in the
literature of urinary pigments. Even at the present time it is some-
times described as the essential colouring matter of urine, an error
which is at once demonstrated if the spectroscopic indications of normal
urine and of weak solutions of pure urobilin are compared.

Separation. — When zinc chloride and ammonia are added to urine in due
proportion, a precipitate is obtained (cf. " Separation of Creatinin," p. 599), which
contains much of the urobilin present. This method of precipitation was used
by Jaffe, and from the zinc precipitate lie succeeded in extracting the pigment
in a remarkably pure condition, but in small quantity, and by a somewhat
complicated procedure.

Menu 5 later showed that saturation of the urine with ammonium sulphate,
after acidification with weak sulphuric acid, produced a complete precipitation
of this pigment. The precipitate thus produced, which mainly consists of
pigmented urates, will yield to acid alcohol a solution, in which the character-
istic absorption-band of acid urobilin, to be later described, is easily seen.
Even when normal urine has been employed, the spectrum may be observed
after this procedure, for the bandless chromogen is decomposed by the acid

1 G-azz. med. di Torino, 1896, vol. xlvii. No. 12.

2 Arch. ital. di din. med., Milan, 1896, vol. xxxv. p. 505.
sJourn. PhysioL, Cambridge and London, 1897, vol. xxi. p. 190.

4 CentraM.f. d. med. Wissensch., Berlin, 1868, Bd. vi. S. 243 ; Virchow's Archiv, 1869,
Bd. xlvii. S. 405.

5 Bull. Acad. de med., Paris, 1878, tome vii. p. 671.

UROBILIN. 621

employed. When a urine rich in urobilin is saturated with ammonium
sulphate (best after previous removal of the urates by preliminary saturation
with chloride of ammonium), and acidified with sulphuric acid, it will yield
the pigment when shaken with a mixture of ether and chloroform. From this
organic solvent distilled water will again remove all the urobilin, and from
the water it may be precipitated by the further use of ammonium sulphate.
A method of separation may be based upon these facts which will yield a
very pure product in comparatively large amount.1

Properties, — Urobilin is an extremely soluble substance, dissolving
freely in all ordinary solvents. It is, however, proportionately less
soluble in water than is urochrome, though much more readily soluble
than the latter in alcohol and other organic liquids. Its solutions, when
concentrated, have a brown colour ; when more dilute tbey are yellow ;
on great dilution they exhibit a highly characteristic change to a dull
pink colour.

An alcoholic solution of the pure pigment free from extraneous acid
or alkali exhibits a green fluorescence quite apart from the addition of
reagents. When, however, zinc chloride and ammonia are added, a
greatly increased fluorescence is produced. This striking reaction is of
much value in the identification of urobilin ; it may be obtained after
great dilution.

Solutions of urobilin exhibit very definite spectroscopic phenomena.
In clear acid solutions of moderate strength, a single absorption-band is
seen between tbe Fraunhofer lines I and F, slightly overlapping the
latter ; situate, therefore, at the junction of the green and blue of the
spectrum (Fig. 57, Spectrum 4). In highly concentrated solution this band
is lost in a general absorption of the more refrangible rays. On diluting
such a concentrated solution a broad band first appears with a region of
complete blackness towards red, and a dark shading towards violet. As
dilution proceeds the shading first disappears, and then the dark portion
of the band shrinks till its limits extend from about X 508 to X 486.
After this the width of the band is constant, until with very large
dilution it grows faint and ultimately disappears (Fig. 57, Spectrum 5).
The activity of the pigment in absorbing light in this region is enormous,
and a solution so dilute as to have a very faint colour indeed, will show
a well-marked band. An absorption-band of an intensity such as is
occasionally seen in normal urine, would correspond to that of an
almost colourless solution of the pure substance.

Urobilin, like most animal pigments, shows acidic tendencies, and
forms compounds with bases, being liberated from these combinations
on the addition of an acid.

If ammonia be added to a solution of the free pigment, the colour
changes to a canary-yellow, and unless the solution be very strong the
absorption-band disappears. The sodium and potassium compounds
have a colour in solution more like that of the free pigment, and show
an analogous band, which is situate, however, somewhat nearer the red.
The zinc compound in ammoniacal solution fluoresces, as we have
already stated, and shows with the spectroscope a band almost identical
with that of the potassium and sodium compounds. The calcium com-
pound is yellow in solution and shows no band. Mercury forms a pink
compound, with a band nearer to the red than any of those previously
referred to. A solution of mercuric chloride will develop a pink colour
] Garrod and Hopkins, Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 120.

622 THE CHEMISTRY OF THE URINE.

when applied to tissues stained with nrobilin, and may thus be used as
a test for such staining (Adolf Schmidt).

When to a concentrated solution of nearly pure urobilin in sodic or
potassic hydrate, sufficient sulphuric or hydrochloric acid is added to
render the liquid faintly acid, a slight turbidity is observed, due to the
liberation of the free pigment from its more soluble alkaline combination.
If the turbid liquid be examined with the spectroscope, there is seen, in
addition to the ordinary acid band between & and F, a sharply-defined
narrow band in the green, enclosing, and being almost bisected by the
Fraunhofer line E (Fig. 57, Spectrum 6). This extra band is most probably
due to the special light absorption exercised by the impalpable particles of
solid urobilin in suspension. It wholly disappears when the precipitate
is filtered off, or when it is redissolved, the ordinary band alone being
then visible.1

Solid urobilin is an amorphous red-brown substance, which, when
isolated and dry, may be kept without decomposition. It is not
deliquescent, but fuses at comparatively low temperatures, afterwards
solidifying to a brittle transparent shellac-like form. It has a slight
but peculiar and characteristic odour.

Physiological relations. — Urinary urobilin is identical with the chief
pigment of faeces (stercobilin). So certain is the identity of these two
substances, that it is undesirable to retain separate names for them.

Urobilin is closely related to the pigments of the bile. This was
from the first recognised by Jaffe ; and shortly after the discovery of
the pigment, Maly prepared a substance (hydrobilirubin) by the
reduction of bilirubin with sodium amalgam, which he held to be
identical with urobilin. That the urinary pigment is a reduction pro-
duct of bilirubin is likely, but it is probable that hydrobilirubin, as
described by Maly, represents an intermediate stage in the reduction.
It differs at any rate somewhat from urobilin as it occurs naturally.

Urobilin is formed, however, when bile decomposes out of contact
with the air, and it may be extracted from the bile removed post-
mortem from the gall bladder.

Several observers have shown that intestinal micro-organisms can
effect the reduction of bilirubin to urobilin.

This pigment, or substances closely allied to it, can be prepared direct from
haemoglobin derivatives — haematin and hsematoporphyrin — by reduction pro-
cesses. It has been stated that oxidation is also capable of yielding urobilin
from bile and blood pigments respectively, but it is not conceivable that
both reduction and oxidation could lead to the same chemical result, and there
is in this matter an anomaly which requires explanation. It must not be
forgotten that peroxides (peroxide of hydrogen and peroxide of lead, have
been employed in this connection) may in a sense act as reducing agents, free
oxygen being given off by the interaction of the peroxide and any easily
reducible compound with which it is brought in contact.

Urinary urobilin has not yet been analysed. If the formula of
hydrobilirubin be compared with those of the related pigments, it will
be seen that both reduction and hydration probably occur in its
formation.

Hasmatin . . . C32H32N404Fe
Bilirubin . . . C32H36N406
Hydrobilirubin . . C32H40N40T
1 Garrod and Hopkins, Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 125.

UROERYTHRIN. 623

The change from bilirubin to hydrobilirubin may be thus ex-
pressed—

C3,H36N4Ott + H20 + H2 = C32H40N407

If urobilin differs from hydrobilirubin, the difference is possibly,
as already stated, in the direction of increased reduction.

The origin of urinary urobilin is probably threefold — from absorp-
tion of the ready-formed pigment in the bowel ; from direct production
in the liver ; and, lastly, from reduction of the blood pigment in the
organs, independently of hepatic agency.

Of the precise nature of the ckromogen of urobilin we have no
knowledge. It is precipitated intact when normal urine is saturated
with ammonium sulphate in the absence of mineral acid.1 It is possible
that oxidation may decompose it, as some urines originally showing
no absorption-band will develop such on standing. This phenomenon
might follow, however, from the decomposition during standing of
some compound of the pigment with lime or other base.

(c) Uroerythrin. — This pigment is best known as the colouring
matter of pink urate deposits. It is a substance of the greatest interest,
but one which has proved, from its marked instability, elusive and
difficult of investigation.

It was first dealt with as far back as 1800, by Louis Proust,
under the name of acide rosacique. Its present name was assigned
to it by F. Simon in 1850 — the term "purpurin," earlier proposed by
Golding Bird, being still sometimes used. Heller published an account
of the pigment in 1854, and Macmunn first accurately described its
spectrum in 1883. Very important contributions to our knowledge of
uroerythrin have recently been made by Eiva, Zoja, and A. E. Garrod.2

The quantity of the pigment excreted is, under any circumstances,
very small ; but its tinctorial power is extremely high, and when in
solution it may materially contribute to the coloration of the urine.
It is certainly to be looked upon as a pigment of normal urine, as
urates coloured by it frequently separate from the excretion of persons
in health.

Separation. — A quantity of pink urate deposit is collected upon a filter,
washed with ice-cold water, dried, and soaked in absolute alcohol. The
alcohol, though a solvent for uroerythrin, does not extract it from the urates.
The spirit is poured off and the precipitate dissolved in warm water ; from the
aqueous solution so obtained the pigment is easily and completely extracted by
shaking with amylic alcohol (Riva). Garrod has shown that if the pink urates
are first dissolved in warm water, and are then reprecipitated by saturation
with ammonium chloride, the pigment is carried down with them afresh, and
in such a condition that it may now be extracted with alcohol. An alcoholic
solution, if diluted with water, may be washed by shaking with neutral
chloroform, which removes impurities but no uroerythrin. But if after this
preliminary washing a fresh supply of chloroform is added, together with a
single drop of acetic acid, on shaking, the pigment is now found to be transferred
completely to the chloroform as an effect of the acidification of the liquid.

Properties. — The most striking properties of uroerythrin are — (1) Its
remarkable affinity for uric acid compounds ; (2) the ease with which

1 Eicholz, Jo-urn. Physiol., Cambridge and London, vol. xiv. p. 326.
"Journ. Physiol., Cambridge and London, 1895, vol. xvii. p. 439. Full references to
the literature will here be found.

624

THE CHEMISTRY OF THE URINE.

its solutions are decolorised by light ; and (3) its colour reactions
with the caustic alkalies and mineral acids. The pigment invariably
associates itself with urates during their precipitation ; either when they
separate naturally from a urine containing it, or when they are arti-
ficially added to its pure solutions, and are allowed afterwards to separate.

7. I

2.

B. C.

D.

E. b. F.

FIG. 57.— Chart of spectra.

1. Acid hsematoporphyrin.

2. Alkaline hsematoporphyrin.

3. Hsematoporphyrin as found in urate sediments.

4. Acid urohilin— concentrated.

5. Acid urobilin — dilute.

6. The E band spectrum.

7. Uroerythrin.

8. Urorosein concentrated — on dilution the band

shrank rapidly from redward end.

It apparently forms a loose compound with the urates, as a special
absorption-spectrum is seen when light passes through the pink pre-
cipitate, differing from that proper to solutions of the pigment (Garrod).
The best solvent of uroerythrin is amylic alcohol ; acetic ether is but
little inferior, and the pigment is also soluble in alcohol, chloroform, and

H^MATOPORPHYRIN. 625

water. The solutions have a rich orange colour ; only when very dilute
and quite free from impurity do they exhibit a pink tint. All solutions
of the pigment are decolorised on exposure to light, even to subdued
daylight. On the other hand, light has little effect upon the solid
pigment, and none at all upon pink urate sediments.

When solid uroerythrin is treated with solutions of the caustic
alkalies, a remarkable green coloration is produced (Thudichum). Green
derivatives from animal pigments are so uncommon that the reaction is
highly characteristic. It can be well seen when a little pink urate
deposit is collected upon a filter, dried, and then touched with a drop of
sodium-hydrate solution. If a solution of the pigment be treated with the
same reagent, a rapid play of colours may frequently be seen, from pink,
through purple and blue, to grass-green. With acids, colour-reactions
also occur, but they are somewhat less certain, being dependent upon
exact conditions of experiment. If to a solution of the pigment
sulphuric acid be added, the deep orange colour changes to a brilliant
carmine. Hydrochloric acid produces a rose-pink, phosphoric acid a
salmon-pink.

Examined spectroscopically, a solution of uroerythrin, at a suitable
degree of dilution, shows two somewhat ill-defined absorption-bands
united by a shading of less intensity (Macmunn). The more red-ward of
these is seen in the green between the lines D and E, and nearer the
latter ; the other closely agrees in position with the ordinary urobilin
band at F (Fig. 57, Spectum 7). Pink urate sediments and the carmine
derivative produced by sulphuric acid agree in giving a single banded
spectrum, namely, a broad band extending from the D line towards violet.

(d) Hsematoporphyrin. — In 1881, Neusser1 and Macmunn2 observed
the occurrence in urine of pigments closely related to hsematoporphyrin.
During the following decade the work of le Nobel, Stockvis, Salkowski,
Hammarsten, Copeman, and others extended this discovery, and it
became established that hsematoporphyrin itself is a constituent of
certain pathological urines. In 1892, A. E. Garrod3 showed that it
is also to be found in normal urine.

In health the pigment is excreted in very small amount, and can
scarcely be said to function as an active colouring matter of the urine ;
but it is of the highest interest to recognise that this iron-free deriva-
tive of hsematin, which in the laboratory is only to be obtained by the
use of strong reagents, is a normal physiological product. In patho-
logical conditions, and especially after the use of certain drugs, it is
present in greatly increased amount.

Isolation from normal urine. — The method recommended by Garrod de-
pends upon the fact that the pigment is carried down by the precipitate of
phosphates produced on the addition of caustic alkali to the urine. After
special treatment of this precipitate, the pigment may be obtained in chloroform
solution. The chloroform is evaporated, and the residue washed with neutral
alcohol and dissolved in acidified alcohol, when a solution is obtained of pure
pink colour, comparable with solutions of the purest specimens of the pigment
obtained from blood, and showing the spectrum of acid hsematoporphyrin with
distinctness.

lSitzungsb. d. k. Akad. d. Wissensch., Wien, 1881, Bd. Ixxxiv. S. 536.
2 Proc. Roy. Soc. London, vol. xxxi. p. 206.

3Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 598 ; ibid., 1894, vol. xvii.
p. 349.

VOL. I. — 40

626 THE CHEMISTRY OF THE URINE.

Pathological urines rich in the pigment will generally yield it easily to
acetic ether and to amylic alcohol.

Properties. — An account of the properties of haematoporphyrin will
be found in the section devoted to blood pigments ; but the pigment as
found in the urine has certain peculiarities which must be referred to here.

When the urine is sufficiently rich in the pigment for the absorption-
bands to be visible without treatment (always a pathological condition),
it is found that the bands observed are those of the so-called alkaline
hgematoporphyrin (Fig. 57, Spectrum 2). Indeed, if a solution of the
pigment showing the acid spectrum (but, of course, free from excess of
mineral acid) be added to urine, the bands are seen to change to those
of the alkaline form, even though the» urine itself be of normal acidity.
Acid sodium phosphate will, in fact, yield base to the haematoporphyrin,
unless, indeed, the salt is in great excess, when it can, on the other
hand, convert the alkaline form of the pigment into the acid. These
facts form an interesting commentary on what we have said in the
section devoted to the acidity of the urine, as to the complex conditions
which govern the phenomena of chemical reaction in the fluid.

Urinary hcnematoporphyrin may be in the form of unstable modi-
fications. Alkaline solutions of the pigment obtained from many
specimens exhibit a five-banded instead of a four-banded spectrum
(Macmunn). Occasionally, too, urate sediments may be pigmented with
a form of the pigment which, in alkaline or neutral solution, shows a
spectrum of two bands resembling that of oxyhsemoglobin (Fig. 57,
Spectrum 3). Dilute mineral acids, however, promptly change this spec-
trum to that of ordinary acid hsematoporphyrin (Fig. 57, Spectrum 1).
There is some evidence that a colourless chromogenic substance, related
to haematoporphyrin, may occur in the urine, as the pigment has been
observed to increase in amount after standing.

Chromogenic substances in urine. — Two, at least, of the pig-
ments we have now described (urobilin and hsematoporphyrin) may
exist, as we have seen, in the form of chromogens — colourless, or less
coloured, precursors. But the urine contains other chromogenic sub-
stances, which in the original urine always, or nearly always, retain
their colourless form ; and, as a rule, take no share in the true
pigmentation of the fluid.

We do not include, under the term of " chromogen," all substances which,
by the action of strong reagents, happen to be capable of yielding a coloured
derivative.

We purposely exclude such bodies as the so-called " humous substances " of
Udransky — indefinite products of wholly doubtful nature — obtained by such
processes as fusing urinary precipitates with caustic alkali, or boiling the
previously concentrated urine for hours with hydrochloric acid. These are
probably derived from the carbohydrates and other constituents of the urine,
by the destructive action of the reagents. Beyond the fact that they happen
to be amorphous, and yellow or brown in colour, there is nothing to suggest
that they are related to urochrome or any other definite pigment.

We shall deal only with those chromogenic substances which are of
importance, either because they may, though with great rarity, appear
as actual pigments, or because they yield their coloured derivatives
with comparative ease, and may thus lead to confusion when the urine
is being investigated in other connections.

CHROMOGENIC SUBSTANCES IN URINE. 627

(a) Indoxyl (indigo-blue and indigo-red). — Indoxyl (cf. pp. 607
and 631) easily oxidises to indigo-blue, or to the isomeric substance
indigo-red. The relation between indoxyl and its blue derivative is
expressed by the following equation : —

CH + °* = C°

(indoxyl) (indigo-blue)

The formula of indigo-red is C6H c = G u N> and it

arises, like its blue isomer, when, by oxidation, four atoms of hydrogen
are removed from two molecules of indoxyl. Oxidising reagents when
added to urine may, according to the conditions of the experiment, give
rise to the formation of either or both of these coloured derivatives.
The blue substance, however, is more easily and more generally
obtained.

It is of great rarity for the urine to be actually pigmented
with indigo-blue. As we have already seen (p. 607), the urinary
indoxyl is excreted in the form of a conjugated sulphate, and
this compound resists oxidation. Only when the indoxyl is first
liberated from its combination does the action of oxidising reagents
produce the blue colour. It is stated, however, that the urine of
cholera may sometimes exhibit a blue shade from the presence of
indigo-blue. We have seen that the amount of indoxyl sulphate is
increased in the urine whenever bacterial putrefaction of albuminous
substances is occurring to a greater extent than usual, whether in the
bowel or elsewhere in the body (putrid abscesses, etc.). The most
ready method of demonstrating the amount of indoxyl is by converting
it into indigo-blue. Jaffa's test.1 — The urine is mixed with an equal
bulk of strong hydrochloric acid, by which means the "indican"
(indoxyl sulphate) is decomposed and the indoxyl liberated. With a
pipette, a solution of a hypochlorite is now added to the mixture drop
by drop, when, by oxidation of the indoxyl, indigo-blue is formed. By
shaking up the liquid with chloroform, a solution of the blue substance
is obtained in the latter (Stockvis, Senator, and others). Otherwise,
a crystal of potassium chlorate is placed at the bottom of a test tube
and covered with the urine to be examined. Strong hydrochloric acid
is then allowed to run down the side of the tube so as to reach the
crystal without mixing with the urine. The latter floats upon the acid,
and at the junction of the fluids a blue ring is seen of intensity varying
with the amount of indoxyl present.

But indigo-blue is itself an easily oxidisable substance. It is
instantly decolorised by nitric acid, and without difficulty by hypo-
chlorites. In Jaffe's test, as above described, it is therefore necessary
to add the oxidising agent with great care, or the blue colour will
disappear as soon as formed. In Obermayer's2 method, the urine is
first precipitated by acetate of lead, and filtered ; to the filtrate is added
an equal bulk of strong hydrochloric acid, containing two or three parts
per thousand of ferric chloride. The mixture is shaken for a short
time, and the liberated pigment taken up, as before, in chloroform. In

1 Arch.f. d. ges. PhysioL, Bonn, 1870, Bd. iii. S. 448.

2 Wien. Tclin. Wchnschr., 1890, S. 176.

628 THE CHEMISTRY OF THE URINE.

this case the ferric salt acts as a mild oxidising agent, sufficient to form
but not to destroy the pigment.

With care a certain amount of indigo-blue may be obtained from
most normal urines ; and, apart from the increase in actual disease,
indoxyl may be present in considerable amount, and the urine yield
a well-marked indigo reaction, when nothing more than constipation
exists.1

Indigo-red is more liable to be formed from the urinary indoxyl
when Jaffe's test is applied with the aid of gentle heat. Higher
temperatures favour the formation of the red isomer, lower tempera-
tures the blue.2 In Weber's test for indicanuria both pigments are
formed. The urine is treated, as in ojher methods, with its own volume
of hydrochloric acid ; one to three drops of dilute nitric acid are then
added, and the mixture heated to boiling. After cooling it is shaken
with ether, when the urine, if rich in indoxyl, is found to retain a blue
colour, while the supernatant ether is red or violet. The formation of
indigo-red has no significance beyond such as is attached to that of
indigo-blue. It may sometimes arise from the urine on the addition of
strong hydrochloric acid alone (infra).

(b) Urorosein. — Quite distinct from indigo-red is the red pigment,
named " urorosein " by Nencki and Sieber,3 and since carefully studied
by H. Rosin.4 It is produced from its chromogen by the action of
mineral acids ; best with the aid of an oxidising reagent, but frequently
appearing when the urine is treated with strong hydrochloric acid alone,
especially after standing. It is freely taken up, after its formation, by
amyl alcohol, but is not soluble in ether. Alkalies immediately destroy
its colour. The chromogen of urorosein is precipitated by saturation
with ammonium sulphate.5

(c) Skatoxyl-red, which is formed from skatoxyl on oxidation, is never
obtained from urine under ordinary circumstances (Rosin), though it may be
produced in the urine of animals when skatoxyl has been given by the mouth
(Brieger).

It may be stated generally that when a red colour is produced in
urine by the addition of strong acids (with or without the assistance
of oxidising reagents), it will in the great majority of cases be due to
urorosein or to indigo-red. The two pigments may be easily distin-
guished, in that urorosein, unlike the indigo pigment, is not taken up
on shaking with ether or chloroform, and is easily decolorised by
alkalies.6

THE PIGMENTATION OF PATHOLOGICAL URINES.

All the pigments and chromogens that we have so far described may be
excreted in increased amount in disease. There are other pigments which
only appear in the urine pathologically.

In the urine of fever a well-marked band of tirobilin may generally be
seen without preliminary treatment, and uroerythrin is often present in more

1 Cf. v. Jaksch, " Klinische Diagnostik," 1896, Aufl. 4, S. 406.

2 Rosin, Firchow's Archiv, 1891, Bd. cxxiii. S. 519.

3 Journ. f. prakt. Chem., Leipzig 1882, Bd. xxvi. S. 333.

4 Deutsche mcd. Wchnsclir., Leipzig, 1893, S. 51.

5 Garrod and Hopkins, Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 134.

6 Rosin, Virchow's Archiv, 1891, Bd. cxxiii. S. 519.

PIGMENTATION OF PATHOLOGICAL URINES. 629

than normal amount. I have also frequently observed that urochrome itself
takes a share in the increased pigmentation of febrile urine.

Urobilin is found in large amount when extensive haemolysis, or large
internal haemorrhages, have occurred ; it is also greatly increased in certain
cases of hepatic cirrhosis. The high colour of the urine of pernicious anaemia
is in part due to urobilin ; other pigments may take a large share in the increase
in colour, but it is characteristic of this disease for free urobilin to be present
instead of the chromogen, for even in pale specimens, which are sometimes
passed, an absorption-band between b and F is usually visible. It is common
for free urobilin to be present in diabetes. An increase of uroerythrin is
seen in many forms of hepatic disorder. Haematoporphyrin does not appear to
depend upon haemolysis for increased excretion. After excessive use of drugs
of the sulphonal type, the urine may exhibit a deep port-wine colour ; part,
but not the whole, of this pigmentation is due to an enormously increased
excretion of haematoporphyrin, which may be quite unassociated with any
decrease in the haemoglobin of the blood. Increase of this pigment, but of
much slighter degree, occurs also in plumbism and in certain other diseased
conditions.

The so-called pathological urobilin. — Several observers have made a
distinction between normal urobilin and a pathological form of the pigment.
The differences found have been mainly those of spectroscopic appearances ; the
pathological form showing a proportionately broader band between b and F,
and additional bands elsewhere. The various descriptions of the pathological
pigment are in no sense consistent one with the other. Evidence has recently
been brought forward to show that the points of distinction may be all
explained as the result of impurities, and that urobilin is one and the same
substance wherever found.1

Special pathological pigments— Blood pigments. — In hcematuria, due
to whatever cause, the urine usually contains unaltered haemoglobin. In
general the pigment may be recognised in solution spectroscopically, while red
blood corpuscles are found in the deposit. Some specimens of urine preserve
the integrity of the corpuscles very completely, and in slight cases of haematuria,
while no pigment may be found in solution, the deposit obtained by.centrifuging
will show a red layer of corpuscles. In hwmoglobinuria the pigment is passed
wholly in solution, and no corpuscles are found. Not infrequently methcemo-
globin is present in place of or in addition to oxyhaemoglobin, even when
the urine is first passed. Specimens which are spoken of as " smoky " usually
contain this latter form of pigment.

If the quantity of pigment is too small to show a recognisable spectrum
direct, the urine may be heated with caustic alkali, filtered, and a few
drops of ammonium sulphide added. The more powerful absorption-bands
of haemochromogen will then be generally visible. Or, the urine may be
boiled with caustic alkali, when, in the presence of blood, a greenish tint is
produced, and the phosphates are precipitated with a brownish-red colour, due
to haematin (Heller). The blue colour produced by the addition of guaiacum
tincture and an ethereal solution of hydrogen peroxide, is a delicate but not
wholly conclusive test when applied to urine.

Bile pigments appear in the urine in most cases of jaundice, generally in
the form of bilimbin, when the urine is saffron-coloured ; but occasionally
partly as biiiverdin, when a greenish tint predominates. When present in
large amount, there is no difficulty in the recognition of these pigments.
Gmelin's reaction is obtained by allowing the urine to run gently on to the
surface of some fuming nitric acid contained in a test tube. The test is made
more delicate if the urine be first repeatedly filtered through a clean white

1 Hopkins, Guy's Hoy}. Rep., London, 1893, vol. 1. p. 363 ; Garrod and Hopkins, "The
unity of Urobilin," Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 130.

630 THE CHEMISTR Y OF THE URINE.

filter paper ; the paper is stained yellow, and a drop of fuming nitric acid
allowed to fall upon it produces the characteristic play of colours. When
only traces of the pigment are present, Gmelin's test is best applied to the
precipitate produced in the urine by the addition of lime-water with the
subsequent passage of a stream of carbon dioxide ; the precipitate is filtered
off, dried, and touched with nitric acid.

Carboluria. — In poisoning by carbolic acid, and often to a less degree after
the substance has been freely used as a drug, the urine has a greenish-brown
or dark brown colour, which increases on exposure to the air. This colour is
due to oxidation products of some of the aromatic substances present in normal
urine, which have been dealt with on p. 607 et seq. They are excreted in much
greater quantity after the administration of phenol. Pyrocatechin and
hydrochinon are especially responsible for the colour effect.

Alcaptonuria (cf. p. 607). — A phenomenon very similar to that present in
carboluria is seen in certain other conditions, where an alkaline urine, as it
stands in the air, takes first a brown colour at the surface, which gradually
spreads through the fluid, and may finally result in the whole urine becoming
nearly black. Such urine always reduces copper solutions. The phenomenon
was first observed by Boedecker in 1859, and it was later ascribed by him to a
substance which he called alcapton.

But alcapton, as already stated, is not a definite compound, and the colour
phenomena are probably due to the action of oxygen upon some of the
aromatic bodies present ; probably, at times, upon pyrocatechin and uroleucic
acid, but more often perhaps upon the homogentisic acid of Wolkow and
Baumann (vide p. 606).

Although thought to be especially frequent in various forms of tuberculosis,
alcaptonuria must not be looked upon as specifically associated with any parti-
cular diseased conditions ; it indicates rather some peculiar independent changes
of metabolism, and is not infrequently met with in conditions of apparent
health. In one case where there was a tendency for homogentisic acid to
appear in the urine, it was found that the quantity of this substance and the
associated colour phenomenon might be enormously increased by administering
tyrosine, and it is suggested that, when homogentisic acid or other aromatic
substances appear in excess, it is due to the action of special micro-organisms
on the tyrosine of the bowel.

Drug pigments. — The urine may contain purely accidental pigments due to
the use of drugs, notably of rhubarb, senna, logwood, and santonin.

THE INOKGANIC CONSTITUENTS.

To a large extent the inorganic constituents of the urine arise
directly from the food, which always contains a large excess of salts.
It does not follow, however, that the bases and acids are to be found in
the urine in the same combinations as when ingested, and indeed an
interchange of base and acid may occur in special circumstances between
the salts of the food and those of the tissue fluids. Thus, excess of
potassium in the food may lead to increased elimination of sodium
(Bunge). The sulphates, moreover, form an exception to the general
rule of direct origin from the ingesta, very small quantities of these
salts being present in a normal dietary. The urinary sulphates are
derived almost entirely from proteid metabolism ; a small proportion of
the phosphates arising in the same way.

Sulphuric acid and other sulphur compounds. — About 80 per
cent, of the total sulphur in normal human urine is present in the
fully oxidised form of sulphuric acid ; from 2 to 2*5 grms. of the acid,

SULPHURIC ACID AND SULPHUR COMPOUNDS. 631

combined as salts, being excreted per diem. Two forms of salts exist —
(1) the ordinary and strictly inorganic sulphates of the form M'2S04,
and (2) the so-called conjugated or ethereal sulphates, which contain
organic radicles; the composition of these will be clear from what
follows.

If ordinary alcohol be boiled with its own bulk of strong sulphuric
acid, under a vertical condenser, a crystalline product is formed which
is known as ethylhydrogen sulphate, or sulphovinic acid. The com-
position of this is explained by the following equation : —

C2Hr.OH H—0. H20 C2H5— Ov

+ >S02 = + >S02

H— 0/ H— 0— /

(alcohol) (sulphuric acid) (water) (ethylhydrogen sulphate)

By elimination of water, the ethyl radicle (C2H5 - ) becomes " con-
jugated " with the sulphuric acid, and a monovalent acid is formed,
which yields salts of the type M'C.2H5 : S04. On boiling such salts
with hydrochloric acid, the sulphovinic acid is first liberated, and then,
by absorption of water, splits up once more into alcohol and sulphuric
acid.

The " conjugated sulphates " of the urine are precisely analogous
salts, which undergo like decomposition when boiled with HC1. But,
instead of ethyl, the radicles conjugated with the sulphuric acid are
nearly always derived from aromatic precursors. In fact, as we have
already seen, most of the aromatic compounds of the urine described on
p. 605 et seq. are present as conjugated sulphates ; and the proportion of
the sulphuric acid present in this form depends upon the factors which
increase or decrease these aromatic substances. The chief salts present,
therefore, under ordinary circumstances, are those of kresyl- indoxyl-
and skatoxyl-sulphuric acids.

Normally, the sulphuric acid so combined amounts to about one-
tenth of the whole ; nine-tenths being in the form of ordinary sulphates.
An increased proportion of ethereal sulphates is found when, for any
reason, there is increase of proteid putrefaction in the body, and especi-
ally in the bowel ; and also when larger amounts of aromatic compounds
than usual are taken by the mouth. In man they may be greatly in-
creased during starvation, whereas, according to I. Munk, they are absent
from the urine of a starving dog.

For the detection and estimation of the sulphates we rely upon the forma-
tion of the insoluble barium salt. All the sulphuric acid originally present as
ordinary sulphates is precipitated as white crystalline barium sulphate, when a
soluble barium salt is added to the urine, previously made acid with acetic acid.
On the other hand, the barium salts of the conjugated sulphuric acids are soluble,
so that when the barium precipitate, obtained as above, is filtered off, the
ethereal sulphates still exist in the filtrate. But, as we have seen, they are
decomposed on boiling with hydrochloric acid, splitting up into sulphuric acid
and the hydrate of the conjugated radicle. It is evident, therefore, that if the
above-mentioned filtrate be so boiled with hydrochloric acid, a further precipi-
tate of barium sulphate may be obtained, the amount of which will be a
measure of the proportion of ethereal sulphates present.

One-fifth of the total sulphur of the urine is present, not in any form
of sulphate, .but in less oxidised compounds. This fraction may be
spoken of as the "neutral sulphur" in contradistinction to the "acid

632 THE CHEMISTRY OF THE URINE.

sulphur " of the sulphates.1 We have but little knowledge of the actual
forms in which this neutral sulphur is excreted. As one source of the
unoxidised sulphur compounds, we may look to the taurin of the bile,
since it has been shown (in the dog) that when the bile is diverted
from the bowel by means of a fistula, the neutral sulphur of the urine is
diminished ; experimental or pathological blocking of the bile duct, on
the other hand, increases it.2 A second portion is probably present in
a compound or compounds analogous to cystine,3 and in actual cystinuria
the neutral sulphur is, of course, greatly increased (cf. p. 603).

Minute quantities of sulphocyanides are always present, probably
owing to reabsorption from the saliva which is swallowed, and these
contribute to the " neutral " sulphur.* But none of the sources we
have mentioned will account for the whole of the unoxidised sulphur
present, which must partly exist in compounds of which we have no
knowledge.

To estimate the neutral sulphur, a small quantity of the urine is evaporated,
and the residue fused with alkaline carbonates and nitrate of potassium. By
this means the whole of the sulphur present is oxidised to sulphates, and these
are estimated as barium sulphate. A separate estimation of the sulphuric acid
originally present is made, and the amount deducted from the figure obtained,
as above. The excess is a measure of the neutral sulphur, in terms of sulphuric
acid.

Phosphoric acid. — The greater part of the phosphates of the
urine is derived directly from those ingested with the food, but a small
proportion arises from the oxidation of the nuclein, lecithin, and
protagon of the tissues. The phosphates are increased by animal food,
especially when this is rich in nucleo-proteids (Weintraud), and are
diminished by vegetable diet. The phosphoric acid of plants is mostly
present as insoluble earthy phosphates, which are not absorbed. On
this account the urine of herbivora is notably poor in phosphates. In
man the quantity is necessarily very variable, and ranges from 1 to
8 grms. of phosphoric acid in the urine of twenty-four hours ; it com-
monly amounts to about 3*5 grms.

The nature of the salts present has been fully discussed in the
section devoted to the chemical reaction of the urine. Part of the
phosphoric acid is present in combination with lime and magnesia, but
a greater part is combined with the alkalies. Some" importance has
been attached to a change in the relative proportion of the " earthy "
and "alkaline" phosphates in diseased conditions, the estimation being
made by adding ammonia to the urine and so precipitating the former.
But the information so obtained may be misleading, as whatever the
form of calcium or magnesium salt originally present in the urine (e.g.
sulphates or chlorides), a precipitate produced by ammonia would contain
these bases as phosphates, since an interchange of acids would take
place with the alkaline phosphates. From alkaline urines magnesium
ammonium phosphate (triple-phosphate) frequently separates in char-
acteristic crystals ; and in the deposit from feebly acid specimens

1 Salkowski, Virchoio's ArcMv, 1875, Bd. Iviii. S. 472.

2 Cf. Kunkel, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 344.

3 Goldmann and Bauraann, Ztschr. f. pTiysiol. Chem., Strassburg, 1888, Bd. xii.
S. 254.

4 Leared, Proc. Roy. Soc. London, 1870, vol. xvi. p. 18; I. Munk, Virchow's ArcTtiv,
1877, Bd. Ixix. S. 354.

HYDROCHLORIC ACID.

633

calcium phosphate is found in star-shaped masses of fine prisms (stellar
phosphate) (Fig. 58).

Pathologically, a diminution of the urinary phosphates is seen in nephritis
(Purdy), and an increase is said to occur in certain nervous diseases. The
phosphates may be greatly increased in diabetes insipidus.

For the estimation of phosphoric acid the urine is first treated with acetic
acid and sodium acetate, and is then titrated with a standard solution of
uranium nitrate. Ferrocyanide of potassium or cochineal tincture may be used
as an indicator to mark the end point of the titration.

Hydrochloric acid. — There can be little doubt that the greater
part of the hydrochloric acid of urine exists as sodium, chloride, and it

FIG. 58. — A. Stellar phosphates ; B. Triple phosphates.

certainly arises mainly from the common salt present in the food. The
tissues and fluids of the body maintain a very constant content of sodium
chloride, any excess is at once excreted, and any diminution in the
supply immediately reduces the excretion. The amount in the urine
depends, therefore, in normal circumstances, almost entirely upon the
quantity ingested, and falls to a minimum during starvation, or when
a salt-free diet is taken. Pathologically, striking alterations in the
chlorides of the urine may be observed. Thus, whenever considerable
exudations occur, as in pneumonic processes, or where pleuritic effusion
is taking place, the consequent removal of chlorides from the blood may
lead almost to a cessation of their excretion ; and conversely, during the
reabsorption of such exudations, the urinary chlorides may considerably
increase, even when but little salt is being taken by the mouth. Apart
from such exudations, fever appears to have a specific effect in pro-

634 THE CHEM1STR Y OF THE URINE.

moting a retention of chlorides ; a fact for which we have no sufficient
explanation.1

Upon ordinary diet, about from 6 to 10 grms. HC1 is excreted per
diem by a healthy adult.

To demonstrate the presence of chlorides, the urine is diluted, made
acid with nitric acid, and mixed with nitrate of silver solution ; a white
curdy precipitate of silver chloride falls, which, if filtered off, is found
to be soluble in ammonia.

To estimate the hydrochloric acid, a known quantity of silver salt is added,
together with nitric acid, to a measured amount of urine, taking care that the
silver is in excess. The precipitate is filtered off, and the excess of silver
titrated in the nitrate with a standard solution of ammonium thiocyanate,
ferrous sulphate being used as an indicator. Knowing the amount of silver
added, and that left in the nitrate, the difference indicates that combined as a
chloride, from which the hydrochloric acid can be calculated (Volhard's
method).

Carbonic acid is found even in acid urines ; some 50 c.c. being
present per litre.2 In acid urines the greater part is not in firm chemical
combination, as it is driven out of solution by the passage of a stream
of air. But when the urine contains abundant fixed bases, and especially
when it is actually alkaline from these, considerable quantities of car-
bonates may be present, the urine of herbivora being exceptionally rich
in these.

Nitric and nitrous acids may be present in normal urine in the
form of salts, but in quite unimportant quantity.

The nitrates are derived, not from metabolism, but directly from the
food ; the nitrites are not present when the urine is first passed, but
appear to arise always from the nitrates, as an effect of the reducing
action of micro-organisms.

Silicic and hydrofluoric acids may appear in traces, simply as
an effect of the presence of their salts in various foodstuffs.

Sodium and potassium. — Of sodium about 5 grms. per diem is
excreted upon a mixed diet, and of potassium about half this quantity.
The proportion of the latter metal is increased when the dietary is more
exclusively composed of flesh, and it is raised during starvation, and in
febrile conditions.3 We have already referred to the interesting fact
that the ingestion of large quantities of potassium salts may lead to
increased elimination of sodium from the body, and it is this driving out
of the latter essential constituent of the body-fluids which makes the
consumption of common salt with the food a necessity in all cases
where the diet is rich in potassium.4

Calcium and magnesium. — In human urine, about 0-2 to 0'4 grms.
of lime (CaO) is excreted per diem.

Of the lime salts present in the food, only a small proportion is
excreted by the urine. Much of the lime remains in an insoluble form,
and is not absorbed at all, while of that which does enter the circulation

1 Of. Salkowski and Leube, " Lehre vom Earn," 1882, S. 174, 464, 465 ; see also Kast,
Ztschr. f. pliysiol. Chem., Strassburg, 1888, Bd. xii. S. 271.

2 Wurster and Schmidt, Centralbl. f. Physiol., Leipzig u. Wien, 1887, Bd. i. S. 421.

3 Of. Salkowski, rirchota'sArchiv, 1871, Bd. liii. S. 209 ; Munk, Berl. Uin, JFcJinschr.,
1887, S. 432.

4 Bunge, "Lehrbuch der physiol. Chem."

CHARACTERISTICS OF URINARY EXCRETIVES. 635

a considerable fraction is re-excreted into the lower bowel.1 The
administration of dilute mineral acids, which decomposes to some extent
the insoluble phosphates of the food, increases the urinary lime salts,
and, conversely, when sodium phosphate is taken in large quantities, the
lime may almost disappear from the urine.

Very interesting is the observation of G. Hoppe-Seyler,2 who found
that the excretion of lime salts by the kidneys is much greater during
conditions of rest than during exercise, a fact which doubtless depends,
in part at least, upon the effect of exercise on the excretion into the
bowel.

As a general rule, the urine contains about twice as much magnesia
as lime.3 Most food-stuffs, other than milk and eggs, contain more
magnesium than calcium salts. The phosphates of the former are also
more soluble, and as both bases are largely present as phosphates in the
food, it is to be understood that more magnesium will be absorbed and
excreted. When, as during starvation, the ingestion of magnesium salts
ceases, the lime is found to be in the greater proportion.

The presence of calcium in urine is easily demonstrated, and its amount
determined by acidifying the fluid with acetic acid, and adding ammonium
oxalate, when all the lime separates as the insoluble crystalline calcium oxalate,
which may be filtered off and weighed as calcium carbonate, into which it
is converted on gentle ignition. In the filtrate from this, the magnesium is
precipitated as triple phosphate upon the addition of ammonium chloride,
ammonia, and, if necessary, of some extraneous alkaline phosphate.

Iron. — The urine contains, as a rule, a very minute quantity of iron,
and frequently no detectable trace. It has been found increased in
diseases, such as pernicious anaemia, but never rises to more than a few
milligrammes in the twenty-four hours. It is a remarkable fact that
this metal, if present at all, is, to a" large extent, precipitated in association
with the pigmented crystals of uric acid, which separate when the urine
is acidified with hydrochloric acid. It may be detected in the ash of
large quantities of the urine, by taking a solution of this to dryness with
a little nitric acid, dissolving the residue in water, and testing with
potassium sulphocyanide, which gives with ferric salts a blood red
coloration.

GENERAL CHARACTERISTICS OF THE URINARY EXCRETIVES.

It might perhaps be expected that the waste products of meta-
bolism, on leaving the body, would in general represent the simplest
compounds of physiological chemistry, and would stand farthest of all
removed from the complexity of the tissue proteids. That this is not
entirely the case, however, will have been clear from the facts set forth
in previous sections ; it is, indeed, striking to observe how many of the
organic excretives arise by synthetic processes from simpler precursors
in the body.

There is one form of chemical change which takes an important and

1 Voit, Ztsehr. f. Biol., Miinchen, 1892, Bd. xi. S. 387-397, where other references
will be found.

2 Ztsehr. f. physiol. Chem., Strassburg, 1891, Bd. xv. S. 161.

3 Most analyses bear out this statement, but those of Bunge, given on p. 573, show an
excess of lime.

636 THE CHEMISTR Y OF THE URINE.

even dominant share in the processes of constructive metabolism : that,
namely, of dehydrolysis — the synthesis of larger molecules by a con-
jugation of smaller, associated with elimination of the elements of
water. This process is known to chemists as one of " condensation."
In destructive metabolism, on the other hand, the converse process
of hydrolysis is an important factor.

While of most obvious importance in the physiology of plants,
in which constructive metabolism starts from a lower chemical level,
" condensation " is also prominent in all constructive processes of which
we have any accurate knowledge in the animal organism. Being thus
in general so characteristic of assimilative processes, it is remarkable
how frequently dehydrolytic synthesis interrupts the course of meta-
bolic breakdown and reappears as a final step before excretion.

We have dealt with a typical instance of this in the formation of
hippuric acid from benzoic acid and glycine in the kidney, and we have
seen that a like process occurs in the production of ethereal sulphates,
and the conjugate compounds of glycuronic acid. We may note, too,
that many substances introduced experimentally into the body undergo
kindred conjugations before excretion.

The theory of the origin of uric acid and the alloxuric bases from
nucleins, does not perhaps predicate any synthetic step in the produc-
tion of this group of excretives ; but however far-reaching may be the
truth of this theory, it must be admitted that there is much reason for
ascribing the origin of at least some fraction of these substances, as
found in the urine, to conjugative processes in the liver and kidney. In
birds there can be little doubt that uric acid arises by a synthetic
change.

In the most important of the chemical changes antecedent to
excretion — the formation of urea from ammonium carbonate in the
mammalian liver — we have a process which I venture to think belongs
essentially to the same chemical picture. Though not resulting, properly
speaking, in a synthesis, the dehydrolysis which here occurs is a chemical
change against the line of least resistance, and suggests an influence of
the same type as that producing the synthetic results just discussed.
Without misuse of the vague and somewhat discredited terms " organic "
and " inorganic," we are entitled to look upon the dehydrolysis of am-
monium carbonate as a return from the latter to the former category ;
the excretive stands physiologically on a higher level than its precursor.

To complete whatever of suggestion these considerations may contain,
we may note finally the dehydrolysis which creatin suffers before ex-
cretion as creatinin. Even here we meet with a change which, for the
conditions under which it occurs, is one from a more stable to a less
stable substance.

It would seem that just before excretion there occurs an arrest of
the normal processes of down-grade metabolism (in which hydrolysis
goes hand in hand with oxidation, resulting in a series of compounds of
increasing stability), and a brief return to dehydrolysis and to the type
of constructive processes. It is at any rate interesting to observe that
the renal excretives are as a class more complex or less stable than
their immediate precursors in the body. When the urine decomposes,
under the destructive influence of enzymes derived from micro-
organisms, many of the precursors reappear ; the urea again becomes
ammonium carbonate ; hippuric acid and its analogues give place to

COMPARATIVE CHEMISTRY OF THE URINE. 637

benzole acid, creatinin may again take up water, and uric acid is
rapidly hydrolysed.

The urinary nitrogen, it will have been observed, always appears
either as ammonia (NH3), or more typically in compounds containing
the derived amido ( - NH2) or imido ( — NH) groups. Compounds con-
taining the other fundamental form of organic nitrogen, the cyanogen
type ( - C = N, or - N = C), are represented only by the minute
quantity of potassium sulphocyanide, which is in all probability directly
derived from the saliva. Although a small proportion of the nitrogen
is excreted in aromatic compounds, it is never, in human urine, present
in the benzene nucleus of these, but always in side chains or accessory
atomic groups within the molecule.

The carbon ring of the benzene nucleus is especially resistant to
oxidation in the body, the open chain of carbon atoms, proper to
substances of the fatty series, being much less so ; and for the most
part we find that the normal renal excretives do not reach such
molecular size as to contain as many as six carbon atoms, unless they
contain the aromatic nucleus. As illustrating the degree of molecular
complexity found in the organic urinary compounds, we may remember
that the molecular weight of urea is 60, that of creatinin is 113,
of uric acid 168, and of hippuric acid 181. The intact renal
epithelium, it is true, passes substances, such as the pigments, the
molecular weight of which is much greater than the above, but only
in small quantities.

COMPAEATIVE CHEMISTRY OF THE URINE.

In mammals, amphibia, fishes, and in certain molluscs, urea is the
chief end-product of nitrogenous metabolism. In birds, reptiles, and
arthropods, on the other hand, the nitrogen is excreted mainly in the
form of uric acid. In spiders and in some few other groups of inverte-
brates, the chief excretive has been shown to be guanin.

A study of the renal function, from a comparative point of view,
offers one aspect of great interest and some difficulty, to which Sir
William Eoberts has called attention. It is remarkable that the wide
differences in the nature of the renal excretion in mammals and the
Sauropsida respectively, should yet be associated with almost complete
identity in the anatomical structure of the kidney. The kidney of
the bird has a glomerular mechanism identical with that of the
mammalian organ, and the same tubular arrangement of a secretory
epithelium ; and yet practically the sole function of the organ of the
bird, in contrast to the remarkably complex duties performed by that of
the mammal, is to secrete quadriurates. " The chlorides, phosphates, and
sulphates, the lime and magnesia salts, the pigments and the large
volume of water — all of which figure as prominent and even essential
components of mammalian urine — are either wholly absent from the
urine of birds and serpents, or are only present in such minute traces
as might be derived from the lubricating mucus and epithelial debris
with which the secretion is incidentally admixed " (Eoberts).

The physiological differentiation, whereby soluble urea takes the
place of insoluble uric acid, in accordance with the needs of an
organism excreting a liquid urine, is now known to occur quite at the
final stages of metabolism. It is almost certain that, in the main, the

638 THE CHEMISTR Y OF THE URINE.

waste products which leave the tissues are the same in birds and
mammals. In the liver of the former these products are prepared for
excretion by a change into the form of uric acid, while in the latter
the hepatic influence produces urea. There is a great preponderance of
experimental evidence to show that when uric acid is administered to
mammals it is converted into urea before excretion, and that when urea
is given to birds the converse change occurs. The contention of Haig,
that when uric acid is taken by the mouth (in man) it is excreted
unchanged, is not supported by other observers.

As to the small quantity of uric acid found, nevertheless, in the
urine of mammals, if we accept the theory of its exclusive origin from
nucleins, it is clear that we camiojb look upon it as in any sense
physiologically akin to the main part of the normal excretion of birds,
for this must represent the waste nitrogen of the tissues as a whole.
But this theory apart, the view is plausible, and indeed it cannot be said
to be yet disproved, that we have in the mammalian uric acid a vestigial
relic of the earlier type of excretion — " something analogous with the
vermiform appendix, the ductus arteriosus, or the ear-point." The
actual proportion present in the urine of different mammals is very
variable. In most animals the relative amount is less than in man, but,
except occasionally in the cases of the cat and dog, it has never been
found to be absent. The presence of the small amount of uric acid in
the urine of mammals is paralleled by the existence of minute quantities
of urea in that of birds and reptiles.

Creatinin has been found wherever looked for in the urine of various
species of mammals, but is said to be absent from the excretion of birds.

Hippuric acid is represented in birds by the analogous compound,
ornithuric acid, which is a condensation product of benzoic acid with
diainidovalerianic acid. An aromatic acid, apparently peculiar to the
urine of dogs, is known as kynurenic acid, and has the composition of
an oxychinolin-carboxylic acid (OH.C9H5KCOOH).

The large proportion of hippuric acid in, and the absence of
ammonium salts from, herbivorous urine, have been shown in previous
sections to be, in common with the alkaline reaction of the fluid and
its richness in salts, a direct effect of diet.

Of the urinary pigments in the lower animals we have no accurate
knowledge.

It is impossible at present, owing to the wide gaps in our knowledge,
to take any broad view of the comparative chemistry of the urine. A
series of analyses are much needed, from the results of which we could
form some judgment as to the line of evolution which has led from
the simple renal excretions of the invertebrates to that most complex
of physiological fluids— mammalian urine.1

1 See on the subject of the comparative chemistry of the urine, Rywosch, Wien. med.
Wclinschr., 1893, Nos. 47 and 48.

THE MECHANISM OF THE SECRETION OF URINE.

By ERNEST H. STARLING.

CONTENTS. — Theories of Urinary Secretion, p. 639— Theory of Bowman, p. 639—
Theory of Ludwig, p. 640— Secretion of Water, p. 641— Methods, p. 642—
The Concentration of the Urine, p. 650— Heidenhairi's Criticism of the Theory
of Ludwig, p. 652— Experiments of Nussbaum, p. 655— Experiments of Ribbert,
p. 656 — Experiments of Bradford, p. 656 — The Influence of the Nervous
System on the Secretion of Urine, p. 659.

THEORIES OF URINARY SECRETION.

IN all the organs of the body whose functions have been investigated by
physiologists, it has been found that ;i difference of function is invariably
associated with a difference in structure, so that the interdependence
of function and structure has become an axiom. AYe are therefore
justified in founding theories concerning the physiological function of
an organ on a purely anatomical study of its structure, although the
Complete establishment of such theories must ultimately be afforded

^

The kidney differs from all other secretory glands, in the fact that
at the blind end of its tubulus we find a structure — the glomerulus —
where the vascular capillaries abut directly on the lumen of the tubulus, %
without the interposition of any lymph space. Ever since the publication
of "Ho wi n an 's /ffiaffl i* rm_ t,h e Ma.] pi gl i i a/n bodies of the kidney, these have
been looked upon as the essential source of the watery constituents of

Theory of Bowman. — Bowman.1 who founded his theory of urinary
formation exclusively on the anatomical structure of the kidnev in
jajipjisJanimals. concluded that "as the t.nhp.a fl-nf ''thpiv plexus of

capillaries were proba >ly the parts concerned in the secretion of that,
portion of the urine to which its characteristic properties are due (the
invH. lithic acid, etc.), the Malpighian bodies might be an apparatus
jjestined to^se^arate i'rom the blood the watery portion."

The following are the grounds on which Bowman based this
hypothesis : —

(a) That the tubes are secretory.

(1) The extent of surface obtained by the involutions of the

tubules.

(2) The fact that the lining membrane of the tubules is formed

by thick epithelial cells, similar to those found on the
secreting surface of all true glands.

1PM. Trans., London. 1842, p. 57. 0

640 THE SECRETION OF URINE.

(3) The capillary network surrounding the uriniferous tubes is
the counterpart of that investing the tubes of the testis,
allowance being made for the difference in the capacity of
these canals in the two glands.

(6) That the Malpighian bodies differ from the secreting parts of
true glands.

(1) The Malpighian bodies comprise but a small part of the

inner surface of each kidney, there being but one to each
tortuous tube.

(2) The epithelium immediately changes its characters as the

tube expands to embrace the tuft of vessels.

(3) The blood vessels, instead of being on the deep surface of

the membrane, " pass through it and form a tuft on its
free surface."

(4) The peculiar arrangement of the vessels in the Malpighian

tufts is clearly designed to produce a retardation of the
blood through them, while the orifice of the tubule is
encircled by cilia in active motion directing a current
towards the tubule, so tending to remove pressure from
the free surface of the vessels and to encourage the escape
of their more fluid contents. " Why is so wonderful an
apparatus placed at the extremity of each uriniferous
tube, if not to furnish water to aid in the separation and
solution of the urinous products from the epithelium of
the tube ? "

The appearance ui' this paper fell at a time when, led by Ludwig,.
Helmholtz, and du Bois Keyraond, physiologists were endeavouring to,
replace the misty " vitalistic " conceptions which had until then prevailed,
by an accurate comparison of vital phenomena with their physical or
chemical counterparts, and seeking to establish physiology as an exact
experimental science on a par with physics. It was impossible, therefore,
that the views of Bowman, devoid as they were of experimental founda-
tion, should remain unchallenged.

Theory of Ludwig.— In 1844, Ludwig1 put forward his well-known
mechanical theory, for the establishment and testing of which a large
volume of work has been done, the greater part under the direction of
Ludwig himself. According to this theory, all the energy for the secretion
of urine is ultimately derived from the heart-beat. In consequence of
the high pressure obtaining in the capillaries of the glomeruli, a fluid
is filtered through, containing all the constituents of the urine in very
dilute solution. This dilute solution passes down the tubules, and in its
passage undergoes changes, in consequence of diffusion between it and
the fluid (lymph) surrounding the tubules. Since water will always
pass from a dilute to a more concentrated fluid, and since the glomerular
filtrate is, according to the theory, poorer in solid constituents than
the serum, water will pass from urine to lymph, and the urine will
become more concentrated until it acquires the normal characters of
urine.

In this theory of Ludwig there are three distinct propositions to be
investigated. These are —

1. That the secretion of water is a purely mechanical process,

1 Wagner's " Handworterbuch," 1844, Bd. ii. S. 637; " Lehrbuch der Physiologic,'
Aufl. 2, 1858, Bd. ii. S. 373.

SECRETION OF WATER,

641

depending only on the blood pressure in the glomerular capillaries
and the permeability of the filtering membrane.

2. That this dilute urine is concentrated in the tubules by giving up
its water to the surrounding lymph, in consequence of differences of
concentration between the glomerular filtrate and the lymph.

3. That all the urinary constituents are turned out of the blood
through the glomeruli (i.e. with the water) in dilute solution.

In discussing the experimental data bearing on these propositions,
we shall find that only in the first part of the theory are the
experimental facts consonant with Ludwig's hypothesis, and that it is
impossible to explain the formation of normal urine without assuming
the active intervention (i.e. the performance of work) by certain of the
living elements of the Iddney in the process. In this case, as in so
many others in physiology, the "how" of the cellular activity is
at present absolutely unknown to us, although we may confidently
expect, with the advance of the science, to be able to trace the
manner in which the cell utilises the energy of its food for this special
purpose.

Secretion of water.— One of the strongest facts in favour of Ludwig's
hypothesis is the indubitable
connection which exists be-
tween the circulation through
the kidney and the amount
of urine, i.e. of water, secreted.
It is evident that a mechanical
filtration or separation of the
watery and crystalloid consti-
tuents of the blood in the
glomeruli must depend on two
factors —

1. The difference . of pres-
sure between the blood in the
glomerular capillaries and the
urine in Bowman's capsule.
Since under normal circum-
stances there is a free outflow
of urine from the capsule by
means of the tubules, we may
regard its pressure as practi-
cally nil, so that the only
changeable factor in the pro-
cess will be the blood pressure
in the capillaries.

2. The rapidity of the blood flow through the glomeruli must also
have some influence on the filtration, as this process will go on the
more readily the more often the fluid presented to the filter is renewed.
As a rule, the changes that raise the pressure in the capillaries also
increase the velocity of the blood through them, so that it becomes
difficult to dissociate the part played by each factor in influencing the
urinary secretion.

If we consider the manner in which changes in the glomerular
circulation are brought about, we see that it may be affected by changes
either in the general blood pressure or in the calibre of the smaller
VOL. i. — 41

FIG. 59. — Roy's oncometer. (For explanation of
lettering, see next figure. )

642

THE SECRETION OF URINE.

arteries. The pressure in the glomerular capillaries will be raised and
the velocity of the blood increased —

1. By a rise of general blood pressure. This may be due to —
(a) Increased force or frequency of the heart beat ;

(&) Constriction of vascular areas in other parts of the body.

2. By dilatation of the renal arterioles, the general blood pressure
remaining constant.

3. By obstruction of the renal vein. In this case the velocity will
be diminished.

FIG. 60. — Diagrammatic section through Roy's oncometera to show position
of kidney. A, outer, and B, inner, brass capsules. These are fixed
together by the screw C. G, the kidney. D, a clamp for fastening
the two halves together after the kidney has been inserted. K, renal
vessels and ureter.

The pressure and velocity in the glomerular capillaries will be
diminished —

1. By diminished general blood pressure, which may arise from
a weakening or slowing of the heart-beat, or from dilatation of vascular
areas in other parts of the body.

2. By constriction of the vessels in the kidney itself.

Methods. — In the earlier researches 1 on the connection between the
renal circulation and the flow of the urine, the observers had to content them-

xMax Hermann, Sitzungsb. d. Tc. ATcad. d. Wissensch., Wien, 1859, Bd. xxxvi. S. 349 ;
1861, Bd. xlv. S. 317 ; Ustimowitsch; Arb. a. d. physiol. Anst. zu Leipzig, 1870.

METHODS.

643

selves with a measurement of the general blood pressure, and could only
obtain direct evidence as to the local changes in the renal circulation by
inspection of the kidney. It was not until the ingenious application of
plethysmographic methods to the kidney in situ, by Roy,1 that we could
obtain a precise and quantitative estimate of the changes produced on the
circulation through this organ by the measures employed by the older observers.

Roy's instrument for registering changes in the volume of the kidney
consists of two parts, in one of which, the oncometer, the kidney is placed,
while another, called the oncograph, serves as the recording part of the
apparatus. The oncometer consists of two halves hinged together, each of
which is formed of two metal capsules screwed together by the screw C, and
holding between them the membrane H. The two halves thus form a box.
When the two halves are ap-
proximated, the box is closed
except at one point K, opposite
the hinge, where there is an
opening to allow the passage of
the renal vessels and nerves,
and the ureter to the kidney,
which is placed within the box.
During use, the space between
the membrane and the metal
box is filled with warm oil
through the opening in the
screw. The opening in one-half
is then closed with a plug,
while the other communicates
by a tube E, with the onco-
graph. It is evident that any
change in the volume of the
kidney will be communicated
to the oil between the mem-
brane and the capsule, oil being FlG 61.— Roy's oncograph. Diagrammatic section,
driven out into the tube t, The cylinder M is filled with oil, and corn-

when the kidney swells, and municates by the tube K with the oncometer.

being sucked in directly any Changes in the height of the oil are communi-

•u • i • £ 4-t. i • j cated by the piston D to the lever H, the ex-

shrmkmg of the kidney occurs. cursions of which serve therefore as an index of

The oncograph, which is prac- the changes in volume of the kidney,

tically a piston - recorder, in

which the piston is made oil-tight by resting on a loose peritoneal membrane
tied round the tube, serves to register the amount of oil driven out or sucked
into the oncometer, and therefore at the same time the changes in the volume
of the kidney.

A simpler and more efficacious form of oncometer, in which air instead of oil
is used, has been devised by Schafer 2 for the spleen, but is equally applicable
to the kidney. A description of it will be found in the section dealing with
the physiology of the circulation.

Nerve supply. — Before discussing the effects of various operative
procedures on the circulation of the kidney, it will be necessary to say a
few words concerning the nerve supply to this organ, since its vessels,
like those of all other parts of the body, are under the direct control of
the central nervous system.

The gross distribution of nerves to the dog's kidney has been the
subject of a careful investigation by Nollner 3 in Eckhard's laboratory.

1 Journ. PhysioL, Cambridge and London, vol. iii. p. 205. 2 Ibid., 1896, vol. xx.

s Beitr. z. Anat. u. PhysioL (Eckhard), Giessen, 1869, Bd. iv. S. 139.

••MB

644 THE SECRETION OF URINE.

The course taken by the nerves is very variable. The nerves are derived
from the sympathetic chain. From the ganglia lying on the head of the
thirteenth rib, or from the cord immediately below this, is given off a
large nerve (larger than the continuation of the sympathetic chain),
which perforates the crus of the diaphragm, and is called the large
splanchnic nerve. Between this ganglion and the next two or three
ganglia below, are given off' three or four smaller filaments, known as the
small splanchnic nerves. (It must be noted that this terminology is not
comparable with that employed in human anatomy, where the term
splanchnics is confined to the nerves given off by the sympathetic chain
while in the thoracic cavity.) These large and small splanchnics form a
plexus situated behind the suprarenals, and from which filaments are
given off to the coeliac and superior mesenteric ganglia and solar plexus.
From the plexus behind the suprarenals arise a number of filaments,
which form a meshwork in the fat and connective tissues between the
suprarenal and kidney, and then pass to the kidney around, and closely
applied to, the renal artery.

According to v. Wittich,1 the renal nerves in the rabbit, dog, and man
consist of two parts ; one part of them forms a plexus closely investing
the renal artery, while the other consists of several filaments which enter
the kidney parallel to the vessels, and can be traced along these as far
as the cortex.

The termination of these nerves in the kidney has been recently inves-
tigated by Berkeley,2 using Golgi's method. He finds that from the vascular
nerves fine filaments arise to be distributed throughout the cortical and
medullary regions in the form of a vast open network. The glomeruli are
surrounded by a wide-meshed plexus of fibres, having terminal end knobs,
approximated closely to Bowman's capsule, but not penetrating that membrane,
nor passing to the glomerular capillaries. Fibres also pass off from the vascular
plexus to be distributed upon the convoluted tubes, with terminations which
penetrate the membrana propria of the tube, presumably to enter the cement
substance between the epithelial cells. Berkeley looks upon these latter nerves
as probably secretory in function.

With regard to the connection of the renal nerves with the central
nervous system, Bradford 3 has shown that, so far as the efferent nerves
to the renal vessels are concerned, these leave the spinal cord through
the anterior roots. Most of the fibres are contained in the eleventh,
twelfth, and thirteenth dorsal nerve roots.

Influence of blood flow on secretion of urine. — We are now in a
position to consider the influence exerted by changes in the circulation
through the kidney on the secretion of urine. It must be remembered
that a rise of general blood pressure does not necessarily carry with it an
increased pressure in the glomerular capillaries or an increased blood flow
through the kidney. Thus, under many conditions, a rise of general
blood pressure is brought about by a constriction of all the visceral
arteries, including those of the kidney, and such constriction is more
than sufficient to counteract the effects of the increased blood pressure.
If we take a tracing of the kidney volume, for instance, in asphyxia, we

1 Konigsberger, Med. Jahrl., Wien, 1860, Bd. iii. S. 52 (quoted from Heideuliain in
Hermann's "Handbuch").

2 Journ. Path, and BacterioL, Edin. and London, 1893, vol. i. p. 406.

3 Journ. PhysioL, Cambridge and London, 1889, vol. x. p. 358.

INFLUENCE OF BLOOD PRESSURE. 645

find, coincident with the rise of general blood pressure, a marked
shrinking of the kidney. On the other hand, a dilatation of the renal
vessels may be ineffectual to produce an increased flow through this organ,
if at the same time there is a large fall of general blood pressure due
to dilatation in other parts of the body. We may consider, in the first
place, experiments in which the chief change has been in general blood
pressure. It is found that, if the aortic pressure sinks below 40 mm. Hg,
the urinary secretion stops absolutely. So long as the aortic pressure is
above this height, the secretion is more or less proportional to the
pressure, and changes with the changes in this pressure. Thus, if we
stimulate the vagus in the neck, using currents sufficiently strong to
produce a slowing of the heart-beat and a fall of blood pressure, there is
a shrinking of the kidney and a diminution in the urinary flow (Goll).
That this diminution in the flow is directly conditioned by the change in
blood pressure due to the cardiac inhibition, is shown by the fact that
stimulation of the vagi below the diaphragm is without effect on the
urine (Eckhard).

We may also alter the aortic pressure by bleeding the animal to a
considerable amount, and later on reinjecting the blood so withdrawn.
It is found that after the bleeding, while the blood pressure is diminished,
the flow of urine is also lessened, but the flow increases when the blood
pressure is raised by reinjecting the blood which had been withdrawn.

If the aortic pressure be raised by ligaturing a number of the larger
arteries, the increased flow of blood through and the increased pressure in
the kidneys are attended with increased secretion of urine. Thus in one
experiment in which Goll 1 ligatured both carotids, both femorals, and
both ascending cervical arteries, the urine was increased from 87 grms
in 30 minutes before the ligature, to 21'2 grms. after the ligature, while
the pressure in the aorta was raised from 127 to 142 mm. Hg.

Division of the spinal cord. — If the spinal cord be divided in the
upper cervical region, the result is a great fall in general blood pressure,
which may be as low as 30 to 40 mm. Hg. In all cases where the blood
pressure falls below 40 mm. Hg, the flow of urine is absolutely abolished.
Since the renal vessels, like those of all other parts of the body, are kept
in a condition of tone by impulses descending from the vasomotor centre
in the medulla, division of the path of these impulses must cause a
relaxation of the renal vessels, which by itself would tend to occasion
increased blood pressure in the glomeruli. As a result of the section,
however, the vessels all over the body are relaxed, so that the capacity of
the vascular system is increased and the peripheral resistance diminished,
both factors concurring to produce the large fall of pressure observed.
This fall of pressure is more than sufficient to counterbalance the local
renal dilatation, so that there is diminished blood flow through the
kidney, as is shown by the marked shrinking of the oncometric curve of
the kidney on section of the cord.

Stimulation of the cord.1 — If the peripheral end of the divided cord be
stimulated with an induction current, universal constriction of the blood
vessels and a large rise of blood pressure are produced. This, however, is
incompetent to bring back the urinary flow which has been abolished by
the previous section, since the renal vessels concur in the general con-
striction, and the kidney shrinks still further in spite of the raised blood
pressure. If, however, this local constriction be prevented by previous

1 Ztschr.f. rat. Med., 1854, N. F., Bd. iv. S. 86 (quoted by Heidenhain).

646 THE SECRETION OF URINE.

division of all the renal nerves, stimulation of the cord causes a large
expansion of the kidney and brings back the urinary flow.

Influence of the splanchnics.1 — The effects of stimulating the splanch-
nic nerves are very similar to those obtained from the stimulation of the
cord. As in the latter case, a large rise of general blood pressure is
produced, but the constriction of the renal vessels more than counteracts
the effects of this rise, so that the kidney shrinks and the flow of urine
is diminished or abolished. The effects of dividing the splanchnics vary
in different animals. In the rabbit, where, in consequence of the extent
of the vascular area supplied by this nerve, a considerable fall of general
blood pressure is produced, no increase in the urinary secretion is
observed. In the dog, on the other h^ad, the lasting effect on the aortic
pressure is insignificant, so that the relaxation of the kidney vessels
caused by the section induces a largely increased flow through this organ,
and a marked increase in the flow of urine.

Influence of renal nerves. — Division of the renal nerves on one side
causes vasomotor paralysis in the organ of that side. The kidney there-
fore swells, and the flow of urine is increased. The swelling and
secretion is still further increased if the general blood pressure be raised
by stimulation of the splanchnics or spinal cord. Stimulation of the
renal nerves causes constriction of the vessels and diminished flow of
urine.

Bradford 2 has brought forward evidence to show that vaso -dilator
fibres run to the kidney with the constrictors, in the eleventh, twelfth, and
thirteenth dorsal nerve roots. If the anterior roots of these nerves be
stimulated with induction shocks, repeated at the rate of one per second,
the effect is often a marked swelling of the kidney without any rise of
blood pressure sufficient to account for the enlargement. A similar
active dilatation of the vessels may be brought about reflexly by stimulat-
ing the posterior roots of these nerves. We have no direct experimental
evidence as to the influence of this active vascular dilatation on the
renal secretion, although it is extremely probable that a similar condi-
tion is the chief factor in the production of the extreme hydruria met
with in hysteria and other nervous affections.

Constriction of renal artery. — In some of the earliest researches on the
connection between the blood flow through the kidney and the urinary
secretion, it was sought to affect the circulation by direct mechanical
constriction of the renal artery. Hermann,3 who carried out experi-
ments of this nature under Ludwig's guidance, showed that when the
artery was constricted to a considerable extent, the result was a dimin-
ished flow of urine. If the constriction were carried so far that the
circulation of the kidney was entirely stopped, the flow of urine instantly
ceased. So far these results are those one would expect on the filtration
hypothesis. It is found, however, that the flow of urine is not restored
at once on relieving the constriction, and that after a few minutes' total
cessation of the renal circulation, more than an hour may elapse between
the restoration of the circulation and the recommencement of the secre-
tion. We have seen that in the case of lymph formation, where a
process of filtration almost certainly comes into play, a temporary
ischsernia increases the permeability of the vessel wall, so that, on the

1 See especially Eckhard, Beitr. z. Anat. u. Physiol. (Eclchard), Giessen, 1869, Bd. iv.
S. 132, and 153-193.

2 Loc. cit. 3 Loc. cit.

A CT10N OF DIURETICS. 647

subsequent restoration of the blood flow, the amount of lymph transuded
is greater than before the ligature. In the kidney the reverse is the
case. A temporary ischoemia abolishes the flow for a considerable period
after the obstruction has been relieved. This fact shows that, for the
normal production of urine, the integrity of the living cells between the
blood and Bowman's capsule is necessary ; but I do not think that it
can be looked upon as definitely proving the active co-operation of these
cells in the process. In the kidney we have two layers of cells, the
vascular endothelium and the glomerular epithelium, intervening between
the blood and urinary tubule, and we have no evidence to guide us as to
the effects of temporary ischsemia on the glomerular epithelium. We
know that in a certain sense it becomes more permeable, inasmuch as
the urine which is first secreted after the restoration of the circulation
contains albumin, which may be traced on its way through the glome-
rular epithelium into the capsule. But this fact in itself might tend to
impede the flow of water through the glomerular membranes.

Ligature of renal vein. — In the case of lymph formation, a rise of
venous pressure tends to increase the amount of lymph produced. In
the kidney, ligature of the renal vein stops the flow of urine at once,
although it must send up the pressure in the glomerular capillaries to a
height approaching that of the renal artery. Now, in this case there are
three factors which might be concerned in causing the cessation of
secretion : the blood flow through the kidney is checked ; the cells of
the glomerular epithelium are asphyxiated ; and the engorgement of the
renal veins causes the interlobular veins to swell up and press on the
adjoining collecting tubules. Heidenhain lays most stress on the first
factor, and, relying mainly on this experimental result, concludes that
the chief agent in exciting glomerular activity is not the blood pressure
in the glomerular capillaries, but the rapidity of the flow through the
capillaries. On the other hand, Ludwig has shown that the effect of the
swelling of the interlobular veins is to obstruct the urinary tubules ; and
he looks upon the cessation of flow as entirely due to this mechanical
obstruction. It is impossible at present to decide which of these
explanations is correct, or indeed whether all of them may not be
involved.

Action of diuretics. — Since the main office of the kidney is to assist
in maintaining the normal constitution of the blood by freeing it from the
waste products of tissue metabolism, we should expect it to react and tq
be sensitive to slight changes in the composition of the blood. As a
jai fact, we find that such ia the caflft, and t.hat t^e, ftam'pntr way fr>-

thfT"rmnfl.ry flnw'ja^jT^^ltprmg- t.hft p.nmpnaiff]'flp nf tho KlnnH, -
te Ifl-ygft rpa.ntit.ies '

fh'nrfttiflfii nf these bodies the only ones we

need discuss are the large class known as saline diuretics and the drugs
caffein and digitalis. 4—^m£2t+&^si*y <&£*<* ^-^

Saline diuretics include practically all crystalloid substances, which
can be injected into the blood in considerable quantities. As examples,
we may cite urea, dextrose, sodium chloride, potassium nitrate, sodium
acetate, etc. If these bodies be injected into the blood, a very copious
secretion of urine is soon evoked, even if, previously to the injection,
the secretion had been at a standstill. In experiments on the excised
kidney, it has in most cases been found necessary to add urea or some
other substance of this group to the defibrinated blood used for the

648 THE SECRETION OP URINE.

artificial circulation, before any secretion could be obtained.1 On
inquiring into the mode of action of these bodies, we find that their
injection is followed by a slight rise of blood pressure accompanied with
a marked expansion of the kidney, and this expansion lasts throughout
the period of increased urinary now. These effects are observed even
after all the renal nerves have been severed, so far as is practically
possible, and it has therefore been concluded that the changes in volume
of the kidney must be due to the substances acting either upon some
peripheral vasomotor mechanism, or even more directly upon the blood
vessels themselves. Since the increased secretion of urine is cotermin-
ous with the increased blood flow through the kidney, it is natural to
place these two events in the relation »f effect and cause. To this con-
clusion it has been objected that one may frequently observe an absolute
standstill of secretion, with a high aortic blood pressure changed into a
copious secretion by the injection of one of these bodies, although the
blood pressure has been practically unaltered. Heidenhain and others
with him, therefore, look upon the action of these bodies as secretomotor.
Against the specific secretomotor action, either of urea or of the salines,
the following arguments may be brought forward. V. Limbeck2 has
shown that the power of these bodies to induce urinary secretion on
injection into the blood stream is proportional to their power of attracting
water ( Wasseranziehungsvermogeri), and is thus a function of their mole-
cular weights. Now it has been proved 3 that the result of injecting these
bodies into the blood is to cause an active flow of water from the tissues
into the blood, which therefore becomes diluted to an extent varying with
the osmotic pressure of the substances injected. The final effect, there-
fore, is the same as if a solution of the substance isotonic with or normal
to the blood had been injected into the circulation, and a condition
of hydraBinic plethora thus induced. We know that a condition of
hydraemic plethora is associated with dilatation (especially of the visceral
vessels), general rise of capillary and venous pressures, and increased
rapidity of blood flow. The fact that the diuretic action of these bodies
is proportional to their osmotic pressures, implies that it is also propor-
tional to the hydrsemic plethora produced by the injection ; and it seems
probable, therefore, that the plethora is the chief agent in causing, first,
the vascular changes in the kidney, and secondly, the diuresis. If these
bodies acted as specific stimulants of the kidney, we should expect the
increased flow of urine to continue until all the substance injected had
been excreted. Such, however, is not the case. The diuresis comes to
an end when only a small amount of the injected substance has been
excreted, and lasts little or no longer than the hydraemic plethora which
accompanies it.

Of the other diuretics, the action of two, caffein and digitalis, has been
very fully investigated. If half a grain of caffein be injected into a vein,
the kidney after a few seconds diminishes in volume, and the flow of urine
is lessened or entirely arrested. This contraction soon passes off, and is
followed by a rapid expansion, which is more considerable and lasts much
longer than the preceding contraction. Simultaneously with the beginning

1 M. Abeles, Sitzungsb. d. k. AJcad. d. Wissensch., Wien, 1883, Bd. Ixxxvii. ; I. Munk,
Virchovfs ArcTiiv, 1886, Bd. cvii. S. 291 ; ibid., S. 187 ; and I. Munk and Senator,
ibid., 18S8, Bd. cxiv. S. 1.

2 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1889, Bd. xxv. S. 69.

3 V. Brasol, Arch. f. PhysioL, Leipzig, 1884, S. 211 ; Starling, Journ. PhysioL, Cam-
bridge and London, 1894, vol. xvii. p. 30 ; Leathes, ibid., 1895, vol. xix. p. 1.

LIGATURE OF THE URETER. 649

of the expansion, the urinary flow recommences and becomes much more
rapid than it was previously to the injection of the drug. On the general
blood pressure the injection of caffein causes an initial slight fall, followed
by a return to normal or a little above normal. In this case we seem to
be dealing with a drug, the most important action of which is on the
renal vessels, and it is probable that the increased pressure in and flow
through the glomerular capillaries induced by the drug is largely
responsible for the augmented flow of urine. According to von
Schroder,1 it is possible, by the administration of chloral, to abolish the
vaso-dilator effect of caffein in rabbits without destroying the diuretic
action of the drug; but too much reliance cannot be placed on this
statement, since the volume of the kidney was not measured in this
observer's experiments.

The effect of digitalis is rather more complex. It slows and
strengthens the cardiac beat, and at the same time constricts the smaller
arteries of the body, so that the arterial pressure is raised. In heart
disease the result of the improved working of the cardiac pump is to
relieve the venous pressure, increase the arterial pressure, and so bring
about an improved blood flow through the kidney. In such cases, there-
fore, digitalis acts as a powerful diuretic. In the healthy animal the
effect of this drug is more doubtful. It causes a constriction of the
renal vessels and therefore a shrinking of the kidney. Under certain
circumstances, however, it does exert an appreciable influence in causing
diuresis, which we .may either explain, with Bradford and Phillips,2
as due to a direct action of the drug on the renal epithelium, or to the
fact that the rise of blood pressure more than counteracts the renal
constriction, so that there is an increased blood flow and pressure in the
glomerular capillaries.

Effects of ligature of the ureter. — If we are to look upon urine as a
filtrate, the amount of it must vary as P — p, where P represents the
pressure in the glomerular capillaries, while p represents the pressure at
the beginning of the urinary tubule. So far, we have only considered
the effects of altering P, and have seen that, in the majority of cases at
any rate, the secretion of urine rises and falls with this pressure. Under
normal circumstances p is so small that it may be neglected, but we
ought to be able to diminish the flow of urine by increasing p. If the
ureter be obstructed by connecting it with a mercurial manometer, it
will be found that the mercury in the manometer rises quickly to 10 or
20 mm. Hg, and then more slowly until, in the dog, it may attain the
height of 50 or 60 mm. Hg, at which pressure the mercury column
remains stationary. The pelvis of the kidney and the ureter above the
ligature are now strongly distended ; the kidney is swollen, and a marked
oedema is soon observed extending to the perinephritic tissues, while
the lymphatics of the hilus are distended with clear fluid. Some hours
later, haemorrhages are found in the fatty capsule and in the pelvis and
ureter. Ludwig interpreted these results as determining the conclusions
he had already drawn from the effects of section of the spinal cord, i.e.,
that, for the production of urine, a certain minimum difference of
pressure P — p is necessary, and that the difference might be reduced
below this limit either by diminution of P or by augmentation of p.

1 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1887, Bd. xxii. S. 39; 1888, Bd.
xxiv. S. 85.

2 Journ. PhysioL, Cambridge and London, 1887, vol. viii. p. 117.

650 THE SECRETION OF URINE.

Heidenhain, however, points out that we have no right to conclude that
the secretion of urine has ceased when the mercury column no longer
rises. This stage in fact corresponds merely to the point at which the
continued secretion of urine is balanced by the reabsorption of the urine
from the tubules, in consequence of the abnormal pressure within
them.

It must be confessed that we have no very definite evidence that
such a reabsorption takes place. It is true that the kidney becomes
oedematous in consequence of the ligature, but the oedema fluid was stated
by Ludwig to consist of lymph and not of urine ; and it has been shown
that increased pressure in the urinary tubules causes them to press on
the adjoining veins, so that the es(*ipe of blood from the kidney is
hindered, and ordinary oedema results. Fresh investigations on this
matter are much to be desired, since the only analyses we have of the
oedema fluid and retained urine are those of Hermann, one of the earliest
observers on the subject. The urine, which is secreted under pressure
and which distends the pelvis and ureter, is light in colour, of low
specific gravity, and contains very little urea. If, after some time, the
ligature round the ureter be relaxed, the result is at once a copious
secretion of watery urine. In man a similar fluid is well known to be
excreted in cases where there is a chronic obstruction of the ureter.

The concentration of the urine. — We have now to consider the
second part of Ludwig's theory, according to which the dilute urine
transuded through the glomeruli is concentrated on its passage down
the tubules, by the absorption of its water. This absorption takes place
in consequence of the fact that the lymph surrounding the tubules is
more concentrated than the urine. A cogent objection to this hypo-
thesis was raised in 1859 by Hoppe (Hoppe-Seyler), who showed that,
if urine were separated by an animal membrane from blood serum of
the same animal, there was a flow of water from serum to urine.1 The
tendency of this urine, therefore, in passing down the urinary tubules,
would have been to become more dilute, in consequence of osmotic
interchanges between it and the serum. At this time our knowledge
of the factors and forces involved in the interchange of water and sub-
stances in solution across animal membranes was meagre and inexact ;
and it is only quite recently that we have acquired the necessary data
for testing the truth of Ludwig's hypothesis and the fitness of Hoppe-
Seyler 's objections.

Pf effer 2 showed that the osmotic attraction of any solution for water
might be determined by measuring its osmotic pressure, and first pointed
out how enormous these pressures were in the case of even relatively
dilute salt solutions. Van t' Hoff later on pointed out that the osmotic
pressure of a solution was proportional to the number of molecules this
contained, and was therefore a colligative property (Ostwald), like certain
other properties of solutions — such as the diminution of the freezing
point and of the vapour tension and the elevation of the boiling
point.

Since these properties of a solution are proportional to one another,
we need only know one to determine any of the others. This fact is of
importance when we wish to determine the osmotic pressure of animal
fluids, since we can substitute for the difficult and inexact determination

1 Virdiow's Archiv, 1859, Bd. xvi. S. 412 (quoted by Heidenhain).

2 "Osmotische Untersuohungen," Leipzig, 1877.

OSMOTIC PRESSURE OF URINE. 651

of osmotic pressures by Pfeffer's method a determination of the freezing-
point of the solution. As van t' Hoff has shown, if A is the depression of
freezing-point and T the absolute freezing-point of the solvent (i.e., for
water, 273°, and w the latent heat of fusion of ice = 79 cal.), then the
work A can be reckoned from the following formula : —

dA = -— x dv.

Thus for 1 per cent, solution of cane-sugar (A = -055)
^ = -05579 X(fo.

^ / O

To reduce this result to gravitation units we must multiply by 424,
and we thus find that to separate the volume dv of pure water as ice
from 1 per cent, cane-sugar solution, a force is necessary equal to the

•055x79x424
pressure of a column of water of - — TQ — ~ metres in height.

A depression of A= — 1° corresponds therefore to an osmotic

79 x424
pressure of — 970"* ? that is to say, to 1227 metres of water. We

have therefore to multiply A by 1227, in order to obtain the osmotic
pressure in metres of water of any solution.

Now it is evident that, according to Ludwig's hypothesis, the osmotic
pressure of the urine might attain to but could never exceed that of
the blood plasma. On estimating the osmotic pressures of these two
fluids, we find that, under normal circumstances, the osmotic pressure of
the urine is considerably greater than that of the blood, so that work
must have been done in the separation of this concentrated fluid from
the more dilute blood plasma. Dreser 1 has estimated this work in a
case in which, during one night, 200 c.c. of urine were secreted with
A = 2'3. This was separated by the kidneys from the blood with
A = -56. In the production of this fluid Dreser finds that the work
done by the kidney amounts to 3 7 '03 7 kilogramme metres. This figure
by no means represents the maximum force which can be exerted by the
kidney. From a cat which had been deprived of water for three days,
Dreser drew off some urine with A = 472 C. The blood at the same
time had an osmotic pressure corresponding to A=0'66 C. These
differences in freezing point denote an osmotic difference of 498 metres
water, i.e. a pressure of 49,800 grins, per square centimetre. If this
work of concentration were carried out by the cells of the tubules,
these results would imply that these cells can exert a force six times
greater than the absolute force of human muscle (8000 grms. per square
centimetre).

Assuming that the whole work of the tubules is confined to the act
of concentration, Dreser seeks, moreover, to demonstrate that the
glomerular secretion also involves the activity of living cells. Since
the blood pressure of 200 mm. Hg = 272 metres water, and A 1°'0 C. =
1227 metres water, the highest possible difference between dilute urine
and blood, assuming that no concentration had taken place, could only
be A = 0'°022 C. Dreser finds, however, that after beer drinking, and

1 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1892, Bd. xxix. S. 307.

652 THE SECRETION OF URINE.

in diabetes insipidus, the urine secreted may have A = 0°'16 C., i.e. a
difference between A of blood and of urine of 4° C. Hence he con-
cludes that the production of urine by the glomeruli is also attended
with the doing of work, and must therefore be looked upon as a process
of secretion. We might, however, still adhere to the theory of glomer-
ular nitration, if we assumed either that the cells of the tubules could
absorb water or solids according to the needs of the organism, or that
they were able to secrete pure water and so dilute the glomerular
trans udation.

Heidenhain's criticism of the theory of Ludwig. — The difficulties
in the way of accepting Ludwig's hypothesis have led Heidenhain, after
a long series of researches on the subject, to reject this theory abso-

Jritph^jr1 favmir nf rmft vp.ry fiiTrnlfl.r fo tV.Qf. p^fr fnrWfir^ ^y "RflwrPa;n— ^

Heidenhain sums up his objections to the mechanical theory under
the following headings : —

1. The hypothesis that a rise of arterial pressure causes increased
transudation through the vessel walls, is not confirmed by our experience
in other parts of the body (lymphatics of the limbs, salivary glands).

2. This hypothesis is rendered the more improbable for the kidney,
since in this situation the glomerular capillaries are covered by a second
layer of epithelium, and we know, from Leber's researches on the cornea,
that such a simple epithelial layer can afford great resistance to
nitration.

3. If we assume that all the constituents of the urine are filtered
off in the glomeruli, the small amount of urea in the blood renders it
necessary that in man about 70 kilos, of fluid should be filtered through
and reabsorbed, in order that the urea produced in the course of
the day may be excreted in the urine, — an amount which is highly
improbable.

4. According to the filtration hypothesis, the amount of urine formed
must always increase with increased capillary pressure, whereas we find
that, on increasing capillary pressure by ligature of the renal vein, the
urinary flow is abolished.

5. The hypothesis that the glomerular transudate is concentrated by
a process of osmosis or diffusion, on its way through the glomeruli, is
rendered impossible by the fact that the osmotic pressure of the
urine may be, and generally is, much higher than that of the lymph
or blood.

6. The filtration hypothesis does not explain why the amount of
urine is increased by the presence of water or crystalloid (hmmfaMg)
substances in the blood.

From his own researches on the subject, Heidenhain conies to the
following conclusions with regard to the mechanism of secretion : —

1. In the kidney, as in all other glands, the secretion depends on the
active intervention of special secretory cells.

2. The first type of these cells is represented by the simple layer
of epithelium covering the glomerular loop of capillaries. The office of
these cells is to secrete water and such salts of the urine as are found
in all other parts of the body in watery solution (e.g. sodium chloride).

3. Another system of secretory cells, forming the lining investment
of the convoluted tubules and ascending tubule of Henle, secrete the
specific constituents of urine (urea, uric acid, etc.). Under some con-
ditions they may at the same time secrete a certain amount of water.

HEIDENHAIN' S THEORY. 653

4. The activity of the two kinds of secretory cells is determined —

(a) By the amount of water or urinary constituents contained in the
blood ;

(b) By the velocity of the blood-flow through the capillaries of the
kidney, inasmuch as on this factor depends the supply of oxygen, and
of substances to be excreted, to the cells.

5. The great variability in the constitution of the urine may be
explained by differences in the secretory activities of these two types of
cell.

The most important part of these conclusions of Heidenhain is a
revival of Bowman's theory, that the specific urinary constituents, urea
and uric acid, are secreted by the tubules, and that the office of the
tubules is secretory rather than absorbent. Tra — L ~""'J 1 *

ity of tho oollo in the tubuloo? $-*+ p
The great solubility and diffusibility of urea render it impossible to
trace this substance on its way through the kidney by micro-chemical
means. A better prospect of success would seem to be afforded by
the more insoluble uric acid and urates ; and both Bowman l and v.
Wittich 2 have described the presence of uric acid crystals in the cells
of the convoluted tubules of birds. Semicrystalline deposits of guanin
have been demonstrated with certainty in the cells of the excretory
organ of molluscs, but later researches by Adolph Schmidt 3 have shown
that the observations of Bowman and v. Wittich must have been due
to faulty methods of preparation. Deposited urates were frequently to
be seen in the urinary tubules of birds, but never in the cells them-
selves. In order to throw light upon this point, Heidenhain had
recourse to a method, devised by Chrzonzsczewsky,4 i.e. the injection of
sodium sulphindigotate (indigo -carmine) into the blood, and the tracing
of this coloured substance through the cells of the kidney.

It is found that this substance is excreted in any quantity by two
glands only of the body, namely, the liver and the kidney. If 5 c.c, of
a saturated watery solution of the sulphindigotate be injected into the
veins of a rabbit, within a few minutes the urine becomes a deep blue,
and on killing the animal the kidneys are found to be stained blue, the
colour being best marked towards the apex of the pyramid. In order to
find out in what portion of the secreting substance of the kidney the
colouring matter is turned out, the flow of urine must be checked, since
otherwise the excreted pigment is at once washed down into the lower
parts of the tubules and ureter. To this end Heidenhain 5 divided the
spinal cord in the neck. The flow of urine being thus stopped, 5 c.c. of
the saturated solution of indigo-carmine is injected into the blood vessels ;
ten minutes later the animal is killed, and the blood vessels of the
kidney washed out with absolute alcohol. By this means the pigment
is precipitated in situ. On cutting into the kidney, it is at once seen to
differ widely in appearance from that of an animal in which the cord
was intact. Instead of being diffusely stained, the kidney now is coloured
a deep blue, in the cortex, the medulla presenting the normal appearance.
On examining a section under the microscope, it is seen that the blue
colour is due to the deposition of pigment granules in the lumen and
in the striated cells lining the convoluted tubules and the ascending

1 LOG. cit. 2 Arch.f. mikr. Anat., Bonn, 1875, Bd. xl. S. 81.

3 Arch.f. d. ges. PhysioL, Bonn, 1890, Bd. xlviii. S. 34.

4 Virchow's Archiv, 1866, Bd. xxxv. S. 158. 5 Loc. cit.

654 THE SECRETION OF URINE.

limb of Henle's loop, the capsules and the collecting tubules as well as
the descending loop of Henle being quite free from pigment.

A very interesting appearance is offered by the kidney, if, previous
to the injection, its surface has been cauterised over a small area with
silver nitrate, the cord being intact. In the cauterised zones, the secre-
tion of water is stopped, but the excretion of indigo -blue is not affected,
so that in these zones the blue colour is confined to the cortex, whereas
in the rest of the kidney the coloration is diffuse. Heidenhain con-
cludes from these observations that the excretion of indigo-blue is due
to the specific secretory activity of the striated cells lining the con-
voluted tubules and ascending loop of Henle. Since these cells are the
only cells of the kidney which hav^ the power of excreting indigo -
carmine, an abnormal constituent of the blood, it is natural to assume
that they may also possess the specific function of secreting the urea of
normal urine.

These conclusions of Heidenhain's have not, however, passed un-
challenged. Various observers have pointed out that, in order to obtain
the results described by Heidenhain, it is necessary to repeat exactly all
the details of his experiments. If we inject larger doses of the
sulphindigotate and kill the animal ten minutes after the injection, it
will be found that, in addition to the staining of the striated cells of the
convoluted tubules, and the deposition of precipitated pigment in the
lumen of these tubules, there is also a slight staining of Bowman's
capsule and the glomerular epithelium. It has been suggested 1 that
Heidenhain's results might be equally well explained on Ludwig's
hypothesis, according to which a dilute solution of the dye would be
exuded into Bowman's capsules, and would be concentrated by absorption
of fluid on its way through the convoluted tubules. Indigo-carmine is
soluble in water and in very weak salt solution, from which it is
precipitated on concentration. Moreover, indigo-carmine is liable to
reduction in the living tissues with the formation of a colourless
product, and these two factors, i.e. reduction of the pigment and the ex-
treme dilution of the glomerular exudation, have been held to explain
the absence of glomerular staining in Heidenhain's experiment. By
increasing the dose injected into the veins and killing the animal soon
after the injection, these two factors are minimised and a staining of the
capsules is brought about. Sobieranski 2 points out that the staining or
deposition of granules in the cells of the convoluted tubules is confined
to the parts of these cells bordering on the lumen — a fact which seems
to indicate that the pigment has been taken up by these cells from the
lumen rather than from the surrounding lymph spaces.

These observations are to a certain extent confirmed by the effects of
the injection of carmine. This substance, which has a much more com-
plicated composition than sodium sulphindigotate, enjoys the correspond-
ing advantage of smaller difrusibility, so that it can be more easily traced
on its way through the tissues of the body. Moreover, it undergoes no
reduction in contact with the living cells. The circulatory disturbance
which often accompanies the injection of this substance may be almost

1 Pautynski, Virchow's Archiv, Bd. Ixxix. S. 393 ; Henschen, Akad. Afhandlung f.
tnedicinska Graden, Stockholm, 1879 (quoted by Sobieranski) ; v. Sobieranski, Arch. f.
exper. Path. u. PharmakoL, Leipzig, 1895, Bd. xxxv. S. 144. (The two first papers are
the subject of a critical paper by Grutzner, Arch. f. d. ges. PhysioL, Bonn, 1881, Bd. xxiv.
S. 441.)

2 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1895, Bd. xxxv. S. ]44.

EXPERIMENTS OF NUSSBA UM. 65 5

entirely avoided by using a solution of carmine in very weak soda, and
carrying out the injection slowly (10 c.c. in five minutes). If we kill
the animal thirty to forty minutes after the injection, and wash out the
kidney from the renal artery with absolute alcohol, we find the glomeruli
stained, the nuclei being red, the glomeruli themselves being of a fainter
reddish tinge. The epithelium of the convoluted tubules contains fine
granules of pigment towards the inner part of the cells, and here and
there deposits of carmine are seen in the straight tubules. Under no
circumstances are the pigment granules ever found in the basal parts of
the epithelial cells. There can be no doubt that these appearances
suggest that the pigment has been taken up by the cells from the lumen
rather than that it is in the act of excretion by the cells. In neither of
these two experiments do the facts at our command allow us to come to
a definite conclusion with regard to their interpretation. In order to
decide the relative functions of the glomeruli and convoluted tubules, it
would be necessary to separate in some manner the activities of these
two parts of the kidney, so as to obtain the action of one or other of
them in an isolated form.

Experiments of Nussbaum. — A method for attaining this object
was devised by Nussbaum,1 and promised at first to be of crucial
importance for the physiology of urinary secretion. The kidneys of
amphibians possess, as Bowman pointed out, a double vascular supply,
i.e. from the renal artery and from the renal portal vein. From the
former vessel are derived the vasa afferentia to the glomeruli, whereas
the latter breaks up into capillaries which anastomose round the
tubules, in conjunction with the capillary ramifications of the efferent
vessels of the glomeruli. Nussbaum imagined, therefore, that the
glomerular activities might be altogether excluded by ligature of
the renal artery. Carrying out a number of experiments of this
description, he obtained results which seemed to decide absolutely in
favour of Heidenhain's hypothesis. Thus, after ligature of the renal
arteries in frogs, the urinary flow was abolished. A flow of urine
might, however, be evoked by the injection of urea into the blood,
proving, according to Nussbaum, that the substance was not excreted
by the glomeruli but by the tubules, and also that the latter struc-
tures could, under the influence of diuretics, secrete part of the water
of the urine. In a normal frog the injection of peptone, egg-albumin,
or sugar into the blood is followed by the excretion of these substances
in the urine. If, however, the renal arteries be previously tied, none
of these substances appear in the urine, even when a urinary flow is
produced by the injection of urea. Carmine also, which is acknow-
ledged by all observers to be excreted by the glomeruli, does not
appear in the urine of the frog, if the renal arteries be ligatured.
Nussbaum concluded, therefore, that the excretory apparatus of the
kidney consisted of two parts, namely, the glomeruli, which excreted
water and salts as well as egg-albumin, peptone, and grape-sugar ; and
the tubules, which excrete urea and probably uric acid, together with
a certain proportion of water.

These experiments are so definite that they would seem to decide
the question as to the part played by the various structures of the
kidney, were it only possible to place reliance on them. This un-
fortunately is not the case. A careful repetition of Nussbaum's ex-

1 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xvii. S. 580.

656 THE SECRETION OF URINE.

periments by Adami,1 working in Heidenhain's laboratory, has shown
that in the frog it is impossible to cut off the blood supply to the
glomeruli by ligaturing the renal arteries. In fact, after this operation,
fully half of the glomeruli may be injected from the aorta, owing to
the free anastomoses between the renal artery and the branches of
the ovarian arteries and the renal portal vein, and it is difficult to
understand how ISTussbaum can have obtained the very definite results
described by him. These, therefore, in spite of the ingenuity of the
methods employed, must be discredited in any discussion concerning the
functions of the various parts of the kidney tubule.

Experiments of Ribbert. — A bold attempt to experimentally disso-
ciate the activities of the two portion^ of the urinary tubule was made
by Eibbert,2 who adopted the method of excising as far as possible the
medulla of the kidney, so as to obtain the glomerular secretion after
it had passed through only the first convoluted tubules. This opera-
tion is only possible in animals such as the rabbit, in which the renal
medulla is made up of one Malpighian pyramid. It was carried out
in the following way: — One kidney having been exposed from the
back, was cut in two by an incision at right angles to the long diameter
of the organ, extending into the pelvis. By means of a gouge, as much
as possible of the pyramid internal to the boundary zone was removed.
The two halves of the kidney were then placed together and secured
by sutures, and the other kidney totally excised. Eibbert found that
such animals during the next twelve to twenty-four hours secreted a
much larger quantity of urine than they had previously done. The
urine was more dilute and much lighter in colour than the urine of
rabbits under normal conditions. No analyses, however, of the fluid
were made. Eibbert interprets these results as confirming Ludwig's
hypothesis. But apart from the increased quantity, which does not
seem to me to be definitely established by Eibbert's experiments, the
production of a more dilute urine would be expected on either
hypothesis, whether we assume with Ludwig that the tubules absorb
water from the urine, or with Heidenhain that they excrete solid
substances into the urine.

Experiments of Bradford. — The very insufficient description of
his experiments given by Eibbert might incline us to discredit them
altogether, were it not that somewhat analogous results have been
obtained by Bradford.3 This observer found that extirpation of one
kidney, combined with excision of a large wedge-shaped piece from the
other kidney, might bring about one of two results —

1. If the amount of kidney substance left amounted to one quarter
of the weight of the two kidneys, the animals (dogs) lived a considerable
time, but suffered from hydruria, i.e. the quantity of urine excreted was
largely increased, but the excretion of urea remained unchanged, so
that the urine was much more dilute than before.

2. If the amount of kidney left was less than one-sixth of the total
kidney substance, polyuria was produced, i.e. a large increase in the
excretion of water as well as of urea. This increased production of urea
was due to a rapid wasting of the proteid constituents, and especially of
the muscles of the body, so that the animals died in a short time in a

1 Journ. PhysioL, Cambridge and London, 1885, vol. vi. p. 382.

2 Virchow's Archiv, 1883, Bd. xciii. S. 169.

3 Proc. Roy. Soc. London, 1892, vol. li.

REACTION OF THE URINE. 657

state of extreme emaciation. This latter result is difficult to explain,
and will be discussed in another section of this volume. The former
result (the hydruria) may, however, be analogous to the results of
Ribbert's experiments, and may be due to a diminution in the actively
absorbing or secretory mechanisms of the kidney, i.e. the convoluted
tubules. It seems probable that a deficiency in the excretory powers of
the organism could be more easily compensated by augmenting the
glomerular transudation by means of the blood supply to the glomeruli,
than by increasing the work of the cells of the convoluted tubules. t

Arguments based upon the reaction of urine. — An objection which has
been frequently urged against the filtration hypothesis is that, whereas
the blood serum or plasma is in all animals alkaline, the urine, except in
those cases where there is a rich supply of alkali in the food, is acid
in reaction. It seems difficult to conceive how a process of filtration
could effect this change in the reaction of the filtrate. Since all author-
ities are agreed that the urine undergoes changes in composition on its
way through the tubules, it becomes important to find out whether the
urine, as it is formed by the glomeruli, is alkaline or acid.

Dreser1 has sought to determine this question by examining the
microchemical reactions in the different parts of the kidney in the frog.
As his indicator he used acid fuchsin (rubin S.) This substance is a
brilliant red in acid solutions, but is almost colourless in weak alkaline
solutions. It is, therefore, a convenient substance to use in order to
demonstrate the formation of acid in muscle during tetanus. A strong
solution of this dye was injected into the dorsal lymph sac of the frog.
An hour or two later the urine that was secreted was of a deep red
colour, and was acid in reaction. On examining the kidneys, the dorsal
part in which the glomeruli are situated was found to be colourless, but
the tubules in the ventral part were filled with red secretion. If the
injection were repeated the red coloration extended to the lining cells
of the tubules. From his experiments with this and other dyes, Dreser
concludes that the production of the acid reaction is effected by the cells
of the convoluted tubules, and that the glomerular transudate is alkaline.

This conclusion is borne out by the results of injecting any kind of
diuretic. If the glomerular transudate is alkaline, and is also rendered
acid in its passage through the tubules, we should expect that the more
abundant the glomerular transudate, the shorter would be the time taken
in its passage through the tubules, so that the urine pouring into the
bladder would tend to approximate in reaction and composition the
original glomerular transudate. Such is found to be the case. Whatever
means we use to induce profuse diuresis, whether by the injection or
administration of drugs such as caffein or theobromin, or the adminis-
tration of saline diuretics, or the production of hydraemic plethora,
we find that the acid reaction of the urine disappears, to be replaced by
a neutral or alkaline reaction. We may conclude, with a high degree of
probability, that the glomerular part of the urinary secretion is alkaline
in reaction, and that the acid reaction of the urine of carnivora or
of starving herbivora is due to the changes wrought on the glomerular
transudate by the cells of the convoluted tubules. Whether this
change is due to the secretion of acid salts, or to the absorption of
alkaline salts by the cells of the tubules, we are not in a position to
determine.

1 Ztschr.f. Bid., Munchen, 1885, Bd. xxi. S. 41.
VOL. l. — 42

658 THE SECRETION OF URINE.

An ingenious attempt has been made by Liebermann1 to explain the
chemical mechanism by which the cells of the tubules effect this change in
reaction. This author has described a class of bodies which may be extracted
from the mucous membrane of the stomach or from the kidney, and which
consist of compounds of lecithin and proteid. These he designates lecith-
albumins. These substances are acid in nature, and are capable of combining
with alkalies. Liebermann imagines that, as the alkaline salts of the blood
plasma pass through the epithelial cells of the kidney, they are split up by these
acid insoluble lecith-albumins, which combine with a portion of the bases, so
that the remainder of the fluid which reaches the lumen of the tubule contains
acid salts or free acid. Of course this process would come to an end as soon as
the acid affinities of the lecith-albumins in the cells were satisfied, and in this
way one might explain the speedy appearance of an alkaline reaction when
large quantities of urine are secreted. Under normal circumstances, however,
Liebermann assumes that the carbon dioxide, which is the normal product of
tissue metabolism in the kidney, splits up the compound formed in the cells
into free lecith-albumin and alkaline carbonates, these latter being then
removed by the venous blood stream. As supporting evidence for this hypo-
thesis, LieJ3ermann states that the kidney tissue, like lecith-albumin itself, if
treated with soda solution, and then washed repeatedly with water to remove
excess of the latter, becomes strongly alkaline. If now the alkaline tissue be
suspended in water, through which a stream of CO., is passed, and be then
again washed thoroughly, it will be found to be strongly acid, having given up
all its soda to the carbon dioxide.

Conclusions. — It is evident that the experimental facts at our pre-
sent disposal do not allow of a definite decision as to the exact manner
in which the secretion of urine is effected. It will be convenient,
therefore, to summarise the two modes of interpretation, either of which
may be applied to the known facts.

According to the Bowman-Heiclenhain. hypothesis, the secretion of
urine is due to the activity of two. sets of cells. The flattened epithelial
cells covering the glomeruli take up from the blood, circulating through
the glomerular capillaries, water and salts, and transfer these substances
to the beginning of the urinary tubule. Their activity is chiefly depend-
ent on the activity of the blood flow through the capillaries. But they
may be also excited to active secretion by the presence of certain of the
urinary constituents in the blood, such as water and salts, or possibly by
diuretics, such as caffein. On the other hand, the roddecl cells, lining the
convoluted tubules and the ascending loop of Henle, secrete specific
urinary constituents, such as urea and uric acid, together with a certain
amount of water. They also secrete certain abnormal constituents of the
blood, such as indigo -car mine. Their activity is chiefly determined by
the amount of urea or uric acid in the blood.

If, on the other hand, we accept Ludwig's hypothesis, we must
introduce into it certain modifications, necessitated by later inquiries,
and assume that in the secretion of urine, as in so many other of the
bodily functions, there is a mixture of what we may term physical and
physiological processes. It seems probable that in the glomeruli the
process is largely if not exclusively physical ; that is to say, we have here
a transudation of the watery and crystalloid constituents (including
urea) of the blood plasma. The extent and nature of this transudation
are determined —

1. By the pressure in the glomerular capillaries.

1 Arch.f. d. ges. PUysioL, Bonn, 1894, Bd. liv. S. 585.

CONCLUSIONS. 659

2. By the velocity of flow through the capillaries.

3. By the permeability of the capillary wall and the glomerular
epithelium.

This watery transudate is concentrated and altered on its way through
the tubules, in consequence of the absorption of water, and probably of
certain of its crystalloid constituents. This absorption must be due to
the active intervention of the cells, since the osmotic pressure of the
urine is considerably higher than that of the blood pressure. Diuretics
may act in two ways. The saline diuretics increase the pressure and
velocity of the blood in the glomerular capillaries, not only by increasing
the volume of the circulating fluid, but also probably by a direct dilator
action on the afferent vessels of the glomeruli. A similar local dilator
effect is produced by drugs such as caffein or theobromin ; but in these
cases the drugs probably exert a paralysing influence on the absorbing
mechanism of the kidney, i.e. the cells of the convoluted tubules, so that
the glomerular transudate may undergo little change on its way to the
ureter and bladder.

One of the strongest arguments in favour of this modified Ludwig hypo-
thesis is the fact that the more we augment the flow of urine, whether by
caffein, saline diuretics, or production of hydraemic plethora, the more nearly
does its osmotic pressure, saline constitution, and reaction approximate that of
the blood plasma. It would seem that in the glomeruli we have an apparatus
which, like the capillaries of the abdominal viscera but in a still higher degree,
reacts to changes in the intracapillary pressure, and so serves to regulate
accurately the amount of fluid circulating in the blood vessels.

Whether we look upon the cells of the convoluted tubules as secre-
tory or absorptive in function, we have at present no evidence that the
cellular covering of the glomeruli acts otherwise than passively in the
production of the glomerular part of the secretion. It must be remem-
bered, however, that under certain circumstances, as after ingestion of large
quantities of fluid, the osmotic pressure of the urine may fall below that
of the blood plasma. Dreser l interprets this as pointing to an activity
of the glomerular epithelium. I have shown above that it may equally
well be explained by assuming an absorption of salts by the water-logged
tubule cells, or an active excretion of water by these cells. I may
mention here that I. Munk and Senator,2 as a result of researches carried
out for the most part on the excised kidney, have come to a conclusion
analogous to that just stated, namely, that in the production of urine we
have a co-operation of physical and physiological factors. According to
these authors, water and part of the urinary salts (especially NaCl)
are transuded through the glomeruli in direct consequence of the blood
pressure, i.e. by a process of filtration, although the rapidity of the blood
flow is at least of equal importance with its pressure. The specific
urinary constituents — urea, uric acid, hippuric acid, etc., together with
another portion of the urinary salts (NaCl, sulphates and phosphates)
— are secreted by the active intervention of the cells of the tubules,
especially the convoluted tubules. These substances are secreted in a
dissolved condition, and must, therefore, take a certain amount of water
with them.

The influence of the nervous system on the secretion of urine.
— The discovery by Berkeley 3 of a distribution of nerve-endings to the
1 Loc. cit. 2 Virchow's Archiv, 1888, Bd. cxiv. S. 1. 3 Loc. tit.

660 THE SECRETION OF URINE,

tubules of the kidney suggests that in this organ, as in the salivary
glands, the secretion of urine may be under the direct control of the
central nervous system, apart from any influence that this system may
have on the renal circulation. We have already seen that the urinary
secretion is extremely susceptible to variations in the pressure and
velocity of the blood in the renal vessels, and also that these latter are
under the direct control of the nervous system by means of vasodilator
and vaso -constrictor nerve fibres.

Various authorities have described experiments which should
demonstrate the existence of secreto-motor nerves to the kidney. Thus,
in 1835, Claude Bernard1 showed that in some cases, where puncture of
the medulla was carried out with the* view of producing diabetes, the
result was an increased flow of urine, containing no sugar, i.e. diabetes
insipidus. These experiments were repeated in much greater detail by
Eckhard,2 who showed that, in the rabbit, polyuria might be caused, not
only by a puncture of the medulla, but also by chemical or mechanical
stimulation of the neighbouring portion of the superior vermis of the
cerebellum, especially if, previously to the operation, the nerves going
to the liver had been divided. Moreover, it is a familiar fact to
clinicians, that injuries to the head, epileptic attacks, and especially
lesions in the neighbourhood of the medulla, may bring about a condi-
tion of diabetes insipidus.

We know already that division of one splanchnic nerve will cause
an increased secretion of urine in the kidney of the same side, and it is
natural to imagine that the mechanism of the increased urinary sec-
tion after the piqtire is of the same nature. Eckhard pointed out, how-
ever, that the course of events is different in the two cases. After division
of one splanchnic, the flow of urine is almost immediately somewhat
increased, and this moderate increase lasts a considerable time (three to
four hours at least). The first result of puncture of the medulla is a
cessation of the urinary flow. This is followed shortly by an increase
much greater than is caused by section of the splanchnic, but only
lasting one to two hours. Moreover, the effect of the diabetic puncture
is observable even after section of the splanchnics, as well as of all the
nerves which may possibly send branches to the kidney. Eckhard con-
cludes, therefore, that the effect must be due to one of two causes :
either an increased general blood pressure, in consequence of the
stimulus caused by the puncture, or the excitation of nerve fibres which
run in the walls of the renal artery itself. The first explanation must
be rejected, since direct measurement of the blood pressure does not
show any definite rise in consequence of the puncture. We must there-
fore accept the second explanation as the correct one. Eckhard regards
these nerve fibres as secreto-motor, and believes that the urinary secre-
tion is under the control of a nerve centre, situated most probably in
the medulla. He bases this hypothesis on the facts that section of the
cord below the medulla stops the flow of urine, and that stimulation of
the cut cord does not bring back the flow, in spite of the rise of blood
pressure which is induced. We know now, however, that the negative
result of stimulating the cut cord is due to the constriction of the renal
vessels, which occurs together with those of other parts of the body, so

1 "Le9ons de pliysiol.," 1835, tome i. p. 339.

2 Beitr. z. Anat. u. PhysioL (Eckhard}, Giessen, 1869, Bd. iv. S. 1-32 and 153-193 ;
1870, Bd. v. S. 147-178 ; 1872, Bd. vi. S. 1-18 and 51-94.

INFL UENCE OF NER VO US S YS2"EM. 66 1

that the increased general blood pressure is powerless to send more
blood through or to raise the pressure in the renal capillaries.

The facts can be equally well explained if we assume that these
hidden nerve fibres are vaso-dilator in function — an assumption which
would be in accord with the numerous other facts we have learnt with
regard to the regulation of the urinary flow by the central nervous
system. We may conclude, therefore, that the existence of secretory
nerves to the kidney is not proved, the subjection of the renal secretion
to nervous influences being effected exclusively through the intermedia-
tion of the vascular nerves.

As an additional argument against the dependence of renal secretion
on the nervous system, Heidenhain quotes a number of experiments
made by Bidder l on frogs, in which the secretion of urine continued
normally, although in some animals the whole spinal cord, in others the
whole nervous system, with the exception of the medulla, had been
destroyed.

1 Arch.f. Anat. u. PhysioL, Leipzig, 1844, S. 376.

THE MECHANISM OF THE SECRETION OF MILK.

•
By E. A. SCHAFER.

CONTENTS : — General Considerations, p. 662 — Influence of the Nervous System, p. 663
— Action of Pilocarpine and Atropine, p. 664 — Influence of Diet, p. 664 —
Place of Formation of the Organic Constituents, p. 665 — Manner in which the
Secreted Materials pass out of the Cells, p. 665 — Mechanism of the Discharge
of Milk, p. 667.

THE composition of milk has been dealt with in a previous article
(pp. 125 to 140). Here it may therefore be simply noted, with regard
to its organic constituents, that these are remarkable in being peculiar
to the milk, not occurring in any of the other secretions or tissues of the
body (cf. however, footnote 1, p. 665), nor in foods which have not been
prepared from milk. The mammary gland-cells, therefore, unquestionably
form the products of secretion themselves from materials derived
through the lymph from the blood, and cannot be regarded, except as
concerns some of the inorganic substances, as acting merely as filtering
agents for allowing the passage of materials in solution from the blood.
And even with regard to the inorganic substances,1 the proportion of
these is so different from that in which they occur in the blood and
lymph, that no filtration hypothesis appears in any way tenable even for
these. The gland-cells are further peculiar in that they only, as a rule,
function actively for a certain period after parturition, being at all
other times entirely inactive, although capable occasionally — it is said
even in the male — of being excited to activity by stimulation of the
nipple by a sucking action, such as that performed by an infant. Prior
to, and during such periods of activity, the whole gland becomes greatly
enlarged, both by an increase in size of existing alveoli, and also, perhaps,
by a sprouting, out of new alveoli. The cells lining the alveoli become
enlarged, and probably also multiply, for they are said to show evidence
of karyokinesis.

The alveolar cells begin to accumulate within them granules,
partly of a proteid, partly of a fatty nature (although the latter may
more fitly be described as globules), and the alveoli get filled, before
there is any call for the pouring out of the secretion, with a clear fiuid
(coagulating to a finely granular material in pieces of the gland thrown
into alcohol), which contains a few fatty globules of different sizes, and here
and there cells filled with granules, staining with osmic acid, and appar-
ently identical with the colostrum corpuscles which are found in the milk of

1 Bimge has shown that, with the exception of iron, the inorganic substances of milk
occur in nearly the same proportion as in the ash of new-born animals ("Text-Book," Woold-
ridge's translation, p. 107).

INFL UENCE OF NER VO US S YSTEM. 663

the first two or three days after parturition, and which are sometimes
even to be detected during full lactation. These colostrum corpuscles are
seen to be amoeboid when examined on the warm stage, and are, there is
little doubt, leucocytes which have wandered out from the interstitial
connective tissue of the gland into the lumen of the alveoli. Some have
regarded them as detached epithelial cells, and look upon their presence
in the alveoli and in the milk as evidence of the normal occurrence of
such detachment during active secretion (see p. 666) ; but it must be
admitted that they have neither the appearance of epithelial cells, nor
do the latter tend to exhibit any such amoeboid movement as is shown
by the colostrum corpuscles. These corpuscles, in fact, seem to be
rather analogous to the salivary corpuscles (see p. 344), and to be
similarly derived from emigrated leucocytes.

During the period of lactation the alveoli secrete milk, not only
whilst the gland is being drawn by the process of sucking or milking,
but in the intervals of such processes, so that the milk accumulates
both in the alveoli and in the ducts. The latter are provided with (in
some animals very considerable) dilatations, which serve as reservoirs
for the accumulated secretion, and it is mainly this accumulated milk
which is poured out during the milking. No doubt fresh milk becomes
secreted to take the place of that which is drawn away ; and as a con-
comitant to this fresh secretion, there is a considerable flush of blood to
the gland. It has been calculated that the udders of a cow could not
contain all the milk which is sometimes drawn at one milking, so that
secretion must be proceeding at the same time. Moreover, the later
drawn portions of milk contain more solids in proportion than those
first drawn.1 Lehmann2 injected sulphindigotate of soda solution
into a vein of a milch goat, and at once had the animal milked.
No blue appeared in the milk until the udders were almost com-
pletely drawn, when there was a slight tinge. On milking the animal
again, after the lapse of an hour or an hour and a half, the milk which
had collected in the udder was completely blue.

Influence of the nervous system on the secretion of milk. —
Although it is a matter of common experience that the quantity and
quality of the milk is in women materially influenced by the condition
of the nervous system, the results of experiments upon animals have
furnished evidence on this subject which is either entirely negative, or
at most of a somewhat conflicting nature. Eckhard,3 who was the first
to attempt to obtain such evidence, found no marked difference in the
milk either in quantity or quality from the udder of a goat, the nerves
(branches of external spermatic) passing to which had been cut, as
compared with the milk drawn from the other side, the nerves of which
were intact. His observations have been repeated by others,4 with
contradictory results, some having obtained an increase of secretion on
cutting the nerves, others a diminution. But even if an increase is
obtained, it has not been determined whether this is due to the
alteration in the vascular supply to the gland rather than to a direct
effect upon the gland-cells, such as is obtained in the case of the

1 For references, see Heidenhain, Hermann's "Handbuch," Bd. iv.

2 Die landwirthsch. Versucht, 1887, Bd. xxiii. S. 473.

3 Beitr. s. Anat. u. PhysioL (Eckhard), Giessen, 1855.

4 Rohrig, quoted by Heidenhain (Hermann's "Handbuch," Bd. iv.) ; de Sine'ty, Gaz.
med. de Paris, 1879, p. 593 ; Valentowicz, Centralbl. f. PhysioL, Leipzig u. Wien, 1888,
Bd. ii. S. 71 ; Mironow, Arch, de sc. biol., St. Petersbourg, 1895, tome iii. p. 453.

664 MECHANISM OF THE SECRETION OF MILK.

(paralytic) secretion of saliva after section of the chorda tympani.
Likewise, the effects which have been got by stimulating the cut nerves,
and which have been usually in the direction of diminishing the
quantity of the secretion, may well be ascribed to vasomotor changes
rather than to direct nervous influence. All that can be said,
therefore, on this question is to repeat the statement, that the
experimental evidence of such an influence is still lacking, however
probable its existence may be from the everyday experience of changes
produced in the milk of nursing women, as the result of emotional
conditions.

Action of pilocarpine and atropine. — The drug which has the most
marked effect in increasing most of thfc secretions of the body, namely,
pilocarpine, is stated to have little or no effect upon the secretion of
milk.1 On the other hand, atropine is well known to be constantly
employed for nursing women, in whom, for one reason or another, it
is desired to dry up the secretion. Short, however, of stopping the
secretion altogether, atropine, given in smaller doses, is found, whilst
diminishing the amount of fluid secreted, to cause the secretion of a
more concentrated milk.2

Influence of diet. — The quantity and quality of the food is well
recognised as having an important influence on the quantity and quality
of the milk. The most abundant and richest milk is yielded when the
diet is liberal, and, in the case of carnivora (bitch) certainly, but less
certainly in the case of herbivora (cow), when it includes a larger pro-
portion than usual of proteid material. And it is not so much the
albuminous constituents of the milk (casein and lact-albumin) which are
increased, but especially the proportion of fat.3 This indeed has freen
held to be one of the most cogent arguments in favour of the view
contended for by Voit, that animal fat is formed mainly from proteids.4
An increase of fat in the food, without a simultaneous increase of
proteid, does not cause an increased secretion of fat in the milk.5
Not only the amount of proteids and fat, but also the amount of sugar,
is increased as the result of giving proteid-rich food.6 Alcohol, given to
goats, has also been found to increase the fat of milk.7

It does not, of course, follow that because an excess of a particular organic
principle in the food produces an increase of certain constituents of the milk,
that these constituents are directly produced from such material, for the effect
may be produced indirectly by the functions of the gland-cells becoming
modified, according to the nature of the pabulum they are receiving. Looked

1 Hammarbacher (goat), Arch. f. d. gcs. Physiol., Bonn, 1884, Bd. xxxiii. S. 228;
Cornevin (Compt. rend. Soc. de biol., Paris, 1891, p. 628) found that in the cow the amount
of milk yielded was not influenced by the daily injection of 0'25 grm. pilocarpine. See
also Mironow, loc. cit.

- Hammarbacher, loc. cit.

3 The evidence for this is given by Heidenhain (Hermann's " Handbuch," 1882, Bd. v.).
where also all the most important references on the influence of diet up to that date will be
found. The following may also be cited — W. Kirchner, Milchzeitung, 1891, Bd. xx. ;
C. Schneider, " Einfluss versch. Fattening auf d. Zusammensetz. der Milch," Diss.,
Leipzig, 1893.

4 See article on "Metabolism."

5 Ssubotin, Firchow's ArcMv, 1866, Bd. xxxvi. ; Centralbl. f. d. med. Wissenscli., Berlin,
1866, S. 337; Kemmerich, ibid., S. 467; Kuhn, Journ. f. Landwirthsch. . 1876, S. 381 ;
Weiske, ibid., 1878, S. 447; Cf. also Juretschke, " Einfluss versch. Oelkuchensorten auf
dem Fettgehalt der Milch," Diss., Leipzig, 1893.

6 I. Munk, Arch.f. wissensch. u. prakt. Thierh., Berlin, 1881, Bd. vii. S. 91.

7 Stumpf, Deutsches Arch.f. klin. Med., Leipzig, 1882, Bd. xxx. S. 201.

FORMATION OF THE ORGANIC CONSTITUENTS. 665

at in this light, certain substances may be said to stimulate the cells of the glands
to increased activity in all directions, tending to the production of a larger
quantity of milk rich in all kinds of solid constituents ; whilst other substances
may be looked upon as stimulating the cells in a special manner, tending
to the increased production of certain only of the constituents of the milk.

Place of formation of the organic constituents. — As already
noticed, the fact that the chief organic constituents of the milk are
peculiar to the secretion, and do not occur as such in the blood or
lymph, may be regarded as sufficient evidence of their being formed in
the gland itself.1 The casein is in all probability produced by a mole-
cular change in the composition of the serum albumin or globulin,
which is supplied to the cells from the blood or lymph. The fat may
be formed by the cells of the gland from proteid, or possibly even from
carbohydrate materials furnished by the blood ; or it may be taken up
directly from fat which has been formed elsewhere, and which is always
present in a certain small amount in blood and lymph. For while, on
the one hand, there exists no clear evidence to show that the mammary
gland can itself manufacture fat, it is extremely probable that, in
common with most if not all other cells in the body, the cells of this
gland do possess such a faculty. With regard to the characteristic
sugar of the secretion, and which, being characteristic, must be pro-
duced by the gland itself, there is some evidence to show that this is
formed from dextrose, which is itself manufactured elsewhere than in
the gland. That this is so would appear from the following experiment
by Paul Bert.2 Bert removed the mammary glands from goats,
then allowed them to become pregnant. After parturition, the
urine, during three days, contained a substance which reduced cupric
oxide and appeared to be dextrose. This was not present before par-
turition, nor was it found in normal animals either before or after
parturition; it was therefore presumably formed in the organism in
larger amount than usual for the purpose of becoming converted into
lactose in the mammary gland.

In view of the fact that lactose is frequently found in the urine in women,
and in mammals generally, immediately before and after parturition,3 this
experiment of Bert seems to need repetition, especially since he appears not to
have isolated or carefully examined the reducing substance which he detected.
The lactose found in the urine after parturition has generally been supposed
to be re-absorbed from the secretion which has formed in the alveoli and ducts
of the mammary glands.

Thierf elder 4 has pointed out that both the casein and sugar of milk could
be derived from the nucleo-proteids or glyco-proteids of the gland-cells by a
process of splitting. In support of this view, a formation of lactose is said to
occur on keeping portions of minced fresh mammary gland in normal saline
solution at the temperature of the body ; the lactose being preceded by a colloid
carbohydrate, identical, according to Landwehr,5 with his " animal gum." This,
however, does not affect the question of the ultimate sources of origin of these

1 A small quantity of casein is said to occur in the secretion of the sebaceous glands
(Neumeister, "Lehrbuch," Aufl. ii. S. 496). This is of interest in connection with
the fact that the mammary glands have been regarded as representing enlarged and
modified sebaceous glands.

" Compt. rend. Acad. d, sc., Paris, 1884, tome xcviii. No. 13.

3 Hofmeister, Ztschr.f.pkysioL Chem., Strassburg, 1878, Bd. i. S. 101.

4 Arch.f. d. ges. PAy*wtf., Bonn, 1883, Bd. xxxii. S. 619.

5 Ibid., 1887, Bd. xl. S. 21.

666 MECHANISM OF THE SECRETION OF MILK.

constituents, which are probably, as already stated, the proteids and carbo-
hydrates derived from the food.

As to the manner in which the secreted materials of the milk
pass out of the secretory cells. — If we put aside, as resting upon no
solid basis of fact, the suggestion of Strieker, which was taken up. more
seriously by Kauber,1 that the organic materials of the milk are carried
into the alveoli by emigrated leucocytes, which there break down and set
free their proteid, fatty, and other constituents, we find ourselves face
to face with three possible methods by which the secreted materials
which are formed and accumulate within the gland-cells may pass into
the lumen of the alveoli. The three methods are as follows : —

1. The cells may, as in the case of the sebaceous glands, bodily
break loose, and, becoming detached and disintegrated, set free their
contents within the alveoli.

2. A part only of each cell, namely, the free end, may break loose,
become detached, and disintegrate.

3. The cells may extrude their secreted materials into the alveoli,much
as in the case of other secretions, without undergoing any histological
disintegration.

Of these three views, the first has found support mainly on the ground
of the analogy with what happens in the case of the sebaceous glands of the
skin (with which the mammary glands might be looked upon as in a certain
sense homologous), in which such a complete disintegration of the whole
cell occurs, its place being supplied by another cell, which is produced by
cell-division. Moreover, the colostrum corpuscles have been regarded as
examples of such detached cells filled with secretion, which have not
become disintegrated. Those corpuscles, however, as we have seen, are
rather to be looked upon as of the nature of leucocytes than as epithelial
cells ; nor do we find such evidence of cell multiplication in the mammary
gland as would be at all sufficient to account for the very large number
of cells which would have to become detached in order to furnish the
organic constituents of the secretion. Heidenhain 2 has calculated that
the gland-cells would have to be totally renewed five times in the
course of every twenty-four hours, in order to yield the solids of the
milk. The second view may be looked upon as, in a sense, a modifica-
tion of the first one. It was due originally to Langer, and has been
ably advocated by Partsch and Heidenhain.3 According to this
view, the secretion products which are formed in the gland become
gradually accumulated within the free ends of the cells, which in the
meanwhile lengthen out, and in place of being flat or cubical become
columnar and project into the lumen of the alveolus. The enlarged free
end is then supposed to burst or to become detached and disintegrated,
and thus to set free the accumulated products, while the fixed ends of
the cells (with the nuclei) are supposed to remain, ready to again go
through a similar process.

The evidence adduced in favour of this view is chiefly of a histological
nature. It is the case that in some alveoli of glands in full secretion,
the cells are occasionally seen projecting somewhat prominently into
the lumen ; and it is certainly the case also that the cells, and perhaps
especially such prominent parts, contain fatty globules, similar in

1 " Ueber den Ursprung der Milch," Leipzig, 1879.

2 Loc. cit. 3 Vide Heidenhain, op. cit.

THE DISCHARGE OF MILK. 667

appearance to those of the milk. Nevertheless, it must be admitted
that such appearances, although they may occasionally be seen, are
decidedly rare. It is so much more common to see, even in the most
actively secreting glands, the alveolar cells uniformly flattened, or at most
very slightly projecting, that I should not hesitate to say that the columnar
appearance, which has been described and figured by Heidenhain, is
quite exceptional, and is in all probability due to the alveoli in which
it occurs being collapsed. Every histologist is aware of the extreme
differences in shape which are produced in epithelial cells by altera-
tions in the conditions of the surface which they cover. Thus, even
the extremely flattened epithelial cells which line the blood vessels
may, when examined in sections of vessels which have been hardened in
a contracted and collapsed condition, project like columnar epithelium
cells into the lumen of the vessel. And the differences in height of
the cells lining the alveoli of the mammary glands may very well be
similarly produced. This is indeed rendered probable from the observa-
tion of Heidenhain,1 that in different lobules of a gland the cells vary
in height, but in the same lobule they have the same height ; and by
the additional observation of the same observer, (a) that in a bitch
which was suckling seven vigorous puppies the cells were very high ;
(b) that in another well-fed milch bitch, which was not sucked for
forty-eight hours, they were remarkably low ; for the alveoli in these
cases would be flaccid and tense respectively.

The histological evidence in favour of this view must therefore be
admitted to be extremely weak, nor, except perhaps in the case of the
unicellular glands of some invertebrates, and the similar unicellular
secreting structures which form the mucus-secreting goblet-cells of verte-
brates, is there any analogous instance of the extrusion of a secretion
by the breaking down of part of the gland-cells. Moreover, the
argument which was used by Heidenhain against the first view, that
it would involve the renewal of the substance of the epithelial cells of
the mammary gland five times in twenty-four hours, will apply with
slight modification equally to the second, and adds a further consider-
able difficulty to its acceptance.

The third view, on the other hand, has the analogy of nearly all
the other secretory structures to support it. It involves no necessity
for assuming such an enormous building up and breaking down of
protoplasm as is required for the other two; and although we must
admit that the present state of our knowledge does not permit us
to understand how and why it is that certain substances are formed
in these cells, and pass from them into the lumen of the alveolus, the
same admission must be made for all other secretions. Nor is the fact
that the fat of the milk is extruded from the cells in an undissolved
condition any obstacle to the acceptance of the view in question, since
it is probable that the granules which are found in many other secretory
cells (e.g. those of the salivary glands), and which are passed into the
lumen of the alveolus, are extruded as granules, and are first dissolved
in the secretion outside the cells.2

1 Loc. cit.

- The microscopical changes in the cells of the mammary gland during secretion have
been recently made the subject of study by Steinhaus (Arch. f. PhysioL, Leipzig, 1892,
Suppl., S. 54) and Szabo (ibid., 1896, S. 32). The former finds evidence of frequent mitotic
division of the cell nuclei (without subsequent division of the cells), and of transforma-

668 MECHANISM OF THE SECRETION OF MILK.

The discharge of milk. — The discharge of milk from the ducts,
which is produced by the action of sucking or milking, is partly the
result of direct mechanical pressure upon the gland, and especially
upon the milk reservoirs of the larger ducts, partly due to a con-
traction of the plain muscular tissue which accompanies these ducts,
and which appears to be set in action by mechanical stimulation
of the nipple. The plain muscular tissue occurs also in the nipple
itself in some abundance, and by its contraction causes a kind of
erection and increased prominence of the nipple. This probably serves
the purpose of keeping open the mouths of the gland-ducts which open
upon the rounded apex of the nipple, thus allowing of the free outflow
of the secretion.1 The flow is also ifi all probability assisted by a vis
a tergo, derived from the swelling of the whole gland by the reflex
dilatation of its arterioles, and consequent increase of capillary pressure,
and of lymph exudation ; and, to a slight degree also, by newly secreted
milk, which begins to be formed by the gland-cells, in response either
to this increased supply of blood and lymph, or to reflex secretory
influences passing directly to the gland-cells.2

tion of the nuclear substance into fat. The latter could find no mitoses during lacta-
tion, although he found two or three nuclei in each cell. He also describes the accumula-
tion in the cells of albuminous granules which undergo peculiar changes of form, and
are ultimately extruded into the alveoli and there dissolved. These observations require
corroboration.

1 Cf. Hellier "On Nipple Reflex," Brit. Med. Journ., London, Nov. 7, 1896.

2 Cf., however, what has been already said on this subject on p. 663.

SECKETION AND ABSORPTION BY THE SKIN.
By E. WAYMOUTH EEID.

CONTENTS : — Chemical Nature of Skin Secretions, p. 669 — The Secretion of Sweat,
p. 676 — Electro-Motive Phenomena in Skin Glands, p. 681 — Absorption by the
Skin of Man, p. 685— -Of lower Mammals, p. 688— Of the Frog, p. 690.

SKIN SECKETIONS.

Comparative. — The secretions of the skin in vertebrates fall readily
into two main classes — (a) Those in which a watery solution is elabo-
rated by the gland-cells, and (b) those in which products of metamor-
phosis or degeneration of the gland-cells themselves form the secretion.

As types of the former class may be instanced the sweat of
mammals, and the slime of fish and many amphibians ; of the latter,
the secretion of the various modifications of sebaceous glands in
mammals ; of the uropygial gland of many birds ; and the fibre secre-
tions of the skins of certain fish (Myxine, Anguilla, etc.).

Such secretions are put to a variety of uses in the vertebrate series.
Of the first class, the sweat of the mammal is at once an excretion and
a means of regulating body temperature by evaporation, while the
slime of the frog or fish is protective in function. Of the second class,
the gr easiness of the sebum of the mammal, or secretion of the tail
gland of the bird, protects skin, hair, or plumage from imbibition of
water ; the secretion of the Meibomian glands of the eyelids prevents
overflow of tears ; the viscosity of the ear wax interferes with the entrance
of foreign bodies into the auditory canal ; while, in special cases, volatile
substances of good or evil odour, contained in the secretion, may serve
the purposes of sexual attraction or protection from enemies.

In hairy mammals, it is only in certain cases, or on certain parts of the body,
that sweating is observed. Rabbits, rats, and mice are not known to sweat at
all, the dog sweats but little, the cat only on the hairless pads of the feet ;
while on the other hand the horse sweats profusely on all parts. The snouts
of pigs and oxen contain glands similar to sweat-glands, the secretion of which
keeps the part moist.

Instances of glands used for purposes of sexual attraction are — the glands of
the suborbital pit of many ruminants and some hogs, the cheek gland of the
elephant, the pectoral glands of certain tropical bats, the flank glands of shrews,
the sacral gland of the peccary, the groin glands of antelopes, the preputial glands
of the beaver and musk-deer, the anal glands of the hare, marsupials, armadillos,
two-toed sloth, otter, hyaenas, and civets, and the glands at the base of the tail
of shrews and the fox. The anal glands of the skunk are used for protection.

The hoof gland of most bisulcate ungulates, opening in the cleft between
the two divisions of the hoof, is probably of use in protecting the horny

670 SECRETION AND ABSORPTION B Y THE SKIN.

matter from imbibition of water ; in the one-horned rhinoceros a gland opens on
the posterior aspect of each foot.

The function of the curious gland at the back of the thigh of male
monotrenies, supplying its secretion by a long duct to the hollow horny spur on
the heel (so like in arrangement to the poison gland and fang of a snake) is
not known with certainty.

There are glands in the skin of the male of the kangaroo, Halmaturus
ntfus, which secrete a red substance adhering to the hair, while the maxillary
glands of the female dwarf antelope, Ceplialoloplius pygmceus, secrete a blue
substance reddened by acid.1

CHEMICAL NATURE OF *$KIN SECRETIONS.

(a) "Watery secretions. — Naturally the composition of the sweat
of man and mammals has received more attention than that of other
skin secretions.

Since the quantity of sweat secreted is dependent upon so many
conditions, it is of little value to quote the numbers obtained by
different observers, apart from a statement of the special conditions
under which the observations took place.

There are several methods of collecting tbe sweat of the whole body,
or of special parts. Evaporation may be hindered by enclosing a part,
such as the forearm and hand, in a rubber bag, and the sweat collected
in a bottle tied into the lower end of the bag.2 The subject may sit in a
Pettenkofer and Voit's respiration chamber (but breathe through tubes
to the exterior), and the water given off by the skin be calculated from
the readings of hygrometers in the ingoing and outgoing currents of
air.3 Or the secretion of the skin may be stimulated by raising the
temperature of the surrounding air, while the whole body, with the
exception of the head, is enclosed in a convenient receptacle.4 By
the hot-air method, Argutinsky 5 collected a quarter of a litre of sweat
in half an hour, at a temperature raised during the, experiment from
27° to 41° C. Schierbeck,6 by the hygrometric method, calculated that
in his own case, when clothed and at rest, the air in contact with the
skin being at the normal temperature within clothing (32° C.), 2 or 3
litres of sweat were given off in twenty-four hours. No calculations of
the total secretion of sweat can be made from local estimates, because the
richness of various districts of the skin in sweat-glands is very different.

In the body at rest the sweat is evaporated as fast as it is formed,
and it is only under conditions exciting the glands to increased action,,
that the fluid collects upon the surface.

In the resting condition of the body the temperature of the
surrounding air must be raised to about 33° C. before the stimulus to
increased activity of the sweat-glands is evoked.7

The following table is of interest as indicating that, at the time of

1 Weber, Arch. f. mikr. Anat., Bonn, 1888, Bd. xxxi. S. 499. For further information
on such glands, see Owen, ''Comparative Anatomy and Physiology of Vertebrata," London,
1868, vol. iii. p. 632 ; Leydig, Ztschr. f. wissensch. ZooL, Leipzig, 1850, Bd. ii. S. 1 (anal
glands).

2 Anselmino, Wagner's " Handworterbuch d. Physiol.," art. "Haut."

3 Schierbeck, Arch. f. PhysioL, Leipzig, 1893, S. 116.

4 Favre, Compt. rend. Acad. d. sc., Paris, 1852, tome xxxv. p. 721.

5 Arch.f. d. gcs. PhysioL, Bonn, 1890, Bd. xlvi. S. 594. 6 Loc. cit.
7 Schierbeck, 'loc. cit.

CHEMICAL NATURE OF SKIN SECRETIONS.

671

the breaking out of sweat, the excretion of carbon dioxide by the skin
is also suddenly increased, a fact probably related to the increased
activity of the gland-cells : —

E.ccretion of Water and Carbon Dioxide by the Skin at various Temperatures

of Surrounding Air.
(Separate experiments on same individual, naked, in a Pettenkofer and Aroit's chamber).1

Temperature of
Chamber.

Water Excretion
(Grms. per Hour).

Water Excretion
(Grms. per Twenty-
four Hours).

Carbon Dioxide
(Grms. per Hour).

Carbon Dioxide
(Grms. per Twenty-
four Hours).

29° -8 C,

22-2

532-8

•37

8-9

30°-4

27-8

667*2

•40

9-6

31° '5

71-9

1725-6

•37

8-9

31°'9

50-3

1207-2

•35

8-4

32° -8

73-4

1761-6

•35

8-4

33°'8

82-6

1982-4

•87

20-9

35° '4

106-8

2563-2

1-04

25-0

35° -7

107-0

2568-0

•9

21-6

38°-4

158-8

3811-2

1-23

29-5

The sweat of man is a colourless, opalescent liquid of salt taste,
poorest in solids of all the secretions, though richest in salts in relation
to organic solids.

Sweat is acid in reaction, even when collected from the palm of the
hand, where there is no danger of admixture of sebaceous secretion.2
This acidity is probably due to volatile fatty acids, which may be
subsequently driven off, leaving an alkaline reaction at the surface of
the skin.8 In profuse sweating the acidity may give way to neutrality,
followed later by alkalinity.4

In 1000 parts.

Favre.

Schottin.

Funke.

Water

995-573

977-40

988-40

Solids

4-427

22-60

11-60

Epithelium

4-20

2-49

Fat . .

•013

Lactates

•317

...

Sudorates .

1-562

Extractives

•005

11-30

Urea . . .

•044

1-55

Sodic chloride

2-230

3-60

Potassic chloride

•024

Sodic phosphate

Traces

1-31

Alkaline sulphates

•on

•39

...

Earthy phosphates
Total salts ....

Traces

7-00

4-36

NOTE TO TABLE. — The sudoric or hidrotic acid of Favre has not been found by any
.subsequent observers. He gives the empirical formula, C10H16H2013. Lactic acid also
has not been found by any other observer.5

1 Schierbeck, loc. cit.

2 Fraii9ois-Franck, "Diet, encycl. d. sc. med.," Paris, 1884, Ser. 3, tome xiii. p. 51,
Art. "Sueur."

3 Tourton, "These de Lyon," 1879, No. 24, Ser. 1.

4 Favre, loc. cit. ; Trumpy and Luchsinger, Arch. f. d. gcs. Physiol., Bonn, 1878,
Bd. xviii. S. 494.

5 For analysis of sweat of a rheumatic patient, see Harnack, Fortschr. d. Med., Berlin, 1893,
S. 91 ; also Hermann, Jahresb. il. d. Fortschr. d. Anat. u. Physiol.. Leipzig, 1895. Bd. ii.
S. 226.

672 SECRETION AND ABSORPTION B Y THE SKIN.

The specific gravity of human sweat is 1003 to 1006.

The table on p. 671, from Beaunis,1 gives the composition of sweat according
to Favre,2 Schottin,3 and Funke : 4 —

Relatively to the chlorides, the sulphates and phosphates of sweat are less
abundant than in urine. The following table is from Kast : 5 —

Chlorides.

Phosphates.

Sulphates.

Sweat

1

•0015

•009

Urine

1

•132

1

•397

There is no doubt that urea is present in the sweat of man; the
variations in estimates of the amount by different observers being
probably caused by differences in the lapse of time between collection
and estimation, and consequent variations in the amount of trans-
formation into ammonium carbonate.

In two lots of sweat collected by the hot-air method, Argutinsky c
found that *363 grin, urea was present in 225 c.c. of sweat collected in
half an hour, and '410 grin, urea in another sample of 330 c.c, collected
in three-quarters of an hour.

Of the total nitrogen excreted by the skin in one case, 68'5 per
cent, was present in urea, and 31 '5 per cent, in ammonia ; while in the
other the numbers given are 74'9 per cent, of total nitrogen in urea, and
251 per cent, in ammonia.

The same observer, by taking severe walking exercise in a special
suit of clothes, which was extracted at the end of the period of
work, and the extract analysed by the Kjeldahl method, obtained results
as follows : —

Work. Mgrms. of Nitrogen

excreted by the Skin.

20 to 22 kilometres in seven hours (July) . . . 704*4
18 to 20 „ with ascent of 1300 metres (August) . 753 '5

1600 metres (October) 219-3

The nitrogen excreted by the skin may amount to 4'7 per cent,
of that by the urine, and hence may have to be taken into account in
some experiments on nitrogenous metabolism.

In ursernic conditions, the excretion of urea by the skin is greatly
increased, so much so, in some cases, that crystals of urea have been
found on the skin.7

According to Capranica,8 creatinine to the extent of '04 per cent,
is present in human sweat. The small amounts of fatty acids are made
up of formic, acetic, butyric, propionic, and caproic acids. Ethereal
sulphates of phenyl and skatoxyl are present in small amount, the
proportion of ethereal to inorganic sulphates being, according to Kast,9

1 " Nouveaux elements de physiologic hnmaine," Paris, 1888, 3rd edition, tome ii. p.
190.

-Loc. cit.

3 "De Sudore," Diss., Leipzig, 1851.

4 Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1858, Bd. iv. S. 36.

5 Ztschr.f. physiol. Chem., Strassburg, 1887, Bd. xi. S. 501. 6 Loc. cit.

7 Schottin, loc. cit.

8 Arch, ital. debiol., Turin, 1882, tome ii. y Loc. cit.

CHEMICAL NATURE OF SKIN SECRETIONS. 673

1 to 12. Indigo is sometimes developed in sweat,1 though whether from
indoxyl secreted, or as the result of the growth of chromogenic
micro-organisms, is not certain.

The sweat of * the horse has heen studied by Leclerc 2 and Fred Smith.3
This secretion normally contains proteids, a fact which may partly account for
the debilitating effects of profuse sweating in horses.

Percentage Composition of Sweat of Horse (Fred Smith).

Alkaline, sp. gr. 1020 ; Water, 94*3776 ; Organic solids, -5288 : Ash,
5-0936.

Serum albumin .... '1049

Serum globulin .... -3273

Fat -0020

Chlorine -3300

Lime -0940

Magnesia -2195

Phosphoric acid .... Trace

Sulphuric acid .... Trace

Soda -8265

Potash 1-2135

Both Leclerc and Smith found urea in the sweat of the horse.

The sweat of the hippopotamus contains a reddish-brown pigment not yet
identified.4

Buisine5 has investigated the constituents of that part of the "sweat" of
sheep which is soluble in water. He found potash soaps of the fatty acids
from acetic to capric ; urea and ammonium carbonate ; potash salts of malic,
glycolic, pyrotartaric, oxalic, succinic, lactic, hippuric, benzoic, and uric acids ;
phenylsulphate of potassium, and traces of leucine and tyrosine. Malic acid
was previously only known as a vegetable product.

Of the watery secretion of the skin of amphibians little is known. The
reaction of the secretion of the " mucous glands " is alkaline, while that of
the " granular glands," 6 chiefly found on the dorsal surface of the flanks
and legs, is acid. According to Ley dig,7 acrid substances are secreted in
addition to mucin, in the case of the tree frog. In the case of the salamander
and toad, poisonous substances have been separated.8

Gratiolet and Cloez 9 state that the poisonous substance in the skin glands of
the toad and salamander is soluble in alcohol and of the nature of an alkaloid.
Yulpian 10 and more recently Phisalix and Bertrand n have investigated this
substance in the case of the toad. The symptoms of poisoning are — paralysis

1Bizio, Sttzungsb. d. k. Akad. d. Wissensch., Wien, Bd. xxxix. S. 33 ; Hofmarm,
Wien. med. Wchnschr., 1873, S. 292 ; Bergmann, St. Petersb. med. Ztschr., 1868,
Bd. xiv. S. 28.

2 Compt. rend. Acad. d. sc., Paris, 1888, tome cvii. p. 123.

3 Jou.rn. PhysioL, Cambridge and London, 1890, vol. xi. p. 497.

4 Weber, "Stud. ii. Saiigethiere, " Jena, 1886, S. 9.

5 Compt. rend. Acad. d. sc., Paris, 1886, tome ciii. p. 66; 1887, tome civ. p. 1292;
and 1888, tome cvi. p. 1426.

6 Hermann, Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xvii. S. 291.

7 Arch. f. mikr. AnaL, Bonn, 1875, Bd. xii. S. 119; and Biol. Centralbl., Erlangen,
1892, Bd. xii. S. 458.

8 Zalesky, Hoppe-Seyler's Med. -chem. Untersuch., Berlin, 1866, Bd. i. S. 85; Casali,
Jahresb. ii. d. Fortschr. d. Thier-Chem., Wiesbaden, 1873, S. 64 ; Fornara, ibid.,
1877, S. 74.

9 Compt. rend. Acad. d. sc., Paris, 1852, tome xxxiv. p. 729.

10 Compt. rend. Soc. de biol., Paris, 1854, p. 135.

11 Arch, de physiol. norm, et path., Paris, 1893, Ser. 5, tome v. p. 511.

VOL. I. — 43

674 SECRETION AND ABSORPTION BY THE SKIN.

commencing in the hind-limbs, slowing and final arrest of the heart, and
constriction of the pupil. Frogs, guinea-pigs, and small birds are killed by
injection of the alcoholic extract of the collection of glands forming the
so-called " parotids " of the toad. The poisonous substance is dialy sable,
and is probably an alkaloid. The blood of toads also contains small amounts
of this substance, and the serum of a toad will kill a frog if introduced into
the dorsal lymph sac.

The slime of fish is secreted by goblet cells in the epidermis, but has been
little investigated from the chemical standpoint, on account of the great
difficulty in obtaining it in sufficient quantities, and free from foreign
substances. The slime of Myxine glutinosa is most easily obtained, and is
found to contain a mucin-like body, which, however, does not yield a
reducing sugar on boiling with dilute acicU1

The reaction of the skin of the eel and of Myxine is alkaline to litmus,
but curiously does not affect phenophthalein. A reducing sugar can be
obtained from the slime of the eel by boiling with dilute acid.'2 According
to Alcock,3 the slime of the Ammocwte larva yields a proteolytic ferment on
extraction.

(5) Sebaceous secretions. — Such secretions are formed by prolifera-
tion and subsequent degeneration of the cells lining the sebaceous
glands, in which karyokinetic figures are frequent.4

These glands are present over the whole surface of the body, with the
exception of the palms of the hands, soles of the feet, dorsal surface of the
third phalanges, and glans penis.

Since it is impossible to collect sufficient quantities of the sebum of
man for analysis, wTe have to rest content with analyses of the contents
of sebaceous cysts, the vernix caseosa of the foetus, or the contents of
derinoid cysts of the ovary.

Glycerin and cholesterin fats, fatty acids, albumin (casein ?), free
cholesterin and isocholesterin, with water and salts, are the main con-
stituents of sebum.

The following table is taken from Hoppe-Seyler : 5 —

Contents of a
Distended
Sebaceous
Gland in Man.

Vernix Caseosa
of Man.

Smegma
Preputii
of Man.

Smegma
Preputii
of Horse.

Water

317-0

669-8

...

Epithelium and albumin

617-5

40-0

56-0

Fat

41-6

475-0

528-0

499-0

Fatty acids ....

12-1

...

Alcoholic extract .

150-0

74-0

96-9

Water extract

33-0

61-0

54-0

Ash . .

11-8

1 Journ. Physiol., Cambridge and London, 1893, vol. xv. p. 488.

2 Reid, Phil. Trans., London, 1894, vol. clxxxv. p. 319.

3 Proc. Phil. Soc., Cambridge, 1891, vol. vii. pt. 5, p. 252.
4Bizzozero and Vasale, Med. Ohir. Centralbl., Wien, 1884, S. 77 and 179.
5 "Physiol. Chem.," Berlin, 1881, Th. 4, S. 761.

CHEMICAL NATURE OF SKIN SECRETIONS. 675

Sotnitschewsky,1 in an analysis of a dermoid cyst of the ovary, found
tripalmitin, tristearin, and trioleiii ; soaps of the acids of these fats and
of caproic and caprylic acids, albumin, cholesterin, and an alcohol of
high molecular weight, which, however, was not cetyl alcohol.'2 Tyrosiiie,
hypoxanthin, xanthin, sugar, and glycogen were absent.

The vernix caseosa of man, according to Ruppel 3 and Liebreich,4 con-
tains cholesterin fats of oleic and palmitic acids, as well as glycerin fats,
and also free cholesterin and isocholesterin.

The cerumen of the ear has been investigated by Petrequin,5 and is
found to contain potash soaps of oleic and stearic acids in the case of man
and the ox, while in the dog the base is lime, and in the horse magnesia.

Wool fat, the sebaceous secretion of the sheep's skin, was proved by
Hartinann ° to contain no glycerin fats, but only those with cholesterin
as alcohol. Schulze and Urich7 confirmed this, and also found free
cholesterin and isocholesterin.

These cholesterin fats (so-called " lanoline ") have been specially
investigated by Liebreich,8 who finds that they are associated with
keratinised structures, and are not necessarily formed in sebaceous
glands, but may be formed within epidermic cells. Tortoiseshell, whale-
bone, horn, quills of porcupine and hedgehog, hoof of horse, and beak of
crow, all contain these fats. The skin of the two-toed sloth has no sebace-
ous glands, and yet contains cholesterin fats, while pigeons bereft of
their uropygial glands still have these substances in their feathers.

Such fats are peculiar, in that they can take up more than their weight
of water, and also in that they do not become rancid, and offer a
complete protection against the entrance of micro-organisms. Liebreich
compares them to the wax of plants, which is an ether of a monohydric
alcohol with a fatty acid.9

The secretion of the tail gland of the bird 10 has been chemically investi-
gated by de Jonge.11

The secretion contains cetyl alcohol, the alcohol of spermaceti. No sugar
or urea is present. Geese deprived of the tail gland and immersed in water are
found to take up from two to two-and-a-half times as much water in their
plumage as normal birds.12

The so-called "pigeons' milk," with which the young birds are fed by both
parents during the earlier days of life, is practically a sebaceous secretion of
temporary glands formed in the lateral pouches of the crop in both cock and

1 Ztschr. f. physiol. Chem., Strassburg, 1880, Bd. iv. S. 345.

2 Ernst Ludwig (Ztschr. f. physiol. Chem., Strassburg, 1897, Bd. xxiii. S. 38) has quite
recently found cetyl alcohol in the contents of dermoid cysts of the ovary.

* lUd., 1895, Bd. xxi. S. 122.
"Verhandl. d. Berl. physiol. Gesellsch.," in Arch. f. Physiol., Leipzig, 1890, S. 363.

5 Gompt. rend, Acad. d. sc., Paris, 1869, tome Ixix. p. 987 ; also 1869, tome Ixviii.
p. 940 ; Jahresb. ii. d. Fortschr. cL Thier-Chem., Wiesbaden, 1871, Bd. i. S. 36 ; 1874,
Bd. ii. S. 33.

6 Inaug. Diss., Gottingen, 1868.

7 Ber. d. deutscli. chem. Gesellsch., Berlin, 1872, Bd. v. S. 1075 ; 1874, Bd. vii. S. 570.

8 Berl. klin. Wchnschr., 1885, Bd. xlvii. S. 761 ; Compt. rend. Acad. d. sc., Paris, 1888,
tome cvi. p. 1176 ; and "Verhandl. d. Berl. physiol. Gesellsch.," in Arch. f. Physiol.,
Leipzig, 1890, S. 363.

9 The secretion of the Harderian gland of the orbit of rodents, though fatty in nature, is
not formed by disintegration of cells ; Wendt, r'"freber die Harder'sche Druse," Strassburg,
1877 ; Kamocki, Biol. Centralbl., Erlangen, Bd. ii. S. 709.

10 For anatomy, see Robby Kossmann, Ztschr. /. ivissensch. Zool., Leipzig, 1871,' Bd.
xxi. S. 568.

11 Ztschr. f. physiol. Chem., Strassburg, Bd. iii. S. 225.
13 Max Joseph, Arch. f. Physiol. Leipzig, 1891, S. 81.

676 SECRETION AND ABSORPTION BY THE SKIN.

hen. It contains fat, a proteid clotting with rennet, globulin, salts, and water,
but is free from sugar.1

The secretion of the leg glands of lizards is probably of sebaceous nature.2
In certain fish, in addition to the secretion of slime by the goblet cells of
the epidermis, a formation of fibrils takes place from specialised cells, termed
" club cells," which may be distributed in the general epidermis or located in
special glandular involutions, as in the Myxinoid fishes. This secretion reaches
its highest development in the Myxinoids, and accounts for the extraordinarily
tenacious slime of this class. The process has, however, also been observed in
the case of the eel and lamprey.3

MECHANISM OF THE SECRETION OF SWEAT.

-

Goltz 4 in 1875 discovered the fundamental fact that excitation of
the peripheral end of the divided sciatic causes the appearance of beads
of sweat on the hairless pads of the hind-foot of the cat. He also saw
the same effect in a dog. In the next year, Ostroumow,5 and Kendall
and Luchsinger 6 confirmed the result, and extended the details of the
experiment.

Ostroumow showed that excitation of the abdominal sympathetic
cord produced the same effect ; that even after ligature of the aorta, sweat
was still secreted upon excitation of the appropriate nerves ; and, finally,
that injection of atropine completely annulled the effect of such excita-
tion.

Kendall and Luchsinger obtained the effect upon the fore-leg of the
cat and dog, by exciting the nerves of the brachial plexus, confirmed
the fact of the persistence of secretion after occlusion of the aorta, or
crural artery in the case of the hind-limb, and further showed that, even
after amputation of the leg, sweat could be produced on the pads of the
foot for some fifteen to twenty minutes, by stimulation of the sciatic.

The fact that the production of sweat is an act of true secretion,
and the existence of sudorific fibres having been demonstrated, the
course of the fibres from the spinal cord next engaged attention.

The existence of sweat-fibres for the lower limb in the abdominal
sympathetic cord, demonstrated by Ostroumow, was confirmed by
Luchsinger 7 and Nawrocki,8 and extended by both the latter observers 9
to the thoracic sympathetic cord, for the fore-limb. Later, sudorific
fibres for the face, running in the cervical sympathetic, were demon-

1 John Hunter, " Observations on Certain Parts of the Animal OZconomy," London, 1786,
p. 191 ; Hasse, Ztschr. f. rat. Med., 1865, Reihe 3, Bd. xxiii.; Claude Bernard, "Les
liquides de 1'organisme," Paris, 1859, tome ii. p. 232; Teichmann, Arch. f. mikr. Anat.,
Bonn, 1889, Bd. xxxiv. S. 225 ; Charbonnel-Salle et Phisalix, Compt. rend. Acad. d. sc.,
Paris, 1886, tome eiii. p. 286 ; Phisalix, Compt. rend. Soc. de biol., Paris, 1890, Ser. 9, tome
ii. p. 368 ; Reid, Hep. Brit. Ass. Adv. Sc., London, 1894, p. 812.

2 Leydig, "Die in Deutschland lebenden Arten der Saurier," 1872; Batelli, Arch. f.
mikr. Anat., Bonn, 1879, Bd. xvii. S. 346.

3 J. Miiller, "Untersuch. ii. die Eingeweide der Fische," Berlin, 1845, S. 11 ; Eolliker,
Wurzb. med. Ztschr., 1860, Bd. i. S. 1 ; F. E. Schulze, Arch. f. mikr. Anat., Bonn, 1867,
Bd. iii. S. 137 ; Fcettinger, Bull. Acad. roy. d. sc. de Belg., Bruxelles, 1876, Ser. 2, tome
xli. p. 599 ; Blomfield, Quart. Journ. Micr. Sc., London, 1882, vol. xxii. p. 355 ; Reid,
Phil. Trans., London, 1894, vol. clxxxv. p. 319.

4 Arch. f. d. ges. Physiol., Bonn, 1875, Bd. xi. S. 71.

5 Ref. in Jahresb. ii. d. Fortschr. d. Anat. u. Physiol., Leipzig, 1877, Bd. v.

6 Arch.f. d. ges. Physiol., Bonn, 1876, Bd. xiii. S. 212.

7 Ibid., Bonn, 1877, Bd. xiv. S. 369.

8 CentralU. f. d. med. Wissensch., Wien, 1878, S. 2.

9 Nawrocki, Centralbl. f. d. med. Wissensch., Berlin, 1878, S. 17 ; Luchsinger, ibid.,
1878, S. 36.

THE SECRETION OF SWEAT. 677

strated by Luchsinger1 and Nawrocki,2 in the horse and pig by the
former observer, and in the pig by the latter. Both agreed that the
fibres reach the sweat-glands of the face by the infra-orbital branch of
the fifth cranial nerve, the junction being effected by branches from the
cavernous plexus of the sympathetic. Neither of these investigators
could satisfy himself of the presence of sweat-fibres in the facial nerve.

The origin of the sudorific fibres in the spinal cord has been studied
by Luchsinger, Nawrocki, Vulpian, Ott,3 and more recently by Langley.4

In the case of the hind-limb of the cat, according to Langley, the
sudorific fibres enter the sympathetic cord by the white rami communi-
cantes of the last two thoracic and first three or four lumbar nerves,
become connected with nerve-cells in the sixth and seventh lumbar, and
first and second sacral ganglia of the sympathetic, and leave by the
grey rami of these "ganglia, to enter the anterior divisions of the corre-
sponding spinal nerves, and so the sciatic. The first and second lumbar
spinal nerves seem to supply the greatest number of secretory fibres.
The grey ramus to the sixth lumbar nerve is found to chiefly supply the
sweat-glands of the inner part of the foot, that to the second sacral
nerve the outer part, and, in the main, the successive rami from above
downward supply strips of the skin of the foot from within outwards,
though considerable, and, in different individuals, varied overlapping of
fields is noted.

In the case of the fore-limb, the same observer finds that the sweat-
nerves are supplied to the sympathetic chain by the fourth to the ninth
thoracic spinal nerves, the main outflow of fibres being usually found in
a nerve near the middle of the series. All these fibres run up in the
sympathetic cord to the ganglion stellatum, where a connection with nerve-
cells is effected, and by the grey rami of this ganglion reach the brachial
plexus,5 and so the median and ulnar nerves for their final distribution.

The grey rami to the sixth and seventh cervical nerves seem to chiefly
supply the inner part of the fore-foot, while that to the first thoracic
nerve chiefly supplies the outer part.

The fibres for the face, according to Nawrocki, leave the cord by the
second, third, and fourth anterior roots, and run up in the cervical sym-
pathetic to finally reach the infra-orbital branch of the fifth cranial
nerve, vid the cavernous plexus.

Vulpian 6 and Ott 7 maintained that, in addition to the sudorific fibres
supplied to the limbs vid the sympathetic, others are supplied directly from
the cord with the nerves forming the limb plexuses. The existence of such
fibres was denied by Nawrocki, and Langley fully confirms the statements of
this observer.

Furthermore, Vulpian and Ott maintained that inhibitory fibres to the
sweat-glands exist, and the theory has been recently revived by Arloing.8

Vulpian's evidence for the existence of such fibres was, that contem-

1 Arch.f. d. ges. Physiol., Bonn, 1880, Bd. xxii. S. 126.

2 Centralbl. f. d. med. Wissensch., Berlin, 1880, S. 945.

3 Compt. retwl. Acad. d. sc., Paris, 1878, tome Ixxxvi. pp. 1308 and 1434 ; Ott, Journ.
Physiol., Cambridge and London, 1879, vol. ii. p. 42.

4 Ibid., 1891, vol. xii. p. 347 ; ibid., 1894, vol. xvii. p. 296.

5 Eckhard (Arch. f. Anat., Physiol. u. wissensch. Med., Berlin, 1849, S. 427) quotes a
case in man where contusion of the brachial plexus led to continuous sweating of the hand
on the side of the injury.

6 Loc. cit. 7 Loc. cit.

8 Arch, dephysiol. norm, et path., Paris, 1890, Se>. 5, tome ii. p. 1 ; and 1891, Se>. 5,
tome iii. p. 241.

678 SECRETION AND ABSORPTION B Y THE SKIN.

poraneous excitation of cut sciatic and abdominal sympathetic causes less sweat
on the pads of a cat's feet than excitation of sciatic alone, and the sweat-
stimulating drug pilocarpine causes more sweating when sciatic or sympathetic
are cut than intact.

Later, Vulpian 1 abandoned this theory. He was led to the idea of the
existence of inhibitory fibres in the cervical sympathetic by consideration of
the old experiment of Dupuy,2 in which section of the cervical sympathetic
in the horse leads to sweating on the face on the side of section. Mere excess
of blood supply to sweat-glands, from the vaso-dilation which occurs simul-
taneously, is probably per se no stimulus to the action,3 but there is no doubt
that the excitability of the glands is thereby raised, and if, with Luchsinger,4
it is admitted that a few sweat-fibres originate with the fifth cranial nerve, the
result is simply due to painful reflex, for J.uchsinger got no sweating on section
of the sympathetic in the neck of a chloralised horse, though stimulation of
the peripheral end gave abundance.

The evidence adduced by Ott is the immediate cessation of a secretion pre-
viously evoked by pilocarpine, on excitation of the peripheral end of the
divided sciatic. Even if it were admissible that the accompanying vasomotor
constriction could cause the effect (which it is not, seeing that in the ampu-
tated foot sweat can still be called forth), the result, he maintains, is obtained
too suddenly to be accounted for in this manner.

Again, he states that irritation of the abdominal sympathetic causes a
dryness of the pads of the foot on the side of irritation, and that pilocarpine
accentuates the difference in condition between the foot on the side of irrita-
tion and the normal foot on the opposite side.

Finally, division of the abdominal sympathetic produces moist pads on the
side of section, and injection of pilocarpine makes these pads sweat before the
others.

In Arloing's experiments on oxen and donkeys, the cervical sympathetic is
divided, and time is allowed to elapse until the vaso-dilation has passed off.
Pilocarpine now produces more marked secretion on the side of section, which
is interpreted as meaning that inhibitory impulses, restraining the action of the
glands on the sound side, have been removed on the side of section.

It has always been a matter of difficulty to differentiate the action of two
oppositely acting sets of fibres running in the same nerve-trunk, and it must
be admitted that the evidence so far for the existence of inhibitory fibres for
sweat secretion is not strong.

Excitation by appropriate stimuli of the regions of the spinal cord
from which the sweat-fibres emerge leads to an outpouring of sweat on
the parts of the skin supplied by these fibres. Thus, if the spinal cord
is divided above the exit of the twelfth thoracic nerve in the cat, and
the animal exposed to heat (60° to 70° C. for five to ten minutes), sweating
still occurs on the hind-limbs.5

Nawrocki 6 and Marine' 7 denied this effect, and maintained that it
is only when there is continuity of the cord with the bulb that such
stimulation causes sweating. Later, however, Nawrocki 8 obtained the

1 Vulpian et Raymond, Compt. rend. Aead. d. sc., Paris, 1879, tome Ixxxix. p. 11 ;
Rev. internal, d. sc. UoL, Paris, 1880, p. 115; and " Lecons sur les substances tox. et
me"dic.," tome i. pp. 148-149.

2 Journ. de me'd., chir., pharm., etc., Paris, 1816, tome xxxvii.

3 But see Levy, " Verhandl. d. Berl. physiol. Gesellsch.," in Arch.f. Physiol., Leipzig,
1892, S. 155.

4 Tagebl. d. Versamml. deutsch. Naturf. in Baden-Baden, 1879.

5 Luchsinger, loc. cit. 6 Centralbl. f. d. med. Wissensch., Wien, 1878, S. 17.

7 Nadir, v. d. k. Gesellsch. d. Wissensch. u. d. Georg.-Aug. Univ., Gb'ttingen, 1878,
p. 102.

8 Centralbl. f. d. med. Wissensch., Berlin, 1878, S. 721.

THE SECRETION OF SWEAT. 679

result in a few cases with divided cord. Obviously a positive case in
such an experiment is worth many negative, since the excitability of
the cord below the section may possibly be depressed at the time of
making the test. It is generally accepted that spinal " sweat-centres "
exist.

On the other hand, no cerebral centres for sweating have yet been
experimentally demonstrated.1

According to Levy Dorn,2 the spinal " sweat-centres " are very re-
sistant to the action of cold. In cats cooled till the rectal temperature
was 22° to 28° C., sweating was still obtained by reflex excitation or
dyspnoea, but heating (70° C.) caused little sweating, the cooled cat
being as it were "protected," in that the heat which is to restore it,
does not, when applied, immediately call forth a reflex outpouring of
sweat, by the subsequent evaporation of which, heat would be abstracted
from the body.

The nervous mechanism of sweat secretion may be called into action
by central stimuli, by reflex action, or by peripheral stimuli. A venous
condition of the blood is one of the most active stimuli to the central
mechanism, and one frequently employed in experimental work. If an
animal be partially asphyxiated, after section of the spinal cord in the
mid-dorsal region, sweat breaks out on the pads of the hind-feet, even
after division of all the posterior roots behind the section.3

Raising the temperature of the blood produces a similar effect, and
the result is also obtained with divided posterior roots, and hence is not
reflex ; moreover, the effect is stopped by section of the sciatic, and hence
is not of peripheral origin as a result of heating of the terminal apparatus.

Certain drugs, especially picrotoxin and strychnia, appear to cause
sweating exclusively by their action on the spinal cord. Nicotine and
eserine cause slight sweating after section of the limb nerves, and are
therefore not exclusively, though mainly, central stimulants.4

Reflexly, it may be broadly stated that stimulation of almost any
afferent channel will cause sweating. A cat will sweat on the pads of
its feet at the sight of a dog, mustard in the mouth causes sweat on the
foreheads of many persons, and the application of heat to the skin is a
familiar cause of increased action of the glands. According to Greiden-
berg,5 in a patient with sweating legs, slight skin stimuli diminished the
secretion, while strong stimuli caused an increase.

Directly from the periphery, the sweat-glands may be excited by
certain drugs or by raising their temperature.

Pilocarpine excites secretion of sweat after complete division of the
nerves, and localised secretion may be produced by introducing it
beneath the skin. Its action is probably in the main upon the termina-
tions of the nerves in the glands, since it is, as a rule, non-effective, when
sufficient time has been allowed to elapse after section of the nerves to
ensure complete degeneration (Luchsinger, Nawrocki, and Vulpian). On
the other hand, Max Levy 6 states that pilocarpine may still give good

1 Bloch, "These de Paris," 1880.

2 "Verhandl. d. Berl. physiol. Gesellsch.," in Arch. f. PhysioL, Leipzig, 1895, S. 198.

3 Luchsinger, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 369.; Robillard,
" These de Doct.," Lille, 1880.

4 Luchsinger, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xv. S. 482; Hogyes, ref. in
Jahresb. u. d. Fortschr. d. Anat. n. PhysioL, Leipzig, 1881, Bd. ix. S. 72.

5 Jahresb. u. d. Fortschr. d. Anat. u. PhysioL, Leipzig, 1882, Bd. x. S. 81,

6 Centralbl.f. PhysioL, Leipzig u, Wien, 1892, Bd. v. S. 68..

680 SECRETION AND ABSORPTION B Y THE SKIN.

secretion, when excitation of previously divided nerves is without effect,
pointing to stimulation of the gland protoplasm by the drug.

According to Rossbach,1 small doses act upon the nerve-endings,
while large doses also affect the gland protoplasm ; and some of the
experiments of Luchsinger, Marme, and Hogyes, in which pilocarpine
caused secretion, long after the time necessary for complete degeneration
of the nerves had elapsed, point to the same conclusion.

There appears to be no central action by pilocarpine, for Eobillard,2
after separating the foot of a cat from the body, with the exception of
the tibial nerve, obtained 110 secretion of sweat on injection of pilo-
carpine into the general circulation ; though the nerve was proved to
conduct, by a profuse sweat caused on asphyxiation.

Muscarine 3 also acts as a peripheral excitant, but is less active than
pilocarpine.

Atropine and duboisine are both antagonistic to pilocarpine and
muscarine.

In the cat an injection into a vein of 3 mgrms. of atropine is sufficient
to make stimulation of the sciatic ineffective ; subsequent intravenous
injection of 10 mgrms. of pilocarpine will cause sweating, though the
nerve is still without action on excitation. In such a case the atropine
poisons the nerve-ending, but the gland protoplasm is still excitable and
responds to pilocarpine. According to Bossbach,4 a dose of 20 to 30
mgrms. of atropine is needed, in the case of a cat, to paralyse the gland-
cells to such an extent that subsequent local application of pilocarpine
is without effect. All glandular apparatus appears to be far more
sensitive to atropine than to pilocarpine.

The local paralysing effect of atropine was elegantly demonstrated
by Aubert.5 If the palm or finger (carefully cleaned) is pressed on to
paper sensitised with silver nitrate, the spots of chloride formed at the
mouths of the sweat-ducts are quite visible. If the experiment is tried,
after a pad soaked in atropine solution has been tied over a limited
surface overnight, that surface is found to yield no spots, in contrast to
the surrounding field.

Finally, the terminal sweat apparatus is very sensitive to change of
temperature. Luchsinger 6 has shown that not only cold but excessive
heating retards the action of the glands. Thus if, on a warm day, one
hand be held in water at 45° to 50° C. for ten minutes, while the other is
immersed in water at 15° to 30° C., and exercise is then taken, the hand
which was in water at the lower temperature commences to sweat at
once, the other not for some considerable time. In experimental work,
in which the excitation of nerves is undertaken and the outbreak of
sweat observed, the greatest caution is necessary to keep the tempera-
ture of the extremities constant, for with a cold foot a nerve root hold-
ing sweat-fibres in reality, may be wrongly considered to hold none, if
the terminal apparatus is depressed by cold.

That the formation of sweat is a true act of secretion, and not
merely filtration, is shown by experiments already quoted, in which it is
noted that after stoppage of the circulation sweat is still secreted on

1 Arch. f. d. ges. PhysioL, Bonn, 1880, Bd. xxi. S. 1. 2 Loc. cit.

3 Triimpy and Luchsinger, Arch. f. d. ges. PhysioL, Bonn, 1878, Bd. xviii. S. 501 ;
Ott and Wood Field, Journ. PhysioL, Cambridge and London, 1878, vol. i. p. 193;
Hogyes, lac. cit.

4 Loc. cit. 5 Lyon mid., 1874.
«Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xviii. S. 478,

ELECTRO-MOTIVE PHENOMENA IN SKIN GLANDS. 681

excitation of nerves ; and further, by the fact that by means of atropine
the secretion of sweat can be stopped in spite of the continued circula-
tion of the blood.

It is probably right to conclude that the blood supply is a necessary
adjuvant to the prolonged activity of the gland-cells, but not the stimu-
lant to their action, though, according to Levy,1 secretion is provoked
upon reinstallation of the circulation, in a limb with cut sciatic, which
has been long kept anaemic. This effect may possibly be due to the
mechanical stimulation of the glands by the pulse.

Levy Dorn 2 placed the hind-limb of a cat in a receptacle within
which the air pressure could be raised, and found that the secretion
could overcome a pressure in excess of that in the large arteries.

Nothing is definitely known as to the existence or not of any
action of the nervous system upon the sebaceous glands.

According to Arloing,3 section of the cervical sympathetic in
donkeys causes exudation of sebum from the sebaceous glands of the
skin of the ear, reaching its maximum fifteen hours after section, and
lasting for sixty-four hours. Stimulation of the peripheral end of the
nerve also causes secretion from these glands.

The glands of the skin of the frog undergo periodic contraction and expan-
sion by means of their muscular sheaths,4 and have been carefully studied by
Engelmann,5 Strieker and Spina,6 and Drasch,7 in the web and membrana
nictitans. The spontaneous movements in the case of the -web glands are
stopped temporarily by section of the sciatic, or seventh, eighth, and ninth
anterior spinal roots. Excitation of the sciatic or reflex stimulation of the skin
leads to contraction of the glands, as also does direct excitation by vapours of
chloroform or ether, or by carbonic acid gas. During contraction of the whole
gland, by its muscular sheath, the lining gland-cells swell, and, according to
Drasch, in the case of the membrana nictitans, the fifth cranial nerve, on ex-
citation, causes contraction of the sheath only, while excitation of the sympa-
thetic causes swelling of the cells. Pilocarpine causes increased secretion by
these glands. Strieker and Spina advanced a theory of secretion based upon
observations of these glands, maintaining that, in the act of swelling, fluid is
sucked in by the cells from the surrounding lymph spaces, and on contraction
forced out into the lumen ; the theory obviously involves the assumption of some
valvular structure in the protoplasm, of which we know nothing, and furthermore
has been disposed of by Drasch, who has found that the glands of the mem-
brana nictitans may secrete freely in stages of immobility of the lining cells.

In the case of fish — in the eel it has been shown that the secretion of the
goblet cells of the epidermis and of the club cells (when present) is under the
influence of the nervous system, but the nerve paths have not been worked out.8

ELECTRO-MOTIVE PHENOMENA IN SKIN GLANDS.

In attempting to demonstrate the existence of currents in the
uninjured muscles of the frog, du Bois Eeymond 9 discovered that the

1 Loc. cit. .

2 " Verhandl. d. Berl. physiol. Gesellsch.," Arch. f. PhysioL, Leipzig, 1893, S. 383.

3 Arch, de physiol. norm, etpath., Paris, 1891, Se"r. 5, tome iii. p. 241.

4 Ascherson, Arch. f. Anat. u. PhysioL, Leipzig, 1840, S. 15.

5 Arch.f. d. ges. PhysioL, Bonn, 1872, Bd. v. S. 498.

6 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1880, Bd. Ixxx. Abth. 3, S. 95.

7 Arch.f. PhysioL, Leipzig, 1889, S. 96.

8 Reid, Phil. Trans., London, 1894, vol. clxxxv. p. 319.

9 " Uiitersuch. ueber thierische Elektricitlit," Bd. ii. Abth. 2, S. 9-20.

682 SECRETION AND ABSORPTION B Y THE SKIN.

skin itself is a seat of electro-motive force, which he located in the
glands. The current is in the direction from the free to the deep sur-
face, the former being electrically negative to the latter. A current so
oriented may be termed " ingoing," and is the normal direction of the
" current of rest " of all secreting membranes, so far investigated.

The discovery was corroborated by Rosen thai,1 and extended to the
case of the stomach and gut mucosse in the frog and rabbit, while
Hermann2 found a similar current in the skins of many fish, and,
more recently, in the tree frog, proteus, and axolotl.3 Such currents as
a rule exhibit spontaneous variations in intensity, especially in the case
of the skin of the frog.

Valentin,4 and later Roeber,5 furthermore found that in the case of
the frog's skin excitation of the cutaneous nerves causes a variation in
the electro-motive force of the resting skin, and the latter observer
that this phenomenon could be produced by reflex excitation, and
was not abolished by curare.

The direction of the " current of action " evoked by excitation of
nerves was not found to be constant by Roeber, a fact corroborated by
all subsequent investigators. Thus Engelmann6 observed a double
excitatory variation of the "current of rest," namely, an outgoing
followed by an ingoing current (negative followed by positive
variation), while Hermann 7 noted an ingoing " current of action,"
often preceded by an outgoing current of short duration, and Bayliss
and Bradford 8 state that it is " scarcely possible to speak of a normal
excitatory variation."

Hermann and Luchsinger9 found that the cat's foot also gave an
ingoing " current of rest," but that the current developed on excitation
of the sciatic was constantly ingoing, and prevented from development
by the exhibition of atropine.

Luchsinger 10 demonstrated the existence of exactly similar currents
in the snout of the pig, goat, cat, and dog on excitation of the cervical
sympathetic or infra-orbital nerve, and Hermann and Luchsinger n in the
tongue glands of the frog, though in the latter case excitation of the
hypoglossal or glossopharyngeal nerve gave a triphasic " current of
action," an outgoing being interpolated in a long lasting ingoing
phase. Tarchanoff 15J has further indicated that parts of the skin of
man rich in sweat-glands (e.g. palm of hand), are negatively electrical
to parts poor in sweat-glands (e.g. skin over deltoid), and that the
ingoing " current of action " of such glands can be excited reflexly by
very slight stimuli, such as sound or even the expectation thereof,
odours, or mental effort.

The well-known Willkilrversuch of du Bois Reymond, in which,
when the index-fingers of the two hands are immersed in vessels of
liquid in circuit with a galvanometer, a voluntary effort of the

1 Arch. f. Physiol., Leipzig, 1865, S. 301.

2 Arch.f. d. ges. Physiol., Bonn, 1882, Bel. xxvii. S. 280.

3 Ibid., 1894, Bd. Iviii. S. 242.

4 Ztschr.f. rat. Med., 1861, Bd. xv. S. 208.

5 Arch. f. Physiol., Leipzig, 1869, S. 633.

6 Arch. f. d. ges. Physiol., Bonn, 1872, Bd. vi. S. 97.

7 Ibid., 1878, Bd. xvii. S. 291 ; and 1882, Bd. xxii. S. 280.

8 Journ. Physiol., Cambridge and London, 1886, vol. vii. p. 223.

9 Arch.f. d. ges. Physiol., Bonn, 1878, Bd. xvii. S. 310.

10 Ibid., 1880,' Bd. xxii. S. 152. u Ibid., 1878, Bd. xviii. S. 460.

12 Ibid., 1890, Bd. xlvi. S. 46.

ELECTRO-MOTIVE PHENOMENA IN SKIN GLANDS. 683

muscles of one forearm (e.g. grasping a rod) gives a current passing up
the contracting arm, is probably to be explained by the concomitant
excitation of the sweat-glands on the side of action.

Not only in the case of membranes containing complex glands is an
ingoing " current of rest " observed, but also in secreting membranes
supplied with unicellular glands (goblet cells), as the pharynx and
cloaca of the frog,1 or the skin of the fish ; 2 and furthermore, in certain
membranes, quite free of secretory structures, and covered only by
stratified epithelium, such as the skin of the pigeon and the mucosa of
the crop of the same bird in winter.3

The attempts to explain the causation of the above currents, it must
be confessed, have not been very satisfactory.

As regards the constantly observed ingoing " current of rest," it is
obviously of the first importance to determine whether it is of purely
epidermic origin, of purely glandular origin, or whether it receives a
component from both sources. The experiments with the non-glandular
skin of the bird above-mentioned show that simple stratified epithelium
can give rise to such a current, and Hermann 4 has further proved that
shaving the epidermis of the cat's foot lowers the electro-motive force of the
" current of rest." Furthermore, Bach and Oehler 5 found that pencilling
the skin of the frog with solution of corrosive sublimate abolished the
" current of rest," though the excitatory change from the glands beneath
could still be obtained by exciting the nerves of the skin.

On the other hand, it can hardly be denied that in such cases as
the gastric mucosa of the frog, where the epithelium is practically all
converted into unicellular glands (goblet cells), the marked ingoing
" current of rest " is of glandular origin,6 and this must also be the case
in such a membrane as the cloacal mucosa of the frog.

It is simplest, in the present state of knowledge, to admit that both
stratified epithelium and gland protoplasm can give rise to currents.

Hermann and Biedermaim consider such currents due to alteration
of metabolic activity in the continuity of protoplasm. Protoplasm
becoming " altered " to mucus in a goblet cell is negative electrically to
the unaltered material at the base of the cell, and the same in the
process of keratinisation in the continuity of epithelium. Since altered
parts are negative electrically to unaltered or less altered, the result will
be an ingoing current, whether we choose the glands or the epidermis,
or both, as the source of the electro-motive force of the " current of rest."

If we turn to the case of the " action current," it is only in the case
of the mammalian glands that any clear explanation on the above
hypothesis is feasible. In these glands, as already mentioned, the
" current of action " is purely ingoing, and it is only necessary to assume
that in action the " difference " between the base and the free border of
the cells becomes more marked than at rest, with a concomitant develop-
ment of electro-motive force with ingoing current.

In the skins and other secreting membranes of amphibians and fish,
we are met with the difficulty that it is not possible to predict with
certainty what will be the direction of the " action current " elicited by

1 Biedermaim, ibid., 1893, Bd. liv. S. 209.

2 Hermann, loc. cit. ; Reid, Phil. Trans., London, 1893, Bd. clxxxiv. p. 335.

3 Reid, Jo urn. Physiol., Cambridge and London, 1894, vol. xvi. p. 359.

4 Arch.f. d. ges. PhysioL, Bonn, 1894, Bd. Iviii. S. 242.

5 Ibid., 1880, Bd. xxii. S. 30. 6 Bohlen, ibid., 1894, Bd. Mi. S. 97.

684 SECRETION AND ABSORPTION B Y THE SKIN.

excitation of the nerves. The strength of the stimulus, and the extent to
which the normal ingoing " current of rest " is developed, affects the result,
and hypotheses have been based upon both of these factors of the case.

Hermann l long ago suggested the possibility of augmenting and inhibitory
fibres to the glands, and in his most recent publication'2 still entertains the
idea. On the other hand, Biedermann suggests that the two sides of protoplasmic
activity (the katabolic and anabolic) in the secretory cells are associated with
generation of electro-motive force, causing currents in opposite directions
in the two cases ; that the electro-motive force of the " current of rest " is
the algebraic sum of these opposing forces at the moment ; and that the results
of nerve excitation are related directly to the ascendancy of one or the other
metabolic action at the time of stimulation.

The production of an outgoing "current of action" is considered by
Biedermann as due to the nerve excitation provoking an excess of anabolic action
in the cell, that of an ingoing " current of action " as due to excess of katabolism,
so that one and the same class of nerve-fibre is supposed to produce quite
opposite results in the cell, the effect being partly conditioned by the state of
the balance in the cell between the two processes at the moment of excitation,
and partly by the strength of the stimulus. He supposes that the cell process
least developed at the time of excitation, tends to be stimulated in excess of its
fellow, so that if the ingoing "current of rest" is weak, as a result of slight
katabolic ascendancy, excitation tends to cause an ingoing " current of action " ;
and, vice versa, if the ingoing " current of rest " is strong, as a result of marked
katabolic ascendancy, the result of excitation of the cell is liable to be the
development of an outgoing " current of action."

Hermann objects to this, that if the electrical sign of excess of anabolism
over katabolism is plus, the induction of such a condition must start from the
deep ends of the cells, i.e. from the ends from which they get their pabulum
from the blood, and excess of positivity of this end of the cell comes, so far as
the direction of current is concerned, to the same thing as excess of negativity
at the free end of the cell, associated by hypothesis with katabolic ascendancy,
and should develop a current in the same direction, i.e. ingoing.

It may also be noted in this connection, that, according to Bohlen,3 in
the gastric mucosa of mammals, cessation of circulation or any interference
with blood supply tends to convert the normal ingoing into an outgoing
" current of rest." If an outgoing current is associated with excess of anabolism
over katabolism, it is difficult to conceive how withdrawal of blood supply can
induce such a change. A similar complete reversal of the direction of the
" current of rest " is obtainable in the secreting membranes of the frog and
fish by abstraction of heat, or by narcotisation with carbonic acid gas, ether,
or chloroform.

A strong stimulus of a nerve trunk may, in practice, cause an outgoing
action current, and a weak stimulus one that is ingoing, but it is again difficult
to conceive that difference in the strength of stimulus of one class of nerve-
fibre can alter the whole character of the metabolism in the cells.

Hermann was at one time of opinion that the two kinds of glands in the
frog's skin might be associated with the two phases of the excitatory variation ;
and the lip of the eel, which contains no club cells but only goblet cells, gives
an outgoing " action current," while the body skin, rich in club cells and poor in
goblets, gives an ingoing " action current " with the same strength of stimulus ; 4
but since the cloacal or pharyngeal mucosa of the frog, containing only one sort
of secretory cell, and the non-glandular crop of the winter pigeon, can give
currents in both directions, the hypothesis is not of universal application.

1 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xvii. S. 303.

2 Ibid., 1894, Bd. Iviii. S. 242. 3 LOG. dt.

4 Reid and Tolputt, Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 203.

ABSORPTION B Y THE SKIN IN MAN. 685

ABSORPTION BY THE SKIN.

Man. — To decide the case for or against the possibility of absorption
by the human skin, would appear a simple problem, yet a literature
reaching back over a century indicates that the production of un-
impeachable testimony on either side has proved a matter of no little
difficulty.

A fluid in contact with the skin is separated from the blood vessels
by layers of epidermic cells with intercellular spaces, but since the
superficial cells (except in the palm of the hand and sole of the foot)
are greasy with sebum, one of the first conditions for absorption is that
the fluid shall be able to wet the surface, so that imbibition by the cells,
or entrance of the fluid into the capillary spaces between them, may
take place. Though lanoline, the natural fat of the skin, takes up
water, such action only occurs slowly, and unless the skin is soaked
long in warm water, it is a familiar observation that it does not easily
become sodden, except in the case of the palms and soles. It is there-
fore not to be expected that water or watery solutions will be capable
of absorption by the skin of man, and the experimental evidence is
distinctly against such an assumption.

The method of some of the older observers, of attempting to decide
the question of absorption of water by immersing a man in a bath after
weighing, and weighing again after a prolonged sojourn therein, we may
dismiss by a bald statement of obvious sources of error.

(a) There is no guarantee that the normal loss of weight of the body
per unit time, through lungs and skin, is the same during the bath as
estimated during preceding hours. (The experiments showed, in different
instances, gains, losses, and absence of change of weight.) 1

Further, mere soakage of the epidermis of palms and soles may
mask an actual loss of weight in the bath.2

(b) It is impossible to be certain that the epidermis of the whole
body is devoid of fissures through which water might reach the deeper
parts.

(c) It is difficult to totally exclude absorption by immersed mucous
surfaces.

(d) A balance sensitive enough to indicate a difference of a few
grammes on a weight of many kilos., is difficult to construct.

(e) A considerable loss of surface epidermis occurs in " drying " the
body with a towel.

An improvement upon the method of total immersion is that of
immersion of a part of the body, but the vessel, instead of being
weighed before and after immersion of the part of the body, as in the
experiments of Vierordt and Eichberg,3 is be'tter graduated as in the
experiments of Falck,4 or provided with a capillary pipette, by means of
which absorption can be determined by fall of level of fluid,5 because,
by the gravimetric method, the error from mere soakage of epidermis
becomes far larger than in the volumetric method, though here also a
slight diminution in volume accompanies imbibition by the palm or sole,

1 Jainin et de Laures, Compt. rend. Acad. d. sc., Paris, 1872, tome Ixxv. p. 60.

2 Poulet, ibid., 1856, tome xlii. p. 435.

3 Arch. f. physiol. Heilk., Stuttgart, 1856. 4 Ibid., 1852.

5 Madden, "An Experimental Inquiry into the Physiology of Cutaneous Absorption,"
Edinburgh, 1838; Fleischer, Inaug. Diss., Erlangen, 1877.

686 SECRETION AND ABSORPTION B Y THE SKIN.

if an arm or leg be used, since the combination of a body with water in
which it is soaked is accompanied by contraction, so that the total
volume after soakage is less than the sum of the initial volumes.1

Fleischer could obtain no positive evidence of absorption of water
by the skin of the arm, immersed in a Mosso's plethysmograph (pro-
vided with a capillary pipette) for three hours.

Solutions of chemical substances easily detected in the secretions
have been much employed, a part of the body being immersed, or the
solution applied by means of a spray. Colouring matters, inorganic
salts, and drugs with marked physiological action, have been used. In
such experiments the chief points to be observed are — (a) Integrity
of the epidermis before the experiment, and absence of destructive
chemical action by the substance usec? during its course ; (&) absolute
exclusion of possibility of absorption by the lungs in the case of a
volatile substance, or of a salt yielding a volatile substance under the
action of the sweat ; (c) the choice of substances capable of recognition
with certainty in minute quantities in the secretions.

Braune,'2 using foot baths of solutions of potassium iodide, iodine,
and hydriodic acid, with a layer of oil over the surface of the solution,
was unable to detect iodine in the secretions. Parisot,3 using baths of
watery solutions of potassium iodide and ferrocyanide, belladonna, digi-
talis, and the colouring matter of rhubarb, repeated twice a day for
three to eight days, obtained no evidence of absorption. Hiifner 4 found
no lithium by the spectroscope in the urine after foot baths of lithium
chloride. V. Wittich5 and Fleischer6 were unable to confirm Eohrig's7
statement, that aqueous solutions of potassium iodide are absorbed.
Winternitz8 could get no evidence of absorption of 10 to 15 per cent,
solutions of lithium chloride in water, and results with cocaine were
negative.9

Again, Fubini and Pierini 10 could get no evidence of absorption of
the following solutions : — Potassium ferrocyanide, 3 per cent. ; santo-
nate of soda, 2 per cent. : salicylate of soda, 5 per cent. ; potassium iodide,
5 per cent. ; and lithium benzoate, 2 per cent., all dissolved in water.

Hence it is probably correct to conclude that watery solutions not
acting chemically upon the epidermis, and water itself, are not capable of
absorption by the intact skin of man.

If we now turn to the case of fluids that can wet the skin, such as
chloroform, ether, alcohol, etc., we find that a certain amount of
evidence of absorption is obtainable in the case of man.

Since chloroform, though an excellent fat solvent, causes pain and
blistering when long in contact with the skin of man, the experiments
have been mostly made with ether and alcohol. Ether is a better
solvent of fats than alcohol, and hence is more likely to give positive
results. Krause 11 maintained that both alcoholic and ethereal solutions
of salts are absorbed by the skin, but Fleischer,12 using a volumetric

1 Quincke, Arch. f. d. ges. Physiol., Bonn, 1870, Bd. iii. S. 332.

2 Diss., Leipzig, 1856.

3 Compt. rend. Soc. de blol., Paris, 1863, tome Ivii. p. 327.

4 Ztschr. /. physiol. Chem., Strassburg, 1880, Bd. iv. S. 378.

5 Hermann's "Handbuch," Leipzig, 1881, Bd. v. Th. 2, S. 257.

6 Loc. tit. 7 " Die Physiologie der Haut," Berlin, 1876.

8 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1891, Bd. xxviii. S. 405.

9 See also Soulier, " Traite" de tberapeutique et de pharmacologie, " 1891, tome i. p. 385.

10 Arch. ital. de UoL, Turin, 1893, vol. xix. p. 357.

11 Wagner's " Handworterbucb," 1844, Bd. ii. S. 174. 12 Loc. cit.

ABSORPTION B Y THE SKIN IN MAN. 687

method, could observe no absorption of absolute alcohol by his own skin
in an hour and a half, and Bitter1 denies entirely the absorption of
alcohol or alcoholic solutions of salts by the human skin. Winternitz 2
got spectroscopic evidence of lithium in the urine after keeping the
skin of the arm in contact with an ethereal solution (with a little added
alcohol) for three and a half hours, but missed the effect with a purely
alcoholic solution. The last-mentioned observer also denies the state-
ment of Parisot,3 that solutions of atropine in alcohol and chloroform,
applied to the forehead, cause mydriasis.

It would appear that previous removal of the grease of the skin
by ether allows a slight absorption of watery solutions to take place,
for Winternitz 4 got traces of lithium in the urine on applying a watery
solution of the chloride to the skin cleaned with ether, but not till nine
hours after the application.

If a substance applied to the skin is volatile at the temperature
of the body, the vapour may possibly pass into the capillary spaces
between the epidermic cells, and dissolve in the fluid in the sweat
ducts, and so finally reach the blood vessels, and be absorbed ; but in
experiments with such substances the greatest precautions must be
taken to exclude absorption by the respiratory tract, and again with
human skin the results of different observers are conflicting. Eohrig's 5
positive results with tincture of iodine are denied by Fleischer,6 who,
wearing a mask with a tube to the outer air, found no iodine in the
urine up till six hours after an application to the skin of the back for
one and a half hours. Next morning Fleischer found iodine in the
urine, but this may have been absorbed by the lungs during sleep,
or the result of the destructive action of the substance on the
epidermis. Mesnil,7 placing the arm in a Mosso's plethysmograph, filled
with vapour of iodine, could get no evidence of absorption after thirty-
two hours' exposure. On the other hand, guaiacol is asserted by several
observers to be absorbed.8

Oily solutions and unguents, since they " wet " the skin, one would
expect to be capable of absorption, but such substances are viscous and
must be mechanically forced into the intercellular spaces and hair
follicles, if any marked effect is to be obtained. According to Winter-
nitz,9 the mere application of oily solutions of veratrine and aconitine to
the skin of man is without effect. Baschkis and Obermayer 10 obtained
evidence of presence of lithium in the urine three hours after rubbing
in an ointment of lithium carbonate, oleic acid, and lanoline, but
Fleischer n could not obtain evidence of absorption of unguents holding
potassium iodide, veratrine, morphia, quinine, and salicylate of soda, nor
could Fubini and Pierini 12 find salicylic acid in urine after painting a
solution in oil of almonds on the hand and forearm.

But the most important case is that of mercurial ointment, which is
undoubtedly absorbed into the system. In this, in addition to fine

1 Diss., Erlangen, 1883. 2 Loc. cit.

3 Compt. rend. Acad. d. sc., Paris, 1863, tome Ivii. p. 327. 4 Loc. cit.

5 Loc. cit. 6 Loc. cit.

7 Oentralbl.f. PhysloL, Leipzig u. Wien, 1894, Bd. vii. S. 775. ref.

8 Sciolla, "Cronaca della clinica medica di Geneva," 1892-93, p. 191 ; Linossier and
Launois, Compt. rend. Soc. de. biol., Paris, 1894, pp. 108-110 and pp. 214-215; Gurnard
and Stourbe, ibid., 1894, pp. 180-182.

9 Loc. cit. 10 Centralbl. f. klin. Mcd., Bonn, Bd. xii. S. 65.
11 Loc. cit. 12 Loc. cit.

688 SECRETION AND ABSORPTION B Y THE SKIN.

globules of mercury, there is present the black oxide of the metal,1
and it is probable that, after formation of calomel by the sodic chloride
of the sweat, in the presence of oxygen a further conversion into
corrosive sublimate takes place, which is finally taken up by the blood.

Though evidence of vaporisation of mercury in mercurial ointment ,
at the body temperature, can be got by hanging a gold leaf over the
preparation, such vapour cannot of course pass through wet capillary
walls into the blood. The theory also of a passage of the fine globules
of mercury through into the blood is denied by Barensprung,2 Hoffmann,3
and Kindfleisch,4 though the fine particles are certainly mechanically
forced into the hair follicles, sweat ducts,5 and the interstices of the
superficial epidermic cells, thence to gradually undergo removal.

Finally, mention may be made of £he fact that by taking advantage
of the cataphoric action of the galvanic current (so-called electro-
osmose),8 it is possible to force watery solutions into the capillary spaces
between the epidermic cells, and so artificially cause absorption, either
by subsequent diffusion into the blood vessels, or by the recoil of
distended spaces forcing fluid into lymphatic channels.7 The direction
in which the fluid is moved is that of the electrical current, and the
quantity carried through a porous partition is directly proportional to
the intensity of the current, but organic membranes are far less
permeable than porous earthenware.8

It is not then to be expected that the effects with human skin
will be very marked, since, in practice, only a few milliamperes can be
passed with comfort to the patient.

Munk 9 got evidence of iodine and quinine in the urine, with
positive electrodes of modeller's clay moistened with potassium iodide,
and quinine in aqueous solution. Herzog 10 amesthetised the skin with
cocaine solution on the positive electrode, when mere application without
passage of current was without effect, as also was passage of current
without cocaine.

Kahn 11 corroborates this, getting complete anaesthesia of the skin in
twenty-five minutes, by a current of 4'5 milliamperes, with return of
sensation in thirty minutes after cessation of current. With a current
of 1 milliampere, the return of sensation was complete in ten minutes.
An excised piece of skin which had been anaesthetised by passing 3-25
milliamperes for thirty minutes through an anode filled with cocaine
solution tinged with a blue dye stuff, on microscopic examination showed
the dye stuff only to the depth of the rete Malpighii.

Lower mammals. — The results of observations upon absorption by
the skin of lower mammals are here considered apart from those obtained
from experiments on man, in order to obviate any tendency to treat the

1 Barensprung, Journ.f.prakt. Chem., Leipzig, 1850, S. 50 ; Voit, Ann. d. Chem. , Leipzig,
1857, Bd. civ. S. 3; Hermann, " Lehrbuch d. exper. Toxicologie," Berlin, 1874, S. 212.

2 Loc, cit. 3 Diss. Wiirzburg, 1854.

4 Arch.f. Dermat. u. Syph., Wien, Bd. iii. S. 309.

5 Neumann, Wien. med. Wchnschr., 1872.

6 Porret, Ann. d. PTiys. u. Chem., Leipzig. Bd. Ixvi. S. 272 ; du Bois-Reymond, Monatsb.
Akad. d. Wissensch., Berlin, 1860, S. 846 ; Wiedemann, Ann. d. Phys. u. Chem., Leipzig,
1852, S. 321 ; and "Elektricitat," Braunschweig, 1883. Bd. ii. S. 166.

7 Pascheles, Arch.f. exper. Path. u. Pharmakol., Leipzig, 1895, Bd. xxxvi. S. 100.

8 Engelmann, Arch. neer. d. sc. exactes (etc.}, 1874, Bd. ix. S. 332.

9 Reichert, Arch.f. PhysioL, Leipzig, 1873, S. 505.

10 Miinchen. med. Wchnschr., Bd. xxxiii. S. 222.

11 Inaug. Diss., Strassburg, 1891.

LOWER MAMMALS. 689

cases as analogous. The skin of the mammals usually employed for such
experiments is thinner than that of man, less horny, more vascular on
account of the hair, and in some cases (rabbit) possessed of hair follicles
with wide mouths. The presence of hair is a source of trouble in experi-
ment, for, if not shaved, excoriations may be passed over, while, on the
other hand, the process of shaving is apt to be accompanied by slight
injuries to the surface.

As with man, so here there is little positive evidence of absorption of
watery solutions, and one is inclined to attribute the results of those
observers who maintain that watery solutions are absorbed, to injuries
produced in shaving, or clipping, or accidental introduction by mouth or
lungs.

Forlanini 1 maintained that rabbits could be poisoned by painting
aqueous solutions of strychnia, acidulated with acetic acid, on the skin,
but v. Wittich 2 could not get the effect on white rats, nor Fubini and
Pierini 3 with guinea-pigs, while Winternitz 4 obtained both positive and
negative results with live rabbits. Fubini and Pierini allowed the tails
of rats to soak in strychnia and potassium cyanide solutions (for forty
minutes in the former case and two hours in the latter) without effect.
Traube-Mengarini 5 painted the skin of dogs daily for two months
with aqueous solution of potassium ferrocyanide, killed the animals, and
treated skin sections with ferric chloride. The blue was only found
between the surface cells, not reaching deeper than the stratum granu-
losum. Acidified borax-carmine solution, applied daily for seventy days,
gave a like result. Fleischer 6 got iodine through the belly skin of a
rabbit (into a watch-glass of water introduced under the skin) in two
hours from a cylinder full of the tincture, but admits that the structure
of the skin was altered.

With ether and chloroform solutions, absorption is more marked
in the thin skin of the rabbit, guinea-pig, and rat, than in that of man.

Waller 7 immersed the leg of a guinea-pig in a mixture of chloroform
and tincture of aconite, and was able to poison the animal, an effect not
produced by the tincture alone. White rats with the foot in a chloro-
form solution of atropine, exhibited a dilated pupil in two or three
minutes ; with the tail (thicker skin) immersed, not till half an hour
had elapsed. Strychnia in the same way he found was absorbed from
solutions in chloroform, but not from those in alcohol.

Winternitz8 also found that rabbits absorb strychnia solution in
chloroform, and points out that this is not merely an effect of " stimu-
lation," because a previous treatment of the skin with mustard or
ammonia does not hasten the intoxication.

Winternitz has also pointed out that cleansing the skin of rabbits
with ether or chloroform allows absorption of aqueous strychnia solution
to take place, and, microscopically, it is found that silver nitrate solution
penetrates more deeply if the skin is so treated. Alcoholic washing of
the skin also tends to make subsequent absorption of aqueous solution
possible, but to a far slighter degree than in the case of chloroform and
ether.

1 Ann. univ. di med. e chir., Milano, 1868, vol. ccv. p. 473.

2 Loc. cit. 3 LOG. cit. 4 Loc. cit.

5 Arch. f. PhysioL, Leipzig, 1892, Supp., S. 1; Arch. ital. de UoL, Turin, 1891,
vol. xvi. p. 159.

6 Loc. cit. 7 Proc. Roy. Soc. London, 1860, vol. x. p. 122. 8 Loc. cit.

VOL. i. — 44

690 SECRETION AND ABSORPTION BY THE SKIN.

Experiments upon the absorption of oils and unguents by the
skin of animals seem to have given conflicting results in the hands
of different observers. Lassar1 anointed rabbits with oil for days in
succession, and maintains that the organs became loaded with oil. V.
Sobieranski 2 asserts the same for vaseline rubbed into the skin of dogs
and rabbits, and states that the substance is found especially in the
muscles. Fleischer 3 denies the effect, as also does Winternitz,4 though
the latter observer was able to kill a rabbit by inunction of strychnia
(2 per cent.) in oil. Adam and Schoumaker 5 got negative results
from the inunction of an ointment of strychnia and vaseline into the
skin of the necks of dogs. Mercury, however, is absorbed by dogs and
horses from mercurial ointment. Thus Mtiller 6 rubbed mercurial oint-
ment into clipped dogs and horses, arTd found mercury in the freces and
urine. An ointment of corrosive sublimate, sodic chloride, and fat, gave
mercury in the fseces and urine ; lead was passed after rubbing in an
ointment of a lead salt, and application of a potassic iodide ointment
gave iodine in the saliva. Aqueous solutions of sublimate were without
effect when applied to the skin of these animals.

Cataphoric transfer of solutions through the skins of lower mammals
can be induced more easily than in the case of man. Munk T was able to
poison rabbits with strychnia in aqueous solution, and Kahn 8 obtained
the pharmacological effects of physostigmine and strychnia on rabbits,
and of apomorphine on dogs, by passing a current of 3'5 milliamperes
through '2 per cent, solutions in the positive electrode, and in all cases
proved that applications of the solutions without concomitant passage
of current was without effect.

Frog. — In the case of the frog the conditions for absorption of
watery solutions by the skin are far more favourable than in that of
mammals, for the surface is kept constantly moist by the secretion of
the skin glands, and no greasy matter is present, so that it is a matter
of common laboratory experience that poisonous solutions applied to
the skin of the animal rapidly produce their specific effects.

Blood vessels are abundant in the skin, especially in that of the
back, and substances must diffuse with ease through or between the
moist epidermic cells into the underlying vessels. It would, however,
appear probable that, in addition to simple diffusion, the physiological
condition of the lower epidermic cells affects the passage of substances
through the skin.

Eeid9 found that the direction of easier osmotic transfer of fluid
through freshly removed frog's skin is (provided the fluids used are
not deleterious) from without inwards, i.e. the reverse of the direction
of easier filtration through the dead skin ; but that, as its vitality
declines, the skin becomes less and less permeable from without
inwards, and finally is more permeable in the reverse direction. The
duration of the first period, during which the skin is more permeable

1 Virchows Archiv, 1879, Bd. Ixxvii. S. 157 ; " Verliandl. d. physiol. Gesellsch.," in
Arch. f. Physiol., Leipzig, 1880, S. 563.

2 Arch.f. cxper. Path. u. Pharmakol., Leipzig, Bd. xxxi. S. 329.

3 Virchow's Archiv, Bd. Ixxix. S. 558. 4 Loc. cit.

5 Jour n. depharmacol., Bruxelles, 1891.

6 Arch. f. wissensch. u. prakt. T/iierh., Berlin, Bd. xvi. S. 309 ; reference in
Centmlbl.f. Physiol., Leipzig u. Wien, 1SP1, Bd. iv. S. 550.

7 Loc. cit. 8 Loc. cit.
9 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 132.

FROG. 691

from without inwards, is directly associated with the vigour of the
animals, lasting seventy to eighty hours after death in strong frogs,
but only twenty-four hours or so in feeble animals at the end of the
breeding season.

Again, the magnitude of an ordinary osmotic stream, maintained
through freshly removed skin by means of solutions, whose injurious
effect on tissue life is minimal, is capable of variation in the direction of
increase or decrease, by such conditions as are known to exalt or depress
the activity of living matter. If an osmotic current is set up in the
direction from without inwards through living frog's skin (the normal
direction of greater permeability when the skin is fresh), the presence
of a stimulant (alcohol) increases, while that of a depressant (chloro-
form) decreases the current ; on the other hand, if the osmotic current
has been set up in the reverse direction, i.e. from within out, the stimu-
lant causes diminution, and the depressant augmentation of the amount
of fluid transferred from the inner to the outer surface of the skin in a
given period of time. The phenomena failed to manifest themselves
when dead skin was made the subject of experiment. The same observer 1
was also able to demonstrate the existence of a current of -6 per cent,
sodium chloride solution from the outer to the inner surface of freshly-
removed skin, when the same solution at equal pressure was on either
side, and hence filtration and osmosis put out of court.

These results are difficult to explain, and must provisionally be
attributed to some unknown epithelial action.

lBrit. Med. Journ., London, 13th Feb. 1892.

CHEMISTRY OF RESPIRATION.

BY M. S. PgMBREY.

CONTENTS : — Historical, p. 692 — Respiratory Changes in Air-Methods, p. 694 —
Conditions affecting Respiratory Exchange, p. 700 — Cold-Blooded Animals, p.
701 — Fishes, p. 704 — Warm-Blooded Animals, p. 706 — Influence of External
Temperature, p. 709— Of Muscular Activity, p. 714— Of Food, p. 717— Of Size
of Animal, p. 720— Of Time of Day, p. 721— Of Age, p. 722— Respiration by
Skin in Amphibia, p. 723 — In Mammals, p. 725 — Effects of Varnishing Skin,
p. 727 — Respiration in Alimentary Canal, p. 728 — Respiration of Foetus,
p. 730— Of Embryo, p. 733— The Respiration of different Gases, p. 735 — The
Respiration of Vitiated Air, p. 741 — Asphyxia, p. 743 — Exchange of Gases
between Blood and Air, p. 745 — Frequency of Respiration in Man, p. 747 — In
Animals, p. 753 — Changes in Composition of Air, p. 754 — Effect of Respiration
on Blood, p. 756 — Gases of Blood- Methods, p. 757 — Arterial and Venous Blood,
p. 760 — Condition of Gases in Blood, p. 765 — Causes of Gaseous Exchange
between Blood and Air, p. 773 — Exchanges of Gases between Blood and
Tissues, p. 780 — Causes of such Exchange, p. 783.

EESPIRATION is essentially the intake of oxygen and the output of
carbon dioxide by living cells. In the higher animals two phases of
respiration are distinguished — the external, the exchange of gases between
the air or water and the blood ; and the internal, the exchange between
the blood, lymph, and the tissues.

Historical Account.1— The view held by Aristotle (384-322 B.C.), and
after him even until the fifteenth century, was that respiration drew air into the
heart and arteries, and so cooled the blood. Malpighi (1621-1694) discovered
the alveoli of the lungs, and saw the blood flowing through the capillaries of
the alveoli of a frog's lung; and Fracassati,2 in 1665, noticed that the lower
layer of a blood clot was much darker in colour than the upper, but that on
exposure to the air the lower became florid red. Hook 3 showed the following
experiment at a meeting of the Eoyal Society in 1667. The ribs and diaphragm
of a dog were cut away, and the trachea connected with a pair of bellows.
The dog fell into convulsions, but revived when air was blown into the lungs.
Numerous small holes were now made in the surface of the lungs, and by means
of two bellows the lungs were kept constantly distended with fresh air ; the
dog lay still, and its heart beat regularly. A piece of lung was cut off, and it
was noticed that the blood circulated even when the lungs were collapsed.
Hook therefore came to the conclusion that the cause of death was not the
stoppage of the circulation, but the want of a sufficient supply of fresh air.
Croon 4 had previously shown before the same Society a similar experiment ;

1 For further details see Bostock's "Physiology," 2nd edition, 1828, vol. ii. p. 61;
Paul Bert, "Lecons sur la physiol. comp. de la respiration," Paris, 1870, p. 1; Zuntz,
Hermann's "Handbuch," Bd. iv. Th. 2, S. 5.

2 Phil. Trans., London, 1667, p. 492. 3 Ibid., 1667, p. 539.
4 Dcrham's "Physico-Theology," 4th edition, 1716, p. 146.

HISTORICAL ACCOUNT. 693

he strangled a pullet until it showed no signs of life, and then restored it by
blowing air into its lungs.

Boyle,1 in 1666, showed by numerous experiments with the air-pump that
a supply of fresh air was essential to life, both animal and vegetable, and he
was of the opinion " that the depuration of the blood was one of the ordinary
and principal uses of respiration."

Mayow 2 (1668-1674) was the first to discover the real function of respira-
tion ; he showed that air was a mixture, and that one of its constituents, which
he named the nitro-aerial gas, was necessary for the support of a flame, that it
combined with sulphur and other substances with the production of acids,
that during calcination metals also combined with it and thus increased in
weight. The nitro-aerial gas (oxygen) was necessary for all forms of life, and
the respiration of an embryo was analogous to that of the adult. Mayow saw
the analogy of respiration to combustion, and held that the function of respira-
tion was to absorb the nitro-aerial gas and to remove the vapours arising from
the blood.

Stephen Hales,3 about the year 1726, showed that animals in a closed
vessel absorb air, and that a similar change is effected by a burning candle.
He also observed, by experiments upon himself, that air is absorbed during
respiration, and that "noxious vapours" are produced by repeatedly breathing
air in a bladder; these noxious substances, he found, could be removed by
potash, and the air rendered fit for breathing. Hales suggested the use of a
bladder of air and such an absorbent in the foul air of coal mines. He believed
that during respiration the air cooled the blood and removed aqueous vapour
and noxious substances, but he rejected the view of Mayow that the blood
combined with the nitro-aerial gas.

About the year 1757, Black4 discovered that a quantity of "fixed air"
(carbon dioxide) was given off from the lungs, and that the expired air chiefly
differed from the inspired by the addition of that gas. He observed that
animals placed in carbon dioxide gas died of suffocation.

In 1772, Priestley 5 published his " Observations on Different Kinds of Air,"
in which he showed that growing plants restored the property of supporting
animal life to air which had been vitiated by the respiration of animals or by
the burning of a candle. He also found that carbon dioxide was produced by
putrefaction and by plants during the night-time. Priestley isolated oxygen
and nitrogen, and showed that the change of colour in venous blood on
exposure to the air was due to the action of oxygen, and that blood changed
colour and gave off " phlogiston " even when it was separated from the air by
a moist membrane and by the walls of the blood vessels in the lungs. He
concluded that respiration deprived the air of a portion of its oxygen and
imparted to it a quantity of aqueous vapour and "phlogiston."

Lavoisier6 (1777) extended and explained the discoveries of Mayow, Black,
and Priestley; he overthrew the old theory of "phlogiston," and pointed out a
distinction between the various so-called phlogistic processes. The calcination
of metals he showed, as Mayow had observed a hundred years before, to be a
combination with oxygen, whereby the metals gained in weight ; in respira-
tion, on the other hand, oxygen was not only absorbed, but combined with
carbon to form carbon dioxide.

Lavoisier and Laplace showed experimentally that animal heat arose from
a process of combustion, oxygen combining, as they thought, with carbon in
the blood ; as regards the seat of this combustion, Lavoisier held that it was

1 Phil. Trans., London, 1666, p. 424 ; 1670, pp. 2011, 2035.

2 Ibid., 1668, p. 833 ; "Tractatus quinque," Oxon. 1674.
"Statical Essays," 2nd edition, 1731, vol. i. p. 236 et seq.

4 "Lectures on Chemistry," ed. Robison, Edinburgh, 1803.

5 Phil. Trans., London, 1772, vol. Ixii., p. 147.

6 Hist. Acad. roy. d. sc., Paris, 1775, 1777, 1780, 1789, and 1790.

694

CHEMISTRY OF RESPIRA TION.

in the lungs, but in earlier works he had admitted that it might be in the
other organs of the body.1

It is now known that the essential seat of respiration is in the tissues and
not in the blood. The demonstration of this fact is chiefly due to the work of
Pfliiger and his pupils.

EESPIRATOEY CHANGES IN AIR.

Methods for the measurement of respiratory exchange. — The

simplest and at the same time the earliest method for the measurement
of respiratory exchange, is the analysis of the air of a bell jar, before
and after an animal has been confined in it. Such a method was used
by Black,2 Priestley,3 Lavoisier and Laglace,4 and others.5 The obvious
objection to this method is that the products of respiratory exchange

FlG. 62. — Regnault and Reiset's respiration apparatus.

accumulate, while the oxygen diminishes, two conditions either of which
disturbs the normal respiratory exchange, and in time causes the death
of the animal.6 Two modifications were introduced by Lavoisier to
remove these defects : in the one, the carbon dioxide was removed as it
accumulated, and a fresh supply of oxygen was added ; in the other, a
constant stream of fresh air was passed through the respiration chamber.
Upon the first of these principles, Eegnault and Eeiset7 constructed the
apparatus with which they made numerous and important experiments
upon respiratory exchange. The above figure shows its construction.

1 " (Euvres," 1862, p. 180. 2 "Lectures on Chemistry," ed. Robison, Edinburgh, 1803.

3 Phil. Trans., London, 1772, vol. Ixii. pp. 147, 168.

4 Hist. Acad. roy. d. sc., Paris, 1780, p. 355. ; "(Euvres de Lavoisier," tome ii. p. 326.

5 Berthollet, Journ. f. Chcm. Physik. u. Min., Berlin, 1808, Bd. v. S. 388 ; Legallois,
Journ. f. Chetn. u. Phys., Niirnberg, 1817, Bd. xx. S. 113 ; Valentin, "Die Emflusse der
Vaguslalmiung auf die Lungen und Hautausdiinstung, " Frankfurt a/M., 1857 ; Arch. f.
exper. Path. u. PharmakoL, Leipzig, 1876, Bd. v. S. 143.

6 Bernard, "Le9ons sur les effets des substances toxiques," 1857, p. 130; Friedlander
and Herter, Ztschr. f. physiol. Chem., Strassburg, Bd. iii. S. 19 ; Stroganow, Arch. f. d.
ges. Physiol., Bonn, 1876, Bd. xii. S. 18. See also this article, p. 743.

7 Ann. de chim. et phys., Paris, 1849, Ser. 3, tome xxvi.

RESPIRA TOR Y CHANGES IN AIR. 695

The carbon dioxide is absorbed from the air by caustic potash, and a
constant supply of oxygen from the reservoirs is driven in, a manometer
in communication with the animal chamber indicating the pressure.
Samples of air for analysis can be drawn from the chamber, and thus
the part played by nitrogen determined, and a control placed upon the
completeness of the supply of oxygen and the removal of carbon
dioxide. Modified forms of Eegnault and Eeiset's apparatus have been
used by Hoppe-Seyler and Stroganow,1 Pfliiger and Colasanti,2 Schulz,3
Seegen and Nowak.4

In Schaiiing's 5 respiration apparatus a constant stream of fresh air
was drawn through the chamber in which the animal was confined. A big
barrel served for the chamber, and air freed from carbon dioxide by
passing through Liebig's potash bulbs was aspirated through the appar-
atus ; on leaving the chamber the air passed through a flask containing
sulphuric acid, which removed the moisture, and through a weighed
potash bulb of huge size, of which the increase in weight gave the
amount of carbon dioxide expired by the animal. As a control, a sample
of air for analysis was removed from the barrel at the beginning and
end of the experiment. In this method the carbon dioxide alone was
determined, and the results were inaccurate, for the absorption was
incomplete, as is shown by the fact that the air leaving the bulbs
rendered lime water turbid. Many other forms of apparatus constructed
upon similar principles have been used.6

With the methods formerly in use it was impossible to maintain a
steady ventilation, and at the same time completely absorb the carbon
dioxide. To overcome this difficulty, Pettenkof er 7 introduced the
following modification. The total amount of air drawn through the
apparatus is measured by a meter ; continuous samples of the air
entering and leaving the chamber are steadily drawn through two
separate systems of absorption tubes and meters for the determination
of the moisture, carbon dioxide, and volume of the samples. The
difference in the amounts of water and carbon dioxide contained in the
two samples, multiplied by the total ventilation, gives the quantity of
moisture and carbon dioxide discharged by the animal. The intake
of oxygen is estimated in the following way. The animal is weighed at
the beginning and at the end of the experiment, and the difference
between the weights of carbon dioxide and water discharged, and the loss
in weight of the animal, represents the oxygen absorbed. Thus if W
represents the initial weight of the animal, and W\ its final weight, then
W - Wl=w, the loss in weight of the animal. Let C02 + H20 represent
the weights of carbon dioxide and water discharged during the experi-
ment, then C02-hH20 - w=02, the oxygen absorbed. In thus estimat-
ing the oxygen, it is assumed that, apart from the carbon dioxide and

1 Arch.f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 18.

2 Ibid., 1877, Bd. xiv. S. 92.

3 Ibid., Bd. xiv. S. 78.

4 Ibid., 1879, Bd. xix. S. 347.

5 Ann. d. Chem. u. Pharm., 1843, Bd. xiv. S. 214.

6 Allen and Pepys, Phil. Trans., London, 1809, pt. 2, p. 412 ; Dulong, Ann. de chim.
et phys., Paris, 1841, Se"r. 3, tome i. p. 440; Despretz, ibid., 1824, tome xxvi. p. 337;
Boussingault, ibid., 18-14, SeV. 3, tome xi. p. 433 ; Journ. f. prnkt. Chem., Leipzig, 1845,
Bd. xxxv. S. 402 ; Senator, Arch. f. Anat., Physiol. u. wissensch. Med., 1872, S. 1 ; Lieber-
meister, Deutsches Arch.f. kliu. Med., Leipzig, 1870, Bd. vii. S. 75.

7 Sitzungsb. d. k.-bayer. Akad. d. Wissensch. zu Munchen, math.-phys. CL, 1862, Bd.
ix. (2), S. 232 ; Ann. d. Chem. u. Pharm., 1862-63, Snpp. Bd. ii. S. 17.

696

CHEMISTR Y OF RESPIRA TION.

water, no weighable amount of nitrogen, or of any other gaseous
substance, is discharged or absorbed by the animal.

The figure below represents the modification of Pettenkofer's
apparatus, which was introduced by Voit for experiments on animals.

The absorption of water is effected by flasks filled with pieces of
pumice saturated with sulphuric acid, and the carbon dioxide is in turn
absorbed by making the air bubble through a long tube filled with a
titrated solution of baryta.1

The advantages of Pettenkof er's method over those previously in use
are these — It is possible, owing to the system of ventilation, to make
experiments upon man ; observations can for a similar reason be much
more prolonged without any danger of disturbance to the normal
respiratory exchange arising from an accumulation of carbon dioxide ;
the absorption of the carbon dioxide is more exact. Notwithstanding
these improvements, Pettenkofer's method possesses several disadvan-
tages and sources of error. The apparatus is complicated and costly, the

FIG. 63. — Volt's respiration apparatus.

determination of the moisture is liable to be inexact, owing to deposition
on the walls of the chamber ; during the process of weighing the animal
there is an intake of oxygen, and an output of carbon dioxide and water,
which are not determined, and can only be calculated approximately ;
the absorption and estimation of carbon dioxide by the titration of the
baryta solution has been shown by Haldane and Pembrey2 to be less
exact than it was thought to be. The result of these errors falls upon
the estimation of the intake of oxygen, for since 02=C02 + H20 — w, it
is evident that the amount of oxygen may be often inexact. This has
been pointed out and proved by C. and E. Voit and Forster.3

It has already been mentioned that Voit4 has constructed, upon
Pettenkofer's principle, a smaller apparatus for the determination of

1 Baryta was first used by Pettenkofer for this purpose, but Dalton had previously used
titrated lime water.

2 London, Edinburgh, and Dublin Phil. Mag., London, April 1890.

3 Ztschr.f. BioL, Mtinchen, 1875, Bd. xi. S. 126. 4 Ibid., 1878, Bd. xiv. S. 57.

RESPIRATOR Y CHANGES IN AIR.

697

the respiratory exchange in animals. It has the advantages and most
of the disadvantages above mentioned. The human respiration apparatus
in the physiological laboratory, Oxford, has been constructed on the

PUMICE &
H2 504

FIG. 64. — Diagram of the human respiration apparatus in the Physiological Laboratory
Oxford. — A. To Aspirator.

principle of Pettenkofer's apparatus, but has been made more exact and
simple by the use of Haldane and Pembrey's method of determining
carbon dioxide and moisture.

A more exact method is that introduced by Haldane.1 It is a

FIG. 65. — Haldane's respiration apparatus. — 1 and 4, soda lime ; 2, 3, and 5, pumice
soaked in sulphuric acid ; Ch, chamber for animal ; M, gasmeter ; J, water mano-
meter ; P, aspirator.

modification of the apparatus used by Scharling and Pettenkofer, but
the chief sources of error have been eliminated or greatly diminished,
and the method has been made extremely simple. The construction is
shown in Fig. 65 : —

1 Journ. Physiol., Cambridge and London, 1892, vol. xiii. p. 419.

698

CHEMISTRY OF RESPIRATION.

The moisture is absorbed by pumice saturated with sulphuric acid,
and the carbon dioxide is removed by soda lime, which has been proved
to be such a rapid and excellent absorbent that the total output of
carbon dioxide can be determined directly.1 The animal is weighed in
the closed chamber before and after the experiment, and thus there is
no need to calculate the respiratory exchange during that process, and
no error arises from the deposition of moisture. The air entering the
chamber is freed from carbon dioxide and moisture, and therefore all
the moisture and carbon dioxide in the air leaving the chamber come

from the animal. The
intake of oxygen is
determined indirectly ;
the animal gives off
only carbon dioxide
and water, it absorbs
only oxygen, and the
amount absorbed is
found by subtracting
the loss in weight of the
chamber and animal
from the total loss of
carbon dioxide and
water.

Haldane's method
has also been adopted
for the determina-
tion of the respira-
tory exchange of small
animals and of chick
embryos.2

Another method,
which has been used
for the observation of
the respiratory ex-
change in man, is the

determination of the volume of air respired during a limited period,
and then, from analysis of samples of the inspired and expired air,
estimating the intake of oxygen and the output of carbon dioxide
and water.3 The more recent and exact forms of apparatus con-

1 Haldane and Pembrey, loc. cit.

2 Pembrey, Journ. PhysioL, Cambridge and London, 1894, vol. xv. p. 401 ; 1894-95,
vol. xvii. p. 331.

3 Davy, "Researches," p. 431 ; Ann. d. Phys. u. Chem., Leipzig, Bd. xix. S. 298 ; Allen
and Pepys, Phil. Trails., London, 1808, p. 250 ; 1809, p. 404 ; Prout, Ann. Phil., London,
1813, vol. ii. p. 330 ; vol. iv. p. 331 ? Journ. f. Chem. u. Phys., Ntirnberg, 1814, Bd. xv. ;
MacGregor, Ann. de chim. etphys., Paris, 1841, Ser. 3. tome ii. p. 538 ; Wertbeim, Deutsches
Arch. f. klin. Med., Leipzig, Bd. xv. ; Wien. med. Wchnschr., 1878 ; Vierordt, "Physiol.
d. Athrnens." Karlsruhe, 1845 ; E. Smith, Phil. Trans., London, 1859, vol. cxlix. p. 682;
Speck, "Untersuch. ueber Sauerstoffverbraucb u. Kohlensaureausathnivmg d. Menschen,"
Cassel, 1871 ; Arch. f. exper. Path. u. PharmaJcoL, Leipzig, Bd. ii. S. 405; Bd. xii.
S. 1 ; Lessen, Ztschr. f. BioL, Miinchen, 1866, Bd. ii. S. 244 ; Berg, Deutsches
Arch. f. Jdin. Med., Leipzig. 1869, Bd. vi. S. 291; Leyden, ibid., Bd. vii. S. 536;
Andral and Gavarret, " Recherches sur 1'acide carbonique exhale"," Paris, 1843;
Marcet, Phil. Trans., London, 1890, B. ; Proc. Roy. Soc. London, 1891, vol. xlix.
p. 103 ; Jolyet, Bergonie', and Sigalas, Compt. rend. Acad. d. sc., Paris, 1887, tome cv.
p. 380.

FIG. 66. — Lowy's respiration apparatus.

RESPIRATORY EXCHANGE IN WATER. 699

structed upon these principles are those used by Zuntz,1 Geppert2 and
Lowy.3 A diagram of such an apparatus is shown in Fig. 66.

The disadvantage of these methods is that, owing to the attention
of the subject being directed to the breathing, the volume of air
respired during a limited period is not a fair sample upon which to
base an exact calculation, and, moreover, the depth and the rate of
breathing are also liable to another source of disturbance, the resistance
of the apparatus. For these and other reasons,4 the results obtained
during short periods of observation are liable to lead to erroneous
conclusions.

Methods similar to those just mentioned have been employed in the
case of animals,5 the mouth and nose being covered with a respiration
mask or the trachea connected by a cannula with the apparatus
necessary for the measurement of the inspired and expired air. It is
obvious that these methods introduce many sources of disturbance ; the
animals, unless horses be used, must be tied down, and in many cases
anaesthetised, conditions which markedly affect the respiratory exchange.6
For these reasons the methods of Pettenkofer and Haldane are in most
cases to be preferred, for the animals are placed under conditions as
far as possible normal ; these methods are, however, unsuitable when
operative procedures have to be carried on at the same time as the
determination of the respiratory exchange.

Methods for the measurement of respiratory exchange in water.—

The respiration of fishes was studied by Humboldt and Proven§al 7 in the follow-
ing manner : — The fishes were placed in a flask of water, the gaseous contents
of which had been analysed, and then after an interval a sample of the water
was examined and the alteration in its gases determined. The quantity of
water present was measured, and thus it was possible to estimate the amount
of gases absorbed and discharged by the fish. A similar method has been
used by Yernon 8 for the measurement of the respiratory exchange in marine
invertebrates.

Baumert 9 improved this method by passing a stream of water through the
flask containing the animals ; the gases contained in a sample of the water
entering and in the water leaving the flask were determined. A modification
of Regnault and Reiset's method was introduced by Jolyet and Keynard;10
a stream of air was made to bubble slowly through the water in which the

1 JBerL klin. Wchnschr., 1887, S. 429 ; Arch. f. Physiol., Leipzig, 1889, S. 166.
'2 Arch.f. exper. Path. u. Pharmakol., Leipzig, 1887, Bd. xxii. S. 368.
>>Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 268; ibid., 1888, Bd. xliii. S. 519;
ibid., 1891, Bd. xlix. S. 492.

4 See p. 754.

5 Sczelkow, Sifzungsb. d. k. AJcad. d. Wissensch. Math.-natunv. Cl., Wien, 1862,
Bd. xlv ; Kowalewsky, Ber. d. k. scich*. Gesellsch. d. Wissensch. Math.-phys. KL, 1866,
Bd. xviii. S. Ill ; Sanders-Ezn, ibid., 1867, Bd. xix. S. 58 ; Arb. a. d. physiol. Anst. zu
Leipzig, 1868, S. 58 ; Scheremetjewski, Bcr. d. k. sdchs. Gesellsch. d. Wissensch. Math.-
phys. KL, 1868, Bd. xx. S. 154 ; Robrig and Zuntz, Arch. f. d. gcs. Physiol., Bonn,
1871, Bd. iv. S. 57 ; Zuntz, ibid., 1876, Bd. xii. S. 522; Finkler and Oertmann, ibid.,
1877, Bd. xiv. S. 38; Pfliiger, ibid., 1878, Bd. xviii. S. 247; Haniiot and Ricliet,
Compt. rend. Soc. de biol., Paris, 1886 ; Compt. rend. Acad. d. sc., Paris, 1887, tome civ.
p. 435; Fredericq, Hen. scient., Paris, 1880 ; Bull. Acad. roy. d. sc. de Belg., Bruxelles,
1886.

6 See p. 717. See also "Animal Heat," this Text-book, vol. i.

7 Mem. de, la Soc. de phys. et de chim. d'Arcueil, Paris, 1807, tome ii. p. 359 ; Journ.
f. Chem. u. Phys., Niirnberg, Bd. i. S. 86.

8 Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 18.

9 "Chem. Untersuch. u. d. Respir. d. Schlammpeitzgers," Breslan, 1855, S. 24.
10 Arch, de physiol. norm, etpoth., Paris, 1877, tome iv. p. 44.

7 oo CHEMISTR Y OF RESPIRA 1*1 ON.

animal was placed ; this air was analysed for carbon dioxide, and the oxygen
absorbed by the animal was replaced by a corresponding amount supplied from
a gasometer.

The consumption of oxygen by animals living in water can be determined
by titrating a sample of the water before and after the confinement of the
animal in a known volume of water. Quinquand1 used for this purpose
sodium hyposulphite, according to Schiitzenberger's method.

The conditions which affect the respiratory exchange. — A de-
termination of the respiratory exchange not only gives the absolute
value of the oxygen absorbed, and of the carbon dioxide and water ex-
creted, but also shows the relationship between the intake of oxygen
and the output of carbon dioxide. This ratio between the volume of
oxygen absorbed and the volume of carbon dioxide discharged is known as

CO
the respiratory quotient -~, and indicates how much of the oxygen coin-

^2

bines with carbon to form carbon dioxide, for one volume of oxygen in
combining with carbon yields one volume of carbon dioxide. Various
conditions influence both the amount of the respiratory exchange and
the relative proportions of the gases, but it must be remembered that
determinations of short duration may give rise to erroneous conclusions,
for oxygen may be stored up for some- time within the body, and
carbon dioxide may still be formed and discharged when there is no
intake of oxygen.

The question here arises, Does nitrogen play any active part in
respiration, is there any absorption or discharge of nitrogen ? 2 The
older observers found that nitrogen was sometimes absorbed by the
lungs, and in nearly all of Eegnault and Eeiset's 3 determinations of the
respiratory exchange in different animals there is an alteration in the
amount of nitrogen present in the air, denoting generally a discharge of
a small quantity of nitrogen from the animal. Marchancl 4 had also ob-
tained similar results ; he found in ten experiments upon guinea-pigs
that the average discharge of nitrogen was equal to 0'94 per cent, of the
output of carbon dioxide, and in three experiments 011 pigeons to 0'85
per cent. Seegen and Nowak5 also found a discharge of nitrogen,
varying from 4 to 9 mgrms. per kilo, and hour in thirty- two experiments
upon rabbits, dogs, and hens.

This discharge of nitrogen in many cases appears to be due to an
error of experiment.6 Analyses, purposely made by Colasanti 7 to test
this point, showed no discharge or absorption of nitrogen by guinea-pigs.
The small amount observed by other experimenters may be due either
to nitrogen discharged from the alimentary canal or to experimental
errors. According to Jolyet, Bergonie, and Sigalas,8 an amount of
nitrogen varying from —^ to -j-^nr °f the oxygen absorbed is taken
up by the blood in its passage through the lungs of a man or a clog.
In any case the amount of nitrogen absorbed or discharged under

1 Compt. rend. Acad. d. sc., Paris, 1873, tome Ixxvi. p. 1141.

2 For further details, see Voit, Hermann's "Handbuch," Bd. vi., Th. 1, S. 37.

3 Ann. de chim. et phys, Paris, 1849, Se"r. 3, tome xxvi.

4 Journ. f. praJct. Chem., Leipzig, 1848, Bd. xliv. S. 1.

5Sitzwngsb. d. k. Akad. d. Wissensch. Math.-naturw. Cl., Wien, 1875, Bd. Ixxi. (3),
S. 329 ; Arch.f. d. ges. PhysioL. Bonn, 1879, Bd. xix. S. 347.

6Pettenkofer and Voit, Ztschr. f. BioL, Miinchen, 1880, Bd. xvi. S. 508.
''Arch.f. d. qes. PhysioL, Bonn, 1877, Bd. xiv. S. 92.
8 Compt. rend. Acad. d. sc., Paris, 1887, tome cv. p. 675.

EXCHANGE OF COLD-BLOODED ANIMALS.

701

ordinary conditions is so small that it may be neglected. It is to
be noted, however, that Colasanti and Tinkler 1 always found small
(quantities of marsh gas and hydrogen in the respiration chamber
in which well-fed guinea-pigs were placed ; these gases probably
came from the alimentary canal, for they were not found in the case
of guinea-pigs deprived of food. Zuntz 2 and Tacke found that three-
quarters of the hydrogen and marsh gas formed in the alimentary
canal of a rabbit were absorbed by the blood and discharged by the
lungs.

The respiratory exchange of cold - blooded animals. — When
compared with warm-blooded animals, the respiratory exchange of
most cold-blooded animals is very small, a fact which explains the
small production of heat observed in this class of animals.3 Some
of the earliest determinations were those made by Vauquelin,4
Spallanzani,5 Newport,6 Treviranus,7 Edwards,8 and Mliller.9 They
showed that the quantity of oxygen consumed and of carbon dioxide
produced was for equal weights of animals generally much less in cold-
blooded than in warm - blooded animals, the most marked exception
being in insects. Later researches have confirmed these general conclu-
sions, and have shown the conditions, which chiefly affect the respiratory
exchange in these animals. Of these conditions the most important is
the external temperature, a rise in temperature causing an increase, a
fall in temperature a decrease in the respiratory exchange. In the
following table the results of various observers are expressed for
1 kilo, weight of animal and 1 hour, in order that they may be
comparable : —

I'-

ll

X * O

g

Animal.

."P

ll 1

|11 i CO.,

3 Jr i
§ o^3 02

1

Remarks.

Observer.

^.S

OJ2'«§»

la. a

1

af

EH

PROTOZOA—

Collozoum imrme.

•1113

1-06

16°

One determination.

Vernon.10

CCELENTERATA—

Carmarina has-

•0087

1-10?

16°

The determinations

tata

of _- S show va-

riations from '36

Cestns veneris

•0037

•79?

16°

to 2-16.
CO

2- varies from

"

1

°a -07 to 2-06.

lArcJi.f. d. ges. Physiol., Bonn, 1877, Bd. xv. S. 603.

^Arch.f. Physiol. , Leipzig, 1894, S. 354. See also this article, p. 729.

3 Article "Animal Heat," this Text-book, vol. i. p. 792.

4 Ann. de. chim., Paris, 1792, tome xii. p. 273.

5 " Mem. sur la respiration," par Senebier, 1803, p. 184; Journ. f. Ckem. Physik.
u. Min., Berlin, Bd. iii. S. 378.

6 Phil. Trans., London, 1837, pt. ii. p. 253.

7 Ztschr. f. Physiol., 1832, Bd. iv. S. 23.

8 " De 1'influence des agens physiques sur la vie," Paris, 1824.

9 " Elements of Physiology," trans. Baly, 1838, vol. i. p. 310.

10 Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 18.

702

CHEMISTR Y OF RESPIRA TION.

TABLE— continued.

JU

|1

Animal.

||

!§!

|i!

C02

1

Remarks.

Observer.

£_e

£|!

I|-I

O

&

S

i

6i

H

VERMBS 1—

Lunibricus .

112 0-1013
| (70-8 c.c.)

0-108
(54-9 c.c.)

•77

9

•

Regnault and
Reiset. 2

0-593

18°-19°

One determination.

Pott.;i

Hirudo

0-645

16"-19°

Mean of two deter-

(328 c c.)

• '

minations.

Hirudo officinulis

2-2

0-0328
(22-98 c.c.)
0-0567

0-0312
(15-9 c.c.)
0-0701

•69
•90

13°'5
13°

Before ^
After P mea1'

Jolyet and
Regnard. 4

(39-70 c.c.)

(35-7 c.c.)

)

INSECTA—

Anthercea (18) .

42-5

0-840
(588 c.c.)

0-916
(465-7 c.c.)

•79

9

Regnault and
Reiset.

39

0-687

0-767

•81

?

(480 c.c.)

(390-7 c.c.)

42)

40

1-170

1-189

•73

?

'

(818 c.c.)

(604-5 c.c.)

Melolontha (40)

40-3

1-076

1-1699

•79

9

(752 c.c.)

(594-8 c.c.)

(37)

37

0-962

1-092

•82

?

1

Geotrupes

0-32

(673 c.c.)

(555 c.c.)
1-130

20°-21°

Mean of two deter-

Pott.

(574 c.c.)

minations.

Melolontha .

2-0

0-987

15°-178

Larva. Mean of four

(503 c.c.)

determinations.

Locusta

0-839

16°-19°

Mean of three deter-

(>

(427 c.c.)

minations.

Gryllus campes-

0-25

2-305

>t

11 11

|f

tris

(1172 c.c.)

0-05

2-127

17°-21°

Mean of two deter-

Blatta orientalis .

(1081 c.c.)
0-268

15°-20°

minations.

Biitschli.8

"

1-045

30°-35°

"

MOLLUSCA —

Octopus vulgaris

2310

•0630
(44'1 c.c.)

•0745
(37-9 c.c.)

•86

lo°-5

••

Jolyet and
Regnard.

»

•1115

•95

16°

Vernon.

Tetliys leporina .

••

•0165

•84

16°

"

CRUSTACEA—

•0543

•0642

Astacus Jluvialis .

31

(38 c.c.)

(32-7 c.c.)

•86

12°-5

Jolyet and

llegnartl.

Gamwiarus pulex

••

(132 c.c.)

(95c.c.)

•72

12°'5

».

Palemon squilla .

(125 c.c.)

(103-8 c.c.)

•83

19°

11

Cancer pagurus .

470

(107 c.c.)

(89-9c.c.)

•84

16°

i

Homarus vulgaris

315

(68 c.c.)

(54-4c.c.)

•80

15°

Palinurus quad-

520

(44 -2 c.c.)

(38 -9 c.c.)

•88

15°

ricorn

1 For experiments upon the respiration of nematoid worms, see Bungc, Ztschr. f.
physiol. Chem., Strassburg, 1883, Bd. viii. S. 48 ; 1890, Bd. xiv. S. 318.

2 Ann. de chim. etphys., Paris, 1849, Ser. 3, tome xxvi.

3 Landwirthsch. Versuclisstat. , Bd. xviii. S. 81.

4 Arch, de physiol. norm, etpath., Paris, 1877, tome iv. p. 44.

5 Biitschli, Arch. /. Anat., Physiol., u. wissensch. Mcd., 1874, S. 348. For further details
on the respiratory exchange of insects, see Spallanzani, Juurn. /. Chem. Physik. u. Min.,
Berlin, Bd. iii. S. 378 ; Vauquelin, Ann. dechim., Paris. 1792, toniexii. ; Treviranus, Ztechr.
f. Physiol., 1832, Bd. iv. S. 23 ; Newport, Phil. Trans., London, 1837, pt. ii. p. 259 ; Detmer,
Landwirthsch. Versuchsstat. , Bd. xv. S. 196 ; Liebe, Jahresb. u. d. Fortschr. d. Thier-Chem.,
Wiesbaden, 1872, S. 332; Schmidt-Schwedt, Berl. entomol. Ztschr., Bd. xxxi. S. 325.

EXCHANGE OF COLD-BLOODED ANIMALS.
TABLE— continued.

7°3

3

o

Q) P

•

^

Bx

'xW^

£

Animal

SPE

£0

111

PI

CO.,

1

Remarks. Observer.

o r3 c

Js c

53

.^H

W ""*

•£w^

S

i

H

PISCES —

Cyprinus aura-

12-14

•0376

•0411

•79

8°

Fasting.

Baumert. J

tus

(26'3 c.c.)

(20-9 c.c.)

>

12-14

•0590

•0617

•76

11°-12°

Fasting. Mean of

!

(41 -3 c.c.)

(31-4 c.c.)

three determina-

tions.

»

33-40

•0655

•0643

•71

12°

Mean of two deter-

Jolyet and

Cyprinus tinea .

222

(45-8 c.c.)
•0796

(32-7 c.c.)
•0721

•66

14°

minations.

Regnard.

(55-7 c.c.)

(36-7 c.c.)

» 5)

500

•1001

?

..

Quinquand. '2

(70-0 c.c.)

»

190-

•0165

•0159

•70

5°

Baumert.

223

(11 -53 c.c.)

(8-09 c.c.)

Cyprinus carpio .

12

0-352

13°-14°

Young. Mean of two

Pott.

(179 c.c.)

determinations.

Colitis fossilis .

43-61

•0455

•0633

1-01

9°-12°

Mean of six deter-

Baumert.

(31 '8 c.c.)

(32'2 c.c.)

minations.

>'

16

•1234

•1323

•78

17°_22°

Jolyet and

Munena anguilla

51

(86-3 c.c.)
•0580

(67-3 c.c.)
•0629

•79

14°

Regnard.

(40-5 c.c.)

(32 c.c.)

u

112

•0686

•0566

•60

15°

(48-0 c.c.)

(28-8 c.c.)

Mullus

28

•1916

•2132

•81

14°

(134 c.c.)

(108-5 c.c.)

Sparus auratus .

75

•2031

•1787

•64

19"

(142 c.c.)

(90-9 c.c.)

Trigla Mrundo .

350

•1351

•1337

•71

15°

(94'5 c.c.)

(68 c.c.)

Murcena conger .

545

•0855

•0865

•72

13°

M

(59 -8 c.c)

(43 c.c.)

Raja torpedo

315

•0672

•0540

•58

14'5°

Mean of two deter-

(47-0 c.c.)

(27-5 c.c.)

minations.

AMPHIBIA —

Axolotl

42

•0646

•0497

•56

11°'5

, f

Jolyet and

(45-2 c.c.)

(25-3 c.c.)

Regnard.

Rana esculenta .

•063
(44 -2 c.c.)
•105
(73-4 c.c.)

0-060
(30-76 c.c.)
0-1134
(577 c.c.)

•69

•78

(Minimal and max-
imal of five ex-
periments.

Regnault and
Reiset.

,, „

(50'46c.c.)

(47-98 c.c.)

•95

17° -7

Oertmann.

;,

••

0-082

17°

Schulz.3

,, temporaria

13-9

0-355
0-502

19°-20°
23° -1

Mean of twenty- two

Pott.
Moleschott.

experiments.

"

31-64

0-038

13°

^ Duration of ex-
periment was

Pembrey.

V three and four

,, ,,

31-64

0'035

..

13°

hours (winter

) frog).

" "

34-47

0-033

12°-5

Winter frog

Vernon.

Au examination of the above results shows that the respiratory
exchange of most of the cold-blooded animals is very small, but that a
marked exception exists in the case of insects, which have a metabolism
equal to that of the larger mammals. This remarkable exception finds
confirmation in the relatively high temperature 4 of insects and in their
wonderful muscular activity.

1 " Cliem. Untersuch. u. d. Respir. d. Schlammpeitzgers," Breslau, 1855, S. 24.

2 Compt. rend. Acad. d. sc., Paris, 1873, tome Ixxvi. p. 1141.

3 Arch. f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 78.

4 Article "Animal Heat," this Text-book, vol. i.

7o4 CHEMISTRY OF RESPIRATION,

The respiration of fishes. — The necessity of air for the life of fishes
was proved by Boyle l during his experiments with the air-pump. He states
that " there is wont to lurk in water many little parcels of interspersed air,
whereof it seems not impossible that fishes may make some use, either by
separating it when they strain the matter through their gills, or by some other
way." Mayow2 (1674) appears to have been the first to understand and to
correctly describe how fish breathed by taking up nitro-aerial gas (oxygen)
from the water by means of the blood flowing through their gills ; and Ber-
nouilli3 in 1690 demonstrated that fish could not live in cold water from
which the air had been expelled by boiling.

The methods employed and quantitative results obtained by different
observers, who have studied the respiration of fishes and other animals living
in water, have already been described. . A few additional facts, however,
must be mentioned. Humboldt and Provencal 4 state that nitrogen was in
some cases absorbed, but when the water was impregnated with oxygen and
hydrogen none of the latter gas was taken up by the fishes ; a certain amount
of cutaneous respiration also occurs, and fishes can breathe in the air as long as
their gills are kept moist with water. The respiration of fishes living in the
sea is facilitated by the absence of any free carbon dioxide in the water, for
any carbon dioxide formed is at once fixed by the excess of alkaline base
present in the water.5

In connection with the respiration of fishes, the swimming-bladder must be
considered, for this organ is one which can secrete gases and in some cases
store up almost pure oxygen.

Biot 6 found that the percentage of oxygen increased with the depth from
which the fish was taken ; the greatest percentage was 87. This was con-
firmed by the observations of Delaroche,7 who obtained 70 per cent, oxygen from
the bladder of fishes drawn up from a greater depth than 50 metres (164 feet),
and 29 per cent, from those taken at smaller depths. Erman,8 Vauquelin,9
Configliachi,10 and Delaroche n analysed the gas in the swimming-bladder of
fresh-water fish, and found the percentage of oxygen generally less than that
in the atmosphere, little or no carbon dioxide, but much nitrogen. The mean
of analyses made by Humboldt and Prove^al showed 7'1 parts of oxygen,
5 '2 of carbon dioxide, and 87 '7 parts of nitrogen in 100 volumes of gas from
the swimming-bladder of a carp, while the results obtained by F. Schultz 12
varied between 1*1 and 13*2 per cent, oxygen and 1'4 and 5*4 per cent, carbon
dioxide.

According to Humboldt and Provencal, the tench (Cyprinus tinea], in which
there is a duct communicating between the air-bladder and the mouth, does
not take hydrogen into its bladder when the water in which it is confined is
saturated with that gas. Moreau obtained similar negative results ; but more

1 "New Experiments, Physico-Mechanical, touching the Spring of the Air," 1662;
Phil. Trans., London, 1670, pp. 2011, 2035 ; "Works," Shaw's edition, vol. i. p. 109.

2 "Tractatus quinque," Oxon., 1674, vol. i. ch. xv. p. 259.

3 "Dissertatio de effervescentia et fermentatione nova hypothesi fundata," ch. xiv.
Basilite, 1690.

4 M£m. de la Soc. de phya. et de chim. d'Arcueil, Paris, 1809, tome ii. p. 359 ; Journ.
f. Chem. u. Phys., Nurnberg, 1811, Bd. i. S. 86.

5 Dittmar, Proc. Phil. Soc. Glasgow, vol. xvi. p. 61 ; M'Kendrick, Nature, London,
1888, Aug. 16 ; Brit. Med. Journ., London, 1888, vol. ii. p. 331 ; Petersen, Scottish
Gcograph. Mag., Edinburgh, 1895, June, p. 294.

6 Mem. de la Soc. de phys. et de chim. d'Arcueil, Paris, 1807, tome i. p. 252 ; Ann. d.
Phys. u. Chem., Leipzig. Bd. xxvi. S. 454.

7 Journ. f. Chem. u. 'Phys., Nurnberg, 1811, Bd. i. S. 122.

8 Ann. d. Phys. u. Chem., Leipzig, 1808, Bd. xxx. S. 113.

9 Vauquelin, quoted from Erman, reference 8.

10 Journ. f. Chem. u. Phys., Niirnberg, 1811, Bd. i. S. 137.

11 Ibid., S. 164.

12 Arch.f. d. ges. Physiol., Bonn, 1872, Bd. v. S. 48.

EXCHANGE OF COLD-BLOODED ANIMALS.

70S

recent experiments by Mengarini 1 show that the goldfish (Carassius auratus)
and roach (Leuciscus), in which there is a dtictus pneumaticus, the mullet
(Mugil cephalus) and rockling (Motella), in which there is no duct, do take up
hydrogen from water saturated with that gas.

Moreau 2 has shown that the withdrawal of the gas of the swimming-bladder
by means of a trocar leads in a short time to the secretion of a gas richer in
oxygen, and that by a repetition of this process the percentage of oxygen can be
raised as high as 85 ; he also states that section of the sympathetic nerve hastens
the process of secretion. These observations have been repeated and extended
by Hiifner3 and Bohr.4 Cod-fish (Gadus callarias) were caught in a net at a
depth of about 14 metres (46 feet), and when they were drawn to the surface
the gas in the air-bladder expanded so much that the fish swam with their backs
downwards. The gas was found in one case to contain 52 per cent, of oxygen ;
but when the fish had been near the surface of the water for some time only 13
per cent, of oxygen was obtained. After the removal of the gas from the bladder,
its secretion begins again : within six hours a little gas has accumulated, and in
twenty-four hours the bladder is again full. The rapidity of the process and the
increase in the percentage of oxygen is shown by the following examples : —

Number of
Experiment.

Hours after the
First Puncture.

Percentage
of Oxygen.

Percentage of
Carbon Dioxide.

Remarks.

(

0

15-0

8 c.c. of gas in the air-bladchr.

24 . •

48

78-5

i-o

7i c.c.

(

71

837

0-5

7 c.c.

I

0

15-0

6 c.c.

25 .

50

78-4

0-8

5 c.c.

/

73

-•72-7 •

1-0

•6 c.c.

15 i

0

16-3

o-i

10 . j

5

.16-3 ..

0-2

Bohr has also shown that after section of the branches (rami intestinales)
of the vagus which- supply the air-bladder, the secretion of the gas ceases en-
tirely, but that no effect upon the secretion is observed after section of the
rami cardiaci or the nervi laterales. These phenomena observed in, the case of
the swimming-bladder can at present be explained only as a process of secretion.
The air is not swallowed, for the fishes with the greatest percentage of oxygen
in their bladders are those which do not come to the surface, but live at great
depths ; in some of them, moreover, such as the cod (Gadus callarias), there is
no communication between the bladder and the mouth. The phenomena can-
not be accounted for by simple diffusion, for the water which surrounds 'the fish
cannot have a higher tension of oxygen than 21 per cent, of an atmosphere.5
Further, Bohr has shown that the percentage of oxygen is not reduced by
diffusion outwards, for when the secretion of fresh oxygen is prevented by
section of the vagus, the high percentage of oxygen is maintained 'for "two or
three days. As long as the swimming-bladder is fresh, it is almost im-
permeable to oxygen, even when the difference of pressures inside and outside
the bladder amounts to one atmosphere. It is to be noted .that .the. membrane
lining the swimming-bladder has a peculiar glandular structure.

lArch.f. Phytiol., Leipzig, 1889, S. 54.

2 Cotnpt. rend. Acad. d. sc., Paris, 1873, tome Ivii. pp. 37, 816 ; "Recherches experi-
mentales stir les i'unctioiies de la vessie natatoire," Paris, 1876 ; " M6m. de physiol.," Paris
1877, pp. 69-86.

3 Arch.f. Physiol. , Leipzig, 1892, S. 54.

4 Journ. Physiol., Cambridge and London, 1894, vol. xv. p. 494 ; Compt. rend. Acad.
d. sc., Paris, 1892, tome cxiv. p. 1560.

5 Biot, Delaroche, Moreau, loc. cit. ; Jakobsen, Ann. d. Chem. u. Pkarm., Bd. clxvii
S. 1 ; Hiifner, Arch.f. PhysipL, Leipzig, 1897, S. 112.

VOL. i. — 45

706

CHEMISTR Y OF RESPIRA TION.

Table of the Respiratory Exchange of Warm-Blooded Animals.

Animal.

Weight

(in
Grms. ).

Oxygen
per Kilo,
and Hour
(in Grms.).

Carbon
Dioxide
per Kilo,
and Hour
(in Grms.).

CO2
O2

i .

Remarks.

Observer.

Bi BBS-

Common Hen r

1280

1-058

1-327

•91

19°

Fed on oats and

Regnault and

J

(740 c.c.)

(675 c.c.)

water.

Reiset. i

~l

1-057

1-403

•96

23°

L

(739 c.c.)

(714 c.c.)

,, f

1578

1-084

1-486

•99

14°

\

(758 c.c.)

(756 c.c.)

•

„

1546

1-067

1-447

•93

19°

1

(746 c.c.)

(736 c.c.)

„

1637

1-109

1-561

1-02

19°

M

M

V

(775 c.c.)

(793-6)

II

1820

1-665

•83

Mean of 12 experi-

Richet.2

ments on 2 hens.

,,

1500

..

1-755

•83

Mean of 7 experi-

,,

ments.

Duck .

1740

..

2-270

•74

Mean of 5 experi-

,,

ments.

Goose (4)

18,400

•677

•649

•69

16°

D e t e r m i n ation

Reiset.3

(473 c.c.)

(330 c.c.)

lasted 25 hrs.,

no food given.

,, (1) • •

2975

1-490

•80

Mean of 12 experi-

Richet.

ments.

Turkey-cock (2) .

12,250

•702

•791

"77

16°

Determination

Reiset.

(490 c.c.)

(402 c.c.)

lasted 18^ hrs.,

no food given.

» (1) -

2650

1-319

•71

Mean of 5 experi-

Richet.

ments.

Pigeon .

325

3-360

•79

Mean of 11 experi-

M

ments.

,, ...

232-

380

••

3-236

••

••

Mean of 10 experi-
ments.

Corin and Van
Beneden.4

Turtle-dove

167

§t

4-591

Mean of llexperi

Boussingault.5

ments on 3

doves.

Greenfinch .

25
25

13-000
(9091 c.c.)
9-742

13-590
(6909 c.c.)
9-246

•76
•69

17°
17°

••

Regnault and
Reiset.

I
Goldfinch .

21-5

(6813 c.c.)

(4701 c.c.)

12-582

•71

Mean of 3 experi-

Richet.

ments.

Sparrow

22

9-595

10-492

•79

18°

n

(6710 c.c.)

(5334 -5 c.c.)

>• •

25

7-783

10°-15°

Mean of two de-

Pott. 6

(3957 c.c.)

terminations.

Crossbill .

28-6

10-974

12-014

•79

17°

Regnault and

(7674 c.c.)

(6108-5 c.c.)

Reiset.

MAMMALIA —

Rabbit . . r

2755

0-987

1-244

•91

21°-22°

>t

I

(690 c.c.)

(632 c.c.)

n • 1

2780

0-877

1-107

•92

23°

M

V

(613 c.c.)

(563 c.c.)

»i •

4140

0-797

1-039

•95

;)

5J

(557 c.c.)

(528 c.c.)

,, ...

1433

1-012

1-354

•97

18°-20°

Fed on swedes.

Pembrey and

Gurber.7

,, ...

1882

0-762

0-943

•90

„

M

n

n •

1931

0-883

1-142

•94

,,

,,

,,

Guinea-pig . .

tt

..

1-35

..

Mean of 6 experi-

Marchand.8

ments.

1 Ann. de chim. etphys., Paris, 1849, Se"r. 3, tome xxvi.

2 Arch, de physiol. norm, etpath., Paris, 1890, tome xxii. p. 485.

3 Ann. de chim. etphys., Paris, 1863, Ser. 3, tome Ixix. p. 129.

4 Trav. du lab. de Liege, 1888, tome i. p. 110.

5 Ann. de chim. et phys., Paris, 1844, Se"r. 3, tome xi. p. 444.

6 Landwirthsch. Versu<:hsstat., Bd. xviii. S. 81.

7 Journ. Physiol. , Cambridge and London, 1894, vol. xv. p. 449.

8 Journ. f. makt. Chem., Leipzig, 1848, Bd. xliv. S. 1.

EXCHANGE OF COLD-BLOODED ANIMALS.

707

TABLE— continued.

Animal.

Weight
(in
Grms.).

Oxygen
per Kilo
and Hour
(in Grms.).

Carbon
Dioxide
per Kilo,
and Hour
(in Grms.).

CO 2
02

Tempera- i
ture.

Remarks.

Observer.

MAMMALIA —

Guinea-pig2

1-612

1-896

•86

18-8

ColasantU

444-9

1-478

1-758

•86

22°

Duration of ex-

Pembrey.

periment was

2J hours.

»

445-6

1-416

1-885

•96

20°

ii

ii

Dog . . .

6213

1-303

1-325

•74

21°

Fed on raw meat.

Regnault and

(911 c.c.)

(674 c.c.)

Reiset.

»>

6158

1-393

1-425

•74

15°

M

•n

20,000-

(975 c.c.)

(724 c.c.)
1-026

•748

Mean of experi-

Richet.3

28,000
13,000-

1-210

•748

ments on 4 dogs.
Mean of experi-

14,000
11,000-

1-380

•748

ments on 5 dogs.
Mean of experi-

12,000

ments on 7 dogs.

»

8000-

j

1-506

•748

Mean of experi-

,,

10,000

ments on 4 dogs.

»>

6000-

1-624

•748

Mean of experi-

,,

7000

ments on 3 dogs.

»>

4700-

1-688

•748

M

5600

„ . . .

2800-
3800

••

1-9C4

•748

Mean of experi-
ments on 6 dogs.

"

»

2200-

2-650

•748

Mean of experi-

>»

2500

ments on 4 dogs.

»

34,000

it

0-709

Leyden and

FrankeU

»

33,000

§t

0-668

Mean of 17 experi-

Pettenkofer

ments.

and Voit.5

i)

18,000

§t

1-230

Grehant and

»»

6750

0-939

Quinquand.6
Wood.7

5300

0-690

Mean of 9 experi-

Senator.8

ments.

»

5200

1-288

Mean of 7 experi-

Bauer and

ments.

Boeck.9

»>•«".

4000

1-126

Mean of 4 experi-

Page. 10

ments.

Cat ...

2464-

1-356

1-397

-3° -2

CarlTheodor.il

3047

(947 c.c.)

(710 c.c.)

0-645

0-766

29° -6

^ %

j j

(450 c.c.)

(389 c.c.)
1-364

Liberal diet of

Bidder and

(693 c.c.)

meat.

Schmidt. 12

M

1-423

M

,,

Sheep .

66,000

0-490

(723 c.c.)
0-671

•99

16°

Exprmnt. lasted

Reiset.

(343 c.c.)

(341 c.c.)

14J hours; no

food during

that time.

M

ti

0-733

Henneberg.i3

ox . ! !

638',000-

0-389-

,,

660,000

0-485

" » . .

710,000

0-488-
0-616

"

1 Arch.f. d. ges. Physiol., Bonn, 1877, Bd. iv. S. 92 and 469.

2 See also Finkler, ibid., Bonn, 1877, Bd. xv. S. 603.

3 Compt. rend. Acad. d. sc., Paris, 1889, tome cix. p. 190; Arch, de physiol. norm, et
path., Paris, 1890, tome xxii. p. 17.

4 Firchow's Archiv, 1879, Bd. Ixxvii. S. 136.

5 Ztschr.f. Biol., Miinchen, 1873, Bd. ix. S. 1.

6 Journ. de Z'anat. etphysioL, etc., Paris, 1882, tome xviii. p. 469.

7 Fever, Smithson. Contrib. Knowl., Washington, 1 880.

8 Arch.f. Anat., Physiol., u. wissensch. Med., 1872, S. 1.

9 Ztschr.f. Biol., Miinchen, 1874, Bd. x. S. 341.

10 Journ. Physiol., Cambridge and London, 1879, vol. ii. p. 228.

11 Ztschr.f. Biol., Miinchen, 1878, Bd. xiv. S. 51.

12 "Die Verdauungssafte und der Stoffwechsel, " Leipzig, 1852, S. 321-362.

13 Landivirthsch. Fersuehsstat. , 1866, Bd. viii. S. 443; " Neue Beitr. z. Bcgriindung
einer rationellen Futterung der Wiederkiiuer," Gb'ttingen, 1870-72.

yo8

CHEMISTR Y OF RESPIRA TION.

TABLE— continued.

Animal.

Weight
(in

Grms.).

Oxygen
per Kilo,
and Hour
(in Grms.).

Carbon
Dioxide
per Kilo,
and Hour
(in Grms.).

C02
O2

Tempera-
ture.

Remarks.

Observer.

MAMMALIA—

Boar .

135,000

0-391

0-443

•82

16°

Expvmnt. lasted

'Reiset.

(273 c.c.)

(225 c.c.)

13k hrs.; food

during the ex-

periment.

Sow . .

105,000

0-561

0-661

•85

17° "9

.

(392 c.c.)

(336 c.c.)

Rat (white) .

80-5

3-518

. . .

7°

Pott,

(1789 c.c.)

„ (grey) .

55'5

4-308

16°

(2190 c.c.)

Mouse (white)

13

8-880

7°

()

(4514 c.c.)

^5

8'4

17°

Pembrey. 1

,, (common)

19-2

6-660

7-443

•80

10° -5

Man . . .

70,000-

..

0-41

ti

"\ Minimum and

Pettenkofer

73,000

I maximum in

and Voit.3

»>

}J

0-61

24 hrs.; man

|f

' at rest.

„

,,

..

0-76

..

Man at work.

,,

„

71,000-

0-373

Hunger.

Ranke.4

74,220

• •

0-52

Very liberal diet.

u

..

65,500

0-512

Scharling.5

ti

82,000

0-497

,,

,,

57J750

0-594

,,

»

57,000-

0-601 '

0-717

•98

Max. -\

Speck.6

60,000

(420 c.c.)

(364 c.c.)

Of

"

»

ti

0*461

0-535

•82

Min. ! 12

(322 c.c.)
0-516

(271 c.c.)
0-619

•87

j" experi-
Mean 1 ments.

(361 c.c.)

(314 c.c.)

J

»

50^K)0

17,000 c.c.

13,000 c.c.

"77

} }

..

ii

16,000 .,,

13,300 ,,

•83

.. ..

! Per hour and !
f 50 kilos. f

Hanriot and
Richet.7

II

18,200 ,,

13,550 „

•75

J J

„ . - .

67,500

222-9 „

2027 „

•88

Eiunger(per minute
and 67^ kilos.).

Lowy.8

»>

60,500

247-2 „

196-1 „

•79

..

Hunger(per minute

M

and 60£ kilos.).

>»

59,000

3-53 '„

2-88 „

14°-

"|

Geppert.9

,,

96,000

3-27 „

2:28 „

19° '8
16-4-
19° "9

Man at rest
v (per kilo, and

,,

>>

72,000

4-41 „

3-47 „

17° -8-

minute).

19° -2

J

1 Journ. Physiol., Cambridge and London, 1894, vol. xv. p. 401.

2 Arch, ital. de biol., Turin, 1891, tome xv. p. 223.

3 Ann. d. Chem. u. Pharm., 1867, .Bd. cxli. S. 295; Ztschr. f. Biol., Mlinchen,
1866, Bd. ii. S. 459 ; .1869, Bd. v. S. 319; Sltzungsb. d. k. Akad. d. Wissensch., Wien,
Nov. 10, 1866 ; Feb. 9, 1867.

4 Arch.f. Anat., Physiol., u. wissensch. Med., 1862, S. 311.
b Ann. d. Chem. u. Pharm., 1843, Bd. xlv. S. 214.

6 " Untersuch. ueber Sauerstoffverbrauch. u. Kohlensaureausathmung des Menschen,"
Cassel, 1871, S. 31.

7 Compt. rend. Acad. d. sc., Paris, 1888, tome cvi. p. 419.

8 Arch.f. d. ges. Physiol. , Bonn, 1888, Bd. xliii. S. 523, 524.

9 Arch.f. exper, Path. u. Pharmakol., Leipzig, 1887, Bd. xxii. S. 381.

EXCHANGE OF WARM-BLOODED ANIMALS. 709

The respiratory exchange of warm-blooded animals. — -The
tissues of warm-blooded animals are the seat of a very energetic
combustion, which is subject to quantitative and qualitative changes,
owing to the influence of certain factors, such as age, size of body,
external temperature, muscular activity, rest, digestion, hunger, and
hibernation. A general comparison between the various members of
the two great classes of the warm-blooded animals, birds and mammals,
will be found in the tables on pp. 706-708.

These tables1 show that, weight for weight, birds have a more
rapid respiratory exchange than mammals, and this difference is
associated with a higher bodily temperature.2 It is also to be
noticed that the respiratory quotient of the herbivorous animals is
nearly unity, but that of the carnivorous animals is about 0*74.
The respiratory exchange of small animals of the same or of
different species is relatively greater than that of large animals.3
The causes of many of these differences will now be discussed in
detail.

The influence of external temperature upon the respiratory ex-
change.— Since the time when Crawford 4 showed by experiment that
external cold increased the discharge of carbon dioxide from a warm-
blooded animal, numerous similar observations have been made by various
observers. The most important result of this work has been the dis-
covery that cold-blooded animals respond to changes of external tempera-
ture in an exactly opposite way to that shown by warm-blooded animals ;
in the former class a rise or fall in the temperature of the surroundings
produces respectively an increase or decrease in the intake of oxygen
and the output of carbon dioxide, whereas in the latter class cold increases
and heat diminishes the respiratory exchange. On this account it will
be well to consider separately the influence of temperature on these two
classes of animals, and then to discuss the causes of the great difference
in the effect.

Cold-blooded animals. — Some of the earliest experiments upon the
influence of temperature upon the respiratory exchange of cold-blooded
animals appear to have been made by Delaroche,5 Treviranus,6 and
Marchand,7 but, owing to imperfect methods, their results are not very
exact, although they show that the respiratory exchange slowly rises
and falls with the external temperature.

In 1857, Moleschott8 made a series of experiments upon frogs, and
found that exposure to an increased external temperature or to light
caused an increase in the output of carbon dioxide.

Eegnault and Eeiset 9 made three observations upon the respiratory
exchange of green lizards at different external temperatures, and obtained
the following results : —

1 Further data will be found in the article by Zuntz, Hermann's " Handbuch," Bd. iv.
Th. 2, S. 129, from which many of the figures in the above tables have been taken. See
also tables in paper by Richet, Arch, de pliysiol. norm, et path., Paris, 1891, tome xxiii.
p. 74.

8 Article "Animal Heat," this Text-book, vol. i. p. 791.

3 See p. 720.

4 "On Animal Heat," London, 1788, pp. 311, 387.

5 Journ. dephys. de chim., etc., Paris, 1813, tome Ixxvii. p. 5.

6 Ztschr.f. Physiol., 1831, Bd. iv. S. 1.

7 Journ. f. prakt. Chcm., Leipzig, Bd. xxxiii. S. 152.

8 Untersuch. z. Natitrl. d. Mensch. u. d. Thiere, 1857, Bd. ii. S. 315.

9 Ann. de chim. etphys., Paris, 1849, Ser. 3, tome xxvi.

7io

CHEMISTR Y OF RESPIRA TION.

Weight.

Oxygen
per Kilo, and
Hour.

Carbon Dioxide
per Kilo, and
Hour.

C02

02

Nitrogen
discharged Tempera-
per Kilo. ture.
and Hour, i

Remarks.

Grins.
3 lizards, 68 '5

Grms. C.c.
0-0246 17'2

Grms. C.c.
0-025 12-6

•73

C.c.
5-732 7°'3

Hibernating.

2 „ 42

0-0646 45-2 i 0'063 32'3

•71

1-905 14°-8

Half awake.

3 „ 62

0-1916 134-0 0-199 10077

•75

2-49 : 23°'4

i

Awake and well ;
fed for a month.

There are, however, several conditions which prevent these results
from being considered comparable ; the hibernating 1 animal has a very
low respiratory exchange, even when the external temperature is higher
than 7°*3 ; in the last experiment the food would increase the respira-
tory exchange; the observations were made at intervals of several
months, and are complicated by the large discharge of nitrogen, which
is probably to be attributed to an error of experiment.2

Biitschli 3 showed that the respiratory exchange of insects varied in
the same direction as the temperature of their surroundings.

The most complete series of observations appear to be those of
Schulz4 upon the edible frog (Rana esculenta). The following table
gives his chief results, obtained upon frogs in summer : —

Temperature
of the Respiration
Chamber.

Temperature
of Frog.

COa-Output
per Kilo, and Hour.
C.c. at 0° and 760 Mm.

CO2-output
per Kilo, and Hour
in Grms.

o°-o i°-o

4'31

0-0084

0°'25 1°'0?

6-097 0-0119

0°-8

l°-5

7-50 0-0147

6°'l

6° -4

34-17 0-0672

15°'8

15°'4

35-30 0-0694

17°'0

15°'2

41-83

0-0822

25°'5

25° -0

76-26

0-1499

25°-5

25° -3

86-75

0-1706

33°'0 33°'0 279-40

0-5495

33°'2 33°'l 314-53

0-6179

34°-2 33°'5 340-48

0-6696

35°-0 34°-0 325-05

0-6392

It is to be noted that in Schulz's experiments the frogs were kept in
the warm or cold surroundings until their temperature was equal to
that of the air, so that the results are strictly upon frogs at different
temperatures. The response of a frog, as shown by its temperature and
respiratory exchange, to a change of external temperature is very slow,
and for this reason observations upon the metabolism of cold-blooded
animals can only be properly compared when the temperature of the
animal and that of the air are known. The above results show that at
temperatures a degree or two above zero the output of carbon dioxide

1 See ''Animal Heat," this Text-book, vol. i.

2 See also Pfliiger, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 73.

3 Arch.f. Anat., PhysioL, u. wissensch. Med., 1874, S. 348.

4 Arch.f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 78.

WARM-BLOODED ANIMALS.

711

is very minute, and rises with the temperature, until at 34° the output
is, weight for weight of body, equal to that of a man.

The observations of Pembrey l and Vernon 2 seem to show that the
output of carbon dioxide in frogs (Rana temporia) does not increase in
exact proportion with the temperature.

Warm-blooded animals. — Since the first experiments by Crawford,3
in which it was shown that a guinea-pig produced more carbon dioxide
in cold than in warm surroundings, numerous observations 4 have been

1

Animal.

Tempera-
ture of
Air.

Oxygen absorbed
per Kilo, and
Hour.

Carbon-Dioxide
discharged
per Kilo,
and Hour.

Water
discharged
per Kilo,
and Hour.

C02

O2

C02
H2O

Observer.

C.c.

C.c.

Guinea-pig j
/

15°'5
6°-0
22°'2

1079-66
1438-31
1050-00

1065-92
1262-67
867-19

•98
•88
•83

j- Colasanti.5

I

6°-3

1592-33

1230-00

•79

J

/! 3°-64
\ 26°'21

1856-50
1118-50

1554-80
1057-40

...

•83
•94

| Finkler.6

Grms.

Grms.

Grms.

f! 3°

9-030

9-505

6-705

•76

1-4

Mouse ; j 5°

8-384

8-641

6-721

•74

1-2

weight about-!

10°-5

6-660

7-443

5-079

•80

1-4

Oddi.7

19 grms.

25°
35°

4-862
5-912

5-400
4-977

5-102
4-736

•80
•65

1-0

1-0

Pigeon . -j

-9°
17°'5

3-016
1-141

...

...

. * .

Corin and Van
Beneden.8

Grms.

Grms.

Grms.

-3° '2

91 ,OQ

99 -fi^

T A .1 9

^

l°-3
18°'0

17-73

i 9 .on

18-92

1 q .QO

10-87

1 O'fiO

...

^CarlTheodor,9

29°'6

13-91

13-12

19-48

...

...

J

For periods of six hours, cat weighing

2557 - 2650 grms. The figures are

not reduced to kilo, and hour.

1 " Proc. Physiol. Soc.," Journ. PhysioL, Cambridge and London, 1894, vol. xvi.

2 Journ. PhysioL, Cambridge and London, 1894-1895, vol. xvii. p. 277.

3 " On Animal Heat," London, 1788, pp. 311, 387.

4 Delaroche, Journ. de phys. de chim. etc., Paris, 1813, tome Ixxvii. p. 5 ; Vierordt,
"Physiol. des Athmens," 1845; Wagner's "Handworterbuch," 1844, Bd. ii. S. 828;
Letellier, Ann. de chim. et phys., Paris, 1845, Se"r. 3, tome xiii. p. 478 ; Lehmann, AbhandL
d. k. sacJis. Gesellsch. d. Wissensch., Leipzig, 1846, S. 463; Liebermeister, Deutsches Arch,
f. Idin. Med., Leipzig, 1872, Bd. x. S. 89, 420 ; Gildemeister, Virchow's Archiv, Bd. Hi.
S. 130; Sanders-Ezn, Ber. d. k. sdclis. Gesellsch. d. Wissensch. Math. -phys. CL, Leipzig,
1867, S. 58 ; Rohrig and Zuntz, Arch. f. d. ges. PhysioL, Bonn, 1871, Bd. iv. S. 57 ;
Pfliiger, ibid., 1876, Bd. xii. S. 282; Regnault and Reiset, Ann. d. Chem. u. Pharm.,
1850, Bd. Ixxiii. S. 260 ; Berthollet, Mem. de la Soc. de phys. et de chim. d'Arcueil, Paris,
tome ii. ; Senator, Arch. f. AnaL, PhysioL, u. wissensch. Med., 1872, S. 1 ; 1874, S. 42,
54 ; Centralbl.f. d. med. Wissensch., Berlin, 1871, Nos. 47 and 48 ; Erler, Arch. f. Anat.,
physiol., u. loissensch. Med., 1876, S. 556 ; Litten, Virchow's Archiv, 1877, Bd. Ixx. S. 10 ;
Fredericq. Arch, de bioL, Gand, 1882, tome iii. pp. 736, 743; Quinquand, Compt. rend.
Acad. d.'sc., Paris, 1887, tome civ. p. 1542.

5 Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xiv. S. 92. See also Pfliiger, ibid.,
S. 469.

6 Ibid., 1877, Bd. xv. S. 603.

7 Arch. ital. de bioL, Turin, 1891, vol. xv. p. 223.

8 Arch, de bioL, Gand, 1887, tome vii. p. 265.

9 Ztschr.f. BioL, Miinchen, 1878, Bd. xiv. S. 51.

7 1 2 CHEMISTR Y OF RESPIRA TION.

made upon the influence of external temperature upon the respiratory
exchange of warm-blooded animals. The general result of this work is
that the intake of oxygen and the output of carbon dioxide increase
with a fall and decrease with a rise of external temperature. This is
shown by the examples, which have been taken from the results obtained
by different observers, and are given in the preceding table.

It appears that, when the external temperature is raised to a point
about 30°, the respiratory exchange shows an increase above the amount
observed at a temperature of 20°. Thus Voit l found in the case of a
man, that the output of carbon dioxide was increased by a fall of 9° or
10° below the average temperature 14°— 15°, and also increased by a rise
of 15° or 16° above that point; the augmentation in the discharge of
carbon dioxide was respectively 36 per cent, and 10 per cent, above that
given off at 14°-15°. A similar result was obtained by Page,2 who
found that at a temperature of 259 the discharge of carbon dioxide by a
dog was at a minimum ; a fall or rise of 10° below that point produced a
mean increase of 31 per cent, and 51 per cent, respectively.3 Unfortun-
ately Voit gives no details as to the temperature of the man during
the experiments, but in one or two cases Page notes that the tempera-
ture of the dog was raised above the normal by exposure to the
warm air.

The earliest experiments upon the influence of external temperature
on the respiratory exchange of man were made by Lavoisier and Seguin,4
who found that a man at rest absorbed in an hour 34'49 grnis. of
oxygen when the air was 32°'5, but 38'31 grms. when the temperature
was 15°. Since that time many observations5 have been made upon
man and the effect of external temperature on his respiratory exchange,
and of these the most important are those made by Lowy.6 The
general result drawn from his experiments is that the effect of external
cold varies in different men. Out of fifty-five experiments, the oxygen
absorbed was increased above 5 per cent, in twenty-six cases, unaltered in
twenty, and diminished in nine cases. In these experiments, in which the
metabolism was increased, for the variations in the output of carbon
dioxide followed those in the absorption of oxygen, the heights to which
it was raised varied between 5 and 90 '8 per cent, above the normal. A
point worthy of note is that the greatest increase in the respiratory
exchange was observed in the men who shivered or moved when they
felt cold, and that the respiratory exchange remained unaltered or
decreased in the men who, notwithstanding the sensation of cold,
remained quiet, and by an effort of the will suppressed any tendency to
move or shiver. Lowy concludes that the only involuntary regulator
of temperature in a man exposed to moderate cold is the skin. It must
be pointed out, however, that increased muscular activity in a man who

1 Ztschr.f. Biol., Mtinchen, 1878, Bd. xiv. S. 80.

2 Journ. Physiol., Cambridge and London, 1879-80, vol. ii. p. 228.

3 See also Rubner, " Biologische Gesetze," Universitats-programm, Marburg, 1887;
abstract in Centralbl. f. PhysioL, Leipzig u. Wien, 1887, S. 700.

4 ".(Euvres de Lavoisier'/' tome ii. .pp. 688, 704; Hist. Acad. roy. cL sc., Paris, 1789,
p. 575. See also Rep. Brit. Ass. Adv. He., London, 1871, p. 189.

5 Vierordt, "Physiol. des Athmens," 1845; E. Smith, Phil. Trans., London, 1859,
vol. cxlix., p. 681 ; Speck, Schrift. d. Gesellsch. z. Beford. d. ges. Naturw. zu Marburg,
1871, Bd. x. ; Liebermeister, Deutsches Arch. f. Win. Med., Leipzig, 1872, Bd. x. S. 89,
420 ; Lehmann, Virchow's Archiv, 1873, Bd. Iviii. S. 92. Johansson, Skandin. Arch. f.
PhysioL, Leipzig, 1897, Bd. vii. S. 123.

6 Arch.f. d. gcs. Physiol. , Bonn, 1890, Bd. xlvi. S. 189.

WARM-BLOODED ANIMALS. 7 1 3

feels cold, is not necessarily brought about by a conscious effort of the
will ; it is to a great extent reflex, and shows itself in the more energetic
performance of work, or, if no work be done, the reflex may become so
imperative as to give rise to involuntary movement, shivering, which is
only of value to the organism as a source of greatly increased heat
production. There is little doubt but that a normal man, who feels cold
and is free to follow the dictates of his sensations, will be more active,
and will produce more carbon dioxide and absorb more oxygen than he
would in warm surroundings. The man who suppresses increased
muscular action when he feels cold, is abnormal. It follows, therefore,
that man is no exception to the general rule that warm-blooded animals
in cold surroundings increase, in warm surroundings diminish, their
respiratory exchange and production of heat.

It has already been shown that a rise or fall in external temperature
determines in the same direction a variation of the respiratory exchange
of cold-blooded animals. What, then, is the cause of the totally opposite
result observed in warm-blooded animals ? To this question only an
incomplete answer can be given. The difference is due to the nervous and
muscular mechanisms which maintain the fairly constant temperature
observed in the warm-blooded animals. For if, as Sanders-Ezn1 and
Pfliiger 2 have shown, the exposure to cold be excessive, and the animal's
temperature falls to 26°, then also there is a fall in the intake of oxygen
and the output of carbon dioxide ; on the other hand, if by means of
warm baths the internal temperature of the animal is raised above the
normal, then there is an increase above the average respiratory exchange.
In fact, a warm-blooded animal responds to a rise or fall in the tempera-
ture of its surroundings with a decrease or increase of its metabolism,
only as long as its internal temperature remains near the normal point.
Moreover, Pfliiger has proved the connection between the normal
response to a change of external temperature and the nervo-muscular
system, for he shows that a mammal paralysed with curari 3 or with its
spinal cord cut in the lower cervical region, absorbs more oxygen and
discharges more carbon dioxide in warm than in cold surroundings ; it
resembles in this respect a cold-blooded animal. A similar cold-blooded
condition can be produced in mammals, as Eumpf,4 Eichet,5 and
Pembrey6 have observed, by exposing the anaesthetised animal to
changes of temperature.

The objection that these experiments are associated with markedly
abnormal conditions, and therefore cannot indicate the true condition of
normal animals, is met by the fact that it is possible to trace the
gradual development of the means whereby an animal increases or
decreases its metabolism and maintains a fairly constant heat of its
body, notwithstanding wide variations in the temperature of its
surroundings. This has been shown by Penibrey7 in a series of
comparative experiments upon full-grown and newly-born animals. In
the full-grown mouse the response to a change of external temperature

1 Ber. d. Jc. sacks. Gesdlsch. d. Wissensch. Math.-phys. KL, Leipzig, 1867, S. 58.
- Arch.f. d. ges. PhysioL, Bonn, 1878, Ed., xviii, S. 247.

3 See also Zuntz, Arch. f. d. ges. PhysioL, Bonn, 1876, Bd. xii. S. 522.

4 Ibid., 1884, Bd. xxxiii. S. 538.

5,Oompt. rend. Acad. d. sc., Paris, 1889, tome cix. p. 190.

6 "Proc. PhysioL Soc.," Journ. PhysioL, Cambridge and London, 1894-95, vol. xvii.

7 Journ. PhysioL, Cambridge and London, 1894, vol. xv. p. 40i ; 1895, vol. xviii.
p. 363.

7*4

CHEMISTR Y OF RESPIRA TION.

is almost immediate. The contrast in the case of young mice of
different ages is shown by the fact that a fall in external tempera-
ture produces a fall in the output of carbon dioxide, and in the
temperature of the young mouse, until it is about nine days old, when
it begins to respond in a similar way to that observed in a full-grown
animal.

A similar development can be observed in other young animals born
in an immature condition, and in the chick1 before and after it is
hatched, but a marked contrast is found in young animals born with a
well-developed and active body.2

The influence of muscular activity upon the respiratory ex-
change.— Muscular activity greatly increases the rate of breathing, the
intake of oxygen, and the output of carbon dioxide. It was but natural,
therefore, that physiologists should attribute the hyperpnoea caused by
excessive muscular exertion to a deficiency of oxygen, or to an accumula-
tion of carbon dioxide in the blood, consequent upon the greatly increased
metabolism. This theory, however, has been proved by experiment to
be erroneous. Mathieu and Urbain 3 determined the gases present in
samples of blood removed from an animal after a period of rest, and
again after a period of activity, and they found as a general result an
increase in the oxygen, and a decrease, in the carbon dioxide of the
blood in the latter condition. Their analyses, however, were subject to
certain sources of error. The question has been more thoroughly
investigated by Geppert and Zuntz,4 who found that muscular activity
is indeed accompanied by an increase in the oxygen and a decrease in
the carbon dioxide of the blood, and that the hyperpnoea is probably due to
some product of muscular activity which is absorbed by the blood and
carried to the medulla oblongata, where it stimulates the respiratory
centre. The chief evidence for these statements will now be given.
After section of the spinal cord of a dog in the dorsal region, tetamsation
of the hind limbs causes an increase in the air inspired, in the intake of
oxygen, and in the output of carbon dioxide.5

Dog weighing 2100 Grms.

Volume of Air inspired
per Minute.

Intake of Oxygen.

Output of Carbon Dioxide.

CO2
02

Condition.

1012 c.C.

Per Kilo. Bod
20-4 c.c.

Y Weight and per Minute.
18-2 c.c.

•89

Rest.

2148 „

36-8 „

31-8 ,,

•86

Tetanus.

863 „

21-6 „

16-2 „

•75

Rest.

1326 „

29-5 „

19-3 „

•66

Tetanus.

1 Pembrey, Gordon, and Warren, Journ. Physiol., Cambridge and London, 1894-95,
vol. xvii. p. 331.

2 See also "Animal Heat," this Text-book, vol. i. p. 803.

3 Arch. dephysiol. norm, ct path., Paris, 1871-72, tome iv. ; Compt. rend. Acad. d. sc.t
Paris, 1872, tome Ixxiv. p. 190.

4 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 189.

5 See also Hanriot and Richet, Compt. rend. Acad. d. sc., Paris, 1888, p. 75.

INFL UENCE OF MUSCULAR A CTIVITY. 7 1 5

Analyses of the gases of blood taken from an animal after voluntary
or involuntary muscular exertion show an increase in the oxygen and a
decrease in the carbon dioxide.

Gases of the Arterial Blood.

OXYGEN

CARBON DIOXIDE

VOLUMES PER CENT.

VOLUMES PER CENT.

Rest.

Activity.

Rest.

Activity.

17-58

38-57

\
/

Dog.

17'33

17-68

36-49

35-01 )

15-88

More than 16 '04

5371

39-06

Rabbit.

Further, if the aorta be compressed in order to shut out the blood
from the stimulated limbs, no hyperpnoaa is caused by the muscular
activity ; section of the vagi, sympathetic and recurrent nerves, or
section of the cord high up, does not prevent the stimulating effect of
muscular exertion upon the respiratory centre. In rabbits the alkalinity
of the blood is diminished by the acid formed during tetanic muscular
activity, and this is probably a cause of the decrease in the carbon
dioxide of the blood. No alteration could be found in the tension of the
oxygen and carbon dioxide present in the blood removed from an
animal after muscular exertion.1

Lehmarm2 has shown that the injection of normal solution of
tartaric acid stimulates and quickens the respiration of a rabbit, whereas
a normal solution of sodium hydrate depresses the respiratory centre.
According to Lowy's3 experiments, the unknown substance which
stimulates the respiratory centre during muscular activity is not
excreted by the kidneys, and is not carbon dioxide ; for whereas the rate
of respiration is doubled by muscular work when the increase above the
normal amount of carbon dioxide in the expired air is only 0'5 per cent.,
yet the same amount of dyspnoea can be produced during rest only by
artificially raising the percentage of carbon dioxide to a much higher
point, about 5 per cent.

The credit of the discovery that work is associated with an increase
in the respiratory exchange, is due to Lavoisier,4 who, in a series of
experiments with Seguin, found that a man at work absorbed 91 '2
grms. of oxygen in an hour, whereas at rest he only absorbed 38'3
grms. Although Vierordt5 and Scharling6 both observed a similar
increase in the output of carbon dioxide in men at work, the first
series of careful experiments on the subject were those performed by

1 For criticism see Speck, Deutsches Arch. f. klin. Med., Leipzig, 1891, Bd. xlvii. S. 509 ;
for reply by Zuntz and Geppert, ibid., 1891, Bd. xlviii. S. 444.

2 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 284.

3 Ibid., S. 281 ; 1890, Bd. xlvii. S. 601.

4 Hist. Acad. roy. d. sc., Paris, 1789, p. 185 ; "(Euvres de Lavoisier," tome ii. pp. 688-
696.

5 "Physiol. des Athmens," Karlsruhe, 1845; Arch. f. physiol. Heilk., Stuttgart,
Bd. iii. S. 536 ; Wagner's " Handworterbuch d. Physiol.," 1844, Bd. ii. S. 828.

6 Ann. d. Chcm. u. Pharm., 1843, Bd. xlv. S. 214; Journ. f. prakt. Chem., Leipzig,
Bd. xlviii. S. 435.

7i6

CHEMISTR Y OF RESPIRATION.

E. Smith.1 He found that a man produced 161/6 c.c. of carbon dioxide per
minute when he was perfectly at rest, as in a deep sleep ; that during a
walk at the rate of two miles (3048 metres) an hour, the discharge of
carbon dioxide was increased to 569'5 c.c., and to 851/2 c.c. when the
rate of walking was quickened to three miles (45 71 '9 metres) an hour.
The greatest increase, ' 1581 '9 c.c. of carbon dioxide per minute, was
caused by work upon a treadmill.

In 1866, Pettenkofer and Voit 2 performed a series of important
observations upon the metabolism of healthy men, under different con-
ditions as regards work and diet, and they found that if unity represent
the value of the output of carbon dioxide and the intake of oxygen
when the man is at rest, then \^ork brings about the following
results : —

Carbon dioxide
Oxygen .

During Hunger,

O • Q
• ^ O

2-1

Moderate Diet.
1-6
1-8

The numerous experiments made by Speck,3 under different con-
ditions as regards the amount and nature of the work performed, show
that the air inspired, the oxygen absorbed, and the carbon dioxide
discharged, are greatly increased; the percentage composition of the
expired air is but little altered, and the respiratory quotient increases
slightly during the work. Hanriot and Richet4 find for each kilo-
grammetre of work performed by a man, an increase of 3168 c.c. in the
oxygen absorbed, and 4*221 c.c. in the carbon dioxide discharged.

In experiments upon horses, Zuntz and Lehmann5 obtained the
following results : —

LITRES PER MINCTE.

CO.,

Air expired.

Cdris?ha?ged!de Oxygen absorbed.

0,.

Rest

44

1-478 1-601

•92

Walk

177

4-342 4-766

•90

Trot

333

7-516 8-093

•93

It is impossible here to discuss fully the quantitative relationship
between metabolism and work, but the conclusions reached by Katzen-
stein 6 are as follows : — The work performed by the arms in turning a
wheel produces, per unit of work done, a greater increase in the respiratory
exchange than walking or climbing ; the absorption of oxygen is per unit
of work performed somewhat greater for light, than for heavy work ;
the absorption of oxygen and the discharge of carbon dioxide increase

1 Phil. Trans., London, 1859, vol. cxlix..pt. 2, p. 681.

2 Ztschr. f. BioL, Munchen, 1866, Bd. ii. S. 459. See also this article, p. 718, and
article by Voit in Hermann's "Handbuch," Bd. vi. Th. 1, S. 201.

3 Deutsches Arch. f. klin. Med., Leipzig, 1889, Bd. xlv. S. 461.

4 Oompt. rend. AcM. d. sc., Paris, 1887, tome civ. p. 1865 ; tome cv. p. .76.

5 Landw. Jahrb., 1889, Bd. xviii. S. 1 ;,Journ. Physiol., Cambridge and London, 1890,
vol. xi. p. 396. , .

6 Arch. f. d. ges. Physiol. , Bonn, 1891, Bd. xlix. S. 380.

INFLUENCE OF FOOD.

717

equally under ordinary conditions, so that the respiratory quotient
remains practically unaltered. It is only immediately after work that
the respiratory quotient increases, and becomes sometimes greater than
unity. The absorption of oxygen needed for the work of walking on
level ground is, per kilo, body weight and minute, 0'1682 c.c.
maximum, and 0'0858 c.c. minimum ; for each kilogrammetre of work
performed in climbing, T5036 c.c. maximum, and 1*1871 minimum; and
similarly, for turning the wheel, 1*957 c.c.

Lowy l shows that there is no definite value which can be assigned to
the increase of the respiratory exchange for the performance of a given
quantity of work under all circumstances, for the metabolism depends
upon the activity of the muscle, which varies under different conditions.
Active muscle working under favourable conditions performs its work
economically ; fatigued muscle working under unfavourable conditions
is the seat of an extravagant metabolism.2

The decrease observed in the respiratory exchange of animals under
the influence of chloroform, ether, chloral, and curari, is to be attributed
chiefly to the great decrease in the activity of the muscles.3

The influence of food upon the respiratory exchange. — The effect
of a meal upon the respiratory exchange is to cause a marked increase
in the intake of oxygen and the output of carbon dioxide ; this is due

Number of
Experiments.

Mean Output of Carbon Dioxide
per Kilo, and Hour.

Condition of Animal.

Grms.

C.c.

52

1-423
0-902

723

458

Pregnant ; very liberal diet of meat.
The same animal ; hunger for 18 dys.

4

0-998

507

15 „

4

0-732

372

18 „

shortly before death.

6

0-847

430

Male, kept at constant weight with

diet of meat.

2

1-364

693

Male, maximal diet of meat.

23

0-888

451

Male, normal diet of meat, but

without water.

12

0-679

345

Male, inanition, but with water

supplied.

7

1-702

865

Female, not full grown ; diet of

meat.

6

1-500

763

Female, diet of fat.

1 Arch. f. d. ges. Physiol., Bonn, 1891, Bd. xlix. S. 405. See also, Gruber, Ztschr. f.
Biol., Milne-hen, 1891, Bd. xxviii. S. 466.

2 ]?or further experiments upon the influence of work upon the respiratory exchange of
(a) man, see Hanriot and Richet, Ann. d. chim. et pJiys., Paris, 1891, Ser. 6, tome
xxii. p. 495 ; and Trav. du lab. de Ch. Richet, 1894, tome 1 ; (b) animals, Grandis, Arch,
ital. de biol., Turin, 1889, tome xii. p. 237 ; Smith, Journ. Physiol., Cambridge and
London, 1890, vol. xi. p. 65. Criticism of the same byZuntz and Lehmann, ibid., p. 396 ;
Grehant, Compt. rend. Soc. de biol., Paris, 1891, p. 14.

3 Zuntz, Arch. f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 522 ; Pniiger, ibid., 1878,
Bd. xviii. S. 247; Rumpf, ibid., 1884, Bd. xxxiii. S. 538 ; Saint Martin, Compt. rend.
Acad. d. sc., Paris, 1887, tome cv. p. 1126 ; Richet, ibid., 1889, tome cix. p. 190 ; Arch.
de physiol. norm, etpath., Paris, 1890, tome ii. p. 221 ; Pembrey, " Proc. Physiol. Soc.,"
Journ. Physiol., Cambridge and London, 1894-95, vol. xvii.

7i8

CHEMISTR Y Of RESPIRATION.

not only to the chemical changes which take place in the food during
digestion and absorption, but also to the increased glandular and
muscular activity of the alimentary canal.1

Although Lavoisier 2 knew that food greatly increased the respiratory
exchange, the first experiments of importance in this connection are those
of Bidder and Schmidt,3 who made numerous observations upon cats ;
the results of some of their experiments are given in the preceding table.

In the case of man and other animals, the influence of food of
various kinds, and of fasting, has been studied by Pettenkofer and
Voit,4 Senator,5 Henneberg,6 Leyden and Frankel,7 Predericq,8 and
others ; 9 the general result is that a meal causes an increase in the
intake of oxygen and the output of carbon dioxide, whereas a day of
fasting causes a decrease. The average results obtained upon man by
Pettenkofer and Yoit 10 are as follows : —

CARBON DIOXIDE.

OXYGEN. 11

Day.

Night.

Day.

Night.

1. Fasting— Rest

Grms.
403

Grms.
314

Grms.
435

Grms.
326

„ Work for nine
hours out of twelve

930

257

922

150

2. Moderate Diet— Rest

533

395

443

449

„ Work for
nine hours out of twelve

856

353

795

211

Upon the fasting-man Cetti, determinations of the respiratory
exchange were made by Zuntz and Lehmann,12 and they found that the
absorption of oxygen and the discharge of carbon dioxide per kilo,
of the man's weight quickly reached its minimum, and did not fall
below this point during the progress of the fast ; in fact there was a
slight increase. Thus the absorption of oxygen per kilo, and minute
was 4'65 c.c. on the third to sixth day, and 473 c.c. on the ninth to
eleventh day of the fast. Before the first meal at the end of the

1 See p. 719.

2 "CEuvres," tome ii. pp. 695-696.

3 " Die Verdauungssafte und der Stoffwechsel, " Leipzig, 1852, S. 321-362.

4 Ann. d. Chem. u. Pharm., 1862-63, Supp. Bd. ii. S. 52-361.

5 Arch. f. Anat., PhysioL, u. wissensch. Med., 1872, S. 1.

6 Landwirthsch. Versuchsstat., 1869, S. 306, 409.

7 Tirchow's Archiv, 1879, Bd. Ixxvi. S. 136.

8 Arch, de bioL, Gand, 1882, tome iii. p. 733.

9 E. Smith, Phil. Trans., London, 1859, vol. cxlix. p. 715 ; Hanriot and Richet,
Compt. rend. Acad. d. sc., Paris, 1888, tome cvi. p. 419.; Zuntz, Fortschr. d. Med., Berlin,
1887, Bd. v. S. 1 ; Meissel, Strohmer, and Lorenz, Ztschr. f. BioL, Mlinchen, 1886, Bd.
xxii. S. 63 ; Bceck and Bauer, ibid., 1874, Bd. x. S. 336 ; Geppert, Arch. f. exper. Path,
u. PharmaJcoL, Leipzig, 1887, Bd. xxii. S. 366; Hanriot and Richet, Ann. de chim. et
phys., Paris, 1891, Ser. 6, tome xxii. p. 495 ; Marcet, Proc. Pioy. Soc. London, 1892,
vol. 1. p. 58 ; 1893, vol. Iii. p. 213 ; Rubner, Beitr. z. PhysioL Carl Ludwig z. s. 70
Geburtst., Leipzig, 1887, S. 259 ; Johansson, Landergren, Sonden, and Tigers tedt, Skandin.
Arch.f. PhysioL, Leipzig, 1896, Bd. vii. S. 29.

10 Ztschr. f. BioL, Munchen, 1866, Bd. ii. S. 459.

11 For criticism of the determination of oxygen, see p. 696.

12 BerL klin. Wchnschr., 1887, S. 428.

A CTIVITY OF THE ALIMENTAR Y CANAL. 7 1 9

fast the absorption of oxygen and the discharge of carbon dioxide were
4'67 c.c. and 3*16 c.c. per kilo, and minute ; after this meal the
figures were respectively 5'05 c.c. and 346 c.c. The effects of the fast
and of food upon the respiratory quotient were as follows : —

CO

On last day of food, mixed diet . . -^ = 0'73

^2
On second day of fasting . . . . „ „ 0 68

On third day of fasting . . , ,, „ 0'65

During the remainder of the fast . „ „ 0'66-0'68

When food, mixed diet, was again taken . ,, „ 0*73-0 '81

Eegarding the influence of diet upon the respiratory quotient, it is
only necessary here to state that an animal fed on a vegetable diet has a
quotient closely approaching unity, for its chief food, the carbohydrates,
contains enough oxygen to combine with the hydrogen to form water ;
that a carnivorous animal has a quotient about 074, and an omnivorous
animal, such as man, a somewhat higher quotient l ; and finally, that
even a herbivorous animal has a low quotient during starvation, for it
then lives upon its own tissues.

The influence of activity of the alimentary canal upon the
respiratory exchange. — It has already been shown that a meal
increases the respiratory exchange, and this effect was originally attri-
buted solely to the oxidation of the food material taken up by the
blood. Speck,'2 however, in 1874, pointed out that this increase in
metabolism followed the taking of food so rapidly that it appeared to be
due, in the first place, to the augmented activity of the alimentary canal.
The first experiments to support this view were those made by Mering
and Zuntz,3 who showed that food placed in the stomach increased the
absorption of oxygen and the discharge of carbon dioxide, whereas sub-
stances such as lactic acid, butyric acid, glycerin, sugar, egg albumin, and
peptone, injected into the blood, increased the output of carbon dioxide, but
had no marked effect upon the intake of oxygen. Eubner 4 and Fredericq5
also found increased metabolism after food, due apparently, in the first
place, to the activity of the glands of the alimentary canal ; 6 and the
observations made by Lehmann and Zuntz T upon the fasting-man
Cetti showed that during the fast the respiratory exchange was
constant, except on two days when Cetti suffered from colic ; there
was then an increase in the intake of oxygen and the output of carbon
dioxide. These pieces of evidence have been followed up by Lowy,8
who determined the respiratory exchange of fasting men before and
after the activity of the alimentary canal had been increased by a dose
of sodium sulphate, or a draught of cold water. Experiments made
upon six men showed that the increased activity of the alimentary canal
brought about in this way increased the intake of oxygen and the
output of carbon dioxide by about 10 per cent. ; the greatest increase

1 See tables on pp. 706-708.

2 Arch.f. e'xper. Path. u. Pharm., Leipzig, 1874, Bd. ii.

3 Arch.f. d. ges. PhysioL, Bonn, 1877, Bd. xv. S. 634 ; 1883, Bd. xxxii. S. 173.

4 Ztschr.f. BioL, Munchen, 1883, Bd. xix. S. 330.

5 Arch, de biol., Gand, 1882, tome iv. p. 433.

6 See also Slosse, Arch. f. Phy.noL, Leipzig, 1890, Suppl. Bd. S. 164 ; Tangl, ibid.,
1894, S. 283.

7 Berl. Tclin. Wchnxchr., 1887, S. 428.

8 Arch. f. d. ges. PhysioL, Bonn, 1888, Bd. xliii. S. 515.

720 CHEMISTR Y OF RESPIRA TION.

was about 24 per cent, in the carbon dioxide, and 17 per cent, in the
oxygen. Sodium chloride and sodium bicarbonate had no effect on the
intestines or upon the respiratory exchange. Lowy suggests that the
therapeutic value of the waters at Carlsbad and Marienbad, in cases of
disordered metabolism, may be partly due to this stimulating effect of
sodium sulphate.

The influence of the size of the animal upon the respiratory
exchange.1 — -The smaller an animal the greater is its surface in relation
to its mass, for the surface increases as the 'square, the mass as the cube.
Now, small mammals and birds' have a temperature equal to or even
higher than that of large animals of the same 'classes ; and, on account of
the relatively greater surface which they expose for the loss of heat,
they must have a relatively far greater production of heat than the
large animals, for there is generally no marked difference in the pro-
tective coat of fur or feathers. Heat is produced by a process of
combustion in the tissues, and the respiratory exchange is a measure,
although it may not be an absolutely exact one, of this combustion.
Theoretically, therefore, a much more vigorous respiratory exchange
should exist in the smaller warm-blooded animals. The experiments of
many observers, especially of Letellier,2 Eegnault and Eeiset,3 Pott,4 and
Kichet,5 have shown that such is the case, not only for animals of the
same species, living upon similar diet and having similar habits, but
also for animals of different species, with very different diets and
habits.6

Paul Bert 7 has shown that this difference in the rate of metabolism
in small and large animals has become habitual, for it persists even
when the animals are put under abnormal conditions of such a kind
that the loss of heat is relatively the same ; in such an experiment a
pigeon absorbed 234 c.c. of oxygen per 100 grms. of its body weight, and
a sparrow 467 c.c. of oxygen.

A series of experiments have been made by Eichet 8 upon thirty-eight
dogs of different sizes, their weights ranging from 2 '2 to 28 kilos., and
the results show that the output of carbon dioxide bears a very constant
relation to the surface of the body, 0'0027 grins, per hour for each
.square centimetre of surface. A similar relation holds good for the
intake of oxygen, the respiratory quotient being 0'748. This difference
in metabolism is controlled by the nervous system, for it was found,
in eighteen dogs of different sizes, ansesthetised with chloral, that the re-
spiratory exchange was proportional to the weight of the body, 0*640 to
0*694 grms. C02 per kilo, and hour. A somewhat similar series of
observations, made upon birds9 of different sizes and species, gave
similar results.

1 For a discussion of this subject, see paper by Hoesslin, Arch. f. Physiol., Leipzig,
1888, S. 323, where numerous references are given ; Rubner, Ztsclir. f. BioL, Munchen,
1883, Bd. xix. S. 535.

2 Ann. de chim. etphys., Paris, 1845, Ser. 3, tome xiii. p. 478.

3 Ibid., Paris, 1849, Ser. 3, tome xxvi. p. 299.

4 Landwirthsch. Versudisstat. , Bd. xviii. S. 81.

5 Arch, de physiol. norm, et path., Paris, 1890, tome xxii. pp. 17, 490; 1891, tome
xxiii. p. 74.

6 See tables, pp. 706-708.

7 "Le9ons sur la physiol. comp. de la respiration," Paris, 1870, p. 503.

8 Compt. rend. Acad. d. sc., Paris, 1889, tome cix. p. 190 ; Arch, de physiol. norm, ct
path., Paris, 1890, tome xxii. p. 17.

9 Arch, de physiol. norm, et path., Paris, 1890, tome xxii. p. 490.

INFLUENCE OF TIME OF DAY.

721

The influence of time of day upon the respiratory exchange.—
During a series of experiments performed in the years 1813 and 1814,
Prout1 discovered that the amount of carbon dioxide discharged from
the lungs appeared to be influenced by the time of day, for there was a
regular daily variation; the maximum was generally between 11 A.M.
and 1 P.M. ; then there was a fall to the minimum at 8 P.M. or 9 P.M. in
the evening, and at this low level the discharge of carbon dioxide
remained until 3 A.M. or 4 A.M., when there was a marked rise. A
similar variation was observed by Vierordt,2 both in the discharge of
carbon dioxide and in the amount of air respired, and the cause of the
rise he attributed to food. The table on p. 722 gives his average results.

Speck 3 determined the daily variation, both in the intake of oxygen
and in the output of carbon dioxide, and showed the influence of food in
producing the maximum.

Further experiments upon the daily variation in the respiratory
exchange have been made by Berg4 and Fredericq.5 The following
curve represents the daily variation observed by Fredericq in the oxygen
absorbed by a man : —

A. M.

P.M.

8 9 10 11 12 1 2 34 3 67

4.5

\

\

\

FIG. 67. — Frederick's curve of daily variation in the absorption of oxygen.
R = time of a meal.

The causes of these variations in the daily respiratory exchange are
to be attributed mainly to food and muscular activity, for during sleep,
as E. Smith,6 Pettenkof er and Voit,7 and others 8 have shown, the meta-
bolism is greatly diminished, and also in a less degree during hunger.
In addition, however, there appears to be a certain periodicity stamped

1 Ann. Phil., London, 1813, vol. ii. p. 330 ; vol. iv. p. 331.

3"Physiol. cl. Athmens." Karlsruhe, 1845: Wagner's "Handworterlmch," Bd. ii.
S. 883.

3 "Untersuch. ueber Sauerstoffserbrauch u. Kolilensaureausathmung des Menschen,"
Cassel, 1871, S. 31 ; Arch. f. exper. Path. u. PharmakoL, Leipzig, 1874, Bd. ii. S. 405 ;
ibid. 188Q, Bd. xii.'S. 1. *

" Einfluss der Athembewegungen auf die Aitsscheidung der Kohlensaure durch die
Lungen," Dorpat, 1869.

5 Arch, de bidl., Gand, 1882, tome iii. p. 729.

fi Phil. Trans., London, 1859, vol. cxlix. p. 681.

1 Ztschr.f. Biol., Miinchen, 1866, Bd. ii. S. 459.

8 Saint-Martin, Compt. rend. Acad. d. sc., Paris, 1887, tome cv. p. 1124; Rubner,
Beitr. %. Physiol. Carl Ludwiy 3. s. 70 Geburtst., Leipzig, 1887, S. 259.
VOL. I. — 46

722

CHZMISTR Y OP RESPIRA T10N.

Hour of Day.

Respirations
per Minute.

Volume of an
Expiration.

Air expired in
One Minute.

CO, expired in
One Minute.

Percentage of
CO? in the
Expired Air.

C.c. (37° and 758 Mm.).

9 A.M.

12'1

503

6090

264

4'32

10 „

11-9

529

6295

282

4-47

11 ,,

11-4

534

6155

278

4-51

12 noon

11-5

496

5578

243

4-36

Dinner.

1 P.M.

12-4

513

6343

276

4-35

2 ,

13'0

516

6799

291

4-27

3 ,

12-3

516

6377

279

4-37

4 ,

12-2

517

6179

265

4-21

5 ,

117

521 6096

252

4-13

6 ,

11 '8

496

5789

238 4-12

7 ,

11-1

489

5428

229 4-22

upon the organism by long-continued habit — a day of work, a night of
rest. This explains the persistence of the daily variation in metabolism,
temperature, pulse, and respiration observed in an animal kept at rest
and without food.

The effect of light in increasing the respiratory exchange is pro-
bably to be attributed chiefly to the increased muscular activity of most
animals in the light.1

The influence of age upon the respiratory exchange. — The
respiration of the foetus is relatively small, and this condition, within
certain limits, persists for a short time after birth. The estimation,
however, of the effect of age upon the respiratory exchange is not so
simple as it at first appears, for there are two factors which have to
be taken into account. In the first place, the young animal has a
relatively greater surface in proportion to its mass than the adult
animal, and this causes a more rapid respiratory exchange ; in the
second place, young animals of different species are born in different
degrees of development. A newly-born guinea-pig is covered with fur,
has its eyes open, and is able to run about and feed ; whereas a newly-
born rabbit, rat, or mouse is naked, blind, and helpless. A similar
contrast is observed in the condition of the newly-hatched chick and
pigeon. Elsewhere it has been shown that newly-born mammals and
birds can be arranged in two classes — those which can and those which
cannot maintain their temperature ; and there is a similar contrast in
the effect of changes of external temperature upon their respiratory
exchange. These factors must, therefore, be remembered in estimating
the effect of age upon the respiratory exchange.

In the case of man, experiments have been made by Andral and
Gavarret,2 but it is difficult to estimate the influence of the ratio
between mass and surface of the body, for the weights of the subjects
are not given. In the following table are some of Scharling's 3 results,
which show that, weight for weight of body, the child discharges more
carbon dioxide than the adult : —

1 Numerous references to the controversy on this point will be found in a paper by
Fubini and Benedicenti, Arch. ital. dc bioL, Turin, 1891, vol. xvi. p. 80.

2 "Recherches sur la quantite d'acide carbonique exhale par le pounion dans 1'espece
hiunaine," Paris, 1843. Extract in Ann. de chim. et phys., Paris, 1843, Ser. 3, tome viii.

3 Ann. d Chem. u. Pharm., 1843, Bd. xlv. S. 214.

RESPIRATION BY THE SKIN.

723

Sex.

Age.

Weight.

Output of
Carbon Dioxide in
Twenty-four Hours.

Output of
Carbon Dioxide
per Kilo, and Hour.

Male .

35 years

Kilo.
65-5

Grins.

80472

Grms.
0-512

! ,. . .

28 „

82

878-95

0-497

»i • •

16 ,,

5775

822-69

0-594

Female .

19 „

5575

608 -22

0-455

Male

91 „

22

488-14

0-925

Female .

10 ,,

23

459-87

0-833

A series of experiments by Pembrey l has shown that the effect of
age upon the respiratory exchange must be considered in relation to the
temperature of the external air and the stage of development in which
the animal is at birth. Animals born in a condition of advanced
development, like that of guinea-pigs and chickens, have a respiratory
exchange which is relatively two or three times greater than that of
the adult. Animals born in a helpless state, like that of mice and
pigeons, have at the ordinary temperature of the air a metabolism
relatively smaller than that of the adult ; but with a rise in the
external temperature towards the temperature of the body the re-
spiratory exchange increases towards the value in the adult. These
differences, which are intimately connected with the temperature of
the animal, are discussed more fully in other parts 2 of this work.

EESPIRATION BY THE SKIN AND ALIMENTARY CANAL.

Cutaneous respiration of amphibia. — In many of the lower animals
the exchange of gases between the skin and the surrounding air or water is
considerable, and in some of the amphibia is equal to, or even greater than, that
effected by the lungs. As early as the end of the last century, Spallanzani 3
showed that many amphibia could readily take up oxygen and discharge
carbon dioxide after their lungs had been removed, and that in this condition
they lived longer than animals of the same species whose skin had been
covered with varnish. These observations were extended by Edwards,4
who found that frogs deprived of their lungs would live a long time, provided
that the external temperature was low. This cutaneous respiration took place
as readily in flowing water as in air, for normal frogs could be kept alive
although never allowed to come to the surface, provided that the temperature
of the water did not exceed 12°; the cutaneous respiration was sufficient for
the small amount of metabolism which occurred at low temperatures. Kegnault
and Eeiset 5 found, by direct experiment, that frogs absorbed as much oxygen
and discharged as much carbon dioxide after, as before, removal of their
lungs. The following figures give their results : —

1 Jo-urn. Pliysiol., Cambridge and London, 1895, vol. xviii. p. 363.

2 See " Animal Heat," this Text-book, vol. i.

3 "Memoires sur la respiration," trad, par Senebier, Geneve, 1803, pp. 72, 114.
"De 1'influence des agens physiques sur la vie," Paris, 1824, pp. 12, 41-62.

5 Ann. de cTiim. etphys., Paris, 1849, Ser. 3, tome xxvi. p. 506.

724

CHEMISTR Y OF RESPIRATION.

Condition of Frog.

Oxygen per
Kilo, and Hour.

Carbon Dioxide
per Kilo.
and Hour.

CO2

02

Temperature.

Remarks.

Normal

Grms.
(Min. 0-063

\Max. 0-105

Grms.
0-045

0-081

•69

•78

15°-9°
»

Result of
five experi-
ments.

After removal of
lungs

J 0-047
( 0-066

0-049
0-071

•76

•79

17°
21°

Berg,1 on the other hand, found the discharge of carbon dioxide considerably
diminished, but this has not been confirmed by Fubini,2 AV!IO observed, in
comparative experiments, only a slight decrease in the output of carbon
dioxide after removal of the lungs.

To all of these experiments there are certain objections. The varnish,
especially when containing alcohol, acts injuriously on the frog, and interferes
with its free movement; the removal of the lungs, apart from the actual injury
done to the animal during the operation, may cause the skin to take on
vicariously the function of respiration. Later experiments by King3 are free
from these objections, for the head of a normal frog was passed through a
rubber collar into one part of a chamber, while the body was retained in the
other part — the pulmonary and cutaneous respiration were thus determined
separately ; and in order to allow for the cutaneous respiration which would
take place on the head, other experiments were made, in which only the nose
projected, and in which section of the vagi nerves, an operation which suspends
the pulmonary respiration, had been performed. The results show that, during
the winter at least, the cutaneous respiration is far more important than the
pulmonary.

Experiment.

Dura-
tion of
Experi-
ment.

Weight
of
Frog.

Sex.

I.— CO2 per
100 Grms. and
24 Hours.
Head and
Lungs.

II.— CO2 per
100 Grms. and
24 Hours.
Body below
Head.

Ratio
of
I. to II.

Remarks.

Hours.

Grms.

Grms.

Grms.

1

3

77

Male

•0581

•1891

1-3-2

Normal.

3

,,

111

,,

•0540

•1902

1-3-5

,,

8

82

Female

•0536

•2361

1-4-4

Only the nose pro-

jected through the

partition.

9

tj

177

5)

•0175

•0786

1-4-4

Both vagi cut ;

membrane as in

Experiment 8.

Dissard 4 has determined the production of carbon dioxide after ligature of
the cutaneous or the pulmonary blood vessels of frogs, and he finds that both
cutaneous and pulmonary respiration are necessary to the animal, for the

1 "Untersuch. ueber d. Hautathmung d. Frosches," Diss., Dorpat, 1868.

2 Untcrsuch. z. Naturl. d. Mensch. u. d. Thicre, 1878, Bd. xii. S. 100.

3 Arch. f. PhysioL, Leipzig, 1884, S. 183.

4 Compt. rend. Acad. d. sc., Paris, 1893, tome cxvi. p. 1153.

CUTANEOUS RESPIRA TION OF MAMMALS. 7 2 5

removal of either causes death after a longer or shorter period. The cutaneous
respiration appears to be the more important during the winter, and the
pulmonary during the summer. The experiments of Marcacci l indicate that
the mucous membrane of the mouth and pharynx is also respiratory in the
frog, and Camerano 2 finds in the case of the salamanders Spelepes fuscus
and Salamandrina perspicillata, in which the lungs are either absent or
rudimentary, that the bucco-pharyngeal respiration is more important than
that carried on by the skin.

Valentin3 determined the absorption of oxygen and the discharge of
carbon dioxide from pieces of skin removed from the body of the frog, and
found that the former process was the more active. This has been confirmed
by Way mouth Reid and Hambly,4 who, from experiments upon the transpira-
tion through the frog's skin, conclude that there is no evidence of any
physiological action by virtue of which carbon dioxide is " secreted " ; the
exchange of gases is the direct result of'a difference of tension on the two sides
of the respiratory septum.

Cutaneous respiration of mammals. — In man and other mammals
the cutaneous respiration is so small that it has been denied by some
observers,5 and explained away by others, as arising from the decom-
position of filth and cutaneous secretions.6 Although Hippocrates and
Galen believed in the absorption of air by the skin, no experiments
appear to have been made until the year 1777, when Milly observed,
during a warm bath, a number of small bubbles attached to the surface
of his body ; some of these bubbles were collected, and on analysis were
found by Lavoisier 7 to be carbon dioxide. Objection was raised to this
experiment, on the ground that carbon dioxide present in the water
might attach itself to the body, as it does to other solid substances.
Cruikshank,8 however, found that air, in which a previously washed
hand or foot had been confined for one hour, caused a marked turbidity
with lime water. These experiments were extended by Abernethy,9
who showed that in ordinary air oxygen was absorbed and carbon
dioxide was given off as readily as in pure oxygen, whereas in carbon
dioxide gas nitrogen was discharged and carbon dioxide absorbed by the
skin of the hand.

In Lavoisier and Seguin's 10 experiments a man was enclosed in an
air-tigbt rubber bag, while he breathed through two tubes connected
with the mouth and nose ; this method was improved by Scharling,11
who prevented the excessive accumulation of moisture by ventilating
the chamber in which the subject of the experiment was confined.
The results of the above and later observers are given in the following
table :—

1 Arch. ital. de bioL, Turin, vol. xxi. p. 1.

2 Ibid., vol. xxi. p. 387.

3 Arch.f. physwL ffeilk., Stuttgart, 1855, S. 474.

4 Journ. PhysioL, Cambridge and London, 1895, vol. xviii. p. 411.

5 Priestley, "On Air," vol. ii. pp. 193, 194; Klapp and Gordon, " Ellis's Inquiry"
Edinburgh, 1807, pp. 189, 354.

6 Hoppe-Seyler, " Physiol. Chem.," Berlin, 1879, Bd. Hi. S. 580.
7 Hist. Acad. roy. d. sc., Paris, 1777, pp. 221, 360.

8 " Experiments on the Insensible Perspiration of the Human Body, showing its
affinity to Respiration," 2nd edition, London, 1795, pp. 81, 82.

9 "Surgical and Physiological Essays," London, 1793, pt. 2, p. 107.

10 "(Euvres de Lavoisier," Paris, 1862, tome ii. p. 708 ; Ann. de chim. et phys.,
Paris, 1814, tome xc. p. 8.

11 Journ. f. prakt. Chem., Leipzig, 1845, Bd. xxxvi. S. 454 ; Ann, de cjrim. et phys.,
Paris, 1843, Se>. 3, tome viii. p. 480.

726

CHE MIS TR Y OF RESPIRATION.

CO2

O.,

Part of Body
Examined.

Gases Discharged.

Gases Absorbed.

Discharged. Absorbed.
For Total Surface of Body

Observer.

in 24 hours.

Hand and foot

Carbon dioxide

Not determined

Cruik shank.1

of man

Hand of man

Carbon dioxide,

Oxygen

14 grins.

Abernethy.2

and some-

times nitro-

gen

Total surface of

)}

Lavoisier and

skin of man

Seguin.3

Portions of skin

Carbon dioxide

Not determined

...

CollarddeMar-

of man
Total surface of

and nitrogen
Carbon dioxide

-

55 35

32-8 grins.

tigny.4
Scharling.5

skin of man

Total surface of

Carbon dioxide

"'

10*9 grms.

? 5

skin of child,

set. 10

Total surface of

55

55 55

23'9 grms.

}j

skin of girl

set. 19

• ? , ,

55 55

5 j

Regnault and

Reiset.6

Portion of skin

>5 55

Oxygen

8 "4 grms.

2 '7 grms.

Gerlach.7

of man

Arm of man

53 5 '

Not determined

2 '2 grms.

; }

Reinhard.8

55 55

14 grms.

) 5

Rdhrig.9

Total surface of

55 5 )

55 5 '

6 -3 grms.

Aubert and

skin of man,

(maximum)

Lange.10

except head

5>

35 53

55 55

2-3 grms.

3 )

> ? ? ?

(minimum)

Hand . . .

35 55

55 35

1*25 grms.

5 )

35 33

Hand and fore-

55 5»

5 5 55

6-80 grms.

5 5

Fubini and

arm

Ronchi."

Upper limb of

55 J 5

55 55

•01 93 grin.12

Bairatt.13

man

Portion of skin

55 55

Oxygen

30'1 grms.

6 '3 grms.

Gerlach.7

of a horse

Total skin of a

55 J J

55

119 grms.

}J

Zuntz, Leh-

horse

man n, and

Hagemann.14

The results of Aubert which have been given above show that the
cutaneous respiration varies in intensity in different parts of the body,
and that for this reason it is impossible to correctly calculate the
cutaneous respiration of the whole body from the data obtained on one
limited part, such as the hand. Further, the exchange of gases from the

1 Loc. cit. 2 Loc. cit.

3 " CEuvres de Lavoisier," Paris, 1862, tome ii. p. 708; Ann. de cliim., Paris,
1814, tome xc. p. 8.

4 Journ. de physiol. ex})^r., Paris, 1830, tome x. p, 162.

5 Journ. f. prakt. Chem., Leipzig, 1845, 15 d. xxxvi. S. 454, Ann. de cliim. ct pltys.,
Paris, 1843, Se"r. 3, tome viii. p. 480.

6 " Recherches sur la respiration des animaux," p. 209.

7 Arch. f. Anat., Physiol. u. ivissensch. Med., 1851, S. 431.

8 Ztschr.f. BioL, Miinchen, 1869, Bd. v. S. 28.

9 Deutsche Klinik, Berlin, 1872, Bd. xxiv. S. 209, 225, 234,

10 Arch.f. d. ges. Physiol., Bonn, 1872, Bd. vi. S. 539.

11 Untersuch. s. Naturl. d. Mensch. n. d. Thiere, 1881, Bd. xii. S. 1.

12 For upper limb alone and for one hour ; temperature of air = 35°.
Li Journ. Physiol., Cambridge and London, 1897, vol. xxi. p. 204.
14 Arch.f. Physiol., Leipzig, 1894, S. 351.

EFFECTS OF VARNISHING THE SKIN.

727

skin is increased by exercise, a rise of temperature, and by any cause
which produces increased vascularity of the skin, such as friction, warm
baths, and electric shocks.1 It is also said to be influenced by food
arid by exposure to light.2

The experiments of Gerlach, Kohrig, and others show that the skin
of animals will absorb carbon dioxide, carbon monoxide, sulphuretted
hydrogen, and the vapour of chloroform and ether.

The effects of varnishing the skin.— The old theory, held by Galen,
Sanctorius, and others, that many diseases were due to the retention of
waste substances which in a normal condition \vould have been dis-
charged from the body, received great support from experiments in
which the skin of animals had been covered by an impermeable layer
of varnish or ointment. At the same time it was held that the results
showed the imperative necessity of cutaneous respiration and perspira-
tion. The symptoms observed after the skin of an animal was varnished
were restlessness, shivering, increased rapidity of breathing and heart-
beat, soon followed by slow respiration and pulse, a fall in temperature
to 20° or 19°, the discharge of albumin in the urine, spasms, and death.
Examination of the body after death showed congestion of the skin,
subcutaneous tissue, muscles, and internal organs.3

The earliest experiments appear to have been made by Fourcault,4
Ducros,5 Becquerel and Brechet,6 Gluge,7 and Magendie.8 The tempera-
ture was observed by Gerlach,9 who obtained the following results for
a rabbit and a horse, after their skins had been covered with a layer of
linseed oil : —

TEMPERATURE BEFORE.

TEMPERATURE AFTER.

REMARKS

Rectal.

Cutaneous.

Rectal.

Cutaneous.

Rabbit

39°7

38°

28°

26°

At time of death,

thirty hours after
varnishing.

Horse .

38°

35°

32°

29°

On the sixth day

after varnishing.

Death on eighth

day.

Edenhuizen 10 showed that death followed even when only one-sixth
of the total cutaneous surface was varnished ; he believed that the
symptoms were due to an alkali which he found in the skin. A further
advance in knowledge was made when Valentin n discovered that the
discharge of carbon dioxide from the lungs was reduced to one-eighth or

1 Gerlach, Aubert, Rohrig, Barratt, loc. tit.

2 Fubini and Roiichi, loc. cit. Here other references will be found.

3 Valentin, Arch. f. physiol. Heilk., Stuttgart, Bd. xi. S. 433.

4 Compt. rend. A cad. d. sc., Paris, Mars 16, 1837.

5 Notiz. a. d. Geb. d. Nat.-u. Heilk., Weimar, 1841, Bd. xix.
0 Arch. gen. de med., Paris, 1841, tome xii. p. 517.

7 Abhandl. z. Physiol. u. Path., Jena, 1841, S. 66.

8 Gas. med. de Paris, Dec. 6, 1843.

9 Arch.f. Anat., Physiol. , u. ivissensch. Med., 1851, S. 431.

10 Nadn\ r. d. k. Gesellscli. d. W-iwiisch. u. d. Georg.-Aiig. Univ., Gottingen," 1861,
S ^88
' u Arch.f. physioL Heilk., Stuttgart, Bd. iu S. 433,

7 2 8 CHE MIS TR Y OF RESPIRA TION.

one-sixth of the normal amount, but that the output of carbon dioxide
was raised to the normal, and death was prevented, when the tempera-
ture of the surroundings was kept at 20°-25°. These observations were
confirmed by Schiff.

The explanation, however, of these experiments was given in 1868,
when Laschkewitsch l showed by calorimetric observations that varnished
animals gave off an abnormally large quantity of heat, that the cutaneous
vessels were dilated and the vasomotor nerves appeared to be paralysed,
that the temperature of the animal fell, and thus caused the character-
istic symptoms and death. When only one limb of a rabbit was
varnished, the temperature under the skin of that part was 34° '5, as
compared with 33°, that of the normal limb ; after one hour, the first
fell to 33°'2, the second to 32°'5. Varnished animals wrapped up in
cotton-wool remained well, and no bad effect was observed when the
body of a normal rabbit was enclosed for six hours in a cylinder filled
with hydrogen, the rabbit breathing through a mask over the nose and
mouth. Laschkewitsch also pointed out that the greater the surface of
the skin in relation to the mass of the body, the sooner death followed
varnishing of the skin. This is shown in the experiments which Gerlach
made upon rabbits and horses, the former dying in thirty hours, the
latter after seven or eight days. The greater the surface in relation to
the mass of the body, the greater is the rate of cooling.

The experiment of varnishing the human body was first made,
according to Laschkewitsch, by the officials of Pope Leo X., who,
wishing during the coronation ceremonies to make a child represent an
angel, gilded the whole of its body ; the child, however, died before it
had fulfilled its part in the ceremony. It is probable that in this
case the gilding contained some poisonous substance. In 1877, Senator2
showed that the whole surface of the human body could be covered with
an impermeable layer, and that even after remaining in this condition
for eight or ten days, no disturbance whatever could be observed ;
no marked change was observed in the temperature, and this explains
the absence of the symptoms which are observed in animals. The
human body has little natural covering arid the most perfect power
of regulating its temperature, conditions which do not obtain in most of
the lower animals.

Extensive but superficial burns of the skin often cause death, and this,
according to some observers, is due to interference with the cutaneous respira-
tion and to retention of waste products, which are normally discharged by the
sweat. There is, however, very little evidence in support of this view, and it
is probable that the fatal result in these cases is due to the following factors —
shock, changes in the plasma and corpuscles of the blood,3 excessive loss of
heat from the hyperaemic skin, and disturbed regulation of temperature, owing
to the absence of the normal sensory impulses from the skin.

Respiration in the alimentary canal.— The quantity and nature of
the gases found in the alimentary canal vary under different circum-

1 Arch.f. Anat., Physiol. u. ivissensch. Med., 1868, S. 61.

'2 Virchoiv* Archiv, 1877, Bd. Ixx. S. 182 ; Arch.f. PhysioL, Leipzig, 1894, S. 178.

3 Max Schultze, Arch.f. mikr. Anat., Bonn, 1865, Bd. i. S. 26 ; Wertheim, Wien. med.
Presse, 1868, No. 13 ; Ponfick, Berl. kiln. Wchnschr., 1877, No. 46 ; Centralbl. f. d. med.
Wissensch., Berlin, 1880, Nos. 11 and 16; Lesser, Firchow's Archiv, 1880, Bd. cxxix.
S. 248 ; Hoppe-Seyler, Ztschr. f. physiol. Chem., Strassburg, 1881, Bd. v., S. 1 and 344 ;
Tappeiner, Centralbl. f. d. med. Wissenscb., Berlin, 1881, Bd. xix. S. 385 and 401.

RESPIRATION IN THE ALIMENTARY CANAL.

729

stances, as is shown by the following table, which gives the results
obtained by Euge1 from the analysis of the gas obtained from the
rectum of the same man under different conditions : —

Gas.

Milk Diet.

Vegetable Diet
for
Four Days.

Animal Diet
for
Three Days.

Oxygen ....

Nitrogen

36-71

18-96

64-41

Hydrogen

54-23

4-03

0-69

Marsh -gas

55-94

26-45

Carbon dioxide

9-06

21-05

8-45

Hydrogen-sulphide

Trace.

...

The distribution of these gases -in the different parts of the aliment-
ary canal was examined by Tappeiner,2 in the body of a criminal, who
had been executed a short time before the examination was made. The
following are the results : —

Gas.

Stomach.

Ileum.

Colon.

Rectum.

Oxygen

9-19

1

\ 67-71

N itrogen

74-26

j

7-46

62-76

Hydrogen .

0-08

3-89

0-46

Marsh-gas .

0-16

0-06

0-90

Carbon dioxide .

16-31

28-40

91-92

36-40

Zuntz, Lehmann, and Hagemann 3 found in the gas drawn off from
the intestine of a living horse about 22 per cent, carbon dioxide, 59 per
cent, marsh-gas, and 2*5 per cent, hydrogen.

These gases have several sources of origin. Oxygen and nitrogen
occur in the air swallowed ; hydrogen, marsh-gas, and carbon dioxide
are formed by the fermentations which take place in the contents of
the alimentary canal; nitrogen and carbon dioxide, under certain
conditions, diffuse from the tissues into the intestines, and carbon
dioxide arises from the neutralisation of the sodium carbonate of the
intestinal secretions. Further details on the origin of these gases will
be found elsewhere ; 4 here it is necessary only to consider the part

1 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1862, Bd. xliv. S. 739.

2 Arb. a. d. path. Inst. zu Miinchen. Stuttgart, 1886, Bd. i. S. 226. See also Planer,
Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1860, Bd. xlii. S. 307 ; Hofmann, Wien. med.
Wchnschr., 1872 : Tappeiner, Ztschr. f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 432 ;
Ztschr. f. RioL, Miinchen, 1883, Bd. xix. S. 228; 1884, Bd. xx. S. 52; Arb. a. d. path.
Inst. zu Miinchen, Stuttgart, 1886, Bd. i. S. 215.

'AArch.f. Physiol., Leipzig, 1894, S. 354.

4 See " Chemistry of Digestion," this Text-book, vol. i.

7 30 CHEMISTR Y OF RESPIRA TION.

some of them play in respiration. The oxygen in the air swallowed is
almost entirely absorbed in the stomach ; the carbon dioxide is gener-
ally 20 to 90 per cent, of the gas present in the intestines, and will
therefore have a partial pressure greater than that of the carbon dioxide
in the blood and tissues, and will diffuse from the intestines into the
blood, to be ultimately discharged in the lungs. As regards the
nitrogen, the quantity present in the alimentary canal is considerable,
but its partial pressure is generally below that of the atmosphere, and
of the tissues, and under these conditions there will be a diffusion of
nitrogen from the blood and tissues into the intestinal tract. It is
important to remember the presence of nitrogen and marsh-gas in the
alimentary canal, for thus it is possib^ to explain those cases in which
an absorption or discharge of nitrogen has been observed during
determinations of the respiratory exchange. When carbon dioxide or
hydrogen-sulphide is injected into the rectum, a portion of the gas is
absorbed and excreted by the lungs.1

Paul Bert 2 observed that a kitten with ligatured trachea lived twenty-one
minutes when a current of air was passed through the alimentary canal,
whereas a kitten of similar age died in thirteen minutes, when the only
operation performed was ligature of the trachea. A similar absorption of
oxygen from the alimentary canal probably takes place in man under special
circumstances ; for swimmers who can remain under water for an exceptional
length of time, state that they swallow air in addition to taking a deep inspira-
tion before a dive.

In warm-blooded animals the alimentary canal plays an unimportant part
in respiration, but this is not the case in some fish, for all the members of the
loach family respire partly by the alimentary canal. The air discharged
under normal conditions from the rectum of Colitis fossilis has the following
composition: 87*18 per cent, nitrogen, 12'03 per cent, oxygen, and 0*79 per
cent, carbon dioxide ; but if the fish be prevented from swallowing air for
several hours, the percentage composition is 91*33 nitrogen, 7 '9 4 oxygen, and
0*73 carbon dioxide.8 Erman4 opened the abdomen of one of these
fish, and noticed that when air was swallowed the intestinal veins and the
liver became bright red, but with hydrogen or nitrogen the colour was, very
dark purple. The mucous membrane of the intestine of Colitis fossilis is,
according to Leydig,5 composed almost entirely of capillary blood vessels, and
a little connective tissue. In the Calliclttliys asper, a fish found in Brazil, the
respiration by the alimentary canal is essential for life, for if the fish be
prevented from coming to the surface of the water to swallow air, it dies
within two hours. The air discharged by the rectum contains 1*5-3*8 per
cent, of carbon dioxide.6

The respiration of the foetus. — The respiration of the foetus was first
understood and described in 1674 by Mayow,7 who in his treatise, "De
Respiratione Foetus in Utero," maintains that the placenta is to be looked
upon as a lung, from which the umbilical vessels take up the nitre-aerial gas

1 Bernard. " Le9ons sur les effets des substances toxiques et medicamen tenses," Paris,
1857, p. 59; Bergeon, Compt. rend. Acad. d. sc., Paris, tome civ. p. 1812; Hanriot and
Richet, Compt. rend. Soc. de biol., Paris, 1887, p. 307 ; Flint, Med. News. Phila., 1887,
vol. li. p. 670.

2 "Physiol. corap. de la respiration," Paris, 1870, p. 173.

3 Baumert, '*Chem. Untersuch. ii. d. Respir. d. Schlammpeitzgers," Breslau, 1855,
S. 24.

4 Ann. d. Phijs. u. Chem., Leipzig, 1808, Bd. xxx. S. 113.

5 Arch. f. Anat., Physiol. u. wissensch. Med., 1853, S. 3.

6 Jobert, Ann. d. sc. nat., Paris, 1877, Zool. (6), tome v., Art. No. 8.

7 "Traetatus Tertius, de Respiratione Foetus in Utero et Ovo," Oxon., 1674.

RESPIRA TION OF THE FCETUS. 731

(oxygen) and carry it to the foetus ; at the same time, he recognises that the
foetus obtains its supply of nutrition in a similar manner. This view of the
foetal respiration was adopted and extended by Hulse,1 and by Ray,2 who
states his view in the following words :— " The maternal blood which flows to
the cotyledons, and encircles the papillae, communicates by them to the blood
of the foetus the air wherewith itself is impregnate ; as the water flowing
about the carneous radii of the fish's gills doth the air that is lodged therein to
them." Mayow's brilliant work was allowed to drop into obscurity, and the
respiration of the foetus was not understood again until the beginning of this
century.

Some physiologists, and among them Leclarc3 and Geoffroy St. Hilaire,4
maintained that the liquor amnii served the purpose of respiration by the skin
of the foetus. Haller,5 Hunter,0 Osiander,7 Autenrieth and Schlitz,8 Emmert,9
Joh. Miiller,10 and E. H. Weber11 stated that no difference could be observed
in the colour of the blood of the umbilical arteries and vein ; on the other
hand, Scheel,12 Herissant and Diest,13 Baudelocque,14 Joerg,15 Jeffray,10 and
Bostock 17 noticed that the blood going from the placenta to the foetus was
of a more arterial hue than that going in the opposite direction, although
there was naturally not so marked a distinction as between the arterial and
venous blood of the adult.

Even as late as 1840 the respiration of the foetus was not under-
stood, for Joh. Miiller,18 the chief physiologist of the time, held that
plasma from the mother passed to the foetus, and so supplied the place
of respiration. Bischoff19 looked upon the placenta as an organ of the
mother, and denied the existence of any special respiration ; this view
was contested by Litzmann,20 who held that the foetus respired by the
placenta. Gradually, owing in a great measure to the work of Schwartz,21
Gusserow,22 and Schultze,23 the truth discovered by Mayow in 1674 was
re-established, and received a final proof when Zweifel,24 following the
suggestion of Hoppe-Seyler, showed in 1876 that the spectrum of
oxyha^moglobin could be clearly seen in the umbilical cord before the
child breathed by its lungs ; that, by taking the precaution to open the
uterus of a pregnant rabbit in warm normal saline solution, and thus

1 Quoted from Ray's book, p. 73.

2 "The Wisdom of God in the Creation," 12th edition, 1759, p. 74.

34367 Quoted from Miiller, "Elements of Physiology," Baly's transL, 1838, vol. i.
pp. 317, 320.

8 "Experimental circa ealorem fetus sangninem ipsius instituta," Tubings, 1799.

9 Arch, f. d. Physiol., Halle, 1811, Bd. x. S. 122.

10 ''De respiratione foetus," Lipsire, 1823, S. 10; " Handbuch der Physiologic," 1840,
Bd. ii. S. 729.

11 Hildebrandt's "Anatomic," Bd. iv. S. 524.

12 " De liquoris amnii aspene arteriae fcfttuum humanoruni natura et usu," Hafnipe,
1799.

13 Haller's " Disputationes," vol. v. pp. 516, 526.

14 Bichat's "Anatomic generale," tome ii. p. 465.

15 "Die Zeugung," Leipzig, 1815, S. 273.
10 "De Placenta."

17 "Physiology," London, 1828, 2nd edition, vol. ii. p. 199.

" Handbuch der Physiologie," 1840, Bd. ii. S. 729. His words are :— " Die von den
Blutgefassen angezogenen Safte dringen sodann direct ins Blut des Fb'tus. Durch diese Art
von Wechselwirkung mit miitterlichen Saften ist bei dem Foetus auch das Athmen ersetzt
oder ein ^Equivalent dafiir gegeben."

" Entwickelungsgeschichte der Saugethiere und des Menschen," 1842, S. 541.

"Ueber die Schwangerschaft," Wagner's "Handworterbuch."

21 " Die vorzeitigen Athembewegungen," Leipzig, 1858.

22 Arch. f. Gynaek., Berlin, Bd. iii.

2y Jenaische Ztschr. f. Med. u. Xatunr., Leipzig, Bd. iv.
24 Arch.f. Gynaek., Berlin, 1876, Bd. ix. S. 291.

732 CHEMISTR Y OF RESPIRA TION.

prevent vigorous contractions of the uterus, the blood in the umbilical
vein of the foetus was brighter than that in the arteries ; and that the
difference in colour of the umbilical vein and arteries disappeared
during asphyxia of the mother, to reappear when artificial respiration
was performed. Pfliiger1 had also noticed that the colour of the
umbilical vein was reddish brown in the normal condition, but became
black during asphyxia.

The results obtained by Zweifel were confirmed and extended by
Zuntz,2 who showed that during asphyxia of the mother the foetal blood
lost oxygen in the placenta, the blood of the umbilical vein becoming
darker than that of the corresponding arteries ; that when the maternal
vessels supplying the placenta were0 compressed the umbilical vein
became as dark as the arteries ; that a foetus respiring air through its
lungs lost oxygen in the placenta, which was left connected with an ex-
cised piece of the uterus ; that during normal breathing of the mother
the umbilical vein coming from the intact placenta contained blood as
red as the arterial blood of the 'uterus, and that movements of the
foetus made the blood of the umbilical arteries darker in colour. Zuntz
maintains that the oxidation taking place in the foetus must be small,
for the difference in the colours of the umbilical arteries and vein is
slight, corresponding to a difference of about 1 per cent, in the amount
of oxygen ; and the foetus can live for a long time upon the oxygen in
its blood, when respiration by the placenta or lungs is prevented.
According to Zuntz's estimate, the human foetus would need daily
0*169 grin, of oxygen per kilo, of its weight, as compared with
14-15 grms., the amount required by an adult.3 Pn tiger4 and
Zuntz found that the blood of the foetus, in comparison with that
of an adult, had a low specific gravity and was poor in corpuscles
and haemoglobin ; these results, however, are opposed to those
of Hayem,5 Hoesslin,6 Sorensen,7 Wiskemann,8 Preyer,9 Denis,10 and
others,11 who found higher values for the foetus than for the
mother.

The difference in the tension of oxygen in the blood of the
umbilical artery of the foetus and the maternal blood is small,
but it is sufficient, owing to the intimate relationship of the
maternal and foetal circulations, to supply the oxygen needed by the
foetus.12

Cohnstein. and Zuntz 13 have analysed the blood of the umbilical
artery of a foetal sheep, which was 53 cm. long, weighed 1535 grms.,

1 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 80.

-Ibid., Bonn, 1877, Bd. xiv. S. 605.

•"•This is contested by Wiener, Arch.f. Gynaek., Berlin, 1884, Bd. xxiii. S. 183. This
paper gives numerous references to the work on the general metabolism of the foetus, but
does not disprove the relatively small oxidation in the foetus.

4 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 61 ; 1875, Bd. x. S. 274.

5 Compt. rend. Acad. d. sc., Paris, 1877, tome Ixxxiv. p. 1166.

6 Ztschr.f. BioL, Munchen, 1882, Bd. xviii. S. 612.

7 Jahresb. u. d. Fortschr. d. Anat. u. PhysioL, Leipzig, 1878, Bd. v. Abth. 3, S. 192.

8 Ztschr.f. BioL, Miinchen, 1876, Bd. xii. S. 434.

9 " Specielle Physiol. des Embryo," Leipzig, 1883, S. 144.

10 Ann. de chim. etphys., Paris, 1842, Ser. 3, tome v. p. 313.

11 Poggiale, Compt. rend. Acad. d. sc., Paris, 1847, tome xxv. p. 112 ; Panum,
Firchoiv's Archil", Bd. xxix. S. 481. See also Cohnstein and Zuntz, Arch.f. d. ges. PhysioL,
Bonn, 1884, Bd. xxxiv. S. 183.

12 Zuntz, ibid., 1877. Bd. xiv. S. 626.

13 Arch.f. d. ges. PhysioL, Bonn, 1884, Bd. xxxiv. S. 206, 231.

RESPIRATION OF THE EMBR YO.

733

and was probably in the last three weeks of iiitra-uteriiie life. The result
was —

Oxygen

Carbon dioxide
Nitrogen

6 '669 volumes per cent.
46-542 „
1-000

Total gas

54-211

Comparative estimations of the gases in the umbilical artery and
vein were also made, and show that the changes undergone by the blood
in the placenta are about one-half as marked as in the lungs of an
adult :—

Oxygen.

Carbon Dioxide.

f Artery

6 '69 vol. p.c.

45'54 vol. p.c. ^ Specimens
of blood

Vein . .

less than 11 '36 ,,

41-82 ,, taken sim-

ultaneous -

Difference .

4-67 ,,

4-72 „ J ly.

Foetal J

Sheep

Artery . .

2-3 „

47.n -\ Sample of
blood from

Vein . .

6-3 „

,Q.K vein taken
" j 24 minutes

^ Difference .

4-0

6.5 after that
" J from artery.

(Difference
Adult J between ven-

8 '15 vol. p.c.

9-2 vol. p.c.

animals l I ous and ar-

l terial blood

From these results Cohnstein and Zuntz calculate that the absorp-
tion of oxygen by a foetal sheep weighing 3600 grms. is 175 c.c. per
minute, or, per kilo, and minute, 049 c.c., which is about one-twelfth the
amount absorbed, weight for weight of body, by a full-grown sheep.

The respiration of the embryo. — The process of respiration in the
embryo has, owing to the natural difficulties of the subject, been chiefly studied
in the eggs of birds and of a few reptiles. The absorption of nitro-aerial gas
(oxygen) through the porous shell of an egg undergoing incubation appears
to have been first recognised by Mayow,2 but the necessity of respiration in
the developing embryo was first shown by the experiments 3 of varnishing
the eggs, covering them with oil or warm water ; under such conditions it was
found that the embryo quickly ceased to develop, and died. If the impervious
covering was only applied to a portion of the shell, the embryo developed, in
some cases normally, in others abnormally with the production of deformities
or monstrosities.4

1 Zuntz, Hermann's " Haiidbucli," Bd. iv. Th. 2, S. 37.
"Tract, quinque," Oxonii, 1674, pp. 131, 313, 321.

3 Paris, Ann. PhiL, London, 1821, N.S., vol. ii. p. 2 ; Home, Phil. Trans., London,
1810, p. 213 ; 1822, p. 339 ; Dareste, Ann. d. sc. not., Paris, 1855, Ser. 4, Zool., tome iv.

L119 ; Compt. rend. Acad. d. sc., Paris, 1855, p. 963 ; Marshall, Med. Times and Gaz.,
ndon, 1840-41, vol. i. p. 242 ; Dusing, Arch. f. d. ge*. PhysioL, Bonn, 1884, Bd.
xxxiii. S. 67. Here other references are given.

4 Gerlach and Koch, BioL CentralU., Erlangen, 1882, Bd. ii. S. 681.

734

CHEMISTR Y OF RESPIRA TION.

In 1834, Theodor Schwann l showed that, when hens' eggs are kept at a
warm temperature in gases containing no oxygen, the germinal membrane
enlarges, and the area pellucida is formed, but no embryo ; eggs would develop
normally in warm air, after they had been in hydrogen for twenty-four hours at
a warm temperature, but not if the exposure to hydrogen had lasted thirty
hours or more.

The first determinations of the respiratory exchange in eggs are due to
Baudrimont and Martin Saint- Anges,2 who showed that the eggs of birds and of
snakes gave off carbon dioxide during incubation, and that the embryos of
frogs died if placed in water free from air. The quantitative results obtained
by these observers are not trustworthy, owing to the defective methods of gas
analysis then in use. The first reliable determinations are those made by
Baumgartner 3 throughout the period of i^ubation of hens' eggs. The follow-
ing table gives some of the results : —

Loss OF WEIGHT OF EGG.

DISCHARGE OF CARBON*
DIOXIDE.

ABSORPTION OF OXYGKX.

INCUBATION.

From the

commencement of
incubation.

On the day in
question.

For one
egg-

For one kilo,
of eggs.

For one
egg.

For one kilo,
of eggs.

Gnus.

Grins.

Grins.

Grins.

Grins.

Grins.

1

...

0-125

0-009

0-16

0-0074

0-13

9

1-853

0-164

0-048

1-01

0-0360

0-76

20

10-479

0-212

0-560

18-93

0-4435

14-90

21

1-008

0-7317

(chick free)

Similar experiments were made by Pott and Preyer,4 who found that a fertile
egg, weighing 50 grms., lost in weight about 10*27 grms. during incubation, an
unfertile one 9 '70 grms., and an egg kept at the temperature of an ordinary
room 1*66 grms., in twenty -one days. The respiratory exchange of a developing
embryo in an egg weighing 50 grms. was, for periods of twenty-four hours : —

Day of Incubation.

Discharge of Carbon Dioxide.

Absorption of Oxygen.

7

Grms.
0-09

Grms.
0-09

13

0-24

0-24

21

0-86

0-68

Pott 5 also showed that the development of the embryo is not hastened or
delayed if the egg is incubated in an atmosphere of oxygen. During incuba-
tion, it has been proved that the temperature of the embryo, owing to its meta-
bolism, is slightly warmer than the temperature of its surroundings.6

1 Arch.f. Anat., Physiol. u. wissensch. Med., 1835, S. 121.

2 Compt. rend. Acad. d. sc., Paris, 1843, tome xvii. p. 1343 ; Ann. de chim. et phys.,
Paris, 1847, Ser. 3, tome xxi. p. 195.

3 " Der Athmungsprozess im Ei," Freiburg im B., 1861.

4 Arch.f. d. ges. Physiol., Bonn, 1882, Bd. xxvii. S. 320.

5 Ibid,, 1883, Bd. xxxi. S. 268.

6 Barensprimg, Arch. f. Anat., Physiol. u. wissensch. Med., ]851, S. 126. See also
" Animal Heat," this Text-book, vol. i.

RESPIRA TION OF DIFFERENT GASES. 735

In connection with the respiration of the embryo chick, it is interesting to
find that the air contained in the air chamber of the egg has been stated to
have a greater percentage of oxygen than that present in the atmosphere.
Thus Eischof l found 23*475 volumes per cent, as the mean of four analyses, and
Dulk 2 obtained in one case 25 '26, in another case 26*77 per cent, of oxygen.
Hiifner,3 however, has repeated and extended these observations, and found
the following composition in the air removed from twelve eggs, unincubated,
and a few weeks old: — Oxygen 18*94, nitrogen 79 '97, and carbon dioxide 1'09
volumes per cent.; and in the case of two goose eggs, incubated for sixteen
days, oxygen 19 '58 and 19*85, nitrogen 79*55 and 78*62, carbon dioxide 0*87
and 1*53 volumes per cent.; these eggs showed no trace of an embryo.
Experiments were also made upon the rate of diffusion of gases through the
egg-shell and the shell-membrane, and it was found that the rates of diffusion
of the different gases did not follow Graham's law ; they were not inversely
proportional to the square roots of the densities of the several gases.

During the period of incubation of a chick the gradual development of the
power of heat regulation can be traced. At first the embryo responds to
changes in external temperature by a similar change in its respiratory ex-
change— a fall of temperature causes a decrease, a rise of temperature an
increase, in the respiratory exchange ; then for a short time there is an inter-
mediate condition in which a change of temperature has no marked effect ; and,
lastly, when the chick is hatched, it responds as a warm-blooded animal.4

If tadpoles and larvae of salamanders (Salamandra maculata) be prevented
from coming to the surface of the water, their metamorphosis is greatly
prolonged, and if well fed they will live for a long time as purely aquatic
animals.5

THE EESPIRATION OF DIFFERENT GASES.

Some gases, such as hydrogen and nitrogen, have no specific effect
when they are respired, and animals supplied with these gases alone die
simply from want of oxygen. Other gases, such as carbon dioxide, carbon
monoxide, nitrous oxide, and hydrogen sulphide, can be taken into the
lungs, and if present in sufficient quantity are absorbed, and produce
specific effects ; while a third class, such as ammonia and nitric oxide,
are irrespirable on account of their irritant action producing spasm of
the glottis.

Oxygen. — Soon after his re-discovery G of oxygen in 1774, Priestley 7
observed, both upon himself and upon animals, the effect of breathing
the pure gas ; in his own case he felt an agreeable facility of respiration,
and in animals he found that oxygen had a greater power than air in
supporting life. These experiments were repeated by Lavoisier,8
Higgins,9 Dumas,10 Beddoes,11 H. Davy,12 Allen and Pepys,13 and in some

1 Journ. f. Chem. u. Phys., Niirnberg, 1823, Bd. xxx. S. 446.

2 Ibid.. Halle, 1830, Bd. Iviii. S. 363.

8 Arch. f. PhysioL, Leipzig, 1892, S. 467.

4 Pembrey, Gordon, and Warren, Journ. Physiol., Cambridge and London, 1894, vol.
xvii. p. 331 ; Pembrey, ibid., 1895, vol. xviii. p. 361.

5 Preyer, "Specielle Physiologie des Embryo," Leipzig, 1885.

6 Mayow can rightly claim to have discovered oxygen before 1674. See his "Tractatus
qiiinque."

7 "On Air," vol. ii. p. 162.

8 Mem. Soc. Roy. Med., 1782, tome iii. p. 576 ; Hist. Acad. roy. d. sc., Paris, 1789, p. 573.

9 "Minutes of 'a Society, etc.," London, 1795, p. 144.

10 « Physiologie," Paris, 1806, 2nd edition, tome iii. p. 59.

11 "On Factitious Airs," Bristol, 1796, part i. p. 13. 12 "Researches," p. 439.
13 Phil. Trans., London, 1808, pp. 266 and 280 ; 1809, pp. 415 and 427.

736 CHEMISTR Y OF RESPIRATION.

cases irritant effects, probably due to the presence of impurities in the
gas, were noticed.

Considerable discussion has arisen concerning the effect of an in-
creased percentage of oxygen in the air breathed upon the respiratory
exchange. Is there or is there not an increase in the absorption of
oxygen and the discharge of carbon dioxide under these conditions ?
Many observers l maintain that there is a distinct augmentation of the
metabolism of the body, others2 find that the respiratory exchange of a
normal animal is the same in amount, whether it breathes air or pure
oxygen. Without entering into a discussion of the numerous con-
tradictory answers to this question, it is permissible to draw the
following conclusions : — The normal animal does not increase its
respiratory exchange when it breathes oxygen instead of air, for its
metabolism is regulated by the needs of its tissues, and not directly
by the amount of oxygen absorbed in the lungs ; in the case of some
diseases, during which the blood, owing to diminished absorption of
oxygen in the lungs, is abnormally venous, the breathing pure oxygen
would increase the percentage of oxygen in the alveolar air, and thus
enable the blood in the lungs to take up more oxygen. In these cases
breathing oxygen under pressure greater than that of the oxygen in
the air would, for a similar reason, be effective, and would also in-
crease the amount of oxygen simply dissolved in the plasma. It
would appear, therefore, that there is strictly no contradiction in
most of the experimental and clinical results, for in the normal
animal breathing ordinary air the arterial blood is almost .saturated
with oxygen, and without doubt contains as much or more oxygen
than the tissues need. This is certainly not the case in some dis-
eases, during which the patients have derived benefit from breathing
oxygen.3

In connection with the respiration of pure oxygen or of air, Paul
Bert 4 made the important discovery that animals exposed to a pressure
of oxygen above six atmospheres died in violent convulsions. This
result is not due to the purely physical effects of the increased pressure,
but to the augmentation in the tension of oxygen, for if the experiment
be made with air, a greater and greater pressure can be borne, until

1 Allen and Pepys, Phil. Trans., London, 1808, pp. 266 and 280; 1809, pp. 415 and
427; Paul Bert, "La pression barome'triqne," Paris, 1878, p. 832. Further references are
given by Phillips, "Materia Medica, Pharmacology, and Therapeutics — Inorganic Sub-
stances," London, 1894, 2nd edition, p. 2.

2 Lavoisier and Sequin, Hist. Acad. roy. d. sc., Paris, 1789, p. 566 ; Regnault and Reiset,
Ann. de chim. ctphys., Paris, 1849, Ser. 3, tome xxvi. ; Dohnien, " Arb. d. Bonner physiol.
Inst.," 1865 ; Speck, Arch. f. d. ges. Physiol., Bonn, 1879, Bd. xix. S. 171 ; Kempner,
Arch. f. Physiol., Leipzig, 1884, S. 396; Lukjanow. Ztschr. f. physiol. Chem., Strassburg,
1883-84, Bd. viii. S. 313 ; Arch. f. Physiol., Leipzig, 1884, S. 308. See also references
given by Phillips, loc. cit. supra.

3Ransome, Med. Chron., Manchester, April 1888, May 1889 ; A. H. Smith, "Oxygen
Gas as a Remedy in Disease," New York, 1870, 2nd edition ; W. G. Thompson, Practi-
tioner, London, 1889, vol. xliii. p. 97. At the end of this article is a list of thirty-two
papers on the subject. See also article "Oxygene" in " Dictionnaire de therapeutique, de
matiere medicale, de pharmacologie, de toxicologie et des eaux minerales, " par Dujardin-
Beaumetz, Paris, 1889, tome iv. p. 101. See also Phillips, loc. cit. supra, and references
there given.

4 Paul Bert, "La pression barometrique, " Paris, 1878, p. 800. See also Lehmann,
Arch. f. d. ges. Physiol., Bonn, 1884, Bd. xxxiii. S. 173 ; Liebig, Arch. f. Physiol.,
Leipzig, 1889, Supp. Bd. S. 41; A. H. Smith, "The Effects of High Atmospheric
Pressure, including the Caisson Disease," Brooklyn, 1873 ; Philippon, Journ. de Tanat. et
'I. etc., Paris, 1894, tome xxx. pp. 296, 414.

RESPIRATION OF DIFFERENT GASES.

737

a point is reached at which the partial pressure of oxygen becomes
dangerous to life. When the arterial blood contains a third more than
its normal quantity of oxygen, the metabolism of the body diminishes
greatly, and the animal dies. The following examples will illustrate
this effect : —

Duration of the
Compression.

Pressure in
Atmo-
spheres.

Pressure of
Oxygen
in Atmo-
spheres.

Percentage Composition
of Gases of Blood.

Rectal
Tempera-
ture.

Remarks.

OxP

20'9

O2.

C02.

Air.

14-9

31-1

38° -5

If

7

21-4

34-3

45 min.

7

25

32-5

73-8

Dog ;

convulsions;

Free air 27

...

16-9

21-0

39° -0

survived.

min. after.

Free air 67

17-0

31-5

min. after.

.

Air.

...

19-8

20-9

38° "5

Oxygen.

4'4

20-9

34-5

65 min.

^Dog;

6

24

26-3

63-5

death.

9

35

30-7

61-5

...

j

Air.

{Sparrow ;
convulsions;

5

21

...

...

33°

death in 30

min.

Air.

8'5

21-5

{Sparrow ;
convulsions
death in 20

min.

The practical importance of these experiments in connection with the symp-
toms observed in men after working in caissons is obvious. Details of numer-
ous cases are given by Paul Bert 1 and others,2 but here it is sufficient to draw
attention to the chief symptoms and changes observed in men working in
compressed air. The earliest and most constant symptom is pain and noise in
the ears, due to the pressure upon the tympanum ; relief is generally obtained
by swallowing, or by a forced expiration with closed nose and mouth ; in some
cases, however, the tympanum has been ruptured. The respiration is slower
and deeper. The danger to life, however, chiefly occurs when the workmen
leave the caisson and come out into the fresh air ; the symptoms then observed
are due to the relative fall in atmospheric pressure, and are chiefly these —
very painful itching of the skin, painful swelling of the muscles and joints,
disturbances in locomotion and sensation, paralysis of the lower limbs,
bladder, and rectum, and more rarely extensive paralysis, unconsciousness,
and sudden death.

1 Loc. cil., p. 369.

2 See ref. given by Paul Bert, loc. cit. ; E. H. Snell, "Compressed Air Illness or so-
called Caisson Disease," London, 1896 ; Heller, Mager, Schrotter, Centralbl. f. PhysioL,
Leipzig u. Wien, 1896, No. 2, S. 40 ; Friedrich and Tauszk, Wien. klin. fiundschau, 1896,
S. 233.

VOL. I.— 47

738 CHEMISTR Y OF RESPIRA TION.

It is impossible to discuss here the different theories l brought forward to
explain the symptoms, but it appears that the most probable explanation is
that given by Bucquoy,2 who maintains that the sudden fall in pressure sets
free the excess of gases dissolved in the blood during the exposure to the
compressed air of the caisson. These particles of gas in some of the small
blood vessels would cause embolism, and this would especially affect the nervous
system. Great support is given to this theory by the fact that workmen rarely
suffer when the change from the compressed air to the open air takes place
gradually by a slow fall in pressure, and that the most effective treatment for
the more serious symptoms is the subjection of the patient to compressed air.
This treatment 3 has been carried out in cases occurring among the workmen
employed in the construction of the Blackwall Tunnel under the Thames.

In experiments upon animals, Paul Bert 4 found that the production
of carbon dioxide was diminished both when the animal was exposed
to a high or to a low atmospheric pressure. Lowy, however, observed
no alteration in the respiratory exchange of man, until the pressure of
the air fell below 300 mm. There was then an increase in the discharge
of carbon dioxide, but no corresponding increase in the intake of
oxygen.5

A gradual fall in the atmospheric pressure acts upon animals only
by decreasing the tension of the oxygen in the air, for, if the percentage
of oxygen be raised, a lower pressure can be borne. In air, discomfort
is felt when the pressure is reduced to half an atmosphere, and the
symptoms become violent with a pressure of 250 mm. ; convulsions,
insensibility, and death supervene. The limit of pressure appears to be
about 200 mm. Such are the results obtained by Paul Bert 6 during
experiments upon animals, and they agree with those observed upon man
during balloon ascents. Thus during the ascent of the Zenith 7 to a
height of 8600 metres, Sivel and Croce-Spinelli died, Tissandier became
unconscious, but recovered during the descent ; the pressure at that
height would correspond to 260 mm., and the tension of oxygen to 52
mm. According to Paul Bert's observations, the oxygen in the arterial
blood would be reduced to 10 volumes per cent.

Many theories have been put forward to explain the symptoms of
" mountain sickness," but the true one appears to be that of Jourdanet, who
maintains that it is due to a condition of anoxyhsemia, a want of sufficient
oxygen in the blood.8 In these cases the absorption of oxygen by the blood
would, at the low pressure of the atmosphere, be insufficient for the needs of the
tissues of a man or animal engaged in the exertion of climbing. It has been
objected9 that this explanation is incorrect, because there appeared to be no
decrease in the amount of oxygen in the blood of dogs, which were subjected
by Frankel and Geppert to a reduced pressure, equal to that of an altitude of

1 For further details, see Paul Bert's work, loc. cit., p. 520.

2 " De 1'air comprimey' 1861. 3 Snell, loc. cit.

4 Loc. cit., pp. 727, 805.

5 For observations upon the effect of reduced atmospheric pressure on respiration, see
G. v. Liebig, Milnchen. med. Wchnschr., 1891, Bd. xxxviii. S. 437 ; Lowy, Arch. f.
Physiol., Leipzig, 1892, S. 545; Speck, Ztschr. /. klin. Med., Berlin, Bd. xii. S. 447.

6 " La pression barome'trique," Paris, 1878, p. 735.

7 Paul Bert, loc. cit., p. 1061 ; Tissandier, Nature, Paris, 1875, p. 337.

8 A full discussion will be found in Paul Bert's work, loc. cit., p. 327. See also Clifford
Allbutt, "System of Medicine," London, 1897, vol. iii. p. 456. For the effects of high
altitudes upon the number of coloured blood corpuscles, see article on " Blood," p. 150.

9 Grawitz, Berl. klin. Wchnschr., 1895, S. 713 and 740.

CARBON DIOXIDE. 739

16,000 feet. This may be so during rest, but it is probable that, on exertion,
the slower rate of absorption would lead to a deficiency in oxygen ; the organism
accommodates, not for a condition of rest, but for exertion also ; it has a reserve
store of energy. Thus, a man with marked anaemia, when he is at rest, absorbs
as much oxygen and produces as much carbon dioxide as a healthy man at
rest, but, directly marked exertion is necessary, the anaemic subject becomes
breathless ; he has no reserve upon which to draw during the greatly aug-
mented metabolism which accompanies muscular work.

Nitrogen. — This gas appears to be quite inactive, and an animal
confined in it dies from want of oxygen. The same seems to be true
for argon. Nitrogen containing 5 per cent, oxygen was found by Sir
George Johnson x to produce satisfactory anaesthesia in man within a
minute ; this result is also to be attributed to want of oxygen.

The question of the absorption or discharge of nitrogen by the lungs
has been discussed in another part of this work.

Hydrogen. — Numerous experiments have been made upon the
effects of respiring hydrogen, and the general conclusion is that it
produces no specific effect, but acts only by the exclusion of oxygen.2
Lavoisier and Seguin found that guinea-pigs respired in a normal
manner in a mixture of equal parts of oxygen and hydrogen, and similar
results were obtained upon dogs, rabbits, and frogs by Eegnault and
Reiset. Many cold-blooded animals can live for several hours in pure
hydrogen.3

Carbon dioxide. — This gas in an undiluted state is irrespirable on
account of the spasm of the glottis which it occasions,4 but when suffi-
ciently diluted with air or oxygen it can be respired, and produces head-
ache, slight giddiness, drowsiness, and hyperpncea. Some of the earliest
experiments with this gas were made by Priestley,5 who found that cats
died from suffocation when placed in carbon dioxide, and butterflies when
held over the fermenting liquor in a brewery became motionless in a few
minutes, but revived on being brought into the fresh air. Since that
time numerous experiments have been made by different observers,6
especially by Paul Bert, whose results will be mentioned later. Brown-
Sequard and d'Arsonval7 state that they were able to breathe air
containing 20 per cent, of pure carbon dioxide for two hours without
any marked distress, but it is probable that there was some error in this
observation, for Haldane and Lorrain Smith 8 found that when they
breathed air containing 18*6 per cent, of this gas the following effects
were produced within a minute or two — hyperpnoea, distress, flushing,
cyanosis, and mental confusion. Haldane 9 has further investigated this
gas in connection with the suffocative gas found in wells and the
" black-damp " of mines.

1 Lancet, London, 1891, vol. i.

2 Scheele, "On Air and Fire," trans, by Forster, London, 1780, p. 160; Fontana,
Phil. Trans., London, 1779, vol. Ixix. p. 337 ; Journ. de phys., Paris, tome xv. p. 99 ;
Pilatre de Rozier, ibid., tome xxviii. p. 425 ; Lavoisier, Hist. Acad. roy. d. sc., Paris, 1789,
p. 574; H. Davy, "Researches," p. 465 ; Allan and Pepys, Phil. Trans., London, 1809,
p. 421.

3 Spallanzani, Edwards, Johannes Miiller. See this article, p. 781.

4 Pilatre de Rozier, Journ. dephy*., Paris, tome xxviii. p. 422.

5 Phil. Trans., London, 1772, vol. Ixii. p. 147.

6 For references, see Benedicenti, Arch. f. PhysioL, Leipzig, 1896, S. 408.

7 Compt. rend. Acad. d. sc., Paris, 1889, llth Feb.

8 Journ. Path, and Bacterial., Edin. and London, 1892, vol. i. p. 175.

9 Trans. Fed. Inst. of Mining Engineers, 1895, vol. viii. p. 549. "The Causes of Death
in Colliery Explosions," Government Blue Book, 1896.

740 CHEMISTR Y OF RESPIRA TION.

Speck1 found, when he breathed a mixture of gases containing 11 '51
per cent, of carbon dioxide, that 528 c.c. carbon dioxide were absorbed by
the blood in a minute, whereas under normal conditions 230 c.c. of that
gas would have been discharged. "In a dog Pfliiger 2 found that there
were, under normal conditions, 29'8 volumes per cent, carbon dioxide 8
in the arterial blood, but 56*8 volumes per cent, after the dog had
breathed for one minute a mixture containing 70 per cent, oxygen
and 30 per cent, carbon dioxide. Zuntz 4 observed an increase to
8 9 '6 volumes per cent, carbon dioxide when a dog breathed for one
minute and a half a mixture containing 36*9 per cent, carbon dioxide.

Numerous experiments were made by Paul Bert 5 upon the action of
this gas upon different forms of life. He found that a percentage of 13 '5
to 17 was fatal for reptiles, 24 to 28*for sparrows, and 30 or more for
mammals. When the air contained 30 to 40 per cent, of carbon dioxide,
death resulted owing to the high tension of the gas in the blood ; thus in
some dogs the percentage of carbon dioxide in the arterial blood was
116, in the venous blood 120. Complete insensibility could be produced
long before any danger to life arose, and thus the gas mixed with air
or oxygen could be used for the production of anaesthesia.6

Carbon monoxide. — The physiological action of this gas is of the
utmost practical importance, since it is every year the cause of
numerous deaths in cases of poisoning from coal gas, the fumes of kilns
and coke fires, and in the air of coal mines, especially after explosions.
Although it has long been known that carbon monoxide is poisonous,
it was about the year 1857 that Claude Bernard7 and Hoppe-Seyler 8
first pointed out that the carbon monoxide displaced the oxygen of
the blood by forming a more stable compound with haemoglobin, and
thus brought about asphyxia.9 The action of this gas has been studied
by many observers.10

The most recent investigations are those of Haldane,11 who has
experimented both upon himself and upon mice. The following are his
chief conclusions : — The symptoms produced in man do not become
sensible until sufficient carbonic oxide has been absorbed for the
corpuscles to become about a third saturated ; with half saturation of
the corpuscles the symptoms become urgent. The symptoms are due
solely to deficiency in the percentage of oxygen in the blood, and are
similar to those experienced by mountaineers and balloonists at high
altitudes. The time required for the symptoms to appear in different
animals is proportional to the respiratory exchange per unit of body weight,
and is about twenty times as long in a man as in a mouse. Hence
it is possible with safety to use a mouse as an indicator of the presence
of poisonous proportions of carbonic oxide in the atmosphere of a coal-

1 CentralU.f. d. med. Wissensch., Berlin, 1876, No. 17.

2 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 103.

3 Measured at 0° and 1 m.

* Arch.f. d. ges. PhysioL, Bonn, 1888, Bd. xlii. S. 408.

5 "La pression barometrique, " Paris, 1878, p. 982. This article, pp. 743-45.

6 See also Gre"hant, Compt. rend. Soc. de Uol., Paris, 1887, p. 542.

7 "Le9ons sur les effets des substances toxiques et me'dicamenteuses," Paris, 1857, p.
184 ; " Lecons sur les liquides de Porganisme, " Paris, 1859, tome i. p. 365 ; tome ii. p. 427.

8 Virchows Archiv, Bd. xi. S. 228 ; Bd. xiii. S. 104.

9 This Text-book, article "Haemoglobin."

10 Gaglio, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1887, Bd. xxii. S. 233 ; Gruber,
Arch.f. Hyg., Munchen u. Leipzig, 1883, Bd. i. S. 145; Welitschkowsky, ibid., S. 210;
Fokker, ibid., S. 503 ; Gre"hant, "Les poisons de 1'air," Paris, 1890.

11 Journ. PhysioL, Cambridge and London, 1895, vol. xviii. p. 430.

AIR VITIATED BY BREATHING.

74i

mine. Distinct symptoms are produced by air containing -05 per cent,
of the gas, and urgent symptoms with '2 per cent. The poisonous
action diminishes as the tension of oxygen increases, and vice versd. At a
tension of two atmospheres of oxygen this poisonous action is abolished
in the case of mice, and this disappearance of the poisonous action is
due to the fact that at high tensions of oxygen the animals can dispense
entirely with the oxygen-carrying function of haemoglobin, and can
obtain enough oxygen from the gas dissolved in the plasma of the
blood.

As regards the gases of the blood, after poisoning with carbon
monoxide, Grehant 1 found that 100 c.c. of blood from the carotid of a
poisoned dog contained 6 c.c. of oxygen, 30*3 c.c. of carbon dioxide, and
20 c.c. of carbon monoxide ; whereas a sample of blood taken before the
administration of the gas yielded 19*5 c.c. of oxygen and 44'2 c.c. of
carbon dioxide. The following figures show the effect of different doses
of carbon monoxide upon the gases of the blood of dogs poisoned by the

GASES OF BLOOD.

CO IN INSPIRED AIR.

C02.

02.

N.

CO.

1 in 1000 .

28 '9 p. ct.

12 '2 p. ct.

1 -5 p. ct.

5 '5 p. ct.

1 ,. 2000 .

51-8 „

15'5 „

1-5 „

2-8 „

1 ,, 3000 .

42-2 ,,

13-4 „

1-8 „

1-7 „

1 „ 4000 .

40-4 „

21-5 „

1-5 „

1-3 „

The administration of small doses of carbon monoxide, enough to
produce unconsciousness, causes a marked reduction in the respiratory
exchange 2 of a mouse, and its temperature falls.

According to Gaglio,3 carbon monoxide present in the blood is not
oxidised, but St. Martin4 states that it is slowly oxidised in the
presence of oxyh^moglobin. The compound of this gas with haemo-
globin is partly dissociated in sunlight,5 but upon these points more
details will be given in the discussion upon the gases of the blood.

The respiration of air vitiated by breathing.— The air vitiated
by respiration, as in overcrowded rooms, is distinctly unwholesome, but
the causes of this deleterious action are not simple, but may arise from
substances given off either from the lungs by respiration, from the body
by perspiration, or from the injurious products of disease or filth.

Even as early as 1674, Mayow6 had stated that an animal died if
kept in a limited quantity of air, because it had used up the respirable
portion, the nitro-aerial gas (oxygen) ; he further pointed out that re-
spiration and combustion produced similar changes in the air. About
the year 1726, Stephen Hales 7 observed by experiments upon himself

1 Compt. rend. Soc. de biol., Paris, 1892, p. 163.

2 Haldane, Journ. PhysioL, Cambridge and London, 1895, vol. xviii. p. 430.

3 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1887, Bd. xxii. S. 233.

4 Compt. rend. Acad. d. sc., Paris, 1891, tome cxii. p. 1232.

5 Haldane, loc. cit.

" Tractatus quinque," Oxonii, 1674.
7 "Statical Essays," 2nd edition, vol. i. p. 2

236 et seq.

742 CHEMISTR Y OF RESPIRA TION.

that the " noxious vapours " produced by repeatedly breathing the same
air could be removed by potash, and the air rendered fit for respira-
tion. A few years later, Black l showed that the " noxious vapours "
were carbon dioxide.

The importance of the several factors mentioned above has been differ-
ently estimated by various observers.2 Brown-Sequard and d'Arsonval 3
concluded that volatile poisons were given off from the lungs of healthy
men and animals, for they found that the condensed vapour of breath
caused death when injected into rabbits ; that rabbits made to breathe
air vitiated by the respiration of other rabbits until the carbon dioxide
was 2 to 6 per cent., died, unless the supposed volatile poisons were
removed by previously passing the aif over pumice soaked in sulphuric
acid; that no bad effects were produced when men breathed for an
hour or two air containing 20 per cent, of pure carbon dioxide.
The experiment of injecting the condensed vapour of breath has been
repeated by Dastre and Loye,4 Hoffmann- Wellenhof,5 Lipari and Crisa-
fulli,6 and Lehmann and Jessen,7 but the results were negative.

Eichardson 8 maintained that breathed air was poisonous, even though
all the carbon dioxide and other impurities had been removed ; the cause
he considered to be " devitalised oxygen," whatever that term may mean.
Jackson 9 thought that carbon monoxide was the poison. From experi-
ments performed upon himself, Angus Smith 10 concluded that air vitiated
by respiration until it contained 1 per cent, carbon dioxide, produced
distinct feelings of discomfort.

Experiments, however, performed by Hermans n have shown that
no volatile poisons are given off by respiration, and more recently
Haldane and Lorrain Smith,12 in an investigation of the subject, both
as regards animals and men, have confirmed and extended Hermans'
work. The following are the chief conclusions given by Haldane and
Lorrain Smith : —

" 1. The immediate dangers from breathing air highly vitiated by
respiration arise entirely from the 'excess of carbon dioxide and
deficiency of oxygen, and not from any special poison.

" 2. The hyperpncea is due to excess of carbon dioxide, and is not
appreciably affected by the corresponding deficiency of oxygen. The
hyperpnrea begins to appear when the carbon dioxide rises to from
3 to 4 per cent. At about 10 per cent, there is extreme distress.

" 3. Excess of carbon dioxide is likewise the cause, or at least one
cause, of the frontal headache produced by highly vitiated air.

" 4. Hyperpnoea from defect of oxygen begins to be appreciable when
the oxygen in the air breathed has fallen to a point which seems to

1 "Lectures on Chemistry," ed. Robison, Edinburgh, 1803.

2 See Merkel, Arch. f. Hyg., Miinchen u. Leipzig, 1892, Bd. xv. S. 1, where further
references are given.

3 Compt. rend. Acad. d. sc., Paris, 1888, tome cvi. pp. 106, 165 ; Comyt. rend. Soc. de
bioL, Paris, 1887, p. 814 ; 1888, pp. 33, 90, 99, 151.

4 Ibid., 1888, pp. 43 and 91.

5 Wien. klin. Wchnschr., December 13, 1888.

6 Butt. gen. de therap. etc., Paris, 1889, No. 46, p. 524.

7 Arch.f. Hyg., Miinchen u. Leipzig, 1890, Bd. x. S. 367.

8 Brit. Med. Journ., London, 1860, vol. ii. ; Chem. News, London, vol. Iv. p. 253.

9 "Proc. Physiol. Soc.," December, 1887, in Journ. PhysioL, Cambridge and London,
vol. ix.

10 "Air and Rain," p. 130.

11 Arch.f. Hyg., Miinchen u. Leipzig, 1883, Bd. i.

12 Journ. Path, and Bacterial., Edin. and London, 1892, vol. i. p. 175.

ASPHYXIA IN A LIMITED QUANTITY OF AIR. 743

differ in different individuals. In one case the hyperpnoea became
appreciable at about 12 per cent., and excessive at about 6 per cent."

These observers also point out that the odorous substances arising
from want of cleanliness of the body or the room, are also causes of the
discomfort experienced in breathing the air of an overcrowded room.

The causes of asphyxia in a limited quantity of air.— A
warm-blooded animal confined in a limited quantity of air soon gives
signs of discomfort ; it becomes restless, breathes more rapidly, and
soon pants for breath. This stage is succeeded by one during which
the animal is quieter, breathes more slowly but more deeply ; it becomes
less sensitive, and falls down ; agonising efforts are made to breathe, the
nostrils are dilated, and the mouth is open. The animal now becomes
unconscious, its pupils are dilated, it gives a few slight and irregular
respirations, it is seized by convulsions, and then, after a slight pause, its
limbs are stretched out with a convulsive shivering movement, its head
is thrown back, and it dies.

The general phenomena of asphyxia are described elsewhere in this
work ; l here it is necessary to consider only the chemical changes in the
air, the alterations they produce in the respiratory exchange of the
animal, and how they cause its death. Upon these questions numerous
experiments have been made.2

The duration of life in a limited quantity of air depends upon
various conditions, such as the amount and temperature of the air, the
nature and age of the animal. The following table of some of Paul
Bert's experiments will illustrate the influence of some of the above con-
ditions, and will show the composition of the air at the time of death : —

Animal.

Tempera-
ture of Air.

Volume
of Air.

Duration of Life.

Percentage Composi-
tion of Air at the
time of Death.

O2.

002.

MAMMALS —

Cat, 1850 grms.

25°

5000 c.c.

25 min.

3-4

17-1

Kitten, 5 days old, 130

15°

1000 ,,

4£ to 6| hrs.

2'0

16-6

grins.

Kitten, 24 hours old, 125

11°

435 „

1 hr. 15 min.

3-0

14-8

grms.

Hedgehog, young, 115

25°

1500 ,,

1 hr. 15 min.

4-0

14-0

grms.

Dormouse, hibernating,

12°

350 ,,

About 1 day

2-2

14-6

50 grms.

Rat, white, 115 grms. .

14°

450 ,,

32 min.

3-0

11-0

,, 125 „

25°

1600 „

Between 2 and

2'2

17-8

3 hrs.

,, ,, adult

30°-35°

2000 ,,

20 min.

11-8

6-5

,, three days old,

25°

100 „

More than 6 hrs.

0-75

17'0

5 grms.

Rabbit, young, 200 grms.

25°

6000 ,,

Alive but insensi-
ble after 6 hrs.

1-9

13-4

BIRDS —

Sparrow, 23 grms.

16°

300 ,,

Ihr.

2-3

13-3

Finch, 25 grms.

11°

428 „

21 min.

5-0

12-4

1 Article " Mechanism of Respiration," this Text-book, vol. ii.

2 Edwards, " De 1'influence des agens physiques sur la vie," Paris, 1824; Collard de

744

CHEMISTR Y OF RESPIRA TION.

Before any conclusions are drawn from the results given in the
foregoing table, it will be advisable to consider the cause or causes of
death in these cases of asphyxia. Do the animals die from a want of
oxygen, or are they poisoned by the accumulation of carbon dioxide ?
In order to answer this question, experiments have been made on the
duration of life of animals confined in air containing an excess of
oxygen, or an excess of both oxygen and carbon dioxide. Many
observations have been made by various physiologists, but the most
complete are those of Paul Bert.1 The following table gives some of
his results : —

An Atmosphere containing an Excess of Oxygen.

Animal.

Tempera-

Volume of

Percentage
Composition of
Gases before,
the Experiment.

Duration of Life.

Composition of
Gases at the
time of Death.

ture of

Gases.

Gases.

Oo.

N.

CO2.

0,.

WARM-BLOODED —

Cat, young, 250

25°

1800 C.C.

55-5

44-5

3 hrs. 25 min.

31

16

grms.

Rat, adult, 80

14°

500 ,,

77

23

1 hr. 45 min.

20

50

grms.

Rat, 6 weeks old,

25°

555 ,,

66

34

2 hrs.

29-5

26

50 grms.

Rat, 4 days old .

22°

120 ,,

81

19

18 hrs. 30 min.

28-5

Rabbit, young,

22°

1400 ,,

71

29

More than 5 hrs.

43-5

11

200 grms.

Sparrow, young

25°

750 „

76

24

More than 5 hrs.

29

COLD-BLOODED —

Grass snake

875 ,,

77

23

8 days

13-5

61

Grey lizard
Toad 1

27°-29°

6°-7°

570 ,,
400 ,,

79
100

21

70 hrs.
7 days

15-7
17

81

Frogs .

6°-7°

400 ,,

100

9 days

137

8

A consideration, of the following results leads to the conclusion, held
by Mayow 2 as early as 1674, that a warm-blooded animal confined in a
limited quantity of air dies from the want of oxygen, and this con-
clusion is supported by the fact that its blood is markedly venous
and contains little or no oxygen. The percentages of oxygen and of
carbon dioxide in the air at the time of death are about 3 and
15 respectively. On the other hand, when there is in the air an
abnormal excess of oxygen, and at the same time a great augmenta-
tion of carbon dioxide, the warm-blooded animal dies from poisoning
with carbon dioxide, and here again the conclusion is strengthened by

Martigny, Arch. gtn. de mdd., Paris, 1827, tome xiv. p. 203 ; Snow, Edin. Med.
Journ., 1846, vol. Ixv. p. 49; Claude Bernard, "Lecons sur les effets des substances
toxiques et me'dicamenteuses," Paris, 1857 ; W. Miiller, Ann. d. Chem. u. Pharm., 1858,
Bd. cviii. S. 257 ; Valentin, Ztschr. f. rat. Med., 1861, Bd. x. S. 33 ; Beau, Arch. gen. de
med., Paris, 1860, Ser. 5, tome xvi. p. 64 ; 1864, Ser. 6, tome iii. p. 1 ; Paul Bert,
"Lemons sur la physiol. comp. de la respiration," Paris, 1870, p. 510.

1 " Le9ons sur la physiol. comp. de la respiration," Paris, 1870, p. 518.

- " Tractatus quinque," Oxonii, 1674. See also this article, p. 741.

ASPHYXIA IN A LIMITED QUANTITY OF AIR. 745

the fact that the blood of the animal is generally arterial in colour.1
The fatal amount of carbon dioxide appears to be about 25 per cent.

An Atmosphere containing an Excess of Oxygen and of Carbon Dioxide.

Animal.

Tempera-
ture of

Gases.

Volume of
Gases.

Percentage
Composition
of Gases before
the Experiment.

Duration of Life.

Composition
of Gases at the
time of Death.

O2.

C02.

C02.

0.

WARM-BLOODED —

Rat, 1 month old.

25°

550 c.c.

90

10

4hrs.

22-5

77-5

32 grnis.

Rat, 1 month old

25°

600 ,,

75

25

20 min.

26-5

73-5

Rat, 3 days old,

25°

150 „

80

20

More than 5 hrs.

29'5

5 grms.

Mouse, young,

22°

235 „

90

10

More than 5 hrs.

24-5

5 grms.

COLD-BLOODED —

Grey lizard

25°-29

550 ,,

90

10

26 hrs.

16

...

Frog .

25°-29°

550 „

90

10

20 „

17

In the cold-blooded animals a marked difference is observed ; death
in such experiments is generally due to an excess of carbon dioxide, and
the fatal percentage, about 16, is much lower than in the case of the
warm-blooded animals.

Important differences have also been observed by Edwards2 and
Paul Bert 3 in the duration of life, under water, of animals of different
species, and in animals of the same species, but of different ages and
exposed to various degrees of external temperature. See table on p. 746.

The importance of these observations lies in the fact that they con-
firm many of the results obtained by experiments upon the respiratory
exchange of different animals. Thus an examination of the above tables
shows that the small animals die more quickly than the big animals,
and it has been proved that weight for weight they have a more rapid
metabolism.4 Further, a marked difference is observed in hens and
ducks, for the latter can live under water three or four times as long as
the former. The explanation of this fact is, according to Paul Bert,5 to
be found in the relatively greater quantity of blood in a duck. A
similar condition appears to obtain in the seal and whale,6 which can
remain under water from fifteen to thirty minutes.

The tables also show that new-born animals born helpless and blind
resist submersion for a much longer time than adults, a fact known and
studied by Harvey,7 Haller,8 Buffon,9 and Legallois,10 but the duration of

Paris, 1824, pp. 629-632.

1 Bernard, quoted from Paul Bert, loc. cit. p. 522.

2 "De 1' influence des agens physiques sur la vie,"

3 Loc. cit., p. 534.

4 This article, p. 720. See also "Animal Heat," this Text-book, vol. i. p. 852.

5 Loc. cit., p. 550.

15 Burdach, "Traite" de physiologic," trad, par Jourdan, tome vi. p. 122.
7 "De Generatione," Amst., 1651. 8 "Elementa physiologise," 1

" Histoire naturelle de 1'homme."
10 "(Euvres de Legallois,'' Paris, 1824, tome i. p. 93.

1761, p. 316.

746

CHEMISTR Y OF RESPIRA TION.

life under water is much shortened when the temperature of the water is
high. The explanation of this is to be sought in the fact that the respi-
ratory exchange of these immature animals is relatively small, and rises
and falls with the external temperature.1

Animal.

Tempera-
ture of
Water.

Duration of
Life.

Remarks.

Observer.

MAMMALS —

Min. Sec.

Dog .

4 25m

Mean of three experiments.

Paul Bert.

five days old

0°

12 5

, , two , ,

Edwards.

} }

22 '°5

55 30

)3

Cat, two months old

2 50

Paul Bert.

two days old

0°

4 33

,, nine ,,

Edwards.

10°

10 23

,, three ,,

s

20°

38 45

,, two ,,

26°

34 30

t

30°

29 0

,, two

i

42°

10 27

, , four , ,

Kitten, very young

14°

27 30

Paul'Bert.

» 3 >

20°

26 0

•>t

3 1 3 >

26°

18 0

tt

33 33

36°

11 30

...

))

Seal, 1 metre long

15-28 0

> 3

Rabbit

3 0

Mean of six experiments ;

rabbits without food for

previous twenty - four

hours.

,,

2 53

Mean of three experiments ;

33

rabbits well fed pre-

viously.

Guinea-pig .

...

2 0

? ,

,, adult

3 35

Moan of three experiments.

Edwards.

,, two to three

...

5 25

six

33

days old

BIRDS —

Sparrow

0°

0 30

Mean of seven experiments.

,,

>3

20°

0 46

33 3» 33

3,

"

40°

0 39

,, six ,,

} 5

0 37

, , two , ,

Paul Bert.

Pigeon

1 16

,, five ,,

3 3

Hen .

3 31

,, six .,

5 J

Duck .

11 17

,, eight ,,

3 J

The practical importance of these experiments in connection with
the cases of suspended animation in children at birth, and in adults
after drowning, is obvious.2

THE EXCHANGE OF GASES BETWEEN THE BLOOD AND THE Am IN
THE LUNGS — EXTERNAL EESPIKATION.

The mechanism of the ventilation of the lungs is described in
another part of this work;3 here it is necessary only to discuss the
frequency and volume of inspiration and expiration, the capacity of the

1 This article, p. 713. See also "Animal Heat," this Text-book, vol. i. p. 865.

2 "Report of the Royal Humane Society," 1865, p. 31.

3 " Mechanism of Respiration," this Text-book, vol. ii.

FREQ UENC Y OF RESPIRA TION IN MAN.

747

lungs, and other factors which bear upon the composition of the air in
the lungs.

The frequency of respiration in man. — Under normal conditions
this could be readily and exactly determined, were it not liable to
variations as soon as the attention of the subject is directed to the
breathing. Apart from this, the most important causes of variations
in the frequency of respiration are age, exercise, and temperature.

Age. — The frequency of breathing decreases from birth to old age,
as shown by the following table, the result of three hundred observations
made by Quetelet l upon human subjects of the male sex.

AGE.

RESPIRATIONS PEE MINUTE.

Maximum.

Minimum.

Mean.

Newly-born

70

23

44

5 years

32

...

26

15-20 ,,

24

16

20

20-25 ,,

24

14

187

25-30 ,,

21

15

16-0

30-50 ,,

23

11

18-1

In healthy infants the respiration is very irregular in frequency,
and often of the Cheyne- Stokes type.2

The average frequency of respiration in 1897 adult males was found
by Hutchinson 3 to be 20 per minute, one-third of the cases breathed
at that rate, and 1731 between 16-24 per minute.

Exercise increases not only the frequency but also the depth of
breathing. This hyperpnoea is not due to a deficiency of oxygen or an
accumulation of carbon dioxide in the blood, but probably to some pro-
duct which is derived from the metabolism in the muscles, and stimulates
the respiratory centre.4

The physiological explanation of the condition, well known to athletes as
" second wind," appears to be unknown ; during violent exercise, such, as
running or rowing, there is, after a time, considerable dyspnoea, but if the
exercise be continued this discomfort disappears, sometimes quite suddenly;
the man has now got his " second wind," and can continue the exertion in com-
parative comfort. The dyspnoea in these cases appears to be partly cardiac,
for the pulse-rate may be more than doubled, but when the " second wind " is
obtained, there appears to be a marked decrease in the frequency of the heart's
contraction.5 The causes of this accommodation are unknown.

1 " Sur 1'homme et le deVeloppement de ses faculte"s," Paris, 1835.

2 See Preyer, "Specielle Physiologic des Embryo," Leipzig, 1885, S. 179; Eckerlein,
Ztachr.f. Geburtsh. u. GynciL, Stuttgart, 1890, Bd. xix. S. 120.

3 Med.-Chir. Trans., London, vol. xxix. p. 137 ; art. "Thorax," Todd's " Cyclopaedia of
Anat. and Physiol.," vol. iv. p. 1085.

4 Geppert and Zuntz, Arch. f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 189.

5 Result of a few observations by Pembrey and Reynolds.

748 CHEMISTRY OF RESPIRATION.

Temperature. — The frequency of respiration is greatly increased
when the temperature of the body is raised above the normal by
exposure to excessive heat, or by disease ; this is especially marked in
the dog, for thereby a much greater loss of heat by evaporation of water
from the respiratory tract is effected. Eichet has shown that this rapid
breathing plays an essential part in the regulation of temperature in
the dog.1

The volume of inspiration and expiration — Tidal air. — The
earliest determinations of the volume of an ordinary inspiration in
man appear to have been made by Borelli,2 and by Jurin ; 3 the latter
estimated the amount at 656 c.c., or 40 cubic inches. Since that time
numerous determinations have been nmde with different methods. The
following are some of the results : — 230 c.c.,4 656 c.c.,5 574 c.c.,6 7
492 c.c,8 278 c.c.,9 328 c.c,10 278 c.c,11 197 c.c,12 270 c.c.13

The causes of these variations are due to differences in the capacity
of the chest of the different subjects of experiment, to individual
differences in the breathing, and to imperfections in the methods
employed. Vierordt u has collected the results of the older observers,
and finds as the minimal capacity of a single inspiration 53 c.c.
(Abilgaard), as the maximal 792 c.c. (Senebier). From his own
numerous determinations Vierordt15 obtained 446 c.c. as the mean
volume of each inspiration, with a frequency of 11*9 per minute,
whereas Speck16 with a frequency of 6 '3 respirations per minute found
a volume of 1195-1031 c.c. for each inspiration.

Hutchinson17 has collected the results of different observers, who
found for the tidal air volumes varying from 49 to 1640 c.c. ; he himself
made eighty determinations on different men, and obtained 114—196 c.c.
during rest, and 262-360 c.c. during exercise; in one case the tidal air
was as high as 1262 c.c.

Marcet18 found, as the result of 210 experiments upon two men, a
mean of 250 c.c. for the tidal air, when the rate of respiration was
16 per minute.

The discrepancy in the results given above is natural ; the cases are
not comparable as regards the height, weight, age, sex, and development
of the different subjects of experiment. It is useless, therefore, to
attempt to give any figure which shall represent a true average, and it

1 See "Animal Heat," this Text-book, vol. i. p. 856 ; Mathieu and Urbain, Compt. rend.
Acad. d. sc., Paris, 1872, tome Ixxiv. p. 190.

2 " De Motu Animalium," p. 2, prop. 81.

3 Phil. Trans., London, 1717-19, vol. xxx. pp. 757, 758.

4 Goodwyn, "Connection of Life with Respiration," London, 1788, p. 28.

5 Menzies, " On Respiration," Edinburgh, 1796, p. 18.

6 Richerand, "Physiology," trans, by De Lys, p. 206.

7 Fontana, Phil. Trans., London, 1779, vol. Ixix. p. 349.

8 Dalton, Mem. Lit. and Phil. Soc. Manchester, Se*r. 2, vol. ii. p. 26.

9 H. Davy, "Researches," p. 433.

10 Jurine, " Encyc. Metropol.," art, "Medicine," vol. i. p. 494.

11 Kite, "Essays," London, 1795, p. 47-

12 Abernethy, "Essays," 1793, p. 142.

13 Allen and Pepys, Phil. Trans., London, 1808, p. 256.

14 Wagner's " Handworterbuch, " Bd. ii. S. 836.

15 "Physiol. d. Athmens," Karlsruhe, 1845, S. 255.

16 " Untersuch. ueber Sauerstoffverbrauch u. Kohlensaureausathmung des Menschen,"
Cassel, 1871, S. 31 ; Arch. f. exper. Path. u. Pharmakol., Leipzig, Bd. xii. S. 19.

17 Article "Thorax," Todd's "Cyclopaedia of Anatomy and Physiology," vol. iv.
p. 1067.

is «proc. Physiol. Soc," Journ. Physiol., Cambridge and London, 1897, vol. xxi.

VOLUME OF INSPIRATION AND EXPIRATION. 749

is much more useful to recognise that the tidal air varies considerably
in different individuals, according to the rate and depth of breathing.

The complemental air. is the term given to the extra volume of air
which can be taken into the lungs by the deepest possible inspiration.
Its average value for an adult is said to be 1500 c.c. H. Davy gives
1951 c.c.,1 Kite 3280,2 and Hutchinson 1722-1804 c.c.3

The reserve or supplemental air is the volume of air which can be
expelled after an ordinary expiration by a forcible and deep expiration.
This is, according to Bostock's 4 determinations, 2624 c.c. (160 cub. in.),
while J. Bell5 gives 1148 c.c. (70 cub. in.), H. Davy, 1263 c.c. (77 cub.
in.), Hutchinson,6 1148-1804 c.c. (70-110 cub. in.), and Vierordt, 1226 c.c.

The residual air is the air which remains in the lungs after the
most forcible expiration ; it cannot be driven out of the lungs during
life. The methods 7 employed to determine this volume of air are of
two kinds, those for observations on the dead, and those for observations
upon the living body. In the first case, the thorax of the corpse is
forcibly placed in the position of a deep expiration, and then the air in
the lungs is measured. For the determination of the residual air of the
living subject, H. Davy 8 introduced an ingenious method ; he found
by experiment that hydrogen underwent no appreciable change in the
lungs, and that it quickly diffused throughout the residual air; he
therefore respired a quantity of this gas in a gasometer, and then made
a forced expiration, the air of which was analysed. From the quantity
of hydrogen left in the lungs, Davy calculated the total quantity of air
in the thorax at the end of the forced expiration, and found it to be
672 c.c. (41 cub. in.). This method has been used by Grehant,9 and in
a modified form by Hermann 10 and Berenstein.11 Several factors have
to be taken into account, such as the absorption of hydrogen by the
blood,12 and its diffusion in the residual air.

Another but less reliable method is Pfluger's 13 pneumonometer. The subject
of the experiment, placed in a special chamber, keeps the chest, as far as
possible, in the position of a forced expiration, the pressure outside the body
is then lowered by a known amount, and the lungs passively give off a certain
quantity of air ; this volume is measured, and from it and the alteration in
pressure the residual air is calculated. The difficulty is to keep the chest in
one position during the experiment.

The results obtained by different observers are given in the follow-
ing table : u—

1 "Chem. and Phil. Remarks," p. 410.

2 "Essays and Observations, Physical and Medical," 1795, p. 47.

3 Article "Thorax," Todd's " Cyclopaedia of Anatomy and Physiology," vol. iv. p. 1067.

4 "An Elementary System of Physiology," London, 2nd edition, 1828, vol. ii. p. 25.

5 "Anatomy," vol. i. p. 193.

6 "Physiologic des Athmens," Karlsruhe, 1845.

7 For further details of different methods, see Jacobson, "Beitrage zur Frage nach dem
Beitr. der Residualluft," Diss., Konigsberg, 1887; and Berenstein, "Ein Beitr. z. Bestim-
mung der Residualluft," Diss., Dorpat, 1891.

"Researches concerning Nitrous Oxide," London, 1800, p. 399.

9 Compt. rend. Acad. d. sc., Paris, 1862, tome Iv. p. 279 ; Journ. de Tanat. et physiol.
etc., Paris, 1864, tome i. p. 523.

10 "Lehrbuch der Physiol.," Berlin, 1896, Aufl. 11, S. 126.

11 Arch.f. d. ges. Physiol., Bonn, 1891, Bd. 1. S. 363.

12 Zuntz, Hermann's "Handbuch," Bd. iv., Th. 2, S. 102.

13 Arch.f. d. ges. Physiol. , Bonn, 1882, Bd. xxix. S. 244.

14 For some other results, see Hutchinson, loc. cit.

75°

CHE MIS TR Y OF RESPIRATION.

Volume of
Residual Air
in C.c.

Method.

Observer.

Remarks.

1,771

On corpse.

Good wy n.1

Mean of seven experi-
ments.

672-4

On living subject.

H. Davy.2

On one subject ; hydro-
gen method used.

1,640

On corpse.

Allen and Pepys.3

...

1,230 }
to \
1,640 J

...

Hutc^inson.4

19,800

10,547 }
to
13,189 J

On living subject.

J) 5>

Neupauer.5
Waldenburg.7

Method defective, re-
sults too high.6

Method defective, re-
sults too high.6

1,885

Gad.8

...

400 )
to \
800 J

) > 35

| Pfliiger. 9

Pneumonometer used.

500

> J 3 J

Kochs.10

» »

1,231 max. )
640 min. V
981 mean J

On nine corpses.

f Hermann and
\ Jacobson.11

...

1,250 max. ]
440 min.
796 mean J

On living subjects,
sixteen males.

{Hermann and
Berenstein.12

Hydrogen method used.

526 max. ~\
347 min. V
478 mean J

On living subjects,
three females.

/ Hermann and
\ Berenstein.12

» »

Vital capacity is the term given by Hutchinson to the volume
of air which can be expelled from the thorax by the most forcible
expiration, following the deepest possible inspiration. The different
values assigned to this volume of air are shown in the following
table : 13—

1 "Connexion of Life with Respiration," London, 1788, p. 25.

2 ''Researches concerning Nitrous Oxide," London, 1800, p. 399.
Phil. Tram., London, 1809, pp. 404, 410, 428.

Article "Thorax," Todd's "Cyclopaedia of Anatomy and Physiology," vol. iv. p.
1066.

Deutsches Arch. f. klin. Med., Leipzig, 1879, Bd. xxiii. S. 481.
Zuntz, Hermann's "Handbuch," Bd. iv. Th. 2, S. 103.
Ztschr.f. klin. Med., Berlin, 1879, Bd. i. S. 27.

8 Tagebl. d. 54 Versamml. deutsch. Naturf. u. Aerzte in Salzburg, 1881, S. 117.

9 Arch.f. d. gcs. Physiol., Bonn, 1882, Bd. xxix. S. 244.

10 Ztschr.f. klin. Med., Berlin, 1884, Bd. vii. S. 487.

11 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xliii. S. 236, 440.
™ Ibid., 1891, Bd. 1. S. 363.

13 See also Julius Jeffreys. "Statics of the Human Chest," 1843 ; Jackson, Am. Med.
Examiner, 1851, p. 51 ; Radclyffe Hall, Trans. Prov. Med. and Surg. Assoc., London,
1851.

VOL UME OF INSPIRA TION AND EXPIRA TION.

751

VITAL CAPACITY.

Observer.

Remarks.

In Cubic
Centimetres.

In Cubic
Inches.

3608

220

Jurin.1

3608

220

Stephen Hales.2

3493

213

H. Davy.3

3058
3280

186-5
200

Thomson.4
Goodwyn.5

Mean of twelve
experiments.

3280

200

Menzies.6

4920

300

Kite.7

...

3558
4838

21 7 Mean |
295 Max. J

Thackrah.8

3558
3700

217
226

Hutchinson.9

Hermann and
Berenstein.10

Mean for 1923
Men.
Mean for sixteen
Men.

From numerous observations upon men, Hutchinson found that the vital
capacity was influenced by the height, weight, and age of the subjects. The
following table shows the progression of the vital capacity with the stature11 : —

Height in Feet
and Inches.

Series from
Observations on
1012 Cases.

Series from
Observations on
1923 Cases.

Cubic In.

Cubic In.

5-2/5'1
H}5'3

175-0

188-5

176-0
191-0

5-6J5'5

206-0

207-0

si}5'7

222-0

228-0

5-10/5'9

237-5

241-0

6-0 J5'11

254-5

258-0

Mean of all
heights

214-0
(3509 c.c.)

217-0
(3558 c.c.)

1 Phil. Trans., London, vol. xxx. p. 757.

'Statical Essays," 2nd ed., London, 1731, vol. i. p. 243.

' Chem. and Phil. Remarks," p. 410.

'Chemistry of Animal Bodies," 1843, p. 610.

' Connexion of Life with Respiration," London, 1788.

' On Respiration," Edinburgh, 1796.

' Essays and Observations, Physical and Medical," 1795, p. 48.

' On the Effects of Arts, Trades, etc., upon Health," London, 1831, p. 21.
9 Loc. cit. 10 Arch.f. d. ges. Physiol., Bonn, 1891, Bd. 1. S. 363.

11 1 Foot = 304-8 mm.; 1 inch = 25 '4 mm. ; 1 cubic inch = 16 -4 c.c.

752

CHMMISTR Y OF RESPIRA TION.

There is an irregular increase of the vital capacity
regards age there is an increase from 15 to 35 years,

FIG. 68. — Hutchinson's spirometer.

with weight, and as
and then a decrease

from 35 to 65 years, even when height is
taken into consideration. When a man is
standing, his vital capacity is 260 cub. in. ;
in sitting erect, recumbent, and prone posi-
tions, it is 255, 230, and 220 cub. in.
respectively.

On the opposite page the average
amounts of complements!, tidal, reserve,
and residual air are given, but it is
necessary to point out again that they are
only Approximate values. The several
volumes have already been shown to vary
considerably in different individuals.

Hermann1 subdivides the residual air
into collapse air, the quantity driven out of
the lungs when the thorax is opened ; and
the minimal air, the quantity which re-
mains in the collapsed lungs.

In newly-born children the volume of
each inspiration in quiet breathing is 35 c.c.,
but during screaming it is raised to 61 c.c.;
the vital capacity is about 120 c.c. The
volume of the lungs of four children born
dead at full term was 40, 55, 55, and 60 c.c.
respectively, and when blown out they con-
tained 25, 30, 50, and 90 c.c. of air respect-
ively.2 For the first few days of life the
lungs completely fill the opened thorax;
there is no collapse air ; the residual air is
the minimal air. The lungs during each
expiration become almost free from air, and
the ventilation is very great, the renewal
of air being almost perfect.3

For the determination of the volumes
of air present in the lungs under different
conditions, Hutchinson used a special
meter, which he termed a spirometer. The
construction of this apparatus is shown in
Fig. 68.4

Since that time many simpler and
improved forms of spirometer have been
introduced.5 The most important precau-
tion is to reduce the resistance of the meter
as much as possible, otherwise the depth
and frequency of respiration become ab-
normal.

1 "Lehrbucli der Physiol.," Berlin, 1896, Aufl. 11, S. 126.

2Eckerlein, Ztschr. f. Gcburtsh. u. Gynak., Stuttgart, 1890, Bd. xix. S. 120.

3 Hermann, loc. cit., S. 127.

4 For further details, see Hutchinson, article "Thorax," Todd's "Cyclopaedia of
Anatomy and Physiology," vol. iv. p. 1069.

5 Fleischl von Marxow, CentralbL /. Physiol., Leipzig u. Wien, 1888, S. 39 ; Clar,
Wien. Tclin. Wchnschr., 1889, No. 18 ; Marcet, " Proc. Physiol. Soc." Journ. Physiol., Cam-
bridge arid London, 1897, vol. xxi. ; Hanriot and Richet, Compt. rend. Soc. de biol., Paris.
1887, p. 405.

RA TE OF RESPIRA TION IN DIFFERENT ANIMALS. 7 5 3

Cubic
Centimetres.

Cubic
Inches.

Complemental air .
Tidal air
Reserve or supplemental air .
Residual air .

1700] Vital
300 \ capacity,
1500J 3500.
1000

104] Vital
18 \ capacity,
9lJ 213.
61

Hyperpnaa, dyspnoea, asphyxia, apnoea, and Cheyne- Stokes' respira-
tion.— These different conditions are considered elsewhere in this work.1
The rate of respiration in different animals. — Numerous observa-
tions upon the rapidity of the respiratory movements in different animals were
made by Paul Bert,2 and the following table gives results obtained chiefly by
him : —

Animal.

Number of

Respirations
per Minute.

Remarks.

Observer.

MAMMALS —

Monkey ....

19

Quiet.

Paul Bert.

Tiger

6

Lion .....

10

3

? >
"

Cat

24

Dog

15

5

n

j 3

Ox

30

Robertson. 3

Rabbit

55

Paul Bert.

Rat, black and white .

210

I

3 3

Rhinoceros ....

6

Drowsy.

10-12

Quiet.

BIRDS —

? J

Condor ....

6

}j

3 j

Pelican ....

4

j 3

Cock

12

Lying down.

3?

Dove

30

Quiet.

j j

House-sparrow

90

55

Canary ....

100

55

??

REPTILES —

Rattle-snake ....

5

55

3 j

Lizard .....

12

55

> J

FISHES —

Skate (Raia liatis) .

51

5 >

Lafont.4

Dogfish . . . .

40

J J

55

Perch

30

55

Paul Bert.

Sole

34

5 5

Lafont.

Conger-eel ....

10

Quiet; length of

Paul Bert.

animal, 1 metre.

55 ....

25

Quiet; length of

55

animal, 50 cm.

CRUSTACEANS —

King-crab (Limulus)

12

Moving.

55

MOLLUSCS —

Poulp

28

Quiet.

5 5

Cuttlefish ....

45

55

Lafont.

Squid

65

5;

Paul Bert.

1 This article, pp. 743, 765 ; also "Mechanism of Respiration," this Text-book, vol. ii.

2 "'Le9ons sur la physiol. comp. de la respiration," Paris, 1870, p. 393.

3 Veterinary Journal, London, 1885, vol. xx. p. 311. The rate of respiration in 250
animals varied from 11 to 106 per minute.

4 Quoted by Paul Bert, loc. cit.

VOL. I. — 48

7 54 CHEMISTR Y OF RESPIRA TION.

The general conclusion to be drawn from these and other similar data is
that the larger animals respire more slowly than the smaller animals of a
similar class. It has been shown that a similar difference obtains in the out-
put of carbon dioxide and the intake of oxygen.

The alveolar surface of the human lungs. — The volume of the lungs
in the mean phase of respiration is about 3500 c.c.; the diameter of a single
alveolus is about 0'2 mm., its volume 0'004 c.mm., and its surface 0"126 s.mm.
In order to contain the air in the lungs, there must be 725 millions of alveoli,
with a surface of about 90 sq. metres.1 The above calculation is the one given
by Zuntz.2

The changes in the composition of the air during respiration.—
The fresh air taken into the lungs during respiration has the following
composition, when it is dry and measured at 0° and 760 mm. pressure,
20*96 volumes per cent, oxygen, 7 9 -02 nitrogen,3 and about 0'03 carbon
dioxide, or by weight per cent., 23'015 oxygen, and 76'985 nitrogen.
Under ordinary conditions, the air contains a quantity of aqueous
vapour, which is liable to considerable variations according to the
temperature and other atmospheric conditions ; the carbon dioxide,
moreover, may in badly-ventilated rooms rise considerably above the
amount just given.

The inspired air is warmed and moistened in passing through the
nose, pharynx, trachea, and bronchi, and rapidly mixes and diffuses with
the air retained in the alveoli of the lungs. The passage of the air
through the nose alone raises the temperature of the air considerably ;
thus Bloch 4 found that, when the temperature of the external air was
-8°, -0°-5 to 3° -5, 12° to 16° and 18°, that of the air entering the pharynx
from the nose was respectively 24°'5, 26°, 30°, and 31°. With a
moderate external temperature the air becomes about one-third saturated
with moisture during its passage through the nasal cavity. The rapidity
of the processes of mixture and diffusion will vary according to the
frequency and depth of breathing and the capacity of the lungs. The
air expired will likewise vary in composition, and under normal condi-
tions will never represent the alveolar air.

The expired air. — The earliest determinations of the composition of
the expired air of man were made by Menzies,5 Lavoisier and Seguin,6
H. Davy,7 Allen and Pepys,8 and Prout.9 The following table gives the
more exact results of recent investigations, but at the same time it is
important to remember that it is impossible to give figures which shall
exactly represent the average composition of the expired air ; the
percentage of oxygen and of carbon dioxide varies according to the
frequency and depth of breathing, and is influenced by various condi-
tions which affect the metabolism of the body, such as muscular
activity, temperature, and food. For these reasons the respiratory ex-
change of an animal should be estimated by the direct determination
of the intake of oxygen and the output of carbon dioxide and water in

1 1 mm. = 0-03937 in., and 1 metre = 39-37079 in.

2 Arch. f. d. ges. PhysioL, Bonn, 1888, Bd. xlii. S. 410.

3 This includes a small quantity of argon, but it appears to have no physiological
importance.

4 Ztschr.f. Ohrerih., Wiesbaden, Bd. xviii. S. 215, 354.

5 "Essay on Respiration," Edinburgh, 1796, p. 50.

6 Ann. de chim., Paris, 1814, tome xci. p. 318.

7 "Researches," London, 1808, p. 331.
s Phil. Trans., London, 1808, 1809.

9 Ann. Phil., London, 1813, vol. ii. p. 328.

COMPOSITION OF THE AIR DURING RESPIRATION. 755

a given time, not by a calculation based upon the alteration in the com-
position of the air of several expirations, multiplied by the average
quantity of expired air and the average number of respirations in a
given time.

Breathing.

Volume of
Expired
Air (per
Minute).

Percentage
of Oxygen
in Expired
Air.

Quantity
of Oxygen
Absorbed
(per

Minute).

Percent-
age of
Carbon
Dioxide in
Expired
Air.

Quantity
of Carbon
Dioxide Dis-
charged (per
Minute).

Observer.

C.C.

C.C.

C.C.

Normal

7,527

16-29

358

4-21

318

1

Very shallow

5,833

15-50

330

4-63

269

I Speck.1

Very deep .

17,647

18-29

437

3-17

560

Normal. Rest

6,158

17-00

240

3-56

218

}

Work

16,191

17-29

587

3-65

593

ISpeck.2

Hard work .

24,323

16-96

964

4-08

993

J

Normal

4,644

16-16

222-9

4-36

202-7

IT- 3

Normal

3,419

16-96

136-8

3-44

117-6

j-Lowy.-1

Vierordt4 concluded from his experiments that the percentage of
carbon dioxide in the expired air diminished, but the total discharge
increased when the respiration was voluntarily quickened, the depth of
breathing remaining the same, 500 c.c. ; similar effects were produced by
breathing more deeply but with the same frequency. The drawback to
these observations is that they were for periods only lasting two or
three minutes, and thus they are no exact measure of changes of meta-
bolism. Even the extended observations of Lossen and Berg have been
the subject of much discussion and criticism between Pfliiger 5 and
Voit.6 It is impossible here to go fully into the causes of some of the
contradictory results, but Pfliiger appears to have shown that the
variations in the breathing have no influence upon the respiratory
metabolism beyond this, that when the respiratory muscles are more
active, an extra amount of metabolism, due to this activity, will occur.
Pfliiger takes the mean of the conflicting results and obtains the
following suggestive figures : —

Carbon dioxide discharged in fifteen minutes —

Authority.

Five Respirations
per Minute.

Sixty Respirations
per Minute.

Lossen .
Berg .

7 "96 grms.
7*712 ,,

6-63 grms.
9-106 „
15-736 ,,
Mean . 7 '868 ,,

15-672 ,,
Mean . 7 '836 ,,

1 Arch. d. Ver.f. tvissensch. ffeilk., Leipzig, 1867, Bd. iii. S. 317.

2 "Physiologic des menschlichen Athmens," Leipzig, 1892 ; Arch. f. Physiol., Leipzig,
1896, S. 465.

:! Arch.f. d. ges. Phijsiol., Bonn, 1888, Bd. xliii. S. 523, et scq.

4 Hesse, Arch.f. ffyg., Munchen u. Leipzig, 1884, Bd. ii. S. 381; "Physiol. d.
Athmens," Karlsruhe, 1845, S. 116, 134.

5 Arch.f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 1, 630.

6 Ztschr. f. JBioL, Munchen, 1878, Bd. xiv. S. 95.

756 CHEMISTR Y OF RESPIRATION.

This conclusion is supported by the work of Pfliiger's pupils, Finkler and
Oertmann,1 who found that artificial respiration and apnoea2 produced no
alteration in the absorption of oxygen by rabbits. The respiratory exchange
is determined by the activity of the tissues, and not by the frequency of
respiration, or the amount of oxygen contained in the blood.

Other changes in the respired air. — It has been shown that in
a man at rest the air respired undergoes a reduction in oxygen to about
16 per cent., and an increase in carbon dioxide to about 4 per cent. ; in
addition, the temperature of the inspired air is raised to that of the
body, and this generally occurs before the air reaches the smaller
bronchi. At this temperature the air is saturated with moisture, and
shows when dried a slight reduction, al^out -^ in volume, when it is com-
pared with the inspired air, and both are measured at 0° and 760 mm.
This decrease in volume is due to the combination and retention of some
of the oxygen in the tissues, to the oxidation of some substances which
leave the body otherwise than by the lungs, and to the combination of
oxygen with hydrogen to form water. The oxygen does not reappear
entirely as oxygen in combination with carbon to form carbon dioxide ;

CO

this is shown by the respiratory quotient, -. — , which in omnivorous and

U2

carnivorous animals is about O'S. The effect of diet and other con-
ditions upon the respiratory quotient is considered elsewhere in this
work, and it has been shown 3 that, under certain conditions, marsh-
gas, hydrogen, and nitrogen may be discharged by the lungs.

THE EFFECT OF KESPIRATION UPON THE BLOOD.

Historical. — The discovery of Harvey that every portion of blood passes
through the lungs during each complete circulation, confirmed the idea of the
early physiologists, that respiration produced important changes in that fluid ;
Harvey 4 himself thought that the blood discharged some noxious substances
as well as aqueous vapour into the air of the lungs.5

In 1669, Lower6 observed, on opening the thorax of a living animal, and
keeping up artificial respiration, that the change of colour from venous to
arterial took place in the capillaries of the lungs ; the blood in the right
ventricle was dark, and if the artificial respiration ceased it passed through the
lungs to the left ventricle without attaining an arterial hue ; venous blood,
when exposed to air outside the body, acquired an arterial colour. Mayow,7
even earlier than 1674, maintained that this change from venous to arterial
colour was due to the absorption by the blood of the nitro-aerial gas (oxygen)
from the air in the lungs, but his work was neglected and forgotten.

About the year 1776, Priestley 8 made a series of experiments, in which he
showed that dark blood clot became red more rapidly in oxygen than in air,
but the red colour was reduced to purple when the clot was placed in nitrogen,
hydrogen, or carbon dioxide ; these alterations in colour also took place when
the blood clot was separated from the air by a piece of moistened bladder, or
by a thin film of milk. These changes were supposed by Priestley to be

1 Arch.f. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 38. See also Pfluger, ibid., S. 9.

2 See also Hanriot and Richet, Compt. rend. Acad. d. sc., Paris, 1887, tome civ. p. 1327.

3 This article, pp. 700, 729.

4 "DeMotu Cordis."

5 For older theories see p. 692, and the references there given.

6 "Tractatus rle Corde," Londini, 1669, pp. 175, 181.

7 "Tractatus Primus," Oxon., 1674, p. 148.

8 Phil. Trans., London, 1776, pt. 1, p. 226,

GASES OP THE BLOOD. 757

similar to those of combustion, but, biassed by his belief in an old theory, he
concluded that the removal of " phlogiston " turned venous into arterial blood,
and for this purification respiration was necessary. For many years there
were two hypotheses to account for the effect of respiration on the blood.
According to the one, which originated apparently with Black,1 and was
accepted by Priestley, Lavoisier,2 and Crawford,3 the oxygen in the inspired air
combined with the carbon in the venous blood of the lungs, and formed
carbon dioxide, which was discharged; whereas, according to the other
hypothesis, proposed by Le Grange,4 the oxygen was absorbed by the blood,
and, during the course of the so-called systemic circulation, combined with
carbon to form carbon dioxide, which was liberated when the blood again
reached the lungs and took up a fresh supply of oxygen.

Notwithstanding the experiments of Spallanzani 5 and of Edwards,6
which proved that snails, frogs, and kittens continued to give out carbon
dioxide in an atmosphere of hydrogen, the view that oxidation took place
in the blood was held until recent times, when the work of Pfliiger and
his pupils showed conclusively that the tissues were the important seat of
combustion.

According to Bohr,7 the tissues of the lungs have a further function than
that of simply absorbing and discharging gases ; they are said to be able to
form carbon dioxide from substances brought to them from other parts of the
body. Thus Bohr and Henriques 8 found that the lungs supplied 68 per cent,
of the respiratory metabolism. It must be pointed out that in many of the
experiments upon which this conclusion is based, the operative procedure was
exceedingly severe, and the condition had no approximation to the normal ;
further, the results are not supported, in fact are contradicted, by the
numerous experiments on internal respiration.

The effect of respiration upon the blood is best studied by a com-
parison of the gases contained in venous blood taken from the right
ventricle, and in arterial blood taken from the carotid artery.

The gases of the blood.— Methods for the extraction and esti-
mation of the gases of the blood. — Historical. — The first demonstration
of the presence of gases in the blood was made by Boyle9 in 1636; he
showed that, when fresh defibrinated blood was exposed to the vacuum of
an air-pump, gas was given off. These particles of gas Mayow,10 in 1674,
considered to be nitro-aerial gas, that is, oxygen. The next important observa-
tion was that made by Priestley,11 who noticed that blood placed in an
atmosphere of hydrogen or nitrogen gave off oxygen. Girtanner 12 observed
the same effect with nitrogen. In 1799, Humphry Davy13 found that
twelve volumes of arterial blood, when heated to 93°, gave off I'l volume of
carbon dioxide, and 0*7 volume of oxygen.

JNasse,14 in 1816, proved that blood gave up oxygen to an atmosphere of

1 "Lectures on Chemistry," edit, by Robison, Edinburgh, 1803.
3 Hist. Acad. roy. d. sc., Paris, 1777, 1789, 1790.

3 " On Animal Heat," 2nd edition, 1788.

4 Hassenfratz, Ann. de chim., Paris, 1791, tome ix. p. 275.

5 "Mem. sur la respiration," trad, par Senebier, 1803.

6 "De 1'influence des agens physiques sur la vie," Paris, 1824.

7 Skandin. Arch. f. Physiol., Leipzig, 1891, Bd. ii. S. 236.

8 CentralU. f. Physiol. , Leipzig u. Wien, 1892, S. 225; Compl. rend. Acad. d. sc.,
Paris, 1892, tome cxiv. p. 1496.

9 "Nova experiments pneumatics respirationem spectantia," Genevse, 1636.

10 "Tractatus quinque," Oxonii, 1674. "Opera omnia," Hagae Com., 1681, p. 133.

11 Phil. Trans., London, 1776, pt. 1, p. 226.

12 Hassenfratz, Ann. de chim., Paris, 1791, tome ix. p. 275.

13 Ann. d. Phys. u. Chem., Leipzig, 1803, Bd. xii. S. 574, 593.

14 Deutsches Arch. f. d. Physiol., Halle, 1816, Bd. ii. S. 195, 435.

758

CHEMISTR Y OF RESPIRA TION.

hydrogen, or of carbon dioxide, and Vogel,1 in 1814, and Collard de Martigny,2
in 1830, obtained carbon dioxide, but no oxygen, from blood subjected to a
vacuum. Notwithstanding these observations, the presence of gases in the
blood was for a long time a subject of controversy. Many physiologists,
among them Johannes Miiller,3 Schroeder van der Kolk,4 Gmelin,5 Mit-
scherlich,5 and Tiedemann,5 maintained that no gas existed in the blood,
whereas Nasse,6 Scudamore,7 Bischoff,8 and Van Euschut 9 obtained from
blood carbon dioxide, but no oxygen. John Davy was at first 10 unable to

extract any gas from
blood, but during a
further research he
obtained carbon dioxide
from both arterial and
venous blood.11

More exact methods
of observation were in-
troduced in 1837 by
Magnus,12 who adopted
and improved, for the
extraction of the gases,
the use of a Torricellian
vacuum, a method due
originally to Collard de
Martigny. The conclu-
sions to which Magnus
arrived were that blood
contained 4-8 volumes
per cent, carbon dioxide,
1-3 '5 volumes per cent,
oxygen, and 0'5 - 2
volumes per cent, nitro-
gen, and that arterial
blood contained more
oxygen than did venous
blood. Fernet,13 in 1857,
published the results of
experiments in which he

had extracted the gases
FIG. 69.— Pfluger's Pump; a, blood bulb; 6, froth-chamber ; f fh }1 -, h & ,,
d, drying tube ; e, mercurial gauge ; h, graduated tube

for collection of gas ; I, m, n, and o, bulbs and tubing passage of a stream of
containing mercury. hydrogen, and the aid

of a vacuum. About

the same time, Lothar Meyer u developed the method 15 of heating the blood
or other liquid for the extraction of its gases, and a still further advance was

I Journ. f. Chem. u. Phys., Niirnberg. 1814, Bd. xi. S. 399.
-Journ. dephysiol. exper., Paris, 1830, tome x. p. 111.

3 "Handbuch d. Physiol.," Bd. i, S. 315.

4 " Dissertatio sistens sanguinis coagulantis historiam."

5 Ztschr. f. Physiol., 1833, Bd. v. S. 6.

6 Loc. cit.

7 "An Essay on the Blood," London, 1824.

8 " Commentatio, etc.," Heidelbergse, 1837.

9 "De respirationis Chymismo," Trajecti ad Ehenum, 1836. pp. 78, 84, 98, 115, 142.

10 Phil. Trans., London, 1823, p. 516.

II "Researches," London, 1839, vol. ii. p. 156, et seq.

12 Ann. d. Phys. u. Chem., Leipzig, 1837, Bd. xl. S. 583 ; 1845, Bd. Ixvi. S. 177.

13 Ann. d. sc. not., Paris, 1857, Ser. 4, Zool., tome viii. p. 125.

14 "Die Gase des Blutes," Gottingen, 1857 : Ztschr. f. rat. Med., N.F., Bd. viii. S. 256.

15 Used originally by H. Davy, Bunsen, and Baumert.

GASES OF THE BLOOD.

759

H

made when Ludwig and Setschenow,1 Pfliiger 2 and Helmholtz,3 constructed
their mercurial gas-pumps, based upon the principle of the Torricellian vacuum.

The mercurial gas-pump. — Numerous forms4 of this apparatus have been
introduced, but here it is only necessary to mention Pfliiger's pump, the
modification of this made by Grehant,5 and the simple apparatus devised by
Leonard Hill. The principle of the first is shown in the diagram on p. 758.

Further details upon the construction and working of these pumps will
be found in text-books of physiological chemistry.6

In Leonard Hill's 7 gas-pump, the chief advantages are simplicity, cheap-
ness, and rapidity of action ;
the working errors are under
1 per cent., and only small
quantities of blood are required.
The construction of the pump
is shown in Fig. 70, and
the successive manipulations
are as follows : — " A blood-
receiver (F) is affixed to the
end of the tube E, and the
receiver is elevated into the
position indicated by the dotted
outline. The reservoir (B) is
then put in connection with
the tube (E) by means of the
three-way tap (D), the reservoir
(A) is raised above the pump,
and the whole system is filled
with mercury to the top of the
blood-receiver (F). The screw-
clip on the rubber tube at the
upper end of F is then closed,
and the reservoir (A) lowered
until the blood-receiver is ex-
hausted, except for 2 or 3 c.c.
of mercury, which is purposely
left within. The screw-clip on
the lower end of F is next closed,
and the blood-receiver now
clipped at either end, exhausted,
detached from tube E, and
weighed. A sample of blood is
then collected. The arterial or
venous cannula is filled with
blood, and immediately afterwards pushed into the rubber tube at the

i-Sitzungsb. d. k. Akad. d. Wissensch. Math-phys. CL, Wien, 1859, Bd. xxxvi. S. 293.

2 " Untersuch. a. d. Bonner physiol. Lab.," 1865, S. 188; Centralbl. f. d. med.
Wissensch., Berlin, 1866, S. 305 ; Arch. f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 61.

3 See Zuntz, Hermann's "Handbuch," Bd. iv. Th. 2, S. 27.

4 A. Schmidt, Ber. d. k. sachs. Gesellsch. d. Wissensch. Math-phys. CL, Leipzig, 1867,
Bd. xix. S. 33 ; Hoppe-Seyler, "Physiol. Chem.," Berlin, 1879, Bd. iii. S. 491 ; Nawrocki,

*-v. iv -i • 7 -r TT» -i T"^__ T>J ^^ Ct T A A . T>,,«^"U /<M,.7, -f ^7 ^ -. Oi,«.n/."«7

FIG. 70. — Leonard Hill's Gas-Pump.

"La pression barome'trique," Paris, 1878, p. 615.

6 Halliburton, "Text-Book of Chemical Physiology and Pathology," London, 1891, p.
30; Hempel, " Gasanalytische Methoden;" Gamgee, "Physiological Chemistry of the
Animal Body," vol. i. pp. 200-206.

7 Journ. Physiol., Cambridge and London, 1894-5, vol. xvii. p. 353 ; Hill and Nabarro,
ibid., 1895, vol. xviii. p. 218.

760 CHEMISTR Y OF RESPIRA TION.

end of the blood-receiver, as far as the closed screw-clip. Before the
insertion of the canmila, the end of the rubber tube is compressed with
the fingers to exclude the air within it. A sufficient quantity of blood
is now withdrawn by opening at the same time the screw-clip and the
clip placed on the blood vessel of the animal. The blood is defibrinated
by shaking it with the mercury left within the blood-receiver for that
purpose, and the latter is then again weighed. The weight of the sample
of blood is then obtained. The blood-receiver is next affixed once more to the
tube (E), in the dependent position shown in the figure, and the tube (E) is
exhausted. Finally, the screw-clip between E and the blood-receiver is
opened, and the gases are withdrawn and collected in the eudiometer. Since
the blood-receiver hangs freely from the tube (E) by means of a piece of
rubber tubing, it can be both immersed in warm water, and shaken to facilitate
the complete escape of the gases. The "bulbous form of the blood-receiver
prevents the blood from frothing over into the pump ; and if the action
becomes too violent, it can be immediately allayed by pouring a few drops
of warm water on to the tube (E). The bubbles are thereby driven back into
the receiver, and the pump is never fouled. The tap (D) is so manipulated
that the gases only, and not the water which condenses in the reservoir (B),
are driven over into the eudiometer. The water is returned back into the
blood-receiver. Three or four exhaustions are sufficient to extract all the gases
from about 10 grms. of blood."

Methods of gas analysis cannot be described here; it is only necessary to refer
the reader to the works of Bunsen, Hempel, and others1 upon this special subject.

In the extraction of the gases of the blood methods are employed which
favour the dissociation of those gases which are present in loose chemical
combination, and also liberate the gases present in a state of simple solution.
These conditions are fulfilled by exposure to a vacuum, by warming and
agitating the blood. The addition of a weak acid favours the evolution of the
carbon dioxide. The effect of these different procedures upon the dissociation
of oxyhsernoglobin will be considered later ; here it is only necessary to recall
the fact that the coefficient of absorption of gases in fluids diminishes with an
increase of temperature, and becomes nil when the boiling point of the fluid is
reached.

For the quantitative estimation of the oxygen contained in blood, Claude
Bernard2 introduced a method based upon the stronger affinity shown by
carbon monoxide than by oxygen for haemoglobin. The blood is shaken with
double its volume of carbon monoxide, which drives out the oxygen from its
combination with hemoglobin. An analysis of the gas collected shows the
percentage of oxygen. Nawrocki 3 has made comparative analyses with this
method and with the ordinary blood pump, and the results are practically the
same. If, however, the blood is left in contact with the carbon monoxide for
longer than twenty-four hours, some of the gas combines with oxygen to form
carbon dioxide, and thus the amount of oxygen is diminished.4 It is possible
that the carbon dioxide formed in these cases is due to putrefaction.

The differences in the gases of arterial and venous blood.-—
A comparative examination of the gases contained in arterial and venous
blood is necessary for the estimation of the qualitative and quantitative
changes which occur during external and internal respiration.

The gases of arterial blood. — The chief results obtained by

1 Bunsen, " Gasometrische Methoden," 1857; " Gasometry, " Roscoe's transl. , London,
1857; cf. also Gamgee, op. cit., pp. 206-215; Hempel, " Gasanalytische Methoden";
Geppert, " Die Gasanalyse," 1885.

2 " Le9ons sur les liquides de 1'organisme," Paris, 1859, tome i. p. 365 ; ii. p. 427.

3 Stud. d. physiol. Inst. zu Breslau, Leipzig, Bd. ii. S. 144.

4 Bernard, loc. cit., Pokrowsky, Virchow's Archiv, 1866, Bd. xxxvi. S. 482.

GASES OF ARTERIAL BLOOD.

761

different observers upon various animals have been collected in tabular
form by Zuntz,1 and are here reproduced with some additions : —

Animal.

Quantity of Gas in Percentage
of Volume of Blood,
Measured at 0° and 760 Mm.

Observer and Number of
Experiments.

Oxygen.

Nitrogen.

Carbon
Dioxide.

Dog .

Mean

22'6

1-8

34-3

Pfliiger,2 twelve experiments, but

only three determinations of

C0a. Rapid method employed.

f

Mean

18-3

1-8

37-7

Forty-four analyses of carotid

Dog . .4

Max.

247

5-5

53'4

blood by Setschenow, Schceffer,

(

Min.

11-4

1-2

23-3

Sczelkow, Nawrocki, Hirsch-

mann, Sachs and Pfliiger. Col-

lected by Pfliiger.3

Dog .

Mean

18-4

2-0

38-8

Blood of femoral artery. Twenty-

five analyses by Pfliiger,3 two

by Hirschmann.

f

Mean

19'4

40-4

One hundred experiments by Paul

Dog . J

Max.

26-4

50-8

Bert.4

I

Min.

14-4

33-0

Dog .

17-58

38-57

Geppert and Zuntz.5

f

15-4

1-5

40-1

Grehant.6

TV _ __

21-2

1-5

45-9

Dog .

15-2

1-8

40-0

I

22-7

1-5

40-4

r

17-3

33-4

Ewa Id.7

TV

15-4

32-4

Dog . . ^

15-8

35-1

I

157

26-35

Dog .

Mean

18-25

37-64

Hill and Nabarro,8 average of

fifty-two samples of arterial

blood.

Cat .

Mean

13-1

1-3

28-8

P. Hering,9 six experiments. The

value of oxygen is too low,

since phosphoric acid was

added to the blood beforehand.

Sheep .

Mean

10-7

1-8

45-1

Sczelkow.10 Two analyses.

Sheep .

Mean

12-8

Three analyses by Preyer11 on

venous blood shaken with air.

Rabbit

Mean

13-2

2-1

34-0

Four analyses by Walter. 12

Rabbit

...

10-9

37-34

Geppert and Zuntz.13

Man .

...

21-6

1-5

40-3

One analysis by Setschenow.

1 Article in Hermann's "Handbuch," Bd. iv. Th. 2, S. 35.

2 CentralU.f. d. med. Wissensch., Berlin, 1867, S. 722.

3 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 274.

4 "La pression barome'trique, " Paris, 1878, p. 1030.

5 Arch.f. d. ges. Physiol. , Bonn, Bd. xlii. S. 189.

6 Compt. rend..Soc. de bioL, Paris, 1892, p. 163.

7 Arch.f. d. ges. Physiol., Bonn, 1873, Bd. vii. S. 575.

8 Journ. Physiol., Cambridge and London, 1895, vol. xviii. pp. 223, 224, 227.

9 " Untersuch. u. d. Zusarnmensetzung der Blutgase wahrend der Apuoe," Diss.j
Dorpat, 1867, Meissners Jahrcsb., 1867, S. 305.

10 Arch.f. Anat., Physiol. u. wissensch. Med., 1864, S. 516.

11 Wien. med. Jahrb., 1865, S. 145.

12 Arch.f. exper. Path. u. Pharmakol., Leipzig, Bd. vii. S. 148.

13 Arch.f. d. ges. Physiol., Bonn, Bd. xlii. S. 189.

762 CHEMISTRY OF RESPIRATION.

The results of analyses of the gases in the blood of birds and of other
animals are given by Zuntz.1

Estor and Saint-Pierre 2 concluded, from a few analyses of arterial blood,
that the amount of oxygen diminished in proportion to the distance of the
artery from the heart ; these results, however, have been shown by Paul Bert,3
Hirschmann,4 and Pfliiger 5 to be erroneous. The blood in the smaller arteries
contains less oxygen, but this is independent of the distance from the heart,
and appears to be due to the smaller number of red corpuscles, and the
lower specific gravity of the blood.6

The results given in the above table show considerable differences in the
percentage composition of the gases of arterial blood, even when the experi-
ments have been made upon similar animals. The causes of these differences
are partly due to variations in the gase^ in the blood, and partly to errors of
analysis. In order to test these points, double analyses of portions of the same
blood have been made by Preyer and Ludwig,7 Pfliiger,8 and others.9 The
most important discovery in this connection is that made by Pfliiger ; 10 the
ordinary methods for the extraction of the gases of the blood give results
which for the oxygen are too low, for the carbon dioxide too high ; arterial
blood, when removed from the body, and kept from contact with the air,
rapidly becomes darker. Some of the oxygen appears to be used up by the
corpuscles with the production of carbon dioxide. If the blood be received
directly from the artery into a large vacuum, and the gases quickly extracted,
then values are obtained which show a higher percentage of oxygen, and a
lower percentage of carbon dioxide than those found by the ordinary slower
methods. The normal amount of oxygen in the fresh arterial blood of the
dog is about 22 per cent. The carbon dioxide naturally shows considerable
variations, but the amount of nitrogen in the most exact determinations is
fairly constant, about 1'8 per cent.

The arterial blood is not quite saturated with oxygen, for by rapid
artificial respiration in the living animal, or by shaking arterial blood
with air, the amount can be raised above 23 volumes per cent.11 Geppert
and Zuntz found in the arterial blood of dogs a relative saturation with
oxygen of 96-99 per cent.12 The quantity of carbon dioxide in arterial
blood is only about one -fifth of the amount which can be held by the
blood, for Paul Bert13 found that clog's blood could take up about 150
volumes per cent, when shaken with pure carbon dioxide. The nitrogen
is simply in solution and the blood appears to be saturated with that
gas, for the ordinary pressure and temperature.

The gases of venous blood. — On account of the differences in the
metabolism of the different tissues of the body, the venous blood is liable

1 Article in Hermann's " Handbuch," Bd. iv. Th. 2, S. 41.

2 Journ. de I'anat. et physiol. etc., Paris, 1865, tome ii. p. 302.

3 "Lemons sur la physiol. comp. de la respiration," Paris, 1870, p. 118.

4 Arch. f. Anat., Physiol. u. wissensch. Med., 1866, S. 502.

5 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 274.

6 Mathieu and Urbain, Arch, de physiol. norm, et path., Paris, 1871, tome iv. ; Pfliiger,
Arch. f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 75.

7 Wien.'med. Jahrb., 1865, Bd. xxi. S. 145.

8 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 61.

9 Hammarsteii, Ber. d. k. sacks. Gesellsch. d. Wissensch. Math.-phys. CL, Leipzig,
1871, Bd. xxiii. S. 630; Afanassiew, ibid., 1872, Bd. xxiv. S. 256 ; Tschiriew, ibid., 1874,
Bd. xxvi. S. 120.

10 Centralbl.f. d. med. Wissensch., Berlin, 1867, S. 321, 722.

11 Setschenow, Sitzungsb. d. L ATcad. d. Wissensch., Wien, Bd. xxxvi. S. 289 ; Pfliiger,
Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 70 ; Ewald, ibid., 1873, Bd. vii. S. 575.

12 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 242.

13 "La pression barometrique," Paris, 1878, p. 1038.

GASES OF VENOUS BLOOD,

763

to corresponding variations in its gaseous constituents. It is therefore
only possible to give a mean value for the gases of the venous blood
when the analyses are performed upon samples removed from the right
ventricle ; this procedure can be carried out by passing a catheter from
the right external jugular vein through the right auricle and into the
right ventricle. The following table gives the results of the few experi-
ments of this kind, together with the data of simultaneous analyses of
the arterial blood : —

ANIMAL.

VENOUS BLOOD FROM EIGHT
VENTRICLK

ARTERIAL BLOOD.

Observer.

Oxygen.

Nitro-
gen.

Carbon
dioxide.

Oxygen.

Nitro-
gen.

Carbon
dioxide.

Dog . .

11-9

1-7

45-3

19-2

2-7

39-5

Schceffer l
(mean of five
experiments).

» •
)>

5-5

56-4
49-0

22-1
19-3

36-1

38-7

1 Paul Bert.2

j j • •

117
9-5

36-5
34-0

17-3
15-4

33-4
32-4

1 Ewald.3

> 3

5 > •

12-5
12-5

36-0
24-96

16-5
16-12

34-8
30-65

1 Tinkler.4

,,

9-9

5475

17-25

42-75

] Mathieu and

5)

5-43

61-08

20-75

47-33

j Urbain.5

The effect of different conditions on the gases of venous Hood, — It has
already been mentioned that the venous blood is liable to marked
differences in its gaseous contents, according to the condition of the
organs from which the blood is received.

The venous blood leaving a muscle varies according to the condition
of the tissues 6 ; when the muscle is actively contracting, the percentage
of oxygen in the blood is much diminished, and the amount of carbon
dioxide is increased, notwithstanding the increase in the volume and
velocity of the circulating blood. The experiments of Bernard7 and
Zuntz 8 show that, after section of the motor nerve, the absorption of
oxygen and the production of carbon dioxide in the muscle are much

1 Sitzungsb. d. k. Akad. d. Wissemck. Math.-naturw. CL, Wien, 1860, Bd. xli.
S. 589.

2 " La pression barometrique, " Paris, 1878, p. 1038.

3 Arch.f. d, ges. Physiol., Bonn, 1873, Bd. vii. S. 575.

4 Ibid., 1875, Bd. x.'S. 368.

5 Compt. rend. Acad. d. sc., Paris, 1872, tome Ixxiv. p. 190.

GSczelkow, Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1862, Bd. xlv. S. 171;
Mathieu and Urbain, Compt. rend. Acad. d. sc., Paris, 1872, tome Ixxiv. p. 190 ; Bernard,
"Lecons sur la chaleur animale," Paris, 1876, p. 147; Zuntz, Berl. klin. Wchnschr.,
1878J No. 10, S. 141 ; von Frey, Arch.f. Physiol., Leipzig, 1885, S. 533; Chauveau and
Kaufmaim, Compt. rend. Acad. d. sc., Paris, 1886, tome ciii. pp. 974, 1057, 1153 ; Hill and
Nabarro, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.

7 Loc. cit. 8 Loc. cit.

764

CHEMISTR Y OF RESPIRATION.

less than in the normal condition, the blood undergoing comparatively
slight changes in its passage through the capillaries.

The following are some of the results obtained by Zuntz : —

BLOOD VESSEL.

PERCENTAGE VOLUME OF GASES
IN BLOOD.

Remarks.

Oxygen.

Carbon dioxide.

;
Femoral vein .

Carotid artery .

1-2

14-4

•

36-32
21-92

Dog at rest.

In the muscles of right \
limb were absorbed and \
produced respectively . J

13-20

14-40

Femoral vein .
Carotid artery .

2-85
13-30

33-16
23-06

After section of sciatic
and crural nerves on
the right side.

In the muscles of right \
limb were absorbed and V
produced respectively . J

10-45

10-1

Calculated from these results, the respiratory exchange before the section
of the nerves was 1'21 c.c. oxygen and 1*32 c.c. carbon dioxide per minute;
after section of the nerves, 0*68 c.c. oxygen and 0'65 c.c. carbon dioxide.

Chauveau and Kaufmann1 estimated the gaseous exchange in the
masticatory muscles of the horse, both when it was at rest, and when it
was actively chewing. The following table gives their results, together
with those of somewhat similar experiments made by Sczelkow,2 Hill
and Nabarro : 3 —

DIFFERENCE BETWEEN THE VENOUS AND ARTERIAL BLOOD.

OBSERVER.

Rest.

Activity.

Carbon dioxide
Oxygen .

+ 6-71
-9

+ 10-79|
-12-26]

f + 32-37

(-36-78

ISczelkow.

Carbon dioxide
Oxygen .

+ 87
-11-4

+ 10-201 f +30-60
1x3 =
- 13-65 J [-40-95

} Chauveau
V and Kauf-
J mann.

Carbon dioxide
Oxygen .

+ 876
-12-92

Tonic
+ 13-90] T+41-70

-13-75/ [-41-25

Clonic.
+ 19-331 f +57-99

f x 3 = i

- 12-65 J [-37-89

) Hill and
f Nabarro.

In the above table the amounts found during activity are multiplied

1 Compt. rend. Acad. d. sc., Paris, 1886, tome ciii. pp. 974, 1057, 1153,
!». d. k. Akad. d. Wissensch., Wien, 1862, Bd. xlv. S. 171.

3 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.

CONNECTION BETWEEN BLOOD AND ITS GASES. 765

by three, in order that allowance may be made for the increased rate of
flow in the blood of an active limb.

As regards the velocity of the circulation, Finkler1 finds that the
difference between the arterial and venous blood increases as the velocity
diminishes. This relationship is well shown by Bernard's 2 observations
upon the submaxillary gland. When the gland is at rest the venous blood
is dark, but becomes almost arterial in colour when the gland becomes
active and its blood vessels are dilated by stimulation of the chorda
tympani. The difference between the arterial and venous blood is less
marked, but the total absorption of oxygen and production of carbon
dioxide are increased.

In the last stage of asphyxia, the arterial blood contains only traces
of oxygen. Thus Ludwig 3 gives, as the result of six analyses made by
Setschenow and Holmgren upon asphyxiated dogs, 0*4 volume per cent,
oxygen, 3 per cent, nitrogen, and 54 per cent, carbon dioxide ; and Zuntz 4
has collected the results of nineteen analyses made by different observers,5
and obtains an average of 0'96 volume per cent, oxygen, 2'07 per cent,
nitrogen, 49'53 per cent, carbon dioxide. These values Zuntz contrasts
with those obtained from averages of seventy-one analyses made by
Pfliiger and others upon normal arterial blood, namely, 18 '3 volumes per
cent, oxygen, 1*9 per cent, nitrogen, and 38'1 carbon dioxide; and he
shows that the ratio between the increase of carbon dioxide and the loss
of oxygen is O66 in asphyxia, as compared with 079 in the normal con-
dition. This difference is to be explained by the retention of some carbon
dioxide in the tissues, owing to the high tension of that gas in the blood.

During apnoea the arterial blood is almost saturated with oxygen, and
contains about one-half its normal amount of carbon dioxide ; the venous
blood, on the other hand, contains less oxygen as well as less carbon
dioxide than it does in the normal condition.6 These results confirm the
work of Pfliiger,7 who found that during apnoea the respiratory exchange
was not greater or smaller than in the ordinary condition of respiration.

The changes which the blood undergoes in passing through the brain
are much less marked than those which occur during its passage through
muscles. Even during marked activity the brain has a comparatively
small respiratory exchange.8

The nature of the connection between the blood and its gases.—
Oxygen. — Magnus9 in 1836 concluded that the gases of the blood were
simply dissolved in that fluid, notwithstanding the fact that his experi-
ments showed that the quantity of oxygen in the blood was much greater
than the amount which could be dissolved in an equal volume of water
exposed to air. Justus Liebig,10 however, pointed out that Eegnault and
Eeiset's n experiments showed that animals absorbed the same amount of
oxygen whether they breathed pure oxygen or air ; he therefore urged

1 Arch.f. d. ges. Physiol., Bonn, 1875, Bd. x. S. 368.

2 "Lemons sur les liquides de 1'organisme, " Paris, 1859, tome ii. p. 435 ; "Le9ons sur la
chaleur animale," Paris, 1876, p. 185.

3 Wien. med. Jahrb., 1865, Bd. xxi. S. 145.

4 Hermann's "Handbuch," Bd. iv. Th. 2, S. 43. 5 See Zuntz, loc. cit.

6 Ewald, Arch. f. d. ges. Physiol., Bonn, 1873, Bd. vii. S. 575.

7 Ibid., 1868, Bd. i. S. 100.

8 Hill and Nabarro, Journ. Physiol. , Cambridge and London, 1895, vol. xviii. p. 218.
See also " Animal Heat," this Text-book, vol. i. p. 808.

9 Ann. d. Phys. u. Chem., Leipzig, 1837, Bd. xl. S. 583 ; 1845, Bd. Ixvi. S. 177.

10 Ann. d. Chem. u. Pharm., 1851, Bd. Ixxix. S. 112.

11 Ann. de chim. etphys., Paris, 1849, Se'r. 3, tome xxvi.

766

CHEMISTR Y OF RESPIRATION.

that the gases of the blood were present in a state of loose chemical
combination with some unknown constituent of the blood, in a similar
way to that in which carbon dioxide is combined in solutions of sodium
phosphate. A few years later, Lothar Meyer l came to a similar con-
clusion, for he found that the amount of oxygen retained in the blood
only varied slightly with alterations of pressure. About the same time
Fernet2 observed that the amount of oxygen chemically combined in
blood saturated with air was about five times greater than the quantity
which could be dissolved at the ordinary atmospheric pressure; this
oxygen was, moreover, chiefly contained in the red corpuscles.

A further proof of the chemical combination of oxygen was obtained
when Bernard 3 and Hoppe-Seyler 4 discovered that the oxygen of the
blood could be displaced by an equal volume of carbon monoxide, a gas
which formed a more stable combination with the blood. The most con-
vincing proof, however, was furnished when Hoppe-Seyler succeeded in
crystallising hse.moglobin, and showed that it combined with oxygen, but
yielded up the gas to a vacuum ; he also showed that the haemoglobin,
for so he named the pigment of the red corpuscles, had a definite spectrum.
A year or two later, in 1864, Stokes 5 discovered that reducing sub-
stances removed oxygen from the haemoglobin and effected a marked
change in its colour and spectrum.

The physical and chemical properties of haemoglobin are described
fully in another part 6 of this work ; here it is only necessary to discuss
the part which the pigment plays in the processes of respiration.

The coefficient of absorption of blood for oxygen is a little lower than
that of water, for the presence of salts in solution diminishes the capacity
of the liquid to absorb gases.7 The following table shows the volume of

OXYGEN ABSORBED

ACCORDING TO DIFFERENT OBSERVERS.

TEMPERATURE.

Bunsen.8

Winkler.9

Hiifner.io

0°

0-04114

0-04890

5°

0-03628

0-04286

10°

0-03250

0-03802

15°

0-02989

0-03415

20°

0-02838

0-03103

0-02844

25°

0-02844

0-02745

30°

0-02616

0-02635

40°

0-02306

0-02447

50°

0-02090

1 "Die Gase des Blutes," Diss., Gottingen, 1857 ; Ztschr. f. rat. Med., Bd. viii. S. 256.

2 A nn. d. sc. nat.,- Paris, 1857, Se"r. 4, Zool., tome viii. p. 125; Journ. de physiol.
exp6r., Paris, 1860, tome iii.

3 "Lecons sur les effets des substances toxiques et medicamenteuses," Paris, 1857, p.
184 ; "Lemons sur les liquides de 1'organisme," Paris, 1859, tome i. p. 365 ; tome ii. p. 427.

4 Virchow's Archiv, Bd. xi. S. 288 ; Bd. xiii. S. 104.

5 Proc. Roy. Soc. London, vol. xiii. p. 357.

6 Article " Haemoglobin, " this Text-book, vol. i.

7 Mackenzie, Ann. d. Phys. u. Chem., Leipzig, 1876, Bd. i. S. 438 ; Setschenow, Ztschr.
f. physical. Chem., Leipzig, 1889, Bd. iv. S. 117; Hlifner, Arch. f. Physiol., Leipzig,
1894, S. 130 ; 1895, S. 209.

8 Ann. d. Chem. u. Pharm., Bd. xciii. S. 1 ; "Gasometrische Methoden," Braunschweig,
1857, S. 136.

9 Ztschr. f. physical. Chem., Leipzig, 1892, Bd. ix. S. 174.

10 Ann. d. Phys. u. Chem., Leipzig, 1876, Bd. i. S. 632; Arch. f. Physiol., Leipzig,
1890, S. 27.

CONNECTION BETWEEN BLOOD AND ITS GASES. 767

oxygen, measured at 0° and 760 mm., which can be absorbed by one
volume of water.

Bohr1 found that the absorption coefficient of oxygen in a 2 per
cent, aqueous solution of haemoglobin at 15° was 0*02249, whereas that
for pure water is, according to Winkler, 0 '0341 5, or 50 per cent, greater
at the same temperature.

It has been shown that arterial blood with a temperature of 37°
contains a large quantity of oxygen, about 22 volumes per cent., an
amount which could not be present in simple solution. Further, when
the red corpuscles are absent, as in plasma and serum, the amount of
oxygen in the fluid is, according to Pfliiger,2 only 0*26 vols. per cent.

In the next place, different observers have shown that crystals of
haemoglobin can absorb large quantities of oxygen.

Condition of Haemoglobin.

Amount of Oxygen
(0° and 760 Mm.).

Observer.

100 grms. moist crystals .....

108-4 c.c.

Hoppe-Seyler.3

,, crystals dried with filter-paper .

76-9 „

ii

, , crj^stals dried at 0° and powdered

54-2 ,,
156-6 ,,

»
Dybkowsky.4

,, ,, from horse ....

44-83-
88-52 ,,
180-3 „

172-4 ,,

Strassburg.5
Preyer.6

, , ,, . . . .

128

Worm Miiller.7

,, ,, . . . . . .

159

Hiifner.8

Mean of 10 determinations.
,, crystals dried at 0° and powdered,
from ox -blood ....

134

Hiifner.9

The causes of these differences are various ; the crystals of
haemoglobin were prepared in different ways, and it is probable that
in some cases methgemoglobin or other products were formed; the
amount of moisture varied, and the methods employed for the extraction
of the oxygen were different.

Bohr,10 however, would explain these differences in another manner,
for he maintains that there are at least four different kinds of haemo-
globin, «-, 13-, y-, and <3-h8emoglobin, which have the same spectrum, but
combine with different amounts of oxygen, 0'4, 0*8, 1'7, and 27 c.c.

1 "Exp. Untersuch. u. d. Sauerstoffaufnahme des Blutfarbsto fifes," Copenhagen, 1885,
S. 37.

2 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 73.

3 Virchow's Archiv, Bd. xxix. S. 598 ; Med.-chem. Untersuch., 1867, Bd. ii. S. 191.

4 Hoppe-Seyler, Med.-chem. Untersuch., 1866, Bd. i. S. 117.

5 Arch.f. d. ges. PhysioL, Bonn, 1871, Bd. iv. S. 454.

6 CentralU.f. d. med. Wisse.nsch., Berlin, 1866, No. 21.

7 Ber. d. Jc. sdchs. Gesellsch. d. Wissensch., Leipzig, 1870, Bd. xxii. S. 351.

8 Ztschr. f. physiol. Chem., Strassburg, 1878, Bd. i. S. 317, 386.

9 Arch.f. PhysioL, Leipzig, 1894, S. 130.

10 Skandin. Arch.f. PhysioL, Leipzig, 1892, Bd. iii. S. 47, 69, 76, 101.

768 CHEMISTR Y OF RESPIRA TION.

of oxygen for 1 grm. of haemoglobin. The usual form of haemoglobin is
/-haemoglobin ; this, when dried, gives a crystalline powder, a-haemo-
globin, which in turn yields, on solution in water, /3-hsemoglobin. A
solution of /-haemoglobin, when kept in a closed tube, is converted
into ^-haemoglobin. These various kinds of haemoglobin have different
" specific oxygen capacities," by wThich term Bohr designates the ratio
between the number of grammes of iron and the number of cubic
centimetres of oxygen present in a given volume of blood, of blood
corpuscles or solutions of haemoglobin, saturated with air at ordinary
pressure and temperature. The red blood corpuscles are said to
undergo alterations in their specific oxygen capacity during their
passage through the circulation.

These results and theories have been subjected to an experimental
examination by Hiifner,1 who maintains that in fresh, healthy ox-blood
there is only one kind of haemoglobin, that the capacity of the fresh
haemoglobin for carbon monoxide and for oxygen is the same, whether
it be haemoglobin directly dissolved from red corpuscles or haemoglobin
first crystallised and then dissolved in water. By experiment, Hiifner
shows that 1 grm. of haemoglobin takes up T33S c.c. of carbon monoxide
or oxygen measured at 0° and 760 mm. This is confirmed by the
following facts. The capacity of haemoglobin to combine with oxygen
appears to depend upon its iron, one atom of which holds two atoms of
oxygen. The haemoglobin of ox-blood contains 0'336 per cent, of iron,
and its molecular weight is 16,669 ; its capacity for carbon monoxide or
oxygen, as calculated from its percentage of iron, is T34 c.c. for 1 grm.,
a figure practically identical with that obtained by direct experiment.2
This is probably also the case with haemoglobin obtained from the
horse, dog, pig, rabbit, and fowl, for Bunge and others 3 have shown
that the general percentage of iron is O335 per cent. Further, the
amount of haemoglobin in human blood is about 14 per cent., and since
1 grm. of haemoglobin can absorb about 1 '34 c.c. of oxygen, it follows that
the amount of oxygen combined in arterial blood should be about 20
volumes per cent., and actual experiment shows that this is the case.4

It is probable that some of Bohr's results are due to mixtures of
pure and partly decomposed haemoglobin, and that some of the haemo-
globin may be in the form of methaemoglobin. The same criticism
may possibly apply to the results obtained by Haldane and Lorrain
Smith.5

The oxygen in the blood of invertebrates. — In many of the invertebrate
animals, haemoglobin, haemocyanin, and other proteids, which can enter into
loose combination with oxygen, are found and play a part in the process of
respiration. It is impossible, however, in a few words, to do justice to this
interesting portion of comparative physiology ; for further details, the article
by Halliburton 6 on the blood of invertebrate animals should be consulted.

1 Arch.f. PhysioL, Leipzig, 1894, S. 130.

2 See also Hoppe-Seyler, Virchow's Archiv, Bd. xxix. S. 598; Med.-chem. Untersuch.,
1867, Bd. ii. S. 191 ; Preyer, "De hsemoglobino observation es et experimenta, " Bonnse,
1866, p. 19 ; GentralU.f. d. med. Wissensch., Berlin, 1866, No. 21.

3 Jaquet, Ztschr. f. physioL Chem. , Strassburg, 1889, Bd. xiv. S. 289.

4 See p. 761.

5 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 468.

6 "Text-Book of Chemical Physiology and Pathology," London, 1891, pp. 316-330. Here
numerous references to previous work on the subject will be found. Among subsequent
papers may be mentioned those of Griffiths, Compt. rend. Acad. d. sc., Paris, 1892,
tome cxv. pp. 259, 419, 474, 669, 738 ; cxvi. p. 1206.

CONNECTION BETWEEN BLOOD AND ITS GASES. 769

Nitrogen. — The blood contains about 1-8 volumes per cent, of
nitrogen, and this is present chiefly in a condition of solution. Thus
Lothar Meyer 1 and others 2 have found that the absorption of nitrogen
by defibrinated blood is proportional to the pressure. This, Paul Bert 3
showed, was also the case in living animals, but, owing to the want of
perfect ventilation of the lungs, the increase did not exactly follow
Dalton's law. Thus —

Pressure in
Atmospheres.

Percentage of
Nitrogen in Dog's
Blood.

Pressure in
Atmospheres.

Percentage of
Nitrogen in Dog's
Blood.

1

2-2

5

6-0

2

3-0

7

7-0

3

3'9

10

9'4

The coefficient of absorption of water for nitrogen is small, and the blood
has even less power of absorption, for Fernet, Setscnenow, Hiifner, and others 4
have shown that the presence of other substances in solution diminishes the
capacity of water to absorb gases. The following table shows the coefficient
of absorption of water for nitrogen at different temperatures : —

TEMPERATURE.

COEFFICIENT OF ABSORPTION.

Bunsen.5

Hiifner.fi

WinklerJ

0°

0-02035

0-02348

5°

0-01794

...

0-02081

10°

0-01607

0-01857

15°

0-01478

...

0-01682

20°

0-01403

0-01406

0-01542

25°

0-01357

0-01431

30°

0-01308

0-01340

37°

0-01239

40°

0-01210

0-01183

1 "Die Gase des Blutes," Inaug. Diss., Gottingen, 1857, S. 56.

2 Setschenow, Sitzungsb. d. k. Akad. d. Wissensch. Maih.-natunv. CL, Wien, Bd. xxxvi.
S. 293.

3 " La pression barometrique," Paris, 1878, p. 661.

4 Fernet, Ann. d. sc. nat., Paris, Ser. 4, "Zool.," tome viii. p. 125 ; Setschenow, Mem.
Acad. imp. d. sc. de St. Petersbourg, 1879, tome xxvi. p. 6; Ztschr. f. physical. Chem.,
Leipzig, 1889, Bd. iv. S. 117; Hiifner, Arch. f. PhysioL, Leipzig, 1894, S. 130; 1895, S.
209; Mackenzie, Ann. d. Phys. u. Chem., Leipzig, 1876, Bd. i. S. 438; Bohr, "Exper.
Untersuch. u. d. Sauerstoifaufnahme des Blutfarbstoffes," Copenhagen, 1885, S. 37.

5 " Gasometrische Methoden," 1857, S. 136 ( " Gasometry, " Roscoe's transl., London,
1857).

6 Ann. d. Phys. u. Chem., Leipzig, 1877, Bd. i. S. 632; Arch. f. PhysioL , Leipzig,
1890, S. 27.

7 Ztschr. f. physical. Chem., Leipzig, 1892, Bd. ix. S. 173.

VOL. I.— 49

770

CHEMISTR Y OF RESPIRA TION.

Further proofs that the nitrogen is simply in solution are afforded by
two experiments made by Pniiger. Blood subjected to the vacuum of a
mercurial pump quickly gives off its nitrogen ; thus at 0° all the nitrogen,
but less than half the oxygen and three-quarters of the carbon dioxide,
were given off in twenty hours.1 The blood of a dog which had pre-
viously breathed for a few minutes a mixture containing only oxygen
and carbon dioxide, yielded no nitrogen to a vacuum ; that gas had
rapidly diffused from the blood into the air of the lungs.2

Carbon dioxide. — The nature of the connection between the carbon
dioxide and the blood, which contains it, is very difficult to follow, and
has given rise to much discussion.3 There is no single substance with
which the whole of the carbon dioxide is combined ; it is present both
in the red corpuscles and plasma, and, after coagulation of the blood,
in both the clot and serum. It will be well, therefore, to consider—
(1) The amount of this gas, which may be in a state of simple solution
in the blood and in serum ; (2) the quantity in loose and firm chemical
combination with substances in the corpuscles and in the plasma and
serum of the blood.

Carbon dioxide is much more soluble in water than oxygen and
nitrogen. Plasma and serum are not able to retain in simple solution
as much carbon dioxide as can a similar volume of pure water, for it
has already been mentioned that the presence of indifferent substances
in solution diminishes the capacity of the fluid to absorb gases. There
are, however, exceptions 4 to this general rule, and it is therefore
necessary to determine experimentally the absorption coefficient of
carbon dioxide in blood before we conclude that it is less than in water.
This experiment was made by Zuntz,5 who neutralised the blood with
phosphoric or oxalic acid in order to eliminate its chemical affinity,
saturated it with carbon dioxide, and then determined the amount
absorbed. He found that the coefficient of absorption for calves' blood
with a specific gravity of 1038 was 1*626, and that for sheep's blood
with a specific gravity of 1052 was T547 at 0°.

PARTIAL PRESSURE OF OO2 IN THE
MIXTURE OF GASES USED.

CARBON DIOXIDE IN DOG'S SERUM (0° and 760 Mm.).

Mm. mercury.

Percentage
of an
Atmosphere.

Total.

Quantity Absorbed.

Quantity in Chemical
Combination.

105-8

13-9

61-1 percent.

20'7 per cent.

46 "4 per cent.

351-4

46-2

122-1

68-8

53-3

747-8

98-4

202-2

146-4

55-8

1 Pfliiger, " Die Kohlensaure des Blutes," Bonn, 1864, S. 12.
2Pfluger, Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 104.

3 For further details see Zuntz, Hermann's "Handbuch," Bd. iv. Th. 2, S. 64;
Hammarsten, " Lehrbueh der physiologischen Chemie," Wiesbaden, 1895, S. 535; Setsche-
now, Mem. Acad. imp. d. sc. de St. Pttersbourg, 1879, tome xxvi. p. 6; Zuntz, " Beitr.
z. Physiologic des Blutes," Inaug. Diss., Bonn, 1868, S. 33.

4 Buchanan, Proc. Roy. Soc. London, 1874, No. 15, p. 192.

5 "Beitr. z. Physiol. des Blutes," S. 39; Hermann's "Handbuch/' Bd. iv. Th. 2,
S. 15.

CONNECTION BETWEEN BLOOD AND ITS GASES. 771

Setschenow 1 calculated that serum held in simple solution 99 per
cent, of the amount of carbon dioxide which distilled water would
absorb under similar conditions, and that one-tenth of the total carbon
dioxide in the serum of dog's blood was in simple solution. The result
of further experiments made by Zimtz 2 upon these points is shown in
the table on p. 770.

In the next place, it is necessary to consider the amount of carbon
dioxide in loose and firm chemical combination with substances in the
corpuscles, plasma and serum. Most of the gas is contained in the
plasma or serum, for these fluids contain a larger quantity of carbon
dioxide than that which can be obtained from an equal volume of blood.
The greater quantity of the gas is in a state of loose chemical combination
in the serum, for much of it can be extracted by the action of the
vacuum of a blood-pump ; the remainder, however, is in firm chemical
combination, and is only set free in the pump by the addition of an
acid. In this respect a marked contrast is observed between blood and
serum, for all the carbon dioxide can be extracted from the former by
the action of the vacuum alone, the haemoglobin of the red corpuscles
playing, apparently, the part of an acid.-''

The following table shows the amount of carbon dioxide in loose and
firm chemical combination in serum : —

CARBON DIOXIDE IN SERTM.
(Volumes per cent.)

CARBON DIOXIDE IN
BLOOD.
(Volumes per cent.)

OBSERVER.

Extracted by
Vacuum.

In Firm Com-
bination.

Total in Com-
bination.

13-4

31-3

447

34-5

Schoeffer.4

21-1

21-9

43*0

35-0

,,

44-6

4'9

49-5

Pflitger.5

35-2

9-3

44-5

»

19-9

6-9

26-8

Zimtz.6

22-0

12-4

34-4

)5

22-5

13-5

36-0

...

>;

26-9

17-0

43-9

»

The differences in these results are due, as Zimtz7 has pointed out,
to the powerful action of Pfliiger's pump, and to the concentration of the
serum during its exposure to the vacuum. The carbonates of the serum give
off their gas more readily when the solution is concentrated ; this complication

1 Loc. cit., CentralN.f. d. mecL Wissensck., Berlin, 1877, No. 35.

2 Hermann's "Handbuch," Bd. iv. Th. 2, S. 68.

3 Setschenow, Sitsungsb. d. k. Akad. d. Wissensch., Wien, 1859, Bd. xxxvi. S. 293;
Pfliiger, " Ueber die Kohlensaure des Blutes," Bonn, 1864, S. 5 ; Zuntz, CentralbL f. d.
med. Wissensch., Berlin, 1867, S. 527.

4 Sitzungsb. d. k. Akad. d. Wis*cnsch. Math.-naturw. CL, Wien, 1860, Bd. xli. S. 616.

5 "Ueber die Kohlensaure des Blutes," Bonn, 1864, S. 11.

6 Centralbl. f. d. med. Wissensch., Berlin, 1867, S. 529; Hermann's "Handbuch,"
Bd. iv. Th. 2, S. 45.

7 Loc. cit.

7 7 2 CHEMISTR Y OF RESPIRA TION.

was avoided in the analyses made by Zimtz, by the addition of distilled water
in sufficient quantity to maintain the concentration of the fluid at its original
point. Preyer l found that the proportion of carbon dioxide in loose and in
firm combination was as 2 to 3 '5.

The next question to discuss is the nature of the substances with
which the carbon dioxide is combined. The facts already mentioned
show that these substances are to be sought chiefly in the serum. In
the first place, analyses of the ash of serum show that the most important
constituents are the alkalies ; thus, according to Bunge's 2 experiments,
the ash from 1000 gnus, of dog's serum contains 4*341 grms. sodium, of
which 3403 grms. is sufficient to saturate the chlorine. The remainder,
0'878 grms. sodium, can combine with 0'623 grms. carbon dioxide (316
c.c. at 0° and 760 mm.) to form sodium carbonate, and, in addition, with
another equal quantity to form sodium bicarbonate. Thus calculated,
a litre of plasma could hold 632 c.c. of carbon dioxide, or 63 volumes
per cent, in chemical combination. This must be considered only as an
approximate result, for the amount of sodium carbonate in serum cannot
be accurately determined by an analysis of the ash or by titration, for
the alkali is combined with other substances, especially with proteids.3

The alkalies of the blood are the most important constituents for
holding carbon dioxide in combination. Serum freed from gas can
combine with as much carbon dioxide as is necessary to form bicarbonates
with its alkalies ; any reduction in the alkalinity of the blood is accom-
panied by a decrease in carbon dioxide. Thus Walter 4 found only
2 to 3 volumes per cent, of carbon dioxide in the blood of rabbits poisoned
by hydrochloric acid ; Geppert and Zuntz 5 observed that the alkalinity
of the blood of rabbits was diminished by -the acid formed during tetanic
muscular activity, and at the same time there was a decrease in the
carbon dioxide of the blood. During diabetic coma the alkali of the blood
appears to be in great part neutralised by combination with /3-oxybutyric
acid ; 6 and Minkowski 7 found only 3*3 volumes per cent, of carbon
dioxide in the blood of a patient suffering from diabetic coma.

Another substance with which the carbon dioxide is supposed to
combine in serum is disodium hydrogen phosphate 8 (Na2HP04), with the
formation of sodium bicarbonate and sodium biphosphate. Thus —

Na2HP04 + C02 + H20 = NaHC03 + NaH2P04.

Sertoli9 and Mroczkowski,10 however, found that the quantity of
phosphoric acid in the serum is so small that, if allowance be made for
that contained in lecithin and nuclein, the amount is quite insufficient

1 Sitzungsb. d. k. AJcad. d. Wissensch. Math.-naturw. CL, Wien, Bd. xlix. S. 27.

2 Ztschr. f. Biol., Miinchen, 1876, Bd. xii. S. 204; "Lehrbuch der physiologischen
und pathologisclien Chemie," Leipzig, 1889, S. 254.

3 Hoppe-Seyler, "Physiol. Chem.," Berlin, 1879, Bd. iii. S. 502; Sertoli, Med.-
chem. Untersuch., Berlin, 1868, Heft 3, S. 350.

4 Arch.f. exper. Path. u. Pharmakol., Leipzig, Bd. vii.

5 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 189. See also this article, p. 714.

6 Stadelmann, Arch. f. exper. Path. u. PharmakoL, Leipzig, Bd. vii. ; Minkowski,
ibid., Bd. xviii. ; Mitth. a. d. med. Klin, zu Konigsberg, Leipzig, 1888.

7 Loc. cit.

8 Fernet, Ann. d. sc. not., Paris, Ser. 4, tome viii. p. 160 ; Heidenhain and L. Meyer,
Stud. d. physiol. Inst. zu Breslau, Leipzig, 1863, Het't 2 ; Ann. d. Chem. u. Pharm.,
1862-63, Supp. Bd. ii. S. 157.

9 Hoppe-Seyler, Med.-chem. Untersuch., Berlin, 1868, Heft 3, S. 350.
10 Centralbl.f. d. med. Wissensch., Berlin, 1878, No. 20, S. 356.

CA USES OF THE EXCHANGE OF GASES. 773

to play any important part in combining with carbon dioxide. Bunge,1 on
the other hand, maintains that in dog's blood the quantity of phosphoric
acid is sufficient, and that only a small quantity is combined with alkalies
in the plasma ; he agrees, however, with the previous observers, that the
amount of phosphoric acid in the blood of the ox and the pig is very 'small.

There is also evidence to show that the proteids, especially the
globulin of serum, play some part in forming combinations with carbon
dioxide. Setschenow 2 considered that the globulin formed a combina-
tion with the carbon dioxide, whereas Sertoli held that the globulin
acted as an acid, and in the serum was combined with an alkali.

The blood corpuscles contain about one-third of the total carbon
dioxide found in the blood.3 The gas is in loose chemical combination
probably with the alkali of the phosphates, globulin, and haemoglobin
of the corpuscles, and directly with the haemoglobin. Setschenow
calculates that in 100 volumes of blood the red corpuscles contain 10
volumes, and the white corpuscles 2'5 volumes of carbon dioxide.

The experiments of Setschenow,4 Zuntz,5 Bohr,6 and Torup7 show
that carbon dioxide combines with haemoglobin even in the absence of an
alkali. A solution of pure crystallised haemoglobin absorbs more carbon
dioxide than does an equal volume of water, and the amount of gas
absorbed is relatively large for low pressures, but relatively small for
high pressures. According to Bohr, 1 grm. of haemoglobin at 18° '4, and
under a pressure of 30 mm., combines with 2*4 c.c. of carbon dioxide ;
the pigmented portion of the haemoglobin is supposed to combine with
oxygen and the proteid portion with carbon dioxide.

Further investigation, however, is necessary before it will be possible
with any exactitude to decide the relative importance of the different
combinations with the carbon dioxide of the blood.

The causes of the exchange of gases between the air in the
lungs and the blood.— The oxygen of the blood is derived from the air
in the alveoli of the lungs ; the carbon dioxide in the expired air comes
from the pulmonary blood, and ultimately from the tissues of the body.
The inspired air contains at 0° and 760 mm. 20*96 volumes per cent,
of oxygen, the expired air about 16 per cent., and the tissues no free
oxygen ; the carbon dioxide is 0*03 volumes per cent, in the inspired
air, about 4 in the expired air, and in the tissues is being constantly
produced. There would, therefore, appear to be sufficient causes, both
physical and chemical, to determine the passage of the oxygen inwards
and of the carbon dioxide outwards.

OXYGEN, Alveolar air ^ Blood — ^ Tissues.

CARBON DIOXIDE, Tissues ^ Blood — ^ Alveolar air.

1 Ztschr. f. Biol., Miiiichen, 1876, Bd. xii. S. 206; " Lehrbuch der physiologischen und
pathologischen Chemie," Leipzig, 1889, S. 256.

2 Arch. f. d. ges. PhysioL, Bonn, 1874, Bd. viii. S. 1 ; Centralbl. f. d. med. Wissensch.,
Berlin, 1877, No. 35; 1879, No. 21 ; Ber. d. deutsch. chem. Gesellsch., Berlin, 1879, Bd. xii.
S. 855 ; Mem. Acad. imp. d. sc. de St. Petersbourg, 1879, tome xxvi. No. 13.

3 Alex. Schmidt, Ber. d. k. sacks. Gesellsch. d. Wissensch. Math.-phys. CL, Leipzig,
1867, Bd. xix. S. 30; Zuntz, Centralbl. f. d. med. Wissensch., Berlin, 1867, S. 529; Her-
mann's "Handbuch," Bd. iv. Th. 2, S. 72 ; Fredericq, ' ' Recherches sur la constitution du
plasma sanguin," Gand, 1878, p. 49.

4 Centralbl. f. d. med. Wissensch., Berlin, 1877.

5 Hermann's "Handbuch," Bd. iv. Th. 2, S. 76.

6 Beitr. z. Physiol. Carl Ludwig z. s. 70 Geburtst., Leipzig, 1887, S. 164; Jahresb.
ii. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xvii. S. 115.

7 Jahresb. u. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xvii. S. 115.

774 CHEMISTR Y OF RESPIRA TION.

The evidence, however, in support of this explanation must be
examined, for of late it has been challenged, especially by Bohr.1 In
the first place, it is necessary to remember that the composition of the
alveolar air is not represented by that of the air expired. The composi-
tion of the inspired and of the expired air and the tension of their
component gases can be readily determined. The tension of oxygen in
the inspired air is 159 mm., under the mean pressure of an atmosphere,
760 mm. It is difficult, however, to obtain with accuracy similar data
for the air of the alveoli. From the numerous analyses of expired air
in a man, it is possible to form only a rough estimate of the alveolar air ;
it probably contains 5 to 6 per cent, of carbon dioxide, and 14 to 15
per cent, of oxygen ; and the tension of the former would be about
36 mm., and of the latter about 114 mm. Lowy2 calculates that the
tension of oxygen in the alveoli of the human lungs is from 12'6 to 13'5
per cent, of an atmosphere, or about 99 mm. of mercury.

In animals, direct determinations of the composition of the alveolar
air of an occluded portion of the lungs have been made. For the
collection of this air Pniiger3 constructed a special catheter (Fig. 71).

It consists of an
ordinary fine elastic
catheter, surrounded,
except at its extrem-
ities, by a tube with
a rubber enlargement
towards the free end
of the catheter. The
instrument is so small
that, when introduced
through the trachea
into a bronchus of a

FIG. 7l.-Pfluger's lung catheter. d°S> {i CaUS6S ?°

ranee to the free

passage of air into the other parts of the lungs. The rubber enlarge-
ment is now inflated, and shuts off' a portion of the lungs, from which
the alveolar air can be withdrawn through the inner tube of the lung
catheter. In such experiments Wolff berg 4 and Nussbaum 5 found
that the alveolar air of a dog contained 3'5 per cent, of carbon dioxide,
whereas the expired air yielded 2 '8 volumes per cent. It is to be noted
that this value for the alveolar air is higher than the normal, for the air
in the alveoli was shut off' from the tidal air, and, in fact, represents the
air after an equilibrium had been established with the gases of the blood
passing through that portion of the lung shut oft' by the catheter.

In the next place, it is necessary to consider the tension of the
oxygen and carbon dioxide present in the blood, and this involves a
preliminary study of the dissociation of oxyhrenioglobin. Under the
ordinary tension of oxygen in the air, haemoglobin readily combines
with oxygen, but if the external pressure be lowered sufficiently, then
oxygen is given off, and the oxyhujinoglobin undergoes dissociation.

1 Skandin. Arch. f. PhysioL, Leipzig, 1891, Bd. ii. S. 236.

2 Arch. f. d. ges. PhysioL, Bonn, 1894, Bd. Iviii. S. 416; " Untersuch. u. d. Respira-
tion und Circulation," 1895, S. 26.

3 Arch. f. d. ges. PhysioL, Bonn, 1872, Bd. vi. S. 43.

4 Ibid., 1871, Bd. iy. S. 465 ; 1872, Bd. vi. S. 23.

5 Ibid., 1873, Bd. vii. S. 296.

CAUSES OF THE EXCHANGE OF GASES.

775

The force with which the oxygen separates from the haemoglobin
under these circumstances is called the tension of dissociation. The
most important researches upon this subject are those of Htifner.1

The conditions of the dissociation of oxyhsemoglobin are the same, whether
it is a solution of freshly-made pure crystals of haemoglobin, or fresh
defibrinated blood. The dissociation is dependent upon the concentration of the
solution of haemoglobin ; thus, a weak solution is more readily dissociated under
a given pressure than a strong solution. It is also affected by temperature.2
As regards pressure, Htifner found in the case of a solution containing 14 per
cent of oxylisemoglobin at 35°, that, under a tension of oxygen of 152mm.,
98*42 per cent, of the pigment was oxy haemoglobin, and 1*58 per cent,
haemoglobin. When the tension of oxygen was reduced to 75 mm., the
percentages of oxyhaemogiobin and of haemoglobin were respectively 96*89 and
3 '11, and with a lower pressure the dissociation became more rapid, as shown
by the following curves : —

/6O

FIG. 72. — Curves of dissociation of oxy hemoglobin. The continuous line is for a
solution containing 14 per cent, of haemoglobin, the interrupted line for a
4 per cent, solution.

It is now necessary to compare with the tension of the oxygen and
carbon dioxide in the alveolar air the tension of those gases in the blood.
For the determination of these tensions in blood Pfliiger'3 used a special
instrument, known as the aerotonometer (see Fig. 73).

The principle of the aerotonometer and of other similar instruments is this :
Blood in contact with a mixture of oxygen, nitrogen, and carbon dioxide gives
up some of its gases if their partial pressures are greater than those of the
corresponding gases in the mixture ; on the other hand, if the tensions of the
gases in the blood be lower than the respective tensions of the gases in the
mixture, the blood takes up gas. Those interchanges persist until equilibrium
is established, until the tension or partial pressure of the gas in the blood is

1 Ztschr. f. physiol. Chem., Strassburg, Bd. vi. S. 109; Bd. xii. S. 582; Bd. xiii.
S. 285 ; Arch. f. Physiol., Leipzig, 1890, S. 1 ; ibid., 1895, S. 213.

2 Brasse, Compt. rend. Soc. de biol., Paris, 1888, S. 660.

3 Described by Strassburg, Arch. f. d. gcs. Phy-nol., Bonn, 1872, Bd. vi. S. 65.

776

CHEMISTR Y OF RESPIRATION.

equal to that of the corresponding gas in the mixture. In the aero tonometer
the blood is made to pass in a thin layer through a glass tube or tubes,

containing mixtures of gases of
known quantity and tension, and
it is arranged by practice that the
tension of the gases in the tubes
shall in the one case be greater,
in the other case smaller, than the
tensions of the corresponding gases
in the blood. The gases in these
tubes, after the blood has passed
through them, are analysed, and
from the alteration in the propor-
tion in the two tubes it is possible
to calculate the partial pressure
of the gases in the blood. The
aerotonometer is surrounded by a
water-jacket with a temperature
of 39°.

Figure 74 shows the con-
struction of a similar aerotono-
meter, devised by Fredericq.1 The
blood of the animal is rendered

// Hi J 11U III -.-HI uncoagulable by the injection of

sP It / 11 TflC peptone, in order that the experi-

MU Hi fW 11 III llvt ment may be continued for an

hour or two. The blood flows
directly from the carotid artery
through the instrument, and re-
turns to the jugular vein.
The aerotonometer contains, for example, at the commencement of the
experiment, oxygen 10 per cent., carbon dioxide 5 per cent., and nitrogen 85
per cent, of an atmosphere. The blood is passed through for one hour, and at
the end of that time the gases in the aerotonometer are analysed, and found to
be 14 per cent oxygen, 2*8 carbon dioxide, and the remainder nitrogen. From
these figures it is concluded that the tension of the oxygen in the blood was
14 per cent, of an atmosphere, and that of the carbon dioxide 2 '8 per cent, of
an atmosphere.

Bohr 2 had previously introduced a modified aerotonometer, the " haemat-
aerometer," through which a constant and rapid stream of blood could be
maintained during each experiment (see Fig. 75).

What, then, are the tensions of the gases of the blood ? The results
obtained by different observers are very discordant, and have given rise to
considerable discussion.3 Nussbaum 4 determined simultaneously on a
dog the tension of the carbon dioxide in the blood from the right side
of the heart and in the air of the alveoli ; he found for the former a
pressure of 3*81 per cent, of an atmosphere, and for the latter 3'84
per cent. The tension of the carbon dioxide in normal alveolar air
would be lower, for it would be mixed to a certain extent with the

1 CentralU. /. PhysioL, Leipzig u. Wien, 1893, S. 33 ; Fredericq et Nuel, ''Elements
de physiologic humaine," 3e Edition, 1893, p. 156.

2 Skandin. Arch. /. PhysioL, Leipzig, 1891. Bd. ii. S. 238.

3 Bohr, loc. dt. ; Fredericq, CentralU. /.' PhysioL, Leipzig u. Wien, 1893, S. 33 ;
Haldane and Lorrain Smith. Journ. PhysioL, Cambridge and London, 1896, vol.
xx. p. 497.

4 Arch. /. d. ges. PhysioL, Bonn, 1873, Bd. vii. S. 296.

FIG. 73.— Pfluger's aerotonometer.

CA USES OF THE EXCHANGE OF GASES.

777

tidal air. Wolff berg l found that the expired air of a dog contained 2*8
volumes per cent, of carbon dioxide, or a tension of 21*3 mm. of mercury.
Strassburg2 found a tension of 5*4 per cent, of an atmosphere for the

FIG. 74. — Frederick's
aerotonometer.

FIG. 75. — Bohr's lisemataerometer.

carbon dioxide in the venous blood of the right side of the heart. This
value, higher than those obtained by Wolffberg and Nussbaum, could be
explained by the fact that the dog's lungs were not so well ventilated,
since tracheotomy had not been performed. In arterial blood Strass-
burg found the tension of carbon dioxide to be 2 '2 to 3*8 per cent,
of an atmosphere, and for the oxygen Herter3 obtained a tension of 10
per cent, of an atmosphere.

Very different results have been obtained by Bohr 4 in experiments
upon dogs. He obtained for the oxygen tension of arterial blood results
as high as 101 to 144 mm. of mercury, and in nearly every case the tension
was higher than the tension of oxygen in the air at the bifurcation of
the trachea, in one case by as much as 38 mm. As regards the tension of
carbon dioxide very discordant results were obtained. In eleven experi-
ments, in which the animal breathed pure air, the tension of the carbon
dioxide in the arterial blood varied between 0 and 28 mm. of mercury; and
in five other experiments, when the air inspired contained carbon dioxide,

1 Arch. f. d. ges. Pkysiol., Bonn, 1871, Bd. iv. S. 478.
-Ibid., 1872, Bd. vi. S. 77.

3 Ztschr.f. physiol. Chem., Strassburg, 1879, Bd. iii. S. 98.

4 Skandin. Arch. f. Physiol. , Leipzig, 1891, Bd. ii. S. 236.

7 ?8 CHEM2STR Y OF RESPIRA TION.

the tension of that gas varied between 0'9 and 57'8 mm. In the majority
of the experiments the air of the trachea contained carbon dioxide with
a higher tension than that of the gas in the blood. From these results
Bohr concluded that the exchange of gases between the air of the alveoli
and the blood in the lungs could not be accounted for by diffusion alone,
and he suggested that the tissues of the lungs played an active part in
the absorption of oxygen and in the excretion of carbon dioxide.

These results are so opposed to those obtained by Pniiger and his
pupils, that they naturally are subject to considerable criticism.1 In the
first place, it is to be noted that the respiratory quotients obtained by
Bohr during his experiments show values varying from 0'54 to 1*01,
results which suggest imperfect and irregular ventilation of the lungs.
Hiifner 2 contests Bohr's results, and suggests that the irregularities in
the results are due to a want of equilibrium in the tension of gases in
the blood and in the air of the hsemataerometer. He finds that equilibrium
only obtains after several minutes and vigorous shaking of the blood in
the apparatus. Similar objections have been made by Fredericq,3 who
obtained, for the tension of oxygen in the peptonised arterial blood of the
dog, results always lower than the partial pressure of oxygen in the air
of the alveoli. Further, the results obtained by Fredericq for the carbon
dioxide agree with those given by Pflliger and his pupils.

The following values are given by Fredericq 4 for the tension of oxygen
and of carbon dioxide in percentages of an atmosphere.

Dog.

External Air. Air of Alveoli. Arterial Blood. Tissues.

Tension of oxygen . . 20'95 > 18 > 14 > 0

External Air. Air of Alveoli. Venous Blood. Tissues.

Tension of carbon dioxide . 0'03 < 2'8 < 3'81-5'4 < 5-9

Quite recently Haldane and Lorrain Smith 5 have studied the tension of
oxygen in the arterial blood of man by a new method, which, they maintain,
avoids the probable sources of fallacy in the aerotonometer. In this new
method the tension of oxygen in the arterial blood is calculated from the
percentage of carbon monoxide breathed by the subject of the experiment, and
from the final saturation of liis blood with carbon monoxide. The results give,
for the oxygen tension of human arterial blood, a value of 26 '2 per cent, of an
atmosphere, or 200 mm. of mercury. This value is about twice as high as that
of the oxygen in the pulmonary alveoli, and if it be correct, it follows that
diffusion alone does not explain the absorption of oxygen by the blood in the
lungs. Haldane and Lorrain Smith discuss some of the possible sources of
error in their method, such as the estimation of the saturation of the blood
with carbon monoxide, the dissociation of carboxyhsemoglobin, the effect of
dilution of the haemoglobin, and the excretion or oxidation of carbon monoxide ;
but the test experiments which they made confirm them in their opinion of its
accuracy.

Before, however, these results are accepted, further experiments are needed
to test the method, for it is impossible with our present knowledge to judge

1 See also criticism by Zuntz, Fortschr. d. Med., Berlin, 1890, Bd. viii. S. 856.

2 Arch. f. PhysioL, Leipzig, 1890, S. 10.

3 CentralU.f. PhysioL, Leipzig u. Wien, 1893, S. 33.

4 Fredericq et Nuel, "Elements de physiologic humaine," Gand, 1893, pp. 156-158.

5 Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 497.

CAUSES OF THE EXCHANGE OP GASES. 779

it correctly. Some of the results obtained by Haldane and Lorrain Smith in
their examination of these sources of fallacy are opposed to those obtained by
Hiifner l and Saint-Martin.2

It is impossible to pass a verdict upon such discordant evidence,
especially since further investigation is necessary to test the soundness
of many of the experiments and of the conclusions based upon the results.
It is permissible, however, to accept the provisional conclusion that the
exchange of gases between the blood and the air in the lungs is effected
by physical and chemical means, of which the most important is
diffusion.

According to the calculations made by Zuntz,3 the surface of the
human lungs is 90 square metres, and through this there diffuse during
quiet breathing about 300 c.c. of carbon dioxide and about the same
quantity of oxygen in a minute. Through the square centimetre of
surface there would pass only the small quantity of 0*0003 c.c. of gas.
Now Exner's 4 experiments show that through the square centimetre of
a soap film 0*6 c.c. of air diffuse into an indifferent gas during one
minute. The velocity of diffusion is proportional to the density of the
gas, therefore a difference in tension of 20100 of an atmosphere, or 0'3
mm. of mercury, would be sufficient to make 0'0003 c.c. of oxygen pass
through such a film in a minute. Further, the velocity of diffusion is
proportional to the coefficient of absorption of the gas in the fluid in
question, and inversely proportional to the square root of its density ;
therefore the velocity for carbon dioxide is about thirty times greater
than that of oxygen, and there is needed for carbon dioxide an even less
difference of tension to cause a diffusion of gas from the blood into the
alveoli. These considerations Zuntz supports by the following experi-
ment. The bronchus of a frog's lung is ligatured, and the lung is placed
in carbon dioxide ; within a minute the lung is distended, owing to the
diffusion of carbon dioxide being, on account of its high coefficient of
absorption, about forty-five times greater than that of air. If a tube be
placed in the bronchus, the diffused gas can be collected and measured.

Diffusion appears to be sufficient to account for the phenomena of gaseous
exchange in the lungs. Other conditions possibly assist in the process. It
has been shown that oxygen in combination with haemoglobin appears to have
the property of driving out carbon dioxide.5

Fleischl von Marxow 6 supposes that the sudden percussion given by the
contraction of the ventricles to the blood assists in the liberation of the
carbon dioxide in the lungs, and of oxygen in the arterioles supplying the
tissues of the body. This theory, however, after the criticisms brought forward
by Zuntz,7 appears to be untenable.

1 Arch.f. Physiol., Leipzig, 1895, S. 213.

2 Compt. rend. Acad. d. sc., Paris, 1891, tome cxii. p. 1232 ; 1892, tome cxv. p. 835.
G Arch.f. d. ges. Physiol. , Bonn, 1888, Bd. xlii. S. 408.

4 Ann. d. Phys. u. Ohcm., Leipzig, 1875, Bd. civ. S. 321, 443.

5 This article, p. 771. See also Holmgren, Sitzungsb. d. k. Akad. d. Wisscnsch.
Math.-naturw. 01., Wien, Bd. xlviii.; Werigo, Arch. f. d. ges. Physiol., Bonn, 1892,
Bd. li. S. 321 ; 1892, Bd. Hi. S. 194 ; Zuntz, ibid., Bd. Hi. S. 191, 198.

"Die Bedeutung des Herzschlages f. d. Athmung, eine neue Theorie des Respiration,"
Stuttgart 1887 ; Centralbl. f. Physiol., Leipzig u. Wien, 1887, S. 231, 662.
7 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 408.

780 CHEMISTR Y OF RESPIRA TION.

THE EXCHANGE OF GASES BETWEEN THE BLOOD AND THE TISSUES.
INTERNAL EESPIRATION.

From a comparative study 1 of the process of respiration, it is seen
that the exchange of gases in the simplest forms of life is between the
external medium and the protoplasm of the cell.

In insects the smallest branches of the tracheal system carry oxygen to the
individual cells,2 which are often the seat of a most energetic combustion. In
no case is this more marked than in the luminous organ of the glowworm
(Lampyris splendidula), where, as Max Schultze3 has shown, there are
special cells at the end of the tracheae. The phosphorescence still continues
after the removal of the organ from the^nsect's body, and under the microscope
is seen to appear first in those parts of the cells which are around the ends of
the tracheae. The luminous cells have a great affinity for oxygen, as shown by
the fact that they cease to give out light if confined in an atmosphere free
from oxygen,4 and readily reduce osmic acid.

In the higher animals the blood is the medium which supplies the
tissues with oxygen and removes their carbon dioxide and other
waste products. Keference has already been made to the theories of
Lavoisier and Crawford 5 concerning processes of oxidation in the blood,
and we may proceed to consider the experimental evidence which has
been advanced in favour of the view, that the blood is the chief seat of
combustion. "When blood is shed and kept at the temperature of the
body, it becomes gradually poorer in oxygen,6 and there is always a dis-
tinct darkening in the colour of arterial blood, even within the first few
minutes after it is shed.7 These changes were investigated by Pnliger in.
a series of determinations of the gases of the blood, and he found that
arterial blood received directly into a large vacuum, surrounded by hot
water, gave a percentage of oxygen from 0*2 to 10 per cent, higher
than the amount extracted by the slower method of the ordinary gas-
pump. About the same time Alexander Schmidt 8 found that when the
blood of an asphyxiated animal was exposed to a known quantity of
oxygen, there was an absorption and disappearance of oxygen, and an
increase in the amount of carbon dioxide. The capacity of blood to bring
about this oxidation varied ; that taken from contracting muscles could
consume from 3 to 4 per cent., that from the heart 2 per cent., and blood
from the hepatic vein 0'8 per cent, oxygen. It was sho\vn by Afanassiew 9
that only the blood corpuscles and not the serum could take up oxygen
in this way, and Tschiriew 10 found that lymph resembled the serum in
containing no reducing substances.

1 See Paul Bert, "Lecons sur la physiologic coinparee de la respiration," Paris, 1870 ;
Johannes Miiller, " Elements of Physiology, " Baly's trans., vol. i. ; Pfliiger, Arch.f. d. ges.
PhysioL, Bonn, 1875, Bd. x. S. 270.

2 Finkler, Arch.f. d. ges. PhysioL, Bonn, 1875, Bd. x. S. 273 ; Kupffer, Beitr. z. Anat.
u. PhysioL als Festgabe 0. Ludwig, Leipzig, 1875, S. 67.

3 Arch.f. mikr. Anal., Bonn, 1865, Bd. i. S. 124.

4 Milne Edwards, " Le9ons sur la physiologie et I'anatomie comparee," tome viii. pp.
93-120. 5 See p. 756.

6 Nawrocki, Stud. d. physiol. Inst. zu Breslau, Leipzig, Bd. ii. S. 144 ; Sachs, Arch. f.
Anat., PhysioL u. wissensch. Med., 1863, S. 348.

7 Pfliiger, Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 61 ; Bernard, Journ. deVanat.
et physiol. etc., Paris, 1858, tome i. S. 233.

8 Bur. d. k. sachs. Gesellsch. d. Wissensch. Math.-phys. CL, Leipzig, 1867, Bd. xix. S. 99 ;
Ccntralbl. f. d. med. Wissensch., Berlin, 1867, S. 356.

9 Ber. d. k. sdchs. Gesellsch. d. Wissensch., Leipzig, 1872, Bd. xxiv. S. 253.
10 Ibid., 1874, Bd. xxvi. S. 116.

INTERNAL RESPIRATION. 781

Alexander Schmidt considered that in the blood an active oxidation
took place, for he concluded from his experiments that readily oxidisable
substances and active oxygen or ozone existed in that fluid, and further
that the oxidation in the body increased with the velocity of the blood.
The haemoglobin was looked upon as the regulator of the consumption
of oxygen, and this erroneous view, propounded by Lothar Mayer, is still
accepted by some medical writers.

As in all tissues, so in the blood there is a certain amount of
oxidation, but the evidence about to be given will show that it is small
and unimportant when compared with that taking place in muscles and
glands. The blood is not the cause of the oxidation of the body, the
cause is in the living cells of the tissues.1

The chief evidence is as follows : — A frog can live in an atmosphere
of nitrogen for seventeen hours, and during this time gives oft' carbon
dioxide, in fact during the first five hours it discharges as much as it would
under normal conditions.2 A frog will live a day or two in oxygen after
its blood has been entirely replaced by normal saline solution,3 and when
in this condition its intake of oxygen and output of carbon dioxide are
equal to that of a normal frog.4 The experiments of Finkler5 show
that the consumption of oxygen is independent, naturally within
certain limits, of the velocity of the circulating blood. Further, the
respiratory exchange of rabbits, deprived by bleeding of one-half of their
haemoglobin, is equal to that of the same animals before the loss of
blood ; 6 patients with simple anaemia or with severe leukaemia absorb
as much oxygen and excrete as much carbon dioxide as healthy men at
rest and upon a similar diet.7

It was long ago shown by Spallanzani that living tissues removed
from a recently killed animal took up oxygen and discharged carbon
dioxide, and that this exchange was greater in most tissues than it was in
blood. Similar experiments have been made by others.8

Paul Bert placed tissues from a recently killed dog in air for
twenty-four hours, the temperature varying from about 0° to 10°, and
obtained the following results : —

100 grms. of muscle absorbed 50'8 c.c. of oxygen, and discharged 56 -8 c.c. of carbon dioxide,

brain ,, 45'8 „ 42'8 ,,

kidney ,, 37'0 ,, 15-6

spleen ,, 27'3 ,, 15'4 ,,

testis ,, 18-3 ,, 27'5
broken \

,, bone & [• ,, 17'2 ,, 8'1 „
marrow J

1 Pfliiger, Arch.f. d. ges. PhysioL, Bonn, 1875, Bd. x. S. 251 ; 1878, Bd. xviii. S. 247 ;
1893, Bd. liv. S. 333.

2 Pfliiger, ibid., 1875, Bd. x. S. 251.

3 Cohnheim, Virchow's Archiv, Bd. xlv.

4 Oertmann, Arch. f. d. ges. PhysioL, Bonn, 1877, Bd. xv. S. 381.

5 Ibid., 1875, Bd. x. S. 368.

(i Pembrey and Gtirber, Journ. PhysioL, Cambridge and London, 1894, vol. xv. p. 449.

7 Hannover, " De quantitate relativa et absoluta acidi carbonici ab homine sano et
n?groto exhalati"; Abstract given by Moller, Ztschr. f. BioL, Miinchen, 1878, Bd. xiv.
S. 546 ; Pettenkofer and Voit, Ztschr. f. BioL, Miinchen, 1869, Bd. v. S. 319.

8 Spallanzani, "Mem. sur la respiration," trad. parSenebier, 1803, p. 86 ; G. Liebig, Arch,
f. Anat., PhysioL u. ivissensch, Med., 1850, Bd. xvii. S. 393 ; Matteucci, Compt. rend. Acad.
d. sc., Paris, 1856, tome xlii. p. 648 ; Ann. de chim. et phys.. Se"r. 3, Paris, tome xlvii. p. 129 ;
Valentin, Arch. f. physiol. Heilk., Stuttgart, 1855, Bd. xiv. S. 431 ; 1857, N.F. Bd. i. S.
285 ; Bernard, " Lemons sur les proprietes physiol. des liquides," Paris, 1859, tome i. p. 403 ;
Paul Bert, " Lecons sur la physiologie comparee de la respiration," Paris, 1870, p. 46;
Regnard, "Rech. exper. sur les combustions respiratoires, " Paris, 1879, p. 23.

782 CHEMISTR Y OF RESPIRA TION.

In pure oxygen the tissues absorb more oxygen, but do not discharge
a much greater quantity of carbon dioxide than they do in air ; even
in nitrogen or hydrogen the tissues continue to give off carbon dioxide.1
The excised tissues of warm-blooded animals have a larger respiratory
exchange than the corresponding tissues of cold-blooded animals, and
differences are also observed in tissues from animals of different species.2
The respiratory exchange of isolated muscle rises and falls, within certain
limits, with the external temperature.3

Experiments made upon excised tissues are liable to several sources
of error. Putrefaction may begin, and cause an absorption of oxygen
and a discharge of carbon dioxide ; 4 this danger, however, is small in
tissues removed directly after the death of the animal, and kept at a low
temperature, and free from septic contamination.5 Another source of
error is the loss of vitality in the tissues, and the accumulation of
carbon dioxide and other waste products in the interior of the tissues.

A much better method for the study of the respiratory changes in
isolated tissues and organs is that introduced by Ludwig ; 6 an artificial
circulation of blood is maintained, and the changes in the blood are
determined. By these and similar experiments it can be shown that
the tissues have the power of taking up oxygen, and also of oxidising
various substances. This power is possessed in a different degree by
the various tissues.7 Schmiedeberg has shown that benzyl alcohol

(C6H5CH2OH), and the aldehyde of salicylic acid C6H4< undergo

no appreciable oxidation when placed in blood, but if blood containing
one of these substances is made to circulate through a freshly excised
kidney then considerable quantities of benzoic acid (C6H5.C02H), or of

salicylic acid (C6H4^ Q|T )> as the case may be, are produced.

Ehiiich8 found that most tissues could reduce and decolorise
alizarine-blue and other pigments, but that the colour returned when
the tissues were exposed to the air. Tissues placed in normal saline
solution containing oxyhaemoglobin quickly reduce that substance, and
in this respect muscle is the most effective. Bernstein9 found the
following values for the rate of reduction : Muscle 100, liver 8147,
involuntary muscle 7 2 '4, and the mucous membrane of the stomach
57*05 ; lung tissue, on the other hand, had a very feeble power of
reduction. This relative power of reduction holds good for tissues
taken from frogs and from mammals. Somewhat similar experiments
had been previously made by Yeo ; 10 he supplied a frog's heart with

1 Spallanzani, "Rapports de 1'air avec les etres organises," par Senebier, Geneve, 1807,
tome i. p. 447 ; tome ii. pp. 44, 56.

2 Paul Bert, loc. tit.

• 3 Regnard, " Rech. expe"r. sur les combustions respiratoires," Paris, 1879, p. 23. See
also "Animal Heat," this Text-book, vol. i. p. 840.

4 Hermann, "Untersuch. u. d. Stoffwechsel der Muskeln," Berlin, 1867, S. 37.

5 Tissot, Arch, de physiol. norm, et path., Paris, 1894, tome xxvi. p. 838 ; 1895, tome
xxvii.

6 Arb. a. d. physiol. Anst. zu Leipzig, 1868.

7 Schmiedeberg, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1876, Bd. vi. S. 233 ;
1881, Bd xiv. S. 288, 379. For further details and references, see Neumeister, " Lehrbuch
der physiol. Chemie," Jena, 1893, Th. 1, S. 8, et seq.

8 "Der Sauerstotfbediirfniss des Organisnms," Berlin, 1885.

9 Untersuch. a. d. physiol. Inst. d. Univ. Halle, 1888, Heft 1, S. 107.

10 Journ. Physiol. , Cambridge and London, vol. vi. p. 93. See also Vierordt, Ztschr. f.
Bid., Miinchen, 1875, Bd. xi. S. 195 ; Denning, ibid., 1883, Bd. xix. S. 483.

GASES BETWEEN BLOOD AND TISSUES. 783

solutions of fresh blood, and determined the reduction of the oxy-
hsemoglobin by means of the spectroscope. The results show that the
heart during contraction reduces the solution about ten times as quickly
as when it is at rest.

The causes of the exchange of gases between the blood and the
tissues. — The cause of the passage of oxygen from the blood to the
tissues, and of carbon dioxide from the tissues to the blood, appears to
be the difference in the tension of these gases in the tissues, and in the
lymph and blood which surround them. It has been shown that the
tissues have a great affinity for oxygen, and even store it up for the
future oxidation of some of their constituents ; and, on the other hand,
that they are constantly producing carbon dioxide, and can even do this
for a time in the absence of free oxygen.

The above conclusion is supported by the analyses of the gases of
lymph and other secretions, and the determinations of the tensions of
the gases in those fluids. Hammarsten l found that the lymph of a dog
contained O'l volume per cent, of oxygen, 3 7 '5 of carbon dioxide, and
1*6 of nitrogen. These results have been confirmed and extended by
other observers.2 Oxygen is present only in traces, but the quantity of
carbon dioxide is less than that found in venous blood. This latter fact
does not prevent the passage of carbon dioxide from the lymph to the
venous blood, for Gaule 3 has shown that the tension of the gas is higher
in the former fluid. It must be admitted, however, that further experi-
ments are needed upon this point, for Gaule's experiments are not con-
clusive, and Strassburg found the tension of carbon dioxide in lymph
to be intermediate between that in arterial and venous blood. Another
probable cause of the smaller quantity of carbon dioxide in lymph is
that many of the analyses were made upon lymph from the thoracic
duct ; the lymph would have been exposed in that situation to the
action of arterial blood. This difficulty, however, is not present in some
of the secretions. Thus, Strassburg 4 found in the urine and bile of a
dog a tension of carbon dioxide equal to 9 — 7 per cent, of an atmo-
sphere. Further, this physiologist has shown that, if air is injected into
a ligatured portion of the intestine of a living dog, and after a short
time is analysed, the tension of carbon dioxide is 7*7 per cent, of an
atmosphere ; that is, considerably greater than the tension of the gas in
the venous blood.

These results are confirmed by the analyses5 of some of the
secretions of the body, and of various pathological transudations (see
tables on p. 784).

Ewald also determined the tension of carbon dioxide in some of these
fluids, and found results as high as 7>>51, 10-92, 10'73, and 11-5 per cent,
of an atmosphere. It is therefore permissible to conclude that the tension
of carbon dioxide in the tissues which produce, and are in contact with,
these fluids is higher than the tension of that gas in the venous blood.

1 JBer. d. k. sticks. Gesellsch. d. Wissensdi. Math.-pkys. 01., Leipzig, 1871, Bd. xxiii.
S. 617.

2 Daehnhardt and Hensen, Virchow's Archiv, Bd. xxxvii. S. 55, 68 ; Tschiriew, Ber.
d. Tc. sacks. Gesellsck. d. Wissensck. Math.-pJiys. 01. , Leipzig, 1874, Bd. xxvi. S. 120;
Buchner, Arb. a. d. pkysiol. Anst. zu Leipzig, 1876, Bd. xi. S. 108.

3 Arch. f. PhysioL, Leipzig, 1878, S. 469.

4 Arck.f. d. ges. PhysioL, Bonn, 1872, Bd. vi. S. 94.

5 Tables given by Halliburton, "Text-Book of Chemical Physiology and Pathology,"
London, 1891, p. 392.

784

CHEMISTR Y OF RESPIRA TION,

DOG.

Tissues.

Tension of carbon dioxide "|

in percentage of an V5 - 9
atmosphere l . . J

Venous
Blood.

Air of
Alveoli.

External
Air.

> 3-81-5-4 > 2-8 > 0-03

CARBON DIOXIDE.

SECRETION.

OXYGEN.

Removable
by
Vacuum.

Removable
by Acid.

•

Total.

NITROGEN.

OBSERVER.

Vols.

Vols.

Vols.

Vols.

Vols.

per cent.

per cent.

per cent.

per cent.

per. cent.

Bile ....

0-2

14-4

417

56-1

0-4

Pfliiger.2

,, .

...

19-5

37-0

56-5

Bogoljubow.3

,, .

17-1

62-5

79-6

3 j

Submaxillary saliva

6 '-4

19-3

29-9

49-2

07

Pfliiger.4

(dog)

Submaxillary saliva

0-6

22-5

42-2

647

0-8

j >

(dog)

Parotid saliva (human)

1-0

3-5

40-60

43-5-63-5

2-5

Kulz.5

CARBON DIOXIDE.

FLUID.

OXYGEN.

NITROGEN.

OBSERVER.

Removable
by
Vacuum.

Removable
by Acid.

Total.

Vols.

Vols.

Vols.

Vols.

Vols.

per cent.

per cent.

per cent.

per cent.

per cent.

Peritoneal

0-139

9-404

4-866

14-27

2-107

Planer.6

Hydrocele
Subcutaneous oedema

016
Traces

32-49
22-25

32 -45
9-11

64-94
31-36

2-05
Traces

Strassburg.7
Ewald.8

Subcutaneous oedema

5 )

21-88

31-18

53-06

tt

3 j

(nephritis)
Pleuritic .

0-68

39-34

15-59

54-93

1-33

,, . . .

0-54

18-54

25-99

44-53

1-87

35 * • •

18-64

41-16

59-80

,, . . .

6-17

25-47

46-82

72-29

1-04

Hydrothorax .

0-29

25-34

48-67

74-01

0-87

» - *

1-01

25-71

55-50

81-21

2-47

1 Fredericq et Nuel, "Elements de physiologie humaine." 1893, 3e Edition, p. 158.

2 Arch.f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 173.

3 Centralbl. f. d. med. Wissensch. , Berlin, 1869, No. 42 ; Kowalewskv and Arnstein, Arch,
f. d. ges. PhysioL, Bonn, 1874, Bd. viii. S. 598.

4 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 686.

5 ZtscJir.f. BioL, Mtincheu, 1887, Bd. xxiii. S. 321.

6 Ztschr. d. Jc.-Jc. Gesellscli. d. Aertze zu Wien, 1859, No. 30.

7 Arch.f. d. ges. PhysioL, Bonn, 1872, Bd. vi. S. 94.

*Arch.f. Anat., PhysioL u. ivissensch. Med., 1873, S. 663 ; 1876, S. 422.

ANIMAL HEAT.

BY M. S. PEMBREY.

CONTENTS : — Thermometry, p. 785 — Warm and Cold Blooded Animals, p. 787 —
Temperature of Man and other Warm-Blooded Animals, p. 788 — Of Cold-
Blooded Animals, p. 792 — Hibernation, p. 794 — Influence of Various Condlv
tions upon Temperature, p. 798 — Time of Day, p. 798 — Age, p. 803 — Muscular
Work, p. 806— Mental Work, p. 807— Food, p. 809— Sleep, p. 810— Sex, p. 810
— Race, p. 811 — Menstruation and Pregnancy, p. 812 — Individual Peculiarities,
p. 812 — Temperature of Surroundings, p. 812— Extreme Heat and Cold, p. 814
—Baths, p. 818— Drugs, p. 820— Temperature of Different' Parts of Body, p. 824 ,
—Of Arterial and Venous Blood, p. 826— Of the Skin, p. 829— Regulation of
Temperature, p 831— -Heat Production, p. 832— Historical, p. 832— Relation to
Chemical Changes, p. 833— Specific Heat of Body, p. 838— Seats of Heat Produc-
tion, p. 839 — Measurement of Heat Production, p. 844 — Calorimetry, p. 844 —
Respiratory Exchange as a Measure of Heat Production, p. 847 — Heat Produc-
tion in Cold- Blooded Animals, p. 849 — Regulation of Heat Loss, p. 850 — Influence
of Size of Body, p. 852 — Influence of Nervous System, p. 854 — Development of
Power of Regulation, p. 865 — Temperature of Body after Death, p. 866.

THE higher animals have within their bodies some source of heat and
some mechanism to regulate the production and loss of heat, for in the
height of summer and in the depth of winter their mean temperature is
constant. Of this fact the ancients had but an imperfect knowledge ;
they had no thermometers, and therefore could only judge from their
sensations. Observations dependent upon the sensations of heat and
cold are necessarily imperfect and often fallacious. The invention,
therefore, of thermometers was imperative, if exact data upon the
temperature of animals were to be obtained

The Introduction of Thermometers. — Towards the close of the six-
teenth century the first thermometers appear to have been made.1 The credit
of the invention has been attributed chiefly to Sanctorius of Padua, and
Galileo ; the former based his thermometer upon the expansion of air enclosed
in a bulb at the end of a tube which contained a coloured liquid ; while Galileo
is said to have made, in 1612, the first alcohol thermometer. Boyle introduced
the alcohol thermometer into England, where Hooke, in 1665, recommended
that the zero of the scale should be the freezing point of water, which he and
Boyle found to be constant. In. 1680, Newton suggested the boiling point of
water for a further graduation of the thermometer, and Halley a few years
later proved that the point was a constant one, and recommended the use of
mercury in the construction of thermometers. 'Fahrenheit first replaced spirit
by mercury in 1720, and, after several attempts at graduation, introduced the '
scale which now bears his name. The introduction of the centigrade ther-

1 Holloway, "The Evolution of the Thermometer," Sc. Prog., London, 1895-96, vol. iv.
p. 413; Liebermeister, " Handbuch d. Path. u. Therap. des Fiebers," Leipzig, 1875, S. 3.

VOL. I. — 50

786 ANIMAL HE A T.

mometer was due to Celsius in 1742.1 Throughout this article the centigrade
scale is employed.

THE DETERMINATION OF TEMPERATURE IN DIFFERENT PARTS
OF THE BODY.

Varying quantities of heat are produced and lost in different parts
of the body, and although the circulation of the blood tends to bring
about a mean temperature of the internal parts, local differences are
present. It is important, therefore, that the determinations should be
made in those parts which have a temperature representing the internal
temperature ; and in order that the results may be comparable, the
observations should as far as possible be made in similar anatomical
positions.

The most suitable place for the application of the thermometer
varies under different conditions, and methods have to be considered,
not only in as far as they are scientifically sound, but also in respect to
their ease in practice.

The rectum naturally offers the readiest access to the internal parts, and
thermometers with or without a metal guard may be safely introduced 5 or
6 cms. This method is the most suitable in the case of animals, and may be
advantageously employed in infants. The vagina, uterus, and bladder of
women and female animals of suitable size have a similar value to that of the
rectum.

In order to obtain the internal temperature of the body, the bulb of the
thermometer, previously warmed in the mouth, may be inserted in the stream
of urine as it leaves the urethra.2 Apart, however, from the limited applica-
bility of this method, there is a danger of a loss of heat by evaporation and
radiation, but with care excellent results may be obtained.

The axilla is a convenient place for thermometric determinations in man,
for it is not liable to great variations in temperature. It is necessary, how-
ever, that the axilla be closed well and long enough for it to attain the
temperature of a closed cavity ; in very thin or wasted subjects it is difficult
to effect this, and the temperature should therefore be taken elsewhere in such
cases.

The groin has also been selected by some physicians for the observation of
temperature, but in man it is not so easy to retain the thermometer in the
fold of the groin as in the closed axilla. The method is useful in the case of
infants.

The mouth, on account of convenience, has been widely selected for the
clinical observation of temperature, but the readings of a thermometer, even
when the bulb is placed under the tongue and the mouth is firmly closed, are
liable to be low, owing to the danger of cooling of the tissues of the mouth,
externally by cold air, internally by the inspired air. The mouth is also liable
to considerable local variation of temperature.

In order to obtain accurate results, the thermometer should be retained for
eight minutes in the mouth, ten minutes in the well-closed and dry axilla, and

1 For an account of the introduction of the thermometer into clinical use, see Wunder-
lich, "Medical Thermometry," New Syd. Soc. Translation, 1871, p. 19; Lorain, "De la
temperature du corps humain," Paris, 1877, tome i. p. 39 et seq.

* Stephen Hales, "Statical Essays," London, 1731, 2nd edition, vol. i. p. 59 ; Martine,
"Essays, Medical and Philosophical," 1740, p. 335; Blagden, Phil, Trans., London, 1775,
vol. Ixv. pt. 1, p. 114 ; Davy, ibid., 1844, pt. 1, p. 63 : Mantegazza, Presse med. beige,
Bruxelles, 1863, tome xv. p. Ill ; Oertmann, Arch. f. d. ges. Physiol., Bonn, 1878, Bd.
xvi. S. 101.

WARM-BLOODED AND COLD-BLOODED ANIMALS. 787

for three or four minutes in the rectum or vagina;1 it should be kept in
position for a minute or two after the mercury has become stationary.

Different values have been given by various observers for the
temperature in the mouth, axilla, and rectum ; these will be critically
examined later, but at present it may be stated that the temperature
in the rectum is generally about three- or four-tenths higher than that
in the axilla or mouth. Under certain circumstances, however, this
relationship is altered. Thus Bosanquet2 found that, although the
temperature in the rectum was almost invariably higher than that in
the mouth, the average difference being four-tenths, yet on some occa-
sions, as immediately after eating, the temperature in the mouth
exceeded that in the bowel ; while on others, as during vigorous
exercise, the heat of the mouth sank considerably, e.g. to 35°'6 (96° F.),
that of the rectum rising to 37°'7 (99°'8) or 37°'8 (100°). Violent
exercise was found by Davy 3 to lower the temperature in the mouth,
and raise that in the axilla. The probable explanations of these differ-
ences are that vigorous exercise would, by the increase of respiration,
cool the mouth, and by increasing the vascularity of the axilla raise the
heat in that part. The increase in the temperature of the mouth
immediately after eating is probably due to the increase in the blood
supply and activity of the muscles and glands in that cavity.

In order to obtain the maximal temperature of the interior of the body,
Kronecker and Meyer 4 used small bulbs of mercury, made according to
the principle of Dulong and Petit's outflow thermometer. The animal
was made to swallow the small bulb, which, after evacuation by the
bowel, was placed in water gradually warmed until the mercury ex-
panded to the point of outflow; the temperature of the water repre-
sented the maximal temperature of the body. It was found by this
method that the maximal temperature of a dog was 3 9° '2 and that of a
rabbit 400>2, the rectal temperatures varying respectively from 37*'8 to
38°'2, and 37°'0 to 37°'9. Special thermo-electric methods will be
mentioned in the discussion of surface temperature.

Warm-blooded and cold-blooded animals. — An important differ-
ence in temperature exists between the higher and lower animals. Those
animals which are high in the scale of evolution, such as birds and
mammals, have a high temperature, which is fairly constant and in-
dependent of the temperature of the surrounding air. The lower
animals, on the contrary, have a temperature dependent upon, and only
slightly above, that of their surroundings, and thus liable to considerable
variations. This difference between the two classes is expressed by
the terms " warm-blooded " and " cold-blooded " animals. The classifica-
tion, however, is not absolutely exact, for there are mammals, such as
the marmot, hedgehog, bat, and dormouse, which are in an intermediate
position ; in warm weather these animals have a high temperature,
which is fairly constant and independent of their surroundings, but in
winter they become inactive, they hibernate, and their temperature
falls and varies with that of their surroundings. On the other hand,
there are bees, animals of a much lower order, which have and maintain

1 Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. pp. 554-559.
" Lancet, London, 1895, vol. i. p. 672.

3 "Researches," London, 1839, vol. i. p. 199.

4 Arch.f. PhysioL, Leipzig, 1878, S. 546.

7 88 ANIMAL HEAT.

a higher temperature than that of most cold-blooded animals, and are
not reduced to spend the winter in a torpid state.

Even in the case of the most perfectly warm-blooded animals there is
a stage in which they resemble cold-blooded animals ; infants and young
animals born in an immature condition cannot maintain the temperature
of their bodies at the normal height of the temperature of the adult ;
they need some accessory source of heat, such as the warmth of the
parent's body.

The terms " warm-blooded " and " cold-blooded " are inexact, for the tem-
perature of a so-called cold-blooded animal living in the tropics may, under
some circumstances, equal that of a mammal. John Hunter1 showed that
the essential difference in the two clashes was in the constancy and incon-
stancy of the temperature of the two groups, and he suggested that the warm-
blooded animals should be called "animals of a permanent heat in all atmo-
spheres;" the cold-blooded, "animals of a heat variable with every atmosphere."
Again, in 1845, Donders2 pointed out the same fact, and called the two groups
of animals, those with a constant and those with an inconstant temperature.
A year or two later, Bergmann 3 discussed very fully the objections to the
old terms, and suggested the definitions, " animals with a constant temperature
and animals with a varying temperature, or liomoiotliermic and poikilothermw
animals." In the present article, however, the terms "warm-blooded" and
" cold-biooded " are retained, for they have been sanctioned by long usage, and
their meaning is well understood. A further reason for their retention is
found in the fact that there is no hard-and-fast line between the animals with
a constant temperature and those with a varying temperature.

The temperature of man and other warm-blooded animals.—
The temperature of man. — The mean daily temperature of a healthy
man varies slightly according to the part of the body in which it is
observed: in the rectum it is 37°'2 (98°'96 F.), in the axilla 36°'9
(98°-45 F.), in the mouth 36°'87 (98°'36 F.). These figures are the
averages selected from the different observations given in the table on
p. 789, and represent the mean temperature of a working day.

The normal temperature of man is generally stated, as the result
of John Davy's numerous observations, to be 36°*9 (98°*4 F.) in the mouth.
This, however, is wrongly looked upon as the mean temperature of
twenty-four hours, for it represents the mean of observations taken
chiefly during the active part of a day, from about 8 A.M. to 12 o'clock
midnight ; all observers agree that the lowest temperatures are found
between midnight and early morning, and for very evident reasons the
observations during this period are few. The mean temperature of
twenty-four hours is therefore without doubt below 360<9 (98°4 F), and
the observations of Casey, Clifford Allbutt, and Ogle show that this
figure is even too high for the mean temperature of a working day.
The average obtained from their results is 36°'7 (98°14 F.) for the
temperature taken in the mouth. The observations upon the tem-
perature between midnight and morning are so few, that it is im-
possible at present to give the mean temperature of a day of twenty-four
hours.

1 "Works," Palmer's edition, London, 1837, vol. iii. p. 16.

2 "Der Stoffwechsel als die Quelle der Eigenwiirme bei Pflanzen und Thieren," Wies-
baden, 1847, S. 12-13.

3 "Gbttinger Studien," 1847, Abth. 1, S. 595.

TEMPERATURE OF MAN AND ANIMALS.

789

Maximum.

Minimum.

Mean Daily
Temperature.

Place of
Observation.

Observer.

37°'2

36°-5

36° '9

Mouth

Davy. l

37°'5

36° '8

37°'2

? >

Gierse.2

37°'0

36°-3

36°-7

Hooper.3

37°'36

36° -63

37°'05

J5

Hallmaun.4

37°'14
37°'12

36°-63
36° -39

36°'93\
36°'81J

J)

Lichtenfels and Frohlich.5

37°'0

36°'l

36°-7

j?

Casey.6

37°'0

36° '6

36°-8

j 3

Clifford Allbutt.7

37°'0

36°'2

36°-65

Ogle.«

38°'0

36°'2

37° -0

Axilla

"Wunderlich.9

37°'3

36°'l

»

Ringer and Stuart.10

37°'44

36°-15

36°'89

5 5

Liebermeister.11

37°'13

36°-73

36°'9

??

Darnrosch.12

37°'4

36°'l

36° -7

5 j

Billet.^

37°'9

36°-3

37°'l

Billroth.14

37° '8
37°'l

36° -5
36°-6

37°'2

36°-85

Rectum

55

Jlirgensen. 15
Neuhauss.]6

37°'l

5 )

Bosanquet.17

37°V35

36°-95

37°'13

Jaeger.18

37°'4

36°'15

36° -8

55

Nicol.19

37°'3

36°'l

36°-9

Urine

Richet.20

37°'95

36° '4

37°'2

Mantegazza. 21

36°'9

5 5

Gley.22

...

37°'l

Rondeau.23

37°'6

36° '2

36° -9

55

Pembrey.24

The temperature of other warm-blooded animals. — The observations
upon the temperature of animals are numerous, but have not been
repeated often enough under different conditions which are known to
affect the temperature of man. On this account, and also because
animals are known to have a somewhat variable temperature, it is
impossible in most cases to give the mean temperature. The following
table gives some of the results obtained by different observers : —

1 Phil. Trans., London, 1845, pt. 2, p. 319.

2 " Qurenam sit Ratio Caloris Organici, etc.," Halae, 1842, p. 40.

3 Med. Times and Gaz., London, 1866, vol. ii. p. 483.

4 Quoted from Landois, " Lehrbuch d. Physiol.," Aufl. 3, S. 406.

5 Denkschriften d. k. Akad. d. Wissensch. Math.-naturw. Cl., Wien, 1852, Bd. iii.
Abth. 2, S. 113.

6 Lancet, London, 1873, vol. i. p. 200.

7 Journ. Anat. and Physiol., London, 1872, vol. vii. p. 106.

8 St. George's Hosp. Rep., London, 1866, vol. i. p. 221.

9 " Medical Thermometry," p. 95.

10 Proc. Roy. Soc. London, 1877, vol. xxvi. p. 186.

11 "Handbuch d. Path. u. Therap. d. Fiebers," 1875, S. 78.

12 Deutsche Klinik, Berlin, 1853, Bd. v. S. 317.

13 These, Strasbourg, 1869.

14 Arch. f. klin. Chir., Berlin, 1862, Bd. ii. S. 331.

15 "Die Korperwarme des gesunden Menschen," Leipzig, 1873.

16 See p. 813.

17 Lancet, London, 1895, vol. i. p. 672.

18 Deutsches Arch. f. klin. Med., Leipzig, 1881, Bd. xxix. S. 522.

19 Result of observations not yet published.

20 Rev. scient., Paris, 1885, tome ix. p. 629.

21 Presse med. beige, Bruxelles, 1863, tome xv. p. 111.

22 Quoted from Richet, Rev. scient., Paris, 1885, tome ix. p. 432.

23 Ibid,

24 Result of observations not yet published.

790

ANIMAL HEAT.

Animals.

Average Rectal
Temperature.

Extremes of
Observations.

Number of
Observations.

Observer.

f

37°'9 (100°'2)

37°-2-38°-6

On 150 horses

Strecker.1

Horse . . .4

37°7 (99°-9)

600 on 100 ,,

Fohringer. l

(

37° '9 (100° -2)

36°'l-38°-6

On 212

Hobday.2

Ox ...

38°'85 (101°-9)

37°'7-40°-3

On 352 cows

Robertson.3

and oxen

I

38°-9 (102°-0)

38° 7-39° -1

39 on 1 cow

Siedamgrotzky.4

Cow . . . <

38°'6 (lor-5)

37°'5-39°-4

On 87 cows

Hobday.2

I

380<6 (10T-5)

37°'7-39°-6

On 100 cows

Singleton.5

(

40°'6 (105'-1)

400'0-41°-07

On 24 sheep

Davy. 6

40°'2 (104°-4)

38° '5-41° '8

284 on 6 ,,

Siedamgrot/ky.4

Sheep . . A

40°'0 (104°'0)

39° '7*40° "2

On more than

Hobday.2

100 sheep

(

40°'l (104°-2)

39°-6-41°'0

On 100 sheep

Singleton.5

(

38°'3 (100°'9)

190 on 17 dogs

Siedamgrotzky.4

37°'91 (100°'2)

37°'15-380-45

4 4 on several ,,

Hoppe.7

Dog . . .1

38°'8 (101°-8)

38°-3-39°-9

6 on 6 ,,

Obernier.8

38°'6 (lor-5)

38°'1-390>2

On more than

Hobday.2

200 dogs

\

38°-8 (101°-8)

38°'0-39°-8

On 100 dogs

Singleton.6

Cat ...

38°'7 (lor-7)

37°'9-39°-7

On 41 cats

Hobday.2

f

390>6 (103°'3)

38°-3-40°-8

169 on 4 young

Siedamgrotzky.4

I

pigs

Pig . . .1

38°7 (101°-7)

38°-7-39°-3

On more than

Hobday.2

I

^100 pigs

39°-2 (102°-5)

37°-3-39°-9

72 on 27 rabbits

Hale White.9

Eabbit .

38°'8 (101°-8)

38° -0-39° -5

7 on 7 „

Obernier.8

38°-7 (101°7)

37°'0-400-8

31 on 10 „

Pembrey.

Ferret .

39°-3 (102°-8)

37°'9-40°-4

On 8 ferrets

Hobday.2

/

38°7 (101°-7)

38°-5-39°-4

About 50 ob-

Finkler.10

servations

37°'93 (100°-2)

37°-0-39°-2

19 on 5 guinea-

Pembrey.

)

pigs

Guinea-pig . . /

39°'21 (102°'6)

37° '9-40° -2

35 observations

Richet.31

37°'4 (99°-4)

36° -0-38° -5

40 on 4 guinea-

Colasanti.12

pigs

38°'85 (101°-9)

38° -0-39° -6

30 on 1 guinea-

Pitts.

Rat (black and white)

37°'5 (99°'5)

37° '0-38° -5

pig
16 on 4 rats

Pembrey.

Rat (white) .

370t96(100°-3)

37°'4-38°-9

60 on 2 rats

Pitts.

Mouse (black and

37°'4 (99°-3)

36°'l-38°-6

27 on 8 mice

Pembrey.

white)

Monkey (Rhesus) .

38°'4 (101°-1)

36°-9-390<7

22 on 2 mon-

Hale White and

keys

Washbourn.13

27°'5 (81°-5)

25° '5-30°

5 on 2 speci-

Mikloucho

(cloaca or in

mens

Maclay. 14

abdomen)

32° -5 (90° -5)

26° -5-34° -2

7 on 7 speci-

Semon.15

(cloaca)

mens

Ornithorhynchus .

24°-8 (76°'6)

24° -4-25° '2

2 on 1 speci-

Mikloucho

(cloaca)

men

Maclay.14

[Continued on next page.

1 Ellenberger, " Vergleichende Physiol. der Haussaugethiere, " 1892, Bd. ii. Th. 2, S. 81.

2 Journ. Comp. Path, and Therap., Edin. and London, 1896, vol. ix. p. 286.

3 Veterinary Journ., London, 1885, vol. xx. p. 311.

4 Deutsche Ztschr. /. Thiermed., Leipzig, 1875, Bd. i. S. 87.

6 Veterinarian, London, 1888. 6 "Researches," London, 1839, vol. i. p. 208.

7 Virchow's Archiv, 1857, Bd. xi. S. 459. 8 " Der Hitzschlag," Bonn, 1867.
9 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 1.

10 Arch.f. d. ges. Physiol., Bonn, 1882, Bd. xxix. S. 112.

11 Rev. scient., Paris, 1884, tome viii. p. 306.

12 Arch. /. d. ges. Physiol., Bonn, 1877, Bd. xiv. S. 123.

13 Journ. Anat. and Physiol., London, vol. xxv. p. 379.

14 Proc. Linn. Soc. New South Wales, 1883. vol. viii. p. 425 ; vol. ix. p. 1205.

15 Arch.f. d. ges. Physiol., Bonn, 1894, Bd. Iviii. S. 229.

TEMPERATURE OF MAN AND ANIMALS.

791

Animals.

Average Rectal
Temperature.

Extremes of
Observations.

Number of
Observations.

Observer.

Fowl (common) . j

42°'8 (1090<0)
41°'6 (106°'9)

41°7-43°-9
40° "6-43° -0

On 14 fowls
On 111 fowls

Davy.1
Hobday.3

Duck . . . j

43°'6 (110°'5)
42°'l (107°'8)

43°-4-43°-9
41° -4-43° -0

On 8 ducks
On 24 ducks

Davy.1
Hobday.2

Goose .

41°7 (107°'0)

410<1-410<7

On 5 geese

Davy. 1

Pigeon .

40°'9 (105°'6)

40° '0-42° "5

20 on 4 pigeons

Corin and Van

Beneden.3

Ostrich .

37°'3 (99°'2)

36°-9-37°'8

On 5 ostriches

Hobday.2

In the next table are collected the results of various observations
upon other mammals and birds ; in most of these cases the figure given
for the temperature represents the result of a single observation 4 : —

Animal.

Temperature.

Place of Observation.

Observer.

Monkey (Simia aygulct)
Ass ....

39°'7 (103°'5)
36°'95 ( 980<5)

Rectum

Davy.
Hunter.5

Elk ....

39°'4 (103°)

,

Davy.6

Goat ....

39°'4 (103°)

}

..

Tiger ....

37°'2 ( 99°)

,

33

Ichneumon

39°'4 (103°)

3

33

Squirrel ....

38°'9 (102°)

5 3

Manatee ....

39°-4 (103°)

Abdomen

Martine.7

Whale

38°'8 (lOr-8)

Greenland whale

38°'9 (102°)

3 3

Scoresby.8

Seal ....

38°'9 (102°)

'

Tiedemann.9

Porpoise
Pigeon ....

37° '5 ( 99°'5)
42°-2 (108°)

Rectum

Davy.

Thrush ....

42°-8 (109°)

3

33

Turkey ....

420<8 (109°)

-

33

Guinea-fowl .

43° -3 (110°)

f

3 3

Pheasant

42°'6 (108°7)

3

Richet.10

Great titmouse

44°'0 (111°'2)

Tiedemann.

Sparrow ....

42°'l (107°'8)

,

Davy.

Swift ....

44°-0 (111°'2)

3

Tiedemann.

Heron ....

41°'0 (105°'8)

Pre" vost and Dumas. 1J

Redwing

43°-3 (109°'9)

3

Hobday.

Fieldfare

43°'7 (110°-6)

j

S3

Yellowhammer

43°'2 (109°'8)

3

3 3

The above tables show that the rectal temperature of most of
the mammals is higher than that of man; the most marked ex-
ception is found in the monotremata, the lowest group of the mam-
malia; thus the temperature of the porcupine echidna (Echidna hystrix)
varies from 25°'5 to 34°'2, that of the duckbilled platypus (Ornitho-

1 "Researches," London, 1839, vol. i. p. 186.

2 Journ. Comp. Path, and Therap., Edin. and London, 1896, vol. ix. p. 286.

3 Arch, de biol., Gand, 1887, tome vii. p. 265.

4 For the temperature of other animals, see Gavarret's " De la chaleur produite par les
etres vivants," Paris, 1855, p. 92 ; Richet, Rev. scient., Paris, 1884, tome viii. p. 298.

5 "Works," Palmer's edition, vol. iii. p. 340.

6 "Researches," London, 1839, vol. i. pp. 181, 188.

7 "Essays, Medical and Philosophical," 1740, p. 337.

8 Milne Edwards, " Le9ons," tome viii. p. 16.

9 "Physiologic," Bd. i. S. 454.

10 Rev. scient., Paris, 1885, tome ix. p. 202.

11 Ann. de chim. etphys., Paris, Ser. 2, tome xxiii. p. 61.

792 ANIMAL HEAT.

rhynchus anatinus) from 24° -4: to 25°'2. In the case of birds the
temperature is generally two or three degrees higher than that of
mammals.

In the observation of the temperature of animals, it is necessary,
if comparable results are to be obtained, to insert the thermometer
to a similar extent each time, and to prevent struggling of the animal
before and during the time of observation. Tinkler 1 found that the
rectal temperature of guinea-pigs was 36°'l, 38°7, and 380>9, at a depth
of 2'5, 6, and 9 cms. respectively. Aronsohn and Sachs2 found
that the rectal temperature of normal rabbits rose to over 40° after
a short chase, Hobday3 observed a rise to 41°'l in the case of sheep
and pigs, and Mott 4 has noticed a *ise of one or two degrees in the
temperature of monkeys, owing to a similar cause. Moreover, the times
of observation should as far as possible be similar, for animals show
a daily variation in temperature. Eabbits extended on their backs and
tied down lose so much heat that their temperature rapidly falls
(Legallois, Eichet:5)

The temperature of cold-blooded animals. — It has already been
shown that there is no hard and fast line between the so-called warm-blooded
animals — those with a constant temperature, and the cold-blooded animals —
those with a varying temperature. Further proofs of this will now be given,
and others will be brought forward when the subject of hibernation is
considered.

John Hunter6 made some interesting observations upon the temperature
of bees. He found in the month of July, when the temperature of the air was
12°*2, and a north wind was blowing, that the temperature at the top of a hive
full of bees was 27°'8. In December the temperature of the hive was 22° '8,
when that of the external air was only 1°'7. A single bee has so little power
of keeping itself warm, that it quickly becomes numb and almost motionless
when exposed to the moderate cold of a summer night. The aggregation,
however, of vast numbers in a hive ensures the production of enough heat to
keep the bees active even in winter, and for this production of heat a constant
supply of food is necessary. The warmth of the hive is needed also for
the eggs, pupae, and larvae, for Hunter found that they would not live in a
temperature of 17°. The wax is by means of the warmth kept so soft that the
bees can model it with ease.

Numerous observations upon the temperature of bees were made by
Newport,7 who found that, when the insects were in a state of activity,
their temperature was above that of their surroundings ; the larva and pupa
had a lower temperature than the imago, and less power of generating as well
as of maintaining their temperature. In winter the temperature of a hive,
when the bees were in a state of repose, fell considerably, and varied slowly
with that of the atmosphere ; the bees did not become torpid, but passed into
a deep sleep, broken at intervals by periods of activity. A very low atmo-
spheric temperature aroused the bees, and thus prevented any great fall in the
temperature of the hive. Thus on January 2, 1836, at 7.15 A.M., when the
temperature of the air was -7°*5, that of the hive was -l°'l, and the bees were
quiet, but after the bees were disturbed by tapping the hive, the temperature

1 Arcli.f. d. ges. Physiol., Bonn, 1882, Bd. xxix. S. 117.
-Ibid., 1885, Bd. xxxvii. S. 232.

3 Journ. Comp. Path, and Therap., Edin. and London, 1896, vol. ix. p. 286.

4 Note communicated to the writer.

5 Rev. sclent., Paris, 1884, tome viii. p. 300.

6 "Works," Palmer's edition, London, 1837, vol. iv. p. 427.

7 Phil. Trans., London, 1837, pt. 2, p. 253.

TEMPERATURE OF COLD-BLOODED ANIMALS. 793

was raised to 21°'l within fifteen minutes. On another occasion, when the
external temperature was 1°*4, that of the hive full of active bees was 38°'9.
The temperatures of individual nurse bees, brooding over the young bees in
the -combs, was as high as 29° '4, while the temperature of the cell after the bee
left it was 24° and that of the air 22°.

Similar results have been obtained by Reaumur,1 Huber,2 Dutrochet,3
Nobili and Melloni,4 and others.

In marked distinction to bees are other insects, such as some wasps and
flies, which can pass the winter in a state of torpor, their temperature varying
with that of their surroundings.

The difference between the temperature of the animal and that of its
surroundings varies in different classes of the cold-blooded animals. The
following are results obtained by different observers : —

Animal.

Temperature of
Animal.

Temperature
of Surroundings.

Observer.

Viper .

20a (68°) 5

14°'4

Hunter.6

Python .

24°'4 (76°)

15°'6

Sclater.7

Turtle .

28°'9 (84°) 5

26°'4

Davy.8

3 > * '

27°'8 (82°)

28°'9

Czermach.9

Frog .

17°'2(63°)5

16°7

Davy.6

3 > * •

14°'4(580)5

14°'4

5>

8°'9 (48°)

6°'7

Czemiach.9

Proteus .

17°'8 (64°)

13°'3

j j

Carp

20°'6 (69°)

18° '6

Hunter.6

Trout .

14°'4 (58°)

13° -3

Davy.8

35 • •

5°'6 (42°)

4° '4

Flying fish .

25°'6 (78°)

25°'3

Shark .

25° (77°)

23°7

Bonito .

37°'2 (99°)

26°'9

Crayfish

26°-l (79°)

26° 7

Crab .

22° -2 (72°)

22°'2 •

Snail (Indian)

24°'6 (76°-25)

24°'6

Earthworms .

14°-7 (58°*5)

13°'3

Hunter.6

Black Slugs .

13° (55°-25)

12°'2

> >

Leeches

13°'9 (57°)

13° '3

> »

Scarabseus

25° (77°)

24°'4

Davy.8

Glow-worm .

23°'3 (74*)

22°'8

»

Locust .

22°-2(72°-5)

16°'7

) j

Papillio Agauicm

27° (80°'5)

25° '6

non

Scorpion

25°'3 (77°'5)

26°'l

»

The results of observations on the temperature of other cold-blooded animals
will be found recorded in the works of Tiedemann,10 Eudolphi,11 Newport,12
Valentin,13 Dutrochet,14 Milne Edwards,15 and Gavarret.16

1 " Me^n. pour servira 1'histoire des insectes," M^m. 13, tome iv.

2 "Nov. obser. sur les abeilles," tome ii. p. 336.

3 Ami. d. sc. nat.. Paris, 1840, "Zoologie," Ser. 2, tome xiii. p. 5.

Rectal.

4 Ann. d. chim. etphys., Paris, Ser. 2, tome xlviii. p. 207.

6 "Works," Palmer's edition, London, 1837, vol. iv. p. 131 et seq.

7 Proc. Zool. Soc., London, 1862, p. 365.

8 "Researches," London, 1839, vol. i. p. 189; ibid., p. 219.

9 Journ. dephys., Paris, 1821. 10 "Physiologic," Bd. i. S. 454.

11 " Grundriss der Physiol.," Bd. i. S. 151 et seq.

12 Phil. Trans., London, 1837, pt. 2, p. 259.

13 Repert.f. Anat. u. Physiol., 1839, Bd. iv. S. 359.

14 Ann. d. sc. nat., Paris, 1840, "Zoologie," Ser. 2, tome xiii. p. 5.

15 " Le9ons sur la physiol.," tome viii. p. 7.

16 Article " Chaleur animale," " Dictionnaire ency eloped ique d. sciences medicales,"
Paris, 1874, Se"r. 1, tome xv. ; " De chaleur produite par les etres vi van ts, " Paris, 1855,
p. 113.

794 ANIMAL HEAT.

A consideration of the above lists shows that the temperature of cold-
blooded animals is generally a few tenths of a degree above that of their
surroundings, but that in some exceptional cases, as that of the python and
a fish known as the bonito (Thynnus pelamys), it may be 10 degrees
above the external temperature. Although these high temperatures are well
authenticated, the causes have not been determined ; it is to be noted, how-
ever, that the high temperature is more marked in the incubating female
python than in the male which does not incubate, and that the bonito has very
vascular red muscles.1

The temperature of many of the cold-blooded animals is often below
that of the air, owing to the great loss of heat by evaporation, and to
the large surface exposed, especially by insects, to cooling by radiation and
conduction.

Hibernation.2 — Certain animals, on the approach of winter, and in some
cases even in summer, retire to their burrows or other shelter, become inactive,
and fall into a torpid state. All the activities of the body are greatly reduced,
and the temperature falls to a point only slightly above that of the surround-
ings. Such is the condition known as hibernation.

The animals in whom hibernation has been definitely proved to take
place, do not belong to any one class ; examples are met with in mammals,
reptiles, amphibians, insects,3 molluscs, and lower animals, but no cases
are known among birds. As regards fishes, no well-authenticated cases of
hibernation are known ; there are doubtful instances in which the fish has
been imprisoned by the freezing of the water, and yet has remained alive for
some time.

The following mammals hibernate — spermophile, marmot, hamster,
squirrel, hedgehog, dormouse, bat, bear, and beaver. In some cases the
animal lays up stores of food, upon which it feeds when it awakes at
intervals during the period of hibernation ; in other cases, there is a special
accumulation of fat within the animal's body before the commencement of the
torpid state.

The further account of this subject refers only to the hibernating
mammals.

The condition of the animal during hibernation. — Respiration. — The
frequency of respiration is greatly diminished, and the rhythm is irregular
and often of the Cheyne-Stokes type. A hibernating dormouse may not give
a single respiration for ten minutes, then may take ten or fifteen breaths, and
again cease breathing for another period of several minutes. The same animal
in an active condition breathes at the rate of eighty or more in a minute.
Similar results have been obtained in the case of other animals.

Determinations of the respiratory exchange have been made. Spallanzani 4
found that during hibernation marmots and bats could be kept for four hours in
carbon dioxide gas without suffering any ill effects, whereas a bird and a rat
placed in the chamber at the same time died at once. Saissy 5 observed that
the amount of oxygen taken up by dormice varied as the activity of the
animal, and that during well-marked hibernation there was hardly any intake.

1 See p. 849.

2 Since this section was written, there has appeared a monograph by Dubois, " Physio-
logic compared de la marmotte," Paris, 1896, which contains a large number of original
observations and an abstract of the previous work upon hibernation. The bibliographical
index contains references to 145 papers.

3 Trimen, "Butterflies of South Africa," vol. i. p. 231. See also Nature, London, 2nd
April and llth June 1896.

4 Spallanzani, "Memoirs on Respiration," edited by Senebier, 1804. See article
"Chemistry of Respiration," this Text-book, vol. i.

5 "Recherches experimentales anatomiques, chimiques," etc., 1808; Reeve, f'0n
Torpidity," 1809; Edwards, " De I'influence des agens physiques sur la vie," Paris,
1824.

HIBERNATION.

795

These results have been extended and confirmed by Marshall Hall,1 Kegnault
and Keiset, Horvath,2 and others.3

Kegnault and Eeiset4 determined the respiratory exchange of several
hibernating marmots, and found that the intake of oxygen was about
one-thirtieth of that of an active animal, and only about two-fifths of the
oxygen appeared in the carbon dioxide discharged. The following are two
examples : —

Condition of Marmot.

Grms. per Kilo, and Hour.

02

Intake.

C02
Output.

CO2
~0t

Hibernating

0-48

0-37

•566

Awake

1-198

1-312

•796

A further proof that oxygen was stored up in the body of the hibernating
animal was found in the increase in weight of a marmot during profound
torpidity; it gained as much as 5 '9 grins, in five days.

The output of carbon dioxide was investigated by Horvath, who found that
the amount varied according to the animal's activity. The following is an
example of his results : —

Animal.

Condition.

Rectal
Temperature.

Temperature
of Air.

Respirations
per Minute.

C02

in Grms.

Sisel,5 163
grms.

Hibernating

9°

9°

5

•025 in three
hours.

AAvake

33°'5

13°

95

•457 in half
an hour.

Similar results have been obtained in the case of dormice and bats.6
According to Saissy,7 a hedgehog can absorb all the oxygen from the
air in which it is confined, and can even live for fifteen minutes in pure
nitrogen, whereas a rat under similar conditions dies in less than three
minutes.

Circulation. — The force and frequency of the heart-beat is much reduced
during hibernation ; in the case of the bat and dormouse to fourteen and
sixteen per minute or even less, the rate in the active animal being above 100
per minute. On applying a stethoscope to the chest of a hibernating bat,
no sound of the heart-beat can be heard, whereas, when the animal awakes and
becomes active, the sounds are so loud that they can be heard by the ear placed
one inch away from the animal (Hill and Pembrey).

1 Phil. Trans., London, 1832, pt. 2, p. 335; Barkow, " Der Winterschlaf," 1846,
here numerous additional references are given.

2 Verhandl. d. phys.-med. Gesellsch. in Wurzburg, 1878, Bd. xii. ; 1879, Bd. xiii. ;
1880, Bd. xiv. ; 1881, Bd. xv.

3 Pembrey and Hale White, Journ. Physiol., Cambridge and London, 1895-96, vol.
xix. p. 477.

4 Ann. d. chim. et phys., Paris, 1849, Ser. 3, tome xxvi. p. 429.

5 Allied to the marmots.

6 Pembrey and Hale White, loc. cit.

7 Deuteches Arch. f. d. Physiol., Halle, 1817, Bd. iii. S. 135.

796 ANIMAL HEAT.

The blood during hibernation has, according to most observers,1 an
arterial colour in the veins ; on the other hand, Marshall Hall states that it
has a venous hue even in the arteries. Further details concerning the
circulation will be found in the works of Reeve, Edwards, Barkow, Horvath,
and Dubois.2

The gases in the blood of hibernating and of active marmots have been
determined by Dubois,3 who found that during hibernation the arterial blood
contained as much oxygen, the venous blood less oxygen, and both arterial
and venous blood an excessive quantity of carbon dioxide, as compared with
the gases of arterial and venous blood from active animals.

Digestion. — The activity of the digestive organs varies according to the
habits of the different animals ; some, such as bats, take no food during the
winter; others, such as the dormouse,»hamster, and marmot, store up food,
which they consume during short periods of activity.4

Nervous system. — The excitability of the nervous system is greatly
depressed, and the nervous and other tissues of the body resemble those of
cold-blooded animals, in retaining their excitability for a long time after
removal from the body.4

Temperature. — During hibernation the temperature resembles that of a
cold-blooded animal, rising and falling with that of the surroundings. In
this way the rectal temperature may fall as low as 2° without injurious effects
following. When the animal awakes from hibernation its temperature
generally rises rapidly many degrees above that of the air ; the most rapid rise
takes place after the rectal temperature has reached 17°, when there may be
a further rise to 32° in. forty minutes ; this is accompanied by an increase in
the activity of the animal, and in the output of carbon dioxide.5

If the animal be fully awake and active, its temperature resembles that of a
warm-blooded animal; a fall in external temperature increases its activity,
temperature, and respiratory exchange, while a considerable rise has the
opposite effect.6

The power of heat regulation in hibernating animals. — The capacity for
maintaining a constant temperature varies according to the condition of the
animal ; during well-marked hibernation this power is very slight, and resembles
that of a cold-blooded animal, but when the animal is active its power of
regulating its temperature is comparable to that of a warm-blooded animal.

There is an intermediate stage when the animal is listless and inactive,
with a bodily temperature below that of its normal in summer, but considerably
above that of its surroundings. In this condition its power of regulation
resembles that of an immature mammal ; within certain narrow limits it is able
to maintain its temperature, but when exposed to cold its temperature falls,
and it passes into a cold-blooded condition.7

The awakening from hibernation. — One of the most interesting phenomena
in hibernation is the sudden rise in temperature which occurs when the animal
awakes from its torpor. This rise is so great and sudden that there is
nothing comparable to it, not even the sudden rise seen in some cases of fever.
Thus Horvath8 found the temperature of a sisel rise from 14° to 32° in
one hour and forty minutes, the temperature of the air remaining 1 4°. In the

1 In addition to other references, see Bernard, "Le9ons sur la chaleur animale," 1876,
p. 374.

2 See references on pp. 794-795.

3 Compt. rend. Soc. de biol., Paris, 1894, 22 decembre.

4 For further details see the works mentioned on p. 794; also Gavarret, " De la
clialeur produite par les etres vivants," Paris, 1855, p. 466.

5 Horvath, loc. cit. ; Pembrey and Hale White, loc. tit.

6 Pembrey and Hale White, loc. cit.; Hunter, "Works," Palmer's' Edition, London,
1837, vol. iv. pp. 141-145.

7 Pembrey and Hale White, loc. tit.

8 Verhandl. d. phys.-mcd. Gcsellsch. in Wiirzburg, 1878, Bd. xii. S. 162.

HIBERNATION.

797

bat and dormouse the rise may be even more rapid, as shown by the following
examples : l —

f = 17° when very quiet }

Bat-Rectal temperature- =34° wh,en ™ke and Temperature of

active, niteen air =10 '5.
I minutes later I

C = 13° 45 when asleep "j

Dormouse- \ =86°'78 when awake I Temperature of

and active, one air = 9 *5.
I hour later J

The rapid rise in temperature is accompanied by a marked quickening of
the respiration and of the heart-beat, and by active movements of the body.
In some cases, especially in the marmot, there is a convulsive shaking of the
body. The increase in the muscular activity appears to be the chief cause of
the increased production of heat, although Horvath 2 and Dubois 3 do not
accept this view. It is to be noted, however, that Horvath draws attention to
the increased respiration and heart-beat, and remarks that when once the
shivering movements of the marmot have commenced, nothing can prevent
the animal from awaking, and its temperature from rising. Dubois considers
that the liver plays the most important part, for he finds that extirpation of
the ganglia of the solar plexus, or ligature of the portal vein, and of the
inferior vena cava just above the liver, prevents the rapid rise of temperature
observed in an awakening marmot. An examination, however, of the experi-
ments made by Dubois shows that the influence of the nervous system is
considerable, for the greater the motor paralysis the smaller was the rise in
temperature.4 Kemoval of the cerebral hemispheres does not prevent hiber-
nation or the rise of temperature observed when the animal awakes. The
latter phenomenon, however, is abolished by section of the spinal -cord at the
level of the fourth cervical vertebra.

In the case of bats and dormice, Pembrey and Hale White have shown
that the sudden rise in temperature, when the animal awakes, is accompanied
by a greatly increased discharge of carbon dioxide.

The causes of hibernation. — The cause generally assigned for hibernation
is cold, but a more careful consideration of the facts long ago showed
that cold could not be the sole cause of the phenomena. Most observers
who have worked at the subject of hibernation have found that even
severe cold will not cause an active animal to hibernate. Saissy 5 observed
that a low temperature alone was ineffectual, but the continued effect of
cold, and a limited amount of air for respiration, caused a marmot to pass
into a typical hibernating condition even in summer. Mangili6 found that
torpid marmots and bats were awakened by exposure to severe cold, and that
confined air would not cause hibernation. Valentin and Horvath7 have
recorded cases of marmots hibernating under normal conditions during
summer; the animals were very fat, and the torpid condition was in all
respects similar to that in winter. Pallas states that if the hamster be buried
four or five feet below ground in a confined space, it begins to hibernate.8

Dormice have been kept throughout the winter in a warm room (16°), and
yet they hibernated, and were not aroused when the external temperature

1 Pembrey and Hale White, loc. tit. 2 Loc. cit., pp. 170, 175.

3 Compt. rend. Soc. de UoL, Paris, 1893, pp. 210, 235 ; 1894, pp. 36, 115.
* Ibid., 1893, p. 156.

5 "Recherches expdrimentales anatomiques," etc., 1808.

6 Arch. f. d. PhysioL, Halle, 1808, Bd. viii. S. 433, 437, 444.

7 Vtrhandl. d. phys.-med. Gesellsch. in Wilrzburg, 1881, Bd. xv. S. 209.

8 See also Paul Bert, "Lecons sur la physiol. com p. de la respiration," Paris, 1870,
p. 508.

798 ANIMAL HEAT.

was 20°; the warmth, however, delayed the onset of torpidity by two
months, and made it less profound.1 Further, it is found that in some cases
hibernation takes place in the dry hot season ; thus there is in Madagascar an
animal, closely allied to the hedgehog, and called the tanrec (Centetes
ecaudatus), which buries itself and becomes lethargic in the dry season, when
its insect food is inaccessible.2 The reptiles and many of the invertebrate
animals of tropical climates seek their hiding-places and fall into a state of
torpor during the dry season, when the heat is most intense. Torpidity in
dormice and hedgehogs may be delayed or prevented by a plentiful supply of
food.3

Want of food and cold seem to be the most important factors, but there
must be some 'other condition, at present unknown, to explain the cases of
marmots hibernating during the summer. It is certain that many species of
animals which become torpid in one country do not become so in another.
This fact, according to Barton,4 is very noticeable in the United States, for
many species which hibernate in Pennsylvania and other more northern
parts of the country, do not hibernate in the Carolinas and other southern
parts of the continent. Attempts have been made, but without success, to
find anatomical differences, especially as regards the blood vessels of the brain,
which would account for hibernation.5

The most recent theory is that of Dubois,6 who maintains that hibernation
is caused by an autonarcosis with carbon dioxide. In support of this theory
he adduces the following facts, namely, the accumulation of carbon dioxide in
the blood, and the production of torpidity in marmots exposed to an atmo-
sphere containing about 40 per cent, of carbon dioxide.

THE INFLUENCE OF VARIOUS CONDITIONS UPON THE TEMPERATURE OF
MAN AND OTHER WARM-BLOODED ANIMALS.

Numerous observers have insisted upon the occurrence of small
variations in the temperature of healthy men and animals, and have
shown by experiments that these variations are due to several causes.

Influence of day and night. — The temperature of man is subject
to slight daily variations ; it rises during the morning and afternoon,
it falls during the evening and early part of the morning. Upon
the points of maximal and minimal temperature, and the range of
variation, the results differ considerably, as the table on p. 799
shows.

It will be seen from these results that there is more agree-
ment upon the time of the minimal daily temperature than upon that
of the maximum. The causes of this difference are mainly two : in the
first place, there appears to be a rise and then a fall in temperature
before the ascent to the maximum begins. Thus Barensprung found a
rise in the early morning to 11 A.M., then a fall to 2 P.M.; and Damrosch
observed that the temperature rose from 7 A.M. to 10 A.M., and then fell

1 Berthold, Arch. f. Anat., Physiol. u. wissensch. Med., 1837, S. 63.

2 This statement of Cuvier and Bruguiere is contested by Brown- Se'quard ("Ex-
perimental Researches applied to Physiology and Pathology," New York, 1851, p. 25), who
maintains that the tanrec hibernates in the winter season, when the external temperature
is from 15 to 23 degrees.

3 Reeve, "An Essay on the Torpidity of Animals," 1809.

4 Trans. Am. Phil. Soc., Phila., 1799, vol. iv. p. 121.

5 Mangili, Arch. f. d. Physiol., Halle, 1808, Bd. viii. S. 446 ; Saissy, Deutsches Arch,
f. d. Physiol., Halle, 1817, Bd. iii. S. 136.

6 Compt. rend. Acad. d. sc., Paris, 1895, tome cxx. p. 458 ; Compt. rend. Soc. de MoL,
Paris, 1895, 3e Mars.

INFLUENCE OF DA Y AND NIGHT.

799

until 1 P.M. This small morning variation preceding the rise to the
maximum would explain some of the uncertainty concerning the
time of the maximum. The second important cause is the difference
in the meals of the English and German people ; the "fruhstuck "
is a small meal compared with the English breakfast, and thus, in
the observations made in England, the morning fall, beginning about
ten o'clock, would be masked by the increased warmth due to a hearty
meal.

Time of Maximum.

Time of Minimum.

Range of

Variations.

Place of
Observation.

Observer.

Between 8 A.M. and

About 1 A.M.

1°

Mouth.

Davy.1

5 P.M.

About mid-day

Between 11 P.M. and

0°-7

»>

Gierse.

2 A.M.

At 7 P.M.

Between 11 P.M. and

0°-72

j>

Hooper.

8 A.M.

Between 10 A.M. and

Between 11 P.M. and

0°'73

''

Hallmann.

7 P.M.

7 A.M.

Between 4 P.M. and

Between 1 A.M. and

0°'511

»

Lichtenfels and

5 P.M.

7 A.M.

0°-56/

Frohlich.

Between 4 P.M. and

About 2 A. M.

0°'9

> ?

Casey.

7 P.M.

Between 4 P.M. and

Between 12 P.M. and

0°'5

})

Clifford Allbutt.

8 P.M.

7 A.M.

About 7 P.M.

About 6 A.M.

0°'8

ii

Ogle.

Between 2 P.M. and

Between 2 A.M. and

0°'6

»i

Crombie.2

8 P.M.

7 A.M.

Between 9 A.M. and

About 1 A.M.

l°-2

Axilla.

Ringer and

6 P.M.

Stuart.

Between 10 A.M. and

Between 2 A.M. and

l°-29

5 >

Liebermeister.

6 P.M.

3 A.M.

About 5 P.M.

Between 7 P.M. and

0°'4

) 1

Damrosch.

7 A.M.

At 3 P.M.

At 3 A.M.

l°-3

; i

Billet.

Between 6 P.M. and

About 4 A.M.

0°'8

5>

Barensprung.3

7 P.M.

Between 4 P.M. and

Between 2 A.M. and

1°'3

Rectum.

Jurgensen.

9 P.M.

8 A.M.

Between 7 A.M. and

Between midnight

l°-4

!J

Jaeger.4

and 7 P.M., gene-

and 4 A.M.

rally about 4 P.M.

About 6 P.M.

About 2 A.M.

l°-25

»

Nicol.

At 4 P.M.

At 7 A.M.

l°-2

Urine.

Richet.5

Between 5 P.M. and

Between 3 A.M. and

1°'4

11

Pembrey.

8 P.M.

6 A.M.

Other causes for the different results are to be sought in the fact
that the observations are not comparable as regards the age, health,
meals, and work of the subjects of the experiment, and the temperature
was taken in different ways.

The following curve (Fig. 76), given by Kinger and Stuart,6 shows the
daily fluctuations of temperature in a boy 12 years old ; the thermometer,
a non-registering one, was kept in the closed axilla throughout the

1 The references are mostly given on p. 789 of this article.

2 Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 550.

3 Arch. f. Anat., Physiol. u. wissensch. Med., 1851, S. 159.

4 Jaeger, Deutsches Arch. f. klin. Med., Leipzig, 1881, Bd. xxix. S. 525.

5 Rev. scient., Paris, 1885, tome ix. pp. 430, 629.

6 Proc. Roy. Soc. London, 1877, vol. xxvi. p. 187.

8oo

ANIMAL HEAT.

Fahr.

time, and the readings were taken every
hour. The boy was in good health, and
was kept in bed during the observations.

In the next chart1 (Fig. 77) are the
daily curves representing the results of
Ogle, Clifford Allbutt, Casey and Eattray,
and those of Crombie, who, during
residence in Bengal, made observations
upon his own temperature and that of
natives.

FIG. 76. — Daily variations
in temperature observed
by Ringer and Stuart.
The observations extend
over 50 hours.

FIG. 77. — Daily variations in temperature
observed by Ogle, Clifford Allbutt,
Casey and Rattray, and Crombie.

The next curves (Fig. 78) represent the daily variation according to
Jiirgensen and Liebermeister's observations.2

37°5

.»

.*-

f..'

||-

«' .»

<-

»,,_

,\

/

*rs,

k

,'

37°

^

**~^t

f

_L

^X

,' \

n

fS

|

A

i

fS

•

/

NJI

'

\ /

~f

-

— t

~?

f

1 —

•

/'

\

ft

i

i

jf

•' /

±

.

^ ^

^

,f j\

j

^

'

K

--»

S

"l

_

»•

-a

|

36°

Mor

7

ling

8

9

10

II

Mi

i
d

-a

i
ay

2

3

4

5

Eve

7

fling

8

9

IO

II
Ni

Fl '
ght

2

3

4

5 I

Mori

7| 8

ling

9

IO

II 1

Mid-

day

FIG. 78. — Daily variations in temperature observed by Jiirgensen and Liebernieister.
The observations extend over 30 hours.

The average results of Thierfelder's 3 observations upon the daily
variations of temperature found in subjects of different age and sex are
shown in the following table : —

1 Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 568.

2 "Handbuch der Pathologic und Therapie des Fiebers," Leipzig, 1875.

3 Schmidt's Jahrb., Leipzig, 1851, Bd. Ixxi.

INFL UENCE OF DA Y AND NIGHT.

801

Morning.

(7-9 A.M.)

Noon.

Evening.

Newly born . . ' .

37°'41

37°'80

37°'61

Children

37°-37

38° -07

37°'12

*Hw£,e» : :

37°'0
37°'22

37°'25
37° '55

36° '60
37°10

Aged ....

37° '25

37°'58

37°'31

The following curve 1 (Fig. 79) represents the mean results of records
of the temperature of the urine taken by Eichet, Gley, and Eondeau ; the
times of meals were 7 A.M., 11 A.M., and 7 P.M., and no observations were
made between 9 o'clock in the evening and 7 o'clock in the morning.

Daily variations in
temperature, similar to
those already described,
have been observed in
natives of different
races living in the
tropics.2

As regards . the
causes of the daily
variation in tempera-
ture, muscular activity
and food appear to be
the most important
factors. In ordinary
life man is most active
and takes food during
the day, and is least
active during the night.
Debczynski3 found that
continuous work carried on throughout the night reversed the variation,
so that the maximal temperature 37°'8 occurred in the morning, and the
minimal 35°'3 in the evening. Night-watching without work had a similar
but smaller effect, the maximal temperature 37°'7 being in the morning,
the minimal 37°'5 in the evening. Jaeger 4 has obtained similar results,
and Krieger 5 states that work during the night and rest during the day
reverse the daily variation. The influence of inversion of the ordinary
routine of daily life has been studied by U. Mosso6; a series of observa-
tions of the rectal temperature was first made during a period when work
was performed in the daytime and sleep taken at night, and the two chief
meals were at 11 A.M. and 6 P.M. ; then there followed another period in
which sleep was taken during the day and work performed at night, and

1 Richet, Rev. scient., Paris, 1885, tome ix. p. 430.

2 Dav)T, "Researches," London, 1839, vol. i. p. 169 ; Jonsset, Arch, de med. nav., Paris,
1883, tome xl. p. 124 ; Maurel, Bull. Soc. d'anthrop. de Paris, 1884, tome vii. p. 381.

3 Jahresb. ii. d. Leistung. . . . d. gcs. Med., Berlin, 1875, Bd. i. S. 248.

4 Jaeger, Deutsches Arch. f. Idin. Med., Leipzig, 1881, Bd. xxix. S. 533.

5 Ztschr.f. Biol., Miinchen, 1869, Bd. v. S. 479.

6 Arch. ital. de biol., Turin, 1887, tome viii. p. 177.

VOL. I. — 51

*

/

\

S

\

\

\

\

\

V

/

\

/

\

IG. 79. — Cfurve of daily variation in the temperature of
the urine.

802

ANIMAL HEAT.

the two chief meals were at 11 P.M. and 6 A.M. Notwithstanding the
inversion of daily routine, Mosso found that the morning rise still took
place about the same time, and, as the following curves (Fig. 80) will
show, the daily variation was not inverted, although the sleep during
the day caused a fall, and getting up in the evening a marked rise, in
temperature. The effect of the experiment was to disturb the regularity
of the daily variation, but on the fourth day the influence of the sleep
during the day was most marked, a fact which seems to indicate that,
if the habit were long continued, a tendency to inversion would be
observed in the daily variation of temperature.

Hour

37°

Nor
t

a. in.

nal.
2

3

4

5 6

7

8

9

10

»

2

1

2

3

4

5

C

7

8

9

IO ,11

i

12

i

[

"flnYi

i

MK«

•— ~~,

.-x

"•x*.

-^-

S

^i^1*

"^•i.

1

/

/

....

*"-•

, /

* - .

• » r

i

:

i

Routine of life inverted,
tth. day, April 13th. 1885.

>

'^x*^

x—

•—\

/

^^^

f

\

/

>

/

\

«

/

/

j

/

\

~jf

1

/

\

j

- - -

• - - .

\

*^+^

z

\

^S^^

s

S,

*^.^

'

Hour

*

2

3

4

5

6

7

8

g

0

II Hours of sleep and rest.

6

7

B

9

10

,1

12

FIG. 80. — Daily variations in temperature observed during U. Mosso's experiments.

Buchser,1 an engineer, who was accustomed to sleep during the day
and work at night, found that his average morning temperature was
370>25, while his evening temperature was 360-8.

There are secondary causes of the daily variation. The periods of
high and low bodily temperature more or less correspond with the times
of day when the external temperature is high and low respectively.
Further, there appears to be a certain periodicity, the result of long-con-
tinued habits of life, stamped upon the processes which regulate tem-
perature. This is shown by the fact that the daily variation still
persists, although it may be slightly modified, during a period of fasting
or night-watching,2 and a similar daily variation is observed in the
respiration and pulse,3 in the discharge of urea,4 and in the capacity

1 Quoted from Carter, Jo urn. Nerv. and Ment. Dis., N.Y., 1890, vol. xvii. p. 785.

2 Jiirgensen, "Die Korperwarme des gesunden Menschen," Leipzig, 1873; Ogle, St.
Georges Hosp. Hep., London, 1866, vol. i. p. 228; Crombie, Indian Ann. Med. Sc.,
Calcutta, 1873, vol. xvi. p. 597; Liebermeister, "Handbuch d. Path. u. Therap. des
Fiebers."

3 Lichtenfels and Frohlich, Denkscliriften d. Jc. Akad. d. Wissensch. Wien, 1852, Bd. iii.
Abth. 2, S. 113 ; Neuhauss, Virchoivs Archiv, 1893, Bd. cxxxiv. S. 365. See also this
article, p. 813 ; Bosanquet, Lancet, London, 1895, vol. i. p. 672 ; Damrosch, Deutsches
Arch.f. klin. Med., Leipzig, 1853, S. 342 ; Jousset, Arch, de med. nav., Paris, 1883, tome
xl. pp. 284-5 ; Chossat, Mem. Acad. d. sc. de I'Inst. de France, Paris, 1843, tomeviii. p. 540.

4 Weigelin, Arch.f. Anat., Physiol. u. ivissensch. Med., Leipzig, 1868, S. 207.

INFLUENCE OF AGE. 803

for muscular work.1 Daily variations in the output of carbon dioxide
and in the intake of oxygen have been observed by Prout, Pettenkofer
and Voit, Fredericq,2 and others ; these variations in metabolism more
or less correspond with those observed in the temperature, and will be
found discussed more fully in another part of this work.3

Best in bed throughout the day does not abolish the daily variation ;
it is still present, although modified, in cases of disease, attended or
unattended by fever ; the morning rise still takes place even when light
is excluded (Ogle).

In animals, daily variations in temperature have also been observed,
but upon this point there are few exact observations taken throughout
the day and night. Strecker,4 from observations upon 150 horses, found
the average temperature between 6.30 A.M. and 8 A.M. to be 37°'9, that
between 5 P.M. and 6.30 P.M. to be 37°'93 ; but the minimum was 37°'2
and the maximum 38°'6. In the case of oxen, Robertson 5 found the
average morning temperature 380-7, the evening temperature 380>9 ; in
the cat the minimum is 37°'8 at 7 A.M. and the maximum 39°*08 at
10 P.M. (Bidder and Schmidt).6 Hunter states that the temperature of
an ass was 0°'5 higher in the evening than in the morning. According
to the observations of Siedamgrotzky,7 the maximal daily temperature in
horses was 38°'2 at 6 P.M., the minimum 37°*5 at 4 A.M. ; in a cow the
maximum was 390<1 at 5 P.M., and the minimum 38°-7 at midnight.
Corin and Van Beneden 8 have observed the daily variation in pigeons,9
and find that the minimum is at 4 A.M. ; that from this time to 8 A.M.
there is a rise, then a fall to noon, followed by a rise to the maximum
at 4 P.M. ; the daily variation amounts to 20<2. In the case of horses,
Hobday10 finds that the rectal temperature at 10 A.M. is 37°'6, and 37°'9
at 5 P.M. ; in the case of the rabbit, cat, and dog, Carter n has shown that
there is a distinct rhythm of temperature, the maximum occurring in
the evening (7-11 P.M.) and the minimum in the morning (7-11 A.M).

We may conclude that the daily variation in temperature is one of
the features of a corresponding variation in the activity of the tissues of
the body, as shown by the rate of the contraction of the heart, the
frequency of respiration, the intake of oxygen, the output of carbon
dioxide, the discharge of urea, and the capacity for muscular work.

The influence of age.— The temperature of newly-born infants and
animals is generally equal to, or even slightly higher than, that of their
parents, but it is much less stable, and is liable to much greater varia-
tions.

Edwards 12 found that the temperature of newly-born pups, kittens,
and rabbits fell when they were removed from their warm surroundings,
and continued to fall until it reached a point a few degrees above the

1 Patrizi, Arch. ital. de bioL, Turin, 1892, tome xvii. p. 134.

2 Trout, Ann. Phil., London, 1813, vol. ii. p. 330 ; vol. iv. p. 331 ; Pettenkofer and
Voit, Ztschr. f. BioL, Miinchen, 1866, Bd. ii. S. 459 ; Fredericq, Arch, de biol., Gand,
1882, tome iii. p. 729.

3 "Chemistry of Respiration," this Text-book, vol. i. p. 721.

4 Ellen berger, " Vergleichende Physiologic derHaussaugethiere" 1892, Bd. ii.Th.2, S. 81.

5 Veterinary Journ. , London, 1885, vol. xx. p. 311.

6 "Die Verdaunngssafte und der Stoff'wechsel," Leipzig, 1852, S. 346.

7 Deutsche Ztschr. f. Thiermed., Leipzig, 1875, Bd. i. S. 87.

8 Arch, de bioL, Gand, 1887, tome vii. p. 265.

9 See also Chossat, Mem. Acad. d. sc. de Vlnst. de France, Paris, 1843, tome viii. p. 540.

10 Journ. Comp. Path, and Therap.. Edinburgh and London, 1896, vol. ix. p. 286.

11 Journ. Nerv. and Ment. Dis., N.Y., 1890, vol. xvii. p. 782.

12 "De I'influence des agens physiques sur la vie," Paris, 1824.

804 ANIMAL HEAT.

temperature of the air. Newly-born guinea-pigs, however, were able
to maintain their temperature, provided that the exposure to cold was
not very great. Edwards therefore divided the young warm-blooded
animals into two classes, the warm-blooded and the cold-blooded. In
the former class the young animals are at birth blind, helpless, in some
cases naked, and cannot maintain their temperature. The members of
the latter class are even at birth in a condition of great development ;
their eyes are open, they are active, and maintain a fairly constant
temperature. It was also found that young birds could be classified
in a similar manner. As the animal grows, the fall in temperature on
exposure becomes less and less, and about the fifteenth day after birth
a fairly constant temperature can be maintained.

Edwards showed by comparative Experiments that the fall in tem-
perature on the exposure of newly-born animals was not due to the
greater cutaneous surface, in proportion to the mass of the body, as com-
pared with the ratio in adults. The absence or presence of feathers or
fur was only of secondary import, for an adult sparrow was able to
maintain its temperature even after all its feathers had been plucked
out.

Kaudnitz1 in 1888 discussed very fully the temperature of infants.
He made observations upon the variations of temperature in infants at
birth and during the first few days after birth. The influence of the
large cutaneous surface in relation to the mass of the body, and the loss
of heat from the skin, were shown by experiment to be only secondary
causes of the irregular temperature. Observations made upon the effect
of affusions of cold water showed that the rectal temperature in infants
a day or two old rose in the case of strong subjects, but remained
stationary or fell in the case of the weak. Kaudnitz concludes that
the imperfect development of the power of regulating temperature is
the chief cause of the variable temperature in infants ; and it has been
shown by the writer 2 that this is also the cause in the case of young
immature animals.

Before birth the temperature of the infant is slightly higher than
that of the mother's uterus ; 3 at birth the average rectal temperature
is 37°'5 (99°'5). Soon after birth, especially after the first bath, the
temperature falls to about 360-75 (98°*15), and during the next week or
two rises somewhat, and remains fairly constant between 37°'25 (99°'05)
and 37°'6 (99°'68). These figures are to be looked upon only as average
results, for all observers appear to agree that the daily fluctuations of
temperature are greater and more uncertain in children than in adults.4

1 Ztsclir.f. Biol., Miinohen, 1888, Bd. xxiv. S. 423. At tlie end of this paper is a very
complete list of papers bearing upon the subject.

2 Pembrey, Journ. PhysioL, Cambridge and London, 1895, vol. xviii. p. 363.
3Wurster, Berl. klin. Wchnschr., 1869, NT. 37; Alexcetf, Arch. f. GynaeJc., Berlin,

Bd. x. S. 141; Fehling, ibid., Bd. vii. S. 146; Preyer, " Specielle Physiologic des
Embryo/' Leipzig, 1885, S. 362.

4 Barensprung, Arch. f. Anat., PhysioL u. wissensch. Med., 1851, S. 138; Finlayson,
"On the Normal Temperature of Children," Glasgow Med. Journ., 1869, p. 186 ; Squire,
Trans. Obst. Soc. London, vol. x. p. 274; Raudnitz, Ztschr. /. Biol., Munchen, 1888,
Bd. xxiv. S. 423; here other references will be found; Jiirgensen, "Die Korperwarme
des gesunden Menschen," 1873, S. 49 ; Davy, "Researches," London, 1839, vol. i. p. 156 ;
Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 594 ; Mignot, These de Paris,
1851 ; Wurster, Berl. klin. Wchnschr., 1869, Bd. vi. S. 37 ; Andral, Compt. rend. Acad.
d. sc., Paris, 1870, p. 815 ; Roger, Arch. gen. de med., Paris, Ser. 4, tome v. p. 273 ; c| De
la temperature chez les enfants," Paris, 1844 ; Lupine, Gaz. med. de Paris, 1870 ; Fehling,
Arch.f. GynaeJc., Berlin, 1874, Bd. vi. S. 385.

INFLUENCE OF AGE.

805

The average temperature falls one- or two-tenths from infancy to
puberty, and about the same amount from puberty to middle age ; after
that stage is reached the temperature rises, and about the eightieth
year is almost as high as in infancy.1 According to Einger and Stuart,2
the average daily maximum in persons under 25 years is 37°'2 (99*), in
those over 40 years, 37°'l (98°-8).

As regards the temperature in old age, all observers seem to agree
that it is equal to or slightly above that of adults. Davy 3 found the
mean temperature of eight healthy old persons, with an average age of
88, to be 36°-9 (98°4o) in the mouth. Charcot4 states, as the result
of numerous determinations, that the rectal temperature in the aged
is 37°'2 to 37°'5, and is rarely higher or lower than in the adult; but
the temperature in the well-closed axilla is often two or three degrees
below that in the rectum, on account of the small and feeble circulation
in the skin of the aged. Mosse' and Ducamp5 have compared the
temperature of the axilla and rectum of aged people, and have obtained
the following results; each figure represents the mean of twelve or
fifteen observations : —

MORNING TEMPERATURE.

EVENING TEMPERATURE.

Age.

Axilla.

Rectum.

Axilla.

Rectum.

75

36°'40

36°'83

36°'58

37°'04

76

36°-48

37°'06

36°'41

36° '86

80

36°'08

36°'46

36°'40

36°'94

The results obtained by Eoger 6 upon seven healthy people, whose
ages ranged between 72 and 95 years, are, for the mean temperature,
36°-68 and 36°'23 ; for the minimum 36° and 35°'5, for the maximum
37°'10 and 37C, in the axilla and mouth respectively.

In the case of young animals born in an advanced condition of develop-
ment, the temperature is generally higher than that of the parents. Thus
foals and calves, several hours after birth, have a temperature 0°'5 to 1° above
that of their mothers. The average temperature of foals for the first five
days is 39° '3, and then gradually falls, as shown by the table on p. 806, which
represents the results of six hundred observations made by Fohringer 7 upon
one hundred horses.

Similar results as regards the effect of age in horses were obtained by
Siedamgrotzky,8 and in the case of cows and sheep by Hobday.9

1 Wunderlich, "Medical Thermometry " ; Biirensprung, Arch. f. Anat., Physiol. u.
wissensch. Med., 1851, S. 148.

2 Proc. Roy. Soc. London, 1877, vol. xxvi. p. 194.

3 Phil. Trans., London, 1844, pt. 1, p. 59; "Researches," London, 1839, vol. in.
p. 4.

4 Gaz. hebd. de med., Paris, 1S69, tome vi. p. 324.

5 Gaz. hebd. d. sc. med. de Montpellier, 1886.

6 Arch. gen. de m6d. , Paris, Se"r. 4, tome v. p. 273.

7 Ellerxberger, " Vergleichende Physiologic der Haussiiugethiere," 1892, Bd. ii. Th. 2,
S. 81.

8 Deutsche Ztschr. f. Thicrmcd., Leipzig, 1875, Bd. i. S. 87.

9 Journ. Comp. Path, and Therap., Edinburgh and London, 1896, Bd. ix. p. 286.

8o6

ANIMAL HEAT.

Age.

In the Stables.

Age.

In the Fields.

4-6 years

38°-05

4-6 years

37°'40

6-8 „

37°'92

6-12 „

37° '24-37° '49

8-18 „

37°'85

12-18 „

37°'48

The influence of muscular work. — During muscular work there is
an increased production of heat, and were it not for the compensation
brought about by the increased loss of heat the temperature of the body
would rise considerably. The effeot^theref ore, of muscular work upon the
mean temperature varies according to the perfection of the compensation.
Jlirgensen l found that the work involved in sawing wood for six hours
raised the temperature of a healthy man 1°*2 above the normal, but
as soon as the work was finished the temperature fell rapidly. Davy 2
made numerous observations upon the effect of active exercise on his
own temperature. The highest readings of the thermometer under the
tongue were 37°'5 (99°'5) and 37°'8 (100°); some previous observations
upon the temperature of men after walking two or three hours showed
a rise of -8° in the temperature of the urine, but no change in that
taken in the mouth ; after a rest the temperature rapidly fell to the
normal. Alpine climbing, even on cold days, was found by Clifford
Allbutt 3 to raise the temperature of the mouth about half a degree ;
the same form of exercise was taken by Liebermeister and Hoffmann,4
who observed the temperature in the axilla during both the ascent and
descent ; the chief results were as follows : —

Liebermeister's temperature, 36° '82 before ascent and 37° '85 maximum during ascent.

Hoffmann's ,, 36° '50 „ ,, ,, 37° '95 ,, ,, ,,

Liebermeister's ,, 36°'60 ,, descent,, 37°'60 ., ,, descent.

Hoffmann's ,, 36°'40 ,, ,, ,, 37°'25 ,', ,,

Results directly opposed to the above have been obtained by Lortet,5
whose observations were made on level ground and during two ascents of
Mont Blanc (4810 metres high) in August 1869. On level ground Lortet
found that, when he was at rest, the temperature of his mouth was 36° '4,
but 360<2 during bodily exercise. During the ascents of Mont Blanc the
temperature fell progressively and even reached as low a point as 31°'8, but
after a few minutes' rest it rapidly reached the normal. Lortet explained
these results by saying that during work the chemical forces which would
have sufficed in the rarefied atmosphere to maintain the normal temperature
of the body, were partly resolved in motion, and therefore the temperature
fell. These results have been criticised by Clifford Allbutt and Liebermeister,
and there can be little doubt but that the low temperatures observed were
due to the cooling of the thermometer in the mouth by the laboured breathing
of the cold air, which was sometimes several degrees below zero. This criticism 6

" Die Korperwarme des gesunden Menschen," Leipzig, 1873, S. 43-46.

2 Phil. Trans., London, 1844, pt. 1, p. 62 ; 1845, pt. 2, p. 322 ; 1850, p. 440.

3 Journ. Anat. and PhysioL, London, 1872, vol. vii. p. 106.

4 Liebermeister, "Handbuch der Path. u. Therap. des Fiebers," 1875, S. 84.

5 Compt. rend. Acad. d. sc., Paris, 1869 p. 709.

6 These sources of error have been shown to exist, for Arkle (experiments made at the
request of the writer, and the results of which will be published later), during mountain
climbing in the summer of 1897, found a constant rise of two or three degrees in the
rectal temperature, but the mouth gave a low temperature. In fact, it was impossible to
obtain accurate results by placing the thermometer in the mouth.

INFLUENCE OF MENTAL WORK. 807

is further supported by the fact that Lortet found a few minutes' rest sufficient
to raise the temperature to the normal.

Marcet,1 shortly before Lortet's observations, found that during an ascent of
some of the Mont Blanc chain of mountains the temperature of his mouth fell.
This result was contested by Vernet, who had determined the rectal tempera-
ture under similar circumstances, and, as the result of the controversy, Marcet
and Vernet'2 in 1888 ascended together one of the highest points of the Jura.
They found that there was a distinct rise in. the rectal temperature. Marcet,
however, does not look upon this result as conclusive ; he attempts to explain
the rise of temperature as due to congestion of the hsemorrhoidal vessels. It
must be pointed out, however, that the increased circulation due to exercise
would probably not cause congestion, and, whether it did or not, the rise in
the temperature of the rectum indicates a rise in the temperature of the
internal parts of the body. Further, Marcet himself shows that cooling the
under surface of the chin causes a fall in the temperature of the mouth, and
this was probably the cause of the low readings observed in his first ascents.

Obernier3 found that a walk for thirty-five minutes/ when the
external temperature was 110<2, raised the rectal temperature from 37°
to 38°. A walk of five miles raised the temperature of Ogle's mouth
from 37° to 37°'4o.4 Similar results have been obtained by others.5

Similar results to the above have been obtained upon animals. The
temperature of a dog during the first hour of work upon a treadmill was
raised 1°'S, but although the work was continued the temperature quickly
fell (U. Mosso).6 In the case of two stallions three years old, Liska6 found
the temperature before work 37°'8 and 38°'0 respectively; after
fifteen minutes' work, 39°'5 and 39°; and again, after twenty minutes'
rest, 37°'7 and 38°. Siedamgrotzky 7 found that exercise raised the
temperature of horses by an amount varying from 0°'3 to 1°, while
Hobday8 found in the case of healthy omnibus horses that the rectal
temperature was generally raised 2° or more by hard work, and in sheep
and pigs the exertion of running caused a similar rise in temperature.

Further details of the production of heat in muscle will be given
later.

In the case of insects the effect of muscular activity is very marked.
Thus Newport 9 found the temperature of the abdomen of a very active humble-
bee (Bombus terrestris) to be 23°, when the air was 19° '3 ; four of these active
bees placed in a glass bottle raised the temperature of the air from 19° '3 to
23°-6.

The influence of mental work.— Mental activity is said to have an
effect both upon the general temperature of the body and upon the local
temperature of the brain and head. Thus Davy 10 found that mental

1 Arch. d. sc. phys. et nat., Geneve, tome xxxvi. p. 247.

2 Marcet, Croonian Lectures, Brit. Med. Journ., London, 1895, vol. i. p. 1367.

3 "Der Hitzschlag," Bonn, 1867, S. 80.

4 St. Georges Hosp. Rep., London, 1866, vol. i. p. 232.

5 Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 579; Koger, " Re-
cherchrs cliniques sur les maladies de 1'ent'ance," tome i. p. 227 ; Speck, Arch. d. Ver. f.
gemeinsch. Arb. z. Ford. d. icisscn»ch. Heilk., Gottirigeii 1862, Bd. vi. S. 161-324; Cuny
Bouvier, Arch. f. d. gcs. Physiol., Bonn, 1869, Bd. ii. S. 386.

6 Ellenberger, " Verglrichende Physiologic der Haussaugethieie," 1892, Bd. ii. Th. 2,
S. 87.

7 Deutsche Zlschr. f. Thicrmed., Leipzig, 1875, Bd. i. S. 87.

8 Journ. Comp. Path, and Thcrap., Edin. and London, 1896, vol. ix. p. 286.

9 Phil. Trans., London 1837, pt. 2, p. 259.

.} 1845, pt. 2, p. 319 ; 1850, p. 443.

8o8

ANIMAL HEAT.

work in England and in the tropics raised his temperature 0°*27 and
l°'l respectively, and an increase varying from 0°'l to 0°7 has been
observed after similar exertion by Speck,1 Rumpf,2 and Gley3; the
temperature was taken in the rectum, axilla, or mouth. Clifford
Allbutt,4 however, in a long series of observations, found that mental
work had no effect upon the temperature.

Cavazzani 5 states that in the case of a man whose skull had been
trephined over the right temporo-occipital region, a thermometer placed
in the dura mater showed a rise of two-tenths of a degree during mental
activity. A. Mosso6 maintains that intense psychical processes may
cause so much heat to be set free in the brain that its temperature may
remain for some time 00<2 to 0°'3 abo^e the temperature of the rectum.
In a curarised dog the action of cocaine may produce a rise of as much
as 4° in the temperature of the brain (37° to 41°). In man, Lombard 7
found that mental activity caused a slight rise in the temperature of the
head, especially in the occipital region.

It is probable, however, that this local rise of temperature is not due,
as Mosso believes, to very active combustion in the ganglion cells, but to
vascular changes consequent upon the mental activity. Hill and
Nabarro,8 have shown that the blood from the venous sinuses of the
skull is less venous in colour than that of the femoral vein, that the
metabolism of the brain is very low, and that it is scarcely increased
during an epileptic fit. The average differences between the gases
in samples of blood from the carotid artery and from the torcular
Herophili of dogs were as follows : —

NORMAL.

TONIC FIT.

CLONIC FIT.

Art.

Tore.

Diff.

Art.

Tore.

Diff.

Art.

Tore.

Diff.

Carbon dioxide

40'86

4474

+ 3-87

44-98

49-04

+ 4-06

30-59

33-58

+ 2-99

Oxygen .

16-81

13-39

-3-42

15-17

10-22

-4-95

15-77

11-46

-4-31

It is probable, therefore, that the temperature of the brain is not
perceptibly greater than that of the blood. The cerebral circulation
changes passively with every alteration of the general arterial or venous
blood pressure,9 and this is apparently the explanation of Lombard and
Mosso's results, Moreover, the experiments of Helmholtz,10 Heiden-
hain,11 and Rolleston 12 have failed to demonstrate the formation of heat
in nerve.

1 Arch.f. exper. Path. u. Pharmakol., Leipzig, 1882, Bd. xv.

2 Arch.f. d. yes. Physiol., Boim, 1884, Bd. xxxiii. S. 601.

3 Compt. rend. Soc. de biol., Paris, 1884, p. 265.

4 Note communicated to the writer.

5 Arch. ital. de bioL, Turin, 1893, tome xviii. p. 328.

6 Proc. Roy. Soc. London, 1892, vol. li. p. 83; "Die Temperature des Gehirns,"
Leipzig. 1894.

7 Arch, de physiol. norm, etpath., Paris, 1868, tome i. p. 670.

8 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.

9 Roy and Sherrington, ibid., 1890, vol. xi. p. 85 ; Hill, ibid., 1895, vol. xviii. p. 15.
wArch.f. Anat., Physiol. u. wissensch. Med., 1848, S. 158.

11 Stud. d. physiol. Inst. zu, Brest au, Leipzig, 1868, Bd. iv. S. 250.

12 Journ. Physiol., Cambridge arid London, 1890, vol. xi. p. 208.

INFLUENCE OF FOOD.

809

The influence of food.— The investigations of many observers l show
that the effect of food upon the temperature of the body is to cause a slight
rise, or, in the case of the evening meals, to postpone for a short time
the customary fall of temperature at that time. The rise is often in-
appreciable and rarely exceeds half a degree; the maximal effect is
seen about one hour and a half after the meal. A draught of cold water
(10°) lowers the temperature about half a degree.2

In the case of the horse the effect of food is to cause a rise of 0°'2
to 0°'8, which persists for three or four hours.

Maurel 3 states that in the rabbit food is the chief cause of the daily
variation in temperature, for if the animal be kept without food during
the day but be fed during the night, the temperature shows a rise to the
maximum, not at the usual time, in the evening, but in the morning.
This is denied by Carter,4 who observed an evening rise in the tempera-
ture of rabbits which had fasted three days.

Bernard 5 determined the temperature of the blood of the portal and
hepatic veins under different conditions as regards the nutrition of the
animals, and caine to the conclusion that more heat was produced in the
liver during digestion. The following are some of his results : —

Blood of Portal
Vein.

Blood of Hepatic
Vein.

Blood of Right
Side of Heart.

Dog — After fasting for four days

37°'8

38°-4

38°-8

,, Beginning of digestion .

39°'9

390<5

...,

,, In full digestion .

39°'7

41°-3

39°'2

The effect of starvation upon the temperature of animals has been
studied chiefly by Chossat,6 and Bidder and Schmidt.7 The first observer
made experiments on twelve pigeons, and he found that the rectal
temperature gradually fell until a short time before death ; during the
period of inanition the daily variation in temperature became more
marked, and towards the end of life a rapid fall in temperature occurred.
The results are shown in the table on p. 810.

On the day of death the temperature of the pigeon fell to 260-2.
Similar experiments on turtle-doves, hens, rooks, rabbits, and guinea-
pigs gave the following temperatures:— 22°'9, 28°'2, 34°'3, 27°'0, and 23°'9
respectively on the day of death.

Bidder and Schmidt experimented upon a cat, and found that after

1 Davy, Phil. Trans., London, 1845, pt. 2, p. 319; ibid., 1850, p. 444; Damrosch,

Hosp. Rep., London, 1866, vol. i. ; Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol.
xvi. p. 581.

2 Liebermeistev, " Handbuch cl. Path. u. Therap. des Fiebers," Leipzig, 1875, S. 123 ;
Wunderlich, "Medical Therniometry " ; Siedamgrotzky, Deutsche Ztschr. f. Thiermed.,
Leipzig, 1875, Bd. i. S. 87.

• Compt. rend. tioc. de Uol, Paris, 1884, p. 588.

4 Journ. Nerv. and Ment. Dis., N.Y., 1890, vol. xvii. p. 785.

5 " Lecons sur la clialeur animale," Paris, 1876.

6"Recherches expeYimentales sur 1' inanition," Paris, 1843, quoted from Gavarret,
" De la chalenr etc.," p. 394.

7 "Die Verdauungssafte mid der Stoffwechsel," Leipzig, 1852, S. 322.

8io

ANIMAL HEAT.

355 hours' hunger the rectal temperature fell from 39°'08 to 380<4 ; after
369 hours, to 38°1 ; after 393, to 35°*5 ; after 415 hours, to 33°7 ; and
again, after 426 hours, to 32°*4, when the animal died.

RECTAL TEMPERATURE.

Midday.

Midnight.

Normal pigeons ....

42°'22

41°'48

0°-74

Complete inanition, first period

42°'l

39°'S

2° -3

,, ,, second ,,

41°'9

38° 7

3° -2

,, ,, third ,,

41°'4

37°'3

4°'l

In the case of the fasting man Tanner,1 no fall in temperature was
observed after thirty days' fast ; the temperature of his mouth was
36°*9 (98°4) on the twenty-fifth day, and 37°1 (98°'8) on the thirtieth
day. It is uncertain whether the fast was perfectly genuine, for Tanner
took a certain amount of liquid. Noyes'2 recorded a temperature of
34°*4 (94°) in the case of a partly demented man, who had taken no food
for forty-five days, but it is to be noted that the condition was compli-
cated by paralysis of the lower limbs.

The influence of sleep.— The heat of the body falls during the night
and <early morning, the time of inactivity and rest, but, according to
Barensprung 3 and Wunderlich,4 sleep in itself has no influence on the
temperature. Crombie,5 on the other hand, found that sleep during the
day caused a fall in temperature of about half a degree, but was
rapidly followed by a rise after awaking. Hunter 6 found that during
sleep the temperature fell about eight-tenths of a degree. The observa-
tions of Jlirgensen and Liebermeister 7 show that the temperature of a
man asleep is not lower than his temperature at a similar time of day
when he is awake and lying still. Inactivity causes a fall in temperature,
and sleep is a condition in which inactivity is most marked. Lieber-
meister 8 found that, by contracting the habit of sleeping each afternoon
for ten days, the mean temperature of his axilla fell to about 360>5,
whereas it had previously been for that time of day 37°'3. Observations
by U. Mosso 9 also show that sleep during the daytime causes a fall in
the rectal temperature of man.

The influence of sex. — Very little difference in temperature can
be observed in the two sexes.10 Women may have a slightly higher
temperature, but the difference does not exceed half a degree ; their
temperature, however, appears to be more liable to variations. Davy n

1 Brit. Med. Journ., London, 1880, vol. ii. p. 171. 2 Ibid., p. 557.

3 Arch. f. Anat., Physiol u. wissensch. Med., 1851, S. 163.

4 "Medical Thermometry," p. 109.

5 Loc. cit., p. 585.

6 Phil. Trans., London, 1778, vol. Ixviii. pt. 1, p. 20; "Works," Palmer's edition,
London, 1837, vol. iv. p. 144.

7 Liebermeister, " Handbuch d. Path. u. Therap. des Fiebers," 1875, S. 87.

8 Ibid., S. 92.

9 Arch. ital. de bioL, Turin, 1887, tome viii. p. 177. See also this article, p. 802.

10 Wunderlich, "Medical Thermometry."

11 Med. Times and Gaz., London, 1864, vol. ii. p. 337.

INFLUENCE OF RACE.

811

concluded that the temperature of women and female animals was lower
than that of the male, but his observations were made upon only three
or four individuals. Thus he states that the temperature of three
healthy men varied between 37°'2 and 37°'5, that of three women
between 36°'5 and 36°'7 ; in the case of three cocks and three hens the
results were 42°'4 and 42°*1 respectively. Barensprung l found no
marked difference, the average temperature of eighteen women being
37°*25. As the result of seventy or eighty observations, Siedamgrotzky 2
gives the temperature of stallions, mares, and geldings as 37°'8, 38°*2,
and 380<05 respectively ; the average temperature of a large number of
ducks was found by Martins 3 to be 41°'96 for the male, and 42°'27 for
the female. Singleton 4 determined the rectal temperature of fifty dogs
and of fifty bitches ; the average for the former was 38°'9, for the latter
38°'7. The observations were made at similar times of the day, but
upon animals of different breeds.

The influence of race — The natives of tropical countries appear to
have a temperature slightly higher than that observed in the inhabitants
of mild or cold climates, but the difference is to be ascribed mainly to
the climate. Davy,5 from observations made upon natives in the
Cape of Good Hope, Isle of France, and Ceylon, found the temperature
to be about 00<6 higher than the average in temperate climates ;
Crombie6 made fifty-two observations on Hindus, Mohammedans, and
East Indians in Bengal, and found that the average temperature from
10 A.M. to 10 P.M. was between 37°'2 and 37°'8, that from 10 P.M. to
10 A.M. between 36°7 and 37°*2. Both of these observers also found
that the temperature of Europeans living in the same district was about
half a degree higher than the average in England. Jousset7 made
numerous observations on natives and Europeans living in tropical
climates, and came to the conclusion that the axillary temperature is
generally 0°7 to 0°'S higher than that observed in temperate climates.
The following figures show that climate, and not race, is the important
factor : —

Natives of Tropics.

Europeans.

Hindus
Cochin-Chinese .

37°'85
37°'60

Officials at Chandernagore

38°'16

Chinese

37°'85

Negroes of Senegal

37°'70

Sailors at Senegal

37°'75

Congo

37°'80

,, Antilles

37°'70

,, Antilles

37°'80

Soldiers at ,, .

37°75

Similar results to the above were obtained by Maurel.8
The temperature of natives in South Africa was found by Livingstone 9
to be 36°7, when the temperature of the air in the shade was 42°'2,

1 Arch. f. Anat., Physiol. u. wissensch. Med.. 1851, S. 155.

2 Deutsche Ztschr. f. Thiermed., Leipzig, 1875, Bd. i. S. 87.

3 Ellenberger, " Vergleichende Physiol. der Haussiiugethiere, " 1892, Bd. ii. Th. 2,
S. 85.

See p. 790.

"Besearches," London, 1839, vol. i. p. 169.

Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 591.

Arch, de med. nav., Paris, 1883, tome xl. pp. 123, 426.

Bull. Soc. d'anthrop. de Paris, 1884, tome vii. p. 380.

"Travels and Eesearches in South Africa," 1857, p. 509.

8i2 ANIMAL HEAT.

but his own temperature was 37°'8, owing probably to the difference in
clothes. Thomson l found the mean temperature of natives in Iceland
to be 37°'27, and Eijkman 2 states that the average temperature of
Europeans living in Batavia is 37°'02, that of the Malays 360-93.

The influence of menstruation and pregnancy.3 — Xormal men-
struation and pregnancy in healthy women have no marked influence
upon the general temperature of the body. During labour the temper-
ature rises somewhat during the pains, but falls again between the pains.
Immediately after delivery a slight fall in temperature occurs.

Individual peculiarities in temperature. — Observations on men,
and especially on animals, show that the mean temperature of different
individuals is not the same, even *vhen the conditions are as far as
possible equal.4 The mean temperature in the axilla of different men
may vary from 36°-5 (97°7) to 37°'25 (99°-05). In animals even
greater differences are found.5

The influence of the temperature of the surroundings. — The
temperature of man and other warm-blooded animals is only slightly
influenced by the temperature of their surroundings. This fact is well
shown by the records of the temperature of men and animals in the
tropics and Arctic regions, where the extremes of the temperature of
the air occur, in the former +59°C., in the latter — 55°C. During a
voyage from England to Ceylon, Davy6 made observations upon the
temperatures of seven healthy men under 30 years of age; he found
that the average temperature under the tongue was about 36°'9 (98°4)
when the temperature of the air was 15°'6 (60°), and 37°'32 (99°'2)
when the air was 26° 4 (79°'5). From these and other observations,7
he concluded that the temperature of man increases in passing
from a temperate into a warm climate, and that the inhabitants of
warm climates have a slightly higher temperature than those of
mild climates. Eeynaud and Blosville8 found the mean temperature
of eight men to be 37° '58 (100°), when under the torrid zone,
the temperature of the air varying from 26° to 30° (79°-86°), and
37°'ll (99°) in the temperate zone, with an external temperature
varying from 12° to 17° (53°-62°). The average temperature of the
mouth was found by Eattray9 to be 37°'25 (99°) in the tropics, with an
external temperature of 25°, as compared with 36°'8 (98°'3), the average
temperature in England during the summer heat (18°).

These and further observations, made by Brown -Sequard and others,10

1 "Ueber Krankheiten und Krankheitsverhaltnisse auf Island," Schleswig, 1855, S. 24.

2 Virchoiv's Archiv, 1895, Bd. cxl. S. 125.

3 Numerous references on this subject will be found in Wunderlich's "Medical Ther-
raometry," New. Syd. Soc. Translation, p. 105. See also Barensprung, Arch. f. Anat.,
PhysioL, u. wissensch. Med., 1851, S. 157 ; Probyn Williams and Lennard Cutler, Lancet,
London, 1895, vol. i. p. 932 ; Giles, Brit. Med. Journ., London, 1894, vol. ii. p. 70. As
regards animals, see Hobday, Veterinary Rec., London, 1896, vol. viii. p. 488.

4 This article, p. 789.

5 This article, p. 790.

6 "Researches," London, 1839, vol. i. p. 161.

7 Phil. Trans., London, 1850, p. 437.

8 "Animal Heat," article by Edwards in Todd's " Cyclopaedia, " vol. ii. p. 659.

9 Proc. Roy. Soc. London, 1870, vol. xviii. p. 526.

10 Brown-Sequard, Journ. de la physiol. de Vhomme, Paris, 1859, tome ii. p. 152 ; Gress-
well, Brit. Med. Journ., London, 1884, vol. ii, p. 164 ; Mantegazza, Presse med. beige,
Bruxelles, 1863, tome xv. p. Ill ; Maurel, Bull. Soc. d'anthrop. de Paris, 1884, tome vii.
p. 371 ; Jousset, Arch, de med. nav., Paris, 1883, tome xl. p. 124 ; Pinkerton, Journ.
Anat. and PhysioL, London, 1881, vol. xv. p. 118; Edoux and Souleyet, Compt. rend.
Acad. d. sc., Paris, 1838 tome vi. p. 456.

INFLUENCE OF EXTERNAL TEMPERATURE.

813

show that the effect of tropical heat is to raise the mean temperature
of the human body, but the increase is generally less than one degree.
Crombie1 found, as the result of 1288 observations upon himself, that
the temperature of the mouth was about 0°'23 higher in Bengal than the
average in England, but the difference was greater during the first few
weeks of residence in the hot climate.

On the other hand, some observers maintain that residence in a
tropical climate does not raise the temperature of the body; thus
Boileau 2 states that the normal axillary temperature is between 36°7
and 37°'2, Thornley 3 and Furnell 4 that it is invariably the same as in
England, 36°'9.

Numerous careful observations recently made by Neuhauss5 during a
voyage round the world, show the effect of external heat upon the daily
temperature, pulse, and discharge of urine. The following are some of the
results : —

TEMPERATURE
OF AIR.

Six A.M.

Twelve
NOON.

Ten P.M.

Six P.M.

REMARKS.

TEMPERATE

ZONE.

Min.

Max.

ir-s

13°-6

36°'6

36°'9

36°'8

37°'l

Temperature in^j Mean flf twent

55

55

56

62

Pulse J

TROPICAL ZONE. |

23°'9

26°'6

36°'9
60

37°'3

68

37°'l
64

37°'3

72

Temperature in} ,r
rectum I Mean of twenty -
Pulse J nve days.

The influence of the different seasons of the year — No marked
effect upon the heat of the body can be ascribed to the different seasons
of the year, apart from that due to variations in external temperature.
The numerous observations made by Davy 6 upon himself tend to show
that the temperature of the mouth is somewhat lower during the winter
months in England, and slightly higher during the summer ; a similar
series taken in the tropics, in Barbadoes, where the mean annual
temperature of the air is 26°7, and the range throughout the year is
about 8°, sho\vs no marked variation during the different seasons.

Jousset 7 found that the cool season caused a fall of two- or three-
tenths of a degree in the average temperature of natives of the tropics.

From Bosanquet's 8 observations of the rectal temperature, it appears
that the highest sustained average temperature occurred in the winter
and early spring months. These determinations were made upon
himself four times a day for a period of three years.

A few observations have been made on the influence of winter and
summer upon the temperature of animals. Thus Edwards9 found in
the case of sparrows that the mean temperature rose progressively from

1 Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 550.

2 Lancet, London, 1878, vol. i. p. 413.

3 Ibid., 1878, vol. i. p. 554.

5 Virchoiv's Archiv, 1893, Bd. cxxxiv. S. 365.

6 Phil. Trans., London, 1845, pt. 2, p. 319 ; and 1850, p. 437.

7 Arch, de med. nav., Paris, 1883, tome xl. p. 124.

8 Lancet, London, 1895, vol. i. p. 672.

9 "Animal Heat," in Todd's " Cyclopedia, " vol. ii. p. 659.

4 Ibid., 1878, vol. ii. p. 110.

8 14 ANIMAL HEAT.

the depth of winter to the height of summer ; in the month of February
the mean temperature was 40°'8, in April 42°, and in July 430>77 ; from
this time the temperature hegan to decline. It was also found that, in
winter, birds could more readily resist the action of extreme cold than
in summer.

Davy1 observed the temperature of sheep during summer and
winter, and his results, although they are not sufficiently consistent
for positive conclusions, seem to show that the temperature of the body
is a little higher in the warm weather than in the cold.

The influence of extreme heat and cold. — The experience of
the inhabitants of tropical climates shows that it is possible to live even
in an atmosphere the temperature of which at times exceeds that of the
body, and that the body is able, by "means of the cooling effect of the
evaporation of sweat, to prevent its temperature rising a degree above
the normal.

Lining,2 in 1738, found that the temperature of his axilla was 36°'l,
and that of his mouth 36°'7, when the heat in the sun's rays was 51°1,
in the shade 36°7, on a hot summer's day in South Carolina. Ellis,3 in
1758, observed that the temperature of his body was not above 36° *1
when he was living in Georgia, and the temperature of the air was
40° '6. Experiments on men and on lower animals have shown that much
greater heat can be borne for short periods. Blagden and Fordyce 4
observed their own temperatures after remaining in heated rooms, and
found that the effect varied according to the amount of moisture
present ; thus, after remaining fifteen minutes in a damp room heated
to 54° -4, the temperature of the mouth and urine was 37°'S, but a
similar exposure in a dry room heated to 1150>5 — 126° *7, and in which
beefsteaks were being cooked by the heat of the air, did not raise the
temperature of the body above the normal. Similar experiments were
made by Dobson,5 who found that the temperature in the mouth of one
man rose to 37°*5 after he had remained about fifteen minutes in a
room heated to 940-4; in another case the rise was to 38°'6, after
twenty minutes' exposure to air at 98° '9 ; and in a third case a stay of
ten minutes in a room at 106°*7 caused a rise to 38° '9.

Tillet 6 had previously observed young girls remain without
any inconvenience for five or ten minutes in a kiln heated to about
130,° but he does not give any records of their temperature. In 1747,
Le Monnier 7 found that he could remain for eight minutes in a bath
supplied by a thermal spring, the temperature of which was 44° to 45° ;
at the end of that time his skin was red and swollen, and his distress so
great that he was obliged to get out. No observations upon the
temperature of the body are given. Kurrer 8 and Neuhauss 9 have ob-
served that the temperature of stokers, working in a stoke-hole at 50°
to 56°, is raised to 37°'6, or even to 38°1.10

Numerous experiments have been made to determine the effect of

1 "Researches," London, 1839, vol. i. p. 20S.

2 Phil. Trans., London, 1748, vol. xlv. p. 338.

3 Ibid., 1758, vol. 1. pt. 2, p. 754.

4 Ibid., 1775, vol. Ixv. pt. 1, pp. Ill and 484.

5 Ibid., 1775, vol. Ixv. pt. 2, p. 463.

6 Hist. Acad. roy. d. sc., Paris, 1764, p. 188.

7 Ibid., 1747, p. 271.

8 Deutsche Vrtljschr. f. off. Gsndhtspflg . , Braunschweig, (2), Bd. xxiv. S. 291.

9 Virchow's Archiv, 1893, Bd. cxxxiv. S. 365.

10 See also Crornbie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 601.

INFLUENCE OF EXTREME HEAT AND COLD.

815

extreme heat upon animals. Provoost and Fahrenheit, working under
the direction of Boerhaave,1 found that a dog and a cat placed in a hot
stove (63°) died in twenty-eight minutes, whilst a sparrow, under
similar conditions, died in seven minutes. Duntze2 observed that
dogs could live in an atmosphere at 42° -2, but died when the
temperature was raised to 45°. It was found by Delaroche3 that
cats, rabbits, pigeons, and various insects could remain for one
hour in a temperature of 36° without fatal results ; the most marked
symptom was the greatly quickened respiration. When the tempera-
ture was raised to 45° or 53°, the cat and rabbit died within two hours,
the pigeon in one hour and twenty minutes, the most marked symptom
being convulsions. A frog, under similar conditions, was alive at the
end of two hours. The temperature of a rabbit exposed to a heat of 45°
for one hour and forty minutes rose from 39° 7 to 43° '8. Exposure to
moist heat quickly raised the temperature of animals, as shown in the
following table : —

Animal.

Temperature
before.

Temperature
after.

Moist Heat.

Time of
Exposure.

Rabbit .

39°'6

43°

38°7

55 minutes

Guinea-pig .

38° "4

44°'2

40° 7

55 „

Pigeon .

41°'8

46°'9

41°'9

42

Frog .

Not stated

26°

25°'6

73 „

»>

> i

27°'8

27°'2

50 „

The effect of dry and moist hot air upon different animals was
determined by Bernard 4 in numerous experiments ; some of the results
are here given : —

Animal.

Dry Air.

Death.

Animal.

Dry Air.

Death.

Pigeon ..

90°

In 6 minutes

Rabbit

100°

In 10 minutes

it •

90°

6*

ii

80°

18

Dog

90°

24

80°

17

Guinea-pig

100°

6

ii

65°

25

5)

100°

6

Dog

100°

18

Rabbit .

100°

10

90°

24

Dog

100°

18

80°

30

Rabbit .

100°

7

In moist hot air the animals died very quickly ; thus, when the
temperature was 80°, 60°, and 45°, the rabbits died in two, three, and
ten minutes respectively. Experiments made by immersing the body
of the animal in hot water gave similar results. To determine the effect
of exposing the body to dry heat without warming the air used for
respiration, Bernard made the following comparative experiments upon
rabbits of similar size : —

1 "Praelect. Anat.," p. 211 ; "ELhn. de chymie," tome i. pp. 148, 277, 278.

2 Quoted from Delaroche (3).

3 Journ. dephys., Paris, 1806, tome Ixiii. pp. 207, 468 ; 1810, tome Ixxi. p. 289.

4 Gaz. m6d. de Paris, 1859, tome xiv. p. 462; " Le9ons sur la chaleur animale,"
1876, p. 349.

816 ANIMAL HEAT.

(a) Kabbit placed in dry air 100° —

Temperature before = 40°

„ after 5 minutes = 41°

„ „ 10 „ =44° — respiration quickened.

„ 16 „ = 44°'5- death.

(&) Head of rabbit placed in dry air 100°, body in cool air —
Temperature before = 40°

„ after 5 minutes = 40°

,, „ 10 =40° — respiration quickened.

15

20
25

„ 30
„ 38

= 41°

= . ,.

— 43° i resPira^lon verJ

»

- 43°— death.

(c) Body of rabbit in dry air 100°, head in cool air —
Temperature before = 3 9° '5

„ after 4 minutes = 42°

„ „ 10 „ =43° — respiration quickened.

15 — 44.°

J) }) **r 5) "~ **

„ 20 „ =45°— death.

Obernier1 found that when the external temperature was first
raised the rectal temperature of dogs and rabbits fell slightly, about
0°*4, but soon after the air reached 30° to 35° the temperature of the
animal began to rise. Death generally resulted before the internal
temperature rose to 45°, but in one case it reached 46° '2. The most
important symptoms were restlessness, quickening of respiration and
pulse, and finally convulsions and loss of consciousness. A short time
before death it was impossible to feel the pulse, a fact explained by the
fibrillar contraction of the heart observed by Obernier when the thorax
was opened. An examination of the body directly after death showed
marked congestion of the brain and lungs; the muscles were inexcitable,
and quickly went into rigor mortis. Similar changes were observed
in the bodies of soldiers who had died from sunstroke.

Numerous facts show that cold-blooded animals can live in hot
media. Thus, internal parasites of mammals and birds can live in sur-
roundings at temperatures of 37° and 430<9; and there are well-authentic-
ated cases of fishes living in springs as hot as 37°-44°.2 Sonnerat3
even states that he saw fish actively swimming about in the hot water
(60°-62°) of thermal springs in New Guinea ; it is doubtful, however,
if the temperature was correctly recorded in this case.

It has been shown by Davenport and Castle 4 that by gradually
raising the temperature tadpoles can be kept alive in warm water.
Hertwig5 has observed that no development takes place in the ova
of the frog when the temperature of the water is zero, but between
2° and 33° it progresses with different rapidity, cold delaying, warmth
hastening the process. A temperature, however, of 34° is fatal.

1 "Der Hitzschlag," Bonn, 1867.

2 Spallanzani, "Opusc. de phys. anim.," tome i. pp. 54-69, 101 ; Desfontaines, quoted
from Gavarret, " De la chaleur produite pas les etres vivants," Paris, 1855, p. 464 ; Tripier,
Compt. rend. Acad. d. sc., Paris, tome ix. p. 602; Cumberland, Biblioth. univ., Geneve,
1839, tome xx. p. 204 ; Prinsep, ibid.

3 "Voyage a la Nouvelle Guinee," Paris, 1776, pp. 38-41.

4 Arch.f. Anat. u. Entwcklngsgesch., Leipzig, 1885, Bd. ii. S. 227.

5 Sitzungsb. d. preuss. Akad. d. Wissensch., 1896, S. 105.

INFLUENCE OF EXTREME HEAT AND COLD.

Numerous observations show that the temperature of animals living
in the Arctic regions is equal to that of animals of the same classes in
temperate climates. The following are some of the results obtained by
different explorers : —

Animal.

Temperature of
Animal.

Temperature of
Air.

Observer.

Arctic fox . J

38°'3

-35° '6
-35° -6

Parry and Lyon.1

1

39°'4

-32°'8

'

Wolf ....

40°'5

-32°'8

y

White hare

38°'3

-29° -4

3

Prairie fowl (male) . -1

43° '2
43° -0

Iilro

Black.2

42°'8

-8° "3

Prairie fowl (female) . 4

43°'3

-8°'0

\

42°'8

-l°'l

(

42°'4

-19°*7

Willow grouse (male) . -j

43°'3

-32°'8

I

43° '3

-35° "8

The limits of extreme cold are generally reached when the water in
which the animals live, or the lymph of their tissues, is frozen. Fishes
live in salt water when the temperature is below zero, but usually die
when the water is frozen.

Boyle3 exposed lampreys in a vessel of water to an exceedingly
sharp frost, and found next day that one lamprey was frozen in the ice ;
when the ice was partly broken and partly thawed the animal was at first
motionless, but in a few minutes recovered, and dragged after it a large
piece of ice in which its tail was fixed. Similar experiments were made
with similar results upon gudgeons and frogs. Hunter 4 found by
experiment that the internal temperature of a frog and an eel could be
reduced to -0°'6, and that, although the animals appeared to be dead,
they revived when the temperature rose. Eegnard 5 found that carp
will live in water containing 2J per cent, of magnesium sulphate,
even when the temperature is a degree or two below zero ; at —2° the fish
appear to be asleep, and at -3° their vitality is so greatly reduced that
they seem to be dead, but revive when the water is gradually warmed.
Pictet6 exhibited at one of his lectures frozen gold fish, pike, and
frogs, and at the next lecture the same animals alive and well after
gradual thawing. According to this observer, fishes can be rapidly
frozen so hard that they can be snapped in two, and yet other fishes
frozen equally hard recover when slowly thawed. It has been observed
by Marcet 6 that gold fish completely embedded in the ice showed no
signs of life on thawing, but one fish, which was partly encased in ice
and was surrounded by .a little water, appeared lifeless, but recovered
perfectly in a short time. Observations and experiments made by

1 Parry, "Journal of a Second Voyage for the Discovery of a North-West Passage,"
London, 1824, p. 157 ; Ann. de chim. et phys., Paris, 1825, Ser. 2, tome xxviii. p. 223.
- Compt. rend. Acad. d. sc., Paris, 1836, tome ii. p. 621.
"Philosophical Works," Shaw's edition, vol. i. p. 688.

4 "Works," Palmer's edition, London, 1837, vol. iv. p. 131 et seq.

5 Compt. rend. Soc. de bioL, Paris, 1895, p. 652.

"Quoted from Marcet, Croonian Lectures, Brit. Med. Journ., London, 1895, vol. i.
p. 1367.

VOL. I. — 52

ANIMAL HEAT.

Gaymard l and Gavarret 2 show that toads and fishes may be frozen
perfectly stiff and yet revive when gradually thawed ; according to the
former observer, the freezing must be gradual, otherwise the animals are
killed. During Franklin's 3 explorations in the Arctic regions, it was
observed that fish frozen completely hard recovered when they were
thawed ; a carp, which had been frozen for thirty-six hours, was able
after it was thawed to leap about with much vigour.

The influence of baths. — A warm or cold bath has a greater effect
upon the temperature of the body than exposure to air at the same
temperature, for the power of conduction of water is greater than that
of air. The first important experiments upon this subject were made
by Currie in 1797.4 He found that the immediate effect of a cold bath
might be a slight rise in the temperature of the mouth, but the per-
manent effect was a fall. The following are some of his results : —

Temperature of
Bath.

Duration of
Bath.

Temperature before
the Bath.

Temperature after
the Bath.

Sea water 6° '7

12 minutes

36°'7

34° -0

5°'7

30 „

36°'3

34°'3

Fresh water 4° '3

34 „

36°-7

33°'7

The temperature was taken in the mouth, and therefore the depres-
sion was greater than it would have been in the rectum.

Fleury5 found the temperature in the mouth sink to 34°, 320<9, and
even to 29° during a cold bath; Virchow6 observed a fall to 34°;
Speck7 found that the immediate effect of a shower bath at 22° was
to raise the temperature of the mouth, but after ten minutes' exposure
the temperature fell 10>23.

Numerous observations have been made by Liebermeister,8 who
selected the temperature of the closed axilla as representing more
exactly the temperature of the body. He concludes that the immediate
effect of a cold bath is to slightly raise the temperature, and that a bath
of moderate cold and duration does not lower the temperature below
the normal, for an increase in the heat production compensates for the
increased loss. Liebermeister, as Currie had previously done, used the
bath as a water calorimeter, and calculated that in a bath of from 20°
to 30° the heat production was three or four times greater than the
normal. Jlirgensen 9 confirmed many of these results ; he found that
the rectal temperature of men did not fall more than 1°, often less, after
remaining twenty-five minutes in a cold bath at 11° to 9°. Eecently
Lefevre 10 has given excellent proofs of the power of regulation of

1 Biblioth. univ., Geneve, 1840, tome xxvi. p. 207.
" De la chaleur produite par les etres vivants," Paris, 185n, p. 502.

3 Franklin, "Journey to the Polar Sea," 1819-1822, 2nd edition, vol. ii. p. 17.

4 "Medical Reports on the Effect of Water, Cold and Warm, as a Remedy in Fever and
other Diseases."

5 Progres med., Paris, 1858, p. 337. G Virchow's Archiv, 1858, Bd. xv. S. 70.

7 Arch. d. Ver. f. gemcinsch. Arb. z. Ford. d. wissensch. Ifeilk., Gottingen, 1861, Bd.
v. S. 422.

8 Arch. f. Anat. Physiol. u. wissensch. Med., Leipzig, 1860, S. 520, 589 ; " Handbuch
d. Path. u/Therap. des Fiebers," 1875, S. 102.

9 Deutsches Arch. f. klin. Med., Leipzig, 1867, Bd. iii. S. 165 ; Bd. iv. S. 110, 323.
10 Compt. rend. Soc. de biol., Paris, 1895, p. 559 ; 1896, pp. 492, 564.

INFLUENCE OF BATHS. 819

temperature in man. He remained three hours in a bath at 15°, and yet
his axillary temperature fell only one degree (37°'30 to 36°v>0 in the
first two hours and a half, and then remained stationary at 36°%30) ; the
amount of heat lost was 800 kilo-calories. A bath in water at 25° for
three hours caused a fall in temperature from 37°'20 to 36°'60, with a
loss of 312 kilo-calories ; while a bath of one hour's duration in water at
7° caused a fall from 37°'70 to 36°, the loss of heat being 530 kilo-
calories.

In comparing the effect of baths on different people, it is important
to consider the size of the body and the amount of subcutaneous fat,
for the greater the size and amount of fat the slower is the cooling of the
body. Liebermeister found that the temperature of the axilla of a fat
man only fell 0°*2 during a bath of 21° to 30°, lasting one hour and a
half.

The effect of a warm bath is to raise the temperature, but after the
bath there is, as Currie and Liebermeister observed, a fall in temperature
followed by a gradual rise to the normal.

It is impossible here to consider all the numerous results, some
contradictory, which have been obtained by different observers.1 It is
important, however, to note that the different results markedly show
the power of compensation possessed by the higher animals. A cold
bath abstracts a large quantity of heat, but within certain limits does
not cause the temperature of the body to fall, for the cutaneous blood
vessels contract and thus diminish the loss of heat, and the cold acting
on the nervous system stimulates the tissues to increased production
of heat ; on the other hand, a hot bath would quickly cause a rise in
temperature, if the animal were not able within certain limits to in-
crease its loss of heat by an excessive vascularity of the skin and to
diminish its production of heat. These compensating factors show their
influence by a rise in temperature after a cold bath and by a fall after
a hot bath, as the case may be. For this reason a hot bath is most
effective in producing a cooling effect upon the body in tropical climates.
The after-effects, however, soon disappear, and the temperature becomes
normal.

The compensation is, in fact, so exact in a healthy man, that any fall
or rise in temperature, caused by too long exposure to cold or heat, is
followed respectively by a rise above or fall below the normal. Thus it
is that the mean daily temperature and the daily variations are very
slightly or not at all affected by baths (Jiirgensen,2 Liebermeister,3 Einger
and Stuart,4 and others). Still it must be remembered that this com-
pensation is only effective within certain narrow limits,5 and does not in
any way invalidate the use of cold baths in the treatment of high
temperatures in cases of fever.

Experiments upon the influence of warm and cold baths have also
been made upon animals, and the results agree with those obtained
upon man. Crawford6 in 1871 found that the temperature of a dog
kept in a hot bath, 45°'6 to 44° 4, rose in thirty minutes to 42°'8, and

1 For further details and references see Liebermeister, "Handbuch d. Path. u. Therap.
des Fiebers," Leipzig, 1875 ; Wunderlich, "Medical Thermometry," p. 109.

2 LOG. tit. 3 Loc. tit.

4 Proc. Hoy. Soc. Loiidon, 1877, vol. xxvi. p. 203.

5 Lovvy, Arch. f. d. ges. Physiol., Bonn, 1889, Bd. xlv. S. 625 j 1890, Bd. xlvi. S.
189; see also "Chemistry of Respiration," this Text-book, vol. i. p. 712.

6 Phil. Trans., London, 1781, vol. l.xxi. p. 486.

820 ANIMAL HEAT,

the dog became very languid ; the venous blood of dogs kept in a warm
bath had an arterial colour, whereas a cold bath, 7° '2, rendered the
blood in the jugular vein very dark. More extended observations were
made by Hoppe l upon both the immediate and after effects of baths
upon dogs. The rectal temperature of a dog placed in water at 48°
for three minutes rose from 3 8° 7 5 to 41° -45 ; a cold bath at 9°'12,
lasting half a minute, caused a fall of 1° ; a bath of freezing water,
lasting respectively two and four minutes, produced a fall of 1°7 and
4° -88 Tjelow the normal. Hoppe found that the temperature fell during
a cold bath but afterwards rose above the normal, that it rose during
a hot bath but afterwards fell below the normal. The sensation of
cold stimulated the organism to an increased production of heat, for
if evaporation from the wet skin wfs rapid the temperature rose, but
if it was hindered by a covering of rubber the temperature fell.

Bernard2 found that very hot baths quickly caused death, the
symptoms being similar to those observed from exposure to hot air.

The influence of certain drugs upon the temperature of the
body. — Alcohol? — The effect of alcohol is a fall in temperature, and
not, as is popularly believed, an increased heat of the body. • It is
true that after the use of alcohol there is a feeling of increased warmth,
but this is due only to the increased vascularity of the skin and the
activity of the sweat glands.

Alcohol seems to act in two ways : it has little or no effect upon
the production of heat in the tissues, but greatly increases the loss of
heat by causing the cutaneous vessels to dilate, stimulating the sweat
glands and quickening the circulation. The normal reaction to cold,
namely, increased production of heat and contraction of the cutaneous
vessels, is partly paralysed by large doses of alcohol, with the result that
drunkards exposed to cold quickly " freeze " to death.

Various observers 4 have found that alcohol taken in ordinary quan-
tities as a beverage causes a slight depression, generally less than half
a degree, in the temperature of healthy men ; on the other hand,
poisonous doses may cause a fall of five or six degrees — in fact, many
of the lowest temperatures recorded in man have been observed in
drunken persons exposed to cold.

Experiments upon animals have given similar results. Walther5
exposed two rabbits to a temperature of 210-2 below zero ; in two and a
quarter hours the temperature of the normal rabbit fell from 3 8° '8 to
35°'6, while that of the rabbit which had received 35 c.c. of brandy fell
from 38°'8 to 19°'8. A guinea-pig was given a dose of 6 or 7 grms.
of brandy, and then exposed to moderate cold; its temperature fell 10°,

1 Virchoitfs Archiv, 1857, Bd. xi. S. 453.

2 This article, p. 815.

3 For further details, see works on therapeutics.

4 Davy, Phil. Trans., London, 1850, p. 444 ; Lichtenfels and Frohlich, DenJcschriften
d. k. Akad. d. Wissensch., Wien, 1852, Bd. iii. Abth. 2, S. 131 ; Lallemand, Perrin, and
Duroy, " Du role de 1'alcool et des anesthe'siques dans 1'organisine," Paris, 1860; Ogle,
St. George's Hosp. Rep,, London, 1866, vol. i. p. 233. Ringer and Bickards, Lancet,
London, 1866, vol. ii. p. 208; Cuny Bouvier, Arch, f. d. ges. Physiol., Bonn, 1869,
Bd. ii. S. 370 ; Godfrin, " De 1'alcool, son action physiologique, ses applications the"ra-
peutiques," 1869 ; Weckerling, Deutsches Arch. f. Tdin. Med., Leipzig, 1877, Bd. xix.
S. 317 ; Zuntz, Fortschr. d. Med., Berlin, 1887 ; Geppert, Arch. /. exper. Path. u. Phar-
maJcol., Leipzig, Bd. xxii. Parkes and Wollowicz, Proc. Roy. Soc. London, 1870, vol. xviii.
p. 362, found that alcohol in ordinary quantities had no effect on the temperature of a
healthy man.

5 Arch. f. Anat., Pkysiol. u. wiswnxch. Med., Leipzig, 1865, S. 45.

B ODIL Y TEMPERA TURE COMPA TIBLE WITH LIFE. 8 2 1

whereas that of a normal animal exposed to cold only varied one, or
two-tenths of a degree. Similar results have been obtained by others.1

Calorimetric observations have been made by Reichert 2 upon the
influence of alcohol on the production and loss of heat in dogs ; he
found that the total heat production was not essentially altered, but the
loss exceeded the production, and therefore the temperature fell. The
doses given were T25, 2 -5, and 5 c.c. per kilo, of the animal's weight.

Chloroform, ether, morphia, chloral, and nicotine. — The general
effect of these drugs is to cause a fall in the temperature of the body,3
and in poisonous doses to so greatly depress the power of heat regulation
that a warm-blooded animal passes into a condition in which it cannot
maintain its temperature, its respiratory exchange and temperature
varying with, and in the same direction as, that of its surroundings
(Rumpf, Pembrey). Calorimetric observations made by J. Rosen thai
show that under the influence of chloral the temperature of rabbits falls,4
the discharge of heat is 30 to 40 per cent, greater than the normal, and
the production of heat and also of carbon dioxide is diminished ; strychnia
and tetanus, on the other hand, increase the production but diminish the
loss of heat.

Cocain,5 atropin, brucin, caffein, and veratrin raise the temperature ;
the most remarkable pyretic drug, however, is /3-tetra hydronaphthyl-
amine, which causes in the case of rabbits a rapid rise of three or four
degrees in the rectal temperature6; curari7 causes a marked fall in
temperature.

The limits of bodily temperature compatible with life. — Although
the range of temperature in a normal man is less than 2°, yet a
much wider range is observed in certain pathological conditions.
Thus by exposure to cold, especially when the subjects are drunk,
the temperature may fall even as low as 24° without a fatal issue.
Reincke8 has recorded numerous cases of low temperature resulting
from the accidental exposure of drunkards to cold air and water.
In two of these cases the rectal temperature was 30° and 24° re-
spectively ; the patients were unconscious, but under treatment

1 Rumpf, Arch. f. d. ges. PhysioL, Bonn, 1884, Bd. xxxiii. S. 538; Ringer and Rickards,
loc. cit. ; Tschescliichin, Arch. f. Anat., PhysioL u. wissensch. Med., 1866, S. 161 ; Cuny
Bouvier, loc. cit.

•2 Therap. Gaz,, Detroit, February, 1890.

3 Dumeril and Demarquay, " Recherches experimentales sur les modifications imprimees
a la temperature auimale par Tether et 1'chlovoforme," 1848 ; Brown-Se'quard, Com.pt. rend.
Soc. de bioL, Paris, 1849, No. 7, p. 102 ; Tschescliichin, loc. cit. ; Lallemand, Perrin, and
Duroy, " Du role de 1'alcool et des anesthesiques dans rorganisme," Paris, 1860 ; Spencer
Wells, Edin. Med. Journ., 1869, 1870 ; Richardson, Practitioner, London, 1869, 1870 ;
Waren Tay, Brit. Med. Journ., London, 1870, vol. i. p. 329 ; Oglesby, Practitioner, London,
1870; Angelesco, Compt. rend. Soc. de bioL, Paris, 1894, p. 786 ; Richet, Compt. rend. Acad.
d. sc., Paris, 1889, tome cix. p. 190 ; Arch, de physiol. norm, ct path., Paris, 1890, tome ii.
p. 221 ; Warter, Med. Times and Gaz., London, 1866, vol. ii. p. 416 ; Lichtenfels and
Frohlich, Denkschriften d. k. Akad. d. Wissensch. Math.-naturw. Cl., Wien, 1852, Bd. iii.
Abth. 2, S. 137 ; Hobday, Journ. Comp. Path, and Therap., Edin. and London, vol. viii.
p. 287; Pembrey, "Proc. Physiol. Soc.," Journ. PhysioL, Cambridge and London, 1894-
1895, vol. xvii.

4 Sitzungsb. d. k. Akad. d. Wissensch. zu Berlin, 1890, Bd. xx. ; xxi. p. 393.

5 Mantegazza, Ann. univ. di med. e chir., Milano, 1859, vol. clxvii. ; U. Mosso, Arch.
ital. de bioL. Turin, 1887, vol. viii. p. 370 ; 1891, vol. xiv. p. 288 ; Hobday, Journ. Comp.
Path, and Therap., Edin. and London, 1895, vol. viii. p. 20 ; 1897, vol. x. p. 80.

6 Stern, Virchow's Archiv, 1889, Bd. cxv. S. 14 ; Fawcett and Hale White, Journ.
Physiol., Cambridge and London, 1897, vol. xxi. p. 435.

17 This article, p. 841.
8 Deutsches Arch. f. klin. Med., Leipzig, 1875, Bd. xvi, S. 12,

822 ANIMAL HEAT.

recovered in a day or two. In other cases, with temperatures 280<4,
27°, and 26°'4, death followed in about twenty-four hours. In a
case observed by Nicolaysen * the rectal temperature was 24° '7, but
the drunkard, who had been exposed for a whole night to air 6°
below zero, completely recovered; the temperature of the vagina and
axilla was 27°'9 in a woman who had had a similar experience, but
within six hours the temperature rose to 36°'3 under treatment, and the
patient completely recovered.2 In four cases of insanity, Lowenhardt 3
has observed temperatures as low as 25°, 290-5, 23°*75, and 28° ; in one
case the range of temperature for several weeks was from 25° to 35°.
The patients were about 60 years of age ; they often ran about naked
in cold weather, and were frequently bathed on account of their dirty
habits, and although they were fairly active they did not take much
food. The observations were taken sometimes in the axilla, sometimes
in the rectum.

Weiland 4 has recorded two cases of adults with temperatures
reduced to 28°'4 and 26° '6 from exposure to cold ; the observations were
taken in the rectum several hours before death ; in a third case, that of
a drunkard who had been exposed to cold, the rectal temperature was
30°*4, and recovery took place. The rectal temperature of a man suffer-
ing from bronchi-ectasis was found by Liebermeister 5 to be 320-6, and
that of a child five days old, suffering from sclerema and icterus,
32°*15 ; the readings were taken a day or two before death, and several
thermometers were used and tested. Kohler 6 observed a temperature
of 28°'2 in the rectum of a drunkard, and found that, notwithstanding
treatment, it remained low until shortly before the man's death a month
later; two cases, with rectal temperatures 26°'8 and 26°'7, were observed
by Quincke ; 7 the subnormal temperature was due to exposure to cold,
but both of the patients recovered. Numerous records of subnormal
temperatures will be found in papers by Janssen,7 Lemcke,8 and Glaser.9

In the case of non-hibernating mammals an artificial cooling of the
body to 18° is in a few hours followed by death, unless artificial respira-
tion and heat be applied. Babbits cooled to 18° are perfectly helpless
and paralysed ; the heart-beat is feeble, 16 to 20 per minute ; the respira-
tion is either exceedingly slow or rapid and shallow; the nerves and
muscles long remain irritable, and during operative procedures there is
very little bleeding, owing to the low blood pressure.10

It was shown by Edwards n that newly-born pups and kittens would
live for two or three days with their temperature reduced as low as 17°
or 20°, and that the application of artificial warmth would restore the
young animals, if this low temperature had not persisted too long.
Adult animals, however, when cooled to 18° or 20°, generally died, even

1 Jahresb. u. d. Leistung. . . . d. ges. Med., Berlin, 1875, Bd. i. S. 283.

2 Peter, Gaz. held, de med., Paris, 1872, p. 499.

:? Allg. Ztschr.f. Psyehiat. , etc. , Berlin, 1868, Bd. xxv. S. 685.

4 Schrift. d. Univ. zu Kiel, 1869, Bd. xvi.

5 "Handbuch d. Path. u. Therap. des Fiebers,'' 1875, S. 69.

6 Schrift. d. Univ. zu Kiel, 1873, Bd. xx.

7 Quoted from Janssen, Deutsches Arch. f. klin. Mcd., Leipzig, 1894, Bd. liii. S. 249.

8 Ibid., 1883-84, Bd. xxxiv. S. 90.

9 "Ueber Vorkommen und Ursachen abnorm niedriger Korperteniperatur," Diss.,
Bern, 1878.

10 Walther, Virchow's Archiv, 1862, Bd. xxv. S. 414; ibid., 1865, S. 25; Horvath,
Verhandl. d. phys.-med. Gesellsch. in Wiirzburg, 1881, Bd. xv. S. 187 ; Tscheschicliin,
Arch. f. Anat., Pliysiol. u. ivissensch. Med. 1866, S. 151.

11 "De 1'inliuence des agens physiques sur la vie," 1824, p. 237.

BODILY TEMPERATURE COMPATIBLE WITH LIFE. 823

when artificial warmth was applied. Similar results were obtained in
the case of recently hatched and old birds.

Hibernating mammals have been observed during winter with
temperatures as low as 2°, and during summer they may be cooled by
artificial means to 10>2 ; in these cases the animals are able to again raise
their temperature without any external aid (Walther, Horvath, and
others).

The eggs of silk-worms and of other insects may be exposed for a
long time to temperatures 20° to 30° below zero, and yet will develop
into larvse when removed to warm surroundings.1 The Arctic ex-
plorer Boss exposed caterpillars to a temperature of -42°, and found
that they recovered when slowly thawed. Colasanti2 observed that
hens' eggs could be exposed for two hours to a temperature of -4°, and
for half an hour to a temperature of -7° to -10°, and yet developed
normally when placed in an incubator.

As already pointed ont on p. 817, in the lower vertebrates the tem-
perature of the body may sink to zero and yet recovery take place.
Hunter 3 placed an eel in a freezing mixture, until the temperature of
its stomach fell to -0°'6, when the animal appeared to be dead, but
by the next day it had recovered ; a similar result was observed in a
frog. Frozen leeches, however, were dead when thawed.

As regards the limit of high temperatures compatible with human
life, there are numerous records of cases of hyperpyrexia. The highest
observed by Wunderlich 4 was 440>75 (112°*55 F.) in a case of tetanus;
one hour after death the temperature was 45°'37. Currie 5 found a
temperature of 44° 45, Woodman6 one of 461 in fatal cases of scarlet
fever ; Ba'umler 7 records a case of sunstroke in a healthy man, the
temperature in the axilla was 42° '9, there was deep coma, and death
took place in eight hours ; in a similar case observed by Casey 8 the
temperature in the axilla was 43°*1, and death occurred within three
hours. Levick 9 gives cases of sunstroke in which the temperature was
420>8, and the patients recovered. Fatal cases with temperatures 43°,
420<5, and 44° are recorded by Simon,10 two cases of tetanus with
temperatures 44° 4 and 41° -6 before death by Lehmann,11 and others
with 43°-4, 43°-6, 42°'75, 43°4, 43°4, 44°-3, and 43° by Quincke.12

On the other hand, Donkin l3 gives cases of temperatures as high as
44° -2, 45°, and 44°'5; in which recovery took place ; the high temperature,
however, appears to have persisted for a very short time. In two cases
of rheumatic hyperpyrexia recorded by Arkle 14 the temperature was
43°'55 (110°4 F.), but the patients recovered.

1 Reaumur, "Me'm. sur les insectes," tomes ii. and v. ; Spallanzani, "Opusc. de phys.
anim.," tome i. pp. 82-85; Bonafous, " Biblioth. univ., Geneve, 1838, tome xvii. p. 200;
Ross, ibid., 1836, tome iii. p. 423; Pictet, Arch. d. sc. phys. ct nat., Geneve, 1893 (3),
tome xxx. p. 293.

2 Arch.f. Anat,., Physiol. u. ivissensch. Med., 1875, S. 477.

3 "Works," Palmer's edition, London, 1837, vol. iv. p. 131 et seq.

4 " Medical Thermometry," p. 204. 5 "Medical Reports, etc."

6 Med. Mirror, London, 1865, p. 77.

7 Med. Times and Gaz., London, 1868, vol. ii. p. 118.

8 Ibid., 1866, vol. ii. p. 26.

9 Penn. Hosp. Hep., Philadelphia, 1868, vol. i. p. 369.

10 Charite-Ann., Berlin, 1865, Bd. xiii. Heft 2, S. 1.

11 Schmidt's Jahrb., Leipzig, 1868, Bd. cxxxix. S. 241.

12 Berl. klin. Wchnsehr., 1869, S. 301.

13 Brit. Med. Jonrn., London, 1879, vol. ii. p. 983.

14 Trans. Clin. Soc. London, 1888, vol. xxi. p. 187,

824 ANIMAL HEAT.

Eichet l has collected three cases in which the temperature rose to
46°, but the patients recovered. Numerous other cases of high
temperature in man are to be found scattered throughout medical
literature.2

Experiments upon animals have determined more exactly the limit of
high temperature. Bernard 3 found that when the internal temperature
of rabbits was artificially raised to 45° they died ; in birds the fatal
limit was 51° or 52°. According to this physiologist, death was due to
stoppage of the heart by the hot blood, which sent the muscle into rigor
mortis. Eosenthal 4 obtained similar results for rabbits, but found that
if the animal was removed to cooler surroundings when its temperature
had reached 44°, recovery might take«place. From these and similar ex-
periments by Obernier,5 Wood,6 and others, it may be concluded that a
bodily temperature of 45° is extremely dangerous, and one of 47° quickly
fatal, to the life of mammals. The limit of high temperatures appears
to be fixed by the point at which the proteids of the body begin to
coagulate.

THE TEMPERATURE OF DIFFERENT PARTS OF THE BODY.

The heat of the body is produced by processes of combustion taking
place chiefly in the muscles and glands, while heat is lost chiefly from the
surface of the skin. The result, therefore, is that the temperature of
the body diminishes from the interior to the surface. It is impossible,
however, to give any exact value to the temperature of different parts,
because the production and loss of heat vary under different conditions
of the animal, such as muscular activity and digestion.

The temperature of internal parts in man. — In considering this
subject, it is important to remember that the temperature taken by a
thermometer placed in a dry, well-closed axilla represents the heat of
an internal cavity ; Einger and Stuart 7 even state that, " due care
being taken and sufficient time allowed, the temperature of the axilla
is always identical with that of the mouth, and with that of the rectum
four to six inches above its termination."

Upon the respective temperatures of the mouth, axilla, and rectum,
there is a great want of agreement among observers. This is in great
part due to the fact that in numerous cases insufficient time is allowed
for the determination of temperature in the mouth and axilla ; but there
is another cause, which is beyond the control of the observer — the
circulation of blood in the mouth and in the skin of the axilla is liable
to marked variations. It will be well, therefore, to mention the dis-
cordant results obtained, and then draw some general conclusion. As
just mentioned, Einger and Stuart state that the temperature in the
axilla is identical with that of the mouth and rectum ; Ogle 8 says that

1 Compt. rend. Soc. de UoL, Paris, 1894, p. 416.

2 Hale "White, Brit. Med. Journ., London, 1894, vol. ii. p. 1093. Here numerous
references will be found. See also Trans. Glin. Soc. London, 1882, vol. xv. p. 261.

3 Gaz. med. de Paris, 1859, tome xiv. p. 462; " Leeons sur la chaleur animale,"
p. 349.

4 " Zur Kenntniss der Warmeregulirung bei den warmbliitigen Thieren." Erlangen,
1872, S. 15.

5 " Der Hitzschlag," Bonn, 1867, S. 71.

6 "Fever," Smithson. Contrib. Knowl., Washington, 1880, No. 357.

7 Proc. Roy. Soc.. London, 1877, vol. xxvi. p. 186.

8 St. George* sHosp. Rep., London, 1866, vol. i. p. 233.

TEMPERATURE OF INTERNAL PARTS IN MAN. 825

if the thermometer be warmed by the hand and then kept under the
tongue in the closed mouth for eight minutes, the reading is the same
as that obtained by inserting the thermometer in the urine as it leaves
the body. On the other hand, Crombie 1 found, as the result of com-
parative experiments in which care was taken to obtain accurate
results, that in fifteen simultaneous observations the mean difference of
temperature in the mouth was O13 above the reading in the axilla, and
in thirty-five determinations the mean difference in the rectum was
0'22 above the temperature in the mouth. A number of simultaneous
observations made by Parkes and Wollowicz2 show that the rectal
temperature of a healthy man may be 0*3 to 0'6 higher than the
temperature in the axilla. G-assot 3 made comparative observations at
different times of the day, with the following results : —

MAX.

WOMAN.

1

Mouth.

Axilla.

Mouth.

Axilla.

Rectum.

7 a.m.

37°'06

37°'78

37°'0

36°'8

37°7

2 p.m.

37°'6

37°'3

37°'6

37°'3

380<0

9 p.m.

37°'4

37°'12

37°'o

37°'3

37°'8

Oertmann 4 observed, when the thermometer was kept in the axilla
for fifteen minutes, in the rectum at a depth of 7 cm. for five minutes,
and in the stream of urine for five seconds, that the temperature of the
urine was generally equal to that of the rectum, but four-tenths of a
degree higher than that of the axilla. Ten simultaneous observations
of the temperature in the mouth and rectum gave an average difference
of O32 in favour of the latter (Cuny Bouvier).5 According to Lieber-
meister,6 the rectal temperature is 0°'l to 0°'4 above that of the axilla.

Lorain 7 maintained that the temperature in the rectum or vagina
alone represented the internal temperature of the body, and that the
rectal temperature was '6° to '8° higher than that in the axilla. The
figures given by Wunderlich 8 for the mean temperature of the rectum,
mouth, and axilla are 37°'3, 37°'lo, and 37° respectively. Eedard,9 on
the other hand, states that the temperature of the mouth is '2° higher
than that in the axilla, and '3° to '6° lower than that of the rectum.
Neuhauss 10 found, as the result of forty comparative experiments, in
which the temperature was observed simultaneously in the rectum
and in the axilla, that the rectal was 00-6 higher than the axillary
temperature.

We may take as our guide the averages obtained from- the results
of different observers, and conclude that the rectum has a temperature

1 Indian Ann. Mcd. Sc., Calcutta, 1873, vol. xvi. p. 558.

2 Proc. Roy. Soc. London, 1869-70, vol. xviii. p. 368.

3 These de Paris, 1873, quoted from Richet, Rev. sclent., Paris, 1885, tome ix. p. 433.

4 Arch.f. d. ges. PhysioL, Bonn, 1878, Bd. xvi. S. 101.

5 Ibid,, 1869, Bd. ii. S. 387.

6 " Handbuch d. Path. u. Therap. des Fiebers," S. 44.

7 " De la temperature du corps humain," Paris, 1877, tome i. p. 434.

8 "Medical Thermometry."

9 " Etudes de therm ometrie clinique," 1874. p. 20.
10 Virchow'x Archir, 1 893, Bd. cxxxiv. S. 365.

826

ANIMAL HEAT.

0°'4 above that of the mouth, and that the difference between the
temperature of the axilla and of the mouth is so small that it may be
neglected, especially since the variation is not constantly in favour of
the one or the other.

The temperature of internal parts in animals. — Numerous
observations have been made upon the temperature of the internal
parts of animals, either during life or immediately after death. Some
of these results are now given in the following tables : 1—

Animal.

Temperature of Part.

Observer.

Rectum, 38°

Hunter.2

Dog

Right ventricle, 38° '3
Liver, 38° '2

; j

J 5

I

Stomach, 38° '3

>5

T-» J

Aorta, 38° '6

Bernard.

Dog . |

Portal vein, 38° '8

(

Rectum, 40° '8

Davy.3

Liver, 41°'4

? }

Lamb
just dead j

Lung, 41° '4
Right ventricle, 41° '1
Left ventricle, 41° '7

t)
i>

Blood of jugular vein, 40° '8

I

Blood of carotid artery, 41°'7

) >

Dogs

Blood in abdominal aorta, 38° '3-38° '6

Bayliss and Hill.4

(

Rectum, 40°, 40°'6, 40°'6, 40°'6

Davy.3

Lambs

Right ventricle, 40° '8, 40° '6, 40° '8,

j ?

(four) j
just dead [

4l°'l
Left ventricle, 41°'l, 41°'l, 41°'4, 4l°'7
Blood of jugular vein, 40°

"

I

Blood of carotid artery, 40° '8

?>

T\ «

Portal vein, 40° "2

Bernard.5

Dog . |

Hepatic vein, 40° '6

, ,

Lambs (
(three),
just dead \

Brain, 40°, 41°, 40°'8
Rectum, 40° '4, 40° '8, 41° '4

Davy.3

Turkey, f
just dead ~|

Cloaca, 42° -2
Gizzard, 42° -8
Pectoral muscle, 42° "2

Davy.6
» j

Hobday 7 finds in the case of horses, cows, sheep, dogs, and pigs, that
the vaginal temperature is generally one-tenth of a degree lower than
that of the rectum ; at the times of oestrum, however, the vagina often
has the higher temperature.

The temperature of arterial and venous blood. — The temperature
of the blood has attracted considerable attention for many years —
first, on account of the ancient view that the heat of the body was
produced in the heart ; and, secondly, because the work of Lavoisier
and Crawford tended to show that heat was produced in the blood
as it passed through the lungs or other parts of the body. More re-
cently, attention has again been directed to this question by Berthelot,8
who shows that a certain amount of heat is formed in the lungs by

1 The results of other observations will be found in Rosenthal's article, Hermann's
" Handbuch," Bd. iv. Th. 2, S. 393.

2 "Works," Palmer's edition, London, 1837, vol. iv. p. 145.

3 "Researches," London, 1839, vol. i. p. 147 ; Phil. Trans., London, 1814, p. 590.

4 Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 351.

5 "Lecons sur la chaleur animale," 1876, p. 188.
G "Researches," London, 1839, vol. i. p. 159.

7 Vet. Record, London, 1896, vol. viii. p. 488. 8 This article, p. 839.

TEMPERATURE OF ARTERIAL AND VENOUS BLOOD. 827

the combination of oxygen with haemoglobin. The numerous results
obtained by different observers have been collected by Bernard,1 and
are given in the following tables : —

TABLE I.

Results in which the Arterial Blood is warmer than the Venous.

Author.

Arterial
Blood.

Venous
Blood.

Differ-
ence.

Animal.

Part Examined.

Method.

Haller2 (1760),

37°'2

36°'l

l°'l

?

?

}

Schwenke

Crawford3 (1778)

38° '8

37°'5

r-a

Sheep.

Carotid artery, jug-

Thermometer

ular vein.

placed in

blood col-

lected.

Krimer (1823)

38°'18

37°'20

0°'98

Man.

Temporal artery,

Thermometer

jugular vein.

in jet of

blood.

37° '5

36°-6

0°-9

Woman.

V

> >

37°'2

36° -3

0°'9

Man.

Amputation of arm,

) >

brachial artery

and vein.

Scudamore4

37°7

36°'6

1°-1

Sheep.

Carotid artery, jug-

. }

(1826)

ular vein.

36°'l

35°-5

0°-6

Man.

Temporal artery,

f)

vein of arm.

Saissy5 (1808)

38°'5

38°-0

0°'5

Marmot.

Right and left

Incision of

ventricle.

heart.

36°'5

36°-0

0°-5

Hedge-

} j

J?

hog.

38°'0

37°'5

0°'5

Squirrel.

,,

Experiments

on two ani-

m a 1 s c o m-

pared.

31°-4

31°-0

0°-4

Bat.

j>

5>

,1. Davy6 (1815)

40° -0

39°'l

0°-9

Lamb.

Carotid artery, jug-

One thermo-

ular vein.

meter in vein,

anotherinjet

of arterial

blood.

40° -5

40° -0

0°-5

t

!

40° "5

40° -0

0°-5

?

j

40° -5

39° -7

0°-8

f

t

40°'5

40° -0

0°-5

t

t

40° -2

39°7

0°-5

EA-e.

,

40° -0

39°-l

0°-9

5

,

40°'0

39°-4

0°-6

|

(

38°'6

37°7

0°'9

Ox.

>

38° -3

38°'3

o°-o

} j

j

Nasse7(1843)

41°'l

40°'8

0°'3

Lamb.

Right and left

Animals just

ventricle ; great

dead, chest

intestine, 40° '0

opened, ven-

41°-1

40 -5

0°'6

> ?

40° -5

tricles in-

41° •]

40° -8

0°'3

40°'5

cised.

42°-8

41°'25

l°-55

j

) j

»5

41°'8

40°-6

l°-2

]

» i

J>

42°'5

41°'25

l°-25

|

»

5 5

[Continued on next page.

1 ' Lemons sur la chaleur animale," 1876, p. 40 et scq.
~ 'Elementa Physiol.," 1760.

3 'Experiments and Observations on Animal Heat," London, 1779.

4 ' An Essay on the Blood," London, 1824.

5 'Recherches experimentales," etc., Paris, 1808, p. 69.
* Phil. Trans., London, 1814.

7 Rheinisch. u. Westplial. Correspondent., 1843, 1844, 1845.

828

ANIMAL HEAT.

TABLE I. — continued.

Author.

Arterial
Blood.

Venous
Blood.

Differ-
ence.

Animal.

Part Examined.

Method.

Becquerel and

0°'84

Dog.

Aorta where it left

Thermo - elec-

Breschet1

o

heart ; inferior

tric needles,

(1839)

vena cava where j chest opened

it entered heart. in animals

just dead.

...

1°-12

55

Crural artery and ,,

vein.

0°'S4

'

0°'84

j j

Carotid artery, cru-

M

ral vein.

38° -90

38°-0

0°'90

«•

Crural artery and

5)

jugular vein.

TABLE II.
Results in which the Venous Mood is warmer than the Arterial.

Author.

Arterial
Blood.

Venous
Blood.

Differ-
ence.

Animal.

Part Examined.

Method.

Berger 2 (1833)

40°'90

41°'40

0°'50

Sheep.

Eight and left

Not stated.

ventricle.

Collard de Mar-

i°-o

Dog.

j y

Animal just

tigny,3 and

dead ; chest

Ma 1 ga ign e

partly open.

(1832)

Magendie and

...

...

Horse.

Right ventricle

Animal alive ;

Claude Ber-

warmer than

circulation

nard (1844)

left.

not inter-

rupted.

Claude Bernard

...

...

Dog.

Inferior vena cava

Animal alive ;

(1849)

at level of liver

thermometer

warmer than

introduced by

aorta.

the abdomen.

Hering4(1850)

38°-77

39° '30

0°'53

Calf with

Right and left

Incision of ven-

ectopia

ventricle.

tricles.

of heart.

G.LiehigB(1854)

36°'32

36° -35

0°'3

Dog.

»>

Animal alive ;
circulation

not inter-

rupted ; ther-

mometers in-

troduced by

vessels of neck

Claude Bernard

38° -0

38°-2

0°-2

Dog.

(1857)

39° "3

39°-5

0°'2

39°-l

390>2

o°-i

38° "6

38°'8

0°-2

38° -5

38° '7

0°-2

38°-6

38° -8

0°-2

39°-l

39°-2

o°-i

38° -7

38°-9

0°-2

38°'8

38°'9

0°'l

39° *2

39° -4

0°-2

40°'12

40°'37

0°'25

Sheep.

39° "92

40° '32

0°'40

t

39°'58

39°'60

0°'02

}

40°'24

40° '39

0°'15

5

39°'58

39° -87

0°'29

>

40° -09

40° '48

0°'39

1 Ann. d. sc. nat., Paris, "Zool.," Ser. 2, tomes iii. and iv.

2 Mem. Soc. de phys. et d'hist. nat. de Geneve, 1833, tome vi. p. 353.

3 Journ. compl. d'. sc. med., Paris, 1832, tome xliii. p. 386.

4 Arch.f. physiol. Heilk., Stuttgart, 1850.

5 " Ueber die Temperaturunterschiede des venosen und arteriellen Blutes," Giessen, 1853.

TEMPERATURE OF THE SKIN. 829

It will be seen from the two tables that the results lead to directly
opposed conclusions, but a critical examination shows that the correct
one is probably that the blood in the right ventricle is 0°*1 to 0°'2
warmer than that in the left. In many of the older experiments the
methods were inexact, the chest was opened and the heart exposed ;
the right ventricle, on account of its thin walls, would cool more quickly
than the left, as shown experimentally by G-. Liebig. The most exact
method appears to be the insertion of delicate thermometers or thermo-
electric needles down the jugular vein and the carotid artery into the
right and left ventricle respectively. This method was employed by
Heidenhain and Korner 1 in numerous experiments upon dogs, with the
result that in all but one of the observations the right side of the heart
was warmer than the left. Thus in one case the difference was '6°,
in two '5° to '6°, in three *5°, in five '3° to -4°, in twenty-seven '2° to "3°,
in thirty-six -1° to '2°, in twenty-one '15°, in one case no difference at
all. To determine whether the inspiration of cold air was the cause of
this difference, Heidenhain and Korner made comparative experiments,
employing for artificial respiration in the one case cold air (17°), and in
the other hot air (40°) saturated with moisture. The difference still
remained, and it was therefore concluded that respiration was not the
cause ; cold air when inspired is warmed and saturated with moisture
before it reaches the alveoli ; 2 further, in passing through the upper
parts of the respiratory tract, the cold air would cool the blood in veins
going to the superior vena cava and thus to the right side of the heart.
These observers conclude that in the dog the right ventricle is warmer
than the left, because its walls lie nearer to the liver and other
abdominal organs, which have a high temperature, while the left
ventricle is surrounded by lung. It was found, in fact, that the
difference in temperature could be reduced to a minus quantity by
artificially lowering the temperature of the abdominal cavity. Bernard
does not accept this explanation as satisfactory ; for he points out that
in Bering's observation the right ventricle was half a degree warmer
than the left, although the heart, owing to a congenital defect, was
outside the thorax.

The temperature of the skin.— The temperature of the human skin
shows differences in different parts of the body, and is also subject to
variations due to alterations in the external temperature, the amount of
natural or artificial covering, the vascularity of the parts, and the
amount of evaporation taking place from the surface. Apart from
these variations, there is a difficulty in measuring accurately the
temperature of the skin ; a mercurial thermometer applied to the skin
receives heat from the surface in contact with the skin, and loses
heat from the surface exposed to the air. If, on the other hand,
the thermometer is covered with a non-conductor, or the external
temperature is raised, then the heat of the part of the skin observed
is increased. To overcome these difficulties, thermo-electric methods
have been used.3

The disadvantages of these thermo-electric methods are the complexity

1 Arch.f. d. gcs. PhysioL, Bonn, 1871, Bd. iv. S. 558.

2 See "Chemistry of Respiration," this Text-book, vol. i. p. 754.

a Christian! and Kronecker, Arch.f. PhysioL, Leipzig, 1878, S. 334; Kunkel, Ztsclir. f.
Biol., Miinchen. 1889, Bd. xxv. S. 55 ; Masje, Virchow't Archiv, Bd. cvii. S. 17, 267 ;
Geigel, Ferhandl. d. phys.-med. Gesellsch. in Wiirzburg, 1888, N. F., Bd. xxii. S. 8 ;
Stewart, Stud. PhysioL Lab. Owens Coll., Manchester, 1891, vol. i. p. 100.

830

ANIMAL HEAT,

of the apparatus required, the necessity of graduation, and the time
taken in observation. Bayliss and Hill 1 found that the wire-resistance
thermometer 2 could not be employed for the investigation of changes
of temperature in a warm-blooded animal ; the slightest movements, as
those of artificial respiration, in the curarised animal producing deflec-
tions of the galvanometer. A flat mercurial thermometer, on the other
hand, is easily applied, and furnishes comparative data of considerable
value.3

Some of the earliest experiments with mercurial thermometers were
made by J. Davy, who obtained the following results, when the
temperature of the room was 21° : —

Sole of the foot .

Between internal malleolus

and tendo Achillis .
Middle of tibia .
Middle of calf
Bend of the knee
Middle of the thigh .

33°-89
33°-06
33°-89
35° -00
34°-44

Middle of the rectus femoris 32° '78

Groin .... 35° '84

One inch below navel . . 35° '00

Left sixth rib over heart . 34° '44

Right sixth rib . . . 33°'89

Axilla (closed) . . . 36° '67

Kunkel 4 used a thermo-electric method, which was exact to about
0°*1, and obtained the following results for the temperature of different
parts of the skin of a healthy muscular man, 35 years of age, 179 cm.
in height, and 84 kilos, in weight. The temperature of the room
was 20° : —

Forehead

Over malar bone .

Cheek under malar bone

Lobe of ear .

Back of hand

Palm of hand (closed for some

time)

Palm of hand (open)
Wrist .
Forearm

„ upper part

34°-l-34°-4

Arm .

. 34°-l

Sternum

. 34°-4

. 28°-8

Over pectoralis major
Over heart .

32°-5-33°-2
some
34°-8-35°-l
34°'4-34°-8
. 33°-l

Right iliac fossa .
Left „
Back, over sacrum
,, over ribs .
Buttock

. 33°-7
. 34°-0

Thigh .
Calf

34°-3

34°-4

34°-7

34°-6

34°-4

34°-6

34°-2

34°-5

320>05

34°-2

33°-6

Experiments were also made upon the effect of exposure to cold.
Thus, after the man lightly clothed had taken a walk for half an hour
in a cold, sharp, north-east wind (-5°), the following temperatures were
observed — face, 270-7-28°7 ; back of hand, 24°'7 ; chest and abdomen,
32° *1 ; arm, 30°'7-310-1 ; but after he had remained for forty minutes in
a room at 15°, the face had a temperature of 34°*6, the back of the hand
310>2, and the abdomen 33°'9.

Working the muscles of one arm raised the temperature of the skin

1 Joimi. Physiol., Cambridge and London, 1894, vol. xvi. p. 352.

2 Rolleston, ibid., 1890, vol. xi. p. 208.

3 Davy, Phil. Trans., London, 1814, vol. civ. p. 590; "Researches," London, 1839,
vol. i. p. 150; Alvarenga, "Precis de thermometrie clinique ge"nerale," 1871, p. 45;
Waller, "Proc. Physiol. Soc.," Journ. Physiol., Cambridge and London, 1894, vol. xv. ;
Hale White, Croonian Lectures, Lancet, London, June 19th, 1897, Brit. Med. Journ.,
London, 1897, vol. i. p. 1654; Pembrey, "Proc. Physiol. Soc.," Journ. Physiol., Cam-
bridge and London, 1897, vol. xxi.

4 Ztschr.f. Biol., Miinchen, 1889, Bd. xxv. S. 55.

5 This low reading Kunkel attributes to the loss of heat by conduction when the man
was sitting down.

REGULATION OF TEMPERATURE. 831

of that part above 34°, whereas the temperature of the abdomen was
only 3 2° *5. The highest temperature observed in healthy men was
35°'6, on the skin of the face.

Kunkel concludes from his observations that the temperature of the
human skin is almost constant, and that the temperature of the body is
regulated to a very slight degree by changes in the temperature of the
skin.

THE EEGULATION OF TEMPERATURE.

Inasmuch as the constancy of temperature varies in different
animals, and even in the same animal under different conditions, such
as age and hibernation, so also various grades of perfection are observed
in the power of regulation. In man this power is so greatly developed
that his temperature is almost the same, whether he lives in the Arctic
regions, with an external temperature 50° below zero, or in the Tropics,
where the temperature of the air may be as high as 48°. For shorter
periods a man can remain in a room heated to 121° without the
temperature of his body rising above the normal.1 Other mammals
have a less perfect regulation, as shown by the greater variations of
their temperature.

In young immature mammals and birds the power of regulation
is imperfect, for when they are exposed to cold their temperature falls,
and they pass into a condition in which they resemble the cold-blooded
animals, their temperature rising and falling with that of their sur-
roundings. A similar imperfection in regulation is seen in some
mammals during hibernation. Lastly, in the so-called cold-blooded
animals, there are various grades in this capacity for regulating tempera-
ture, as is shown by the high temperature of bees in winter, when com-
pared with that of most of the lower animals, in which there is a mere
trace of regulation.

Even in those warm-blooded animals which possess a perfect power
of heat regulation, there are limits to this power. If the animal be
exposed to excessive cold, the loss of heat is great, and only within
certain limits can compensation be effected by an increased produc-
tion of heat. When compensation fails, then the animal's temperature
falls, its bodily and mental activities are diminished, and it passes into
a sleepy, unconscious condition which ends in death. Such a condition
is observed in men or animals before they are " frozen to death."

On the other hand, extreme heat can only be resisted within a
certain range ; the production of heat in the body can be diminished,
but not suspended ; the loss of heat can be greatly increased by sweating
and by a greater exposure of blood in the vessels of the skin, but if the
air be of a temperature equal to, or nearly equal to, that of the body,
and greatly laden with moisture, then the loss of heat is slight or even
suspended. Under such circumstances the internal temperature of the
animal rises rapidly to a point incompatible with life. The extremes
of heat and cold which can be borne without injury to life, have already
been discussed.

The mean temperature of the higher animals is fairly constant
under very great differences of external temperature, and to maintain
such a condition the loss and the production of heat must be almost equal.
That there is no perfect equality has already been shown in the daily

1 Bladgen, Phil. Trans., London, 1775, vol. Ixv. p. 484. This article, p. 814.

832 ANIMAL HEAT.

variation of the temperature of the body, in the rise of temperature
observed after exercise, and during residence in tropical climates.

The regulation of temperature, therefore, embraces two processes —
regulation by varying loss of heat, regulation by varying production of
heat.

The regulation of heat production.— In considering the regulation
of heat production, it is necessary to trace out briefly the various
discoveries which have established, as a fact, that animal heat is due
to combustion within the tissues.

Historical account of facts and theories upon the sources of
animal heat.1 — The ancients considered animal heat to be beyond the reach
of physical and chemical laws. They c^mld assign no cause for it, and there-
fore looked upon it as some innate quality, something essentially "vital."
This " vital " heat was supposed to be concentrated in the heart (Plato, Aris-
totle, Galen), and to be distributed to the body by the blood in the veins. It
was prevented from accumulating by respiration, the chief function of which
was to cool and temper the blood.

As knowledge in physical and chemical processes increased, attempts were
made to give a rational explanation of animal heat. It was well known that
heat arose during fermentation, and by the contact of acid and base ; animal
heat was therefore considered to arise by some similar process or processes
taking place in the blood. Willis,2 about the year 1670, put forward the
theory that there is in the blood a combustion which depends upon the fer-
mentation excited by the combination of different chemical substances. Fric-
tion was another well-known source of heat, and was the explanation given by
Boerhaave ; 3 he considered that animal heat was due to the friction of the
blood corpuscles in the vessels. Stephen Hales 4 adopted this theory, and gave
certain experiments, which he thought supported it.

A much more correct opinion had already been formed in 1674 by Mayo w,5
who, after his experiments on the constitution of air and its relation to the
heat of combustion, extended the analogy of combustion to animal heat. He
held that the function of the lungs was not to cool the blood, but to enable
that fluid to absorb the nitro-aerial gas (oxygen) of the air, and so generate
heat.

Later research has shown that the heat of living things is not due to any
mystical so-called "vital" force, but to the processes of combustion, which
form one of the most important phenomena of life. The different steps by
which this knowledge has been attained are found in the discovery of Black,6
that carbon dioxide was produced in animals by a process of combustion ; in
the work of Lavoisier 7 and Crawford,8 who showed that the heat of an animal
might be accounted for by the processes of combustion ; in the researches of
Dulong 9 and Despretz,10 whose results, when critically examined and explained
by Liebig,11 formed an important support for the law of the conservation of
energy.

1 Accounts of the old theories will be found in C. Bostock, "Essay on Respiration" ;
"An Elementary System of Physiology," 2nd edition, 1828, vol. ii. p. 243 ; Gavarret,
" De la chaleur produite par les etres vivants," Paris, 1855 ; and " Les phenomenes phy-
siques de la vie," Paris, 1869; Lorain, "De la temperature du corps humain," Paris,
1877, vol. i. p. 39; Rubner, Ztschr. f. Eiol., Miinchen, 1893-94, Bd. xxx. S. 73.

- "De Accensione Sanguinis." 3 " Aphor. cum Notis Sweiten," pp. 382, 675.

4 "Statical Essays," 2nd edition, 1733, vol. ii. p. 90.

5 "Tractatus Quinque," Oxonii, 1674.

G " Lectures on Chemistry," edited by Robison, Edinburgh, 1803.
7 Hist. Acad. roy. d. sc., Paris, 1777.

8"De calore Animali," 1779; "Experiments and Observations on Animal Heat,"
1788.

9 Ann. de chim. etphys., Paris, 1843, Ser. 3, tome i. p. 440.
10 Ibid., 1824, Se"r. 2, tome xxvi. p. 337. u "Thiercheinie," S. 28.

CHEMICAL CHANGE AND HEAT PRODUCTION. 833

Helmholtz, Ludwig, Pfliiger, and others, by their investigations upon the
production of heat in muscle, glands, and other tissues, and their determina-
tions of the respiratory exchange of animals, have indicated where and how
heat is produced. Finally, the exact determinations made by Kubner l upon
heat production and metabolism have proved that chemical change is the
cause of animal heat. Simultaneous determinations of the exchange of
material and the production of heat in dogs, under different conditions as
regards diet, were made, and the results show that the heat of combustion of
the food, as determined in a calorimeter, is equal to the heat given off by the
animal ; in fact, the animal must be looked upon as a living calorimeter, in
which the food is burnt. The results are so exact that they prove the con-
servation of energy in a vital process.

Condition of the Animal.

Heat as Calculated.

Heat as found
by Calorimeter.

Percentage
Difference.

Fasting ....

1296-3 cal.

1305-2

+ 0-69

Diet of fat .

1510-1 „

1495-3

-0-97

Diet of flesh and fat

2492-4 ,,

2488-0

-0-17

Diet of flesh

4780-8 „

4769-3

-0-24

The above figures only give some of the results, but the mean of all the
experiments shows that the amount of heat, as determined directly by the
animal calorimeter, is only O47 per cent, less than the amount as calculated
from the heats of combustion of the different substances which have been
decomposed in the animal's body.

THE KELATION OF CHEMICAL CHANGE TO HEAT PRODUCTION.

A consideration of the law of the conservation of energy leads to the
conclusion that the sole cause of animal heat is a chemical process, a
combustion of food substances by the oxygen taken in by the animal ;
as just mentioned, the experimental proof of this conclusion has been
recently given by Kubner. The chemical energy of the ingesta
manifests itself chiefly in two forms, heat and motion.

In this connection it is important to consider the heats of combus-
tion of the various substances which form part of an animal's body or
food, for it will thereby be possible to determine indirectly the amount
of heat produced by an animal. A given amount of chemical action is
accompanied by the production or the absorption of a definite quantity
of heat. The accurate determination of this quantitative relation is
beset with considerable difficulties, for the chemical changes in the
complex substances of animal tissues or food are rarely simple, and are
accompanied by physical changes, which have to be measured and taken
into account before the amount of heat due to the chemical change can
be estimated. Chemical decomposition is attended with the absorption
of a quantity of heat equal to that which would be evolved by the
combination of the same chemical substances.2 Therefore, in the

1 Ztschr.f. Biol, Miinchen, 1894, Bd. xxx. S. 135.

2 Favre and Silbermann, Ann. de chim. et phys., Paris, 1842, Se*r. 3, tome xxxiv.
p. 357 ; Woods, London, Edinburgh, and Diiblin Phil. Mag., London, 1851, vol. ii. p. 268,
1852, vol. iv. p. 370 ; Joule, ibid., 1852, vol. iii. p. 481.

VOL. i.— 53

834

ANIMAL HEAT.

estimation of the production of heat during a complex chemical change,
involving combination and decomposition, it is only necessary to
consider the first and final conditions of the substances, whatever may
have been the intermediate stages.1

The determination of the heat produced or absorbed by chemical
change is made by enclosing the acting substances in a chamber sur-
rounded by water or mercury, the rise or fall of temperature in which
indicates the amount of heat produced or absorbed, as the case may
be.2

The heat of combustion of substances of physiological interest has
been determined by various observers;3 the following table gives the
values of some of the most important substances : —

Substance,
1 grm. (dry).

Heat of
Combustion.

Authority.

Substance,
1 grm. (dry).

Heat of
Combustion.

Authority.

Hydrogen

33,881 cal.4

Andrews.

Casein . . .

5, 855 cal.

Danilewsky.

> » •

34,662 „

Favre and Sil-

, , . .

5,867

Stohmann.

bermann.

, ,

5,849

Carbon . .

7,900 „

Andrews.

Cows' milk .

5,733

Danilewsky.

,, Wood-

1 (

Favre and Sil-

Women's milk

4,837

?j

charcoal

|8,080 ,, |

bermann.

Fat ...

9,686

»

Cheese .

6,114

Frankland.

, , ...

9,423

Rubner.

Potatoes

3,752

>>

Dextrose .

3,939

Rechenberg.9

J 9 '

4,234

Danilewsky.5

Maltose . .

4,163

j}

Lean beef

5,313

Frankland.

Milk sugar .

4,162

»

» •

5,724

Danilewsky.

Starch . . .

4,479

> J

> i • •

5,641

S toh man n.6

,, ...

4,182

Stohmann.

>> •

5,656

Rubner.7

Cane-sugar .

4,176

Danilewsky.

White of egg

4,896

Frankland.

Glycogen . .

4,190

Stohmann.

Yolk of egg

6,460

3 j

Cellulose . .

4,185

?j

Butter

7,264

Urea . . .

2,537

Danilewsky.

Bread crumb

3,984

j j

, j ...

2,537

Stohmann.

Blood fibrin

5,772

Danilewsky.

,, ...

2,525

Berthelot and

j )

5,637

Stohmann.8

Petit.10

Peptone .

4,876

Danilewsky.

,, ...

2,523

Rubner.7

»

5,298

Stohmann.

Uric acid . .

2,741

Stohmann.

Serum albumin

5,917

> >

Hippuric acid

5,678

»

Haemoglobin .

5,885

Faeces . . .

4,479

Rechenberg.

The above table shows that the different foodstuffs have different
values as producers of heat, and from these it is possible to calculate
the physical value of one kind of food in terms of the others. The

1 Hess, quoted from Rubner (Ztschr. f. BioL, Munchen, 1894, Bd. xxx. S. 135).

2 For further details on such calorimeters, see Miller, "Chemical Physics," p. 338, and
Watts' "Dictionary of Chemistry," vol. iii. pp. 28, 103; Stohmann, Journ. /. prdkt.
Chem., Leipzig (2), Bd. xix. S. 115 ; Bd. xxxix. S. 503.

3 Crawford, "On Animal Heat," 1788, 2nd edition, pp. 320, 333, 351 ; Favre and
Silbermann, Ann. de chim. et phys., Paris, 1842, tome xxxiv. p. 357 ; Frankland, London,
Edinburgh, and Dublin Phil. Mag., London, 1866, vol. xxxii. p. 182 ; Hermann, Ber. d.
deutsch. chem. Gesellsch., Berlin, 1868, S. 18, 84 ; Rubner, Ztschr. f. BioL, Munchen, 1885,
Bd. xxi. S. 357; Berthelot, Corny t. rend. Acad. d. sc., Paris, 1886, tome cii. pp. 1211,
1284.

4 Calorie = the heat required to raise 1 grm. of water 1° C. ; kilo-calorie = 1000 calories^
heat required to raise 1 kilo of water 1° C.

5 Arch.f. d. ges. Physiol., Bonn, 1885, Bd. xxxvi. S. 230.

6 Journ. f. prakt. Chem. , Leipzig, Bd. xliv. S. 336.

7 Ztschr. f. BioL, Munchen, 1893-94, Bd. xxx. S. 88.

8 Ibid., 1895, Bd. xxxi. S. 364.

9 "Ueber die Verbrennungswarme organischer Substanzen," Leipzig, 1880.
10 Compt. rend. Acad. d. sc., Paris, 1889, tome cix. p. 759.

CHEMICAL CHANGE AND HEAT PRODUCTION. 835

following table of isodynamic foodstuffs is taken from Danilewsky's
work : —

Fat. '

Starch.

Grape-
Sugar.

Cane-
Sugar.

Cellulose.

Peptone.

Extract of
Meat.

100 grms.
casein =

61

133

151

142

133

121

135

100 grms.
fat

100

220

250

236

221

201

224

100 grms.
starch =

46

100

114

107

100

92

102

The above data are for physical values. It is necessary, therefore,
to determine how far the different foodstuffs undergo combustion in
the living body, and what values they have as producers of heat during
that combustion.

Eubner has shown that some of the products of the combustion of
proteid escape in the foeces as well as in the urine ; the heat value of
these substances must be determined and deducted from the heat of
combustion of proteid. The reduced or physiological heat value of
1 grm. of dry proteid is therefore only about 4000 calories. The fats
and carbohydrates appear to undergo complete oxidation in the body.

An important series of experiments on the sources of animal heat
has been performed by Eubner.1 The experiments were carried on for
several days in succession upon a dog weighing 12 kilos. The animal
was given a known amount of meat once a day ; the urine and faeces
were collected and their heat of combustion determined, and the heat
given off by the animal was measured by a calorimeter. At the same
time the discharge of carbon dioxide and water from the dog were deter-
mined, also the total nitrogen lost in the urine and fteces, and the loss
or gain in weight of the animal. No external work was done by the
dog, for it remained quiet in the calorimeter, and therefore no energy
was lost in the form of work.

The following is an example of the results obtained : —

Heat

Heat

Total Dis-

Carbon

Calcu-

Calcu-

Total Heat

Date.

Condition.

charge of

from

lated

lated

in Twenty-

Nitrogen.

Fat.

from

from

four Hours.

Proteid.

Fat.

16th October 1889

Fasting

3-06

16-38

77'0

201-5

278-5 kilo-cal.

This result, 278'5 kilo-calories, compares well with the heat, 276*8 kilo-
calories, given off by the animal in the calorimeter.

Date.

Condition.

Heat
given to
Calorimeter.

Heat
Lost in
Ventilation.

Heat Lost in
Evaporation
of Water.

Total Heat
in Twent}'-
four Hours.

16th October 1889

Fasting

213-2

17-6

45-9

276-8
kilo-cal.

Ztschr.f. Biol., Miinchen, 1893-94, Bd. xxx. S. 73.

836 ANIMAL HEAT,

Thus it is possible to calculate the production of heat in an animal, if the
quantity and nature of its food and the amount of the discharge of nitrogen in
the urine and faeces be known. This Rubner has done, and has compared the
result with the heat given off by the animal to a calorimeter. Thus : —

-r, , , , , . I 2 28 '06 grms. proteid.

Food of dog during 12 days =

In the urine 30 '0 grms. N were discharged, and the dry faeces amounted
to 16 '8 grms.

Calculation 1, from physiological heat values.

Proteid, 228-06 x 4'0 kilo-cal. = 912'24
Fat, 340-4 x 9 -423 „ = 3207'0

4119-2 kilo-cal. in 12 days.

Calculation 2, from physical heat value with reduction for heat value
of urine and fceces.

Proteid . . = 1222 kilo-cal.
Fat = 3207

4429

OAK o (223-5 heat value of urine.
OOD'Z \ 8i-7 M M

In 12 days 4124 kilo-calories.

The amount of heat actually given off by the dog during this time was
3958 kilo-calories. Thus the calorimeter showed that 96 per cent, of the
energy of the food had appeared as heat.

Eecent work by Kubner1 has shown that the body of a living
animal may be looked upon as a. calorimeter, and may be used as such
for the determination of the heat of combustion of food. Thus the heat
of combustion of 1 grin, of dry meat, determined in this way, is 4007
calories, that of 1 grm. of dry fat 9353 calories, figures which are practic-
ally the same as 4000 and 9423 respectively, the results obtained by
combustion in a Thompson's calorimeter, when allowance is made for
the heat value of the products of the proteid lost in the urine and
faces.

The following is one of Rubner's examples of such a determination : — A
small dog fed upon meat discharged daily 10*09 grms. of nitrogen in its urine
and faeces, and 9 '06 grms. carbon from fat underwent combustion. The heat
produced, as determined by the calorimeter, was 379*5 kilo-calories. On a diet
of meat and fat the same dog discharged 2 -95 grms. of nitrogen, and 19*12 grms.
carbon from fat underwent combustion, while the production of heat was 311
kilo-calories. Now, if the calorimetric value of the nitrogen be represented by
x and that of carbon from fat by y, then —

(1) 10-09a;+ 9*06?/ = 379*5

(2) 2-95aj+19-12y = 311-0

.'. # = 26*7 kilo-calories and y — 12*15 kilo-calories.

The results obtained by direct combustion were 26'0 and 12 '3 kilo-calories.
The heat corresponding to 1 grm. nitrogen = 6 '49 3 grms. dry meat = 26*36
kilo-calories ; that to 1 grm. carbon from fat= 1*3 grm. fat= 12 '16 kilo-calories,
1 Ztschr.f. BioL, Munchen, 1894, Bd, xxx. S. 140.

CHEMICAL CHANGE AND HEAT PRODUCTION. 837

The heat of combustion of food may be determined in three ways —
(1) by direct estimation with a calorimeter, (2) by calculation from the
oxygen necessary for oxidation, and (3) by measurement of the heat
produced by the combustion of the food inside the animal body. Such
determinations have been made by Rubner,1 and the following table is the
isodynamic value of 100 grins, of fat estimated by these three modes : —

First Method.

Second Method.

Third Method.

100 grms. of Fat =

Proteid .

201

193

211

Starch

221

240

232

Cane-sugar

231

249

234

Grape-sugar

243

263

256

It is to be noted that, with the exception of proteid, all food substances
give too low a value for the heat of combustion when it is calculated from
the equivalents of oxygen necessary for combustion. The calculation of the
heat of combustion from the oxygen necessary for oxidation gives results
which are not exact.

The value of these calculations in the estimation of the heat pro-
duced in a living body will be seen by comparing the results with those
obtained by direct determination with the calorimeter. The following
are Vierordt's 2 calculations for the heat production of an adult man in
twenty-four hours : —

(a) Calculation, according to Dulong's principle, from the heat of combus-
tion of carbon and hydrogen.

An adult man consumes in twenty-four hours —

C.

H.

N.

o.

120 grms. proteid .

64-18

8-60

18-88

28-34

90 „ fat ...

70-20

10-26

...

9-54

330 ,, carbohydrate

146-82

(Hydrogen

combined wi

th oxygen)

281-20

18-86

18-88

In urine and faeces

29-80

6-3

...

251-4

12-56

...

251-4 grms. C. x 8,080
12-56 „ H. x 34,460

Total heat production

= 2,031,312 calories.
- 432,818 „

= 2,464,130

1 Ztschr.f. Biol, Mlinchen, 1883, Bd. xix. S. 386.
3 "Grundriss der Physiol.," S. 281.

838

ANIMAL HEAT.

(b) Calculation, according to Frankland's principle, from the heat of
combustion of food substances—

120 grms. proteid
90 „ fat .
330 ,, carbohydrate

- 599,760 calories.

- 816,210

= 1,081,410 „

41 grms. urea .

Total heat production

2,497,380
= 83,066

= 2,414,314 calories.

In the consideration of the calculations by Vierordt it is necessary
to remember that Dulong's principle? only leads to approximate results,
and that the values for the heat of combustion employed in the calcula-
tion according to Frankland's principle have been superseded by
more recent and exact determinations. For this reason the following
calculation is given : —

120 grms. proteid x 4000 . . . - 480,000

90 „ fat x9423 . . . = 848,070

330 „ carbohydrate x 41 82 . . . =1,380,060

Heat produced by an adult man in twenty-four hours =2,708,130 calories.
The calculations of other observers give the following values : —

<

2,732,000

Helmholtz.1

2,706,076

Ludwig.2

1,800,000

/ Minimum of 1
I. nourishment /

Danilewsky.3

Calories for an
adult man in 24-
hours .

3,210,000
3,646,007

/Mixed diet — ^
\ Ordinary work /

/Liberal diet — \
^ Hard work /

: )

3,780,000

/Liberal diet — ~\
\ Very hard work/

) >

I

2,843,000

Rubner.

Scharling, from direct calorimetric observation, found that an adult
man at rest gave 132,000 calories in an hour, 3,168,000 in twenty-four
hours; and Him obtained the following results, 140,000 to 170,000
calories per hour, 3,360,000 to 4,080,000 calories in twenty-four hours.

THE SPECIFIC HEAT OF THE BODY.

The first determinations of the specific heat of animal and
vegetable tissues appear to have been made by Crawford.4 The

1 Encyclop. Worterb. d. med. Wissensch., 1846, Bd. xxxv. S. 523.

2 " Lehrbuch der Physiol.," S. 747.

3 Arch.f. d. ges. PhysioL, Bonn, 1883, Bd. xxx. S. 175.

4 "On Animal Heat," 1788, 2nd edition, p. 139. Determinations were also made by
Kirwan and Dalton.

SEA TS OF HE A T PROD UCTION.

839

following are some of his results, and also those obtained recently by
Rosenthal : 1 —

CRAWFORD.

Lean beef . . . = 0*740

Hide of an ox with the hair - 0*787

Lungs of a sheep . . =0*769

Fresh milk of a cow . =0*999

Arterial blood of a dog . - 1 *030

Venous blood - 0*8928

ROSENTHAL.

Compact bone . . =0*300

Spongy bone . . =0*710

Fat . . . . =0*712

Voluntary muscle . =0*825

Defibrinated blood = 0*927

It is to be noted that Davy,2 Hillersohn, and Stein Bernstein 3 were
unable to find any marked difference between the specific heats of
arterial and venous blood. Recently Hale White 4 has made an in-
genious attempt to obtain the specific heat of a living warm-blooded
animal by experimenting upon a hibernating dormouse. His results
vary between 0*812 and 1*18, but they are only approximately accurate,
for the dormouse, even during hibernation, produces a small amount of
heat.

Since all the tissues of the body contain a quantity of water, the mean
specific heat must be near unity, probably about 0*83.

THE SEATS OF HEAT PRODUCTION.

The work of Mayow (1674), Black (1757), Priestley (1772),
Lavoisier (1777), and Crawford (1779) 5 led to the conclusion that
animal heat was due to a process of combustion occurring in the body,
but concerning the chief seat of this combustion there was no unanimous
opinion. Mayow considered that the oxidation took place in the tissues
all over the body ; Crawford held that the heat was set free chiefly in
the capillaries of the body, owing, as he thought, to a difference in the
specific heat of arterial and venous blood ; Lavoisier was at first un-
decided, and considered that the heat arose in the lungs, and possibly in
other parts of the body, but finally he maintained that the lungs were
the chief seat of combustion. The theory of Lavoisier was contested by
Lagrange,6 who maintained that if all the heat of the body were pro-
duced in the lungs, the tissues of that organ would be destroyed by so
high a temperature. This objection was for long held to be fatal to
Lavoisier's theory, until Berthelot,7 by a careful calculation, showed that,
granting all the heat to be formed in the lungs, the temperature of those
parts would not be raised more than a minute fraction of a degree,
owing to the great volume of air and blood in the lungs and the rapidity
of the circulation, whereby the heat would be quickly distributed.
Moreover, Berthelot has shown by experiment that a small amount of
heat is formed in the lungs by the combination of oxygen with

1 Arch. f. Physiol., Leipzig, 1878, S. 215.

2 "Researches," London, 1839.
sArch.f. PhysioL, Leipzig, 1896, S. 249.

4 Journ. PhysioL, Cambridge and London, 1892, vol. xiii. p. 789 ; Croonian Lectures,
Lancet, London, June 19, 1897 ; Brit. Med. Journ., London. 1897, vol. i. p. 1653.

5 Mayow, " Tractatus Quinque," 1674 ; Black, "Lectures on Chemistry," edited by
Robison, Edinburgh, 1803 ; Priestley, Phil. Trans., London, 1772, vol. Ixii. p. 147 ;
Crawford, "De Galore Animali," 1779 ; "On Animal Heat," 2nd edition, 1788 ; Lavoisier,
Brit. Acad. roy. d. sc., Paris, 1777.

6 Hasseufratz, Ann. de chim., Paris, 1791, tome ix. p. 275.

7 Compt. rend. Acad. d. sc., Paris, 1889, tome cix. p. 776.

840 ANIMAL HEAT.

haemoglobin.1 He found in two experiments that 100 volumes of
blood absorbed respectively 20'2 and 18'5 volumes of oxygen, and
produced thereby 14'63 and 14"91 calories. Now, the combustion of the
oxygen with carbon would produce 97*65 calories, but, in the formation
of oxyhaemoglobin, only 14*8 calories were set free — that is, only a
seventh of the heat of combustion would be set free in -the lungs, the
remaining six-sevenths in the tissues. M'Kendrick2 and Bottomley
have also been able, with a thermo-electric arrangement, to detect the
heat produced by the union of haemoglobin with oxygen.

The production of heat in muscle. — It has already been shown
that during active muscular work the temperature of the body is slightly
raised, although the loss of heat is ^t the same time greatly increased.
The muscles must therefore be an important source of heat, and a
further consideration will show that they are the chief source. The
bulk of the body is chiefly composed of muscle ; thus, in a dog weighing
11,700 grms., the muscles weigh 5400 grms., and the bones 2400 grms.
(Bernard) ; 3 and even in a much less compact animal, a bat weighing
19-94 grms., the muscles weigh 6'378 grms. (Pembrey).4

The production of heat as one of the phenomena of contraction
in a single isolated muscle, and the relation of heat to work during a
single contraction and during tetanus, are considered elsewhere. Here
the muscles have to be examined as seats of heat production, not only
during contraction, but during apparent rest ; and, further, as regards
the part they play in the production and regulation of the warmth of
the body.

The muscles, even when they have been removed from the body, are
the seat of an energetic combustion (Humboldt,5 Liebig,6 Du Bois
Keymond, Valentin,7 Mat teucci8). The following comparative experi-
ments were made by Paul Bert.9 Different tissues were removed from
a dog just killed, and the absorption of oxygen and discharge of carbon
dioxide were determined during a period of twenty-four hours, at a
temperature varying from Oc to 10° : —

100 grms. of muscle absorbed 50*8 c.c. of oxygen, and discharged 56'8 c.c. of carbonic acid.

,, brain ,. 45'8 ,, ,, 42'8

kidney „ 37 "0 „ ,, 15 '6

„ spleen ,, 27'3 ,, ., 15'4

testis ,, 18'3 ,, „ 27-5

broken bone \ ,7.9 _-

and marrow \ ' "

Regnard10 has shown that the respiratory exchange of isolated muscle rises
and falls with the external temperature ; at 10° the discharge of carbon dioxide
by 1 kilo, of muscle is 40 c.c. in one hour, at 25° it is 129 c.c., and at 35° it
amounts to 294 c.c., but above 40° the discharge decreases.

1 See also Davy, "Researches,''' London, 1839, vol. ii. p. 168.
*Brit. Med. Journ., London, 1888, vol. ii. p. 338.

3 " Lecons snr la chaleur animale," 1876, p. 140.

4 Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 485.

5 " Versnche neber die gereizte Mnskel-und Nervenfaser," Berlin, 1797.

6 Arch. f. Anat., Physiol. u. wissensch. Med., 1850, S. 393.

7 Arch, f.physiol. ffeilJc., Stuttgart, 1855, Bd. xiv. S. 431.

sCompt. rend. Acad. d. sc., Paris, 1856, tome xlii. p. 648; Ann. de chim. et phys.^
Paris, 1856, tome xlvii. p. 129.

9 " Le9ons sur la physiol. comparee de la respiration," 1870, p. 46.
10 "Recherches expe"rimen tales sur les combustions respiratoires," Paris, 1879, p. 23.

PRODUCTION OF HEAT IN MUSCLE.

841

Similar results have been obtained by Eubner l in limbs through which an
artificial circulation of blood was maintained.

Although, as Hermann 2 has shown, some of the carbon dioxide may arise
from the action of bacteria, yet these experiments show that even excised
muscle is the seat of an energetic metabolism and of heat production. Tissot 3 has
proved that the absorption of oxygen and the discharge of carbon dioxide occur
in an excised muscle, even when every precaution is taken to maintain asepsis.
The results of Minot's 4 experiments upon the production of carbon dioxide in
resting and active muscle are opposed to those obtained by Paul Bert and
Regnard, but his method has been shown by Zuiitz 5 to be open to serious
objections.

The subject of respiration in muscle will be discussed more fully in other
parts of this work,6 here it is only necessary to point out that the respiratory
exchange of a muscle, even during apparent rest, is very marked, and becomes
enormously increased during activity. This is well shown by the experiments
of Sczelkow,7 von Frey,8 Chauveau and Kaufmann,9 Hill and Nabarro.10

DIFFERENCE BETWEEN VENOUS AND ARTERIAL BLOOD.

Muscle at Rest.

Muscle Active.

Sczelkow . . .4

CO,
02

+ 671
-9-00

+ 32-37
-3678

{

CO,

+ 870

+ 30-60

Chauveau and Kaufmann \

I

02

-11-40

-40-95

Tonic. Clonic.

(

CO,

+ 8-76

+ 41-70 +57-99

Hill and Nabarro . . J

Oo

-12-92

-41-25 -37-89

The muscles during apparent rest are in a state of tone, and are the seat of
an energetic combustion, and therefore of heat production.

Further evidence of the important part played by the muscles in the
production of heat is found in the fact that any cause which suspends
the activity of the muscles, or more correctly the rieuro-muscular
system, lowers the temperature of the body. Curari causes muscular
paralysis and a fall in the temperature of the body ; 11 the respiratory
exchange is greatly diminished, even if the animal's temperature is

1 Arch. f. Physiol., Leipzig, 1885, S. 38; this Text-book, article "Chemistry of
Respiration."

2 " Untersuch. u. d. Stoffwechscl der Muskeln," Berlin, 1867, S. 37.

3 Arch, de physiol. norm, et path., Paris, 1894, tome xxvi. p. 838 ; 1895, tome xxvii.

4 " Die Bildung der CO., innerhalb des ruheuden und erregten Muskeln."

5 Hermann's " Handbuch," Bd. iv. Tli. 2, S. 96.

6 See articles on " Chemistry of Respiration" and on "Metabolism," this Text-book,
vol. i.

7 Sitsungsb. d. k. ATcad. d. Wissensch., Wien, 1862, Bd. xlv.

8 Arch.f. Physiol. , Leipzig, 1885, S. 533.

9 Compt. rend. Acad. d. sc., Paris, 1886, tome ciii. pp. 974, 1057, 1153.

10 Joum. Physiol., Cambridge and London, 1895, vol. xviii. p. 218.

11 Tscheschichin, Arch. /. Anat. Physiol. u. wissensch. Med., 1866, S. 159. During
the convulsions which are at first caused by curari the temperature rises ; Bernard,
"Le9ons sur la chaleur animale," 1876, p. 157 ; Velten, Arch. f. d. yes. Physiol., Bonn,
1880, Bd. xxi. S. 361.

842 ANIMAL HEAT.

artificially maintained at the normal height.1 These experiments have
been extended by PHliger,2 who found in curarised rabbits that the
intake of oxygen and the output of carbon dioxide fell respectively to
3 5 -2 and 374 per cent, of the normal exchange : a rise in the tempera-
ture of the surroundings caused an increase in the respiratory exchange,
a-nd in the temperature of the animal, whereas a fall in the external
temperature produced the opposite effects. These phenomena were not
due to diminished supply of oxygen, for artificial respiration was
maintained, the heart beat strongly, and the venous blood was brighter
than in the normal animal. Further, it is not due to poisoning of the
muscle substance itself, for Colasanti 3 found that the oxidation in the
muscles of a limb with an artificial* circulation was the same whether
the blood did or did not contain curari. Similar results have been
obtained with anaesthetics and drugs which depress the activity of the
nervo-muscular system.4

It will be shown later that section of the spinal cord or of the
motor nerves reduces a warm-blooded animal to a cold-blooded condition ;
its temperature falls, and it can no longer regulate its temperature.
The completeness of the effect seems to depend upon the number of the
muscles paralysed. On the other hand, calorimetric determinations
show that muscular activity greatly increases the production of heat
and the respiratory exchange.

It has already been stated that young mammals and birds, in which
muscular co-ordination is well developed, are able to maintain their
temperature at birth, whereas others born in a helpless condition
resemble cold-blooded animals.

According to D. Macalister,5 the muscles are fatigued as producers of
heat sooner than as producers of work, and the effect of cold upon the
muscles of anaesthetised mammals is to markedly depress the thermo-
genic function.

The involuntary muscular contraction in shivering causes a rise
of temperature,6 and this is especially noticeable in small thin dogs
with little fur ; in fact, shivering must be looked upon as an involuntary
protective mechanism against cold.7 In man, as Lowy8 has shown, it
may increase the metabolism by 100 per cent. The warming effect of
muscular exertion is a matter of ordinary daily experience, and is well
shown by the difference in the walk of a man during cold and hot
weather.

The heat produced by the contraction of the heart.— The work
done by the human heart was estimated by Grehant 9 at 43,800 kilo-
grammetres in twenty-four hours, and this according to the mechanical

equivalent of heat would give - =103,000 calories. Foster10 cal-

culates that the work done by the heart is nearly 60,000 kilogrammetres,

1 Zuntz, Arch.f. d. gcs. Physiol., Bonn, 1876, Bd. xii. S. 522.
z Ibid., 1878, Bd. xviii. S. 255.
* Ibid., 1878, Bd. xvi. S. 157.

4Rumpf, ibid., 1884, Bd. xxxiii. S. 538; Pembrey, " Proc. Physiol. Soc.," Journ.
Physiol., Cambridge and London, 1894-1895, vol. xvii.

5 " Goulstonian Lectures," Lancet, London, 1887, vol. i. p. 558.

6 Beclard, Arch, de med. nav., Paris, 1861, pp. 24, 157, 257.

7 Richet, Compt. rend. Soc. de biol., Paris, 1892, p. 896.

8 Arch.f. d. yes. Physiol., Bonn, 1889, Bd. xlv. S. 625 ; and 1890, Bd. xlvi. S. 189.

9 "Phys. Med.," 1869, p. 229.

10 "Text-Book of Physiology," 1891, 5th edition, pt. 1, p. 254.

PRODUCTION OF HEAT IN GLANDS. 843

Waller l estimates it at 20,000 kilogrammetres, and Nicolls 2 at 54,000
kilogrammetres.

The production of heat in glands.— Glands are the seat of active
chemical changes, accompanied by a production of heat, but during
activity their blood supply is augmented, and the increased temperature
arising from this cause often masks the heat produced by the activity
of the glands.

The submaxillary gland is an instance in which the activity of the
tissue is accompanied by a greatly increased blood flow. Ludwig and
Spiess3 found by the thermo-electric method that the submaxillary
saliva of a dog was 1° to 1°'5 warmer than the blood in the carotid
artery. Bernard 4 ligatured the blood vessels of the gland, and found that
stimulation of the chorda tympani still produced a slight rise in temper-
ature, whereas excitation of the sympathetic produced a slight fall. The
temperature in degrees is not stated, but Bernard brings these observations
forward as additional arguments in favour of frigorific nerves. Morat 5
states that he has been able to confirm Bernard's results ; Heidenhain,6 on
the other hand, observed a rise in temperature when the sympathetic was
stimulated. Eecently, Bayliss and Hill7 have carefully investigated
the question of the formation of heat in salivary glands ; they used both
the thermo-electric method and Geissler's thermometers. Their results
led them to the following conclusions : — The temperature of the gland
and tissues around it is almost as high as that of the aortic blood ; the
saliva is not warmer than the gland and tissues around the duct, and no
formation of heat can be directly determined in the submaxillary gland
by any known method of measuring variations in temperature. On
stimulation of the chorda tympani, the temperature of the saliva never
rose higher than the temperature of the aortic blood. No doubt the
gland produces more heat during activity, but, on account of the small
size of the gland, and the rapid circulation, the difference cannot be
shown.

The intestines and liver. — According to Bernard,8 the blood coming
from the intestines is raised in temperature during digestion, the tem-
perature of the blood in the portal vein being two- or three-tenths of a
degree warmer than that of the abdominal aorta. Bernard also found
that the liver was the warmest organ in the body, that the blood of the
hepatic vein was higher than that of the portal vein, and showed a still
further increase during digestion.

Stimulation of the splanchnic, or of the vagi nerves, produces no
calorific or frigorific effect in the temperature of the liver.9

1 " Human Physiology," 1893, 2nd edition, p. 75.

2 Journ. Physiol., Cambridge and London, 1896, vol. xx. p. 407.

3 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1857, Bd. xxv. S. 584 ; Ludwig, Wien.
med. Wchnschr., 1860, Nos. 28 and 29.

4 " Lemons sur la chaleur anirnale," 1876, p. 428.

5 Arch, de physiol. norm, etpath., Paris, 1893, tome xxv. p. 285.

6 Stud. d. physiol. Inst. zu Sreslau, Leipzig, 1868, Bd. iv.

7 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 351.

8 " Lemons sur la chaleur animale," 1876, p. 190. See also this article, p. 809; Braune,
Virclwws Archiv, 1860, Bd. xix. S. 470, 491.

9 Waymouth Reid, "Proc. Phys. Soc.," Journ. Physiol., Cambridge and London, 1895,
vol. xviii.

844

ANIMAL HEAT.

THE MEASUREMENT OF HEAT PRODUCTION.

The amount of heat produced by an animal can be determined by
the measurement of the heat given off, and also by an estimation of the
heat value of the chemical changes taking place in the body. The most
exact method is that which embraces both of these determinations.

Numerous attempts have
been made to construct
suitable calorimeters, but
it is only within the last
few years that exact
methods have been de-
vised.

Calorimeters.1 — In
1780, Lavoisier and Lap-
lace 2 employed the ice cal-
orimeter, in which the heat
produced by the animal is
estimated from the amount
of ice liquefied. The con-
struction of this calorimeter
is shown in the accompany-
ing diagram. (Fig. 81).

Important results were
obtained by the use of this
method, but they were not
an exact measure of the
heat produced by a normal
animal. The exposure to

FIG. 81. — Diagram of ice calorimeter.

such a low temperature causes an abnormal loss and production of heat, and
it is impossible to rapidly and completely collect the water formed by the
melting of the ice.

Crawford,3 in 1788, introduced the water calorimeter, and indicated the
precautions necessary to obtain accuracy. The method was improved by
Dulong and Despretz.

Although this calorimeter was a great advance upon the ice calori-
meter, yet it has been found by numerous observers to be unreliable. It
is impossible, even by careful mixing, to obtain the exact heat of the water,
for strata of different temperatures are formed, and thus errors easily
arise. Further, the water responds very slowly to any change in the
production of heat by the animal. This method was used by Dulong4
and Despretz,5 and has been again brought into use by Wood, Reichert,
and others.0

The air calorimeter appears to have been first used by Scharling7 in 1849, and

1 A list of researches in which different kinds of calorimeters have been used, will be
found in the paper by Haldane, Hale White, and Washbouru, Journ. FhysioL, Cambridge
and London, 1894, vol. xvi. p. 124.

2 Hist. Acad. roy. d. sc., Paris, 1780, p. 355.

3 " Experiments and Observations on Animal Heat," London, 1788, 2nd edition.

4 Ann. de cliim. etphys., Paris, 1843, Ser. 3, tome i. p. 440 ; Compt. rend. Acad. d. sc.,
Paris, tome xviii. p. 327.

5 Ann. de chim. etphys., Paris, 1824, Ser. 2, tome xxvi. p. 337.

6 Wood, "Fever," Smithson. Contrib. Knowl., Washington, 1880 ; Reichert, Univ.
Med_. Mag., Philadelphia, 1890, vol. ii. p. 173.

7 Journ. f. prakt. Chew,., Leipzig, 1849, Bd. xlviii. S. 435.

CALORIMETERS.

845

the most exact of the modern methods are modifications of this.1 D'Arsonval,2
in 1886, introduced the differential air calorimeter, which has this great advan-
tage, that the loss of
heat by conduction
and radiation from
the calorimeter con-
taining the animal is
compensated by a
similar loss from a
dummy calorimeter of
similar size and con-
struction. This
method has been em-
ployed, and still fur-
ther modified, by
Rosenthal3 and
Rubner,4 but it will
suffice here to describe
only the latest form,
that introduced by
Haldane, Hale White,
and Washbourn.5 In
this calorimeter (Fig.
85) the heat produced
by the animal in one

chamber is balanced by FlGi 82.— Diagram of Dulong's water calorimeter,

the heat given off by a

hydrogen flame burning in another similar chamber. The amount of hydrogen

burnt is estimated, and,
knowing the heat of
combustion of hydro-
gen, one can calculate
the calories produced
by the quantity of
hydrogen used in the
experiment; this num-
ber of calories is equal
to those given off by
the animal. The cal-
orimeter is so arranged
that at the same time
it serves as a respira-
tory apparatus, and the
determination of
the intake of oxygen
and output of carbon dioxide checks the result of the calorimetric observa-
tion.

1 Rosenthal, Arch. f. Physiol., Leipzig, 1878, S. 349 ; Richet, Arch, de physiol. norm,
et path., Paris, 1885, tome vi. p. 237 ; Mosso, Arch. f. exper. Path. u. Pharmakol., Leipzig,
1890, Bd. xxvi. S. 316.

2 Journ. de I'anat. et physiol. etc., Paris, 1886, tome xxii.

3 Arch.f. Physiol., Leipzig, 1888, S. 1.

4 " Calorimetrische Methodik," Marburg, 1891; Beitr. z. Physiol. Carl Ludwig
z. s. 70 Geburtst., Leipzig, 1887 ; Ztschr. f. Biol., Miinchen, 1893-94, Bd. xxx.
£ 92.

5 Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 123; Hale White,
Croonian Lectures, Lancet, London, 1897, vol. ii. ; and Brit. Med. Journ., London, 1897,
vol. ii. p. 11.

FIG. S3.—

F. Layer of felt.
C. Cage.

jram of air calorimeter (Haldane, Hale
Arhite, and Washbourn).

A. Tubes for ventilation.
H. Hydrogen flame.
M. Manometer.

846 ANIMAL HEAT.

For experiments on man, Currie,1 and afterwards Liebermeister 2 and others,
used a bath as a water calorimeter ; this method is liable to many sources of
error. Scharling,3 Vogel,4 and Him 5 used a method which was simple, but at
the same time untrustworthy ; the subject of the experiment was enclosed
within a small chamber standing in a room with a constant temperature ; the
production of heat was determined from the difference between the tempera-
ture of the chamber and that of the room. Leyden employed a partial
calorimeter for experiments in man ; a limb was enclosed in a suitable water
calorimeter.

It is probable that the simplest and most useful method for clinical
purposes is that introduced by Waller 6; the deep and surface temperatures
of different parts of the body are determined, the evaporation of water from
the skin is estimated by a hygrometer, argl the temperature of the surrounding
air is noted. If the calorimetric value of the thermometer scale be pre-
viously determined on a surface giving off heat at a known rate, it is possible
from the data obtained to calculate the emission of heat. The apparatus, in
fact, constitutes a heat manometer measuring the temperature difference
between the skin and atmosphere.

The results of calorimetric experiments.— Lavoisier 7 and Craw-
ford 8 concluded from their results that the heat produced by an animal
could be almost entirely accounted for by the combustion represented
by the discharge of carbon dioxide and water. Dulong 9 and Despretz's 10
data, when corrected by Liebig,11 Helmholtz,12 Gavarret,18 Ludwig,14 Milne
Edwards,15 and Liebermeister,16 lead to a similar conclusion, but since the
more exact experiments of Eubner and others, they have had only a
historical interest.17

The table on p. 847 gives some of the more important results
obtained by various observers.

It has been already shown that the heat, measured directly with a
calorimeter, is equal to that calculated from the heats of combustion of
the constituents of the food (Eubner 18), and it will be seen later that the
production of heat in different warm-blooded animals is proportionate to
the surface of their bodies (Rubner).19 During digestion and muscular
work the production of heat is greatly increased.

According to Langlois,20 the production of heat in children is pro-
portionate to the surface of their skin, and shows a daily variation.

1 " Medical Reports on the Effect of Water, Cold and Warm, as a Remedy in Fever and
other Diseases," Liverpool, 1798.

2 Arch.f. Anat., Physiol. u. wissensch. Med., 1860, S. 520, 589 ; 1861, S. 28 ; " Hand-
buch der Path. u. Therap. des Fiebers," 1875, S. 142.

z Journ. f. prakt. Chem., Leipzig, 1849, Bd. xlviii. S. 435.

4 Arch. d. Ver. f. wissensch. Heilk., Leipzig, 1864, S. 442.

5 " Recherches sur 1'equivalent mecanique de la clialeur," Paris, 1858.

6 " Proc. Physiol. Soc.," Journ. Physiol., Cambridge and London, 1894, vol. xv.

7 Hist. Acad. roy. d. sc., Paris, 1780, p. 355.

8 " Experiments and Observations on Animal Heat," 1788, 2nd edition.

9 Ann. d. chim. etphys., Paris, 1843, Se"r. 3, tome i. p. 440.

10 Ibid., 1824, SeV. 2, tome xxvi. p. 337.

11 "Thierchemie."S. 28.

12 "Encyclop. Worterb. d. med. Wissensch.," 1846, Bd. xxxv. S. 523.

13 " De la chaleur produite paries etres vivants," 1855, p. 219.

14 "Lehrbuch d. Physiol.," 1861, Aufl. 2, Bd. ii. S. 739.

15 " Le9ons sur la physiologic," 1863, tome viii. p. 23.

16 "Handbuch der Path. u. Therap. des Fiebers," 1875, S. 134.

17 For a discussion of these results see Rosenthal, Hermann's "Handbuch," Bd. iv. Th. 2,
S: 358.

™ Ztschr.f. BioL, Munchen, 1894, Bd. xxx. S. 135. This article, pp. 833-37.

19 Ztschr.'f. BioL, Munchen, 1883, Bd. xix. S. 535. This article, p. 853.

20 Centratbl.f. Physiol., Leipzig u. Wien, 1887, S. 237.

MEASURE OF HEAT PRODUCTION.

847

Heat Produced.

Animal.

Remarks.

Observer.

132,000 cal. per hour.

Adult man.

At rest.

Scharling. l

140,000 „

jj 11

»

Him.2

99,000 ,, ,,

11 11

Partial calorimeter

Leyden.3

used.

21,000 cal. per hour.

Dog weighing

One hour after food.

Senator.4

5350-5450 grms.

12,630 ,, ,,

11

Twenty-six hours

after food.

10,900 ,,

11

About forty-nine

hours after food.

2,500 cal. per hour and

Dogs.

About thirty-six

per kilo.

hours after food.

Mean of experiments

on six dogs.

5,920 cal. per hour and

Pigeon.

Normal.

Corin and Van

per kilo.

Beneden.5

6,000 ,, ,,

i i

After removal of

cerebral hemi-

spheres.

The respiratory exchange as a measure of heat production. —

The heat of the body has been shown to be due to processes of com-
bustion occurring in the tissues. The respiratory exchange is a measure
of this combustion, and hence a determination of the intake of oxygen
and the output of carbon dioxide is a measure, although not a perfectly
accurate one, of the heat produced. There is, however, one source of
inaccuracy in this method ; a determination of the respiratory exchange
during a limited time is not an exact indication of the combustion occur-
ring during that time, for we know that oxygen may be taken up and
stored in the body for a considerable period, and carbon dioxide may be
given off by the breaking up of previous combinations ; in fact, may still
be evolved when the tissues are receiving no free oxygen. Nevertheless,
consecutive determinations of the respiratory exchange for long periods,
and careful observations of the animal's temperature, form a most valu-
able method for the study of the regulation of temperature by heat
production, especially since calorimetric experiments are more tedious,
difficult, and more open to accidental sources of error.

In the case of warm-blooded animals, a fall in external tempera-
ture increases, a rise diminishes the intake of oxygen and the out-
put of carbon dioxide. Crawford 6 and Lavoisier 7 came to this
conclusion not only on theoretical grounds, because they believed that
animal heat was due to combustion, but from the results of direct
experiment.

1 Journ. f. prakt. Chem., Leipzig, 1849, Bd. xlviii. S. 435.

2 "Recherches sur 1'equivalent mecanique de la chaleur," Paris, 1858 ; "Exposition
analytique et expe'rimentale dela the'orie me'canique de la chaleur," Paris, 1875, 3e Edition,
tome i. p. 27.

3 Deutsches Arch. /. klin. Med., Leipzig, 1869, Bd. v. S. 273.

4 Centralbl.f. d. med. Wissensch., Berlin, 1871 ; Arch. f. Aiiat., Physi-ol. 11. wissensch.
Med., 1872, S. i. ; 1874, S. 18; " Untersuch. ueber den lieberhaften Process und seine
Behandlung," Berlin, 1873, S. 30.

5 Arch, de biol., Gand, 1887, tome vii. p. 276.

6 " Experiments and Observations on Animal Heat," 1788, 2nd edition.

7 Hist. Acad. roy. d. sc., Paris, 1780, p. 407.

848

ANIMAL HEAT.

Numerous observations have been made, chiefly by Pflliger and his
pupils, upon the effect of changes in external temperature upon the
respiratory exchange of animals in normal and abnormal conditions.
The results of some of the most important experiments will now be
given •} —

Tempera-
ture of Air.

Intake of Oxygen.

Output of Carbon
Dioxide.

C02

o..

Animal.

Observer.

4° '4

210-7 grins, in 6

Man

Voit.2

hours.

weighing

6° '5

206-0 .

71 kilos.

9°'0

192-0

14° -3

...

155-1

23°'7

...

164-8

26°-7

160-0

30° -0

...

170-6

7° -3

1496 -66 c.c. per hour

1203-44 c.c.

0-80

Guinea-

Colasanti.3

and kilo.

pig-

16° '9

1086-8 ,,

937-01 „

0-86

3° -64

1856-8

1564-8

0-83

Guinea -

Finkler.4

26°'21

1118-5 ,,

1057-4

0-94

Pig-

-5°'5

1 7 -48 grms. in 6 hours

19-83

Cat

Herzog

2°-0

15-79

17-87

weighing

Carl

12°-3

1771

17-63

about 2 -5

Theodor.5

20°'l

1278

14-34

kilos.

29°-6

13-91

13-12

-9°-0

...

3016 c.c. per hour
and kilo.

...

Pigeon.

Corin and
VanBene-

17°'5

...

1141

den.6

It will be seen from the above table that the respiratory exchange
decreases with a rise in external temperature, until a point about 35°
is reached, when an increase in the metabolism occurs.7 The response
to a change in temperature is, in the case of small mammals, almost
immediate.8 Thus, within two minutes of a change from 30° to 18°,
a mouse increased its output of carbon dioxide by 74 per cent. ; within
one minute of a change from 330-25 to 17°'5 the increase was 60 per
cent. The response to an increase in temperature does not take place
so quickly ; thus, within two minutes of a rise from 18° to 34° '5,
the decrease in the output of carbon dioxide was 18 per cent. ;
within one minute of a rise from 17° to 32°, the decrease was 5
per cent. The power of maintaining a constant mean temperature is
readily tested in this manner, as the following example will show
(Pembrey) : —

1 See also the preceding article on " Chemistry of Respiration."
* Ztschr.f. £ioL, Miinchen, 1878, Bd. xiv. S. 57.
*Arch.f. d. ges PhysioL, Bonn, 1877, Bd. xiv. S. 92.

4 Ibid., 1877, Bd. xv. S. 603.

5 Ztschr.f. EioL, Munchen, 1878, Bd. xiv. S. 51.

6 Arch de bioL, Gand, 1887, tome vii. p. 274.

7 See also Page, Journ. PhysioL, Cambridge and London, vol. ii. p. 228 ; and
"Chemistry of Respiration," this Text-book, vol. i. p. 712.

8 Pembrey, Journ. PhysioL, Cambridge and London, 1894, vol. xv. p. 401. See also
"Chemistry of Respiration, " this Text-book, vol. i.

PROD UCTION OF HE A T IN COLD-BLOODED ANIMALS. 849

Consecutive Periods of Thirty Minutes.

CO, in
Decimilligrammes.

External
Temperature.

Remarks.

1055
957

ir-o
n°-o

Mouse shivering and active, face and ears pale.
Mouse less active, ears pale.

518
262

31°'5
32°'5

Mouse quiet, sweating, ears flushed.
Mouse sprawled out, sweating, apparently asleep.

815

n°-o

Mouse wakes up, becomes very active, ears pale.

683

11°'0

Mouse quiet, ears pale.

THE PRODUCTION OF HEAT IN COLD-BLOODED ANIMALS.

One of the most characteristic phenomena of life is an exchange of material,
an oxidation which results in the production of heat. In the lowest forms of
life, both vegetable and animal, a certain amount of heat is produced.
Numerous experiments have shown that this is so, although, owing to the
cooling effect of evaporation from the surface of the body, the heat produced
may be masked by the excessive loss ; the temperature of a frog may be
lower than that of the air, notwithstanding that the animal is constantly
producing heat.

It is unnecessary to give here an account of the temperature of plants,1
but, in addition to the facts already stated,2 further details must be brought
forward concerning the production of heat in the lower animals. Hunter 3
found that the temperature of earth-worms, slugs, and leeches might be a degree
above that of their surroundings ; a carp had a temperature of 20° '6, a viper
one of 20°, when that of the surroundings was 18° '6 and 14°*4 respectively.

In bees, even in winter, the capacity for producing heat has already been
shown to be very great. Next in point of interest is the fact, to which
attention was first drawn by Valenciennes,4 that pythons, when coiled
round their eggs during incubation, maintain a temperature even 20°
above that of the surrounding air. The following are some of the results
obtained by Sclater,5 who compared the temperature of a female python with
that of the non-incubating male, which was kept in the same compartment of
the reptile house : —

Dates.

Temperature of
Air in Den.

Temperature of Male.

Temperature
of Female.

Feb. 12

14°'8

On surface, 21° -2
Between folds, 23° '8

22° "8
27°'5

(

On surface, 22° '0

28° "9

March 2

15°-6 4

Between folds, 24° '4

35°'6

1 See on this subject Dutrochet, Ann. d. sc. nat., Paris (Botanique) 1840, SeV. 2, tome
xiii. pp. 5 and 65 ; Gavarret, " De la chaleur produite par les etres vivants," Paris, 1855,
p. 516; Sachs, "Physiology of Plants," p. 404 ; Vines, "Physiology of Plants" ; Van
Tieghem, "Traite de botanique," Paris, 1891, tome i. It is interesting to notice that an
abnormal rise of temperature, fever in fact, has been observed in the tissues around a
wound in a plant. — Annals of Botany, 1897.

2 This article, p. 792.

3 "Works," Palmer's edition, London, 1837, vol. iv. p. 131 et seq.

4 Compt. rend. Acad. d. sc., Paris, 1841, tome xiii. p. 126.

5 Proc. Zool. Soc. London, 1862, p. 365.

VOL. I.— 54

850

ANIMAL HEAT.

Forbes l made similar observations, and found, as the average temperatures
between the folds of the body, 30° and 31°'7 in the case of the male and
female respectively; the maximum was 32°*1 for the male, and 33°'8 for
the female. The greatest difference between the temperature of the air and
the surface of the snake was 4°'6 in the male, and 5°*3 in the female; between
the air and the coils of the snake, 6°'4 in the male, and 9° '3 in the female. It
is worthy of note that the female took no food and little exercise for many
weeks before and during incubation.

In some fishes a temperature several degrees above that of the water has
been observed. Thus Davy 2 found the temperature of deep-seated muscles of
the bonito (Thynnus pelamys) to be 37°'2, when that of the sea was 26°'9.
The tunny (Thynnus thynnus) is said to have a similar high temperature.

The embryo of the chick must be lacked upon as a cold-blooded animal,
for it responds to changes of temperature in a similar manner,3 yet even at an
early stage the production of heat within its tissues can be shown to be
considerable. Thus Barensprung 4 found that the temperature of an egg on
the fourth day of incubation was *6 above that of a dead egg and €8 above
that of the incubator.

THE EEGULATION OF Loss OF HEAT.

An animal may lose heat in various ways — by direct conduction and
radiation from the skin, by evaporation of sweat, by the warming of air
during respiration and by evaporation from the different parts of the
respiratory system, by raising cold food and drink to the temperature
of its body, and by the discharge of urine and faeces. Loss of heat is
controlled chiefly by the skin and the lungs.

The distribution of the loss of heat by an adult man in twenty-four
hours has been estimated by various observers as follows : —

Vierordt.

Helmholtz.

Ludwig.

1

2
3

4
5

1'S % by urine and faeces . . = 47,500 calories,
3 -6% by expired air .. .. = 84,500
7 '2% by evaporation from lungs = 182,120 ,,
14-5% „ „ ,, skin = 364,120 ,,
73 *0% by radiation and conduction
from skin 1,791,820 „

= 2-6%^
= 2-6%
= 14-7% 12,732,000
) f calories.

j-=8o-i/n

2-1% ^
V'2%
> 10.oo, 12,706,076
; 103^ [calories.

78-5 % J

2,500,000

Loss of heat by the skin — Radiation and conduction. — The
amount of heat lost by radiation and conduction is, within certain
limits, in proportion to the difference in the temperature of the body
and of its surroundings ; the warmer the skin and the colder the
surroundings, the greater will be the loss of heat. The heat of the skin
is controlled by the cutaneous circulation, and this in turn is regulated
by the central nervous system. The general result is that the cutaneous
blood vessels are contracted, the circulation is smaller, and the skin
pale and cold, when the external temperature is low ; on the other
hand, the vessels dilate, the circulation becomes greater and the skin
red and warm, when the temperature of the surroundings is high.

1 Proc. Zool. Soc. London, 1881, p. 960.
"Researches," London, 1839, vol. i. p. 219.

3 Pembrey, Gordon, and Warren, Journ. PhysioL, Cambridge and London, 1894-95,
vol. xvii. p. 331.

4 Arch.f. Anat., Physiol. u. wissensch. Med., 1851, S. 131.

REGULATION BY E VAPORATION. 851

Thus it happens that the animal can diminish or increase its loss of heat
according to its needs.

Other conditions, however, play an important part in this regula-
tion. In the case of man the epidermis and the subcutaneous fat are
bad conductors ; and, by means of clothing,1 the greater part of the body
is so protected that it is in contact not with the external air, but with
a fairly stationary layer of air, with a temperature from 24° to 30°. In
other warm-blooded animals protection is afforded by the fur or feathers,
which prevent loss of heat not only by their thickness and slight power
of conduction, but by enclosing strata of more or less stationary warm
air. The more stationary the air the less the loss of heat, for the body
becomes surrounded with a layer of air having a temperature inter-
mediate between that of the body and of the atmosphere. Thus, during
Parry's expedition to the Polar seas, the sailors found that they could
better bear a cold which would freeze mercury ( — 40°), when the air
was perfectly calm, than a temperature of — 12°'2 when there was a
wind.2 The men of Franklin's expedition had the same experience.3
Further, the capacity of dry air to take up heat is much less than that
of moist air ; hence it happens that in dry, calm air several degrees below
zero, much less sensation of cold may be felt than in moist air with a
temperature a few degrees above the freezing point.

In the whale, seal, and walrus, the thick epidermis and the large
amount of subcutaneous fat so perfectly prevent excessive loss of heat,
that their high temperature can be maintained in the Arctic seas.
Greyhounds, on the other hand, feel even moderately cold weather very
quickly, for, as the result of selective breeding, they have little fur and
hardly any subcutaneous fat.4 Vierordt 5 calculated that an adult man
lost 1,791,820 calories, or 73 per cent, of the total loss of heat, by
radiation and conduction from the skin in twenty-four hours. Masje,6
from experiments made with a thermoscope, constructed on the principle
of Langley's bolometer, concludes that the heat lost by radiation from
the skin of an adult man, weighing 82 kilos, and with a surface of
20,000 square cms., is 1,700,000 calories in twenty-four hours. Similar
experiments have also been made by Stewart.7

Evaporation.— Benjamin Franklin 8 observed, during the hot weather
at Philadelphia in 1750, that his temperature remained normal, although
the external temperature was 37°'8 in the shade. He attributed this
result to the cooling effect of the evaporation of sweat. This was proved
by Blagden 9 during his experiments upon the effect of extreme heat on
the body. When the air was rnoist, the temperature of the body rose ;
whereas in dry air, heated to 126°, the temperature did not rise above
the normal. Into the heated room two jars of water were brought, and
a layer of oil was placed on the surface of the water in one, with the

1 Schuster, Arch. f. Hyy., Munchen u. Leipzig, 1888, Bd. viii. S. 1; Rubner, ibid.,
1890, Bd. xi. S. 255.

2 "Journal of a Second Voyage to the Arctic Regions."

3 Franklin, " Journey to the Polar Sea, 1819-1822," 2nd edition, vol. ii. pp. 27, 28. See
also Ross, "Narrative of a Second Voyage in Search of a North- West Passage," London,
1835, pp. 285, 287, 297.

4 Bergmann, " Gottinger Studien," 1847, Abth. 1, S. 595.

5 " Grundriss der Physiol. des Menschen."

6 Virclwufs Archiv, 1887, Bd. cvii. S. 17, 267.

7 Stud. Physiol. Lab. Owens Coll., Manchester, 1891, vol. i. p. 100.

8 "Experiments and Observations on Electricity," London, 1769, p. 366.

9 Blagden, Phil. Trans., London, 1775, vol. Ixv. pp. Ill and 484.

852 ANIMAL HEAT.

result that it quickly boiled, owing to the absence of evaporation;
whereas the water in the other jar rose to 60°, but did not boil, evapora-
tion taking place freely from the surface and thus cooling the water.
Upon the loss of heat by evaporation Crawford,1 in 1781, made some
interesting experiments upon frogs ; he compared the rates of warming
of a dead and a living frog by exposure to warm air and to warm water,
and found that the temperature of the former rose more rapidly than
that of the latter.

In another experiment he found that, when the air was 25°, the skin of a
living frog was 20°, the stomach 21°'4; when the water was 16°'l, the skin of
a living frog was 16°*2, the stomach 19°'2. It is to be noted that when the
frog was kept in water its nose was above^the surface, so that it might breathe ;
in this way heat might be lost by evaporation from the lungs. Crawford,
however, concluded from his experiments that the cooling was not solely due
to evaporation, and that animals had the power of " producing cold."

In 1810, Delaroche 2 published some instructive experiments, similar to
those of Blagden, to show the effect of evaporation. He placed an alcarraza 3
full of water at 35°, and a rabbit whose temperature was 39° '7, in a stove
heated to 45° ; the temperature of the rabbit gradually rose to 43° '8, while
that of the alcarraza fell to 31°'4, and remained stationary. In the second
experiment he placed a frog and two pieces of moist sponge in a stove heated
to 36° *5, and found at the end of an hour that the frog's temperature was
stationary at 28° '2, and that of the pieces of sponge at 27° "9 and 27° '6.
Delaroche contests the results of Crawford's experiments on frogs, and main-
tains that these animals quickly take the temperature of the water in which
they are placed, and that in this respect there is no difference between a dead
and a living frog.

According to the calculations of Vierordt and Ludwig, from 10 to 20
per cent, of the total daily loss of heat in an adult man is due to
evaporation from the skin and respiratory tract. Further details on the
discharge of water from the skin and lungs are given in another part of
this work.4 The following values for the discharge of moisture from
various parts of the human skin were observed by Waller : 5 —

Palm of hand . 24 mgrms. per 20 sq. cm. (per 10 minutes)^
Sole of foot . 14 ,,

Forehead . 12 „

Cheek ' ' /tempera-

ture, 20".

Axilla . . 10

Popliteal space 10

Forearm . .. 5

Leg . . 5

External

The influence of the size of the body upon the regulation of tem-
perature.—The importance of the relation between the surface of the
body and its mass, in respect to the loss and production of heat, was first
pointed out by Bergmann.6 The bigger an animal the greater the ratio of

1 Crawford, Phil. Trans., London, 1781, vol. Ixxi. p. 485.

2 Delaroche, Journ. dephys., Paris, 1810, tome Ixxi. pp. 294-296.

3 A porous jar used for keeping water cool in hot climates. See also Edwards, "De
rinfluence des agens physiques sur la vie," p. 84.

4 "Chemistry of Respiration," this Text-book, vol. i. p. 711.

5 " Proc. Physiol. Soc.," Journ. Physiol., Cambridge and London, 1894, vol. xv. For
further observations see Hale White, Croonian Lectures, Lancet, London, 1897, June 19
and 26, and Brit. Med. Journ., London, 1897, vol. i. p. 1654 et seq.

6 "Gottinger Studien," 1847, Abth. 1, S. 595.

REGULATION OF TEMPERATURE.

853

its volume or weight to its surface, for weight or volume increases as the
cube, surface increases as the square. Thus, if the dimensions of a body
be increased from 1 to 2, the surface increases from 1 to 4, and the cubic
content from 1 to 8. A small animal, therefore, has a far greater
surface in relation to its weight than a large animal, and if it is to
maintain its temperature at a similar height, it must have either special
means for preventing an excessive loss of heat or a more rapid produc-
tion of heat. Both of these means are employed, and so effective are
they, that the temperature of the smallest mammals and birds is often
higher than that of the biggest. A mouse has a thicker covering
of hair, and, relatively to its weight, a greater production of heat, than a
horse. Further, as remarked by Bergmann, the smaller animals need a
relatively greater supply of food.

The large animals living in the tropics, such as the elephant and
hippopotamus, are often remarkable for the small amount of hair upon the
body and for their love of bathing, whereby the loss of heat is favoured.
The largest mammals, the whales, are able by means of their enormous
size and special layers of fat to resist the cold of the Arctic seas, and
maintain a temperature equal to that of mammals living in the tropics.
Water-fowl, especially those which inhabit cold regions, are noted for
the protection afforded against cold by their down and feathers.

These indications from the natural history of animals are fully con-
firmed by experimental observations. The determinations made by
Letellier,1 and by Eegnault and Keiset,2 show that the intake of oxygen
and the output of carbon dioxide are relatively greater in small than in
large animals 3 ; starvation is more rapidly fatal to small than to large
animals,* for during life they consume a relatively larger quantity of
proteid.5 Further, Eubner 6 has determined the heat production of dogs
of different size, and finds that the smaller animals produce relatively
more heat in proportion to their weight than the larger animals, and that
the heat production is proportional to the surface of the body. The
following table gives some of these results : —

Weight,

Surface.

Surface per Kilo.
Weight.

Heat Production per
Kilo, per Day.
Air=*15°.

Heat Production per
Square Metre of
Surface.

Kilo.
31-2

Sq. Cm.
10,750

Sq. Cm.
344

Kilo-cal.
35-68

Kilo-cal.
1036

18-2

7662

421

46-20

1097

9-6

5286

550

65-16

1183

6-5

3724

573

66-07

1153

3-19

2423

726

88-07

1212

Similar results have been obtained by Langlois7 in the case of
children.

1 Ann. de chim. et phys., Paris, Se>. 3, tome xiii. p. 478.

2 Ibid., 1849, tome xxvi. p. 299 ; 1863, tome Ixix. p. 129.

3 See article "Chemistry of Respiration," this Text-book, vol. i. pp. 706-8.

4 Chossat, "Recherches expe"rimentales sur 1'inanition," Paris, 1843.

5 Voit, Hermann's "Handbuch," Bd. vi. S. 88.

6 Ztschr.f. JBioL, Miinchen, 1883, Bd. xix. S. 535.

7 Centralbl.f. PhysioL, Leipzig u. Wien, 1887, S. 237.

854 ANIMAL HEAT.

Rubner calculates that the tissues of a rat produce five and one-
third times, the tissues of a sparrow thirteen times, as much heat as the
same weight of tissue in a man.

THE INFLUENCE OF THE NERVOUS SYSTEM UPON THE
EEGULATION OF TEMPERATURE.

The nervous system exercises a control on both of the factors
concerned in the regulation of temperature ; upon the loss of heat
by means of the vasomotor system, which regulates the amount of
blood in the deep and superficial parts of the body, and by the respira-
tory centre which controls the frequency and depth of respiration ; upon
the production of heat through the nerves which control the activity
of the tissues, chiefly the muscles. The control is of the nature of
a reflex, and the sensory nerves of the skin and muscles are probably
the most usual lines of the afferent impulses. The most important
nervous centres are the vasomotor and the respiratory, but in addition
to these and the so-called "motor" centres some physiologists maintain
that special " heat centres " exist in the brain.

Vasomotor control of temperature. — The blood distributed to the
body comes from the heart, where the temperature is, with the excep-
tion of the liver and a few other internal parts, the highest in the body ;
this warm blood is carried to the extremities and the surface of the
body, where the temperature is lower. Now, three zones may, as
Bosenthal l has pointed out, be recognised — an internal warm zone, an
intermediate temperate zone, and an external cool zone ; the first is
represented by the deep organs and tissues, the second by the more
superficial parts, and the third by the skin and subcutaneous tissue.
Under ordinary circumstances the temperature will decrease from
within outwards, for the most important seats of chemical change and
heat production are situated within the first two zones, and the loss of
heat is greatest from the surface of the skin. The blood circulating in
the vessels distributes the warm blood of the interior to the superficial
parts, and carries back cooler blood from the surface to the interior.
The difference, therefore, in temperature between the interior and the
surface will depend upon the rapidity and the quantity of the blood
circulating through the different zones of the body ; this distribution is
regulated by the central nervous system through the vaso-constrictor
and vaso-dilator nerves. The vasomotor nerves have their centre in
the medulla oblongata, and probably subordinate ones in the spinal cord ;
the distribution, however, of these centres and nerves is discussed else-
where; here they will be considered merely as part of the nervous
mechanism which regulates temperature.

When the cutaneous and subcutaneous vessels are constricted, the
quantity of blood distributed to the skin is diminished, the difference
between the temperature of the surface of the body and its surroundings
is less, and consequently less heat is lost. This condition is brought
about by external cold, and thus the heat of the body is economised and
its normal temperature is maintained, or may, under certain circum-
stances, be raised, for it has already been shown that the first effect of a
cold bath is to raise the temperature in the axilla and rectum. On the
other hand, exposure to warmth causes a dilatation of the cutaneous

1 Hermann's "Handbuch," 1882, Bd. iv. Th. 2, S. 381.

VASO MOTOR CONTROL OF TEMPERATURE. 855

vessels, the difference between the temperature of the skin and its
surroundings is increased, and likewise the loss of heat. Thus the first
effect of a warm bath may be a fall in the temperature of the internal
parts. The loss of heat by this flushing of the skin with hot blood and
by sweating may be very great, as shown by the rapid fall in tempera-
ture during the sweating state of ague or the crisis of pneumonia.

These changes in the calibre of the vessels can be brought about
reflexly, not only by sensations of heat and cold but by those of pain ;
further, emotions can effect these changes, as in the blushing of excite-
ment or shame, and the pallor of fright or anger ; in fact, emotions may
in different individuals have opposite effects upon the vascularity of the
skin.

An impression conveyed by the sensory nerves of one part of the
body can influence the calibre of the vessels, not only on the same side
but also on the opposite side. Thus, Brown-Sequard and Tholozan,1 found
that plunging one hand in warm water raised the temperature of the
opposite hand also. Waller,2 however, has failed to confirm this.

The explanation of the part played by the vasomotor nerves in
the regulation of temperature is not so simple as may appear from a
first consideration, for the problem is complicated by the fact that
an increase or decrease in the vascularity of the skin is accom-
panied by a similar change in the production of sweat ; further, it is
possible that the alterations in vascularity may affect the metabolism
of the tissues. Upon this latter point there has been considerable dis-
cussion. The first and most important experiment in this connection
is that of Bernard,3 who found that section of the cervical sympathetic
caused a dilatation of the blood vessels and a rise of temperature in the
ear of the same side. The enlargement of the blood vessels results in a
greater and more rapid flow of blood through the ear, and this would
naturally raise the temperature of the part. Bernard, however, did not
look upon this explanation as complete ; he held that the nervous
system regulated not only the circulation but also the production of
heat in the tissues, for he states, among other arguments, that section of
the cervical sympathetic, after previous ligature of the veins of the ear,
still caused a rise of temperature. According to Bernard, the nerve was
both vaso-constrictor and frigorific. It was to be expected, however,
that this view would be contested, for although a certain amount of
heat would be produced in the ear, as in the metabolism of all tissues,
yet that amount would be small, for the cartilage and other tissues of
the ear are not the seats of an active exchange of material.

Numerous experimenters 4 have decided against Bernard's theory, and
have attributed the changes in the temperature of the ear to alterations

1 Journ. de I'anat. et physiol. etc., Paris, 1858, tome i. p. 497.

2 Note communicated to the writer.

3 "Le9ons sur la physiologic et la pathologic du systeme nerveux," 1858, tome ii.
p. 490 ; "Lecons sur la chaleur animale," 1876, p. 297.

4 Brown-S'e'quard, Med. Exam., Philadelphia, 1852, p. 489, and 1853, p. 9 ; Budge,
Compt. rend. Acad. d. sc., Paris, tome xxvi. p. 337; Ztsclir. r. d. Vcrein f. Heilk. in
Preussen, 1853, Bd. xxii. S. 149; Waller, Compt. rend. Acad. d. sc., Paris, 1854,
tome xxxvi. p. 378: De Ruyter, " De actione atropfe belladonna?," Diss., 1853; Schiff,
"Untersuch. z. Physiol. des Nervensystems," 1855, Bd. i. S. 124 ; AUg. Wien. med. Ztg.,
1859, S. 318 ; Kiissmaul and Tenner, Untersuch. z. Naturl. d. Mensch. u. d. Thiere,
1855, Bd. i. S. 92 ; Callenfels, Ztschr. f. rat. Med., 1858, Bd. vii. S. 157 ; Jacobson and
Landre, Nederl. Tijdschr. v. Geneesk.,^ Amsterdam, Bd. i. Heft 3 ; Donders, Wunderlich's
" Medical Thermometry," p. 148; Bayliss and Hill, Journ. Physiol, Cambridge and London,
1894, vol. xvi. p. 351.

856 ANIMAL HEAT.

in the blood supply alone. The difference in the temperature of the
two ears, after section of the cervical sympathetic on one side, may be
even as great as 12° or 16°, but it is proportionate to the difference in
the quantity of blood (Schiff). If the two subclavians and the carotid
on the same side as the divided sympathetic are ligatured, the tempera-
ture of the ear falls below the normal, owing to the want of collateral
circulation ; on the other hand, the temperature of the ear can be raised
by ligature of the subclavians without section of the sympathetic nerve ;
this is due to the increased pressure of blood in the carotid artery
(Kussmaul and Tenner). The ears of a rabbit are to be looked upon as
part of the mechanism for regulating temperature by the varying
quantity of blood exposed ; section ^)f one sympathetic causes a fall in
the temperature of the ear of the opposite side (Jacobson and Landre).

In addition to the vasomotor nerves of the skin, it is important to
remember that the vasomotor nerves to the respiratory tract and lungs
may play an important but subordinate part in the regulation of the
loss of heat.1 The importance of this method of regulation without doubt
varies in different animals, and is greater in those with a thick coat of
fur, as in the dog, who, when he is too hot, pants with open mouth and
lolling tongue. This rapid respiration, 150-200 per minute in heated
dogs, has been specially studied by Ackerniann,2 Goldstein,3 and Biegel ; 4
more recently, Eichet 5 has shown that a dog gives off from its respiratory
tract, every hour, about 1 grin, of water for every kilo, of its body
weight, when the external temperature is moderate, but when exposed
to a hot sun it discharges ten times as much moisture and increases its
respirations from 28 to 230 per minute. Any cause which prevents a
clog from breathing rapidly and freely, such as a tight muzzle, causes a
rise of two or three degrees in the animal's temperature.

The temperature of the body after damage or section of the
spinal cord. — An examination of the numerous observations made upon
the influence of injury or section of the spinal cord shows at first sight
much confusion and apparent contradiction in the results. In the
majority of cases, however, the results can be harmonised by taking into
account the numerous factors of secondary import. In the first place,
the experiments are only strictly comparable when they are performed
upon similar animals under similar conditions. Thus the effect will vary
according to the level of the injury or section of the spinal cord ; a
section high up in the cord will involve a more extensive paralysis than
one low down, and the more extensive the paralysis the smaller the
production, and the greater the loss of heat, owing to the dilated cutane-
ous vessels. A section above the splanchnic area will obviously have a
greater effect than one below that area ; a section high up in the cord
will interfere with the movements of respiration, whereas one low down
will have comparatively little effect. Again, an animal with only the
lower extremities and part of the trunk paralysed, may be able to main-
tain its temperature by greater variations in the production and loss of
heat in the parts still under control. The size of the animal is import-
ant, for the bigger the animal the smaller is its surface in relation to its

1 Bradford and Dean, Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 34.
Here an account of previous work on the subject will be found.

2 Deutsches Arch. f. Telin. Med., Leipzig, Bd. ii. S. 361.

3 Inaug. Abhandlung, Verhandl. d. pliys. -med. Gcsellsch. in IVurzburg, 1871, S. 156.

4 Virchoio's Archiv, 1874, Bd. Ixi. S. 396.

5 Compt. rend. Soc. de biol., Paris, 1887, p. 482.

NER VO US CONTR OL OF TEMPERA TURE. 857

mass, and thus the loss of heat due to vasomotor paralysis is less serious
than in a small animal. Animals also differ in their method of
regulation ; some, as in the case of man, have a well-developed vaso-
motor system for the cutaneous surface, which is so slightly protected by
natural covering ; others, as in the case of dogs, have a thick fur, and
regulate their temperature chiefly by variations in the production of
heat and in the loss of heat from the respiratory tract. The distribu-
tion and part played by the sweat glands varies greatly, as shown by a
comparison of men and horses with dogs and cats. It is to be noticed
further, in this respect, that marked differences exist even in individuals
of the same race and variety ; thus, some men and horses sweat much
more readily and profusely than others.

In addition to the above factors, it is necessary to consider the
external conditions under which the injured animal finds itself. The
external temperature greatly modifies the part played by the loss of heat
from the paralysed parts. Most animals adopt a different posture,
according to their need of heat or cold ; thus a heated dog, rabbit, or
mouse lies with extended trunk and limbs, whereas the same animal
when it is cold, coils or huddles itself together. It is almost unneces-
sary to point out that a paralysed animal could not assume these
instinctive postures. A normal rabbit tied down in an extended position
loses an abnormal quantity of heat, and its temperature falls, and in
some cases the body is so greatly cooled that death results.1

The above facts must therefore be borne in mind during any ex-
amination of the effects of section or injury of the spinal cord.

Attention was first drawn to the influence of the nervous system upon
temperature, by the experiments and clinical observations of Benjamin
Brodie.2 He found that, after the head of an animal was cut off, or the
cord divided high up in the cervical region, the circulation of the blood
still continued when artificial respiration was performed, but the tem-
perature fell even more quickly than in a dead animal. This Brodie
correctly attributed to the great loss of heat from the circulating blood, for
if the circulation was stopped by ligature of the heart, the fall of tem-
perature was much retarded. It was also found that woorara (curari) and
essential oil of almonds, by suspending the action of the central nervous
system, also caused a fall in temperature. Brodie further compared the
discharge of carbon dioxide by normal rabbits with that of rabbits with
the brain removed or poisoned by woorara or the essential oil of almonds ;
he states that the same quantity of carbon dioxide is formed in each of
these cases, and therefore that the heat production is not due to chemical
change but to nervous action. This conclusion is not warranted by the
results of the determinations of the respiratory exchange, and the
results themselves are not comparable, for, even when it was possible, the
experiments were not made upon the same animals.

The work of Brodie led to numerous experiments and discussions on
this subject by Chossat,3 Hale,4 Legallois,6 Wilson Philip,6 Hastings,7

1 Legallois, Ann. de chim. etphys., Paris, 1817, S£r. 2, tome iv. p. 21.

2 Phil. Trans., London, 1811, vol. ci. p. 36 ; 1812, vol. cii. p. 378 ; Med.-Chir. Trans.,
London, 1837, vol. xx. p. 146.

3 Deutsches Arch. f. d. PhysioL, Halle, 1822, Bd. vii. S. 282.

4 London Med. and Phys. Journ., vol. xxii.

5 Ann. de chim. ctphys., Paris, 1817, Ser. 2, tome iv.

6 "Experimental Inquiry into the Laws of the Vital Functions," London, 1818, 2nd
edition, p. 197 et seq.

7 Quart. Journ. Sc. Lit. and Arts, London, 1823, vol. xiv. p. 96.

858 ANIMAL HEAT.

and C. J. B. Williams.1 The results on some points confirmed, on others
contradicted, Brodie's conclusions. Wilson Philip found that artificial
respiration caused a fall in the temperature of intact animals, and that a
slow ventilation prevented the temperature of the brainless animal
from falling as quickly as that of a dead animal. Hastings obtained
similar results, and Williams confirmed the observations of Wilson
Philip, that the temperature of a brainless animal might even be slightly
raised by artificial respiration. Legallois carried out a very complete
series of experiments upon the subject, and came to the following con-
clusions : that a brainless animal upon which artificial respiration was
performed suffered a reduction of temperature, but it was from one to
three degrees less than in a dead ajiimal ; that in cooling through a
certain number of degrees it parted with more heat than a dead animal :
that inflation of the lungs of normal animals lowered their temperature,2
and if the ventilation were continued for a long time they might die of
cold ; and, finally, that a fall in temperature might be produced by any
condition which constrained or impeded the respiration.

Tscheschichin 3 found that section of the spinal cord between the
third and fourth cervical vertebrae caused the temperature of a rabbit to
fall from 38°*9 to 32°*1. This he attributed to the increased loss of heat
from the paralysed cutaneous vessels, and to diminished production of
heat ; the higher the section, the more extensive the paralysis of the blood
vessels, and the greater the loss of heat ; stimulation of the peripheral
end of the cord caused contraction of the blood vessels, and the loss of
heat was less.

In rabbits, section of the spinal cord at the commencement of the
dorsal region caused the rectal temperature to fall from 40° to 24° in
five hours (Bernard).4 In guinea-pigs, section of the upper dorsal region
produced a progressive fall in the rectal temperature from 3 8° '9 to 16°
in twenty-four hours, when the animal died (Pochoy).5

Fischer6 found a rise of 0°'5 to 1°*7 in the temperature of dogs and
rabbits after complete section of the cervical portion of the spinal cord,
but no rise when the operation was performed in the dorsal or lumbar
regions. He concluded that an inhibitory centre for heat existed in
the cervical region of the cord. A series of experiments were made by
Naunyn and Quincke7 upon the effect of crushing the spinal cord.
They selected dogs of large size, and with thick fur, in order to diminish
the importance of the loss of heat. They found that, after the cord was
crushed at the level of the sixth cervical vertebra, the rectal tempera-
ture fell, unless, the excessive loss of heat due to vasomotor paralysis was
prevented by a fairly high external temperature ; if the air was warm, the
temperature rose two or three degrees, and even higher after death.
These observers concluded that there were nerve fibres which, passing
from the brain to the spinal cord, inhibited the production of heat s ; and
that, after section, the production as well as the loss of heat were

1 "Observations on the Changes produced in the Blood in the course of its Circulation,"
London, 1835.

2 See also Fawcett and Hale White, Journ. Physiol., Cambridge and London, 1897,
vol. xxi. p. 435.

3 Arch. /. Anat., Physiol. u. wissensch. Med., 1866, S. 151.

4 "Lecons sur la chaleur aniraale," 1876, p. 161.

5 These, Paris, 1870.

6 Centralbl.f. d. med. Wissensch., Berlin, 1869, No. 17.

7 Arch. f. Anat., Physiol. u. wissensch. Med., 1869, S. 174, 521.

8 See also Ott and Collmar, Journ. Nerv. and Ment. Dis., N.Y., 1887, p. 428.

NERVOUS CONTROL OF TEMPERATURE.

859

increased, and if the augmentation of the latter was not excessive, the
temperature of the body rose. On the other hand, Riegel 1 found that
the production of heat was diminished, and he explains the rise of
temperature in Naunyn and Quincke's cases as due to absence of the
rapid breathing whereby normal dogs regulate their temperature.
Further, Schroff2 found a rise in the temperature of dogs when they
were kept in a warm chamber after opening of the spinal canal, without
damage to the spinal cord.

Eosenthal3 repeated Naunyn. and Quincke's experiments, but never
found any rise of temperature, unless the animals were kept in a
chamber warmed to 32°. If the section was made lower down in the
cord, more muscles remained under the control of the animal, and by
the contraction of these muscles more heat was produced, and the
temperature raised when the external air was warm. Rosenthal further
points out that it is probable that septic fever was the cause of the rise
of temperature in some of Naunyn and Quincke's dogs.

Pfliiger's 4 experiments upon the respiratory exchange of rabbits, after
section of the spinal cord in the lower cervical region, show that such
an animal is comparable to a cold-blooded animal; a rise in external
temperature increases, a fall diminishes, the metabolism and the
temperature of the animal. The same result is even more markedly
shown in the case of a smaller animal. Thus the following figures
show the effect of sudden changes in the external temperature upon the
output of carbon dioxide of a mouse before and after section of the spinal
cord in the lower cervical region : 5 —

BEFORE SECTION OF CORD. CONSECUTIVE
PERIODS OF 15 MINUTES.

THREE HOURS AFTER SECTION OF CORD. CON-
SECUTIVE PERIODS OF 15 MINUTES.

CO2in
Decimilli-
grammes.

Tempera-
ture of
Water Bath.

Remarks.

CO2in
Decimilli-
grammes.

Tempera-
ture of
Water Bath.

Remarks.

391

25° -0

Mouse very quiet.

222

22° -0

Mouse quiet.

372

24° -0

11 3) 55

229

22° -0

?5 J J

558
572

12° -5
12°'5

Mouse active.

55 55

250
158

ll°-75
ll°-75

Mouse moves its fore-
limbs very actively.
Mouse quiet.

We may conclude, therefore, that in animals the general effect of
section of the spinal cord in the lower cervical region is a fall in the
temperature of the body, due to a reduction in the metabolism of the
paralysed muscles, and to excessive loss of heat consequent upon the
vasomotor paralysis. The exceptional cases appear to be due to a high
external temperature, and to interference with the rate of respiration,
which in dogs plays an important part in the cooling of the body.

1 Arch.f. d. ges. Physiol., Bonn, 1872, Bil. v. S. 629.

3 Siteungsb. d. Jc. Akad. d. Wissensch. Math.-natunv. 01., Wien, Bd. Ixxiii. Abth. 3,
S. 141.

3 "Zur Keimtniss d. Warmereguliermig bei den warmbliitigen Thieren," S. 35 ; Hermann's
" Handbucb," Bd. iv. Th. 2, S. 437.

4 Arch.f. d. ges. Physiol., Bonn, 1878, Bd. xviii. S. 321.

5 Pembrey, " Proc. Physiol. Soc.," Journ. Physiol., Cambridge and London, 1894-
1895, vol. xvii.

86o

ANIMAL HEAT.

An examination, of the cases of crushed spinal cord in man shows
discordant results, in some cases a marked rise, in others a fall in the
temperature of the body. The following table gives the chief data in
some of the cases recorded : —

Sex and
Age.

Seat of Injury.

Temperature.

Remarks.

Observer.

M.

Crush at level

43°'9 (111° F.), be-

Diaphragmatic breath-

Brodie.1

of fifth and

tween scrotum and

ing ; respiration slow

sixth cervi-

thigh.

and irregular ; pulse

cal verte-

weak ; countenance

brae.

• livid ; death twenty-

four hours after acci-

dent.

M.,28.

Crush at level

35° (95° F.), rectal.

Paralysis extended to 1

Hutchinson.2

of fifth and

in. above nipple line ;

sixth cervi-
cal verte-

patient complained of
feeling cold.

bra?.

35° (95° F.), rectal

Death on fifth day ; no

and axillary just

injury to other parts

before death.

of body.

M.,53.

Crush at level

Below 35° (95°), 4

Complete paralysis of

» >

of fifth cer-

P.M., first day.

all limbs ; diaphrag-

vical verte-

matic breathing ; skin

bra.

cold and dry ; pulse

72.

Below 35° (95°), 6.30

Skin cold and clammy ;

P.M., first day.

patient complains of

feeling cold.

Below 35°(95°),11. 30

Pulse 50.

P.M., first day.

36°-8 (98°-2), morn-

Skin warm and dry ;

ing, second day.

pulse 64.

36° -9 (98° -4), even-

Skin hot and dry.

ing, second day.

38° '9 (102°), after-

Death.

noon, third day.

M., 36.

Crush at level

36°'9 (98°-4), sixth

Diaphragmatic breath-

j j

of seventh
cervical ver-

hour after acci-
dent.

ing ; imperfect paraly-
sis of arms ; patient

tebra.

felt very cold.

38°'6 (101° -5), third

Skin of natural warmth ;

day.

pulse 72.

38° -0(1 00° -4), fourth

day.

39°-0 (102°-2), fifth

Pulse 99.

day.

37°'45 (99°'4), sixth

Face mottled ; pulse 84 ;

day.

death.

M.

Crush at level
of fifth cer-

40°'0 (104°-0), first
day, axilla.

Slight power of moving
shoulders and upper

Churchill.3

vical verte-

arms ; skin flushed

bra.

and very hot.

400'3(1040>5), second

Pulse 96, regular, quiet.

day.

38° -9 (102° -0), third

day.

[Continued on next page.

1 Med. Chir. -Trans., London, 1837, p. 146.

2 Lancet, London, 1875, vol. i. pp. 713, 747.

3 Quoted from Hutchinson, loc. cit.

NERVOUS CONTROL OF TEMPERATURE.

861

Sex and

Age.

Seat of Injury.

Temperature.

Remarks.

Observer.

M.—

Crush at level

41° -1 (106°), fourth

40° '2 (104° -4) on foot;

Churchill.1

contd.

of fifth cer-
vical verte-

day.

patient died soon after
in a violent spasm, and

bra.

a quarter of an hour

after death, tempera-

ture in axilla = 43° '3

(110°).

M., 48.

Crush at level

33° -5 (92° -3), on ad-

Temperature, taken in

Wagstaffe.1

of sixth cer-

mission to hos-

both rectum and ax-

vical verte-

pital.

illa, fell steadily until

bra ; frac-

death.

ture of skull.

27°'6 (81°7), forty-

Death.

eight hours later.

M., 22.

Crush between
sixth and

33°-9 (93°-0), on ad-
mission.

Patient drowsy and pro-
strate.

LeGros Clarke.1

seventh cer-
vical verte-

27°'8 (82°-0), a few
hours before death.

Death about forty-eight
hours after accident.

brae.

M., 39.

Crush at level

34°'5 (94°'l), four

Billroth.2

of fourth

hours after the

and fifth

accident.

cervical ver-

36° -5 (97° 7), eighth

tebra.

hour.

41°'6 (106°-9), 7

A.M., second day.

42°-4(108°-3),lp.M.,

Death at 2. 5 p. M. on sec-

second day.

ond day ; post-mortem

rise to 42° "9 (109° '2)

in ten minutes.

M., 34.

Crush at level
of fifth and

37°'6 (99°7), five
hours after acci-

Complete paralysis of
trunk and limbs ; dia-

Frerichs.8

sixth cervi-
cal verte-

dent.
40° '9 (105° -6), twelfth

phragmatic breathing.

br;e.

hour.

42° -1 (107° -8), fifth-

teenth hour.

43° -6 (110° -5), nine-

teenth hour,

eleventh minute.

43°'2 (109°-7), nine-

Death.

teenth hour,

thirty-fifth min-

ute.

These discordant results have to be explained. It is worse than useless to
say that the effects are due to the removal of the regulating influence of
" heat centres " in the brain, centres whose very existence is problematical.
Observations upon the deep and surface temperature, and upon the amount
of moisture given off by the skin, are needed to show whether the changes in
temperature are due to disturbance in the production or in the loss of heat,
or more probably in both, The data upon these points are insufficient, but,
recently, such observations have been made by Pembrey,4 in the case of two

1 Quoted from Hutchinson, loc. cit.

-Arch.f. Jclin. Chir., Berlin, 1868, Bd. ix. S. 161.

3 Recorded by Lorain, " De la temperature du corps humain," tome i. p. 500.
4"Proc. Physiol. Soc.," Journ. PhysioL. Cambridge and London, 1897, vol. xxi. ;
Brit. Med. Journ., London, 1897, vol. ii. p. 883.

862 ANIMAL HE A T.

patients suffering from traumatic section of the spinal cord. The general result
is a subnormal temperature so long as the patient's condition is not complicated
by other internal or external disturbance. The subnormal temperatures are
due to excessive loss and diminished production of heat, owing to the
vasomotor and motor paralysis. The section of the spinal cord high up in the
cervical region abolishes the power of regulating temperature. When the
patient is exposed even to moderate cold, his temperature falls owing to the
increased loss of heat and to the diminished production of heat. On the
other hand, if the weather be hot and the patient be too well covered with
bedclothes, his temperature rises, and may reach a dangerous height, owing to
the diminished loss and the increased production of heat in the body. In the
paralysed man the production of heat rises and falls with the external tempera-
ture. In the case of the high temperatures there are several factors which
may play an important part ; the paralysed parts soon cease to sweat ; in fact,
Horsley has shown that, by the use of pilocarpine, it is possible to localise
the level of the injury to the cord. The respiration is hampered, it is only
diaphragmatic ; the ventilation of the lungs is therefore imperfect, and less
heat is lost by the cooling of the inspired air, and by the evaporation of
water from the respiratory tract to saturate the expired air with moisture.
Further, the warmer the paralysed tissues the greater is their metabolism and
production of heat.

It naturally follows that, in cases of section of the spinal cord in the
dorsal or lumbar regions, the regulation of temperature is less disturbed.

The influence of the brain upon the regulation of temperature.
— It is impossible to state concisely and dogmatically the influence of
the brain upon the temperature of the body. With our present know-
ledge it is only permissible to review the chief results obtained by
various observers, and to draw some provisional conclusions.

In 1866, Tscheschichin 1 published the results of experiments, which
showed that a section between the medulla oblongata and the pons
Varolii caused a rise in the temperature of rabbits. In one case the
rectal temperature rose in two hours from 39°'4 to 42°'6, and at the
same time there was a corresponding increase in the rate of the pulse
and respiration. On the other hand, section of the spinal cord between
the third and fourth cervical vertebrae caused, in another rabbit, a fall
in temperature from 38°'9 to 32°'l. From these experiments Tsches-
chichin concluded that a moderator centre exists in the brain, and pre-
vents the excessive activity of an augmentor heat centre in the medulla
oblongata. Lewizky2 repeated but could not confirm these experi-
ments ; he observed a steady fall in temperature after the operation.
The subject was then taken up, under the guidance of Heidenhain, by
Bruck and Giinther,8 who, working upon rabbits, obtained positive
results in eleven, negative in twelve cases. They found in one case a
rise from 390-31 to 42°'5 in the rectal temperature, two or three hours
after the operation. These observers further found that simple puncture
with a probe between the pons and medulla was more effectual than
section, and they noticed that the rise in temperature occurred not only
in the interior, but also in the peripheral parts of the body, a fact which
indicates that the rise is due to increased production of heat. Bruck
and Giinther do not agree with Tscheschichin's view of a moderator
centre, for they point out that the results can be produced by electrical

1 Arch.f. Anat., Physiol. u. ivissensch. Med., 1866, S. 151.
• 2 Virchow's Archiv, 1869, Bd. xlvii. S. 357.
3 Arch,f, d. yes, Physiol., Bonn, 1870, Bd. iii. S. 578.

INFL UENCE OF BRAIN ON HE A T REGULA TION 863

stimulation as well as by puncture of that portion of the nervous
system, and are probably due to traumatic stimulation. It is to be
noted that irregular muscular movements were observed in many of the
cases.

Schreiber,1 from the results of experiments performed upon rabbits,
came to the conclusion that a rise of temperature followed injury
to all parts of the pons, to the peclunculi cerebri, cerebellum, and
cerebrum, when the animal was protected by a covering of wool or
flannel against excessive loss of heat; injury between the medulla
oblongata and the pons always caused a rise in temperature. In most
cases, however, the rise in temperature was very small, and the experi-
ments were often complicated by spasms of the muscles.

Observations upon the production of heat, as determined by a
calorimeter, and also upon the animal's temperature after lesions of
various parts of the central nervous system, were made by Wood.2
Section of the spinal cord above the origin of the splanchnic nerves
produced an increase in the loss but a decrease in the production of
heat ; on the other hand, section between the medulla oblongata and the
pons caused an increase in both the production and loss of heat, and for
this reason Wood supported the view of Tscheschichin, that a moderator
centre exists in or above the pons.

Eulenberg and Landois 3 found that in dogs destruction of a portion
of the cortex of the brain in the neighbourhood of the sulcus cruciatus
caused a rise of temperature, which was most marked on the side of
the body opposite to the lesion ; they looked upon this effect as due to
vasomotor disturbance. These results were confirmed by Hitzig 4 and
Wood, but on rabbits Klissner 5 and H. Eosenthal 6 obtained negative
results.

Injury to the front of the brain was found by Eichet 7 to produce a
rise of temperature, and Ott 8 obtained a similar result by injury to the
corpus striatum ; this observation was confirmed by Girard,9 Baginsky
and Lehmann.10 In 1885, Aronsohn and Sachs11 published the results
of an important series of experiments upon rabbits ; they found that
puncture with a probe, the greatest thickness of which was 3 mm.,
had no effect upon the temperature of the body when the operation was
performed upon the front part of the cerebral hemispheres, but a
puncture passing through the median side of the corpus striatum near
the nodus cursorius of Nothnagel caused, within a few hours, a rise of
temperature which persisted for two or three days. The rise varied
from lc<7 to 2° *4, and could also be produced by electrical stimulation of
the corpus striatum. Control experiments showed that the injury to

1 Arch.f. d. ges. Physiol., Eoim, 1874, Bd. viii. S. 576.

2 "Fever, a Study in Morbid and Normal Physiology," Smithson. Contrib. KnowL,
Washington, 1880.

3 CentralbL f. d. mecl. Wissensch., Berlin, 1876, No. 15; Virchow's Archiv, 1876,
Bd. Ixviii. S. 245.

4 CentralbL f. d. med. Wissensch., Berlin, 1876, No. 18.

5 Ibid., 1877, No. 45.

6 " Einfluss des Grosshirns auf des Korperwarme, " Diss., Berlin, 1877.

7 Compt. rend. Soc. de biol., Paris, 29th March 1884, p. 189 ; Compt. rend. Acad. d. sc.,
Paris, 31st March 1884 ; Arch, de physiol. norm, etpath., Paris, tome vi.

8 Journ. Nerv. and Ment. Dis., N.Y., 1884, Nos. 7 and 8 ; 1887, p. 152 ; 1888, p. 551 ;
Therap. Gaz., Detroit, 1887 ; Brain, London, 1889.

9 Arch, de physiol. norm, et path., Paris, 1886, tome viii.

10 Vircliows Archiv, 1886, Bd. cvi. S. 258.

11 Arch, f, d. ges. Physiol, Bonn, 1885, Bd. xxxvii. S. 232.

864

ANIMAL HEAT.

the cortex during the performance of the puncture did not cause any
rise of temperature. The high internal temperature after puncture of
the corpus striatum was accompanied by an increase in the temperature
of the skin, and by an increase in the respiratory exchange, and in the
discharge of nitrogen in the urine. The mean result of the determina-
tions of the respiratory exchange was as follows : —

RECTAL TEMPERATURE.

OXYGEN.

CARBON DIOXIDE.

inc.c. atO'C., 760m.

tn. per Kilo, and Hour.

Before puncture
After puncture

38° '5

39°'8

664°'0

749°7

626°7

715°-8

Aronsohn and Sachs conclude that the rise in temperature after the
puncture is due to increased production of heat, and increased metabolism,
arising from the stimulation of the corpus striatum.

These experiments have been repeated and extended by Hale White,1
who found no rise in the temperature of rabbits after lesions of the
white matter of the cerebrum, but an almost constant effect after injury
of the corpus striatum and optic thalamus. In the case of lesions of
the corpus striatum, the rectal temperature rose to 41° -6 in two cases,
to 41°'l in eleven cases, and to 40° in eighteen ; while in three cases
there was a slight rise, and in two a fall in temperature. The average
rise was 10<7, and was attained within four to sixteen and a half hours
after the operations, and persisted for about sixty-two hours. After
lesions of the optic thalamus, the average rise of temperature was 1°'4.
Hale White concludes that the corpus striatum and the optic thalamus
can modify the temperature of the body, and that they do not work
directly through the vasomotor system. No increase in the discharge of
carbon dioxide was observed in rabbits after damage to the corpus
striatum.2

Several cases of a rise in temperature in man after a haemorrhage
into the corpus striatum have been recorded.3

Eecently Tangl 4 has observed the effect of puncture through the
anterior part of the optic thalamus in horses. In one case the tempera-
ture rose to 40° -8 within twenty-four hours, in another to 40° '4 within
sixteen hours of the operation, and in two other cases there was no
effect. The temperature remained only for a short time at the above
height, and then fell.

Fredericq5 found that removal of the cerebral hemispheres in pigeons
caused practically no difference in the daily curve of their rectal
temperature. This observation has been confirmed by Corin and Van
Beneden,6 who have, in addition, shown that the pigeons without their
cerebral hemispheres produce the same amount of carbon dioxide and heat

1 Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 1.

2 Hale White, Croonian Lectures, Lancet, London, 1894, July 10, axidJSrit. Med. Journ.,
London, 1897, vol. ii. p. 71.

3 Bourneville, Ferrier, J. H. Bryant, Hale White ; references given by Hale White, Brit.
Med. Journ., London, 1894, 17th Nov.

4 Arch. f. d. ges. PhysioL, Bonn, 1895, Bd. Ixi. S. 559.
6 Arch, de Mot., Gand, 1882, tome iii. p. 747.

6 Ibid., 1889, tome vii. p. 265.

DEVELOPMENT OF HEAT REGULATION. 865

as do normal pigeons. The rapid rise in temperature which occurs
when a hibernating marmot awakes, is not prevented by removal of the
cerebral hemispheres.

An impartial examination of the above evidence leads to the verdict
that the existence of the so-called " heat centres " in the brain has not
been proved. In the first place, the results, even in the hands of the
same experimenter, are inconsistent ; some observers obtain exactly
opposite effects from apparently similar lesions. Further, in many
cases rabbits have been used for these experiments, and it is notorious
that their temperature is liable to considerable variations during
operative procedures. Even if the existence of these centres be
granted, even if it be allowed that after puncture there is an increase in
metabolism and in the production of heat, it by no means follows that
the centres are special centres for the regulation of temperature, and
give off " thermic nerves."

It seems more probable that the mechanism of heat regulation
has the same cerebral representation as the voluntary muscles. In
the lower warm-blooded animals the representation of these in the
cerebral cortex is not well developed, and it has likewise been shown
that the removal of the cortex in them has little or no effect upon
the regulation of temperature.

THE DEVELOPMENT OF THE POWER OF MAINTAINING A CONSTANT

TEMPERATURE.

In the cold-blooded animals there are traces of the power of maintaining
a constant temperature, as shown by the high temperature which a female
python is able to maintain for many weeks when she is incubating her eggs.
This instance is the more remarkable because during that time the python
takes no food or exercise. Further instances have already been mentioned in
the case of bees, and some species of fish.

It is possible to trace in the warm-blooded animals the gradual develop-
ment of this power of regulation. Thus, during the development of a chick
there is first a stage in which the embryo responds to changes of temperature
in a similar manner to that of a cold-blooded animal ; then a stage of transition
in which there is a regulation for moderate changes of temperature ; and
finally, when a chick is hatched, the power of regulation resembles that of
a warm-blooded animal.1 In 1824, Edwards2 pointed out that young
mammals and birds may be divided into two classes, the warm-blooded
and the cold-blooded, according as they are, or are not, able to maintain their
temperature when removed from the warmth of the parents. The difference
lies in the relative development of the two classes — active young animals
covered with fur or feathers, as in the case of the guinea-pig and chick, belong
to the former class ; while young animals born naked, blind, and helpless,
belong to the cold-blooded group. The inability to maintain a constant
temperature is due to diminished production of heat on exposure, and only
secondarily to excessive loss of heat. It has recently been shown that the
chick and guinea-pig can at birth regulate their production of heat, that young
cold-blooded mammals and birds are able to regulate only for moderate changes
of external temperature ; for, when exposed to cold, their temperature and

1 Pembrey, Gordon, and Warren, Journ. PhysioL, Cambridge and London, 1894-95,
vol. xvii. p. 331.

2 " De I'influence des agens physiques sur la vie," 1824.

VOL. I. — 55

866 ANIMAL HEAT.

production of carbon dioxide fall, and they resemble cold-blooded animals.
About the fifteenth day after birth, they respond to a fall in the temperature
of their surroundings with increased muscular activity and output of carbon
dioxide, and thus maintain their temperature (Pembrey 1).

In the lowest mammals the temperature is much lower than in the higher
members of the group. Thus the temperature of the Echidna Jiystrix is 27° '5,
and that of the Ornithorhynchus, 24° '8.'2

Further, a hibernating mammal is an instance of an animal at one time warm-
blooded and at another time cold-blooded, and its power of regulation is in
many respects similar to that of an immature mammal.3 Additional proofs
of the gradual development of the power of maintaining a constant tempera-
ture are found in the unstable temperature of infants and animals. In
premature and weak infants the power i* imperfect, and the temperature is
below the normal.4 It is in man that the perfection of this power is reached ;
he of all animals has the most constant temperature under extreme differences
of external heat and cold.

It is impossible with our present knowledge to state what are the
structural differences which accompany the development of the power of
regulation. This much we may say : the power appears to be associated
chiefly with the control of the nervous system over the skeletal muscles and
those of the blood vessels. An anaesthetic, or curari, or section of the spinal
cord reduces a warm-blooded animal to a cold-blooded condition ; its tempera-
ture and production of carbon dioxide vary with, and in the same direction as,
the temperature of its surroundings. In a hibernating animal the fall of
temperature is accompanied by greatly diminished activity of the muscular
and nervous systems ; and the sudden rise in temperature, when the animal
awakes from its torpidity, is marked by a sudden increase in the discharge
of carbon dioxide and in muscular activity. Those young mammals and birds
which are born with well-developed control over their muscular system, are
able to regulate their temperature even at birth, whereas those born in a
helpless condition do not attain this power until a week or two after birth,
at a time when their power of co-ordination is much increased.

THE TEMPERATURE OF THE BODY AFTER DEATH.

After death the temperature of the body generally falls, the loss of heat
varying according to the difference between the temperature of the corpse
and that of its surroundings ; another important factor is the surface of the
body in relation to its mass, for the corpse of an infant or of a wasted
subject cools more rapidly than that of a well-developed adult.5 In some
cases, however, a rise of temperature is observed in the corpse, especially
when death has resulted from tetanus, acute rheumatism, typhoid fever, small-
pox, cholera, or injuries to the brain and spinal cord. A few of the cases
recorded are given in the following table : —

1 Journ. PhysloL, Cambridge and London, 1895, vol. xviii. p. 363.

2 Mikloucho Maclay, Proc. Linn. Soc. New South Wales, 1883, vol. viii. p. 425 ; vol. ix.
p. 1205 ; Semon, Arch. f. d. ges. Physiol., Bonn, 1894, Bd. Iviii. S. 229.

3 Pembrey and Hale White, Journ. Physiol., Cambridge and London, 1896, vol. xix.
p. 477.

4 Crombie, Indian Ann. Med. ,S'c., Calcutta, 1873, vol. xvi. p. 597; Raudnitz, Ztschr.
f. JBiol., Munchen. 1888, Bd. xxiv. S. 423.

5 Taylor and Wilks, Guy's Hosp. Rep., London, 1863, p. 184 ; observations on one
hundred cases ; Sutton, Brit. Med. Journ., London, 1874, vol. i. p. 153 ; Bidder and
Schmidt, " Die Verdauungssafte und der Stoffwechsel, " S. 323 ; Womack, St. Earth. Hosp.
Rep., London, 1887, vol. xxii. p. 193; Niderkorn, " De la rigidite cadaverique chez
1'homme," Paris, 1872.

TEMPERATURE OF THE BOD Y AFTER DEATH. 867

Temperature
before Death.

Temperature after
Death.

Disease.

Place of
Observation.

Observer.

45°

Pyaemia

Left ventricle.

Davy.1

(3^ lirs. post-mortem)

42°-2

Sudden death, cause

> j

(5| lirs. post-mortem)

undetermined.

43° 75

Small-pox.

Axilla.

Simon.2

(1 hour post-mortem)

44°'5

>

>»

41V'l

44°'5

Sunstroke.

i j

Levick.3

44°'75

45°'4

Tetanus.

Wunderlich.4

(57 min. post-mortem)

»

41°'2

Cholera.

Rectum.

Mackenzie.5

42°'-3

43° '2

Erysipelas.

Axilla.

Eulenburg.6

(15 min. post-mortem)

40°'4

42° -3

f.f

? ?

}j

(20 min. post-mortem)

41°-8

Sunstroke.

Thompson.7

36V'l

38° '3

Apoplexy.

, ,

De Haen.8

(7^ miii. post-mortem)

41°-6

43°

Tetanus.

»

Lehmann.9

(30 min. post-mortem)

43° -01

44°-03

Pyaemia.

Rectum.

Quincke and

(1 hour post-mortem)

Brieger.10

42° -1

43°'4

Pneumonia

j 5

j j

(1 hour post-mortem)

delirium tremens.

41°'l

43° '3

Crush of

Axilla.

Churchill.1

(15 min. post-mortem)

spinal cord.

The causes of this post-mortem rise in temperature have been investigated
by various observers.12 The most important factors are these. When the
circulation and respiration cease at death, the normal loss of heat from these
causes and from sweating also comes to an end, but the tissues live for a short
time and produce heat even after the death of the organism as a whole. If
this production of heat is greater than the loss of heat from the corpse, the
temperature rises ; if, on the other hand, it is less, then, the effect is only to
delay the fall of temperature. The next source of heat is in the muscles on
the onset of rigidity ; and, finally, when decomposition sets in, and this may
after some diseases occur exceedingly rapidly, there is a further production of
heat due to putrefaction. In some cases the temperature of a corpse does not
fall to that of the atmosphere even in four or five days.13

1 "Researches," London, 1839, vol. i. p. 228.

-Ann. d. Char.-KranTcenJi. . . . zu Berlin, 1865, Bd. xiii. Heft 2, S. 1.
a Penn. Hasp. Rep., Philadelphia, 1868, vol. i. p. 369.
, 4 Arch. d. Heilk., Leipzig, 1861, Bd. ii. S. 547.
'° London Hosp. Rep., vol. iii. p. 454.

6 CentralM.f. d. med. Wissensch., Berlin, 1866, No. 5.

7 Brit. Med. Journ., London, 9th July 1870.

8 Quoted from Valentin, Deutsches Arch. f. klin. Med., Leipzig, 1869, S. 201.

9 Schmidt's Jahrb., Leipzig, 1868, Bd. cxxxix. S. 241.

10 Deutsches Arch. f. klin. Med., Leipzig, 1879, Bd. xxiv. S. 284.

11 Churchill, quoted from Hutchinson, Lancet, London, 1875, vol. i. p. 713.

12 Besides those above enumerated, the following may be mentioned : — Seume, Thesis,
Leipzig, 1856 ; Erb, Deutsches Arch. f. klin. Med., Leipzig, 1865 ; Thomas, Arch. d. Heiik.,
Leipzig, 1868, Bd. ix. S. 17, 31 ; Goodhart, Brit. Med. Journ., London, 1874, vol. i.
p. 303 ; Huppert, Arch. d. Heilk., Leipzig, 1867. Bd. viii. S. 321 ; Fick and Dybkowsky
Vrtljschr. d. naturf. GeseUsch. in Zurich, 1867 ; Schiffer, CentralU.f. d. med. Wissensch.
Berlin, 1867. S. 849 ; Arch. f. Anat., Physiol. u. wissensch. Med., 1868, S. 442.

13 The author is indebted to Drs. Haldane, Hale, White, and Waller for valuable
suggestions on various points, dealt with both in this and in the preceding article.

METABOLISM.

By E. A. SCHAFER.

•

CONTENTS : — Introductory, p. 868 — Balance of Nutrition, p. 871 — Composition of
Foodstuffs, p. 872 — Heat Value of Foodstuffs, p. 874 — Necessary Amount of
Proteid, p. 875 — Special Constituents of Diet, and their Effect on Metabolism,
p. 878— Gelatin, p. 878— Carbohydrates, p. 880— Fats, p. 881— Inorganic Sub-
stances, p. 882 — Metabolism in Inanition, p. 887 — With purely Proteid Diet,
p. 891 — Relative Metabolic Activity of Tissues, p. 895— Nitrogenous Meta-
bolism, p. 896 — Influence of the Liver on Proteid Metabolism, p. 900 — Influence
of Muscular Activity on Proteid Metabolism, p. 911 — Metabolism of Carbo-
hydrates, p. 916 — Glycogen formation, p. 919 — Phloridzin Diabetes, p. 920 —
Glycogenesis, p. 922 — Puncture Diabetes, p. 926 — Action of Pancreas on
Carbohydrate Metabolism, p. 927 — Metabolism of Fat, p. 930 — Source and
Formation of Fat, p. 931 — Action of Liver on Metabolism of Fat, p. 935.

Introductory. — The word " metabolism " has come into use in this
country as the equivalent of the German word StoffwecJisel, which
strictly means " exchange of material." The subject which it denotes
embraces all that is known or conjectured regarding the changes which
occur within the body in the materials of the food, or foodstuff's, and
in the materials which compose the tissues and organs of the body
itself, or bodystuffs. Generally, however, the digestive changes in the
food are excluded from the scope of the expression. There is 110 special
reason, other than that of convenience of description, why this should be
the case, for the digestive changes in the food must, like all other
chemical changes occurring within the body, influence the general con-
ditions of the economy. The usual course will, however, be followed
in this article, and I shall confine what I have to say to the changes that
occur after the food is absorbed, in so far as they have not been already
treated of in the articles in this work dealing with the chemistry of the
urine and with the chemical processes of respiration and heat production,
both of which .subjects constitute essential parts of the whole subject
of metabolism.

The metabolic changes which are undergone by the tissues must bo
of two kinds, which are opposite in nature.1 For, on the one hand, the
complex molecules which constitute living tissue or bioplasm,2 are built

1 Hering, " Vorgiinge der lebenden Materie," Prag, 1888. A translation, by Miss F. A.
Welbv, of this extremely important and interesting article will be found in Brain, London,
1807, vol. xx. p. 232.

2 I use the word bioplasm as a synonym for living substance, rather than protoplasm,
because the latter word has come to have a definite histological rather than a physiological
signification ; and, on the one hand, is used to include portions of cell substance which, for
aught we know, may not be actually living matter, whilst, on the other hand, it does not
include the living substance of the cell nucleus, which would be included in the expression
"bioplasm."

INTRODUCTORY. 869

up from non-living materials, furnished by the food ; and, on the other
hand, they are broken down into simpler substances, which pass
away from the tissue into the blood, and ultimately from the body
with the excreta, or, as in the case of secretory glands, directly into
secretions. The building-up process, whereby fresh molecules of bioplasm
are formed, has come to be spoken of as an anabolic change (anabolism,
assimilation), and the breaking - down process as a katabolic change
(katabolism, dissimilation). It is clear that these two processes will
produce opposite effects upon the bioplasm, the one increasing and the
other diminishing its bulk. But, on the other hand, it is conceivable
that even within the same cell there may be, at the same time, both a
building up or anabolic change proceeding, so that fresh molecules of
bioplasm are being formed, and also a breaking-down or katabolic change,
affecting molecules which have been formed previously, and the net
result to the bulk of the tissue may be nil, provided that these two
processes balance one another ; that is to say, the bioplasm, although
undergoing active metabolic changes, and furnishing products of its
metabolism to the secretions or to the blood, is not altered in amount
(autonomous equilibrium). But although both processes are occurring
simultaneously, they nevertheless do not exactly balance one another,
there will be as the net result either a gain or loss of bioplasm, i.e. the
bioplasm of the cell will increase or diminish in amount. If every cell
were entirely composed of bioplasm, this would evidently involve an
increase or diminution in the bulk of the cell itself. But besides the
actual bioplasm, all cells contain in a variable proportion products of
the activity of their bioplasm ; " formed material," in the sense of
Lionel Beale, as distinguished from " formative matter." If these
products remain within the cell, it may, in spite of the fact that kata-
bolic processes are proceeding • within it more actively than anabolic
processes, still increase in bulk, even to a very large extent, but without
any corresponding increase, indeed even with an actual diminution, of
its bioplasm.

Various circumstances may determine the general direction of the
metabolism of a cell, whether upward in the direction of increased
anabolism with increase of bioplasm, or downward in the direction of
increased katabolisni with decrease of bioplasm. One such circumstance
is undoubtedly the amount and nature of the pabulum supplied to the
cell. Another is to be found in the general physical conditions of the
environment, such as variations of temperature, supply of water and of
oxygen, and the like. And in the case of many animal cells we may
well suppose (and indeed the point may be said to have been determined
for specific instances) that impulses derived from the nervous system
may set up respectively, according to their nature, or the nervous channel
along which they are conveyed, metabolic changes in either an anabolic
or a katabolic direction. Thus it has been suggested by Gaskell that the
heart nerves act upon its muscular substance, so as to produce respect-
ively anabolic changes (vagus fibres, inhibitory impulses) and katabolic
changes (sympathetic fibres, augmentor and accelerator impulses), accom-
panied by diminished activity in the one case, by increased activity in
the other. The possibility must, however, be also borne in mind that the
same nerve fibres may set up both anabolic and katabolic changes, as
when a secretory nerve is stimulated, provoking it may be for hours a
discharge of products of katabolisni from secretory cells ; for it is in

870 METABOLISM.

such cases necessary to assume a continuous process of anabolism going
on at the same time within the same cells.

Upon evidence founded mainly, but not exclusively, upon the investigation
of certain electrical and visual phenomena, Hering has concluded that in all
cases where either katabolic or anabolic changes are proceeding in any portions
of bioplasm, they tend to render the bioplasm more and more resistant to the
effects of the excitation which is producing the change (reaction) ; that in any
given cell the longer or more strongly metabolic changes of the one character
have been proceeding, the greater will be the tendency towards metabolic changes
of the opposite character, so that even if, as may happen, in consequence of the
action of an external stimulus (A), anabolic changes are proceeding at first more
rapidly than katabolic, so that the balance is in favour of the building up
or assimilation processes, the reaction which is thereby provoked will, after a
time, by increasing the katabolism of the cell, tend again to produce a condition
of balance. Only in this case the balance will be struck with the general
bioplasm of the cell in a condition above par, as compared with that from which
it was assumed to start (A — allonomous equilibrium). And, mutatis mutandis^
increased katabolic processes due to external stimuli are (D) assumed to produce
by reaction an increase of anabolism in adjacent portions of bioplasm, which
increase becomes eventually sufficient to balance the increased katabolism
induced by the stimulus, so that again the metabolism of the whole cell strikes
a balance as it were, but now in a condition below par, as compared with the
normal (D — allonomous equilibrium). Upon the cessation of the stimulus in
either case, the tendency, say, to increased anabolism being removed with the
stimulus, the opposite condition of increased katabolism, which was provoked
by the increased anabolism, will for a time prevail, and there will be a falling
off of the general assimilation of the cell, until what may be considered the
normal condition is again established, the two processes again exactly balancing
one another. And the same, mutatis mutandis, for the removal of a stimulus
which was producing a condition of increased anabolism. There is thus
assumed to be a sort of internal self -adjustment of metabolism in bioplasm.

It is a part of the theory of Hering that the anabolic and katabolic changes
in the bioplasm are the direct or indirect cause of many, if not of all,
physiological phenomena exhibited by living tissue, and that the prevalence
of one kind of change in any portion of bioplasm will tend to start a
change of the opposite kind in adjacent portions. But this is a subject
which we need not here specially concern ourselves with, since the most
important application of it to the explanation of physiological phenomena
concerns the effects produced by the stimulation of the retina by light, and
will be discussed in the article dealing with this question.

In connection with this subject, one other point must be borne in mind,
namely, the possibility, indeed probability, that many metabolic changes in the
body are not necessarily associated with the building up or breaking down of
bioplasm, but are effected outside the actual molecules of which the bioplasm
is composed, although under the influence of the activity of the bioplasm.
Such changes as these may be distinguished from the metabolic changes of the
bioplasm itself by the name of " contact changes," and they also involve both
the building up of complex materials and the subsequent breaking down of
such materials into simpler products associated frequently with oxidation.
Such contact changes are analogous to those which are produced by organised
ferments, such as yeast, outside the actual organism, although directly by its
activity, and they must be sharply differentiated from the changes which the
bioplasm itself is at the same time undergoing. This distinction will be
referred to again in a subsequent section.

The understanding of the metabolic processes presupposes an acquaintance
with the composition of the foodstuffs and of the bodystuffs, both of which

BALANCE OF NUTRITION.

871

have been dealt with in previous articles. So far as the bodystuffs are con-
cerned (and to a somewhat less extent with regard to the foodstuffs), it cannot
be said that we possess an acquaintance so intimate as to enable us fully to
understand the changes which they undergo ; and as a consequence it will be
found that our knowledge of metabolism, in spite of the enormous amount of
work that has been done to elucidate it within the last five and twenty years,
is still in an unsatisfactory condition.

Balance of nutrition.— The first determinations that require to be
made in any inquiry into the metabolism of the body are those of its
incomings and outgoings.1 The incomings of the body consist of food
and oxygen ; the outgoings, of the various excreta, and of the carbon
dioxide and water lost by the lungs and skin. If the incomings of the
body exactly balance the outgoings, so that the animal neither gains nor
loses weight, the body is said to be in complete nutritive equilibrium.

Sufficient information can be usually obtained regarding the balance
of metabolism of the body, if the nitrogen and carbon only are determined
in the ingesta and egesta.

As an instance of complete equilibrium in a man weighing 70 kilos.,
embracing both the nitrogen and carbon of the ingesta and egesta, the
following balance table may be given (Burdon Sanderson 2) : —

INCOMINGS.

OUTGOINGS.

Food.

N.

C.

Excreta.

N.

C.

Proteids . lOOgrms.
Fat . . 100 ,,
Carbohydrates 250 ,,

15-5

53
79
93

Urine
Faeces
Respiration

14-4
1-1

6-16

10-84
208-00

15-5

225

15'5

225

We may also have a condition in which the body either gains or
loses weight, and in which consequently the incomings and outgoings do
not exactly balance one another, but during which, nevertheless, the
nitrogen which is taken into the body, and that which leaves the body,
may strike an exact balance, while the other elements which compose
the food and excreta, and especially the carbon, hydrogen, and oxygen,
may not be similarly balanced. When the nitrogen of the food exactly
balances the nitrogen excreted, the body is said to be in nitrogenous
equilibrium. Under these circumstances we may assume that the living
material of the tissues (which is essentially composed of nitrogenous
substance) is neither diminished nor increased in amount ; whereas, if
at the same time the other constant elements of the food — the carbon,
hydrogen, and oxygen — are met with in diminished or increased quantity
in the excreta, we may assume that substances in the body other than
the living tissues are either becoming laid on, or becoming diminished

1 For the methods of determining these may be consulted, C. Voitin Hermann's "Hand-
buch," 1881, Bd. vi. S. 6 et seq., and numerous papers which have appeared since then
chiefly in the Arch. f. d. ges. PhysioL, Bonn (by Pfluger, Zuntz, and their pupils), and in
the Ztschr. f. Biol., Munchen (by Voit and his pupils). See also v. Noorden, "Grundriss
einer Methodik der Stoffwechsel-Untersuchungen," Berlin, 1892. For the methods of deter-
mining the respiratory products, see article "Chemistry of Respiration").

2 " Syllabus of Lectures on Physiology," 1879.

872

METABOLISM,

in amount. These substances are mainly the fats, to a much less
extent the carbohydrates, whereas the substances which form the
actual tissues are composed of proteids and nucleo-proteids.

The following is an instance of a balance table : of a man weighing 70
kilos., showing nitrogenous equilibrium only, some of the carbon of the ingesta
(mostly representing stored fat) not reappearing in the excreta : —

INCOMINGS.

OUTGOINGS.

Foodstuffs.

N.

C.

Excreta.

•

N.

C.

Proteids . 137grms.
Fat . . 117 „
Carbo-hydrates 352 ,,

19-5

j- 315-5

Urine
Faeces
Respiration

17-4
2-1

12-6
14'5
248-6

19-5

315-5

19-5

275-7

Whether the material which forms the bioplasm of the tissues has an
essentially different molecular constitution during life from that which is met
with in it after death, is not certainly known, but is extremely probable. This
is obviously a point which is difficult of determination, because we cannot
investigate the material composing bioplasm without previously killing it.
All we are able to do is to determine, as far as possible, the changes which the
tissues undergo, by investigating the products which they give off during life.
Our knowledge of these products has led some physiologists to the conclusion
that the substance of living material is composed of unstable cyanogen or
aldehyde compounds, whereas it is well known that dead proteid yields bodies
of an amide nature.2

Composition of foodstuffs. — The most important general fact that
we need concern ourselves with in this place regarding the composition
of foodstuffs is that, with ordinary mixed diet, they are composed in
certain not very definite proportions of three chief kinds of organic
material, namely, proteids, carbohydrates, and fats ; in addition to
which, water and salts are a necessary part of the food. The most
general proportion of these three primary varieties of foodstuffs
to one another in ordinary diet is found to be about one part of
proteid material to from four to six parts of non-proteid, while the non-
proteid constituents stand to one another in about the proportion of one
part of fat to from five to ten parts of carbohydrate, this ratio having
been arrived at by investigating the composition of freely chosen diets
of persons in various occupations and stations of life. At the same time,
it must be pointed out that departures from these proportions are by no
means unfrequently met with, and especially is this the case with
certain races of mankind, e.g. some of the Asiatic races, where a very
much larger proportion of non-proteid material is ordinarily taken with
the diet than is the case with Europeans ; whereas, on the contrary, in
parts of South America and Australia, where meat is plentiful, the pro-
portion of proteid to non-proteid may be far larger than that above given.

1 C. Voit, Hermann's "Handbuch," Bd. vi. S. 513. The table in the simplified form
here given is from Neumeister, "Lehrbuch," Jena, 1897, Aufl. 2, S. 344.

2 Cf. Halliburton, this Text-book, vol. i. p. 38.

COMPOSITION OF FOODSTUFFS. 873

On the whole, however, the above proportions are found to be fairly well
maintained, the ratio of carbohydrates to fats in the diet varying more
than the proportion of proteid to non-proteid material. As a general
rule, it will be found that with the more wealthy classes there is a
relatively greater amount of proteid and fat as compared with carbo-
hydrates ; whereas with the poorer classes the carbohydrates increase in
proportion, and the proteids and fats diminish. With a diet composed
of vegetable matter alone, the proportions are liable to be considerably
modified, since, in order to obtain a sufficient amount of proteid from
most vegetables, a much larger proportionate amount of carbohydrate
food is inevitably consumed. On the other hand, since with flesh food
the amount of proteid necessary for carrying on the metabolic processes
of the body is much more easily obtained than from vegetable food,
and since flesh food invariably contains a considerable amount of fat,
the proportion of proteid and fat to carbohydrate is apt to be much
greater than the normal when the diet is mainly composed of animal
matter.

For the determination of the value of the chief organic materials of the
foodstuffs in nutrition, the most important point to be ascertained regarding
their composition is the amount of nitrogen and carbon in each. In round
numbers, this may be stated as follows : — Proteids contain 15 to 17 per cent.
N, and 50 to 55 per cent. C l ; animal fats, on an average, 76 '5 per cent. C ; and
carbohydrates, such as starch and sugar, 40 to 45 per cent. C. Since the amounts
of proteid fat, and carbohydrates in all the ordinary foodstuffs has been accur-
ately determined,2 and is given in the form of tables, it is not difficult, if the
amounts of each which are ingested are carefully weighed, to determine by
calculation the total K" and C of the ingesta. For very accurate work,
however, it is necessary to make direct determinations of the N and C in
the food taken; this is effected by ordinary chemical methods (that of the
nitrogen usually by Kjeldahl's method).

The amount of flesh or fat which is at any time becoming lost or laid on
can be easily approximately determined by an examination of a balance table,
for the nitrogen in the urine represents metabolised proteid, the amount
of which is arrived at by multiplying the numbers of grms. of nitrogen found
by 6'25 (since proteids contain 16 per cent. N). Since any excess or deficit
of proteids represents flesh lost or laid on, the amount of such loss or addition
can be directly obtained by taking each gramme N in excess or deficit to
represent 30 grms. flesh (since flesh contains about 3 '4 per cent. H") (Voit).
And, after reckoning off the carbon which the proteid metabolised would contain
(53 per cent.), any further excess or deficit of carbon in the ingesta would
represent the carbon of fat lost or laid on, and the amount of this may be
approximately obtained by multiplying the number of grms. of carbon in the
excess or deficit by 1'3 (since fat contains about 7 6 '5 per cent, carbon). Thus,
in the balance table on p. 872, the man under observation retained 39*8 grms.
C, representing 52 grms. fat laid on.

The following table (from Bunge) gives the percentage composition of
some of the chief foodstuffs ; the remainder in each case is mainly water with
a variable amount of salts — the numbers are taken from Kb'nig. They are
given in inverse order to the proportion of proteid they contain : —

1 Argutinsky determined the percentage composition of beef, completely divested of fat
and dried, to be as follows :— C 49'6, N 15'3, H 6'9, 0 + S 23 '0, ash 5'2 (Arch. f. d. ges.
Physiol, Bonn, 1893, Bd. Iv. S. 345).

2 Konig, "Chemie der menschl. Nahmngs-u. Genussmittel," Berlin, 1882, Aufl. 2.

874

METABOLISM.

Foodstuff.

Proteid.

Fat.

Carbohydrate.

Apples

0-4

13

Carrots

1-1

0-2

9

Potatoes .

2

o-i

20

Human milk

2

4

6

Cabbages .

3-3

0-7

7

Cow's milk

3-4

4

5

Rice .

8

0-9

77

Maize

10

4-6

71

Wheat

12

1-7

70

White of eggs

13

0-3

Fat pork .

15

37

Yolk of eggs

16

•°2

Fat beef .

17

26

Fish (pike)
Lean beef .

18
21

0-5
1-5

Peas .

23

1-8

58

Heat value of foodstuffs. — A most important determination to be
made regarding any diet is its caloric (calorific) value. This is arrived at
by multiplying the number of grammes of its several organic constituents
by a number, determined by exact experiment, representing the amount
of heat produced by the oxidation of 1 grm. of the carbohydrate, fat, or
proteid to water and carbon dioxide and to urea. Such calorimetric
experiments were first carried out systematically by Frankland,1 who
determined the caloric value of various articles of diet, and his results
have since been extended and confirmed or amended by various
observers,2 using improved calorimetric methods.

According to Eubner, the average caloric value of the proteid of the
aliment is 4124 calories, i.e. I grm. proteid oxidised to urea yields 4124
grm. degrees (or 41 kilogram-degrees) of heat ; of the fat, 9321 calories
(9-3 kilogram-degrees); and of the carbohydrate (starch), 4116 calories
(41 kilogram-degrees). Applying these numbers to Voit's diet (see
next page), we obtain in round numbers —

105 grms. assimilated proteid x 41 = 430

56 „ fat x 9-3 - 520

500 „ carbohydrate x 41 = 2050

= 3000 kilo-calories,

or 3,000,000 calories, as the energy value per diem of the food of a man
of about 70 kilos., doing hard muscular work.

This amount is probably a little too high, since the whole of the fat and
carbohydrate of a mixed diet is not assimilated. Rubner estimates the actual
production at 2,843,000 calories. Hultgren and Lantergren, however, found
that Swedish workmen, of an average weight of only 67 kilos., consumed on an
average per diem 159 grms. proteid, 93 grms. fat, and 570 grms. carbohydrate,
which, even allowing for the non-assimilation of a certain proportion of each,
would still give a higher caloric value for the total foodstuffs. Probably,

1 "On the Origin of Muscular Power," London, Edinburgh, and Dublin Phil. Mag.,
London, 1866, vol. xxxii. p. 182.

2 Stohmann, Journ. f. prakt. Chem., Leipzig, 1879, Bd. xix. S. 115 ; Ztschr. f. Biol,
Miinchen, 1894, Bd. xxxi. S. 364 ; Danilewsky, Arch. f. d. gen. Physiol., Bonn, 1885, Bd.
xxxvi. S. 237 ; Rubner, Ztschr. f. Biol., Miinchen, 1883, Bd. xix. S. 313; 1885, Bd. xxi.
S. 250 u. 337 ; 1886, Bd. xxii. S. 40 ; 1894, Bd. xxx. S. 73.

MINIMAL AMOUNT OF PROTEID IN FOOD. 875

therefore, 3000 kilo-calories may be taken as a fair average for the calorie
value of the ingesta of a man weighing about 70 kilos., which would give
about 43 calories for each kilogram body weight.1

In women the amount is somewhat less than this, both absolutely and also
relatively. In children, though absolutely less, it is relatively greater.

Since the combustion of 1 grm. fat produces 9*3 kilo-calories, and the
combustion of 1 grm. proteid to urea C02 and H20 and of 1 grm. starch
to C02 each produces 4*1 kilo-calories, the combustion of 100 grms. fat
will produce an equal amount of energy with the combustion of 227 grms.,
either of proteid or of starch. This amount, therefore, of proteid or of
starch is said to be of the same " isodynamic value" as 100 grms. fat.
It has been shown by the carefully conducted calorimetric investigations
of Eubner,2 that the isodynamic values are as nearly as possible the
same, whether the combustion occurs in air, or in the tissues of the
animal body.3

Minimal amount of proteid necessary in food. — There has been
much disputation as to the minimal amount of proteid which it is
possible for a man in health and doing work to take in his diet in the
course of twenty-four hours. Ranke gave as a normal diet for an
average man (70 kilos.) not engaged in muscular work, 100 grms. of
proteid, 100 grms. of fat, and 240 grms. of carbohydrate.4 Voit
allowed for a man of 70 to 75 kilos., doing ten hours' muscular
work, 118 grms. of proteid, 56 grms. of fat, and 500 grms. of carbo-
hydrate.5 It has, however, been shown that, provided the non-proteids
in the diet are increased — not only in proportion to the caloric value of
proteid withdrawn, but considerably more than in such proportion — a
man can maintain equilibrium and can do work upon considerably less
proteid than that allowed in the diets of Eanke and of Voit.

Thus Hirschfeld (70 kilos.)6 found that he could maintain himself for a
considerable time in perfect health with a diminution of proteid down to
75 grms., or even for a time down to 49 grms. per diem, but under these
circumstances it was necessary to increase enormously the amount of non-
proteid and especially of carbohydrate material taken with the diet.

1 Hultgren and Lantergren, working with Tigerstedt, found the heat value of the food
of six persons living on a freely chosen diet to vary from 33 to 49 calories per kilogramme.
They found that the heat value of the proteid was about 16 to 19 per cent, of the total
heat value of the food, that of the fat being about 21 to 24 per cent., and that of the
carbohydrate about 60 per cent. Ranke's diet (vide infra), with a heat value of only
2,365,000 calories, is for a man performing no muscular work.

* Ztschr.f. BioL, Munchen, 1894, Bd. xxx. S. 73.

3 A more complete account of the heat values of the foodstuffs is given in the article on
"Animal Heat" in p. 833. For the influence of food on the respiratory exchange, see
article "Chemistry of Respiration," p. 717; see also Magnus-Levy, Arch. f. d. ges.
Physiol., Bonn, 1893, Bd. Iv. S. 1.

4 To this may be added 25 grms. salts and 2535 grms. water (including that contained
in the solid food). These several constituents are contained in a daily ration of 250 grms.
meat, 400 grms. bread, 70 grms. starch or sugar, 100 grms. fat, 10 grms. salt, and 2100
water (J. Ranke, "Die Ernahrung des Menschen," Mimchen, 1876).

5 Such a diet contains about 18 '3 grms. N, and about 328 grms. C, whereas Ranke's
diet contains about 15 '5 grms. N, and about 220 grms. C. It should be added that about
13 grms. of the 118 grms. proteid of Voit's diet is not absorbed or assimilated, so that the
available proteid is about 105 grms. This closely corresponds with the results of Bleibtreu
and Bohland (with Prliiger), who give 1 '5 grms. per kilo, body-weight. This would be a
little over 105 grms. for a man weighing 70 kilos. (Arch. f. d. ges. Physiol., Bonn, 1886,
Bd. xxxviii. S. 1). In Hultgren and Lantergren's observations the actual amount of the
ingested proteid which underwent metabolism averaged 101 '3 grms.

6 Arch. /. d. ges. Physiol., Bonn, 1887, Bd. xli.' S. 533; and 1889, Bd. xliv. S. 428;
also Virchoios Archiv, 1888, Bd. cxiv. S. 301.

876 METABOLISM.

Klemperer 1 reduced the amount of proteid in his own diet to as little as
25 grms. per diem, but required 262 grins, fat, and 406 grms. carbohydrate
(with a total caloric value of more than 5,000,000 calories) to maintain
equilibrium.

I. Munk brought a dog into nitrogenous equilibrium with a diet con-
sisting mainly of proteid. If, now, one -half the proteid of the diet was
removed and replaced by non-pro teid, an amount of non-pro teid having a
caloric value of about two-fifths more than that of the proteid removed was
required to maintain equilibrium ; and the more the proteid removed from the
diet, the greater the proportionate amount of non-proteid required. Ultimately,
the amount of proteid was reduced to T5 grms. per kilo, body-weight; under
these circumstances an amount of non-proteid, twelve to fifteen times the
caloric value of the proteid removed, wlls required to maintain equilibrium.2
After the lapse of some weeks, the animal failed properly to digest the large
amount of non-proteid required, and it became necessary to reduce this and
increase the proteid.

The amount of nitrogen taken in these experiments was distinctly less
than the amount which would be lost in the fasting condition.

Of the two chief kinds of non-proteid food, v. Noorden and Kayser 3 have
found that carbohydrates are of greater value as proteid-sparers than fats. In
a mixed diet, therefore, containing just enough proteid and non-proteid for
the needs of the economy, fats cannot be substituted for their caloric
equivalent of carbohydrates without loss of proteid occurring. Gelatin is of
still greater value as a proteid-sparing food than are either fats or carbohydrates
(see p. 878), and by its use, although it cannot be built up into tissue, the
amount of tissue proteid lost from the body can be reduced, according to Yoit,
to about the half of that which is normally lost, and which on Voit's estimate
amounts to about 33 grins, daily,4 or 1 per cent, of the actual living substance.5
The importance of gelatin as an article of diet will be specially treated of
later on.6

In spite of such experiments, it may be doubted whether a diet which
includes considerably less proteid than 100 grms. for the twenty-four
hours could maintain a man of average size and weight for an indefinite
time. It has frequently been asserted that many Asiatics consume a
very much smaller proportion of proteid than is the case with Europeans.
The inhabitants of India, Japan, and China chiefly consume rice as the
normal constitution of their diet, which contains relatively little proteid ;
and this has been advanced as an argument in favour of the view that
the minimal amount of proteid is much less than that ordinarily given
as essential to the maintenance of nutritive equilibrium. It must,
however, be stated that we have no definite statistics to show that, in

1 Arch. f. Physiol., Leipzig, 1889, S. 361. Similar experiments have been made by
Peschel (Diss., Berlin, 1890) and Graham Lnsk, Ztschr. f. Biol., Miinchen, 1891, Bd. xxvii.
S. 459. See also E. Voit, Miinchen. med. Wchnschr., 1889, S. 748 ; and C. Voit, ibid.,
1891, S. 195.

* Arch. f. Physiol., Leipzig, 1891, S. 338 (Verliandl. d. physiol. Gesellsch.) and
Virchow's Archiv, 1893, Bd. cxxxii. S. 91. See also Rosenheim, Arch. f. d. ges. Physiol.,
Bonn, 1893, Bd. liv. S. 61 ; and Ritter, Miinchen. med. Wchnschr., 1893, Nos. 31 and 32.

3 Arch. f. Physiol., Leipzig, 1893, S. 371.

4 The half of this amount, since it can be replaced by gelatin, is set down by Voit to
disintegration of "circulating proteid" instead of actual "tissue proteid."

5 Hermann's "Handbuch," Bd. vi. S. 302, and /Aschr. f. Biol., Miinchen, 1889, Bd.
vii. S. 284.

6 Pagliese, Centralbl. f. Physiol., Leipzig u. Wicn, 1897, S. 329, has found that fats,
carbohydrates, and gelatin, not only diminish the amount of the nitrogen excreted, but
also the phosphoric acid, and this even in a greater proportion, and probably by diminish-
ing the waste of the nucleo-proteids of the tissues.

CONSTITUTION OF DIETS.

877

proportion to their body weight, Asiatics doing the same amount of work
as Europeans require a less amount of proteids ; indeed, such evidence as
is forthcoming is rather in favour of the opposite conclusion.1

The following table (from Hultgren and Lantergren) gives the average
amounts of the proteids, fats, and carbohydrates in freely chosen diets of
workmen of different countries, together with the total heat values of such diets :

Proteid.

Fat.

Carbohy-
drate.

Kilo-
calories.

{Russian workmen (Erisman)

131-8

79-7

583-8

3675-2

Moderately
hard work

Munich workmen (Forster)

131-9

81-5

457-4

3174-1

Swedish workmen (H. and L. ) .

134-4

79-4

522-8

3436

Hard work

Swedish workmen (H. and L.) .

189

110

714

4726

With these may be compared the following :—

Soldiers on active service (Voit)

Proteid.
145

Fat,
100

Carbohy
drate.

Kilo-
calories.
500 3574-5

The average proportion of proteid to non-nitrogenous constituents of the
food is given by Hultgren and Lantergren at 1 : 4-27 by weight, and 1 : 4-95
by heat value ; of fat to carbohydrate at 1 : 6-34 by weight, and 1 : 2-80 by
heat value.

The manner in which the proteid and non-proteid constituents of
the diet are most advantageously taken into the body, or, in other words,
the constitution of dietaries, forms a subject belonging more properly to
the domain of personal hygiene. It would, moreover, occupy far too
much space to discuss at all adequately the constitution of diets of
different people and in different countries. It is sufficient to state
that under ordinary circumstances the proteids are taken in such
forms as flesh, egg, and cheese, bread and other cereals, and leguminous
foods, the fat in the form of meat-fat and butter, and the carbo-
hydrate in the form of starch or cane-sugar derived from or contained
in vegetable food. With a purely vegetarian diet the proteid
of the food may be derived largely from the leguminous plants and
to a somewhat less extent from the cereals, and the fat from the seeds
of plants.2 We may now proceed to consider the effects upon nutrition
of some of the more important constituents of the diet.

1 Cf. Kumagawa, Virclwiu's Archiv, 1889, Bd. cxvi. S. 370 ; Kellner and Mori, Ztschr.
f. BioL, Miinchen, 1889, Bd. xxv. S. 102 ; I. Munk, ibid., 1893, Bd. cxxxii. S. 91.

2 For statistics concerning diet see J. Ranke, "Die Ernahrung des Menschen,"
Miinchen, 1876; C. Voit in Hermann's "Handbuch," Bd. vi. ("Physiologic des
allgemeinen Stoffwechsels und der Ernahrung"), Leipzig, 1881; Konig, "Chem. d.
menschl. Nahrungs-u. Genussmittel," Berlin, 1882, Aufl. 2 ; I. Munk and Uffelmann,
"Ernahrung des Menschen," Wien u. Leipzig, 1887, in which also the literature of the
subject up to that date will be found ; Scheube, Mitth. d. deutsch. Gesellsch.f. Nat.-u. VolTccrk.
Ostasiens, Yokohama, 1882, No. 24, and-4rc/i./. Hyg., Miinchen u. Leipzig, 1884, Bd. i. S.
352 (diet of Japanese) ; Hultgren and Lantergren, "Untersuch. ii. d. Ernahr. Schwedischer
Arbeitern," Stockholm, 1891 ; Studemund, Arch. f. d. ges. PhysioL, Bonn, 1891, Bd. xlviii.
S.578 ; Ohlmiiller, Ztschr. f. £ioL, Miinchen. 1884, Bd. xviii. S. 393; G. Bunge, "DerVege-
tarianismus," Berlin, 1885; Kumagawa, Virchows Archiv, 1889, Bd. cxvi. S. 370; Albertoni
and Novi, Arch.f. d. ges. PhysioL, Bonn, 1894, Bd. Ivi. S. 213 (criticised by Hultgren, ibid.,
1895, Bd. Ix. S. 205). Diet statistics will also be found in most text-books of physiology.

878 METABOLISM.

Special constituents of the diet. — Proteids. — Proteids are chiefly
taken in the diet in the form of egg-albumin, vitellin, myosin, casein,
the proteids of cereals and of leguminous seeds (mainly globulins). The
nutritive value of the proteids from any one of these sources is pretty
nearly the same, with the exception that somewhat less of the proteid
of vegetable food is digested and assimilated than that of animal origin,
and the less, the larger the amount of cellulose which is contained in the
food.

Peptones and albumoses have about the same caloric and nutritive
value as the proteids from which they have been formed.1 Certain
proteids are assimilated and have the same nutritive value, if injected
into the blood vessels or under the skin, as when digested and absorbed
from the intestines. This is the case with serum-albumin and serum-
globulin, and also with acid or alkali albumin (even if prepared from
egg-albumin) and phytovitellin.2 Other forms of proteid are not thus
directly assimilable, but on injection appear at once in the urine. Such
are egg-albumin,3 casein,4 peptone, and albumoses. Haemoglobin must
also be reckoned with these, although if injected as blood (with the
blood corpuscles intact), it remains intact. If injected dissolved in
water or in serum, it becomes partly broken up and converted into bile
pigment and partly appears in the urine as haemoglobin.

Most, if not all, proteids contain sulphur, and the nucleo-proteids
contain phosphorus; an increase of sulphates and sometimes of phos-
phates in the urine may therefore be expected, if their metabolism is
increased. The metabolism of proteids will be subsequently dealt with.
Gelatin.— Gelatin, although its elementary composition is very
nearly the same as that of proteids, and although it becomes, like
proteids, converted into peptones by digestion, and after being assimi-
lated is oxidised into urea C02 and H20, is different from proteids in
its chemical constitution (see " Chemical Constituents of Body and
Food, pp. 31 and 70), and cannot wholly replace proteid as an article
of diet. This arises from the fact that the bioplasm of the tissues
is unable to be produced from it. In spite, therefore, of its con-
taining nitrogen and all the elements of the proteid molecule, it is a
non-proteid food, and takes its place as such along with the fats and
carbohydrates. Like them also it acts as a proteid-sparer, so that a
certain amount of proteid can be removed from the diet and replaced
by gelatin ; about twice as much of this must, however, be added, as
proteid is removed.5 As a proteid-sparer, gelatin acts more efficiently
than carbohydrates, and still more than fats. This is shown by an
experiment by Yoit upon a dog weighing 32 kilos., which had been
maintained very nearly on nitrogenous equilibrium by a daily allowance

1 Politzer, Arch. f. d. ges. PhysioL, Bonn, 1885, Bd. xxxvii. S. 301.

2 Plosz and Gyergai, Arch. f. d. ges. PhysioL, Bonn, Bd. ix. S. 325, and Bd. x. S. 536 ;
Maly, ibid., Bd. ix. S. 605; Adamkiewicz, Virchow's Archiv, Bd. Ixxv. S. 144; Stokvis,
Gentralbl. f. d. med. Wissensch., Berlin, 1864, S. 596; Lehmann, Virchow's Archiv, 1864,
Bd. xxx. S. 593 ; Ponfick, Virchow's Archiv, 1875, Bd. Ixii. S. 273 ; Forster, Ztschr.

f. BioL, Miinclien, 1875, Bd. xi. S. 517 ; Tizzoni, Arch. ital. de biol., Turin, 1884, Bd.
vi. S. 395; Neumeister, Sitzungsb. d. phys.-med. Gesellsch. zu Wiirzburg, 1889, S. 64;
Ztschr. f. Biol., Miinchen, 1891, Bd. xxvii. S. 309.

3 Bernard, " Le9ons sur les propr. physiol. etc.," Paris, 1859, tome ii. p. 467.

4 Runeberg, Deutsches Arch.f. klin. Med., Leipzig, 1879, Bd. xxiii. S. 68.

5 According to Voit, one-fifth of the ordinary amount of proteid may be so replaced. I.
Munk, however, in the dog got at least two-thirds of the proteid of the food replaced
by gelatin with maintenance of equilibrium (Arch.f. d. ges. Physiol., Bonn, 1894, Bd. Iviii.
S. 309, and Bd. Ixi. S. 607).

SPECIAL ARTICLES OF DIET.

879

of 500 grms. of meat. On removing 100 grms. of this from the diet, and
replacing it by 200 grms. of gelatin, there was a gain of nitrogen to the
body representing the putting on of 44 grms. of flesh, whereas when the
100 grms. of meat was replaced by 200 grms. of fat, or by 250 grms. of
starch, there was a loss of nitrogen representing a loss of flesh to the
amount respectively of 50 and 39 grms.

The following experiments of Voit on a dog are also instructive.
The numbers represent grammes : —

Expt.

Lean Meat.

Gelatin.

Flesh lost or gained.

! (

500

0

-22

'I

500

200

+ 54

(

2000

0

+ 30

2. \

\

2000

200

+ 376

I

200

200

-118

3. \

\

200

300

-82

{

200

200

+ 25

4. •]

1

0

200

-118

That it cannot wholly replace proteid is shown by the fact that
even when very large quantities are given either alone or in combination
with fat and carbohydrate, an excess of nitrogen appears in the excreta
— in other words, there is still a loss of flesh from the body.1 To a
certain extent gelatin will act as a fat-sparer, i.e., when given along
with proteid, it may prevent the oxidation of body fat, but its activity in
this respect is far below that of either fats or carbohydrates.2 Even
the collagenous tissues can apparently not be formed from gelatin
ingested, since this wholly appears (as urea, etc.) in the excreta ; these
tissues must therefore be formed, like all others, from proteid food.3
Gelatin is also not assimilated if injected into the blood or under the
skin ; it appears at once in the urine.4

Nucleins and nucleo-proteids, as well as lecithins, are found in all
forms of mixed diet ; and although nuclein is not digested by the gastric
juice, nor, according to Bokay,5 by artificial pancreatic juice, there are
reasons for believing that a part at least of the nuclein of the food is
absorbed and converted in the body into other substances. It is found,
for example, that the ingestion of foodstuffs containing much nuclein
causes a marked increase of uric acid in the urine,6 and, as we shall
show later on, there is strong reason to believe that the iron necessary
for the formation of haemoglobin is derived from some forms of nuclein.

1 For the evidence of this, see C. Voit, op. tit., S. 122.

2 C. Voit, op. cit., S. 126.

3 An interesting historical account of the question of gelatin as an article of diet is
given by Voit (op. cit., S. 395).

4 Cl. Bernard and Barreswil, Journ. de pharm. et chim., Paris, 1844, Se>. 3, tome v.
p. 425.

5 Ztsckr. f. physiol. Chem., Strassburg, 1877, Bd. i. S. 157.

6 Horbaczewski, Sitzungsb. d. k. Akad. d. IVissensch.^ien, 1891, Bd. c. Abth. 3, S. 78.

88o METABOLISM.

The phosphorus of any nuclein which is absorbed is probably converted
into phosphoric acid, and excreted as phosphates by the urine. There
is no evidence that the nuclein which is absorbed is taken up by the
tissues, and by them again converted into tissue nucleins ; it is more
probable that these arise by independent synthesis from proteid and
phosphates. That this may occur was shown by Miescher,1 who found
in the case of the salmon, which travels from the sea to the upper
Khine, there to deposit its spawn, and which during the whole period of
its journey and sojourn in the river, lasting some weeks or even months,
takes no food whatever (the alimentary canal being always found empty),
that the ovaries increase in size at the expense of the muscular tissue.
Now the ovaries, being mainly composed of ova, contain large quantities
of nuclein and lecithin, whereas the muscles contain mainly ordinary
proteids and very little of these substances : the latter must therefore
be formed by synthesis, the materials for such synthesis being derived
from the proteids, the fats, and the phosphates of the muscles.

Amido - acids. — Experiments to determine the nutrition, and
especially the proteid-sparing value of amido-acids, have chiefly been
made with asparagin, which occurs in some quantity in certain vegetables.
The general result of these inquiries is to show that in herbivora (rabbit,
goose, sheep), the amido-acids can act as proteid-sparers, whereas in
carnivora (dog) and omnivora (rat) they have not proteid-sparing
effects when added to the diet.2

Creatine has been found to have no nutritive value. If given with
the food, it appears wholly in the urine as creatinine.3

Carbohydrates. — Apart from the small amount of glycogen or sugar
which may be contained in flesh foods, and from the lactose of milk, the
carbohydrates of the food are wholly derived from the vegetable king-
dom. The chief carbohydrate constituents of an ordinary diet are starch
and cane-sugar, with a certain amount of grape-sugar when there is
much consumption of certain fruits. Neither starch (in solution) nor
cane-sugar (Bernard) is directly assimilable when injected into the blood
vessels, and the same is true for maltose and lactose.4 These sub-
stances all appear under such circumstances at once in the urine.

On the other hand, dextrose can be directly assimilated, even in large
amounts. It is necessary that the injection should be conducted slowly,
so that the liver should have time to convert it into glycogen before the
proportion of dextrose in the blood much exceeds about 0*2 per cent.
Injected too rapidly, or in too large doses (more than 1 grm. per kilo,
body weight), glycosuria results ; 5 and if its elimination by the kidneys

1 Arch.f.Anat. u. Entivcklngsgecch. , Leipzig, 1881, S. 193 ; and "Statistische u. biol. Beitr.
z. Kenntniss vom Leben des Rheinlachses," 1880 (quoted from Bunge's " Handbtich ").

2 Weiske, Ztschr. f. Biol., Munchen, 1879, Bd. xv. S. 261 ; 1881, Bd. xvii. S. 415 ;
1884, Bd. xx. S. 277 ; 1894, Bd. xxx. S. 254 ; Zuntz and Bahlmann, Arch. /.
Physiol., Leipzig, 1882, S. 424 (Verhandl. d. phys. Gesellsch.) ; Potthast, Arch. f. d. yes.
Physiol., Bonn, 1883, Bd. xxxii. S. 280 ; I. M.mik,'Virchow's Archiv, 1883, Bd. xciv. S. 436 ;
and 1884, Bd, xcviii. S. 364 ; Mauthner, Ztschr. f. Biol., Miinchen, 1892, Bd. xxviii.
S. 507 ; E. Voit, Sitzunysb. d. k.-bayer. Akad. d. Wissensch. zu Munchen, 1883, S. 401 ;
Ztschr. f. Biol., Munchen, 1892, Bd. xxvii. S. 492; 1893, Bd. xxix. S. 125; Gabriel, ibid.,
S. 115.

3 Meissner, Ztschr. f. rat. Med., 1868. Bd. xxxi. S. 283.

4 According to Dastre (Arch, de physiol. norm, etpath., Paris, 1889, p. 718), galactose is
directly assimilable.

5 Biedl and Kraus ( Wien. klin. Wchnschr., 1896, S. 55) state, however, that they were
able to inject as much as 200 to 300 grms. of grape-sugar, in 10 per cent, solution, into the
vein of a man, without producing either polyuria nor any but a slight temporary glycosuria.

SPECIAL CONSTITUENTS OF THE DIET. 881

be prevented, as by tying the ureters, the excess of sugar under-
goes changes which result in the formation of lactic acid, acetone,
diacetic acid, and other substances, the production of which is
accompanied by convulsions, and eventually coma, as in severe natural
diabetes.1

Very large amounts of starch can be taken into the alimentary canal,
and corresponding amounts of dextrose absorbed into the blood, without
producing glycosuria in a normal animal. But if the assimilation
powers have been reduced by starvation, glycosuria is found to occur on
the ingestion of a large amount of starch.2 On the other hand, if cane-
sugar, maltose or lactose, and even laevulose, are taken by the mouth in
large quantities, even without a previous starvation period, part of the
sugar ingested appears in the urine (alimentary glycosuria).3 This is
apparently due to the fact that the blood vessels of the intestine cannot
carry away all the absorbed sugar with sufficient rapidity to the liver,
and some of it consequently passes to the general circulation by way of
the thoracic duct,4 and thus to the kidneys, which always immediately
eliminate any excess of sugar in the blood passing through them.
G-lycosuria also occurs when sugar solutions are injected into the large
intestine of dogs.5

Cellulose is not readily digested by carnivora nor by man, but in
some forms of food (carrots, cabbage, celery, lettuce) a considerable
proportion of the cellulose present may become dissolved and absorbed ; 6
in herbivora it undergoes digestion, and is eventually absorbed as
dextrose. Its chief value in the diet of animals seems, however, to
be due to its action in promoting peristalsis of the intestines. Eabbits
die from inflammation of the intestines if devoid of cellulose ; its place can
be supplied in them by horn-shavings, which have the same mechanical
effect. In carnivora and man this is not so important, as the gut is
shorter, but probably the cellulose of mixed food tends to prevent
constipation. A purely milk diet is well known to be constipating
(Bunge).

The fate of the carbohydrates after assimilation will be treated of in
a special section on carbohydrate metabolism.

Fats are taken in largely in the form of animal fat (fats of flesh and
milk), but also largely, especially in some countries, in the form of
vegetable fats, such as olive oil and the fats met with in certain seeds.
In the last-named form they are protected by cellulose, and are far less
easily digested and assimilated. The changes which they undergo in
the processes of digestion and absorption have already been fully con-
sidered (pp. 443-463), also their caloric value, and their importance as
proteid-sparers. Their assimilation to the natural fat of the body, and
their formation within the body, will be treated of subsequently.

Fatty acids and soaps have been shown by I. Munk (in dogs) to
have very nearly the same nutritive value as the fats from which they

1 V. Harley, Arch. f. PhysioL, Leipzig, 1893, Suppl., S. 46.

2 Hofmeister, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1889, Bd. xxv. S. 240 ; and
1890, Bd. xxvi. S. 355.

3 Worm-Miiller, Arch. f. d. ges. PhysioL, Bonn, 1884, Bd. xxxiv. S. 576 ; Hofmeister,
Arch.f. exper. Path. u. PharmakoL, Leipzig, 1889, Bd. xxv. S. 240 ; C. Voit, Ztschr.f. BioL,
Miinchen, 1892, Bd. xxviii. S. 265 ; Miura, ibid., 1896, Bd. xxxii. S. 281.

4 Ginsberg, Arch.f. d. ges. PhysioL, Bonn, 1889, Bd. xliv. S. 306.

5 Eichhorst, ibid., 1871, Bd. iv. S. 601.

6 Weiske, Ztschr. f. BioL, Miinchen, 1870, Bd. vi. S. 456 ; Knierem, ibid,, 1885, Bd.
xxi. S. 67. See also Luntz, Arch.f. d. ges. PhysioL, Bonn, 1891, Bd. xlix. S. 477.

VOL. I. — 56

882

METABOLISM.

are formed. This has, however, been already discussed (p. 750), and
will be again referred to later on.

Glycerin has been found to act in some measure as a fat and
carbohydrate-sparer, but not as a proteid-sparer.1 Of the total
amount ingested, from 21 to 37 per cent, is secreted in the urine
unaltered, when given in large doses.^ The sparing effect of glycerin
on the conversion of liver glycogen into sugar will be subsequently
referred to.

Alcohol. — The nutritive value of alcohol has been the subject of
considerable discussion, and not a few experiments. Some of these
tend to show that in moderate non-poisonous doses it acts as a non-
proteid food in diminishing the oxidation of proteid, doubtless by
becoming itself oxidised.3 Its action, however, in this respect is
relatively small, and indeed a certain proportion of alcohol ingested
is exhaled with the air of respiration. Moreover, in large doses, it
may act in the contrary manner, increasing the waste of tissue proteid.4
It cannot, in fact, be doubted that any small production of energy
resulting from its oxidation is more than counterbalanced by its
deleterious influences as a drug upon the tissue elements, and especially
upon those of the nervous system.

It is of interest, in connection with this subject, to point out that
alcohol has been regarded by some physiologists as probably formed
at a stage in the metabolism of carbohydrates prior to their complete
oxidation, traces of alcohol having been obtained from fresh tissues by
distillation with water.6

Inorganic substances. — Mineral salts, especially chloride of sodium
and phosphates of lime and of the alkalies, are essential parts of
any diet. The following table from Bunge gives the proportions

KaO.

Na.,0.

CaO.

MgO.

Fe-jOjj.

P205.

Cl.

Beef

1-66

0'32

0'029

0-15

0-02

1-83

0'28

Wheat ....

0-62

0-06

0-065

0-24

0-026

0-94

?

Potato ....

2-28

0-11

o-ioo

0-19

0-042

0-64

0-13

White of egg .

1-44

1-45

0-130

0-13

0-026

0-20

1-32

Peas

1-13

0-03

0-137

0-22

0-024

0-99

?

Human milk .

0-58

0-17

0-243

0-05

0-003

0-35

0-32

Yolk of egg

0-27

0-17

0-380

0-06

0-040

1-90

0-35

Cow's milk

1-67

1-05

1-51

0-20

0-003

1-86

1-60

1 I. Munk, Virchow's Archir, Bd. Ixxvi. S. 119 ; Bd. Ixxx. S. 39.

2 Tschirwinsky, Ztschr. f. BioL, Miinchen, 1880, Bd. xv. ; Arnschink, ibid., 1888, Bd.
xxiii. S. 413.

3 Strassmann, Arch. /. d. ges. PhysioL, Bonn, 1891, Bd. xlix. S. 315. Chittenden
(Journ. PhysioL, Cambridge and London, 1892, vol. xii. p. 220), experimenting upon
dogs, obtained very little influence on proteid metabolism. For the earlier literature
of this question, cf. C. Voit, op. cit., pp. 169 and 415.

4 Miura, Ztschr. /. klin. Mcd., Berlin, 1892, Bd. xx. S. 137. I. Munk obtained similar
results upon dogs (VerhandL d. PhysioL Gesellsch., 1878-79, No. 6 in Arch. f. PhysioL).

5 Hoppe-Seyler and Rajewsky, Arch. f. d. ges. PhysioL, Bonn, 1875, Bd. xi. S.
122.

INORGANIC SUBSTANCES. 883

per cent, in which the different salts of the ash occur in dried food-
stuffs.1

Animals from whose food the salts have been extracted, some-
times die even more rapidly than animals which have been altogether
deprived of food, with the supervention of various symptoms indicating
a disturbance of the central nervous system and of the digestive system.2
This more rapid end of such animals is due, according to Bunge,3
to chronic acid-poisoning, produced by the oxidation of the sulphur
of the proteids ; such acid being normally neutralised by the basic salts
(phosphates, carbonates, and alkali-albuminates) taken in with the food,
whereas in the absence of these, basic substances are removed from the
tissues to take their place. The experiments of Lunin (in Bunge's
laboratory) upon mice fed respectively upon salt-free food, or upon the
same food to which sufficient sodium carbonate was added to exactly
neutralise the sulphuric acid which would be formed in the oxidation
of the proteid of the food, seem to show that Bunge's conjecture is
correct ; for such animals lived considerably longer than those to which
no soda was given, or than those to which it was given combined with
chlorine.4 This, however, is probably not the whole explanation, for in
both the dog and man the faculty of resisting the effects of acids in the
ingesta depends in part, at least, on their neutralisation by ammonia,
which is derived from metabolised proteid.5

It would appear that some at least of the mineral matters of the
food must be in their natural condition, which is probably that
of combination with the proteid substances. For Lunin found that
although mice will live indefinitely on desiccated milk, yet if they
are given an artificial food consisting of a mixture of salt-freed casein and
lactose, to which have been added the same inorganic salts which are
present in the original milk, the animals will die at about the same period
as if sodium carbonate alone had been added to the casein and sugar.6

As Bunge has pointed out, the addition of chloride of sodium to the
ordinary food appears to be essential to the well-being of all animals
the food of which contains a large proportion of potassium salts, as
occurs in most vegetables. In conformity with this, we find that those
races of mankind which subsist mainly on vegetable food find salt an
absolute necessity of life ; and that the same is the case with herbivorous
animals is shown by the fact that these are often found to travel
hundreds of miles to reach a place where salt is to be found (salt-licks).
Carnivorous animals, on the other hand, and those herbivora which
consume plants and herbage which do not contain a great excess of
potassium salts, show no such inclination to seek salt. The same is true
for those races of mankind who live almost exclusively on fish or flesh,

1 Note especially the small amount of Na20 in wheat and peas ; the large amount of
CaO in milk and egg yolk, and the very small amount of iron in milk. On the other
hand, the ash of the foetus contains a very large proportionate amount of iron.

2Forster, Ztschr. f. BioL, Munchen, 1873, Bd. ix. S. 297.

3 Ztschr. f. BioL, Munchen, 1874, Bd. x. S. 130. See also "Lectures," pp. 114-118.

* Ztschr. f. physiol. Chem., Strassburg, 1881, Bd. v. S. 31. See also Socin, ibid., 1891,
Bd. xv. S. 100.

5 Schmiedeberg and Walter, Arch. f. exper. Path. u. PharmakoL, Leipzig, Bd. vii.
S. 148 ; Hallervorden and Coranda, ibid., Bd. xii. S. 76.

6 Somewhat similar conclusions were arrived at by Bnnge and Socin from experiments
upon another artificial food, which had been first deprived of salts, but to which these
were afterwards added. This food, although apparently containing all needful materials
for nutrition, was unable to keep the mice which were fed upon it alive.

884 METABOLISM.

or on such vegetable food, e.g. rice, in which the potassium salts are
only present in small quantity. It is further noteworthy that the
peoples who live on an animal diet, without salt, carefully avoid a loss
of blood when they slaughter the animals, for the blood contains a far
larger amount of sodium in proportion to potassium than any other tissue
or organ. The explanation of these facts is thus offered by Bunge l : —

" The amount of salt which herbivorous animals take in with their food is,
compared with the weight of the body, generally not much less than that
consumed by carnivorous animals. On the other hand, there is a considerable
difference in another constituent of the ash of their food, in the potassium.
Herbivorous animals take at least three or four times as much of salts of
potassium as the carnivora. This fact letds me to imagine that the abundance
of potassium in vegetable food is the cause of the need for salt in the
herbivora. If, for instance, a salt of potassium, such as potassium carbonate,
meets with common salt or chloride of sodium in solution, a partial exchange
takes place — chloride of potassium and carbonate of sodium are formed. Now,
chloride of sodium is well known to be the chief constituent among the
inorganic salts of blood plasma. When, therefore, salts of potassium reach the
blood by the absorption of food, an exchange takes place. Chloride of
potassium and the sodium salt of the acid which was combined with the
potassium, are formed. Instead of the chloride of sodium, therefore, the blood
now contains another sodium salt, which did not form part of the normal
composition of the blood, or at any rate not in so large a proportion. But the
kidneys possess the function of maintaining the same composition of the
blood, and of thus eliminating every abnormal constituent, and any excess of a
normal constituent. The sodium salt formed is therefore ejected by the
kidneys, together with the chloride of potassium, and the blood becomes
poorer in chlorine and sodium. Common salt is therefore withdrawn from the
organism by the ingestion of potassium salts. This loss can only be made up
from without, and this explains the fact that animals which live on a diet
rich in potassium have a longing for salt."

In confirmation of this deduction, Bunge found that the addition of
potassium salts to his diet produced a striking increase in the excretion
of chlorine and sodium. Thus 18 grms. of K20, taken in the form of
phosphate or citrate, caused the loss of an extra 6 grms. of chloride of
sodium (as well as 2 grms. of sodium in other forms), about one-half of
the common salt which is contained in the 5 litres of a man's blood.
And 18 grms. of potash is an amount much less than may be introduced
with many important articles of vegetable diet, such as potatoes, which
contain 20 to 28 grms. K20 in each 1000 grms. of dehydrated material.
" Having regard to the important part which salt plays in the organism
(as in the formation of the digestive secretion, or in dissolving the
globulins), even a small diminution may be prejudicial to certain func-
tions, and may give rise to the need of recovering the loss." 2

There are two other constituents of the food which need special
consideration, namely, iron and lime.

The amount of iron which is egested is exceedingly small, and it
may be expected therefrom that the amount present in the food
under ordinary circumstances would also be small. Stockman has

1 " Lectures," translated by Wooldridge, p. 119.

2 Bunge, op. cit., p. 121. The student is referred to Bunge' s original publications
( " Lectures" and Ztsclir. f. Biol., Miinchen, 1874, Bd. x.) for a full and very interesting
discussion of this important subject.

INORGANIC SUBSTANCES.

885

shown that only about 10 mgrms. a day is ingested in an ordinary diet.1
Of this amount, 1 mgrm.is egested by the urine, the remainder by the feces.
This cannot, however, represent all the iron metabolised, for the iron of
the hemoglobin of disintegrated blood corpuscles is retained, mainly by
the liver, and is no doubt again built up into blood pigment. The nuclei
of most cells, both animal and vegetable, contain appreciable quantities
of iron, and in this form, and in the hemoglobin of meat, it must occur in
most food.2 In both these cases it forms an integral part of the molecule
of the proteid or nucleo-proteid, and under ordinary circumstances there
is no inorganic iron, nor any iron salt of organic acid present in the diet.
Such compounds of iron as are contained in nucleins — such, for instance,
as the nuclein of the yolk of the egg — have been termed by Bunge Jicema-
togens. As this nuclein is the only iron-containing constituent of the
yolk, it is clear that the hemoglobin of the developing red corpuscles of
the chick must derive its iron from it. It has further been shown by
Socin, working in Bunge's laboratory,3 that in mammals also haemoglobin
is manufactured when the only iron contained in the food is in the form of
the same yolk-hematogen, and that the urine of animals (dogs) fed freely
with egg yolk shows a marked increase in the amount of iron present.

It is noteworthy, as has been pointed out by Bunge, that the natural
food of the infant, namely, milk, contains mere traces of iron, although
the formation of hemoglobin is actively proceeding. This is accounted
for by the fact that the foetus lays up a store of iron (in its liver and else-
where) before birth, and gradually draws upon such store for the manufac-
ture of hemoglobin. Thus Bunge 4 found 18 '2 mgrms. iron per 100 grins,
body weight in a new-born rabbit, as compared with 3*2 mgrms. per 100
grms. in an animal twenty-four days old; and Zalesky,5 four to nine times as
much iron in the liver of a new-born puppy as in that of a full-grown dog.

In all other respects the composition of the ash of milk nearly
corresponds with the composition of the ash of the sucking animal, as
may be seen in the following table from Bunge, which gives the result
of two experiments : — •

'.Br-
ing iron

PUPPY.

MILK OF BITCH.

A.

B.

A.

B.

K00 .
Na,0
CaO .
MgO .
Fe,03
P205 .
Cl

11-42
10-64
29-52
1-82
0-72
39-42
8-35

8-50
8-20
35-8
1-60
0-34
39-80
7-30

14-98
8-80
27-24
1-54
0-12
34-22
16-90

10-70
6-10
34-40
1-50
0-14
37-50
12-40

it. Med. Journ., London, 1893, vol. i. pp. 881, 942 (contains the literature regard-
absorption up to that date) ; Journ. Physiol., Cambridge and London, 1895, vol.

xviii. p. 485 ; also, with Greig, ibid., 1897, vol. xxi. p. 55.

2 Bunge, Ztschr. f. physiol. Chem., Strassburg, 1885, Bd. ix. S. 49. For the micro-
chemical evidence of the presence of iron in cell-nuclei, see Macallum, Proc. Roy. Soc. London,
1891, vol. 1. p. 277 ; and Quart. Journ. Micr. Sc., London, vol. xxxviii. p. 175. This will
probably account for the fact that the faeces, which includes many disintegrated cells of the
alimentary passages, sometimes shows a greater percentage of iron than is present in the
food, although the secretions poured into the intestines only contain iron in minute amounts.

3 Ztschr. f. physiol. Chem., Strassburg, 1891, Bd. xv. S. 93 and 133.

4 Ibid., 1892, Bd. xvi. S. 177.

5 Ibid., 1886, Bd. x. S. 479 and 495.

886 METABOLISM.

In spite of the fact that it is the general experience of members of the
medical profession, that the administration of iron salts promotes the formation
of haemoglobin in certain forms of anaemia (chlorosis), there is no satisfactory
evidence that the administered iron enters into the formation of the newly-
formed haemoglobin, and it has even been denied that the alimentary canal is
capable of absorbing iron given in such form. The experiments of Kunkel,1
however, show that if iron salts are administered to animals along with their
food, the blood, liver, spleen, and other organs exhibit an excess of iron over
that of control animals. Hall 2 also obtained distinct evidence of iron
absorption under like circumstances. When iron salts are injected sub-
cutaneously into a vein, most of the iron appears at once in the urine, some
is secreted into the intestine,3 but somg is stored in the liver and is only
gradually eliminated. Experiments upon animals, in which the haematogens
of Bunge have been removed from the food and replaced by iron salts, have
been attempted,4 but have presented serious difficulties.5 Marfori,6 however,
working with Schmiedeberg, obtained a large amount of absorption of iron
when given to dogs in artificial combination with albumin. Macallum also
has shown that iron, both in organic and inorganic combination, is absorbed
by the intestinal mucous membrane.7

Lime is taken in and assimilated by the organism, also in all probability
in the form of organic compounds, probably with proteids.8 It occurs in
large amount in milk, but in most other forms of foodstuffs it is deficient
as compared with other constituents of the ash; the leguminosse
contain more than most foodstuffs. The only food which has the same
amount as milk is the yolk of egg, which should therefore always
be given to children when milk is either not procurable or cannot be
digested." 9

The withholding of lime from the food of growing animals causes rickets ; 10
but rickets may occur in children, in spite of their food containing an adequate
amount of lime.11 Probably, owing to abnormal conditions of nutrition, the
lime is under these circumstances not assimilated.

In adult animals (pigeons), feeding with foods containing little or no lime
has been found eventually to cause alterations in the bones, which become
unusually brittle and thin (osteoporosis).12

1 Arch.f. d. ges. Physiol., Bonn, 1891, Bd. 1. S. 11; 1895, Bd. Ixi. S. 595.

2 Arch. f. Physiol. , Leipzig, 1894, S. 456 ; and 1896, S. 49.

3 Mayer, Diss., Dorpat, 1850, quoted by Bunge. Quincke (Arch.f. Anat., Physiol. u.
wissensch. Med., 1868, S. 150) failed to find it in an isolated portion of intestine with a
Thiry fistula, but Macallum (Journ. Physiol., Cambridge and London, 1894, vol. xvi. p.
268) obtained evidence of it in the crypts of Lieberkuhn.

4 Socin, Ztschr. f. physiol. Chem., Strassburg, 1891, Bd. xv. S. 93 ; v. Hosslin, Ztschr.
f. Biol., Miinchen, 1882, Bd. xviii. S. 612 ; Hall, Arch.f. Physiol., Leipzig, 1896, S. 142.

5 Consult upon the subject, Bunge, " Lehrbuch," 1894, 3te Aufgabe, S. 83 ; and Wool-
dridge's translation; also Neumeister, "Lehrbuch," Jena, 1897, 2te Aufl., S. 3827392,
where the subject is very fully treated and many more references to the literature will be
found.

6 Arch. f. exper. Path. u. PharmaM., Leipzig, 1892, Bd. xxix. S. 212.

7 Op. cit., 1894.

8 Fokker, Arch.f. d. ges. Physiol., Bonn, 1873, Bd. vii. S. 274.

9 Bunge, " Lectures," Wooldridge's translation, p. 111.

10 J. Forster, Ztschr. f. Biol., Miinchen, 1873, Bd. ix. S. 369 ; and 1876, Bd. xii. S. 464 ;
E. Voit, ibid., 1880, Bd. xvi. S. 55 ; Baginsky, Arch. f. Physiol., Leipzig, 1881, S. 357 ;
and Virchow's Archiv, 1882, Bd. Ixxxvii/S. 301 ; Seem'ann, Ztschr. /. klin. Med., Berlin,
1882, Bd. v. S. 1 and 152.

11 Riidel, Arch. f. exper. Path. u. PharmaJcoL, Leipzig, 1893, Bd. xxxiii. S. 90 ; 0.
Vierordt, Verhandl. d. xii. Cong. f. innere Med., Wiesbaden, 1893, S. 230.

12 Chossat, Compt. rend. Acad. d. sc., Paris, 1842, tome xiv. p. 451 ; C. Voit, Ber. d. Vers.
d. Naturf. z. Miinchen, 1877, S. 243; Art. "Ernahrung" in Hermann's "Hanclbuch,"
Bd. vi. S. 379 ; the earlier literature of the subject will be found in this article.

METABOLISM D URING INANITION. 887

METABOLISM DURING INANITION.

The problems of metabolism naturally subdivide themselves into
those which concern the fate of the foodstuffs after they are absorbed
and before they reach the tissues, and those which concern the fate
of the stuffs which form the tissues, or which undergo changes within
and by the agency of the tissues. The simplest condition of meta-
bolism is therefore obtained when food is altogether withheld, as under
these circumstances we have only to determine the changes which
occur in the bodystuffs. On this account a very large amount of
attention has been paid, both recently and previously, to the changes
which occur in the tissues, as evidenced by the excreta during inanition
in animals and man.

There is one main fact which comes out in all experiments on
inanition, namely, that in spite of the withholding of food, all the
excretions continue, not certainly to their normal amount, but at least
to a considerable extent. This is even the case with the faeces
which, in the absence of food, might be expected not to be formed.
But, as a matter of fact, it is found that, during starvation, animals
pass, if not every day, at least every two or three days, a fairly regular
amount. This is composed of mucus and of inspissated digestive juices,
a good deal altered in their composition, together with epithelial cells
and other debris. Urine is also regularly passed during a period of
inanition. The secretion of the skin is given off; carbon dioxide and
water continue to be exhaled from the lungs ; and in consequence of all
these losses from the body the animal gradually loses in weight.
The greatest proportionate amount lost is always during the first day
of a fasting period. This is owing to the fact that the products of
metabolism of the proteid food previously absorbed and that still within
the alimentary canal are then got rid of. But after the first day or two
it is found that the loss in weight is pretty definite, and nearly regular
from day to day, and that fairly regular, or at least only gradually
decreasing, amounts of the various excreta are lost daily.1 Thus Voit,2
experimenting upon a cat, found that about 4 to 5 grms. of urea were
passed each day, representing a loss of tissue of from 25 to 30 grms.,
and this with great regularity until the twelfth day, when there was a
marked rise in the amount of urea eliminated. And similar results
have been obtained both with other animals and men in a condition
of inanition.

The time at which this regular daily loss of nitrogen begins, depends
upon the previous condition of nourishment. Thus, in a dog experi-
mented upon by Voit, three series of experiments were made, each
extending over eight days of total deprivation of food. The animal had
received before the first series, 2500 grms. of flesh daily ; before the
second, 1500 grrns. ; and before the third, a mixed diet with relatively
little proteid. The results obtained are shown in the table on p.
888. It will be seen that the regular loss begins at once in the third
series, but not until the fifth day in the first series, in which the animal
received most proteid during the previous period. The actual amount of
proteid excreted per diem and per kilo, bodyweight was found by Voit

1 The amount of fat metabolised in the dog was found by Pettenkofer and Voit to be
less during the first days than during the subsequent period.

2 Hermann's " Handbuch," Bd. vi.

888

METABOLISM.

Urea Excretion in Grammes per Diem.

Day of
Inanition.

Series I.

Series II.

Series III.

1

60-1

26-5

13-8

2

24-9

18-6

11-5

3

19-1

157

10-2

4

17-3

14-9

12-2

5

12-3

14-8

12-1

6

13-3

12-8

12-6

7

12-5

12-9

11-3

8

10-1

. 12-1

107

to vary greatly with different dogs; small animals metabolise more
proteid per kilo, than large ; lean animals more than fat. Small dogs
have a larger proportionate surface, and relatively a smaller amount of
body-fat.1

Many similar observations have been made on fasting men. One
of these (Cetti) was under observation at different times and by
different observers. His weight was about 57 kilos. The amount of
urea excreted per diem, during the first ten days of fasting, was a little
over 20 grms., equivalent to from 10 to 11 grms. N. Another (younger)
man, weighing about 60 kilos., was also found by I. Munk to excrete per
diem, during the first ten days of fasting, about 11 grms. N, representing
an average loss per diem of about 70 grms. proteid. In these cases there
was but little body-fat. In other individuals, in which there was abund-
ance of body-fat, the N excreted has been found to be much less. Thus
Succi (weight 63 kilos, at beginning, 52 kilos, at end of period) was found
by Luciani, during a thirty days' fast, to excrete on the tenth day
67 grms. ; on the twentieth, 4'3 grms. ; and on the last day 3 -2 grms. N ;
and Jacques (62 kilos.), observed by Noel Paton and Stockman, gave an
average daily loss of 5*29 N. Praussnifcz determined the amount of N
excreted by ten persons during the second day of fasting, and found the
average, for a man weighing about 70 kilos., to be 13*7 grms., equivalent
to a loss of 90 grms. proteid per diem, or about 1*2 grms. per kilo,
body weight. This may therefore be regarded as representing the
amount which it is absolutely necessary to supply in the food, for the
maintenance of nitrogenous equilibrium.

In herbivora there may be an actual increase in the nitrogenous excreta
at the beginning of a starvation period, instead of a diminution ; due to
the fact that, under these circumstances, such animals, being reduced to living
upon their tissues, become practically carnivorous. As in carnivora, such
increase may become greater towards the end of inanition, in consequence of
the exhaustion of the fat of the body, and an increased destruction of the tissue
proteids.2

Now, the amount of urea in the urine during a fasting period of not
too long duration is probably a definite measure of the necessary de-
struction of tissue proteid which goes on within the body, and it may
therefore be taken as a result of such experiments, that the amount of
this metabolism is fairly constant. Such destruction occurs in spite of

1 Rubner, Ztschr. f. BioL, Miinchen, 1883, Bd. xix. S. 535.

2 Rubner, ibid., 1881, Bd. xvii. S. 214 ; Heymans, Bull. Acad. roy. d. sc. de Bely.,
Bruxelles, 1896, p. 38.

METABOLISM DURING INANITION. 889

the fact that there is still plenty of non-nitrogenous material (fat) able
to be drawn upon. The sudden increase which is sometimes met with
after a prolonged period of starvation is due no doubt to the fact that
by this time the non-proteid materials of the body, which have been
up to that time used for the production of energy by their oxidation,
are now practically exhausted, and the whole energy and heat of the
body must necessarily be derived from the tissues themselves ; since
these are composed essentially of proteid, there is a considerable rise
of proteid metabolism.

The carbon dioxide exhaled from the lungs during starvation con-
tinues to be given off in proportion to the weight of the body, to the
work done, and in inverse proportion to the temperature of the environ-
ment. In a man weighing 71 kilos., Pettenkofer and Voit found that
during the first day of fasting 201 -3 grms. C were given off by the respir-
ation, and 5*8 grms. by the urine, in which also 12'5 grms. N was elimin-
ated. This corresponded to a loss of 78 grms. proteid (370 grms. flesh)
and 215 grms. fat. The same man was found by Pettenkofer and Voit
to lose, when working on the first day of fasting, 75 grms. proteid (478
grms. flesh) and 380 grms. fat. The amount of oxygen taken in in the
two cases was 760 and 1072 grms. respectively, and the amount of water
exhaled 889 and 1777 grms. Pianke found on the second day of fasting,
in a fat subject weighing about 70 kilos., 8 grms. N and 3'7 grms. C in
the urine, and 180-9 grms. C given off by the lungs ; corresponding to
50 grms. proteid (235 grms. flesh) and 204 grms. fat.

For a considerable time, as a result of the oxidation of fat and body
proteid, the temperature of a fasting animal is maintained to about its
normal amount. Towards the end, however, of starvation, the temperature
begins to sink, and finally rapidly falls, the meaning of this being that
the animal has now practically exhausted all the nutriment which it
can take from the tissues, and that the amount of oxidation has become
reduced, so that the temperature is no longer capable of being main-
tained at normal. The change is also, in part, doubtless due to the
fact that the heat regulating functions of the nervous system are
beginning to break down in consequence of the deficiency of nutriment.
It has been suggested that an animal dying of starvation practically
dies of cold ; and it is undoubtedly true that the life of a starved animal
can be prolonged considerably by the employment of artificial warmth,
since this diminishes the amount of oxidation necessary for maintaining
the animal heat, and thus economises the energy-producing substances
within the body; but it is, of course, not possible for the artificial
warming of an animal to prolong life to any great extent under
circumstances of complete deprivation of food.

Numerous experiments have been made to determine the amount of
loss of the several organs and tissues of the body which have occurred
during starvation, and also the relative composition of such tissues and
organs as compared with those of a well-nourished animal. All such
experiments tend to show that the most essential organs of the body,
such as the heart and nervous system, live during a period of starvation
at the expense of the other tissues.1

1 Bidder and Schmidt, " Verdaunngssafte u. Stoffwechsel," 1852; Bisehoff and Voit,
"Die Gesetze der Ernahning des Fleischfressers," 1860; Pettenkofer and Voit, Ztschr.
f. Biol., Miinchen, Bde. ii. and v. ; J. Ranke, " Die Ernahning des Menschen," 1876 ; Voit,
'"Ernaliruiig," Hermann's "Handbuch," 1881, Bd. vi.

METABOLISM.

The first substances to disappear, as may well be supposed, are those which
are least essential to the maintenance of life, and we find accordingly that the
adipose tissue first begins to lose weight. Finally, at the end of starvation,
90 per cent., or more, of the fats of the body (except the fatty substances
which are found in the nervous system) have disappeared. At the same time
the glycogen which may have been stored in the liver and muscles also
begins to disappear ; but it is a long while, in some animals, before the last
traces of it are used up, especially the glycogen of muscle. Certain of the
organs especially become diminished in weight. Among these the first to
show a falling off are the spleen and the glandular organs, especially those
concerned in digestion. Since there is very little secretion going on, these are
not called upon to exercise their normal functions. Next follows marked
diminution in the amount of the musculaf substance, and this it is, no doubt,
which accounts for the muscular weakness which manifests itself. When all
the less essential organs have contributed as much as appears possible to the
maintenance of the normal condition of the blood, in order that it may suffi-
ciently nourish the most essential tissues, the latter, namely, the heart and
those of the nervous system, might next be expected to contribute their
quota. Apparently, as soon as this call is made, they fail to respond to it,
and the result is that death speedily supervenes.

Voit gives the following percentage loss for the several tissues and organs
in a cat killed after thirteen days' deprivation of food : —

Adipose tissue

Spleen .

Liver

Testes .

Muscles .

Blood .

Kidneys .

Integument

Lungs

Intestines

Pancreas

Bones

Heart .

Central nervous system

In 100 Parts of
Fresh Organs.

. 97

. 67

. 54

. 40

. 31

. 27

. 26

. 21

. 18

. 18

. 17

. 14

3

3

In 100 Parts of
Dry Organs.

63
57

30

18
21

19

Tominaga l has determined (by Kjehldal's method) the amount of N lost
from the several organs during a prolonged starvation period in rats and
rabbits, as follows : —

Organ.

Rat.

Rabbit.

Spleen ......

98'48

67-06

Stomach and intestines .
Muscles ......
Heart

59-47
35-98
18-01

26-80
18-59
22-74

Brain ......
Liver ......

11-79
9-69
3'48

29-13
57-60
24-80

The discrepancies in these results, both as compared with one another and
as compared with the loss in the dry organs as determined by Voit, are so con-
siderable, that they cannot be accepted without confirmation.

1 OentralbLf. Physiol., Leipzig u. Wien, 1893, Bd. vii. S. 381.

NUTRITION WITH A PURELY PROTEID DIET. 891

The literature of the subject, since the article by Voit in Hermann's
" Handbuch " (1881), will be found mainly in the memoirs noted below.1

NUTRITION WITH A PURELY PROTEID DIET.

Under the circumstances we have been considering, namely, complete
deprivation of food, the nitrogen excreted must come from the nitrogen
of the tissues, and it might be supposed that if we supply a starving
animal with food containing the exact amount of nitrogen (in the form
of proteid) which it is losing, we should be able to entirely prevent such
waste of the tissues, and that any loss then occurring would arise solely
from non-proteid substances. This, however, is not the case. For if
this experiment is performed, it is found that the animal loses more
nitrogen than we give it. The whole of the nitrogen of the added
proteid appears in the urine as urea, and in addition there is a certain
amount, although not as much as during complete starvation, of tissue
nitrogen still present in the urine. In order to keep up nitrogenous
equilibrium, Voit found that it was necessary to give two and a half
times as much proteid as the animal had metabolised during fasting.
This result, which is at first sight somewhat unexpected, is due to the
fact that the ingestion of proteid food directly excites the tissues to
increased metabolic activity, so that tissue proteid itself still becomes
split up and oxidised.

How and why the activity of the living tissues is thus stimulated
by increased proteid pabulum is a problem as to which we are entirely
in the dark. Non-proteid substances do not produce this effect. On the
contrary, the giving of gelatin, carbohydrates, and fat has, as we have
seen, a sparing effect upon proteid metabolism, and tends to dimmish
the amount of tissue proteid which is becoming broken down. This is
also shown very conclusively in Voit's experiments on dogs which had
been kept in a condition of N-equilibrium with proteid food. The con-
dition of N-equilibrium could be produced with a far smaller amount
of proteid, provided that for the amount removed an adequate quantity
of fat or carbohydrate was added to the diet.2

If to a starving animal, instead of what would appear to be just a
sufficient amount of proteid, an excess be given, a point is at length
reached at which the building-up process exceeds the breaking-down,
and the tissues, and therefore the body generally, gain in weight.
This increase in body weight, due to the laying on of tissue, proceeds
to a certain point with any constant amount of added proteid, until
a balance between the N laid on and the N lost is struck, when a
condition of N-equilibrium is again obtained. A further increase of

1Lnciani, "Fisiol. d. digiuno," German translation, "Das Hunger," 1889; Richet,
" L'inanition," Travaux, 1893, tome ii. ; Tucsek, Centralbl. f. d. med. Wissensch. , Berlin, 1 885,
S. 69 ; Lehmann, M tiller, Senator, Zuntz, I. Munk, and others, Berl. klin. Wchnschr., 1887,
S. 425 ; and Virchoivs Archiv, 1893, Bd. cxxxi., Suppl.-Heft; I. Munk, Centralbl. f. d.
med. Wissensch., Berlin, 1889, S. 833; Noel Paton and Stockman, Proc. Roy. Soc. Edin.,
1889, p. 121 ; Praussnitz, Munchen. med. Wchnschr., 1891, No. 18 ; and Ztschr. f. BioL,
Mtinchen, 1893, Bd. xi. S. 151 ; R. May, ibid., 1893, Bd. xii. S. 29 ; I. Munk, Arch. f.
d. ges. Physiol., Bonn, 1894, Bd. Iviii. S. 309 ; Johansson, Landgren, Sonden and
Tigerstedt, Skandin. Arch. f. PhysioL, Leipzig, 1896, Bd. vii. S. 29 ; C. Voit, Ztschr.
f. Biol., Munchen, 1894,. Bd. xxx. S. 510 (comparison of weight of organs in well-nourished
and starved dogs). See also on this subject, LukjanoAV. Ztschr. f. physiol. Chem.,
Strasslmrg, 1889, Bd. xiii. S. 339.

2 Voit, op. cit.

892 METABOLISM.

proteid food will now again produce an increase of tissue and of body
weight, until again a condition of ^-equilibrium is established. And
this may apparently be carried up to the limit of the power of digestion
of the animal for proteid food, so that ultimately fifteen times as much
proteid may be metabolised as in the condition of inanition.1 On the
other hand, diminution of the amount of proteid food tends in the same
way to gradually establish ^-equilibrium on a lower level, and with a
diminished body weight ; the animal losing flesh until such equilibrium
becomes established, and then maintaining itself, provided the N ingested
be constant, at a constant but lower level of N-equilibrium. In short,
" ^equilibrium is possible with the most different amounts of proteid
in the food." 2

The fact that the amount of urea excreted is directly dependent
upon the amount of proteid ingested, is well illustrated by the
following observations of Voit upon a dog fed on lean meat; the
numbers are grms. : —

Meat per diem . 300 600 900 1200 1500 1800 2000 2500
Urea per diem . 32 49 68 88 106 128 144 173

About 80-85 per cent, of the ingested proteid is usually oxidated
and eliminated, and only about 15-20 per cent, is laid on.

ON THE BUILDING-UP AND BREAKING-DOWN OF THE BODYSTUFFS.

The food of animals consists, besides water and a certain amount of
inorganic salts, of organic constituents, nitrogenous (some of which must
be proteid) and non-nitrogenous. The food of the higher plants, on
the other hand, consists normally of inorganic materials, some of which
must be nitrogenous ; and, as has been long recognised, plants have the
power of building up from these materials complex organic substances,
such as proteids, carbohydrates, and fats, whereas animals have not this
power ; the materials built up by plants serving as the food of animals.
Hence arose the belief that it was an essential difference between the
plant and animal organisation, that the one possessed extensive
powers of effecting syntheses, whereas the other had practically no
powers of synthesis, but must receive its materials already synthetised,
either directly from plants or indirectly from plants through the bodies
of other animals, such materials being subsequently broken down into
simpler materials, which, after being oxidised within the tissues, are got
rid of in such simple forms as urea, water, carbon dioxide, and salts.

These views have undergone considerable modification of late years,
since we are now familiar with numerous instances of syntheses occur-
ring in animals. The first well-established case of the kind was
determined by Wohler in 1824. Wohler found that when benzoic acid
is taken with the food, it appears as hippuric acid in the urine. Now,
hippuric acid is formed synthetically from benzoic acid and glycine.

1 C. Voit, Hermann's " Handbuch, " Bd. vi. S. 105. Volt's dog, weighing 35 kilos.,
was able to maintain N-equilibriuin with as little as 500 and as much as 2500 grins,
flesh, containing 548 grms. dry proteid. With larger amounts than this, digestion was
interfered with. The same fact is still more strikingly shown by the experiments of
Pfliiger, who kept a large dog in a condition of nitrogenous equilibrium on an almost
exclusively proteid diet. A man weighing 70 kilos, is, as a rule, unable to digest more
than 1500 grms. of lean meat per diem.

2 C. Voit, loc. int., S. 111.

B UILDING- UP AND BREAKING-DO WN BODYSTUFFS. 893

It is produced when these two substances are allowed to act upon one
another at a high temperature, and under pressure, as when they are
heated together for some hours in a glass tube to a temperature of 160°
C., or more simply by heating monochloracetic acid with benzamide : —

C6H5CO.NH2+CH2C1.COOH=(CGH5CO)NH.CH2.COOH+HC1

(benzamide) (monochloracetic acid) (hippuric acid)

This synthesis of hippuric acid in vitro was speedily followed by that of
urea (Wohler, 1828).

The synthesis of hippuric acid was proved by Bunge and Schmiede-
berg to occur in dogs exclusively in the kidney, and may be produced
even at the temperature of the room, by passing oxygenated blood
containing benzole acid, or a benzoate, and glycine through the blood
vessels of the organ, or even by allowing such blood to stand for a
while in contact with the minced kidney of a fresh-killed animal.
When, however, the kidney cells are destroyed, as by being pounded with
sand in a mortar, no hippuric acid is produced. If benzole acid be
given by the mouth, hippuric acid appears in the urine ; the glycine for
the synthesis is furnished by the tissues. If the kidneys are previously
extirpated, no hippuric acid is found in any %of the organs after the
exhibition of benzole acid; but if the ureters are merely ligatured,
hippuric acid is found in abundance.

In frogs and rabbits the synthesis of hippuric acid is not confined to the
kidneys, but is found to occur after the extirpation of these organs.1

Other syntheses besides that of hippuric acid, which are known to
occur in the animal body, are that of urea in the liver, from ammonium
carbonate and ammonium carbamate ; that of uric acid in the bird's liver,
also from ammonia compounds ; that of glycogen, from glucose in the
liver, and also in muscles and in many other tissues ; that of proteids,
from peptones in the mucous membrane of the alimentary canal ; that of
fats, from fatty acids and glycerin in the intestinal mucous membrane ;
that of fats from carbohydrates, or from the elements of the broken-down
carbohydrate molecule ; and also, in all probability, that of fats from the
non-nitrogenous moiety of the broken-down proteid molecule. It is clear
from these instances that the importance of syntheses in the animal
economy cannot be overrated, and although the most striking feature in
animal metabolism is the breaking down of complex substances into
others of more simple form, yet even in the case of these broken-down
products there is frequently a subsequent synthesis before they are got
rid of from the body. Instances of this occur in the case of several urinary
products, such as hippuric acid, urea, and uric acid.2

As Bunge3 remarks : " There are two reasons why these synthetic
processes in the animal body have excited the interest of physio-
logists and chemists. In the first place, they were in contradiction
to the long dominant doctrine of Liebig, as to the contrast be-
tween the metabolic processes in plants and animals;4 and, in the

1 Bunge and Schmiedeberg, Arch,, f. exper. Path. u. Pharmakol., Leipzig, 1876, Bd. vi.
S. 233 ; Hoffman, ibid., 1877, Bd. vii. S. 239 ; Kochs, Arch. f. d. ges. PhysioL, Bonn. 1879,
Bd. xx. S. 64 ; Salomon., Ztsclir. f. physiol. Chem., Strassbnrg, Bd. iii. S. 365.

2 On the importance of synthetic processes in animal metabolism, see Pfliiger, Arch. f. d.
ges. PhysioL, Bonn, 1888, Bd. xlii. S. 144. 3 "Lehrbuch," 1894, S. 288.

4 Nevertheless, the main distinction propounded by Liebig, that most plants are able
to obtain their nitrogen, and to build it up into proteid from inorganic materials, whereas
animals do not possess this power, still holds good.

894 METABOLISM.

second place, the methods of synthesis in animal (and vegetable)
organisms are still an unsolved problem, in spite of the fact that
it is the rapid progress in our knowledge of the syntheses of organic
combinations which constitutes the greatest triumph of modern
chemistry. Chemists are already able artificially to build up atom for
atom out of their elements a series of organic compounds, some of a very
complicated nature. We no longer doubt that all the rest, even the
most complex, will be thus produced. Nevertheless the processes
employed in no way represent the synthetic processes of the living cell,
for all artificial syntheses can only be achieved by the application of
forces and agents which can never play a part in vital processes, such as
extreme pressure, high temperature, concentrated mineral acids, and free
chlorine — agents which are immediately fatal to any living cell."

It must nevertheless be admitted, in spite of the numerous instances
of syntheses of organic compounds which have accumulated of late years,
that, so far as the formation of bioplasm is concerned, the only material
from which the animal organism is capable of forming it is proteid, and
this proteid must be present as such in the food. No doubt the ultimate
change of the circulatory or blood proteids to the proteid of bioplasm must
depend upon a special synthesis, but we are necessarily completely ignor-
ant as to the manner in which such synthesis occurs, since we are ignorant
of the actual chemical constitution of both living tissue and dead proteid.

With respect to the breaking-down of the bodystuffs in the process
of metabolism, there are reasons for believing that this consists of two
phases, namely, a splitting of the complex molecules into simpler mole-
cules, and an oxidation of some or all of the simpler substances thus
arising. It is probable that in the metabolism of proteid these two
phases usually, if not invariably, occur at different times, and even in
different places in the body ; for example, the materials derived from
the splitting up of the metabolised proteids of muscle do not all leave
the muscle in a fully oxidated condition, but are, in part at least, in
the form of oxidisable substances, such as lactic acid. Doubtless, in
the formation of the ultimate products, oxidation is the prominent
feature, for these products, in the form in which they leave the body, are,
as compared with the materials that enter the tissues, unquestionably
in a condition of oxidation, in some cases of complete oxidation. There
is, however, no distinct evidence that the process of splitting of the
complex molecules is necessarily immediately combined with that of
oxidation. On the other hand, there is reason to think that such
splitting may occur without immediate oxidation ; for example, the
splitting of proteids, which are taken in the food, into urea and non-
nitrogenous substances. For, in a dog fed with proteid, the urea was
found by Feder to make its appearance in the urine within fourteen
hours after feeding, whereas the removal of the remainder of the proteid
molecule in the form of carbon dioxide and water did not occur for
twenty-four hours after, so that the splitting of the proteid molecule
must have occurred at one time, and its complete oxidation at another.1

It is found that any conditions which tend to diminish the normal
oxidations of the body generally, or of the individual tissues (such as
the ingestion of prussic acid or the cutting off or diminution of the
arterial supply to an organ), cause such substances as lactic acid and
dextrose, which are probably products of proteid and carbohydrate

1 C. Voit, Ztschr.f. SioL, Miinchen, 1891-2, Bd. xxviii. S. 292.

METABOLIC ACTIVITY OF TISSUES AND ORGANS. 895

metabolism respectively, to appear in larger amount than usual in the
blood, and to become excreted in the urine.1

EELATIVE METABOLIC ACTIVITY OF THE TISSUES AND ORGANS.

Before we trace the fate of the foodstuffs in the body, it is
important we should have an idea of the relative metabolic activity of
the tissues, since all essential changes which contribute to the pro-
duction of the energy of the body occur within the tissues.

It was at one time believed that the blood was the seat of
important oxidation processes; but whilst it cannot be denied that a
certain amount of oxidation may occur in the blood, as shown by the
rapid diminution in the oxygen of the oxyhsemoglobin, on allowing blood
to stand in a closed vessel,2 it is certain that by far the greatest part of
the oxidations in the body occurs in the tissues, and especially in the
muscles. It was found by Pfliiger, that frogs whose blood had been
wholly replaced by salt solution took in just as much oxygen, and gave
off just as much C02, as normal animals.3 Moreover, Pembrey and
Giirber found hardly any alteration in the oxidation processes in rabbits
which had been deprived of a large proportion of their blood.4

Placing the tissues in order of relative activity, the muscles must
take the first place ; next to these the secreting glands ; and next to
these the tissues of the nervous system, especially the grey matter.
Last in the scale come the skeletal tissues, which, performing as they
do a passive function, may be assumed to exhibit comparatively little
metabolic activity. With regard to the most active of the tissues,
namely, the muscles and the cells of secreting glands, we may note, in
passing, that their chemical composition is by no means identical.
The most prominent organic material in muscular tissue is native
proteid of the globulin class, whereas the most prominent organic
materials in the living tissue of gland cells are nucleo-proteids. This
distinction, though frequently ignored, is one of considerable import-
ance, for the nucleo-proteids have a constitution more complex than
that of proteids, consisting as they do of a combination of proteid with
phosphorus-containing substances, which yield as products of decomposi-
tion, xanthine bases, nucleins, paranucleins, and phosphoric acid, and
some of them, at all events, a carbohydrate (see pp. 66, 67).5

There can be very little doubt that the greater part of the oxidation
of the body occurs in the muscles. The formation of heat can, in fact,
be shown to be mainly due to the chemical activity of the muscles, an
activity called into play under the influence of the- nervous system ;

1 Zillesen, Ztschr. f. physiol. Chem., Strassburg, 1891, Bd. xv. S. 387; Araki, ibid.,
1891-4, Bde. xv., xvi., xvii., xix.

2 The disappearance of the oxygen of oxy haemoglobin which occurs in blood on standing,
has been ascribed to the presence of hypothetical substances, to which the term "reducing
substances " has been applied. No chemical substances having such a reducing power have,
however, been either isolated from blood or chemically investigated. Moreover, the reduc-
tion of oxyhsemoglobin in blood on standing, may be due to its oxygen being removed
by the bioplasm both of the white corpuscles and of putrefactive bacteria, which rapidly
begin to appear and multiply in drawn blood. Reduction even occurs with solutions of
pure crystallized oxyhsemoglobin hermetically sealed in glass tubes.

3 Arch.f. d. ges. Physiol., Bonn, Bd. x. S. 251 ; see also (Ertmann, ibid., 1877, Bd. xv.
S. 382.

4 Journ. Physiol., Cambridge and London, 1894, vol. xv. p. 449.

6 In connection with this question, the possibility must not be forgotten that even
ordinary proteids may have a carbohydrate nucleus in their molecule (cf. p. 64).

896 METABOLISM.

and the greater the amount of muscular activity the greater the amount
of oxidised materials in the form of carbonic acid and water that are
formed and got rid of from the body. It is probable that the oxidation
processes which occur in gland cells are by no means so active, for
although a gland when stimulated to activity receives a larger amount
of oxygenated blood, yet a considerable amount of the oxygen of that
blood simply passes through the capillaries without being absorbed, so
much so, in fact, that, as noted by Bernard, the blood of the veins of the
salivary glands during stimulation of their cranial nerves flows almost
as bright red as that of an artery. And in confirmation of this we find
that the largest gland in the body, the liver, is supplied with a relatively
small amount of arterial blood, and that almost the whole of its
metabolic activity is carried on with "blood which already has passed
through the intestinal capillaries, and which has thereby been deprived
of a large part of its oxygen. Further, it was noted by Ludwig that the
saliva flowing from the duct of the submaxillary gland contains more
oxygen, than is dissolved in the plasma of the arterial blood, an
indication that the cells of the salivary glands cannot be greedy of
oxygen since they pass oxygen out along with the secretion rather than
retaining it for the formation of carbon dioxide and water. The
salivary glands, moreover, have been shown by the recent careful
observations of Bayliss and Hill l not to produce any appreciable amount
of heat ; and although it is stated that the blood flowing through the
liver is the warmest blood in the body,2 and warmer than that flowing
through the muscles, it must be borne in mind that it is almost
impossible to measure exactly the normal temperature of the blood
flowing from the muscles, because the operation necessary for observing
the temperature of such blood would tend to expose it to loss of heat.3

In conformity with the conclusion that the muscles are the organs which
possess by .far the greatest amount of metabolic activity, it has been estimated
that the muscular tissues contain about one-fourth of the whole blood of the
body. The liver, which has important special functions to perform in
metabolism — functions which are, however, probably in large measure inde-
pendent of oxidation — contains another fourth of the blood, one-fourth is
employed in keeping full the larger arteries and veins, and all the rest of the
body put together has for its capillary supply only the remaining fourth. It
is clear, then, that in all observations and experiments upon the metabolism
of the body, the metabolism of the muscles must occupy a prominent place.

NITROGENOUS METABOLISM IN THE TISSUES.

Of the proteids of the body Voit distinguishes two kinds — (1) Those
which form an integral part of the living substance or bioplasm, and (2)
those which occur in the tissue juice and in contact with the bioplasm,
but which are not to be regarded as forming an integral part of that
substance itself. To this latter kind he has given the name of " circu-

1 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 351. Previously to this
work, it had been accepted, on the authority of Ludwig and others, that the secretion of
saliva is accompanied by a marked production of heat within the submaxillary gland.

2 See p. 826. Waymouth Reid was unable to find any effect on the temperature of the

le result of stimulating the splanchnic and vagi nerves ("Proc. Phys.

liver as the

1895, p. xxxi., in Journ. PhysioL, Cambridge and London, vol. xviii.).

3 In his experiments upon the gaseous exchange in blood perfused through "surviving "
mammalian muscle, v. Frey found that the blood leaving the muscle was slightly warmer
than that entering it (Arch. f. PhysioL, Leipzig, 1885, p. 559).

NITROGENOUS METABOLISM IN THE TISSUES. 897

lating proteid," while the proteid which is assumed to actually form the
living substance of the tissues is termed by Voit, Organeiweiss, which
may be rendered in English by "organ- or tissue-proteid." 1 If the
term " circulating proteid " be used to include the proteids of the blood
and lymph as well as those which occur in the actual interstices, if
any, of the bioplasm, no exception can be taken to it, but if it
is used, as has been sometimes done by Voit, in a restricted sense,
merely to indicate proteid material which is interpolated amongst the
molecules of the proteid forming the bioplasm, without itself actually con-
stituting part of that substance, it must be admitted with Pfliiger 2 that
such employment of the term can only be misleading. Using, however,
the term circulating or unorganised proteid in the wider sense, there are
still two possibilities open as to the manner in which the proteids of the
body undergo metabolic changes — (1) We may assume that the circu-
lating proteid, reaching the tissues and becoming imbibed by them,
must be completely incorporated and built up into them before it is
split up and oxidised ; or (2) it is open to us to suppose that the
unorganised proteid may be split up and oxidised outside the actual
molecules of the organised proteid of the living substance, but as a
consequence of the action of that substance. In the one case we may
suppose it to produce a direct formation or building up of bioplasm — a
transformation, in fact, of unorganised into organised proteid ; in the
other case, as undergoing contact changes by the action of the bioplasm,
much in the same way as contact changes are brought about by organised
ferments.

One reason for believing that the circulating proteid only becomes
in part built up into the material of the bioplasm, is derived from the
following observation (Voit). If, to an animal kept upon a diet con-
sisting of non-proteid food (fat), gelatin is given in an amount sufficient
to replace a caloric equivalent of such non-proteid material, it is found
that, reckoning for the amount of nitrogen due to the metabolised
gelatin, which always appears in full as urea, there is less nitrogen given
off from the body than before ; that is to say, there is less tissue substance
broken down. But in the total absence of nitrogenous food there is a
definite amount of body proteid metabolised ; and since, when gelatin
is given, it is metabolised instead of part of this proteid, although it
cannot itself be built up into tissue substance (p. 878), it must be
assumed that the gelatin has taken the place of proteid which, although
in such intimate contact with the bioplasm as to become metabolised
under its influence, did not actually form bioplasm. It may further
be argued that the rapidity with which metabolic changes in proteids
occur within the body, and the large amount of such metabolism, when
excess of proteid is taken as food, render it improbable that all meta-
morphosed proteid has been built up to form bioplasm.

1 C. Voit, "Die Ernahrang," Hermann's "Handbuch," Bd. vi. S. 301. The terms
"organised" and "unorganised" proteid are preferable to "tissue-" and "circulating-"
proteid, which have been used at different times in different senses. In earlier publications
(Ztsclir. f. BioL, Miinchen, 1874, Bd. x.) Voit included the proteids of blood plasma under
the designation "Organeiweiss," founding this view upon the fact that, as the experiments
of Tschirievv (Ber. d. k. sdchs. Gesellsch. d. PTissensch., 1874, S. 411) and Forster (Sitzungsb.
d. k.-bayer. Akad. d. Wisscnsch. zu Miinchen, 1875, S. 206) seemed to sho\v, transfusion
of blood does not increase the proteid metabolism of the body. Pfliiger, however (loc. cit.,
infra, pp. 362 et seq.) has shown that the results of Tschiriew and Forster are capable of
a diametrically opposite interpretation.

2 Arch.f. d. ges. Physiol., Bonn, 1893, Bd. liv. S. 333.

VOL. i.— 57

898 METABOLISM.

Voit has drawn a much sharper distinction between the organised and
unorganised (tissue and circulating) proteid than that above indicated. He
denies that tissue proteid can as such undergo metabolism, even in inanition.
According to his view, it must first be dissolved up and take the form of
circulating proteid, and be carried in this form to other tissues (e.g. from the
muscles to the heart and nervous system), to be metabolised as circulating
proteid in these.1 This view is, however, difficult to reconcile with the
supposition that there is no chemical difference between the two forms of
proteid,2 for if there is no such difference, it is not clear why the proteid
should not become metabolised in the tissues themselves, but should need to
be conveyed outside them before undergoing metabolic changes. Moreover, it
is entirely inconsistent with the experiments of Oertmann and Pfliiger, of
Pembrey and Giirber, and of Schondorflf (with Pfliiger), which will be subse-
quently referred to.

The arguments and experiments by which Voit has endeavoured to support
his position are, however, quite insufficient to carry conviction, and it must be
regarded as having been rendered completely untenable by the experiments
and criticisms of Pfliiger.3 A view exactly the contrary to that of Voit was
taken by Liebig, and has been maintained by Hoppe-Seyler, and in a some-
what qualified form by Pfliiger. According to this view, it is only organised
proteid which can undergo metabolic changes — never unorganised. Unorgan-
ised proteid must therefore first be converted into organised before it is
capable of metabolism ; in other words, tissue bioplasm must be built up out of
circulating proteids before these last, which then of course have become
tissue proteids, can be broken down and oxidised. It is therefore denied that
any metabolism of proteids can occur outside the actual molecules of the living
substance — that, in short, there can be any contact action. It has, however,
been shown in the case of yeast, that chemical action may take place outside
the living cells, although under their direct agency, so that the possibility of
metabolic changes occurring under the influence of, but outside, the actual
molecules of the protoplasm of cells cannot be denied. Moreover, it is not
probable that the non-proteid materials (fat, carbohydrate, gelatin) of the
food become after assimilation built up into bioplasm, and although they are
undoubtedly taken into cell protoplasm they can hardly be regarded as
forming constituent parts of the molecules of its bioplasm. In this sense,
therefore, they are outside, although in contact with, the bioplasm of the
tissues ; nevertheless they are found to undergo metabolic changes under the
influence of that substance. It may, of course, be argued that they also are
really built up into the living proteid molecule, and must be so before they
can become metabolised, but there is absolutely no evidence that this is the
case, or that fat or carbohydrate are necessary constituents of bioplasm.

The fat drops which we see embedded in the protoplasm of cells, are
certainly not constituent parts of the bioplasm, although under its influence
they undergo physical and chemical changes, and the same is the case with
the glycogen clumps which can be seen in the liver cells, to say nothing of
the starch, aleuron, and fat granules of vegetable cells. The phenomenon of
contact change is in short too universal to be denied. Since this is so, the
most reasonable view to be taken of the matter appears to be one which
supposes that metabolism may occur both as a splitting-up and oxidation of
the molecules of living tissue or bioplasm, and as a splitting-up and oxidation

1 Loc. tit., S. 303.

2 " Ich will also nicht damit einen chemischen Unterschied bezeicbnen, sondern
zunachst nur einen Unterschied in dem Orte an dem es sich befindet. . . . Ein und dasselbe
Molekiil Eiweiss kann in einem bestimmten Momente Eiweiss des Blutplasmas, in einem
nachsten Eiweiss der Ernabrungsflussigkeit, in einem anderen Eiweiss der Lymphe oder
auch Organeiweiss sein " (loc. cit., S. 301).

3 Loc. tit.

NITROGENOUS METABOLISM IN THE TISSUES. 899

both of unorganised proteid and of non-proteid materials outside but in
contact with the molecules of bioplasm. Such a view, which is in a sense
intermediate between the extreme opinions advocated by Voit and Pfliiger
respectively, is consistent with all the known facts, and is more readily applic-
able to the phenomena, both of animal and vegetable metabolism, than the
exclusive acceptance of either of those opinions.

Whether directly or indirectly, tissue proteid normally undergoes meta-
bolism to the extent of about 1 per cent, of its substance per diem (Voit).

The proteids of the food are converted by digestion into albumoses
and peptones ; ultimately, probably, entirely into peptones. They are,
however, not absorbed as peptones, for no peptones are found in the
blood or chyle leaving the intestines. It is clear, therefore, that the
process of assimilation or the reconversion of peptones into proteids
must occur during their absorption, that is to say, in the substance of
the mucous membrane. It must not be forgotten, however, that a
certain amount of the proteid of food may possibly, as occurs in vitro,
be broken down beyond the stage of peptone into simpler nitrogenous
bodies, such as the amido-acids; and these, if their formation really
occurs to any extent in the intestinal tract, would be absorbed as such
into the portal blood and conveyed by it to the liver. Now we know
that the addition of amido-acids to the blood which is allowed to circu-
late through the liver, as well as their administration with the
food, causes an increase in the amount of urea in the blood after it has
passed through that organ, and an increased excretion of urea by
the kidneys.1 From this it may be assumed that any amido-acids
absorbed are converted by a process of synthesis (possibly preceded by
a previous more complete breaking-down, into ammonia compounds) into
urea. If this process of formation of amido-acids occurs at all in natural
digestion, it is obviously a change by which the proteids of the food
would not be directly serviceable for the production of tissue ; and in
this sense such conversion of peptones into amido-acids may be looked
upon as a direct waste of proteid food. It is extremely improbable that
such a change occurs to any extent in the normal organism, nor has the
presence of these substances to any marked degree been determined in
the normal intestinal contents. Moreover, as Bunge remarks, there
is not sufficient carbon in the proteid molecule to permit of all the
nitrogen issuing as amido-acids.2 In any case, these bodies must
probably be split up and oxidised into carbon dioxide and ammonia, and
from these urea become formed by synthesis in the liver. We may
therefore probably put aside as exceptional this mode of transformation
of proteid into urea, and consider only the change which is undergone
by the proteid which is actually assimilated.

With regard to the agents in the mucous membrane which produce the
assimilation of proteids, that is to say the conversion of peptones into proteids,
there can be very little doubt that the columnar epithelium occupies the first
place. It is, however, difficult to prove that the change, which is one of
synthesis and dehydration, does actually occur in these cells. We have chiefly
analogy to guide us in coming to this conclusion. It can be definitely proved
that a synthesis of fat does occur in them ; and it is therefore probable that

1 Schnltzen and Nencki, Ztschr. f. BioL, Miinchen, 1872, Bd. viii. S. 124 ; Salkowski,
Ztschr. f.physiol. Chem., Strassburg, 1879, Bd. iv. S. 100 ; v. Knieriem, Ztschr. f. Biol.,
Munchen, 1874, Bd. x. S. 279.

2 " Lectures," p. 320.

9oo METABOLISM.

other syntheses which accompany assimilation, such as the formation of
proteids from peptones, must also occur within them. Hofmeister l has
suggested that the leucocytes may also take an important part in determining
the assimilation of the foodstuffs. They are present in great abundance in
the intestinal mucous membrane, and especially those parts of that membrane
where absorption proceeds most extensively ; and they are also, it has been
shown, greatly increased in number during the process of absorption. It is,
however, difficult to obtain affirmative evidence upon this point, and since
leucocytes elsewhere do not possess this power, it is improbable that they are
the agents for such conversion in the intestine.

After assimilation the proteids are absorbed by the blood vessels of
the intestinal mucous membrane. *The evidence for this has been
already given in the article on " Digestion and Absorption " (p. 433).
If any proteids are taken up by the lacteals of the small intestine, they
do not get into the thoracic duct,2 but must be transferred to the blood
vessels in passing through the mesenteric glands. At any rate we may
assume that nearly the whole of the proteids are ultimately taken by the
portal vein to the liver. The portal vein, therefore, contains the absorbed
material derived from digestion and assimilation of proteid food; it
must have, therefore (besides the ordinary constituents of blood plasma),
an additional amount of serum albumin or of serum globulin, obtained by
the transformation of the peptones into these materials ; also extractives
of the meat or other forms of proteid diet (which are absorbed equally
by the blood vessels of the intestine), and in addition any products
of further decomposition of peptones, such as the amido-acids, the
possibility of the presence of which we have already discussed. But it
must be borne in mind that the blood flow through the portal system is
so large and rapid, that one could hardly expect these substances to be
absorbed into it in such a proportion that it would be possible to detect
by chemical means any appreciable difference of composition between
the blood of the portal vein and that of the system generally, nor are
there any satisfactory analyses directly showing such difference. Never-
theless there is a distinct physiological difference between the portal
blood collected during absorption of food, and especially of proteid food,
and the same blood collected during the intervals of digestion ; for it has
been shown that in the former case such blood, on being passed through
the liver, shows an increased amount of urea, whereas in the latter case
such an increase is not noticed. It is certain, at any rate, that the
products of absorption and assimilation of proteid foods are carried
to the liver, and, having traced them to this organ, we have next to
consider — (1) Whether they are stored at all within it; (2) whether
they undergo any change in passing through it.

Influence of the liver on proteid metabolism.— With regard to the
possible storage of proteid in the liver, it is open to us to suppose
that an excess of proteid material which is present in the portal blood
as the result of the absorption of proteid food, might be temporarily
taken up, at least in some measure, by the hepatic cells, and, after being

1 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1884-7, Bde. xix. S. 1 ; xx. S. 29 ; xxii.
S. 306.

2 Asher and Barbera found, however, in a dog a marked rise both in the amount of
chyle and of the nitrogen of the chyle (estimated by Kjeldahl's method) during digestion
of purely proteid food, given by a gastric fistula. The rise was greatest at the sixth hour
after feeding, but there Avas a primary culmination at the second hour (CentralbL f.
PhysioL, Leipzig u. Wien, 1897, Bd. xi. S. 403).

INFLUENCE OF LIVER ON PROTEID METABOLISM. 901

stored within them for a time, passed on into the hepatic blood to reach
the general circulation. There is, however, no clear evidence that such
storage takes place in the liver, or that if it does the stored proteid
undergoes any change within the liver cells.

When we examine the secretion of the liver, we find that it contains
a considerable amount of nitrogenous organic material (bile salts), in-
cluding a certain amount of sulphur in organic combination (taurine).
These nitrogenous and sulphur-containing materials can only be derived
from proteids, and since they are formed in greater amount during absorp-
tion of digested products than at other times, it might well be supposed
that they may be formed, at least in part, from the absorbed products
of proteid digestion. As against this conjecture, we cannot, however,
fail to notice that the appearance of these nitrogenous and sulphur-
containing materials in the bile salts is accompanied by a considerable
amount of material in the form of bile pigments, which can only be
derived from the haemoglobin of the red blood corpuscles; and since
haemoglobin readily decomposes into haeniatin, which is probably the
part directly converted, with elimination of iron, into bile pigment, and
a proteid or proteids, it has been conjectured, and with some pro-
bability, that the bile acids are actually derived from this proteid part
of the broken-down haemoglobin molecule. The only direct evidence
that we have of the breaking-down of blood corpuscles within the liver
is derived from certain enumeration experiments, which appear to show
that the number of blood corpuscles per cubic millimetre passing to the
liver is greater than the number per cubic millimetre in the blood flow-
ing from the liver.1 This by itself is not very strong evidence, but it
becomes stronger when we remember that the blood flowing from the
liver may be expected to contain less water than that which reaches
the liver, since there has passed away from it the water of the bile
and also a large amount of lymph. Moreover, the constant presence of
lecithin and cholesterin in the bile may well be associated with the
destruction of red blood corpuscles, which contain, relatively, consider-
able amounts of these substances.

While, therefore, the presence of the bile acids is a clear indication
of the breaking-down of proteid in the liver, their presence does not
necessarily indicate that such proteid is derived from the blood plasma,
bub it is, on the whole, more probable that it arises from the haemo-
globin of blood corpuscles.2

The storage of glycogen in the liver, under circumstances when it
can only be supposed to be formed from proteid, indicates another
change which proteids may undergo in this organ. Such a formation
of glycogen from proteid probably occurs hardly at all during absorption
of a mixed meal, because the amount of carbohydrate absorbed from
such a meal would be more than sufficient to account for the glycogen
stored in the liver ; but, in the absence of carbohydrate from the food,
the proteids may become so split up that one portion of the proteid
becomes converted into urea, or into materials which ultimately form
urea, and the other portion, possibly by becoming first somewhat
broken down and then again synthetised, into glycogen.

A similar conjecture may be made with regard to the fat which is

1 Nicolaides, Arch, de physiol. norm, ctpatli., Paris, 1882, p. 531.

2 According to Kunkel, taurine may be formed from proteids in the tissues generally,
and carried to the liver, Ber. d. k. sachs. Geselisch. d. Wissensch., 1875.

902 METABOLISM,

found in the liver cells during absorption. We must, it is true, assume
that when fat is present in the food, the fat which occurs in the liver
cells during absorption is derived from it ; for the absorbed fat, after
passing through the columnar epithelium cells, in which there is little
doubt that it undergoes metabolic changes, gets into the thoracic duct,
and so into the blood, in which it is carried to the liver and elsewhere.
Nevertheless, in the absence of fat from the food, any fat which is
found within the liver cells may be supposed to be obtained from
proteid after the splitting off of the elements of the urea molecule;
but we must suppose a considerable breaking - down and a re-
synthesis to occur. In both carbohydrate and fat formation we must
recognise the possibility of the preliminary splitting of the proteid
molecule occurring elsewhere than in the liver, although there is no
reason to suppose that the protoplasm of the hepatic cell does not
possess, in common with protoplasm in general, the power to produce
this change. The possibility of fat being formed from proteid is shown
by the fact that in dogs subjected to a twelve-day period of inanition,
and to which phosphorus is then administered, the liver contains from
two to four times as much fat as in the normal animal — the amount
of fat in the muscles being also greatly in excess of the normal amount.1
This question of the formation of carbohydrate and of fat from proteid,
both within the liver cells and elsewhere, will be considered later on.

The circumstances that in mammals urea, and in birds uric acid,
occur in a larger proportion in the liver than in any other organ in the
body, that there is an increase of urea in blood which has been passed
through the liver, provided such blood is derived from an animal during
absorption of proteid food, and that if blood containing certain ammonia
compounds is passed through the liver it receives a very appreciable
addition of urea,2 all point to the fact, which is now unquestioned, that
urea and uric acid are produced, if not exclusively, at all events mainly,
in this organ.

But the urea which is found in the liver, and which is passed by the
hepatic capillaries into the hepatic blood, although ultimately derived
from the proteids of the food, is in all probability not to any appreciable
extent immediately so derived. If this were to be the case, we should
have, as with the formation of leucine and tyrosine in the intestine, so
far as the tissues generally are concerned, a waste of nutritive material —
a condition which is unlikely to obtain to any extent in the animal
economy. It may therefore be taken for granted that the great part of
the proteid which is absorbed from the intestine passes on through the
hepatic veins into the general circulation, without being stored or at
once modified in the liver ; and since, after the absorption of any large
amount of proteid from the alimentary canal, the relative and absolute
amount of proteid in the blood and lymph is not materially altered, we
may assume that the excess proteid is stored somewhere else.

The place of such storage is probably not far to seek. The fact that
an increase of assimilated proteid in the blood rapidly increases the
metabolism of muscles, points at once to such proteid passing into the

1 Storch, Diss., Kjobenhavn, 1865 ; Deutsches Arch. f. Jclin. Med., Leipzig, 1867, Bd. ii.
S. 264; Bauer, Ztsclir. f. Biol., Miinchen, 1871, Bd. vii. S. 63 ; 1878, Bd. xiv. S. 527 ;
Caseneuve, Rev. mens. demed. etchir., Paris, 1880, tome iv. pp. 265, 444 ; Stolnikow. Arch,
f. PhysioL, Leipzig, 1887, Suppl., S. 1.

2 v. Schroder, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1882, Bd. xv. S. 364 ;
ibid., 1885, Bd. xix. S. 273 ; Salomon, Virclww's Archiv, 1884, Bd. xcvii. S. 149.

INFLUENCE OF LIVER ON PROTEID METABOLISM. 903

muscles ; and since such increased metabolism continues during some
time, the excess proteid must be supposed to be in the first instance
stored within them.

The influence of assimilated proteids in increasing the metabolism of
the tissues, and the manner in which such increased metabolism is
brought about, has received the attention of many workers. According
to the view held by Voit, which has been already referred to, such
additional proteid is not built up into the bioplasm of the tissues, but
passes into the tissues, and, by contact with the bioplasm, stimulates it
to increased metabolism ; such metabolism occurring, according to Voit,
entirely in the circulating proteid, and outside, in a sense, the actual
bioplasm. On the other hand, according to the view which has been
strenuously supported by Pfltiger, such excess of proteid is directly
stored, not in the interstices of the bioplasm, but by being built up into
its constitution ; so that this substance grows at the expense of any
excess of proteid pabulum which is brought to it by the circulating
fluid, and such growth or increased nutrition of living substance in itself
directly promotes an increased destruction.

That this view is, at least in part, correct, appears from the experi-
ments by Schondorff, which were carried out under Pfliiger's direction.1
Schondorff perfused blood, taken from a dog which had been kept fasting
for some days — (1) through the limbs, and then through the liver, of a
well-nourished dog, which had been kept chiefly upon proteid food, and
which was killed immediately before the experiment ; (2) through the
limbs, and then through the liver, of a dog which had been kept fasting
for some days ; and (3) blood, which was taken from a well-nourished dog,
was passed through the limbs and liver of a fasting animal. In five
experiments in which blood from a fasting animal was sent through the
organs of a well-nourished dog, the urea of the perfused blood was in-
creased by amounts varying from about a quarter to more than double
its original quantity. Out of five experiments, in which the blood of a
fasting animal was sent through the organs of a fasting animal, the
amount of urea was diminished in two by 9'55 and 6'9 per cent., while
in three it was hardly appreciably altered. In these cases, there-
fore, there was practically no proteid metabolism. In two experiments
in which the blood of a well-nourished animal was sent through the
organs of a fasting animal, the urea of the blood was diminished by
13'5 and 144 per cent. There was therefore also here no proteid meta-
bolism, the diminution of the urea having been probably due to diffusion
out of the blood into the tissues. That the increase which was obtained
by passing the blood of a fasting animal through well-nourished organs
was not due to the diffusion of pre-existing urea from the well-nourished
liver, was determined by a control experiment, in which it was found
that the amount of such diffusion was at most very small.2

These experiments show, according to Pfliiger,3 that the effect of increased
proteid food has been to produce change in the bioplasm, directly causing
this to grow and to become more active in its metabolism ; whereas, on the
other hand, a diminution of proteid food has produced the reverse change,
namely, diminution in amount of bioplasm, with inactivity of proteid

1 Arch.f. d. ges. PhysioL, Bonn, 1893, Bd. liv. S. 420.

2 The amount of urea in the blood of the starved dogs averaged 0*0348 per cent. ; the
maximum amount in the proteid-fed dogs, 0'1529 per cent.

3 Arch.f. d. ges. PhysioL, Bonn, 1893, Bd. liv. S. 408.

904 METABOLISM.

metabolism, even at a time when the tissues are temporarily supplied with
circulating proteid from the blood of a well-nourished animal.

That a continuance of liberal proteid diet does produce an increased growth
of muscular tissue, may also be looked upon as extremely probable, from the
daily experience of athletes. As is well known, the diet upon which training
is chiefly carried out consists very largely of proteid matter, the proteids of the
food being in much larger proportion to the fats and carbohydrates than in the
normal diet of untrained persons. It would appear likely that this, which is
the result of the experience of many generations of trainers, must have a
physiological basis, and that the effect of such excess of proteid in the diet
must in itself not only cause an increase of the proteid metabolism, but also
lead to the formation of actual tissue proteid. Under ordinary circumstances,
however, whether the proteid which passers to the muscles is actually built up
into their tissue, or whether it is simply included in the interstices of the
living substance, it is not stored there for long ; for it is found, after a meal
containing much proteid, that within a few hours practically the whole of the
proteid which has been absorbed is removed in the form of urea.

That the change in proteid which results in the formation of urea
must primarily occur within the muscles, within which, as we have
seen, the greater part of the oxidations of the body occur, there can be very
little doubt. But there has always been this difficulty in connection
with the question, that although urea is the ultimate product of proteid
metabolism, the muscles practically contain either no urea or only a
very small amount. An exception is, it is true, found in certain animals,
e.g. the Elasmobranchf fishes, the muscles of which contain a considerable
amount of urea. But this is not the case with most animals, and it
cannot be supposed that urea is formed to any appreciable amount in
the muscles, especially since we know that by far the greatest amount
is actually formed in the liver.

What precursor, therefore, of urea is formed in the muscles from the
proteid which is metabolised within them ? The nitrogenous substance
which could best be supposed to be produced from the metabolism of pro-
teids, is creatine, since this is the one found in largest amount within
the muscles ; and it is natural to suppose that creatine, which is capable
of being converted in the laboratory without any great difficulty into
urea and sarcosine, might be the immediate precursor of urea. It is,
however, found that if creatine is injected into the blood or subcutane-
ously, or if it is taken with food, and thus absorbed into the blood, it
does not become converted into urea, but is found in the urine as
creatinine ; and we cannot therefore suppose that the creatine of the
muscles is absorbed by the blood, and carried by that fluid to the liver,
and there converted into urea, since we find that creatine added to the
blood does not become so converted.

Without ignoring the possibility that the creatine which is found in
muscle may still be a preliminary stage in the transformation of
proteid into urea, we must look for other products of nitrogenous
metabolism passing from the muscles which, whether derived immedi-
ately from the proteid or indirectly from it through creatine, may be
supposed to be the real precursors of urea. As a matter of fact, such
products are found in the form of ammonia salts. It was noticed by
Schondorff, in the experiments already quoted, that in cases in which
the blood of a fasting animal was sent through the limbs only of a well-
1 Stiideler and Frerichs, Journ. f. prakt. Chem., Leipzig, 1858, Bd. Ixxiii. S. 48.

INFLUENCE OF LIVER ON PROTEID METABOLISM. 905

nourished animal, there was an increase of ammonia salts in the blood.
It is also a well-established fact that certain ammonia salts passed
through the liver along with the blood become synthetised within the
liver into urea. The actual form which such ammonia salts probably
take is that of a combination with sarcolactic acid, which is also,
as is well known, produced in muscle, and which is found, probably
in combination with ammonia, in the blood generally.1 These facts
render it not improbable that the ultimate condition of the proteid
which has been metabolised in muscle is lactate of ammonia (whether
passing through the intermediate condition of creatine or not). This
lactate of ammonia passing into the general circulation and being
conveyed to the liver is there converted in mammals into urea, in
birds into uric acid, in which form it is excreted by the kidneys. In
conformity with this it was found by Marfori 2 that lactate of ammonia
injected into the vein of a dog at the rate of 60 to 100 mgrms. per
kilo, per hour, was wholly changed to urea.3 The rest of the molecule,
there can be very little doubt, is oxidised and got rid of in the form
of carbon dioxide and water.

What intermediate changes may be gone through between the
splitting of the proteid molecule into a nitrogenous and non-nitrogenous
part, and the ultimate oxidation of the non - nitrogenous part into
carbon dioxide and water, is a matter mainly of conjecture ; but since we
find within the muscular tissue, as an almost constant constituent,
glycogen, it is conceivable that in part at least the split-off non-
nitrogenous portion of the proteid molecule may first become converted
into that substance, and possibly into grape-sugar, to be subsequently
further split up and oxidised to form the ultimate products of oxidation.

That the proteid molecule can split up into a nitrogenous part and a
part which is capable of being converted into carbohydrate, is shown
very strikingly by the phenomena of diabetes, whether natural and of
the severe form, or whether due to the administration of phloridzin or
pancreatic extirpation. In these cases, even when the diet is ex-
clusively proteid, or even when food is altogether withheld and the
starving animal is compelled to live mainly upon the proteids of its own
tissue, sugar becomes formed in great amount, and must be produced by
the transformation of proteids. It is not unreasonable to suppose that
this is merely an abnormally heightened form of the normal condition
of things, and that under ordinary circumstances a similar transformation
of the proteid molecule may go on in the muscles, for in phloridzin
diabetes at any rate 4 the formation of sugar is independent of the liver.

With regard to the sulphur of the metamorphosed proteids, this

1 Gaglio, Arch. f. Physiol. , Leipzig, 1886, S. 400. Gaglio showed not only that lactic
acid is constantly present in the blood, but that its amount is increased in blood perfused
through various "surviving " organs (kidneys, lungs). See also p. 159 of this volume.
V. Frey also obtained an increase of lactic acid in blood which had been perfused through
"surviving" muscle (Arch. f. Physiol., Leipzig, 1885, S. 533).

2 Arch.f. exper. Path. u. PharmakoL, Leipzig, 1893, Bd. xxxi. S. 71.

3 Minkowski found that in geese, after extirpation of the liver, the ammonia of the urine,
Which in normal geese amounts to from 9 to 18 per cent, of the total nitrogen, Avas
increased to from 50 to 60 per cent. (Arch.f. exper. Path. u. PharmakoL, Leipzig, 1886, Bd.
xxi. S. 41; and ibid., 1893, Bd. xxxi. S. 214), whilst the uric acid almost disappeared.
The ammonia was in the form of lactate, although in the normal animal there is no
appreciable amount of lactic acid in the urine.

4 In pancreatic diabetes, according to Marcuse ( Verhandl. d. physiol. Gesellsch. zu
Berlin, 1893-4, S. 98), this is not the case. Frogs deprived of liver, as well as pancreas,
although they lived 3 to 5 days, showed no glycosuria.

906 METABOLISM.

undoubtedly is mainly transformed by oxidation into sulphate, for it is
found that the sulphates of the urine go hand in hand with the amount
of proteid metabolism which is proceeding (see also p. 630).

Nitrogenous metabolism in the liver. — That a very important part
of the nitrogenous metabolism of the body occurs in the liver, has been
insisted upon, and the experiments which have led to our knowledge on
this matter have already been incidentally referred to.

Urea. — The evidence of the formation of urea in the liver was
obtained by v. Schroder in a series of researches of remarkable interest
and importance. Schroder1 first determined that this substance was not
formed in the kidneys, at least exclusively. He found that when the
kidneys were extirpated in a dog, the amount of urea in the blood was
increased in the next twenty -four hours to four times the normal
quantity (from 0'05 per cent, to 0*2 per cent.). Nor was he able to
obtain any increase of urea in blood passed through the kidney, even
when such blood contained substances (e.g. carbonate of ammonia) which,
by the liver, are capable of being synthetised into urea. This is the
more striking, because, as we have seen, the kidneys are capable of
performing such an important synthetic process as the formation of
hippuric acid from benzoic acid and glycine (Bunge).

Schroder also showed that urea is not formed in the muscles.
He found that blood containing carbonate of ammonia, when perfused
through the hind-limbs of a dog, showed no increase of urea. On the
other hand, blood similarly treated, and passed several times through
the liver of a freshly-killed animal, was found to contain twice or three
times the amount of urea which it had before passing through the
organ. It was necessary for success in these experiments that the liver
should be taken from a well-nourished animal. If removed from a
fasting dog no urea was formed. A similar result, obtained by
Schondorff, has been already referred to (p. 903).

These experiments were repeated by Salomon2 both upon sheep
and dogs. They show conclusively that the liver is capable of
forming urea from carbonate of ammonia. We have already seen
that it is also capable of forming urea from blood containing the
products of digestion. Other salts of ammonia besides carbonate
are found to be effective; amongst others lactate and carbamate
of ammonia, and also the amido-acids, such as leucine and glycine.
On the other hand, in extensive disease of the liver, especially
of rapid occurrence, and in experiments involving removal of the
liver in mammals, combined with the establishment of a communica-
tion between the portal and the general venous system, so that
there should be no stasis of blood in the capillaries of the intestinal
circulation, ammonia salts are found to largely replace urea in the urine,
such salts taking the form of lactates and of carbamates (p. 908). With
partial extirpation of the liver,8 and also with phosphorus poisoning, in
which the liver cells undergo extensive degeneration, there is also a
greater or less diminution of urea in the urine, and a corresponding
increase of ammonia; as regeneration occurs, the urea becomes again
gradually increased. The same has also been noted in extensive disease
of the liver, especially when of rapid occurrence, but also in cases of

1 See note 2, p. 902. 2 Ibid.

3 Ponfick (in rabbit), Virchow's Archiv, Bde. cxviii. S. 225 ; cxix. S. 193, cxxxviii. Suppl.
S. 81 ; v. Meister (in cat and dog), C'entralbl. f. allg. Path. u. path. Anat., Jena, 1891, Bd. ii.

UREA. 907

cirrhosis ; the ammonia is usually accompanied by lactic acid.1 In acute
yellow atrophy there is besides a considerable amount of leucine and
tyrosiiie. When carbonate of ammonia is administered to mammals, the
excretion of ammonia is not increased in the urine, but urea is formed
in proportion to the amount of ammonium carbonate ingested.2

It is possible that, as Drechsel 3 supposes, carbamate of ammonia may be
the immediate precursor of urea, the carbonate being first converted into
carbamate and then into urea. By elimination of one molecule of water,
carbonate of ammonia forms carbamate, and by elimination of a second
molecule, urea.4

/0(NH4) /NH2 /NH2

c=o c=o c=o

\0(NH4) \0(NH4) \NH2

(carbonate of ammonia) (carbamate of ammonia) (urea)

When chloride of ammonia is administered with the food in herbivora
(rabbits), the whole of the ingested ammonia appears as urea in the urine,
but in carnivora and in man some of the ammonia is excreted in the urine.5
The difference is due to the fact that the inorganic salts of the food of
herbivora contain an excess of potassium carbonate. This takes the hydro-
chloric acid from the chloride of ammonia, and carbonate of ammonia is
formed, which is readily converted into urea. But when there is an excess of
proteid in the diet, sulphuric acid is formed by oxidation, and this combines
with any bases present, so that the ammonia is not set free from the hydro-
chloric acid, and the chloride of ammonia passes unchanged (Bunge). In
fasting dogs all the ammonia administered may be recovered from the urine.6

It is obvious that the formation by synthesis of the neutral substance
urea from the alkaline salt, carbonate of ammonia, which is formed in the
metabolism of proteid, is a protection from the deleterious effects which
might otherwise ensue from too high an alkalinity of the circulating fluid
and urine.

The presumption, therefore, undoubtedly is, that under ordinary
circumstances the ultimate transformation of the products of nitro-
genous metabolism takes place under the influence of the hepatic cells.7

1 For references consult Bunge's "Lectures," pp. 327 and 345; also Neumeister,
"Lehrbuch,"S. 315.

2 Hallervorden (with Schmiedeberg), Arch. f. exper. Path. u. PharmaJcoL, Leipzig,
1880, Bd. xii. S. 237 ; Federand E. Voit, Ztschr. f. Biol., Miinehen, 1880, Bd. xvi. S. 177.
Feder and Voit found that acetate of ammonia also forms urea. The same thing was
determined for citrate of ammonia by Lohrer, with Buchheim (Diss., Dorpat, 1862). This
is the reason why citrate of ammonia does not, like citrate of potash, make the urine
alkaline. Both citrates are converted into carbonates in the body, but the carbonate
of ammonia becomes transformed into the neutral urea, while the carbonate of potash
passes as such into the urine.

3 Ber. d. k. sacks. Gesellsch. d. Wissensch., 1875, S. 171 ; Journ. f. praU. Chcm.,
Leipzig, 1875, 1ST.F., Bd. xii. ; 1877, Bd. xvi. ; 1880, Bd. xxii. ; Arch. f. Physiol., Leipzig,
1880, S. 550.

4 Hoppe-Seyler (Ber. d. deutsch. chem. Gesellsch., Berlin, 1874, Bd. vii. S. 34) and
Salkowski (Centralbl. f. d. med. Wissensch., Berlin, 1875, S. 913 ; and Ztschr. f. physiol.
Chem., Strassburg, 1877, Bd. i. S. 26) regard it as probable that cyanic acid may be the
immediate precursor of urea, which is readily formed from cyanate of ammonia. But the
evidence in favour of this supposition is by no means sufficient, whereas that in favour
of ammonium carbonate (and carbamate) being the precursor, is very strong.

5 v. Knieriem, Ztschr. f. Biol., Miinehen, 1874, Bd. x. S. 263; Salkowski, Ztschr. f.
physiol. Chem., Strassburg, 1897, Bd. i. S. 1.

"6 Feder, Ztschr. f. Biol., Miinehen, 1877, Bd. xiii. S. 256.

7 Richet has shown that a urea-forming ferment can be precipitated by alcohol from
aqueous extract of liver (Oompt. rend. Soc. de biol., Paris, 1894, p. 525).

908 METABOLISM.

It must not, however, be assumed that the whole of this ultimate
metabolism occurs in the liver, for, as a matter of fact, after complete
destruction of the liver by disease, or after its complete removal or
destruction by operation, the urea of the urine does not wholly dis-
appear, although in large measure replaced by ammonium salts (and
under some circumstances by leucine and tyrosine). It is not certainly
known in what other organs urea may be formed. The occurrence of a
large amount of urea in the muscles of Elasmobranchs might seem to
point to the muscles as the possible source of such urea.1 But, on the
other hand, as we have seen, v. Schroder was unable to obtain any
evidence of the appearance of urea in blood perfused through muscles
of dogs. It is, on the whole, more probable that other glandular organs
may have some share in its production.2

The total removal or destruction of the liver in mammals has been
rendered possible, by the discovery that it is feasible to establish a permanent
communication between the portal vein and the inferior vena cava (Eck's
fistula),3 and thus, after tying the hepatic artery as well as the portal vein, to
shunt the liver altogether out of the circulation ; in fact, after such a fistula
is established, the organ may be altogether removed. A large number of
such operations have been made upon dogs by Halm, Massen, Nencki,
and J. Pawlow, and the results upon general, and especially nitrogenous
metabolism, carefully recorded.4 About one-third of the number in which
the fistula was established recovered from the effects of the operation, but
those in which the organ was completely removed only lived a few hours.
Many of those with the Eck fistula refused food. These soon showed
symptoms of convulsions, and eventually died. Those which fed well
recovered weight, and showed no very obvious symptoms, unless given an
excess of proteid food; this invariably brought on convulsions. The same
result was produced by giving carbamic salts with the food (although these
produce no such symptom in normal dogs). The urea was only slightly
diminished in those with the Eck fistula only (but greatly so when the liver
was completely removed) ; the uric acid excreted was at first greatly increased
(four times), but afterwards became normal ; the ammonium salts in the urine
were increased, and were partly in the form of carbamate. Merely tying the
hepatic artery in rabbits may also cause the appearance of ammonium lactate in
the urine,5 a result probably due to interference with its oxidation to car-
bonate of ammonia, and the synthesis of this to urea. The amount gradually
diminishes, under these circumstances, as a collateral arterial circulation
becomes established in the liver.

Nencki, Pawlow, and Zaleski6 found that the portal blood of flesh-fed dogs
contains three and a half times as much ammonia as the hepatic blood.
Nevertheless the amount in the portal vein (which they calculated to have
been 4 '73 grms. in ten hours in a dog weighing 9 '5 kilos.) was too small to

1 The muscles of Elasmobranchs were found by v. Schroder (Ztschr. f. pliysiol. Chem,,
Strassburg, 1890, Bd. xiv. S. 576) to contain 2 per cent, of urea ; the blood, 2' 6 per cent. ; the
liver, 1 '36 per cent. The amount found in the muscles remained the same after removal
of the liver. It is therefore evident that the conditions of nitrogenous metabolism are
quite different in these animals from those met with in mammals.

2 Cf. Miinzer, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1894, Bd. xxxiii. S. 164;
Kaufmami, Arch, de physiol. norm, etpath., Paris, 1894, p. 531.

3 Eck, Trav. Soc. d. natur. de St. P&ersbmirg, 1879, tome x.

4 Arch, de sc. biol., St. Petersbourg, 1892, tome i. p. 401 ; Arch. f. exper. Path,
u. Pharmakol., Leipzig, 1893, Bd. xxxii. S. 161. See also Stern, ibid., Bd, xix. S. 45 ;
and v. Schroder, ibid., S. 373.

5 Zillessen, Ztschr. f. physiol. Chem., Strassburg, 1891, Bd. xv. S. 387.

6 Arch. f. exper. Path. u. Pharmakol., Leipzig, 1896, Bd. xxxvii. S. 26.

URIC ACID. 909

account for the whole of the urea excreted by the kidneys ; they consider,
therefore, that it must be partly formed in other organs.

Uric acid. — In those animals in which the ultimate product of
nitrogenous metabolism is uric acid instead of urea, it is probable that
the primary changes which go on in the muscles result in the formation
of similar substances (lactic acid and ammonia) as are formed as
antecedents of urea, and that the secondary change to uric acid occurs
in the liver. For, after extirpation of the liver in birds, these substances
are found in the urine replacing uric acid.1

Minkowski 2 removed the liver in geese, taking advantage of the fact that
in birds there exists a vein (Jacobson's vein) which effects a communication
between the portal vein and the vena advehens of the kidney, so that when the
portal vein is tied beyond this communication the blood of the mesenteric veins
passes through the kidneys, and is not caused to stagnate as in mammals. In
some animals he merely tied the portal vein, in others he completely removed
the liver ; these, however, only survived the operation a few hours (at most
twenty). The uric acid of the urine sank as the result of this operation, so that
from representing 60 to 70 per cent, of the total nitrogen of that secretion, as in
normal animals, it represented only 3 to 6 per cent., the amount of ammonia in
the form of lactate being correspondingly increased. The lactic acid found in
the urine under these circumstances is the sarcolactic which is formed in
muscular tissue ; it is present in even larger proportions than ammonia, so that
the urine is strongly acid. Altogether half the solids of the urine were formed
of ammonium lactate, although in the normal animal none is present. No
amido-acids were found in the urine, and no sulphates. The urea and creatine
were unaltered in amount. In the blood, lactic acid was present and also some
leucine and tyrosine. Urea injected into the stomach appeared as such in
the urine, although in the normal goose it is converted into uric acid. The
administration of glycine and asparagine caused a great increase in the
ammonia of the urine. The same effect as extirpation — namely, the replace-
ment of uric acid by lactate of ammonia — may be produced by merely tying
the hepatic artery in birds,3 a result which is probably due to the fact that the
oxidations within the organ have been thereby so greatly interfered with, that
the transformation of the lactate of ammonia into carbonate and the subsequent
synthesis of uric acid has been prevented. That uric acid can be formed in
vitro from lactic acid, ammonia, and carbonic acid, has been shown by
Horbaczewski, who obtained uric acid by heating trichlorlactamide with urea
(see p. 587).

We are, however, not justified in assuming that the uric acid which
is found in the urine of mammals runs a parallel course in its formation
with that taken in the formation of urea. For, in the first place, it is not
in them, as in birds, necessarily increased in amount by the ingestion of
proteid food, nor does it go hand in hand with the excretion of urea.
And whereas in birds the ingestion of the amido-acids and of ammonia

1 v. Schroder showed that uric acid is not formed in the kidneys in birds and snakes,
but that after the removal of those organs it accumulates in the blood and tissues (Arch. f.
PhysioL, Leipzig, 1880, Suppl. S. 113; Beitr. z. Physiol. C. Ludwig z. s. 70 Geburtst.,
Leipzig, 1887, S. 89). v. Schroder also showed, in confirmation of an earlier observation of
Meissner, that the liver of birds contains more uric acid than the blood. According to
A. Garrod (Proc. Roy. Soc. London, 1893, vol. liii. p. 478), there is no uric acid normally
in birds' blood, and this contains as much urea as that of a mammal. Garrod is of opinion
that uric acid is produced in the kidneys by synthesis of urea and glycine. If the results
of v. Schroder are correct, it is difficult to understand this conclusion.

*Arch.f. exper. Path. u. PharmakoL, Leipzig, 1886, Bd. xxi. S. 41.

3 Minkowski, ibid., 1893, Bd, xxxi. S. 214.

9io METABOLISM.

salts is followed by an increase of uric acid in the urine, such substances
given with the food to mammals and man produce only an increase in
the urea excreted. The same thing occurs even when uric acid itself is
given to dogs, whereas the addition of urea to the food of birds produces
an increase in the uric acid excreted.1 There is in fact a fundamental
difference in this respect between the proteid metabolism of mammals as
compared with birds and reptiles, but the difference is in the later stage
of such metabolism, which occurs in the liver, and not in the earlier
stage, which occurs in the muscles. It has been noticed that in
mammals the diet which most tends to produce an increase of uric
acid is glandular substance and especially thymus gland, which con-
tains a large amount of nucleo-proieid. It is not increased by a
flesh diet, unless this includes nucleo-proteids ; whereas in affections in
which there is an increased formation (and presumably therefore also an
increased destruction) of lymph cells (leucocytosis), a marked increase of
uric acid has been noticed (e.g. in leukemia).2

For a further discussion of this subject, see " Chemistry of the
Urine," pp. 593-596.

Mares 3 found the uric acid of the urine to be increased during digestion ;
he ascribes this to the activity of glandular cells and increased metabolism of
nucleo-proteids. In accordance with this view, he found pilocarpine to
produce a similar increase. Horbaczewski 4 found the uric acid diminished
in cases of cirrhosis of the liver, and concludes, therefore, that it is not
formed in man in this organ. On the other hand, by digesting spleen
pulp (which normally contains neither uric acid nor xanthin nor hypo-
xanthin) with arterial blood at 40° C., he obtained a considerable forma-
tion of uric acid, and the same when nuclein was used instead of spleen
pulp.

Uric acid given to mammals (dogs) with their food does not increase the
uric acid of the urine but the urea. In all probability it becomes transformed
into urea in the liver. The uric acid which is found in the urine, and which
has probably been formed from the nucleo-proteid of the food, or of degenerated
cells of the tissues, may be supposed to have reached the kidneys without
having passed through the liver.

If in a dog with an Eck's fistula the uric acid in the urine be estimated,
and the hepatic artery then tied, it is found that the uric acid in the urine is
largely increased. This may be explained by supposing that the uric acid
formed from the products of disintegration of nucleo-proteids of cells, such as
those of the spleen and lymphatic glands, has not been transformed into urea,
as would be the case were it allowed to pass through the liver. Those
products of disintegration are proteids, phosphates, and xanthin- (alloxuric)
bases. The latter partly undergo further oxidation into uric acid, partly are
eliminated directly by the kidneys as xanthin or hypoxanthin. They are
increased in blood which has been perfused through almost all organs of

1 Hypoxanthin given to birds also markedly increases the uric acid of the urine ; this
also occurs, however, when the liver is removed. It is therefore probably transformed by
a process of simple oxidation in the tissues (v. Mach, with Minkowski, Arch. f. exper.
Path. u. PharmakoL, Leipzig, 1887, Bd. xxiii. S. 139).

2 Stadthagen, Virchow's Archiv, 1887, Bd. cix. S. 390, found no uric acid in the spleen
or liver in cases of leukaemia, but abundance of xanthin and hypoxanthin. There was a great
increase of uric acid in the urine, but this was not further increased by giving uric acid
with the food.

3 Arch, slaves de biol., Paris, 1887, tome iii. p. 207.

4 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1889, Bd. xcviii., Abth. 3, S. 301 ; ibid.,
1891, Bd. c. S. 78 ; Arch. f. PhysioL, Leipzig, 1893, S. 109, Of, Mares, Sitzungsb. d. k.
Akad. d. Wissensch., Wien, Bd. ci., Abth. 3, S. 12.

INFLUENCE OF ACTIVITY ON PROTEID METABOLISM. 911

the body, but especially those with much lymphoid tissue.1 In amphibia
and fishes the oxidation to uric acid does not occur, and this substance is not
found in the urine.2 Part of the uric acid of the bird's urine appears to be
produced in the same manner as in mammals, and does not disappear after
extirpation of the liver.3

Influence of muscular activity on proteid metabolism. — As
we have already insisted upon, the greater part of the metabolism of
the body goes on in the muscles. This is the case both when at rest
and in activity, but their metabolism is greatly increased during activity.
This is sufficiently shown by the fact that a much larger amount of
carbonic acid is given off from the body when the muscles are con-
tracting actively than when in a condition of rest ; and the chemical
changes which can be shown to occur in the muscles as a result of
contraction, such as the production of sarcolactic acid and of C02, as
well as the disappearance of glycogen, must mean increased metabolism.

Although there is a general consensus of opinion that the C02 output
of the body is largely increased as a result of muscular activity, the evidence
that the C02 leaves the muscles as such is by no means conclusive. The
observations which have been made upon this subject are of two kinds,
namely, (a) the observation of the C02 given off by excised "surviving"
frog's muscle, tetanised at intervals, as compared with the amount given off by
corresponding muscle at rest ; and (b) the observation of the amount of C02 in
the venous blood of the muscles of mammals, taken during conditions of rest
and of contraction of the muscles respectively. The best-known experiments
of the first kind are those of L. Hermann,4 in confirmation of the results of
Matteuci 5 and Valentin,6 who found that the C02 yielded by tetanised frog
muscles was greater in amount than that yielded by resting muscles under like
conditions. The difference, however, was greatly diminished by agitation of
non-contracting muscles. A careful repetition of this experiment, conducted
in 1893-4 in my laboratory, by L. Hill,7 failed to show to the most careful
analysis any appreciable difference in the C02 output of two such
sets of muscles (contracting and resting). Similar experiments by Tissot8
yielded results confirmatory of those of Hermann. Recently the question
has been again investigated by Fletcher,9 who employed a titration method
for the estimation of the C02, and made use of the extremely accurate ap-
paratus devised by Blackman 10 for estimating the gaseous exchanges in plants.
Fletcher, both with skeletal and with cardiac muscle (tortoise), was able
to obtain only the smallest possible difference of C02 output between rest
and contraction, and he comes to the conclusion that the contrary
results obtained by Hermann and others are due to the prolonged stimula-
tion inducing the commencement of rigor mortis, a condition which is
attended by a considerable output of C02. The other method of investi-
gation, by the estimation of the C02 contained in the blood which has
passed through muscular tissue, as compared with that entering it, was
first undertaken by Ludwig and Sczelkow n upon muscles in situ in the

1 Horbaczewski, Monatsh. f. Chem., Wien, 1889, Bd. x. S. 624, and loc. cit., supra.
2Nebelthau, Ztschr. f Biol. , Miinchen, 1889, Bd. xxv. S. 129.

3 Minkowski, loc. cit.

4 " Stoffwechsel der Muskeln," Berlin, 1867.

5 Ann. de chim. etphys., Paris, 1856, Ser. 3, tome 47.

6 Arch. f. physiol. ffeilk., Stuttgart, 1857.

7 Hitherto unpublished.

8 Arch, de physiol. norm, etpath., Paris, 1894-5.

9 Communication to the Physiological Society, May 1897, not yet published.
10 Phil. Trans., London, 1895, vol. clxxxvi. p. 485.

"Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1862, Bd. xlv.

912 METABOLISM.

living animal, and by Ludwig and Schmidt1 upon separated and perfused
muscles of the dog. Most of these experiments showed an increase of CO.,
during contraction, but in some there was no increase. Minot2 (also with
Ludwig), using serum for perfusion instead of blood, could find no relation
between the C02 output and the contraction of the muscles. He came to the
conclusion that CO., is not one of the disintegration products formed during
contraction. Frey and Gruber,3 using somewhat improved methods, have,
however, obtained more distinct evidence of an increase of C02 during con-
traction ; and a similar result was got by Chauveau and Kaufmann,4 who
investigated the amount of C02 in the blood passing to and from the levator
labii inferioris of the horse when at rest, and when in natural activity during
mastication. It must be stated, however, that the results obtained by per-
fusion of separated mammalian muscles are not altogether free from the
objection raised by Fletcher regarding the excised surviving muscles of the
frog, that prolonged excitation may tend to hasten the approach of rigor.

It is therefore not absolutely certain whether the C02, which is ultimately
produced as a result of muscular activity, actually leaves the muscle as such,
or in some other form, such as lactic acid, which is destined to be further
oxidised elsewhere.5

The most interesting question in connection with the special meta-
bolism of the muscles which remains to be considered, is the effect
which their exercise produces upon the proteid metabolism of the body.
It was the opinion of Liebig that the energy of muscular contraction
was produced by the oxidation of muscular substance, and it would
follow from this that the exercise of the muscles must tend, ceteris
paribus, to increase the amount of nitrogen excreted in the urine.
This doctrine of Liebig was accepted for many years by physio-
logists, but was, for a time at least, completely overthrown by the
results of the famous experiment of Fick and Wislicenus,6 known as
the experiment of the ascent of the Faulhorn. It was shown by
these observers that at least three times as much work was clone
during the ascent as could be accounted for by the oxidation of proteid,
as estimated by the amount of nitrogen eliminated by them during and
after the work.

The work, therefore, could only have been caused by the oxidation
of non-proteid matter. Similar results were obtained by Parkes 7 and
others in man, and by C. Voit in dogs.8 This, combined with the fact
that the C02 output of the body is increased in proportion to the
amount of exercise, led to the view being widely adopted that the
energy of the body is mainly, if not entirely, obtained by oxidation of
non-proteid materials, and that the splitting and oxidation of proteid

1 Arb. a. d. physiol. Anst. zu Leipzig, 1868.

2 Ibid., 1877.

3 Arch. f. Physiol., Leipzig, 1885, S. 519.

4 Compt. rend. Acad. d. sc., Paris, 1887.

5 For other observations and statistics on the subject, see article "Chemistry of
Respiration."

6 Vrtljschr. d. naturf. Gesellsch. in Zurich, 1865, Bd. x. S. 317.

7 Proc. Ray. Soc. London, 1872, vol. xx. p. 402.

8 See Hermann's "Handbuch," Bd. vi. S. 187. The experiments of Parkes, Voit, and
North (as well as those by Pavy, Austin Flint, and others, which cannot here be re-
ferred to in detail), were made upon men and dogs taking walking exercise. It has been
determined by Zuntz and Katzenstein (in man and horse) that each kilogram metre of ascent
work is accompanied by a consumption of oxygen thirteen times that consumed in each
metre of walking exercise (Arch. f. Physiol., Leipzig, 1890, S. 367, Verhandl. d. physiol.
Gesellsch. zu Berlin).

INFLUENCE OF ACTIVITY ON PROTEID METABOLISM. 913

must contribute, under the ordinary circumstances of a mixed diet, but
little to the production of muscular energy.

Many other experiments have been performed of a like nature, and
leading practically to the same conclusion. A few, however, have given a
result which has shown a somewhat increased amount of nitrogenous
excretion,1 but it will be found on an examination of these that in every
case there has either been an excessive amount of work done, leading to
probably an abnormal condition of metabolism,2 or there has been taken
in with the food an insufficient amount of non-proteid material to pro-
vide the necessary oxidation and energy for the work required to be done,
plus the maintenance of body-temperature. Under such circumstances,
it is clear that the proteid material of the food must be called upon for
oxidation and the formation of energy, and we should then naturally
expect an increased amount of urea in the urine.

Based upon experiments which come under this heading, Pniiger 3
and his pupils have shown a tendency of late years to return to the
original doctrine of Liebig, and to throw over the view which has been
accepted almost exclusively since the experiment of Tick and Wislicenus
above referred to. Thus Argutinsky,4 working with Pfliiger, found, in
repeating the experiment of Tick and Wislicenus in a somewhat modified
form, that there was a marked increase (12 to 25 per cent.) of nitrogen
excreted, if not so much during the actual performance of the work, at
any rate during the two days succeeding it, and that from 75 to 100 per
cent, of the total work done could be accounted for by oxidation of
proteid ; even with 100 grins, of sugar added to the diet, there was still
an excess of N excreted sufficient to account for 25 per cent, of the
work done. Similar experiments by Krummacher and others yielded a
like result.5 It has, however, been pointed out by I. Munk,6 that the
conditions of the experiments of Argutinsky are not the same as those of
Tick and Wislicenus, in so far as the amount of food which was taken
by Argutinsky and Krummacher had an insufficient caloric value to
produce the required amount of energy, that of Argutinsky representing
only 18 calories per kilo. ; that of Krummacher only 28 calories per
kilo., whereas a man at rest requires 32 calories per kilo. ; as a natural
result, a part of the proteids of the body was called upon for the pro-
duction of the necessary energy. That, given a sufficient amount of
proteid food, and an insufficient amount of non-proteid food, a large
amount of muscular energy can be produced by oxidation of the proteid
is no doubt true. Thus, a dog which was kept by Pfliiger for some
months upon lean meat, containing a very small amount of non-proteid

1 Cf., for example, Austin Flint, Journ. Anat. and PhysioL, London, vol. xi. p. 109,
and vol. xii. p. 91 ; Pavy, Lancet, London, 1876, vol. ii. Nos. 22-26 ; 1877, vol. i. No. 2 ;
W. North, Proc. Hoy. Soc. London, 1883, vol. xxxvi. p. 11.

2 That such nitrogen increase is associated with abnormal conditions, appears from the
experiments of Oppenheimer (Arch. f. d. ges. PhysioL, Bonn, 1880, Bd. xxii. S. 40 and
Bd. xxiii. S. 446), of Zuntz and Scherniberg (Arch. f. PhysioL, Leipzig, 1895, S. 378), and of
Oddi and Tarulli (Bull. d. r. Accad. med. di Roma, tome xix. pp. 2 and 57).

3 "Die Quelle der Muskelkraft, " Arch. f. d. ges. PhysioL, Bonn, 1891, Bd. 1. S. 98.

4 Arch.f. d. ges. PhysioL, Bonn, 1889, Bd. xlvi. S. 552.

5 Ibid., 1890, Bd. xlvii. S. 454; see also Pfliiger and Bohlaud, ibid., 1885, Bd. xxxvi.
S. 165 ; Bleibtreu and Bohland, ibid., 1886, Bd. xxxviii. S. 1.

6 Arch. f. PhysioL, Leipzig, 1890, S. 557 (Verhandl. d. physiol. Gesellsch. zu Berlin,
1889-90, No. 12). Cf. also Hirschfeld, Firdww's Archiv, 1890, Bd. cxxi. S. 501, who
obtained a marked increase of N in the excreta when working on insufficient diet, but not
when the diet, whether proteid or non-proteid, was sufficient. Further, Sonde'n and
Tigerstedt, Skandin. Arch.f. PhysioL, Leipzig, 1895, Bd. vi. S. 181.

VOL. I. — 58

914 METABOLISM.

matter, was nevertheless able to perform a large amount of muscular
work, metabolising at the same time a very considerable amount of
proteid, the oxidation of which could have been the only source of the
greater part of the energy. Whether, however, as Pnliger holds, the
living tissue prefers to employ proteid, when it has sufficient offered to it,
for the production of work, or whether, as is generally supposed, it
uses up first the available non-proteid material for the production of
energy, and only secondarily calls upon the proteid for the purpose of
oxidation and energy production, is a matter which it is not at all easy
to settle. That proteids enter largely into the diet of athletes is a
fact which is of some importance in connection with the question.
But "although for short periods athletes are unquestionably capable of
doing a very large amount of work, it must be remembered that their
diet is by no means rigidly confined to proteid substances. It must
also be borne in mind that there is a large class of labourers both in
this, but more especially in other countries, who get through a much
larger average amount of work per diem than is performed by athletes,
and who, nevertheless, frequently have an amount of proteid in their diet
the oxidation of which is altogether insufficient to account for the work
done. The fact that a proteid diet has been selected for training purposes
may be due, in the first place, to the more ready assimilation of proteid by
the body ; and, in the second place, to the fact that it is specially required
in these cases, because during training it is important to encourage the
building up of muscular tissue, and for this purpose proteid is necessary ;
not because the proteid of the diet is itself more readily oxidised and
converted into energy by oxidation than the non-proteid materials.

But whether there may be produced under some circumstances as
the result of muscular exercise an increase in the nitrogen of the egesta,
it is certain that the most prominent effect upon the egesta of activity
of the muscles is an increase in the amount of carbon dioxide,1 such
increase being either unaccompanied by, or altogether disproportionate
to, any rise in the nitrogen egested. It must therefore arise from the
oxidation of non-nitrogenous materials, i.e. fat and carbohydrates.

01. Bernard was of opinion that the grape-sugar which he had dis-
covered in the liver and in the blood might by its oxidation in the
tissues take an important part in the production both of heat and of
mechanical energy. Seegen2 is disposed to go much further than
this, holding that muscular energy is obtained solely from the oxidation
of dextrose brought to the muscles by the blood. He finds, as others
have done, that sugar is never absent from the blood even after pro-
longed fasting, and that there is an excess of glucose in the hepatic
blood, independent of the presence or absence of glycogen in the liver.
He also finds in most cases a diminution in the percentage amount of
sugar in the venous blood leaving a muscle, as compared with that in
arterial blood. Some of Seegen's results are, however, paradoxical,
nor have they received adequate confirmation, although a similar

1 Of. article " Chemistry of Respiration."

2 "Die Zuckerbildung im Thierkorper," Berlin, 1890 ; and Arcli.f. d. ges. Physiol. , Bonn,
189], Bd. 1., which volume also contains a criticism of Seegen's views by Pfliiger. See also
on this subject I. Munk, Verhandl. d. physiol. Gesellsch. zu Berlin, in the Arch. f. Physiol.,
Leipzig, 1896, S. 372 ; Zuntz, ibid., S. 538, and CentralU.f. Physiol., Leipzig u. Wien, 1896,
S. 561 ; and Mosse, Arch.f. d. ges. Physiol., Bonn, 1896, Bd. Ixiii. S. 613. Other papers by
Seegen relating to this subject will be found in the Centralbl. f. Physiol., Leipzig u. Wien,
during the last few years, and in the Arch. f. Physiol., Leipzig, 1895 and 1896.

INFLUENCE OF ACTIVITY ON PROTEID METABOLISM. 915

difference in the amount of sugar of the blood passing to and from an
active muscle has been obtained by Chauveau and Kauf mann ; 1 such
differences as are found generally fall within the limits of experimental
error. Chauveau2 has further endeavoured to show that in dogs
muscular work is not effected at all at the expense either of the
proteids of the body or of the food ; but, as I. Munk has pointed
out, the results obtained cannot be accepted as conclusive.3 That
glycogen disappears both from the liver and from the muscles of
dogs, and from the " surviving " excised muscles of the frog, con-
comitantly with the production of muscular work,4 is held to be an
argument in favour of this work being done at the expense of this
carbohydrate. Under certain circumstances, however, the glycogen of
the muscles may be caused to entirely disappear, although they are still
capable of performing a large amount of work, which must, under
these circumstances, be otherwise derived, however probable it may
be that under normal circumstances the oxidation of dextrose or
glycogen plays an important part in its production.

In support of the view that muscular energy may be largely derived
from the oxidation of carbohydrate materials, it has been observed by
Tiegel,5 that the Japanese rickshaw runners consume rice in large
quantities, and at frequent intervals, during their periods of work,
whereas on off-days they live mainly on a flesh diet.6

Pfliiger 7 kept a dog of 30 kilos, weight in equilibrium upon perfectly lean
meat, containing a very large preponderance of proteids over non-proteids.
When caused to pass from a condition of rest to hard work, it lost flesh if kept
on the same diet, until it assumed a lower position of ^"-equilibrium, but main-
tained or even added to its weight if the amount of flesh was increased 500
grms. per diem ; about 50 per cent, of the potential energy of the additional
proteid appearing as work. If now, whilst in ^-equilibrium on lean flesh, fat
and carbohydrate were added to the diet, these were not utilised for the pro-
duction of energy, but were stored as fat ; hence, Pfliiger argues, the living
tissue prefers to use the proteid, and only takes non-proteid if insufficient proteid
is offered to it. It should, however, be pointed out that Pfliiger's dog was,
with its purely proteid diet, in a condition of extreme emaciation,8 and the cir-

1 Compt. rend. A cad. d. sc., Paris, 1887, tome civ. pp. 1126, 1352, and 1409. Similar
results (disappearance of sugar from blood passing through active muscles) have been
obtained by Morat and Dufourt (Arch, de physiol. norm, et path., Paris, 1892, p. 327), who
also found a certain disappearance after the work, which they suppose due to glycogen stored.

2 With Contejean, Compt. rend. Acad. d. sc., Paris, tome cxxii. pp. 429, 504.

3 Verhandl. d. physiol. Gesellsch. zu Berlin, 8 Mai, in Arch. f. Physiol., Leipzig, 1896.

4 0. Nasse, Arch.f. d. ges. Physiol., Komi, 1869, Bd. ii. S. 97 ; also Weiss, Sitzungsb. d. k.
Akad. d. Wissensch., Wicn, 1876, Bd. Ixiv. S. 288; Marcuse, Arch. f. d. ges. Physiol.,
Bonn, 1886, Bd. xxxix. S. 425; Manche, Ztschr. f. Biol, Miinchen, 1889, S. Bd. xxv.
164 ; and ibid., 1877, Bd. xiv. S. 473.

5 Ibid., 1883, Bd. xxxi. S. 607.

6 U. Mosso and Paoletti (Atti d. Accad. d. Lincei, Koma, 1893) and V. Harley
(Proc. Roy. Soc. London, 1893, p. 480, and Journ. Physiol., Cambridge and London, 1894,
vol. xv. p. 97) using the ergograph of A. Mosso, found that they could perform a greater
amount of voluntary muscular work when a large amount of cane-sugar was added to the
diet. Experiments of this nature are, however, liable to a psychical error, and, as a
matter of fact, experiments by Langemeyer (with Stokvis) made upon different persons
failed to give similar results (see discussion in Brit. Med. Journ., London, 1895, vol. ii.
pp. 1280-1285).

7 Arch.f. d. ges. Physiol., Bonn, 1891, Bd. 1. S. 98, and Bd. Ii. S. 317.

8 It may be noted in this connection that the " Banting cure " for obesity depends upon
the principle of selecting a diet not necessarily insufficient, but consisting mainly of lean
meat. As in the case of Pfliiger's dog, the tissues under these conditions use up the body-
fat, which thus becomes gradually reduced in amount.

9i6 METABOLISM.

cumstance of the fat and liver cells seizing upon non-proteid materials and storing
them as fat and glycogen in an animal in this condition, is not surprising,
and is quite compatible with the view that in a normally nourished animal,
where they are in excess, the non-proteids are the main energy producers.

The most probable view appears to be that muscle, like other cells,
although it can only actually build up its bioplasm out of proteid, is
nevertheless able to produce muscular energy by oxidation — perhaps
occurring outside the actual molecules of the bioplasm, but under their
direct influence — of any or all the organic foodstuffs,1 and that this
process is attended only by such small disintegration and loss of the
proteid material of the bioplasm as is necessarily attendant upon its
functional activity — a loss which is Comparable to the wear and tear of
the working parts of a machine as distinct from its consumption of fuel.

As a matter of fact, it has been shown by Zuntz,2 that in a dog,
abundantly fed on a mixed diet and caused to produce external work,
the amount of extra proteid used during the period of work was less
than one-twentieth part of the amount the oxidation of which would
have been necessary to account for the work done. Moreover, in in-
anition it is the glycogen and fat of the body which is first drawn upon,
and this both at rest and during work. When the same dog was made
to work during fasting, the IST-secretion rose only very slowly; the
work was almost entirely done on the non-proteids of the body.

It may be remarked that muscular activity is always accompanied
by a production of energy far in excess of that which is necessary for
the performance of the external work done. Thus it was found by
Hanriot and Eichet 3 that when work was done there was seven times
as much C02 produced as would have been accounted for by the oxida-
tion necessary to perform the work. The additional energy appears of
course as heat. On the other hand, it has been doubted whether there
is any production of heat in the total absence of muscular activity.4

Hanriot and Kichet found the C02 to increase in greater proportion than
the oxygen absorbed, so that the respiratory quotient became larger. Severe
muscular exercise is stated to increase both the phosphoric acid5 and the
sulphur of the urine ; 6 the former more in proportion than the increase of N
which may occur ; the latter about in proportion to the increased N", and in
the form of ordinary sulphates.7 Along with the increase of phosphoric acid,
there is also an increased excretion of lime, indicating, according to I. Munk,
destruction of bony tissue.

METABOLISM OF CARBOHYDRATE.

The formation of glycogen. — The carbohydrates of the food are
mainly converted by digestion into maltose, which passes in the process
of absorption and assimilation into dextrose, this being the only sugar

1 Of. Noel Paton, Edin. Med. Journ., June 1895. Also Rep. Lab. Roy. Coll. Phys.,
Edin., 1891, vol. iii.

2 With Frentzel and Loeb, Arch. f. PhysioL, Leipzig, 1894, S. 541 (VerhandL d.
physiol. Gesellsch. zu Berlin}. See also'Speck, ibid., 1895, S. 465.

3 "Travaux du laboratoire de Ch. Richet," 1893, tome i.

4 Of. on this subject Speck, Centralbl. f. d. med. Wissensch., Berlin, 1889 ; also article
"Animal Heat," p. 840.

5 Klug and Olsavsky, Arch. f. d. ges. PhysioL, Bonn, 1893, Bd. liv. S. 21.

6 Beck and Benedikt, ibid., S. 27.

7 I. Munk, Verhamll. d. physiol. Gesellsch. zu Berlin, 5th April 1895 (in Arch. f.
PhysioL, Leipzig).

METABOLISM OF CARBOHYDRA TE. 917

which is unmistakably found in the circulating fluids and in the tissues
of the body. The path of absorption of carbohydrates is the same as
that of proteids,1 the absorbed dextrose being taken up by the blood,
conveyed by the portal vein to the liver, and there stored. The portal
blood taken during digestion is, in fact, the only blood in the body in
which it can be conclusively shown that normally there is an excess
of sugar. If taken in the intervals of digestion, it contains the same
amount of sugar (one to two parts per thousand) as any other sample
of blood.

The blood of the hepatic vein, on the other hand, although it is said
to contain an excess of sugar in the intervals of absorption of foods
containing carbohydrates (but vide infra, p. 923), does not, during the
actual process of such absorption, contain nearly as much sugar as the
blood of the portal vein ; we must therefore assume that the sugar
which is carried to the liver by the portal vein is arrested in that
organ. As a matter of fact, it is found that the immediate result of
the digestion and absorption of a meal containing much carbohydrate
food is to promote a considerable accumulation of glycogen in the liver,
and the same is found if in a fasting animal solution of dextrose is
slowly injected into a vein of the mesentery,2 or if dextrose is injected
subcutaneously (in rabbits).3 The same is even found if blood contain-
ing dextrose is perfused through the " surviving " liver of a dog.4 The
amount of glycogen in the liver (which would contain in man at most
150 grms. of this substance)5 is not sufficient to account for the storage
of the whole of the carbohydrate which is absorbed from a meal con-
taining much starch or sugar. A part of the absorbed carbohydrate,
when it is in excess, must therefore pass through the liver into the
general circulation. Here it is apparently taken up by the muscles, for
in a well-nourished animal, especially one nourished upon mixed food,
the muscles may contain as much as 1 per cent, or even more of
glycogen. Although this is not by any means as large a proportion as
may be contained in the liver itself,6 the muscles may collectively hold
as much as is present in the liver.7 Even, however, if we take into
consideration the whole of the glycogen in the liver, that in the muscles,
and that in other tissues in the body in which it might be stored, it will
still be found that the whole of the carbohydrates of a meal which
contains much of these substances is not represented in the body,
either by the glycogen of the organs or by the sugar present in the

1 See this Text-book, vol. i. pp. 432-436.

2 Bernard, "Lecons de physiol. exper.," Paris, 1855.

3 G. Lusk (with Yoit), Ztsehr.f. Biol., Miinchen, 1892, S. 288. The ingestion or sub-
cutaneous injection of leevulose will also cause a production of glycogen ; galactose and
lactose do not (C. Voit, Ztsehr.f. Bid. , Miiuchen, 1 892, Bd. xxviii. S. 245). Kausch and Solin
(Arch. f. exper. Path. u. Pharmakol., Leipzig, 1893, Bd. xxxi. S. 398) obtained positive
results with lactose and galactose. Cf. also Creraer, ibid., 1893, Bd. xxix. S. 484 ; Haycraft,
Ztsehr.f. physiol. Ohem., Strassburg, 1894, Bd. xix. S. 141. Whether the kevulose is first
converted into dextrose, and this into glycogen, or whether the glycogen is formed directly
from laevulose, the ketone group of Irevulose must in either case become converted into an
aldehyde group (Neurneister, "Lehrbuch," Aufl. 2, S. 326). On the subject of the forma-
tion of glycogen from carbohydrates, see further, E. Voit, Ztsehr.f. Biol., Miinchen, 1889,
Bd. xxv. S. 551 ; C. Voit, ibid., 1892, Bd. xxviii.

4 Luchsinger, Inaug. Diss., Zurich, 1875.

5 Bunge, "Lectures," p. 383.

6 Pavy found in rabbits and dogs fed with a large amount of carbohydrate-containing
food, that the amount of glycogen of the liver might rise as high as 17 per cent. (" Physio-
logy of Carbohydrates," p. 116).

7 Bohm, Arch.f. d. gcs. Physiol,, Bonn, 1880, Bd. xxiii. S, 51.

9i8 METABOLISM.

circulating fluid. The amount which is not accounted for may possibly
pass into the constitution of the proteids and nucleo-proteids, and also
of those albuminoids from which a carbohydrate material has been
obtained on decomposition with acids, and it may be that the excess is
in this way stored until required. In the embryo, glycogen is much
more widely distributed and occurs in much larger proportion than
after birth, especially in the developing muscles ; at this time the liver
may contain very little. It occurs also in considerable amount in the
placenta.

The glycogen, both of the liver and of the muscles, gradually dis-
appears in starvation, and first from the liver.1 The disappearance is
accelerated by muscular work,2 and iji warm-blooded animals by external
cold ; 3 it is probable, therefore, that the glycogen is used for the pro-
duction of both work and heat. The rate at which it disappears in
starvation varies greatly in different animals. Aldehoff found it in large
quantity in the muscles of a horse which had fasted for nine days ;
in dogs it may be found after three weeks, and has been detected
after thirty-five days' fasting ; 4 in rabbits it has disappeared usually
within a week. In frogs it accumulates in the liver towards the
end of the summer, and gradually disappears during the winter;
but even if they take no food, there is still some present at the end
of the winter, but more in the muscles than in the liver. The same
is the case with hibernating animals (Voit). On the other hand, if
carbohydrates are given to animals deprived of their glycogen by
starvation, this substance very rapidly reappears in the muscles and
liver.5

The diminution of the glycogen of the muscles, concomitantly with their
activity, has been already referred to in connection with muscular metabolism
(p. 915). In the passage of excised muscles into the condition of rigor mortis
there is a certain amount of disappearance, amounting, according to Werther,6
to as much as 50 per cent, of the original amount, but far less than as the
result of tetanising the muscles. In either case, what becomes of it is not
clear ; the sarcolactic acid which makes its appearance is not derived from it ;
the formation of the acid is not dependent upon the presence or absence of
glycogen. If rigor is allowed to come on in the cold, the acid still appears, but
there is no appreciable disappearance of glycogen.7 On cutting the nerve pro-
ceeding to a muscle, the glycogen becomes increased in quantity.8 The increase
proceeds up to the fourth day. Section of the tendon of a muscle has a
similar effect.9

According to the observations of Kiilz, glycogen begins to appear in the liver

1 Aldehoff, Ztschr. f. BioL, Miinchen, 1889, Bd. xxv. S. 137 ; Hergenhalin, ibid., 1890,
Bd. xxvi. S. 225.

2 Manche, Ztschr. /. Biol., Mlinchen, 1889, Bd. xxv. S. 163. The glycogen of muscles
disappears after a period of tetanus, and also in frogs poisoned by strychnia, but not in
the muscles of a leg the sciatic nerve of which has previously been cut.

3 Kiilz, Arch.f. d. ges. PhysioL, Bonn, 1881, Bd. xxiv. S. 46. In cold-blooded animals
external warmth produces the disappearance of glycogen from the liver (Langley).

4 Qninquand, Compt. rend. Soc. de UoL, Paris, 1886, p. 285.

5 For references, see Bun ge, "Lectures," pp. 383-385. See also Langley, Proc. Hoy.
Soc. London, 1882, vol. xxxiv. p. 22 (histological observations) ; Quinquand, Compt. rend.
Soc. de UoL, Paris, 1889, p. 285 ; Deweyre, ibid., 1892, No. 19.

6 Arch. f. d. ges. PhynoL, Bonn, 1890, Bd. xlvi. S. 63.

7 Bbhm, ibid., 1880, Bd. xxiii. S. 44.

8 Bernard, Compt. rend. Acad. d. sc., Paris, 1859, tome xlviii. p. 683.

9 Boldt, Diss., Wiirzburg, 1893; Vay, Arch.f. exper. Path. u. Pharmakol., Leipzig,
1894, Bd. xxxiv. S. 45.

FORMA TION OF GL YCO GEN. 9 1 9

of starved rabbits two to four hours after a meal containing carbohydrates, and
disappears after five to eight hours' hard muscular work (dog). It is formed
in the muscles of a frog which has been deprived of its liver;1 and may be
increased in muscular tissue by perfusing blood, to which grape-sugar has been
added, through the vessels of the muscle.2

The formation of glycogen from other than carbohydrate material.
—That glycogen can be formed in the entire absence of carbohydrate
material from the food, is shown by the fact that animals which have
been for a long time fed on lean meat, deprived as much as possible of
carbohydrate, are found to have even considerable amounts of glycogen
in their liver and muscles. Indeed, if an animal be allowed to fast
for some days, and to perform also severe muscular work, — circum-
stances under which practically the whole of the glycogen can be made
to disappear both from the liver and muscles, — on now administering
proteid3 or gelatin4 food, altogether free from carbohydrates, glycogen
will reappear both in the liver and in the muscles. Even without the
administration of food, by the employment of narcotic drugs, such as
chloral, which tend to diminish or arrest muscular activity, glycogen
will reappear ; 5 in this case it must be formed from the proteids of the
body. The administration of fat without proteid does not cause such
reappearance, nor does the addition of fat to the food, even in consider-
able excess, increase the amount of glycogen in the liver.6 Arsenic
poisoning causes a diminution in the glycogen both of the liver and of
the muscles; probably by impairing the vitality of their bioplasm. On the
other hand, the administration of glycerin promotes the storage of gly-
cogen in the liver ;7 it acts, however, apparently rather by preventing the
removal of the glycogen, than by becoming itself converted into that
substance, or than by its becoming itself oxidized and thus acting as a
glycogen sparer (Eansom). Thus it is found that with glycerin adminis-
tration the sugar puncture is not able to produce glycosuria.

The administration of ammonium carbonate was also found by Eohmann 8
to promote the accumulation of glycogen in the liver, and this property is
shared by many ammonium compounds,9 but how they may act has not as yet

3 Kiilz, Arch. f. d. yes. Physiol., Bonn, 1881, Bd. xxiv. S. 64. This volume contains
several other papers by Kiilz on the conditions of formation of glycogen.

2 Kiilz, Ztschr. f. Biol., Miinchen, 1891, Bd. xxvii. S. 237: there was, however,
only an increase in three out of eleven experiments.

3 ISTaunyn, Arch. f. expcr. Path. u. Pharmakol., Leipzig, 1875, Bd. iii. S. 94 ; v.
Mering, Arch. f. d. ges. Physiol., Bonn, 1876, Bd. xiv. S. 281 ; Kiilz, Funfzigj. Loct.-
Jubelf. d. . . . Carl Ludwig, Marburg, 1890.

4 Salomon, Virchow's Archiv, 1874, Bd. Ixi. S. 352 ; Luchsinger, Inaug. Diss., Zurich,
1875 ; v. Mering, loc. cit.

5 Zuntz u. Vogelius (Arch. f. Physiol, Leipzig, 1893, S. 378, Verhandl. d. physiol.
Gesellsch. zu Berlin] obtained a reappearance of glycogen on administering chloral to
starved and strychnised rabbits.

6 Chauveau has come to the conclusion that carbohydrate may be formed from fat in
the animal body (Compt. rend. Acacl. d. sc., Paris, 1887, tome cxxii. p. 1098), and Seegen,
"Die Zuckerbildung," also holds this view, but the evidence in its favour appears to be very
insufficient.

7 Weiss, Sitzungsb. d. k. Akad. d. Wisscnsch., Wien, 1873, Bd. Ixvii. S. 13 ; Eckhard,
loc. cit. ; Luchsinger, Inaug. Diss., Zurich, 1875 ; W. Ransom, Journ. Physiol., Cambridge
and London, 1887, vol. viii. p. 99 ; Schenck, Arch. f. d. gcs. Physiol., Bonn, 1894, Bd.
Ivii. S. 569.

8 Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxix. S. 21. Of. also Kiilz (Funfzigj.
Doct.-Jubelf. d. . . . Carl Ludwig, Marburg, 1890), who found that urea as well as
ammonia salts increased the glycogen of the liver.

9 Nebelthau, Ztschr. f. BioL, Miinchen, 1892, Bd. xxviii. S. 138.

920 METABOLISM.

been determined. Bicarbonate of soda is stated by Dufourt to have the effect
of increasing the amount of glycogen in the liver. Dufourt's experiments
were made upon dogs on a flesh diet after a period of fasting.1

Glycogen becomes formed in the embryo chick in considerable
amount, although there is very little glycogen or carbohydrate at all
in the egg. Here also it must in all probability be formed from proteid.
Glycogen can only be supposed to be produced from proteids in the
animal body by a process of synthesis, preceded by a breaking down of
the proteid molecule.2 It is highly probable that dextrose is a stage in
the course of such synthesis ; and since dextrose is constantly found in
the blood, even in prolonged inanition, it may well be inquired whether
the carbohydrate of the body is in¥ariably converted into glycogen,
prior to being employed by the tissues for the production of energy.
Under certain circumstances it appears clear that the synthesis of
carbohydrate never passes beyond the stage of dextrose. Thus, in the
diabetes produced by successive doses of phloridzin there may be no
glycogen whatever in the liver and muscles, and yet within the proteid-
fed and in the fasting animal large quantities of dextrose are formed
and eliminated with the urine.

Phloridzin is a glucoside obtained from the root-bark of certain
trees (apple and cherry), but it does not act by virtue of its glucose
group, for the same action is got by the employment of the non-glucoside
phloretin which is obtained from phloridzin. If injected under the
skin, or taken into the alimentary canal, either phloridzin or phloretin
produces within a very short time the appearance of sugar in the urine,
and this appearance of sugar in the urine is accompanied by a diminution
of the liver glycogen.3 The glycogen in the liver does not, however,
completely disappear as the result of a single dose of phloridzin ; both in
that organ and in the muscles a certain amount remains, but if a second
dose of phloridzin is given, glycosuria is again produced, and by repeating
the administration once or twice the glycogen can be completely removed
from the liver. Each successive dose of phloridzin will, however, cause
a fresh appearance of sugar in the urine even after complete removal of
glycogen from the liver, which shows that, although part of the sugar
which has appeared in consequence of the action of phloridzin may have
been produced from the glycogen in the liver, a part must be produced
in some other way. As by the employment of successive doses of this
drug all the appreciable glycogen in the body can be got rid of,4 it is
almost certain that the sugar which then appears is derived from the
metabolism of proteid ; and this is rendered the more likely since it is

1 Arch, de med. exper. ef, d'anat. path., Paris, 1890, tome ii. p. 424.

2 Cf. Pfiiiger, Arch.f. d. ges. Phyxiol., Bonn, 1888, Bd. xlii. S. 144.

a v. Mering, Verhandl. d. Cong. f. innere Med. , Wiesbaden, 1887, S. 349 ; Ztschr.f. Uin.
Med., Berlin, 1888, Bd. xiv. S. 405 ; 1889, Bd. xvi. S. 431. See also on phloridzin
diabetes, Cremer and Ritter, Ztschr. f. BioL, Miinchen, 1892, Bd. xviii. S. 459, and Bd.
xix. S. 256 ; and Praussnitz, ibid. S. 168.

4 Kiilz and Wright (Ztschr. f. BioL, Miinchen, 1891, Bd. xxvii.) have shown that the
glycogen is not so readily got rid of as v. Mering supposed, and that as a matter of fact
there may still have been some glycogen left in the animals employed by v. Mering. These
authors state that phloridzin does not produce glycosuria in frogs. It did, however,
produce glycosuria in birds (v. Mering, Verhandl. d. Cong. f. innere Med., Wiesbaden, 1887),
in which pancreatic extirpation failed to cause glycosuria ; it also increases the amount of
sugar in the urine of animals suffering from pancreatic diabetes (Minkowsld, Arch. f. exper.
Path. u. PharmakoL, Leipzig, 1893, Bd. xxxi. S. 148) ; and, further, Cremer has obtained
phloridzin diabetes in frogs by taking special measures to ensure the action of the drug
(Ztschr. f. BioL, Miinchen, 1892-3, Bd. xxix. S. 175).

FORMA TION OF GL YCOGEN. 92 1

noticed that the amount of nitrogen in the urine goes hand in hand with
the amount of sugar excreted.1 Further, it is found that if the glycogen
in the body be reduced as much as possible by a prolonged period of
starvation, followed by excessive muscular action, such as is caused by a
dose of strychnine, the administration of phloridzin will still cause
glycosuria; much more sugar appearing under these circumstances in
the urine than can be accounted for by any glycogen which might remain
either in the liver or any other tissues of the body. It seems, therefore,
clear that the sugar must have been derived from proteid ; in this case
the proteids of the body itself. It may further be mentioned that Pick 2
has found that if the liver be rendered functionless by injecting dilute
sulphuric acid into the bile ducts, its glycogen disappears in twelve
hours, but phloridzin still produces glycosuria, although other agents
which usually cause glycosuria, such as carbon monoxide, fail to produce
this effect. As with the glycosuria produced by phloridzin, so also with
severe cases of natural diabetes in man, there appears to be no doubt
that a direct formation of sugar from proteid may occur without any
formation of glycogen. It may be supposed with some probability that
such a direct formation of sugar (mainly by the liver, for phloridzin
diabetes is produced in the absence of the liver),3 but also by other organs;4
and its passage into the blood may occur to some extent normally ; that
in fact a part of the carbohydrate produced from proteid may be at
once passed into the blood in the form of dextrose, and a part further
synthetised into glycogen and stored as such.5 We might then explain
phloridzin diabetes, and possibly certain severe cases of natural diabetes,
by supposing that the further synthesis into glycogen is in some way
interfered with, so that an excess of the carbohydrate formed is passed
into the blood in the form of sugar.

It must, however, be stated that the production of the severest forms
of diabetes above mentioned, and also that produced by removal of the
pancreas (see p. 927) and by the sugar-puncture (see p. 926), is still exceed-
ingly obscure. According to v. Mering and most other observers, there
is a fundamental difference between the diabetes caused by phloridzin
and that produced by pancreatic removal or sugar-puncture, in that in
the former there is no excess of sugar in the blood, — in fact the amount
may be less than normal,6 — whereas in the two last-mentioned forms the

1 v. Mering, loc. tit., found the proportion of urea to sugar in phloridzin diabetes = 1 : 2,
in cases of natural diabetes = l : 1. See also Moritz and Praussnitz, Ztschr. f. BioL,
Munchen, 1891, Bd. xxvii. S. 81 ; Praussnitz, loc. Git.; Cremer and Hitter, Ztschr. f. BioL,
Miinchen, 1893, Bd. xxix. S. 256. v. Mering and Minkowski (Arch. f. exper. Path. u.
PharmakoL, Leipzig, 1889, Bd. xxvi.) found the proportion of sugar to nitrogen =3: 1 in
pancreatic diabetes.

2 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1894, Bd. xxxiii. S. 305.

3 Thiel, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1887, Bd. xxiii.

4 Cornevin (Compt. rend. Acacl. d. sc., Paris, 1895, tome cxvi. p. 263) has shown that
phloridzin causes a marked increase in the amount of sugar eliminated in the milk.

5 Seegen states that he obtained a formation of sugar (in excess of that produced by
transformation of any glycogen present) in a mixture of chopped liver and arterial blood, to
which peptone had been added, and even with the addition of fat in place of peptone.
But his results have not been confirmed by other workers. Cf. Bohm u. Hoffmann,
Arch. f. d. ges. PhysioL, Bonn, 1880, Bd. xxiii.; Girard, ibid., Bd. xvi. S. 294;
Neumeister, Ztschr. f. BioL, Miinchen, 1890, S. 346. The possibility of the formation of
carbohydrate from fat in animals, although not experimentally proved, must not be
ignored. For there is clear evidence that such a transformation may occur in germinating
seeds of plants (Sachs, "Text-Book of Botany," transl. by Bennett and Thiselton Dyer,
1875, p. 638), and if plant bioplasm is capable of effecting the transformation, animal
bioplasm might also be expected to have a similar power.

6 No diminution but an increase in the amount of blood-sugar was found by Pavy to

922 METABOLISM-

percentage of sugar in the blood is greatly increased. This seems to point to
the fact that phloridzin, besides any action it may have upon the metabolism
of carbohydrate in the liver and muscles, increases the permeability of the
kidney tubules to sugar, or causes the epithelium of the tubules to be more
susceptible to the presence of sugar in the blood, so that the kidney removes
sugar from that fluid more rapidly than under normal circumstances, and thus
the percentage is even diminished below normal.1 On the other hand, the
diminution in the percentage caused by such removal, even if it were in-
appreciable to chemical methods of analysis, might be supposed to excite the
sugar-producing tissues to increased activity, thus adding constantly more sugar
to the blood, to be again removed by the kidneys, and so on in a vicious circle.
On the other hand, Levene2 has given reasons for believing that the
sugar in phloridzin diabetes may be produced in the kidneys, a view which
was previously expressed by TJschinsky (quoted by Levene). Thus, after
trying the renal blood vessels and then injecting phloridzin, there was no
accumulation of sugar in the blood ; indeed, the percentage of sugar in that
fluid was, if anything, diminished. Minkowski 3 had previously failed to find
an increase above the normal after ablation of the kidneys and injection of
phloridzin, and Schabacl4 obtained analogous results after tying the ureters.
Levene also finds that the amount of sugar in the kidneys is increased as the
result of giving phloridzin, and that under the same circumstances there is
rather more sugar in the blood of the renal vein than in that of the corre-
sponding artery. He admits, however, the probability that it is formed in
other organs as well as in the kidney. Minkowski 5 has put forward the
suggestion that phloridzin becomes split up in the kidney into phloretin and
sugar ; the latter becoming eliminated, and the former combining again with
sugar in the organism, and then again yielding this to the kidney, and so on.

Glycogenesis — Theory of Bernard. — As regards the fate of
the carbohydrates of the food, there is no doubt that, whether they
inevitably go through the stage of glycogen or not, they ultimately
undergo oxidation into carbon dioxide, and removal in the form of this
substance and water. The carbohydrate of the food directly increases
the amount of carbon dioxide given off, and in proportion to the amount
of such food taken. This elimination of carbon dioxide is not immediate,
for most of the carbohydrate taken in is in the first instance stored,
and only becomes oxidised gradually, as the needs of the organism
demand. The view which has been most commonly held with regard to
the method of transformation of the stored carbohydrate into the
products of its oxidation, originated with Bernard. Having found that
the blood of the hepatic vein constantly contains more sugar than
the blood of the portal vein, except during the absorption of food,
he concluded that the glycogen which he had discovered in the
liver,6 and which is no doubt the chief store of carbohydrate material in

occur iu cats to which phloridzin had been administered ("Proc. Physiol. Soc.," Nov. 14,
1896, Journ. Physiol., Cambridge and London, vol. xx.), and he therefore denies that
diiriinished glycsemia is a feature of this form of diabetes.

1 v. Mering, loc. cit. ; Minkowski, " Untersuch. it. d. Diabetes mellitus," Leipzig, 1893 ;
Zuntz, Arch.f. Physiol., Leipzig, 1895, S. 570.

2 Journ. Physiol., Cambridge and London, 1894-95, vol. xvii. p. 259.

3 Loc. cit.

4 Frach., St. Petersburg, 1892, No. 49, quoted from Minkowski.

5 Op. cit., p. 152.

6 The fact that sugar is formed in the liver was discovered by Bernard in 1848
(Com.pt. rend. Acad. d. sc., Paris, 1848, tome xxvii. pp. 249, 253, 514 ; "Nouvelle fonction
du foie, etc.," Paris, 1853), but the substance (glycogen), from which it is produced was
not found until 1857 (by Bernard, and also independently by Hensen). For a full list of
Bernard's writings on this subject, see " L'ceuvre de Claude Bernard," Paris, 1881.

GL YCOGENE$IS~- THEOR Y OF BERNARD. 923

the body, gives off such material into the blood in the form of dextrose.
This dextrose is taken to the tissues and is used by them, becoming
oxidised within them. Whether this oxidation occurs outside the actual
bioplasm, or whether the dextrose which is taken to the bioplasm
becomes first of all built up into its molecules and then split up
and oxidised, and whether .the products of its oxidation leave the
muscles in their ultimate forms, are questions which we need not
now consider. In either case the effect of such oxidation is to produce
energy (in the form of heat and mechanical work).

This view of Bernard's has, on the whole, met with general favour among
physiologists. Some there are, indeed, who have so far proceeded beyond
Bernard, as to assert that the wJtole energy of the body is derived from the
oxidation of carbohydrate. Such carbohydrate, which is taken to the tissues
in the blood in the form of glucose, is assumed to be formed either from the
stored carbohydrate of the liver, as Bernard supposed, or independently of this
from proteid, or even from fatty materials in the liver cells, and being carried
to the tissues to be taken up by them, oxidised within them, and thus become
the immediate source of the energy of the body, whether this takes the
form of heat or work. It is in fact assumed that the main result of
metabolism within the body is the production in one part, and the destruction
in another, of carbohydrate. Such a view has been chiefly contended for by
Seegen l and Chauveau, who hold that even the proteid material of the food,
at least its non-nitrogenous part, must ultimately become converted into
carbohydrate before it can become oxidised in the tissues (see p. 914).

It is obvious that Bernard's theory is, in the main, dependent upon the
circumstance that sugar is continually being passed from the liver into the
hepatic blood, even during starvation, and this, in fact, has been directly
affirmed by Bernard and others. Even in the fasting animal, sugar is found in
the blood, except at the extreme end of an inanition period ; and, according to
the analyses of Seegen, it always occurs in larger amount in the hepatic blood,
whatever be the nature of the food, whether proteid, fat, or carbohydrate,
than in blood from any other source. This occurrence of dextrose in
larger proportion in the hepatic blood than in the rest of the blood of the
body, if it were completely and satisfactorily determined, would be a fact of
fundamental importance, and would go very far to establish Bernard's theory
upon a firm basis. But there are reasons for believing that such an excess of
sugar as has been found by Seegen and other observers is not present
under absolutely normal conditions. Seegen's experiments were made without
anaesthetics, and it is a well-established fact that any operation upon an
animal, which involves the production of pain, will immediately produce
a transformation of the glycogen of the liver into sugar, and the appearance of
an excess of sugar in the hepatic blood.2 It is, in fact, admitted by Seegen

1 "Die Zuckerbildung im Thierkbrper," Berlin, 1890, S. 218, and numerous papers in
the Arch.f. d. yes. Physiol., Bonn, and in the Ccntralbl. f. Physiol., Leipzig u. Wien.

2 Seegen calculates that in man from 500 to 1000 grms. of dextrose may pass into
the blood from the liver in twenty-four hours. But since his calculations are based upon
experiments made upon animals in an abnoimal condition so far as the carbohydrate
metabolism is concerned, these numbers cannot be accepted. Cf. Abeles, Med. Jahrb.,
Wien, 1886, S. 383; I. Munk, Berl. Tclin. Wchnschr., 1890, S. 595; also Pfluger,
Arch. f. d. ges. Physiol. , Bonn, 1891, Bd. 1. S. 330, 396 ; Mosse, ibid., 1896, Bd. Ixiii. S.
613 ; 'L\mtz* Centralbl. f. Physiol., Leipzig u. Wien, 1896, S. 561. The blood is obtained
either directly from one of the hepatic veins, or by passing a catheter up into the inferior
cava, this vein being then blocked just below the reception of the hepatic veins by the
inflation of an india-rubber bag ; or a tube is passed down from the jugular vein through
the right auricle into the inferior cava, and its bent end is made to enter one of the
hepatic veins.

924 METABOLISM.

himself, that when the blood from the hepatic vein is collected under
conditions of anaesthesia, the difference between the percentage amount of
sugar in the hepatic blood and that in ordinary arterial blood becomes
greatly diminished, if it does not altogether disappear.1

Bernard's views have been combated strenuously by Pavy,2 whose
method of experimentation is not open to the same objection as that
of Seegeii and others who have found a constant excess of sugar in
the hepatic blood. Pavy takes blood from the animal immediately
after it has been killed by a blow upon the head, and before there
has been time for any change to have occurred in the liver, and he
finds that blood which is collected *mder these circumstances from
the inferior vena cava (including, therefore, the blood which has passed
out from the liver) never shows any appreciable excess of reducing
substances over blood obtained from other parts of the body. Eesults
similar to those of Pavy have also been obtained, although under
somewhat different conditions, by other observers.

We are therefore landed in this difficulty, as the result of the
imperfection of our present methods, that we cannot be sure whether
the blood of the hepatic vein does or does not, normally, contain an
excess of sugar. If it does, we are bound to assume that sugar is
being continually passed off from the liver into the general blood of the
body, and since this sugar does not pass off by the urine, it can only be
available for the nutrition of the tissues, and the production of energy
by oxidation. If sugar does not pass from the liver into the blood, we
should require to find some form in which the glycogen, which is
undoubtedly stored up in the liver, is got rid of, and also to find some
meaning for its presence there and in the muscles.

It has been suggested by Pavy3 that such stored glycogen may
become converted into fat. There is no doubt that carbohydrate
food does become converted in the body into fat, and there are
many instances of the formation of fat from carbohydrate material in
plants; it is therefore not altogether wanting in probability, that the
glycogen which is stored up in the liver cells and muscles may also
become converted into fat. Such fat may be assumed to be gradually
removed by the blood and carried to the different organs, and in them
ultimately oxidised to carbonic acid and water.

Another supposition, which we have already considered, is that it
becomes directly oxidised, and produces heat. As most of the
oxidation of the body occurs in the muscles, and as the muscles retain
their glycogen in starvation longer than the liver, although the latter
organ contains normally a much larger proportion, it seems very
probable that the glycogen passes from the liver to the muscles. This
cannot be as glycogen, for glycogen is not present in blood plasma, and

1 Centralbl.f. PhysioL, Leipzig u. Wien, 1896-97, Bd. x. S. 497, 822.

2 "The Physiology of the Carbohydrates," London, 1894. Here other papers by the
same author are referred to.

3 Ibid., pp. 245 to 252. In connection with the question of sugar production by the
liver, it may be mentioned that removal of this organ or cutting off its blood supply in
rabbits (Boik and Hoffmann, "Exper. Studien u. Diabetes," Berlin, 1874), dogs (Seegen.
"Die Zuckerbildung," and Tanyl and v. Harley, Arch. f. d. ges. PhysioL, Bonn, 1895,
Bd. Ixi. S. 551), geese (Minkowski, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1882,
Bd. xx. S. 41), is followed by either disappearance or marked diminution of the sugar of the
blood.

GL YCO GENESIS— THE OR Y OF BERNARD. 9 2 5

what little there is in the blood is in the white corpuscles — a property
they share with most other protoplasmic structures. It is therefore
natural to conclude, even if we cannot show the fact conclusively
by analysis, that it passes from the liver to the muscles in the form of
grape-sugar. The extra amount of sugar in the hepatic blood might be
so small as easily to fall within the limits of experimental error, and
yet sufficient to transport a very large amount of carbohydrate in the
course of twenty-four hours.1 Nor can it be said that we have any
means of exactly estimating the amount of sugar in the blood at all.
What has been estimated hitherto in the blood is not sugar alone, but
substances which reduce cupric salts. That a part of these substances
consists of glucose, is shown by the reaction with phenylhydrazine.
But it must not be forgotten that there occur in the blood other
substances which, although not glucose, also reduce metallic salts ; nor
can we say what proportion these hold to the glucose in the blood.
Hence any mere determinations of the reducing substances do not give
us a direct measure of the amount of glucose, and it is impossible to
admit as proven any theory which is entirely built up upon observations
of the amount of reduction yielded by the blood, on the assumption that
such reduction is exclusively produced by glucose. If, therefore, we
accept Bernard's theory, it must be understood that the evidence in its
favour is mainly of an indirect character. There exists an analogy in
the case of plants, in which the stored insoluble carbohydrate (starch) is
conveyed from one part to another in the form of soluble sugars. And
it must further be looked upon as a powerful argument in favour of
Bernard's hypothesis, that under certain circumstances there is rapidly
produced a very appreciable transformation of the liver glycogen into
dextrose. This occurs as the result of stimulation of almost any sensory
nerve, as the result of interference with the hepatic circulation,2 and as
the result of administration of many drugs. And it also occurs, as was
found by Bernard early in his investigation of the subject, very rapidly
after death, especially if the liver be kept at the body temperature. On
the other hand, this transformation can be prevented by subjecting the
liver, immediately after the animal is killed, to a sufficient amount of
heat, as by throwing it in pieces into boiling water, or of cold, as by
ice-cold salt solution,3 or by a freezing mixture.4 It has been held
that this transformation, which occurs during the " survival " of the
liver cells, is due to a continuance of such chemical processes as occur
in the cells during life, and which lead to the change of their glycogen
into sugar, just as the chemical changes which occur in muscle which is
passing into rigor are generally similar to those produced during the

1 Foster, "Text-Book of Physiology," 1889, pt. 2, 5th edition, p. 726.

2 For these reasons conclusions should be drawn very cautiously from such experiments
as those of the brothers Cavazzani (Centralbl. f. Physiol., Leipzig u. Wien, 1894, Bd. viii.
S. 33), who obtained disappearance of glycogen in the liver, and increase of sugar in the
hepatic blood, on stimulation of the coeliac plexus. The same remark applies to the results
obtained by Morat and Dufourt by excitation of the vagus (Arch, de physiol. norm, ct path.,
Paris, 1894, pp. 631 and 371).

3 Dastre states that a temperature of 55° C. is sufficient to destroy the amylolytic action,
and that prolonged exposure to ice-cold salt solution has the same effect. He argues
from this that the action is not that of a ferment, but of cell protoplasm (Arch, de physiol.
norm, et path., Paris, 1888, p. 69). On the other hand, Nasse found that liver digested
with chloroform water has a free amylolytic action, which must in that case be due to a
ferment (Rostocker Ztg., 1889, No. 105). See also Salkowski, Centralbl. f. d. mcd.

Wissensch., Berlin, 1889, No. 13).

4 Pavy, " Physiology of Carbohydrates," p. 134.

926 METABOLISM.

activity of the muscular tissue ; and accordingly anything, such as the
sudden application of heat, able to instantly kill the liver cells stops
such change.1 On the other hand, it may also be that the trans-
formation is caused by an amylolytic ferment, which is produced by
the cells. This view was in fact held by Bernard,2 but he afterwards
supposed that the ferment was derived from the blood.3

It has been denied that such a ferment can be obtained from the liver, and
it has therefore been contended that the transformation of glycogen into sugar
must be produced by the direct metabolic action of the cell protoplasm. It
has also been argued that, since the sugar which is produced by the digestive
amylolytic ferments is maltose, and not dextrose, the production of dextrose in
the surviving liver cannot be due to a f?rment. Pavy, however, has shown
that an active amylolytic ferment is obtainable from the alcohol hardened
liver both in rabbits and cats, and that the sugar which is produced by it is
closely similar to, if not identical with, that formed in the " surviving " organ.4
A ferment converting glycogen into dextrose has also been obtained from
the liver by Arthus and Huber,5 and by Bial,6 who states that it is identical
with and probably derived from the diastatic ferment of blood and lymph.7

Puncture diabetes. — Bernard8 also discovered the fact that certain
lesions of the central nervous system, and especially a puncture in the
region of the floor of the fourth ventricle, which corresponds, as we now
know, very nearly to the position of the vasomotor centre, produces a con-
dition of glycosuria ; and that this is caused by a transformation of the
glycogen of the liver into sugar, which is then taken up by the hepatic
veins in so considerable a quantity, and increases so much the percentage
of sugar in the blood, as to cause its excretion by the kidney. That this
is the origin of the sugar in the so-called " puncture diabetes," is proved
by the fact that, if precautions are taken to render the liver devoid of
glycogen, as by a prolonged period of inanition,9 with or without severe
muscular activity, the glycosuria ordinarily resulting from puncture of
the fourth ventricle does not appear, nor does it occur in frogs with the
liver removed. It has been conjectured, with much probability, that

1 Noel Paton found that if the liver substance be bruised up in a mortar with sand, so as
to crush and thus destroy the liver cells, the change of glycogen into sugar does not occur
(Phil. Trans., London, 1894, vol. clxxxi. p. 233). But a repetition of his experiments by
Pavy ("Epicriticism," London, 1895. p. 79) has not yielded the same results, and, since
they were only few in number, they can hardly be accepted without further confirmation.
Paton has, moreover, in later experiments, himself failed to verify his earlier results
(Journ. Physiol. , Cambridge and London, 1897, vol. xxii. p. 121).

2 " Le9ons sur le diabete," Paris, 1877.

3 Compt. rend. Acad. d. sc., Paris, tome xli. p. 461.

4 There seems to be little doubt that this sugar is mainly if not entirely dextrose
(Seegen and Kratschmer, Arch. f. d. ges. Physiol., Bonn, 1880, Bd. xxii. S. 214), but
according to Chittenden and Lambert (Stud. Lab. Physiol. Chem., New Haven, 1885)
there is some maltose. Kiilz arid Vogel also found a certain amount of both maltose
and isomaltose in the fresh liver (Centralbl. f. d. med. Wissensch., Berlin, 1894, S. 769).
The remark that has been already made regarding the sugar found in blood applies to all
these determinations of liver sugar, namely, that what is actually determined is the
amount of reduction of cupric oxide, and that there may be, and undoubtedly are, other
substances present besides sugar which effect this reduction.

5 Arch, de physiol. norm, etpath., Paris, 1892, p. 651.

6 Arch.f. d. ges. Physiol., Bonn, 1893, Bd. Iv. S. 434.

7 See article " Blood," p. 160.

8 " Le9ons sur la physiol. et la pathol. du systeme nerveux," Paris, 1858, tome i. p.
401. See also Eckhard, Beitr. z. Anat. u. Physiol. (Eckhard], Giessen, 1869, Bd. iv. S. i.
Kiihne found the same thing to happen in frogs (Inaug. Diss., Gottingen, 1856).

9 Luch singer, loc. cit.

PUNCTURE DIABETES. 927

the condition of the liver which results from such puncture, and which
tends to cause this transformation of the glycogeii into sugar, is due to
a disturbance of the hepatic circulation, and especially of the circula-
tion in the hepatic artery, thus indirectly producing an alteration in the
normal metabolism of the organ ; but this cannot be considered as con-
clusively proved, and it may be due to a direct interference with the
action of the nerves to the liver cells. Diabetes does not, however,
occur on section of the splanchnic nerves alone.1 But in all probability
the vasomotor centre is stimulated by the puncture, for other forms of
stimulation of the vasomotor centre also tend to produce a temporary
diabetes, such as the prolonged stimulation2 of most sensory or afferent
nerves (e.g. the sciatic, the central end of the vagus,3 and the depressor 4),
which are known so to influence the vasomotor centre as to produce
constriction or dilatation of the arteries of the body generally. It is
possible, therefore, that this may be the manner in which the effect is
produced in the liver, and that the glycaemia is due to the diminution
of the amount of oxygenated blood passing to the liver through the
hepatic artery, causing an excitation of the liver cells, and such conse-
quent alteration in their metabolic activity as ordinarily accompanies
excitation.5 Many drugs produce temporary diabetes, e.g. acids, such as
phosphoric, lactic, and hydrochloric, also strychnine, curari, phosphorus,
arsenic, carbon monoxide. Some of these may act by affecting the
circulation, others by producing a dyspnoeic condition of the liver cells,
others again may be direct stimulants to the hepatic cells.6

It must be looked upon as a strong argument in favour of the glycogenetic
theory of Bernard, that we find as a concomitant of the altered (increased?)
activity of the hepatic cells, both after removal of the liver from the body,
and after the diabetic puncture, such an increased production of sugar in the
organ. It is certainly easier to explain the occurrence of puncture diabetes as
an excess of the normal production of sugar in the liver, than as a phenomenon
entirely sui generis.

Action of the pancreas on carbohydrate metabolism. — Until
recently, it was not known that the pancreas had any more influence
upon metabolism than other glands of the same type, such as the
salivary glands. There had, however, been isolated instances recorded
in which disease of the pancreas was accompanied by a condition of
diabetes ; but this, for the most part, was ascribed to the implication of
the sympathetic ganglia, which are in anatomical relationship to the
pancreas, and no special importance was attached to the pancreas in
connection with the symptom.7 It was, however, shown in 1889, by

1 According to Kaufmann (Compt. rend. Soc. de biol., Paris, 1894, p. 284), puncture
diabetes is not produced, if the nerves both to the pancreas and liver are cut ; but if one
set only is severed, it is found to occur.

2 Even that produced by sections, Kiilz, Arch. f. d. yes. PhysioL, Bonn, 1881, Bd. xxiv.
S. 97. Here also will be found references to previous papers on the subject.

3 Bernard, "Legons sur le systeme nerveux," Paris, 1858, tome ii. ; Eckhard, Beitr.
z. Anat. u. PhysioL (Eckhard), Giesen, Bd. viii.

4 Filehne, Gentralbl. f. d. med. Wissensch., Berlin, 1878, No. 18.

5 Cf. Araki, Ztschr. f. physiol. Chem., Strassburg, 1893, Bd. xvii.

6 References to the literature of some of these substances will be given later ; others will
be found in Kiilz, loc. cit., supra ; and in Neumeister, "Lehrbuch," AuH. 2, S. 328.

7 Since the discovery by v. Mering and Minkowski of the effects of total removal of the

})ancreas, several cases of severe diabetes in man, associated with disease of that gland,
lave been recorded (G. Hoppe-Seyler, Deutsches Arch. f. Uin. Mcd., Leipzig, 1893, Bd. Hi.
S. 171 ; Buss, Diss., Gottingen, 1895). It must not be supposed, however, that this is at
all common. In most cases of diabetes no affection of the pancreas can be substantiated.

928 METABOLISM.

von Mering and Minkowski,1 that complete removal of the pancreas in
the dog, cat, and pig,2 is inevitably followed by a very severe form of
diabetes, having the usual characters of that disease in man, namely, an
enormous increase in the excretion of water, and the appearance in the
urine, besides sugar, of aceto-acetic acid, acetone, and sometimes of oxy-
butyric acid. That this condition is not in any way due to the abolition
of the secretion of the gland, was further shown by the observation that
it does not occur if the duct of Wirsung be tied, or if it and its branches
be blocked by the injection of paraffin into them, and the gland left in
situ, nor even if a certain proportion of the gland be left, its secretion
being prevented from passing into the intestine ; nor does it occur if a
portion of the pancreas be detached from its normal position and trans-
planted elsewhere, either underneath tne skin or in the peritoneal cavity,3
and the remainder of the organ subsequently removed, although diabetes
will appear in the severest form immediately after the removal of the
transplanted portion from its subcutaneous situation.

The observations of v. Mering and Minkowski have been repeated
and extended by Minkowski himself and by many other physiologists.
The removal of the organ is less difficult than might be supposed, the
chief precaution to take being to interfere as little as possible with the
supply of blood to the duodenum. The complete removal is found
invariably to be immediately followed by a considerable increase of
sugar in the blood, where the amount of sugar may reach as high as 046
per cent., and its consequent appearance in the urine, in which the
amount may rise to as much as 8 per cent, or more. In the increased
amount in the blood pancreatic diabetes agrees with puncture diabetes,
and differs from phloridzin diabetes, in which, as already stated, the
amount of sugar in the blood is not increased, although there is a large
increase of sugar in the urine. Concomitantly with this increase of
sugar in the blood and its consequent appearance in the urine the
glycogen of the liver disappears.4 When no carbohydrate is given with
the food, and even during prolonged fasting, the sugar continues to be
eliminated in considerable quantity ; and since, under these circum-

1 Arch.f. exper. Path. u. PharmaJcoL, Leipzig, 1889, Bd. xxvi. ; see also Minkowski, ibid.,
1893, Bd. xxxi. S. 85. The experiments of v. Mering and Minkowski have been repeated by
many observers, amongst whom may be mentioned especially Dominicis (Gior. internaz. d. -sr.
med., Napoli, 1889), Hedon, Thiroloix, Gley, and Lepine (numerous papers during the last
seven years in the Compt. rend. Acad. d. sc., Paris ; and in the Compt. rend. Soc. de
bioL, Paris; in the Arch, de physiol. norm, et path., Paris; and Arch, de med. exptr.
et d'anat. path., Paris) ; Vaughan Harley, Journ. Anat. and PhysioL, London, 1891, vol.
xxvi. ; Journ. PhysioL, Cambridge and London, 1891, vol. xii. p. 391 ; Caparelli (Atti d.
Accad. Gionenia disc, nat.in Catania, 1892, tome v. ; Sandmeyer, Ztschr.f. BioL, Miinchen,
1893, Bd. xxix. S. 86.

2 The results in the rabbit were somewhat doubtful, and negative results were obtained
in birds and in the frog. Aldehoff (Ztschr. f. BioL, Miinchen, 1892, Bd. xxviii.), however,
has obtained pancreatic glycosuria in the frog ; as has also Marcuse (Verhandl. d. physiol.
Gesellsch. zu Berlin, 1893-94, S. 98, in Arch. f. PhysioL, Leipzig), who states that it fails
to occur if the liver be previously removed. This is also the case, according to Langen-
dorff (Arch. f. PhysioL, Leipzig, 1887, S. 138), with the diabetes produced by strychnine
and by puncture, but not with that produced by curari. Of. , however, Rohmann, Centralbl.

f. PhysioL, Leipzig u. Wieu, 1887, Bd. i. S. 122.

3 Thiroloix (" Le diabete pancreatique," Paris, 1892) at first obtained a contrary result,
but in later experiments (Arch, de physiol. norm, et path., Paris, Oct. 1892) succeeded in
confirming the original statement of v. Mering and Minkowski.

4 According to He"don (Arch, de physiol. norm, et path., Paris, 1893), the sugar in the
liver may nevertheless be increased in pancreatic diabetes. The administration of
Isevulose causes the reappearance of glycogen in the liver, although dextrose does riot
(Minkowski, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1893, Bd. xxxi.).

PANCREAS AND CARBOHYDRATE METABOLISM. 929

stances, its amount, as in the case of phloridzin glycosuria, rises and
falls with the amount of nitrogen in the urine (see p. 921), it may
be assumed that it is derived in these cases also from the splitting of
proteids.

The exact amount of the pancreas which it is necessary to leave in
order to prevent the occurrence of glycosuria cannot be exactly given,
but a comparatively small amount is sufficient. If somewhat less than
this minimum be removed, diabetes of a less severe type than that
following complete removal may occur. There is, however, a tendency
for it to become more severe in process of time, probably from a certain
amount of atrophy occurring in the pancreatic tissue which has been
left.1

Cause of pancreatic diabetes. — It appears probable that the pancreas
exerts its influence upon carbohydrate metabolism, either by promoting
the formation of glycogen in the liver from the dextrose taken to it by
the portal blood, or by furthering the oxidation of dextrose in the tissues
generally. In either case the effect would be the prevention of the
accumulation of dextrose in the blood, so that the percentage of sugar
in this fluid would be kept down to its normal, small amount. Whether
this is brought about by the direct action of the organ upon dextrose
which reaches it with the blood, or whether it acts indirectly in promot-
ing the metabolism of dextrose by an internally secreted material, which
passes out from the organ into the blood and tissues, is a question which
it is impossible at present to give an answer to. Diabetes which results
from removal of the pancreas, is not necessarily due to an increased
glycogenesis from transformation of glycogen (although this is the cause
of the glycosuria which first makes its appearance), for it will continue
after the glycogen has completely disappeared from the liver and muscles.
Moreover, the amount of sugar which is passed is altogether too great
to be accounted for by the amount of glycogen present in the body.
Nor is it due to a diminished consumption of sugar by the tissues.2
It has been suggested that it is caused by the absence of the glyco-
lytic ferment, which is described as being usually present in the blood.
Lepine 3 has supposed that the pancreas forms such a glycolytic ferment,
which effects the splitting of sugar prior to its oxidation in the tissues.
But Minkowski 4 has shown that the blood of an animal deprived of its
pancreas still possesses just as much power of glycolysis as a normal
animal. Kausch,5 who succeeded in producing diabetes in ducks and
geese by pancreatic extirpation, also found that, after removal of the
liver in the diabetic animal, moderate amounts of sugar were still con-
sumed in the tissues. Pancreatic glycosuria diminishes or disappears
during fever.6

The symptoms are not allayed by giving raw pancreas with the
food, as those of thyroidectomy are by feeding with raw thyroid. Nor

1 Cf. Hedon, Compt. rend. Acad. d. sc., Paris, 1893, tome clvi. p. 649 ; and Thiroloix,
Arch, de physiol. norm, etpath., Paris, 1892.

2 Kaufmann, Compt. rend. Acad. d. sc., Paris, 1894, tome cxviii. p. 656; Arch, dephysiol.
norm, etpat.h., Paris, 1896, p. 151.

3 " Le ferment glycolytique et la pathogenic du diabete," Paris, 1891. Lt'pine's theory
is supported by Vaughan Harley (Brit. Med. Journ., London, 27th August 1892), and
has been criticised by, amongst others, Spitzer (Berl. klin. Wchnschr., 1894, S. 949).

4 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1893, Bd. xxxi.

5 Ibid., 1896, Bd. xxxvii. S. 274 ; and 1897, Bd. xxxix. S. 219.

6 Kaufmann, Compt. rend. Soc. de biol., Paris, 1896, p. 227. Fever was found by Poore
to diminish sugar in natural diabetes (Trans. Clin. Soc. London, 1894).

VOL. i. — 59

930 METABOLISM.

are they due to any toxic substance accumulating in the blood (from
which it might be supposed to be normally removed by the pancreas),
as has been thought to be the case in the analogous instances of thyroid
and suprarenal extirpation, for the blood of an animal rendered diabetic
by pancreatic removal is not found to render a normal animal diabetic.

The facts clearly show that the diabetes which results from pancreatic
extirpation is not the result of any interference with the sympathetic nerves
in the neighbourhood of the organ, nor is it due to the arrest of the passage
of the secretion of the gland into the intestine, but is exclusively the result
of the removal of something belonging to the gland which acts in independ-
ence of its functions in connection with digestion. Since we find in the
pancreas, if we compare its structure with^ similar glands such as the salivary,
that the only important difference is the occurrence in the parenchyma of the
pancreas of certain cell islands of an epithelium-like appearance richly supplied
with blood vessels, and entirely unconnected with alveoli or gland ducts, it
seems reasonable to suppose that the influence, whatever it may be, which the
pancreas exerts upon carbohydrate metabolism, and which results in the
excessive formation of sugar on its removal, is due to this particular tissue.1

That the salivary glands have no such influence upon metabolism as the
pancreas was shown by Fehr,2 and also conclusively by Minkowski,3 who, after
removal in dogs of all the salivary glands, including the orbital glands, found
no appreciable effects either upon carbohydrate or any other form of metabolism
to follow the removal. I have myself, in conjunction with Moore, repeated this
experiment in a dog, removing in successive operations all the salivary glands
upon both sides, leaving, however, the orbital glands. The animal remained
in perfect health for several months, and no disturbances could be determined
in either carbohydrate or proteid metabolism.4

METABOLISM OF FAT.

Is the fat of the body directly derived from the fat of the food ?
— That the fat of the body should be derived from the fat of the food
seems at first sight extremely probable. But, on consideration, it will
appear that before it is laid down as the fat of the tissues it would
probably undergo a change. For the fat of different animals has by
no means the same composition. Whereas some, such as the dog and
man, have a large amount of olein in their adipose tissue, and conse-
quently their fat has a comparatively low melting point, others, such as
the sheep, have a large proportion of stearin, and the fat of such animals
has a relatively high melting point.

Now, if a dog or a man is fed upon sheep's flesh and fat, the fat
which is laid up in the body has not a different composition from that
which it ordinarily possesses. That is to say, a man living upon mutton
will have his body-fat, not of the consistency of mutton suet, but of the
ordinary consistency of the fat of the human body, having a melting
point far lower and containing a much larger amount of olein in its
composition.

If, therefore, the fat of the food is laid down as the fat of the body,
it must undergo important modifications. It is possible to suppose that
only such portions of the fat of the food as would make fat of the

1 Schafer, "On Internal Secretions," Brit. Med. Journ., London. August 1895.

2 Inaug. Diss., Giessen, 1862 (quoted from Minkowski).

:! Arch.f. exper. Path. u. FharmakoL, Leipzig, 1893, Bd. xxxi. S. 141.

4 "Proc. Physiol. Soc.," Journ. PliysioL, Cambridge and London, 1896, vol. xix. p. xiii.

METABOLISM OF FAT.

931

composition normal to the particular species of animal, are laid down
directly, and that other portions, such as the excess of stearin which
occurs in mutton fat, become broken down completely, and either directly
oxidised, or the products of their decomposition again built up to form
the normal fat. It has indeed been conclusively proved that the fat of
the food may be to a certain extent laid down unaltered in the body-
fat. Dogs which have been starved for a considerable time, so that
practically the whole of the body-fat has become removed, will, if fed
upon an excess of mutton fat and sufficient proteid, lay down a body-fat
of a melting point and composition very similar to mutton-fat. This
shows that at least a portion of the fat introduced with the food has
been, for a time at any rate, laid down directly as body-fat.1

It has been further shown that dogs to which there has been
administered, along with their food, forms of fat which do not ordinarily
occur in the animal economy, will lay down a certain amount of this
along with their body-fat. This has been determined for spermaceti,
linseed oil, and rape oil.2 That in pigs the fat of the body may also be
derived from the fat of the food, was shown in some of the experiments
by Lawes and Gilbert.3

Formation of fats from fatty acids. — The question of the form
in which fats are absorbed has been already considered in a previous article
dealing with that subject, and it has there been shown that the fats of the food
are in large part not absorbed in the form of fat, but in that of fatty acid,
into which and glycerin they are broken up by the fat-splitting ferment of
the pancreatic juice ; and that they undergo a subsequent synthesis into fat
by combination with glycerin in the columnar epithelial cells of the small
intestine.

That such synthesis is possible even in the absence of glycerin given with
the food, is shown by the experiments of I. Munk, who found that when a
dog was fed upon fatty acids in place of the fats of its ordinary food, just as
much fat was absorbed into the chyle and was laid down in the body as if
it had been fed with the complete fat. The columnar epithelial cells become
filled with fat globules, as after a meal containing actual fats ; and the synthesis
of fatty acid and glycerin to form fat must therefore have occurred in these
cells, which must themselves have produced, in some way which is not under-
stood, the glycerin necessary for the synthesis.4

Are fats formed from carbohydrate ? — This is a question of great
practical importance, seeing that carbohydrate foods are the cheapest forms
of nutriment, and that the fattening of animals is an important branch of
agricultural industry. The experience of all rearers of animals for market
points to the fact that carbohydrates do produce fat. Sheep and oxen
fed purely upon grass, which contains hardly any fat and but little
proteid in proportion to the carbohydrate present, lay on a large amount
of fat, and the artificial foods which are used for fattening purposes

1 Lebedeff, CentralU. f. d. med. Wissensch., Berlin, 1882, S. 129 ; Ztschr. f. physiol.
Chem., Strassburg, 1882, Bd. vi. S. 149 ; Arch. /. d. ges. Physiol., Bonn, 1883, Bd. xxxi.
S. 11; I. Munk, Arch. f. Physiol, Leipzig, 1883, S. 273 (Verhandl. d. physiol.
Gesellsch. zu Berlin) ; Virchow's Archiv, 1884, Bd. xcv. S. 407.

2 Radziewski, Virchow's Archiv, 1868, Bd. xliii. S. 286 ; Lebedeff, loc. cit. ; I. Munk,
loc. cit. See also Minkowski, Arch. f. exper. Path. u. PharmakoL, Leipzig, 1886, Bd. xxi.
S. 373, and I. Munk and Rosenstein, Virchow's Archiv, 1891, Bd. cxxii. S. 230, for evidence
that foreign fats pass into the chyle.

3 See note 2 on next page.

4 For further details regarding these and similar experiments, see article on "Fat
Absorption," p. 443.

932 METABOLISM.

also for the most part contain, in addition to a certain amount of
proteid, a large proportion of carbohydrate. In spite, however, of this
almost universal experience, it has been held by C. Voit1 that the
carbohydrates of the food are not directly transformed into the fat of
the body, but that they only act in promoting the fattening of animals
by sparing the oxidation of proteid, so that the non-nitrogenous portion
of the proteid molecule may become transformed into fat. It has been,
in fact, altogether denied by Voit that the carbohydrates themselves can
be transformed by the animal economy into fat, in spite of the well-
established fact that in plants there frequently occurs, especially in the
ripening of many seeds, a considerable transformation of carbohydrate
material into fat. The question was^however, brought to the test of
direct experiment by Lawes and Gilbert.2 These observers took two
pigs of the same litter, killed one as a control, and determined the total
amount of fat in its body, and kept another one alive for some weeks,
feeding it with proteid and an excess of carbohydrate food, and
determining the exact amount of proteid in such food, then killed it,
and determined the total amount of fat in its body. They found that
the amount of fat which had been added on during the time could not
be accounted for by supposing it to be derived from the proteids of
the food, since there was not sufficient proteid in the food during the
period of the experiment to account for more than two-thirds of the
fat which had been formed, even supposing the whole of its non-
nitrogenous moiety to have been transformed into fat. Therefore a
part at least of the fat formed must have been derived from the
carbohydrate in the food.

This experiment has since been repeated by subsequent observers on
different animals,3 and always with the same result, so that it may be taken
as conclusively proved that the carbohydrate of the food may be converted
into fat. The same fact may be shown by balance experiments, in which,
with nitrogenous equilibrium, there is carbon disappearance in the egesta,
showing that carbon is stored in the body in quantity more than to be
accounted for by the carbon of the proteid metabolised ; such laid up carbon
must be mainly stored as fat.4 Nor is this formation of fat from carbohy-
drate by any means a unique phenomenon in the organic world. As we have
seen, it occurs in plants, in the seeds of which fat is deposited at the expense
of sugar or starch ; and in the process of fermentation of sugar, acids of the

1 Hermann's "Handbuch," 1882, Ed. vi. S. 251 to 260.

2 The very numerous original experiments by these observers, which were begun in
1847 in the private experimental agricultural station at Rothamstead, are described in
the following amongst other publications: — Rep. Brit. Ass. Adv. Sc., London, 1852 and
1854; Journ. Hoy. Agric. Soc. Eng., London, 1849, 1851, 1852, 1853, 1855, and 1860;
Phil. Trans., London, 1859 ; Scient. Proc. Roy. Dublin Soc., 1864 ; London, Edinburgh, and
Dublin Phil. Mag., London, 1866 ; Journ. Anat. and PhysioL, London, 1877. An excellent
historical and critical account of the part taken by the various foodstuff's in the metabolic
processes of the animal economy is given by the same authors in Journ. Roy. Agric. Soc.
Eng., London, 1895, Ser. 3, vol. vi. pp. 47-141.

3 Soxhlet, Ztschr. d. Landiv. Vereins in Bayern, 1881 ; B. Schultze (geese), Landiv.
Jahrb., 1882 ; Tscherwinsky, Landw. Versuchst., Berlin, 1883, Bd. xxix. S. 317. (These
are quoted from Neumeister, "Lehrbuch," S. 368.) See also Chaniewski (geese),
Ztschr. f. Biol., Miinchen, 1884, Bd. ii. S. 179 ; C. Voit, Sitzungsb. d. k.-bayer. Akad.
d. Wissensch. zu Miinchen, 1885, S. 288 ; Meissl, Strohmer, and v. Lorenz (pig), Ztschr.
f. Biol., Miinchen, 1886, Bd. xxii. S. 63 ; I. Munk (dog), Virchow's Archiv, 1886, Bd.
ci. S. 91 ; Rubner (dog), Ztschr. f. Biol., Miinchen, 1886, Bd. xxii. S. 272.

4 Meissl and Strohmer, Monatsh. f. Chcm., Wien, 1883, Bd. iv. S. 801 ; Sitzungsb. d. k.
Akad. d. Wissensch., Wien, 1883, Bd. Ixxxviii. ; and Ztschr. f. Biol., Miinchen, 1886,
loc. cit. ; Rubner, loc. cit.

ARE FATS FORMED FROM PROTEIDS OF FOOD 1 933

fatty series are formed. And although it is not easy at first sight to
understand, from a chemical point of view, how carbohydrate molecules are
transformed into fatty molecules, we are not obliged to assume direct trans-
formation, for it may well be that the carbohydrates are broken down into
comparatively simple compounds, and that these are built up again by the
organism into fat.

The observations of Hanriot, with Richet,1 furnish indirect evidence of the
transformation of carbohydrate into fat. These observers found that, with the
administration of carbohydrate food, there is a greatly increased output of
carbon dioxide without a corresponding increase of oxygen intake. This fact
may be explained, according to Hanriot, by a transformation of carbohydrate
into fat,2 in conformity with such an equation as the following : —

13(0^,0,) = C55H10406 + 23(C02) + 26(H20)

(oleo-stearo-
palmitin)

Are fats formed from the proteids of the food ? — This is a question
which was for many years held to have been settled by the experiments
of Pettenkofer and Voit, and subsequently of Voit.3 These observers
found that if a dog is kept in a respiration chamber, and fed entirely on
lean meat, all the ingesta and egesta of the body being carefully deter-
mined and analysed, a comparison of the results shows clearly that in
many cases carbon of the proteid is retained within the body, and is
presumably in the form of fat, the amount of fat and carbohydrate in
the food being altogether too small to suppose that the carbon laid by
could have been derived from anything but the proteids of the food.
Moreover, proteid food increases the amount of fat in the milk of
suckling animals, and a bitch fed upon lean meat may produce much
more fat in her milk than can be accounted for by the fat and carbo-
hydrates of the food — produces, indeed, milk especially rich in fat, when
fed exclusively on lean meat.4

In confirmation of observations of this kind have been adduced the
statements that the milk of suckling animals and of nursing women
is richer in cream in proportion to the amount of proteid taken in the
diet ; that fat becomes formed in large amount by the larvae of blow-
flies, which are fed upon defibrinated blood, containing only very small
quantities of non-proteid organic material ; 5 that in the ripening of
cheese there is a diminishing amount of proteid, and an increasing
amount of fat ; 6 and that in the formation of adipocere from flesh, there
is found a diminished amount of. proteids, and an increased amount of
fatty acids.7 The formation of fat in the liver and tissues of a starving

1 Compt. rend. Acad. d. sc., Paris, 1892, tome cxiv. p. 371.

2 Cf. also Gautier, ibid. , p. 374.

3 Ann. d. Chem. u. Pharm., 1862, Suppl. Bd. S. 52 and 361; Ztschr. f. Biol,
Miinchen, 1869, Bd. v. ; also 1870 and 1871, Bde. vi. and vii. ; art. " Ernahrung, " in
Hermann's "Handbuch," Bd. vi. S. 249.

4 Ssubotin, Virchow's Archiv, 1886, Bd. xxxv. S. 561 ; and Centralbl.f. d. med. Wiss-
ensch., Berlin, 1866, S. 337; Kemmerich, ibid., S. 467. Both Ssubotin and Kemmerich
worked with Pfliiger. See also Voit, Ztschr. f. BioL, Miinchen, 1869, Bd. v. S. 137.

5 Fr. Hofmann, Ztschr. f. BioL, Miinchen, 1872, Bd. viii. S. 159.

6 See on the changes accompanying the ripening of cheese, Sieber, Journ. f. prakt.
&hem., Leipzig, 1880, N. F., Bd. xxi. S. 203 : Jacobsthal, Arch. f. d. ges. PhysioL, Bonn,
1893, Bd. liv. S. 484.

7 Lehmann (Sitzunysb. d. phys.-mcd. Gesellsch. zu Wiirzburg, 1885, S. 19) obtained an
increase of fatty acids to the extent of 3*7 per cent, in meat kept in running water for some
months. E. Voit (Miinchen. med. Wclmschr., 1888, S. 518) got an increase of 2 per cent,
when it was kept in milk of lime, thus excluding fungi.

934

METABOLISM.

animal poisoned by phosphorus J also affords strong presumption of the
conversion of proteid into fat. The fact that in the deposition of fat in
embryonic adipose tissue the fatty globules are preceded by albuminous
granules may also be given as evidence in the same direction.

So important did the extent of such formation of fat from proteid
appear to Voit, that he endeavoured, as already stated, to account for the
fattening qualities of carbohydrate food by supposing that it mainly
acts by sparing the oxidation of the proteids (and fats), thus allowing a
larger amount of these to be transformed into body-fat.2 In support of
his views, he pointed out that if the proteid molecule is supposed to be
split up, and a portion be removed in combination with the nitrogen
as urea, the carbon, oxygen, and hydrogen which remain are not very
different from the proportion of these elements which would be neces-
sary for the formation of fat. It was indeed calculated by Henneberg 3
that 51 '4 per cent, of proteid taken as food might, under the most
favourable circumstances, be supposed to be converted into fat. Kubner,
however, has shown that this estimate is too high. He calculates that
the utmost amount which could be converted into fat would be about
46 -9 per cent.

The view that the fat of the body is exclusively derived from the pro-
teid of the food is, however, no longer held by any physiologists, and Voit
has himself shown that it must in some circumstances be derived from
carbohydrate.4 The above view cannot, indeed, be held, if we accept, as
we undoubtedly must, the conclusions to be drawn from experiments like
those of Lawes and Gilbert. These experiments do not by any means
exclude the formation of fat from proteid, but do exclude the possibility
of its being formed entirely from proteid, and not from any other article
of diet. That a certain amount of proteid is necessary to be added to the
diet of a fattening or suckling animal is a matter of everyday experi-
ence ; but it does not seem to be necessary that this proteid should be
greatly in excess of that which is necessary to make up for the proteid
lost from the tissues, or, in the case of the suckling animal, for that also
which appears as caseinogen in the milk. If, however, the amount of
proteid in the food is too much decreased, there is more call upon the
carbohydrates and fats of the food for the immediate production of
energy, and as a result there will be less of these to be transformed into fat.

1 Storch, abstr. in Deutsches Arch. f. klin. Med., Leipzig, 1867, Bd. ii. S. 264 ; Bauer,
Ztschr. f. SioL, Miinchen, 1871, Bd. vii. S. 63 ; ibid., 1878, Bd. xiv. S. 527 ; Caseneuve,
Rev. mens. de tried, et chir., Paris, 1880, tome iv. pp. 265 and 444 ; Stolnikoff, Arch. f.
PhysioL, Leipzig, 1887, Suppl. S. 1. Bauer found in a fasting dog, to which phosphorus had
been administered, as much as 42 per cent, of fat in the muscles, and 30 in the dry liver
substance, as against 167 in the muscles and 10 per cent, in the liver of control dogs. The
nitrogen excreted is at the same time greatly increased, this also pointing to increased meta-
bolism of proteid, while there is at the same time a diminished excretion of carbon dioxide,
and correspondingly less oxygen taken in. A similar formation of fat from proteid in
phosphorus poisoning has been shown by Leo (Ztschr. f. physiol. Chem., Strassburg, 1885,
Bd. ix. S. 483) to occur in frogs. On the other hand, Lebedeff (Arch. f. d. ges. PhysioL,
Bonn, 1883, Bd. xxxi. S. 11) found in dogs which had previously been fed with linseed oil,
that the fat in the liver cells, which was formed after administration of phosphorus, had
the same characters as that Avhich had been laid on in the adipose tissue ; thus indicating
a transference of fat to the liver rather than its formation there from proteid. Stolnikow
found in frogs, after extirpation of the "fat-body," that the liver became enlarged, and fat
accumulated in it under conditions of both carbohydrate and proteid nutriment, even with-
out the addition of phosphorus to the diet.

2 For further details of the evidence in favour of this view, see Voit, in Hermann's
"Handbuch," Bd. vi. S. 243-251.

3 Quoted by Voit, Art. in Hermann's "Handbuch," S. 250.

4 Siol Centralbl., Erlangeu, 1886-7, Bd. vi. S. 243.

ACTION OF LIVER IN METABOLISM OF FATS. 935

That fat is formed from proteid, although not in the exclusive form in
which Voit at one time was disposed to assert, has been almost universally
accepted by physiologists ; but this view has been strenuously attacked of late
by Pfliiger 1 who has criticised the conclusions drawn by Voit from his experi-
ments of feeding dogs upon meat, and has shown that in all probability the meat
employed contained sufficient fat to account for the fat laid on in the body with-
out supposing this to have been derived from proteid. In a dog kept by himself
and fed upon a large quantity of meat containing the least possible fat, no fat
whatever appeared to be laid on ; but what was originally present disappeared,
so that the dog, although muscular and capable of performing severe work,
was reduced to a condition of extreme leanness. Pfliiger is therefore disposed
to deny altogether the formation of fat in the animal body from proteid,2 and
considers that its sources are to be looked for exclusively in the fats and
carbohydrates of the food.3

In this it would appear probable that Pfliiger has gone as much to
the one extreme as Voit originally went to the other. It is unquestionable
that certain forms of bioplasm are capable of transforming proteid into fat
(as in the instances cited on p. 933). This is, in fact, admitted by Pfliiger, who,
however, contends that we have no right to assume that other forms of
bioplasm, such as that of the cells of the higher animals, possess the same
power. He is disposed to regard the change as due in all the cases cited to
the action of bacteria and fungi, such as would undoubtedly be present in
ripening cheese, in putrefying blood, in putrefying flesh, and the like. But it
has been shown that in flesh kept in milk of lime, and therefore under con-
ditions unfavourable to the growth of bacteria, fatty acids are still found to a
small extent, at the expense of the proteid; and the production of fatty degenera-
tion in the cells of starved animals, to which phosphorus has been adminis-
tered, is strong evidence in favour of their possessing such a power of forming
fat from proteid; these, taken in conjunction with the numerous other instances
which have been cited, appear to indicate that this power of forming fat
from proteid is a general property of bioplasm.

As regards the ultimate fate of .fat, there seems to be no doubt that it
becomes oxidised into carbon dioxide and water, thus producing energy which
may take the form of either heat or work, and that this oxidation takes place
mainly in the muscular tissue.

Action of the liver in connection with the metabolism of fats.—
Very little is known on this question beyond the fact that, under certain
circumstances, there is a considerable accumulation of fat in the liver
cells. This has been held by Pavy 4 to indicate the correctness of his
view, that fat may be formed both in the liver and elsewhere by the
direct transformation of glycogen. But it has not been shown that the
glycogen and fat have any vicarious relation to one another ; indeed, the
contrary was found to be the case by Langley 5 and by Noel Paton.6
Nevertheless, Paton's experiments show a marked increase in the fatty

1 Arch.f. d. ges. Physiol. t Bonn, 1892, Bd. li. S. 229 ; ibid., 1892, Bd. lii. S. 1 and 239.

2 Kumagawa and Kaneda, Mitth. a. d. med. Fac. d. Tc.-jap. Univ., Toldo, 1894, Bd. iii.
(abstr. in Centralbl. f. Physiol., Leipzig u. Wien, 1895, S. 721), were also unable to obtain
evidence of fat formation in dogs fed upon food consisting almost exclusively of proteid.

3 For a reply to Pniiger's criticisms, see E. Voit, Munchen. mcd. Wchnschr., 1892,
S. 460, and Ztsclir. f. BioL, Munchen, 1896, Bd. xxxii. S. 139; also Cremer, ibid., 1897,
S. 811. Pfliiger's answer to these is in Arch. f. d. ges. Physiol., Bonn, 1897, B. Ixviii.
S. 176. See also on this subject, I. Munk. Arch.f. d. ges. Physiol., Bonn, 1894, Bd. Iviii.
S. 309 ; also Berl. Idin. Wchnschr., 1889, No. 9.

4 " Physiology of Carbohydrates," p. 258.

5 Proc. Roy. Soc. London, 1882, vol. xxxiv. p. 20 ; and 1885, vol. xxxix. p. 234.

6 Journ. Physiol., Cambridge and London, 1896, vol. xix. p. 167. Langley's state-
ments are founded upon microscopical observations (in the frog) ; Paton's, upon chemical
evidence.

936 METABOLISM.

acids of the liver of the rabbit at a period after food when the glycogen
is diminishing, and he concludes that they may have been formed from
the glycogen.1 Langley2 has shown that in frogs there is a gradual
accumulation of fat in the liver, chiefly in the outer zones of the cells,
during the winter months, a time during which the glycogen is also
gradually increasing ; and, further, that both the liver fat and glycogen
tend to diminish on warming the animals in winter. The glycogen
becomes rapidly used up in the spring, and this is also the case with
the fat. Paton found (in pigeons) that the liver fat did not appreciably
diminish as the result of a four days' fast. Taken by itself, the presence
of fat in the hepatic cells merely indicates that these cells may act as a
temporary storehouse for fat. Whetlier such fat has been formed by
them from carbohydrate or proteid, or whether it is directly derived
from the fat of the food, and is in process of transformation in the
liver cells into a fat more intimately allied to the fat of the body, are
points which have not yet been determined, but the latter supposition
appears the more probable ; for excess of fat in the food is certainly
largely stored in the liver cells.3 And it has been noticed by Lebedeff,4
and this observation is confirmed by Paton,5 that the fats of the liver
contain less oleic acid, and have a higher melting point, than those of
the body generally. Moreover, as Hofmann showed,6 there is a higher
proportion of free fatty acids in the liver, pointing, according to Nasse,
to an active metabolism of fats in that organ.7 Lebedeff8 found in
geese which had been fed for six weeks upon peas, which are rich in
proteid but contain very little fat, that the liver, although containing
much lecithin, had no fat ; and that the fat of the omen turn was also
only present in small amount. A large amount of proteid in the diet
of rabbits and kittens was found by Paton not to lead to any accumula-
tion of fat in the liver.9

1 According to Paton, nearly one-half of the fatty acids of the liver are in combination
with lecithin. See also Heffter, Arch. f. expcr. Path. u. Pharmakol., Leipzig, 1891, Bd.
xxviii. S. 97 ; and Stolnikow, Arch. f. PhysioL, Leipzig, 1887, Suppl. Heft. S. 1.

2 Loc. cit.

3 Paton, loc. cit., p. 202.

4 Ztschr.f. physiol. Chem., Strassburg, 1882, Bd. vi. S. 139.

5 Loc. cit., p. 179.

6 Beitr. 2. PhysioL C. Ludwig z. s. 70, Geburtst., Leipzig, S. 134.

7 Biol. CentralbL, Erlangen, 1886-7, Bd. vi. S. 235.

8 Loc. cit. 9 Loc. cit., p. 211.

THE INFLUENCE OF THE DUCTLESS GLANDS UPON
METABOLISM— INTERNAL SECRETIONS.1

BY E. A. SCHAFER.

CONTENTS :— Introductory, p. 937— The Thyroid Gland, p. 938— The Pituitary Body,
p. 945— The Suprarenal Capsules, p. 948— The Spleen, p. 959.

CERTAIN organs of the body have a special influence upon some of the
metabolic processes of the body. Thus the liver fulfils important
special functions in connection with the metabolism of carbohydrates
and proteids, and of those organic compounds which contain iron ;
the pancreas has an obscure but absolutely essential function in con-
nection with carbohydrate metabolism ; and removal of a large portion
of the kidneys has been shown by Bradford to produce a large increase
in the proteid waste of the tissues.2 It is also a matter of common
knowledge that removal of the ovaries or testicles may produce
profound modifications in the development of other organs, and in the
general nutrition of the body. In the case of the pancreas (and perhaps
in that of the kidney) it is by no means improbable that the gland
yields to the blood some material which influences the carbohydrate
(and nitrogenous) metabolism of other tissues. In the case of the
generative glands this is perhaps less probable : it is on the whole
more likely that these react upon the rest of the organism through the
nervous system. Numerous observations have of late been published,
commencing with those of Brown-Sequard, which have seemed to indicate
that extracts of or the expressed juices of these glands produce, when
injected hypodermically, beneficial effects upon the nervous and muscular
systems, but it is not clear that this property is not shared by other
organs rich in nuclein. Watery extracts or decoctions of the generative
glands have very much the same action, if injected into a vein, as have
extracts of other glands. In addition to the above instances, there are
certain organs of a glandular structure, but destitute of ducts, which
yield to the blood substances, which are in some cases at least
absolutely essential to the due nutrition of the body, so that the results
of the complete removal of these organs is inevitably fatal. These
substances are no doubt formed by a process of secretion, but since they
do not find their way to any free surface by means of a duct, but

1 The substance of this chapter was originally given in the form of an address to the
British Medical Association, and was published in the British Medical Journal for August
10, 1895. For the purposes of this book it has been carefully edited and many additions
have been made to it ; references to literature have also been appended.

2 Proc. Roy. Soc. London, 1892. vol. li. These researches of Bradford have already
been noticed in a previous article (p. 656). See also Meyer, Arch, dc, physiol. norm, etpath.,
Paris, 1894, p. 179.

938 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

presumably reach the blood by means of the lymphatics or blood vessels
of the organ, they have been termed " internal secretions." l

THE INTERNAL SECRETION OF THE THYROID GLAND.

The first internal secretion which may be considered is that of the
thyroid gland. That the thyroid is a secreting gland no one who
studies its structure and its mode of development can well doubt;
except that it is unprovided in the adult state with a duct, it has all
the features of structure of secreting glands. It is formed of alveoli
which are lined by epithelial cells ; and although these cells have not
been observed to exhibit changes characteristic of secretory activity
so marked as those which have been noticed under like circumstances
in the cells of ordinary glands,2 we can observe the secreted material
within the vesicles of the thyroid in the form of the substance known
as " colloid." Various attempts have been made to isolate the active
principle of the secretion ; these are referred to in a previous article.3
According to Drechsel,4 there is probably more than one active substance,
and the secretion may subserve more than one essential function.5

The gland is extremely vascular and very richly provided with
nerves, and both blood vessels and nerves come into very close relation-
ship with the secreting epithelium. The glandular structure of the
thyroid is more obvious in young than in old animals, and as age
advances, as has been shown by Hale White6 and others, the organ
undergoes a gradual process of degeneration, so that in advanced age its
normal glandular structure can only with difficulty be recognised.

Effects of ablation and disease. — As long ago as 1856, Schiff7 found
that extirpation of the thyroid in dogs is invariably followed by a fatal
result. This observation, important as it now seems, fell for many
years into oblivion, and it was not until clinical observations had again
pointed to the importance of the gland that Schiff s experiments were
remembered. It has indeed long been recognised that extensive
disease of the thyroid, such as occurs in advanced forms of goitre,
are accompanied by a swollen appearance of the integument, giving a
misshapen aspect to the features and to the extremities, and leading to
an idiotic or semi-idiotic condition, which is known as cretinism. In
1873, Gull8 described a series of symptoms, and especially a condition
of the integumental connective tissue, similar to that which is met
with in cretins, the name "myxcedema" being subsequently given to
it, because it was believed to be an cedematous condition charac-
terised by the presence of a large amount of mucin. That there is an
excess of mucin over that in ordinary connective tissue has been shown

1 In one sense all the tissues and organs of the body form internal secretions, for they all
pass into the blood materials which have been formed as products of their meta-
bolism.

a Hiirthle, Arch. f. d. ges. PhysioL, Bonn, 1894, Bd. Ivi. S. 1 ; Anderson, Arch. f.
Anat. u. Entwcklngsgesch., Leipzig, 1894, S. 177 ; Schmidt, Arch. f. mikr. Anat., Bonn,
1896, Bd. xlvii. S. 181 ; Galeotti, ibid., Bd. xlviii. S. 305.

3 Halliburton, " Chemistry of the Tissues and Organs," p. 88.

4 Centralbl.f. PhysioL, Leipzig u. Wien, 1895, S. 705.

5 Of. also Notkio, Virchoivs Archiv, 1896, Suppl. Bd. cxliv. S. 224 ; Hutchison,
Journ. PhysioL, Cambridge and London, 1896, vol. xx. p. 474.

6 Lancet, London. 1888, vol. i. p. 521.

7 "Untersuch. ii. die Zuckerbildung," Wtirzburg, 1859.

8 Trans. Clin. Soc. London, October 24, 1873 (in vol. vii., 1874).

THE THYROID GLAND. 939

by the analyses of Halliburton ; l but not to the extent believed when
the term myxoedema was applied to this condition. Nor is the condi-
tion really one of oedema, but rather of hyperplasia of the connective
tissue, which becomes altered, assuming a more embryonic character,
hence its richness in mucin (see note 1, p. 942). The connection of
myxoedema with affections of the thyroid was first recognised by Ord 2
in 1878 — an observation which has since been abundantly confirmed.
In 1882, J. L. Eeverdin 3 described the symptoms which follow com-
plete removal of the thyroid body for goitre in man, and recognised
these symptoms as identical with those of the disease which had been
described under the name of myxoedema; he accordingly termed
the collection of symptoms " operative myxoedema." 4 The results of
Eeverdin were speedily followed by those of Kocher, who described, in
a large number of cases, similar symptoms as following entire removal
of the thyroid in man.5 Kocher pointed out that the effects are most
marked in young subjects, and that they may not occur at all or
be little manifest as age advances. These observations of Eeverdin
and Kocher led to a renewal of his former experiments by Schiff,6 who
in 1884 published the results of sixty thyroidectomies upon dogs, in all
of which the result was speedily fatal,7 the operation being quickly
followed by the supervention of symptoms — tremors, spasms, and
convulsions — which seemed to point to a serious derangement in the
nutrition of the central nervous system.8 Schiff also discovered the
fact that the symptoms are prevented by a previous graft of a portion
of the gland beneath the skin or into the peritoneal cavity.

Dogs do not show the swollen condition of the connective tissues
which is a characteristic feature after thyroidectomy in man; this
appears to be due to the fact that in them a fatal result usually occurs
too rapidly to allow of the development of the so-called " myxoedema."
They are liable, amongst other symptoms, to a form of conjunctivitis

1 Trans. Clin. Soc. London, 1888, vol. xxi. Suppl. ; Journ. Path, and Bacterial., Edin.
and London, 1892.

2 Med.-CMr. Trans., London, 1878. See also Hadden, Brain, London, 1883, p. 193,
and S. Mackenzie, Trans. Clin. Soc. London, 1888 (Report of Committee on Myxoedenia), for
an account of the symptoms of myxoedema in the human subject. For a very full bibliography
of observations on the thyroid and its connection with inyxcedema, see Ord, in Allbutt's
"System of Medicine," 1897, vol. iv.

3 Rev. med. de la Suisse Rom., Geneve, 1882, p. 539; 1883, Nos. 4 to 6 ; 1887, pp.
275, 328.

4 Termed also "cachexia strumipriva" and " cachexia thyreopriva."

5 Arch. f. Uin. Chir., Berlin, 1883, Bd. xxix. S. 254.

6 Rev. med. de la Suisse Rom., Geneve, Feb. and Aug. 1884, Bd. xviii. S. 25.

7 Schiff 's dogs lived at longest fourteen days, when both lobes were simultaneously
removed ; if the removal was effected in two sittings, at a certain interval apart, the advent
of the characteristic symptoms was delayed or altogether averted.

8 These experiments of Schiff have been confirmed by many subsequent observers, but the
literature of the subject is enormous, and only a few papers can here be mentioned — Wagner,

Wien. med. BL, 1884, S. 25 and 30 ; Sanguirico and Canalis, Arch. per le sc. med., Torino,
1884, tome viii. ; Horsley, Proc. Roy. Soc. London, 1884 and 1886, and Brit. Med. Journ.,
London, 1885, vol. i. p. 3 ; 1892, vol. i. p. 267 ; also Festwhr. Rudolf Virchow, Berlin,
1891; Fuhr, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1886, Bd. xxi.; 1889, Bd. xxv. ;
Rogowitsch, Centralbl. f. d. med. Wissensch., Berlin, 1886, S. 530, and Arch, de physiol.
norm, etpath., Paris, 1888, p. 419 ; Albertoni and Tizzoni, Centralbl. f. d. med. Wissensch.,
Berlin, 1885, S. 419 ; Hoffa, Sitzungsb. d. phys.-med. Gesellsch. zu Wiirzburg, 1887,
S. 104; Ewald, Berl. Uin. Wchnschr., 1887, 1889, and 1895 ; v. Eiselsberg, " Ueber
Tetanic im Anschluss an Kropfexstirpationen," Wien. Tclin. Wchnschr., 1890 ; Gley,
Arch, de physiol. norm, etpath., Paris, 1892, and subsequent volumes ; Cristiani, ibid., 1893 ;
Langhans, Virchow's Archiv, 1892, Bd. cxxviii. S. 400 ; Domenicis, Wien. med. Wchnschr.,
1895, S. 1620; G. Rouxeau, Arch, de physiol. norm, etpath., Paris, 1897, tome ix. p. 136.

940 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

with leucocytic infiltration of the cornea.1 Horsley was the first to
operate upon monkeys. He found that these animals survive the
removal of the thyroid much longer than do dogs, and that in them, as
in man, a " myxoedematous " condition gradually supervenes. They
also pass into a condition which is unmistakably similar to cretinism,
besides which, as in dogs, they are subject to the supervention of muscular
tremors. These, however, may be greatly abated, or their onset delayed,
if the animals are kept in a very warm atmosphere.

It was further found by Allara 2 and by Ewald 3 that no results are
obtainable by thyroidectomy in birds (although it is fatal to reptiles),
and most observers found the same to be the case with rodents and
herbivora generally.4 It is a notewoiihy fact that in aged dogs thyroid-
ectomy does not produce the normal symptoms. In man also it is
found that the supervention of operative myxcedema is less frequent as
age advances.5 The absence of the result in birds has never yet been
satisfactorily explained ; but various attempts have been made to
explain the frequent absence of result in herbivora.6 It may be, either
that a portion of the gland has been left behind, or that the animals
were not kept under observation for a sufficient time (Horsley), or
that there existed in the particular case in question accessory thyroids
and parathyroids, separated from the main body and not removed in
the operation. This is the explanation which is given by Gley of the
negative results which usually attend thyroidectomy in rabbits. Gley
states that if in these animals care be taken to remove the accessory
structures as well, the usual symptoms supervene and are very rapidly
fatal.7 Moreover, he finds that if in young dogs all the parathyroids
are removed, while the main body of the thyroid is left intact, the
symptoms which have been regarded as characteristic of complete
thyroid removal nevertheless supervene, an observation which, if con-
firmed, shows that it is these structures which are physiologically the
more important part of the organ.8

The symptoms which follow thyroidectomy are of two classes —
nervous and metabolic, although we are not able to say that the
nervous symptoms are not produced by metabolic changes in the tissues
of the nervous system ; nor is it certain that the metabolic changes in

1 Gley and Rothon-Duvigneaud, Arch, de physiol. norm, etpath., Paris, 1894, p. 101.

2 Sperimentalc, Firenze, 1885, p. 281.

3 Ewald and Rockwell, Arch. f. d. ges. Physiol., Bonn, 1890, Bd. xlvii. S. 160.

4 Sanguirico and Orecchia (abstract in Centralbl. f. PhysioL, Leipzig u. Wien, 1887,
Bd. i. S. 587).

5 Bourneville and Bricon (Arch. deneurol., Paris, 1886) have shown that the liability
to constitutional symptoms usually ceases at about the thirtieth year.

6 According to Briesacher (Arch.f. Physiol. , Leipzig, 1890, S. 509), the character of the food
in dogs modifies the effects of thyroidectomy. Dogs fed with milk bear the operation better
than those fed on flesh, nor do they exhibit, as the latter often do, convulsions after a meal.

7 Compt. rend. Soc. de biol., Paris, 1891, pp. 841, 843. See also Edmunds, " Proc. Phys.
Soc.," Journ. Physiol., Cambridge and London, 1895, vol. xviii. Hofmeister (Beitr. z.
Jdin. Chir., Tubingen, 1894, Bd. ii. S. 441), and Leonhardt (Virchows Archiv, 1897,
Bd. cxlix. S. 341) have also got positive results in rabbits ; and G. R. Murray has succeeded
in producing symptoms of myxoedema in a rabbit from which he had some time previously
removed the thyroids (Brit. Med. Journ., London, 1896, vol. i. p. 204).

8 Gley, Compt. rend. Soc. de biol., Paris, 1897, p. 181 ; Vassale and Generale, Arch,
ital. de biol., Turin, 1895 and 1896, tome xxv. p. 459 ; and tome xxvi. p. 61 ; Edmunds,
"Proc. Phys. Soc.," Journ. Physiol., Cambridge and London, 1896, vol. xx. ; also Trans.
Path. Soc. London, 1895, 1896, and Journ. Path, and Bacterial., Edin. and London,
1896, vol. iii. p. 488. Blmnenreich and Jacoby (Berl. klin. Wchnschr., 1896, S. 327) state,
on the other hand, that the inclusion or exclusion of parathyroids is immaterial to the
result of thyroidectomy (but cf. Gley, Arch.f. d. gcs. Physiol., Bonn, Bd. Ixvi. S. 308).

THE THYROID GLAND.

941

the tissues are not consequent on alterations in the nervous system.1
The most characteristic nervous symptoms are those which have been
already mentioned — muscular tremors, passing gradually into clonic
spasms, and finally, into convulsive attacks (tetany) ; there is also apathy
and unsteadiness of gait, and, with the advance of time, the gradual
supervention of a cretinic condition, together with a lowering of the
body temperature and a diminution of cutaneous sensibility. The tremors
also gradually cease. Monkeys die in from five to seven weeks after the
operation. The tremors are of central origin ; they disappear on section
of the motor nerve (Schiff), but not on removal of the cortical brain
area concerned with the movements of the part (Horsley). They also
disappear when a voluntary effort is made, and on reflex irritation. In
monkeys there is extensor paralysis of the upper limb, and there may
occur attacks of functional hemiplegia.2 The attacks are diminished by
administration of potassium bromide.3 The number of red corpuscles
per c.inm. becomes mark-
edly diminished, while the
white corpuscles tend to
increase in number. The
salivary glands become
swollen and enlarged, and
contain an excess of
mucin. Changes in the
composition of the blood
have also been observed,4
and in the proportions of
the blood gases,5 and de-
generative changes have
been described in the
kidneys.6 It has been
shown that the excita-
bility of the cortex of the
brain, and even of the
lower centres, is increased
in animals which have
suffered from thyroid-
ectomy,7 but with the FlG> 84.— Monkey deprived of thyroid.— HORSLEY.
supervention of the cretinous condition it is diminished.8 The metabolic
changes which occur are most obvious in the connective tissues, and

1 Whitwell (Brit. Med. Journ., London, 1892, vol. i. p. 430) found what he regards as
pathological changes in the nerve-cells of the Rolandic area in a case of myxredema. Marked
changes in the nervous elements have also been described as a feature of the condition
of cachexia thyreopriva ; Kopp, Ttrchow's Archiv, 1892, Bd. cxxviii. S. 290; Langhans,
•ibid., S. 318; Capobianeo, Internal. Monthly Journ. of Anat. and Physiol., 1894, Bd. xi.
S. 471 (abstract in CentralbL f. PhysioL, Leipzig u. Wien, 1893, Bd. vii. S. 112) ; Lorrain
Smith and Pembrey, " Proc. Physiol. Soc.," Journ. PhysioL, Cambridge and London,
1894, vol. xv.; Quervain, Vircliow's Archiv, 1893, Bd. cxxxiii. S. 481. Vassale and
Donaggio found degeneration in the pyramidal tract (!) of dogs, after extirpation of the
parathyroids (Arch. ital. de biol., Turin, 1896, tome xxvii. p. 129).

2 Horsley, loc. cit.

3 Gley, Compt. rend. Soc. de biol., Paris, 1892, p. 300.

4 Halliburton, loc. cit. ; Ducceschi, CentralbL f. Physiol, Leipzig u. Wien, 1895, p.
359, and 1896, p. 217 ; also Arch. ital. de biol., Turin, tome xxvi. p. 209.

5 Albertoni and Tizzoni, loc. cit. (see also p. 943).

6 Rosenblatt, Arch. d. sc. biol., St. Pe"tersbourg, 1894, p. 53.

7 Autokratoff (abstract in Brain, London, 1890, vol. xxiii. p. 424),

8 Horsley, Brit. Med. Journ., London, 1892, vol. i. p. 267.

942 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

especially in the integument. These tissues become swollen and contain
a superabundance of inucin ; l the integument especially swells and the
eyelids become puffy, but at the same time the surface becomes dry,
and there is a tendency to the shedding of hairs and of the superficial
epithelium. This hyperplastic change is followed, if the animal remains
alive for a sufficient time, by atrophic changes. The nervous affection
which primarily results is usually accompanied by slight fever. Later
on this passes off, and the temperature becomes reduced even to some
degrees below normal.2

As Schiff originally showed, these effects of thyroidectomy can be
temporarily prevented by a graft of thyroid ; they may also be caused
to disappear either by injection of l^hyroid juice into a vein or under
the skin,3 or even by taking thyroid juice or raw thyroid by the
mouth. The effects of grafts are to all intents and purposes permanent,
and it has been found, as in the case of the pancreas, that removal of
the graft which has maintained the health of the animal after extir-
pation of its own thyroid, is speedily followed — as with primary removal
of the organ — by the usual symptoms of thyroidectomy. It appears,
however, to be somewhat difficult to ensure the graft taking.4

Theories of action of thyroid extirpation.— Various theories have
been advanced to account for the effects of removal of the gland.
H. Munk 5 held that the effects of removal are due, not to interference
with the functions of the gland, but to interference with adjoining
nervous structures in the neck. But this, as with the similar theory
propounded to account for the effects of extirpation of the pancreas,
is absolutely negatived if the results of thyroid grafting are to be
accepted. Besides this theory, two others, out of the many which have
been put forward, deserve consideration.6 Of these the one may be
called the theory of " autotoxication " and the other that of " internal
secretion." The autotoxication theory assumes that there are one or
more toxic substances constantly tending to accumulate in the blood,
and which it is the purpose of the thyroid gland to remove and

1 F. Semon (Brit. Med. Journ., London, 1883, vol. ii. p. 1073) has enunciated a theory
which deserves consideration here, to the effect that removal of the thyroid produces an
interference with the full chemical development of the constituents of the connective
tissues, so that these tend to take on an embryonic character ; and it is well known that
excess of mucin is characteristic of embryonic connective tissue.

2 See on this subject, Horsley, Brit. Med. Journ., London, 1892 ; Ughetti, Riforma
fried., Roma, 1890, vol. vi. p. 228.

3 Vassale, Riv. sper. di freniat., Reggio-Emilia, 1890, tome xvi. p. 439 (abstract in
Centralbl.f. d. med. Wissensch., Berlin, 1891, S. 14) ; and Arch. ital. de biol., Turin, 1892,
tome xvii. p. 173 ; Gley, Compt. rend. Soc. de biol., Paris, 1891, p. 251 ; G. R. Murray,
Brit. Med. Journ., London, 1891, vol. ii. p. 796; 1892, vol. ii. p. 449; 1893, vol. ii. p.
677 ; Schwarz, Sperimentale, Firenze, 1892, vol. xlvi. ; Arch. ital. de biol., Turin, tome
xvii. p. 330 ; Chopinet, Compt. rend. Soc. de Uol, Paris, 1892, p. 602 ; Brown-Sequard,
Arch, de physiol. norm, etpath., Paris, 1892.

4 v. Eiselsberg, Wien. Idin. IVchnschr., 1892, S. 81. For a successful case of thyroid
grafting in the human subject, see Macpherson, Edin. Med. Journ., May 1892.

5 Sitzungsb. d. Jc. Akad. d. Wissensch. zu Berlin, 1887, S. 823, and 1888, p. 1059.
See on the subject of Munk's experiments, and also on thyroid grafting, Halstead, Johns
Hopkins Hosp. Rep., Baltimore, 1896, p. 373. The bulk of this paper deals with the
hypertrophy of the remaining portion which follows the removal of a part only of the
thyroid. In a recent paper (Virchow's Archiv, 1897, Bd. cl. S. 271) Munk endeavours to
maintain his position. He denies that either cachexia or myxcedema necessarily follows
thyroidectomy, but in this he is at variance with nearly all other experimenters and with
the result of clinical experience.

6 For older theories regarding the functions of the thyroid, see Horsley, Brit. Med.
Journ., London, 1892, vol. i. p. 267 et seq.

EFFECT OF THYROID JUICE. 943

render innocuous.1 According to this, the function of the thyroid
would be primarily excretory. This view is supposed to be sup-
ported by the observation, that the urine of animals becomes, after
removal of the thyroid, more toxic than that of normal animals,2 and that
the blood is toxic for other animals, and especially for those which have
already had the thyroid removed, although this operation may have
been performed only a short time previously, and before the
symptoms of thyroidectomy have had time to develop. It is not stated
what the probable nature of this substance is, or by what tissues it
may be formed.

Effect of thyroid juice. — The " internal secretion " theory would
explain the phenomena of extirpation as due to the absence of a
secretion which is formed within the thyroid or parathyroids, and
passes from them into the blood ; a secretion which is necessary for
certain of the metabolic processes of the animal body, and especially
for those connected with the nutrition of the central nervous system
and of the connective tissues. That this view of the function of
the thyroid, which was the one given originally by Schiff, is in the
main the true one, is shown by the fact that beneficial and not
toxic effects follow the exhibition of thyroid juice, both in cases of
thyroidectomy in animals and in myxcedema and other affections in
man. Moreover, extracts of thyroid gland produce distinct physiological
effects in the normal subject.3 If a decoction of the gland be injected
into a vein, the blood pressure markedly falls (Fig. 85), although the
beats of the heart remain at about the same rate and of the same
strength as before.4 This lowering of the blood pressure is not, however,
peculiar to the thyroid, but occurs with extracts of some other
secreting glands. But it has been shown by G-. Oliver,5 that the
exhibition of thyroid juice or other preparations of thyroid seems to
possess a specific tendency to increase the calibre of the radial artery in
the human subject. It would seem, therefore, that the juice of the
thyroid, and extracts which are obtained from the gland, have a distinct
action upon the vascular system. It has further been noticed that feeding
with thyroid tends to cause increased metabolism in the body, accom-
panied by diuresis and diminution of fat, so that it has been proposed as
a cure for obesity.6 Thyroidectomy alters the conditions of the gaseous
exchange,7 and this in all probability by an indirect effect through
the vasomotor system. Lorrain Smith8 found that in animals which
have been deprived of the thyroid body, the reaction to changes of
temperature is abnormally rapid. When normal animals are exposed to
a cold atmosphere, the production of carbon dioxide becomes increased,
consistently with the increased oxidation which is necessary to cause

1 Horsley, Proc. Roy. Soc. London, 1886, vol. xl. p. 6 ; Brit. Med. Journ., London,
1892 ; Blumenreich and Jacoby, Arch. f. d. ges. Physiol., Bonn, 1896, Bd. xiv. S. 1.

2 Laulanie, Compt. rend. Soc. de biol., Paris, 1891, p. 307 ; see also Gley, ibid., 1894,
p. 192 ; and Masoin, ibid., p. 105.

3 Gley, Arch, de physiol. norm, etpath., Paris, 1894, p. 484.

4 Oliver and Schafer, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 277.

5 Croonian Lectures, Lancet, London, 13th June 1896.

6 Leichteustern, Deutsche med. IVchnschr., Leipzig, 1894, No. 50. See on the physio-
logical action of thyroid extract, Ewald, loc. tit. ; Donatti, Virchow's Archiv, 1896, Suppl.
Bd. cxliv. S. 253 ; Berkeley, Johns Hopkins Hosp. Bull., Baltimore, July 1897. Berkeley
examined the nerve centres of animals which had died from prolonged administration of
thyroid extract, but could find no evidence of any changes in the nerve cells.

7 Michaelsen, Arch. f. d. ges. Physiol., Bonn, 1889, Bd. xlv. S. 622.

8 Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 378.

944 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

an increased production of heat. This increase of carbonic acid does not
take place immediately, but only conies on after a certain period of
time ; the temperature of the body being in the meanwhile maintained
normal by those physical changes which occur in the circulation, and
which allow the quantity of blood brought to the skin, and the amount
of heat thereby lost from the general surface of the body, to be varied.
Now, it is precisely these vasomotor changes which appear to be lack-
ing after removal of the thyroid ; for the production of carbon dioxide
becomes almost immediately increased by exposing thyroid ectomised
animals to a low temperature. Cardiac palpitations with increased

M/\A

FIG. 85. — Effect in the dog upon the blood pressure of the intravenous injection of decoc-
tion of thyroid. Time in seconds. The line above the time tracing is the abscissa
of the mercurial manometer.

pulse frequency, often accompanied by a feeling of giddiness, may
sometimes be produced by large doses of fresh thyroid; after a time
glycosuria and increase of urea appear.1 Experiments upon the effect
of thyroid feeding on metabolism have been made by various observers.2
Eichter3 found in man no marked effect on nitrogenous metabolism,
but Bleibtreu and Wendelstadt and also Roos got a distinct increase
of excreted nitrogen during thyroid feeding. Schondorff obtained an
increased excretion of nitrogen during the first eight days (in dog) ;
after that, N-balance was maintained, while the body-fat was greatly
diminished in amount. The sodium chloride and phosphoric acid were
also somewhat increased. Bettmann 4 states that thyroid feeding tends
to produce "alimentary glycosuria" (see p. 881).

1 Georgiewsky, Centralbl. f. d. med. Wissensch., Berlin, 1895, Bd. xxvii.

2 Napier, Lancet, London, 1 893, vol. ii. p. 805 ; Vermehren, Deutsche med. Wchnschr. , Leipzig,
1893, No. 11 ; Dening, Munchen. med. Wchnschr., 1895, S. 464 ; Bleibtreu and Wendelstadt,
Deutsche med. Wchnschr., Leipzig, 1895, S. 346; Mediger, Diss., Greifswald, 1895
(abstract in Centralbl. f. Nervenh. u. Psychiat., Coblenz u. Leipzig, Bd. xviii. S. 289) ;
Lanz, Deutsche med. Wchnschr., Leipzig, 1895, S. 597 ; Irsal, Vas. and Gara, ibid., 1896,
Bd. xxii. S. 439; Schondorff, Arch. f. d. ges. PhysioL, Bonn, 1896, Bd'. Ixiii. S. 423;
Gluziriski and Lemberger, Centralbl. f. innereMed., Leipzig, Bd. xviii. S. 90 ; Roos, Ztschr.
f. physiol. Chem., Strassburg, 1895, 'Bd. xxi. S. 19 ; and 1896, Bd. xxii. S. 18; Giirber,

Sitzungsb. d. phys.-med. Gesellsch. zu Wiirzburg, 1896, S. 101.

3 CentralU.f. innere Med., Leipzig, 1896, S. 65.

4 Berl. Uin. Wchnschr., 1897, S. 518.

THE PITUITARY BOD Y. 945

That the thyroid gland yields an internal secretion which subserves a
useful purpose within the body, appears to follow conclusively from these
data, and the effects which follow thyroidectomy are probably due to
the loss of that secretion. Whether the gland also possesses the
function of destroying toxic products of metabolism which would other-
wise tend to accumulate in the blood, a function which has been
attributed to it by some authors, is a point the evidence regarding
which is at present insufficient.

On account of its extreme vascularity and its direct connection with
the vessels which supply blood to the head, the thyroid has also been
regarded as exercising a regulatory function on the blood supply to the
brain, — short-circuiting by vaso-dilatation the cerebral blood How, or vice
versd. This view, which was long previously enunciated by J. Simon,1
has been of late again brought into prominence by Stahel,2 whose
opinion is supported by that of Waldeyer,3 both of whom approach
the subject from the anatomical standpoint. More recently the matter
has been the subject of physiological experimentation by Cyon,4 who
finds that the nerves passing to the thyroid contain powerful vaso-
dilatators, and that their stimulation may greatly lower the pressure in
the carotid. Cyon further states that they are called into action
very easily on excitation of the cut ends of the vagi, of the depressors,
or of the cardiac branches of the recurrent laryngeal nerves. After
removal of the gland, the excitability of these nerves is diminished, but
it is increased by the administration of thyroid preparations.

The mode of connection which unquestionably exists between turg-
escence of the thyroid and the other nervous and vascular symptoms
which characterise Graves's disease (exophthalmic goitre), is still quite
obscure. This affection is not, like ordinary goitre and myxoedema, bene-
fited by thyroid feeding ; but various observers have obtained consider-
able benefit by administration of the uncooked thymus of young animals.5

THE PITUITARY BODY.

The next organ the internal secretion of which we may shortly con-
sider, is the pituitary body. As is well known, the anterior lobe of
the pituitary body is a structure which may in general terms be described
as glandular, and although not in all respects resembling the thyroid,
there are nevertheless certain points both in connection with its mode
of development, and in the structure of the fully formed organ, which
might lead to the supposition that there is something functionally
common to the two organs.

Effects of removal and disease. — So far as destruction of the
pituitary body is concerned, experiments have given interesting results.
The organ has been removed successfully in a number of cases in cats by
Marinesco,6 and in dogs by Vassale and Sacchi.7 In all instances of
complete removal death ensued, usually within a fortnight of the

1 Phil. Trans., London, 1844, p. 295.

- Deutsche med. Wchnschr., Leipzig, 1887, S. 227 (quoted by Waldeyer).

3 fieri. Uin. Wchnschr., 1887, S. 233.

4 CentralU.f. PhysioL, Leipzig u. Wien, 1897, S. 357.

5 For the literature of this disease, see Ord and H. Mackenzie, in Allbutt's "System of
Medicine," 1897, vol. iv. p. 508.

6 Compt. rend. Soc. de Uol., Paris, 1892, p. 509.

7 Arch. ital. de Uol., Turin, 1895, tome xxii. p. 133.

VOL. I. — 60

946 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

operation. The symptoms observed were — (1) Diminution of the body
temperature; (2) anorexia and lassitude; (3) muscular twitchings
and tremors, developing later into spasms ; (4) dyspnoea. Many
of the symptoms show abatement after injection of pituitary extract.1
Vassale and Sacchi conclude that the pituitary must furnish an
internal secretion which is useful in maintaining the nutrition of
the nervous and muscular systems. Some of these symptoms, especi-
ally the muscular twitchings, are similar to those seen on removal of
the thyroid. It has been stated that after thyroidectomy the pituitary
body becomes enlarged ; and Eogowitsch2 has supposed that the fact that
in rabbits a thyroidectomy sometimes fails to produce the usual results,
is due to the pituitary taking on a vicarious action, the pituitary being-
larger in proportion in the rabbit than in most animals.3

Similar statements have been made with regard to its enlargement in
some cases of myxoedema, in which the pituitary has been examined. But,
on the other hand, Schonemann,4 who examined the pituitary in a large
number of cases of goitre, got no distinct evidence of its enlargement in
that disease, nor of any constant change in it, although, in common with
other structures, it frequently showed pathological alterations. And
whereas enlargement and degeneration of the thyroid is accompanied
by cretinism and myxoedema, there appears to be a connection between
enlargement and degeneration of the pituitary body and an entirely
different disease, to which the name "acromegaly" has been given by
Marie,5 the most obvious symptoms of which are hypertrophy of the
bones of the extremities and of the face, with some hypertrophy of the
skin and mucous membranes, but without mucinoid degeneration.6

Effects of extracts. — The theory that the thyroid and pituitary
may act vicariously, appears to be negatived by the physiological effects
which are produced by extracts of the last-named gland, and which
differ altogether from those furnished by the thyroid.7 These differences
are exemplified in Figs. 85 and 86, which show that, whereas decoction
of thyroid produces no obvious effect upon the contractions of the
heart, decoction of the pituitary body causes great augmentation in
the force of the heart's beat, without, however, any accompanying
acceleration of the rate. Further, the effect upon the arteries is
precisely the reverse of that which is obtained by extract of thyroid,
for, in place of falling, the blood pressure rapidly rises. That this
rise is not due simply to augmentation of the heart's beats, but that it

1 Brown-Se"quard, Compt. rend. Soc. de Uol, Paris, 1893, p. 527.

2 Beitr. z. path. Anat. u. z. allg. Path., Jena, 1889, Bd. iv. S. 453.

3 See also, on the subject of the possible connection between thyroid and pituitary, H.
Stieda, Beitr. z. path. Anat. u. z. allg. Path., Jena, 1890, Bd. vii. S. 537 ; Pisenti and
Viola, Centralbl. f. d. med. Wissensch.\ Berlin, 1890, S. 25 and 26 ; Hofmeister, loc. tit.,
1894 ; de Coulon, Virchows Archiv, 1896, Bd. cxlvii. S. 53 ; and Leonhardt, loc. cit., 1897.

4 Virchow's Archiv, 1892, Bd. cxxix. S. 310.

5 Brain, London, 1889, vol. xii. p. 59. See also Massalonso, Centralbl. f. Nervcnh. u.
Psychiat., Coblenz u. Leipzig, 1895, Bd. xviii. S. 281. A. Schiff (Wien. klin. Wchnschr.,
1896, Bd. x. S. 277) obtained a marked increased excretion of phosphoric acid on feeding
with pituitary tablets, with only a very slight increase of nitrogen. He regards this
experiment as indicating an influence of the extract upon the metabolism of bone.

6 Enlargement of the pituitary only occurred in three cases of acrornegaly out of seven
described by Souza-Leite (Neurol. Centralbl., Leipzig, 1890, Bd. ix. S. 447), who states
that, on the other hand, persistence of the thymus appears to be a fairly constant accom-
paniment of that disease. Dreschfeld (Brit. Med. Journ., London, 1894, vol. i. p. 6)
looks upon the enlargement of the pituitary body as a symptom rather than the cause of
acromegaly.

7 Oliver and Schiifer, Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 277.

EFFECTS OF EXTRACTS.

947

is also due to contraction of the arterioles, is sufficiently shown by the
fact that if salt solution containing pituitary extract be passed through
the blood vessels of a frog, the entire nervous system of which has been

e

if

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t*

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-3°
2 5

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sit

destroyed, the vessels markedly contract. This experiment conclusively
shows that the effect upon the arteries is a direct one, and in all pro-
bability the action upon the heart is also direct.

948 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

We may assume, then, that the pituitary body furnishes to the
blood an internal secretion, and that this internal secretion tends to
increase the contraction of the heart and arteries, and perhaps influences
the nutrition of some of the tissues, especially bone and the tissues of
the nervous system.1

THE SUPRARENAL BODIES.

Effects of disease and ablation.— The immense importance of these
glands in nutrition was indicated by Addison,2 who, in 1855, pointed out
that the symptoms of the disease now known by his name, the most
prominent of which are extreme asthenia, and the appearance of bronze
patches upon the skin and on some of the mucous membranes, are
associated with pathological alterations of the suprarenal capsules.
This observation was tested experimentally by Brown-Sequard,3 who
found (in 1856) that removal of the suprarenal bodies was rapidly and
unfailingly fatal in all animals (usually within twelve hours). Removal
of one capsule produces no obvious effect, but when the second is re-
moved, even after a long interval of time, the usual symptoms caused by
total ablation at once supervene. The symptoms following the removal
are practically those of Addison's disease, although much more acute.
There is extreme muscular weakness, and great loss of tone of the
vascular system, with loss of appetite, and other signs of general pro-
stration. Death appears to result from paralysis of the respiratory
muscles. But the pigmentation which usually accompanies disease of
the capsules was not noticed by Brown-Sequard, and he inferred that this
absence of pigmentation was probably due to the fact that a fatal result
appears so rapidly after the complete removal of the capsules in animals,
that time is not afforded for the development of this symptom. This
conjecture appears to have been confirmed by an experiment of
Nothnagel,4 who found pigmented patches to appear after crushing the
capsules, and also by F. and S. Marino-Zucco,5 who state that by inocu-
lating the suprarenals of rabbits with pseudo-tubercle bacillus they
have succeeded in obtaining, not only the slow development of the
ordinary symptoms of suprarenal removal, but also an augmentation
in the pigmentation of the skin and hair. Tizzoni also has obtained
skin-pigmentation after complete and partial removal of the capsules in
rabbits, which lived a certain time after the operation.

It is needless to state that Brown-Sequard's results, following as
they did upon Addison's observations, attracted much attention, and
numerous investigators set to work to verify them. But many of these6
failed to confirm the results which were obtained by Brown-Sequard,
probably by reason of the removal being incomplete, or of the existence

1 The thromboses which Mairet and Bosc (Arch, dephysioL norm, et path., Paris, 1896,
p. 600) obtained from intravenous injection of glycerin- and water-extracts of pituitary
into rabbits, were doubtless caused by nucleo-proteids. Subcutaneous injection produced
slight rise of temperature with lassitude und gastric troubles, but as it does not appear
that the material used was aseptic, these observations are of little value.

- "On the Constitutional and Local Effects of Disease of the Suprarenal Capsules,"
London, 1855.

3 Compt. rend. Acad. d. sc., Paris, 1856, pp. 422 and 542 ; Arch. gen. de m^d., Paris,
1856 ; Journ. de la physiol. de I'homme, Paris, 1858, tome i. p. 160.

4 Ztschr.f. Iclin. Med., Berlin, 1879, Bd. i. S. 77.

5 Riforma med., Eoma, 1892, tome i.

6 Philippeaux, Compt. rend. Acad. d. sc., Paris, 1856 ; Gratiolet, ibid. ; G. Harley, Brit.
$nd For, Med.-Chir. Rev., London, 1858, vol. xxi. p. 204.

THE SUPRARENAL BODIES. 949

of accessory capsules ; and after a few months of controversy the subject
gradually dropped, and became for a long time almost forgotten. The
interest in this subject has been, however, recently revived, and the
experiments of Brown-Sequard have been repeated by various observers
(Tizzoni, 1 Abelous and Langlois,2 and many others). I have myself
made several experiments of the same kind on various animals
(monkeys, dogs, cats, and guinea-pigs). All these observations have
tended to confirm the original statements of Brown-Sequard. They
show that animals deprived of their suprarenal capsules die rapidly,
usually in the course of one to three days, with the symptoms above
noted. The further fact is mentioned by Abelous and Langlois, and
this is also confirmatory of a statement of Brown-Sequard,3 that the
blood 4 of animals dying in consequence of the removal of the supra-
renal capsules is toxic for other animals which have recently been
deprived of their capsules, although it causes no toxic results in normal
animals ; whereas the transfusion of normal blood into the veins of
" decapsuled " animals tends markedly to prolong their survival of the
operation.6

The symptoms caused by this blood are said by Abelous and
Langlois to be those of curari poisoning — paralysis, that is to say, of
the intramuscular nerves ; ti and since the most marked phenomena
resulting from removal of the capsules is extreme muscular weakness,
it has been concluded by them that after removal of these glands
a certain toxic product of muscular metabolism accumulates in the
blood, and that the function of the glands is to remove or destroy
this toxic principle.

This is the " autotoxication " theory of the suprarenal capsules, and
is similar to that which has been applied to the thyroid body. Like
the other autotoxication theories, it is chiefly founded upon the fact
that the blood of animals which are moribund in consequence of the

1 Arch. ital. de bioL, Turin, 1886, tome x. p. 372; Beitr. z. path. Anat. u. z. ally.
Path., Jena, 1889, Bd. vi. S. 1. Tizzoni thought that removal of one capsule only
was fatal ; this conclusion was shown to be erroneous by Stilling (Rev. dc med., Paris,
1890). Tizzoni found in many of his rabbits alterations in various parts of the central
nervous system, apparently brought on by haemorrhages into the grey matter.

2 Cvm.pt. rend. Soc. de bioL, Paris, 1891, p. 835 ; 1892, p. 388 : Langlois, ibid., 1893, p.
444 ; also in tome iv. of " Travaux du Laboratoire de Ch. Riehet," 1897, where will be
found a full bibliography (234 papers) and historical account of the subject of the physiology
of these organs. Langlois states that it is sufficient to leave TV of the total weight of the
capsules in the dog in order to insure the survival of the animal.

3 Journ. de la p/tysiol. de Vhomme, Paris, 1858, tome i.

4 Also, according to Gonrfein (Compt. rctid. Acad. d. sc., Paris, 1897, tome cxxv. p. 188),
alcoholic extracts of the blood and organs of "decapsuled" animals.

5 It is stated by Brown-Sequard that injection of extract of suprarenal under the skin
of animals the suprarenal capsules of which have been removed, has a partial success in
prolonging life (Compt. rend. Soc. de biol., Paris, 1892, tome xliv. p. 410). But it is
doubtful if they can be kept alive for any length of time, either by injection in this way
or by the taking of suprarenal by the mouth. It appears, however, to be true that some
cases of Addison's disease are distinctly benefited by extract of suprarenal capsule, taken
by the mouth, but whether any such cases have been cured is doubtful. (For reference
to such cases, see Langlois, "Travaux du Laboratoire de Ch. Richet," 1897, tome iv. p. 93
el seq.). Abelous (Compt. rend. Soc. de biol., Paris, 1892, Nov. 12) and Gourfein (Rev. med.
dc la Suisse Rom., Geneve, 1896, p. 113) have succeeded in effecting suprarenal grafts
in the frog, which prevented the occurrence of the usual symptoms when the animal's own
suprarenals were destroyed ; on afterwards removing the graft, the symptoms supervened
as usual. Dominicis ( Wien. med. Wchnschr., 1897, S. 18), on the other hand, operating
on rabbits and dogs, invariably found a fatal result to follow removal of the second supra-
renal, after the first one had been successfully grafted.

6 This statement is, however, denied by Gourfein (Rev. med. de la Suisse Rom., Geneve,
1896, p. 113).

INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

particular extirpation is toxic, especially for other animals which have
been submitted to the operation. But it is probable that the blood
of an animal dying slowly as the result of any disease, would be to
some extent toxic, and the toxic principles would more powerfully affect
animals whose resisting power had been lessened by a recent severe
operation. However this may be, whether the suprarenal capsules do
or do not destroy a toxic principle which is formed elsewhere, and which
would otherwise accumulate in the blood, they unquestionably produce
a material which has entirely different properties from those stated to
be possessed by the blood of animals deprived of their capsules. This
material, which is probably the basis of the internal secretion of the
glands, has most active physiological properties.

Hypodermic injection of extracts — General effects. — The action
upon normal animals of extracts of suprarenal was first inves-
tigated by Pellacani and Foa,1 both alone and in conjunction. They
injected subcutaneously extracts of the glands, made with water, and
observed the symptoms which resulted. They found that animals
(dogs) were killed by subcutaneous injection of extract of calf suprarenal.
Their results were criticised by Alexander,2 wTho pointed out that
there was liability to chemical change in their preparations, and were
not confirmed by other observers, but they are, nevertheless, in the
main correct.

In conjunction with G. Oliver,3 I have myself made a number of
observations upon the effect of subcutaneous injection of water and
glycerin extracts of suprarenal. We found that the animals were
usually unaffected by moderate doses, but witli larger doses showed
quickening and augmentation of the heart-beat, shallow and fast
respirations, and fall of temperature. Guinea-pigs, we found, would
stand a large subcutaneous dose of suprarenal extract without
showing any symptoms at all, or with only a slight acceleration
and increase of the force of the pulse. The same appeared to be
the case with the cat and with the dog, unless a very large dose
were injected, when the symptoms above enumerated became very
marked. Rabbits, on the other hand, were more susceptible to the
influence of suprarenal extracts. If a large dose wrere given, the animal
succumbed within half an hour. If, on the other hand, the dose was
only moderate in quantity, it did not show any symptoms at all for
some hours, but then it might suddenly succumb. This primary absence
of symptoms was also noted by Foa and Pellacani in dogs. They state
that in many of the animals which they experimented upon in this way,
there were no symptoms at all apparent upon the day upon which the
injection was given, but that the next morning the animal was usually
found dead. The cause of death, it may be added, is not by any
means clear. Foa and Pellacani have supposed that it may be due to
paralysis of the respiratory centre, but the slight effect which intra-
venous injection of suprarenal extract produces upon this centre does
not lend support to this conjecture.

In frogs we found the effect of the water extract or decoction injected
into the dorsal lymph sac was to produce a temporary paralysis, which

1 Arch, per U sc. mcd., Torino, 1879, 1880, tomes iii., iv., and vii. ; Arch. Hal. de
biol., Turin, 1888, p. 56.

2 Beitr. z. path. anat. u. z. ally. Path., Jena, 1892, Bd. xi.

3 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 235.

INTRA VENOUS INJECTION OF SUPRARENAL EXTRACT. 95 1

showed itself in very slow and languid movements. This may, however,
be due to the veratrine-like effect which the extract produces upon
muscular tissue (see below). The subject has been worked at more
recently in my laboratory by Swale Vincent.1 who has performed
a large number of experiments upon various animals, and has not only
confirmed most of our results, but has added several other facts.
Vincent commonly obtained fatal results in guinea-pigs with doses of
6 grms. of fresh gland. In rabbits he found the results to be inconstant.
The hind-limbs become paralysed before the fore-limbs in all animals
investigated. Doses insufficient to cause a fatal result produce im-
munity to larger doses which would otherwise be fatal, and this effect may
last a few weeks. The action is produced by the medulla of the gland
only ; extracts of a large number of other organs and tissues were tried,
but none produced any effect when injected hypoclermically (Vincent).

Intravenous injection. — The intravenous injection of suprarenal
extract produces a powerful physiological action upon the muscular
system in general, but especially upon the muscular walls of the blood
vessels, and the muscular wall of the heart. A certain amount of action
is also manifested
upon some of the
nerve centres in
the bulb, especi-
ally the cardio-
inhibitory centre,
and to a less
extent upon the
respirator y
centre.2

Action on
skeletal muscle. —
The effect upon
the skeletal
muscles is well
shown in the frog
(Fig. 8 7), and can
also be seen in
mammals. The

o FIG. 87. — Effect of suprarenal extract upon muscle contraction in
the frog. A, Normal muscle curve of gastrocnemius ; B, Curve
during suprarenal poisoning, but otherwise under the same

taken
conditions as A.

Time tracing, 100 per sec. 3

contraction of the muscle in response to a single excitation of its nerve

1 Journ. Physiol., Cambridge and London, 1897, vol. xxii. p. 111.

2 Oliver and Schafer, " Proc. Physiol. Soc.," March 1894 (Journ. Physiol., Cambridge
and London, vol. xvi.) ; "Proc. Physiol. Soc.," March 1895 (ibid., vol. xvii.). These
were preliminary communications. The detailed account of the experiments is to be found
in the Journ. Physiol., Cambridge and London, vol. xviii. pp. 230-276. The chemical
work in connection with our experiments was carried out by Moore ; his papers on the
subject will be found referred to by Halliburton, on pp. 90-92. Since the first com-
munication to the Physiological Society there have appeared a large number of papers
on the subject, for the most part confirming the results there announced. The follow-
ing are some of these — Szymonowicz, Anz. d. Akad. d. Wiss. in Krakau, February
1895; Arch. f. d. ges. Physiol., Bonn, 1896, Bd. Ixiv. S. 97; Cybulski, Gaz. lek.,
Warszawa, and Anz. d. Akad. d. Wiss. in Krakau, 1895, reported in Centralbl. f. Physiol.,
Leipzig u. Wien, 1895, S. 172 ; Velich, Wien. mcd. BL, 1896 ; Biedl, Anz. d. k. k. Ges. d.
Aerzte, in Wien, 1896, &nd Arch. f. d. ges. Physiol., Bonn, 1897, Bd. Ixvii. ; Gottlieb, Arch.
/. expcr. Path. u. PharmakoL, Leipzig, 1896, S. 99; Ocaiia. Ad. d. I. soc. cxp. d. Hist.
Nat., Madrid, 1897.

3 Figs. 87, 88, 89, 90, and 91 are taken from the Journ. Physiol., Cambridge and
London, 1895, vol. xviii. No. 3.

952 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

is as ready as in the normal animal ; but it is greatly prolonged, so that
the result is comparable to that produced by a small dose of veratria,

.

"o o

o p

o

.- o

which, as is well known, has the effect of enormously increasing the
contraction resulting from a single stimulation of the muscle or its

II

X

^ o

=3 S

n

INTRA VENOUS INJECTION OF SUPRARENAL EXTRACT. 953

nerve. It is in no way comparable to a curari effect, for the muscles
remain as excitable through their nerves as before. It is therefore an
effect en-
tirely dif-
ferent from
the s o-
calledauto-
toxication
paralysis
which is
stated to
result after
removal of
the supra-
renal cap-
s u 1 e s in
a n i m a 1 s
(but sec
note 6, p.
949), and
the materi-
al which is
extracted
by water,
therefore,
from the
suprarenal
capsules is
certainly
not the
same ma-
terial that
is said to
accumulate
in the blood
after the
removal of
those or-
gans.

Action on
heart and
vessels. —
The action
upon the
circulatory
s y s t e m
may be di-
vided into
the action
upon the
heart and

the action upon the arterial system. Upon the heart the effect
according as the vagi are cut or uncut. When the vagi are

• - o

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o %

8.5

•2 .5 o

o"~5j o

-gl

-
SJH

OS * <?

differs,
uncut

954 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

and the heart is therefore still in connection with the cardio-inhibitory
centre in the medulla oblongata, the action of suprarenal extract is to
slow, and even to entirely stop, the contractions of the auricle. Under
these circumstances the ventricle continues beating with an independent
slow rhythm (Fig. 88). The result is to cause the pulse to be very
slow. On the other hand, when the vagi are cut or their cardiac ends
paralysed by atr opine, the effect upon the heart is precisely the reverse
(Fig. 89). The strength and frequency of the auricular contractions
are markedly increased, and those of the ventricle are correspond-
ingly augmented. This naturally has the effect of sending a vastly
greater amount of blood into the arteries, which by itself would alone
produce a great rise in the arterial pressure. The direct action upon

FIG. 90. — Effect of suprarenal extract upon heart, limb, spleen, and blood pressure, after
section of cord and vagi. The forearm in this experiment was at first passively
expanded, but its contraction is afterwards manifest. (Reduced to one-half.)

the arteries is, however, quite as marked as that upon the heart.
If the blood pressure be taken in a dog in the usual way, by connect-
ing a mercurial manometer with the femoral artery, and if a minute
dose of suprarenal extract be now injected into a vein, it is found that
even with the vagi uncut, and the heart therefore slowed by the action
of the extract, the blood pressure rises considerably (Fig. 88). But
with the vagi cut or paralysed by atropine the rise can only be
characterised as enormous (Fig. 89).

The contraction of the arteries is further exemplified by the fact that
if an organ, such as a limb or the kidney or the spleen, be enclosed within

2NTRA VENOUS INJECTION OF SUPRARENAL EXTRACT. 955

a plethysmograph or oncometer, the instrument indicates a great
diminution in volume of the organ, which can only be accounted for by a
contraction of its arterioles.1 This contraction is produced by the direct
action of the drug upon the muscular tissue of the smaller arteries, and
not indirectly through the vasomotor centre ; for it obtains in the mammal
equally well with the spinal cord cut or the bulb destroyed (Fig. 90), or
even in the case of the arm after the brachial plexus has been severed
(Fig. 91). In the frog it is produced also with the brain and spinal cord
completely destroyed, when salt solution containing suprarenal extract is
allowed to flow through the arteries. Under these circumstances the
flow of fluid, which, without the suprarenal extract, may have been com-
paratively rapid, becomes almost completely stopped, and this can only
be due to the direct action of the extractive substance upon the muscular
tissue of the smaller arteries.

The enormous rise of blood pressure which is got after the vagi have
been cut, is shown in the tracings (Figs. 89 and 90) : the pressure may rise
to four or five times its original height. Hardly any other agent will
produce such an enormous increase of pressure, except direct stimulation
of the vasomotor centre. It is not the case, however, that the elevation
of blood pressure, and the contraction of the arteries, is due to the
stimulation of the vasomotor centre by the drug, as was supposed by
Cybulski and Szymonowicz, for, as we have seen, the action is essentially
a peripheral one. As shown by Oliver,2 it will occur if the extract be
directly applied to the vessels of the mesentery, either during life or
in the " surviving " condition.

The effect of intravenous injection upon the blood pressure passes off in the
course of a few minutes. After a dose, no matter whether small or large, has
been injected into a vein, and has produced the results which we have
recorded, the blood vessels slowly resume their ordinary calibre, the augmenta-
tion and increased frequency of the heart's beats become gradually lessened,
and the blood pressure recovers its normal condition. Whilst the pressure is
raised under the action of suprarenal extract, there is apparently no possibility
of inhibiting the arterial contraction ; even the strongest stimulation of the
depressor nerve, which under ordinary circumstances produces through the
vasomotor centre a marked dilatation of the arterioles, is without result during
the activity of this extract. The question naturally arises, How is it that the
effect so soon disappears ? In what manner is the active principle eliminated ?
It is not eliminated by the kidneys, for the effect passes oft' just as quickly
even although the renal arteries are clamped. It is not eliminated by the
suprarenals themselves, for the same fact holds good for the suprarenals. It
passes off almost equally quickly if the aorta and vena cava are tied in the
upper part of the abdomen, so that there is no circulation of blood whatever in
the abdominal organs. It is not oxidised or otherwise destroyed by the blood,
for it retains its full potency even after it has been twenty-four hours in
contact with that fluid. The most probable explanation of the disappearance
of the effect seems to be that the active principle becomes packed away, and
eventually rendered innocuous in certain organs. That the muscles take most
part in this storage is probable, from the fact that the physiological effects upon
the skeletal muscles are manifested for a long time after the effects upon the
heart and arteries have disappeared.

1 In man the effect of taking suprarenal extract 1>y the mouth is to produce a general
diminution in calibre of the arteries as measured by "the arteriometer (Oliver, "Ooonian
Lectures," Lancet, London, 1896).

2 "Proc. Physiol. Soc. , " Journ. Physiol., Cambridge ami London, March 1897.

956 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

Source of the active material. — The physiologically active material
is yielded entirely by the medulla of the capsules ; no appreciable amount

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can be obtained from the cortex. This result, which was arrived at by
Cybulski and by ourselves from an investigation of the mammalian

SO URGE OF THE A CTIVE MA TERIAL OF SUPRARENAL. 957

organ, has been confirmed in an interesting manner by the observations
of Swale Vincent upon the glands of fishes.1 Elasmobranchs possess
two sets of organs, which appear from their structure to represent the
suprarenal capsules of other vertebrates ; the one of these, the inter-renal
lody of Balfour, lies between the posterior part of the kidneys in the
middle line ; the other, the paired bodies of Balfour, forms a series lying
on either side, segmentally arranged, on the branches of the dorsal aorta.
Teleosts possess only one kind of gland representing the suprarenal ;
this in its structure is similar to the inter-renal of Elasmobranchs. As
Vincent has shown, the minute structure of the paired bodies of
Elasmobranchs resembles that of the medulla of the suprarenal of other
vertebrates, while the inter-renal body is similar to the cortex of the
ordinary vertebrate suprarenal.2 The physiological test shows this in a
striking manner, for injection of an extract of the paired bodies of
Elasmobranchs produces in a marked degree the phenomena which are
characteristic of the medulla of the mammalian suprarenal, while extracts
of the inter-renals of Elasmobranchs and of the corresponding organs
of Teleosts have no such effect.3

Dose. — One of the most interesting and important facts regarding
the material which is yielded by the suprarenals, is the minuteness of
the dose which is necessary to produce the results. As little as 0*0055
grms. (5J mgrms.) of dried suprarenal is sufficient to obtain a maximal
effect upon the heart and arteries in a dog weighing 10 kilos. For each
kilogramme of body weight, therefore, the necessary quantity to produce
a maximal effect is 0'00055 grms., or little more than half a mgrm.4
The active principle is, however, contained only in the medulla of the
gland, not in the cortex, and the medulla in all probability does not form
more than one-fourth of the capsule by weight. Of the dried medulla
certainly not less than nine-tenths is composed of proteid and other
material which is not dialysable, and which otherwise does not conform
to the chemical properties which are associated with the active substance
of the gland. So that, if we take these facts into consideration, we find
that,in order to produce a maximal effect, a dose of not more than fourteen-
millionths of a grin, of the active material per kilo, of body-weight
is all that is necessary. Now it is certainly true to say that one-
fourteenth of this dose will produce some effect, although not perhaps a
very large one. We thus arrive at the astounding conclusion, that the
active principle of the suprarenal capsules, administered in the pro-
portion of not more than one-millionth part of a grm. per kilo, of body
weight, which would be equivalent to ysiroTr grrns. (less than ¥^ of a
grain) for an adult man, is still sufficient to produce distinct physio-
logical results upon the heart and arteries.5

1 Anat. Anz., Jena, 1897, S. 47 ; " Proc. Physiol. Soc.," Journ. PhysioL, Cambridge and
London, March 1897, and Proc. Roy. Soc. London, 1897, vol. Ixi. p. 64; and vol. Ixii. p. 176.

- These homologies were long since inferred by Leydig from a study of their structure
(" Fische u. Reptilien," Berlin, 1853), and later by Balfour from a study of their develop-
ment (" Comparative Embryology," 1881, vol. ii. p. 549).

3 It is, however, difficult to avoid contamination with the paired bodies in extracting
the inter-renal. Vincent has also found, in an experiment which is not yet published, that
an eel will survive, for some weeks at all events, removal of the glands which appear to be
the only representative of the mammalian suprarenals, but contain no medullary tissue.

4 The proportion of suprarenal capsule to body weight is given by Langlois as from
TTJHnr to TT^TRr in the dog.

5 The chemical nature of this active principle is still obscure, since, in spite of much work
on this subject, it has never been isolated. The history of this has been already dealt
with by Halliburton, along with the chemistry of the suprarenals, on pp. 90-92.

958 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

Conclusions. — It may be considered probable that the suprarenal
capsules are continually secreting into the blood an active material, which,
although present in that fluid only in minute quantities, may yet be suf-
ficient to produce very distinct effects upon the metabolic processes of
muscular tissue, and especially the muscular tissues of the vascular

system. It has, in fact, been stated by
Cybulski, and this statement has been
confirmed by Langlois and by Biecll,1 that
the blood of the suprarenal vein contains
a sufficient amount of the active prin-
ciple of suprarenal extract to produce a
marked f ise of blood pressure when intra-
venously injected. I have, in spite of
careful experiments, not been able myself
to confirm this statement. Nor is it
easy to understand how it can be true,
A- since such blood is constantly flowing

B.

FIG. 92. — A. Ergograph tracing of a person suffering from Addison's disease.
B. Tracing from the same person after six weeks' treatment with suprarenal
extract.— Langlois. A, natural size ; B, reduced to one-half.

into the vena cava in larger quantity than these observers injected.
But whether we are able to show it experimentally or not, there is
very little doubt of the fact that the materials formed pass somehow
or other into the blood ; and when we compare the results of supra-
renal injection with the effects obtained from the removal and from
disease of these organs, we can come to no other conclusion than
that we have before us a notable instance of internal secretion; and
that the effect of such secretion passed into the blood is beneficial
to the muscular contraction and tone of the cardiac and vascular
walls, and even of the skeletal muscles, appears very evident from
the results both of removal of the organs and of injection of their
extracts.2

1 Arcli.f. d. ges. PhysioL, Bonn, 1897, Bd. Ixvii.

- This conclusion, which is the one arrived at by Oliver and myself, is different from that
of Abelous and Langlois, which they formulate thus : — "Les capsules surre'nales out pour
fonction de neutraliser ou de detruire des substances toxiques e'labore'es an cours des
echanges chimiques et specialement au cours du travail des muscles." This statement,
which may be taken to set forth the auto-intoxication theory (supra, p. 949), was made in
1891, and therefore before the effects of injection of the extract of the medulla were known.

INFLUENCE OF THE SPLEEN ON METABOLISM, 959

In advanced cases of Addison's disease, with complete degeneration of the
medulla of the suprarenals, an extract of these organs is devoid of all physio-
logical activity.1 Such patients show, as already stated, extreme muscular
weakness, and very rapidly become fatigued, and their capability of raising a
weight, as estimated by Mosso's ergograph, is extraordinarily small. In one
such case, which was treated by exhibition of fresh capsules of the calf, the
amelioration of this condition was found by Langlois to be very manifest.
The above is well illustrated by the accompanying tracings — Fig. 92, A, in a
patient with Addison's disease ; Fig. 92, B, in the same patient after six weeks'
treatment with suprarenal capsules of the calf.- The tracings are not strictly
comparable, for the second one was taken with half the weight, but on the
other hand it has been reduced to one-half.

INFLUENCE OF THE SPLEEN ON METABOLISM.

The constant occurrence and relatively large size of this organ in
vertebrates, the very large supply of blood which it receives, and its
intimate anatomical relationships with the digestive organs, would seem
to render it probable that it must have important functions to perform
in connection with the nutrition of the body.

Effects of removal. — This supposition is not, however, borne out by
the result of experiment, for it has been abundantly proved that
the spleen can be completely removed in animals and in man without
their exhibiting any abnormal symptoms whatever.3

Whether the functions of the organ can be taken up under these
circumstances by other organs, such as the lymphatic glands, is a point
which has not yet been determined. In a dog from which I had removed
the spleen several months previously, and which was examined for me
with regard to this point by Swale Vincent, there appeared to be a
larger number of haemal lymphatic glands than in normal dogs,4 but it
would require a long series of observations to establish this point
conclusively. Certainly such a function as the formation of lymph
corpuscles may well be carried on by the abundant lymphoid tissue
which is present in other organs of the body; but the spleen has
undoubtedly, in addition to this, a certain influence upon the haemoglobin
of some, at least, of the blood corpuscles which are passing through its
tissue, for we find haemoglobin in various stages of transformation into
other kinds of pigments within the cells of the organ, and also find a
relatively considerable amount of iron in loose organic combination. It
has therefore been supposed that the cells of the spleen pulp may
produce disintegration of effete red blood corpuscles, and that their
pigment may pass to the liver, either as free haemoglobin or as formed
bile pigment. Neither free haemoglobin 5 nor bile pigment can, how-
ever, be detected in the blood of the splenic vein.

On the other hand, the function of producing new red blood
corpuscles has been ascribed to the spleen, on the grounds that

1 Oliver and Schafer, loc. cit.

2 For other references and observations on "the connection between the suprarenals and
Addison's disease, see H. D. Rolleston, Goulstonian Lectures, Brit. Med. Journ., London,
1895, vol. i.; and Langlois, " Maladie d'Addison," " Dictionnaire de physiologic de Ch.
Richet," Paris, 1895.

3 There is considerable literature on this subject. It has been collected by Fernet, and
is given by him in the British Medical Journal for November 26, 1896.

4 For an account of these organs, see Swale Vincent and Harrison, Journ. Anat. and
Physiol., London, 1897, vol. xxi. p. 182.

s Schafer, "Proc. Physiol. Soc.," May 1890, in Journ. Physiol., Cambridge and
London, vol. xi.

960 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM.

in some animals, e.g. rabbits, after extensive blood-letting, nucleated
erythroblasts, .such as those which are found in bone-marrow, occur
both in the spleen pulp and in the blood of the splenic vein ; and that
if a spleenless animal is bled, the recovery of the usual percentage of
red corpuscles is less rapid than in a normal animal.1

Whatever may be the nature of its functions in relation to the blood,
it is certain that the organ is in no way essential to the normal
nutrition of the body. It is, on the other hand, not at all improbable
that the main function of the spleen is to serve a mechanical pur-
pose, answering as a reservoir at certain periods of digestion fo;r the
blood which has to pass through the portal system ; and the fact that,
as was first shown by Eoy, the spleen normally exhibits regular rhythmic
contractions and dilatations, seems to point to its exercising an influ-
ence in assisting the flow of blood through the portal vein, and thus
through the liver.2

1 Laudenbach, Arch, de physiol. norm, etpath., Paris, 1897, pp. 200, 385, and 893.

2 The functional connection of the spleen with the vascular system is dealt with in the
article on " Circulation " in the next volume. Extracts and decoctions of spleen appear to
have no specific effect, either when injected snbcutaneously or intravenously. Nor is any-
thing known as to any specific functions possessed by the thynms. body or by the carotid
and coccygeal glands. Extracts and decoctions of the thynms appear to have no specific
effect when injected intravenously (Oliver and Sehafer. Journ. PhysioL, Cambridge and
London. 1895, vol. xviii.) or subcutaneously (Vincent, ibid., 1897, vol. xxii.). It has
been stated that removal of the thy mu s in frogs is followed by a fatal result (Abelous and
Billard, Arch, de physiol. norm, et path., Paris, 1896, p. 898), but the statement requires
corroboration.

PLATE I.

PLATE II.

PLATE III.

B c

E b

INDICES.

VOL. I. — 6 1

INDEX OF SUBJECTS.

PAGE

ABRIN, 55

Absorption of acid albumin, . . 437

,, ,, alburaose, . . 437, 439

,, alimentary, channels of, . 432

,, ,, seat of, . 432, 541

,, of alkali albumin, . . 437

,, ,, aromatic decomposition

products, . . . 469
,, ,, bile salts, . . 391, 563

,, by blood vessels, 302,303,306,

309, 900

,, of carbohydrates, . 431, 434

,, ,, dissolved foodstuffs, . 433

,, by epithelial cells, 435, 436, 451,

449, 454, 457, 486, 488, 659, 685

of fats, 369,392,443,449,451,

459, 462

,, ,, fatty acids, . 450, 454, 457

intestinal, 284, 302, 432, 433, 436,

442, 557

,, of isotonic fluids, . . 304

,, bylacteals, . 457,462,610

,, of lymph, . . . 302, 306

,, ,, oxygen by alimentary

canal, . . . .730
,, ,, peptone, . . 437, 439

,, ,, proteids, 431, 436, 437, 440, 900

,, by rectum, . . . 436

,, relation, .... 215

,, by renal tubules, . . 650

,, ,, skin, . . . 685, 688

,, of soaps, . .451, 456, 457

by stomach, . . 432, 541
,, of tyrosine, . . . 469

,, ,, water, . . . .433

Acetic acid, 5, 19, 31, 34, 75, 355, 464, 471,

615, 673

Acetone, . ... 616, 881, 928

Acetylene haemoglobin, . . . 242

Acetyl-lactic acid, . . . .106

Achromic point, ..... 322

Achroo-dextrin, . . . 16, 395

Acid-albumin, . . 50, 167, 404, 408

,, ,, absorption of, . 436, 437

,, ,, carbohydrate from, . 64

,, ,, vegetable, . . .51

Acids of bile. See Bile acids.

,, of body, ..... 1

Acrite, 6

Acrolein, 18, 133

Acromegaly, 946

Acrose, . . . . . . 5, 6

Acrylic acid, . . . . 18, 31, 32

PAGE

Activity co-efficient, . . . 261, 268
Adamkiewicz's reaction, ... 47
Addison's disease, . . . 948, 959
Adenine, . 60, 65, 66, 67, 88, 93, 596

Adenyl, 67

Adenylic acid, ..... 66

Adipocere, 20, 933

Adipose tissue, fat of, . . . . 17

,, ,, pigment of, . . . 20

Admaxillary glands, . . . 476, 479

Adsorption, 275

Aero tonometer, ..... 775
Aethalium septicum, . . . .80
Affinity, mechanical, . . . .275

Air, alveolar, 774

,, changes in, during respiration, 754, 756
Alanine, ...... 31

Albino rabbit, .... 37, 173

Albrecht's GlasJcorper, . . . 222

Albumin, 49

acid. See Acid albumin.
alkali, . . .29, 50, 96, 436
, , reducing substance from, 6 4
of aqueous humour, . . 122
ash-free, .... 25
assimilation of, . . .878
of blood plasma, . . 161,163
„ cells, ... 81, 82
,, chyle, . . . .183
coagulation temperature of, . 43
egg. See Egg albumin.
formula of, . . . .26
of intestinal juice, . . 557
,, kidney, .... 92
,, lens, . . . .124

,, liver, .... 86
„ lymph, .... 182
,, milk. See Lactalbumin.
molecular weight of, . . 26
of muscle, . . .96, 97, 98
,, nervous tissues, . . 118
,, peas, osazone from, . . 64
precipitation of, mechanical, 43
„ by salts, . 42
rotatory power of, . . 46
of sebum, .... 674
,, serum. See Serum albumin.
,, thyroid, . . . .^ 89
in urine, . . . 437, 604
vegetable, . . . 51, 54
Albuminates, . . . . .28, 40, 50
,, vegetable, ... 51

Albuminoid degeneration, ... 74

964

INDEX Of SUBJECTS.

Albuminoids,

,, digestion of,

Albumino-mncous glands,
Albuminous cells,

,, glands,

1, 2,

PAGE

, 114

. 429
. 478
477, 478
477, 503

residue of haemoglobin, 243, 244
Albuminuria, . . . . .604
,, alimentary, . . .437

Albumoid, 124

Albumone, ...... 41

Albumose, 50, 401, 403, 404, 405, 416, 899
,, absorption of, . . 437,439
,, in bacterial digestion, . . 466
,, carbohydrate from, . . 64

,, classification of, . . . 410

,, from fibrin, . . .167*

,, of gastric juice, . . 353, 355
,, influence of, on coagulation, 146,
147, 177, 181

,, „ ,, epithelium on, 440

of intestinal juice, . . 557
molecular weight of, . . 27
nutritive value of, . . 878
primary, . . . 412, 416
secondary, . . . .412

separation of, . . 411, 412
of urine, . . . .604

Albumosuria, ..... 604

Alcapton, 607, 630

Alcaptonuria, .... 607, 630

Alcohol, 7

action of, on proteids, . . 41

cerotyl, 20

ethyl, 470

hexatomic, .... 4

influence of, on body tempera-
ture, . .. . . .820

nutritive value of, . . . 882
ortho-nitrobenzyl, ... 5
Aldehyde, aspartic, ... 38, 39
,, benzole, . . . .34

Aide palmitic acid, . . . .133

Aldoses, . . . . . . 4

Aleuron grains, .
Alimentary albuminuria,

, , glycosuria,
Alkali-albumin,

51, 52
. 437

436, 609, 881, 945
29, 50, 96, 436

absorption of, . .437
,, carbohydrate from, . 64

,, vegetable, . . .51

Alkaline tide, ..... 579
Alkaloids, action of, on body tempera-
ture, . . 821
milk secretion, 664
pancreatic secre-
tion, . 548, 550
renal secretion, 648
salivary secretion, 512

animal,

,, in bacterial products,
Alloxan, ....
,, reaction of proteids,

ring, .
Alloxantin, .

skin secretion, 673, 679
34, 58, 673

Alloxuric bases, .

,, nitrogen,
Aluminium,
Alveolar air,

, , surface of lungs,

66, 67,

59, 465
. 597
. 48
. 597
. 592

98, 597
. 597
. 78
. 774
754

1'AGE

Alveoli, mammary, . . . 662, 666
,, pancreatic, .... 546

,, salivary, .... 477, 507

Amanitine, ...... 60

Amido-acetic acid, . . 31,373,378
Amido-acids, action of liver on, . . 906
,, from bile acids, . . 378

,, ,, proteid decomposi-

tion, . 29, 30, 31, 32, 403
,, in digestion, 419, 420, 421, 899

,, nutritive value of . . 880

Amido-butyric acid, .... 31

Amido-caproic acid, . . 28, 31, 421
Amido -ethyl sulphuric acid, . . . 373
Amidogen, ...... 395

Amido-glucose, ..... 9

Amido-isethionic acid, . . . 379

Amido-isobutylactic acid, ... 28
Amido-oxethylsulphonic acid, . . 379
Amido-pyrotartaric acid, . 32, 421, 426
Amido-succinamic acid, . . . 425
Amido-succinic acid, . 29, 32, 421, 425

Amido-valerianic acid, . . .72, 421
Amido- valeric acid, . . . 31,32,82

Amidulin 14, 395

Amigdulin, . . . . . 395

Amines, ...... 34

Ammonia from decomposition of albumi-
noids, 71, 72,
73
,, ,, ,, „ cerebro-

sides, 119

,, ,, ,, ,, proteids, 28,

30, 31, 32, 34

in digestion, 29. 76, 427, 472

„ faeces, . . . 473

,, putrefaction, . . .76
,, saliva, .... 346

,, urine, . . 76, 585, 905
Ammonio-magnesic phosphate, 78, 473, 632
Ammonium carbamate, 582, 583, 673, 906,

907

carbonate, . . 78, 582

chloride, ... 78, 907
lactate, . . 905, 906, 909
purpurate, . . . 592

salts in blood, . 905, 907, 919
„ ,,body, ... 78
urate, .... 78

Amphibia, respiration of, . . 703, 723

,, skin secretions of, . . 673

Amphicreatinine, . . .61, 101

Ampho-albumose, . . . .417

Ampho-peptone, . . 104, 405, 416, 418
Amphoteric reaction, .... 576

Amylodextrin, . . . 14, 395

Amyloid, animal, . . . .133

,, degeneration, ... 74

,, substance, ... 70, 73

Amylolytic ferments. See also Ferments. 393

Amylopsin, . . 326, 328, 336, 338, 393

,, action of, on amyloses, 326, 394

,, influence of reaction on, . 339

,, ,, ,, temperature on, 339

Amyloses, action of enzymes on, . . 326

Anabolism, . . . . . 869, 892

Aniline, ...... 34

Animal alkaloids, . . 34, 58, 673

,, amyloid, 133

,, dextran, . . . . .16

INDEX OF SUBJECTS.

965

PAGE

Animal gum, 14, 16, 62, 65, 126, 133, 158,

613, 665

heat, ..... 785
proteids, . . . . .49
proteid poisons, ... 55
quinoidine, . . . .59
sinistrin, .... 64

Annelids, haemoglobin of, . .187

Anthrax toxin, ..... 58
Antialbnmate, . . 402, 404, 406, 408
Antialbumid, . 403, 404, 405, 406, 408
Antialbumose, . . . 405, 407, 418
Antilytic secretion, .... 522
Antiparalytic secretion, . . . 522
Antipeptone, . 103, 405, 416, 418, 420
,, molecular weight of, . 27

Antitoxins, . . . . . .55

Antivenin, 56

Apatite, 112

Apncea, condition of blood in, . . 765
Apobiotic change, . . . .519
Aqueous humour, . . 24, 122, 182

Arabinose, . . . . 2, 3, 16, 612
Arachic acid, . . . . .133

Arctic hare, injection of colloids in, . 37

Arginine, 29, 33

,, production of urea from, . 34
Argon, respiration of, . . . .754
Aromatic decomposition products, absorp-
tion of, 469

,, ,, »? of proteids, 46,

467, 468

d'Arsonval's calorimeter, . . . 845
Arterial blood, fibrin from, . . .167
gases of, . . 154, 760
haemoglobin of, . .180
jecorin of, . . .165
sugar of, . . . 1 50
Arterin . . . .190, 192, 225
Arthropoda, skeletins of, . . 74

,, urea in muscles of, . .102

Ash-free albumin, . . . .25

Ash of blood, 77

bone, .... 77, 112
casein ogen, . . . .139
foodstuffs, . . . .882

liver, ..... 77

lungs, 77

lymph, 77

milk, . . 77, 131, 662, 885
muscle, .... 77, 109
nervous tissues, . . 77, 116

pancreatic juice, . . 367, 368
proteids, ..... 25
saliva, .... 347, 348
serum, .... 77, 772
spleen, ..... 77
succus entericus, . . . 369

tooth, ]12

urine, ..... 77

Asparagine, ...... 425

Asparaginic acid. See Aspartic Add.
Aspartic acid, ..... 425

,, in digestion, . 417, 421, 425

,, ,, proteid decomposition, 28,

29, 32, 34, 36, 73

,, aldehyde, ... 38, 39

Asphyxia, blood in, . . . 765

,, in limited quantity of air, . 743

Asses' milk, 131

Assimilable proteids, .
Assimilation,

,, of proteids,

Atmidalbumin,
Atmidalbumose,

PAGE
. 437
. 869
38, 889
. 403
403

Atropine, action of, on body temperature, 821
,, ,, ,, milk secretion, 664
,, ,, ,, pancreatic secre-
tion, . . 548
,, ,, ,, salivary secretion,

512, 514, 518

,, ,, ,, skin secretion, . 680

Augmented secretion, . . . 497, 525

Auriculo-temporal nerve, . . . 482

Aussalzung, 41

Autotoxication, .... 942, 949

Avidity coefficient, .... 357

„ law of, 357

Avogadro's hypothesis, . . . 266

Axilla, temperature of, . 787, 788, 824

BACTERIA, action of, in fermentation, 312,

313, 334

,, ,, gastric juice on, 364,

402
,, ,, on proteids in

intestine, . 29

,, intestinal, . . . 470

Bacterial digestion, absorption of pro-
ducts of, . 469
,, ,, of carbohydrates, 464,

470

„ fats, . . 471
gastric, . . 463
,, ,, intestinal, . . 464

,, ,, of lecithin, . . 471

„ proteids, . . 465
,, poisons, proteid, . . 55, 59
,, products, alkaloids of, . 59

Bacterium, acidi lactici, . . 7, 12, 356

Balance of nutrition,
Band of Soret, .
Bar feed's reaction,
Barley, proteids of,
Basophil corpuscles,
Bees, temperature of, ,
Beeswax,

Benzamido-acetic acid,
Benzene,
Benzoic acid,

,, aldehyde,
Benzoylglycine, .
Benzoylglycocoll,
Betaine,

Bicarbonate of sodium,
Bile, .
acids,

. 871

. 226, 227, 246
. 11
. 54
. 152
. 792, 807
. 20
. 600
34, 72, 605
34, 90, 600, 673, 892
. 34
. 600
. 470
. 60
. 78
. 369, 901
372, 465, 474, 562

cleavage products of, . . 378
,, isolation of, . . . 374
,, properties of, . 375, 376, 377
,, tests for, . . . .377
action of, on fats, 369, 392, 444, 455,

459, 461

,, ,, foodstuffs, . . 369

,, ,, pancreatic diastase, . 369

„ pialyn, . . .339

of animals, . . . 370, 373, 374

chemical composition of, . .369

cholesterin of, 370, 371, 391, 564, 569,

901

966

INDEX OF SUBJECTS.

PAGE

Bile, constituents, formation of, . . 559
,, ,, specific, . . .371

,, crystallised, .... 373
,, diastatic ferment of, . . 369, 390
,, fats in, . 17, 370, 371, 390, 564
,, inorganic constituents of, . 371, 560
,, lecithin of, . . 370, 371, 391, 564
,, nucleo-proteid of. . 371, 561, 569
„ pigments, 371, 382, 473, 563, 569, 629,

901

,, ,, connection of, with hae-

moglobin, 388, 389, 563
,, ,, spectrum of, 383, 386, 387, 388

,, . ,, tests for, . 384, 385, 386
, , precipitation of proteids by, . . 392»
,, pressure, . . . . .560

,, resin, 372

,, salts, 371, 372, 456, 562, 568, 569, 901
,, ,, action of, on heart-beat, . 378
,, ,, functions of, . . .391
,, ,, reabsorption of, . . 391, 563
,, ,, separation of, . . 374

,, secretion, direct influence of nerves

on, . . . . 567
,, ,, factors in, . . 564

,, ,, influence of bile-salts on, 568

,, ,, ,, ,, chemical sub-

stances on, 567
,, food on, . 565
,, ,, ,, ,, haemoglobin

on, . . 567

,, ,, ,, ,, hepatic cir-

culation on, 565

,, ,, ,, ,, movement on, 567

,, ,, ,, ,, respiration on, 567

,, ,, ,, ,, splanchnic

nerves on, 565

,, ,, ,, ,, starvation on, 565

,, ,, mechanism of, . 559, 569

,, ,, relation of, to other he-

patic functions, . . 569
,, solution of fatty acid in, . 454, 456
,, spectra of, . . . . . 390
,, tension of gases of, . . . 784

„ water of, 559

Bilianic acid, ..... 381
Biliary fistula, .... 370, 460

Bilic acid, 381

Bilicyanin, ..... 385, 386

Bilifulvin, 383

Bilifuscin, ...... 386

Bilihumin, ...... 387

Biliphain, . . . . . 382, 383

Biliprasin, 387

Bilipurpurin, . . . . .385

Bilirubin, 382, 383, 389, 474, 563, 567, 622, 629

Biliverdin, . 382, 384, 385, 473, 474, 629

Bioplasm, ..... 868, 872

Birds, gastric glands of, ... 533

,, hsematoporphyrin in, . . 260

,, haemoglobin of, 187, 198, 199, 201,

204, 206

,, nest, edible, .... 63
rennin of, . . . . . 384
respiration of, . . 706, 709, 753
tail-gland of, . . . 675

temperature of, . . . 787, 791
thyroid of, .... 940
uric acid of, .... 909
78, 590, 602, 637, 653

PAGE

Biurates, 588, 590

Biuret, 581

,, reaction, .... 48, 583

Blood, 141

,, absorption of solutions by, . 279
,, acidity of, . . . .145

,, action of snake- venom on, . . 57
,, alkalinity of, . . . . 144
,, ammonium salts in, . . . 905
,, amount of, .... 141
,, of animals, . . . .153
,, in apnoea, ..... 765
,, arterial, gases of, . . . 760
,, bilirubin in, .... 383
,, cane-sugar in, .... 10
,, carbonic oxide in, . 237,240,741
,, cholesterin of, . 155, 156, 157, 159
,, coagulation of, . . 145, 168, 173
,, ,, ,, by colloids, . 37

,, ,, ,, ,, nucleo-proteids, 55

colour of, . 142, 233, 237, 240, 241
,, composition of, . . . .153
„ corpuscles, . . 141, 147, 152
action of spleen on, . 959
amount of, . .147
composition of, . 153
number of, . 149, 152
permeability of, 271, 277
red, . . 155, 188, 959
white, 83, 141, 152, 158,
175, 179

defibrinated, composition of, . 154
dextrose in, 6, 10, 158, 610, 894,

914, 916, 917, 920, 923,
925, 928

dichroism of, . . . . 233
effect of respiration on, . . 756
ferments of, . . 160, 929

gases of, . . . . 154, 235
,, after muscular activity, 715
,, condition of, 765, 769, 770
,, estimation of, . . 757
tensions of, . . . 776

in hibernation,

lactic acid in,

laking of, .

nitric oxide in,

of portal vein,

oxidation in,

peptone and albumose in,

pigments in urine, .

plasma,

amount of, .
carbohydrates of,
coagulation of,
composition of,
fats of,

. 796

106, 159, 894, 905
. 142, 145
. 238

. 900, 908, 917
. 781, 895
. 439
629

141

156
147
157
146
153
17, 159

inorganic constituents of, 157
lactic acid in,
lipochrome of,
nitrogenous constituents
of, ....
organic constituents or,

159
159

160

157

proteids of, . . 24, 161
platelets, . . . 141, 156, 180
pressure, influence of, on lymph-
flow, 299,
300
,, ,, ,, urinary

secretion, , r , 644

INDEX OF SUBJECTS.

967

PAGE

Blood, quotient, ..... 152
reaction of, . . . .144
reducing substances of, . 152, 925
specific gravity of, . . .143
spectrum of, . . 208, 211, 225
sulpho-cyanate in, . . . 346
temperature of, . . . . 826
uncoagulable, . . . 173, 178
urea in, . . . 160, 900, 902
venous, gases of, . . 760, 762
vessels, absorption of lymph by, 302,
303, 306

„ „ ,, ,, proteids by, 309,

900

Bone ash, 112

,, chemistry of, . . . .111

„ earth, Ill

Border cells, .... 532, 554

Bottcher's test, 7

Bowman's theory of urinary secret^n, 639,

653, 658
Boyle's law, ..... 265

Brain. See Nervous tissues.

Breast, . . . .124, 662, 665

Bromanil, ...... 34

Bromelin, ...... 54

Bromoform, ..... 34

Brucin, influence of, on body tempera-
ture, 821

Brucke's method of estimating proteo-

lysis, . . . 323

,, ,, ,, separating proteids, 40

Brunner's glands, .... 554

Buccal mucus, .... 344, 348

,, nerve, 482

Buffalo, milk of, . . . . 131, 132

Bufly layer, 146

Butalanine, .... 31, 32, 421

Butter, 133, 834

,, pigment of, . . . .20
Butyric acid, 34, 133, 355, 470, 471, 615, 672

Cachexia strumipriva vel thyreopriva, . 939
Cadaverine, . . . . 59, 60
Caffein, action of, on renal secretion, . 648
,, influence of, on body tempera-
ture, 821

Caisson disease, . . . . .737

Calcium, 2

,, carbonate, . 76, 78, 111, 344, 501

,, caseate, .... 135, 136

,, chloride, . . . .111

fluoride, ... 78, 111

,, in liver, 87

,, oxalate, .... 78, 614

phosphate, 76,78,111,113,136,153

157, 473, 633, 882

,, salts in body, . ... 78
„ egg-yolk, . . .886
,, milk, . . . .886
influence of, on coagulation, 42,
134,146,147,169,175,177,179
nutritive value of, . . 886
in proteids, . . .25
in urine, . . . 634

,, sulphate, .... 78

,, urate, 78

Calorie, 834

Calorimeter, ..... 844

Calorinietric experiments, .. , , 846

Camel, milk of, .
Cane-sugar, 2, 4, 9, 10,

PAGE

. 131

)8, 435, 556, 834,
835, 837
. 435
. 880, 881
. 398

10, 398, 556, 558
. 881
750, 753

,, absorption of,

,, assimilation of,

,, digestion of,

,, inversion of,

,, in urine,

Capacity, vital, ....

Capillaries, absorption of lymph by, . 306

,, alimentary, absorption by, . 433

,, permeability of, . . . 296

Capric acid, .... 133, 470, 673

Caproic acid, .... 133, 672

Caprylic acid, .... 34, 133

Caramel, 6, 7, 10

Carbonate of ammonium, . . 906, 907
Carbohydrates, . . . . . 1, 2
absorption of, . . 431
bacterial digestion of, 464, 470
of blood plasma, . .157
carbon of, . . .873
classification of, . . 4
in diet, . . 872, 876
digestion of, . 355, 393
fat formation from, . 931
heat value of, . 874, 875
influence of, on bile

secretion, . . .566
of meat, ... 96
metabolism of, . .916
of milk, . . .132
nitrogen of, . . .873
from nucleic acid, 66, 67

nutritive value of, . 880
from proteids, . . 64
of urine, . . .607
Carbolic acid, . . . 606, 607, 630
Carboluria, . . . . . 607, 630

Carbon, 2

of foodstuffs, . . . .873
Carbon-dioxide haemoglobin, . . 242
Carbonate of ammonium,
,, ,, calcium,
,, ,, sodium,
Carbonates of body,
,, serum,

,, urine,
Carbonic acid,

. 78

76, 78, 111, 344, 501
. 76, 78, 145, 157
. 79
. 772
. 634

. . 76, 77
absorption of, by haemo-
globin, . . .773
of alimentary canal, . 729
,, blood, . . .154
in bacterial digestion, 29, 470,
472

excretion during inanition, 889
in fermentation, . 7, 319
influence of, on coagula-
tion, . . . .177
of milk, . . . 129, 130
in muscle, 110, 840, 895, 911
,, proteid decomposition, 25,
28, 31, 34, 71
,, respiration. (See also
Respira-
tion, res-
piratory
exchange.)

692, 700
,, ,, estimation of, 695

968

INDEX OF SUBJECTS.

Carbonic acid, respiration of, . 739,
of saliva, . 346, 501,
,, serum,
,, sweat,
,, urine,
tension of, in alveolar air,

,, ,, blood,

oxide in blood, . 237, 240,
,, ,, hsematin,

,, ,, hfemochromogen, 240, 241,

,, ,, haemoglobin,

,, ,, ,, photographic

spectrum of,

,, ,, ,, preparation of,

,, ,, ,, reactions of,

,, ,, ,, spectro-photo-

metric con-
stants of, .

,, ,, ,, spectrum of,

,, ,, methsemoglobin, .

,, ,, respiration of,

Carboxyacids, aromatic, of urine, .
Cardia, nerve-centres of, ...
Cardiac glands, .... 532,

Carnic acid, .... 100, 103,

Carniferrin, ......

Gamine, . . . 100, 102, 596,
Garni vora, bacterial digestion in, .

, , elimination of phosphates by,
,, respiratory exchange of,
Carotid gland, .....

Carp, ichthulin of, ....

Carrotin, ......

Cartilage, chemistry of, ...
,, fat in, .

hyalogenof,
,, mucoid of, .
Caseate of lime, .... 135,

Casein, 134, 137, 138, 665, 834, 835,
of colostrum, . . .127,
dicalcium, ....

digestion of, . . . 330,
leucine and tyrosine from,
pancreatic, ....

rotatory power of,

of sebaceous secretion,

soluble, .....

tri calcium, ....

Caseinogen, 126, 128, 134, 135, 137,

,, action of rennin on, . 326,

,, crystallisation of,

,, digestion of, ...
mechanical precipitation of,

742
504
157
671
634
774
775
741
257
257
239

240
239
240

Castor-oil bean, .....
Cat, haemoglobin of,

,, milk of,

,, salivary glands of, ...
Catalysis, ......

Cell albumin, .... 81

,, globulin, 81, 82, 84, 87, 91, 118,

,, ,, coagulation of,
a, ,

Cells, action of, in nitration,
albuminous,
basophil,
border,

chemical characters of,
chief, .

82,
477,
53*2,
532,

239
239
249
740
606
538
536
420
103
598
465
79
709
960
64
20
113
17
64
63
136
878
129
136
429
425
137
46
665
135
137
138
334
44
429
43
50
55
193
130
475
317
, 82
170
43
82
156
283
478
152
534
80
544

PAGE

Cells, demilune, 478

eosinophil, .... 84

of gastric glands, . . 531,532
,, intestinal glands, . . .554
,, mammary glands, . . 662, 665
metabolism in, . . . . 869
mucous, ..... 477
osmotic pressure of, . .276

oxidation in, ... 780, 781
oxyphil, . . . . .152
of pancreas, .... 546
permeability of, . . . . 277
of renal tubules, . . . 654, 659
,, salivary glands, 477, 479, 485, 524, 526

Cellular absorption, 435, 436, 449, 451, 454,

659, 685
,, digestion, .... 399

Cellulose, . '. .4, 14, 16, 834, 835
,, bacterial decomposition of, . 470

,, digestion of,
,, in digestion,
Cephalopods, skeletins of,
Cerebrin of cells, .

,, ,, nervous tissues, .

,, ,, spleen,
Cerebrosides,
Cerebro-spinal fluid, .
Cerolein, ....
Cerotic acid,
Cerotyl alcohol, .
Cerumen, ....
Cervical ganglion, superior, .
Cetyl alcohol,

470
. 471, 881
. 70
82, 83

116, 118, 119

. 87

. 119, 120

24, 181, 183

20

. 20
. 20
. 675
. 484, 523
20, 675

Cetylid, 120

Charcot's crystals, .... 94

Charles's law, 265

Cheese, .... 134, 834, 933
,, alkaloids in, . . .59

,, oxide, 421

Chenocholic acid, .... 377

Chenotaurocholic acid, . . . 373, 377

Chief cells, 532, 544

Chinese wax, ..... 20

Chitin, 74

Chitosan, . . . . . .75

Chloral, influence of, on body temperature, 821

Chlorazol, 34

Chloride of ammonium,
,, ,, calcium,

potassium, .

78, 907
. Ill

25, 76, 77, 93, 157
sodium, 25, 76, 77, 93, 1]3, 154,
157, 882, 883
. 633
. 2, 77, 87

Chlorides in urine,
Chlorine,

Chloro-cruorin, . . . . .61
Chloroform, influence of, on body tem-
perature, . . . . . .821

Cholagogues, 567

Cholalic acid, 373, 374, 378, 380, 381, 562

. 373, 381
. 372
. 383
. 383
. 59
58

Choleic acid,
Choleinsaure,
Cholephain, .
Cholepyrrhin,
Cholera, alkaloids in,
toxo-peptone,

Cholesterin,

20, 22

of bile, 370, 371, 391, 564, 569, 901
,, blood, . 155, 156, 157, 159
,, cells, . . .82, 83, 84
„ chyle, .... 183

INDEX OF SUBJECTS.

969

PAGE

Cholesterhi of lens, . . . .123

meconium, . . .474
milk, . 126, 128, 129, 133
muscle, . . . .103

nervous tissues, . .116
red corpuscles, . .156
retina, .... 121

sebum, . . . 674, 675
spleen, .... 87

synovia, . . .184
testis, . . . .93

torpedo organ, . . Ill
Choletelin, ..... 385, 388

Cholic acid, ...... 373

Choline, . . . 21, 60, 118, 471

Cholohsematin, .... 390, 564

Choloidinic acid, ..... 382

Chondrigeri, . . . . 70, 114

Chondrin, ..... 71, 114

,, balls, ..... 114

Chondroitic acid, . . . . .114

Chondroitin, ..... 115

Chondroitin-sulphuric acid, . 64, 85, 114
Chondro-mucoid, . . . . 63, 116

Chondrosia reniformis, hyalogen of, . 63
Chondrosidin, ..... 63

Chondrosin, . . . . 63, 115

Chorda saliva, 343, 496, 497, 498, 506, 507, 511

,, tympani, 479, 505, 509, 519

Chord o-lingual nerve, . . . .479

Choroid coat, ..... 121

Chromatic fibres, nucleins of,
Chromogens of urine, ..
Chromophanes, ...
Chyle, ....

,, percentage of fat in, .

,, ,, ,, proteid in,

Chymosin, . . . .
Cinchonine, ...

Circulating proteids, ..
Citric acid, . . . .
Classification of albumoses,

181

. 66
. 626
20, 122
183, 900
. .17
. . 24
. .134
.. 34
.. 896
126, 128, 130
. .410

aromatic derivatives of

proteids, ... 46
carbohydrates, . . 4
chemical constituents

of body, ... 1
compound proteids, . 61
enzymes, . . . 326
nmcoids, ... 63
nucleins, . . 65, 66
nucleo- proteids, . . 67
polysaccharides, . . 14
proteids, . . 46, 49
sugars, ... 2
Cleavage theory of proteid digestion, 405,

406, 414, 416

Coagulable lymph, . . . 164, 1 68

,, proteid of digestion, . 420,441

Coagulated proteids, . . . .50

,, ,, vegetable, . . 51

Coagulating ferments. (See also Fibrin-

ferment.) . 326, 334

of milk, . 328,334

,, ,, ,, pancreatic juice, 553

,, ,, stomach, . 326

Coagulation of aqueous humour, . .183

,, blood, .... 145

„ ,, plasma, . . 146

,, causes of, .... 178

PAGE

Coagulation, by colloids, . 37, 146, 174

,, fractional, . . . .43

by heat, .... 42

influence of albumose on, 146,

147, 177

,, ,, ,, lime salts on, 42,

134, 146, 147, 169,
170, 175, 177, 179
,, ,, ,, liver and lungs

on, . . 178

,, ,, ,, lymph cells on, 175

,, ,, ,, nucleo-proteids

on, 55, 68, 170,176
,, ,, ,, vascular epi-

thelium on, 180

,, intra vascular, . . 173, 177
,, ,, by snake venom, 57,

146, 174

,, of lymph, . . .182, 285
milk, . 134, 138, 326, 334
muscle plasma, . 95, 96, 97
peptone plasma, . . 174
pericardial fluid, . .183
proteids by alcohol, . 41
,, temperature of, . . . 43
,, theories of, ... 168

,, water in, . . . . 319
Cobalt reaction of proteids, ... 48
Cobra, venom of, .... 58

Cobric acid, 56

Cocain, influence of, on body temperature, 821

.960
. 60
. 261, 268
. 357
. 268
. 354

209, 214, 216,
234, 239
. 281
270

Coccygeal gland, .

Cod, alkaloid in, .

Coefficient of activity, .
,, avidity, .
,, dissociation,
,, distribution,
,, extinction,

,, filtration,

isotonic, ....
CO-haematin, CO-hremochromogen, CO-
hsemoglobin, CO - methremoglobin.
See Carbonic oxide hcemoglobin.
Cold, effects of, on body, . . 814,821
Cold-blooded animals, temperature of, 787, 792
Collagen, . 70, 111, 112, 114, 121, 429
Collapse air, . . . . .752

Collidine, 34, 59

Colloid substances, .... 43

substance of thyroid, 89,90,938

Colloidal solution, .... 262

Colloide, 36

,, amido-benzoique, ... 36

,, aspartique, . . . .36

Colloids, filtration of, . . . . 282

,, intestinal, absorption of, . 431

osmotic pressure of, 272, 278, 308

,, synthesised, . . 36, 146, 181

Colostrum, 127, 129

,, corpuscles, .... 662
Combustion, heat of, . . . 834, 837
Complemental air, . . . 749, 753
Compound proteids, ... 49, 61
,, digestion of, . . 428
Compressed air, respiration of, . . 737
Conchiolin, . . . . .74, 75, 76
Concretions, salivary, .... 345
Condensation, chemical, . . . 636
Conduction in heat regulation, . . 850

970

INDEX OF SUBJECTS.

PAGE

Conductivity, molecular, . . . 261
Conger-eel, poison of, . . . .55

Conglutin, ...... 51

Congo-red test, ..... 365

Constants, spectro-photometric, . 213, 223,

234, 239

Contact action, . . . 870, 897, 898
Contraction of muscle, chemical changes

during, 109

Copper, . . . . 2, 61, 78, 87

,, reaction of proteids, . . 48

Coral, 75, 78

Cornea, ...... 121

Cornea-mucoid, . . . . 63, 121

Cornein, 74, 75, 76

Cornicrystallin, .

Corpus luteum, pigment of, .

Corpuscles, basophil, .

„ of blood. See Blood corpus-

cles.

,, colostrum, .

,, eosinophil, .

75

20

152

syphil,
ilivar

. 662
. 84
. 152

salivary, . . 344, 501, 663
Cortex, cerebral, influence of, on salivary

secretion, ..... 484

Cotton seed, proteids of, . . . 54

Cow, milk of, 129

Cranial nerves to salivary glands, 479, 482,

504, 512

Crawford's calorimeter, . . . 844
Crayfish, pepsin of, . . . . 330

Cream, 125, 133

Creatine, 100

of blood-plasma, . . .160
,, kidney, .... 92
,, milk, . . . .126

,, muscle, . . . 100, 904
,, nervous tissues, . . .116
nutritive value of, . . . 880
relation of, to lysatine, . 33, 427
oftestis, .... 93
,, torpedo organ, . . .111
,, urine, .... 598
Creatinine, .... 60, 100, 598
of blood plasma, . 1 60

estimation of, . . . 599
identification of, . .101
isolation of, ... 599
mercuric-chloride, . . 599
of milk, . . . .126
,, muscle, .... 100
properties of, . . 598

relation of, to lysatinine, 33, 427
salts of, .... 599
of sweat, .... 672
tests for, . . . .599
of urine, . 571, 572, 598, 638

zinc-chloride,

Cresol, ...

Crotlain,

Cruorin, purple, .

Crusocreatinine, .

Crustacea, hsemocyanin of,
,, haemoglobin of,
,, respii'ation of,
,, shell of,
,, skeletins of,

Crypts of Lieberklihn, .

Crystallin, .

599

46, 470, 606, 607
56

. 229

61, 101

61

. 187
. 702, 703
. 78
. 74
. 554
43, 123

Crystalline lens, ....

,, fat in,

,, ,, proteid in, .

Crystallisation of CO-haemoglobin,
hsemin,

PAGE

. 123
17, 123
24, 123

. 239
252, 253

hsemoglobin, 193, 194, 203,
205, 232

,, intraglobular, 191
NO-hsemoglobin, . 241
proteids, . . 43, 163
,, vegetable, 27, 52

Crystallised bile, 373

Crystalloids, . . . . 43, 53
Crystals, Teichmann's, . . 252, 253
Curari, influence of, on body tempera-
ture, 821, 841

Curd, 134

Currents of action, .... 682
,, ingoing, .... 682

,, outgoing 682

,, of rest 682

Cutaneous respiration, .... 723

,, of amphibia, . 723

,, ,, mammals, . 725

Cuttle-fish, skeletins of, ... 74

Cyanalcohols, ..... 39

Cyanhffimatin, ..... 249

Cyanogen haemoglobin, . . . 242

,, inethaemoglobin, . . .248

Cyanuric acid, ..... 581

Cystein, 34

Cystin, .... 34, 92, 602

Cystinuria, 59, 632

Cytoglobin, 68

Cytosine, 66, 632

DALTON'slaw, 266

Degeneration, amyloid or waxy, . . 74
Dehydrocholalic acid, . . . .381

Dehydrolysis, 636

Demilune cells, 478

,, glands, . . . .478

Dentine, 112

Deposit, lateritious, . . . .588

Dermoid cyst, ..... 675

Descemet's membrane, . . 64, 121

Desoxycholalic acid, .... 381

Deutero- album ose, . 410, 412, 413, 414,

416, 418, 420

Deutero-elastose, ... 72, 430

Deutero-gelatose, . . . 71, 429

Deutero-proteose, ... 45, 46

Devoto's method of separating proteids, 40
Dextran, animal, . . . .16

Dextrin, 4, 13, 14, 16, 105, 393, 395, 396
,, absorption of, . . . . 434

Dextrosazone, . . . . 8, 612

Dextrose, 4, 6, 8, 9, 10, 15, 396, 397, 435,

834, 835, 837

,, assimilation of, . . 880, 881

of blood, 158,610,894,914,916,

917, 920, 923, 925, 928

,, muscle, . 100, 105, 110, 606

,, urine, . 608, 881, 894, 920,

926, 928

Diabetes, . . . 921, 926, 927, 929
Diabetic puncture, . . . .919

Diacetio acid, .... 616, 881

Diacetin, ...... 18

Dialysis of proteid solutions, . . 4.3

INDEX OF SUBJECTS.

97.1

Diamido-caproic acid, .
,, valerianic acid,
Diastase animal ou salivaire,
Diastase, malt, .
,, nature of,
Diastasimetry,
Diastatic ferments,

PAGE

31, 427
. 33
. 327
393, 394
54

. 322, 325

160, 319, 322, 325, 326,
338, 341, 369, 390, 393,
398, 399, 503, 552, 556,
558, 925, 926, 929
of blood, . 160, 929

,, ,, estimation of activity

of, . . 322, 325
,, ,, influence of, on coagu-

lation, . . 146, 147
,, ,, vegetable, . . 51

Dibromacetic acid, .... 34
Dicalcium casein, . . . .136

Diet, composition of, . . . 872, 875
,, heat value of, . . 874, 875

,, proteid, 891

,, special constituents of, . . 878

,, table of, 877

Diffusion, ...'.. 262
,, ofproteoses, ... 45

,, in respiratory exchange, . 779
tion of albuminoids, . . . 429
bacterial, absorption of pro-
ducts of, . . 469
of carbohydrates, 464, 470
,, fats, . . .470
gastric, . . . 463
intestinal, . . 464
ofproteids, . . 465
of cane-sugar, . . . 398
,, carbohydrates, . 355, 393

cellular, .... 399

of cellulose 470

chemistry of, . . .312
of compound proteids, . . 428

,, fats, 443

„ fibrin, . . . .404

rtric glands during, . . 531
ing hibernation, . .796
in vitro, . . . .321
mechanism of, . . .531
peptic, . . . 401, 418, 428
ofproteids, 333, 338, 399, 402, 414,
418, 428, 541

, , theories of, 400, 405, 406,
414, 416

,, vegetable, . . 51
of starch, . . 393, 396, 556
tryptic, . . 414, 418, 428
amido-acids of, . 421
ammonia of, . . 427
chromogen of, . 427

cleavage theory of, . 405
organic bases of, . 426
Digestive enzymes, . . . 326, 327
„ extracts, 315, 322, 337, 542, 552, 557
,, ferments, 312. See also Enzymes.
,, secretions, composition of, . 342
Digitalis, action of, on renal secretion, . 649
Dihydroxyphenyl-propionic acid, . . 606
Diphtheria toxin, . . . .58

Dippel's oil, 34

Disaccharides, . . . . . 4, 9

Dissimilation, 869

Dissociation coefficient, . . . 268

PAGE

Dissociation of oxyhsemoglobin, . . 774

,, tension of, ... 775

Distearyl-glycero-phosphoric acid, . 22

lecithin, .... 22

Distribution coefficient, . . . 354

Diureides, 586

Diuretics, 647

Dog, haemoglobin of, 193, 198, 199, 201, 202,

203, 206

,, milk of. .... 130, 131

,, respiratory exchange of, . . 707

,, saliva of, . 327, 345, 346, 347, 348

,, salivary glands of, . . . 475

Dolphin, milk of, . . . .131

Drechsel's bases, ... 33, 34, 426

Duboisine, action of, on sweat secretion, 680

Dulcite, 4

Dulong's calorimeter, .... 844
Dysalbumose, ..... 410
Dyslysins, .... 378, 380, 382
Dyspeptone, .... 403, 429

Dyspnoaic secretion of saliva, 493, 521, 522

ECK'S fistula, 908

Edestin, 54

Egg albumin, . . . .25, 26, 27
action of formaldehyde on, 50
crystallisation of, . . 43
leucine and ty rosin e from, 425
mechanical precipitation

of, .... 43
reducing substance from, 64
rotatory power of, . . 46
temperature of coagulation
of, .... 43

shell, 78

white, composition of, . . . 874
digestibility of, . . . 333
heat value of, . . . 834
mucoid of, . . . .63
yolk, composition of, . .874

fat of, 17

haematogen of, . . . 68
heat value of, ... 834
pigment of, . . . .20
lime in, .... 886
Ehrlich's test for bilirubin, . . . 384
Eiiveisskorpcr, . . . . .49
Elasmobranchs, muscles of, . . 904, 908

Elastin,

suprarenal s of,

70, 71, 95, 111

decomposition of,
derivatives of, .
digestion of, .
peptone, ....
Elec rical changes in salivary glands,

,, ,, skin glands, .
currents. (See Currents.}
organs, ....
Electrolytes, diffusion of,

,, osmotic pressure of,

,, permeability of,

Electro-osmose, .
Eleidin granules, .
Elementary particles, .
Elephant, milk of,
Embryo, respiration of,
Emulsification,

,, in intestine, .

Emulsion, ....

957
112
32

. 71
. 430
72, 430
. 517
. 681
. 682
. 110
263
268
276
. 688
. 73
. 141
. 131
. 733
19, 444
447, 457, 557
19, 125, 444

261,

972

INDEX OF SUBJECTS.

Emulsion theories of fat absorption, 449, 457
Emulsive ferment, . . . .448

Emydin, ...... 53

Enamel, ...... 112

Encephalin, . . . .119, 120

Endosinometer of Dutrochet, . . 273
,, ,, Vierordt, . . .273

Endosmose, 273

Endosmotic equivalent, . . . 274

Enumeration of blood corpuscles, . 149, 152

Enzymes. (See also Ferments. ) , .312

,, action of. (See also Zymo-

lysis.) .... 317
activity of, . . . 322, 325
chemical nature of, . .316
classification of, . . . 326
digestive, . . 312, 326, 327
gastric, 326, 330, 334, 350, 532, 542,

543

intestinal, . 341, 397, 398, 556
isolation of, . . . .313
mechanical precipitation of, . 314
pancreatic, 314, 326, 336, 340, 369,
397, 443, 551

salivary, . 326, 327, 397, 503

Eosiiiophil cells, ..... 84

,, granules, .... 84

Epithelium, absorption by, 435, 436, 486, 488

,, cutaneous, . . .685

,, in fat absorption, 449, 451, 454,

457

gastric, . . . 531, 532
,, influence of, in absorption

ofalbumose, . . . 440
,, intestinal, . . . 554

,, mammary, . . 662, 665

,, pancreatic, .x . . 546

,, proteids of, ... 84

„ renal, 639, 640, 647, 652, 659

,, salivary, . . . .477

,, vascular, influence of, on

coagulation, . . .180

Equilibrium, nitrogenous, . . 871, 891

,, nutritive, . . .871

Equivalent, endosmotic, . . . 274

Erythrocytes, 141

Erythrodextrin, . . . .16, 395

Erythrogranulose. . . . .14

Erythrose, ...... 2

Esbach's reagent, . . . . .15

Eserine, action of, on sweat secretion, . 679

Esters, 24, 159

Ethal, . . . . . . .20

Ether, influence of, on body temperature, 821
Ethers, glyceric, . . ... .17

Ethyl alcohol, . . . . .470

Ethylene lactic acid, .... 106

Ethylenimine, ..... 94

Ethylidene lactic acid, . . . 106,117

Ethyl-pyrrol, 31

Evaporation in heat regulation, . . 851
Exchange, respiratory. See Respiratory

exchange.
Excretine, ...... 474

Excretives, urinary, characteristics of, . 635

Excretoleic acid, 474

Exosmose, ...... 273

Expiration, influence of, on lymph flow, 300
,, air of, . . . 754, 774
,, volume of, .... 748

Extinction-coefficient,

PAGE

209, 214, 216, 234,
239

Extractives of muscle, . . 95, 100, 110

Extract of pituitary, .... 946

,, ,, suprarenal, . . . 950, 951

,, ,, thyroid 943

Extracts, digestive, 315, 322, 325, 336, 337,

542, 552, 557
121

Eye, chemistry of,
K&CES,

472
59
472
472
473
887
834
388
473

alkaloids in, .

,, amount and consistency of,
,, colour of, ...

,, composition of,
,, during inanition,
,, heat of combustion of,
,, pigments of,
,, reaction of,
Fasting. See Inanition.

Fat-body, 934

Fat formation from carbohydrates, . 931

,, ,, fatty acids, . . 931

., ,, glycogen, . 924, 935

,, proteids, . 902, 933

Fat-splitting ferments, 160, 325, 326, 336,

339, 443, 448, 553

Fatigue, relation of lactic acid to, . 108

Fats, 1 2, 17

absorption of, .

,, channels of,

,, emulsion theories of,

,, fatty acid theory of,

443
462

449
454

influence of bile on, 369, 392,
459, 461
pancreatic
juice on, . 459, 461

,, solution theories of,
action of bile on, .

,, on bile secretion, .

,, pancreatic juice on,

,, steapsin on, .
bacterial digestion of, .
of bile,

,, blood plasma, .
,, bone,
carbon of, .
of cells,
,, chyle,
,, colostrum,
decomposition of,
in diet,
digestion of,
emulsification of,
heat value of,
of lens,

451

444
566
443
326
. 471

370, 371, 390
. 159
. Ill
. 873
. 82, 83, 84
. 183
. 127, 129
. 19
. 872, 876
. 443
. 444, 557
834, 835, 837, 874, 875
123

,, liver, ... 85, 901, 935
,, marrow, . . . . .19

,, meat, 96

metabolism of, . . . . 930
,, ,, influence of liver on, 935

of milk, 19,125,128,133,664,665
,, muscle, . . 17, 95, 100, 105

,, nervous tissues, . . .116
neutral, . . . . 18, 19
nutritive value of, . . . 881
oxidation of, . . . .19
pigment of, .... 20

of retina, ..... 121
,, sebum, .... 674, 675

INDEX OF SUBJECTS.

973

Fats of sweat,

,, synovia, .

, , synthesis of, .

,, torpedo organ, ..

,, white corpuscles,

,, wool,
Fatty acids,

,, absorption of, .

,, in fat absorption,

VAGE

. 671
. 184

893, 899, 931
. Ill
. 83
. 675

17, 19, 21, 444
450, 454, 457
450, 454

fat formation from, . . 931
in intestines, . . 465, 471
nutritive value of, . . 881
in proteid decomposition, 29, 34

,, skin secretions,
,, ,, thyroid,

,, ,, torpedo organ,

,, ,, urine, .

Feathers, red pigment of,

,, skeletin of,
Fehling's test,
Fellic acid, .
Ferment or Ferments
glycogen,
,, amylolytic.
diastatic.
„ of blood,
,, coagulating,

672, 674
. 88
. Ill
. 615
. 61
. 72
7, 610
. 373, 381
of, on

. 15
See Ferments,

action

. 160, 929
. 326, 553
of milk, 127, 134, 326,
334, 336

,, ,, ,, pancreas, . 326

,, ,, stomach, . 326

,, diastatic, 160, 319, 322, 325, 326,

338, 341, 369, 390, 393,

398, 399, 503, 552, 556,

558, 925, 926, 929

of bile, . 369,390

,, blood, . 160, 929

,, ,, influence of, on

coagulation, 146, 147

,, ,, vegetable, . 51

,, digestive. (See also Enzymes.)

312, 326

,, emulsive, . . . .448

,, fat-splitting, 160, 325, 326, 336,

339, 443, 448, 551

,, fibrin, 82, 83, 146, 160, 168, 170,
175, 179, 319

,, glycoly tic, of blood, . 160,161

inverting, 10, 12, 313, 319, 342,

393, 397, 556, 558

,, of liver, .... 926

,, myosin, .... 97

,, organised, . . . .312

proteolytic, . 313, 319, 323, 326,

334, 551, 674

,, ,, vegetable, 51, 54, 330,

403

,, soluble. (See also Enzymes. ) 312
,, steatolytic. See Ferments,

fat-splitting.

,, urinary, .... 582
,, urea-forming, . . . 907
Fermentation, action of gastric juice on, 364
of cane-sugar, . . 10
chemical changes in, . 319
of disaccharides, . . 10
,, glutaminic acid, . 32
,, glycogen, . . .15
,, isomaltose, . . 11
lactic acid, . . 7, 12, 126

PAGE

Fermentation of lactose, . 12, 132, 334
,, maltose, . . .11
micro-organisms in, 312, 313
of rnonosaccharides, . 7
nature of, . . .317
of urine, . . 313, 582
yeast, . . . .611

Ferratin, 86

Ferric oxide, ..... 77
,, sulphide, ..... 78

Fibrin, 153, 166

absorption of pepsin by, . 401, 542

of chyle, 183

digestion of, . . 333, 404, 420
ferment, 82, 83, 146, 160, 168, 170,
175, 179, 319

formation, factors of, . .178

heat value of, . . . . 834
leucine and tyrosine from, . 452

of lymph, 182

myogen, ..... 98
myosin, ..... 98
Fibrinogen, . . . 161, 163, 164, 179
A-, . . . 166, 175, 176
of aqueous humour, . 122,182

B-,

mechanical precipitation of,
of pericardial fluid,
rotatory power of,
temperature of coagulation
of,.

Fibrinogens, tissue,
Fibrino-globulin, .

,, plastic substance,
Fibroin, .....

Fick's law,

Filtration, .....

through living membranes,

175

43

183
46

43

. 55, 68, 173, 176
. 165, 170
. 163
74, 76
. 262
. 280
283

,, in lymph absorption,
,, ,, ,, production,
,, ,, urinary secretion,

Fishes, alkaloids in,

,, bile of, .

,, haemoglobin of,

,, proteid poisons of, .

,, rennin of,

,, respiration of,

,, slime of, .
,, temperature of,
Fistula, biliary, .

Eck,

,, gastric, .
, , pancreatic,
,, parotid, .
,, Pawlow,
„ Thiry, .
„ Vella, .
Flax-seed, proteids of, .
Flcischsaure,
Flour, proteids of,
Fluoride of calcium,
Fluorine,
Foetus, respiration of, .

Food, ash of, 882

,, chemical constituents of, . . 1

,, carbon of, 873

,, composition of, . . . . 872

,, digestion of. See Digestion.

,, heat value of, . 834, 835, 837, 874

306

288, 290
. 640
59, 60
. 372, 376
. 187, 198
. 55
. 334

702, 704, 730,
753

. 674, 676
. 850
. 370, 460
. 908

349, 352, 536
366, 459, 547
. 489
. 349
. 368, 555
. 368, 555
54

. 103, 420
. 53
78, 111
. 2, 77, 113
730

974

INDEX OF SUBJECTS.

PAGE

Food, influence of, on bile secretion, . 565
,, ,, ,, body temperature, 809

,, gastric secretion,

540, 545

,, ,, ,, intestinal secre-

tion, . . 555

,, ,, ,, milk, . . 664

,, ,, ,, pancreatic secre-

,, ,, ,, tion, . 551, 554

,, ,, ,, respiratory ex-

change, . 717, 721
,, ,, ,, salivary scretion,

490, 491

,, ,, ,, urine, 575, 585, 579,

593, 630, 632

,, nitrogen of, .... 873
,, putrefying, alkaloids of, . . 59
,, special constituents of, . . 878
,, sulphur of, .... 563
,, vegetable, in diet, . . . 472
Formic acid, 5, 19, 31, 34, 66, 75, 117, 133,

615, 672

Formose, 5

Fossil bones, . . . . .111
Fredericq's aerotonometer, . . . 776
Frog, cutaneous respiration of, . . 723
,, fat-body of, .... 934
,, gastric glands of, ... 524
,, haemoglobin of, . . . .193
,, nmcinogen of, . . .62

,, pepsin of, . . . . 330, 533
,, respiratory exchange of, 703,709,710

,, skin absorption in,

,, ,, glands of, .
Fructose, ....
Fruit gum, ....
Fumaric acid,
Fundus of stomach,
Fungi, chitin in, .
Funke's method of preparing

globin, ....
Furfurol test,
Fuscin, ....

haemo-

690
681
:, 12
612

34
534

74

194
608
121

GADININE, ...... 60

Galactonic acid, ..... 4

Galactosazone, . . . . 8, 612

Galactose, . 4, 7, 8, 10, 12, 16, 119, 120

Gall stones,. . . 383, 386, 387, 391

Ganglia of salivary glands, 480, 482, 484, 523

,, ,, stomach, .... 538

Ganglion, inferior mesenteric, . .550

otic, 482

semilunar, . . . . 550
sublingual, . . . 480, 481
submaxillary, . . 480, 481
superior cervical, . . 484, 523
Gases of alimentary canal, . . . 728
,, arterial blood, . . . 760
,, blood. See Blood gases.
,, ,, plasma, . . .157

,, cutaneous respiration, . . 725

,, lymph, 783

„ milk, .... 129, 130
,, muscle, .... 110, 911
respiration of different, . . 735
of saliva, . . . 346, 347, 504
,, secretions, tensions of, . . 783
,, serum, ..... 157
,, venous blood, . . .762

Gas-pump, .
Gastric absorption,

,, enzymes, .

,, fistula,

,, glands, cells of,

» juice,

,, ,, acid of,

Gelatin

PAGE

. 759
. 432, 541
326, 330, 334, 350
. 349, 352, 536
. 531, 532
. 349, 536
. 351

action of, on bacteria, 364, 402,
463

,, ,, ,, cane-sugar, . 398
,, butyric acid of, . . 355
,, composition of, . 354, 544
,, ferments of, 326, 330, 334, 350
,, hydrochloric acid of. See

Hydrochloric acid.
,, lactic acid of, . , 351, 355
,, methods of obtaining, . 349
,, phosphoric acid of, . . 356
, , variations in, during diges-
tion, . . . .544
secretion, histological changes

during, . . 531

influence of nerves on, 537
,, ,, peptones on, 541
,, ,, on urine, 359
latent period of, . 549
local stimulation of, . 540
mechanism of, . . 531

70

. 59
. 31, 32, 70
. 429
. 95
. 116
. 876, 878
85, 88, 92, 121

alkaloid from,
derivatives of,
digestion of, .
from muscle, .

,, nervous tissues
nutritive value of, .
from organs,

torpedo organ, . . 110
j, peptones, ... 70, 429
,, tyrosine and leucine from, . 425
Girgensohn's method of separating pro-

teids, 40

Glands, albuminous, . . .477, 503
albumino-nmcous, . . .478
of Brunner, . . . .554
cardiac, .... 532, 536
chemistry of, . . . .85
demilune, .... 478
ductless, influence of, on meta-
bolism, . . . .937
during inanition, . . . 890
of frog's skin, . . . .681
gastric, .... 531, 532
Harderian, .... 675
heat production in, . . . 843
lachrymal, .... 475
mammary, . . . .124
metabolic activity of, . . 895
mixed salivary, . . .477
muco-albuminous . . . 478
mucous, salivary, . . 477, 503
pyloric, . . . 532, 534, 536
salivary. See Salivary glands.
sebaceous, .... 674
of skin, electrical changes in, . 681
thyroid. See Thyroid gland.

Glia'din, 53, 54

Globin, 26, 244

Globulin or Globulins, animal, . 49, 895
,, ,, of aqueous hum-

our, 122

INDEX OF SUBJECTS.

975

PAGE

Globulin or Globulins of blood plasma, 161,

163

,, ,, „ cells, 81, 82, 84, 87

„ chyle, . . 183
,, ,, coagulation-tem-

perature of, . 43

,, ,, from fibrin, . 167

,, ,, of intestinal juice, 557

,, ,, ,, kidney, . . 92

,, ,, ,, lens, . 123, 124

,, ,, ,, liver, . . 86

„ lymph, . . 182
,, ,, ,, milk. See

Lactoglobulin.

,, ,, ,, muscle, . 97, 98

,, ,, ,, nervous tissues, 118

,, ,, precipitation of,

by salts, . 42

,, ,, ofproteid diges-

tion, 405, 416, 420
,, ,, ,, serum. See

Serum globulin.

,, ,, „ spleen, . . 87

,, ,, ,, torpedo organ, 110

,, ,, ,, urine, . 604, 605

,, ,, vegetable, . 51, 54

Globuloses, 50

Glomeruli of kidney, 639, 641, 652, 655, 659
Glow-worm, phosphorescence of, . . 780
Gluconic acid, . . . . . 4, 6

Gluco-proteids, . . . .61, 64, 67

Glucosamine, . . .9, 75, 85. 115
Glucosane, . . . . . .6

Glucosazone, .... 8, 608

Glucose. (See also Dextrose.) 2, 6, 15, 16

,, from proteid decomposition, . 30

Glucoside, theory of proteids, . . 64

Glutaminic acid, . 29, 31, 32, 35, 71, 73,

421, 426

Gluten, 53, 333

,, ferment, 53

,, fibrin, ..... 53

Gluteuin, . . . . . .54

Glyceric ethers, . . . . .17

Glycerides, 17, 120

Glycerin, . . . .17, 18, 19, 882

Glycerol, 18

Glycero-phosphoric acid, 21, 22, 118, 160, 471
Glycerose, ...... 2

Glycine. (See also Glycocine and Glyco-

coll.) . . 378, 562, 568, 892, 893
Glycocholate of soda, . . . .371

Glycocholic acid, .... 372, 373

,, ,, preparation of, . .374

,, ,, properties of, . . 375

Glycocholonic acid, . . . .375

Glycocine, . 31, 32, 71, 72, 75, 76, 378

,, of muscle, ... 95, 103

Glycocoll, . . . 373, 378, 469, 470

,, synthesis of, . . .379

Glycogen, ... 3, 4, 13, 14, 834

,, action of enzymes on, . 326,397

,, of cells, . . 82, 83, 84, 158

,, ,, embryo, . . . .918

,, fat-formation from, . 924, 935

formation, . . .916, 922

,, ,, from proteids, 901, 905,

919
,, ,, influence of pen-

tose and manuose on, . 3

PAGE

Glycogen, of kidney, .... 92

„ liver, 85, 569, 917, 918, 919, 922

„ lymph, .... 182

,, „ muscle, 95, 100, 104, 110, 911,

915, 917

,, „ notochord, . . .113
,, ,, placenta, . . . .918
,, ,, plants, . . . .921
,, ,, plasma, .... 158
,, ,, spleen, .... 87
,, synthesis of, ... 893

Glycogenesis, 922

,, Bernard's theory of, . . 922

Glycollic acid, .... 5, 673
Glycolytic ferment of blood, 160, 161, 929
Glycosuria, alimentary, 436, 609, 881, 945
,, pathological, 610, 880, 920, 926'

Glycuronic acid, . 5, 115, 469, 608, 610, 613
Gmelin's test, .... 385, 629

Goat's milk, 130

Goose bile, 373, 377

Gorgonia cavolinii, iodine in, . . 90
Granules, secretory, gastric, . . 531

,, ,, intestinal, . . 554

,, ,, mammary, . . 668

,, ,, pancreatic, . . 546

,, ,, salivary, . .479

Grape-sugar. See Dextrose.
Griinhagen's method of estimating pro-
teolysis, . .... . .324

Guanine,

from nuclein, .
pancreas,
retina,
testis,
thyroid, .
urine,

60, 596
66, 67, 98
. 92
. 121
. 93
. 88
596, 637, 653

Guinea-pig, admaxillary gland of, . 476

,, haemoglobin of, . 193, 194, 198,

204, 205, 206

Gum, 4, 14

„ animal, 14, 16, 62, 65, 126, 133, 158,

613, 665
,, arabic, ..... 16

,, vegetable, . . . . .16

,, wood, ...... 16

Gummose, . . . . . .62

Gunzberg's test for hydrochloric acid, . 365

H.EMACYTOMETER, .... 150

Hsemataerometer, .... 776
Hsematin, 207, 236, 243, 246, 250, 388, 473,

563, 622

,, carbonic oxide, . . . 257

,, hydrochloride, . . 250, 252

,, ,, spectrum of, 254

,, iron-free, .... 251

,, preparation of, . . . 250

,, properties of, ... 250

,, reduced. See Hccmochromogcn.

,, spectrum of, ... 251

Hsematinometer, . . . . . 210

Hfematocrit, . . . 148, 150, 271

Hsematogens, .... 68, 885

Hcematoidin, . . . 260, 384, 389

Heematoporphyrin, 246, 251, 256, 258, 382,

389

,, preparation of, . 258

properties of, . 259, 626

,, spectrum of, . 260, 626

976

INDEX OF SUBJECTS.

Haematoporphyrin of urine, .

Hfematoscope,

Hsematuria,

Haemin,

crystals, .
Hffiinochromogen,

nitric oxide,
preparation of,
properties of,
spectrum of,

PAGE

618, 622, 625,
629

,, separation of, 625
. 210
. 629
. 250, 252
. 252, 253
236, 243, 250, 254, 629
carbonic oxide, 240, 241,
257
. 258
. 255
. 255
251, 255

Haemocyanin, .... 43, 61
Haemoglobin. (See also Oxy haemoglobin,

Reduced hccmoglobin.} 61,
153, 155, 185, 229, 834
,, absorption of carbonic acid

by, . . 773

,, oxygen by, 767

,, albuminous residue of, 243,244

,, of animals, 185, 193, 198,

199, 201, 202, 205,

206, 225

,, carbonic oxide. See Car-

bonic oxide hccmoglobin.
,, compounds of, . . . 237

,, with acety-
lene, 242
,, ,, ,, ,, carbonic

acid, 242
,, ,, cyanogen, 242

» ^hydro-
cyanic acid, 241
,, connection of, with bile

pigments, . . 388, 389
,, crystallisation of, 43, 193, 194,

203, 232

,, decomposition of, in liver, 901

,, digestion of, . . . 428

,, distribution of, . . 186

,, estimation of, . . .151

,, formula of, . . . 27

, , influence of, in bile secretion, 567

,, iron of, . .201, 768, 885

,, of marrow cells, . . 84

,, muscles, . 97, 99, 187
,, nitric oxide, . . .241

,, oxygen capacity of, . . 768

,, reduced. See Reduced

haemoglobin.
,, relation of, to stroma of

corpuscles, . . .188

,, of spleen, ... 87

,, sulphur of, ... 202

, , in urine, . . . 629

Hsemoglobinometer, . . . 151, 152

Hsemoglobinuria, ..... 629

Haemoscope, 210

Hair, fat in, 17

Haptogen membrane, . . . . 125

Harderian gland, .... 675

Hare, arctic, . . . . 37, 173

Heart, heat production by, . . . 842

Heat, animal, .... 785, 832

,, centres, . . 854, 858, 862, 865

,, coagulation of proteids, . 42,43

,, of combustion, . . 834, 837, 874

effects of, on body, . . 814, 823

PAGE

Heat loss, regulation of, . . .850
,, ,, by skin, . . . 850, 855
,, production in cold-blooded animals, 849
by foodstuffs, 834, 835, 837
in glands, . . 516, 843
in heart, . . . 842
in intestines, . . 843
in liver, . . . 843
measurement of, . 844

in muscles, . . 840

relation of chemical

changes to, . . 833
,, ,, respiratory exchange

as measure of, . 847

,, ,, seats of, . . . 839

,, regulation, . . 831, 832, 850, 865
,, ,, in hibernating animals,

796, 831
,, ,, influence of body-size

on, . 852
,, ,, ,, nervous

system on, 854, 859,
862

,, specific, 838

, , value. See Heat of combustion.
Helico-proteid, ..... 64

Heller's test, 605

Hemialbumose, . . . 405, 409, 418
Hemicellulose, . . . . 14, 16
Hemicollin, . . . . . 71, 430
Hemielastin, .... 72, 430
Hemipeptone, . . . 405, 417, 418
Hemiprotein, ..... 405
Henry, law of, ..... 266

Hepatin, 69, 86

Heptoses, ...... 2

Herbivora, bacterial digestion in, . 465

cellulose in digestion in, . 471
elimination of phosphates by, 79
inanition in, . . . 888
respiratory exchange of, . 709
sodium chloride in food of, 883, 887
thyroid gland of, . . 940
urine of, 585, 601, 606, 607, 615,
632, 634

Hetero-albumose, 410, 412, 414, 416, 418
Hetero-proteose, diffusibility of, . . 46
Hetero-xanthin, .... 596, 598

Hexahydroxybenzene, .... 606

Hexatomic alcohols, .... 4

Hexoses, 2, 3

Hibernation, .... 794, 866
,, causes of, ... 797

,, respiratory exchange dur-

ing, . . . .710

Hidrotic acid, 671

Hippokoprosterin, . . . .24
Hippomelanin, ..... 121
Hippopotamus, sweat of, . . 673

Hippuric acid, ....
, , of blood plasma,

heat value of,
of suprarenal body,
of sweat,
synthesis of, .
tests for,
of urine, 571, 572

. 600
. 160
. 834
. 90
. 673
600, 892
. 601
600, 605,
638

estimation of, . 601
origin of, . 601

INDEX OF SUBJECTS.

977

TAGE

Histidine, ...... 93

Histohrematin, ..... 99

Histon, 82

Hoffman's test for tyrosine, . . . 424
Homocerebrin, . . . . 119, 120
Homogentisic acid, . . 606, 607, 630
Homoiotheniiic animals, . . . 788

Hoof, skeletin of, 72

Hoplocephalus, venom of, . . 58

Hordein, . . . . . .54

Horn, leucine and tyrosine from, . . 425
,, skeletin of, .... 72

Horse, gastric digestion of, . . . 355

,, haemoglobin of, 193, 194, 199, 200,

201, 202, 203, 205, 233

,, milk of, 131

,, saliva of, . . . 327, 345, 347

,, salivary glands of, . . .477

,, sweat of, . . . . .673

Huppert's test for bile pigments, . .386

Hutohinson's spirometer, . . . 752

Hyalins, ...... 63

Hyalogens, 61, 63

Hydracrylic acid, . . . .106

Hydrobilirubin, 384, 385, 387, 389, 474, 622
Hydrochinon, .... 606, 607
Hydrochloric acid, . . . .76
,, of gastric juice, 276,351

,, ,, ,, estima-

tion of,

365, 545
,, ,, ,, function

of, 364, 463
,, origin of,

359, 533
,, ,, ,, source

of, . 358

,, ,, ,, tests for, 364

,, in urine, . . . 633

Hydrocollidine, ..... 59

Hydrocyanic acid, . . . .34

,, haemoglobin, . . 241

,, methremoglobin, . 248

Hydrofluoric acid in urine, . . .634

Hydrogen, 2, 29, 470

,, in alimentary canal, . . 729
,, peroxide, .... 76
,, respiration of, . . 739

,, sulphuretted, 29, 32, 72, 73, 76,

470, 473

Hydrolysis, 319, 636

of disaccharides, . . 10
,, fats, .... 19
in fermentation, . .319

of gelatin, .... 70
„ polysaccharides, . . 13
,, proteids, . 31, 57, 64, 400
,, starch, . 13, 14, 396

,, urea, .... 582
Hydrolytic agents, . . . .319
,, theory of peptonisation, . 400
Hydronapthylamine, influence of on body

heat,

Hydroparacuinaric acid,
Hydrostatic pressure, .
Hydroxybutyric acid, .
Hyocholalic acid,
Hyoglycocholic acid,
Hyperisotonic solutions,
Hyperpyrexia, . .

VOL. I. — 62

821
. 466, 467
. 280
. 616
. 376
. 373, 376
142, 271, 277
823

PAGE

Hypisotonic solutions, . . . 142, 276
Hypoxanthine, ... 60, 101, 591
of blood plasma, . . 160
,, kidney, . . .92
in leuk.'emia, . .910
of liver, . . 85, 86
,, mamma, . . . 124
,, milk, . . .126
,, muscle, . . 100, 101
,, nervous tissues, . 116
from nucleins, . 65, 66, 67
of pancreas, ... 92
,, spleen, ... 87
,, testis, ... 93
,, thymus, ... 88
,, thyroid, ... 88
,, urine, . . . 596

ICELAND moss, 14

Ichthin, 53

Ichthulin, 53, 64

Imbibition, ...... 275

,, in lymph absorption, . 307

Inanition, carbonic acid excretion during,

faeces during,

in herbivora,

metabolism during,

muscle glycogen during,

organs during,

secretions during,

temperature during,

urea excretion during,
Indican,

887
. 888
. 887
. 104
. 890
. 887
. 889
887, 888
607, 627

Indicanuria, 628

Indigo-blue, .... 627, 673

,, red, 607, 627

Indol, . 29, 47, 72, 467, 468, 473, 607
,, compounds of proteid decomposi-
tion, 47

,, excretion of, .... 470

,, tests for, 468

Indoxyl, . . . 468, 470, 607, 627

,, glycuronic acid, . . . 613

,, sulphuric acid, . . 607,631

Inhibition, nervous, of secretions, 512, 526,

548, 549

Inogen, 110

Inorganic constituents. See also Ash.

of bile, . 371,560

,, blood, . . 153

,, ,, ,, plasma, 153,

157

„ body, . . 1, 76
,, ,, bone, . . Ill

,, cells, . 82, 83
,, ,, cerebro-spinal

fluid, . .184

,, food, . 882, 883

,, ,, gastric juice, . 350

,, ,, kidney, . 92

,, liver, . . 87

„ lymph, . 182, 286

,, ,, meat, . . 96

,, milk, 128, 129, 130,

131, 662

,, ,, muscle, 95, 109

,, ,, nervous tissues, 116

,, ,, pancreatic juice,

,, proteids,

367, 368
25

978

INDEX OF SUBJECTS.

PAGE

Inorganic constituents of red corpuscles, 155
,, ,, retina, . . 121

,, saliva, 345, 347, 494,
496, 498, 499, 503
87

, urine, .

Insects, haemoglobin of,
pepsin of,
poisons of,
respiratory exchange of,

,, ,, succus enteri-

cus, . . 369
,, ,, sweat, . 671, 672

,, ,, synovia, . 184

,, ,, thyroid, . 88

,, ,, urine, . 572, 630

Inosinic acid, .... 100, 103
Inosite, . . . .16, 82, 87, 90
of kidney, .... 92
muscle, . . . 100, 105
nervous tissues, . . .116
spleen, .... 92

testis, 93

thyroid, .... 88
torpedo organ, . . .111

urine, 606

. 187
. 330
. 55
702, 703,
710

,, temperature of, . . 792, 807

Inspiration, air of, ... 754, 774

,, influence of, on lymph flow, 300

,, volume of, ... 748

Internal respiration, . . . 692, 780

,, secretions, .... 937

Inter- renal body, . . . .957

Intestinal bacilli, .... 470

,, contents, reaction of, . 452, 464
,, emulsion, .... 447

juice, . . . 368, 397, 398
,, enzymesof, 341, 397, 398,556
,, ,, percentage of proteids

in, .... 24

,, secretion, amount of, . . 557
,, ,, histological changes

during, . . 554
,, ,, influence of food on, 555

,, ,, ,, ,, nerves on,555

,, „ „ ,, pilocar-

pine on, 555,
557

,, ,, mechanism of, . 554

Intestines, absorption by, 284, 302, 432, 433,

557

„ enzymes of, 341, 397, 398, 556
gases of, . . . . 729

,, heat production in, . .843
Intraglobular crystallisation, . . 191
Inulin, . . . . . . 4, 14

Inversion, . . . . . .10

,, of cane-sugar, 10, 398, 556, 558

,, „ lactose, . . . 10, 399

,, ,, maltose, . . .10, 397

Inverting ferments, 10, 12, 313, 319, 342,

393, 397, 556, 558

Involuntary muscle, chemistry of, . 99
Iodine, ...... 2

,, in animal tissues, ... 90
,, ,, thymus, .... 89

,, „ thyroid, .... 89

lodo-gorgonic acid, .... 90

Iris, 121

Iron, 2, 78

Iron, assimilation of, .

in bile,

,, faeces,

,, foetus,

,, food,

of haematin,

,, haemochromogen,

,, haemoglobin, .

in liver,

,, milk,

,, nuclei, .

,, nucleo-proteids,

,, proteids,

,, urine,
Iron-free haematin,
*Isocholesterin,
Isodynamic value,
Isomaltose, . . 4, 11
Isotonic coefficients,

,, fluids, absorption
,, solutions,

PAGE

. 885, 886

. 561

. 885

. 885

. 884

. 250, 258

. 256, 258

186, 201, 768, 885

86, 87, 563

. 132

. 885

. 68, 69, 86, 885
25, 61

. 635, 885, 886

. 251

24, 674, 675

. 835, 837, 875

, 15, 397, 612, 926

. 270

of, . . 304
. 142, 270

JACOBSON'S nerve, 343, 482, 498, 499, 506,

508

,, vein, 909

Jaffe's test, . . . . . 599, 627
Jecorin, . . . .86, 87, 91, 160
Jequirity seed, ..... 55

KATABOLISM,
Kephalines, .
Kephir fungus,
Kerasin,
Keratin,

,, derivatives of,
Keratinose, .
Ketoses,

Kidney of amphibia, .
chemistry of,

. 869, 894
. 119
. 12
. 119, 120
70, 72, 473
. 73
. 73
4

. 655
. 92

epithelium of, 639, 640, 641, 652, 659
glomeruli of, 639, 641, 652, 655, 659
influence of, in phloridzin diabetes, 922
nerve supply of, . . 643, 659
tubules of, . 639, 650, 652, 655
Kidney bean, proteids of, . . . 54
Kinji-crab, skeletins of, ... 74
Kjeldahl's method of nitrogen-estimation, 580
Knop and Hiifner's method of urea-esti-
mation, 584

Koprosterin, ..... 24

Krasser's reaction, .... 48

Kreatine. See Creatine.

Kreatinine. See Creatinine.

Kresol. See Cresol.

Kresolsulphuric acid, . . . 470, 631

Kynurenic acid, .... 607, 638

LACHRYMAL gland, . . . .475

Lactalbumin, . 124, 126, 127, 134, 139

,, carbohydrate from, . . 64

,, coagulation temperature of, 43

,, rotatory power of, . . 46

Lactate of ammonium, . 905, 906, 909

Lactation, urine during, . . .611

Lacteals, absorption of fat by, . 457, 462

Lactic acid, 106, 586

,, in bacterial digestion, 355, 470

., blood, 106, 159, 881, 894, 905

,', fermentation, 7, 12, 126, 334

,, ,, gastric juice, . . 351, 355

INDEX OF SUBJECTS.

979

PAGE

Lactic acid in milk, . . . 126, 133
muscle, . 99, 100, 106, 110
nervous tissues, . 116,117
pancreas, ... 92
sweat, . . . 671, 673
urine, .... 894

tests for, . . . .366

Lactoglobulin, . 126, 127, 129, 134, 139
Lactoprotein, . . . . .135

Lactosazone, . . . . .12

Lactose, 4, 9, 10, 12, 126, 127, 128, 129, 132,

399, 665, 834

,, absorption of, ... 435

,, assimilation of, . . 880, 881

,, in urine, . . .611, 881

Lactosuria, . . . . . .612

Lsevulose. See Levulose.

Laiose, ...... 7

Laking of blood, .... 142, 145

Lanoline, 24, 675

Lardacein, .73

Lardaceous degeneration, ... 73
Latent period of secretion, . 494, 505, 549
Lateritious deposit, . . . .588
Laurie acid, ..... 133

Lauristic acid, ..... 20

Lead, 2, 78, 87

Lecithalbumins, ... 61, 69, 658

Lecithin, 20, 21

action of pancreatic juice on, 463
bacterial decomposition of, . 471
of bile, . 370, 371, 391, 564, 901
,, blood, . . . 155, 160
„ cells, . . .82, 83, 84
,, chyle, . . . .183
decomposition of, . . . 22
distearyl, . . . .22
of lens, . . . .123
,, milk, . . 126, 129, 133
,, muscle, . . . .103
,, nervous tissues, . 116, 119
nutritive value of, . . 879
production of alkaloids from, 58
of red corpuscles, . . .156
retina, . . . .121
spleen, .... 87
synovia, . . . .184
testis, .... 93
torpedo organ, . . .111
Leech extract, . . . 152, 174, 175
,, ,, effect of, on coagulation, 147
,, hemoglobin of, . . . .187
Legal 's reaction, .... 469,616
Legumin, 51, 333

Lens, chemistry of,

Leo's method of estimating hydrochloric
acid, ......

Lethal,

Leuceine, ......

,, in synthesis of proteids,
Leucimide, .
Leucine,

constitution of,

123

366
20

. 31
. 35
. 34
28, 421
. 422

from different substances, . 425
in decomposition of albuminoids, 71,
73, 74, 76

,, digestion, .... 437
,, kidney, .... 92

,, liver, 86

,, nervous tissues, . . . 116

PAGE

Leucine in pancreas, .... 92
,, pancreatic juice, . . . 367
,, proteid decomposition, 28, 31,
32, 34, 63

,, putrefaction, . . . 470
separation of, from tyrosine, . 424
in spleen, .... 87
,, sweat, .... 673
synthesis of, . . . . 421
in synthesis of proteids, . . 35
,, testis, .... 93

tests for, . . . .423
in tryptic digestion, 405, 406, 416,

421

,, urine, . . . . 602

Leucocytes, 141, 152, 158, 286, 344, 440,

450, 501, 519, 663

, , in fat absorption, . . 457
,, influence of, on coagulation, 175,

179

Leucocytopenic phase, . . .152

Leucocytosis and uric acid formation, 67, 594,

595, 596

Leucocytotic phase, . . . .152
Leucomaines, .... 58, 101

Leucosin, 54

Levulinic acid, . . . . 7, 63, 66

Levulose, . 4, 5, 7, 8, 10, 12, 435, 611, 917
Lichenin, . . . . . .14

Lieberkiihnis, crypts, . .- . 554

jelly, .... 50

Liebermann's reaction, . . 23, 48

Lignin, ...... 16

Lime. (See also Calcium salts.) . 77, 87

Lipase, 160

Lipochromes, . 20, 122, 133, 157, 159
Liquor amnii, fat in, . . . .17

,, ,, proteid in, . . 24

,, sanguinis. See Blood plasma.
Lithium, ...... 2

Liver, amylolytic ferment of, . 925, 926
chemistry of, . . .85

extirpation of, 105, 905, 908, 909, 910
fat in, . . 17, 85, 901, 935

formation of urea in, . . . 906
, , uric acid in, . . 909
glycogen of, 85, 569, 917, 918, 919,

922

,, heat production in, . . 843, 896
,, influence of, on coagulation, . 178
,, ,, ,, fat metabolism, 935

,, ,, ,, proteid meta-

bolism, . . 900

,, nitrogenous metabolism in, . 906

,, nucleo-proteid of, ... 81

,, proteids of, ... 24, 85

,, urea-forming ferment of, . . 907

Living proteids. (See also Bioplasm.} 38,80

Lizard, respiratory exchange of, . . 710

Lung catheter, ..... 774

Lungs, alveolar surface of, . . . 754
,, influence of, on coagulation, . 178

Lupino-toxin, 55

Lutein, 20, 95

Lutidine, ...... 34

Lymph, absorption of, . . 302, 306

,, amount of fat in, ... 17
,, ,, proteids in, . 24

,, chemistry of, . . . .181

,, coagulable, . . . 164, 168

980

INDEX OF SUBJECTS.

PAGE

Lymph, corpuscles of, . . . .141

,, dextrose in, . . 6, 182

,, functions of, . . . .310

,, gases of, . . . . . 783

,, hearts, . . . . 301

, , influence of aortic obstruction on, 292

,, blood pressure on, 299,

300

,, ,, capillaries on, . 296

,, ,, hydnemia on, . 293

,, ,, lymphagogues on, 293,

297

,, ,, muscular contrac-

tion on, . . 300
,, ,, plethora on, . . 293

,, ,, respiration on, . 300

,, ,, venous obstruction

on, . . .291

,, movement of, . . . 299, 300

,, pressure of, . . . . 299

„ production of, . . 285, 286, 298

,, of salivary glands, . . . 510

,, ,, thoracic duct, . . . 290

Lymphagogues, . . . 290, 293, 297

Lymphatic glands, chemistry of, . 81, 88

Lymphatics, absorption by, . 302, 433, 610

Lysatine, 33, 426

Lysatininc, . . 29, 33, 72, 73, 421, 426
Lysine, . . 29, 33, 72, 73, 421, 426

MACKEREL, alkaloid in,

Magnesium, .

, , palmitate,

, , phosphate,

. 2, 77, 87
. 78

76, 78, 111, 113,
153, 157
. 78
. 25
634

,, salts in body, .

,, ,, proteids,
,, ,, of urine, .

,, stearate, . . . .78

,, sulphate, precipitation of

proteids by, ... 42
Maize, proteids of .... 54
Malaminic acid, .... 34

Malic acid, . .... 673

Malt diastase, . . . 393, 394

Maltodextrin, . . .16, 396

Maltosazone, . . . .11

Maltose, 4, 7, 9, 10, 13, 15, 394, 395, 396,
397, 398, 916, 926

,, absorption of, . . .435

,, assimilation of, . . 880, 881

,, heat value of, ... 834

,, in urine, . . . . 881

Mammalia, cutaneous respiration of, . 725

,, frequency of respiration of, 753

,, haemoglobin of, . . . 187

,, respiratory exchange of, 706, 709

,, skin absorption of, . . 688

,, temperature of, . . .787

,, urine of, .... 637

Mammary glands, . . 124, 662, 665

Manganese, 2, 78, 87

Mannite, 4, 6, 7

Mannonic acid, . . . . . 4, 6

Mannosaccharic acid, .... 4

Mannose, . . . . 3, 4, 6, 7, 8, 16

Mannoso-cellulose, . . . .16

Marrow cells, proteids of, . . 84

,, fat of, . . . . 17, 19

,, nucleo-proteid of, . . 81

PAGE
Mastication, influence of, on salivary

secretion, 490, 491

Max Schultze's method of preparing

haemoglobin, ..... 194
Meat, constituents of, . . . 96, 874
Mechanical affinity, .... 275
Meconium, . . . . .473, 474
Medulla, salivary secretion after punc-
ture of, 484

Medullic acid, 19

Melanin, . . . . . .121

Melanotic sarcoma, iron in, ... 78

Melebiose, 12

Membrane of Descemet, . . 64, 121
» Membranes, filtration through, . 280, 283

permeability of,

,, semipermeable,

Membranin,

Mesenteric ganglion, inferior,

Mesostate, . , .

Meta-amido-benzoic acid,

Metabolism,

,, carbohydrates in,

,, of carbohydrates,

264, 273, 274,
276, 296, 308
. 264
64, 121
. 550
. 536
36

914, 915
. 616

action of pan-
creas on, . 927

,, conditions affecting, . . 869

,, contact changes in, . . 870

,, during inanition, . . 887

,, of fat, . . . .930

,, ,, influence of liver on, 935

,, of foetus, . . 732

, , influence of assimilated pro-

teid on, . 903
,, ,, ,, ductless glands

on, . . 937

,, ,, ,, spleen on, . 959

,, ,, ,, temperature on, 848

,, ,, ,, after section

of cord, . 859

,, katabolism in, . . . 894

muscular, 895, 902, 904, 911,

915, 918

,, nitrogenous, in liver, . 906

,, ,, in tissues, . 896

,, oxidation in, . . . 894

of proteids, . . .897
,, ,, influence of liver on, 900

,, ,, ,, ,, muscular

activity on, . 911

,, reaction in, . . .870

,, synthesis in, . . . 893

,, of tissues, relative activ-

ity, • -

,, urea in,

,, uric acid in,

Metacasein, ....
Metalbumin,
Metapeptone,
Metaphosphoric acid, .
Methaemoglobin, .

compounds of,

oxygen of, .

reactions of,

spectrum of,

in urine, .

Methal,

Methane,

Methylenitan,

. 895
. 906
. 909
. 127
. 63
. 403
. 21
243, 244
248, 249
. 247
. 246
. 246
. 629
. 20

16, 470, 471, 472, 473, 729
5

INDEX OF SUBJECTS.

981

PAGE

Methyl glycine, 598

glycocoll, .... 427

glycocyanin, .... 598
indol, .... 469, 607
mercaptan, .... 470
pyrrol, ..... 31
Micellar theory of peptonisation, . . 400

Micelli, 400

Microchemical methods, . . .66
Micrococcus urecc, . . . .601
Milk, alkaloids in, .... 59
of animals, . . . .130

ash of, .... 662, 885
carbohydrates of, . . .132
chemistry of, . . .125

coagulation of, . . 134, 138, 334
coagulating ferment of, 127, 134, 326,
334, 336

composition of, . . . . 874
constituents of, . . . .126

of cow, 129

discharge of, .... 667
effect of boiling on, . . .126
fats of, ... 17, 19, 133

gases of, . . . . 129, 130
globules, . . . . .125
heat value of, . . . 834

human,
lime in,

phospho-carnic acid of,
pigeon's, .
plasma,
proteids of,
reaction of,

127, 133, 138
. 886
. 104
. 675
. 125
24, 134
126

secretion, action of atropine on, . 664

,, ,, ,, pilocarpine on, 664

,, cells during, . 662, 665
,, formation of organic

constituents in, . 665

,, influence of diet on, . 664

,, ,, ,, nervous

system on, 663

,, mechanism of, . . 662

See Lactose.

sugar
Millon's reaction, .
Mineral constituents.
constituents.
Minimal air,

See Inorganic

47

752

198,

Mixed saliva, . . . .344, 348

,, salivary glands,
Molar salivary gland, .
Molecular conductivity,

weight of albumin,
,, , albumoses, .
,, , antipeptone, .
,, , deuteroproteose,
,, , haemoglobin, .
,, , peptone,
,, , proteids,
,, , protoproteose,
Molecules of proteids, .
Mollusca, haemocyanin of, .
,, hemoglobin of,
,, muscle of, .
,, respiration of,
,, skeletins of, .
Monacetin, .....
Monobromacetic acid, .
Monobromobenzoic acid,
Monosaccharides,

477
476
261
26
27
27
46
203
. ' 46
26, 27
. 46
26, 45
. 61
. 187
. 95
702, 753
74

. 18

. 34

34

• 4,7

PAGE

Moore's test, ..... 7
Morphia, influence of, on body tempera-
ture, 821

Mountain sickness, .... 738

Mouth, temperature of, . 787, 788, 824
Mucedin, ...... 53

Mucic acid, ...... 4

Mucilage, 14, 16

Mucin, ....

61, 84

of bile, .

370, 371, 569
. Ill

f
, c

j
5

?

»
»
> »

> i

»
5 J
> J

5 J

Mucinog

ecomposition of,
f epithelial tissues, .
, faeces, .
kidney,
liver, .
lymphatic glands,

. 62

. 84
. 473, 474
. 92
85, 569
. 88
. Ill

saliva, . . 343,
salivary glands, .
skin secretions,
succus entericus, .
synovia,
torpedo organ,
urine, .
vitreous humour, .
en, .

344, 501, 503
92
. 673
. 368, 369
. 184
. 110
. 604
. 123
62, 92, 123

Mucinoids, . . . . . .63

Muco-albuminous glands, . . . 478
Mucoids, . . . .61, 63, 121, 123

Mucous cells, 477

,, glands, salivary, . .477, 503
,, secretion of mouth, . . 344,348

Mucus, 17, 84, 85

Mule, milk of, . . . . . 131
Munena, poison of, . . .55

Murexide test, 592

Muscarine, 60, 472

,, action of, on salivary secretion, 513
,, ,, ,, sweat secretion, . 680

Muscle albumin, coagulation tempera-
ture of, .... 43
,, chemistry of, . . . 95, 109
creatine in, . . . 100, 904
,, digestibility of, ... 333
,, extractives of, . . . 100, 110
,, fat of, . . 17, 95, 100, 105
,, gases of, . . . . 110, 911
,, glycogen of, 95, 100, 104, 108, 110,
911, 915, 917

,, haemoglobin of, . 97, 99, 187

,, heat production in, . . . 840

,, during inanition, . . 104, 890

,, inorganic constituents of, . . 109

,, involuntary, chemistry of, . 99

,, leucine and tyrosine of, . . 425

metabolic activity of, 895, 904, 911,

915, 918

,, plasma, . . . . 95, 96
,, proteids in, . . 24,95,96,97
,, in proteid metabolism, 902, 904,

911

,, reducing power of, . . . 782
,, ,, substances of, . .110

,, respiratory exchange of, . . 840
,, sarcolactic acid of, 95, 99, 104, 106,

110, 911

,, serum, ..... 96
,, su^ar, . . 100, 105, 110, 606
,, urea in, . . .100, 102, 904

INDEX OF SUBJECTS.

Muscular contraction, chemical changes

during, . . 109
,, influence of, on

lymph flow, . 300
,, ,, proteid meta-

bolism, . 911
,, ,, muscle glyco-

gen, 110, 915, 918
. 97
59, 60
. 75
119

Musculin,

Mussel, alkaloids in, .

,, skeletins of,
Myelines,
Myogen,

,, fibrin, .
Myo-globulin,
Myo- haematin,
Myo-proteid,
Myosin,

,, ferment, .

,, fibrin,

,, vegetable,
Myosinogen,

,, coagulation

of,

. 98
97, 98

. 98

. 95

. 97

. 98

53, 54

. 97, 98, 99

temperature

43

,, mechanical precipitation

of, .... 43

Myosinoses, ...... 50

Myricin 20

Myricyl alcohol, palmitate of, . . 20

Myristic acid, .... 20. 133

Mytilotoxin, ..... 60

Myxcedema, 938

NEGATIVE phase, 37, 57, 68, 146, 173, 176

Neossidin, 63

Neossin, 63

Nerve or Nerves, auriculo-temporal, . 482

,, buccal, 482

,, chorda tympani, . . 479, 519
„ chordo-lingual. (See also Chorda

saliva.} . . 479, 505, 509

,, fat in, 17

,, influence of, on salivary secre-
tions, . 343, 487, 493, 494, 506,
519, 525

,, of Jacobson, . 343, 482, 498, 499,

506, 507

kidney, . . . 643, 659
lachrymal gland, . . 475

orbital gland, . . . 482
parotid gland, . . .482
salivary glands, . . 479, 483
,, ,, cranial, 479, 482,
493, 504

,, ,, section of, . 519
,, ,, sympathetic, 479,
483, 494, 522

,, secretory. See Secretory nerves. 526
,, section, effect of, on muscle gly-

cogen, ..... 105
,, of skin secretion, . . 676, 677
,, small superficial petrosal, . 482

,, of sublingual gland, . . 479
,, ,, submaxillary gland, . . 479
,, trophic, of salivary glands, 526,528
,, vaso-constrictor. See Vaso-con-

strictor nerves.
,, vaso-dilator. See Vaso-dilator

nerves.
Nerve-centres of cardia, . . . 538

Nerve-fibres, frigorific, .

,, secre to-inhibitory, of sali-

vary cells, .

,, secretory,

,, thermic, .

,, trophic, .

Nerve-ganglia of salivary glands,

PAGE

855

526
. 526
. 865
. 526
480, 482,
484
. 115
. 17
. 187
24, 117
. 117
. 60

. 22, 60, 160, 472
. 75
72, 116, 117
Neurostearic acid, . . . .120
Neutral fats, . . . . 18, 19
,, salts, precipitation of proteids

by, 41

Nickel reaction of proteids, . . .48
Nicotine, action of, on body tempera-
ture, . . 821
,, ,, ,, salivary secre-

tion, 480, 484, 515
,, ,, ,, sweat secre-

tion, . .679
Nitrate of urea, ..... 581

Nervous tissues, chemistry of,

fat of,

,, haemoglobin of,

,, proteids of,

,, reaction of,

Neuridine, ....
•Neurine,
Neurochitin,
Neurokeratin,

Nitrates of urine, .

Nitric oxide in blood, ....

,, ,, haemochromogen,

,, ,, haemoglobin,
Nitrites, action of, on oxyhsemoglobin,

compounds of, with methsemo-

globin, .
of saliva, .

,, urine.

634
238
258
241

245,

247

Nitrogen,

of alimentary canal,

alloxuric,

of blood,

of chyle,

elimination,

248
. 346
. 634
. 2, 30
. 729
. 597

761, 769
. 900

580, 876

daring inanition, 887,
888

,, with proteid diet, 891

estimation, Kjeldahl's method

of, 580

excretion by skin, . . 672

of foodstuffs, . . .873
,, meat, .... 96
in respiration, . 700, 704, 739
of urine, . 580, 637, 864, 912
Nitrogenous constituents of blood plas-
ma, . 160
,, ,, body, . 1

,, ,, urine, . 580

equilibrium, . . 871, 891
extractives of muscle, . 1 00
metabolism in liver, . 906
,, ,, tissues, . 896

NO-hsernochromogen, NO-hremoglobin.

See Nitric oxide.
Non-nitrogenous constituents of blood

plasma, 157
body, 1

,, extractives of muscle, 100,

104, 110

INDEX OF SUBJECTS.

983

PAGE

Nonoses, 2

Notochord, 113

Nubecula of urine, . . . .85
Nucleic acid, . . . .66

Nuclein, 61, 65, 80

bases, . . . .66, 67, 88
of bone, ..... Ill

crystallisation of,

of faeces,

„ fibrin,

influence of, on
puscles,

iron of, .

of liver, .

,, nervous tissues, ,

nutritive value of, ,

of pancreas, .

,, pus cells, .

,, red corpuscles,

,, testis,

,, yeast, .
Nucleo-albumin, .

,, of bile,

,, digestion of,

Nucleo-histon,
Nucleoli, nucleic acid of,

,, nucleins of, .
Nucleon, .
Nucleo-proteid, 61, 66,

white

44

. 473
. 167
sor-

. 152

. 885
85, 86
. 116
. 879
3

. 83

155, 198

93

67, 428

371, 561, 569

. 428

68, 82, 604, 605

. 104, 139
67, 181, 428,
895

,, of blood plasma, . 161, 165,

171

,, cells, . .81, 82, 84
,, compared with colloids, 37

,, digestion of, . . 428

,, of h'bririogen, . . 165

,, influence of, on coagula-

tion, 170,
176, 179

,, ,, ,, uric acid

excre-
tion, . 594

,, ,, ,, w h i t e

c o r -
puscles, 179

of kidney, ... 92

,, ,, liver, . . 85, 86

,, ,, mamma, . . . 124

,, in metabolism, . . 910

,, of mucus, ... 84

,, ,, muscle, ... 98

,, ,, nervous tissues, . 118

,, ,, nuclei, ... 82

,, nutritive value of, . 879

,, of pancreas, . . 3, 6, 64

,, as poisons, ... 55

,, precipitation of, . . 42

,, of red corpuscles, . . 155

,, , spleen, ... 87

,, submaxillary gland, 92

,, suprarenal body, . 91

,, testis, ... 93

,, , thyroid, ... 89

,, urine, . . 85, 603

Nucleus, iron in . . . . . 885

,, nucleins of, . . . 66, 81

,, nucleo-proteid of, . . . 82

Nutrition, balance of, . . . . 871

Nutritive equilibrium, . . . .871

Ny lander's test, 610

OATS, proteids of,
Octoses,
Oekoid,
Oleic acid, .
Olein, .
Oleyl, .
Oncograph, .
Oncometer, .

PAGE

. 54

2

. 188

. 18, 24, 133, 456, 675

18, 133, 159

18, 22

. 643

643

Onuphis tubicola, hyalogen from, . . 64
Ophridium versatile, zoocytium of, . 16
Optimum point, ..... 320
Orbital salivary gland, . 476, 478, 482
Organeiweiss, . . . . .897
Organic constituents of blood plasma, . 157
„ body, . . 1
,, ,, bone, . . Ill

„ cells, . 82, 83
,, ,, gastric juice, . 350

„ liver, . 85, 86
,, ,, pancreatic juice, 367,

368

,, ,, red corpuscles, . 155

,, saliva, 344, 347, 494,
496, 498, 500, 507

spleen,
thyroid

Organised ferments,
Organs, chemistry of, .
Ornithin,
Ornithuric acid, .
Orthodihydroxybenzene,
Orthonitrobenzyl alcohol,
Osazone, . . 3,

of acrose,

,, albumin of peas,

Osmosis,

87
88
572
. 312
. 80
. 33
. 602, 638
. 606
5

9, 10, 11, 12, 30

5

64

decomposition products of

proteids,
dextrose, .
disaccharides, .
formose,
galactose, .
glucose,
isomaltose,
lactose,
levulose, .
maltose,
rnannose, .
monosaccharides,
pentose,
sugar of tendon-mucin,

in lymph absorption,
,, ,, production,
,, salivary secretion,

Osmotic pressure,

Osones,

Ossein,

Otic ganglion,

Otoliths,

Ovarian dermoids,

,, fluid, mucoid of,

Ovary, chemistry of, .

Ovomucoid, .

30, 64
8, 612
. 10
5

8, 612
8, 608
12, 613
. 12
8

. 11
8
8

3, 612
. 62
. 264
. 307
. 288
. 529

265, 276, 308, 650
. 6, 9
70, 111
. 482
. 78
. 675
. 63
. 94
63, 85

Ox bile, . . 370, 373, 381, 385, 390
,, ,, nucleo-proteid of, . . . 84
,, hemoglobin of, 193, 199, 201, 202, 206
,, respiratory exchange of, . . . 707
,, salivary glands of, . . . . 477

Oxalate of calcium, . . . 78,614

INDEX OP SUBJECTS.

PAGE

Oxalate of urea, ..... 581

Oxalated blood, 147, 165, 166, 169, 171, 175

Oxalic acid, . 5, 30, 31, 34, 571, 614, 673

Oxaluria, . . . . .614

Oxidation in blood, . .781. 895

,, ,, cells, . . 780, 781

,, ,, metabolism, . . 894

of proteids, . 34

,, in tissues, . . . 895

Oxybutyric acid, . . 928

Oxycarnic acid, . . 103

Oxychinolin-carboxylic acid . . 638

Oxygen, ... 2

,, absorption of, by haemoglobin, 767

,, of alimentary canal, . . 729

,, „ blood, . 153, 154, 185, 229, 757,

761, 762, 765, 768

,, capacity of haemoglobin, . . 768
,, of contracting muscle, . . ]10
,, ,, methaemoglobin, . . . 247
,, milk, .... 129, 130
,, ,, oxy haemoglobin, . . . 236
,, respiration of, . . . 735, 742
,, in respiration. (See also Re-
spiratory exchange, Re-
spiration.) . 692, 695, 700
,, respiratory, . .185, 235, 236
,, of saliva, .... 346, 504
,, secretion by swimming bladder, 705
,, of serum, ..... 157
,, tension of, in alveolar air, . 774
,, blood, . . . 775
185, 193

Oxyhaemoglobin,

Oxylic acid,

action of nitrites on, . 245,
247

amount of oxygen in, 236
crystals of, . 203, 205

decomposition of, 207, 243
derivatives of, . . 243
difl'usibility of, . 203, 207
dissociation of, . . 774
elementary composi-
tion of, . . . 197
preparation of, . 193, 200
quantitative determina-
tion of, . . . 234
reactions of, . 207, 236
reduction of, . . 229
solubility of, . 203, 205
spectrophotometric

constants of, 213, 223
spectrum of, . 208, 210
,, photo-
graphic, 225
103

Oxyphenylalanine,

Oxyphil corpuscles,

32

amido-propionic acid, 29
propionic acid, . 29, 106

152

PALMITATE of cetyl alcohol, . . 20

,, ,, magnesium, . . .78

,, ,, myricyl alcohol, . . 20

Palmitic acid, 18, 20, 24, 119, 456, 675

Palmitin, . . . . 18, 133, 159

Palmityl, 18, 22

Pancreas, action of, on carbohydrate

metabolism, . . . 927
,, changes in, during digestion, 546
,, chemistry of, ... 92

PAGE

Pancreas, nucleo-proteid of, . . 3, 6, 64

,, pentose from, . . 64, 612

Pancreatic casein, . . . .137

,, diabetes, . . . 927, 929

,, enzymes. (See Enzymes.) . 336

,, extracts, .... 336

,, ,, activity of, . 325, 552

fistula, . . 366. 459, 547

juice, 366

,, ,, action of, on fats, . 443

,, ,, ,, ,, lecithin, 463

,, ,, ,, ,, proteids, 414

„ starch, . 393

,, ,, of animals, . . 367

0 ,, ,, coagulating ferment of, 326

,, ,, composition of, . . 367

,, ,, emulsive action of, . 448

,, ,, enzymes of. (See En-

zymes.) . . 336

,, ,, ferments of. See En-

zymes. 336

,, ,, influence of, on fat

absorption, . 459, 461
,, ,, methods of obtaining, 547

,, ,, proteids of, 24, 367, 368

,, ,, rate of secretion of, . 368

,, ,, variations in, during

digestion, . . 553
,, secretion, histological changes

during, . .546
., ,. influence of alka-

loids

on, 548,
550

» n n ii l)lood

flow on, 549
,, gastric

juice on, 551
n n ii nervous

system on, . 547
,, ,, latent period of, . 549

,, ,, local stimulation of, 551

., ,, mechanism of, . 546

,, ,, paralytic, . .550

Papain, 51, 54, 55

,, plant, proteids of, . . 51, 54
,, ,, proteolytic ferment of, 54, 403

Papoyotin, 403

Paracascin, . . . . . .134

Paradihydroxybenzene, . . . 606
Parafibrinogen, . . . . .164

Paraglobulin, 163

Parahfemoglobin, .... 207

Parahydroxyphenyl-acetic acid, . . 606
,, propionic acid, . 606

Parakresol, ... 29, 466, 467, 606
Paralactic acid, . . .106, 183, 465
Paralbumin, ..... 63

Paralytic secretion of pancreatic juice, 550

,, ,, saliva, . . 519

Paramucin, . ..... 63

Paramyosinogen, . . . .97, 98, 99

Paranucleins, ..... 66

Paraoxy ben zoic acid, .... 34

Paraoxyphenyl-acetic acid, . . 466, 467
,, amido-propionic acid,

421, 423, 467

,, propionic acid, . 466, 467

Parapeptone, . . . 402, 404, 408
Parathyroids, . . . . .940

INDEX OF SUBJECTS.

985

PAGE

Paraxanthin, .... 596, 598

Parotid fistula, ..... 489

,, gland of animals, . . 476, 478

,, ,, nerves of, . . 482, 483

saliva, 327, 343, 346, 347, 494, 495

Parotids of toad, 674

Parvoline, ...... 59

Pavy's test, . . . . . .611

Pawlow fistula, ..... 349

Peas, osazone from, .... 64

Pelias berus, venom of, . . .58
Pentosanes, ...... 3

Pentoses, . . . . . . 2, 3

,, from pancreas, . . 64, 612
,, physiological action of, . . 3
,, in urine, ... 3, 612

Pentosuria, 612

Pepsin, 326, 330, 350, 358, 402, 532, 534
absorption of, by fibrin, . 404, 542

action of, on proteids,
of animals,

digestion, effects of form of pro-
teid on, .

,, ,, ,, reaction on, .

,, ,, ,, temperature on

estimation of activity of,
formation of, .
hydrochloric acid,

326
330

333
331
331
323

542, 544
. 331
in muscle, .... 97

preparation of, ... 314

separation of, from rennin, . 335
Pepsinogen, . . . 425, 532, 536

Peptic digestion, . . . 401, 418, 428
,, ,, cleavage theory of, 405, 406,

414, 416

,, ,, proteids of, 402,414,541

Peptones, 50, 51, 400, 401, 403, 405, 411,

416, 899

absorption of, . . 437, 439
of bacterial digestion, . . 466
carbohydrate from, . . 64
in cells, .... 82

in cerebro-spinal fluid, . . 184
divisibility of, . . 45, 46
elastin, ... 72, 430

of gastric juice, . . . 353
gelatin, . . .70, 429
heat value of, . . 834, 835
influence of epithelium on, . 440
,, ,, injection on white

blood-corpuscles, 152, 179
molecular weight of, . . 46
of muscle, .... 97

nutritive value of, . . 878

of peptic digestion, . 403,416
as poisons, .... 55

precipitants of, . . . 40
of pus cells, . . .83

of spleen, .... 88

of tryptic digestion, . . 420
in urine, . . . 604, 605
vegetable, .... 51

Peptonisation, hydrolytic theory of, . 400

,, micellar theory of, . 400

,, by superheated steam, . 403

Peptonised blood, 147, 152, 166, 174, 177,

182
Peptonuria, ...... 604

Pericardia! fluid, . . . . 24, 183

Permeability of blood corpuscles, . 271, 277

PAGE

Permeability of membranes, . 264, 273, 274

„ „ living, 276, 296,

308

Pernicious anaemia, alkaloids in, . . 59
Peroxide of hydrogen, .... 76
Petrosal nerve, small superficial, . . 482
Pettenkofer's test, . . . .377

Phaselin, 54

Phaseolin, 54

Phenaceturic acid, . . . 470, 601
Phenol, . . 29, 34, 46, 72, 466, 467
,, compounds of proteid decom-
position, . . 46
,, elimination of, . . . . 470

,, glycuronic acid, . . 613, 614
in urine, .... 606, 607

Phenyl compounds in proteid decom-
position, ...... 46

Phenylacetic acid, 29, 46, 466, 467, 470

Phenylacetyl glycine, . . . .106

Phenylhydrazine test, ... 8, 608
Phenyl propionic acid, . 29, 46, 466, 467,

470, 601
Phenylsnlphuric acid, .... 470

Phlebin, .... 190, 192, 225

Phloretin, 920

Phloridzin, 920

,, diabetes, .... 920

Phosphate, ammonio-magnesic, 78, 473, 632

calcic, 76, 78, 111, 113, 136,

153, 157, 473, 633, 882

„ magnesic, 76, 78, 111, 113, 153,

157

potassic, 76, 78, 82, 87, 108

,, sodic, 76, 78, 113, 145, 157

,, ofspermine, ... 94

Phosphates in body, . . . .79

,, of serum, .... 772

Phosphocarnic acid, . . 103, 104, 139

Phospho-gluco-proteids, . . 61, 64, 67

Phosphorescence, .... 780

Phosphoric acid, 25, 30, 77, 79, 87, 153,

356, 575, 632

,, of gastric juice, . . 356

,, ., torpedo organ, . Ill

Phosphorus, ' 2, 25

,, elimination of, . . . 575

, , .in liver, .... 87
,, ,, nuclein of muscle, . 98

,, ,, nucleo-proteid of cells, 81,84

,, ,, proteids, . . 25, 26

,, ,, vitellin, . . .53

Phrenosine, .... . . 120

Phycocyanin, 52

Phylloporphyrin, . . . .382

Phymatorusin, . . . . .121
Physostigmine, action of, on pancreatic

secretion, ..... 550

Phytalbumose, ..... 53

Pialyn, . . . 326, 336, 339, 553

,, effect of bile on, . . .339

,, ,, reaction on, . . 339

,, ,, temperature on, . . 339

Picoline, 34

Picromel, 372

Picrotoxin, action of, on sweat secretion, 679

Pig, bile of, . . ' . . 370, 373, 376

hemoglobin of, . 193, 197, 199, 201,

202, 205, 206

,. milk of, 131

986

INDEX OF SUBJECTS.

Pigeon's milk,
Pigments, biliary.

See Bile pigments.

PAGE
675

of blood,

,, „ in urine,

,, butter, .

,, choroid, .

,, corpus luteum,

,, of egg yolk, .

,, faeces,

,, fatty tissues, .

,, pathological urine,

,, pus,

respiratory,

of retina,

,, serum,

,, skin,

,, sweat,

,, tumours,

,, urine,

159, 185
629
20
121
20
20
388
20
628
84
61

. 121
. 20
. 121
. 673
. 121

388, 571, 572, 591,
616, 628
Pilocarpine, action of, on intestinal

secretion, 555,
557
,, ,, ,, milk secre-

tion, . 664
,, ,, ,, pancreatic

secretion, 548
,, ,, ,, salivary

secretion,
481, 492, 493,
498, 500,
508, 513
,, ,, ,, sweat secre-

tion, . 679
,, ,, ,, uric acid

excretion, . 595

Pine-apple, proteolytic ferment of, . 54
Piotrowski's reaction, .... 48

Piperidine, ..... 34, 92

Pituitary body, excision of, . . . 945
,, ,, influence of, on meta-

bolism, . . .945
,, extract, . . . .946

Placenta, blood of, .... 733

,, glycogen of, . . . . 918

Plants, synthesis in, . . . . 892

,, temperature of, ... 849
Plasma of blood. See Blood plasma.

,, ,, milk, ..... 125

,, ,, muscle, ... 95, 96
Plasmahaut, ..... 276

Plasmine, ...... 164

Plasmodium of dStkaliwn scpticum, . 80

270, 277
66

141, 156
.373
. 749
. 788
322
. 320
. 55
143

Plasmolysis,

Plastin,

Platelets, blood

Plattner's crystallised bile,

Pneumonometer, .

Poikilothermic animals,

Point, achromic,

,, optimum, ..

Poisons, proteid, ..

Polycythsemia,

Polysaccharides, . . . . . 4, 12

Pore diffusion, ..... 274

Portal vein, blood of, . . 900, 908, 917

Potash, ..... 77, 87

Potassium, ...... 2

chloride, . 25, 76, 77, 93, 157
phosphate, . 76, 78, 82, 87, 108

Potassium salts in body,
,, ,, proteids,

urine,
sulphate,

PAGE
. 77
. 25
633, 634
. 76, 78, 113, 157

Precipitants of proteids, chemical,

,, ,, mechanical,

Preglobin, .....
Pressure, atmospheric, influence of,

, , blood. See Blood pressure.

,, hydrostatic, .

,, lymphatic, .

,, osmotic,

,, ,, of cells, .

,, secretory, of bile, .
ii saliva»

ii ii ii urme,

Propalanine,

Propepsine, ....
Propeptones,
Propionic acid, .

40
43
68

738

280
. 299

265, 308, 650
. 276
. 560
. 511, 525
. 649
31

. 554
. 405

. 19, 34, 615, 672

Protagon, . . . 82, 116, 118, 156
Protalbumose, . 410, 412, 414, 416, 418
,, of cerebro-spinal fluid, . 184

Protamine, 93

Proteid or Proteids, . . . 1, 2, 24
,, absorption of, . 431, 436, 437, 900
by blood vessels, 309
pepsin by, . .404
action of alcohol on, . . 41

bacteria on, 29, 464, 465
pepsin on, . . 326, 418
proteolytic enzymes on, 326
superheated steam on, 403
trypsin on, 326, 415, 418
animal, ..... 49
of aqueous humour, . 122,182,183
aromatic decomposition products

of, ... 46, 467, 468
artificial production of urea from, 33
,, ,, sugar from, 30

ash of, 25

assimilable, .... 437
assimilation of, . . 38, 899
bacterial digestion of, 29, 464, 465

of blood, 153

,, ,, plasma, . . 153, 161

„ bone, Ill

carbohydrate from, ... 64
carbon of, .... 873
of cerebro-spinal fluid, . . 184

„ chyle, 183

circulating, . . . 896, 898
classification of, ... 49
cleavage of, by acids, . . 406
coagulable, of digestion, . 420, 441
coagulated, .... 50
,, vegetable, . . 51

colour reactions of, . . . 46
composition of, ... 25
compound, ... 49, 61
,, digestion of, . . 428

constitution of, . . 38, 64
crystallisation of, . . 43

decomposition of, . . 28

, by acids, . 32
,, alkalies, . 29
bacterial, . 466
putrefactive, . 465
in vitro, . 29
dialysis of, . . . .43

INDEX OF SUBJECTS.

987

Proteid

PAGE

or Proteids, diet, . . .891

PAGE

Proteid or Proteids, of sweat, . . 673

55

in diet, . . 872, 875, 878, 888

of synovia, . . . .184

digestibility of, . . 333, 338

synthesis of, . . 35, 893, 899

„

digestion of, . . . . 399

,, in vegetables, 25, 892

55
55

,, ,, nature of, . 400, 405
dry distillation of, . . . 34

of testis, 93
theories of constitution of, 38, 64

55

empirical formula of, . . 26

of thyroid, . . . 88, 89

55

of epithelium, ... 84

tissue, .... 897, 898

3 J

,, flour, 53

transudation of, . . .311

formation of fats from, . 902, 933

tryptic digestion of, 405, 406, 414, 416

,,

,, ,, glycogen from, . 901,

unorganised, . . . 897, 898

905, 919

ureide theory of, . . . 36

53

of gastric juice, . . . 350

of urine, . . . .85, 603

3 3

gmcoside theory of, . . . 64

„ tests for, . . .605

33

heat coagulation of, . . . 42

vegetable, . . .49, 51, 53

35

,, value of, . . 837, 874, 875

,, crystalline, . 27, 43, 52

hydrolysis of, . . 31, 64, 400

,, digestibility of, 51, 333,

5

,, 35 by snake venom, 57

441

indiffusibility of, . . . 43

of vitreous humour, . . .123

influence of, on bile secretion, . 566

'

of kidney, .... 92

Proteide, 428

„ lens, 123

Protein 29

f

living and non-living. (See also

Proteinchromogen, ... 29, 428

Bioplasm.} ... 38, 80

of liver, 85

,, estimation of, . . . 323

1

„ lymph, . . . 182, 286

Proteolytic ferments, 313, 319, 326, 334,

,

,, lymphatic glands, . . 81

551, 674

5

,, meat, 97

,, ,, activity of, . . 323

metabolism of, ... 897

,, vegetable, 51, 54, 330,

f

of milk, . 126, 128, 129, 134, 665

403

,

molecular weight of, . 26, 27

Proteoses. (See also Albumose.} . , 50

|

of muscle, . . 24, 95, 96, 97

, in blood, .... 165

f

,, nervous tissues, . . 116, 117

,, cells, ... 82, 83

5

nitrogen of, . . . .873

, ,, cerebro-spinal fluid, . .184

non-assimilable, . . . 437

, diffusibility of, ... 45

33

organised, . . . 897, 898

, in digestion, . . . 405

35

oxidation of, . . . .34

, from fibrin solution, . . 167

33

of pancreas, . . . .92

, in muscles, .... 97

55

,, pancreatic juice, . 24, 367, 368

, as poisons, ... 55, 56

55

peptic digestion of, 401, 405, 406,
414, 541
of peptic digestion, . . . 402

, precipitants of, . . . 40
, in proteid decomposition, 28, 32
, rotatory power of, . . 46

J}

percentage of, in tissues, . . 24

, in spermatozoa, ... 94

35

of pericardial fluid, . . . 183

, in spleen, .... 88

55

,, plasma, . . . 153, 161

, synthesis of, . . . .38

} ,

poisons, . . . . .55

vegetable, . . 51, 53, 54

55

precipitation of, . . 40, 41

Prothrombin, . . 160, 166, 175, 179

by bile, . . 392

, 3

', ,, salts, . . 41

Protoelastose, . . . . 72, 430

55

production of alkaloids from, . 58

Protogelatose, . . . . 71, 429

properties and reactions of, . 39

Protoplasm, chemical nature of, . . 80

35

of protoplasm, . . . .81

,, proteids of, ... 81

of pus cells, .... 83

,, of pus cells, . . .83

53

putrefaction of. (See also Putre-

,, reducing power of, . . 38

faction.} . . . .465

Protoproteose, diffusibility of, . 45, 46

j j

quantitative estimation of, . 41

,, molecular weight of, . 46

?J

quotient 162, 182

Pseudechis, venom of, . . . 58, 174

rational formula of, . . 27, 34

Pseudo-cerebrin, 120

of red corDtisclos 155

feeding . . . 539

55

,, red marrow cells, ... 84

fibrin, 164

55

reducing power of, . . 38, 49

haemoglobin, .... 237

•

of retina, . . . .121

mucin, .... 63, 456

rotatory power of, . . .46

nuclein, . . .65, 66, 67, 136

3 3

of saliva, .... 344, 503

,, from phosphogluco-pro-

3

separation of, from solution, . 40

teid, ... 64

solubilities of* » 39 50

3

of spleen, .... 87

, xan thine, . . . .101

3

,, succus entericus, . 368, 369, 557

Psychical feeding, . . • 539, 541

,, suprarenal body, ... 91

Ptomaines, 58, 465

33

sulphocyanate from, . . 346

Ptyalin, . . . 326, 327, 344, 393

988

INDEX OF SUBJECTS.

Ptyalin, action of, on amyloses,
in animals,
effect of acids on,
,. reaction on,
,, temperature on, .
reactions of,
separation of, .
Ptyalose, .
Puncture diabetes,
Purple cruorin, ....
Purpurate of ammonium,
Purpuiin, .....
Pus-cells, cerebrosides of,

,, chemical composition of,
,, nuclein of,
proteids of,

32

PAGE

326, 394
. 327
. 329
. 329
. 327
. 328
7, 328
394
926
229
592
623
120
83

65, 83
83

Putrefaction, aromatic products of, 46, 467,468
,, fatty products of, . . 470

,, of proteids, . . . 465

,, tyrosine derivatives of, . 467

Putrescine, 59, 60

Pycnometer, ..... 144

Pyloric glands, . . . 532, 534, 536

,, region of stomach, . . . 534

,, secretion, . . 532, 534, 544

Pylorus, nerve-centres of, . .538

Pyocyanin, ...... 84

Pyogenin, . . . . . .120

Pyosin, 120

Pyoxanthin, ..... 84

Pyrenin, 66

Pyridine, 34

Pyrocatechin, . . 63, 92, 184, 606, 607
Pyroglutaminic acid, .... 35
Pyrotartaric acid, .... 673
Pyrrol, 31, 34, 35

QUADRIURATES, .

Quinoidine, animal,
Quotient, proteid,
,, respiratory,

588, 589, 590
59

. 162, 182
700, 719, 756

RABBIT, albino, .... 37, 173
,, haemoglobin of, . . .193

,, milk of, 131

,, parotid gland of, . . . 476

,, respiratory exchange of, . . 706

Radiation in heat regulation, . . 850

Raffinose, 12

Rat, haemoglobin of, . . 193, 194, 206
Receptaculum chyli, .... 285
Rectum, absorption by, . . .436
,, . temperature of, . 787, 788, 824
Reduced haematin. See Hccmochromogen.

haemoglobin, . . . .185
crystallisation of, 232
decomposition of, 243
derivatives of, . 243
dichroism of, . 233
production of, . 230
quantitative de-
termination of, 234
reactions of, . 236
spectro - photome-
tric constants of, 234

,, ,, spectrum of, 227,

234, 236

Reducing power, . . . . . 7, 11
,, ,, of dextrose, . . 7, 11

,, ,, ,, disaccharides, 10, 11

Reducing power of galactose,
lactose, .
levulose,
maltose,
monosaccharides,

PAGE

11
12

. 11
11, 12
7

proteids, . 38, 49
substance of aqueous humour, 122
blood, . 152, 925
contracting muscle,! 10
mamma, . . 124
protagon, . . 119
suprarenal body, 91
Reflex inhibition of salivary secretion, .
,, stimulation of salivary glands, .
Reindeer, milk of, ....
Renal artery, ligature of,

,, vein, ligature of, ...
Rennet,

,, action of, on milk,

512
489
130
. 646
. 647

134, 334, 335
126, 134

,, ,, ,, pancreatic casein, 138

,. zymogen, ..... 543

Rennin, . . .134, 326, 334; 350
,, action of, on caseinogen, . 326

,, effect of acids and alkalis on, . 335
,, ,, temperature on, . . 335

,, formation of, . . . .543

,, reactions of, . . . . 335

,, separation of, from pepsin, . 335

Reptiles, haemoglobin of, . . .187

,, respiration of, ... 753

,, uric acid in muscles of, . . 101

,, urine of, ... 78, 637

Resch's test for hydrochloric acid, . 365

Reserve air, ..... 749, 753

Residu fixe, . . . . . .31

Residual air, .... 749, 753

Residue, albuminous, of haemoglobin, 243, 244

Resin of bile, 372

Respiration in alimentary canal, . .728
apparatus, 694, 695, 696, 697
of carbonic acid, . 739, 742

,, ,, oxide, . . 740
changes in air during, 754, 756
chemistry of, . . . 692
of compressed air, . . 737
cutaneous, . . . 723, 725
effect of, on blood, . . 756
external, . . . .692
of foetus, . . . 730, 733
„ fishes, . . 699, 704, 730
frequency of, . 747, 753, 854
of gases, .... 735
during hibernation, . . 794
of hydrogen, . . . 739
influence of, on bile secretion, 567
,, ,, lymph flow, 300

internal, . . . 692, 789
of nitrogen, . . . 739
,, oxygen, . . . 735, 742
,, vitiated air, . . . 741
volume of, . . . . 748
Respiratory exchange in air, . . 694

,, causes of, . 773, 783

,, of cold - blooded

animals, . 701, 709
,, conditions affect-

ing, . 700, 709, 756
,, cutaneous. See

Cutaneous re-
spirctiion.

INDEX OF SUBJECTS.

989

PAGE

Respirator}'' exchange, diffusion in, . 779
in eggs, . . 734
,, in foetus, . 733, 745

,, influence of activity

of ali-
mentary
canalon,719

,, ,, age on, 722

,, ,, body size

on, 720, 745

,, ,, food on, 717,

721, 727

,, ,, muscular

activity
on, . 714,
721, 727

,., ,, tempera-

ture on, 701,
709, 727,
735, 746,
748
,, ,, time of

day on, 721
, , as measure of heat

production, . 847
,, measurement of,

694, 754

,, tables of. See Tables.

,, in tissues, . 780, 840,

895
,, of warm-blooded

animals, . 709, 711

,, in water, . . 699

Respiratory oxygen, . . 185, 235, 236

,, pigments, .... 61

,, quotient, . . 700, 719, 756

Reticulin, 70, 72, 88

,, decomposition of, . . .32

Retina, 121

Retinal cones, ..... 20

Retrolingual salivary gland, . . . 476
Reversion, ...... 10

Rhamnose, ...... 2

Rhodopsin, 122

Ricin, ....... 55

Rickets, 886

Rigor mortis, .... 95, 97
Rotation, specific, .... 6
Rotatory power of chitosan, . 75

cholesterin, . . 23
dextrins, . . .16
disaccharides, . 10, 12
gelatin, . . .70
glycogen, . . 15

glycuronic acid, . 5
inulin, . . .14
leucine, ... 28
proteids, . . .46
starch, . . .14
Ruminants, salivary secretion of, . . 489
Rye, proteids of, . . . . .54

SACCHARIC acid . . . . 4, 5, 34
Saccharo-lactonic acid, ... 5

Salamander, respiration of, . . . 725

Saliva, 342, 501

,, abnormal constituents of, . . 504
,, action of, on starch, . . . 393
,, amount of, .... 491

„ of animals, . . . 327, 345

PAGE

Saliva, antilytic secretion of, . . 522
,, antiparalytic secretion of, . . 522
,, augmented secretion of, . 497, 525
,, chorda, 343, 496, 497, 498, 500, 506,

507, 511

,, composition of, effect of rate of se-
cretion on, 499
,, ,, stimula-
tion on, . 498

,, dyspnoeic secretion of, 493, 521, 522
,, gases of, . . . 346, 347, 504
,, influence of blood variations on, . 508
,, mixed, .... 344, 348
,, organic constituents of, 344, 347, 494,
496, 498, 500, 507

,, paralytic secretion of, . .519
„ parotid, 327, 343, 346, 347, 494, 495
,, percentage of fat in, . . . 17
,, pilocarpine, 481, 492, 493, 498, 500,

508

,, proteids of, .... 503
,, reflex secretion of, . . 489

,, spheres of, .... 502

,, sublingual, . 343, 347, 494, 495
,, submaxillary, 327, 342, 346, 347, 494,

495

,, sulphocyanate of, 342, 343, 344, 345,

504

,, sympathetic, 343, 494, 498, 500, 506,
507, 511, 525

,, tables of analysis of, . . 347,348

, , tension of gases of, . . . 784

Salivary concretions, .... 345

corpuscles, . . 344, 501, 663

„ enzyme, . . 326, 327, 397, 503

,, ferment. See Enzymes.

,, glands, 475

,, ,, action of alkaloids on, 512

,, ,, admaxillary, . 476, 479

,, ,, albumino-mucous, . 478

,, ,, albuminous, . . 477

,, ,, alveolar cells of, . 477, 485

,, alveoli of, . . 477, 507
,, ,, anatomical characters

of, .... 475
,, ,, of animals, . . . 478

,, ,, blood flow of, . 504, 505

,, ,, changes in, during

secretion, . . 485

,, ,, chemistry of, . . 92

,, ,, demilune, . . .478

,, „ ducts of, . . 477

,, ,, electrical changes of, . 517

,, ,, extirpation of," . 524,930

,, ,, heat- production in, 516, 843

,, ,, histological characters

of, . . . . 477
,, ,, influence of cortical sti-

mulation
on, . 484

,, ,, ,, medulla on 484

,, ,, irritability of cells of, 524

,, ,, lymph flow of, . 510

,, ,, mixed, . . 477

,, ,, muco-albuminous, 478

,, ,, mucous, . . 477

,, ,, nerves of, cranial, 479, 482,

504, 512, 518

,, ,, ,, sympathetic, 479,

483, 504, 518, 522, 526

990

INDEX OF SUBJECTS.

Salivary glands, nerve-ganglia of,

PAGE

480, 482,
484, 523
orbital, . . 476, 478
secreto-inhibitory fibres
of, ....
secretory fibres of,
,, pressure of,

526
526
511,
525
519

,, section of nerves of,
,, stimulation of cranial
nerves
of, 493, 505,
506
,, ,, ,, reflex, 489

,, sympa-
thetic nerves of, 494, 505,
506

trophic fibres of, . 526, 528
,, weight of, . . . 476
secretion, antilytic, . . . 522
latent period of, 494, 505
osmosis in, . . 529
paralytic, . . .519
reflex inhibition of, . 512
,, through peri-
pheral ganglia, 523

,, ,, in ruminants, . .489

Salkowski's reaction, .... 23

Salmine, 93

Salts. See Inorganic constituents.

Saponifi cation, . . . .19, 446

Saprine, 60

Sarcolactic acid of aqueous humour, . 122
blood plasma, . 157, 159
liver, ... 85
muscle, 95, 99, 104, 106,
110, 911

spleen, ... 78
thymus, ... 88
thyroid, ... 88
urine, . . . 616
Sarcolemma, chemical nature of, . . 95
Sarcoma, melanotic, iron in, . . 78
Sarcosin, ...... 427

Sarkin, 596

Sauropsida, urinary excretion of, . . 637
Sausages, alkaloids in, .... 59
Scherer's test, .... 423, 424
Schizoneura lagunisosa, . . .16
Schlieren-apparat, . . . .269
Schlosing's method of estimating am-
monia, 586

Schultze's Glaskorper, . . . .217
Schweitzer's reagent . . . .16

Sclerotic 121

Scyllite, 87

Sebaceous glands, . . . .674
,, secretion, . . . .674
,, ,, influence of nerves

on, . . . 681

Sebum 674

Second wind, 747

Secretion of bile. See Bile secretion.
Secretion, digestive, .... 342
,, gastric. (See also Gastric

secretion.} . . .349
,, internal, . . . . 937
,, intestinal. See Intestinal

secretion.
milk. See Milk secretion.

PAGE

Secretion, mucous, of mouth, . 344, 348
,, pancreatic. See Pancreatic

secretion.
, , salivary. See Saliva, Salivary

secretion.

,, skin. See Skin secretion.
,, urinary. See Urinary secre-
tion.

Secreto-inhibitory nerves of pancreas, 549, 550
,, ,, salivary

glands, . 526

Secreto-motor nerves of kidney, . . 660

Secretory granules, gastric, . . . 531

,, ,, intestinal, . . 554

,, ,, mammary, . . 668

,, ,, pancreatic, . .546

,, ,, salivary, . . 479

,, nerves, ..... 526

,, ,, of kidney, . . . 660

,, ,, ,, orbital gland, . 482

,, ,, ,, pancreas, . 549, 550

,, ,, ,, salivary glands, 479, 482,

493, 494, 512, 525, 526

,, pressure of bile, . . . 560

,, ,, ,, saliva, . . 511, 525

Selachians, urea in organs of, . .103

Semen, chemistry of, . . . .93

Semicollin, 71, 430

Semiglutin, 71, 430

Semilunar ganglion, .... 550

Seminose, ...... 7

Semipermeable membranes, . . . 264
Sepia, skeletin of, .... 74

Sepsine, 59

Septic fluids, alkaloid of, . . . 59
Septicine, . . . . . .59

Sericin, ..... 74, 76

Serine, . . . . . .163

Serous fluids, . . . . .181

Serum albumin, . . . 161, 163, 182
of aqueous humour, . 122
carbohydrate from, . 64
carbonic acid in, . .771
coagulation temperature
of, . . . .43

crystallisation of, . 43

heat value of, . .834
mechanical precipita-
tion of, . . . 43
,, ,, rotatory power of, . 46

ash of, . . . . 25, 772

,, bilirubin in, . . . . 383

,, fibrinogen, . . . .176

,, gases of, 157

globulin, . . . 161, 163, 182
,, ,, of aqueous humour, . 122

,, ,, carbohydrate from, . 64

,, ,, mechanical precipita-

tion of, ... 43
,, ,, rotatory power of, . 46

,, ,, temperature of coagula-

tion of, . . . 43
lutein, . . . 20, 159

,, of muscle, .... 96
,, pigment of, . . . 20, 159

Shark, bile of, 373

Sheep, haemoglobin of, . . . .193

,, milk of, 130

,, salivary glands of, . . .477
Shell-fish, alkaloids in, ... 59

INDEX OF SUBJECTS.

991

Silica, .

Silicic acid, .

,, in liver,
,, ,, urine,

Silicon,

Silk, skeletin of, .

Silkworm, skin of,

Sinistrin,

PAGE

25, 79, 473

. 77

. 87

. 634

2

. 76

. 16

64

Skatol, 29, 47, 72, 467, 468, 469, 473, 607
,, excretion of, . . . 470

,, tests for, 469

Skatol-carbonic acid, . . 29, 47, 467, 468

,, „ tests for, . .469

Skatoxyl, .... 470, 607, 628

,, glycuronic acid, . . .613
red, ...... 628

,, sulphuric acid, . . . 631

Skeletal tissues, chemistry of, . .111

Skeletins, ... 70, 72, 74, 75, 76

Skin, absorption by, in animals, . 688, 690

,, ,, ,, in man, . 669, 685

,, glands, electrical phenomena

of, 681

,, loss of heat from, . . 850,855
,, respiration by, . . . 723, 725
,, secretions. (See also Sweat,

Sebaceous secretion.) . 669
alkaloid in, . . 673
chemical nature of, . 670
functions of, . . 669
nervous mechanism of, 676
of vertebrates, . 669, 673
watery, . . .670
,, temperature of, . . . . 829
,, varnishing, ..... 727
Slime of fishes, .... 674, 676
Smegma preputii, .... 674
Snail, gluco-proteids of, . . 62, 64
,, skeletins of, . . . .75
Snakes, temperature of, ... 849
,, urine of, . . . . 590, 909
,, venom of, . . 55, 56, 181
,, ,, action of, 57, 146, 174, 179

,, ,, toxic power of, . . 58

Soaps, 19, 20, 446

,, absorption of, . 451, 456, 457, 463
,, nutritive value of, . . . 881

Soda, 77, 87

Sodium, 2

,, bicarbonate, .... 78

carbonate, . . 76, 78, 145, 157

chloride, 25, 76, 77, 93, 113, 154,

157, 882, 883

,, precipitation of pro-
teids by, . . 42
,, phosphate, . 76, 78, 113, 145, 157
,, salts of body, .... 77
,, ,, proteids, ... 25

,, urine, . . 633, 634
sulphate, . . 76, 78, 113
Soluble ferments. (See also Enzymes.} 312
,, starch, ... 13, 14, 395

Sorbite, 4

Soret's band, . . . 226, 227, 246
Specific gravity of blood, . . .143
heat of body, . . . .838
,, rotation. (See also Rotatory

power.} ..... 6

Spectrophotometer of Hiifner, . . 220

„ Vierordt, . . 216

PAGE

Spectrophotometric constants of CO-hae-

m og-
lobin, 239

,, ,, oxyhae-

m o g-
lobin,

213, 223

,, „ reduced

haemo-
globin,

Spectrophotometry,
Spectrum of bile, .

pigments,

CO-haemoglobin,

hsematin,

haematoporphyrin,

234

209, 216, 313
. 390

383, 386, 387,
388
. 239
. 251
260, 382,
626

251, 255
. 248
. 246
. 241
208, 211
. 377
225, 236
240

,, haemochromogen,
,, HCN-haemoglobin,
,, methaemoglobin,
,, NO-haemoglobin,
,, oxy haemoglobin,
in Pettenkofer's test,
photographic,

,, of CO-haemoglobin,
,, ,, o x y h ae m o-

globin, 225

of reduced haemoglobin, 234, 236
,, retinal pigments, . .123
,, urine, .... 617
„ urobilin, . . . .621
,, uroerythrin, . . . 625
visible, . . . 208, 234

Spermaceti, 20

Spermatozoa, composition of, . . 93

,, nuclein of . . 65, 66

Spermine, phosphate of, ... 94

Spheres, salivary, .... 502

Spider, poison of, .... 55

, , urinary secretion of, . . 637

,, web of, 76

Spinal cord, percentage of proteids in, 24

Spirographidin, 64

Spirographin, ..... 64
Spirographis, hyalogen of, . . . 64

Spirometer, 752

Splanchnic nerves, influence of, on gastric

secretion, 539

Spleen, chemistry of, . . . .87

,, during inanition, . . . 890

,, influence of, on metabolism, . 959

Sponge, skeletin of, . . .75

Spongin, 74, 75, 76

Sputum mucin, ..... 62
Squirrel, haemoglobin of, . 193, 195, 198,

204, 206

Starch, . . . . 4, 13, 14, 473
absorption of, . . . 434, 435
action of ferments on, .326, 393, 394
,, acids on, . . . 396
assimilation of, ... 880

bacterial digestion of, . . 470

cellulose, 14

digestion of, . . 393, 396, 556
granulose, . . . .14

heat value of, . . 834, 835, 837
hydrolysis of, . . 13, 14, 396
paste, ..... 14
soluble, ... 13, 14, 395

992

INDEX OF SUBJECTS.

PAGE

Starvation. See Inanition.
Steapsin, .... 326, 336, 339
Stearate of magnesium, ... 78
Stearic acid, . . 18, 20, 22, 118, 119,

456, 675
Stearin, .... 18, 133, 159

Stearyl, 18, 22

Steatolytic ferments. See Ferments.
Stercobilin, . . . 388, 474, 622

Stethal, 20

Stoffwechsely 868

Stokes's reagent, 230

Stomach, absorption by, . . .730
changes in, during digestion, 531
fundus of, . . . 534, 544
gases of, .... 729
nerves of, .... 537
nerve-centres of, . . . 538
,, plexuses of, . . . 538
pyloric region of, . . 534, 544
Strorna of corpuscles, . . . 188, 191
Strychnia, action of, on sweat secre-
tion, 679

Sturine, 93

Sublingual ganglion, . . . 480, 481

,, gland in animals, . 475, 478

,, ,, nerves of, . . 479, 483

saliva, . 343, 347, 494, 495

Submaxillary ganglion, . . 480, 481

,, gland in animals, . .478

,, heat production in, 516,

843

,, nerves of, . 479, 483

,, mucin, . . . .62

saliva, 327, 342, 346, 347, 494,

495

Succinic acid, . .104, 465, 470, 673
Succus entericus. (See also Intestinal
secretion.) . . . 368, 397, 398
enzymes of, 341, 397, 398,
556
., ,, mechanism of secretion

of, . . . . 554
,, ,, proteids of, . . 24

Sudoric acid, 671

Sugar. (See also Monosaccharides, Di-
saccharides.) . . . . . 2, 4
,, absorption of, . . . . 435
,, bacterial digestion of, . . 470
„ in blood, . 6, 10, 158, 610, 894, 914,
916, 917, 920, 923,
925, 926, 928
,, cane, . . 2, 4, 9, 10, 398, 435

,, of chyle, 183

,, in digestion of glycogen, . . 397
„ ,, ,, >» starch, . . 393
,, heat value of, . . . .834
,, of liver, .... 85, 926

„ „ lymph, 182

,, in metabolism, . . . .922
,, ,, milk, (See Lactose.) . . 9, 12
,, ,, muscle, . 100, 105, 110, 606

,, production of, from proteids, . 30
,, synthesis of, .... 5
,, of tendon mucin, ... 62
,, of urine. (See also Olycosuria,

Lactosuria.) . . . 608, 612

Sulphates, calcic, .... 78

potassic, . 76, 78, 113, 157

sodic, ... 76, 78, 113

PAGE

Sulphates of body, . . . 26,79
,, ,, sweat, . . . 672, 673

,, urine, . 26, 79, 613, 631, 906
Sulphide of iron, ..... 78
Sulphocyanate of proteid metabolism, 346
,, saliva, 342, 343, 344, 345,
504, 632

249
2

74

901

575

563

202

73

85

26, 29

Bfilpho-metheemoglobin,
Sulphur, ....

,, of amyloid substance,

,, bile, .

,, elimination of,
,, of food, .

haemoglobin,
keratin,

liver cells, . • .
proteids,

taurine, . . . .379
urine, .... 630, 631
Sulphuretted hydrogen, 29, 32, 72, 73, 76,

470, 473
,, ,, of alimentary canal,

729

Sulphuric acid, . 25, 26, 30, 77, 87, 630
Supplemental air, . . . 749, 753

Suprarenal body, chemistry of, . . 90
,, ,, of Elasmobranchs, . 957

,, ,, excision of, . . 948

,, extract of, 950, 951, 957
,, ,, influence of, on meta-

bolism, . . 948, 958
,, ,, ofTeleostei, . . 957

Sweat. (See also Skin secretions.) . 670
of animals, .... 673
carbonic acid of, . . .671

centres, 679

chemical composition of, . .671
creatinine of, . . . .672
ethereal sulphates of, . . 672, 673
fatty acids of, . . . 672, 673
nitrogen-excretion by, . . 672
percentage of fat in, . . .17
proteids of, .... 673
secretion, action of alkaloids on, 679
,, ,, ,, temperature

on, . . 680

,, mechanism of, . . 676
,, nervous influence on, . 676
salts of, . . . 671, 672, 673
urea of, . . 671, 672, 673

Swimming-bladder, . . . .704
Sympathetic nerves of salivary glands, 497,

483, 504
,, ,, ,, ,, section

of, . 522

,, ,, ,, ,, stimu-

lation of, 494, 505, 506,
508, 526

,, saliva, 343, 494. 498, 506, 507,

511, 525

Synovia, 181, 184

,, percentage of fat in, . . 17
,, proteid in, . 24

Synthesis of alkaloids,
,, ,, choline, .

,, fats,

,, ,, glycocoll,

,, ,, glycogen,

,, ,, hippuric acid,

,, leucine, .

60

. 21

893, 899, 931

. 379

. 893

. 600, 892

. 421

INDEX OF SUBJECTS.

993

PAGE

Synthesis of organic substances by ani-
mals, 892
ii ii » i, plants,

25, 892

,, proteids, . 35, 893, 899

,, sugars, . . . . 5, 6
,, taurine, .... 379
,, urea, . . .581, 893
,, uric acid, . 586, 893, 909
Synthesised colloids, .... 36
Syntonin. (See also Acid albumin.) 50, 404
,, rotatory power of, . . 46

TABLE of analysis of bile, . 370, 371, 568
elastin, . . 71
keratin, . . 73
lymph, . .182
mucins, . . 62
oxyhaemoglobin, . 198
pancreatic juice, . 367
placental blood, . 733
saliva, 347, 348, 496,
498, 499, 500, 508

,, ,, ,, skeletins,
,, ash of milk, .
,, bile pressures,
,, carbonic acid absorption,
,, ,, ,, in serum,
,, composition of blood, .
colostrum,
foodstuffs,

76

. 885
. 560
. 770
. 771
153, 154
. 127
. 874

milk, 128, 129, 130
nervous tissues, 116,
117

protagon, . 119
sebum, . . 674
sweat, . 671, 673
urine, . 572, 573
,, constituents of meat, . . 96
,, copper, nickel, and cobalt re-
actions of proteids, . . 48
,, diets, .... 877, 879
,, diffusions, .... 264
,, enzymes, .... 326
,, experiments in asphyxia, 743, 744,
745, 746

,, ,, ,, respiration of

carbonic

oxide, 741

ii HJ.VM oxygen, 737
,, expired air, . . . .755
,, nitrations, . . . 282, 283
,, frequency of respiration, 747, 753
,, gases of alimentary canal, . 729
,, ,, ,, blood, . 715, 761, 763,
764, 769

,, heat of combustion, . . 834
„ „ loss, .... 850
,, ,, production, 833, 838, 847, 853
,, hydrolysing processes of fer-
ments, .... 58
,, inorganic constituents of body, 77
„ food, 882

,, isodynamic foodstuffs, . 835, 837
,, leucine and tyrosine, . . 425
,, nitrogen absorption, . . 769
,, ,, and sulphur elimina-
tion, . . .562

VOL. I. — 63

PAGE

Table of nitrogen loss in inanition, . 890
,, ,, nutritive equilibrium, . 871, 872
,, ,, osmotic pressures, 265, 266, 267,

278

,, ,, oxygen absorption, . 766, 767
,, ,, percentage of chlorides in

body fluids, 77, 78

,, ,, ,, ,, fat in tissues, 17

,, ,, ,, ,, iron in haemo-

globin, . 201

,, ,, ,, ,, phosphorus in

nucleo - pro-
teids, . . 81
,, ,, ,, ,, proteids in

tissues, . 24
,, ,, ,, ,, water in

muscle, 95
» » ii » nervous

tissues, 115

,, ,, proteids, .... 48

„ ,, „ of lens, . . .124

,, ,, ,, ,, plasma, . . 162

,, ,, residual air, .... 750

,, ,, respiratory exchanges, . 701, 706,

710, 711, 714, 716, 718,

722, 723, 724, 726, 734,

795, 841, 848, 859, 864

,, ,, rotatory power of proteids, . 43

,, ,, salts of milk, . . .131

,, ,, ,, sweat, . . .672

,, ,, solubilities of albumins and

globulins, . 50
,, ,, ,, ,, casein and

caseinogen, . 138

,, ,, sweat secretion, . . . 671

,, ,, temperature of blood, . . 827

„ „ „ „ body, 789, 790, 791,

793, 795, 799, 801,

805, 806, 808, 809,

810, 811, 813, 815,

817, 818, 825, 826,

860, 867

,, ,, ,, ,, coagulation of

proteids, . 43

,, ,, ,, after skin-var-

nishing, . 727

,, ,, urea excretion in inanition, . 888

,, ,, vital capacity, . .751, 753

,, ,, weights of salivary glands, . 477

Tail-gland of birds, .... 675

Tannin, precipitation of proteids by, . 40

Tartar, 345

Tartaric acid, 5

Taurine, 379

„ in bile, 372, 373, 378, 379, 562, 632,

901

,, ,, kidney, .... 92
,, ,, muscle, . . . 100, 103
,, from proteids, . . . .901
,, in suprarenal body, ... 90
Taurocholic acid, . 372, 373, 374, 376, 392,

454

,, ,, of suprarenal body, . 90

Teichmann, crystals of, . . . 252

Teleostei, suprarenals of, . . 957

Temperature of axilla, . . 787, 788, 824

,, bees, . . . 792, 807

,, birds, . . . 787, 791

„ blood, . . . .826

„ body, .... 788

994

INDEX OP SUBJECTS.

PAGE

Temperature of body, determination of, 786,

792

,, coefficient of filtration, . 281

,, of cold-blooded animals, 787,

792, 849, 865

,, compatible with life, . 821

,, conditions affecting, . 798

,, constant, development of, 865

„ after death, . . .866

,, diurnal variations in, . 798

,, during hibernation, . 796

,, ,, inanition, . . 889

,, individual peculiarities in, 812

,, influence of age on, . . 803

„ baths on, . 818
,, ,, ,, drugs on, . 820

,, food on, . 809
,, ,, ,, heat and cold

on, . . 814
•,, ,, ,, menstruation

on, . . 812
,, ,, ,, mental work

on, . . 807
,, pregnancy on, 812
,, ,, ,, race on, . 811

,, ,, ,, season on, . 813

,, ,, ,, sex on, . . 810

,, ,, ,, sleep on, . 810

,, ,, ,, surrounding

temperature
on, . . 812

,, ,, ,, work on, . 806

,, ,, ,, on zymolysis, 320,

327, 331, 335, 337, 339
,, internal, . . . 824, 826

,, of mammals, . . . 787

,, of mouth, . 787, 788, 824

,, of plants, . . .849

,, of rectum, . 787, 788, 824

,, regulation. (See also Heat.} 831

,, after section of cord, . 856

,, of skin, .... 829

,, after skin-varnishing, . 727
,, vasomotor control of, . 854

,, of warm-blooded animals, 787,

788, 865

Tendon mucin, 62

,, section of, effect of on muscle

glycogen, .... 105
Tension of dissociation, . . .775
Testis, chemistry of, . . . .93

Tetanine, 59, 60

Tetanus, alkaloid in, . . . .59
Tetra paper, . ... . 365

Tetronerythrin, 20

Tetroses, 2

Tewfikose, . . . .132

Theory or Theories, cleavage, of proteid

digestion, . 405, 406,
414, 416

,, of fat absorption, . 449,

451, 457

• ,, ,, glycogenesis, . 922

- ,, • hydrolytie, of pep-

tonisation, . . 400

,, of metabolism, . 870
,, micellar, ofpeptoni-

sation, . . 400
,, of proteid constitu-
tion, ... 38

PAGE

Theories of urinar secre-

Theory

tion, .....

Thermometers, ....
Thioglycollic acid,
Thiolactic acid, ....
Thiry fistula, ....

,, Vella fistula,
Thoracic duct, ....
sources of lymph, of,
160, 166, 170,

. 639

. 785

26

. 34
368, 555
. 555
. 285
. 290
175, 179
165, 172
67
66, 93

Thrombin, .

Thrombosin,

Thymic acid,

Thymin,

Thymus, chemistry of,

function of, . . . .960
iodine in, . . .89

nucleic acid of, . . . 66
percentage of proteid in, . 24
phosphorus of nucieo-proteid

of, 81

Thyreo-antitoxin, .... 89

Thyreoproteid, 89

Thyroid, ablation of, . . 938, 940, 942
chemistry of, . . .88

extract, . . . .943

feeding, . . . .944

grafting, . . . 939, 942
internal secretion of, . . 938

Thyroiodin, 89

Tidal air, 748, 753

Tide, alkaline, 579

Tissue tibrinogens, . . 55, 68, 173, 176

,, proteid, ..... 897

,, tension, ..... 307

Tissues, chemistry of, . . . .80

Toad, parotids of, .... 674

,, skin secretion of, ... 673

Toll ens' reaction, 612

Tomato, pigment of, . . . . 20
Tooth, chemistry of, . . . .112
Topler Schlierenapparat, . . . 269
Torpedo mucin, . . . . .110
,, organ, . . . . .110

Torulaurea, 313

Toxalbumoses, ..... 56
Toxic power of anthrax albumose, . 58
,, ,, cholera toxo-peptone, . 58

,, ,, diphtheria toxin, . . 58

,, ,, peptone, . . .55

,, ,, snake- venoms, . . 58

Toxins, 55, 59

Transudation of proteids, . . . 311

Traube cell, 269

Trehalose, 12

Triacetin, ]8

Tribromarmdo-benzoic acid, ... 34
Tricalcium casein, . . . .136

Trichloracetic acid as precipitant of
proteids, ...... 40

Trichlorethylglycuronic acid, . . 614
Trihydroxyphenyl-propionic acid, . 606

Triolein, 18

Trioses, 2

Trioxybutyric acid, .... 5

Tripalmitin, 18

Tristearin, 18

Trommer's test, ..... 7
Tropfeolin test for hydrochloric acid, . 365

Trophic nerves,
Trypsin,

526, 528
326, 336, 337, 415, 552

INDEX OF SUBJECTS.

995

PAGE

Trypsin, action of, on proteids, 326. 405, 406,

416

„ milk, . . 127

estimation of activity of, . 323
influence of reaction on, . . 337
,, temperature on, . 337
preparation of, . . .315
reactions of, . . . . 337
Trypsinogen, . . . .551

Tryptic digestion, . . 414, 418, 428
,, amido-acids of, . 421

,, ammonia of, . . 427

,, chromogen of, . . 427

,, • cleavage theory of, 405,

406, 416

,, organic bases of, . 426

Tryptophan, . . .417, 421, 427
Tubules, renal, . . 639, 650, 652, 655
Tunica media, percentage of proteids in, 24

Tunicata, test of, 16

Tunicin, 4, 14, 16

Turacin, ...... 61

Turbellarians, haemoglobin of, . . 187
Typhoid fever, alkaloid in, . . 59, 60
Typhotoxin,. . . . . 59, 60

Tyroleucine, ..... 3*1

Tyrosine, . . . . . .423

,, absorption of, ... 469

,, in bacterial digestion, . . 466
,, constitution of, . . . 423
,, from decomposition of albumi-
noids, 72, 73,
74, 75, 76

,, ., ,, ,, proteids, 28,

29, 31, 32, 34, 46, 63

derivatives of putrefaction,
from different substances, .
in digestion, 405, 406, 416,
423

,, ,, liver, ...

,, ,, pancreas, ...

,, separation of, from leucine,

,, in spleen, . . .

,, ,, sweat, ...

,, ,, testis, ...

,, tests for, .... 424

,, in urine, .... 602

Tyrosine-hydantoin, .... 602
Tyrotoxicon, ..... 59

467
425
421,
437

86

92
424

87
673

93

U u ATE of ammonium,

,, ,, calcium,
Urates,
Urea,

amount of, .

in aqueous humour,

artih'cial production of,

in bile,

,, blood, . .160

chemical composition of,

in chyle, .

decomposition of,

estimation of, .

excretion during inanition, .

ferment, .

formation of, in liver, .

heat value of,

hydrolysis of, .

587, 588,

33,

900,

. 78
. 78

590, 591
. 581
. 892

122, 183

427, 581
. 390

902, 919
. 581
. 183

581, 582
. 583

887, 888

. 907

. 906

. 834

582

PAGE

Urea, in intestinal juice, . . . 557

kidney, 92

liver, ... 86, 562, 902

lymph, 182

metabolism, .... 906

milk, 126

muscle, . . . 100, 102, 904
nervous tissues, . . . 116
nitrate of, . . . . . 581

oxalate of, 581

oxidation of, .... 583
preparation of, . . . 583

production of, from arginine, . 33
,, ,, ,, creatine, . 904

,, ,, ,, lysatine, . 33

properties of, .... 581
in proteid decomposition, 28, 33, 34, 427
quantity of, .... 584
relation of, to ammonium carbonate, 582
,, uric acid, . 586, 593
in saliva, ..... 344

salts of, 581

in sweat, . . . 671, 672, 673
synthesis of, . . . 581, 893
in synthesis of proteids, . . 35

tests for, 583

in torpedo organ, . . .111
,, urine, . . 571, 572, 581, 637
Ureide theory of proteids, ... 36

Ureides, 586

Ureter, ligature of, . . . .649

Uric acid, ...... 586

,, in blood plasma, . . .160
,, chemical constitution of, . 586
,, condition of, in urine, . . 588
, , effect of diet on production of, 593
,, estimation of, ... 592
,,- excretion in disease, . . 596
,, ,, individual varia-

tions in, . . 595
,, ,, influence of drugs on, 595

,, ,, j> » exercise

on

,, heat value of,
,, ntestinal excretion of,
,, n kidney, .
leucocytosis,
leukaemia,
liver,
metabolism,

muscle,

nervous tissues,

new-born children,

pancreas, .
preparation of,
properties of,

595
834
595
. 92
. 67
. 910

85, 86, 902, 909
. 909
. 100, 101
. 116
595
92
591
587

from proteid decomposition,

quantity of, .

reactions of,

relation of, to xanthine bases,

urea,

28
586
592
67,
596
586, 593

salts, 587

in spleen, .... 87
spontaneous separation of, 578, 588
in sweat, .... 673
synthesis of, . 586, 893, 909
tests for, . . . .592
variations in amount of, . 593
of urine, 571, 572, 586, 637, 653

INDEX OF SUBJECTS.

Urinary excretion, characteristics of, . 635
„ pigments, . . 388, 571, 572
,, secretion, Bowman's theory

of, . . 639, 650
,, ,, concentration of, . 650

,, ,, Heidenhain's theory

of, . . 652, 658
,, ,, influence of circula-

tion on,

641, 644
,, ,, ,, ,, diuretics

on, . 647

,, „ ,, ,, ligature

of renal
artery
on, . 646

,, ,, ,, ,, ligature

of renal
veinon, 647

,, ,, ,, ligature

of ureter

on, .
nerves

649

Urine,

on, 645, 659

,, Ludvvig's theory of, 640,

658

,, mechanism of, 639, 658

,, pressure of, . . 649

,, theories of, . . 639

water, secretion of, 641, 644, 647,

656

570

acetone in, 928

acids of, .
albumin of,
album ose in,
alkaloids in,
amido- acids of, .
ammonia of,
ammonium salts in,
animal gum of, .
aromatic carboxyacids in,

. 571, 574
. 604, 605
. 694
. 59
. 602
. 585

906, 908, 909
. 613
606

constituents of, . 605, 631

bases of, 571

bile pigments in, . . 384, 629
blood pigments in, . . . 629
calcium salts of, ... 634
cane-sugar in, . . . .10
carbohydrates of, . . . 607
carbolic acid in, . . 606, 607

carbonic acid of, ... 634
chemical reaction of, . . 574, 657
chemistry of, . . . . 570
chlorides of, .... 633
chromogens of, . . . . 626
colour of, . . . . . 616
comparative chemistry of, . . 637
composition of, . . . .572
creatinine of, . 571, 572, 598, 638
dextrose in, 6, 608, 881, 894, 920,
926, 928
diabetic. (See also Glycosuria,

Diabetes.) . . 3, 6, 14, 106
drug- pigments in, . . 630

estimation of acidity of, . . 576
ethereal sulphates of,

fermentation of,
globulin of,

26, 467, 469,
613

313, 582
604, 605

glycogen in, . . . .15

PAGE

Urine, glycuronic acid in, . . 5, 613
,, hnematoporphyrin in, 260, 625, 629
,, hemialbumose in, . . 410

,, hippuric acid of. See Hippuric

acid.

,, hydrochinon in, . . 606, 607

,, hydrochloric acid of, . . . 633
,, hydrofluoric acid of, . . . 634
,, indoxyl of, ... 607, 627
,, influence of food on, . 573,575,579,
585, 593, 610, 630, 682
,, ,, of gastric secretion on, 359

,, ,, ,, muscular activity

on, . . . 916
., ,, ,, sex on, . . . 573

,, inorganic constituents of, . 572, 630
,, inosite in, . . . . . 606
,, iron in, . . 635, 885, 886

,, isomaltose in, . . . 12, 612
,, kresol in, .... 606, 607
,, in lactation, . . . .611
,, lactic acid in, 106,109,894,907,909
,, lactose in, . . . . 12, 611
,, levulose in, . . . 6, 611
,, magnesium salts of, . . . 634
maltose in, . . . .881
mucin of, . . . . . 604
mucoid, ..... 85
mucus of, . . . . .85
nitric and nitrous acid of, . . 634
nitrogen of, . . 580, 684, 912
nitrogenous constituents of, 580, 637
nubecula of, . . .85

nucleo-proteid of, ... 603
organic constituents of, . . 572
ornithuric acid in, . . 602, 638
oxalic acid of, . . . .614
parakresol in, . . . 606

pentoses in, ... 3, 612
peptones in, ... 604, 605
phenaceturic acid of, . . .601
phenol of, . . . . 606, 607
phosphates of, . 575, 578, 590, 632
pigments of, 388, 571, 572, 591, 616
,, ,, pathological, . . 628
poisonous properties of, . . 61
potassium salts of, . . 633, 634
proteids of, ... 85, 603
,, ,, tests for, . . .605
pyrocatechin of, . . 606, 607
quantity of, .... 573
secretion of. See Urinary secretion.
silicic acid of, . . . 634

skatol carbonic acid in, . . 467
skatoxylof, . . . .607
sodium salts of, . . , 633, 634
specific gravity of, . .573

spectrum of, . . . .617
sugar in. (See also Glycosuria,

Ladosuria. ) . 10, 608, 611
,, tests for, . . . 608, 610
sulphates of, . . . 631, 905
sulphocyanate in, . . . 346
sulphur of, .... 630
urea of. See Urea.
uric acid of. See Uric acid.
urobilin of, . . 620, 628, 629
urochrome of, . . . 618, 629
uroerythrin of, . . 623, 628, 629
variations in acidity of, . .597

INDEX OF SUBJECTS.

997

PAGE

Urine, volatile fatty acids of, . .615
,, water of, secretion of, 641, 644, 647,

656
,, xanthine bases of. See Xanthine

bases.

Urobilin, . . 388, 474, 620, 628, 629

,, physiological relations of, . 622

,, properties of, ... 621

,, separation of, . . . 620

,, spectrum of, . . . . 621

Urochrome, . . . . .618, 629

,, physiological relations of, . 620

,, preparation of, . . . 619

,, properties of, . .619

Urochloralic acid, .... 614

Uroerythrin, . .618, 623, 628, 629

,, properties of, . . 623

,, separation of, . . . 623

,, spectrum of, . . . 625

Urorosein, ...... 628

VAGUS NERVE, influence of, on gastric se-
cretion, 537,
539
,, pancreatic

secretion, 548
Valerianic acid, .... 470, 471

Valeric acid, ..... 34

Varnishing, effects of, . . . .727

Vaso-constrictor nerves of kidney, . 646
,, ,, ,, salivary glands,

479, 504

Vaso-dilator nerves of kidney, . .646

,, ,, ,, salivary glands, . 479,

482, 504

Vasomotor control of temperature, . 854
Vegetable albumin, leucine, and tyros-

ine from, .... 425

alkaloids, ... 34, 60

,, ferments, coagulating, . . 334

,, ,, diastatic . . 51

proteolytic, 51, 54, 330,

403

,, food in diet, . . . 472
gums, . . . . 14, 16

,, proteids, . . .49, 51, 53
,, ,, crystalline, . 27, 43

,, „ digestibility of, . 51,

333, 440

,, ,, glutamic acid from, 426

,, ,, as poisons, . . 55

,, vitellin, . . .52, 53, 54

Vella fistula, .... 368, 555

Venom of snakes. See Snake venom.
Venous blood, fibrin from, . . . 167
gases of, . 154, 760, 762
,, haemoglobin of, . .185

,, jecorin of, . . .160

,, sugar of, . . .158

Veratrin, influence of, on body tem-
perature, ...... 821

Vermes, haemoglobin of, . . .187

,, respiratory exchange of, . . 702

Vernix caseosa, .... 674, 675

Vertebrata, hemoglobin of . . . 186

,, skin secretions of, . . 669

Viperine, ...... 56

Visual purple, . . . . .122

Vital action, . . . 276, 283, 284

PAGE

Vital capacity, 750

Vitellin, . . . . . 52, 69
,, vegetable, ... 52, 53
,, coagulation temperature of, . 43
,, mechanical precipitation of, . 43

Vitelloses, 50

Vitreous humour, . . . .122

,, mucinogen of, ... 62
,, mucoid of, . . .63

,, percentage of fat in, . . 17

WAIIM-BLOODED animals, temperature

of, 787, 788

Water 1, 76

,, absorption of, . . 433, 685, 689

,, in coagulation, . . . 319

, , extracting power, . . 270, 277

,, in fermentation processes, . 319

,, ,, fluids of body, . 127,128,129,

153, 157, 183, 347, 559,

641, 644, 647, 656

,, ,, organs, . . 82, 85, 88, 95, 96
,, ,, prote id decomposition, . 28, 29
,, ,, tissues, . Ill, 113, 115, 121, 127,

128, 129

Wax, of bees, 20

,, Chinese, 20

Waxy degeneration, .... 74
Weber's test for indicanuria, . . 628
Weidel's reaction, . . . .598

Weyl's reaction, 599

Whartonian jelly, . . . .62
Wheat, proteids of, ... 53, 54

Whey, 134

„ proteids, 139

White of egg. See Egg white.

Witches' milk, . . . " . .127

Wood gum, ...... 16

Wool, fat, 675

„ skeletin of, 72

Work, influence of, on alkalinity of

blood, . 144

,, ,, ,, metabolism, . 911

,, ,, ,, muscle gly-

cogen, . 105
,, ,, ,, number of

corpuscles, 150
,, ,, ,, respiratory

exchange, . 715
Worth of blood corpuscles, . . .152

XANTHINE, 60, 596

,, of blood plasma, . . 160

,, ,, nervous tissues, . . 116

,, from nuclein, . . 66, 67

of organs, . 85, 86, 87, 88, 92,

93, 98, 100, 101, 111

,, bases of nucleins, . . 65, 66
,, ,, properties of, . . 597

,, ,, relation of, to uric acid, 67,

596

,, ,, tests for, . . .598

,, ,, of urine, . . . 596

„ ,, ,, ,, amount of, 597, 598

,, ,, ,, ,, estimation of, . 597

,, ,, ,, ,, separation of, . 597

Xantho-creatiniue, . . .60, 101

Xantho-proteic acid, .... 34

998

INDEX OF SUBJECTS.

PAGE

Xantho-proteic reaction, ... 47
Xylose, . . . . 2, 3, 16, 612

YEAST, action of, on monosaccharides, . 7
,, fermentation, . . . .611
,, inverting ferment of, . .10

,, nuclein, . . . . . 3, 64

PAGE
ZEIN, ....... 54

Zymogens, .... 83. 543, 551

Zymolysis, 320. See also Enzymes.

,, effect of chemical reaction on, 320

,, ,, ,, concentration on, . 322

,, ,, „ fermentation pro-

ducts on, . . 320
„ ,, ,, temperature on, 320, 327,

331, 335, 337, 339

INDEX OF AUTHORS.

ABEL on Charcot's crystals,
,, ,, melanin,

phymatorusin,
a blo<

Abeles on blood plasma,

,, ,, diuretics,

» ,, glycogenesis,

,, ,, muscle glycogen, .

,, spleen, .
Abelmann on pancreatic juice,

,, ,, starch absorption,

Abelous on blood,

,, ,, starch digestion,

,, ,, suprarenals,

,, ,, thymus,
Abernethy on cutaneous respiration, 725, 726

PAGE

94

. 122
. 121
. 160
. 648
. 923
. 104
. 87

443, 448, 459
435
. 152
. 397
949, 959
960

tidal air,

Abilgaard on respiration,
Ackermarin on heat regulation,

,, ,, pyloric secretion, .

Adami on renal secretion,

,, ,, skin absorption, .
Adarnkiewicz on proteid assimilation,

,, ,, a reaction of proteids,

Addison on suprarenals,
Adie on osmotic pressure,

,, ,, semipermeable membranes,
Adler on lymph, ....
Adrian on intestinal secretion,

,, ,, salivary secretion,
Aeby on bone, ....
,, ,, dentine, ....
Atfanasiev on bile,

,, ,, bilirubin,

,, ,, gases of blood,
,, ,, pancreatic secretion,

Akermann on pepsin, .
Albertoni on diet,

,, ,, thyroicleetomy,
,, ,, trypsin, .
Albrecht on spectrophotometry, .
Alcock on Ammoccete, .
Aldehoff on diabetes, .
,, glycogen, .

Alexander on suprarenal extract, .
Alexceff on body temperature,
Allan on biuratf-s,
Allara on thyroid gland,
Allbutt on body temperature, 788, 789, 799,

800, 806, 808

Allen on creatinine, .... 599
,, „ respiration, 695, 698, 735, 750, 754
,, ,, ,, of hydrogen, . 739

„ „ ,, ,, oxygen, . . 736

748
748
856
532
656
690
878
47
948
. 267
. 265
. 285
. 555
. 495
. Ill
. 112
. 567
. 563
762, 780
. 548
. 331
. 877
939, 941
. 336
. 218
. 674
. 928
918
950
804
588
940

104,

Allen on sugar in urine,
,, ,, tidal air,

„ ,, urea, ....
,, ,, urine,

Allilm on reducing power, .
Altmann on fat absorption, .

,, ,, intestinal emulsion, .
,, ,, nucleiu,

Alvarenga on skin temperature, .
Amermann on albumoses,
,, ,, digestion,

Ammon on milk, ....
Anderson on salivary secretion,

,, ., secreting cells, .
Andral on body temperature,

,, ,, respiratory exchange, .
Angelesco on body temperature, .
v. Anrep on CO-methajmoglobin, .

,, ., gastric absorption,
Anselm on iron in bile,
Anselmino on sweat,
Ansiano on fractional coagulation,
Araki on chitosan,
,, ,, diabetes,

,, ,, lactic acid, . . 106
,, ,, sarcolactic acid,
,, ,, sulpho-methfiemoglobin, .
Argutinsky on meat, .

,, ,, proteid metabolism,

,, ,, sweat, .

Aristotle on animal heat,

,, ,, respiration,
Arkle on body temperature, .
Arloing on skin secretion, . 677,
Arnaud on carrotin,

,, ,, cholesterin,
Arnschink on glycerin,
Arnsteiri on salivary nerves, .
,, ,, tension of gases,
,, ,, wandering cells,
Aronsohn on body temperature, 792.
Aronstein on ash-free albumin,
Arrhenius on diffusion,

,, ,, dissociation, .
Arronet on blood,
d'Arsonval on blood spectrum,
,, ,, calorimeter, .

,, ,, respiration,

Arthus on blood ferment,

,, ,, coagulation, 147, 168,

„ „ fibrin, ....
,, ,, lacto-globulin,

PAGE

. 608
. 748

574, 584

. 609

7

445, 455
. 448
. 66
. 830
. 411
. 322
. 127
. 524
. 938
. 804

698, 722
. 821
. 249
. 432
. 561
. 670
. 43
. 75
. 927

109, 895
. 616
. 249
. 873
. 913

670, 672
. 832
. 692

806, 823

678, 681
20, 21
. 24
. 882
. 525
. 784
. 450

863, 864
. 25

263, 284

261, 268
. 154
. 225
. 845

739, 742

. 161

169, 170,

171

167, 405
139

1000

INDEX OF A UTHORS.

PAGE

Arthus on liver ferment, . . . 926

,, ,, milk coagulation, . .135

Ascherson on haptogen membrane, . 125

,, ,, skin glands, . . . 681

Asellius on lacteals, . . . 286, 302

Ashdown on glycuronic acid, . 5, 614

Asher on absorption of proteids, . . 900

„ „ lymph 295

,, ,, venous absorption, . . 303

Astaschewsky on saliva, . . . 343

Aubert on cutaneous respiration, . 726, 727

,, „ milk, 131

,, ,, skin secretions, . . . 680

Auerbach on thyroiodin, ... 89

Auld on suprarenal body, ... 90

Autenrieth on foetal respiration, . . 731

Autokratoff on thyroidectomy, . . 941

Avicenna on mesenteric veins, . . 286

Axenfeld on hsematin, .... 250

Ayres on chromophanes, ... 20

BABES on pus, ..... 84

Bach on electrical currents, . . . 683

Baeyer on indol, ..... 468

,, ,, Pettenkofer's test, . .377

Baginsky on bile, . . . . 85

,, ,, body temperature, . . 863

,, ,, coagulating ferments, . 334

,, ,, lime in food, . . .886

Bahlmann on amido-acids, . . . 880

Baisch on urine, . . . 605,609,613

Baldi on bile salts, . . . .391

„ „ jecorin, ... 86, 160

,. ,, spleen, ..... 87

Balfour on bile, .... 371, 560

,, ,, suprarenal body, . . . 957

Balke on antipeptone, .... 420

,, ,, carnic acid, .... 103

Barbera on absorption of proteids, . 900

„ „ bile, 566

Barbieri on cholesterin, . . .24

,, ,, leucine, .... 29

Bardeleben on gastric fistula, . . 537

Barensprung on body temperature, 734, 798,

799, 804, 805, 810, 811,

812, 850

,, ,, skin absorption, . 688

Barfoed on sugars, . . . .11
Barkow on hibernation, . . 795, 796
Barlow on osmosis, . . . .273
Bar ral on sugar in blood, . . 160,161
Barratt on cutaneous respiration, . 726, 727
Barreswil on gastric juice, . . 352. 353
,, ,, gelatin, .... 879
v. Barth on ty rosin, . . . .423
Bartholin on lymphatics, . 286, 288, 310
Barton on hibernation, . . . 798

de Bary on digestion, . . . 356, 429
Baschkis on skin absorption, . . 687
Bassorin on bile pigments, . . . 389
Bassow on gastric fistula, . . . 537
Bastianelli on succus entericus, . . 398
Batelli on sebaceous glands, . . . 676
Battistini on muscle, . . . .108
,, ,, nervous tissues, . . 117
Baudelocque on foetal respiration, . 731
Baudrimont on respiratory exchange, . 734
Bauer on fat formation, . . 902, 934
,, ,, proteid absorption, . . 436

PAGE

Bauer on respiration, . . . 707, 718
Baumann on alcapton, .... 607
,, ,, alkaloids in urine, . . 61
,, ,, aromatic substances of

urine, .... 605
cadaverine, ... 59
cystine, . . . 602, 603
indol, .... 468
proteids, ... 26, 34
ptomaines, . . .466
putrefaction, . . . 467
putrescine, ... 60
reducing power, . . 39
sulphates of urine, . . 26
sulphur of urine, . . 632
thyroiodin, . . .89
tyrosine, .... 467
urine, . 605, 606, 609, 630
Baumert on gases of alimentary canal, . 730
,, ,, respiration, . . 699, 703
Baumgartner on respiratory exchange, . 734
Baumler on hyperpyrexia, . . . 823
Baumstark on protagon, . . .118
Bayer on choline, .... 21

,, ,, ptyalin, .... 327

Bayliss on body temperature, 826, 830, 855
,, ,, electrical currents, . 517, 682
„ „ lymph, .... 290
,, ,, salivary glands, . 517, 843, 896

Beale on cells, 869

,, ,, intraglobular crystallisation, . 191
Bean on asphyxia, . . . .744

Beaumont on gastric secretion,

355, 402,
536, 540
. 537
. 133
. 33
. 485
. 916
. 398
. 551
498, 499
. 269
. 842
. 828

128, 130, 131
. 727
. 735
. 214
. 586, 587
21

,, ,, ,, fistula, .

Bechamp on carbohydrates of milk,

,, ,, egg white,
Bechterew on salivary secretion, .
Beck on muscular metabolism,
v. Becker on cane-sugar,

,, ,, pancreatic secretion,

„ saliva, .

Beckmann on freezing point,
Be'clard on heat production, .
Becquerel on blood heat,

,, ,, milk,

,, ,, skin varnishing,

Beddoes on respiration,

Beer on Lambert's law,

Behrend on uric acid, .

Bein on lipochromes, .

Bel on stereochemical isomerides, . .106

Bell on reserve air, .... 749

Bence-Jones on animal alkaloids, . . 59

,, ,, quadriurates, . . 588

,, urine, . . 410, 579, 608

v. Beneden on animal heat, 791, 803, 847, 864

,, ,, haemoglobin, . .187

,, ,, respiration, . 848, 706, 711

Benedicenti on respiration, . . 722, 739

Benedikt on muscular metabolism, . 916

Beneke on cholesterin, ... 24

Benjamin on casein, . . . .137

Bensch on biurates, . . . .588

,, ,, milk, 130

Berard on fractional coagulation, . . 43
Berdez on phymatorusin, . . .121
Berend on alkalinity of blood, . . 144
Berenstein on respiration, . 749, 750, 751
Berg on cutaneous respiration, . 723, 724

INDEX OF A UTHORS.

1001

PAGE

Berg on expired air, .... 755

,, ,, respiratory exchange, . 698, 721

Bergeat on digestibility of proteids, . 333

Bergeen on gases of alimentary canal, . 730

Bergengnien on blood corpuscles, . .191

Berger on blood heat, . . . 828

Bergmann on animal heat, . .788

,, ,, heat regulation 851,852,853

,, ,, sweat, . . . 673

Bergonie on respiration, . 698, 700

Berkeley on renal nerves, . 644, 659

,, ,, salivary nerves, . . 525

,, ,, thyroid extract, . . 943

Berlinerblau on lactic acid in blood, 159, 160

,, ,, muscarine, ... 60

Berlioz on urine, ..... 573

Bernard on acid of gastric juice, 352, 353, 533

,, ,, asphyxia, . . . 744,745^

,, ,, body temperature, 8^9, 811), 820,"

82(4, 826, 828,' 82S,

840,' 841, 855, 858

,, ,, cane-sugar, . . . 398 v

,, ,, cerebro-spinal fluid, . . 184*
,, ,, chorda tympani, . . 482

„ ,, dextrose, . . . 158, 914
,, ,, diabetes, .... 927
,, ,, diabetic puncture, . . 660
,, ,. digestion of fats, . . 443

,, ,, gas analysis, . . .760*
,, ,, gases of alimentary canal, . 730 x
,, „ ,, blood, 760, 763V 765; 766,

780 "

,, ,, gastric juice, . . . 350 -
,, ,, gelatin, .... 879'-
» glycogen, 15, 16, 397, 917, 918

922

,, ,, glycogenesis, 922, 923, 924, 925
» j> glycoly tic ferment of blood, 161
,, ,, heat production, . . 843
,, ,, internal respiration, . . 78lK
,, ,, intestinal emulsion, . 447,448
,, ,, pancreatic chromogen, . 427 1
digestion, . . 414
,, ,, ,, fistula, . . 366

,, „ ,, secretion, 368, 547, 550

,, ,, paralytic secretion, . . 519"
» » pigeon's milk, . . . 676'
,, ,, proteid food, . . . 878 :
,, ,, puncture diabetes, . . 926
,, ,, respiration of CO, . . 740
,, ,, respiratory exchange, . 694-

,, „ salivary glands, . 482, 483, 516,

625, 896

,, ,, nerves, . 482, 483, 492,

524

,, „ ,, secretion, 484, 490, 491,

492, 495, 504, 505, 523

,, ,, submaxillary ganglion, 480, 481

,, „ temperature of blood, . 8271

Bernhart on nervous tissue, . . .115

Bernouilli on respiration, . . . 704

Bernstein on muscle, ... 99, 782

,, ,, pancreatic secretion, 547, 548,

,, ,, „ fistula,

,, ,, residual air,
,, }i specific heat,
Bert on alimentary respiration,
,, ,, asphyxia,

,, caisson disease,

553

. 839
. 730

743, 744, 745. 746
737, 738

PAGE

Bert on frequency of respiration, . . 753
„ „ gases of blood, 761,762,763,768,

769

,, ,, heat production, . . 840, 841
,, ,, hibernation, .... 797

,, ,, lacteals, 302

,, ,, lactose, 665

„ ,, origin of respiration, 692, 753, 780,

781, 782

,, ,, reducing substance of mamma, 124
,, ,, respiration of C02, . . 739,740
„ „ .. „ 0, . . . 736
, , , , respiratory exchange, . . 720
Berthelot on animal heat, . . . 839
chitin, .... 74
coefficient of distribution, 354
heat of combustion, . .834
pialyn, .... 340
temperature of blood, . 826
tunicin, . . . .16
Berthold on hibernation, . . . 798
Berthollet on respiratory exchange, 694, 711
Bertrand on skin secretion,
Berzelius on biliverdin,
,, crystallin,

673
382
123

fuscin 121

. 108
. 348
. 944
. 160
. 926
. 152
85

. 287
. 392
560, 565

,, ,, lactic acid,

,, ,, saliva,

Bettmann on thyroid feeding,
Bial on diastatic ferment of blood,

, , , , ferment of liver,
Biarnes on blood,
v. Bibra on liver,
Bichat on exhalant arteries, .
Bidder on absorption of bile salts, .
bile,

body temperature, 803, 809, 866
fat absorption, . . . 460
ferments, .... 320
gastric fistula, . . . 537
,, juice, . . 352, 538
inanition, .... 889
intestinal secretion, . . 555
mucus, .... 344

pancreatic juice, . . . 368
proteolysis, .... 323
renal secretion, . . .661
respiration, . . . 707, 718
saliva, . 347, 348, 487, 505, 523
Bidloo on red corpuscles, . . .188
Biedermann on electrical currents, 519, 684
,, ,, skin glands, . . . 683

Biedert on milk, 138

Biedl on grape-sugar, .... 880
,, ,, suprarenals, . . . 951, 958
Biel on milk, .... 128,131
Bienstock on bacterial digestion, . . 466
Biernacki on pepsin, .... 331
,, ,, trypsin, .... 337
Billard on thymus, . . . .960
Billet on animal heat, . . . 789, 799
Billroth on body temperature, . . 789

spinal injury,
Bimmermann on maltose,
Binet on bile,
Birch on bile,
Biot on respiration,

,, ,, swimming bladder,
Bischoff on inanition, .
,, ,, respiration,

. 861
. 397, 398
. 392, 563
560, 561, 562
. 704
. 705
. 889
731, 735, 758

1002

INDEX OF A UTHORS.

Bistrow on haemoglobin,
Bizio on glycogen,

,, ,, sweat,
Bizzozero on blood platelets,

,, ,, salivary cells, .

,, ,, sebaceous glands,
Blachstein on lactic acid,
Black on animal heat, .

PAGE

. 242
15, 104
. 673
. 156
. 485
. 674
. 107

817, 832, 839
,, ,, respiration, . 693, 694, 742, 757
Blackmail on muscular metabolism, . 911
Blagclen on body temperature, 786, 814, 851,

852

,, ,, freezing point of solutions, . 269

,, ,, heat regulation, . . 831

Blanchard on hemoglobin, . . .187

Blankenthorn on protagon, . . .118

Bleibtreu on blood, . . . .149

,, ,, ,, corpuscles. . . 149

,, ,, foodstuffs, .' . . 875

,, ,, muscular metabolism, . 913

,, ,, thyroid feeding, . . 944

Blennard on proteids, .... 34

Blitstein on intestinal secretion, . . 556

Blix on blood corpuscles, . . .148

Bloch on respiration, .... 764

,, ,, sweat centres, . . .679

Blome on acidity of muscle, . . .108

Blomtield on fish slime, . . . 676

Blondlot on gastric tistula, . . . 537

,, ,, ,, juice, . . 352, 360

Blosville on body juice, . 352,360,537

,, ,, ,, temperature, . . 812

Blum on egg albumin, .... 50

Blumenreich on parathyroids, . . 940

,, ,, thyroidectomy, . . 943

Blumenthal on milk, . . . .104

Blyth on cobric acid, . . . .56

Boas on gastric juice, . . . 356, 366

,, ,\ pialyn, 340

,, ,, rennin, .... 334, 335

,, ,, trypsin, . . ... . 337

Bochefontaine on salivary secretion, . 485

Bodtker on estimation of urea, . .584

Boeck on respiration, . . . 707, 718

Boedeker on alcapton, . . . 607, 630

,, ,, chondroitic acid, . .114

,, ' ,, milk, . . . . 130

,, „ pus, 83

Boeklisch on putrescine, ... 60

Boerhaave on animal heat, . .815, 832

Bogdanow on muscle-fat, . . .106

Bogoljubow on bile, . . . .784

Bogomoloff on bile, . . . . 390

,, ,, bile salts, . . . 378

Bohland on foodstuffs, . . . .875

,, ,, muscular metabolism, . 913

Bohlen on electrical currents, . . 684

,, ,, gastric glands, . . . 683

Bohm on lactic acid, .... 109

,, ,, muscarine, .... 60

,, ,, muscle glycogen, . . .917

,, ,, sugar formation, . . . 921

,, ,, trypsin, .... 338

Bohr on coagulation, .... 178

,, ,, C02 haemoglobin, . . 242,243

,, ,, gases of blood, . . 769, 777

,, ,, haemoglobin, . . 767, 768, 773

,, ,, htemataerometer . . . 776

,, ,, milk fat, . . . .133

,, ,, oxy hemoglobin, . 192, 205, 225

PAGE

Bohr on respiration, . . 757, 774, 778

,, ,, swimming bladder, . . . 705

Boileau on body temperature, . . 813

du Bois Reymond on electrical currents, 517,

681, 682

,, electro-osmose, . 688
,, lactic acid, . .108
,, muscles, . . 840
,, reaction of muscle, 99
,, torpedo organ, . Ill
Bokay on lecithin, .... 463
,, ., nuclein, .... 879
Bokorny on albumin, .... 26
,, ,, protoplasm, ... 38
Boldt on muscle glycogen, . . .918
Boll on torpedo organ, . . . .111
Bonafous on animal heat, . . . 823
Boridonneau on starch digestion, . . 395
Borelli on inspiration, . . , .748
Bornhardt on proteids,. ... 41
Bornstein on fats of blood, . . .159
Boruttau on inosite, . . . .105
,, ,, muscle, .... 99
,, ,, ,, glycogen, . . 104
Bosanquet on animal heat, 787, 789, 802, 813
Bose on pituitary extract, . . . 948
Boshard on leucine, . . .29, 423
Bostock on animal heat, . . . 832
,, ,, respiration, . 692, 731, 749
Bottazzi on spleen, .... 87
Bb'ttcher on dextrose, .... 610
,, ,, intraglobular crystallisation, 191
Bbttger on Charcot's crystals, . . 94
,, ,, sulphocyanate of saliva, . 345
Bottomley on heat formation, . . 840
Bouchard on leucomaines, ... 61
Bouchardat on gluten, .... 53
,, ,, starch digestion, . .393

Bourneville on body temperature, . 864

,, ,, myxoedema, . . . 940

Bourquelot on maltose, . . . 397
,, ,, succus entericus, . . 397

Bous.singault on respiration,. . 695,706
Bovet on putrefaction, .... 468
Bowman on urinary secretion,

639, 640, 652,
653, 655, 658
. 817
. 757
. 693, 704
785

Boyle on effects of cold,
,, ,, gases of blood,
,, ,, respiration,

,, ,, thermometer, ....
Braconnet on gastric juice, .

,, ,, leucine, ....
Bradford on ablation ot kidney, .

diuresis, ....
electrical currents, 517, 518
heat regulation,,
renal nerves,
salivary secretion,
section of chorda tympani,
,, ,, Jacobson's nerve,
sympathetic saliva,
urinary secretion,
Brain ard on snake venom,
Bramwell on proteids, .
Brandl on melanin,

644,

,, ,, phymatorusin,

v. Brasol on diuretics, .

,, ,, hydnernia,

Braume on heat production,

Biaun on salivary secretion,

352
421
937
649
682
856
646
522
520
521
. 523
656, 937
57

. 44
. 122
. 121
. 648
. 294
. 843
485, 492

INDEX OF A UTHORS.

1003

PAGE

Braune on skin absorption, . . . 686

Bredert on milk, ..... 138

Breed on brain, . . . . .77

Brensinger on cystine, ..... 602

Breschet on blood heat, . . . 828

,, ,, skin varnishing, . .727

Brewster on spectrum, . . . . 208

Bricon on myxoedema, .... 940

Brieger on alkaloids, . . .59, 60, 61

,, ,, aromatic substances of urine, 605

,, ,, body temperature, . . 867

,, ,, indol, 468

,, ,, neuridine, .... 60

,, ,, ptomaines, . . . .466

,, ,, putrefaction, . . . 467
,, ,, putrescine, .... 60

,, skatol, . . . .469

,, ,, skatoxyl, .... 628

Briesacher on thyroidectomy, . . 940
Bright on fat absorption, . . . 459
Brisegger on iutraglobular crystallisa-
tion, ...... 191

Brodie on blood platelets, . . .156
body temperature, . 857, 858
casein, . . . . .137

coagulation,. . . 145, 171
nucleo-proteids, . . 68, 81, 83
pancreatic casein, . . 137

,, juice, . . . 553
proteids, . 24, 32, 34, 41, 165
spinal injury, . . . 860
sulphates, .... 26

Bromeis on milk fats, . . . .133

Brosicke on bone, . . . .111

Brown on achroodextrin, . . . 396
carbohydrate absorption, . 435
cerebrum, . . . .120

dextrin, . . . .12

diastatic ferments, . 12, 13
enzymes, . . . 397, 399
fat absorption, . . . 452
galactose, .... 7

inulin, ..... 14

ptyalin, .... 328

reducing power, ... 7
starch digestion, . . 394, 397
succus entericus, . . . 398
Brown-Sequard on body temperature, 812,

821, 855

generative glands, . 937
hibernation, . . 798
pituitary extract, . 946
respiration, . 739, 742
suprarenals, . 948, 949
thyroidectomy, . 942
Bruch on intraglobular crystallisation, . 191
Bruck on animal heat, . . . 862

Briicke on acids of gastric juice, 356, 360, 533
,, bile pigments, . . 382, 387
,, ,, coagulation, . . . 179

,, ,, dichroisrn of blood, . . 233
,, ,, digestive solutions, 323, 536, 542
,, ,, emulsion, . . . 445, 446
,, , , erythrodextrin, . . . 395
fat absorption, . . .449
gastric fistula, . . . 537
glycogen, . . . .15

Eippuric acid, . . . 601
isolation of enzymes, . .314
lymph flow, . . . 302

PAGE

Briicke on muscle glycogen, . . .104
oekoid, . . . .188
pepsin, 97, 33], 333, 404, 542

Piotrowski's reaction, . . 48
pore diffusion, . . 274, 275
precipitation, ... 40
proteid digestion, . . . 405
ptyalin, .... 329
red corpuscles, . . .188
starch, .... 14
sugar in urine, . . 608, 609
zymolysis, .... 320
Bruguiere on hibernation, . . . 798
de Bruin on bile pigments, . . .391
Brummer on milk, . . . .128
Brunner on proteids, .... 41
Brunton on alkaloids, .... 59
,, bacterial digestion, . . 470

,, intestinal secretion, . 555, 556

,, nuclei, ... 65, 81

,, saliva, .... 343

,, snake venom, ... 56

Bryant on body temperature, . .864
Bubnow on thyreoproteid, ... 89
Buchanan on fibrin ferment, . . 168, 179
,, ,, gases of blood, . . . 770
Biicheler on oxyhaemoglobin, . 199, 200
Buchheim on ammonia in urine, . . 907
,, ,, gastric juice, . . . 360

Buchner on gases of lymph, . . . 783
„ gelatin, .... 71
Buchser on body temperature, . . 802
Bucquay on respiration of compressed

air, 738

Budge on body temperature, . . . 855
,, ,, intestinal secretion, . . 555
Buff on salivary secretion, . . 492, 512
Buffon on asphyxia, .... 745
Buisine on sweat, ..... 673
Bunge on ammonia in urine, . . 907

ash of serum, . . .772

bile, 371

blood, . 148, 153, 154, 157, 188
,, gases, . . .157, 773

diet, 877

digestion of cellulose, . 470, 471
foodstuffs, . 873, 881, 882, 885
gastric juice, . . 361,363,364
glycogen, . . . 917, 918
hsematogens, . . .68, 69
haemoglobin, . . . 203, 768
hippuric acid, . . 893, 906
intestinal emulsion, . . 448
iron in foetus, . . . 885
,, „ food, . . . .885
lime in food, . . . .886
,, salts of urine, . . 635

milk, 662

muscle ash, . . . .109
potassium in food, . 630, 634

proteid digestion, . . . 899
respiration, .... 700

saliva, 327

salts of food, .... 884
,, ,, milk, 128, 131, 132, 662
soda in body, . . 77, 78
syntheses in metabolism, . 893
urine, .... 572, 601
Bunsen on extinction coefficient, . . 214
,, ,, gas analysis, . . .760

INDEX OF A UTHORS.

PAGE

Bunsen on oxygen of blood, . . . 766
,, ,, spectroscope, . . .216
Buonaparte on viperine, . . .56
Burchard on cholesterin, ... 23
Burckhardt on blood proteids, . .162
Burdach on asphyxia, .... 745
,, lymph, . 287
Burdon Sanderson on balance of nutri-
tion, 871

Busch on gas pump, .... 759

,, ,, gastric absorption, . . 432

Butlerow on methylenitan, ... 5

Biitschli on respiration exchange, . 702, 710

CAHN on cataract,

,, ,, gastric juice, .

„ ,, retina, .
Cahours on legumin,
Callenfels on body temperature,
Calmette on snake poison,
Camerano on salamander,
Camerer on milk, .

,, ,, uric acid, .
,, ,, xanthine bases,
Campbell on bile, .
Camus on lacteals,
Canalis on thyroid ectomy,
Caparelli on diabetes, .
Capobianco on thyroidectomy,
Capranica on lutein,
,, ,, sweat,
Carlier on coagulation, .
Carter on body temperature,
Casali on skin secretion,
Caseneuve on fat formation, .
Casey on body temperature, 788,

. 123
, 358
. 121
. 51
. 855
56, 58
. 725
. 128

67, 594, 595, 597
. 598
. 386, 390
. 302
. 939
. 928
. 941
20

. 672
. 169

803, 809
. 673

902, 934
789, 799,

800, 806, 823
Cash on bacterial digestion, . . . 464
,, ,, digestion of fats, . . . 443
,, ,, fat absorption, . . . 459

,, ,, intestinal emulsion, . .448

,, ,, reaction of intestinal contents, . 452
Castle on body temperature, . . .816
Cavazzani on body temperature, . . 808
,, ,, diastatic ferment of blood, 161
„ glycogen, . . . .925
,, ,, starch absorption, . . 435
Cazeneuve on milk, . . . .126
Celsius on thermometer, . . . 786
Chabrie" on proteids, . . . .41
Chandelon on muscle glycogen, . .105
Chaniewski on fat formation, . . 932
Chapoteaux on gastric juice, . . .546
Charbonel-Salle on pigeon's milk, . . 676
Charcot on body temperature, . . 805
Chateauburg on urine, .... 604
Chauveau on blood gases, . . 763, 764
carbohydrates, . . .919
C02 of muscle, . . . 912
dextrose in blood, . 158, 915
metabolism, . . .923
muscle, .... 841
respiratory exchange, . 841
Chavvas on aqueous humour, . . 122
Chevalier on nervous tissues, . . 116

Chevreul on milk fat, . . . .133
Children on gastric juice, . . . 352
Chiodera on urochrome, . . . 620
Chischin on gastric secretion, 541, 542, 545,

546

PAGE

Chischin on Pawlow fistula, . . . 537

Chittenden on albumoses, 50, 407, 408, 409,

410, 411, 412, 413

,, ,, alcohol, . . . 882

,, ,, anti-albumid, . . 406

,, ,, bile salts, . . . 392

bromelin, . . .55
caseiuogen, . . .136
copper albuminate, . 26
digestion, . 47, 322, 406
dyspeptone, . . .429
elastin, . 71, 72, 430

enzymes, . . .314
fractional coagulation, . 43
gelatin, . 47, 429, 430

, , peptone,
glycocine,
glycogenesis,
milk, .
muscle,

,, glycogen,
myosin,
neurokeratin,
peptones,
proteids,
proteoses,
ptyalin,
saliva, .
tendon,

,, mucin,
trypsin,
vegetable proteids,

71
. 103

. 926
. 128
95

. 104
97, 98
72. 117
. ' 25
42, 46, 333
45

. 329,330
. 328,344
62
62

. 338
54

Chopinet on thyroidectomy, . . . 942
Chossat on body temperature, 802, 803, 809,

853, 857
886
829
653
484
. 61
860, 861
. 471
. 280
. 752
. 861
127, 128
. 381
. 86
. 87
. 673
. 90
. 74
. 459
. 364
. 422

proteids, .... 34

salivary glands, . . . 477
Cohnheim on blood, . . . 143, 151
internal respiration, . 781
lymph, . . . 296, 298
pancreatic diastase, . . 340
ptyalin, . . . 328, 330
. zymolysis, . . .320
Cohnstein o i alkalinity of blood, . .144
foetal blood, . . .732
,, respiration, . 732, 733
lymph, . . . 295, 304
Colasanti on body temperature, . . 790
,, ,, curare, .... 842
,, effects of cold, . . .823

,, ,, lime in food,
Christiani on skin temperature,
Chrzonszczewsky on urinary secretion,
Chtapowski on saliva, .
Church on turacin,
Churchill on spinal injury, .
Cienkowski on cellulose,
Cima on nitration,
Clar on spirometers,
Clarke on spinal injury,
Clemm on milk, .
Cleve on cholalic acid, .
Cloetta on liver, .
,, „ spleen,
Cloez on skin secretions,

,, ,, suprarenal body,
Cohn on amyloid substance, .

fat absorption,

gastric juice, .

leucine, .

INDEX OF A UTHORS.

1005

PAGE

Colasanti on respiration, 695, 700, 701, 707,

711, 848
,, ,, sarcolactic acid, . 106, 616

Colby on milk, 131

Colin on fractional coagulation, . . 43

,, ,, lymph, 302

,, ,, salivary glands, 477,489,490,491
,, ,, ,, secretion, . . . 490
Collard de Martigny on asphyxia, . . 744
., ,, ,, blood heat, . 828

,, ,, ,, ,, gases, . 758

,, ,, ,, cutaneous re-

spiration, . 726

Collmar on heat regulation, . . . 858

,, ,, suppuration, . . .84

Colls on blood, .... 160, 161

,, ,, creatinine, .... 101

,, ,, proteids, 41

,, ,, sugar in urine, . . . 609

Commaille on milk, .... 128

Configliachi on respiration, . . . 704

Contejean on coagulation, . .175, 178

,, ,, gastric secretion, . . 534

,, ,, muscular metabolism, . 915

Cooper on coagulation, .... 179

Copeman on bile, . . . . .371

,, ,, blood, . . . .143

,, ,, hfematoporphyrin, . . 625

Coppet on freezing point, . . . 269

Coranda on salts of food, . . .883

Corin on body temperature, 791, 803, 847, 864

,, ,, fractional coagulation, . . 43

,, ,, respiration, . . 706, 711, 848

Cornevin on milk secretion, . . . 664

,, ,, phloridzin, . . . 921

Corvisart on trypsin, .... 338

,, ,, tryptic digestion, . 414, 415

de Coulon on pituitary body, . . 946

Courant on caseate of lime, . . .136

,, ,, milk, 126

Cramer on coagulation, . . .172

,, ,, fibroin, .... 76

,, ,, muscle glycogen, . . .104

Crawford on body heat, 819, 826, 827, 832,

838, 839, 844, 846, 847, 852

,, ,, heat of combustion, . . 834

,, ,, respiration, 709, 711, 757, 780

Creite on inosinic acid, . . . .103

Cremer on glycogen, . . . .15

,, ,, pentoses, .... 3

,, ,, phloridzin diabetes, . 920, 921

Cristafulli on respiration, . . . 742

Cristiani on thyroidectomy, . . . 939

Crombie on body heat, . 787, 799, 800, 802,

804, 807, 809, 810, 811,

813, 814, 825, 866

Crookewitt on spongin, ... 76

Croon on respiration, . . . .692

Cruikshank on cutaneous respiration, 725,726

,, lymph, . . . .287

Cumberland or animal heat, . . 816

Cummins on bile salts, .... 392

,, ,, proteids, ....

-, » trypsin, .... 338

Cunv Bovier on body temperature, 807, 820,

821, 825

Currie on body heat, . 818, 819, 823, 846

Curtius on gelatin, . . . .71

,, ,, hemoglobin, . . .231

Cutler on body temperature, . .812

PAGE

Cuvier on hibernation, .... 798
Cybulski on suprarenal extract, . 951,955,

957, 958

Cyon on thyroid gland, . . .945

Czermach on animal heat, . . . 793

Czermak on salivary nerves, . . 483, 494

,, ,, ,, secretion, . . 506

Czerny on absorption, .... 437

,, ,, digestion, .... 442

DAGNANI on bile, . . . .561
Dahnhardt on ferment of mammary

gland, . . .140

,, ,, lymph, . 77, 182, 783

Dalton on respiration, . . . 696, 748

,, ,, specific heat, . . . 838

Damrosch on body temperature, . 789, 798,

799, 802, 809

Dana on succus eiitericus, . . . 398
Danilewsky on caseinogen, . . . 136
enzymes, . . . 340
foodstuffs, . . . 835
heat values, . 834, 838, 874
pancreatic juice, . 337, 338
proteid digestion, . 400, 415
Dareste on respiration of embryo, . . 733
Darwin on proteolytic secretions, . .330
Dastre on biliary fistula, . . . 460
coagulation, . . . .178
enzymes, .... 341

fibrin, 167

galactose, .... 880
lactose, . . ... 399
liver ferment, . . . 925
lymph, . . . .181
maltose, .... 397
peptone plasma, . . . 175
respiration, .... '742
Davenport on body temperature, . .816
Davidson on pepsin, .... 332
Davies on thyroid, .... 89
,, ,, uric acid, .... 595
Davis on phymatorusin, . . .122
Davy on body heat, . 786, 787, 788, 789,
791, 793, 799, 801, 804, 805, 806,
807, 809, 810, 811, 812, 813, 814,
820, 827, 828, 830, 839, 840, 850
,, ,, gases of blood, . . 757,758
,, ,, respiration, . 698, 735, 748, 749,
750, 751, 754

Dean on heat regulation, . . . 856
Debczynski on body temperature, . 801
Decaisne on milk, .... 128
Delaroche on body temperature, . 815, 852
,, ,, respiratorv exchange, 704, 709,

711

Dele"pine on melanine, . . . .122

Delezenne on coagulation, . .146, 178

Demant on creatine, . . . .100

,, ,, succus entericus, . . 399

Demarcay on bile, .... 372

Demarquay on body temperature, . 821

Dening on thyroid feeding, . . . 944

Denis on plasmine, . . . .164

,, ,, proteids, . . . .42

,, ,, respiration, .... 732

Deschamp on chymosin, . . .334

Desfontaines on animal heat, . . 816

Despretz on animal heat, . 832, 844, 846

,, ,, respiration, . . . 695

ioo6

INDEX OF AUTHORS.

PAGE

Detmar on ptyalin, .... 329
,, ,, respiratory exchange, . . 702
Devoto on proteids, . . . 40, 41
Deweyre on glycogen, . . . .918
Diacoiiow on cerebrins, . . .120
,, „ lecithin, ... 21, 22
,, ,, protagon, . . . 118

Dickinson on leech extract, . . .147
,, ,, salivary nerves, . . 484
,, ,, ,, secretion, . . f>15
Diest on foetal respiration, . . . 731
Dietrich on pepsin, .... 332
Dissard on respiration, .... 724
Dittmar on respiration of fishes, . . 704
Dobroslawin on intestinal secretion, . 556
Dobson on body temperature, . .814
Dodds on bile secretion, . . . 569
Dogiel on salivary nerves, . . .525
Dohmen on respiration of oxygen, . 736
Dolinski on pancreatic secretion, . 549, 551
Domiiiicis on diabetes, . . . 928

,, ,, suprarenals, . . .949
,, ,, thyroidectomy, . .939
Donaggio on parathyroids, . . . 941
Donatti on thyroid extract, . . . 943
Donders on animal heat, . . 788, 855
,, ,, CO-hfemoglobin, . . 238
,, ,, lymph -pressure, . . . 299
Donkin on hyperpyrexia, . . . 823
Dormeyer on fats, . . 17, 96, 105

Dorn on sweat secretion, . . 679, 681
Draconow on spermatozoa, . . .93
Dragenddrf on milk, . . . .131
Drasch on skin glands, . . . 681
Drechsel on biuret reaction, ... 49
elastin, . . . .72
iodo-gorgonic acid, . . 90
jecorin, .... 86
keratin, . . . .73
lactic acid in blood, . .159
lysine and lysatine, 32, 33, 426, 427
Pettenkofer's test, . . 377
proteids, . . 24, 27, 32, 52
thyroid gland, . . . 938
urea formation, . . .907
Dreser on glomeruli, .... 659
,, ,, osmotic pressure, , 272, 650, 651
,, ,, reaction of urine, . . . 657
Drouin on alkalinity of blood, . . 144
Druebin on blood platelets, . . . 156
Dubois on hibernation, 794, 796, 797, 798
Dubrunfaut on digestion of starch, . 394
Ducceschi on thyroidectomy, . .941
Duchamp on body temperature, . . 805
Duclaux on milk fats, . . . .133
Ducros on skin varnishing, . . . 727
Dufourt on glycogen, . . . 920, 925
,, ,, muscular metabolism, . .915
Dufresne on ptyalin, . . . .330
Duggan on fractional coagulation, . 43
Dulk on air chamber of egg, . . 735
Dulong on animal heat, 832, 837, 838, 844, 846
,, ,, respiration, .... 695
Dumas on body temperature, . . 791
,, ' ,, legumin, .... 51

„ ,, milk, 130

,, ,, respiration, .... 735
Dumeill on body temperature, . . 821
Dunglison on gastric juice, . . . 352
Duntze on body temperature, . .815

849
513

867

767

51

PAGE

Dupre on animal alkaloids, ... 59
Dupuy on skin secretion, . . . 678
During on creatine, . . . .73
Duroy on body temperature, . 820, 821
Dusing on respiration of embryo, . . 733
Dutrochet on animal heat, . . .793
,, ,, osmosis, . . 273, 284, 287
,, ,, plant temperatures, .
Duval on salivary secretion, .
Dybkowsky on body temperature,

,, ,, haemoglobin,

Dyer on proteolytic ferments,

EBKRLE on gastric juice, . . . 402

• ,, ,, intestinal emulsion, . . 447

Eberth on wandering cells, . . . 450

Ebstein on digestive extracts, . 324, 542

,, ,, gastric glands, . . 532,534

,, ,, pentoses, . . . 3, 612

,, ,, pepsin, .... 331

„ ,, ptyalin, .... 329

Eck on removal of liver, . . . 908

Eckerlein on respiration, . . 747, 752

Eckhard on diabetes, . . . 926, 927

,, ,, diabetic puncture, . . 660

,, ,, filtration, .... 281

,, glycogen, . . . .919

,, ,, milk secretion, . . . 663

,, ,, renal secretion, . . 645, 646

,, salivary secretion, 328, 342, 343,

484, 489, 495, 502, 503,

504, 506, 509, 523

,, ,, ,, nerves, . . 482

,, ,, sweat nerves, . . . 677

Edelberg on intra vascular coagulation, . 173

Edenhuizen on skin varnishing, . . 727

Edkins on absorption, .... 432

coagulation of milk, . . 137
gastric secretion, . . . 531
metacasein, . . . .127

pancreatic extracts, . . 552
pepsin, . . . 332, 543

Edmunds on casein, .... 137

,, ,, milk coagulation, . 134, 135
,, ,, thyroidectomy, . . 940
,, ,, urates, .... 42

Edoux on body temperature, . .812

Edwards on asphyxia, . . 743, 745, 746

,, ,, body temperature, 793, 803, 804,

813, 822, 846, 865

,, ,, heat regulation, . . 852

,, ,, hibernation, . . 794, 796

,, ,, phosphorescence, . . 780

,, ,, respiration, . 701, 723, 757

,, of hydrogen, . 739

Ehrenthal on intestinal secretion, . 556

Khrlich on glycogen of blood, . . 158

Eichberg on skin absorption, . . 685

Eichholz on bile pigments, . . . 338

,, ,, chromogen of urobilin, . 623

Eichhorst on glycosuria, . . . 881

,, ,, proteid absorption, . . 436

,, ,, succus entericus, . . 398

Eichwald on mucins. . . ... 62

,, ,, pus-cells, .... 83

Eijkman on body temperature, . .812
Einhof on legurnin, .... 51

v. Eiselsberg on thyroid grafting, . 942

,, ,, thyroidectomy, . . 939

Ekunina on lactic acid, . . .108

INDEX OF A UTHORS.

1007

PAGE

Ellenberger on bile, . . . .369
,, ,, body temperature, . 803, 805,

807, 810

,, ,, gastric digestion, . . 356

,, ,, proteolytic ferments, . 51

,, ,, salivary secretion, . 489, 491

,, ,, sulphocyanate of saliva, . 345

Ellinger on lymph, . . . .182

Ellis on body temperature, . . .814

Ely on ptyalin, ..... 329

,, ,, saliva, . . . . . 344

Emicb on taurocholic acid, . . . 392

Emmerling on proteids, ... 29

Emmert on footal respiration, . . 731

Emmet on gastric juice, . . . 352

Emmingliaus on lymph-production, . 289

Engel on proteid quotient, . . .162

Engelmann on electrical currents, . 682

,, ,, electro-osmose, . . 688

,, ,, skin glands, . . . 681

v. Ensclmt on blood gases, . . . 758

Erb on body temperature, . . . 867

Erlenmeyer on tyrosin, . 29, 423, 425

Erler on respiratory exchange, . . 711

Erlich on bilirubin, .... 384

,, ,, internal respiration, . . 782

Erman on respiration, . . . 704, 730

Errara on glycogen, . . . .15

Escombe on chitin, . . . .74

Estor on blood gases, . . . .762

Etzinger on collagen, .... 428

,, elastin, ... 72, 430

Eulenberg on animal heat, . . . 863

Eves on ptyalin, ..... 329

Ewald on bacterial digestion, . . 464

bile, 369

blood gases, . 761, 762, 763, 765
collagen, .... 430
elastin, .... 72

fat absorption, . . .452
gastric digestion, . . 349, 356
internal respiration, . . 783
muscle, . . . .95

neurokeratin, ... 72
pleuritic fluid, . . .784
proteid absorption, . . 437
.succus entericus, . . . 399
thyroid extract, . . . 943
thyroidectomy, . . 939, 940
trypsin, . . . 338, 552
Ewart on rigor mortis, ... 97

Exner on diffusion, .... 779
Eyckmann on blood, . . . .149
Eylert on marrow, . . . ] 9

FAHRENHEIT on body temperature, . 815
Falck on skin absorption, . . . 685
Falk on gastric juice, .... 364

,, ,, ptyalin, 329

Fano on albumose in blood, . . . 439

,, ,, coagulation, . . . .147
Favre on heat of combustion, . 833,834

,, ,, sweat, . . . 670, 671, 672
Fawcett on body temperature, . 821, 858

„ gout, 596

Fawlitsky on gastric juice, . . . 366
Fayrer on snake venom, ... 56
Feder on ammonia in urine, . . . 907

,, .,, metabolism, . . . . 894
Fehling on .body temperature, . . 804

PAGE

Fehling on dextrose, .... 610
,, ,, salivary glands, . . 524,930
Fehr on salivary glands, . . 524, 930
Fenwick on sulphocyanate of saliva, . 346
Fermi on trypsin, . 430

Fernet on blood gases, . 758, 766, 769, 772

Ferrier on body temperature,
Fick on body temperature, .

diffusion,

endosmotic equivalent,

osmosis

pepsin,

proteid metabolism,

red corpuscles, .
Field on sweat secretion,
Filehne on diabetes,
Fillipi on digestion and absorption,
Finkler on blood -gases, . . 7
, , , , body temperature,
,, ,, internal respiration,

864
867
262
274
275
404
912
150
680
927
442

763, 765
90, 792
. 781

respiration,

699, 700, 701, 707,
711, 756, 780, 848

Finlayson on body temperature, . . 804
Fischer on animal heat, . . . 858
carbohydrates, ... 2
dextrose in urine, . . 608

formose, .... 5

gelatin, . . . 33, 71
glycuronic acid, ... 5
isomaltose, . . . .11

lysine, '•","'"• - - 426

mannose, .... 7

osmosis, . . . .273

sugars, . . . 3, 6, 9, 35

xanthine, .... 596

Fitz on pus, . ..... 84

Flaum on pepsin, ... . . . 331

Fleischer on milk, . . . .130

,, ,, skin absorption, 685, 686, 687,

689, 690

v. Fleischl on haemoglobin, . . .152

Fleischmann on colostrum, . . .129

., milk, . . . 125, 130

Flensburg on urine, .... 603

Fletcher on muscle, . . . 911, 912
,, ,, proteids, .... 38

,, saliva, 344, 494, 499, 500, 504,
509; 510

Fleury on body .temperature, . .818

Flint on gases of alimentary canal, . 730

,, ,, muscular metabolism, . .913

Floresco on peptone plasma, . .175

Foa on intra vascular coagulation, . .173

,, ,, suprarenal body, . . 90, 950

Fodcra on pancreatic fistula, . . 366

Foettinger on fish slime, . . . 676

Foh in an n on lymph, .... 287

Fohringer on body temperature, . 790, 805

Fokker on lime in food, . . . 886

,, ,, respiration of CO, . . 740

Fontana on respiration of hydrogen, . 739

,, ,, snake venom, ... 57

,, ,, tidal air, .... 748

Forbes on body heat, .... 850

Fordos on pus, ..... 84

Fordyce on temperature, . . . 814
Forlanini on skin absorption, . . 689
Fornara on skin secretion, . . . 673
Forrest on marrow cells, . . .84
Forster on lime in food, . . . 886

ioo8

INDEX OF A UTHORS.

PAGE

Forster on proteid food, . . .878
,, ,, proteid metabolism, . . 897
,, ,, respiration, .... 696
,, ,, salts of food, . . . 883

Fortunatow on fat absorption, . . 450

Foster on fat absorption, . . . 462
>> » glycogenesis, . . . 925

,, ,, heart work, .... 842
,, ,, proteid digestion, . . 438

,, ,, rennin, .... 134

Fourcault on skin varnishing, . . 727

Fracassati on respiration, . . . 692

Framm on caramel, .... 7
,, ,, Moore's test, ... 7

Fran9ois-Franck on pancreatic secretion, 550
,, ,, sweat, . . . 671

Frank on fat absorption, . . .462
,, ,, gastric juice, .... 364

Frankel on blood, . . . .150
,, ,, carnic acid, . . .104
,» tflycogen, .... 15
,, ,, inosinic acid, . . .103
,, ,, respiration, . 707, 718, 738
,, ,, suprarenal body, . . 91
,, ,, thyroid body, . . 88, 89

Frankland on heat of combustion, 834, 838,

874
„ milk, . . . .131

Franklin on animal heat, . 818, 851, 858

Fraser on snake poison,

Frassineto on fractional coagulation,

,, ,, proteid-quotient,
Fredericq on animal heat,

,, ,, blood gases,

,, ,, fractional coagulation,

,, ,, hsemocyanin,
,, respiration,

721,

,, ,, tension of gases,
Frederikse on fibrin, .
Fremont on gastric juice,
Fre'my on cartilage,
,, ,, fossil bones, .
,, ,, gelatin,
,, ,, ichthin,

Frentzal on muscular metabolism,
Frerichs on bile, .

„ „ pigments, .
,, ,, liver, .
» » pancreas, .
,, ,, saliva,

,, spinal injury,
,, spleen,

,, succus entericus,
,, thymus,
,, thyroid, .
,, ,, torpedo organ, .
,, ,, urea in muscle, .
Freudberg on alkalinity of blood,
Freund on acidity of urine, .
,, M animal gum,
„ ,, coagulation,
v. Frey on C02 of muscle,
,, emulsion,
,, gases of blood,
,, lactic acid in blood,
,, respiratory exchange,
,, salivary secretion,
,, sarcolactic acid, .
,, temperature of blood,

56
43
162
864
778
43
61

711, 718, 719,
776, 803
. 784
. 167
. 349
. 114
. Ill
. 70
. 52
. 916
. 371
. 389
. 86
92

. 348
. 861
. 87
. 369
. 88
. 88
. Ill
. 102
. 144
. 577
. 158

167, 169, 175
. 912
. 445, 447
. 763
. 905
.841
. 505, 506
. 106
896

PAGE

Frey tag on cerebrins, . . . .120

,, ,, protagon, .... 118

Friedberg on rennet, . . . .134

Friedlander on respiratory exchange, . 694

Friedrich on amyloid substance, . . 74

,, ,, caisson disease, . . 737

Friend on aqueous humour, . . 122, 182

,, ,, red corpuscles, . . .155

Frohlich on body temperature, 789, 799, 802,

820, 821

Fubini on cutaneous respiration, 723. 726,

727

,, ,, respiratory exchange, . . 722

,, ,, saliva, . . . .343

, „ ,, skin absorption, . 686, 687, 689

,, ,, ,, secretions, . . . 671

Funke on blood crystals, 203, 205, 206, 208

,, ,, hemoglobin, . . .194

,, ,, intestinal secretion, . . 556

,, ,, intraglobular crystallisation, 191

,, ,, sweat, 672

Furnell on body temperature, . . 813

v. Fiirth on lactic acid, . . . 109

,, ,, muscle plasma, ... 98

Fusari on salivary nerves, . . . 525

GABRIEL on amido-acids, . . . 880
,, bone, . . . 112, 113
,, . ,, egg albumin, ... 43
,, ,, tooth, . . . .112
Gabritschewsky on glycogen of blood, . 158
Gad on emulsion, . . . 445, 446

,, ,, residual air, .... 750
Gaertuer on h?ematocrit, . . 148, 271
Gaglio on lactic acid in blood, 159, 160, 905
oxalates in food, . . .614
respiration of CO, . 740, 741

sarcolactic acid, . . .106
Galen on animal heat, .... 832
cutaneous respiration, . . 725
on functions of skin, . . 727
Galeotti on secretory cells, . . . 938
Galileo on thermometer, . . . 785
Galloise on inosit, .... 606
Gamgee on acid of gastric juice, 355, 363, 365
,, ,, amido-acids, . . . 421

„ „ bile, 390

,, ,, blood corpuscles, . .188

,, ,, chitin, .... 74
coagulation, . . . 168
coefficient of distribution, 354,
355

CO-hamioglobin, . . 238, 240
fteces, . . . .473

gas analysis, . . . 760
,, pump, . . . .759
gastric juice, . . . 349
hsematin, .... 254
hsemochromogen, . .255
haemoglobin, . . 185. 187
indol, ..... 468
intestinal fistulse, . . 368
lysine and lysatine, . . 427
methsemoglobin, . 245, 246, 247,
248

pancreatic extracts, . . 137
phenol, . . . .467
protagon, . . 118, 119, 120
proteids, ....
salivary secretion, . . 525

INDEX OF A UTHORS.

1009

Gamgee on Soret's band,
,, ,, succus entericus,
, , , , sulphocyanate of saliva,
,, ,, tryptic digestion,
,, ,, turacin,
Gara on thyroid feeding,
Garland on succus entericus,
Garrod on bile pigments,
,, blood plasma,
,, red corpuscles,
,, uric acid,
,, urinary pigments,

,, urobilin,
,, urorosein,

Garvoch on bile pigments, .
Gaskell on lymphatics,

,, ,, metabolism,

,, ,, nervous system, .

,, ,, salivary nerves, .
Gassot on body temperature,
Gaule on lymph gases, .
Gautier on alkaloids in urine,

,, ,, animal alkaloids,

,, ,, fat formation,

,, ,, leucomaines,

,, ,, snake- venom,
Gavarret on body heat, 791,

PAGE

. 226
555, 556
. 504
421, 552
. 61
. 944
. 398
. 888
. 160
. 152

587, 596, 909
260, 619, 620,
623, 624, 625
621, 622, 629
. 628
. 388
. 300
. 869
. 184
. 482
. 825
. 783
61

. 59, 60, 61
. 933
. 101
. 56

793, 796, 832,
846
. 818
, 722
849
818
51
829
940
300
127
116
120
65

,, ,, effects of cold, .

,, ,, respiratory exchange,

, , , , temperature of plants,

Gaymard on effects of cold, .

v. Gehlen on legumin, .

Geigel on skin temperature, .

Generale on parathyroids,

Genersich on lymph-flow,

Genser on milk, ....

Geoghegan on brain,

,, ,, cerebrin,

,, ,, nuclein,

Georgiewsky on thyroidectomy, . . 944

Geppert on blood, . . . 144, 150

„ „ „ gases, 715, 761, 762, 772

,, ,, body temperature, . . 820

„ ,, gas analysis, . . .760

,, ,, respiration, 699, 708, 714, 718,

728, 747

Gerber on milk, 128

Geiiach on cutaneous respiration, . 726, 727
,, ,, gastric juice^ . . . 361
,, ,, respiration of embryo, . 733

,, ,, skin-varnishing, . . 727, 728
Giacosa on mucinogen, . . . .62
Gianuzzi on salivary glands, . .511

Gibson on chitin, ..... 74
Gierse on animal heat, . . . 789, 799
Gies on tendon, ..... 62
Gilbert on fats, . . .931, 932, 934
Gildemeister on respiratory exchange, . 711
Giles on body temperature, . . . 812
Gilson on choline, .... 22
Ginsberg on glycosuria, . . 609, 881
Girard on body temperature, . .863
Girgensohn on proteids, . . .40
Girtanner on blood gases, . 757, 762, 772
Gladstone on spectrum, . . .213
Glaser on body temperature, . . 822
Gleiss on acidity of muscle, . . . 108
Gley on body temperature, . 789, 801, 808
VOL. I. 64

PAGE

Gley on coagulation, . . . 174, 178
diabetes, 928

lacteals,
parathyroids, .
salivary secretion, .
thyroid extract,
thyroidectomy, 939, 940, 941

Gluge on skin -varnish ing,
Gluzinski on thyroid feeding,
Gmelin on absorption, .
bile, .

,, pigments,
blood gases,
gastric juice,
gelatin,
leuciue,

lymph absorption,
pancreatic secretion,
proteids,
saliva,
taurine,
tryptophan,

Gnezda on biuret reaction, .
Gobley on lecithin,
Godfrin on body temperature,
Goebeb on proteolytic secretions,
Goldfuss on blood plasma,
Golding-Bird on purpurin, .
Goldmann on cystine, .

,, ,, sulphur of urine,
Goldschmidt on digestion, .

,, ,, ptyalin,

Goldstein on heat regulation,
Goll on urine,
Goltz on nerves of stomach, .

,, ,, sweat secretion,
Gonnermann on gelatin,
Goodhart on body temperature,
Goodwyn on respiration,
Gordon on cutaneous respiration, .
,, ,, heat regulation, .
,, ,, respiratory exchange, .
,, ,, temperature of embryo,
Gorup-Besanez on aqueous humour,
bile,

fats, . .

milk,
muscle,
proteids,

302
940
514
943
942,
943
. 727
. 944
. 431
. 372

382, 385, 629
. 758

352, 536, 540
. 430
29, 422
. 303
. 368
25

. 345, 348
. 379
. 427
. 48
. 21
. 820
330
160
. 623
. 603
. 632
. 356
. 327
. 856
. 645
. 538
. 676
. 71
. 867

748, 750, 751
. 725
. 735
. 714
850, 865
. 183
. 371
. 17
. 129
. 95
. 24
51
87
87
88

proteolytic ferments,
spleen,
thymus, .
thyroid, .

Gottlieb on pancreatic secretion, . 549, 551

,, ,, suprarenal extract, . . 951

,, ,, thyro-iodin, ... 89

Gottwalt on nitration, . . 280, 282, 283

,, ,, kidney tissue, ... 92

Gourfein on suprarenals, . . . 949

Gourlay on peptone in spleen, . . 88

,, ,, proteids, . . . 41, 87, 89

Gow on pancreatic casein, . . .137

,, ,, ,, extracts, . . .336

Gowers on haemoglobin, . . 150, 152

de Graaf on pancreatic fistula, . . 366

Graham on diffusion, 43, 262, 263, 284, 361

Graham-Lusk on proteid food, . . 876

Grandis on respiratory exchange, . .717

Graser on bacteria of urine, . . . 583

TOIO

INDEX OF AUTHORS.

Gratiolet on skin secretions,

,, ,, suprarenals,

Grawitz on blood,

,, ,, mountain sickness,
Green on coagulation of blood,
,, „ milk,

ferments,
fibrin, .
neossin,

vegetable albumin,
Greliant on blood,

heart-work,
respiration,

Greidenberg on sweat secretion, .
Gresswell on body temperature, .
Griess on nitrites of saliva, .
Griessmayer on proteid digestion,
,, ,, starch digestion, .

Griffiths on alkaloids in urine,

,, ,, blood gases,

,, ,, neurochitin,

,, ,, reducing power of protoplasm
Grimaux on coagulation,

,, ,, synthesis of pro teids,
Griswold on ptyalin, ....
Groger on bacterial digestion,
Groper on fat absorption,
Groves on uric acid, ....
Gruber on carbohydrate digestion,

PAGE

. 673
. 948
. 143, 150
. 738
. 169
. 135
51, 55
. 167
. 63
. 51

. 141, 142, 160
. 759
. 842

707, 717, 740, 741,
749
679
812
346
400
395
61
768
75
39

C02 of muscle,
gastric juice,

ptyalin, ....
respiration of CO,
respiratory exchange, .
urine, .....
Griibler on crystallised proteids, .

molecular weight of proteids,
vegetable proteids,
Grundelach on taurocholic acid, .
Grimhagen on aqueous humour, .
,, ,, digestive solutions,

,, ,, saliva, .

Grunzweig on milk fat,
Griitzner on diastasimetry, .

digestive solutions, ,
gastric glands, .
,, juice, .
muscle,
pepsin,
pialyn, . .
proteolysis,
renal secretion, .
rennet ferment, .
saliva,

salivary secretion,
Gryns on isotony,

,, ,, permeability of corpuscles,
Gscheidlen on blood, .

haemoglobin, .
lactic acid,
muscle, .
nervous tissues,
sulphocyanate of saliva,
,, ,, urine,

Gubler on milk, .... 127, 131
Guinard on skin absorption, . . 687

Gull on myxcedema, .... 938

181

. 36
. 328
. 471
. 461
. 595
394, 395,

434
. 912
. 356
. 328
. 740
. 717
. 580
. 52
27
52

. 376
122, 183
. 324
. 525
. 133
. 325
. 324
532, 534
536, 544
. 110
331, 542
. 339
. 324
. 654
. 544
. 327
. 484
. 271
. 277
. 141
. 194
. 106
. 110
. 117

345

346

PAGE

Gulland on glycogen, .... 924

Gumilewski on succus entericus, . 369, 556

Gumlich on ammonia in urine, . . 585

,, ,, caseinogen, . . . 137

,, ,, nucleo-proteids, . . 67

Gunsberg on gastric juice, . . . 365

,, gluten, .... 53

Giinther on animal heat, . . . 862

Giirber on crystalline albumin, . 44, 163

,, ,, oxidation in tissues, . . 895

,, ,, respiration, . . . 706, 781

,, ,, thyroid feeding, . . .944

,, ,, white blood corpuscles, . 171

Gusserow on foetal respiration, . . 731

Gyergyai on albumose in blood, . . 439

* ,, ,, proteid food, . . . 878

HAAS on proteids,
Habermann on aspartic acid,

,, ,, glutaminic acid, .

,, ,, hevulose,

,, ,, leucine and tyrosine,

,, ,, proteids,

Hadden on myxcedema,

,, ,, salivary secretion,
Haddon on milk,
Hagemann on butter, .

,, ,, respiration, .

Halm on caseinogen, .

,, ,, liver, ....
„ pepsin . . .

Haig on uric acid,
Haldane on blood gases,
,, calorimetry,
,, ,, respiration,

Hale on body temperature,
Hales on body temperature,

,, ,, respiration, .
Hall on hibernation, .
,, iron in food, .
,, ,, ,, liver, .
,, residual air,
Haller on asphyxia,

,, blood heat, .
,, chyle, ....
,, foetal respiration, .
Hallervorden on ammonia in urine,

.. ,, salts in food,

Halley on thermometer,
Halliburton on aqueous humour, .
,, ,, artificial colloids, .

. 46
29, 425
32, 426
5

. 425
32, 34
. 939
. 492
. 126
. 133
. 726, 729
. 136
. 908
. 332, 333
. 593, 598, 638
768, 776, 778, 779
. 844, 845
696, 697, 698, 699,
739, 740, 741, 742
. 857
. 786, 832
693, 741, 751
. 795, 796

blood of invertebrates,

. 750
. 745
. 827
. 287
. 731
. 907
. 883
. 785
122, 182
173, 177,
181
186,
768

82, 156, 188
. 16

cell globulin,
cellulose,
cerebro-spinal fluid,
chemical constituents of

body,
chitin, .
coagulation, .
gas pump, .
hsemocyanin,
haemoglobin,
lactic acid, .
lactoglobulin,
muscle serum,
myohffimatin.
myxcedema, .

184

. 1, 80
. 74

109, 173, 177
. 759
. 61
. 204
. 109
. 139

939

INDEX OF A UTHORS.

ion

PAGE

Halliburton on nervous tissues, . 117, 118

„ ,, micleo-proteids, 68,81,83,84,

155, 170, 181

,, ,, pancreatic casein, . . 137

,, ,, ,, extracts, . 553

,, ,, paramyosinogen, . 97, 98

,, ,, pericardial fluid, . . 183

,, ,, proteids, 41, 42, 43. 86, 118,

122, 161, 162, 872

„ ,, ,, of plasma, 161, 162,

163, 165, 166, 167
pyrocatechin, . . 606
renal tissue, ... 92
Schmidt's extract, 170, 171
secretions, . . . 783
sulphates in tissues, . 26
tetronery thrin, . . 21
thyroidectorny, . . 941
xan thine in plasma, . 160
Hall maim on body temperature, . 789, 799
Halstead on thyroid grafting, . . 942
Hambly on cutaneous respiration, . 725
Hamburger on absorption, . . 304, 307
„ blood, . . . 142, 149
,, ,, diastatic ferment of

blood, . . .160
,, ,, isotony, . .142, 271

,, ,, salts o"f lymph, . . 286

,, ,, succus entericus, . . 398

Hammarbacher on milk, . . .664
,, ,, saliva, . . .348

Hammarsten on Adamkiewicz's reaction, 47
ascitic fluid, . . 63

85, 370, 373, 374
383

bile,

bilirubin,
blood gases,

, , proteids,
casein,
caseinogen,
cholalic acid,
coagulation of blood,

enzymes, .

fseces,

fibrin,

fibrinogen, .

gastric juice,

gelatin,

hpematoporphyrin,

heemochromogen ,

helico- proteid,

keratin,

lactic acid, .

lymph gases,

mammary gland,

milk, .

mucin,

mucinogen

mucoids,

musculin,

762, 770
162, 165
. 137
. 136
. 381
168,
171

. 317
. 473
. 167

164, 170, 172
. 350, 363
70
625
256
64
73
109
783
124

129, 135, 334
62
62
63
97

nucleo-proteids, . 3, 64, 67
oxalate plasma, . .169
pancreatic extracts, . 337
pepsin, . . 330, 331
precipitation of pro-
teids, . . .392
proteids, . . 42. 49
prothrombin, . 175, 179
ptyalin, . . .329
rennet, . 134, 335, 543

PAGE

Hammarsten on rennin, . 334, 335, 544
saliva, ... 92
salivary cells, . .477
skeletins, ... 76
synovia, . . .184
vitellin, ... 69
Hammerschlag on blood, . . 143, 144
Hankin on coagulation, . . . 152
Hannover on respiratory exchange, . 781
Hanriot on diastatic ferment of blood, . 160
,, ,, gases of alimentary canal, . 730
,, ,, respiratory exchange, . 699, 708,
714, 716, 717, 718,
756, 916, 933

,, ,, spirometer, . . . 752

Hansen on proteolytic ferments, . . 51
Hardy on succus entericus, . . . 554
,, ,, white corpuscles, . . . 152
Harley on diabetes, . . . 928, 929
fat absorption, . . .459
glycosuria, .... 881
lactic acid in blood, . .160
muscular metabolism, . .915
reaction of intestinal con-
tents, . . . 452, 453
,, ,, sugar in blood, . . . 161
,, ,, suprarenals, . . . . 948
Harnack on ash-free albumin, . . 25
, , , , formula of albumin, . . 26
,, ,, muscarine .... 60
,, ,, sweat, .... 671

Harris on casein, 137

hsematin, .... 250
intestinal bacteria, . . 29
milk, . . . 125, 126, 135
pancreatic casein, . . 137

,, extracts, . . 336

reducing power of sugars, . 7
Harrison on spleen, .... 959
Hart on elastin, ... 71, 72, 430
Hartig on vegetable proteid, . . 52
Hartmann on wool-fat, . . . 675
Harvey on asphyxia, . . . .745
,, ,, respiration, .... 756
Harzer on osmosis, .... 274
Hasebrock on bacterial digestion, . . 472
,, fibrin, . . . .167
,, ,, lecithin, . . .463
,, ,, proteid digestion, . .405
Hasse on pigeons' milk, . . . 676
Hassenfratz on blood gases, . . . 757
,, ,, heat production, . . 839

Hastings on animal heat, . „ . 857, 858
Haubner on cellulose, .... 470

Hauffonmilk, 127

Hausmann on acidity of urine, . 578, 580
Haycraft on bile pigments, . . . 383
,, coagulation, 42, 43, 147, 169
,, glycogen, . . .917

,, ,, levulose, . . . .611
,, ,, reaction of blood, . .144
Hay em on blood, . . . . .150
,, ,, fetal respiration, . . 732
Heckel on cholesterin, .... 24
,, ,, lecithin, .... 21
Hedenius on keratin, . . . .73
Hedin on blood, . . . 142, 148, 149
,, ,, coagulation, . . . .178

gelatin,,
haematocrit,

72
271

1012

INDEX OF A UTHORS.

PAGE

Hedin on keratin, . . . .73
,, ,, lysine and lysatine, 33, 426, 427

,, „ testis, 93

He"don on biliary fistula, . . . 460
,, „ diabetes, . . . 928, 929
,, ,, fat absorption, . . . 460
Heffter on fatty acids of liver, . . 936
Heidenhain on absorption, . 284, 432, 433,
441, 458, 461, 462
„ bile, . . . 560, 565
,, ,, blood gases, . . . 772

coagulation, . . .147
dialysis, . . . 321
gastric fistula, . . 537
,, glands, . . 532
,, secretion, . 363, 538,
539, 540, 541

,, heat formation in nerve, 808
,, intestinal emulsion, . 448
,, ,, secretion, . 555
,, Jacobson's nerve, . . 483
,, lactic acid, . . .108
,, lymph, . . . 181
,, ,, production, 289, 290,
291, 292, 293, 295, 297,
298, 310

,, milk, . . 140, 663, 664
,, ,, secretion, . 666, 667
,, paralytic secretion, 519, 521,
522

,, pancreatic cells, . .546
fistula, . 366
,, ,, secretion, 368, 547,
548, 549,
551, 553

,, parotid saliva, . . 508
,, pepsin, . . . 331
,, pyloric secretion, . 532, 534,
535
,, reaction of nervous

tissues, . . .117
, , salivary cells, . . 477
,, nerves, . 482, 483
,, ,, secretion, 343, 344,
485, 486, 487, 495, 496,
498, 499, 500, 503, 507,
508, 509, 510, 511, 513,
514, 515, 520, 525, 527
,, salts of saliva, . . 494
,, secretion of urine, 647,648,
650, 652, 653, 654,
656, 658, 661

secretory nerves, . .526
submaxillary gland, 516,843
temperature of blood, . 829
tetanus, . . .110
trypsin, . . 338, 552
Heine on microchemical methods, . 66
Heintz on amphoteric reaction, . . 577
biliphain, . . . .382
biliverdin, .... 385
bone, ..... 77
chenocholic acid, . . . 377

fuscin, 121

milk coagulation, . . 334
,, fat, .... 133
Heller on caisson disease, . . . 737
lymph flow, .... 302
urine, . . . 605, 611, 629
uroerythrin, .... 623

Hellier on discharge of milk,
Helm on gastric fistula,
Helmholtz on calorimetry, .
gas pump,
heat loss,
,, production,
, , value, .
muscle, .
Van Helm out on digestion, .
v. Heltzl on enzymes, .
Hemala on tryptophan.
Hempel on caseinogen,
,, ,, gas analysis,
,, ,, pump, .
milk, .

808

PAGE

668
537
846
759
850
833
838
110
401
314
428
139
760
759
128

,, ,, 11HJ.IV, . . .

Henle on lymph, 287

Henneberg on fat formation, . . 934

,, ,, respiration, . . 707, 718

Henninger on peptones, . . . 400

He"nocque on haemoglobin, . . . 231

Henriques on jecorin, .... 160

,, lungs 757

Hensen on glycogen, .
» » lymph,

Henschen on renal secretion,

Hergenhahn on glycogen, .

Hering on blood gases,
„ ,, heat, .
,, ,, metabolism,
,, ,, salivary secretion,

Herissant on foetal respiration,

1'Heritier on milk,

Hermann on bile secretion, .
,, ,, electrical currents,

827,

faeces,

fibrin,

gastric fistula, .
hremoscope,
heat production,

,, value,
inogen, .
internal respiration,
intestinal secretion,
lecithin, .
muscle, .
NO in blood, .
proteids, .
proteid digestion,
red corpuscles, .
renal circulation,
residual air,
secretion of urine,
skin absorption,
,, glands, .
sweat,

tryptic digestion,
vital capacity, .
Hermans on respiration,
Hermite on diffusion, .
Heron on carbohydrate absorption,
enzymes,
fat absorption,
ptyalin,

starch digestion, .
succus entericus, .
Herringham on uric acid,
Herroun on bile, ..... 371
Herschel on spectrum, . . . 208
Herter on blood gases, . . . .777

15, 397, 922
. 182, 783
. 654
. 918
. 761
. 828
870
529
. 731
. 128
. 567
. 517, 519,
682, 683, 684
. 473
. 167
. 537
. 210
. 841
. 834
. 110
782
556
21

. 911
. 238, 241
. 46
. 405
. 156, 189
. 642

749, 750, 752
. 646, 650
. 688
. 673, 683
. 671
. 416
. 751, 752
. 742
. 275
. 435
397, 399
. 452
. 328
394, 397
. 398
595

INDEX OF A UTHORS.

1013

PAGE

Herter on pancreatic secretion, . . 368

,, ,, respiratory exchange, . . 694

,, ,, saliva, ... . . 347, 348

Herth on proteid digestion, . . . 400

Hertwig on body temperature, . .816

Herz on animal amyloid, . . .133

Herzen on gastric juice, . . .349

Herzfeld on maltodextrin, . . . 396

Herzog on respiratory exchange, . . 848

,, ,, skin absorption, . . . 688

Hess on heat production, . . . 834

Hesse on cholesterin, . . . .24

,, ,, expired air, .... 755

,, ,, lactose, 12

Hester on uric acid, .... 594
Hewlett on fractional coagulation, . 43
,, ,, lactoglobulin, . . . 139
Hewson on blood, . . . .145
chyle, . . . .287
coagulable lymph, . . 164
coagulation, . . . 168
lymphatics, . . . 303
red corpuscles, . . .188
Heynsius on ash-free albumin, . . 25

,, , bile, 390

,, , bilicyanin, . . . 386

Higgins on respiration, . * . 735

Hill on blood gases, . 761, 763, 764, 765
body temperature, 808, 826, 830, 855

808
. 759
. 795
841, 911

841

517, 843,

839
. 474
. 725
. 846
838, 847
7

. 875

. 122

. 913

594

761

cerebral circulation,
gas pump,
hibernation,
muscle,

respiratory exchange,
salivary glands,
Hillersohn on specific heat, .
Hinterberger on excretin,
Hippocrates on skin absorption, .
Hirn on calorimetry,

,, ,, heat production,
Hirschberger on mannose,
Hirschfeld on diet,

,, ,, fuscin, .

,, ,, muscular metabolism

,, ,, uric acid,

Hirschler on lymphatic glands,

,, ,, spleen, .

,, ,, tryptic digestion,

Hirschmann on blood gases,

His on cornea, ....

Hitzig on body heat, .

Hjort on vegetable ferments,

Hlasivvetz on aspartic acid, .

,, ,, glutaminic acid,

,, ,, leucine and tyrosine,

,, ,, levulose, .

,, ,, proteids, .

Hobday on body temperature, 790, 791, 792,

803, 805, 807, 812, 821, 826

Hochhaus on iron in liver, ... 86

Hoessliu on respiration, . . 720, 732

van t'Hoff on osmosis, 265, 266, 284, 650, 651

,, ,, ,, stereochemical isomerides, 106

Hoffa on thyroidectomy, . * . 939

Hofiemann on creatin in urine, . . 598

Holfmann on body temperature, . .806

,, ,, endosmotic equivalent, . 274

,, ,, hippuric acid, . . . 893

,, liver fat, . . . .936

,, ,, proteid quotient, . . 162

87
427
762
. 121
. 863
. 55
29, 425
32, 426
. 425
5
32, 34

PAGE
41

688
921
424
742
560
933
729
182
. 673
. 595
. 276
. 43
. 439
. 900
. 369
. 70
. 42
. 471
. 316
. 432
. 356
. 430
. 70
. 881
. 12
611, 665
. 400
. 946
439, 440,
441

proteids, ... 32
proteolytic ferments, . 51
pus cells, ... 83
salivary secretion, . 343, 347,
489, 491

starch, .... 14
sulphocyanate of saliva, . 345
. 940
679, 680
• 785
. 90
765, 779
. 537
.167
. 733
. 692
. 785
789, 799

Hoffmann on proteids, .

,, ,, skin absorption,
,, ,, sugar formation,
,, ,, tyrosine, .
Hoffmann- Wellenhof on respiration,
Hofmann on bile secretion, .
,, ,, fat formation, .
,, ,, gases of alimentary canal,

,, lymph, .
,, ,, sweat,
Hofmeier on uric acid, .
Hofmeister on adsorption,

,, ,, albumin crystals, .
albumose in blood,
assimilation, .
bile,

collagen,
colloids,
digestion,
enzymes,

gastric absorption, .
, , digestion, .
gelatin,

,, peptones, .
glycosuria,
lactose, .

,, in urine,
peptones,
pituitary body,
proteid absorption,

,, ,, thyroidectomy,

Hogyes on sweat secretion, .
Holloway on thermometer, .
Holm on suprarenals, ..
Holmgren on blood gases, .
,, ,, gastric fistula,
Holzmann on fibrin, . .
Home on foetal respiration, .
Hook on respiration, ..
,, ,, thermometer, .

Hooper on body temperature,
Hopkins on pigments of fseces,
,, ,, precipitation by

salts,

,, ,, uric acid, .
,, ,, urine,
,, ,, urobilin, .
,, ,, urorosein, .
Hoppe-Seyler on adipocere, .
,, ,, alcohol,

neutral

. 42
. 592
. 570

621, 622, 629
. 628
. 20
. 882

aqueous humour, . 183
arterin and phlebin, . 190,
191, 192, 193, 196
bile, . 370, 374, 376, 389,
390, 560, 562, 566
blood, . 147, 148, 160
corpuscles, 147, 155,
156

,, crystals, . 203, 208

,, gases, . 766, 772

,, spectrum, . .208

body temperature, 790, 820

ioi4

INDEX OF A UTHORS.

Hoppe-Seyler on bone,

PAGE

111, 112

, , j j

burns,

.

728

» »

cartilage, .

.

113

5) ))

casein,

,

125

5> )

cellulose, .

t

471

)) )

cerebrins, .

.

119

33 )

chitosan, .

75

5 J

cholesterin,

159,

391

chyle,

183

}

CO in blood,

237,

240

> 3

collagen, .

,

70

3 3

creatinine .

f

101

> )

crystallin, .

123

3 3

diabetes, .

927

J J J

digestion of cane sugar,

398

> 5>

enamel,

112

3 3 3

excretion of lime sa

Jtsj

635

, ,

fat absorption, .

.

452

} }

fats of blood,

,

159

J J

filtration, .

.

282

, ,

ferments, .

313,

319

> 3

gas pump, .

.

759

, j

gelatin,

.

70

, ,

glycogen of blood,

.

158

1 >

hfematin, .

252,

254

9 y

haematinometer,

§

210

> l>

hsematoporphyrin,

259

> »

haemin,

.

253

> 5>

haemochromogen,

243,

250,

255,

256,

257

» > 5>

haemoglobin,

152,

185,

186, 189, 195,

198,

199,

206, 208, 225,

229,

232,

241, 242, 258,

767,

768

Jl >5

humous substances, .

122

PAGE

Horbaczewski on uric acid, 67, 586, 587, 594,

596, 909, 910
,, ,, xan thine bases, . . 911

lactic acid, . . 109
lecithin, ... 21
liver, .... 86
metabolism, . . 898
methaemoglobin, 244, 245,
246

milk, . . 126, 129

muscle, . . 95, 103
nuclei, ... 81
uucleins, . . 65, 66, 81
oxyhaemoglobin, 188, 199,
200, 205

pancreatic secretion, . 368
parahaemoglobin, . 207
pepsin, . . . 330
protagon, . . 118, 156
Proteide, . . .428
proteids, . . 41, 46, 65
pus cells, . . .83
respiration, 695, 725, 731,
740

sebum, . . . 674
secretion of urine, . 650
spleen, ... 87
sulpho-methaemoglobin, 249
Teichmann's crystals, . 252
urea, .... 907
urinary pigment, . 388
vegetable globulins, . 51
vitellin, . . 53, 69
HorbaczeAVski on elastin, . 32, 71, 72, 430
,, keratin, . . .73
,, leucocytosis, . 67, 594
,, nuclein, . . . 879
,, proteids, . . .32

Home on coagulation,

Hornemann on levulose,

Horsley on myxcedema,

,, ,, spinal injuries,

,, ,, thyroidectomy,

170
5

. 862

939, 940, 941,
942, 943

Horton-Smith on peptonised milk, . 136

Horvath on animal heat, . . . 822

,, ,, hibernation, 795, 796, 797, 823

v. Hosslin on iron of food, . . . 886

Houlston on coagulable lymph, . .164

^Jowell on blood proteids, . . 162, 163

Huber on body temperature, . .793

,, ,, fibrin, ..... 405

,, ,, liver ferment, . . . 926

,, ,, proteid absorption, . . 437

,, ,, salivary nerves, . . . 525

Hubrecht on haemoglobin, . . .187

Hiifner on air chamber of egg, . . 735

,, ,, bile acids, . . . .374

,, ,, blood crystals, . . . 233

,, „ „ gases, . . 766, 769

,, ,, haemoglobin, 185, 192, 193, 195,

196, 197, 201, 202, 229, 231,

232, 237, 241, 767, 768, 775

,, ,, leu cine, . . .29, 422

,, ,, oxygen of blood, . 234,236,766

,, ,, ,, ,, methaemoglobin, . 245,

247, 248

,, ,, oxyhaemoglobin, . 192, 199, 200,
203, 205, 206, 223

,, ,, respiration, . . 735, 778, 779

,, ,, skin absorption, . . .686

,, ,, spectrophotometer, 216, 217, 218,

219, 220, 221, 222

,, ,, spectrophotometric constants, 224,

234, 239

,, ,, spectrum of blood, . . 209
,, ,, sAvimming bladder, . . 705
,, ,, trypsin, . . . 337, 340
,, ,, tyrosine, .... 423

,, ,, urea, 584

Huizinga on glycogen, . . . .15
Hulse on respiration of foetus, . . 731
Hultgren on diet, .... 877

,, „ heat values, . . 874, 875
Humboldt on animal heat, . . . 840
„ „ respiration, . . 699, 704
v. Humnicki on cholesterin, . . .24
Hundeshagen on lecithin, . . .22
Hunefeld on blood of earthworm, . . 186
Hunter on animal heat, 788, 791, 792, 793,
803, 810, 817, 823, 826, 849

bile pigments,
cadaverine, .
foetal respiration,
hibernation,
lymph,
pigeons' milk,
polycythaemia,
Huppert on bile, .

,, ,, body temperature,
,, ,, glycogen, .

,, of blood,
,, ,, proteids, .
Huppert-Neubauer on urine,
Hurthle on cholesterin,

287,

563
59
731

796
303
676
. 143
386, 563
. 867
14, 15
. 158
41, 45
61
24, 159

INDEX OF A UTHORS.

1015

PAGE

Hiirthle on thyroid, . . . .938
Husemann on carrotin, . . 20, 21

Husson on haematin, .... 250
Hutchinson on respiration, 747, 748, 749, 750,

751, 752

,, ,, salivary secretion, . 492

,, ,, spinal injury, . . 860

Hutchison on reaction of blood, . .144

,, ,, thyroid, . . 89, 938

IDE on antipeptone,
,, ,, carnic acid,

Inoko on hsemoglobin, .

Irisawa on acidity of organs,
,, ,, lactic acid in blood,
,, ,, sarcolactic acid, .

Irsal on thyroid feeding,

Isbert on saliva, ....

JACKSON on residual air,
,, ,, respiration,
Jacobsen on jecorin in blood,
Jacobson on bile,

,, ,, body temperature,
,, ,, lecithin, .
,, ,, residual air,
Jacobsthal on ripening of cheese, .
Jacoby on parathyroids,

,, ,, thyroidectomy,
Jacubowitsch on ptyalin,

,, ,, saliva,

Jaderholm on CO-hrematin,

,, ,, hsemochromogen,
Jaeger on body temperature, 789,
Jaffe on amido-acids in urine,
bilicyanin,
creatinine,
glycuronic acid,
hsematoidiii,

indoxyl, ....
ornithin, ....
spectrum of bile pigments,
urobilin, . . 388,

Jakobsen on swimming bladder, .
Jakowski on bacterial digestion, .
v. Jaksch on alcaptonuria, .

,, alkalinity of blood, .
,, blood plasma, .
,, dextrose in urine,
, , fatty acids of urine, .
,, gastric juice, .
,, indoxyl in urine,
,, melanin, .
,, nuclein, .
,, peptone in spleen,
,, uric acid, .
Jam in on skin absorption, .
Jankau on bile, ....
Jankowski on lymph, .
Jansen on osmotic pressure,
Janssen on body temperature,
Jaquet on haemoglobin, 27, 199, 200,

Jastrowitz on pentose,
Jeffray on foetal respiration,
Jeffreys on residual air,
Jeffries on alkalinity of blood,
Jernstrom on mucinogen,
Jessen on digestion,
,, ,, respiration, .

420
103
198
108
159
106
944
328

. 750

. 742

. 160

371, 374

855, 856

21

749, 750

. 933

. 940

. 943

. 329

347, 348

. 257

256, 258

799, 801

. 602

. 386

. 599

5

. 384

. 627

. 33

. 386

620, 622

. 705

. 464

. 607

. 144

. 160

. 608

. 615

. 366

. 628

. 122

. 65

. 88

. 592

. 685

561, 564

296, 298

. 276

. 822

201, 202,

203, 768

3

. 731

. 750

. 144

62

. 333
. 742

PAGE

Joerg on foetal respiration, . . .731

Johannsen on gluten, .... 53

Johannson on inanition, . . . 891

,, ,, respiratory exchange, 712, 718

John on ptyalin, ..... 329

Johnson on creatinine, 100, 101, 598, 599

,, ,, respiration of nitrogen, . 739

,, ,, urine, . . . 608, 609

Jolin on bile, 376

Jolly on osmosis, .... 274
Jolyet on respiration, 698, 699, 700, 702, 703
Jones on blood, 143

,, ,, osmotic pressure, . . . 269
de Jonge on tail-gland, . . . 675
Joseph on tail-gland, .... 675
Joubert on gases of alimentary canal, . 730
Joule on heat of combustion, . . 833
Jourdanet on mountain sickness, . . 738
Jousset on body temperature, 801, 802, 811,

812, 813

Jtidell on lecithin, .... 21
Jungfleisch on coefficient of distribution , 354
Juretschke on milk fat, . . .664
Jiirgensen on body temperature, 789, 799, 800,
802, 804, 806, 809, 810, 818, 819
Jurin on tidal air, . . . .748

,, ,, vital capacity, . . .751

KAHN on skin absorption, .
Kamocki on Harderian gland,
Kaneda on fat formation,
Kanthack on snake venom, .

,, ,, white corpuscles,

Kast on chlorides of urine, .

,, ,, sweat, ....
Katz on muscle ash,
Katzenstein on muscular metabolism
,, ,, respiratory exchange,

Kauch on glycogen,

,, ,, liver cholesterin, .
Kauder on blood proteids, .

,, ,, globulins, .
Kaufmann on bile,

,, blood-gases, .
,, CO 2 of muscle,
,, dextrose in blood, .
,, diabetes,
,, glycogen in blood, .
,, muscle, .

,, respiratory exchange,
,, urea formation,
,, ,, in muscles,
Kayser on diet, ....
Kehrer on milk, ....
Kekule on amyloid substance,
Kellner on proteid food,
Kemmerich on caseinogen, .
,, ,, creatinine,

,, ,, fat formation,

„ milk, .
,, ,, ,, fat,

Kenchel on salivary glands, .
Kendall on sweat,
Khigine on gastric secretion,
Kiliani on levulose,
Kinkel on assimilation of iron,
Kirchner on milk secretion, .
Kirk on alcapton,

,, ,, uroleucic acid,
Kinvan on specific heat,

688, 690
. 675
. 935
. 56
. 152
. 634
. 672
. 109
, . 912
. 716
. 917
. 564
. 163
. 42
. 369
763, 764
. 912
. 915
. 927
158, 915
. 841
. 841
. 908
. 103
. 876
126
74
877
140
101
933
130
664
512
676
546
5

886
664
607
606
838

125,

ioi6

INDEX OF A UTHORS.

Kisch on proteids,

Kisser on proteose.

Kite on respiration,

KjeldaH on nitrogen estimation,

,, ptyalin, .

Klapp on cutaneous respiration,
Klebs on intraglobular crystallisation,
Klecki on intestinal secretion,
Klein on admaxillary gland,
Klemensiewicz on gastric fistula,

,, ,, tymph absorption,

„ ., pepsin,

,, ,, pyloric secretion,

Klemperer on diet,
Klug on cutaneous respiration,
muscular metabolism,
pepsin, .
pyloric secretion,

v. Knierem on amido-acids in blood
,, ammonia in urine,
, , aspartic acid,
,, cellulose,
Knop on urea,
Kobert on hsemoglobin, 24

,, ,, proteid poisons, .
Kobler on urea,
Koch on foetal respiration,

,, ,, gastric juice, .
Kochs on hippuric acid,

,, ,, residual air, .
Kocker on myxoedema, .
Koefoed on butter,
Koeppe on blood, .

,, ,, hsematocrit, .

,, ,, hydrochloric acid oi

,, ,, muscarin,

,, ,, osmotic pressure, .

,, ,, solutions,
Kohler 011 body temperature,
Kohlrausch on electrical conductivity,
Kolbe on taurine,

,, ,, trypsin,
van d. Kolk on blood gases,
Kolliker on fish slime, .
,, ,, intraglobular cr_
,, ,, leucine and tyrosine,
Konig on colostrum,

,, ,, diet,

,, ,, foodstuffs,

,, ,, milk,

,, ,, proteids,
Konigsberger on renal nerves,
Konowaloff on gastric juice, .
Kopp on thyroidectomy,
Koppe on muscarine,
Korner on body temperature,
Korolkow on salivary nerves,
Korowin on amylopsin,

,, ,, ptyalin,
Koschlakoff on bile salts,
Kossel on adenyl, .

,, ,, cerebrins,

,, ,, gas-pump, .

,, ,, muscle,

,, ,, notochord,

,, ,, nuclei, .

, , , , nucleic acid, .

,, ,, nuclein,

,, ,, nucleo-histon,

,, ,, oxyhsemoglobin,

PAGE

PAGE

41

Kossel on phrenosine, ....

120

.

. 51

protagon, . . . 118,

119

748,

749, 751

protamine, ....

93

i, .

580, 581

pseudo-nuclein,

65

. 327

saponification,

19

,

. 725

testis, .....

93

satioi

i, . 191

thymic acid, ....

67

. 557

Kossler on gastric juice,

366

,

476, 479

Kossmann on

tail gland,

675

"•, •

. 537

Koster 011 whey proteid,

135

>tion,

. 306

Kostiurin on amyloid substance, .

47

.

. 331

Kowalewsky on gas tensions,

784

ion,

532, 535
. 876

,, ,, respiratory exchange, .
Kowaski on muscle, ....

699
103

. 724

Kft,mm on urochrome,

619

,

. 916

Krasser on proteids, ....

48

. 331

535, 536

Kratschmer on glycogenesis,
Krauch on proteolytic ferments,

926
51

lood,

. 899

Kraus on acidity of blood,

145

e,

. 907

?J

,, alkalinity of blood,

145

. 425

,, ,, glycolytic ferment of blood, .

161

470,

471, 881

,, ,, grape sugar,

880

.

. 584

Krause on skin absorption, .

686

245,

248, 249
. 55

Krauss on muscle glycogen, .
Krawkow on amyloid substance, .

105
74

. 585

74

]

. 733

"

u

oroteids, ....

64

p

. 364

v. Krehl on fat absorption, . . 451,

455

,

. 893

,, ,, intestinal emulsion, .

448

.

. 750

,, ,, suppuration,

84

. 939

Kretschy on gastric fistula, .

537

.

. 133

Kretzschmar on reducing power of proto-

. 142

plasm, ......

39

,

. 271

Kreusler on aspartic acid,

425

;oma<

jh, 276

j )

. , glutaminic acid, . 32,

426

60, 513

,, keratin, ....

73

. 272

Krieger on body temperature,

801

.

. 278

Krimer on blood heat, ....

827

.

. 822

Kroger on pancreatic diastase,

339

tivifr

r, . 261

Krolow on Brunner's glands,

554

.

. 379

Kronecker on

body heat,

787

.

. 415

5 > >'

skin temperature, .

829

. 758

Kriiger on alloxuric substances, 67, 597,

598

t

. 676

calcium in liver, .

87

llisat

ion, 191

gelatin, ....

70

. 438

lysine, .....

426

,

. 129

phospho-carnic acid,

104

,

873, 877

proteids, ....

29

p

. 873

saponification,

19

129,

130, 131

spleen, ....

87

.

41

sulphur in proteids,

26

,

. 644

Krukenberg on JEthalium, .

81

,

. 350

bilirubin,

389

t

. 941

biuret reaction,

49

.

. 60

carnine,

102

. 829

chitin, ....

74

. 525

chlorocruorin,

61

.

. 336

chondroitin-sulphuric acid,

114

. 327

conchiolin,

76

(

. 378

Ehrlich's test,

384

. 67

electrical organs, .

110

. 120

fuscin, ....

122

. 759

98, 99

glycogen,
hepato-pancreas, .

15
336

.

. 113

hyalogens, . . 63

,64

. 81

keratinoses, .

73

.

66, 67

lipochrome of blood,

159

3, 64, 65

proteids,

403

.

. 68

saliva, ....

327

.

199, 200

serum lutein,

21

INDEX OF AUTHORS.

1017

Krukenberg on tetronerythrin,
„ ,, tryptophan, .

,, ,, urea in muscle,

Krummacher on metabolism,
Kvliss on spectro-photometry,
Kuczynski on Brunner's glands,
Kudrewetzky on pancreatic secretion,
Kuhn on aqueous humour, .
milk fat,

PAGE

. 21
. 428
. 103
. 913
216, 218
. 554
549
183
664

Kiihne on albumoses, . 410, 411, 412, 413
amyloid substance, . . 74
antialbumid, . . 403, 406

antialbuminate, . . . 402
antialbumose, . . . 407
antipeptone, . . . 420

aqueous humour, . . .122
bacterial decomposition, . 466
bile pigments, . . . 389
blood, . . . .141, 155
chromophanes, ... 20
collagen, .... 430
crystallin, .... 123
diabetes, . . . .926
elastin, .... 72

emulsions, .... 445
enzymes, 312, 320, 340, 341, 517
glycogen, . . . .15
haemoglobin, 186, 197, 206, 207, 232
,, crystals, . . 232
hemialbumose, . 408, 409, 4]0

indol 466

intraglobular crystallisation, . 191
isolation of enzymes, . .314
keratin, .... 73
lactic acid, . . . 108, 109
leucine and tyrosine, 421, 423, 425,

437
lipochromes, .... 21

milk, 130

Millon's reaction, ... 47
muscle plasma, ... 96
myosin, .... 97
neiirokeratin, . . 72, 117
oxyhsemoglobin, . . . 244
pancreas, . . . .547
pancreatic casein, . . .137
,, juice, . . . 448
,, secretion, . . 551
paraglobulin, . . . 163
pepsin, .... 333

peptones, .... 25
proteids, ... 42, 46
proteid digestion, . 405, 416, 438
proteoses, . . . .45
red corpuscles, . . .155
rhodopsin, . . . .122
saliva, .... 327, 503
trypsin, 315, 317, 337, 338, 415, 552
. 428
. 927
. 349

918, 919,920, 926
. 11
. 129
104

tryptophan,
Ki z on diabetes,

gastric juice, .
glycogen, 15, 397
isomaltose,
milk gases,
muscle glycogen,
pentose, .
saliva,

. 346, 485, 784

starch, . . . . .14
,, digestion, . . . 397
suprarenals, .... 90

Kiilz on urine, . . .
Kumagawa on diet, . .
,, ,, fat formation,

,, ,, proteid food, .

Kunde on blood crystals, .
Kunkel on bile,

,, ,, ,, salts, ..

,, ,, body temperature,

,, ,, sulphur of urine, .

,, ,, taurine, ..
Kuuz on pus, ...
Kupffer on respiration, . . "
Kurrer on body temperature,
Kussmaul on body temperature,
Kiissner on animal heat, .
Kytinanov on gastric juice, .

829,

PAGE
.611
.877
. 935
.877

204, 208

563

. 392

830,831
. 632
. 901
. 84
. 780
.814

855, 856
. 863
.537

v. LAAE, on keratin, . . . .73

Laborde on acid of gastric juice, . . 354

Lachowitz on parahsemoglobin, . .207

Ladenberg on cadaverine, . . .60

,, ,, Charcot's crystals, . . 94

Lafont on lacteals, .... 302

,, ,, respiration, . . . 753

Lagrange on animal heat, . . . 839

,, ,, respiration, . . . 757

Lahousse on peptone blood, . . .177

Lallemand on body temperature, . 820, 821

Lamansky on intestinal secretion, . 555

Lambert on glycogenesis, . . . 926

,, ,, light absorption, . . 214

Landenbach on spleen, .... 960

Landgren on inanition, . . . 891

Landois on alkalinity of blood, . . 144

,, ,, animal heat, . . . 863

Landre on body heat, . . . 855, 856

Landwehr on animal gum, 16, 62, 124, 133,

613, 665

,, ,, nmcin, .... 63
,, ,, nucleo-proteid of bile, . 371
,, ,, 'synovia, . . . .184
Lane on gastric juice, .... 540
v. Lang on haemoglobin, . .204, 205
Lang on taurine, . . . . .379
Langaard on milk, . . . .138
Lange on blood, . . . . .149
,, ,, cutaneous respiration, . . 726
Langemeyer on muscular metabolism, . 915
Langendorff on diabetes, . . 928, 929
„ ,, nervous tissues, . .117

,, ,, salivary nerves, . . 483

Langer on milk secretion, . . . 666
Langhans on thyroidectomy. . 939, 941
Langley on antilytic secretion, . . 522
augmented secretion, . . 497
demilune cells, . . . 478
gastric cells, . . 531,534
,, digestion. . . 534

liver fat, . ' . . 935, 936
„ glycogen, . . 918, 935
pepsin, 332, 404, 542, 543, 544
ptyalin, . . . 329, 330
pyloric cells, . . 532, 536
rennin, .... 335
saliva, 344, 494, 496, 499, 500, 503,
504, 509, 510

salivary glands, . 475, 485, 486,
488, 505, 513, 514, 515, 520,
521, 522, 523, 524, 527

ioi8

INDEX OF AUTHORS.

PAGE

Langley on salivary nerves, 480, 483, 484, 506

,, ,, sweat nerves, . . .677

,, ,, trypsin, . . . 338, 552

Langlois on heat production, . 846, 853

,, ,, suprarenals, 949,957,958,959

Lankester on chlorocruorin, ... 61

,, ,, haemoglobin, 186, 187, 209, 242,

249

Lannois on intestinal secretion, . . 556

,, ,, skin absorption, . . . 687

Lantergren on diet, . , . .877

,, ,, heat values, . . 874, 875

,, ,, respiratory exchange, . 718

Lanz on thyroid feeding, . . .944

Lapicque on iron in milk, . . .86

Laplace on calorimetry, . . .844

,, ,, respiration, . . . 693, 694

Lappe on lactose, . . . . .399

Laptschinsky on lens, . . . .123

Laroche on respiration, . . . 704

,, ,, swimming bladder, . . 705

Laschkewitsch on skin varnishing, . 728

Lassaigne on saliva, .... 347

Lassar on alkalinity of blood, . . 144

,, ,, lymph, . . . .298

,, ,, skin absorption, . . . 690

Lassar-Cohn on cholalic acid, . . 381

,, ,, choleic acid, . . 381

,, ,, fellicacid, . . .373

Latham on proteids, . . . 39, 109

Latschenberger on absorption, . . 437

,, ,, bile pigments, . . 389

Latschinoff on cholalic acid, . . 380

,, ,, choleic acid, . . 373, 381

,, , , taurocholic acid, . . 455

Laulanie on thyroidectomy, . . . 943

de Lauras on skin absorption, . . 685

Lavdowsky on orbital gland, . . 478

,, ,, salivary cells, . .485

Laves on milk fat, . . . .133

,, ,, muscle glycogen, . . .105

Lavoisier on animal heat, 826, 832, 839, 846,

847

,, ,, calorimetry, . . . 844
,, ,, cutaneous respiration, 725, 726
,, ,, oxygen, . . . .736
,, ,, respiration, 693, 694, 712, 715,
718, 735, 754, 757, 780
,, ,, ,, of hydrogen, . 739

Lawes on fat formation, . 931, 932, 934
Lazarus-Barlow on absorption,
Lea on digestion, . . . 321
ferments, ....
haemochromogen,
leucine and tyrosine,
pancreas, ....
ptyalin, ....
rennin, ....
urine, ....
Leared on sulphocyauate of saliva,

,, ,, sulphur of urine, .
Leathes on diuretics,
,, ,, lymph,
,, ,, paramucin,
,, ,, venous absorption,
Lebedeff on fat formation,
Leber on filtration,
Leclarc on foetal respiration,
Leclerc on sweat, .
Ledderhose 011 chitin, .

305, 306
394, 434
313, 320
. 256
. 438
. 547
. 328
. 334
. 583
. 345
. 632
. 648

294, 308, 310
. 63
303, 304
934, 936
283, 652
. 731
. 673
74, 75

931,

PAGE

Lefevre on body temperature, . .818
Legal on acetone, . . . . .616

,, ,, indol, 469

Legallois on animal heat, . 792, 857, 858

,, ,, asphyxia, . . . 745

,, ,, respiratory exchange, . 694

Lehmann on adipocere, . . 20, 933

,, ,, alkalinity of blood, . . 145

„ blood, . . . .145

,, ,, ,, crystals, . . 204, 244

,, body temperature, . 823,863

,, ,, caseinogen, . . 139, 140

,, ,, copper in food, . . 79

,, ,, gastric juice, . . . 352

,, ,, haemoglobin, . . 204, 206

,, ,, inanition, . . . 891

,, ,, inosite, .... 105

,, ,, invert sugar, . . . 398

,, ,, lactic acid in muscle, . 99

„ milk, . . . 128, 663

,, ,, muscle, .... 100

,, ,, proteid food, . . .878

,, ,, respiration, 711, 712, 715, 717,

718, 719, 726, 742

„ saliva, . . . 343, 347

,, ,, spectrum, . . . 208

Leichtenstern on thyroidectomy, . . 943

Lemaire on isomaltose. ... 12

,, ,, lactose, '. . . .12

Lemberger on thyroid feeding, . . 944

Lemcke on body temperature, . .822

Lentner on milk, ..... 131

Lenz on calcium in liver, ... 87

,, ,, diffusion, .... 263

Leo on diabetic urine, .... 6

,, ,, fat formation, . . . .934

,, ,, gastric juice, .... 366

Leon. See Mendus de Leon.

Leonhardt on pituitary body, . . 946

,, ,, thyroidectomy, . .940

Lupine on body temperature, . . 804

„ „ diabetes, . . . 928, 929

» » glycolytic ferment of blood, . 161

,, ,, intestinal secretion, . .556

,, ,, secretion of saliva, . . 485

,, ,, sugar in blood, . . 160, 161

Lerch on milk fat, . . . .133

Lesser on burns, ..... 728

Letellier on respiratory exchange, 711, 720,

853

Leube on chlorides of urine, . . .634

,, ,, digestion of starch, . . 393

,, ,, gastric juice, .... 349

,, ,, glycogen, .... 14

,, ,, succus entericus, . . 369, 398

,, ,, urine, . . . 582, 583, 604

Leubuscher on gastric secretion, . . 540

Leuchs on saliva, ..... 327

Levenne on diabetes, . . . 922

Levick on hyperpyrexia, . . . 823

Levy on my ohae matin, . . . .99

,, ,, skin secretion, . . . 679

,, ,, sweat secretion, . 678, 679, 681

Lewaschew 011 bile secretion, . 568, 569

,, ,, pancreatic secretion, . 549

Lewin on fat absorption, . . 460, 462

,, ,, intestinal emulsion, . . 448

,, ,, pancreatic fistula, . . . 366

Lewith on colloids, . . . .42

Lewizky 011 animal heat, . . . 862

INDEX OF AUTHORS.

1019

PAGE

Leyden on calorimetry, . . .846
heat production, . . . 847
respiration, . . 698, 707, 718
Leydig on anal glands, .... 670
intestinal respiration, . .730
sebaceous glands, . . . 676
skin secretion, . . . 673
suprarenals, . . . 957
Liciitenfels on body temperature, . 789, 799,

802, 820, 821

Liebe on respiratory exchange, . . 702
Lieben on lutein, ..... 20
Lieberkiihn on albumin, ... 26
,, ,, taurocholic acid, . . 375
Liebermann on cholesterin, . . .23
dextran, . . .16
fats, .... 20
kidney, ... 92
lecith-albumins, . 69, 658
nuclein, ... 65
proteids, ... 48
Liebermeister on body temperature, . 789,
799, 800, 802, 806, 809,
810, 818, 819, 822, 825
,, ,, calorimetry, . . 846

,, ,, respiratory exchange, . 695,

711, 712

,, ,, thermometer, . . 785

Liebig on animal heat, 828, 829, 832, 840, 846

blood gases,
creatinine, .
nitration,
gelatin,
inosinic acid,
legumin,
metabolism, .
proteids,
respiration, .
sarcolactic acid,
tyros in e,
urea estimation,

. 765
. 598
. 280
. 96
. 103
51

893, 898, 912
30

. 738, 781

. 106

. 423

584

Lieblein on urine, . . . .577
Liebreich on cerebrins, . . .120

,, ,, haemoglobin, . . . 242
,, ,, lanoline, .... 675
,, ,, protagon, . . . 21, 118
,, ,, vernix caseosa, . . 675

Lietsch on gastric juice, . . .364
Likiernik on leucine, . . . 29, 422
Lilienfeld on blood platelets, . . 156
coagulation, . 167, 172, 173
fibrinogen, . . .164
nucleo-histon, ... 68
,, proteid of blood, . 170
phosphorus, ... 84
proteids, . . . .38
thrombosin, . . .165
thymus cells, ... 82
v. Limbeck on alkalinity of blood, . 144
,, ,, diuresis, . . 295, 648
Limbourg on blood, . . . .167
,, ,, heat coagulation, . . 42
Limpricht on inosite, . . . .105
,, ,, leucine, .... 421
,, ,, protic acid, . . .103
,, ,, taurine, . . . .103
Lindberger on trypsin, . . . 338

Lindeman on pentoses, ... 3

Linder on osmotic pressure, . . . 272
,, ,, solutions, .... 262

PAGE

Lindvall on horn, 73

. 814
. 258
. 687
. 328
. 742
29, 423
. 807
. 179
. 711
730, 731

Lining on body temperature,
Linossier on NO-hsemochromogen,

,, ,, skin absorption,
Lintner on saliva,
Lipari on respiration, .
Lipp on tyrosine, ....
Liska on body temperature, .
Lister on coagulation, .
Litten on respiratory exchange,
Litzmann on foetal respiration,
Liversedge on diastatic zymogen of pan-

creas, ....
Livingstone on body temperature,
Loch on Jacobson's nerve, .
,, ,, salivary secretion, .
Locke on coagulation, ..
Loeb on muscular metabolism,

,, ,, salivary secretion, .
Loebisch on tendon, ..
Loew on albumin, ..
formose, ..

nucleins, ..
proteid constitution,
,, digestion, .
proteolytic secretions,
urea,

xanthoproteic reaction,
Loewy n alkalinity of blood, .
animal heat, .

filtration,

552

. 811
. 483
. 484
. 97
. 916
483, 484
62, 63
. 26
. 5
. 65
. 38
. 400
. 330
33

. 47
144,145
819, 842
821, 283

respiration, . 699, 708, 712, 715,
717, 719, 720, 738, 755, 774
Lohmeyer on aqueous humour, . 122, 183
Lohrer on ammonia in urine, . . 907
Loiseau on raffinose, . . . .12
Lombard on body temperature, . . 808
Long on diffusion, .... 263
Lonnberg on urine, . . . .85
Loomis on osmotic pressure, . . . 269
Lorain on animal heat, . 786, 825, 832

Lorenz on respiratory exchange, . . 718
Lortet on body temperature, . 806, 807
Lossen on egg-white, .... 33
,, ,, respiration, . . . 698, 755
Lossnitzer on pancreatic enzymes, . 340
Lovibond on colour measurement, . 152
Lowenhardt on body temperature, . 822
Lower on respiration, . . . .756
Lowit on blood platelets, . . . 156
,, ,, coagulation, .... 180
» » polycythaemia, . . 143, 152
Loye on gastric secretion, . . . 540
,, ,, respiration, .... 742
Lubavin on dyspeptone, . . 428, 429
,, ,, nuclein, .... 65
,, ,, proteid decomposition, . 403
de Lucca on cellulose, . . . .16
Luchsinger on electrical currents, . . 682
,, ,, glycogen, . 104, 917, 919
,, sweat, . . 671, 676, 677,
678, 679, 680

Luciani on inanition, .
Liicke on hydatid cysts,

,, ,, pus,

Liideking on osmotic pressure,
Ludwig on albumoses, .

,, ,, animal heat,

,, ,, blood gases,

891
. 63

. 84

. 272

. .440

833, 843, 846,

850, 852

. 762, 765

1020

INDEX OF A UTHORS.

PAGE

Ludvvig on collagen, .... 430

,, ,, dermoid cysts, . . . 675

,, ,, digestion and absorption, . 442

,, ,, haemoglobin, . . 230, 231

,, „ heat value, .... 838

,, lymph flow, . . 300, 310

,, ,, ,, pressure, . . . 299

,, ,, production, . 287, 288,

289, 290, 293

„ muscle, . . . 911, 912

,, ,, osmosis, .... 275

,, ,, pancreatic secretion, . . 547

,, ,, respiration, . . . 759, 782

,, saliva, . . . 498, 499

,, ,, salivary glands, . . 482,494,

511, 516, 896

,, ,, „ nerves, . . .482

,, ,, secretion of urine, . 640, 641,

647, 649, 650, 651,

652, 654, 656, 658

,, ,, uric acid, .... 592

Luff on uric acid, .... 592

Lukjanow on bile secretion, . . . 565

,, ,, bone, .... Ill

,, inanition, . . .891

Lunin on salt-free food, . . . 883

Lusk on glycogen, . . . .917

,, ,, lactose, 399

Lussana on acid of gastric juice, . . 360
Luther on sugar in urine, . . . 609
Lyon on animal heat, . . . .817

MAASE on liver fat, ..
Macalister on heat production,
Macallum on chromatin, .
,, ,, iron absorption,

in nuclei,

. 936

. 842
. 69
. 886

69, 885, 886
. 470

Macfadyeu on bacterial digestion,

., ,, reaction of intestinal con-

tents, . . .464

MacGregor on respiratory exchange, . 698
v. Mach on hypoxanthin, . . .910
Mackay on bile salts, . . . .378
M'Kendrick on heat production, . .840
,, ,, respiration of fishes, . 704

Mackenzie on blood gases, . . 766, 769
,, ,, Graves' disease, . . 945

,, ,, myxoedema, . . . 939
Maclay on body heat, . . . 790, 866
MacMunn on bile pigments, . . 388

chlorocruorin, . . 61

hsematoporphyrin, . . 260
haemochromogen in supra-

renal .... 90
haemoglobin, . . .187
myohfematin, ... 99
ox-bile, .... 386
spectrum of bile, . . 390
tetronerythrin, . . 21
urinary pigments, 623, 625, 626
Macpherson on thyroid grafting, . .942
M 'William on precipitation of proteids, 41
Madden on skin absorption, . . 685

Magendie on blood heat, . . . 828
„ lymph, . . . 288, 303
,, ,, skin varnishing, . . 727
Mager on caisson disease, . . .737
Magnus on blood gases, . 229, 758, 765
Mairet on pituitary extract. . . . 948
Majert on Charcot's crystals, . . 94

Makris on milk, .
Malassez on blood,
Malfatti on mucin of urine, ,

,, ,, nucleins, .
Malgaigne on blood heat,
Mall on reticulin,
Malpighi on respiration,
Maly on acid of gastric juice.

avidity, .
bacterial digestion,
bilirubin,
biliverdin,
cholalic acid, .
choletelin,

PAGE

. 128, 138
. 150
. 604
65

. 828
. 72
. 692

352, 358, 359,
360, 361
. 357
. 464
. 384, 389
. 385
. 380
. 388
. 388
. 353, 355
. 387, 622
. 421, 425
. 21
. 331, 333
. 400
. 46
. 145

345, 346, 347, 348
. .392
. 155
90, 91
105, 918
. 915
797, 798
403

gastric juice, .
hydrobilirubin,
leucine, .
lipochromes, .
pepsin, .
proteid digestion,
proteids,

reaction of blood,
saliva,

taurocholic acid,
Manasse on blood corpuscles,
., ,, suprarenal body,
Manche on glycogen, .

,, ,, muscular metabolism,
Mangili on hibernation,
Mann on peptic digestion,

,, ,, trypsin, ..... 415
Manning on succus entericns, 341, 369, 399
Mantegazza on body temperature, 786, 789,

812, 821

Maquenne on inosite, .... 17
Marcacci on respiration, . . . 725
Marcano on bromelin, . . . .54
Marcet on bacterial digestion, . . 464
blood plasma, . . .160
body temperature, . 807, 817
emulsification, . . 444, 455
excretin, .... 474
fat digestion, . . . 443
fatty acids, . . . .451
respiration, . . 698, 718, 748
spirometer, .... 752
xanthin, . . . .596
Marchand on respiration, . 700, 706, 709
Marchlawski on phylloporphyrin, . .382
Marcuse on casein, . . . .137
,, diabetes, . . 905, 928, 929
,, ,, muscular metabolism, . 915
,, ,, sarcolactic acid, . . .106
Mares on urea, . . . . .585
,, uric acid, . . . 594, 910
Marfori on ammonium lactate, . . 905
,, ,, iron absorption, . . . 886
,, ,, oxalates in urine, . .614
Marie on acromegaly, . . . .946
Marignac on diffusion, .... 263
Marinesco on pituitary body, . . 945
Marino-Zucco on neurine in blood, . 160
,, ,, suprarenals, 90, 948, 958
Marker on starch digestion, . . . 393
Marme on sweat, .... 678, 680
Marquardt on animal alkaloids, . . 59
Marshall on alcapton, . . . .607
„ bile, 374

INDEX OF AUTHORS.

1021

PAGE

. 733

. 377
. 758
. 55
. 58
. 369
. 49

170, 174, 175, 178
. 282
. 180
53

nucleo- proteid of blood plasma, 165
papain, ... 51, 54
proteid digestion, . . 403

proteids ... 27, 41
pus, ..... 83
saliva, ..... 328
snake venom, . 56, 57, 58, 146

Marshall on foetal respiration,
Marson on chenotaurocholic acid,
Martigny on blood gases,
Martin on abrin, .

anthrax-toxin,

bile, .

biuret reaction,

coagulation, .

nitration,

leucocytes, .

liver proteid

spleen,

vegetable albumin,
Martine on body temperature,
Martins on body temperature,
v. Marxow on respiration,
,, ,, spirometer,
Mascagni on lymph absorption,
Maschke on proteid crystals,
Masius on stercobilin, .
Masje on body heat,
Masloff on intestinal enzymes,
,, ,, ,, secretion,
Masoin 011 thyroidectomy,
Massalongo on pituitary body,
Masse on fatty acids of liver,
Massen on extirpation of liver,
Mathieu on blood gases,
,, ,, respiration,
Matteuci on muscle,

,, ,, respiration,
Matthes on proteids,

,, ,, suppuration,
Maurel on body temperature,

88
. 51
. 786, 791
. 811
. 779
. 752
. 287, 303
52

. 388, 474

. 829, 851

. 341

398, 555, 556

. 943

. 946

. 936

. 908

. 762, 763

. 714, 748

. 840, 911

. 781

41

. 84

801, 809, 811,
812
. 880
. 122
. 891
3

. 338
144

Mauthner on amido-acids,
May on fuscin, .
,, ,, inanition,
,, ,, pentoses, ....
,, ,, trypsin, ....
Mayer on alkalinity of blood,

,, ,, elimination of iron, . . »»0

,, ,, haemoglobin, . . . .731

Mayovv on animal heat, . . 832, 839

,, ,, blood gases, . . . 757

,, ,, oxygen, .... 735

,, ,, respiration, 693, 704, 730, 731,

733, 741, 744, 756

Meade-Smith on gastric absorption, . 432

Meara on atmid-albumoses, . . .50

Meckel on nitration, .... 280

Medians on uric acid, .... 586

Mediger on thyroid feeding, . . . 944

Me"hu on urobilin, . . . .620

Meissel on fat formation, . . . 932

,, ,, respiratory exchange, . . 718

Meissner on blood plasma, . . .160

,, ,, creatine, .... 880

,, muscle, . . . 101, 105

,, ,, peptic digestion, 402,403,404

,, ,, trypsin, .... 338

v. Meister on extirpation of liver, . 906

Melloni on body temperature, . . 793

Melzer on lymph, .

,, ,, pancreatic diastase,

,, ,, trypsin,
Mendel on lactose,

,, ,, succus entericus, .
Mendus deLeon on milk,
Mengarini on respiration,
Menzies on respiration,
Merejkowski on tetronerythrin,
v. Mering on carbohydrate absorption,

diabetes,

PAGE

. 285
. 339
. 337, 338
. 399
. 398
. 128
. 705

748, 751, 754
21
434,
435
920, 921, 922, 928

dextrose in blood, . .158
fat absorption, . . . 459
gastric absorption, . 432, 541
glycuronic acid, . . 5
haemoglobin, . . .191
maltose, . . . .394
muscle glycogen, . .919
ptyalin, . . . .328
respiratory exchange, . 719
starch digestion, . . 397
urochloralic acid, . . 614
Merkel on respiration, . . . . 742
., ,, salivary ducts, . . . 488
Mesnil on skin absorption, . . . 687
Mester on gastric juice, . . . 364
Metroz on sugar in blood, . . .161
Mett or Mette on gastric digestion, . 545
,, ,, pancreatic secretion, . 549,554

,, ,, proteolysis, .... 325
Meunier on sorbite, .... 4
Meyer on ablation of kidneys, . . 937
blood gases, 229, 237, 758, 766, 769
glycuronic acid, ... 5
haemoglobin, .... 238
internal temperature, . 787, 789
iron in milk, .... 86

lactose, 399

,. , starch digestion, . . . 395

Mialhe on ptyalin, . . . . 327

Michaelsen on thyroidectomy, . . 943

Michel on blood proteids, . . .163

,, ,, proteid crystals, . . 44, 163

Miescher on nuclein, . . 65, 66, 81, 880

,, ,, protamine, ... 93

„ pus, 83

,, ,, spermatozoa, ... 93
Mignot on body temperature, . . 804
Millar on calorimetry, .... 834
,, ,, inulin, ..... 14
,, ,, maltose, .... 10
,, ,, reducing power, . .. . 7
Millon on a reaction of proteids, . . 47
Milly on cutaneous respiration, . . 725
Milroy on muscle proteids, . . .98
,, ,, thymic acid, ... 67

Minkowski on absorption, . . 443, 459
acetone, . . . .616
ammonia in urine, . . 905
bile, . . . 562, 563
,, pigments, . . 389
COo of blood, . . . 772
diabetes, . 772, 922, 929
extirpation of pancreas, . 928
fat absorption and meta-
bolism, . 461, 462, 931
glycosuria, . 920, 921, 922
hypoxanthin, . . 910

lactic acid in urine, . 909

1022

INDEX OF A UTHORS.

PAGE
. 105
. 448
. 145
. 930
. 106
. 435
. 911
841, 912
. 364

Mironow 011 milk, .... 663, 664

. 488
485, 488
56, 180
63

. 758
343, 347
16

Minkowski on muscle glycogen,
pancreatic juice,
reaction of blood,
salivary glands,
sarcolactic acid,
starch absorption,
urine of birds,

Minot on respiratory exchange,

Miquel on gastric juice,

Mislawsky on salivary ducts,

,, ,, ,, secretion,
Mitchell on snake venom,
Mitjukoff on paramucin,
Mitscherlich on blood gases, .

,, ,, saliva,

Mittelmeier on dextrin,

Miura on alcohol, .... 882

,, ,, dextrose of blood, . . .158

,, ,, glycosuria, .... 881

,, ,, inulin, ..... 14

,, ,, inversion, .... 399

Mohr on gastric juice, . . . .366

,, ,, keratin, 73

,, ,, marrow fats, . . . 19, 20

Moleschott on acidity of muscle, . . 108

,, ,, nervous tissues, 115,116,117

,, ,, respiratory exchange, 703, 709

Molinari on muscle glycogen, . .105

Molisch on phycocyanin, ... 52

,, ,, sugar in urine, . . . 609

Monari on creatinine, . . . .100

le Monnier on body temperature, . .814

Monro on lymph, 287

Montgomery on protagon, . . .21

Monti on milk, . . . . .125

,, ,, phosphorus, .... 84

Moore on chemistry of digestion, . . 312

,, ,, intestinal , emulsion, . . 448

,, ,, reaction of intestinal contents, 453,

465

„ salivary glands, . . 524,930
,, ,, solubility of fatty acids, 455,456,

458

,, ,, suprarenal body, . 91,92,951
Moraczewski on caseinogen, . . 136, 139
,, ,, nuclein, ... 44

Morat on glycogen, . . . .925
,, ,, muscular metabolism, . .915
,, ,, submaxillary gland, . 516, 843
Morax on sulphates of urine, . . 26
Moreau on intestinal secretion, . . 555
,, ,, respiration, . . . 704, 705
,, ,, swimming bladder, . . 705
Mori on proteid food, .... 877
Moriggia on glycogen, . . . .15
,, ,, pepsin, .... 330
Moritz on diabetes, .... 921
,, ,, glycosuria, . . . 609, 610
Morkotun on thyroid, . . . .89
Morner on chondrin, . . . .114
chondroitin-sulphuric acid, . 115
cornea, .... 121
,, mucoid, . . 63, 121
fuscin, 121

hippomelanin,
hydrochloric acid,
keratin,
lens, .
melanin,

121
365
73
123
122

Morner on membranin, .

nmcin of urine, .
ovomucoid, .
serum globulin, .
urea, .
urine, .
Morochowetz on chondrin,
,, ,, cornea,

,, ,, elastin,

Morris on achroodextrin,
,, ,, cerebrins,
,, ,, dextrin,
,, ,, diastatic ferments,
,, ,, galactose,
,, ,, inulin, .
,, ,, maltose,
,, ,, starch digestion, .
Moscatelli on sarcolactic acid,
„ thymus, .
,, thyroid, .

Mosen on blood platelets,
Mosse on body temperature, .
,, ,, glycogenesis, .
,, ,, muscular metabolism,
Mosso on body temperature,

,, ,, calorimetry,

,, ,, fatigue,

,, ,, muscular metabolism, .
,, ,, proteid poisons,
Mott on body temperature, .
Moussu on saliva, ....

,, ,, salivary nerves, .
Mroczkowski on phosphoric acid in blood,
Miihsam on fats of blood,
Muir on blood platelets,
Mulder on gelatin, ....
,, ,, keratin. .
,, ,, neossin, . . . .
,, ,, proteids, . . . .
Miiller on cerebrin, ....
,, ,, chondrin, .
,, ,, digestion, .
,, ,, elastin, . . . .

,, ,, fat absorption,
,, ,, fish slime, ....
,, ,, haemoglobin,

inanition, ....
lymphatics, .
mucus, .
nervous tissues,
phospho-carnic acid,
ptyalin,

PAGE

. 64
. 604
. 63
. 64
. 584
. 85
. 114
. 121
. 72
. 396
. 120
. 12
12, 13
7

14

. 10
. 397
106, 616
. 88

88

. 156
. 805
. 923
. 914

801, 802, 807,
808, 810, 821
. 845
. 108
. 915
. 55
. 792
. 489
. 482
772
159
. 156

70

. 73
. 63
. 29
. 120
. 121
. 438
. 71
. 459
. 676
. 187
. 891

287, 303, 304
. 85
. 116, 117
. 104
. 328

respiration, 701, 731,

,, ,, skin absorption,
,, ., sputum mucin,
Munk on alcohol,

,, ,, amido-acids, .
,, ,, ammonia in urine,
,, ,, bile secretion,
,, biliary fistula,
,, blood plasma,
„ diet, .
,, diuretics,
, , fat absorption,

,, ,, formation,
,, gelatin,
,, glycerin,

39, 744, 758,
780
. 690
. 62
. 882
. 880
. 585
. 565
. 460
. ]60
. 876
. 648

450, 451, 454, 455,
462, 881

. 931, 932, 935
. 878

INDEX OF AUTHORS.

1023

PAGE

Munk on glycogenesis, . . . 923

inanition, . . . 888, 891
lymph, . . . .182

milk, .... 128, 664
muscular metabolism, . 914, 916
potassium of urine. . . 634
proteid food, . . .877

,, metabolism, . 913, 915
skin absorption, . . 688, 690

soaps, 463

sulphocyanate of saliva, 345, 346
sulphur of urine, . . . 632
thyroid gland, . . . 942
grafting, . . .942
urine, . . . .631, 659
Miintz on iron in blood, . . .150

Miinzer on urea, 908

Murray on myxoedema, . . . 940
,, ,, thyroidectomy, . . . 942
Musculus on achroodextrin, . . . 395
,, carbohydrate absorption, . 434
,, glycuronic acid, . . 5
,, maltose, .... 394
,, ptyalin, . . . .328
,, starch digestion, 393, 394, 397
,, urochloralic acid, . . 614
Mylius on cholalic acid, . . 380, 381
,, ,, Pettenkofer's test, . . 377

NABARRO on blood gases, 761,
, , , , body temperature,
,, ,, gas pump,
,, ,, respiration,
,, ,, suprarenal body,
Nageli on crystalloids, .
Napier on thyroid feeding, .
Nasse on blood gases, .
„ „ ,, heat, . .
,, ,, colloids,
,, ,, gelatin,

763,

ictic acid, .

liver ferment,

Millon's reaction, .

muscle glycogen, .
, , sugar,

muscular metabolism,

proteids,

ptyalin,

ptyalose,

starch digestion, .
Naunyn on animal heat,

,, bile, . 561, 562,

„ glycogen, .
Nawrocki on blood gases,
,, ,, creatinine,
,, ,, gas pump,
,, ,, haemoglobin,
., ,. salivary nerves,
, , , , sweat nerves, .
,, ,, ,, secretion,

563,
760,

186,
676,

Nebelthau on glycogen,

,, ,, sarcolactic acid,
,, ,, urine of fishes, .
Nencki on acid of gastric juice,
,, ,, amido-acids in blood,
,, ,, bilirubin, .
,, ,, collidine,
,, ,, ferments,

764, 765
. 808
. 759
. 841
. 91
. 52
. 944
. 757
. 827
. 42
. 70
. 15
. 108
. 925
. 47
. 104
. 105
. 915
. 30
. 330
. 394
. 395

858, 859

564, 569
. 919

761, 780
. 100
. 759

238, 249
. 483
. 676

677, 678,
679
. 919
. 106
. 911
. 359
. 899

384, 389

. 59

319

Nencki on haematin,

hsematoporphyrin,

intestinal bacteria,

lactic acid in blood,

leucine and tyrosine, .

melanin,

muscle,

parahsemoglobin,

phymatorusin,

pialyn,

portal blood,

proteids,

,, in diet, .
putrefaction,
reaction of intestinal

tents,

reduced haemoglobin,
Teichmann's crystals,
tryptophan,
urea in muscle, .
urorosein,
Nernst on osmosis,
Neubaner on ammonia in urine,

creatinine,

laiose, . • .

muscle, .

quadriurates, .

spleen,
Neuhauss on body temperature,

Neumann on notochord,

,, nuclein,

, , , , skin absorption,
,, ,, thymic acid, .
,, ,, thymin,

Neumeister on albumoses,

amanitine, .
ammonia in urine,
atmidalbumoses, .
bacterial digestion,
bile salts, .
diabetes,
glycosuria, .
hsemochromogen, .
hemipeptone,
indol, .

internal respiration,
iron in food,
ovomucoid, .
peptones,
peptonisation,
proteid digestion, .

,, food,
proteids,
ptyalin,

sebaceous secretion,
sugar formation, .
tryptic digestion, .

PAGE

250, 253
. . 259
. 470
. 159
. 425
. 122
. 103
. 207
. 121
339, 340
. 908
. 55
. 562
. 468
con-

. 464
232, 233
. 252
. 29
. 103
. 628
. 266, 273
. 585
. 599
7

. 100, 101
. 588
. 87
. 789, 802,
813, 814, 825
113

tryptophan, .
vegetable ferments,
Neupauer on residual air,
Neusser on urinary pigments,
Newell on coagulation,
Newport on respiration,

,, ,, temperature of insects, 792, 793,

807

Newton on thermometer, . . . 785
Nicati on gastric juice, . . . 364

. 688

. 67

66, 67

411, 412, 413,

439, 441
. 60
. 907
. 50
. 466
. 392
. 927
. 610
. 256
. 414
. 468
. 782
. 886
. 63
. 400

403, 404
. 405
. 878
32, 49

327, 328
. 656
. 921
415, 416,

417, 419
29, 428
. 55
. 750
. 625
. 178

701, 702

1024

INDEX OF A UTHORS.

PAGE

Nicol on animal heat, . . . 789, 799

Nicolaides on blood corpuscles in liver, 901

Nicolas on intestinal juice, . . . 554

Nicolaysen. on body temperature, . .822

Nicolls on heart work, .... 843

Niderkorn on body temperature, . . 866

Niebel on sugars, .... 3

Nilson on colostrum, . . . .129

,, ,, lichenin, . . . .14

Nissen on bile salts, . . . . 39 1

le Nobel on fat absorption, . . . 459

,, ,, hsematoporphyrin, . . 625

,, ,, peptone, .... 48

Nobili on temperature of bees, . . 793

Nocard on reaction of blood, . .145

Noll on lymph, . . . 287, 288, 299

Nollet on osmosis, .... 273

Nollner on kidney nerves, . . . 643

v. Noorden on balance of nutrition, . 871

,, „ diet, . . . .876

,, ,, spectrophotometry, . 224

North on muscular metabolism, . 912, 913

Nothnagel on bile pigments,

,, ,, suprarenals,
Notkin on thyreoproteid,

,, thyroid,

Novi on diet, ....
,, ,, ptomaines,
,, ,, saliva, .
Nowak on respiration, .
Noyes on body temperature,
Nuck on lymphatics, .
Nuel on blood gases,

,, ,, tension of gases,
Nussbaum on alveolar air, .

,, ,, secretion of urine, .
,, ,, tension of blood gases,

Nuttall on bacterial digestion,
,, ,, intestinal bacteria,
Nylander on dextrose, .
Nyldn on ptyalin,

OBERMAYEE, on indigo,

„ urine, .

Obermeyer on proteids,

,, ,, skin absorption,

Oberm tiller on cholesterin, .
saponification,

. 389
. 948
. 89
. 938
. 877
. 58
. 510

695, 700
. 810
. 302

776, 778
. 784
. 774

655, 656
. 776,
777
. 465
. 26
. 610

329, 330

. 627
. 85

41

. 687
. 23

19

Obernier on body temperature, 790, 807, 816,

824

Obolensky on mucin, ... 62, 63

O'Brien on proteids of flour, . . .54

Ocana on suprarenal extract, . . 951

Oddi on chondroitin-sulphuric acid, . 115

„ ,, muscular metabolism, . .913

,, ,, respiration, . . . 708, 711

Oehl on saliva, . . 342, 343, 345, 492

Oehler on electrical currents, . . 683

Oertmann on body temperature, . 786, 825

,, ,, respiration, 699, 703, 756, 781,

895

Offer on uric acid, .... 592

Ogata on collagen, .... 430

,, ,, digestion, .... 442

Ogle on body temperature, 788, 789, 799, 800,

803, 807, 809, 820, 824

Oglesby on body temperature, . . 821
Ohlmuller on diet, . . . .877
Oidtmann on kidney, .... 92

PAGE

Oidtmann on liver, . . . 77, 87
,, spleen, ... 77, 87
,, ,, thyroid, .... 88
Oliver on blood corpuscles, . . 150, 152
hsemoglobinometer, . . 152
pituitary extract, . . .946
saliva, ..... 525
suprarenals, 90, 950, 951, 955, 959
thymus, .... 960
thyroid extract, . . .943
Olsavsky on muscular metabolism, . 916
Openchowski on gastric nerves, . . 538
Oppenheimer on muscular metabolism, . 913
Ord on Graves' disease, . . . 945

,, ,, thyroid, 939

Ore" on bile secretion, . . . .565
Orecchia on thyroidectomy, . . . 940
Orlow on absorption, .... 304
Osborne on diastase, .... 54
,, ,, fractional coagulation, . 43
,, ,, vegetable proteids, . . 54
,, ,, vitellin, .... 53
Osiander on foetal respiration, . . 731
Osier on blood platelets, . . .156
Ostroumow on sweat secretion, . . 676
Ostwald on mechanical affinity, . 275, 276
,, ,, solutions, . . . 354, 650
O'Sullivan on maltose, .... 394
,, ,, reducing power of dextrose, 7

Ott on animal heat, . . . 858, 863
,, ,, skin secretion, . . 677, 678, 680
,, ,, suppuration, .... 84
Otto on carbohydrate absorption, . . 435
,, ,, cerebrins, . . . .120

,, ,, dextrose in blood, . . .158
,, ,, oxyhsemoglobin, 197, 199, 200, 205
,, ,, tryptic digestion, . . .416
Overton on plasmolysis, . . .277
Owen on skin glands, .... 670
Owsjannikow on intraglobular crystalli-
sation, . . .191
,, ,, salivary secretion, . 492

PAAL on gelatin, 70

,, ,, ,, peptones, ... 71
,, ,, proteids, .... 27
Pachon on coagulation, . . 174, 178
Page on respiration, . . 707, 712, 848
Pages on coagulation, 135, 147, 169, 170, 171
Pagliese on nitrogen excretion, . . 876
Paijkull on bile, . ... 84, 372
Painter on ptyalin, .... 330
Pallas on hibernation, .... 797
Panasci on salivary nerves, . . . 525
Paneth on succus entericus, . . . 554
Panormoff on muscle sugar, . . .105
Pantyuski on renal secretion, . . 654
Panum on foetal blood, . . . 732

,, ,, gastric fistula, . . .537
,, ,, sepsine, .... 59
Paoletti on muscular metabolism, . 915

Pappel on milk, 131

„ ,, tewfikose, . . . .132
Pappenheim on tryptic digestion, . 414

Parcus on cerebrin 120

Parisat on skin absorption, . . 686, 687

Parke on lecithin, .... 21

,, ,, taurocholic acid, . . . 375

Parkes on body temperature, . 820, 825

,, ,, muscular metabolism, . . 912

INDEX OF A UTHORS.

1025

PAGE

Parkes on urine, . . . .572

Parrot on osmosis,
Parry on animal heat, .
Partsch on milk secretion,
Pascheles on electro-osmose,
Paschkis on bile salts, .
,, ,, ,, secretion,
,, ,, cholagogues,
Paschutin on cane-sugar,
,, ,, curari,

„ ,, enzymes

. .273
. 817
. 666

. 688
. 391
. 567
. 568, 569
. 398
. 298

329, 339, 340, 342,
556

,, ,, lymph .... 289
,, ,, succus entericus, . 398, 399

Pasteur on racemic acid, . . . 107
Paton on bile, .... 371, 561
,, ,, ,, pigments, . . 563, 569
,, ,, ,, secretion, . 559, 560, 567
,, ,, fasting, .... 888, 891
,, ,, fat absorption, . . . 460
,, ,, ,, production, . . 924, 935
fatty acids of liver, . 935,936
liver fat, . . . 935, 936
,, glycogen, . . 926, 935
,, tissue, .... 564
muscular energy, . . .916
proteid crystals, ... 44
Patrizi on body temperature, . . 803
Paulesco on proteid quotient, . .162
Pautz on aqueous humour, . . . 122

,, ,, lactose, 399

,, ,, succus entericus, . . . 398
Pavy on amylolytic ferment of liver, . 926
,, ,, dextrose in blood, . 158,159,161
,, ,, fat formation, . . . 935

,, „ glycogen, 16, 917, 924, 925, 926
,, ,, glycoly tic ferment of blood, . 161
,, ,, lactose, . . . . .12
,, ,, phloridzin diabetes, . . 921
,, ,, proteids, ... 30, 64

,, „ sugar in urine, . . 608, 609
Pawlow on coagulation, . . .178
gastric fistula, . . . 537
,, secretion, 349, 539, 540
pancreatic secretion, 547, 548, 549

proteids of diet,
salivary glands,
urea formation, .

Payen on starch digestion, .

Pecquet on lacteals,

Peiper on blood, .

Pekelharing on albumoses, .
,, ,, cell globulin,

562
487, 488, 512

. 393
. 286
143, 144
. 411
. 82

coagulation, 167, 170, 175,
177, 179

,, fibrin ferment, . . 82

,, ,, nucleo-proteid of blood, 165,

166, 171

,, ,, ,, ,, muscle, 98

,, ,, proteose of blood, . 165

Pellacani on intra vascular coagulation, 173

,, ,, suprarenals, . . 90, 950

Pelouse on gastric juice, . . . 352

Pembrey on animal heat, 785, 789, 790, 799,

804, 821, 830, 840, 848,

850, 859, 861, 865

,, ,, cachexia thyreopriva, . 941

,, ,, heat regulation, . 735,866

,, hibernation, 795, 796, 797, 866

,, ,, oxidation in tissues, . . 895

VOL. I. — 65

PAGE

Pembrey on respiration, 692, 696, 697, 698,

703, 706, 707, 708,

717, 723, 781

,, ,, second wind. . . . 747
,, ,, warm-blooded animals, 713, 714,

866

Pepys on respiration, 695, 698, 735, 736, 739,

748, 750, 754

Perewoznikoff on fat absorption, . . 451
Pernet on spleen, .... 959

Pernon on iron in milk, ... 86
Perreri on body temperature, . .821
Perrin on body temperature, . . 820
Peschel on proteid food, . . . 876

Peters on casein, 137

,, ,, hepatin, .... 69

Petersen on respiration of fishes, . . 704

Petit on enzymes, . . . .317

,, ,, heat value, .... 834

Petri on toxopeptone, .... 58

Petriquin on cerumen, . . . .675

Petrowsky on nervous tissues, 115, 116, 118

Pettenkofer on bile acids, . . . 377

,, ,, fat absorption, . . 454

,, ,, ,, formation, . . 933

,, ,, inanition, . . 887, 889

,, ,, respiration, 695, 696, 699, 700,

707,708,716,718,

721, 781, 803

Pfeffer on gases of saliva, . . . 346
,, ,, osmosis, . . . 276, 284
,, ,, osmotic pressure, . 265, 266, 267,

278, 650

,, ,, semipermeable membranes, . 264
Pfeiffer on melanin, . . . .122

,, milk, 128

,, ,, pepsin, .... 333

,, ,, phymatorusin, . . .121

Pflliger on animal heat, . . 833, 859

,, ,, balance of nutrition, . .871

,, blood gases, 154, 761, 762, 767,

770, 771, 775, 778, 780

,, ,, curari, .... 842

, , , , gases of bile, . . . 784

„ saliva, . 346, 347, 504

,, ,, gas pump, .... 759

,, ,, glycogen, .... 920

,, ,, glycogenesis, . . . 923

,, ,, metabolism, . 914, 924, 935

,, milk, 130

,, ,, oxidation, .... 781
,, ,, proteid diet, . . .892
,, ,, ;, metabolism, 898, 903, 913,

915

,, ,, proteids, . . 38, 897, 899

,, ,, reducing substances of blood, 152

,, ,, respiration, . 694, 695, 699, 710,

711, 713, 717, 732, 740,

749, 750, 755, 756, 757,

765, 774, 780, 848, 895

,, ,, synthesis in metabolism, 25, 893

,, ,, urea estimation, . . . 584

Philip on animal heat, . . . 857, 858

Philippeaux on suprarenals, . . .948

Philips on maltose, .... 397

Phillips on diuresis, .... 649

,, ,, respiration of oxygen, . 736

Phisalix on pigeons' milk, . . . 676

,, ,, skin secretions, . . . 673

Picard on blood plasma, . . .160

1026

INDEX OF A UTHORS.

PAGE

Piccard on protamine, .... 93
Piccolo on lutein, .... 20

Pick on glycosuria, . . . .921
Pickardt on dextrose in blood, . .158
Pickering on biuret reaction, . . 48
coagulation, . . 173, 177
colloids, ... 37, 146
copper reaction of proteids, 48
proteids, . . . .49
synthesis of proteids, . 37
xantho-proteic reaction, . 47
Pictet on animal heat, .... 823
,, ,, effects of cold, . . . 817
Picton on osmotic pressure, . . . 272

,, ,, solutions, 262

Pierini on skin absorption, . 686, 687, 689
Pilatre de Rozier on respiration of hydro-

. 739
5

. 812
. 424
. 561
. 946
. 790
130, 131

gen, ....
Piloty on glycuronic acid,
Pinkerton on body heat,
Piria on tyrosine,
Pirri on bile,

Pisenti on pituitary body,
Pitts on body temperature,
Pizzi on milk,

Planer on gases of alimentary canal,

,, ,, peritoneal fluid, .
Plato on animal heat, .
Plattner on bile salts, .
Plosz on albumose in blood, .
,, ,, liver proteids,
,, ,, nuclein, ....
,, ,, proteid food, .
Plugge on ptyalin,
Pochoy on animal heat,
Podolinski 011 NO-hsemoglobin, .
,, ,, pancreatic extract, .

,, ,, trypsin, .

v. Poehl on proteid digestion,

,, ,, spermine, .
Poggiale on foetal blood,

,, ,, milk,
Pohl on carbohydrates,
,, „ nuclein, ....
» ?> polysaccharides,
,, ,, proteid absorption, .
Politzer on proteid food,
Ponfick on burns.

, , , , extirpation of liver,
,, ,, proteid food,
Popielski on pancreatic secretion, .

. 729
. 784
. 832
373, 374
. 439
85, 86
65, 81
. 878
. 330
. 858
. 239
. 552
. 338
. 400
. 94
. 732
. 130
. 42
. 65
. 13
. 441
. 878
. 728
. 906
. 878
549, 550,

551
. 137
. 67
. 333

688

Popoff on caseinogen, . .
,, ,, nucleo-proteids,

,, proteids, . . .
Porret on electro-osmose, . .
Porter on excrements, . . . .77

,, ,, urine, 77

Possell on spongin, .... 76
Pott on respiration, 702, 703, 706, 708, 720,

734

Potthast on amido-acids, . . . 880

Pouchet on leucomaines, ... 61

Poulet on skin absorption, . . .685

Praussnitz on diabetes, . . . 921

,, ,, glycogen, . . . 105

,, inanition, . . 888, 891

,, ,, vegetable proteids, . . 51

Pregl on succus entericus, 342, 369, 556, 557

Prevost on bile, 533

PAGE

Provost on bile salts, . . . .392
,, ,, body temperature, . . 791
,, ,, nmscarine, . . . 514, 520
Preyer on blood crystals, 194, 205, 208, 209
,, gases, . .761, 762. 772
body temperature, . . 804

globin, 244

hemoglobin, 189, 195, 198, 248,
767, 768
in traglobular crystallisation, . 191

respiration, .
Pribram on blood salts,

,, ,, gastric juice,
Priestley on animal heat,

,, ,, blood gases,
• ,, ,, cutaneous secretion, .

,, ,, lymph hearts, .

,, ,, respiration, 693, 694,

732, 734, 735, 747
157
361
839
757
725
301
739,
756

Prochaska on lymph, .
Prompt on salivary secretion,
Proust on leucine,

,, ,, uroerythrin, .
Prout on acid of gastric juice,

,, ,, respiration, . 698, 721
Provencal on respiration,
Provoost on body temperature, .
Purdie on lactic acid, .
Purdy on urinary phosphates,
Purkinje on tryptic digestion,
Putzeys on pepsin,
Pye-Smith on intestinal secretion,
„ ,, salivary secretion, .

351,

•35,

287
490
421
623
352
754; 803
699, 704
. 815
. 107
. 633
. 414
. 332
555, 556
523

QTJAIN on adipocere, ...
Quatrefages on chlorocruorin, .
Quervaiii on thyroidectomy, .

Quetelet on respiration, . .
Quevenne on milk, . . .
Quincke on body temperature, 822,

, elimination of iron, .

, emulsion, . . .

. gastric juice, . .

, hepatin, ...

, iron in liver, . .

, milk globules, . .

, skin absorption, .

, succus entericus, .

, urine, ...
Quinquaud on blood, . . .

,, ,, glycogen, . .

„ „ haemoglobin, . .

,, ,. respiration, 700, 703

. 20
. 61
.941
. 747

127, 131
823, 858,

859, 867
. 886

445, 446
.359
. 69
.86

125, 446
. 686
. 369
. 580

141, 160
. 918
.231

707, 711

RACHFORD on emulsions, . 444, 445, 448

,, ,, fat absorption, . 452,461

,, ,, pancreatic fistula, . . 366

,, ,, pialyn, .... 340

Radziejewski on aspartic acid, . . 425

,, ,, fat absorption, . 451,931

,, ,, tyrosine, . . . 423

Rahn on salivary nerves, . . . 482

Rajewsky on alcohol, . . . .882

Ralfe on gastric juice, . . . .360

Ramsden on fractional coagulation, . 43

Ranke on diet, .... 875, 877

,, ,, fatigue, . . . .108

,, ,, inanition, . . . .889

INDEX OF AUTHORS.

1027

PAGE

. 708
. 110
. 919
. 84
. 476
. 264
. 269
. 24
. 759
. 812
. 665, 666
. 804, 866
. 126
. 83
. 731
. 678
. 793, 823
. 401, 536
. 834
. 299
. 825
. 373
. 796, 798
281, 282, 283
. 115
. 817, 841
. 540
. 187

699, 700, 702, 703,
781, 782, 840
. 795

694, 700, 703, 706,
707, 709, 711, 720, 723, 726,
736, 739, 762, 765, 853
. 821, 844
. 688
56, 180
. 725
. 261
. 684
. 280
. 284

690, 691, 725
. 669

674, 676, 681
. 161
. 843, 896
. 821
726
23

. 81
24

. 15
. 795

694, 700, 702, 703,
706, 707, 708, 709, 711, 720,
723, 726, 736, 739, 765, 853
Eeiss on mannose, .... 7
Reober on electrical currents, . .682
Reoch on gastric juice, .... 365
Retzius on salivary nerves, . . . 525
Reverdin on thyroidectomy, . . 939

Rey on lime excretion, . . . .78
Reynaud on body temperature, . . 812
Reynolds on second wind, . . .747
Ribbert on secretion of urine, . 656,657
Richardson on body temperature, . 821

,, ,, intraglobular crystallisa-

tion, . . . .191
,, ,, respiration, . . .742

Ranke on respiration, .

,, ,, tetanus,
Ransom on glycogen, .
Ranvier on glycogen, .

,, ,, retrolingual gland,
Raoult on diffusion,

,, ,, osmotic pressure, .
Rappel on isocholesterin,
Raps on gas pump,
Rattray on body temperature,
Rauber on milk secretion,
Raudnitz on body temperature,

,, milk,

Rauscheiibach on pus cells, .
Ray on respiration,
Raymond on sweat nerves, .
Reaumur on animal heat,

, , , , gastric digestion,
Reclienberg on heat value, .
Recklinghausen on lymphatics,
Redard on body temperature,
Redtenbacher on taurine,
Reeve on hibernation, .
v. Rege"czy on nitration, 280,
de Regibus on nervous tissues,
Regnard on body temperature,

,, ,, gastric secretion,

,, „ haemoglobin,

,, ,, respiration,

Regnault on hibernation,
,, ,, respiration,

Reichert on body temperature,
,, ,, iodine in urine, .
,, ,, snake venom,
Reid on cutaneous respiration,
diffusion,

electrical currents, .
filtration,

intestinal absorption,
skin absorption,
,, secretions,
slime of eel, .
sugar of blood,
temperature of liver,
Re ncke on body temperature,
Re nhard on cutaneous respiration,
Re nitzer on cholesterin,
Reinke on dSthalium, .
,, ,, cholesteriii, .
,, ,, glycogen, .
Reiset on hibernation,
,, ,, respiration,

PAGE

Richerand on tidal air, . . . 748

Richet on body temperature, 789, 790, 791,

792, 799, 801, 821, 824,

842, 845, 856, 863

,, ,, gases of alimentary canal, . 730
,, ,, gastric fistula, . . . 537
,, ,, ,, juice, 349, 353, 354, 355,

539, 545

,, ,, inanition, .... 891
,, ,, respiration, 699, 706, 707, 708,
709, 713, 714, 716, 717, 718,
720, 748, 752, 756, 916, 933

,, ,, urea- forming ferment,
Richmond on milk, . .
,, ,, tewfikose, .
Richter on thyroid feeding, .
Rickards on body temperature,
Riegel on animal heat, . .
Riess on sarcolactic acid in urine,
Rindfleisch on skin absorption,
Ringer on animal heat,

,. ,, casenogen,

,, ,, coagulation,

,, ,, oxalate of lime,
Risler on hemoglobin,
Ritter on diabetes, .

, , , , proteid food, .

,, ,, skin absorption. . .

,, ,, urea,

,, ,, uric acid, ...
Ritthausen on aspartic acid, .

carbohydrates of milk,

907
.131
.132
. 944
820, 821
856, 859
.616
. 688

789, 799, 805, 809,
819, 820, 821, 824
... 137
... 136
42, 43, 135, 169. 170
. 171
.231
920, 921
. 876
. 687

glutaminic acid,
legumin,
mucedin,
proteid crystals,
Riva on urochrome,
,, ,, uroerythrin,
Roberts on digestive solutions,
metacasein,
pancreatic casein

. 33
. 592
. 425
. 132
32, 426
. 51
53, 54
. 52
. 620
. 623
. 322
. 127
. 137

enzymes, 336, 337, 338,
339

ptyalin, .... 327
quadriurates, . . 588, 589
urates, . . 572, 588, 590
uric acid, .... 591

urine, 637

Robertson on body temperature, . 790, 803
,, ,, gastric fistula, . . .537
,, ,, respiration, . . . 753
Robillard on sweat, . . . 679, 680
Robin on htematoidin, .... 384
Robson on bile, . . 371,560,561,562
Roch on proteids, .... 41

Rockwood on antipeptone, . . . 420
,, fatty acids, . . 455, 456
,, ,, intestinal emulsion, . 448

,, ,, reaction of intestinal con-
tents, . . . 453, 465
Rodewald on cholesterin, ... 24
,, ,, glycogen, ... 15
Roger on body temperature, . . 804, 805
Roget on body temperature, . . . 807
Rogowicz on lymph production, . . 289
,, ,, pituitary body, . . . 946
,, ,, thyroidectomy, . . 939

Rohmann on absorption, . 399,431,462

1028

INDEX OF AUTHORS.

PAGE

Rohmann on acidity of organs, . . 108
biliary fistula, . . .460
diabetes, . . . 928, 929
diastatic ferment of blood, 160

fats in blood,
glycogen, .
intestinal secretion.

. 159
. 919
368, 555,
556
. 12
86

. 435
. 161
560, 565
. 159
667

isomaltose,
liver,

starch absorption,
sugar in blood,
Rohrig on bile,

,, ,, fats of blood,

,, ,, milk secretion,

,, ,, respiration, . 699, 711, 726, 727

,, ,, skin absorption, . . 686, 687

Rolleston on heat formation in nerve, . 808

,, ,, skin temperature, . . 830

,, ,, suprarenals, . . . 959

Rollett on blood, 142, 143, 145, 212, 213, 233

,, ,, ,, of earthworm, . . 186

,, ,, hemoglobin, 194, 204, 230, 231,

232

,, ,, red corpuscles, . . . 188

,, ,, tendon, .... 62

Ronchi on cutaneous respiration, . 726, 727

Rondeau on body temperature, . 789, 801

Roos on sugar in urine, . . .608

,, ,, thyroid feeding, . . . 944

,, ,, thyroiodin, .... 89

Roosen on uric acid, . . . 586, 587

Roscoe on extinction coefficient, . .214

Rose on bile, 77

Rose on paracasein, . . . .134

Rosenbach on bile pigments, . .386

Rosenberg on bile, . 560, 563, 566, 568

,, ,, fat absorption, . .459

Rosenblatt on thyroidectomy, . . 941

Rosenheim on proteid food, . . . 876

Rosenstein on fat, . . . 462, 931

,, ,, lymph, .... 182

Rosenthal on body heat, 812, 824, 826, 839,

845, 846, 854, 859, 863

,, ,, electrical currents, . . 682

Rosin on indoxyl, .... 628

,, ,, urorosein, .... 628

Rosow on fuscin, . . . . .121

Ross on animal heat, . . . 823, 851

Rossbach on sweat secretion, . . 680

Rothon-Duvigneaud on thyroidectomy, 939

Rouelle on urea, . . . . .581

Roux on reaction of blood. . . .145

,, ,, tetanus toxin, ... 58

Rouxeau on thyroidectomy, . . . 939

Rovida on hyaline substance, . . 68

Roy on cerebral circulation, . . . 808

,, ,, oncograph, .... 643

,, oncometer, 643

,, ,, specific gravity of blood, .

,, ,, spleen, ....

de Rozier. (See Pilatre de Rozier. )

Rubbrecht on blood proteids, .

Rtibner on calorimetry, . .

,, ,, carbohydrate absorption,

,, ,, fat formation, . .

. 144
. 960

. 162
. 845
. 436
932, 934

heat production, . 832, 833, 834,

835, 836, 837, 841,

846, 851, 853, 854

„ value, . . 834, 838, 874

PAGE

Riibner on inanition, .... 888

,, ,, isodynamy, . . . .875

,, ,, respiration, 712, 718, 719, 720, 721

Riidbeck on lymphatics, . 286, 299, 310

Riidel on rickets, 886

,, ,, uric acid, .... 588

,, ,, urine, 580

Rudneff on amyloid substance, . . 74

Rudolphi on animal heat, . . . 793

,, ,, proteids, .... 38

Riidorff on freezing point of solutions, . 269

Ruge on gases of rectum, . . . 729

Rumpf on body temperature, 808, 821, 842

,, ,, respiratory exchange, . 713, 717

Runeberg on casein, .... 878

,, filtration, . . 280, 281, 282

Ruppel on milk fats, . . . .133

,, ,, protagon, .... 116

,, ,, vernix caseosa, . . .678

Russ on glycogen, . . . .15

Russell on blood platelets, . . . 153

Rustiksky on marrow, . . . .111

Rutgers on proteids, .... 52

Rutherford on bile secretion, 567, 568, 569

,, ,, gastric secretion, . . 537

de Ruyter on body temperature, . . 855

ST. ANGES on respiration, . . . 734

St. Bondzynski on cholesterin, . . 24

St. Hilaire on foetal respiration, . .731

St. Martin on respiration, 717, 721, 741, 779

St. Pierre on blood gases, . . .762

Sabanejeff on glycogen, . . .13

,, ,, osmotic pressure, . .272

,, ,, proteids, ... 27

,, ,, proteoses, ... 46

Sacchi on pituitary body, . . 945, 946

Sachs on blood. 780

,, „ ,, gases, . . . .761
,, ,, body temperature, . 792,863,864
,, ,, carbohydrates, . . . 921
,, ,, temperature of plants, . . 849
Sachsse on vegetable proteids, . 52, 53
Sainsbury on coagulation, . 42, 169, 170
Saissy on blood heat, .... 827
,, ,, hibernation, . 794, 795, 797, 798
Salkowski on amido-acids in blood, . 899
,, ,, ammonia in urine, . . 585
,, ,, aspartic acid, . . . 425
,, ,, bacterial digestion, . 466, 467
blood, . . . .152
caseinogen, . . 136, 137
chlorides of urine, . . 634
cholesterin, . . .23
creatinine, . . .598
dyspeptone, . . . 429
fatty acids, . . . 451
,, ,, of urine, . 615
gelatin, .... 70
hfematoidin, . . . 384
indol, . . . .468
liver ferment, . . . 925
Millon's reaction, . . 47
muscle, .... 96
ovomucoid, ... 63
pentoses, . . . 3, 612
pigments of urine, . . 625
potassium in urine, . . 634
proteids, ... 26, 46

INDEX OF AUTHORS.

1029

Salkowski on pseudo-nuclein,

skatol-carbonic acid,
sulphates of urine, .
synovia, "
urea,

467

PAGE

136
, 469
632
184
907

uric acid, . 592, 594, 595

xanthin bases, . . 597

xanthoproteic reaction, . 47
Salomon on glycogen, . . 14, 15, 919

of blood,
hippuric acid,
lactic acid in blood,
pus, .
urea, .

,, formation, .
Salvioli on albumoses, .
,, ,, coagulation,
,, ,, lymph,
,, ,, peptone blood,
,, ,, proteid quotient,
Samojloff on digestive solutions,
Sanctorius on skin,

,, ,, thermometer, .
Sanders-Ezn on respiratory exchange,

Sandmeyer on caseinogen,

,, ,, diabetes,

,, ,, intestinal emulsions,

„ ,, pancreas,
Sandras on starch digestion,
Sanguirico on thyroidectomy,
Santesson on nitration,
Sarokin on creatinine, .
Schabad on diabetes,
Schaer on saliva,

158
893
159
84
906
902
440
147
182
177
162
325
27
85
699,

711, 713
. 137
. 928
. 448
. 443, 459
. 393
. 939, 940
280, 281, 283
. 100
. 922
346

Schafer and Bohm. See Bohm.

Schafer on blood, 141

coagulation, . 168, 171, 172
fat absorption, . 450, 457, 458

fibrin, 167

gastric secretion, . . .540
internal secretions, . . 937
metabolism, . . .868
milk secretion, . . . 662
oncometer, .... 643
oxalated blood, . . 135, 147
pituitary extract, . . 946

proteids, .... 42
reaction of blood, . .144

red corpuscles, . 155, 188, 189
salivary glands, . 524, 525, 930
spleen, .... 960
suprarenal body, . . 90, 91
,, extract, 950, 951, 959

thymus, .... 960
thyroid juice, . . . 943
white blood corpuscles, 83, 158
Schaffer on intestinal secretion, . . 554
Schalfijew on hsemin, . . . 252, 253
Schardinger on lactic acid, . . .107
Scharling on calorimetry, . . 844, 846
,, ,, heat production, . 838,847

respiration,

695, 708, 715, 722,
725, 726

Scheel on foetal respiration, . . . 731

Scheele on respiration of hydrogen, . 739

,, ,, uric acid, .... 586

Scheffer on diffusion, .... 263

Scheibe on milk, 128

Scheibler on cane-sugar, . . .10

Scheibler on dextrin,

,, ,, raffinose, .
Schenck on bile salts, .

,, „ glycogen, .

,, ,, glycolytic action of blood,
Scheremetjewski on respiratory exchange, 699

PAGE
16
12
378
919
161

Scherer on blood plasma,
,, ,, fuscin,
,, inosite,
,, ,, leucine,
,, liver, .
muscle,

nervous tissue, .
pancreas,
quadriurates,
spleen,
thymus,
thyroid,
tyrosine,

Schermberg on muscular metabolism,
Scheube on diet, ....
Schierbach on ptyalin, .
„ ,, sweat, .

Schiff on body temperature,
chorda tympani,
dextrin,
fat absorption,
gastric fistula,

,, secretion,
Pettenkofer's test,
pituitary body,
ptyalin,
red corpuscles,
salivary nerves,

, , secretion,
skin varnishing,
succus entericus,
thyroid gland,

101,

160
121
105
423
86
105
116
92
588
87
88
88
424
913
877
. 329
670, 671
855, 856
. 483
. 542
459, 461
. 537
. 542
. 377
. 946
. 330
151

. 482

490, 502, 523
.728
. 342, 398
938, 939, 941, 942,
943
SchifFer on body temperature, . . 867

,, ,, ptyalin 327

Schindler on nuclein bases of thymus,

,, testis,
Schlagenhauffen on cholesterin

,, ,, lecithin,

Schlesinger on ptyalin,
Schlosing on ammonia of urine, .
Schlossberger on milk, .
,, ,, muscle,

,, ,, nervous tissues, .

Schlossmann on milk proteids,
Schmaltz on blood,
Schmelz on muscle glycogen,
Schmidt on ash-free albumin,
„ „ bile, . . .
,, ,, salts, .
„ blood,

104,

93
24
21
329

586
127
95
116
134
143
105
. 25
560, 565
. 392

145, 153, 154, 155, 157,
163, 166

,, gases, . . 773, 780
body temperature, 803, 809, 866
Charcot's crystals, . . 94
C02 in urine, . . . 634
coagulation, 168, 170, 171, 175,
179, 319, 334

cytoglobin, ... 68
endosmotic equivalent, . 274
fat absorption, . . .460
ferments, . . . .320
filtration, . . 281, 282, 283
gas pump, .... 759

1030

INDEX OF A UTHORS.

Schmidt on gastric fistula, . . . 537

,, ,, ,, juice, 349, 350, 351, 352,

353, 356, 538

„ haemoglobin, 195, 198, 206, 230,
231, 244

inanition, .... 889
intestinal secretion, . . 555
lungs, .... 77
mucus, .... 344
muscle, . . . .912
pancreatic juice, . 367, 368
pepsin, .... 332
peptone plasma, . . 175
proteids, . . . .41
proteolysis, . . . 323
reducing substance of muscle, 110
renal epithelium, . . 653

respiration
saliva,

secretory cells, .
sepsine, ....
urobilin, ....
Schmidt- Miilheim on albumose in blood,
casein,

707, 718, 781
. 347, 348
. 938
59

. 622
439
140
147

coagulation,
leucine in digestion, 438
peptone in blood, 41, 439
proteid absorption, 434,
437

Schmidt-Schwedt on respiration, . . 702
Schmiedeberg on absorption of iron, . 886
ammonia in urine, . 907
chitin, ... 75
chondroitin - sulphuric

acid, . . .115
chondro-mucoid, . 114
crystallised proteids, . 52
ferratin, ... 86
glycuronic acid, . . 5
hippuric acid, . 601, 893
internal respiration, . 782
muscarine, . 60, 513

salts of food, . . 883
spermatozoa, . . 93
Schmitz on gastric juice, . . .364
Schmoger on lactose, . . . .12
Schneider on milk secretion, . . 664
Schoffer on blood gases, 154, 761, 763, 771
,, ,, leucine and tyrosine, . . 425
Schofield on bile pigments, . . . 383
Scholkotf on blood, . . . .143
Schonbein on saliva, .... 346
Schondorff on metabolism, . 903, 904, 906
,, ,, osmosis, .... 277

,, ,, thyroid feeding, . .944

,, ,, urea in muscle, . . 103

Schonemann on pituitary body, . . 946
Schotten on cholalic acid, . . . 380
,, ,, fatty acids, . . . 615
,, fellicacid, . . 373, 381

Schottin on skin secretion, . . 671, 672
„ ,, testis, .... 93
Schoumaker on skin absorption, . . 690
Schoumow-Simanowsky on gastric juice, 349,

350, 359, 539

Schreiber on animal heat, . . . 863

Schreiner on Charcot's crystals, . . 94

v. Schroder on diuresis, . . . 649

,, ,, muscle,. . . . 908

„ urea, 103, 160, 562, 902, 906

PAGE

v. Schroder on uric acid, . . . 909
Schrodt on milk, . . . .131

Schroff on animal heat, . . . 859
Schroter on milk, . . . .138

Schrotter on caisson disease, . . 737

Schuchardt on septicine, ... 59
Schultz on respiration, . . . 704

Schultze on burns, .... 728

fat production, . . .932
glow-worm, . . .780
haemoglobin, . . .194
respiration, . . .731
uric acid, .... 594

wool fat, .... 24

Schultzen on amido-acids in blood, . 899

,, ,, sarcolactic acid in urine, . 616

Schulz on proteids, . . . .26

,, ,, respiration, . . 695, 703, 710
Schulze on arginine, .... 33

aspartic acid. ... 29

cholesterin, . . .24

fats, ..... 17

h'sh slime, . . . .676

hemicellulose, . . .16
lecithin, .... 21

leucine, . . 29, 422, 423
muscarine, .... 60

paracasein, . . . .134

proteoses, .... 51

ptyalin, . . . .329

starch digestion, . . . 393
wool fat, . . . .675

Schumberg on rennin, .... 334

Schunck on phylloporphyrin, . . 382

Schuster on heat regulation, . . . 851

Schutz on foetal respiration, . . . 731

,, ,, zymolysis, .... 322

Schutz- Schultzerstein on alkalinity of
blood, ...... 144

Schiitzenberger on gelatin, . . 47, 70, 71
,, ,, haemoglobin, . . 231

,, ,, leucine and tyrosine, 425

proteids,

Schwalbe on bile secretion,

,, ,, lutein,

Schwann on blood corpuscles,

„ pepsin, .
,, ,, respiration,
,, ,, saliva,
Schwartz on elastin,

,, ,, respiration,
Schwarz on thyroidectomy, .
Schwarzer on starch digestion,
Schweigger-Seidel on lymphatics,
Schwenke on blood heat,
Sciolla on skin absorption, .
Sclater on temperature of snake,
Scoresby on body temperature,
Scudamore on blood gases, .
,, ,, heat, .
Sczelkow on blood gases,
,, ,, muscle,
,, ,, respiration,
Sebelien on caseinogen,
colostrum, .
lactalbumin,
lacto -globulin
milk,
proteids, .

26, 30, 31, 32,
35, 36, 38, 403
. 560
. 20
. 188
. 402
. 734
. 327, 489
71, 72
. 731
. 642
. 393
. 300
. 827
. 687
793, 849
. 791
. 758
. 827

154, 761, 763, 764
. 841, 911
. 699, 841

136

137
127
139
139
126
41, 46

INDEX OF A UTHORS.

1031

PAGE

Seegen on carbohydrates, . . 919, 921
dextrose, . . . 914, 923
glycogen, . . . .397
glycogenesis, . . 923, 926
glycolytic ferment of blood, . 161
invert sugar, . . .398
respiration, . . . 695, 700
starch digestion, . . . 394
sugar in blood, . . 158, 159
,, ,, urine, . . 608, 609
Seeman on lime in food, . . . 886
Seguin on respiration, . 712, 715, 725, 726,

736, 739, 754

Seitler on muscle, . . . .108
Seligsohn on suprarenals, ... 90
Selmi on animal alkaloids, ... 59
Semon on animal heat, . . 790, 866

,, ,, thyroid gland, . . . 942
Senator on creatinine, .... 600
diuretics, .... 648
heat production, . . 847

inanition, .... 891
indoxyl, . . . 607, 627
respiration, . 675, 711, 718
secretion of urine, . . 659
skin varnishing, . . .728
Senebier on respiration, . . . 748
Sertoli on blood gases, . 157, 772, 773

,, ,, phosphoric acid of blood, . 153
,, ,, saliva, ..... 342

,, ,, testis, 93

Setschenow on blood gases, . 759, 761, 762,

765, 766, 769, 770, 771, 773

,, ,, milk, .... 130

Seurne on body temperature, . . 867

Sewall on gastric secretion, . . 531, 532

Shepard on blood plasma, . . .160

Sherdngton on blood, .... 143

,, ,, cerebral circulation, . 808

,, ,, eosinophil granules, . 84

,, ,, white corpuscles, . .152

Shore on albuinose absorption, . . 439

,, ,, lymph, 182

,, ,, peptone in blood, . . . 440

,, ,, small intestine, . . . 399

Sieber on bilirubin, . . . 384, 389

,, ,, cheese, 933

,, ,, fuscin, ..... 121
,, ,, gastric juice, . . . 364

,, ,, Iwematin, .... 250
,, ,, hsematoporphyrin, . . 259
,, ,, h;emoglobin, . . 207, 232

,, ,, intestinal bacteria, . . 470
,, ,, reaction of intestinal con-
tents, . . . .464
,, Teichmann's crystals, 232, 252, 253
,, ,, urorosein, .... 628
Siedamgrotzky on body temperature, 790, 803,
805, 807, 809, 811

Siegfried on carnic acid, . '27, 103, 104
conglutin, ... 33

glutamic acid, . . . 426
lysine, .... 426
muscle, . . .106, 420
nucleon, . . . .139
pseudo-haemoglobin, . . 237
reticulin, ... 32, 72
Sigalas on respiration, . . . 698, 700
Silbermann on coagulation, . . . 174
,, ,, heat value, . . 833,834

Simon on blood plasma,

,, ,, body temperature,

,, ,, milk, .

,, ,, thyroid body,

,, ,, uroerythrin, .
Simony on bilifuscin, .
de Sine'ty on milk secretion,
Singleton on body temperature, .
Sisel on hibernation, .
Sjoqvist on antipeptone,

,, ,, gastric juice,

,, ,, urea, .

Skrebitzki on pancreatic secretion,
Slosse on respiratory exchange,
Smirnow on salivary ducts, .
Smith, A., on respiration,

PAGE

. 160
823, 867
. 130
. 945
. 623
. 387
. 663
790, 811
. 795
. 421
. 365
. 584
. 368
. 719
. 488
. 742

E., on respiration, 698, 712, 716, 717,
718, 721

,, F., on sweat, .... 673

L., on blood gases, 768, 776, 778, 779

,, respiration, . . 739, 742

,, ,, thyroid gland, . . 943

,, ,, thyroidectomy, . . 941

M'G., on ptyalin, ." . . 329

,, ,, snake venom, . . 56

,, ,, uric acid, . . . 594

Snell on caisson disease, . . 737, 738

Snow on asphyxia, .... 744

v. Sobieranski on renal secretion, . . 654

,, ,, skin absorption, . 690

Socin on iron of food, .... 885

,, ,, salts of food, . . . 883, 886

Socoloff on bile salts, . . . .563

Soemmering on lymphatics, . . . 303

Solberg on milk, 130

Soldner on milk, . . . 126,128,130
,, ,, caseate of lime, . . .136
Solera on sulphocyanate of saliva, . 345
Solin on glycogen,

Solley on gelatin, . 47, 71, 429, 430

Somerfeld on bile, .... 85

Sonden on inanition, .... 891

,, ,, muscular metabolism, . . 913

,, ,, respiratory exchange, . 718

Sonnerat on body temperature, . . 816

Sorby on blood, . . . .187, 209

Sorensen on foetal respiration, . . 732

Soret on blood spectrum, . . 225, 226

Sotnitschewsky on glycogen, . . 15

,, ,, liver, ... 86

,, ,, sebum, . . . 675

Souleyet on body temperature,

Soulier on skin absorption, . . . 686

Sourdat on milk, . . . . .128

Souze-Leite on pituitary body, . . 946

Soxhlet on caseate of lime, . . . 136

,, ,, emulsions, .... 447

fat production, . . . 932

„ milk, .... 130, 131

Spallanzani on animal heat, . 816, 823

,, ,, gastric digestion, . 364,402,

536

,, ,, hibernation, . ^ . 79-4

,, respiration, 701, 702, 723,

739, 757, 781, 782

Speck on blood gases, . . .715

,, ,, body temperature, 807,808,818

,, ,, muscular metabolism . . 916

,, ,, respiration, 698,708,712,716,719,

721, 738, 740, 748,-. 755-

1032

INDEX OF A UTHORS.

PAGE

Spiess on heat production, . . . 843

,, ,, salivary glands, . . . 516

Spilker on uric acid, . . . 594, 595

Spina on skin glands, .... 681

Spiro on bile, 562

,, ,, ,, salts, .... 392
,, ,, lactic acid in blood, . .159

,, ,, lymph, 182

,, ,, sarcolactic acid, . . . 106
Spitzer on diabetes, . . . .929
,, ,, glycolysis in blood, . . 161
Spong on bile, . . . 560, 561, 562
Squire on body temperature, . . 804
Ssubotin on fat, .... 664, 933
,, milk, . . . 128. 130
Stadeler on bile pigments, . . 382J 384
bilifuscin, .... 387
biliverdin, . . . 385

leucine, .... 425

liver, 86

nervous tissues, . . .116
pancreas, , . . .92
spleen, .... 87
spongin, . . . .75
thymus, . . . .88
thyroid, .... 88
torpedo organ, . . .111
urea, .... 33, 102
Stadelman on bile, . . . 567, 568
bilirubin, . . .563
diabetes, . . .772
pancreatic digestion, 29, 427
proteinchromogen, . 29, 428
suprarenal body, . . 90
Stadthagen on alkaloids in urine, . 61

leukaemia, . . .910
putrescine, ... 60
Staffel on muscle, .... 77

Stahel on thyroid gland, . . . 945
Starke on proteids, .... 46
Starling on absorption, 303, 304, 305, 307,

309

diuretics, .... 648
lymph, . . 285, 290, 295
osmotic pressure, . 272, 308
proteids, .... 41
secretion of urine, . . 639
Stefan on diffusion, .... 262
Steiger on arginine, . . . .33
Stein on gastric juice, . . . . 359
Steiner on emulsions, .... 445
Steinhaus on mammary cells, . . 667
Stenhouse on Pettenkofer's test, . . 377
Stern on body temperature, , . .821
,, ,, dextrose, .... 7
,, ,, reducing power, ... 7
,, ,, removal of liver, . . . 908
Sternberg on notochord, . . .113
Stevens on gastric digestion, 402, 536, 537
Stewart on body heat, . . . 829, 851
Stieda on pituitary body, . . . 946
Stierlin on blood corpuscles, . . 151

Stillmark on ricin, .... 55
Stockman on fasting, .... 888
,, ,, inanition, . . . 891
,, ,, iron in food, . . 78, 884
Stohmann on heat values, . . 834, 874
Stokes on blood spectrum, 208, 229, 251, 254
,, ,, hremoglobin,

Stoklasa on lecithin,

230, 243, 766
21

Stoklasa on proteid food,
Stokvis on muscular energy,
,, ,, urinary pigments,
Stolnikoff on fat formation, .

,, ,, fatty acids of liver, .
Storch on fat formation,
Stourbe on skin absorption, .
Strassburg on blood gases, .
,, ,, haemoglobin, .

,, ,, hydrocele fluid,
,, ,, lymph gases, .

Strassmann on alcohol,
Straus on reaction of blood, .
Strecker on bile acids, . 373, 374
blood plasma, .
body temperature,
fatty acids,
lecithin,

nervous tissues, .
xanthine, .
Strieker on milk secretion, .
saliva,
skin glands,
Stroganow on respiratory exchange,
•Strohmer on fat formation, .

,, ,, respiratory exchange,
Struckmann on milk, .
Struve on peptone in blood, .
Stuart on body temperature, 789,

Studemund on diet,
Stumpf on fat of milk,
Stutzer on pepsin,
,, ,, saliva,
Sundberg on pepsin,
Sundwik on chitin,
Suter on proteids,
Sutton on body temperature,
Swieci?ki on pepsin,
Sylvius on digestion, .
Szabo on acid of gastric juice,
Szigeti on cyanhsematin,
Szontagh on casein ogen,
Szymonowicz on suprarenal extract,

PAGE

. 878
. 915

625, 627

902, 934
. 936

902, 934
. 687

775. 777
. 767
. 784
. 783
. 882
. 145

376, 380
. 160

790, 803
. 454
. 22
. 116
. 596

665, 666
. 346
. 681

694, 695

. 932

. 718

. 130

41

799, 805,

809, 824
. 877
. 664
. 333
. 328

316, 328
. 74
. 26
. 866
. 330
. 401

354, 365
. 249
. 139

951, 955

TACKE on gases of alimentary canal, .
Taddei on gluten, ....
Tafel on sugars, .....
Tambach on thyroid, ....
Tamman on blood salts, . . .
,, ,, freezing point of solutions,

,, ,, osmosis,

,, ,, semipermeable membranes,
Tangl on animal heat, .

,, respiratory exchange,
Tanszk on caisson disease, .
Tappeiner on absorption of bile salts, .
burns, .
cellulose,.

gases of alimentary canal,
gastric absorption, .
urea, .
Tarchanoff on bile, . . . .

,, pigments,
electrical currents, .
Tarulli on muscular metabolism, .
Tatlock on milk, .
Tay on body heat,
Taylor on body temperature,

701
53
9

88
157
269,
272

272, 274
264
864
719
737
392
728
471
729
432
. 33
. 567
. 389
. 682
. 913
129, 130
. 821
. 866

INDEX OF AUTHORS.

Tebb on small intestine,
Teichmann on fat absorption,
,, ,, pigeons' milk,
Tenner on body temperature,
Thackrah on vital capacity, .
v. Thanhoffer on fat absorption,
Thenard on bile, .
Theodor on respiration,
Thiel on phloridzin diabetes,
Thierfelder on animal gum, .

bacterial digestion,

body temperature,

casein, .

cerebrins,

galactose,

glycuronic acid

intestinal bacteria,

milk,

reducing subst;

mamma,

Thiroloix on diabetes, .
Thiry on succus entericus, 368,

Tholozan on body temperature,
Thoma on hsemacytometer, .
Thomas on body temperature,
,, ,, cholesterin,
,, ,, hsemacytometer,
,, ., urinary secretion,
Thomson on " avidity law," .

,, ,, coefficient of distri
Thomson on body temperature,
,, ., gastric juice,
,, ,, vital capacity, .
Thorner on milk, .
Thornley on body temperature,
Thudichum on bilirubin,
,, ,, biliverdin,

,, ,, kephalines, .

,, ,, lutein, .

,, ,, phrenosine, .

,, ,, urochrome, .

,, ,, uroerythrin, .

Thuiller on reaction of blood,
Tidy on milk,
Tiedemann on absorption,

,, bile pigments,
., blood gases, .
,, body temperature,
,, gastric secretion

,, lymph absorption,
., pancreatic secretion
,, saliva, .
,, tryptophan,
Tiegel on blood proteids,
,, ,, metabolism, .
v. Tieghem on temperature of plants, . 849
Tigerstedt on filtration, . 280, 281, 283
,, heat value, . . . 875
,, inanition, . . . 891
,, lymph production, . . 289
,, muscular metabolism, . 913
,, respiratory exchange, . 718
Tilanus on elastin, . . . .71

,, ,, horn, 73

Tillet on body temperature, . . . 814
Tissandier on respiration, . . . 738
Tissot on respiration, . . 782,841,911
Tizzoni on proteid food, . . . 878

PAGE

§

. 399

.

458, 459

. 676

855, 856

. 751

}

. 450

t

. 372

707,

711, 848

. 921

(

. 124

>n,

398, 465

e, .

. 800

. 140

. 120

7

5

ia,

26

. 665

ance

of

. 124

.

928, 929

369,

398, 555,

556

. 855

g

. 150

. 867

. 564

. 150

t

. 639

357,

358, 361

ibutio

n, . 355

.

. 812

. 352

. 751

. 126

.

. 813

384, 389

. 385

119, 120

,

20, 95

4

. 120

618, 619

. 625

. 145

t

127, 128

. 431

. 382

. 758

re, .

791, 793

}

352, 536,

540

)n, .

. 303

tion,

. 368

345, 348

,

. 427

. 162

.

. 915

Tizzoni on suprarenals,

,, ,, thyroidectomy,
Toepfer on hydrochloric acid
Tollens on carbohydrates,
Tolmatscheff on milk, .
Tolputt on skin glands,
Tomes on enamel,
Tominaga on inanition,
Tomsa on lymph production
Torup on haemoglobin, .
Tour ton on sweat,
Traube on semipermeable membranes,

PAGE

948, 949
939, 941
. 366
2, 612
128

684
112
890
289
773
671
264,
273
Traube-Mengarini on skin absorption, . 689

Treskin on testis, 93

Treviranus on respiration, . 701, 702, 709

,, ,, sulphocyanate of saliva, . 345

Trimen on hibernation, . . . 794

Tripier on animal heat, . . .816

Triimpy on sweat, . . . 671,680

Tscherewkow on absorption, . . 305

,, ,, diastatic ferment of

blood, . . .161
Tschermak on amyloid substance, . 74
Tscherwinsky on fat formation, . . 932
Tscheschichin on body heat, 821, 822, 841,

858, 862, 863

Tschiriew on blood gases, . . .762

,, ,, lymph, . . . 780, 783

,, ,, proteid metabolism, . . 897

, , , , salivary secretion, . . 492

Tschirwinsky on glycerin, . . . 882

Tschlenoff on urea, .... 585

Tubby on succus entericus, . 341, 369, 399

,, ,, venous absorption, . . 303

Tucsek on inanition, .... 891

Tuczek on salivary secretion, . . 491

Tunniclitfe on piperidine, ... 92

v. UDRANSKY, on cadaverine, . . 59
Pettenkofer's test, . 377
ptomaines, . . 466
putrescine, . . 60
urine, 61, 609, 613, 626
Uffelmann on collagen, . . . 429
diet, . . . .877
gastric fistula, . . 537
lactic acid, . . . 366
Ughetti on thyroidectomy, . . . 942
Ulrich on leucine in urine, . . . 602
,, ,, wool fat, . . . .675
Umber on uric acid, . . .67, 594
Urbain on blood gases, . . . 762, 763
,, ,, respiration, . . . 714, 748
Urich on sebaceous secretions, . . 675
Uschinsky on diabetes, . . . 922
Ustimowitsch on renal circulation, . 642

VAHLAN on cholalic acid, . . . 380
Vaillard on tetanus toxin, ... 58
Valenciennes on body heat, . . .849
,, ,, ichthin, ... 52

Valentin on body temperature, 793, 840, 867
electrical currents, . . 682
hibernation, . . . 797
muscle, . . . .911
respiration, 694, 725, 727, 744,
781

skin currents, . . .682
,, varnishing, . . 727

1034

INDEX OF AUTHORS.

Valentiner on bilirabin,
Valentovvicz on milk secretion,
Van de Velden on gastric juice,

PAGE

. 382

. 663

330, 355,

545

388, 474
. 944
940, 941
945, 946
. 674
. 942
. 33(5
. 366

Vanlair on stercobilin, .
Vas on thyroid feeding,
Vasale on parathyroids,
, , , , pituitary body,
,, ,, sebaceous glands, .
,, ., thyroidectomy,
Vassiliew on pancreatic enzymes,

,, ,, n fistula,

Vaudin on colostrum, . . . . l'2Q

„ milk, 130

Vaughan on ptomaines, . . 58, 59
Vauquelin on respiration, . 701, 702, 704
Vay on iron in liver, . . . .86
Velich on suprarenal extract, . .951
Vella on succus entericus, 368, 397, 398, 555
Velten on animal heat, . . .841
Veragutt on urea, . . . .585
Verdeil on blood, . . . 77, 160

Vermehren on thyroid feeding, . . 944
Vernet on body temperature, . . 807
Vernois on milk, . . . 128, 130, 131
Vernon on respiration, . 699, 701, 702, 703,

711

Viault on red corpuscles, . . .150
Vierordt on blood corpuscles, . .149
,, spectrum, . . 209, 213
body heat, 837, 838, 850, 851, 852
osmosis, .... 273
reduced hemoglobin, . 231, 234
reducing power of tissues, . 782
respiration, 698, 711, 712, 715,
721, 748, 749, 755
rickets, . . . .886
skin absorption, . . 685

spectrophotometry, 214, 215, 216,
218, 219, 220, 221, 222
Vignal on bile secretion, . . . 569
Vignon on fibrin, . . . .76

Ville on biliary fistula, . . . 460

,, ,, fat absorption, . . . 460

Vincent on paired bodies, . . 957, 959
,, ,, suprarenal extract, . . 951
,, ,, suprarenals, . . .92
,, thymus, . . . .960
Vines on aleuron grains, . . .52
,, ,, proteoses, .... 51
,, ,, temperature of plants, . . 849
Viola on pituitary body, . . . 946
Virchow on adipocere, .... 20
amyloid substance, . . 74
body temperature, . . 818
hsematoidin, . . 260, 384
leucine, .... 421
. 92
. 846

pancreas, .
Vogel on animal heat, .

blood gases, .... 758
calorimetry, .... 846
isomaltose, . . . .11

lactose, 399

laiose, ..... 7

glycogen, . . . 15, 397
glycogenesis, .... 926

pentose, ....... 8

quadriurates, . . . .588

starch digestion, . . .397
succus entericus, . . .398

PAGE

Vogelius on glycogen, . . . .919
Voigtlander on diffusion, . . . 263
Voit on acid of gastric juice, . . 358

adipocere, . . . .933

alcohol, 882

amido-acids, .... 880
ammonia in urine, . . . 907
balance of nutrition, 871, 872, 873
biliary fistula, . . . .460
blood plasma, . . . .160
creatine in muscle, . . . 100
diet, . 875, 876, 877, 878, 891

faeces, 472

fat absorption, . . . .454
,, formation, 664, 932, 933, 934, 935
gelatin, .... 878, 879
glycogen, . . 15, 917, 918

glycosuria, .... 881
heat regulation, . . .853
inanition, . 887, 889, 890, 891

intestinal secretion, . . . 556

lactose, 399

lime in food, . . . 635, 886
muscle, ..... 100
muscular metabolism, . . 912
proteid absorption, . . . 436
,, food, . . 876, 892, 894
proteids, . . 896, 897, 898, 903
respiration, 696, 700, 707, 708, 712,
716, 718, 721, 755, 781, 803, 848
,, ,, skin absorption, . . . 688
Volhard on urine, .... 634

Voorhees on wheat proteids, . . 54

de Vries on isotony, .... 142
,, ,, osmotic pressure, . . 270
Vulpian on chorda tympani, . . 520

,, ,, skin secretion, . . 673, 677
,, ,, suprarenal body, . 90, 91

,, ,, sweat, . . . 678, 679

WAAMPELMEYER on bone, .
Waddell on abrin,
Wagner on carnine,

,, ,, respiratory exchange, .

,, ,, thyroidectomy, .
Wagstaffe on spinal injury, .
"Walden on semipermeable membranes,

Waldenburg on residual air, .
Waldeyer on thyroid gland, .
Walker on lactic acid, .
Wall on snake venom, .
Waller on body temperature,

,, ,, calorimetry, .

,, ,, heart work, .

,, ,, skin absorption, .
Walter on alkalinity of blood,

,, ,, blood gases,

,, ,, „ salts, .

,, ,, ichthulin,
v. Walther on animal heat, .
,, ,, fat absorption,
Wanklyn on butter,
Warden on abrin,
Warren on acidity of muscle,

,, ,, body temperature,

respiratory exchange,
Warrington on bacteria in urine,
Warter on body temperature,
Washbourn on body temperature,

113

55
102
711
939
861
264,
275
. 750
. 945
. 107
. 56

830, 852, 855

. 846

. 843

. 689

. 145

. 761, 772

. 883

64

820, 822, 823

. 450, 462

. 133

. 55

. 108

735, 850, 865
714
583
821
790

INDEX OF AUTHORS.

I035

Washbourn on calorimetry, .
Wassilieff on pancreatic secretion,
Wassraann on gastric juice, .
Watson on ptyalin, - .
Waurinski on peptonisation,
Weber on diffusion,

,, ,, foetal respiration, .
,, ,, indicanuria, .
,, ,, serum, .
,, ,, sweat, .

Weckerling on body temperature,
Wedensky on salivary secretion, .

,, urine,

Wegscheider on faeces, .
Weidel on carnine,
,, ,, xanthin,
Weidenbaum on glycogen, .
Weigelin on body heat,
Weiland on body temperature,
Wein on milk fat,
Weinniann on pancreatic juice,
Weintraud on caseinogen,

,, ,, phosphates of urine,
,, ,, uric acid,

,, ,, xanthin,

Weisbach on nervous tissues,
Weiske on amido-acids,
,, ,, cellulose,
,, ,, milk, .

,, „ fat,
Weiss on bile salts,
glycogen,
lymph pressure,
muscular metabolism,
pancreatic secretion,
red corpuscles,
. trypsin,
Welcker on blood,
Welitschkowsky on respiration,
Wells on body temperature,

,, ,, red corpuscles,
Wendelstadt on thyroid feeding,
Wendt on Harderian gland, .
Wenz on albumoses,

,, ,, intestinal enzymes,
,, ,, proteids,
Werigo on albumin,

PAGE

844, 845
. 554
. 534
. 329
. 333
. 263
. 628
. 731
. 77

670, 673
. 820
. 493

609, 613
. 473
. 102
. 598
15

. 802
. 822
. 133
. 547
. 137
. 632
67, 594, 595
. 598
. 115
. 880

470, 881
. 131
. 664

392, 563

105, 919
. 299
. 915
. 547
. 151
. 338

141, 149
. 740
. 821
. 188
. 944
. 675
. 411
. 341
. 42
. 25

. 779

Wertheim on burns, .... 728

,, ,, respiratory exchange, . 698

Wertheimer on bile, . . . 560, 565

„ ,, ,, pigments, . . 564

,, ,, salivary secretion, . 524

Werther on lactic acid, . . . 109

,, ,, rigor mortis,

,, saliva,

. 918

344, 348, 488, 494, 499,
500, 527
. 554
. 20
65

. 249
. 599
. 52

Wesbrook on succus entericus,

Wetherill on adipocere,

Weydemann on proteids,

Weyl on CO-methfenioglobin,
creatinine,
crystalline proteids,

muscle, 108

putrefaction, . . . .467
sericin, ..... 76
torpedo organ, . . 110, 111

White on body temperature, 790, 821, 824,

830, 839, 852, 858, 864

,, ,, calorimetry, . . . 844, 845

PAGE

White on hibernation, . 795, 796, 797, 866

,, ,, levulose, . . . .611

,, ,; thyroid gland, . . 89, 938

Whitehouse on copper albuminate, . 26

Whitfield on nucleo-proteid of muscle, 97, 98

Whitwell on thyroidectomy, . . 941

Wiedemann on biuret, .... 48

,, ,, electro-osmose, . . 68S

Wiemar on fat absorption, . . . 458

Wiener on respiration, .... 732

Wildenow on caseinogen, . . .137

,, dyspeptone, . . .429

Wildenstein on milk, .... 77

Wilks on body temperature, . . 866

Will on fat absorption, . . 451, 452

Williams on bile, 369

,, ,, body temperature, . 812,858

Williamson on blood, . . . .144

Willis on animal heat, . . . .832

Winkler on oxygen of blood, . 766, 767

Winogradoff on albumin, ... 25

Winston on bile, ..... 371

Winteler on bile salts, .... 392

Winternitz on alkalinity of blood, . 145

,, ,, haemoglobin. . . .152

,, ,, proteids, ... 49

,, ,, skin absorption, 686, 687, 689,

690

Winterstein on chitin, .... 74

Wiskemann on foetal blood, . . . 732

Wislicenus on chenocholic acid, . . 377

,, ,, muscle, .... 106

,, ,, source of muscular energy, 912

Wissel on bacterial digestion, . • 464

v. Wistinghausen on coagulation, . 172

,, ,, fat absorption, . 461

v. Wittich on digestive extracts, . 315, 316,

328

enzymes, . 317, 320, 337
fat absorption, . . 461
glycogen, . . .15
lymph hearts, . . 301

pancreatic diastase, . . 340
pepsin, . 331, 404, 535, 535,
542

renal nerves, . . .644
,, secretion, . . 653
saliva, .... 495
skin absorption, . 686, 689
Wittmaack on milk, . . . .104
Wittstein on fats, . . . .19
Wladimiroff on isotony, . . .271
Wb'hler on hippuric acid, . . . 892
,, urea, ... 35, 581, 893
Wolfenden on mucinogen, ... 62
,, ,, snake venoms, . . 56

Woltf on pepsin, 333

Wolffberg on respiration, . . 774, 777
Wolkow on urine, . 605, 606, 607, 630
Wolkowicz on proteids, ... 38

Woll on milk, 125

Wollowicz on body temperature, . 820, 825

Woltering on iron in liver, ... 86

Womack on body temperature, . . 866

Wood on animal heat, . . 824, 844, 863

,, ,, respiration, .... 707

Woodman on hyperpyrexia, . . . 823

Woods on heat value, .... 833

Wooldridge on coagulation, . 37, 146, 173

,, ,, colloids, . . .180

1036

INDEX OF A UTHORS.

PAGE

Wooldridge on fibrinogen, 55, 68, 166, 176,

178

„ ,, peptone plasma, . 174,175

,, ,, red corpuscles, . .155

Worm-Miiller on glycosuria, . . 881

,, ,, haemoglobin, . . 767

„ ,,„ nuclein, ... 65

,, ,, starch, ... 14

Wortman on bacterial digestion, . .470

Wright on coagulation, . 170, 173, 180

„ „ fibrinogen, 166, 175, 176, 177, 178

„ „ glycogen, .... 920

,, ,, peptone plasma, . . .176

Wroblewski on caseinogen, . . .139

Wulff on alloxuric substances, 67, 597, 598

"Wullner on osmotic pressure, . . 272

Wunderlich on body temperature, 786, 789,

805, 809, 810, 812, 823, 825, 855

Wurm on tetronerythrin, 21

Wiirster on Adamkiewicz's reaction, . 47

, , , , body temperature, . . 804

,, ,, C02 in urine, . . . 634

,, ,, hydrogen peroxide, . . 76

Wurtz on choline, . . . .21

,, ,, papain, . . . 51, 54

,, pepsin, . . . .404

,, ,, urea in lymph, . . .182

YEOonbile, 371

,, ,, reducing power of tissues, . 782

Yersin on diphtheria toxin, . . .58

Young on bone, ..... Ill

,, ,, carbohydrates, ... 42

,, ,, polysaccharides, . . .13

,, ,, reticulin, .... 72

,, ,, vitreous humour, . . 62,123

Yvon on cerebro-spinal fluid, . .184

,, urine, . . 573

ZACKE on respiration,
Zahor on proteids,
Zalesky on bile, .

701

41

560

PAGE

Zalesky on bone, . . . . 111,112

,, „ hepatin, ... 69, 86

,, ,, iron in foetus, . . . 885

„ proteids of diet, . 562, 908

,, ,, skin glands, . . . 673

Zalocostas on spongin, . . . .75

Zander on polysaccharides, . . .14

Zawadski on pancreatic juice, . . 368

Zawarykin on fat absorption, . . 450

Zawilski on fat absorption, . . 462, 463

,, ,, water absorption, . . 433

Ziegelroth on blood, . . . .143

Ziehl on fat absorption, . . .459

Ziemke on gastric juice, . . . 364

Zjllesen on lactic acid in urine, . 895, 908

Zinoffsky on haemoglobin, 27, 196, 201, 202

,, ,, oxy haemoglobin, . 199, 200

Zoja on lecithin, 92

,, ,, uroerythrin, .... 623
Zumft on proteids, . . «• . 467

Zuntz on amido-acids, .... 880
balance of nutrition, . .871
blood, . 143, 144, 145, 151, 732
,, gases, . 715, 761, 762, 763,
764, 765, 770, 771, 772, 773, 778
body temperature, 820, 841, 842
CO-hgemoglobin, . . . 238
gases of alimentary canal, . 729
glycogen, . . . .919
glycogenesis, . . .923

glycosuria, .... 922
inanition, .... 891

lungs, 754

muscular metabolism, 912, 913, 914
proteid metabolism, . . 916
respiration, 692, 699, 701,709, 711,
713, 714, 716, 717, 718, 719, 726,
732, 733, 740, 747, 749, 750, 779
Zweifel on amylopsin, .... 336
„ ,,. pepsin, .... 330
,, ,, ptyalin, . . . .327
,, ,, rennin, .... 334
,, ,, respiration, . . 731, 732

END OF VOL. I.

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